JP2000338327A - Laminated body with improved polarization characteristics and surface protective film therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate which is free of foreign matter, etc., at a surface protective film for protecting the surface not provided with a tacky adhesive layer for a polarizing plate, phase difference plate or visual field angle magnifying film, has excellent polarization characteristics and facilitates visual foreign matter inspection and the surface protective film therefor. SOLUTION: The laminate is so positioned that the direction of the orientation crystal main axis of a biaxially oriented polyester film of the surface protective film and the direction of the orientation axis of the polarizing plate, the phase difference plate or the visual field angle magnifying film are substantially aligned or attain 90 deg.. The biaxially oriented polyester film is >=1200 nm in the retardation value R expressed by equation R=Δn.d. In the equation, Δn denotes the double refractive index of the film and (d) denotes the thickness (nm) of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate having improved polarization characteristics and a surface protective film therefor, and more particularly to a laminate having excellent polarization characteristics and easy visual inspection of foreign substances and a surface protective film therefor. .

[0002]

2. Description of the Related Art In recent years, CRTs have been used as display products.
Next to displays, liquid crystal displays are used in products such as notebook computers, word processors and car navigation systems, and their share is steadily increasing. Liquid crystal displays can be made lighter and thinner than CRT displays, and have the advantages of low power consumption. It spreads rapidly, and its growth is also large.

[0003] However, the manufacturing process of the liquid crystal display is very complicated, and it is reluctant to mix foreign substances and the like. For this reason, protective films are used as surface protection for optical components and optical laminates such as polarizing plates, retardation plates and viewing angle widening films which are components. A polarizing plate, a retardation plate or a viewing angle widening film is provided with an adhesive layer on one surface, and a release film as exemplified in JP-A-7-101 026 is provided as a protection thereof. However, it is necessary and important that the other surface be protected from the attachment of foreign substances such as dust until the liquid crystal display is manufactured. Therefore, it is necessary to bond a surface protective film provided with a weak adhesive layer.

[0004] However, the manufacturing cost of the liquid crystal display is still high, and one of the points in the future is how low-priced display can be manufactured. For example, a large screen TFT system or STN
In the production of liquid crystal displays of the system and the like, the incidence of defective products is still high, and there is an urgent need to rationalize costs by improving the yield. Among them, a polarizing plate, a retardation plate, or a viewing angle widening film are necessary and important components for changing the brightness and hue of transmitted light of a liquid crystal display, and maintaining quality during production is an important issue. At present, the standards for process inspection, quality inspection, and shipping inspection are becoming stricter.

[0005] A polarizing plate, a retardation plate or a viewing angle widening film is provided with an adhesive layer on one of the surfaces, and is cut and cut into various sizes from a roll state in which a release film is laminated on the adhesive layer. Although it is provided for liquid crystal displays, one of the important items in the inspection at the time of its manufacture is the inspection for contamination and adhesion of foreign matter. In particular, the foreign substance inspection in the final inspection step is a visual inspection by a human by the crossed Nicols method (a method in which two polarizing plates are stretched perpendicular to each other and a release film is inserted between the polarizing plates and observed with transmitted light). For large screens, accurate visual inspection may be hindered due to the optical anisotropy of the biaxially oriented polyester film that is the base of the release film on the adhesive layer,
For this reason, there is a problem in that the oversight of foreign matter is generated at a considerable frequency, and foreign matter is detected on the liquid crystal display of the final product, and the yield may be reduced. To solve this problem, the use of a release film as exemplified in the above-mentioned Japanese Patent Application Laid-Open No. 7-101026 has made it possible to improve the testability.

However, a large-screen liquid crystal display such as a TFT system or an STN system is required to have a high-definition image quality higher than that of a CRT. Become. The inspection shall be carried out with a polarizing plate, a retardation plate or a viewing angle widening film attached to a release film on the adhesive layer side and a surface protective film with a weak adhesive layer on the other side. There are many. Therefore, the surface protection film also needs to be as easy to inspect as the release film. The surface protection film is
After the manufacture and assembly of the liquid crystal display or the like is completed or during actual use, it is removed by peeling.

Conventionally, a transparent olefin-based film such as polyethylene or polypropylene has been used as a base material for a surface protective film. However, olefin-based films and the like have poor transparency and many gels such as fish eyes, so that it has been difficult to accurately perform a defect inspection of a polarizing plate, a retardation plate, or a viewing angle widening film.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to protect a surface of a polarizing plate, a retardation plate or a viewing angle widening film on which an adhesive layer is not provided. It is an object of the present invention to provide a laminate which is free from foreign matter and the like, has excellent polarization characteristics, and is easy to visually inspect for foreign matter, and a surface protective film therefor.

[0009]

The present invention comprises the following two constitutions. 1. A surface on which an adhesive layer is provided on one surface of a polarizing plate, a retardation plate or a viewing angle widening film, and the surface opposite to the adhesive layer is provided with an adhesive layer on one surface using a biaxially oriented polyester film as a base material. A laminate in which a protective film is laminated via the pressure-sensitive adhesive layer, wherein (1) the laminate has a direction of an oriented crystal main axis of a biaxially oriented polyester film in the surface protective film, a polarizing plate, a retardation plate or The orientation axes of the viewing angle widening film are substantially the same, or 90
°, and (2) the biaxially oriented polyester film in the surface protective film has an improved polarizing property, wherein the retardation value (R) represented by the following formula is 1200 nm or more. Laminate. R = Δn · d (where, Δn is the birefringence of the film, that is, the refractive index (ny) in the longitudinal (winding) direction of the film and the lateral (vertical) direction in visible light (wavelength λ = 589 nm). The difference (nx-ny) from the refractive index (nx), and d is the thickness of the film (n
m). )

[0010] 2. A surface protection film comprising a biaxially oriented polyester film as a base material and an adhesive layer provided on one surface thereof, wherein the biaxially oriented polyester film has a retardation value (R) represented by the following formula of 1200 nm.
A protective film for inspecting a polarizing plate, a retardation plate or a viewing angle widening film, which is characterized by the above. R = Δn · d (where, Δn is the birefringence of the film, that is, the refractive index (ny) in the longitudinal (winding) direction of the film and the lateral (vertical) direction in visible light (wavelength λ = 589 nm). The difference (nx-ny) from the refractive index (nx), and d is the thickness of the film (n
m). Further, according to the present invention, the MOR value of the biaxially oriented polyester film as the base film measured by a microwave transmission type molecular orientation meter is preferably in a range of 1.3 or more and 1.8 or less.

Hereinafter, the present invention will be described in detail. First, the surface protective film constituting the laminate of the present invention will be described. The surface protective film of the present invention comprises at least a biaxially oriented polyester film as a substrate and an adhesive layer. Further, at least one of an antistatic agent and a release agent can be provided as a layer on the surface opposite to the adhesive layer.

[Plastic Film] In the present invention, a biaxially oriented polyester film is used as a base material of the surface protective film. The polyester constituting such a biaxially oriented polyester film is preferably a crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component, for example, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene- 2,6-naphthalenedicarboxylate and the like can be mentioned. Further, a copolymer in which a part of these is substituted by another component, or a mixture with polyalkylene glycol or another resin may be used. As the biaxially oriented polyester film, a biaxially oriented polyester film, and more preferably a biaxially oriented polyethylene-2,6-naphthalenedicarboxylate film. Further, in the configuration, a multilayer structure having an arbitrary number of layers by co-extrusion may be adopted. The biaxially oriented polyester film needs to have a retardation value (R) defined by the following formula of 1200 nm or more. R = Δn · d (where, Δn is the birefringence of the film, that is, the refractive index (ny) in the longitudinal (winding) direction of the film and the lateral (vertical) direction in visible light (wavelength λ = 589 nm). The difference (nx-ny) from the refractive index (nx), and d is the thickness of the film (n
m). Preferably, the film thickness is between 25 and 50 μm,
It is a biaxially oriented polyester film having a retardation value (R) of 1300 nm or more.

Since the biaxially oriented polyester film is a birefringent material, when light enters, the incident light propagates as two linearly polarized lights whose vibration planes are orthogonal to each other. The difference between these two linearly polarized lights (ordinary ray and extraordinary ray) is defined as a phase difference (retardation: R), and this phase difference poses a problem as a color and as an interference color in a polarizing plate inspection process. As already shown in Japanese Patent Application Laid-Open No. 7-101026, in the crossed Nicols, according to the interference color chart (polarization microscope) of the modified Michel-Levy, a dark field (black) is found in the low retardation region. In proportion to the retardation, the interference color changes from yellow → red → purple → blue → green, then returns to yellow again and repeats this cycle. However, when the retardation (R) exceeds 1200 nm, the density of the interference color sharply decreases, and when the retardation (R) is sufficiently large, the interference color becomes extremely small and does not hinder visual inspection.

Next, the biaxially oriented polyester film was measured for MOR (Max.
(Imum Oriented Ratio) value is preferably in a range of 1.3 or more and 1.8 or less, more preferably in a range of 1.35 or more and 1.75 or less. The MOR value is a ratio (maximum value / minimum value) of the maximum value and the minimum value of the transmitted microwave intensity measured by the transmission type molecular orientation meter. This MOR value is determined by film winding (longitudinal
The difference between the stretching ratio in the (longitudinal) direction and the vertical (horizontal) direction is small, that is, the more the film is balanced, the smaller the difference.
The larger the difference, that is, the greater the stretching strength in one direction, the larger the difference. It is not preferable that the MOR value is too small or too large in the above range. Further, it is preferable that the MOR value does not vary at each position of the film. Specifically, the difference between the minimum value and the maximum value of the MOR value is 0.2%.
The following is preferred. Here, the difference between the minimum value and the maximum value of the MOR value is 3% in the film width direction, that is, 10%, 50% from one end of the straight line in the film width direction.
%, The difference between the minimum value and the maximum value of the MOR value measured at three places at a distance of 90%. This difference is, in particular, 0.15
The following is preferred.

In the biaxially oriented polyester film, the inclination (orientation angle, θ) of the main axis of the oriented crystal measured with a polarizing microscope with respect to the transverse (width) direction of the film is −20 ° ≦.
It is preferable that θ ≦ 20 °. Outside this range, the color of light interference becomes strong in the visual foreign matter inspection by the crossed Nicols method (orthogonal Nicols method), which is not preferable for the inspection.
Stretching conditions satisfying these conditions are to increase the stretching ratio in the transverse (width) direction during film formation, and to reduce the variation (bowing phenomenon) of the main orientation crystal axis in the film width direction, particularly in the width direction at the edge. Therefore, it is preferable that the main alignment axis be closer to the width direction of the film.

The above-mentioned polyester film is preferably a biaxially stretched film. The biaxially stretched film may be produced by a conventionally known method such as a sequential biaxial stretching method or a simultaneous biaxial stretching method. Can be. Particularly preferred is a sequential biaxial stretching method, which can be performed by the following method. After the polyester polymer is sufficiently dried, it is extruded from a die (for example, a T-die, an I-die, etc.) onto a cooling drum by a melt extrusion method and quenched to obtain an unstretched film or a co-extruded unstretched film. The unstretched film is then produced in a longitudinal direction at a temperature of
At a temperature of 80 to 150 ° C., and at a temperature of 80 to 150 ° C., at least 3 times in the horizontal direction, and at a magnification of 0.5 times or more than that in the vertical direction.
As described above, the film can be produced by stretching at 0.7 or more, and heat-setting at a temperature of 170 to 260 ° C. for 1 to 100 seconds. The stretching ratio in the transverse direction is preferably 6 times or less. In addition, it is preferable to add an isotropic treatment means for reducing the bowing phenomenon at the front width of the film during the heat setting treatment after the biaxial stretching. In addition, it is preferable to use an electrostatic adhesion method during melt extrusion.

The thickness of the film is not particularly limited.
250 μm is preferred. Particularly, from the viewpoint of retardation, 25 to 50 μm is preferable.

The biaxially oriented polyester film has a lubricating agent such as calcium carbonate, alumina, kaolin, etc., in order to improve the slipperiness when the film is wound and the handling during processing such as application of an adhesive. And inorganic fine particles such as silica, titanium oxide, barium sulfate, and zeolite, and organic fine particles such as silicone resin, cross-linked polystyrene, and acrylic resin, and other additives such as a stabilizer and an ultraviolet absorber. , A flame retardant, an antistatic agent and the like. The timing of adding the fine particles and additives is not particularly limited as long as it is a stage before forming the polyester film. For example, it may be added at the polymerization stage or may be added at the time of film formation.

The biaxially oriented polyester film has a center line average roughness (Ra) of not less than 2 nm and not more than 500 nm.
The following is preferred. If the surface roughness is less than 2 nm, there is a possibility that the transferability such as slipping during processing may be impaired, and if the surface roughness is more than 500 nm, the transparency deteriorates and the testability deteriorates. When the adhesive layer is transferred from the release paper to the biaxially oriented polyester film by the method, there is a concern that the adhesive layer may not be uniformly adhered due to the unevenness of the biaxially oriented polyester film.

Further, in the biaxially oriented polyester film, foreign matter of 25 μm or more is present in a film (area: 310.8 cm ² ) having a side length of 210 mm and a side length of 148 mm orthogonal thereto. No, 5
It is preferable that the number of particles is 10 μm or more and less than 25 μm. When a foreign substance of 25 μm or more is present, voids or the like are generated during application or transfer of the adhesive, and the adhesive is removed or swells only in a portion larger than the size, so that a local area that can be visually confirmed. Appearance defects. Further, when there are more than 10 foreign substances having a size of 5 μm or more and less than 25 μm, although the size is hard to be visually confirmed, a defect may be noticeable due to the large size.

[Adhesive Layer] The surface protective film according to the second constitution of the present invention has a layer constitution in which the above-mentioned biaxially oriented polyester film is used as a base material and an adhesive layer is laminated on one surface thereof. The adhesive constituting the adhesive layer should be used not only indoors but also outdoors, and it is necessary to withstand various rays during inspection, especially UV rays. Acrylic adhesives are particularly preferred to prevent migration. The acrylic pressure-sensitive adhesive to be used is not particularly limited, but for example, the pressure-sensitive adhesive described below is preferable. The acrylic pressure-sensitive adhesive includes a solvent-based pressure-sensitive adhesive, an emulsion-based pressure-sensitive adhesive, and the like, and a solvent-based pressure-sensitive adhesive can be preferably used in terms of stability such as adhesion and adhesion to a substrate. As the acrylic solvent-based pressure-sensitive adhesive, one obtained by solution polymerization is used to satisfy various properties. As a raw material, a known material for solution polymerization of an acrylic pressure-sensitive adhesive can be used. For example, as a main monomer as a skeleton, acrylates such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and octyl acrylate; as comonomers to improve cohesion, vinyl acetate, acrylonitrile, styrene, and methyl methacrylate In order to further promote high cross-linking, and to impart a stable low adhesive strength, as a functional group-containing monomer, methacrylic acid, acrylic acid, itaconic acid, hydroxyethyl methacrylate, glycidyl methacrylate, and the like, and low tackiness and tackiness In order to achieve high cross-linking with an isocyanate-based curing agent in order to impart high cohesive strength, those containing a large number of hydroxyl groups are particularly preferable. The synthesis of the pressure-sensitive adhesive can be performed by a known method. For example, in the presence of an organic solvent such as ethyl acetate or toluene, the necessary raw materials are charged into a reaction furnace, and heated using a peroxide system such as benzoyl peroxide or an azobis system such as azobisisobutyronitrile as a catalyst. It can be polymerized below. As the curing agent for the pressure-sensitive adhesive, a general isocyanate-based curing agent or epoxy-based curing agent can be used particularly in the case of an acrylic solvent, but in order to obtain a uniform film, the fluidity of the pressure-sensitive adhesive over time and a high cross-linking state are required. As required, isocyanate-based curing agents are preferred. In particular, an aromatic type such as toluylene diisocyanate (TDI) is preferable in order to obtain a low and stable adhesive force over time and to form a harder adhesive layer. The pressure-sensitive adhesive may contain additives such as a stabilizer, an ultraviolet absorber, a flame retardant, and an antistatic agent.

The application of the pressure-sensitive adhesive solution to the biaxially oriented polyester film can be performed at any stage. Also,
When applying the coating solution to the biaxially oriented polyester film, if necessary, as a preliminary treatment to improve adhesion and coating properties, the surface can be treated with flame, corona discharge, plasma discharge, etc. Physical surface treatment of
Alternatively, during or after film formation, by applying a chemical surface treatment of applying an organic resin-based or inorganic resin-based paint, the adhesion between the pressure-sensitive adhesive and the biaxially oriented polyester film can be strengthened. . The thickness of the pressure-sensitive adhesive layer is preferably in the range of 1 to 500 μm, more preferably in the range of 2 to 50 μm. Since the adhesive strength depends on the thickness of the adhesive, if the thickness is less than 1 μm, in combination with uneven thickness of the biaxially oriented polyester film, partially, for example, insufficient contact with a mating substrate such as a polarizing plate becomes insufficient. , It is difficult to obtain the necessary adhesive strength. In addition, the thickness of the adhesive is 500 μm
If it is larger, the cost increases, and sufficient hardening does not proceed in processing, cohesive failure occurs between the adhesive layers when the adhesive is peeled off after being attached to a mating substrate such as a polarizing plate, and the adhesive remains. There is fear. As the method for applying the adhesive, any known method can be used, and examples thereof include a die coater method, a gravure roll coater method, a blade coater method, a spray coater method, an air knife coat method, a comma coater method, and a dip coat method. They are preferably mentioned, and can be used alone or in combination. The application of the pressure-sensitive adhesive to the biaxially oriented polyester film may be directly applied to the film by the above-described coating method. And the adhesive may be transferred. In order to prepare a surface protective film having a smoother surface of the adhesive layer, it is preferable to apply once to a release paper having a smoother surface and to transfer this to a biaxially oriented polyester film. The drying temperature at this time is preferably such that the residual solvent is as small as possible.
It is preferable to provide a drying time of 10 seconds to 5 minutes at a temperature of 150 ° C. When an isocyanate-based curing agent or the like is used, the reaction is not yet completed immediately after heating and drying, and curing is required to complete the reaction and obtain stable adhesive strength. Generally, when heated at room temperature for about one week or more, for example, at about 50 ° C., three days or more are preferable.
In the case of heating, if the temperature is too high, the flatness of the plastic film may be deteriorated.

[Antistatic Layer / Release Layer] In the surface protective film of the present invention, a polarizing plate is provided on the opposite side of the adhesive layer of the biaxially oriented polyester film when the surface protective layer is peeled off.
In order to prevent the FT from being destroyed due to peeling electrification, and to prevent dust or adhesive from being adhered when one side of the surface protection film is cut or to easily remove the dust,
A layer containing an antistatic agent and / or a release agent can be provided.

The antistatic agent and the release agent may be mixed and provided in one layer, or each may be formed as one layer. Also,
The antistatic layer may be mixed with the pressure-sensitive adhesive layer, or may be provided between the pressure-sensitive adhesive layer and the biaxially oriented polyester film.

An antistatic agent and a release agent are used as a binder to improve the strength of the layer, the adhesion to the biaxially oriented polyester film, the water resistance, the solvent resistance and the blocking property. It is preferable to contain a high molecular compound such as a thermoplastic resin such as a polyester resin and an acrylic resin and / or a thermosetting resin such as a thermosetting acrylic resin, a urethane resin, a melamine resin, and an epoxy resin. Further, it is particularly preferable that the crosslinking agent contains at least one selected from methylolated or alkylolated melamine-based, urea-based, acrylamide-based compounds, epoxy compounds, and polyisocyanates.

The antistatic agent is not particularly restricted but includes, for example, quaternary ammonium salts, pyridinium salts,
Various cationic antistatic agents having a cationic property such as a primary to primary amino group, a sulfonate group, a nitrate ester group,
Various types of anionic antistatic agents such as phosphate bases, etc., amphoteric antistatic agents such as amino acids and aminosulfates, and nonionic antistatic agents such as amino alcohols, glycerin and polyethylene glycol Surfactant-type antistatic agents, and the above polymerized ones, etc. can be used. In addition, conductive polymers such as polyaniline, polypyrrole, and polythiophene, and tin and antimony fillers dispersed therein can also be used. Furthermore, a metal layer such as silver or tin is vapor-deposited or vacuum-deposited,
It may be provided by a sputtering method or a plasma CVD method.

Since the purpose of the release agent is to prevent the surface protective film from being stained, it is preferable that the release agent has an appropriate peeling force and is durable. Examples of such release agents include silicone-based, fluorine-based, and alkyl polymer-based release agents. In order to prevent contamination in the process, an alkyl polymer system having particularly low migration property is preferable.

In order to provide the biaxially oriented polyester film with the antistatic agent and the release agent, it can be applied before the completion of the crystal orientation at the time of film formation or after the film formation at the completion of the crystal orientation. Any known method can be applied as a method for coating the biaxially oriented polyester film. For example,
A roll coating method, a gravure coating method, a reverse coating method, a spray coating method and the like can be used alone or in combination.

The surface protective film of the present invention is required to have high transparency for easy inspection. Specifically, the light transmittance is preferably 70% or more, and the haze is preferably 10% or less. If the light transmittance is less than 70% and the haze is more than 10%, the transparency is poor.
For example, there is a concern that foreign matter cannot be detected in defect inspection of foreign matter and the like when the surface protective film is bonded to the polarizing plate.

[Release Paper] In the present invention, a release paper is preferably provided for the purpose of protecting the pressure-sensitive adhesive layer of the surface protective film. The base material of the release paper is not particularly limited, but the above-mentioned biaxially oriented polyester film is preferably used. On at least one side of this release paper,
It is preferable to form a release layer. Examples of the release layer component include a silicone resin, a fluororesin, an aliphatic wax or an olefin resin. Further, depending on the type of the adhesive, the release layer may not be provided. Various known additives can be added to the components forming the release layer as long as the object of the present invention is not hindered. Examples of the additive include an ultraviolet absorber, a pigment, an antifoaming agent, and an antistatic agent. The release layer can be applied by applying a coating liquid containing a component forming the release layer to a base film and drying by heating to form a coating film. 80 to 16 heating conditions
0 ° C for 10 to 120 seconds, especially 120 to 150 ° C for 20 seconds
~ 60 seconds is preferred. As the coating method, any known method can be used, and examples thereof include a roll coater method and a blade coater method. In the case of an olefin resin such as polyethylene or polypropylene, it can be obtained by single extrusion or extrusion lamination to a base film.

[Laminate] The laminate of the first constitution of the present invention is composed of a biaxially oriented polyester film in the above-mentioned surface protective film, the crystal orientation main axis direction measured by a microwave transmission type molecular orientation meter, It is necessary that the directions of the orientation axes of the polarizing plate, the retardation plate or the viewing angle widening film are substantially the same, or they are positioned so as to be 90 °. Here, "substantially the same" means that the two directions may be completely coincident or slightly deviated to such an extent that the visual inspection is not substantially hindered. Usually, a deviation of 5 ° or less, preferably 3 ° or less, is acceptable.

In general, the direction of the main axis of crystal orientation of a biaxially oriented aromatic polyester film measured by a microwave transmission type molecular orientation meter (hereinafter, this may be simply abbreviated to “main axis of orientation”) is the length of the film. Direction (longitudinal direction) or transverse direction (width direction), so that, for example, the longitudinal direction of the film and the longitudinal direction of the polarizing plate, retardation polarizing plate or retardation plate (length direction; orientation axis direction) And the above-mentioned lamination conditions can be satisfied.

In the laminate of the present invention, the alignment principal axis of the surface protective film and the alignment axis of the polarizing plate, retardation polarizing plate or retardation plate are coincident or deviated by 90 degrees. No interference color is generated, and foreign substances and defects can be easily detected. In addition, when the orientation main axis of the film and the orientation axis are coincident with each other, the inspection is performed in a bright field. On the other hand, when the orientation axis is shifted by 90 degrees, the inspection is performed in a dark field with only reflected light. Inspection is easy. For example, inspection can be easily performed even with a size of 900 mm in length and 600 mm in width, and almost no foreign matter or defect is overlooked.

As the pressure-sensitive adhesive layer of the polarizing plate, the retardation plate, and the viewing angle widening film, those conventionally known or used per se can be used.

[0035]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, each physical property value in an Example and a comparative example was measured as follows.

(1) Retardation value Using a Abbe refractometer, the refractive index (ny) in the longitudinal (winding) direction and the refractive index (nx) in the lateral (vertical) direction at a wavelength of 589 nm are determined. , The difference Δn (that is, nx−
ny) multiplied by the film thickness d (nm) is defined as the retardation value.

(2) MOR value, inclination of oriented crystal main axis (orientation angle) Using a microwave molecular orientation meter manufactured by Kanzaki Paper Co., Ltd., MOR value, inclination of oriented crystal main axis (orientation) Angle).

(3) Light Transmittance / Haze The light transmittance is measured at a wavelength of 550 nm by measuring the transmittance and the haze (Poick Haze Meter SEP-HS-D1 manufactured by Nippon Seimitsu Kogyo Co., Ltd.).

(4) Number of Foreign Substances in Plastic Film A plastic film sample was 210 mm long and 14 mm wide.
8 mm (area 310.8 cm ² ) was cut out, and the whole area of the film was inspected for foreign substances by visual inspection by the cross Nicol method. Next, the detected foreign matter in the sample film was observed by transmitted light using an optical microscope, and the maximum diameter of a portion observed as an optically abnormal range was defined as the size (diameter) of the foreign matter. In addition, when a cavity (void) existing around the foreign particle is observed as an optically abnormal range, it is included in the size of the foreign particle. Then, the size of the foreign particles was divided into those having a size of 25 μm or more and those having a size of 5 μm or more and less than 25 μm.

(5) Visual Inspection Status (Effect of Light Interference under Crossed Nicols) A surface protective film is attached to one surface of a polarizing plate so that both longitudinal (longitudinal) directions of the film coincide with each other.
A polarizing plate for cross Nicol inspection is superimposed on the surface protective film such that the longitudinal (longitudinal) direction of the film is vertical. Then, light is irradiated from the side of the polarizing plate, a visual inspection is performed from the side of the polarizing plate for inspection, and the occurrence of light interference is evaluated based on the following criteria. ：: No light interference occurred. 光: Light interference occurred, but inspection was possible.

Examples 1-2, Comparative Examples 1-2 A polyethylene terephthalate polymer having an intrinsic viscosity of 0.62 and containing 0.1% by weight of spherical silica particles having an average particle size of 0.15 μm was melted by an extruder. Then, it was brought into close contact with a rotary cooling drum maintained at 40 ° C. from a die by using an electrostatic contact method and rapidly cooled to obtain an unstretched film. Next, the unstretched film was stretched in the longitudinal direction and subsequently in the transverse direction under stretching conditions based on the conditions in Table 1. Further processing was performed at the heat setting temperature shown in Table 1 to obtain a biaxially oriented polyethylene terephthalate film having a thickness of 38 μm. Then, one surface of this film was subjected to corona treatment. Next, as an acrylic pressure-sensitive adhesive, 2-ethylhexyl acrylate as a main monomer, methyl acrylate as a comonomer, and hydroxyethyl methacrylate as a functional group-containing monomer at a ratio of 3: 1: 1 as a reaction catalyst in a solvent of ethyl acetate. Solution polymerization using azobisisobutyronitrile,
An adhesive polymer having a weight average molecular weight of about 450,000 was prepared. A TDI-based isocyanate cross-linking agent is added to the pressure-sensitive adhesive polymer, applied to a release paper prepared by the method described below so that the thickness after drying becomes 20 μm, and the corona of the previously prepared biaxially oriented polyethylene terephthalate film is used. The treated surfaces were bonded together to form a surface protective film by a transfer method.

Further, as a release paper, a coating solution prepared by the following method was applied to one surface of a 38 μm biaxially oriented polyethylene terephthalate film at an application amount of 6 g / m ² (wet), and the coating solution was applied at a temperature of 140 ° C. After heating and drying for 1 minute and curing, a release film having a release layer thickness of 0.1 μm was prepared. The coating liquid is obtained by dissolving an addition-reaction-type curable silicone composed of polydimethylsiloxane having vinyl groups and dimethylhydrogensilane in a toluene solvent to form a solution having a solid concentration of 2%, and adding a platinum catalyst to the solution. Created. Table 1 shows the properties of the surface protective film thus produced.

The symbols B, C and F in Table 1 represent the total width (2130 mm) of the film-formed film divided into three equal parts (710 mm).
This is the film part when slitting. B: Film portion on the left side when viewed from the film winding position C: Central film portion when viewed from the film winding position F: Film portion on the right side from the film winding position

[Reference Example 1] In Example 1, particles to be contained in a polyethylene terephthalate polymer having an intrinsic viscosity of 0.61 as a polymer for a base material of a surface protective film were spherical silica particles having an average particle diameter of 0.5 μm. A film was formed in the same manner except that the content was changed to 0.5% by weight to obtain a biaxially oriented polyester film, and a surface protective film was prepared. The characteristics are shown in Table 1.

[0045]

[Table 1]

As is evident from Table 1, the laminate and the surface protective film of the present invention shown in the Examples have good transparency, and have a defect and an inspection by a crossed Nicols visual inspection for foreign matters and interference colors. It has improved ease of inspection and is easy to inspect.

In Table 1, the film used in Example 2 and the film used in Comparative Example 1 were obtained by dividing the same biaxially oriented polyester film into three in the width direction. As described above, even in a film formed at the same time, depending on the width direction, the position of the orientation main axis caused by the bowing phenomenon at the time of film formation changes, so that the MOR value and the maximum value and the minimum value thereof are determined. The difference may be different, and suitability as a surface protective film may be different.

[0048]

The surface protective film of the present invention comprises a polarizing plate,
By bonding at a specific angle to the surface of the retardation plate or the viewing angle magnifying film surface on which the adhesive layer is not provided, the polarizing characteristics are excellent, and since there are no foreign substances, the bonded polarizing plate, retardation In the final foreign substance inspection of the plate or the viewing angle widening film, it is greatly improved that the inspection is difficult and the yield is poor due to the foreign substance, interference color and the like caused by the surface protection film.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 2G051 AA41 AA90 AB02 AC22 CA11 2H049 BA02 BA06 BB03 BB20 BB23 BB51 BB54 BB67 BC14 BC22 2H091 FA08X FA08Z FA11X FA11Z FC25 FC30 FD14 GA16 GA17 LA07 LA19 4F100B AR00 AR00 AR00A03 BA04 BA05 BA07 BA10A BA10C BA10D BA10E BA22 EJ38C GB41 JA20C JG03D JK15C JL02 JL13A JL14E JN01 JN10B JN30B JN30C YY00 YY00C

Claims (12)

[Claims] 1. An adhesive layer is provided on one surface of a polarizing plate, a retardation plate or a viewing angle widening film, and a biaxially oriented polyester film is used as a base material on the surface opposite to the adhesive layer to adhere to one surface. A laminate in which a surface protective film provided with a layer is laminated via the adhesive layer, and (1) the laminate includes:
The direction of the oriented crystal main axis of the biaxially oriented polyester film in the surface protective film and the direction of the orientation axis of the polarizing plate, retardation plate or viewing angle widening film are substantially the same, or are positioned so as to be 90 °, and (2) The biaxially oriented polyester film in the surface protective film,
The retardation value (R) represented by the following formula is 120
A laminate having an improved polarization characteristic, which is not less than 0 nm. R = Δn · d (where, Δn is the birefringence of the film, that is, the refractive index (ny) in the longitudinal (winding) direction of the film and the lateral (vertical) direction in visible light (wavelength λ = 589 nm). The difference (nx-ny) from the refractive index (nx), and d is the thickness of the film (n
m). ) 2. The biaxially oriented polyester film in the surface protective film has an MOR value measured by a microwave transmission type molecular orientation meter in a range of 1.3 to 1.8.
The laminate according to the above. 3. The laminate according to claim 2, wherein the difference between the minimum value and the maximum value of the MOR value of the biaxially oriented polyester film in the surface protective film is 0.2 or less. 4. The biaxially oriented polyester film in the surface protective film has an inclination (orientation angle, θ) of an oriented crystal main axis measured by a polarizing microscope with respect to a lateral direction of the film.
The laminate according to any one of claims 1 to 3, wherein -20 ° ≤ θ ≤ 20 °. 5. The centerline average surface roughness (Ra) of the surface of the biaxially oriented polyester film in the surface protective film is 2 nm or more and 500 nm or less, and the length of one side is 210 m.
m and a range of the length of the side orthogonal to the length of 148 mm (area 3
No foreign matter having a diameter of 25 μm or more is present on the film surface of 10.8 cm ² ), and no more than 10 foreign matter having a diameter of 5 μm or more and less than 25 μm. Further, the film has a visible light transmittance of 70% or more and a haze value of 10 % Or less. 6. The surface of the biaxially oriented polyester film of the surface protective film opposite to the surface provided with the pressure-sensitive adhesive layer,
The laminate according to any one of claims 1 to 5, further comprising an antistatic layer. 7. On the surface of the surface protective film opposite to the surface provided with the pressure-sensitive adhesive layer of the biaxially oriented polyester film,
The laminate according to any one of claims 1 to 6, further comprising a release layer. 8. A surface protection film comprising a biaxially oriented polyester film as a substrate and an adhesive layer provided on one surface thereof, wherein the biaxially oriented polyester film has a retardation value (R) represented by the following formula: Is 1200 nm or more, a protective film for inspection of a polarizing plate, a retardation plate or a viewing angle widening film. R = Δn · d (where, Δn is the birefringence of the film, that is, the refractive index (ny) in the longitudinal (winding) direction of the film and the lateral (vertical) direction in visible light (wavelength λ = 589 nm). The difference (nx-ny) from the refractive index (nx), and d is the thickness of the film (n
m). ) 9. The biaxially oriented polyester film has a MOR value of 1.3 to less as measured by a microwave transmission type molecular orientation meter.
9. The protective film according to claim 8, which has a range of 1.8. 10. The biaxially oriented polyester film has a M
The protective film according to claim 9, wherein the difference between the minimum value and the maximum value of the OR value is 0.2 or less. 11. The biaxially oriented polyester film has an inclination (orientation angle, θ) of an oriented crystal main axis measured with a polarizing microscope with respect to a lateral direction of the film in a range of −20 ° ≦ θ ≦ 20 °. The protective film according to any one of claims 10 to 10. 12. The center line average surface roughness (Ra) of the biaxially oriented polyester film surface is 2 nm or more and 500 nm or less, and a range of 210 mm on one side and 148 mm on a side orthogonal thereto (area 310.8 cm) ² ) No foreign matter having a diameter of 25 μm or more exists on the film surface, and no more than 10 foreign matter having a diameter of 5 μm or more and less than 25 μm, and the visible light transmittance of the film is 70% or more and the haze value is 10% or less. The protective film according to any one of claims 8 to 11.