CN115197457A

CN115197457A - Optical laminate and flexible display device

Info

Publication number: CN115197457A
Application number: CN202210379160.6A
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: KR20220142369A; JP2022163714A; TW202302719A

Abstract

An optical laminate comprising a base layer composed of a polyimide resin film and a functional layer composed of a cured product of a curable resin, wherein the optical laminate has a stress of 110MPa or more when the strain is 3% in a tensile test in an environment having a temperature of 60 ℃ and a humidity of 93%.

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 such as a solar cell or an image display device. However, in response to recent demands for size reduction, thickness reduction, weight reduction, and flexibility, glass is not a material having sufficient characteristics, and various films have been studied as a substitute material 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 No. 2014/046180).

Disclosure of Invention

Flexible electronic devices such as flexible display devices are used in various environments. In particular, in the case of a flexible electronic device, since folding operation, winding operation, and the like are involved in use, there is a possibility that a polyimide resin film used as a front panel in the device may be subjected to folding operation and the like under various environments. Therefore, the front panel is required to be free from breakage, whitening, and the like even when folded or the like is performed under various environments. In particular, it is important that cracking, whitening, and the like do not occur even when used under high temperature conditions or high humidity conditions. However, in the conventional optical film and optical laminate, it cannot be said that the breakage, whitening, and the like at the time of folding operation under such high temperature conditions and high humidity conditions can be sufficiently prevented. Accordingly, an object of the present invention is to provide an optical laminate which does not cause cracking, whitening, and the like even when used under high-temperature conditions or high-humidity conditions.

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

That is, the present invention includes the following aspects.

[ 1] an optical laminate comprising: the polyimide resin film has a substrate layer composed of a polyimide resin film and a functional layer composed of a cured product of a curable resin, and has a stress of 110MPa or more when the strain is 3% in a tensile test in an environment of 60 ℃ and 93% humidity.

An optical laminate according to [ 1], wherein the yield strain in a tensile test at 60 ℃ and 93% humidity is 1.50% or more.

[3 ] the optical laminate according to [ 1] or [ 2], wherein the proof stress in a tensile test is 70MPa or more in an environment having a temperature of 60 ℃ and a humidity of 93%.

An optical laminate according to any one of [ 1] to [3 ], wherein the elastic modulus in a tensile test is 4.0GPa or more in an environment having a temperature of 60 ℃ and a humidity of 93%.

The optical laminate according to any one of [ 1] to [4 ], wherein the polyimide resin film has a coefficient of humidity expansion of 40ppm/K or less.

The optical laminate according to any one of [ 1] to [ 5 ], wherein the polyimide resin film has a moisture absorption rate of 3% or less under conditions of a temperature of 60 ℃ and a humidity of 90%.

The optical laminate according to any one of [ 1] to [ 6 ], which has a thickness of 15 to 120 μm and a number of times of bending resistance of 30 ten thousand or more measured with R =1.5 mm.

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

[ in formula (1), X represents an organic group having a valence of 2, Y represents an organic group having a valence of 4, and X represents a bonding end ], wherein Y in formula (1) has a structure represented by formula (3),

[ in the formula (3), R ¹ Independently of one another, represents a halogen atom, an alkyl group which may have a halogen atom, an alkoxy group, an aryl group or an aryloxy group, R ² ～R ⁵ Independently of each other, a hydrogen atom,Or a hydrocarbon group having a valence of 1 which may have 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 a group having ² ～R ⁵ In at least 1 benzene ring of (2), R ² ～R ⁵ At least 3 of which are 1-valent hydrocarbon groups that may have halogen atoms.]

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

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

The flexible display device according to any one of [ 9 ] and [ 10 ], further comprising a polarizing plate.

According to the optical laminate of the present invention, there can be provided an optical laminate which does not cause cracking, whitening, or the like even when used under high-temperature conditions or high-humidity conditions.

Drawings

FIG. 1 is a graph showing stress-strain curves of the optical layered bodies obtained in examples and comparative examples, measured at a temperature of 60 ℃ and a humidity of 93%.

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 limit values are described for a specific parameter, any of the upper and lower limit values may be combined to form a preferable range.

< optical layered body >

The optical laminate of the present invention is 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, and having a stress of 110MPa or more at a strain of 3% in a tensile test in an environment of 60 ℃ and 93% humidity.

When the stress at 3% strain in a tensile test of an optical laminate in an environment of 60 ℃ and 93% humidity is less than 110MPa, an operation involving deformation such as a folding operation is performed under high temperature and high humidity conditions, and when a flexible electronic device including an optical body is used, the occurrence of cracking, whitening, and the like cannot be sufficiently prevented. The reason for this is not clear, but when a stress higher than the yield stress is applied to the optical laminate, a region in which the strain becomes large is generated even in the substrate layer, and therefore, the force applied only to the functional layer of the cured product including the curable resin becomes large. As a result, it is considered that strain is likely to occur in the functional layer, and whitening and cracking of the film are likely to occur. The stress at 3% strain in a tensile test in an environment of 60 ℃ and 93% humidity of the optical laminate is preferably 111MPa or more, and more preferably 112MPa or more, from the viewpoint of easily reducing cracking and whitening when used under high-temperature and high-humidity conditions. The upper limit of the stress at 3% strain is preferably 200MPa or less. The stress at 3% strain is a value obtained by measuring the stress at 3% strain in a stress-strain curve obtained under the conditions of a temperature of 60 ℃, a humidity of 93%, an environment, a chuck pitch of 70mm, and a tensile rate of 10 mm/min, using the optical laminate as a measurement sample, and can be measured, for example, by the method described in examples.

The method for adjusting the stress at the time of 3% strain of the optical laminate to the above range is not particularly limited, but examples thereof include: a method of using a polyimide resin film having a yield stress described later as a base material layer and laminating a functional layer including a cured product of a curable resin; a method of laminating a polyimide resin film containing a polyimide resin described later as a base layer and a functional layer containing a cured product of a curable resin; and the like.

The Yield strain (hereinafter, sometimes referred to as YS) of the optical laminate of the present invention in a tensile test in an environment of 60 ℃ temperature and 93% humidity is measured using a tensile tester (test conditions: 60 ℃ temperature, 93% humidity, 70mm chuck spacing, 10mm tensile speed/min), and is preferably 1.50% or more, more preferably 1.60% or more, further preferably 1.70% or more, further more preferably 1.80% or more, and preferably 3.0% or less. When YS is within the above range under a high-temperature and high-humidity environment, fracture and whitening during use under high-temperature and high-humidity conditions are likely to be further reduced. YS is the strain at the point where the stress-strain curve intersects when a straight line having an equal slope to the modulus of elasticity is drawn with reference to the point where the strain of the stress-strain curve obtained using a tensile testing machine under the conditions of a temperature of 60 ℃ and a humidity of 93%, a chuck pitch of 70mm, and a tensile speed of 10 mm/min, and can be measured, for example, by the method described in examples. The stress at this point is a proof stress described later.

The proof stress in the tensile test in the environment of 60 ℃ and 93% humidity of the optical laminate of the present invention is measured using a tensile tester (test conditions: temperature 60 ℃, humidity 93%, chuck pitch 70mm, tensile speed 10 mm/min), and is preferably 70MPa or more, more preferably 75MPa or more, still more preferably 79MPa or more, and preferably 200MPa or less. When the durability under a high-temperature and high-humidity environment is within the above range, the fracture and whitening during use under high-temperature and high-humidity conditions are likely to be further reduced.

The elastic modulus in the tensile test in the environment of 60 ℃ and 93% humidity of the optical laminate of the present invention is measured using a tensile tester (test conditions: temperature 60 ℃, humidity 93%, chuck pitch 70mm, tensile speed 10 mm/min), and is preferably 4.0GPa or more, more preferably 4.1GPa or more, and usually 100GPa or less. When the elastic modulus in a high-temperature and high-humidity environment is not less than the above-described lower limit, the occurrence of cracks, wrinkles, and the like can be more effectively suppressed even when the sheet is repeatedly bent, particularly in a high-temperature and high-humidity environment. The elastic modulus in a high-temperature and high-humidity environment can be measured by the method described in examples.

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, measured at a temperature of 60 ℃ and a humidity of 93% 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, wrinkles, and the like can be effectively suppressed even when bending is repeated particularly in a high-temperature and high-humidity environment. 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. In addition, when calculating the absolute value of the difference in yellowness YI (hereinafter also referred to as Δ YI) of the optical laminate before and after 30 ten thousand bending tests performed under the above-described conditions, the optical laminate of the present invention preferably has a small Δ YI, and Δ YI is more preferably 0.8 or less, still more preferably 0.5 or less, still more preferably 0.3 or less, and particularly preferably 0.25 or less.

From the viewpoint of improving the folding resistance and preventing wrinkles and scratches, the elastic modulus at room temperature of the optical laminate of the present invention is preferably 4.0GPa or more, more preferably 4.5GPa or more, further preferably 4.8GPa or more, further preferably 5.2GPa or more, particularly preferably 6.0GPa or more, and usually 100GPa or less. The elastic modulus can be measured using a tensile tester (room temperature, humidity 50%, chuck spacing 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 at room temperature 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, measured as R =1.5mm under conditions of room temperature and humidity of 50%. If the number of times of bending resistance is equal to or more than the lower limit, the occurrence of cracks, fractures, wrinkles, and the like can be effectively suppressed even when bending is repeated. The number of times of bending resistance can be measured by 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) of less than 3.0. When the YI is less than 3.0, visibility of, for example, an image or the like observed through the optical laminate is easily improved. From the viewpoint of more easily improving the visibility of an image or the like through the optical layered body, the YI of the optical layered body 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 of the optical laminate is not more than the above upper limit, the transparency is good, and high visibility can be provided when the optical laminate is used for a front panel of a display device. The YI can be calculated by measuring the transmittance of light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer, obtaining 3 stimulus values (X, Y, Z), and calculating based on the formula YI =100 × (1.2769X-1.0592Z)/Y. The method for adjusting YI of the optical laminate to the above range is not particularly limited, but includes: a method of using a polyimide-based resin, a method of adding a blue coloring matter, a method of forming a thin film, a method of introducing a side chain into an aromatic ring of a monomer main chain, and the like, which are described later.

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 is easily improved when the optical laminate is incorporated into a display device as a front panel. Since the optical laminate of the present invention generally exhibits a high total light transmittance, the light emission intensity of a display element or the like necessary to obtain a certain brightness can be suppressed as compared with 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 backlight light is reduced, and this can contribute to energy saving. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance may be measured, for example, in accordance with JIS K7361-1: 1997 for benchmark, haze computer was used for the determination. The total light transmittance may be a total light transmittance in a range of the thickness of the optical laminate described later. In the present specification, the excellent optical properties of the optical laminate mean that the total light transmittance is high, the haze is low, and the YI is low, and are used in the same sense as the improvement or enhancement of the transparency in some cases.

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 more 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 in the above range, the visibility is easily improved when the optical laminate is incorporated into a display device, particularly as a front panel. The haze may be measured according to JIS K7136: the haze was measured using a haze computer on a 2000 basis.

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 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, further more preferably 80 μm or less, particularly preferably 60 μm or less, and a preferable range may be a combination of these upper and lower limits. When the thickness of the optical laminate is within the above range, the bending resistance of the optical laminate in a high-temperature and high-humidity environment can be more easily improved. The thickness of the optical layered body can be measured using a micrometer or the like, and can be measured, for example, by the method described in examples. The optical laminate of the present invention may preferably have a thickness of 15 to 120 μm, more preferably 20 to 100 μm, and still more preferably 25 to 80 μm.

The total light transmittance and the haze vary depending on the thickness of the optical laminate, and the total light transmittance decreases and the haze increases as the thickness increases. That is, in a film having a large thickness, it tends to be difficult to produce an optical laminate having a high total light transmittance and a low haze. In a preferred embodiment of the present invention, the optical laminate of the present invention has a high level of transparency, and therefore can exhibit a high total light transmittance and a low haze even when 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 more preferably 25 μm or more, particularly preferably 30 μm or more, particularly more preferably 35 μm or more, particularly more preferably 40 μm or more, preferably 100 μm or less, more preferably 80 μm or less, and further preferably 60 μm or less. The thickness of the optical laminate can be measured by a film thickness meter or the like, and can be measured, for example, by the method described in examples.

(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 an optical laminate having the above-mentioned specific yield stress can be obtained. In the present specification, the polyimide-based resin means at least 1 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 referred to as polyamic acid. The polyimide resin film contained in the optical laminate of the present invention may contain 1 kind of polyimide resin, or may contain 2 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 easily suppressing the occurrence of cracks, whitening, and the like even when the optical laminate of the present invention is used under high-temperature and high-humidity conditions.

In a preferred embodiment of the present invention, the polyimide resin is preferably an aromatic resin from the viewpoint of easily reducing the occurrence of cracking and whitening during folding, particularly folding under high-temperature and high-humidity conditions, and easily improving the chemical stability. In the present specification, the aromatic resin means a resin in which a structural unit contained in the polyimide resin is mainly an aromatic structural unit.

In the above-described 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, further preferably 80 mol% or more, and further more preferably 85 mol% or more, from the viewpoint of facilitating reduction of breakage and whitening during folding and from the viewpoint of facilitating improvement of chemical stability. Here, the structural unit derived from an aromatic monomer is a structural unit derived from a monomer at least a part of which contains an aromatic structure such as an aromatic ring, and at least a part of which contains an aromatic structure such as 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 comprising a structural unit represented by formula (1),

[ in formula (1), Y represents an organic group having a valence of 4, X represents an organic group having a valence of 2, and X represents a bonding end ], wherein Y in formula (1) has a structure represented by formula (3),

[ in the formula (3), R ¹ Independently of one another, represents a halogen atom, an alkyl group which may have a halogen atom, an alkoxy group, an aryl group or an aryloxy group, R ² ～R ⁵ Independently of each other, a hydrogen atom or a 1-valent hydrocarbon group which may have a halogen atom,

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

n represents an integer of 1 to 4,

* Denotes a bonding terminal wherein R is ² ～R ⁵ In at least 1 benzene ring of (2), R ² ～R ⁵ At least 3 of them are 1-valent hydrocarbon groups which may have 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 organic group is an organic group in which a hydrogen atom in the organic group may be substituted with a substituent, and the substituent is preferably a halogen atom, a hydrocarbon group that may have a valence of 1 of the halogen atom, for example, an alkyl group, an aryl group, or the like, an alkoxy group, or an aryloxy group, and in this case, the carbon number of the hydrocarbon group that may have a valence of 1 of the 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 or different from each other.

In the polyimide resin, Y in formula (1) preferably has a structure represented by formula (3). In the formula (3), R ¹ Independently of one another, represents a halogen atom, an alkyl group which may have 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-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl 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 Preferably, the halogen atom, an 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. In an optical laminate comprising a polyimide resin film, R is a group that is easy to reduce cracking and whitening during folding and easy to improve transparency ¹ The alkyl group or the alkoxy group may have a halogen atom, and the alkyl group having 1 to 6 carbon atoms or the alkoxy group having 1 to 6 carbon atoms may have a halogen atom is more preferable.

In the 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 fracture and whitening during folding of the optical laminate and facilitating improvement of transparency.

In the formula (3), R ² 、R ³ 、R ⁴ And R ⁵ Independently of each other, a hydrogen atom or a 1-valent hydrocarbon group which may have a halogen atom ² ～R ⁵ In at least 1 benzene ring of (2), R ² ～R ⁵ At least 3 of which are 1-valent hydrocarbon groups that may have 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-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl 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 the halogen atoms described above. R ² ～R ⁵ Preferably, the substituents independently represent a hydrogen atom, an aryl group having 6 to 12 carbon atoms which may have a halogen atom, a cycloalkyl group having 4 to 8 carbon atoms, or an alkyl group having 1 to 6 carbon atoms. From the viewpoints of easy improvement in solubility of the resin in a solvent, easy reduction in fracture and whitening when the optical laminate is folded, and easy improvement in transparency, R ² ～R ⁵ The alkyl groups are preferably, independently of each other, a hydrogen atom or an alkyl group which may have a halogen atom, more preferably a hydrogen atom or an alkyl group which may have 1 to 6 halogen atoms, and still more preferably a hydrogen atom or an alkyl group which may have 1 to 3 halogen atoms.

Having R in formula (3) ² ～R ⁵ In at least 1 benzene ring of (2), R ² ～R ⁵ When at least 3 of them are a 1-valent hydrocarbon group which may have a halogen atom, the optical laminate is liable to be reduced in cracking and whitening upon folding. In addition, the solubility of the polyimide resin in a solvent can be improved.

From the viewpoints of easy improvement in solubility of the resin in a solvent, easy reduction in cracking and whitening when the optical laminate is folded, and easy improvement in transparency, it is more preferable to use R when n is2 or more ² ～R ⁵ In at least 2 benzene rings of (2), R ² ～R ⁵ At least 3 of them are 1-valent hydrocarbon groups which may have a halogen atom, and more preferably have R ² ～R ⁵ In all benzene rings of (2), R ² ～R ⁵ At least 3 of them are 1-valent hydrocarbon groups which may have halogen atoms.

In the 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 viewpoint of easily improving the elastic modulus and transparency of the polyimide-based resin film and easily reducing the occurrence of cracking and whitening when the optical laminate is folded. In the structural unit represented by formula (1), 1 or more kinds of structures represented by formula (3) may be contained as Y.

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

in [ formula (3'), a represents a bonding end. ]. That is, at least a part of Y in formula (1) is preferably represented by formula (3'). In this manner, when the optical laminate is folded, the occurrence of cracking and whitening is easily reduced, and the transparency is easily improved.

In one embodiment of the present invention, the proportion of the structural unit represented by formula (3) in Y in the structural unit represented by formula (1) is preferably 10 mol% or more, more preferably 30 mol% or more, further preferably 45 mol% or more, further more 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 laminate is likely to be reduced in breakage and whitening when folded. 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. Proportion of structural units in which Y is represented by the formula (3)As can use ¹ H-NMR, or calculated from the feed ratio of the raw materials.

In the polyimide resin, Y in the formula (1) preferably has a structure represented by the formula (5),

[ in the formula (5), B represents a single bond, -O-, diphenylmethylene, a 2-valent hydrocarbon group which may have 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 each other, represents a hydrogen atom or an alkyl group which may have a halogen atom,

R ⁷ independently of one another, represents a halogen atom, an alkyl group which may have a halogen atom, an alkoxy group, an aryl group or an aryloxy group,

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

* Representing a bond end. ]. When Y in formula (1) further includes the structure represented by formula (5), the optical laminate is likely to be reduced in breakage and whitening upon folding, and is more likely to be improved in transparency.

In the formula (5), R ⁷ Independently of one another, represents a halogen atom, an alkyl group which may have a halogen atom, an alkoxy group, an aryl group or an aryloxy group. Examples of the halogen atom, the alkyl group which may have a halogen atom, the alkoxy group, the aryl group and the aryloxy group include R of the formula (3) ¹ The illustrated atoms or groups. From the viewpoint of ease of reducing fracture and whitening and ease of improving transparency when the optical laminate is folded, R ⁷ The alkyl groups are preferably alkyl groups having 1 to 6 carbon atoms which may have a halogen atom, and more preferably alkyl groups having 1 to 3 carbon atoms which may have a halogen atom.

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 viewpoint of facilitating reduction of fracture and whitening upon folding of the optical laminate and facilitating improvement of transparency.

B in the formula (5) independently represents a single bond, -O-, diphenylmethylene, a 2-valent hydrocarbon group which may have 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 each other, represents a hydrogen atom or an alkyl group which may have a halogen atom.

Examples of the hydrocarbyl group having a valence of 2 and optionally having a halogen atom include R in the formula (3) ² ～R ⁵ In (2), 1 hydrogen atom in the 1-valent hydrocarbon group which may have a halogen atom is further removed to obtain a 2-valent group. The 2-valent hydrocarbon group which may have a halogen atom may form a ring by replacing 2 hydrogen atoms in the hydrogen atoms contained in the group, that is, by replacing the 2 hydrogen atoms with bonding ends and connecting the 2 bonding ends, and examples of the ring include a cycloalkane ring having 3 to 12 carbon atoms. Further, the group represented by formula (5) is represented by-N (R) contained in B ^B1 ) -and-Si (R) ^B2 ) ₂ R in (A-C) ^B1 And R ^B2 In (3), an alkyl group which may have a halogen atom includes R ¹ The above-exemplified groups may have a halogen atom in the alkyl group.

From the viewpoints of ease of reducing cracking and whitening and ease of improving transparency when the optical laminate is folded, B in formula (5) preferably includes a single bond or a 2-valent hydrocarbon group which may have 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 preferable examples include a single bond and-C (CH) ₃ ) ₂ -or-C (CF) ₃ ) ₂ Further more preferably a single bond or-C (CF) ₃ ) ₂ -C (CF) is particularly preferable ₃ ) ₂ -。

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

in [ formula (5'), a represents a bonding end. ]. That is, in a preferred embodiment, at least a part of Y in formula (1) is represented by formula (5'). In this manner, the optical laminate can be easily reduced in breakage and whitening during folding, and can be more easily improved in transparency.

The proportion of the structural unit represented by formula (3) in formula (1) in the structural unit represented by formula (1) is preferably 0.1 mol or more, more preferably 0.4 mol or more, further preferably 1.0 mol or more, preferably 2.3 mol or less, more preferably 1.9 mol or less, and further preferably 1.7 mol or less, relative to 1 mol of the structural unit represented by formula (5) in formula (1). When the ratio of the structural unit represented by formula (3) to the structural unit represented by formula (5) for Y in formula (1) is not less than the lower limit, the elastic modulus of the polyimide resin film can be easily increased. When the ratio is not more than the upper limit, the optical laminate is likely to be reduced in breakage and whitening when folded, and the transparency is more likely to be improved. 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 utilized, for example ¹ H-NMR, or calculated from the feed ratio of the starting materials.

The proportion of the structural unit represented by formula (5) in formula (1) in Y in formula (1) in the structural unit represented by formula (1) is preferably more than 30 mol%, more preferably 35 mol% or more, further preferably 38 mol% or more, further more preferably 40 mol% or more, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 55 mol% or less, further more 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 is equal to or higher than the lower limit described above with respect to the total molar amount of the structural units represented by formula (1), the optical laminate is likely to be reduced in breakage and whitening upon folding, and is more likely to be improved in transparency. When the ratio is not more than the above upper limit, the polyimide content can be easily increasedThe elastic modulus of the amine resin film and the optical laminate. 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 calculated from the feed ratio of the starting materials.

In one embodiment of the present invention, the total ratio of the structural unit represented by formula (3) for Y and the structural unit represented by 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 formula (1). When the total ratio is in the above range, the elastic modulus and the transparency of the polyimide resin film are easily improved, and the optical laminate is easily reduced in breakage and whitening when folded. The total ratio can be used, for example ¹ H-NMR, or calculated from the feed ratio of the starting materials.

In formula (1), Y may include not only the structure represented by formula (3) but also the structure represented by formula (5) and the structures represented by 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.

In formulas (20) to (29), denotes a bonding end, W ¹ Represents a single bond, -O-, diphenylmethylene, or a 2-valent hydrocarbon group which may have 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 which may have a fluorine atom, and a specific example thereof is a phenylene group. R is ^W1 And R ^W2 Independently of one another, represent a hydrogen atom, orWith an alkyl group having a halogen atom. Y in formula (1) may be a group in which a hydrogen atom in the group represented by formula (20) to formula (29) is substituted by a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, or a chain hydrocarbon group having 4 valences and 6 or less carbon atoms. The hydrogen atom on the ring in formulae (20) to (29) may be substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include R of the formula (3) ¹ And the groups 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 breakage and whitening are easily reduced, the elastic modulus is easily increased, and the transparency is more easily improved when the optical laminate is folded. In addition, with respect to W ¹ From the viewpoints that when the optical laminate is folded, the breaking and whitening are easily reduced, the elastic modulus is easily increased, and the transparency is easily increased, it is preferable that the optical laminate 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 the formula (1), X represents an organic group having a valence of 2, preferably an organic group having a valence of 2 and having 4 to 40 carbon atoms.

In the present invention, the polyimide-based resin preferably contains at least 1 of a 2-valent aromatic group, a 2-valent alicyclic group, and a 2-valent aliphatic group, and more preferably contains a 2-valent aromatic group, from the viewpoints that cracking and whitening are easily reduced, the elastic modulus is easily increased, and the transparency is easily increased when the optical laminate is folded. Examples of the aromatic group having a valence of 2 includeAs R in formula (3) ² ～R ⁵ And 2-valent aromatic hydrocarbon groups in which 1 hydrogen atom of the hydrogen atoms in the aromatic hydrocarbon groups exemplified above is replaced by a bonding end; at least 1 or more of the 2-valent aromatic hydrocarbon groups are linked by a linking group, e.g., V described later ¹ And the like, to which the linking group is bonded. As the alicyclic group having a valence of 2, there may be mentioned, for example, R in the formula (3) ² ～R ⁵ And a 2-valent alicyclic hydrocarbon group in which 1 hydrogen atom of the hydrogen atoms in the alicyclic hydrocarbon groups exemplified above is replaced by a bonding end; at least 1 or more of the 2-valent alicyclic hydrocarbon groups are bonded by a linking group, e.g., V described later ¹ And a group obtained by bonding the linking group. Examples of the aliphatic group having a valence of 2 include R in the formula (3) ² ～R ⁵ And 2-valent aliphatic hydrocarbon groups in which 1 hydrogen atom of the hydrogen atoms in the aliphatic hydrocarbon groups exemplified above is replaced by a bonding end; at least 1 or more of the 2-valent aliphatic hydrocarbon groups are linked by a linking group, e.g., V described later ¹ And the like, to which the linking group is bonded.

X in formula (1) preferably represents a c 4-40 2-valent organic group having a cyclic structure such as an alicyclic ring, aromatic ring, heterocyclic ring structure, etc., more preferably represents a c 4-40 2-valent aromatic group and a c 4-40 2-valent alicyclic group, and still more preferably represents a c 4-40 2-valent aromatic group. In the organic group, a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the 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 contain a plurality of kinds of X, and the plurality of kinds of X may be the same or different from each other. Examples of X include groups represented by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17), and formula (18); those represented by the formulae (10) to (18) wherein the hydrogen atom is substituted by 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 the formulae (10) to (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 1-valent hydrocarbon group having 1 to 12 carbon atoms which may have a halogen atom. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms and optionally having a halogen atom include R of the formula (3) ² ～R ⁵ The group exemplified above may have a 1-valent hydrocarbon group of a halogen atom.

1 example is 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 independently preferably a meta position or a para position to each ring, and more preferably a para position. The hydrogen atom on the ring in formulae (10) to (18) may be substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include R of the formula (3) ¹ And the groups exemplified above.

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

[ in the formula (4), A represents a single bond, -O-, diphenylmethylene, a 2-valent hydrocarbon group which may have 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 which may have a halogen atom,

R ⁶ independently of one another, represents a halogen atom, an alkyl group which may have a halogen atom, an alkoxy group, an aryl group or an aryloxy group,

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

* Representing a bond end. ]. In this manner, the elastic modulus and the transparency of the polyimide resin film and the optical laminate can be easily improved, and the breakage and whitening can be easily reduced when the optical laminate is folded. In addition, the structural unit represented by formula (1) may include 1 or more kinds of structures represented by formula (4) as X.

R ⁶ Independently of one another, represents a halogen atom, an alkyl group which may have a halogen atom, an alkoxy group, an aryl group or an aryloxy group. Examples of the halogen atom, the alkyl group which may have a halogen atom, the alkoxy group, the aryl group and the aryloxy group include R of the formula (3) ¹ And the groups exemplified above.

Among these, R is a group that easily improves the elastic modulus and transparency of the polyimide resin film and the optical laminate, and easily reduces the breakage and whitening when the optical laminate is folded ⁶ Preferably an alkyl group having 1 to 6 carbon atoms or a haloalkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms, and preferably a perfluoroalkyl group. 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 elastic modulus and transparency of the polyimide-based resin film and the optical laminate and easily reducing the occurrence of cracking and whitening when the optical laminate is folded.

In a preferred embodiment of the present invention, among the benzene rings, preferred are: s is 1, substituted with R in the ortho-position with respect to-A-) ⁶ And R is ⁶ Is methyl, fluoro, chloro or trifluoromethyl.

In the formula (4), the positions of the bonding ends are preferably meta-or para-positions independently of each other, more preferably para-positions, based on-a-from the viewpoint of easily improving the elastic modulus and transparency of the polyimide-based resin film and the optical laminate and easily reducing the breakage and whitening when the optical laminate is folded.

A in the formula (4) independently represents a single bond, -O-, diphenylmethylene, a 2-valent hydrocarbon group which may have 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 each other, represents a hydrogen atom or an alkyl group which may have a halogen atom.

As the 2-valent hydrocarbon group which may have a halogen atom, R of the formula (3) may be mentioned ² ～R ⁵ In (2), 1 hydrogen atom in the 1-valent hydrocarbon group which may have a halogen atom is further removed to obtain a 2-valent group. The 2-valent hydrocarbon group which may have a halogen atom may form a ring by replacing 2 hydrogen atoms in the hydrogen atoms contained in the group, that is, replacing the 2 hydrogen atoms with bonding ends and connecting the 2 bonding ends 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 In (3), an alkyl group which may have a halogen atom includes R ¹ The above-exemplified groups may have a halogen atom in the alkyl group.

Preferred examples of a in formula (4) include a single bond and-CH from the viewpoints that when the optical laminate is folded, breakage and whitening are easily reduced, the elastic modulus is easily increased, and the transparency is easily increased 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 preferable examples are a single bond or-C (CF) ₃ ) ₂ The above-mentioned is particularly preferably a single bond.

In a preferred embodiment of the present invention, the polyimide resin film and the optical laminate are easily improvedIn the formula (4), R is R in view of the elastic modulus and transparency of the optical laminate and the tendency to reduce the occurrence of fracture and whitening when the optical laminate is folded 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 X in formula (1) is preferably represented by formula (4'). In this manner, when the optical laminate is folded, the breakage and whitening are easily reduced, the elastic modulus is easily increased, and the transparency is easily improved.

In one embodiment of the present invention, when X in formula (1) includes a structure represented by formula (4), 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 more 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) X is in the above range, the optical laminate is likely to be reduced in fracture and whitening when folded, and the elastic modulus is likely to be further improved. The ratio of the structural unit represented by the formula (4) for X can be used, for example ¹ H-NMR, or calculated from the feed ratio of the starting materials.

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

[ in formula (2), Z and X independently represent a 2-valent organic group, and represent a bonding end. ]. The following describes formula (2). In this embodiment, the proportion of the amide component contained in the polyamideimide resin is preferably 5 mol% or more, more preferably 10 mol% or more, even more preferably 15 mol% or more, and even more preferably 20 mol% or more, based on the amount of all the structural units contained in the polyamideimide resin, from the viewpoint of facilitating reduction of fracture and whitening upon folding the optical laminate and further facilitating improvement of the elastic modulus.

In the formula (2), Z is an organic group having a valence of 2, preferably an organic group having a valence of 2 and having a valence of 4 to 40, which may be 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 (hydrogen atoms in these groups may be substituted by a halogen atom, preferably a fluorine atom), and more preferably an organic group having a valence of 2 and having a cyclic structure and a valence of 4 to 40, which may be 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 (hydrogen atoms in these groups may be substituted by 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 formula (3) described later ^3a And R ^3b The same applies to the illustrations referred to. 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 having 2 bonds of the groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29) in which non-adjacent 2 bonds are replaced with a hydrogen atom, and a chain hydrocarbon group having 6 or less carbon atoms and a valence of 2,

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-, where Ar independently of one another represents hydrogenAn arylene group having 6 to 20 carbon atoms (e.g., phenylene group) in which the atom may be substituted with a fluorine atom]Examples of the heterocyclic structure of Z include a group having a thiophene ring skeleton. From the viewpoint of easily reducing the YI 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 formulae (26), (28), and (29).

As the organic group of Z, more preferred are 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'):

in [ formulae (20 ') to (29'), W ¹ And as defined in formulae (20) to (29).]. The hydrogen atoms on the ring in the formulae (20) to (29) and (20 ') to (29') may be 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 (the hydrogen atoms in these groups may be substituted by a halogen atom, preferably a fluorine atom).

As to the polyamideimide resin, when Z in the formula (2) has a structural unit represented by any one of the above-mentioned formulae (20 ') to (29'), particularly when Z in the formula (2) has a structural unit represented by the formula (6) described later, the polyamideimide resin preferably has a structural unit derived from a carboxylic acid represented by the following formula (d 1) in addition to the structural unit, from the viewpoint of easily improving the film-forming property of a varnish and easily improving the uniformity of a film,

[ in the formula (d 1), R ⁴¹ Independently of each other, R in the formula (6) to be described later ^3a A defined group or a hydrogen atom, R ⁴² Represents R ⁴¹ or-C (= O) -, which denotes a bonding end.]. 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.

In the polyamideimide resin, as Z in the formula (2), a plurality of Z may be contained, and a plurality 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, Z in formula (2) preferably 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 contained in (A) are independently substituted by halogen atoms, and W is independently 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 or a C1-12 hydrocarbon group which may be substituted with a halogen atom, s is an integer of 0 to 4, t is an integer of 0 to 4, and u is an integer of 0 to 4, and represents a bonding end.]，

More preferably at least a structural unit represented by the formula (6'):

[ formula (6'), [ wherein R ^3a 、R ^3b S, t, u, W and are as defined in formula (6).]. In the present specification, Z in formula (2) in the polyamideimide resin has the formula (6)The structural unit and the polyamideimide resin have the same meaning as that Z in the formula (2) has a structure represented by the formula (6), and Z in the structural unit representing at least a part of the structural units represented by the formula (2) that can be contained in the polyamideimide resin is 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-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl 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 the elastic modulus, surface hardness, and flexibility of the polyimide resin film and the optical laminate, R ^3a And R ^3b Preferably independently of each other, an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. Herein, R is ^3a And R ^3b The hydrogen atoms contained in (a) may be independently substituted by halogen atoms.

R ⁹ Represents a hydrogen atom, a C1-12 hydrocarbon group which may be substituted with a halogen atom. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, and,N-pentyl group, 2-methylbutyl group, 3-methylbutyl group, 2-ethylpropyl group, n-hexyl group, n-heptyl group, n-octyl group, t-octyl group, n-nonyl group, n-decyl group, etc., which may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

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, and more preferably 1 or 2.

In the formula (6) and the formula (6'), s is an integer in the range of 0 to 4, and when s is in this range, the elastic modulus and the bending resistance of the polyimide-based resin film and the optical laminate are easily improved, and the breakage and whitening are easily reduced when the optical laminate is folded. 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 more easily improving the elastic modulus and the bending resistance of the polyimide-based resin film and the optical laminate. Regarding the polyamideimide resin, Z may contain 1 or 2 or more kinds of the structural unit represented by the formula (6) or the formula (6').

In a preferred embodiment of the present invention, Z is preferably represented by formula (6) or formula (6') where s is 0 and u is preferably 1 to 3, more preferably 1 or 2, from the viewpoints of improvement in elastic modulus and bending resistance and reduction in YI of the polyimide-based resin film and the optical laminate. Further, it is also preferable that the structural unit represented by the above formula (d 1) is further contained in addition to the structural unit represented by the formula (2) having Z represented by the formula (6) or the formula (6') wherein 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, further more preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, further preferably 80 mol% or less, 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%. If the structural unit represented by formula (6) or formula (6') isWhen the ratio of the element is not less than the lower limit, the elastic modulus and the bending resistance of the polyimide 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, the increase in viscosity of the resin-containing varnish due to hydrogen bonding between amide bonds of formula (6) can be easily suppressed, and the film processability can be easily improved. The proportion of the structural unit represented by formula (1), formula (2), formula (6) or formula (6') can be used, for example ¹ H-NMR, or calculated from the feed ratio of the starting materials.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, and still more preferably 50 mol% or more of Z in the polyamideimide resin is a structural unit represented by formula (6) or formula (6') wherein s is 0 to 4. When the 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 elastic 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') in which s is 0 to 4 in the resin can be used, for example ¹ H-NMR, or calculated from the feed ratio of the starting materials.

When the polyimide-based 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 more 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 elastic modulus of the polyimide 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), or may contain a structural unit represented by formula (1), a structural unit represented by formula (2) as the case may be, and a structural unit represented by formula (30) and/or a structural unit represented by formula (31).

In the formula (30), Y ¹ Is a 4-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As 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 4 valences and 6 or less carbon atoms. 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 as or different from each other.

In the formula (31), Y ² Is a 3-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y ² Examples thereof include a group in which 1 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 by a hydrogen atom, and a chain hydrocarbon group having 3 valences and 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 as or different from each other.

In formulae (30) and (31), X ¹ And X ² Independently of each other, a 2-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As X ¹ And X ² Examples thereof include the above-mentioned formula (10), formula (11), formula (12), formula (13), and formula(s) ((iii))14 A group represented by 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 by 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 includes 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 reducing the breakage and whitening upon folding the optical laminate, easily improving the bending resistance, and easily improving the transparency and elastic modulus of the polyimide resin film, the proportion of the structural units represented by the formulae (1) and (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 the formulae (1) and (2) and, in some cases, the formulae (30) and (31). The ratio of the structural units represented by the formulae (1) and (2) in the polyimide-based resin 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/or (31). The above ratio can be used, for example ¹ H-NMR, or calculated from the feed ratio of the starting 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, preferably 99.5 parts by mass or less, and 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 elastic modulus of the polyimide-based resin film are easily improved, and the optical laminate is easily reduced in breakage and whitening when folded.

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 more preferably 270,000 or more, particularly preferably 280,000 or more, and particularly more preferably 300,000 or more in terms of standard polystyrene, from the viewpoint of facilitating reduction of fracture and whitening upon folding the optical laminate and facilitating improvement of the elastic modulus and the bending resistance. 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, 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 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, for example, a halogen atom such as a fluorine atom which can be introduced through the above-mentioned fluorine-containing substituent or the like. In the case where the polyimide-based resin contains a halogen atom, the elastic modulus of the polyimide-based resin film and the optical laminate is easily increased, and YI is easily reduced. When the YI of the polyimide resin film is low, the transparency and visibility of the film are easily improved. The halogen atom is preferably a fluorine atom. In order to contain a fluorine atom in the polyimide resin, preferable examples of the fluorine-containing substituent 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 in the above range, the elastic modulus of the polyimide resin film and the optical laminate can be more easily increased, the YI can be more easily reduced, the transparency and the visibility can be more easily improved, and the synthesis can be more easily performed.

In another preferred embodiment of the present invention, since a tendency of lowering the glass transition temperature is observed when silicon atoms are contained, it is preferable that the content of silicon atoms contained in the polyimide-based resin is small. 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, further preferably 1% by mass or less, and further more preferably 0.5% by mass or less, based on the mass of the polyimide resin. The polyimide resin particularly preferably contains substantially no silicon atom.

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

The coefficient of thermal expansion under humidity (hereinafter also referred to as "CME") of the polyimide resin film contained as the base layer in the optical laminate of the present invention is preferably 40ppm/K or less, more preferably 35ppm/K or less, further preferably 30ppm/K or less, further more preferably 25ppm/K or less, particularly preferably 20ppm/K or less, and usually 0ppm/K, from the viewpoint of easily reducing the cracking and whitening of the optical laminate including the film when folded under high-temperature and high-humidity conditions. The smaller the humidity expansion ratio, the better. The CME can be the humidity expansion rate of the membrane when the membrane is maintained at 60 ℃ and 90% humidity for 1 hour, and can be measured, for example, by the method described in examples.

The moisture absorption rate of the polyimide resin film under the conditions of 60 ℃ temperature and 90% humidity is preferably 3% or less, more preferably 2.8% or less, and even more preferably 2.7% or less, from the viewpoint of easily reducing the breakage and whitening during folding under high temperature and high humidity conditions of an optical laminate including the film. The moisture absorption rate under the conditions of the temperature of 60 ℃ and the humidity of 90% can be measured by a thermomechanical analyzer, for example, by the method described in examples.

The thickness of the polyimide-based resin film is preferably 5 μm or more, more preferably 10 μm or more, further preferably 20 μm or more, further more preferably 25 μm or more, particularly preferably 30 μm or more, particularly more preferably 40 μm or more, extremely preferably 45 μm or more, preferably 200 μm or less, more preferably 100 μm or less, further more preferably 80 μm or less, particularly preferably 60 μm or less, and the preferable range may be a combination of these upper and lower limits. When the thickness of the polyimide resin film is within the above range, the stress or the like at the time of straining the optical layered body by 3% can be easily adjusted within the above range, and the occurrence of cracking and whitening during folding under high-temperature and high-humidity conditions of the optical layered body can be easily reduced.

The elastic modulus, the folding endurance, the YI, the total light transmittance and the haze of the polyimide resin film contained 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 producing the polyimide resin preferably contains at least a compound represented by the formula (X):

[ in the formula (X), R ¹ ～R ⁵ N and m are respectively equal to R in the formula (3) ¹ ～R ⁵ N and m are the same.]

More preferably, a compound represented by the formula (Y):

[ formula (Y) wherein B and R ⁷ And t is respectively the same as B and R in the formula (5) ⁷ And t are the same.]。

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, and a commercially available product can also be used.

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

Examples of the tetracarboxylic acid compound used for the synthesis of the polyimide-based resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compounds may be used alone or in combination of 2 or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound, in addition to the dianhydride.

Examples of the tetracarboxylic acid compound used for producing the resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. The tetracarboxylic acid compounds may be used alone or in combination of 2 or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound, in addition to the dianhydride.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4,4 '-oxydiphthalic dianhydride, 3',4 '-benzophenonetetracarboxylic dianhydride, 2',3,3 '-benzophenone tetracarboxylic dianhydride, 3,3',4,4 '-biphenyl tetracarboxylic dianhydride (hereinafter sometimes referred to as BPDA), 2,2',3,3 '-biphenyl tetracarboxylic dianhydride, 3,3',4,4 '-diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4' - (hexafluoroisopropylidene) diphthalic dianhydride (sometimes referred to as 6 FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, and the like 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4'- (p-phenylenedioxy) diphthalic dianhydride, 4' - (m-phenylenedioxy) diphthalic dianhydride. 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, 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, bis (3, 4-dicarboxyphenyl) methane dianhydride, 3,4' -bis (3, 4 '-dicarboxyphenyl) methane dianhydride, and further preferably, 3,4' -phthalic dianhydride, 4'- (4, 4' -dicarboxyphenyl) methane dianhydride. These may be used alone or in combination of 2 or more.

Examples of the aliphatic tetracarboxylic acid dianhydride include cyclic and acyclic aliphatic tetracarboxylic acid 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 2 or more. Specific examples of the acyclic aliphatic tetracarboxylic acid dianhydride include 1,2,3, 4-butanetetracarboxylic acid dianhydride, and 1,2,3, 4-pentanetetracarboxylic acid dianhydride, and these can be used alone or in combination of 2 or more. In addition, cyclic aliphatic tetracarboxylic dianhydrides and acyclic aliphatic tetracarboxylic dianhydrides can be used in combination.

Among the tetracarboxylic dianhydrides, 4' -oxydiphthalic dianhydride, 3',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 producing 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 may include an aliphatic group or other substituent in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but 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 may contain an aromatic ring or other substituent in a part of the structure.

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

As the aromatic diamine, there may be mentioned, examples thereof include aromatic diamines having 1 aromatic ring such as p-phenylenediamine, m-phenylenediamine, 2, 4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene, 2, 6-diaminonaphthalene, 4 '-diaminodiphenylmethane, and the like 4,4' -diaminodiphenylpropane, 4 '-diaminodiphenyl ether, 3' -diaminodiphenyl ether, 4 '-diaminodiphenyl sulfone, 3,4' -diaminodiphenyl sulfone, 3,3' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2' -dimethylbenzidine aromatic diamines having 2 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 2 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 2 or more.

Among the diamine compounds, 1 or more selected from aromatic diamines having a biphenyl structure are preferably used from the viewpoints of high elastic modulus, high transparency, high flexibility, high bending resistance, and low coloring property of a polyimide resin film. More preferably, 1 or more 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 producing 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 2 or more of them may be used in combination. Specific examples thereof include isophthalic acid; naphthalenedicarboxylic acid; 4,4' -biphenyldicarboxylic acid; 3,3' -biphenyldicarboxylic acid; dicarboxylic acid compound of chain hydrocarbon with carbon number of 8 or less and 2 benzoic acids are formed from single bond, -CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -or phenylene group-linked compounds, and acid chloride compounds thereof. Specifically, 4 '-oxybis (benzoyl chloride) (sometimes referred to as OBBC), terephthaloyl chloride, or isophthaloyl chloride is preferable, and it is more preferable to use 4,4' -oxybis (benzoyl chloride) and terephthaloyl chloride in combination.

The polyimide resin may be obtained by further reacting a tetracarboxylic acid, a tricarboxylic acid, and anhydrides and derivatives thereof with the tetracarboxylic acid compound in 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 and an aliphatic tricarboxylic acidAnd the like, and 2 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; phthalic anhydride and benzoic acid consisting of single bond, -O-, -CH ₂ -、-C(CH ₃ ) ₂ -、-C(CF ₃ ) ₂ -、-SO ₂ -or phenylene linkage.

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, but is, for example, 5 to 350 ℃, preferably 20 to 200 ℃, and more preferably 25 to 100 ℃. The reaction time is also not particularly limited, but is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out in an inert atmosphere or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or in an inert gas atmosphere while stirring. 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 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 solvents such as ethylene carbonate and propylene carbonate; and combinations thereof, i.e., mixed solvents, and the like. Among these, an amide solvent can be suitably 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 imidization reaction, it is preferable to use an acid anhydride in addition to the imidization catalyst. Examples of the acid anhydride include conventional acid anhydrides 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 separated 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 embodiment, the resin can be separated 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 further contain at least 1 filler in addition to the polyimide resin. Examples of the filler include organic particles and inorganic particles, and preferable examples thereof include inorganic particles. Examples of 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, and among these, silica particles, zirconia particles and alumina particles are preferable, and silica particles are more preferable, from the viewpoint of easily improving the elastic modulus of the polyimide-based resin film and the optical laminate. These fillers may be used alone or in combination of 2 or more.

The average primary particle diameter of the filler (preferably 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 more preferably 70nm or less, particularly preferably 60nm or less, particularly more 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 easily improved. The average primary particle size of the filler can be measured by the BET method. The average primary particle size may be measured by image analysis using a transmission electron microscope or a scanning electron microscope.

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

The polyimide resin film may further contain additives other than a filler and an ultraviolet absorber. Examples of the other additives include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, and leveling agents. When other additives are contained, the content thereof may be preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and still more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the polyimide resin film.

[ method for producing polyimide resin film ]

The method for producing the polyimide resin film of the present invention is not particularly limited, but 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, a varnish is prepared by dissolving a polyimide resin in a solvent, and adding the above-mentioned additives such as a filler and an ultraviolet absorber, if necessary, and mixing them with stirring. When silica particles are used as the filler, a silica sol containing silica particles may be added to a resin in a dispersion liquid of the silica sol, the silica sol being substituted with a solvent capable of dissolving the resin, for example, a solvent used in the preparation of a varnish described below.

The solvent used for the preparation of the varnish is not particularly limited as long as it can dissolve the resin. Examples of the 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 solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, an amide solvent or a lactone solvent is preferable. These solvents may be used alone or in combination of two or more. The varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, and still more preferably 5 to 15% by mass.

In the coating step, a varnish may be 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 methods, comma knife coating methods, lip coating methods, spin coating methods, screen coating methods, jet coating methods, dipping methods, spray coating methods, and cast molding methods.

In the film forming step, the coating film is dried and peeled from the support material, thereby forming a polyimide resin film. A step of drying the polyimide resin film may be further provided after the peeling. The drying of the coating film can be usually carried out at a temperature of 50 to 350 ℃. The coating film may be dried in an inert atmosphere or under reduced pressure as necessary. The polyimide resin film obtained may have a slight residual of a part of the solvent contained in the varnish. The amount of the solvent contained in the polyimide resin film is preferably 1.5% or less, more preferably 1.2% or less, further preferably 1.1% or less, and further more preferably 1.0% or less, with respect to 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, further preferably 0.1% or more, and further more preferably 0.3% or more.

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

[ functional layer ]

The optical laminate of the present invention includes a base layer formed of the above-described polyimide resin film, and a functional layer including a cured product of a curable resin. Examples of the functional layer of the 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 1 or two or more kinds of 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 still more preferably 4 to 30 μm. When the thickness of the hard coat layer is in the above range, fracture and whitening at the time of folding the optical laminate can be reduced, impact resistance can be further improved, and the bending resistance tends not to be easily lowered. The hard coat layer can be formed by curing a hard coat composition containing a reactive material capable of forming a cross-linked structure by irradiation with active energy rays or application of thermal energy, preferably a layer formed by irradiation with active energy rays. The active energy ray is defined as an energy ray capable of decomposing a compound capable of generating an active species to generate an active species, and examples thereof include visible light, ultraviolet ray, infrared ray, X-ray, α -ray, β -ray, γ -ray, electron beam, and the like, and preferable examples thereof include ultraviolet ray. The hard coat composition contains at least 1 polymer of 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, and specifically include a vinyl group and a (meth) acryloyl group. When the radical polymerizable compound has 2 or more radical polymerizable groups, the radical polymerizable groups may be the same or different. The number of radical polymerizable groups in 1 molecule of the radical polymerizable compound is preferably 2 or more in terms of increasing the hardness of the hard coat layer. The radical polymerizable compound preferably includes a compound having a (meth) acryloyl group in view of high reactivity, specifically, a compound called a multifunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in 1 molecule, an epoxy (meth) acrylate, a urethane (meth) acrylate, an oligomer called a polyester (meth) acrylate having several (meth) acryloyl groups in a molecule and having a molecular weight of several hundreds to several thousands, and preferably 1 or more 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 contained in 1 molecule of the cationically polymerizable compound is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

Among the above cationically polymerizable compounds, preferred are compounds having at least 1 of an epoxy group and an oxetane group as a cationically polymerizable group. A cyclic ether group such as an epoxy group or an oxetane group is preferable in that the shrinkage accompanying the polymerization reaction is small. In addition, the compound having an epoxy group in a cyclic ether group has the following advantages: it is easy to obtain compounds having various structures, to exert no adverse effect on the durability of the obtained hard coat layer, and to control the compatibility with the radical polymerizable compound. In addition, the oxetanyl group in the cyclic ether group has the following advantages as compared with the epoxy group: a hard coat layer which is easily increased in polymerization degree and low in toxicity, and which is obtained by forming a network of a cationically polymerizable compound in the hard coat layer at a high speed, and which forms an independent network without leaving unreacted monomers in the film even in a region where the hard coat layer is mixed with a radically polymerizable compound; 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 above hard coat composition may further comprise a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and they can be appropriately selected and used. These polymerization initiators are substances which are decomposed by at least one of irradiation with active energy rays and heating, and generate radicals or cations to advance radical polymerization and cationic polymerization.

The radical polymerization initiator may be one that can release 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 hydrogen abstraction 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, the cationic polymerization can be initiated by either or both of the irradiation with active energy rays or the heating, depending on the structural difference.

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

The hard coating composition may further include one or more selected from solvents and additives.

The solvent is a solvent capable of dissolving or dispersing the polymerizable compound and the polymerization initiator, and may be used in a range not interfering with the effects of the present invention, as long as it is known as a solvent for a hard coat composition in the art.

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

In a functional layer containing a cured product of a curable resin, for example, a hard coat layer, a coating film is irradiated with high-energy rays such as active energy rays to cure the coating film, thereby forming the 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 activating 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 generation during the curing reaction can be suppressed. The irradiation time is not particularly limited, and may be suitably selected depending on the composition of the curable composition, and the cumulative light amount represented by the product of the irradiation intensity and the irradiation time is preferably 10 to 10,000mJ/cm ² More preferably 50 to 1,000mJ/cm ² More preferably 80 to 500mJ/cm ² . When the cumulative light amount is within the above range, a sufficient amount of active species derived from the polymerization initiator can be generated, the curing reaction can be more reliably advanced, and the irradiation time can be kept from being excessively long to maintain good productivity. In addition, the hard coat layer can be further increased in hardness by the irradiation step in this range, and therefore, this is useful. From increasing hardnessFrom the viewpoint of smoothness of the coating layer and further improvement of visibility of the optical film in the wide angle direction, the kind of solvent, the component ratio, optimization of the solid content concentration, addition of a leveling agent, and the like can be mentioned.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, and is formed of a main material selected from, for example, an ultraviolet curing type transparent resin, an electron beam curing type transparent resin, and a thermosetting type 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 may be used. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

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 a capsule adhesive as "a substance having adhesiveness at normal temperature and adhering to an adherend under light pressure" (JIS K6800), or as "an adhesive capable of maintaining stability until a protective film (microcapsule) is broken by an appropriate means such as pressure or heat by including a specific component in the protective film" (JIS K6800).

The color tone adjusting layer is a layer having a function of adjusting a color tone, 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, and diketopyrrolopyrrole-based compounds; bulk pigments such as barium sulfate and calcium carbonate; and basic dyes, acid dyes, mordant dyes and the like.

The refractive index adjustment layer is a layer having a function of adjusting the refractive index, and is, for example, a layer having a refractive index different from that of 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 layer containing an appropriately selected resin and, in some cases, a pigment, or may be a thin film of a metal. Examples of the pigment for adjusting the refractive index include silica, alumina, 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 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 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 visible side of 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 curling of the image display device. A front panel of a flexible display device used in association with such repeated bending operations is required to have high bending resistance. In addition, high visibility is also required for the front panel. Films for front panels of image display devices, particularly for front panels of flexible display devices, are required to have higher visibility and higher bending resistance than films for substrates of image display devices used inside the image display devices. For example, the film of the present invention preferably has the total light transmittance, haze and/or YI described above from the viewpoint of facilitating improvement in visibility when used as a front panel of a flexible display device, and preferably has a bending resistance number of 10 ten thousand or more, more preferably 20 ten thousand or more in the MIT bending fatigue test from the viewpoint of facilitating improvement in bending resistance when used as a front panel of a flexible display device.

Examples of the image display device include wearable devices such as a television, a smartphone, a mobile phone, a car navigation system, a tablet computer, a portable game machine, electronic paper, a pointer, a bulletin board, a clock, and a smart watch. Examples of the flexible display device include all image display devices having a flexible property, such as the rollable display and the foldable display described above. A rollable display is an image display device used in a state where an image display portion including a front panel is rolled up and is pulled out to be flat or curved, and is an image display device that performs an operation such as rolling up each time it is used. The foldable display is an image display device used in a state where an image display portion including a front panel is folded and the image display portion is opened to be a flat surface or a curved surface, and is an image display device which performs an operation such as folding 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 laminate of the present invention is preferably used as a front panel in a flexible display device. The flexible display device is formed from a laminate for flexible display devices and an organic EL display panel, and the laminate for flexible display devices is disposed on the visible side of the organic EL display panel and is configured so as to be bendable. The laminate for a flexible display device may contain a window film, a polarizing plate, and a touch sensor as the optical laminate of the present invention, and the lamination order thereof is arbitrary, and it is preferable to laminate the window film, the polarizing plate, and the touch sensor in this order or the window film, the touch sensor, and the polarizing plate in this order from the visible side. The presence of the polarizing plate on the visible side of the touch sensor is preferable because the pattern of the touch sensor is less likely to be observed and the visibility of the display image is improved. The members may be laminated using an adhesive, a bonding agent, or the like. Further, the light-shielding film may include a light-shielding pattern formed on at least one surface of any one of the window film, the polarizing plate, and the touch sensor.

[ polarizing plate ]

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 linear polarizing plate and the λ/4 retardation plate do not necessarily have to be stacked adjacent to each other, 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 necessarily the case in practical applications, and therefore, the circularly polarizing plate in the present invention also includes an elliptically polarizing plate. It is also preferable to further laminate a λ/4 phase difference film on the viewing side of the linear polarizing plate to circularly polarize the emitted light, thereby improving the visibility when 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 linearly polarizing plate may be a single linearly polarizing plate or a linearly polarizing plate including a linearly polarizing plate and a protective film bonded to at least one surface thereof. 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 not to be easily lowered.

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

In addition, another example of the polarizing plate is 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 a liquid crystalline compound having a high-order alignment state such as a smectic state because it can exhibit high polarization performance. The liquid crystalline compound preferably has a polymerizable functional group.

The dichroic dye may have liquid crystallinity or may have a polymerizable functional group. 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 onto 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 is 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 further 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. As the orientation agent, for example, polyvinyl alcohols, polyacrylates, polyamide acids, and polyimides can be used. In the case of applying photo-alignment, it is preferable to use an alignment agent containing a cinnamate group (cinnamate group). The weight average molecular weight of the polymer that can be used as the orientation agent may be, for example, about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000nm, and more preferably 10 to 500nm, from the viewpoint of alignment regulating force. The liquid crystal polarizing layer may be formed by transferring after being peeled off from the substrate, or may be formed by directly laminating the substrate. 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 used may be a polyolefin such as polyethylene, polypropylene, polymethylpentene, norbornene, or a cycloolefin derivative having a unit of a monomer containing a cycloolefin, a (modified) cellulose such as diacetylcellulose, triacetyl cellulose, or propionyl cellulose, or an acrylic such as a methyl methacrylate (co) polymer, a polystyrene such as a styrene (co) polymer, an acrylonitrile-butadiene-styrene copolymer, an acrylonitrile-styrene copolymer, an ethylene-vinyl acetate copolymer, a polyvinyl chloride, a polyvinylidene chloride, a polyethylene terephthalate, a polybutylene terephthalate, a polyethylene naphthalate, a polycarbonate, or a polyarylate, a polyester such as nylon, a polyamide such as a polyimide, a polyamideimide, a polyether imide, a polyether sulfone, a polysulfone, a polyvinyl alcohol, a polyvinyl acetal, a polyurethane, or an epoxy resin, and a film of a polyamide, a polyamideimide, a polyester, a cellulose, a polyimide, a polyester, or a polyolefin film is preferable in terms of transparency and heat resistance. These polymers may be used alone or in combination of 2 or more. These films may be used in an unstretched state, or as uniaxially or biaxially stretched films. Cellulose-based films, olefin-based films, acrylic films, and polyester films are preferable. The protective film may be a coating type protective film obtained by applying 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 colorant such as a pigment or 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 is preferably 200 μm or less, and more preferably 1 to 100 μm. If the thickness of the protective film is in 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 retardation 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, or the like may be contained. 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 crystal compound having a property of exhibiting a liquid crystal state such as a nematic, cholesteric, or 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, as described above for the 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 off 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, the birefringence is large as the wavelength is shorter, and the birefringence is small as the wavelength is longer. In this case, since a retardation of λ/4 cannot be achieved in all visible light regions, an in-plane retardation of λ/4, that is, 100 to 180nm, preferably 130 to 150nm, is often designed in the vicinity of 560nm, which has high visibility. The use of an inverse dispersion λ/4 phase difference plate using a material having a birefringence wavelength dispersion characteristic opposite to that of the usual one is preferable because visibility can be improved. As such a material, a material described in japanese patent application laid-open No. 2007-232873 and the like is preferably used also in the case of a stretched retardation plate, and a material described in japanese patent application laid-open No. 2010-30979 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 those of 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 in any case, when the liquid crystal coating type retardation plate is used, the thickness can be reduced, and therefore, it is preferable.

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 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. A 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, but the capacitance type is preferable. The capacitive touch sensor may be divided into an active region and a non-active region located at a peripheral portion of the active region. The active region is a region corresponding to a display portion, which is a region on the display panel where a screen is displayed, and is a region where a touch by a user is sensed, and the inactive region is a region corresponding to a non-display portion, which is a region on the display device where a screen is not displayed. The touch sensor may include: a substrate having flexible properties; a sensing pattern formed in an active region of the substrate; and each sensing line formed in a non-active region of the substrate and connecting the sensing pattern to an external driving circuit via a pad (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 cracks in 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 portion 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 in the same layer, and the patterns must be electrically connected in order to sense a touched position. 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 2 or more. ITO may be preferably used. The metal usable for the wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, and the like, and 2 or more kinds thereof may be used alone or in combination.

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 sensor 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 2 nd pattern may be connected to the bridge electrode through a contact hole formed in 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 a copolymer containing different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.

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 constituting each layer, such as a linear polarizing plate and a λ/4 retardation plate, 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, or 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 and the type of the adhesive used may be the same or different.

The aqueous solvent-volatile adhesive may be a polymer in an aqueous dispersion state such as a polyvinyl alcohol polymer, a water-soluble polymer such as starch, 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 properties can be imparted 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 when the aqueous solvent volatile adhesive is used 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 and the type of the adhesive may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material that forms an adhesive layer by irradiation with an active energy ray. The active energy ray-curable composition may contain at least 1 polymer of a radical polymerizable compound and a cation polymerizable compound similar to those of the hard coat composition. The radical polymerizable compound may be the same kind as that of the hard coat composition. The radical polymerizable compound used in the adhesive layer is preferably a compound having an acryloyl group. In order to reduce the viscosity of the adhesive composition, a monofunctional compound is preferably contained.

The cationic polymerizable compound may be the same kind as that of the hard coat composition. The cationically 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.

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

The active energy ray-curable composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, an antifoaming agent, an additive, and a solvent. 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 one or both of the adhesive layers, and then the adhesive layers are bonded to each other, and the composition is cured by irradiating the active energy ray through one or both of the adhesive layers. The thickness of the adhesive layer when the active energy ray-curable adhesive is used is 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 pressure-sensitive adhesive may be classified into an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, and the like according to the base polymer, and any of them may be used. The adhesive may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler, and the like in addition to the main polymer. The adhesive layer or the adhesive layer can be 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 when the adhesive is used is 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 (bezel) or a housing of the flexible image display device. The wiring disposed at the edge portion of the flexible image display device is hidden by the light shielding pattern, so that the wiring is not easily viewed, thereby improving the visibility of an image. The light-shielding pattern may be in the form of a single layer or a plurality of layers. The color of the light-shielding pattern is not particularly limited, and may 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 an acrylic resin, an ester resin, an epoxy resin, polyurethane, or silicone. They may be used alone or in the form of a mixture of 2 or more. The light-shielding pattern can be formed by various methods such as printing, photolithography, and 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

The present invention will be described in more 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)" mean "% by mass" and "part(s) by mass", respectively, unless otherwise specified. First, a method for measuring each physical property value and the like is described.

< measurement of weight average molecular weight >

Gel Permeation Chromatography (GPC) assay

(1) Pretreatment method

To the polyamideimide membrane, DMF eluent (a solution to which 10mmol/L lithium bromide was added) was added so that the concentration thereof became 2mg/mL, and the solution was heated while stirring at 80 ℃ for 30 minutes, cooled, and then filtered with a 0.45 μm membrane filter, and the obtained solution 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 (with addition of 10mmol/L lithium bromide)

Flow rate: 1.0 mL/min

A detector: RI detector

Column temperature: 40 deg.C

Sample injection amount: 100 μ L

Molecular weight standard: standard polystyrene

< measurement of Yellowness (YI) >

The yellowness (Yellow Index: YI) of the optical laminates obtained in examples and comparative examples was measured in accordance with JIS K7373: 2006, measurement was performed using an ultraviolet-visible near-infrared spectrophotometer (manufactured by Nippon spectral Co., ltd., V-670). After the background measurement was performed without a film, the film was set on a sample holder, and transmittance measurement was performed for light of 300 to 800nm to obtain 3 stimulus values (X, Y, Z). YI is calculated based on the following equation.

YI＝100×(1.2769X-1.0592Z)/Y

[ thickness of polyimide resin film and optical laminate ]

The thicknesses of the polyimide resin film and the optical laminate were measured at 10 points or more using a digital display scale (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).

< film bending test >

The optical layered bodies obtained in examples and comparative examples were used as measurement samples, and bending tests were performed using a bending tester (ML 11MC-CET02A, manufactured by YUASA SYSTEM MACHINE, inc.).

(high temperature high humidity bending test)

The bending test was repeated 30 ten thousand times under conditions of a temperature of 60 ℃, a humidity of 93%, 60 times/min, and R =1.5mm, during which the number of times whitening and breaking of the film was measured. YI was measured for 10 ten thousand cycles of bending, and the difference from YI before the bending test was calculated as Δ YI.

< tensile test >

The optical layered bodies obtained in examples and comparative examples were cut into a dumbbell shape according to JIS No. 2 using a dumbbell knife, to obtain samples. The measurement was carried out using a table-top precision universal tester (Autograph AGS-X, manufactured by Shimadzu corporation) and a constant temperature and humidity chamber (THC 1, manufactured by Shimadzu corporation). A sample was set in a table type precision universal testing machine under the conditions of a temperature of 60 ℃, a humidity of 93%, a chuck gap of 70mm, and a drawing speed of 10 mm/min, and a stress-strain curve was measured at the time when the temperature and the humidity became constant. The elastic modulus was calculated from the slope of the obtained stress-strain curve. When a straight line having a slope equal to the elastic modulus is drawn with reference to the point of 0.2% strain of the stress-strain curve, the strain at the point intersecting the stress-strain curve is denoted as YS, and the stress at this point is calculated as proof stress. Then, the stress at 3% strain was calculated as the stress at 3% strain.

< measurement of coefficient of humidity expansion CME >

After the temperature and humidity were adjusted from 60 ℃ and 0% to 60 ℃ and humidity 90%, the optical laminate was held for 1 hour with a load of 20mN, and the expansion ratio of the optical laminate at this time was measured by using a thermomechanical analyzer (TMA/SS 6100, manufactured by Hitachi Kagaku Co., ltd.), and the humidity-average linear expansion coefficient was determined from the obtained expansion ratio.

< measurement of moisture absorption Rate under conditions of temperature 60 ℃ and humidity 90% >

The measurement was carried out using a differential thermogravimeter (TG/DTA 6200, manufactured by SEIKO electronics industries, ltd.). The pieces cut into pieces 15mm square were placed in a sample cell, and the temperature and humidity were set to 60 ℃ and 90%. After the sample was allowed to stand until the mass of the sample was stabilized, the mass of the sample was measured every 10 seconds, the average value of the measured values for one minute was obtained, and the moisture absorption rate was calculated from the change in mass according to the following equation.

Sample mass (mg) when moisture absorption amount (mg) = humidity 90% — sample mass (mg) before humidification

Moisture absorption rate (%) = moisture absorption amount (mg) ÷ sample mass before humidification (mg) × 100

< production example 1: preparation of photocurable resin composition A for hard coating >

Urethane acrylate (Miwon Specialty Chemical co., ltd., MIRAMER PU 620D) 19 parts by mass, polyfunctional acrylate (Miwon Specialty Chemical co., ltd., MIRAMER SP 1106) 19 parts by mass, antimony pentoxide (TYS-F90-KR, manufactured by TOYO INK corporation) 20 parts by mass, methyl ethyl ketone (tokyo Chemical industry corporation) 38 parts by mass, leveling agent (BYK Japan, manufactured by BYK (registered trademark) -307) 0.3 parts by mass were stirred and mixed to obtain photocurable resin composition a.

< production example 2: preparation of photocurable resin composition B for hard coating >

A photocurable resin composition B was obtained by stirring and mixing 18 parts by mass of urethane acrylate (Miwon Specialty Chemical co., ltd., MIRAMER PU 620D), 18 parts by mass of polyfunctional acrylate (Miwon Specialty Chemical co., ltd., MIRAMER SP 1106), 1.8 parts by mass of lithium salt containing a (meth) acrylate group and an anion (MTFSiLi, manufactured by specialic Polymers), 60 parts by mass of methyl ethyl ketone (manufactured by tokyo Chemical industries), and 0.3 part by mass of a leveling agent (manufactured by BYK Japan, registered trademark) -307).

< production example 3: preparation of polyamideimide 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 the flask while stirring at room temperature, to dissolve the DMAc. Then, 6FDA 4.797g (10.80 mmol) and 6.679g (10.8 mmol) of tetracarboxylic dianhydride (TMPBP-TME) represented by the following formula (A) were added to the flask, and the mixture was stirred at room temperature for 16 hours.

Thereafter, 6.576g (32.39 mmol) of TPC and 313.6g of DMAc were put into the flask, and stirred at room temperature for 2 hours. Then, 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 charged into 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 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 (1). The Mw of the polyamideimide resin (1) was 360,000.

< production example 4: production of Polyamide-imide film (1) >

DMAc was added to the polyamideimide resin (1) obtained in production example 3 so that the concentration became 10.5 mass%, thereby producing a polyamideimide varnish (1). The obtained polyamideimide varnish (1) was applied to a smooth surface of a glass substrate using a coater so that the thickness of the free-standing 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.

< example 1: production of optical laminate (1) >

One surface of the polyamideimide film (1) obtained in production example 4 was coated with the photocurable resin composition a by a bar coater so that the thickness after drying became 10 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 under nitrogen atmosphere and high pressure mercury (UV exposure amount: 500 mJ/cm) ² Ultraviolet illuminance: 200mW/cm ² ) Under the condition of the reaction. The thickness of the hard coat layer in the optical laminate (1) obtained was 10 μm.

< example 2: production of optical laminate (2) >

An optical laminate (2) was obtained in the same manner as in example 1, except that the photocurable resin composition a was applied to one surface of the polyamideimide film (1) obtained in production example 4 by a bar coater so that the thickness after drying became 5 μm. The thickness of the hard coat layer in the optical laminate (2) was 5 μm.

< production example 5: preparation of GBL dispersed silica Sol >

393.4G of methanol-dispersed silica sol (MA-ST-G-ML 1, manufactured by Nissan chemical industries, ltd.; primary particle diameter 27nm, silica particle solid content 30.5% by mass) and 261.0G of GBL were put into a 2000mL flask, and methanol was evaporated by a vacuum evaporator under conditions of 400hPa for 40 minutes and 250hPa for 60 minutes in a hot water bath at 45 ℃. Then, the temperature was raised to 80 ℃ at 250hPa, and the mixture was heated for 30 minutes to obtain a GBL dispersed silica sol.

< production example 6: production of Polyamide-imide film (2) >

The polyamideimide resin (1) obtained in production example 3 was dissolved in GBL, and the GBL-dispersed silica sol obtained in production example 5 was added thereto and sufficiently mixed to obtain a polyamideimide resin (1)/silica particle mixed varnish. The solid content concentration determined from the total mass of the polyamideimide resin (1) and the silica particles with respect to the mass of the varnish obtained was set to 10.0 mass%, and the mass ratio of the polyamideimide resin (1) to the silica particles was set to 80:20 to give a polyamideimide varnish (2). A polyamideimide film (2) having a thickness of 50 μm was obtained in the same manner as in production example 4 except that the polyamideimide varnish (2) was used in place of the polyamideimide varnish (1).

< example 3: production of optical layered body (3) >

An optical laminate (3) was obtained in the same manner as in example 2, except that the polyamideimide film (2) obtained in production example 6 was used in place of the polyamideimide film (1) obtained in production example 4. The thickness of the hard coat layer in the optical laminate (3) was 5 μm.

< production example 7: preparation of polyamideimide resin (2) >

313.6g of DMAc was charged into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, 18.36g (57.33 mmol) of TFMB was charged at room temperature with stirring, and the mixture was dissolved in DMAc. Then, 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, OBBC 1.7091g (5.791 mmol) and TPC 6.576g (32.39 mmol) were added to the flask and stirred at 10 ℃ for 2 hours. Then, 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 charged into 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. Then, the precipitate was dried under reduced pressure at 80 ℃ to obtain a polyamideimide resin (2). The Mw of the polyamideimide resin (2) was 300,000.

< production example 8: production of Polyamide-imide film (3) >

The polyamideimide resin (2) obtained in production example 7 was dissolved in GBL, and the GBL-dispersed silica sol obtained in production example 5 was added thereto and sufficiently mixed to obtain a polyamideimide resin (2)/silica particle mixed varnish. The solid content concentration determined from the total mass of the polyamideimide resin (2) and the silica particles with respect to the mass of the varnish obtained was set to 10.5 mass%, and the mass ratio of the polyamideimide resin (2) to the silica particles was set to 80:20, a polyamideimide varnish (3) was obtained. A polyamideimide film (3) having a thickness of 50 μm was obtained in the same manner as in production example 4 except that a polyamideimide varnish (3) was used in place of the polyamideimide varnish (1).

< comparative example 1: production of optical layered body (4) >

An optical laminate (4) was obtained in the same manner as in example 1, except that the photocurable resin composition B was applied to one surface of the polyamideimide film (3) obtained in production example 8 by a bar coater so that the thickness after drying became 10 μm. The thickness of the hard coat layer in the optical laminate (4) was 10 μm.

The polyamide-imide films (1) to (3) or the optical laminates (1) to (4) obtained as described above were measured for yellowness YI, Δ YI, the number of times of bending, elastic modulus, proof stress, YS, and stress at 3% strain according to the measurement methods described above. The results obtained are shown in table 1. Further, stress-strain curves measured at 60 ℃ and 93% humidity for the optical layered bodies (1) to (4) are shown in fig. 1.

[ TABLE 1]

Claims

1. An optical stack, comprising: a substrate layer comprising a polyimide resin film, and a functional layer comprising a cured product of a curable resin,

the optical laminate has a stress of 110MPa or more at a strain of 3% in a tensile test in an environment having a temperature of 60 ℃ and a humidity of 93%.

2. The optical stack of claim 1,

the yield point strain in a tensile test in an environment of 60 ℃ and 93% humidity is 1.50% or more.

3. The optical laminate according to claim 1 or 2, wherein the proof stress in a tensile test in an environment having a temperature of 60 ℃ and a humidity of 93% is 70MPa or more.

4. The optical laminate according to any one of claims 1 to 3, wherein the elastic modulus in a tensile test in an environment having a temperature of 60 ℃ and a humidity of 93% is 4.0GPa or more.

5. The optical stack according to any one of claims 1 to 4,

the polyimide resin film has a coefficient of humidity expansion of 40ppm/K or less.

6. The optical stack according to any one of claims 1 to 5,

the polyimide resin film has a moisture absorption rate of 3% or less under the conditions of a temperature of 60 ℃ and a humidity of 90%.

7. The optical laminate according to any one of claims 1 to 6, which has a thickness of 15 μm to 120 μm and a number of times of bending resistance of 30 ten thousand or more measured with R =1.5 mm.

8. The optical stack according to any one of claims 1-7,

the polyimide resin film contains a polyimide resin containing a structural unit represented by the formula (1),

in the formula (1), X represents an organic group having a valence of 2, Y represents an organic group having a valence of 4, 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 of each other, represents a hydrogen atom or a 1-valent hydrocarbon group optionally having a halogen atom, m independently of each other 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 position of ² ～R ⁵ In at least 1 benzene ring of (2), R ² ～R ⁵ At least 3 of which are 1-valent hydrocarbon groups optionally having halogen atoms.

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

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

11. The flexible display device according to claim 9 or 10, further provided with a polarizing plate.