JP2021148938A - Optical film and flexible display device - Google Patents

Abstract

To provide a flexible display device excellent in visibility in a wide-angle direction that includes an optical film having a low in-plane phase difference R0.SOLUTION: An optical film 1 including at least one kind of resin selected from a group composed of polyimide resin and polyamide resin has total light transmittance of 85% or more, haze of 0.5% or less, and an in-plane phase difference R0 of 40-300nm.SELECTED DRAWING: Figure 1

Description

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

Conventionally, glass has been used as a material for display members such as solar cells and image display devices. However, in response to recent demands for miniaturization, thinning, weight reduction, and flexibility, glass does not have a sufficient material, and various films are being studied as alternative materials for glass. Examples of such a film include a polyimide film (for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2009-2154412 Japanese Unexamined Patent Publication No. 2020-3781

When a polyimide resin film is applied to a transparent member such as the front plate of a flexible display device, the image may be displayed with the image display surface bent, so the angle is wider than that of the non-flexible image display surface. Excellent visibility in the direction is required. However, according to the study of the present inventor, there are cases where the conventional polyimide resin film cannot sufficiently satisfy the visibility in the wide-angle direction. Further, the present inventor states that when the in-plane retardation R ₀ is too large, the optical film is warped when the optical film is subjected to high-temperature heat treatment, or when the optical film is a laminated body, the optical film is warped. Although it has been found that delamination may occur, the in-plane retardation R ₀ may be too large in the conventional polyimide resin film.

Further, for example, the optical films described in Patent Documents 1 and 2 have been examined by the present inventor, and there are cases where the visibility in the wide angle direction and the visibility of the projected image are lowered.

Therefore, an object of the present invention is to provide _{an optical film having excellent visibility in a wide-angle direction and having a low in-plane phase difference R 0} , and a flexible display device including the optical film.

As a result of diligent studies to solve the above problems, the present inventors have found that an optical film containing at least one resin selected from the group consisting of a polyimide resin and a polyamide resin has a total light transmittance. 85% or more, haze of 0.5% or less, tensile elasticity at 25 ° C. of 5.1 GPa or more, in-plane retardation R ₀ of 40 to 300 nm, and transmission imageability of the optical film. We have found that the above problems can be solved by an optical film in which the values (C ₆₀ (MD), C ₆₀ (TD) and C _{0) satisfy a predetermined relationship, and have completed the present invention.} That is, the present invention includes the following aspects.

[1] An optical film containing at least one resin selected from the group consisting of a polyimide resin and a polyamide resin, having 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 to 300 nm.
When the direction parallel to the machine flow direction at the time of manufacture in the optical film plane is the MD direction and the direction perpendicular to the machine flow direction is the TD direction,
The first transmission mapping property value C in the direction inclined by 60 ° in the MD direction from the direction perpendicular to the plane of the optical film, which is obtained when the width of the optical comb is 0.125 mm in accordance with JIS K 7374. _{The 60 (MD), the second transmission mapping property value C 60} (TD) in the direction inclined by 60 ° from the vertical direction to the TD direction, and the third transmission mapping property value C _{0 in} the vertical direction are
Formula (1):
87% ≤ C ₆₀ (MD) ≤ 100% ... (1),
Formula (2):
87% ≤ C ₆₀ (TD) ≤ 100% ... (2), and mathematical formula (3):
0.8 ≤ C ₆₀ (MD) / C ₀ ≤ 1.0 ... (3)
An optical film that meets the requirements.
[2] The second transmission mapping property value and the third transmission mapping property value are calculated by the mathematical formula (4):
0.9 ≤ C ₆₀ (TD) / C ₀ ≤ 1.0 ... (4)
The optical film according to the above [1].
[3] The in-plane phase difference R ₀ nm and the phase difference R _th nm in the thickness direction are mathematical formulas (5):
3 ≤ R _th / R ₀ ≤ 200 ... (5)
The optical film according to the above [1] or [2], which satisfies the above conditions.
[4] The optical film according to any one of [1] to [3] above, wherein the difference ΔHaze of the haze before and after the bending resistance test according to JIS K 5600-5-1 is less than 0.3%.
[5] Difference in first transmission mapping property value before and after the bending resistance test according to JIS K 5600-5-1 ΔC ₆₀ (MD), difference in second transmission mapping property value ΔC ₆₀ (TD), and The optical film according to any one of [1] to [4] above, wherein _{the difference ΔC 0} of the third transmission mapping property value is 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 the polyimide resin and the polyamide resin is 350,000 or less.
[7] The optical film according to any one of [1] to [6] above, which has a thickness of 10 to 150 μm.
[8] The optical film according to any one of [1] to [7] above, which has a hard coat layer on at least one surface.
[9] The optical film according to [8], wherein the hard coat layer has a thickness of 3 to 30 μm.
[10] A flexible display device including the optical film according to any one of the above [1] to [9].
[11] The flexible display device according to the above [10], further comprising a touch sensor.
[12] The flexible display device according to the above [10] or [11], further comprising a polarizing plate.

According to the present invention, an optical film having excellent visibility in a wide angle direction and _{having a low in-plane phase difference R 0} so that warpage and peeling are unlikely to occur even after heat treatment at a high temperature, and a flexible display including the optical film. Equipment can be provided.

FIG. 1 is a diagram showing an optical axis in measuring the first transmission mapping property value. FIG. 2 is a diagram showing an optical axis in the measurement of the second transmission mapping property value. FIG. 3 is a diagram showing an optical axis in the measurement of the third transmission mapping property value. It is a process cross-sectional view which shows typically the preferable embodiment of the manufacturing method of the optical film of this invention. It is a process cross-sectional view which shows typically the preferable embodiment of the heating process in the manufacturing method of the optical film of this invention. It is a process cross-sectional view which shows typically the preferable embodiment in the tenter furnace in the manufacturing method of the optical film of this invention. It is the schematic for demonstrating the manufacturing method of the optical film in an Example. It is the schematic for demonstrating the manufacturing method of the optical film in an Example.

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention. Further, when a plurality of upper limit values and lower limit values are described for a specific parameter, any upper limit value and lower limit value among these upper limit values and lower limit values can be combined to form a suitable numerical range.

<Optical film>
The optical film of the present invention is an optical film containing at least one resin selected from the 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 the in-plane retardation R ₀ is 40 nm to 300 nm.
When the direction parallel to the machine flow direction at the time of manufacture in the optical film plane is the MD direction and the direction perpendicular to the machine flow direction is the TD direction,
The first transmission mapping property value C in the direction inclined by 60 ° in the MD direction from the direction perpendicular to the plane of the optical film, which is obtained when the width of the optical comb is 0.125 mm in accordance with JIS K 7374. _{The 60 (MD), the second transmission mapping property value C 60} (TD) in the direction inclined by 60 ° from the vertical direction to the TD direction, and the third transmission mapping property value C _{0 in} the vertical direction are
Formula (1):
87% ≤ C ₆₀ (MD) ≤ 100% ... (1),
Formula (2):
87% ≤ C ₆₀ (TD) ≤ 100% ... (2), and mathematical formula (3):
0.8 ≤ C ₆₀ (MD) / C ₀ ≤ 1.0 ... (3)
Meet.

The MD direction is a direction parallel to the machine flow direction at the time of manufacture in the plane of the optical film, and indicates, for example, a direction parallel to the direction in which the optical film is conveyed when manufactured by the solution casting method. The TD direction is a direction perpendicular to the machine flow direction, and indicates, for example, a direction perpendicular to the conveyed direction. When the directions are unknown, the MD direction and the TD direction in the optical film plane are determined by the following method. For MD and TD, at least 20 points or more of the optical film are cross-sectioned in different directions. More specifically, assuming a circle centered on any one point of the optical film, the semicircle is cut out from the optical film, and the central angle of the fan shape after cutting the semicircle becomes substantially uniform. As described above, the optical film is cut in a straight line, and 20 or more cross sections are formed. The center of the thickness of the obtained plurality of cross sections is measured by laser Raman, and the one having the highest peak intensity near ^{1,620 cm -1 is defined as the MD direction.}

に基づいて第１透過写像性値Ｃ_６０（ＭＤ）を算出する。透過写像性値（第１透過写像性値、並びに後述の第２透過写像性値及び第３透過写像性値）は、写像性測定器を用いて測定することができる。 The first transmissivity value C ₆₀ (MD) is obtained in accordance with Japanese Industrial Standards (JIS) K 7374, and is a transmissivity in a direction inclined by 60 ° from the vertical direction to the MD direction with respect to the plane of the optical film. The value. The first transmission mapping property value C ₆₀ (MD) will be described more specifically with reference to FIG. FIG. 1 is a diagram showing an optical axis in measuring the first transmission mapping property value. An axis (first optical axis) inclined at an angle of 60 ° in the MD direction from an axis perpendicular to the optical film 1 (vertical axis 3) with an arbitrary point (first incident position 11) on the surface of the optical film 1 as a fulcrum. The optical film 1 is irradiated with the first incident light 10 (white light: indicated by a solid line in FIG. 1) along 14). Next, the first a transmitted light 12 (indicated by a broken line in FIG. 1) transmitted through the optical film 1 is transmitted to the first optical comb 16 extending perpendicular to the first optical axis 14. Next, the first b transmitted light 18 (denoted by the alternate long and short dash line in FIG. 1) transmitted through the first optical comb 16 is received by the first receiver 19 extending perpendicular to the first optical axis 14. The first optical comb 16 has an opening for transmitting the first a transmitted light 12 and a light shielding portion for blocking the first a transmitted light 12. The slit width (width of the opening) of the first optical comb 16 is 0.125 mm.
The first optical comb 16 is moved by a predetermined unit width in the direction parallel to the plane of the first optical comb 16 and in which the slits in the first optical comb 16 are arranged (direction of arrow A) to transmit the first b. The light 18 is repeatedly received to obtain a light receiving waveform. From the obtained received light waveform, the maximum value M and the minimum value m of the relative light amount are obtained. Formula (7): from the obtained M and m:

The first transmission mapping property value C ₆₀ (MD) is calculated based on the above. The transmission mapping property value (the first transmission mapping property value, and the second transmission mapping property value and the third transmission mapping property value, which will be described later) can be measured using a mapping property measuring device.

When the first transmission mapping property value C ₆₀ (MD) satisfies the mathematical formula (1), the optical film is excellent in visibility in the wide-angle direction in the MD direction. The first transmission mapping property value C ₆₀ (MD) is 87% or more in the mathematical formula (1), and is preferably 88% or more, more preferably 88% or more from the viewpoint of further improving the visibility of the optical film in the wide-angle direction in the MD direction. Is 89% or more, more preferably 90% or more, even more preferably 91% or more, particularly preferably 92% or more, and usually 100% or less.

The second transmission mapping property value C ₆₀ (TD) is a transmission mapping property value obtained in accordance with JIS K 7374 in a direction inclined by 60 ° in the TD direction from the direction perpendicular to the plane of the optical film. The second transmission mapping property value C ₆₀ (TD) will be described more specifically with reference to FIG. FIG. 2 is a diagram showing an optical axis in the measurement of the second transmission mapping property value. An axis (second optical axis) inclined at an angle of 60 ° in the TD direction from an axis perpendicular to the optical film 1 (vertical axis 3) with an arbitrary point (second incident position 21) on the surface of the optical film 1 as a fulcrum. The optical film 1 is irradiated with the second incident light 20 (white light: indicated by a solid line in FIG. 2) along 24). Next, the second a transmitted light 22 (indicated by a broken line in FIG. 2) transmitted through the optical film 1 is transmitted to the second optical comb 26 extending perpendicularly to the second optical axis 24. Next, the second b transmitted light 28 (indicated by the alternate long and short dash line in FIG. 2) transmitted through the second optical comb 26 is received by the second light receiver 29 extending perpendicular to the second optical axis 24. The second optical comb 26 has an opening for transmitting the second a transmitted light 22 and a light shielding portion for blocking the second a transmitted light 22. The slit width (width of the opening) of the second optical comb 26 is 0.125 mm.
The second optical comb 26 is moved by a predetermined unit width in the direction in which the slits are arranged in the second optical comb 26 (direction of arrow B) and is parallel to the plane of the second optical comb 26, and is transmitted through the second b. The light 28 is repeatedly received to obtain a light receiving waveform. From the obtained received light waveform, the maximum value M and the minimum value m of the relative light amount are obtained. _{The second transmission mapping property value C 60} (TD) is calculated from the obtained M and m based on the mathematical formula (7).

When the second transmission mapping property value C ₆₀ (TD) satisfies the mathematical formula (2), the optical film is excellent in visibility in the wide-angle direction in the TD direction. The second transmission mapping property value C ₆₀ (TD) is 87% or more in the mathematical formula (2), and is preferably 88% or more, more preferably 88% or more, from the viewpoint of further improving the visibility of the optical film in the wide-angle direction in the TD direction. Is 89% or more, more preferably 90% or more, even more preferably 91% or more, particularly preferably 92% or more, and usually 100% or less.

The third transmission mapping property value C ₀ is a transmission mapping property value in the direction perpendicular to the plane of the optical film, which is obtained in accordance with JIS K 7374. This will be specifically described with reference to FIG. 3 with reference to a third transmission mapping property value C _0. FIG. 3 is a diagram showing an optical axis in the measurement of the third mapping property value. The third incident light 30 (white light: represented by a solid line in FIG. 3) along the axis parallel to the axis (vertical axis 3) perpendicular to the optical film 1 and the axis parallel to the optical film 1 (third optical axis 34) of the optical film 1. Irradiate an arbitrary point (third incident position 31) on the surface. Next, the third a transmitted light 32 (indicated by a broken line in FIG. 3) transmitted through the optical film 1 is transmitted to the third optical comb 36 extending perpendicularly to the third optical axis 34. Next, the third b transmitted light 38 (indicated by the alternate long and short dash line in FIG. 3) transmitted through the third optical comb 36 is received by the receiver 39 extending perpendicularly to the third optical axis 34. The third optical comb 36 has an opening for transmitting the third a transmitted light 32 and a light shielding portion for blocking the third a transmitted light 32. The slit width (width of the opening) of the third optical comb 36 is 0.125 mm.
The third optical comb 36 is moved by a predetermined unit width in the direction parallel to the plane of the third optical comb 36 and in which the slits in the third optical comb 36 are arranged (direction of arrow C) to transmit the third b. The light 38 is repeatedly received to obtain a light receiving waveform. From the obtained received light waveform, the maximum value M and the minimum value m of the relative light amount are obtained. From the obtained M and m, the third transmission mapping property value C ₀ is calculated based on the mathematical formula (7).

When the first transmission mapping property value C ₆₀ (MD) and the third transmission mapping property value C ₀ satisfy the mathematical formula (3), the optical film is excellent in visibility in the MD direction with respect to the vertical direction of the optical film. _{The ratio (C 60} (MD) / C ₀ ) of the first mapping property value C ₆₀ (MD) to the third transmission mapping property value C ₀ is 0.8 or more in the formula (3), and the visibility in the MD direction is determined. From the viewpoint of further improvement, it is preferably 0.89 or more, more preferably 0.90 or more, still more preferably 0.93 or more, still more preferably 0.94 or more, and usually 1.0 or less.

The third transmission mapping property value C ₀ is preferably 97% or more, more preferably 98% or more. The first transmission mapping property value C ₆₀ (MD) is preferably 89% or more, more preferably 90% or more, still more preferably 92% or more.

The transmission image quality values (more specifically, the first transmission image quality value C ₆₀ (MD), the second transmission image quality value C ₆₀ (TD), and the third transmission image quality value C ₀ ) are the optical film surfaces. It can be adjusted by improving the smoothness of the optical film and suppressing scattering of transmitted light on the surface of the optical film. Further, the smoothness of the optical film surface is determined by, for example, the composition of the optical film (more specifically, the type of filler, the particle size and the content, etc.), and the manufacturing conditions of the optical film (more specifically, the drying temperature). , Drying time, airflow in the drying system, thickness of the coating film, transport speed in the drying step, amount of solvent in the varnish, etc.) can be adjusted. When the optical film further contains a hard coat layer, it can be adjusted by improving the smoothness of the surface of the hard coat layer and suppressing scattering or the like on the surface of the hard coat layer. The smoothness of the hard coat layer can be adjusted by, for example, adjusting the type of solvent, component ratio, solid content concentration, adding a leveling agent, and the like, in addition to the method for adjusting the smoothness of the optical film.

From the viewpoint of enhancing the visibility of the optical film of the present invention in the TD direction with respect to the vertical direction, the second transmission mapping property value and the third transmission mapping property value are calculated by the mathematical formula (4):
0.9 ≤ C ₆₀ (TD) / C ₀ ≤ 1.0 ... (4)
It is preferable to further satisfy. From the viewpoint of further enhancing the visibility in the TD direction of the present invention, the ratio of the first transmission mapping property value to the third transmission mapping property value (C ₆₀ (TD) / C ₀ ) is preferably 0.9 or more. It is more preferably 0.91 or more, still more preferably 0.92 or more, even more preferably 0.93 or more, particularly preferably 0.94 or more, and usually 1.0 or less.

The second transmission mapping property value C ₆₀ (TD) is preferably 89% or more, more preferably 90% or more, still more preferably 92% or more. The third transmission mapping property value C ₀ is preferably 97% or more, more preferably 98% or more, and further preferably 99% or more.

Further, the optical film of the present invention may satisfy mathematical formulas (1) to (3) (in some cases, further mathematical formula (4)) when light is transmitted from at least one surface of the optical film. , More preferably, the mathematical formulas (1) to (3) (in some cases, further mathematical formula (4)) are satisfied when light is transmitted from any surface of the optical film. If the mathematical formula is satisfied even when light is transmitted from any surface, for example, even if any surface of the optical film is adopted as the image display surface of the electronic device, the visibility in the wide-angle direction is excellent.

In particular, when the optical film of the present invention is applied to the front plate of a flexible device, the first transmission map before and after the bending resistance test based on JIS K 5600-5-1 from the viewpoint of further improving visibility in the wide angle direction. The absolute value ΔC ₆₀ (MD) of the difference between the sex values, the absolute value ΔC _{60 (TD) of the difference between the second transmission mapping properties, and the absolute value ΔC 0} of the difference between the third transmission mapping values are preferably less than 15, respectively. Is. When the difference between the transmission mapability values before and after the bending resistance test is less than 15, the image display surface of the flexible device is used in a bent state and / or even after being used in a bent state. Has excellent visibility in the wide-angle direction. ΔC ₆₀ (MD) is more preferably less than 1.5, even more preferably less than 1.0, even more preferably less than 0.5. ΔC ₆₀ (TD) is more preferably less than 2.8, even more preferably less than 2.3, even more preferably less than 2.1, and particularly preferably less than 1.5. ΔC ₀ is more preferably less than 2, even more preferably less than 1, even more preferably less than 0.7, and particularly preferably less than 0.5.

Further, in the optical film of the present invention, the total light transmittance is 85% or more, the haze is 0.5% or less, and the in-plane retardation R ₀ is 40 to 300 nm. When the optical film satisfies the above characteristics, the visibility in the wide angle direction of the optical film is sufficient, and the visibility in the wide angle direction of the optical film after heat treatment at a high temperature and the visibility of the projected image can be enhanced. If the total light transmittance is less than 85% or the haze is less than 0.5%, sufficient visibility of the optical film cannot be achieved due to the low initial optical properties of the optical film. Further, since it is difficult to manufacture an optical film having an in-plane retardation R ₀ of less than 40 nm by a manufacturing method including a stretching step, it is difficult to manufacture a film having high wide-angle visibility. When the in-plane retardation R ₀ exceeds 300 nm, the strain of the resin constituting the optical film is too large, so that the optical film is warped and / or interlayered by heat treatment when laminating the functional layer on the optical film. Easy to peel off. Therefore, it is considered that the visibility in the wide-angle direction and the visibility of the projected image are lowered in, for example, an optical film in which functional layers are laminated after such heat treatment.

The total light transmittance of the optical film of the present invention is 85% or more, and is preferably 87% or more, more preferably 88% or more, still more preferably 89% or more from the viewpoint of further improving visibility in the wide-angle direction. Yes, usually 100% or less. The total light transmittance of the optical film can be measured using a haze computer in accordance with JIS K 7361-1: 1997, for example, by the method described in Examples. Since the optical film of the present invention exhibits high total light transmittance, for example, it is necessary to suppress the emission intensity of a display element or the like required to obtain a constant brightness as compared with the case of using a film having low transmittance. Is possible. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is incorporated into an image display device, a bright display tends to be obtained even if the amount of light from the backlight is reduced, which can contribute to energy saving. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance may be the total light transmittance in the range of the thickness of the optical film described later.

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

The tensile elastic modulus of the optical film of the present invention at 25 ° C. makes it easy to improve the visibility in the wide angle direction and the visibility of the projected image of the optical film on which the functional layers are laminated after the heat treatment, and the optical film has dents and the like. From the viewpoint that defects are less likely to occur, it is preferably 5.1 GPa or more, more preferably 5.2 GPa or more, and further preferably 5.3 GPa or more. The tensile elastic modulus is preferably 10 GPa or less, more preferably 9 GPa or less, still more preferably 8 GPa or less, from the viewpoint of easily improving the flexibility of the optical film. The elastic modulus can be measured using a tensile tester (distance between chucks 50 mm, tensile speed 10 mm / min), for example, by the method described in Examples. When the tensile elastic modulus is within the above range, dent defects are less likely to occur in the optical film. In addition, it is easy to suppress a 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, by the method described in Examples. The tensile elastic modulus can be adjusted within the above range, for example, by increasing the draw ratio when producing an optical film, or by using a resin having a preferable structure described later.

The tensile elastic modulus of the optical film of the present invention at 80 ° C. is preferably 4 to 9 GPa, more preferably 4.5 to 8.5 GPa. When the tensile elastic modulus is within the above range, dent defects are less likely to occur in the optical film. The elastic modulus can be measured according to JIS K 7127, for example, by the method described in Examples.

_{The in-plane retardation 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 becomes difficult to obtain a film having excellent optical characteristics. Further, when the in-plane retardation R ₀ exceeds 300 nm, the optical film is likely to be warped and / or delaminated due to heat treatment or the like when laminating the functional layer on the optical film. The in-plane retardation R ₀ is preferably 50 nm or more, more preferably 60 nm or more, still more preferably 70 nm or more from the viewpoint of film surface smoothness, and preferably 290 nm from the viewpoint of lamination with other members. Below, it is more preferably 280 nm or less.
R ₀ can be measured by a phase difference measuring device, for example, by the method described in Examples. The in-plane phase difference R ₀ can be adjusted within the above range by a method using a preferable resin described later, a method of adjusting the draw ratio, or 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 are mathematical formulas (5):
Equation (5):
3 ≤ R _th / R ₀ ≤ 200 ... (5)
It is preferable to satisfy. _{R th} / R ₀ in the formula (5) is preferably 3 or more, more preferably 4 or more, still more preferably 5 or more, preferably 190 or less, more preferably 180 or less, still more preferably 150 or less. .. When R _th / R ₀ is not more than the above lower limit, it is easy to prevent the film from becoming too hard and to prevent cracking when the film is deformed. Further, when R _th / R ₀ is not more than the above upper limit, it is easy to improve the smoothness of the film. _Rth can be measured by a phase difference measuring device, for example, by the method described in Examples.

R _th of the optical film of the present invention is not particularly limited, from the viewpoint of flexibility of the film, preferably 100nm or more, more preferably 300nm or more, even more preferably 500nm or more, in view of the optical visibility From, it is preferably 4,000 nm or less, more preferably 3,900 nm or less, still more preferably 3,800 nm or less.

The YI value, which is an index of the yellowness of the optical film of the present invention, is preferably 4.0 or less, more preferably 3.0 or less, still more preferably 2.5 or less, and further, from the viewpoint of further improving visibility. It is more preferably 2.0 or less, particularly preferably 1.9 or less, and particularly more preferably 1.8 or less. The YI value is preferably -5 or more, more preferably -2 or more. The YI value was measured by measuring the transmittance of light at 300 to 800 nm using an ultraviolet-visible near-infrared spectrophotometer, and the tristimulus values (X, Y, Z) were obtained, and YI = 100 × (1.2769X−). It can be calculated based on the formula of 1.0592Z) / Y.

The number of times the optical film of the present invention is bent is preferably 20,000 times or more, more preferably 100,000 times or more, still more preferably 200,000 times or more, still more preferably 200,000 times or more from the viewpoint of improving the folding resistance. It is 350,000 times or more, particularly preferably 400,000 times or more, particularly more preferably 500,000 times or more, particularly preferably 600,000 times or more, and particularly preferably 700,000 times or more. When the number of times of bending is equal to or more than the above lower limit, cracks and cracks are unlikely to occur even if the optical film is bent. The upper limit of the number of bends is usually 50,000,000 or less. The number of times the optical film is bent can be measured by a MIT folding fatigue resistance test conforming to ASTM standard D2176-16. The MIT fold resistance fatigue test is, for example, the test described in Examples. Further, the optical film of the present invention preferably has high wide-angle visibility even in the optical film after the MIT fold resistance test under the above conditions. For example, the mapability before and after the MIT fold resistance test under the above conditions. It is more preferable that the difference in value and / or the difference in haze is within the range of the difference in mapping property value and / or the difference in haze before and after the bending resistance test.

The thickness of the optical film of the present invention may be appropriately adjusted depending on the intended use, but 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. Below, it is more preferably 150 μm or less, still more preferably 100 μm or less, and even more preferably 85 μm or less. When the thickness of the optical film is within the above range, the tensile elastic modulus and the piercing strength of the optical film can be easily increased. The thickness of the optical film can be measured using a micrometer, for example, by the method described in Examples.

<Polyimide-based resin and polyamide-based resin>
The optical film of the present invention contains at least one resin selected from the group consisting of polyimide-based resins and polyamide-based resins. In the present specification, the polyimide-based resin represents at least one resin selected from the group consisting of a polyimide resin, a polyamide-imide resin, a polyimide precursor resin, and a polyamide-imide precursor resin. The polyimide resin is a resin containing a repeating structural unit containing an imide group, and the polyamide-imide resin is a resin containing a repeating structural unit containing both an imide group and an amide group. The polyimide precursor resin and the polyamide-imide precursor resin are pre-imidization precursors that give the polyimide resin and the polyamide-imide resin by imidization, respectively, and are also called polyamic acids. Further, in the present 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 contain one type of polyimide resin or polyamide-based resin, or may contain two or more types of polyimide-based resin and / or polyamide-based resin in combination. From the viewpoint that the optical film of the present invention can easily increase the tensile elasticity and bending resistance of the optical film, _{easily adjust R 0} to the above range, and easily improve the visibility of the optical film after heat treatment at a high temperature. It preferably contains a polyimide resin, and the polyimide resin is preferably a polyimide resin or a polyamideimide resin, and more preferably a polyamideimide resin.

In a preferred embodiment of the present invention, the tensile elastic modulus and bending resistance of the optical film can be easily increased, R ₀ can be easily adjusted to the above range, and the visibility of the optical film after heat treatment at a high temperature can be easily improved. The polyimide resin and the polyamide resin are preferably aromatic resins. In the present specification, the aromatic resin refers to a resin in which the constituent unit contained in the polyimide resin and the polyamide resin is mainly an aromatic constituent unit.

In the above preferred embodiment, from the viewpoint that the tensile elastic modulus and bending resistance of the optical film can be easily increased, R ₀ can be easily adjusted to the above range, and the visibility of the optical film after heat treatment at a high temperature can be easily improved. The ratio of the structural units derived from the aromatic monomer to all the structural units contained in the polyimide resin and the polyamide resin is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more. , Even 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 the aromatic structure (for example, an aromatic ring). It is a structural unit included in. Examples of the aromatic monomer include an aromatic tetracarboxylic acid compound, an aromatic diamine, and an aromatic dicarboxylic acid.

［式（１）中、Ｙは４価の有機基を表し、Ｘは２価の有機基を表し、＊は結合手を表す］
で表される構成単位を有するポリイミド樹脂であるか、又は、式（１）で表される構成単位及び式（２）：

［式（２）中、Ｚ及びＸは、互いに独立に、２価の有機基を表し、＊は結合手を表す］
で表される構成単位を有するポリアミドイミド樹脂であることが好ましい。また、ポリアミド系樹脂は、式（２）で表される構成単位を有するポリアミド樹脂であることが好ましい。以下において式（１）及び式（２）について説明するが、式（１）についての説明は、ポリイミド樹脂及びポリアミドイミド樹脂の両方に関し、式（２）についての説明は、ポリアミド樹脂及びポリアミドイミド樹脂の両方に関する。 In one preferred embodiment of the present invention, the polyimide resin is represented by the formula (1):

[In formula (1), Y represents a tetravalent organic group, X represents a divalent organic group, and * represents a bond]
It is a polyimide resin having a structural unit represented by, or a structural unit represented by the formula (1) and the formula (2):

[In formula (2), Z and X represent divalent organic groups independently of each other, and * represents a bond]
It is preferable that the polyamide-imide resin has a structural unit represented by. Further, the polyamide resin is preferably a polyamide resin having a structural unit represented by the formula (2). The formulas (1) and (2) will be described below, but the description of the formula (1) relates to both the polyimide resin and the polyamide-imide resin, and the description of the formula (2) describes the polyamide resin and the polyamide-imide resin. Regarding both.

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

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 a cyclic structure and having 4 to 40 carbon atoms. show. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic ring structure, which can easily increase the tensile elastic modulus and bending resistance of the optical film, _{easily adjust R 0} to the above range, and perform optics after heat treatment at a high temperature. From the viewpoint of easily enhancing the visibility of the film, an aromatic ring is preferable. The organic group is an organic group in which the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine, in which case the hydrocarbon group and the hydrocarbon group substituted with fluorine are used. The number of carbon atoms is preferably 1 to 8. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of types of Y, and the plurality of types of Y may be the same as or different from each other. As Y, the following formulas (20), formulas (21), formulas (22), formulas (23), formulas (24), formulas (25), formulas (26), formulas (27), formulas (28) And a group represented by the formula (29); a group in which a hydrogen atom in the groups represented by the formulas (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; In addition, a chain hydrocarbon group having 4 or less valences of 6 carbon atoms is exemplified.

In the formula (20) to (29), * represents a bond, ^{W 1} is 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) represents a 2 -Ar- or _-Ar-SO 2 -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include a phenylene group. When there are a plurality of Ars, the Ars may be the same or different from each other. The hydrogen atom on the ring in the formulas (20) to (29) may be substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified in the formula (3) described later.

Among the groups represented by the formulas (20) to (29), the tensile elastic modulus and bending resistance of the optical film can be easily increased, R ₀ can be easily adjusted to the above range, and the optical film after heat treatment at a high temperature can be easily adjusted. From the viewpoint of easily enhancing the visibility of the above, the group represented by the formula (26), the formula (28) or the formula (29) is preferable, and the group represented by the formula (26) is more preferable. Further, W ¹ is easy to increase 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 a high temperature. from reduced easily viewpoint YI value, independently of one another, preferably a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -Or -C (CF ₃ ) _2- , more preferably 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- , particularly preferably a single bond or -C (CF ₃ ) _2- .

In a preferred embodiment of the present invention, Y in the polyimide resin is preferably represented by the formula (26) in an amount of preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more. Y is the formula within the above range in the polyimide resin (26), preferably ^{W 1} is a single bond, -C _{(CH 3) 2} - or -C _{(CF 3) 2} - a is the formula (26), more preferably When W ¹ is represented by the equation (26) which is a single bond or −C (CF ₃ ) _2−, it is easy to increase the tensile elastic modulus and bending resistance of the optical film, and R ₀ is adjusted to the above range. It is easy to reduce the YI value of the optical film. The ratio of the structural unit in which Y in the polyimide resin is represented by the formula (26) ^{can be measured using, for example, 1 1} H-NMR, or can be calculated from the charging ratio of the raw materials.

［式（４）中、Ｒ^２〜Ｒ^７は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^２〜Ｒ^７に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、Ｖは、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^８）−を表し、Ｒ^８は、水素原子、又はハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、＊は結合手を表す］
で表される基を含む。すなわち、複数の式（１）で表される構成単位中のＹのうち、少なくとも一部のＹが式（４）で表される基であることが好ましい。このような態様であると、光学フィルムの引張弾性率及び耐屈曲性を高めやすく、Ｒ_０を上記の範囲に調整しやすく、光学フィルムのＹＩ値を低減しやすい。なお、式（１）で表される構成単位は、Ｙとして式（４）で表される基を１種又は複数種含んでいてもよい。 In one preferred embodiment of the present invention, the structural unit represented by the formula (1) is Y, and the formula (4):

[In the formula (4), R ^{2 to} R ⁷ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. hydrogen atoms contained in R ² to R ^7, independently of each other, may be substituted with a halogen atom, V is a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - Represents CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- , -S-, -CO- or -N (R ⁸ )-, and R ⁸ Represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom, and * represents a bond.]
Includes groups represented by. That is, it is preferable that at least a part of Y in the structural unit represented by the plurality of formulas (1) is a group represented by the formula (4). In such an embodiment, the tensile elastic modulus and bending resistance of the optical film can be easily increased, R ₀ can be easily adjusted to the above range, and the YI value of the optical film can be easily reduced. The structural unit represented by the formula (1) may contain one or more groups represented by the formula (4) as Y.

In formula (4), R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ are independent of each other, such as a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Represents an aryl group having 6 to 12 carbon atoms. The alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms are the alkyl group having 1 to 6 carbon atoms and carbon ^{in R 3a in the formula (3), respectively.} Examples of the alkoxy group having the number 1 to 6 or the aryl group having the number of carbons 6 to 12 can be mentioned above. ^{Examples of R 3a} in the formula (3) are given above. R ^{2 to} R ⁷ represent independently of each other, preferably a hydrogen atom 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 here, R ² to R 7 The ^{hydrogen atom contained in R 7} may be substituted with a halogen atom independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. V is a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) 2 -, - Represents SO _2- , -S-, -CO- or -N (R ⁸ )-, where R ⁸ is a monovalent hydrocarbon having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Represents a group. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include those exemplified above with respect to ^{R 9 in W in the formula (3) described later.} Among these, the viewpoints that it is easy to improve the tensile elastic modulus, optical characteristics, 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 a high temperature. Therefore, V is preferably a single bond, -O-, -CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- or -C (CF ₃ ) _2- , and is a single bond. , -C (CH ₃ ) _2- or -C (CF ₃ ) _2- , more preferably single bond or -C (CF ₃ ) _2- .

［式（５）中、Ｒ^１８〜Ｒ^２５は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^１８〜Ｒ^２５に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、＊は結合手を表す］
及び／又は式（９）：

［式（９）中、Ｒ^３５〜Ｒ^４０は、互いに独立に、水素原子、炭素数１〜６のアルキル基又は炭素数６〜１２のアリール基を表し、Ｒ^３５〜Ｒ^４０に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、＊は結合手を表す］
で表される。複数の式（１）中のＹの少なくとも一部が式（５）で表される、及び／又は、式（９）で表されると、光学フィルムの引張弾性率及び光学特性を向上させやすい。 In a preferred embodiment of the present invention, at least a part of Y in the plurality of formulas (1) is the formula (5) :.

[In formula (5), R ^{18 to} R ²⁵ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. The ^{hydrogen atoms contained in R 18 to} R ²⁵ may be substituted with halogen atoms independently of each other, and * represents a bond.]
And / or equation (9):

[In the formula (9), R ^{35 to} R ⁴⁰ represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and hydrogen contained in ^{R 35 to} R ^40. Atoms may be substituted with halogen atoms independently of each other, with * representing a bond]
It is represented by. When at least a part of Y in the plurality of formulas (1) is represented by the formula (5) and / or is represented by the formula (9), it is easy to improve the tensile elastic modulus and the optical characteristics of the optical film. ..

In formula (5), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ and R ²⁵ are independent of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and 1 carbon atom. Represents an alkoxy group of ~ 6 or an aryl group of 6-12 carbon atoms. The alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms are the alkyl group having 1 to 6 carbon atoms and carbon ^{in R 3a in the formula (3), respectively.} Examples of the alkoxy group having the number 1 to 6 or the aryl group having the number of carbons 6 to 12 can be mentioned above. R ^{18 to} R ²⁵ represent independently of each other, preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably an hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and here, R ^{18 to} R ^25. The hydrogen atoms contained in may be substituted with 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. R ^{18 to} R ²⁵ are more preferably hydrogen atoms from the viewpoint of easily increasing the tensile elasticity and bending resistance of the optical film and easily increasing the transparency and maintaining the transparency independently of each other. , Methyl group, fluoro group, chloro group or trifluoromethyl group, more preferably R ¹⁸ , R ¹⁹ , R ²⁰ , R ²³ , R ²⁴ and R ²⁵ are hydrogen atoms, R ²¹ and R ²² are hydrogen atoms. , Methyl group, fluoro group, chloro group or trifluoromethyl group, and particularly preferably R ²¹ and R ²² are methyl groups or trifluoromethyl groups.

^{In the formula (9), R 35 to} R ⁴⁰ are preferably hydrogen from the viewpoint of easily increasing the tensile elasticity and bending resistance of the optical film, and easily increasing the transparency and maintaining the transparency. It is an atom 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 further preferably a hydrogen atom. Here, the ^{hydrogen atoms contained in R 35 to} R ⁴⁰ may be substituted with halogen atoms independently of each other, 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 are exemplified above.}

で表される。すなわち、複数のＹの少なくとも一部は、式（５’）及び／又は式（９’）で表される。この場合、光学フィルムの引張弾性率及び耐屈曲性を高めやすい。さらに、式（５）が式（５’）で表される場合、フッ素元素を含有する骨格によりポリイミド系樹脂の溶媒への溶解性を高め、該樹脂を含有するワニスの保管安定性を向上しやすいと共に、該ワニスの粘度を低減しやすく、光学フィルムの加工性を向上しやすい。その結果、数式（１）〜（３）を満たす本発明の光学フィルムを製造しやすい。また、フッ素元素を含有する骨格により、光学フィルムの光学特性を向上しやすい。 In a preferred embodiment of the present invention, formula (5) is represented by formula (5'), and formula (9) is represented by formula (9') :.

It is represented by. That is, at least a part of the plurality of Ys is represented by the formula (5') and / or the formula (9'). In this case, the tensile elastic modulus and bending resistance of the optical film can be easily increased. Further, when the formula (5) is represented by the formula (5'), the skeleton containing a fluorine element enhances the solubility of the polyimide resin in the solvent and improves the storage stability of the varnish containing the resin. In addition to being easy, it is easy to reduce the viscosity of the varnish and improve the processability of the optical film. As a result, it is easy to manufacture the optical film of the present invention satisfying the formulas (1) to (3). Further, the skeleton containing a fluorine element makes it easy to improve the optical characteristics of the optical film.

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, still more preferably 70 mol% or more, according to the formula (5), particularly the formula (5). It is represented by'). When Y in the above range in the polyimide resin is represented by the formula (5), particularly the formula (5'), the skeleton containing a fluorine element enhances the solubility of the polyimide resin in the solvent and contains the resin. It is easy to reduce the viscosity of the varnish, 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 satisfying the mathematical formulas (1) to (3). Further, the skeleton containing a fluorine element makes it easy to improve the optical characteristics of the optical film. It should be noted that preferably, 100 mol% or less of Y in the polyimide resin is represented by the formula (5), particularly the formula (5'). Y in the polyimide resin may be of the formula (5), particularly the formula (5'). The ratio of the structural unit represented by the formula (5) of Y in the polyimide resin ^{can be measured using, for example, 1 1} H-NMR, or can be calculated from the charging ratio of the raw materials.

［式（２０）〜式（２９）中、Ｗ^１は、単結合、−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−又は−Ａｒ−ＳＯ_２−Ａｒ−を表し、ここで、Ａｒは、互いに独立に、水素原子がフッ素原子で置換されていてもよい炭素数６〜２０のアリーレン基（例えばフェニレン基）を表し、＊は結合手を表す］
で表される基の結合手のうち、隣接しない２つが水素原子に置き換わった基及び炭素数６以下の２価の鎖式炭化水素基が例示され、Ｚのヘテロ環構造としてはチオフェン環骨格を有する基が例示される。光学フィルムのＹＩ値を低減しやすい観点、全光線透過率を高めやすい観点及びヘーズを低減しやすい観点から、Ｚにおける環状構造としては、式（２０）〜式（２９）で表される基、及び、チオフェン環骨格を有する基が好ましく、式（２６）、式（２８）及び式（２９）で表される基がより好ましい。 In the formula (2), Z is a divalent organic group, preferably an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms (these groups). The hydrogen atom in the above is a divalent organic group having 4 to 40 carbon atoms, which may be substituted with a halogen atom (preferably a fluorine atom), and more preferably 1 to 6 carbon atoms. Alkyl group, alkoxy group having 1 to 6 carbon atoms, or aryl group having 6 to 12 carbon atoms (the hydrogen atom in these groups may be substituted with a halogen atom (preferably a fluorine atom)). It may be a divalent organic group having a cyclic structure and having 4 to 40 carbon atoms. Examples of an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms include examples relating to ^{R 3a} and R ^{3b in the formula (3) described later.} The same applies. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic ring structure. 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 equation (29):

Wherein (20) to Formula (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-, Represents -Ar-C (CH ₃ ) _2- Ar- or -Ar-SO _2- Ar-, where Ar has 6 to 6 carbon atoms in which hydrogen atoms may be substituted with fluorine atoms independently of each other. Represents 20 allylene groups (eg phenylene groups), * represents a bond]
Among the group bonds represented by, a group in which two non-adjacent groups are replaced with hydrogen atoms and a divalent chain hydrocarbon group having 6 or less carbon atoms are exemplified, and the heterocyclic structure of Z is a thiophene ring skeleton. The group having is exemplified. From the viewpoint of easily reducing the YI value of the optical film, easily increasing the total light transmittance, and easily reducing the haze, the annular structure in Z includes the groups represented by the formulas (20) to (29). A group having a thiophene ring skeleton is preferable, and a group represented by the formulas (26), (28) and (29) is more preferable.

［式（２０’）〜式（２９’）中、Ｗ^１及び＊は、式（２０）〜式（２９）において定義した通りである］
で表される２価の有機基がより好ましい。なお、式（２０）〜式（２９）及び式（２０’）〜式（２９’）における環上の水素原子は、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基（これらの基における水素原子はハロゲン原子（好ましくはフッ素原子）で置換されていてもよい）で置換されていてもよい。 Examples of the organic group of Z include the formula (20'), the formula (21'), the formula (22'), the formula (23'), the formula (24'), the formula (25'), the formula (26'), and the formula. (27'), equation (28') and equation (29'):

In formula (20 ') to formula (29'), ^{W 1} and * are as defined in formula (20) to (29)]
The divalent organic group represented by is more preferable. The hydrogen atom on the ring in the formulas (20) to (29) and the formulas (20') to (29') is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. It may be substituted with an aryl group having 6 to 12 carbon atoms (the hydrogen atom in these groups may be substituted with a halogen atom (preferably a fluorine atom)).

［式（ｄ１）中、Ｒ^４１は、互いに独立に、後述する式（３）中のＲ^３ａについて定義する基又は水素原子であり、Ｒ^４２は、Ｒ^４１又は−Ｃ（＝Ｏ）−＊を表し、＊は結合手を表す］
で表されるカルボン酸由来の構成単位をさらに有することが、ワニスの成膜性を高めやすく、光学フィルムの均一性を高めやすい観点から好ましい。構成単位（ｄ１）としては、具体的には、Ｒ^４１及びＲ^４２がいずれも水素原子である構成単位（ジカルボン酸化合物に由来する構成単位）、Ｒ^４１がいずれも水素原子であり、Ｒ^４２が−Ｃ（＝Ｏ）−＊を表す構成単位（トリカルボン酸化合物に由来する構成単位）等が挙げられる。 When the polyamide-based resin or the polyamide-imide resin has a structural unit in which Z in the formula (2) is represented by any of the above formulas (20') to (29'), among them, in the formula (2). When Z has a structural unit represented by the formula (3') described later, the polyamide-based resin or the polyamide-imide resin is added to the structural unit and has the following formula (d1):

[In the formula (d1), R ⁴¹ is a group or a hydrogen atom that defines ^{R 3a} in the formula (3) described later independently of each other ^{, and R 42} is R ⁴¹ or −C (= O) − *. Represents, * represents a bond]
It is preferable to further have a carboxylic acid-derived structural unit represented by (1) from the viewpoint of easily improving the film-forming property of the varnish and easily improving the uniformity of the optical film. Specifically, as the structural unit (d1), R ⁴¹ and R ⁴² are both hydrogen atoms (constituent units derived from the dicarboxylic acid compound), and R ⁴¹ is both hydrogen atoms, and R ^42. Examples thereof include a structural unit (a structural unit derived from a tricarboxylic acid compound) representing −C (= O) − *.

［式（３）中、Ｒ^３ａ及びＲ^３ｂは、互いに独立に、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基を表し、Ｒ^３ａ及びＲ^３ｂに含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、Ｗは、互いに独立に、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^９）−を表し、Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、ｓは０〜４の整数であり、ｔは０〜４の整数であり、ｕは０〜４の整数であり、＊は結合手を表す］
、より好ましくは式（３’）：

［式（３’）中、Ｒ^３ａ、Ｒ^３ｂ、ｓ、ｔ、ｕ、Ｗ及び＊は、式（３）において定義した通りである］
で表される構成単位を少なくとも有することが好ましい。なお、本明細書において、ポリアミド系樹脂又はポリアミドイミド樹脂が式（２）中のＺが式（３）で表される構成単位を有することと、ポリアミド系樹脂又はポリアミドイミド系樹脂が式（２）中のＺとして式（３）で表される構造を有することとは、同様の意味を有し、ポリアミド系樹脂又はポリアミドイミド樹脂に含まれ得る複数の式（２）で表される構成単位のうち、少なくとも一部の構成単位におけるＺが式（３）で表されることを意味する。当該記載は、他の同様の記載にもあてはまる。 The polyamide-based resin or the polyamide-imide 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 as or different from each other. In particular, from the viewpoint of easily increasing the tensile elastic modulus of the optical film of the present invention and easily increasing the optical characteristics, Z in the formula (2) is preferably used in the formula (3):

[In the formula (3), R ^3a and R ^3b independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and R ^3a. and hydrogen atoms contained in ^{R 3b} are each independently may be substituted with a halogen atom, W is, independently of one another, 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 monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom, s is an integer of 0 to 4, and t is an integer of 0 to 4. u is an integer from 0 to 4, and * represents a bond]
, More preferably equation (3'):

[In equation (3'), R ^3a , R ^3b , s, t, u, W and * are as defined in equation (3)]
It is preferable to have at least a structural unit represented by. In the present specification, the polyamide-based resin or the polyamide-imide resin has a structural unit in which Z in the formula (2) is represented by the formula (3), and the polyamide-based resin or the polyamide-imide-based resin has the formula (2). ) Has the same meaning as having a structure represented by the formula (3) as Z in (), and is a structural unit represented by a plurality of formulas (2) that can be contained in the polyamide-based resin or the polyamide-imide resin. Of these, it means that Z in at least a part of the constituent units is represented by the equation (3). This statement also applies to other similar statements.

In formulas (3) and (3 '), W, independently of one another, 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 )-, preferably from the viewpoint of bending resistance of the optical film. It represents −O− or −S−, more preferably −O−.
R ^3a and R ^3b independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group and 2-methyl-. Butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group and the like can be mentioned. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group and a cyclohexyloxy group. Can be mentioned. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xsilyl group, a naphthyl group, a biphenyl group and the like. From the viewpoint of tensile elasticity, surface hardness and flexibility of the optical film, and from the viewpoint of easily improving the visibility of the optical film after heat treatment at a high temperature, R ^3a and R ^3b are independent of each other, preferably having 1 carbon atom. It represents an alkyl group of to 6 or an alkoxy group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. 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 monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group and n-pentyl group. 2-Methyl-butyl group, 3-methyl-butyl group, 2-ethyl-propyl group, n-hexyl group, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group Etc., and these may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

In the formula (3) and the formula (3'), t and u are independently integers of 0 to 4, preferably an integer of 0 to 2, and more preferably 1 or 2.

In the formula (3) and the formula (3'), s is an integer in the range of 0 to 4, and when s is in this range, the tensile elastic modulus and bending resistance of the optical film can be easily improved. The s is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, and still more preferably 0 or 1, from the viewpoint of more easily improving the tensile elastic modulus and bending resistance of the optical film. Even more preferably, it is 0. The polyamide-imide resin or the polyamide-based resin may contain one or more structural units represented by the formula (3) or the formula (3') in Z.

In a preferred embodiment of the present invention, from the viewpoint of improving the tensile elastic modulus, elastic modulus and flexural modulus of the optical film and reducing the YI value, Z has s of 0 and u is preferably 1 to 1. It is preferably represented by the formula (3) or the formula (3'), which is 3, more preferably 1 or 2. Furthermore, in addition to the structural unit represented by the formula (3) in which s is 0 or the structural unit represented by the formula (2) having Z represented by the formula (3'), it is represented by the above formula (d1). It is also preferred to have additional building blocks.

When the polyamide-imide resin or the polyamide-based resin has a structural unit represented by the formula (3) or the formula (3'), the ratio thereof is the configuration represented by the formula (1) of the polyamide-imide resin or the polyamide-based resin. When the total of the units and the constituent units represented by the formula (2) is 100 mol%, it is preferably 20 mol% or more, more preferably 30 mol% or more, still more preferably 40 mol% or more, still more preferably. It is 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less. When the ratio of the structural units represented by the formula (3) or the formula (3') is equal to or higher than the above lower limit, the tensile elastic modulus and bending resistance of the optical film can be easily increased, and the optics after the heat treatment at a high temperature can be easily increased. It is easy to improve the visibility of the film. When the ratio of the constituent units represented by the formula (3) or the formula (3') is not more than the above upper limit, the increase in the viscosity of the resin-containing varnish due to the hydrogen bond between the amide bonds derived from the formula (3) is suppressed, and the film is formed. It is easy to improve the workability of. The ratio of the structural units represented by the formula (1), the formula (2), the formula (3) or the formula (3') ^{can be measured by using, for example, 1 1} H-NMR, or the raw material is charged. It can also be calculated from the ratio.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, still more preferably 50 mol% of Z in the polyamide-imide resin or the polyamide-based resin. % Or more is a structural unit represented by the formula (3) or the formula (3') in which s is 0 to 4. When the above lower limit of Z or more is a structural unit represented by the formula (3) or the formula (3') in which s is 0 to 4, it is easy to increase the tensile elastic modulus and the bending resistance of the optical film, and , It is easy to improve the visibility of the optical film after heat treatment at high temperature. Further, 100 mol% or less of Z in the polyamide-imide resin or the polyamide-based resin may be a structural unit represented by the formula (3) or the formula (3') in which s is 0 to 4. The ratio of the structural units represented by the formula (3) or the formula (3') in which s is 0 to 4 in the resin ^{can be measured by using, for example, 1 1} H-NMR, or the raw material. It can also be calculated from the charge ratio.

In formulas (1) and (2), X is a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms, more preferably a cyclic structure having 4 to 40 carbon atoms, independently of each other. Represents a divalent organic group of. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure. In the organic group, the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine, in which case the number of carbon atoms of the hydrocarbon group and the hydrocarbon group substituted with fluorine is preferable. Is 1 to 8. In one embodiment of the present invention, the polyamide resin and the polyimide resin of the present invention may contain a plurality of types of X, and the plurality of types of X may be the same as or different from each other. X is represented by the formula (10), the formula (11), the formula (12), the formula (13), the formula (14), the formula (15), the formula (16), the formula (17) and the formula (18). Groups; Groups in which the hydrogen atom in the groups represented by the formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain having 6 or less carbon atoms. The formula hydrocarbon group is exemplified.

In equations (10) to (18), * represents a bond,
V ^{1, V 2} and ^{V 3} independently of one another, a single _{bond, -O -, - S -,} - CH 2 -, - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH ₃ ) _{Represents 2-} , -C (CF ₃ ) _2- , -SO _2- , -CO- or -N (Q)-. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include the groups mentioned above for R ^9.
In one 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 positions of V 1} and V ² with respect to each ring and the bonding positions of V ² and V ³ with respect to each ring are independent of each other, preferably in the meta position or para position with respect to each ring, and more preferably in the para position. It is a place.

Among the groups represented by the formulas (10) to (18), the formulas (13), the formula (14), the formula (15), and the formula ( The groups represented by the formulas (16) and (17) are preferable, and the groups represented by the formulas (14), (15) and (16) are more preferable. Further, V ¹ , V ² and V ³ are independent of each other, preferably single bond, -O- or -S-, more preferably single bond or, from the viewpoint of easily increasing the tensile elastic modulus and flexibility of the optical film. -O-.

［式（５）中、Ａｒ^２は互いに独立に置換基を有していてもよい２価の芳香族基を表し、Ｖは、単結合、−Ｏ−、ジフェニルメチレン基、フルオレニル基、炭素数１〜１２の２価の炭化水素基、−ＳＯ_２−、−Ｓ−、−ＣＯ−、−ＰＯ−、−ＰＯ_２−、−Ｎ（Ｒ^ａ）−又は−Ｓｉ（Ｒ^ｂ）_２−を表し、ここで、該炭化水素基は脂環式構造を含んでいてもよく、該炭化水素基に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、Ｒ^ａ及びＲ^ｂは、互いに独立に、水素原子、又はハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、ｍは０〜３の整数を表し、＊は結合手を表す］
で表される２価の有機基を含む。構成単位（１）及び構成単位（２）が、Ｘとして式（５）で表される２価の有機基を含む場合、構成単位（１）及び構成単位（２）は、Ｘとして、式（５）で表される１種類又は２種類以上の２価の有機基を含んでよい。構成単位（１）及び構成単位（２）は、Ｘとして、式（５）で表される２価の有機基の他に、式（５）で表される２価の有機基に該当しない他の２価の有機基を含んでいてもよい。 In a preferred embodiment of the present invention, the polyamide-based resin and / or the polyimide-based resin is represented by X in the formula (1) or X in the formula (2), and the formula (5):

[In formula (5), Ar ² represents a divalent aromatic group which may have a substituent independently of each other, and V is a single bond, —O—, a diphenylmethylene group, a fluorenyl group, and the number of carbon atoms. 1 to 12 divalent hydrocarbon groups, -SO _2- , -S-, -CO-, -PO-, -PO _2- , -N ( ^Ra )-or -Si (R ^b ) _2- Represented here, the hydrocarbon group may contain an alicyclic structure, and the hydrogen atoms contained in the hydrocarbon group may be independently substituted with halogen atoms, ^Ra and R. ^b represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom independently of each other, m represents an integer of 0 to 3, and * represents a bond. show]
Contains a divalent organic group represented by. When the structural unit (1) and the structural unit (2) include a divalent organic group represented by the formula (5) as X, the structural unit (1) and the structural unit (2) are represented by the formula (X). It may contain one kind or two or more kinds of divalent organic groups represented by 5). The structural unit (1) and the structural unit (2) are, as X, a divalent organic group represented by the formula (5) and a non-divalent organic group represented by the formula (5). It may contain a divalent organic group of.

^{Ar 2} in the formula (5) represents a divalent aromatic group which may have a substituent. A divalent aromatic group is a group in which two hydrogen atoms of a monocyclic aromatic ring, a condensed polycyclic aromatic ring, or a ring-assembled aromatic ring are replaced by a bond. The divalent aromatic group may contain an aromatic ring in which a ring (single ring, condensed polycycle or ring assembly) is formed only by carbon atoms, or a ring is formed by containing atoms other than carbon atoms. It may contain a heteroaromatic 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 to 18, more preferably 5 to 14, and even more preferably 5 to 12. Ar ² there are a plurality if m in the formula (5) is 1 or more, may be identical to one another or may be different.

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

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

Examples of the ring-assembled aromatic ring include a structure in which two or more monocyclic aromatic rings and / or fused polycyclic aromatic rings are connected by a single bond, and an example thereof is a monocyclic aromatic ring. Alternatively, as an example of a fused polycyclic aromatic ring, a group in which two or more of the rings described above are linked by a single bond, for example, biphenyl, terphenyl, quaterphenyl, binaphthyl, 1-phenylnaphthalene, 2-phenylnaphthalene, Bipyridine and the like can be mentioned.

From the viewpoint of easily increasing the tensile elasticity of the optical film, the divalent aromatic group which may have a substituent is preferably two aromatic hydrocarbon rings which may have a substituent. A group in which a hydrogen atom is replaced by a bond, more preferably a group in which two hydrogen atoms of benzene, biphenyl, terphenyl or quaterphenyl, which may have a substituent, are replaced in a bond, more preferably. It is a group in which two hydrogen atoms of benzene or biphenyl, which may have a substituent, are replaced with a bond.

As ^{the substituent in Ar 2} , a halogen group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, or a hydrogen atom contained therein is a halogen atom. Substituted groups can be mentioned.

The alkyl group having 1 to 12 carbon atoms may be a linear or branched alkyl group having 1 to 12 carbon atoms, preferably a linear or branched alkyl group having 1 to 6 carbon atoms. be. Examples of such groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl-butyl group, 3 Examples thereof include -methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group and n-decyl group.

Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group and a cyclohexyloxy group. Can be mentioned.

Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xsilyl group, a naphthyl group, a biphenyl group and the like.

Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

As ^{the substituent in Ar 2} , a halogen group or an alkyl group having 1 to 12 carbon atoms in which the hydrogen atom may be substituted with a halogen atom is preferable, and a methyl group, a fluoro group, a chloro group or a trifluoromethyl group is preferable. More preferred.

V in the formula (5) is a single bond, -O-, a diphenylmethylene group, a fluorenyl group, a divalent hydrocarbon group having 1 to 12 carbon atoms, -SO _2- , -S-, -CO-,-. It represents PO −, −PO ₂₋ , −N ( ^Ra ) − or −Si (R ^b ) ₂₋ . Here, the hydrocarbon group may contain an alicyclic structure, and the hydrogen atoms contained in the hydrocarbon group may be substituted with halogen atoms independently of each other, and ^Ra and R ^b are Represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom independently of each other. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group and an n-pentyl group. 2-Methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group, cyclopentyl group , Cyclohexyl group and the like, which may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. V in the formula (5) is preferably a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms and their hydrocarbons from the viewpoint of easily improving the tensile elasticity and bending resistance of the optical film. A group in which at least a part of hydrogen atoms contained in the group is substituted with a halogen atom, 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 single bond, -C (CH ₃ ) _2- or -C (CF ₃ ) _2- , even more preferably single bond or -C (CF ₃ ) _2- .

M in the formula (5) represents an integer of 0 to 3, and is preferably 0 to 2, more preferably 0 or 1, and even more preferably 1 from the viewpoint of easily increasing the tensile elastic modulus of the optical film.

The structural unit (1) and / or the structural unit (2) that can be contained in the polyamide resin and / or the polyimide resin contained in the optical film of the present invention is a divalent group represented by the formula (5) as X. In a preferred embodiment of the present invention containing an organic group, the formula (1) is set to 100 mol% when the total of the structural units (1) and the structural units (2) is 100 mol% from the viewpoint of easily increasing the tensile elasticity of the optical film. The total of the structural units in which X is a divalent organic group represented by the formula (5) and the structural units in which X in the formula (2) is a divalent organic group represented by the formula (5). The ratio is preferably 70 to 100 mol%, more preferably 80 to 100 mol%, still more preferably 90 to 100 mol%, and in all the constituent units of the constituent unit (1) and the constituent unit (2), X is It may be a divalent organic group represented by the formula (5).

［式（５ａ）中、Ｒ^２は、炭素数１〜１２のフルオロアルキル基を表し、ｐ及びｑは、互いに独立に、１〜４の整数を表し、ただし、ｐ及び／又はｑが２〜４の整数を表す場合に複数存在するＲ^２は、互いに同一であってもよく、異なっていてもよく、＊は結合手を表す］
で表される２価の有機基を含む。なお、式（５ａ）で表される２価の有機基は、式（５）で表される２価の有機基に包含される基であり、具体的には、式（５）中のＶが単結合を表し、Ａｒ^２が炭素数１〜１２のフルオロアルキル基（Ｒ^２）で置換されたベンゼン環を表し、ｍが０〜３の整数を表す２価の有機基に相当する基である。構成単位（１）及び構成単位（２）が、Ｘとして式（５ａ）で表される２価の有機基を含む場合、構成単位（１）及び構成単位（２）は、Ｘとして、式（５ａ）で表される１種類又は２種類以上の２価の有機基を含んでよい。構成単位（１）及び／又は構成単位（２）は、Ｘとして、式（５ａ）で表される２価の有機基の他に、式（５ａ）で表される２価の有機基に該当しない他の２価の有機基を含んでいてもよい。 In a preferred embodiment of the present invention, the structural unit represented by the formula (1) and / or the structural unit represented by the formula (2) is represented by the formula X from the viewpoint of easily increasing the tensile elastic modulus of the optical film. (5a):

[In formula (5a), R ² represents a fluoroalkyl group having 1 to 12 carbon atoms, p and q represent integers 1 to 4 independently of each other, where p and / or q are 2 to 2. R ² is more present when representing an integer of 4 may be the same as each other or different, * represents a bond]
Contains a divalent organic group represented by. The divalent organic group represented by the formula (5a) is a group included in the divalent organic group represented by the formula (5), and specifically, V in the formula (5). Represents a single bond, Ar ^{2 represents a benzene ring substituted with a fluoroalkyl group (R 2} ) having 1 to 12 carbon atoms, and m is a group corresponding to a divalent organic group representing an integer of 0 to 3. be. When the structural unit (1) and the structural unit (2) include a divalent organic group represented by the formula (5a) as X, the structural unit (1) and the structural unit (2) are represented by the formula (X). It may contain one kind or two or more kinds of divalent organic groups represented by 5a). The structural unit (1) and / or the structural unit (2) correspond to a divalent organic group represented by the formula (5a) in addition to the divalent organic group represented by the formula (5a) as X. It may contain other divalent organic groups that do not.

^{R 2} in the formula (5a) represents a fluoroalkyl group having 1 to 12 carbon atoms. A fluoroalkyl group having 1 to 12 carbon atoms is a group in which at least one hydrogen atom of a linear or branched alkyl group having 1 to 12 carbon atoms is substituted with a fluorine atom. Examples of the linear or branched fluoroalkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group. n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group and n- Examples thereof include a group in which at least one hydrogen atom in a decyl group is replaced with a fluorine atom. Specific examples of the fluoroalkyl group having 1 to 12 carbon atoms include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a pentafluoroethyl group, and a heptafluoro. Examples thereof include a propyl group and a nonafluorobutyl group. The fluoroalkyl group preferably has 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2.

p and q represent integers 1 to 4 independently of each other. 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 from the viewpoint of easily increasing the tensile elastic modulus of the optical film. Here, if p and / or q is an integer of 2 to 4, R ² existing in plural, may be the same as each other, but may be different, R ² are identical to each other there are a plurality of Is preferable.

The positions of the two bonds in the formula (5a) are not particularly limited and may be in the ortho position, the meta position, or the para position, but from the viewpoint of easily increasing the tensile elastic modulus of the optical film. , The joints are preferably located in para positions with each other.

As a preferable example of the divalent aromatic group represented by the formula (5a), R ² in the formula (5a) represents a perfluoroalkyl group having 1 to 12 carbon atoms, p is 2 and q is 1. Or two, and / or aromatic groups in which the two binding hands are located in para positions with respect to 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 is preferably a divalent organic group represented by the formula (5a) as X. In one embodiment, from the viewpoint of easily increasing the tensile elasticity of the optical film, when the total of the structural units (1) and the structural units (2) contained in the polyamide-imide resin is 100 mol%, the formula (1) The total of the structural units in which X is a divalent organic group represented by the formula (5a) and the structural units in which X in the formula (2) is a divalent organic group represented by the formula (5a). The ratio is preferably 70 to 100 mol%, more preferably 80 to 100 mol%, still more preferably 90 to 100 mol%, and in all the constituent units of the constituent unit (1) and the constituent unit (2), X is It may be a divalent organic group represented by the formula (5a).

［式（４）中、Ｒ^１０〜Ｒ^１７は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^１０〜Ｒ^１７に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、＊は結合手を表す］
で表される構造を含む。式（１）及び式（２）で表される複数の構成単位中のＸの少なくとも一部が式（４）で表される構造であると、光学フィルムの引張弾性率及び透明性を高めやすい。 In a preferred embodiment of the present invention, the polyamide-based resin and the polyimide-based resin are represented by X in the formula (1) or X in the formula (2), and the formula (4):

[In formula (4), R ^{10 to} R ¹⁷ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. The ^{hydrogen atoms contained in R 10 to} R ¹⁷ may be substituted with halogen atoms independently of each other, and * represents a bond.]
Includes the structure represented by. When at least a part of X in the plurality of structural units represented by the formulas (1) and (2) has a structure represented by the formula (4), the tensile elastic modulus and transparency of the optical film can be easily increased. ..

In formula (4), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ are independent of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and 1 carbon atom. Represents an alkoxy group of ~ 6 or an aryl group of 6-12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms in the formula (3). Examples thereof include groups exemplified as groups or aryl groups having 6 to 12 carbon atoms. R ^{10 to} R ¹⁷ represent independently of each other, preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably an hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and here, R ^{10 to} R ¹⁷ The hydrogen atoms contained in may be substituted with 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. R ^{10 to} R ¹⁷ are more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, independently of each other, from the viewpoint of tensile elasticity, transparency and bending resistance of the optical film. Even 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 groups, fluoro groups, chloro groups or trifluoromethyl groups. Particularly preferably, R ¹¹ and R ¹⁷ are methyl groups or trifluoromethyl groups.

で表される構成単位であり、すなわち、式（１）及び式（２）で表される複数の構成単位中のＸの少なくとも一部は、式（４’）で表される構成単位である。この場合、フッ素元素を含有する骨格によりポリイミド系樹脂又はポリアミド系樹脂の溶媒への溶解性を高め、該樹脂を含有するワニスの保管安定性を向上しやすいと共に、該ワニスの粘度を低減しやすく、光学フィルムの加工性を向上しやすい。その結果、数式（１）〜数式（３）を満たす本発明の光学フィルムを製造しやすい。また、フッ素元素を含有する骨格により、光学フィルムの光学特性を向上しやすい。 In one preferred embodiment of the present invention, the structural unit represented by the formula (4) is the formula (4'):

That is, at least a part of X in the plurality of structural units represented by the equations (1) and (2) is the structural unit represented by the equation (4'). .. In this case, the skeleton containing a fluorine element enhances the solubility of the polyimide resin or the polyamide resin in the solvent, and it is easy to improve the storage stability of the varnish containing the resin, and it is easy to reduce the viscosity of the varnish. , It is easy to improve the workability of the optical film. As a result, it is easy to manufacture the optical film of the present invention satisfying the mathematical formulas (1) to (3). Further, the skeleton containing a fluorine element makes it easy to improve the optical characteristics of the optical film.

In a preferred embodiment of the present invention, the formula (4) is preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more of X that can be contained in the polyimide resin or the polyamide resin. ), Especially expressed by equation (4'). When X in the above range in the polyimide resin or the polyamide resin is represented by the formula (4), particularly the formula (4'), the obtained optical film is dissolved in the solvent of the resin by the skeleton containing a fluorine element. It is easy to improve the properties, improve the storage stability of the varnish containing the resin, easily reduce the viscosity of the varnish, and easily produce the optical film of the present invention satisfying the formulas (1) to (3). Further, the skeleton containing a fluorine element makes it easy to improve the optical characteristics of the optical film. It should be noted that preferably, 100 mol% or less of X in the polyimide resin or the polyamide resin is represented by the formula (4), particularly the formula (4'). X in the resin may be of formula (4), especially of formula (4'). The ratio of the structural unit represented by the formula (4) of X in the resin ^{can be measured by using, for example, 1 1} H-NMR, or can be calculated from the charging ratio of the raw materials.

The polyimide-based resin may contain a structural unit represented by the formula (30) and / or a structural unit represented by the formula (31), and may also include the structural unit represented by the formula (1) and, in some cases, the formula (2). In addition to the structural unit represented by the formula (30), the structural unit represented by the formula (30) and / or the structural unit represented by the formula (31) may be included.

In the formula (30), Y ¹ is a tetravalent organic group, preferably an organic group in which the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of Y ¹ include formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and A group represented by the formula (29), a group in which a hydrogen atom in the groups represented by the formulas (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a group. A chain hydrocarbon group having a tetravalent carbon number of 6 or less is exemplified. In one embodiment of the present invention, a polyimide resin may include a plurality of kinds of Y ^1, Y ¹ of the plurality of kinds may be the same as each other or may be different.

In the formula (31), Y ² is a trivalent organic group, preferably an organic group in which the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of Y ² include the above equations (20), (21), (22), (23), (24), (25), (26), (27), and (28). ) And a group in which any one of the bonds of the group represented by the formula (29) is replaced with a hydrogen atom, and a chain hydrocarbon group having a trivalent carbon number of 6 or less are exemplified. In one embodiment of the present invention, a polyimide resin may include a plurality of kinds of Y ^2, Y ² a plurality of species may be the same as each other or may be different.

In formulas (30) and (31), X ¹ and X ² are divalent organic groups independently of each other, and preferably a hydrocarbon group in which a hydrogen atom in the organic group is substituted with a hydrocarbon group or fluorine. It is an organic group that may be substituted with. Examples of X ¹ and X ² include the above equations (10), (11), (12), (13), (14), (15), (16), (17) and A group represented by the formula (18); a group in which a hydrogen atom in the groups represented by the formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; A chain hydrocarbon group having 6 or less carbon atoms is exemplified.

In one embodiment of the present invention, the polyimide-based resin has a structural unit represented by the formulas (1) and / or the formula (2), and optionally a configuration represented by the formulas (30) and / or the formula (31). It consists of units. Further, from the viewpoint that the tensile elastic modulus, optical characteristics and bending resistance of the optical film can be easily improved, and the visibility of the optical film after heat treatment at a high temperature can be easily improved, the above-mentioned polyimide-based resin has the formulas (1) and the formula. The proportion of the structural units represented by (2) is preferably 80 mol based on the formulas (1) and (2) and, optionally, all the structural units represented by the formulas (30) and (31). % Or more, more preferably 90 mol% or more, still more preferably 95 mol% or more. In the polyimide resin, the proportions of the structural units represented by the formulas (1) and (2) are the formulas (1) and (2), and in some cases, the formulas (30) and / or the formula (31). It is usually 100% or less with respect to the total of all the constituent units represented by. The above ratio can be measured using, for example, ^{1 1} H-NMR, or can be calculated from the raw material charging ratio.

In one embodiment of the present invention, the content of the polyimide resin and / or the polyamide resin in the optical film is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, based on 100 parts by mass of the optical film. It is more preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, and more preferably 95 parts by mass or less. When the content of the polyimide resin and / or the polyamide resin is within the above range, the tensile elastic modulus, optical characteristics, and bending resistance of the optical film can be easily improved. In addition, it is easy to improve the visibility of the optical film after the heat treatment at a high temperature.

The weight average molecular weight of the polyimide resin and the polyamide resin is preferably 100,000 or more, more preferably 130,000 or more, and further preferably 130,000 or more in terms of standard polystyrene from the viewpoint of easily increasing the tensile elastic modulus and bending resistance of the optical film. It is preferably 150,000 or more, even more preferably 170,000 or more, particularly preferably 200,000 or more, particularly more preferably 230,000 or more, particularly preferably 250,000 or more, and particularly preferably 260,000 or more. be. The weight average molecular weight of the polyimide resin and the polyamide resin is preferably 1,000,000 from the viewpoint that the solubility of the resin in a solvent is easily improved and the stretchability and processability of the optical film are easily improved. Below, more preferably 800,000 or less, still more preferably 700,000 or less, even more preferably 500,000 or less, particularly preferably 400,000 or less, particularly more preferably 350,000 or less, especially still more preferably 300, It is 000 or less. The weight average molecular weight can be determined by, for example, GPC measurement and standard polystyrene conversion, and may be calculated by, for example, the method described in Examples. When the weight average molecular weight (Mw) of the polyimide resin and the polyamide resin is not more than the above upper limit, it is easy to increase the solid content of the varnish containing the resin and to reduce the viscosity of the varnish. It becomes easy to manufacture the optical film of the present invention satisfying (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 the formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol, with respect to 1 mol of the structural unit represented by the formula (1). More than mol, more preferably 1.0 mol or more, even more preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, still more preferably 4.5 mol or less. be. When the content of the structural unit represented by the formula (2) is at least the above lower limit, the tensile elastic modulus of the optical film can be easily increased. Further, when the content of the structural unit represented by the formula (2) is not more than the above upper limit, the thickening due to the hydrogen bond between the amide bonds in the formula (2) is suppressed, and the optical film is produced. Since the viscosity of the varnish is easily lowered, it is easy to manufacture the optical film of the present invention satisfying the formulas (1) to (3).

In a preferred embodiment of the present invention, the polyimide resin and / or the polyamide resin contained in the optical film may contain a halogen atom such as a fluorine atom which can be introduced by, for example, the above-mentioned fluorine-containing substituent or the like. .. When the polyimide resin and / or the polyamide resin contains a halogen atom, the tensile elastic modulus of the optical film can be easily improved and the YI value can be easily reduced. When the tensile elastic modulus of the optical film is high, it is easy to suppress the occurrence of scratches and wrinkles, and it is easy to improve the visibility of the optical film after heat treatment at a particularly high temperature. Further, when the YI value of the optical film is low, it becomes easy to improve the transparency and visibility of the film. The halogen atom is preferably a fluorine atom. Preferred fluorine-containing substituents for containing a fluorine atom in the polyimide resin include, for example, a fluoro group and a trifluoromethyl group.

The content of halogen atoms in the polyimide resin and the polyamide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, still more preferably 5 to 40% by mass, based on the mass of the polyimide resin and the polyamide resin, respectively. It is 5 to 30% by mass. When the content of the halogen atom is at least the above lower limit, the tensile elastic modulus of the optical film can be more easily improved and the YI value can be more easily reduced. As a result, it is easy to improve the visibility of the optical film especially after the heat treatment at a high temperature. When the content of halogen atoms is not more than the above upper limit, synthesis becomes easy.

The imidization ratio of the polyimide resin and the polyamide-imide resin is preferably 90% or more, more preferably 93% or more, still more preferably 96% or more. From the viewpoint of easily improving the optical characteristics of the optical film, the imidization ratio is preferably at least the above lower limit. The upper limit of the imidization rate is 100% or less. The imidization ratio indicates the ratio of the molar amount of the imide bond in the polyimide resin to twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin. When the polyimide resin contains a tricarboxylic acid compound, the value is twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin, and the molar amount of the structural unit derived from the tricarboxylic acid compound. The ratio of the molar amount of the imide bond in the polyimide-based resin to the total of the above is shown. The imidization rate can be determined by an IR method, an NMR method, or the like.

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

(Resin manufacturing method)
The method for producing the polyimide resin and the polyamide resin contained in the optical film of the present invention is not particularly limited. The polyimide resin and the polyimide precursor resin can be produced, for example, using a tetracarboxylic acid compound and a diamine compound as main raw materials, and the polyamide-imide resin and the polyamide-imide precursor resin can be produced, for example, by a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound. Can be produced as a main raw material, and the polyamide resin can be produced, for example, using a diamine compound and a dicarboxylic acid compound as the main raw materials.

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

Examples of the diamine compound used in the production of the resin include aliphatic diamines, aromatic diamines and mixtures thereof. In addition, in this embodiment, "aromatic diamine" represents a diamine in which an amino group is directly bonded to an aromatic ring, and an aliphatic group or other substituent may be contained in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferably exemplified. Further, the "aliphatic diamine" represents a diamine in which an amino group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be contained as a part of the structure thereof.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornanediamine and 4,4'. − Examples include cyclic aliphatic diamines such as diaminodicyclohexylmethane. These can be used alone or in combination of two or more.

Examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylene diamine, p-xylylene diamine, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene and the like. , 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'- Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4) -Aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 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'-diaminodiphenyl (with TFMB) (May be described), 4,4'-bis (4-aminophenoxy) biphenyl, 9,9-bis (4-aminophenyl) fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene , 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9,9-bis (4-amino-3-fluorophenyl) fluorene, and other aromatic diamines having two or more aromatic rings. These can be used alone or in combination of two or more.

The aromatic diamines are preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3 , 3'-diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 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'-diaminodiphenyl (TFMB), 4,4'-bis (4-aminophenoxy) biphenyl, more preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl. Propane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, 2,2- Bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB), 4,4'- Biphenyl (4-aminophenoxy) biphenyl. These can be used alone or in combination of two or more.

Among the above diamine compounds, it is selected from the group consisting of aromatic diamines having a biphenyl structure from the viewpoint of easily increasing the tensile elastic modulus, transparency, flexibility and bending resistance of the optical film and easily reducing the YI value. It is preferable to use seeds or more. One selected from the group consisting of 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, 4,4'-bis (4-aminophenoxy) biphenyl and 4,4'-diaminodiphenyl ether. It is more preferable to use the above, and it is even more preferable to use 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB).

Examples of the tetracarboxylic acid compound used in the production of the resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic acid dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic acid dianhydride. Be done. The tetracarboxylic acid compound may be used alone or in combination of two or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound in addition to dianhydride.

Specific examples of the aromatic tetracarboxylic acid dianhydride include a non-condensed polycyclic aromatic tetracarboxylic acid dianhydride, a monocyclic aromatic tetracarboxylic acid dianhydride, and a condensed polycyclic aromatic tetra. Examples include carboxylic acid dianhydride. Examples of the non-condensation polycyclic aromatic tetracarboxylic acid dianhydride include 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, and 2,2. ', 3,3'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (sometimes referred to as BPDA), 2,2', 3,3 '-Biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2, 2-Bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4'-(hexafluoroisopropyridene) diphthalic acid Dianhydride (sometimes referred to 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) diphthalic acid dianhydride, 4,4'-(m-phenylenedioxy) diphthalide Acid dianhydride can be mentioned. Examples of the monocyclic aromatic tetracarboxylic acid dianhydride include 1,2,4,5-benzenetetracarboxylic acid dianhydride, and the condensed polycyclic aromatic tetracarboxylic acid dianhydride. Examples thereof include 2,3,6,7-naphthalenetetracarboxylic acid dianhydride.

Among these, preferably 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride. Anhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic hydride, 3,3', 4,4'-diphenyl Sulfontetracarboxylic acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2- Bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA), 1,2-bis (2,3-dicarboxyphenyl) Etan 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-) Phenylene dioxy) diphthalic acid dianhydride and 4,4'-(m-phenylenedioxy) diphthalic acid dianhydride are mentioned, more preferably 4,4'-oxydiphthalic acid dianhydride, 3,3',. 4,4'-biphenyltetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic acid dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA) , Bis (3,4-dicarboxyphenyl) methane dianhydride and 4,4'-(p-phenylenedioxy) diphthalic hydride. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydride. The cyclic aliphatic tetracarboxylic acid dianhydride is a tetracarboxylic acid dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride. Cycloalkanetetracarboxylic acid dianhydride such as 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, bicyclo [2.2] .2] Oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, dicyclohexyl-3,3', 4,4'-tetracarboxylic acid dianhydride and their positional isomers. Be done. These can be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride and the like. These can be used alone or in combination of two or more. Further, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

Among the above tetracarboxylic acid dianhydrides, 4,4'-oxydiphthalic acid dianoxide is easy to increase the tensile elasticity, surface hardness, transparency, flexibility and bending resistance of the optical film, and easily reduce the YI value. Anhydrous, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyl Tetracarboxylic acid dianhydride, 3,3', 4,4'-diphenylsulfone Tetracarboxylic acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 4,4'- (Hexafluoroisopropyridene) diphthalic acid dianhydride, and mixtures thereof, are preferred, with 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and 4,4'-(hexafluoroisopropyridene) diphthalic acid. Dianoxides, as well as mixtures thereof, are more preferred, 4,4'-(hexafluoroisopropylidene) diphthalic acid dianhydride (6FDA) and 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride ( BPDA) is even more preferred.

Examples of the dicarboxylic acid compound used in the synthesis of the resin include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, acid chloride compounds related thereto, acid anhydrides, and the like, and two or more of them may be used in combination. Specific examples include terephthalic acid; isophthalic acid; 2-methoxyterephthalic acid; 2-methylterephthalic acid; 2,5-bis (trifluoromethyl) terephthalic acid; isophthalic acid; 2,5-dimethylterephthalic acid; 2,5. -Dimethoxyterephthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; 2,2'-bis (trifluoromethyl) -4,4'-biphenyldicarboxylic acid; carbon number A dicarboxylic acid compound of a chain hydrocarbon of 8 or less and two benzoic acids are single-bonded, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- or phenylene. Examples include compounds linked by a group and their acid chloride compounds. Among these dicarboxylic acid compounds, 4,4'-oxybis benzoic acid, terephthalic acid, isophthalic acid, 2-methoxyterephthalic acid, 2-methylterephthalic acid from the viewpoint of easily increasing the tensile elasticity and bending resistance of the optical film. , 2,5-dimethylterephthalic acid, 2,5-dimethoxyterephthalic acid, 2,5-bis (trifluoromethyl) terephthalic acid, 2,2'-bis (trifluoromethyl) -4,4'-biphenyldicarboxylic acid And their acid chlorides are preferred, 2-methoxyterephthalic acid, 2-methylterephthalic acid, 2,5-dimethylterephthalic acid chloride (DMTPC), 2,5-dimethoxyterephthalic acid chloride (MOTPC), 2,5-bis ( Trifluoromethyl) terephthalic acid chloride (6FTPC), terephthaloyl chloride (TPC), isophthaloyl chloride are more preferred, terephthaloyl chloride (TPC), 2-methoxyterephthalic acid, 2-methylterephthalic acid, 2,5 -Dimethylterephthalic acid chloride (DMTPC), 2,5-dimethoxyterephthalic acid chloride (MOTPC) is more preferred, 2-methoxyterephthalic acid, 2-methylterephthalic acid, 2,5-dimethylterephthalic acid chloride (DMTPC) and 2, 5-Dimethoxyterephthalic acid chloride (MOTPC) is even more preferred.

The polyimide resin contains other tetracarboxylic acids and tricarboxylic acids, and their anhydrides and derivatives, in addition to the tetracarboxylic acid compounds used in the resin synthesis, as long as the various physical properties of the optical film are not impaired. It may be further reacted.

Examples of other tetracarboxylic acids include water adducts of the anhydrides of the tetracarboxylic acid compounds.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, acid chloride compounds related thereto, acid anhydrides, and the like, and two or more of them may be used in combination. Specific examples include an anhydride of 1,2,4-benzenetricarboxylic acid; an acid chloride compound of 1,3,5-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthal. A compound in which an acid anhydride and benzoic acid are single-bonded, -O-, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- or a phenylene group. Can be mentioned.

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

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, but 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, but is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out under conditions of an inert atmosphere or reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and / or an atmosphere of an inert gas with stirring. The reaction is preferably carried out in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and for example, water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, etc. Alcohol-based solvents such as 2-butoxyethanol and propylene glycol monomethyl ether; ester-based solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, γ-valerolactone, propylene glycol methyl ether acetate and ethyl lactate; Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane and heptane; alicyclic hydrocarbon solvents such as ethyl cyclohexane; toluene and xylene Aromatic hydrocarbon solvents such as; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amides such as N, N-dimethylacetamide and N, N-dimethylformamide. System solvents; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, an amide-based solvent can be preferably used from the viewpoint of solubility.

In the imidization step in the production of the polyimide resin, imidization can be performed in the presence of an imidization catalyst. Examples of imidization catalysts include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidin, N-propylpiperidin, N-butylpyrrolidin, N-butylpiperidin, and N-propylhexahydro. Alicyclic amines such as azepine (monocyclic); azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2. 2] Alicyclic amines such as nonane (polycyclic); and pyridine, 2-methylpyridine (2-picolin), 3-methylpyridine (3-picolin), 4-methylpyridine (4-picolin), 2- Ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and Examples include aromatic amines such as isoquinolin. Further, from the viewpoint of easily promoting the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. Examples of the acid anhydride include conventional acid anhydrides used in the imidization reaction, and specific examples thereof include acetic anhydride, propionic anhydride, aliphatic acid anhydrides such as butyric anhydride, and aromatics such as phthalic acid. Acid anhydride and the like can be mentioned.

Polyimide-based resins and polyamide-based resins are separated, purified, and isolated by conventional methods, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization, and column chromatography, or separation means combining these. Also, in a preferred embodiment, it can be isolated by adding a large amount of alcohol such as methanol to the reaction solution containing the transparent polyamide-imide resin, precipitating the resin, and performing concentration, filtration, drying and the like.

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

(Filler)
The optical film of the present invention may contain at least one filler. Examples of the filler include organic particles and inorganic particles, and preferably inorganic particles. Examples of the inorganic particles include metal oxide particles such as silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide, antimony oxide, and cerium oxide, magnesium fluoride, sodium fluoride, and the like. Among these, silica particles, zirconia particles, and alumina particles are preferable from the viewpoint of increasing the elasticity and / or tear strength of the optical film and easily improving the impact resistance. , More preferably silica particles. These fillers can be used alone or in combination of two or more.

The average primary particle size of the filler, preferably silica particles, is 1 nm or more, more preferably 5 nm or more, still more preferably 10 nm or more, even more preferably 15 nm or more, particularly preferably 20 nm or more, preferably 100 nm or less, more preferably. Is 90 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, particularly preferably 60 nm or less, particularly more preferably 50 nm or less, and particularly preferably 40 nm or less. When the average primary particle size of the silica particles is within the above range, the aggregation of the silica particles can be suppressed and the optical characteristics of the obtained optical film can be easily improved. The average primary particle size of the filler can be measured by the BET method. The average primary particle size may be measured by image analysis of a transmission electron microscope or a scanning electron microscope.

The content of the filler in the optical film of the present invention, for example, inorganic particles, particularly silica particles, is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass, based on the total mass of the optical film. Hereinafter, it is even more preferably 40% by mass or less, and preferably 0% by mass or more. When the content of the filler is not more than the above upper limit, the elastic modulus of the obtained optical film can be easily increased, and the optical characteristics of the optical film can be easily improved. Here, the tensile elastic modulus of the optical film tends to be increased by increasing the content of the filler such as silica particles, but when the content of the filler such as silica particles is too large, the obtained optical film is obtained. May be difficult to satisfy the above formulas (1) to (3). Therefore, in the optical film of the present invention, it is preferable to set the content of silica particles to the above upper limit or less from the viewpoint of easily increasing the tensile elastic modulus of the optical film and easily maintaining high visibility in the wide angle direction. In the present specification, when the content of, for example, silica particles in the optical film is equal to or less than the above upper limit with respect to the total mass of the optical film, the content of the silica particles is 0% by mass, that is, the silica particles. Indicates that the amount of silica is not contained, or even if it is contained, the amount is equal to or less than the above upper limit.

(UV absorber)
The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber can be appropriately selected from those usually used as an ultraviolet absorber in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400 nm or less. Examples of the ultraviolet absorber include triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzoate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and salicylate-based ultraviolet absorbers. .. These may be used alone or in combination of two or more. Since the optical film contains an ultraviolet absorber, deterioration of the resin is suppressed, so that visibility can be improved when the optical film of the present invention is applied to a display device or the like. As used herein, the term "system compound" refers to a derivative of a compound to which the "system compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a maternal skeleton and a substituent attached to benzophenone. Suitable commercially available UV absorbers include, for example, Sumisorb® 340 manufactured by Sumika Chemtex Co., Ltd., ADEKA STAB® LA-31 manufactured by ADEKA Corporation, and BASF Japan Ltd. Chinubin (registered trademark) 1577 and the like can be mentioned.

When the optical film of the present invention contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the polyamide-imide resin contained in the optical film. It is more preferably 1 to 8 parts by mass, still more preferably 2 to 7 parts by mass. When the content of the ultraviolet absorber is at least the above lower limit, the ultraviolet absorption is likely to be improved. When the content of the ultraviolet absorber is not more than the above upper limit, the decomposition of the ultraviolet absorber due to heat during the production of the base material can be suppressed, the optical characteristics can be easily improved, and for example, the haze can be easily reduced.

The use of the optical film of the present invention is not particularly limited, and it may be used for various purposes. The optical film of the present invention may be a single layer or a laminated body, the optical film of the present invention may be used as it is, or may be used as a laminated body with another film. .. Since the optical film of the present invention has excellent visibility in a wide-angle direction, it is useful as an optical film in an image display device or the like. When the optical film is a laminated body, it is referred to as an optical film including all the layers laminated on one side or both sides of the optical film.

The use of the optical film of the present invention is not particularly limited, and the optical film may be used for various purposes. Since the optical film of the present invention is excellent in visibility in the wide angle direction, it is useful as an optical film in an image display device or the like. In particular, the optical film of the present invention is useful as a front plate of an image display device, particularly a front plate (window film) of a flexible display. The flexible display has, for example, a flexible functional layer and the above-mentioned optical film which is superposed on the flexible functional layer and functions as a front plate. That is, the front plate of the flexible display is arranged on the visible side above the flexible functional layer. This front plate has a function of protecting the flexible functional layer.

<Manufacturing method of optical film>
The optical film of the present invention is not particularly limited, but for example, the following steps:
(A) A step of preparing a liquid containing the resin and optionally the filler (hereinafter, may be referred to as varnish) (varnish preparation step).
(B) A step of applying varnish to a base material to form a coating film (coating step), and (c) a step of drying the applied liquid (coating film) to form an optical film (optical film forming step). )
It can be manufactured by a method including.

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

The solvent used for preparing the varnish is not particularly limited as long as the resin can be dissolved. Examples of such a solvent include amide solvents such as N, N-dimethylacetamide (hereinafter, may be abbreviated as DMAc) and N, N-dimethylformamide (hereinafter, may be abbreviated as DMF); γ-butyrolactone (hereinafter, may be abbreviated as DMF). , GBL), lactone-based solvents such as γ-valerolactone; sulfur-containing solvents such as dimethylsulfon, dimethylsulfoxide and sulfolane; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Be done. Among these, the solvent used for the varnish is preferably an amide solvent or a lactone solvent from the viewpoint of easily producing an optical film satisfying the formulas (1) to (3). These solvents can be used alone or in combination of two or more. Further, the varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent 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, a varnish is applied onto the substrate by a known coating method to form a coating film. Known coating methods include, for example, wire bar coating method, reverse coating, roll coating method such as gravure coating, die coating method, comma coating method, lip coating method, screen coating method, fountain coating method, salivation molding method and the like. ..

In the optical film forming step, the coating film is dried (referred to as first drying), peeled from the substrate, and then the dried coating film is further dried (referred to as second drying or post-baking treatment) to form an optical film. .. The first drying may be carried out under conditions of an inert atmosphere or reduced pressure, if necessary. The first drying is preferably carried out at a relatively low temperature for a long time under negative pressure conditions such as in a negative pressure tenter furnace. When the first drying is performed under negative pressure conditions, the reason is not clear, but the transmittance value of the produced optical film easily satisfies the formulas (1) to (3), and the total light beam of the optical film is formed. It is easy to increase the transmittance and easily decrease the haze and YI. It is considered that this is because the solvent volatilized and removed from the optical film 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, even if the first drying is performed at a relatively low temperature for a long time, the surface of the optical film tends to be uniform, and the transmissibility values of the produced optical film are mathematical formulas (1) to (3). Easy to meet. Further, since the oxidative deterioration of the resin during drying is suppressed, the total light transmittance of the optical film is likely to be increased, and the haze and YI are likely to be lowered.

Here, in the case of industrially producing the optical film of the present invention, the actual manufacturing environment is often disadvantageous in improving the visibility in the wide-angle direction as compared with the manufacturing environment at the laboratory level, and as a result, It may be difficult to improve the visibility of the optical film in the wide-angle direction. As mentioned above, it is preferable to carry out the first drying under negative pressure conditions at a relatively low temperature for a long time, but at the laboratory level, when the first drying is carried out, the drying is sealed. Since it can be performed in the vessel, the surface of the optical film is relatively less likely to be roughened due to external factors. On the other hand, in the case of industrially producing an optical film, for example, since it is necessary to heat a large area in the first drying, a blower may be used at the time of heating. As a result, the surface condition of the optical film tends to be rough, and it is difficult to improve the visibility of the optical film in the wide-angle direction.

When drying by heating, especially when the optical film is industrially produced, the temperature of the first drying is preferably 60 to 150 ° C., more preferably 60 to 130 ° C. in consideration of the above-mentioned external factors. , More preferably 70 to 120 ° C. The first drying time is preferably 5 to 60 minutes, more preferably 10 to 40 minutes. In particular, in consideration of the above-mentioned external factors when industrially producing an optical film, it is preferable that the first drying is carried out under three or more stages of drying temperature conditions. The multi-step conditions can be carried out at the same or different temperature conditions and / or drying times in each step, for example, drying may be carried out in 3 to 10 steps, preferably 3 to 8 steps. When the first drying is carried out under a multi-step condition of three or more steps, the transmitted mapability value of the produced optical film easily satisfies the mathematical formulas (1) to (3), and the visibility in the wide-angle direction is improved. In aspects of multi-step conditions of three or more steps, it is preferred that the temperature profile of the first drying includes temperature rise and fall. That is, it is preferable that the first drying condition in the optical film forming step is a heating temperature condition in which the temperature profile includes three or more steps including temperature raising and lowering. Taking the case of four stages as such a temperature profile as an example, the temperature of the first drying is 70 to 90 ° C (first temperature), 90 to 120 ° C (second temperature), and 80 to 120 ° C, respectively. (Third temperature) and 80-100 ° C. (fourth temperature). In this example, the temperature of the first drying is raised from the first temperature to the second temperature, then lowered from the second temperature to the third temperature, and further from the third temperature to the fourth temperature. To lower the temperature. Here, the time of the first drying is, for example, 5 to 15 minutes in each step. The first drying is preferably carried out so that the residual amount of the solvent in the dry coating film is preferably 5 to 15% by mass, more preferably 6 to 12% by mass with respect to the mass of the dry coating film. When the residual amount of the solvent is in the above range, the peelability of the dry coating film from the substrate is good, and the transmission mapping property value of the produced optical film easily satisfies the formulas (1) to (3).

The temperature of the second drying is preferably 150 to 300 ° C, more preferably 180 to 250 ° C, and even 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 may be carried out by a single-wafer method, but in the case of industrial production, it is preferable to carry out the second drying by a roll-to-roll method from the viewpoint of production efficiency. In the single-wafer type, it is preferable to dry the leaves in a state of being uniformly extended in the in-plane direction.
In the roll-to-roll method, from the viewpoint that the obtained optical film easily satisfies the formulas (1) to (3), it is preferable to dry the dried coating film in a state of being stretched in the transport direction, and the transport speed is set to. It is preferably 0.1 to 5 m / min, more preferably 0.2 to 3 m / min, and even more preferably 0.7 to 2.5 m / min. The second drying may be carried out under one-step or multi-step conditions. The multi-step conditions can preferably be carried out in each step with at least one selected from the same or different temperature conditions, drying time and hot air velocity, eg, 3-10 steps, preferably 3 steps. Drying may be carried out in 8 steps, and it is preferable to carry out the drying under a multi-step condition from the viewpoint that the optical film can easily satisfy the range of the formulas (1) to (3). Further, at each stage, the wind speed of the hot air is preferably 5 to 20 m / min, more preferably 10 to 10 from the viewpoint that the transmitted mapability value of the produced optical film easily satisfies the mathematical formulas (1) to (3). It is 15 m / min, more preferably 11-14 m / min.

When the optical film of the present invention includes a hard coat layer, for example, the hard coat layer is formed by applying a curable composition to at least one surface of the optical film to form a coating film, and high energy rays are applied to the coating film. It can be formed by irradiating and curing the coating film.

Examples of the base material are a SUS plate for metal, PET film, PEN film for resin, other polyimide resin or polyamide resin film, cycloolefin polymer (COP) film, acrylic film. Etc., or those resin films having a hard coat layer, a glass substrate, and the like can be mentioned. Among them, PET film, COP film, resin film having a hard coat layer, and SUS plate from the viewpoint of excellent smoothness and heat resistance and the viewpoint that the transmission imageability value of the optical film easily satisfies the formulas (1) to (3). , A glass plate or the like is preferable, and a SUS plate or a resin film having a hard coat layer is more preferable, and a SUS plate or a PET film having a hard coat layer is further preferable from the viewpoint of adhesion to an optical film and cost.

From the viewpoint of facilitating the production of an optical film satisfying the above formulas (1) to (3), the coating film is dried in the above optical film forming step, the coating film is dried to a predetermined amount of solvent, and then the base material is peeled off. Then, it is preferable to carry out by a manufacturing method including a step of obtaining a raw material film and a heating step of heating the raw material film in a tenter furnace in which the inside is divided into a plurality of spaces. Further, in the tenter furnace, it is preferable that the heating step is performed by the hot air treatment method in at least one space, and the heating step is performed by the radiation treatment method in at least one space. The tenter furnace refers to a furnace in which both ends in the film width direction are fixed and heated. The heating device for heating the raw material film, including the tenter furnace, is also referred to as an oven in the present specification. Further, it is preferable that the pressure inside the tenter furnace is adjusted so that the pressure inside the tenter furnace becomes negative with respect to the pressure outside the tenter furnace.

The method for producing the optical film of the present embodiment will be described with reference to the drawings. FIG. 4 is a process cross-sectional view schematically showing a preferred embodiment of the method for producing an optical film according to an embodiment of the present invention. In FIG. 4, the raw material film 44 containing at least the polyimide resin and / or the polyamide resin is carried into the tenter furnace 100, heated in the heating zone in the tenter furnace 100, and then carried out from the tenter furnace 100. In the present specification, a film that has been transported during the heating process or in the oven although there is a change with time such as the amount of the solvent before the heating process is referred to as a raw material film, and the film is carried out from the oven through the heating process. The film is called an optical film.

The raw material film 44 may be unwound from the roll in 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 step immediately before that. FIG. 5 is a process cross-sectional view schematically showing a preferred embodiment of the heating process in the method for producing an optical film of the present invention. As shown in FIG. 5, the raw material film 44 is a tenter furnace in a state where both ends of the film are fixed in a direction (also referred to as a TD direction or a width direction) perpendicular to the film transport direction (also referred to as MD direction or longitudinal direction). It is preferable to carry the inside. The fixing may be performed by, for example, the gripping device 43.

Both ends can be fixed by using a gripping device generally used in a film manufacturing apparatus such as a pin sheet, a clip, and a film chuck. Both ends to be fixed can be appropriately adjusted by the gripping device used, but it is preferable that both ends are fixed at a distance of 50 cm or less from the end of the film. As shown in FIG. 5, the raw material film may be conveyed while gripping both ends thereof with a plurality of gripping devices 43. It is preferable that the distance between the plurality of gripping devices 43 installed at one end of the film is such that the distance between the adjacent gripping devices can suppress defects such as cracks caused by fluttering of the film or dimensional change due to heating. The distance between adjacent gripping devices is preferably 1 to 50 mm, more preferably 3 to 25 mm, and even more preferably 5 to 10 mm. Further, when the straight line orthogonal to the film transport axis is aligned with the center of the grip portion of any gripping device at one end of the film, the gripping device is closest to the intersection of the straight line and the other end of the film. It is preferable that the gripping device is installed so that the distance from the center of the gripping portion is preferably 3 mm or less, more preferably 2 mm or less, still more preferably 1 mm or less. As a result, the difference in stress between both ends of the opposing film can be reduced, and the homogeneity of the obtained optical film can be improved. Further, by drying the film while fixing it using a gripping device under such conditions, fluttering during drying of the film is suppressed, and the above-mentioned formulas (1) to (3) are satisfied. It becomes easier to manufacture an optical film.

As an example of the operation of fixing both ends of the film with the gripping device, a plurality of films provided so as to face each other in the width direction of the film at a timely time before being carried into the tenter furnace or after being carried into the tenter furnace. A method of fixing both ends of the film in the width direction with a chuck can be mentioned. By these operations, it is possible to obtain an optical film in which fluttering of the film is suppressed and defects such as thickness unevenness and scratches are sufficiently suppressed. In addition, it becomes easy to manufacture the optical film of the present invention that satisfies the above mathematical formulas (1) to (3). The fixing of both ends of the film may be performed in the tenter furnace or after being carried out from the tenter furnace, as long as it is released in a timely manner after the heating step is performed.

The total length of the tenter furnace used in the heating step in the film transport direction is usually 10 to 100 m, preferably 15 to 80 m, and more preferably 15 to 60 m. The inside of the tenter furnace may be one space or may be divided into a plurality of spaces, but in the embodiment of the present invention, the inside of the tenter furnace in which the heating step is performed is divided into a plurality of spaces. Adopt what is being done. The space may be a space in which temperature conditions, wind speed conditions, etc. can be controlled, and may not have a physical boundary such as a partition plate. When the inside of the tenter furnace is divided into a plurality of spaces, the inside of the tenter furnace may be divided into a plurality of spaces perpendicularly or parallel to the film transport direction. The number of spaces is usually 2 to 20, preferably 3 to 18, more preferably 4 to 15, and even more preferably 5 to 10. Regardless of the internal structure of the tenter furnace, the entire tenter furnace may be a heating zone, or a part of the inside may be a heating zone. With reference to FIG. 4, all three zones 40, 41, and 42 may be heating zones, or one of these, for example, zone 42, may be a heating zone.

A plurality of tenter furnaces can be used. The number of tenter furnaces in this case is not particularly limited, but may be, for example, 2 to 12. The inside of each tenter furnace can have the structure described above. The plurality of tenter furnaces can be continuously installed so that the film is conveyed without being exposed to the outside air. When a plurality of tenter furnaces are used, all the tenter furnaces may be in the heating zone, or some tenter furnaces may be in the heating zone. Further, in addition to the tenter furnace, an oven may be used in combination as another device. In the present specification, the oven means a device capable of heating a film, and includes a heating furnace and a drying furnace. The heating furnace may be either hot air treatment or radiation treatment, and may be a heating furnace in which these are used in combination. When an oven is used in combination, the internal structure of the oven, the number to be used, and the heating conditions may be appropriately adjusted within the range in which the optical film of the present invention can be obtained, but the same as in the tenter furnace described in the present specification. It is preferable to do so.

The circulation and exhaust of air inside the tenter furnace is preferably performed in each space when the inside of the tenter furnace is divided into a plurality of spaces, and is performed in each tenter furnace when there are a plurality of tenter furnaces. preferable. From the viewpoint of facilitating the production of the optical film of the present invention satisfying the above formulas (1) to (3), the pressure inside the tenter furnace is set to be negative inside the tenter furnace with respect to the pressure outside the tenter furnace. It is preferable that the pressure is adjusted to. 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 settings for each space may be the same or different. However, it is preferable that the temperature of each tenter furnace or space satisfies the temperature range described later.

In the tenter furnace 100 in which the heating step is performed, the heating step is performed in at least one space by a hot air treatment method, and the heating step is performed in at least one space by a radiation treatment method. In the heating step, it is preferable that all the spaces where this step is performed are performed by a hot air treatment method. The heating step of the radiation treatment method may be performed in a space different from that of the hot air treatment method, but it is preferable that the heating step is performed in combination with the hot air treatment method.

The heating process 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, a hot air treatment method using a nozzle and a radiation treatment method using an IR heater will be described below in order from the hot air treatment method using a nozzle.

With reference to FIG. 4, in the tenter furnace 100 in which the heating step is performed, a plurality of upper nozzles 46 are provided on the inner upper surface 100a, and a plurality of lower nozzles 47 are provided on the inner lower surface 100b. ing. The upper nozzle 46 and the lower nozzle 47 are provided so as to face each other in the vertical direction. As the nozzles, for example, 4 pairs of nozzles (8 in total) may be provided as in the zone 42 of FIG. 4, or 10 pairs of nozzles (20 in total) may be provided as in the zone 41 of FIG. Well, it can be installed as appropriate depending on the structure of the oven. The distance between the adjacent nozzles is preferably 0 from the viewpoint of uniformly heating the raw material film while simplifying the structure of the tenter furnace and from the viewpoint of easily producing an optical film satisfying the formulas (1) to (3). It is 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 provided in each space can usually be 5 to 30. From the viewpoint of facilitating the production of the optical film of the present invention satisfying the above formula, the number of nozzles is preferably 8 to 20. When the number of nozzles is in the above range, the curvature of the floating film tends to be too large, and the film tends to float between the nozzles, that is, to float easily.

The upper nozzle 46 provided on the upper surface 100a of the tenter furnace 100 has an outlet at the lower portion, and can blow hot air in the downward direction (arrow B direction). On the other hand, the lower nozzles 47 provided on the lower surface of the tenter furnace 100 each have an outlet at the upper portion, and can blow hot air in the upward direction (arrow C direction). Although not shown in FIG. 4, the upper nozzle 46 and the lower nozzle 47 have a depth of a predetermined size in the direction perpendicular to the paper surface of FIG. 4 so that the raw material film can be uniformly heated in the width direction. have. Here, it is conceivable to set the nozzle orientation sideways with respect to the film surface, but in that case, although the reason is not clear, an optical film satisfying the mathematical formulas (1) to (3) is manufactured. It's difficult.

In the method for producing an optical film of the present embodiment, the blowing air velocity of hot air at the outlets from all the upper nozzles 46 and all the lower nozzles 47 provided in the heating zone is preferably 2 to 25 m / sec. The blown wind speed is more preferably 2 to 23 m / sec, still more preferably 8 to 8 to 23 m / sec, from the viewpoint of easily producing the optical film of the present invention satisfying the above formula and easily increasing the optical uniformity of the optical film. It is 20 m / sec. Further, from the same viewpoint, the amount of air blown from the outlet of each nozzle 46 or 47 per 1 m of nozzle length along the width direction of the raw material film is preferably 0.1 to ³ m 3 / sec. It is more preferably 0.1 to 2.5 m ³ / sec, and even more preferably 0.2 to ² m 3 / sec.

Further, when the heating step is performed under the above conditions, it is easy to produce the optical film of the present invention satisfying the above formula, and since the film is uniformly heated, the variation in the amount of solvent remaining in the film is small, and the entire surface of the film is covered. It is easy to obtain an optical film with a more uniform elastic modulus. Therefore, variation in flexibility is unlikely to occur on the entire surface of the film, and damage due to the difference in flexibility on the film surface can be suppressed.

In the tenter furnace, the raw material film 44 is heated from room temperature to a temperature at which the solvent contained in the raw material film evaporates, but the length of the raw material film in the width direction is held by the gripping device 43 so as to be almost unchanged. , It tends to hang down easily due to thermal expansion. When the blown air velocity and the blown air volume are within the above ranges, the raw material film 44 can be sufficiently heated, and the raw material film 44 can be suppressed from sagging or fluttering.

The hot air blowing speed can be measured at the hot air outlets of the nozzles 46 and 47 using a commercially available hot anemometer. Further, the amount of air blown out from the air outlet can be obtained by the product of the air velocity of the air blown out and the area of the air outlet. From the viewpoint of measurement accuracy, the hot air blowing air velocity is preferably measured at about 10 points at the blowing port of each nozzle and used as the average value.

The blown air velocity and the blown air volume of the hot air may be appropriately adjusted depending on the physical properties (optical characteristics, mechanical properties, etc.) of the optical film to be manufactured, but it is preferable that the blown air velocity and the blown air volume are within the above ranges in any form. As a result, it is easy to manufacture the optical film of the present invention that satisfies the above mathematical 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. As the heating zone, it is more preferable that the blowing air velocity is 25 m / sec or less and the blowing air volume is 2 m ^{3 / sec or less in all the heating zones.}

In the present embodiment, the wind speed of the hot air at the position where the raw material film 44 should be held is preferably 5 m / sec or less in a state where the raw material film 44 is not introduced into the tenter furnace 100, and at least in the heating zone, such The wind speed is more preferable. By heating the raw material film 44 with such hot air, it is easy to produce the optical film of the present invention satisfying the above mathematical formulas (1) to (3), and after the bending resistance test of the optical film. It is easy to improve visibility in the wide-angle direction.

In the heating zone, the difference between the maximum value and the minimum value in the width direction (direction perpendicular to the paper surface of FIG. 4) of the hot air blowing air velocity at the outlets of the nozzles 46 and 47 is preferably 4 m / sec or less. .. By using hot air having little variation in wind speed in the width direction in this way, it is easy to manufacture the optical film of the present invention satisfying the above formulas (1) to (3), and after the bending resistance test of the optical film. It is easy to improve the visibility in the wide angle direction.

In the present embodiment, it is preferable that the wind speed of the hot air blown on the film is higher than the wind speed of the other transport paths in the oven immediately after being carried into the oven. Immediately after being delivered to the oven (hereinafter referred to as "transport path 1"), if the inside of the oven is not divided into multiple parts, the length from the oven inlet to the oven length (the length from the oven inlet to the outlet) It means a distance less than 1/10 of the above. The transport path 1 refers to the space through which the film first passes when the inside of the oven is divided into a plurality of spaces. When multiple ovens are used, the internal structure of the oven used first may be the same as described above, or the oven passed first may be set higher than the wind speed in the second and subsequent ovens. It may be done.

The other transport path means a transport path portion located at 1/10 or more of the oven length from the oven carry-in port when the inside of the oven is not divided into a plurality of sections. When the inside of the oven is divided into a plurality of spaces, it means an arbitrary space in the second and subsequent spaces through which the film passes. When multiple ovens are used, the internal structure of the oven used first may be the same as described above, or the second and subsequent ovens may be the oven through which the wind speed in any oven passes first. The wind speed may be set lower than that.

The difference between the wind speed of the transport path 1 and the wind speed of the other transport paths in the oven is preferably in the range of 0.1 to 15 m / sec. The difference in wind speed is more preferably 0.2 m / sec or more, 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 a second. When the wind speed immediately after being brought into the oven is made larger than the wind speed of other transport paths in the oven so that the difference in wind speed is within the above range, the solvent in the film tends to be removed more efficiently. If the difference in wind speed is too large, the film may flutter 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 formulas (1) to (3). In addition, it may cause a defect in the surface shape of the obtained optical film or a variation in optical characteristics such as a phase difference.

The difference between the wind speed of the transport path 1 and the wind speed of the other transport paths in the oven is that of the hot air blown out from the nozzles installed in the transport path 1 and the hot air from the nozzles installed in the other transport paths. It can be calculated as the difference from the blown wind speed. If there is a difference of 2 m / sec or more between the wind speed of the hot air blown onto the film and the wind speed of the hot air blown out from the nozzle, it can be calculated as the difference in the wind speed of the hot air near the film in each of the transport paths 1 and other transport paths. good.

The other transport route is preferably a transport route (hereinafter referred to as “transport route 2”) located next to the transport route 1. The transport path 2 refers to a transport path portion located at 2/10 of the oven length from the oven carry-in port when the inside of the oven is not divided into a plurality of parts. The transport path 2 refers to a second space through which the film passes when the inside of the oven is divided into a plurality of spaces. If more than one oven is used, the internal structure of the first oven may be similar to the one described above, or the wind speed of the second oven may be set lower than the first oven to pass through. It may be.

When the difference in wind speed between the transport path 1 and the transport path 2 is set as described above, the wind speed of the transport path after the transport path 2 may be within the range of the blown wind speed of the hot air. The wind speed of the transport path after the transport path 2 is preferably the difference between the wind speeds of the transport path 1 or the transport path 2 and the wind speed of 0.1 to 12 m / sec, and the wind speed is 0.2 to 8 m / sec. It is more preferable that the difference is. If the difference in wind speed is within such a range, the fluttering of the film due to the difference in wind speed can be suppressed, and the optical film of the present invention satisfying the above formulas (1) to (3) can be easily manufactured, and the optical film of the present invention can be easily manufactured. There is a tendency that the weight reduction rate of the obtained optical film can be easily adjusted within a desired range.

When the inside of the oven is not divided into a plurality of spaces, the difference in wind speed may be adjusted by adjusting the position where the nozzle is provided, the blowing speed and volume of hot air from the nozzle, the flow of airflow in the oven, and the like. If the inside of the oven is divided into multiple spaces, adjust the position where the nozzle is installed, the speed and volume of hot air from the nozzle, the flow of airflow in the oven, etc. in the first space and the space after that. You just have to adjust. When using multiple ovens, depending on the structure of the first oven, the same procedure as described above may be performed, or the position and nozzle where the nozzles are provided so that the wind speed differs between the first oven and the second and subsequent ovens. The blowing speed and volume of hot air, the air flow in the oven, etc. may 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, still more preferably 150 to 400 mm. By arranging the upper nozzle and the lower nozzle at such an interval L, the fluttering of the film in each step can be suppressed more reliably, and the present invention satisfying the above formulas (1) to (3). It becomes easier to manufacture the optical film of.

Further, the difference (ΔT) between the maximum temperature and the minimum temperature in the width direction of hot air (perpendicular to the paper surface in FIG. 4) at the outlets of the nozzles 46 and 47 provided in the heating zone is preferably all 2 ° C. Below, more preferably, all are 1 ° C. or less. By heating the film with hot air having a sufficiently small temperature difference in the width direction in this way, it becomes easy to manufacture the optical film of the present invention satisfying the above formulas (1) to (3). The temperature of the hot air is preferably 150 to 400 ° C, more preferably 150 to 300 ° C, and even more preferably 150 to 250 ° C.

As a nozzle that can be used in the optical film manufacturing method, a nozzle generally used in a film manufacturing apparatus can be used. As an example, a nozzle having a slit-shaped outlet extending in the width direction of the raw material film is a jet nozzle. (Also referred to as a slit nozzle), and a nozzle having a plurality of outlets arranged in the transport direction of the raw material film and the width direction of the raw material film, respectively, is a punching nozzle (also referred to as a perforated nozzle).

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

The jet nozzle has a slit extending in the width direction of the film as a hot air outlet. The slit width of the slit is preferably 5 mm or more, more preferably 5 to 20 mm. By setting the slit width to 5 mm or more, the optical uniformity of the obtained optical film can be further improved. The area of the outlet per jet nozzle can be obtained by the product of the length of the jet nozzle in the width direction and the slit width. The product of the area of the blowout port per nozzle and the blowout air velocity is the amount of hot air blown out per nozzle. By dividing the amount of hot air blown out by the length of the slit along the width direction of the film, the amount of hot air blown out per 1 m of nozzle length along the width direction of the film can be obtained.

The punching nozzle may have a rectangular shape or a trapezoidal shape whose cross section perpendicular to the longitudinal direction is divergent toward the surface facing the raw material film 44. The punching nozzle has a plurality of openings (for example, circular openings) on the lower surface, which is the surface facing the film. The hot air outlet of the punching nozzle is composed of a plurality of openings provided on the outlet surface. The plurality of openings are outlets for hot air, and the hot air is blown out from the openings at a predetermined wind speed. A plurality of openings are arranged in the longitudinal direction of the film, and a plurality of openings are also arranged in the width direction. The openings can be arranged in a staggered pattern, for example.

The area of the outlet per punching nozzle can be obtained by the sum of the areas of all the openings provided in one punching nozzle. The product of the area of the blowout port per nozzle and the blowout air velocity is the amount of hot air blown out per nozzle. By dividing the amount of hot air blown out by the length of the slit along the width direction of the film, the amount of hot air blown out per 1 m of nozzle length along the width direction of the film can be obtained.

When a punching nozzle is used, the difference between the maximum blowing air velocity and the minimum blowing air velocity in the width direction of the hot air at the nozzle outlet is the maximum blowing speed and the minimum blowing speed of the hot air blown out from a plurality of openings provided on the same nozzle. It can be obtained as the difference from the blowing speed. Similarly, the difference between the maximum temperature and the minimum temperature in the width direction of the hot air at the outlet of the nozzle can be obtained.

If all the nozzles provided in the tenter furnace 100 are punching nozzles, the total area of the hot air outlets in the entire tenter furnace 100 can be increased. Therefore, the wind pressure of the hot air that hits the film can be reduced, and the fluttering of the film can be further reduced. This makes it easy to manufacture the optical film of the present invention that satisfies the above mathematical formulas (1) to (3). In the tenter furnace or in the heating zone, the raw material film 44 is heated from room temperature to a temperature at which the solvent contained in the raw material film evaporates, but is held by the gripping device 43 so that the length of the raw material film 44 in the width direction is almost unchanged. Therefore, it tends to hang down easily due to thermal expansion. By using the punching nozzle in the heating zone, it is possible to further suppress the sagging and fluttering of the raw material film 44, and it becomes easy to manufacture the optical film of the present invention satisfying the above formulas (1) to (3).

The size and number of openings provided on the surface of the punching nozzle are such that the hot air blown air velocity at each opening is 2 to 25 m / sec, and the blown air volume from each nozzle is the length of the nozzle along the width direction of the film. It can be appropriately adjusted within the range of ^{0.1 to 3} m 3 / sec per 1 m.

From the viewpoint of making the blowing air velocity 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 to 10 mm, more preferably 3 to 8 mm.

When a punching nozzle is used, the length of the surface per nozzle in the film transport direction is preferably 50 to 300 mm. Further, the distance from the adjacent punching nozzle is preferably 0.3 m or less. Further, the ratio of the total area of the punching nozzle openings (the area of the outlet) to ^{the length of the punching nozzle in the film width direction (the total area of the punching nozzle openings (m 2} ) / the length of the punching nozzle in the film width direction). (M)) is preferably 0.008 m or more.

By using such a punching nozzle, the area of the hot air outlet can be increased. This makes it possible to sufficiently reduce the wind speed of the hot air and blow out the hot air with a sufficient amount of air, so that the film can be heated more uniformly. As a result, it becomes easy to manufacture the optical film of the present invention that satisfies the above mathematical formulas (1) to (3).

Like the nozzle, the tenter furnace 100 in which the heating step is performed is provided with an IR heater on the upper surface 100a inside the furnace or the lower surface 100b inside the tenter furnace 100, and may be provided so as to face each other in the vertical direction. Further, a plurality of IR heaters may be provided. As the IR heater, an IR heater generally used in a film manufacturing apparatus may be used.

The radiation beam applied to the film is preferably a heat ray having a wavelength of 3 to 7 μm. Further, in the radiation treatment method, if the temperature of the space where the heating step is performed is within the above temperature range, radiation at a temperature higher than the temperature of the space by 30 ° C. or more may be applied to the raw material film.

In the embodiment of the present invention, it is preferable that the nozzle (hot air treatment method) and the IR heater (radiation ray treatment method) are used in combination in the tenter furnace 100 in which the heating step is performed. In that case, an IR heater may be installed between adjacent nozzles or between the nozzles and the inner wall of the tenter furnace (including the wall that partitions the space).

In this case, the temperature of the space where the heating step is performed may be within the above temperature range, and in the radiation processing method, radiation at a temperature higher than the temperature of the space may be applied to the film. The temperature of the radiation ray may be, for example, a temperature higher than the temperature of the space by 30 ° C. or more, or a temperature higher than the temperature of the space by 150 ° C. or more. Here, the temperature of the radiant ray refers to a temperature set by a device that emits radiant heat, such as a set temperature of an IR heater. The difference between the temperature of the radiant ray and the temperature of the radiant ray hitting the film is preferably 5 ° C. or lower, more preferably 3 ° C. or lower, still more preferably 1 ° C. or lower.

In the tenter furnace 100, when a nozzle (hot air treatment method) and an IR heater (radiation ray treatment method) are used in combination, radiation rays higher than the temperature in the heating zone or the tenter furnace (atmospheric temperature) are applied to the raw material film. Nevertheless, the heating step can be performed while suppressing the temperature in the heating zone or the tenter furnace from becoming too high.

The heating process that uses both the hot air treatment method and the radiant ray treatment method is located in the middle of the total length of the tenter furnace from the space where the raw material film first passes among the multiple spaces in which the heating process is performed in the tenter furnace. It is preferable that it is performed before the space. As a result, not only the time required for the heating step can be shortened, but also an optical film having more excellent uniformity of in-plane phase difference can be manufactured.

The heating step is preferably carried out in the range of 150 to 350 ° C. In the embodiment of the present invention, when the heating step is in this temperature range, the raw material film tends to be easily adjusted so as to have the weight loss rate M described later. This temperature range is more preferably 170 ° C. or higher, further preferably 180 ° C. or higher, more preferably 300 ° C. or lower, still more preferably 250 ° C. or lower, and particularly preferably 230 ° C. or lower. When the temperature of the heating step is in the above range, the YI value of the obtained optical film can be easily adjusted within the above preferable range. The temperature of the space where the heating step is performed is more preferably 170 ° C. or higher, still more preferably 180 ° C. or higher. The temperature in the tenter furnace in which the heating step is performed may be such that the heating zone is in the above range. When there are a plurality of tenter furnaces or when the inside of the tenter furnace is divided into a plurality of spaces, adjustments can be made as appropriate, but it is preferable that all the tenter furnaces or spaces are within the above range.

The moving speed of the raw material film 44 in the tenter furnace 100 can be appropriately adjusted within the range of usually 0.1 to 50 m / min. The upper limit of the moving speed is preferably 20 m / min, more preferably 15 m / min. The lower limit of the moving speed is preferably 0.2 m / min, more preferably 0.5 m / min, still more preferably 0.7 m / min, and particularly preferably 0.8 m / min. If the moving speed is high, the length of the tenter furnace becomes long in order to secure the desired drying time, and the equipment tends to become large. In the embodiment of the present invention, when the moving speed of the raw material film 44 in the tenter furnace 100 is within the above range, the raw material film tends to be easily adjusted to have the weight reduction rate M described later. Further, it is easy to manufacture an optical film satisfying 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 may be appropriately adjusted in consideration of conditions such as the temperature of the tenter furnace, the moving speed, the wind speed of hot air, and the air volume.

In one embodiment of the present invention, the method for producing an optical film may be an operation of changing the width of the film or an operation of holding and transporting the film width during the heating step. An example of an operation of changing the width of the film is an operation of stretching the film in the width direction. The draw ratio is preferably 0.7 to 1.3 times, more preferably 0.8 to 1.2 times, still more preferably 0.8 to 1.1 times. An example of an operation of holding and transporting the film width is an operation of holding the film so that the length in the width direction is almost unchanged. The optical film obtained through these operations can have a length of about 0.7 to 1.3 times the length in the width direction of the raw material film, and is stretched from the length in the width direction of the raw material film. It may have the same size or a contracted length. The stretch ratio is determined as the ratio of the width of the film after stretching (excluding the gripped portion) to the width of the film excluding the gripped portion.
In FIG. 5, in the operation of stretching the width direction of the film, the case where the stretching ratio exceeds 1 time is shown by a solid line, and the case where the stretching ratio is equal to or less than 1 time is shown by a dotted line.

The optical film that has undergone the heating step may be continuously supplied to the next step after being carried out from the tenter furnace, or may be wound into a roll and supplied to the next step. When the optical film is wound on a roll, another film such as a surface protective film and another optical film may be laminated and wound. As the surface protective film laminated on the optical film, the same surface protective film as the surface protective film laminated on the raw material film described later can be used. The thickness of the surface protective film laminated on the optical film is usually 10 to 100 μm, preferably 10 to 80 μm.

<Raw material film>
The raw material film supplied to the above heating step contains at least a polyimide resin and / or a polyamide resin. The raw material film preferably contains the same components as those contained in the varnish used for forming the raw material film described later, but it does not have to be the same because structural changes of the components and evaporation of a part of the solvent may occur. good. The raw material film may be a self-supporting film or a gel film.

The raw material film is referred to as thermogravimetric-differential thermal measurement (hereinafter referred to as "TG-DTA measurement") regardless of whether or not it contains an inorganic material, from the viewpoint of facilitating the production of an optical film satisfying mathematical formulas (1) to (3). The weight loss rate M from 120 ° C. to 250 ° C. determined by) is preferably about 1 to 40%, more preferably 3 to 20%, still more preferably 5 to 15%, and particularly preferably 5 to 5. It is preferable that a part of the solvent is removed from the varnish so as to be 12%. The weight loss rate M of the raw material film can be measured by the following method using a commercially available TG-DTA measuring device. As the TG-DTA measuring device, TG / DTA6300 manufactured by Hitachi High-Tech Science Corporation can be used.

First, about 20 mg of a sample is obtained from the raw material film, the sample is heated from room temperature to 120 ° C. at a heating rate of 10 ° C./min, held at 120 ° C. for 5 minutes, and then 10 ° C./min to 400 ° C. The weight change of the sample is measured while heating under the condition that the temperature is raised at the heating rate. Next, from the result of TG-DTA measurement, the weight loss rate M (%) from 120 ° C. to 250 ° C. may be calculated by the following formula. In the following formula, W ₀ indicates the weight of the sample after holding at 120 ° C. for 5 minutes, and W ₁ indicates the weight of the sample at 250 ° C.
M (%) = 100- (W ₁ / W ₀ ) x 100

When the weight reduction rate M of the raw material film is large to some extent, when the raw material film is wound as a laminate with the base material or the surface protection film, deformation such as bending of the laminate is suppressed, and the takeability of the laminate is improved. It tends to improve. Further, it becomes easy to manufacture an optical film satisfying the mathematical formulas (1) to (3).

If the weight reduction rate M of the raw material film is small to some extent, the raw material film tends to be difficult to adhere to the base material or the surface protective film when the raw material film is wound as a laminate with the base material or the surface protective film. Therefore, the laminate can be easily unwound from the roll while maintaining the uniform transparency of the raw material film.

The raw material film can be formed by drying the above coating film and peeling it from the base material. The coating film can be dried at a temperature of usually 50 to 350 ° C. If necessary, the coating film may be dried under conditions of an inert atmosphere or reduced pressure. The raw material film obtained as described above can be supplied to the heating step to produce the optical film of the present invention. The raw material film may be continuously conveyed and supplied to the heating step, or may be supplied after being wound once.

<Functional layer>
One or more functional layers may be laminated on at least one surface of the optical film of the present invention. Examples of the functional layer include an ultraviolet absorbing layer, a hard coat layer, a primer layer, a gas barrier layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. The functional layer can be used alone or in combination of two or more.

(UV absorption layer)
The ultraviolet absorbing layer is a layer having an ultraviolet absorbing function. For example, a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, and the main material thereof. It is composed of a dispersed UV absorber.

(Hard coat layer)
The hard coat layer cures, for example, a composition for forming a hard coat (hereinafter, also referred to as “hard coat composition”) containing a reactive material capable of forming a crosslinked structure by irradiation with active energy rays or application of heat energy. It is a layer that can be formed by allowing the layer to be formed, and a layer that can be formed by irradiation with active energy rays is preferable. Active energy rays are defined as energy rays that can generate active species by decomposing compounds that generate active species, and are visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays, and electron beams. And the like, preferably ultraviolet rays. The hard coat composition contains at least one polymer of a radically polymerizable compound and a cationically polymerizable compound. The thickness of the hard coat layer is not particularly limited, but is preferably 2 to 50 μm, more preferably 2 to 40 μm, and further, from the viewpoint of easily preventing cracking at the interface between the hard coat layer or the hard coat layer and the optical film. It is preferably 3 to 20 μm, and even more preferably 3 to 15 μm. When the thickness of the hard coat layer is within the above range, sufficient scratch resistance can be ensured, bending resistance is unlikely to decrease, and the problem of curl generation due to curing shrinkage tends to be less likely to occur. ..

In the hard coat layer forming step, the coating film is irradiated with high energy rays (for example, active energy rays) to cure the coating film to form a hard coat layer. The irradiation intensity is appropriately determined by the composition of the curable composition and is not particularly limited, but irradiation in a wavelength region effective for activating the polymerization initiator is preferable. The irradiation intensity is preferably 0.1~6,000mW / cm ^2, more preferably 10~1,000mW / cm ^2, more preferably from 20 to 500 mW / cm ^2. When the irradiation intensity is within the above range, an appropriate reaction time can be secured, and yellowing and deterioration of the resin due to heat radiated from the light source and heat generated during the curing reaction can be suppressed. The irradiation time may be appropriately selected depending on the composition of the curable composition and is not particularly limited, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is preferably 10 to 10,000 mJ /. It is set to be cm ² , more preferably 50 to 1,000 mJ / cm ² , and even more preferably 80 to 500 mJ / cm ^2. When the integrated light amount is within the above range, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and the irradiation time does not become too long, resulting in good productivity. Can be maintained. Further, it is useful because the hardness of the hard coat layer can be further increased by going through the irradiation step in this range. From the viewpoint of improving the smoothness of the hard coat layer and further improving the visibility of the optical film in the wide-angle direction, optimization of the type of solvent, component ratio, solid content concentration, addition of a leveling agent, and the like can be mentioned.

The radically polymerizable compound is a compound having a radically polymerizable group. The radically polymerizable group contained in the radically polymerizable compound may be a functional group capable of causing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, and specifically, a vinyl group. , (Meta) acryloyl radicals and the like. When the radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same as each other or may be different from each other. The number of radically polymerizable groups contained in one molecule of the radically polymerizable compound is preferably 2 or more from the viewpoint of improving the hardness of the hard coat layer. Examples of the radically polymerizable compound include compounds having a (meth) acryloyl group, preferably from the viewpoint of high reactivity, and specifically, 2 to 6 (meth) acryloyl groups in one molecule. Compounds called polyfunctional acrylate monomers and epoxy (meth) acrylates, urethane (meth) acrylates, and polyester (meth) acrylates have a molecular weight of several hundreds of (meth) acryloyl groups in the molecule. Thousands of oligomers are mentioned, preferably one or more selected from epoxy (meth) acrylates, urethane (meth) acrylates and polyester (meth) acrylates.

The cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetanyl group, and a vinyl ether group. The number of cationically polymerizable groups contained in one molecule of the cationically polymerizable compound is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.
Further, as the cationically polymerizable compound, a compound having at least one epoxy group and an oxetanyl group as the cationically polymerizable group is preferable. A cyclic ether group such as an epoxy group or an oxetanyl group is preferable because the shrinkage associated with the polymerization reaction is small. Further, among the cyclic ether groups, compounds having an epoxy group are easily available, compounds having various structures are easily available, the durability of the obtained hard coat layer is not adversely affected, and compatibility with radically polymerizable compounds is easily controlled. There is an advantage. Further, among the cyclic ether groups, the oxetanyl group tends to have a higher degree of polymerization than the epoxy group, accelerates the network formation rate obtained from the cationically polymerizable compound of the obtained hard coat layer, and is mixed with the radically polymerizable compound. There are advantages such as forming an independent network without leaving unreacted monomers in the film even in the region where the polymer is formed.
Examples of the cationically polymerizable compound having an epoxy group include polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, or a cyclohexene ring or cyclopentene ring-containing compound with an appropriate oxidizing agent such as hydrogen peroxide or peracid. Alicyclic epoxy resin obtained by epoxidation; polyglycidyl ether of aliphatic polyhydric alcohol or its alkylene oxide adduct, polyglycidyl ester of aliphatic long chain polybasic acid, homopolymer of glycidyl (meth) acrylate, An aliphatic epoxy resin such as a copolymer; a glycidyl ether produced by reacting bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or derivatives such as alkylene oxide adducts and caprolactone adducts thereof with epichlorohydrin. And novolak epoxy resin and the like, and glycidyl ether type epoxy resin derived from bisphenols and the like can be mentioned.

The hard coat composition may further contain a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and a cationic polymerization initiator, and the like, which are appropriately selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate radicals or cations to promote radical polymerization and cation polymerization.
The radical polymerization initiator may be any as long as it can release a substance that initiates radical polymerization by at least one of active energy ray irradiation and heating. For example, examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisbutyronitrile.
Active energy ray radical polymerization initiators include Type 1 radical polymerization initiators, which generate radicals by decomposition of molecules, and Type 2 radical polymerization initiators, which coexist with tertiary amines and generate radicals by hydrogen abstraction type reaction. Yes, they are used alone or in combination.
The cationic polymerization initiator may be any one as long as it can release a substance that initiates cationic polymerization by at least one of activation 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. These can initiate cationic polymerization by either irradiation with active energy rays or heating, depending on the structure.

The polymerization initiator can preferably contain 0.1 to 10% by mass based on 100% by mass of the entire hard coat composition. When the content of the polymerization initiator is in the above range, curing can proceed sufficiently, and the mechanical properties and adhesive strength of the finally obtained coating film can be in a good range. Poor adhesive strength due to curing shrinkage, cracking phenomenon, and curling phenomenon tend to be less likely to occur.

The hard coat composition may further comprise one or more selected from the group consisting of solvents and additives.
The solvent can dissolve or disperse the polymerizable compound and the polymerization initiator, and any solvent known as a solvent for hard coat compositions in the present technology does not impair the effects of the present invention. In the range, it can be used.
The additive may further contain inorganic particles, a leveling agent, a stabilizer, a surfactant, an antistatic agent, a lubricant, an antifouling agent and the like.

(Adhesive layer)
The adhesive layer is a layer having an adhesive function, and has a function of adhering an optical film to another member. As a material for forming the adhesive layer, a commonly known material can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used. In this case, the resin composition can be polymerized and cured by supplying energy after the fact.

The adhesive layer may be a layer called a pressure-sensitive adhesive (Pressure Sensitive Adhesive, PSA), which is attached to an object by pressing. The pressure-sensitive adhesive may be an adhesive that is "a substance that has adhesiveness at room temperature and adheres to an adherend with a light pressure" (JIS K6800), and "protects a specific component (microcapsules). It may be a capsule type adhesive which is "an adhesive which can maintain stability until the film is broken by an appropriate means (pressure, heat, etc.)" (JIS K6800).

(Hue adjustment layer)
The hue adjusting layer is a layer having a hue adjusting function, and is a layer capable of adjusting a laminate containing an optical film to a desired hue. The hue adjusting layer is, for example, a layer containing a resin and a colorant. Examples of this colorant include inorganic pigments such as titanium oxide, zinc oxide, petals, titanium oxide-based calcined pigments, ultramarine, cobalt aluminate, and carbon black; azo compounds, quinacridone compounds, anthracinone compounds, and the like. Organic pigments such as perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, slene compounds, and diketopyrrolopyrrole compounds; extender pigments such as barium sulfate and calcium carbonate; and basic dyes, Examples thereof include dyes such as acidic dyes and medium dyes.

(Refractive index adjustment layer)
The refractive index adjusting layer is a layer having a function of adjusting the refractive index, for example, a layer having a refractive index different from that of an optical film and capable of imparting a predetermined refractive index to the optical laminate. The refractive index adjusting layer may be, for example, a resin layer appropriately selected and, in some cases, a resin layer further containing a pigment, or a thin film of metal. Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide and tantalum oxide. The average primary particle size of the pigment may be 0.1 μm or less. By setting the average primary particle size of the pigment to 0.1 μm or less, diffuse reflection of light transmitted through the refractive index adjusting layer can be prevented, and deterioration of transparency can be prevented. Examples of the metal used for the refractive index adjusting layer include metals such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride. Oxides or metal nitrides can be mentioned.

(Protective film)
In one embodiment of the present invention, the optical film may have a protective film on at least one side (one side or both sides). For example, when the functional layer is provided on one side of the optical film, the protective film may be laminated on the surface on the optical film side or the surface on the functional layer side, and is laminated on both the optical film side and the functional layer side. You may. When the optical film has functional layers on both sides, the protective film may be laminated on the surface on one functional layer side or on the surfaces on both functional layer sides. The protective film is a film for temporarily protecting the surface of the optical film or the functional layer, and is not particularly limited as long as it is a peelable film capable of protecting the surface of the optical film or the functional layer. Examples of the protective film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resin films such as polyethylene and polypropylene films, acrylic resin films, and the like, and polyolefin resin films and polyethylene. It is preferable to select from the group consisting of a terephthalate resin film and an 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, but 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 laminated body, for example, the optical film produced as described above may be used as it is, or a laminated body with another film. May be used as.

In a preferred embodiment of the present invention, the optical film of the present invention is in front of a front plate of an image display device, particularly a front plate of a flexible display device (hereinafter also referred to as "window film"), particularly a rollable display or a foldable display. Very useful as a face plate. The flexible display device has, for example, a flexible functional layer and an optical film that is superposed on the flexible functional layer and functions as a front plate. That is, the front plate of the flexible display device is arranged on the visual side on the flexible functional layer. This front plate has a function of protecting the flexible functional layer.

Examples of the image display device include wearable devices such as televisions, smartphones, mobile phones, car navigation systems, tablet PCs, portable game machines, electronic papers, indicators, bulletin boards, watches, and smart watches. Examples of the flexible display device include all image display devices having flexible characteristics.

[Flexible display device]
The present invention also provides a flexible display device including the optical film of the present invention. The optical film of the present invention is preferably used as a front plate in a flexible display device, and the front plate may be referred to as a window film. The flexible display device includes a laminated body for a flexible display device and an organic EL display panel, and the laminated body for the flexible display device is arranged on the visual side with respect to the organic EL display panel and is configured to be bendable. The laminated body for a flexible display device may contain the optical film (window film), the circularly polarizing plate, and the touch sensor of the present invention, and the stacking order thereof is arbitrary, but the window film and the circularly polarized light from the visual side. It is preferable that the plate, the touch sensor or the window film, the touch sensor, and the circularly polarizing plate are laminated in this order. The presence of a circularly polarizing plate on the visible side of the touch sensor is preferable because the pattern of the touch sensor is less likely to be visually recognized and the visibility of the displayed image is improved. Each member can be laminated using an adhesive, an adhesive, or the like. Further, a light-shielding pattern formed on at least one surface of any layer of the window film, the circularly polarizing plate, and the touch sensor can be provided.

[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 a function of transmitting only a right circularly polarized light or a left circularly polarized light component by laminating a λ / 4 retardation plate on a linear polarizing plate. For example, the external light is converted to right-handed circularly polarized light and reflected by the organic EL panel to block the left-handed circularly polarized light, and only the light emitting component of the organic EL is transmitted to suppress the influence of the reflected light. It is used to make it easier to see. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizing plate and the slow axis of the λ / 4 retardation plate must theoretically be 45 °, but practically, they are 45 ± 10 °. The linear polarizing plate and the λ / 4 retardation plate do not necessarily have to be laminated adjacent to each other, and the relationship between the absorption axis and the slow phase axis may satisfy the above range. It is preferable to achieve perfect circularly polarized light at all wavelengths, but it is not always necessary in practical use. Therefore, the circularly polarizing plate in the present invention also includes an elliptical polarizing plate. It is also preferable to further laminate a λ / 4 retardation film on the visible side of the linear polarizing plate to convert the emitted light into circularly polarized light to improve the visibility when wearing polarized sunglasses.

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

The linear polarizer may be a film-type polarizer produced by dyeing and stretching a polyvinyl alcohol (hereinafter, also referred to as “PVA”) film. A dichroic dye such as iodine is adsorbed on the PVA-based film oriented by stretching, or the dichroic dye is oriented in a state of being adsorbed on the PVA to exhibit polarization performance. In the production of the film-type polarizer, other steps such as swelling, cross-linking with boric acid, washing with an aqueous solution, and drying may be included. The stretching and dyeing steps may be performed on the PVA-based film alone, or may be performed in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10 to 100 μm, and the draw ratio is preferably 2 to 10 times.

Further, as another example of the polarizer, there is a liquid crystal coating type polarizer formed by coating a liquid crystal polarizing composition. The liquid crystal polarizing composition may contain a liquid crystal compound and a dichroic dye compound. The liquid crystal compound may have a property of exhibiting a liquid crystal state, and is particularly preferable when it has a higher-order orientation state such as a smectic phase because it can exhibit high polarization performance. It is also preferable that the liquid crystal compound has a polymerizable functional group.
The dichroic dye is a dye that is oriented together with the liquid crystal compound to exhibit dichroism, and may have a polymerizable functional group, and the dichroic dye itself has a liquid crystal property. You may. Any compound in the liquid crystal polarizing composition has a polymerizable functional group.

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

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

The alignment film can be produced, for example, by applying an alignment film forming composition on a base material and imparting orientation by rubbing, polarized light irradiation, or the like. The alignment film forming composition may contain a solvent, a cross-linking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like in addition to the alignment agent. Examples of the alignment agent include polyvinyl alcohols, polyacrylates, polyamic acids, and polyimides. When applying photo-orientation, it is preferable to use an orientation agent containing a synnamate group. The weight average molecular weight of the polymer used as the alignment agent may be, for example, about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000 nm, and more preferably 10 to 500 nm from the viewpoint of orientation regulating force.

The liquid crystal polarizing layer can be peeled off from the base material, transferred and laminated, or the base material can be laminated as it is. It is also preferable that the base material serves as a transparent base material for a protective film, a retardation plate, and a window film.

The protective film may be a transparent polymer film, and specifically, the polymer film used has a unit of a monomer containing polyethylene, polypropylene, polymethylpentene, norbornene or cycloolefin. Polyimides such as cycloolefin derivatives, (modified) celluloses such as diacetyl cellulose, triacetyl cellulose, propionyl cellulose, acrylics such as methyl methacrylate (co) polymer, polystyrenes such as styrene (co) polymer, acrylonitrile -Butadiene-styrene copolymers, acrylonitrile-styrene copolymers, ethylene-vinyl acetate copolymers, polyvinyl chlorides, polyvinylidene chlorides, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, poly Films such as polyesters such as allylate, polyamides such as nylon, polyimides, polyamideimides, polyetherimides, polyethersulfones, polysulfones, polyvinyl alcohols, polyvinylacetals, polyurethanes, epoxy resins, etc. In terms of excellent transparency and heat resistance, preferred examples include polyamide, polyamideimide, polyimide, polyester, olefin, acrylic or cellulose-based film. Each of these polymers can be used alone or in combination of two or more. These films are used unstretched or as uniaxially or biaxially stretched films. Cellulose-based films, olefin-based films, acrylic films, and polyester-based films are preferable. It may be a coating type protective film obtained by applying a cationic curing composition such as an epoxy resin or a radical curing composition such as acrylate and curing the film. Plasticizers, UV absorbers, infrared absorbers, colorants such as pigments and dyes, optical brighteners, dispersants, heat stabilizers, light stabilizers, antioxidants, antioxidants, lubricants, as needed. It may contain a solvent or the like. The thickness of the protective film is preferably 200 μm or less, more preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the protective film is unlikely to decrease.

The λ / 4 retardation plate is a film that gives a phase difference of λ / 4 in a direction orthogonal to the traveling direction of incident light, that is, in the in-plane direction of the film. The λ / 4 retardation plate may be a stretch-type retardation plate manufactured by stretching a polymer film such as a cellulose-based film, an olefin-based film, or a polycarbonate-based film. The λ / 4 retardation plate may be used as a retardation adjuster, a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or a dye, a fluorescent whitening agent, a dispersant, a heat stabilizer, and the like. It may contain a light stabilizer, an antioxidant, an antioxidant, a lubricant, a solvent and the like. The thickness of the stretched retardation plate is preferably 200 μm or less, more preferably 1 to 100 μm. When the thickness is in the above range, the flexibility of the film tends to be difficult to decrease.

Further, as another example of the λ / 4 retardation plate, there is a liquid crystal coating type retardation plate formed by coating a liquid crystal composition. The liquid crystal composition contains a liquid crystal compound having a property of exhibiting a liquid crystal state such as nematic, cholesteric, and smectic. Any compound, including the liquid crystal compound in the liquid crystal composition, has a polymerizable functional group. The liquid crystal composition can further contain an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a cross-linking agent, a silane coupling agent and the like. The liquid crystal coating type retardation plate can be manufactured by applying and curing a liquid crystal composition on an alignment film to form a liquid crystal retardation layer in the same manner as described in the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed to be thinner than the stretch type retardation plate. The thickness of the liquid crystal polarizing layer is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. The liquid crystal coating type retardation plate can be peeled off from the base material, transferred and laminated, or the base material can be laminated as it is. It is also preferable that the base material serves as a transparent base material for a protective film, a retardation plate, and a window film.

In general, there are many materials that exhibit greater birefringence at shorter wavelengths and smaller birefringence at longer wavelengths. In this case, since it is not possible to achieve a phase difference of λ / 4 in the entire visible light region, an in-plane phase difference of λ / 4 with respect to the vicinity of 560 nm having high visual sensitivity, that is, preferably 100 to 180 nm. , More preferably, it is often designed with an in-plane phase difference of 130 to 150 nm. A reverse dispersion λ / 4 retardation plate using a material having a birefringence wavelength dispersion characteristic opposite to the usual one is preferable in that visibility can be improved. As such a material, those described in JP-A-2007-232873 for stretch-type retardation plates and those described in JP-A-2010-30979 for liquid crystal-coated retardation plates should be used. Is also preferable.

Further, as another method, a technique for obtaining a wideband 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 by the same material and method as the λ / 4 retardation plate. The combination of the stretchable retardation plate and the liquid crystal coating type retardation plate is arbitrary, but in either case, it is preferable to use the liquid crystal coating type retardation plate in that the thickness can be reduced.

A method of laminating a positive C plate on the circularly polarizing plate in order to enhance visibility in an oblique direction is also known (Japanese Unexamined Patent Publication No. 2014-224738). The positive C plate may be a liquid crystal coating type retardation plate or a stretched retardation plate. The phase difference 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 means. Various types of touch sensors have been proposed, such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and a capacitance method. Any method may be used, but the capacitance method is preferable. .. The capacitive touch sensor is divided into an active region and an inactive region located outside the active region. The active area is an area corresponding to the display unit, which is the area where the screen is displayed on the display panel, the area where the user's touch is sensed, and the inactive area is the area where the screen is not displayed on the display device. This is the area corresponding to the non-display part. The touch sensor is formed on a substrate having flexible characteristics; a sensing pattern formed in an active region of the substrate; and is formed in an inactive region of the substrate, and is connected to an external drive circuit via the sensing pattern and a pad portion. Each sensing line for can be included. As the substrate having flexible properties, the same material as the polymer film can be used. The substrate of the touch sensor preferably has a toughness of 2,000 MPa% or more from the viewpoint of suppressing cracks in the touch sensor. More preferably, the toughness may be 2,000 to 30,000 MPa%. Here, toughness is defined as the lower area of the curve to the fracture point by the stress-strain curve obtained through the tensile experiment of the polymer material.

The sensing pattern can 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 from each other. The first pattern and the second pattern are formed in the same layer, and each pattern must be electrically connected in order to sense the touched point. The first pattern is a form in which each unit pattern is connected to each other via a joint, but the second pattern has a structure in which each unit pattern is separated from each other into an island form, so that the second pattern is electrically connected. A separate bridge electrode is required for connection. As an electrode for electrically connecting the second pattern, a well-known transparent electrode material can be applied. Examples of the transparent electrode material include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc oxide oxide (IZTO), and indium gallium zinc oxide (IGZO). Examples thereof include cadmium tin oxide (CTO), PEDOT (poly (3,4-ethylenedioxythiophene)), carbon nanotubes (CNT), graphene, metal wire, etc., and these can be used alone or in combination of two or more. .. ITO can be preferably used as the transparent electrode material. The metal used for the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, etc., and these may be used alone or in combination of two or more. Can be done.

The bridge electrode can be formed on the upper part of the insulating layer via the insulating layer on the upper part of the sensing pattern, the bridge electrode is formed on the substrate, and the insulating layer and the sensing pattern can be formed on the bridge electrode. The bridge electrode can also be formed of the same material as the sensing pattern and is made of a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium or an alloy of two or more of these. You can also do it. Since the first pattern and the second pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer can be formed only between the joint of the first pattern and the bridge electrode, or can be formed as a layer covering the entire sensing pattern. When formed as a layer covering the entire sensing pattern, the bridge electrode can connect the second pattern via a contact hole formed in the insulating layer.

The touch sensor has a difference in transmittance between a patterned region in which a pattern is formed and a non-patterned region in which a pattern is not formed, specifically, a light transmittance induced by a difference in refractive index in these regions. An optical control layer may be further included between the substrate and the electrodes as a means to adequately compensate for the difference. The optical control layer may contain an inorganic insulating material or an organic insulating material. The optical control layer can be formed by coating a photocurable composition containing a photocurable organic binder and a solvent on a substrate. The photocurable composition may further contain inorganic particles. The refractive index of the optical control layer can be increased by the inorganic particles.
The photocurable organic binder may contain, for example, a copolymer of each monomer such as an acrylate-based monomer, a styrene-based monomer, and a carboxylic acid-based monomer. The photocurable organic binder may be, for example, a copolymer containing different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.
Examples of the inorganic particles include zirconia particles, titania particles, alumina particles and the like. The photocuring composition may further contain additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

[Adhesive layer]
Each layer such as a window film, a polarizing plate, and a touch sensor forming the laminated body for a flexible display device, and a film member such as a linear polarizing plate and a λ / 4 retardation plate constituting each layer can be adhered with an adhesive. can. Adhesives include water-based adhesives, organic solvent-based adhesives, solvent-free adhesives, solid adhesives, solvent volatilization adhesives, moisture-curable adhesives, heat-curable adhesives, anaerobic curable adhesives, and water-based adhesives. It is widely used in solvent volatilization adhesives, active energy ray-curable adhesives, hardener mixed adhesives, heat-melt adhesives, pressure-sensitive adhesives, pressure-sensitive adhesives, re-wet adhesives, etc. Things can be used. Of these, water-based solvent volatilization adhesives, active energy ray-curable adhesives, and adhesives are often used. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive force and the like, and is preferably 0.01 to 500 μm, more preferably 0.1 to 300 μm. The laminated body for a flexible image display device may have a plurality of adhesive layers, but the thickness of each and the type of adhesive used may be the same or different.

As the water-based solvent volatilization type adhesive, a polyvinyl alcohol-based polymer, a water-soluble polymer such as starch, an ethylene-vinyl acetate-based emulsion, a styrene-butadiene-based emulsion, or the like in an aqueous-dispersed state can be used as the main component polymer. In addition to water and the main component polymer, a cross-linking agent, a silane compound, an ionic compound, a cross-linking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent and the like may be blended. When adhering with the water-based solvent volatilization type adhesive, the water-based solvent volatilization type adhesive can be injected between the layers to be adhered, the adherend layers are bonded, and then dried to impart adhesiveness. When the water-based solvent volatilization type adhesive is used, the thickness of the adhesive layer may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the water-based solvent volatilization type adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the 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 that is irradiated with active energy rays to form an adhesive layer. The active energy ray-curable composition can contain at least one polymer of a radically polymerizable compound and a cationically polymerizable compound similar to the compounds described for the hard coat composition. As the radically polymerizable compound, the same type as the compound described for the hard coat composition can be used. As the radically polymerizable compound used for the adhesive layer, a compound having an acryloyl group is preferable. In order to reduce the viscosity of the adhesive composition, it is also preferable that the composition contains a monofunctional compound.

As the cationically polymerizable compound, the same type as the compound described for the hard coat composition can be used. As the cationically polymerizable compound used in the active energy ray-curing composition, an epoxy compound is more preferable. 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 can further contain a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, and these can be appropriately selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate radicals or cations to promote radical polymerization and cation polymerization. In the description of the hard coat composition, an initiator that can initiate at least one of radical polymerization or cationic polymerization by irradiation with active energy rays can be used.

The active energy ray-curing composition further comprises an ion scavenger, an antioxidant, a chain transfer agent, an adhesion imparting agent, a thermoplastic resin, a filler, a fluid viscosity modifier, a plasticizer, a defoaming agent solvent, an additive, and a solvent. Can be included. When two layers to be adhered are bonded by the active energy ray-curable adhesive, the active energy ray-curable composition is applied to one or both of the layers to be adhered, then bonded, and one of them is adhered. Adhesion can be achieved by irradiating active energy rays through the layer or both layers to be adhered to cure the composition. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive used may be the same or different.

The pressure-sensitive adhesive is classified into an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and the like according to the main component polymer, and any of these can be used. In addition to the main polymer, the pressure-sensitive adhesive may contain a cross-linking agent, a silane compound, an ionic compound, a cross-linking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler and the like. An adhesive layer (adhesive layer) is formed by dissolving and dispersing each component constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, applying the pressure-sensitive adhesive composition on a substrate, and then drying the mixture. Will be done. The adhesive layer may be directly formed, or a separately formed base material may be transferred. It is also preferable to use a release film to cover the adhesive surface before bonding. When the pressure-sensitive adhesive is used, the thickness of the adhesive layer is preferably 1 to 500 μm, more preferably 2 to 300 μm. When the pressure-sensitive adhesive is used for forming a plurality of layers, the thickness of each layer and the type of pressure-sensitive adhesive used may be the same or different.

[Shading pattern]
The shading pattern can be applied as at least a part of the bezel or housing of the 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 see, thereby improving the visibility of the image. The shading pattern may be in the form of a single layer or multiple layers. The color of the light-shielding pattern is not particularly limited, and can have various colors such as black, white, and metallic. The light-shielding pattern can be formed of a pigment for embodying color and a polymer such as an acrylic resin, an ester resin, an epoxy resin, polyurethane, or silicone. They can also be used alone or in mixtures of two or more. The shading pattern can be formed by various methods such as printing, lithography, and inkjet. The thickness of the shading pattern is preferably 1 to 100 μm, more preferably 2 to 50 μm. It is also preferable to give a shape such as an inclination in the thickness direction of the light-shielding pattern.

Hereinafter, the present invention will be described in more detail with reference to Examples. Unless otherwise specified, "%" and "part" in the example mean mass% and parts by mass. First, the evaluation method will be described.

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

<Haze>
In accordance with JIS K 7136: 2000, the optical films obtained in Examples and Comparative Examples were cut into a size of 30 mm × 30 mm, and a haze computer (manufactured by Suga Test Instruments Co., Ltd., “HGM-2DP”) was used. Haze (%) was measured using.

<YI value>
The YI value (Yellow Index) of the optical film was measured using an ultraviolet-visible near-infrared spectrophotometer "V-670" manufactured by JASCO Corporation in accordance with JIS K 7373: 2006. After performing background measurement without a sample, an optical film is set in the sample holder, transmittance is measured for light of 300 to 800 nm, and tristimulus values (X, Y, Z) are obtained, and the following formula is used. The YI value was calculated based on.
YI = 100 × (1.2769X-1.0592Z) / Y

<Measurement of weight average molecular weight>
Gel Permeation Chromatography (GPC) Measurement (1) Pretreatment Method Add DMF eluent (10 mmol / L lithium bromide solution) to a polyamide-imide film to a concentration of 2 mg / mL, and stir at 80 ° C. for 30 minutes. After heating and cooling, the solution was filtered through a 0.45 μm membrane filter to prepare a measurement solution.
(2) Measurement condition Column: TSKgel α-2500 manufactured by Tosoh Corporation ((7) 7.8 mm diameter x 300 mm) x 1, α-M ((13) 7.8 mm diameter x 300 mm) x 2 eluent : DMF (10 mmol / L lithium bromide added)
Flow rate: 1.0 mL / min Detector: RI detector Column temperature: 40 ° C
Injection volume: 100 μL
Molecular weight standard: Standard polystyrene

<Measurement of thickness>
The thickness of the optical film was measured using an ABS Digimatic Indicator (“ID-C112BS” manufactured by Mitutoyo Co., Ltd.).

<Tension modulus>
The elastic modulus of the optical films obtained in Examples and Comparative Examples at a temperature of 25 ° C. and a relative humidity of 50% was measured using "Autograph AG-IS" manufactured by Shimadzu Corporation. More specifically, a film having a width of 10 mm in length and width was produced, a stress-strain curve (SS curve) was measured under the conditions of a distance between chucks of 50 mm and a tensile speed of 10 mm / min, and the elastic modulus was calculated from the inclination.

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

<Measurement of transmission mapping property value of optical film>
Using a mapping property measuring device (“ICM-1” manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K 7345, the transmission mapping property value of the optical film was measured by the transmission method as follows.
The optical film was placed on the image quality measuring instrument. Before installation, both sides of this optical film were lightly wiped with ethanol and dried to remove foreign matter from the surface before installation. Next, the amount of light and the cross-sectional area were adjusted, and white light adjusted to parallel light was applied to the optical film installed from an angle (incident angle) inclined by 60 ° in the MD direction with respect to the optical film plane. The transmitted light transmitted through the optical film was transmitted to an optical comb extending perpendicular to the optical axis of the irradiation light by adjusting the cross-sectional area, and the light transmitted through the optical comb was received by the receiver.
It is parallel to the plane of the optical comb, and the optical comb (slit width: 0.125 mm) is moved by a predetermined unit width in the direction in which the slits in the optical comb are arranged, and the transmitted light of the optical comb is repeatedly received. rice field. As a result, a received light waveform was obtained. From the obtained received light waveform, the maximum value M and the minimum value m of the relative light amount were obtained. _{The first transmission mapping property value C 60} (MD) was calculated from the obtained M and m based on the mathematical formula (7).

The first transmission mapping property value except that the angle of incidence was changed from a direction perpendicular to the optical film plane to an angle inclined by 60 ° in the TD direction and an angle perpendicular to the optical film plane (an angle inclined by 0 °). In the same manner as above, the second transmission mapping property value C ₆₀ (TD) and the third transmission mapping property value C ₀ were calculated, respectively.

<Imidization rate>
The imidization ratio was ^{determined by 1} H-NMR measurement as follows.
(1) Pretreatment Method An optical film containing a polyimide resin _{was dissolved in deuterated dimethyl sulfoxide (DMSO-d 6} ) to prepare a 2% by mass solution, which was used as a measurement sample.
(2) Measuring conditions Measuring device: JEOL 400MHz NMR device JNM-ECZ400S / L1
Standard substance: DMSO-d ₆ (2.5 ppm)
Sample temperature: Room temperature Accumulation number: 256 times Relaxation time: 5 seconds (3) Imidization rate analysis method (imidization rate of polyimide resin)
^{In the 1} H-NMR spectrum obtained from the measurement sample containing the polyimide resin, the integrated value of benzene proton A derived from the structure that does not change before and after imidization among the observed benzene protons was defined as Int _A. In addition, the integral value of the amide proton derived from the amic acid structure remaining in the observed polyimide resin was defined as Int _B. From these integrated values, the imidization rate of the polyimide resin was determined based on the following formula.
Imidization rate (%) = 100 × (1-Int _B / Int _A )

(Imidization rate of polyamide-imide resin)
^{In the 1} H-NMR spectrum obtained from the measurement sample containing the polyamide-imide resin, the structure derived from the structure of the observed benzene protons that does not change before and after imidization and the structure derived from the amic acid structure remaining in the polyamide-imide resin. The integrated value of the benzene proton C, which is not affected by the above, was defined as Int _C. Further, among the observed benzene protons, the integrated value of benzene proton D, which is derived from the structure that does not change before and after imidization and is influenced by the structure derived from the amic acid structure remaining in the polyamide-imide resin, was defined as Int _D. The β value was calculated from the obtained Int _C and Int _D by the following formula.
β = Int _D / Int _C
Next, the β value of the above formula and the imidization rate of the polyimide resin of the above formula were obtained for a plurality of polyamide-imide resins, and the following correlation formula was obtained from these results.
Imidization rate (%) = k × β + 100
In the above correlation equation, k is a constant.
By substituting β into the correlation equation, the imidization rate (%) of the polyamide-imide resin was obtained.

<Varnish viscosity>
The measurement was performed using an E-type viscometer DV-II + Pro manufactured by Brookfield Co., Ltd. in accordance with JIS K 8803: 2011. The measurement temperature was 25 ° C.

<Bending resistance test>
The optical film was subjected to a bending resistance test in accordance with JIS K 5600-5-1. The bending resistance test was carried out using a small tabletop bending tester (manufactured by Yuasa System Co., Ltd.). For the optical film after the bending resistance test, the transmission mapping property value and the haze were measured in the same manner as in the above-mentioned measuring method. Take the absolute values of the difference between the transmission mapping property value and the haze before and after the bending resistance test, and take the difference between the transmission mapping property values (difference in the first transmission mapping property value ΔC ₆₀ (MD), difference in the second transmission mapping property value). The difference between ΔC ₆₀ (TD) and the third transmission _{mapability value ΔC 0} ) and the difference in haze (ΔHaze) were calculated, respectively.

<Fold resistance test (MIT)>
In accordance with ASTM standard D2176-16, the number of times the optical film was bent in Examples and Comparative Examples was determined as follows. The optical film was cut into strips having a width of 15 mm and a length of 100 mm using a dumbbell cutter to prepare a measurement sample. The measurement sample was set in the main body of the MIT folding fatigue tester (“Model 0530” manufactured by Toyo Seiki Seisakusho Co., Ltd.). Specifically, one end of the measurement sample was fixed to the load clamp, the other end was fixed to the bending clamp, and tension was applied to the measurement sample. In this state, under the conditions of a test speed of 175 cpm, a bending angle of 135 °, a load of 0.75 kgf, and a bending radius of the bending clamp R = 3 mm, a reciprocating bending motion was performed in the front and back directions until the measurement sample broke. The number of bends was measured.

<Visibility>
The optical film was cut into 10 cm squares. The MD direction of the polarizing plate with an adhesive layer of the same size and the MD direction of the cut optical film were aligned, and the polarizing plate with an adhesive layer was bonded to the optical film to prepare a sample for evaluation. Two evaluation samples were prepared for each of the optical films of one example and the comparative example. In addition, two evaluation samples were prepared for each of the optical films of the examples and comparative examples after the bending resistance test.
For one of the two evaluation samples, the fluorescent lamp is located in the direction perpendicular to the evaluation sample plane, and the longitudinal direction of the fluorescent lamp is horizontal to the MD direction of the evaluation sample. Fixed on the table.
The observer visually observed the fluorescent lamp image reflected on the surface of the evaluation sample from an angle of 30 ° with respect to the vertical direction of the evaluation sample plane.
The other evaluation sample was fixed on a table and the fluorescent lamp image was observed in the same manner except that the longitudinal direction of the fluorescent lamp was changed from horizontal to vertical.
From the observation results, the visibility was evaluated based on the following evaluation criteria.
(Visibility evaluation criteria)
⊚: The distortion of the fluorescent lamp image is hardly visible.
◯: The distortion of the fluorescent lamp image is slightly visible.
Δ: Distortion of the fluorescent lamp image is visually recognized.
X: Distortion of the fluorescent lamp image is clearly visible.

(Production Example 1: Preparation of Polyamide-imide 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 was 6.08% by mass, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 6 FDA was added to the flask so as to be 40.82 mol% with respect to TFMB, and the mixture was stirred at room temperature for 16 hours. Then, after cooling to 10 ° C., OMTPC was added so as to be 27.55 mol% with respect to TFMB, and after stirring for 10 minutes, OMTPC was further added so as to be 27.55 mol% with respect to TFMB, and the mixture was stirred for 20 minutes. bottom. Then, the same amount of DMAc as the initially added DMAc 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. Next, 61.22 mol% of diisopropylethylamine and 4-picoline were added to the flask with respect to TFMB, and 285.71 mol% of acetic anhydride was added with respect to TFMB, and the mixture was stirred for 30 minutes, and then the internal temperature was raised to 70 ° C. Then, the mixture was further stirred for 3 hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of filaments, the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60 ° C. to obtain a polyamide-imide resin (1). The weight average molecular weight of the obtained polyamide-imide resin (1) was 300,000, and the imidization ratio was 99.1%.

(Production Example 2: Preparation of Polyamide-imide Resin (2))
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 was 5.22% by mass, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 6 FDA was added to the flask so as to be 41.24 mol% with respect to TFMB, and the mixture was stirred at room temperature for 16 hours. Then, after cooling to 10 ° C., 2,5-dimethylterephthalic acid chloride (hereinafter, may be abbreviated as DMTPC) is added so as to be 27.84 mol% with respect to TFMB, and after stirring for 10 minutes, DMTPC is further added. It was added to 27.84 mL with respect to TFMB, and the mixture was stirred for 20 minutes. Then, the same amount of DMAc as the initially added DMAc was added, and the mixture was stirred for 10 minutes, then DMTPC was added so as to be 6.19 mol% with respect to TFMB, and the mixture was stirred for 2 hours. Next, diisopropylethylamine and 4-picoline were added to the flask in an amount of 61.86 mol% based on TFMB, and acetic anhydride was added in an amount of 288.66 mol% based on TFMB, and the mixture was stirred for 30 minutes, and then the internal temperature was raised to 70 ° C. Then, the mixture was further stirred for 3 hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of filaments, the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60 ° C. to obtain a polyamide-imide resin (2). The weight average molecular weight of the obtained polyamide-imide resin (2) was 280,000, and the imidization ratio was 98.9%.

(Production Example 3: Preparation of silica dispersion)
The solvent methanol in the methanol-dispersed organic-treated silica (average primary particle size 25 nm) was replaced with γ-butyrolactone (GBL) to obtain GBL-dispersed organic-treated silica (solid content 30.5%). This dispersion was designated as the dispersion (1).

(Production Example 4: Preparation of varnish)
The varnishes (1) and (2) were obtained by adding a polyamide-imide resin to GBL so as to have the solid content shown in Table 1 and stirring at room temperature for 24 hours to completely dissolve the varnishes (1) and (2).
The varnish (3) was obtained by adding the polyamide-imide resin and the dispersion liquid 1 to the GBL solvent at room temperature so as to have the solid content shown in Table 1 and stirring until uniform. The mass ratio of the polyamide-imide resin in the varnish (3) to the filler (silica) contained in the dispersion 1 was set to 60:40.

(Production Example 5: Production of composition for forming a hard coat layer)
35 parts by mass of urethane acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .; UA-122P), 35 parts by mass of urethane acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd .; UA-232P), 25 parts by mass of methyl ethyl ketone, 4. A hard coat layer forming composition (1) was produced by mixing 5 parts by mass of a photoinitiator (1-hydroxycyclohexylphenyl ketone) and 0.5 parts by mass of a leveling agent (manufactured by Big Chemie; BYK-3570). ..

<Example 1>
(Manufacturing of optical film (1))
The production 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 material 51 having a thickness of 188 μm (manufactured by Toyobo Co., Ltd .: Cosmo Shine (registered trademark) A4100, hereinafter sometimes referred to as PET film base material 51) is unwound. The varnish (1) contained in the tank 522 was coated on the PET film base material 51 from the nozzle 521 by salivation molding with a width of 500 mm while being conveyed at a linear speed of 0.30 m / min. Then, while transporting at the same linear speed, the applied varnish was dried by heating in a dryer 53 at 120 ° C. for 20 minutes, 95 ° C. for 10 minutes, and 85 ° C. for 10 minutes. Subsequently, the protective film 54 (manufactured by Sanei Kaken Co., Ltd .; NSA-33T) is unwound from the roll and bonded to the surface of the dry coating film opposite to the surface in contact with the PET film base material 51. The PET film base material 51 was peeled off from the dry coating film and wound up as a PET film base material roll 55, and the remaining laminate was obtained as a laminate roll 56 having a length of 100 m.

Next, as shown in FIG. 8, the laminated film is unwound from the obtained laminated body roll 56 at a transport speed of 0.5 m / sec, the protective film 54 is peeled from the laminated film, and the film is wound as the protective film roll 57. The remaining dry coating film was passed through the nip rolls 201 and 202, and then dried in the tenter type dryer 58 under the following conditions. The tenter type dryer 58 includes a mechanism for gripping both ends of the film using clips. Further, the inside is divided into rooms 1 to 6 in order from the entrance side of the film.
<Tenter type dryer 58>
Clip grip width (distance from one end of the film to the corresponding clip grip): 25 mm
Ratio of the distance between clips at the outlet of the dryer to the distance between clips at both ends of the film at the inlet of the dryer: 1.0
Dryer temperature: 200 ° C
Wind speed of each room in the dryer: 13.5 m / sec in the 1st room, 13 m / sec in the 2nd room, 11 m / sec in the 3rd to 6th rooms

After leaving the tenter dryer 58, the clip was released from being gripped at the edge of the film. After passing through the nip rolls 203 and 204, the obtained film is slit at the clip gripping portion of the film by the slit device 59, then the PET protective film 60 is attached, and the film is wound around an ABS 6-inch core to have a thickness of 50 μm. The optical film 61 of the above was obtained as a roll. The residual amount of solvent in the obtained optical film 61 was 1.0% by mass.

<Example 2>
The optical film (except that the varnish (1) was changed to the varnish (2) and the drying conditions in the dryer 53 were changed to heating at 120 ° C. for 20 minutes, 100 ° C. for 10 minutes, and 90 ° C. for 10 minutes. In the same manner as in the production method of 1), an optical film (2) having a thickness of 49 μm and having a residual amount of solvent in the film of 1.0% by mass was produced.

<Example 3>
(Manufacturing of optical film (3))
The composition (1) for forming a hard coat layer produced in Production Example 5 was applied to the surface of the optical film (2) obtained in Example 2 in contact with the PET base film at the time of film formation, after curing. 1 The hard coat layer was applied so as to have a thickness of 3 μm, and dried in an oven at 80 ° C. for 1 minute. ^{Then, light was irradiated with a light amount of 350 mJ / cm 2} using a high-pressure mercury lamp to cure the coating film to form a first hard coat layer, thereby producing an optical film (3) containing the hard coat layer.

<Example 4>
The solvent in the film was the same as the method for producing the optical film (1), except that the varnish (1) was changed to the varnish (3) and the linear velocity was changed from 0.30 m / min to 0.50 m / min. An optical film (4) having a thickness of 51 μm and having a residual amount of 1.0% by mass was produced.

<Comparative example 1>
As the optical film (5), a polyimide film having a thickness of 50 μm (manufactured by Ube Industries, Ltd .; UPILEX) was prepared.

The formulation of the composition and the composition of the optical film are summarized in Table 2. In Table 2, the column "with or without HC" indicates that the optical film has a hard coat layer and does not have a hard coat layer.

For the films obtained in Examples and Comparative Examples, the physical property values were measured according to the above method. The obtained results are shown in Tables 3 to 6.

It was confirmed that the optical films of Examples 1 to 4 in which the total light transmittance and the haze were within the predetermined ranges and the formulas (1) to (3) were satisfied were excellent in visibility in the wide angle direction. Further, in a preferred embodiment of the present invention, the optical film of the present invention has a small difference in mapping property values and a difference in haze before and after the bending resistance test, and is excellent in visibility in the wide-angle direction even after repeated bending operations. It was confirmed that. Further, 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 considered that such an optical film is unlikely to cause warpage or delamination during high temperature treatment. On the other hand, the optical film of Comparative Example 1 in which the total light transmittance and the haze were not within the predetermined ranges and did not satisfy the mathematical formulas (1) to (3) was not excellent in visibility in the wide-angle direction. Further, R ₀ exceeds 300 nm, and it is considered that the film has a large distortion.

1 Optical film 3 Vertical axis 10 1st incident light 11 1st incident position 12 1st a transmitted light 14 1st optical axis 16 1st optical comb 18 1st b transmitted light 19 1st receiver 20 2nd incident light 21 2nd incident Position 22 2nd a transmitted light 24 2nd optical axis 26 2nd optical comb 28 2nd b transmitted light 29 2nd receiver 30 3rd incident light 31 3rd incident position 32 3a transmitted light 34 3rd optical axis 36 3rd optical Comb 38 3b transmitted light 39 3rd receiver 40 zone 41 zone 42 zone 43 gripping device 44 raw material film 45 resin film 46 upper nozzle (nozzle)
47 Lower nozzle (nozzle)
48 Nozzle 49 IR heater 100 Tenter furnace 100a Upper surface 100b Lower surface A Film transport direction 51 PET film base material 521 Nozzle 522 Tank 53 Dryer 54 Protective film 55 PET film base material roll 56 Laminated roll 57 Protective film roll 58 Tenter type drying Machine 201 Nip Roll 202 Nip Roll 59 Slit Device 60 PET Protective Film 61 Optical Film 201-204 Nip Roll 101-109 Guide Roll

Claims (12)

An optical film containing at least one resin selected from the group consisting of a polyimide resin and a polyamide resin, having a total light transmittance of 85% or more, a haze of 0.5% or less, and in-plane. The phase difference R ₀ is 40 nm to 300 nm, and the phase difference R 0 is 40 nm to 300 nm.
When the direction parallel to the machine flow direction at the time of manufacture in the optical film plane is the MD direction and the direction perpendicular to the machine flow direction is the TD direction,
The first transmission mapping property value C in the direction inclined by 60 ° in the MD direction from the direction perpendicular to the plane of the optical film, which is obtained when the width of the optical comb is 0.125 mm in accordance with JIS K 7374. _{The 60 (MD), the second transmission mapping property value C 60} (TD) in the direction inclined by 60 ° from the vertical direction to the TD direction, and the third transmission mapping property value C _{0 in} the vertical direction are
Formula (1):
87% ≤ C ₆₀ (MD) ≤ 100% ... (1),
Formula (2):
87% ≤ C ₆₀ (TD) ≤ 100% ... (2), and mathematical formula (3):
0.8 ≤ C ₆₀ (MD) / C ₀ ≤ 1.0 ... (3)
An optical film that meets the requirements. The second transmission mapping property value and the third transmission mapping property value are calculated by the mathematical formula (4):
0.9 ≤ C ₆₀ (TD) / C ₀ ≤ 1.0 ... (4)
The optical film according to claim 1, further satisfying the above. The in-plane phase difference R ₀ nm and the thickness direction phase difference R _th nm are mathematical formulas (5):
3 ≤ R _th / R ₀ ≤ 200 ... (5)
The optical film according to claim 1 or 2, which satisfies the above conditions. The optical film according to any one of claims 1 to 3, wherein the haze difference ΔHaze before and after the bending resistance test according to JIS K 5600-5-1 is less than 0.3%. The difference in the first transmission mapping property value before and after the bending resistance test according to JIS K 5600-5-1 ΔC ₆₀ (MD), the difference in the second transmission mapping property value ΔC ₆₀ (TD), and the third. The optical film according to any one of claims 1 to 4, wherein _{the difference ΔC 0} of the transmission mapping property values is less than 15, respectively. The optical film according to any one of claims 1 to 5, wherein the resin selected from the group consisting of a polyimide resin and a polyamide resin has a weight average molecular weight of 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 surface. The optical film according to claim 8, wherein the hard coat layer has a thickness of 3 to 30 μm. A flexible display device comprising the optical film according to any one of claims 1 to 9. The flexible display device according to claim 10, further comprising a touch sensor. The flexible display device according to claim 10 or 11, further comprising a polarizing plate.

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