JP7584548B2 - Optical laminate and display device - Google Patents

Description

The present invention relates to an optical laminate and a display device, and more specifically, to an optical laminate that covers the display surface of a display panel, and a display device having the optical laminate.

In recent years, flexible display devices have been attracting attention. Flexible display devices can be installed on surfaces that are not flat, such as curved or bent surfaces. In addition, flexible display devices can be folded or rolled up to improve portability. In such flexible display devices, the optical laminate that covers the display surface is also required to be flexible.

Optical laminates used in flexible display devices are required to be not only flexible but also impact resistant. In addition to this, it is desirable to make the optical laminates thinner and lighter not only for practical reasons but also for cost reduction and resource conservation.

Patent Document 1 describes an optical laminate having a substrate with a protective layer formed on one side thereof, a first transparent adhesive layer, and a first buffer layer (abstract). A sample in which the optical laminate and a display panel are bonded with an adhesive sheet is said to have good impact resistance and bending resistance (paragraphs [0118] and [0125]).

JP 2018-55098 A

However, the optical laminate of Patent Document 1 still does not have sufficient properties, particularly bending resistance, and therefore the emergence of an optical laminate with improved bending resistance is desirable.

The present invention aims to solve the above problems, and its purpose is to provide an optical laminate with excellent bending resistance and impact resistance.

The present invention provides an optical laminate having a front panel, at least one adhesive layer, and an impact-resistant layer, the impact-resistant layer having a thickness of 5 to 140 μm.

In one embodiment, the optical laminate has a thickness of 100 to 500 μm.

In one embodiment, the impact-resistant layer has a tensile modulus of elasticity of 0.1 to 10 GPa.

In one embodiment, the optical laminate comprises, in the inward direction of the front plate, a first adhesive layer, an impact-resistant layer, and a second adhesive layer, in this order.

In one embodiment, the first and second adhesive layers and the impact-resistant layer have a total thickness of 80 to 200 μm.

In one embodiment, the material of the impact-resistant layer is selected from the group consisting of polycarbonate-based resins, polyimide-based resins, and polyester-based resins.

In one embodiment, the first adhesive layer and the second adhesive layer have a thickness ratio r of 15/85 to 85/15.

In one embodiment, the optical laminate exhibits a flex resistance of 150,000 or more times in a continuous flex test in which the optical laminate is flexed and stretched 180° with the front panel facing inward under conditions of a temperature of 25°C, a flex speed of 30 rpm, and a flex radius of 1.00 mm.

The present invention also provides a display device comprising any one of the optical laminates described above and a display unit disposed inwardly of the optical laminate.

The present invention provides an optical laminate that has excellent bending resistance and impact resistance, and is also thinner.

FIG. 1 is a cross-sectional view showing an example of a structure of an optical laminate of the present invention. FIG. 1 is a cross-sectional view showing an example of a structure of a display device of the present invention.

[Optical laminate]
Fig. 1 is a cross-sectional view showing an example of the structure of the optical laminate of the present invention. The optical laminate 10 shown in Fig. 1 includes a front plate 1, a first pressure-sensitive adhesive layer 2, an impact-resistant layer 3, and a second pressure-sensitive adhesive layer 4, in this order from the viewing side.

The shape of the optical laminate in the plane direction may be, for example, a square shape, preferably a square shape having long sides and short sides, and more preferably a rectangle. When the shape of the optical laminate in the plane direction is a rectangle, the length of the long side may be, for example, 10 to 1400 mm, and preferably 50 to 600 mm. The length of the short side is, for example, 5 to 800 mm, preferably 30 to 500 mm, and more preferably 50 to 300 mm. Each layer constituting the optical laminate may have rounded corners, notched ends, or perforated.

The thickness of the optical laminate is preferably 100 to 500 μm. By adjusting the thickness of the optical laminate to this range, it becomes easier to improve the bending resistance while maintaining the impact resistance. The thickness of the optical laminate is more preferably 100 to 200 μm, and even more preferably 120 to 190 μm. In one embodiment, the thickness of the optical laminate is 120 to 300 μm, preferably 130 to 200 μm, and more preferably 135 to 200 μm. By adjusting the thickness of the optical laminate to the above range, good impact resistance and good bending resistance can be obtained.

[Front panel]
The front plate 1 of the optical laminate is located on the front side of the optical laminate, as shown in Fig. 1. In Fig. 1, the upper direction indicates the external direction in which the optical laminate is viewed, and the lower direction indicates the internal direction in which the optical laminate is attached to a display unit or the like.

There are no limitations on the material or thickness of the front panel 1 as long as it is a plate-like body that allows light to pass through, but from the viewpoint of impact resistance and flexibility, it is preferable to use a resin plate-like body (e.g., a resin plate, a resin sheet, a resin film, etc.). The front panel may be composed of only one layer, or may be composed of two or more layers.

When the front panel 1 is a resin plate-like body, examples of the material include acrylic resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; polyolefin resins such as polyethylene, polypropylene, polymethylpentene, and polystyrene; cellulose resins such as triacetyl cellulose, acetyl cellulose butyrate, propionyl cellulose, butyryl cellulose, and acetyl propionyl cellulose; polyvinyl resins such as ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, and polyvinyl acetal; sulfone resins such as polysulfone and polyethersulfone; ketone resins such as polyether ketone and polyether ether ketone; polyetherimide; polycarbonate resins; polyester resins; polyimide resins; polyamideimide resins; and polyamide resins. These polymers can be used alone or in a mixture of two or more kinds. Among them, from the viewpoint of improving strength and transparency, it is preferable to use polycarbonate resins, polyester resins, polyimide resins, polyamideimide resins, or polyamide resins.

A polycarbonate-based resin is a polymer containing a repeating structural unit having a carbonate group. Examples of polycarbonate-based resins include bisphenol A polycarbonate, branched polycarbonate obtained by polymerizing trihydric phenol, and copolymer polycarbonate obtained by copolymerizing aliphatic or aromatic dicarboxylic acid and aliphatic or alicyclic dihydric alcohol. In the embodiments according to the present invention, an appropriate one can be selected from these and used.

A polyester resin is a polymer containing a repeating structural unit having an ester bond. Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane dimethyl naphthalate. In the embodiments of the present invention, an appropriate one can be selected from these and used.

In this specification, a polyimide-based resin refers to a polymer containing one or more selected from polyimide and polyamideimide. A polyimide refers to a polymer containing a repeating structural unit having an imide group, and a polyamideimide refers to a polymer containing a repeating structural unit having an imide group and a repeating structural unit having an amide group. A polyamide-based resin refers to a polymer containing a repeating structural unit having an amide group.

The polyimide resin according to this embodiment has a repeating structural unit represented by formula (10). Here, G represents a tetravalent organic group, and A represents a divalent organic group. G and/or A may contain two or more different repeating structural units represented by formula (10). In addition, the polyimide resin according to this embodiment may contain one or more repeating structural units represented by formula (11), formula (12), or formula (13) to the extent that the various physical properties of the resulting transparent resin film are not impaired.

It is preferable from the viewpoint of strength and transparency of the transparent resin film if the main structural unit of the polyimide resin is a repeating structural unit represented by formula (10). In the polyimide resin according to this embodiment, the repeating structural unit represented by formula (10) is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, still more preferably 90 mol% or more, and particularly preferably 98 mol% or more, based on the total repeating structural units of the polyimide resin. The repeating structural unit represented by formula (10) may be 100 mol%.

G and ^G1 each independently represent a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. Examples of ^G and G1 include groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29), and tetravalent chain hydrocarbon groups having 6 or less carbon atoms. In formulae (20) to (29), * represents a bond, and Z represents a single bond, -O-, _-CH2- , -CH2 _-CH2- , -CH( _CH3 )-, _-C ( _CH3 ) _2- , -C( _CF3 ) _2- , -Ar-, -SO2-, _-CO- , -O-Ar-O-, -Ar-O-Ar-, -Ar-CH2-Ar-, -Ar-C( _CH3 ) ₂ -Ar- or -Ar- _SO2 -Ar-. Ar represents an arylene group having ₆ to 20 carbon atoms which may be substituted with a fluorine atom, and a specific example is a phenylene group. Since the yellowness of the obtained transparent resin film is easily suppressed, G and ^G1 are preferably groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26) or formula (27).

^G2 represents a trivalent organic group, preferably a trivalent organic group having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. Examples of ^G2 include a group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), or formula (29) in which one of the bonds is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. Examples of Z in formulas (20) to (29) are the same as the examples of Z in the description of G.

^G3 represents a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. Examples of ^G3 include a group in which two non-adjacent bonds among the bonds of the group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), or formula (29) are replaced with hydrogen atoms, and a divalent chain hydrocarbon group having 6 or less carbon atoms. Examples of Z in formulas (20) to (29) are the same as the examples of Z in the description of G.

The organic group of ^G3 includes those represented by the formula (20'), the formula (21'), the formula (22'), the formula (23'), the formula (24'), the formula (25'), the formula (26'), the formula (27'), the formula (28') and the formula (29'):

［式（２０’）～式（２９’）中、Ｗ^１は、式（２０）～式（２９）において定義したＺと同義であり、＊は、式（２０）～式（２９）において定義した通りである］で表される２価の有機基がより好ましい。

[In formulae (20') to (29'), ^W1 is the same as Z defined in formulae (20) to (29), and * is as defined in formulae (20) to (29)] is more preferred.

In the polyimide resin, when ^G3 has a constitutional unit represented by any one of the above formulas (20') to (29'), particularly when Z has a constitutional unit represented by the formula (101') described below, the polyimide resin may further have a constitutional unit represented by the following formula (100):

［式（１００）中、Ｒ^１は、互いに独立に、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基又は炭素数６～１２のアリール基を表し、Ｒ^２は、Ｒ^１又は－Ｃ（＝Ｏ）－＊を表し、＊は結合手を表す］
で表されるカルボン酸由来の構成単位をさらに有していてよい。この構造単位を有するポリイミド系樹脂は、透明樹脂フィルムを製造する際に使用する樹脂ワニスの流動性を高めやすいため好ましい。

[In formula (100), R ¹ 's each 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 ² represents R ¹ or -C(=O)-*, and * represents a bond.]
The polyimide resin may further have a structural unit derived from a carboxylic acid represented by the following formula: A polyimide resin having this structural unit is preferred because it is easy to increase the fluidity of a resin varnish used in producing a transparent resin film.

In ^R1 , 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 each include those exemplified in the formula (101) described below. Specific examples of the structural unit (100) include a structural unit in which ^R1 and ^R2 are both hydrogen atoms (structural unit derived from a dicarboxylic acid compound), a structural unit in which ^R1 is both hydrogen atoms and ^R2 is -C(=O)-* (structural unit derived from a tricarboxylic acid compound), and the like.

The polyimide resin may contain a plurality of types of ^G3 as ^G3 , and the plurality of types of ^G3 may be the same or different from each other. In particular, from the viewpoint of easily reducing the haze after the mandrel test of the optical film and easily increasing the yield point strain and the elastic modulus, ^G3 is preferably represented by the formula (101):

［式（１０１）中、
Ｒ^３ａ及びＲ^３ｂは、互いに独立に、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、又は炭素数６～１２のアリール基を表し、Ｒ^３ａ及びＲ^３ｂに含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ｗは、互いに独立に、単結合、－Ｏ－、－ＣＨ_２－、－ＣＨ_２－ＣＨ_２－、－ＣＨ（ＣＨ_３）－、－Ｃ（ＣＨ_３）_２－、－Ｃ（ＣＦ_３）_２－、－ＳＯ_２－、－Ｓ－、－ＣＯ－又は－Ｎ（Ｒ^９）－を表し、Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１～１２の１価の炭化水素基を表し、
ｓは０～４の整数であり、
ｔは０～４の整数であり、
ｕは０～４の整数であり、
＊は結合手を表す］
で表され、より好ましくは式（１０１’）：

[In formula (101),
R ^3a and R ^3b each independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and a hydrogen atom contained in R ^3a and R ^3b each independently may be substituted with a halogen atom;
W each 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 )-, where R ⁹ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom;
s is an integer from 0 to 4;
t is an integer from 0 to 4;
u is an integer from 0 to 4;
* represents a bond.
More preferably, the compound represented by formula (101'):

［式（１０１’）中、Ｒ^３ａ、Ｒ^３ｂ、ｓ、ｔ、ｕ、Ｗ及び＊は、式（１０１）において定義した通りである］
で表される、構成単位を少なくとも有することが好ましい。

[In formula (101'), R ^3a , R ^3b , s, t, u, W and * are as defined in formula (101)]
It is preferable that the copolymer has at least a structural unit represented by the following formula:

In formula (101) and formula (101'), W each 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 )-, and from the viewpoint of the bending resistance of the optical film, preferably represents -O- or -S-, more preferably represents -O-.

R ^3a and R ^3b each independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methyl-butyl group, a 3-methyl-butyl group, a 2-ethyl-propyl group, and an n-hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, 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 viewpoint of easily reducing the haze after a mandrel test of the optical film and easily increasing the yield strain and elastic modulus, R ^3a and R ^3b each independently preferably represent an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. Here, the hydrogen atoms contained in R ^3a and R ^3b each independently may be substituted with a halogen atom.

^R9 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methyl-butyl group, a 3-methyl-butyl group, a 2-ethyl-propyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a tert-octyl group, an n-nonyl group, and an n-decyl group, which may be substituted with a halogen atom.
Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

In formula (101) and formula (101'), t and u are each independently an integer from 0 to 4, preferably an integer from 0 to 2, and more preferably 0 or 1.

The A, A ¹ , A ² and A ³ each represent a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms, in which case the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. Examples of A, A ¹ , A ² and A ³ include groups represented by formula (30), formula (31), formula (32), formula (33), formula (34), formula (35), formula (36), formula (37) or formula (38), groups in which these are substituted with one or more of 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 formulae (30) to (38), * represents a bond, and Z ¹ , Z ² and Z ³ each independently represent a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -S-, -SO ₂ -, -CO- or -N(R ³ )-. Here, R ³ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Here, R ³ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Z ¹ and Z ² , and Z ² and Z ³ are preferably located at the meta position or para position relative to each ring.

In the present invention, the resin composition forming the transparent resin film may be a polyamide resin. The polyamide resin according to this embodiment is a polymer mainly composed of a repeating structural unit represented by formula (13). Preferred examples and specific examples of ^G3 and ^A3 in the polyamide resin are the same as the preferred examples and specific examples of ^G3 and ^A3 in the polyimide resin.
The polyamide resin may contain two or more types of repeating structural units represented by formula (13) in which ^G3 and/or ^A3 are different.

Polyimide resins can be obtained, for example, by polycondensation of diamines and tetracarboxylic acid compounds (such as tetracarboxylic dianhydrides), and can be synthesized, for example, according to the method described in JP-A-2006-199945 or JP-A-2008-163107. Commercially available polyimides include Neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd. and KPI-MX300F manufactured by Kawamura Sangyo Co., Ltd.

Tetracarboxylic acid compounds used in the synthesis of polyimide resins include aromatic tetracarboxylic acids and their anhydrides, preferably their dianhydrides, and other aromatic tetracarboxylic acid compounds, and aliphatic tetracarboxylic acids and their anhydrides, preferably their dianhydrides, and other aliphatic tetracarboxylic acid compounds. In addition to anhydrides, the tetracarboxylic acid compounds may also be tetracarboxylic acid compound derivatives such as tetracarboxylic acid chloride compounds, and these can be used alone or in combination of two or more.

Specific examples of aromatic tetracarboxylic acid dianhydrides include non-condensed polycyclic aromatic tetracarboxylic acid dianhydrides, monocyclic aromatic tetracarboxylic acid dianhydrides, and condensed polycyclic aromatic tetracarboxylic acid dianhydrides. Non-condensed polycyclic aromatic tetracarboxylic acid dianhydrides include 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2',3,3'-benzophenone tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride, 2,2',3,3'-biphenyl tetracarboxylic acid dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, and 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride. dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (sometimes referred to as 6FDA), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic dianhydride, and 4,4'-(m-phenylenedioxy)diphthalic dianhydride. In addition, an example of a monocyclic aromatic tetracarboxylic dianhydride is 1,2,4,5-benzenetetracarboxylic dianhydride, and an example of a condensed polycyclic aromatic tetracarboxylic dianhydride is 2,3,6,7-naphthalenetetracarboxylic dianhydride.

Among these, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, Examples of the dianhydride include 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic dianhydride, and 4,4'-(m-phenylenedioxy)diphthalic dianhydride, and more preferably 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), bis(3,4-dicarboxyphenyl)methane dianhydride, and 4,4'-(p-phenylenedioxy)diphthalic dianhydride. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic and non-cyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkane tetracarboxylic dianhydrides such as 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, and 1,2,3,4-cyclopentane tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, and positional isomers thereof. These can be used alone or in combination of two or more. Specific examples of the non-cyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butane tetracarboxylic dianhydride and 1,2,3,4-pentane tetracarboxylic dianhydride, and these can be used alone or in combination of two or more. Additionally, a combination of a cyclic aliphatic tetracarboxylic acid dianhydride and an acyclic aliphatic tetracarboxylic acid dianhydride may be used.

Among the tetracarboxylic acid compounds, the alicyclic tetracarboxylic acid dianhydrides or non-condensed polycyclic aromatic tetracarboxylic acid dianhydrides are preferred from the viewpoint of improving the tensile modulus, bending resistance, and optical properties of the transparent resin film. More preferred examples include 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride, 2,2',3,3'-biphenyl tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA). These can be used alone or in combination of two or more.

The polyimide-based resin according to this embodiment may be a product obtained by further reacting tetracarboxylic acids, tricarboxylic acid compounds, dicarboxylic acid compounds, their anhydrides, and their derivatives in addition to the anhydrides of the tetracarboxylic acids used in the synthesis of the polyimide described above, to the extent that the various physical properties of the resulting transparent resin film are not impaired.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and acid chloride compounds and acid anhydrides related thereto, which may be used in combination of two or more. Specific examples thereof include anhydride of 1,2,4-benzenetricarboxylic acid, acid chloride compound of 1,3,5-benzenetricarboxylic acid, 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride, and compounds in which phthalic anhydride and benzoic acid are linked via a single bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, or a phenylene group.

The dicarboxylic acid compound includes aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds, acid anhydrides, etc., and these may be used in combination of two or more kinds.
Specific examples thereof include dicarboxylic acid compounds of terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, chain hydrocarbons having 8 or less carbon atoms, and compounds in which two benzoic acid skeletons are linked by _-CH2- , -S-, -C( _CH3 ) _2- , ^-C ( _CF3 )2-, -O-, -N( _R9 )-, -C(=O)-, _-SO2- or a phenylene group. These can be used alone or in combination of two or more. Here, ^R9 represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom.

The dicarboxylic acid compound is preferably terephthalic acid, isophthalic acid, 4,4'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, or a compound in which two benzoic acid skeletons are linked via _-CH2- , -C(=O)-, -O-, -N( ^R9 )-, _-SO2- or a phenylene group, and more preferably terephthalic acid, 4,4'-biphenyldicarboxylic acid, or a compound in which two benzoic acid skeletons are linked via -O-, -N( ^R9 )-, -C(=O)- or _-SO2- . These may be used alone or in combination of two or more.

The ratio of the tetracarboxylic acid compound to the total of the tetracarboxylic acid compound, the tricarboxylic acid compound, and the dicarboxylic acid compound is preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 98 mol% or more.

The diamines used in the synthesis of polyimide resins include aliphatic diamines, aromatic diamines, and mixtures thereof. In this embodiment, the term "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 substituents as part of its structure. The aromatic ring may be a single ring or a condensed ring, and examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited to these. Of these, a benzene ring is preferable. The term "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may include an aromatic ring or other substituents as part of its structure.

Specific examples of aliphatic diamines 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, which can be used alone or in combination of two or more.

Specific examples of aromatic diamines include aromatic diamines having one aromatic ring, such as p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, and 2,6-diaminonaphthalene, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, and bis[4-(4-amino Examples of aromatic diamines having two or more aromatic rings include aromatic diamines having two or more aromatic rings, such as bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (sometimes referred to as TFMB), 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 9,9-bis(4-amino-3-chlorophenyl)fluorene, and 9,9-bis(4-amino-3-fluorophenyl)fluorene. These can be used alone or in combination of two or more.

As the aromatic diamine, preferably, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl )-4,4'-diaminodiphenyl (TFMB), 4,4'-bis(4-aminophenoxy)biphenyl, more preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB), 4,4'-bis(4-aminophenoxy)biphenyl. These can be used alone or in combination of two or more.

The diamine may also have a fluorine-based substituent. Examples of the fluorine-based substituent include a perfluoroalkyl group having 1 to 5 carbon atoms, such as a trifluoromethyl group, and a fluoro group.

Among the above diamines, from the viewpoint of high transparency and low coloration, preferably, one or more selected from the group consisting of aromatic diamines having a biphenyl structure are used, and specific examples thereof include one or more selected from the group consisting of 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB), and 4,4'-bis(4-aminophenoxy)biphenyl. More preferably, diamines having a biphenyl structure and a fluorine-based substituent are used, and specific examples thereof include 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB).

Polyimide resins are condensation polymers formed by polycondensation of diamines and tetracarboxylic acid compounds (including tetracarboxylic acid compound derivatives such as acid chloride compounds and tetracarboxylic acid dianhydrides) and contain repeating structural units represented by formula (10). In addition to these, tricarboxylic acid compounds (including tricarboxylic acid compound derivatives such as acid chloride compounds and tricarboxylic acid anhydrides) and dicarboxylic acid compounds (including derivatives such as acid chloride compounds) may also be used as starting materials. Polyamide resins are condensation polymers formed by polycondensation of diamines and dicarboxylic acid compounds (including derivatives such as acid chloride compounds) and contain repeating structural units represented by formula (13).

The repeating structural units represented by formula (10) and formula (11) are usually derived from diamines and tetracarboxylic acid compounds. The repeating structural unit represented by formula (12) is usually derived from diamines and tricarboxylic acid compounds. The repeating structural unit represented by formula (13) is usually derived from diamines and dicarboxylic acid compounds. Specific examples of diamines, tetracarboxylic acid compounds, tricarboxylic acid compounds, and dicarboxylic acid compounds are as described above.

The molar ratio of the diamine to the carboxylic acid compound, such as a tetracarboxylic acid compound, can be appropriately adjusted within a range of preferably 0.9 mol to 1.1 mol of tetracarboxylic acid per 1.00 mol of diamine. Since it is preferable that the resulting polyimide resin has a high molecular weight in order to exhibit high folding resistance, it is more preferable that the molar ratio of the tetracarboxylic acid is 0.98 mol to 1.02 mol, and even more preferable that the molar ratio is 0.99 mol to 1.01 mol, per 1.00 mol of diamine.

In addition, from the viewpoint of suppressing the yellowness of the obtained transparent resin film, it is preferable that the ratio of amino groups in the obtained polymer terminals is low, and it is preferable that the amount of carboxylic acid compound such as tetracarboxylic acid compound is 1.00 mol or more per 1.00 mol of diamine.

By adjusting the number of fluorines in the molecules of the diamine and carboxylic acid compound (e.g., tetracarboxylic acid compound), the amount of fluorine in the resulting polyimide resin can be set to 1% by mass or more, 5% by mass or more, 10% by mass or more, or 20% by mass or more based on the mass of the polyimide resin. Since the raw material cost tends to increase as the fluorine content increases, the upper limit of the fluorine content is preferably 40% by mass or less. The fluorine-based substituents may be present in either the diamine or the carboxylic acid compound, or in both. The inclusion of fluorine-based substituents may particularly reduce the YI value.

The polyimide resin according to the present embodiment may be a copolymer containing a plurality of different types of the repeating structural units described above. The weight average molecular weight of the polyimide resin in terms of standard polystyrene is usually 100,000 to 800,000. Since a large weight average molecular weight of the polyimide resin improves the flexibility when formed into a film, it is preferably 200,000 or more, more preferably 250,000 or more, and even more preferably 280,000 or more. In addition, since a varnish with a suitable concentration and viscosity is obtained and film formability tends to be improved, it is preferably 750,000 or less, more preferably 600,000 or less, and even more preferably 500,000 or less. Two or more types of polyimide resins having different weight average molecular weights may be used in combination. Furthermore, other polymer materials may be mixed within a range that does not impair physical properties.

When polyimide-based resins and polyamide-based resins contain fluorine-containing substituents, the tensile modulus of elasticity is improved when the resin is made into a film, and the YI value tends to be reduced. When the tensile modulus of elasticity of a film is high, the occurrence of scratches and wrinkles tends to be suppressed. From the viewpoint of film transparency, it is preferable that polyimide-based resins and polyamide-based resins have a fluorine-containing substituent. Specific examples of fluorine-containing substituents include a fluoro group and a trifluoromethyl group.

The content of fluorine atoms in the polyimide resin and the mixture of polyimide resin and polyamide resin is preferably 1% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 40% by mass or less, based on the mass of the polyimide resin or the sum of the mass of the polyimide resin and the mass of the polyamide resin, respectively. When the content of fluorine atoms is within the above range, there is a tendency that the YI value when made into a film can be further reduced and the transparency can be further improved.

In the present invention, the content of polyimide-based resin and/or polyamide-based resin in the resin composition constituting the transparent resin film is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the solid content of the resin composition, and may be 100% by mass. When the content of polyimide-based resin and/or polyamide-based resin is equal to or more than the above lower limit, the flexibility of the transparent resin film is good. The solid content refers to the total amount of components excluding the solvent from the resin composition.

The imidization rate of the polyimide resin and the polyamideimide resin is preferably 90% or more, more preferably 93% or more, and even more preferably 96% or more. From the viewpoint of easily increasing the optical homogeneity of the optical film and/or the optical laminate, it is preferable that the imidization rate is equal to or higher than the above lower limit. The upper limit of the imidization rate is 100% or less. The imidization rate indicates the ratio of the molar amount of imide bonds in the polyimide resin and the polyamideimide resin to twice the molar amount of the constituent units derived from the tetracarboxylic acid compound in the polyimide resin or the polyamideimide resin. In addition, when the polyimide resin and the polyamideimide resin contain a tricarboxylic acid compound, it indicates the ratio of the molar amount of imide bonds in the polyimide resin and the polyamideimide resin to the sum of twice the molar amount of the constituent units derived from the tetracarboxylic acid compound in the polyimide resin and the polyamideimide resin and the molar amount of the constituent units derived from the tricarboxylic acid compound. In addition, the imidization rate can be determined by the IR method, the NMR method, etc., and for example, in the NMR method, it can be measured by the method described in the Examples.

In the present invention, the resin composition forming the transparent resin film may further contain inorganic materials such as inorganic particles in addition to the polyimide-based resin and/or polyamide-based resin. Examples of inorganic materials include inorganic particles such as silica particles, titanium particles, aluminum hydroxide, zirconia particles, and barium titanate particles, as well as silicon compounds such as quaternary alkoxysilanes such as tetraethyl orthosilicate. From the viewpoints of the stability of the varnish and the dispersibility of the inorganic materials, silica particles, aluminum hydroxide, and zirconia particles are preferred, and silica particles are more preferred.

The average primary particle size of the inorganic material particles is preferably 10 to 100 nm, more preferably 10 to 90 nm, even more preferably 10 to 50 nm, and even more preferably 10 to 30 nm. If the average primary particle size of the silica particles is 100 nm or less, transparency tends to be improved. If the average primary particle size of the silica particles is 10 nm or more, the cohesive force of the silica particles is weakened, and they tend to be easier to handle.

In the present invention, the silica particles may be a silica sol in which silica particles are dispersed in a solvent or a silica fine powder produced by a gas phase method, but it is preferable to use a silica sol produced by a liquid phase method because it is easy to handle.

The average primary particle size of the silica particles in the transparent resin film can be determined by observation with a transmission electron microscope (TEM). The particle size distribution of the silica particles before forming the transparent resin film can be determined with a commercially available laser diffraction particle size distribution analyzer.

In the present invention, when the resin composition contains an inorganic material, the content thereof is preferably 0.001% by mass or more and 90% by mass or less, more preferably 0.001% by mass or more and 60% by mass or less, and even more preferably 0.001% by mass or more and 40% by mass or less, based on the solid content of the resin composition. When the content of the inorganic material in the resin composition is within the above range, it tends to be easy to achieve both transparency and mechanical strength of the transparent resin film. The solid content refers to the total amount of components excluding the solvent from the resin composition.

The resin composition constituting the transparent resin film may further contain other components in addition to the components described above. Examples of other components include antioxidants, release agents, light stabilizers, bluing agents, flame retardants, lubricants, and leveling agents.

In the present invention, when the resin composition contains other components other than the resin component such as a polyimide resin and the inorganic material, the content of the other components is preferably 0.001% or more and 20% or less by mass, more preferably 0.001% or more and 10% or less by mass, based on the total mass of the transparent resin film.

In the present invention, the transparent resin film can be produced from a resin varnish prepared by adding a solvent to a reaction liquid of a polyimide resin and/or a polyamide resin obtained by reacting a selected one of the tetracarboxylic acid compound, the diamine, and the other raw materials, and mixing and stirring the reaction liquid and a resin composition containing an inorganic material and other components as necessary. In the resin composition, a solution of a purchased polyimide resin or a solution of a purchased solid polyimide resin may be used instead of the reaction liquid of the polyimide resin or the like.

As a solvent that can be used to prepare a resin varnish, one that can dissolve or disperse resin components such as polyimide resins can be appropriately selected. From the viewpoint of the solubility, coatability, and drying property of the resin components, the boiling point of the solvent is preferably 120 to 300°C, more preferably 120 to 270°C, even more preferably 120 to 250°C, and particularly preferably 120 to 230°C. Specific examples of such solvents include amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; lactone-based solvents such as γ-butyrolactone and γ-valerolactone; ketone-based solvents such as cyclohexanone, cyclopentanone, and methyl ethyl ketone; acetate-based solvents such as butyl acetate and amyl acetate; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate-based solvents such as ethylene carbonate and propylene carbonate, and the like. Among these, a solvent selected from the group consisting of N,N-dimethylacetamide (boiling point: 165°C), γ-butyrolactone (boiling point: 204°C), N-methylpyrrolidone (boiling point: 202°C), butyl acetate (boiling point: 126°C), cyclopentanone (boiling point: 131°C) and amyl acetate (boiling point: 149°C) is preferred because of its excellent solubility in polyimide resins and polyamide resins. As the solvent, one type may be used alone, or two or more types may be used in combination. When two or more types of solvents are used, it is preferable to select the type of solvent so that the boiling point of the solvent with the highest boiling point falls within the above range.

The amount of solvent is not particularly limited as long as it is selected so that the viscosity of the resin varnish is easy to handle, but it is preferably 50 to 95% by mass, more preferably 70 to 95% by mass, and even more preferably 80 to 95% by mass, based on the total amount of the resin varnish.

The transparent resin film of the present invention is obtained by applying the above-mentioned resin varnish onto a support and pre-drying it. The transparent resin film is peelably laminated onto the support. Peelable means that the film can maintain its shape and can be peeled off from the support without breaking. Specifically, pre-drying means drying so that an appropriate amount of solvent remains. If the amount of residual solvent is too large, the film cannot maintain its shape, and if the amount of residual solvent is too small, the film will not adhere to the support and will break when peeled off. The appropriate amount of residual solvent varies depending on the type of resin composition, solvent, and support of the transparent resin film, and needs to be adjusted appropriately. However, the content of the solvent in the transparent resin film is usually 0.1% by mass or more relative to the total mass of the transparent resin film. The upper limit of the solvent content in the transparent resin film is not particularly limited as long as it is within the range in which the film can maintain its shape, but is usually 50% by mass or less relative to the total mass of the transparent resin film.

The thickness of the resin plate is preferably 10 to 200 μm. By adjusting the thickness of the resin plate to fall within this range, it becomes easier to improve bending resistance while maintaining impact resistance.
The thickness of the resin plate is more preferably 20 to 100 μm, and further preferably 30 to 80 μm.

The yellowness index (YI value) of the transparent resin film is preferably 3.0 or less, more preferably 2.7 or less, even more preferably 2.5 or less, and particularly preferably 2.0 or less. If the yellowness index of the optical laminate is equal to or less than the upper limit, transparency is easily improved, and for example, visibility is easily improved when the optical laminate is used as a front panel of a display device. The yellowness index is usually -5 or more, preferably -2 or more, more preferably 0 or more, even more preferably 0.3 or more, even more preferably 0.5 or more, and particularly preferably 0.7 or more. The yellowness index (YI) can be calculated based on the formula YI = 100 x (1.2769X - 1.0592Z) / Y by measuring the transmittance of light of 300 to 800 nm using an ultraviolet-visible-near infrared spectrophotometer in accordance with JIS K 7373:2006, determining the tristimulus values (X, Y, Z).

The total light transmittance of the transparent resin film is preferably 80% or more, more preferably 85% or more, even more preferably 89%, and particularly preferably 90% or more. If the total light transmittance is equal to or more than the above lower limit, visibility is easily improved when the front panel is incorporated into an image display device.
The upper limit of the total light transmittance is usually 100% or less. The total light transmittance can be measured, for example, using a haze computer in accordance with JIS K 7361-1:1997.

The haze of the transparent resin film is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, still more preferably 0.5% or less, and particularly preferably 0.3% or less. When the haze of the transparent resin film is equal to or less than the above upper limit, the transparency is good, and when the film is used as a front panel of an image display device, for example, the visibility of the image is easily improved.
The lower limit of the haze is usually 0.01% or more. The haze can be measured using a haze computer in accordance with JIS K 7136:2000.

The front panel 1 may be a film having a hard coat layer on at least one side of the base film to further improve the hardness. As the base film, a film made of the above resin can be used. The hard coat layer may be formed on one side or both sides of the base film. By providing a hard coat layer, a resin film having improved hardness and scratch resistance can be obtained. The hard coat layer is, for example, a cured layer of an ultraviolet-curable resin. Examples of ultraviolet-curable resins include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coat layer may contain additives to improve strength. The additives are not limited, and examples include inorganic fine particles, organic fine particles, and mixtures thereof.

When the optical laminate is used in a display device, the front panel 1 may function as a window film in the display device. The front panel 1 may have a blue light blocking function, a viewing angle adjustment function, etc. The front panel 1 may be a layer that constitutes the outermost surface of the display device.

The thickness of the front panel 1 is preferably 20 to 220 μm. By adjusting the thickness of the front panel 1 to be within this range, it becomes easier to improve bending resistance while maintaining impact resistance, and it is also possible to impart hardness. The thickness of the front panel 1 is more preferably 35 to 110 μm, and even more preferably 40 to 70 μm.

The tensile modulus of the front panel 1 is preferably 3 GPa or more, more preferably 4 GPa or more, and even more preferably 5 GPa or more. The tensile modulus of the front panel 1 is preferably 10 GPa or less, more preferably 9 GPa or less. If the tensile modulus is equal to or greater than the lower limit, defects such as dents are less likely to occur in the front panel when it is subjected to an external impact, and the strength of the front panel is easily increased. If the tensile modulus is equal to or less than the upper limit, the bending resistance of the front panel is easily improved. The tensile modulus needs to satisfy the above range in at least one of the MD (machine direction, the direction in which the film is molded) and TD (transverse direction, the direction perpendicular to the MD), and it is preferable that the tensile modulus satisfies the above range in both directions.

[Adhesive layer]
The adhesive layer is located between the non-adhesive layers constituting the optical laminate, or between the non-adhesive layers constituting the optical laminate and an adherend such as a display unit. The adhesive layer is a layer that bonds members present on both sides of the adhesive layer. In one embodiment, referring to FIG. 1, the optical laminate 10 has a first adhesive layer 2 and a second adhesive layer 4. The first adhesive layer 2 is located between the front plate 1 and the impact-resistant layer 3 described below, and bonds them together. The second adhesive layer is located on the inner surface of the impact-resistant layer 3, and bonds the impact-resistant layer and the adherend. Examples of the adherend include a polarizing plate, a circular polarizing plate, and a touch sensor of the display unit. Each adhesive layer may be made of the same material or different materials.

The adhesive layer can be composed of an adhesive composition mainly composed of a resin such as a (meth)acrylic, rubber, urethane, ester, silicone, or polyvinyl ether resin. Among them, an adhesive composition having a (meth)acrylic resin as a base polymer, which has excellent transparency, weather resistance, heat resistance, etc., is preferred. The adhesive composition may be of the active energy ray curing type or the heat curing type.

As the (meth)acrylic resin (base polymer) used in the adhesive composition, for example, a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, is preferably used. A polar monomer is preferably copolymerized into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, etc., such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

The adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups, with polyisocyanate compounds being preferred.

The active energy ray curable pressure-sensitive adhesive composition has a property of being cured by irradiation with active energy rays such as ultraviolet rays and electron beams, and has adhesiveness even before irradiation with active energy rays, can be adhered to an adherend such as a film, and can be cured by irradiation with active energy rays to adjust the adhesive strength. The active energy ray curable pressure-sensitive adhesive composition is preferably an ultraviolet ray curable type. The active energy ray curable pressure-sensitive adhesive composition further contains an active energy ray polymerizable compound in addition to a base polymer and a crosslinking agent.
If necessary, a photopolymerization initiator, a photosensitizer, etc. may also be contained.

The adhesive composition may contain additives such as fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, tackifiers, fillers (metal powders and other inorganic powders, etc.), antioxidants, UV absorbers, dyes, pigments, colorants, defoamers, corrosion inhibitors, and photopolymerization initiators.

The adhesive layer can be formed by applying an organic solvent diluted solution of the adhesive composition to a substrate and drying it. When an active energy ray curable adhesive composition is used, the formed adhesive layer can be irradiated with active energy rays to form a cured product having the desired degree of cure.

The adhesive layer has viscoelasticity and functions to absorb impacts applied to the optical laminate. In the optical laminate of the present invention, the properties of the adhesive layer are appropriately adjusted to improve the impact resistance of the optical laminate against impacts applied to the front surface. In other words, even if an impact is applied to the surface of the optical laminate, the touch sensor layer and the wiring and elements of the display panel covered by the optical laminate are less likely to be damaged.

The inventors' investigations revealed that the elasticity, thickness, and position of the adhesive layer are related to the impact resistance of the optical laminate. The lower the storage modulus of the adhesive layer, the greater the impact mitigation effect of the adhesive layer. The thicker the adhesive layer, the greater the impact mitigation effect of the adhesive layer. And the closer the adhesive layer is to the display panel, the greater the effectiveness of the impact mitigation effect of the adhesive layer.

The pressure-sensitive adhesive layer preferably has a storage modulus of 0.01 to 0.80 MPa at 25° C. If the storage modulus of the pressure-sensitive adhesive layer is less than 0.01 MPa, the impact resistance of the optical laminate decreases, and if it exceeds 0.80 MPa, the flexibility of the optical laminate decreases.
The storage modulus of the pressure-sensitive adhesive layer at 25° C. is preferably 0.02 to 0.75 MPa, more preferably 0.03 to 0.70 MPa, and even more preferably 0.05 to 0.3 MPa or less, and may be 0.1 to 0.25 MPa.

The thickness of each adhesive layer is preferably 5 to 100 μm. If the thickness of the adhesive layer is 5 μm or more, the impact resistance of the optical laminate is improved, and if the thickness is 100 μm or less, the flexibility of the optical laminate is improved. The thickness of each adhesive layer is preferably 5 to 100 μm, and more preferably 15 to 85 μm.

The total thickness of the pressure-sensitive adhesive layers in the optical laminate is preferably 10 to 200 μm. When the total thickness of the pressure-sensitive adhesive layers is 10 μm or more, the impact resistance of the optical laminate is improved, and when it is 200 μm or less, the flexibility of the optical laminate is improved.
The total thickness of the pressure-sensitive adhesive layers in the optical laminate is preferably 30 to 150 μm, and more preferably 40 to 120 μm.

When the optical laminate has, for example, a front panel 1, a first adhesive layer 2, an impact-resistant layer 3, and a second adhesive layer 4 in this order from the viewing side as shown in FIG. 1, the ratio (b/c) of the thickness b of the first adhesive layer to the thickness c of the second adhesive layer is preferably 15/85 to 85/15. When the ratio r is 15/85 or more, the flexibility of the optical laminate is improved, and when it is 85/15 or less, the impact resistance of the optical laminate is improved. The ratio is preferably 25/75 to 85/15, and more preferably 30/70 to 80/20.

In a preferred embodiment, the total thickness of the first and second adhesive layers and the impact-resistant layer described below is in the range of 100 to 190 μm. When the total thickness of the adhesive layer and the impact-resistant layer is 100 μm or more, the impact resistance of the optical laminate is improved, and when the total thickness is 190 μm or less, the flexibility of the optical laminate is improved. The total thickness is preferably 120 to 190 μm, more preferably 135 to 190 μm. In one embodiment, the total thickness of the first and second adhesive layers and the impact-resistant layer described below may be 80 to 200 μm, preferably 80 to 150 μm. By adjusting the total thickness to the above range, good impact resistance and good flexibility can be obtained.

[Impact-resistant layer]
The impact-resistant layer 3 is located toward the inside of the front plate, and has a function of absorbing an impact when the front surface of the display device is subjected to the impact, thereby preventing damage to the wiring and elements of the display panel, etc. The impact-resistant layer 3 preferably has a function of improving the bending resistance of the optical laminate.

When a material is bent, the deformation energy applied to the material reaches a threshold, causing damage to the material such as breakage, cracks, or wrinkles.

Therefore, the impact-resistant layer is preferably made of a material that has a high tolerance for deformation energy, for example, a thermoplastic resin that is hard and tenacious (i.e., has high toughness). Examples of such resins include polycarbonate-based resins, polyimide-based resins, polyamide-based resins, polyamideimide-based resins, and polyester-based resins. Furthermore, since the present invention is intended for use in display devices, it is preferable to use a resin that has excellent light-transmitting properties (preferably optically transparent).

The impact-resistant layer preferably has a tensile modulus of 0.1 to 10 GPa. If the impact-resistant layer has a tensile modulus of 0.1 GPa or more, the impact resistance of the optical laminate is improved, and if it is 10 GPa or less, the flexibility of the optical laminate is improved. The impact-resistant layer preferably has a tensile modulus of 1.0 to 8.0 GPa, and more preferably has a tensile modulus of 3.0 to 7.0 GPa. The tensile modulus needs to satisfy the above range in at least one of MD (machine direction, the direction in which the film is molded) or TD (transverse direction, the direction perpendicular to MD), and preferably satisfies the above range in both.

The impact-resistant layer may be an impact-resistant layer that also has an optical function such as a retardation film or a brightness enhancement film. For example, a retardation film having an arbitrary retardation value can be obtained by stretching (uniaxially or biaxially stretching, etc.) a film made of the above-mentioned thermoplastic resin or forming a liquid crystal layer or the like on the film.

The impact-resistant layer has a thickness of 5 to 140 μm. If the thickness of the impact-resistant layer is 5 μm or more, the impact resistance of the optical laminate is improved, and if the thickness is 140 μm or less, the flexibility of the optical laminate is improved. The thickness of the impact-resistant layer is preferably 10 to 120 μm, more preferably 30 to 110 μm, and even more preferably 35 to 105 μm, and may be 40 to 100 μm.

[Method of manufacturing optical laminate]
The optical laminate of the present invention is produced by bonding the front panel and the impact-resistant layer using a pressure-sensitive adhesive layer and forming a pressure-sensitive adhesive layer on the inner surface of the impact-resistant layer. Alternatively, the optical laminate of the present invention can be produced by forming a pressure-sensitive adhesive layer on the inner surface of the impact-resistant layer and bonding the impact-resistant layer and the front panel using the pressure-sensitive adhesive layer.

The front panel and the impact-resistant layer can be bonded by forming an adhesive layer on the bonding surface of one layer and then laminating the other layer, or by forming an adhesive layer on each bonding surface of both layers and then bonding the adhesive layers together. The adhesive layer can be formed on the bonding surface of the layers by using an adhesive composition as described above, or by preparing a sheet-like adhesive that can be handled independently and attaching it to the surface.

The optical laminate has excellent bending resistance. The bending resistance here means that when the laminate is bent 180° and then returned to its original state, no break occurs at the bent portion. The bending radius when bending is, for example, 5 mm or less, preferably 3 mm or less, and more preferably 1 mm or less.
The bending speed during bending is, for example, 30 to 60 rpm, preferably 30 rpm or less. When the bending speed is slow, the number of bending cycles may decrease, but the optical laminate of the present invention has high bending resistance even when the bending speed is slow.

When a continuous bending test is conducted in which the optical laminate is continuously bent and stretched 180° with the front panel facing inward until the bent portion breaks, the optical laminate typically exhibits a bending resistance of 100,000 or more, preferably 150,000 or more, and more preferably 200,000 or more. In this case, the conditions for the continuous bending test are a temperature of 25°C, a bending speed of 30 rpm, and a bending radius of 1.00 mm.

[Display Device]
FIG. 2 is a cross-sectional view showing an example of the structure of the display device of the present invention. The display device 20 has an optical laminate 10 arranged on its front surface (visible side) and a display unit 5. The display unit may be configured to be foldable with the visible side surface facing inward, or may be configured to be rollable. The display unit may also be configured as a touch panel type display device. Specific examples of the display unit include a laminate in which a touch sensor layer and a polarizing layer are formed on the display surface of a display element. Specific examples of the display element include a liquid crystal display element, an organic EL display element, an inorganic EL display element, a plasma display element, and a field emission display element.

The display device 20 can be used as mobile devices such as smartphones and tablets, televisions, digital photo frames, electronic billboards, measuring instruments and gauges, office equipment, medical equipment, computing equipment, etc.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. In these examples, the unit "parts" for the proportion of the substances is based on mass unless otherwise specified.

<Production Example 1>
Synthesis of polyamide-imide resin Under a nitrogen gas atmosphere, a reaction vessel equipped with a stirring blade in a separable flask and an oil bath were prepared. 45 parts of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 768.55 parts of N,N-dimethylacetamide (DMAc) were put into the reaction vessel placed in the oil bath. TFMB was dissolved in DMAc while stirring the contents in the reaction vessel at room temperature. 19.01 parts of 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA) were further put into the reaction vessel, and the contents in the reaction vessel were stirred at room temperature for 3 hours. 4.21 parts of 4,4'-oxybis(benzoyl chloride) (OBBC) and then 17.30 parts of terephthaloyl chloride (TPC) were put into the reaction vessel, and the contents in the reaction vessel were stirred at room temperature for 1 hour. 4.63 parts of 4-methylpyridine and 13.04 parts of acetic anhydride were further added to the reaction vessel, and the contents in the reaction vessel were stirred at room temperature for 30 minutes. After stirring, the temperature in the vessel was raised to 70°C using an oil bath, and the mixture was stirred for another 3 hours while maintaining the temperature at 70°C to obtain a reaction liquid. The reaction liquid obtained was cooled to room temperature, and the mixture was poured into a large amount of methanol in the form of a thread to precipitate a precipitate. The precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. The precipitate was dried under reduced pressure at 100°C to obtain polyamideimide resin 1. The weight average molecular weight of the obtained polyamideimide resin 1 was 400,000, and the imidization rate was 99.0%.

<Production Example 2>
Manufacture of Optical Film for Front Panel The polyamideimide resin (TPC/6FDA/OBBC/TFMB=60/30/10/100) obtained in Manufacturing Example 1 was diluted with γ-butyrolactone (GBL), and GBL-substituted silica sol was added and thoroughly mixed to obtain a resin/silica particle mixed varnish. At this time, the mixed varnish was prepared so that the concentration of the resin and silica particles was 9.7% by mass. The obtained polyamideimide varnish was filtered through a filter with an opening of 10 μm, and then applied to a smooth surface of a polyester substrate ("A4100" (trade name) manufactured by Toyobo Co., Ltd.) so that the thickness of the free-standing film was 45 μm, and the coating film of the varnish was formed by drip molding. At this time, the linear speed was 0.8 m/min. The coating film of the varnish was heated at 80° C. for 10 minutes, further heated at 100° C. for 10 minutes, and further heated at 90° C. for 10 minutes. Thereafter, the coating film was heated (post-baked) at 200° C. for 25 minutes to obtain a polyimide film having a thickness of 40 μm, a total light transmittance of 89.9 (%), a YI of 1.6, and a haze of 0.2 (%).

<Production Example 3>
Preparation of photocurable resin composition for hard coat Trimethylolpropane triacrylate ("A-TMPT" (trade name) manufactured by Shin-Nakamura Chemical Co., Ltd.) 28.4 parts by mass, pentaerythritol tetraacrylate ("A-TMMT" (trade name) manufactured by Shin-Nakamura Chemical Co., Ltd.) 28.4 parts by mass, 1-hydroxycyclohexyl phenyl ketone ("Irgacure" (registered trademark) 184 manufactured by BASF) as a photopolymerization initiator 1.8 parts by mass, leveling agent ("BYK" (registered trademark)-307 manufactured by BYK Japan Co., Ltd.) 0.1 parts by mass, and propylene glycol 1-monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) 39 parts by mass were stirred and mixed to obtain a photocurable resin composition.

<Production Example 4>
Manufacture of front panel The photocurable resin composition prepared in Production Example 3 was applied to one side of the polyamideimide film (optical film) manufactured in Production Example 2 by roll-to-roll coating so that the thickness after drying was 10 μm. Then, the film was dried in an oven at 80° C. for 3 minutes, and cured by irradiating ultraviolet light to obtain a front panel. The ultraviolet light was irradiated using a high-pressure mercury lamp so that the amount of light to be laminated was 500 mJ/cm ^2. The thickness of the hard coat layer in the front panel was 10 μm. The tensile modulus of the obtained front panel (including the hard coat layer) was 6.5 GPa.

<Production Example 5>
Synthesis of polyimide (PI) resin A reactor equipped with a silica gel tube, a stirrer and a thermometer in a separable flask, and an oil bath were prepared. 75.52 g of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 54.44 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB) were added to the flask. 519.84 g of N,N-dimethylacetamide (DMAc) was added while stirring at 400 rpm, and stirring was continued until the contents of the flask became a uniform solution. Next, stirring was continued for another 20 hours while adjusting the temperature in the container to be in the range of 20 to 30 ° C. using an oil bath, and polyamic acid was produced by reaction. After 30 minutes, the stirring speed was changed to 100 rpm. After stirring for 20 hours, the reaction system temperature was returned to room temperature, and 649.8 g of DMAc was added to adjust the polymer concentration to 10% by mass. Furthermore, 32.27 g of pyridine and 41.65 g of acetic anhydride were added, and the mixture was stirred at room temperature for 10 hours to perform imidization. The polyimide varnish was removed from the reaction vessel. The obtained polyimide varnish was dropped into methanol to perform reprecipitation, and the obtained powder was heated and dried to remove the solvent, thereby obtaining a transparent polyimide resin as a solid content. When the obtained polyimide resin was subjected to GPC measurement, the weight average molecular weight was 360,000.

<Production Example 6>
Manufacture of polyimide (PI) film for impact-resistant layer The polyimide resin (6FDA/TFMB=100/100) obtained in Manufacturing Example 5 was diluted with GBL/DMAc=10/90 to prepare a polyimide varnish with a concentration of 15.7% by mass. The obtained polyimide varnish was filtered through a filter with a mesh size of 10 μm, and then applied to a smooth surface of a polyester substrate ("A4100" (trade name) manufactured by Toyobo Co., Ltd.) using an applicator so that the thickness of the free-standing film was 85 μm. After drying at 50 ° C. for 30 minutes and then at 140 ° C. for 15 minutes, the resulting coating film was peeled off from the polyester substrate to obtain a free-standing film. The free-standing film was fixed to a metal frame and further dried at 200 ° C. for 40 minutes under air to obtain a polyimide film (optical film) with a thickness of 80 μm.

Example 1
Manufacture of optical laminate As an impact-resistant layer, a polyimide (PI) film having a thickness of 80 μm and a tensile modulus of 4.0 GPa obtained in Manufacturing Example 6 was prepared. As a first adhesive layer, a (meth)acrylic transparent adhesive sheet (OCA) having a thickness of 25 μm and a storage modulus of 0.1 MPa at 25° C. was prepared. As a second adhesive layer, a (meth)acrylic transparent adhesive sheet having a thickness of 25 μm and a storage modulus of 0.1 MPa at 25° C. was prepared.

The front panel and impact-resistant layer obtained in Manufacturing Example 4 were laminated via a first adhesive layer. A second adhesive layer was laminated on the surface of the impact-resistant layer that did not have the first adhesive layer laminated thereon to obtain an optical laminate.

Example 2
An optical laminate was produced in the same manner as in Example 1, except that a polyethylene terephthalate (PET) film (product name: SH82, manufactured by SKC Corporation) having a thickness of 80 μm and a tensile modulus of elasticity of 4.6 GPa was used as the impact-resistant layer instead of the polyimide film.

Example 3
An optical laminate was produced in the same manner as in Example 2, except that a (meth)acrylic transparent adhesive sheet having a thickness of 50 μm and a storage modulus at 25° C. of 0.1 MPa was used as the second adhesive layer.

Example 4
An optical laminate was produced in the same manner as in Example 2, except that a (meth)acrylic transparent adhesive sheet having a thickness of 85 μm and a storage modulus at 25° C. of 0.1 MPa was used as the second adhesive layer.

Example 5
An optical laminate was produced in the same manner as in Example 2, except that a (meth)acrylic transparent adhesive sheet having a thickness of 50 μm and a storage modulus at 25° C. of 0.1 MPa was used as the first adhesive layer.

Example 6
An optical laminate was produced in the same manner as in Example 2, except that a (meth)acrylic transparent adhesive sheet having a thickness of 85 μm and a storage modulus at 25° C. of 0.1 MPa was used as the first adhesive layer.

Example 7
An optical laminate was produced in the same manner as in Example 1, except that a polyethylene terephthalate (PET) film having a thickness of 38 μm and a tensile modulus of elasticity of 4.6 GPa was used as the impact-resistant layer instead of the polyimide film.

Example 8
An optical laminate was produced in the same manner as in Example 1, except that a polyethylene terephthalate (PET) film having a thickness of 100 μm and a tensile modulus of elasticity of 4.6 GPa was used as the impact-resistant layer instead of the polyimide film.

<Comparative Example 1>
An optical laminate was produced in the same manner as in Example 1, except that a polyurethane (PU) film having a thickness of 150 μm and a tensile modulus of elasticity of 0.03 GPa was used as the impact-resistant layer instead of the polyimide film.

<Evaluation of optical properties of optical film for front panel>
[Film yellowness]
The yellowness index (YI value) of the optical film was measured using a spectrophotometer CM-3700A manufactured by Konica Minolta, Inc. Specifically, after background measurement was performed without a sample, the optical laminate was set in a sample holder and transmittance measurement was performed for light of 300 to 800 nm to determine tristimulus values (X, Y, Z), and the YI value was calculated based on the following formula.

YI=100×(1.2769X-1.0592Z)/Y

[Total light transmittance]
The total light transmittance (Tt) was measured in accordance with JIS K 7105:1981 using a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd.

[Haze]
In accordance with JIS K 7136:2000, the optical films obtained in the examples and comparative examples were cut to a size of 30 mm x 30 mm, and the haze (%) was measured using a haze computer (manufactured by Suga Test Instruments Co., Ltd., "HGM-2DP").

<Performance evaluation of optical laminate>
[Impact resistance test]
The optical laminates prepared in Examples 1 to 8 and Comparative Example 1 were placed on a 125 μm thick polyimide substrate on a stone surface plate (manufactured by Unisei Corporation, first grade). The optical laminates were placed so that the front plate was facing upward. A pressure measurement film ("Prescale" (registered trademark), manufactured by Fujifilm Corporation, grade: HS (product name)) was sandwiched between the optical laminate and the polyimide substrate (thickness 125 μm). A weight with a mass of 5.6 g and a circular surface with a diameter of 0.75 mm that collided with the sample was prepared. This weight was dropped vertically three times from a position of a height of 10 cm. The bottom stress was measured from the discoloration of the pressure-sensitive paper at the drop point using a pressure image analysis system ("FPD-8010J" (product name), manufactured by Fujifilm Corporation), and the average value of the three measured values was calculated, and the impact resistance was evaluated as follows.

◎...Very good: 73 MPa or less ◯...Good: Over 73 MPa, 77 MPa or less △...Fair: Over 77 MPa, 85 MPa or less ×...Poor: Over 85 MPa

[Flexibility test]
The bending test was carried out at a temperature of 25°C. The optical laminates obtained in the examples and comparative examples were cut into a size of 10 mm width using a dumbbell cutter. The cut optical laminates were set in a jig of a surface condition no-load U-shaped stretch tester ("DMLHB-FS" (product name) manufactured by Yuasa System Equipment Co., Ltd.) so that they could be bent with the front panel on the inside, and the operation of bending and stretching them by 180° was repeated so that the distance between the opposing front panels was 2.0 mm (bending radius 1 mm). The bending speed was 30 rpm. The number of bendings (number of bending resistance) at which the optical laminate broke was evaluated as an index of bending resistance as follows.

◎: Very good: Resistance to bending is 200,000 times or more. 〇: Good: Resistance to bending is 150,000 times or more but less than 200,000 times. △: Fairly good: Resistance to bending is 100,000 times or more but less than 150,000 times. ×: Poor: Resistance to bending is less than 100,000 times.

[Storage modulus of pressure-sensitive adhesive layer]
The viscoelasticity was measured using a viscoelasticity measuring device ("MCR-301" (trade name) manufactured by Anton Paar). The same adhesive layer as that used in the examples and comparative examples was cut to a width of 20 mm x length of 20 mm, and a plurality of sheets were laminated to a thickness of 150 μm. After bonding the laminated adhesive layer to a glass plate, the measurement was performed in a temperature range of -20°C to 100°C under conditions of a frequency of 1.0 Hz, a deformation amount of 1%, and a temperature rise rate of 5°C/min in a state where the measurement chip was attached, and the storage modulus value at 25°C was confirmed.

[Tensile modulus]
The impact-resistant layer and the front plate used in the examples and comparative examples were cut into strips of 10 mm x 100 mm using a dumbbell cutter to obtain samples. The stress-strain curve of the sample was measured using an autograph AG-IS manufactured by Shimadzu Corporation under conditions of a chuck distance of 50 mm and a tensile speed of 10 mm/min, and the tensile modulus of the impact-resistant layer was calculated from the slope of the curve. The measurement of the tensile modulus was performed in an environment of a temperature of 23°C and a relative humidity of 55%.

[Method of measuring layer thickness]
The thickness of each layer was measured using a contact type film thickness measuring device (manufactured by Nikon Corporation under the trade name "MS-5C"). However, the polarizer layer and the alignment film were measured using a laser microscope (manufactured by Olympus Corporation under the trade name "OLS3000"). The results are shown in Table 1.

1...Front panel,
2...first adhesive layer,
3...Impact-resistant layer,
4...second pressure-sensitive adhesive layer,
5...Display unit,
10...Optical laminate,
20...Display device.

Claims (6)

An optical laminate having a front plate, at least one pressure-sensitive adhesive layer, and an impact-resistant layer,
The impact resistant layer has a thickness of 30 to 140 μm,
the impact-resistant layer has a tensile modulus of 3.0 to 7.0 GPa;
In a continuous bending test in which the front panel is bent and stretched 180° inward under conditions of a temperature of 25°C, a bending speed of 30 rpm, and a bending radius of 1.00 mm, the product exhibited a bending resistance of more than 150,000 times.
The pressure-sensitive adhesive layer includes a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, and the first pressure-sensitive adhesive layer, the impact-resistant layer, and the second pressure-sensitive adhesive layer are provided in this order toward the inside of the front panel,
The second pressure-sensitive adhesive layer has a storage modulus of 0.01 to 0.80 MPa at 25° C. The optical laminate according to claim 1, having a thickness of 100 to 500 μm. 3. The optical laminate according to claim 1, wherein the first and second pressure-sensitive adhesive layers and the impact-resistant layer have a total thickness of 80 to 200 μm. 4. The optical laminate according to claim 1, wherein the material of the impact-resistant layer is selected from the group consisting of polycarbonate-based resins, polyimide-based resins, and polyester-based resins. The optical laminate according to any one of claims 1 to 4 , wherein the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer have a thickness ratio r of 15/85 to 85/15. A display device comprising the optical laminate according to any one of claims 1 to 5 and a display unit disposed inwardly of the optical laminate.

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