CN113227212A

CN113227212A - Optical film

Info

Publication number: CN113227212A
Application number: CN201980086121.3A
Authority: CN
Inventors: 杉山纮子; 宫本皓史; 池内淳一; 片宝蓝; 增井建太朗; 望月胜纪; 金成民
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-12-28
Filing date: 2019-12-24
Publication date: 2021-08-06
Also published as: TW202037642A; KR20210110642A

Abstract

The invention provides an optical film with low haze and yellow color even after being stored for a long time in a high-temperature and high-humidity environment in a bent state. The optical film of the present invention has a yield point strain of 1.5% or more and a tensile strain in Hz after the mandrel test_aThe haze value is 1.5% or less, and the mandrel test is a test in which the glass sheet is bent 1 time at a bending radius of 1mm at room temperature and then returned to a flat shape.

Description

Optical film

Technical Field

The present invention relates to an optical film used for materials of a flexible display device and the like, and a flexible display device including the optical film.

Background

Display devices such as liquid crystal display devices and organic EL display devices have been widely and flexibly used for various applications such as mobile phones and smartwatches. Glass has been conventionally used as a front panel of such a display device, but since glass is very rigid and easily broken, it is difficult to use the glass as a front panel material of a flexible display device. As one of materials replacing glass, optical films having high heat resistance and the like using a polymer such as a polyimide resin have been studied (for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese Kokai publication No. 2014-528490

Disclosure of Invention

Problems to be solved by the invention

A flexible display device using such an optical film as a material may be exposed to a high-temperature and high-humidity environment in a bent state. However, according to the study of the inventors of the present application, it has been found that when a conventional optical film is exposed to such severe durability conditions, the optical characteristics are degraded, and the haze and the yellowness are increased.

Accordingly, an object of the present invention is to provide an optical film having low haze and low yellowness even after being stored in a bent state for a long time in a high-temperature and high-humidity environment, and a flexible display device including the optical film.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above problems can be solved by adjusting the yield strain of an optical film to 1.50% or more and adjusting the haze after a mandrel test (which is a test of recovering to a flat shape after being bent 1 time at a bending radius of 1mm at room temperature) to 1.5% or less, thereby completing the present invention. That is, the present invention includes the following preferred embodiments.

[1]An optical film having a yield point strain of 1.50% or more and a tensile modulus in Hz after mandrel test_aThe haze value is 1.5% or less, and the mandrel test is a test in which the glass sheet is bent 1 time at a bending radius of 1mm at room temperature and then returned to a flat shape.

[2] The optical film according to [1], which comprises a polyamideimide resin.

[3] The optical film according to [2], wherein the polyamideimide resin comprises a structural unit represented by formula (1) and a structural unit represented by formula (2).

[ chemical formula 1]

[ in formula (1), X represents a 2-valent organic group, Y represents a 4-valent organic group, and X represents a bond ]

[ chemical formula 2]

[ in the formula (2), X and Z independently represent a 2-valent organic group and represent a bond ]

[4]Such as [1]]～[3]The optical film of any one of the above, wherein the film is produced in Hz before the mandrel test_bThe haze value is 1.0% or less.

[5] The optical film according to any one of [1] to [4], wherein a content of the filler is 30% by mass or less with respect to a mass of the optical film.

[6] The optical film according to any one of [1] to [5], which has a thickness of 20 to 100 μm.

[7] The optical film according to any one of [1] to [6], wherein the elastic modulus is 1.0GPa or more.

[8] A flexible display device comprising the optical film according to any one of [1] to [7 ].

[9] The flexible display device according to [8], further comprising a touch sensor.

[10] The flexible display device according to [8] or [9], further comprising a polarizing plate.

ADVANTAGEOUS EFFECTS OF INVENTION

The optical film of the present invention has low haze and yellowness even after being stored in a bent state for a long time in a high-temperature and high-humidity environment. Therefore, it can be preferably used as a material for a flexible display device or the like.

Detailed Description

[ optical film ]

The optical film of the present invention has a yield point strain of 1.50% or more and a tensile strain in Hz after the mandrel test_aThe haze value is 1.5% or less, and the mandrel test is a test in which the glass sheet is bent 1 time at a bending radius of 1mm at room temperature and then returned to a flat shape. The inventors of the present application found that if the yield point strain of the optical film is 1.50% or more and Hz_aWhen the content is 1.5% or less, the haze and yellowness (hereinafter, may be referred to as YI value) of the optical film are low even after the optical film is stored in a bent state in a high-temperature and high-humidity environment for a long time. This is presumably because, in a state where the optical film is bent under high temperature and high humidity, the optical film is easily deformed and the color tone is easily changed by moisture absorption deformation, but if the haze after the mandrel test is low, that is, the bending resistance is high and the yield point strain is high, the increase in the haze and the YI value due to the deformation can be suppressed. In the present specification, the haze or YI value after long-term storage or exposure in a high-temperature and high-humidity environment in a bent state may be referred to as the haze or YI value after storage, and the haze or YI value may be referred to as the haze or YI value after storage, and after a mandrel test in which the bent state is returned to a flat shape after being bent 1 time at a bending radius of 1mm at room temperatureIs made of Hz_aHaze expressed is abbreviated as haze after mandrel test or Hz_a。

The yield point strain of the optical film of the present invention is 1.50% or more, preferably 1.60% or more, more preferably 1.70%, still more preferably 1.80% or more, and particularly preferably 1.90% or more. When the yield strain is not less than the above lower limit, the YI value after storage tends to be lowered. The yield point strain is usually 3.0% or less. The yield point strain is an index indicating rubber properties or the like, and is a value indicating the strain at the intersection of the slope of the region following young' S law, the intercept of the strain axis, and the S-S curve measured using a tensile tester, and can be obtained, for example, by the method described in examples. The yield point strain is a value at 30 ℃ and a relative humidity of 50%.

Hz_aIs 1.5% or less, preferably 1.3% or less, more preferably 1.0% or less, further preferably 0.8% or less, and usually 0% or more. Hz_aWhen the amount is less than the upper limit, the haze and YI value after storage tend to be reduced. The mandrel test is as follows: the optical film was uniformly bent along a cylindrical mandrel having a bending radius of 1mm at room temperature (25 ℃ C.) and then immediately the bent optical film was returned to a flat shape. In addition, Hz_aThe bending portion in the mandrel test is measured by using a haze computer or the like, and can be obtained by the method described in examples, for example.

Mandrel Pre-test of the optical films of the invention by Hz_bThe haze is preferably 1.0% or less, more preferably 0.8% or less, further preferably 0.5% or less, and usually 0% or more. Hz_bAt an upper limit or lower, Hz_aAnd the haze after storage tends to be low. Further, the optical film has high transparency, and can exhibit high visibility when used for, for example, a front panel of a display device. Note that Hz_bThe measurement can be performed by using a haze computer or the like, and can be performed by the method described in examples, for example.

The YI value of the optical film of the present invention before mandrel test is preferably 2.0 or less, more preferably 1.9 or less, and usually-5 or more, preferably-2 or more. When the YI value before the mandrel test is equal to or less than the upper limit, the YI value after storage tends to be low. The optical film has high transparency, and can contribute to high visibility when used for a front panel of a display device or the like. The YI value can be calculated by measuring the transmittance for light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer to obtain the tristimulus value (X, Y, Z) and calculating the YI value based on the formula of 100 × (1.2769X-1.0592Z)/Y. For example, the calculation can be performed by the method described in the examples.

The optical film of the present invention has a total light transmittance of preferably 85% or more, more preferably 88% or more, further preferably 90% or more, particularly preferably 91% or more, and usually 100% or less. When the total light transmittance is not less than the above lower limit, the transparency is high, and high visibility can be exhibited when the composition is used for, for example, a front panel of a display device. The total light transmittance may be measured in accordance with JIS K7105: 1981, the haze can be measured by using a haze computer, for example, by the method described in the examples. In the present specification, the total light transmittance and haze may be those within the range of the thickness of the optical film of the present invention.

The elastic modulus of the optical film of the present invention is preferably 1.0GPa or more, more preferably 2.0GPa or more, further preferably 3.0GPa or more, further more preferably 4.0GPa or more, particularly preferably 5.0GPa or more, and usually 100GPa or less. When the elastic modulus is not less than the above-described lower limit, a force to return to the original shape when the optical film is deformed acts strongly, and therefore, when a predetermined yield point strain is satisfied, the optical film is not easily deteriorated even when bent for a long time under a higher temperature and higher humidity environment, and the haze and YI value after storage are easily lowered. The elastic modulus can be measured using a tensile tester, and can be measured, for example, by the method described in examples. The elastic modulus is a value at a temperature of 25 ℃ and a relative humidity of 50%.

The optical film of the present invention can suppress the increase in haze and YI value even when exposed or stored for a long time under a high-temperature and high-humidity environment, and therefore can maintain the haze and YI value at low levels even after the storage. Therefore, when used in a flexible display device or the like, the optical film can have high transparency even when left in a bent state under severe conditions, and is useful as an optical film. The optical film of the present invention has a haze after being stored for 24 hours in an environment of 85 ℃ and 85% relative humidity in a state of being bent at a bending radius of 1mm and at a temperature of 85 ℃ for a relative humidity of 1% of preferably 1.5% or less, more preferably 1.3% or less, still more preferably 1.0% or less, and particularly preferably 0.8% or less, and a YI value after storage of the optical film is preferably 2.3 or less, more preferably 2.1 or less, still more preferably 1.9 or less, and particularly preferably 1.8 or less. The haze and YI values after storage are measured by the same methods as described above, for example, the methods described in examples, except that the optical film after storage is returned to a flat shape after 24 hours, left to stand at 30 ℃ and 50% relative humidity for 30 minutes, and then the haze and YI values of the bent portions are measured.

The thickness of the optical film of the present invention can be suitably adjusted depending on the application, but is preferably 20 μm or more, more preferably 25 μm or more, further preferably 30 μm or more, further more preferably 35 μm or more, particularly preferably 40 μm or more, preferably 100 μm or less, more preferably 80 μm or less, and further preferably 60 μm or less. When the thickness of the optical film is within the above range, the haze and YI value after storage are easily reduced. The thickness of the optical film may be measured by a film thickness meter or the like, and may be measured by the method described in examples, for example.

< resin >

The optical film of the present invention preferably contains a resin. The resin is preferably a transparent resin, and examples thereof include polyester resins such as polyethylene terephthalate, polycarbonate resins, polyarylate resins, polyethersulfone resins, polyimide resins, and acrylic resins. These resins may be used alone or in combination of two or more.Of these, from Hz_aThe polyimide resin is preferred in view of ease of reduction and ease of increase in yield strain.

The polyimide resin refers to a polyimide resin and a polyamideimide resin. The polyimide resin refers to a polymer containing a repeating structural unit containing an imide group, and the polyamideimide resin refers to a polymer containing a repeating structural unit containing an imide group and a repeating structural unit containing an amide group. For the optical film of the present invention, it is easy to reduce Hz_aFurther, from the viewpoint of easily increasing the yield strain, it is more preferable to contain a polyamideimide resin as the resin.

Easy reduction of Hz of optical film_aIn addition, the polyimide-based resin included in the optical film of the present invention preferably includes a structural unit represented by formula (1) from the viewpoint of easily increasing the yield strain and the elastic modulus.

[ chemical formula 3]

The polyamideimide resin preferably contains a structural unit represented by formula (1) or formula (2).

[ chemical formula 4]

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

In the formula (2), Z is a 2-valent organic group, preferably a 2-valent organic group having 4 to 40 carbon atoms which may be substituted by a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine, and more preferably a 2-valent organic group having 4 to 40 carbon atoms which may be substituted by a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine and has a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. Examples of the organic group of Z include a group obtained by replacing 2 nonadjacent hydrogen atoms in the chemical bonds of the groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29) and a 2-valent chain hydrocarbon group having 6 or less carbon atoms, and examples of the heterocyclic structure of Z include a group having a thiophene ring skeleton. From the viewpoint of easily lowering the YI value of the optical film, groups represented by formulae (20) to (27) and groups having a thiophene ring skeleton are preferable.

[ chemical formula 5]

[ formula (20) to formula (29),

W¹represents a single bond, -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-or-Ar-SO₂Ar-wherein Ar independently represents an arylene group having 6 to 20 carbon atoms (for example, phenylene group) in which hydrogen atoms may be substituted with fluorine atoms, and represents a bond]

The organic group of Z is more preferably a 2-valent organic group represented by formula (20 '), formula (21'), formula (22 '), formula (23'), formula (24 '), formula (25'), formula (26 '), formula (27'), formula (28 ') and formula (29').

[ chemical formula 6]

[ wherein W¹And the same as defined in formulae (20) to (29)]

The hydrogen atom on the ring in the formulae (20) to (29) and (20 ') to (29') may be substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include groups exemplified by the following formula (3).

When the polyimide-based resin has a structural unit in which Z in formula (2) is represented by any one of formulae (20 ') to (29 '), particularly when Z in formula (2) has a structural unit represented by formula (3 ') described later, the polyimide-based resin may further have a structural unit derived from a carboxylic acid represented by formula (d1) in addition to the structural unit, which is preferable from the viewpoint of the flowability of the varnish.

[ chemical formula 7]

[ in the formula (d1), R²⁴Independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R²⁵Represents R²⁴or-C (═ O) -, denotes a bond]

R²⁴In the above formula (3), examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include those exemplified below. Specific examples of the structural unit (d1) include R²⁴And R²⁵Structural units each of which is a hydrogen atom (structural units derived from a dicarboxylic acid compound), R²⁴Are all hydrogen atoms and R²⁵A structural unit representing-C (═ O) -, a structural unit derived from a tricarboxylic acid compound, and the like.

In the polyimide-based resin of the present invention, the formula(2) The Z in (2) may include plural kinds of Z, and the plural kinds of Z may be the same as or different from each other. In particular, easily lowering the Hz of the optical film_aIn view of facilitating the increase in yield point strain and elastic modulus, Z in formula (2) is preferably represented by formula (3), more preferably represented by formula (3'), and preferably has at least a structural unit represented by formula (2).

[ chemical formula 8]

[ in the formula (3),

R^3aand R^3bIndependently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R^3aAnd R^3bThe hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

w independently of one another represent a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹)-，R⁹Represents a hydrogen atom, a C1-valent hydrocarbon group which may be substituted with a halogen atom and has 1 to 12 carbon atoms,

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 chemical bond ]

[ chemical formula 9]

[ formula (3') wherein R^3a、R^3bS, t, u, W and are as defined in formula (3)]

In the formulae (3) and (3'), W independently represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹) From the viewpoint of the bending resistance of the optical film, the compound preferably represents-O-or-S-, and more preferably represents-O-.

R^3aAnd R^3bIndependently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methyl-butyl group, a 3-methylbutyl group, a 2-ethyl-propyl group, and an n-hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a cyclohexyloxy group, and the like. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. Easy reduction of Hz of optical film_aR is a group of compounds which are easy to improve yield point strain and elastic modulus^3aAnd R^3bIndependently of each other, the alkyl group preferably has 1 to 6 carbon atoms or the alkoxy group has 1 to 6 carbon atoms, and more preferably has 1 to 3 carbon atoms or the alkoxy group has 1 to 3 carbon atoms. Here, R^3aAnd R^3bThe hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other.

R⁹Represents a hydrogen atom, a C1-valent hydrocarbon group which may be substituted with a halogen atom and has 1 to 12 carbon atoms. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and n-decyl groups, which may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

T and u in the formulae (3) and (3') are each independently an integer of 0 to 4, preferably an integer of 0 to 2, and more preferably 0 or 1.

S in the formula (3) is an integer in the range of 0 to 4, and when s is in this range, it is easy to reduce Hz of the optical film_aAnd easily increase the yield point strain and elastic modulus. Easy reduction of Hz of optical film_aIn addition, s in the formulae (3) and (3') is preferably an integer in the range of 0 to 3, and more preferably an integer in the range of 0 to 2, from the viewpoint of facilitating the improvement of yield point strain and elastic modulus. The structural unit represented by the formula (3) or (3 ') wherein s is 0 is, for example, a structural unit derived from terephthalic acid or isophthalic acid, and the structural unit is particularly preferably a structural unit wherein s and u in the formula (3) or (3') are each 0, or s is 0 and u is 1 or 2 (preferably R is^3bAn alkyl group or a fluoroalkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms, more preferably an alkoxy group having 1 to 3 carbon atoms). Easy reduction of Hz of optical film_aIn addition, the polyimide resin preferably contains a structural unit derived from terephthalic acid, from the viewpoint of easily increasing the yield strain and the elastic modulus. The polyimide-based resin may contain 1 or 2 or more kinds of the structural units represented by the formula (3) or the formula (3') in Z.

In addition, from the viewpoint of lowering the YI value of the optical film, the polyimide-based resin may include 2 or more structural units having different values of s in the formula (3) or the formula (3 '), for example, 2 or 3 structural units having different values of s in the formula (3) or the formula (3'). In this case, from the viewpoint of reducing the YI value of the optical film, the polyimide-based resin may contain a structural unit represented by formula (3) in which s is 0 as Z in the structural unit represented by formula (2), or may contain a structural unit represented by formula (3) in which s is 1 in addition to the structural unit.

In a preferred embodiment of the present invention, the polyimide-based resin has a structural unit in which s and u are each 0, or s and u are each 0 and R is a structural unit represented by formula (3) or formula (3')/in the polyimide-based resin^3bIs a methyl, methoxy or trifluoromethyl (preferably methoxy) structural unit. In such a manner, the Hz of the optical film can be easily reduced_aAnd easily increase the yield point strain and elastic modulus.

When the polyimide resin of the present invention has the structural unit represented by formula (3) or formula (3'), the proportion thereof is preferably 5 mol% or more, more preferably 10 mol% or more, further preferably 15 mol% or more, particularly preferably 20 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, further preferably 80 mol% or less, and particularly preferably 70 mol% or less, when the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) of the polyimide resin is taken as 100 mol%. When the proportion of the structural unit represented by the formula (3) or the formula (3') is not less than the above lower limit, the optical film can easily be reduced in Hz_aAnd easily increase the yield point strain and elastic modulus. When the proportion of the structural unit represented by formula (3) or formula (3') is not more than the above upper limit, the viscosity increase of the resin-containing varnish due to hydrogen bonding between amide bonds derived from formula (3) is easily suppressed, and the film processability is improved.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, and particularly preferably 50 mol% or more of Z in the polyimide-based resin of the present invention is a structural unit represented by formula (3) or formula (3'). When the lower limit or more of Z is a structural unit represented by formula (3) or formula (3'), it is easy to reduce the Hz of the optical film_aAnd easily increase the yield point strain and elastic modulus. In addition, 100 mol% or less of Z in the polyimide resin may be a structural unit represented by formula (3) or formula (3'). The proportion of the structural unit represented by the formula (3) or (3') in the resin may be, for example, the one represented by¹H-NMR, or the ratio of the raw materials charged may be calculated.

In the formula (1), Y independently represents a 4-valent organic group, preferably a 4-valent organic group having 4 to 40 carbon atoms, and more preferably a 4-valent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. The organic group is an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. The polyimide-based resin according to one embodiment of the present invention may contain a plurality of kinds of Y, and the plurality of kinds of Y may be the same as or different from each other. Examples of Y may include groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29); a group obtained by substituting a hydrogen atom in the group represented by the formulae (20) to (29) with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having a valence of 4 and 6 or less carbon atoms.

[ chemical formula 10]

In the formulae (20) to (29), W represents a bond¹Represents a single bond, -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-or-Ar-SO₂-Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include phenylene groups. The hydrogen atom on the ring in the formulas (20) to (29) may be substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include those exemplified in the formula (3).

Among the groups represented by the formulae (20) to (29), the Hz of the optical film can be easily lowered_aFrom the viewpoint of facilitating the increase in yield point strain and elastic modulus, 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, the Hz of the optical film is easily reduced_aAnd W is considered to easily increase the yield point strain and the elastic modulus¹Independently of one another, are preferably single bonds, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-, more preferably a single bond, -O-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-is more preferably a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-, more preferably a single bond or-C (CF)₃)₂-C (CF) is particularly preferred₃)₂-。

In a preferred embodiment of the present invention, the structural unit represented by formula (1) contains a group (or structure) represented by formula (4a) and/or a group (or structure) represented by formula (4b) as Y. That is, at least a part of Y in the plurality of formulas (1) is represented by formula (4a) and/or formula (4 b). In such a manner, the Hz of the optical film can be easily reduced_aFurther, the yield point strain is increased, and therefore, the haze and YI value after storage are easily reduced.

[ chemical formula 11]

[ in the formula (4a), R²～R⁷Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R²～R⁷Wherein the hydrogen atoms contained in (A) may be substituted independently by halogen atoms, and V represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁸)-，R⁸Represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and represents a bond]

[ chemical formula 12]

[ in the formula (4b), R⁹And R¹⁰Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R⁹And R¹⁰The hydrogen atoms contained in (A) may be substituted independently of each other by halogen atoms, representing a chemical bond]

In the formula (4a), R²、R³、R⁴、R⁵、R⁶And R⁷Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include the groups exemplified above in the formula (3). R²～R⁷Independently of each other, the alkyl group preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R²～R⁷The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

V in the formula (4a) represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁸)-，R⁸Represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, and n-decyl group, which may be substituted with a halogen atom. Examples of the halogen atom include the halogen atoms mentioned above. Of these, the Hz of the optical film is easily lowered_aAnd V is preferably a single bond, -O-, -CH from the viewpoint of increasing yield strain and elastic modulus₂-、-CH(CH₃)-、-C(CH₃)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-, most preferably-C (CF)₃)₂-。

In the formula (4b), R⁹And R¹⁰Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include the groups exemplified above in the formula (3). Of these, the Hz of the optical film is easily lowered_aAnd R is a group of compounds having a higher yield strain and a higher elastic modulus⁹And R¹⁰Independently of each other, the alkyl group preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R⁹And R¹⁰The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. Examples of the halogen atom include the halogen atoms mentioned above.

In a preferred embodiment of the present invention, in formula (4a), R²～R⁷Independently represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and V represents a single bond or-C (CH)₃)₂-or-C (CF)₃)₂-. In such a manner, the Hz of the optical film can be easily reduced_aAnd the yield point strain and the elastic modulus are improved.

In a preferred embodiment of the present invention, in formula (4b), R is⁹And R¹⁰Independently of each other, a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. In such a manner, the Hz of the optical film can be easily reduced_aAnd the yield point strain and the elastic modulus are improved.

In a more preferred embodiment of the present invention, formula (4a) is represented by formula (7a) or formula (7b), and formula (4b) is represented by formula (7 c).

[ chemical formula 13]

[ chemical formula 14]

That is, at least a part of the plurality of Y is represented by formula (7a), formula (7b), or formula (7 c). In such a manner, the Hz of the optical film can be easily reduced_aAnd the yield point strain and the elastic modulus are improved. In the case where at least a part of the plurality of Y is represented by the formula (7a), the solubility of the resin in the solvent is improved by the fluorine element-containing skeleton, and the viscosity of the resin varnish can be suppressed to a low level, thereby easily improving the processability of the optical film. Further, the optical properties such as haze and YI value are easily reduced by the skeleton containing fluorine element.

In one embodiment of the present invention, when the polyimide resin of the present invention has a structural unit represented by formula (4a) and/or (4b) as Y in formula (1), the proportion thereof is preferably 10 mol% or more, more preferably 20 mol% or more, further preferably 30 mol% or more, particularly preferably 35 mol% or more, preferably 95 mol% or less, more preferably 90 mol% or less, and further preferably 85 mol% or less, when the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) of the polyimide resin is taken as 100 mol%. When the proportion of the structural unit represented by the formula (4a) and/or (4b) is not less than the lower limit, it is easy to reduce the Hz of the optical film_aAnd easily increase the yield point strain and elastic modulus. When the proportion of the structural unit represented by formula (4a) and/or (4b) is not more than the upper limit, the viscosity of the varnish containing the resin is easily inhibited from increasing due to hydrogen bonding between amide bonds derived from formula (3), and the film processability is improved.

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of Y in the polyimide-based resin of the present invention is a structural unit represented by formula (4a) and/or (4 b). Above and below YWhen the structural unit represented by the formula (4a) and/or (4b) is contained in the above range, the Hz of the optical film can be easily reduced_aAnd easily increase the yield point strain and elastic modulus. In addition, 100 mol% or less of Z in the polyimide resin may be a structural unit represented by formula (4a) and/or (4 b). The proportion of the structural unit represented by the formula (4a) or (4b) in the resin may be, for example, the one represented by¹H-NMR, or the ratio of the raw materials charged may be calculated.

In a preferred embodiment of the present invention, V in the formula (4a) is represented by-O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁸) When the group represented by the formula (4a ') is represented by formula (4a '), in the case where the polyimide resin of the present invention has a structural unit represented by formula (4a ') for Y in formula (1), the proportion thereof is preferably 35 mol% or more, and more preferably 40 mol% or more, when the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) in the polyimide resin is 100 mol%. When the above lower limit or more of Y is a structural unit represented by the formula (4 a'), it is easy to reduce the Hz of the optical film_aAnd easily increase the yield point strain and elastic modulus. When the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) in the polyimide-based resin is defined as 100 mol%, the proportion of the structural unit represented by formula (4 a') in Y in formula (1) is preferably 95 mol% or less, more preferably 90 mol% or less, and still more preferably 85 mol% or less. The proportion of the structural unit represented by the formula (4 a') in the resin may be, for example, used¹H-NMR, or the ratio of the raw materials charged may be calculated.

In the formulae (1) and (2), X independently represents a 2-valent organic group, preferably a 2-valent organic group having 4 to 40 carbon atoms, and more preferably a 2-valent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. The organic group may have hydrogen atoms substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyimide-based resin of the present invention may contain a plurality of kinds of X, and the plurality of kinds of X may be the same as or different from each other. Examples of X may include groups represented by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group obtained by substituting a hydrogen atom in the groups represented by the formulae (10) to (18) with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

[ chemical formula 15]

In the formulae (10) to (18),

the symbol represents a chemical bond,

V¹、V²and V³Independently of each other, represents a single bond, -O-, -S-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -CO-or-N (Q) -. Wherein Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms include those exemplified above.

An example is: v¹And V³Is a single bond, -O-or-S-, and, V²is-CH₂-、-C(CH₃)₂-、-C(CF₃)₂-or-SO₂-。V¹And V²Bonding position with respect to each ring, and V²And V³The bonding position to each ring is preferably meta-or para-position, and more preferably para-position, independently from each ring.

In a preferred embodiment of the present invention, the structural unit represented by formula (1) and/or the structural unit represented by formula (2) contains a group (or structure) represented by formula (34) as X. That is, at least a part of X in formula (1) and/or formula (2) is a group represented by formula (34). In such a manner, it is easyReduction of Hz in optical films_aAnd easily increase the yield point strain and elastic modulus.

[ chemical formula 16]

[ formula (34) wherein Ar is¹And Ar²Independently represent a 2-valent aromatic group which may have a substituent, and W independently represent a single bond, -O-, diphenylmethylene, -SO₂-、-S-、-CO-、-PO-、-PO₂-、-N(R¹⁵)-、-Si(R¹⁶)₂Or a divalent hydrocarbon group having 1 to 12 carbon atoms, wherein hydrogen atoms contained in the hydrocarbon group may be independently substituted with a halogen atom or 2 hydrogen atoms may be substituted to form a ring, R¹⁵And R¹⁶Independently represent a hydrogen atom or a C1-12 monovalent hydrocarbon group which may be substituted with a halogen atom, and q represents an integer of 0-4]

Ar in formula (34)¹And Ar²Independently of each other, represents a 2-valent aromatic group which may have a substituent. The 2-valent aromatic group means a 2-valent monocyclic aromatic group, a 2-valent condensed polycyclic aromatic group, or a 2-valent ring-assembled aromatic group. The 2-valent aromatic group is preferably a 2-valent aromatic group having 5 to 20 carbon atoms.

The 2-valent monocyclic aromatic group includes a 2-valent group obtained by removing 2 hydrogen atoms from carbon atoms constituting a monocyclic aromatic hydrocarbon ring such as a benzene ring, preferably a monocyclic aromatic hydrocarbon ring having 6 to 15 carbon atoms; and 2-valent groups obtained by removing 2 hydrogen atoms directly bonded to carbon atoms or heteroatoms constituting a monocyclic aromatic heterocyclic ring containing at least 1 heteroatom selected from a sulfur atom, a nitrogen atom and an oxygen atom (preferably a monocyclic aromatic heterocyclic ring having 5 to 15 carbon and heteroatoms, for example, a pyridine ring, a diazepine ring, a triazine ring, a furan ring, a thiophene ring, a pyrrole ring, a diazole ring, a triazole ring, an oxazole ring, an oxadiazole ring, a thiazole ring, a thiadiazole ring, etc.).

Examples of the 2-valent condensed polycyclic aromatic group include 2-valent groups obtained by removing 2 hydrogen atoms from carbon atoms constituting a condensed polycyclic aromatic hydrocarbon ring such as a naphthalene ring, an anthracene ring, or a phenanthrene ring, preferably a condensed polycyclic aromatic hydrocarbon ring having 10 to 20 carbon atoms; and 2-valent groups obtained by removing 2 hydrogen atoms directly bonded to carbon atoms or hetero atoms constituting a condensed polycyclic aromatic heterocycle containing at least 1 hetero atom selected from a sulfur atom, a nitrogen atom and an oxygen atom (preferably a condensed polycyclic aromatic heterocycle having 8 to 20 carbon and hetero atoms, for example, an azanaphthalene ring, a naphthyridine ring, a carbazole ring, a dibenzofuran ring, a dibenzothiophene ring, a dibenzosilacyclopentadiene ring (dibenzosilole), a phenoxazine ring, a phenothiazine ring, an acridine ring, etc.). The monocyclic aromatic hydrocarbon ring and the monocyclic aromatic heterocyclic ring are collectively referred to as a monocyclic aromatic ring, and the condensed polycyclic aromatic hydrocarbon ring and the condensed polycyclic aromatic heterocyclic ring are collectively referred to as a condensed polycyclic aromatic ring.

The 2-valent ring-aggregated aromatic group represents a 2-valent group obtained by removing 2 hydrogen atoms directly bonded to a carbon atom or a heteroatom constituting a ring-aggregated aromatic ring (preferably a ring-aggregated aromatic ring having 10 to 40 carbon and heteroatom atoms) formed by connecting monocyclic aromatic rings and/or condensed polycyclic aromatic rings by a single bond. The 2-valent ring-aggregated aromatic group may be composed of 1 or more monocyclic aromatic rings, 1 or more condensed polycyclic aromatic rings, or a combination of these groups. Specifically, the 2-valent ring-aggregated aromatic group includes a 2-valent group obtained by removing 2 hydrogen atoms directly bonded to a carbon atom or a heteroatom constituting a ring-aggregated aromatic ring such as a biphenyl ring, a bipyridine ring, a phenylnaphthyl ring, a terphenyl ring, or a terpyridine ring.

Of the 2-valent aromatic group, the Hz of the optical film can be easily reduced_aIn addition, from the viewpoint of easily increasing the yield strain and the elastic modulus, a 2-valent monocyclic aromatic group or a 2-valent ring-assembled aromatic group is preferable, and a 2-valent monocyclic aromatic ring such as a phenylene group is preferable.

Examples of the alkyl group having 1 to 12 carbon atoms include a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms. Examples of the linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl and the like. The alkyl group having 1 to 12 carbon atoms may be a linear alkyl group, a branched alkyl group, or an alicyclic alkyl group having an alicyclic hydrocarbon structure. The alkyl group having 1 to 12 carbon atoms preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and further preferably 1 or 2 carbon atoms. The alkyl group having 1 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the halogen atoms mentioned above. The alkyl group having 1 to 12 carbon atoms is preferably a group in which at least 1 hydrogen atom is substituted with a halogen atom (may be referred to as a haloalkyl group), more preferably a fluoroalkyl group, and still more preferably a perfluoroalkyl group. Here, when the alkyl group having 1 to 12 carbon atoms is substituted with a substituent containing a carbon atom (for example, an alkyl group having 1 to 4 carbon atoms), the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the alkyl group having 1 to 12 carbon atoms. For example, the group in which the alkyl group having 1 to 12 carbon atoms is substituted with an alkyl group having 1 to 4 carbon atoms is a group in which the alkyl group having 1 to 12 carbon atoms is the main chain and at least 1 hydrogen atom of the alkyl group is substituted with an alkyl group having 1 to 4 carbon atoms. When the number of carbon atoms of the alkyl moiety which becomes the main chain is 1 to 12, the number of carbon atoms of the alkyl group as a whole may be more than 12. In the case where the number of carbon atoms of the alkyl group exceeds 12, the group in which an alkyl group having 1 to 12 carbon atoms is substituted with an alkyl group having 1 to 4 carbon atoms is also included in the definition of a branched alkyl group having 1 to 12 carbon atoms.

Examples of the alkoxy group having 1 to 12 carbon atoms include methoxy, ethoxy, propyloxy, isopropyloxy, n-butoxy, isobutyloxy, tert-butoxy, pentyloxy, hexyloxy, cyclohexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy and the like. The alkylene moiety in the alkoxy group having 1 to 12 carbon atoms may be any of linear, branched, or alicyclic. The alkoxy group having 1 to 12 carbon atoms preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and further preferably 1 or 2 carbon atoms. The alkoxy group having 1 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the halogen atoms described above. When the alkoxy group having 1 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the alkoxy group having 1 to 12 carbon atoms.

Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a naphthyl group, and a biphenyl group. The number of carbon atoms of the aryl group having 6 to 12 carbon atoms is preferably 6, 10 or 12, more preferably 6 or 12. The above-mentioned aryl group having 6 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the halogen atoms described above. When the aryl group having 6 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the aryl group having 6 to 12 carbon atoms.

Examples of the aryloxy group having 6 to 12 carbon atoms include a phenoxy group, a naphthyloxy group, a biphenyloxy group and the like. The number of carbon atoms of the aryloxy group having 6 to 12 carbon atoms is preferably 6, 10 or 12, and more preferably 6 or 12. The aryloxy group having 6 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted by a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the halogen atoms described above. Here, when the aryloxy group having 6 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the aryloxy group having 6 to 12 carbon atoms.

The carbonyl group-containing group having 1 to 12 carbon atoms represents a carbonyl-containing group, and is, for example, — CO-R^a、*-R^b-CO-R^a、*-CO-O-R^a、*-R^b-CO-O-R^a、*-O-CO-R^aor-R^b-O-CO-R^aThe groups represented (— represents a chemical bond). As R^aExamples of the above-mentioned group for the alkyl group having 1 to 12 carbon atoms include R^bExamples thereof include a C1-12 alkylene group having a valence of 2, wherein at least 1 hydrogen atom of the above-mentioned group is replaced by a chemical bond with respect to an alkyl group having 1-12 carbon atoms.

Examples of the halo group include a fluoro group, a chloro group, a bromo group, and an iodo group.

Of these, the Hz of the optical film is easily lowered_aAnd the substituent is preferably selected from alkyl groups having 1 to 12 carbon atoms from the viewpoint of easily improving yield strain and elastic modulus; a halogenated alkyl group having 1 to 12 carbon atoms (preferably a fluoroalkyl group, more preferably a perfluoroalkyl group); and an alkoxy group having 1 to 12 carbon atoms, more preferably a haloalkyl group having 1 to 12 carbon atoms. The number of carbon atoms in these groups is preferably 1 to 6, more preferably 1 to 4, and further preferably 1 or 2.

Easy reduction of Hz of optical film_aAr in formula (34) is Ar from the viewpoint of easily increasing yield point strain and elastic modulus¹And Ar²Independently of each other, a substituted-free 2-valent phenylene group or a 2-valent phenylene group having a haloalkyl group having 1 to 12 carbon atoms (preferably a fluoroalkyl group, more preferably a perfluoroalkyl group) is preferable.

W in formula (34) independently represents a single bond, -O-, diphenylmethylene, -SO₂-、-S-、-CO-、-PO-、-PO₂-、-N(R¹⁵)-、-Si(R¹⁶)₂Or a divalent hydrocarbon group having 1 to 12 carbon atoms, wherein hydrogen atoms contained in the hydrocarbon group may be independently substituted with a halogen atom or 2 hydrogen atoms may be substituted to form a ring, R¹⁵And R¹⁶Independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. As R¹⁵And R¹⁶Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom in (1) include the groups exemplified above.

Examples of the divalent hydrocarbon group having 1 to 12 carbon atoms in W in the formula (34) and the monovalent hydrocarbon group having 1 to 12 carbon atoms in V in the formula (4) include divalent groups obtained by further removing 1 hydrogen atom from the monovalent hydrocarbon group having 1 to 12 carbon atoms in V in the formula (4), and these may be substituted with a halogen atom. Examples of the halogen atom include the halogen atoms mentioned above. The hydrocarbon compound may form a ring by replacing 2 hydrogen atoms from among the hydrogen atoms contained in the divalent hydrocarbon group having 1 to 12 carbon atoms, that is, the 2 hydrogen atoms may be replaced with chemical bonds and the 2 hydrogen atoms may be bonded to form a ring, and examples of the ring include a cycloalkane ring having 3 to 12 carbon atoms. Among these W, the Hz of the optical film can be easily lowered_aAnd, from the viewpoint of easily improving the yield strain and elastic modulus, a single bond, or a divalent hydrocarbon group having 1 to 12 carbon atoms and a group obtained by substituting at least a part of hydrogen atoms contained in the hydrocarbon group with a halogen atom are preferable, and a single bond, -CH is more preferable₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-, further preferably a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-, particularly preferably a single bond or-C (CF)₃)2-。

Q in the formula (34) is an integer of 0 to 4, which makes it easy to reduce the Hz of the optical film_aAnd, from the viewpoint of easily improving the yield strain and the elastic modulus, an integer of 0 to 3 is preferable, an integer of 0 to 2 is more preferable, 0 or 1 is further preferable, and 1 is particularly preferable.

In a preferred embodiment of the present invention, formula (34) is represented by formula (32).

[ chemical formula 17]

[ in the formula (32), R²⁶～R³³Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R²⁶～R³³Wherein the hydrogen atoms contained in (A) may be substituted independently of each other by halogen atoms, W^aRepresents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-, diphenylmethylene, -SO₂-、-S-、-CO-、-PO-、-PO₂-、-N(R³⁴) -or-Si (R)³⁵)₂-，R³⁴And R³⁵Independently represent a hydrogen atom or a C1-12 monovalent hydrocarbon group which may be substituted with a halogen atom]

That is, the structural unit represented by formula (1) and/or the structural unit represented by formula (2) contains a group (or structural unit) represented by formula (32) as X. In such a manner, the Hz of the optical film can be easily reduced_aAnd easily increase the yield point strain and elastic modulus. In addition, the structural unit represented by formula (1) and/or the structural unit represented by formula (2) may contain 1 or more kinds of groups (or structural units) represented by formula (32) as X.

R²⁶～R³³Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include the groups exemplified above in the formula (3). Here, R²⁶～R³³The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. Examples of the halogen atom include the halogen atoms mentioned above.

Of these, the Hz of the optical film is easily lowered_aR is a group of compounds which are easy to improve yield point strain and elastic modulus²⁶～R³³Independently of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a haloalkyl group having 1 to 6 carbon atoms is preferable, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a fluoroalkyl group (preferably perfluoroalkyl group) having 1 to 6 carbon atoms is more preferable, a hydrogen atom, a methyl group, a chloro group, or a trifluoromethyl group is further preferable, and R is further preferable²⁶、R²⁸、R²⁹、R³⁰、R³¹And R³³Is a hydrogen atom, R²⁷And R³²Is hydrogen, methyl, fluoro, chloro or trifluoromethyl, particularly preferably R²⁷And R³²Is a hydrogen atom or a trifluoromethyl group.

W in formula (32)^aIndependently of each other, represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-, diphenylmethylene, -SO₂-、-S-、-CO-、-PO-、-PO₂-、-N(R³⁴) -or-Si (R)³⁵)₂-，R³⁴And R³⁵Independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and easily reduce the Hz of the optical film_aAnd preferably represents a single bond, -CH from the viewpoint of easily increasing the yield strain and elastic modulus₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-, more preferably represents a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-, more preferably represents a single bond or-C (CF)₃)₂-. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include those exemplified above as V in the formula (4).

In a preferred embodiment of the present invention, in formula (32), R²⁶～R³³Independently represent a hydrogen atom or a halogenated alkyl group having 1 to 6 carbon atoms, W^aRepresents a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-。

In a preferred embodiment of the present invention, formula (32) is represented by formula (35a) or formula (35 b).

[ chemical formula 18]

That is, at least a part of X in formula (1) and/or formula (2) is represented by formula (35a) or formula (35 b). In such a manner, the Hz of the optical film can be easily reduced_aAnd easily increase the yield point strain and elastic modulus. In the structural unit represented by formula (1) and/or formula (2), X may include 1 or more groups represented by formula (35a) or (35 b).

In one embodiment of the present invention, in the case where the polyimide resin of the present invention has a structural unit represented by formula (34) for X in formula (1) and/or formula (2), and particularly in the case where the structural unit represented by formula (32) is present, the proportion thereof is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, and preferably 100 mol% or less, when the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) of the polyimide resin is 100 mol%. When the ratio of the structural unit in which X is represented by formula (34) in formula (1) and/or formula (2) is within the above range, it is easy to reduce the Hz of the optical film_aAnd easily increase the yield point strain and elastic modulus of the optical film. The proportion of the structural unit represented by the formula (34) in X in the formula (1) and/or the formula (2) can be determined, for example¹H-NMR, or the ratio of the raw materials charged may be calculated.

In one embodiment of the present invention, W in the formula (32)^afrom-O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-, diphenylmethylene, -SO₂-、-S-、-CO-、-PO-、-PO₂-、-N(R³⁴) -or-Si (R)³⁵)₂When the group represented by-is represented by the formula (32'), the groups represented by the formulae (1) and (2)When the total molar amount of X, Y and Z is 100 mol%, the proportion of at least one structural unit selected from the structural units represented by formula (4a ') for Y in formula (1) and the structural units represented by formula (32') for X in formula (1) and/or formula (2) is preferably 17 mol% or more, more preferably 20 mol% or more, further preferably 25 mol% or more, particularly preferably 35 mol% or more, preferably 85 mol% or less, and more preferably 75 mol% or less. When the ratio of the structural units is not less than the lower limit, the Hz of the optical film is easily lowered_aAnd easily increase the yield point strain and elastic modulus. The ratio of the structural units may be, for example, the ratio¹H-NMR, or the ratio of the raw materials charged may be calculated.

The polyimide-based resin in the present invention may contain a structural unit represented by formula (30) and/or a structural unit represented by formula (31) in addition to the structural units represented by formula (1) and formula (2).

[ chemical formula 19]

In the formula (30), Y¹Is a 4-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y¹Examples thereof may include groups represented by the formulae (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29), groups in which a hydrogen atom in the groups represented by the formulae (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and chain hydrocarbon groups having 4-valent carbon atoms of 6 or less. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of kinds of Y¹Plural kinds of Y¹May be the same as or different from each other.

In the formula (31), Y²Is a 3-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y²Examples thereof may include the above-mentioned formulae (20), (21), (22) and (III)(23) A group obtained by replacing any one of the chemical bonds of the groups represented by formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29) with a hydrogen atom, and a chain hydrocarbon group having 3-valent carbon atoms of 6 or less. In one embodiment of the present invention, the polyimide-based resin may contain a plurality of kinds of Y²Plural kinds of Y²May be the same as or different from each other.

In the formulae (30) and (31), X¹And X²Independently of one another, are 2-valent organic groups, preferably organic groups in which the hydrogen atoms of the organic groups can be replaced by hydrocarbon groups or fluorine-substituted hydrocarbon groups. As X¹And X²Examples of the "substituent" may include groups represented by the above-mentioned formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group obtained by substituting a hydrogen atom in the group represented by the formula (10) to the formula (18) with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyimide-based resin is formed from the structural units represented by the formulae (1) and (2) and, if necessary, the structural units represented by the formulae (30) and/or (31). In addition, the Hz of the optical film is easily reduced_aIn view of facilitating the improvement of yield point strain and elastic modulus, the proportion of the structural unit represented by formula (1) and the structural unit represented by formula (2) in the polyimide-based resin is preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more, based on the total of the structural units represented by formula (1) and formula (2) and, if necessary, formula (30) and formula (31). In the polyimide-based resin, the proportion of the structural units represented by the formulae (1) and (2) is usually 100% or less relative to the total of the structural units represented by the formulae (1) and (2) and, if necessary, the formulae (30) and/or (31). The above ratio can be used, for example¹H-NMR, or the ratio of the raw materials charged may be calculated.

In the polyimide-based resin of the present invention, the proportion of the structural unit represented by formula (2) is preferably 0.01 relative to 1 mole of the structural unit represented by formula (1)The molar ratio is more than, preferably 0.05 molar ratio or more, further preferably 0.1 molar ratio or more, particularly preferably 0.2 molar ratio or more, preferably 20 molar ratio or less, more preferably 10 molar ratio or less, further preferably 5 molar ratio or less, and particularly preferably 3 molar ratio or less. When the ratio of the structural unit represented by formula (2) is not less than the lower limit, the Hz of the optical film is easily lowered_aAnd easily increase the yield point strain and elastic modulus. When the content is not more than the above upper limit, the viscosity of the resin varnish can be reduced by suppressing the thickening due to the hydrogen bond between the amide bonds in the formula (2), and the optical film can be easily produced.

In a preferred embodiment of the present invention, the polyimide-based resin of the present invention may contain a halogen atom such as a fluorine atom, which can be introduced through the above-mentioned fluorine-containing substituent or the like. When the polyimide resin contains a halogen atom, the Hz of the optical film can be easily reduced_aAnd YI value, and easily increase yield point strain and elastic modulus. In addition, when the elastic modulus of the optical film is high, the occurrence of scratches, wrinkles, and the like is easily suppressed. In addition, when the YI value of the optical film is low, the transparency and visibility of the film are easily improved. The halogen atom is preferably a fluorine atom. Examples of the preferable fluorine-containing substituent for making the polyimide resin contain a fluorine atom include a fluorine group and a trifluoromethyl group.

The content of the halogen atom in the polyimide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and still more preferably 5 to 30% by mass, based on the mass of the polyimide resin. When the content of the halogen atom is not less than the lower limit, the Hz of the optical film is easily lowered_aAnd YI value, and easily increase yield point strain and elastic modulus. When the content of the halogen atom is not more than the above upper limit, the synthesis becomes easy.

The imidization ratio of the polyimide resin is preferably 90% or more, more preferably 93% or more, and still more preferably 96% or more. The imidization ratio is preferably not less than the above-described lower limit from the viewpoint of easily improving the optical properties of the optical film. The upper limit of the imidization rate is 100% or less. The imidization ratio represents a ratio of a molar amount of imide bonds in the polyimide-based resin to a value 2 times a molar amount of structural units derived from a tetracarboxylic acid compound in the polyimide-based resin. When the polyimide resin contains a tricarboxylic acid compound, the molar amount of the imide bond in the polyimide resin is represented by a ratio of a value 2 times the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin to the total molar amount of the structural unit derived from the tricarboxylic acid compound. The imidization ratio can be determined by an IR method, an NMR method or the like.

Easy reduction of Hz of optical film_aIn addition, the weight average molecular weight of the resin is preferably 10,000 or more, more preferably 30,000 or more, further preferably 50,000 or more, further more preferably 100,000 or more, and particularly preferably 150,000 or more in terms of standard polystyrene, from the viewpoint of facilitating improvement of the stretchability and processability of the optical film, and is preferably 1,000,000 or less, more preferably 800,000 or less, further preferably 700,000 or less, and particularly preferably 500,000 or less. The weight average molecular weight can be determined by GPC measurement and conversion to standard polystyrene, for example, and can be calculated by the method described in examples.

In one embodiment of the present invention, the resin contained in the optical film is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 60% by mass, particularly preferably 80% by mass or more, and preferably 100% by mass or less, based on 100% by mass of the optical film.

< method for producing resin >

The method for producing the resin, preferably the polyimide resin, contained in the optical film of the present invention is not particularly limited. In one embodiment of the present invention, the polyamideimide resin in the polyimide-based resin can be obtained by polycondensation or the like of a diamine compound, a tetracarboxylic acid compound, a dicarboxylic acid compound, and, if necessary, a tricarboxylic acid compound. The polyimide resin can be obtained by a polycondensation reaction or the like of a diamine compound and a tetracarboxylic acid compound.

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

Examples of the tetracarboxylic acid compound that can be used for the synthesis of the polyimide-based 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 2 or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound, in addition to the dianhydride.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic acid dianhydride include 4,4 ' -oxydiphthalic anhydride (4,4 ' -oxydiphthalic dianhydride), 3,3 ', 4,4 ' -benzophenonetetracarboxylic acid dianhydride, 2 ', 3,3 ' -benzophenonetetracarboxylic acid dianhydride, 3,3 ', 4,4 ' -biphenyltetracarboxylic acid dianhydride (sometimes referred to as BPDA), 2 ', 3,3 ' -biphenyltetracarboxylic acid dianhydride, 3,3 ', 4,4 ' -diphenylsulfonetetracarboxylic acid dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 ' - (hexafluoroisopropylidene) diphthalic anhydride (4,4 ' - (hexafluoroisopropylidene) dicarboxylic anhydride, which is sometimes referred to as 6FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4 ' - (p-phenylenedioxy) diphthalic anhydride, 4 ' - (m-phenylenedioxy)) diphthalic anhydride. Examples of the monocyclic aromatic tetracarboxylic acid dianhydride include 1,2,4, 5-benzenetetracarboxylic acid dianhydride [ pyromellitic dianhydride (PMDA) ], and examples of the condensed polycyclic aromatic tetracarboxylic acid dianhydride include 2,3,6, 7-naphthalenetetracarboxylic acid dianhydride.

Of these, pyromellitic dianhydride (PMDA), 4,4 '-oxydiphthalic anhydride, 3, 3', 4,4 '-benzophenonetetracarboxylic dianhydride, 2', 3,3 '-benzophenonetetracarboxylic dianhydride, 3, 3', 4,4 '-biphenyltetracarboxylic dianhydride, 2', 3,3 '-biphenyltetracarboxylic dianhydride, 3, 3', 4,4 '-diphenylsulfonetetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4, 4' - (hexafluoroisopropylidene) bisphthalic anhydride (6FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (6FDA), etc. are preferable, 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4,4 '- (terephthaloxy) bisphthalic anhydride and 4, 4' - (m-phenylenedioxy) bisphthalic anhydride, more preferably 4,4 '-oxydiphthalic anhydride, 3, 3', 4,4 '-biphenyltetracarboxylic dianhydride (BPDA), 2', 3,3 '-biphenyltetracarboxylic dianhydride, 4, 4' - (hexafluoroisopropylidene) bisphthalic anhydride (6FDA), bis (3, 4-dicarboxyphenyl) methane dianhydride and 4, 4' - (p-phenylenedioxy) diphthalic anhydride. These can be used alone or in combination of 2 or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic and acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkanetetracarboxylic dianhydrides such as 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, 1,2,3, 4-cyclobutanetetracarboxylic dianhydride and 1,2,3, 4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, dicyclohexyl-3, 3 ', 4, 4' -tetracarboxylic dianhydride and positional isomers thereof. These may be used alone or in combination of 2 or more. Specific examples of the acyclic aliphatic tetracarboxylic acid dianhydride include 1,2,3, 4-butanetetracarboxylic acid dianhydride, and 1,2,3, 4-pentanedicarboxylic acid dianhydride, and these can be used alone or in combination of 2 or more. In addition, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

In the tetracarboxylic dianhydride, the Hz of the optical film can be easily reduced_aAnd also from the viewpoint of easily improving the yield strain and the elastic modulus, pyromellitic dianhydride (PMDA), 4,4 ' -oxydiphthalic anhydride, 3,3 ', 4,4 ' -benzophenone tetracarboxylic dianhydride, 3,3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride, 2 ', 3,3 ' -biphenyl tetracarboxylic dianhydride, 3,3 ', 4,4 ' -diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 4,4 ' - (hexafluoroisopropylidene) diphthalic anhydride, and mixtures thereof are preferable, pyromellitic dianhydride (PMDA), 3,3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride (BPDA), 4,4 ' - (hexafluoroisopropylidene) diphthalic anhydride (6FDA), and mixtures thereof are more preferable, further preferred is 4, 4' - (hexafluoroisopropylidene) diphthalic anhydride (6 FDA).

Examples of the dicarboxylic acid compound that can be used for the synthesis of the resin include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds, acid anhydrides, and 2 or more kinds thereof may be used in combination. Specific examples thereof include terephthalic acid; 2, 5-bis (trifluoromethyl) terephthalic acid; isophthalic acid; 2, 5-dimethyl terephthalic acid; 2, 5-dimethoxyterephthalic acid; naphthalenedicarboxylic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -biphenyldicarboxylic acid; 2,2 '-bis (trifluoromethyl) -4, 4' -biphenyldicarboxylic acid; a dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acids via a single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene group-linked compounds, and acid chloride compounds thereof. Among these dicarboxylic acid compounds, the Hz of the optical film can be easily lowered_aFrom the viewpoint of easily increasing the yield strain and the elastic modulus, 4 ' -oxybis benzoic acid, terephthalic acid, isophthalic acid, 2, 5-dimethyl terephthalic acid, 2, 5-dimethoxy terephthalic acid, 2, 5-bis (trifluoromethyl) terephthalic acid, 2 ' -bis (trifluoromethyl) -4,4 ' -bis (trifluoromethyl) terephthalate are preferablePhthalic acid and acid chlorides thereof, more preferably 2, 5-dimethylterephthaloyl chloride (DMTPC), 2, 5-dimethoxyterephthaloyl chloride (moppc), 2, 5-bis (trifluoromethyl) terephthaloyl chloride (6FTPC), terephthaloyl chloride (TPC), isophthaloyl chloride, and further preferably terephthaloyl chloride (TPC) and 2, 5-dimethoxyterephthaloyl chloride (moppc).

The polyimide resin may be a product obtained by reacting other tetracarboxylic acids, tricarboxylic acids, anhydrides thereof, and derivatives thereof in addition to the tetracarboxylic acid compound usable in the resin synthesis, within a range that does not impair various physical properties of the optical film.

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

Examples of the tricarboxylic acid compound include an aromatic tricarboxylic acid, an aliphatic tricarboxylic acid, and a similar acid chloride compound or acid anhydride thereof, and 2 or more kinds thereof may be used in combination. Specific examples thereof include anhydrides of 1,2, 4-benzenetricarboxylic acid; acid chloride compounds of 1,3, 5-benzenetricarboxylic acid; 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; phthalic anhydride and benzoic acid through single bond, -O-, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene groups.

Examples of the diamine compound that can be used for the synthesis of the resin include aliphatic diamines, aromatic diamines, and mixtures thereof. In this embodiment, the "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or another substituent in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Of these, benzene rings are preferred. The "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituent in a part of the structure.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as 1, 6-hexamethylenediamine, and cyclic aliphatic diamines such as 1, 3-bis (aminomethyl) cyclohexane, 1, 4-bis (aminomethyl) cyclohexane, norbornanediamine, and 4, 4' -diaminodicyclohexylmethane. These may be used alone or in combination of 2 or more.

Examples of the aromatic diamine include aromatic diamines having 1 aromatic ring such as p-phenylenediamine, m-phenylenediamine, 2, 4-tolylenediamine, m-xylylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene and 2, 6-diaminonaphthalene, 4 ' -diaminodiphenylmethane, 4 ' -diaminodiphenylpropane, 4 ' -diaminodiphenyl ether, 3 ' -diaminodiphenyl ether, 4 ' -diaminodiphenyl sulfone, 3 ' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene, 2, 6-diaminonaphthalene, etc., 4 ' -diaminodiphenyl methane, 4 ' -diaminodiphenyl propane, 4 ' -diaminodiphenyl ether, 3,4 ' -diaminodiphenyl ether, 4-diaminodiphenyl sulfone, 3 ' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-amino-phenoxy) benzene, bis (4-phenylene) sulfone, bis (4-phenylene) benzene, bis (4-phenylene) benzene, bis (bis) benzene) sulfone, bis (4-phenylene) benzene, bis (4-phenylene) benzene, bis (p) benzene, bis (4-phenylene) benzene, bis (p-phenylene) benzene, bis (2, bis (p-phenylene) benzene, 2, bis (p-phenylene) benzene, 2, bis (p-phenylene) benzene, bis (p-phenylene) benzene, 2, bis (bis) benzene, 2, bis (p) benzene, 2, bis (p-phenylene) benzene, Bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 ' -dimethylbenzidine, 2 ' -bis (trifluoromethyl) -4,4 ' -diaminobiphenyl (sometimes referred to as TFMB), 4 ' - (hexafluoropropylidene) diphenylamine (sometimes referred to as 6FDAM), 4 ' -bis (4-aminophenoxy) biphenyl, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, 9-bis (4-amino-3-fluorophenyl) fluorene and the like having 2 or more aromatic groups Cyclic aromatic diamines. These may be used alone or in combination of 2 or more.

The aromatic diamine is preferably 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 3' -diaminodiphenylether, 4 '-diaminodiphenylsulfone, 3' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4,4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl, more preferably 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenyl ether, 4' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2 ' -dimethylbenzidine, 2 ' -bis (trifluoromethyl) -4,4 ' -diaminobiphenyl (TFMB), 4 ' - (hexafluoropropylidene) diphenylamine (6FDAM), 4 ' -bis (4-aminophenoxy) biphenyl. These may be used alone or in combination of 2 or more.

Of the diamine compounds, the Hz of the optical film can be easily lowered_aIn addition, from the viewpoint of easily increasing the yield strain and the elastic modulus, it is more preferable to use 1 or more selected from the group consisting of 2,2 ' -dimethylbenzidine, 2 ' -bis (trifluoromethyl) -4,4 ' -diaminobiphenyl (TFMB), 4 ' -bis (4-aminophenoxy) biphenyl, 4 ' - (hexafluoropropyl) diphenylamine (6FDAM), and 4,4 ' -diaminodiphenyl ether, and it is further preferable to use 2,2 ' -bis (trifluoromethyl) -4,4 ' -diaminobiphenyl (TFMB) and/or 4,4 ' - (hexafluoropropyl) diphenylamine (6 FDAM).

In the production of the polyimide-based resin, the amount of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound to be used may be appropriately selected depending on the ratio of each structural unit of the desired resin.

In the polyimide 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 ℃, preferably 10 to 200 ℃, and more preferably 20 to 100 ℃. The reaction time is also not particularly limited, and is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out in an inert atmosphere or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or in an inert gas atmosphere while stirring. In addition, the reaction is preferably carried out in a solvent which is inactive to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include alcohol solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ -butyrolactone, γ -valerolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl ketone; 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; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvents). Among these, an amide solvent is preferably used from the viewpoint of solubility.

In a preferred embodiment of the present invention, the method for producing the polyamideimide resin comprising the above-mentioned structural unit (1) and structural unit (2) is not particularly limited as long as the polyamideimide resin can be obtained, and the reduction in Hz of the optical film is facilitated_aIn view of easy improvement of yield strain and elastic modulus, it is preferable to produce a polyamideimide resin by a production method in which a dicarboxylic acid compound is added in portions and a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound are reacted; more preferably, the polyamideimide resin is produced by a method comprising the step (I) of reacting a diamine compound with a tetracarboxylic acid compound to produce an intermediate (a), and the step (II) of reacting the intermediate (a) with a dicarboxylic acid compound, wherein the dicarboxylic acid compound is added in portions in the step (II). When the method of adding the dicarboxylic acid compound in portions is used, the reason is not clear, but it is easy to lower the Hz of the optical film_aAnd easily increase the yield point strain and elastic modulus. In addition, the weight average molecular weight of the polyamideimide resin can be easily adjusted to the above range.

Therefore, the polyamideimide resin contained in the optical film of the present invention is preferably a resin obtained by a production method of adding a dicarboxylic acid compound in portions and reacting a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound, and more preferably a resin obtained by a production method comprising reacting a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compoundA step (I) of reacting a diamine compound with a tetracarboxylic acid compound to produce an intermediate (A), and a step (II) of reacting the intermediate (A) with a dicarboxylic acid compound, and a resin produced by the production method wherein the dicarboxylic acid compound is added in portions in the step (II). In addition, when a solvent is further added in the step (II), the Hz of the optical film is easily lowered_aAnd easily increase the yield point strain and elastic modulus. Examples of the solvent include the solvents exemplified above.

When the polyamideimide resin is produced by the production method comprising the above-mentioned step (I) and step (II), the reaction temperature of the step (I) for producing the intermediate (a) by reacting a diamine compound with a tetracarboxylic acid compound is not particularly limited, and may be, for example, 5 to 200 ℃, preferably 10 to 100 ℃, more preferably 15 to 50 ℃, and still more preferably 20 to 30 ℃. The reaction time may be, for example, 1 minute to 72 hours, preferably 10 minutes to 24 hours. The reaction may be carried out in air or an inert gas atmosphere such as nitrogen or argon while stirring, or may be carried out under normal pressure, increased pressure or reduced pressure. In a preferred embodiment, the stirring is carried out under normal pressure and/or under the inert gas atmosphere.

In the step (I), the diamine compound reacts with the tetracarboxylic acid compound to produce the intermediate (a), i.e., polyamic acid. Therefore, the intermediate (a) contains a structural unit derived from a diamine compound and a structural unit derived from a tetracarboxylic acid compound.

Next, in the step (II), the intermediate (a) is reacted with a dicarboxylic acid compound, and here, the dicarboxylic acid compound is preferably added in portions. The intermediate (a) is reacted with a dicarboxylic acid compound by adding the dicarboxylic acid compound to the reaction solution obtained in the step (I) in portions. By adding the dicarboxylic acid compound in portions rather than at once, the Hz of the optical film can be easily lowered_aAnd easily increase the yield point strain and elastic modulus. In addition, the weight average molecular weight of the polyamideimide resin can be easily adjusted to the above-mentioned preferred range. In the present specification, the batch addition means: the dicarboxylic acid compound to be added is added in several portions, more specifically, the dicarboxylic acid compound to be added is addedThe dicarboxylic acid is added in a specific amount and added at predetermined intervals or for a predetermined time. The prescribed interval or prescribed time also includes a very short interval or time, and therefore the batch addition also includes continuous addition or continuous feeding.

In the step (II), the number of times of addition of the dicarboxylic acid compound in portions may be appropriately selected depending on the scale of the reaction, the kind of the raw material, and the like, and is preferably 2 to 20 times, more preferably 2 to 10 times, and still more preferably 2 to 6 times.

The dicarboxylic acid compound may be added in an equal amount or in an unequal amount. The time between each addition (hereinafter, sometimes referred to as an addition interval) may be the same or different. In addition, in the case of adding two or more dicarboxylic acid compounds, the term "adding in portions" means adding all the dicarboxylic acid compounds in portions, and the method of adding the dicarboxylic acid compounds in portions is not particularly limited, and for example, the dicarboxylic acid compounds may be added together or in portions, or the dicarboxylic acid compounds may be added in portions, or a combination thereof.

In the step (II), the dicarboxylic acid compound is preferably added in an amount of 1 to 40 mol%, more preferably 2 to 25 mol%, based on the total molar amount of the dicarboxylic acid compound to be added, when the weight average molecular weight of the polyamideimide resin is preferably 10% or more, more preferably 15% or more, based on the weight average molecular weight of the polyamideimide resin to be obtained.

The reaction temperature in the step (II) is not particularly limited, and may be, for example, 5 to 200 ℃, preferably 10 to 100 ℃, more preferably 15 to 50 ℃, and still more preferably 20 to 30 ℃. The reaction may be carried out in air or under an inert gas atmosphere such as nitrogen or argon with stirring, or may be carried out under normal pressure, under increased pressure or under reduced pressure. In a preferred embodiment, the step (II) is performed under normal pressure and/or under the inert gas atmosphere while stirring.

In the step (II), the dicarboxylic acid compound is added in portions, and then the mixture is reacted by stirring for a predetermined time, whereby a polyamideimide precursor can be obtained. The polyamideimide precursor may be isolated, for example, by: the polyamideimide precursor is precipitated by adding a large amount of water or the like to a reaction solution containing the polyamideimide precursor, followed by filtration, concentration, drying, and the like.

In the step (II), the intermediate (a) is reacted with a dicarboxylic acid compound to obtain a polyamideimide precursor. Accordingly, the polyamideimide precursor means a polyamideimide before imidization (before ring closure) containing a structural unit derived from a diamine compound, a structural unit derived from a tetracarboxylic acid, and a structural unit derived from a dicarboxylic acid compound.

The method for producing a polyamideimide resin may further include the step (III) of imidizing the polyamideimide precursor in the presence of an imidization catalyst. By subjecting the polyamideimide precursor obtained in the step (II) to the step (III), a structural unit having a polyamic acid structure in a structural unit of the polyamideimide precursor is partially imidized (ring-closed), and a polyamideimide resin comprising a structural unit represented by the formula (1) and a structural unit represented by the formula (2) can be obtained. Examples of the imidization catalyst include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; n-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepino

Alicyclic amines (monocyclic); azabicyclo [2.2.1]Heptane, azabicyclo [3.2.1]Octane, azabicyclo [2.2.2]Octane, and azabicyclo [3.2.2]Alicyclic amines (polycyclic) such as nonane; and aromatic amines such as pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-dimethylpyridine, 2,4, 6-trimethylpyridine, 3, 4-cyclopentenopyridine, 5,6,7, 8-tetrahydroisoquinoline, and isoquinoline. In addition, from the viewpoint of facilitating the imidization reaction, it is preferable to use an acid anhydride together with an imidization catalyst. The acid anhydride may be a conventional acid anhydride used in the imidization reaction, and the likeSpecific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydride, and aromatic acid anhydrides such as phthalic acid.

The polyamide-imide resin can be separated (separated and purified) by a conventional method, for example, a separation means such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a separation means combining these, and in a preferred embodiment, the separation can be carried out by: a large amount of an alcohol such as methanol is added to a reaction solution containing a polyamideimide resin to precipitate the resin, followed by concentration, filtration, drying, and the like.

< additive >

The optical film of the present invention may contain at least 1 filler in addition to the resin. Examples of the filler include organic particles and inorganic particles, and preferably inorganic particles. Examples of the inorganic particles include silicon dioxide, zirconium dioxide, aluminum oxide, titanium dioxide, zinc oxide, germanium oxide, indium oxide, tin oxide, Indium Tin Oxide (ITO), metal oxide particles such as antimony oxide and cerium oxide, and metal fluoride particles such as magnesium fluoride and sodium fluoride, and among these, the elastic modulus and the bending resistance of the optical film are easily improved, and the Hz is easily decreased_aFrom the viewpoint of (1), preferred examples thereof include silica particles, zirconia particles and alumina particles, and more preferred examples thereof include silica particles. These fillers may be used alone or in combination of 2 or more.

The average primary particle diameter of the filler, preferably the silica particles, is usually 1nm or more, preferably 5nm or more, more preferably 10nm or more, further preferably 15nm or more, particularly preferably 20nm or more, preferably 100nm or less, more preferably 90nm or less, further preferably 80nm or less, further preferably 70nm or less, particularly preferably 60nm or less, particularly preferably 50nm or less, and particularly preferably 40nm or less. When the average primary particle diameter of the silica particles is within the above range, the elastic modulus and the bending resistance of the optical film are easily improved, and Hz is easily decreased_a. In addition, aggregation of silica particles is easily suppressed, and the optical characteristics of the obtained optical film are easily improvedAnd (4) sex. The average primary particle diameter of the filler can be measured by the BET method. The average primary particle size may be measured by image analysis using a transmission electron microscope or a scanning electron microscope.

When the optical film of the present invention contains a filler, preferably silica particles, the content of the filler is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less with respect to 100% by mass of the optical film, from the viewpoint of easily increasing the yield strain of the optical film, and the elastic modulus and the bending resistance of the optical film are easily increased, and Hz is easily decreased_aFrom the viewpoint of (2), it is preferably 0.1% by mass or more, more preferably 1% by mass or more, and still more preferably 5% by mass or more.

The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber can be appropriately selected from those generally used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400nm or less. Examples of the ultraviolet absorber include at least 1 compound selected from the group consisting of benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds. The ultraviolet absorber may be used alone or in combination of two or more. Since the optical film contains the ultraviolet absorber, deterioration of the resin can be suppressed, and thus, the visibility can be improved when the optical film is applied to an image display device or the like. In the present specification, the term "related compound" refers to a derivative of a compound to which the "related compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a matrix skeleton and a substituent bonded to benzophenone.

When the optical film contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 3% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less, relative to 100% by mass of the optical film. The preferable content varies depending on the ultraviolet absorber used, but if the content of the ultraviolet absorber is adjusted so that the light transmittance at 400nm becomes about 20 to 60%, the light resistance of the optical film can be improved and the transparency can be easily improved.

The optical film of the present invention may further contain other additives besides the filler and the ultraviolet absorber. Examples of the other additives include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, and leveling agents. When other additives are contained, the content thereof may be preferably 0.001 to 20% by mass, more preferably 0.01 to 15% by mass, and still more preferably 0.1 to 10% by mass, relative to 100% by mass of the optical film.

The application of the optical film of the present invention is not particularly limited, and the optical film can be used for various applications. As described above, the optical film of the present invention may be a single layer or a laminate, and the optical film of the present invention may be used as it is, or may be used in the form of a laminate with another film. When the optical film is a laminate, all layers including the optical film laminated on one surface or both surfaces thereof are referred to as optical films.

When the optical film of the present invention is a laminate, it is preferable that at least one surface of the optical film has 1 or more functional layers. Examples of the functional layer include a hard coat layer, a primer layer, a gas barrier layer, an ultraviolet absorbing layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. The functional layers may be used alone or in combination of two or more.

The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100 μm. When the thickness of the hard coat layer is within the above range, the impact resistance can be improved, the bending resistance is less likely to be lowered, and the problem of curling due to curing shrinkage is less likely to occur. The hard coat layer may be formed by: curing the hard coating composition including the reactive material capable of forming a cross-linked structure by irradiating active energy rays or imparting thermal energy; preferably by irradiation with active energy rays. The active energy ray is defined as an energy ray that can decompose a compound that generates an active species to generate an active species, and examples thereof include visible light, ultraviolet light, infrared light, X-ray, α -ray, β -ray, γ -ray, and electron beam, and preferable examples thereof include ultraviolet light. The hard coat composition contains at least 1 polymer selected from the group consisting of a radically polymerizable compound and a cationically polymerizable compound.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound may be a functional group capable of undergoing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, specifically, a vinyl group and a (meth) acryloyl group. When the radical polymerizable compound has 2 or more radical polymerizable groups, the radical polymerizable groups may be the same or different. The number of radical polymerizable groups in 1 molecule of the radical polymerizable compound is preferably 2 or more in terms of increasing the hardness of the hard coat layer. The radical polymerizable compound preferably includes a compound having a (meth) acryloyl group in view of high reactivity, specifically, a compound called a polyfunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in 1 molecule, an oligomer called epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate having several (meth) acryloyl groups in a molecule and having a molecular weight of several hundred to several thousand, and preferably 1 or more selected from the group consisting of epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate.

The cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetane group, or a vinyl ether group. The number of the cationically polymerizable groups contained in 1 molecule of the cationically polymerizable compound is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

Among the above cationically polymerizable compounds, preferred are compounds having at least 1 of an epoxy group and an oxetanyl group as a cationically polymerizable group. A cyclic ether group such as an epoxy group or an oxetane group is preferable in that shrinkage accompanying the polymerization reaction is small. In addition, the compound having an epoxy group in a cyclic ether group has the following advantages: it is easy to obtain compounds having various structures, to exert no adverse effect on the durability of the obtained hard coat layer, and to control the compatibility with the radical polymerizable compound. In addition, the oxetanyl group in the cyclic ether group has the following advantages as compared with the epoxy group: the polymerization degree is easily increased, the forming speed of the network obtained by the cationic polymerizable compound of the obtained hard coat layer is increased, and even in the area mixed with the radical polymerizable compound, the unreacted monomer is not remained in the film, and the independent network is formed; and so on.

Examples of the cationically polymerizable compound having an epoxy group include: polyglycidyl ethers of polyhydric alcohols having an alicyclic ring or alicyclic epoxy resins obtained by epoxidizing compounds containing a cyclohexene ring or cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or a peroxy acid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyols or alkylene oxide adducts thereof, polyglycidyl esters of aliphatic long-chain polybasic acids, homopolymers and copolymers of glycidyl (meth) acrylate; glycidyl ethers produced by the reaction of bisphenols such as bisphenol a, bisphenol F and hydrogenated bisphenol a, or their derivatives such as alkylene oxide adducts and caprolactone adducts with epichlorohydrin, and glycidyl ether type epoxy resins derived from bisphenols such as Novolac epoxy resins.

The aforementioned hard coating composition may further comprise a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and they can be appropriately selected and used. These polymerization initiators are decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, and radical polymerization and cationic polymerization are performed.

The radical polymerization initiator may be a substance that can release and initiate radical polymerization by at least one of irradiation with active energy rays and heating. Examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisbutyronitrile.

The active energy ray radical polymerization initiator includes a Type1 radical polymerization initiator which generates radicals by decomposition of molecules and a Type2 radical polymerization initiator which generates radicals by hydrogen abstraction reaction in the coexistence of a tertiary amine, and they can be used alone or in combination.

The cationic polymerization initiator may be a substance which can release a substance for initiating cationic polymerization by at least one of irradiation with active energy rays and heating. As the cationic polymerization initiator, aromatic iodonium salts, aromatic sulfonium salts, cyclopentadienyl iron (II) complexes, and the like can be used. Depending on the difference in structure, they can initiate cationic polymerization by either or both of irradiation with active energy rays or heating.

The polymerization initiator may be preferably contained in an amount of 0.1 to 10% by mass based on 100% by mass of the entire hard coat composition. When the content of the polymerization initiator is within the above range, the curing can be sufficiently advanced, the mechanical properties and the adhesion of the finally obtained coating film can be in a good range, and poor adhesion, a crack phenomenon, and a curl phenomenon due to curing shrinkage tend to be less likely to occur.

The hard coating composition may further include one or more selected from the group consisting of a solvent and an additive.

The solvent may be used in a range that does not impair the effects of the present invention, as long as it is a solvent that can dissolve or disperse the polymerizable compound and the polymerization initiator and is known as a solvent for a hard coat composition in the art.

The aforementioned additives may further include inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

The ultraviolet absorbing layer is a layer having an ultraviolet absorbing function, and is composed of a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, and an ultraviolet absorber dispersed in the main material.

The pressure-sensitive adhesive layer is a layer having a pressure-sensitive adhesive function and has a function of bonding the optical film to another member. As a material for forming the adhesive layer, a generally known material can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used. In this case, the thermosetting resin composition or the photocurable resin composition can be polymerized and cured by supplying energy after the polymerization.

The Pressure-Sensitive Adhesive layer may be a layer called a Pressure-Sensitive Adhesive (PSA) that is pressed and attached to an object. The pressure-sensitive adhesive may be a capsule adhesive as "a substance having adhesiveness at normal temperature and adhering to an adherend under light pressure" (JIS K6800) or as "an adhesive which contains a specific component in a protective film (microcapsule) and can maintain stability until the film is broken by an appropriate means (pressure, heat, or the like)".

The hue adjustment layer is a layer having a hue adjustment function and is a layer capable of adjusting the optical film to a target hue. The hue adjustment layer is, for example, a layer containing a resin and a colorant. Examples of the colorant include inorganic pigments such as titanium oxide, zinc oxide, red iron oxide, titanium oxide-based calcined pigments, ultramarine blue, cobalt aluminate, and carbon black; organic pigments such as azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, perylene-based compounds, isoindolinone-based compounds, phthalocyanine-based compounds, quinophthalone-based compounds, threne-based compounds, and diketopyrrolopyrrole-based compounds; bulk pigments such as barium sulfate and calcium carbonate; and basic dyes, acid dyes, mordant dyes, and the like.

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

In one embodiment of the present invention, the optical film may have a protective film on at least one side (one side or both sides). For example, when one surface of the optical film has a functional layer, the protective film may be laminated on the surface of the optical film or the surface of the functional layer, or may be laminated on both the optical film and the functional layer. When the optical film has functional layers on both surfaces thereof, the protective film may be laminated on the surface on one functional layer side, or may be laminated on the surfaces on both functional layers. The protective film is not particularly limited as long as it is a peelable film that can temporarily protect the surface of the optical film or the functional layer. Examples of the protective film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; the resin film is preferably selected from the group consisting of polyolefin resin films, polyethylene, polypropylene films and the like, acrylic resin films and the like. When the optical film has 2 protective films, the protective films may be the same or different.

The thickness of the protective film is not particularly limited, but is usually 10 to 120 μm, preferably 15 to 110 μm, and more preferably 20 to 100 μm. When the optical film has 2 protective films, the thicknesses of the respective protective films may be the same or different.

[ method for producing optical film ]

The optical film of the present invention is not particularly limited, and can be produced, for example, by a method including the following steps:

(a) a step of preparing a liquid (sometimes referred to as a resin varnish) containing the resin (varnish preparation step),

(b) a step (coating step) of applying a resin varnish to a base material to form a coating film; and

(c) and a step of drying the applied liquid (coating film) to form an optical film (optical film forming step).

In the varnish preparation step, the resin is dissolved in a solvent, and the additive is added as needed, and stirred and mixed to prepare a varnish.

The solvent that can be used in the preparation of the varnish is not particularly limited as long as the aforementioned resin can be dissolved. Examples of the solvent include amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; lactone solvents such as γ -butyrolactone and γ -valerolactone; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, amide solvents or lactone solvents are preferable. These solvents may be used alone or in combination of two or more. The resin varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25 mass%, more preferably 5 to 15 mass%. In the present specification, the solid content of the varnish refers to the total amount of components remaining after the solvent is removed from the varnish.

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

In the optical film forming step, the coating film is dried and peeled from the substrate, whereby an optical film can be formed. After the peeling, a drying step of drying the optical film may be further performed. The drying of the coating film can be carried out at a temperature of 50 to 350 ℃. In order to obtain a film having a low YI value, the temperature is preferably 300 ℃ or lower, more preferably 250 ℃ or lower, and still more preferably 230 ℃ or lower. From the viewpoint of reducing the haze and YI value of the bent portion in a high-temperature and high-humidity environment, the drying treatment time at 180 ℃ or more is preferably 120 minutes or less, more preferably 90 minutes or less, still more preferably 60 minutes or less, and particularly preferably 50 minutes or less. On the other hand, if the drying treatment is not sufficient, the haze may be increased in a high-temperature and high-humidity environment. From this viewpoint, the maximum temperature of drying is preferably 100 ℃ or higher, more preferably 150 ℃ or higher, and still more preferably 180 ℃ or higher. The drying time is preferably 10 minutes or longer, more preferably 20 minutes or longer, and still more preferably 30 minutes or longer. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure.

Examples of the substrate include a PET film, a PEN film, another polyimide resin, a polyamide resin film, and the like. Among them, a PET film, a PEN film, and the like are preferable from the viewpoint of excellent heat resistance, and a PET film is more preferable from the viewpoint of adhesion to an optical film and cost.

In the present invention, the composition of the optical film, for example, the kind and composition ratio of the repeating structural units constituting the resin contained in the optical film; the production conditions of the resin; the thickness of the optical film; or conditions for producing the optical film, and the like, particularly, a method for easily reducing the Hz of the optical film_aIn addition, the yield point strain and Hz can be easily increased by the method described above, which is a method for easily increasing the yield point strain_aAdjusted to be within the scope of the invention. For example, it is possible to use the structural units represented by the formulae (1) and (2) as the structural units of the resin, particularly X, Y and Z in the formulae (1) and (2) as the structural units that easily reduce the Hz of the optical film_aAnd easily increase the yield pointThe strain mode can be combined with the above-mentioned modes as appropriate, or the yield point strain and Hz can be adjusted by using a dicarboxylic acid added in portions as a method for producing a resin or the like_aAdjusted to be within the scope of the invention of the present application.

In addition, when using the structural unit in which Y in the formula (1) is represented by the formula (4a) and/or the formula (4b), the structural unit in which Z in the formula (2) is represented by the formula (3) and/or the formula (3'), and the structural unit in which X in the formula (1) and/or the formula (2) is represented by the formula (34) (or the formula (32)), or when using these structures within the preferable ranges, yield point strain and Hz are easily induced_aAdjusted to be within the scope of the invention of the present application. In particular, by including a structural unit in which Y in formula (1) is represented by formula (32 ') and a structural unit in which X in formula (1) and/or formula (2) has a structure represented by formula (32'), among the structural units constituting the polyamideimide resin, it is possible to adjust the yield point strain and Hz by adjusting the ratio of these structural units preferably within the above range_aAdjusted to be within the scope of the invention.

In addition, the optical film may contain a filler, and preferably, the Hz may be adjusted to be within the above range by appropriately containing the filler_aAdjusted to be within the scope of the invention. It should be noted that the greater the amount of filler present, the Hz_aAnd the smaller the strain at yield point, whereas the smaller the content of filler present, the lower the Hz_aAnd the greater the tendency of yield point strain. Therefore, when the optical film contains a filler, the filler can be used in accordance with the Hz of the optical film itself_aAnd the value of the yield point strain to adjust the filler content.

The optical film of the present invention can be suitably used as a front panel (hereinafter, sometimes referred to as a window film) of a display device, particularly a flexible display device. The front panel has a function of protecting the display elements of the flexible display device. Examples of the display device include wearable devices such as televisions, smartphones, mobile phones, car navigation systems, tablet PCs, portable game machines, electronic paper, indicators, bulletin boards, clocks, and smartwatches. Examples of the flexible display include a display device having a flexible property, such as a television, a smart phone, a mobile phone, and a smart watch.

[ Flexible display device ]

The present invention includes a flexible display device provided 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 referred to as a window film. The flexible display device includes a laminate for flexible display device and an organic EL display panel, and the laminate for flexible display device is disposed on the viewing side of the organic EL display panel and is configured to be bendable. The laminate for a flexible display device may further include a polarizing plate and a touch sensor, and the lamination order thereof is arbitrary, and it is preferable that a window film, a polarizing plate and a touch sensor are laminated in this order or a window film, a touch sensor and a polarizing plate are laminated in this order from the viewing side. If the polarizing plate is present on the viewing side of the touch sensor, the pattern of the touch sensor is less likely to be observed, and the visibility of the display image is improved, which is preferable. The members may be laminated using an adhesive, or the like. Further, the light-shielding film may include a light-shielding pattern formed on at least one surface of any one of the window film, the polarizing plate, and the touch sensor.

[ polarizing plate ]

As described above, the flexible display device of the present invention preferably further includes a polarizing plate, particularly a circular polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only a right-handed circularly polarized light component or a left-handed circularly polarized light component by laminating a λ/4 phase difference plate on a linearly polarizing plate. For example, can be used for: the external light is converted into right-handed circularly polarized light, the external light reflected by the organic EL panel to become left-handed circularly polarized light is blocked, and only the light emitting component of the organic EL is transmitted, thereby suppressing the influence of reflected light and facilitating the viewing of images. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizer and the slow axis of the λ/4 phase difference plate need to be 45 ° in theory, and 45 ± 10 ° in practical application. The linear polarizing plate and the λ/4 phase difference plate do not have to be laminated adjacent to each other as long as the relationship between the absorption axis and the slow axis satisfies the aforementioned range. It is preferable to completely circularly polarize light at all wavelengths, but it is not essential in practical use, and therefore, the circularly polarizing plate in the present invention also includes an elliptically polarizing plate. It is also preferable that a λ/4 retardation film is further laminated on the viewing side of the linear polarizing plate to convert the emitted light into circularly polarized light, thereby improving visibility in a state where the polarized sunglasses are worn.

The linear polarizing plate is a functional layer having a function of transmitting light vibrating in the transmission axis direction, but blocking polarized light of a vibration component perpendicular thereto. The linear polarizer may be a single linear polarizer or a structure having a linear polarizer and a protective film attached to at least one surface of the linear polarizer. The thickness of the linearly polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness of the linear polarizer is within the above range, the flexibility of the linear polarizer tends to be less likely to decrease.

The linear polarizer may be a film-type polarizer produced by dyeing and stretching a polyvinyl alcohol (hereinafter, abbreviated as PVA) film. Polarizing performance can be exhibited by adsorbing a dichroic dye such as iodine to a PVA-based film that has been oriented by stretching, or by orienting a dichroic dye by stretching the film in a state of being adsorbed to PVA. The film-type polarizer may be produced by swelling, crosslinking with boric acid, washing with an aqueous solution, and drying. The stretching and dyeing step may be performed on the PVA-based film alone or in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA film to be used is preferably 10 to 100 μm, and the stretching ratio is preferably 2 to 10 times.

In addition, another example of the polarizer is a liquid crystal coating type polarizer formed by coating a liquid crystal polarizing composition. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic pigment compound. The liquid crystalline compound may have a property of exhibiting a liquid crystal state, and is preferably capable of exhibiting high polarizing performance if it has a high-order alignment state such as a smectic phase. The liquid crystalline compound preferably has a polymerizable functional group.

The dichroic pigment compound is a pigment which exhibits dichroism by being aligned with the liquid crystal compound, and may have a polymerizable functional group, and the dichroic pigment itself may have liquid crystallinity.

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

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

The alignment film can be produced by, for example, applying an alignment film-forming composition to a base material, and imparting alignment properties by rubbing, polarized light irradiation, or the like. The alignment film-forming composition may contain an alignment agent, and may further contain a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like. Examples of the orientation agent include polyvinyl alcohols, polyacrylates, polyamide acids, and polyimides. When an alignment agent that imparts alignment properties by polarized light irradiation is used, an alignment agent containing a cinnamate group (cinnamate group) is preferably used. The weight average molecular weight of the polymer that can be used as the orientation agent is, for example, about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000nm, and more preferably 10 to 500nm in view of sufficiently developing an alignment controlling force.

The liquid crystal polarizing layer may be laminated by being peeled off from a substrate and transferred, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

The protective film may be a transparent polymer film, and may be made of the same material or additive as that used for the transparent base material of the window film. Further, the coating-type protective film may be obtained by applying and curing a cationically curable composition such as an epoxy resin or a radically curable composition such as an acrylate. The protective film may contain a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like, as necessary. The thickness of the protective film is preferably 200 μm or less, and more preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the film tends not to be easily lowered.

The λ/4 retardation plate is a film that imparts a retardation of λ/4 in a direction perpendicular to the traveling direction of incident light, that is, in the in-plane direction of the film. The λ/4 retardation plate may be a stretched retardation plate produced by stretching a polymer film such as a cellulose film, an olefin film, or a polycarbonate film. The λ/4 retardation plate may contain a retardation regulator, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like, as required.

The thickness of the stretched phase difference plate is preferably 200 μm or less, and more preferably 1 to 100 μm. When the thickness of the stretched retardation film is within the above range, the flexibility of the stretched retardation film tends to be less likely to decrease.

Another example of the λ/4 retardation plate is a liquid crystal coating type retardation plate formed by coating a liquid crystal composition.

The liquid crystal composition contains a liquid crystalline compound that exhibits a liquid crystal state such as a nematic state, a cholesteric state, or a smectic state. The liquid crystalline compound has a polymerizable functional group.

The aforementioned liquid crystal composition may further include 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 coated retardation plate can be produced by coating a liquid crystal composition on a substrate and curing the coating to form a liquid crystal retardation layer, as in the liquid crystal polarizing layer. The liquid crystal coated retardation plate can be formed to a smaller thickness than the stretched retardation plate. The thickness of the liquid crystal polarizing layer is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

The liquid crystal coated retardation plate may be laminated by being peeled from a substrate and transferred, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

In general, the birefringence is large as the wavelength is shorter, and the birefringence is small as the wavelength is longer. In this case, since a retardation of λ/4 cannot be achieved in all visible light regions, the in-plane retardation is designed to be preferably 100 to 180nm, more preferably 130 to 150nm so as to be λ/4 in the vicinity of 560nm, which is high in visibility. The inverse dispersion λ/4 phase difference plate using a material having a wavelength dispersion characteristic of birefringence opposite to that of ordinary use is preferable in view of good visibility. As such a material, for example, as for the stretched phase difference plate, the stretched phase difference plate described in japanese patent application laid-open No. 2007-232873 and the like can be used, and as for the liquid crystal coated phase difference plate, the liquid crystal coated phase difference plate described in japanese patent application laid-open No. 2010-30979 and the like can be used.

As another method, a technique of obtaining a wide-band λ/4 phase difference plate by combining with a λ/2 phase difference plate is also known (for example, japanese patent application laid-open No. h 10-90521). The λ/2 phase difference plate can be manufactured by the same material method as the λ/4 phase difference plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is arbitrary, and the thickness can be made thin by using the liquid crystal coating type retardation plate.

For the circularly polarizing plate, a method of laminating a positive C plate is known in order to improve visibility in an oblique direction (for example, japanese patent application laid-open No. 2014-224837). The positive C plate may be a liquid crystal coated retardation plate or a stretched retardation plate. The retardation in the thickness direction of the retardation plate is preferably from-200 to-20 nm, more preferably from-140 to-40 nm.

[ touch sensor ]

As described above, the flexible display device of the present invention preferably further includes a touch sensor. A touch sensor is used as an input mechanism. The touch sensor includes various types such as a resistive film type, a surface acoustic wave type, an infrared ray type, an electromagnetic induction type, and a capacitance type, and preferably includes a capacitance type.

The capacitive touch sensor can be divided into an active region and an inactive region located at an outer periphery of the active region. The active area is an area corresponding to a display portion area of a display screen on the display panel and is an area where a user's touch is sensed, and the inactive area is an area corresponding to a non-display portion area of the display device where the screen is not displayed. The touch sensor may include: a substrate having flexible properties; a sensing pattern formed on the active region of the substrate; and each sensing line formed in the inactive region of the substrate and used for connecting the sensing pattern with an external driving circuit through a pad (pad). As the substrate having a flexible property, the same material as the transparent substrate of the window film can be used.

The sensing pattern may include a 1 st pattern formed in a 1 st direction and a 2 nd pattern formed in a 2 nd direction. The 1 st pattern and the 2 nd pattern are arranged in different directions from each other. The 1 st pattern and the 2 nd pattern may be formed on the same layer, and in order to sense the touch position, the patterns must be electrically connected. The 1 st pattern is a form in which a plurality of cell patterns are connected to each other via a joint, and the 2 nd pattern has a structure in which a plurality of cell patterns are separated from each other in an island form, and therefore, in order to electrically connect the 2 nd pattern, an additional bridge electrode is required. As the electrode for connecting the 2 nd pattern, a known transparent electrode can be used. Examples of the material of the transparent electrode include Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), zinc oxide (ZnO), Indium Zinc Tin Oxide (IZTO), Indium Gallium Zinc Oxide (IGZO), Cadmium Tin Oxide (CTO), PEDOT (poly (3,4-ethylenedioxythiophene), poly (3, 4-ethylenedioxythiophene)), Carbon Nanotube (CNT), graphene, and a metal wire, and ITO is preferably used. These can be used alone or in combination of 2 or more. The metal used in the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, and the like, and these metals may be used alone or in combination of 2 or more.

The bridge electrode may be formed on the insulating layer with an insulating layer interposed therebetween on the sensing pattern, the bridge electrode may be formed on the substrate, and the insulating layer and the sensing pattern may be formed thereon. The bridge electrode may be formed of the same material as the sensing pattern, or may be formed of molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of 2 or more of these.

The 1 st pattern and the 2 nd pattern must be electrically insulated, and thus, an insulating layer may be formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the tab of the 1 st pattern and the bridge electrode, or may be formed as a layer covering the entire sensing pattern. In the case of a layer covering the entire sensing pattern, the 2 nd pattern may be connected to the bridge electrode through a contact hole formed in the insulating layer.

In the touch sensor, as a means for appropriately compensating for a difference in transmittance between a pattern region where a sensing pattern is formed and a non-pattern region where no sensing pattern is formed, specifically, a difference in transmittance due to a difference in refractive index in these regions, an optical adjustment layer may be further included between the substrate and the electrode. The optical adjustment layer may contain an inorganic insulating substance or an organic insulating substance. The optical adjustment layer may be formed by applying a photocurable composition including a photocurable organic binder and a solvent onto a substrate. The aforementioned photocurable composition may further comprise inorganic particles. The refractive index of the optical adjustment layer can be increased by the aforementioned inorganic particles.

The photocurable organic binder may contain a copolymer of monomers such as an acrylate monomer, a styrene monomer, and a carboxylic acid monomer within a range not to impair the effects of the present invention. The photocurable organic binder may be, for example, a copolymer containing mutually different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.

Examples of the inorganic particles include zirconia particles, titania particles, and alumina particles.

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

[ adhesive layer ]

The layers of the laminate for a flexible display device, such as a window film, a circularly polarizing plate, and a touch sensor, and the film members of the layers, such as a linearly polarizing plate and a λ/4 retardation plate, may be bonded to each other with an adhesive. As the adhesive, a commonly used adhesive such as an aqueous adhesive, an organic solvent adhesive, a solventless adhesive, a solid adhesive, a solvent volatile adhesive, an aqueous solvent volatile adhesive, a moisture curable adhesive, a heat curable adhesive, an anaerobic curable adhesive, an active energy ray curable adhesive, a curing agent hybrid adhesive, a hot melt adhesive, a pressure sensitive adhesive, a remoistenable adhesive, or the like can be used, and an aqueous solvent volatile adhesive, an active energy ray curable adhesive, or a bonding agent can be preferably used. The thickness of the adhesive layer can be adjusted as appropriate in accordance with the required adhesive strength, etc., and is preferably 0.01 to 500 μm, more preferably 0.1 to 300 μm. The laminate for a flexible display device has a plurality of adhesive layers, and the thickness and type of each layer may be the same or different.

The aqueous solvent-volatile adhesive may be a polyvinyl alcohol polymer, a water-soluble polymer such as starch, or a water-dispersed polymer such as an ethylene-vinyl acetate emulsion or a styrene-butadiene emulsion. In addition to the main polymer and water, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be added. In the case of bonding with the aqueous solvent volatile adhesive, adhesiveness can be provided by injecting the aqueous solvent volatile adhesive between the layers to be bonded, and bonding the layers to be bonded together, followed by drying. When the aqueous solvent volatile adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.1 to 1 μm. When the aqueous solvent-volatile adhesive is used in a plurality of layers, the thickness and type of each layer 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, which forms the adhesive layer, by irradiation with an active energy ray. The active energy ray-curable composition may contain at least 1 polymer selected from the group consisting of the same radical polymerizable compounds and cationic polymerizable compounds as those contained in the hard coat composition. The radical polymerizable compound may be the same as the radical polymerizable compound in the hard coat composition.

The cationic polymerizable compound may be the same compound as the cationic polymerizable compound in the hard coat composition.

As the cationically polymerizable compound which can be used in the active energy ray-curable composition, an epoxy compound is preferable. In order to reduce the viscosity as an adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

For the active energy ray composition, a monofunctional compound may be contained in order to reduce the viscosity. Examples of the monofunctional compound include an acrylate monomer having 1 (meth) acryloyl group in 1 molecule, a compound having 1 epoxy group or oxetanyl group in 1 molecule, and glycidyl (meth) acrylate.

The active energy ray composition may further include a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and they can be appropriately selected and used. These polymerization initiators can be decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, thereby allowing radical polymerization and cationic polymerization to proceed. An initiator capable of initiating at least either of radical polymerization or cationic polymerization by irradiation with active energy rays as described in the description of the hard coating composition may be used.

The active energy ray-curable composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, an antifoaming agent, an additive, and a solvent. When 2 layers to be bonded are bonded with the active energy ray-curable adhesive, the following means may be used for bonding: the active energy ray-curable composition is applied to one or both of the adhesive layers, and then the adhesive layers are bonded to each other, and the adhesive layers are cured by irradiation with active energy rays. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used to form a plurality of adhesive layers, the thickness and type of each layer may be the same or different.

As the adhesive, any of those classified into acrylic adhesives, urethane adhesives, rubber adhesives, polysiloxane adhesives, and the like can be used depending on the base polymer. The pressure-sensitive adhesive may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler, and the like in addition to the main polymer. The pressure-sensitive adhesive layer (adhesive layer) can be formed by dissolving and dispersing the components constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, applying the pressure-sensitive adhesive composition to a substrate, and drying the applied pressure-sensitive adhesive composition. The adhesive layer may be formed directly or by transferring an adhesive layer separately formed on the substrate. It is also preferable to use a release film for covering the pressure-sensitive adhesive surface before bonding. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.1 to 500 μm, more preferably 1 to 300 μm. When a plurality of the above-mentioned adhesives are used, the thickness and kind of each layer may be the same or different.

[ light-shielding pattern ]

The light-shielding pattern may be applied as at least a part of a bezel (bezel) or a housing of the flexible display device. The wiring disposed at the edge of the flexible display device is hidden by the light-shielding pattern and is not easily viewed, thereby improving visibility of an image. The light-shielding pattern may be in the form of a single layer or a plurality of layers. The color of the light-shielding pattern is not particularly limited, and may be various colors such as black, white, and metallic colors. The light-shielding pattern may be formed of a pigment for color, and a polymer such as an acrylic resin, an ester resin, an epoxy resin, polyurethane, or polysiloxane. They may be used alone or in the form of a mixture of 2 or more. The light-shielding pattern can be formed by various methods such as printing, photolithography, and inkjet. The thickness of the light-shielding pattern is preferably 1 to 100 μm, and more preferably 2 to 50 μm. Further, it is also preferable to provide a shape such as an inclination in the thickness direction of the light-shielding pattern.

Examples

The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the examples, "%" and "part(s)" refer to% by mass and part(s) by mass unless otherwise specified. First, the measurement and evaluation method will be explained.

< mandrel test at room temperature (25 ℃ C.) by Hz_aHaze of

The optical films obtained in examples and comparative examples were cut into a size of 68mm × 28mm using a dumbbell cutter, and subjected to a vacuum slitting in accordance with JIS K5600-5-1: 1999 mandrel test. In the mandrel test, the tube was bent uniformly along a cylindrical mandrel having a bending radius of 1mm at room temperature (25 ℃). Immediately thereafter (after 1 to 2 seconds), the bent optical film was returned to a flat shape, and the haze of the bent portion in the spindle Test was measured using a haze computer ("HGM-2 DP", manufactured by Suga Test Instruments co.

< haze after storage at 85 ℃ and 85% relative humidity in a bent state >

The optical films obtained in examples and comparative examples were cut into 68mm × 28mm sizes using a dumbbell cutter, and subjected to the following durability test. First, in a constant temperature and humidity environment durability tester ("CL 09-type01D01-FSC 90", ltd. "), both ends of the folded optical film were held in parallel, and the optical film was stored in an environment of 85 ℃ relative humidity 85% for 24 hours in a state of being folded at a bending radius of 1 mm. Thereafter, the folded optical film was returned to a flat shape and allowed to stand for 30 minutes in an environment of 30 ℃ and 50% relative humidity. Then, the haze and YI values of the bent portions in the storage test were measured.

< thickness of optical film >

The thickness of the optical film obtained in examples and comparative examples was measured using an ABS number dial gauge ("ID-C112 BS", manufactured by Mitutoyo corporation).

< Haze (Haze) >

According to JIS K7136: the optical film after the mandrel Test and after being stored in a bent state at 85 ℃ and 85% relative humidity was cut into a size of 30mm × 30mm, and the haze (%) was measured using a haze computer (Suga Test Instruments co., ltd., "HGM-2 DP"). In examples 1 and 2, the measured values in Hz before the mandrel test were obtained_bHaze indicated.

< YI value >

The tri-stimulus value (X, Y, Z) was obtained using an ultraviolet-visible near-infrared spectrophotometer (V-670, manufactured by japan spectro-photometer) for the optical film after the mandrel test and after the optical film was stored in a bent state at a temperature of 85 ℃ and a relative humidity of 85%, and the YI value was calculated by substituting the tri-stimulus value into the following calculation formula.

YI＝100×(1.2769X-1.0592Z)/Y

In examples 1 and 2, the YI value before the mandrel test was also calculated.

< full light transmittance >

According to JIS K7105: 1981, the total light transmittance (Tt) of the optical films obtained in examples and comparative examples was measured by a fully automatic direct haze computer HGM-2DP manufactured by Suga Test Instruments co.

< determination of weight average molecular weight >

Gel Permeation Chromatography (GPC) measurement

(1) Pretreatment method

To the polyamideimide resins (samples) obtained in examples and comparative examples, a DMF eluent (10mmol/L lithium bromide solution) was added so that the concentration became 2mg/mL, and the mixture was heated while stirring at 80 ℃ for 30 minutes, cooled, and then filtered with a 0.45 μm membrane filter, and the obtained filtrate was used as a measurement solution.

(2) Measurement conditions

Column: TSKgel α -2500 (7)7.8mm diameter. times.300 mm). times.1, and α -M ((13)7.8mm diameter. times.300 mm). times.2, manufactured by Tosoh Corporation

Eluent: DMF (with addition of 10mmol/L lithium bromide)

Flow rate: 1.0 mL/min

A detector: RI detector

Column temperature: 40 deg.C

Sample introduction amount: 100 μ L

Molecular weight standard: standard polystyrene

< determination of elastic modulus and yield Point Strain >

The elastic modulus of the optical films obtained in examples and comparative examples was measured at a temperature of 25 ℃ and a relative humidity of 50% by using "AUTOGRAPH AG-IS" manufactured by Shimadzu corporation. More specifically, a film having a width of 10mm was produced, a stress-strain curve (S-S curve) was measured under conditions of an inter-chuck distance of 50mm and a stretching speed of 20 mm/min, and the elastic modulus was calculated from the slope of the curve.

The yield point strain was calculated as follows.

Data collation of S-S curves

10 points are continuously sampled from the starting point of measurement in the S-S curve, and fitted to a quadratic function by using the least square method. Then, 1 point was excluded from the left side of the measurement starting point, and 1 point on the right side was added until a convex shape was formed by quadratic function fitting of 10 points in the sampling range. And finishing data sorting at the time point when the fitting function forms the upward projection.

Calculation of tangent equation of S-S curve

Based on the n-th to i-j (j-2 to 50) data of the data of item 1, the slope and intercept are obtained by the least square method. Then, for j-1 slopes, the k-th (k 1 to 48) to 49-th data were fitted to a 1-th-order function by the least square method, and the slope at which strain became 0 was obtained by extrapolation. The median of the 48 points obtained was obtained and defined as the slope of the line at which the strain was 0 (S-S curve tangent). The intercept is calculated in the same manner, and an equation of a tangent to the S-S curve when the strain is 0 is obtained.

3. Calculation of yield point strain

The tangent line of the S-S curve obtained in the above 2, at which the strain is 0, was shifted in parallel by 0.2% in the strain direction. The yield point strain is defined as the strain value at which the measured stress exceeds the stress of the straight line after the parallel translation.

< example 1 >

18.51g (55.37mmol) of 4, 4' - (hexafluoroisopropylidene) diphenylamine (6FDAM) and 313.57g of DMAc were charged into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, and 6FDAM was dissolved in DMAc with stirring at room temperature. Next, 9.69g (21.81mmol) of 6FDA was added to the flask, and the mixture was stirred at room temperature for 3 hours. Thereafter, 5.99g (29.45mmol) of TPC was added to the flask, and stirred at room temperature for 30 minutes. Then, 313.57g of DMAc was added, and after stirring for 10 minutes, 0.66g (3.27mm o.l) of TPC was further added to the flask, and the mixture was stirred at room temperature for 2 hours. Subsequently, 3.05g (32.72mmol) of 4-methylpyridine and 15.59g (152.69mmol) of acetic anhydride were added thereto, and the mixture was stirred at room temperature for 30 minutes, then heated to 70 ℃ using an oil bath, and further stirred for 3 hours to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 100 ℃ to obtain a polyamide-imide resin (TPC/6FDA/6 FDAM: 60/40/100 (molar ratio)). The weight average molecular weight of the polyamideimide resin was 73,000.

The obtained polyamideimide resin was dissolved in DMAc to prepare a 10% solution, the obtained polyamideimide varnish was filtered through a filter having a mesh of 10 μm, and then applied to a polyester substrate (Toyo Boseki) using an applicator so that the thickness of the self-supporting film became 55 μmA coating film obtained by Kabushiki Kaisha, trade name "A4100") was peeled off from a polyester substrate to obtain a self-supporting film after drying the coating film at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes on a smooth surface. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 40 minutes under the atmosphere to obtain an optical film having a thickness of 50 μm. Hz of optical film_b0.3% and YI of 1.7.

< example 2 >

14.90g (46.54mmol) of TFMB and 250.00g of DMAc were put into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, and the TFBM was dissolved in DMAc with stirring at room temperature. Next, 4.16g (9.35mmol) of 6FDA was added to the flask, and the mixture was stirred at room temperature for 3 hours. Thereafter, 7.85g (33.68mmol) of 2-methoxy-terephthaloyl chloride (OMTPC) was added to the flask, and stirred at room temperature for 30 minutes. Then, 313.57g of DMAc was added, and after stirring for 10 minutes, 0.87g (3.74mm o.l) of OMTPC was further added to the flask, and the mixture was stirred at room temperature for 2 hours. Subsequently, 3.49g (37.42mmol) of 4-methylpyridine and 6.69g (65.48mmol) of acetic anhydride were added thereto, and the mixture was stirred at room temperature for 30 minutes, then heated to 70 ℃ using an oil bath, and further stirred for 3 hours to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 100 ℃ to obtain a polyamide-imide resin (OMTPC/6 FDA/TFMB: 20/80/100 (molar ratio)). The weight average molecular weight of the polyamideimide resin was 190,000.

The obtained polyamideimide resin was dissolved in DMAc to prepare a 10% solution, the obtained polyamideimide varnish was filtered with a filter having a mesh of 10 μm, and then applied to a smooth surface of a polyester substrate (manufactured by tokyo corporation, trade name "a 4100") using an applicator so that the thickness of the self-supporting film became 55 μm, followed by drying at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes, and the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. Fixing the self-supporting film on a metal frame, and further drying at 200 deg.C for 40 min under atmospheric pressure to obtain a film with a thickness of50 μm optical film. Hz of optical film_b0.3% and YI of 1.9.

< comparative example 1 >

In a 1L separable flask equipped with a stirring blade, 40g (124.91mmol) of TFMB and 682.51g of DMAc were placed under a nitrogen atmosphere, and the TFMB was dissolved in the DMAc with stirring at room temperature. Then, 16.78g (37.77mmol) of 6FDA was added to the flask, and the mixture was stirred at room temperature for 3 hours. Thereafter, 3.72g (12.59mmol) of OBBC was added to the flask, followed by 15.34g (75.55mmol) of TPC, and the mixture was stirred at room temperature for 1 hour. Subsequently, 8.21g (88.14mmol) of 4-methylpyridine and 15.43g (151.10mmol) of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes, then heated to 70 ℃ using an oil bath, and further stirred for 3 hours to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 100 ℃ to obtain a polyamide-imide resin (TPC/OBBC/6 FDA/TFMB: 60/10/30/100 (molar ratio)). The weight average molecular weight of the polyamideimide resin was 400,000.

The obtained polyamideimide resin was diluted with GBL, added with GBL-substituted silica sol and thoroughly mixed to obtain a resin: the weight ratio of silicon dioxide is 6: 4 of the resin/silica particles mixed varnish. A mixed varnish was prepared so that the concentration of the resin and the silica particles became 11.0 mass%. The obtained polyamide-imide varnish was filtered through a filter having a mesh size of 10 μm, applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 55 μm, dried at 50 ℃ for 30 minutes, and then dried at 140 ℃ for 15 minutes, and the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 40 minutes under the atmosphere to obtain an optical film having a thickness of 50 μm.

< comparative example 2 >

In a 1L separable flask equipped with a stirring blade, 53.05g (165.66mmol) of TFMB and 670.91g of DMAc were placed under a nitrogen atmosphere, and TFMB was dissolved in DMAc with stirring at room temperature. Then, 22.11g (49.77mmol) of 6FDA and 4.88g (16.59mmol) of 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride (BPDA) were added to the flask, and 20.21g (99.54mmol) of TPC was added thereto, followed by stirring at room temperature for 1 hour. Subsequently, 10.53g (133.08mmol) of pyridine and 13.77g (134.83mmol) of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes, then heated to 70 ℃ using an oil bath, and further stirred for 3 hours to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 100 ℃ to obtain a polyamide-imide resin (TPC/BPDA/6 FDA/TFMB: 60/10/30/100 (molar ratio)). The weight average molecular weight of the polyamideimide resin was 190,000.

The obtained polyamideimide resin was diluted with DMAc to prepare a polyamideimide varnish having a concentration of 22 mass%. The obtained polyamide-imide varnish was filtered through a filter having a mesh size of 10 μm, applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 55 μm, dried at 50 ℃ for 30 minutes, and then dried at 140 ℃ for 15 minutes, and the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ℃ for 40 minutes under the atmosphere to obtain an optical film having a thickness of 50 μm.

< comparative example 3 >

The obtained polyamideimide resin was dissolved in DMAc to prepare a 10% solution, the obtained polyamideimide varnish was filtered with a filter having a mesh of 10 μm, and then applied to a smooth surface of a polyester substrate (manufactured by tokyo corporation, trade name "a 4100") using an applicator so that the thickness of the self-supporting film became 55 μm, followed by drying at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes, and the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 40 minutes under the atmospheric air to obtain a polyamideimide film (optical film) having a thickness of 50 μm.

As shown in Table 1, the elastic modulus (GPa), the total light transmittance (Tt,%), and the Hz of the optical films obtained in examples 1 and 2 and comparative examples 1 to 3 were measured_a(%), yield point strain (%), and Hz (%) and YI values after storage in a bent state at 85 ℃ and 85% relative humidity.

[ Table 1]

As shown in Table 1, it was confirmed that the yield point strain was 1.5% or more and Hz was obtained_aThe optical films of examples 1 and 2 having a refractive index of 1.5% or less had a lower YI after storage at 85 ℃ and a relative humidity of 85% in a folded state than those of comparative examples 1 and 2, and had a lower Hz after storage than those of comparative examples 2 and 3.

Therefore, it is understood that the optical films obtained in examples 1 and 2 have low haze and yellowness even after being stored in a folded state under a high-temperature and high-humidity environment for a long time.

Claims

1. An optical film having a yield point strain of 1.50% or more and a tensile modulus in Hz after mandrel test_aThe haze value is 1.5% or less, and the mandrel test is a test in which the glass sheet is bent 1 time at a bending radius of 1mm at room temperature and then returned to a flat shape.

2. The optical film of claim 1, comprising a polyamideimide resin.

3. The optical film according to claim 2, wherein the polyamideimide resin comprises a structural unit represented by formula (1) and a structural unit represented by formula (2),

[ chemical formula 1]

In formula (1), X represents a 2-valent organic group, Y represents a 4-valent organic group, and X represents a chemical bond;

[ chemical formula 2]

In formula (2), X and Z independently represent a 2-valent organic group, and represent a bond.

4. The optical film of any one of claims 1-3, wherein the mandrel is tested prior to being tested in Hz_bThe haze value is 1.0% or less.

5. The optical film according to any one of claims 1 to 4, wherein the content of the filler is 30% by mass or less with respect to the mass of the optical film.

6. The optical film according to any one of claims 1 to 5, which has a thickness of 20 to 100 μm.

7. The optical film according to any one of claims 1 to 6, which has an elastic modulus of 1.0GPa or more.

8. A flexible display device comprising the optical film according to any one of claims 1 to 7.

9. The flexible display device of claim 8, further provided with a touch sensor.

10. The flexible display device according to claim 8 or 9, further comprising a polarizing plate.