TW202000435A - Method of manufacturing resin film manufacturing a resin film containing at least one of a polyimide-based resin or a polyamide-based resin - Google Patents

Abstract

An object of the present invention is to provide a method of manufacturing a resin film that does not have defects such as damage that can affect visibility, and has the optical and physical properties required by a front panel of a flexible display device. The present invention is a method of manufacturing a resin film, which is a method of manufacturing a resin film containing at least one of a polyimide-based resin or a polyamide-based resin, and has a heating step of heating a raw material film with hot air. The above heating step is performed by hot air from the outlets of a pair of nozzles facing each other. Regarding the above-mentioned nozzles, the speed of blowing air at the outlets is 2 m/s or more and 25 m/s or less. The air volume from the outlet of each nozzle is 0.1 to 3 m3/s per 1 meter in length of the nozzles along the width direction of the raw material film.

Description

Manufacturing method of resin film

The present invention relates to a method for producing a resin film containing at least either a polyimide-based resin or a polyamide-based resin.

In recent years, image display devices have been required to be thinner, lighter, and more flexible. However, previously used glass substrates or glass front panels do not have sufficient material characteristics to meet the above requirements. Therefore, the development of materials or substrates to replace glass has progressed. One of them is a resin film containing polyimide resin. From the viewpoint of flexibility, transparency, and heat resistance, a resin film containing a polyimide resin can be used for various purposes. (Patent Literature 1). [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2009-286826

[Problems to be solved by the invention]

When a film containing a polyimide-based resin is used as a front panel of an image display device, a step of heating the film under high-temperature conditions is performed for the purpose of improving surface hardness. However, there is a problem that the yellowing of the film due to heating under high temperature conditions impairs the film quality. In addition, the front panel is arranged on the viewing side of the image display device, so it is required to have no defects such as damage that can affect the visibility, and also have the optical and physical properties required by the front panel. Furthermore, from a manufacturing point of view, there is also a need for a method for efficiently manufacturing resin films of such physical properties. [Technical means to solve the problem]

The present invention has been completed in view of the above-mentioned problems, and provides a method for manufacturing a resin film that suppresses defects such as damage caused by the shaking of the film during the manufacturing process and has the optical properties and physical properties required by the front panel. Moreover, a manufacturing method capable of efficiently manufacturing such a resin film is provided. That is, the present invention provides the following method of manufacturing a resin film. [1] A method for manufacturing a resin film, which is a method for manufacturing a resin film containing at least either a polyimide-based resin or a polyamido-based resin, and has a heating step of heating the raw material film with hot air, the above heating The step is performed by the hot air from the blowing outlet of a pair of nozzles facing each other. With respect to the above nozzles, the blowing air velocity of the blowing outlet is 2 m/sec or more and 25 m/sec or less, and the blowout from each nozzle The air volume is 0.1 to 3 m ³ /sec per 1 m length of the nozzle along the width direction of the raw material film. [2] The method for producing a resin film according to [1], wherein the blowing wind speed of the outlet is 2 m/sec or more and less than 25 m/sec. [3] The method for producing a resin film according to [1] or [2], wherein the nozzle is a nozzle having a slit-shaped blowing port extending in the width direction of the raw material film, or is provided with a transport in the raw material film In the direction and the width direction of the raw material film, a plurality of nozzles with openings for the blowout openings are arranged. [4] The method for producing a resin film according to any one of [1] to [3], wherein in the heating step, the hot air blown from each of the nozzles of the nozzles to which hot air is blown to the raw material film is to the width of the film The difference between the maximum blowing wind speed and the minimum blowing wind speed in the direction is 4 m/sec or less. [5] The method for producing a resin film according to any one of [1] to [4], wherein the above heating step is performed in a clean room. [6] The method for manufacturing a resin film according to any one of [1] to [5], wherein the heating step is performed in an oven with a cleanliness level of 1,000 or less. [Effect of invention]

According to the present invention, a defect such as damage suppression is provided, having the optical properties required by the front panel (uniform in-plane phase difference and low yellowness, etc.) and physical properties (uniform thickness and high flexibility, etc.) The manufacturing method of the resin film. Moreover, a manufacturing method capable of efficiently manufacturing such a resin film is provided. The resin film obtained by the present invention can be used as an optical film such as a front panel of a flexible display.

Hereinafter, embodiments of the present invention will be described in detail. In addition, the scope of the present invention is not limited to the embodiments described herein, and various changes can be made without departing from the gist of the present invention.

<Manufacturing method of resin film> The manufacturing method of the resin film of this embodiment has a heating step of heating the raw material film with hot air, and the heating step uses the hot air from the outlet of a pair of nozzles facing each other to heat the film Method. Regarding the above nozzles, the blowing air velocity of the blowing outlet is 2 m/sec or more and 25 m/sec or less, and the blowing air volume from the blowing outlet of each nozzle is 0.1 to 1 m per length of the nozzle along the width direction of the raw material film 3 m ³ /sec. The blowing wind speed of the blowing outlet is preferably 2 m/sec or more and less than 25 m/sec.

The heating step may be performed in a heating area provided with a pair of nozzles facing each other, for example, in an oven. In this specification, the so-called oven refers to a machine that can heat the film, including a heating furnace, a drying furnace, and a tenter furnace (furnace that fixes both ends in the width direction of the film to heat). The heating furnace may be either hot air treatment or radiant heat treatment, or a combination of these heating furnaces.

The manufacturing method of the resin film of this embodiment will be described with reference to the drawings. FIG. 1 is a step cross-sectional view schematically showing a preferred embodiment of the method for manufacturing a resin film of the present invention. Referring to FIG. 1, a raw material film 20 containing at least either a polyimide-based resin or a polyamide-based resin is carried into an oven 100, heated in a heating area in the oven 100, and then removed from the oven 100. In this specification, the film in the heating step before the heating step and the change in the amount of solvent present over time or transferred to the oven is referred to as a raw material film, and the film that has undergone the heating step and carried out of the oven is referred to as a resin film.

The raw material film 20 may be unwound from a reel on which the raw material film is wound and carried into the oven, or may be continuously carried into the oven from the nearest step before it. FIG. 2 is a step cross-sectional view schematically showing a preferred embodiment of the heating step in the method for manufacturing a resin film of the present invention. Referring to FIG. 2, the raw material film 20 is preferably fixed in the direction (also referred to as the TD direction and the width direction) perpendicular to the film conveying direction (also referred to as the MD direction).

The fixing of both ends can be performed using a holding device such as a needle plate, a jig, and a film chuck, which are usually used in a film manufacturing device. Both ends of the fixation can be adjusted appropriately according to the holding device used, preferably fixed within 50 cm from the end of the membrane. Referring to FIG. 2, a plurality of holding devices 18 may be used to hold both ends of the film while being transported. As a plurality of holding devices 18 provided at one end of the film, the distance between the adjacent holding devices is preferably a distance that can suppress defects such as cracks caused by dimensional changes caused by the shaking or heating of the film. The distance between adjacent holding devices is preferably 1 to 50 mm, more preferably 3 to 25 mm, and still more preferably 5 to 10 mmm. Also, the holding device is preferably arranged in such a way that when the straight line orthogonal to the film transport axis is aligned with the center of the holding portion of any holding device at one end of the film, the intersection point of the straight line and the other end of the film is separated from the The distance of the center of the holding portion of the holding device closest to the intersection is preferably 3 mm or less, more preferably 2 mm or less, and further preferably 1 mm or less. By this, the difference in the respective stresses at both ends of the opposing film can be reduced, and thus the resulting resin film can suppress the occurrence of uneven optical properties.

As an example of the operation of fixing the two ends of the film with a holding device, the following methods can be cited: at an appropriate time before or after being transferred to the oven, in the width direction of the film, by a plurality of oppositely arranged The film chuck fixes both ends of the film in the width direction. Through these operations, it is possible to suppress the shaking of the film, etc., and obtain a resin film in which defects such as uneven thickness or damage are sufficiently suppressed. After the heating step is performed, the fixing of both ends of the film may be released in a timely manner, which may be carried out in the oven, or after being carried out from the oven.

The total length of the film transport direction of the oven used in the heating step may be 10 to 100 m, preferably 15 to 80 m, and more preferably 15 to 60 m. Regarding the oven, the interior can be a space or a plurality of spaces. The above space may be a space that can control temperature conditions, wind speed conditions, etc., and may not have physical boundaries such as partition plates. When the inside of the oven is divided into a plurality of spaces, it can be divided into a plurality of spaces perpendicular or parallel to the film transport direction. The number of spaces may be 2-20, preferably 3-18, more preferably 4-15, and still more preferably 5-10. Independent of the internal structure of the oven, the entire oven can be the heating area, or a part of the interior can be the heating area. Referring to FIG. 1, all three of the regions 10, 12, and 14 may become heating regions, or one of them, for example, the region 14 may become a heating region.

A plurality of ovens can also be used. In this case, the number of ovens is not particularly limited, and may be 2 to 12, for example. The inside of each oven may be of the aforementioned structure. A plurality of ovens can be set up continuously in such a way that the film is transported without contact with external air. In the case of using a plurality of ovens, all of the ovens may become the heating area, or a part of the ovens may become the heating area.

Regarding the air circulation and exhaust inside the oven, when the interior of the oven is divided into a plurality of spaces, it is preferably performed in each space, and when there are a plurality of ovens, it is preferably performed in each oven. The temperature inside the oven (ambient temperature in the oven) is preferably adjustable for each oven. When the inside of the oven is divided into a plurality of spaces, it is preferable to adjust the temperature independently in each space. The temperature setting of each space can be the same or different. However, the temperature of each oven or space preferably satisfies the following temperature range.

Referring to FIG. 1, as the oven 100, a plurality of upper nozzles 30 are provided on the inner upper surface 100 a thereof, and a plurality of lower nozzles 32 are provided on the inner lower surface 100 b thereof. The upper nozzle 30 and the lower nozzle 32 are provided so as to face each other in the vertical direction. For example, the nozzles can be provided with 4 pairs of nozzles (a total of 8) as shown in area 14 of FIG. 1, or with 10 pairs of nozzles (a total of 20) as shown in area 12 of FIG. 1, which can be appropriately set according to the structure of the oven. The distance between adjacent nozzles is preferably 0.1 to 1 m, more preferably 0.1 to 0.5 m, and further preferably 0.1 to 0.3 m from the viewpoint of simplifying the structure of the oven and uniformly heating the raw material film.

In the case where the inside of the oven is divided into a plurality of sections, the number of hot air blowing nozzles installed in each space can usually be 5-30. From the viewpoint of obtaining a resin film having more excellent optical uniformity, the number of nozzles is preferably 8-20. If the number of nozzles is within the above range, the curvature of the floating film tends not to become too large, and the film tends to float between the nozzles, that is, it tends to float.

The nozzle 30 provided on the upper surface 100a of the oven 100 has a blower outlet at the lower portion, and can blow out hot air in the downward direction (arrow B direction). On the other hand, the nozzles 32 respectively provided below the lower surface of the oven 100 have blowing ports at the upper part, and can blow out hot air in the upward direction (arrow C direction). In addition, the upper nozzle 30 and the lower nozzle 32 have a depth of a specific size in a direction perpendicular to the paper surface of FIG. 1 so that the raw material film can be uniformly heated in the width direction, but they are not shown in FIG. 1.

In the method for manufacturing a resin film of this embodiment, the air volume from the outlet of each nozzle 30 or 32 is 0.1 to 3 m ³ /sec per 1 m length of the nozzle in the width direction of the raw material film. From the viewpoint of obtaining a resin film having more excellent optical uniformity as the blowing wind speed, it is preferably 2 to 23 m/sec, and more preferably 8 to 20 m/sec. In addition, from the viewpoint of obtaining a resin film with more excellent optical uniformity as the amount of air blown, it is preferably 0.1 to 2.5 m ³ /sec per 1 m length of the nozzle in the width direction of the film, and more preferably It is 0.2～2 m ³ /sec.

If the blowing air velocity and air volume from the nozzle are within the above-mentioned range, the raw material film can be uniformly heated, so that the entire surface of the film tends to be easily obtained as a film with optically and physically uniform physical properties, which is preferable. Specifically, if the heating step is performed under the above conditions, the unevenness of the in-plane retardation value in the film width direction becomes small, and it is easy to obtain a resin film having a more uniform in-plane retardation value over the entire surface of the film. Therefore, when applied to a display device, the unevenness of contrast is suppressed, and it becomes a front panel with better visibility. In addition, if the heating step is performed under the above conditions, uniform heating can be achieved, so that the unevenness of the amount of solvent remaining in the film becomes small, so that it is easy to obtain a resin film having a more uniform elastic modulus over the entire surface of the film. Therefore, the unevenness of the flexibility of the entire surface of the film is unlikely to occur, and the occurrence of damage due to the difference in the flexibility of the film surface can be suppressed.

In the oven, the raw material film 20 is heated from room temperature to the temperature at which the solvent contained in the raw material film evaporates, but is held by the holding device 18 in such a way that the length of the raw material film in the width direction is almost unchanged, so there is a tendency to sag due to thermal expansion The tendency. If the blowing air speed and the blowing air volume are within the above-mentioned ranges, the raw material film 20 can be sufficiently heated, and the raw material film 20 can be suppressed from drooping or shaking.

The blowing speed of the hot air can be measured at the hot air blowing outlets of the nozzles 30 and 32 using a commercially available thermal anemometer. In addition, the amount of blowing air from the blowing outlet can be obtained by the product of the blowing wind speed and the area of the blowing outlet. In addition, as the blowing air speed of the hot air, from the viewpoint of measurement accuracy, it is preferable to perform measurement at about 10 points at the outlet of each nozzle, and take the average value.

The blowing air speed and the blowing air volume of the hot air can be appropriately adjusted according to the physical properties (optical characteristics, mechanical properties, etc.) of the resin film to be produced, and it is preferably within the above-mentioned range in any form. By this, a resin film with a more uniform phase difference and a sufficiently high axis accuracy can be obtained. In the heating area, in all heating areas, the blowing wind speed is 2 m/sec or more and 25 m/sec or less, preferably 2 m/sec or more and less than 25 m/sec, and the amount of air blown is along the raw material film The nozzle in the width direction is 0.1 to 3 m ³ /sec per 1 m length, preferably 0.1 m ³ /sec or more and 2 m ³ /sec or less.

In this embodiment, in a state where the raw material film 20 is not introduced into the oven 100, the wind speed of the hot air that should maintain the position of the raw material film 20 is preferably 5 m/sec or less, and more preferably at least in the heating area for this purpose Kind of wind speed. By heating the raw material film 20 using such hot air, a resin film with more excellent optical uniformity can be obtained.

In the heating area, the difference between the maximum value and the minimum value of the width direction (direction perpendicular to the paper surface of FIG. 1) of the hot air blowing speed of the nozzles 30 and 32 is preferably 4 m/sec or less. By using hot air with less uneven wind speed in the width direction in this way, a resin film with higher optical uniformity in the width direction can be obtained. By using hot air with less uneven wind speed in this way, a resin film with even higher optical uniformity can be obtained.

In the heating area of the oven 100, the interval L (shortest distance) between the upper nozzle 30 and the lower nozzle 32 facing each other is preferably 150 mm or more, more preferably 150 to 600 mm, and further preferably 150 to 400 mm . By arranging the upper nozzle and the lower nozzle at such an interval L, it is possible to further reliably suppress the shaking of the film in each step.

In addition, the difference between the maximum temperature and the minimum temperature (ΔT) of the hot air in the width direction (the direction perpendicular to the paper surface of FIG. 1) of each nozzle 30 and 32 provided in the heating area is preferably 2° C or less, more Preferably, it is all below 1°C. By using hot air with a sufficiently small temperature difference in the width direction to heat the film in this way, the unevenness of the alignment in the width direction can be further suppressed. Furthermore, the temperature of the hot air is preferably 150 to 400°C, more preferably 150 to 300°C, and still more preferably 150 to 250°C.

Examples of nozzles that can be used in the method of manufacturing a resin film include nozzles having slit-shaped blowout ports extending in the width direction of the raw material film, and transport directions of the raw material film and the width direction of the raw material film. Each is equipped with a plurality of nozzles with openings for blowing. In this specification, a nozzle having a slit-shaped blowing outlet extending in the width direction of the raw material film is referred to as a spray nozzle (slit nozzle), and is arranged in the transport direction of the raw material film and the width direction of the raw material film Nozzles with multiple openings are called perforated nozzles (multi-hole nozzles).

3 is a schematic cross-sectional view showing an example of the shape of a spray nozzle preferably used in the method of manufacturing a resin film of the present invention. 4 is a schematic cross-sectional view showing an example of the shape of a perforated nozzle preferably used in the method of manufacturing a resin film of the present invention. 5 is a schematic cross-sectional view showing another example of the shape of the perforated nozzle preferably used in the method of manufacturing a resin film of the present invention. The oven 100 in this embodiment preferably includes one or both of the jet nozzle shown in FIG. 3 and the perforated nozzle shown in FIGS. 4 and 5.

FIG. 3 shows the injection nozzle 34, and FIGS. 4 and 5 show the perforated nozzles 36 and 38, respectively. In addition, the injection nozzle 34 of FIG. 3, the perforation nozzle 36 of FIG. 4, and the perforation nozzle 38 of FIG. 5 are provided in the upper surface 100a of the oven 100 and blow out hot air downward (in the direction of arrow B). Moreover, the injection nozzle 34, the perforation nozzle 36, and the perforation nozzle 38 are provided in the lower surface 100b of the inside of the oven 100, and blow out hot air upwards (direction of arrow C in FIG. 3). The nozzles 34, 36, and 38 have a specific depth in a direction perpendicular to the paper surface of FIG. 1, but are not shown in FIGS. 3 to 4. The length of the depth is preferably longer than the width of the raw material film 20.

The spray nozzle 34 has a slit 40 extending in the width direction of the film as an outlet for hot air. The slit width D of the slit 40 is preferably 5 mm or more, and more preferably 5-20 mm. By setting the slit width D to the above range, the optical uniformity of the obtained resin film can be further improved. Furthermore, the area of the outlet of each spray nozzle 34 can be obtained by multiplying the length of the nozzle width direction of the spray nozzle 34 (the depth direction in FIG. 3) and the slit width D. The product of the area of the blowing outlet of each nozzle and the blowing wind speed becomes the blowing air volume of the hot wind of each nozzle. By dividing the blown air volume of the hot air by the length of the slit 40 in the width direction of the film, the blown air volume of the hot air per 1 m length of the nozzle in the width direction of the film can be obtained.

The perforated nozzle 36 has a rectangular shape as shown in FIG. 4 in a cross section perpendicular to its longitudinal direction. The perforated nozzle 36 has a plurality of openings (for example, circular openings) 42 on the surface 36a below the surface facing the raw material film 20. The outlet of the hot air of the perforating nozzle 36 includes a plurality of openings 42 provided on the surface 36a. The plurality of openings 42 are outlets of hot air, and the hot air is blown out from the openings 42 at a specific wind speed. A plurality of openings 42 are arranged in the transport direction of the raw material film 20, and a plurality of openings are also arranged in the width direction. The opening 42 may be arranged in a zigzag pattern, for example. In addition, the area of the outlet of each perforating nozzle 36 can be obtained by the sum of the areas of all the openings 42 provided in one perforating nozzle 36. The product of the area of the blowing outlet of each nozzle and the blowing wind speed becomes the blowing air volume of the hot wind of each nozzle. By dividing the blown air volume of the hot air by the length of the slit in the width direction of the film, the blown air volume of the hot air per 1 m length of the nozzle in the width direction of the film can be obtained.

As shown in FIG. 5, the cross section perpendicular to the longitudinal direction of the perforated nozzle 38 has a trapezoidal shape that gradually expands toward a surface 38 a facing the raw material film 20. The perforating nozzle 38 has a plurality of openings (for example, circular openings) 44 on the surface 38a below the surface facing the film. The hot air outlet of the perforating nozzle 38 includes a plurality of openings 44 provided on the surface 38a. The plurality of openings 44 are outlets of hot air, and the hot air is blown out from the openings 44 at a specific wind speed. A plurality of openings 44 are arranged in the transport direction of the raw material film 20, and a plurality of openings are also arranged in the width direction. The opening 44 may be arranged in a zigzag pattern, for example. Furthermore, the area of the outlet of each perforating nozzle 38 can be obtained by the sum of the areas of all the openings 44 provided in one perforating nozzle 38. The product of the area of the blowing outlet of each nozzle and the blowing wind speed becomes the blowing air volume of the hot wind of each nozzle. The blowing amount of hot air per 1 m length of the nozzle along the width of the film can be obtained by the same method as the perforated nozzle 36.

In the case of using a perforated nozzle 36 or 38, the difference between the maximum blowing air velocity and the minimum blowing air velocity in the width direction of the hot air at the outlet of the nozzle can be used to blow out from a plurality of openings 42 or 44 provided on the same nozzle 36 or 38 It is calculated by the difference between the maximum blowing speed and the minimum blowing speed of hot air. The difference between the maximum temperature and the minimum temperature in the width direction of the hot air at the outlet of the nozzle can also be obtained in the same way.

If all the nozzles installed in the oven 100 are perforated nozzles 36 or 38, the total area of the hot air blowing outlet of the entire oven 100 can be increased. Therefore, the wind pressure of the hot air blown onto the raw material film 20 can be reduced, and the shaking of the raw material film 20 can be further reduced. Thereby, the optical uniformity of the obtained resin film can be further improved. In the oven or in the heating area, the raw material film 20 is heated from room temperature to the temperature at which the solvent contained in the raw material film evaporates, but is held by the holding device 18 in such a way that the length of the raw material film in the width direction is almost unchanged, so there is a reason The tendency to sag easily due to thermal expansion. By using the perforated nozzles 36 or 38 in the heating area 10, the raw material film 20 can be further suppressed from sagging or shaking.

The size and number of the openings 42 and 44 provided on the surfaces 36a and 38a of the perforated nozzles 36 and 38 can be adjusted within the following range: the hot air blowing speed of each opening 42 and 44 becomes more than 2 m/sec and does not reach 25 m/sec, and the air volume from each nozzle becomes 0.1 to 3 m ³ /sec per 1 m length of the nozzle along the width of the film.

From the viewpoint of making the blowing wind speeds from the openings of the perforated nozzles 36 and 38 more uniform, the shapes of the openings 42 and 44 are preferably circular. In this case, the diameter of the openings 42 and 44 is preferably 2-10 mm, more preferably 3-8 mm.

When the perforated nozzles 36 and 38 are used, the length of the film conveying direction of the surfaces 36a and 38a of each nozzle is preferably 50 to 300 mm. Furthermore, the interval between adjacent perforated nozzles is preferably 0.3 m or less. In addition, the ratio of the total area of the openings 42 and 44 of the perforation nozzles 36 and 38 (the area of the outlet) to the length of the perforation nozzles 36 and 38 in the film width direction (the total area of the openings of the perforation nozzles (m ² ) / The length (m) of the film width direction of the perforated nozzle is preferably 0.008 m or more.

By using such perforated nozzles 36, 38, the area of the outlet of the hot air can be increased. With this, the wind speed of the hot air can be sufficiently reduced and the hot air can be blown out with a sufficient air volume, and the film can be heated more uniformly. Therefore, a film with a more uniform phase difference and further higher axis accuracy can be manufactured.

In addition to the aforementioned spray nozzles and perforated nozzles, IR (Infrared, Infrared) heaters (radiant heat treatment) can also be used in combination. The IR heater can be installed in the oven or in the heating area, and the IR heater furnace can also be used as an oven.

In this embodiment, the wind speed of the hot air blown to the film is preferably the wind speed immediately after being transported into the oven greater than the wind speed of other transport paths in the oven. The so-called just after being transferred into the oven (hereinafter referred to as the conveying path 1), when the inside of the oven is not divided into plural, it means that the length of the oven from the oven entrance is not reached (the length from the oven entrance to the exit) 1/10 of the distance. When the inside of the oven is divided into a plurality of spaces, the conveying path 1 refers to the space through which the film initially passes. When a plurality of ovens are used, it can be the same as the previous description according to the internal structure of the oven used initially, or it can be set so that the wind speed in the initially passed oven is greater than the wind speed in the second and subsequent ovens.

The so-called other conveying paths refer to the conveying path from the oven inlet to 1/10 of the length of the oven when the inside of the oven is not divided into plural. When the inside of the oven is divided into a plurality of spaces, it refers to any space after the second through the membrane. In the case of using multiple ovens, it can be the same as the previous description according to the internal structure of the initially used oven, or it can be set to the wind speed in any oven in the second and subsequent ovens is less than the wind speed in the originally passed oven .

The difference between the wind speed of the conveying path 1 and the wind speed of other conveying paths in the oven is preferably 0.1 or more, more preferably 0.2 or more, preferably 15 or less, more preferably 8 or less, and further preferably 5 or less, particularly preferably 3 or less. The above upper limit and lower limit can be arbitrarily combined. If the wind speed immediately after being transported into the oven is greater than the wind speed of other conveying paths in the oven so that the difference in wind speed becomes the above range, there is a tendency that the solvent in the film can be more efficiently removed. If the difference in wind speed is within the above range, there is a tendency that the film sway due to the difference in wind speed is less likely to occur, and defects in the surface shape of the resulting resin film or unevenness in optical characteristics such as phase difference tend to become smaller.

The difference between the wind speed of the conveying path 1 and the wind speed of the other conveying paths in the oven can be obtained as the difference between the blowing speed of the hot air from the nozzles provided in the conveying path 1 and the hot air from the nozzles provided in the other conveying paths . When there is a difference between the wind speed of the hot air blown to the film and the blown air speed of the hot air from the nozzle of 2 m/sec or more, it can also be used as the difference between the wind speed of the hot air near the respective films of the conveying path 1 and other conveying paths Obtained.

The other transport path is preferably a transport path located below the transport path 1 (referred to as transport path 2). As the conveying path 2, when the inside of the oven is not divided into plurals, it refers to the conveying path portion located from the oven inlet to 2/10 of the length of the oven. As the conveying path 2, when the inside of the oven is divided into a plurality of spaces, it refers to the second space through which the film passes. In the case of using multiple ovens, it can be the same as the previous description according to the internal structure of the initially used oven, or it can be set that the wind speed of the second oven is less than the wind speed of the originally passed oven.

When the difference in the wind speed between the conveying path 1 and the conveying path 2 is set as described above, the wind speed of the conveying path after the conveying path 2 may be within the range of the blowing air speed of the hot air. The difference between the wind speed of the transport path after the transport path 2 and the respective wind speed of the transport path 1 or the transport path 2 is preferably 0.1 to 12 m/sec, more preferably 0.2 to 8 m/sec. If it is such a difference in wind speed, there is a tendency to suppress the shaking of the film caused by the difference in wind speed, and it is easy to adjust the weight reduction rate of the resulting resin film to a desired range.

As the difference of the above-mentioned wind speed, when the inside of the oven is not divided into a plurality of spaces, it can be adjusted by adjusting the position of the installed nozzle, the blowing speed and air volume of the hot air of the nozzle, the flow of the airflow in the oven, etc. When the inside of the oven is divided into a plurality of spaces, it can be adjusted in the initial space and the following space by adjusting the position of the nozzle, the blowing speed and volume of the hot air of the nozzle, the flow of the airflow in the oven, etc. . When using a plurality of ovens, it can be done in the same way as the previous description according to the structure of the original oven, or the position of the nozzle can be set in a way that the wind speed in the first oven and the second and subsequent ovens are different. The blowing speed and air volume of the hot air from the nozzle, the air flow in the oven, etc.

In this embodiment, the heating step is usually performed in the range of 150 to 350°C, preferably 170°C or higher, more preferably 180°C or higher, still more preferably 300°C or lower, more preferably 250°C or lower, and It is preferably 230°C or lower. In the embodiment of the present invention, if the heating step is in this temperature range, the raw material film tends to be adjusted so that the weight reduction rate M described below tends to occur, and the yellowness of the resulting resin film tends to be less than 3 or more. . As the temperature in the oven in which the heating step is performed, the heating area may be within the above range. In the case where there are plural ovens and the case where the oven is divided into plural spaces, it can be adjusted appropriately, and it is preferable that all the ovens or spaces are within the above range.

The moving speed of the raw material film 20 in the oven 100 can usually be adjusted appropriately within the range of 0.1-50 m/min. The above moving speed is preferably 20 m/min or less, more preferably 15 m/min or less, preferably 0.2 m/min or more, more preferably 0.5 m/min or more, and further preferably 0.7 m/min or more, especially Preferably, it is 0.8 m/min or more. If the moving speed is within the above range, there is a tendency that the length of the oven will not be too long and the equipment will be too large in order to ensure the desired drying time, and there is also a way that the raw material film becomes the following weight reduction rate M The tendency to make adjustments further suppresses the sloshing of the film, thereby suppressing the tendency of the film surface to be damaged.

The treatment time in the heating step is usually adjusted within the range of 60 seconds to 2 hours, preferably within the range of 10 minutes to 1 hour. The processing time can be adjusted appropriately considering the conditions of the temperature, moving speed, hot air speed and air volume of the above-mentioned oven.

The manufacturing method of the resin film of this embodiment can perform the operation of changing the film width or the operation of keeping the film width and transporting in the heating step. As an example of the operation of changing the film width, an operation of extending the width direction of the film can be mentioned. In the operation of extending the film in the width direction, the stretching ratio is preferably 0.7 to 1.3 times, more preferably 0.8 to 1.2 times, and still more preferably 0.8 to 1.1 times. As an example of the operation of conveying while maintaining the width of the film, an operation of maintaining the film in such a manner that the length in the width direction of the film is almost constant can be cited. The resin film in which such operations are performed may have a length of about 0.7 to 1.3 times relative to the length of the width direction of the raw material film, and may be a length extending, equal, or contracted from the length of the width direction of the raw material film. The stretching magnification can be obtained as the ratio of the film width after stretching (excluding the holding portion) to the film width excluding the holding portion. In addition, in FIG. 2, the case where the stretch magnification exceeds 1 times in the operation of stretching the width direction of the film is indicated by a solid line, and the case where the stretch magnification is equal to or less than 1 times is indicated by a broken line.

The resin film can be used for optical applications such as a front panel of an image display device such as a flexible display device. Therefore, it is preferable that the adhesion amount of foreign matter or the like is small. Therefore, the cleanliness of the heating step is preferably 10,000 or less, and more preferably 1,000 or less. Specifically, it is preferable that the oven 100 that performs the heating step is installed in a clean room, and it is preferable that the cleanliness inside the oven 100 is higher than the cleanliness of the clean room (less foreign matter in the air). The clean room is preferably 10,000 cleanliness. In addition, the cleanliness in the oven 100 is preferably less than 1,000. The "cleanliness level" in this manual refers to the cleanliness level specified in the United States Federal Standard (USA FED.STD) 209D, and the so-called "cleanliness level 1000" refers to the particles contained in the air with a particle size of 0.5 μm or less In an environment not exceeding 1,000 per 1 cubic foot (1 ft ³ ). Incidentally, the cleanliness level 1,000 specified in the US Federal Standard 209D is equivalent to the cleanliness level 6 specified in JIS B9920 "Evaluation Methods for Cleanliness of Air Cleanliness of Clean Rooms".

After the resin film after the heating step is carried out from the oven, it can be continuously fed to the next step, or it can be wound into a roll and fed to the next step. In the case of winding the resin film into a reel, the surface protective film and other optical films and other films may be stacked and wound. As the surface protective film laminated on the resin film, the same as the surface protective film laminated on the raw material film described below can be used. The thickness of the surface protective film deposited on the resin film is usually 10 to 100 μm, preferably 10 to 80 μm.

<raw film> The raw material film supplied to the heating step contains at least either a polyimide-based resin or a polyamide-based resin. The raw material film preferably contains the same components as those contained in the varnish used in the formation of the raw material film described below. However, since the structural changes of the components or the evaporation of a part of the solvent may occur, they may be different. The raw material film may be a self-supporting film or a gel film.

Whether the raw material film contains or does not contain an inorganic material, the weight reduction rate M from 120°C to 250°C obtained by thermogravimetric-differential thermal measurement (hereinafter sometimes referred to as "TG-DTA measurement") is preferably 1 to It is about 40%, more preferably 3 to 20%, further preferably 5 to 15%, and particularly preferably 5 to 12%. The weight reduction rate M of the raw material film can be measured by the following method using a commercially available TG-DTA measuring device. As a measuring device for TG-DTA, TG/DTA6300 manufactured by Hitachi High-Tech Science Co., Ltd. can be used.

First, about 20 mg of the sample was taken from the raw material film, while the sample was heated from room temperature to 120°C at a temperature increase rate of 10°C/min, and after being held at 120°C for 5 minutes, at a temperature increase rate of 10°C/min When heated to 400°C, the weight change of the sample is measured. Next, from the measurement result of TG-DTA, the weight reduction rate M (%) from 120°C to 250°C may be calculated by the following formula. In the following formula, W ₀ represents the weight of the sample held at 120°C for 5 minutes, and W ₁ represents the weight of the sample at 250°C. M(%)=100－(W ₁ /W ₀ )×100

If the weight reduction rate M of the raw material film is large to a certain extent, when the raw material film is wound as a laminate with the base material or the surface protection film, the deformation of the laminate, such as bending, is suppressed, and the rollability of the laminate is improved The tendency.

If the weight reduction rate M of the raw material film is small to a certain extent, when the raw material film is wound up as a laminate with the base material or surface protection film, the raw material film tends to be difficult to stick to the base material or surface protection film. Therefore, the uniform transparency of the raw material film can be maintained, and the laminate can be easily rolled out from the reel.

(Polyimide resin and polyimide resin) The polyimide-based resin contained in the raw material film and the resin film refers to a polymer selected from the group consisting of repeating structural units containing an imide group (hereinafter, sometimes referred to as polyimide), and containing At least one polymer in the group consisting of a polymer of repeating structural units of both an iminium group and an amide group (hereinafter, sometimes referred to as a polyimide amide imine). In addition, the polyamide resin refers to a polymer containing a repeating structural unit containing an amide group.

The polyimide-based resin preferably has a repeating structural unit represented by formula (10). Here, G is a tetravalent organic group, and A is a divalent organic group. The polyimide-based resin may contain two or more types of repeating structural units represented by formula (10) in which G and/or A are different.

The polyimide-based resin may contain one or more types selected from the group consisting of repeating structural units represented by formula (11), formula (12), and formula (13) within a range that does not damage various physical properties of the resin film .

In formula (10) and formula (11), G and G ¹ are each independently a tetravalent organic group, preferably an organic group that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G and G ¹ , there can be exemplified: formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or a group represented by formula (29) and a chain hydrocarbon group having a carbon number of 4 or less and a carbon number of 6 or less. In terms of easily suppressing the yellowness (YI value) of the resin film, among them, formula (20), formula (21), formula (22), formula (23), formula (24), and formula (25) are preferred ), formula (26) or formula (27).

In formula (20) to formula (29), * represents a bonding bond, and Z represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C( CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -Ar-, -SO ₂ -, -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH _2- Ar-, -Ar-C(CH ₃ ) ₂ -Ar- or -Ar-SO ₂ -Ar-. Ar represents a C 6-20 arylene group which may be substituted by a fluorine atom, and specific examples include phenylene group.

In formula (12), G ² is a trivalent organic group, preferably an organic group that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G ² , there can be exemplified: formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) ) Or any one of the bonding bonds of the group represented by formula (29) is substituted with a hydrogen atom and a trivalent chain hydrocarbon group having a carbon number of 6 or less.

In formula (13), G ³ is a divalent organic group, preferably an organic group that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As G ³ , there can be exemplified: formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) ) Or the bonding bond of the group represented by formula (29), two groups that are not adjacent to each other and are substituted by hydrogen atoms and a chain hydrocarbon group having 6 or less carbon atoms.

In formula (10) to formula (13), A, A ¹ , A ² and A ³ are each independently a divalent organic group, preferably an organic group that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of A, A ¹ , A ² and A ³ include formula (30), formula (31), formula (32), formula (33), formula (34), formula (35), formula (36), Groups represented by formula (37) or formula (38); those substituted with methyl, fluoro, chloro or trifluoromethyl; and chain hydrocarbon groups with a carbon number of 6 or less.

In formula (30) to formula (38), * represents a bonding bond, and Z ¹ , Z ² and Z ³ independently represent a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH (CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or -CO-. An example is: Z ¹ and Z ³ are -O-, and Z ² is -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, or -SO ₂ -. The bonding positions of Z ¹ and Z ² to each ring, and the bonding positions of Z ² and Z ³ to each ring are preferably meta or para to each ring, respectively.

As the polyimide-based resin, from the viewpoint of easily improving visibility, a polyamidoamide having at least a repeating structural unit represented by formula (10) and a repeating structural unit represented by formula (13) is preferred amine. In addition, the polyamide resin preferably has at least a repeating structural unit represented by formula (13).

In one embodiment of the present invention, the polyimide-based resin system uses a diamine and a tetracarboxylic acid compound (a related compound of a tetracarboxylic acid compound such as an acetyl chloride compound and a tetracarboxylic dianhydride), and a dicarboxylic acid if necessary Condensed polymer obtained by reacting (polycondensing) acid compounds (dicarboxylic acid compounds such as acetyl chloride compounds) and tricarboxylic acid compounds (tricarboxylic acid compounds such as acetyl chloride compounds and tricarboxylic anhydrides), etc. The repeating structural unit represented by formula (10) or formula (11) is usually derived from a diamine and a tetracarboxylic acid compound. The repeating structural unit represented by formula (12) is usually derived from diamine and tricarboxylic acid compounds. The repeating structural unit represented by formula (13) is usually derived from a diamine and a dicarboxylic acid compound.

In one embodiment of the present invention, the polyamide resin is a condensation-type polymer obtained by reacting (condensing) a diamine and a dicarboxylic acid compound. That is, the repeating structural unit represented by formula (13) is usually derived from a diamine and a dicarboxylic acid compound.

Examples of the tetracarboxylic acid compound include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compound may be used alone or in combination of two or more. In addition to the dianhydride, the tetracarboxylic acid compound may also be a tetracarboxylic acid compound related compound such as an acetyl chloride compound.

Specific examples of the aromatic tetracarboxylic dianhydride include: 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2 ,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetra Carboxylic dianhydride, 3,3',4,4'-diphenylene tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2 ,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4'-(hexafluoroisopropylidene) di-o-benzene Dicarboxylic dianhydride (6FDA), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1, 2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane Dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride and 4,4'-(p-phenylene dioxy) diphthalic dianhydride and 4,4'-(m-phenylene Dioxy) diphthalic dianhydride. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydride. The cycloaliphatic tetracarboxylic dianhydride refers to a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure. Specific examples thereof include: 1,2,4,5-cyclohexanetetracarboxylic dianhydride, Cycloalkane tetracarboxylic dianhydride such as 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, bicyclo[2.2.2]octane- 7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride and positional isomers of these. These can be used alone or in combination of two or more. Specific examples of the non-cyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butane tetracarboxylic dianhydride, 1,2,3,4-pentane tetracarboxylic dianhydride, etc. , These can be used alone or in combination of two or more. In addition, cyclic aliphatic tetracarboxylic dianhydride and non-cyclic aliphatic tetracarboxylic dianhydride can be used in combination.

Among the above-mentioned tetracarboxylic dianhydrides, from the viewpoint of high transparency and low colorability, 1,2,4,5-cyclohexanetetracarboxylic dianhydride and bicyclo[2.2.2]octan-7 are preferred -Ene-2,3,5,6-tetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof. In addition, as the tetracarboxylic acid, a water adduct of the acid anhydride of the above-mentioned tetracarboxylic acid compound can be used.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and related acetyl chloride compounds, acid anhydrides, and the like, and two or more kinds may be used in combination. Specific examples include: anhydride of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; a single bond between phthalic anhydride and benzoic acid,- A compound formed by connecting CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or phenylene.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and related acetyl chloride compounds, acid anhydrides, and the like, and two or more of them may be used in combination. As specific examples of these, terephthaloyl dichloride (terephthaloyl dichloride (TPC)); m-xylylene dichloride; naphthalene dichloromethane; 4,4'-linked Phthaloyl dichloride; 3,3'-biphenyl dimethyl dichloride; 4,4'-oxybis(benzoyl chloro) (OBBC); dicarboxylic acid of chain hydrocarbons with carbon number below 8 The compound and the two benzoic acids are connected by a single bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or phenylene.

Examples of diamines include aliphatic diamines, aromatic diamines, and mixtures of these. In addition, in this embodiment, the "aromatic diamine" refers to a diamine in which an amine group is directly bonded to an aromatic ring, and a part of its structure may contain an aliphatic group or other substituents. The aromatic ring may be a single ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a stilbene ring, but are not limited thereto. Among these, the aromatic ring is preferably a benzene ring. The "aliphatic diamine" refers to a diamine in which an amine group is directly bonded to an aliphatic group, and a part of its structure may contain an aromatic ring or other substituents.

Examples of the aliphatic diamine include non-cyclic aliphatic diamines such as hexamethylene diamine, 1,3-bis(aminomethyl)cyclohexane, and 1,4-bis(aminomethyl)cyclohexane. Cyclic aliphatic diamines such as alkanes, norane diamines, 4,4'-diaminodicyclohexylmethane, etc. These can be used alone or in combination of two or more.

Examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, and 2 , 6-diaminonaphthalene and other aromatic diamines with one aromatic ring; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'- Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylbenzene, 3,4'-diamine Diphenyl benzene, 3,3'-diaminodiphenyl benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 4 ,4'-diaminodiphenyl sulfone, bis[4-(4-aminophenoxy)phenyl] phenanthrene, bis[4-(3-aminophenoxy)phenyl] phenanthrene, 2,2 -Bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethyl Aniline, 2,2'-bis(trifluoromethyl) benzidine (2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB)), 4,4'- Bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl) stilbene, 9,9-bis(4-amino-3-methylphenyl) stilbene, 9, 9-bis(4-amino-3-chlorophenyl) stilbene, 9,9-bis(4-amino-3-fluorophenyl) stilbene and other aromatic diamines having two or more aromatic rings. These can be used alone or in combination of two or more.

Among the above diamines, from the viewpoint of high transparency and low colorability, it is preferable to use one or more selected from the group consisting of aromatic diamines having a biphenyl structure, and it is more preferable to use one selected from the group consisting of 2 ,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl and 4,4'-diamine More than one of the group consisting of diphenyl ether is further preferably 2,2'-bis(trifluoromethyl)benzidine.

The polyimide-based resin is obtained by mixing the above raw materials such as the diamine, the tetracarboxylic acid compound, the tricarboxylic acid compound, and the dicarboxylic acid compound by conventional methods such as stirring, etc. The resulting intermediate is subjected to imidization in the presence of an imidization catalyst and optionally a dehydrating agent. The polyamide resin is obtained by mixing the raw materials such as the above-mentioned diamine and dicarboxylic acid compound by a conventional method such as stirring.

The imidate catalyst used in the imidate step is not particularly limited, and examples thereof include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N -Alicyclic amines (monocyclic) such as ethyl piperidine, N-propyl piperidine, N-butyl pyrrolidine, N-butyl piperidine, and N-propyl hexahydropyrazine; azabicyclo[ 2.2.1] Heptane, azabicyclo[3.2.1]octane, azabicyclo[2.2.2]octane and azabicyclo[3.2.2]nonane and other alicyclic amines (polycyclic); And 2-picoline, 3-picoline, 4-picoline, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-lutidine, 2,4, Aromatic amines such as 6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline and isoquinoline.

The dehydrating agent used in the amide imidization step is not particularly limited, and examples thereof include acetic anhydride, propionic anhydride, isobutyric anhydride, trimethylacetic anhydride, butyric anhydride, and isovaleric anhydride.

In the mixing of each raw material and the amide imidization step, the reaction temperature is not particularly limited, for example, 15 to 350°C, preferably 20 to 100°C. The reaction time is also not particularly limited, and is, for example, about 10 minutes to 10 hours. If necessary, the reaction can be carried out under an inert environment or under reduced pressure. In addition, the reaction can be carried out in a solvent, and examples of the solvent include, for example, the solvent used in the preparation of varnish. After the reaction, the polyimide resin or the polyimide resin is refined. Examples of the purification method include a method such as adding a poor solvent to the reaction solution, depositing the resin by the reprecipitation method, drying and taking out the precipitate, and washing and drying the precipitate with a solvent such as methanol as necessary. In addition, for the production of the polyimide-based resin, for example, the production method described in Japanese Patent Laid-Open No. 2006-199945 or Japanese Patent Laid-Open No. 2008-163107 can be referred to. In addition, commercially available products may be used for the polyimide-based resin. Specific examples thereof include Neopulim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd., and KPI-MX300F manufactured by Kawamura Industries (Co., Ltd.).

The weight average molecular weight of the polyimide-based resin or the polyamidoamine-based resin is preferably 200,000 or more, more preferably 250,000 or more, and further preferably 300,000 or more, preferably 600,000 or less, and more preferably 500,000 or less. The greater the weight-average molecular weight of the polyimide-based resin or the polyamide-based resin, the greater the tendency to exhibit higher flex resistance during film formation. Therefore, from the viewpoint of improving the flex resistance of the resin film, the weight average molecular weight is preferably at least the above lower limit. On the other hand, the smaller the weight average molecular weight of the polyimide-based resin or the polyamide-based resin, the easier it is to lower the viscosity of the varnish and to improve the processability. In addition, there is a tendency to easily improve the extensibility of the polyimide-based resin or the polyamide-based resin. Therefore, from the viewpoint of processability and extensibility, the weight average molecular weight is preferably equal to or less than the above upper limit. In addition, in this case, the weight average molecular weight can be measured by gel permeation chromatography (GPC), and can be calculated by standard polystyrene conversion, for example, by the method described in the examples.

The imidate ratio of the polyimide-based resin is preferably 95 to 100%, more preferably 97 to 100%, still more preferably 98 to 100%, and particularly preferably 100%. From the viewpoints of the stability of the varnish and the mechanical properties of the resulting resin film, the imidate ratio is preferably at least the above lower limit. Furthermore, the imidate ratio can be obtained by IR method, NMR (nuclear magnetic resonance, nuclear magnetic resonance) method, or the like. From the above viewpoint, the polyimide-based resin contained in the varnish preferably has an imidization ratio within the above range.

In a preferred embodiment of the present invention, the polyimide-based resin or the polyamide-based resin contained in the resin film of the present invention may contain, for example, fluorine atoms that can be introduced through the above-mentioned fluorine-containing substituents, etc. Halogen atom. When the polyimide-based resin or the polyamide-based resin contains halogen atoms, it is easy to increase the elastic modulus of the resin film and reduce the yellowness (YI value). If the elastic modulus of the resin film is high, it is easy to suppress the occurrence of damage and wrinkles of the film, and if the yellowness of the resin film is low, it is easy to improve the transparency of the film. The halogen atom is preferably a fluorine atom. Examples of preferred fluorine-containing substituents for containing a fluorine atom in the polyimide-based resin or polyamidoamine-based resin include a fluorine group and a trifluoromethyl group.

The content of halogen atoms in the polyimide resin or polyimide resin is based on the mass of the polyimide resin or polyimide resin, preferably 1 to 40% by mass, more preferably 5 to 40% by mass, more preferably 5 to 30% by mass. If the content of halogen atoms is within the above range, it is easy to further increase the elastic modulus at the time of film formation, reduce the water absorption rate, further reduce the yellowness (YI value), further improve the transparency, and sometimes the synthesis becomes easy.

In one embodiment of the present invention, as the content of the polyimide-based resin and/or the polyamide-based resin in the resin film, based on the total mass of the resin film, it is preferably 40% by mass or more, more preferably It is 50% by mass or more, and more preferably 70% by mass or more. From the viewpoint of easy improvement of flex resistance and the like, the content of the polyimide-based resin and/or the polyamide-based resin is preferably at least the above lower limit. In addition, the content of the polyimide-based resin and/or the polyamide-based resin in the resin film is generally 100% by mass or less based on the total mass of the resin film.

(additive) The resin film of the present invention may further contain additives. Examples of such additives include silicon dioxide particles, ultraviolet absorbers, whitening agents, silicon dioxide dispersants, antioxidants, pH adjusters, and leveling agents.

(Silica particles) The resin film of the present invention may further contain silica particles as additives. The content of silicon dioxide particles is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, and preferably 60% by mass based on the total mass of the resin film. It is more preferably 50% by mass or less, and further preferably 45% by mass or less. In addition, the content of silicon dioxide particles can be any combination of the lower limit and the upper limit among the upper limit and the lower limit. If the content of silica particles is within the numerical range of the upper limit and/or the lower limit, the resin film of the present invention tends not to aggregate, and the silica particles tend to be uniformly dispersed in the state of primary particles. The decrease in visibility of the resin film of the present invention can be suppressed.

The particle size of the silicon dioxide particles is preferably 1 nm or more, more preferably 3 nm or more, and further preferably 5 nm or more, particularly preferably 8 nm or more, preferably 30 nm or less, more preferably 28 nm or less, Furthermore, it is preferably 25 nm or less, and particularly preferably 20 nm or less. The particle size of the silica particles can be any combination of the lower limit and the upper limit among the upper limit and the lower limit. If the content of silicon dioxide particles is within the numerical range of the upper limit and/or lower limit, the resin film of the present invention is less likely to interact with light of a specific wavelength in white light, so the present invention can be suppressed The visibility of the resin film is reduced. In this specification, the particle size of silica particles means the average primary particle size. The particle size of the silicon dioxide particles in the resin film can be measured from a camera using a transmission electron microscope (TEM). The particle size of the silica particles before the production of the resin film (for example, before addition to the varnish) can be measured by a laser diffraction particle size distribution meter. The method for measuring the particle size of silicon dioxide particles is described in detail in the examples.

Examples of the form of the silica particles include silica sol in which silica particles are dispersed in an organic solvent and the like, and silica powder prepared by a vapor phase method. Among these, from the viewpoint of workability, silica sol is preferred.

The silicon dioxide particles may be subjected to surface treatment. For example, the silicon dioxide particles may be replaced with a solvent (more specifically, γ-butyrolactone, etc.) from a water-soluble alcohol-dispersed silica sol. The water-soluble alcohol is an alcohol having a carbon number of 3 or less per hydroxyl group in one molecule of the water-soluble alcohol, and examples thereof include methanol, ethanol, 1-propanol, and 2-propanol. Generally, if the silica particles are surface-treated, the compatibility with the polyimide-based resin contained in the resin film increases, and the dispersibility of the silica particles tends to increase, so the visibility of the present invention can be suppressed The decrease, but also depends on the affinity of the silica particles and the type of polyimide resin or polyimide resin.

(UV absorber) The resin film of the present invention may further contain an ultraviolet absorber. For example, three types of ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzoate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, etc. can be cited. These can be used alone or in combination of two or more. Preferred commercially available ultraviolet absorbers include, for example, Sumika Chemtex (registered trademark) Sumisorb (registered trademark) 340, ADEKA (registered trademark) Adekastab (registered trademark) LA-31, and BASF JAPAN (shared) The TINUVIN (registered trademark) 1577 and so on. The content of the ultraviolet absorber is preferably 1 phr or more and 10 phr or less, more preferably 3 phr or more and 6 phr or less, based on the mass of the resin film of the present invention.

(Brightener) The resin film of the present invention may further contain a whitening agent. The whitening agent can be added for the purpose of adjusting the color tone when, for example, an additive other than the whitening agent is added. Examples of the whitening agent include monoazo dyes, triarylmethane dyes, phthalocyanine dyes, and anthraquinone dyes. Among these, anthraquinone-based dyes are preferred. Examples of preferred commercially available whitening agents include MACROLEX (registered trademark) Violet B manufactured by Lanxess, Sumiplast (registered trademark) Violet B manufactured by Sumika Chemtex (share), and Diaresin manufactured by Mitsubishi Chemical (share) (Registered trademark) Blue G, etc. These can be used alone or in combination of two or more. When the whitening agent is contained, its content is based on the mass of the resin film of the present invention, preferably 1 to 50 ppm, more preferably 1 to 45 ppm, further preferably 3 to 40 ppm, particularly preferably 5 to 35 ppm.

(Method of manufacturing raw material film) The raw material film is not particularly limited, and for example, it can be produced by a method including the following steps. (a) Preparation steps for preparing a varnish containing the above resin and the above filler liquid (hereinafter sometimes referred to as varnish); (b) The coating step of applying varnish to the substrate to form a coating film; and (c) The step of forming the raw material film by drying the coating film.

In the varnish preparation step, the above resin is dissolved in a solvent, the above filler and other additives as needed are added and mixed with stirring, thereby preparing a varnish. Furthermore, in the case of using silica as a filler, the above-mentioned resin-soluble solvent, such as the solvent used in the preparation of the following varnish, can be replaced by a dispersion of silica-containing silica sol Silica sol is added to the resin.

The solvent used in the preparation of the varnish is not particularly limited as long as it can dissolve the above resin. Examples of the solvent include: amide-based solvents such as N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide (DMF); γ-butyrolactone (GBL), Lactone-based solvents such as γ-valerolactone; sulfur-based solvents such as dimethyl ash, dimethyl sulfoxide, and ciprool; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and the like combination. Among these, an amide-based solvent or a lactone-based solvent is preferred. These solvents can be used alone or in combination of two or more. In addition, the varnish may contain water, alcohol solvents, ketone solvents, acyclic ester solvents, ether solvents, and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass.

In the coating step, the varnish is coated on the substrate by a known coating method to form a coating film. Known coating methods include, for example, roll coating methods such as wire bar coating, reverse coating, and gravure coating, die coating methods, comma coating methods, and die lip coating methods. , Screen coating method, spray coating method, spray method, casting method, etc.

In the forming step, the coating film is dried and peeled from the base material, whereby a raw material film can be formed. The drying of the coating film can usually be carried out at a temperature of 50 to 350°C. If necessary, the coating film can be dried under an inert environment or under reduced pressure. The obtained raw material film is supplied to the above-mentioned heating step, and may be continuously transported and supplied to the heating step, or may be provisionally wound up and supplied.

As an example of the base material, if it is a metal type, it may include: SUS (Steel Use Stainless, Japanese stainless steel standard) endless belt, if it is a resin type, it may include: PET (polyethylene terephthalate, polyethylene terephthalate ) Film, PEN (polyethylene naphthalate, polyethylene naphthalate) film, other polyimide resin or polyamide resin film, cycloolefin polymer (COP) film, acrylic film, etc. Among them, from the viewpoint of excellent smoothness and heat resistance, PET films, COP films, and the like are preferable, and further, from the viewpoint of adhesion to resin films and cost, PET films are more preferable.

The raw material film can be formed as a laminate on the surface protection layer of its surface area, and the laminated surface protection film can be peeled off before the heating step. The surface protection film is laminated on the surface of the raw material film opposite to the substrate. When the laminated body is wound in a roll shape, if there is a problem such as sticking, it is possible to add a layered surface protective film on the surface of the substrate opposite to the raw material film. The surface protective film attached to the raw material film is a film for temporarily protecting the surface of the raw material film, and it is not particularly limited as long as it can protect the surface of the raw material film and can be peeled off. For example, polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resin films such as polyethylene and polypropylene films; The acrylic resin film and the like are preferably selected from the group consisting of polyolefin resin film, polyethylene terephthalate resin film and acrylic resin film. When the surface protection films are attached to both sides of the laminate, the surface protection films on each side may be the same or different.

The thickness of the surface protective film is not particularly limited, but it is usually 10 to 100 μm, preferably 10 to 80 μm, and more preferably 10 to 50 μm. When the surface protection film is attached to both sides of the laminate, the thickness of the surface protection film on each side may be the same or different.

The layered product (the base material, the raw material film, and the surface protective film as needed) wound around the core in a roll is called a layered film roll. In the continuous production of laminated film rolls, due to other constraints of space, it is often stored temporarily in the form of a film roll, and the laminated film roll is also one of them.

Examples of the material constituting the core of the laminate film roll include polyethylene resin, polypropylene resin, polyvinyl chloride resin, polyester resin, epoxy resin, phenol resin, melamine resin, silicone resin, and polyamine group. Formate resin, polycarbonate resin, ABS (acrylonitrile-butadiene-styrene resin) resin and other synthetic resins; aluminum and other metals; fiber reinforced plastic (FRP (fiber reinforced plastice): Composite materials that contain fibers such as glass fibers in plastic to increase strength) etc. The winding core is formed into a cylindrical shape or a cylindrical shape, and the diameter thereof is, for example, 80 to 170 mm. In addition, the diameter of the film roll after winding is not particularly limited, but is usually 200 to 800 mm.

<Resin film> The resin film obtained in the production method of the present invention contains at least either a polyimide-based resin or a polyamide-based resin. The thickness of the resin film is preferably 10 μm or more, more preferably 20 μm or more, further preferably 30 μm or more, preferably 120 μm or less, more preferably 100 μm or less, still more preferably 80 μm or less, particularly preferably Below 60 μm. If the thickness is within the above range, it is advantageous from the viewpoint of protection of the interior when the resin film is incorporated into the display device, and from the viewpoint of folding resistance, cost, transparency, and the like. The measurement method is described in detail in the examples.

The weight reduction rate M of the resin film subjected to the heating step determined by TG-DTA measurement from 120°C to 250°C is preferably 3% or less, more preferably 2% or less, and further preferably 1.5% or less, Especially preferred is below 1%. In addition, the lower limit of the weight reduction rate M is not particularly limited, and may be 0.1%, for example. If the weight reduction rate M of the resin film is in the above range, a film having both the sufficient hardness and flexibility required by the front panel of the flexible display device can be obtained, and the film surface is not too soft and is not easily generated Damage, so there is a case where the operation of the film becomes easy in the subsequent steps.

The haze of the resin film is preferably 1% or less, more preferably 0.8% or less, further preferably 0.5% or less, and particularly preferably 0.3% or less from the viewpoint of visibility. The haze of the resin film can be measured in accordance with JIS K 7136:2000. The measurement method is described in detail in the examples. If the haze of the resin film is within the above range, it can be preferably used for the front panel of the flexible display device.

The total light transmittance of the resin film is preferably 85% or more, more preferably 87% or more, and still more preferably 89% or more. The total light transmittance of the resin film can be measured in accordance with JIS K 7361-1:1997. The measurement method is described in detail in the examples. If the total light transmittance of the resin film is in the above numerical range, when incorporated in an image display device, a sufficient film appearance can be ensured.

The yellowness of the resin film is preferably 3.0 or less, more preferably 2.7 or less, and further preferably 2.5 or less. The yellowness of the resin film can be measured in accordance with JIS K 7373:2006. The measurement method is described in detail in the examples. Within this range, visibility is excellent, and it can be preferably used as a display member such as a front panel.

As the in-plane retardation of the resin film, the ratio Re(P1/P2) and the ratio Re(P1/P3) of the in-plane retardation value measured at a wavelength of 590 nm are preferably 0.75 or more. Re(P1/P2) and ratio Re(P1/P3) were calculated by the following method. First, the resin film is equally divided into 5 parts in the film width direction, the center point in the film width direction is set to P1, and the points on both sides of P1 are set to P2 and P3, respectively. Secondly, the in-plane phase difference value of each point is measured, and the ratio of the in-plane phase difference value of P1 to the in-plane phase difference value of P2 or P3 can be regarded as Re(P1/P2) and Re(P1/P3), respectively. Figure it out. The ratio Re(P1/P2) and the ratio Re(P1/P3) are preferably 0.80 or more. If the ratio is within the above range, the unevenness of the retardation value of the resin film is further reduced, and the retardation value of the film becomes more uniform. The in-plane phase difference of the resin film can be measured by a commercially available device. Examples of commercially available devices include a retardation film and optical material inspection device (trade name "RETS100") manufactured by Otsuka Electronics Co., Ltd.

The resin film produced by the production method of the present invention can be used as a single layer of the resin film, or can be used as a laminate in which other layers are laminated. The resin film or the laminate containing it has excellent quality, so it is useful as an optical film in an image display device, etc., particularly a flexible display front panel (window film).

Examples of other layers that can be laminated on the resin film include layers (functional layers) having various functions such as a hard coat layer, an ultraviolet absorption layer, an adhesive layer, a refractive index adjustment layer, and an undercoat layer. The resin film may have a singular or plural functional layers. Also, one functional layer may have multiple functions. In addition, as other layers than the functional layer, a polarizing film, a polarizing plate, a touch sensor, a colored light-shielding pattern printed around a frame having a single layer or a plurality of layers, and the like are included in the display device. member.

The hard coat layer is preferably arranged on the visible side surface of the film. The hard coat layer may have a single-layer structure or a multi-layer structure. The hard coat layer can be formed by hardening a hard coating composition containing a reactive material that forms a cross-linked structure by irradiation of light or heat energy.

Examples of the reactive material include light or thermosetting resin. Examples thereof include acrylic resins such as (meth)acrylate monomers and oligomers, epoxy resins, urethane resins, benzyl chloride resins, vinyl resins, and polysiloxanes. It is a resin or mixed resin such as ultraviolet curing type, electron beam curing type or thermosetting type resin. From the viewpoint of mechanical properties such as surface hardness and industrial viewpoints, the composition for hard coating preferably contains an acrylic resin.

In addition to the above resin, the composition for hard coating may contain a solvent and a photopolymerization initiator as needed. In addition, the inorganic filler, leveling agent material, stabilizer, antioxidant, UV (ultraviolet) absorber, surfactant, lubricant, Additives such as antifouling agents.

The hard coat layer can be formed by applying the hard coating composition to at least one side of the resin film obtained by the present invention and hardening it. The thickness of the hard coat layer is not particularly limited, and may be 5 to 100 μm, for example. If the thickness of the hard coat layer is within the above range, sufficient surface hardness can be ensured, and there is a tendency that the problem of curling due to hardening shrinkage is unlikely to occur due to good flex resistance.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays. For example, it includes a main material selected from the group consisting of a UV-curable transparent resin, an electron beam-curable transparent resin, and a thermosetting transparent resin, and ultraviolet rays dispersed in the main material Absorbent. By providing an ultraviolet absorbing layer as a functional layer, the change in yellowness due to light irradiation can be easily suppressed.

The adhesive layer is a layer having an adhesive function, and has a function of attaching the film of the present invention to other components. As the material for forming the adhesive layer, generally known ones can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used.

The adhesive layer may contain a resin composition containing a component having a polymerizable functional group. In this case, the resin composition constituting the adhesive layer can be polymerized after the film is closely adhered to other members, thereby achieving a firm adhesion. The adhesive strength of the film and the adhesive layer of the present invention may be 0.1 N/cm or more or 0.5 N/cm or more.

The adhesive layer may contain a thermosetting resin composition or a photocurable resin composition as a material. In this case, the resin composition can be polymerized and hardened by supplying energy afterwards.

The adhesive layer may also be a layer containing an adhesive called Pressure Sensitive Adhesive (PSA) that is attached to the object by pressing. Pressure-sensitive adhesives can be adhesives, that is, "substances that have adhesiveness at room temperature and adhere to the adherend with lighter pressure" (JIS K 6800), or capsule-type adhesives, that is, "specific The component is contained in a protective film (microcapsule), and an adhesive agent that can maintain stability until the film is broken by an appropriate method (pressure, heat, etc.) (JIS K 6800).

The hue adjustment layer is a layer having a hue adjustment function, which can adjust the film of the present invention to a target hue. The hue adjustment layer is, for example, a layer containing resin and coloring agent. Examples of the colorant include inorganic pigments such as titanium oxide, zinc oxide, red lead, oxytitanium-based calcined pigments, ultramarine blue, cobalt aluminate, and carbon black; azo-based compounds, quinacridone-based compounds, and anthraquinone Organic compounds, perylene-based compounds, isoindolinone-based compounds, phthalocyanine-based compounds, quinophthalone-based compounds, threne-based compounds, and pyrrolopyrrole-diketone-based organic pigments; barium sulfate and calcium carbonate Other body pigments; and dyes such as basic dyes, acid dyes and mordant dyes

The refractive index adjustment layer is a layer having a refractive index adjustment function, which has a refractive index different from that of the layer containing polyimide amide imide resin A in the film of the present invention, and can impart a specific refractive index to the film of the present invention . The refractive index adjustment layer may be, for example, a resin layer containing a suitably selected resin, and optionally a pigment, or a metal thin film.

Examples of the pigments for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle size of the pigment can be 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, it is possible to prevent diffuse reflection of light passing through the refractive index adjustment layer, and to prevent transparency from decreasing.

Examples of the metal used in the refractive index adjustment layer include titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and nitride Metal oxides or metal nitrides such as silicon.

The optical member laminated on the resin film may be laminated on the resin film through the adhesive layer or the adhesive layer, or may not be laminated on the resin film through the adhesive layer or the adhesive layer. [Example]

Hereinafter, the present invention will be described in detail by examples. In the example, "%" and "parts", unless otherwise specified, indicate mass% and mass parts. In the examples, the measurement method and evaluation method of each item were performed by the following methods.

(Thickness of resin film) Using a micrometer ("ID-C112XBS" manufactured by Mitutoyo Co., Ltd.), the thickness of the resin film of 10 points or more is measured, and the average value thereof is calculated.

(Thermogravimetric-differential thermal (TG-DTA) measurement) TG/DTA6300 manufactured by Hitachi High-Tech Science Co., Ltd. was used as the measuring device for TG-DTA. A sample of about 20 mg was obtained from the produced transparent resin film (polyimide film). While the sample was heated under the following conditions, the weight change of the sample was measured, that is, the temperature was increased from room temperature to 120°C at a heating rate of 10°C/min, and after maintaining at 120°C for 5 minutes, the temperature was measured at 10°C/min. The heating rate is increased to 400°C. FIG. 1 shows the TG-DTA measurement results of the polyimide film produced in Example 1 below.

Based on the TG-DTA measurement results, the weight reduction rate M (%) from 120°C to 250°C was calculated by the following formula. M(%)=100－(W1/W0)×100 Here, W0 represents the weight of the sample held at 120°C for 5 minutes, and W1 represents the weight of the sample at 250°C.

(Measurement of in-plane retardation value of resin film) The in-plane retardation of the resin film is an in-plane retardation value Re measuring a wavelength of 590 nm using a retardation film and optical material inspection device (trade name "RETS100") manufactured by Otsuka Electronics Co., Ltd. The measurement was performed on a total of 36 points with a width of 700 mm centered on the center of the resin film in the width direction, divided at 20 mm intervals, and calculated as the average of these values. The ratio of the in-plane phase difference value in Table 2 is calculated by the following method. First, let the center point of the film width of the resin film be P1, and set the points 120 mm away from P1 toward the ends of the film as P2 and P3, respectively. Next, measure the in-plane phase difference value of each point, and calculate the ratio of the in-plane phase difference value of P1 to the in-plane phase difference value of P2 or P3 as Re(P1/P2) and Re(P1/P3), respectively. Out.

(Viscosity of varnish) The viscosity (cps) of the varnish is based on JIS K 8803:2011, measured using an E-type viscometer at 25°C. In addition, the resin concentration of the varnish means the concentration (mass %) of the resin contained in the varnish, which is calculated based on the mass of the resin contained in the varnish based on the total mass of the varnish.

(Particle size of silica particles) The particle diameter of the silicon dioxide particles is calculated based on the measured value of specific surface area by the BET (Brunauer-Emmett-Teller, Buert) adsorption method according to JIS Z 8830. Using a specific surface area measuring device ("Monosorb (registered trademark) MS-16" manufactured by Yuasa-ionics Co., Ltd.), the specific surface area of the powder obtained by drying the silica sol at 300°C was measured.

(Weight average molecular weight) Gel permeation chromatography (GPC) determination (1) Pre-processing method After dissolving the sample in γ-butyrolactone (GBL) to make a 20% by mass solution, it was diluted to 100 times with a DMF eluent, and a filter using a 0.45 μm membrane filter was used as the measurement solution. (2) Measurement conditions Column: TSKgel SuperAWM-H×2＋SuperAW2500×1 (6.0 mm I.D.×150 mm×3 pieces) Dissolution solution: DMF (addition of 10 mmol/L lithium bromide) Flow rate: 0.6 mL/min Detector: RI detector Column temperature: 40℃ Injection volume: 20 μL Molecular weight standard: standard polystyrene

(Evaluation method of resin film transportability) From the entrance of the tenter drying furnace to the exit of the drying furnace, visually check whether there is any shaking of the film (vibration in the vertical direction).

(Poor appearance of resin film) It was confirmed that the jig portion of the obtained film was not cracked, and the film was irradiated with LED (light-emitting diode) light to confirm whether there was an increase in damage before and after the drying furnace.

<Production Example 1: Production of Polyimide Resin 1> Prepare a flask equipped with a silicone tube, a stirring device and a thermometer, and an oil bath in a separable flask. Put 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) 75.6 g and 2,2'-bis(trifluoromethyl)-4,4'-di in the flask Aminobiphenyl (TFMB) 54.5 g. While stirring it at 400 rpm, 530 g of N,N-dimethylacetamide (DMAc) was added, and stirring was continued until the contents of the flask became a uniform solution. Then, while using an oil bath, the temperature in the container was adjusted so as to be in the range of 20 to 30° C., and the stirring was continued for 20 hours to cause the reaction to produce polyamic acid. After 30 minutes, the stirring speed was changed to 100 rpm. After stirring for 20 hours, the temperature of the reaction system was returned to room temperature, 650 g of DMAc was added, and adjusted so that the polymer concentration became 10% by mass. Furthermore, 32.3 g of pyridine and 41.7 g of acetic anhydride were added, and the mixture was stirred at room temperature for 10.5 hours to perform amide imidization. Remove the polyimide varnish from the reaction vessel. The obtained polyimide varnish was added dropwise to methanol for reprecipitation, and the obtained powder was heated and dried to remove the solvent to obtain polyimide-based resin 1 as a solid component. GPC measurement was performed on the obtained polyimide-based resin 1, and the weight average molecular weight was 365,000. In addition, the imidate ratio of polyimide was 99.0%.

<Production Example 2: Production of Polyimide Resin 2) Under a nitrogen atmosphere, 45 g (140.52 mmol) of TFMB and 768.55 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 6FDA 18.92 g (42.58 mmol) was added to the flask and stirred at room temperature for 3 hours. Thereafter, 4.4'-oxybis(benzyl chloride) (OBBC) 4.19 g (14.19 mmol) was added to the flask, followed by terephthaloyl chloride (TPC) 17.29 g (85.16 mmol), in Stir at room temperature for 1 hour. Then, 4.63 g (49.68 mmol) of 4-methylpyridine and 13.04 g (127.75 mmol) of acetic anhydride were added to the flask, and after stirring at room temperature for 30 minutes, the temperature was raised to 70°C using an oil bath, and the mixture was further stirred for 3.5 hours to obtain The reaction solution. The obtained reaction liquid was cooled to room temperature, poured into a large amount of methanol in a linear form, and the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100°C to obtain polyimide-based resin 2. The weight average molecular weight of the polyimide-based resin 2 is 455,000. The polyimide has an imidization rate of 98.9%.

<Production Example 3: Production of Dispersion Liquid 1> The methanol-dispersed organic silicon dioxide (particle size measured by BET method: 27 nm) was replaced with γ-butyrolactone (GBL) to obtain GBL-dispersed organic silicon dioxide (solid content 30.3% by mass). This dispersion liquid is referred to as dispersion liquid 1.

<Production Example 4: Production of varnish (1)> The varnish (1) was obtained by dissolving a polymer in a solvent with the composition shown in Table 1, and obtained a varnish (1) having a solid content of 15.5% by mass calculated according to the addition amount and a viscosity of 36,500 cps at 25°C.

<Production Example 5: Production of varnish (2)> The varnish (2) is mixed in a GBL solvent at room temperature in such a way that the composition ratio of the polymer and the filler becomes 60:40, in which the relative mass of the polymer and the silica becomes 5.7 phr or 35 ppm Add Sumisorb 340 (UVA) and Sumiplast Violet B (BA) in a manner and stir until uniform. A varnish (2) having a solid content calculated from the added amount of 10.3% by mass and a viscosity of 25,500 °C of 38,500 cps.

[Table 1]

<Production Example 6: Film formation of the raw material film 1> Cast varnish (1) on PET (polyethylene terephthalate) film ("COSMOSHINE (registered trademark) A4100" manufactured by Toyobo Co., Ltd., thickness 188 μm, thickness distribution ±2 μm) by casting Instead, a coating film is formed. At this time, the line speed was 0.4 m/min, and the coating film was dried under the following conditions: after heating at 70°C for 8 minutes, at 100°C for 10 minutes, then at 90°C for 8 minutes, and finally at 80°C Heat for 8 minutes. Thereafter, the coating film was peeled from the PET film to obtain a raw material film 1 having a width of 700 mm and a thickness of 86 μm. The weight reduction rate M of the raw material film 1 is 9.6%.

<Production Example 7: Film formation of the raw material film 2> Cast varnish (2) on PET (polyethylene terephthalate) film ("COSMOSHINE (registered trademark) A4100" manufactured by Toyobo Co., Ltd., thickness 188 μm, thickness distribution ±2 μm) by casting Instead, a coating film is formed. At this time, the linear velocity is 0.3 m/min. Furthermore, the coating film was dried under the following conditions: after heating at 80°C for 10 minutes, at 100°C for 10 minutes, then at 90°C for 10 minutes, and finally at 80°C for 10 minutes. Thereafter, the coating film was peeled from the PET film to obtain a raw material film 2 having a width of 700 mm and a thickness of 58 μm. The weight reduction rate M of the raw material film 2 was 9.2%.

<Example 1: Production of resin film 1> The raw material film 1 obtained in Production Example 6 was heated using a tenter drying furnace (a structure divided into six chambers in total) shown in FIG. 1 using a jig as a holding device. For the raw material film, spray nozzles were used in a total of 6 chambers in the furnace. The opening area of the tenter drying furnace is 0.0055 m ² . The solvent was removed to obtain a resin film 1 with a thickness of 79 μm. At this time, the conditions in the drying furnace are: the temperature in the drying furnace is 200°C, the holding width of the jig is 25 mm, the conveying speed of the film is 1.1 m/min, the film width (distance between the jigs) at the entrance of the drying furnace and drying The ratio of the film width at the furnace outlet is 1.0 and the wind speed shown in Table 2. After that, the clip part was torn off (cut), a PET-based surface protective film was stuck to the film, and wound up to a 6-inch core made by ABS to obtain a rolled film. The conveyability at this time, the appearance of the film after the tenter drying furnace, and the weight reduction rate M of the obtained resin film 1 are shown in Table 2.

<Example 2: Production of resin film 2> In addition to using the raw material film 2 obtained in Manufacturing Example 7, the film conveying speed was changed to 0.9 m/min, and the ratio of the film width at the entrance of the drying furnace (distance between fixtures) to the film width at the outlet of the drying furnace was changed to 0.98 times In addition to changing the wind speed to the conditions shown in Table 2, processing was performed under the same conditions as in Example 1 to obtain a resin film 2 having a thickness of 49.5 μm. Table 2 shows the transportability at this time, the appearance of the film after the tenter drying furnace, and the weight reduction rate M of the resulting resin film 2.

<Comparative Example 1: Production of resin film 3> A resin film 3 having a thickness of 49 μm was obtained from the raw material film 2 in the same manner as in Example 2 except that the wind speed was changed to the conditions shown in Table 2. The conveyability at this time, the appearance of the film after the tenter drying furnace, and the weight reduction rate M of the obtained resin film 3 are shown in Table 2. Due to damage or cracking, the in-plane phase difference measurement was not performed.

[Table 2]

10, 12, 14‧‧‧ region 18‧‧‧holding device 20‧‧‧raw film 30‧‧‧Upper nozzle (nozzle) 32‧‧‧Lower nozzle (nozzle) 34‧‧‧Jet nozzle 36、38‧‧‧Piercing nozzle 36a, 38a‧‧‧‧ 40‧‧‧ slit 42, 44‧‧‧ opening 100‧‧‧Oven 100a‧‧‧upper surface 100b‧‧‧Lower surface A‧‧‧Moving direction of film

FIG. 1 is a step cross-sectional view schematically showing a preferred embodiment of the method for manufacturing a resin film of the present invention. 2 is a step cross-sectional view schematically showing a preferred embodiment of the heating step of the method for manufacturing a resin film of the present invention. 3 is a schematic cross-sectional view showing an example of the shape of a spray nozzle preferably used in the method of manufacturing a resin film of the present invention. 4 is a schematic cross-sectional view showing an example of the shape of a perforated nozzle preferably used in the method of manufacturing a resin film of the present invention. 5 is a schematic cross-sectional view showing another example of the shape of the perforated nozzle preferably used in the method of manufacturing a resin film of the present invention.

10, 12, 14‧‧‧ region

20‧‧‧raw film

30‧‧‧Upper nozzle (nozzle)

32‧‧‧Lower nozzle (nozzle)

100‧‧‧Oven

100a‧‧‧upper surface

100b‧‧‧Lower surface

A‧‧‧Moving direction of film

Claims (11)

A method for manufacturing a resin film, which is a method for manufacturing a resin film containing at least either a polyimide-based resin or a polyamide-based resin, and has a heating step of heating the raw material film with hot air, the heating step is borrowed It is carried out by the hot air from the blowing outlet of a pair of nozzles facing each other. With regard to the above nozzles, the blowing air velocity of the blowing outlet is 2 m/sec or more and 25 m/sec or less. The nozzle of the raw material film in the width direction is 0.1 to 3 m ³ /sec per 1 m length. The method for manufacturing a resin film according to claim 1, wherein the blowing wind speed of the blowing outlet is 2 m/sec or more and less than 25 m/sec. The method for manufacturing a resin film according to claim 1, wherein the nozzle is a nozzle having a slit-shaped blowing port extending in the width direction of the raw material film, or has a transport direction of the raw material film and a width of the raw material film In the direction, a plurality of nozzles with open outlets are arranged respectively. The method for manufacturing a resin film according to claim 2, wherein the nozzle is a nozzle having a slit-shaped blowing port extending in the width direction of the raw material film, or has a transport direction of the raw material film and a width of the raw material film In the direction, a plurality of nozzles with open outlets are arranged respectively. The method for manufacturing a resin film according to any one of claims 1 to 4, wherein in the heating step, the hot air blown from each of the nozzles of the nozzles that blow hot air to the raw material film is blown out in the width direction of the film The difference between the wind speed and the minimum blowing wind speed is less than 4 m/sec. The method for manufacturing a resin film according to any one of claims 1 to 4, wherein the above heating step is performed in a clean room. The method for manufacturing a resin film according to claim 5, wherein the above heating step is performed in a clean room. The method for manufacturing a resin film according to any one of claims 1 to 4, wherein the heating step is performed in an oven with a cleanliness level of 1000 or less. The method for manufacturing a resin film according to claim 5, wherein the above heating step is performed in an oven with a cleanliness level of 1000 or less. The method for manufacturing a resin film according to claim 6, wherein the heating step is performed in an oven with a cleanliness level of 1000 or less. The method of manufacturing a resin film according to claim 7, wherein the heating step is performed in an oven with a cleanliness level of 1000 or less.

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