TW202016182A - Resin film and manufacturing method thereof - Google Patents

Abstract

The present invention addresses the problem of providing: a resin film which has optical properties required for a front panel, while being suppressed in defects such as damage due to rattling of thefilm during production; and a method for producing the resin film. The invention provides a resin film. The resin film contains at least one of a polyimide resin or a polyamide resin, and the center point in the width direction of the film is set as TDc; the in-plane phase difference value R (TDc) of TDc and the in-plane phase difference value R (TD80) of TD80, which are measured at a wavelength of 590 nm, satisfy formula (1), where TD80 is the point of 80% of the length from the center point in the width direction to the end portion with the center point being 0%. R (TDc)/R (TD80) ≥ 0.35 (1).

Description

Resin film and its manufacturing method

The present invention relates to a resin film containing at least either a polyimide-based resin or a polyamide-based resin and a method of manufacturing the same.

In recent years, thinner, lighter, and more flexible image display devices have been pursued, but the glass substrates or glass front panels previously used do not have sufficient material characteristics that can meet the above requirements. Therefore, the development of materials or substrates replacing glass is being promoted. One of them is a resin film containing polyimide resin. The resin film containing a polyimide resin is used for various applications from the viewpoint of flexibility, transparency, and heat resistance (Patent Document 1). [Prior Technical Literature] [Patent Literature]

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

[Problems to be solved by the invention]

In the case where 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 and the like. However, there is a problem that the yellowing of the film due to heating under high-temperature conditions damages the quality of the film. In addition, since the front panel is disposed on the viewing side of the image display device, it is required to have no defects such as damage that may affect visibility, and to have the optical and physical properties required for the front panel. [Technical means to solve the problem]

The present invention has been completed in view of the above-mentioned problems, and provides a resin film having defects such as damage due to film sloshing in the manufacturing process suppressed and having optical properties required for a front panel, and a manufacturing method thereof. That is, the present invention provides the following method of manufacturing a resin film. [1] A resin film, which is a resin film containing at least either a polyimide-based resin or a polyamido-based resin, and the center point in the width direction of the film is set to TD _c , and In the length from the center point to the end, when the center point is set to 0% and the point at 80% of the length is set to TD ₈₀ , the in-plane phase difference value R(TD _c ) of TD _c measured at a wavelength of 590 nm and the retardation value R (TD ₈₀₎ satisfies formula (1) TD ₈₀ of the inner surface. R(TD _c )/R(TD ₈₀ )≧0.35 (1) [2] The resin film as described in [1], in which the center point of the resin film in the width direction of the film is TD _c , and the width direction is In the length from the center point to the end, when the center point is set to 0% and the point with a length of 66% is set to TD ₆₆ , the in-plane phase difference value R(TD _c ) of TD _c measured at a wavelength of 590 nm and the retardation value R (TD ₆₆₎ satisfies formula (2) TD ₆₆ of the inner surface. R(TD _c )/R(TD ₆₆ )≧0.40 (2) [3] The resin film as described in [1] or [2], wherein the resin film satisfies formula (3). R(TD _c )/R(TD ₆₆ )－R(TD _c )/R(TD ₈₀ )<0.15 (3) [4] The resin film as described in any one of [1] to [3], wherein the resin The weight reduction rate of the film is 3% or less. [5] The resin film according to any one of [1] to [4], wherein the total width of the resin film in the width direction is 300 to 2,200 mm. [6] A flexible display device including the resin film according to any one of [1] to [5]. [7] The flexible display device described in [6], which further includes a touch sensor. [8] The flexible display device described in [6] or [7], further including a polarizing plate. [9] A method of manufacturing a resin film, which is a method of manufacturing a resin film containing at least either a polyimide-based resin or a polyamide-based resin, and has a tenter furnace divided into a plurality of spaces inside In the heating step of heating the raw material film in the tenter furnace, the heating step is performed by hot air treatment in at least one space, and the radiation step is performed by radiation treatment in at least one space. [10] The method of manufacturing a resin film as described in [9], wherein the heating step is performed in the same space of the tenter furnace by two methods of hot air treatment and radiation treatment. [11] The method for manufacturing a resin film as described in [9] or [10], wherein the heating step of the above radiation treatment method is performed by irradiating the raw material film with a higher temperature than the space where the heating step is performed by the radiation treatment method Radiation at temperatures above 30°C. [12] The method for producing a resin film according to any one of [9] to [11], wherein the raw material film contains a solvent, and the weight reduction rate of the raw material film is 40% or less. [Effect of invention]

According to the present invention, there is provided a resin film in which defects such as damage are suppressed, and which have uniform in-plane retardation and low yellowness and other excellent optical properties required for the front panel. 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, the embodiment 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.

<Resin film> The resin film of the present invention contains at least either a polyimide-based resin or a polyamide-based resin, and the center point of the film width direction is set to TD _c , and the width direction In the length from the center point to the end, when the center point is set to 0% and the point with a length of 80% is set to TD ₈₀ , the in-plane phase difference value R(TD _c of TD _c measured at a wavelength of 590 nm retardation value R (TD ₈₀₎ satisfies formula (1) in-plane) and the TD _80. R(TD _c )/R(TD ₈₀ )≧0.35 (1)

The resin film satisfying the above formula (1) is in a direction (film width direction, also referred to as TD direction) perpendicular to the film transport direction (also referred to as MD direction) when continuously manufacturing the resin film of the present invention, from the TD direction From the central part to both ends of the film, the deviation of the in-plane phase difference value is small. If such a resin film is used for a front panel of an image display device such as a flexible display device, the deviation of the sharpness of the image viewed can be suppressed, so the visibility is excellent.

R(TD _c )/R(TD ₈₀ ) in the formula (1) is preferably 0.36 or more, more preferably 0.37 or more, still more preferably 0.38 or more, still more preferably 0.42 or more, and particularly preferably 0.44 or more. The closer R(TD _c )/R(TD ₈₀ ) of the formula (1) is to 1, it means that the deviation of the in-plane phase difference between the film center portion in the TD direction and the film both ends is smaller, so it is preferable.

The resin film is a resin film containing at least either a polyimide-based resin or a polyamidide-based resin, and the center point in the width direction of the film is set to TD _c , from the center point in the width direction to the end When the center point is set to 0% and the point at 66% of the length is set to TD ₆₆ , the in-plane phase difference value R (TD _c ) of TD _c measured at a wavelength of 590 nm and the in-plane of TD ₆₆ The phase difference value R (TD ₆₆ ) satisfies equation (2). R(TD _c )/R(TD ₆₆ )≧0.40 (2)

R(TD _c )/R(TD ₆₆ ) in the formula (2) is more preferably 0.45 or more, still more preferably 0.50 or more, still more preferably 0.52 or more, and particularly preferably 0.58 or more. The closer R(TD _c )/R(TD ₆₆ ) is to 1, it means that the deviation of the in-plane phase difference between the film center in the TD direction and both ends of the film is smaller, which is preferable.

If the value of formula (1) or formula (2) is within the above range, when the resin film is used as a front panel, even if it is close to both ends of the film can be used in the product, the yield becomes higher, so Better.

The resin film preferably has a difference between the ratio R(TD _c )/R(TD ₆₆ ) and the ratio R(TD _c )/R(TD ₈₀ ) satisfying formula (3). The difference between these ratios is more preferably 0.13 or less, further preferably 0.12 or less, still more preferably 0.11 or less, and particularly preferably 0.10 or less. If the difference of the ratios is within this range, the deviation of the phase difference in the plane of the resin film is small. R(TD _c )/R(TD ₆₆ )－R(TD _c )/R(TD ₈₀ )＜0.15 (3)

The resin film preferably satisfies the formula (1) and the formula (2), and satisfies the formula (3), and more preferably satisfies the formulas (4) to (6) below the formula (1) to (3) All. This type of resin film is preferable for the following reasons: the deviation of the phase difference in the plane of the resin film is smaller, and when the resin film is used as the front panel, even the parts close to both ends of the film can be used in the product, yield Become higher. R(TD _c )/R(TD ₈₀ )≧0.37 (4) R(TD _c )/R(TD ₆₆ )≧0.45 (5) R(TD _c )/R(TD ₆₆ )－R(TD _c )/ R(TD ₈₀ )≦0.13 (6)

In the resin film, the total width in the width direction is preferably 300 to 2,200 mm. In this specification, the "full width" refers to the entire direction (width direction, also referred to as the TD direction) in the resin film of the present invention that is perpendicular to the transport direction of the film during continuous manufacturing. The total width in the film width direction is more preferably 400 to 2,100 mm, and further preferably 500 to 2,000 mm.

The thickness of the resin film is preferably 10 μm or more, more preferably 20 μm or more, and still more preferably 30 μm or more. In addition, the thickness is preferably 120 μm or less, more preferably 100 μm or less, and further preferably 80 μm or less. A thickness of 30 μm or more is advantageous from the viewpoint of protection of the interior when the resin film is incorporated into the display device, and a thickness of 120 μm or less is advantageous from the viewpoint of folding resistance, cost, transparency, etc. . The measurement method is described in detail in the examples.

The resin film that has undergone the heating step preferably has a weight reduction rate M of 120% to 250°C determined by TG-DTA measurement of 3% or less. The weight reduction rate M is more preferably 2% or less, further preferably 1.5% or less, and still more preferably 1% or less. In addition, the lower limit of the weight reduction rate M is not particularly limited, and it can be set to 0.1%, for example.

If the weight reduction rate M of the resin film is within the above range, there is a tendency to obtain a film having both sufficient hardness and flexibility required for the front panel of the flexible display device. When the amount of residual solvent is more than the above upper limit, there is a case where the surface of the film is relatively soft and easily damaged, so that the operation of the film becomes difficult in the subsequent steps.

From the viewpoint of visibility, 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. 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.

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, it is possible to ensure a sufficient film appearance when incorporated into an image display device.

The yellowness of the resin film is preferably 3.0 or less, more preferably 2.7 or less, and still more 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.

<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 in a tenter furnace divided into a plurality of spaces inside, and in the tenter furnace, a heating step is performed by hot air treatment in at least one space, In addition, the heating step is performed by radiation treatment in at least one space. The tenter furnace refers to a furnace that fixes both ends in the width direction of the film and heats it.

The method of manufacturing the resin film of this embodiment will be described with reference to the drawings. 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 a tenter furnace 100, and heated in a heating area in the tenter furnace 100, and thereafter The tenter furnace 100 is moved out. In this specification, a film that has undergone a heating step and changes in the amount of solvent over time, but is in the heating step or transported in the oven is called a raw material film, and a film that is transported out of the oven after the heating step Called 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 tenter furnace 100, or may be continuously carried into the tenter furnace from its latest step. 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 preferably fixes both ends of the film in a direction (TD direction, also known as the width direction) perpendicular to the film transport direction (MD direction, also known as the length direction) to the tenter furnace Carry out within.

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 commonly used in film manufacturing devices. The two fixed ends can be adjusted appropriately by the holding device used, preferably within 50 cm from the end of the membrane. Referring to FIG. 2, both ends of the film can be held by a plurality of holding devices 18 while being transported on one side. The plurality of holding devices 18 provided at one end of the film is preferably a distance between adjacent holding devices that is capable of suppressing defects such as sloshing of the film or cracking of dimensional changes caused by heating. The distance between the adjacent holding devices 18 is preferably 1 to 50 mm, more preferably 3 to 25 mm, and still more preferably 5 to 10 mm. Furthermore, the holding device is preferably arranged in such a way that when a 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 line and the other end of the film is closest to The distance of the center of the holding portion of the holding device of the intersection point is preferably 3 mm or less, more preferably 2 mm or less, and further preferably 1 mm or less. By this, the difference in stress applied to the two ends of the opposing film can be reduced, and thus the resulting resin film can suppress the occurrence of deviations in optical properties.

As an example of the operation of fixing the both ends of the film with a holding device, an appropriate timing before or after being carried into the tenter furnace can be cited, and a plurality of devices arranged in such a manner as to face the width direction of the film can be used A method for fixing two ends of the film in the width direction of each film chuck 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. The fixing of both ends of the film may be released in a timely manner after the heating step, and may be carried out in the tenter furnace or after being carried out from the tenter furnace.

The total length of the film transfer direction of the tenter furnace used for the heating step is usually 10 to 100 m, preferably 15 to 80 m, and more preferably 15 to 60 m. The inside of the tenter furnace can be one space or can be divided into a plurality of spaces. In the embodiment of the present invention, the inside of the tenter furnace that performs the heating step is divided into a plurality of spaces. The above-mentioned space may be a space capable of controlling temperature conditions, wind speed conditions, etc., or may not have physical boundaries such as partition plates. When the inside of the tenter furnace is divided into a plurality of spaces, it can be divided into a plurality of spaces perpendicular or parallel to the conveying direction of the film. The number of spaces is usually 2-20, preferably 3-18, more preferably 4-15, and still more preferably 5-10. Not depending on the internal structure of the tenter furnace, the entire tenter furnace becomes the heating area, and a part of the interior can also become the heating area. Referring to FIG. 1, all three of the regions 10, 12, and 14 may become heating regions, and one of the regions, for example, region 14 may become a heating region.

A plurality of tenter furnaces can also be used. In this case, the number of tenter furnaces is not particularly limited, but it can be set to 2 to 12, for example. The inside of each tenter furnace may be the structure described previously. A plurality of tenter furnaces can be continuously installed in such a manner that the film is transported without contacting the outside atmosphere. When a plurality of tenter furnaces are used, all tenter furnaces can be used as heating areas, or a portion of tenter furnaces can be used as heating areas. In addition to the tenter furnace, it can also be used as an oven for other equipment. In this specification, the so-called oven refers to equipment that can heat the film, including a heating furnace and a drying furnace. The heating furnace may be either hot air treatment or radiation treatment, or a combination of these heating furnaces. In the case of using an oven together, the internal structure of the oven, the number of uses, and the heating conditions can be adjusted as long as the resin film of the present invention can be obtained, and it is preferably set as The same is true.

Regarding the circulation and exhaust of the air inside the tenter furnace, it is preferably performed in each space when the interior of the tenter furnace is divided into a plurality of spaces, and preferably when there are a plurality of tenter furnaces For each tenter furnace. The temperature inside the tenter furnace (temperature of the environment in the tenter furnace) is preferably adjustable according to each tenter furnace, and when the inside of the tenter furnace is divided into a plurality of spaces, it is preferable that each space is independent Temperature adjustment. The temperature setting of each space can be the same or different. Among them, the temperature of each tenter furnace or space preferably satisfies the following temperature range.

The tenter furnace 100 that performs the heating step performs the heating step by hot air treatment in at least one space, and performs the heating step by radiation treatment in at least one space. The heating step is preferably performed by hot air treatment in all spaces where the step is performed. The heating step of the radiation treatment method can be performed in a space different from the hot air treatment method, and it is preferable to perform the heating step together with the hot air treatment method.

The heating step of the hot air treatment method can be performed by providing a nozzle for blowing hot air in the tenter furnace. The heating step of the radiation treatment method can be performed by irradiating the film with radiation by installing an IR (infrared radiation, infrared radiation) heater or the like in the tenter furnace.

As an example of an embodiment of the present invention, a hot air treatment method using a nozzle and a radiation treatment method using an IR heater will be described in order from the hot air treatment method using a nozzle.

Referring to FIG. 1, a tenter furnace 100 that performs a heating step is provided with a plurality of upper nozzles 30 on its inner upper surface 100a, and a plurality of lower nozzles 32 on its inner lower surface 100b. 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 (8 in total) as in the region 14 of FIG. 1, or 10 pairs of nozzles (20 in total) as in the region 12 of FIG. 1, which can be appropriately set according to the structure of the oven. From the viewpoint of simplifying the structure of the tenter furnace and uniformly heating the raw material film, the interval between adjacent nozzles is preferably 0.1 to 1 m, more preferably 0.1 to 0.5 m, and still more preferably 0.1 to 0.3 m.

In the case where the inside of the tenter furnace is divided into a plurality of sections, the number of hot air blowing nozzles provided in each space can usually be set to 5 to 30. From the viewpoint of obtaining a resin film with 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 tenter furnace 100 has a blower outlet in the lower part, and can blow out hot air in a downward direction (arrow B direction). On the other hand, the nozzles 32 respectively provided on the lower surface of the lower surface of the tenter furnace 100 have blowing outlets at the upper portion, and can blow out hot air in the upward direction (arrow C direction). Although not shown in FIG. 1, the upper nozzle 30 and the lower nozzle 32 have a specific depth in a direction perpendicular to the paper surface of FIG. 1 to uniformly heat the raw material film in the width direction.

In the manufacturing method of the resin film of this embodiment, the blowing speed of hot air from the outlets of all the upper nozzles 30 and all the lower nozzles 32 provided in the heating area is preferably 2 to 25 m/s. From the viewpoint of obtaining a resin film having further excellent optical uniformity, the blowing wind speed is more preferably 2 to 23 m/s, and further preferably 8 to 20 m/s. Also, the amount of air blown from the outlet of each nozzle 30 or 32 is preferably 0.1 to 3 m ³ /s per 1 m length of the nozzle along the width direction of the raw material film. In addition, from the viewpoint of obtaining a resin film having further excellent optical uniformity, the amount of blown air is more preferably 0.1 to 2.5 m ³ /s per 1 m length of the nozzle along the width direction of the film, and further preferably 0.2～2 m ³ /s.

If the blowing air velocity and air volume from the nozzle are within the above-mentioned range, the raw material film is uniformly heated, so that it is easy to obtain a film having a uniform optical and physical property over the entire surface of the film, which is preferable. Specifically, if the heating step is performed under the above conditions, the variation in 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 variation in contrast is suppressed, and it becomes a front panel with better visibility. Furthermore, if the heating step is performed under the above conditions, it is uniformly heated, so that the variation in the amount of solvent remaining in the film becomes small, so that it is easy to obtain a resin film with a more uniform elastic modulus over the entire surface of the film. Therefore, it is difficult for the entire surface of the film to have deviations in bendability, and it is possible to suppress the damage caused by the difference in the bendability of the film surface.

In the tenter furnace, the raw material film 20 is heated from room temperature to the temperature at which the solvent contained in the raw material film evaporates, and is held by the holding device 18 in such a way that the length of the raw material film in the width direction hardly changes, so it is easy The tendency to sag due to thermal expansion. If the blowing air speed and the blowing air volume are within the above ranges, the raw material film 20 can be sufficiently heated, and the raw material film 20 can be prevented from sagging or shaking.

The blowing speed of the hot air can be measured at the hot air 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, from the viewpoint of measurement accuracy, it is preferable that the blowing air speed of the hot air is measured at about 10 points at the outlet of each nozzle, and set as the average value.

The blowing air speed and blowing air volume of the hot air can be appropriately adjusted according to the physical properties (optical characteristics, mechanical properties, etc.) of the produced resin film, and it is preferably within the above-mentioned range in any form. Thereby, a resin film with a more sufficiently uniform phase difference and a further sufficiently high axis accuracy can be obtained. The heating area is more preferably in all heating areas, the blowing air velocity is 25 m/s or less and the blowing air volume is 2 m ³ /s or less.

In this embodiment, in the state where the raw material film 20 is not introduced into the tenter furnace 100, the wind speed of the hot air which should maintain the position of the raw material film 20 is preferably 5 m/s or less, more preferably at least in the heating area For this kind of wind speed. By heating the raw material film 20 using such hot air, a resin film with more sufficiently excellent optical uniformity can be obtained.

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

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 to the oven (hereinafter referred to as the conveying path 1), when the inside of the oven is not separated by a plurality, it refers to the length of the oven from the oven entrance (the length from the oven entrance to the exit) 1/10 of the distance. When the conveying path 1 is divided into a plurality of spaces inside the oven, it refers to the space through which the film first passes. In the case of using multiple ovens, according to the internal structure of the initially used oven, it may be the same as the previous record, or it may be set 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 path refers to the conveying path part which is 1/10 or less of the length of the oven when the oven is not separated by plurals. 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, according to the internal structure of the initially used oven, it can be the same as the previous record, 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 in the range of 0.1 to 15 m/s. The difference in the above wind speed is more preferably 0.2 m/s or more, and more preferably 12 m/s or less, further preferably 8 m/s or less, still more preferably 5 m/s or less, and particularly preferably 3 m/s. s below. If the wind speed immediately after being transferred 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 removed more efficiently. If the difference in the wind speed is too large, there may be sloshing of the film due to the difference in wind speed, which may cause a defect in the surface shape of the resulting resin film or a deviation in optical characteristics such as phase difference.

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 blowing air speed of the hot air from the nozzles provided in the other conveying paths . When there is a difference of 2 m/s or more between the speed of the hot air blown to the film and the blown air speed of the hot air from the nozzle, it can also be used as the speed of the hot air near the film in each of the transport path 1 and other transport paths Find the difference.

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

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 wind speed of the conveying path after the conveying path 2 is preferably a difference of 0.1 to 12 m/s, and more preferably a difference of 0.2 to 8 m/s. . If it is such a difference in wind speed, there is a tendency to suppress the shaking of the film due to the difference in wind speed, and it is easy to adjust the weight reduction rate of the resulting resin film to the desired range.

When the difference of the above-mentioned wind speed is not divided into a plurality of spaces inside the oven, it can be adjusted by adjusting the position of the setting nozzle, the blowing speed and air volume of the hot air of the nozzle, and the flow direction of the air flow in the oven. When the inside of the oven is divided into a plurality of spaces, it can be adjusted by adjusting the position of the nozzle, the blowing speed and the amount of hot air of the nozzle, the flow direction of the air flow in the oven, etc. by adjusting the initial space and the subsequent space. . In the case of using multiple ovens, according to the structure of the original oven, it can be carried out in the same way as the previous description, or the position of the nozzles can be set in such a way that the wind speed in the first oven and the second and subsequent ovens are different , The hot air blowing speed and air volume of the nozzle, the air flow in the oven, etc.

In the heating area of the tenter furnace 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 still more 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 in FIG. 1) of each of the nozzles 30 and 32 provided in the heating area is preferably 2° C. Below, more preferably, all are below 1°C. By heating the film with hot air having such a sufficiently small temperature difference in the width direction, the deviation 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.

As a nozzle that can be used in the method of manufacturing a resin film, a nozzle generally used in a film manufacturing apparatus can be used. As an example thereof, a nozzle having a slit-shaped blowing port extending in the width direction of the raw material film can be cited. A nozzle (jet nozzle) (also called a slit nozzle), and a punching nozzle (also called a porous nozzle) that has a plurality of openings with openings arranged in the transport direction of the raw material film and the width direction of the raw material film .

The nozzle is configured to blow hot air toward the film downward on the upper surface 100a of the tenter furnace 100, and blow hot air toward the film upward on the lower surface 100b provided in the tenter furnace 100.

The spray nozzle has a slit extending in the width direction of the film as a blowing port for hot air. The slit width of the slit is preferably 5 mm or more, more preferably 5-20 mm. By setting the slit width to 5 mm or more, the optical uniformity of the resulting resin film can be further improved. Furthermore, the area of the outlet of each jet nozzle can be obtained by the product of the length of the jet nozzle in the width direction and the width of the slit. 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 along the width direction of the film, the blown air volume of the hot air per 1 m length of the nozzle along the width direction of the film can be obtained.

Regarding the punching nozzle, the cross section perpendicular to the longitudinal direction thereof may have a rectangular shape, or a trapezoidal shape gradually expanding toward a surface 38a facing the raw material film 20. The punching nozzle has a plurality of openings (for example, circular openings) on the surface 36a below the surface facing the film. The hot air outlet of the punching nozzle is composed of a plurality of openings provided on the blowing surface. A plurality of openings are hot air blowing outlets, and the hot air is blown out from the openings at a specific wind speed. A plurality of openings are arranged in the longitudinal direction of the film, and a plurality of openings are also arranged in the width direction. The opening may be configured, for example, in a zigzag shape.

The area of the outlet of each punching nozzle can be obtained by the sum of the areas of all the openings provided in one punching nozzle. 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 along the width direction of the film, the blown air volume of the hot air per 1 m length of the nozzle along the width direction of the film can be obtained.

In the case of using a punching nozzle, the difference between the maximum blowing velocity and the minimum blowing velocity of the hot air at the outlet of the nozzle in the width direction can be used as the maximum blowing velocity and the minimum of the hot air blowing from a plurality of openings provided on the same nozzle It is calculated from the difference in blowing speed. The difference between the maximum temperature and the minimum temperature of the hot air at the outlet of the nozzle in the width direction can also be obtained in the same way.

If all the nozzles installed in the tenter furnace 100 are punching nozzles, the total area of the hot air blowing outlet of the entire tenter furnace 100 can be increased. Therefore, the wind pressure of the hot air blown to the membrane can be reduced, and the sloshing of the membrane can be further reduced. Thereby, the optical uniformity of the obtained resin film can be further improved. In the tenter furnace or 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, because the length of the raw material film in the width direction is hardly changed by the holding device 18, Therefore, it tends to sag due to thermal expansion. By using a punching nozzle in the heating area, the raw material film 20 can be further suppressed from sagging or shaking.

The size and number of openings provided on the face of the punching nozzle can be 2 to 25 m/s for the blowing speed of the hot air at each opening, and the amount of blowing air from each nozzle is relative to the nozzle along the width direction of the film The length per 1 m is adjusted within a range of 0.1 to 3 m ³ /s.

From the viewpoint of making the blowing wind speed from each opening of the punching nozzle more uniform, the shape of the opening is preferably circular. In this case, the diameter of the opening is preferably 2-10 mm, more preferably 3-8 mm.

In the case of using a punching nozzle, the length of the film transport direction on the surface of each nozzle is preferably 50 to 300 mm. Furthermore, the distance from the adjacent punching nozzle is preferably 0.3 m or less. In addition, the ratio of the total area of the opening of the punching nozzle (the area of the blowout outlet) to the length in the film width direction of the punching nozzle (the total area of the opening of the punching nozzle (m ² )/film of the punching nozzle The length (m) in the width direction is preferably 0.008 m or more.

By using such a punching nozzle, 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 further uniformly heated. Therefore, a film with a more uniform phase difference and a higher axis accuracy can be manufactured.

The tenter furnace 100 that performs the heating step may be provided with an IR heater on its inner upper surface 100a or its inner lower surface 100b in the same manner as the nozzle, and is installed so as to face in the up-down direction. In addition, a plurality of IR heaters may be provided. As the IR heater, an IR heater generally used in a film manufacturing apparatus may be used.

The radiation irradiated to the film is preferably a heat ray with a wavelength of 3 to 7 μm. Furthermore, in the radiation treatment method, if the temperature of the space in which the heating step is performed falls within the above-mentioned temperature range, the raw material film may be irradiated with a radiation temperature higher than the temperature of the space by 30° C. or more.

In the embodiment of the present invention, it is preferable to use the above-described nozzle (hot air treatment method) and IR heater (radiation treatment method) in the tenter furnace 100 performing the heating step. In this case, it is sufficient to provide an IR heater between the adjacent nozzles or between the nozzles and the inner wall of the tenter furnace (including the wall partitioning the space).

In this case, as long as the temperature of the space where the heating step is performed is within the above-mentioned temperature range, in the radiation treatment method, the film may also be irradiated with radiation having a temperature higher than the temperature of the space. The temperature of the radiation may be, for example, a temperature higher than 30°C higher than the space temperature, or a temperature higher than 150°C. Here, the temperature of the radiant rays, for example, the set temperature of the IR heater refers to the temperature set in the device that emits radiant heat. The difference between the temperature of the radiation and the temperature of the radiation irradiated to the film is preferably 5°C or lower, more preferably 3°C or lower, and further preferably 1°C or lower.

If the nozzle (hot air treatment method) and the IR heater (radiation treatment method) are used together in the tenter furnace 100, although the raw material film is irradiated with radiation higher than the temperature in the heating area or the tenter furnace (ambient temperature) It is also possible to perform the heating step while suppressing the temperature in the heating zone or the tenter furnace from becoming too high. By this, the weight reduction rate can be adjusted more quickly in a state where the yellowness (YI) of the resulting resin film is kept at a smaller value compared to the case where only one of the treatment methods is used for the heating step For a specific range. Furthermore, by irradiating the raw material film with radiation higher than the temperature in the heating zone or the tenter furnace, the resin in the raw material film is easily aligned or realigned, so there is a surface of the center portion of the resulting resin film and both ends of the film The deviation of the internal phase difference value tends to become smaller. Therefore, when the resulting resin film is applied to a display device as described above, the visibility of the image is more excellent.

The heating step in which the hot air treatment method and the radiation treatment method are used together is preferably between the space where the raw material film initially passes in the plurality of spaces from the tenter furnace in which the heating step is performed to the space which is located in the middle of the full length of the tenter furnace get on. By this, not only can the time required for the heating step be shortened, but also a resin film with more uniform in-plane retardation can be manufactured.

The heating step is preferably performed in the range of 150 to 350°C. If the heating step is in this temperature range in the embodiment of the present invention, the raw material film tends to be easily adjusted to the weight reduction rate M described below. The temperature range is more preferably 170°C or higher, further preferably 180°C or higher, and still more preferably 300°C or lower, still more preferably 250°C or lower, and particularly preferably 230°C or lower. If the temperature in the heating step is within the above range, the yellowness of the resulting resin film tends to exceed 3 in the preferred range. In addition, the temperature of the space in which the heating step is performed is more preferably 170°C or higher, and further preferably 180°C or higher. The temperature in the tenter furnace in which the heating step is performed may be as long as the heating area is within the above range. In the case where there are a plurality of tenter furnaces and the case where the tenter furnace is divided into a plurality of spaces, it can be adjusted appropriately, and it is preferable that all tenter furnaces 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 upper limit of the moving speed is preferably 20 m/min, more preferably 15 m/min. The lower limit of the moving speed is preferably 0.2 m/min, more preferably 0.5 m/min, further preferably 0.7 m/min, and particularly preferably 0.8 m/min. If the moving speed is faster, the tenter furnace length becomes longer and the equipment tends to be larger in order to ensure the required drying time. In the embodiment of the present invention, if the moving speed of the raw material film 20 in the tenter furnace 100 is within the above range, there is a tendency to easily adjust the raw material film to the following weight reduction rate M. In addition, the sloshing of the film is suppressed and the tendency to damage the film surface can be suppressed.

The treatment time in the heating step is usually 60 seconds to 2 hours, preferably 10 minutes to 1 hour. The processing time may be appropriately adjusted in consideration of the above-mentioned conditions such as the temperature, moving speed, hot air speed and air volume of the tenter furnace.

In the manufacturing method of the resin film of this embodiment, the operation of changing the width of the film in the heating step or the operation of keeping the width of the film and transporting may also be performed. As an example of the operation of changing the width of the film, an operation of extending the width direction of the film can be cited. The stretching magnification 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 such that the length in the width direction of the film hardly changes can be cited. The resin film that has been subjected to these operations may be set to a length of about 0.7 to 1.3 times the length of the raw material film in the width direction, or may be a length that extends from the length of the raw material film in the width direction, is equal to or shrinks . The stretching ratio can be obtained as the ratio of the width of the film after stretching (excluding the holding portion) to the width of the film excluding the holding portion. In addition, in FIG. 2, the solid line indicates the case where the stretch magnification in the operation of extending the width direction of the film exceeds 1 times, and the broken line indicates the stretch magnification in the operation of extending the width direction of the film is equal to or less than 1 Times the situation.

The resin film after the heating step can be continuously fed to the next step after being carried out from the tenter furnace, or it can be wound into a roll shape and fed to the next step. In the case where the resin film is wound into a roll, it may be laminated with another film such as a surface protective film and other optical films for winding. As the surface protective film laminated on the resin film, the same as the surface protective film laminated on the following raw material film 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 to form the raw material film described below, but it may be different because structural changes of the components or evaporation of a part of the solvent may occur. The raw material film may be a self-supporting film or a gel film.

The raw material film preferably has a weight reduction rate M from 120° C. to 250° C. obtained by thermogravimetric-differential thermal measurement (hereinafter sometimes referred to as “TG-DTA measurement”) whether or not it contains an inorganic material. Preferably, a part of the solvent is removed from the varnish in such a manner that it is about 1 to 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 Corporation can be used.

First, obtain a sample of about 20 mg from the raw material film, heat the sample from room temperature to 120°C at a rate of 10°C/min, and hold it at 120°C for 5 minutes, while increasing the temperature at a rate of 10°C/min The temperature was increased to 400° C. and heated, and the weight change of the sample was measured. Then, the weight reduction rate M (%) from 120° C. to 250° C. can be calculated from the results of TG-DTA measurement 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 some extent, when the raw material film is wound as a laminate with the base material or the surface protection film, deformation such as bending of the laminate is suppressed, and the laminate Tendency to improve coilability.

If the weight reduction rate M of the raw material film is small to some extent, there is a tendency that the raw material film does not easily adhere to the base material or surface protective film when the raw material film is wound as a laminate with the base material or surface protective film . Therefore, while maintaining uniform transparency of the raw material film, 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 amide group (hereinafter sometimes referred to as polyimide), and containing amide. At least one polymer in the group consisting of a polymer having a repeating structural unit of both an amine group and an amide group (hereinafter sometimes referred to as polyamide amide imide). In addition, the "polyamide resin" means 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.

[Chemical 1]

The polyimide-based resin may also include one selected from the group consisting of repeating structural units represented by formula (11), formula (12), and formula (13) within a range that does not impair various physical properties of the resin film More than one species.

[Chem 2]

In formula (10) and formula (11), G and G ¹ are independently a tetravalent organic group, preferably an organic group that may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of G and G ^{1 include} formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), and formula ( 28) The group represented by the formula (29) and a 4-valent chain hydrocarbon group having 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).

[Chemical 3]

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

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

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. As A, A ¹ , A ² and A ³ , there can be exemplified: formula (30), formula (31), formula (32), formula (33), formula (34), formula (35), formula (36), A group represented by formula (37) or formula (38); a group substituted by a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group; and a chain hydrocarbon group having a carbon number of 6 or less.

[Chemical 4]

In formula (30) to formula (38), * represents a bonding bond, and Z ¹ , Z ² and Z ³ each 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-. In one example, 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 relative to each ring, and the bonding positions of Z ² and Z ³ relative to each ring are respectively relative to each ring, preferably meta or para.

From the viewpoint of easily improving visibility, the polyimide-based resin is preferably a polyimide amide imide having at least a repeating structural unit represented by formula (10) and a repeating structural unit represented by formula (13). 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) such as acid compound (dicarboxylic acid compound related to acetyl chloride compound), tricarboxylic acid compound (tricarboxylic acid related compound such as acetyl chloride compound, tricarboxylic anhydride). 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 a diamine and a tricarboxylic acid compound. 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 polymer obtained by reacting (polycondensing) 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'-diphenylbenzene 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-ortho Phthalic 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-extenyl benzene Base 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 is 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, it may be used in combination with cyclic aliphatic tetracarboxylic dianhydride and non-cyclic aliphatic tetracarboxylic dianhydride.

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]octane are preferred -7-ene-2,3,5,6-tetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof. In addition, as the tetracarboxylic acid, an aqueous adduct of the anhydride of the above-mentioned tetracarboxylic acid compound can also be used.

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

Examples of the dicarboxylic acid compounds include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and related substances such as acetyl chloride compounds and acid anhydrides, and two or more of them may be used in combination. As specific examples thereof, terephthaloyl chloride (TPC); m-xylylene chloride; naphthalene dicarboxylate chloride; 4,4'-biphenyldicarboxylate chloride; 3 ,3'-Biphenyldicarboxyl chloride; 4,4'-oxybis(benzoyl chloride) (OBBC); dicarboxylic acid compound of chain hydrocarbons with carbon number below 8 and 2 benzoic acids with single bond , -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or a compound formed by connecting phenylene groups.

Examples of the diamines include aliphatic diamines, aromatic diamines, and mixtures of these. In the present embodiment, the term "aromatic diamine" refers to a diamine in which an amine group is directly bonded to an aromatic ring, and may include an aliphatic group or other substituents in a part of its structure. 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 fused ring, but are not limited thereto. Among these, the aromatic ring is preferably a benzene ring. In addition, the "aliphatic diamine" refers to a diamine in which an amine group is directly bonded to an aliphatic group, and may include an aromatic ring or other substituents in a part of its structure.

Examples of the aliphatic diamine include non-cyclic aliphatic diamines such as hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, and 1,4-bis(aminomethyl) ) Cycloaliphatic diamines such as cyclohexane, noranediamine, 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'- Diamino diphenyl ether, 3,4'-diamino diphenyl ether, 3,3'-diamino diphenyl ether, 4,4'-diamino diphenyl ether, 3,4'-di Amino diphenyl sulfone, 3,3'-diamino diphenyl ash, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy) Benzene, 4,4'-diaminodiphenyl satin, bis[4-(4-aminophenoxy)phenyl] satin, bis[4-(3-aminophenoxy)phenyl] satin , 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'- Dimethylbenzidine, 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) Aromatics with more than 2 aromatic rings such as stilbene, 9,9-bis(4-amino-3-chlorophenyl) stilbene, 9,9-bis(4-amino-3-fluorophenyl) stilbene Diamine. These can be used alone or in combination of two or more.

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

The polyimide-based resin can be obtained by mixing the above-mentioned diamine, tetracarboxylic acid compound, tricarboxylic acid compound, dicarboxylic acid compound and other raw materials by a conventional method, for example, stirring, etc. It is obtained by carrying out amide imidization in the presence of a catalyst and optionally a dehydrating agent. Polyamide-based resins can be obtained by mixing various raw materials such as the above-mentioned diamines and dicarboxylic acid compounds by a conventional method, such as stirring.

The imidate catalyst used in the imidate step is not particularly limited, and examples 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 hexahydropyridine; azabicyclic [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-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-lutidine, 2, Aromatic amines such as 4,6-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, pivalic 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 as the solvent, for example, those exemplified as the solvent used in the preparation of varnish can be cited. After the reaction, the polyimide-based resin or the polyamide-based resin is purified. Examples of the purification method include a method in which a poor solvent is added to the reaction solution, the resin is precipitated by a reprecipitation method, dried to remove the precipitate, and the precipitate is washed with a solvent such as methanol and dried 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 polyimide-based resins can also be used. Specific examples thereof include Neopulim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd., and KPI-MX300F manufactured by Kawamura Industries Co., Ltd. and the like.

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 still more preferably 300,000 or more, and preferably 600,000 or less, more preferably 500,000 or less. There is a tendency that the higher the weight average molecular weight of the polyimide-based resin or the polyamide-based resin, the higher the bending resistance at the time of filming. Therefore, from the viewpoint of improving the bending resistance of the resin film, the weight average molecular weight is preferably equal to or higher than 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 the easier it is to improve the processability. In addition, there is a tendency that the extensibility of the polyimide-based resin or the polyamide-based resin tends to be improved. Therefore, from the viewpoint of workability and extensibility, it is preferable that the weight average molecular weight is 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, it is preferable that the imidate ratio is above the lower limit. In addition, the imidate ratio can be obtained by IR method, NMR (nuclear magnetic resonance, nuclear magnetic resonance) method, or the like. From the above viewpoint, it is preferable that the polyimide-based resin contained in the varnish has an imidization ratio within the above range. The above-mentioned imidate ratio can be obtained by the method described in Japanese Patent Application No. 2018-007523, for example.

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 include, for example, fluorine atoms introduced by 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 in the film, and if the yellowness of the resin film is low, the transparency of the film is easily improved. 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 the polyamide-based resin include a fluorine group and a trifluoromethyl group.

The content of halogen atoms in the polyimide-based resin or polyamidide-based resin is preferably 1 to 40 mass%, more preferably 5 to, based on the mass of the polyimide-based resin or polyamidide-based resin. 40% by mass, and more preferably 5 to 30% by mass. If the content of halogen atoms is 1% by mass or more, 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), and further improve the transparency. If the content of halogen atoms is 40% by mass or less, synthesis may be easy.

In one embodiment of the present invention, the content of the polyimide-based resin and/or polyamide-based resin in the resin film is preferably 40% by mass or more, more preferably 50 based on the total mass of the resin film The mass% or more, and more preferably 70 mass% or more. When the content of the polyimide-based resin and/or the polyamide-based resin is at least the above lower limit, it is preferable from the viewpoint of easily improving bending resistance. Furthermore, 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 based on the total mass of the resin film, 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 or less, It is more preferably 50% by mass or less, and still more preferably 45% by mass or less. In addition, the content of silicon dioxide particles can be selected from any of the upper limit and the lower limit in combination with any lower limit and upper limit. If the content of silicon dioxide particles is within the numerical range of the upper limit and/or the lower limit, there is a tendency that the silicon dioxide particles in the resin film of the present invention are not easily aggregated and are 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, and 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 silicon dioxide particles can be combined with any 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 the 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 silica particles in the resin film can be measured by using a transmission electron microscope (TEM). The particle size of the silica particles before the production of the resin film (for example, before being added 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 prepared by dispersing silica particles in an organic solvent and the like, and silica powder prepared by a gas phase method. Among these, from the viewpoint of workability, silica sol is preferred.

The silicon dioxide particles may be surface-treated, for example, may be silicon dioxide particles obtained by substituting a solvent (more specifically, γ-butyrolactone, etc.) from a silica sol dispersed in a water-soluble alcohol. The water-soluble alcohol is an alcohol having 3 or less carbon atoms per hydroxyl group in the one water-soluble alcohol molecule, and examples thereof include methanol, ethanol, 1-propanol, and 2-propanol. Although it depends on the compatibility of the silica particles with the type of polyimide-based resin or polyamidide-based resin, usually, if the silica particles are surface-treated, they will be mixed with the polyimide contained in the resin film. The compatibility of the amine resin is improved, and the dispersibility of the silica particles tends to be improved, so that the decrease in visibility of the present invention can be suppressed.

(UV absorber) The resin film of the present invention may further contain an ultraviolet absorber. For example, there may be mentioned three ultraviolet absorbers, benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, benzoate ultraviolet absorbers, and cyanoacrylate ultraviolet absorbers. 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 (produced) TINUVIN (registered trademark) 1577, etc. The content of the ultraviolet absorber is based on the mass of the resin film of the present invention, preferably 1 phr or more and 10 phr or less, and more preferably 3 phr or more and 6 phr or less.

(Brightener) The resin film of the present invention may further contain a whitening agent. The whitening agent can be added to adjust the color tone when additives other than the whitening agent are added, for example. 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 brighteners include Macrolex (registered trademark) Violet B manufactured by Lanxess Corporation, Sumiplast (registered trademark) Violet B manufactured by Sumika Chemtex Corporation, and Diaresin manufactured by Mitsubishi Chemical Corporation. (Registered trademark) Blue G, etc. These can be used alone or in combination of two or more. The content of the whitening agent is based on the mass of the resin film of the present invention, and is preferably 0 to 50 ppm, more preferably 1 to 45 ppm, still more preferably 3 to 40 ppm, and particularly preferably 5 to 35 ppm.

(Method of manufacturing raw material film) The raw material film is not particularly limited, and can be produced by, for example, a method including the following steps. (a) Preparation steps for preparing varnish containing a solution of the above resin and the above filler (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 the mixture is stirred and mixed, thereby preparing a varnish. Furthermore, when silica is used as a filler, the dispersion of silica dioxide sol containing silica can also be replaced with a solvent capable of dissolving the above resin, such as the solvent used in the preparation of the following varnish The resulting 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 resin. Examples of the solvent include: amide-based solvents such as N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide; γ-butyrolactone (GBL) and γ-pentane Lactone-based solvents such as lactones; sulfur-containing solvents such as dimethyl ash, dimethyl sulfoxide and cis-butane; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. 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-based solvents, ketone-based solvents, acyclic ester-based solvents, ether-based solvents, and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, and more preferably 5 to 20% by mass.

In the coating step, a varnish is coated on the substrate by a known coating method to form a coating film. Examples of known coating methods include roll coating methods such as wire bar coating method, reverse coating method, and gravure coating method, die coating method, comma coating method, and die coating method. Lip coating method, spin coating method, screen coating method, spray coating method, dipping method, spray method, casting method, etc.

In the forming step, the coating film is dried and peeled off from the substrate, 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 in 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 temporarily wound up and then supplied to the heating step.

As an example of the base material, if it is a metal system, an endless SUS tape can be cited, and if it is a resin system, a PET (polyethylene terephthalate) film, PEN (polyethylene naphthalate, polynaphthalene) can be cited. Ethylene dicarboxylate) film, other polyimide-based 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 also be formed into a laminate by layering a surface protection film on its surface area, and the deposited 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 there is a problem such as sticking when the laminate is rolled into a roll shape, it may be further added, and a surface protection film is formed on the area of the base material 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 is a peelable film that can protect the surface of the raw material film. For example, polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resin films such as polyethylene and polypropylene films; acrylic The resin film or the like is 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 as each other 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. In the case where 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 shape is called a layered film roll. In most cases, the laminate film roll is temporarily stored in the form of a film roll due to space and other constraints during continuous manufacturing, and the laminate 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 polyurethane. Synthetic resins such as ester resins, polycarbonate resins, ABS (acrylonitrile-butadiene-styrene, acrylonitrile-butadiene-styrene) resins; metals such as aluminum; fiber-reinforced plastics (FRP: the plastic contains glass fibers and other fibers And composite materials to improve strength) and so on. 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 (diameter after winding) is not particularly limited, but is usually 200 to 800 mm.

<Use of resin film> The resin film of the present invention can be used in the form of a single layer of the resin film, or in the form of a laminate in which other layers are laminated. The resin film or the laminate containing it has excellent surface quality, so it can be used as an optical film in an image display device or the like, especially a front panel (window film) of a flexible display.

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 single or plural functional layers. In addition, 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 a 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.

The composition for hard coating may contain a solvent and a photopolymerization initiator as necessary in addition to the above-mentioned resin. Or in the composition for hard coating, inorganic fillers, leveling agents, stabilizers, antioxidants, UV absorbers, surfactants, lubricants, antifouling agents, etc. may be included within the range that does not impair the effects of the invention additive.

The hard coat layer can be formed by applying the hard coating composition to at least one surface 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 bending resistance is hard to be reduced, and it is difficult to cause problems such as curling caused by hardening shrinkage.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, for example, it is composed of a main material selected from a transparent resin of ultraviolet curing type, a transparent resin of electron beam curing type, and a transparent resin of thermosetting type, and dispersed in the main material The UV absorber composition. By providing an ultraviolet absorption layer as a functional layer, the change in yellowness caused by 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 a material for forming the adhesive layer, commonly known ones can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used.

The adhesive layer may also be composed of a resin composition containing a component having a polymerizable functional group. In this case, the resin composition constituting the adhesive layer is further polymerized after the film is in close contact with other members, whereby firm adhesion can be achieved. 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 also contain a thermosetting resin composition or a photocurable resin composition as a material. In this case, by supplying energy afterwards, the resin composition can be polymerized and hardened.

The adhesive layer may also be a layer composed of an adhesive called Pressure Sensitive Adhesive (PSA) that is attached to the object by pressing. The pressure-sensitive adhesive can be "a substance that has adhesiveness at room temperature and adheres to the material to be adhered by slight pressure" (JIS K 6800), that is, an adhesive, or it can be "loading a specific component into a protective film In (microcapsule), an adhesive that can maintain stability until the coating is destroyed by an appropriate method such as pressure or heat (JIS K 6800) is a capsule-type adhesive.

The hue adjustment layer is a layer having a hue adjustment function, and 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, titanium oxide-based calcined pigments, ultramarine blue, cobalt aluminate, and carbon black; azo-based compounds, quinacridone-based compounds, and anthracene Organic pigments such as quinone compounds, perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, indanthrene compounds, and pyrrolopyrrole dione compounds; barium sulfate, and Constitution pigments such as calcium carbonate; and dyes such as basic dyes, acid dyes and mordant dyes.

The refractive index adjustment layer is a layer having the function of refractive index adjustment, and has a different refractive index from the layer of the polyimide amide imide resin A in the film of the present invention, which can impart a specific refractive index to the film of the present invention Floor. The refractive index adjustment layer may be, for example, a resin layer containing an appropriately 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 a decrease in transparency.

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 silicon nitride Such as metal oxide or metal nitride.

The optical member laminated on the resin film may be laminated on the resin film through an adhesive layer or an adhesive layer, or may be laminated without an adhesive layer or an adhesive layer.

<Flexible image display device> The present invention includes a flexible display device provided with the above optical film. The optical film of the present invention is preferably used as a front panel in a flexible image display device, and the front panel is sometimes referred to as a window film. The flexible image display device is configured to be bendable, and includes a laminate for a flexible image display device, and an organic EL display panel, and the flexible image is arranged on the viewing side with respect to the organic EL display panel Laminated body for display device. As a laminate for a flexible image display device, it may further include a polarizing plate and a touch sensor, and the lamination order thereof is arbitrary. Preferably, the window film, the polarizing plate, and the touch sense are laminated in order from the viewing side Sensor, or window film, touch sensor, polarizing plate. If the polarizing plate is present on the side closer to the visual recognition than the touch sensor, it is difficult to visually recognize the pattern of the touch sensor, and the visibility of the displayed image becomes better, so it is preferable. Each member can be laminated using an adhesive, an adhesive, or the like. Furthermore, a light-shielding pattern formed on at least one surface of any layer of the window film, the polarizing plate, and the touch sensor may be provided.

[Polarizer] As described above, the flexible display device of the present invention includes a polarizing plate, preferably a circular polarizing plate. The circular polarizing plate is a functional layer having a function of transmitting only the right or left circular polarizing component by laminating a linear polarizing plate with a λ/4 phase difference plate. For example, it is used to convert external light into right circularly polarized light and block the outer light that is reflected by the organic EL panel to become left circularly polarized light. Only the light-emitting components of the organic EL are transmitted, thereby suppressing the influence of reflected light and making the image easy Observed. In order to achieve the function of circular polarized light, the absorption axis of the linear polarizer and the retardation axis of the λ/4 retardation plate must theoretically be 45°, but practically 45±10°. The linear polarizing plate and the λ/4 retardation plate do not necessarily need to be adjacent and stacked, as long as the relationship between the absorption axis and the slow phase axis satisfies the above range. It is preferable to achieve complete circular polarized light at all wavelengths, but it is not necessarily necessary in practice, so the circular polarizing plate in the present invention also includes an elliptical polarizing plate. It is also preferable to further deposit a λ/4 retardation film on the viewing side of the linear polarizing plate to convert the outgoing light into circularly polarized light, thereby improving the visibility in the state of wearing polarized sunglasses.

The linear polarizing plate is a functional layer having a function of passing light vibrating in the transmission axis direction, but blocking polarized light of the vibration component perpendicular thereto. The linear polarizing plate may be a linear polarizing element alone or a structure including a linear polarizing element and a protective film attached to at least one surface thereof. The thickness of the linear polarizing plate may be 200 μm or less, preferably 0.5-100 μm. If the thickness of the linear polarizing plate is within the above range, there is a tendency that the flexibility of the linear polarizing plate is difficult to decrease.

The linear polarizing element may be a film-type polarizing element manufactured by dyeing and stretching a polyvinyl alcohol (hereinafter sometimes simply referred to as PVA)-based film. Dichromatic dyes such as iodine are adsorbed on the PVA-based film aligned by stretching, or stretched while being adsorbed on the PVA, thereby aligning the dichroic dyes and exerting polarizing performance. In the manufacture of the film-type polarizing element described above, there may be additional steps of swelling, crosslinking by boric acid, washing by an aqueous solution, and drying. The stretching or dyeing step can be performed on the PVA-based film alone or in a state of being laminated with other films such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10 to 100 μm, and the above-mentioned elongation ratio is preferably 2 to 10 times.

Furthermore, as another example of the above-mentioned polarizing element, a liquid crystal coating type polarizing element formed by coating a liquid crystal polarizing composition can be cited. The liquid crystal polarizing composition may contain a liquid crystal compound and a dichroic dye compound. The above-mentioned liquid crystalline compound only needs to have the property of showing a liquid crystal state, and particularly, if it has an alignment state with a higher order of the smectic layer, it can exert higher polarizing performance, which is preferable. In addition, the liquid crystal compound preferably has a polymerizable functional group. The dichroic dye compound is a dye that is aligned with the liquid crystal compound and shows dichroism, and may have a polymerizable functional group, and the dichroic dye itself may have liquid crystallinity.

Any of the compounds contained in the liquid crystal polarizing composition has a polymerizable functional group. The liquid crystal polarizing composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a cross-linking agent, a silane coupling agent, and the like.

The liquid crystal polarizing layer is manufactured by applying a liquid crystal polarizing composition on an alignment film to form a liquid crystal polarizing layer. The liquid crystal polarizing layer may be formed to be thinner than the film-type polarizing element, and its thickness is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

The above-mentioned alignment film is produced, for example, by applying an alignment film-forming composition on a substrate and imparting alignment by rubbing, polarized light irradiation, or the like. The above-mentioned alignment film-forming composition contains an alignment agent, and may further contain a solvent, a cross-linking agent, an initiator, a dispersing agent, a leveling agent, a silane coupling agent, and the like. Examples of the alignment agent include polyvinyl alcohols, polyacrylates, polyamic acids, and polyimides. When using an alignment agent that imparts alignment by polarized light irradiation, it is preferable to use an alignment agent containing a cinnamate group. The weight average molecular weight of the polymer used as the alignment agent is, for example, about 10,000 to 1,000,000. The thickness of the above-mentioned alignment film is preferably 5 to 10,000 nm, and more preferably 10 to 500 nm in terms of fully exhibiting alignment regulation force.

The liquid crystal polarizing layer may be peeled off from the substrate and transferred to be laminated, or the substrate may be directly laminated. It is also preferable that the above-mentioned base material functions as a transparent base material for a protective film, a phase difference plate, or a window film.

As the protective film, a transparent polymer film may be used, and the same materials or additives as those used for the transparent substrate of the window film may be used. In addition, it may be a coating-type protective film obtained by coating and curing a cationic curing composition such as epoxy resin or a radical curing composition such as acrylate. The protective film may contain plasticizers, ultraviolet absorbers, infrared absorbers, coloring agents such as pigments or dyes, fluorescent whitening agents, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants as needed , Lubricants, solvents, etc. The thickness of the protective film is preferably 200 μm or less, and more preferably 1 to 100 μm. If the thickness of the protective film is within the above range, there is a tendency that the flexibility of the film is difficult to decrease.

The aforementioned λ/4 retardation plate is a film that imparts a λ/4 retardation to a direction orthogonal to the traveling direction of incident light (in-plane direction of the film). The λ/4 retardation plate may be an extended retardation plate manufactured by stretching a polymer film such as a cellulose-based film, an olefin-based film, and a polycarbonate-based film. The aforementioned λ/4 retardation plate may contain a retardation adjuster, a plasticizer, an ultraviolet absorber, an infrared absorber, a coloring agent such as a pigment or dye, a fluorescent whitening agent, a dispersing agent, a heat stabilizer, a light Stabilizers, antistatic agents, antioxidants, lubricants, solvents, etc.

The thickness of the extended retardation plate is preferably 200 μm or less, and more preferably 1 to 100 μm. If the thickness of the extended retardation plate is within the above range, there is a tendency that the flexibility of the extended retardation plate is difficult to decrease.

Furthermore, as another example of the aforementioned λ/4 retardation plate, a liquid crystal-coated retardation plate formed by coating a liquid crystal composition can be cited.

The liquid crystal composition contains a liquid crystal compound showing a liquid crystal state in which the nematic phase, the cholesterol phase, and the smectic phase are equal. The liquid crystal compound has a polymerizable functional group.

The liquid crystal composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a cross-linking agent, a silane coupling agent, and the like.

The liquid crystal coating type retardation plate can be manufactured by applying and curing a liquid crystal composition on a substrate in the same manner as the liquid crystal polarizing layer to form a liquid crystal retardation layer. The liquid crystal coating type retardation plate may be formed to be thinner than the extension type retardation plate. The thickness of the liquid crystal polarizing layer is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

The liquid crystal coating type retardation plate may be peeled off from the substrate and transferred to be laminated, or the substrate may be directly laminated. It is also preferable that the above-mentioned base material functions as a transparent base material for a protective film, a phase difference plate, or a window film.

Generally speaking, the shorter the wavelength, the greater the birefringence, and the longer the wavelength, the smaller the birefringence. In this case, since the phase difference of λ/4 cannot be achieved in the full visible light region, the in-plane phase difference is designed to be preferably 100 to 180 nm in such a way that the vicinity of 560 nm with high visual sensitivity becomes λ/4. More preferably, it is 130 to 150 nm. The inverse dispersion λ/4 retardation plate using a material having a birefringence wavelength dispersion characteristic opposite to the usual one is preferable in terms of better visibility. As such a material, for example, those described in Japanese Patent Laid-Open No. 2007-232873 can be used for the extended type retardation plate, and those described in Japanese Patent Laid-Open No. 2010-30979 can be used for the liquid crystal coating type phase difference plate.

As another method, a technique of obtaining a wide-band λ/4 phase difference plate by combining with a λ/2 phase difference plate is also known (for example, Japanese Patent Laid-Open No. 10-90521, etc.). The λ/2 phase difference plate is also manufactured by the same material method as the λ/4 phase difference plate. The combination of the extended retardation plate and the liquid crystal coating retardation plate is arbitrary, and any combination can be made thinner by using the liquid crystal coating retardation plate.

A method of stacking a positive C plate on the above circular polarizing plate to improve visibility in an oblique direction (for example, Japanese Patent Laid-Open No. 2014-224837, etc.) is known. The positive C plate may be a liquid crystal coated retardation plate or an extended retardation plate. The phase difference in the thickness direction of the phase difference plate is preferably -200 to -20 nm, and more preferably -140 to -40 nm.

[Touch Sensor] As described above, the flexible display device of the present invention preferably includes a touch sensor. The touch sensor is used as an input mechanism. As the touch sensor, various types such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and an electrostatic capacitance method can be cited. Preferably, the electrostatic capacitance method is used. The electrostatic capacitance type touch sensor is divided into an active area and an inactive area located outside the outline of the active area. The active area is the area corresponding to the area (display portion) of the display screen in the display panel, and is the area that senses the user's touch, and the inactive area is the area corresponding to the area (non-display portion) of the display device where the screen is not displayed. . The touch sensor may include a substrate having flexible characteristics, a sensing pattern formed in the active area of the substrate, and an inactive area formed on the substrate and used to communicate with the outside through the sensing pattern and the pad portion Sensing lines connected to the driving circuit. As the substrate having flexibility, the same material as the transparent substrate of the window film described above can be used.

The sensing pattern may include a first pattern formed in the first direction and a second pattern formed in the second direction. The first pattern and the second pattern are arranged in mutually different directions. The first pattern and the second pattern are formed on the same layer. In order to sense the touched part, the respective patterns must be electrically connected. The first pattern is a form in which a plurality of unit patterns are connected to each other via a joint, and the second pattern is a structure in which the plurality of unit patterns are separated into islands. Therefore, in order to electrically connect the second pattern, an additional bridge electrode is necessary. As the electrode used for the connection of the second pattern, a well-known transparent electrode can be used. Examples of materials for the transparent electrode include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc tin oxide (IZTO), and indium gallium zinc oxide (IGZO) ), cadmium tin oxide (CTO), PEDOT (poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)), carbon nanotubes (CNT), graphene, metal wires, etc., Preferably, ITO is listed. These can be used alone or in combination of two or more. The metal used in the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, and chromium. These can be used alone or in combination of two or more.

The bridge electrode may be formed above the insulating layer via an insulating edge layer on the upper part of the sensing pattern, a bridge electrode may be formed on the substrate, and an insulating layer and a sensing pattern may be formed thereon. The bridge electrode may be formed of the same material as the sensing pattern, or may be formed of molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of two or more of them.

Since the first pattern and the second pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the joint of the first pattern and the bridge electrode, or may be formed as a layer covering the entire sensing pattern. In the case of a layer covering the entire sensing pattern, the bridge electrode may be connected to the second pattern through a contact hole formed in the insulating layer.

The above-mentioned touch sensor may further include an optical adjustment layer between the substrate and the electrode to appropriately compensate for the difference in transmittance between the pattern area where the sensing pattern is formed and the non-pattern area where the sensing pattern is not formed. The mechanism of the difference in light transmittance induced by the difference in refractive index in these areas. The optical adjustment layer may contain an inorganic insulating substance or an organic insulating substance. The optical adjustment layer can be formed by coating a photo-curable composition containing a photo-curable organic binder and a solvent on a substrate. The photocurable composition may further contain inorganic particles. The inorganic particles can increase the refractive index of the optical adjustment layer.

The photocurable organic binder may include copolymers of monomers such as acrylate monomers, styrene monomers, and carboxylic acid monomers, as long as the effects of the present invention are not impaired. The photocurable organic binder may be, for example, a copolymer containing repeating units different from each other such as repeating units containing an epoxy group, acrylate repeating units, and carboxylic acid repeating units.

Examples of the inorganic particles include zirconia particles, titanium oxide particles, and alumina particles.

The photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

[Next layer] Each layer (window film, circular polarizer, touch sensor) forming the laminate for the flexible image display device described above and the film members (linear polarizer, λ/4 retardation plate, etc.) constituting each layer can be obtained by Adhesive bonding. As the adhesive, water-based adhesives, water-based solvent volatile adhesives, organic solvent-based, solvent-free adhesives, solid adhesives, solvent evaporative adhesives, moisture-curable adhesives, heat-curable adhesives can be used , Anaerobic hardening type, active energy ray hardening type adhesive, hardener mixed type adhesive, hot melt type adhesive, pressure sensitive type adhesive (adhesive), rewet type adhesive and other commonly used adhesives, etc., Preferably, an aqueous solvent evaporative adhesive, an active energy ray hardening adhesive, or an adhesive can be used. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive force, etc., preferably 0.01 to 500 μm, more preferably 0.1 to 300 μm. There are a plurality of adhesive layers in the laminate for flexible image display devices described above, and the respective thicknesses or types may be the same or different.

As the above-mentioned water-based solvent evaporative adhesive, water-soluble polymers such as polyvinyl alcohol-based polymers, starch and other water-soluble polymers such as ethylene-vinyl acetate-based emulsions and styrene-butadiene-based emulsions can be used as main components Agent polymer. In addition to the above-mentioned main component polymer and water, a crosslinking agent, silane-based compound, ionic compound, crosslinking catalyst, antioxidant, dye, pigment, inorganic filler, organic solvent, etc. can also be formulated. In the case of adhesion by the water-based solvent-scattering adhesive, the water-based solvent-scattering adhesive is injected between the layers to be adhered to be adhered to the layer to be adhered, and then dried, whereby adhesion can be imparted. In the case of using the above-mentioned water-based solvent-scattering adhesive, the thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.1 to 1 μm. When the above-mentioned water-based solvent-scattering adhesive is used for multiple layers, the thickness or type of each layer may be the same or different.

The active energy ray hardening type adhesive can be formed by curing an active energy ray hardening composition containing a reactive material that forms an adhesive layer by irradiating an active energy ray. The active energy ray hardening composition may contain at least one polymer of the radical polymerizable compound and the cationic polymerizable compound similar to those contained in the hard coating composition. As the radical polymerizable compound, the same compound as the radical polymerizable compound in the hard coating composition can be used.

As the above cationic polymerizable compound, the same compound as the cationic polymerizable compound in the hard coating composition can be used.

As the cationic polymerizable compound used in the active energy ray hardening composition, an epoxy compound is particularly preferred. In order to reduce the viscosity of the adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

The active energy ray composition may contain a monofunctional compound in order to reduce the viscosity. Examples of the monofunctional compound include an acrylate monomer having one (meth)acryloyl group in one molecule, or a compound having one epoxy group or oxetanyl group in one molecule. For example, glycidyl (meth)acrylate.

The active energy ray composition may further include a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radicals and cationic polymerization initiators, and the like can be appropriately selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate free radicals or cations, and perform free radical polymerization and cation polymerization. In the description for the hard coating composition, at least any one of radical polymerization or cationic polymerization can be started by active energy ray irradiation.

The active energy ray hardening composition may further include an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a fluid viscosity adjuster, a plasticizer, a defoamer solvent, an additive, and a solvent. When two active layers are adhered by the active energy ray hardening type adhesive, the active energy ray hardening composition is applied to any one or both of the adhered layers, and then bonded together. One of the adhered layers or both of the adhered layers is irradiated with active energy rays to harden it, whereby bonding can be performed. In the case of using the active energy ray-curable adhesive, the thickness of the adhesive layer is preferably 0.01-20 μm, more preferably 0.1-10 μm. When the above active energy ray-curable adhesive is used to form a plurality of adhesive layers, the thickness or type of each layer may be the same or different.

The above-mentioned adhesives are classified into acrylic adhesives, urethane adhesives, rubber adhesives, polysiloxane adhesives, etc. according to the main polymer, and any of them can be used. In the adhesive, in addition to the main polymer, it can also be formulated with crosslinking agents, silane compounds, ionic compounds, crosslinking catalysts, antioxidants, adhesion imparting agents, plasticizers, dyes, pigments, inorganic fillers, etc. . Each component constituting the above-mentioned adhesive is dissolved and dispersed in a solvent to obtain an adhesive composition, which is applied to a substrate and then dried, thereby forming an adhesive layer adhesive layer. The adhesive layer can be formed directly, or it can be transferred and formed on the substrate. In order to cover the adhesive surface before bonding, it is also preferable to use a release film. In the case of using the active energy ray-curable adhesive, the thickness of the adhesive layer is preferably 0.1 to 500 μm, and more preferably 1 to 300 μm. When the above adhesive is used for multiple layers, the thickness or type of each layer may be the same or different.

[Shading pattern] The light-shielding pattern may be used as at least a part of a frame or a casing of the flexible image display device. The wiring arranged at the edge of the flexible image display device is hidden by the light-shielding pattern to make it difficult to recognize, thereby improving the visibility of the image. The light-shielding pattern may be in the form of a single layer or multiple layers. The color of the shading pattern is not particularly limited, and can be various colors such as black, white, and metallic colors. The light-shielding pattern can be formed by pigments for achieving color, and polymers such as acrylic resins, ester resins, epoxy resins, polyurethanes, and polysiloxane. These can be used alone or in a mixture of two or more. The light-shielding pattern can be formed by various methods such as printing, lithography, and inkjet. The thickness of the light-shielding pattern is preferably 1-100 μm, more preferably 2-50 μm. Moreover, it is also preferable to give a shape such as an inclination to the thickness direction of the light-shielding pattern. [Example]

The present invention will be described in further detail by examples below. Unless otherwise specified, "%" and "parts" in the examples mean 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.

(Full light transmittance and haze of resin film) The total light transmittance and haze of the resin film are based on JIS K 7361-1: 1997 and JIS K 7136: 2000, respectively, using a fully automatic direct-read haze meter (Haze computer) HGM-2DP manufactured by Suga Test Instruments. Determination. The measurement sample was produced by cutting the resin films of Examples and Comparative Examples to a size of 30 mm×30 mm. In Table 2, the total light transmittance is described as Tt.

(Yellowness of resin film) The yellowness (Yellow Index: YI value) of the resin film is measured in accordance with JIS K 7373: 2006 using an ultraviolet-visible near-infrared spectrophotometer ("V-670" manufactured by Japan Spectroscopy Corporation). After performing background measurement without a sample, the resin films obtained in Examples and Comparative Examples were set in a sample holder, and transmittance measurement with respect to light of 300 to 800 nm was performed to obtain 3 stimulus values (X, Y, Z). Based on the specifications of ASTM D1925 and based on the following formula, the YI value was calculated from the obtained three stimulus values. In addition, in Table 2, the yellowness of the resin film is described as YI. YI＝100×(1.2769X－1.0592Z)/Y

(Thermogravimetric-differential thermal (TG-DTA) measurement) As a TG-DTA measuring device, TG/DTA6300 manufactured by Hitachi High-Tech Science Co., Ltd. was used. A sample of about 20 mg was obtained from the produced resin film. The sample was heated from room temperature to 120°C at a heating rate of 10°C/min, and after being held at 120°C for 5 minutes, the sample was heated while being heated to 400°C at a heating rate of 10°C/min. Such weight changes. FIG. 1 shows the TG-DTA measurement results of the polyimide film produced in Example 1 below.

The weight reduction rate M (%) from 120°C to 250°C was calculated from the measurement result of TG-DTA by the following formula. M(%)=100-(W ₁ /W ₀ )×100 Here, 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.

(Measurement of in-plane retardation value of resin film) The in-plane retardation of the resin film is an in-plane retardation value R measured at a wavelength of 590 nm using a retardation film and optical material inspection device (trade name "RETS-100") manufactured by Otsuka Electronics Co., Ltd. The measurement is to take a 700 mm wide range centered on the center of the resin film in the width direction, divide the 700 mm wide range at intervals of 20 mm, and conduct a total of 36 points to average the values measured at these 36 points The value is calculated.

The ratio of the in-plane phase difference values in Table 2 is calculated as follows. First, the center point of the film width of the resin film is set to TD _c , and the in-plane phase difference value at a point (2 points) at which TD _{c is} set at 0% toward both ends of the film is measured. The average of the in-plane phase difference values at these two points is TD ₈₀ . R(TD _C )/R(TD ₈₀ ) represents the ratio of the in-plane phase difference value of TD _c relative to TD ₈₀ . Similarly, the in-plane phase difference value at a point where TD _{c is} set to 0% at 66% (two points) away from both ends of the film is measured. The average of the in-plane phase difference values at these two points is set to TD ₆₆ . R(TD _C )/R(TD ₆₆ ) represents the ratio of the in-plane phase difference value of TD _c relative to TD ₆₆ .

(Solid content and viscosity) The viscosity (cps) of the varnish is measured according to JIS K 8803:2011 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 from 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 silica particles is calculated based on the measured value of specific surface area measured by the BET (Brunauer-Emmett-Teller, Buert) adsorption method according to JIS Z 8830. The specific surface area of the powder obtained by drying the silica sol at 300°C was measured using a specific surface area measuring device ("Monosorb (registered trademark) MS-16" manufactured by Yuasa-ionics Co., Ltd.).

(Weight average molecular weight) Determination by gel permeation chromatography (GPC) (1) Pretreatment method After dissolving the sample in γ-butyrolactone (GBL) to prepare a 20% by mass solution, it was diluted to 100 times with DMF (Dimethyl formamide, dimethylformamide) dissolution solution and filtered with a 0.45 μm membrane filter , And set the obtained as the measurement solution. (2) Measurement conditions Column: TSKgel SuperAWM-H×2＋SuperAW2500×1 (6.0 mmI.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

<Production Example 1: Production of Polyimide Resin 1) Under a nitrogen atmosphere, add 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) 45 g (140.52 mmol) to a 1 L separable flask equipped with a stirring wing And 768.55 g of N,N-dimethylacetamide (DMAc), dissolving TFMB in DMAc while stirring at room temperature. Next, 18.4 g (42.58 mmol) of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) was added to the flask, and stirred at room temperature for 3 hours. Thereafter, 4.4'-oxybis(benzoyl chloride) (OBBC) 4.19 g (14.19 mmol) was added to the flask, followed by addition of terephthaloyl chloride (TPC) 17.29 g (85.16 mmol) to the flask ), stirred 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 resulting reaction liquid was cooled to room temperature, poured into a large amount of methanol in a filament form, and the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 100°C to obtain polyimide-based resin 1. The weight average molecular weight of the polyimide-based resin 1 is 455,000. The polyimide has an imidization rate of 98.9%.

<Production Example 2: Production of Dispersion Liquid 1> The organically-treated silica dispersed in methanol (particle size measured by BET method: 27 nm) was replaced with GBL to obtain the organically-treated silica dispersed in GBL (solid content 30.3% by mass). Let this dispersion be Dispersion 1.

<Production Example 3: Production of Varnish 1> Varnish 1 is in the composition shown in Table 1. At room temperature, the polymer and the filler are mixed in a GBL solvent at a composition ratio of 60:40, and Sumisorb 340 (UVA) and Sumiplast Violet B (BA) are mixed with Relative to the total mass of polymer and silica, 5.7 phr or 35 ppm were added to them, and stirred until uniform. A varnish 1 with a solid content of 10.3% by mass and a viscosity of 38,500 cps at 25°C was obtained.

[Table 1]

<Production Example 4: Film formation of the raw material film 1> By casting, varnish 1 was formed on PET (polyethylene terephthalate) film ("COSMOSHINE (registered trademark) A4100" manufactured by Toyobo Co., Ltd., thickness 188 μm, thickness distribution ± 2 μm) Coated film. At this time, the line speed 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 1 having a thickness of 58 μm and a width of 700 mm. The weight reduction rate of the raw material film 1 was 9.2%, the total light transmittance was 89.5%, the haze was 0.2%, and the yellowness YI was 1.5.

<Example 1> Using a tenter dryer (1 to 6-chamber configuration) equipped with a jig as a holding device and equipped with an IR heater as a radiation source, the solvent was removed from the raw material film 1 obtained in Production Example 4 to obtain a thickness of 49 μm之 Resin film 1. The tenter dryer is equipped with nozzles and IR heaters as shown in FIG. At this time, the temperature of the warm air in the drying furnace of 1 to 6 chambers was set to 200°C, the IR heaters of the 3rd and 4th chambers were set to 230°C, the clamp holding width was 25 mm, and the film transfer speed was 1.8 m/min, the ratio of the film width of the inlet of the drying furnace (distance between fixtures) to the film width of the outlet of the drying furnace is 0.98. In addition, the wind speed of each chamber was adjusted so that 1 chamber became 13.5 m/s, 2 chambers became 13 m/s, and 3-6 chambers became 11 m/s, and NOK KLUBER (share) was used as a lubricant for the rail The manufactured "BARRIERTA J400V" is heated. After detaching the film from the jig, slit (cut) the jig portion, apply a PET-based surface protective film to the film, take up a 6-inch core made of ABS, and obtain a rolled film. Table 2 shows the optical characteristics (phase difference value, total light transmittance, haze, yellowness YI) and weight reduction rate of the resin film 1 after the tenter drying furnace.

<Example 2> The resin film 2 was obtained by the method similar to Example 1 except having changed the conveyance speed to 2.7 m/min. Table 2 shows the optical characteristics (phase difference value, total light transmittance, haze, yellowness YI) and weight reduction rate of the film after the tenter drying furnace.

[Table 2]

10: Area 12: Area 14: Area 18: Holding device 20: Raw film 30: Upper nozzle (nozzle) 32: Lower nozzle (nozzle) 35: Nozzle 37: IR heater 100: oven 100a: upper surface 100b: lower surface A: Film transport direction B: down C: Upward L: interval

1 is a step cross-sectional view schematically showing a preferred embodiment of the method for manufacturing a resin film of the present invention. 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. FIG. 3 is a step cross-sectional view schematically showing a preferred embodiment of the tenter furnace in the method for manufacturing a resin film of the present invention.

10: Area

12: Area

14: Area

20: Raw film

twenty two

30: Upper nozzle (nozzle)

32: Lower nozzle (nozzle)

100: oven

100a: upper surface

100b: lower surface

A: Film transport direction

B: down

C: Upward

L: interval

Claims (15)

A resin film, which is a resin film containing at least either a polyimide-based resin or a polyamide-based resin, and the center point of the film width direction is set to TD _c , from the center point of the width direction to When the center point is set to 0% and the point at 80% of the length of the end is set to TD ₈₀ , the in-plane phase difference value R(TD _c ) and TD ₈₀ of TD _c measured at a wavelength of 590 nm The in-plane phase difference value R(TD ₈₀ ) satisfies equation (1), R(TD _c )/R(TD ₈₀ )≧0.35 (1). The resin film according to claim 1, wherein the resin film is 66% when the center point of the film width direction is set to TD _c and the center point is set to 0% in the length from the center point of the width direction to the end when point ₆₆ is set to the length of the TD, the retardation value measured at a wavelength of the surface TD _c R (TD _c) the TD ₆₆ and the inner surface of the retardation value R (TD ₆₆₎ satisfies formula (2) 590 nm under, R (TD _c )/R(TD ₆₆ )≧0.40 (2). As in the resin film of claim 1, wherein the resin film satisfies formula (3), R(TD _c )/R(TD ₆₆ )-R(TD _c )/R(TD ₈₀ )<0.15 (3). As in the resin film of claim 2, wherein the resin film satisfies formula (3), R(TD _c )/R(TD ₆₆ )-R(TD _c )/R(TD ₈₀ )<0.15 (3). The resin film according to any one of claims 1 to 4, wherein the weight reduction rate of the resin film is 3% or less. The resin film according to any one of claims 1 to 4, wherein the total width of the resin film in the width direction is 300 to 2,200 mm. The resin film according to claim 5, wherein the total width of the resin film in the width direction is 300 to 2,200 mm. A flexible display device provided with the resin film according to any one of claims 1 to 7. As in the flexible display device of claim 8, it is further provided with a touch sensor. The flexible display device according to claim 8 or 9 further includes a polarizing plate. A method of manufacturing a resin film, which is a method of manufacturing a resin film containing at least either a polyimide resin or a polyimide resin, and A heating step of heating the raw material film in a tenter furnace divided into a plurality of spaces inside, In the above tenter furnace, the heating step is performed in a hot air treatment manner in at least one space, and the heating step is performed in a radiant heat treatment manner in at least one space. The method for manufacturing a resin film according to claim 11, wherein the above heating step is performed in the same space of the tenter furnace in two ways of hot air treatment and radiant heat treatment. The method of manufacturing a resin film according to claim 11, wherein the heating step of the radiant heat treatment method is by irradiating the raw material film with radiant heat rays having a temperature higher than the temperature of the space where the heating step is performed by the radiant heat treatment method by more than 30°C get on. The method of manufacturing a resin film according to claim 12, wherein the heating step of the above-mentioned radiant heat treatment method is by irradiating the raw material film with a radiant heat ray having a temperature higher than the temperature of the space where the heating step is performed by the radiant heat treatment method by 30° C. get on. The method for manufacturing a resin film according to any one of claims 11 to 14, wherein the raw material film contains a solvent, and the weight reduction rate of the raw material film is 40% or less.

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