Laminates and display devices

Abstract

To provide a laminate that has excellent flexibility and optical characteristics even when subjected to ultraviolet irradiation of a large integrated amount of luminous energy.SOLUTION: A laminate has, in the order stated, a front layer, a first adhesive layer which is formed using a first adhesive composition, a polarizing plate that includes at least a linear polarizing layer, a second adhesive layer which is formed using a second adhesive composition, and a rear layer. Assuming that D1[%] is a coefficient of linear contraction under the condition that the temperature of a first reference adhesive layer which is formed in a thickness of 0.6 mm using the first adhesive composition is 25°C after irradiation of the first reference adhesive layer with ultraviolet ray in an integrated amount of 100 J / cm2, the load is 1N, and the strain is 350%, and that D2[%] is a coefficient of linear contraction under the condition that the temperature of a second reference adhesive layer which is formed in a thickness of 0.6 mm using the second adhesive composition is 25°C after irradiation of the second reference adhesive layer with ultraviolet ray in an integrated amount of 100 J / cm2, the load is 1N, and the strain is 350%, the relationships of formulas (1) and (2) are satisfied. (1): D1≥D2, (2): 2.5≤D1≤6.5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate and a display device. [Background technology]

[0002] In flexible displays equipped with a bendable display panel, it is known that the stress relaxation characteristics of the adhesive layer contained in the laminate used for the display panel are adjusted in order to achieve good flexibility (for example, Patent Documents 1, 2, 4, and 5). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Korean Published Patent No. 10-2014-0085299 [Patent Document 2] Japanese Patent Publication No. 2018-27995 [Patent Document 3] Japanese Patent Publication No. 2017-125195 [Patent Document 4] Japanese Patent Publication No. 2018-28573 [Patent Document 5] Special Publication No. 2019-528330 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] It has been found that when laminates used in display panels are exposed to ultraviolet irradiation with a large amount of accumulated light, their flexibility decreases and their optical properties deteriorate.

[0005] The present invention aims to provide a laminate that has excellent flexibility and optical properties even when subjected to ultraviolet irradiation with a large cumulative light intensity, and a display device including the same. [Means for solving the problem]

[0006] The present invention provides the following laminates and display devices. [1] The device has, in this order, a front layer, a first adhesive layer formed using a first adhesive composition, a polarizing plate including at least a linear polarizing layer, a second adhesive layer formed using a second adhesive composition, and a back layer. A cumulative amount of 100 J / cm² is applied to a first reference adhesive layer formed to a thickness of 0.6 mm using the first adhesive composition. 2 The linear shrinkage rate of the first reference adhesive layer after irradiation with ultraviolet light, under conditions of a temperature of 25°C, a load of 1N, and a strain of 350%, is defined as D1[%]. A cumulative amount of 100 J / cm² is applied to a second reference adhesive layer formed to a thickness of 0.6 mm using the second adhesive composition. 2 When the linear shrinkage rate of the second reference adhesive layer after irradiation with ultraviolet light is D2[%] under conditions of a temperature of 25°C, a load of 1N, and a strain of 350%, A laminate that satisfies the following relationships (1) and (2). D1≧D2 (1) 2.5 ≤ D1 ≤ 6.5 (2) [2] The laminate according to [1], wherein the gel fraction of the first reference adhesive layer after irradiation with ultraviolet light is 50% or more and 90% or less. [3] The laminate according to [1] or [2], wherein the thickness of the first adhesive layer is 15 μm or more and 100 μm or less. [4] The laminate according to any one of [1] to [3], wherein the glass transition temperature of the first adhesive layer is -55°C or lower. [5] The first adhesive composition comprises a (meth)acrylic polymer, The laminate according to any one of [1] to [4], wherein the (meth)acrylic polymer includes a structural unit derived from an alkyl (meth)acrylate ester having an alkyl group having 1 to 24 carbon atoms. [6] The laminate according to [5], wherein the (meth)acrylic polymer includes structural units derived from an alkyl (meth)acrylate ester having an alkyl group with 20 or more carbon atoms and 24 or fewer carbon atoms. [7] The laminate according to [5] or [6], wherein the content of constituent units derived from monomers having reactive functional groups for all constituent units of the (meth)acrylic polymer is 2% by mass or less. [8] The front layer includes a first base material layer and a coating layer formed on at least one side of the first base material layer, The coating layer is formed using a composition containing a (meth)acrylic compound having a dendrimer structure, and is the laminate according to any one of [1] to [7]. <0​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Figures 1 and 2 are schematic cross-sectional views illustrating an example of the laminate of this embodiment. Laminates 1 and 2 have, in this order, a front layer 11, a first adhesive layer 21 formed using a first adhesive composition, a polarizing plate 30 including at least a linear polarizing layer, a second adhesive layer 22 formed using a second adhesive composition, and a back layer 15.

[0011] The front layer 11 is a layer provided on the viewing side of the polarizing plate 30, and the back layer 15 is a layer provided on the side opposite to the viewing side of the polarizing plate 30. In the laminates 1 and 2, it is preferable that the first adhesive layer 21 is in direct contact with the front layer 11 and the polarizing plate 30. It is preferable that the second adhesive layer 22 is in direct contact with the polarizing plate 30 and the back layer 15. The polarizing plate 30 includes at least a linear polarizing layer 31, and may be a linear polarizing plate or a circular polarizing plate, as will be described later.

[0012] As described later, the laminates 1 and 2 can be applied to display devices (flexible displays) that can be bent, wound, etc. In particular, the laminates 1 and 2 have excellent flexibility when bent so that the front layer 11 side is on the inside.

[0013] A cumulative amount of 100 J / cm² is applied to a first standard adhesive layer formed to a thickness of 0.6 mm using the first adhesive composition. 2 The linear shrinkage rate of the first reference adhesive layer after irradiation with ultraviolet light (hereinafter sometimes referred to as "first reference adhesive layer after UV irradiation") under the conditions of a temperature of 25°C, a load of 1N, and a strain of 350% is defined as D1[%]. A cumulative amount of 100 J / cm² is applied to a second standard adhesive layer formed to a thickness of 0.6 mm using the second adhesive composition. 2 When the linear shrinkage rate of the second reference adhesive layer after irradiation with ultraviolet light (hereinafter sometimes referred to as the "second reference adhesive layer after UV irradiation") is D2[%] under conditions of a temperature of 25°C, a load of 1N, and a strain of 350%, Laminates 1 and 2 satisfy the following relationships (1) and (2). D1≧D2 (1) 2.5 ≤ D1 ≤ 6.5 (2)

[0014] The linear shrinkage rates D1 and D2 are values calculated by the following formulas (3) and (4). D1 [%] = {1 - (T 10 1 / T01)} × 100 (3) D2 [%] = {1 - (T 10 2 / T02)} × 100 (4) [In formula (3), T01 is the thickness [μm] of the first reference adhesive layer immediately after applying a load of 1 N and a strain of 350% at a temperature of 25°C to the first reference adhesive layer after UV irradiation, T 10 1 is the thickness [μm] of the first reference adhesive layer measured after holding for 10 hours in a state where a load of 1 N and a strain of 350% are applied to the first reference adhesive layer after UV irradiation at a temperature of 25°C. T02 is the thickness [μm] of the second reference adhesive layer immediately after applying a load of 1 N and a strain of 350% at a temperature of 25°C to the second reference adhesive layer after UV irradiation, T 10 2 is the thickness [μm] of the first reference adhesive layer measured after holding for 10 hours in a state where a load of 1 N and a strain of 350% are applied to the second reference adhesive layer after UV irradiation at a temperature of 25°C.]

[0015] The linear shrinkage rates D1 and D2, the thicknesses T01 and T 10 1 of the first reference adhesive layer, and the thicknesses T02 and T 10 2 of the second reference adhesive layer can be measured by the methods described in the examples below, and each of the above thicknesses is measured by a viscoelasticity measuring device.

[0016] The linear shrinkage rate D1 is 2.5 or more, may be 3.0 or more, may be 3.5 or more, may be 4.0 or more, and is 6.5 or less, may be 6.0 or less, may be 5.5 or less, may be 5.0 or less.

[0017] The linear shrinkage rate D1 can be adjusted by the type and amount of polymer contained in the first adhesive composition, the weight-average molecular weight of the polymer, the type and amount of monomer used to form the polymer, the type and amount of polymerization initiator and additives contained in the first adhesive composition, and so on.

[0018] The linear contraction rate D2 may be 1.5 or greater, 2.0 or greater, 2.5 or greater, 3.0 or greater, and may also be 6.5 or less, 6.0 or less, 5.5 or less, 5.0 or less, or 4.5 or less.

[0019] The linear shrinkage rate D2 can be adjusted by the type and amount of polymer contained in the second adhesive composition, the weight-average molecular weight of the polymer, the type and amount of monomer used to form the polymer, and the type and amount of polymerization initiators and additives contained in the second adhesive composition.

[0020] By satisfying the relationship between equations (1) and (2) above, laminates 1 and 2 can have excellent flexibility and optical properties even when subjected to ultraviolet irradiation with a large amount of accumulated light.

[0021] When the laminates 1 and 2 are bent so that the front layer 11 is on the inside, the bending radius of the first adhesive layer 21 becomes smaller than the bending radius of the second adhesive layer 22. Therefore, it is desirable that the first adhesive layer 21 shrinks as easily as or more easily than the second adhesive layer 22. As such, by satisfying the relationship between equations (1) and (2) above, it is possible to suppress the generation of bubbles in the first adhesive layer 21 and / or the second adhesive layer 22, and the occurrence of delamination between the front layer 11 and the first adhesive layer 21, even when the laminates 1 and 2 that have been subjected to ultraviolet irradiation with a large amount of accumulated light are bent so that the front layer 11 is on the inside.

[0022] In particular, by satisfying the relationship in equation (2) above, the degradation of the first adhesive layer 21 can be suppressed and the deterioration of optical properties can be suppressed even when the laminates 1 and 2 are subjected to ultraviolet irradiation with a large amount of accumulated light.

[0023] The gel fraction of the first reference adhesive layer after UV irradiation and the gel fraction of the second reference adhesive layer after UV irradiation may independently be 50% or more, 60% or more, 70% or more, 90% or less, preferably 85% or less, 80% or less, or 75% or less. The gel fraction of the first reference adhesive layer after UV irradiation and the gel fraction of the second reference adhesive layer after UV irradiation may be the same or different. The gel fractions of the first reference adhesive layer and the second reference adhesive layer can be adjusted, for example, by the amount of constituent units derived from monomers having reactive functional groups in the (meth)acrylic polymer described later and contained in the first and second adhesive compositions, the amount of crosslinking agent contained in the first and second adhesive compositions, etc. The gel fraction can be measured by the method described in the examples described later.

[0024] By using a first adhesive layer 21 formed with a first adhesive composition capable of forming a first reference adhesive layer having the above-mentioned gel fraction, and / or a second adhesive layer 22 formed with a second adhesive composition capable of forming a second reference adhesive layer having the above-mentioned gel fraction, it becomes easier to obtain laminates 1 and 2 that have excellent flexibility and optical properties even when subjected to ultraviolet irradiation with a large cumulative light intensity.

[0025] The thickness of the laminates 1 and 2 is preferably 100 μm or more, may be 150 μm or more, may be 2000 μm or less, may be 1000 μm or less, may be 500 μm or less, preferably 250 μm or less, and may be 200 μm or less.

[0026] (1st adhesive layer, 2nd adhesive layer) The thickness of the first adhesive layer 21 may be 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 100 μm or less, 80 μm or less, 60 μm or less, or 50 μm or less. The thickness of the first adhesive layer 21 is preferably 15 μm or more and 100 μm or less, and more preferably 20 μm or more and 80 μm or less.

[0027] The thickness of the second adhesive layer 22 may be 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 100 μm or less, 80 μm or less, 60 μm or less, or 50 μm or less.

[0028] By ensuring that the thickness of the first adhesive layer 21 and / or the second adhesive layer 22 meets the above range, it becomes easier to obtain laminates 1 and 2 that have excellent flexibility and optical properties even when subjected to ultraviolet irradiation with a large cumulative light intensity.

[0029] The glass transition temperatures of the first adhesive layer 21 and the second adhesive layer 22 may be -55°C or lower, -56°C or lower, or -57°C or lower, and are usually -80°C or higher. Having glass transition temperatures within the above ranges for the first adhesive layer 21 and / or the second adhesive layer 22 makes it easier to obtain laminates 1 and 2 with excellent flexibility and optical properties even when subjected to high-intensity ultraviolet irradiation. The glass transition temperatures of the first adhesive layer 21 and the second adhesive layer 22 may be the same or different. The glass transition temperatures of the first adhesive layer 21 and the second adhesive layer 22 can be adjusted, for example, by the type and amount of polymer contained in the adhesive composition, the type and amount of monomer used to form the polymer, etc. The glass transition temperature can be measured by the method described in the examples below.

[0030] (First adhesive composition, second adhesive composition) The first adhesive composition and the second adhesive composition (hereinafter, both may be collectively referred to as "adhesive composition") preferably each independently contain a (meth)acrylic polymer. The composition of the first adhesive composition and the composition of the second adhesive composition may be the same or different. In this specification, "(meth)acrylic polymer" refers to at least one selected from the group consisting of acrylic polymers and methacrylic polymers. The same applies to other terms prefixed with "(meth)".

[0031] The (meth)acrylic polymer preferably contains structural units derived from an alkyl (meth)acrylate (monomer) having an alkyl group with 1 to 24 carbon atoms. More preferably, the (meth)acrylic polymer contains structural units derived from an alkyl (meth)acrylate (monomer) having an alkyl group with 20 to 24 carbon atoms. The alkyl group may be linear or branched. By forming the first adhesive layer 21 and / or the second adhesive layer 22 using an adhesive composition containing the above structural units, laminates 1 and 2 with excellent flexibility and optical properties can be easily obtained even when subjected to ultraviolet irradiation with a large cumulative light intensity.

[0032] Examples of alkyl (meth)acrylate esters having the alkyl group mentioned above include butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, and docosyl (meth)acrylate. The alkyl (meth)acrylate esters mentioned above may be used individually or in combination of two or more.

[0033] The content of constituent units derived from the alkyl ester (meth)acrylate having the alkyl group, relative to all constituent units of the (meth)acrylic polymer, is preferably 50% by mass or more, may be 60% by mass or more, may be 70% by mass or more, may be 99% by mass or less, may be 97% by mass or less, or may be 90% by mass or less.

[0034] The (meth)acrylic polymer preferably contains constituent units derived from the above-mentioned alkyl (meth)acrylate, specifically those derived from alkyl (meth)acrylates whose homopolymer glass transition temperature is -40°C or lower (hereinafter sometimes referred to as "low Tg monomer"), and constituent units derived from alkyl (meth)acrylates whose homopolymer glass transition temperature is above 0°C (hereinafter sometimes referred to as "high Tg monomer"). By forming the first adhesive layer 21 and / or the second adhesive layer 22 using such an adhesive composition containing a (meth)acrylic polymer, laminates 1 and 2 with excellent flexibility and optical properties can be easily obtained even when subjected to ultraviolet irradiation with a large cumulative light intensity. One or more types of low Tg monomers and high Tg monomers may be used. The glass transition temperature of the alkyl (meth)acrylate homopolymer can be based on literature values ​​such as those in the POLYMER HANDBOOK (Wiley-Interscience).

[0035] The (meth)acrylic polymer may further contain constituent units derived from alkyl (meth)acrylates (hereinafter sometimes referred to as "intermediate Tg monomers") whose homopolymer glass transition temperature is greater than -40°C and less than or equal to 0°C. One or more intermediate Tg monomers may be used.

[0036] The glass transition temperature of the low-Tg monomer may be -45°C or lower, or -50°C or lower. The content of constituent units derived from the low-Tg monomer relative to the total constituent units of the (meth)acrylic polymer may be, for example, 10% by mass or more, 30% by mass or more, 40% by mass or more, or 95% by mass or less, 80% by mass or less, or 60% by mass or less.

[0037] The glass transition temperature of the high-Tg monomer may be 5°C or higher, 10°C or higher, 100°C or lower, 50°C or lower, or 30°C or lower. The content of constituent units derived from the high-Tg monomer relative to the total constituent units of the (meth)acrylic polymer may be, for example, 1% by mass or higher, 3% by mass or higher, 5% by mass or higher, 20% by mass or lower, 15% by mass or lower, or 10% by mass or lower.

[0038] (Meth)acrylic polymers may contain constituent units derived from monomers having reactive functional groups. Reactive functional groups include those that can react with other functional groups to form covalent bonds by irradiation with active energy rays, heat treatment, or heat-induced moisture treatment. Heat-induced moisture treatment is a treatment in which the polymer is brought into contact with water or steam in a high-temperature environment (e.g., 80°C), and may also be a humidification treatment in a high-temperature environment. Examples of reactive functional groups include hydroxyl groups, carboxyl groups, amino groups, epoxy groups, and amide groups.

[0039] Examples of monomers having reactive functional groups include: Hydroxylated (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-(2-hydroxyethoxy)ethyl (meth)acrylate, 2- or 3-chloro-2-hydroxypropyl (meth)acrylate, and diethylene glycol mono(meth)acrylate; Ethylene-unsaturated carboxylic acids such as (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, and β-carboxyethyl (meth)acrylate; (Meth)acrylates having an amino group, such as (meth)acrylate aminoethyl, (meth)acrylate n-butylaminoethyl, (meth)acrylate dimethylaminopropyl, and (meth)acrylate N,N-dimethylaminoethyl; (meth)acrylates having epoxy groups, such as (3,4-epoxycyclohexyl)methyl (meth)acrylate and glycidyl (meth)acrylate; (meth)acrylates having an amide group, such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-methylol(meth)acrylamide; Monomers having heterocyclic groups, such as (meth)acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, vinylpyridine, and tetrahydrofurfuryl(meth)acrylate; Examples include the above. A monomer having a reactive functional group may be used alone or in combination of two or more.

[0040] The content of constituent units derived from monomers having reactive functional groups relative to the total constituent units of the (meth)acrylic polymer is preferably 2% by mass or less, may be less than 2% by mass, or 1% by mass or less. The (meth)acrylic polymer does not need to contain constituent units derived from monomers having reactive functional groups. By forming the first adhesive layer 21 and / or the second adhesive layer 22 using a (meth)acrylic polymer with a reduced content of constituent units derived from monomers having reactive functional groups, laminates 1 and 2 with excellent flexibility and optical properties can be easily obtained even when subjected to ultraviolet irradiation with a large cumulative light intensity.

[0041] The (meth)acrylic polymer may contain monofunctional (meth)acrylic monomers having alkoxy groups, etc.

[0042] Examples of alkoxy groups in the above monofunctional (meth)acrylic monomers include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and tert-butoxy groups. Examples of monofunctional (meth)acrylic monomers having alkoxy groups include ethoxyethoxyethyl acrylate (EOEOEA) and nonylphenol EO-modified acrylate [NP(EO)8A]. The above monofunctional (meth)acrylic monomers may be used individually or in combination of two or more.

[0043] The content of the monofunctional (meth)acrylic monomer-derived structural units relative to the total structural units of the (meth)acrylic polymer is preferably 1% by mass or more, may be 2% by mass or more, may be 10% by mass or more, may be 20% by mass or more, may be 30% by mass or more, may be 50% by mass or less, or may be 40% by mass or less.

[0044] (Meth)acrylic polymers are obtained by mixing the above-mentioned monomers and polymerizing the monomers by adding polymerization initiators, etc. The polymerization method is not particularly limited, but known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and photopolymerization can be used. (Meth)acrylic polymers may be random copolymers, block copolymers, or graft copolymers.

[0045] The polymerization initiator can be selected according to the polymerization method, and examples include cationic polymerization initiators or radical polymerization initiators. When the polymerization method is photopolymerization, a photopolymerization initiator can be used. One or more types of photopolymerization initiators can be used.

[0046] When using two or more photopolymerization initiators, it is preferable to use a first photopolymerization initiator with a maximum absorption wavelength of 250 nm or less and a second photopolymerization initiator with a maximum absorption wavelength greater than 250 nm and less than or equal to 300 nm. By including both the first and second photopolymerization initiators in the polymerization initiator, the polymerization reaction of the (meth)acrylic polymer can be sufficiently advanced, thereby suppressing a decrease in the physical properties of the first adhesive layer 21 and / or the second adhesive layer 22 formed using the (meth)acrylic polymer. The maximum absorption wavelength of the photopolymerization initiator can be measured by the method described in the examples below.

[0047] Examples of first photopolymerization initiators include ketone-based photopolymerization initiators such as 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methylpropiophenone, and (2,4-cyclopentadien-1-yl)[(1-methylethyl)benzene]-Fe(II) hexafluorophosphate.

[0048] Examples of secondary photopolymerization initiators include phenylglyoxylate-based photopolymerization initiators such as 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and a mixture of oxyphenyl-acetic acid 2-[2-oxo-2-phenylacetoxy-ethoxy]-ethyl ester and oxyphenyl-acetic acid 2-[2-hydroxyethoxy]-ethyl ester.

[0049] The weight-average molecular weight (Mw) of the (meth)acrylic polymer is preferably 600,000 or more, may be 700,000 or more, may be 900,000 or more, may be 2,000,000 or less, may be 1,800,000 or less, and preferably 1,500,000 or less. The above weight-average molecular weight can be measured by gel permeation chromatography (GPC).

[0050] The adhesive composition may contain one or more of the above-mentioned (meth)acrylic polymers, and may further contain a (meth)acrylic compound and a polymerization initiator.

[0051] The adhesive composition preferably contains two or more (meth)acrylic polymers. The content of (meth)acrylic polymers relative to the solid content of the adhesive composition is, for example, 70% by mass or more, may be 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or less, 98% by mass or less, or 97% by mass or less. The content of (meth)acrylic polymers is the total amount when the adhesive composition contains two or more (meth)acrylic polymers.

[0052] Examples of (meth)acrylic compounds include alkyl (meth)acrylate esters having an alkyl group with 1 to 24 carbon atoms as described above. The (meth)acrylic compound contained in the adhesive composition may be one type or two or more types. The content of the (meth)acrylic compound relative to the solid content of the adhesive composition may be, for example, 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 1.5% by mass or more, 10.0% by mass or less, 5.0% by mass or less, or 3.0% by mass or less.

[0053] The alkyl group of the alkyl (meth)acrylate having the above alkyl group is preferably 1 to 15, may be 2 to 10, and is preferably at least one of butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. The content of the above alkyl (meth)acrylate relative to the solid content of the adhesive composition is, for example, 0.1% by mass or more, may be 0.5% by mass or more, may be 1.0% by mass or more, may be 1.5% by mass or more, may be 10.0% by mass or less, may be 5.0% by mass or less, or may be 3.0% by mass or less.

[0054] Polymerization initiators included in the adhesive composition include photopolymerization initiators and thermal polymerization initiators. One or more polymerization initiators may be used. The content of the polymerization initiator relative to the solid content of the adhesive composition is, for example, 0.1% by mass or more, may be 1% by mass or more, may be 10% by mass or less, or may be 5% by mass or less.

[0055] Examples of photopolymerization initiators include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methylpropiophenone, (2,4-cyclopentadiene-1-yl)[(1-methylethyl)benzene]-Fe(II) hexafluorophosphate, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, a mixture of oxyphenyl-acetic acid 2-[2-oxo-2-phenylacetoxy-ethoxy]-ethyl ester and oxyphenyl-acetic acid 2-[2-hydroxyethoxy]-ethyl ester, benzyldimethyl ketal, and 1-hydroxycyclohexylphenyl ketone.

[0056] Examples of thermal polymerization initiators include azo compounds, organic peroxides, and inorganic peroxides. Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane1-carbonitride), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

[0057] Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, and diacetyl peroxide.

[0058] Examples of inorganic peroxides include potassium persulfate, ammonium persulfate, and hydrogen peroxide.

[0059] The adhesive composition may contain additives such as crosslinking agents, silane coupling agents, crosslinking catalysts, weather stabilizers, tackifiers, plasticizers, softeners, dyes, pigments, inorganic fillers, light-scattering fine particles, and antistatic agents such as ionic compounds.

[0060] Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, amine-based crosslinking agents, melamine-based crosslinking agents, aziridine-based crosslinking agents, hydrazine-based crosslinking agents, aldehyde-based crosslinking agents, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents.

[0061] Examples of silane coupling agents include organosilicon compounds having at least one alkoxysilyl group in their molecule. Examples of silane coupling agents include: Polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; Silicon compounds having an epoxy structure, such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; Mercapto group-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; amino group-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; Condensates of 3-chloropropyltrimethoxysilane, 3-isocyanatetopropyltriethoxysilane, or at least one thereof with alkyl group-containing silicon compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane. These are some examples.

[0062] The adhesive composition can be prepared by mixing a (meth)acrylic polymer, a (meth)acrylic compound, a polymerization initiator, and additives. The adhesive composition itself, or a diluted solution of the adhesive composition in an organic solvent, can be applied to a substrate and dried to form a first adhesive layer 21 or a second adhesive layer 22. Examples of methods for applying the adhesive composition or its diluted solution in an organic solvent include bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0063] The adhesive composition applied to the substrate may be subjected to irradiation with active energy rays or heat treatment to form a first adhesive layer 21 or a second adhesive layer 22. Examples of active energy rays include ultraviolet rays and electron beams, with ultraviolet rays being preferred.

[0064] (front layer) The front layer 11 may be the front plate that constitutes the outermost surface on the viewing side of the display device when the laminates 1 and 2 are applied to the display device, or it may be the third base layer of a protective film that includes a third base layer and a first adhesive layer 21. The protective film is usually provided so as to be peelable from the polarizing plate 30.

[0065] The front layer 11 may have a single-layer structure or a multilayer structure. The thickness of the front layer 11 may be, for example, 10 μm or more, 20 μm or more, 30 μm or more, 500 μm or less, 200 μm or less, or 100 μm or less.

[0066] When the front layer 11 is a front plate, the front layer 11 may be a resin plate (e.g., a resin plate, a resin film, etc.) or a glass plate (e.g., a glass plate, a glass film, etc.). The resin plate is not limited as long as it is capable of transmitting light. Examples of resins that constitute a resin plate such as a resin film include films made of polymers such as triacetylcellulose, acetylcellulose butyrate, ethylene-vinyl acetate copolymer, propionylcellulose, butyrylcellulose, acetylpropionylcellulose, polyester, polystyrene, polyamide, polyetherimide, poly(meth)acrylic, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyetherether ketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers can be used individually or in combination of two or more. From the viewpoint of improving strength and transparency, the resin film is preferably made of a polymer such as polyimide, polyamide, or polyamideimide.

[0067] The resin plate-like body may be a first base layer having a coating layer such as a hard coat layer from the viewpoint of hardness. The coating layer may be formed on one side of the first base layer or on both sides. The resin film described above is an example of the first base layer.

[0068] The coating layer is preferably formed using a composition containing a (meth)acrylic resin, such as a monofunctional (meth)acrylic resin, a polyfunctional (meth)acrylic resin, or a (meth)acrylic compound having a dendrimer structure, and more preferably using a composition containing a (meth)acrylic compound having a dendrimer structure. The coating layer can be a cured layer of an ultraviolet-curable resin. Examples of ultraviolet-curable resins include the above-mentioned (meth)acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, epoxy resins, and the like.

[0069] The coating layer may contain additives to improve its strength. The additives are not particularly limited and may include inorganic fine particles, organic fine particles, or mixtures thereof. When the coating layer is present on both sides of the first substrate layer, the composition and thickness of each coating layer may be the same or different.

[0070] The glass plate is preferably made of tempered glass for displays. By using a glass plate, a front panel with excellent mechanical strength and surface hardness can be constructed.

[0071] If the front layer 11 is the third base layer of the protective film, the third base layer may be a resin film. The resin film can be formed, for example, from a thermoplastic resin used to form the protective film as a protective layer, as described later.

[0072] The tensile modulus of the front layer 11 at a temperature of 60°C is preferably 2 GPa or more and 10 GPa or less, more preferably 3 GPa or more and 9 GPa or less, and even more preferably 4 GPa or more and 8 GPa or less, from the viewpoint of flexibility. The above tensile modulus can be measured at a temperature of 60°C using a tensile testing machine (AG-1S, manufactured by Shimadzu Corporation).

[0073] (Polarizing plate) The polarizing plate 30 only needs to include at least a linear polarizing layer. The polarizing plate 30 may be a linear polarizing plate (Figure 1) or a circular polarizing plate (Figure 2). The linear polarizing plate has a protective layer 32 on one or both sides of the linear polarizing layer 31. The protective layer 32 may be provided directly on one or both sides of the linear polarizing layer 31, or it may be provided via a bonding layer (adhesive layer or tack layer). As shown in Figures 1 and 2, it is preferable that the linear polarizing plate has a protective layer 32 on at least the front layer 11 side of the linear polarizing layer 31.

[0074] As shown in Figure 2, the circular polarizer has a linear polarizing layer 31 and a first phase difference layer 33 (phase difference layer) in that order from the front layer 11 side. The circular polarizer may also have a linear polarizer having a protective layer 32 on one or both sides of the linear polarizing layer 31 and a first phase difference layer 33. The first phase difference layer 33 is a λ / 4 phase difference layer, and may be an inverse wavelength dispersive λ / 4 phase difference layer.

[0075] The circular polarizer may have a second phase difference layer 34 in addition to the first phase difference layer 33. The second phase difference layer 34 may be provided between the linear polarizing layer 31 and the first phase difference layer 33, or, as shown in Figure 2, between the first phase difference layer 33 and the back layer 15. The second phase difference layer 34 is preferably a λ / 2 phase difference layer or a positive C layer. The first phase difference layer 33 and the second phase difference layer 34 may be laminated via a bonding layer 38 (adhesive layer or tack layer).

[0076] As shown in Figure 2, if the circular polarizer includes a linear polarizer, the linear polarizer may have a protective layer 32 on one side of the linear polarizer layer 31. In this case, a first phase difference layer 33 or a second phase difference layer 34 may be provided on the side of the linear polarizer layer 31 opposite to the protective layer 32 via a bonding layer (adhesive layer or adhesive layer) 37.

[0077] (Linearly polarized layer) The linearly polarized layer has the property of transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis when unpolarized light is incident on it. The linearly polarized layer may be a polyvinyl alcohol-based resin film (hereinafter sometimes referred to as "PVA-based film") on which iodine is adsorbed and oriented, or it may be a film containing a liquid crystalline linearly polarized layer formed by coating a base film with a composition containing a compound having absorption anisotropy and liquid crystalline properties. The compound having absorption anisotropy and liquid crystalline properties may be a mixture of a dye having absorption anisotropy and a compound having liquid crystalline properties, or it may be a dye having absorption anisotropy and liquid crystalline properties.

[0078] Examples of linearly polarized layers made of PVA-based film include polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and partially saponified ethylene-vinyl acetate copolymer film, which have been subjected to iodine dyeing and stretching treatments. If necessary, the PVA-based film on which iodine has been adsorbed and oriented by the dyeing treatment may be treated with an aqueous boric acid solution, followed by a washing step to wash off the aqueous boric acid solution. Known methods can be used for each step.

[0079] Polyvinyl alcohol-based resins (hereinafter sometimes referred to as "PVA-based resins") can be produced by saponifying polyvinyl acetate-based resins. Polyvinyl acetate-based resins can be polyvinyl acetate, which is a homopolymer of vinyl acetate, or copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having ammonium groups.

[0080] The degree of saponification of PVA resins is typically around 85-100 mol%, preferably 98 mol% or higher. PVA resins may be modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The average degree of polymerization of PVA resins is typically around 1,000-10,000, preferably 1,500-5,000. The degree of saponification and average degree of polymerization of PVA resins can be determined in accordance with JIS K 6726 (1994). If the average degree of polymerization is less than 1,000, it is difficult to obtain desirable polarization performance, and if it exceeds 10,000, film processability may be poor.

[0081] A method for manufacturing a linearly polarized film made of PVA may include the steps of preparing a base film, applying a resin solution such as a PVA resin onto the base film, and drying to remove the solvent to form a resin layer on the base film. A primer layer may be formed in advance on the surface of the base film on which the resin layer is formed. As the base film, a film made of a resin material described later as a thermoplastic resin used to form a protective film as a protective layer can be used. As the material for the primer layer, examples include a resin obtained by crosslinking a hydrophilic resin used in the linearly polarized film.

[0082] Next, the amount of solvent, such as water, in the resin layer is adjusted as needed. Then, the base film and the resin layer are uniaxially stretched, and subsequently, the resin layer is stained with iodine to adsorb and orient the iodine into the resin layer. Next, if necessary, the resin layer with the adsorbed and oriented iodine is treated with an aqueous boric acid solution, and then a washing step is performed to wash off the aqueous boric acid solution. This produces a PVA-based film in which the resin layer with the adsorbed and oriented iodine, i.e., the linearly polarized layer, is formed. Known methods can be used for each step.

[0083] The amount of boric acid in the boric acid-containing aqueous solution used to treat the PVA-based film or resin layer on which iodine is adsorbed and oriented is usually about 2 to 15 parts by mass per 100 parts by mass of water, and preferably 5 to 12 parts by mass. This boric acid-containing aqueous solution preferably contains potassium iodide. The amount of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by mass per 100 parts by mass of water, and preferably 5 to 12 parts by mass. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50°C or higher, preferably 50 to 85°C, and more preferably 60 to 80°C.

[0084] Uniaxial stretching of the PVA film, as well as the base film and resin layer, may be performed before dyeing, during dyeing, or during the boric acid treatment after dyeing, or uniaxial stretching may be performed at each of these multiple stages. The PVA film, as well as the base film and resin layer, may be uniaxially stretched in the MD direction (film transport direction), in which case uniaxial stretching may be performed between rolls with different peripheral speeds, or uniaxial stretching may be performed using a heated roll. The PVA film, as well as the base film and resin layer, may also be uniaxially stretched in the TD direction (direction perpendicular to the film transport direction), in which case the so-called tenter method can be used. Furthermore, the stretching may be dry stretching performed in air, or wet stretching performed while the PVA film or resin layer is swollen with a solvent. In order to exhibit the performance of the linearly polarized layer, the stretching ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. There is no particular upper limit to the stretching ratio, but from the viewpoint of suppressing breakage, etc., 8 times or less is preferred.

[0085] A linearly polarized film layer produced using a manufacturing method that utilizes a base film can be obtained by peeling off the base film after laminating a protective layer. This method allows for further thinning of the linearly polarized film layer.

[0086] The thickness of the linearly polarizing layer, which is a PVA-based film, is preferably 1 μm or more, may be 2 μm or more, may be 5 μm or more, preferably 30 μm or less, more preferably 15 μm or less, may be 10 μm or less, or may be 8 μm or less.

[0087] A film containing a liquid crystalline linear polarizing layer can be a linear polarizing layer obtained by coating a base film with a composition containing a dye having liquid crystalline properties and absorption anisotropy, or a composition containing a dye having absorption anisotropy and a polymerizable liquid crystal. The liquid crystalline linear polarizing layer can be a cured product of a polymerizable liquid crystal compound and may contain an alignment layer. An example of an alignment layer is an alignment layer included in the phase difference layer described later. A film containing a liquid crystalline linear polarizing layer may be a liquid crystalline linear polarizing layer, or it may have a laminated structure of a liquid crystalline linear polarizing layer and a base film. An example of a base film is a film using a resin material described as a thermoplastic resin used to form a protective film as a protective layer, described later. An example of a film containing a liquid crystalline linear polarizing layer is a polarizing layer described in Japanese Patent Application Publication No. 2013-33249, etc.

[0088] The total thickness of the base film and the linearly polarized layer formed as described above is preferably small, but if it is too small, the strength decreases and the processability tends to be poor. Therefore, it is usually 20 μm or less, preferably 5 μm or less, and more preferably 0.5 to 3 μm.

[0089] (protective layer) Examples of protective layers include a protective film formed from a thermoplastic resin that has excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and stretchability; and an overcoat layer formed from a composition that has excellent solvent resistance, transparency, mechanical strength, thermal stability, shielding properties, and isotropy. The protective film is preferably laminated onto the linear polarization layer 31 via a laminating layer, and the overcoat layer is preferably laminated so as to be in direct contact with the linear polarization layer 31.

[0090] Specific examples of thermoplastic resins for forming protective films include cellulose resins such as triacetylcellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resins; polysulfone resins; polycarbonate resins; polyamide resins such as nylon and aromatic polyamides; polyimide resins; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; cyclic polyolefin resins having cyclo and norbornene structures (also called norbornene resins); (meth)acrylic resins; polyarylate resins; polystyrene resins; polyvinyl alcohol resins; and mixtures thereof. The thickness of the protective film is preferably 3 μm or more, more preferably 5 μm or more, and preferably 50 μm or less, and more preferably 30 μm or less.

[0091] The overcoat layer can be formed, for example, by applying a material (composition) for forming the overcoat layer onto the linearly polarized light layer. Examples of materials constituting the overcoat layer include photocurable resins and water-soluble polymers, and (meth)acrylic resins, polyvinyl alcohol resins, polyamide epoxy resins, etc., can be used. The thickness of the overcoat layer can be, for example, 0.1 μm to 10 μm.

[0092] The protective layer may have anti-reflective properties, anti-glare properties, hard coat properties, etc. (Hereinafter, a protective layer having such properties may be referred to as a "functional protective layer"). If the protective layer is not a functional protective layer, a surface functional layer such as an anti-reflective layer, anti-glare layer, or hard coat layer may be provided on one side of the linear polarizing plate. It is preferable that the surface functional layer be provided so as to be in direct contact with the protective layer. It is preferable that the surface functional layer be provided on the side of the protective layer opposite to the linear polarizing layer.

[0093] (1st retardation layer, 2nd retardation layer) The first phase difference layer and the second phase difference layer (hereinafter, both may be collectively referred to as the "phase difference layer") may be a stretched film or may contain a cured layer of polymerizable liquid crystal compound, but a cured layer is preferred.

[0094] When the phase difference layer is a stretched film, conventionally known stretched films can be used, and films in which a phase difference has been imparted by uniaxial or biaxial stretching of a resin film can be used. Examples of resin films that can be used include, but are not limited to, cellulose films such as triacetylcellulose and diacetylcellulose, polyester films such as polyethylene terephthalate, polyethylene isophthalate and polybutylene terephthalate, acrylic resin films such as polymethyl (meth)acrylate and polyethyl (meth)acrylate, polycarbonate films, polyethersulfone films, polysulfone films, polyimide films, polyolefin films, and polynorbornene films.

[0095] When the phase difference layer is a stretched film, the thickness of the phase difference layer is usually 5 μm to 200 μm, preferably 10 μm to 80 μm, and more preferably 40 μm or less.

[0096] If the phase difference layer includes the above-mentioned cured layer, known polymerizable liquid crystal compounds can be used as the polymerizable liquid crystal compound. The polymerizable liquid crystal compound is a compound having at least one polymerizable group and possessing liquid crystalline properties.

[0097] The type of polymerizable liquid crystal compound is not particularly limited, and rod-shaped liquid crystal compounds, disc-shaped liquid crystal compounds, and mixtures thereof can be used. The cured layer formed by polymerizing the polymerizable liquid crystal compound exhibits a phase difference when cured with the polymerizable liquid crystal compound oriented in a suitable direction. When the rod-shaped polymerizable liquid crystal compound is oriented horizontally or vertically with respect to the planar direction of the laminate, the optical axis of the polymerizable liquid crystal compound coincides with the longitudinal axis of the polymerizable liquid crystal compound. When the disc-shaped polymerizable liquid crystal compound is oriented, the optical axis of the polymerizable liquid crystal compound exists in a direction perpendicular to the disc surface of the polymerizable liquid crystal compound. As the rod-shaped polymerizable liquid crystal compound, for example, those described in Japanese Patent Publication No. 11-513019 (Claim 1, etc.) can be suitably used. As disc-shaped polymerizable liquid crystal compounds, those described in Japanese Patent Publication No. 2007-108732 (paragraphs

[0020] to

[0067] , etc.) and Japanese Patent Publication No. 2010-244038 (paragraphs

[0013] to

[0108] , etc.) can be suitably used.

[0098] The polymerizable groups in a polymerizable liquid crystal compound refer to groups that participate in polymerization reactions, and are preferably photopolymerizable groups. Photopolymerizable groups are groups that can participate in polymerization reactions through active radicals or acids generated from photopolymerization initiators. Examples of polymerizable groups include vinyl groups, vinyloxy groups, 1-chlorovinyl groups, isopropenyl groups, 4-vinylphenyl groups, (meth)acryloyloxy groups, oxyranyl groups, oxetanyl groups, styryl groups, and allyl groups. Among these, (meth)acryloyloxy groups, vinyloxy groups, oxyranyl groups, and oxetanyl groups are preferred, with acryloyloxy groups being more preferred. The liquid crystalline properties of a polymerizable liquid crystal compound may be thermotropic or lyotropic, and if thermotropic liquid crystals are classified by their degree of order, they may be nematic or smectic. When two or more polymerizable liquid crystal compounds are used in combination to form a cured layer of the polymerizable liquid crystal compound, it is preferable that at least one of them has two or more polymerizable groups in its molecule.

[0099] If the phase difference layer includes the cured layer, the phase difference layer may also include an orientation layer. The orientation layer has an orientation restricting force that orients the polymerizable liquid crystal compound in a desired direction. The orientation layer may be a vertical orientation layer in which the molecular axis of the polymerizable liquid crystal compound is oriented perpendicular to the planar direction of the laminate, a horizontal orientation layer in which the molecular axis of the polymerizable liquid crystal compound is oriented horizontally to the planar direction of the laminate, or a gradient orientation layer in which the molecular axis of the polymerizable liquid crystal compound is tilted relative to the planar direction of the laminate. If the phase difference layer includes two or more orientation layers, the orientation layers may be the same or different from each other.

[0100] The orientation layer is preferably one that has solvent resistance, meaning it does not dissolve when coated with a liquid crystal layer forming composition containing a polymerizable liquid crystal compound, and has heat resistance to solvent removal and heat treatment for orientation of the polymerizable liquid crystal compound. Examples of orientation layers include an orientation polymer layer formed from an orientation polymer, a photo-orientation polymer layer formed from a photo-orientation polymer, and a groove orientation layer having an uneven pattern or multiple grooves on its surface.

[0101] The above-mentioned cured layer can be formed by applying a composition for forming a phase difference layer, which contains a polymerizable liquid crystal compound, a solvent, and various additives as needed, onto an orientation layer to form a coating film, and then solidifying (curing) this coating film. Alternatively, the above composition may be applied onto a substrate film to form a coating film, and the cured layer may be formed by stretching this coating film together with the substrate film. In addition to the polymerizable liquid crystal compound and solvent described above, the above composition may also contain polymerization initiators, reactive additives, leveling agents, polymerization inhibitors, etc. Known polymerizable liquid crystal compounds, solvents, polymerization initiators, reactive additives, leveling agents, polymerization inhibitors, etc., can be used as appropriate.

[0102] As the base film, a film made of a resin material can be used. For example, a film made of a resin material described as a thermoplastic resin used to form the protective film as the protective layer described above can be used. The thickness of the base film is not particularly limited, but generally it is preferably 1 to 300 μm or less, more preferably 20 to 200 μm, and even more preferably 30 to 120 μm, from the viewpoint of strength and workability such as handling. The base film may be incorporated into the laminate together with the cured product layer of the polymerizable liquid crystal compound, or the base film may be peeled off and only the cured product layer of the polymerizable liquid crystal compound, or the cured product layer and the orientation layer may be incorporated into the laminate.

[0103] (back layer) The back layer may be a separator, or it may be a back panel, which is a component located on the side of the display device opposite to the viewing side. The back panel may be, for example, a touch sensor panel, a display element, or a combination thereof.

[0104] The thickness of the back layer may be, for example, 5 μm or more, 10 μm or more, 30 μm or more, 50 μm or more, or 2000 μm or less, 1000 μm or less, or 500 μm or less.

[0105] When the back layer is a separator, the separator is provided so as to be removable from the second adhesive layer and covers and protects the surface of the second adhesive layer. The separator comprises a second base material layer and a release treatment layer. The second base material layer may be a resin film. The resin film can be formed, for example, from a thermoplastic resin used to form the protective film as described above. The release treatment layer may be any known release treatment layer, for example, a layer formed by coating the base material layer with a release agent such as a fluorine compound or a silicone compound.

[0106] A touch sensor panel can detect the position where a user touches it with their finger or other object. The touch sensor panel included in the back layer can be, for example, a resistive touch sensor, a capacitive touch sensor, an optical touch sensor, an ultrasonic touch sensor, an electromagnetic induction touch sensor, or a surface acoustic wave touch sensor.

[0107] When the back layer includes a display element, the display element is not particularly limited, but is preferably an organic EL display element. The organic EL display element may have, for example, an emissive layer and electrodes.

[0108] The tensile modulus of the back layer at a temperature of 60°C is preferably 2 GPa or more and 10 GPa or less, more preferably 3 GPa or more and 9 GPa or less, and even more preferably 4 GPa or more and 8 GPa or less, from the viewpoint of flexibility. The above tensile modulus can be measured at a temperature of 60°C using a tensile testing machine (AG-1S, manufactured by Shimadzu Corporation).

[0109] (Bonding layer) The bonding layer is an adhesive layer or a bonding agent layer. If the bonding layer is an adhesive layer, it is an adhesive layer formed using an adhesive. The adhesive exhibits adhesion by being attached to the substrate itself, and is a so-called pressure-sensitive adhesive. The adhesive may be the adhesive composition described above, or any known adhesive with excellent optical transparency can be used. Known adhesives include, for example, adhesives containing base polymers such as acrylic polymers, urethane polymers, silicone polymers, and polyvinyl ethers. The adhesive may also be an active energy ray curing adhesive or a thermosetting adhesive. Among these, an adhesive with an acrylic resin as the base polymer, which has excellent transparency, adhesive strength, re-peelability (reworkability), weather resistance, heat resistance, etc., is preferred. The adhesive layer is preferably composed of an adhesive containing (meth)acrylic resin, a crosslinking agent, and a silane coupling agent, and may contain other components.

[0110] The thickness of the adhesive layer is not particularly limited, but is preferably 5 μm or more, may be 10 μm or more, may be 15 μm or more, may be 20 μm or more, may be 25 μm or more, and is usually 300 μm or less, may be 250 μm or less, may be 100 μm or less, or may be 50 μm or less.

[0111] Examples of water-based adhesives include adhesives in which polyvinyl alcohol resin is dissolved or dispersed in water. There are no particular limitations on the drying method when using water-based adhesives, but methods such as using a hot air dryer or an infrared dryer can be employed.

[0112] Examples of active energy ray curing adhesives include solvent-free active energy ray curing adhesives containing curable compounds that harden upon irradiation with active energy rays such as ultraviolet light, visible light, electron beams, and X-rays. By using a solvent-free active energy ray curing adhesive, the adhesion between layers can be improved.

[0113] As an active energy ray curable adhesive, it is preferable to include either a cationic curable compound, a radical curable compound, or both, as these exhibit good adhesion. The active energy ray curable adhesive may further contain a cationic polymerization initiator, such as a photocationic polymerization initiator, or a radical polymerization initiator for initiating the curing reaction of the above-mentioned curable compound.

[0114] When the bonding layer is an adhesive layer, its thickness is preferably 0.1 μm or more, may be 0.5 μm or more, and preferably 10 μm or less, and may be 5 μm or less.

[0115] (display device) The display device includes laminates 1 and 2. Preferably, the display device is a flexible display that can be bent so that the front layer 11 faces inward. Flexibility means that the laminates 1 and 2 can be bent without generating air bubbles or adhesive leakage, even after fewer than 100,000 bending cycles in the high-temperature flexibility test described later.

[0116] The laminates 1 and 2 included in the display device preferably have a front layer 11 which is a front panel, and a back layer 15 which preferably includes at least one of a touch sensor panel and a display element. The display device is not particularly limited, but it is preferably an organic EL display device.

[0117] The display device may be a mobile device such as a smartphone or tablet, or it may be a television, digital photo frame, electronic signboard, measuring instrument or gauge, office equipment, medical equipment, computer equipment, etc. [Examples]

[0118] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0119] [Measurement of thickness] The thickness was measured using a contact-type film thickness measuring device (Nikon Corporation's "ZC-101").

[0120] [Measurement of linear shrinkage rate (D1 or D2) of the reference adhesive layer after UV irradiation] (Preparation of standard adhesive sheet) A standard adhesive sheet having a layer structure of separator A / standard adhesive layer / separator B was obtained using the same procedure as for preparing the adhesive sheet described later, except that the adhesive composition described later was used and the thickness of the standard adhesive layer was set to 0.6 mm. An integrated light intensity of 100 J / cm² was applied to this standard adhesive sheet. 2 , illuminance is 100mW / cm 2 Ultraviolet (UV) irradiation was performed to meet the (UVV standard).

[0121] A standard adhesive sheet, after UV irradiation, was cut to a width of 20 mm x length of 20 mm. The standard adhesive layer obtained by peeling off the separator was bonded to a plate of a viscoelasticity measuring device (MCR-301, Anton Paar Co., Ltd.), and the thickness T0 [μm] of the standard adhesive layer was confirmed immediately after applying a load of 1 N and a strain of 350%. Subsequently, the thickness T0 of the standard adhesive layer was determined after maintaining the above load and strain conditions for 10 hours. 10 The [μm] was confirmed. The obtained thicknesses T0 and T 10 The linear contraction rate (D1 or D2) was determined using the following formula. Linear contraction rate (D1 or D2) [%] = {1 - (T 10 / T0)} × 100

[0122] [Measurement of gel fraction of the standard adhesive layer after UV irradiation] The standard adhesive sheet containing the standard adhesive layer described above is subjected to an integrated light intensity of 100 J / cm². 2 , illuminance is 100mW / cm 2 Ultraviolet (UV) irradiation was performed to meet the (UVV standard). After UV irradiation, the standard adhesive sheet was cut to a size of 80 mm wide x 80 mm long, and the standard adhesive layer contained in the cut standard adhesive sheet was used as the sample. The sample was wrapped in a polyester mesh (mesh size 200), and its mass was weighed using a precision balance. The mass M1 of the sample alone was calculated by subtracting the mass of the mesh alone from the weighed mass.

[0123] Next, the standard adhesive layer wrapped in the polyester mesh described above was immersed in ethyl acetate at room temperature (23°C) for 72 hours, and the sample was removed (hereinafter, the removed sample will be referred to as the "immersion sample"). The immersion sample was air-dried for 24 hours in an environment of 23°C and 50% relative humidity, and then dried in an oven at 120°C for 4 hours, after which its mass was weighed using a precision balance. The mass M2 of the immersion sample alone was calculated by subtracting the mass of the mesh alone from the weighed mass. The gel fraction was determined from masses M1 and M2 according to the following formula. Gel fraction [%] = (M2 / M1) × 100

[0124] [Measurement of glass transition temperature] The separator was peeled off from the adhesive sheet described later to obtain an adhesive layer. The glass transition temperature of the obtained adhesive layer was measured using a differential scanning calorimeter (DSC) "EXSTAR DSC6000" manufactured by SII Nanotechnology Co., Ltd., under nitrogen atmosphere conditions, with a measurement temperature range of -80 to 50°C and a heating rate of 10°C / min.

[0125] [Measurement of maximum absorption wavelength] The maximum absorption wavelength of the polymerization initiator was determined by placing a solution of the polymerization initiator dissolved in methyl ethyl ketone into a quartz cell and measuring the visible ultraviolet spectrum from wavelengths of 200 nm to 600 nm using a Shimadzu UV-2450 ultraviolet-visible spectrophotometer.

[0126] [Lightfastness and Flexibility Test] The laminates obtained in the examples and comparative examples were cut out using a super cutter to create test specimens measuring 10 mm in width and 100 mm in length. Using a flexural resistance tester (cylindrical mandrel method) manufactured by TP Giken Co., Ltd., the test specimens were wrapped around a cylindrical core (mandrel) with the front layer side of the specimen facing inward. In this state, an ultraviolet tester (Sanko Denki Co., Ltd. "CT UVT-15W UV B lamp") was used to measure the cumulative light intensity at 100 J / cm². 2 After irradiating the specimen with ultraviolet light, the presence or absence of bubbles in the first or second adhesive layer of the test piece, and the presence or absence of delamination between the first adhesive layer and the front layer were checked.

[0127] The above procedure was performed by changing the diameter of the core, and the minimum diameter of the core was determined when no air bubbles were generated in the first or second adhesive layer, and no delamination occurred between the first adhesive layer and the front layer. This was then evaluated according to the following criteria. A smaller minimum diameter of the core indicates a laminate with superior light resistance and flexibility. A: The minimum diameter of the determined spindle was 10 mm or less. B: The minimum diameter of the chosen spindle was over 10 mm.

[0128] [Lightfastness test] The test specimens were prepared and irradiated with ultraviolet light according to the procedure described in the weather resistance and flexibility test above. The transmitted b of the test specimens before and after ultraviolet light irradiation was measured using a colorimeter "V7100" manufactured by JASCO Corporation. * Measure and transmit b * The absolute value of the change was calculated and evaluated according to the following criteria. a: Transparent b * The absolute value of the change was 0.9 or less. b: Transparent b * The absolute value of the change was greater than 0.9.

[0129] [Preparation of (meth)acrylic polymers A1-A6] A 1 L reactor equipped with a cooling device to facilitate temperature control by refluxing nitrogen gas was filled with a mixture of monomer components shown in Table 1 in the proportions shown in Table 1. To remove oxygen, nitrogen gas was refluxed into the reactor for 1 hour, and the mixture was maintained at a temperature of 60°C. After homogenizing the mixture, polymerization initiators shown in Table 1 were added in the proportions shown in Table 1, and the mixture was irradiated with a UV lamp (10 mW) while stirring to obtain (meth)acrylic polymers A1 to A6. The proportions shown in Table 1 represent the mass ratio to the total mass of monomer components and photopolymerization initiators. The results are shown in Table 1.

[0130] [Table 1]

[0131] The abbreviations in Table 1 are as follows: HA: Hexyl acrylate (glass transition temperature: -57℃) IDA: Isodecyl acrylate (glass transition temperature: -60°C) EOEOEA: Ethoxyethoxyethyl acrylate (glass transition temperature: -56℃) EA: Ethyl acrylate (glass transition temperature: -24℃) 2-EHA: 2-ethylhexyl acrylate (glass transition temperature: -70°C) BA: Butyl acrylate (glass transition temperature: -55℃) 2-HEA: 2-hydroxyethyl acrylate (glass transition temperature: -15℃) LA: Lauryl acrylate (glass transition temperature: 15°C) DCA: Docosyl Acrylate I-184: 1-Hydroxycyclohexylphenyl ketone (Maximum absorption wavelength: 246 nm) D-1173 (Darocure1173): 2-Hydroxy-2-methylpropiophenone (Maximum absorption wavelength: 245nm) I-754: A mixture of 2-[2-oxo-2-phenylacetoxyethoxy]-ethyl oxyphenyl acetate and 2-[2-hydroxyethoxy]-ethyl oxyphenyl acetate (maximum absorption wavelength: 255 nm) I-2959: 2-Hydroxy-4'-(2-Hydroxyethoxy)-2-Methylpropiophenone (Maximum absorption wavelength: 276 nm)

[0132] [Preparation of adhesive compositions B1 to B7] The acrylic polymers, compounds, and polymerization initiators shown in Table 2 were mixed in the amounts shown in Table 2 to obtain adhesive compositions B1 to B7. The amounts shown in Table 2 represent the mass ratio to the total mass of the polymer, compound, and polymerization initiator.

[0133] [Table 2]

[0134] The abbreviations in Table 2 are as explained in Table 1.

[0135] [Preparation of adhesive sheets (1) to (7)] The adhesive composition shown in Table 3 was applied to the release-treated surface of separator A (a polyethylene terephthalate film coated with a release agent containing a silicone compound) so that the thickness of the adhesive layer was as shown in Table 3. Separator B (a polyethylene terephthalate film coated with a release agent containing a silicone compound) was then laminated onto the coated layer so that the release-treated side faced the coated layer side. UV irradiation was then performed to obtain adhesive sheets (1) to (7) having a layer structure of separator A / adhesive layer / separator B. The UV irradiation was performed with an integrated light intensity of 400 mJ / cm². 2 The illuminance is 1.8 mW / cm². 2 The procedure was carried out to conform to the UVV standard. The glass transition temperature Tg was measured for the adhesive layer of the obtained adhesive sheets (1) to (7). In addition, a reference adhesive sheet was prepared using the adhesive composition used to prepare adhesive sheets (1) to (7) in the procedure described above, and the linear shrinkage rate and gel fraction were measured using this sheet in the procedure described above. The results are shown in Table 3.

[0136] [Table 3]

[0137] [Examples 1 and 4, Comparative Examples 1, 4 and 5] (Preparing the front panel) As the front layer, a front plate was prepared in which a hard coat layer (10 μm thick) was formed on one side of a resin film (polyimide resin film, 40 μm thick) as the first base layer. The hard coat layer was a layer formed from a composition containing a (meth)acrylic compound having a dendrimer structure with polyfunctional acrylic groups at its ends.

[0138] (Preparation of circular polarizer (1)) A protective film (cycloolefin resin film, 18 μm thick) as a protective layer and a polyvinyl alcohol film linear polarizing layer (8 μm thick) on which iodine is adsorbed and oriented were bonded together using a water-based adhesive to obtain a linear polarizing plate (1) having a layer structure of protective layer / adhesive layer / linear polarizing layer.

[0139] A phase difference laminate (1) was obtained in which a first phase difference layer (thickness 3 μm), an adhesive layer (thickness 1 μm), and a second phase difference layer (thickness 2 μm) were laminated in this order. The first phase difference layer was a λ / 4 phase difference layer and was a cured product layer of a polymerizable liquid crystal compound. The adhesive layer was a cured product layer of an epoxy adhesive, which is a photocurable adhesive composition. The second phase difference layer was a positive C layer and was a cured product layer of a polymerizable liquid crystal compound.

[0140] The linear polarizing layer side of the linear polarizing plate (1) obtained above and the first phase difference layer side of the phase difference laminate (1) were bonded together using a bonding layer (an adhesive layer using an acrylic adhesive, with a thickness of 5 μm) to obtain a circular polarizing plate (1) as a polarizing plate. The layer structure of the circular polarizing plate (1) was linear polarizing plate (1) (protective layer / adhesive layer / linear polarizing layer) / bonding layer / phase difference laminate (1) (first phase difference layer / adhesive layer / second phase difference layer).

[0141] (Fabrication of laminates) The first base material layer (resin film) side of the front panel obtained above and the linear polarizing plate (1) side of the circular polarizing plate (1) were bonded together using the first adhesive layer shown in Tables 4 and 5. The second adhesive layer shown in Tables 4 and 5 and a separator (polyimide resin film, 50 μm thick) as a back layer were laminated to the phase difference laminate (1) side of the circular polarizing plate to produce laminates (1), (4), (7), (10), and (11). The layer structure of these laminates was front layer (hard coat layer / first base material layer) / first adhesive layer / linear polarizing plate (1) (protective layer / adhesive layer / linear polarizing layer) / bonding layer / phase difference laminate (1) (first phase difference layer / adhesive layer / second phase difference layer) / second adhesive layer / back layer. Lightfastness and light resistance tests were performed on the obtained laminates. The results are shown in Tables 4 and 5.

[0142] [Examples 2 and 5, Comparative Example 2] (Preparation of circular polarizer (2)) A phase difference laminate (2) was obtained in which a second phase difference layer (thickness 2 μm), an adhesive layer (thickness 2 μm), and a first phase difference layer (thickness 1 μm) were laminated in this order. The second phase difference layer was a λ / 2 phase difference layer and was a cured product layer of a polymerizable liquid crystal compound. The adhesive layer was a cured product layer of an epoxy adhesive, which is a photocurable adhesive composition. The first phase difference layer was a λ / 4 phase difference layer and was a cured product layer of a polymerizable liquid crystal compound.

[0143] The linear polarizing layer side of the linear polarizing plate (1) obtained by the procedure described in Example 1 and the second phase difference layer side of the phase difference laminate (2) obtained above were bonded together using a bonding layer (an adhesive layer using an acrylic adhesive, with a thickness of 5 μm) to obtain a circular polarizing plate (2) as a polarizing plate. The layer structure of the circular polarizing plate (2) was linear polarizing plate (1) (protective layer / adhesive layer / linear polarizing layer) / bonding layer / phase difference laminate (2) (second phase difference layer / adhesive layer / first phase difference layer).

[0144] (Fabrication of laminates) The first base material layer (resin film) side of the front layer obtained by the procedure described in Example 1 and the linear polarizing plate (1) side of the circular polarizing plate (2) were bonded using the first adhesive layer shown in Tables 4 and 5. The second adhesive layer shown in Tables 4 and 5 and a separator (polyimide resin film, 50 μm thick) as a back layer were laminated to the phase difference laminate (2) side of the circular polarizing plate to produce laminates (2), (5), and (8). The layer structure of these laminates was front layer (hard coat layer / first base material layer) / first adhesive layer / linear polarizing plate (1) (protective layer / adhesive layer / linear polarizing layer) / bonding layer / phase difference laminate (2) (second phase difference layer / adhesive layer / first phase difference layer) / second adhesive layer / back layer. Lightfastness bending tests and lightfastness tests were performed on the obtained laminates. The results are shown in Tables 4 and 5.

[0145] [Examples 3 and 6, Comparative Example 3] (Preparation of circular polarizer (3)) A linear polarizing plate (2) was fabricated according to the procedure for the [polarizer layer] in the example of Japanese Patent Publication No. 2020-138376, having an overcoat layer as a protective layer and a linear polarizing layer which is a cured polymerizable liquid crystal compound layer. The layer structure of the linear polarizing plate (2) was protective layer / linear polarizing layer / orientation layer / TAC film.

[0146] The protective layer side of the linear polarizing plate (2) obtained above and the first phase difference layer side of the phase difference laminate (1) obtained by the procedure described in Example 1 were bonded together using a bonding layer (an adhesive layer using an acrylic adhesive, with a thickness of 5 μm) to obtain a circular polarizing plate (3) as a polarizing plate. The layer structure of the circular polarizing plate (3) was linear polarizing plate (2) (TAC film / orientation layer / linear polarizing layer / protective layer) / bonding layer / phase difference laminate (1) (first phase difference layer / adhesive layer / second phase difference layer).

[0147] (Fabrication of laminates) Corona treatment (output 0.3kW, speed 3m / min) was applied to the surface of the TAC film on the linear polarizing plate (2) side of the circular polarizing plate (3). This corona-treated surface and the first base material layer (resin film) side of the front layer obtained by the procedure described in Example 1 were bonded using the first adhesive layer shown in Tables 4 and 5. The second adhesive layer shown in Tables 4 and 5 and a separator (polyimide resin film, thickness 50μm) as a back layer were laminated to the phase difference laminate (1) side of the circular polarizing plate to produce laminates (3), (6), and (9). The layer structure of these laminates was front layer (hard coat layer / first base material layer) / first adhesive layer / linear polarizing plate (2) (TAC film / orientation layer / linear polarizing layer / protective layer) / bonding layer / phase difference laminate (1) (first phase difference layer / adhesive layer / second phase difference layer) / second adhesive layer / back layer. The resulting laminates were subjected to lightfastness and light resistance tests. The results are shown in Tables 4 and 5.

[0148] [Table 4]

[0149] [Table 5] [Explanation of symbols]

[0150] 1,2 Laminate, 11 Front layer, 15 Back layer, 21 First adhesive layer, 22 Second adhesive layer, 30 Polarizing plate, 31 Linear polarizing layer, 32 Protective layer, 33 First phase difference layer (phase difference layer), 34 Second phase difference layer, 37,38 Laminating layers.

Claims

1. A laminate having, in this order, a front layer, a first adhesive layer formed using a first adhesive composition, a polarizing plate including at least a linearly polarizing layer, a second adhesive layer formed using a second adhesive composition, and a back layer, The laminate is bendable such that the front layer side faces inward. The first adhesive composition and the second adhesive composition each contain a (meth)acrylic polymer, The (meth)acrylic polymer contained in the first adhesive composition and the second adhesive composition each independently comprises a constituent unit (i) derived from an alkyl (meth)acrylate ester having an alkyl group with 1 to 24 carbon atoms, and a constituent unit derived from a monofunctional (meth)acrylic monomer having an alkoxy group. A cumulative amount of 100 J / cm² is applied to a first reference adhesive layer formed to a thickness of 0.6 mm using the first adhesive composition. ２ The linear shrinkage rate of the first reference adhesive layer after irradiation with ultraviolet light, under conditions of a temperature of 25°C, a load of 1N, and a strain of 350%, is defined as D1 [%]. A cumulative amount of 100 J / cm² is applied to a second reference adhesive layer formed to a thickness of 0.6 mm using the second adhesive composition. ２ When the linear shrinkage rate of the second reference adhesive layer after irradiation with ultraviolet light is D2 [%] under conditions of a temperature of 25°C, a load of 1N, and a strain of 350%, The following equations (1) and (2) are satisfied, A laminate in which the gel fraction of the first reference adhesive layer after irradiation with ultraviolet light is 50% or more and 90% or less. D1 ≥ D2 (1) 2.5 ≤ D1 ≤ 6.5 (2)

2. The laminate according to claim 1, wherein the thickness of the first adhesive layer is 15 μm or more and 100 μm or less.

3. The laminate according to claim 1 or 2, wherein the glass transition temperature of the first adhesive layer is -55°C or lower.

4. The laminate according to any one of claims 1 to 3, wherein the (meth)acrylic polymer contained in the first adhesive composition and the second adhesive composition is such that the content of the constituent unit (i) relative to all constituent units of the (meth)acrylic polymer is independently 90% by mass or less.

5. The laminate according to any one of claims 1 to 4, wherein the (meth)acrylic polymer contained in the first adhesive composition includes a structural unit derived from an alkyl (meth)acrylate having an alkyl group having 20 or more carbon atoms and 24 carbon atoms.

6. The laminate according to any one of claims 1 to 5, wherein the content of constituent units derived from monomers having reactive functional groups for all constituent units of the (meth)acrylic polymer contained in the first adhesive composition is 2% by mass or less.

7. The front layer comprises a first substrate layer and a coating layer formed on at least one side of the first substrate layer. The laminate according to any one of claims 1 to 6, wherein the coating layer is formed using a composition containing a (meth)acrylic compound having a dendrimer structure.

8. The laminate according to any one of claims 1 to 6, wherein the polarizing plate is a circular polarizing plate having, in order from the front layer side, the linear polarizing layer and the phase difference layer.

9. The laminate according to any one of claims 1 to 8, wherein the back layer is a separator having, in order from the second adhesive layer side, a release treatment layer and a second substrate layer.

10. A display device comprising a laminate according to any one of claims 1 to 9.

11. The display device according to claim 10, wherein the front layer is flexible so that it faces inward.

Images