CN117355583A

CN117355583A - Pressure-sensitive adhesive sheet, optical laminate, and image display device

Info

Publication number: CN117355583A
Application number: CN202280036356.3A
Authority: CN
Inventors: 长田润枝; 山本悟士; 久世雅大; 外山雄祐
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-05-21
Filing date: 2022-05-20
Publication date: 2024-01-05
Also published as: JP2022179183A; WO2022244886A1; TW202311470A; KR20240012456A

Abstract

The present invention provides an adhesive sheet, wherein the peak value of stress X (peak stress X) in a stress-strain curve obtained for the adhesive sheet is determined by the following evaluation test _max ) Is more than 0.5 MPa. Evaluation test: the end face of the probe for evaluation (cylindrical shape having a diameter of 5mm, made of stainless steel) was brought into contact with the adhesive surface of the adhesive sheet adhered to the glass plate, and the contact load of 100N was applied to the thickness direction of the adhesive sheet and held for 300 seconds, so that the probe for evaluation was brought into close contact with the adhesive sheet. Next, the probe for evaluation was displaced in a direction perpendicular to the adhesive sheet at a constant speed of 2. Mu.m. The stress X and strain Y in the thickness direction of the adhesive sheet generated by the displacement of the evaluation probe were measured, and the curve was obtained from the measured stress X and strain Y. The adhesive sheet is suitable for suppressing an optical layerThe optical film contained in the stack changes in size, and durability can also be ensured.

Description

Pressure-sensitive adhesive sheet, optical laminate, and image display device

Technical Field

The invention relates to an adhesive sheet, an optical laminate, and an image display device.

Background

In recent years, image display devices typified by liquid crystal display devices and Electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have been rapidly spreading. The various image display devices described above generally have a laminated structure of an image forming layer such as a liquid crystal layer or an EL light emitting layer and an optical laminate including an optical film and an adhesive sheet. The pressure-sensitive adhesive sheet is mainly used for bonding films included in an optical laminate and bonding an image forming layer to the optical laminate. Examples of the optical film are a polarizing plate, a retardation film, and a polarizing plate with a retardation film in which the polarizing plate and the retardation film are integrated. Patent documents 1 and 2 disclose examples of the optical laminate.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open No. 2008-031214

Patent document 2: japanese patent laid-open No. 2009-98665

Disclosure of Invention

Problems to be solved by the invention

Excessive changes in the size of the optical film accompanying temperature changes cause light leakage and color unevenness in the image display device. Light leakage and color unevenness are particularly likely to occur in an image display device having a large size using a polarizing plate with a retardation film. In addition, image display devices in which the frame (bezel) is designed to be narrow (narrowed frame) are becoming popular, and suppression of dimensional changes is becoming more important. In order to suppress the dimensional change, it is considered to increase the elastic modulus of the adhesive sheet contained in the optical laminate. However, if the elastic modulus is merely increased, the durability of the adhesive sheet may be reduced, and the adhesive sheet may not follow the dimensional change.

The purpose of the present invention is to provide an adhesive sheet which is suitable for suppressing dimensional changes of an optical film contained in an optical laminate and which is also ensured in durability.

Means for solving the problems

The present invention provides an adhesive sheet, the peak stress X of which _max Satisfying the following formula (1),

X _max ≥0.5MPa (1)

In the above peak stress X _max The peak value of stress X in the stress-strain curve obtained for the adhesive sheet by the following evaluation test.

Evaluation test-

The end face of the probe for evaluation (cylindrical shape having a diameter of 5mm, made of stainless steel) was brought into contact with the adhesive surface of the adhesive sheet adhered to the glass plate, and the probe for evaluation was brought into close contact with the adhesive sheet by applying a contact load of 100N in the thickness direction of the adhesive sheet and holding for 300 seconds. Then, the evaluation probe was displaced in a direction perpendicular to the pressure-sensitive adhesive sheet at a constant speed of 2. Mu.m. The stress X and strain Y in the thickness direction of the pressure-sensitive adhesive sheet generated in the pressure-sensitive adhesive sheet due to the displacement of the evaluation probe are measured, and a stress-strain curve is obtained from the measured stress X and strain Y.

In another aspect, the present invention provides an optical laminate comprising the adhesive sheet of the present invention described above and an optical film.

In another aspect, the present invention provides an image display device comprising the optical laminate of the present invention.

ADVANTAGEOUS EFFECTS OF INVENTION

The pressure-sensitive adhesive sheet of the present invention is a sheet which is suitable for suppressing dimensional changes of an optical film contained in an optical laminate and which is ensured in durability.

Drawings

Fig. 1 is a cross-sectional view schematically showing an example of the pressure-sensitive adhesive sheet of the present invention.

Fig. 2A is a schematic diagram for explaining an evaluation test for obtaining a stress-strain curve of the adhesive sheet.

Fig. 2B is a schematic diagram for explaining an evaluation test for obtaining a stress-strain curve of the adhesive sheet.

Fig. 2C is a schematic diagram for explaining an evaluation test for obtaining a stress-strain curve of the adhesive sheet.

Fig. 2D is an enlarged view of the area a of fig. 2C.

Fig. 3 is a graph showing an example of stress-strain curves of the adhesive sheet.

Fig. 4 is a schematic diagram for explaining a change in volume of the adhesive sheet accompanying a change in size of the optical film.

Fig. 5 is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

Fig. 6 is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

Fig. 7 is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

Fig. 8 is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

Fig. 9 is a cross-sectional view schematically showing an example of the image display device of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments shown below.

[ adhesive sheet ]

An example of the pressure-sensitive adhesive sheet of the present embodiment is shown in fig. 1. Peak stress X of adhesive sheet 1 of fig. 1 _max The following formula (1) is satisfied.

X _max ≥0.5MPa (1)

In the peak stress X _max The peak value of stress X in the stress-strain curve obtained by the following evaluation test on the adhesive sheet 1.

[ evaluation test ]

An evaluation test for obtaining a stress-strain curve of the adhesive sheet 1 will be described with reference to fig. 2A to 2D. First, the end face 53 of the probe 52 for evaluation (cylindrical shape with a diameter of 5mm, made of stainless steel) was brought into contact with the adhesive surface 11 (exposed surface) of the adhesive sheet 1 adhered to the glass plate 51, and the contact load 54 of 100N was applied in the thickness direction of the adhesive sheet 1 and held for 300 seconds, so that the probe 52 for evaluation was brought into close contact with the adhesive sheet 1 (fig. 2A and 2B). The end face 53 is the bottom face of the probe 52 and has a diameter of 5mm. In order to measure the stress X and the strain Y with good accuracy, the thickness of the adhesive sheet 1 to be adhered is preferably 200 μm or more. In the case where the thickness is less than 200. Mu.m, the thickness can be made to be 200. Mu.m or more by superposing two or more adhesive sheets 1 and bonding them to each other by heating I using an autoclave or the like. The glass plate 51 may be selected from those having a flat surface to which the adhesive sheet 1 is to be adhered and in which peeling of the adhesive sheet 1 does not occur in the evaluation test. The adhesion of the adhesive sheet 1 to the glass plate 51 may be performed so that the adhesive sheet 1 does not peel off during the evaluation test. The bonding state of the adhesive sheet 1 and the glass plate 51 can be stabilized by heating II using an autoclave or the like as necessary. The conditions for heating I and II are, for example, 30 to 90℃and 0.5 to 4 hours, and in the case of using an autoclave, for example, 30 to 70℃and 5 to 30 minutes and 2 to 10 atmospheres (absolute pressure). The heating I and the heating II may be performed simultaneously in a state where the superimposed pressure-sensitive adhesive sheet 1 is adhered to the glass plate 51. As the evaluation probe 52, a probe for a predetermined probe tack test based on ASTM D-2979 can be used.

Next, the evaluation probe 52 is displaced in a direction perpendicular to the surface of the adhesive sheet 1 and away from the adhesive sheet 1 (fig. 2C). This direction generally coincides with the thickness direction of the adhesive sheet 1. The speed of displacement was kept constant at 2 μm/min. The stress X and the strain Y in the thickness direction generated in the adhesive sheet 1 by the displacement of the evaluation probe 52 are measured, and a stress-strain curve is obtained based on the measured stress X and strain Y with the strain Y as the horizontal axis and the stress X as the vertical axis. The evaluation test may be performed by a tensile tester, for example. The stress X can be measured by, for example, a load cell of a tensile testing machine connected to the evaluation probe 52. Regarding the strain Y, the thickness (initial thickness) of the adhesive sheet 1 before the displacement of the evaluation probe 52 can be set to t ₀ (μm) from the beginning of the displacementThe displacement of the probe 52 for evaluation is D (μm) (see fig. 2D obtained by enlarging the region a in fig. 2C), and the formula is represented by strain y=d/t ₀ And the result was obtained. The displacement d corresponds to the deformation t in the thickness direction of the adhesive sheet 1 associated with the displacement of the evaluation probe 52 ₁ 。

An example of stress-strain curves of the adhesive sheet is shown in fig. 3. Stress-strain curves 101, 102, 103, 104, respectively, exhibited by four types of adhesive sheets are shown in fig. 3. The adhesive sheet 1 showing the curves 101, 103 and 104 satisfies the formula (1). The adhesive sheet exhibiting the curve 102 does not satisfy the formula (1). Regarding curve 101, X is implemented at its vertex a _max 。

As shown in fig. 4, if the size of the optical film 111 is changed, the volume of the adhesive sheet 112 bonded thereto is also changed. In the example of fig. 4, the volume of the pressure-sensitive adhesive sheet 112 increases by the amount of the enlarged region 115 with the expansion of the optical film 111 in the in-plane direction (note that the symbols 114 and 116 are the end portions of the optical film 111 before and after expansion, respectively, and the symbol 113 is an adherend such as a glass substrate). Peak stress X _max A pressure-sensitive adhesive sheet 1 of 0.5MPa or more means that the stress against the above-mentioned volume change is sufficiently large, whereby the durability can be ensured while suppressing the dimensional change of the optical film 111. The above-described evaluation test in which the evaluation probe 52 was displaced at a very small speed (2 μm/min) was considered to reflect the pattern of volume change of the adhesive sheet 112 accompanying the dimensional change of the optical film 111 well.

X _max The pressure may be 0.6MPa or more, 0.8MPa or more, 0.9MPa or more, 1.0MPa or more, 1.2MPa or more, 1.4MPa or more, and further may be 1.5MPa or more. X is X _max The upper limit of (2) is, for example, 5MPa or less.

In the stress-strain curve, the stress X reaches the peak stress X _max Strain Y at time _m The following expression (2) can be satisfied.

Y _m ≥0.05 (2)

The adhesive sheet 1 showing the curves 101, 104 of fig. 3 satisfies the formula (2). Y of curve 101 _m Implemented at vertex a. Y is Y _m When the volume of the pressure-sensitive adhesive sheet 1 is 0.05 or more, the pressure-sensitive adhesive sheet can resist the change even when the volume is changed more greatly. Y is Y _m The ratio may be 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, and further may be 0.16 or more. Y is Y _m The upper limit of (2) is, for example, 0.3 or less.

In the stress-strain curve, peak stress X is reached at stress X _max Strain Y at the time of later falling to 0.15MPa _0.15 The following expression (3) can be satisfied.

Y _0.15 ≥0.28 (3)

The adhesive sheet 1 exhibiting the curve 101 satisfies the formula (3). Y of curve 101 _0.15 Implemented at point B. Y is Y _0.15 By 0.28 or more, it is meant that after the stress of the pressure-sensitive adhesive sheet 1 against volume change passes over the peak, a certain stress can be maintained until a larger strain by, for example, suppressing the generation of an area (void or the like) in the interior of the pressure-sensitive adhesive sheet 1 where no pressure-sensitive adhesive component is present. Y is Y _0.15 The ratio may be 0.29 or more, 0.30 or more, 0.31 or more, 0.32 or more, and further 0.33 or more. Y is Y _0.15 The upper limit of (2) is, for example, 1.00 or less.

Y _0.15 Satisfies the above range and the strain Y _m The pressure-sensitive adhesive sheet 1 of 0.09 or more, particularly 0.13 or more is particularly preferable for improvement of durability. In addition, Y _0.15 Satisfies the above range and peak stress X _max The pressure-sensitive adhesive sheet 1 having a thickness of 0.9MPa or more, particularly 1MPa or more, 1.1MPa or more, and further 1.2MPa or more is particularly preferable for achieving a balance between suppression of dimensional change and maintenance of durability.

In the stress-strain curve, the stress X reaches the peak stress X _max Strain Y at the time of later falling to 0.15MPa _0.15 Peak stress X with respect to stress X _max Strain Y at time _m Ratio Y of _0.15 /Y _m The following expression (4) can be satisfied.

Y _0.15 /Y _m ≥2 (4)

The adhesive sheet 1 showing the curve 101 of fig. 3 satisfies the formula (4). Ratio Y _0.15 /Y _m A stress of 2 or more means that the pressure-sensitive adhesive sheet 1 resistant to volume change reaches a larger strain after passing the peak, and the occurrence of voids and the like and the rate of occurrence can be suppressed. Ratio Y _0.15 /Y _m May be 2.1 or more. Ratio Y _0.15 /Y _m The upper limit of (2) is, for example, 10 or less.

X of the adhesive sheet 1 _max 、Y _m Y and Y _0.15 For example, based on the type, glass transition temperature (Tg) and composition of the base polymer contained in the adhesive composition; the kind and the compounding amount of the cross-linking agent; the type and amount of additives such as a thickener (thickener); and drying (curing) conditions for forming an adhesive sheet from the adhesive composition.

The thickness of the pressure-sensitive adhesive sheet 1 may be, for example, 1 to 200. Mu.m, or 5 to 150. Mu.m, or further 10 to 100. Mu.m.

The storage modulus G' (25 ℃) of the pressure-sensitive adhesive sheet 1 is, for example, 0.15MPa or more, 0.2MPa or more, 0.25MPa or more, 0.3MPa or more, 0.5MPa or more, 0.6MPa or more, 0.7MPa or more, 0.8MPa or more, 0.9MPa or more, 1.0MPa or more, 1.1MPa or more, and further may be 1.2MPa or more. The upper limit of the storage modulus G' (25 ℃) is, for example, 5MPa or less, may be 3.0MPa or less, 2.5MPa or less, and further may be 2.0MPa or less. The adhesive sheet 1 having a high elastic modulus in the above range of the storage modulus G' is more preferable for suppressing dimensional change of the optical film.

The storage modulus (25 ℃) of the adhesive sheet 1 can be evaluated by the following method. First, a sample for measurement formed of a material constituting the adhesive sheet 1 is prepared. The measurement sample was disk-shaped, and the bottom surface of the measurement sample had a diameter of 8mm and a thickness of 2mm. The measurement sample may be obtained by punching out a laminate in which a plurality of adhesive sheets 1 are laminated into a disc shape. Next, a dynamic viscoelasticity measurement is performed on the measurement sample, and for example, ARES-G2 manufactured by TA Instruments is used for the dynamic viscoelasticity measurement. From the result of the dynamic viscoelasticity measurement, the storage modulus G' of the adhesive sheet 1 at 25 ℃ can be determined. The conditions for dynamic viscoelasticity measurement are as follows.

Measurement conditions

Frequency: 1Hz

Deformation mode: torsion

Measuring temperature: -70-150 DEG C

Heating rate: 5 ℃/min

The gel fraction of the pressure-sensitive adhesive sheet 1 is, for example, 60% or more, 65% or more, and more preferably 70% or more. The upper limit of the gel fraction is, for example, 99% or less, 98% or less, 97% or less, 96% or less, and further 95% or less. The adhesive sheet 1 having the gel fraction within the above range is more preferable for suppressing the dimensional change of the optical film.

The gel fraction of the adhesive sheet 1 can be evaluated by the following method. First, about 0.2g was scraped from the adhesive sheet 1 to obtain a small sheet. Next, the obtained small pieces were wrapped with a stretched porous film of polytetrafluoroethylene (NTF 1122, average pore size 0.2 μm, manufactured by Nitto electric Co., ltd.) and bound with kite string to prepare test pieces. Next, the weight a of the obtained test piece was measured. The weight A is the sum of the weights of the small pieces of the adhesive sheet, the stretched porous film and the kite string. The total weight B of the stretched porous film and kite string used was measured in advance. Next, the test piece was immersed in a 50mL container filled with ethyl acetate, and allowed to stand at 23℃for 1 week. After standing, the test piece was taken out from the container, dried in a dryer set at 130℃for 2 hours, and then the weight C of the test piece was measured. According to the measured weights A, B and C and according to the formula: gel fraction (wt%) the gel fraction of the adhesive sheet 1 was calculated as = (C-B)/(a-B) ×100 (%).

The adhesive sheet 1 can be used for optical applications, for example. The adhesive sheet 1 may be used for an optical laminate and/or an image display device. The pressure-sensitive adhesive sheet 1 is suitable for use in, for example, an image display device having a narrow frame, an image display device having a large screen size, and the like, and is particularly required to suppress dimensional changes in an optical film. By using these image display devices, for example, peeling of a film contained in an optical laminate can be suppressed.

The adhesive sheet 1 may be formed of an adhesive composition, for example, as described below. As for the solvent-based adhesive composition, for example, an adhesive composition or a mixture of an adhesive composition and a solvent is applied to a base film, and the resulting coated film is dried to form the adhesive sheet 1. The adhesive composition thermally cures by heat upon drying. In the active energy ray-curable (photocurable) adhesive composition, for example, a mixture of a base film and a solvent and an additive such as a polymerization initiator or a crosslinking agent, which contains a monomer (group) that is polymerized to form an adhesive polymer and, if necessary, a part of the monomer (group), is applied to the base film, and an active energy ray is irradiated to form the adhesive sheet 1. The solvent may be removed by drying before irradiation with the active energy ray. The base film may be a film (release film) obtained by subjecting the coated surface to a release treatment. The type of the adhesive composition is not limited to the above examples.

The type of the adhesive composition may be, for example, emulsion type, hot melt type (hot melt type). The adhesive composition may be solvent-based in view of being able to form the adhesive sheet 1 having more excellent durability. The solvent-based adhesive composition may not contain a light curing agent such as an ultraviolet curing agent.

The adhesive sheet 1 formed on the base film may be transferred to an arbitrary layer. In addition, the base film may be an optical film, and in this case, an optical laminate including the adhesive sheet 1 and the optical film can be obtained.

The substrate film may be coated by a known method. The coating may be performed by, for example, a roll coating method, a gravure coating method, a reverse coating method, a roll brushing method, a spray coating method, a dip roll coating method, a bar coating method, a blade coating method, an air knife coating method, a shower coating method, a die lip coating method, an extrusion coating method using a die coater, or the like.

The solvent type is used, and the drying temperature after coating is, for example, 40 to 200 ℃. The drying temperature of the adhesive composition (I) to be described later may be 160℃or lower, 150℃or lower, 130℃or lower, 120℃or lower, and further 100℃or lower. For example, the combination of the adhesive composition (I) and the drying temperature of 130 ℃ or lower, 120 ℃ or lower, and further 100 ℃ or lower can give the adhesive sheet 1 having more excellent durability. In other words, the adhesive sheet 1 can be obtained by drying the coating film containing the adhesive composition (I) at a temperature of 130 ℃ or less, 120 ℃ or less, and further 100 ℃ or less. The drying time is, for example, 5 seconds to 20 minutes, may be 5 seconds to 10 minutes, and may be further 10 seconds to 5 minutes. In the case of the active energy ray-curable type, the drying temperature and the drying time in the case of drying after coating may be in the above ranges.

The compositions and mixtures applied to the substrate film preferably have a viscosity suitable for handling and application. Thus, with respect to the active energy ray-curable type, the applied mixture preferably contains a partial polymer of the monomer(s).

In one example of the release film, the coated surface is subjected to a release treatment by an organosilicon compound.

The adhesive sheet 1 may be an acrylic adhesive sheet formed of an acrylic adhesive composition.

As an example of the adhesive composition capable of forming the adhesive sheet 1, the adhesive composition (I) will be described. However, the adhesive composition used for forming the adhesive sheet 1 is not limited to the adhesive composition (I).

[ adhesive composition (I) ]

The adhesive composition (I) comprises a (meth) acrylic polymer (A) and a crosslinking agent (B). The (meth) acrylic polymer (a) is contained in the composition as a main component. In other words, the adhesive composition (I) is an acrylic adhesive composition. The adhesive sheet 1 formed from the adhesive composition (I) contains, for example, a crosslinked product of the (meth) acrylic polymer (a).

In the present specification, "(meth) acrylic" means acrylic acid and methacrylic acid. In addition, "(meth) acrylate" means acrylate and methacrylate.

The main component is the component having the largest content in the composition. The content of the main component is, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, and further 75% by weight or more.

[ (meth) acrylic Polymer (A) ]

The (meth) acrylic polymer (a) preferably has a structural unit derived from a (meth) acrylic monomer (A1) having an alkyl group having 1 to 30 carbon atoms in a side chain as a main unit. The alkyl group may be linear or branched. The (meth) acrylic polymer (a) may have one or two or more structural units derived from the (meth) acrylic monomer (A1). Examples of the (meth) acrylic monomer (A1) are methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, n-hexyl (meth) acrylate, isohexyl (meth) acrylate, isoheptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate and n-tetradecyl (meth) acrylate. In the present specification, "main unit" means, for example, a unit which occupies 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and still more preferably 80% by weight or more of all the structural units of the polymer.

The (meth) acrylic polymer (a) may have a structural unit derived from a (meth) acrylic monomer (A1) having a long-chain alkyl group in a side chain. An example of the monomer (A1) is n-dodecyl (meth) acrylate (lauryl (meth) acrylate). In the present specification, "long-chain alkyl group" means an alkyl group having 6 to 30 carbon atoms.

The (meth) acrylic polymer (a) may have a structural unit derived from a (meth) acrylic monomer (A1) having a glass transition temperature (Tg) in the range of-70 to-20 ℃ when formed into a homopolymer. An example of this monomer (A1) is n-butyl acrylate.

The (meth) acrylic polymer (a) may have a structural unit other than the structural unit derived from the (meth) acrylic monomer (A1). The structural unit is derived from a monomer (A2) copolymerizable with the (meth) acrylic monomer (A1). The (meth) acrylic polymer (a) may have one or two or more of the structural units.

Examples of the monomer (A2) are aromatic ring-containing monomers. The aromatic ring-containing monomer may be an aromatic ring-containing (meth) acrylic monomer. Examples of aromatic ring-containing monomers are phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, ethylene oxide modified nonylphenol (meth) acrylate, hydroxyethylated beta-naphthol (meth) acrylate, biphenyl (meth) acrylate. The content of the structural unit derived from the aromatic ring-containing monomer in the (meth) acrylic polymer (a) is, for example, 0 to 50% by weight, may be 1 to 30% by weight, 5 to 25% by weight, 8 to 20% by weight, 10 to 18% by weight, and may be 12 to 16% by weight. By providing the (meth) acrylic polymer (a) with a structural unit derived from an aromatic ring-containing monomer, for example, the compatibility of the (meth) acrylic polymer (a) with the crosslinking agent (B) can be improved. The improvement in compatibility can form the adhesive sheet 1 into a crosslinked structure excellent in uniformity, and inhibit the precipitation of the crosslinking agent (B) or its self-polymers. In other words, the improvement of the compatibility can contribute to the further improvement of the durability of the adhesive sheet 1. The above effect due to the improvement of the compatibility is particularly advantageous when the blending amount of the crosslinking agent (B) is increased in order to achieve high elasticity and the like.

Other examples of the monomer (A2) are hydroxyl group-containing monomers. The hydroxyl group-containing monomer may be a hydroxyl group-containing (meth) acrylic monomer. Examples of the hydroxyl group-containing monomer are hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate and 12-hydroxylauryl (meth) acrylate, and (4-hydroxymethylcyclohexyl) methyl acrylate. The hydroxyl group may react with the crosslinking agent (B). The content of the structural unit derived from the hydroxyl group-containing monomer in the (meth) acrylic polymer (a) may be 1 wt% or less, may be 0.5 wt% or less, may be 0.1 wt% or less, and may be 0 wt% (may not contain the structural unit) from the viewpoint of improving the uniformity of the crosslinked structure.

The monomer (A2) may be a carboxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer. Examples of carboxyl group-containing monomers are (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid and butenoic acid. Examples of amino group-containing monomers are N, N-dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate. Examples of the amide group-containing monomer are acrylamide-based monomers such as (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-isopropyl acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-hydroxymethyl-N-propyl (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaptomethyl (meth) acrylamide and mercaptoethyl (meth) acrylamide; n-acryl heterocyclic monomers such as N- (meth) acryl morpholine, N- (meth) acryl piperidine and N- (meth) acryl pyrrolidine; n-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-. Epsilon. -caprolactam. The self-polymerizability of the crosslinking agent (B) can be improved, for example, by providing the (meth) acrylic polymer (a) with a structural unit derived from a carboxyl group-containing monomer, particularly, acrylic acid. The improvement of the self-polymerizability of the crosslinking agent (B) can contribute particularly to the suppression of peeling of the adhesive sheet in a humidified environment and the stabilization of the physical properties of the adhesive sheet in a system having a high content of the crosslinking agent (B).

The monomer (A2) may be a polyfunctional monomer. Examples of the polyfunctional monomer are polyfunctional acrylates such as hexanediol di (meth) acrylate (1, 6-hexanediol di (meth) acrylate), butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate; divinylbenzene. The multifunctional acrylate is preferably 1, 6-hexanediol diacrylate, dipentaerythritol hexa (meth) acrylate.

The total content of the structural units derived from the carboxyl group-containing monomer, the amino group-containing monomer, the amide group-containing monomer and the polyfunctional monomer in the (meth) acrylic polymer (a) is preferably 20% by weight or less, more preferably 10% by weight or less, and still more preferably 8% by weight or less. When the (meth) acrylic polymer (a) has the structural unit, the total content may be, for example, 0.01% by weight or more, or 0.05% by weight or more. The (meth) acrylic polymer (a) may not contain a structural unit derived from a polyfunctional monomer.

Examples of the other monomer (A2) are alkoxyalkyl (meth) acrylates such as 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, methoxytriethylene glycol (meth) acrylate, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate; epoxy group-containing monomers such as glycidyl (meth) acrylate and methyl glycidyl (meth) acrylate; sulfonic acid group-containing monomers such as sodium vinylsulfonate; a phosphate group-containing monomer; (meth) acrylic esters having alicyclic hydrocarbon groups such as cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and vinyl toluene; olefins such as ethylene, propylene, butadiene, isoprene and isobutylene, or dienes; vinyl ethers such as vinyl alkyl ether; vinyl chloride.

The total content of the structural units derived from the other monomer (A2) in the (meth) acrylic polymer (a) is, for example, 30% by weight or less, or 10% by weight or less, preferably 0% by weight (excluding the structural units).

The (meth) acrylic polymer (a) can be formed by polymerizing one or two or more monomers described above by a known method. The monomers may also be polymerized with a partial polymer of the monomers. The polymerization may be carried out by, for example, solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, active energy ray polymerization. Since the pressure-sensitive adhesive sheet 1 excellent in optical transparency can be formed, solution polymerization and active energy ray polymerization are preferable. The polymerization is preferably carried out while avoiding contact between the monomer and/or a part of the polymer and oxygen, and for this purpose, polymerization in an inert gas atmosphere such as nitrogen or polymerization in a state of blocking oxygen by a resin film or the like may be used. The (meth) acrylic polymer (a) to be formed may be in any form of a random copolymer, a block copolymer, a graft copolymer, and the like.

The polymerization system forming the (meth) acrylic polymer (a) may contain one or two or more polymerization initiators. The type of the polymerization initiator may be selected according to the polymerization reaction, and may be, for example, a thermal polymerization initiator or a photopolymerization initiator.

The solvent used in the solution polymerization is, for example, esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; ketones such as methyl ethyl ketone and methyl isobutyl ketone, but the solvent is not limited to the above examples. The solvent may be a mixed solvent of two or more solvents.

The polymerization initiator used in the solution polymerization is, for example, azo-based polymerization initiator, peroxide-based polymerization initiator, and redox-based polymerization initiator. The peroxide-based polymerization initiator is, for example, dibenzoyl peroxide or t-butyl peroxymaleate. Among them, the azo-based polymerization initiator disclosed in Japanese patent application laid-open No. 2002-69411 is preferable. The azo-based polymerization initiator is, for example, 2 '-Azobisisobutyronitrile (AIBN), 2' -azobis (2-methylbutyronitrile), dimethyl 2,2 '-azobis (2-methylpropionate), 4' -azobis (4-cyanovaleric acid), but the polymerization initiator is not limited to the above examples. The azo-based polymerization initiator may be used in an amount of, for example, 0.05 to 0.5 part by weight or 0.1 to 0.3 part by weight based on 100 parts by weight of the total amount of the monomers.

The active energy rays used for active energy ray polymerization include, for example, ionizing rays such as α rays, β rays, γ rays, neutron rays, and electron rays, and ultraviolet rays. The active energy ray is preferably ultraviolet ray. Polymerization by irradiation with ultraviolet rays is also called photopolymerization. The polymerization system of active energy ray polymerization typically contains a photopolymerization initiator. The polymerization conditions for the active energy polymerization are not limited as long as the (meth) acrylic polymer (a) can be formed.

The photopolymerization initiator is, for example, benzoin ether type photopolymerization initiator, acetophenone type photopolymerization initiator, α -ketonic type photopolymerization initiator, aromatic sulfonyl chloride type photopolymerization initiator, photoactive oxime type photopolymerization initiator, benzoin type photopolymerization initiator, benzil type photopolymerization initiator, benzophenone type photopolymerization initiator, ketal type photopolymerization initiator, thioxanthone type photopolymerization initiator, but the photopolymerization initiator is not limited to the above examples.

The benzoin ether photopolymerization initiator is, for example, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-dimethoxy-1, 2-diphenylethane-1-one, anisole methyl ether. Examples of the acetophenone photopolymerization initiator include 2, 2-diethoxyacetophenone, 2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl) dichloroacetophenone. The α -ketonic photopolymerization initiator is, for example, 2-methyl-2-hydroxyphenylacetone, 1- [4- (2-hydroxyethyl) phenyl ] -2-methylpropan-1-one. The aromatic sulfonyl chloride-based photopolymerization initiator is, for example, 2-naphthalenesulfonyl chloride. The photo-active oxime photopolymerization initiator is, for example, 1-phenyl-1, 1-propanedione-2- (O-ethoxycarbonyl oxime). The benzoin photopolymerization initiator is, for example, benzoin. The benzil photopolymerization initiator is, for example, benzil. Examples of the benzophenone photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3' -dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α -hydroxycyclohexyl phenyl ketone. The ketal photopolymerization initiator is, for example, benzil dimethyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-diisopropylthioxanthone and dodecylthioxanthone.

The photopolymerization initiator may be used in an amount of, for example, 0.01 to 1 part by weight or 0.05 to 0.5 part by weight based on 100 parts by weight of the total amount of the monomers.

The weight average molecular weight (Mw) of the (meth) acrylic polymer (a) is, for example, 100 to 250 ten thousand, and may be 120 ten thousand or more, and further 140 ten thousand or more from the viewpoint of the durability and heat resistance of the pressure-sensitive adhesive sheet. The weight average molecular weight (Mw) of the polymer and oligomer in the present specification is a value (in terms of polystyrene) obtained by measurement based on GPC (gel permeation chromatography).

The content of the (meth) acrylic polymer (a) in the adhesive composition (I) may be, for example, 50% by weight or more, 60% by weight or more, 70% by weight or more, and further 80% by weight or more, based on the solid content. The upper limit of the content is, for example, 99% by weight or less, 97% by weight or less, 95% by weight or less, 93% by weight or less, and further 90% by weight or less.

[ Cross-linking agent (B) ]

The crosslinking agent (B) is typically a multifunctional crosslinking agent having 2 or more crosslinking reactive groups per 1 molecule. The crosslinking agent (B) may be a crosslinking agent having 3 or more functions and having 3 or more crosslinking reactive groups per 1 molecule. The upper limit of the number of crosslinking reactive groups per 1 molecule is, for example, 5.

The crosslinking agent (B) is, for example, an isocyanate-based crosslinking agent. The isocyanate-based crosslinking agent contains an isocyanate group as a crosslinking reactive group. The isocyanate-based crosslinking agent (B) may be an aromatic isocyanate compound, a cycloaliphatic isocyanate compound, or an aliphatic isocyanate compound.

Examples of the aromatic isocyanate compound which can be used for the crosslinking agent (B) are phenylene diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 2' -diphenylmethane diisocyanate, 4' -toluidine diisocyanate, 4' -diphenyl ether diisocyanate, 4' -biphenyl diisocyanate (4, 4' -diphenyl diisocyanate), 1, 5-naphthalene diisocyanate, xylylene diisocyanate.

Examples of the alicyclic isocyanate compound which can be used for the crosslinking agent (B) are 1, 3-cyclopentene diisocyanate, 1, 3-cyclohexane diisocyanate, 1, 4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate and hydrogenated tetramethylxylylene diisocyanate.

Examples of aliphatic isocyanate compounds which can be used as the crosslinking agent (B) are trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1, 2-propylene diisocyanate, 1, 3-butylene diisocyanate, dodecamethylene diisocyanate and 2, 4-trimethylhexamethylene diisocyanate.

The crosslinking agent (B) may be a derivative of the isocyanate compound. Examples of the derivative are a polymer (dimer, trimer, pentamer, etc.), an adduct (adduct) obtained by adding a polyol such as trimethylolpropane, a urea modified product, a biuret modified product, an allophanate modified product, an isocyanurate modified product, a carbodiimide modified product, and a urethane prepolymer obtained by adding a polyether polyol, a polyester polyol, an acrylic polyol, a polybutadiene polyol, a polyisoprene polyol, etc.

The crosslinking agent (B) is preferably an aromatic isocyanate compound or a derivative thereof, more preferably toluene diisocyanate or a derivative thereof (in other words, more preferably toluene diisocyanate-based (TDI-based) crosslinking agent). The TDI-based crosslinking agent is excellent in uniformity of reaction as compared with xylylene diisocyanate and its derivatives (in other words, xylylene diisocyanate-based (XDI-based) crosslinking agents). Examples of TDI-based crosslinkers are adducts of toluene diisocyanate with polyfunctional alcohols, more specific examples are trimethylol propane/toluene diisocyanate trimer adducts.

As the crosslinking agent (B), commercially available ones can be used. Examples of commercial products are Milliconate MT, milliconate MTL, milliconate MR-200, milliconate MR-400, coronate L, coronate HL and Coronate HX (all trade names above), and Takenate D-102, takenate D-103, takenate D-110N, takenate D-120N, takenate D-140N, takenate D-160N, takenate D-165N, takenate D-170HN, takenate D-178N, takenate and Takenate 600 (all trade names above). As the crosslinking agent (B), it is preferable to use Coronate L, takenate D-102 and Takenate D-103 (both trimethylolpropane/toluene diisocyanate trimer adducts).

The adhesive composition (I) may contain one or two or more crosslinking agents (B).

The amount of the crosslinking agent (B) blended in the adhesive composition (I) may be, for example, 0.5 to 30 parts by weight, or 1 to 28 parts by weight, 5 to 25 parts by weight, 8 to 20 parts by weight, 10 to 18 parts by weight, more than 10 parts by weight and 15 parts by weight, 11 to 13 parts by weight, or less, based on 100 parts by weight of the (meth) acrylic polymer (a).

According to the studies by the present inventors, if the blending amount of the crosslinking agent (B) is 5 parts by weight or more, particularly 8 parts by weight or more, 10 parts by weight or more, and further 11 parts by weight or more, the crosslinking agent (B) reacts with each other to form a self-polymer of the crosslinking agent (B), that is, a polymer containing a structural unit derived from the crosslinking agent (B) as a main component, easily when the adhesive sheet 1 is formed. In the self-assembled substance, the content of the structural unit derived from the crosslinking agent (B) may be, for example, 70% by weight or more, 90% by weight or more, 95% by weight or more, and further 99% by weight or more. The polymer may be formed only from the structural units derived from the crosslinking agent (B). The formation of the self-assembly substance contributes to achieving a higher peak stress X by imparting a sufficient cohesive force to the adhesive sheet 1 _max . The adhesive sheet 1 may have an interpenetrating network (IPN) structure of a crosslinked product of the (meth) acrylic polymer (a) and a self-polymer of the crosslinking agent (B). Durability improvement of IPN structure to adhesive sheet 1High is desirable.

Other examples of the crosslinking agent (B) are peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents and multifunctional metal chelates. Among them, the crosslinking agent (B) is preferably an isocyanate. When the adhesive composition (I) contains the crosslinking agent (B) other than isocyanates, the total amount thereof is preferably 0.1 to 5 parts by weight, more preferably in the order of 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, and 0.1 to 1 part by weight, relative to 100 parts by weight of the (meth) acrylic polymer (a). The adhesive composition (I) may contain no crosslinking agent (B) other than isocyanate, for example, an epoxy crosslinking agent.

[ (meth) acrylic oligomer ]

The adhesive composition (I) may further comprise a (meth) acrylic oligomer (D).

The (meth) acrylic oligomer (D) may have the same composition as the (meth) acrylic polymer (a) described above, except that the weight average molecular weight (Mw) is different. The weight average molecular weight (Mw) of the (meth) acrylic oligomer (D) is, for example, 1000 or more, or 2000 or more, 3000 or more, and 4000 or more. The upper limit of the weight average molecular weight (Mw) of the (meth) acrylic oligomer is, for example, 30000 or less, or 15000 or less, 10000 or less, and further 7000 or less.

The (meth) acrylic oligomer (D) has, for example, one or two or more structural units derived from each of the following monomers: (meth) acrylic acid alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, and dodecyl (meth) acrylate; esters of (meth) acrylic acid and alicyclic alcohols such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and dicyclopentanyl (meth) acrylate; aromatic ring-containing (meth) acrylates such as phenyl (meth) acrylate and benzyl (meth) acrylate; and (meth) acrylic esters derived from terpene compound derivative alcohols.

The (meth) acrylic oligomer (D) preferably has a structural unit derived from a (meth) acrylic monomer having a relatively large-volume structure. In this case, the adhesiveness of the adhesive sheet can be further improved. Examples of the acrylic monomer are alkyl (meth) acrylates containing an alkyl group having a branched structure such as isobutyl (meth) acrylate and t-butyl (meth) acrylate; esters of (meth) acrylic acid and alicyclic alcohols such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and dicyclopentanyl (meth) acrylate; aromatic ring-containing (meth) acrylates such as phenyl (meth) acrylate and benzyl (meth) acrylate. Preferably, the monomer has a cyclic structure, and more preferably, has 2 or more cyclic structures. In addition, from the viewpoint that polymerization and/or formation of an adhesive sheet is not easily hindered when ultraviolet irradiation is performed in polymerizing the (meth) acrylic oligomer (D), it is preferable that the monomer does not have an unsaturated bond, and for example, an ester of (meth) acrylic acid and an alicyclic alcohol containing an alkyl group having a branched structure can be used.

Specific examples of the (meth) acrylic oligomer (D) are butyl acrylate, a copolymer of methyl acrylate and acrylic acid, a copolymer of cyclohexyl methacrylate and isobutyl methacrylate, a copolymer of cyclohexyl methacrylate and isobornyl methacrylate, a copolymer of cyclohexyl methacrylate and acryloylmorpholine, a copolymer of cyclohexyl methacrylate and diethylacrylamide, a copolymer of 1-adamantyl acrylate and methyl methacrylate, a copolymer of dicyclohexyl methacrylate and isobornyl methacrylate, a copolymer of at least one selected from the group consisting of dicyclohexyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate and cyclopentyl methacrylate, a homopolymer of dicyclohexyl acrylate, a homopolymer of 1-adamantyl methacrylate and a homopolymer of 1-adamantyl acrylate.

The polymerization of the (meth) acrylic oligomer (D) may be carried out by the polymerization method of the (meth) acrylic polymer (a) described above.

When the adhesive composition (I) contains the (meth) acrylic oligomer (D), the amount thereof to be blended is, for example, 70 parts by weight or less, 50 parts by weight or less, and further 40 parts by weight or less, based on 100 parts by weight of the (meth) acrylic polymer (a). The lower limit of the amount to be blended is, for example, 1 part by weight or more, may be 2 parts by weight or more, and further may be 3 parts by weight or more, based on 100 parts by weight of the (meth) acrylic polymer (a). The adhesive composition (I) may also be free of the (meth) acrylic oligomer (D).

[ additive ]

The adhesive composition (I) may also contain other additives. Examples of the additives include colorants such as silane coupling agents, pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, re-operation improvers, softeners, antioxidants, age inhibitors, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (alkali metal salts as ionic compounds, ionic liquids, ionic solids, etc.), inorganic fillers, organic fillers, powders such as metal powders, particles, and foils. The additive may be blended in a range of, for example, 10 parts by weight or less, preferably 5 parts by weight or less, more preferably 1 part by weight or less, per 100 parts by weight of the (meth) acrylic polymer (a).

Examples of the silane coupling agent include epoxy-containing silane coupling agents such as 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl methyl diethoxysilane and 2- (3, 4-epoxycyclohexyl) ethyl trimethoxysilane, amino-containing silane coupling agents such as 3-aminopropyl trimethoxysilane, N-2- (aminoethyl) -3-aminopropyl methyl dimethoxysilane, 3-triethoxysilyl-N- (1, 3-dimethylbutylidene) propylamine and N-phenyl-gamma-aminopropyl trimethoxysilane, (meth) acryl-containing silane coupling agents such as 3-acryloxypropyl trimethoxysilane and 3-methacryloxypropyl triethoxysilane, and isocyanate-containing silane coupling agents such as 3-isocyanate propyl triethoxysilane.

When the adhesive composition (I) contains a silane coupling agent, the amount of the silane coupling agent to be blended is, for example, 5 parts by weight or less, 3 parts by weight or less, 1 part by weight or less, 0.5 part by weight or less, 0.2 part by weight or less, 0.1 part by weight or less, and further 0.05 part by weight or less based on 100 parts by weight of the (meth) acrylic polymer (a). The adhesive composition (I) may also contain no silane coupling agent.

The type of the adhesive composition (I) is, for example, emulsion type, solvent type (solution type), active energy ray curing type (photo curing type), hot melt type (hot melt type). The adhesive composition (I) may be a solvent type from the viewpoint of being able to form an adhesive sheet more excellent in durability. The solvent-based adhesive composition (I) may contain no photo-curing agent such as an ultraviolet curing agent.

[ optical laminate ]

Fig. 5 shows an example of the optical laminate of the present embodiment. The optical laminate 10A of fig. 5 includes an adhesive sheet 1 and an optical film 2, and the adhesive sheet 1 and the optical film 2 are laminated to each other. The optical laminate 10A may be used in the form of an optical film with an adhesive sheet.

Examples of the optical film 2 are laminated films including a polarizing plate, a phase difference film, and a polarizing plate and/or a phase difference film. The optical film 2 is not limited to the above examples, and the optical film 2 may include a glass film.

The polarizer comprises a polarizer. A polarizer protective film may be bonded to at least one surface of the polarizer. Any adhesive or bonding agent may be used for bonding the polarizer to the polarizer protective film. The adhesive sheet 1 may be used for bonding. The polarizer is typically a polyvinyl alcohol (PVA) film obtained by orienting iodine by stretching in a gas atmosphere (dry stretching), boric acid water stretching, or the like.

The retardation film is a film having birefringence in the in-plane direction and/or the thickness direction. The retardation film is, for example, a stretched resin film or a film obtained by aligning and fixing a liquid crystal material.

The retardation film may be a λ/4 plate, a λ/2 plate, an antireflection retardation film (see, for example, paragraphs 0221, 0222, and 0228 of japanese unexamined patent application publication No. 2012-133303), a retardation film for viewing angle compensation (see, for example, paragraphs 0225 and 0226 of japanese unexamined patent application publication No. 2012-133303), or a tilt orientation retardation film for viewing angle compensation (see, for example, paragraph 0227 of japanese unexamined patent application publication No. 2012-13303). The retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and/or the thickness direction. The retardation value, the arrangement angle, the three-dimensional birefringence, the single layer or the multiple layers of the retardation film are not limited. The retardation film may be a known film.

The thickness of the optical film 2 is, for example, 1 to 200. Mu.m. The thickness of the optical film 2 as a polarizing plate is, for example, 1 to 150. Mu.m, and may be 100 μm or less, 75 μm or less, 50 μm or less, 20 μm or less, and further 15 μm or less. The lower limit of the thickness may be 10 μm or more, 20 μm or more, 50 μm or more, 75 μm or more, and further 100 μm or more.

The optical film 2 may be a single layer or a laminated film composed of 2 or more layers. In the case where the optical film 2 is a laminated film, the adhesive sheet 1 may be used for bonding the layers.

Fig. 6 shows another example of the optical laminate of the present embodiment. The optical laminate 10B of fig. 6 has a laminated structure in which the release liner 3, the adhesive sheet 1, and the optical film 2 are laminated in this order. The optical laminate 10B may be used in the form of an optical film formed as a pressure-sensitive adhesive sheet by peeling the release liner 3.

The release liner 3 is typically a resin film. Examples of the resin constituting the release liner 3 are polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, polycarbonates, acrylic, polystyrene, polyamide, and polyimide. The surface of the release liner 3 contacting the adhesive sheet 1 may be subjected to a release treatment. The peeling treatment is, for example, a treatment using an organosilicon compound. However, the release liner 3 is not limited to the above example. The release liner 3 can be peeled off when the optical laminate 10B is used, for example, when it is attached to an image forming layer.

Fig. 7 shows another example of the optical laminate of the present embodiment. The optical laminate 10C of fig. 7 has a laminated structure in which a release liner 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, and a polarizing plate 2B are laminated in this order. The optical laminate 10C may be used by, for example, attaching the release liner 3 to an image forming layer after peeling.

The interlayer adhesive 4 may be any known adhesive, or the adhesive sheet 1 may be used for the interlayer adhesive 4.

Fig. 8 shows another example of the optical laminate of the present embodiment. The optical laminate 10D of fig. 8 has a laminated structure in which a release liner 3, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B, and a protective film 5 are laminated in this order. The optical laminate 10D may be used by, for example, attaching the release liner 3 to an image forming layer after peeling.

The protective film 5 has a function of protecting the optical film 2 (polarizing plate 2B) as the outermost layer in the case of distribution and storage of the optical laminate 10D and in the case of introducing the optical laminate 10D into an image display device. In addition, the protective film 5 may function as a window to the outside space in a state of being introduced into the image display apparatus. The protective film 5 is typically a resin film. The resin constituting the protective film 5 is, for example, polyester such as PET, polyolefin such as polyethylene and polypropylene, acrylic, cycloolefin, polyimide, and polyamide, and polyester is preferable. The protective film 5 is not limited to the above example, and the protective film 5 may be a glass film or a laminated film including a glass film. The protective film 5 may be subjected to surface treatments such as antiglare, antireflection, antistatic, and the like.

The protective film 5 may be bonded to the optical film 2 via an arbitrary adhesive, or may be bonded by the pressure-sensitive adhesive sheet 1.

The optical laminate of the present embodiment can be distributed and stored in the form of a wound body obtained by winding a band-shaped optical laminate, or in the form of a sheet-shaped optical laminate, for example.

The optical layered body of the present embodiment is typically used for an image display device. The image display device is, for example, an EL display such as a liquid crystal display, an organic EL display, and an inorganic EL display.

[ image display device ]

Fig. 9 shows an example of the image display device according to the present embodiment. The image display device 20 of fig. 9 has a laminated structure in which a substrate 7, an image forming layer (for example, an organic EL layer or a liquid crystal layer) 6, an adhesive sheet 1, a retardation film 2A, an interlayer adhesive 4, a polarizing plate 2B, and a protective film 5 are laminated in this order. The image display device 20 has the optical layered bodies 10A, 10B, 10C, 10D of fig. 5 to 8 (except for the release liner 3). The substrate 7 and the image forming layer 6 may have the same configuration as those of a substrate and an image forming layer provided in a known image display device.

The image display device 20 of fig. 9 may be an organic EL display or a liquid crystal display. However, the image display device 20 is not limited to this example, and the image display device 20 may be an Electroluminescence (EL) display, a Plasma Display (PD), a field emission display (FED: field Emission Display), or the like. The image display device 20 can be used for home appliance applications, vehicle-mounted applications, public Information Display (PID) applications, and the like.

The image display device of the present embodiment may have any configuration as long as the image display device includes the optical layered body of the present embodiment.

Examples

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the examples shown below.

First, the evaluation methods of the (meth) acrylic polymer and the adhesive sheet produced in examples and comparative examples are shown.

[ weight average molecular weight (Mw) ]

The weight average molecular weight (Mw) of the (meth) acrylic polymer was evaluated by GPC under the following conditions.

Analysis device: waters, acquisition APC

Chromatographic column: east Cao System, G7000HXL+GMHXL+GMHXL

Column temperature: 40 DEG C

Eluent: tetrahydrofuran (acid addition)

Flow rate: 0.8 mL/min

Injection amount: 100 mu L

Detector: differential Refractometer (RI)

Standard sample: agilent made Polystyrene (PS)

[ stress-strain curve ]

The stress-strain curve of the adhesive sheet was obtained by the above-described evaluation test using an adhesion tester (manufactured by rhesa, TAC 1000). Wherein, EAGLE XG manufactured by Corning was used for the glass plate 51. After the produced pressure-sensitive adhesive sheets were stacked on the glass plate 51, they were bonded to each other by heating I (50 ℃, 5 atmospheres (absolute pressure), 15 minutes) using an autoclave, and an evaluation sheet having a thickness of 200 μm or more was adhered. After the adhesion, the bonding between the evaluation sheet and the glass plate 51 was stabilized by heating II (50 ℃, 5 atmospheres (absolute pressure), 15 minutes) using an autoclave. As the evaluation probe 52, a 5 mm. Phi. Probe (SUS) manufactured by RHECA, which is a standard in accordance with ASTM D-2979, was used. From the obtained curves, peak stress X was obtained for each adhesive sheet _max Strain Y _m Strain Y _0.15 And calculate the ratio Y _0.15 /Y _m . Evaluation tests were carried out at 23℃and 55% RH atmosphere.

[ storage modulus G' (25 ℃ C.)

The storage modulus G' (25 ℃) of the adhesive sheet was evaluated by the method described above. The laminated body obtained by laminating the produced adhesive sheets was punched out into a disc shape, and a sample for measurement was prepared. Dynamic viscoelasticity of the measurement sample was measured using ARES-G2 manufactured by TA Instruments.

[ gel fraction ]

Gel fraction of the adhesive sheet was evaluated by the above method.

[ humidification durability ]

The wet durability (corresponding to an accelerated test of durability) of the adhesive sheet was evaluated by the following method. First, a circularly polarizing plate with an adhesive sheet having the adhesive sheets produced in examples and comparative examples on one exposed surface was formed. Next, the circularly polarizing plate was fixed to the surface of a glass plate (Eagle XG, corning) via the adhesive sheet, and the fixation of the circularly polarizing plate was performed in an atmosphere of 23 ℃ and 50% rh. Then, after 15 minutes of treatment in an autoclave at 50℃and 5 atmospheres (absolute pressure), the sheet was allowed to stand until cooled to 23℃to stabilize the bonding between the circularly polarizing plate and the glass plate, and then the sheet was allowed to stand in a heated and humidified atmosphere at 60℃and 95% RH for 500 hours. After leaving the glass plate, the glass plate was returned to an atmosphere of 23℃and 50% RH, and whether or not peeling of the circularly polarizing plate from the glass plate and foaming between the glass plate and the circularly polarizing plate were observed by naked eyes were confirmed, and the humidification durability was evaluated as described below.

A: no change in appearance such as foaming and peeling was observed.

B: a small amount of separate peeling or foaming was observed at the end, but in a range where there was no problem in practical use.

C: a small amount of continuous peeling or foaming was observed at the end, but in a range where there was no problem in practical use.

D: significant peeling or foaming was observed at the end, and there was a problem in practical use.

The method for forming the circularly polarizing plate with an adhesive sheet used for evaluating the wet durability is shown below.

< production of polarizer P1 >)

(production of polarizer)

A long polyvinyl alcohol (PVA) -based resin film (product name "PE3000", 30 μm thick, made by kohly) was uniaxially stretched (total stretching ratio 5.9 times) in the longitudinal direction using a roll stretcher, and each treatment of swelling, dyeing, crosslinking, washing and drying was sequentially performed on the resin film, to prepare a polarizer having a thickness of 12 μm. In the swelling treatment, the resin film was stretched 2.2 times while being treated in pure water at 20 ℃. In the dyeing treatment, the resin film was stretched 1.4 times while being treated in an aqueous solution of 30℃containing iodine and potassium iodide in a weight ratio of 1:7. The iodine concentration in the aqueous solution was adjusted so that the transmittance of the monomer of the polarizer produced reached 45.0%. The crosslinking treatment used 2 stages. In the crosslinking treatment in the 1 st stage, the resin film was stretched 1.2 times while being treated in an aqueous solution of 40 ℃ in which boric acid and potassium iodide were dissolved. The content of boric acid in the aqueous solution used in the crosslinking treatment in the stage 1 was 5.0 wt% and the content of potassium iodide was 3.0 wt%. In the crosslinking treatment in the 2 nd stage, the resin film was stretched 1.6 times while being treated in an aqueous solution of 65 ℃ in which boric acid and potassium iodide were dissolved. The content of boric acid in the aqueous solution used in the crosslinking treatment in the 2 nd stage was 4.3 wt% and the content of potassium iodide was 5.0 wt%. An aqueous potassium iodide solution at 20℃was used for the washing treatment. The content of potassium iodide in the aqueous solution used in the washing treatment was set to 2.6 wt%. The drying treatment was carried out at 70℃for 5 minutes.

(production of polarizing plate P1)

Cellulose Triacetate (TAC) films (product name "KC2UA", product name 25 μm, manufactured by konicarb) were respectively bonded to the main surfaces of the polarizer manufactured as described above using a polyvinyl alcohol-based adhesive. Wherein a hard coat layer (thickness 7 μm) is formed on the main surface of the TAC film bonded to one main surface on the side opposite to the polarizer side. Thus, a polarizer P1 having a structure of a protective layer with a hard coat layer/a polarizer/a protective layer (without a hard coat layer) was obtained.

< preparation of phase-difference film R1 >

(production of the 1 st phase-difference film)

26.2 parts by weight of Isosorbide (ISB), 100.5 parts by weight of 9,9- [4- (2-hydroxyethoxy) phenyl ] fluorene (BHEPF), 10.7 parts by weight of 1, 4-cyclohexanedimethanol (1, 4-CHDM), 105.1 parts by weight of diphenyl carbonate (DPC) and 0.591 part by weight of cesium carbonate (0.2% by weight aqueous solution) as a catalyst were charged into a reaction vessel, and dissolved in a nitrogen atmosphere (about 15 minutes). At this time, the temperature of the heat medium in the reaction vessel was 150℃and, if necessary, stirred. Next, the pressure in the reaction vessel was reduced to 13.3kPa, while taking 1 hour to raise the temperature of the heat medium to 190 ℃. Phenol generated with the increase in the temperature of the heat medium is discharged to the outside of the reaction vessel (the same applies hereinafter). Next, after the temperature in the reaction vessel was kept at 190 ℃ for 15 minutes, the pressure in the reaction vessel was changed to 6.67kPa, and it took 15 minutes to raise the temperature of the heat medium to 230 ℃. At the time of the increase in the stirring torque of the stirrer provided in the reaction vessel, it took 8 minutes to raise the temperature of the heat medium to 250℃and further the pressure in the reaction vessel was set to 0.200kPa or less. After a predetermined stirring torque was reached, the reaction was terminated, and the resultant reactant was extruded into water to be pelletized. Thus, a polycarbonate resin having a composition of BHEPF/ISB/1, 4-chdm=47.4 mol%/37.1 mol%/15.5 mol% was obtained. The glass transition temperature of the obtained polycarbonate resin was 136.6 ℃and the reduced viscosity was 0.395dL/g.

After the pellets of the produced polycarbonate resin were dried under vacuum at 80℃for 5 hours, a long resin film having a thickness of 120 μm was obtained by using a film-forming apparatus equipped with a single screw extruder (Isuzu Chemical Industries, screw diameter 25mm, cylinder set temperature 220 ℃), T-die (width 200mm, set temperature 220 ℃), chilled rolls (set temperature 120 to 130 ℃) and a winder. Next, the obtained resin film was stretched in the width direction by a tenter at a stretching temperature of 137 to 139 ℃ and a stretching ratio of 2.5 times, to obtain a 1 st retardation film.

(production of No. 2 retardation film)

A liquid crystal coating liquid was prepared by dissolving 20 parts by weight of a side chain type liquid crystal polymer (weight average molecular weight: 5000) represented by the following chemical formula (I) (in the formula, 65 and 35 are mol% of each structural unit), 80 parts by weight of a polymerizable liquid crystal (manufactured by BASF under the trade name of "Paliocor LC 242") exhibiting a nematic liquid crystal phase, and 5 parts by weight of a photopolymerization initiator (manufactured by Ciba Specialty Chemicals under the trade name of "IRGACURE 907") in 200 parts by weight of cyclopentanone. Next, the prepared liquid crystal coating liquid was applied on the surface of a norbornene-based resin film (trade name "ZEONEX" manufactured by japan rayleigh) as a base film by a bar coater, and then heated and dried at 80 ℃ for 4 minutes, so that the liquid crystal contained in the coating film was aligned. Then, the coating film was cured by irradiation of ultraviolet rays, and a liquid crystal fixed layer (thickness 0.58 μm) was formed as a 2 nd retardation film on the base film. The liquid crystal fixing layer has an in-plane retardation Re of 0nm for light having a wavelength of 550nm and a retardation Rth in the thickness direction of-71 nm (nx= 1.5326, ny= 1.5326, nz= 1.6550), and the liquid crystal fixing layer exhibits refractive index characteristics of nz > nx=ny.

[ chemical formula 1]

(production of retardation film R1)

One surface of the 1 st retardation film produced as described above was bonded to the liquid crystal fixing layer of the 2 nd retardation film with an adhesive, to produce a retardation film R1.

< production of circular polarizer with adhesive sheet >

(preparation of interlayer adhesive)

A four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser was charged with a monomer mixture containing 79.9 parts by weight of butyl acrylate, 15 parts by weight of benzyl acrylate, 5 parts by weight of acrylic acid, and 0.1 part by weight of 4-hydroxybutyl acrylate. Then, 0.1 part by weight of 2,2' -azobisisobutyronitrile as a polymerization initiator was added together with ethyl acetate to 100 parts by weight of the monomer mixture, and after nitrogen substitution was performed in the flask by introducing nitrogen gas while stirring slowly, the liquid temperature in the flask was kept at about 55℃for 7 hours, and polymerization was performed. Next, ethyl acetate was added to the obtained reaction solution, and the solid content concentration was adjusted to 30% by weight, to obtain a solution of a (meth) acrylic polymer for an interlayer adhesive. The weight average molecular weight of the obtained polymer was 220 ten thousand.

Next, 0.5 parts by weight of a trimethylolpropane/toluene diisocyanate trimer adduct (trade name "cornonate L" manufactured by eason corporation), 0.1 parts by weight of benzoyl peroxide as a peroxide-based crosslinking agent, 0.2 parts by weight of an epoxy-containing silane coupling agent (trade name "KBM-403" manufactured by the shin-Etsu chemical industry corporation) and 0.5 parts by weight of a polyether compound having a reactive Silyl group (trade name "olyl SAT 10" manufactured by Kaneka corporation) were mixed with 100 parts by weight of the solid content of the obtained (meth) acrylic polymer solution, to obtain an adhesive composition PSA1 used for an interlayer adhesive for joining a polarizing plate P1 to a retardation film R1.

(production of polarizing plate with adhesive layer between layers)

The adhesive composition PSA1 prepared above was applied to the release surface of a polyethylene terephthalate (PET) film (mitsubishi chemical polyester film, MRF 38) whose release surface was treated with silicone, the release surface of which was coated with the adhesive composition PSA1 so that the thickness of the dried layer became 12 μm, and the layer was dried at 155 ℃ for 1 minute, thereby forming an interlayer adhesive layer. Next, the formed interlayer adhesive layer was transferred to the protective layer (no hard coat layer) side of the polarizing plate P1, to obtain a polarizing plate with an interlayer adhesive layer.

(production of circular polarizing plate with adhesive sheet)

Each of the adhesive sheets produced in examples and comparative examples was transferred from the release film to the 2 nd retardation film side of the retardation film R1 (the norbornene-based resin film used as the base film at the time of producing the 2 nd retardation film was peeled off) and attached. Next, the produced polarizing plate with the interlayer adhesive layer was attached to the 1 st retardation film side of the retardation film R1 via the interlayer adhesive layer, to obtain a circular polarizing plate with an adhesive sheet. The retardation film R1 and the polarizing plate having the interlayer adhesive layer are attached such that the angle between the slow axis of the 1 st retardation film and the absorption axis of the polarizer is 45 degrees in the counterclockwise direction when viewed from the 1 st retardation film side.

Next, a method for producing each adhesive sheet of examples and comparative examples will be described.

The abbreviations or names shown in the following description correspond to the compounds as follows.

BA: acrylic acid n-butyl ester

BzA: benzyl acrylate

AA: acrylic acid

HBA: acrylic acid 4-hydroxybutyl ester

AIBN:2,2' -azobisisobutyronitrile

C/L: trimethylolpropane/toluene diisocyanate trimer adduct (isocyanate-based crosslinking agent; tosoh, coronate L)

TetradC:1, 3-bis (N, N-diglycidyl aminomethyl) cyclohexane (multifunctional epoxy-based crosslinking agent; mitsubishi gas chemical systems, detrad C)

KBM403: 3-epoxypropoxypropyltriethoxysilane (silane coupling agent; KBM403, xinyue chemical industry Co., ltd.)

[ (meth) acrylic Polymer (A) production ]

Synthesis example 1

94.9 parts by weight of BA, 5.0 parts by weight of AA and 0.1 part by weight of HBA were charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a condenser. Next, 0.1 part by weight of AIBN as a polymerization initiator was added to 100 parts by weight of a mixture of BA, AA and HBA, nitrogen was introduced while stirring slowly to replace the inside of the flask with nitrogen, and then the liquid temperature in the flask was kept at around 55℃to carry out a polymerization reaction for 7 hours. Then, ethyl acetate was added to the obtained reaction solution, and the solid content concentration was adjusted to 12% by weight, thereby obtaining a solution of the (meth) acrylic polymer (a-1). The weight average molecular weight (Mw) of the (meth) acrylic polymer (A-1) was 220 million.

Synthesis example 2

A solution of a (meth) acrylic polymer (A-2) was obtained in the same manner as in Synthesis example 1 except that the monomers used were changed to 79.9 parts by weight of BA, bzA 15.0.0 parts by weight of AA, 5.0 parts by weight of HBA and 0.1 parts by weight of HBA. The weight average molecular weight (Mw) of the (meth) acrylic polymer (A-2) was 220 million.

The types and amounts of the monomers and the polymerization initiators used in synthesis examples 1 and 2, and the weight average molecular weights (Mw) of the obtained polymers are summarized in table 1 below.

TABLE 1

[ production of adhesive composition and adhesive sheet ]

Examples 1 to 7 and comparative examples 1 and 2

As shown in table 2 below, a solvent-based adhesive composition was obtained by mixing a crosslinking agent or the like with 100 parts by weight of the solid content of the (meth) acrylic polymer (a).

TABLE 2

The unit of the blending amount is weight part

Next, the obtained adhesive composition was applied to the release surface of a PET film (manufactured by mitsubishi chemical polyester film, MRF 38) having a thickness of 38 μm, which was a release film having been subjected to silicone treatment, and then dried in an air circulation type constant temperature oven set at a predetermined temperature for a predetermined period of time, thereby forming adhesive sheets (thickness 15 μm) of examples 1 to 7 and comparative examples 1 and 2. The adhesive composition was applied using a spray coater (fountain coater). The drying conditions for forming the adhesive sheet are shown in table 3, and the evaluation results of the formed adhesive sheet are shown in table 4.

TABLE 3

TABLE 4

As shown in Table 4, the adhesive sheet has a peak stress X of 0.5MPa or more than that of the adhesive sheet of the comparative example _max The adhesive sheet of the embodiment of (2) is suitable for suppressing dimensional changes and exhibits high durability.

Industrial applicability

The pressure-sensitive adhesive sheet of the present invention can be used for an image display device, for example.

Claims

1. Adhesive sheet with peak stress X _max Satisfying the following formula (1),

X _max ≥0.5MPa (1)

wherein the peak stress X _max The peak value of stress X in the stress-strain curve obtained for the adhesive sheet by the following evaluation test,

evaluation test:

an end face of an evaluation probe (cylindrical shape having a diameter of 5mm, made of stainless steel) was brought into contact with an adhesive surface of an adhesive sheet attached to a glass plate, a contact load of 100N was applied to the adhesive sheet in the thickness direction thereof and held for 300 seconds, the evaluation probe was brought into close contact with the adhesive sheet, and then the evaluation probe was displaced in a direction perpendicular to the adhesive sheet at a constant speed of 2 μm/direction, and stress X and strain Y in the thickness direction of the adhesive sheet generated by the displacement of the evaluation probe were measured, and a stress-strain curve was obtained from the measured stress X and strain Y.

2. The adhesive sheet according to claim 1, wherein,

In the stress-strain curve, the stress X reaches the peak stress X _max Strain Y at time _m Satisfying the following formula (2):

Y _m ≥0.05 (2)。

3. the adhesive sheet according to claim 1 or 2, wherein,

in the stress-strain curve, the stress X reaches the peak stress X _max Strain Y at the time of later falling to 0.15MPa _0.15 Satisfying the following formula (3):

Y _0.15 ≥0.28 (3)。

4. the adhesive sheet according to claim 3, wherein,

in the stress-strain curve, the stress X reaches the peak stressX _max Strain Y at time _m Is 0.09 or more.

5. The adhesive sheet according to claim 3 or 4, wherein,

the peak stress X _max Is more than 0.9 MPa.

6. The adhesive sheet according to any one of claims 1 to 5, wherein,

in the stress-strain curve, the stress X reaches the peak stress X _max Strain Y at the time of later falling to 0.15MPa _0.15 Reaching said peak stress X with respect to said stress X _max Strain Y at time _m Ratio Y of _0.15 /Y _m Satisfying the following formula (4):

Y _0.15 /Y _m ≥2 (4)。

7. the adhesive sheet according to any one of claims 1 to 6, wherein,

the adhesive sheet has a storage modulus G' at 25 ℃ of 0.5MPa or more.

8. The adhesive sheet according to any one of claims 1 to 7, comprising an acrylic adhesive.

9. The adhesive sheet according to any one of claims 1 to 8, which is formed from an adhesive composition comprising a (meth) acrylic polymer (a) and a crosslinking agent (B).

10. The adhesive sheet according to claim 9, wherein,

the cross-linking agent (B) is an isocyanate cross-linking agent.

11. The adhesive sheet according to claim 9 or 10, wherein,

the amount of the crosslinking agent (B) is 5 parts by weight or more based on 100 parts by weight of the (meth) acrylic polymer (A).

12. The adhesive sheet according to any one of claims 9 to 11, wherein,

the (meth) acrylic polymer (A) has a structural unit derived from an aromatic ring-containing monomer.

13. An optical laminate comprising:

the adhesive sheet according to any one of claims 1 to 12, and

an optical film.

14. An image display device comprising the optical laminate according to claim 13.