CN113574428A

CN113574428A - Laminate and display device comprising same

Info

Publication number: CN113574428A
Application number: CN202080021497.9A
Authority: CN
Inventors: 李昇祐; 金正熙
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2019-03-18
Filing date: 2020-02-18
Publication date: 2021-10-29
Also published as: TW202039236A; WO2020189145A1; KR20210141518A; JP6935530B2; JP2020154308A

Abstract

The invention provides a laminate which is improved in durability by suppressing the generation of air bubbles in an adhesive layer. The invention provides a laminated body, which sequentially comprises a front panel, a1 st adhesive layer formed by using a1 st adhesive composition, a polarizer layer, a 2 nd adhesive layer formed by using a 2 nd adhesive composition and a back panel; in the case where the 1 st adhesive reference layer is formed using the 1 st adhesive composition and the 2 nd adhesive reference layer is formed using the 2 nd adhesive composition in such a manner that the thickness of the 1 st adhesive reference layer and the thickness of the 2 nd adhesive reference layer become the same, the 1 st adhesive reference layer and the 2 nd adhesive reference layer satisfy a relationship of Δ R1 ≦ Δ R2.

Description

Laminate and display device comprising same

Technical Field

The present invention relates to a laminate and a display device thereof.

Background

Korean patent No. 10-2016 and 0053788 (patent document 1) and korean patent No. 10-2017 and 0093610 (patent document 2) each describe a laminate for a display device having a plurality of adhesive layers.

Documents of the prior art

Patent document

Patent document 1, Korean patent No. 10-2016-

Patent document 2, korean patent No. 10-2017-0093610 specification

Disclosure of Invention

The pressure-sensitive adhesive layer used in such a laminate is generally excellent in stress relaxation performance for relaxing external stress. However, when the laminate is bent at room temperature, bubbles are often generated in the pressure-sensitive adhesive layer, and therefore, it is required to improve the durability of the pressure-sensitive adhesive layer.

In view of the above circumstances, an object of the present invention is to provide a laminate having improved durability by suppressing the generation of bubbles in an adhesive layer, and a display device including the laminate.

The invention provides the following laminated body and display device comprising the same.

[1] A laminate comprising, in order: a front panel, a1 st adhesive layer formed using the 1 st adhesive composition, a polarizer layer, a 2 nd adhesive layer formed using the 2 nd adhesive composition, and a back panel;

in the case where the 1 st adhesive reference layer is formed using the 1 st adhesive composition and the 2 nd adhesive reference layer is formed using the 2 nd adhesive composition such that the thickness of the 1 st adhesive reference layer and the thickness of the 2 nd adhesive reference layer become the same, the 1 st adhesive reference layer and the 2 nd adhesive reference layer satisfy the following relationship (1):

ΔR1≤ΔR2 (1)

[ in the formula (1),. DELTA.R 1 represents a value obtained by subtracting R1B from R1A,

Δ R2 represents the value of R2A minus R2B,

R1A represents the 1 st shear creep rate (%/μm) which is the shear creep value per 1 μm thickness at 25 ℃ determined for the 1 st adhesive reference layer after the repeated deformation test,

R1B represents the 2 nd shear creep rate (%/μm) determined as the shear creep value per 1 μm thickness at 25 ℃ of the 1 st adhesive reference layer before the repeated strain application test is performed,

R2A represents the 3 rd shear creep rate (%/μm) which is the shear creep value per 1 μm thickness at 25 ℃ determined for the 2 nd adhesive reference layer after the repeated deformation test,

R2B represents the 4 th shear creep rate (%/μm) as a value of shear creep per 1 μm thickness at 25 ℃ determined for the 2 nd adhesive reference layer before the repeated deformation test.

The laminate according to [1], wherein the 2 nd shear creep rate (%/μm) is 0.1 to 0.2.

The laminate according to [1] or [2], wherein at least one of the 1 st adhesive layer and the 2 nd adhesive layer has a thickness of 20 μm to 50 μm.

The laminate according to any one of [1] to [3], wherein 1 or more retardation layers are provided between the polarizer layer and the back sheet.

The laminate according to any one of [1] to [4], wherein the back panel is a touch sensor panel.

A display device comprising the laminate according to any one of [1] to [ 5 ].

[ 7] the display device according to [ 6], which can be bent with the front panel side as an inner side.

According to the present invention, a laminate having improved durability by suppressing the generation of bubbles in an adhesive layer and a display device including the laminate can be provided.

Drawings

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

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

Fig. 3 is a sectional view of a laminate according to the present invention, schematically showing a method for producing the laminate.

Detailed Description

A laminate according to an embodiment of the present invention (hereinafter simply referred to as "laminate") will be described below 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 a front plate 101, a1 st adhesive layer 102 formed using a1 st adhesive composition, a polarizer layer 103, a 2 nd adhesive layer 104 formed using a 2 nd adhesive composition, and a back plate 105 in this order. Hereinafter, the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 are collectively referred to as "adhesive layers".

The thickness of the laminate 100 is not particularly limited, and is, for example, 30 to 1500 μm, preferably 40 to 1000 μm, and more preferably 50 to 500 μm, since it varies depending on the functions required for the laminate, the application of the laminate, and the like.

The planar view shape of the laminate 100 may be, for example, a square shape, preferably a square shape having a long side and a short side, and more preferably a rectangle. When the shape of the laminate 100 in the plane direction is rectangular, the length of the long side may be, for example, 10mm to 1400mm, and preferably 50mm to 600 mm. The length of the short side may be, for example, 5mm to 800mm, preferably 30mm to 500mm, and more preferably 50mm to 300 mm. In each layer constituting the laminate, the corner portion may be subjected to R processing, and the end portion may be subjected to notch processing or punching processing.

The laminate 100 is suitable for use 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, and an electroluminescence display device. The display device may have a touch panel function. Further, the display device to which the laminate 100 is applied can be used as a flexible display which can be bent, rolled, or the like. The display device is preferably curved with the front panel 101 side being inside. However, the laminate 100 may be curved with the front panel 101 side as the outer side.

Adhesive layer (1 st adhesive layer formed using 1 st adhesive composition and 2 nd adhesive layer formed using 2 nd adhesive composition) ]

As described above, the laminate 100 contains the 1 st adhesive layer 102 formed using the 1 st adhesive composition and the 2 nd adhesive layer 104 formed using the 2 nd adhesive composition. In the laminate 100, the following relationship is established between the 1 st adhesive composition for forming the 1 st adhesive layer 102 and the 2 nd adhesive composition for forming the 2 nd adhesive layer 104. That is, in the case where the 1 st adhesive reference layer is formed using the 1 st adhesive composition and the 2 nd adhesive reference layer is formed using the 2 nd adhesive composition such that the thickness of the 1 st adhesive reference layer and the thickness of the 2 nd adhesive reference layer become the same, the 1 st adhesive reference layer and the 2 nd adhesive reference layer satisfy the relationship of the following formula (1): the thickness of the 1 st adhesive reference layer and the thickness of the 2 nd adhesive reference layer may be, for example, 200 μm.

ΔR1≤ΔR2 (1)

Δ R2 represents the value of R2A minus R2B,

R1A represents the 1 st shear creep rate (%/μm) determined as the shear creep value per 1 μm thickness at 25 ℃ of the 1 st adhesive reference layer after the repeated deformation application test,

R1B represents the 2 nd shear creep rate (%/μm) per 1 μm thickness at 25 ℃ determined for the 1 st adhesive reference layer before the deformation repeated application test was performed,

R2A represents the 3 rd shear creep rate (%/μm) per 1 μm thickness at 25 ℃ determined for the 2 nd adhesive reference layer after the repeated deformation application test,

R2B represents the 4 th shear creep rate (%/μm) as a value of shear creep per 1 μm thickness at 25 ℃ determined for the 2 nd adhesive reference layer before the deformation repeated application test was performed.

The shear creep value (%) at 25 ℃, the 1 st shear creep rate (%/μm) indicating R1A, the 2 nd shear creep rate (%/μm) indicating R1B, the 3 rd shear creep rate (%/μm) indicating R2A, and the 4 th shear creep rate (%/μm) indicating R2B were determined by the measurement methods described in the first column of examples to be described later, respectively.

In the laminate 100, the 1 st and 2 nd

adhesive layers

102 and 104, which are the adhesive layers included therein, can be formed by using the 1 st and 2 nd adhesive compositions that can form the 1 st and 2 nd adhesive reference layers satisfying the relationship of the above formula (1). In this case, the laminate 100 can improve durability by suppressing the generation of bubbles in the adhesive layer. In particular, when the front panel 101 is bent inward, the laminate 100 can further suppress the generation of air bubbles in the adhesive layer. Therefore, the laminate 100 is suitable for use in a laminate of a type in which the front panel side is bent inward (so-called fold-in type), and a display device including the laminate. The 1 st adhesive reference layer and the 2 nd adhesive reference layer preferably satisfy the relationship of the formula (2) represented by Δ R1 < Δ R2.

The above-described effects are obtained when the 1 st pressure-sensitive adhesive layer 102 and the 2 nd pressure-sensitive adhesive layer 104 are formed of the 1 st pressure-sensitive adhesive composition and the 2 nd pressure-sensitive adhesive composition that can constitute the 1 st pressure-sensitive adhesive reference layer and the 2 nd pressure-sensitive adhesive reference layer satisfying the relationship of the above-described formula (1), respectively, and the reason for this is not specifically described, but it is considered that the following mechanism is caused. First, in the course of a study conducted by the present inventors and the like, it was found that: when the laminate is bent with the front panel side being the inner side, air bubbles may be generated in the pressure-sensitive adhesive layer, and in this case, the air bubbles are generated in many places near the 1 st pressure-sensitive adhesive layer side which is the pressure-sensitive adhesive layer on the front panel side.

Here, in the case where the 1 st adhesive reference layer and the 2 nd adhesive reference layer satisfy the relationship of the above formula (1), the 1 st adhesive composition is a composition having the same or less change in shear creep rate (%/μm) before and after repeated deformation application as compared to the 2 nd adhesive composition. Further, the feature that the change in shear creep rate (%/μm) is small means that the adhesive layer is excellent in performance (i.e., durability) capable of maintaining the properties inherent in the adhesive layer against external stress. Therefore, it is considered that the adhesive layer formed using the 1 st adhesive composition (the 1 st adhesive layer 102) can be made to have the same or more excellent durability against bending as compared with the adhesive layer formed using the 2 nd adhesive composition (the 2 nd adhesive layer 104).

From the above, the present inventors configured an adhesive layer (1 st adhesive layer 102) formed using the 1 st adhesive composition, which has excellent durability against bending, as an adhesive layer on the front panel side where bubbles are frequently generated. Thus, when the laminate 100 is bent with the front panel 101 side facing inward, the laminate 100 can suppress the generation of air bubbles in the pressure-sensitive adhesive layer. Specifically, as shown in the examples described below, when the laminate 100 is folded along a mandrel bar (mandrel) which is a cylindrical jig having a diameter (Φ) of more than 10mm and 15mm or less, the laminate 100 is disposed inside the front panel 101, the generation of bubbles in the adhesive layer can be suppressed (such a performance is hereinafter referred to as "excellent bending durability").

In the present specification, "bent" includes a bent form in which a curved surface is formed at a bent portion. In the bent form, the radius of curvature of the inner surface to be bent is not limited, unless otherwise specified. The term "bend" includes, unless otherwise specified, a bent form in which the inner surface has a bending angle of more than 0 degrees and less than 180 degrees, and a folded form in which the inner surface has a radius of curvature of approximately zero or a bending angle of 0 degrees.

The values of Δ R1 and Δ R2 are preferably 0.01 to 4, more preferably 0.05 to 0.5, and particularly preferably 0.05 to 0.2, respectively.

The 1 st shear creep rate R1A (%/μm) is preferably 0.05 to 1.0, more preferably 0.2 to 0.5. The 2 nd shear creep rate R1B (%/μm) is preferably 0.01 to 0.3, more preferably 0.05 to 0.2. The 3 rd shear creep rate R2A (%/μm) is preferably 0.05 to 1.0, more preferably 0.2 to 0.5. The 4 th shear creep rate R2B (%/μm) is preferably 0.01 to 0.3, more preferably 0.05 to 0.2.

In the laminate 100, the 2 nd shear creep rate (%/μm) is preferably 0.1 to 0.2. In this case, the 1 st adhesive layer 102 is an adhesive layer having appropriate hardness in addition to excellent flexibility and durability, and thus can impart excellent surface hardness to the laminate 100. Specifically, as shown in examples described later, when a load of 100g was applied to the surface of the front plate 101 of the laminated body 100 using a pencil having a lead hardness of 6B, the recessed portion formed on the surface was able to disappear in less than 1 hour (such a property is hereinafter also referred to as "excellent surface hardness").

The gel fraction of the adhesive layer may be 40% to 90%, or 50% to 80%. The gel fraction of the pressure-sensitive adhesive layer can be measured by the method described in the examples below.

In the laminate 100, at least one of the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 preferably has a thickness of 20 to 50 μm.

Here, as a method for preparing the 1 st adhesive composition and the 2 nd adhesive composition constituting the 1 st adhesive reference layer and the 2 nd adhesive reference layer satisfying the relationship of the above formula (1), for example, there can be mentioned: these may be formed from the adhesive composition a described later, or the types of monomers constituting the (meth) acrylic polymer a described later may be changed, or the molecular weight of the (meth) acrylic polymer a may be adjusted. The adhesive composition a will be specifically described below.

< adhesive composition A >)

The 1 st adhesive layer 102 and the 2 nd adhesive layer 104 have different compositions, but both can be formed of an adhesive composition containing a (meth) acrylic polymer (hereinafter referred to as an adhesive composition a) in one embodiment. 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 1 selected from acrylic polymers and methacrylic polymers. The same applies to other terms with "(methyl)". When 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 referred to as "(meth) acrylic polymer a".

(active energy ray-curable adhesive composition)

When the pressure-sensitive adhesive composition a is an active energy ray-curable pressure-sensitive adhesive composition, the structural unit derived from the monomer having a reactive functional group in the (meth) acrylic polymer a contained in the pressure-sensitive adhesive composition a is preferably 1% by mass or less 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 improves the flexibility of the pressure-sensitive adhesive layer, and tends to easily suppress the generation of bubbles in the pressure-sensitive adhesive layer at room temperature. In the (meth) acrylic polymer a, from the viewpoint of suppressing the generation of bubbles at the time of bending, the structural unit derived from the monomer having a reactive functional group is more preferably 0.01% by mass or less based on the total mass of the polymer, and further preferably, no structural unit derived from the monomer having a reactive functional group is present, and further preferably, no hydroxyl group, carboxyl group, amino group, amide group, and epoxy group is present.

The (meth) acrylic polymer A may contain a structural 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) acrylates, such as 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 having 1 or 2 or more of the above-mentioned alkyl (meth) acrylates as a monomer. The content of the (meth) acrylic polymer a in the pressure-sensitive adhesive composition a is, for example, 50 to 100 mass%, preferably 80 to 99.5 mass%, and more preferably 90 to 99 mass% with respect to 100 parts by mass of the solid content of the pressure-sensitive adhesive composition a.

The weight average molecular weight (Mw) of the (meth) acrylic polymer a may be, for example, 10 to 200 ten thousand, and preferably 50 to 150 ten thousand from the viewpoint of suppressing bubbles at the time of bending. The weight average molecular weight in the present specification can be determined based on a value in terms of standard polystyrene measured by a Gel Permeation Chromatography (GPC) method, as described in the column of examples described below.

The adhesive composition a may contain 1 or 2 or more (meth) acrylic polymers a. The pressure-sensitive 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 crosslinking agent which forms a carboxylate metal salt between carboxyl groups in a metal ion having a valence of 2 or more; a crosslinking agent which forms an amide bond between carboxyl groups in the polyamine compound; a crosslinking agent which forms an ester bond between carboxyl groups in a polyepoxy compound or polyol; and a crosslinking agent which forms an amide bond between carboxyl groups in the polyisocyanate compound. Among them, polyisocyanate compounds are preferable. When the pressure-sensitive adhesive composition a contains a crosslinking agent, the content of the crosslinking agent may be, for example, 5 parts by mass or less, preferably 3 parts by mass or less, more preferably 1 part by mass or less, and still more preferably 0.5 part by mass or less, relative to 100 parts by mass of the (meth) acrylic polymer a. The adhesive composition a sometimes does not contain a crosslinking agent.

The active energy ray-curable adhesive composition is an adhesive composition having a property of being cured by irradiation with an active energy ray such as an ultraviolet ray or an electron beam, and also having a property of having an adhesive property before the irradiation with the active energy ray, thereby being closely adhered to an adherend such as a film, and being cured by the irradiation with the active energy ray to adjust the adhesion force or the like. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition.

When the pressure-sensitive adhesive composition a is an active energy ray-curable pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition a may further contain an active energy ray-polymerizable compound, a photopolymerization initiator, a photosensitizer, and the like.

Examples of the active energy ray-polymerizable compound include (meth) acrylate monomers having at least 1 (meth) acryloyloxy group in the molecule; a (meth) acrylic compound such as a (meth) acryloyloxy group-containing compound such as a (meth) acrylate oligomer having at least 2 (meth) acryloyloxy groups in the molecule, which is obtained by reacting 2 or more kinds of functional group-containing compounds. The binder 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 binder composition a.

Examples of the photopolymerization initiator include benzophenone, benzyl dimethyl ketal, and 1-hydroxycyclohexyl ketone. When the adhesive composition a contains a photopolymerization initiator, 1 or 2 or more species may be contained. If the adhesive composition a contains a photopolymerization initiator, for example, the total content of the photopolymerization initiator may be 0.01 to 1.0 part by mass with respect to 100 parts by mass of the solid components of the adhesive composition a.

The adhesive composition a may contain additives such as fine particles, beads (resin beads, glass beads, and the like), glass fibers, resins other than the base polymer, adhesion-imparting agents, fillers (metal powder, other inorganic powder, and the like), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoaming agents, and corrosion inhibitors, which impart light scattering properties. From the viewpoint of preventing the problem of reduction in durability due to residual solvent, the adhesive composition a preferably does not contain an 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 a substrate. When an active energy ray-curable pressure-sensitive adhesive composition is used, a cured product having a desired degree of curing can be obtained by irradiating the pressure-sensitive adhesive layer formed with an active energy ray.

(Heat-curable adhesive composition)

When the pressure-sensitive adhesive composition a is a heat-curable pressure-sensitive adhesive composition, the (meth) acrylic polymer a preferably contains, as monomer units constituting the polymer, an alkyl (meth) acrylate having an alkyl group and 2 to 20 carbon atoms and a monomer having a reactive functional group in a molecule (reactive functional group-containing monomer). When the adhesive composition a is a thermosetting adhesive composition, it preferably further contains a thermal crosslinking agent.

In the (meth) acrylic polymer A, preferable adhesiveness can be exhibited by using an alkyl (meth) acrylate having an alkyl group and 2 to 20 carbon atoms as a monomer unit constituting the polymer. The alkyl (meth) acrylate having an alkyl group with 2 to 20 carbon atoms preferably contains a homopolymer having a glass transition temperature (Tg) of-40 ℃ or lower (hereinafter, also referred to as "low Tg alkyl acrylate"). By containing the low Tg alkyl acrylate as a constituent monomer unit, the flexibility of the pressure-sensitive adhesive layer is improved, and therefore, the generation of bubbles during bending can be more easily suppressed. The glass transition temperature (Tg) of the (meth) acrylic polymer a can be determined by using a conventionally known method such as Differential Thermal Analysis (DTA).

Examples of the low Tg alkyl acrylate include n-butyl acrylate (Tg-54 ℃ C.), n-octyl acrylate (Tg-65 ℃ C.), isooctyl acrylate (Tg-58 ℃ C.), 2-ethylhexyl acrylate (Tg-70 ℃ C.), isononyl acrylate (Tg-58 ℃ C.), isodecyl acrylate (Tg-60 ℃ C.), isodecyl methacrylate (Tg-41 ℃ C.), n-lauryl methacrylate (Tg-65 ℃ C.), tridecyl acrylate (Tg-55 ℃ C.), and tridecyl methacrylate (-40 ℃ C.). Among them, the low Tg alkyl acrylate is more preferably a homopolymer having a Tg of-45 ℃ or lower, particularly preferably-50 ℃ or lower. In particular, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. These may be used alone, or 2 or more of them may be used in combination.

The lower limit of the monomer unit constituting the (meth) acrylic polymer a is preferably 85 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more of the low Tg alkyl acrylate.

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

From the viewpoint of further exhibiting the effects of the present invention, the content of a monomer having a glass transition temperature (Tg) of more than 0 ℃ as a homopolymer (hereinafter, may be referred to as "hard monomer") in the (meth) acrylic polymer a is preferably as small as possible. Specifically, the content of the hard monomer in the (meth) acrylic polymer a is preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 5% by mass or less, as an upper limit 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 (Tg10 ℃ C.), methyl methacrylate (Tg105 ℃ C.), ethyl methacrylate (Tg65 ℃ C.), n-butyl methacrylate (Tg20 ℃ C.), isobutyl methacrylate (Tg48 ℃ C.), tert-butyl methacrylate (Tg107 ℃ C.), n-stearyl acrylate (Tg30 ℃ C.), n-stearyl methacrylate (Tg38 ℃ C.), cyclohexyl acrylate (Tg15 ℃ C.), cyclohexyl methacrylate (Tg66 ℃ C.), phenoxyethyl acrylate (Tg5 ℃ C.), phenoxyethyl methacrylate (Tg54 ℃ C.), benzyl methacrylate (Tg54 ℃ C.), isobornyl acrylate (Tg94 ℃ C.), isobornyl methacrylate (Tg180 ℃ C.), acryloylmorpholine (Tg145 ℃ C.), adamantyl acrylate (Tg115 ℃ C.), adamantyl methacrylate (Tg141 ℃ C.), acrylic acid (Tg105 ℃ C.), dimethylacrylamide (Tg89 ℃ C.), and so forth, Acrylic monomers such as acrylamide (Tg165 ℃ C.), vinyl acetate (Tg32 ℃ C.), styrene (Tg80 ℃ C.), and the like.

The (meth) acrylic polymer a contains a reactive functional group-containing monomer as a monomer unit constituting the polymer, and thus reacts with a thermal crosslinking agent described later through a reactive functional group derived from the reactive functional group-containing monomer. Thereby, a crosslinked structure (three-dimensional network structure) is formed as a whole, and an adhesive having a desired cohesive force can be obtained.

The reactive functional group-containing monomer contained in the (meth) acrylic polymer a as a monomer unit constituting the polymer includes, preferably, 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), and the like. Among them, the hydroxyl group-containing monomer is particularly preferable because the glass transition temperature (Tg) is usually 0 ℃ or lower.

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 these, at least one of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate is preferable from the viewpoint of the glass transition temperature (Tg), the reactivity of the hydroxyl group in the obtained (meth) acrylic polymer a with a thermal crosslinking agent, and the copolymerizability with other monomers. These may be used alone, or 2 or more of them may be used in combination.

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 2 or more of them may be used in combination.

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

The lower limit of the monomer unit constituting the (meth) acrylic polymer a is preferably 0.1 mass% or more, particularly preferably 0.5 mass% or more, and more preferably 1 mass% or more of the reactive functional group-containing monomer. The lower limit of the content of the reactive functional group-containing monomer in the (meth) acrylic polymer a is preferably 10% by mass or less, more preferably 8% by mass or less, and still more preferably 5% by mass or less. This tends to more easily suppress the generation of air bubbles during bending.

In the (meth) acrylic polymer a, as a monomer unit constituting the polymer, acrylic acid as a hard monomer may not be contained in some cases. Since the carboxyl group is an acid component, the presence of no carboxyl group-containing monomer can suppress the occurrence of defects caused by an acid on the object to which the adhesive is attached, and for example, even when a transparent conductive film such as tin-doped indium oxide (ITO), a metal film, a metal mesh, or the like is present, the occurrence of such defects (corrosion, a change in resistance value, or the like) caused by an acid can be suppressed.

The (meth) acrylic polymer a may contain other monomers as a monomer unit constituting the polymer, as desired. The other monomer is preferably a monomer not containing a reactive functional group because it does not interfere with the action of the reactive functional group-containing monomer. Examples of the other monomer include, in addition to alkoxyalkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate, a monomer having a glass transition temperature (Tg) of a homopolymer of more than-40 ℃ and not more than 0 ℃ (hereinafter, sometimes referred to as "medium Tg alkyl acrylate"). Examples of the medium Tg alkyl acrylate include ethyl acrylate (Tg-20 ℃ C.), isobutyl acrylate (Tg-26 ℃ C.), 2-ethylhexyl methacrylate (Tg-10 ℃ C.), n-lauryl acrylate (Tg-23 ℃ C.), and isostearyl acrylate (Tg-18 ℃ C.). These may be used alone, or 2 or more of them may be used in combination.

The polymerization system 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 more preferably 40 ten thousand or more. When the lower limit of the weight average molecular weight of the (meth) acrylic polymer a is not less than the above range, troubles such as leaching of the binder can be suppressed. The weight average molecular weight in the present specification can be determined based on a value in terms of standard polystyrene measured by a Gel Permeation Chromatography (GPC) method, as described in the column of examples described below.

The upper limit of the weight average molecular weight of the (meth) acrylic polymer a is preferably 200 ten thousand or less, particularly preferably 150 ten thousand or less, and further preferably 130 ten thousand or less. When the upper limit of the weight average molecular weight of the (meth) acrylic polymer a is the above-mentioned or less, the flexibility of the pressure-sensitive adhesive layer can be secured, and the effects of the present invention can be easily exhibited.

In the 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.

When the adhesive composition A containing a thermal crosslinking agent is heated, the thermal crosslinking agent crosslinks the (meth) acrylic polymer A to form a three-dimensional network structure. This can improve cohesive force while ensuring flexibility of the binder, and when the adhesive is applied to a laminate, the adhesive can have hardness that can improve surface hardness of the laminate.

The thermal crosslinking agent may be any agent that can react 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, oxazoline-based crosslinking agents, metal alkoxide-based crosslinking agents, metal complex-based crosslinking agents, metal salt-based crosslinking agents, and ammonium salt-based crosslinking agents. 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 in 1 kind, or may be used in combination of 2 or more kinds.

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

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

The content of the thermal crosslinking agent in the adhesive composition a is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more, relative to 100% by mass of the (meth) acrylic polymer a. Further, the content is preferably 1% by mass or less, more preferably 0.8% by mass or less, and further preferably 0.5% by mass or less. When the content of the thermal crosslinking agent is in the above range, appropriate hardness can be more easily obtained by increasing the cohesive force.

The adhesive composition a preferably contains the silane coupling agent. In this way, the pressure-sensitive adhesive layer obtained has improved adhesion to each member in the laminate as an adherend, and has more excellent durability against bending.

As the Silane Coupling (SC) agent, preferred are: an organosilicon compound having at least 1 alkoxysilyl group in the molecule, and having good compatibility with the (meth) acrylic polymer A and light transmittance.

Examples of the silane coupling agent include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane and methacryloxypropyltrimethoxysilane, epoxy-containing silicon compounds such as 3-glycidoxypropyltrimethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, mercapto-containing silicon compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, amino-containing silicon compounds such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, amino-containing silicon compounds such as N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, and the like, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, or a mixture of at least 1 of these with an alkyl-containing silicon compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane. These can be used alone in 1 kind, also can be combined with 2 or more kinds.

The content of the silane coupling agent in the adhesive composition a is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more, based on 100% by mass of the (meth) acrylic polymer a. Further, the content is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.3% by mass or less. When the content of the silane coupling agent is in the above range, the adhesion to each member in the laminate can be further improved.

The adhesive composition a may be added with the above-mentioned various additives as desired. In the present specification, the polymerization solvent and the diluting solvent are not included in the additive constituting the adhesive composition a.

The (meth) acrylic polymer a can be produced by polymerizing a mixture of monomers constituting the polymer by a general radical polymerization method. The polymerization of the (meth) acrylic polymer a is preferably carried out 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 thereof may be used in combination.

The polymerization initiator includes azo compounds, organic peroxides, and the like, and 2 or more kinds thereof may be used in combination. 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-methoxyvaleronitrile), dimethyl 2,2' -azobis (2-methylpropionate), 4' -azobis (4-cyanovaleric acid), 2' -azobis (2-hydroxymethylpropionitrile), and 2,2' -azobis [2- (2-imidazolin-2-yl) propane ].

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

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

When the (meth) acrylic polymer a is obtained, a binder composition a (coating solution) diluted with a solvent can be obtained by adding a thermal crosslinking agent, a silane coupling agent, and if desired, an additive and a diluting solvent to a solution of the (meth) acrylic polymer a and sufficiently mixing them. The adhesive composition a can be produced by a known method, for example, by mixing the components together using a mixer or the like. Further, the 1 st adhesive composition and the 2 nd adhesive composition can be prepared from the adhesive composition a obtained in this manner.

In the case where a solid component is used for any of the above components, or in the case where a precipitate is generated when the component is mixed with another component in an undiluted state, the component may be dissolved or diluted in a diluting solvent alone in advance and then mixed with another component.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane and cyclohexane, 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, and cellosolve-based solvents such as ethyl cellosolve.

The concentration and viscosity of the pressure-sensitive adhesive composition a (coating solution) thus prepared are not particularly limited as long as they are within a range enabling coating, and can be appropriately selected according to the situation. For example, it can be prepared in the following manner: the concentration of the binder composition a in the solution is 10 to 60% by mass. The addition of the diluting solvent or the like to obtain the coating solution is not essential, and the diluting solvent may not be added as long as the viscosity or the like of the adhesive composition a can be applied. In this case, the adhesive composition a is a coating solution in which a polymerization solvent of the (meth) acrylic polymer a is directly prepared as a dilution solvent.

The adhesive layer can be obtained by crosslinking the adhesive composition a described above. Crosslinking of the adhesive composition a may be performed by heat treatment. The heating treatment may be used in combination with a drying treatment performed when a diluent solvent or the like is volatilized from a coating film of the binder composition a applied to a desired object.

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

After the heat treatment, the composition may be aged at room temperature (e.g., 23 ℃ C., 50% RH) for about 1 to 2 weeks, if necessary. In the case where such a curing period is required, the adhesive layer may be formed after the curing period has elapsed. In the case where the curing period is not required, the adhesive layer may be formed after the above-described heat treatment is completed.

By the heat treatment (and curing), the (meth) acrylic polymer a is sufficiently crosslinked via the crosslinking agent to form a crosslinked structure, and thus the pressure-sensitive adhesive layers (the 1 st pressure-sensitive adhesive layer 102 and the 2 nd pressure-sensitive adhesive layer 104) can be obtained.

< adhesive sheet >

The adhesive sheet may comprise an adhesive layer formed from the adhesive composition a described above. The adhesive layer may be formed by coating the adhesive composition a on a substrate. When an active energy ray-curable pressure-sensitive adhesive composition is used as the pressure-sensitive adhesive composition a, a cured product having a desired degree of curing can be obtained by irradiating the pressure-sensitive adhesive layer formed with an active energy ray. When a thermosetting adhesive composition is used as the adhesive composition, a cured product having a desired degree of curing can be produced by applying heat treatment (and curing) to the formed adhesive layer.

The substrate may be a release film subjected to a release treatment. The pressure-sensitive adhesive sheet can be produced by applying the pressure-sensitive adhesive composition a to a release film to form a pressure-sensitive adhesive layer in a sheet form, and further bonding another release film to the pressure-sensitive adhesive layer.

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

[ front panel ]

The front panel 101 is not limited in material and thickness as long as it is a plate-like body that can transmit light, or may be constituted by only 1 layer, or may be constituted by 2 or more layers. Examples thereof include a plate-like body made of resin (for example, a resin plate, a resin sheet, a resin film, etc.), a plate-like body made of glass (for example, 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 plate 101 may be, for example, 10 to 1000. mu.m, preferably 20 to 500. mu.m, and more preferably 30 to 300. mu.m. In the present invention, the thickness of each layer can be measured by the thickness measurement method described in the examples described below.

When the front panel 101 is a resin plate-like body, the resin plate-like body is not limited as long as light can be transmitted therethrough. Examples of the resin constituting the resin plate body such as a resin film include films formed of polymers such as triacetyl cellulose, acetyl cellulose butyrate, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, acetyl propionyl 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, polymethylmethacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and polyamideimide. These polymers may be used alone or in combination of 2 or more. From the viewpoint of improving strength and transparency, a resin film made of a polymer such as polyimide, polyamide, polyamideimide, or the like is preferable.

From the viewpoint of hardness, the front panel 101 is preferably a film in which a hard coat layer is provided on at least one surface of a base film. As the base film, a film made of the above resin can be used. The hard coat layer may be formed on one surface of the substrate 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 a cured layer of, for example, 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 coating may also contain additives for strength enhancement. The additive is not limited, and examples thereof include inorganic fine particles, organic fine particles, and a mixture thereof.

When the front plate 101 is a glass plate, a strengthened glass for display is preferably used as the glass plate. The thickness of the glass plate may be, for example, 10 to 1000 μm, or 50 to 1000 μm.

By using the glass plate, the front panel 101 having excellent mechanical strength and surface hardness can be constituted.

When the laminate 100 is used for a display device, the front panel 101 may have a function of protecting the front surface (screen) of the display device (a function as a window film), a function as a touch sensor, a blue light prevention function, a viewing angle adjustment function, and the like.

[1 st adhesive layer ]

The 1 st adhesive layer 102 is a layer interposed between the front panel 101 and the polarizer layer 103 and bonded thereto, and is, for example, a layer made of an adhesive or a bonding agent or a layer obtained by applying some treatment to the layer. The 1 st adhesive layer 102 may be an adhesive layer disposed closest to the front panel 101 among the adhesive layers constituting the laminate 100. Herein, the "adhesive" is also referred to as a pressure-sensitive adhesive in the present specification. Further, the "adhesive" in the present specification means an adhesive other than an adhesive (pressure-sensitive adhesive), and can be clearly distinguished from the adhesive. The 1 st adhesive layer 102 may be 1 layer or may be formed of 2 or more layers, but is preferably 1 layer.

1 st adhesive layer 102 as described above, may be formed using the 1 st adhesive composition. 1 st adhesive composition as described above, adhesive composition a can be used to form. In the 1 st adhesive layer 102, when the 1 st adhesive reference layer is formed using the 1 st adhesive composition and the 2 nd adhesive reference layer is formed using the 2 nd adhesive composition described later such that the thickness of the 1 st adhesive reference layer and the thickness of the 2 nd adhesive reference layer become the same, the 1 st adhesive reference layer and the 2 nd adhesive reference layer satisfy the relationship of the formula (1) represented by Δ R1 ≦ Δ R2. The thickness of the 1 st adhesive reference layer and the thickness of the 2 nd adhesive reference layer may be set to 200 μm, for example. The 1 st adhesive reference layer and the 2 nd adhesive reference layer preferably satisfy the relationship of the formula (2) represented by Δ R1 < Δ R2. The 1 st adhesive composition is not limited to the adhesive composition a as long as the relationship with the 2 nd adhesive composition satisfies the above formula (1), and may be formed directly from an arbitrary adhesive composition or may be formed using an adhesive sheet having an adhesive layer formed using an arbitrary adhesive composition. However, the 1 st adhesive composition is preferably formed from the adhesive composition a, or is also preferably formed using an adhesive sheet formed by applying the adhesive composition a to a substrate.

That is, in the 1 st pressure-sensitive adhesive layer 102, the composition and blending components of the 1 st pressure-sensitive adhesive composition constituting the layer, the type of the 1 st pressure-sensitive adhesive composition (active energy ray-curable type, thermosetting type, etc.), the additives that can be blended in the 1 st pressure-sensitive adhesive composition, the method for producing the 1 st pressure-sensitive adhesive layer, the thickness of the 1 st pressure-sensitive adhesive layer, and the like can be as described in the column of [ pressure-sensitive adhesive layer (1 st pressure-sensitive adhesive layer formed using the 1 st pressure-sensitive adhesive composition and 2 nd pressure-sensitive adhesive layer formed using the 2 nd pressure-sensitive adhesive composition) ].

In the laminate 100, at least one of the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 preferably has a thickness of 20 μm to 50 μm. Therefore, the thickness of the 1 st pressure-sensitive adhesive layer 102 may be, for example, 3 μm to 100 μm, preferably 5 μm to 50 μm, or 20 μm or more. Most preferably, the thickness of the 1 st adhesive layer 102 is 20 μm to 50 μm.

[ polarizer layer ]

Examples of the polarizer layer 103 include a stretched film or a stretched layer that adsorbs a dichroic dye, a layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound, and the like. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. The dichroic organic dye includes a dichroic direct dye formed of a bisazo compound such as c.i. direct RED 39, and a dichroic direct dye formed of a compound such as trisazo or tetraazo.

Examples of the polarizer layer obtained 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, for example, a layer obtained 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. A polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable liquid crystal is preferable because it is not limited in the bending direction as compared with a stretched film or a stretched layer adsorbing a dichroic dye.

In the laminate 100, the polarizer layer 103 can function as a circularly polarizing plate by combining with a retardation layer described later, for example.

< polarizer layer as stretched film or stretched layer >

The polarizer layer as a stretched film for adsorbing a dichroic dye can be generally produced through the following steps: a step of uniaxially stretching a polyvinyl alcohol resin film; a step of dyeing a polyvinyl alcohol resin film with a dichroic dye to adsorb the dichroic dye; treating the polyvinyl alcohol resin film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; and a step of washing with water after the treatment with the boric acid aqueous 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, and may be 20 μm or less, further 15 μm or less, and further 10 μm or less.

The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, a copolymer of vinyl acetate and another monomer copolymerizable therewith may be used. 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 mol% to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, aldehyde-modified polyvinyl formal or polyvinyl acetal may be used. The polymerization degree of the polyvinyl alcohol resin is usually 1000 to 10000 or less, and preferably 1500 to 5000 or less.

The polarizer layer as the stretched layer for adsorbing the dichroic dye can be generally produced through the following steps: a step of applying a coating liquid containing the polyvinyl alcohol resin to a base film; a step of uniaxially stretching the obtained laminated film; a step of dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminate film with a dichroic dye, and adsorbing the dichroic dye to form a polarizer layer; treating the film having the dichroic dye adsorbed thereon with an aqueous boric acid solution; and a step of washing with water after the treatment with the boric acid aqueous solution. The stretched layer having the dichroic dye adsorbed thereon, that is, the polarizer layer may be peeled and removed from the polarizer layer as necessary. 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 the stretched film or the stretched layer may be combined with the laminate in a form in which a thermoplastic resin film is bonded to one surface or both surfaces thereof. The thermoplastic resin film can function as a protective film for the polarizer layer 103 or a retardation film. The thermoplastic resin film may be formed of a polyolefin resin such as a chain polyolefin resin (e.g., a polypropylene resin) or a cyclic polyolefin resin (e.g., a norbornene resin); cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins; or a mixture thereof, and the like.

The thermoplastic resin film may or may not have a retardation. From the viewpoint of thinning, 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, and still more preferably 60 μm or less. The thickness of the thermoplastic resin film is usually 5 μm or more, preferably 20 μm or more. 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 obtained 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, and for example, a layer obtained by applying and curing a composition containing a polymerizable dichroic dye having liquid crystallinity or a composition containing a dichroic dye and a polymerizable liquid crystal onto a base film.

The polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound may be removed by peeling the base material film from the polarizer layer as necessary. 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 have an orientation film. The alignment film can be peeled off.

The polarizer layer obtained by applying and curing a composition containing a dichroic dye and a polymerizable compound may be combined with the optical laminate in a form in which a thermoplastic resin film is bonded to one or both surfaces thereof. As the thermoplastic resin film, the same thermoplastic resin film as that used in the polarizer layer which is 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 obtained by applying and curing the composition containing the dichroic dye and the polymerizable compound may have an Overcoat (OC) layer as a protective layer formed on one or both surfaces 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; vinyl alcohol polymers such as polyvinyl alcohol and ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, (meth) acrylic acid or anhydride thereof-vinyl alcohol copolymers; a carboxyvinyl polymer; 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, and may be 5 μm or less, and may be 0.05 μm or more, and may be 0.5 μm or more.

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

[2 nd adhesive layer ]

The 2 nd adhesive layer 104 is an adhesive layer disposed between the polarizer layer 103 and the back surface plate 105. The 2 nd adhesive layer may be an adhesive layer disposed closest to the back panel 105 among the adhesive layers constituting the laminate 100. The 2 nd adhesive layer 104 may be 1 layer or may be formed of 2 or more layers, but is preferably 1 layer.

2 nd adhesive layer 104 as described above, may be formed using the 2 nd adhesive composition. 2 nd adhesive composition as described above, can be formed using adhesive composition a. In the 2 nd adhesive layer 104, in the case where the 2 nd adhesive reference layer is formed using the 2 nd adhesive composition and the 1 st adhesive reference layer is formed using the 1 st adhesive composition so that the thickness of the 1 st adhesive reference layer becomes the same as the thickness of the 2 nd adhesive reference layer, the 1 st adhesive reference layer and the 2 nd adhesive reference layer satisfy the relationship of the formula (1) represented by Δ R1 ≦ Δ R2. The thickness of the 1 st adhesive reference layer and the thickness of the 2 nd adhesive reference layer may be set to 200 μm, for example. The 1 st adhesive reference layer and the 2 nd adhesive reference layer preferably satisfy the relationship of the formula (2) represented by Δ R1 < Δ R2. The 2 nd adhesive composition is not limited to the adhesive composition a, and may be formed directly from an arbitrary adhesive composition or may be formed using an adhesive sheet having an adhesive layer formed using an arbitrary adhesive composition, as long as the relationship with the 1 st adhesive composition satisfies the above formula (1). However, the 2 nd adhesive composition is preferably formed of the adhesive composition a, or is also preferably formed using an adhesive sheet formed by applying the adhesive composition a to a substrate.

That is, the 2 nd adhesive layer 104 is different from the 1 st adhesive layer 102 in composition, but is preferably the same in point of being formed of the adhesive composition a. Therefore, in the 2 nd pressure-sensitive adhesive layer 104, as for the composition and blending components of the 2 nd pressure-sensitive adhesive composition constituting the same, the type of the 2 nd pressure-sensitive adhesive composition (whether it is an active energy ray-curable type, a thermosetting type, or the like), additives that can be blended in the 2 nd pressure-sensitive adhesive composition, the method for producing the 2 nd pressure-sensitive adhesive layer, the thickness of the 2 nd pressure-sensitive adhesive layer, and the like, the same can be said as described in the column of [ pressure-sensitive adhesive layer (1 st pressure-sensitive adhesive layer formed using the 1 st pressure-sensitive adhesive composition and 2 nd pressure-sensitive adhesive layer formed using the 2 nd pressure-sensitive adhesive composition) ].

In the laminate 100, at least one of the 1 st adhesive layer 102 and the 2 nd adhesive layer 104 preferably has a thickness of 20 μm to 50 μm. Therefore, the thickness of the 2 nd pressure-sensitive adhesive layer 104 may be, for example, 3 μm to 100 μm, preferably 5 μm to 50 μm, or 20 μm or more. Most preferably, the 2 nd adhesive layer 104 has a thickness of 20 μm to 50 μm.

[ Back Panel ]

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

The thickness of 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 rear plate 105 may be formed of only 1 layer or 2 or more layers, and the plate-like body exemplified for the plate-like body described above for front plate 101 may be used.

Examples of the structural elements used in the back plate 105 and applicable to a general display device include a spacer, a touch sensor panel, and an organic EL display element. Examples of the order of lamination of the components in the display device include a front panel, a circularly polarizing plate, a spacer, a front panel, a circularly polarizing plate, an organic EL display device, a front panel, a circularly polarizing plate, a touch sensor panel, an organic EL display element, a front panel, a touch sensor panel, a circularly polarizing plate, and an organic EL display element. The back panel 105 is preferably a touch sensor panel.

(touch sensor panel)

The touch sensor panel is not limited as long as it is a sensor capable of detecting a touch position, and examples thereof include touch sensor panels of a resistive film type, a capacitive coupling type, an optical sensing type, an ultrasonic wave type, an electromagnetic induction coupling type, a surface acoustic wave type, and the like. From the viewpoint of low cost, a resistive-film type or capacitive-coupling type touch sensor panel is preferably used.

An example of a resistive touch sensor panel includes a pair of substrates arranged to face each other, an insulating spacer sandwiched between the pair of substrates, a transparent conductive film provided on the front surface of the inner side of each substrate as a resistive film, and a touch position detection circuit. In an image display device provided with a resistive touch sensor panel, if a surface of a front panel is touched, an opposing resistive film is short-circuited, and a current flows through the resistive film. The touch position detection circuit can detect the voltage change at this time and detect the touched position.

An example of a capacitive coupling type touch sensor panel includes a substrate, a position detection transparent electrode 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 the front panel is touched, the transparent electrode can be grounded at the touched point via the capacitance of the human body. The touch position detection circuit can detect grounding of the transparent electrode and detect the touch position.

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

[ phase difference layer ]

The laminate 100 may have 1 or more phase difference layers between the polarizer layer 103 and the back surface plate 105. The retardation layer may be laminated on another layer (including another retardation layer) via the 1 st pressure-sensitive adhesive layer 102, the 2 nd pressure-sensitive adhesive layer 104, or a layer made of a pressure-sensitive adhesive or an adhesive other than these layers (hereinafter referred to as a laminating layer).

Examples of the retardation layer include a photo-alignment material parallel alignment film (positive-a plate) and a photo-alignment material perpendicular alignment film (positive-C plate) such as a λ/4 plate and a λ/2 plate. The retardation layer may be, for example, a retardation film that can be formed from 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 the latter is preferable. The thickness of the retardation film may be the same as that of the thermoplastic resin film. The thickness of the retardation layer obtained by curing the polymerizable liquid crystal compound is, for example, 0.1 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 6 μm.

The retardation layer obtained by curing the polymerizable liquid crystal compound can be formed by applying a composition containing the polymerizable liquid crystal compound onto a substrate film and curing the composition. An alignment layer may be formed between the substrate 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 combined with the laminate 100 in the form of an alignment layer and/or a substrate film. The back surface plate 105 may be a substrate film coated with the above composition.

[ adhesive layer ]

The laminating 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 bonding layer may be the same adhesive exemplified for the adhesive composition constituting the 1 st adhesive layer 102 and the 2 nd adhesive layer 104, or may be other adhesives such as (meth) acrylic adhesives, styrene adhesives, silicone adhesives, rubber adhesives, polyurethane 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 water-based adhesives, active energy ray-curable adhesives, and the like, for example. Examples of the aqueous adhesive include a polyvinyl alcohol resin aqueous solution and an aqueous two-pack polyurethane emulsion adhesive. The active energy ray-curable adhesive is an adhesive that is cured by irradiation with an active energy ray such as ultraviolet ray, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable polyurethane monomer, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing active substances that generate neutral radicals, anionic radicals, and cationic radicals by irradiation with active energy rays such as ultraviolet rays.

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

As shown in fig. 2, for example, the laminate 200 according to another embodiment of the present invention may further include a bonding layer 108, a1 st retardation layer 106, a bonding layer 109, and a 2 nd retardation layer 107, in addition to the front plate 101, the 1 st adhesive layer 102, the polarizer layer 103, the 2 nd adhesive layer 104, and the back plate 105.

[ method for producing laminate ]

The laminate 100,200 can be produced by a method including the steps of: and a step of bonding the layers constituting the

laminates

100 and 200 to each other via an adhesive layer or further via an adhesive layer. When the layers are bonded 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 side or both sides of the bonding surface for the purpose of improving the adhesion.

The polarizer layer 103 may be formed directly on a thermoplastic resin film or substrate film, which may be combined with the laminate 100,200, or may be peeled off from the polarizer layer 103 without being a structural element of the laminate.

< display device >

A display device according to an embodiment of the present invention includes the above-described

laminate

100, 200. The display device is not particularly limited, and examples thereof include image display devices such as an organic EL display device, an inorganic EL display device, a liquid crystal display device, and an electroluminescence display device. The display device may have a touch panel function.

The

laminated bodies

100 and 200 described above have improved durability by suppressing the generation of bubbles in the adhesive layer, and are therefore preferably used for display devices having flexibility that enables bending, or the like.

In the display device, the

laminated bodies

100 and 200 are disposed on the viewing side of the display element included in the display device, with the front panel facing the outside (the side opposite to the display element side, i.e., the viewing side). The display device is preferably curved with the front panel 101 side of the laminate 100,200 as the inside.

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 signboards, measuring instruments, office equipment, medical equipment, computer equipment, and the like.

Examples

The present invention will be described in further detail with reference to examples, but the present invention is not limited to these examples. In the present example, when the terms "%" and "part" are used for explanation, these terms mean mass% and part, unless otherwise specified.

[ measurement method ]

The measurement method and calculation method of each physical property value (weight average molecular weight, each physical property of the pressure-sensitive adhesive layer, etc.) used in the present example are as follows.

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

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

Specifically, the (meth) acrylic polymer a as the test object was dissolved in tetrahydrofuran at a concentration of about 0.05 mass%, and 10 μ L was injected into SEC. The mobile phase flowed at a rate of 1.0 mL/min. As the column, PLGel MIXED-B (manufactured by Polymer Laboratories) was used. As the detector, a UV-VIS detector (trade name: Agilent GPC) was used.

Thickness of layer

The film thickness was measured using a contact type film thickness measuring apparatus ("MS-5C" manufactured by Nikon K.K.). The polarizer layer and the alignment film were measured using a laser microscope ("OLS 3000" manufactured by olympus corporation).

< repeated deformation application test >

The strain repeated application test was performed by using a viscoelasticity measuring apparatus (MCR-301, Anton Paar Co.). The specific test method is as follows. That is, adhesive sheets (adhesive sheet a11, adhesive sheet a12, etc.) having adhesive layers formed thereon, which will be described later, were cut to a width of 20mm × length of 20mm, and 8 sheets were laminated while peeling off the release film, thereby forming adhesive reference layers (1 st adhesive reference layer and 2 nd adhesive reference layer) having a thickness of 200 μm.

Next, the adhesive reference layer was bonded to a glass plate. Further, the adhesive reference layer on the glass plate was subjected to repeated strain application tests by repeatedly applying 0% and 1000% of string (in "%") for 1000 seconds (thus, 0% and 1000% of string (strain) was repeatedly applied to the adhesive sheet over 1000 seconds) under the conditions of 25 ℃ temperature, Normal Force Free, and frequency of 2Hz in a state of being bonded to the measurement chip in the above-described apparatus.

< shear creep value and shear creep rate >)

The shear creep values (in "%") at 25 ℃ were obtained for the 1 st and 2 nd adhesive reference layers before the deformation repetitive application test and for the 1 st and 2 nd adhesive reference layers after the deformation repetitive application test, respectively, by the following methods. Namely, the shear creep value at 25 ℃ was measured by using the viscoelasticity measuring apparatus (MCR-301, Anton Paar Co., Ltd.). Specifically, the shear creep value over the elapsed time was determined by bonding the adhesive reference layer on the glass plate before or after the repeated strain application test to the measurement chip in the apparatus at 25 ℃ for 1200 seconds under the condition of Normal Force 1N, Torque 1200 μ Nm.

Further, each value obtained as a shear creep value before and after the strain repetitive application test was performed was divided by the thickness (200 μm) of the 1 st adhesive reference layer or the 2 nd adhesive reference layer. Thus, a1 st shear creep rate (R1A, unit "%/μm", the same applies hereinafter) which is a shear creep value per 1 μm thickness of the 1 st adhesive reference layer after the deformation repetitive application test was performed, a 2 nd shear creep rate (R1B) which is a shear creep value per 1 μm thickness of the 1 st adhesive reference layer before the deformation repetitive application test was performed, a 3 rd shear creep rate (R2A) which is a shear creep value per 1 μm thickness of the 2 nd adhesive reference layer after the deformation repetitive application test was performed, and a 4 th shear creep rate (R2B) which is a shear creep value per 1 μm thickness of the 2 nd adhesive reference layer before the deformation repetitive application test were calculated. Next, the 2 nd shear creep rate was subtracted from the 1 st shear creep rate, and the 4 th shear creep rate was subtracted from the 3 rd shear creep rate to obtain respective differences as Δ R1 and Δ R2.

< gel fraction of adhesive layer >

The gel fraction of the pressure-sensitive adhesive layers (pressure-sensitive adhesive layer a11 and pressure-sensitive adhesive layer a12) was measured in accordance with the following (I) to (V).

(I) An adhesive layer having an area of about 8cm by about 8cm was bonded to a metal mesh (mass is Wm) comprising S US304 of about 10cm by about 10 cm.

(II) the mass of the bonded product obtained in the above (I) was measured, and the mass was Ws, and then the bonded product was folded 4 times so as to wrap the adhesive layer, and the bonded product was stapled by a stapler (stapler) and then measured, and the mass was Wb.

(III) the net stapled with the stapler in (II) above was placed in a glass container, and after dipping with 60mL of ethyl acetate, the glass container was stored at room temperature for 3 days.

(IV) the net of the above (III) was taken out of the glass container, dried at 120 ℃ for 24 hours, and weighed, and the mass thereof was Wa.

(V) the above-measured mass was substituted into a formula of gel fraction (% by mass) [ { Wa- (Wb-Ws) -Wm }/(Ws-Wm) ] × 100, thereby calculating the gel fraction of the adhesive layer.

[ production of adhesive sheet ]

[1] Production of adhesive sheet A11

(1) Preparation of (meth) acrylic Polymer A

A mixed solution of 81.8 parts by mass of acetone, 98.6 parts by mass of butyl acrylate, 1.0 part by mass of 2-hydroxyethyl acrylate and 0.4 part by mass of acrylic acid was charged into a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, and the atmosphere in the vessel was replaced with nitrogen gas so as to be free of oxygen and the internal temperature was raised to 55 ℃. Thereafter, 0.14 parts by mass of azobisisobutyronitrile (polymerization initiator) was dissolved in 10 parts by mass of acetone, and the whole was added. 1 hour after the addition of the polymerization initiator, acetone was continuously added into the reaction vessel at an addition rate of 17.3 parts by mass/hr so that the concentration of the acrylic resin excluding the monomer was 35% by mass, the temperature was maintained at an internal temperature of 54 to 56 ℃ for 12 hours, and finally acetone was added to adjust the concentration of the acrylic resin to 20% by mass. The weight average molecular weight Mw of the obtained acrylic resin in terms of polystyrene by GPC was 1270000. This was used as a (meth) acrylic polymer a. The structural unit derived from 2-hydroxyethyl acrylate which is a hydroxyl group-containing unsaturated monomer in the (meth) acrylic polymer a was 1 mass%, and the structural unit derived from acrylic acid which is a carboxyl group-containing unsaturated monomer was 0.4 mass%.

(2) Preparation of adhesive composition A11

100 parts by mass (solid content equivalent; the same applies hereinafter) of the (meth) acrylic polymer A obtained in the above step, a polyisocyanate (product name "Coronate L", manufactured by Tosoh corporation) as the thermal crosslinking agent B, and 3-glycidoxypropyltrimethoxysilane (product name "KBM 403", manufactured by shin-Etsu chemical Co., Ltd.) as the silane coupling agent C were mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition A11. The respective formulations (solid content equivalent) of the pressure-sensitive adhesive composition a11 when the (meth) acrylic polymer was prepared in 100 parts by mass (solid content equivalent) are shown in table 1. The abbreviation "BA" in Table 1 means n-butyl acrylate, "2 EHA" means 2-ethylhexyl acrylate, "AA" means acrylic acid. Tg (. degree. C.) of BA, 2EHA and AA was determined by Differential Thermal Analysis (DTA).

(3) Production of adhesive sheet A11

The coating solution of the adhesive composition a11 was applied to the release-treated surface of a1 st release film (product name "SP-PET 752150" manufactured by linetec) by a knife coater to form a coated product. The coating was subjected to a heat treatment at 90 ℃ for 1 minute to form a coating layer. Next, the coating layer on the 1 st release film was laminated to a 2 nd release film (manufactured by linetec corporation, product name "SP-PET 382120") so that the release treated surface of the 2 nd release film was in contact with the coating layer, and cured at 23 ℃ and 50% RH for 7 days to produce a 25 μm thick psa sheet a11 having a psa layer, i.e., a psa sheet a11 having a composition of 1 st release film/psa layer (thickness: 25 μm)/2 nd release film, formed using the psa composition a 11. In this example, the adhesive layer of the adhesive sheet a11 is also referred to as an adhesive layer a 11.

[2] Production of adhesive sheet A12

(1) Preparation of (meth) acrylic Polymer A

A (meth) acrylic polymer a used for producing the pressure-sensitive adhesive sheet a11 was prepared.

(2) Preparation of adhesive composition A12

A coating solution of a pressure-sensitive adhesive composition a12 was obtained in the same manner as in the preparation of the pressure-sensitive adhesive composition a11, except that the amount of Coronate L as a thermal crosslinking agent was changed to the amount shown in table 1 with respect to 100 parts by mass of the (meth) acrylic polymer a.

(3) Production of adhesive sheet A12

The coating solution of the adhesive composition a12 was used in the same manner as in the production process of the adhesive sheet a11, to produce an adhesive sheet a 12. In this example, the adhesive layer of the adhesive sheet a12 is also referred to as an adhesive layer a 12.

The respective formulations (solid content equivalent) of the pressure-sensitive adhesive composition a12 when the (meth) acrylic polymer was prepared in 100 parts by mass (solid content equivalent) are shown in table 1. Table 1 shows the gel fraction values of the pressure-sensitive adhesive composition a11 and the pressure-sensitive adhesive composition a12 obtained by the above-described methods.

[ Table 1]

Further, OCA8146-02 and CEF3004 (both manufactured by 3M of U.S. Pat. No. 3) were prepared as commercially available pressure-sensitive adhesive sheets.

[3] Production of adhesive sheet B11

(1) Preparation of (meth) acrylic Polymer B1

In order to make the temperature adjustment easy by refluxing the nitrogen gas, a cooling device was provided in the reaction vessel. The monomer mixture described in table 2 was charged into the reaction vessel. A nitrogen purge was performed for 1 hour to remove oxygen. The monomer mixture was uniformly mixed while maintaining the temperature at 60 ℃, and then the photopolymerization initiator described in table 2 was added. Then, the mixture was stirred and irradiated with ultraviolet light (10mW) from a UV lamp to produce (meth) acrylic polymer B1.

(2) Preparation of adhesive composition B11

The (meth) acrylic polymer B1, the active energy ray-polymerizable compound, and the photopolymerization initiator were mixed so that the contents thereof were in the proportions shown in table 3, to produce a pressure-sensitive adhesive composition B11.

(3) Production of adhesive sheet B11

Adhesive composition B11 was coated on a silicon release-treated release film to a thickness of 25 μm. After further laminating a release film on the coating film, the coating film was irradiated with ultraviolet rays (cumulative light amount 400 mJ/cm)²Illuminance of 1.8mW/cm²UVV standard), a psa sheet B11 was produced. In this embodiment, the adhesive layer of the adhesive sheet B11 is also referred to as an adhesive layer B11.

[4] Production of adhesive sheet B21

(1) Preparation of (meth) acrylic Polymer B2

In order to make the temperature adjustment easy by refluxing the nitrogen gas, a cooling device was provided in the reaction vessel. The monomer mixture described in table 2 was charged into the reaction vessel. A nitrogen purge was performed for 1 hour to remove oxygen. The monomer mixture was uniformly mixed while maintaining the temperature at 60 ℃, and then the photopolymerization initiator described in table 2 was added. Then, the mixture was stirred and irradiated with ultraviolet light (10mW) from a UV lamp to produce (meth) acrylic polymer B2.

(2) Preparation of adhesive composition B21

The (meth) acrylic polymer B2, the active energy ray-polymerizable compound, and the photopolymerization initiator were mixed so that the contents thereof were in the proportions shown in table 3, to produce a pressure-sensitive adhesive composition B21.

(3) Production of adhesive sheet B21

Adhesive composition B21 was coated on a silicon release-treated release film to a thickness of 25 μm. After further laminating a release film on the coating film, the coating film was irradiated with ultraviolet rays (cumulative light amount 400 mJ/cm)²Illuminance of 1.8mW/cm²UVV standard), a psa sheet B21 was produced. In this embodiment, the adhesive layer of the adhesive sheet B21 is also referred to as an adhesive layer B21.

[ Table 2]

The abbreviation "LA" in Table 2 means lauryl acrylate, "BA" means n-butyl acrylate, "2-PHA" means 2-propylheptyl acrylate, "C22A" means behenyl acrylate, and "ODA" means octyldecyl acrylate.

[ Table 3]

The abbreviation "IDA" in Table 3 means isodecyl acrylate and "IBOA" means isobornyl acrylate.

The adhesive sheet was prepared by preparing adhesive base layers having a thickness of 200 μm by the above method, and the shear creep values (%) and the difference (%/μm) in shear creep rate were obtained before and after the repeated strain application test for each adhesive base layer. The results are shown in Table 4. Also shown in table 4 are values of the shear creep rate (%/μm) before the deformation repeated application test was performed for each adhesive reference layer.

[ Table 4]

[ production of laminate ]

[ front Panel (Window film) ]

A polyimide film (thickness: 50 μm) having a hard coat layer (thickness: 10 μm) on one surface was prepared as a front panel.

[ polarizer layer ]

1. Material preparation

The following materials were prepared.

1) TAC film with thickness of 25 μm

2) Composition for forming oriented film

< Polymer 1 >

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

The polymer 1 was dissolved in cyclopentanone at a concentration of 5% by mass to obtain a solution, and the solution was prepared 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 >

As the polymerizable liquid crystal compound, a polymerizable liquid crystal compound represented by the formula (1-1) [ hereinafter also referred to as compound (1-1) ] and a polymerizable liquid crystal compound represented by the formula (1-2) [ hereinafter also referred to as compound (1-2) ] were prepared.

The compound (1-1) and the compound (1-2) were synthesized according to the method described in Lub et al, Recl, Trav, Chim, Pays-Bas, 115, 321-328 (1996).

< dichroic dye >

As the dichroic dye, azo dyes described in examples of Japanese patent application laid-open publication No. 2013-101328 represented by the following formulae (2-1a), (2-1b), and (2-3a) were prepared.

The composition for forming a polarizer layer [ hereinafter also referred to as composition (a-1) ] was prepared by mixing 75 parts by mass of the compound (1-1), 25 parts by mass of the compound (1-2), 2.5 parts by mass of each of the azo dyes represented by the above formulae (2-1a), (2-1b) and (2-3a) as dichroic dyes, 6 parts by mass of 2-dimethylamino-2-phenyl-1- (4-morpholinophenyl) butyl-1-one (Irgacure369, manufactured by BASF Japan) as a polymerization initiator, and 1.2 parts by mass of a polyacrylate compound (BYK-361N, BYK-Chemie) as a leveling agent in 400 parts by mass of toluene as a solvent, and stirring the resulting mixture at 80 ℃ for 1 hour.

4) Composition for forming protective layer (OC layer)

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

2. Manufacturing method

1) The TAC film side was coated with the alignment film-forming composition as follows. That is, first, 1 corona treatment was applied to the TAC film side. The conditions of the corona treatment were an output of 0.3kW and a treatment speed of 3 m/min. Thereafter, the composition (D-1) obtained as described above was applied to this TAC by a bar coating method, and heat-dried in a drying oven at 80 ℃ for 1 minute. The obtained dried film was subjected to polarized UV irradiation treatment to form a1 st alignment film (AL 1). The polarized light UV treatment was performed under the following conditions: light irradiated from a UV irradiation apparatus (SPOT CURE SP-7; manufactured by Ushio Inc.) was transmitted through a wire grid (UIS-27132# #, manufactured by Ushio Inc.) and the cumulative quantity of light measured at a wavelength of 365nm was 100mJ/cm². The thickness of the 1 st alignment film (AL1) was 100 nm.

2) The composition for forming a polarizer layer was applied to the alignment film side as follows. That is, first, the composition (a-1) was applied to the 1 st alignment film (AL1) by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. Using the above UV irradiation apparatus, the cumulative light amount was 1200mJ/cm²The dried film was irradiated with ultraviolet light (365nm basis) to form a polarizer layer (pol). The thickness of the obtained polarizer layer (pol) was measured by a laser microscope (OLS 3000, Olympus corporation) to be 1.8. mu.m. Thus, a laminate comprising "TAC/AL 1/pol" was obtained.

3) The composition for forming a protective layer (OC layer) was applied to the polarizer layer side as follows. That is, the composition (E-1) was applied to the polarizer layer (pol) by a bar coating method so that the thickness after drying was 1.0 μm, and dried at 80 ℃ for 3 minutes. Thus, a laminate containing "TAC film/cPL (AL1+ pol + protective layer)" was obtained.

[ phase difference layer ]

1. Material preparation

The following materials were prepared.

1) PET film with thickness of 100 μm

2) Composition for forming oriented film

The polymer 1 was dissolved in cyclopentanone at a concentration of 5% by mass to obtain a solution, and the solution was prepared as a composition for forming an alignment film (composition (D-1)).

3) Composition for forming phase difference layer

The following components were mixed, and the resulting mixture was stirred at 80 ℃ for 1 hour to obtain 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 (Irgacure369, 2-dimethylamino-2-phenyl-1- (4-morpholinophenyl) butyl-1-one, manufactured by BASF Japan): 6 parts by mass

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

Solvent (cyclopentanone): 400 parts by mass.

2. Manufacturing method

1) The composition for forming an alignment film was coated on a PET film as follows. That is, a polyethylene terephthalate film (PET) having a thickness of 100 μm as a substrate was prepared, 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 light UV treatment Using the UV irradiation device, the cumulative light amount measured at a wavelength of 365nm was 100mJ/cm²The conditions of (1) are carried out. The polarization direction of the polarized light UV is performed at 45 ° with respect to the absorption axis of the polarizer layer. In this manner, a laminate including "substrate (PET)/2 nd alignment film (AL 2)" was obtained.

2) The retardation layer-forming composition was applied to the orientation film side of the PET film as follows. That is, the above-mentioned composition contains "base material (PET)/2 nd alignment film (AL)2) "the composition (B-1) was applied to the 2 nd alignment film (AL2) of the laminate by a bar coating method, dried by heating in a drying oven at 120 ℃ for 1 minute, and then cooled to room temperature. Using the above UV irradiation apparatus, the cumulative light amount was 1000mJ/cm²The obtained dried film was irradiated with ultraviolet light (365nm basis) to form a retardation layer. The thickness of the obtained retardation layer was measured by using a laser microscope (OLS 3000, manufactured by Olympus corporation), and it was 2.0. mu.m. The phase difference layer is a lambda/4 plate (QWP) that shows a phase difference value of lambda/4 in the in-plane direction. In this manner, a laminate including "substrate (PET)/retardation portion (AL2+ QWP)" was obtained.

[ common adhesive sheet ]

1) Polymerization of acrylic resins

The following components were stirred under a nitrogen atmosphere and reacted at 55 ℃ to obtain an acrylic resin.

Butyl acrylate: 70 parts by mass

Acrylic acid methyl group: 20 parts by mass

Acrylic acid: 2.0 parts by mass

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

2) Preparation of adhesive composition

The following ingredients were mixed to obtain an adhesive composition.

Acrylic resin: 100 parts by mass

Crosslinking agent (Tosoh Coronate L.): 1.0 part by mass

Silane coupling agent (product of shin-Etsu chemical Co., Ltd. "X-12-981"): 0.5 part by mass.

Ethyl acetate was added to the above adhesive composition so that the total solid content concentration was 10 mass%, to prepare a solution.

3) Manufacture of common adhesive sheet

The release-treated surface of the polyethylene terephthalate film (heavy separator, thickness 38 μm) after the release treatment was coated with the above-mentioned liquid-formulated adhesive composition by a coater so that the thickness after drying was 5 μm, to obtain a coating layer. 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) after the mold release treatment was attached to the exposed surface of the pressure-sensitive adhesive layer. Thereafter, the sheet was aged at 23 ℃ and 50% RH relative humidity for 7 days to obtain a common adhesive sheet having a layer structure of light separator/common adhesive layer/heavy separator.

[ Back Panel ]

As the back plate, a PET film having a thickness of 100 μm was prepared.

[ example 1]

The laminate was produced by the steps shown in FIGS. 3(a) to (e). First, as shown in fig. 3(a), the polarizer layer 410[ TAC film 301/cPL ((AL1+ pol)302/OC layer 303) ] and the common adhesive sheet 420 (light spacer 304/common adhesive layer 305/heavy spacer 306) are prepared. Corona treatment (output of 0.3kW, speed 3 m/min) was applied to the OC layer 303 side of the polarizer layer 410 and the surface of the common adhesive sheet 420 from which the light separator 304 was peeled, and then the laminate was laminated to obtain a1 st laminate precursor 430 shown in fig. 3 (b). Further, as shown in fig. 3(b), the retardation layer 440[ base material (PET) 308/retardation portion (AL2+ QWP)307] is prepared.

Next, the phase difference portion 307 side of the phase difference layer 440 and the surface of the 1 st laminate precursor 430 from which the heavy separator 306 was peeled were subjected to corona treatment (output 0.3kW, treatment speed 3 m/min), and then bonded to obtain the 2 nd laminate precursor 450 shown in fig. 3 (c). Thereafter, as shown in fig. 3(c), the adhesive sheet a12 was prepared as an adhesive sheet 460 (1 st release film 309/adhesive layer 310/2 nd release film 311). The adhesive layer 310 of the adhesive sheet 460 corresponds to the 2 nd adhesive layer.

The surface of the 2 nd laminate precursor 450 from which the base material (PET)308 was peeled and the surface of the adhesive sheet 460 from which the 1 st release film 309 was peeled were subjected to corona treatment (output of 0.3kW, treatment speed of 3 m/min), and then bonded to each other, thereby obtaining a 3 rd laminate precursor 470 shown in fig. 3 (d).

Further, the psa sheet a11 was prepared as a psa sheet 490 (1 st release film 314/psa layer 315/2 nd release film 316), and the surface from which the 1 st release film 314 was peeled and the polyimide film 313 side of the front panel 480 (polyimide film 313/hardcoat layer 312) were subjected to corona treatment (output 0.3kW, treatment speed 3 m/min), and then laminated, thereby obtaining a 4 th laminate precursor 500 shown in fig. 3 (d). The adhesive layer 315 of the adhesive sheet 490 corresponds to the 1 st adhesive layer.

Next, the surface of the 4 th laminate precursor 500 from which the 2 nd release film 316 was peeled and the TAC301 side of the 3 rd laminate precursor 470 were subjected to corona treatment (output of 0.3kW, treatment speed of 3 m/min), and then bonded, thereby obtaining a 6 th laminate precursor 300 shown in fig. 3 (e). Finally, the 2 nd release film 311 was peeled off from the 6 th laminate precursor 300, and the peeled surface and one surface of a100 μm thick PET film prepared as a back surface plate were subjected to corona treatment (output 0.3kW, treatment speed 3 m/min), followed by lamination, thereby obtaining a laminate of example 1. The laminate of example 1 had a thickness of 240 μm and a length of 190mm × a width of 150 mm.

Examples 2 to 5 and comparative examples 1 to 2

Laminates of examples 2 to 5 and comparative examples 1 to 2 were produced by applying the same production method as the laminate of example 1 except that adhesive sheets having adhesive layers shown in table 5 were used instead of the adhesive sheets a11 and a12 used in example 1.

Table 5 shows the kinds of the adhesive compositions used for forming the 1 st adhesive layer and the 2 nd adhesive layer in the laminates of examples 1 to 5 and comparative examples 1 to 2. Examples 1 to 5 satisfy the relationship of Δ R1 ≦ Δ R2, and comparative examples 1 to 2 satisfy the relationship of Δ R1 ≦ Δ R2.

[ Table 5]

Example 1

Example 2

Example 3

Example 4

Example 5

Comparative example 1

Comparative example 2

1 st adhesive layer

A11

A12

A11

B11

A12

CEF3004

2 nd adhesive layer

A12

8146-02

B21

A11

8146-02

Further, the laminates of examples 1 to 5 and comparative examples 1 to 2 were subjected to a bending durability test and a surface hardness test by the methods described later. The results are shown in Table 6.

< bending durability test (mandrel bar test) >

Test pieces 100mm long and 10mm wide were cut out from the laminates of each example and each comparative example using a Super cutter (Super cutter). The test piece was subjected to a bending durability test (Mandrel bar test) by winding the test piece around a cylindrical Mandrel bar (Mandrel) so that the front panel of the test piece (laminate) was located inside, and bending the test piece in the longitudinal direction at a temperature of 25 ℃. From this, the minimum diameter of the mandrel bar in which no bubble was generated in the pressure-sensitive adhesive layer of the test piece (laminate) was determined, and the grade was determined based on the following criteria. In the bending durability test, the smaller the value of the minimum diameter, the more excellent the bending durability of the adhesive layer can be evaluated.

A: at the time of winding to

In the case of the following mandrel bar, bubbles were generated in the adhesive layer

B: when the core rod is wound up to a diameter of more than 10mm and not more than 15mm, bubbles are generated in the adhesive layer

C: when the core rod is wound around a mandrel rod having a diameter of more than 15mm and not more than 20mm, bubbles are generated in the adhesive layer

D: in the case of winding up to a mandrel exceeding Φ 20mm, bubbles were generated in the adhesive layer.

< surface hardness test >

The surface of the front plate of each laminate of examples and comparative examples was measured at a temperature of 25 ℃ using a pencil hardness tester (PHT, manufactured by SUKBO SCIENCE, korea). A pencil (manufactured by Mitsubishi Pencil) with a load of 100g (hardness of core: 6B) was used to form a concave mark on the surface. In this case, the time until the recessed portion mark disappeared was obtained, and the surface hardness of the laminate of each example and each comparative example was evaluated based on the following standard scale. In this surface hardness test, the shorter the time until the dent mark disappears, the more excellent the surface hardness property can be evaluated.

A: disappearance of dent marks in less than 30 minutes

B: when the time is 30 minutes or more and less than 60 minutes, the dent mark disappears

C: when the time is 60 minutes or more and less than 90 minutes, the dent mark disappears

D: even after 90 minutes, the dent mark did not disappear.

[ Table 6]

Example 1

Example 2

Example 3

Example 4

Example 5

Comparative example 1

Comparative example 2

Core rod test (25 ℃ C.)

A

B

A

D

Surface hardness test (25 ℃ C.)

A

B

A

B

D

From the above, it is understood that examples 1 to 5 satisfy the relationship of Δ R1 ≦ Δ R2, and that the evaluation of bending durability and surface hardness is excellent for comparative examples 1 to 2 having the relationship of Δ R1 > Δ R2.

Description of the reference numerals

100,200 laminates, 101 front panel, 102 1 st adhesive layer, 103 polarizer layer, 104 nd 2 nd adhesive layer, 105 back panel, 106 1 st retardation layer, 107 nd 2 nd retardation layer, 108, 109 lamination layer.

Claims

1. A laminate comprising, in order: a front panel, a1 st adhesive layer formed using the 1 st adhesive composition, a polarizer layer, a 2 nd adhesive layer formed using the 2 nd adhesive composition, and a back panel;

in the case where a1 st adhesive reference layer is formed using the 1 st adhesive composition and a 2 nd adhesive reference layer is formed using the 2 nd adhesive composition in such a manner that the thickness of the 1 st adhesive reference layer becomes the same as the thickness of the 2 nd adhesive reference layer, the 1 st adhesive reference layer and the 2 nd adhesive reference layer satisfy the following relationship of formula (1):

ΔR1≤ΔR2 (1)

in the formula (1), Δ R1 represents a value obtained by subtracting R1B from R1A,

Δ R2 represents the value of R2A minus R2B,

R1A represents the 1 st shear creep rate in%/μm, which is the shear creep value per 1 μm thickness at 25 ℃ determined for the 1 st adhesive reference layer after the repeated deformation application test,

R1B represents the 2 nd shear creep rate, which is the value of shear creep per 1 μm thickness at 25 ℃ determined for the 1 st adhesive reference layer before the deformation repeated application test is performed, and has a unit of%/μm,

R2A represents the 3 rd shear creep rate, which is the shear creep value per 1 μm thickness at 25 ℃ determined for the 2 nd adhesive reference layer after the repeated deformation application test, and the unit is%/μm,

R2B represents the 4 th shear creep rate, which is the value of shear creep per 1 μm thickness at 25 ℃ determined for the 2 nd adhesive reference layer before the repeated deformation application test was performed, and is expressed in%/μm.

2. The laminate according to claim 1, wherein the 2 nd shear creep rate is 0.1 to 0.2 in%/μm.

3. The laminate according to claim 1 or 2, wherein at least one of the 1 st adhesive layer and the 2 nd adhesive layer has a thickness of 20 μm to 50 μm.

4. The laminate according to any one of claims 1 to 3, wherein 1 or more phase difference layers are provided between the polarizer layer and the back sheet.

5. The laminate according to any one of claims 1 to 4, wherein the back sheet 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 can be bent with the front panel side as an inner side.