TW202142408A - Optical film and flexible display device that comprises at least one resin selected from a group consisting of a polyimide resin and a polyamide resin and has a total light transmittance of 85% or more and a haze of 0.5% or less, and an in-plane phase difference RO of 40-300 nm - Google Patents

Abstract

The present invention provides an optical film that is excellent in visibility in a wide-angle direction and has a low in-plane phase difference R0 and a flexible display device including the optical film. An optical film which comprises at least one resin selected from a group consisting of a polyimide resin and a polyamide resin and has a total light transmittance of 85% or more and a haze of 0.5% or less, and an in-plane phase difference RO of 40-300 nm, when the direction of the in-plane of the optical film parallel to a machine flow direction during manufacturing is defined as a MD direction, and the direction perpendicular to the machine flow direction is defined as a TD direction, according to JIS K 7374, when the width of an optical comb is 0.125 mm, a first transmission image definition degree C60(MD) obtained in a direction inclined by 60 DEG toward the MD direction from a direction perpendicular to the plane of the optical film, a second transmission image definition degree C60(TD) in a direction inclined by 60 DEG toward the TD direction from the perpendicular direction, and a third transmission image definition degree C0 in the perpendicular direction satisfy the following formulas: Formula (1): 87% ≤ C60(MD) ≤ 100% … (1); Formula (2): 87% ≤ C60(TD) ≤ 100% … (2); and Formula (3): 0.8 ≤ C60(MD)/C0 ≤ 1 … (3).

Description

Optical film and flexible display device

The present invention relates to an optical film containing at least one resin selected from the group consisting of polyimide resins and polyamide resins, and a flexible display device provided with the optical film.

Previously, glass was used as a material for display components such as solar cells or image display devices. However, in response to recent requirements for miniaturization, thinning, weight reduction, and flexibility, glass materials cannot meet the requirements, and various films have been studied as alternative materials for glass. As such a film, for example, there is a polyimide film (for example, Patent Documents 1 and 2). [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2009-215412 [Patent Document 2] Japanese Patent Laid-Open No. 2020-3781

[The problem to be solved by the invention]

When a polyimide-based resin film is applied to a transparent member such as a front panel of a flexible display device, it is sometimes necessary to display an image in a state where the image display surface is curved, so it is similar to a non-flexible image display surface. Compared with, it is required to have excellent visibility in the wide-angle direction. However, according to the research of the present inventors, there are cases where the prior polyimide-based resin film cannot sufficiently satisfy the visibility in the wide-angle direction. In addition, the inventors found that when the in-plane phase difference R _{0 is} too large, the optical film may warp when the optical film is subjected to high-temperature heat treatment, or interlayer peeling may occur when the optical film is a laminate. In the polyimide resin film, the in-plane phase difference R _{0 may be} too large.

Furthermore, according to the research of the present inventors, for example, the optical films described in Patent Documents 1 and 2 have a situation in which the visibility in the wide-angle direction and the visibility of the projected image are reduced.

Therefore, an object of the present invention is to provide an optical film having excellent visibility in a wide-angle direction and a low in-plane phase difference R ₀ , and a flexible display device provided with the optical film. [Technical means to solve the problem]

The inventors of the present invention have made diligent studies to solve the above-mentioned problems, and as a result, they have found that the following optical film can solve the above-mentioned problems to complete the present invention. The optical film includes a polyimide-based resin and a polyimide-based resin. At least one resin in the group, the total light transmittance is 85% or more, the haze is 0.5% or less, the tensile modulus of elasticity at 25°C is 5.1 GPa or more, and the in-plane phase difference R ₀ is 40～300 nm , The transmission image clarity values (C ₆₀ (MD (Machine direction, machine direction)), C ₆₀ (TD (Transverse Direction, lateral _{direction)) and C 0} ) of the above-mentioned optical film satisfy the specified relationship. That is, the following aspects are included in the present invention.

[1] An optical film comprising at least one resin selected from the group consisting of polyimide-based resins and polyimide-based resins, and has a total light transmittance of 85% or more and a haze of 0.5% Hereinafter, the in-plane phase difference R ₀ is 40 to 300 nm, and when the direction parallel to the mechanical flow direction at the time of manufacture of the above-mentioned optical film is set to the MD direction, and the direction perpendicular to the mechanical flow direction is set to the TD direction, According to JIS K 7374 when the width of the optical comb is 0.125 mm, the first transmission image clarity value C ₆₀ (MD _{), the second transmission image sharpness value C 60} (TD) in the direction inclined 60° from the vertical direction to the TD direction, and the third transmission image sharpness value C _{0 in} the vertical direction satisfy the following formula, Mathematical formula (1): 87%≦C ₆₀ (MD)≦100%……(1); Mathematical formula (2): 87%≦C ₆₀ (TD)≦100%……(2); and Mathematical formula ( 3): 0.8≦C ₆₀ (MD)/C ₀ ≦1.0……(3). [2] The optical film of the above [1], wherein the second transmission image sharpness value and the third transmission image sharpness value further satisfy the formula (4): 0.9≦C ₆₀ (TD)/C ₀ ≦1.0……(4). [3] The optical film as in [1] or [2] above, wherein the in-plane phase difference R ₀ nm and the thickness direction phase difference R _th nm satisfy the formula (5): 3≦R _th /R ₀ ≦200... …(5). [4] The optical film according to any one of [1] to [3] above, wherein the difference ΔHaze between the haze before and after the bending resistance test according to JIS K 5600-5-1 is less than 0.3%. [5] The optical film according to any one of [1] to [4] above, wherein the difference ΔC ₆₀ ( MD), the difference ΔC ₆₀ (TD) of the above-mentioned second transmission image sharpness value, and the difference ΔC _{0 of the} above-mentioned third transmission image sharpness value are less than 15 respectively. [6] The optical film according to any one of [1] to [5] above, wherein the weight average molecular weight of the resin selected from the group consisting of polyimide-based resins and polyimide-based resins is 350,000 or less. [7] The optical film of any one of [1] to [6] above, which has a thickness of 10 to 150 μm. [8] The optical film of any one of [1] to [7] above, which has a hard coat layer on at least one side. [9] The optical film of the above [8], wherein the thickness of the hard coat layer is 3-30 μm. [10] A flexible display device including the optical film of any one of [1] to [9] above. [11] The flexible display device of [10] above, which further includes a touch sensor. [12] The flexible display device of [10] or [11] above, which is further provided with a polarizing plate. [Effects of the invention]

According to the present invention, it is possible to provide an optical film and a flexible display device provided with the optical film. The optical film has excellent visibility in the wide-angle direction and _{low in-plane phase difference R 0} , so even after heat treatment at a high temperature Warping and peeling are not easy to occur.

Hereinafter, embodiments of the present invention will be described in detail. Furthermore, the scope of the present invention is not limited to the embodiments described herein, and various changes can be made without departing from the spirit of the present invention. In addition, when a plurality of upper limit values and lower limit values are recorded for a specific parameter, any upper limit value and lower limit value of the upper limit value and lower limit value can be combined to make a preferable value. Scope.

<Optical film> The optical film of the present invention contains at least one resin selected from the group consisting of polyimide resins and polyamide resins, and has a total light transmittance of 85% or more and a haze of 0.5 % Or less, the in-plane phase difference R ₀ is 40 nm to 300 nm, and the direction parallel to the mechanical flow direction at the time of manufacture of the above-mentioned optical film is set to the MD direction, and the direction perpendicular to the mechanical flow direction is set to the TD direction According to JIS K 7374, when the width of the optical comb is 0.125 mm, the first transmission image clarity value C _{60 is obtained from a direction perpendicular to the plane of the optical film to a direction inclined 60° to the MD direction (MD), the second transmission image sharpness value C 60} (TD) in the direction inclined 60° from the vertical direction to the TD direction, and the third transmission image sharpness value C _{0 of} the vertical direction satisfy the following values Formula (1): 87%≦C ₆₀ (MD)≦100%……(1); Formula (2): 87%≦C ₆₀ (TD)≦100%……(2); and Formula (3): 0.8≦C ₆₀ (MD)/C ₀ ≦1.0……(3).

The MD direction is the direction in the optical film plane parallel to the direction of the mechanical flow during manufacture, for example, it means the direction parallel to the direction in which the optical film is transported when manufactured by the solution casting method. The TD direction is the direction perpendicular to the above-mentioned mechanical flow direction, for example, it means the direction perpendicular to the conveyed direction. When the MD direction and TD direction in the optical film surface are not clear, use the following method to determine. Regarding MD and TD, cut the optical film at least 20 points in different directions. In more detail, suppose a circle centered on any one point of the optical film, cut out a semicircle from the optical film, and then form the optical film into a straight line so that the central angle of the fan shape after cutting the semicircle becomes approximately equal Shape cutting, and cut more than 20 cross-sections. The center of the thickness of the plurality of cross-sections measured by Raman laser, the ^{highest peak intensity near 1,620 cm -1} is taken as the MD direction.

由所得之M及m算出第1透射圖像清晰度值C₆₀ (MD)。透射圖像清晰度值(第1透射圖像清晰度值、以及後述之第2透射圖像清晰度值及第3透射圖像清晰度值)可使用圖像清晰度值測定器進行測定。The first transmission image sharpness value C ₆₀ (MD) is a transmission image sharpness value obtained from a direction perpendicular to the plane of the optical film to the MD direction inclined 60° according to the Japanese Industrial Standard (JIS) K 7374 . 1, the first transmission image sharpness value C ₆₀ (MD) will be explained more specifically. Fig. 1 is a diagram showing the optical axis when the sharpness value of the first transmission image is measured. The optical film 1 is irradiated with the first incident light 10 (white light: marked by a solid line in Fig. 1) along the following axis (the first optical axis 14), and the axis is defined as an arbitrary point on the surface of the optical film 1 (the first The incident position 11) is the fulcrum, which is inclined at an angle of 60° from the axis perpendicular to the optical film 1 (vertical axis 3) to the MD direction. Then, the 1a-th transmitted light 12 (marked by a dotted line in FIG. 1) transmitted through the optical film 1 is transmitted through the first optical comb 16 extending perpendicular to the first optical axis 14. Then, the first light receiver 19 extending perpendicular to the first optical axis 14 receives the 1b transmitted light 18 (marked by a single-dot chain line in FIG. 1) that has passed through the first optical comb 16. The first optical comb 16 has an opening through which the 1a transmitted light 12 passes, and a light shielding section that blocks the 1a transmitted light 12. The slit width (width of the opening) of the first optical comb 16 is 0.125 mm. Repeatedly move the first optical comb 16 in the direction parallel to the plane of the first optical comb 16 and the direction in which the slits in the first optical comb 16 are arranged (the direction of arrow A) by a predetermined unit amplitude and receive the 1b through Light 18, so as to obtain the received light waveform. Obtain the maximum value M and the minimum value m of the relative light intensity from the received light waveform. Based on the formula (7):

From the obtained M and m, the first transmission image sharpness value C ₆₀ (MD) is calculated. The transmission image sharpness value (the first transmission image sharpness value, and the second transmission image sharpness value and the third transmission image sharpness value described later) can be measured using an image sharpness value measuring device.

If the first transmission image clarity value C ₆₀ (MD) satisfies the formula (1), the optical film has excellent visibility in the wide-angle direction in the MD direction. The first transmission image clarity value C ₆₀ (MD) is 87% or more in the formula (1). From the viewpoint of further improving the visibility of the optical film in the wide-angle direction in the MD direction, it is preferably 88% Above, it is more preferably 89% or more, still more preferably 90% or more, still more preferably 91% or more, particularly preferably 92% or more, and usually 100% or less.

The second transmission image sharpness value C ₆₀ (TD) is a transmission image sharpness value obtained in accordance with JIS K 7374 from a direction perpendicular to the plane of the optical film inclined by 60° to the TD direction. 2, the second transmission image sharpness value C ₆₀ (TD) will be explained more specifically. Fig. 2 is a diagram showing the optical axis when the sharpness value of the second transmission image is measured. The optical film 1 is irradiated with the second incident light 20 (white light: marked by a solid line in FIG. 2) along the following axis (the second optical axis 24), and the axis is defined as an arbitrary point on the surface of the optical film 1 (the second The incident position 21) is the fulcrum, which is inclined at an angle of 60° from the axis perpendicular to the optical film 1 (vertical axis 3) to the TD direction. Then, the 2a transmitted light 22 (marked by a dotted line in FIG. 2) that has passed through the optical film 1 is transmitted through the second optical comb 26 extending perpendicularly to the second optical axis 24. Then, the second light receiver 29 extending perpendicular to the second optical axis 24 receives the 2b transmitted light 28 (marked by a single-dot chain line in FIG. 2) that has passed through the second optical comb 26. The second optical comb 26 has an opening through which the 2a transmitted light 22 passes, and a light shielding section for blocking the 2a transmitted light 22. The slit width (width of the opening) of the second optical comb 26 is 0.125 mm. Repeatedly move the second optical comb 26 along the direction parallel to the plane of the second optical comb 26 and the direction in which the slits in the second optical comb 26 are arranged (the direction of arrow B) by a predetermined unit amplitude and receive the second b through Light 28, so as to obtain the received light waveform. Obtain the maximum value M and the minimum value m of the relative light intensity from the received light waveform. _{The second transmission image sharpness value C 60} (TD) is calculated from the obtained M and m based on the equation (7).

If the second transmission image clarity value C ₆₀ (TD) satisfies the formula (2), the optical film has excellent visibility in the wide-angle direction in the TD direction. The second transmission image clarity value C ₆₀ (TD) is 87% or more in the formula (2). From the viewpoint of further improving the visibility of the optical film in the wide-angle direction in the TD direction, it is preferably 88% Above, it is more preferably 89% or more, still more preferably 90% or more, still more preferably 91% or more, particularly preferably 92% or more, and usually 100% or less.

The third transmission image clarity value C ₀ is a transmission image clarity value obtained in accordance with JIS K 7374 in a direction perpendicular to the plane of the optical film. 3, the third transmission image sharpness value C ₀ will be explained more specifically. Fig. 3 is a diagram showing the optical axis when the third image sharpness value is measured. Irradiate any point (third incident position 31) on the surface of the optical film 1 with the third incident light 30 (white) along an axis (third optical axis 34) parallel to the axis perpendicular to the optical film 1 (vertical axis 3) Light: marked with a solid line in Figure 3). Then, the 3a transmitted light 32 (marked by a dotted line in FIG. 3) transmitted through the optical film 1 is transmitted through the third optical comb 36 extending perpendicularly to the third optical axis 34. Then, the light receiver 39 extending perpendicularly to the third optical axis 34 receives the 3b transmitted light 38 (marked by a single-dot chain line in FIG. 3) that has passed through the third optical comb 36. The third optical comb 36 has an opening through which the 3a transmitted light 32 passes, and a light shielding section for blocking the 3a transmitted light 32. The slit width (width of the opening) of the third optical comb 36 is 0.125 mm. Repeatedly move the third optical comb 36 along the direction parallel to the plane of the third optical comb 36 and the direction in which the slits in the third optical comb 36 are arranged (the direction of arrow C) by a predetermined unit amplitude, and receive the third b The operation of the transmitted light 38 obtains the received light waveform. Obtain the maximum value M and the minimum value m of the relative light intensity from the received light waveform. _{The third transmission image sharpness value C 0 is} calculated from the obtained M and m based on the equation (7).

If the first transmission image definition value C ₆₀ (MD) and the third transmission image definition value C ₀ satisfy the formula (3), the visibility of the optical film in the MD direction relative to the vertical direction of the optical film Excellent. The ratio of the first image sharpness value C ₆₀ (MD) to the third transmission image sharpness value C ₀ (C ₆₀ (MD)/C ₀ ) is 0.8 or more in the formula (3), which is further improved From the viewpoint of visibility in the MD direction, it is preferably 0.89 or higher, more preferably 0.90 or higher, still more preferably 0.93 or higher, still more preferably 0.94 or higher, and usually 1.0 or lower.

The third transmission image clarity value C _{0 is} preferably 97% or more, more preferably 98% or more. The first transmission image sharpness value C ₆₀ (MD) is preferably 89% or more, more preferably 90% or more, and still more preferably 92% or more.

Transmission image sharpness value (more specifically, the first transmission image sharpness value C ₆₀ (MD), the second transmission image sharpness value C ₆₀ (TD), and the third transmission image sharpness value C ₀ ) It can be adjusted by improving the smoothness of the surface of the optical film and suppressing the scattering of transmitted light on the surface of the optical film. Furthermore, the smoothness of the surface of the optical film can be used, for example, by the composition of the optical film (more specifically, the type, particle size and content of the filler, etc.), and the manufacturing conditions of the optical film (more specifically, drying temperature, drying time, The airflow in the drying system, the thickness of the coating film, the conveying speed in the drying step, and the amount of solvent in the varnish, etc.) are adjusted. When the optical film further includes a hard coat layer, it can be adjusted by improving the smoothness of the hard coat layer surface and suppressing scattering on the hard coat layer surface. The smoothness of the hard coat layer can be adjusted by adjusting the type of the solvent, the component ratio, the solid content concentration, and the addition of a leveling agent in addition to the above-mentioned adjustment method of the smoothness of the optical film.

From the viewpoint of improving the visibility of the present invention in the TD direction relative to the vertical direction of the optical film, it is preferable that the second transmission image sharpness value and the third transmission image sharpness value further satisfy the numerical value Formula (4): 0.9≦C ₆₀ (TD)/C ₀ ≦1.0……(4). From the viewpoint of further improving the visibility in the TD direction of the present invention, the ratio of the first transmission image sharpness value to the third transmission image sharpness value (C ₆₀ (TD)/C ₀ ) Preferably it is 0.9 or more, more preferably 0.91 or more, still more preferably 0.92 or more, still more preferably 0.93 or more, particularly preferably 0.94 or more, and usually 1.0 or less.

The second transmission image clarity value C ₆₀ (TD) is preferably 89% or more, more preferably 90% or more, and still more preferably 92% or more. The third transmission image clarity value C _{0 is} preferably 97% or more, more preferably 98% or more, and still more preferably 99% or more.

Furthermore, the optical film of the present invention only needs to satisfy formula (1) to formula (3) (and satisfy formula (4) as the case may be) when light is transmitted through at least any one surface of the optical film, and more It is preferable to satisfy the equation (1) to the equation (3) (and further satisfy the equation (4) as the case may be) when the light is transmitted through any surface of the optical film. If this formula is satisfied when light is transmitted from any surface, for example, no matter which surface of the optical film is used for the image display surface of the electronic device, the visibility in the wide-angle direction is excellent.

Especially when the optical film of the present invention is applied to the front panel of a flexible device, from the viewpoint of further improving the visibility in the wide-angle direction, the first before and after the bending resistance test according to JIS K 5600-5-1 The absolute value of the difference between the transmission image sharpness values ΔC ₆₀ (MD), the absolute value of the second transmission image sharpness value ΔC ₆₀ (TD), and the absolute value of the third transmission image sharpness value difference ΔC _{0 is} preferably less than 15 respectively. If the difference in the clarity value of the transmission image before and after the bending resistance test is less than 15, especially the image display surface of the flexible device even when used in the bent state and/or after the use in the bent state, it has Excellent visibility in the wide-angle direction. ΔC ₆₀ (MD) is more preferably less than 1.5, still more preferably less than 1.0, and still more preferably less than 0.5. ΔC ₆₀ (TD) is more preferably less than 2.8, still more preferably less than 2.3, still more preferably less than 2.1, and particularly preferably less than 1.5. ΔC _{0 is more} preferably less than 2, further more preferably less than 1, even more preferably less than 0.7, and particularly preferably less than 0.5.

Furthermore, the total light transmittance of the optical film of the present invention is 85% or more, the haze is 0.5% or less, and the in-plane phase difference R ₀ is 40 to 300 nm. When the optical film satisfies the above-mentioned characteristics, the wide-angle visibility of the optical film becomes sufficient, and the wide-angle visibility of the optical film and the visibility of the projected image after heat treatment at a high temperature can be improved. When the total light transmittance is less than 85% or the haze is less than 0.5%, since the initial optical properties of the optical film are low, the full visibility of the optical film cannot be achieved. Furthermore, it is difficult to manufacture an optical film with an in-plane retardation R _{0 of} less than 40 nm by a manufacturing method including a stretching step, and therefore it is difficult to manufacture a film with high wide-angle visibility. In addition, when the in-plane phase difference R ₀ exceeds 300 nm, the strain of the resin constituting the optical film is too large, so the optical film is likely to warp and/or delamination due to heat treatment during the lamination of the functional layer of the optical film. . Therefore, it is considered that the visibility in the wide-angle direction and the visibility of the projected image of an optical film laminated with a functional layer after such a heat treatment will decrease.

The total light transmittance of the optical film of the present invention is 85% or more. From the viewpoint of further improving the visibility in the wide-angle direction, it is preferably 87% or more, more preferably 88% or more, and still more preferably 89% or more, And it is usually less than 100%. The total light transmittance of the optical film can be measured using a haze meter in accordance with JIS K 7361-1:1997, for example, it can be measured by the method described in the examples. The optical film of the present invention exhibits a higher total light transmittance, and therefore, compared with the case of using a film with a lower transmittance, for example, the luminous intensity of a display element and the like required to obtain a certain brightness can be suppressed. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is assembled into an image display device, there is a tendency to obtain a bright display even if the amount of light in the backlight is reduced, which can contribute to energy saving. The upper limit of total light transmittance is usually below 100%. Furthermore, the total light transmittance may be the total light transmittance within the thickness range of the optical film described later.

The haze of the optical film of the present invention is 0.5% or less, and from the viewpoint of further improving the visibility in the wide-angle direction, it is preferably 0.4% or less, more preferably 0.3% or less. The haze of the optical film can be measured in accordance with JIS K 7136:2000. The haze can be measured using a haze meter in accordance with JIS K 7136:2000, for example, it can be measured by the method described in the examples. In addition, the absolute value of the difference ΔHaze of the above-mentioned haze before and after the bending resistance test according to JIS K 5600-5-1 of the optical film of the present invention is preferably 0.3% or less, more preferably 0.2% or less.

Regarding the tensile modulus of elasticity at 25°C of the optical film of the present invention, it is easy to improve the visibility in the wide-angle direction and the visibility of the projected image of the optical film laminated with functional layers after heat treatment, and the optical film is not prone to dents. From the viewpoint of other defects, it is preferably 5.1 GPa or more, more preferably 5.2 GPa or more, and still more preferably 5.3 GPa or more. In addition, from the viewpoint of easy improvement of the flexibility of the optical film, the tensile modulus of elasticity is preferably 10 GPa or less, more preferably 9 GPa or less, and even more preferably 8 GPa or less. The elastic modulus can be measured using a tensile testing machine (the chuck spacing is 50 mm, the tensile speed is 10 mm/min), for example, it can be measured by the method described in the examples. If the tensile modulus of elasticity is within the above range, the optical film is less prone to dent defects. In addition, it is easy to suppress the decrease in visibility in the wide-angle direction due to repeated bending operations. The tensile elastic modulus of the optical film can be measured using a tensile tester in accordance with JIS K 7127, for example, it can be measured by the method described in the examples. The tensile modulus of elasticity can be adjusted to the above-mentioned range by, for example, increasing the stretching ratio at the time of manufacturing the optical film, using a resin having a preferable structure described later, or the like.

The tensile modulus of elasticity at 80°C of the optical film of the present invention is preferably 4-9 GPa, more preferably 4.5-8.5 GPa. If the tensile modulus of elasticity is within the above range, the optical film is less prone to dent defects. The elastic modulus can be measured in accordance with JIS K 7127, for example, it can be measured by the method described in the examples.

The in-plane phase difference R ₀ of the optical film of the present invention is 40 to 300 nm. When the in-plane phase difference R _{0 is} less than 40 nm, it is difficult to obtain a film with excellent optical properties. In addition, when the in-plane retardation R ₀ exceeds 300 nm, the optical film is likely to be warped and/or delamination due to heat treatment when the functional layer is laminated on the optical film. Regarding the in-plane phase difference R ₀ , from the viewpoint of the smoothness of the film surface, it is preferably 50 nm or more, more preferably 60 nm or more, and still more preferably 70 nm or more, from the viewpoint of stacking with other members In particular, it is preferably 290 nm or less, and more preferably 280 nm or less. R ₀ can be measured by a phase difference measuring device, for example, can be measured by the method described in the examples. The in-plane phase difference R ₀ can be adjusted to the above-mentioned range by a method of using a preferable resin described later, a method of adjusting a stretching ratio, and the like.

_{The in-plane retardation R 0} nm of the optical film of the present invention and the thickness direction retardation R _th nm preferably satisfy the equation (5). Formula (5): 3≦R _th /R ₀ ≦200……(5) R _th /R ₀ in the formula (5) is preferably 3 or more, more preferably 4 or more, and still more preferably 5 or more, And it is preferably 190 or less, more preferably 180 or less, and still more preferably 150 or less. When R _th /R ₀ is more than the above lower limit, it is easy to prevent the film from becoming too hard and to prevent the film from breaking when it is deformed. In addition, when R _th /R ₀ is less than or equal to the above upper limit, it is easy to improve the smoothness of the film. In addition, R _th can be measured by a phase difference measuring device, for example, can be measured by the method described in the examples.

_{The R th} of the optical film of the present invention is not particularly limited. From the viewpoint of the flexibility of the film, it is preferably 100 nm or more, more preferably 300 nm or more, and still more preferably 500 nm or more. From a viewpoint, it is preferably 4,000 nm or less, more preferably 3,900 nm or less, and still more preferably 3,800 nm or less.

Regarding the YI value as a standard of yellowness of the optical film of the present invention, from the viewpoint of facilitating further improvement of visibility, it is preferably 4.0 or less, more preferably 3.0 or less, further preferably 2.5 or less, and still more preferably 2.0 or less, more preferably 1.9 or less, especially more preferably 1.8 or less. In addition, the YI value is preferably -5 or more, more preferably -2 or more. Furthermore, the YI value can be measured with an ultraviolet-visible-near-infrared spectrophotometer for the transmittance of light from 300 to 800 nm to obtain the tristimulus value (X, Y, Z), and based on YI=100×(1.2769X －1.0592Z)/Y.

Regarding the number of times of bending of the optical film of the present invention, from the viewpoint of improving the folding resistance, it is preferably 20,000 times or more, more preferably 100,000 times or more, still more preferably 200,000 times or more, and still more preferably 350,000 times or more , Particularly preferably 400,000 times or more, especially more preferably 500,000 times or more, especially more preferably 600,000 times or more, particularly preferably 700,000 times or more. If the number of times of bending is greater than or equal to the above lower limit, even if the optical film is bent, cracks, breakage, etc. are less likely to occur. In addition, the upper limit of the number of bending times is usually 50,000,000 times or less. The bending times of the optical film can be measured by the MIT bending fatigue test according to ASTM (American Society for Testing Materials, American Society for Testing Materials) standard D2176-16. The MIT flexural fatigue test is, for example, the test described in the examples. In addition, the optical film of the present invention preferably has high wide-angle visibility even after the MIT flex fatigue test under the above conditions, and more preferably, for example, the image before and after the MIT flex fatigue test under the above conditions The difference in image sharpness value and/or the difference in haze is within the range of the difference in image sharpness value and/or the difference in haze before and after the bending resistance test.

The thickness of the optical film of the present invention can be appropriately adjusted according to the application, and is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 25 μm or more, still more preferably 30 μm or more, and preferably 200 μm Hereinafter, it is more preferably 150 μm or less, still more preferably 100 μm or less, and still more preferably 85 μm or less. If the thickness of the optical film is within the above range, it is easier to increase the tensile elastic modulus and puncture strength of the optical film. Furthermore, the thickness of the optical film can be measured using a micrometer, for example, it can be measured by the method described in the Example.

<Polyimide resin and polyimide resin> The optical film of the present invention contains at least one resin selected from the group consisting of polyimide resin and polyimide resin. In this specification, polyimide resin means selected from the group consisting of polyimide resin, polyimide imide resin, polyimide precursor resin, and polyimide imide precursor resin At least one resin. The polyimide resin is a resin containing a repeating structural unit containing an amide group, and the polyimide resin is a resin containing a repeating structural unit containing both an amide group and an amide group. The polyimide precursor resin and the polyimide imide precursor resin provide the polyimide resin and the polyimide imide resin as the precursor of the polyimide resin through imidization, respectively, And it is also called polyamide resin. In addition, in this specification, the polyamide-based resin is a resin containing a repeating structural unit containing an amide group. The optical film of the present invention may include one type of polyimide-based resin or polyimide-based resin, and may also include two or more types of polyimide-based resins and/or polyimide-based resins in combination. From the standpoint that it is easy to improve the tensile elastic modulus and bending resistance of the optical film, it is easy to _{adjust R 0} to the above range, and it is easy to improve the visibility of the optical film after heat treatment at high temperature, the optical film of the present invention is more Preferably, a polyimide resin is included, and the polyimide resin is preferably a polyimide resin or a polyimide resin, and more preferably a polyimide resin.

In a preferred embodiment of the present invention, it is easy to improve the tensile elastic modulus and bending resistance of the optical film, it is easy to _{adjust R 0} to the above range, and it is easy to improve the visibility of the optical film after heat treatment at high temperature. From a viewpoint, the polyimide-based resin and the polyimide-based resin are preferably aromatic resins. In this specification, the aromatic resin means a resin in which the structural unit contained in the polyimide resin and the polyimide resin is mainly an aromatic structural unit.

In one of the above-mentioned preferred embodiments, it is easy to improve the tensile elastic modulus and bending resistance of the optical film, it is easy to _{adjust R 0} to the above range, and it is easy to improve the visibility of the optical film after heat treatment at a high temperature. In other words, the ratio of the structural unit derived from the aromatic monomer to all the structural units contained in the polyimide-based resin and the polyimide-based resin is preferably 60 mol% or more, more preferably 70 mol% Ear% or more, more preferably 80 mol% or more, and still more preferably 85 mol% or more. Here, the structural unit derived from an aromatic monomer is derived from a monomer containing at least a part of an aromatic structure (for example, an aromatic ring), and at least a part of a structural unit contains an aromatic structure (for example, an aromatic ring). Examples of aromatic monomers include aromatic tetracarboxylic acid compounds, aromatic diamines, and aromatic dicarboxylic acids.

[式(1)中，Y表示4價有機基，X表示2價有機基，*表示鍵結鍵] [化2]

[式(2)中，Z及X相互獨立地表示2價有機基，*表示鍵結鍵] 又，聚醯胺系樹脂較佳為具有式(2)所示之結構單元之聚醯胺樹脂。以下，對式(1)及式(2)進行說明，關於式(1)之說明涉及聚醯亞胺樹脂及聚醯胺醯亞胺樹脂兩者，關於式(2)之說明涉及聚醯胺樹脂及聚醯胺醯亞胺樹脂兩者。In a preferred embodiment of the present invention, the polyimide resin is preferably a polyimide resin having a structural unit represented by formula (1), or a structural unit represented by formula (1) and formula (2) Polyimide resin of the structural unit shown. [化1]

[In formula (1), Y represents a tetravalent organic group, X represents a divalent organic group, and * represents a bonding bond] [化2]

[In formula (2), Z and X independently represent a divalent organic group, and * represents a bonding bond] In addition, the polyamide resin is preferably a polyamide resin having a structural unit represented by formula (2) . Hereinafter, the formula (1) and formula (2) will be described. The description of formula (1) relates to both polyimide resin and polyimide resin, and the description of formula (2) relates to polyamide. Both resin and polyimide resin.

The structural unit represented by formula (1) is a structural unit formed by the reaction of a tetracarboxylic acid compound and a diamine compound, and the structural unit represented by formula (2) is a structural unit formed by the reaction of a dicarboxylic acid compound and a diamine compound.

In the formula (1), Y represents a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably a tetravalent organic group having 4 to 40 carbon atoms having a cyclic structure. As the cyclic structure, there are alicyclic, aromatic, and heterocyclic structures. It is easy to improve the tensile elastic modulus and bending resistance of the optical film, it is easy to _{adjust R 0} to the above range, and it is easy to increase heat treatment at high temperature. From the viewpoint of the visibility of the subsequent optical film, it is preferable to include an aromatic ring. The above-mentioned organic group is an organic group in which the hydrogen atom in the organic group can be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group. In this case, the carbon number of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1-8. In one embodiment of the present invention, the polyimide-based resin may contain plural kinds of Y, and the plural kinds of Y may be the same or different from each other. As Y, the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula ( 28) and the group represented by formula (29); the hydrogen atom in the group represented by formula (20) to formula (29) is substituted by methyl, fluoro, chloro or trifluoromethyl; and carbon A tetravalent chain hydrocarbon group with a number of 6 or less.

[化3]

In formulas (20) to (29), * represents a bonding bond, W ¹ 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 an aryl group having 6 to 20 carbon atoms in which a hydrogen atom can be replaced by a fluorine atom, and a specific example includes a phenyl group. When there are a plurality of Ar, Ar may be the same or different from each other. The hydrogen atoms on the rings in formulas (20) to (29) may be substituted by alkyl groups having 1 to 6 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons. Examples of the alkyl group having 1 to 6 carbons, the alkoxy group having 1 to 6 carbons, and the aryl group having 6 to 12 carbons include those exemplified in the formula (3) described below, respectively.

Based on the formulas (20) to (29), it is easy to improve the tensile modulus of elasticity and bending resistance of the optical film, it is easy to _{adjust R 0} to the above range, and it is easy to increase the From the viewpoint of the visibility of the optical film, the base represented by formula (26), formula (28) or formula (29) is preferred, and the base represented by formula (26) is more preferred. In addition, it is easy to improve the tensile elastic modulus and bending resistance of the optical film, and it is easy to _{adjust R 0} to the above range, and it is easy to improve the visibility of the optical film after heat treatment at high temperature, and it is easy to reduce the YI of the optical film. In terms of value, W ¹ is preferably a single bond independently of each other, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) _2- Or -C(CF ₃ ) ₂ -, more preferably a single bond, -O-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -or -C(CF ₃ ) _2- , More preferably a single bond, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, most preferably a single bond or -C(CF ₃ ) ₂ -.

In a preferred embodiment of the present invention, Y in the polyimide resin is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more. (26) Representation. If Y in the above-mentioned range in the polyimide resin is represented by formula (26), it is preferably a formula in which W ¹ is a single bond and -C(CH ₃ ) ₂ -or -C(CF ₃ ) _2- (26) means that, more preferably, W ¹ is a single bond or -C(CF ₃ ) ₂ -is expressed by the formula (26), it is easy to improve the tensile elastic modulus and bending resistance of the optical film, and it is easy to change R _{Adjusting 0} to the above range can easily reduce the YI value of the optical film. The ratio of the structural unit represented by formula (26) of Y in the polyimide-based resin can ^{be measured, for example, using 1} H-NMR ( ¹ H-nuclear magnetic resonance), or can also be calculated based on the addition ratio of raw materials.

[式(4)中，R² ～R⁷ 相互獨立地表示氫原子、碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基，R² ～R⁷ 中所含之氫原子可相互獨立地被鹵素原子取代，V表示單鍵、-O-、-CH₂ -、-CH₂ -CH₂ -、-CH(CH₃ )-、-C(CH₃ )₂ -、-C(CF₃ )₂ -、-SO₂ -、-S-、-CO-或-N(R⁸ )-，R⁸ 表示氫原子或可經鹵素原子取代之碳數1～12之1價烴基，*表示鍵結鍵] 即，較佳為於複數個式(1)所示之結構單元中之Y中，至少一部分Y為式(4)所示之基。若為此種態樣，則易於提高光學膜之拉伸彈性模數及耐彎曲性，易於將R₀ 調整為上述範圍，且易於降低光學膜之YI值。再者，式(1)所示之結構單元可含有1種或複數種式(4)所示之基作為Y。In a preferred embodiment of the present invention, the structural unit represented by formula (1) contains the group represented by formula (4) as Y. [化4]

[In formula (4), R ² to R ⁷ independently represent a hydrogen atom, an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons, R ² to The hydrogen atoms contained in R ⁷ can be independently substituted by halogen atoms, and V represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C( CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁸ )-, R ⁸ represents a hydrogen atom or the number of carbons that can be substituted by a halogen atom A monovalent hydrocarbon group of 1 to 12, * represents a bonding bond] That is, it is preferable that among Y in the structural unit represented by the formula (1), at least a part of Y is a group represented by the formula (4). In this aspect, it is easy to improve the tensile elastic modulus and bending resistance of the optical film, it is easy to _{adjust R 0} to the above-mentioned range, and it is easy to reduce the YI value of the optical film. Furthermore, the structural unit represented by formula (1) may contain one or more types of groups represented by formula (4) as Y.

In formula (4), R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbons, an alkoxy group having 1 to 6 carbons, or carbon The number of aryl groups from 6 to 12. Examples of alkyl groups having 1 to 6 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons include the above-mentioned as R ^3a in the formula (3) with carbon numbers of 1 to The alkyl group of 6, the alkoxy group of 1 to 6 carbons, or the aryl group of 6 to 12 carbons are exemplified. ^{Regarding R 3a} in the formula (3), those exemplified in the above can be cited. R ² ~ R ⁷ each independently represents preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, the more preferably represents a hydrogen atom or a carbon atoms in the alkyl group of 1 to 3, where, R ² ~ R ⁷ The hydrogen atoms contained can be replaced by halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. V represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁸ )-, R ⁸ represents a hydrogen atom or a monovalent hydrocarbon group with 1 to 12 carbon atoms which can be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include those exemplified for R ^{9 in W in the formula (3) described later.} Among them, it is easy to improve the tensile elastic modulus, optical properties, surface hardness and bending resistance _{of the optical film, it is easy to adjust R 0} to the above range, and it is easy to improve the visibility of the optical film after heat treatment at high temperature. From a viewpoint, V is preferably a single bond, -O-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, more preferably a single bond A bond, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, more preferably a single bond or -C(CF ₃ ) ₂ -.

[式(5)中，R¹⁸ ～R²⁵ 相互獨立地表示氫原子、碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基，R¹⁸ ～R²⁵ 中所含之氫原子可相互獨立地被鹵素原子取代，*表示鍵結鍵] [化6]

[式(9)中，R³⁵ ～R⁴⁰ 相互獨立地表示氫原子、碳數1～6之烷基或碳數6～12之芳基，R³⁵ ～R⁴⁰ 中所含之氫原子可相互獨立地被鹵素原子取代，*表示鍵結鍵] 若複數個式(1)中之Y之至少一部分由式(5)表示及/或由式(9)表示，則易於提高光學膜之拉伸彈性模數及光學特性。In a preferred embodiment of the present invention, at least a part of Y in the plurality of formulas (1) is represented by formula (5) and/or formula (9). [化5]

[In formula (5), R ¹⁸ to R ²⁵ independently represent a hydrogen atom, an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons, R ¹⁸ to The hydrogen atoms contained in R ²⁵ can be replaced by halogen atoms independently of each other, and * represents a bonding bond] [化6]

[In formula (9), R ³⁵ to R ⁴⁰ independently represent a hydrogen atom, an alkyl group with 1 to 6 carbons or an aryl group with 6 to 12 carbons, and the hydrogen atoms contained in ^{R 35} to R ^{40 may mutually} Independently substituted by halogen atoms, * represents a bonding bond] If at least a part of Y in the formula (1) is represented by the formula (5) and/or is represented by the formula (9), it is easy to increase the stretching of the optical film Elastic modulus and optical properties.

In formula (5), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ and R ²⁵ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbons, and a carbon number of 1 to 6 The alkoxy group or the aryl group with 6-12 carbons. Examples of alkyl groups having 1 to 6 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons include the above-mentioned as R ^3a in the formula (3) with carbon numbers of 1 to The alkyl group of 6, the alkoxy group of 1 to 6 carbons, or the aryl group of 6 to 12 carbons are exemplified. R ¹⁸ ~ R ²⁵ each independently preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, the more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, the where, R ¹⁸ ~ R ²⁵ as The hydrogen atoms contained can be replaced by halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. From the viewpoints of easy improvement of the tensile modulus of elasticity and bending resistance of the optical film, and the viewpoint of easy improvement of transparency and easy maintenance of the transparency, R ¹⁸ to R ²⁵ are independent of each other and are more preferably hydrogen atoms, A R ¹⁸ , R ¹⁹ , R ²⁰ , R ²³ , R ²⁴ and R ²⁵ are hydrogen atoms, and R ²¹ and R ²² are hydrogen atoms, methyl groups, A fluoro group, a chloro group or a trifluoromethyl group, and R ^{21 and R 22} are particularly preferably a methyl group or a trifluoromethyl group.

^{In formula (9), R 35} to R ^{40 are} preferably hydrogen atoms from the viewpoints of easy improvement of the tensile modulus of elasticity and bending resistance of the optical film, and easy improvement of transparency and easy maintenance of the transparency. Or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably a hydrogen atom. Here, ^{the hydrogen atoms contained in R 35} to R ⁴⁰ may be independently substituted with halogen atoms, and examples of the halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Examples of the alkyl group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms in R ³⁵ to R ^{40 include those exemplified above.}

即，複數個Y之至少一部分由式(5')及/或式(9')表示。於此情形時，易於提高光學膜之拉伸彈性模數及耐彎曲性。進而，於式(5)由式(5')表示之情形時，藉由含有氟元素之骨架會提高聚醯亞胺系樹脂於溶劑中之溶解性，從而易於提高含有該樹脂之清漆之保管穩定性，並且易於降低該清漆之黏度，從而易於提高光學膜之加工性。其結果，易於製造滿足數式(1)～(3)之本發明之光學膜。又，藉由含有氟元素之骨架而易於提高光學膜之光學特性。In a preferred embodiment of the present invention, formula (5) is represented by formula (5'), and formula (9) is represented by formula (9'). [化7]

That is, at least a part of a plurality of Y is represented by formula (5') and/or formula (9'). In this case, it is easy to improve the tensile elastic modulus and bending resistance of the optical film. Furthermore, in the case where the formula (5) is represented by the formula (5'), the fluorine-containing skeleton will increase the solubility of the polyimide resin in the solvent, thereby easily improving the storage of the varnish containing the resin Stability, and easy to reduce the viscosity of the varnish, thereby easy to improve the processability of the optical film. As a result, it is easy to manufacture the optical film of the present invention that satisfies the mathematical formulas (1) to (3). In addition, it is easy to improve the optical properties of the optical film by the skeleton containing the fluorine element.

In a preferred embodiment of the present invention, Y in the polyimide resin is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more. (5) is represented, especially by formula (5'). If Y in the above range in the polyimide resin is represented by formula (5), especially by formula (5'), the skeleton containing the fluorine element will increase the polyimide resin in the solvent It is easy to reduce the viscosity of the varnish containing the resin, and it is easy to improve the processability of the optical film. As a result, it is easy to manufacture the optical film of the present invention that satisfies the mathematical formulas (1) to (3). In addition, it is easy to improve the optical properties of the optical film by the skeleton containing the fluorine element. Furthermore, it is preferable that 100 mole% or less of Y in the polyimide resin is represented by formula (5), especially represented by formula (5'). Y in the polyimide resin may be formula (5), especially formula (5'). The ratio of the structural unit represented by the formula (5) of Y in the polyimide-based resin can ^{be measured, for example, using 1} H-NMR, or can also be calculated based on the addition ratio of the raw materials.

[式(20)～式(29)中，W¹ 表示單鍵、-O-、-CH₂ -、-CH₂ -CH₂ -、-CH(CH₃ )-、-C(CH₃ )₂ -、-C(CF₃ )₂ -、-Ar-、-SO₂ -、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂ -Ar-、-Ar-C(CH₃ )₂ -Ar-或-Ar-SO₂ -Ar-，此處，Ar相互獨立地表示氫原子可被氟原子取代之碳數6～20之伸芳基(例如伸苯基)，*表示鍵結鍵] 作為Z之雜環結構，可例示具有噻吩環骨架之基。就易於降低光學膜之YI值之觀點、易於提高全光線透過率之觀點及易於降低霧度之觀點而言，作為Z中之環狀結構，較佳為式(20)～式(29)所示之基及具有噻吩環骨架之基，更佳為式(26)、式(28)及式(29)所示之基。In formula (2), Z is a divalent organic group, preferably an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons or an aryl group with 6 to 12 carbons (in these groups The hydrogen atom can be substituted by a halogen atom (preferably a fluorine atom). A divalent organic group with 4 to 40 carbons, more preferably an alkyl with 1 to 6 carbons, and an alkane with 1 to 6 carbons. An oxy group or an aryl group with 6 to 12 carbons (the hydrogen atoms in these groups may be substituted by halogen atoms (preferably fluorine atoms)) and a divalent organic group with 4 to 40 carbons that has a cyclic structure. Furthermore, as examples of alkyl groups having 1 to 6 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons, the same applies to R ^3a and R ^{3b in the formula (3) described later} Related examples. Examples of the cyclic structure include alicyclic, aromatic, and heterocyclic structures. As the organic group of Z, the formula (20), the formula (21), the formula (22), the formula (23), the formula (24), the formula (25), the formula (26), the formula (27), the formula ( 28) and a group in which two non-adjacent bonding bonds of the group represented by formula (29) are substituted with hydrogen atoms; and a divalent chain hydrocarbon group with 6 or less carbon atoms, [化8]

[In formulas (20) to (29), W ¹ 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-, where Ar represents independently of each other an aryl group having 6 to 20 carbon atoms in which hydrogen atoms can be substituted by fluorine atoms (for example, phenylene Group), * represents a bonding bond] As the heterocyclic structure of Z, a group having a thiophene ring skeleton can be exemplified. From the viewpoint of easy reduction of the YI value of the optical film, the viewpoint of easy improvement of the total light transmittance, and the viewpoint of easy reduction of the haze, the ring structure in Z is preferably represented by formulas (20) to (29) The groups shown and the groups having a thiophene ring skeleton are more preferably groups represented by formula (26), formula (28) and formula (29).

[式(20')～式(29')中，W¹ 及*如式(20)～式(29)中之定義] 再者，式(20)～式(29)及式(20')～式(29')中之環上之氫原子可被碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基(該等基中之氫原子可被鹵素原子(較佳為氟原子)取代)取代。As the organic group of Z, it is more preferably formula (20'), formula (21'), formula (22'), formula (23'), formula (24'), formula (25'), formula (26') , Formula (27'), formula (28') and formula (29') as shown in the divalent organic group. [化9]

[In formulas (20') to (29'), W ¹ and * are as defined in formulas (20) to (29)] Furthermore, formulas (20) to (29) and (20') ～The hydrogen atom on the ring in formula (29') can be replaced by an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons or an aryl group with 6 to 12 carbons (the hydrogen atoms in these groups It may be substituted by a halogen atom (preferably a fluorine atom).

[式(d1)中，R⁴¹ 相互獨立為關於後述之式(3)中之R^3a 所定義之基或氫原子，R⁴² 表示R⁴¹ 或-C(=O)-*，*表示鍵結鍵] 作為結構單元(d1)，具體而言，可舉出：R⁴¹ 及R⁴² 均為氫原子之結構單元(源自二羧酸化合物之結構單元)；R⁴¹ 均為氫原子，R⁴² 表示-C(=O)-*之結構單元(源自三羧酸化合物之結構單元)等。When the polyamide resin or polyamide imine resin has a structural unit in which Z in formula (2) is represented by any one of the above formula (20') to formula (29'), where there is When Z in the formula (2) is a structural unit represented by the following formula (3'), from the viewpoint that it is easy to improve the film-forming properties of the varnish and the uniformity of the optical film, the polyamide resin or The polyamidoimide resin preferably has, in addition to the structural unit, a structural unit derived from a carboxylic acid represented by the following formula (d1). [化10]

[In formula (d1), R ^{41 is} independent of each other for the group or hydrogen atom defined by ^{R 3a} in formula (3) described later ^{, R 42} represents R ⁴¹ or -C(=O)-*, * represents bonding Bond] As the structural unit (d1), specific examples include: ^{structural units in which R 41} and R ⁴² are both hydrogen atoms (structural units derived from dicarboxylic acid compounds); R ⁴¹ are both hydrogen atoms, and R ⁴² Represents the structural unit of -C(=O)-* (the structural unit derived from the tricarboxylic acid compound), etc.

[式(3)中，R^3a 及R^3b 相互獨立地表示碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基，R^3a 及R^3b 中所含之氫原子可相互獨立地被鹵素原子取代，W相互獨立地表示單鍵、-O-、-CH₂ -、-CH₂ -CH₂ -、-CH(CH₃ )-、-C(CH₃ )₂ -、-C(CF₃ )₂ -、-SO₂ -、-S-、-CO-或-N(R⁹ )-，R⁹ 表示氫原子、可經鹵素原子取代之碳數1～12之1價烴基，s為0～4之整數，t為0～4之整數，u為0～4之整數，*表示鍵結鍵] [化12]

[式(3')中，R^3a 、R^3b 、s、t、u、W及*如式(3)中之定義] 再者，本說明書中，聚醯胺系樹脂或聚醯胺醯亞胺樹脂具有式(2)中之Z由式(3)表示之結構單元之表述、與聚醯胺系樹脂或聚醯胺醯亞胺系樹脂具有式(3)所示之結構作為式(2)中之Z之表述具有相同含義，且係指於聚醯胺系樹脂或聚醯胺醯亞胺樹脂中可包含之複數個式(2)所示之結構單元中，至少一部分結構單元中之Z由式(3)表示。該記載亦適配於其他同樣之記載。The polyamide resin or polyamide resin may contain a plurality of types of Z as Z in the formula (2), and the plurality of types of Z may be the same or different from each other. In particular, from the viewpoint of easy improvement of the tensile elastic modulus of the optical film of the present invention and easy improvement of optical properties, it is preferable to have at least Z in the formula (2), preferably represented by the formula (3), more preferably It is a structural unit represented by formula (3'). [化11]

[In formula (3), R ^3a and R ^3b independently represent an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons. In R ^3a and R ^3b The hydrogen atoms contained can be replaced by halogen atoms independently of each other, and W 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 -, -S-, -CO- or -N(R ⁹ )-, R ⁹ represents a hydrogen atom, the number of carbons that can be substituted by a halogen atom A monovalent hydrocarbon group of 1 to 12, s is an integer of 0 to 4, t is an integer of 0 to 4, u is an integer of 0 to 4, * represents a bonding bond] [化12]

[In formula (3'), R ^3a , R ^3b , s, t, u, W, and * are as defined in formula (3)] Furthermore, in this specification, polyamide resin or polyamide resin The amine resin has the expression of the structural unit represented by the formula (3) in Z in the formula (2), and the polyamide resin or the polyamide resin has the structure represented by the formula (3) as the formula (2) The expression of Z in) has the same meaning, and refers to the plurality of structural units represented by formula (2) that can be contained in polyamide resins or polyamide imide resins, and at least a part of the structural units Z is represented by formula (3). This record is also adapted to other similar records.

In formula (3) and formula (3'), W independently represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁹ )-, from the viewpoint of the bending resistance of the optical film, it is preferable to indicate -O- or -S-, more preferably -O-. R ^3a and R ^3b independently represent an alkyl group having 1 to 6 carbons, an alkoxy group having 1 to 6 carbons, or an aryl group having 6 to 12 carbons. Examples of alkyl groups having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, t-butyl, n-pentyl, 2-methyl Butyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, etc. Examples of alkoxy groups having 1 to 6 carbon atoms include: methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, and pentoxy Group, hexyloxy, cyclohexyloxy, etc. Examples of aryl groups having 6 to 12 carbon atoms include phenyl, tolyl, xylyl, naphthyl, and biphenyl. From the viewpoints of the tensile elastic modulus, surface hardness, and flexibility of the optical film, as well as the viewpoint of the ease of improving the visibility of the optical film after heat treatment at high temperature, R ^3a and R ^3b are independently of each other and preferably represent carbon An alkyl group having 1 to 6 or an alkoxy group having 1 to 6 carbons, more preferably an alkyl group having 1 to 3 carbons or an alkoxy group having 1 to 3 carbons. Here, ^{the hydrogen atoms contained in R 3a} and R ^3b may be substituted with halogen atoms independently of each other. R ⁹ represents a hydrogen atom or a monovalent hydrocarbon group with 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, second butyl, tertiary butyl, n-pentyl, 2-methyl Butyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, n-heptyl, n-octyl, tertiary octyl, n-nonyl, n-decyl, etc., which can be substituted by halogen atoms . As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned.

In formula (3) and formula (3′), t and u are independently an integer of 0-4, preferably an integer of 0-2, and more preferably 1 or 2.

In formula (3) and formula (3'), s is an integer in the range of 0-4. If s is in this range, the tensile modulus and bending resistance of the optical film can be easily improved. From the viewpoint of easier improvement of the tensile modulus of elasticity and bending resistance of the optical film, the above-mentioned s is preferably an integer in the range of 0-3, more preferably an integer in the range of 0-2, and more preferably 0 Or 1, more preferably 0. The polyamide imide resin or polyamide resin may contain one or more structural units represented by formula (3) or formula (3') as Z.

In a preferred embodiment of the present invention, from the viewpoint of improving the tensile elastic modulus, elastic modulus, and bending resistance of the optical film, and lowering the YI value, Z is preferably from s to 0 and u is more preferred It is represented by formula (3) or formula (3') of 1 to 3, more preferably 1 or 2. Furthermore, it is also preferable to have a structural unit represented by the above formula (d1) in addition to the structural unit represented by the formula (2) represented by the formula (3) or formula (3') where s is 0 .

When the polyamide resin or polyamide resin has the structural unit represented by the formula (3) or formula (3'), the ratio is greater than that of the polyamide resin or polyamide resin When the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) of the resin is set to 100 mol%, it is preferably 20 mol% or more, more preferably 30 mol% or more, and then Preferably it is 40 mol% or more, more preferably 50 mol% or more, particularly preferably 60 mol% or more, and preferably 90 mol% or less, more preferably 85 mol% or less, and still more preferably It is less than 80 mol%. If the ratio of the structural unit shown in formula (3) or formula (3') is above the above lower limit, it is easy to improve the tensile elastic modulus and bending resistance of the optical film, and it is easy to improve the optical film after heat treatment at high temperature The visibility. If the ratio of the structural units represented by the formula (3) or formula (3') is below the above upper limit, it is easy to suppress the increase in the viscosity of the resin-containing varnish due to the hydrogen bonding between the amide bonds derived from the formula (3) , So it is easy to improve the processability of the film. Furthermore, the ratio of structural units represented by formula (1), formula (2), formula (3) or formula (3') can ^{be measured using 1} H-NMR, or can also be calculated based on the addition ratio of raw materials .

In a preferred embodiment of the present invention, Z in the polyamide imide resin or polyamide resin is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more, and more preferably 50 mol% or more are structural units represented by formula (3) or formula (3') in which s is 0-4. If the above lower limit of Z is a structural unit represented by formula (3) or formula (3') where s is 0-4, it is easy to increase the tensile elastic modulus and bending resistance of the optical film, and it is easy to increase the The visibility of the optical film after heat treatment. Moreover, as long as 100 mol% or less of Z in the polyamide resin or polyamide resin is a structural unit represented by formula (3) or formula (3') where s is 0-4. In addition, the ratio of the structural unit represented by formula (3) or formula (3') in which s is 0 to 4 in the resin can ^{be measured, for example, using 1} H-NMR, or can also be calculated based on the addition ratio of the raw materials.

In formula (1) and formula (2), X independently represents a divalent organic group, preferably a divalent organic group having 4 to 40 carbons, and more preferably a cyclic structure having 4 to 40 carbons. The divalent organic base. Examples of the cyclic structure include alicyclic, aromatic, and heterocyclic structures. The above-mentioned organic group may be substituted by a hydrocarbyl group or a fluorine-substituted hydrocarbyl group for the hydrogen atom in the organic group. In this case, the carbon number of the hydrocarbyl group and the fluorine-substituted hydrocarbyl group is preferably 1-8. In one embodiment of the present invention, the polyamide resin and polyimide resin of the present invention may include a plurality of types of X, and the plurality of types of X may be the same or different from each other. Examples of X include: formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17), and formula (18) The group shown; the hydrogen atom of the group shown in the formula (10) to the formula (18) is substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group with a carbon number of 6 or less .

[化13]

In formulas (10) to (18), * represents a bonding bond, and V ¹ , V ² and V ³ independently represent a single bond, -O-, -S-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -CO- or -N(Q)-. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbons which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbons include the groups described above for R ⁹ . For example, V ¹ and V ³ are single bonds, -O- or -S-, and V ² is -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -or- SO ₂ -. The bonding position of V ¹ and V ^{2 with} respect to each ring, and the bonding position of V ² and V ^{3 with} respect to each ring are independent of each other, and are preferably meta or para, and more preferably para.

Among the bases represented by formulas (10) to (18), from the viewpoint of easily improving the tensile modulus of elasticity and bending resistance of the optical film, formulas (13), (14), and ( 15) The base represented by formula (16) and formula (17) is more preferably the base represented by formula (14), formula (15) and formula (16). Moreover, from the viewpoint of easy improvement of the tensile modulus of elasticity and flexibility of the optical film, V ¹ , V ² and V ³ are independently of each other preferably a single bond, -O- or -S-, more preferably a single bond, -O- or -S- Key or -O-.

[式(5)中，Ar² 相互獨立地表示可具有取代基之2價芳香族基，V表示單鍵、-O-、二苯基亞甲基、茀基、碳數1～12之2價烴基、-SO₂ -、-S-、-CO-、-PO-、-PO₂ -、-N(R^a )-或-Si(R^b )₂ -，此處，該烴基可包含脂環式結構，該烴基中所含之氫原子可相互獨立地被鹵素原子取代，R^a 及R^b 相互獨立地表示氫原子或可經鹵素原子取代之碳數1～12之1價烴基，m表示0～3之整數，*表示鍵結鍵] 於結構單元(1)及結構單元(2)含有式(5)所示之2價有機基作為X之情形時，結構單元(1)及結構單元(2)可含有式(5)所示之1種或2種以上之2價有機基作為X。結構單元(1)及結構單元(2)除含有式(5)所示之2價有機基作為X以外，亦可含有不相當於式(5)所示之2價有機基之其他2價有機基作為X。In a preferred embodiment of the present invention, the polyamide resin and/or polyimide resin contains the divalent organic group represented by formula (5) as X in formula (1) or formula (2) Among the X. [化14]

[In formula (5), Ar ² independently represents a divalent aromatic group that may have a substituent, and V represents a single bond, -O-, diphenylmethylene, stilbene, 2 of carbon number 1-12 Valence hydrocarbon group, -SO ₂ -, -S- _{, -CO-, -PO-, -PO 2} -, -N(R ^a )- or -Si(R ^b ) ₂ -, where the hydrocarbon group may contain fat Cyclic structure, the hydrogen atoms contained in the hydrocarbon group can be independently substituted by halogen atoms, R ^a and R ^b independently represent a hydrogen atom or a monovalent hydrocarbon group with 1 to 12 carbon atoms that can be substituted by a halogen atom, m Represents an integer from 0 to 3, * represents a bonding bond] When the structural unit (1) and the structural unit (2) contain the divalent organic group represented by the formula (5) as X, the structural unit (1) and the structure The unit (2) may contain one type or two or more types of divalent organic groups represented by formula (5) as X. The structural unit (1) and the structural unit (2) may contain the divalent organic group represented by the formula (5) as X, and may also contain other divalent organic groups that are not equivalent to the divalent organic group represented by the formula (5) Base as X.

^{Ar 2} in the formula (5) represents a divalent aromatic group which may have a substituent. The divalent aromatic group is a group in which two hydrogen atoms of a monocyclic aromatic ring, a condensed polycyclic aromatic ring, or an aggregate ring aromatic ring are substituted to form a bonding bond. The divalent aromatic group may include an aromatic ring (monocyclic, condensed polycyclic, or collective ring) formed only by carbon atoms, or may include a heteroaromatic ring including atoms other than carbon atoms to form a ring. Examples of atoms other than carbon atoms include nitrogen atoms, sulfur atoms, and oxygen atoms. The total number of carbon atoms and atoms other than carbon atoms forming the aromatic ring is not particularly limited, but is preferably 5-18, more preferably 5-14, and still more preferably 5-12. When m in formula (5) is 1 or more, the plurality of Ar ² may be the same or different from each other.

Examples of the monocyclic aromatic ring include benzene, furan, pyrrole, thiophene, pyridine, imidazole, pyrazole, azole, thiazole, imidazoline, and the like.

Examples of the condensed polycyclic aromatic ring include naphthalene, anthracene, phenanthrene, indole, benzothiazole, benzimidazole, and benzoxazole.

As the aggregate ring aromatic ring, there can be mentioned a structure in which two or more monocyclic aromatic rings and/or condensed polycyclic aromatic rings are connected by a single bond. As an example, the above can be mentioned as Groups in which two or more of the rings described in the examples of monocyclic aromatic rings or condensed polycyclic aromatic rings are connected by single bonds, such as biphenyl, triphenyl, bitetraphenyl, binaphthyl, 1-benzene Base naphthalene, 2-phenyl naphthalene, bipyridine, etc.

From the viewpoint of easy improvement of the tensile elastic modulus of the optical film, the divalent aromatic group which may have a substituent is preferably the aromatic hydrocarbon ring which may have a substituent. Two hydrogen atoms of the aromatic hydrocarbon ring are substituted to form a bonding bond. Group, more preferably a group in which two hydrogen atoms of benzene, biphenyl, terphenyl or bitetraphenyl which may have substituents are substituted to form a bonding bond, and more preferably a group of benzene or biphenyl which may have substituents Two hydrogen atoms are substituted to form a bonding bond group.

Examples ^{of the substituents in Ar 2} include halogen groups, alkyl groups having 1 to 12 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons, or those contained in these groups. A group in which a hydrogen atom is replaced by a halogen atom.

The C1-C12 alkyl group may be a C1-C12 linear or branched alkyl group, preferably a C1-C6 linear or branched alkyl group. Examples of such groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, second butyl, tertiary butyl, n-pentyl, 2-methylbutyl, 3 -Methylbutyl, 2-ethylpropyl, n-hexyl, n-heptyl, n-octyl, tertiary octyl, n-nonyl and n-decyl, etc.

Examples of alkoxy groups having 1 to 6 carbon atoms include: methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tert-butoxy, and pentoxy Group, hexyloxy, cyclohexyloxy, etc.

Examples of aryl groups having 6 to 12 carbon atoms include phenyl, tolyl, xylyl, naphthyl, and biphenyl.

As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned.

The substituent in Ar ² is preferably a halogen group or an alkyl group having 1 to 12 carbon atoms in which a hydrogen atom can be substituted by a halogen atom, and more preferably a methyl group, a fluoro group, a chloro group or a trifluoromethyl group.

V in the formula (5) represents a single bond, -O-, diphenylmethylene, stilbene, a divalent hydrocarbon group with 1 to 12 carbons, -SO ₂ -, -S-, -CO-, -PO -, -PO ₂ -, -N(R ^a )- or -Si(R ^b ) ₂ -. Here, the hydrocarbyl group may include an alicyclic structure, the hydrogen atoms contained in the hydrocarbyl group may be independently substituted by halogen atoms, and R ^a and R ^b independently represent a hydrogen atom or a carbon number that may be substituted by a halogen atom. 1 ~12 monovalent hydrocarbon group. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, second butyl, tertiary butyl, n-pentyl, 2-methyl Butyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, n-heptyl, n-octyl, tertiary octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, etc., These can be substituted by halogen atoms. As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned. From the viewpoint of easily improving the tensile elastic modulus and bending resistance of the optical film, V in formula (5) is preferably a single bond, or a divalent hydrocarbon group with 1 to 12 carbons, and those contained in the hydrocarbon group A group in which at least a part of the hydrogen atoms is substituted by halogen atoms, more preferably a single bond, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -or- C(CF ₃ ) ₂ -, more preferably a single bond, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, still more preferably a single bond or -C(CF ₃ ) ₂ -.

In the formula (5), m represents an integer of 0 to 3, and from the viewpoint that it is easy to increase the tensile elastic modulus of the optical film, it is preferably 0 to 2, more preferably 0 or 1, and even more preferably 1.

The structural unit (1) and/or the structural unit (2) that can be contained in the polyamide resin and/or polyimide resin contained in the optical film of the present invention contains 2 represented by formula (5) In a preferred aspect of the present invention where the valence organic group is X, from the viewpoint of easily improving the tensile elastic modulus of the optical film, the total of the structural unit (1) and the structural unit (2) is set to 100 Mole%, X in formula (1) is the structural unit of the divalent organic group shown in formula (5) and X in formula (2) is the structural unit of the divalent organic group shown in formula (5) The total ratio of is preferably 70-100 mol%, more preferably 80-100 mol%, and still more preferably 90-100 mol%, which can be used in all of the structural unit (1) and the structural unit (2) X in the structural unit is a divalent organic group represented by formula (5).

[式(5a)中，R² 表示碳數1～12之氟烷基，p及q相互獨立地表示1～4之整數，其中，於p及/或q表示2～4之整數之情形時存在之複數個R² 相互可相同亦可不同，*表示鍵結鍵] 再者，式(5a)所示之2價有機基係包含於式(5)所示之2價有機基中之基，具體而言係相當於式(5)中之V表示單鍵，Ar² 表示經碳數1～12之氟烷基(R² )取代之苯環，m表示0～3之整數之2價有機基的基。於結構單元(1)及結構單元(2)含有式(5a)所示之2價有機基作為X之情形時，結構單元(1)及結構單元(2)可含有式(5a)所示之1種或2種以上之2價有機基作為X。結構單元(1)及/或結構單元(2)除含有式(5a)所示之2價有機基作為X以外，亦可含有不相當於式(5a)所示之2價有機基之其他2價有機基作為X。In a preferred embodiment of the present invention, from the viewpoint of easily increasing the tensile elastic modulus of the optical film, the structural unit represented by formula (1) and/or the structural unit represented by formula (2) contains the formula The divalent organic group shown in (5a) is referred to as X. [化15]

[In formula (5a), R ² represents a fluoroalkyl group having 1 to 12 carbon atoms, and p and q independently represent an integer of 1 to 4, where p and/or q represent an integer of 2 to 4 The existence of a plurality of R ² may be the same or different from each other, * represents a bonding bond] Furthermore, the divalent organic group represented by formula (5a) is a group contained in the divalent organic group represented by formula (5) Specifically, it corresponds to the formula (5) where V represents a single bond, Ar ^{2 represents a benzene ring substituted by a fluoroalkyl group (R 2} ) with 1 to 12 carbon atoms, and m represents an integer of 0 to 3 divalent The base of the organic base. When the structural unit (1) and the structural unit (2) contain the divalent organic group represented by the formula (5a) as X, the structural unit (1) and the structural unit (2) may contain the formula (5a) One type or two or more types of divalent organic groups are used as X. Structural unit (1) and/or structural unit (2) may contain the divalent organic group represented by formula (5a) as X, and may also contain other 2 that is not equivalent to the divalent organic group represented by formula (5a) The valence organic group is X.

^{R 2} in the formula (5a) represents a fluoroalkyl group having 1 to 12 carbon atoms. The fluoroalkyl group having 1 to 12 carbon atoms is a group in which at least one hydrogen atom of a linear or branched chain alkyl group having 1 to 12 carbon atoms is substituted with a fluorine atom. Examples of linear or branched fluoroalkyl groups having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl. Base, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, n-heptyl, n-octyl, tertiary octyl, n-nonyl and n-decyl A group in which at least one hydrogen atom is replaced by a fluorine atom. Specific examples of the fluoroalkyl group having 1 to 12 carbon atoms include: fluoromethyl, difluoromethyl, trifluoromethyl, fluoroethyl, difluoroethyl, trifluoroethyl, and pentafluoro Ethyl, heptafluoropropyl, nonafluorobutyl, etc. The carbon number of the fluoroalkyl group is preferably 1-6, more preferably 1-4, and still more preferably 1 or 2.

p and q represent an integer of 1 to 4 independently of each other. From the viewpoint of easy improvement of the tensile elastic modulus of the optical film, p is preferably an integer of 1 or 2, and more preferably 2. From the viewpoint of easily increasing the tensile elastic modulus of the optical film, q is preferably an integer of 1 or 2, and more preferably 1. Here, when p and/or q represent an integer of 2 to 4, the plurality of R ² present may be the same or different from each other, and it is preferable that the plurality of R ^{2 present} are the same as each other.

Regarding the two bonding bonds in formula (5a), the mutual position is not particularly limited, and can be any of ortho, meta, and para. From the viewpoint of easy improvement of the tensile elastic modulus of the optical film, The bonding keys are preferably positioned opposite to each other.

Preferred examples of the divalent aromatic group represented by formula (5a) include the following aromatic groups: R ² in formula (5a) represents a perfluoroalkyl group having 1 to 12 carbon atoms, and p is 2, q is 1 or 2 and/or the two bonding bonds are positioned opposite each other.

The structural unit (1) and/or the structural unit (2) that can be contained in the resin contained in the optical film of the present invention contains a divalent organic group represented by the formula (5a) as one of the preferred implementations of the present invention In the method, from the viewpoint of easy improvement of the tensile elastic modulus of the optical film, the total of the structural unit (1) and the structural unit (2) contained in the polyimide-imide resin is set to 100 mol When ear%, X in formula (1) is the structural unit of the divalent organic group shown in formula (5a) and X in formula (2) is the structural unit of the divalent organic group shown in formula (5a) The total ratio is preferably 70-100 mol%, more preferably 80-100 mol%, and still more preferably 90-100 mol%, which can be used in all structures of structural unit (1) and structural unit (2) X in the unit is a divalent organic group represented by formula (5a).

[式(4)中，R¹⁰ ～R¹⁷ 相互獨立地表示氫原子、碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基，R¹⁰ ～R¹⁷ 中所含之氫原子可相互獨立地被鹵素原子取代，*表示鍵結鍵] 若式(1)及式(2)所示之複數個結構單元中之X之至少一部分為式(4)所示之結構，則易於提高光學膜之拉伸彈性模數及透明性。In a preferred embodiment of the present invention, the polyamide resin and polyimine resin include the structure represented by formula (4) as X in formula (1) or X in formula (2). [化16]

[In formula (4), R ¹⁰ to R ¹⁷ independently represent a hydrogen atom, an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons, R ¹⁰ to The hydrogen atoms contained in R ¹⁷ can be independently substituted by halogen atoms, and * represents a bonding bond] If at least a part of X in the plural structural units shown in formula (1) and formula (2) is formula (4) The structure shown in) is easy to improve the tensile elastic modulus and transparency of the optical film.

In formula (4), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbons, and a carbon number of 1 to 6 The alkoxy group or the aryl group with 6-12 carbons. Examples of alkyl groups having 1 to 6 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons include the alkyl groups having 1 to 6 carbons in formula (3), The group exemplified by the alkoxy group having 1 to 6 or the aryl group having 6 to 12 carbon atoms. R ¹⁰ to R ¹⁷ independently of each other preferably represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, where R ¹⁰ to R ¹⁷ are The hydrogen atoms contained can be replaced by halogen atoms independently of each other. As a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned, for example. From the viewpoints of the tensile modulus of elasticity, transparency, and bending resistance of the optical film, R ¹⁰ to R ¹⁷ are independently of each other and are more preferably a hydrogen atom, a methyl group, a fluorine group, a chlorine group, or a trifluoromethyl group, More preferably, R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are hydrogen atoms, and R ¹¹ and R ¹⁷ are hydrogen atoms, methyl, fluoro, chloro, or trifluoromethyl, and most preferably Where R ¹¹ and R ¹⁷ are methyl or trifluoromethyl.

即，式(1)及式(2)所示之複數個結構單元中之X之至少一部分為式(4')所示之結構單元。於此情形時，藉由含有氟元素之骨架會提高聚醯亞胺系樹脂或聚醯胺系樹脂於溶劑中之溶解性，從而易於提高含有該樹脂之清漆之保管穩定性，並且易於降低該清漆之黏度，從而易於提高光學膜之加工性。其結果，易於製造滿足數式(1)～數式(3)之本發明之光學膜。又，藉由含有氟元素之骨架而易於提高光學膜之光學特性。In a preferred embodiment of the present invention, the structural unit represented by formula (4) is the structural unit represented by formula (4'), [化17]

That is, at least a part of X in the plural structural units represented by formula (1) and formula (2) is a structural unit represented by formula (4'). In this case, the fluorine-containing skeleton will increase the solubility of the polyimide resin or polyimide resin in the solvent, thereby easily improving the storage stability of the varnish containing the resin and reducing the The viscosity of the varnish makes it easy to improve the processability of the optical film. As a result, it is easy to manufacture the optical film of the present invention that satisfies the mathematical formulas (1) to (3). In addition, it is easy to improve the optical properties of the optical film by the skeleton containing the fluorine element.

In a preferred embodiment of the present invention, the X that can be contained in the polyimide resin or polyimide resin is preferably 30 mol% or more, more preferably 50 mol% or more, and more Preferably, 70 mol% or more is represented by formula (4), especially represented by formula (4'). In the polyimide-based resin or polyimide-based resin, X within the above-mentioned range is represented by formula (4), especially when represented by formula (4'), the resulting optical film is obtained by containing a fluorine element The skeleton improves the solubility of the resin in the solvent, thereby easily improving the storage stability of the varnish containing the resin, and easily reducing the viscosity of the varnish, thereby making it easy to manufacture the present invention satisfying the formula (1) to the formula (3)的optical film. In addition, it is easy to improve the optical properties of the optical film by the skeleton containing the fluorine element. Furthermore, it is preferable that 100 mol% or less of X in the polyimide-based resin or polyimide-based resin is represented by formula (4), especially represented by formula (4'). X in the above resin may be formula (4), especially formula (4'). The ratio of the structural unit represented by the formula (4) of X in the above resin can ^{be measured, for example, using 1} H-NMR, or can also be calculated based on the addition ratio of the raw materials.

The polyimide-based resin may contain the structural unit represented by formula (30) and/or the structural unit represented by formula (31), and can be in addition to the structural unit represented by formula (1) and optionally included formula In addition to the structural unit shown in (2), it also includes the structural unit shown in formula (30) and/or the structural unit shown in formula (31). [化18]

In formula (30), Y ¹ is a tetravalent organic group, preferably an organic group in which the hydrogen atom in the organic group can be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ¹ , there can be exemplified: formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) ) And the group represented by the formula (29); the hydrogen atom in the group represented by the formula (20) to the formula (29) is substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a tetravalent group Chain hydrocarbon group with carbon number 6 or less. In one embodiment of the present invention, the polyimide-based resin may contain multiple types of Y ¹ , and the multiple types of Y ¹ may be the same or different from each other.

In formula (31), Y ² is a trivalent organic group, preferably an organic group in which the hydrogen atom in the organic group can be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ² , the above formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula ( 28) A group in which any one of the bonding bonds of the group represented by the formula (29) is substituted with a hydrogen atom; and a trivalent chain hydrocarbon group with a carbon number of 6 or less. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of types of Y ² , and the plurality of types of Y ² may be the same or different from each other.

In formula (30) and formula (31), X ¹ and X ² are independently a divalent organic group, preferably an organic group in which the hydrogen atom in the organic group can be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of X ¹ and X ² include the above-mentioned formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), and formula (17) And the group represented by the formula (18); the hydrogen atom in the group represented by the formula (10) to the formula (18) is substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a carbon number of 6 The following chain hydrocarbon groups.

In one embodiment of the present invention, the polyimide-based resin includes structural units represented by formula (1) and/or formula (2), and optionally includes formula (30) and/or formula (31). Show the structural unit. In addition, in terms of the ease of improving the tensile modulus, optical properties, and bending resistance of the optical film, and the ease of improving the visibility of the optical film after heat treatment at a high temperature, among the above-mentioned polyimide-based resins, Based on formula (1) and formula (2), as well as all the structural units shown in formula (30) and formula (31) included as appropriate, the ratio of the structural units shown in formula (1) and formula (2) is better It is 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. Furthermore, in the polyimide-based resin, the ratio of the structural units represented by formula (1) and formula (2) to formula (1) and formula (2), as well as formula (30) and formula (30) and /Or the total of all structural units represented by formula (31) is usually 100% or less. In addition, the above-mentioned ratio can ^{be measured using 1} H-NMR, for example, or it can also be calculated based on the addition ratio of raw materials.

In one embodiment of the present invention, the content of the polyimide resin and/or polyimide resin in the optical film is preferably 10 parts by mass or more, more preferably 30 parts by mass relative to 100 parts by mass of the optical film Parts or more, more preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, more preferably 95 parts by mass or less. If the content of the polyimide-based resin and/or the polyimide-based resin is within the above range, it is easy to improve the tensile modulus, optical properties, and bending resistance of the optical film. In addition, it is easy to improve the visibility of the optical film after heat treatment at a high temperature.

Regarding the weight average molecular weight of polyimide resins and polyimide resins, in terms of easy improvement of the tensile modulus of elasticity and bending resistance of the optical film, it is preferably 100,000 in terms of standard polystyrene. Above, more preferably 130,000 or more, still more preferably 150,000 or more, still more preferably 170,000 or more, even more preferably 200,000 or more, especially more preferably 230,000 or more, especially more preferably 250,000 or more, particularly preferably 260,000 or more. In addition, from the viewpoint of easily improving the solubility of the resin in a solvent and easily improving the extensibility and processability of the optical film, the weight average molecular weight of the polyimide resin and the polyamide resin is preferably 1,000,000 Hereinafter, it is more preferably 800,000 or less, still more preferably 700,000 or less, still more preferably 500,000 or less, particularly preferably 400,000 or less, especially more preferably 350,000 or less, and especially more preferably 300,000 or less. The weight average molecular weight can be determined by, for example, GPC (gel permeation chromatography) measurement and conversion using standard polystyrene. For example, it can be calculated by the method described in the Examples. When the weight average molecular weight (Mw) of the polyimide resin and the polyimide resin is less than the above upper limit, it is easy to increase the solid content of the varnish containing the resin, and it is easy to reduce the viscosity of the varnish, and the result becomes It is easy to manufacture the optical film of the present invention that satisfies the formula (1) to (3). In addition, it becomes easier to maintain visibility in the wide-angle direction after the bending resistance test.

In the polyamide imide resin, the content of the structural unit represented by formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol relative to 1 mol of the structural unit represented by formula (1) Above, it is more preferably 1.0 mol or more, still more preferably 1.5 mol or more, and preferably 6.0 mol or less, more preferably 5.0 mol or less, and still more preferably 4.5 mol or less. If the content of the structural unit represented by formula (2) is more than the above lower limit, it is easy to increase the tensile modulus of the optical film. Moreover, if the content of the structural unit represented by the formula (2) is below the above upper limit, it is easy to suppress the increase in the viscosity due to the hydrogen bonding between the amide bonds in the formula (2), and it is easy to reduce the production of the optical film. The viscosity of the varnish makes it easy to manufacture the optical film of the present invention that satisfies the equations (1) to (3).

In a preferred embodiment of the present invention, the polyimide-based resin and/or polyimide-based resin contained in the optical film may contain, for example, halogen atoms such as fluorine atoms that can be introduced by the above-mentioned fluorine-containing substituents. . When the polyimide-based resin and/or the polyimide-based resin contains halogen atoms, it is easy to increase the tensile modulus of the optical film, and it is easy to decrease the YI value. If the tensile elastic modulus of the optical film is high, it is easy to suppress the occurrence of damage and wrinkles, and it is especially easy to improve the visibility of the optical film after heat treatment at a high temperature. Moreover, if the YI value of the optical film is low, it is easy to improve the transparency and visibility of the film. The halogen atom is preferably a fluorine atom. As a preferable fluorine-containing substituent for making a polyimide resin contain a fluorine atom, a fluorine group and a trifluoromethyl group are mentioned, for example.

The content of the halogen atom in the polyimide resin and the polyimide resin is based on the mass of the polyimide resin and the polyimide resin, and is preferably 1-40% by mass, more preferably 5 -40% by mass, more preferably 5-30% by mass. If the content of halogen atoms is more than the above lower limit, it is easier to increase the tensile modulus of the optical film, and it is easier to lower the YI value. As a result, it is particularly easy to improve the visibility of the optical film after heat treatment at a high temperature. If the content of the halogen atom is less than the above upper limit, it is easy to synthesize.

The polyimide resin and the polyimide resin have an imidization rate of preferably 90% or more, more preferably 93% or more, and still more preferably 96% or more. From the viewpoint of easy improvement of the optical properties of the optical film, the imidization rate is preferably at least the above lower limit. In addition, the upper limit of the imidization rate is 100% or less. The imidization rate represents the value of the molar amount of the amide bond in the polyimine resin relative to the molar amount of the tetracarboxylic acid compound-derived structural unit in the polyimine resin. The ratio. Furthermore, when the polyimide-based resin contains a tricarboxylic acid compound, the imidization rate means the molar amount of the imine bond in the polyimide-based resin relative to that in the polyimide-based resin The ratio of the value of twice the molar amount of the structural unit derived from the tetracarboxylic acid compound to the total molar amount of the structural unit derived from the tricarboxylic acid compound. In addition, the imidization rate can be obtained by an IR (infrared radiation) method, an NMR method, or the like.

In the present invention, the optical film may contain a polyamide-based resin. The polyamide resin of this embodiment is a polymer mainly composed of the repeating structural unit represented by formula (2). The preferable examples and specific examples of Z in the formula (2) in the polyimide-based resin are the same as the preferable examples and specific examples of Z in the polyimide-based resin. The above-mentioned polyamide-based resin may include two or more types of repeating structural units represented by formula (2) different in Z.

(Manufacturing method of resin) The manufacturing method of the polyimide resin and polyimide resin contained in the optical film of this invention is not specifically limited. Polyimide resins and polyimide precursor resins can be manufactured, for example, using tetracarboxylic acid compounds and diamine compounds as main raw materials. Polyimide resins and polyimide precursor resins can be, for example, Tetracarboxylic acid compounds, dicarboxylic acid compounds, and diamine compounds are produced as main raw materials, and polyamide resins can be produced, for example, using diamine compounds and dicarboxylic acid compounds as main raw materials.

The structural units represented by formula (1) and formula (30) are usually derived from diamine compounds and tetracarboxylic acid compounds. The structural unit represented by formula (2) is usually derived from a diamine compound and a dicarboxylic acid compound. The structural unit represented by formula (31) is usually derived from a diamine compound and a tricarboxylic acid compound.

As the diamine compound used in the production of the resin, for example, aliphatic diamine, aromatic diamine, and mixtures thereof can be cited. Furthermore, in this embodiment, "aromatic diamine" means a diamine in which an amine group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituents in a part of its structure. This aromatic ring may be a monocyclic ring or a condensed ring, and a benzene ring, a naphthalene ring, an anthracene ring, a sulphur ring, etc. can be illustrated, but it is not limited to these. Among these, a benzene ring is preferably exemplified. In addition, "aliphatic diamine" means a diamine in which an amine group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituents in a part of its structure.

As aliphatic diamines, for example, acyclic aliphatic diamines such as hexamethylene diamine; 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(amino) Cycloaliphatic diamines such as methyl)cyclohexane, noralkanediamine and 4,4'-diaminodicyclohexylmethane, etc. These can be used individually or in combination of 2 or more types.

Examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,6-Diaminonaphthalene and other aromatic diamines with one aromatic ring; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4' -Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3, 4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-amino) Phenoxy) benzene, bis[4-(4-aminophenoxy)phenyl] ash, bis[4-(3-aminophenoxy)phenyl] ash, 2,2-bis[4- (4-aminophenoxy)phenyl)propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2 '-Bis(trifluoromethyl)-4,4'-diaminobiphenyl (sometimes referred to as TFMB), 4,4'-bis(4-aminophenoxy)biphenyl, 9,9- Bis(4-aminophenyl) pyrene, 9,9-bis(4-amino-3-methylphenyl) pyrene, 9,9-bis(4-amino-3-chlorophenyl) pyrene, Aromatic diamines with more than two aromatic rings, such as 9,9-bis(4-amino-3-fluorophenyl)sulfonate. These can be used individually or in combination of 2 or more types.

The aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3' -Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 1,4-bis(4-aminophenoxy)benzene , Bis[4-(4-aminophenoxy)phenyl] ash, bis[4-(3-aminophenoxy)phenyl] ash, 2,2-bis[4-(4-amino) Phenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(tris Fluoromethyl)-4,4'-diaminobiphenyl (TFMB), 4,4'-bis(4-aminophenoxy)biphenyl, more preferably 4,4'-diaminodiphenyl Methyl methane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 1,4-bis(4- Aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl] chrysene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2, 2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), 4,4'-bis(4-aminophenoxy) ) Biphenyl. These can be used individually or in combination of 2 or more types.

Among the above-mentioned diamine compounds, it is preferable to use aromatic compounds selected from the group consisting of biphenyls in terms of easy improvement of the tensile elastic modulus, transparency, flexibility, and bending resistance of the optical film, and easy reduction of the YI value. One or more of the group consisting of diamines. More preferably, use selected from 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl and At least one of the group consisting of 4,4'-diaminodiphenyl ether, and more preferably 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB).

Examples of the tetracarboxylic acid compound used in the production of the resin 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 kinds. In addition to the dianhydride, the tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as a chloride compound.

Specific examples of aromatic tetracarboxylic dianhydrides include: non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides Carboxylic dianhydride. Examples of non-condensed polycyclic aromatic tetracarboxylic dianhydrides include: 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid Acid dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (sometimes referred to as BPDA), 2 ,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxybenzene Base) propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4 '-(Hexafluoroisopropylidene) diphthalic dianhydride (sometimes described as 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, 4,4'-(p-phenylenedioxy) di-o-benzene Dicarboxylic dianhydride, 4,4'-(isophthaloxy)diphthalic dianhydride. Moreover, as the monocyclic aromatic tetracarboxylic dianhydride, for example, 1,2,4,5-benzenetetracarboxylic dianhydride can be cited, and as the condensed polycyclic aromatic tetracarboxylic dianhydride, for example, For example, 2,3,6,7-naphthalenetetracarboxylic dianhydride.

Among these, preferred examples include 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3, 3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3 ,3',4,4'-Diphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyl) Phenyl) propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic 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, 4,4'-(terephthalic acid) dianhydride and 4,4'-(isophthalic acid) The dianhydride, more preferably 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'- Biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), bis(3,4-dicarboxyphenyl)methane dianhydride and 4,4 '-(Phenyldioxy)diphthalic dianhydride. These can be used individually or in combination of 2 or more types.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. Cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure. Specific examples include: 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1 , 2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride and other cycloalkane tetracarboxylic dianhydrides; bicyclo[2.2.2]oct- 7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride and their positional isomers. These can be used individually or in combination of 2 or more types. Specific examples of acyclic 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 kinds. Moreover, it is also possible to combine cyclic aliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride and use.

Among the above-mentioned tetracarboxylic dianhydrides, 4,4' is preferred in terms of easy improvement of the tensile modulus, surface hardness, transparency, flexibility and bending resistance of the optical film, and easy reduction of the YI value. -Oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2, 2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl) ) Propane dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride, and mixtures thereof, more preferably 3,3',4,4'-biphenyltetracarboxylic acid Dianhydride and 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride, and mixtures of these, and more preferably 4,4'-(hexafluoroisopropylidene) diphthalene Dicarboxylic dianhydride (6FDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).

Examples of the dicarboxylic acid compound used in the synthesis of the resin include aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and similar chlorinated compounds, acid anhydrides, etc., and two or more kinds can be used. Specific examples include: terephthalic acid; isophthalic acid; 2-methoxyterephthalic acid; 2-methylterephthalic acid; 2,5-bis(trifluoromethyl)p-benzene Dicarboxylic acid; isophthalic acid; 2,5-dimethylterephthalic acid; 2,5-dimethoxyterephthalic acid; naphthalenedicarboxylic acid; 4,4'-biphthalic acid; 3,3 '-Biphthalic acid; 2,2'-bis(trifluoromethyl)-4,4'-biphthalic acid; dicarboxylic acid compound of chain hydrocarbon with carbon number less than 8 and 2 benzoic acid by Compounds formed by linking single bonds, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or phenylene groups, and these chlorinated compounds. Among these dicarboxylic acid compounds, 4,4'-oxydibenzoic acid, terephthalic acid, and isophthalic acid are preferred from the viewpoint of easily improving the tensile elastic modulus and bending resistance of the optical film , 2-methoxyterephthalic acid, 2-methylterephthalic acid, 2,5-dimethylterephthalic acid, 2,5-dimethoxyterephthalic acid, 2,5-bis (Trifluoromethyl)terephthalic acid, 2,2'-bis(trifluoromethyl)-4,4'-biphthalic acid and these chlorines, more preferably 2-methoxy-p-benzene Dicarboxylic acid, 2-methylterephthalic acid, 2,5-Dimethylterephthalate chloride (DMTPC), 2,5-Dimethoxyterephthalate chloride (MOTPC), 2,5 -Bis (trifluoromethyl) terephthalate chloride (6FTPC), terephthalate chloride (TPC), meta-phthalate chloride, more preferably terephthalate chloride (TPC), 2 -Methoxy terephthalic acid, 2-methyl terephthalic acid, 2,5-dimethyl terephthalate chloride (DMTPC), 2,5-dimethoxy terephthalate chloride ( MOTPC), more preferably 2-methoxyterephthalic acid, 2-methylterephthalic acid, 2,5-dimethylterephthalate chloride (DMTPC) and 2,5-dimethoxy Base para-phthalic acid chloride (MOTPC).

Furthermore, the above-mentioned polyimide-based resin can be in a range that does not damage the various physical properties of the optical film. In addition to the tetracarboxylic acid compound used in the synthesis of the above-mentioned resin, other tetracarboxylic and tricarboxylic acids and these The acid anhydride and its derivatives are formed by the reaction.

Examples of other tetracarboxylic acids include hydrates of acid anhydrides of the above-mentioned tetracarboxylic acid compounds.

As a tricarboxylic acid compound, aromatic tricarboxylic acid, aliphatic tricarboxylic acid, and these similar chlorinated compounds, acid anhydride, etc. are mentioned, and it can use combining 2 or more types. Specific examples include: anhydride of trimellitic acid; anhydride of trimellitic acid; chloro compound of trimellitic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; Phthalic anhydride and benzoic acid are linked by single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or phenylene The compound.

In the production of the resin, the usage amount of the diamine compound, the tetracarboxylic acid compound and/or the dicarboxylic acid compound can be appropriately selected according to the ratio of each structural unit of the resin required.

In the production of the resin, the reaction temperature of the diamine compound, the tetracarboxylic acid compound, and the dicarboxylic acid compound is not particularly limited, and is, for example, 5 to 350°C, preferably 20 to 200°C, and more preferably 25 to 100°C. The reaction time is also not particularly limited, and is, for example, about 30 minutes to 10 hours. The reaction can be carried out in an inert atmosphere or under reduced pressure as needed. In a preferred aspect, the reaction is carried out while stirring under normal pressure and/or an inert gas atmosphere. In addition, the reaction is preferably carried out in a solvent that is inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction. For example, water, methanol, ethanol, ethylene glycol, isopropanol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, Alcoholic solvents such as 1-methoxy-2-propanol, 2-butoxyethanol, propylene glycol monomethyl ether; ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, Ester solvents such as γ-valerolactone, propylene glycol methyl ether acetate and ethyl lactate; ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl isobutyl ketone, etc. Solvents; aliphatic hydrocarbon solvents such as pentane, hexane and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; tetrahydrofuran and dimethoxy Ether solvents such as methyl ethane; chlorine-containing solvents such as chloroform and chlorobenzene; amine solvents such as N,N-dimethylacetamide and N,N-dimethylformamide; Sulfur-containing solvents such as methyl sulfenite and cyclobutyl sulfide; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations of these. Among these, from the viewpoint of solubility, an amide-based solvent can be suitably used.

In the imidization step in the production of the polyimide resin, the imidization can be carried out in the presence of an imidization catalyst. Examples of the imidization catalyst include: aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, N-propylpiperidine, Alicyclic amines such as N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepine (monocyclic); azabicyclo[2.2.1]heptane, azabicyclo[3.2 .1] octane, azabicyclo[2.2.2]octane, and azabicyclo[3.2.2]nonane and other alicyclic amines (polycyclic); and pyridine, 2-methylpyridine (2- picoline), 3-picoline, 4-picoline, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine Aromatic amines such as pyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and isoquinoline. Moreover, from the viewpoint of facilitating the promotion of the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. The acid anhydrides include commonly used acid anhydrides used in the imidization reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride; aromatic acid anhydrides such as phthalic acid and the like.

Polyimide resins and polyimide resins can be separated and refined by common methods, such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography and other separation methods or a combination of separation methods. In addition, in a preferred aspect, a large amount of alcohol such as methanol is added to the reaction solution containing the transparent polyimide resin to precipitate the resin, and the resin can be separated by concentration, filtration, drying, etc.

＜Additives＞ The optical film of the present invention may further contain additives. Examples of such additives include fillers, ultraviolet absorbers, brighteners, antioxidants, pH adjusters, and leveling agents.

(filler) The optical film of the present invention may contain at least one filler. As the filler, for example, organic particles, inorganic particles, etc. can be cited, and preferably, inorganic particles can be cited. Examples of inorganic particles include: metal oxide particles such as silicon dioxide, zirconium oxide, aluminum oxide, titanium oxide, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide, antimony oxide, and cerium oxide; Metal fluoride particles such as magnesium and sodium fluoride; among these, in terms of easy improvement of the elastic modulus and/or tear strength of the optical film, and easy improvement of the impact resistance, the preferred example is dioxide Silicon particles, zirconia particles, and alumina particles, more preferably, silicon dioxide particles. These fillers can be used individually or in combination of 2 or more types.

The filler, preferably silica particles, have an average primary particle size of 1 nm or more, more preferably 5 nm or more, still more preferably 10 nm or more, still more preferably 15 nm or more, particularly preferably 20 nm or more, and It is preferably 100 nm or less, more preferably 90 nm or less, still more preferably 80 nm or less, still more preferably 70 nm or less, particularly preferably 60 nm or less, especially more preferably 50 nm or less, and especially more preferably Below 40 nm. If the average primary particle size of the silica particles is within the above range, it is easy to inhibit the aggregation of the silica particles, thereby easily improving the optical properties of the resulting optical film. The average primary particle size of the filler can be measured by the BET (Brunauer-Emmett-Teller, Buert) method. Furthermore, the average primary particle size can also be measured by image analysis of a transmission electron microscope or a scanning electron microscope.

The filler in the optical film of the present invention, for example, the content of silica particles in inorganic particles relative to the total mass of the optical film is preferably 60% by mass or less, more preferably 50% by mass or less, and more preferably 45% by mass % Or less, more preferably 40% by mass or less, and preferably 0% by mass or more. If the content of the filler is below the above upper limit, it is easy to increase the elastic modulus of the obtained optical film, and it is easy to improve the optical properties of the optical film. Here, the tensile elastic modulus of the optical film tends to increase by increasing the content of fillers such as silica particles. However, when the content of fillers such as silica particles is too high, it is difficult to obtain the optical film. It satisfies the above equations (1) to (3). Therefore, in the optical film of the present invention, in terms of easy to increase the tensile modulus of the optical film and easy to maintain high visibility in the wide-angle direction, it is preferable that the content of silica particles is the above Below the upper limit. Furthermore, in this specification, the so-called content of silicon dioxide particles in the optical film relative to the total mass of the optical film is below the above upper limit, which means that the content of silicon dioxide particles is 0% by mass, that is, it does not contain silicon dioxide. The particles, or even if they are contained, are in an amount less than the above upper limit.

(Ultraviolet absorber) The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber can be appropriately selected from those generally used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light with a wavelength below 400 nm. As the ultraviolet absorber, for example, three-type ultraviolet absorber, benzophenone-type ultraviolet absorber, benzotriazole-type ultraviolet absorber, benzoate-type ultraviolet absorber, and cyanoacrylate-type ultraviolet absorber can be mentioned. UV absorbers, salicylate-based UV absorbers, etc. These can be used alone, or two or more of them can be used. Since the optical film contains the ultraviolet absorber to suppress the deterioration of the resin, the visibility can be improved when the optical film of the present invention is applied to a display device or the like. In this specification, "system compound" refers to a derivative of the compound with the "system compound". For example, "benzophenone-based compound" refers to a compound having benzophenone as a parent skeleton and a substituent bonded to benzophenone. As a preferred commercially available ultraviolet absorber, for example, Sumisorb (registered trademark) 340 manufactured by Sumika Chemtex Co., Ltd., Adekastab (registered trademark) LA-31 manufactured by ADEKA Co., Ltd., and BASF Japan Co., Ltd. TINUVIN (registered trademark) 1577 and so on.

When the optical film of the present invention contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 0.01-10 parts by mass relative to 100 parts by mass of the polyamide-imide-based resin contained in the optical film, More preferably, it is 1-8 mass parts, More preferably, it is 2-7 mass parts. If the content of the ultraviolet absorber is more than the above lower limit, it is easy to improve the ultraviolet absorbability. If the content of the ultraviolet absorber is less than the above upper limit, the decomposition of the ultraviolet absorber due to the heat during the production of the base material can be suppressed, and the optical properties can be easily improved, for example, the haze can be easily reduced.

The use of the optical film of the present invention is not particularly limited, and it can be used for various purposes. The optical film of the present invention may be a single layer or a laminate, and the optical film of the present invention may be used directly or as a laminate with other films. The optical film of the present invention has excellent visibility in the wide-angle direction, and therefore is useful as an optical film in image display devices and the like. Furthermore, when the optical film is a laminate, all layers including all layers laminated on one or both sides of the optical film are called optical films.

The use of the optical film of the present invention is not particularly limited, and it can be used for various purposes. The optical film of the present invention has excellent visibility in the wide-angle direction, and therefore is useful as an optical film in image display devices and the like. In particular, the optical film of the present invention is useful as a front panel of an image display device, especially a front panel (window film) of a flexible display. The flexible display has, for example, a flexible functional layer and the above-mentioned optical film superimposed on the flexible functional layer to function as a front panel. That is, the front panel of the flexible display is arranged on the visible side of the flexible functional layer. The front panel has the function of protecting the flexible functional layer.

＜Manufacturing method of optical film＞ The optical film of the present invention can be manufactured by, for example, a method including the following steps, which are not particularly limited, namely: (a) A step of preparing a liquid containing the above resin and optionally containing the above filler (hereinafter, sometimes referred to as a varnish) (varnish preparation step), (b) The step of applying varnish to the substrate to form a coating film (coating step); and (c) The step of drying the applied liquid (coating film) to form an optical film (optical film forming step).

In the varnish preparation step, the varnish is prepared by dissolving the above-mentioned resin in a solvent, adding the above-mentioned fillers and other additives as necessary, and stirring and mixing.

The solvent used in the preparation of the varnish is not particularly limited as long as it can dissolve the above-mentioned resin. Examples of the solvent include: N,N-dimethylacetamide (hereinafter, sometimes abbreviated as DMAc), N,N-dimethylformamide (hereinafter, sometimes abbreviated as DMF), etc. Amine-based solvents; lactone-based solvents such as γ-butyrolactone (hereinafter, sometimes referred to as GBL) and γ-valerolactone; sulfur-containing solvents such as dimethyl sulfide, dimethyl sulfide, and cyclobutane; carbonic acid Carbonate-based solvents such as ethylene glycol and propylene carbonate; and combinations thereof. Among them, the solvent used in the varnish is preferably an amide-based solvent or a lactone-based solvent from the viewpoint of easy production of an optical film that satisfies the mathematical formulas (1) to (3). These solvents can be used alone or in combination of two or more kinds. 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, more preferably 5 to 20% by mass.

In the coating step, the varnish is coated on the substrate by a well-known coating method to form a coating film. Examples of well-known coating methods include: wire bar coating; roll coating methods such as reverse coating and gravure coating; die nozzle coating method; comma coating method; die lip coating Method; Screen coating method; Jet coating method; Casting method, etc.

In the optical film forming step, after the coating film is dried (referred to as the first drying) and peeled from the substrate, the dried coating film is further dried (referred to as the second drying or post-baking treatment) to form an optical film. The first drying may be carried out under an inert atmosphere or under reduced pressure as needed. For example, the first drying is preferably performed under negative pressure conditions such as in a negative pressure tenter furnace and at a relatively low temperature. Although the reason is not clear, if the first drying is carried out under negative pressure, the clarity value of the transmission image of the produced optical film can easily satisfy the equations (1) to (3), and it is easy to improve the overall quality of the optical film. Light transmittance, easy to reduce haze and YI. It is considered that the reason is that the solvent removed from the optical film by volatilization under the first drying condition is prevented from staying on the surface of the optical film, and as a result, the surface of the optical film becomes uniform. In addition, by taking time for the first drying at a relatively low temperature, the surface of the optical film is easily uniform, and the clarity value of the transmission image of the manufactured optical film can easily satisfy the equations (1) to (3). In addition, the oxidative degradation of the resin during drying is suppressed, so it is easy to increase the total light transmittance of the optical film, and it is easy to reduce the haze and YI.

Here, in the case of industrial production of the optical film of the present invention, compared with the laboratory-level manufacturing environment, in most cases the actual manufacturing environment is not conducive to improving the visibility in the wide-angle direction. As a result, it is difficult to improve the optical film The situation of visibility in the wide-angle direction. As mentioned above, it is better to carry out the first drying under negative pressure and at a relatively low temperature. At the laboratory level, when the first drying is carried out, the drying can be carried out in a closed dryer, so it is relatively difficult to cause external factors. The surface of the optical film is rough. On the other hand, when the optical film is industrially produced, for example, a large area needs to be heated in the first drying, so there are cases where a blower is used for heating. As a result, the surface condition of the optical film tends to become rough, and it is difficult to improve the visibility of the optical film in the wide-angle direction.

In the case of drying by heating, especially in the industrial production of optical films, taking into account the above-mentioned external factors, the temperature of the first drying is preferably 60-150°C, more preferably 60-130°C, and more preferably 70～120℃. The first drying time is preferably 5 to 60 minutes, more preferably 10 to 40 minutes. In particular, when the optical film is industrially produced, taking into consideration the above-mentioned external factors, the first drying is preferably performed under the drying temperature condition of three stages or more. Multi-stage conditions can be implemented in each stage under the same or different temperature conditions and/or drying time. For example, 3-10 stages, preferably 3-8 stages, can be used for drying. If the first drying is performed under a multi-stage condition of three or more stages, the clarity value of the transmission image of the produced optical film can easily satisfy the equations (1) to (3), and the visibility in the wide-angle direction is improved. In the case of a multi-stage condition with more than 3 stages, it is preferable that the temperature distribution of the first drying includes heating and cooling. That is, the first drying condition in the optical film forming step is preferably a heating temperature condition in which the temperature distribution includes three stages or more of temperature increase and temperature decrease. As an example of this temperature distribution, the temperature of the first drying is 70-90°C (first temperature), 90-120°C (second temperature), 80-120°C ( The third temperature) and 80 to 100°C (the fourth temperature). In this example, the temperature of the first drying increases from the first temperature to the second temperature, then decreases from the second temperature to the third temperature, and then decreases from the third temperature to the fourth temperature. Here, the time for the first drying is, for example, 5 to 15 minutes in each stage. The first drying is preferably carried out in an embodiment in which the solvent remaining amount of the dried coating film is preferably 5 to 15% by mass, and more preferably 6 to 12% by mass relative to the mass of the dried coating film. If the residual amount of solvent is in the above range, the peelability of the dried coating film from the substrate becomes good, and the clarity value of the transmission image of the produced optical film easily satisfies the equations (1) to (3).

The temperature of the second drying is preferably 150 to 300°C, more preferably 180 to 250°C, and still more preferably 180 to 230°C. The second drying time is preferably 10 to 60 minutes, more preferably 30 to 50 minutes.

The second drying can be performed in a single-piece type, but in the case of industrial production, from the viewpoint of manufacturing efficiency, it is preferably performed in a roll-to-roll method. In the single-piece type, it is preferable to perform drying in a state uniformly elongated in the in-plane direction. In the roll-to-roll method, from the viewpoint that the obtained optical film easily satisfies the equations (1) to (3), it is preferable to dry the dried coating film in a state in which the dried coating film is stretched in the transport direction, and the transport speed is relatively high. It is preferably 0.1 to 5 m/min, more preferably 0.2 to 3 m/min, and still more preferably 0.7 to 2.5 m/min. The second drying can be carried out under one-stage or multi-stage conditions. The multi-stage conditions are preferably implemented in each stage under at least one condition selected from the same or different temperature conditions, drying time and hot air speed, for example, 3-10 stages can be used, preferably 3-8 Drying is carried out in a single stage. From the viewpoint that the optical film easily satisfies the range of formula (1) to formula (3), it is preferably carried out under multi-stage conditions. In addition, in each stage, in terms of the clarity value of the transmission image of the produced optical film easily satisfying the equations (1) to (3), the wind speed of the hot air is preferably 5-20 m/min, It is more preferably 10-15 m/min, and still more preferably 11-14 m/min.

When the optical film of the present invention has a hard coat layer, the hard coat layer can be formed, for example, by applying a curable composition to at least one side of the optical film to form a coating film, and irradiating the coating film with high energy Thread to harden the coating film.

As an example of the base material, if it is a metal-based, SUS (Steel Use Stainless, Japanese stainless steel standard) plate, if it is a resin-based, PET (polyethylene terephthalate, polyethylene terephthalate) film, PEN (polyethylene naphthelate, polyethylene naphthalate) film, other polyimide resins or polyamide resin films, cycloolefin polymer (COP) films, acrylic films, etc., or can include Hard coat resin films, glass substrates, etc. Among them, from the viewpoint of excellent smoothness and heat resistance and the viewpoint that the clarity value of the transmission image of the optical film easily satisfies the formula (1) to the formula (3), a PET film, a COP film, and a rigid film are preferred. Coated resin film, SUS plate, glass plate, etc., from the viewpoint of adhesion to the optical film and cost, more preferably SUS plate, resin film with hard coat, more preferably SUS plate, Hard-coated PET film.

From the viewpoint of ease of manufacturing an optical film satisfying the above-mentioned formulas (1) to (3), it is preferable to use the following manufacturing method to dry the coating film in the above-mentioned optical film forming step, the manufacturing method comprising: After the coating film is dried to a predetermined amount of solvent, the step of peeling off the base material to obtain the raw film; and the heating step of heating the raw film in a tenter furnace whose interior is divided into a plurality of spaces. Furthermore, in the tenter furnace, the heating step is performed by hot air treatment in at least one space, and the heating step is performed by radiation treatment in at least one space. Furthermore, the tenter furnace refers to a furnace that fixes both ends in the width direction of the film to heat it. Furthermore, the heating device for heating the raw film including the tenter furnace is also referred to as an oven in this specification. In addition, the pressure inside the tenter furnace is preferably adjusted so that the pressure inside the tenter furnace becomes a negative pressure relative to the pressure outside the tenter furnace.

The manufacturing method of the optical film of this embodiment is demonstrated with reference to drawings. 4 is a cross-sectional view schematically showing a preferred embodiment of a method of manufacturing an optical film in an embodiment of the present invention. In FIG. 4, the raw film 44 containing at least polyimide resin and/or polyimide resin is carried into the tenter furnace 100, heated in the heating zone in the tenter furnace 100, and then removed from the tenter furnace 100 Move out. In this specification, the film before the heating step and the film that is still in the heating step or being transported in the oven despite changes in the amount of solvent over time is referred to as the raw film, and the film that has passed the heating step and moved out of the oven is referred to as the raw film. For optical film.

The raw material film 44 may be rolled out from the 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 the next step. 5 is a schematic cross-sectional view of a preferred embodiment of the heating step in the method of manufacturing the optical film of the present invention. As shown in FIG. 5, the raw film 44 is preferably in a state where both ends of the film in the direction (TD direction, also called the width direction) perpendicular to the transport direction of the film (MD direction, also called the length direction) are fixed. Transported in the stenter furnace. The fixing can be performed by using the holding device 43, for example.

The two ends can be fixed using pin seats, clips, film chucks, and other holding devices commonly used in film manufacturing devices. The two ends to be fixed can be adjusted appropriately with the holding device used, preferably at a distance within 50 cm from the end of the film. As shown in Fig. 5, the raw film can be transported while being held by a plurality of holding devices 43 at both ends. The plurality of holding devices 43 arranged at one end of the film is preferably a distance between adjacent holding devices that can prevent defects such as cracks caused by the shaking of the film or the dimensional change caused by heating. The distance between adjacent holding devices is preferably 1-50 mm, more preferably 3-25 mm, and still more preferably 5-10 mm. In addition, the holding device is preferably arranged in the following manner: when the straight line orthogonal to the film conveying axis is aligned with the center of the holding portion of any holding device at one end of the film, the intersection point of the straight line and the other end of the film is closest to the The distance between the center of the holding part of the holding device at the intersection is preferably 3 mm or less, more preferably 2 mm or less, and still more preferably 1 mm or less. Thereby, the difference in the stress applied to the opposite ends of the film can be reduced, and therefore the homogeneity of the obtained optical film can be improved. In addition, by using a holding device to fix the film while drying under such conditions, the shaking of the film during drying is suppressed, and the optical fiber of the present invention that satisfies the above equations (1) to (3) can be easily manufactured. membrane.

As an example of the operation of fixing the two ends of the film with the holding device, the following method can be cited: at the appropriate time before or after the stenter is moved into the stenter furnace, the method is installed in a manner facing each other in the width direction of the film. A plurality of film chucks fix both ends of the film in the width direction. By these operations, the shaking of the film is suppressed, and an optical film with defects such as thickness unevenness or damage sufficiently suppressed can be obtained. In addition, it is easy to manufacture the optical film of the present invention that satisfies the above-mentioned formulas (1) to (3). The fixing of both ends of the film only needs to be released at an appropriate time after the heating step. It can be carried out in the tenter furnace or after being carried out from the tenter furnace.

The total length of the film conveying direction of the tenter furnace used in the heating step is usually 10-100 m, preferably 15-80 m, more preferably 15-60 m. The inside of the tenter furnace may be one space or divided into a plurality of spaces. In the embodiment of the present invention, the inside of the tenter furnace in 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 transport 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. Regardless of the internal structure of the stenter furnace, the entire stenter furnace can be used as a heating area, or a part of the interior can be used as a heating area. Referring to FIG. 4, all three of the regions 40, 41, and 42 can be used as heating regions, or one of these, for example, the region 42 can be used as a heating region.

Multiple stenter furnaces can also be used. The number of tenter furnaces in this case is not particularly limited, and it can be set to 2-12, for example. The inside of each stenter furnace can have the above-mentioned structure. A plurality of tenter furnaces can be continuously installed so that the film is transported without contacting the outside atmosphere. In the case of using a plurality of tenter furnaces, all tenter furnaces can be used as heating areas, or part of the tenter furnaces can be used as heating areas. Moreover, in addition to the tenter furnace, an oven can be used as other equipment. In this manual, the oven refers to equipment that can heat the film, including heating furnaces and drying furnaces. The heating furnace can be a heating furnace using either hot air treatment or radiation treatment, or a heating furnace using these. In the case of a practical oven, the internal structure of the oven, the number of ovens used, and the conditions for heating can be appropriately adjusted within the scope that the optical film of the present invention can be obtained. The width of the furnace is the same.

Regarding the circulation and exhaust of the air inside the tenter furnace, when the inside of the tenter furnace is divided into a plurality of spaces, it is preferably performed in each space, and when the tenter furnace has a plurality of spaces, it is preferably performed in each space. In a stenter furnace. From the viewpoint of easy manufacture of the optical film of the present invention that satisfies the above equations (1) to (3), the pressure inside the tenter furnace is preferably adjusted to the pressure inside the tenter furnace relative to the pressure outside the tenter furnace And become negative pressure. The temperature inside the tenter furnace is preferably adjustable for each tenter furnace, and when the inside of the tenter furnace is divided into a plurality of spaces, it is preferable that the temperature can be adjusted independently in each space. 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 temperature range described later.

The tenter furnace 100 performing 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. Regarding the heating step, it is preferable to perform hot air treatment in all the 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 by using the hot air treatment method.

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

As an example of the embodiment of the present invention, the following describes the hot air treatment method using the nozzle and the radiation treatment method using the IR heater in order from the hot air treatment method using the nozzle.

4, the tenter furnace 100 performing the heating step is provided with a plurality of upper nozzles 46 on the inner upper surface 100a, and a plurality of lower nozzles 47 on the inner lower surface 100b. The upper nozzle 46 and the lower nozzle 47 are arranged to face each other in the vertical direction. Regarding the nozzles, for example, 4 pairs of nozzles (8 in total) can be provided in the area 42 of FIG. 4, or 10 pairs of nozzles (20 in total) can be provided in the area 41 of FIG. 4, which can be appropriately set according to the structure of the oven. Regarding the distance between adjacent nozzles, from the viewpoint of simplifying the structure of the tenter furnace and uniformly heating the raw film, and the viewpoint of easy production of optical films satisfying the equations (1) to (3), it is preferably 0.1 to 1 m, more preferably 0.1 to 0.5 m, still more preferably 0.1 to 0.3 m.

When the inside of the tenter furnace is divided into a plurality of sections, the number of hot air blowing nozzles installed in each space can usually be 5-30. From the viewpoint of easy production of the optical film of the present invention that satisfies the above-mentioned formula, the number of nozzles is preferably 8-20. If the number of nozzles is in the above range, the curvature of the floating film will not easily become too large, and the film will easily float between the nozzles, that is, it will tend to float easily.

The nozzle 46 provided on the upper side of the upper surface 100a of the tenter furnace 100 has a blowing port in the lower part, and can blow hot air downward (in the direction of arrow B). On the other hand, the nozzles 47 respectively provided on the lower surface of the lower surface of the tenter furnace 100 have blowing outlets on the upper part, and can blow hot air upward (in the direction of arrow C). Furthermore, although not shown in FIG. 4, the upper nozzle 46 and the lower nozzle 47 have a predetermined depth in the direction perpendicular to the paper surface of FIG. 4 so that the raw film can be uniformly heated in the width direction. Here, it is also considered to set the orientation of the nozzle to be transverse to the film surface. In this case, although the reason is unknown, it is difficult to manufacture an optical film that satisfies the equations (1) to (3).

In the manufacturing method of the optical film of this embodiment, the blowing speed of hot air from the blowing outlets of all the upper nozzles 46 and all the lower nozzles 47 provided in the heating area is preferably 2-25 m/sec. From the viewpoint of ease of manufacturing the optical film of the present invention that satisfies the above formula and easy improvement of the optical uniformity of the optical film, the blowing wind speed is more preferably 2 to 23 m/sec, and more preferably 8 to 20 m/sec . In addition, from the same viewpoint, the blowing air volume from the outlet of each nozzle 46 or 47 is preferably 0.1 to 3 m ³ /sec for every 1 m of the length of the nozzle along the width direction of the raw film. It is preferably 0.1 to 2.5 m ³ /sec, and more preferably 0.2 to 2 m ³ /sec.

In addition, if the heating step is performed under the above conditions, it is easy to manufacture the optical film of the present invention that satisfies the above formula, and since the uniform heating is performed, the deviation of the amount of solvent remaining in the film becomes small, so that it is easy to obtain the elastic modulus An optical film that is more uniform on the entire surface of the film. Therefore, it is not easy to produce a deviation in the flexibility of the film on the entire surface, and it is possible to suppress the occurrence of damage due to the difference in the flexibility of the film surface.

In the tenter furnace, the raw film 44 is heated from room temperature to the temperature at which the solvent contained in the raw film evaporates. The holding device 43 is used to hold the raw film in such a way that the length in the width direction of the raw film is almost constant. The tendency to sag easily due to thermal expansion. If the blowing air speed and the blowing air volume are within the above-mentioned ranges, the raw film 44 can be sufficiently heated, and the raw film 44 can be suppressed from sagging or shaking.

The blowing speed of the hot air can be measured at the hot air blowing outlets of the nozzles 46 and 47 using a commercially available thermal anemometer. In addition, the amount of air blown from the blow-out port can be obtained by the product of the blow-out wind speed and the area of the blow-out port. Furthermore, from the viewpoint of measurement accuracy, the blowing speed of the hot air is preferably measured at about 10 points at the blowing outlet of each nozzle, and the average value thereof is taken.

The blowing speed and the blowing air volume of the hot air can be appropriately adjusted according to the physical properties (optical properties, mechanical properties, etc.) of the optical film to be manufactured, and it is preferably within the above-mentioned range in any form. Thereby, it is easy to manufacture the optical film of the present invention that satisfies the above-mentioned formulas (1) to (3), and it is easy to improve the visibility in the wide-angle direction after the bending resistance test of the optical film. The heating zone is more preferably that the blowing wind speed in all heating zones is 25 m/sec or less and the blowing air volume is 2 m ³ /sec or less.

In this embodiment, when the raw film 44 is not introduced into the tenter furnace 100, the wind speed of the hot air that should maintain the position of the raw film 44 is preferably 5 m/sec or less, more preferably at least in the heating zone. Kind of wind speed. By using such hot air to heat the raw film 44, it is easy to manufacture the optical film of the present invention that satisfies the above formulas (1) to (3), and it is easy to improve the wide-angle direction of the optical film after the bending resistance test The visibility.

In the heating zone, the difference between the maximum value and the minimum value of the blowing speed of the hot air at the blowing outlet of each nozzle 46 and 47 in the width direction (the direction perpendicular to the paper surface of FIG. 4) is preferably 4 m/sec or less. By using hot air with less deviation of the wind speed in the width direction as described above, it is easy to manufacture the optical film of the present invention that satisfies the above equations (1) to (3), and it is easy to improve the bending resistance of the optical film The visibility in the wide-angle direction after the test.

In this embodiment, regarding the wind speed of the hot air blown to the film, it is preferable that the wind speed immediately after being transported into the oven is greater than the wind speed of other conveying paths in the oven. In the case where the inside of the oven is not divided into multiple pieces, just after being loaded into the oven (hereinafter referred to as "transport path 1") means that the length of the oven from the inlet of the oven is less than the length of the oven (the length from the inlet of the oven to the outlet of the oven) ) Is 1/10 of the distance. When the inside of the oven is divided into a plurality of spaces, the conveying path 1 refers to the space through which the film first passes. When using multiple ovens, you can set the same as the previous description based on the internal structure of the oven used initially, or set the wind speed in the first passing oven to be greater than the wind speed in the second and subsequent ovens.

The so-called other conveying path, when the inside of the oven is not divided into a plurality of pieces, refers to the conveying path part located after 1/10 of the oven length from the entrance of the oven. When the inside of the oven is divided into a plurality of spaces, it refers to any space after the second through which the film passes. In the case of using multiple ovens, you can set the same as the previous record according to the internal structure of the oven used initially, or set the wind speed in any oven in the second and subsequent ovens to be lower than the oven initially passed through The wind speed inside.

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 0.1-15 m/sec. The above-mentioned difference in wind speed is more preferably 0.2 m/sec or more, still more preferably 12 m/sec or less, still more preferably 8 m/sec or less, still more preferably 5 m/sec or less, and particularly preferably 3 m/sec. Less than seconds. If the wind speed just after being transported into the oven is greater than the wind speed of other conveying paths in the oven in such a way that the difference in wind speed falls within the above range, there is a tendency that the solvent in the film can be removed more efficiently. If the difference in wind speed is too large, the film may shake due to the difference in wind speed, and it may be difficult to manufacture the optical film of the present invention that satisfies the above equations (1) to (3). In addition, there is a possibility that it may cause a defect in the surface shape of the obtained optical film or a deviation in optical characteristics such as a phase difference.

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

The other conveyance path is preferably the next conveyance path after conveyance path 1 (hereinafter referred to as "conveyance path 2"). In the case where the inside of the oven is not divided into a plurality of cases, the conveying path 2 refers to the conveying path part located at 2/10 of the oven length from the entrance of the oven. When the inside of the oven is divided into multiple spaces, the conveying path 2 refers to the second space through which the film passes. In the case of using multiple ovens, it can be set in the same way as the previous description based on the internal structure of the oven initially used, or the wind speed of the second oven can be set to be lower than the wind speed of the oven that passes through at first.

When the wind speed difference 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 only needs to be within the range of the blowing wind speed of the hot air. The wind speed of the conveying path after conveying path 2 preferably has a wind speed difference of 0.1-12 m/sec from the respective wind speeds of conveying path 1 or conveying path 2, and more preferably a wind speed difference of 0.2-8 m/sec. If the wind speed difference is in this range, the film shaking caused by the wind speed difference can be suppressed, so that the optical film of the present invention that satisfies the above equations (1) to (3) can be easily manufactured, and the obtained optical film can be easily manufactured. The weight reduction rate of the film is adjusted to the tendency of the desired range.

Regarding the above difference in wind speed, when the inside of the oven is not divided into a plurality of spaces, it can be adjusted by adjusting the position of the nozzle, the blowing speed and air volume of the hot air from the nozzle, and the flow of the air flow in the oven. When the inside of the oven is divided into multiple spaces, just adjust the position of the nozzles, the blowing speed and air volume of the nozzles, the flow of airflow in the oven, etc. in the initial space and the subsequent spaces. Can. In the case of using multiple ovens, it can be carried out in the same way as the previous description according to the structure of the first oven, or the position of the nozzles and nozzles can be installed in a way that the wind speeds in the first oven and the second and subsequent ovens are different. The hot air blowing speed and air volume, the air flow in the oven, etc. can be set.

In the heating zone of the tenter furnace 100, the distance L (shortest distance) between the upper nozzle 46 and the lower nozzle 47 facing each other is preferably 150 mm or more, more preferably 150 to 600 mm, and more preferably 150 to 400 mm. By arranging the upper nozzle and the lower nozzle at such an interval L, the film shaking in each step can be suppressed more reliably, and the optical film of the present invention that satisfies the above equations (1) to (3) can be easily manufactured.

In addition, the difference between the highest temperature and the lowest temperature (ΔT) of the hot air at the outlets of the respective nozzles 46 and 47 in the heating area in the width direction (the direction perpendicular to the paper surface of FIG. 4) is preferably 2°C. Below, it is more preferable that all are 1 degreeC or less. By heating the film with hot air with a sufficiently small temperature difference in the width direction as described above, it is easy to manufacture the optical film of the present invention that satisfies the above-mentioned formulas (1) to (3). 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 the nozzle that can be used in the manufacturing method of the optical film, the nozzle usually used in the film manufacturing device can be used. As an example, a nozzle having a slit-shaped blowing port extending in the width direction of the raw film can be cited As a jet nozzle (also called a slit nozzle); and a nozzle with a plurality of openings arranged in the conveying direction of the raw film and the width direction of the raw film as a punching nozzle (also called a porous nozzle).

The nozzle is a structure that is arranged on the upper inner surface 100a of the tenter oven 100 and blows hot air downward toward the film, and a structure that is arranged on the inner and lower surface 100b of the tenter furnace 100 and blows hot air upward toward the film.

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 obtained optical film can be further improved. Furthermore, the area of the blow-out port of each spray nozzle can be obtained by multiplying the length of the nozzle in the width direction of the spray nozzle and the slit width. The product of the area of each outlet of the nozzle and the blowing wind speed becomes the blowing volume of the hot air from each nozzle. By dividing the blowing volume of the hot air by the length of the slit along the width of the film, the blowing volume of the hot air per 1 m of the length of the nozzle along the width of the film can be obtained.

The punching nozzle may have a rectangular shape in a cross-section perpendicular to its longitudinal direction, or a trapezoidal shape that gradually expands toward the surface opposite to the raw material film 44. The punching nozzle has a plurality of openings (for example, circular openings) on the surface opposite to the film, that is, the surface on the lower side. The hot air blowing outlet of the punching nozzle is composed of a plurality of openings provided on the blowing surface. The plurality of openings are the outlets for the hot air, and the hot air is blown out from the openings at a specified wind speed. A plurality of openings are arranged in the length direction of the film, and a plurality of openings are also arranged in the width direction. The opening may be arranged in a staggered shape, for example.

The area of the blow-out port of each punching nozzle can be calculated by the sum of the area of all the openings provided in a punching nozzle. The product of the area of each outlet of the nozzle and the blowing wind speed becomes the blowing volume of the hot air from each nozzle. By dividing the blowing volume of the hot air by the length of the slit along the width of the film, the blowing volume of the hot air per 1 m of the length of the nozzle along the width of the film can be obtained.

In the case of using a punching nozzle, the difference between the maximum blowing speed and the minimum blowing speed of the hot air at the outlet of the nozzle in the width direction can be used as the maximum blowing speed of the hot air blowing from multiple openings on the same nozzle. Calculate the difference between the minimum blowing speed. The difference between the highest temperature and the lowest temperature in the width direction of the hot air at the nozzle outlet can also be obtained in the same way.

If all the nozzles provided in the tenter furnace 100 are punched nozzles, the total area of the hot air outlet in the entire tenter furnace 100 can be increased. Therefore, the wind pressure exerted by the hot air on the film can be reduced, and the shaking of the film can be further reduced. Thereby, it is easy to manufacture the optical film of the present invention that satisfies the above-mentioned formulas (1) to (3). In the tenter furnace or in the heating zone, the raw film 44 is heated from room temperature to the temperature at which the solvent contained in the raw film evaporates, because the holding device 43 is used in such a way that the length of the raw film 44 in the width direction is almost constant. Keep it, so it tends to sag easily due to thermal expansion. By using the punching nozzle in the heating zone, sagging and shaking of the raw film 44 can be further suppressed, and the optical film of the present invention satisfying the above-mentioned formulas (1) to (3) can be easily manufactured.

Regarding the size and number of the openings on the surface of the punching nozzle, the blowing speed of the hot air at each opening can be 2-25 m/sec, and the blowing rate from each nozzle is less than that of the nozzles along the film width. The length should be adjusted appropriately within the range of 0.1 to 3 m ^{3 /sec per 1 m.}

From the viewpoint of making the blowing 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 punching nozzles, the length of the film conveying direction of each nozzle surface is preferably 50-300 mm. Furthermore, the distance between the adjacent punching nozzles is preferably 0.3 m or less. In addition, the ratio of the total area of the openings of the punching nozzle (the area of the blowing outlet) to the length of the film width direction of the punching nozzle (the total area of the openings of the punching nozzle (m ² )/the film of the punching nozzle The length (m) in the width direction is preferably 0.008 m or more.

By using this punching nozzle, the area of the hot air outlet can be enlarged. Thereby, the wind speed of the hot air can be sufficiently reduced, and the hot air can be blown out with a sufficient air volume, so that the film can be heated more uniformly. As a result, it is easy to manufacture the optical film of the present invention that satisfies the above-mentioned formulas (1) to (3).

The tenter furnace 100 that performs the heating step is provided with an IR heater on the inner upper surface 100a or the inner lower surface 100b, similar to the nozzle, and can be arranged to be opposite in the up and down direction. In addition, multiple IR heaters may be provided. As the IR heater, an IR heater usually used in film manufacturing equipment may be used.

As the radiation irradiated to the film, a heat ray having a wavelength of 3 to 7 μm is preferable. Furthermore, in the radiation treatment method, as long as the temperature of the space where the heating step is performed is within the above temperature range, the raw film can also be irradiated with radiation at a temperature higher than the temperature of the space by more than 30°C.

In the embodiment of the present invention, it is preferable to use the above-mentioned nozzle (hot air treatment method) and IR heater (radiation treatment method) in the tenter furnace 100 where the heating step is performed. In this case, as long as the IR heater is installed between the adjacent nozzles or between the nozzles and the inner wall of the tenter furnace (including the wall of the partition 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 can also be irradiated with radiation whose temperature is higher than the temperature of the space. The temperature of the radiation can be, for example, a temperature higher than the temperature of the space by 30°C or more, or a temperature higher than 150°C. Here, the temperature of the radiant line refers to the temperature set in a device that emits radiant heat, such as the set temperature of an IR heater. The difference between the temperature of the radiation and the temperature of the radiation irradiated to the film is preferably 5°C or less, more preferably 3°C or less, and still more preferably 1°C or less.

If the stenter furnace 100 uses a nozzle (hot air treatment method) and IR heater (radiation line treatment method), even if the raw film is irradiated at a higher temperature than the temperature in the heating zone or the stenter furnace (atmosphere temperature) The radiation can also be heated while suppressing the temperature in the heating zone or the stenter furnace from becoming too high.

The heating steps of the conventional hot air treatment method and the radiation treatment method are preferably in the plurality of spaces in the tenter furnace where the heating step is performed, from the space through which the raw material film first passes to about the middle of the full length of the tenter furnace Between spaces. Thereby, not only the time required for the heating step can be shortened, but also an optical film with more excellent uniformity of the in-plane phase difference can be manufactured.

The heating step is preferably performed in the range of 150 to 350°C. In the embodiment of the present invention, if the heating step is in this temperature range, the raw material film tends to be easily adjusted to the weight reduction rate M described later. The temperature range is more preferably 170°C or higher, still more preferably 180°C or higher, and more preferably 300°C or lower, still more preferably 250°C or lower, and particularly preferably 230°C or lower. If the temperature of the heating step is in the above-mentioned range, it is easy to adjust the YI value of the obtained optical film within the above-mentioned preferred range. In addition, the temperature of the space where the heating step is performed is more preferably 170°C or higher, and still more preferably 180°C or higher. The temperature in the tenter furnace for the heating step only needs to be such that the heating area is within the above-mentioned range. It can be adjusted appropriately when there are a plurality of tenter furnaces and when the inside of the tenter furnace is divided into a plurality of spaces, but it is preferable that all the tenter furnaces or spaces are within the above-mentioned range.

The moving speed of the raw film 44 in the tenter furnace 100 can usually be adjusted appropriately within the range of 0.1-50 m/min. The upper limit of the aforementioned moving speed is preferably 20 m/min, more preferably 15 m/min. The lower limit of the aforementioned 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 fast, the length of the tenter oven will be longer in order to ensure the required drying time, and the equipment will tend to become larger. In the embodiment of the present invention, if the moving speed of the raw material film 44 in the tenter furnace 100 is within the above-mentioned range, the raw material film tends to be easily adjusted to the weight reduction rate M described later. In addition, it is easy to manufacture an optical film that satisfies the mathematical formulas (1) to (3).

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

In one embodiment of the present invention, the manufacturing method of the optical film can perform the operation of changing the film width during the heating step or the operation of maintaining the film width for conveyance. As an example of the operation of changing the width of the film, an operation of extending the film in the width direction can be cited. The stretching ratio is preferably 0.7 to 1.3 times, more preferably 0.8 to 1.2 times, and still more preferably 0.8 to 1.1 times. As an example of the operation of holding the film width and carrying it out, there can be mentioned an operation of holding the film so that the length in the width direction of the film is almost constant. The optical film obtained through these operations can have a length of about 0.7 to 1.3 times the length of the width direction of the raw film, and can be a length that extends from the length of the width direction of the raw film, equals or shrinks. The stretching ratio is calculated as the ratio of the width of the stretched film (except for the holding part) to the width of the film except for the holding part. Furthermore, in FIG. 5, the solid line indicates the case where the stretching ratio exceeds 1 in the operation of extending the film in the width direction, and the dotted line indicates the case where the stretching ratio is equal to or less than 1 time.

After the optical film that has undergone the heating step is unloaded from the tenter furnace, it can be continuously supplied to the next step, or it can be rolled into a roll and supplied to the next step. When the optical film is rolled into a roll, the surface protective film and other optical films can be laminated and then rolled up. As the surface protection film laminated on the optical film, the same thing as the surface protection film laminated on the raw material film mentioned later can be used. The thickness of the surface protection film laminated on the optical film is usually 10-100 μm, preferably 10-80 μm.

＜Raw film＞ The raw material film supplied to the heating step contains at least a polyimide-based resin and/or a polyimide-based resin. The raw material film preferably contains the same components as those contained in the varnish used in the formation of the raw material film described later, but it may be different in order to cause structural changes of the components and evaporation of a part of the solvent. The raw material film may be a self-supporting film, or a gel film.

From the viewpoint of ease of manufacturing an optical film satisfying the equations (1) to (3), whether or not the raw film contains inorganic materials, it is preferable to remove a part of the solvent from the varnish so that it can be weighted by heat- The weight loss rate M from 120°C to 250°C obtained by differential thermal measurement (hereinafter, sometimes referred to as "TG-DTA measurement") is preferably about 1 to 40%, more preferably 3 to 20%, and further It is preferably 5 to 15%, and particularly preferably 5 to 12%. The weight reduction rate M of the raw film can be measured by the following method using a commercially available TG-DTA measuring device. As a TG-DTA measuring device, TG/DTA6300 manufactured by Hitachi High-Tech Science can be used.

First, obtain about 20 mg of the sample from the raw material film, and measure the weight change of the sample while heating the sample under the following conditions: heating from room temperature to 120°C at a heating rate of 10°C/min, and at 120°C After holding for 5 minutes, the temperature is increased to 400°C at a temperature increase rate of 10°C/min. Then, based on the result of the TG-DTA measurement, the weight reduction rate M (%) from 120°C to 250°C can be calculated using the following formula. In the following formula, W ₀ represents the weight of the sample after being kept 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 film is large to a certain extent, when the raw film is wound into a laminate with the base material or the surface protection film, the bending and other deformation of the laminate can be suppressed, thereby improving the performance of the laminate. The tendency of coiling. In addition, it becomes easy to manufacture an optical film that satisfies the equations (1) to (3).

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

The raw material film can be formed by drying the above-mentioned coating film and peeling it from the base material. The drying of the coating film can usually be carried out at a temperature of 50 to 350°C. If necessary, the coating film can be dried under an inert atmosphere or under reduced pressure. The raw material film obtained in the above-mentioned manner can be supplied to the above-mentioned heating step to manufacture the optical film of the present invention. The raw material film may be continuously conveyed and supplied to the heating step, or may be wound up before being supplied.

＜Functional layer＞ One or more functional layers can be used in at least one area layer of the optical film of the present invention. As the functional layer, for example, an ultraviolet absorbing layer, a hard coat layer, an undercoat layer, a gas barrier layer, an adhesion layer, a hue adjustment layer, a refractive index adjustment layer, etc. may be mentioned. The functional layer can be used alone or in combination of two or more.

(Ultraviolet absorption layer) The ultraviolet absorbing layer is a layer having an ultraviolet absorbing function, for example, includes a main material selected from ultraviolet curable transparent resin, electron beam curable transparent resin, and thermosetting transparent resin, and an ultraviolet absorber dispersed in the main material.

(Hard coating) The hard coat layer is a layer in which, for example, a composition for forming a hard coat containing a reactive material capable of forming a cross-linked structure by irradiating active energy rays or imparting heat energy (hereinafter, also referred to as "hard coat composition ") It is formed by curing, preferably a layer that can be formed by irradiating active energy rays. Active energy rays are defined as energy rays that can decompose compounds that produce active species to produce active species. Examples include visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, γ-rays, and electron beams. For example, ultraviolet rays. The above-mentioned hard coating composition contains at least one polymer of a radical polymerizable compound and a cation polymerizable compound. The thickness of the hard coat layer is not particularly limited. From the viewpoint of easy prevention of cracking at the hard coat layer or the interface between the hard coat layer and the optical film, it is preferably 2-50 μm, more preferably 2-40 μm, and further It is preferably 3-20 μm, and still more preferably 3-15 μm. If the thickness of the hard coat layer is in the above range, sufficient scratch resistance can be ensured, and the bending resistance is unlikely to decrease, and there is a tendency that the problem of curling due to hardening shrinkage is unlikely to occur.

In the hard coat layer forming step, high energy rays (for example, active energy rays) are irradiated to the coating film to harden the coating film to form a hard coat layer. The irradiation intensity is appropriately determined according to the composition of the curable composition and is not particularly limited. It is preferable to perform irradiation in a wavelength region effective for activation of the polymerization initiator. The irradiation intensity is preferably 0.1 to 6,000 mW/cm ² , more preferably 10 to 1,000 mW/cm ² , and still more preferably 20 to 500 mW/cm ² . If the irradiation intensity is within the above range, an appropriate reaction time can be ensured, and the yellowing and deterioration of the resin due to the heat radiated from the light source and the exothermic heat during the curing reaction can be suppressed. The irradiation time can be appropriately selected according to the composition of the curable composition, and is not particularly limited. It is set as follows: the cumulative light amount expressed by the product of the above-mentioned irradiation intensity and irradiation time is preferably 10 to 10,000 mJ/cm ² , more preferably 50 to 1,000 mJ/cm ² , still more preferably 80 to 500 mJ/cm ² . If the cumulative amount of light is within the above range, a sufficient amount of active species derived from the polymerization initiator can be generated, so that the curing reaction can proceed more reliably, and the irradiation time will not become too long, so that good production can be maintained sex. In addition, by going through the irradiation step within this range, the hardness of the hard coat layer can be further increased, which is useful. In terms of improving the smoothness of the hard coat layer and further improving the visibility of the optical film in the wide-angle direction, examples include: the type of solvent, the component ratio, the optimization of the solid component concentration, and the addition of a leveling agent Wait.

The above-mentioned radically polymerizable compound is a compound having a radically polymerizable group. The radical polymerizable group possessed by the above radical polymerizable compound may be a functional group capable of undergoing a radical polymerization reaction. Examples include groups containing a carbon-carbon unsaturated double bond. Specifically, Examples include vinyl groups, (meth)acryloyl groups, and the like. In addition, when the above-mentioned radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same or different from each other. In terms of increasing the hardness of the hard coat layer, the number of radical polymerizable groups contained in one molecule of the radical polymerizable compound is preferably 2 or more. As the above-mentioned radically polymerizable compound, in terms of high reactivity, a compound having a (meth)acryloyl group is preferably used. Specifically, there are 2 to 6 ( (Meth)acrylic acid is a compound called multifunctional acrylate monomer, or epoxy (meth)acrylate, urethane (meth)acrylate, polyester (meth)acrylate The oligomer having several (meth)acrylic acid groups in the molecule and having a molecular weight of several hundred to several thousand, preferably selected from epoxy (meth)acrylate, urethane (former One or more of acrylate and polyester (meth)acrylate.

The above-mentioned cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetanyl group, and a vinyl ether group. In terms of increasing the hardness of the hard coat layer, the number of cationically polymerizable groups that the above-mentioned cationically polymerizable compound has in one molecule is preferably 2 or more, more preferably 3 or more. In addition, as the above-mentioned cationically polymerizable compound, a compound having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group is preferable. In terms of small shrinkage accompanying the polymerization reaction, cyclic ether groups such as epoxy groups and oxetanyl groups are preferred. In addition, the compound having the epoxy group in the cyclic ether group has the following advantages: it is easy to obtain compounds of various structures, does not adversely affect the durability of the obtained hard coat layer, and is compatible with radical polymerizable compounds It is also easy to control. In addition, the oxetanyl group in the cyclic ether group has the following advantages: Compared with the epoxy group, the degree of polymerization tends to be higher, thereby accelerating the formation speed of the network obtained from the cation polymerizable compound of the hard coat layer. , And in the area where the radical polymerizable compound is mixed, it will not leave unreacted monomer in the film and form an independent network. Examples of cationic polymerizable compounds having epoxy groups include: using appropriate oxidizing agents such as hydrogen peroxide and peracid to make polyglycidyl ethers of polyhydric alcohols with alicyclic rings or cyclohexene-containing rings and ring Cycloaliphatic epoxy resin obtained by epoxidation of compound of pentene ring; polyglycidyl ether of aliphatic polyol or its alkylene oxide adduct, polyglycidyl ester of aliphatic long-chain polyacid, (methyl ) Aliphatic epoxy resins such as homopolymers and copolymers of glycidyl acrylate; by bisphenols such as bisphenol A, bisphenol F or hydrogenated bisphenol A, or these alkylene oxide adducts, Glycidyl ethers produced by the reaction of derivatives such as lactone adducts and epichlorohydrin, and novolac epoxy resins, etc., are glycidyl ether type epoxy resins derived from bisphenols.

The above-mentioned hard coat composition may further contain a polymerization initiator. As a polymerization initiator, a radical polymerization initiator, a cationic polymerization initiator, a radical and a cationic polymerization initiator, etc. are mentioned, It can select suitably and use. The polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate free radicals or cations for radical polymerization and cationic polymerization. The radical polymerization initiator may release a substance that initiates radical polymerization by at least one of active energy ray irradiation and heating. For example, as a thermal radical polymerization initiator, organic peroxides, such as hydrogen peroxide and perbenzoic acid, azo compounds, such as azobisisobutyronitrile, etc. are mentioned. As active energy ray radical polymerization initiators, there are Type 1 radical polymerization initiators that generate free radicals by the decomposition of molecules, and Type 2 radicals that coexist with tertiary amines to generate free radicals by hydrogen abstraction reaction. Radical polymerization initiators, which can be used singly or independently. The cationic polymerization initiator may release a substance that initiates cationic polymerization by at least one of active energy ray irradiation and heating. As the cationic polymerization initiator, an aromatic iodonium salt, an aromatic sulfonium salt, a cyclopentadienyl iron (II) complex, and the like can be used. Depending on the structure, the cationic polymerization can be started by either active energy ray irradiation or heating, or both can start cationic polymerization.

The polymerization initiator may be contained in an amount of 0.1 to 10% by mass relative to 100% by mass of the entire hard coating composition. If the content of the polymerization initiator is in the above range, the curing can be carried out sufficiently, and the mechanical properties and adhesion of the finally obtained coating film can be in a good range, and it is difficult to produce adhesive force due to curing shrinkage. Defects, cracks and crimping tendencies.

The above-mentioned hard coating composition may further contain one or more selected from the group consisting of solvents and additives. The above-mentioned solvent can dissolve or disperse the above-mentioned polymerizable compound and polymerization initiator, as long as it is a well-known solvent as a solvent for the hard coat composition in the technical field, and it can be used within a range that does not hinder the effect of the present invention. The above-mentioned additives may further include inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

(Adhesive layer) The adhesive layer is a layer with the function of adhesion, and has the function of adhering the optical film to other components. As the forming material of the adhesive layer, commonly known materials can be used. For example, a thermosetting resin composition or a photocuring resin composition can be used. In this case, by supplying energy afterwards, the resin composition can be polymerized and hardened.

The adhesive layer may also be a layer that is called a pressure sensitive adhesive (PSA) that is adhered to an object by pressing. Pressure-sensitive adhesives can be used as "substances that are adhesive at room temperature and adhere to the material to be bonded under light pressure" (JIS K6800), or they can be used as "protective coating (microcapsules)" (JIS K6800). ) An adhesive that contains specific ingredients and can maintain stability until the film is destroyed by appropriate means (pressure, heat, etc.)" (JIS K6800), which is a capsule adhesive.

(Hue adjustment layer) The hue adjustment layer is a layer with a hue adjustment function, and is a layer that can adjust the layered body including the optical film to the target hue. The hue adjusting layer is, for example, a layer containing resin and coloring agent. Examples of the coloring agent include inorganic pigments such as titanium oxide, zinc oxide, red lead, titanyl calcined pigments, ultramarine blue, cobalt aluminate, and carbon black; azo compounds, quinacridone compounds, Organic pigments such as anthraquinone compounds, perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, threne compounds, and diketopyrrolopyrrole compounds; barium sulfate, And extender pigments such as calcium carbonate; and dyes such as basic dyes, acid dyes, and mordant dyes.

(Refractive index adjustment layer) The refractive index adjustment layer is a layer having a refractive index adjustment function, and is, for example, a layer that has a refractive index different from that of an optical film and can provide a predetermined refractive index to the optical laminate. The refractive index adjustment layer may be, for example, a resin layer containing appropriately selected resin and pigments as needed, or a metal film. Examples of pigments that adjust the refractive index include silica, alumina, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle size of the pigment may be 0.1 μm or less. By setting the average primary particle size of the pigment to 0.1 μm or less, the diffuse reflection of the light passing through the refractive index adjustment layer can be prevented, and the decrease in transparency can be prevented. Examples of metals 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 nitrogen oxide. Metal oxides or metal nitrides such as silicide.

(Protective film) In one embodiment of the present invention, the optical film may have a protective film on at least one side (single side or both sides). For example, when the optical film has a functional layer on one side, the protective film may be laminated on the surface on the optical film side or on the functional layer side, or on both the optical film side and the functional layer side. When there are functional layers on both sides of the optical film, the protective film can be laminated on the surface on the side of the functional layer on one side, or on the surface on the side of the functional layer on both sides. The protective film is a film for temporarily protecting the surface of the optical film or the functional layer, and it is not particularly limited as long as it can protect the surface of the optical film or the functional layer and can be peeled off. Examples of protective films include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene films. Resin film; acrylic resin film, etc.; preferably selected from the group consisting of polyolefin resin film, polyethylene terephthalate resin film, and acrylic resin film. When the optical film has two protective films, each protective film may be the same or different.

The thickness of the protective film is not particularly limited, and is usually 10 to 120 μm, preferably 15 to 110 μm, and more preferably 20 to 100 μm. When the optical film has two protective films, the thickness of each protective film may be the same or different.

The optical film of the present invention may be a single layer or a laminate. For example, the optical film manufactured in the above manner may be used as it is, or may be used as a laminate with other films.

In a preferred embodiment of the present invention, the optical film of the present invention is used as the front panel of an image display device, especially a flexible display device front panel (hereinafter, also referred to as "window film"), especially a rollable display Or the front panel of the foldable display is very useful. The flexible display device has, for example, a flexible functional layer and an optical film superimposed on the flexible functional layer to function as a front panel. That is, the front panel of the flexible display device is arranged on the visible side of the flexible functional layer. The front panel has the function of protecting the flexible functional layer.

Examples of image display devices include televisions, smart phones, mobile phones, car navigation, tablet PCs (Personal Computers), portable game consoles, electronic paper, indicators, bulletin boards, clocks, and smart phones. Wearable devices such as type watches, etc. As the flexible display device, all image display devices having flexible characteristics can be cited.

[Flexible display device] The present invention also provides a flexible display device equipped with the optical film of the present invention. The optical film of the present invention is preferably used as a front panel in a flexible display device, and the front panel is sometimes called a window film. The flexible display device includes a laminate for a flexible display device and an organic EL (Electroluminescence) display panel. With respect to the organic EL display panel, the laminate for a flexible display device is arranged on the visible side, and the structure is Can be bent. The laminate for a flexible display device may include the optical film (window film) of the present invention, a circular polarizing plate, and a touch sensor. The order of these layers is arbitrary, and it is preferable to follow the window film and the circle from the viewing side. The sequential stacking of polarizing plate, touch sensor or window film, touch sensor, and circular polarizing plate. If there is a circular polarizer on the viewing side of the touch sensor, the pattern of the touch sensor is not easily visible, and the visibility of the displayed image becomes better, which is better. Each member can be laminated using adhesives, adhesives, etc. In addition, it may be provided with a light-shielding pattern formed on at least one surface of any layer of the window film, the circular polarizer, and the touch sensor.

[Polarizer] The flexible display device of the present invention may further include a polarizing plate, preferably a circular polarizing plate. The circular polarizing plate is a functional layer having the function of laminating a λ/4 retardation plate on the linear polarizing plate to transmit only the right circularly polarized light or the left circularly polarized light component. For example, it is used to convert external light into right circularly polarized light and reflect it on the organic EL panel to become left circularly polarized light. The image is easy to see. In order to realize the circularly polarized light function, the absorption axis of the linear polarizer and the retardation axis of the λ/4 retardation plate need to be 45° in theory, but 45±10° in practice. The linear polarizing plate and the λ/4 retardation plate do not necessarily need to be laminated adjacently, as long as the relationship between the absorption axis and the slow axis satisfies the above range. It is preferable to realize complete circularly polarized light at the full wavelength, but this is not necessary in practice. Therefore, the circular polarizing plate in the present invention also includes an elliptical polarizing plate. It is also preferable to laminate a λ/4 retardation film on the visibility side of the linear polarizer to make the emitted light circularly polarized light, thereby improving the visibility when wearing polarized sunglasses.

The linear polarizer is a functional layer that has the function of passing light that vibrates in the direction of the transmission axis, and blocking the polarized light of the vibration component perpendicular to it. The above-mentioned linear polarizing plate may be a single linear polarizing element, or a composition having a linear polarizing element and a protective film attached to at least one side of the linear polarizing element. The thickness of the linear polarizer may be 200 μm or less, preferably 0.5-100 μm. If the thickness of the linear polarizing plate is in the above range, the flexibility tends to be less likely to decrease.

The linear polarizing element may be a film-type polarizing element manufactured by dyeing and stretching a polyvinyl alcohol (hereinafter, also referred to as "PVA") film. Dichroic pigments such as iodine are adsorbed on the PVA-based film aligned by stretching, or the dichroic pigments are aligned while being adsorbed on PVA, and the polarization performance is exerted. In the production of the above-mentioned film-type polarizing element, in addition to this, it may also have steps such as swelling, cross-linking with boric acid, washing with aqueous solution, and drying. The stretching and dyeing steps can be carried out with a separate PVA-based film, or in the state of being laminated with other films such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10-100 μm, and the stretching ratio is preferably 2-10 times.

Furthermore, as another example of the above-mentioned polarizing element, a liquid crystal coating type polarizing element formed by applying a liquid crystal polarizing composition can be cited. The above-mentioned 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 exhibiting a liquid crystal state. In particular, if it has an alignment state of the same order as the smectic sequence, it can exhibit higher polarization performance, so it is preferred. Moreover, it is also preferable that the liquid crystal compound has a polymerizable functional group. The dichroic dye is a dye that is aligned together with the liquid crystal compound to exhibit dichroism, and may have a polymerizable functional group, and the dichroic dye itself may have liquid crystallinity. Any compound in the liquid crystal polarizing composition has a polymerizable functional group.

The above-mentioned liquid crystal polarizing composition may further contain an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.

The above-mentioned liquid crystal polarizing layer is manufactured by coating a liquid crystal polarizing composition on an alignment film to form a liquid crystal polarizing layer. The liquid crystal polarizing layer can be formed thinner than the film-type polarizing element. The thickness of the above-mentioned liquid crystal polarizing layer is preferably 0.5-10 μm, more preferably 1-5 μm.

The above-mentioned alignment film can be manufactured, for example, by coating an alignment film forming composition on a substrate, and imparting alignment properties by rubbing, polarized light irradiation, or the like. In addition to the alignment agent, the aforementioned alignment film forming composition may also contain a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like. Examples of the alignment agent include polyvinyl alcohols, polyacrylates, polyamides, and polyimines. In the case of applying optical alignment, it is preferable to use an alignment agent containing a cinnamate group. The weight average molecular weight of the polymer used as the above-mentioned alignment agent can be, for example, about 10,000 to 1,000,000. From the viewpoint of the alignment restriction force, the thickness of the alignment film is preferably 5 to 10,000 nm, and more preferably 10 to 500 nm.

The liquid crystal polarizing layer may be peeled from the base material and transferred to be laminated, or the base material may be directly laminated. The above-mentioned base material also preferably functions as a transparent base material for protective films, phase difference plates, and window films.

As the above-mentioned protective film, as long as it is a transparent polymer film, specifically, as the polymer film to be used, there may be mentioned: polyethylene, polypropylene, polymethylpentene, norene or having a ring-containing Polyolefins such as cycloolefin derivatives of olefin monomer units; (modified) celluloses such as diacetyl cellulose, triacetyl cellulose, propylene cellulose, etc.; methyl methacrylate (co)polymerization Acrylics such as materials; polystyrenes such as styrene (co)polymers; acrylonitrile-butadiene-styrene copolymers; acrylonitrile-styrene copolymers; ethylene-vinyl acetate copolymers; poly Vinyl chloride; polyvinylidene chloride; polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate and other polyesters; nylon Polyamides; Polyimines; Polyimides; Polyetherimines; Polyethers; Polyvinyls; Polyvinyl alcohols; Polyvinyl acetals; Polyamines Carbamates; epoxy resins and other films; in terms of excellent transparency and heat resistance, preferred examples include: polyamide, polyimide, polyimide, polyester, Olefin, acrylic or cellulosic film. These polymers can be used individually or in mixture of two or more types. These films are kept in an unstretched state or used as films that have been stretched uniaxially or biaxially. Preferably, it is a cellulose-based film, an olefin-based film, an acrylic film, and a polyester-based film. It can also 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. If necessary, it can also contain plasticizers, ultraviolet absorbers, infrared absorbers, coloring agents such as pigments or dyes, fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, and antioxidants , Lubricants, solvents, etc. The thickness of the protective film is preferably 200 μm or less, more preferably 1-100 μm. If the thickness of the protective film is in the above range, the flexibility of the protective film will not easily decrease.

The above-mentioned λ/4 retardation plate is a film that provides a λ/4 retardation in the direction orthogonal to the traveling direction of the incident light, that is, the in-plane direction of the film. The above-mentioned λ/4 retardation plate may be a stretched retardation plate manufactured by stretching a polymer film such as a cellulose-based film, an olefin-based film, or a polycarbonate-based film. The above-mentioned λ/4 retardation plate may also contain retardation adjusters, plasticizers, ultraviolet absorbers, infrared absorbers, coloring agents such as pigments or dyes, fluorescent brighteners, dispersants, and heat stabilizers as needed. Agents, light stabilizers, antistatic agents, antioxidants, lubricants, solvents, etc. The thickness of the above-mentioned extended phase difference plate is preferably 200 μm or less, more preferably 1-100 μm. If the thickness is in the above range, the flexibility of the film tends not to decrease easily.

Furthermore, as another example of the above-mentioned λ/4 retardation plate, a liquid crystal coating type retardation plate formed by applying a liquid crystal composition can be cited. The above-mentioned liquid crystal composition contains a liquid crystalline compound, and the liquid crystalline compound has the property of exhibiting a liquid crystal state such as nematic, cholesteric, and smectic. Any compound containing a liquid crystal compound in the liquid crystal composition has a polymerizable functional group. The above-mentioned liquid crystal composition may further contain an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like. The liquid crystal coating type retardation plate can be manufactured by applying a liquid crystal composition on an alignment film and curing it to form a liquid crystal retardation layer in the same manner as the description of the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed thinner than the extension type retardation plate. The thickness of the above-mentioned liquid crystal polarizing layer is preferably 0.5-10 μm, more preferably 1-5 μm. The liquid crystal coating type retardation plate may be peeled from the base material and transferred and laminated, or the base material may be directly laminated. The above-mentioned base material also preferably functions as a transparent base material for protective films, phase difference plates, and window films.

Generally, the shorter the wavelength of the material, the greater the birefringence, and the longer the wavelength, the smaller the birefringence. In this case, the phase difference of λ/4 cannot be achieved in the entire visible light region, so it is often designed to become the in-plane phase difference of λ/4 such as near 560 nm where the visual sensitivity is relatively high, that is, it is preferably 100-180 nm, more preferably 130-150 nm in-plane phase difference. In terms of improving visibility, it is preferable to use a reverse dispersion λ/4 retardation plate of a material having a birefringence wavelength dispersion characteristic which is opposite to that of usual. As such a material, it is also preferable to use the one described in Japanese Patent Laid-Open No. 2007-232873 etc. in the case of an extended retardation plate, and it is also preferable to use Japan in the case of a liquid crystal coating type retardation plate. It is described in Patent Publication No. 2010-30979.

In addition, as another method, a technique of obtaining a wide-band λ/4 retardation plate by combining with a λ/2 retardation plate is also known (Japanese Patent Laid-Open No. 10-90521). The λ/2 retardation plate is also manufactured using the same materials and methods as the λ/4 retardation plate. The combination of the extension type retardation plate and the liquid crystal coating type retardation plate can be arbitrary, but in any case, it is preferable to use a liquid crystal coating type retardation plate in terms of making the thickness thinner.

There is also known a method of laminating a positive C plate on the above-mentioned circular polarizing plate to improve the visibility in the oblique direction (Japanese Patent Laid-Open No. 2014-224837). The positive C plate can be a liquid crystal coating type retardation plate or an extended type retardation plate. The retardation in the thickness direction of the retardation plate is preferably -200 to -20 nm, more preferably -140 to -40 nm.

[Touch Sensor] The flexible display device of the present invention may further include a touch sensor. The touch sensor is used as an input member. As the touch sensor, various styles such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and an electrostatic capacitance method are proposed. Any method may be used, but the electrostatic capacitance method is preferred. The capacitive touch sensor is divided into an active area and an inactive area located outside the active area. The active area is the area of the display panel that corresponds to the display portion, and is the area that perceives the user's touch. The inactive area is the area of the display device that does not display the picture, that is, the area corresponding to the non-display portion. The touch sensor may include: a substrate with flexible characteristics; a sensing pattern formed on the active area of the substrate; and a sensing pattern formed on the inactive area of the substrate, and used to connect the sensing pattern to the outside via a bonding pad. Each sensing line connected to the drive circuit. As a substrate having flexibility, the same material as the above-mentioned polymer film can be used. Regarding the substrate of the touch sensor, in terms of suppressing cracks of the touch sensor, it is preferably one with a toughness of 2,000 MPa% or more. More preferably, the toughness may be 2,000 to 30,000 MPa%. Here, toughness is defined as the area under the curve up to the point of failure in the stress-strain curve obtained through the tensile test of polymer materials.

The aforementioned 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 different directions. The first pattern and the second pattern are formed on the same layer. In order to sense the touched point, the patterns must be electrically connected. The first pattern is a form in which the unit patterns are connected to each other via a joint, and the second pattern is a structure in which the unit patterns are separated from each other in the form of islands. Therefore, in order to electrically connect the second pattern, an additional bridge electrode is required. As the electrode for electrically connecting the second pattern, a known transparent electrode material can be used. Examples of the transparent electrode material include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc tin oxide (IZTO), indium gallium oxide (IGZO), cadmium tin oxide (CTO) ), PEDOT (poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)), carbon nanotube (CNT), graphene, metal wire, etc., these can be used alone or in combination Two or more kinds are used. As the transparent electrode raw material, ITO can be preferably used. The metal used in the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, etc., and these can be used alone or in combination of two or more.

The bridging electrode may be formed on the upper part of the insulating layer via the insulating layer on the upper part of the sensing pattern, and the bridging electrode may be formed on the substrate, and the insulating layer and the sensing pattern may be formed on the bridging electrode. The above-mentioned bridge electrode can be formed by using the same raw material as the sensing pattern, or by using metals such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or alloys of two or more of these . The first pattern and the second pattern must be electrically insulated, so an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the joints of the first pattern and the bridging electrodes, or may be formed as a layer covering the entire sensing pattern. When it is formed as a layer covering the entire sensing pattern, the bridge electrode connects the second pattern via the 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 as a member for appropriately compensating the difference in transmittance between the patterned area with the pattern and the non-patterned area with no pattern, Specifically, it is the difference in light transmittance induced by the difference in refractive index in these regions. The above-mentioned optical adjustment layer may contain an inorganic insulating material or an organic insulating material. The optical adjustment layer can be formed by coating a photo-curing composition containing a photo-curing organic binder and a solvent on a substrate. The above-mentioned photocurable composition may further contain inorganic particles. The above-mentioned inorganic particles can increase the refractive index of the optical adjustment layer. The photocurable organic adhesive may contain, for example, copolymers of monomers such as acrylate-based monomers, styrene-based monomers, and carboxylic acid-based monomers. The photocurable organic adhesive may be, for example, a copolymer containing repeating units that are different from each other, such as epoxy-containing repeating units, acrylate repeating units, and carboxylic acid repeating units. Examples of the above-mentioned inorganic particles include zirconium oxide particles, titanium oxide particles, and aluminum oxide particles. The above-mentioned photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

[Next layer] The window film, polarizing plate, touch sensor and other layers forming the laminated body for the flexible display device, and the film members such as the linear polarizing plate and the λ/4 phase difference plate constituting each layer can be adhered with an adhesive. As the adhesive, water-based adhesives, organic solvent-based adhesives, solvent-free adhesives, solid adhesives, solvent-volatile adhesives, moisture-curing adhesives, heat-curing adhesives, and anaerobic-curing adhesives can be used. Adhesives, water-based solvent volatile adhesives, active energy ray hardening adhesives, hardener mixed adhesives, hot-melt adhesives, pressure-sensitive adhesives, pressure-sensitive adhesives, rewetting adhesives, etc. are usually used By. Among them, it is preferable to use an aqueous solvent volatile adhesive, an active energy ray hardening adhesive, and an adhesive. The thickness of the subsequent layer can be appropriately adjusted according to the required adhesive force, etc., and is preferably 0.01 to 500 μm, more preferably 0.1 to 300 μm. There may be a plurality of adhesive layers in the above-mentioned laminate for flexible image display devices, and their respective thicknesses and types of adhesives used may be the same or different.

As the above-mentioned water-based solvent-volatile adhesive, water-soluble polymers such as polyvinyl alcohol-based polymers and starches, and water-dispersed polymers such as ethylene-vinyl acetate emulsions and styrene-butadiene emulsions can be used as the main components. Agent polymer. In addition to water and the above-mentioned main agent polymer, crosslinking agents, silane-based compounds, ionic compounds, crosslinking catalysts, antioxidants, dyes, pigments, inorganic fillers, organic solvents, etc. can also be formulated. In the case of bonding using the water-based solvent-volatile adhesive, the water-based solvent-volatile adhesive may be injected between the bonded layers to bond the bonded layers and then dry them to impart adhesiveness. In the case of using the above-mentioned water-based solvent-volatile adhesive, the thickness of the adhesive layer is 0.01-10 μm, preferably 0.1-1 μm. When the above-mentioned water-based solvent-volatile adhesive is used for the formation of multiple layers, the thickness of each layer and the type of the above-mentioned adhesive may be the same or different.

The active energy ray curable adhesive can be formed by curing an active energy ray curable composition containing a reactive material for irradiating active energy rays to form an adhesive layer. The active energy ray hardening composition may contain at least one polymer of a radical polymerizable compound and a cation polymerizable compound similar to the compound described in the hard coat composition. As the above-mentioned radically polymerizable compound, the same type as the compound described in the hard coat composition can be used. The radically polymerizable compound used in the adhesive layer is preferably a compound having an acryl group. In order to reduce the viscosity of the adhesive composition, it is also preferable that the composition contains a monofunctional compound.

As the above-mentioned cationically polymerizable compound, the same type as the compound described in the hard coat composition can be used. The cationic polymerizable compound used in the active energy ray curing composition is more preferably an epoxy compound. In order to reduce the viscosity of the adhesive composition, it is also preferable that the composition contains a monofunctional compound as a reactive diluent.

The active energy ray composition may further contain a polymerization initiator. As a polymerization initiator, a radical polymerization initiator, a cationic polymerization initiator, a radical and a cationic polymerization initiator, etc. are mentioned, These can be selected suitably and used. The polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate free radicals or cations to allow radical polymerization and cationic polymerization to proceed. In the description of the hard coating composition, an initiator that can start at least one of radical polymerization and cationic polymerization by active energy ray irradiation can be used.

The active energy ray hardening composition may further contain ion scavengers, antioxidants, chain transfer agents, adhesion imparting agents, thermoplastic resins, fillers, flow viscosity modifiers, plasticizers, defoamer solvents, additives, and solvents. When using the active energy ray curable adhesive to bond two adhesive layers together, the bonding can be performed by applying the active energy ray curable composition to either or both of the adhesive layers After that, bonding is performed, and active energy rays are irradiated through either or both of the bonded layers to harden the composition. 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 active energy ray-curable adhesive is used for the formation of multiple layers, the thickness of each layer and the type of adhesive used may be the same or different.

The above-mentioned adhesives are classified into acrylic adhesives, urethane-based adhesives, rubber-based adhesives, silicone-based adhesives, etc. according to the main agent polymer, and any of these can be used. In addition to the main agent polymer, the adhesive can also be blended with crosslinking agents, silane-based compounds, ionic compounds, crosslinking catalysts, antioxidants, adhesion imparting agents, plasticizers, dyes, pigments, inorganic fillers, etc. Each component constituting the adhesive is dissolved and dispersed in a solvent to obtain an adhesive composition, and the adhesive composition is applied on a substrate and then dried to form an adhesive layer (adhesive layer). The adhesive layer can be directly formed, or it can be transferred to a substrate formed separately. In order to protect the adhesive surface before bonding, it is also preferable to use a release film. In the case of using the aforementioned adhesive, the thickness of the adhesive layer is preferably 1 to 500 μm, more preferably 2 to 300 μm. When the above-mentioned adhesive is used for the formation of multiple layers, the thickness of each layer and the type of adhesive used may be the same or different.

[Shading Pattern] The above-mentioned light-shielding pattern can be applied as at least a part of the frame or housing of the above-mentioned flexible image display device. The light-shielding pattern hides the wiring arranged at the edge of the flexible image display device to make it difficult to be seen, thereby improving the visibility of the image. The above-mentioned 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 have various colors such as black, white, and metallic. The light-shielding pattern can be formed by pigments used to present colors, and polymers such as acrylic resins, ester resins, epoxy resins, polyurethanes, and silicones. These can be used alone or in a mixture of two or more kinds. The above-mentioned 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]

Hereinafter, the present invention will be explained in more detail using examples. The "%" and "parts" in the examples indicate mass% and mass parts as long as there is no special record. First, the evaluation method is explained.

＜Measurement of total light transmittance＞ The total light transmittance (Tt) of the optical film is measured in accordance with JIS K 7105:1981, using the automatic direct reading haze meter HGM-2DP manufactured by Suga Test Instruments Co., Ltd.

＜Haze＞ According to JIS K 7136: 2000, the optical films obtained in the examples and comparative examples were cut into a size of 30 mm×30 mm, and the haze was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd., "HGM-2DP") (%).

＜YI value＞ According to JIS K 7373: 2006, the YI value (Yellow Index) of the optical film is measured using the UV-Vis-NIR spectrophotometer "V-670" manufactured by JASCO Corporation. After the background measurement is performed without the sample, the optical film is set in the sample holder, and the transmittance of light from 300 to 800 nm is measured to obtain the tristimulus value (X, Y, Z), and based on the following The formula calculates the YI value. YI=100×(1.2769X－1.0592Z)/Y

＜Determination of weight average molecular weight＞ Gel Permeation Chromatography (GPC) determination (1) Pretreatment method Add DMF eluent (10 mmol/L lithium bromide solution) to the polyimide imide membrane so that the concentration becomes 2 mg/mL, and heat it while stirring at 80°C for 30 minutes. After cooling, it will pass through 0.45 μm. The membrane filter is used as the measurement solution. (2) Measurement conditions Column: TSKgel α-2500 ((7) 7.8 mm diameter × 300 mm) × 1 piece, α-M ((13) 7.8 mm diameter × 300 mm) × 2 pieces manufactured by Tosoh Co., Ltd. Eluent: DMF (addition of 10 mmol/L lithium bromide) Flow rate: 1.0 mL/min Detector: RI detector Column temperature: 40℃ Injection volume: 100 μL Molecular weight standard: standard polystyrene

＜Measurement of thickness＞ The thickness of the optical film is measured using an Absolute Digimatic Indicator (manufactured by Mitutoyo Co., Ltd., "ID-C112BS").

＜Tensile modulus of elasticity＞ The "Autograph AG-IS" manufactured by Shimadzu Corporation was used to measure the elastic modulus of the optical films obtained in the examples and comparative examples at a temperature of 25° C. and a relative humidity of 50%. In more detail, a film with a vertical and horizontal width of 10 mm was produced, and the stress-strain curve (S-S curve) was measured under the conditions of a chuck spacing of 50 mm and a stretching speed of 10 mm/min, and the elastic modulus was calculated from its slope.

＜R ₀ and R _th ＞ The obtained optical film was cut into 10 cm squares in vertical and horizontal directions, and the in-plane phase difference (R ₀ ) and thickness were calculated using the phase difference film and optical material inspection device RETS-100 manufactured by Otsuka Electronics Co., Ltd. The phase difference of the direction (R _th ).

<Measurement of the clarity value of the transmission image of an optical film> According to JIS K 7345, using an image clarity value measuring device ("ICM-1" manufactured by Suga Test Instruments Co., Ltd.), the optical film was measured by the transmission method as follows The clarity value of the transmission image of the film. Set the optical film to the image clarity value measuring device. The optical film is installed in a state where both sides are lightly wiped with ethanol and dried to remove foreign matter from the surface before installation. Then, the amount of light and the cross-sectional area are adjusted, and the white light adjusted to be parallel light is irradiated to the installed optical film from an angle (incident angle) inclined at 60° to the MD direction with respect to the optical film plane. The cross-sectional area of the transmitted light that passes through the optical film is adjusted to pass the comb that extends perpendicular to the optical axis of the irradiated light, and the light that passes through the comb is received by a light receiver. Repeatedly move the optical comb (slit width: 0.125 mm) along the plane parallel to the plane of the optical comb and the direction in which the slits in the optical comb are arranged with a prescribed unit amplitude to receive the transmitted light of the optical comb. As a result, the received light waveform is obtained. Obtain the maximum value M and the minimum value m of the relative light intensity from the received light waveform. Based on the equation (7), the first transmission image sharpness value C ₆₀ (MD) is calculated from the obtained M and m.

In addition to changing the incident angle to an angle of 60° from the direction perpendicular to the optical film plane to the TD direction, and an angle perpendicular to the optical film plane (angle of 0° inclination), the first transmission image is clear In the same way as the degree value, the second transmission image clarity value C ₆₀ (TD) and the third transmission image clarity value C ₀ are respectively calculated.

<The rate of imidization> The rate of imidization is ^{determined by 1} H-NMR measurement as follows. (1) Pretreatment method Dissolve an optical film containing a polyimide-based resin in deuterated dimethyl sulfide (DMSO-d ₆ ) to prepare a 2% by mass solution as a measurement sample. (2) Measuring condition measuring device: 400 MHz NMR device JNM-ECZ400S/L1 manufactured by JEOL Standard material: DMSO-d ₆ (2.5 ppm) Sample temperature: Room temperature Cumulative times: 256 times Relaxation time: 5 seconds (3) The analysis method of the imidization rate (the imidization rate of the polyimide resin) In the ¹ H-NMR spectrum obtained from the measurement sample containing the polyimide resin, the observed benzene protons are derived from The integral value of the benzene proton A of the unchanged structure before and after the imidization is taken as Int _A. In addition, the integral value of the observed protons of amide derived from the amide acid structure remaining in the polyimide resin was taken as Int _B. Based on the following formula, the imidization rate of the polyimide resin is obtained from these integral values. The imidization rate (%)=100×(1－Int _B /Int _A )

^{(The imidization rate of polyimide resin) In the 1} H-NMR spectrum obtained using a measurement sample containing polyimide resin, the ratio of the benzene proton C among the observed benzene protons The integral value is taken as Int _C. The benzene proton C is derived from a structure that does not change before and after the imidization, and is not affected by the structure derived from the residual acid structure in the polyimide resin. In addition, the integral value of the benzene proton D in the observed benzene protons is taken as Int _D. The benzene proton D is derived from a structure that does not change before and after the imidization, and will not be affected by the polyimide resin. The influence of the structure of the remaining amide acid structure. Use the following formula to find the β value _{from the obtained Int C} and Int _D. β=Int _D /Int _C Then, for a plurality of polyimide resins, the β value of the above formula and the imidization rate of the above formula of the polyimide resin are calculated, and the following relationship is obtained based on the results Mode. The imidization rate (%)=k×β+100 In the above relational formula, k is a constant. Substituting β into the relational formula to obtain the imidization rate (%) of the polyimide resin.

＜Viscosity of varnish＞ According to JIS K 8803:2011, the measurement was carried out using the E-type viscometer DV-II+Pro manufactured by Brookfield Company. The measurement temperature was set to 25°C.

<Bending resistance test> For the optical film, a bending resistance test was carried out in accordance with JIS K 5600-5-1. The bending resistance test was carried out using a small desktop bending tester (manufactured by Yuasa System Co., Ltd.). For the optical film after the bending resistance test, the clarity value of the transmission image and the haze were measured in the same manner as the above-mentioned measuring method. Obtain the absolute values of the difference between the transmission image sharpness value and haze before and after the bending resistance test, and calculate the difference of the transmission image sharpness value (the first transmission image sharpness value difference ΔC ₆₀ (MD) , The difference ΔC ₆₀ (TD) of the second transmission image sharpness value and the difference ΔC ₀ ) of the third transmission image sharpness value and the difference of the haze (ΔHaze).

＜Folding resistance test (MIT)＞ According to ASTM standard D2176-16, the bending times of the optical films in the examples and comparative examples are calculated as follows. A dumbbell cutter was used to cut the optical film into short strips with a width of 15 mm and a length of 100 mm to prepare a measurement sample. The measurement sample was set in the body of the MIT flexural fatigue testing machine ("Model 0530" manufactured by Toyo Seiki Seisakusho Co., Ltd.). Specifically, one end of the measurement sample is fixed to a load clamp (clamp), the other end is fixed to a bending clamp, and tension is applied to the measurement sample. In this state, the test speed is 175 cpm, the bending angle is 135°, the load is 0.75 kgf, and the bending radius of the bending clamp is R=3 mm. The bending movement is carried out in the forward and reverse directions until the test sample breaks. . Measure the number of folds mentioned above.

＜Visibility＞ Cut the optical film into 10 cm squares. Make the MD direction of the polarizing plate with the adhesive layer of the same size coincide with the MD direction of the cut optical film, and bond the polarizing plate with the adhesive layer to the optical film to prepare an evaluation sample. For the optical films of one example and comparative example, two evaluation samples were prepared respectively. In addition, for the optical films of the examples and the comparative examples after the bending resistance test, two evaluation samples were also produced respectively. Fix one of the two evaluation samples on the table as follows: the fluorescent lamp is positioned in the vertical direction of the evaluation sample plane, and the length direction of the fluorescent lamp is between the length of the evaluation sample MD direction is horizontal. The observer visually observes the fluorescent lamp image reflected on the surface of the evaluation sample at an angle of 30° from the vertical direction of the evaluation sample plane. Except for changing the length direction of the fluorescent lamp from horizontal to vertical, another evaluation sample was fixed on the table in the same manner to observe the fluorescent lamp image. Based on the following evaluation criteria, the visibility is evaluated based on the observation results. (Assessment criteria for visibility) ◎: The distortion of the fluorescent lamp image is hardly recognized. ○: The distortion of the fluorescent lamp image can be slightly seen. △: Distortion of the fluorescent lamp image is visually recognized. ×: The distortion of the fluorescent lamp image is clearly recognized.

(Production Example 1: Preparation of polyamide imine resin (1)) Under a nitrogen atmosphere, TFMB and DMAc were added to a separable flask equipped with a stirring blade so that the solid content of TFMB became 6.08% by mass, and stirred at room temperature to dissolve TFMB in DMAc. Then, 6FDA was added to the flask so that it might become 40.82 mol% with respect to TFMB, and it stirred at room temperature for 16 hours. Then, after cooling to 10°C, OMTPC was added so as to become 27.55 mol% with respect to TFMB, and after stirring for 10 minutes, OMTPC was further added so as to become 27.55 mol% with respect to TFMB, and the mixture was stirred for 20 minutes. Then, the same amount of DMAc as the DMAc added first was added, and after stirring for 10 minutes, OMTPC was added so as to be 6.12 mol% with respect to TFMB, and the mixture was stirred for 2 hours. Then, 61.22 mol% of diisopropylethylamine and 4-picoline relative to TFMB, and 285.71 mol% of acetic anhydride relative to TFMB were added to the flask, and after stirring for 30 minutes, the internal temperature The temperature was raised to 70°C and further stirred for 3 hours to obtain a reaction liquid. The obtained reaction liquid was cooled to room temperature, and was linearly poured into a large amount of methanol, 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 60°C to obtain polyimide resin (1). The weight average molecular weight of the obtained polyamide imide resin (1) was 300,000, and the imidization rate was 99.1%.

(Production Example 2: Preparation of polyimide resin (2)) Under a nitrogen atmosphere, in a separable flask equipped with a stirring blade, TFMB and DMAc were added so that the solid content of TFMB became 5.22% by mass, and stirred at room temperature to dissolve TFMB in DMAc. Then, 6FDA was added to the flask so that it might become 41.24 mol% with respect to TFMB, and it stirred at room temperature for 16 hours. Then, after cooling to 10°C, 2,5-dimethylterephthalate chloride (hereinafter, sometimes referred to as DMTPC) was added so as to be 27.84 mol% with respect to TFMB, and after stirring for 10 minutes, DMTPC was added so as to be 27.84 mol% with respect to TFMB, and stirred for 20 minutes. Then, the same amount of DMAc as the DMAc added first was added, and after stirring for 10 minutes, DMTPC was added so as to be 6.19 mol% with respect to TFMB, and the mixture was stirred for 2 hours. Then, 61.86 mol% of diisopropylethylamine and 4-picoline relative to TFMB, and 288.66 mol% of acetic anhydride relative to TFMB were added to the flask, and after stirring for 30 minutes, the internal temperature The temperature was raised to 70°C and further stirred for 3 hours to obtain a reaction liquid. The resulting reaction solution was cooled to room temperature, and was linearly poured into a large amount of methanol, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60°C to obtain polyimide resin (2). The weight average molecular weight of the obtained polyamide imide resin (2) was 280,000, and the imidization rate was 98.9%.

(Manufacturing Example 3: Preparation of Silica Dispersion Liquid) The solvent methanol in the silicon dioxide (average primary particle size 25 nm) that has been organically dispersed by methanol is replaced with γ-butyrolactone (GBL) to obtain silicon dioxide (solid content) that has been organically dispersed by GBL 30.5%). This dispersion liquid is referred to as dispersion liquid (1).

(Production Example 4: Preparation of Varnish) Varnishes (1) and (2) were prepared by adding polyimide imine resin to GBL so as to become the solid components shown in Table 1, and stirring at room temperature It is obtained by completely dissolving it in 24 hours. Varnish (3) is obtained by adding polyamideimide resin and dispersion liquid 1 to GBL solvent so as to become the solid components shown in Table 1 at room temperature, and stirring until uniform. Furthermore, the mass ratio of the polyimide imine resin in the varnish (3) to the filler (silica) contained in the dispersion liquid 1 is set to 60:40. [Table 1] Varnish Polyimide resin Dispersions Viscosity (cp) Solid content (mass%) (1) (1) - 40,000 8.5 (2) (2) - 41,000 9.0 (3) (1) (1) 37,000 12.0

(Production Example 5: Production of composition for forming hard coat layer) 35 parts by mass of urethane acrylate (manufactured by Shinnakamura Chemical Industry Co., Ltd.; UA-122P) and 35 parts by mass of urethane acrylate (manufactured by Shinnakamura Chemical Industry Co., Ltd.; UA-232P) , 25 parts by mass of methyl ethyl ketone, 4.5 parts by mass of photoinitiator (1-hydroxycyclohexyl phenyl ketone), and 0.5 parts by mass of leveling agent (manufactured by BYK-Chemie; BYK-3570) The composition (1) for forming a hard coat layer was produced.

<Example 1> (Manufacturing of Optical Film (1)) The manufacture of the optical film (1) will be described with reference to Figs. 7 and 8. First, as shown in FIG. 7, a polyethylene terephthalate film base 51 (manufactured by Toyobo Co., Ltd.: COSMOSHINE (registered trademark) A4100) with a thickness of 188 μm, hereinafter, may be referred to as PET film base 51 ) Is rolled out, and while being transported at a linear speed of 0.30 m/min, the PET film substrate 51 is cast from a nozzle 521 to a width of 500 mm to coat the varnish (1) charged in the tank 522 by casting. Then, while conveying at the same linear speed, it is heated in the dryer 53 at 120°C for 20 minutes, 95°C for 10 minutes, and 85°C for 10 minutes to dry the applied varnish. Then, the protective film 54 (manufactured by SUN A. KAKEN Co., Ltd.; NSA-33T) was rolled out from the reel, and was attached to the surface of the dry coating film on the opposite side to the surface in contact with the PET film substrate 51 , The PET film base material 51 was peeled off from the dried coating film and wound into a PET film base material roll 55, and the remaining laminate was obtained in the form of a laminate roll 56 with a length of 100 m.

Next, as shown in FIG. 8, the laminated film is rolled out from the obtained laminated body roll 56 at a conveying speed of 0.5 m/sec, and the protective film 54 is peeled off from the laminated film and wound into a protective film roll 57, and the rest is dried After the coating film passes through the nip rolls 201 and 202, it is dried in the tenter dryer 58 under the following conditions. Furthermore, the tenter dryer 58 is equipped with a mechanism for holding both ends of the film using clamps. In addition, the inside is divided into the first chamber to the sixth chamber in order from the entrance side of the membrane. ＜Stenter dryer 58＞ Clamp holding width (the distance from one end of the film to the corresponding clamp holding part): 25 mm The ratio of the clamp spacing between the two ends of the film at the outlet of the dryer to the clamp spacing between the two ends of the film at the inlet of the dryer: 1.0 Temperature inside the dryer: 200℃ The wind speed of each chamber in the dryer: 13.5 m/sec in the first chamber, 13 m/sec in the second chamber, 11 m/sec in the third to sixth chamber

After leaving the tenter dryer 58, the clamps are released from the end of the film. After the obtained film passes through the nip rollers 203 and 204, the clip holding part of the film is cut into long strips by the cutting device 59, and then the PET protective film 60 is laminated and wound on ABS (Acrylonitrile Butadiene Styrene, Acrylonitrile Butadiene Styrene, Acrylonitrile Butadiene Styrene). A 6-inch core made of styrene), and an optical film 61 with a thickness of 50 μm is obtained in the form of a roll. The residual amount of the solvent in the obtained optical film 61 was 1.0% by mass.

<Example 2> Except changing the varnish (1) to varnish (2), and changing the drying conditions in the dryer 53 to heating at 120°C for 20 minutes, heating at 100°C for 10 minutes, and heating at 90°C for 10 minutes, the optical film ( In the same way as the manufacturing method of 1), an optical film (2) with a residual solvent content of 1.0% by mass and a thickness of 49 μm in the film was manufactured.

<Example 3> (Production of optical film (3)) The hard-coat layer-forming composition (1) produced in Production Example 5 was applied to the hard-coat layer so that the thickness of the first hard-coat layer after curing became 3 μm The surface in contact with the PET base film of the optical film (2) obtained in Example 2 was dried in an oven at 80°C for 1 minute. Then, a high-pressure mercury lamp was used to ^{irradiate light with a light amount of 350 mJ/cm 2} to harden the coating film to form a first hard coat layer, thereby manufacturing an optical film (3) including a hard coat layer.

<Example 4> Except for changing the varnish (1) to varnish (3) and changing the line speed from 0.30 m/min to 0.50 m/min, the remaining amount of solvent in the film manufactured in the same way as the manufacturing method of the optical film (1) is 1.0% by mass optical film (4) with a thickness of 51 μm.

<Comparative example 1> A polyimide film (manufactured by Ube Industries Co., Ltd.; UPILEX) with a thickness of 50 μm was prepared as an optical film (5).

The formula of the composition and the composition of the optical film are summarized in Table 2. In addition, in Table 2, the column "HC presence or absence" means that the case where the optical film is provided with a hard coat layer is set to be present, and the case where the optical film is not provided is set to be absent.

[Table 2] Varnish Film thickness T (μm) HC with or without Example 1 (1) 50 none Example 2 (2) 49 none Example 3 (2) 52 have Example 4 (3) 51 none Comparative example 1 - 50 none

For the films obtained in the examples and comparative examples, the physical property values were measured according to the above-mentioned methods. The obtained results are shown in Table 3 to Table 6.

[table 3] Optical properties Image clarity value (%) Tt (%) Haze (%) YI C ₀ C ₆₀ (MD) C ₆₀ (TD) C ₆₀ (MD)/C ₀ C ₆₀ (TD)/C ₀ Example 1 90.8 0.3 1.4 98.0 89.1 89.5 0.909 0.913 Example 2 91.0 0.2 1.6 98.0 91.8 91.0 0.937 0.929 Example 3 90.8 0.3 1.6 97.9 91.5 91.1 0.935 0.931 Example 4 90.2 0.3 1.7 98.4 92.0 92.1 0.935 0.936 Comparative example 1 26.1 3.4 120 95.1 90.7 83.8 0.953 0.881

[Table 4] Tensile modulus E (GPa) Folding endurance test (times) R ₀ R _th R _th /R ₀ Example 1 5.5 ＞400,000 280 2,800 10.00 Example 2 6.0 ＞400,000 273 2,750 10.07 Example 3 6.1 ＞400,000 260 2,500 9.62 Example 4 7.3 ＞400,000 105 1250 11.90 Comparative example 1 9.6 ＞800,000 532 1,500 2.82

[table 5] Image clarity value (%) Difference of image sharpness value (%) Haze Before bending After bending ∆C ₆₀ (MD) ∆C ₆₀ (TD) ∆C ₀ ∆Haze (%) C ₆₀ (MD) C ₆₀ (TD) C ₆₀ (MD) C ₆₀ (TD) Example 1 89.1 89.5 85.3 84.5 3.8 5.0 0.5 0.3 Example 2 91.8 91.0 90.8 90.2 1.0 0.8 0.6 0.3 Example 3 91.5 91.1 90.5 90.0 1.0 1.1 0.5 0.2 Example 4 92.0 92.1 91.8 90.5 0.2 1.6 0.5 0.3 Comparative example 1 90.7 83.8 85.2 74.3 5.5 9.5 1.0 0.5

[Table 6] Visibility Vertical direction horizontal direction Example 1 △ △ Example 2 〇 〇 Example 3 〇 〇 Example 4 ◎ ◎ Comparative example 1 X X

It was confirmed that the optical films of Examples 1 to 4 in which the total light transmittance and the haze are within the predetermined ranges and satisfy the equations (1) to (3) are films with excellent visibility in the wide-angle direction. In addition, it was confirmed that the optical film of the present invention is in a preferred aspect of the present invention, the difference in image sharpness value before and after the bending resistance test and the difference in haze are small, even after repeated bending operations in the wide-angle direction Visibility is also excellent. In addition, the optical film of the present invention has the above-mentioned characteristics and R _{0 is} in the range of 40 to 300 nm. It is believed that this kind of optical film is not prone to warpage and interlayer peeling during high-temperature processing. In contrast, the optical film of Comparative Example 1 in which the total light transmittance and haze are not within the prescribed ranges and does not satisfy the equations (1) to (3) has poor visibility in the wide-angle direction. In addition, R ₀ exceeding 300 nm is considered to be a film with a large strain.

1: Optical film 3: vertical axis 10: 1st incident light 11: The first incident position 12: 1a transmitted light 14: 1st optical axis 16: 1st optical comb 18: 1b transmitted light 19: The first light receiver 20: 2nd incident light 21: 2nd incident position 22: 2a transmitted light 24: 2nd optical axis 26: 2nd light comb 28: 2b transmitted light 29: The second light receiver 30: 3rd incident light 31: 3rd incident position 32: 3a transmitted light 34: 3rd optical axis 36: 3rd light comb 38: 3b transmitted light 39: 3rd receiver 40: area 41: area 42: area 43: holding device 44: raw film 45: Resin film 46: Upper nozzle (nozzle) 47: Lower side nozzle (nozzle) 48: Nozzle 49: IR heater 51: PET film substrate 53: Dryer 54: Protective film 55: PET film substrate roll 56: Laminated body reel 57: Protective film roll 58: Tenter dryer 59: Cutting device 60: PET protective film 61: Optical film 100: Tenter furnace 100a: upper surface 100b: bottom surface 101～109: Guide roller 201: nip roller 202: nip roller 201～204: nip roller 521: Nozzle 522: slot A: The transport direction of the film

Fig. 1 is a diagram showing the optical axis when the sharpness value of the first transmission image is measured. Fig. 2 is a diagram showing the optical axis when the sharpness value of the second transmission image is measured. Fig. 3 is a diagram showing the optical axis when the third transmission image sharpness value is measured. 4 is a schematic cross-sectional view showing the steps of a preferred embodiment of the method of manufacturing the optical film of the present invention. 5 is a schematic cross-sectional view of a preferred embodiment of the heating step in the method of manufacturing the optical film of the present invention. Fig. 6 is a schematic cross-sectional view showing the steps of a preferred embodiment in the tenter furnace in the manufacturing method of the optical film of the present invention. FIG. 7 is a schematic diagram for explaining the manufacturing method of the optical film in the embodiment. Fig. 8 is a schematic diagram for explaining the manufacturing method of the optical film in the embodiment.

1: Optical film

3: vertical axis

10: 1st incident light

11: The first incident position

12: 1a transmitted light

14: 1st optical axis

16: 1st optical comb

18: 1b transmitted light

19: The first light receiver

A: The transport direction of the film

Claims (12)

An optical film comprising at least one resin selected from the group consisting of polyimide resins and polyimide resins, with a total light transmittance of 85% or more, and a haze of 0.5% or less. The internal phase difference R ₀ is 40 nm to 300 nm. When the direction parallel to the mechanical flow direction during manufacture of the above-mentioned optical film is set to the MD direction, and the direction perpendicular to the mechanical flow direction is set to the TD direction, it is based on JIS K 7374, when the width of the optical comb is 0.125 mm, is the first transmission image clarity value C ₆₀ (MD), obtained from a direction perpendicular to the plane of the optical film, which is inclined 60° to the MD direction, _{The second transmission image sharpness value C 60} (TD) in the direction inclined 60° from the vertical direction to the TD direction, and the third transmission image sharpness value C _{0 in} the vertical direction satisfy the following formula: (1): 87%≦C ₆₀ (MD)≦100%……(1); formula (2): 87%≦C ₆₀ (TD)≦100%……(2); and formula (3) : 0.8≦C ₆₀ (MD)/C ₀ ≦1.0……(3). Such as the optical film of claim 1, wherein the second transmission image clarity value and the third transmission image clarity value further satisfy the formula (4): 0.9≦C ₆₀ (TD)/C ₀ ≦1.0... (4). For the optical film of claim 1 or 2, the in-plane phase difference R ₀ nm and the thickness direction phase difference R _th nm satisfy the formula (5): 3≦R _th /R ₀ ≦200......(5). The optical film of any one of claims 1 to 3, wherein the difference ΔHaze between the above-mentioned haze before and after the bending resistance test according to JIS K 5600-5-1 is less than 0.3%. The optical film of any one of claims 1 to 4, wherein the difference between the first transmission image clarity value ΔC ₆₀ (MD) before and after the bending resistance test according to JIS K 5600-5-1, the second The difference ΔC ₆₀ (TD) of the transmission image sharpness value and the difference ΔC _{0 of} the third transmission image sharpness value are less than 15 respectively. The optical film according to any one of claims 1 to 5, wherein the weight average molecular weight of the resin selected from the group consisting of polyimide resins and polyimide resins is 350,000 or less. The optical film according to any one of claims 1 to 6, which has a thickness of 10 to 150 μm. The optical film according to any one of claims 1 to 7, which has a hard coat layer on at least one side. The optical film of claim 8, wherein the thickness of the hard coat layer is 3-30 μm. A flexible display device is provided with the optical film as claimed in any one of claims 1-9. For example, the flexible display device of claim 10 further includes a touch sensor. For example, the flexible display device of claim 10 or 11 is further provided with a polarizing plate.

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