WO2018180304A1 - Optical film and image display device - Google Patents

Abstract

One embodiment of the present invention provides a foldable optical film 10 which is used in an image display device, and which is provided with: a resin substrate 11 that is formed from one or more resins selected from the group consisting of polyimide resins, polyamide-imide resins, polyamide resins and polyester resins; a functional layer 12 that is arranged on a first surface 11A side of the resin substrate 11; and a first optical adjustment layer 13 that is arranged between the resin substrate 11 and the functional layer 12 so as to be adjacent to the functional layer 12.

Description

Optical film and image display device Reference to related applications

The present application enjoys the benefit of the priorities of the prior Japanese applications, Japanese Patent Application No. 2017-64583 (filing date: March 29, 2017) and Japanese Patent Application No. 2018-35426 (filing date: February 28, 2018). The entire disclosure of which is incorporated herein by reference.

The present invention relates to an optical film and an image display device.

Conventionally, image display devices such as smartphones and tablet terminals are known, but a foldable image display device is currently being developed. Usually, smartphones and tablet devices are covered with a cover glass, but glass generally does not bend although it has excellent hardness, so if you use a cover glass for the image display device, try to fold it. Then there is a high risk of breaking. For this reason, it has been studied to use a foldable optical film including a bendable resin base material and a hard coat layer instead of a cover glass in a foldable image display device (for example, Japanese Patent Application Laid-Open No. 2016-2006). No. 125063).

In such a foldable optical film, the resin constituting the resin substrate that is generally bent has a high refractive index, so that the difference in refractive index between the resin substrate and the hard coat layer becomes large. For this reason, there is a possibility that interference fringes that are iridescent unevenness may occur due to the difference in refractive index between the resin base material and the hard coat layer.

In order to suppress the occurrence of interference fringes, there is a method of increasing the film thickness of the hard coat layer, but if the film thickness of the hard coat layer is increased, there is a problem that the hard coat layer is broken during folding. For this reason, the present condition is that the optical film which can be folded and does not produce an interference fringe is not obtained.

On the other hand, in such an optical film, dust adheres during the assembly process to be incorporated in the image display device, and may be damaged, resulting in a decrease in yield. Since the base material used for the foldable optical film is very expensive, it is desired to improve the yield. For this reason, the protective film may be attached to both sides of the optical film, but when the protective film is peeled off from the optical film, both sides of the optical film are charged, so the yield cannot be improved. However, it is the current situation.

The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a foldable optical film in which interference fringes are unlikely to occur, and an image display device including the foldable optical film. It is another object of the present invention to provide a foldable optical film that can improve the yield of the assembly process of the image display device, and an image display device including the foldable optical film.

According to one aspect of the present invention, a foldable optical film used for an image display device, which is selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyamide resin, and a polyester resin. A resin base material composed of a resin of a kind or more, a functional layer provided on the first surface side of the resin base material, provided between the resin base material and the functional layer, and adjacent to the functional layer An optical film comprising a first optical adjustment layer is provided.

In the optical film, the refractive index of the first optical adjustment layer may be lower than the refractive index of the resin base material and higher than the refractive index of the functional layer.

In the optical film, the film thickness of the first optical adjustment layer may be 30 nm or more and 200 nm or less.

The optical film may further include a second optical adjustment layer provided between the resin base material and the first optical adjustment layer and adjacent to the resin base material.

In the optical film, the film thickness of the second optical adjustment layer may be 30 nm or more and 200 nm or less.

The optical film further includes a resin layer having a film thickness of 50 μm or more and 300 μm or less provided on the second surface side opposite to the first surface side in the resin base material, and the optical film has a temperature of 25 ° C. The shear storage modulus G ′ in the frequency range of 500 Hz to 1000 Hz is more than 200 MPa and not more than 1200 MPa, and the shear loss modulus G ″ in the frequency range of 25 ° C. and 500 Hz to 1000 Hz in the optical film. May be 3 MPa or more and 150 MPa or less.

The optical film may further include a third optical adjustment layer provided on the second surface opposite to the first surface of the resin base material.

The optical film may further include a third optical adjustment layer provided between the resin base material and the resin layer and adjacent to the resin base material.

In the optical film, a yellow index of the optical film may be 15 or less.

In the optical film, when the test is repeated 10,000 times so that the functional layer is on the inner side and the distance between the opposing side portions of the optical film is 10 mm, cracking or breaking may not occur. preferable.

In the optical film, when the test is repeated 10,000 times so that the functional layer is on the outer side and the distance between the opposing sides of the optical film is 30 mm, cracking or breaking may not occur. preferable.

According to another aspect of the present invention, there is provided a foldable optical film used in an image display device, the light transmissive substrate and a first surface provided on the first surface side of the light transmissive substrate. There is provided an optical film comprising: an antistatic layer; and a second antistatic layer provided on the second surface side opposite to the first surface of the light-transmitting substrate.

In the optical film, a yellow index of the optical film may be 15 or less.

In the optical film, the first antistatic layer may be an antistatic hard coat layer.

The optical film may further include an optical adjustment layer provided on the opposite side of the first antistatic layer from the light transmissive substrate side.

The optical film may further include a hard coat layer provided between the light transmissive substrate and the first antistatic layer.

In the optical film, the absolute value of the saturation voltage on the surface of the optical film when a voltage of 10 kV is applied from a distance of 50 mm from the surface of the optical film in an environment of 23 ° C. and a relative humidity of 50%, It may be over 0 kV.

In the optical film, it is preferable that no cracking or breakage occurs when the test of folding 180 ° is repeated 100,000 times so that the distance between the opposing sides of the optical film is 3 mm.

In the optical film, the light transmissive substrate may be a substrate made of a polyimide resin, a polyamide resin, or a mixture thereof.

According to another aspect of the present invention, there is provided a foldable image display device comprising: a display element; and the above-described optical film disposed closer to an observer than the display element. .

In the above image display device, the display element may be an organic light emitting diode element.

According to one aspect of the present invention, it is possible to provide a foldable optical film in which interference fringes are unlikely to occur. Moreover, according to the other aspect of this invention, the foldable optical film which can improve the yield of the assembly process of an image display apparatus can be provided. Furthermore, according to the other aspect of this invention, an image display apparatus provided with such an optical film can be provided.

FIG. 1 is a schematic configuration diagram of an optical film according to the first embodiment. FIGS. 2A to 2C are diagrams schematically showing the state of the continuous folding test. FIG. 3A and FIG. 3B are diagrams schematically showing a state of the folding stationary test. FIG. 4 is a schematic configuration diagram of another optical film according to the first embodiment. FIG. 5 is a schematic configuration diagram of another optical film according to the first embodiment. FIG. 6 is a schematic configuration diagram of another optical film according to the first embodiment. FIG. 7 is a schematic configuration diagram of another optical film according to the first embodiment. FIG. 8 is a schematic configuration diagram of a solid shearing jig used when measuring the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″. 1 is a schematic configuration diagram of an image display device according to a first embodiment. It is a schematic block diagram of the optical film which concerns on 2nd Embodiment. It is a schematic block diagram of the other optical film which concerns on 2nd Embodiment. It is a schematic block diagram of the image display apparatus which concerns on 2nd Embodiment.

[First Embodiment]
Hereinafter, an optical film and an image display device according to a first embodiment of the present invention will be described with reference to the drawings. In this specification, terms such as “film” and “sheet” are not distinguished from each other only based on the difference in designation. Therefore, for example, “film” is used to include a member that is also called a sheet. FIG. 1 is a schematic configuration diagram of an optical film according to the present embodiment, and FIGS. 2A to 2C are diagrams schematically showing a state of a continuous folding test, and FIG. 3A and FIG. FIG. 3B is a diagram schematically showing a state of the folding stationary test. 4 to 7 are schematic configuration diagrams of other optical films according to the embodiment, and FIG. 8 is a diagram of a solid shearing jig used for measuring the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″. It is a schematic block diagram.

<<< Optical film >>>
The optical film 10 shown in FIG. 1 is used for an image display device and can be folded.

The optical film 10 is provided between the resin substrate 11, the functional layer 12 provided on the first surface 11A side which is one surface of the resin substrate 11, and the resin substrate 11 and the functional layer 12. A first optical adjustment layer 13 (hereinafter, also simply referred to as “optical adjustment layer 13”) adjacent to the functional layer 12 is provided. In the optical film 10 shown in FIG. 1, a second optical adjustment layer 14 (hereinafter simply referred to as “optical”) provided between the resin base material 11 and the first optical adjustment layer 13 and adjacent to the resin base material 11. And the third optical adjustment layer 15 (hereinafter referred to as “adjustment layer 14”) provided on the second surface 11B which is the surface opposite to the first surface 11A of the resin base material 11. It may be simply referred to as “optical adjustment layer 15”). The second optical adjustment layer 14 and / or the third optical adjustment layer 15 may not be provided. Further, the optical film 10 may further include a resin layer on the second surface 11B side of the resin base material 11 as in an optical film 40 described later. The “functional layer” in the present specification is a layer intended to exhibit some function in the optical film. Specifically, examples of the functional layer include a hard coat layer, an antistatic layer, and an antifouling layer. The functional layer 12 functions as a hard coat layer. Moreover, although the functional layer 12 has a single layer structure, the functional layer may have not only a single layer structure but also a multilayer structure of two or more layers. In addition, each “optical adjustment layer” in the present specification has a single-layer structure and is not a multilayer structure of two or more layers. In FIG. 1, two optical adjustment layers, a first optical adjustment layer 13 and a second optical adjustment layer 14, are provided between the resin base material 11 and the functional layer 12. Another optical adjustment layer or the like may be further provided between the one optical adjustment layer 13 and the second optical adjustment layer 14 to form a structure of three or more layers.

In FIG. 1, the surface 10 </ b> A of the optical film 10 is the surface 12 </ b> A of the functional layer 12. In the present specification, the surface of the optical film is used as meaning the surface of one side of the optical film, so that the surface opposite to the surface of the optical film is distinguished from the back surface in order to distinguish it from the surface of the optical film. Shall be called. The back surface 10 </ b> B of the optical film 10 is a surface 15 </ b> A on the side opposite to the surface on the resin base material 11 side in the optical adjustment layer 15.

The optical film 10 can be folded. Specifically, the test (continuous folding test) of continuously folding the optical film 10 was repeated 10,000 times so that the functional layer 12 was inside and the distance between the opposing sides of the optical film 10 was 10 mm. Even if it is a case, it is preferable that a crack or a fracture | rupture does not arise in the optical film 10, and it is more preferable that a crack or a fracture | rupture does not arise in the optical film 10 even if it is a case where a continuous folding test is repeated 20,000 times. Even when it is repeated 100,000 times, it is more preferable that the optical film 10 is not cracked or broken. When a continuous folding test is repeated 10,000 times on the optical film 10, if the optical film 10 is cracked or the like, the folding property of the optical film 10 becomes insufficient. In addition, the test (continuous folding test) in which the optical film 10 is continuously folded so that the functional layer 12 is on the outside and the distance between the opposing sides of the optical film 10 is 30 mm is repeated 10,000 times. However, it is preferable that the optical film 10 is not cracked or broken, and it is more preferable that the optical film 10 is not cracked or broken even when the continuous folding test is repeated 20,000 times. Even when repeated, it is more preferable that the optical film 10 is not cracked or broken.

The continuous folding test in which the optical film 10 is continuously folded so that the functional layer 12 is on the inside is performed as follows. As shown in FIG. 2A, in the continuous folding test, first, the side portion 10C of the optical film 10 and the side portion 10D opposite to the side portion 10C are fixed by the fixing portions 20 arranged in parallel, respectively. . In addition, although the optical film 10 may be arbitrary shapes, it is preferable that the optical film 10 in a continuous folding test is a rectangle (for example, rectangle of 30 mm x 100 mm). In addition, as shown in FIG. 2A, the fixing portion 20 is slidable in the horizontal direction.

Next, as shown in FIG. 2 (B), by moving the fixing portion 20 so as to be close to each other, the functional layer 12 is on the inside, that is, the surface 10A of the optical film 10 is on the inside. And, the optical film 10 is deformed so as to be folded, and further, as shown in FIG. 2 (C), the optical film 10 is fixed to a position where the distance between two opposing side parts fixed by the fixing part 20 of the optical film 10 is 10 mm. After the part 20 is moved, the fixing part 20 is moved in the reverse direction to eliminate the deformation of the optical film 10.

As shown in FIGS. 2A to 2C, the optical film 10 can be folded by 180 ° by moving the fixing portion 20. In addition, a continuous folding test is performed so that the bent portion 10E of the optical film 10 does not protrude from the lower end of the fixed portion 20, and the interval when the fixed portion 20 is closest is controlled to 10 mm. The interval between the two opposing sides can be 10 mm. In this case, the outer diameter of the bent portion 10E is regarded as 10 mm. In addition, since the thickness of the optical film 10 is a sufficiently small value compared with the interval (10 mm) of the fixed portion 20, the result of the continuous folding test of the optical film 10 is not affected by the difference in the thickness of the optical film 10. It can be regarded as not received. In the optical film 10, cracking or breaking occurs when the continuous folding test is repeated 10,000 times so that the functional layer 12 is on the inner side and the distance between the opposing sides of the optical film 10 is 10 mm. More preferably, no cracks or breaks occur when the continuous folding test is repeated 10,000 times so that the functional layer 12 is on the inside and the distance between opposing sides of the optical film 10 is 2 mm. Most preferably not.

In the optical film 10, as shown in FIG. 3A, the side portion 10C of the optical film 10 and the side portion 10D facing the side portion 10C are separated by a distance of 10 mm between the side portion 10C and the side portion 10D. As shown in FIG. 3 (B), a folding stationary test is performed in which the optical film 10 is folded in a state where the optical film 10 is folded for 12 hours. In addition, the folding portion is released by removing the fixing portion 25 from the side portion 10D after the folding stationary test, and the opening angle θ, which is the angle at which the optical film 10 naturally opens in the optical film 10 after 30 minutes at room temperature, is measured. In this case, the opening angle θ of the optical film 10 is preferably 100 ° or more. The larger the opening angle θ is, the better the restoring property is, and the maximum is 180 °. The folding stationary test may be performed so that the optical film 10 is folded so that the functional layer 12 is on the inner side, or may be performed so that the optical film 10 is folded so that the functional layer 12 is on the outer side. However, in any case, the opening angle θ is preferably 100 ° or more.

The surface 10A of the optical film 10 (the surface 12A of the functional layer 12) has a hardness (pencil hardness) of 3H or more when measured by a pencil hardness test specified in JIS K5600-5-4: 1999. Preferably, it is 4H or more. In the pencil hardness test, the optical film 10 cut out to a size of 30 mm × 100 mm is fixed with cello tape (registered trademark) manufactured by Nichiban Co., Ltd. so that there is no folding or wrinkle on the glass plate, and the pencil hardness is applied to the surface of the optical film. Using a testing machine (product name “Pencil Scratch Coating Film Hardness Tester (Electric Type)”, manufactured by Toyo Seiki Seisakusho Co., Ltd.), a load of 750 g was applied to the pencil (product name “Uni”, manufactured by Mitsubishi Pencil Co., Ltd.). It is assumed that the pencil is moved at a moving speed of 1 mm / sec while being added. The pencil hardness is the highest hardness at which the surface of the optical film was not damaged in the pencil hardness test. The pencil hardness is measured using a plurality of pencils having different hardnesses. The pencil hardness test is performed five times for each pencil, and the surface of the optical film is scratched four times or more out of the five times. If not, it is determined that the surface of the optical film was not scratched with the pencil having this hardness. The above-mentioned scratches refer to those that are visually observed through transmission observation of the surface of the optical film subjected to the pencil hardness test under a fluorescent lamp.

The surface resistance value of the surface 10A of the optical film 10 is preferably 10 ¹² Ω / □ or less. The surface resistance value can be measured using a resistivity meter (product name “HIRESTA-UP MCP-HT450”, manufactured by Mitsubishi Chemical Analytech Co., Ltd., probe: URS) in accordance with JIS K6911: 2006. The surface resistance value of the surface 10A of the optical film 10 is obtained by randomly measuring 10 surface resistance values of the surface 10A of the optical film 10 cut into a size of 50 mm × 50 mm, and calculating the arithmetic average of the measured surface resistance values at 10 locations. Value.

In the optical film 10, the saturation voltage on the surface 10A of the optical film 10 is 0 kV when a voltage of 10 kV is applied from a distance of 50 mm from the surface 10A of the optical film 10 in an environment of 23 ° C. and 50% relative humidity. Is preferably exceeded. Similarly, the saturation band voltage on the back surface 10B of the optical film 10 is 0 kV when a voltage of 10 kV is applied from a distance of 20 mm from the back surface 10B of the optical film 10 in an environment of 23 ° C. and 50% relative humidity. It is preferable to exceed. The saturation voltage is the maximum voltage that can be stored in the optical film. When an optical film having an antistatic hard coat layer is arranged closer to the viewer than the touch sensor, the position of a finger or the like may not be detected by the touch sensor depending on the antistatic hard coat layer, but the surface of the optical film 10 If the saturation band voltage at 10A exceeds 0 kV, the position of a finger or the like can be detected by the touch sensor even when the optical film 10 is arranged closer to the viewer than the touch sensor. The saturation charge voltage can be measured using a charged charge decay rate measuring device (product name “H-0110”, manufactured by Shishido electrostatic Co., Ltd.). The saturation voltage is an arithmetic average value of values obtained by measuring three times for an optical film cut out to a size of 100 mm × 100 mm. The lower limit of the saturation band voltage is more preferably 0.1 kV or more, and the upper limit of the saturation band voltage is more preferably 3 kV or less.

The optical film 10 preferably has a yellow index (YI) of 15 or less. If YI of the optical film 10 is 15 or less, the yellowishness of the optical film can be suppressed, and the optical film 10 can be applied to applications requiring transparency. The upper limit of the yellow index (YI) of the optical film 10 is more preferably 10 or less. The yellow index (YI) is a light source on the back side of an optical film cut into a size of 50 mm × 100 mm in a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation, light source: tungsten lamp and deuterium lamp). The chromaticity tristimulus values X, Y, and Z are calculated from the transmittance of the optical film having a wavelength of 300 nm to 780 nm measured in a state of being arranged on the side according to the arithmetic expression described in JIS Z8722: 2009. It is a value calculated from X, Y, Z according to the arithmetic expression described in ASTM D1925: 1962. The upper limit of the yellow index (YI) of the optical film 10 is more preferably 10 or less. The yellow index (YI) is measured three times for one optical film, and is the arithmetic average value of the values obtained by measuring three times. In UV-2450, the yellow index is calculated by reading the transmittance measurement data on a monitor connected to UV-2450 and checking the item “YI” in the calculation item. . The transmittance at a wavelength of 300 nm to 780 nm is measured by measuring the transmittance for at least 5 points between 1 nm and 1 nm before and after the wavelength 300 nm to 780 nm under the following conditions, and calculating the average value. . In addition, if the spectral transmittance spectrum is wavy, the smoothing process may be performed at a delta of 5.0 nm.
(Measurement condition)
-Wavelength range: 300nm to 780nm
・ Scanning speed: High speed ・ Slit width: 2.0
・ Sampling interval: Auto (0.5 nm interval)
・ Lighting: C
Light source: D2 and WI
・ Field of view: 2 °
・ Light source switching wavelength: 360 nm
・ S / R switching: Standard ・ Detector: PM
・ Autozero: 550nm after baseline scan

In order to adjust the yellow index (YI) of the optical film 10, for example, at least one of the resin base material 11, the functional layer 12, and the optical adjustment layers 13 and 14 contains a blue pigment that is a complementary color of yellow. Also good. Even if yellowishness becomes a problem due to the use of a polyimide base material as the resin base material, the yellow index of the optical film can be obtained by including a blue pigment in the resin base material 11 or the like. (YI) can be reduced.

The blue pigment may be either a pigment or a dye. For example, when the optical film 10 is used in an organic light emitting diode display device, it is preferable to have both light resistance and heat resistance. As the above-mentioned blue pigment, polycyclic organic pigments, metal complex organic pigments, etc. are used in applications where light resistance is required because the degree of molecular breakage due to ultraviolet rays is small compared to the molecular dispersion of dyes and the light resistance is remarkably superior More specifically, phthalocyanine-based organic pigments and the like are preferable. However, since the pigment is particle-dispersed with respect to the solvent, transparency inhibition due to particle scattering exists, and therefore it is preferable to put the particle size of the pigment dispersion in the Rayleigh scattering region. On the other hand, when the transparency of the optical film is regarded as important, it is preferable to use a dye that is molecularly dispersed in the solvent as the blue pigment. Moreover, you may use inorganic pigments, such as cobalt blue, as said blue pigment | dye.

L ^* a ^* in the light (transmitted light) transmitted through the optical film 10 by irradiating the optical film 10 with light having a continuous spectrum from the optical adjustment layer 15 side in the wavelength region of 300 nm to 780 nm at an incident angle of 0 ° ^. b ^* color system of the color coordinates a ^*, when asked for b ^*, a ^* is at -3.0 to 2.0, it is preferable b ^* is -2.0 to 8.0 . If a ^* and b ^* are within the above ranges, the yellow index can be made 15 or less. Measurement of a ^* and b ^* can be performed using a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation). Examples of the light source include a tungsten halogen (WI) lamp alone or a combination of a deuterium (D2) lamp and a tungsten halogen (WI) lamp. In this specification, “light with an incident angle of 0 °” means light in the normal direction when the normal direction of the first surface of the optical film is 0 °. “L ^* a ^* b ^* color system”, “a ^* ”, and “b ^* ” are based on JIS Z8729: 2004.

The spectral transmittance at a wavelength of 380 nm of the optical film 10 is preferably 8% or less. When the spectral transmittance of the optical film exceeds 8%, when the optical film is used for a mobile terminal, the polarizer may be exposed to ultraviolet rays and may be easily deteriorated. The transmittance can be measured using a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation). The measurement conditions of the spectral transmittance are the same as the measurement conditions of the spectral transmittance at the wavelength of 300 nm to 780 nm. The said transmittance | permeability is measured 3 times with respect to the optical film cut out to the magnitude | size of 50 mm x 100 mm, and is taken as the arithmetic average value of the value obtained by measuring 3 times. The upper limit of the transmittance of the optical film 10 is more preferably 5%. In addition, the said transmittance | permeability of the optical film 10 can be achieved by adjusting the addition amount of the ultraviolet absorber mentioned later.

The total light transmittance of the optical film 10 is preferably 85% or more. If the total light transmittance of the optical film 10 is 85% or more, sufficient image visibility can be obtained when the optical film 10 is used in a mobile terminal. The total light transmittance of the optical film 10 is more preferably 87% or more, and most preferably 90% or more.

The total light transmittance can be measured by a method based on JIS K7361-1: 1997 using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory Co., Ltd.). The total light transmittance is measured three times for one optical film after cutting the optical film into a size of 50 mm × 100 mm, placing it without curls or wrinkles, and without fingerprints or dust. It is set as the arithmetic average value of the value obtained by measuring 3 times. In this specification, “measuring three times” means not measuring the same place three times, but measuring three different places. In the optical film 10, the visually observed surface 10A is flat, the layers to be laminated such as the functional layer 12 are also flat, and the variation in film thickness is within ± 10%. Therefore, it is considered that the average value of the total light transmittance of the entire optical film in the whole plane can be obtained by measuring the total light transmittance at three different positions of the cut out optical film. The variation in the total light transmittance is within ± 10% regardless of whether the object to be measured is as long as 1 m × 3000 m or the size of a 5-inch smartphone. In the case where the optical film cannot be cut out to the above size, for example, HM-150 has an inlet opening for measurement of 20 mm.phi., So that the sample size needs to be 21 mm or more in diameter. For this reason, you may cut out an optical film suitably in the magnitude | size of 22 mm x 22 mm or more. When the size of the optical film is small, the measurement points are set to three positions by gradually shifting within a range where the light source spot is not removed or changing the angle.

The haze value (total haze value) of the optical film 10 is preferably 2.5% or less. If the said haze value of an optical film is 2.5% or less, when an optical film is used for a mobile terminal, whitening of an image display surface can be suppressed. The haze value is more preferably 1.5% or less, and more preferably 1.0% or less.

The haze value can be measured by a method based on JIS K7136: 2000 using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory Co., Ltd.). The haze value is measured three times for one optical film after cutting the optical film into a size of 50 mm × 100 mm, placing it without curls or wrinkles, and without fingerprints or dust. The arithmetic average value of the values obtained by repeated measurements. In the optical film 10, the visually observed surface 10A is flat, the layers to be laminated such as the functional layer 12 are also flat, and the variation in film thickness is within ± 10%. Therefore, it is thought that the average value of the haze value of the approximate whole in-plane of an optical film is obtained by measuring a haze value in three different places of the cut-out optical film. The variation in the haze value is within ± 10% regardless of whether the measurement target is as long as 1 m × 3000 m or the size of a 5-inch smartphone. In the case where the optical film cannot be cut out to the above size, for example, HM-150 has an inlet opening for measurement of 20 mm.phi., So that the sample size needs to be 21 mm or more in diameter. For this reason, you may cut out an optical film suitably in the magnitude | size of 22 mm x 22 mm or more. When the size of the optical film is small, the measurement points are set to three positions by gradually shifting within a range where the light source spot is not removed or changing the angle.

When another film such as a polarizing plate is provided on the first surface side of the optical film 10 via an adhesive layer or an adhesive layer, the other film is peeled off together with the adhesive layer or the adhesive layer, and then folded. A test, a folding stationary test, a yellow index measurement, a total light transmittance measurement, and a haze value measurement shall be performed. Other films can be peeled as follows, for example. First, the laminate with other films attached to the optical film through an adhesive layer or adhesive layer is heated with a dryer, and the blade edge of the cutter is inserted into the part that appears to be the interface between the optical film and the other film. I will do it. By repeating such heating and peeling, the pressure-sensitive adhesive layer, the adhesive layer, and other films can be peeled off. In addition, even if there exists such a peeling process, there is no big influence on these tests and these measurements. The haze value is measured after the adhesive layer or the adhesive layer is peeled off, and the dirt on the adhesive layer or the adhesive layer is further wiped off with alcohol.

In recent years, a light emitting diode (Light Emitting Diode) has been actively adopted as a light source for a backlight of an image display device such as a personal computer or a tablet terminal. The light emitting diode strongly emits light called blue light. . This blue light is a light with a wavelength of 380 nm to 495 nm and has a property close to that of ultraviolet rays. Since it has strong energy, it reaches the retina without being absorbed by the cornea or the crystalline lens. It is said to cause serious fatigue and adverse effects on sleep. For this reason, when an optical film is applied to an image display device, it is preferable that the optical film has excellent blue light shielding properties without affecting the color of the display screen. Therefore, from the viewpoint of shielding blue light, the optical film 10 has a spectral transmittance of less than 1% at a wavelength of 380 nm, a spectral transmittance of less than 10% at a wavelength of 410 nm, and a spectral transmittance of 70 at a wavelength of 440 nm. % Or more is preferable. If the spectral transmittance at a wavelength of 380 nm is 1% or more or the spectral transmittance at a wavelength of 410 nm is 10% or more, the problem due to blue light may not be solved, and the spectral transmittance at a wavelength of 440 nm is 70%. This is because if it is less than the range, the color of the display screen of the image display device using the optical film may be affected. The optical film 10 sufficiently absorbs light in the wavelength region of 410 nm or less of the wavelength of blue light, while sufficiently transmitting light of wavelength 440 nm or more without affecting the color of the display screen. Blue light shielding properties can be improved. Moreover, when the optical film 10 having excellent blue light shielding properties is applied to an organic light emitting diode (OLED) display device as an image display device, it is also effective in suppressing deterioration of the organic light emitting diode element.

The light transmittance of the optical film 10 is almost 0% up to a wavelength of 380 nm, it is preferable that the light transmission gradually increases from a wavelength of 410 nm, and the light transmission rapidly increases in the vicinity of a wavelength of 440 nm. Specifically, for example, it is preferable that the spectral transmittance changes between a wavelength of 410 nm and 440 nm so as to draw a sigmoid curve. The spectral transmittance at a wavelength of 380 nm is more preferably less than 0.5%, still more preferably less than 0.2%, and the spectral transmittance at a wavelength of 410 nm is more preferably less than 7%, more preferably less than 5%. The spectral transmittance at a wavelength of 440 nm is more preferably 75% or more, and still more preferably 80% or more. The optical film 10 preferably has a spectral transmittance of less than 50% at a wavelength of 420 nm. By satisfying such a spectral transmittance relationship, the optical film 10 has a sharply improved transmittance around a wavelength of 440 nm, and has an excellent blue light shielding property without affecting the color of the display screen. Can be obtained.

The spectral transmittance at a wavelength of 380 nm in the optical film 10 is more preferably less than 0.1%, the spectral transmittance at a wavelength of 410 nm is more preferably less than 7%, and the spectral transmittance at a wavelength of 440 nm is 80% or more. It is more preferable that

In the optical film 10, it is preferable that the slope of the transmission spectrum in the wavelength range of 415 to 435 nm obtained by using the least square method is larger than 2.0. When the inclination is 2.0 or less, light cannot be sufficiently cut in the blue light wavelength region, for example, the wavelength region of 415 to 435 nm, and the blue light cut effect may be weakened. Further, there is a possibility that the light wavelength region of blue light (wavelength 415 to 435 nm) is cut too much. In that case, the backlight of the image display device or the light emission wavelength region (for example, light emission from the wavelength 430 nm of the OLED) There is a possibility that a problem such as a problem that the color becomes worse due to interference with the color is increased. For example, a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation) capable of measuring in increments of 0.5 nm is used for the inclination, and transmittance data for at least 5 points between 1 nm and 1 nm is obtained. It can be calculated by measuring between 415 and 435 nm.

The optical film 10 preferably has a blue light shielding rate of 40% or more. If the blue light shielding rate is less than 40%, the above-described problems caused by blue light may not be sufficiently solved. The blue light shielding rate is, for example, a value calculated according to JIS T7333: 2005. Such a blue light shielding rate can be achieved, for example, when the functional layer 12 contains a sesamol type benzotriazole-based monomer described later.

The use of the optical film 10 is not particularly limited. Examples of the use of the optical film 10 include image display devices such as smartphones, tablet terminals, personal computers (PCs), wearable terminals, digital signage, televisions, and car navigation systems. Can be mentioned. The optical film 10 is also suitable for in-vehicle use. The form of each image display device is also preferable for applications that require flexibility such as foldable and rollable.

The optical film 10 may be cut into a desired size, but may be in a roll shape. When the optical film 10 is cut into a desired size, the size of the optical film is not particularly limited, and is appropriately determined according to the size of the display surface of the image display device. Specifically, the size of the optical film 10 may be, for example, not less than 2.8 inches and not more than 500 inches. In the present specification, “inch” means the length of a diagonal line when the optical film has a quadrangular shape, means the diameter when the optical film is circular, and has the short diameter when it is elliptical. And the average value of the sum of the major axes. Here, when the optical film has a quadrangular shape, the aspect ratio of the optical film when obtaining the inch is not particularly limited as long as there is no problem as a display screen of the image display device. For example, length: width = 1: 1, 4: 3, 16:10, 16: 9, 2: 1, and the like. However, the aspect ratio is not particularly limited in in-vehicle applications and digital signage that are rich in design. Moreover, when the magnitude | size of the optical film 10 is large, after cutting out to A5 size (148 mm x 210 mm) from arbitrary positions, it shall cut out to the magnitude | size of each measurement item.

The location of the optical film 10 in the image display device may be inside the image display device, but is preferably near the surface of the image display device. When used near the surface of the image display device, the optical film 10 functions as a cover film used instead of the cover glass.

<< Resin substrate >>
The resin base material 11 has light transmittance. The “light transmittance” in the present specification means a property of transmitting light. For example, the total light transmittance is 50% or more, preferably 70% or more, more preferably 80% or more, and particularly preferably 90%. Including that. The light transmissive property does not necessarily need to be transparent, and may be translucent.

The resin substrate 11 is a group composed of one or more resins selected from the group consisting of polyimide resins, polyamideimide resins, polyamide resins, and polyester resins (for example, polyethylene terephthalate resins and polyethylene naphthalate resins). It is a material.

Among these resins, not only is cracking or breaking difficult to occur in the continuous folding test, but also has excellent hardness and transparency, and excellent heat resistance. From the viewpoint of imparting transparency, a polyimide resin, a polyamide resin, or a mixture thereof is preferable.

The polyimide resin is obtained by reacting a tetracarboxylic acid component and a diamine component. Although it does not specifically limit as polyimide-type resin, For example, it selects from the group which consists of a structure represented by following General formula (1) and following General formula (3) from the point which has the outstanding light transmittance and the outstanding rigidity. It is preferable to have at least one kind of structure.

In the general formula (1), R ¹ is a tetravalent group which is a tetracarboxylic acid residue, R ² is a trans-cyclohexanediamine residue, a trans-1,4-bismethylenecyclohexanediamine residue, 4,4 It represents at least one divalent group selected from the group consisting of a '-diaminodiphenylsulfone residue, a 3,4'-diaminodiphenylsulfone residue, and a divalent group represented by the following general formula (2). . n represents the number of repeating units and is 1 or more. In this specification, the “tetracarboxylic acid residue” means a residue obtained by removing four carboxyl groups from tetracarboxylic acid, and a residue obtained by removing an acid dianhydride structure from tetracarboxylic dianhydride; Represents the same structure. The “diamine residue” refers to a residue obtained by removing two amino groups from a diamine.

　上記一般式（２）において、Ｒ^３およびＲ^４はそれぞれ独立して、水素原子、アルキル基、またはパーフルオロアルキル基を表す。

In the general formula (2), R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.

In the general formula (3), R ⁵ represents a cyclohexanetetracarboxylic acid residue, a cyclopentanetetracarboxylic acid residue, a dicyclohexane-3,4,3 ′, 4′-tetracarboxylic acid residue, and 4,4 ′. At least one tetravalent group selected from the group consisting of-(hexafluoroisopropylidene) diphthalic acid residues, R ⁶ represents a divalent group that is a diamine residue. n ′ represents the number of repeating units and is 1 or more.

In the general formula (1), R ¹ is a tetracarboxylic acid residue, and can be a residue obtained by removing the acid dianhydride structure from the tetracarboxylic dianhydride as exemplified above. R ¹ in the general formula (1) is, among others, 4,4 ′-(hexafluoroisopropylidene) diphthalic acid residue, 3,3 ′, from the viewpoint of improving light transmittance and improving rigidity. 4,4'-biphenyltetracarboxylic acid residue, pyromellitic acid residue, 2,3 ', 3,4'-biphenyltetracarboxylic acid residue, 3,3', 4,4'-benzophenonetetracarboxylic acid residue Selected from the group consisting of a group, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic acid residue, 4,4′-oxydiphthalic acid residue, cyclohexanetetracarboxylic acid residue, and cyclopentanetetracarboxylic acid residue At least one selected from the group consisting of 4,4 '-(hexafluoroisopropylidene) diphthalic acid residue, 4,4'-oxydiphthalic acid residue, and 3,3', 4,4'- The It is preferable to include at least one selected from the group consisting of phenylsulfonetetracarboxylic acid residues.

In R ¹ , these suitable residues are preferably contained in a total amount of 50 mol% or more, more preferably 70 mol% or more, and still more preferably 90 mol% or more.

R ¹ is selected from the group consisting of 3,3 ′, 4,4′-biphenyltetracarboxylic acid residue, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid residue, and pyromellitic acid residue. A group of tetracarboxylic acid residues (group A) suitable for improving rigidity such as at least one selected from 4,4 ′-(hexafluoroisopropylidene) diphthalic acid residues, 2,3 ′ , 3,4′-biphenyltetracarboxylic acid residue, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic acid residue, 4,4′-oxydiphthalic acid residue, cyclohexanetetracarboxylic acid residue, and cyclohexane It is also preferable to use a mixture of a tetracarboxylic acid residue group (group B) suitable for improving transparency, such as at least one selected from the group consisting of pentanetetracarboxylic acid residues. There.

In this case, the content ratio of the tetracarboxylic acid residue group (group A) suitable for improving the rigidity and the tetracarboxylic acid residue group (group B) suitable for improving transparency is, 0.05 mol of the tetracarboxylic acid residue group (group A) suitable for improving the rigidity is 1 mol per 1 mol of the tetracarboxylic acid residue group (group B) suitable for improving the transparency. It is preferably 9 mol or less, more preferably 0.1 mol or more and 5 mol or less, still more preferably 0.3 mol or more and 4 mol or less.

R ² in the general formula (1) is, among others, 4,4′-diaminodiphenylsulfone residue, 3,4′-diaminodiphenylsulfone residue from the viewpoint of improving light transmittance and improving rigidity. And at least one divalent group selected from the group consisting of a divalent group represented by the general formula (2), and is preferably a 4,4′-diaminodiphenylsulfone residue, 3 , 4′-diaminodiphenylsulfone residue, and at least one divalent group selected from the group consisting of a divalent group represented by the general formula (2) wherein R ³ and R ⁴ are perfluoroalkyl groups The group is preferably.

R ⁵ in the general formula (3) is, among others, 4,4 ′-(hexafluoroisopropylidene) diphthalic acid residue, 3,3 ′, from the viewpoint of improving light transmittance and improving rigidity. It preferably contains a 4,4′-diphenylsulfone tetracarboxylic acid residue and an oxydiphthalic acid residue.

In R ⁵ , these suitable residues are preferably contained in an amount of 50 mol% or more, more preferably 70 mol% or more, and even more preferably 90 mol% or more.

R ⁶ in the general formula (3) is a diamine residue, and can be a residue obtained by removing two amino groups from the diamine as exemplified above. R6 in the general formula (3) is, among others, a 2,2′-bis (trifluoromethyl) benzidine residue, bis [4- (4- Aminophenoxy) phenyl] sulfone residue, 4,4′-diaminodiphenylsulfone residue, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane residue, bis [4- (3-amino Phenoxy) phenyl] sulfone residue, 4,4′-diamino-2,2′-bis (trifluoromethyl) diphenyl ether residue, 1,4-bis [4-amino-2- (trifluoromethyl) phenoxy] benzene Residue, 2,2-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane residue, 4,4′-diamino-2- (tri Fluoromethyl) diphenyl ether residue, 4,4′-diaminobenzanilide residue, N, N′-bis (4-aminophenyl) terephthalamide residue, and 9,9-bis (4-aminophenyl) fluorene residue It preferably contains at least one divalent group selected from the group consisting of 2,2′-bis (trifluoromethyl) benzidine residue, bis [4- (4-aminophenoxy) phenyl] sulfone residue. The group preferably contains at least one divalent group selected from the group consisting of a group and a 4,4′-diaminodiphenylsulfone residue.

In R ⁶ , these suitable residues are preferably contained in a total amount of 50 mol% or more, more preferably 70 mol% or more, and still more preferably 90 mol% or more.

R ⁶ is a bis [4- (4-aminophenoxy) phenyl] sulfone residue, 4,4′-diaminobenzanilide residue, N, N′-bis (4-aminophenyl) terephthalamide residue, A group of diamine residues suitable for improving the rigidity such as at least one selected from the group consisting of a paraphenylenediamine residue, a metaphenylenediamine residue, and a 4,4′-diaminodiphenylmethane residue (group) C), 2,2′-bis (trifluoromethyl) benzidine residue, 4,4′-diaminodiphenylsulfone residue, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane residue Group, bis [4- (3-aminophenoxy) phenyl] sulfone residue, 4,4′-diamino-2,2′-bis (trifluoromethyl) diphenyl Ether residue, 1,4-bis [4-amino-2- (trifluoromethyl) phenoxy] benzene residue, 2,2-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexa As at least one selected from the group consisting of fluoropropane residues, 4,4′-diamino-2- (trifluoromethyl) diphenyl ether residues, and 9,9-bis (4-aminophenyl) fluorene residues It is also preferable to use a mixture with a diamine residue group (group D) suitable for improving the transparency.

In this case, the content ratio of the diamine residue group (group C) suitable for improving the rigidity and the diamine residue group (group D) suitable for improving transparency improves transparency. The diamine residue group (group C) suitable for improving the rigidity is 0.05 mol or more and 9 mol or less with respect to 1 mol of the diamine residue group (group D) suitable for the treatment. More preferably, it is preferably 0.1 mol or more and 5 mol or less, and more preferably 0.3 mol or more and 4 mol or less.

In the structures represented by the general formula (1) and the general formula (3), n and n 'each independently represent the number of repeating units and are 1 or more. The number of repeating units n in the polyimide is not particularly limited as long as it is appropriately selected depending on the structure so as to exhibit a preferable glass transition temperature described later. The average number of repeating units is usually 10 to 2000, and more preferably 15 to 1000.

Moreover, the polyimide resin may contain a polyamide structure in a part thereof. Examples of the polyamide structure that may be included include a polyamideimide structure containing a tricarboxylic acid residue such as trimellitic anhydride and a polyamide structure containing a dicarboxylic acid residue such as terephthalic acid.

The polyimide resin preferably has a glass transition temperature of 250 ° C. or higher, and more preferably 270 ° C. or higher, from the viewpoint of heat resistance. On the other hand, the glass transition temperature is preferably 400 ° C. or lower, and more preferably 380 ° C. or lower, from the viewpoint of easy stretching and reduction of the baking temperature.

Examples of the polyimide resin include compounds having a structure represented by the following formula. In the following formula, n is a repeating unit and represents an integer of 2 or more.

Among the polyimide resins, a polyimide resin or a polyamide resin having a structure in which charge transfer within a molecule or between molecules is unlikely to occur is preferable, and specifically, the above formula (4). Fluorinated polyimide resins such as (11) to (11), and polyimide resins having an alicyclic structure such as the above formulas (13) to (16).

In addition, since the fluorinated polyimide resins of the above formulas (4) to (11) have a fluorinated structure, they have high heat resistance, and heat during the production of a polyimide film made of the polyimide resin. Since it is not colored by, it has the outstanding transparency.

Polyamide resin is a concept including not only aliphatic polyamide but also aromatic polyamide (aramid). Examples of the polyamide-based resin include compounds having a skeleton represented by the following formulas (21) to (23). In the following formula, n is a repeating unit and represents an integer of 2 or more.

Commercially available materials may be used as the base material made of the polyimide resin or polyamide resin represented by the above formulas (4) to (20) and (23). Examples of the commercially available base material made of the polyimide-based resin include Neoprim manufactured by Mitsubishi Gas Chemical Co., Ltd., and examples of the commercially available base material made of the polyamide-based resin include Mikutron manufactured by Toray Industries, Inc. Is mentioned.

The polyimide resin or polyamide resin represented by the above formulas (4) to (20) and (23) may be synthesized by a known method. For example, a method for synthesizing a polyimide resin represented by the above formula (4) is described in Japanese Patent Application Laid-Open No. 2009-132091, and specifically, 4,4′-hexa represented by the following formula (24): It can be obtained by reacting fluoropropylidenebisphthalic dianhydride (FPA) with 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl (TFDB).

The weight average molecular weight of the polyimide resin or polyamide resin is preferably in the range of 3000 to 500,000, more preferably in the range of 5000 to 300,000, and in the range of 10,000 to 200,000. More preferably. When the weight average molecular weight is less than 3000, sufficient strength may not be obtained. When the weight average molecular weight exceeds 500,000, the viscosity increases and the solubility decreases, so that a substrate having a smooth surface and a uniform film thickness can be obtained. It may not be obtained. In the present specification, the “weight average molecular weight” is a polystyrene conversion value measured by gel permeation chromatography (GPC).

The resin substrate 11 is a fluorinated polyimide resin represented by the above formulas (4) to (11) or a polyamide system having a halogen group such as the above formula (23) from the viewpoint of improving the hardness. It is preferable to use a substrate made of a resin. Especially, it is more preferable to use the base material which consists of a polyimide-type resin represented by the said Formula (4) from a viewpoint which can improve hardness more.

Examples of the polyester-based resin include resins having at least one of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as constituent components.

The refractive index of the resin base material 11 is higher than the refractive index of the functional layer 12. The refractive index of the resin base material 11 can be measured by, for example, the Becke method. When the refractive index of the resin base material 11 is measured using the Becke method, ten pieces of the resin base material 11 are cut out, and the refractive index is determined by the Becke method using the refractive index standard solution in the cut out ten pieces. Each of them is measured, and the average value of ten measured refractive indexes of the fragments is taken as the refractive index of the resin base material 11. The refractive index of the resin base material 11 may be 1.500 or more and 1.800 or less. The refractive index of the resin substrate 11 is obtained by measuring the average reflectance at a wavelength of 380 to 780 nm using a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation), and obtaining the average reflectance. May be obtained by the following equation (1). The average reflectance (R) of the resin substrate 11 is such that a black vinyl tape having a width larger than the measurement spot area (for example, product name “Yamato Vinyl Tape NO200-38-21”, manufactured by Yamato Co., Ltd.) is used to prevent back surface reflection. , 38 mm width) is attached to the back surface of the resin base material 11 and then measured.
^{_{R 1 = (1-n 1}} ) 2 / (1 + n 1) 2 ... (1)
In the above formula (1), R ₁ represents the average reflectance (%) of the resin substrate at a wavelength of 380 to 780 nm, and n ₁ represents the refractive index of the resin substrate.

The thickness of the resin base material 11 is preferably 10 μm or more and 100 μm or less. If the thickness of the resin substrate is 10 μm or more, curling of the optical film can be suppressed and sufficient hardness can be obtained, and even when the optical film is manufactured by Roll to Roll, wrinkles are generated. There is no risk of deterioration of the appearance. On the other hand, when the thickness of the resin base material is 100 μm or less, the optical film has good folding performance, can satisfy the requirements of the continuous folding test, and is preferable in terms of weight reduction of the optical film. The thickness of the resin base material 11 is obtained by taking a cross-section of the resin base material 11 using a scanning electron microscope (SEM), measuring the thickness of the resin base material 11 at 10 points in the cross-sectional image, The arithmetic average value of the film thickness. The lower limit of the resin base material 11 is more preferably 25 μm or more, and the upper limit of the resin base material 11 is more preferably 80 μm or less.

<< Functional layer >>
The functional layer 12 is a layer that functions as a hard coat layer. The functional layer 12 may have a function other than the hard coat property in addition to the hard coat property. The functional layer 12 has antistatic properties in addition to hard coat properties. That is, the functional layer 12 is an antistatic hard coat layer. The “hard coat layer” in this specification means a layer having a Martens hardness of 375 MPa or more at the center of the cross section of the hard coat layer. In this specification, the “Martens hardness” is the hardness when the indenter is pushed in by 500 nm by the hardness measurement by the nanoindentation method. The measurement of the Martens hardness by the nanoindentation method is performed using “TI950 TriboIndenter” manufactured by HYSITRON Co., Ltd. for the measurement sample. Specifically, first, a block in which an optical film cut out to 1 mm × 10 mm is embedded with an embedding resin is prepared, and a uniform thickness without a hole or the like is obtained from this block by a general section manufacturing method. Cut the following sections. “Ultramicrotome EM UC7” (Leica Microsystems) can be used for preparing the slice. The remaining block from which a uniform section without holes or the like is cut out is taken as a measurement sample. Next, in the cross section obtained by cutting out the section in such a measurement sample, a Berkovich indenter (triangular pyramid) as the above indenter is pushed into the center of the cross section of the functional layer by 500 nm under the following measurement conditions and held constant. After the residual stress is relaxed, the unloading is performed, and the maximum load after the relaxation is measured. Using the maximum load P _max (μN) and the indentation area A (nm ² ) having a depth of 500 nm, P _max / From A, the Martens hardness is calculated. The Martens hardness is the arithmetic average value of the values obtained by measuring 10 locations.
(Measurement condition)
・ Loading speed: 10 nm / second ・ Retention time: 5 seconds ・ Load unloading speed: 10 nm / second ・ Measurement temperature: 25 ° C.

The functional layer 12 preferably has a Martens hardness at the center of the cross section of the functional layer 12 of 500 MPa to 2000 MPa. If the Martens hardness of the functional layer 12 is 500 MPa or more, sufficient hardness as a hard coat layer can be obtained, and if it is 2000 MPa or less, good optical film folding performance can be obtained. The lower limit of the Martens hardness at the center of the cross section of the functional layer 12 is preferably 600 MPa or more, and the upper limit is preferably 1500 MPa or less.

The refractive index of the functional layer 12 may be 1.400 or more and 1.800 or less. The refractive index of the functional layer 12 is determined by measuring an average reflectance at a wavelength of 380 to 780 nm using a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation), and using the obtained average reflectance. The following equation (2) can be obtained. The average reflectance of the functional layer 12 is 1 to 10 μm thick when the composition for a functional layer is applied on a 50 μm thick polyethylene terephthalate (PET) base material that has not been subjected to an easy adhesion treatment and cured. A black vinyl tape having a width larger than the measurement spot area (for example, the product name “Yamato”) is formed on the surface (back surface) opposite to the functional layer side surface of the PET substrate. It is assumed that measurement is performed after affixing a vinyl tape NO200-38-21 "(manufactured by Yamato, 38 mm width).
R ₂ = (1-n ₂ ) ² / (1 + n ₂ ) ² (2)
In the above formula (2), R ₂ represents the average reflectance (%) of the functional layer at a wavelength of 380 to 780 nm, and n ₂ represents the refractive index of the functional layer.

The film thickness of the functional layer 12 is preferably 2 μm or more and 40 μm or less. If the thickness of the functional layer 12 is 2 μm or more, sufficient hardness as a hard coat layer can be obtained, and if it is 40 μm or less, deterioration of workability can be suppressed. In the present specification, the “film thickness of the functional layer” means a film thickness (total thickness) obtained by adding up the film thicknesses of the respective functional layers when the functional layer has a multilayer structure. The upper limit of the functional layer 12 is more preferably 30 μm or less, and further preferably 20 μm or less.

The thickness of the functional layer 12 is obtained by photographing a cross section of the functional layer 12 using a scanning transmission electron microscope (STEM) or a transmission electron microscope (TEM), and determining the thickness of the functional layer 12 in the image of the cross section. Twenty points are measured, and the arithmetic average value of the film thicknesses at the 20 points is taken. A specific method for taking a cross-sectional photograph is described below. First, a block in which an optical film cut out to a size of 1 mm × 10 mm is embedded with an embedding resin is produced, and a uniform thickness without a hole or the like is obtained from this block by a general section preparation method. Cut out sections. For the preparation of the section, “Ultra Microtome EM UC7” (Leica Microsystems Co., Ltd.) or the like can be used. A uniform section having no holes or the like is used as a measurement sample. Thereafter, a cross-sectional photograph of the measurement sample is taken using a scanning transmission electron microscope (STEM) (product name “S-4800”, manufactured by Hitachi High-Technologies Corporation). When taking a cross-sectional photograph using the S-4800, the cross-section is observed with the detector set to “TE”, the acceleration voltage set to “30 kV”, and the emission current set to “10 μA”. The magnification is appropriately adjusted from 5000 to 200,000 times while adjusting the focus and observing whether each layer can be distinguished. A preferred magnification is 10,000 to 100,000 times, a more preferred magnification is 10,000 to 50,000 times, and a most preferred magnification is 25,000 to 50,000 times. When taking a cross-sectional photograph using the above S-4800, the aperture is set to “beam monitor aperture 3”, the objective lens aperture is set to “3”, and the W.S. D. May be set to “8 mm”. When measuring the film thickness of the hard coat layer, it is important that the interface contrast between the functional layer and another layer (for example, a resin substrate) can be observed as clearly as possible when the cross section is observed. If it is difficult to see this interface due to insufficient contrast, a dyeing process such as osmium tetroxide, ruthenium tetroxide, or phosphotungstic acid can be used to easily see the interface between the organic layers. Also, the interface contrast may be difficult to understand when the magnification is high. In that case, the low magnification is also observed at the same time. For example, observe at two magnifications, high and low, such as 25,000 times and 50,000 times, and 50,000 times and 100,000 times, obtain the arithmetic average value described above at both magnifications, and further calculate the average value of the functional layer The value is the film thickness.

Since the functional layer 12 is an antistatic hard coat layer, it includes a binder resin and an antistatic agent present in the binder resin. In addition, when the functional layer 12 is a hard coat layer having no antistatic property, the antistatic agent may not be included. Moreover, the functional layer 12 is, for example, particles such as inorganic particles and organic particles, an ultraviolet absorber, an adhesion improver, and a leveling agent as long as the effects of the present invention are not impaired as required, in addition to a binder resin. Further, additives such as a thixotropic agent, a coupling agent, a plasticizer, an antifoaming agent, a filler, a colorant, and a filler may be included.

<Binder resin>
The binder resin contains a polymer (cured product) of a polymerizable compound (curable compound). The polymerizable compound has at least one polymerizable functional group in the molecule. Examples of the polymerizable functional group include ethylenically unsaturated groups such as a (meth) acryloyl group, a vinyl group, and an allyl group. The “(meth) acryloyl group” means to include both “acryloyl group” and “methacryloyl group”.

As the polymerizable compound, polyfunctional (meth) acrylate is preferable. Examples of the polyfunctional (meth) acrylate include trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, pentaerythritol tri ( (Meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate , Ditrimethylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate , Tetrapentaerythritol deca (meth) acrylate, isocyanuric acid tri (meth) acrylate, isocyanuric acid di (meth) acrylate, polyester tri (meth) acrylate, polyester di (meth) acrylate, bisphenol di (meth) acrylate, di Glycerin tetra (meth) acrylate, adamantyl di (meth) acrylate, isobornyl di (meth) acrylate, dicyclopentane di (meth) acrylate, tricyclodecane di (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and these Examples thereof include those modified with PO, EO, caprolactone and the like.

Among them, those having 3 to 6 functional groups are preferable because they can satisfy the above-mentioned Martens hardness, and examples thereof include pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), and pentaerythritol tetraacrylate (PETTA). Dipentaerythritol pentaacrylate (DPPA), trimethylolpropane tri (meth) acrylate, tripentaerythritol octa (meth) acrylate, tetrapentaerythritol deca (meth) acrylate, and the like are preferable. In the present specification, “(meth) acrylate” means “acrylate” and “methacrylate”.

In addition, a monofunctional (meth) acrylate monomer may be further included for adjusting the hardness, the viscosity of the composition, improving the adhesion, and the like. Examples of the monofunctional (meth) acrylate monomer include hydroxyethyl acrylate (HEA), glycidyl methacrylate, methoxypolyethylene glycol (meth) acrylate, isostearyl (meth) acrylate, 2-acryloyloxyethyl succinate, acryloylmorpholine, N -Acryloyloxyethyl hexahydrophthalimide, cyclohexyl acrylate, tetrahydrofuryl acrylate, isobornyl acrylate, phenoxyethyl acrylate, adamantyl acrylate and the like.

The weight average molecular weight of the monomer is preferably less than 1000, more preferably 200 or more and 800 or less, from the viewpoint of improving the hardness of the functional layer. The weight average molecular weight of the polymerizable oligomer is preferably 1000 or more and 20,000 or less, more preferably 1000 or more and 10,000 or less, and further preferably 2000 or more and 7000 or less.

<Antistatic agent>
The antistatic agent used for the functional layer 12 is not particularly limited as long as it has good compatibility with the binder resin. As the antistatic agent, there are an ion conduction type antistatic agent and an electron conduction type antistatic agent, and from the viewpoint of compatibility with the binder resin, the ion conduction type antistatic agent is preferable.

Examples of the ion conduction type antistatic agent include cationic antistatic agents such as quaternary ammonium salts and pyridium salts, and alkali metal salts such as sulfonic acid, phosphoric acid and carboxylic acid (for example, lithium salts, sodium salts, Anionic antistatic agents such as potassium salts), amphoteric antistatic agents such as amino acids and amino acid sulfate esters, and nonionic antistatic agents such as amino alcohols, glycerins, and polyethylene glycols. Among these, quaternary ammonium salts and lithium salts are preferable because they exhibit excellent compatibility with the binder resin.

Examples of the electron conductive antistatic agent include conductive polymers such as polyacetylene-based and polythiophene-based conductive polymers, metal particles, and metal oxide particles. Among these, antistatic agents, metal particles, and metal oxide particles in which a dopant is combined with a conductive polymer such as polyacetylene and polythiophene are preferable. Moreover, electroconductive particle can also be contained in the said electroconductive polymer.

Specific examples of the antistatic agent composed of the conductive polymer include polyacetylene, polyaniline, polythiophene, polypyrrole, polyphenylene sulfide, poly (1,6-heptadiyne), polybiphenylene (polyparaphenylene), polyparafinylene sulfide, Examples thereof include conductive polymers such as polyphenylacetylene, poly (2,5-thienylene), and derivatives thereof. Preferably, a polythiophene-based conductive organic polymer (for example, 3,4-ethylenedioxythiophene (for example, PEDOT)).

By using the antistatic agent comprising the conductive organic polymer, the antistatic property can be maintained over a long period of time with little humidity dependency, and also has high transparency, low haze, and high hard coat properties, particularly Pencil hardness and scratch resistance against steel wool can be remarkably improved.

The metal constituting the metal particles is not particularly limited, and examples thereof include Au, Ag, Cu, Al, Fe, Ni, Pd, and Pt alone or an alloy of these metals. Further, no particular limitation is imposed on the metal oxide constituting the metal oxide particles, for example, tin oxide _(SnO 2), antimony oxide _{(Sb 2 O} 5), antimony doped tin oxide (ATO), indium tin oxide ( ITO), aluminum-doped zinc oxide (AZO), fluorine-doped tin oxide (FTO), zinc oxide (ZnO) and the like.

Although it does not specifically limit as content of an antistatic agent, It is preferable that it is 1 to 50 mass parts with respect to 100 mass parts of polymeric compounds of the composition for functional layers. If it is 1 part by mass or more, the above-described antistatic property can be sufficiently obtained, and if it is 50 parts by mass or less, a highly transparent film having a small haze value and good total light transmittance can be obtained. The lower limit of the content of the antistatic agent is more preferably 10 parts by mass or more, and the upper limit is more preferably 40 parts by mass or less.

The functional layer 12 may further contain an ultraviolet absorber, a spectral transmittance adjusting agent, and / or an antifouling agent.

<Ultraviolet absorber>
The optical film is particularly preferably used for a mobile terminal such as a foldable smartphone or tablet terminal. However, such a mobile terminal is often used outdoors, and therefore, the optical film is disposed closer to the display element than the optical film. There is a problem that the polarizer is easily deteriorated by being exposed to ultraviolet rays. However, since the functional layer 12 is disposed on the viewer side of the polarizer, if the functional layer 12 contains an ultraviolet absorber, deterioration due to exposure of the polarizer to ultraviolet rays can be suitably prevented. it can. In addition, the said ultraviolet absorber (UVA) may be contained in the resin base material 11 instead of the functional layer 12. FIG.

Examples of ultraviolet absorbers include triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, and benzotriazole-based ultraviolet absorbers.

Examples of the triazine ultraviolet absorber include 2- (2-hydroxy-4- [1-octyloxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine. 2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2 , 4-Bis [2-hydroxy-4-butoxyphenyl] -6- (2,4-dibutoxyphenyl) -1,3,5-triazine, 2- [4-[(2-hydroxy-3-tridecyl) Oxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, and 2- [4-[(2-hydroxy-3- ( '- ethyl) hexyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine. Examples of commercially available triazine ultraviolet absorbers include TINUVIN 460, TINUVIN 477 (both manufactured by BASF), LA-46 (manufactured by ADEKA), and the like.

Examples of the benzophenone ultraviolet absorber include 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxy. Examples thereof include benzophenone, 2-hydroxy-4-methoxybenzophenone, hydroxymethoxybenzophenone sulfonic acid and its trihydrate, hydroxymethoxybenzophenone sulfonate sodium, and the like. Examples of commercially available benzophenone ultraviolet absorbers include CHMASSORB81 / FL (manufactured by BASF).

Examples of the benzotriazole ultraviolet absorber include 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate, 2 -(2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl- 6- (tert-butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-tert-pentylphenol, 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole, 2- (2′-hydroxy-3) -Tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy- 3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3 -Tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) and 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole Etc. Examples of commercially available benzotriazole ultraviolet absorbers include KEMISORB71D, KEMISORB79 (all manufactured by Chemipro Kasei Co., Ltd.), JF-80, JAST-500 (all manufactured by Johoku Chemical Co., Ltd.), ULS-1933D (one side) And RUVA-93 (manufactured by Otsuka Chemical Co., Ltd.).

Among these, triazine ultraviolet absorbers and benzotriazole ultraviolet absorbers are preferably used as the ultraviolet absorber. It is preferable that the ultraviolet absorber has high solubility with the resin component constituting the functional layer, and it is preferable that the bleedout after the continuous folding test described above is small. The ultraviolet absorber is preferably polymerized or oligomerized. As the ultraviolet absorber, a polymer or oligomer having a benzotriazole, triazine, or benzophenone skeleton is preferable. Specifically, (meth) acrylate having a benzotriazole or benzophenone skeleton and methyl methacrylate (MMA) at an arbitrary ratio. It is preferable that it has been heat copolymerized. In addition, when an optical film is applied to an organic light emitting diode (OLED) display device, the ultraviolet absorber can also serve to protect the OLED from ultraviolet rays.

Although it does not specifically limit as content of a ultraviolet absorber, It is preferable that they are 1 mass part or more and 6 mass parts or less with respect to 100 mass parts of solid content of the composition for functional layers. If it is 1 mass part or more, the effect which makes the functional layer contain the ultraviolet absorber mentioned above can fully be acquired, and if it is 6 mass parts or less, remarkable coloring and strength reduction do not occur in the functional layer. As for the minimum of content of the said ultraviolet absorber, it is more preferable that it is 2 mass parts or more, and it is more preferable that an upper limit is 5 mass parts or less.

　式中、Ｒ^７は水素原子又はメチル基を表す。Ｒ^８は炭素数１～６の直鎖状又は枝分かれ鎖状のアルキレン基又は炭素数１～６の直鎖状または分岐鎖状のオキシアルキレン基を表す。 <Spectral transmittance adjusting agent>
The spectral transmittance adjusting agent adjusts the spectral transmittance of the optical film. For example, when the functional layer 12 contains a sesamol-type benzotriazole monomer represented by the following general formula (25), the above-described spectral transmittance can be preferably satisfied.

In the formula, R ⁷ represents a hydrogen atom or a methyl group. R ⁸ represents a linear or branched alkylene group having 1 to 6 carbon atoms or a linear or branched oxyalkylene group having 1 to 6 carbon atoms.

The sesamol type benzotriazole monomer is not particularly limited, but specific substance names include 2- [2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzo Triazol-5-yl] ethyl methacrylate, 2- [2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yl] ethyl acrylate, 3- [2- (6 -Hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yl] propyl methacrylate, 3- [2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H -Benzotriazol-5-yl] propyl acrylate, 4- [2- (6-hydroxybenzo [1,3] dioxol-5-yl -2H-benzotriazol-5-yl] butyl methacrylate, 4- [2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yl] butyl acrylate, 2- [ 2- (6-Hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yloxy] ethyl methacrylate, 2- [2- (6-hydroxybenzo [1,3] dioxol-5- Yl) -2H-benzotriazol-5-yloxy] ethyl acrylate, 2- [3- {2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yl} prop Noyloxy] ethyl methacrylate, 2- [3- {2- (6-hydroxybenzo [1,3] dioxol-5-yl -2H-benzotriazol-5-yl} propanoyloxy] ethyl acrylate, 4- [3- {2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yl } Propanoyloxy] butyl methacrylate, 4- [3- {2-(6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yl} propanoyloxy] butyl acrylate, 2 -[3- {2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yl} propanoyloxy] ethyl methacrylate, 2- [3- {2- (6 -Hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazol-5-yl} propanoyloxy] ethyl acrylate 2- (methacryloyloxy) ethyl 2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazole-5 carboxylate, 2- (acryloyloxy) ethyl 2- (6- Hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazole-5-carboxylate, 4- (methacryloyloxy) butyl 2- (6-hydroxybenzo [1,3] dioxol-5-yl)- 2H-benzotriazole-5-carboxylate, 4- (acryloyloxy) butyl 2- (6-hydroxybenzo [1,3] dioxol-5-yl) -2H-benzotriazole-5-carboxylate, etc. it can. Further, these sesamol type benzotriazole monomers may be used alone or in combination of two or more.

<Anti-fouling agent>
The antifouling agent is not particularly limited, and examples thereof include silicone antifouling agents, fluorine antifouling agents, silicone type and fluorine antifouling agents, which may be used alone or in combination. May be. The antifouling agent may be an acrylic antifouling agent.

The content of the antifouling agent is preferably 0.01 to 3.0 parts by mass with respect to 100 parts by mass of the polymerizable compound described above. If it is 0.01 part by mass or more, sufficient antifouling performance can be imparted to the functional layer, and if it is 3.0 parts by mass or less, the hardness of the functional layer does not decrease.

The antifouling agent preferably has a weight average molecular weight of 5000 or less, and is a compound having preferably 1 or more, more preferably 2 or more reactive functional groups in order to improve the durability of the antifouling performance. Among them, excellent scratch resistance can be imparted by using an antifouling agent having two or more reactive functional groups.

When the antifouling agent does not have a reactive functional group, the antifouling agent is transferred to the back surface of the optical film when it is stacked, whether it is a roll or a sheet. When an attempt is made to attach or apply another layer to the back surface, the other layer may be peeled off and may be easily peeled off by performing a plurality of continuous folding tests.

Furthermore, the antifouling agent having the reactive functional group has good antifouling performance durability (durability), and in particular, the functional layer containing the above-described fluorine-based antifouling agent is difficult to have a fingerprint ( Less noticeable) and good wiping property. Furthermore, since the surface tension at the time of application of the functional layer composition can be lowered, the leveling property is good, and the appearance of the functional layer to be formed is good.

The functional layer containing a silicone-based antifouling agent has good sliding properties and good steel wool resistance. A touch sensor in which an optical film containing such a silicone antifouling agent is mounted on the functional layer has good tactile sensation because of good sliding when touched with a finger or a pen. Further, fingerprints are hardly attached to the functional layer (not easily noticeable), and the wiping property is improved. Furthermore, since the surface tension at the time of application of the functional layer composition can be lowered, the leveling property is good, and the appearance of the functional layer to be formed is good.

Examples of commercially available silicone antifouling agents include SUA1900L10 (manufactured by Shin-Nakamura Chemical Co., Ltd.), SUA1900L6 (manufactured by Shin-Nakamura Chemical Co., Ltd.), Ebecryl 1360 (manufactured by Daicel Cytec Co., Ltd.), UT3971 (manufactured by Nippon Gosei Co., Ltd.), and BYKUV3500 (BIC Chemie). BYKUV3510 (by Big Chemie), BYKUV3570 (by Big Chemie), X22-164E, X22-174BX, X22-2426, KBM503, KBM5103 (manufactured by Shin-Etsu Chemical), TEGO-RAD2250, TEGO-RAD2300, TEGO- RAD2200N, TEGO-RAD2010, TEGO-RAD2500, TEGO-RAD2600, TEGO-RAD2700 (manufactured by Evonik Japan), Megafuck RS854 (DIC) Ltd.) and the like.

Commercially available fluorine-based antifouling agents include, for example, OPTOOL DAC, OPTOOL DSX (manufactured by Daikin Industries, Ltd.), Megafuck RS71, Megafuck RS74 (manufactured by DIC), LINC152EPA, LINC151EPA, and LINC182UA (manufactured by Kyoeisha Chemical Co., Ltd.) Examples of the solvent include 650A, 601ENT, 602, and 602.

Examples of commercially available antifouling agents having fluorine-based and silicone-based reactive functional groups include, for example, MegaFac RS851, MegaFac RS852, MegaFac RS853, MegaFac RS854 (manufactured by DIC), Opstar TU2225, Opstar TU2224 ( JSR), X71-1203M (Shin-Etsu Chemical Co., Ltd.) and the like.

<< first optical adjustment layer >>
The optical adjustment layer 13 is a layer for suppressing the generation of interference fringes. The refractive index of the optical adjustment layer 13 is preferably lower than the refractive index of the resin substrate 11 and higher than the refractive index of the functional layer 12 from the viewpoint of suppressing the occurrence of interference fringes. Since the refractive index of the optical adjustment layer 13 can be measured by the same method as the refractive index of the functional layer, the description is omitted here.

The difference in refractive index between the optical adjustment layer 13 and the functional layer 12 (refractive index of the optical adjustment layer−refractive index of the functional layer) is preferably 0.005 or more and 0.100 or less. If this refractive index difference is 0.005 or more, interface reflection occurs between the optical adjustment layer 13 and the functional layer 12 but interference fringes cannot be visually recognized. Although some fringes are confirmed, it can be set to a level at which there is no problem in actual use. The lower limit of the refractive index difference is more preferably 0.007 or more, and the upper limit is more preferably 0.090 or less. The refractive index of the optical adjustment layer 13 may be 0.010 or more and 0.080 or less.

The film thickness of the optical adjustment layer 13 is preferably 30 nm or more and 200 nm or less. If the thickness of the optical adjustment layer 13 is 30 nm or more, sufficient adhesion between the functional layer 12 and the optical adjustment layer 13 can be secured, and if it is 200 nm or less, interference fringes can be further suppressed and folded. Can be improved. The film thickness of the optical adjustment layer 13 is determined by the same method as that for the functional layer 12. The lower limit of the optical adjustment layer 13 is more preferably 50 nm or more, and the upper limit is more preferably 150 nm or less.

The optical adjustment layer 13 may be composed only of a resin, but preferably contains a binder resin and particles for adjusting the refractive index. The binder resin of the optical adjustment layer 13 is selected from the group consisting of (meth) acrylic resin, cellulose resin, urethane resin, vinyl chloride resin, polyester resin, polyolefin resin, polycarbonate, nylon, polystyrene, and ABS resin. It is preferable that it is at least one selected resin. The particles of the optical adjustment layer 13 are at least one selected from the group consisting of low refractive index particles such as silica and magnesium fluoride, metal oxide particles such as titanium oxide and zirconium oxide, and inorganic pigments such as cobalt blue. Preferably there is. Among these, a combination of a polyester resin and metal oxide particles such as titanium oxide and zirconium oxide is more preferable from the viewpoint of adhesion and refractive index difference adjustment.

The optical adjustment layer 13 may contain an antistatic agent in order to obtain antistatic properties. When the optical adjustment layer 13 contains an antistatic agent, the optical adjustment layer 13 also functions as an antistatic layer. By including the antistatic agent in the optical adjustment layer 13, the surface resistance value on the surface 10 </ b> A of the optical film 10 can be further stabilized. When the antistatic agent is included in the optical adjustment layer 13, the surface resistance value on the surface 10 </ b> A of the optical film 10 can be further stabilized by including the antistatic agent in the functional layer 12. As the antistatic agent contained in the optical adjustment layer 13, the same antistatic agent as described in the column of the functional layer 12 can be used, and therefore, the description thereof is omitted here.

<< second optical adjustment layer >>
The optical adjustment layer 14 is a layer for improving the adhesion between the resin substrate 11 and the optical adjustment layer 13 mainly without generating interference fringes. By providing the optical adjustment layer 14 between the resin base material 11 and the optical adjustment layer 13, adhesion can be improved as compared with the case where the resin base material 11 and the optical adjustment layer 13 are in direct contact.

The refractive index of the optical adjustment layer 14 is preferably lower than the refractive index of the resin substrate 11 and higher than the refractive index of the optical adjustment layer 13 from the viewpoint of interference fringes. Since the refractive index of the optical adjustment layer 14 can be measured by the same method as that of the functional layer 12, the description thereof is omitted here.

The difference in refractive index between the optical adjustment layer 14 and the optical adjustment layer 13 (refractive index of the second optical adjustment layer−refractive index of the first optical adjustment layer) is preferably 0.005 or more and 0.100 or less. . If this refractive index difference is 0.005 or more, interface reflection occurs between the optical adjustment layer 14 and the optical adjustment layer 13 but interference fringes cannot be visually recognized. If it is 0.100 or less, Although some interference fringes are confirmed, the interference fringes can be set to a level that is not problematic in actual use. The lower limit of the refractive index difference is more preferably 0.007 or more, and the upper limit is more preferably 0.090 or less. The refractive index of the optical adjustment layer 13 may be 0.010 or more and 0.080 or less.

The thickness of the optical adjustment layer 14 is preferably 30 nm or more and 200 nm or less. If the film thickness of the optical adjustment layer 14 is 30 nm or more, sufficient adhesion between the optical adjustment layer 13 and the optical adjustment layer 14 and the resin substrate 11 and the optical adjustment layer 14 can be secured, and if it is 200 nm or less, Due to the refractive index difference between the optical adjustment layer 14 and the optical adjustment layer 13, interference fringes are not generated, and the folding property can be improved. The film thickness of the optical adjustment layer 14 is determined by the same method as that for the functional layer 12. The lower limit of the optical adjustment layer 14 is more preferably 50 nm or more, and the upper limit is more preferably 150 nm or less.

The optical adjustment layer 14 may be composed only of a resin, but preferably contains a binder resin and particles for adjusting the refractive index. The resin of the optical adjustment layer 14 is selected from the group consisting of (meth) acrylic resin, cellulose resin, urethane resin, vinyl chloride resin, polyester resin, polyolefin resin, polycarbonate, nylon, polystyrene, and ABS resin. It is preferable that it is at least one kind of resin. The particles of the optical adjustment layer 13 are at least one selected from the group consisting of low refractive index particles such as silica and magnesium fluoride, metal oxide particles such as titanium oxide and zirconium oxide, and inorganic pigments such as cobalt blue. Preferably there is. Among these, a combination of a polyester resin and metal oxide particles such as titanium oxide and zirconium oxide is more preferable from the viewpoint of adhesion and refractive index difference adjustment.

The optical adjustment layer 14 may contain an antistatic agent in order to obtain antistatic properties. When the optical adjustment layer 14 contains an antistatic agent, the optical adjustment layer 14 also functions as an antistatic layer. When the optical adjustment layer 14 contains an antistatic agent, the surface resistance value on the surface 10A of the optical film 10 can be further stabilized. When the antistatic agent is included in the optical adjustment layer 14, the surface resistance value on the surface 10 </ b> A of the optical film 10 can be further stabilized by including the antistatic agent in the functional layer 12. As the antistatic agent contained in the optical adjustment layer 14, the same antistatic agent as that described in the column of the functional layer 12 can be used, and therefore the description thereof is omitted here.

<< Third optical adjustment layer >>
The optical adjustment layer 15 is a layer that improves the light transmittance of the optical film 10. The refractive index of the optical adjustment layer 15 is higher than 1.000 which is the refractive index of air and lower than the refractive index of the resin base material 11. Since the refractive index of the optical adjustment layer 15 can be measured by the same method as the refractive index of the functional layer 12, the description is omitted here.

The difference in refractive index between the resin substrate 11 and the optical adjustment layer 15 (the refractive index of the resin substrate−the refractive index of the third optical adjustment layer) is preferably 0.005 or more and 0.700 or less. If this refractive index difference is 0.005 or more, the light transmittance of the optical film 10 can be improved, and if it is 0.700 or less, the transparency of the optical film 10 is not impaired. The lower limit of the refractive index difference is more preferably 0.010 or more, and the upper limit is more preferably 0.600 or less. The refractive index of the optical adjustment layer 15 may be 0.050 or more and 0.500 or less.

The film thickness of the optical adjustment layer 15 is preferably 30 nm or more and 1 μm or less. If the film thickness of the optical adjustment layer 15 is 30 nm or more, the light transmittance of the optical film 10 can be further improved, and if it is 1 μm or less, deterioration of workability can be suppressed. The film thickness of the optical adjustment layer 15 can be obtained by the same method as that for the functional layer 12. The lower limit of the optical adjustment layer 15 is more preferably 50 nm or more, the upper limit is more preferably 700 nm or less, and further preferably 500 nm or less.

The configuration of the optical adjustment layer 15 is not particularly limited as long as the refractive index is higher than 1.000 and lower than the refractive index of the resin base material 11. The optical adjustment layer 15 can be made of a resin. In addition to the resin, the optical adjustment layer 15 may include low refractive index particles having a refractive index lower than that of the resin in order to further reduce the refractive index. The optical adjustment layer 15 may contain an antistatic agent in order to obtain antistatic properties. When the optical adjustment layer 15 contains an antistatic agent, the optical adjustment layer 15 also functions as an antistatic layer. Further, the optical adjustment layer 15 may contain a color adjusting agent such as the spectral transmittance adjusting agent in order to adjust the color of the optical film 10.

<Resin>
The resin is at least one selected from the group consisting of (meth) acrylic resin, cellulose resin, urethane resin, vinyl chloride resin, polyester resin, polyolefin resin, polycarbonate, nylon, polystyrene, and ABS resin. It is preferable that the resin is. Among these, from the viewpoint of adhesion with the resin base material 11, (meth) acrylic resins, urethane resins, polyester resins, and the like are preferable.

Examples of the (meth) acrylic resin include polymethyl methacrylate. Examples of the cellulose resin include diacetyl cellulose, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB). As said urethane type resin, a urethane resin etc. are mentioned, for example.

Examples of the vinyl chloride resin include polyvinyl chloride and vinyl chloride-vinyl acetate copolymers. Moreover, as said polyester-type resin, a polyethylene terephthalate etc. are mentioned, for example. Moreover, as said polyolefin resin, polyethylene, a polypropylene, etc. are mentioned, for example.

<Low refractive index particles>
Examples of the low refractive index particles include solid or hollow particles made of silica or magnesium fluoride. Among these, hollow silica particles are preferable, and such hollow silica particles can be produced by, for example, the production method described in Examples in JP-A-2005-099778.

The average particle size (average primary particle size) of the low refractive index particles is preferably 5 nm or more and 100 nm or less. When the average particle diameter of the low refractive index particles is within the above range, the transparency of the optical adjustment layer 15 is not impaired, and a good particle dispersion state is obtained. The average particle diameter of the low refractive index particles is the particle diameter of 20 low refractive index particles from the cross-sectional image of the optical adjustment layer 15 taken using a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM). Is determined as the arithmetic average value of the particle diameters of the 20 low refractive index particles. The lower limit of the average particle diameter of the low refractive index particles is more preferably 10 nm or more, the upper limit is more preferably 80 nm or less, and further preferably 70 nm or less.

As the low refractive index particles, silica particles having reactive groups on the surface (reactive silica particles) are preferably used, and reactive hollow silica particles are particularly preferable. Such silica particles having a reactive group on the surface can be prepared by surface-treating the silica particles with a silane coupling agent or the like. As a method of treating the surface of the silica particles with a silane coupling agent, a dry method in which the silane coupling agent is sprayed on the silica particles, or a wet method in which the silica particles are dispersed in a solvent and then the silane coupling agent is added and reacted. Etc.

<Antistatic agent>
As the antistatic agent contained in the optical adjustment layer 15, the same antistatic agent as described in the column of the functional layer 12 can be used, and therefore, the description thereof is omitted here.

<< Optical Film Manufacturing Method >>
The optical film 10 can be produced as follows, for example. First, the second optical adjustment layer composition for forming the optical adjustment layer 14 is applied onto the first surface 11A of the resin base 11 by a coating device such as a bar coater, and the second optical adjustment layer 14 is applied. A coating film of the composition for the adjustment layer is formed.

<Second composition for optical adjustment layer>
The 2nd composition for optical adjustment layers contains particles, such as binder resin precursor and a metal oxide, and a solvent. The “binder resin precursor” in the present specification is a component that becomes a binder resin by removing the solvent or by curing with heat or ionizing radiation. Examples of the binder resin precursor include solvent-drying resins and polymerizable compounds that are cured by heat or ionizing radiation. Examples of the ionizing radiation in this specification include visible light, ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays. In addition, the second optical adjustment layer composition contains at least one of low refractive index particles such as silica and magnesium fluoride, inorganic pigments such as cobalt blue, a leveling agent, and a polymerization initiator, if necessary. You may go out. In addition, when a polyester resin is used as the binder resin precursor, the second optical adjustment layer composition may be a (meth) acrylic resin, a cellulose resin, or a urethane resin as necessary. One or more resins selected from the group consisting of vinyl chloride resin, polyolefin resin, polycarbonate, nylon, polystyrene, and ABS resin may be included.

After forming the coating film of the composition for the second optical adjustment layer, the coating film is dried by, for example, heating at a temperature of 40 ° C. or more and 200 ° C. or less for 10 seconds to 120 seconds by various known methods, Is evaporated or cured, and if necessary, the coating film is irradiated with ionizing radiation such as ultraviolet rays to form the optical adjustment layer 14 adjacent to the resin substrate 11.

Next, the first optical adjustment layer composition for forming the optical adjustment layer 13 is applied onto the optical adjustment layer 14 by a coating device such as a bar coater. Form a coating film.

<First optical adjustment layer composition>
The 1st composition for optical adjustment layers contains particles, such as a binder resin precursor and a metal oxide, and a solvent. In addition, the first optical adjustment layer composition contains at least one of low refractive index particles such as silica and magnesium fluoride, an inorganic pigment such as cobalt blue, a leveling agent, and a polymerization initiator, if necessary. You may go out. In addition, when a polyester resin is used as the binder resin precursor, the first optical adjustment layer composition may be a (meth) acrylic resin, a cellulose resin, or a urethane resin as necessary. One or more resins selected from the group consisting of vinyl chloride resin, polyolefin resin, polycarbonate, nylon, polystyrene, and ABS resin may be included.

After forming the coating film of the first optical adjustment layer composition, the coating film is dried by heating at a temperature of, for example, 40 ° C. to 200 ° C. for 10 seconds to 120 seconds by various known methods, The optical adjustment layer 13 is formed by evaporating or curing the film and irradiating the coating film with ionizing radiation such as ultraviolet rays as necessary.

After the optical adjustment layer 13 is formed, a functional layer composition for forming the functional layer 12 is applied onto the optical adjustment layer 13 by a coating device such as a bar coater, and a coating film of the functional layer composition Form.

<Composition for functional layer>
The functional layer composition contains a polymerizable compound that becomes a binder resin after curing. In addition, the functional layer composition may contain an antistatic agent, an ultraviolet absorber, a spectral transmittance adjusting agent, an antifouling agent, inorganic particles, a leveling agent, a solvent, and a polymerization initiator, if necessary.

(solvent)
Examples of the solvent include alcohols (eg, methanol, ethanol, propanol, isopropanol, n-butanol, s-butanol, t-butanol, benzyl alcohol, PGME, ethylene glycol, diacetone alcohol), ketones (eg, acetone, methyl ethyl ketone, Methyl isobutyl ketone, cyclopentanone, cyclohexanone, heptanone, diisobutyl ketone, diethyl ketone, diacetone alcohol), ester (methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, methyl formate, PGMEA), aliphatic Hydrocarbons (eg, hexane, cyclohexane), halogenated hydrocarbons (eg, methylene chloride, chloroform, carbon tetrachloride), aromatic hydrocarbons (eg, benzene, toluene, xylene), Amide (eg, dimethylformamide, dimethylacetamide, n-methylpyrrolidone), ether (eg, diethyl ether, dioxane, tetrahydrofuran), ether alcohol (eg, 1-methoxy-2-propanol), carbonate (dimethyl carbonate, diethyl carbonate, Ethyl methyl carbonate), and the like. These solvents may be used alone or two or more of them may be used in combination. Especially, as said solvent, methyl isobutyl ketone and methyl ethyl ketone are preferable at the point which can dissolve or disperse | distribute components, such as urethane (meth) acrylate, and another additive, and can apply the composition for functional layers suitably. .

(Polymerization initiator)
The polymerization initiator is a component that is decomposed by irradiation with ionizing radiation to generate radicals to initiate or advance polymerization (crosslinking) of the polymerizable compound.

The polymerization initiator is not particularly limited as long as it can release a substance that initiates radical polymerization by irradiation with ionizing radiation. The polymerization initiator is not particularly limited, and known ones can be used. Specific examples include, for example, acetophenones, benzophenones, Michler benzoylbenzoate, α-amyloxime ester, thioxanthones, propiophenone. , Benzyls, benzoins, acylphosphine oxides. Further, it is preferable to use a mixture of photosensitizers, and specific examples thereof include n-butylamine, triethylamine, poly-n-butylphosphine and the like.

After forming the coating film of the functional layer composition, the coating film is dried by heating at a temperature of 30 ° C. or more and 120 ° C. or less for 10 seconds to 120 seconds by various known methods, and the solvent is evaporated.

After drying the coating film, the coating film is irradiated with ionizing radiation such as ultraviolet rays to cure the coating film. Thereby, the functional layer 12 adjacent to the optical adjustment layer 13 is formed.

After the functional layer 12 is formed, the third optical adjustment layer composition for forming the optical adjustment layer 15 is applied onto the second surface 11B of the resin base material 11 by a coating device such as a bar coater. Then, a coating film of the third composition for optical adjustment layer is formed.

<Third optical adjustment layer composition>
The 3rd composition for optical adjustment layers contains the resin precursor and the solvent. The third optical adjustment layer composition may further contain at least one of low refractive index particles, an antistatic agent, an inorganic pigment such as cobalt blue, a leveling agent, and a polymerization initiator, if necessary. Good. In addition, when a polyester-based resin is used as the resin precursor, the third optical adjustment layer composition may be a (meth) acrylic resin, a cellulose-based resin, a urethane-based resin, One or more kinds of resins selected from the group consisting of vinyl chloride resin, polyolefin resin, polycarbonate, nylon, polystyrene, and ABS resin may be included. Since the solvent is the same as the solvent described in the column of the functional layer composition, the description is omitted here.

After forming the coating film of the third optical adjustment layer composition, the coating film is dried by heating at a temperature of, for example, 40 ° C. or more and 200 ° C. or less for 10 seconds to 120 seconds by various known methods, The optical adjustment layer 15 is formed by evaporating or curing the film and irradiating the coating film with ionizing radiation such as ultraviolet rays as necessary. Thereby, the optical film 10 shown in FIG. 1 is obtained.

<<< Other optical films >>>
The optical film may be the optical film 30, 40, 50, 60 shown in FIGS. The optical films 30, 40, 50, and 60 shown in FIGS. 4 to 7 are also used in the image display device and can be folded.

The optical film 30 shown in FIG. 4 is provided between the resin base material 11, the functional layer 12 provided on the first surface 11A side of the resin base material 11, and the resin base material 11 and the functional layer 12. The optical adjustment layer 13 adjacent to the functional layer 12 is provided. In the optical film 30 shown in FIG. 4, the optical adjustment layer 14 is not provided, and the optical adjustment layer 13 is adjacent to the functional layer 12 and the resin base material 11. Since the physical properties of the optical film 30 are the same as the physical properties of the optical film 10, the description thereof will be omitted here. The surface 30A of the optical film 30 is the surface 12A of the functional layer 12, and the back surface 30B of the optical film 30 is the surface 15A opposite to the surface of the optical adjustment layer 15 on the resin base material 11 side. .

The optical film 40 shown in FIG. 5 is provided between the resin base material 11, the functional layer 12 provided on the first surface 11A side of the resin base material 11, and the resin base material 11 and the functional layer 12. The optical adjustment layer 13 adjacent to the functional layer 12 and the resin layer 41 provided on the second surface 11B of the resin substrate 11 are provided. In the optical film 40 shown in FIG. 5, the optical adjustment layer 14 is not provided, and the optical adjustment layer 13 is adjacent to the functional layer 12 and the resin base material 11. The surface 40A of the optical film 40 is the surface 12A of the functional layer 12, and the back surface 30B of the optical film 40 is a surface 41A opposite to the surface of the resin layer 41 on the resin base material 11 side.

The optical film 50 shown in FIG. 6 is provided between the resin base material 11, the functional layer 12 provided on the first surface 11A side of the resin base material 11, and the resin base material 11 and the functional layer 12. The optical adjustment layer 13 adjacent to the functional layer 12, the resin layer 41 provided on the second surface 11B side of the resin base material 11, and the resin base material 11 provided between the resin base material 11 and the resin layer 41. And an optical adjustment layer 15 adjacent to. In the optical film 50 shown in FIG. 6, the optical adjustment layer 14 is not provided, and the optical adjustment layer 13 is adjacent to the functional layer 12 and the resin base material 11. The surface 50A of the optical film 50 is the surface 12A of the functional layer 12, and the back surface 50B of the optical film 50 is a surface 41A opposite to the surface of the resin layer 41 on the resin base material 11 side.

The optical film 60 shown in FIG. 7 is provided between the resin base material 11, the functional layer 12 provided on the first surface 11A side of the resin base material 11, and the resin base material 11 and the functional layer 12. The optical adjustment layer 13 adjacent to the functional layer 12, the optical adjustment layer 14 provided between the resin base material 11 and the optical adjustment layer 13 and adjacent to the resin base material 11, and the second surface of the resin base material 11 A resin layer 41 provided on the 11B side, and an optical adjustment layer 15 provided between the resin base material 11 and the resin layer 41 and adjacent to the resin base material 11 are provided. The surface 60A of the optical film 60 is the surface 12A of the functional layer 12, and the back surface 60B of the optical film 60 is a surface 41A opposite to the surface of the resin layer 41 on the resin base material 11 side. Yes.

In the optical films 40, 50 and 60, the shear storage elastic modulus G ′ in the frequency range of 25 ° C. and 500 Hz to 1000 Hz is more than 200 MPa and 1200 MPa or less. If the shear storage modulus G ′ of the film exceeds 200 MPa, when an impact is applied to the surface of the optical film, not only the deformation of the optical film itself but also the adhesive layer is disposed inside the image display device rather than the optical film. Even in this case, plastic deformation of the adhesive layer can be suppressed. Moreover, if the shear storage elastic modulus G ′ of the optical films 40, 50, 60 is 1200 MPa or less, the optical film 40 can be prevented from cracking during folding. The lower limit of the shear storage modulus G ′ of the optical films 40, 50, 60 is preferably 400 MPa or more, and more preferably 500 MPa or more. By setting it as such a lower limit, more excellent impact resistance can be obtained. The upper limit of the shear storage modulus G ′ of the optical films 40, 50, 60 is preferably less than 800 MPa. By setting it as such an upper limit, when it is folded and left still and opened again, a good restoring property can be obtained.

In the optical films 40, 50 and 60, the shear loss elastic modulus G ″ in the frequency range of 25 ° C. and 500 Hz to 1000 Hz is 3 MPa to 150 MPa. If the shear loss elastic modulus G ″ of the optical film is 3 MPa or more, it is possible to suppress a decrease in impact absorption performance. Moreover, if the shear loss elastic modulus G ″ of the optical films 40, 50, 60 is 150 MPa or less, a decrease in the hardness of the resin layer 41 can be suppressed. The lower limit of the shear loss elastic modulus G ″ of the optical film 40 is preferably 20 MPa or more, and the upper limit of the shear loss elastic modulus G ″ of the optical film 40 is thin of the optical films 40, 50, 60. From the viewpoint of conversion, it is preferably 130 MPa or less, and more preferably 100 MPa or less.

The shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ can be measured by a dynamic viscoelasticity measuring device (DMA). When measuring the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ of the optical film 40 using a dynamic viscoelasticity measuring device (DMA), first, the optical film 40 is punched into a 10 mm × 5 mm rectangular shape. Get a sample. Then, two samples are prepared and attached to a solid shearing jig which is an option of a dynamic viscoelasticity measuring apparatus (product name “Rheogel-E4000”, manufactured by UBM Co., Ltd.). Specifically, as shown in FIG. 8, the solid shearing jig 70 is arranged on one metal solid shear plate (inner plate) having a thickness of 1 mm and on both sides of the solid shear plate 71. Two L-shaped brackets 72 (outer plates) are provided, and one sample is sandwiched between the solid shear plate 71 and one L-shaped bracket 72, and the solid shear plate 71 and the other L-shaped bracket 72 Hold the other sample. In this case, the sample S is sandwiched so that the resin layer is on the solid shear plate 51 side and the functional layer is on the L-shaped metal fitting 72 side. Then, the L-shaped metal fitting 72 is tightened with the screws 53 to fix the sample S. Next, after attaching a tensile test chuck consisting of an upper chuck and a lower chuck to a dynamic viscoelasticity measuring device (product name “Rheogel-E4000”, manufactured by UBM Co., Ltd.), a solid is placed between the upper chuck and the lower chuck. A shearing jig is attached with a distance between chucks of 20 mm. The distance between chucks is a distance between the upper chuck and the lower chuck. And set temperature is 25 degreeC and it heats up at 2 degree-C / min. In this state, the solid viscoelasticity measurement of the solid at 25 ° C. is performed while giving the longitudinal vibration in the range of 1% distortion and frequency of 500 Hz to 1000 Hz to the two L-shaped metal fittings 72 while fixing the solid shear plate 71. Then, the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ of the optical films 40, 50, 60 are measured. Here, the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ in the frequency range of 500 Hz to 1000 Hz in the optical film respectively give longitudinal vibrations of frequencies 500 Hz, 750 Hz, and 950 Hz to the L-shaped brackets, respectively. The shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ of the optical film are measured at the frequency of, and an arithmetic average value of these shear storage elastic modulus G ′ and shear loss elastic modulus G ″ is obtained. The measurement is repeated three times, and the three arithmetic average values obtained are further calculated as arithmetic average values. In the above description, the frequency range of 500 Hz to 1000 Hz is that the frequency of the frequency range is from several microns to several tens of microns when an object is freely dropped from a height of several centimeters. This is because it is a frequency that is deformed and is a frequency that damages the display panel and the like existing inside the image display device from the optical film.

Since the physical properties and the like of the optical films 40, 50, and 60 are the same as the physical properties of the optical film 10 except for the above, description thereof will be omitted here.

<< Resin layer >>
The resin layer 41 is a layer made of a resin having optical transparency. The resin layer 41 is a layer having shock absorption. The resin layer may have a multilayer structure including two or more resin layers.

The film thickness of the resin layer 41 is 50 μm or more and 300 μm or less. If the film thickness of the resin layer 41 is 50 μm or more, a decrease in the hardness of the resin layer 41 can be suppressed, and if it is 300 μm or less, the thickness can be reduced and the workability can be deteriorated. Absent. The film thickness of the resin layer 41 is obtained by photographing a cross section of the resin layer 41 using a scanning electron microscope (SEM), measuring 20 film thicknesses of the resin layer 41 in the image of the cross section, The arithmetic average value of thickness. The lower limit of the resin layer 41 is more preferably 60 μm or more, the upper limit of the resin layer 41 is more preferably 150 μm or less, and further preferably 100 μm or less.

The resin constituting the resin layer 41 is a resin in which the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ in the frequency range of 25 ° C. and 500 Hz to 1000 Hz in the optical film 40 are within the above ranges. There is no particular limitation. Examples of such resins include acrylic gels, urethane gels, silicone gels, urethane resins, and epoxy resins. Among these, acrylic gel is preferable. “Gel” generally refers to a dispersion having high viscosity and loss of fluidity. In addition, the resin layer 41 may contain rubber | gum and a thermoplastic elastomer other than an acrylic-type gel and a urethane-type resin.

(Acrylic gel)
As the acrylic gel, various polymers can be used as long as they are polymers obtained by polymerizing a monomer containing an acrylate ester used for an adhesive or the like. Specifically, examples of acrylic gels include ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, and i-butyl (meth) acrylate. 2-ethylhexyl (meth) acrylate, n-hexyl (meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, octyl (meth) acrylate, i-octyl (meth) acrylate, i-myristyl (Meth) acrylate, lauryl (meth) acrylate, nonyl (meth) acrylate, i-nonyl (meth) acrylate, i-decyl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, i-stearyl (meth) ) Such as acrylate It can be used obtained by polymerizing or copolymerizing acrylic monomers. In the present specification, “(meth) acrylate” means both “acrylate” and “methacrylate”. In addition, the acrylic ester used in the (co) polymerization may be used alone or in combination of two or more.

(Urethane resin)
The urethane-based resin is a resin having a urethane bond. Examples of the urethane resin include a cured product of an ionizing radiation curable urethane resin composition and a cured product of a thermosetting urethane resin composition. Among these, a cured product of an ionizing radiation-curable urethane resin composition is preferable from the viewpoint of obtaining high hardness, high curing speed, and excellent mass productivity.

The ionizing radiation curable urethane-based resin composition includes urethane (meth) acrylate, and the thermosetting urethane-based resin includes a polyol compound and an isocyanate compound. The urethane (meth) acrylate, polyol compound, and isocyanate compound may be any of a monomer, an oligomer, and a prepolymer.

The number of (meth) acryloyl groups (the number of functional groups) in the urethane (meth) acrylate is preferably 2 or more and 4 or less. If the number of (meth) acryloyl groups in the urethane (meth) acrylate is less than 2, the pencil hardness may be lowered, and if it exceeds 4, the curing shrinkage increases and the optical film curls. In addition, there is a risk of cracks in the resin layer during bending. The upper limit of the number of (meth) acryloyl groups in the urethane (meth) acrylate is more preferably 3 or less. The “(meth) acryloyl group” means to include both “acryloyl group” and “methacryloyl group”.

The weight average molecular weight of urethane (meth) acrylate is preferably 1500 or more and 20000 or less. If the weight average molecular weight of the urethane (meth) acrylate is less than 1500, the impact resistance may be lowered. If it exceeds 20000, the viscosity of the ionizing radiation-curable urethane resin composition increases, and the coating is applied. May deteriorate. The lower limit of the weight average molecular weight of the urethane (meth) acrylate is more preferably 2000 or more, and the upper limit is more preferably 15000 or less.

　上記一般式（２６）中、Ｒ^９は分岐鎖状アルキル基を示し、Ｒ^１０は分岐鎖状アルキル基又は飽和環状脂肪族基を示し、Ｒ^１１は水素原子又はメチル基を示し、Ｒ^１２は、水素原子、メチル基又はエチル基を示し、ｍは０以上の整数を示し、ｘは０～３の整数を示す。 Moreover, as a repeating unit which has a structure derived from urethane (meth) acrylate, the structure etc. which are represented by the following general formula (26), (27), (28) or (29) are mentioned, for example.

In the general formula (26), R ⁹ represents a branched alkyl group, R ¹⁰ represents a branched alkyl group or a saturated cycloaliphatic group, R ¹¹ represents a hydrogen atom or a methyl group, and R ¹² represents , A hydrogen atom, a methyl group or an ethyl group, m represents an integer of 0 or more, and x represents an integer of 0 to 3.

　上記一般式（２７）中、Ｒ^９は分岐鎖状アルキル基を示し、Ｒ^１０は分岐鎖状アルキル基又は飽和環状脂肪族基を示し、Ｒ^１１は水素原子又はメチル基を示し、Ｒ^１２は、水素原子、メチル基又はエチル基を示し、ｎは１以上の整数を示し、ｘは０～３の整数を示す。

In the general formula (27), R ⁹ represents a branched chain alkyl group, R ¹⁰ represents a branched alkyl group or a saturated cyclic aliphatic group, R ¹¹ represents a hydrogen atom or a methyl group, R ¹² is , Represents a hydrogen atom, a methyl group or an ethyl group, n represents an integer of 1 or more, and x represents an integer of 0 to 3.

　上記一般式（２８）中、Ｒ^９は分岐鎖状アルキル基を示し、Ｒ^１０は分岐鎖状アルキル基又は飽和環状脂肪族基を示し、Ｒ^１１は水素原子又はメチル基を示し、Ｒ^１２は、水素原子、メチル基又はエチル基を示し、ｍは０以上の整数を示し、ｘは０～３の整数を示す。

In the general formula (28), R ⁹ represents a branched alkyl group, R ¹⁰ represents a branched alkyl group or a saturated cycloaliphatic group, R ¹¹ represents a hydrogen atom or a methyl group, and R ¹² represents , A hydrogen atom, a methyl group or an ethyl group, m represents an integer of 0 or more, and x represents an integer of 0 to 3.

　上記一般式（２９）中、Ｒ^９は分岐鎖状アルキル基を示し、Ｒ^１０は分岐鎖状アルキル基又は飽和環状脂肪族基を示し、Ｒ^１１は水素原子又はメチル基を示し、Ｒ^１２は、水素原子、メチル基又はエチル基を示し、ｎは１以上の整数を示し、ｘは０～３の整数を示す。

In the general formula (29), R ⁹ represents a branched alkyl group, R ¹⁰ represents a branched alkyl group or a saturated cycloaliphatic group, R ¹¹ represents a hydrogen atom or a methyl group, and R ¹² represents , Represents a hydrogen atom, a methyl group or an ethyl group, n represents an integer of 1 or more, and x represents an integer of 0 to 3.

It should be noted that the structure of the resin constituting the resin layer 41 is formed by the polymer chain (repeating unit) of the structure, for example, by analyzing the resin layer 41 by pyrolysis GC-MS and FT-IR. Judgment is possible. In particular, pyrolysis GC-MS is useful because it can detect monomer units contained in the resin layer 41 as monomer components.

The resin layer 41 absorbs ultraviolet rays if the shear storage elastic modulus G ′ and shear loss elastic modulus G ″ in the frequency range of 25 ° C. and 500 Hz to 1000 Hz in the optical films 40, 50, and 60 are within the above ranges. Agent, spectral transmittance adjusting agent, antifouling agent, inorganic particles and / or organic particles may be included. As the ultraviolet absorber and the like, those similar to the ultraviolet absorber and the like described in the column of the functional layer 12 can be used, and thus description thereof is omitted here.

<<< Image display device >>>
The optical films 10, 30, 40, 50 and 60 can be used by being incorporated in a foldable image display device. FIG. 9 is a schematic configuration diagram of the image display apparatus according to the present embodiment. As shown in FIG. 9, the image display device 80 mainly has a housing 81 in which a battery or the like is stored, a protective film 82, a display element 83, a circularly polarizing plate 84, and a touch sensor 85 toward the viewer. , And the optical film 10 are laminated in this order. Between the display element 83 and the circularly polarizing plate 84, between the circularly polarizing plate 84 and the touch sensor 85, and between the touch sensor 85 and the optical film 10, a light-transmitting adhesive layer 86 is disposed. These members are fixed to each other by the adhesive layer 86. The adhesive layer 86 is disposed between the display element 83 and the circularly polarizing plate 84, between the circularly polarizing plate 84 and the touch sensor 85, and between the touch sensor 85 and the optical film 10. The arrangement location of is not particularly limited as long as it is between the optical film and the display element.

The optical film 10 is arranged such that the functional layer 12 is closer to the observer side than the resin base material 11. In the image display device 80, the surface 10 </ b> A of the optical film 10 (the surface 12 </ b> A of the functional layer 12) constitutes the surface 80 </ b> A of the image display device 80.

In the image display device 80, the display element 83 is an organic light emitting diode element including an organic light emitting diode. The touch sensor 85 is disposed on the viewer side with respect to the circularly polarizing plate 84, but may be disposed between the display element 83 and the circularly polarizing plate 84. The touch sensor 85 may be an on-cell method or an in-cell method. As the adhesive layer 86, for example, OCA (Optical Clear Adhesive) can be used.

According to this embodiment, the resin base material 11 made of one or more kinds of resins selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyamide resin, and a polyester resin is used. Since the optical adjustment layer 13 adjacent to the functional layer 12 is provided between the functional layer 12 and the functional layer 12, the generation of interference fringes can be suppressed while being foldable.

When the back surface of the optical film is a resin substrate, the resin substrate comes into contact with the air layer, so reflection at the interface between the resin substrate and the air layer increases, thereby reducing light transmittance. There is a risk of it. In particular, when a resin substrate made of one or more resins selected from the group consisting of polyimide resins, polyamideimide resins, polyamide resins, and polyester resins is used as the resin substrate, these resins are used. Since the refractive index of the substrate is relatively high, interface reflection tends to occur. On the other hand, in this embodiment, the optical adjustment layer 15 having a refractive index higher than 1.000 and lower than the refractive index of the resin base material 11 is provided on the second surface 11B of the resin base material 11. Therefore, compared with the case where the resin base material is in contact with the air layer, the interface reflection can be reduced, and the light reflectance can be reduced. Thereby, the light transmittance of the optical films 10 and 30 can be improved.

When the optical adjustment layer 15 includes an antistatic agent, the optical films 10, 30, 50, and 60 are functional layers that are antistatic hard coat layers on the first surface 11 A side of the resin substrate 11. 12 and the optical adjustment layer 15 containing an antistatic agent is provided on the second surface 11B side of the resin base material 11, dust or the like may adhere to the optical films 10, 30, 50, 60. Can be suppressed. In this case, even if the protective film is peeled off from the optical films 10, 30, 50, 60 in a state where protective films (not shown) are attached to both surfaces of the optical films 10, 30, 50, 60, The charging of the optical films 10, 30, 50, 60 can be suppressed. Thereby, the yield of the assembly process of an image display apparatus can be improved.

Since an optical film used for a foldable image display device may be subjected to an impact on the surface of the optical film, impact resistance may be required. Here, when an impact is applied to the surface of the optical film, the surface of the optical film may be recessed, and a member such as a display panel (for example, an organic light-emitting diode panel) existing inside the optical film in the image display device May be damaged. Regarding the dent on the surface of the optical film, there are a dent resulting from the optical film itself and a dent resulting from a soft layer such as an adhesive layer disposed inside the image display device rather than the optical film. “The dent caused by the optical film itself” means a dent caused by the deformation of the optical film itself due to the impact when an impact is applied to the surface of the optical film. Because the layer is soft, when an impact is applied to the surface of the optical film, the soft layer placed inside the image display device causes plastic deformation rather than the optical film, and the optical film follows the plastic deformation of the soft layer. It means a dent caused by doing. Therefore, at present, in the optical film, when an impact is applied to the surface of the optical film, the dent caused by the optical film itself and the dent caused by the soft layer are suppressed, and the inside of the image display device is more than the optical film. It is preferable that excellent impact resistance is obtained such that a member existing in the substrate is not damaged. Here, the shear loss tangent tan δ is conventionally known as an index representing the impact absorbing performance. Therefore, the impact resistance in an optical film having a structure in which a functional layer is provided on the first surface side of the resin substrate and a resin layer on the second surface side may be expressed as a shear loss tangent tan δ. Then, when an impact is applied to the surface of the optical film (the surface of the functional layer), the dent on the surface of the optical film caused by the optical film itself and the dent on the surface of the optical film caused by the soft layer It was not possible to suppress damage to members located inside the image display device. This is considered to be because the shear loss tangent tan δ is a ratio (G ″ / G ′) between the shear loss elastic modulus G ″ and the shear storage elastic modulus G ′. As a result of further diligent research by the present inventors, the surface dent caused by the optical film itself and the surface dent caused by the soft layer when an impact is applied to the surface of the optical film, and the image display rather than the optical film. In order to suppress damage to members located inside the apparatus, it has been found that the balance of the resin layer thickness, the shear storage elastic modulus G ′, and the shear loss elastic modulus G ″ is important. According to the present embodiment, in the optical films 40, 50, 60 having a structure in which the functional layer 12 is provided on the first surface 11 </ b> A side of the resin base material 11 and the resin layer 41 is provided on the second surface 11 </ b> B side, The film thickness is as thin as 50 μm or more and 300 μm or less, the shear storage elastic modulus G ′ in the optical film 40 is more than 200 MPa and 1200 MPa or less, and the shear loss elastic modulus G ″ in the optical film 40 is Since it is 3 MPa or more and 150 MPa or less, it is possible to fold, but when an impact is applied to the surface 40A of the optical film 40, the recesses of the surfaces 40A, 50A, 60A caused by the optical films 40, 50, 60 themselves And the optical films 40, 50 caused by a soft layer existing inside the image display device rather than the optical films 40, 50, 60. , 60 can be suppressed, and damage to members such as the display element 83 located inside the image display apparatus can be suppressed. Thereby, the outstanding impact resistance can be obtained.

[Second Embodiment]
Hereinafter, an optical film and an image display device according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a schematic configuration diagram of an optical film according to this embodiment, FIG. 11 is a schematic configuration diagram of another optical film according to this embodiment, and FIG. 12 is a schematic configuration of an image display device according to this embodiment. FIG.

<<< Optical film >>>
The optical film 90 shown in FIG. 10 is used for an image display device and can be folded.

The optical film 90 includes a light transmissive substrate 91 and a first antistatic layer 92 (hereinafter simply referred to as an antistatic layer 92) provided on the first 91A side which is one surface of the light transmissive substrate 91. And a second antistatic layer 93 (hereinafter simply referred to as “charging”) provided on the second surface 91B side which is the surface opposite to the first surface 91A of the light-transmitting substrate 91. And may be referred to as a prevention layer 93). Note that a functional layer may be provided between at least one of the light-transmitting substrate 91 and the antistatic layer 92 and between the light-transmitting substrate 91 and the antistatic layer 93.

A protective film may be attached to the surface of the antistatic layers 92 and 93 opposite to the surface of the light-transmitting substrate 91. However, since the protective film is peeled off during use, the protective film does not constitute a part of the optical film. In addition, the physical property value of the optical film 90 in this specification is a value in the state in which the protective film is not provided.

In FIG. 10, the surface 90A of the optical film 90 is the surface 92A of the antistatic layer 92. The back surface 90 </ b> B of the optical film 90 is a surface 93 </ b> A on the side opposite to the surface of the antistatic layer 93 on the light transmissive substrate 91 side.

Although the optical film 90 can be folded, specifically, even when the folding test described below (continuous folding test) is repeated 100,000 times on the optical film 90, the optical film 90 can be folded. It is preferable that no cracks or breaks occur, and even when the continuous folding test is repeated 200,000 times, it is more preferable that the optical film 90 is not cracked or broken, and when it is repeated 1 million times. Even if it exists, it is more preferable that the optical film 90 does not crack or break. When a continuous folding test is repeated 100,000 times on the optical film 90 and the optical film 90 is cracked, the folding property of the optical film 90 becomes insufficient. The continuous folding test may be performed so that the optical film 90 is folded so that the antistatic layer 92 is on the inner side, or may be performed so that the optical film 90 is folded so that the antistatic layer 92 is on the outer side. In any case, it is preferable that the optical film is not cracked or broken. The continuous folding test is performed by the same method as in the first embodiment, but the continuous folding test of the present embodiment is performed in a state where the interval between the side portions is 3 mm.

In the same manner as in the first embodiment, the optical film 90 is subjected to a folding stationary test in which the optical film 90 is allowed to stand at 70 ° C. for 240 hours, and then the folded state is released. Is measured, the opening angle θ of the optical film 90 is preferably 100 ° or more. The folding stationary test may be performed so that the optical film 90 is folded so that the antistatic layer 92 is on the inner side, and is performed so that the optical film 90 is folded so that the antistatic layer 92 is on the outer side. However, in any case, the opening angle θ is preferably 100 ° or more.

The surface resistance of the surface 90A and rear surface 90B of the optical film 90 is preferably at ^{10 12 Ω} / □ or less. The surface resistance value is measured by a method similar to the method described in the first embodiment.

The surface 90A of the optical film 90 (the surface 92A of the antistatic layer 92) has a hardness (pencil hardness) of F or more when measured by a pencil hardness test specified in JIS K5600-5-4: 1999. Is preferable, and 2H or more is more preferable. The pencil hardness test is measured by a method similar to the method described in the first embodiment.

In the optical film 90, when a voltage of 10 kV is applied from a distance of 50 mm from the surface 90A of the optical film 90 in an environment of 23 ° C. and a relative humidity of 50% for the same reason as described in the first embodiment. It is preferable that the saturation voltage on the surface 90A of the optical film 90 exceeds 0 kV. The saturation voltage is measured by a method similar to the method described in the first embodiment. The lower limit of the absolute value of the saturation band voltage is more preferably 0.1 kV or more, and the upper limit of the absolute value of the saturation band voltage is more preferably 1.0 kV or less.

The optical film 90 preferably has a yellow index (YI) of 15 or less for the same reason as described in the first embodiment. The yellow index is measured by a method similar to the method described in the first embodiment. The upper limit of the yellow index (YI) of the optical film 90 is more preferably less than 10, and most preferably less than 1.5.

L ^* a ^* in the light (transmitted light) transmitted through the optical film 90 by irradiating the optical film 90 with light having a continuous spectrum from the side of the antistatic layer 93 in the wavelength region of 300 nm to 780 nm at an incident angle of 0 ° ^. b ^* color system of the color coordinates a ^*, when asked for b ^*, a ^* is -5 or more +5 or less and a b ^* is -5 or more +5. If a ^* and b ^* are within the above ranges, the yellow color of the image is not a concern when the optical film is used in a mobile terminal. It is assumed that a ^* and b ^* are measured by a method similar to the method described in the first embodiment.

The haze value (total haze value) of the optical film 90 is preferably 2.5% or less for the same reason as described in the first embodiment. The haze value is measured by the same method as that described in the first embodiment. The haze value is more preferably 1.5% or less, and more preferably 1.0% or less.

The luminous reflectance (reflection Y value) of light having a wavelength of 380 nm to 780 nm of the optical film 90 is preferably 15% or less. If the luminous reflectance of the optical film is 8% or less, when the optical film is used for a mobile terminal, there is little reflected light, and visual recognition becomes easy. The luminous reflectance is obtained by using a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation, light source: tungsten lamp and deuterium lamp) to emit light having a wavelength of 380 nm to 780 nm from the surface side of the optical film. It is measured from light having a wavelength of 380 nm to 780 nm which is irradiated and reflected from the optical film. Specifically, light with an incident angle of 5 degrees is irradiated from the surface side of the optical film cut out to a size of 5 cm × 10 cm, and the reflected light in the specular direction reflected by the optical film is received and 380 nm to 780 nm. The reflectance in the wavelength range is measured, and then the luminous reflectance is calculated by software (for example, software built in UV-2450) that converts the brightness as perceived by human eyes. The luminous reflectance is more preferably 10% or less, and further preferably 3% or less.

Since other physical properties, applications, and sizes of the optical film 90 are the same as those of the optical film 10, the description thereof is omitted here.

<< light transmissive substrate >>
The light transmissive substrate 91 is a substrate made of a resin having light transmittance. The thickness of the light transmissive substrate 91 is preferably 10 μm or more and 100 μm or less for the same reason as described in the first embodiment. The thickness of the light transmissive substrate 91 is measured by the same method as the thickness of the resin substrate 11. The lower limit of the light transmissive substrate 71 is more preferably 25 μm or more, and the upper limit of the light transmissive substrate 91 is more preferably 80 μm or less.

The light transmissive substrate 91 is preferably a resin substrate. As the resin constituting the resin base material, the same resin as that of the resin base material 11 can be used, and the description thereof will be omitted here.

<< first antistatic layer >>
The antistatic layer 92 is a layer that imparts antistatic properties to the surface 90 </ b> A of the optical film 90. The antistatic layer 92 may have a function other than the antistatic property in addition to the antistatic property. The antistatic layer 92 has hard coat properties in addition to antistatic properties. That is, the antistatic layer 92 is an antistatic hard coat layer. The antistatic hard coat layer is a hard coat layer having antistatic properties.

The antistatic layer 92 preferably has a Martens hardness at the center of the cross section of the antistatic layer 92 of 500 MPa to 2000 MPa. If the Martens hardness of the antistatic layer 92 is 500 MPa or more, sufficient hardness as an antistatic hard coat layer can be obtained, and if it is 2000 MPa or less, good optical film folding performance can be obtained. The lower limit of the Martens hardness at the center of the cross section of the antistatic layer 92 is preferably 600 MPa or more, and the upper limit is preferably 1500 MPa or less. The Martens hardness of the antistatic layer 92 is measured by the same method as that described in the first embodiment.

The film thickness of the antistatic layer 92 is preferably 1 μm or more and 50 μm or less. If the film thickness of the antistatic layer 92 is 1 μm or more, sufficient hardness as an antistatic hard coat layer can be obtained, and if it is 50 μm or less, deterioration of workability can be suppressed. In the present specification, the “antistatic layer thickness” means the total thickness of the antistatic layers when the antistatic layer has a multilayer structure. To do. The film thickness of the antistatic layer 92 is measured by the same method as the film thickness of the functional layer 12. The upper limit of the antistatic layer 92 is more preferably 40 μm or less, and further preferably 30 μm or less.

The antistatic layer 92 contains a binder resin and an antistatic agent present in the binder resin. The antistatic layer 92 may be a binder resin or the like, if necessary, within a range not impairing the effects of the present invention, for example, particles such as inorganic particles and organic particles, an ultraviolet absorber, an adhesion improver, a leveling agent, Additives such as a thixotropic agent, a coupling agent, a plasticizer, an antifoaming agent, a filler, a colorant, and a filler may be included.

<Binder resin>
Since the binder resin is the same as the binder resin described in the column of the functional layer 12, the description is omitted here.

<Antistatic agent>
Since the antistatic agent is the same as the antistatic agent described in the column of the functional layer 12, the description thereof is omitted here.

The antistatic layer 92 may further contain an ultraviolet absorber, a spectral transmittance adjusting agent, and / or an antifouling agent. The ultraviolet absorber, the spectral transmittance adjusting agent, and the antifouling agent are the same as the ultraviolet absorber, the spectral transmittance adjusting agent, and the antifouling agent described in the section of the functional layer 12, and therefore the description thereof is omitted here. To do.

<< second antistatic layer >>
The antistatic layer 93 is a layer that imparts antistatic properties to the back surface 90 </ b> B of the optical film 90. The film thickness of the antistatic layer 93 is preferably 1 nm or more and 0.5 μm or less. If the film thickness of the antistatic layer 93 is 1 nm or more, sufficient antistatic performance can be obtained, and if it is 0.5 μm or less, deterioration of workability can be suppressed. The film thickness of the antistatic layer 93 is measured by the same method as the film thickness of the functional layer 12.

If the film thickness of the antistatic layer 93 is 40 nm or more and 90 nm or less, the yellow index of the optical film 70 can be lowered. Therefore, from the viewpoint of color adjustment, the film thickness of the antistatic layer 93 is 40 nm or more and 90 nm or less. It is preferable.

The antistatic layer 93 contains an antistatic agent. The antistatic layer 93 may contain a binder resin in addition to the antistatic agent.

<Antistatic agent>
Since the antistatic agent contained in the antistatic layer 93 is the same as the antistatic agent described in the column of the functional layer 12, the description thereof is omitted here.

<Binder resin>
The binder resin is at least one selected from the group consisting of (meth) acrylic resin, cellulose resin, urethane resin, vinyl chloride resin, polyester resin, polyolefin resin, polycarbonate, nylon, polystyrene, and ABS resin. Preferably it is a seed. Among these, (meth) acrylic resins and urethane resins are preferable from the viewpoint of the hardness and transparency of the binder resin.

Examples of the (meth) acrylic resin include polymethyl methacrylate. Examples of the cellulose resin include diacetyl cellulose, cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB). As said urethane type resin, a urethane resin etc. are mentioned, for example.

Examples of the vinyl chloride resin include polyvinyl chloride and vinyl chloride-vinyl acetate copolymers. Moreover, as said polyester-type resin, a polyethylene terephthalate etc. are mentioned, for example. Moreover, as said polyolefin resin, polyethylene, a polypropylene, etc. are mentioned, for example.

<< Optical Film Manufacturing Method >>
The optical film 90 can be produced as follows, for example. First, the first antistatic layer composition for obtaining the antistatic layer 92 is applied onto the first surface 91A of the light-transmitting substrate 91 by a coating device such as a bar coater. A coating film of the composition for antistatic layer is formed.

<First antistatic layer composition>
The 1st composition for antistatic layers contains the polymeric compound and antistatic agent which become binder resin after hardening. The first antistatic layer composition may further contain an ultraviolet absorber, a spectral transmittance adjusting agent, an antifouling agent, inorganic particles, a leveling agent, a solvent, and a polymerization initiator, if necessary. Since the solvent and the polymerization initiator are the same as the solvent and the polymerization initiator described in the column of the functional layer composition, the description thereof is omitted here.

After forming the coating film of the first antistatic layer composition, the coating film is dried by heating at a temperature of 30 ° C. to 120 ° C. for 10 seconds to 120 seconds by various known methods, Evaporate.

After drying the coating film, the coating film is irradiated with ionizing radiation such as ultraviolet rays to cure the coating film. Thereby, the antistatic layer 92 is formed.

After forming the antistatic layer 92, a second antistatic layer composition for forming the antistatic layer 93 on the second surface 91 </ b> B of the light-transmitting substrate 91 by a coating device such as a bar coater. Is applied to form a coating film of the second antistatic layer composition.

<Second antistatic layer composition>
The second antistatic layer composition contains an antistatic agent and a solvent. In addition, the second antistatic layer may contain a binder resin. Since the solvent is the same as the solvent described in the column of the functional layer composition, the description is omitted here.

After forming the coating film of the second antistatic layer composition, the coating film is dried, for example, by heating at a temperature of 30 ° C. to 120 ° C. for 10 seconds to 120 seconds by various known methods, and the solvent is removed. Evaporate. Thereby, the antistatic layer 93 can be formed, and the optical film 90 shown in FIG. 10 is obtained.

<<< Other optical films >>>
The optical film may be the optical film 100 shown in FIG. The optical film 100 shown in FIG. 11 is also used in an image display device and can be folded.

The optical film 100 includes a light transmissive substrate 101, a hard coat layer 102 as a functional layer provided on the first surface 101A side of the light transmissive substrate 101, and a light transmissive substrate in the hard coat layer 102. A first antistatic layer 103 (hereinafter also simply referred to as an antistatic layer 103) provided on the side opposite to the 101 side and an antistatic layer 103 provided on the side opposite to the hard coat layer 102 side. The optical adjustment layer 104 and the second antistatic layer 105 (hereinafter simply referred to as “charging”) provided on the second surface 101B side opposite to the first surface 101A of the light-transmitting substrate 101. And may be referred to as a prevention layer 105). Since the physical properties and the like of the optical film 100 are the same as the physical properties and the like of the optical film 100, description thereof will be omitted here.

The surface 100A of the optical film 100 is the surface 104A of the optical adjustment layer 104. The back surface 100 </ b> B of the optical film 100 is a surface 105 </ b> A opposite to the surface of the antistatic layer 105 on the light transmissive substrate 101 side.

<< light transmissive substrate and hard coat layer >>
Since the light transmissive substrate 101 is the same as the light transmissive substrate 91, the description thereof is omitted here. Since the hard coat layer 102 is the same as the antistatic layer 92 except that it does not contain an antistatic agent, the description thereof is omitted here.

<< First Antistatic Layer and Second Antistatic Layer >>
Since the antistatic layers 103 and 105 are the same as the antistatic layer 93, description thereof is omitted here. That is, the antistatic layer 103 does not have a hard coat property.

<< Optical adjustment layer >>
The optical adjustment layer 104 is a layer for adjusting optical properties such as color and reflectance of the optical film 100. When a base material containing a polyimide resin is used as the light transmissive base material, the light transmissive base material exhibits a yellowish colour. Therefore, the optical adjustment layer 104 is a base material containing a polyimide resin as the light transmissive base material 91. It is particularly effective when used.

The film thickness of the optical adjustment layer 104 is preferably 30 nm or more and 500 nm or less. If the film thickness of the optical adjustment layer 104 is 30 nm or more, the optical characteristics (transmittance / reflectance / hue) can be adjusted, and if the film thickness is 500 nm or less, deterioration of processing can be suppressed. The film thickness of the optical adjustment layer 104 is measured by the same method as the film thickness of the functional layer 12. The upper limit of the optical adjustment layer 104 is more preferably 400 nm or less, and further preferably 200 nm or less.

When the thickness of the optical adjustment layer 104 is 30 nm or more and 300 nm or less, the refractive index of the optical adjustment layer 104 is preferably lower than the refractive index of the antistatic layer 103. With such a configuration, the optical adjustment layer 104 functions as a low refractive index layer, so that the reflectance of external light can be reduced. In this case, the refractive index of the optical adjustment layer 104 is preferably 1.38 or more and 1.60 or less. The refractive index of the optical adjustment layer 104 or the antistatic layer 103 is calculated from a reflection spectrum measured by a spectrophotometer and an optical model of a thin film using the Fresnel equation, with a constant refractive index in the wavelength region of 380 nm to 780 nm. It can obtain | require by fitting with the spectrum which carried out. Further, the refractive index of the optical adjustment layer 104 or the antistatic layer 103 may be obtained by forming an independent layer and then measuring it with an Abbe refractometer (product name “NAR-4T”, manufactured by Atago Co., Ltd.) or an ellipsometer. Good. Further, as a method of measuring the refractive index after the optical film 100 is obtained, the optical adjustment layer 104 and the antistatic layer 103 are scraped off with a cutter or the like to prepare a powder sample, and a method B (powder of JIS K7142: 2008) Becke line method (for Cargill reagent with a known refractive index), place the powdered sample on a glass slide, drop the reagent onto the sample, and remove the sample with the reagent. A method of observing the state by microscopic observation, and setting the refractive index of the reagent so that the bright line (Becke line) generated in the sample outline cannot be visually observed due to the difference in refractive index between the sample and the reagent. ) Can be used. The absolute value of the refractive index difference between the antistatic layer 103 and the optical adjustment layer 104 is preferably 0.005 or more. The upper limit of the absolute value of the refractive index difference between the antistatic layer 103 and the optical adjustment layer 104 is preferably 0.3 or less.

The optical adjustment layer 104 is made of an inorganic oxide such as silicon oxide or aluminum oxide. The optical adjustment layer 104 can be formed by, for example, a vapor deposition method such as a physical vapor deposition (PVD) method such as a sputtering method or an ion plating method, or a chemical vapor deposition (CVD) method.

The optical adjustment layer 104 may contain an antifouling agent. The antifouling agent is the same as the antifouling agent described in the column of the functional layer 12, and thus the description thereof is omitted here.

<<< Image display device >>>
The optical films 90 and 100 can be used by being incorporated in a foldable image display device. FIG. 12 is a schematic configuration diagram of an image display apparatus according to the present embodiment. As shown in FIG. 12, the image display device 110 mainly has a housing 81 in which a battery or the like is stored, a protective film 82, a display element 83, a circularly polarizing plate 84, and a touch sensor 85 toward the viewer. , And the optical film 90 are laminated in this order. Between the display element 83 and the circularly polarizing plate 84, between the circularly polarizing plate 84 and the touch sensor 85, and between the touch sensor 85 and the optical film 90, a light-transmitting adhesive layer 86 is disposed. These members are fixed to each other by the adhesive layer 86. In FIG. 12, members denoted by the same reference numerals as those in FIG. 9 are the same as the members shown in FIG.

The optical film 90 is disposed so that the antistatic layer 92 is closer to the viewer than the light-transmitting substrate 91. In the image display device 110, the surface 90A of the optical film 90 (the surface 92A of the antistatic layer 92) constitutes the surface 110A of the image display device 110.

According to this embodiment, the optical film 90 includes the antistatic layers 92 and 93 on both sides of the light transmissive substrate 91, and the optical film 100 has the antistatic layer 103 on both sides of the light transmissive substrate 101. , 105 are provided, it is possible to suppress dust and the like from adhering to the optical films 90, 100. Moreover, even if it peels off a protective film from the optical films 90 and 100 in the state which stuck the protective film (not shown) on both surfaces of the optical films 90 and 100, electrification of the optical films 90 and 100 can be suppressed. Thereby, the yield of the assembly process of an image display apparatus can be improved.

Since the optical adjustment layer is a thin film, the scratch resistance of the optical film can be improved without providing the optical adjustment layer. Since the optical film 90 does not include the optical adjustment layer on the antistatic layer 92, the optical film 90 has better scratch resistance than the optical film 100 including the optical adjustment layer 104 on the antistatic layer 103.

For a foldable optical film, the binder resin of the hard coat layer must be selected so that it can be folded. In addition, when an antistatic agent is kneaded into the hard coat layer as in the optical film 90, it is necessary to use an antistatic agent exhibiting good compatibility with the selected binder resin. There are fewer choices. On the other hand, in the optical film 100, since the antistatic layer 103 is a layer different from the hard coat layer 102, options for the antistatic agent can be expanded.

In order to describe the present invention in detail, examples will be described below, but the present invention is not limited to these descriptions. In addition, the following “100% solid content conversion value” is a value when the solid content in the solvent diluted product is 100%.

<Preparation of composition for optical adjustment layer>
First, each component was mix | blended so that it might become a composition shown below, and the composition for optical adjustment layers was obtained.
(Composition 1 for optical adjustment layer)
・ Urethane-modified polyester resin (product name “UR-3200”, manufactured by Toyobo Co., Ltd.): 85 parts by mass (100% solid content conversion value)
Zirconium oxide (average particle size 20 nm, manufactured by CIK Nanotech): 15 parts by mass (converted to 100% solid content)
・ Methyl isobutyl ketone (MIBK): 170 parts by mass

(Composition 2 for optical adjustment layer)
・ Urethane-modified polyester resin (product name “UR-1700”, manufactured by Toyobo Co., Ltd.): 70 parts by mass (100% solid content conversion value)
Zirconium oxide (average particle diameter 20 nm, manufactured by CIK Nanotech): 30 parts by mass (100% solid content conversion value)
・ Methyl isobutyl ketone (MIBK): 170 parts by mass

(Composition 3 for optical adjustment layer)
Quaternary ammonium group salt-containing antistatic agent (product name “1SX-3000”, manufactured by Taisei Fine Chemical Co., Ltd.): 100 parts by mass (converted to 100% solid content)
Photopolymerization initiator (product name “Irg184”, manufactured by BASF Japan): 4 parts by mass Methyl isobutyl ketone (MIBK): 150 parts by mass

(Composition 4 for optical adjustment layers)
-Urethane-modified polyester resin (product name "UR-3200", manufactured by Toyobo Co., Ltd.): 70 parts by mass (100% solid content conversion value)
Zirconium oxide (average particle size 20 nm, manufactured by CIK Nanotech): 15 parts by mass (converted to 100% solid content)
Cobalt blue (average particle size 40 nm, manufactured by CIK Nanotech): 15 parts by mass (converted to 100% solid content)
・ Methyl isobutyl ketone (MIBK): 170 parts by mass

(Composition 5 for optical adjustment layer)
Polyolefin resin (product name “P-901”, manufactured by Mitsui Chemicals): 70 parts by mass (converted to 100% solid content)
Zirconium oxide (average particle diameter 20 nm, manufactured by CIK Nanotech): 30 parts by mass (100% solid content conversion value)
・ Methyl isobutyl ketone (MIBK): 170 parts by mass

<Preparation of composition for antistatic layer>
First, each component was mix | blended so that it might become the composition shown below, and the composition for antistatic layers was obtained.

(Antistatic layer composition 1)
A mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (product name “KAYARAD PET-30”, manufactured by Nippon Kayaku Co., Ltd.): 90 parts by mass. Antistatic polymer containing quaternary ammonium salt (product name “UV-ASHC-01”) ”, Nippon Kasei Co., Ltd.): 10 parts by mass / polymerization initiator (product name“ Irgacure (registered trademark) 184 ”, manufactured by BASF): 2 parts by mass

(Antistatic layer composition 2)
Quaternary ammonium salt-containing antistatic polymer (product name “UV-ASHC-01”, manufactured by Nippon Kasei Co., Ltd.): 100 parts by mass • Polymerization initiator (product name “Irgacure (registered trademark) 184”, manufactured by BASF): 0.5 parts by mass

<Composition for hard coat layer>
Each component was mix | blended so that it might become the composition shown below, and the composition for hard-coat layers was obtained.
(Composition 1 for hard coat layer)
・ Urethane resin (product name “U-6LPA”, Shin-Nakamura Chemical Co., Ltd.): 70 parts by mass ・ Urethane resin (product name “UV2750B”, manufactured by Nippon Synthetic Chemical Co., Ltd.): 20 parts by mass Salt-containing antistatic agent (product name “1SX-3000”, manufactured by Taisei Fine Chemical Co., Ltd.): 10 parts by mass (converted to 100% solid content)
Photopolymerization initiator (product name “Irg184”, manufactured by BASF): 4 parts by mass UV absorber (product name “TINUVIN477”, manufactured by BASF): 5 parts by mass (converted to 100% solid content)
Antifouling agent (product name “BYKUV3500”, manufactured by Big Chemie): 1.5 parts by mass (converted to 100% solid content)
・ Methyl isobutyl ketone (MIBK): 150 parts by mass

(Composition 2 for hard coat layer)
A mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (product name “KAYARAD PET-30”, manufactured by Nippon Kayaku Co., Ltd.): 100 parts by mass • polymerization initiator (product name “Irgacure (registered trademark) 184”, BASF Product: 2 parts by mass

<Preparation of resin layer composition>
Each component was mix | blended so that it might become the composition shown below, and the composition for resin layers was obtained.
(Composition 1 for resin layer)
・ Urethane acrylate (product name “UV3310B”, manufactured by Nippon Synthetic Chemical Co., Ltd., bifunctional): 85 parts by mass • Phenoxyethyl acrylate (product name “Biscoat # 192”, manufactured by Osaka Organic Chemical Industry Co., Ltd.): 5 parts by mass Mixture of erythritol acrylate, mono and dipentaerythritol acrylate, and polymentaerythritol acrylate (product name “Biscoat # 802”, manufactured by Osaka Organic Chemical Industry Co., Ltd.): 10 parts by mass / polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product) Name “Irgacure (registered trademark) 184” manufactured by BASF Japan Ltd.): 5 parts by mass / methyl isobutyl ketone: 10 parts by mass

(Composition 2 for resin layer)
-Urethane acrylate (product name "UV3310B", manufactured by Nippon Synthetic Chemical Co., Ltd., bifunctional): 85 parts by mass-Phenoxyethyl acrylate (product name "Biscoat # 192", manufactured by Osaka Organic Chemical Industry Co., Ltd.): 15 parts by mass Agent (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 5 parts by mass / methyl isobutyl ketone: 10 parts by mass

(Composition 3 for resin layer)
・ Urethane acrylate (product name “UV3310B”, manufactured by Nippon Synthetic Chemical Co., Ltd., bifunctional): 80 parts by mass ・ Phenoxyethyl acrylate (product name “Biscoat # 192”, manufactured by Osaka Organic Chemical Industry Co., Ltd.): 5 parts by mass Mixture of erythritol acrylate, mono and dipentaerythritol acrylate, and polymentaerythritol acrylate (product name “Biscoat # 802”, manufactured by Osaka Organic Chemical Industry Co., Ltd.): 10 parts by mass of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate Mixture (product name “KAYARAD DPHA”, manufactured by Nippon Kayaku Co., Ltd.): 5 parts by mass / polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184”, BASF Japan Manufactured): 5 parts by massMethyl isobutyl ketone: 10 parts by mass

(Composition 4 for resin layer)
・ Urethane acrylate (product name “UV3310B”, manufactured by Nippon Synthetic Chemical Co., Ltd., bifunctional): 95 parts by mass ・ Phenoxyethyl acrylate (product name “Biscoat # 192”, manufactured by Osaka Organic Chemical Industry Co., Ltd.): 5 parts by mass Agent (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan Ltd.): 5 parts by mass / methyl isobutyl ketone: 10 parts by mass

(Resin Layer Composition 5)
-Urethane acrylate (product name "UV3310B", manufactured by Nippon Synthetic Chemical Co., Ltd., bifunctional): 85 parts by mass-Mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (product name "KAYARAD DPHA", Nippon Kayaku Co., Ltd. 15 parts by mass / polymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184” manufactured by BASF Japan): 5 parts by mass / methyl isobutyl ketone: 10 parts by mass

<< Example A and Comparative Example A >>
<Example A1>
As a resin substrate, a polyimide substrate having a refractive index of 1.630 and a thickness of 30 μm (product name “Neoprim”, manufactured by Mitsubishi Gas Chemical Company) is prepared, and the first surface which is one surface of the polyimide substrate The composition 2 for optical adjustment layers was apply | coated with the bar coater, and the coating film was formed. Thereafter, the formed coating film was heated at 90 ° C. for 1 minute to evaporate the solvent in the coating film, thereby forming a second optical adjustment layer having a refractive index of 1.562 and a film thickness of 100 nm. After forming the second optical adjustment layer, the optical adjustment layer composition 1 was applied to the surface of the second optical adjustment layer with a bar coater to form a coating film. Thereafter, the formed coating film was heated at 90 ° C. for 1 minute to evaporate the solvent in the coating film, thereby forming a first optical adjustment layer having a refractive index of 1.544 and a film thickness of 100 nm. After forming the first optical adjustment layer, the hard coat layer composition 1 was applied to the surface of the first optical adjustment layer with a bar coater to form a coating film. Then, the solvent in the coating film is evaporated by heating the formed coating film at 70 ° C. for 1 minute, and ultraviolet rays are removed from the air using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb). The coating was cured by irradiation so that the integrated light amount was 200 mJ / cm ² to form a hard coat layer having a refractive index of 1.531 and a thickness of 10 μm. As a result, an optical film was obtained in which the first optical adjustment layer was adjacent to the hard coat layer and the second optical adjustment layer was adjacent to the polyimide base material. In addition, the surface of the optical film which concerns on Example A1 was the surface of the hard-coat layer, and the back surface was the 2nd surface on the opposite side to the 1st surface of a polyimide-type base material.

The refractive index of the hard coat layer and the optical adjustment layer is such that the hard coat layer composition and the optical adjustment layer composition are respectively coated on 50 μm thick PET without easy adhesion treatment, and cured to a thickness of 1 to 10 μm. Black vinyl tape with a width larger than the measurement spot area (for example, to prevent back-surface reflection) on the surface (back surface) where the hard coat layer composition or optical adjustment layer composition in PET was not applied. Yamato vinyl tape NO200-38-21 38 mm width) was applied, and the average reflectance at a wavelength of 380 to 780 nm was measured using a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation). It calculated | required based on the said Formula (2) using the average reflectance. In Examples A2 to A12 and Comparative Examples A1 and A2, the refractive index of each layer was measured in the same manner as in Example A1.

The film thickness of each layer was determined by photographing a cross section of the optical film using a scanning transmission electron microscope (STEM) (product name “S-4800”, manufactured by Hitachi High-Technologies Corporation). The film thickness was measured at 20 locations, and the arithmetic average value of the film thicknesses at the 20 locations was measured. A cross-sectional photograph of the optical film was taken as follows. First, a block in which an optical film cut out to 1 mm × 10 mm is embedded with an embedding resin is prepared, and a uniform section with no hole or the like is cut out from this block by a general section manufacturing method. It was. For the preparation of the sections, “Ultra Microtome EM UC7” (Leica Microsystems Co., Ltd.) or the like was used. And the uniform section | slice without this hole etc. was made into the measurement sample. Thereafter, a cross-sectional photograph of the measurement sample was taken using a scanning transmission electron microscope (STEM). When taking this cross-sectional photograph, STEM observation was performed with the detector set to “TE”, the acceleration voltage set to “30 kV”, and the emission current set to “10 μA”. The magnification was appropriately adjusted from 5000 times to 200,000 times while adjusting the focus and observing whether each layer could be distinguished. When taking a cross-sectional photograph, the aperture is set to “beam monitor aperture 3”, the objective lens aperture is set to “3”, and D. Was set to “8 mm”. Also in Examples A2 to A12 and Comparative Examples A1 and A2, the refractive index and film thickness of each layer were measured by the same method as in Example A1.

<Example A2>
In Example A2, except that a third optical adjustment layer having a refractive index of 1.536 and a film thickness of 100 nm was formed on the surface of the polyimide-based substrate opposite to the surface on the second optical adjustment layer side. In the same manner as in Example 1, an optical film was obtained. A 3rd optical adjustment layer apply | coats the composition 3 for optical adjustment layers with the bar coater on the 2nd surface in a polyimide-type base material, forms a coating film, 70 degreeC with respect to the formed coating film, The solvent in the coating film is evaporated by heating for 1 minute, and using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb), the total amount of light in the air is 100 mJ / cm ^2. It was formed by irradiating the film to cure the coating film. In addition, the surface of the optical film which concerns on Example A2 was the surface of the hard-coat layer, and the back surface was the surface of the 3rd optical adjustment layer.

<Example A3>
In Example A3, an optical film was obtained in the same manner as in Example A1, except that the thickness of the first optical adjustment layer was 200 nm.

<Example A4>
In Example A4, an optical film was obtained in the same manner as in Example A1, except that the thickness of the second optical adjustment layer was 200 nm.

<Example A5>
In Example A5, an optical film was obtained in the same manner as in Example A1, except that the optical adjustment layer composition 4 was used instead of the optical adjustment layer composition 1. In addition, the refractive index of the 1st optical adjustment layer formed using the composition 4 for optical adjustment layers was 1.547.

<Example A6>
In Example A6, an optical film was obtained in the same manner as in Example A1, except that the optical adjustment layer composition 5 was used instead of the optical adjustment layer composition 2. In addition, the refractive index of the 2nd optical adjustment layer formed using the composition 5 for optical adjustment layers was 1.563.

<Example A7>
In Example A7, an optical film was obtained in the same manner as in Example A1, except that the thickness of the hard coat layer was 20 μm.

<Example A8>
In Example A8, an optical film was obtained in the same manner as in Example A1, except that the thickness of the hard coat layer was 40 μm.

<Example A9>
In Example A9, a polyimide imide base material (product name “THD-30”, manufactured by Kolon Co., Ltd.) having a refractive index of 1.661 and a thickness of 30 μm was used instead of the polyimide base material. An optical film was obtained in the same manner as in Example A1.

<Example A10>
In Example A10, Example A1 and Example A1 were used except that a polyamide base material (product name “Aramid” manufactured by Toray Industries, Inc.) having a refractive index of 1.701 and a thickness of 30 μm was used instead of the polyimide base material. In the same manner, an optical film was obtained.

<Example A11>
In Example A11, Example A1 and Example A1 were used except that a polyester base material (product name “U403”, manufactured by Toray Industries, Inc.) having a refractive index of 1.654 and a thickness of 23 μm was used instead of the polyimide base material. In the same manner, an optical film was obtained.

<Example A12>
As a resin substrate, a polyimide substrate having a refractive index of 1.630 and a thickness of 30 μm (product name “Neoprim”, manufactured by Mitsubishi Gas Chemical Company) is prepared, and the first surface which is one surface of the polyimide substrate The composition 1 for optical adjustment layers was apply | coated with the bar coater, and the coating film was formed. Thereafter, the solvent in the coating film is evaporated by heating the formed coating film at 90 ° C. for 1 minute, and the first optical film having a refractive index of 1.544 and a film thickness of 100 nm adjacent to the polyimide base material is obtained. An adjustment layer was formed. After forming the first optical adjustment layer, the hard coat layer composition 1 was applied to the surface of the first optical adjustment layer with a bar coater to form a coating film. Thereafter, the formed coating film is heated at 90 ° C. for 1 minute to evaporate the solvent in the coating film, and ultraviolet rays are removed from the air using an ultraviolet irradiation device (light source H bulb manufactured by Fusion UV System Japan). The coating was cured by irradiation so that the integrated light amount was 200 mJ / cm ² to form a hard coat layer having a refractive index of 1.531 and a thickness of 10 μm. Thus, an optical film in which the first optical adjustment layer was adjacent to the hard coat layer and the polyimide base material was obtained. In addition, the surface of the optical film which concerns on Example A1 was the surface of the hard-coat layer, and the back surface was the 2nd surface on the opposite side to the 1st surface of a polyimide-type base material.

<Example A13>
In Example A13, a polyimide imide base material (product name “THD-30”, manufactured by Kolon Co., Ltd.) having a refractive index of 1.661 and a thickness of 30 μm was used instead of the polyimide base material. An optical film was obtained in the same manner as in Example A12.

<Example A14>
In Example 14, Example A12 was used except that a polyamide base material (product name “Aramid”, manufactured by Toray Industries, Inc.) having a refractive index of 1.701 and a thickness of 30 μm was used instead of the polyimide base material. In the same manner, an optical film was obtained.

<Example A15>
In Example A15, Example A12 and Example A12 were used except that a polyester base material (product name “U403”, manufactured by Toray Industries, Inc.) having a refractive index of 1.654 and a thickness of 23 μm was used instead of the polyimide base material. In the same manner, an optical film was obtained.

<Example A16>
In Example A16, the same procedure as in Example A12 was conducted, except that a resin layer was formed on the surface of the polyimide-based substrate opposite to the surface on the first optical adjustment layer side as follows. An optical film was obtained. When forming the resin layer, first, the resin layer composition 1 is applied to the surface of the polyimide base material opposite to the surface on the first optical adjustment layer side with a bar coater to form a coating film. did. And the solvent in a coating film is evaporated by heating at 70 degreeC with respect to the formed coating film for 1 minute, and ultraviolet rays are air-released using an ultraviolet irradiation device (Fusion UV System Japan company make, light source H bulb). integrated light quantity in the medium is irradiated so that the 1200 mJ / cm ² to cure the coating film to form a resin layer made of refractive index 1.504 and thickness 200μm urethane resins.

<Example A17>
In Example A17, an optical film was obtained in the same manner as in Example A16, except that the thickness of the resin layer was 50 μm.

<Example 18>
In Example A18, an optical film was obtained in the same manner as in Example A16, except that the thickness of the resin layer was 300 μm.

<Example A19>
In Example A19, an optical film was obtained in the same manner as in Example A16, except that the resin layer composition 2 was used instead of the resin layer composition 1. In addition, the refractive index of the resin layer formed using the composition 2 for resin layers was 1.509.

<Example A20>
In Example A20, an optical film was obtained in the same manner as in Example A16 except that the resin layer composition 3 was used instead of the resin layer composition 1. In addition, the refractive index of the resin layer formed using the composition 3 for resin layers was 1.507.

<Example A21>
In Example 21, an optical film was obtained in the same manner as in Example A20, except that the thickness of the resin layer was 50 μm.

<Example A22>
In Example A22, an optical film was obtained in the same manner as in Example A20, except that the thickness of the resin layer was 300 μm.

<Example A23>
In Example A23, except that the third optical adjustment layer having a refractive index of 1.536 and a film thickness of 100 nm was formed between the polyimide-based substrate and the resin layer, A film was obtained. Before the resin layer is formed, the third optical adjustment layer is formed by applying the optical adjustment layer composition 3 to the second surface of the polyimide base material with a bar coater to form a coating film. The film is heated at 70 ° C. for 1 minute to evaporate the solvent in the coating, and using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb), ultraviolet rays are accumulated in the air. Was formed by irradiating the film so as to be 100 mJ / cm ² and curing the coating film. After forming the third optical adjustment layer, the resin layer was formed on the surface of the third optical adjustment layer in the same manner as in Example A16. In addition, the surface of the optical film which concerns on Example A23 was the surface of the hard-coat layer, and the back surface was the surface of the resin layer.

<Example A24>
In Example A24, except that a resin layer made of a urethane-based resin having a refractive index of 1.504 and a film thickness of 200 μm is formed on the surface of the third optical adjustment layer opposite to the surface on the polyimide-based substrate side. Obtained an optical film in the same manner as in Example A2. The resin layer was formed on the surface of the third optical adjustment layer in the same manner as in Example A16.

<Comparative Example A1>
As a resin substrate, a polyimide substrate having a refractive index of 1.630 and a thickness of 30 μm (product name “Neoprim”, manufactured by Mitsubishi Gas Chemical Company) is prepared, and the first surface which is one surface of the polyimide substrate Then, the hard coat layer composition 1 was applied with a bar coater to form a coating film. Then, the solvent in the coating film is evaporated by heating the formed coating film at 70 ° C. for 1 minute, and ultraviolet rays are removed from the air using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb). An optical film in which a hard coat layer having a film thickness of 10 μm is formed by irradiating with an integrated light amount of 200 mJ / cm ² to cure the coating film and having a hard coat layer adjacent to the polyimide-based substrate. Obtained. In addition, the surface of the optical film which concerns on Comparative example A1 was the surface of the hard-coat layer, and the back surface was the surface on the opposite side to the 1st surface of a polyimide-type base material.

<Comparative Example A2>
In Comparative Example A2, an optical film was obtained in the same manner as Comparative Example A1, except that the thickness of the hard coat layer was 50 μm.

<Comparative Example A3>
In Comparative Example A3, an optical film was prepared in the same manner as in Comparative Example A1, except that a resin layer was formed on the surface of the polyimide-based substrate opposite to the surface on the hard coat layer side as follows. Got. When forming the resin layer, first, the resin layer composition 1 was applied to the surface of the polyimide-based substrate opposite to the surface on the hard coat layer side with a bar coater to form a coating film. And the solvent in a coating film is evaporated by heating at 70 degreeC with respect to the formed coating film for 1 minute, and ultraviolet rays are air-released using an ultraviolet irradiation device (Fusion UV System Japan company make, light source H bulb). The coating was cured by irradiating it so that the accumulated light amount was 1200 mJ / cm ² to form a resin layer made of a urethane resin having a refractive index of 1.504 and a film thickness of 30 μm.

<Comparative Example A4>
In Comparative Example A4, an optical film was obtained in the same manner as in Comparative Example A3, except that the thickness of the resin layer was 350 μm.

<Comparative Example A5>
In Comparative Example A5, an optical film was obtained in the same manner as in Comparative Example A3, except that a resin layer having a thickness of 200 μm was formed using the resin layer composition 4 instead of the resin layer composition 1. . In addition, the refractive index of the resin layer formed using the composition 4 for resin layers was 1.506.

<Comparative Example A6>
In Comparative Example A6, an optical film was obtained in the same manner as in Comparative Example A3, except that a resin layer having a thickness of 200 μm was formed using the resin layer composition 5 instead of the resin layer composition 1. . In addition, the refractive index of the resin layer formed using the composition 5 for resin layers was 1.509.

<Comparative Example A7>
In Comparative Example A7, an optical film was obtained in the same manner as in Example A1, except that the thickness of the first optical adjustment layer was 3 μm (3000 nm).

<Interference fringe evaluation>
In the optical films according to Examples A1 to A24 and Comparative Examples A1 to A7, it was evaluated whether interference fringes were observed. Specifically, a black acrylic plate for preventing back-surface reflection is attached to the back surface of the optical film via a transparent adhesive, and each optical film is irradiated with light from the surface side of the optical film, and interference fringes are confirmed. It was observed visually. A three-wavelength tube fluorescent lamp was used as the light source. The occurrence of interference fringes was evaluated according to the following criteria.
(Double-circle): The interference fringe was not confirmed.
○: Some interference fringes were confirmed, but the level was not problematic in actual use.
X: Interference fringes were clearly confirmed.

<Continuous foldability and adhesion before durability test>
The optical films according to Examples A1 to A24 and Comparative Examples A1 to A7 were cut into a 30 mm × 100 mm rectangle to prepare a sample, and this sample was subjected to an endurance tester (product name “DLDMMLH-FS”, Yuasa System Equipment). (Manufactured by the company), the short side (30 mm) side of the sample is respectively fixed with a fixing part, as shown in FIG. 2 (C), attached so that the minimum distance between two opposing side parts is 10 mm, A continuous folding test (a test in which the hard coat layer is on the inside and the base material, the third optical adjustment layer or the resin layer is on the outside) is performed 10,000 times to fold the surface side of the sample 180 °, and the base material and the hard It was examined whether or not a float (gap) was generated between the coating layer and whether or not the bent portion was cracked or broken. The results of the continuous folding test were evaluated according to the following criteria, divided into continuous folding and adhesion. In addition, the sample used for the continuous folding test was cut from the optical film before performing the durability test described later.
(Continuous foldability)
(Double-circle): The crack or fracture | rupture did not arise in the bending part in the continuous folding test.
○: In the continuous folding test, cracks or breakage occurred slightly in the bent part, but it was at a level causing no problem in actual use.
X: In the continuous folding test, cracks or breaks were clearly generated in the bent portion.
(Adhesion)
A: No floating occurred between the base material and the hard coat layer in the continuous folding test.
○: In the continuous folding test, there was slight floating between the base material and the hard coat layer, but it was at a level where there was no problem in practical use.
X: In the continuous folding test, there was clearly floating between the base material and the hard coat layer.

<Continuous foldability and adhesion after durability test>
The optical film according to Examples A1 to A24 and Comparative Examples A1 to A7 was subjected to a durability test in which the optical film was left in an environment of 60 ° C. and 90% relative humidity for 12 hours. A sample is prepared by cutting into a 30 mm x 100 mm rectangle, and this sample is put on an endurance tester (product name “DLDMMLH-FS”, manufactured by Yuasa System Equipment Co., Ltd.) with the short side (30 mm) side of the sample at the fixed part. As shown in FIG. 2 (C), each sample is fixed and attached so that the minimum distance between two opposing sides is 10 mm, and the surface side of the sample is folded 180 ° (the hard coat layer is inside) And the base material, the third optical adjustment layer or the resin layer are folded so that the outer side is outside) 10,000 times, and a float (gap) is generated between the base material and the hard coat layer. In addition, it was examined whether cracks or breaks occurred in the bent portion. The results of the continuous folding test were evaluated according to the following criteria, divided into continuous folding and adhesion.
(Continuous foldability)
(Double-circle): The crack or fracture | rupture did not arise in the bending part in the continuous folding test.
○: In the continuous folding test, cracks or breakage occurred slightly in the bent part, but it was at a level causing no problem in actual use.
X: In the continuous folding test, cracks or breaks were clearly generated in the bent portion.
(Adhesion)
A: No floating occurred between the base material and the hard coat layer in the continuous folding test.
○: In the continuous folding test, there was slight floating between the base material and the hard coat layer, but it was at a level where there was no problem in practical use.
X: In the continuous folding test, there was clearly floating between the base material and the hard coat layer.

<Pencil hardness>
The pencil hardness on the surfaces of the optical films according to Examples A1 to A24 and Comparative Examples A1 to A7 was measured based on JIS K5600-5-4: 1999, respectively. In the pencil hardness test, an optical film cut out to a size of 30 mm × 100 mm is fixed on a glass plate with cello tape (registered trademark) manufactured by Nichiban Co., Ltd. so that there is no crease or wrinkle. Using a machine (product name “Pencil Scratch Coating Film Hardness Tester (Electric Type)”, manufactured by Toyo Seiki Seisakusho Co., Ltd.), a load of 750 g was applied to the pencil (product name “Uni”, manufactured by Mitsubishi Pencil Co., Ltd.). The pencil was moved at a moving speed of 1 mm / sec. The pencil hardness is the highest hardness at which the surface of the optical film was not damaged in the pencil hardness test. The pencil hardness is measured using a plurality of pencils having different hardnesses. The pencil hardness test is performed five times for each pencil, and the surface of the optical film is measured under a fluorescent lamp four times or more out of five times. In the case where no scratch is visually recognized on the surface of the optical film during the transmission observation, it is determined that the surface of the optical film is not scratched with the pencil having this hardness. In addition, as an optical film, the optical film before the said durability test was used.

<Peeling antistatic property>
A protective film was attached to the surface of the optical film according to Examples A1 to A24 and Comparative Examples A1 to A7, and the amount of peel charge when the protective film was peeled off from the surface of the optical film was measured. The size was evaluated. Specifically, a protective film with an adhesive layer (product name “SAT2038T-JSL”, manufactured by Sanei Kaken Co., Ltd.) is bonded to the surface of the optical film, and the optical film is placed under an environment of 23 ° C. and a relative humidity of 50%. The surface potential of the optical film when the protective film is peeled 180 ° from the surface at a peeling speed of 300 mm / min is 50 mm from the surface using an electrostatic meter (product name “KSD-0103”, manufactured by Kasuga Denki Co., Ltd.). The peel charge amount was measured from the distance. The peel charge amount was measured 10 times on the surface of the optical film, and the arithmetic average value of the peel charge amount measured 10 times. The evaluation criteria were as follows. In addition, as an optical film, the optical film before the said durability test was used.
○: The peel charge amount on the surface of the optical film was in the range of −10 kV to 10 kV.
X: The peeling charge amount on the surface of the optical film exceeded ± 10 kV.

<Saturation band voltage>
The saturation voltage on the surface of the optical films according to Examples A1 to A24 and Comparative Examples A1 to A7 was measured. Specifically, in an environment of 23 ° C. and 50% relative humidity, a voltage of 10 kV is applied from a distance of 50 mm from the surface of the optical film cut out to a size of 100 mm × 100 mm, and a charged charge attenuation measuring device (product) The saturation withstand voltage of the surface of the optical film was measured using the name “H-0110” (manufactured by SHISIDO electrostatic company). The saturation voltage was defined as an arithmetic average value obtained by measuring three times. In addition, as an optical film, the optical film before the said durability test was used.

<Surface resistance value>
In the optical films according to Examples A1 to A24 and Comparative Examples A1 to A7, the resistivity of the surface was measured using a resistivity meter (product name “HIRESTA-UP MCP-HT450”, manufactured by Mitsubishi Chemical Analytech Co., Ltd., probe: URS). The value was measured. The surface resistance value was obtained by randomly measuring 10 surface resistance values on the surface of the optical film cut out to a size of 50 mm × 50 mm, and calculating the arithmetic average value of the 10 measured surface resistance values. In addition, as an optical film, the optical film before the said durability test was used.

<Yellow Index (YI)>
In the optical films according to Examples A1 to A24 and Comparative Examples A1 to A7, the yellow index was measured. Specifically, first, an optical film cut into a size of 50 mm × 50 mm is optically placed in a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation, light source: tungsten lamp and deuterium lamp). The film was placed so that the substrate side was the light source side. The optical film had no defects (contamination of foreign matters), no cracks, no wrinkles, no dirt, and was held in a spectrophotometer in a flat state without curling. In this state, the transmittance for at least 5 points was measured between 1 nm and 1 nm before and after the wavelength of 300 nm to 780 nm under the following measurement conditions, and the average value was calculated. Then, the transmittance measurement data was read on a monitor connected to UV-2450, and YI was obtained by checking “YI” in the calculation item. In addition, as an optical film, the optical film before the said durability test was used.
(Measurement condition)
-Wavelength range: 300nm to 780nm
・ Scanning speed: High speed ・ Slit width: 2.0
・ Sampling interval: Auto (0.5 nm interval)
・ Lighting: C
Light source: D2 and WI
・ Field of view: 2 °
・ Light source switching wavelength: 360 nm
・ S / R switching: Standard ・ Detector: PM
・ Autozero: 550nm after baseline scan

<Total light transmittance measurement>
For the optical films according to Examples A1 to A24 and Comparative Examples A1 to A7, using a haze meter (product name “HM-150”, manufactured by Murakami Color Research Laboratory Co., Ltd.), all rays according to JIS K7361-1: 1997 The transmittance was measured. The total light transmittance is determined so that the hard coat layer side becomes the non-light source side without curling or wrinkling and without fingerprints or dust after being cut into a size of 50 mm × 100 mm. The optical average value of the values obtained by measuring three times for one optical film was obtained. In addition, as an optical film, the optical film before the said durability test was used.

<Measurement of G ′, G ″, and tan δ>
The shear storage modulus G ′, shear loss modulus G ″, and shear loss tangent tan δ of the optical films according to Examples A16 to A24 and Comparative Examples A3 to A6 were measured. Specifically, first, an optical film was punched into a 10 mm × 5 mm rectangular shape to obtain a sample. Then, two samples were prepared and attached to a measuring jig of a dynamic viscoelasticity measuring apparatus (product name “Rheogel-E4000”, manufactured by UBM Co., Ltd.). Specifically, the solid shearing jig includes a single metal solid shearing plate having a thickness of 1 mm and two L-shaped fittings arranged on both sides of the solid shearing plate. And one L-shaped metal fitting, and the other sample was sandwiched between the solid shear plate and the other L-shaped metal fitting. In this case, the sample was sandwiched so that the resin layer was on the solid shear plate side and the hard coat layer was on the L-shaped bracket side. Then, the L-shaped brackets were tightened with screws to fix the sample. Next, after attaching a tensile test chuck consisting of an upper chuck and a lower chuck to a dynamic viscoelasticity measuring device (product name “Rheogel-E4000”, manufactured by UBM Co., Ltd.), a solid is placed between the upper chuck and the lower chuck. A shearing jig was installed at a chuck distance of 20 mm. And set temperature was 25 degreeC and it heated up at 2 degree-C / min. In this state, while measuring the solid viscoelasticity of the solid at 25 ° C. while applying a longitudinal vibration with a strain of 1% and a frequency of 500 Hz to 1000 Hz to the two L-shaped brackets while fixing the solid shear plate, The shear storage modulus G ′, shear loss modulus G ″ and shear loss tangent tan δ of the film were measured. Here, the shear storage elastic modulus G ′, the shear loss elastic modulus G ″, and the shear loss tangent tan δ in the frequency range of 500 Hz to 1000 Hz in the optical film are the longitudinal vibrations of frequencies 500 Hz, 750 Hz, and 950 Hz applied to the L-shaped bracket. The shear storage elastic modulus G ′, the shear loss elastic modulus G ″ and the shear loss tangent tan δ of the optical film are measured at the respective frequencies, and the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ are measured. And the arithmetic average value of the shear loss tangent tan δ was obtained, and this measurement was repeated three times, and the three arithmetic average values obtained were further arithmetically averaged. In addition, as an optical film, the optical film before the said durability test was used.

<Impact resistance test>
The optical films according to Examples A16 to A24 and Comparative Examples A3 to A6 are directly placed on the surface of soda glass having a thickness of 0.7 mm so that the soda glass side is the resin layer side, and the weight is 100 g from a position of 30 cm in height. The impact resistance test A in which an iron ball having a diameter of 30 mm was dropped on the surface of the hard coat layer of the optical film was performed three times. Also, the optical films according to Examples A16 to A24 and Comparative Examples A3 to A6 were placed on a 0.7 mm thick soda glass so that the soda glass side would be the resin layer side. Placed through a transparent double-sided tape 8146-2 (manufactured by 3M), and dropped an iron ball having a weight of 100 g and a diameter of 30 mm from the position of 30 cm height onto the surface of the hard coat layer of the optical film B Was performed three times. In the impact resistance tests A and B, the position where the iron ball was dropped was changed each time. Then, in the optical film after the impact resistance test A, whether or not the surface of the hard coat layer had a dent was visually evaluated and whether or not the soda glass was cracked was evaluated. Moreover, in the optical film after the impact resistance test B, it was evaluated whether a dent was generated on the surface of the hard coat layer by visual observation. The evaluation results were as follows.
(Evaluation of dents on the surface of the hard coat layer)
◯: No dent was confirmed on the surface of the hard coat layer in both cases where the hard coat layer was observed from the front and oblique directions.
Δ: When the hard coat layer was observed from the front, no dent was observed on the surface of the hard coat layer, but when observed obliquely, a dent was confirmed on the surface of the hard coat layer.
X: A clear dent was observed on the surface of the hard coat layer both when the hard coat layer was observed from the front and obliquely.
(Soda glass crack evaluation)
A: Soda glass was not broken.
○: Soda glass was scratched but not broken.
Δ: Cracking occurred in the soda glass once or twice.
X: The soda glass was cracked three times.

The results are shown in Tables 1 to 3 below.

The following describes the results. In the optical films according to Comparative Examples A1 and A3 to A6, since the optical adjustment layer adjacent to the hard coat layer was not provided between the polyimide base material and the hard coat layer, the interference fringes were clearly observed. It was done. Moreover, in the optical film which concerns on comparative example A2, since the film thickness of the hard-coat layer was thick, generation | occurrence | production of the interference fringe was suppressed, but it was inferior to continuous foldability. In the optical film according to Comparative Example A7, the first optical adjustment layer adjacent to the hard coat layer was provided between the polyimide base material and the hard coat layer. Since the film thickness of was thick, it was inferior in continuous foldability. On the other hand, in the optical films according to Examples A1 to A24, the first optical adjustment layer adjacent to the hard coat layer was provided between the various substrates and the hard coat layer. Occurrence was suppressed and continuous folding was excellent. In the optical films according to Examples A1 to A24, since the first optical adjustment layer was thinner than the optical film according to Comparative Example A7, the interference fringes were suppressed as compared with the optical film according to Comparative Example A7. It had been. Further, as can be seen from the adhesion evaluation after the heat resistance test, the optical films according to Examples A1 to A11 were provided with the second optical adjustment layer, and thus were not provided with the second optical adjustment layer. The adhesion between the base material and the first optical adjustment layer was improved as compared with the optical films according to Examples A12 to A24.

In addition, in the optical films according to Examples A1 and A8, the short side (30 mm) side of the sample prepared by cutting into a rectangle of 30 mm × 100 mm is parallel so that the distance between the opposing side portions of the sample is 10 mm. A folding stationary test was performed in which the optical film was folded and fixed for 12 hours at 70 ° C. while being fixed to the fixed portions arranged. Then, by removing the fixing part from one side after the folding stationary test, the folded state is released, and the opening angle is an angle at which the optical film naturally opens after 30 minutes at room temperature (see FIG. 3B). Was measured, the opening angle of the optical film according to Example A1 was 100 ° or more, which was larger than the opening angle of the optical film according to Example A8. In addition, as an opening angle, the folding stationary test was carried out both when the hard coat layer was folded so that it was on the inside and when the hard coat layer was folded so that it was on the outside, and the one with the smaller angle was adopted.

Furthermore, in the optical film according to Comparative Example A3, since the resin layer is too thin, the shock cannot be absorbed, so that the soda glass is cracked in the impact resistance test A, and in the impact resistance test B. The amount of dents on the surface of the hard coat layer was large by following the plastic deformation of the adhesive sheet. In the optical film which concerns on comparative example A4, since the film thickness of the resin layer was too thick, it was inferior to foldability. In the optical film according to Comparative Example A5, since the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ are too small, the impact cannot be absorbed, and the soda glass is slightly cracked in the impact resistance test A. It was. In the optical film according to Comparative Example A6, since the shear storage elastic modulus G ′ is too large and the shear loss elastic modulus G ″ is too small, the impact cannot be absorbed, and the soda glass is cracked in the impact resistance test A. In some cases, it was inferior in foldability. On the other hand, in the optical films according to Examples A16 to A24, since the balance of the resin layer thickness, the shear storage elastic modulus G ′ and the shear loss elastic modulus G ″ is good, after the impact resistance tests A and B No dents on the surface of the hard coat layer were confirmed, and soda glass was not cracked.

In addition, using the optical films according to Examples A1 to A24 before and after the durability test, a sample having the same size as described above was prepared, and the minimum distance between two opposing sides of the sample was 3 mm. In the same way as above, the sample is attached to an endurance tester (product name “DLDMMLH-FS”, manufactured by Yuasa System Equipment Co., Ltd.), and the surface side of the sample is folded 180 ° (the hard coat layer is on the inside, the base Material, the third optical adjustment layer or the resin layer are folded so that the resin layer is on the inside) 10,000 times, continuous folding and adhesion before the durability test, and continuous folding and adhesion after the durability test Each of the optical films according to Examples A1 to A15 was evaluated by the same evaluation criteria as described above. Continuous folding and adhesion after successive folding and adhesion, as well as the durability test before sexual test was good.

Further, using the optical films according to Examples A1 to A24 and Comparative Examples A1 to A6 before and after the durability test, a sample having the same size as the above was prepared, and two opposite side portions of the sample were formed. Attach the sample to an endurance tester (product name “DLDMMLH-FS”, Yuasa System Equipment Co., Ltd.) in the same way as above so that the minimum gap is 30 mm, and then fold the sample backside 180 ° (hard coat) The test is performed 10,000 times so that the base layer, the third optical adjustment layer, or the resin layer is the inner side), and the continuous foldability and adhesion before the durability test and after the durability test. When the continuous foldability and the adhesiveness were evaluated according to the same evaluation criteria as described above, the same results as in Table 1 were obtained.

Further, when measured using the Martens hardness of the hard coat layer of the optical film according to Examples A1 to A24, the Martens hardness of the hard coat layer was 650 MPa. The Martens hardness was measured by pressing a Berkovich indenter (triangular pyramid) 500 nm at the center of the cross section of the hard coat layer under the following measurement conditions using a “TI950 TriboIndenter” manufactured by HYSITRON (Hydron), and maintaining the constant stress. After the relaxation, the maximum load after relaxation was measured, and the maximum load P _max (μN) and the indentation area A (nm ² ) having a depth of 500 nm were used, and P _max / A Calculated. The Martens hardness was an arithmetic average value of values obtained by measuring 10 locations.
(Measurement condition)
・ Loading speed: 10 nm / second ・ Retention time: 5 seconds ・ Load unloading speed: 10 nm / second ・ Measurement temperature: 25 ° C.

A quaternary ammonium group salt-containing antistatic agent (product name “1SX-3000”, manufactured by Taisei Fine Chemical Co., Ltd.) is formed on the surface opposite to the surface on the first optical adjustment layer side in the polyimide-based substrate according to Example A1. ) A composition for an antistatic layer containing 100 parts by mass (converted to a solid content of 100%), 4 parts by mass of a photopolymerization initiator (product name “Irg184”, manufactured by BASF Japan Ltd.) and 150 parts by mass of a solvent (MIBK) is applied. Then, the antistatic layer composition was applied with a bar coater to form a coating film. And the solvent in a coating film was evaporated by heating at 70 degreeC with respect to the formed coating film for 1 minute, the antistatic layer with a film thickness of 100 nm was formed, and the optical film was obtained. The surface of this optical film was the surface of the hard coat layer, and the back surface was the surface of the antistatic layer. And when the protective film was bonded to the front and back surfaces of this optical film, and the peel charge amount when the protective film was peeled off from the front and back surfaces of the optical film was measured, the peel charge amount on the front and back surfaces of the optical film was measured. Were in the range of −10 kV to 10 kV, respectively.

<< Example B and Comparative Example B >>
<Example B1>
Prepare a polyimide substrate (product name “Neoprim”, manufactured by Mitsubishi Gas Chemical Co., Inc.) with a thickness of 50 μm as a light-transmitting substrate, and charge it with a bar coater on the first surface, which is one surface of the polyimide substrate. The composition 1 for prevention layers was apply | coated and the coating film was formed. Then, the solvent in the coating film is evaporated by heating the formed coating film at 70 ° C. for 1 minute, and ultraviolet rays are removed from the air using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb). The coating film was cured by irradiation so that the accumulated light amount was 200 mJ / cm ² to form a first antistatic layer having a film thickness of 20 μm as an antistatic hard coat layer. Next, the antistatic layer composition 2 was applied to the second surface of the polyimide base material opposite to the first surface with a bar coater to form a coating film. By heating the formed coating film at 70 ° C. for 1 minute, the solvent in the coating film is evaporated to form a second antistatic layer having a film thickness of 100 nm, and antistatic is applied to both surfaces of the polyimide base material. An optical film having a layer was formed. The surface of the optical film according to Example B1 was the surface of the first antistatic layer, and the back surface was the surface of the second antistatic layer. The antistatic layer thickness was measured by taking a cross section of the antistatic layer using a scanning electron microscope (SEM) and measuring the thickness of the antistatic layer at 20 locations in the cross section image. It was set as the arithmetic average value of the film thickness of the location. In Examples B2 and B3 and Comparative Examples B1 to B3, the film thickness of the antistatic layer was measured by the same method as in Example B1.

<Example B2>
In Example B2, an optical film was obtained in the same manner as in Example B1, except that the thickness of the second antistatic layer was 10 μm. In addition, the surface of the optical film which concerns on Example B2 was the surface of the 1st antistatic layer, and the back surface was the surface of the 2nd antistatic layer.

<Example B3>
Prepare a polyimide substrate with a thickness of 50 μm (product name “Neoprim”, manufactured by Mitsubishi Gas Chemical Company) as a light-transmitting substrate, and harden it with a bar coater on the first surface, which is one surface of the polyimide substrate. The coating layer composition 2 was applied to form a coating film. Then, the solvent in the coating film is evaporated by heating the formed coating film at 70 ° C. for 1 minute, and ultraviolet rays are removed from the air using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb). The coating was cured by irradiating it so that the accumulated light amount was 200 mJ / cm ² to form a hard coat layer having a thickness of 20 μm. Next, the antistatic layer composition 2 was applied to the surface of the hard coat layer with a bar coater to form a coating film. The solvent in the coating film was evaporated by heating the formed coating film at 70 ° C. for 1 minute to form a first antistatic layer having a thickness of 80 nm. Thereafter, in the high frequency sputtering apparatus, a high frequency power having a frequency of 13.56 MHz and a power of 5 kW is applied to the electrode to cause discharge in the chamber, and the film thickness is 100 nm on the surface of the first antistatic layer. And the silica vapor deposition layer as an optical adjustment layer whose refractive index is 1.46 was formed. Thereafter, the antistatic layer composition 2 was applied to the second surface of the polyimide substrate opposite to the first surface with a bar coater to form a coating film. The formed coating film is heated at 70 ° C. for 1 minute to evaporate the solvent in the coating film, thereby forming a second antistatic layer having a thickness of 80 nm. An optical film provided with a prevention layer was formed. In addition, the surface of the optical film which concerns on Example B3 was the surface of the silica vapor deposition layer, and the back surface was the surface of the 2nd antistatic layer.

<Comparative Example B1>
Prepare a polyimide substrate with a thickness of 50 μm (product name “Neoprim”, manufactured by Mitsubishi Gas Chemical Company) as a light-transmitting substrate, and harden it with a bar coater on the first surface, which is one surface of the polyimide substrate. The coating layer composition 2 was applied to form a coating film. Then, the solvent in the coating film is evaporated by heating the formed coating film at 70 ° C. for 1 minute, and ultraviolet rays are removed from the air using an ultraviolet irradiation device (Fusion UV System Japan, light source H bulb). The coating film was cured by irradiation so that the integrated light amount was 200 mJ / cm ² to form a hard coat layer having a thickness of 20 μm, and an optical film was obtained. In addition, the surface of the optical film which concerns on comparative example B1 was the surface of the hard-coat layer, and the back surface was the surface on the opposite side to the 1st surface which is one surface of a polyimide base material.

<Comparative Example B2>
In Comparative Example B2, an optical film was obtained in the same manner as in Example B1, except that the second antistatic layer was not formed. In addition, the surface of the optical film which concerns on Comparative Example B2 was the surface of the 1st antistatic layer, and the back surface was the surface on the opposite side to the 1st surface of a polyimide base material.

<Comparative Example B3>
In Comparative Example B3, an optical film was obtained in the same manner as in Example B3, except that the second antistatic layer and the silica deposited layer were not formed. In addition, the surface of the optical film which concerns on comparative example B3 was the surface of the 1st antistatic layer, and the back surface was the surface on the opposite side to the 1st surface of a polyimide base material.

<Peeling antistatic property>
A protective film was bonded to the front and back surfaces of the optical films according to Examples B1 to B3 and Comparative Examples B1 to B3, and the amount of peel charge when the protective film was peeled off from the front and back surfaces of the optical film was measured. The magnitude of the peel charge amount was evaluated. Specifically, a protective film with an adhesive layer (product name “Sanitect Series”, manufactured by Sanei Kaken Co., Ltd.) is bonded to the front and back surfaces of the optical film, and the optical film is used in an environment of 23 ° C. and 50% relative humidity. Electrostatic potential measuring device (product name “KSD-0103”, manufactured by Kasuga Denki Co., Ltd.) when the protective film was peeled 180 ° from the front and back surfaces of the film at a peeling rate of 10 mm / sec. Was measured from a distance of 50 mm from the front surface and the back surface, and the peel charge amount was measured. The peel charge amount was measured 10 times on both surfaces of the optical film, and the arithmetic average value of the peel charge amount measured 10 times. The evaluation criteria were as follows.
A: The peel charge amounts on the front and back surfaces of the optical film were both in the range of 0 kV to 5 kV.
X: Either the peeling charge amount on the front surface or the back surface of the optical film exceeded 5 kV.

<Surface resistance value>
In the optical films according to Examples B1 to B3 and Comparative Examples B1 to B3, the surface resistance values of the front and back surfaces were measured under the same measurement conditions as in Example A.

<Continuous foldability>
Samples produced by cutting the optical films according to Examples B1 to B3 and Comparative Examples B1 to B3 into a rectangle of 30 mm × 100 mm were placed on an endurance tester (product name “DLDMMLH-FS”, manufactured by Yuasa System Equipment Co., Ltd.). A continuous folding test in which the short side (30 mm) side of the sample is fixed by a fixing portion, the minimum distance between two opposing side portions is 3 mm, and the surface side of the sample is folded 180 ° (first) The antistatic layer, the optical adjustment layer or the hard coat layer of the inner layer and the second antistatic layer or the polyimide base material are folded so that the outer side is the outer side) were tested 100,000 times, and the bent portion was cracked or broken. I checked for it. In addition, a new sample produced in the same manner as described above using the optical films according to Examples B1 to B3 and Comparative Examples B1 to B3 is attached to the durability tester in the same manner as described above, and the back side of the sample is folded by 180 °. The test (a test in which the first antistatic layer, the optical adjustment layer or the hard coat layer is on the outside and the second antistatic layer or the polyimide base material is on the inside) is performed 100,000 times, and the bent portion is cracked or It was examined whether breakage occurred. The results of the continuous folding test were evaluated according to the following criteria.
○: In any continuous folding test, no crack or break occurred in the bent portion.
X: In any one of the continuous folding tests, the bent portion was cracked or broken.

<Pencil hardness>
The surface of the optical film according to Examples B1 to B3 and Comparative Examples B1 to B3 was subjected to a pencil hardness test based on JIS K5600-5-4: 1999 and evaluated. In the pencil hardness test, a 2H pencil was used, and an optical film cut out to a size of 50 mm × 100 mm was fixed to the pencil with a Nichiban cello tape (registered trademark) so that there was no folding or wrinkle on the glass plate. The test was performed by moving the pencil at a speed of 1 mm / sec while applying a load of 1 kg. The pencil hardness test was performed 5 times, and the surface of the optical film after the pencil hardness test was observed under transmission under a fluorescent lamp to check how many times the surface was not scratched. The evaluation criteria were as follows.
A: No scratch was visually recognized on the surface of the 2H pencil.
X: In 2H pencil, scratches were visually recognized on the surface.

<Saturation band voltage>
The saturation voltage on the front and back surfaces of the optical films according to Examples B1 to B3 and Comparative Examples B1 to B3 was measured under the same measurement conditions as in Example A.

<Yellow Index (YI)>
In the optical films according to Examples B1 to B3 and Comparative Examples B1 to B3, the yellow index was measured and evaluated under the same conditions as in Example A. The evaluation criteria were as follows.
A: YI was less than 1.5.
○: YI was 1.5 or more and less than 10.0.
(Triangle | delta): YI was 10.0-15.0.
X: YI exceeded 15.0.

<Visual reflectance>
In the optical films according to Examples B1 to B3 and Comparative Examples B1 to B3, the luminous reflectance of light having a wavelength of 380 nm to 780 nm was measured and evaluated. The luminous reflectance was measured on the surface side of an optical film cut out to a size of 5 cm × 10 cm using a spectrophotometer (product name “UV-2450”, manufactured by Shimadzu Corporation, light source: tungsten lamp and deuterium lamp). The light was irradiated with light having a wavelength of 380 nm to 780 nm and measured from light having a wavelength of 380 nm to 780 nm reflected from the optical film. Specifically, light with an incident angle of 5 degrees is irradiated from the surface side of each optical film, and the reflected light in the specular direction reflected by each optical film is received, and the reflectance in the wavelength range of 380 nm to 780 nm is obtained. Then, the luminous reflectance was calculated by software (for example, software built in UV-2450) that converts the brightness as perceived by human eyes. The evaluation criteria were as follows.
A: The luminous reflectance was 3% or less.
○: Luminous reflectance exceeded 3% and was 10% or less.
(Triangle | delta): The luminous reflectance exceeded 10% and was 15% or less.
X: Luminous reflectance exceeded 15%.

The results are shown in Table 4 below.

The following describes the results. In the optical films according to Comparative Examples B1 to B3, since the first antistatic layer and / or the second antistatic layer was not provided, the antistatic properties when peeled off the protective film were poor. . In contrast, in the optical films according to Examples B1 to B3, since the first antistatic layer and the second antistatic layer were provided, the antistatic properties when peeled off the protective film were excellent. .

In addition, in the optical films according to Examples B1 to B3, the short side (30 mm) side of the sample manufactured by cutting into a rectangle of 30 mm × 100 mm is parallel so that the interval between the opposing side portions of the sample is 3 mm. A folding stationary test was performed in which the optical film was folded and fixed at 70 ° C. for 240 hours while being fixed to the respective fixed portions. And after releasing a fixed part from one side part after a folding stationary test, when a folding state was open | released and the opening angle which is an angle which an optical film opens naturally after 30 minutes at room temperature was measured, Example B2 The opening angle of the optical film according to the present invention was 100 ° or more, which was larger than the opening angle of the optical film according to Examples B1 and B3. In addition, as the opening angle, the folding static test was performed both when the first antistatic layer was folded so that it was on the inside and when the first antistatic layer was folded so that the angle was The smaller one was adopted.

Moreover, when the Martens hardness of the 1st antistatic layer of the optical film which concerns on Example B1, B2 and the hard-coat layer of the optical film which concerns on 3rd was measured on the conditions similar to Example A, it was 1st The Martens hardness of the antistatic layer and the hard coat layer was 612 MPa.

10, 30, 40, 50, 60, 90, 100 ... Optical films 10A, 12A, 30A, 40A, 50A, 60A, 90A, 92A, 100A, 104A ... Surface 11 ... Resin substrate 11A ... First surface 11B ... Second surface 12 ... functional layer 13 ... first optical adjustment layer 14 ... second optical adjustment layer 15 ... third optical adjustment layer 80, 110 ... image display device 83 ... display elements 92, 103 ... first Antistatic layers 93, 105 ... second antistatic layer 102 ... hard coat layer 104 ... optical adjustment layer

Claims (21)

A foldable optical film used in an image display device,
A resin base material composed of one or more resins selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyamide resin, and a polyester resin;
A functional layer provided on the first surface side of the resin substrate;
A first optical adjustment layer provided between the resin substrate and the functional layer and adjacent to the functional layer;
An optical film comprising: The optical film according to claim 1, wherein a refractive index of the first optical adjustment layer is lower than a refractive index of the resin base material and higher than a refractive index of the functional layer. The optical film according to claim 1, wherein the film thickness of the first optical adjustment layer is 30 nm or more and 200 nm or less. The optical film according to claim 1, further comprising a second optical adjustment layer provided between the resin base material and the first optical adjustment layer and adjacent to the resin base material. The optical film according to claim 1, wherein the film thickness of the second optical adjustment layer is 30 nm or more and 200 nm or less. The resin base material further includes a resin layer having a film thickness of 50 μm or more and 300 μm or less provided on the second surface side opposite to the first surface side, and the optical film has a temperature of 25 ° C. and 500 Hz to 1000 Hz. The shear storage elastic modulus G ′ in the frequency range is more than 200 MPa and not more than 1200 MPa, and the optical film has a shear loss elastic modulus G ″ in the frequency range of 25 ° C. and 500 Hz to 1000 Hz, but not less than 3 MPa and not more than 150 MPa. The optical film according to claim 1, wherein: The optical film according to claim 1, further comprising a third optical adjustment layer provided on a second surface opposite to the first surface of the resin base material. The optical film according to claim 6, further comprising a third optical adjustment layer provided between the resin base material and the resin layer and adjacent to the resin base material. The optical film according to claim 1, wherein a yellow index of the optical film is 15 or less. In the optical film, when the test is repeated 10,000 times so that the functional layer is on the inner side and the interval between opposing sides of the optical film is 10 mm, no cracking or breakage occurs. Item 5. The optical film according to Item 1. In the optical film, when the test is repeated 10,000 times so that the functional layer is on the outer side and the interval between opposing sides of the optical film is 30 mm, no cracking or breakage occurs. Item 5. The optical film according to Item 1. A foldable optical film used in an image display device,
A light transmissive substrate;
A first antistatic layer provided on the first surface side of the light transmissive substrate;
A second antistatic layer provided on a second surface side opposite to the first surface of the light transmissive substrate;
An optical film comprising: The optical film according to claim 12, wherein a yellow index of the optical film is 15 or less. The optical film according to claim 12, wherein the first antistatic layer is an antistatic hard coat layer. The optical film according to claim 12, further comprising an optical adjustment layer provided on a side of the first antistatic layer opposite to the light transmissive substrate side. The optical film according to claim 12, further comprising a hard coat layer provided between the light transmissive substrate and the first antistatic layer. The absolute value of the saturation voltage on the surface of the optical film when a voltage of 10 kV is applied from a distance of 50 mm from the surface of the optical film in an environment of 23 ° C. and a relative humidity of 50% exceeds 0 kV. Item 13. The optical film according to Item 12. The optical film according to claim 12, wherein the optical film is not cracked or broken when a test of folding 180 ° so that a distance between opposing sides of the optical film is 3 mm is repeated 100,000 times. The optical film according to claim 12, wherein the light-transmitting substrate is a substrate made of a polyimide resin, a polyamide resin, or a mixture thereof. A display element;
The optical film according to claim 1 or 12, which is disposed closer to the viewer than the display element;
A foldable image display device comprising: The image display device according to claim 20, wherein the display element is an organic light emitting diode element.

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