CN113490869B

CN113490869B - Laminate body

Info

Publication number: CN113490869B
Application number: CN202080015815.0A
Authority: CN
Inventors: 李昇祐; 金正熙
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2019-02-27
Filing date: 2020-02-07
Publication date: 2023-11-07
Anticipated expiration: 2040-02-07
Also published as: JP2020138543A; CN113490869A; WO2020175092A1; TW202032179A; KR20210132074A

Abstract

The purpose of the present invention is to provide a laminate which can suppress the generation of bubbles even when the front panel side is bent inward, and which has excellent adhesion in a high-temperature environment. The present invention provides a laminate comprising, in order, a front panel, a 1 st adhesive layer formed using a 1 st adhesive composition, a polarizer layer, a 2 nd adhesive layer formed using a 2 nd adhesive composition, and a back panel, wherein the following relational expression (1) is satisfied if the reduction rate of the thermal decomposition mass of the 1 st adhesive layer is R1[% ], and the reduction rate of the thermal decomposition mass of the 2 nd adhesive layer is R2[% ]: r1 > R2 (1), and the reduction rate of the thermal decomposition mass of the 1 st adhesive layer and the 2 nd adhesive layer is 10 to 20 mass%.

Description

Laminate body

Technical Field

The present invention relates to a laminate.

Background

Japanese patent application laid-open No. 2018-28573 (patent document 1) discloses a laminate for a flexible image display device having a plurality of adhesive layers.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2018-28573

Disclosure of Invention

In a display device including a laminate having a front panel and a plurality of adhesive layers, when the front panel side is bent inward, air bubbles may be generated in the adhesive layers in the laminate. In addition, the adhesive force of the adhesive layer is weak under a high-temperature environment, and floating or peeling may occur between the adhesive layer and the adherend.

The purpose of the present invention is to provide a laminate which can suppress the generation of bubbles even when the front panel side is bent inward, and which has excellent adhesion in a high-temperature environment.

The present invention provides the following laminate.

A laminate comprising, in order, a front panel, a 1 st adhesive layer formed using a 1 st adhesive composition, a polarizer layer, a 2 nd adhesive layer formed using a 2 nd adhesive composition, and a back panel,

the following relational expression (1) is satisfied if the thermal decomposition mass reduction rate of the 1 st adhesive layer is set to R1[% ], and the thermal decomposition mass reduction rate of the 2 nd adhesive layer is set to R2[% ]:

R1＞R2 (1)，

the reduction rate of the thermal decomposition mass of the 1 st adhesive layer and the 2 nd adhesive layer is 10 to 20 mass%.

[ 2 ] the laminate according to [ 1 ], wherein the 1 st adhesive composition and the 2 nd adhesive composition each contain a (meth) acrylic polymer,

in the (meth) acrylic polymer, the constituent unit derived from the monomer having a reactive functional group is less than 5 mass% based on the total mass.

The laminate according to [ 1 ] or [ 2 ], wherein the 1 st adhesive layer and the 2 nd adhesive layer each contain a (meth) acrylic polymer,

The weight average molecular weight (Mw) of the (meth) acrylic polymer is 20 to 150 ten thousand.

The laminate according to any one of [ 1 ] to [ 3 ], wherein the back plate is a touch sensor panel.

A display device comprising the laminate of any one of [ 1 ] to [ 4 ].

The display device according to [ 6 ], wherein the front panel side can be curved inward.

According to the present invention, it is possible to provide a laminate which can suppress the generation of bubbles even when the front panel side is bent inward and which has excellent adhesion under a high-temperature environment.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a laminate of the present invention.

Fig. 2 is a schematic cross-sectional view showing an example of the laminate of the present invention.

Fig. 3 is a schematic diagram illustrating a method of the bending test.

Fig. 4 is a cross-sectional view schematically showing a method for producing a laminate of the present invention.

Detailed Description

Hereinafter, a laminate according to an embodiment of the present invention (hereinafter, also simply referred to as "laminate") will be described with reference to the drawings.

< laminate >

Fig. 1 is a schematic cross-sectional view of a laminate according to an embodiment of the present invention. The laminate 100 includes, in order, a front panel 101, a 1 st adhesive layer 102 formed of a 1 st adhesive composition, a polarizer layer 103, a 2 nd adhesive layer 104 formed of a 2 nd adhesive composition, and a back panel 105. Hereinafter, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 may be collectively referred to as an adhesive layer.

The thickness of the laminate 100 is not particularly limited, and is, for example, 50 μm to 4000 μm, preferably 100 μm to 2000 μm, and more preferably 150 μm to 1000 μm, because it varies depending on the function required for the laminate, the use of the laminate, and the like.

The planar shape of the laminate 100 may be, for example, a square shape, preferably a square shape having long sides and short sides, and more preferably a rectangle. When the laminate 100 has a rectangular shape in the plane direction, the length of the long side may be, for example, 10mm to 1400mm, and preferably 50mm to 600mm. The length of the short side is, for example, 5mm to 800mm, preferably 30mm to 500mm, more preferably 50mm to 300mm. Each layer constituting the laminate may be formed by rounding a corner (R-angle), cutting an end, or punching.

The laminate 100 can be used in, for example, a display device. The display device is not particularly limited, and examples thereof include an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, an electroluminescence display device, and the like. The display device may have a touch panel function.

[ physical Properties of adhesive layer ]

In the laminate 100, if the thermal decomposition mass reduction rate of the 1 st adhesive layer 102 is R1[% ], and the thermal decomposition mass reduction rate of the 2 nd adhesive layer 104 is R2[% ], the following relational expression (1) is satisfied:

R1＞R2 (1)。

The thermal decomposition mass reduction rate [% ] of the adhesive layer differs depending on the composition of the adhesive composition forming the adhesive layer, and if the composition of the adhesive composition is the same, it can be regarded that the thermal decomposition mass reduction rate is the same. Therefore, the reduction rate of thermal decomposition mass R1[% ] of the 1 st adhesive layer 102 and the reduction rate of thermal decomposition mass R2[% ] of the 2 nd adhesive layer 104 can be obtained by measuring the adhesive layers formed using the same adhesive composition without directly measuring the 1 st adhesive layer 102 and the 2 nd adhesive layer 104. The reduction rate of thermal decomposition mass R1[% ] of the 1 st adhesive layer 102 and the reduction rate of thermal decomposition mass R2[% ] of the 2 nd adhesive layer 104 are measured according to the measurement method described in the column of examples described later.

If the thermal decomposition mass reduction rate of the 1 st adhesive layer 102 is set to R1[% ] and the thermal decomposition mass reduction rate of the 2 nd adhesive layer 104 is set to R2[% ], the following relational expression (2) and relational expression (3) are satisfied:

10≤R1≤20 (2)

10≤R2≤20 (3)，

preferably, the following relational expression (2 a) and relational expression (3 a) are satisfied:

11≤R1≤19 (2a)

11≤R2≤19 (3a)，

more preferably, the following relational expression (2 b) and relational expression (3 b) are satisfied:

13≤R1≤19 (2b)

11≤R2≤14 (3b)。

the laminate 100 can be bent with the front panel 101 side inward. In a display device including a laminate, if the front panel side is bent inward, air bubbles may be generated in the adhesive layer. This generation of bubbles is particularly remarkable in the adhesive layer on the side close to the front panel, that is, the 1 st adhesive layer 102 in the laminate 100. As a result of the study, the inventors of the present invention found that, when the reduction ratios of the thermal decomposition masses of the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 satisfy the relational expressions (1), (2), and (3), even if the front panel 101 side is made to be inside and bent in a normal temperature environment, bubbles generated in the adhesive layer in the laminate 100 can be suppressed, and the performance of the adhesive layer can be maintained even in a high temperature environment. More specifically, even if the laminate 100 is repeatedly bent 10 ten thousand times so that the bending radius of the inner surface of the laminate 100 is 3mm, air bubbles generated in the adhesive layer in the laminate 100 (hereinafter also referred to as having excellent "normal temperature bendability") can be suppressed. The room temperature bendability can be evaluated according to the evaluation method described in the column of examples described below. The laminate 100 may be bent with the front panel side being the outer side. The display device to which the laminate 100 is applied can be used as a flexible display capable of bending, winding, or the like. In the present specification, the bending includes a bending form in which a curved surface is formed in a bending portion, and a bending radius of an inner surface of the bending is not particularly limited. In addition, the bending also includes bending in which the bending angle of the inner surface is greater than 0 degrees and less than 180 degrees and folding in which the bending radius of the inner surface is approximately zero or the bending angle of the inner surface is 0 degrees.

As a method for preparing the 1 st adhesive composition and the 2 nd adhesive composition so that the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 satisfy the relation (2) and the relation (3), for example, a method in which an adhesive layer is constituted of an adhesive composition a described later, the kind of a monomer constituting a (meth) acrylic polymer a described later is changed, the molecular weight of the (meth) acrylic polymer a is adjusted, or a compound having a nitrogen atom and a (meth) acryloyl group is contained, and the like are exemplified.

[ adhesive composition ]

In one embodiment, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 are formed of an adhesive composition (hereinafter, also referred to as an adhesive composition a) containing a (meth) acrylic polymer. The adhesive composition a may be an active energy ray-curable type or a thermosetting type. In the present specification, "(meth) acrylic polymer" means at least one selected from the group consisting of acrylic polymers and methacrylic polymers. The same applies to other expressions with "(methyl)". In the case where the 1 st adhesive composition and the 2 nd adhesive composition each contain a (meth) acrylic polymer, the (meth) acrylic polymers may be the same or different. Hereinafter, the (meth) acrylic polymer contained in the adhesive composition a is also referred to as a (meth) acrylic polymer a.

The weight average molecular weight (Mw) of the (meth) acrylic polymer a is preferably 20 to 150 tens of thousands, more preferably 30 to 120 tens of thousands, from the viewpoint of easily satisfying the relation (2) or the relation (3) in the obtained adhesive layer.

In the (meth) acrylic polymer a contained in the adhesive composition a, the constituent unit derived from the monomer having a reactive functional group is preferably less than 5 mass% based on the total mass of the polymer. Examples of the reactive functional group include a hydroxyl group, a carboxyl group, an amino group, an amide group, and an epoxy group. This increases the flexibility of the adhesive layer, and tends to easily suppress the generation of bubbles in the adhesive layer at high temperatures. In the (meth) acrylic polymer a, from the viewpoint of suppressing bubbles during bending, the constituent unit derived from the monomer having a reactive functional group is more preferably 0.01 mass% or less based on the total mass of the polymer, still more preferably no constituent unit derived from the monomer having a reactive functional group, still more preferably no hydroxyl group, carboxyl group, amino group, amide group and epoxy group.

(1) Active energy ray-curable adhesive composition

When the adhesive composition a is an active energy ray-curable adhesive composition, the (meth) acrylic polymer a contained in the adhesive composition a may contain a constituent unit derived from a (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms. Examples of the (meth) acrylic monomer having a linear or branched alkyl group having 1 to 24 carbon atoms include alkyl (meth) acrylate, and examples thereof include butyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, isooctyl (meth) acrylate, isodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isobornyl (meth) acrylate. The (meth) acrylic polymer a may be a polymer or copolymer containing 1 or 2 or more of the above alkyl (meth) acrylates as monomers. The content of the (meth) acrylic polymer a in the adhesive composition a may be, for example, 50 to 100% by mass, preferably 80 to 99.5% by mass, and more preferably 90 to 99% by mass, relative to 100 parts by mass of the solid content of the adhesive composition a.

The weight average molecular weight (Mw) of the (meth) acrylic polymer a may be, for example, 20 to 80 tens of thousands, and is preferably 30 to 70 tens of thousands from the viewpoint of suppressing bubbles at the time of bending. The weight average molecular weight (Mw) can be measured according to the measurement method described in the column of examples described later.

The adhesive composition a may contain 1 or 2 or more (meth) acrylic polymers a. The adhesive composition a may contain only the (meth) acrylic polymer a as a constituent component thereof, or may further contain a crosslinking agent. Examples of the crosslinking agent include: a metal ion having a valence of 2 or more and forming a metal carboxylate with the carboxyl group; a polyamine compound and a substance forming an amide bond with a carboxyl group; a substance which is a polyepoxide or a polyhydric alcohol and forms an ester bond with a carboxyl group; and substances which form an amide bond with the carboxyl group in the polyisocyanate compound. Among them, polyisocyanate compounds are preferable. When the adhesive composition a contains a crosslinking agent, the content of the crosslinking agent may be, for example, 5 parts by mass or less, preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, still more preferably 0.1 part by mass or less, relative to 100 parts by mass of the (meth) acrylic polymer a, and the adhesive composition a most preferably contains no crosslinking agent.

The active energy ray-curable adhesive composition is an adhesive composition which has a property of being cured by irradiation with active energy rays such as ultraviolet rays and electron beams, and has a property of having adhesiveness to an adherend such as a film even before irradiation with active energy rays and being cured by irradiation with active energy rays, thereby adjusting an adhesion force and the like.

The active energy ray-curable adhesive composition is preferably an ultraviolet ray-curable adhesive composition.

In the case where the adhesive composition a is an active energy ray-curable adhesive composition, the adhesive composition a may further contain an active energy ray-polymerizable compound, a photopolymerization initiator, a photosensitizing agent, or the like.

Examples of the active energy ray-polymerizable compound include (meth) acrylate monomers having at least 1 (meth) acryloyloxy group in the molecule; (meth) acrylic compounds such as (meth) acryloyloxy-containing compounds, such as (meth) acrylate oligomers having at least 2 (meth) acryloyloxy groups in the molecule, obtained by reacting 2 or more functional group-containing compounds. The adhesive composition a may contain 0.1 to 10 parts by mass of the active energy ray-polymerizable compound per 100 parts by mass of the solid content of the adhesive composition a.

Examples of the photopolymerization initiator include diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide, benzyl dimethyl ketal, and 1-hydroxycyclohexyl phenyl ketone. When the adhesive composition a contains a photopolymerization initiator, 1 or 2 or more kinds may be contained. In the case where the adhesive composition a contains a photopolymerization initiator, the total content thereof may be, for example, 0.01 to 1.0 parts by mass relative to 100 parts by mass of the solid content of the adhesive composition a.

The adhesive composition a preferably contains a compound having a nitrogen atom and a (meth) acryl group. The adhesive composition a may contain only 1 kind of compound having a nitrogen atom and a (meth) acryl group, or may contain a plurality of kinds. At least one of the 1 st adhesive composition and the 2 nd adhesive composition is preferably an adhesive composition a containing a compound having a nitrogen atom and a (meth) acryloyl group. The 1 st reference adhesive layer and the 2 nd reference adhesive layer satisfying the above-described relational expressions (2) and (3) can be easily formed by the adhesive composition a containing the compound having a nitrogen atom and a (meth) acryloyl group. The adhesive composition a may contain, for example, 0.1 to 10 parts by mass, preferably 1 to 5 parts by mass of a compound having a nitrogen atom and a (meth) acryloyl group in 100 parts by mass of the solid content of the adhesive composition a. The content of the compound having a nitrogen atom and a (meth) acryloyl group can be adjusted so as to satisfy the above-described relational expressions (2) and (3).

The compound having a nitrogen atom and a (meth) acryloyl group is preferably a compound having a nitrogen atom bonded to a (meth) acryloyl group, that is, preferably an amide bond. The compound having a nitrogen atom and a (meth) acryloyl group may be a primary amide, a secondary amide, or a secondary amide. The compound having a nitrogen atom and a (meth) acryloyl group is not particularly limited, and examples thereof include N-butoxymethacrylamide, N-dimethylacrylamide, and the like.

The adhesive composition a may contain fine particles for imparting light scattering properties, beads (resin beads, glass beads, etc.), glass fibers, resins other than the base polymer, an adhesion imparting agent, a filler (metal powder, other inorganic powder, etc.), an antioxidant, an ultraviolet absorber, a dye, a pigment, a colorant, a defoaming agent, an anticorrosive agent, and other additives. From the viewpoint of preventing the durability from being lowered by the residual solvent, the adhesive composition a preferably contains no organic solvent.

In the case where the adhesive layer is formed of the adhesive composition a, the adhesive layer may be formed by coating the adhesive composition a on the substrate. In the case of using the active energy ray-curable adhesive composition, a cured product having a desired degree of cure can be produced by irradiating the formed adhesive layer with active energy rays.

The active energy ray is preferably ultraviolet ray. The light source may be a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp, or the like. The cumulative light amount of the active energy rays is preferably 0.1J/cm ² ～1.0J/cm ² More preferably 0.2J/cm ² ～0.9J/cm ² . The irradiation of active energy rays under such conditions can easily adjust the thermal decomposition mass reduction rate of the adhesive layer to a predetermined range.

(2) Heat-curable adhesive composition

When the adhesive composition a is a thermosetting adhesive composition, the (meth) acrylic polymer a preferably contains an alkyl (meth) acrylate having 2 to 20 carbon atoms and a monomer having a reactive functional group in the molecule (a monomer having a reactive functional group) as monomer units constituting the polymer.

The (meth) acrylic polymer a can exhibit preferable adhesion by containing an alkyl (meth) acrylate having 2 to 20 carbon atoms as an alkyl group as a monomer unit constituting the polymer. The alkyl (meth) acrylate having 2 to 20 carbon atoms as the alkyl group is preferably an alkyl (meth) acrylate having a glass transition temperature (Tg) of-40 ℃ or lower (hereinafter, sometimes referred to as "low Tg alkyl acrylate") as a homopolymer. By containing the low Tg alkyl acrylate as a constituent monomer unit, the flexibility of the adhesive layer is improved, and the generation of bubbles during bending tends to be easily suppressed.

As the low Tg alkyl acrylate, for example, n-butyl acrylate (Tg of-55 ℃), n-octyl acrylate (Tg of-65 ℃), isooctyl acrylate (Tg of-58 ℃), 2-ethylhexyl acrylate (Tg of-70 ℃), isononyl acrylate (Tg of-58 ℃), isodecyl acrylate (Tg of-60 ℃), isodecyl methacrylate (Tg of-41 ℃), n-lauryl methacrylate (Tg of-65 ℃), tridecyl acrylate (Tg of-55 ℃) and tridecyl methacrylate (-40 ℃) are preferable. Among them, the low Tg alkyl acrylate is more preferably a low Tg alkyl acrylate having a homopolymer Tg of-45 ℃ or less, particularly preferably a low Tg alkyl acrylate having a Tg of-50 ℃ or less, from the viewpoint of being easy to satisfy the relation (2) or (3). In particular, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. These may be used alone or in combination of 2 or more.

The (meth) acrylic polymer a preferably contains 85 mass% or more of a low Tg alkyl acrylate, more preferably 90 mass% or more, and still more preferably 95 mass% or more, as the monomer unit constituting the polymer, in terms of the lower limit value. If the content is within such a range, the obtained adhesive layer can easily satisfy the relation (2) or (3).

The monomer unit constituting the (meth) acrylic polymer a preferably contains 99.9 mass% or less, more preferably 99.5 mass% or less, and still more preferably 99 mass% or less of the low Tg alkyl acrylate as the upper limit value. By containing 99.9 mass% or less of the low Tg alkyl acrylate, an appropriate amount of other monomer components (particularly, reactive functional group-containing monomers) can be introduced into the (meth) acrylic polymer a.

In order to easily set the glass transition temperature (Tg) of the main polymer of the adhesive of the present embodiment to the above range, the content of the monomer (hereinafter, sometimes referred to as "hard monomer") having a glass transition temperature (Tg) exceeding 0 ℃ as a homopolymer is preferably reduced as much as possible. Specifically, in the (meth) acrylic polymer a, the content of the hard monomer is preferably 15 mass% or less, more preferably 10 mass% or less, and still more preferably 5 mass% or less as the upper limit value of the monomer unit constituting the polymer. The hard monomer also includes a reactive functional group-containing monomer described later.

Examples of the hard monomer include methyl acrylate (Tg of 10 ℃), methyl methacrylate (Tg of 105 ℃), ethyl methacrylate (Tg of 65 ℃), n-butyl methacrylate (Tg of 20 ℃), isobutyl methacrylate (Tg of 48 ℃), t-butyl methacrylate (Tg of 107 ℃), n-stearyl acrylate (Tg of 30 ℃), n-stearyl methacrylate (Tg of 38 ℃), cyclohexyl acrylate (Tg of 15 ℃), cyclohexyl methacrylate (Tg of 66 ℃), phenoxyethyl acrylate (Tg of 5 ℃), phenoxyethyl methacrylate (Tg of 54 ℃), benzyl methacrylate (Tg of 54 ℃), isobornyl acrylate (Tg of 94 ℃), isobornyl methacrylate (Tg of 180 ℃), acryloylmorpholine (Tg of 145 ℃), adamantyl acrylate (Tg of 115 ℃), adamantyl methacrylate (Tg of 141 ℃), acrylic acid (Tg of 103 ℃), dimethylacrylamide (Tg of 89 ℃), acrylamide (Tg of 165 ℃), vinyl acetate (Tg of 32 ℃), and the like).

The (meth) acrylic polymer a has a crosslinked structure (three-dimensional network structure) by reacting a reactive functional group derived from a reactive functional group-containing monomer, which is contained as a monomer unit constituting the polymer, with a thermal crosslinking agent described later, to thereby obtain a pressure-sensitive adhesive having a desired cohesive force.

The reactive functional group-containing monomer contained in the (meth) acrylic polymer a as the monomer unit constituting the polymer may preferably be a monomer having a hydroxyl group in the molecule (hydroxyl group-containing monomer), a monomer having a carboxyl group in the molecule (carboxyl group-containing monomer), a monomer having an amino group in the molecule (amino group-containing monomer), or the like. Among these, hydroxyl group-containing monomers are particularly preferable because most of them have a glass transition temperature (Tg) of 0 ℃ or less.

Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, at least one of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate and 4-hydroxybutyl acrylate is preferable from the viewpoints of glass transition temperature (Tg), reactivity of the hydroxyl groups in the obtained (meth) acrylic polymer a with a thermal crosslinking agent, and copolymerizability with other monomers. These may be used alone or in combination of 2 or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used alone or in combination of 2 or more.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone or in combination of 2 or more.

The (meth) acrylic polymer a preferably contains 0.1 mass% or more, particularly preferably 0.5 mass% or more, and further preferably 1 mass% or more of a reactive functional group-containing monomer, in terms of the lower limit, as a monomer unit constituting the polymer. The upper limit is preferably 10% by mass or less, particularly preferably 8% by mass or less, and further preferably less than 5% by mass. If the (meth) acrylic polymer a contains a reactive functional group-containing monomer, particularly a hydroxyl group-containing monomer, as a monomer unit in the above amount, the resulting adhesive layer easily satisfies the relationship (2) or the relationship (3).

The (meth) acrylic polymer a may not contain a carboxyl group-containing monomer, particularly, may not contain acrylic acid which is a hard monomer, as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, even when a member causing a problem due to acid, for example, a transparent conductive film, a metal mesh, or the like of tin-doped indium oxide (ITO)) is present in the object to be adhered of the adhesive, these problems (corrosion, change in resistance value, or the like) caused by acid can be suppressed by not containing the carboxyl group-containing monomer.

The (meth) acrylic polymer a may contain other monomers as monomer units constituting the polymer, if necessary. As the other monomer, a monomer having a reactive functional group is also preferably not contained in order not to interfere with the action of the reactive functional group-containing monomer. Examples of the other monomer include, in addition to an alkoxyalkyl (meth) acrylate such as methoxyethyl (meth) acrylate or ethoxyethyl (meth) acrylate, a monomer having a glass transition temperature (Tg) of more than-40℃and not more than 0℃as a homopolymer (hereinafter, sometimes referred to as "medium Tg alkyl acrylate"), and examples of the medium Tg alkyl acrylate include ethyl acrylate (Tg: 20 ℃), isobutyl acrylate (Tg: 26 ℃), 2-ethylhexyl methacrylate (Tg: 10 ℃), n-lauryl acrylate (Tg: 23 ℃) and isostearyl acrylate (Tg: 18 ℃), and these may be used singly or in combination of 2 or more.

The polymerization form of the (meth) acrylic polymer a may be a random copolymer or a block copolymer.

The lower limit of the weight average molecular weight of the (meth) acrylic polymer a is preferably 20 ten thousand or more, particularly preferably 30 ten thousand or more, and further preferably 40 ten thousand or more. If the lower limit of the weight average molecular weight of the (meth) acrylic polymer a is not less than the above, the adhesive bleeding and other defects can be suppressed. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by Gel Permeation Chromatography (GPC).

The upper limit of the weight average molecular weight of the (meth) acrylic polymer a is preferably 150 ten thousand or less, particularly preferably 135 ten thousand or less, and further preferably 120 ten thousand or less. If the upper limit of the weight average molecular weight of the (meth) acrylate polymer a is not more than the above, the obtained adhesive layer easily satisfies the relation (2) or the relation (3).

In the pressure-sensitive adhesive composition a, 1 kind of the (meth) acrylic polymer a may be used alone, or 2 or more kinds may be used in combination.

If the adhesive composition a containing the thermal crosslinking agent is heated, the thermal crosslinking agent crosslinks the (meth) acrylic polymer a to form a three-dimensional network structure. Thus, the cohesive force of the obtained adhesive is improved, and the obtained adhesive layer easily satisfies the relation (2) or the relation (3).

The thermal crosslinking agent may be any one that reacts with the reactive group of the (meth) acrylic polymer a, and examples thereof 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, and the like,An oxazoline-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, an ammonium salt-based crosslinking agent, and the like. Among the above, when the reactive group of the (meth) acrylic polymer a is a hydroxyl group, an isocyanate-based crosslinking agent having excellent reactivity with the hydroxyl group is preferably used. The thermal crosslinking agent may be used alone or in combination of 2 or more.

The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret, isocyanurate, and adduct products which are reaction products with low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, etc. Among them, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates are preferred, and trimethylolpropane-modified toluene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are particularly preferred.

Examples of the epoxy-based crosslinking agent include 1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane, N' -tetraglycidyl m-xylylenediamine, ethylene glycol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine, and the like.

The content of the thermal crosslinking agent in the adhesive composition a is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and still more preferably 0.1 mass% or more, relative to 100 mass% of the (meth) acrylic polymer a. The content is preferably 1% by mass or less, more preferably 0.8% by mass or less, and still more preferably 0.5% by mass or less. When the content of the thermal crosslinking agent is in the above range, the obtained adhesive layer easily satisfies the relation (2) or the relation (3).

The adhesive composition a preferably contains the above silane coupling agent. Thus, the adhesion between the obtained adhesive layer and each member in the flexible laminate as an adherend is improved, and the durability against bending is further improved.

As the silane coupling agent, an organosilicon compound having at least 1 alkoxysilyl group in the molecule, and a compound having excellent compatibility with the (meth) acrylic polymer a and light transmittance is preferable.

Examples of the silane coupling agent include silicon compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyl trimethoxysilane; silicon compounds having an epoxy structure such as 3-glycidoxypropyl trimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyl trimethoxysilane; mercapto group-containing silicon compounds such as 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane, and 3-mercaptopropyl dimethoxymethylsilane; amino group-containing silicon compounds such as 3-aminopropyl trimethoxysilane, N- (2-aminoethyl) -3-aminopropyl trimethoxysilane and N- (2-aminoethyl) -3-aminopropyl methyldimethoxysilane; and a condensate of 3-chloropropyl trimethoxysilane, 3-isocyanatopropyl triethoxysilane, or at least one of these with an alkyl group-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, or the like. These may be used alone or in combination of 1 or more than 2.

The content of the silane coupling agent in the adhesive composition a is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and still more preferably 0.1 mass% or more, relative to 100 mass% of the (meth) acrylic polymer a. The content is preferably 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.3% by mass or less. When the content of the silane coupling agent is within the above range, the resulting adhesive layer is a layer having more preferable adhesion to each member in the flexible laminate as an adherend.

The adhesive composition a may contain the above-mentioned various additives as required. The additive constituting the adhesive composition a does not contain a polymerization solvent or a dilution solvent.

The (meth) acrylic polymer a can be produced by polymerizing a mixture of monomers constituting the polymer by a usual radical polymerization method. The polymerization of the (meth) acrylic polymer a is preferably performed by a solution polymerization method using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and 2 or more kinds of solvents may be used in combination.

The polymerization initiator may be an azo compound, an organic peroxide, or the like, or may be used in combination of 2 or more. Examples of the azo compound include: 2,2' -azobisisobutyronitrile, 2' -azobis (2-methylbutyronitrile), 1' -azobis (cyclohexane 1-carbonitrile), 2' -azobis (2, 4-dimethylvaleronitrile), 2' -azobis (2, 4-dimethyl-4-methoxypentanenitrile), dimethyl 2,2' -azobis (2-methylpropionate), 4' -azobis (4-cyanovaleric acid), 2' -azobis (2-hydroxymethylpropionitrile), 2' -azobis [2- (2-imidazolin-2-yl) propane ], and the like.

Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxyvalerate, peroxy (3, 5-trimethylhexanoyl), dipropyl peroxide, and diacetyl peroxide.

In the polymerization step, a chain transfer agent such as 2-mercaptoethanol is blended to adjust the weight average molecular weight of the obtained polymer.

After the (meth) acrylic polymer a is obtained, a thermal crosslinking agent, a silane coupling agent, and a diluting solvent according to the desired additives are added to the solution of the (meth) acrylic polymer a and mixed thoroughly, thereby obtaining an adhesive composition a (coating solution) diluted with the solvent.

In any of the above components, when a solid component is used or when precipitation occurs when the solid component is mixed with other components in an undiluted state, the solid component may be dissolved or diluted in a diluting solvent alone and then mixed with the other components.

As the diluent solvent, for example, aliphatic hydrocarbons such as hexane, heptane, cyclohexane, etc. can be used; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and dichloroethane; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; cellosolve solvents such as ethyl cellosolve and the like.

The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as they are within a range that can be coated, and may be appropriately selected according to the situation. For example, the adhesive composition a is diluted so that the concentration thereof is 10 to 60 mass%. In addition, the addition of a diluting solvent or the like is not necessarily required in obtaining the coating solution, and if the adhesive composition a is of a viscosity or the like that can be applied, the diluting solvent may not be added. At this time, the adhesive composition a becomes a coating solution in which the polymerization solvent of the (meth) acrylic polymer a is directly used as a diluting solvent.

The adhesive agent which is preferable as the adhesive agent of the present embodiment is obtained by crosslinking the adhesive agent composition a. Crosslinking of the adhesive composition a may be performed by a heat treatment. The heat treatment may be used in combination with a drying treatment for evaporating a diluting solvent or the like from a coating film of the adhesive composition a applied to a desired object.

The heating temperature of the heating treatment is preferably 50 to 150 ℃, more preferably 70 to 120 ℃. The heating time is preferably 10 seconds to 10 minutes, more preferably 50 seconds to 2 minutes.

After the heat treatment, a curing period of about 1 to 2 weeks may be set at normal temperature (e.g., 23 ℃ C., 50% RH) as needed. When the aging period is required, the adhesive is formed after the aging period is passed, and when the aging period is not required, the adhesive is formed after the heat treatment is completed.

By the above-mentioned heat treatment (and curing), the (meth) acrylic polymer a is sufficiently crosslinked via the crosslinking agent to form a crosslinked structure, and an adhesive is obtained. The adhesive layer obtained by the adhesive easily satisfies the relation (2) or the relation (3).

The adhesive sheet of the present invention comprises an adhesive layer formed from the adhesive composition a of the present invention described above. The adhesive layer may be formed by coating the adhesive composition a on a substrate. When a thermosetting adhesive composition is used as the adhesive composition a, a cured product having a desired degree of cure can be produced by subjecting the formed adhesive layer to a heat treatment (and curing). The conditions for heat treatment and aging were as described above.

The substrate may be a release film subjected to a release treatment. The pressure-sensitive adhesive sheet can be produced by forming a pressure-sensitive adhesive-containing layer in a sheet form on a release film, and then bonding another release film to the pressure-sensitive adhesive layer.

As a method of applying the coating liquid of the adhesive composition a, for example, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, or the like can be used.

The adhesive composition a can be produced by mixing the components together by a known method, for example, using a mixer or the like.

[ front panel ]

The front panel 101 is not limited in material and thickness as long as it is a plate-like body that transmits light, and may be composed of only 1 layer or 2 or more layers. Examples thereof include a resin plate-like body (e.g., a resin plate, a resin sheet, a resin film, etc.), a glass plate-like body (e.g., a glass plate, a glass film, etc.), and a touch sensor panel described later. The front panel may constitute the outermost surface of the display device.

The thickness of the front panel 101 may be, for example, 10 μm to 500 μm, preferably 30 μm to 200 μm, and more preferably 50 μm to 100 μm. In the present invention, the thickness of each layer can be measured according to the thickness measurement method described in examples described later.

In the case where the front panel 101 is a resin plate-like body, the resin plate-like body is not limited as long as it is transparent to light. Examples of the resin constituting the resin plate-like body such as a resin film include films made of polymers such as triacetylcellulose, acetylcellulose butyrate, ethylene-vinyl acetate copolymer, propionylcellulose, butyrylcellulose, levulinyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly (meth) acrylic acid, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyetherketone, polyetheretherketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers may be used singly or in combination of 2 or more. From the viewpoint of improving strength and transparency, a resin film formed of a polymer such as polyimide, polyamide, or polyamideimide is preferable.

From the viewpoint of improving the hardness, the front panel 101 is preferably a film having a hard coat layer provided on at least one surface of a base film. As the base film, a film formed of the above resin can be used. The hard coat layer may be formed on one surface of the base film or on both surfaces. By providing the hard coat layer, a resin film having improved hardness and scratch resistance can be produced. The hard coat layer is, for example, a cured layer of an ultraviolet curable resin. Examples of the ultraviolet curable resin include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coat layer may contain additives for improving hardness. The additive is not limited, and examples thereof include inorganic fine particles, organic fine particles, or a mixture thereof.

In the case where the front panel 101 is a glass plate, the glass plate is preferably reinforced glass for display. The thickness of the glass plate may be, for example, 30 μm to 1000 μm. By using a glass plate, the front panel 101 having excellent mechanical strength and surface hardness can be constituted.

In the case where the laminate 100 is used for a display device, the front panel 101 may have not only a function of protecting the front surface (screen) of the display device (a function as a window film) but also a function as a touch sensor, a blue light cut-off function, a viewing angle adjustment function, and the like.

[ 1 st adhesive layer ]

The 1 st pressure-sensitive adhesive layer 102 is a layer interposed between the front panel 101 and the polarizer layer 103 and bonded to each other, and may be a layer made of a pressure-sensitive adhesive or an adhesive, or a layer obtained by subjecting the layer to a certain treatment. The 1 st adhesive layer may be an adhesive layer disposed at a position closest to the front panel among the adhesive layers constituting the laminate. Adhesives are also known as pressure sensitive adhesives. In the present specification, the term "adhesive" refers to an adhesive other than an adhesive (pressure sensitive adhesive), and is clearly distinguished from an adhesive. The 1 st adhesive layer 102 may be formed of 1 layer or may be formed of 2 or more layers, and is preferably 1 layer.

The 1 st adhesive layer 20 may be formed directly from an adhesive composition, or may be formed using an adhesive sheet having an adhesive layer formed using an adhesive composition. The adhesive composition may be formed from adhesive composition a as described above.

The thickness of the 1 st pressure-sensitive adhesive layer 102 is, for example, preferably 3 μm to 100. Mu.m, more preferably 5 μm to 50. Mu.m, and may be 20 μm or more.

[ polarizer layer ]

Examples of the polarizer layer 103 include a stretched film or a stretched layer having a dichroic dye adsorbed thereto, and a layer obtained by applying a composition containing a dichroic dye and a polymerizable compound and curing the composition. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. The dichroic organic dye includes a dichroic direct dye composed of a disazo compound such as c.i. direct RED (c.i. direct RED) 39, and a dichroic direct dye composed of a compound such as trisazo or tetraazo.

Examples of the polarizer layer formed by applying and curing a composition containing a dichroic dye and a polymerizable compound include a polarizer layer containing a cured product of a polymerizable liquid crystal compound, such as a layer formed by applying and curing a composition containing a dichroic dye having liquid crystallinity or a composition containing a dichroic dye and a polymerizable liquid crystal.

The polarizer layer formed by applying and curing a composition containing a dichroic dye and a polymerizable compound is preferably used because the bending direction of the polarizer layer is not limited as compared with a stretched film or a stretched layer to which the dichroic dye is adsorbed.

[ polarizer layer as stretched film or stretched layer ]

The polarizer layer as a stretched film having a dichroic dye adsorbed thereto can be generally produced by the following steps: a step of uniaxially stretching the polyvinyl alcohol resin film; a step of adsorbing a dichroic dye by dyeing a polyvinyl alcohol resin film with the dichroic dye; a step of treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereto with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

The thickness of the polarizer layer 103 is, for example, 2 μm to 40 μm. The thickness of the polarizer layer 103 may be 5 μm or more, may be 20 μm or less, further may be 15 μm or less, and further may be 10 μm or less.

The polyvinyl alcohol resin is obtained by saponifying a polyvinyl acetate resin. As the polyvinyl acetate resin, a copolymer of vinyl acetate and other monomers copolymerizable therewith may be used in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with an aldehyde may be used. The polymerization degree of the polyvinyl alcohol resin is usually 1000 to 10000, preferably 1500 to 5000.

The polarizer layer as the stretched layer having the dichroic dye adsorbed thereto can be generally produced by the following steps: a step of applying a coating liquid containing the polyvinyl alcohol resin onto a base film; uniaxially stretching the obtained laminated film; a step of forming a polarizer by dyeing a polyvinyl alcohol resin layer of a uniaxially stretched laminate film with a dichroic dye to adsorb the dichroic dye; a step of treating the film having the dichromatic pigment adsorbed thereto with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

The substrate film may be peeled off from the polarizer layer as needed. The material and thickness of the base film may be the same as those of the thermoplastic resin film described later.

The polarizer layer as a stretched film or a stretched layer may be assembled in a laminate in such a manner that a thermoplastic resin film is bonded to one or both surfaces thereof. The thermoplastic resin film can function as a protective film or a retardation film for the polarizer layer 103. The thermoplastic resin film may be a polyolefin resin such as a chain polyolefin resin (polypropylene resin or the like) or a cyclic polyolefin resin (norbornene resin or the like); cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate resin; (meth) acrylic resins; or a mixture thereof, or the like.

From the viewpoint of thickness reduction, the thickness of the thermoplastic resin film is usually 300 μm or less, preferably 200 μm or less, more preferably 100 μm or less, still more preferably 80 μm or less, still more preferably 60 μm or less, and further usually 5 μm or more, preferably 20 μm or more.

The thermoplastic resin film may or may not have a retardation.

The thermoplastic resin film may be bonded to the polarizer layer 103 using an adhesive layer, for example.

[ polarizer layer obtained by applying and curing a composition comprising a dichroic dye and a polymerizable compound ]

Examples of the polarizer layer formed by applying and curing a composition containing a dichroic dye and a polymerizable compound include a polarizer layer containing a cured product of a polymerizable liquid crystal compound, such as a layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable liquid crystal to a base film.

The substrate film may be peeled off from the polarizer layer as needed. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above. The polarizer layer may be provided with an alignment film. The orientation film may also be peeled off.

The polarizer layer obtained by applying and curing the composition containing the dichroic dye and the polymerizable compound may be assembled in the optical laminate in a state in which a thermoplastic resin film is bonded to one or both surfaces thereof. As the thermoplastic resin film, a thermoplastic resin film similar to that which can be used in the polarizer layer as a stretched film or a stretched layer can be used. The thermoplastic resin film may be bonded to the polarizer layer using an adhesive layer, for example.

The polarizer layer formed by applying and curing a composition containing a dichroic dye and a polymerizable compound may be formed with an Overcoat (OC) layer as a protective layer on one or both sides thereof. Examples thereof include photocurable resins and water-soluble polymers. Examples of the photocurable resin include (meth) acrylic resins, urethane resins, (meth) acrylic urethane resins, epoxy resins, and silicone resins. Examples of the water-soluble polymer include poly (meth) acrylamide polymers; polyvinyl alcohol and vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, vinyl alcohol polymers such as (meth) acrylic acid or anhydride-vinyl alcohol copolymers; carboxyvinyl polymers; polyvinylpyrrolidone; starches; sodium alginate; polyethylene oxide polymers, and the like. The thickness of the OC layer is preferably 20 μm or less, more preferably 15 μm or less, still more preferably 10 μm or less, but may be 5 μm or less, or 0.05 μm or more, or 0.5 μm or more.

The thickness of the polarizer layer obtained by applying and curing the composition containing the dichroic dye and the polymerizable compound is usually 10 μm or less, preferably 0.5 μm to 8 μm, and more preferably 1 μm to 5 μm.

[ adhesive layer 2 ]

The 2 nd adhesive layer 104 is an adhesive layer disposed between the polarizer layer 103 and the back plate 105. The 2 nd adhesive layer may be an adhesive layer disposed at a position closest to the back surface plate among the adhesive layers constituting the laminate. The 2 nd adhesive layer 104 may be 1 layer, or may be composed of 2 or more layers, and is preferably 1 layer.

The composition and the component of the adhesive composition constituting the 2 nd adhesive layer 104, the type of the adhesive composition (whether or not it is an active energy ray-curable type or a thermosetting type, etc.), the additive that can be blended in the adhesive composition, the method for producing the 2 nd adhesive layer, and the thickness of the 2 nd adhesive layer are the same as those shown in the description of the 1 st adhesive layer 102.

The 2 nd adhesive layer 104 may be the same as or different from the 1 st adhesive layer 102 in terms of the composition, the compounding ingredients, the thickness, and the like of the adhesive composition.

[ Back plate ]

As the back plate 105, a plate-like body that can transmit light, a component used in a general display device, or the like can be used.

The thickness of the back plate 105 may be, for example, 5 μm to 2000 μm, preferably 10 μm to 1000 μm, and more preferably 15 μm to 500 μm.

The plate-like body used for the back plate 105 may be composed of only 1 layer, or may be composed of 2 layers or more, and the plate-like body exemplified for the plate-like body described in the front plate 101 may be used.

Examples of the components used in a typical display device for the back plate 105 include a spacer, a touch sensor panel, and an organic EL display element. Examples of the lamination order of the constituent elements in the display device include a front panel/circularly polarizing plate/spacer, a front panel/circularly polarizing plate/organic EL display element, a front panel/circularly polarizing plate/touch sensor panel/organic EL display element, a front panel/touch sensor panel/circularly polarizing plate/organic EL display element, and the like.

(touch sensor Panel)

The touch sensor panel is not limited to a detection method as long as it is a sensor capable of detecting a touched position, and examples thereof include a resistive film type, a capacitive coupling type, a photo sensor type, an ultrasonic type, an electromagnetic induction coupling type, a surface acoustic wave type, and the like. In view of low cost, a touch sensor panel of a resistive film type or a capacitive coupling type can be preferably used.

An example of a resistive touch sensor panel is composed of a pair of substrates disposed opposite to each other, an insulating spacer sandwiched between the pair of substrates, a transparent conductive film provided as a resistive film on the inner front surface of each substrate, and a touch position detection circuit. In an image display device provided with a resistive film type touch sensor panel, if the surface of a front panel is touched, the opposing resistive film is shorted, and a current flows through the resistive film. The touch position detection circuit detects a voltage change at this time, thereby detecting a touched position.

An example of a capacitive-coupling type touch sensor panel is composed of a substrate, a transparent electrode for detecting a position provided on the entire surface of the substrate, and a touch position detection circuit. In an image display device provided with a capacitive coupling type touch sensor panel, if the surface of a front panel is touched, a transparent electrode is grounded via the capacitance of a human body at the point where the touch is made. The touch position detection circuit detects the grounding of the transparent electrode, thereby detecting the touched position.

The thickness of the touch sensor panel may be, for example, 5 μm to 2000 μm or 5 μm to 100 μm.

[ phase-difference layer ]

The laminate 100 may further include 1 layer or 2 or more retardation layers. The phase difference layer is typically disposed between the polarizer layer 103 and the back plate 105. The retardation layer may be laminated on the 1 st adhesive layer 102 and the 2 nd adhesive layer 104, or may be laminated on another layer (including another retardation layer) through a layer (hereinafter also referred to as a bonding layer) composed of an adhesive or an adhesive other than these layers.

[ adhesive layer ]

The lamination layer is a layer disposed between the 1 st adhesive layer 102 and the 2 nd adhesive layer 104, and is a layer made of an adhesive or an adhesive. The adhesive constituting the adhesive layer may be the same as exemplified for the adhesive composition constituting the 1 st adhesive layer 102 or the 2 nd adhesive layer, or may be other adhesives such as (meth) acrylic adhesives, styrene adhesives, silicone adhesives, rubber adhesives, urethane adhesives, polyester adhesives, epoxy copolymer adhesives, and the like.

The adhesive constituting the adhesive layer may be formed by combining 1 or 2 or more kinds of aqueous adhesives, active energy ray-curable adhesives, and the like, for example. Examples of the aqueous adhesive include an aqueous polyvinyl alcohol resin solution and an aqueous two-part urethane emulsion adhesive. The active energy ray-curable adhesive is an adhesive cured by irradiation with active energy rays such as ultraviolet rays, and examples thereof include adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin, adhesives containing a binder resin and a photoreactive crosslinking agent, and the like. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers and photocurable urethane monomers, and oligomers derived from these monomers. Examples of the photopolymerization initiator include those containing active species such as neutral radicals, anionic radicals, and cationic radicals generated by irradiation with active energy rays such as ultraviolet rays.

The thickness of the bonding layer may be, for example, 1 μm or more, preferably 1 μm to 25 μm, more preferably 2 μm to 15 μm, and still more preferably 2.5 μm to 5 μm.

The laminate 200 shown in fig. 2 includes a front plate 101, a 1 st adhesive layer 102, a polarizer layer 103, a bonding layer 108, and a back plate 105, and further includes a 1 st retardation layer 106, a bonding layer 109, a 2 nd retardation layer 107, and a 2 nd adhesive layer 104.

Examples of the retardation layer include a photo-alignment material parallel alignment film (positive-a plate) such as a λ/4 plate or a λ/2 plate, and a photo-alignment material perpendicular alignment film (positive-C plate).

The retardation layer may be, for example, a retardation film that can be formed of the thermoplastic resin film, or a layer obtained by curing a polymerizable liquid crystal compound, that is, a layer containing a cured product of a polymerizable liquid crystal compound, and is preferably the latter.

The thickness of the retardation film may be the same as that of the thermoplastic resin film described above. The thickness of the retardation layer obtained by curing the polymerizable liquid crystal compound is, for example, 0.1 μm to 10. Mu.m, preferably 0.5 μm to 8. Mu.m, more preferably 1 μm to 6. Mu.m.

The retardation layer obtained by curing the polymerizable liquid crystal compound can be formed by applying a composition containing the polymerizable liquid crystal compound to a base film and curing the composition. An alignment layer may be formed between the base film and the coating layer. The material and thickness of the base film may be the same as those of the thermoplastic resin film described above.

The retardation layer obtained by curing the polymerizable liquid crystal compound may be incorporated into the laminate 100 in the form of an alignment layer and/or a base film. The back surface plate 105 may be a base film coated with the above composition.

As described above, the adhesive layer 108 may be an adhesive or an adhesive. The adhesive may be the adhesive composition a described above.

As the adhesive, an aqueous adhesive or an active energy ray-curable adhesive can be used. Examples of the aqueous adhesive include an adhesive composed of an aqueous polyvinyl alcohol resin solution, an aqueous two-part urethane emulsion adhesive, and the like.

The active energy ray-curable adhesive is an adhesive cured by irradiation with active energy rays such as ultraviolet rays, and examples thereof include adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin, adhesives containing a binder resin and a photoreactive crosslinking agent, and the like.

Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable (meth) acrylic monomers and photocurable urethane monomers, and oligomers derived from photopolymerizable monomers.

The photopolymerization initiator includes those containing active species such as neutral radicals, anionic radicals, and cationic radicals generated by irradiation with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, an active energy ray-curable adhesive containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

[ method for producing laminate ]

The laminate 100 may be manufactured by a method including the steps of: the layers constituting the laminate 100 are bonded to each other via an adhesive layer or further via an adhesive layer. In the case of bonding the layers to each other via an adhesive layer or an adhesive layer, it is preferable to apply a surface activation treatment such as corona treatment to one or both of the bonding surfaces in order to improve the adhesion.

The polarizer layer 103 may be directly formed on a thermoplastic resin film or a base film, which may be incorporated in the laminate 100 or may be peeled off from the polarizer layer 103 without being a constituent of the laminate.

< display device >)

The display device of the present invention includes the laminate 100 of the present invention described above. The display device is not particularly limited, and examples thereof include image display devices such as organic EL display devices, inorganic EL display devices, liquid crystal display devices, and electroluminescent display devices. The display device may also have a touch panel function. The optical laminate is suitable for a display device having flexibility capable of bending or bending.

In the display device, the optical laminate is arranged on the viewing side of the display element included in the display device with the front panel facing outward (opposite to the display element side, that is, on the viewing side).

The display device of the present invention can be used as mobile devices such as smart phones and tablet computers, televisions, digital photo frames, electronic tags, measuring devices, instruments, office equipment, medical equipment, computer equipment, and the like.

< adhesive composition >

The adhesive composition of the present invention is preferably the adhesive composition a described above. The adhesive composition of the present invention can be produced by mixing the components together by a known method, for example, using a mixer or the like.

< adhesive sheet >

The adhesive sheet of the present invention comprises an adhesive layer formed from an adhesive composition comprising a (meth) acrylic polymer and a compound having a nitrogen atom and a (meth) acryloyl group, preferably an adhesive layer formed from an adhesive composition a. The adhesive layer may be formed by coating the adhesive composition on a substrate. When the active energy ray-curable adhesive composition is used as the adhesive composition, a cured product having a desired degree of cure can be produced by irradiating the formed adhesive layer with active energy rays. In the case of using a thermosetting adhesive composition as the adhesive composition, a cured product having a desired degree of cure can be produced by subjecting the formed adhesive layer to a heat treatment (and curing).

The adhesive layer of the adhesive sheet of the present invention has excellent heat resistance. If the thermal decomposition mass reduction rate formed from the adhesive composition used in the formation of the adhesive layer is set to R [% ], the following relational expression (4) is preferably satisfied:

10≤R≤20 (4)，

more preferably, the following relational expression (4 a) is satisfied:

11≤R≤19 (4a)。

the present invention will be described in further detail with reference to examples, but the present invention is not limited to these examples.

Examples

[ adhesive sheet Using Heat-curable adhesive composition ]

[1] Production of adhesive sheet A11

(1) Preparation of (meth) acrylic polymers

54 parts by mass of n-butyl acrylate, 45 parts by mass of 2-ethylhexyl acrylate and 1 part by mass of 4-hydroxybutyl acrylate were copolymerized to prepare a (meth) acrylic polymer. The molecular weight of the (meth) acrylic polymer was measured by the method described below, and as a result, the weight average molecular weight (Mw) was 80 ten thousand.

(2) Preparation of adhesive composition

100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth) acrylic polymer obtained in the above-described step, 0.25 part by mass of trimethylolpropane-modified xylylene diisocyanate (product name "TD-75" manufactured by Ming. Chemie Co., ltd.) as a thermal crosslinking agent, and 0.2 part by mass of 3-glycidoxypropyl trimethoxysilane (product name "KBM403" manufactured by Xin Yue Chemie Co., ltd.) as a silane coupling agent were mixed and sufficiently stirred, and diluted with methyl ethyl ketone, whereby a coating solution of the adhesive composition was obtained. Table 1 shows the blending (solid content conversion value) of each adhesive composition when the (meth) acrylic polymer was taken as 100 parts by mass (solid content conversion value). The abbreviations and the like described in table 1 indicate the following meanings.

BA: acrylic acid n-butyl ester

2EHA: 2-ethylhexyl acrylate

4HBA: acrylic acid 4-hydroxybutyl ester

(3) Production of adhesive sheet A11

The coating solution of the obtained adhesive composition was applied to the release treated surface of a light separator (manufactured by Lintec Co., ltd., product name "SP-PET 752150") by a knife coater. Then, for the coating layer, heat treatment was performed at 90 ℃ for 1 minute to form the coating layer. Next, the coating layer on the light separator obtained above was bonded to a heavy separator (manufactured by Lintec corporation under the product name "SP-PET 382120") so that the release treated surface of the separator was in contact with the coating layer, and cured under the conditions of 23 ℃ and 50% rh for 7 days, thereby producing an adhesive sheet a11 having an adhesive layer with a thickness of 25 μm, that is, an adhesive sheet a11 composed of a light separator/adhesive layer (thickness: 25 μm)/heavy separator. The adhesive layer of the adhesive sheet a11 was used as the adhesive layer a11. The measured thermal decomposition mass reduction rate of the adhesive sheet a11 is shown in table 1. The thickness and the thermal decomposition mass reduction rate of the adhesive layer a11 were measured by the method described later.

[2] Production of pressure-sensitive adhesive sheets A12 to A16

(1) Preparation of (meth) acrylic polymers

The proportions of the monomers constituting the (meth) acrylic polymer were adjusted as shown in table 1, and the (meth) acrylic polymer having a weight average molecular weight (Mw) shown in table 1 was produced in the same manner as in the production process of the adhesive sheet a 11.

(2) Preparation of adhesive composition

100 parts by mass of the (meth) acrylic polymer obtained in the above step, trimethylolpropane-modified xylylene diisocyanate (product name "TD-75" manufactured by Sony chemical Co., ltd.) as a thermal crosslinking agent, and 3-glycidoxypropyl trimethoxysilane (product name "KBM403" manufactured by Xinyue chemical industry Co., ltd.) as a silane coupling agent were mixed in the mixing ratio shown in Table 1, and the mixture was thoroughly stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

(3) Production of pressure-sensitive adhesive sheets A12 to A16

Using the obtained coating solution of the adhesive composition, adhesive sheets a12 to a16 were produced in the same manner as in the production process of the adhesive sheet a 11. The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets a12 to a16 were used as the pressure-sensitive adhesive layers a12 to a16. The thicknesses and thermal decomposition mass reduction rates of the pressure-sensitive adhesive layers a12 to a16 measured by the method described later are shown in table 1 for the pressure-sensitive adhesive sheets a12 to a16.

TABLE 1

[ adhesive sheet Using active energy ray-curable adhesive composition ]

[1] Production of adhesive sheet A21

(1) Preparation of (meth) acrylic Polymer A21

A monomer mixture composed of 84.4 mass% of 2-ethylhexyl acrylate (2-EHA) monomer, 15 mass% of Butyl Acrylate (BA) monomer and 0.5 mass% of 2-hydroxyethyl acrylate (2-HEA) monomer was charged into a 1L reactor provided with a cooling device for refluxing nitrogen gas so as to easily adjust the temperature, and then, the nitrogen gas was refluxed for 1 hour to remove oxygen, and maintained at 80 ℃. After the monomer mixture was uniformly mixed, 0.05 mass% of benzyl dimethyl ketal (I-651) and 0.05 mass% of 1-hydroxycyclohexyl phenyl ketone (I-184) were charged as photopolymerization initiators. Subsequently, a UV lamp (10 mW) was irradiated while stirring, and a (meth) acrylic polymer a21 having a weight average molecular weight (mW) of 37 ten thousand was produced.

The ratio of each monomer to each component of the acrylic polymer a21 is shown in table 2. Abbreviations and the like described in table 2 indicate the following meanings.

2-EHA: 2-ethylhexyl acrylate (Tokyo chemical industry Co., ltd., japan),

BA: butyl acrylate (tokyo chemical industry Co., ltd., japan),

2-HEA: 2-hydroxyethyl acrylate (Tokyo chemical industry Co., ltd., japan),

2-HEMA: 2-ethylhexyl methacrylate (Tokyo chemical industry Co., ltd., japan),

LA: lauryl acrylate (tokyo chemical industry co., japan),

i-651: benzyl dimethyl ketal (photopolymerization initiator, BASF, germany),

i-184: 1-hydroxycyclohexyl phenyl ketone (photopolymerization initiator, BASF, germany).

(2) Preparation of adhesive composition

The (meth) acrylic polymer obtained in the above step was mixed with 1 mass% of isodecyl acrylate (IDA, miwon specialty chemical, korea) as an additive, 3 mass% of N-butoxymethylacrylamide (NBMA, tokyo chemical industry co., japan), 0.5 mass% of diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (TPO, tokyo chemical industry co., japan) as a photopolymerization initiator, and 0.5 mass% of 1-hydroxycyclohexyl phenyl ketone (I-184, basf, germany) as a solid content conversion value, followed by sufficient stirring, and diluted with methyl ethyl ketone, to thereby obtain a coating solution of the adhesive composition. Table 3 shows the blending (solid content conversion value) of each adhesive composition. Abbreviations and the like described in table 3 indicate the following meanings.

IDA: isodecyl acrylate (Miwon specialty chemical, korea)

NBMA: N-Butoxymethacrylamide (NBMA, tokyo chemical industry Co., ltd., japan)

TPO: diphenyl (2, 4, 6-trimethylbenzoyl) phosphine oxide (tokyo chemical industry Co., ltd., japan)

I-184: 1-hydroxycyclohexyl phenyl ketone (BASF, germany)

(3) Production of adhesive sheet A21

The coating solution of the obtained adhesive composition was applied to a light separator (poly-pairEthylene terephthalate film, thickness 38 μm). Next, the coating layer on the light separator obtained above was bonded to Sup>A heavy separator (polyethylene terephthalate film, thickness 38 μm) so that the release treated surface of the separator was in contact with the coating layer, and UV irradiation was performed (light source: UV-A, irradiation intensity 100 mW/cm) ² Cumulative light quantity 0.4J/cm ² ) An adhesive sheet a21 having an adhesive layer with a thickness of 25 μm, that is, an adhesive sheet made of a light separator/adhesive layer (thickness: 25 μm)/the adhesive sheet a21 constituted by the heavy separator. The adhesive layer of the adhesive sheet a21 was used as the adhesive layer a21. The measured thermal decomposition mass reduction rate of the adhesive sheet a21 is shown in table 3. The thickness and the thermal decomposition mass reduction rate of the adhesive layer a21 were measured by the method described later.

[2] Production of pressure-sensitive adhesive sheets A22, A23

(1) Preparation of (meth) acrylic polymers A22, A23

The proportions of the monomers constituting the (meth) acrylic polymers were adjusted as shown in table 2, and the (meth) acrylic polymers a22 and a23 having weight average molecular weights (Mw) shown in table 2 were produced in the same manner as in the production process of the adhesive sheet a 21.

(2) Preparation of adhesive composition

The (meth) acrylic polymer obtained in the above step and the additive were mixed in the mixing ratio shown in table 3, and the mixture was sufficiently stirred and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

(3) Production of pressure-sensitive adhesive sheets A22, A23

Using the obtained coating solution of the adhesive composition, adhesive sheets a22 and a23 were produced in the same manner as in the production process of the adhesive sheet a 21. The pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets a22 and a23 were used as the pressure-sensitive adhesive layers a22 and a23. The thicknesses and thermal decomposition mass reduction rates of the adhesive layers a22 and a23 measured by the methods described later are shown in table 3 for the adhesive sheets a22 and a23.

TABLE 2

TABLE 3

< determination of weight average molecular weight (Mw) >)

The weight average molecular weight (Mw) of the (meth) acrylic polymer was determined by size exclusion chromatography (size SEC) described below using tetrahydrofuran as the mobile phase, as the number average molecular weight (Mn) in terms of polystyrene.

The measured (meth) acrylic polymer was dissolved in tetrahydrofuran at a concentration of about 0.05 mass%, and 10. Mu.L was injected into SEC. The mobile phase was flowed at a flow rate of 1.0 mL/min. As a column, PLgel MIXED-B (manufactured by Polymer Laboratories) was used. The detector used was a UV-VIS detector (trade name: agilent GPC).

< thickness of layer >

The measurement was performed using a contact film thickness measuring apparatus (MS-5C manufactured by Nikon Co., ltd.).

Among them, the polarizer layer and the alignment film were measured using a laser light-emitting microscope (OLS 3000 manufactured by Olympus corporation).

< thermal decomposition Mass reduction Rate >)

The adhesive sheet was cut into a width of 25mm by a length of 100mm. After removing the release film from the adhesive sheet, the adhesive layer was placed in a pan (pan), and the adhesive layer was heated from room temperature to 200℃at a heating rate of 10℃per minute by a thermogravimetric analysis apparatus (product name: TGA550, manufactured by TA Instrument Co.). Based on the mass W of the adhesive layer at room temperature _r [g]And mass W of the adhesive layer after heating to 200 DEG C ₂₀₀ [g]The thermal decomposition mass reduction rate R is calculated from the following formula (5).

R＝{(W _r -W ₂₀₀ )/W _r }×100[％] (5)

Front panel (Window film)

As the front panel, a polyimide film (thickness 50 μm) having a hard coat layer (thickness 10 μm) on one side was prepared.

[ polarizer layer ]

1. The following materials were prepared.

1) TAC film with thickness of 25 μm.

2) Composition for forming an alignment film.

< Polymer 1 >)

A polymer 1 having a photoreactive group constituted of the following structural units was prepared.

A solution in which polymer 1 was dissolved in cyclopentanone at a concentration of 5 mass% was used as a composition for forming an alignment film [ hereinafter also referred to as composition (D-1) ].

3) Composition for forming polarizer layer

< polymerizable liquid Crystal Compound >

The polymerizable liquid crystal compound represented by the formula (1-1) [ hereinafter also referred to as compound (1-1) ] and the polymerizable liquid crystal compound represented by the formula (1-2) [ hereinafter also referred to as compound (1-2) ] are used.

Compound (1-1) and compound (1-2) were synthesized by the methods described in Lub et al, recl. Trav. Chim. Pays-Bas, 115, 321-328 (1996).

< dichroic dye >)

As the dichroic dye, an azo dye described in examples of Japanese patent application laid-open No. 2013-101328 represented by the following formulas (2-1 a), (2-1 b) and (2-3 a) is used.

The composition for forming a polarizer layer [ hereinafter also referred to as composition (a-1) ] is prepared by: 75 parts by mass of compound (1-1), 25 parts by mass of compound (1-2), each of the azo pigments represented by the above-mentioned formula (2-1 a), formula (2-1 b) and formula (2-3 a) as dichroic dyes, 6 parts by mass of 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one (Irgacure) 369, manufactured by BASF Japan (BASF Japan) company, and 1.2 parts by mass of a polyacrylate compound (BYK-361N, manufactured by BYK-Chemie) company as a leveling agent were mixed into 400 parts by mass of toluene as a solvent, and the resultant mixture was stirred at 80℃for 1 hour.

4) Composition for forming protective layer (OC layer)

Composition for forming protective layer (OC layer) [ hereinafter also referred to as composition (E-1) ] is prepared by mixing water: 100 parts by mass of a polyvinyl alcohol resin powder (manufactured by Kuraray Co., ltd., average polymerization degree 18000, trade name: KL-318): 3 parts by mass of a polyamide epoxy resin (crosslinking agent, trade name: SR650 (30)) manufactured by Chemtex Co., ltd.): 1.5 parts by mass.

2. Manufacturing method

1) The composition for forming an alignment film was applied to the TAC film side in the following manner.

First, a primary corona treatment was performed on the TAC film side. The conditions for the corona treatment were 0.3kW output and a treatment speed of 3 m/min. Thereafter, the composition (D-1) obtained as described above was coated on the TAC by a bar coating method, and dried by heating in a drying oven at 80℃for 1 minute. The obtained dried film was subjected to polarized UV irradiation treatment to form a 1 st alignment film (AL 1). The polarized UV treatment was carried out by passing light irradiated by a UV irradiation device (SPOTCURE SP-7; manufactured by Uso Motor Co., ltd.) through a wire grid (UIS-27132 #, manufactured by Uso Motor Co., ltd.) and measuring the cumulative light quantity at a wavelength of 365nm at 100mJ/cm ² Is carried out under the condition of (2). The 1 st alignment film (AL 1) has a thickness of 100nm.

2) The composition for forming a polarizer layer was applied to the alignment film side in the following manner.

First, the composition (a-1) was applied to the 1 st alignment film (AL 1) formed by the bar coating method, and after drying by heating in a drying oven at 120 ℃ for 1 minute, it was cooled to room temperature. Using the above UV irradiationDevice for accumulating 1200mJ/cm of light ² Ultraviolet rays were irradiated to the dried film (365 nm basis), thereby forming a polarizer layer (pol). The thickness of the resulting polarizer layer (pol) was measured by a laser microscope (OLS 3000 manufactured by Olympus Co., ltd.) and found to be 1.8. Mu.m. In this manner, a laminate composed of "TAC/AL1/pol" was obtained.

3) The protective layer (OC layer) forming composition was applied to the polarizer layer side in the following manner.

The composition (E-1) was applied to the polarizer layer (pol) thus formed by bar coating, and dried at 80℃for 3 minutes so that the thickness of the composition after drying became 1.0. Mu.m. In this manner, a laminate composed of "TAC film/cPL (al1+pol+protective layer)" was obtained.

[ phase-difference layer ]

1. Material preparation

The following materials were prepared.

1) A PET film having a thickness of 100 μm.

2) Composition for forming an alignment film.

< Polymer 1 >)

3) Composition for forming retardation layer

The following components were mixed, and the resulting mixture was stirred at 80℃for 1 hour, thereby obtaining a composition (B-1).

A compound b-1 represented by the following formula: 80 parts by mass

A compound b-2 represented by the following formula: 20 parts by mass

Polymerization initiator (Irgacure 369, 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one, manufactured by BASF Japan Co., ltd.): 6 parts by mass

Leveling agent (BYK-361N, polyacrylate compound, manufactured by BYK-Chemie Co.): 0.1 part by mass

Solvent (cyclopentanone): 400 parts by mass

2. Manufacturing method

1) The composition for forming an alignment film was applied to the PET film in the following manner.

A polyethylene terephthalate film (PET) having a thickness of 100 μm was prepared as a base material, and the composition (D-1) was applied to the film by a bar coating method, and dried by heating in a drying oven at 80℃for 1 minute. The obtained dried film was subjected to polarized UV irradiation treatment to form a 2 nd alignment film (AL 2). Polarized UV treatment Using the above UV irradiation apparatus, the cumulative light amount measured at 365nm wavelength was 100mJ/cm ² Is carried out under the condition of (2). In addition, the polarized UV was polarized in such a manner that the polarization direction was 45 ° with respect to the absorption axis of the polarizer layer. In this manner, a laminate composed of "substrate (PET)/2 nd alignment film (AL 2)" was obtained.

2) The composition for forming a retardation layer was applied to the orientation film side of the PET film in the following manner.

On the 2 nd orientation film (AL 2) of the 1 st substrate obtained in this manner, the composition (B-1) was applied by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. The obtained dry film was irradiated with an accumulated light of 1000mJ/cm using the UV irradiation apparatus ² Ultraviolet rays (365 nm basis), thereby forming a retardation layer. The thickness of the retardation layer was measured by a laser microscope (OLS 3000 manufactured by Olympus Co., ltd.) and found to be 2.0. Mu.m. The retardation layer is a lambda/4 plate (QWP) exhibiting a retardation value of lambda/4 in the in-plane direction. In this manner, a laminate composed of "substrate (PET)/AL 2/QWP" was obtained.

[ common adhesive sheet ]

1) Polymerization of acrylic resins

The following components were reacted at 55℃while stirring them under a nitrogen atmosphere, whereby an acrylic resin was obtained.

Butyl acrylate: 70 parts by mass

Methyl acrylate: 20 parts by mass

Acrylic acid: 2.0 parts by mass

Radical polymerization initiator (2, 2' -azobisisobutyronitrile): 0.2 part by mass

2) Liquid conditioning of adhesive composition

The following ingredients were mixed to obtain an adhesive composition.

Acrylic resin: 100 parts by mass

Crosslinking agent (Coronate L, tosoh Co.): 1.0 part by mass

Silane coupling agent ("X-12-981" manufactured by singe silicon corporation): 0.5 part by mass

Ethyl acetate was added so that the total solid content concentration became 10 mass%, to obtain a binder composition.

3) Production of adhesive sheet

The obtained adhesive composition was applied to the release treated surface of a release treated polyethylene terephthalate film (heavy separator, thickness 38 μm) with an applicator so that the thickness after drying became 5 μm. The coating layer was dried at 100 ℃ for 1 minute to obtain a film having an adhesive layer. Thereafter, another polyethylene terephthalate film (light separator, thickness 38 μm) subjected to release treatment was laminated on the exposed surface of the adhesive layer. Thereafter, the mixture was cured at a temperature of 23℃and a relative humidity of 50% RH for 7 days to obtain a light separator/common adhesive layer/heavy separator.

Example 1

The laminate was produced by the steps shown in fig. 4 (a) to (e). First, a laminate 410 including the above-described polarizer layer [ tac film 301/cPL ((al1+pol) 302/OC layer 303) ] and the above-described common adhesive sheet 420 (light separator 304/common adhesive layer 305/heavy separator 306) ] are prepared (fig. 4 (a)). The OC layer 303 side of the laminate 410 including the polarizer layer and the surface of the common adhesive sheet 420 from which the light separator 304 was peeled were subjected to corona treatment (output 0.3KW, speed 3 m/min), and then laminated to obtain a laminate a430. The retardation layer 440[ base material (PET) 308/AL2/QWP 307] (fig. 4 (b)) was prepared.

Next, the surface of the heavy separator 306 on the QWP 307 side from which the retardation layer 440 was peeled off and the laminate a 430 was subjected to corona treatment (output 0.3KW, speed 3 m/min), and then bonded to obtain a laminate b 450. Thereafter, the adhesive sheet a12 produced as described above was prepared as the adhesive sheet 460 (light separator 309/adhesive layer 310/heavy separator 311) (fig. 4 (c)). The adhesive layer 310 of the adhesive sheet 460 corresponds to the 2 nd adhesive layer.

The surface of laminate b450 from which the base material (PET) 308 was peeled off and the surface of the adhesive sheet 460 from which the light separator 309 was peeled off were subjected to corona treatment (output 0.3KW at a speed of 3 m/min), and then laminated to obtain laminate c470. Further, the adhesive sheet a11 produced as described above was prepared as an adhesive sheet 490 (light separator 314/adhesive layer 315/heavy separator 316), and the surface from which the light separator 314 was peeled off and the polyimide film 313 side of the front panel 480 (polyimide film 313/hard coat layer 312) were subjected to corona treatment (output 0.3KW, speed 3 m/min), and then laminated to obtain a laminate d500 (fig. 4 (d)). The adhesive layer 315 of the adhesive sheet 490 corresponds to the 1 st adhesive layer.

The surface of laminate d500 from which heavy separator 316 was peeled off and TAC film 301 side of laminate c470 were subjected to corona treatment (output 0.3KW, speed 3 m/min), and then laminated to obtain laminate 300 of example 1 (fig. 4 (e)). The laminate of example 1 was evaluated for normal temperature bendability and normal temperature adhesion durability by the method described below. The results are shown in Table 4.

Examples 2 to 5 and comparative examples 1 and 2

Laminates of examples 2 to 5 and comparative examples 1 and 2 were produced in the same manner as in example 1, except that the adhesive sheets a11 and a12 were replaced with the adhesive sheets having the adhesive layers shown in table 4 in example 1. The laminates of examples 2 to 5 and comparative examples 1 and 2 were evaluated for normal temperature bendability and normal temperature adhesion durability by the method described below. The results are shown in Table 4.

< bending at Normal temperature >

The laminate obtained in each example and each comparative example was subjected to an evaluation test for confirming normal temperature bendability using a bending apparatus (STS-VRT-500, manufactured by Science Town). The heavy separator 311 was peeled off and bonded to a PET film having a thickness of 100 μm to obtain a laminate. The PET film corresponds to the back plate. Fig. 3 is a diagram schematically showing a method of the evaluation test. As shown in fig. 3, two placement tables 501 and 502 each movable are arranged so that the gap C becomes 6.0mm (3R), and the laminate is fixedly arranged with the center in the width direction at the center of the gap C and the hard coat layer 312 at the upper side (fig. 3 a). Then, the two tables 501 and 502 are rotated upward by 90 degrees about the center of the rotation axis at the positions P1 and P2, and a bending force (bending force for setting the front panel 480 inward) is applied to the region of the laminate corresponding to the gap C between the tables (fig. 3 (b)). Thereafter, the two tables 501 and 502 are returned to the original positions (fig. 3 (a)). The above series of operations were completed, and the number of times of application of the bending force was counted as 1. After repeating this at a temperature of 25 ℃, it was confirmed whether or not air bubbles in the adhesive layer were generated in the region of the laminate corresponding to the gap C between the tables 501 and 502. The movement speed of the tables 501 and 502 and the bending force application step were the same conditions in the evaluation test for each laminate. The "adhesive peeling" means that the adhesive layer oozes out from the end portion of the laminate.

A: no bubbles were generated even when the bending force was applied for 20 ten thousand times.

B: the number of times of application of the bending force is 15 ten thousand or more and less than 20 ten thousand, and bubbles are generated.

C: the number of times of application of the bending force is 10 ten thousand or more and less than 15 ten thousand, and bubbles are generated.

D: the number of times of application of the bending force is 5 ten thousand or more and less than 10 ten thousand, and bubbles are generated.

E: the number of bending force applications is less than 5 ten thousand times to generate bubbles/adhesive shedding.

< high temperature adhesion durability >)

The laminate obtained in each example and each comparative example was cut into a width of 100mm×a length of 100mm. The heavy separator 311 was peeled off and bonded to alkali-free glass. The mixture was autoclaved (50 ℃ C., 5 atm) for about 20 minutes and kept at constant temperature and humidity (23 ℃ C., 50% RH) for 4 hours. The sample was placed in an oven at 85 ℃ and after 250 hours, the presence or absence of floating, flaking, and bubbles was judged. In the laminated body, the alkali-free glass corresponds to the back plate.

O: hardly any change in appearance such as floating, flaking, foaming, etc. was observed.

Delta: the appearance changes such as floating, flaking, foaming, etc. were slightly observed.

X: the appearance changes of floating, flaking, foaming and the like are obvious.

TABLE 4

Examples 1 to 5 satisfy the relationship "R1 > R2", and R1 and R2 are both contained in the range of 10 to 20 mass%.

Symbol description

100. 200 laminated body, 101 front panel, 102 1 st adhesive layer, 103 polarizer layer, 104 nd adhesive layer, 105 back panel, 106 1 st phase difference layer, 107 nd phase difference layer, 108, 109 lamination layer, 301TAC film, 302pol,303oc layer, 305 common adhesive layer, 306, 311, 316 heavy separator, 307qwp,308 base material, 304, 309, 314 light separator, 310, 315 adhesive layer, 312 hard coat layer, 313 polyimide film, 410 laminated body including polarizer layer, 420 common adhesive sheet, 430 laminated body a,440 phase difference layer, 450 laminated body b,460, 490 adhesive sheet, 470 laminated body c,500 laminated body d,501, 502 mounting table.

Claims

1. A laminate comprising, in order, a front panel, a 1 st adhesive layer, a polarizer layer, a 2 nd adhesive layer, and a back panel, wherein the 1 st adhesive layer is formed using a 1 st adhesive composition, the 2 nd adhesive layer is formed using a 2 nd adhesive composition,

if the thermal decomposition mass reduction rate of the 1 st adhesive layer is R1 and the thermal decomposition mass reduction rate of the 2 nd adhesive layer is R2, the following relational expressions (1), (2) and (3) are satisfied:

R1＞R2 （1），

10≤R1≤20 （2），

10≤R2≤20 （3），

the front panel comprises a resin plate-shaped body, a glass plate-shaped body or a touch sensor panel,

The laminate can be repeatedly bent 10 ten thousand times with the front panel side being the inner side and with the bending radius of the inner surface of the laminate being 3 mm.

2. The laminate according to claim 1, wherein the 1 st adhesive composition and the 2 nd adhesive composition each comprise a (meth) acrylic polymer,

3. The laminate according to claim 1 or 2, wherein the 1 st adhesive layer and the 2 nd adhesive layer each contain a (meth) acrylic polymer,

the weight average molecular weight Mw of the (meth) acrylic polymer is 20 to 150 ten thousand.

4. The laminate according to claim 1 or 2, wherein the back panel is a touch sensor panel.

5. A laminate according to claim 3, wherein the back panel is a touch sensor panel.

6. A display device comprising the laminate according to any one of claims 1 to 5.

7. The display device according to claim 6, wherein the front panel side is curved inward.