TW202142604A - Optical film and flexible display device with excellent visibility in a wide-angle direction and sufficient mechanical properties even in a low temperature environment - Google Patents

Abstract

Provided are an optical film with excellent visibility in a wide-angle direction and sufficient mechanical properties even in a low temperature environment and a flexible display device equipped with the optical film. The optical film of this invention contains at least one resin selected from a group consisting of polyimide resin and polyamide resin, having a full light-transmissive rate of 85% or more, a haze of 0.5% or less, and a tensile modulus of elasticity of 5.1 GPa or more; when the direction parallel to the machine travel direction in the film plane during manufacturing is defined as the MD direction, and the direction perpendicular to the machine travel direction is defined as the TD direction, for at least any surface of the optical film, the first reflection image clarity value CMD obtained in accordance with JIS K 7374 when the slit width of the optical comb is 0.125 mm and in the direction inclined 60 degrees from the vertical direction to the MD direction with respect to the film plane and the second reflection image clarity value CTD inclined 60 degrees from the vertical direction to the TD direction satisfy the following: formula (1) 45% ≤ CMD ≤ 100%; formula (2) 30% ≤ CTD ≤ 100%; and formula (3) 35% ≤ (CMD + CTD)/2 ≤ 100%, and the breaking strain [epsilon]1 of the optical film at -40 DEG C and the breaking strain [epsilon]2 at 25 DEG C satisfy the formula (4): 0.70 ≤ [epsilon]1/[epsilon]2 ≤ 1.20.

Description

Optical film and flexible display device

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

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

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

[The problem to be solved by the invention]

When a polyimide resin film is applied to a transparent member such as a front panel of a flexible display device, the image may be displayed in a state where the image display surface is curved. Therefore, it is compared with a non-flexible image display surface. , Requires excellent visibility in the wide-angle direction. However, according to the research of the present inventors, the prior polyimide-based resin film may not sufficiently satisfy the visibility in the wide-angle direction. In addition, especially when the optical film of the present invention is used in a low temperature environment, there are cases where sufficient mechanical properties of the optical film cannot be obtained.

In addition, the inventors of the present invention have discovered that, for example, the optical films described in Patent Documents 1 and 2 may not sufficiently satisfy the visibility in the wide-angle direction.

Therefore, the object of the present invention is to provide an optical film having excellent visibility in a wide-angle direction and sufficient mechanical properties even in a low temperature environment, and a flexible display device provided with the optical film. [Technical means to solve the problem]

The inventors of the present invention have made painstaking research to solve the above-mentioned problems. As a result, they have found that the above-mentioned problems can be solved by the following optical film. The above-mentioned optical film contains a polyimide resin and a polyamide resin At least one resin in the group of resins, with a total light transmittance of 85% or more, a haze of 0.5% or less, a tensile modulus of 5.1 GPa or more at 25°C, and an optical film's -40°C The breaking strain ε ₁ and the breaking strain ε _{2 at} 25°C satisfy a specific relationship. That is, the following aspects are included in the present invention.

[1] An optical film containing at least one resin selected from the group consisting of polyimide resins and polyimide resins, and has a total light transmittance of 85% or more and a haze of 0.5% Hereinafter, when the tensile modulus of elasticity is 5.1 GPa or more, the direction parallel to the mechanical flow direction during manufacture is set as the MD direction in the above optical film plane, and the direction perpendicular to the mechanical flow direction is set as the TD direction. At least any surface of the above optical film is obtained in accordance with JIS K 7374 when the slit width of the optical comb is 0.125 mm from a direction perpendicular to the plane of the optical film to a direction inclined 60° in the MD direction. 1 The reflected image sharpness value C _{MD and the second reflected image sharpness value C TD in a} direction inclined 60° from the above vertical direction to the above TD direction satisfy the equation (1): 45%≦C _MD ≦100%・・・(1), formula (2): 30%≦C _TD ≦100%・・・(2), and formula (3): 35%≦(C _MD ＋C _TD )/2≦100%・・· (3), at the break of the optical film of -40 ℃ strain ε ₁ and broken off at the breaking strain ε ₂ 25 ℃ satisfy equation _{(4): 0.70 ≦ ε 1} / ε 2 ≦ 1.20 · · · (4 ). [2] The optical film of [1] above, wherein the difference ΔHaze between the haze before and after the bending resistance test according to JIS K 5600-5-1 is less than 0.3%. [3] The optical film of [1] or [2] above, wherein the difference ΔC _MD between the first reflection image sharpness value before and after the bending resistance test according to JIS K 5600-5-1 and the second reflection The difference in image sharpness value ΔC _{TD is} less than 15. [4] The optical film of any one of [1] to [3] above, which has a thickness of 10 to 150 μm. [5] The optical film according to any one of [1] to [4] above, wherein the content of the filler in the optical film is 0 to 5% by mass relative to the total mass of the optical film. [6] The optical film according to any one of [1] to [5] above, which has a hard coat layer on at least one side. [7] The optical film of the above [6], wherein the thickness of the hard coat layer is 3-30 μm. [8] A flexible display device including the optical film of any one of [1] to [7] above. [9] The flexible display device of [8] above, which further includes a polarizing plate. [10] The flexible display device of [8] or [9] above, which is further provided with a touch sensor. [Effects of the invention]

According to the present invention, it is possible to provide an optical film having excellent visibility in a wide-angle direction and sufficient mechanical properties even in a low temperature environment, and a flexible display device provided with the optical film.

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

<Optical film> The optical film of the present invention contains at least one resin selected from the group consisting of polyimide resins and polyamide resins, and has a total light transmittance of 85% or more and a haze of 0.5% or less, When the tensile modulus of elasticity at 25°C is 5.1 GPa or more, the direction parallel to the mechanical flow direction during manufacture is set as the MD direction in the above-mentioned optical film plane, and the direction perpendicular to the mechanical flow direction is set as the TD direction , On at least any one surface of the above-mentioned optical film, obtained in accordance with JIS K 7374 when the slit width of the optical comb is 0.125 mm from a direction perpendicular to the plane of the above-mentioned optical film to the above-mentioned MD direction inclined by 60° The first reflected image sharpness value C _{MD in the direction and the second reflected image sharpness value C TD in a} direction inclined 60° from the vertical direction to the TD direction satisfy the formula (1): 45%≦C _MD ≦ 100%・・・(1), formula (2): 30%≦C _TD ≦100%・・・(2), and formula (3): 35%≦(C _MD ＋C _TD )/2≦100 ·% (3), at the break of the optical film of -40 ℃ strain ε ₁ and broken off at the breaking strain ε ₂ 25 ℃ satisfy equation _{(4): 0.70 ≦ ε 1} / ε 2 ≦ 1.20 · ·・(4).

The MD direction is a direction parallel to the direction of mechanical flow during manufacture in the optical film plane, for example, indicates a direction parallel to the direction of transporting the optical film when manufactured by a solution casting method. The TD direction is a direction perpendicular to the above-mentioned mechanical flow direction, for example, it means a direction perpendicular to the conveying direction. The MD direction and TD direction in the optical film plane are determined by the following method when their directions are not clear. Regarding MD and TD, at least 20 points of cross-section of the optical film in different directions are cut. In more detail, suppose a circle with any one point of the optical film as the midpoint, cut out a semicircle from the optical film, and then cut the semicircle with the central angle of the fan shape being approximately equal, the optical film is Cut in a straight line and cut more than 20 cross-sections. The center of the thickness of a plurality of cross-sections obtained by laser Raman measurement, and the ^{highest peak intensity near 1,620 cm -1} is set as the MD direction.

。 反射圖像清晰度值(第1反射圖像清晰度值及下述第2反射圖像清晰度值)可使用圖像清晰度測定器而測定。The first reflected image sharpness value C _MD is a reflected image sharpness value obtained in accordance with Japanese Industrial Standards (JIS) K 7374 from a direction perpendicular to the plane of the optical film to a direction inclined 60° to the MD direction. With reference to Fig. 1, the first reflected image sharpness value C _MD will be described in more detail. Fig. 1 is a diagram showing the optical axis in the measurement of the first reflected image sharpness value. Along an arbitrary point on the surface of the optical film 1 (first irradiation position 11) as a fulcrum, from an axis perpendicular to the optical film 1 (vertical axis 3) to an axis with an angle of 60° in the MD direction (first optical axis 14) , Irradiate the optical film 1 with the first irradiation light 10 (white light: indicated by a solid line in FIG. 1). Then, the first specular reflection light 12 (indicated by the dotted line in FIG. 1) is transmitted through the first optical comb extending perpendicularly to the first direction with the first irradiation position 11 as a fulcrum and inclined from the vertical axis 3 to the MD direction by -60° 16. Then, the first light receiver 19 extending in the first direction receives the first transmitted light 18 (indicated by a single-dot chain line in FIG. 1) that has passed through the first optical comb 16. The first optical comb 16 has an opening portion through which the first specular reflection light 12 passes, and a light shielding portion that blocks the first specular reflection light 12. The slit width (width of the opening) of the first optical comb 16 is 0.125 mm. 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 (the direction of arrow A), the first optical comb 16 is moved by a specific unit width and receives the first transmitted light 18. Repeat the operation to obtain the received light waveform. Obtain the maximum value M and the minimum value m of the relative light intensity from the received light waveform. From the obtained M and m, calculate the first reflection image sharpness value C _{MD based on the equation (5)}

. The reflected image sharpness value (the first reflected image sharpness value and the second reflected image sharpness value described below) can be measured using an image sharpness measuring device.

If the first reflected image sharpness value C _MD satisfies the formula (1), the visibility of the optical film in the wide-angle direction of the MD direction is excellent. The first reflected image clarity value C _MD is 45% or more in the formula (1). From the viewpoint of further improving the visibility of the optical film in the wide-angle direction in the MD direction, it is preferably 47% or more, more preferably It is 48% or more, more preferably 50% or more, still more preferably 55% or more, particularly preferably 60% or more, and usually 100% or less.

The second reflection image definition value C _TD is a reflection image definition value obtained in accordance with JIS K 7374 from a direction perpendicular to the plane of the optical film to a direction inclined 60° toward the TD direction. With reference to Fig. 2, the second reflection image sharpness value C _TD will be described in more detail. Fig. 2 is a diagram showing the optical axis in the measurement of the sharpness value of the second reflected image. Along an arbitrary point on the surface of the optical film 1 (second irradiation position 21) as a fulcrum, from the axis perpendicular to the optical film 1 (vertical axis 3) to an axis with an angle of 60° in the TD direction (second optical axis 24) , Irradiate the optical film 1 with the second irradiation light 20 (white light: indicated by a solid line in FIG. 2). Then, the second specular reflection light 22 (marked by a dotted line in FIG. 2) is transmitted through a second optical comb extending perpendicular to the second direction from the vertical axis 3 toward the TD direction by -60° with the second irradiation position 21 as a fulcrum. 26. Then, the light receiver 29 extending in the second direction receives the second transmitted light 28 (indicated by a single-dot chain line in FIG. 2) that has passed through the second optical comb 26. The second optical comb 26 has an opening through which the second specular reflection light 22 passes, and a light shielding part which blocks the second specular reflection light 22. The slit width (width of the opening) of the second optical comb 26 is 0.125 mm. In the direction in which the slits in the second optical comb 26 are arranged parallel to the plane of the second optical comb 26 (the direction of arrow B), the second optical comb 26 is moved by a specific unit width and receives the second transmitted light 28. Repeat the operation to obtain the received light waveform. Obtain the maximum value M and the minimum value m of the relative light intensity from the received light waveform. From the obtained M and m, the second reflection image sharpness value C _{TD is} calculated based on the equation (5).

If the second reflection image sharpness value C _TD satisfies the formula (2), the optical film has excellent visibility in the wide-angle direction of the TD direction. The second reflection image sharpness value C _TD in the formula (2) is 30% or more. From the viewpoint of further improving the visibility of the optical film in the wide-angle direction in the TD direction, it is preferably 35% or more, more preferably It is 38% or more, more preferably 40% or more, still more preferably 45% or more, particularly preferably 50% or more, especially more preferably 55% or more, and usually 100% or less.

If the average value of the first reflection image definition value C _MD and the second reflection image definition value C _TD {(C _MD ＋C _TD )/2} satisfies the formula (3), then the optical film is in the MD direction and TD The difference in visibility between the direction and the wide-angle direction is small. (C _MD + C _TD )/2 is 35% or more. From the viewpoint of further reducing the difference in the visibility of the optical film in the wide-angle direction between the MD direction and the TD direction, it is preferably 38% or more, more preferably 40% Above, it is more preferably 44% or more, still more preferably 45% or more, particularly preferably 50% or more, particularly more preferably 55% or more, and usually 100% or less.

The reflection image definition value (more specifically, the first reflection image definition value C _MD and the second reflection image definition value C _TD ) can improve the smoothness of the optical film surface and suppress the Adjust for scattering, etc. Furthermore, the smoothness of the optical film surface can be determined by, for example, the composition of the optical film (more specifically, the type, particle size and content of the filler, etc.) and the manufacturing conditions of the optical film (more specifically, drying temperature, drying time, The airflow in the drying system, the thickness of the coating film, the conveying speed in the drying step, and the amount of solvent in the varnish, etc.) are adjusted. When the optical film further contains a hard coat layer, it can be adjusted by improving the smoothness of the hard coat layer surface and suppressing the scattering of the hard coat layer surface. In addition to the smoothness adjustment method of the optical film described above, the smoothness of the hard coat layer can also be adjusted by, for example, the type of solvent, the component ratio, the adjustment of the solid content concentration, and the addition of a leveling agent.

In addition, for the optical film of the present invention, it is sufficient that at least one of the surfaces of the optical film satisfies the formula (1) to the formula (3), and it is more preferable that the optical film satisfies the formula (1) on both sides of the optical film. ~ Numerical formula (3). If the equations (1) to (3) are satisfied on both sides, for example, when either side of the optical film is used for the image display surface of an 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 panel of a flexible device, from the viewpoint of further improving the visibility in the wide-angle direction, the first before and after the bending resistance test according to JIS K 5600-5-1 _{The absolute value ΔC MD} of the difference between the sharpness value of 1 reflection image _{and the absolute value ΔC TD} of the difference between the sharpness value of the second reflection image are preferably less than 15 respectively. If the difference in the clarity value of the reflected image before and after the bending resistance test is less than 15, even if the image display surface of the flexible device is used in a curved state and/or after being used in a curved state, it will have a wide angle Excellent visibility of direction. ΔC _{MD is} preferably less than 15, more preferably 14 or less, and still more preferably 13 or less. ΔC _{TD is} preferably less than 15, more preferably 14 or less, and still more preferably 13 or less.

Furthermore, regarding the optical film of the present invention, the total light transmittance is 85% or more, the haze is 0.5% or less, and the tensile modulus of elasticity at 25° C. is 5.1 GPa or more. When the total light transmittance is less than 85% or the haze is less than 0.5%, the initial optical properties of the optical film are low, so the full visibility of the optical film cannot be achieved. In addition, when the tensile modulus of elasticity is less than 5.1 GPa, the bending resistance of the optical film cannot be sufficiently improved. And, at the break -40 ℃ optical film of the present invention and the breaking off of strain ε ₁ of 25 deg.] C at a strain ε ₂ off a number satisfying the formula _{(4): 0.70 ≦ ε 1} / ε 2 ≦ 1.20 · · · (4) . When ε ₁ /ε _{2 is} less than 0.70, the breaking strain at low temperature is too low, so sufficient mechanical properties of the optical film such as tensile elastic modulus under low temperature environment cannot be obtained.

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

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

The tensile modulus of elasticity at 25°C of the optical film of the present invention is 5.1 GPa or more. When the tensile modulus of elasticity is lower than the above lower limit, the bending resistance of the optical film cannot be sufficiently improved. As the tensile modulus of elasticity at 25° C., from the viewpoint that the bending resistance of the optical film is easily improved, and the optical film is not prone to defects such as dents, it is preferably 5.2 GPa or more, more preferably 5.3 GPa or more. In addition, the tensile modulus of elasticity is preferably 10 GPa or less, more preferably 9 GPa or less, and even more preferably 8 GPa or less from the viewpoint of easily improving the flexibility of the optical film. The elastic modulus can be measured using a tensile testing machine (the distance between the chucks is 50 mm, the tensile speed is 10 mm/min), for example, it can be measured by the method described in the examples. If the tensile modulus of elasticity is within the above range, the optical film is less prone to dent defects. The tensile elastic modulus of the optical film can be measured using a tensile tester in accordance with JIS K 7127, for example, it can be measured by the method described in the examples. The tensile modulus of elasticity can be adjusted to the above range by, for example, increasing the stretching ratio when manufacturing the optical film, using the following resin having a preferable structure, or the like.

The optical film of the present invention, the break-off at -40 ℃ the strain ε ₁ and broken off at the 25 deg.] C strain ε ₂ satisfies equation _{(4): 0.70 ≦ ε 1} / ε 2 ≦ 1.20 · · · (4) . _{The ε 1} /ε ₂ in the formula (4) is 0.70 or more. From the viewpoint of improving the mechanical properties of the optical film in a low temperature environment, it is preferably 0.73 or more, more preferably 0.75 or more. In addition, as the ε ₁ /ε ₂ in the formula (4), considering that the plastic film is usually difficult to stretch when the temperature drops, and by adding fillers, it can be stretched even at low temperatures, so it is usually less than 1.20, preferably It is 1.15 or less, more preferably 1.10 or less, and still more preferably 1.05 or less. Furthermore, the breaking strains ε ₁ and ε ₂ can be obtained from the magnitude of the strain when the optical film breaks in the stress-strain curve measured by ASTM D638-14 at -40°C or 25°C, respectively. The breaking strain can be measured in accordance with ASTM D638-14 paragraph A2.6 using, for example, a tensile testing machine. As a measurement method, it can measure by the method described in an Example, for example. As a _{method of adjusting ε 1} /ε ₂ to the above-mentioned range, for example, a method of using the following preferable resins, etc. can be exemplified.

_{As the breaking strain ε 1} at -40°C of the optical film of the present invention, it is preferably 5.0 or more, more preferably 6.0 or more from the viewpoint of easily improving the mechanical properties and bending resistance of the film at low temperatures, and further It is preferably 7.0 or more, and from the viewpoint of the hardness of the film, it is preferably 50 or less, and more preferably 45 or less.

_{As the breaking strain ε 2} at 25°C of the optical film of the present invention, from the viewpoint of the flexibility of the film, it is preferably 5.0 or more, more preferably 6.0 or more, and still more preferably 7.0 or more, in terms of film hardness From a standpoint, it is preferably 50 or less, and more preferably 45 or less.

The YI value, which is an indicator 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 even more preferably 2.0 or less from the viewpoint that it is easy to further improve visibility. , Is particularly preferably 1.9 or less, particularly more preferably 1.8 or less, particularly still more preferably 1.7 or less, still more preferably 1.6 or less, preferably -5 or more, and more preferably -2 or more. Furthermore, the YI value can be measured with a UV-visible-near-infrared spectrophotometer to measure the transmittance of light from 300 to 800 nm to obtain the tristimulus value (X, Y, Z), based on YI=100×(1.2769X- 1.0592Z)/Y.

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

The thickness of the optical film of the present invention can be appropriately adjusted according to the application, and is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 25 μm or more, still more preferably 30 μm or more, and preferably 200 μm or less , More preferably 150 μm or less, still more preferably 100 μm or less, and still more preferably 85 μm or less. If the thickness of the optical film is within the above range, it is easy to further increase the tensile modulus of the optical film, and it is easy to _{adjust ε 1} /ε ₂ to the above range. Furthermore, the thickness of the optical film can be measured using a micrometer, for example, it can be measured by the method described in the Example.

<Polyimide resin and polyimide resin> The optical film of the present invention contains at least one resin selected from the group consisting of polyimide resin and polyimide resin. In this specification, the so-called polyimide resin refers to a polyimide resin, a polyimide imide resin, a polyimide precursor resin, and a polyimide imide precursor resin. At least one resin in the group. The polyimide resin is a resin containing a repeating structural unit containing an amide group, and the polyimide resin is a resin containing a repeating structural unit containing both an amide group and an amide group. The polyimide precursor resin and the polyimide imide precursor resin provide the polyimide resin and the polyimide imide resin as the precursor of the polyimide resin through imidization, respectively, It is also called polyamide resin. In addition, in this specification, the polyamide-based resin is a resin containing a repeating structural unit containing an amide group. The optical film of the present invention may contain one polyimide resin or polyimide resin, or a combination of two or more polyimide resins and/or polyimide resins. From the viewpoints that it is easy to improve the tensile elastic modulus and bending resistance of the optical film, the visibility in the wide-angle direction is easy to improve, and the ε ₁ /ε ₂ is easy to adjust to the above-mentioned range, the optical film of the present invention preferably contains poly The polyimide resin is preferably a polyimide resin or a polyimide resin, and the polyimide resin is more preferably a polyimide resin.

In a preferred embodiment of the present invention, it is easy to improve the tensile elastic modulus and bending resistance of the optical film, easy to improve the visibility in the wide-angle direction, and it is easy to _{adjust ε 1} /ε ₂ to the above-mentioned range. Preferably, the polyimide resin and the polyimide resin are aromatic resins. In this specification, the so-called aromatic resin refers to polyimide resins and resins in which the structural units contained in polyimide resins are mainly aromatic structural units.

In the above-mentioned preferred embodiment, from the viewpoints that the tensile elastic modulus and bending resistance of the optical film are easily improved, the visibility in the wide-angle direction is easily improved, and ε ₁ /ε ₂ is easily adjusted to the above-mentioned range, the source The ratio of the structural unit from the aromatic monomer to all the structural units contained in the polyimide-based resin and the polyamide-based resin is preferably 60 mol% or more, more preferably 70 mol% or more, More preferably, it is 80 mol% or more, and still more preferably 85 mol% or more. Here, the so-called structural unit derived from an aromatic monomer refers to a monomer derived from a structure containing an aromatic system (for example, an aromatic ring) in at least a part, and a structure containing an aromatic system in at least a part (for example, an aromatic The structural unit of the ring). As an aromatic monomer, an aromatic tetracarboxylic acid compound, an aromatic diamine, an aromatic dicarboxylic acid, etc. are mentioned, for example.

[式(1)中，Y表示4價之有機基，X表示2價之有機基，*表示鍵結鍵] 或具有式(1)所表示之結構單元及式(2)所表示之結構單元之聚醯胺醯亞胺樹脂： [化2]

[式(2)中，Z及X相互獨立地表示2價之有機基，*表示鍵結鍵]。 又，聚醯胺系樹脂較佳為具有式(2)所表示之結構單元之聚醯胺樹脂。以下對式(1)及式(2)進行說明，針對式(1)之說明係關於聚醯亞胺樹脂及聚醯胺醯亞胺樹脂之兩者，針對式(2)之說明係關於聚醯胺樹脂及聚醯胺醯亞胺樹脂之兩者。In a preferred embodiment of the present invention, the polyimide resin is preferably a polyimide resin having a structural unit represented by formula (1): [化1]

[In formula (1), Y represents a tetravalent organic group, X represents a divalent organic group, * represents a bonding bond] or has a structural unit represented by formula (1) and a structural unit represented by formula (2) The polyamide imide resin: [化2]

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

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

In formula (1), Y represents a tetravalent organic group, preferably a tetravalent organic group with 4 to 40 carbons, and more preferably a tetravalent organic group with 4 to 40 carbons having a cyclic structure base. Examples of cyclic structures include: alicyclic, aromatic, and heterocyclic structures. It is easy to improve the tensile elastic modulus and bending resistance of the optical film, and it is easy to improve the visibility in the wide-angle direction, and it is easy to change ε ₁ /ε ₂ From the viewpoint of adjusting to the aforementioned range, an aromatic ring may preferably be mentioned. The above-mentioned organic group is an organic group in which the hydrogen atom in the organic group can be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. In this case, the carbon number of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1-8. In one embodiment of the present invention, the polyimide-based resin may contain plural kinds of Y, and the plural kinds of Y may be the same or different from each other. As Y, the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula ( 28) and the group represented by the formula (29); the hydrogen atom in the group represented by the formula (20) ~ formula (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and A tetravalent chain hydrocarbon group with a carbon number of 6 or less.

[化3]

In formulas (20) to (29), * represents a bonding bond, W ¹ represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C (CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -Ar-, -SO ₂ -, -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar-C(CH ₃ ) ₂ -Ar- or -Ar-SO ₂ -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and as a specific example, a phenylene group may be mentioned. When there are a plurality of Ars, the Ars may be the same or different from each other. The hydrogen atoms on the rings in formulas (20) to (29) may be substituted with alkyl groups having 1 to 6 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons. As a C1-C6 alkyl group, a C1-C6 alkoxy group, and a C6-C12 aryl group, the thing exemplified in the following formula (3) can be mentioned, respectively.

In the formula (20) ~ formula (29), it is easy to improve the tensile elastic modulus and bending resistance of the optical film, it is easy to improve the visibility in the wide-angle direction, and it is easy to _{adjust ε 1} /ε ₂ to the above range From a viewpoint, the group represented by formula (26), formula (28) or formula (29) is preferable, and the group represented by formula (26) is more preferable. In addition, as W ¹ , it is easier to improve the tensile modulus of elasticity and bending resistance of the optical film, to reduce the YI value of the optical film, and to _{adjust ε 1} /ε ₂ to the above-mentioned range. It is 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 Is a single bond, -O-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, more preferably a single bond, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, 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 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more. Formula (26) expressed. If Y in the above range in the polyimide resin is represented by formula (26), preferably W ¹ is a single bond, -C(CH ₃ ) ₂ -or -C(CF ₃ ) _2- ), more preferably, W ¹ is a single bond or -C(CF ₃ ) ₂ -represented by the formula (26), it is easy to increase the tensile elastic modulus and bending resistance of the optical film, and it is easy to reduce the YI of the optical film Value, it is easy to _{adjust ε 1} /ε ₂ to the above range. The ratio of the structural unit represented by the formula (26) of Y in the polyimide-based resin can be ^{measured, for example, using 1} H-NMR, or can also be calculated from the feed ratio of the raw materials.

[式(4)中，R² ～R⁷ 相互獨立地表示氫原子、碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基，R² ～R⁷ 中所含之氫原子可相互獨立地被取代為鹵素原子，V表示單鍵、-O-、-CH₂ -、-CH₂ -CH₂ -、-CH(CH₃ )-、-C(CH₃ )₂ -、-C(CF₃ )₂ -、-SO₂ -、-S-、-CO-或-N(R⁸ )-，R⁸ 表示氫原子或可經鹵素原子取代之碳數1～12之1價之烴基，*表示鍵結鍵]。 即，較佳為複數個式(1)所表示之結構單元中之Y中，至少一部分Y係式(4)所表示之基。若為此種態樣，則易於提高光學膜之拉伸彈性模數及耐彎曲性，易於減低光學膜之YI值，易於將ε₁ /ε₂ 調整為上述範圍。再者，式(1)所表示之結構單元可含有一種或複數種式(4)所表示之基作為Y。In a preferred embodiment of the present invention, the structural unit represented by formula (1) contains the group represented by formula (4) as Y: [化4]

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

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

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

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

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

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

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

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

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

That is, at least a part of the plural Y is represented by the formula (5') and/or the formula (9'). In this case, it is easy to improve the tensile modulus and bending resistance of the optical film. Furthermore, in the case where the formula (5) is represented by the formula (5'), the solubility of the polyimide resin to the solvent is improved by the skeleton containing the fluorine element, thereby easily improving the performance of the varnish containing the resin Storage stability, and easy to reduce the viscosity of the varnish, easy to improve the processability of the optical film. As a result, it is easy to manufacture the optical film of the present invention that satisfies the mathematical formulas (1) to (3). In addition, the fluorine-containing skeleton makes it easy to improve the optical properties 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, and still more preferably 70 mol% or more. The formula (5), especially the formula (5'). If Y in the above-mentioned range in the polyimide resin is represented by formula (5), especially formula (5'), the solubility of the polyimide resin to solvents by the skeleton containing the fluorine element It is easy to reduce the viscosity of the varnish containing the resin, and it is easy to improve the processability of the optical film. As a result, it is easy to manufacture the optical film of the present invention that satisfies the mathematical formulas (1) to (3). In addition, the fluorine-containing skeleton makes it easy to improve the optical properties of the optical film. Furthermore, it is preferable that 100 mol% or less of Y in the polyimide resin is represented by formula (5), especially formula (5'). Y in the polyimide resin may be formula (5), especially formula (5'). The ratio of the structural unit represented by the formula (5) of Y in the polyimide-based resin can be ^{measured, for example, using 1} H-NMR, or can also be calculated from the feed ratio of the raw materials.

[式(20)～式(29)中，W¹ 表示單鍵、-O-、-CH₂ -、-CH₂ -CH₂ -、-CH(CH₃ )-、-C(CH₃ )₂ -、-C(CF₃ )₂ -、-Ar-、-SO₂ -、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂ -Ar-、-Ar-C(CH₃ )₂ -Ar-或-Ar-SO₂ -Ar-，此處，Ar相互獨立地表示氫原子可被取代為氟原子之碳數6～20之伸芳基(例如伸苯基)，*表示鍵結鍵]， 作為Z之雜環結構，可例示具有噻吩環骨架之基。就易於減低光學膜之YI值之觀點、易於提高全光線透過率之觀點及易於減低霧度之觀點而言，作為Z，較佳為式(20)～式(29)所表示之基及具有噻吩環骨架之基，更佳為式(26)、式(28)及式(29)所表示之基。又，就易於提高光學膜之拉伸彈性模數之觀點、及易於將ε₁ /ε₂ 調整為上述範圍之觀點而言，Z較佳為經碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基(該等基中之氫原子可被取代為鹵素原子(較佳為氟原子))取代之式(26)、式(28)及式(29)所表示之基，更佳為經碳數1～6之烷基或碳數1～6之烷氧基(該等基中之氫原子可被取代為鹵素原子(較佳為氟原子))取代之式(26)、式(28)及式(29)所表示之基。In formula (2), Z is a divalent organic group, preferably an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons (such The hydrogen atom in the group may be substituted with a halogen atom (preferably a fluorine atom)). A divalent organic group with 4 to 40 carbons, more preferably an alkyl group with 1 to 6 carbons, and 1 ～6 alkoxy group or aryl group with 6 to 12 carbons (the hydrogen atoms in these groups can be substituted with halogen atoms (preferably fluorine atoms)) substituted with cyclic structure of 4 to 40 carbons Divalent organic base. Furthermore, as an example of an alkyl group having 1 to 6 carbons, an alkoxy group having 1 to 6 carbons, or an aryl group having 6 to 12 carbons, the same applies to the following formula (3) for R ^3a and An example of R ^3b. The cyclic structure may, for example, be an alicyclic ring, an aromatic ring, or a heterocyclic 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 among the bonding bonds of the groups represented by formula (29), two non-adjacent groups are substituted with hydrogen atoms and a divalent chain hydrocarbon group with 6 or less carbon atoms: [化 8]

[In formulas (20) to (29), W ¹ represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -Ar-, -SO ₂ -, -CO-, -O-Ar-O-, -Ar-O-Ar-, _{-Ar-CH 2} -Ar-,- Ar-C(CH ₃ ) ₂ -Ar- or -Ar-SO ₂ -Ar-, where Ar represents independently of each other an aryl group with 6 to 20 carbon atoms (for example, Phenyl), * represents a bonding bond], as the heterocyclic structure of Z, a group having a thiophene ring skeleton can be exemplified. From the viewpoint of ease of reducing the YI value of the optical film, the viewpoint of ease of increasing the total light transmittance, and the viewpoint of ease of reducing the haze, as Z, it is preferable to have a base represented by formulas (20) to (29) and have The group of the thiophene ring skeleton is more preferably the group represented by the formula (26), the formula (28) and the formula (29). In addition, from the viewpoints that it is easy to increase the tensile elastic modulus of the optical film and that it is easy to _{adjust ε 1} /ε ₂ to the above-mentioned range, Z is preferably an alkyl group having 1 to 6 carbon atoms, and a carbon number of 1 ～6 alkoxy or 6-12 aryl groups (the hydrogen atoms in these groups can be substituted with halogen atoms (preferably fluorine atoms)) substituted by formulas (26), (28) and formulas The group represented by (29) is more preferably an alkyl group having 1 to 6 carbons or an alkoxy group having 1 to 6 carbons (the hydrogen atoms in these groups may be substituted with halogen atoms (preferably fluorine atoms) )) Substituted groups represented by formula (26), formula (28) and formula (29).

[式(20')～式(29')中，W¹ 及*係如式(20)～式(29)中所定義]。 再者，式(20)～式(29)及式(20')～式(29')中之環上之氫原子可被取代為碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基(該等基中之氫原子可被取代為鹵素原子(較佳為氟原子))。就提高光學膜之拉伸彈性模數，易於將ε₁ /ε₂ 調整為上述範圍，尤其易於提高低溫下之力學特性之觀點而言，Z較佳為經碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基(該等基中之氫原子可被取代為鹵素原子(較佳為氟原子))取代之式(26')、式(28')及式(29')所表示之基，更佳為經碳數1～6之烷基或碳數1～6之烷氧基(該等基中之氫原子可被取代為鹵素原子(較佳為氟原子))取代之式(26')、式(28')及式(29')所表示之基，進而更佳為經碳數1～6之烷基或碳數1～6之烷氧基(該等基中之氫原子可被取代為鹵素原子(較佳為氟原子))取代之式(28')所表示之基。As the organic group of Z, it is more preferably formula (20'), formula (21'), formula (22'), formula (23'), formula (24'), formula (25'), formula (26') , Formula (27'), formula (28') and formula (29') expressed by the divalent organic group: [化9]

[In formulas (20') to (29'), W ¹ and * are as defined in formulas (20) to (29)]. Furthermore, the hydrogen atoms on the rings in formulas (20) to (29) and (20') to (29') can be substituted with alkyl groups with 1 to 6 carbons, and those with 1 to 6 carbons. An alkoxy group or an aryl group having 6 to 12 carbons (the hydrogen atom in these groups may be substituted with a halogen atom (preferably a fluorine atom)). From the viewpoint of increasing the tensile modulus of the optical film, easily _{adjusting ε 1} /ε ₂ to the above range, and particularly easy to improve the mechanical properties at low temperature, Z is preferably an alkyl group having 1 to 6 carbon atoms, An alkoxy group having 1 to 6 carbons or an aryl group having 6 to 12 carbons (the hydrogen atoms in these groups may be substituted with halogen atoms (preferably fluorine atoms)) substituted by formula (26'), formula ( 28') and the group represented by formula (29'), more preferably an alkyl group having 1 to 6 carbons or an alkoxy group having 1 to 6 carbons (the hydrogen atoms in these groups may be substituted with halogen atoms (Preferably a fluorine atom)) The substituted group represented by the formula (26'), the formula (28') and the formula (29'), more preferably an alkyl group having 1 to 6 carbons or a carbon number of 1 to The group represented by the formula (28') substituted by the alkoxy group of 6 (the hydrogen atom in these groups may be substituted with a halogen atom (preferably a fluorine atom)).

[式(d1)中，R⁴¹ 相互獨立為關於下述式(3)中之R^3a 所定義之基或氫原子，R⁴² 表示R⁴¹ 或-C(=O)-*，*表示鍵結鍵]。 作為結構單元(d1)，具體可例舉：R⁴¹ 及R⁴² 均為氫原子之結構單元(源自二羧酸化合物之結構單元)、R⁴¹ 均為氫原子且R⁴² 表示-C(=O)-*之結構單元(源自三羧酸化合物之結構單元)等。When the polyamide resin or polyamide imide resin has a structural unit in the formula (2) where Z is represented by any of the above formulas (20') to (29'), where In the case where Z in the formula (2) is represented by the following formula (3'), from the viewpoint that the film-forming properties of the varnish and the uniformity of the optical film are easily improved, the poly In addition to the structural unit, the amide resin or polyimide resin has a carboxylic acid-derived structural unit represented by the following formula (d1): [化10]

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

[式(3)中，R^3a 及R^3b 相互獨立地表示碳數1～6之烷基、碳數1～6之烷氧基或碳數6～12之芳基，R^3a 及R^3b 中所含之氫原子可相互獨立地被取代為鹵素原子，W相互獨立地表示單鍵、-O-、-CH₂ -、-CH₂ -CH₂ -、-CH(CH₃ )-、-C(CH₃ )₂ -、-C(CF₃ )₂ -、-SO₂ -、-S-、-CO-或-N(R⁹ )-，R⁹ 表示氫原子、可經鹵素原子取代之碳數1～12之1價之烴基，s為0～4之整數，t為0～4之整數，u為0～4之整數，*表示鍵結鍵]， 更佳為式(3')所表示之結構單元： [化12]

[式(3')中，R^3a 、R^3b 、s、t、u、W及*係如式(3)中所定義]。 再者，於本說明書中，聚醯胺系樹脂或聚醯胺醯亞胺樹脂具有式(2)中之Z由式(3)所表示之結構單元與聚醯胺系樹脂或聚醯胺醯亞胺系樹脂具有式(3)所表示之結構作為式(2)中之Z係具有相同含義，係指聚醯胺系樹脂或聚醯胺醯亞胺樹脂中可含有之複數個式(2)所表示之結構單元中，至少一部分之結構單元中之Z係由式(3)所表示。該記載亦適用於其他相同之記載。The polyamide resin or polyamide resin may contain a plurality of types of Z as Z in the formula (2), and the plurality of types of Z may be the same or different from each other. Especially in terms of the ease of improving the tensile modulus of elasticity of the optical film of the present invention and the ease of improving the optical properties, Z in formula (2) preferably has at least formula (3): [化11]

[In formula (3), R ^3a and R ^3b independently represent an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons. In R ^3a and R ^3b The hydrogen atoms contained can be independently substituted with halogen atoms, and W independently represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C (CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁹ )-, R ⁹ represents a hydrogen atom, a carbon that can be substituted by a halogen atom A monovalent hydrocarbon group of 1 to 12, s is an integer of 0 to 4, t is an integer of 0 to 4, u is an integer of 0 to 4, * represents a bonding bond], more preferably represented by formula (3') The structural unit of expression: [化12]

[In formula (3'), R ^3a , R ^3b , s, t, u, W and * are as defined in formula (3)]. Furthermore, in this specification, polyamide-based resin or polyamide-imide resin has a structural unit represented by formula (3) as Z in formula (2) and polyamide-based resin or polyamide-imide resin The imine resin has the structure represented by the formula (3) as the Z in the formula (2) has the same meaning. Among the structural units represented by ), Z in at least a part of the structural units is represented by formula (3). This record also applies to other similar records.

In formula (3) and formula (3'), W independently represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁹ )-, from the viewpoint of the bending resistance of the optical film, it is preferable to indicate -O- or -S-, more preferably -O-. R ^3a and R ^3b independently represent an alkyl group having 1 to 6 carbons, an alkoxy group having 1 to 6 carbons, or an aryl group having 6 to 12 carbons. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, second butyl, tertiary butyl, n-pentyl, 2-methyl Base-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, etc. Examples of alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, tertiary butoxy, and pentoxy. Group, hexyloxy, cyclohexyloxy, etc. As a C6-C12 aryl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a biphenyl group etc. are mentioned, for example. From the viewpoint of the tensile elastic modulus, surface hardness and flexibility of the optical film, R ^3a and R ^3b are independent of each other, and preferably represent an alkyl group with 1 to 6 carbons or an alkoxy group with 1 to 6 carbons , More preferably represents an alkyl group having 1 to 3 carbons or an alkoxy group having 1 to 3 carbons. Here, ^{the hydrogen atoms contained in R 3a} and R ^3b may be substituted with halogen atoms independently of each other. R ⁹ represents a hydrogen atom, a monovalent hydrocarbon group of 1 to 12 carbons which may be substituted with a halogen atom. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, second butyl, tertiary butyl, n-pentyl, and 2 -Methyl-butyl, 3-methyl-butyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tertiary octyl, n-nonyl, n-decyl, etc., etc. Can be substituted by halogen atoms. As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned.

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

In formula (3) and formula (3'), s is an integer in the range of 0-4, and if s is within this range, the tensile modulus and bending resistance of the optical film are easily improved. In formulas (3) and (3'), s is preferably an integer in the range of 0 to 3, more preferably 0 to from the viewpoint of further improving the tensile modulus of elasticity and bending resistance of the optical film. The integer in the range of 2 is more preferably 0 or 1, and even more preferably 0. The polyamide imide resin or polyamide resin may contain one or two or more structural units represented by formula (3) or formula (3') in Z.

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

When the polyamide resin or polyamide resin has the structural unit represented by formula (3) or formula (3'), the ratio is higher than that of polyamide resin or polyamide resin When the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) of the resin is 100 mol%, it is preferably 20 mol% or more, more preferably 30 mol% or more, and then Preferably it is 40 mol% or more, further more preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, and still more preferably Below 80 mol%. If the ratio of the structural unit represented by the formula (3) or the formula (3') is more than the above lower limit, it is easy to improve the tensile modulus of elasticity and the bending resistance of the optical film. If the ratio of the structural units represented by the formula (3) or the formula (3') is below the above upper limit, the increase in the viscosity of the resin-containing varnish caused by the hydrogen bond between the amido bonds derived from the formula (3) will be suppressed, It is easy to improve the processability of the film. Furthermore, the ratio of structural units represented by formula (1), formula (2), formula (3), or formula (3') can be ^{determined, for example, using 1} H-NMR, or can also be determined from the feed ratio of raw materials Figure out.

In a preferred embodiment of the present invention, Z in the polyamideimide resin or polyamide resin is preferably 30 mol% or more, more preferably 40 mol% or more, and still more preferably 45 mol% or more, and more preferably 50 mol% or more is a structural unit represented by formula (3) or formula (3') in which s is 0-4. If the above lower limit of Z is a structural unit represented by formula (3) or formula (3') in which s is 0-4, the tensile modulus and bending resistance of the optical film are easily improved. Moreover, 100 mol% or less of Z in the polyamide resin or polyamide resin may be a structural unit represented by formula (3) or formula (3') in which s is 0 to 4. Furthermore, the ratio of structural units represented by formula (3) or formula (3') in which s in the resin is 0-4 can be ^{measured, for example, using 1} H-NMR, or can also be calculated from the feed ratio of the raw materials .

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

[化13]

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

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

[式(5)中，Ar² 相互獨立地表示可具有取代基之2價之芳香族基，V表示單鍵、-O-、二苯基亞甲基、伸茀基、碳數1～12之2價之烴基、-SO₂ -、-S-、-CO-、-PO-、-PO₂ -、-N(R^a )-或-Si(R^b )₂ -，此處，該烴基可含有脂環式結構，該烴基中所含之氫原子可相互獨立地被取代為鹵素原子，R^a 及R^b 相互獨立地表示氫原子或可經鹵素原子取代之碳數1～12之1價之烴基，m表示0～3之整數，*表示鍵結鍵]。 於結構單元(1)及結構單元(2)含有式(5)所表示之2價之有機基作為X之情形時，結構單元(1)及結構單元(2)可含有式(5)所表示之一種或兩種以上之2價之有機基作為X。結構單元(1)及結構單元(2)可除式(5)所表示之2價之有機基外，亦含有不屬於式(5)所表示之2價之有機基之其他2價之有機基作為X。In a preferred embodiment of the present invention, the polyamide resin and/or polyimide resin contains the divalent organic group represented by formula (5) as X in formula (1) or formula (2) ) Of X: [Transformation 14]

[In formula (5), Ar ² independently represents a divalent aromatic group that may have a substituent, and V represents a single bond, -O-, diphenylmethylene, ethylene group, and carbon number 1-12 The divalent hydrocarbon group, -SO ₂ -, -S- _{, -CO-, -PO-, -PO 2} -, -N(R ^a )- or -Si(R ^b ) ₂ -, where the hydrocarbon group May contain an alicyclic structure, the hydrogen atoms contained in the hydrocarbon group may be independently substituted with halogen atoms, R ^a and R ^b independently represent a hydrogen atom or 1 of carbon number 1-12 that may be substituted by a halogen atom A valence hydrocarbon group, m represents an integer from 0 to 3, and * represents a bonding bond]. When the structural unit (1) and the structural unit (2) contain the divalent organic group represented by the formula (5) as X, the structural unit (1) and the structural unit (2) may contain the formula (5) One or more than two divalent organic groups are used as X. The structural unit (1) and the structural unit (2) may not only contain the divalent organic group represented by the formula (5), but also contain other divalent organic groups that do not belong to the divalent organic group represented by the formula (5) As X.

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

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

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

As an assembling aromatic ring, there can be mentioned a structure in which two or more monocyclic aromatic rings and/or condensed polycyclic aromatic rings are connected by a single bond. As an example, it can be exemplified as a single ring An example of a condensed polycyclic aromatic ring or a condensed polycyclic aromatic ring. Two or more of the rings described above are connected by a single bond, such as biphenyl, terphenyl, bitetraphenyl, binaphthyl, 1- Phenylnaphthalene, 2-phenylnaphthalene, bipyridine, etc.

From the viewpoint of easy improvement of the tensile elastic modulus of the optical film, the divalent aromatic group which may have a substituent is preferably an aromatic hydrocarbon ring which may have a substituent. Two hydrogen atoms of the aromatic hydrocarbon ring are substituted as a bonding bond The group is more preferably substituted benzene, biphenyl, terphenyl or bitetraphenyl. Two hydrogen atoms are substituted as bonding groups, and more preferably substituted benzene or biphenyl The two hydrogen atoms are replaced by the bonding bond group.

Examples of substituents in Ar ² include halogen groups, alkyl groups having 1 to 12 carbons, alkoxy groups having 1 to 6 carbons, or aryl groups having 6 to 12 carbons, or hydrogen contained in these groups. Atoms are substituted with halogen atoms.

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

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

As a C6-C12 aryl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a biphenyl group etc. are mentioned, for example.

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

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

The V in the formula (5) represents a single bond, -O-, diphenylmethylene, phenylene, a divalent hydrocarbon group with 1 to 12 carbons, -SO ₂ -, -S-, -CO-, -PO-, -PO ₂ -, -N(R ^a )- or -Si(R ^b ) ₂ -. Here, the hydrocarbon group may contain an alicyclic structure, the hydrogen atoms contained in the hydrocarbon group may be independently substituted with halogen atoms, and R ^a and R ^b independently represent a hydrogen atom or the number of carbon atoms that can be substituted by a halogen atom A monovalent hydrocarbon group of 1-12. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, second butyl, tertiary butyl, n-pentyl, 2- Methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tertiary octyl, n-nonyl, n-decyl, cyclopentyl, cyclo Hexyl, etc., which may be substituted by halogen atoms. As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned. As V in formula (5), from the viewpoint of easy improvement of the tensile modulus of elasticity and bending resistance of the optical film, it is preferably a single bond or a divalent hydrocarbon group with 1 to 12 carbons and the content of these hydrocarbon groups At least part of the hydrogen atoms contained is substituted with halogen atoms, more preferably single bonds, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) _2- Or -C(CF ₃ ) ₂ -, more preferably a single bond, -C(CH ₃ ) ₂ -or -C(CF ₃ ) ₂ -, still more preferably a single bond or -C(CF ₃ ) _2- .

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

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

[式(5a)中，R² 表示碳數1～12之氟烷基，p及q相互獨立地表示1～4之整數，其中，於p及/或q表示2～4之整數之情形時，存在複數個之R² 相互可相同亦可不同，*表示鍵結鍵]。 再者，式(5a)所表示之2價之有機基係包含於式(5)所表示之2價之有機基中之基，具體而言，係相當於式(5)中之V表示單鍵，Ar² 表示經碳數1～12之氟烷基(R² )取代之苯環，m表示0～3之整數之2價之有機基的基。於結構單元(1)及結構單元(2)含有式(5a)所表示之2價之有機基作為X之情形時，結構單元(1)及結構單元(2)可含有式(5a)所表示之一種或兩種以上之2價之有機基作為X。結構單元(1)及/或結構單元(2)可除式(5a)所表示之2價之有機基外，亦含有不屬於式(5a)所表示之2價之有機基之其他2價之有機基作為X。In a preferred embodiment of the present invention, from the viewpoint of easily increasing the tensile elastic modulus of the optical film, the structural unit represented by formula (1) and/or the structural unit represented by formula (2) contains the formula (5a) The divalent organic group represented as X: [化 15]

[In formula (5a), R ² represents a fluoroalkyl group having 1 to 12 carbon atoms, and p and q independently represent an integer of 1 to 4, where p and/or q represent an integer of 2 to 4 , There are a plurality of R ² which may be the same or different from each other, and * indicates a bonding bond]. Furthermore, the divalent organic group represented by the formula (5a) is a group included in the divalent organic group represented by the formula (5), specifically, it is equivalent to the V in the formula (5) representing the unit A bond, Ar ^{2 represents a benzene ring substituted with a fluoroalkyl group (R 2} ) having 1 to 12 carbon atoms, and m represents an integer of 0 to 3 as a divalent organic group. When the structural unit (1) and the structural unit (2) contain the divalent organic group represented by the formula (5a) as X, the structural unit (1) and the structural unit (2) may contain the formula (5a) One or more than two divalent organic groups are used as X. The structural unit (1) and/or the structural unit (2) may not only contain the divalent organic group represented by the formula (5a), but also contain other divalent organic groups that do not belong to the divalent organic group represented by the formula (5a) The organic group is used as X.

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

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

Regarding the two bonding bonds in the formula (5a), the mutual position is not particularly limited, and it can be any of ortho, meta, and para. It is easy to increase the tensile elastic modulus of the optical film. In other words, the bonding keys are preferably located in opposite positions.

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 2 and/or 2 aromatic groups in which the bonding bonds are in the para position with each other.

The structural unit (1) and/or the structural unit (2) that can be contained in the resin contained in the optical film of the present invention contains a divalent organic group represented by formula (5a) as X, a preferred one of the present invention In the embodiment, from the viewpoint of easily improving the tensile elastic modulus of the optical film, the total of the structural unit (1) and the structural unit (2) contained in the polyimide-based resin is set to 100 mol When ear%, X in formula (1) is the structural unit of the divalent organic group represented by formula (5a) and X in formula (2) is the structure of the divalent organic group represented by formula (5a) The total ratio of the units is preferably 70-100 mol%, more preferably 80-100 mol%, and still more preferably 90-100 mol%, and may also be: in the structural unit (1) and the structural unit (2) In all the structural units of ), X is a divalent organic group represented by formula (5a).

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

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

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

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

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

In a preferred embodiment of the present invention, the X that can be contained in the polyimide resin or polyimide resin is preferably 30 mol% or more, more preferably 50 mol% or more, and more Preferably, 70 mol% or more is represented by formula (4), especially formula (4'). When X in the above-mentioned range in the polyimide resin or polyimide resin is represented by formula (4), especially formula (4'), for the obtained optical film, by containing The skeleton of the fluorine element and the solubility of the resin in the solvent are improved, 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, and it is easy to manufacture to satisfy the formula (1) to the formula (3). Invented optical film. In addition, it is easy to improve the optical properties of the optical film by the skeleton containing the fluorine element. Furthermore, it is preferable that 100 mol% or less of X in the polyimide resin or polyimide resin is represented by formula (4), especially formula (4'). X in the above resin may be formula (4), especially formula (4'). The ratio of the structural unit represented by the formula (4) of X in the above resin can be ^{measured, for example, using 1} H-NMR, or can also be calculated from the feed ratio of the raw materials.

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

In the formula (30), Y ¹ is a tetravalent organic group, preferably an organic group in which the hydrogen atom in the organic group can be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ¹ , there can be exemplified: formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) ) And the group represented by the formula (29); the hydrogen atom in the group represented by the formula (20) ~ formula (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and 4 A chain hydrocarbon group with a valence of less than 6 carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain multiple types of Y ¹ , and the multiple types of Y ¹ may be the same or different from each other.

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

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

In one embodiment of the present invention, the polyimide-based resin includes structural units represented by formula (1) and/or formula (2), and optionally represented by formula (30) and/or formula (31) The structural unit. In addition, from the viewpoint of easily improving the tensile modulus, optical properties, and bending resistance of the optical film, in the above-mentioned polyimide-based resin, among the structural units represented by formulas (1) and (2) The ratio is based on all the structural units represented by formula (1) and formula (2), and as the case may be, formula (30) and formula (31), preferably 80 mol% or more, more preferably 90 mol% Above, more preferably 95 mol% or more. Furthermore, in the polyimide-based resin, the ratio of the structural units represented by formula (1) and formula (2) to formula (1) and formula (2), as well as formula (30) and/or as appropriate Or the total of all structural units represented by formula (31) is usually 100% or less. In addition, the above-mentioned ratio can be ^{measured using 1} H-NMR, for example, or it can also be calculated from the feed ratio of raw materials.

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

As the weight average molecular weight (Mw) of polyimide resin and polyimide resin, it is easy to improve the tensile modulus of elasticity and bending resistance of the optical film, and it is easy to _{adjust ε 1} /ε ₂ to the above From the viewpoint of the range, in terms of standard polystyrene, it is preferably 100,000 or more, more preferably 130,000 or more, still more preferably 150,000 or more, still more preferably 170,000 or more, particularly preferably 200,000 or more, especially more preferably 230,000 or more, especially more preferably 250,000 or more, still more preferably 260,000 or more. In addition, as the weight average molecular weight of the polyimide resin and the polyimide resin, it is preferable from the viewpoints that the solubility of the resin to the solvent is easily improved, and the elongation and processability of the optical film are easily improved. It is 800,000 or less, more preferably 700,000 or less, still more preferably 600,000 or less, still more preferably 500,000 or less, particularly preferably 400,000 or less, especially more preferably 350,000 or less, and especially even more preferably 300,000 or less. The weight average molecular weight can be measured, for example, by GPC, and can be obtained by standard polystyrene conversion, and can be calculated, for example, by the method described in the examples. When the weight average molecular weight (Mw) of the polyimide resin and the polyimide resin is below the above upper limit, it is easy to increase the solid content of the varnish containing the resin, and it is easy to reduce the viscosity of the varnish, as a result, It is easy to manufacture the optical film of the present invention that satisfies the formula (1) to (3). In addition, it is easy to maintain the visibility in the wide-angle direction after the bending resistance test.

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

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

The content of the halogen atoms in the polyimide resin and the polyimide resin is based on the mass of the polyimide resin and the polyimide resin, and is preferably 1-40% by mass, more preferably 5 -40% by mass, more preferably 5-30% by mass. If the content of halogen atoms is more than the above lower limit, it is easy to further increase the tensile modulus of the optical film, and it is easy to further reduce the YI value. If the content of the halogen atom is less than the above upper limit, it is easy to synthesize.

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

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

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

The structural units represented by formula (1) and formula (30) are usually derived from diamine compounds and tetracarboxylic acid compounds. The structural unit represented by 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.

As the diamine compound used in the production of the resin, for example, aliphatic diamine, aromatic diamine, and mixtures thereof can be mentioned. Furthermore, in the present embodiment, the term "aromatic diamine" refers to a diamine in which an amine group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituents in a part of its structure. The aromatic ring may be a monocyclic ring or a condensed ring. A benzene ring, a naphthalene ring, an anthracene ring, a sulphur ring, etc. may be exemplified, but it is not limited to these. Among these, a benzene ring is preferably exemplified. The so-called "aliphatic diamine" refers to a diamine in which an amine group is directly bonded to an aliphatic group, which may contain an aromatic ring or other substituents in a part of its structure.

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

As the aromatic diamine, for example, p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene and other aromatic diamines with one aromatic ring, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4' -Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'- Diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy) ) Benzene, bis[4-(4-aminophenoxy)phenyl] ash, bis[4-(3-aminophenoxy)phenyl] ash, 2,2-bis[4-(4- Aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis (Trifluoromethyl)-4,4'-diaminobiphenyl (sometimes referred to as TFMB), 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4 -Aminophenyl) pyrene, 9,9-bis(4-amino-3-methylphenyl) pyrene, 9,9-bis(4-amino-3-chlorophenyl) pyrene, 9,9 -Aromatic diamines with two or more aromatic rings such as bis(4-amino-3-fluorophenyl) pyridium. These can be used alone or in combination of two or more.

The aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'- Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 1,4-bis(4-aminophenoxy)benzene, double [4-(4-Aminophenoxy)phenyl] ash, bis[4-(3-aminophenoxy)phenyl] ash, 2,2-bis[4-(4-aminophenoxy) Yl)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethane) )-4,4'-diaminobiphenyl (TFMB), 4,4'-bis(4-aminophenoxy)biphenyl, more preferably 4,4'-diaminodiphenylmethane , 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylene, 1,4-bis(4-aminobenzene Oxy)benzene, bis[4-(4-aminophenoxy)phenyl] chrysene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'- Dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), 4,4'-bis(4-aminophenoxy)biphenyl . These can be used alone or in combination of two or more.

Among the above-mentioned diamine compounds, it is preferable to use aromatic compounds selected from the group consisting of biphenyl structure in terms of easily improving the tensile elastic modulus, transparency, flexibility, and bending resistance of the optical film, and easily reducing the YI value. One or more of the group consisting of diamines. More preferably, use selected from 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl and 4,4'-diaminodiphenyl ether is composed of more than one kind, and more preferably 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 dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compound may be used alone or in combination of two or more kinds. In addition to the dianhydride, the tetracarboxylic acid compound may also be a tetracarboxylic acid compound analogue such as a chlorine compound.

Specific examples of aromatic tetracarboxylic dianhydrides include: non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Carboxylic dianhydride. Examples of non-condensed polycyclic aromatic tetracarboxylic dianhydrides include 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid Acid dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (sometimes referred to as BPDA), 2 ,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxybenzene Base) propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4 '-(Hexafluoroisopropylidene) diphthalic dianhydride (sometimes 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) two Phthalic dianhydride, 4,4'-(m-phenylenedioxy) diphthalic dianhydride. In addition, as a monocyclic aromatic tetracarboxylic dianhydride, for example, 1,2,4,5-benzenetetracarboxylic dianhydride can be exemplified, and as a condensed polycyclic aromatic tetracarboxylic dianhydride, for example For example: 2,3,6,7-naphthalenetetracarboxylic dianhydride.

Among these, preferred examples include: 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride , 3,3',4,4'-diphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3- Dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic acid Anhydride (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 dianhydride and 4,4'-(m-phenylenedioxy) ) Diphthalic dianhydride, more preferably: 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2 ',3,3'-Biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), bis(3,4-dicarboxyphenyl) Methane dianhydride and 4,4'-(p-phenylenedioxy) diphthalic dianhydride. These can be used alone or in combination of two or more.

The aliphatic tetracarboxylic dianhydride may, for example, be a cyclic or acyclic aliphatic tetracarboxylic dianhydride. The so-called cyclic aliphatic tetracarboxylic dianhydride refers to tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, as a specific example thereof, 1,2,4,5-cyclohexane tetracarboxylic dianhydride , 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride and other cycloalkane tetracarboxylic dianhydrides, bicyclo[2.2.2]octane -7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride and their positional isomers. These can be used alone or in combination of two or more. Specific examples of acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butane tetracarboxylic dianhydride and 1,2,3,4-pentane tetracarboxylic dianhydride Etc., these can be used alone or in combination of two or more. Moreover, cycloaliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride can be used in combination.

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

The dicarboxylic acid compound used in the synthesis of the resin may, for example, be aromatic dicarboxylic acid, aliphatic dicarboxylic acid, and similar chlorinated compounds, acid anhydrides, etc., 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)p-benzene Dicarboxylic acid; isophthalic acid; 2,5-dimethylterephthalic acid; 2,5-dimethoxyterephthalic acid; naphthalene dicarboxylic acid; 4,4'-biphenyl dicarboxylic acid; 3 ,3'-biphenyldicarboxylic acid; 2,2'-bis(trifluoromethyl)-4,4'-biphenyldicarboxylic acid; dicarboxylic acid compound of chain hydrocarbon with carbon number less than 8 and 2 Compounds in which benzoic acid is linked by single bonds, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or phenylene, and these chlorinated compounds . Among these dicarboxylic acid compounds, 4,4'-oxybisbenzoic acid, terephthalic acid, and isophthalic acid are preferred from the viewpoint of easily improving the tensile elastic modulus and bending resistance of the optical film. Dicarboxylic acid, 2-methoxyterephthalic acid, 2-methylterephthalic acid, 2,5-dimethylterephthalic acid, 2,5-dimethoxyterephthalic acid, 2,5 -Bis(trifluoromethyl)terephthalic acid, 2,2'-bis(trifluoromethyl)-4,4'-biphenyldicarboxylic acid and these chlorinated acids, more preferably 2-methoxy Terephthalic acid, 2-methylterephthalic acid, 2,5-dimethylterephthalate chloride (DMTPC), 2,5-dimethoxyterephthalate chloride (MOTPC), 2,5-Bis (trifluoromethyl) terephthalic acid chloride (6FTPC), terephthalic acid chloride (TPC), meta-phthalic acid chloride, more preferably 2-methoxyterephthalic acid Formic acid, 2-methyl terephthalic acid, terephthalic acid chloride (TPC), 2,5-dimethyl terephthalic acid chloride (DMTPC), 2,5-dimethoxy terephthalic acid Methyl chloride (MOTPC), more preferably 2-methoxyterephthalic acid, 2-methylterephthalic acid, 2,5-dimethylterephthalate chloride (DMTPC) and 2,5- Dimethoxy terephthalic acid chloride (MOTPC).

Furthermore, the above-mentioned polyimide-based resin may be within the range of not damaging various physical properties of the optical film. In addition to the tetracarboxylic acid compound used in the synthesis of the above-mentioned resin, other tetracarboxylic acid, tricarboxylic acid, and These acid anhydrides and derivatives are formed by the reaction.

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

The tricarboxylic acid compound may, for example, be aromatic tricarboxylic acid, aliphatic tricarboxylic acid, and similar chlorinated compounds, acid anhydrides, etc., and two or more of them may be used in combination. As a specific example, anhydrides of 1,2,4-benzenetricarboxylic acid; chlorine compounds of 1,3,5-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3 -Anhydride; phthalic anhydride and benzoic acid with single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -or phenylene Compound formed by linking.

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

In the imidization step in the production of the polyimide resin, the imidization can be carried out in the presence of an imidization catalyst. As the imidization catalyst, for example, aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, N-propylpiperidine, N- Alicyclic amines such as butylpyrrolidine, N-butylpiperidine and N-propylhexahydroazepine (monocyclic); azabicyclo[2.2.1]heptane, azabicyclo[3.2.1] Alicyclic amines (polycyclic) such as octane, azabicyclo[2.2.2]octane and azabicyclo[3.2.2]nonane; and pyridine, 2-picoline, 3 -Picoline (3-picoline), 4-picoline (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-lutidine, 2, Aromatic amines such as 4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline and isoquinoline. Furthermore, from the viewpoint of facilitating the promotion of the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. The acid anhydride may be exemplified by the commonly used acid anhydrides used in the imidization reaction, and specific examples thereof may include aliphatic anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, aromatic anhydrides such as phthalic acid, etc. .

Polyimide resins and polyimide resins can be separated and refined by conventional methods such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography and other separation methods, or a combination of these separation methods Therefore, in a preferred aspect, a large amount of methanol and other alcohols are added to the reaction liquid containing the transparent polyimide resin to precipitate the resin, and the resin can be concentrated, filtered, dried, etc., so that the separation can be performed .

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

(filler) The optical film of the present invention may contain at least one filler. As the filler, for example, organic particles, inorganic particles, etc. may be mentioned, preferably, inorganic particles may be mentioned. Examples of inorganic particles include metal oxide particles such as silicon oxide, zirconium oxide, aluminum oxide, titanium oxide, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide, antimony oxide, and cerium oxide, and fluoride Metal fluoride particles such as magnesium and sodium fluoride. Among them, silicon oxide particles are preferable in terms of improving the elastic modulus and/or tearing strength of the optical film and improving the impact resistance. , Zirconia particles, alumina particles, more preferably silica particles. These fillers can be used alone or in combination of two or more.

The filler preferably has an average primary particle size of silicon oxide particles of 1 nm or more, more preferably 5 nm or more, still more preferably 10 nm or more, still more preferably 15 nm or more, particularly preferably 20 nm or more, more preferably 100 nm or less, more preferably 90 nm or less, still more preferably 80 nm or less, still more preferably 70 nm or less, particularly preferably 60 nm or less, especially more preferably 50 nm or less, and particularly preferably 40 nm the following. If the average primary particle size of the silica particles is within the above range, the agglomeration of the silica particles is suppressed, and the optical properties of the obtained optical film can be easily improved. The average primary particle size of the filler can be measured by the BET (Brunauer-Emmett-Teller, Buert) method. Furthermore, the average primary particle size can be measured by image analysis of a transmission electron microscope or a scanning electron microscope.

For the filler in the optical film of the present invention, such as inorganic particles, the content of silica particles relative to the total mass of the optical film is preferably 5% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass Hereinafter, it is more preferably 2% by mass or less, particularly preferably 1% by mass or less, particularly more preferably less than 1% by mass, and even more preferably 0.5% by mass or less. Furthermore, the lower limit of the filler content in the optical film of the present invention is 0% by mass or more. If the content of the filler is below the above upper limit, it is easy to increase the elastic modulus of the obtained optical film, and it is easy to improve the optical properties of the optical film. Here, the tensile elastic modulus of the optical film tends to increase by increasing the content of fillers such as silica particles. However, when the content of fillers such as silica particles is excessive, the optical film may be difficult to obtain. It satisfies the above formula (1) to (3). Therefore, in the optical film of the present invention, when the content of silica particles is below the above upper limit, it is better to increase the tensile modulus of the optical film and obtain higher visibility in the wide-angle direction. good. Furthermore, in this specification, the so-called that the content of silicon oxide particles in the optical film relative to the total mass of the optical film is below the above upper limit means that the content of silicon oxide particles is 0% by mass, that is, it does not contain silicon oxide particles. Or even if it is contained, the amount is less than the above upper limit.

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

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

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

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

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

In the varnish preparation step, the above-mentioned resin is dissolved in a solvent, and the above-mentioned fillers and other additives are added as needed and stirred and mixed, thereby preparing a varnish.

The solvent used in the preparation of the varnish is not particularly limited as long as it can dissolve the above-mentioned resin. As the solvent, for example, N,N-dimethylacetamide (hereinafter, sometimes abbreviated as DMAc), N,N-dimethylformamide (hereinafter, sometimes abbreviated as DMF), etc. Amine-based solvents; lactone-based solvents such as γ-butyrolactone (hereinafter, sometimes abbreviated as GBL) and γ-valerolactone; sulfur-containing solvents such as dimethyl sulfide, dimethyl sulfide, and cyclobutane; Carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among them, the solvent used in the varnish is preferably an amide-based solvent or a lactone-based solvent from the viewpoint of easy production of an optical film that satisfies the mathematical formulas (1) to (3). These solvents can be used alone or in combination of two or more. In addition, water, alcohol-based solvents, ketone-based solvents, acyclic ester-based solvents, ether-based solvents, etc. may be contained in the varnish. 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 can be coated on the substrate by a well-known coating method to form a coating film. As well-known coating methods, for example, roll coating methods such as wire bar coating, reverse coating, and gravure coating, die nozzle coating method, chipped wheel coating method, die lip coating method, Screen coating method, spray coating method, casting method, etc.

In the optical film forming step, the coating film is dried (referred to as the first drying), and after peeling from the substrate, the dried coating film is further dried (referred to as the second drying or post-baking treatment), thereby forming an optical film. The first drying can be carried out in an inert environment or under reduced pressure as needed. The first drying is preferably performed at a lower temperature for a period of time under negative pressure conditions such as in a negative pressure tenter furnace. If the first drying is performed under negative pressure, the clarity value of the reflected image of the produced optical film can easily satisfy the equations (1) to (3), and it is easy to increase the total light transmittance of the optical film. The haze and YI are reduced, but the reason is not clear. It is considered that the reason is that 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, due to the first drying at a relatively low temperature for a period of time, the surface of the optical film is also easy to become uniform, and the clarity value of the reflected image of the produced optical film can easily satisfy the equations (1) to (3). ). In addition, the oxidative degradation of the resin during drying is suppressed, so it is easy to increase the total light transmittance of the optical film, and it is easy to reduce the haze and YI.

Here, in the case of industrial production of the optical film of the present invention, compared with the manufacturing environment of the laboratory level, the actual manufacturing environment is often unfavorable for improving the visibility in the wide-angle direction. As a result, it is difficult to improve the visibility. The visibility of the wide-angle direction of the optical film. As mentioned above, the first drying is preferably performed under negative pressure and at a lower temperature for a period of time. However, in the laboratory level, when the first drying is performed, it can be dried in a closed dryer, so it is more It is not easy to produce roughness of the optical film surface caused by external factors. On the other hand, in the case of industrial production of optical films, for example, a large area must be heated in the first drying, so there is also a case where a blower is used during heating. As a result, the surface condition of the optical film tends to become rough, and it is difficult to improve the visibility of the optical film in the wide-angle direction.

In the case of drying by heating, especially in the industrial production of optical films, if the above-mentioned external factors are considered, the temperature of the first drying is preferably 60-150°C, more preferably 60-130°C, and more Preferably, it is 70 to 120°C. The first drying time is preferably 5 to 60 minutes, more preferably 10 to 40 minutes. In particular, if external factors such as the above are considered during the industrial production of optical films, the first drying is preferably carried out under a drying temperature condition of, for example, two or more stages, and preferably three or more stages. As a multi-stage condition, in each stage, the same or different temperature conditions and/or drying time can be implemented. For example, the drying can be carried out in 3-10 stages, preferably 3-8 stages. If the first drying is performed under a multi-stage condition of three or more stages, the clarity value of the reflected image of the produced optical film can easily satisfy the equations (1) to (3), and the visibility in the wide-angle direction is improved. In the case of a multi-stage condition of more than 3 stages, it is preferable that the temperature distribution of the first drying includes heating and cooling. That is, the first drying condition in the optical film forming step is preferably a heating temperature condition in which the temperature distribution includes three stages or more of temperature increase and temperature decrease. As such a temperature distribution, if a four-stage case is taken 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 (second temperature). 3 temperature) and 80 to 100°C (the fourth temperature). In this example, the temperature of the first drying is increased from the first temperature to the second temperature, then the temperature is decreased from the second temperature to the third temperature, and then the temperature is decreased from the third temperature to the fourth temperature. Here, the time for the first drying is, for example, 5 to 15 minutes in each stage. It is preferable to perform the first drying so that the residual amount of the solvent of the dried coating film is preferably 5 to 15% by mass, and more preferably 6 to 12% by mass relative to the mass of the dried coating film. If the residual amount of solvent is in the above range, the peelability of the dried coating film from the substrate becomes good, and the clarity value of the reflected image of the produced optical film easily satisfies the equations (1) to (3).

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

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

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

As an example of a base material, if it is a metal system, it can be exemplified: SUS (Steel Use Stainless, stainless steel) plate, if it is a resin system, it can be, for example: PET (polyethylene terephthalate, polyethylene terephthalate) Film, PEN (polyethylene naphthalate, polyethylene naphthalate) film, other polyimide resin or polyamide resin film, cycloolefin polymer (COP) film, acrylic film, etc., or have a hard coating Layers of such resin films, glass substrates, etc. Among them, from the viewpoint of excellent smoothness and heat resistance, and the viewpoint that the optical film's reflected image clarity value easily satisfies the equations (1) to (3), PET films, COP films, and hard films are preferred. Coated resin film, SUS plate, glass plate, etc., from the viewpoint of adhesion to the optical film and cost, more preferably SUS plate, resin film with hard coat, more preferably SUS plate, Hard-coated PET film.

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

The method of manufacturing the optical film of this embodiment will be described with reference to the drawings. FIG. 3 is a schematic cross-sectional view showing the steps of a preferred embodiment of a method of manufacturing an optical film according to an embodiment of the present invention. In FIG. 3, the raw film 44 containing at least polyimide resin and/or polyimide resin is carried into the tenter furnace 100, heated in the heating zone in the tenter furnace 100, and then removed from the tenter furnace 100 . In this specification, if it is before the heating step, the amount of solvent will change over time, but as long as it is in the heating step or transported in the oven, the film is called the raw film, and will pass through the heating step. The film removed from the oven is called an optical film.

The raw film 44 can be rolled out from the reel on which the raw film is wound, and carried into the tenter furnace 100, or can be continuously carried into the tenter furnace from the latest step. 4 is a schematic cross-sectional view showing a preferred embodiment of the heating step in the method of manufacturing the optical film of the present invention. As shown in FIG. 4, the raw film 44 is preferably in a state where both ends of the film in the direction (TD direction, also called the width direction) perpendicular to the transport direction of the film (MD direction, also called the length direction) are fixed. Transported in the stenter furnace. The fixing can be performed by the holding device 43, for example.

The fixing of the two ends can be carried out by holding devices such as needle plates, clamps, and film chucks that are usually used in film manufacturing equipment. Both ends of the fixation can be adjusted appropriately by the holding device used, preferably at a distance of less than 50 cm from the end of the membrane. As shown in FIG. 4, the raw material film can be conveyed while fixing its both ends with a plurality of holding devices 43. Regarding the plurality of holding devices 43 arranged at one end of the film, it is preferable that the distance between adjacent holding devices be a distance that can suppress defects such as cracks due to sway of the film or dimensional changes caused by heating. The distance between adjacent holding devices is preferably 1-50 mm, more preferably 3-25 mm, and still more preferably 5-10 mm. In addition, the holding device is preferably arranged in the following manner: when the straight line orthogonal to the film conveying axis is aligned with the center of the holding portion of any holding device at one end of the film, the intersection of the straight line and the other end of the film is the same distance from the intersection point closest The distance between the center of the holding part of the holding device is preferably 3 mm or less, more preferably 2 mm or less, and still more preferably 1 mm or less. Thereby, the difference between the stresses on the opposite ends of the film can be reduced, so the homogeneity of the obtained optical film can be improved. In addition, since the film is dried while fixing the film using the holding device under such conditions, the shaking of the film during drying is suppressed, and the optical film of the present invention satisfying the above-mentioned formulas (1) to (3) can be easily manufactured.

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

The total length of the film conveying direction of the tenter furnace used in the heating step is usually 10-100 m, preferably 15-80 m, more preferably 15-60 m. Regarding the tenter furnace, the inside may be one space or divided into a plurality of spaces. In the embodiment of the present invention, the inside of the tenter furnace that performs the heating step is divided into a plurality of spaces. The above-mentioned space may be a space capable of controlling temperature conditions, wind speed conditions, etc., and may not have physical boundaries such as partition plates. When the inside of the tenter furnace is divided into a plurality of spaces, it can be divided into a plurality of spaces perpendicular or parallel to the transport direction of the film. The number of spaces is usually 2-20, preferably 3-18, more preferably 4-15, and still more preferably 5-10. Regardless of the internal structure of the tenter furnace, the entire tenter furnace can be a heating area, or a part of the interior can be a heating area. Referring to FIG. 3, all three of the areas 40, 41, and 42 may be heating areas, or one of them, for example, the area 42 may be a heating area.

Multiple stenter furnaces can also be used. The number of tenter furnaces in this case is not particularly limited, and may be, for example, 2-12. The inside of each tenter furnace may have the above-mentioned structure. A plurality of tenter furnaces can be continuously installed in such a way that the film is transported without contact with the outside atmosphere. In the case of using a plurality of tenter furnaces, all the tenter furnaces may be the heating area, or a part of the tenter furnaces may be the heating area. In addition to the tenter furnace, an oven can also be used as other equipment. In this specification, the so-called oven refers to a machine that can heat the film, including a heating furnace and a drying furnace. The heating furnace may be any one of hot air treatment or radiation treatment, or a heating furnace that uses these in combination. When an oven is used in combination, the internal structure of the oven, the number of uses, and the heating conditions may be appropriately adjusted within the range in which the optical film of the present invention can be obtained, and it is preferably the same as the tenter oven described in this specification.

Regarding the circulation and exhaust of the air inside the tenter furnace, when the inside of the tenter furnace is divided into a plurality of spaces, it is preferably performed in each space, and when there are multiple tenter furnaces, it is preferably Performed in each stenter furnace. From the viewpoint of ease of manufacturing the optical film of the present invention that satisfies the above formulas (1) to (3), the pressure inside the tenter furnace is preferably the pressure inside the tenter furnace relative to the pressure outside the tenter furnace Adjust the way of negative pressure. The temperature inside the tenter furnace is preferably adjustable for each tenter furnace, and when the inside of the tenter furnace is divided into a plurality of spaces, it is preferable to independently adjust the temperature in each space. The temperature setting of each space can be the same or different. Among them, the temperature of each tenter furnace or space preferably satisfies the following temperature range.

The tenter furnace 100 performing the heating step performs the heating step by hot air treatment in at least one space, and performs the heating step by radiation treatment in at least one space. The heating step is preferably performed by hot air treatment in all the space where the step is performed. The heating step of the radiation treatment method can be performed in another space separate from the hot air treatment method, but it is preferable to perform the heating step in combination with the hot air treatment method.

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

As an example of the embodiment of the present invention, regarding the hot air treatment method using nozzles and the radiation treatment method using IR heaters, the following describes the hot air treatment method using nozzles in order.

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

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

The nozzle 46 provided on the upper side of the upper surface 100a of the tenter furnace 100 has a blowing port at the lower part, and can blow hot air in the downward direction (arrow B direction). On the other hand, the nozzles 47 respectively provided on the lower surface of the lower surface of the tenter furnace 100 have blowing outlets on the upper part, and can blow hot air in the upward direction (the arrow C direction). Furthermore, the upper nozzle 46 and the lower nozzle 47 have a depth of a specific size in a direction perpendicular to the paper surface of FIG. 3 in a manner that can uniformly heat the raw film in the width direction, but they are not shown in FIG. 3. Here, it is also considered that the orientation of the nozzle is set in the transverse direction with respect to the film surface. However, in this case, it is difficult to produce a tensile modulus of elasticity at 25° C. above the above lower limit and satisfying equations (1) to The reason for the optical film of formula (3) is not clear.

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

If the heating step is carried out under the above conditions, it is easy to manufacture the optical film of the present invention that satisfies the above formula and is uniformly heated. Therefore, the unevenness of the amount of solvent remaining in the film becomes smaller, and it is easy to obtain a more uniform film over the entire surface. Optical film with elastic modulus. Therefore, the unevenness of the film surface is not easy to produce, and the occurrence of breakage caused by the difference of the film surface can be suppressed.

In the tenter furnace, the raw film 44 is heated from room temperature to the temperature at which the solvent contained in the raw film evaporates, but it is held by the holding device 43 in such a way that the length of the raw film in the width direction is almost constant, so it is prone to thermal expansion And the tendency to droop. If the blowing air speed and the blowing air volume are within the above-mentioned ranges, the raw material film 44 can be sufficiently heated, and the raw material film 44 can be suppressed from sagging or shaking.

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

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

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

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

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

The so-called other conveying path refers to the conveying path part after 1/10 of the length of the oven from the oven inlet when the inside of the oven is not divided into multiple ones. When the inside of the oven is divided into a plurality of spaces, it refers to any space after the second through which the film passes. When using multiple ovens, according to the internal structure of the oven initially used, it can be the same as the above description, or it can be set so that the wind speed in any of the second and subsequent ovens is lower than the wind speed of the oven that passes through at first.

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

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

The other conveying path is preferably a conveying path located at a position below the conveying path 1 (hereinafter referred to as "conveying path 2"). In the case where the inside of the oven is not divided into plural pieces, the conveying path 2 refers to the conveying path part located at 2/10 of the oven length from the oven import entrance. When the inside of the oven is divided into multiple spaces, the conveying path 2 refers to the second space through which the film passes. When using multiple ovens, according to the internal structure of the oven initially used, it can be the same as the above description, or it can be set so that the wind speed of the second oven is lower than that of the oven initially passed.

When the wind speed difference between the conveying path 1 and the conveying path 2 is set as described above, the wind speed of the conveying path after the conveying path 2 only needs to be within the range of the blowing wind speed of the hot air. The wind speed of the conveying path after conveying path 2 preferably has a wind speed difference of 0.1-12 m/sec from the respective wind speeds of conveying path 1 or conveying path 2, and more preferably a wind speed difference of 0.2-8 m/sec. If the difference in wind speed is in this range, there is a tendency to suppress the shaking of the film due to the difference in wind speed, and it is easy to manufacture the optical film of the present invention that satisfies the above equations (1) to (3). The weight reduction rate of the obtained optical film is adjusted to the desired range.

Regarding the above-mentioned difference in wind speed, when the inside of the oven is not divided into multiple spaces, it can be adjusted by adjusting the position of the nozzle, the blowing speed and air volume of the hot air from the nozzle, and the flow of the air flow in the oven. When the inside of the oven is divided into multiple spaces, it can be adjusted by adjusting the position of the nozzles, the blowing speed and air volume of the nozzles, the flow of airflow in the oven, etc. in the initial space and the subsequent spaces. In the case of using multiple ovens, according to the structure of the initial oven, it can be carried out in the same way as the above description, or the wind speed of the initial oven and the second and subsequent ovens can be different. Set the nozzle position and nozzle The blowing speed and air volume of the hot air, the air flow in the oven, etc.

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

In addition, the difference (ΔT) between the highest temperature and the lowest temperature (ΔT) in the width direction (the direction perpendicular to the paper surface of FIG. 3) of the hot air outlet of each nozzle 46 and 47 installed in the heating area is preferably all below 2°C, More preferably, all are 1°C or less. By using such a hot-air heating film with a sufficiently small temperature difference in the width direction, it is easy to manufacture the optical film of the present invention that satisfies the above-mentioned formulas (1) to (3). Furthermore, the temperature of the hot air is preferably 150 to 400°C, more preferably 150 to 300°C, and still more preferably 150 to 250°C.

As the nozzle that can be used in the manufacturing method of the optical film, the nozzle usually used in the film manufacturing device can be used. As an example, it can be exemplified: a blowing port having a slit shape extending in the width direction of the raw film The nozzle is a jet nozzle (also called a slit nozzle); and a nozzle with a plurality of openings arranged in the conveying direction of the raw film and the width direction of the raw film, namely, the punching nozzle ( punching nozzle) (also known as multi-hole nozzle).

The nozzle has a structure that is installed on the upper surface 100a of the tenter oven 100 to blow hot air downward to the film, and installed on the lower surface 100b of the tenter furnace 100 to blow hot air upward to the film.

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

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

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

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

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

The size and number of the openings provided on the surface of the punching nozzle can be appropriately adjusted in the following way: the blowing speed of the hot air from each opening becomes 2-25 m/sec, and the amount of air blowing from each nozzle is at the edge of the film. The length of the nozzle in the width direction is in the range of 0.1 to 3 m ³ /sec per 1 m.

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

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

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

The tenter furnace 100 that performs the heating step is the same as the nozzle, and an IR heater is provided on the upper inner surface 100a or the lower inner surface 100b of the inner upper surface 100a, and the IR heater can be arranged in a manner facing up and down. In addition, multiple IR heaters can be installed. As the IR heater, an IR heater usually used in film manufacturing equipment may be used.

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

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

In this case, as long as the temperature of the space where the heating step is performed is within the above temperature range, in the radiation treatment method, the film can be irradiated with radiation at a temperature higher than the temperature of the space. The temperature of the radiation can be, for example, a temperature higher than the temperature of the space by 30°C or more, or a temperature higher than 150°C. Here, the so-called radiant temperature refers to, for example, the temperature set by a device that generates radiant heat like the set temperature of an IR heater. The difference between the temperature of the radiation and the temperature of the radiation irradiated to the film is preferably 5°C or less, more preferably 3°C or less, and still more preferably 1°C or less.

In the stenter furnace 100, if the nozzle (hot air treatment method) and IR heater (radiation treatment method) are used in combination, even if the raw film is irradiated with radiation whose temperature is higher than the temperature in the heating zone or the stenter furnace (ambient temperature) It is also possible to perform the heating step while preventing the temperature in the heating zone or the tenter furnace from becoming too high.

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

The heating step is preferably performed in the range of 150 to 350°C. If the heating step is within this temperature range in the embodiment of the present invention, it tends to be easily adjusted so that the raw material film becomes the following weight reduction rate M. The temperature range is more preferably 170°C or higher, still more 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. If the temperature of the heating step is in the above-mentioned range, it is easy to adjust the YI value of the obtained optical film into the above-mentioned preferable range. In addition, the temperature of the space where the heating step is performed is more preferably 170°C or higher, and still more preferably 180°C or higher. Regarding the temperature in the tenter furnace where the heating step is performed, the heating area only needs to be in the above-mentioned range. When there are a plurality of tenter furnaces and a situation where the inside of the tenter furnace is divided into a plurality of spaces, it can be adjusted appropriately, and it is preferable that all the tenter furnaces or the spaces are within the above-mentioned range.

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

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

In one embodiment of the present invention, the manufacturing method of the optical film can be carried out during the heating step to change the width of the film or to maintain the width of the film while conveying. As an example of the operation of changing the width of the film, an operation of extending the film in the width direction can be mentioned. The stretching ratio is preferably 0.7 to 1.5 times, more preferably 0.8 to 1.4 times, and still more preferably 0.8 to 1.3 times. As an example of the operation of maintaining the width of the film and conveying, for example, the operation of holding such that the length of the film in the width direction is almost constant. As an optical film obtained through these operations, it can be about 0.7 to 1.5 times the length of the raw film in the width direction, and can be extended, kept equal, or contracted from the length of the raw film in the width direction. The stretching ratio is calculated as the ratio of the width of the stretched film (excluding the holding part) to the width of the film excluding the holding part. Furthermore, in FIG. 4, in the operation of stretching the film in the width direction, the solid line indicates the case where the stretching ratio exceeds 1 time, and the dotted line indicates the case where the stretching ratio remains equal or less than 1 time.

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

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

From the viewpoint of the ease of manufacturing an optical film satisfying the mathematical formulas (1) to (3), the raw material film is preferably measured by thermogravimetric-differential calorimetry (hereinafter sometimes referred to as "TG-DTA measurement") The weight reduction rate M from 120°C to 250°C obtained is preferably about 1-40%, more preferably 3-20%, and still more preferably 5-15%, especially It is a method of 5-12% to remove part of the solvent from the above varnish. The weight reduction rate M of the raw film can be measured by the following method using a commercially available TG-DTA measuring device. As a TG-DTA measuring device, TG/DTA6300 manufactured by Hitachi High-Tech Science can be used.

First, take a sample of about 20 mg from the raw material film, and measure the weight change of the sample while heating it under the following conditions: the temperature is increased from room temperature to 120°C at a temperature increase rate of 10°C/min, and the temperature is maintained at 120°C for 5 Minutes later, the temperature was increased to 400°C at a temperature increase rate of 10°C/min. Next, from the result of the TG-DTA measurement, the weight reduction rate M (%) from 120°C to 250°C can be calculated by the following formula. In the following formula, W ₀ represents the weight of the sample after being kept at 120°C for 5 minutes, and W ₁ represents the weight of the sample at 250°C. M(%)=100－(W ₁ /W ₀ )×100

If the weight reduction rate M of the raw film is large to some extent, when the raw film is wound as a laminate with a substrate or a surface protective film, the deformation of the laminate is suppressed, and the coilability of the laminate is improved The tendency. In addition, it is easy to manufacture an optical film that satisfies the mathematical formulas (1) to (3).

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

The raw material film can be formed by drying the above-mentioned coating film and peeling it from the base material. The drying of the coating film can usually be carried out at a temperature of 50 to 350°C. If necessary, the coating film can be dried in an inert environment or under reduced pressure. The raw material film obtained as described above is supplied to the above heating step to produce the optical film of the present invention. The raw film can be continuously transported and supplied to the heating step, or it can be temporarily wound and supplied.

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

(Ultraviolet absorption layer) The ultraviolet absorbing layer is a layer that has the function of absorbing ultraviolet rays, such as a main material selected from the group consisting of ultraviolet curable transparent resin, electron beam curable transparent resin, and thermosetting transparent resin, and ultraviolet rays dispersed in the main material Absorbent.

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

In the hard coat layer forming step, the coating film is irradiated with high energy rays (for example, active energy rays) to harden the coating film to form a hard coat layer. The irradiation intensity is appropriately determined according to the composition of the curable composition and is not particularly limited, but it is preferably irradiation in a wavelength region effective for activation of the polymerization initiator. The irradiation intensity is preferably 0.1 to 6,000 mW/cm ² , more preferably 10 to 1,000 mW/cm ² , and still more preferably 20 to 500 mW/cm ² . If the irradiation intensity is within the above range, an appropriate reaction time can be ensured, and the yellowing or deterioration of the resin caused by the heat radiated from the light source and the heat generated during the curing reaction can be suppressed. The irradiation time may be appropriately selected according to the composition of the curable composition, and is not particularly limited. The cumulative light amount represented by the product of the above-mentioned irradiation intensity and irradiation time is preferably 10 to 10,000 mJ/cm ² , more preferably 50 to 1,000 mJ/cm ² , and more preferably 80 to 500 mJ/cm ² . If the cumulative amount of light is within the above range, a sufficient amount of active species will be generated from the polymerization initiator, so that the curing reaction can proceed more reliably, and the irradiation time will not be too long, and good productivity can be maintained. In addition, by going through the irradiation step within this range, the hardness of the hard coat layer can be further increased, which is useful. 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, examples include: the type of solvent, the ratio of components, the optimization of the solid content concentration, and the addition of leveling agents, etc. .

The above-mentioned radically polymerizable compound is a compound having a radically polymerizable group. As the radical polymerizable group possessed by the above-mentioned radical polymerizable compound, any functional group capable of generating a radical polymerization reaction may be sufficient, and a group containing a carbon-carbon unsaturated double bond can be exemplified. Specific examples include: Vinyl, (meth)acrylic acid, etc. In addition, when the above-mentioned radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same as or different from each other. As the number of radical polymerizable groups which the said radically polymerizable compound has in 1 molecule, it is preferable that it is 2 or more from the point which improves the hardness of a hard-coat layer. As the above-mentioned radically polymerizable compound, in terms of high reactivity, a compound having a (meth)acryloyl group is preferably exemplified, and specific examples include: having 2 to 6 (formaldehyde) in one molecule Acrylic acid-based compounds called polyfunctional acrylate monomers or epoxy (meth)acrylate, polyurethane (meth)acrylate, polyester (meth)acrylic acid The ester is an oligomer with several (meth)acrylic acid groups in the molecule and a molecular weight of several hundred to several thousand, preferably selected from epoxy (meth)acrylate and polyurethane One or more of (meth)acrylate and polyester (meth)acrylate.

The above-mentioned cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetanyl group, and a vinyl ether group. The number of cationically polymerizable groups contained in one molecule of the above-mentioned cationically polymerizable compound is preferably 2 or more, more preferably 3 or more in terms of increasing the hardness of the hard coat layer. In addition, as the above-mentioned cationically polymerizable compound, a compound having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group is preferable. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferable in terms of less shrinkage accompanying the polymerization reaction. In addition, the compound having an epoxy group in the cyclic ether group has a compound that is easy to obtain a variety of structures, does not adversely affect the durability of the obtained hard coat, and the compatibility with the radical polymerizable compound is also easy to control advantage. In addition, in the cyclic ether group, the oxetanyl group has a higher degree of polymerization than the epoxy group, which speeds up the formation speed of the network structure obtained from the cationically polymerizable compound of the hard coat layer. The region where the radical polymerizable compound is mixed will not leave unreacted monomers in the film, forming an independent network structure and other advantages. As a cationic polymerizable compound having an epoxy group, for example, polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, or by using a compound containing a cyclohexene ring and a cyclopentene ring with hydrogen peroxide , Peracid and other appropriate oxidizing agent to obtain cycloaliphatic epoxy resin; ( Aliphatic epoxy resins such as homopolymers and copolymers of glycidyl methacrylate; by bisphenols such as bisphenol A, bisphenol F or hydrogenated bisphenol A, or their alkylene oxide adducts , Glycidyl ether produced by the reaction of derivatives such as caprolactone adducts and epichlorohydrin, and novolac epoxy resins, that is, glycidyl ether type epoxy resins derived from bisphenols.

The above-mentioned hard coat composition may further contain a polymerization initiator. The polymerization initiator may, for example, be a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, etc., which are appropriately selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate free radicals or cations, thereby performing radical polymerization and cationic polymerization. The radical polymerization initiator may release a substance that initiates radical polymerization by at least any one of active energy ray irradiation and heating. For example, as a thermal radical polymerization initiator, organic peroxides, such as hydrogen peroxide and perbenzoic acid, azo compounds, such as azobisbutyronitrile, etc. are mentioned. As active energy ray radical polymerization initiators, there are Type1 radical polymerization initiators that generate free radicals by the decomposition of molecules, and those that coexist with tertiary amines and generate free radicals by hydrogen abstraction type reactions. Type 2 radical polymerization initiator, which can be used alone or in combination. The cationic polymerization initiator may release a substance that initiates cationic polymerization by at least one of active energy ray irradiation and heating. As the cationic polymerization initiator, an aromatic iodonium salt, an aromatic sulfonium salt, a cyclopentadienyl iron (II) complex, and the like can be used. Depending on the structure, the cationic polymerization can be started by either irradiation with active energy rays or heating, or both can start cationic polymerization by irradiation with active energy rays or heating.

The polymerization initiator may preferably contain 0.1 to 10% by mass relative to 100% by mass of the entire hard coating composition. If the content of the polymerization initiator is in the above range, there is a tendency that curing can be carried out sufficiently, and the mechanical properties or adhesive force of the finally obtained coating film can be in a good range, and adhesion caused by curing shrinkage is unlikely to occur. Poor force or cracking and curling.

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

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

The adhesive layer may be a layer called a Pressure Sensitive Adhesive (PSA) that adheres to an object by pressing. Pressure-sensitive adhesives can be used as "substances that are adhesive at room temperature and adhere to the material to be bonded with a lighter pressure" (JIS K 6800), or can be used as "a specific component contained in the protective film" (Microcapsules), an adhesive that can maintain stability until the film is broken by an appropriate method (pressure, heat, etc.)" (JIS K 6800) capsule type adhesive.

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

(Refractive index adjustment layer) The refractive index adjustment layer is a layer having a refractive index adjustment function, for example, a layer that has a refractive index different from that of an optical film and can give a specific refractive index to the optical laminate. The refractive index adjustment layer may be, for example, a resin layer containing appropriately selected resin and pigments as appropriate, or a metal thin film. As the pigment for adjusting the refractive index, for example, silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide may be mentioned. The average primary particle size of the pigment may be 0.1 μm or less. By making the average primary particle size of the pigment to be 0.1 μm or less, the diffuse reflection of the light passing through the refractive index adjustment layer can be prevented, thereby preventing the decrease in transparency. As the metal used in the refractive index adjustment layer, for example, titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, nitrogen Metal oxides or metal nitrides such as silicide.

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

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

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

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

Examples of image display devices include televisions, smart phones, mobile phones, car navigation, tablet PCs (personal computers), portable game consoles, electronic paper, indicators, bulletin boards, watches , And wearable devices such as smart watches. As the flexible display device, all image display devices having flexible characteristics can be cited.

[Flexible display device] The present invention also provides a flexible display device equipped with the optical film of the present invention. The optical film of the present invention is preferably used as a front panel in a flexible display device, and the front panel is sometimes called a window film. The flexible display device includes a laminate for a flexible display device and an organic EL display panel. The laminate for a flexible display device is arranged on the viewing side of the organic EL display panel and is configured to be flexible. The laminate for a flexible display device may contain the optical film (window film) of the present invention, a circular polarizer, and a touch sensor. The order of these layers is in any order, and it is preferable to use the window film, Circular polarizing plate, touch sensor or window film, touch sensor, circular polarizing plate are laminated in sequence. If there is a circular polarizer on the visible side of the touch sensor, it is difficult to see the pattern of the touch sensor, and the visibility of the displayed image becomes better, which is better. Each member can be laminated using adhesives, adhesives, etc. In addition, it may be provided with a light-shielding pattern formed on at least one surface of any layer of the window film, the circular polarizer, and the touch sensor.

[Polarizer] The flexible display device of the present invention may further include a polarizing plate, preferably a circular polarizing plate. The circular polarizing plate is a functional layer that has a function of transmitting only right-handed circularly polarized light or left-handed circularly polarized light components by laminating a λ/4 retardation plate on the linear polarizing plate. For example, it is used for the following purposes: converting external light into right-handed circularly polarized light, blocking the outer boundary light of the left-handed circularly polarized light reflected by the organic EL panel, and allowing only the light-emitting components of the organic EL to pass through, thereby suppressing reflection The effect of light makes it easy to view the image. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizer and the retardation axis of the λ/4 retardation plate must be 45 degrees in theory, and 45±10 degrees in practice. 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 axis only needs to satisfy the above-mentioned range. It is preferable to achieve complete circularly polarized light in all wavelengths, but this is not necessary in practice. Therefore, the circular polarizing plate of the present invention also includes an elliptical polarizing plate. It is also preferable to laminate a λ/4 retardation film on the visibility side of the linear polarizer to make the emitted light circularly polarized light, thereby improving the visibility when wearing polarized sunglasses.

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

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

Furthermore, as another example of the above-mentioned polarizing element, a liquid crystal coating type polarizing element formed by applying a liquid crystal polarizing composition can be exemplified. The above-mentioned liquid crystal polarizing composition may contain a liquid crystal compound and a dichroic dye compound. The above-mentioned liquid crystalline compound only needs to have the property of displaying a liquid crystal state, especially if it has an alignment state of the order of the order of smectic alignment, it can exhibit higher polarization performance, so it is preferable. In addition, it is also preferable when the liquid crystal compound has a polymerizable functional group. The dichroic dye is a dye that is aligned with the liquid crystal compound and exhibits dichroism, and may have a polymerizable functional group, and the dichroic dye itself may have liquid crystallinity. Any compound in the liquid crystal polarizing composition has a polymerizable functional group.

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

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

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

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

As the above-mentioned protective film, it is sufficient as long as it is a transparent polymer film. Specifically, as the polymer film used, there may be mentioned: polyethylene, polypropylene, polymethylpentene, and a Cycloolefin derivatives such as olefin monomer units, polyolefins, diacetyl cellulose, triacetyl cellulose, propylene cellulose, etc. (modified) cellulose, methyl methacrylate Acrylics such as (co)polymers, polystyrenes such as styrene (co)polymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, ethylene-vinyl acetate copolymers Materials, polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, etc. Polyamides such as esters and nylons, polyimines, polyimines, polyetherimines, polyethers, polyvinyls, polyvinyl alcohols, and polyvinyl acetals Films such as polyamides, polyurethanes, epoxy resins, etc., in terms of excellent transparency and heat resistance, preferably, polyamide, polyimide, polyimide, Polyester, olefin, acrylic or cellulosic film. These polymers can be used alone or in combination of two or more. These films can be used in an unstretched state, or used as a uniaxially or biaxially stretched film. Preferred are cellulose-based films, olefin-based films, acrylic-based films, and polyester-based films. It can be a coating type protective film obtained by coating and curing a cationic curing composition such as epoxy resin or a radical curing composition such as acrylate. If necessary, it may contain plasticizers, ultraviolet absorbers, infrared absorbers, coloring agents such as pigments or dyes, fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, and lubricants , Solvents, etc. The thickness of the protective film is preferably 200 μm or less, more preferably 1-100 μm. If the thickness of the protective film is in the above range, the flexibility of the protective film will not easily decrease.

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

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

Generally, the shorter the wavelength, the greater the birefringence, and the longer the wavelength, the smaller the birefringence. In this case, the λ/4 phase difference cannot be achieved in the entire visible light region, so it is designed to have a λ/4 in-plane phase difference near 560 nm where the visual sensitivity is higher, which is preferably 100-180 nm, more preferably There are many cases where the in-plane phase difference is between 130 and 150 nm. It is preferable to use a reverse dispersion λ/4 retardation plate using a material having a birefringence wavelength dispersion characteristic opposite to the usual one in terms of improving visibility. As such a material, in the case of the extension type retardation plate, the one described in Japanese Patent Laid-Open No. 2007-232873 etc. is used, and in the case of the liquid crystal coating type retardation plate, the Japanese Patent Laid-Open No. 2010-30979 is used. It is also better when the situation is recorded in the bulletin.

In addition, as another method, a technique of obtaining a wide-band λ/4 retardation plate by combining 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 materials and methods as the λ/4 retardation plate. The combination of the extension type retardation plate and the liquid crystal coating type retardation plate is arbitrary, and when the liquid crystal coating type retardation plate is used in either case, it is relatively thin in terms of making the thickness thinner. good.

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

[Touch Sensor] The flexible display device of the present invention may further include a touch sensor. The touch sensor is used as an input mechanism. As a touch sensor, various styles such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and an electrostatic capacitance method have been proposed. Any method may be used, and an electrostatic capacitance method is preferred. The capacitive touch sensor is divided into an active area and an inactive area located outside the active area. The active area is the area corresponding to the display part of the display panel, which is the area corresponding to the user's touch, and the inactive area is the area corresponding to the non-display part of the display device where no picture is displayed. The touch sensor may include: a substrate with flexible characteristics; a sensing pattern formed in the active area of the substrate; and an inactive area formed on the substrate and used to communicate with the outside through the sensing pattern and the pad part. Each sensing line connected to the drive circuit. As a substrate with flexibility, the same material as the above-mentioned polymer film can be used. Among the substrates of the touch sensor, the toughness of 2,000 MPa% or more is better in terms of crack suppression of the touch sensor. The toughness can be 2,000～30,000 MPa% better. Here, the toughness system is defined as the area under the curve up to the failure point in the stress-strain curve obtained by the tensile test of the polymer material.

The aforementioned sensing pattern may include a first pattern formed in the first direction and a second pattern formed in the second direction. The first pattern and the second pattern are arranged in mutually different directions. The first pattern and the second pattern are formed on the same layer. In order to sense the touch location, each pattern must be electrically connected. The first pattern is a form in which each unit pattern is connected to each other via a joint, and the second pattern is a structure where each unit pattern is separated into an island form. Therefore, in order to electrically connect the second pattern, another bridge electrode is required. As the electrode for electrically connecting the second pattern, a well-known transparent electrode material can be used. Examples of the transparent electrode material include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc tin oxide (IZTO), and indium gallium zinc oxide (IGZO) , Cadmium tin oxide (CTO), PEDOT (poly(3,4-ethylenedioxythiophene), poly(3,4-ethylenedioxythiophene)), carbon nanotube (CNT), graphene, metal wire, etc., These can be used alone or in combination of two or more. As the transparent electrode material, ITO can be preferably used. The metal used in the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, and chromium. These can be used alone or in combination of two or more.

The bridging electrode can be formed on the upper part of the insulating layer via the insulating layer on the upper part of the sensing pattern, and the bridging electrode can be formed on the substrate, and the insulating layer and the sensing pattern can be formed thereon. The above-mentioned bridge electrode can be formed by the same material as the sensing pattern, or by metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of two or more of these And formed. The first pattern and the second pattern must be electrically insulated, so an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the joints of the first pattern and the bridging electrodes, or may be formed as a layer covering the entire sensing pattern. When it is formed as a layer covering the entire sensing pattern, the bridge electrode may be connected to the second pattern via a contact hole formed in the insulating layer.

The above-mentioned touch sensor may further include an optical adjustment layer between the substrate and the electrode, as a suitable compensation for the difference in transmittance between the patterned patterned area and the unpatterned non-patterned area, specifically because of these The mechanism of the difference in light transmittance induced by the difference in refractive index in the area. The above-mentioned optical adjustment layer may contain an inorganic insulating material or an organic insulating material. The optical adjustment layer can be formed by coating a photo-curing composition containing a photo-curing organic binder and a solvent on a substrate. The above-mentioned photocurable composition may further contain inorganic particles. The above-mentioned inorganic particles can increase the refractive index of the optical adjustment layer. The photocurable organic adhesive may contain, for example, copolymers of monomers such as acrylate-based monomers, styrene-based monomers, and carboxylic acid-based monomers. The photocurable organic adhesive may be, for example, a copolymer containing repeating units that are different from each other, such as epoxy-containing repeating units, acrylate repeating units, and carboxylic acid repeating units. Examples of the above-mentioned inorganic particles include zirconia particles, titanium oxide particles, and alumina particles. The above-mentioned photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

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

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

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

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

The active energy ray composition may further contain a polymerization initiator. The polymerization initiator may, for example, be a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, etc., 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 free radicals or cations, thereby performing radical polymerization and cationic polymerization. In the description that the hard coat composition can be used, an initiator that can start at least any one of radical polymerization or cationic polymerization by active energy ray irradiation.

The active energy ray hardening composition may further contain ion scavengers, antioxidants, chain transfer agents, adhesion imparting agents, thermoplastic resins, fillers, flow viscosity modifiers, plasticizers, defoamer solvents, additives, and solvents. When using the active energy ray curable adhesive to adhere two layers to be bonded, apply the active energy ray curable composition to either or both of the layers to be adhered, and then bond them through either The bonded layer or two bonded layers are irradiated with active energy rays to harden the composition, thereby enabling bonding. In the case of using the active energy ray-curable adhesive, the thickness of the adhesive layer is preferably 0.01-20 μm, more preferably 0.1-10 μm. When the above-mentioned active energy ray-curable adhesive is used in the formation of multiple layers, the thickness of each layer and the type of adhesive used may be the same or different.

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

[Shading Pattern] The light-shielding pattern can be used as at least a part of the frame 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 so that it is not easily visible, thereby improving the visibility of the image. The above-mentioned light-shielding pattern may be in the form of a single layer or multiple layers. The color of the shading pattern is not particularly limited, and can have multiple colors such as black, white, and metallic. The light-shielding pattern can be formed by pigments used to develop colors, acrylic resins, ester resins, epoxy resins, polyurethanes, polysiloxanes, and other polymers. These can be used alone or in a mixture of two or more. The above-mentioned light-shielding pattern can be formed by various methods such as printing, lithography, and inkjet. The thickness of the light-shielding pattern is preferably 1-100 μm, more preferably 2-50 μm. In addition, it is also preferable to give a shape such as an inclination to the thickness direction of the light-shielding pattern. [Example]

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

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

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

＜YI value＞ According to JIS K 7373: 2006, the YI value of the optical film is measured using the UV-Visible-Near-Infrared Spectrophotometer "V-670" manufactured by JASCO Corporation. After measuring the background without the sample, set the optical film in the sample holder and measure the transmittance of light from 300 to 800 nm to obtain the tristimulus values (X, Y, Z), based on The YI value is calculated by the following formula. YI=100×(1.2769X－1.0592Z)/Y

＜Determination of weight average molecular weight＞ Gel Permeation Chromatography (GPC) determination (1) Pretreatment method Add DMF lysate (10 mmol/L lithium bromide solution) to the polyimide membrane to a concentration of 2 mg/mL, heat it while stirring at 80°C for 30 minutes, and filter with a 0.45 μm membrane filter after cooling , And use the obtained as the measurement solution. (2) Measurement conditions Column: TSKgel α-2500 ((7)7.8 mm diameter×300 mm)×1, α-M((13)7.8 mm diameter×300 mm)×2 pieces manufactured by Tosoh (shares) Eluent: DMF (add 10 mmol/L lithium bromide) Flow rate: 1.0 mL/min Detector: RI detector Column temperature: 40℃ Injection volume: 100 μL Molecular weight standard: standard polystyrene

＜Measurement of thickness＞ The thickness of the optical film was measured using an ABS digital gauge (manufactured by Mitutoyo Co., Ltd., "ID-C112BS").

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

<Low temperature tensile test> Using "Autograph AG-IS" manufactured by Shimadzu Corporation, the elastic modulus at the temperature of -40°C of the optical films obtained in the Examples and Comparative Examples was measured. In more detail, a film with a width of 10 mm in vertical and horizontal directions was produced, and the stress-strain curve (SS curve) was measured under the conditions of a distance between the chucks of 50 mm and a stretching speed of 10 mm/min, and the elastic modulus was calculated from the slope of the film. Breaking strain ε ₁ .

<Measurement of the reflection image clarity value of the optical film> When the optical film obtained in the Examples and Comparative Examples has a protective film, the following measurement and evaluation are performed using the optical film in a state where the protective film is peeled off. In accordance with JIS K 7374, using an image clarity measuring device ("ICM-1" manufactured by Suga Test Instruments Co., Ltd.), the reflective image clarity value of the optical film was measured by the reflection method in the following manner. The optical film is set on the image clarity measuring device. For the optical film, wipe both sides with ethanol lightly before installation to dry it, and install it with foreign matter removed from the surface. Then, the amount of light and the cross-sectional area are adjusted, and the white light adjusted to be parallel light is irradiated to the installed optical film from an angle (incident angle) inclined at 60° in the MD direction with respect to the optical film plane. Here, the irradiated surface of the optical film of Examples 1, 3, and 4 was the surface that was in contact with the substrate during the production of the optical film. The irradiated surface of the optical film of Example 2 was the surface where the hard coat layer was applied to the surface in contact with the substrate during the production of the optical film. The specular reflection light from the optical film is transmitted through an optical comb whose cross-sectional area is adjusted and extending perpendicular to the optical axis of the specular reflection light, and the light passing through the optical comb is received by a light receiver. In the direction parallel to the plane of the optical comb and where the slits in the optical comb are arranged, move the optical comb (slit width: 0.125 mm) by a specific unit width and receive the transmitted light of the optical comb, and repeat the operation. As a result, the received light waveform is obtained. Obtain the maximum value M and the minimum value m of the relative light intensity from the received light waveform. From the obtained M and m, the first reflection image sharpness value C _{MD is} calculated based on the equation (5).

Except that the incident angle of the irradiated light is changed to an angle that is inclined 60° from the direction perpendicular to the optical film plane to the TD direction, the second reflected image is calculated in the same way as the first reflected image sharpness value. Degree value C _TD .

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

(Imidation rate of polyamide imide resin) In the ¹ H-NMR spectrum obtained with a measurement sample containing polyamide imide resin, the observed benzene protons are derived from The integral value of the benzene proton C, which has the unchanged structure before and after amination, and which is not affected by the structure derived from the residual amide acid structure in the polyamide imide resin, is set to Int _C. In addition, the integral of the benzene proton D derived from the unchanged structure before and after the imidization of the observed benzene proton, and the structure of the benzene proton D derived from the residual acid structure in the polyimide resin The value is set to Int _D. Calculate the β value _{from the obtained Int C} and Int _D based on the following formula. β=Int _D /Int _C Next, for a plurality of polyimide resins, the β value of the above formula and the imidization rate of the polyimide resin of the above formula are calculated, and the following correlations are obtained from these results Mode. The imidization rate (%)=k×β+100 In the above correlation formula, k is a constant. Substitute β into the correlation formula to obtain the imidization rate (%) of the polyimide resin.

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

<Bending resistance test> According to JIS K 5600-5-1, a bending resistance test was performed on the optical film. The bending resistance test was carried out using a small desktop bending tester (manufactured by Yuasa System Co., Ltd.). For the optical film after the bending resistance test, the sharpness value and haze of the reflected image were measured by the same method as the above-mentioned measurement method. Take the absolute value of the difference between the sharpness value of the reflected image and the haze before and after the bending resistance test respectively, and calculate the difference of the sharpness value of the reflected image (the difference of the first reflected image sharpness value ΔC _MD , the second reflection image The difference in image sharpness value ΔC _TD ) and the difference in haze (ΔHaze).

＜Folding resistance test (MIT)＞ According to ASTM standard D2176-16, the number of times of bending of the optical films of the Examples and Comparative Examples was calculated as follows. Using a dumbbell cutter, cut the optical film into short strips with a width of 15 mm and a length of 100 mm to prepare a measurement sample. The measurement sample was set in the main body of the MIT flexural fatigue testing machine ("Model 0530" manufactured by Toyo Seiki Seisakusho Co., Ltd.). Specifically, one end of the measurement sample is fixed to a load jig, the other end is fixed to a bending jig, and tension is 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 jig R=3 mm, perform a reciprocating bending movement in the forward and reverse directions until the test specimen is broken. Off. Measure the number of folds mentioned above.

＜Visibility＞ Cut the optical film into 10 cm squares. Align the MD direction of the adhesive layer-attached polarizing plate of the same size with the MD direction of the above-mentioned optical film, and bond the adhesive layer-attached polarizing plate to the above-mentioned optical film to prepare an evaluation sample. Two evaluation samples were prepared for the optical films of 1 Example and Comparative Example, respectively. In addition, for the optical films of the Examples and Comparative Examples after the bending resistance test, two evaluation samples were also produced. One of the two evaluation samples is fixed on the table in the following manner: the fluorescent lamp is located in the vertical direction of the evaluation sample plane, and the length direction of the above-mentioned fluorescent lamp is relative to that of the evaluation sample. The MD direction becomes horizontal. The observer visually observes the fluorescent lamp image reflected on the surface of the evaluation sample at an angle of 30° from the vertical direction relative to the plane of the evaluation sample. Except that the length direction of the fluorescent lamp was changed from horizontal to vertical, another sample for evaluation was fixed on the table in the same manner, and the fluorescent lamp image was observed. Based on the following evaluation criteria, the visibility was evaluated from the observation results. (Evaluation criteria for visibility) ◎: The deformation of the fluorescent lamp image is hardly recognized. ○: Visually recognizes a slight distortion of the fluorescent lamp image. △: Distortion of the fluorescent lamp image is visually recognized. ×: The deformation of the fluorescent lamp image is clearly recognized.

<Projected image visibility> The optical film was cut into a length of 300 mm and a width of 200 mm, which was used as a sample for evaluation. In a dark room, the LED light source (manufactured by Linshiji Industry Co., Ltd.; LA-HDF15T), the above-mentioned evaluation sample and a white screen for movie viewing (manufactured by Theater House Co., Ltd.; BTP600FHD-SH1000) were combined with the LED light source The distance between the sample is 2 m, and the distance between the sample and the screen is 0.3 m, and it is set on a straight line. The sample is irradiated with light from the light source, the image is projected onto the screen, and the transmitted image is observed. Based on the following evaluation criteria, the visibility of the projected image was evaluated from the observation results.

(Evaluation criteria for visibility of projected images) ◎: The shade of the projected image is hardly seen. ○: The lightness of the projected image can be recognized slightly. △: The intensity of the projected image is visually recognized. ×: The intensity of the projected image is clearly recognized.

(Production Example 1: Preparation of polyamide imine resin (1)) Under a nitrogen atmosphere, in a separable flask equipped with a stirring blade, add 2,2'-bis(trifluoromethyl)benzidine (hereinafter sometimes referred to as TFMB) and DMAc, while stirring at room temperature, dissolve TFMB in DMAc. Next, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (hereinafter, sometimes referred to as 6FDA) is added to the flask so that it becomes 30.46 mol% relative to TFMB, at room temperature Stir for 18 hours. Then, after cooling to 10°C, 2-methoxyterephthalic acid chloride (hereinafter, sometimes referred to as OMTPC) was added so as to become 31.98 mol% with respect to TFMB, and after stirring for 10 minutes, the ratio Add OMTPC so that TFMB becomes 31.98 mol%, and stir for 20 minutes. After that, the same amount of DMAc as the DMAc added at the beginning was added, and after stirring for 10 minutes, OMTPC was added so as to be 7.11 mol% with respect to TFMB, and the mixture was stirred for 2 hours. Then, diisopropylethylamine and 4-picoline were added to the flask so that they were 71.07 mol% relative to TFMB, and acetic anhydride was added so that they were 213.20 mol% relative to TFMB. After stirring for 30 minutes, The internal temperature was raised to 70°C, and further stirred for 3 hours to obtain a reaction liquid. The obtained reaction liquid was cooled to room temperature, and was thrown into a large amount of methanol in the form of filaments, and the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60°C to obtain a polyamide imide resin (1). The weight average molecular weight of the obtained polyimide resin (1) was 260,000, and the imidization rate was 98.5%.

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

(Production Example 3: Preparation of polyimide resin (3)) Under a nitrogen atmosphere, in a separable flask equipped with a stirring blade, add TFMB and DMAc so that the solid content of TFMB becomes 6.08% by mass, and dissolve TFMB in DMAc while stirring at room temperature. Next, 6FDA was added to the flask so that it might become 40.82 mol% with respect to TFMB, and it stirred at room temperature for 16 hours. Then, after cooling to 10°C, OMTPC was added so that it became 27.55 mol% with respect to TFMB, and after stirring for 10 minutes, OMTPC was further added so that it became 27.55 mol% with respect to TFMB, and stirring was carried out for 20 minutes. After that, the same amount of DMAc as the DMAc added at the beginning was added, and after stirring for 10 minutes, OMTPC was added so as to be 6.12 mol% with respect to TFMB, and the mixture was stirred for 2 hours. Then, diisopropylethylamine and 4-picoline were added to the flask so that they were 61.22 mol% relative to TFMB, and acetic anhydride was added so that they were 285.71 mol% relative to TFMB. After stirring for 30 minutes, The internal temperature was raised to 70°C, and further stirred for 3 hours to obtain a reaction liquid. The obtained reaction liquid was cooled to room temperature, and was thrown into a large amount of methanol in the form of filaments, and the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60°C to obtain polyimide resin (3). The weight average molecular weight of the obtained polyimide resin (3) was 300,000, and the imidization rate was 99.1%.

(Production Example 4: Preparation of varnish) The above polyamide imine resin was added to GBL so as to become the solid components shown in Table 1, and it was completely dissolved by stirring at room temperature for 24 hours to obtain a varnish (1)～(3). [Table 1] Varnish Polyimide resin Viscosity (cp) Solid content (mass%) Varnish 1 (1) 37,000 9.5 Varnish 2 (2) 36,000 9.0 Varnish 3 (3) 38,000 8.0

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

<Example 1> (Manufacturing of Optical Film (1)) The manufacture of the optical film (1) will be described with reference to FIGS. 6 and 7. First, as shown in FIG. 6, a polyethylene terephthalate film substrate 51 (manufactured by Toyobo Co., Ltd.: COMOSHINE (registered trademark) A4100) with a thickness of 188 μm is rolled out, sometimes referred to as PET film substrate 51. ), while conveying at a linear speed of 0.30 m/min, the varnish (1) loaded into the tank 522 is applied from the nozzle 521 to the PET film substrate 51 by casting with a width of 500 mm. After that, while being transported at the same linear speed, it was heated in the dryer 53 at 120°C for 20 minutes and at 90°C for 20 minutes to dry the applied varnish. Then, the protective film 54 (manufactured by SUN A.KAKEN Co., Ltd.; NSA-33T) was unrolled from the reel and attached to the surface of the dry coating film on the opposite side to the surface of the PET film substrate 51, The PET film base material 51 was peeled from the dried coating film, and wound into a PET film base material roll 55, and the remaining laminate was obtained in the form of a laminate roll 56 with a length of 100 m.

Next, as shown in Fig. 7, from the obtained laminate roll 56, the laminate film is rolled out at a conveying speed of 0.5 m/sec, the protective film 54 is peeled off from the laminate film, and is wound into a protective film roll 57 to make the remaining After passing through the nip rollers 201 and 202, the dried coating film is dried in a tenter dryer 58 under the following conditions. Furthermore, the tenter dryer 58 is equipped with a mechanism for holding both ends of the film using a clamp. In addition, the inside is divided into the first chamber to the sixth chamber in order from the entrance side of the membrane. Clamp holding width (the distance from one end of the film to the corresponding clamp holding part): 25 mm The ratio of the distance between the clamps at the outlet of the dryer to the distance between the clamps at both ends of the film at the inlet of the dryer: 1.0 Internal temperature of stenter dryer 58: 200℃ The wind speed of each chamber in the stenter dryer 58: 13.5 m/sec in the first chamber, 13 m/sec in the second chamber, 11 m/sec in the third to sixth chamber

After the stenter dryer 58 is removed, the holding of the clamp at the end of the film is released. After the obtained film is passed through the nip rollers 203 and 204, the clamp holding part of the film is cut into long strips with the slit device 59, and then the PET protective film 60 is attached and wound onto a 6-inch core made of ABS. An optical film 61 with a thickness of 50 μm was obtained in the form of a roll film. The residual amount of solvent in the obtained optical film 61 was 1.0% by mass.

<Example 2> (Production of optical film (2)) The hard-coat layer-forming composition (1) produced in Production Example 5 was applied so that the thickness of the first hard-coat layer after curing became 3 μm The surface of the optical film 61 obtained in Example 1 that was in contact with the PET base film during film formation was dried in an oven at 80°C for 1 minute. Thereafter, a high-pressure mercury lamp was used to ^{irradiate light with a light amount of 350 mJ/cm 2} to harden the coating film to form a first hard coat layer, and an optical film (2) containing a hard coat layer was produced.

<Example 3> Except that varnish (1) is changed to varnish (2), and heated at 120°C for 20 minutes, and at 95°C for 20 minutes, the film is manufactured in the same manner as the method of manufacturing the optical film (1) The residual amount of solvent is 1.0% by mass for an optical film (3) with a thickness of 49 μm.

<Example 4> Except changing the varnish (1) to varnish (3) and changing the line speed from 0.30 m/min to 0.25 m/min, the solvent remains in the manufactured film in the same way as the manufacturing method of the optical film (1) The amount is 1.0% by mass of an optical film (4) with a thickness of 51 μm.

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

The formula of the composition and the composition of the optical film are summarized in Table 2. In addition, in Table 2, in the "HC presence or absence" column, the case where the optical film has a hard coat layer is recorded as yes, and the case where it does not have a hard coat layer is recorded as no.

[Table 2] Varnish Film thickness T (μm) HC with or without Example 1 (1) 50 none Example 2 (1) 53 have Example 3 (2) 49 none Example 4 (3) 51 none Comparative example 1 - 50 none

Regarding the films obtained in the Examples and Comparative Examples, each physical property value was measured according to the above-mentioned method. The results obtained are shown in Table 3 to Table 6.

[table 3] Optical properties Image clarity value (%) Folding Endurance Test (MIT) Tt (%) Haze (%) YI C _MD C _TD (C _MD +C _TD )/2 Bending times (times) Example 1 91.0 0.2 1.4 67.5 61.1 64.3 ＞400,000 Example 2 90.8 0.3 1.6 67.2 60.8 64.0 ＞400,000 Example 3 90.8 0.3 1.3 61.1 55.2 58.2 ＞400,000 Example 4 90.9 0.3 1.2 55.6 50.6 53.1 ＞400,000 Comparative example 1 26.1 3.4 120 42.5 26.7 34.6 ＞800,000

[Table 4] Tensile modulus E (GPa) Room temperature breaking strain ε ₁ (%) -40℃ breaking strain ε ₂ (%) ε ₂ /ε ₁ Example 1 5.5 11.5 9.9 0.86 Example 2 5.5 9.5 7.8 0.82 Example 3 6.0 10.4 8.4 0.81 Example 4 5.5 10.5 9.7 0.99 Comparative example 1 9.6 28.5 20.5 0.72

[table 5] Image clarity value (%) Difference of image sharpness value (%) Haze Before bending After bending ΔC _MD ΔC _TD ΔHaze (%) C _MD C _TD C _MD C _TD Example 1 67.5 61.1 62.5 55.3 5.0 5.8 0.2 Example 2 67.2 60.8 61.3 53.5 5.9 7.3 0.3 Example 3 55.6 50.6 44.3 38.1 11.3 12.5 0.2 Example 4 48.0 40.0 35.0 26.1 13.0 13.9 0.2 Comparative example 1 42.5 26.7 27.2 11.3 15.3 15.4 0.5

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

[Table 7] Projected image visibility Example 1 ◎ Example 2 〇 Example 3 〇 Example 4 △ Comparative example 1 X

It was confirmed that the total light transmittance, haze, and tensile modulus of elasticity were within specific ranges and that the optical films of Examples 1 to 4 satisfying the equations (1) to (3) were films with excellent visibility in the wide-angle direction. In addition, it is confirmed that the optical film of the present invention is in a preferred aspect of the present invention, the difference in image sharpness value before and after the bending resistance test and the difference in haze are small, and the visibility in the wide-angle direction even after repeated bending operations Also excellent. Furthermore, it was confirmed that the optical film systems of Examples 1 to 4 are not only excellent in the visibility of the reflected image, but also excellent in the visibility of the projected image. In addition, it was confirmed that the optical film of the present invention has the above-mentioned characteristics while having ε ₁ /ε ₂ in the range of 0.70 to 1.20, and has excellent mechanical properties even in a low temperature environment. In contrast, the optical film of Comparative Example 1 in which the total light transmittance and haze are not within the specified range and does not satisfy the equations (1) to (3) is not the one that has excellent visibility in the wide-angle direction and the visibility of the projected image .

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

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

1: Optical film

3: vertical axis

10: The first irradiation light

11: The first irradiation position

12: 1st mirror reflection light

14: 1st optical axis

16: 1st optical comb

18: The first transmitted light

19: The first light receiver

A: The transport direction of the film

Claims (10)

An optical film containing at least one resin selected from the group consisting of polyimide resins and polyamide resins, and has a total light transmittance of 85% or more, and a haze of 0.5% or less. When the modulus of elasticity is 5.1 GPa or more, the direction parallel to the mechanical flow direction during manufacture is set as the MD direction in the above-mentioned optical film surface, and the direction perpendicular to the mechanical flow direction is set as the TD direction. At least any one of the surfaces, according to JIS K 7374, when the slit width of the optical comb is 0.125 mm, the first reflection image is obtained from a direction perpendicular to the plane of the optical film to a direction inclined 60° to the MD direction. 60 ° oblique direction of the image clarity value C _MD from said vertical direction toward the TD direction of the second reflected image clarity value C satisfies _TD (1) _{equation: 45% ≦ C MD ≦ 100} % · · · ( 1), Mathematical formula (2): 30%≦C _TD ≦100%...(2), and Mathematical formula (3): 35%≦(C _MD ＋C _TD )/2≦100%...(3 ), at the break of the optical film of -40 ℃ strain ε ₁ and broken off at the breaking strain ε ₂ 25 ℃ satisfy equation _{(4): 0.70 ≦ ε 1} / ε 2 ≦ 1.20 · · · (4). Such as the optical film of claim 1, wherein the difference ΔHaze between the above-mentioned haze before and after the bending resistance test according to JIS K 5600-5-1 is less than 0.3%. The optical film of claim 1 or 2, wherein the difference between the above-mentioned first reflection image definition value ΔC _MD and the above-mentioned second reflection image definition value before and after the bending resistance test according to JIS K 5600-5-1 The difference ΔC _TD did not reach 15. The optical film of any one of claims 1 to 3, which has a thickness of 10 to 150 μm. The optical film according to any one of claims 1 to 4, wherein the content of the filler in the optical film is 0 to 5% by mass relative to the total mass of the optical film. The optical film according to any one of claims 1 to 5, which has a hard coat layer on at least one side. The optical film of claim 6, wherein the thickness of the hard coat layer is 3-30 μm. A flexible display device provided with the optical film as claimed in any one of claims 1 to 7. Such as the flexible display device of claim 8, which is further provided with a polarizing plate. For example, the flexible display device of claim 8 or 9 further includes a touch sensor.

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