CN115197458A

CN115197458A - Optical laminate and flexible display device

Info

Publication number: CN115197458A
Application number: CN202210382937.4A
Authority: CN
Inventors: 片宝蓝; 申在贤; 宫本皓史
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2021-04-14
Filing date: 2022-04-12
Publication date: 2022-10-18
Also published as: TW202302718A; JP2022163622A; KR20220142371A

Abstract

The invention provides an optical laminate which is not easy to generate a dent on the surface due to the contact with an external element. An optical laminate comprising a substrate layer composed of a polyimide resin film and a functional layer comprising a cured product of a curable resin, wherein the yield stress at a tensile rate of 100 mm/min is 100MPa or more.

Description

Optical laminate and flexible display device

Technical Field

The present invention relates to an optical laminate including a substrate layer made of a polyimide resin film and a functional layer including a cured product of a curable resin, and a flexible display device including the optical laminate.

Background

Conventionally, glass has been used as a front panel of a display member of a solar cell, an image display device, or the like. However, in response to recent demands for size reduction, thickness reduction, weight reduction, and flexibility, glass does not have sufficient characteristics, and various films have been studied as alternative materials for glass. Examples of such a film include a polyimide resin film (e.g., japanese patent application laid-open nos. 2008-12675, 2020-64236, and international publication nos. 2014/046180).

Disclosure of Invention

A surface of a polyimide resin film used as a front panel in a flexible electronic device such as a flexible display device may come into contact with an external element such as a stylus pen, and thus the front panel is required to be less likely to have a dent on the surface due to contact with the external element, or to be less likely to recover from the dent surface. However, the resistance to such a sag phenomenon is not sufficient for conventional optical films and optical laminates. Accordingly, an object of the present invention is to provide an optical layered body in which a surface is less likely to be dented by contact with an external element.

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above problems are solved by an optical laminate which contains a substrate layer composed of a polyimide resin film and a functional layer composed of a cured product of a curable resin and satisfies specific physical property values, and have completed the present invention.

Namely, the present invention includes the following aspects.

[ 1] an optical laminate comprising: a substrate layer composed of a polyimide resin film, and a functional layer composed of a cured product of a curable resin, wherein the yield stress at a tensile rate of 100 mm/min is 100MPa or more.

An optical laminate according to [ 1], wherein the polyimide resin film has a yield stress of 200MPa or more at a tensile rate of 0.1 m/sec.

[3 ] the optical laminate according to [ 1] or [ 2], which has a thickness of 15 to 120 μm and a number of times of bending resistance of 20 ten thousand or more measured with R =1.5 mm.

The optical laminate according to any one of [ 1] to [3 ], wherein a permanent depression depth measured with a load of 200g using a jig having a compressive modulus of elasticity of 3.0GPa and a tip having a diameter of 0.7mm is 0.5 μm or less.

The optical laminate according to any one of [ 1] to [3 ], wherein a permanent depression depth measured with a load of 1000g using a jig having a compressive elastic modulus of 1.0GPa and a tip having a diameter of 0.7mm is 0.5 μm or less.

[ 6 ] the optical laminate according to any one of [ 1] to [ 5 ], wherein a pencil hardness of a surface on the functional layer side is H or more.

An optical laminate according to any one of [ 1] to [ 6 ], wherein the polyimide resin film contains a polyimide resin containing a structural unit represented by formula (1),

[ in formula (1), X represents a divalent organic group, Y represents a 4-valent organic group, and X represents a bonding end ], and Y in formula (1) includes a structure represented by formula (3),

[ in the formula (3), R ¹ Independently of one another, represents a halogen atom, an alkyl, alkoxy, aryl or aryloxy group optionally having a halogen atom, R ² ～R ⁵ Independently represent a hydrogen atom or a monovalent hydrocarbon group optionally having a halogen atom, m independently represents an integer of 0 to 3, n represents an integer of 1 to 4, and represents a bonding end, and R is a group having ² ～R ⁵ In at least one benzene ring of (2), R ² ～R ⁵ At least three of them being monovalent hydrocarbon groups optionally having halogen atoms]。

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

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

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

According to the optical laminate of the present invention, it is possible to provide an optical laminate in which a surface is less likely to be dented due to contact with an external element.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the scope of the present invention. When a plurality of upper and lower limits are described for a specific parameter, any of these upper and lower limits may be combined to form a preferred range. In the present specification, unless otherwise specified, the term "dent" means a dent in a pull-scribe test and a permanent dent.

< optical laminate >

The optical laminate of the present invention comprises a base layer made of a polyimide resin film and a functional layer comprising a cured product of a curable resin, and has a yield stress of 100MPa or more at a tensile rate of 100 mm/min.

When the yield stress is less than 100MPa, the occurrence of depressions on the surface due to contact with external elements is less likely to be reduced, and the recovery of the depressions is insufficient. From the viewpoint of further reducing the dishing easily, the yield stress is preferably 105MPa or more, and more preferably 110MPa or more. From the viewpoint of facilitating further improvement of the folding resistance of the optical laminate, the yield stress is preferably 160MPa or less, more preferably 150MPa or less, and still more preferably 140MPa or less. The yield stress is a value obtained from a stress-strain curve obtained by a tensile test in accordance with ASTM D638-14 at a tensile speed of 100 mm/min using an optical laminate as a measurement sample, and can be measured, for example, by the method described in examples.

The method of adjusting the yield stress of the optical laminate to the above range is not particularly limited, and examples thereof include a method of using a polyimide resin film having the yield stress described later as a base material layer and laminating a functional layer including a cured product of a curable resin, and a method of using a polyimide resin film including a polyimide resin described later as a base material layer and laminating a functional layer including a cured product of a curable resin.

The pencil hardness of the optical laminate of the present invention on the surface on the functional layer side is preferably H or more, and more preferably 2H or more. When the pencil hardness is within the above range, the occurrence of depressions on the surface due to contact with external elements can be more easily reduced.

The pencil hardness is measured in accordance with JIS K5600-5-4: 1999. the weight at the time of the test was 1kg, and the measurement speed was 60 mm/min.

The optical laminate of the present invention has a tensile elastic modulus of preferably 4.8GPa or more, more preferably 5.2GPa or more, further preferably 6.0GPa or more, and usually 100GPa or less, from the viewpoint of further reducing the occurrence of dents on the surface due to contact with an external element, from the viewpoint of easily recovering the generated dents, from the viewpoint of easily improving folding resistance, and from the viewpoint of easily preventing wrinkles, scratches, and the like. The tensile modulus can be measured using a tensile tester (test conditions: distance between chucks 50mm, tensile speed 10 mm/min).

The optical laminate of the present invention preferably has excellent bending resistance. The number of times of bending resistance of the optical laminate of the present invention is preferably 20 ten thousand or more, more preferably 25 ten thousand or more, and further preferably 30 ten thousand or more, when measured with R =1.5 mm. If the number of times of bending resistance is not less than the above lower limit, the occurrence of cracks, fractures, creases, and the like can be effectively suppressed even when bending is repeated. The number of times of bending resistance can be measured using a folding tester, and can be measured, for example, by the method described in examples.

The optical laminate of the present invention preferably has a yellowness index (hereinafter, sometimes referred to as YI value) of less than 3.0. When the YI value is less than 3.0, the visibility of, for example, an image or the like is easily improved through the optical layered body. From the viewpoint of facilitating further improvement in the visibility of an image or the like through the optical laminate, the YI value of the optical laminate of the present invention is preferably 2.8 or less, more preferably 2.6 or less, further preferably 2.5 or less, preferably-5 or more, and more preferably-2 or more. When the YI value of the optical layered body is equal to or less than the upper limit, the transparency becomes good, and when the optical layered body is used for a front panel of a display device, the optical layered body can contribute to high visibility. The YI value can be calculated based on the formula YI =100 × (1.2769X-1.0592Z)/Y by measuring the transmittance of light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer to obtain tristimulus values (X, Y, Z). The method for adjusting the YI value of the optical layered body to the above range is not particularly limited, and examples thereof include a method using a polyimide-based resin as described later, a method of adding a blue dye, a method of making a thin film, a method of introducing a side chain into an aromatic ring of a monomer main chain, and the like.

The total light transmittance of the optical laminate of the present invention is preferably 85% or more, more preferably 88% or more, further preferably 89% or more, and particularly preferably 90% or more. When the total light transmittance is not less than the lower limit, the visibility can be easily improved when the optical laminate is incorporated into a display device as a front panel. The optical laminate of the present invention generally has a high total light transmittance, and therefore can suppress the emission intensity of a display element or the like required to obtain a certain luminance more than in the case of using a film having a low transmittance, for example. Therefore, power consumption can be reduced. For example, when the optical laminate of the present invention is incorporated into a display device, bright display tends to be obtained even if the amount of light from the backlight is reduced, and this contributes to energy saving. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance may be, for example, in accordance with JIS K7361-1: 1997 and measured using a haze computer. The total light transmittance may be a total light transmittance within a thickness range of an optical laminate described later. In the present specification, the optical laminate having excellent optical properties means that the total light transmittance is high, the haze is low, and the YI value is low, and the optical laminate may be used in the same sense as the optical laminate having high or improved transparency.

The haze of the optical laminate of the present invention is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, particularly preferably 1% or less, particularly preferably 0.8% or less, particularly preferably 0.5% or less, and usually 0.01% or more. When the haze of the optical laminate is within the above range, the optical laminate is easily improved in visibility when incorporated into a display device, particularly as a front panel. The haze may be measured according to JIS K7136: 2000 and measured using a haze computer.

The thickness of the optical laminate of the present invention is preferably 10 μm or more, more preferably 15 μm or more, further preferably 20 μm or more, still more preferably 25 μm or more, particularly preferably 30 μm or more, preferably 200 μm or less, more preferably 120 μm or less, further preferably 100 μm or less, still more preferably 80 μm or less, particularly preferably 60 μm or less, and may be a combination of these upper and lower limits. When the thickness of the optical laminate is within the above range, the yield stress and the tensile elastic modulus of the optical laminate tend to be further improved. The thickness of the optical layered body can be measured using a micrometer, for example, by the method described in examples. The optical laminate of the present invention preferably has a thickness of preferably 15 to 120 μm, more preferably 20 to 100 μm, and further preferably 25 to 80 μm, and a bending resistance number of times measured as R =1.5mm is preferably 20 ten thousand or more, more preferably 25 ten thousand or more, and further preferably 30 ten thousand or more.

The total light transmittance and the haze vary depending on the thickness of the optical laminate, and the larger the thickness is, the lower the total light transmittance and the higher the haze is. That is, it is difficult to produce an optical laminate having a high total light transmittance and a low haze with respect to a film having a large thickness. In a preferred embodiment of the present invention, the optical laminate of the present invention has a high level of transparency, and thus can exhibit high total light transmittance and low haze even if the thickness is relatively large. Therefore, the thickness of the optical laminate of the present invention is preferably 10 μm or more, more preferably 15 μm or more, further preferably 20 μm or more, further preferably 25 μm or more, particularly preferably 30 μm or more, particularly preferably 35 μm or more, particularly preferably 40 μm or more, preferably 100 μm or less, more preferably 80 μm or less, further preferably 60 μm or less. The thickness of the optical layered body can be measured by a film thickness meter or the like, and can be measured, for example, by the method described in examples.

In the present specification, the critical load is the maximum load at which the optical laminate is not visually recognized by a press-in and pull-out test.

The permanent depression depth is a depth at which the depression recovers to a constant value after 24 hours after the depression is formed by performing a press-in and draw-out test on the optical layered body.

In the optical laminate of the present invention, the permanent depression depth measured with a load of 200g using a jig having a compressive elastic modulus of 3.0GPa and a tip having a diameter of 0.7mm is preferably 0.5 μm or less, more preferably 0.4 μm or less, still more preferably 0.3 μm or less, and yet more preferably 0.2 μm or less on the surface on the functional layer side. The details of the method for measuring the depth of permanent pit are as described in the examples.

In the optical laminate of the present invention, the permanent depression depth measured with a load of 1000g using a jig having a compressive elastic modulus of 1.0GPa and a tip having a diameter of 0.7mm is preferably 0.5 μm or less, more preferably 0.4 μm or less, and still more preferably 0.3 μm or less on the surface on the functional layer side.

(substrate layer)

The optical laminate of the present invention includes a base material layer composed of a polyimide resin film. The polyimide resin contained in the polyimide resin film is not particularly limited as long as the optical laminate having the above-mentioned specific yield stress can be obtained. In the present specification, the polyimide-based resin means at least one resin selected from the group consisting of a polyimide resin, a polyamideimide resin, a polyimide precursor resin, and a polyamideimide precursor resin. The polyimide resin is a resin containing a repeating structural unit containing an imide group, and the polyamideimide resin is a resin containing a repeating structural unit containing both an imide group and an amide group. The polyimide precursor resin and the polyamideimide precursor resin are precursors before imidization, which provide the polyimide resin and the polyamideimide resin, respectively, by imidization, and are also called polyamic acid resins. The polyimide resin film contained in the optical layered body of the present invention may contain one kind of polyimide resin, or may contain two or more kinds of polyimide resins in combination. The polyimide resin contained in the polyimide resin film is preferably a polyimide resin or a polyamideimide resin, and more preferably a polyamideimide resin, from the viewpoint of facilitating the reduction of the occurrence of dents due to contact with external elements in the optical laminate of the present invention.

In a preferred embodiment of the present invention, the polyimide resin is preferably an aromatic resin, from the viewpoint of further reducing the occurrence of depressions due to contact with external elements and from the viewpoint of improving chemical stability. In the present specification, the aromatic resin means a resin in which the structural unit contained in the polyimide resin is mainly an aromatic structural unit.

In the preferred embodiment, the proportion of the structural unit derived from the aromatic monomer to the total structural units contained in the polyimide resin is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and even more preferably 85 mol% or more, from the viewpoint of further reducing the occurrence of sink marks due to contact with external elements and from the viewpoint of improving chemical stability. Here, the structural unit derived from an aromatic monomer is a structural unit at least a part of which includes an aromatic structure, for example, an aromatic ring, derived from a monomer at least a part of which includes an aromatic structure, for example, an aromatic ring. Examples of the aromatic monomer include an aromatic tetracarboxylic acid compound, an aromatic diamine, and an aromatic dicarboxylic acid.

In a preferred embodiment of the present invention, the polyimide-based resin may be a polyimide-based resin containing a structural unit represented by formula (1),

[ in formula (1), Y represents a 4-valent organic group, X represents a 2-valent organic group, and X represents a bonding end ], and Y in formula (1) includes a structure represented by formula (3),

[ formula (3) wherein R ¹ Independently of one another, represents a halogen atom, an alkyl, alkoxy, aryl or aryloxy group optionally having a halogen atom, R ² ～R ⁵ Independently of each other, a hydrogen atom or a monovalent hydrocarbon group optionally having a halogen atom,

m independently of one another represents an integer of 0 to 3,

n represents an integer of 1 to 4,

* Represents a bonding terminal, and has R ² ～R ⁵ In at least one benzene ring of (2), R ² ～R ⁵ At least three of them being monovalent hydrocarbon groups optionally having halogen atoms]。

In formula (1), Y independently represents a 4-valent organic group, preferably a 4-valent organic group having 4 to 80 carbon atoms, and more preferably a 4-valent organic group having 4 to 60 carbon atoms and having a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. The above organic group is an organic group in which a hydrogen atom in an organic group is optionally substituted with a substituent, preferably a halogen atom, a monovalent hydrocarbon group optionally having a halogen atom, such as an alkyl group, an aryl group or the like, an alkoxy group or an aryloxy group, in which case the carbon number of the monovalent hydrocarbon group optionally having a halogen atom, the alkoxy group or the aryloxy 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.

The polyimide-based resin preferably contains a structure represented by formula (3) as Y in formula (1). In the formula (3), R ¹ Independently of one another, represents a halogen atom, an alkyl group optionally having a halogen atom, an alkoxy group, an aryl group or an aryloxy group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a 2-methyl-butyl group, a 3-methylbutyl group, a 2-ethyl-propyl group, and a n-hexyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and a cyclohexyloxy group. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. Examples of the aryloxy group include a phenoxy group, a naphthoxy group, and a biphenyloxy group. R ¹ Independently of one another, the alkyl group having 1 to 6 carbon atoms, which may have a halogen atom, an alkoxy group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an aryloxy group having 6 to 12 carbon atoms is preferred. In the optical laminate comprising a polyimide-based resin film, R is a group that is likely to further reduce the occurrence of depressions due to contact with external elements and is likely to improve the transparency ¹ Independently of each other, an alkyl group or an alkoxy group having an optional halogen atom is preferable, and an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms having an optional halogen atom is more preferable.

In formula (3), m independently represents an integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0, from the viewpoint of facilitating reduction of dishing and improvement of transparency in the optical laminate.

In the formula (3), R ² 、R ³ 、R ⁴ And R ⁵ Independently of one another, represents a hydrogen atom or optionally a halogen atomA monovalent hydrocarbon group having R ² ～R ⁵ In at least one benzene ring of (2), R ² ～R ⁵ At least three of them are monovalent hydrocarbon groups optionally having halogen atoms. Examples of the hydrocarbon group include an aromatic hydrocarbon group, an alicyclic hydrocarbon group, and an aliphatic hydrocarbon group. Examples of the aromatic hydrocarbon group include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenyl. Examples of the alicyclic hydrocarbon group include a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group. Examples of the aliphatic hydrocarbon group include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl 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, an n-hexyl group, an n-heptyl group, an n-octyl group, a tert-octyl group, an n-nonyl group, and an n-decyl group. Examples of the halogen atom include those described above. R ² ～R ⁵ Independently of each other, it preferably represents a hydrogen atom, or an aryl group having 6 to 12 carbon atoms, a cycloalkyl group having 4 to 8 carbon atoms, or an alkyl group having 1 to 6 carbon atoms, which may have a halogen atom. From the viewpoints of solubility of the resin in a solvent, easy reduction of dishing in the optical layered body, and easy improvement of transparency, R ² ～R ⁵ Independently of each other, a hydrogen atom or an alkyl group having an optional halogen atom is preferable, a hydrogen atom or an alkyl group having 1 to 6 carbon atoms having an optional halogen atom is more preferable, and a hydrogen atom or an alkyl group having 1 to 3 carbon atoms having an optional halogen atom is further preferable.

When in formula (3) has R ² ～R ⁵ In at least one benzene ring of (2), R ² ～R ⁵ When at least three of them are monovalent hydrocarbon groups optionally having halogen atoms, it is easy to reduce the dishing in the optical layered body. In addition, the solubility of the polyimide resin in a solvent can be improved.

From the viewpoint of solubility of the resin in a solvent, ease of reducing dishing in the optical layered body, and ease of improving transparency, when n is 2 or more, R is more preferably contained ² ～R ⁵ In at least two benzene rings of (2), R ² ～R ⁵ At least three of them are monovalent hydrocarbon groups optionally having halogen atoms, and further preferably having R ² ～R ⁵ In all benzene rings of (2), R ² ～R ⁵ At least three of them are monovalent hydrocarbon groups optionally having halogen atoms.

In formula (3), n represents an integer of 1 to 4, and is preferably an integer of 1 to 3, more preferably 2 or 3, and even more preferably 2, from the viewpoints of easily improving the tensile elastic modulus and transparency of the polyimide-based resin film and easily reducing the occurrence of sag in the optical laminate. The structural unit represented by formula (1) may include one or more structures represented by formula (3) as Y.

In a preferred embodiment of the present invention, formula (3) is represented by formula (3').

[ in formula (3'), a symbol represents a bonding end ]

That is, at least a part of Y in formula (1) is represented by formula (3'). In this manner, the optical layered body can be easily reduced in the number of depressions, and the transparency can be easily improved.

In one embodiment of the present invention, the proportion of the structural unit represented by formula (3) in Y among the structural units represented by formula (1) is preferably 10 mol% or more, more preferably 30 mol% or more, further preferably 45 mol% or more, further preferably 50 mol% or more, particularly preferably 55 mol% or more, preferably less than 70 mol%, more preferably 65 mol% or less, further preferably 62 mol% or less, and particularly preferably 60 mol% or less, relative to the total molar amount of the structural units represented by formula (1). When the ratio of the structural unit represented by formula (3) for Y is not less than the above lower limit, the optical layered body can be easily reduced in dishing. When the ratio of the structural unit represented by formula (3) for Y is not more than the upper limit, the transparency of the optical laminate can be easily improved. The proportion of the structural unit represented by the formula (3) for Y can be used, for example ¹ H-NMR, or may be calculated from the charge ratio of the raw materials.

The polyimide-based resin further preferably contains a structure represented by formula (5) as Y in formula (1),

[ in the formula (5), B represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group optionally having a halogen atom, -SO ₂ -、-S-、-CO-、-COO-、-PO-、-PO ₂ -、-N(R ^B1 ) -or-Si (R) ^B2 ) ₂ -，

R ^B1 And R ^B2 Independently of one another, represents a hydrogen atom or an alkyl group optionally having a halogen atom,

R ⁷ independently of one another, represents a halogen atom, an alkyl group, an alkoxy group, an aryl group or an aryloxy group, optionally having a halogen atom,

t independently of one another represents an integer from 0 to 3,

* Representing a bond end ]. In the case where the structure represented by formula (5) is further included as Y in formula (1), it is easy to further reduce the dishing in the optical laminate, and it is easy to further improve the transparency.

In the formula (5), R ⁷ Independently of one another, represents a halogen atom, an alkyl group optionally having a halogen atom, an alkoxy group, an aryl group or an aryloxy group. As the halogen atom, the alkyl group, alkoxy group, aryl group and aryloxy group which may have a halogen atom, R is exemplified as R of the formula (3) ¹ Those illustrated. From the viewpoint of reducing the number of depressions in the optical layered body and improving the transparency, R is ⁷ Independently of each other, an alkyl group having 1 to 6 carbon atoms optionally having a halogen atom is preferable, and an alkyl group having 1 to 3 carbon atoms optionally having a halogen atom is more preferable.

In formula (5), t represents an integer of 0 to 3, and preferably represents an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0, from the viewpoints of reducing the sag in the optical layered body and improving the transparency.

B in formula (5) independently represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group optionally having a halogen atom, -SO ₂ -、-S-、-CO-、-COO-、-PO-、-PO ₂ -、-N(R ^B1 ) -or-Si (R) ^B2 ) ₂ -，R ^B1 And R ^B2 Independently of one another, represents a hydrogen atom or an alkyl group optionally having a halogen atom.

As the divalent hydrocarbon group optionally having a halogen atom, there may be mentioned R in the formula (3) ² ～R ⁵ And (3) a divalent group obtained by further removing one hydrogen atom from the monovalent hydrocarbon group optionally having a halogen atom. The divalent hydrocarbon group optionally having a halogen atom may form a ring instead of two hydrogen atoms among the hydrogen atoms contained in the group, that is, the two hydrogen atoms may be replaced by bonding ends and the two bonding ends may be connected to form a ring, and examples of the ring include a cycloalkane ring having 3 to 12 carbon atoms. Further, as-N (R) contained in B in the formula (5) ^B1 ) -and-Si (R) ^B2 ) ₂ R in (A-C) ^B1 And R ^B2 The alkyl group optionally having a halogen atom in (1) includes R in the formula (3) ¹ The alkyl group optionally having a halogen atom in (b) and those exemplified above.

From the viewpoint of facilitating the reduction of dishing and the improvement of transparency in the optical laminate, B in the formula (5) preferably includes a single bond or a divalent hydrocarbon group optionally having a halogen atom, and more preferably includes a single bond, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -or-C (CF) ₃ ) ₂ Further preferably, a single bond, -C (CH) ₃ ) ₂ -or-C (CF) ₃ ) ₂ Further preferable examples include a single bond or-C (CF) ₃ ) ₂ - (CF) is particularly preferably-C ₃ )2-。

In a preferred embodiment of the present invention, formula (5) is represented by formula (5'),

[ in formula (5'), a bonding end is represented. That is, in a preferred aspect, at least a part of the plurality of Y in formula (1) is represented by formula (5'). In this manner, the optical layered body can be easily reduced in the number of depressions, and the transparency can be easily further improved.

Among the structural units represented by formula (1), the proportion of the structural unit represented by formula (3) in Y in formula (1) is preferably 0.1 mole or more, more preferably 0.4 mole or more, further preferably 1.0 mole or more, preferably 2.3 mole or less, more preferably 1.9 mole or less, and further preferably 1.7 mole or less, relative to 1 mole of the structural unit represented by formula (5) in Y in formula (1). When the ratio of the structural unit represented by formula (3) for Y in formula (1) to the structural unit represented by formula (5) for Y in formula (1) is not less than the lower limit, the tensile elastic modulus of the polyimide resin film can be easily increased. When the ratio is not more than the above upper limit, the optical layered body can be easily further reduced in dishing and can be easily further improved in transparency. The ratio of the structural unit represented by formula (3) for Y in formula (1) to the structural unit represented by formula (5) for Y in formula (1) can be used, for example ¹ H-NMR, or may be calculated from the charge ratio of the raw materials.

Among the structural units represented by formula (1), the proportion of the structural unit represented by formula (5) in Y in formula (1) is preferably more than 30 mol%, more preferably 35 mol% or more, further preferably 38 mol% or more, further preferably 40 mol% or more, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 55 mol% or less, further preferably 50 mol% or less, and particularly preferably 45 mol% or less, relative to the total molar amount of the structural units represented by formula (1).

When the proportion of the structural unit represented by formula (5) in Y to the total molar amount of the structural units represented by formula (1) is not less than the above-described lower limit, the optical layered body tends to further reduce dishing and to further improve transparency. When the ratio is not more than the above upper limit, the tensile elastic modulus of the polyimide resin film and the optical laminate can be easily increased. The ratio of the structural unit in which Y in the formula (1) is represented by the formula (5) can be used, for example ¹ H-NMR, or the ratio of the raw materials may be calculated.

In the present inventionIn one embodiment, the total proportion of the structural unit represented by the formula (3) for Y and the structural unit represented by the formula (5) for Y is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and preferably 100 mol% or less, based on the total molar amount of the structural units represented by the formula (1). When the total ratio is in the above range, the tensile elastic modulus and the transparency of the polyimide resin film are easily improved, and the sag of the optical laminate is easily further reduced. The total ratio can be used, for example ¹ H-NMR, or may be calculated from the charge ratio of the raw materials.

In addition to the structure shown in formula (3), formula (1) may also include, as Y, the structure shown in formula (5) and the structures shown in formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), and formula (29), as the case may be.

[ formula (20) to formula (29) ] represents a bonding end, W ¹ Represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group optionally having a halogen atom, such as-CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -and etc, -Ar-, -SO ₂ -、-S-、-CO-、-PO-、-PO ₂ -、-N(R ^W1 )-、-Si(R ^W2 ) ₂ -、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH ₂ -Ar-、-Ar-C(CH ₃ ) ₂ -Ar-or-Ar-SO ₂ -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms and optionally having a fluorine atom, and specific examples thereof include a phenylene group. R ^W1 And R ^W2 Independently of one another, represents a hydrogen atom or an alkyl group optionally having a halogen atom. Y in formula (1) may be a group in which a hydrogen atom in a group represented by formula (20) to formula (29) is substituted with a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group; and a chain hydrocarbon group having 4 or less carbon atoms and 6 or less carbon atoms. In addition, among formulas (20) to (29), the following are preferredThe hydrogen atom on the ring is optionally substituted by 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 R of the formula (3) ¹ But those exemplified above.

Among the groups represented by formulae (20) to (29), the group represented by formula (26), formula (28) or formula (29) is preferable, and the group represented by formula (26) is more preferable, from the viewpoints that the number of depressions in the optical laminate is further reduced, the tensile elastic modulus is further increased, and the transparency is further improved. In addition, W is easy to further reduce the sag in the optical laminate, to improve the tensile elastic modulus, and to further improve the transparency ¹ Preferably represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -or-C (CF) ₃ ) ₂ -, more preferably represents a single bond, -O-, -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) 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 -particularly preferably-C (CF) ₃ ) ₂ -。

In formula (1), X represents a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms.

In the present invention, the polyimide-based resin in formula (1) preferably contains at least one of a divalent aromatic group, a divalent alicyclic group, and a divalent aliphatic group, and more preferably contains a divalent aromatic group, from the viewpoints that the sag is further reduced, the tensile elastic modulus is easily increased, and the transparency is further easily improved in the optical laminate. Examples of the divalent aromatic group include: as R in formula (3) ² ～R ⁵ A divalent aromatic hydrocarbon group in which one hydrogen atom is replaced with a bonding end among the hydrogen atoms in the above-mentioned exemplary aromatic hydrocarbon groups; at least one of the divalent aromatic hydrocarbon groupsPlural or more via linking groups, e.g. V described later ¹ And a group obtained by bonding the linking groups. Examples of the divalent alicyclic group include: as R in formula (3) ² ～R ⁵ A divalent alicyclic hydrocarbon group in which one hydrogen atom is replaced with a bonding end among the hydrogen atoms in the above-exemplified alicyclic hydrocarbon groups; at least one or more of the divalent alicyclic hydrocarbon groups is bonded via a linking group, e.g., V described later ¹ And a group obtained by bonding the linking groups. Examples of the divalent aliphatic group include: as R in formula (3) ² ～R ⁵ A divalent aliphatic hydrocarbon group in which one hydrogen atom is replaced with a bonding end among the hydrogen atoms in the above-exemplified aliphatic hydrocarbon groups; at least one of the divalent aliphatic hydrocarbon groups is bonded via a linking group, for example, V described later ¹ And a group obtained by bonding the linking groups.

X in formula (1) preferably represents a divalent organic group having 4 to 40 carbon atoms and having a cyclic structure such as an alicyclic ring, aromatic ring, heterocyclic ring structure, etc., more preferably represents a divalent aromatic group having 4 to 40 carbon atoms and a divalent alicyclic group having 4 to 40 carbon atoms, and still more preferably represents a divalent aromatic group having 4 to 40 carbon atoms. With respect to the organic group, the hydrogen atom in the organic group is optionally substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in that case, the carbon number of 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 may include a plurality of kinds of X, and the plurality of kinds of X may be the same or different. Examples of X include: a group represented by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) or formula (18); a group in which a hydrogen atom in the group represented by the formulae (10) to (18) is substituted 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.

[ formula (10) to formula (18),

* Which is indicative of a bond end,

V ¹ 、V ² and V ³ Independently of each other, represents a single bond, -O-, -S-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -CO-or-N (Q) -. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms and optionally having a halogen atom.]

Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms and optionally having a halogen atom include R of the formula (3) ² ～R ⁵ The monovalent hydrocarbon group optionally having a halogen atom of (1) and those exemplified above.

In one example, V ¹ And V ³ Is a single bond, -O-or-S-, and V ² is-CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -or-SO ₂ -。V ¹ And V ² Bonding position with respect to each ring, and V ² And V ³ The bonding position to each ring is preferably meta-or para-position, and more preferably para-position, independently from each ring. The hydrogen atom on the ring in the formulae (10) to (18) is optionally substituted by 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 R of the formula (3) ¹ But those exemplified above.

In a preferred embodiment of the present invention, the polyimide-based resin may include a structure represented by formula (4) as X in formula (1),

[ in the formula (4), A represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group optionally having a halogen atom, -SO ₂ -、-S-、-CO-、-PO-、-PO ₂ -、-N(R ^A1 ) -or-Si (R) ^A2 ) ₂ -，

R ^A1 And R ^A2 Independently of one another, represents a hydrogen atom or optionally has a halogen atom(ii) an alkyl group of a subgroup,

R ⁶ independently of one another, represents a halogen atom, an alkyl group, an alkoxy group, an aryl group or an aryloxy group, optionally having a halogen atom,

s independently of one another represent an integer from 0 to 4,

* Representing a bond end ]. In this manner, the tensile modulus and the transparency of the polyimide resin film and the optical laminate can be easily improved, and the optical laminate can be easily subjected to further reduction in dishing. In addition, the structural unit represented by formula (1) may contain one or more structures represented by formula (4) as X.

R ⁶ Independently of one another, represents a halogen atom, an alkyl group optionally having a halogen atom, an alkoxy group, an aryl group or an aryloxy group. Examples of the halogen atom, the alkyl group optionally having a halogen atom, the alkoxy group, the aryl group or the aryloxy group may include R of the formula (3) ¹ But those exemplified above.

Among these, R is a group that is easy to improve the tensile elastic modulus and transparency of the polyimide resin film and the optical laminate, and is easy to further reduce the dishing in the optical laminate ⁶ Independently of each other, an alkyl group having 1 to 6 carbon atoms or a haloalkyl group having 1 to 6 carbon atoms is preferable, an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms is more preferable, and a perfluoroalkyl group is preferable. In a preferred mode, R ⁶ Independently of one another, methyl, chloro or trifluoromethyl. s independently represents an integer of 0 to 4, and is preferably an integer of 1 to 3, more preferably 1 or 2, and even more preferably 1, from the viewpoints of easily improving the tensile elastic modulus and transparency of the polyimide resin film and the optical laminate and easily reducing the occurrence of a dent in the optical laminate.

In a preferred embodiment of the present invention, it is preferred that s is 1 and R is bonded to the ortho-position based on-A-for each benzene ring ⁶ Is substituted and R ⁶ Is methyl, fluoro, chloro or trifluoromethyl.

In formula (4), the position of the bonding end is preferably meta-or para-position, more preferably para-position, based on-a-from the viewpoints of easily improving the tensile elastic modulus and transparency of the polyimide-based resin film and the optical laminate and easily reducing the dishing of the optical laminate.

A in the formula (4) independently represents a single bond, -O-, diphenylmethylene, a divalent hydrocarbon group optionally having a halogen atom, -SO ₂ -、-S-、-CO-、-PO-、-PO ₂ -、-N(R ^A1 ) -or-Si (R) ^A2 ) ₂ -，R ^A1 And R ^A2 Independently of one another, represents a hydrogen atom or an alkyl group optionally having a halogen atom.

As the divalent hydrocarbon group optionally having a halogen atom, there may be mentioned R in the formula (3) ² ～R ⁵ And (3) a divalent group obtained by further removing one hydrogen atom from the monovalent hydrocarbon group optionally having a halogen atom. The divalent hydrocarbon group optionally having a halogen atom may form a ring instead of two hydrogen atoms among the hydrogen atoms contained in the group, that is, the two hydrogen atoms may be replaced with bonding ends and the two bonding ends may be connected to form a ring, and examples of the ring include a cycloalkane ring having 3 to 12 carbon atoms. Further, the group represented by formula (4) is represented by-N (R) contained in A ^A1 ) -and-Si (R) ^A2 ) ₂ R of (A-C) ^A1 And R ^A2 The alkyl group optionally having a halogen atom in (1) includes R in the formula (3) ¹ The alkyl group optionally having a halogen atom in (b) and those exemplified above.

Preferred examples of a in formula (3) include a single bond and-CH from the viewpoints of further reducing the sag, improving the tensile elastic modulus, and further improving the transparency of the optical laminate ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -or-C (CF) ₃ ) ₂ More preferably, a single bond, -C (CH) ₃ ) ₂ -or-C (CF) ₃ ) ₂ Further preferably, a single bond or-C (CF) is mentioned ₃ ) ₂ Particularly preferred is a single bond.

In a preferred embodiment of the present invention, from the viewpoint of easily improving the tensile elastic modulus and transparency of the polyimide-based resin film and the optical laminate and easily further reducing the dishing in the optical laminate, in the formula (4),R ⁶ independently of each other, a C1-6 haloalkyl group, s 1 or 2, A a single bond, -C (CH) ₃ ) ₂ -or-C (CF) ₃ ) ₂ -。

In a preferred embodiment of the present invention, formula (4) is represented by formula (4'),

that is, at least a part of the plurality of xs in formula (1) is preferably represented by formula (4'). In this manner, the optical laminate can be easily reduced in the number of depressions, can be easily improved in tensile elastic modulus, and can be easily further improved in transparency.

In one embodiment of the present invention, when the structure represented by formula (4) is contained as X in formula (1), the proportion of the structural unit represented by formula (4) in X is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, further preferably 80 mol% or more, particularly preferably 90 mol% or more, and preferably 100 mol% or less, relative to the total molar amount of the structural units represented by formula (1). When the ratio of the structural unit represented by formula (4) in X is in the above range, the optical laminate is likely to have further reduced dishing and to have further improved tensile elastic modulus. The ratio of the structural unit represented by the formula (4) for X can be used, for example ¹ H-NMR, or the ratio of the raw materials may be calculated.

In a preferred embodiment of the present invention, the plurality of structural units represented by formula (1) preferably further include a structural unit represented by formula (9) in addition to the structural unit represented by formula (5). When Y is further contained in the structural unit represented by formula (9), the optical laminate is likely to further reduce dishing and to further increase the tensile elastic modulus.

The polyimide-based resin containing the structural unit represented by the formula (1) may be a polyamideimide resin further having the structural unit represented by the formula (2),

[ in formula (2), Z and X independently represent a divalent organic group, and represent a bonding end ]. The following describes formula (2). In this respect, from the viewpoint of facilitating reduction of breakage and whitening upon folding of the optical laminate and further facilitating improvement of the elastic modulus, the proportion of the amide component contained in the polyamideimide resin is preferably 5 mol% or more, more preferably 10 mol%, further preferably 15 mol% or more, and still further preferably 20 mol% or more, relative to the amount of the entire structural units contained in the polyamideimide resin.

In formula (2), Z is a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms optionally 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 (the hydrogen atoms in these groups are optionally substituted with a halogen atom, preferably a fluorine atom), more preferably a divalent organic group having 4 to 40 carbon atoms having a cyclic structure optionally 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 (the hydrogen atoms in these groups are optionally substituted with a halogen atom, preferably a fluorine atom). Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include R in the following formula (3) ^3a And R ^3b The same applies to the illustrations of (1). Examples of the cyclic structure include an alicyclic structure, an aromatic ring, and a heterocyclic structure. Examples of the organic group of Z include a group in which two non-adjacent groups are replaced with a hydrogen atom and a divalent chain hydrocarbon group having 6 or less carbon atoms among the bonding ends 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), examples of the heterocyclic structure of Z include a group having a thiophene ring skeleton,

in [ formula (20) to formula (29), W ¹ Represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-Ar-、-SO ₂ -、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH ₂ -Ar-、-Ar-C(CH ₃ ) ₂ -Ar-or-Ar-SO ₂ Ar-in which Ar independently represents an arylene group having 6 to 20 carbon atoms (e.g., phenylene group) in which a hydrogen atom is optionally substituted by a fluorine atom, and represents a bonding end]. From the viewpoint of easily reducing the YI value of the polyimide-based resin film, easily improving the total light transmittance, and easily reducing the haze, the cyclic structure in Z is preferably a group represented by formulae (20) to (29) or a group having a thiophene ring skeleton, and more preferably a group represented by formula (26), formula (28), and formula (29).

As the organic group of Z, 2-valent organic groups represented by formula (20 '), formula (21'), formula (22 '), formula (23'), formula (24 '), formula (25'), formula (26 '), formula (27'), formula (28 ') and formula (29') are more preferable,

in [ formulae (20 ') to (29'), W ¹ And as defined in formulas (20) to (29)]. The hydrogen atoms on the ring in the formulae (20) to (29) and (20 ') to (29') are optionally 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, in which the hydrogen atoms are optionally substituted with a halogen atom (preferably a fluorine atom).

When the polyamideimide resin has a structural unit wherein Z in the formula (2) is represented by any one of the above-mentioned formulae (20 ') to (29 '), particularly when it has a structural unit wherein Z in the formula (2) is represented by the following formula (3 '), the polyamideimide resin further has a structural unit derived from a carboxylic acid represented by the following formula (d 1) in addition to the structural unit,

[ in the formula (d 1), R ⁴¹ Independently of one another, with respect to R in the following formula (3) ^3a A group as defined or a hydrogen atom, R ⁴² Represents R ⁴¹ or-C (= O) -, represents a bonding end]This is preferable from the viewpoint of easily improving the film formability of the varnish and easily improving the uniformity of the film. Specific examples of the structural unit (d 1) include R ⁴¹ And R ⁴² Structural units each of which is a hydrogen atom (structural units derived from a dicarboxylic acid compound), R ⁴¹ Are all hydrogen atoms and R ⁴² A structural unit (structural unit derived from a tricarboxylic acid compound) representing-C (= O) -, and the like.

The polyamideimide resin may contain a plurality of kinds of Z as Z in the formula (2), and the plurality of kinds of Z may be the same or different from each other. In particular, from the viewpoint of easily improving the tensile elastic modulus of the film and easily improving the optical properties, it is preferable that Z in formula (2) has at least a structural unit represented by formula (6),

[ in the formula (6), R ^3a And R ^3b Independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R ^3a And R ^3b Wherein the hydrogen atoms are independently optionally substituted by halogen atoms, and W independently represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -S-, -CO-or-N (R) ⁹ )-，R ⁹ Represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 12 carbon atoms optionally substituted with a halogen atom, s is an integer of 0 to 4, t is an integer of 0 to 4, u is an integer of 0 to 4, and represents a bonding end]More preferably a structural unit represented by the formula (6'),

[ formula (6')In, R ^3a 、R ^3b S, t, u, W and as defined in formula (6)]. In the present specification, both the case where the polyamideimide resin has the structural unit represented by the formula (6) Z in the formula (2) and the case where the polyamideimide-based resin has the structure represented by the formula (6) Z in the formula (2) have the same meaning, each mean that Z in at least a part of the structural units is represented by the formula (6) among a plurality of structural units represented by the formula (2) which the polyamideimide resin may contain, are both intended to be represented by the formula (6). This description is also applicable to other similar descriptions.

In the formulae (6) and (6'), W independently represents a single bond, -O-, -CH ₂ -、-CH ₂ -CH ₂ -、-CH(CH ₃ )-、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -, -S-, -CO-or-N (R) ⁹ ) From the viewpoint of the bending resistance of the polyimide resin film and the optical laminate, preferably represents-O-or-S-, more preferably represents-O-.

R ^3a And R ^3b Independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of 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 propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and a cyclohexyloxy group. 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. From the viewpoints of tensile modulus, surface hardness, and flexibility of the polyimide resin film and the optical laminate, R ^3a And R ^3b Independently of each other, the alkyl group preferably has 1 to 6 carbon atoms or the alkoxy group having 1 to 6 carbon atoms, and more preferably has 1 to 3 carbon atoms or the alkoxy group having 1 to 3 carbon atoms. Herein, R is ^3a And R ^3b Are independently of each other optionally substituted by halogen atoms.

R ⁹ Represents a hydrogen atomA monovalent hydrocarbon group having 1 to 12 carbon atoms optionally substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methyl-butyl group, a 3-methyl-butyl group, a 2-ethyl-propyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a tert-octyl group, an n-nonyl group, an n-decyl group, and the like, which are optionally 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.

In the formulae (6) and (6'), t and u are each independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 1 or 2.

In the formulae (6) and (6'), s is an integer in the range of 0 to 4, and when s is in this range, the tensile elastic modulus and the bending resistance of the polyimide-based resin film and the optical laminate are easily improved, and further the dishing in the optical laminate is easily reduced. In the formulae (6) and (6'), s is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, even more preferably 0 or 1, and even more preferably 0, from the viewpoint of facilitating further improvement in the tensile elastic modulus and the bending resistance of the polyimide-based resin film and the optical laminate. The polyamideimide resin may include one or more than two kinds of structural units represented by formula (6) or formula (6') in Z.

In a preferred embodiment of the present invention, from the viewpoint of improving the tensile elastic modulus and the bending resistance of the polyimide-based resin film and the optical laminate and reducing the YI value, Z is preferably represented by formula (6) or formula (6') in which s is 0 and u is preferably 1 to 3, more preferably 1 or 2. Further, it is also preferable that the structural unit represented by the above formula (d 1) is contained in addition to the structural unit represented by the formula (2) having Z represented by the formula (6) or the formula (6') in which s is 0.

When the polyamideimide resin has the structural unit represented by formula (6) or formula (6'), the proportion thereof is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, and further 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) of the polyamideimide resin is 100 mol%More preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, and still more preferably 80 mol% or less. When the proportion of the structural unit represented by formula (6) or formula (6') is not less than the above lower limit, the tensile elastic modulus and the bending resistance of the polyimide-based resin film and the optical laminate can be easily improved. When the proportion of the structural unit represented by formula (6) or formula (6') is not more than the above upper limit, it is easy to suppress an increase in viscosity of the varnish containing the resin due to hydrogen bonds between amide bonds derived from formula (6), and to improve the film processability. The proportion of the structural unit represented by formula (1), formula (2), formula (6) or formula (6') may be used, for example ¹ H-NMR, or may be calculated from the charge ratio of the raw materials.

In a preferred embodiment of the present invention, Z in the polyamideimide resin is a structural unit represented by formula (6) or formula (6') wherein s is 0 to 4, preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, and still more preferably 50 mol% or more. When the above lower limit or more of Z is a structural unit represented by formula (6) or formula (6') in which s is 0 to 4, the tensile modulus and the bending resistance of the polyimide-based resin film and the optical laminate can be easily improved. 100 mol% or less of Z in the polyamideimide resin may be a structural unit represented by formula (6) or formula (6') wherein s is 0 to 4. The proportion of the structural unit represented by formula (6) or formula (6') wherein s is 0 to 4 in the resin can be used, for example ¹ H-NMR, or may be calculated from the charge ratio of the raw materials.

When the polyimide resin is a polyamideimide resin, the content of the structural unit represented by formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol or more, further preferably 1.0 mol or more, further preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, and further preferably 4.5 mol or less based on 1 mol of the structural unit represented by formula (1). When the content of the structural unit represented by formula (2) is not less than the above lower limit, the impact resistance and tensile elastic modulus of the polyimide-based resin film and the optical laminate can be easily improved. When the content of the structural unit represented by formula (2) is not more than the upper limit, thickening due to hydrogen bonds between amide bonds in formula (2) is easily suppressed, and the processability of the polyimide resin film is easily improved.

The polyimide-based resin may contain a structural unit represented by formula (30) and/or a structural unit represented by formula (31), and 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, optionally, formula (2).

In formula (30), Y ¹ Is a 4-valent organic group, preferably an organic group in which a hydrogen atom in the organic group is optionally substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ¹ Examples thereof 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), groups in which a hydrogen atom in the groups represented by formula (20) to formula (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and chain hydrocarbon groups having a valence of 4 and a number of carbon of 6 or less. In one embodiment of the present invention, the polyimide-based resin may include a plurality of kinds of Y ¹ Plural kinds of Y ¹ May be the same or different from each other.

In formula (31), Y ² Is a trivalent organic group, preferably an organic group in which a hydrogen atom in the organic group is optionally substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine. As Y ² Examples thereof include a group in which any one of the bonding ends of the groups represented by the above formulae (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29) is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may include a plurality of kinds of Y ² Plural kinds of Y ² May be the same or different from each other.

In the formulae (30) and (31), X ¹ And X ² Independently of each otherIs a divalent organic group, preferably an organic group in which a hydrogen atom in the organic group is optionally substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As X ¹ And X ² Examples thereof include groups represented by the above formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group in which a hydrogen atom in the group represented by the formula (10) to (18) is substituted 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 a structural unit represented by formula (1) and/or formula (2), and optionally a structural unit represented by formula (30) and/or formula (31). In addition, from the viewpoint of easily improving the reduction of the dent in the optical laminate, the bending resistance, and the transparency and tensile elastic modulus of the polyimide resin film, the proportion of the structural unit represented by formula (1) and formula (2) in the polyimide resin is preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more, based on all the structural units represented by formula (1) and formula (2) and, in some cases, 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 based on all the structural units represented by the formulae (1) and (2) and, in some cases, the formulae (30) and (31). The above ratio can be used, for example ¹ H-NMR, or may be calculated from the charge ratio of the raw materials.

In one embodiment of the present invention, the content of the polyimide-based resin in the polyimide-based resin film is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, further preferably 50 parts by mass or more, and preferably 99.5 parts by mass or less, more preferably 95 parts by mass or less, per 100 parts by mass of the film. When the content of the polyimide-based resin is within the above range, the chemical stability, optical characteristics, impact resistance, and tensile elastic modulus of the polyimide-based resin film are easily improved, and the depressions in the optical laminate are easily further reduced.

From the viewpoint of reducing the dishing easily in the optical laminate and improving the tensile elastic modulus and the bending resistance easily, the weight average molecular weight of the polyimide resin is preferably 200,000 or more, more preferably 230,000 or more, further preferably 250,000 or more, further preferably 270,000 or more, particularly preferably 280,000 or more, and particularly preferably 300,000 or more in terms of standard polystyrene. From the viewpoint of easily improving the solubility of the resin in a solvent and easily improving the stretchability and processability of the polyimide resin film, the weight average molecular weight of the polyimide resin is preferably 1,000,000 or less, more preferably 800,000 or less, even more preferably 700,000 or less, and even more preferably 500,000 or less. The weight average molecular weight can be determined by GPC measurement and conversion to standard polystyrene, for example.

In a preferred embodiment of the present invention, the polyimide resin contained in the polyimide resin film may contain a halogen atom such as a fluorine atom which can be introduced by the fluorine-containing substituent or the like. When the polyimide resin contains a halogen atom, the tensile elastic modulus of the polyimide resin film and the optical laminate can be easily increased, and the YI value can be easily reduced. When the YI value of the polyimide resin film is low, the transparency and the visibility of the film are easily improved. The halogen atom is preferably a fluorine atom. Preferred examples of the 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 tensile elastic modulus of the polyimide resin film and the optical laminate can be further improved, the YI value can be further reduced, and the transparency and the visibility can be further improved. When the content of the halogen atom is not more than the above upper limit, the synthesis becomes easy.

In another preferred embodiment of the present invention, the content of silicon atoms contained in the polyimide resin is preferably small because the glass transition temperature tends to decrease when the silicon atoms are contained. The content of the silicon atom contained in the polyimide resin is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and still more preferably 0.5% by mass or less, based on the mass of the polyimide resin. Particularly, the polyimide resin is preferably substantially free of silicon atoms.

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 characteristics of the polyimide-based resin film and the optical laminate. The upper limit of the imidization rate is 100% or less. The imidization ratio indicates a ratio of a molar amount of an imide bond in the polyimide-based resin to a value twice as large as a molar amount of a structural unit 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 a ratio of twice the molar amount of the structural unit derived from a tetracarboxylic acid compound in the polyimide resin to the total molar amount of the structural units derived from a tricarboxylic acid compound. The imidization ratio can be determined by an IR method, an NMR method, or the like.

The yield stress at a tensile rate of 0.1 m/sec of the polyimide-based resin film included as the base layer in the optical laminate of the present invention is preferably 200MPa or more, more preferably 210MPa or more, more preferably 220MPa or more, further preferably 230MPa or more, and still further preferably 240MPa or more. When the yield stress of the polyimide-based resin film is less than the lower limit, the functional layer is likely to be deformed with a large strain together with the optical layered body when pressure is applied, and depressions generated on the surface due to external contact via the functional layer are likely to remain. When the yield stress of the polyimide resin film is not less than the lower limit, the occurrence of depressions on the surface due to contact with external elements can be easily reduced, and the recovery of the depressions can be easily improved. From the viewpoint of more easily improving the folding resistance of the optical laminate, the yield stress of the polyimide-based resin film at a tensile rate of 0.1 m/sec is preferably 400MPa or less, and more preferably 300MPa or less. The yield stress is a value obtained from a stress-strain curve obtained by a tensile test according to ASTM D638-14 at a tensile speed of 0.1 m/sec using a polyimide resin film as a measurement sample, and can be measured, for example, by the method described in examples.

The thickness of the polyimide resin film is preferably 5 μm or more, more preferably 10 μm or more, further preferably 20 μm or more, further preferably 25 μm or more, particularly preferably 30 μm or more, particularly preferably 40 μm or more, very preferably 45 μm or more, preferably 200 μm or less, more preferably 100 μm or less, further preferably 80 μm or less, particularly preferably 60 μm or less, and a combination of these upper and lower limits may be used. When the thickness of the polyimide resin film is within the above range, the yield stress of the optical layered body can be easily adjusted to be within the above range, and the dishing can be easily reduced in the optical layered body.

The tensile elastic modulus, the folding endurance, the YI value, the total light transmittance and the haze of the polyimide resin film included as the base layer in the optical laminate of the present invention are preferably within the preferable ranges described above for the optical laminate of the present invention, from the viewpoint of easily obtaining the above-described characteristics of the optical laminate.

The polyimide resin and the polyimide precursor resin can be produced, for example, from tetracarboxylic acid compounds and diamine compounds as main raw materials, and the polyamideimide resin and the polyamideimide precursor resin can be produced, for example, from tetracarboxylic acid compounds, dicarboxylic acid compounds and diamine compounds as main raw materials.

The tetracarboxylic acid compound used for the production of the polyimide-based resin preferably contains at least a compound represented by the formula (X),

[ in the formula (X), R ¹ ～R ⁵ N and m are each independently of R in formula (3) ¹ ～R ⁵ N and m are the same]More preferably further comprises a compound represented by the formula (Y),

[ in the formula (Y), B and R ⁷ And t is independently from B and R in the formula (5) ⁷ Same as t]。

The compound represented by the formula (X) can be obtained by a conventional method, for example, by reacting trimellitic anhydride or a derivative thereof with an aromatic diol, or a commercially available product can be used.

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

Examples of the tetracarboxylic acid compound used for 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 two or more kinds thereof may be used in combination. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound, in addition to the dianhydride.

Examples of the tetracarboxylic acid compound used for the production of the resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic acid dianhydride. The tetracarboxylic acid compound may be used alone, or two or more thereof may be used in combination. 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. <xnotran> , 4,4'- ,3,3', 4,4'- ,2,2', 3,3'- ,3,3', 4,4'- (, BPDA), 2,2',3,3'- ,3,3', 4,4'- ,2,2- (3,4- ) ,2,2- (2,3- ) ,2,2- (3,4- ) ,4,4' - ( ) (, 6 FDA), 1,2- (2,3- ) ,1,1- (2,3- ) ,1,2- (3,4- ) ,1,1- (3,4- ) , (3,4- ) , (2,3- ) ,4,4'- ( ) ,4,4' - ( ) . </xnotran> Examples of the monocyclic aromatic tetracarboxylic acid dianhydride include 1,2,4,5-benzenetetracarboxylic acid dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic acid dianhydride include 2,3,6,7-naphthalenetetracarboxylic acid dianhydride.

Among these, preferred are 4,4' -oxydiphthalic dianhydride, 3,3',4,4' -benzophenonetetracarboxylic dianhydride, 2,2',3,3' -benzophenonetetracarboxylic dianhydride, BPDA, 2,2',3,3' -biphenyltetracarboxylic dianhydride, 3,3',4,4' -diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 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' - (di-o-phenylenedicarboxylic) methane dianhydride and di (4 ' - (m-phenylenedidianhydride, more preferably, 4,4' -oxydiphthalic dianhydride, BPDA, 2,2',3,3' -biphenyltetracarboxylic dianhydride, 6FDA, bis (3, 4-dicarboxyphenyl) methane dianhydride and 4,4' - (p-phenylenedioxy) diphthalic dianhydride are mentioned. These may be used alone or in combination of two 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' -tetracarboxylic dianhydride and positional isomers thereof. These may be used alone or in combination of two 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 two or more. In addition, a combination of a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used.

Among the tetracarboxylic dianhydrides, 4' -oxydiphthalic dianhydride, 3' are preferred from the viewpoint of high impact resistance, high tensile elastic modulus, high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring property of the polyimide-based resin film and the optical laminate, 4,4' -benzophenone tetracarboxylic dianhydride, BPDA, 2', 3' -biphenyl tetracarboxylic dianhydride, 3', 4' -diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 6FDA and a mixture thereof, more preferably BPDA and 6FDA and a mixture thereof, and further preferably 6FDA and BPDA.

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

Examples of the aliphatic diamine include acyclic aliphatic diamines such as 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 two or more.

<xnotran> , , ,2,4- , , ,1,5- ,2,6- ,4,4' - ,4,4' - ,4,4' - ,3,4 ' - ,3,3' - ,4,4' - ,3,4 ' - , </xnotran> 3,3' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2' -dimethylbenzidine aromatic diamines having two or more aromatic rings, such as 2,2' -bis (trifluoromethyl) -4,4' -diaminodiphenyl (may be referred to as TFMB), 4' -bis (4-aminophenoxy) biphenyl, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, and 9, 9-bis (4-amino-3-fluorophenyl) fluorene. These may be used alone or in combination of two or more.

<xnotran> 4,4'- ,4,4' - ,4,4'- ,3,3' - ,4,4'- ,3,3' - ,1,4- (4- ) , 〔 4- (4- ) 〕 , 〔 4- (3- ) 〕 ,2,2- [4- (4- ) ] ,2,2- [4- (3- ) ] ,2,2 '- , TFMB, 4,4' - (4- ) , 4,4'- ,4,4' - ,4,4'- ,4,4' - ,1,4- (4- ) , 〔 4- (4- ) 〕 ,2,2- [4- (4- ) ] ,2,2 '- , TFMB, 4,4' - (4- ) . </xnotran> These may be used alone or in combination of two or more.

Among the above diamine compounds, from the viewpoint of high tensile elastic modulus, high transparency, high flexibility, high bending resistance and low coloring property of the polyimide-based resin film, at least one selected from aromatic diamines having a biphenyl structure is preferably used. More preferably, at least one selected from the group consisting of TFMB, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) benzidine, 4 '-bis (4-aminophenoxy) biphenyl, and 4,4' -diaminodiphenyl ether is used, and still more preferably, TFMB is used.

As the dicarboxylic acid compound used for the production of the resin, terephthalic acid, isophthalic acid, 4' -oxybis benzoic acid, or an acid chloride compound thereof is preferably used. In addition to terephthalic acid, isophthalic acid, 4' -oxybis-benzoic acid or their acid chloride compounds, other dicarboxylic acid compounds may also be used. Examples of the other dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds and acid anhydrides, and two or more of them may be used in combination. Specific examples thereof include isophthalic acid; naphthalene dicarboxylic acid; 4,4' -biphenyldicarboxylic acid; 3,3' -biphenyldicarboxylic acid; dicarboxylic acid compound of chain hydrocarbon having carbon number of 8 or less and single bond, -CH for two benzoic acids ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ A compound in which a-or phenylene group is bonded, and an acid chloride compound thereof. Specifically, 4' -oxybis (benzoyl chloride) (hereinafter, may be referred to as OBBC), terephthaloyl chloride (hereinafter, may be referred to as TPC) or isophthaloyl chloride is preferable, and OBBC and TPC are more preferably used in combination.

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

Examples of the 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 two or more of them may be used in combination. Specific examples thereof include anhydrides of 1,2, 4-benzenetricarboxylic acid; anhydrides of 1,3, 5-benzenetricarboxylic acid; 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; single bond, -O-, -CH for phthalic anhydride and benzoic acid ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -or phenylene group.

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

In the production of the resin, the reaction temperature of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound is not particularly limited, and is, for example, 5 to 350 ℃, preferably 20 to 200 ℃, and more preferably 25 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 aspect, the reaction is stirred and carried out under normal pressure and/or an inert gas atmosphere. The reaction is preferably carried out in a solvent 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-based solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ -butyrolactone (hereinafter, sometimes referred to as GBL), 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 (hereinafter sometimes referred to as DMAc) and N, N-dimethylformamide (hereinafter sometimes referred to as DMF); sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof, i.e., mixed solvents, and the like. Among these, an amide-based solvent can be preferably used from the viewpoint of solubility.

In the imidization step in the production of the polyimide-based resin, imidization may be performed in the presence of an imidization catalyst. Examples of the imidization catalyst include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; n-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepino

Alicyclic amines (monocyclic); azabicyclo [2.2.1]Heptane, azabicyclo [3.2.1 ] s]Octane, azabicyclo [2.2.2]Octane, and azabicyclo [3.2.2]Alicyclic amines (polycyclic) such as nonane; and aromatic amines such as pyridine, 2-picoline (2-picoline ), 3-picoline (3-picoline ), 4-picoline (4-picoline ), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-lutidine, 2,4, 6-trimethylpyridine, 3, 4-cyclopentenopyridine, 5,6,7, 8-tetrahydroisoquinoline, and isoquinoline. In addition, from the viewpoint of facilitating the acceleration of 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 specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic acid anhydrides such as phthalic anhydride.

The polyimide-based resin can be isolated by separation and purification by a conventional method, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or separation means combining these, and in a preferred aspect, the resin can be isolated by adding a large amount of an alcohol such as methanol to a reaction solution containing the transparent polyimide-based resin, precipitating the resin, concentrating, filtering, drying, or the like.

The polyimide resin film may contain at least one filler in addition to the polyimide resin. Examples of the filler include organic particles and inorganic particles, and preferable examples thereof include inorganic particles. The inorganic particles include silica, zirconia, alumina, titania, 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, among which silica particles, zirconia particles and alumina particles are preferable, and silica particles are more preferable, from the viewpoint of easily improving the tensile elastic modulus of the polyimide-based resin film and the optical laminate. These fillers may be used alone or in combination of two or more.

The average primary particle diameter of the filler and preferably the silica particles is usually 1nm or more, preferably 5nm or more, more preferably 10nm or more, further preferably 11nm or more, particularly preferably 13nm 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 filler, preferably the silica particles, is within the above range, aggregation of the filler, preferably the silica particles, is easily suppressed, and the optical characteristics of the resulting polyimide-based resin film and optical laminate are improved. 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 TEM or a scanning electron microscope SEM.

When the polyimide resin film contains a filler, preferably silica particles, the content of the filler is usually 0.1 part by mass or more, preferably 1 part by mass or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, further preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 60 parts by mass or less, per 100 parts by mass of the polyimide resin film. When the content of the filler is not less than the lower limit, the tensile elastic modulus of the obtained polyimide resin film is easily improved. When the content of the filler is not more than the above upper limit, the optical properties of the polyimide resin film can be easily improved.

The polyimide resin film may further contain an ultraviolet absorber. The ultraviolet absorber may 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 one compound selected from benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds. The ultraviolet absorbers may be used alone or in combination of two or more. Since the polyimide resin film contains the ultraviolet absorber, deterioration of the resin is suppressed, and the optical layered body obtained can be improved in visibility when applied to an image display device or the like. In the present specification, the term "family compound" refers to a derivative of a compound to which the "family compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a parent skeleton and a substituent bonded to benzophenone.

When the polyimide resin film contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 6 parts by mass or less, per 100 parts by mass of the polyimide resin film. The preferable content varies depending on the ultraviolet absorber used, but when 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 polyimide resin film is improved and the transparency is easily improved.

The polyimide resin film may further contain other additives besides the filler and the ultraviolet absorber. Examples of the other additives include an antioxidant, a mold release agent, a stabilizer, a bluing agent, a flame retardant, a pH adjuster, a silica dispersant, a lubricant, a thickener, and a leveling agent. When other additives are contained, the content thereof may be preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and still more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the polyimide-based resin film.

[ method for producing polyimide resin film ]

The method for producing the polyimide resin film of the present invention is not particularly limited, and for example, a production method including at least the following steps:

(a) A varnish preparation step of preparing a resin composition (hereinafter, also referred to as a "varnish") containing at least the polyimide-based resin and a solvent,

(b) A coating step of applying a varnish to a support material to form a coating film, and

(c) And a polyimide resin film forming step of forming a polyimide resin film by drying the coating film.

In the varnish preparation step, the polyimide resin is dissolved in a solvent, and if necessary, the filler, the ultraviolet absorber, and other additives are added and mixed with stirring to prepare a varnish. When silica particles are used as the filler, a silica sol obtained by replacing a dispersion of a silica sol containing silica particles with a solvent capable of dissolving the resin, for example, a solvent used for the preparation of a varnish described below, may be added to the resin.

The solvent used for the preparation of the varnish is not particularly limited as long as it can dissolve the resin. Examples of such a solvent include amide solvents such as DMAc and DMF; lactone solvents such as GBL and gamma valerolactone; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, amide solvents or lactone solvents are preferred. These solvents may be used alone or in combination of two or more. The varnish may contain water, alcohol-based solvents, ketone-based solvents, acyclic ester-based solvents, ether-based solvents, and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, and still more preferably 5 to 15% by mass.

In the coating step, a varnish is applied to the support material 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 cast molding.

In the film forming step, the polyimide resin film can be formed by drying the coating film and peeling it from the support material. After the peeling, a step of drying the polyimide resin film may be further provided. The drying of the coating film can be usually carried out at a temperature of 50 to 350 ℃. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure. A part of the solvent contained in the varnish may slightly remain in the obtained polyimide resin film. The amount of the solvent contained in the polyimide resin film is preferably 1.5% or less, more preferably 1.2% or less, still more preferably 1.1% or less, and still more preferably 1.0% or less, based on the mass of the polyimide resin film. The lower limit of the amount of the solvent is preferably 0% or more, more preferably 0.02% or more, still more preferably 0.1% or more, and still more preferably 0.3% or more.

Examples of the support material include a metal-based SUS plate, and a resin-based resin plate include a PET film, a PEN film, a polyamide-based resin film, another polyimide-based resin film, a cycloolefin-based polymer film, and an acrylic film. Among them, from the viewpoint of excellent smoothness and heat resistance, a PET film, a cycloolefin polymer film, and the like are preferable, and from the viewpoint of adhesion to a polyimide resin film and cost, a PET film is more preferable.

[ functional layer ]

The optical laminate of the present invention comprises a base layer formed of the above polyimide resin film, and a functional layer comprising a cured product of a curable resin. Examples of the functional layer of a cured product containing the curable resin include a hard coat layer, an ultraviolet absorbing layer, a primer layer, a gas barrier layer, an adhesive layer, a color tone adjusting layer, and a refractive index adjusting layer. The optical laminate of the present invention may have one or two or more functional layers. The functional layer of the cured product containing the curable resin is preferably a hard coat layer.

When the optical laminate of the present invention has a hard coat layer as a functional layer of a cured product containing a curable resin, the thickness of the hard coat layer is not particularly limited, but is preferably 2 to 100 μm, more preferably 3 to 50 μm, and further preferably 4 to 30 μm. When the thickness of the hard coat layer is within the above range, the impact resistance can be further improved, the bending resistance is less likely to be lowered, and the problem of occurrence of curling due to curing shrinkage tends to be less likely to occur. The hard coat layer may be formed by curing a hard coat composition containing a reactive material capable of forming a crosslinked structure by irradiation with an active energy ray or by imparting thermal energy, and a hard coat layer irradiated with an active energy ray is preferable. The active energy ray is defined as an energy ray capable of decomposing a compound generating an active species to generate an active species, and includes visible light, ultraviolet light, infrared light, X-ray, α -ray, β -ray, γ -ray, electron beam, and the like, and preferably includes ultraviolet light. The hard coat composition contains at least one polymer selected from a radical polymerizable compound and a cation 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, a (meth) acryloyl group, and the like. When the radical polymerizable compound has two or more radical polymerizable groups, the radical polymerizable groups may be the same or different. The number of the radical polymerizable groups in one molecule of the radical polymerizable compound is preferably 2 or more in order to increase 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 multifunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in one molecule, an epoxy (meth) acrylate, a urethane (meth) acrylate, and an oligomer called a polyester (meth) acrylate having several (meth) acryloyl groups in a molecule and having a molecular weight of several hundred to several thousand, and preferably, one or more compounds selected from the group consisting of an epoxy (meth) acrylate, a urethane (meth) acrylate, and a polyester (meth) acrylate.

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

Among the above cationically polymerizable compounds, preferred are compounds having at least one 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. Among cyclic ether groups, compounds having an epoxy group have the following advantages: it is easy to obtain compounds of various structures, does not adversely affect the durability of the resulting hard coat layer, and is also easy to control the compatibility with a radical polymerizable compound. Among cyclic ether groups, an oxetanyl group has the following advantages compared to an epoxy group: the polymerization degree is easy to be improved; low toxicity; accelerating the formation speed of a network obtained from the cationic polymerizable compound of the obtained hard coat layer; even in the region where the radical polymerizable compound is present in a mixed state, an independent network is formed without leaving unreacted monomers in the film; and so on.

Examples of the cationically polymerizable compound having an epoxy group include polyglycidyl ethers of polyhydric alcohols having an alicyclic ring, and alicyclic epoxy resins obtained by epoxidizing compounds having 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 polyhydric alcohols or alkylene oxide adducts thereof, polyglycidyl esters of aliphatic long-chain polybasic acids, homopolymers and copolymers of glycidyl (meth) acrylate, and the like; glycidyl ethers produced by the reaction of a bisphenol such as bisphenol a, bisphenol F, hydrogenated bisphenol a, an alkylene oxide adduct thereof, a derivative thereof such as a caprolactone adduct, and epichlorohydrin, and glycidyl ether-type epoxy resins derived from a bisphenol such as a phenol novolac epoxy resin.

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

The radical polymerization initiator may be one capable of releasing a substance that initiates 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 azobisisobutyronitrile.

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 a hydrogen abstraction-Type reaction in the coexistence of a tertiary amine, and these may be used alone or in combination.

The cationic polymerization initiator may be one 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. For them, cationic polymerization can be initiated by either or both of irradiation with active energy rays or heating, depending on the structural difference.

The polymerization initiator may be contained preferably in an amount of 0.1 to 10% by mass based on 100% by mass of the entire hard coating 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 favorable range, and poor adhesion, a cracking phenomenon, and a curling phenomenon due to curing shrinkage tend to be less likely to occur.

The hard coating composition may further comprise one or more selected from a solvent and an additive.

The solvent is a solvent capable of dissolving or dispersing the polymerizable compound and the polymerization initiator, and if it is a solvent known as a solvent for a hard coat composition in the art, it can be used within a range not to impair the effects of the present invention.

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

In a functional layer, for example, a hard coat layer, which is a cured product of a curable resin, a coating film is irradiated with high-energy radiation such as active energy rays and cured to form a hard coat layer. The irradiation intensity is appropriately determined depending on the composition of the curable composition, and is not particularly limited, but irradiation in a wavelength region effective for activation of the polymerization initiator is preferable. The irradiation intensity is preferably 0.1 to 6,000mW/cm ² More preferably 10 to 1,000mW/cm ² More preferably 20 to 500mW/cm ² . When the irradiation intensity is within the above range, an appropriate reaction time can be secured, and yellowing and deterioration of the resin due to heat radiated from the light source and heat generated during the curing reaction can be suppressed. The irradiation time may be appropriately selected depending on the composition of the curable composition, and is not particularly limited, but is determined by the irradiation intensity and the irradiation timeThe cumulative quantity of light expressed by the product is preferably set to 10 to 10,000mJ/cm ² More preferably 50 to 1,000mJ/cm ² More preferably, it is set to 80 to 500mJ/cm ² . When the integrated light amount is within the above range, a sufficient amount of active species derived from the polymerization initiator can be generated, and the curing reaction can be more reliably performed. In addition, it is useful to further increase the hardness of the hard coat layer by performing the irradiation step within this range. From the viewpoint of improving the smoothness of the hard coat layer and further improving the visibility of the optical film in the wide angle direction, the kind of the solvent, the component ratio, optimization of the curing component concentration, addition of the leveling agent, and the like can be given.

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 adhesive layer is a layer having an adhesive function, and has a function of bonding the polyimide resin 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 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 attached to an object by pressing. The pressure-sensitive adhesive may be an adhesive as follows: "a substance having adhesiveness at normal temperature and adhering to an adherend by a light pressure" (JIS K6800); the capsule adhesive may be one of the following: "an adhesive capable of holding a specific component in a protective film (microcapsule) and maintaining stability until the film is broken by an appropriate means such as pressure and heat" (defined in JIS K6800).

The color tone adjusting layer is a layer having a color tone adjusting function, and is a layer capable of adjusting a laminate including a polyimide-based resin film to a target color tone. The color tone adjusting 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 (japanese laid-open: 12473\1252431); 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 refractive index adjustment function, and is, for example, a layer having a refractive index different from that of the polyimide resin film and capable of providing a predetermined refractive index to the optical laminate. The refractive index adjustment layer may be, for example, a resin selected as appropriate, a resin layer further containing a pigment as the case may be, or 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 a decrease in transparency can be prevented. Examples of the metal used 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 a preferred embodiment of the present invention, the optical laminate of the present invention is very useful as a front panel of an image display device, particularly a front panel of a flexible display device (hereinafter, also referred to as a window film), a front panel of a rollable display, or a front panel of a foldable display. The flexible display device includes, for example, a flexible functional layer and an optical laminate that is stacked on the flexible functional layer and functions as a front panel. That is, the front panel of the flexible display device is disposed on the visual recognition side above the flexible functional layer. The front panel has the function of protecting a flexible functional layer, such as an image display element within a flexible display. The flexible display device is a display device used in association with operations such as repeated bending and repeated winding of the image display device. In the front panel of the flexible display device used in association with such repeated bending operations, high bending resistance is required. In addition, the front panel is also required to have high visibility. In comparison with a film for a substrate of an image display device used inside the image display device, a film for a front panel of the image display device, particularly a front panel of a flexible display device, is required to have higher visibility and higher bending resistance. For example, the film of the present invention preferably has the total light transmittance, haze and/or YI value as described above from the viewpoint of easily improving the visibility in the case of use as a front panel for a flexible display device, and preferably satisfies the number of times of bending resistance in the MIT bending fatigue test as described above from the viewpoint of easily improving the bending resistance in the case of use as a front panel for a flexible display device.

Examples of the image display device include wearable devices such as televisions, smartphones, mobile phones, car navigation systems, tablet computers, portable game machines, electronic paper, indicators, bulletin boards, clocks, and smartwatches. Examples of the flexible display device include all image display devices having flexible characteristics, such as the rollable display and the foldable display described above. The rollable display is an image display device in which an image display portion including a front panel is rolled up and used in a state where the image display portion is extended to form a flat surface or a curved surface, and is an image display device in which an operation such as rolling up is performed every time it is used. The foldable display is an image display device in which an image display portion including a front panel is bent and used in a state where the image display portion is opened to form a flat surface or a curved surface, and is an image display device in which an operation such as bending is performed every time it is used. An image display device in which such operations such as winding and bending are repeated is referred to as a flexible image display device.

[ Flexible display device ]

The present invention also provides a flexible display device including the optical laminate of the present invention. The optical stack of the present invention is preferably used as a front panel in a flexible display device. The flexible display device is formed of a laminate for flexible display device, which is disposed on the viewing side of the organic EL display panel and is configured to be foldable, and the organic EL display panel. The laminate for a flexible display device may contain the window film, polarizing plate and touch sensor which are the optical laminate of the present invention, and the order of lamination is arbitrary, and it is preferable to laminate the window film, polarizing plate and touch sensor in the order from the viewing side or the window film, touch sensor and polarizing plate in the order. If the polarizing plate is present on the visual recognition side of the touch sensor, the pattern of the touch sensor is not easily visually recognized, and the visual recognition of the displayed image is improved, which is preferable. The respective members may be laminated using an adhesive, or the like. The liquid crystal display device may further 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 ]

The flexible display device of the present invention may further include a polarizing plate, preferably a circularly polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only a right-circularly polarized light component or a left-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 which is reflected by the organic EL panel and becomes left-handed circularly polarized light is blocked, only the light-emitting component of the organic EL is transmitted, and therefore the influence of reflected light is inhibited, and the image can be easily viewed.

In order to achieve the circularly polarized light function, the absorption axis of the linearly polarizing plate and the slow axis of the λ/4 phase difference plate need to be 45 ° in theory, but in practical use, 45 ± 10 °. The linearly polarizing plate and the λ/4 phase difference plate are not necessarily laminated adjacently, and the relationship between the absorption axis and the slow axis may satisfy the above range. It is preferable to achieve completely circularly polarized light at all wavelengths, but this is not necessary 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 the viewing ability in a state where the polarized sunglasses are worn.

The linear polarizing plate is a functional layer having the following functions: light vibrating in the direction of the transmission axis is passed through, and polarized light of a vibration component perpendicular to the light is blocked. The linear polarizing plate may be a single linear polarizer or a linear polarizer and a protective film attached to at least one surface of the linear polarizer.

The thickness of the linear polarizer may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness is within the above range, the flexibility 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, also referred to as PVA) film. The polarizing performance is exhibited by orienting a dichroic dye such as iodine by adsorbing the dichroic dye to a PVA film oriented by stretching or by stretching the film while the film is adsorbed to PVA. The production of the film-type polarizing plate may further include steps of swelling, crosslinking with boric acid, washing with an aqueous solution, drying, and the like. The stretching and dyeing step may be performed as a PVA-based film alone, or may be performed in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA film to be used is preferably 10 to 100 μm, and the stretch ratio is preferably 2 to 10 times.

In addition, another example of the polarizing plate may be a liquid crystal coating type polarizing plate formed by coating a liquid crystal polarizing composition. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The liquid crystalline compound may have a property of exhibiting a liquid crystal state, and is preferably one having a high-order alignment state such as a smectic state because it exhibits high polarization performance. The liquid crystalline compound preferably has a polymerizable functional group.

The dichroic dye may have liquid crystal properties or may have a polymerizable functional group, and may be a dye that exhibits dichroism by being aligned together with the liquid crystal compound. Any of the compounds 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 is produced by applying a liquid crystal polarizing composition to an alignment film to form a liquid crystal polarizing layer.

The liquid crystal polarizing layer can be formed to a thinner thickness than the film-type polarizing plate. The thickness of the liquid crystal polarizing layer may be preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

The above-described alignment film can be produced, for example, by: the alignment film-forming composition is applied to a substrate, and alignment properties are imparted by rubbing, polarized light irradiation, or the like. The alignment film forming composition may contain a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like in addition to the alignment agent. Examples of the orientation agent include polyvinyl alcohols, polyacrylates, polyamide acids, and polyimides. In case photo-alignment is applied, it is preferred to use an alignment agent comprising cinnamate groups. The weight average molecular weight of the polymer used as the orientation agent may be 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, from the viewpoint of alignment regulating force. The liquid crystal polarizing layer may be laminated by being peeled from the substrate and then 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 specifically, the polymer film to be used includes polyolefins such as polyethylene, polypropylene, polymethylpentene, norbornene, and cycloolefin derivatives containing a monomer unit of cycloolefin, (modified) celluloses such as diacetylcellulose, triacetylcellulose, and propionyl cellulose, and acrylics such as a methyl methacrylate (co) polymer, polystyrenes such as a styrene (co) polymer, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, ethylene-vinyl acetate copolymers, polyvinyl chlorides, polyvinylidene chlorides, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyesters such as polyarylates, polyamides such as nylon, polyimides, polyamideimides, polyetherimides, polyethersulfones, polysulfones, polyvinyl alcohols, polyvinyl acetals, polyurethanes, and epoxy resins, and preferably, a polyamide, polyamideimide, polyester, polyolefin, acrylic, polyolefin, or polyimide film is used because of its excellent transparency and heat resistance.

These polymers may be used alone or in combination of two or more. These films are used as they are in an unstretched state, or are used as uniaxially or biaxially stretched films. Cellulose-based films, olefin-based films, acrylic films, and polyester-based films are preferable. The protective film may be a coating type protective film obtained by coating and curing a cationically curable composition such as an epoxy resin or a radically curable composition such as an acrylate. If necessary, 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, or the like may be contained.

The thickness of the protective film may be 200 μm or less, and preferably 1 to 100 μm. If the thickness of the protective film is within the above range, the flexibility of the protective film is not easily reduced.

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, in other words, 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. If necessary, a phase difference adjusting agent, 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 may be included. The thickness of the stretched phase difference plate may be 200 μm or less, preferably 1 to 100 μm. When the thickness is within the above range, the flexibility of the film tends not to be easily lowered.

Further, another example of the λ/4 retardation plate may be a liquid crystal coating type retardation plate formed by coating a liquid crystal composition. The liquid crystal composition contains a liquid crystalline compound having a property of exhibiting a liquid crystal state such as a nematic state, a cholesteric state, or a smectic state. Any compound including a liquid crystalline compound in the liquid crystal composition has a polymerizable functional group. The liquid crystal coating type retardation plate may further contain an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like. The liquid crystal coated retardation plate can be produced by coating a liquid crystal composition on an alignment film and curing the coating to form a liquid crystal retardation layer in the same manner as described in the above liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed to a smaller thickness than the stretching type retardation plate. The thickness of the liquid crystal polarizing layer may be usually 0.5 to 10 μm, preferably 1 to 5 μm. The liquid crystal-coated retardation film may be laminated by being peeled from a substrate and then 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, there are many materials that exhibit birefringence more strongly at shorter wavelengths and less strongly at longer wavelengths.

In this case, since a retardation of λ/4 cannot be achieved in all visible light regions, it is often designed to have an in-plane retardation of λ/4, i.e., 100 to 180nm, preferably 130 to 150nm, in the vicinity of 560nm, which has high visibility. The use of a reverse dispersion λ/4 phase difference plate using a material having a wavelength dispersion characteristic of birefringence opposite to that of the usual one is preferable because visibility can be improved. As such a material, a material described in jp 2007-232873 a and the like is preferably used also in the case of a stretched retardation plate, and a material described in jp 2010-30979 a is preferably used also in the case of a liquid crystal coated retardation plate.

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

For the circularly polarizing plate, a method of laminating a positive C plate is also 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 phase difference in the thickness direction is usually from-200 to-20 nm, preferably from-140 to-40 nm.

[ touch sensor ]

The flexible display device of the present invention may further include a touch sensor. The touch sensor may be used as an input mechanism. As the touch sensor, 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 have been proposed, and any type may be used. Among them, the electrostatic capacitance system is preferable. The capacitive touch sensor is divided into an active region and a non-active region located at a peripheral portion of the active region. The active area is an area corresponding to a display portion, which is an area of the display panel where a screen is displayed, and is an area where a touch by a user is sensed, and the inactive area is an area corresponding to a non-display portion, which is an area of the display device where a screen is not displayed. The touch sensor may include: a substrate having flexible characteristics; a sensing pattern formed in an active region of the substrate; and each sensing line formed in the non-active region of the substrate and connecting the sensing pattern to an external driving circuit via a pad portion. As the substrate having a flexible property, the same material as the polymer film can be used. The substrate of the touch sensor preferably has a toughness of 2,000mpa% or more in terms of suppressing cracking of the touch sensor. The toughness may be more preferably 2,000 to 30,000mpa%. Here, the toughness is defined as the area of the lower part of a Stress (MPa) -strain (%) curve (Stress-strain curve) obtained by a tensile test of a polymer material up to a failure point.

The sensing pattern may include a 1 st pattern formed along a 1 st direction and a 2 nd pattern formed along 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 are formed on the same layer, and in order to sense a touched position, the respective patterns must be electrically connected. The 1 st pattern is a form in which the unit patterns are connected to each other via a tab, and the 2 nd pattern is a structure in which the unit patterns are separated from each other into islands, and therefore, in order to electrically connect the 2 nd pattern, an additional bridge electrode is required. The sensing pattern may use a known transparent electrode raw material. Examples thereof 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 these may be used alone or in combination of two or more. Preferably, ITO may be used. The metal used in the wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, and chromium. These may be used alone or in combination of two 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 a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of 2 or more of these metals. The 1 st pattern and the 2 nd pattern must be electrically insulated, and thus, an insulating layer is 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 in a layer structure covering the sensing pattern. In the latter case, the bridge electrode may be connected to the 2 nd pattern via a contact hole formed on the insulating layer. In the touch sensor, as means for appropriately compensating for a difference in transmittance between a pattern region where a pattern is formed and a non-pattern region where no 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, and the optical adjustment layer may include an inorganic insulating substance or an organic insulating substance. The optical adjustment layer can be formed by applying a photocurable composition containing a photocurable organic binder and a solvent onto a substrate. The above-mentioned photocurable composition may further comprise inorganic particles. The refractive index of the optical adjustment layer can be increased by the inorganic particles.

The photocurable organic binder may include a copolymer of monomers such as an acrylate monomer, a styrene monomer, and a carboxylic acid monomer. The photocurable organic binder may be, for example, a copolymer containing repeating units different from each other, such as repeating units containing an epoxy group, repeating units containing an acrylate, repeating units containing a carboxylic acid, and the like.

The inorganic particles may include, for example, zirconia particles, titania particles, alumina particles, and the like. The photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing assistant.

[ adhesive layer ]

Each layer of the laminate for a flexible display device, such as a window film, a polarizing plate, and a touch sensor, and a film member, such as a linear polarizing plate and a λ/4 retardation plate, constituting each layer may be bonded 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, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic curable adhesive, an aqueous solvent-volatile adhesive, an active energy ray-curable adhesive, a curing agent-mixed adhesive, a hot-melt adhesive, a pressure-sensitive adhesive, and a remoistenable adhesive can be used. Among them, an aqueous solvent volatile adhesive, an active energy ray-curable adhesive, and a pressure-sensitive adhesive are generally used. The thickness of the adhesive layer can be adjusted as appropriate depending on the required adhesive strength and the like, and is, for example, 0.01 to 500. Mu.m, preferably 0.1 to 300. Mu.m. The laminate for a flexible image display device may have a plurality of adhesive layers, and the thickness of each adhesive layer may be the same or different from the type of adhesive used.

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 water and the above-mentioned main agent polymer, 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 blended. In the case of bonding with the aqueous solvent volatile adhesive, the adhesive can be provided by injecting the aqueous solvent volatile adhesive between the layers to be bonded, bonding the layers to be bonded, and then drying the layers. The thickness of the adhesive layer in the case of using the above-mentioned aqueous solvent volatile adhesive may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the aqueous solvent volatile adhesive is used for forming a plurality of layers, the thickness of each layer may be the same as or different from the type of the adhesive.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material that forms an adhesive layer by irradiation with an active energy ray. The active energy ray-curable composition may contain at least one polymer selected from the group consisting of a radically polymerizable compound and a cationically polymerizable compound, as in the case of the hard coat composition. As the radical polymerizable compound, the same type of radical polymerizable compound as that of the hard coat composition can be used, as in the hard coat composition. As the radical polymerizable compound used for the adhesive layer, a compound having an acryloyl group is preferable. In order to reduce the viscosity of the adhesive composition, a monofunctional compound is preferably contained.

As the cationic polymerizable compound, the same kind of cationic polymerizable compound as that of the hard coat composition can be used, as in the hard coat composition. The cationic polymerizable compound used in the active energy ray-curable composition is more preferably an epoxy compound. To reduce the viscosity of the adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

In the active energy ray composition, a polymerization initiator may be further contained. The polymerization initiator is a radical polymerization initiator, a cationic polymerization initiator, a radical or cationic polymerization initiator, and the like, and can be appropriately selected and used. These polymerization initiators are those which are decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations to effect radical polymerization and cationic polymerization. The hard coat composition may be used as an initiator capable of initiating at least one of radical polymerization and cationic polymerization by irradiation with active energy rays.

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. In the case of bonding with the active energy ray-curable adhesive, the bonding can be performed by: the active energy ray-curable composition is applied to either one or both of the adhesive layers and then bonded to each other, and the adhesive layers are irradiated with active energy rays through either one or both of the adhesive layers and cured to thereby bond the adhesive layers. The thickness of the adhesive layer in the case of using the active energy ray-curable adhesive may be usually 0.01 to 20 μm, preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive used may be the same or different.

The adhesive may be classified into an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, and the like, depending on the base polymer, and may be used. The binder 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 adhesive layer or the adhesive layer is formed by dissolving and dispersing the components constituting the adhesive in a solvent to obtain an adhesive composition, applying the adhesive composition to a substrate, and then drying the adhesive composition. The adhesive layer may be formed directly or an adhesive layer formed separately on a substrate may be transferred. A release film is also preferably used to cover the pressure-sensitive adhesive surface before bonding. The thickness of the adhesive layer in the case of using the above adhesive may be usually 1 to 500. Mu.m, preferably 2 to 300. Mu.m. When the above-mentioned adhesive is used for forming a plurality of layers, the thickness of each layer and the kind of the adhesive used may be the same or different.

[ light-shielding pattern ]

The light shielding pattern may be applied as at least a part of a bezel or a housing of the flexible image display device. The wiring disposed at the edge of the flexible image display device is hidden by the light shielding pattern and is not easily visually recognized, thereby improving the visual recognition of the 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 have various colors such as black, white, metallic color, and the like. The light-shielding pattern may be formed of a pigment for color development, and a polymer such as acrylic resin, ester resin, epoxy resin, polyurethane, silicone, or the like. They may be used alone or in a mixture of two or more. The light-shielding pattern can be formed by various methods such as printing, photolithography, and ink jet. The thickness of the light-shielding pattern is usually 1 to 100. Mu.m, preferably 2 to 50 μm. Further, it is preferable to provide a shape such as an inclination in the thickness direction of the light-shielding pattern.

[ examples ] A

The present invention will be described in further detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, "%" and "part(s)" are "% by mass" and "part(s) by mass", respectively, unless otherwise specified.

< determination of weight average molecular weight >

Gel Permeation Chromatography (GPC) measurement

(1) Pretreatment method

To the polyamideimide membrane, a DMF eluent (a solution to which 10mmol/L lithium bromide was added) was added so as to give a concentration of 2mg/mL, and the mixture was heated while stirring at 80 ℃ for 30 minutes, cooled, and then filtered through a 0.45 μm membrane filter, and the obtained filtrate was used as a measurement solution.

(2) Measurement conditions

Column: TSKgel alpha-2500 (7) 7.8mm diameter. Times.300 mm. Times.1 and alpha-M ((13) 7.8mm diameter. Times.300 mm). Times.2 from Tosoh

Eluent: DMF (adding 10mmol/L lithium bromide)

Flow rate: 1.0 mL/min

A detector: RI detector

Column temperature: 40 deg.C

Injection amount: 100 μ L

Molecular weight standard: standard polystyrene

[ production example 1]

Production of Polyamide-imide resin (1)

In a 1L separable flask equipped with a stirring blade, 313.6g of DMAc was charged under a nitrogen atmosphere, and 16.77g (52.37 mmol) of TFMB was added to dissolve in DMAc while stirring at room temperature. Subsequently, 6FDA 4.797g (10.80 mmol) and 6.679g (10.80 mmol) of tetracarboxylic dianhydride represented by the following formula (A) (TMPBP-TME) were added to the flask and stirred at room temperature for 16 hours.

Thereafter, TPC 6.576g (32.39 mmol) and DMAc 313.6g were added to the flask, and stirred at room temperature for 2 hours. Subsequently, 5.582g (43.19 mmol) of N, N-diisopropylethylamine, 7.716g (75.58 mmol) of acetic anhydride, and 4.022g (43.19 mmol) of 4-methylpyridine 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, stirred, and methanol was slowly charged in an amount by mass 1.385 times the mass of the reaction solution, and thereafter water was slowly charged in an amount by mass 0.6924 times the mass of the reaction solution. The precipitated precipitate was taken out and washed with methanol. Then, the precipitate was dried under reduced pressure at 80 ℃ to obtain a polyamideimide resin (1). The Mw of the polyamideimide resin (1) was 360,000.

[ production example 2]

Production of Polyamide-imide resin (2)

313.6g of DMAc was charged into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, and 17.43g (54.43 mmol) of TFMB was charged into the flask at room temperature while stirring to dissolve the DMAc. Subsequently, 6FDA 2.493g (5.610 mmol) and TMPBP-TME 6.942g (11.22 mmol) were added to the flask, and the mixture was stirred at room temperature for 16 hours.

Then, 7.975g (39.28 mmol) of TPC and 313.6g of DMAc were put into the flask and stirred at room temperature for 2 hours. Subsequently, 5.077g (39.28 mmol) of N, N-diisopropylethylamine, 12.03g (117.84 mmol) of acetic anhydride, and 3.658g (39.28 mmol) of 4-methylpyridine 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, whereby a reaction solution was obtained. The obtained reaction solution was cooled to room temperature, stirred, and slowly charged with methanol in an amount of 1.385 times by mass of the reaction solution, and then slowly charged with water in an amount of 0.6924 times by mass of the reaction solution. The precipitated precipitate was taken out and washed with methanol. Then, the precipitate was dried under reduced pressure at 80 ℃ to obtain a polyamideimide resin (2). The Mw of the polyamideimide resin (2) was 330,000.

[ production example 3 ]

Production of Polyamide-imide resin (3)

313.6g of DMAc was charged into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, and 18.36g (57.33 mmol) of TFMB was charged into the flask at room temperature with stirring to dissolve the DMAc. Subsequently, the reaction solution was cooled to 10 ℃. After cooling, 6FDA 7.718g (17.37 mmol) was added to the flask, and the mixture was stirred for 16 hours while maintaining the temperature at 10 ℃. Thereafter, 1.709g (5.791 mmol) of OBBC, 7.054g (34.75 mmol) of TPC, and 313.6g of DMAc were put into the flask, and stirred at 10 ℃ for 2 hours. Subsequently, 5.240g (40.54 mmol) of N, N-diisopropylethylamine, 12.416g (121.6 mmol) of acetic anhydride, and 3.775g (40.54 mmol) of 4-methylpyridine were added to the flask, and after stirring at room temperature for 30 minutes, the temperature was raised to 70 ℃ using an oil bath, and further stirring was carried out for 3 hours, whereby a reaction solution was obtained. The obtained reaction solution was cooled to room temperature, stirred, and slowly charged with methanol in an amount of 1.385 times by mass of the reaction solution, and then slowly charged with water in an amount of 0.6924 times by mass of the reaction solution. The precipitated precipitate was taken out and washed with methanol. Subsequently, the precipitate was dried under reduced pressure at 80 ℃ to obtain a polyamideimide resin (3). The Mw of the polyamideimide resin (3) was 430,000.

[ production example 4 ]

Preparation of silica sols

393.4G of methanol-dispersed silica sol (MA-ST-G-ML 1, manufactured by Nissan chemical Co., ltd.; average particle diameter 27 μm, silica particle solid content 30.5% by mass) and 261.0G of GBL were put into a 2L flask, and methanol was evaporated at 400hPa for 40 minutes and at 250hPa for 60 minutes in a hot water bath at 45 ℃ by a vacuum evaporator. Further, the temperature was raised to 80 ℃ at 250hPa, and the mixture was heated for 30 minutes to obtain GBL dispersed silica sol 1.

[ production example 5 ]

Preparation of curable resin composition A

A curable resin composition A was obtained by stirring and mixing 19 parts by mass of urethane acrylate (MIWon Specialty Chemical Co., ltd., manufactured by Ltd., MIRAMER 620D), 19 parts by mass of polyfunctional acrylate (MiWon Specialty Chemical Co., manufactured by Ltd., MIRAMER SP 1106), 20 parts by mass of antimony pentoxide (manufactured by TOYO INK, TYS-F90-KR), 38 parts by mass of methyl ethyl ketone (manufactured by Tokyo Kasei Co., ltd.), and 0.3 part by mass of leveling agent (manufactured by BYK Chemie Japan, BYK (registered trademark) -307).

[ production example 6 ]

Preparation of curable resin composition B

A mixture of 3, 4-epoxycyclohexylmethyl 3, 4-epoxycyclohexanecarboxylate (manufactured by Daicel, CELLOXIDE 2021P) 9.5 parts by mass, 3, 4-epoxycyclohexylmethyl methacrylate (manufactured by Daicel, cyclomer M100) 18.9 parts by mass, 4-functional acrylate (manufactured by Newzhonghama chemical Co., ltd., A-TMMT) 18.9 parts by mass, 3-functional acrylate (manufactured by Newzhonghama chemical Co., ltd., A-TMPT) 9.5 parts by mass, acryl-modified silica particles (manufactured by Nissan chemical Co., ltd., PGM-2140Y; average primary particle diameter 10 to 15 nm) 40 parts by mass, iodonium (4-methylphenyl) [4- (2-methylpropyl) phenyl ] -hexafluorophosphate and propylene carbonate was mixed at a mass ratio of 3:1 (IRGACURE (registered trademark) 250, manufactured by BASF JAPAN, 1.0 parts by mass), 2.2 parts by mass of 1-hydroxy-cyclohexyl-phenyl-ketone (IRGACURE (registered trademark) 184, manufactured by BASF JAPAN, and 0.1 part by mass of a silicone leveling agent (BYK Chemie Japan, manufactured by BYK (registered trademark) -307), were mixed by stirring to obtain a curable resin composition B.

[ production example 7 ]

Production of Polyamide-imide film (1)

DMAc was added to the polyamideimide resin (1) to prepare a polyamideimide varnish (1) in an amount of 10.5% by mass. The obtained polyamideimide varnish (1) was coated on a smooth surface of a glass substrate using an applicator so that the thickness of the finally obtained film became 50 μm, and dried at 140 ℃ for 30 minutes to obtain a free-standing film. The obtained free-standing film was fixed to a metal frame and dried at 210 ℃ for 90 minutes to obtain a polyamideimide film (1) having a thickness of 50 μm.

[ production example 8 ]

Production of Polyamide-imide film (2)

A polyamideimide film (2) having a thickness of 50 μm was obtained in the same manner as in production example 7, except that 8.4% by mass of a polyamideimide varnish (2) was prepared by adding DMAc to the polyamideimide resin (2).

[ production example 9 ]

Production of Polyamide-imide film (3)

The polyamideimide (1) was dissolved in GBL, and GBL-dispersed silica sol 1 was added thereto and mixed thoroughly to obtain a polyamideimide resin (1)/silica particle mixed varnish. Except that the solid content concentration determined from the total mass of the polyamide imide resin (1) and the silica particles with respect to the mass of the varnish obtained was 8.5 mass%, and the ratio of the polyamide imide resin (1) to the silica particles was prepared to be 95: 5A polyamideimide film (3) having a thickness of 50 μm was obtained in the same manner as in production example 7.

[ production example 10 ]

Production of Polyamide-imide film (4)

Using the polyamideimide resin (3), GBL was added so that the solid content concentration became 7.7 mass%, to prepare a polyamideimide varnish (4). A polyamideimide film (4) having a thickness of 50 μm was obtained in the same manner as in production example 7, except that the polyamideimide varnish (4) thus obtained was used.

[ example 1]

The curable resin composition a prepared in production example 5 was applied to one surface of the polyamide-imide film (1) by a bar coater so that the thickness after drying became 5 μm. Thereafter, the laminate was dried at 80 ℃ for 3 minutes and cured by irradiation with ultraviolet light to obtain an optical laminate 1. Irradiation of ultraviolet rays Using high-pressure Mercury under a nitrogen atmosphere (UV exposure amount: 500 mJ/cm) ² Ultraviolet illuminance: 200mW/cm ² ) The process is carried out. The thickness of the hard coat layer in the obtained optical laminate 1 was 5 μm.

[ example 2]

An optical laminate 2 was produced in the same manner as in example 1, except that the polyamideimide film (2) was used instead of the polyamideimide film (1).

[ example 3 ]

An optical laminate 3 was produced in the same manner as in example 1, except that the curable resin composition B prepared in production example 6 was used for one surface of the polyamideimide film (1).

[ example 4 ]

An optical laminate 4 was produced in the same manner as in example 3, except that the polyamideimide film (2) was used in place of the polyamideimide film (1).

[ example 5 ]

An optical laminate 5 was produced in the same manner as in example 1, except that the thickness of the hard coat layer was set to 10 μm.

[ example 6 ]

An optical laminate 6 was produced in the same manner as in example 1, except that the polyamideimide film (3) was used instead of the polyamideimide film (1).

[ comparative example 1]

The curable resin composition a prepared in production example 5 was applied to one surface of the polyamideimide film (4) by a bar coater so that the thickness after drying became 5 μm. Thereafter, the laminate was dried at 80 ℃ for 3 minutes and cured by irradiation with ultraviolet light to obtain an optical laminate 7. Irradiation of ultraviolet rays Using high-pressure Mercury under a nitrogen atmosphere (UV exposure amount: 500 mJ/cm) ² Ultraviolet illuminance: 200mW/cm ² ) The process is carried out. The thickness of the hard coat layer in the optical laminate 7 obtained was 5 μm.

[ comparative example 2]

An optical laminate 8 was produced in the same manner as in example 1, except that a polyester film (E5000; manufactured by toyobo co., ltd.) was used instead of the polyamideimide film (1).

[ indentation and drawing test ]

Optical laminates obtained in examples 1 to 6 and comparative examples 1 to 2, glass, a 100 μm substitute for an organic EL panel, and a 25 μm (meth) acrylic pressure-sensitive adhesive sheet were sequentially bonded to prepare a push-in pull test specimen having a width of 6cm and a length of 10 cm. In each test sample, the surface of the optical laminate on the hard coat layer side was set as the outermost surface. In an environment with a temperature of 23 ℃ and a humidity of 50%, a stylus a having a pen tip diameter of 0.7mm and a compressive elastic modulus of 1.0GPa and a stylus B having a pen tip diameter of 0.7mm and a compressive elastic modulus of 3.0GPa were provided, respectively, and a load was applied so that the pen was 90 ° with respect to the outermost surface of the test piece with the mass of the weight set to 50g, and the test piece was subjected to a push-in pull test by reciprocating once over a distance of 30mm at a speed of 500 mm/min so as to have a return waiting time of 2 seconds. Next, a press-in pull-out test was similarly performed in another place of the same test sample while changing the load of the weight to 100 to 1100g in 100g units. Thereafter, the test piece was left to stand in an environment of 23 ℃ and 50% humidity, and the maximum load at which the dent was not visually recognized after 2 hours from the pull-out test was determined as the critical load. The larger the maximum load, the less likely it is to dent.

[ dent of scratch (permanent dent depth) ]

In the same manner as the above-mentioned indentation pull test, a pull test was performed, and the test sample was left standing for 24 hours in an environment of a temperature of 23 ℃ and a humidity of 50%. Thereafter, a Stylus profilometer system (manufactured by Bruker Japan, dektak XT-Standard) was used to obtain a Stylus profile measured by Stylus radius:2 μm, stylus Fore: outline of the concave shape of the 3mg drawn portion. The minimum value was obtained from the quadratic curve of the obtained profile with the stationary plane 0 as a reference as the permanent depression depth.

[ tensile test ]

The optical layered bodies obtained in examples 1 to 6 and comparative examples 1 to 2 were each cut into a dumbbell shape according to JIS No. 2 using a dumbbell cutter, to obtain samples. Tensile tests were conducted on these samples using a table-top precision universal tester (AUTOGRAPH AGS-X, manufactured by SHIMADZU CO., LTD.) under conditions of a chuck spacing of 80mm and a tensile speed of 100 mm/min, to obtain a stress-strain curve.

In the obtained curve, the time at which the curve first changes from linear to nonlinear is set as the yield point, and the stress value at that time is obtained as the yield stress.

[ high speed tensile test ]

The polyamideimide films obtained in production examples 7 to 10 were each cut into a dumbbell shape according to JIS No. 2 using a dumbbell cutter, to obtain samples. The stress-strain curves of these samples were obtained using a high-speed tensile tester (Hydroshot HITS-T10, manufactured by Shimadzu corporation) having a load cell with a maximum load of 2KN under conditions of a chuck pitch of 80mm and a tensile speed of 0.1 m/sec. In the obtained curve, the time at which the linear shape is first changed to the nonlinear shape is set as a yield point, and a stress value at that time is obtained as a yield stress.

[ Pencil hardness test ]

According to JIS K5600-5-4: 1999, pencil hardness was measured on the surface of the optical layered body on the hard coat layer side obtained in examples 1 to 6 and comparative examples 1 to 2. The load during the measurement was 1kg, and the measurement speed was 60 mm/min.

[ bending resistance test ]

The optical laminates obtained in examples 1 to 6 and comparative examples 1 to 2 were each cut into a size of 10mm in width and 100mm in length using a laser cutter. The cut optical layered bodies were placed on a jig plate (R =1.5 mm) of a FOLDING MACHINE (YM-RT-330, manufactured by foruhu) so that the hard coat layer became inside at the time of bending, and a repeated bending test was performed at a test speed of 60rpm in a room temperature environment, and the number of times that the optical layered bodies could be bent without breaking was measured to determine the number of times each optical layered body was bent.

[ thickness of polyimide resin film and optical laminate ]

The thicknesses of the polyimide resin film and the optical layered body were measured at 10 points or more using a digimatic indicator (ID-C112 XBS, manufactured by Mitutoyo corporation) and the average value thereof was calculated.

[ thickness of functional layer ]

The thickness of the functional layer was measured using a desktop film thickness system (F20, manufactured by filmetics).

The above evaluations were performed on the polyamideimide films obtained in the above production examples or the optical laminates obtained in examples 1 to 6 and comparative examples 1 to 2. The results are shown in Table 1.

[ Table 1]

The optical layered bodies described in examples 1 to 6 have high critical loads for two types of touch pens having different compression elastic moduli. Therefore, it was confirmed that the optical laminate of the present invention is an optical laminate in which a dent is not easily generated on the surface by contact with an external element and the surface of the dent is easily restored. In contrast, the optical layered bodies described in comparative examples 1 and 2 have low critical loads for both types of touch pens and do not have sufficient dent resistance.

Claims

1. An optical laminate comprising: and a functional layer comprising a cured product of a curable resin, wherein the optical laminate has a yield stress of 100MPa or more at a tensile rate of 100 mm/min.

2. The optical laminate according to claim 1, wherein the polyimide-based resin film has a yield stress of 200MPa or more at a tensile rate of 0.1 m/sec.

3. The optical laminate according to claim 1 or 2, which has a thickness of 15 μm to 120 μm and a number of times of bending resistance measured with R =1.5mm of 20 ten thousand or more.

4. The optical laminate according to any one of claims 1 to 3, wherein the permanent depression depth measured at a load of 200g is 0.5 μm or less using a jig having a compressive modulus of elasticity of 3.0GPa and a tip having a diameter of 0.7 mm.

5. The optical laminate according to any one of claims 1 to 3, wherein the permanent depression depth measured at a load of 1000g is 0.5 μm or less using a jig having a compressive modulus of elasticity of 1.0GPa and a tip having a diameter of 0.7 mm.

6. The optical laminate according to any one of claims 1 to 5, wherein the pencil hardness of the surface on the functional layer side is H or more.

7. The optical laminate according to any one of claims 1 to 6, wherein the polyimide resin film contains a polyimide resin containing a structural unit represented by formula (1),

in the formula (1), X represents a 2-valent organic group, Y represents a 4-valent organic group, and X represents a bonding end,

y in the formula (1) includes a structure represented by the formula (3),

in the formula (3), R ¹ Independently of one another, represents a halogen atom, an alkyl, alkoxy, aryl or aryloxy group optionally having a halogen atom, R ² ～R ⁵ Independently represent a hydrogen atom or a 1-valent hydrocarbon group optionally having a halogen atom, m independently represents an integer of 0 to 3, n represents an integer of 1 to 4, and represents a bonding end, wherein R is in the structure ² ～R ⁵ In at least one benzene ring of (2), R ² ～R ⁵ At least 3 of which are 1-valent hydrocarbon groups optionally having halogen atoms.

8. A flexible display device comprising the optical laminate 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 provided with a polarizing plate.