Adhesive composition, adhesive, and adhesive sheet

Abstract

Provided is an adhesive composition that can be used for multi-stage curing, that can obtain excellent adhesive properties in a low cross-linked state after one-time curing, that can be efficiently subjected to multi-stage curing even when the amount of active energy rays during curing is small, and that can be used for multi-stage curing. Alternatively, during curing, multi-stage curing can be efficiently performed using active energy rays in the visible light region, and after final curing, high elasticity of the adhesive layer can be achieved, and excellent adhesive properties, reliability, and shape stability can be obtained. A pressure-sensitive adhesive composition containing: an acrylic resin (A) having a glass transition temperature, calculated from dynamic viscoelasticity, of 12 DEG C to 40 DEG C; and a structural unit derived from an alkyl (meth) acrylate (a1) having an alkyl group having 5 or more carbon atoms, and a structural unit derived from an ethylenically unsaturated monomer (a3) containing an amide group.

Description

TECHNICAL FIELD

[0001] The present application relates to an adhesive composition, an adhesive, and an adhesive sheet. BACKGROUND

[0002] In recent years, touch panels combining a display and a position input device are widely used in television sets and monitors for personal computers, notebook computers and mobile phones, smartphones, tablet terminals, and the like. Among them, electrostatic capacitance type touch panels are generally becoming widespread.

[0003] A touch panel is generally composed of a display containing an organic EL or a liquid crystal, a transparent conductive film substrate (ITO substrate), a protective film (protective glass), and the like. A transparent adhesive sheet is used in the bonding of these touch panel components.

[0004] In recent years, displays of complex shapes such as curved surfaces have been developed in order to improve the design freedom of shapes, like organic EL displays. In the case of an adhesive for a transparent adhesive sheet that bonds a laminate composed of a display of a complex shape such as a curved surface, bonding is performed in a low crosslinked state (primary curing) before final curing, and then it is finally cured. Therefore, sufficient adhesive properties are required during the period until the adhesive layer in the low crosslinked state (primary curing) is finally cured.

[0005] In addition, in the case of bonding a transparent adhesive sheet to a component of a complex shape, bonding defects such as attachment to a site other than the target site are likely to occur. Therefore, a transparent adhesive sheet with low tackiness is required. In order to simultaneously fix components of complex shapes to each other, it is required to suppress the peeling of the transparent adhesive sheet from the components in a state where stress is applied. Therefore, a transparent adhesive sheet with high constant load holding force even in the low crosslinked state (primary curing) is also required.

[0006] In addition, as a recent trend, thinning and omission of components are being promoted for the purpose of weight reduction and power saving of mobile terminals, and as a result, there is a tendency that the mechanical strength of the entire laminate is reduced. Therefore, for an adhesive for a transparent adhesive sheet, performance that improves the strength of the entire laminate after final curing and is also excellent in adhesive properties such as adhesion and reliability when bonding various components such as a polarizing plate and / or glass is required.

[0007] Furthermore, due to the influence of the thinning and omission of components such as a polarizing plate, components such as an organic EL element inside become likely to be exposed to ultraviolet rays. Therefore, in order to suppress degradation, the incorporation of an ultraviolet absorber in each component such as an adhesive layer is being studied.

[0008] Therefore, for an adhesive for a transparent adhesive sheet, it is required to have a performance of improving the mechanical strength of the entire laminate after final curing, and also excellent in adhesion properties such as adhesion strength, and durability when adhering various members such as a polarizing plate and / or a glass.

[0009] Further, it is required that the adhesive composition is cured by light other than ultraviolet light region, such as visible light region, when the adhesive composition is cured by irradiation of active energy rays.

[0010] For example, in order to obtain excellent durability after final curing, it is required to have a low crosslinking degree before adhering to an adherend, and in addition, it is required to effectively increase the crosslinking degree at the time of final curing.

[0011] Therefore, it is required that a transparent adhesive sheet can be sufficiently adhered to an adherend by adhering to the adherend in a low crosslinking state (primary curing), and that the transparent adhesive sheet becomes a high crosslinking degree by performing final curing in a state of adhering to the adherend in a low crosslinking state (primary curing), and durability can be expected to be improved.

[0012] A transparent adhesive sheet is generally once cured by crosslinking through heat or irradiation of active energy rays, and then, final curing is performed by crosslinking through irradiation of active energy rays. As an adhesive sheet using the adhesive having the above-described multi-stage curing property, for example, the adhesive sheets described in Patent Documents 1 to 3 can be listed.

[0013] Prior Art Documents

[0014] Patent Documents

[0015] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-522393

[0016] Patent Document 2: Japanese Patent Application Laid-Open No. 2022-063964

[0017] Patent Document 3: International Publication No. 2021 / 181767

[0018] In addition, in order to improve the mechanical strength of the laminate, it is considered that the high-elasticization of the adhesive layer is effective, but when a large amount of crosslinking component is introduced and the crosslinking density is increased in order to high-elasticize, the adhesion strength cannot be maintained, and therefore it is required that the elastic modulus of the acrylic resin itself used in the adhesive is high. SUMMARY

[0019] PROBLEMS TO BE SOLVED BY THE INVENTION

[0020] However, none of Patent Documents 1 to 3 considers the adhesive properties in the low crosslinked state at the time of primary curing. Therefore, the adhesive sheets disclosed in Patent Documents 1 to 3 have insufficient adhesive properties in the low crosslinked state at the time of primary curing, and there is room for improvement. In addition, in order to increase the strength of the entire body after final curing, high elasticization of the adhesive layer is required, and at the same time, excellent adhesive properties and reliability are required, and further, excellent visible light curing properties at the time of final curing are preferably required.

[0021] Therefore, an object of the present application is to provide an adhesive composition which is an adhesive composition capable of being used for multi-stage curing, which can achieve excellent adhesive properties in the low crosslinked state at the time of primary curing, and which can efficiently perform multi-stage curing even with a small amount of active energy rays at the time of curing, or which can efficiently perform multi-stage curing using active energy rays in the visible light region at the time of curing, and which can achieve high elasticization of the adhesive layer after final curing, and which can further achieve excellent adhesive properties, reliability, and shape stability. In addition, the present application provides an adhesive obtained by crosslinking the above-described adhesive composition, and an adhesive sheet having an adhesive layer formed of the above-described adhesive.

[0022] Solution to the problem

[0023] In order to solve the above-described problems, the present inventors and others have conducted intensive studies, and as a result, it has been found that, by using an adhesive composition containing an acrylic resin having a specific structural unit and a photopolymerization initiator, an adhesive composition which can achieve excellent adhesive properties in which the tackiness is low and the constant load retention is high even in the low crosslinked state at the time of primary curing, which can efficiently cure even with a small amount of active energy rays at the time of curing, and which can further achieve excellent adhesive properties, reliability, and shape stability after final curing can be obtained.

[0024] In addition, the present inventors and others have found that, by using an adhesive composition containing an acrylic resin having a specific structural unit and a specific photopolymerization initiator, an adhesive composition which can achieve excellent adhesive properties in which the tackiness is low and the constant load retention is high even in the low crosslinked state at the time of primary curing, which can efficiently cure using active energy rays in the visible light region at the time of curing, and which can further achieve excellent adhesive properties, reliability, and shape stability after final curing can be obtained.

[0025] Furthermore, it has been found that a laminate obtained by adhering using an adhesive sheet having an adhesive layer containing an adhesive obtained by crosslinking the adhesive composition has excellent mechanical strength.

[0026] The gist of the present application is as follows.

[0027] [1] An adhesive composition containing an acrylic resin (Al) and a photopolymerization initiator (B), wherein,

[0028] The acrylic resin (A1) has a glass transition temperature of 12°C to 40°C calculated from dynamic viscoelasticity.

[0029] The acrylic resin (A1) contains a structural unit derived from an alkyl (meth)acrylate (a1) having an alkyl group having a carbon number of 5 or more and a structural unit derived from an amide group-containing olefinically unsaturated monomer (a3).

[0030] [2] The adhesive composition according to [1], wherein the content of the structural unit derived from the alkyl (meth)acrylate (a1) having an alkyl group having a carbon number of 5 or more is 20% by mass to 70% by mass with respect to the entire acrylic resin (A1).

[0031] [3] The adhesive composition according to [1] or [2], wherein the content of the structural unit derived from the amide group-containing olefinically unsaturated monomer (a3) is 5% by mass to 40% by mass with respect to the entire acrylic resin (A1).

[0032] [4] The adhesive composition according to any one of [1] to [3], wherein the acrylic resin (A1) contains a structural unit derived from an alkyl (meth)acrylate (a2) having an alkyl group having a carbon number of 1 to 4.

[0033] [5] The adhesive composition according to any one of [1] to [4], wherein the acrylic resin (A1) has a weight average molecular weight of 50,000 to 600,000.

[0034] [6] The adhesive composition according to any one of [1] to [5], wherein the photopolymerization initiator (B) contains a hydrogen abstraction type photopolymerization initiator (b).

[0035] [7] The adhesive composition according to any one of [1] to [6], further containing a crosslinking agent (C).

[0036] [8] An adhesive which is obtained by crosslinking the adhesive composition according to any one of [1] to [7].

[0037] [9] The adhesive according to [8], wherein the crosslinking is performed by irradiation of active energy rays.

[0038]

[10] An adhesive sheet having an adhesive layer formed of the adhesive according to [8], the adhesive layer showing a multi-stage curing property of being cured in a plurality of stages.

[0039]

[11] An adhesive sheet having an adhesive layer formed of the adhesive according to [9], the adhesive layer showing a multi-stage curing property of being cured in a plurality of stages.

[0040]

[12] An adhesive composition containing an acrylic resin (A2) and a photopolymerization initiator (B), wherein,

[0041] The acrylic resin (A2) described above has a glass transition temperature calculated from dynamic viscoelasticity of 12°C to 40°C,

[0042] The acrylic resin (A2) described above contains a structural unit derived from an alkyl (meth)acrylate (al) having an alkyl group having a carbon number of 5 or more,

[0043] The photopolymerization initiator (B) described above contains a photopolymerization initiator (βl) having a molar absorption coefficient of 30 to 5,000 (L / mol·cm) in a range of wavelengths of 380 nm to 450 nm.

[0044]

[13] The adhesive composition according to

[12] , wherein the content of the structural unit derived from the alkyl (meth)acrylate (al) having an alkyl group having a carbon number of 5 or more is 20 mass% to 70 mass% relative to the entire acrylic resin (A2).

[0045]

[14] The adhesive composition according to

[12] or

[13] , wherein the acrylic resin (A2) contains a structural unit derived from an alkyl (meth)acrylate (a2) having an alkyl group having a carbon number of 1 to 4.

[0046]

[15] The adhesive composition according to any one of

[12] to

[14] , wherein the acrylic resin (A2) has a structural unit derived from an ethylenically unsaturated monomer (a3) containing an amide group.

[0047]

[16] The adhesive composition according to any one of

[12] to

[15] , wherein the acrylic resin (A2) has a weight average molecular weight of 50,000 to 600,000.

[0048]

[17] The adhesive composition according to any one of

[12] to

[16] , further containing a crosslinking agent (C).

[0049]

[18] An adhesive obtained by crosslinking the adhesive composition according to any one of

[12] to

[17] .

[0050]

[19] The adhesive according to

[18] , wherein the crosslinking is performed by irradiation of active energy rays.

[0051]

[20] An adhesive sheet having an adhesive layer formed of the adhesive according to

[18] , the adhesive layer showing a multi-stage curing property of curing in a plurality of stages.

[0052]

[21] An adhesive sheet having an adhesive layer formed from the adhesive of

[19] , the adhesive layer exhibiting a multi-stage curability that cures in multiple stages.

[0053] Effects of the Invention

[0054] According to the present invention, an adhesive composition capable of multi-stage curing can be produced, which can achieve excellent adhesive properties in a low crosslinked state after primary curing, efficiently perform curing even with a small amount of active energy rays at the time of curing, and furthermore, can achieve excellent adhesive properties, reliability, and shape stability after final curing.

[0055] In addition, according to the present invention, an adhesive composition capable of multi-stage curing can be produced, which can achieve excellent adhesive properties in a low crosslinked state after primary curing, efficiently perform curing using active energy rays in the visible light region at the time of curing, and furthermore, can achieve excellent adhesive properties, reliability, and shape stability after final curing.

[0056] Furthermore, a laminate obtained by attaching an adhesive sheet having an adhesive layer containing an adhesive obtained by crosslinking the above-described adhesive composition has excellent mechanical strength. DETAILED DESCRIPTION

[0057] Hereinafter, the present invention will be described in detail, which is one example indicating a preferred embodiment.

[0058] In addition, the meanings of the following terms in the present specification are as shown below.

[0059] "(Meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0060] "(Meth)acryloyl group" means acryloyl group and / or methacryloyl group.

[0061] "(Meth)acrylate" means acrylate and / or methacrylate.

[0062] "Acrylic resin" means a resin obtained by polymerizing a monomer component containing at least one (meth)acrylic monomer, and the monomer component containing at least one (meth)acrylic monomer is preferably a main component with respect to the entire polymerization component. Here, the main component is usually 50% by weight or more, preferably 60% by weight or more, and particularly preferably 70% by weight or more with respect to the entire polymerization component.

[0063] "Sheet" is a term conceptually including sheets, films, and tapes.

[0064] "~" indicating a numerical range means that the values written before and after it are included as lower limit values and upper limit values.

[0065] In the present specification, "x and / or y (x, y are arbitrary constituents)" means at least one of x and y, and means only x, only y, or both x and y.

[0066] As for the numerical range described in stages in the present specification, the upper limit value or the lower limit value of the numerical range of a certain stage can be combined with the upper limit value or the lower limit value of the numerical range of another stage arbitrarily. In addition, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range can be replaced with the value shown in the examples.

[0067] <Adhesive composition>

[0068] The adhesive composition of one embodiment of the present application (hereinafter referred to as "the present adhesive composition 1") contains an acrylic resin (A1) and a photopolymerization initiator (B), the glass transition temperature calculated from dynamic viscoelasticity of the acrylic resin (A1) is 12°C to 40°C,

[0069] The acrylic resin (A1) contains a structural unit derived from an alkyl (meth) acrylate (a1) having an alkyl group having a carbon number of 5 or more and a structural unit derived from an amide group-containing ethylenically unsaturated monomer (a3).

[0070] In addition, the adhesive composition of another embodiment of the present application (hereinafter referred to as "the present adhesive composition 2") contains an acrylic resin (A2) and a photopolymerization initiator (B),

[0071] The glass transition temperature calculated from dynamic viscoelasticity of the acrylic resin (A2) is 12°C to 40°C, the acrylic resin (A2) contains a structural unit derived from an alkyl (meth) acrylate (a1) having an alkyl group having a carbon number of 5 or more, and the photopolymerization initiator (B) contains a photopolymerization initiator (β1) having a molar absorption coefficient of 30 to 5,000 (L / mol·cm) in a range of a wavelength of 380 nm to 450 nm.

[0072] Hereinafter, the present adhesive composition 1 and the present adhesive composition 2 are sometimes collectively referred to as "the present adhesive composition".

[0073] In addition, hereinafter, the acrylic resin (A1) and the acrylic resin (A2) are sometimes collectively referred to as "the acrylic resin (A)".

[0074] The present adhesive composition can contain a crosslinking agent (C), a silane coupling agent (D), and other arbitrary components, in addition to the acrylic resin (A), the photopolymerization initiator (B), as necessary.

[0075] Hereinafter, each component is described in order.

[0076] <Acrylic resin (A)>

[0077] The adhesive composition 1 contains an acrylic resin (Al) containing a structural unit derived from an alkyl (meth)acrylate (al) having an alkyl group having a carbon number of 5 or more and a structural unit derived from an olefinically unsaturated monomer (a3) containing an amido group, preferably a structural unit derived from an alkyl (meth)acrylate (a2) having an alkyl group having a carbon number of 1 to 4, and a structural unit derived from other polymerizable monomer (a4) as necessary.

[0078] The above acrylic resin (Al) is obtained by copolymerizing an alkyl (meth)acrylate (al) having an alkyl group having a carbon number of 5 or more and an olefinically unsaturated monomer (a3) containing an amido group, preferably an alkyl (meth)acrylate (a2) having an alkyl group having a carbon number of 1 to 4, and other polymerizable monomer (a4) as necessary (hereinafter, sometimes collectively referred to as "copolymerization component").

[0079] The above copolymerization component refers to a general term of monomer components having a polymerizable double bond, and the copolymerization component does not include a polymerization initiator, a polymerization solvent.

[0080] In addition, the adhesive composition 2 contains an acrylic resin (A2) containing a structural unit derived from an alkyl (meth)acrylate (al) having an alkyl group having a carbon number of 5 or more, preferably a structural unit derived from an alkyl (meth)acrylate (a2) having an alkyl group having a carbon number of 1 to 4, a structural unit derived from an olefinically unsaturated monomer (a3) containing an amido group, and a structural unit derived from other polymerizable monomer (a4) as necessary.

[0081] The above acrylic resin (A2) is obtained by copolymerizing an alkyl (meth)acrylate (al) having an alkyl group having a carbon number of 5 or more, preferably an alkyl (meth)acrylate (a2) having an alkyl group having a carbon number of 1 to 4, an olefinically unsaturated monomer (a3) containing an amido group, and other polymerizable monomer (a4) as necessary (hereinafter, sometimes collectively referred to as "copolymerization component").

[0082] Each copolymerization component is described below in order.

[0083] 〔Alkyl (meth)acrylate (al) having an alkyl group having a carbon number of 5 or more〕

[0084] As the above-mentioned (meth)acrylic acid alkyl ester (a1) having an alkyl group having 5 or more carbons (hereinafter, sometimes referred to as "(meth)acrylic acid alkyl ester (a1)"), for example, (meth)acrylic acid alkyl ester (a1-1) having a linear alkyl group having 5 or more carbons (hereinafter, sometimes referred to as "(meth)acrylic acid linear alkyl ester (a1-1)") and (meth)acrylic acid branched alkyl ester (a1-2) having an alkyl group having 5 or more carbons (hereinafter, sometimes referred to as "(meth)acrylic acid branched alkyl ester (a1-2)") can be exemplified.

[0085] Further, the number of carbons of the alkyl group of the above-mentioned (meth)acrylic acid alkyl ester (a1) is preferably 8 or more. As an upper limit, it is 24 or less, and preferably 18 or less.

[0086] As the above-mentioned (meth)acrylic acid linear alkyl ester (a1-1), for example, (meth)acrylic acid n-pentyl ester, (meth)acrylic acid n-hexyl ester, (meth)acrylic acid n-heptyl ester, (meth)acrylic acid n-octyl ester, (meth)acrylic acid lauryl ester, (meth)acrylic acid n-tridecyl ester, (meth)acrylic acid n-stearyl ester, (meth)acrylic acid behenyl ester, and the like can be exemplified.

[0087] Further, as the above-mentioned (meth)acrylic acid branched alkyl ester (a1-2), for example, (meth)acrylic acid isoamyl ester, (meth)acrylic acid 1-methylheptyl ester, acrylic acid 2-ethylhexyl ester (Tg = -70°C), methacrylic acid 2-ethylhexyl ester (Tg = -10°C), acrylic acid isononyl ester (Tg = -58°C), methacrylic acid isononyl ester, acrylic acid isodecyl ester (Tg = -62°C), methacrylic acid isodecyl ester (Tg = -41°C), (meth)acrylic acid isotridecyl ester, (meth)acrylic acid isomyristyl ester, (meth)acrylic acid isostearyl ester, and the like can be exemplified. These can be used alone or in combination of two or more.

[0088] Among them, as the (meth)acrylic acid alkyl ester (a1), from the aspect of being able to be efficiently cured with active energy rays, a (meth)acrylic acid branched alkyl ester (a1-2) is preferred.

[0089] Further, from the aspect of being excellent in active energy ray curability at the time of curing, among the (meth)acrylic acid branched alkyl esters (a1-2), (meth)acrylic acid 2-ethylhexyl ester and (meth)acrylic acid isodecyl ester are preferred.

[0090] The (meth)acrylic acid alkyl ester (a1) has a glass transition temperature (Tg) of -80°C to 0°C, and particularly preferably -75°C to 20°C when forming a homopolymer. By using a (meth)acrylic acid alkyl ester (a1) having a glass transition temperature (Tg) in the above range, there is a tendency that the active energy ray curability at the time of making an adhesive and the adhesive properties after curing can be improved.

[0091] 〔having an alkyl group having a carbon number of 1 to 4 (a2)〕

[0092] As the above-mentioned (meth)acrylic acid alkyl ester (a2) having an alkyl group having a carbon number of 1 to 4 (hereinafter, sometimes referred to as "(meth)acrylic acid alkyl ester (a2)"), for example, methyl acrylate (Tg = 8°C), methyl methacrylate (Tg = 105°C), ethyl acrylate (Tg = -22°C), ethyl methacrylate (Tg = 65°C), n-butyl acrylate (Tg = -55°C), n-butyl methacrylate (Tg = 20°C), isobutyl acrylate (Tg = -26°C), isobutyl methacrylate (Tg = 48°C), t-butyl acrylate (Tg = 14°C), t-butyl methacrylate (Tg = 107°C), and the like can be exemplified. They can be used alone or in combination of two or more.

[0093] Among them, the above-mentioned (meth)acrylic acid alkyl ester (a2) is preferably a (meth)acrylic acid alkyl ester having an alkyl group having a carbon number of 1 to 2. By using the (meth)acrylic acid alkyl ester (a2) having an alkyl group having a carbon number within the above-mentioned range, the polarity of the acrylic resin (A) can be increased, and there is a tendency that the adhesion to a high-polar adherend such as glass is increased when the adhesive is produced.

[0094] Further, the glass transition temperature (Tg) of the above-mentioned (meth)acrylic acid alkyl ester (a2) when forming a homopolymer is preferably -30°C to 150°C, further preferably 0°C to 120°C, and particularly preferably 5°C to 105°C. By using the (meth)acrylic acid alkyl ester (a2) having a glass transition temperature (Tg) within the above-mentioned range, the elastic modulus of the acrylic resin (A) can be increased, and there is a tendency that the tackiness at the time of primary curing can be reduced and the shape stability after the final curing can be increased when the adhesive is produced.

[0095] [olefinically unsaturated monomer (a3) containing an amide group]

[0096] As the above-mentioned olefinically unsaturated monomer (a3) containing an amide group, for example, (meth)acrylamide, N-butyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, and the like containing a primary amide group and a secondary amide group, N,N'-dimethyl (meth)acrylamide, N-methyl-N'-ethyl (meth)acrylamide, N,N'-diethyl (meth)acrylamide, N,N'-dibutyl (meth)acrylamide, N,N'-dihexyl (meth)acrylamide, N,N'-dioctyl (meth)acrylamide, and the like N,N'-disubstituted (meth)acrylamide, acryloyl morpholine, methacryloyl morpholine, and the like can be exemplified.

[0097] Among them, from the viewpoint of excellent tackiness at the time of one-shot curing at the time of production of an adhesive, the viewpoint of excellent active energy ray-curing property at the time of curing, and the viewpoint of excellent shape stability after curing, N,N'-disubstituted (meth)acrylamide is preferred, more preferably N,N'-dimethyl (meth)acrylamide, N-methyl-N'-ethyl (meth)acrylamide, N,N'-diethyl (meth)acrylamide, further preferably N,N'-dimethyl (meth)acrylamide, N,N'-diethyl (meth)acrylamide, particularly preferably N,N'-dimethyl (meth)acrylamide.

[0098] [Other polymerizable monomer (a4)]

[0099] As the above other polymerizable monomer (a4), for example, an ethylenically unsaturated monomer having 1 ethylenically unsaturated group, an ethylenically unsaturated monomer having 2 or more ethylenically unsaturated groups, and the like can be exemplified.

[0100] As the above-mentioned ethylenically unsaturated monomer having 1 ethylenically unsaturated group, for example, there can be mentioned hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, N-hydroxymethyl (meth)acrylamide, N-(2-hydroxyethyl)acrylamide, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2,2-dimethyl 2-hydroxyethyl (meth)acrylate, and the like; aromatic ring-containing monomers such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, phenoxy polyethylene glycol-polypropylene glycol- (meth)acrylate, o-phenylphenoxyethyl (meth)acrylate, nonylphenol ethylene oxide adduct (meth)acrylate, and the like; alicyclic ring-containing monomers such as cyclohexyloxyalkyl (meth)acrylate; ether chain-containing monomers such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-butoxydiethylene glycol (meth)acrylate, methoxy diethylene glycol (meth)acrylate, methoxy triethylene glycol (meth)acrylate, ethoxy diethylene glycol (meth)acrylate, methoxy dipropylene glycol (meth)acrylate, methoxy polyethylene glycol (meth)acrylate, octyloxy polyethylene glycol-polypropylene glycol mono (meth)acrylate, lauryloxy polyethylene glycol mono (meth)acrylate, stearyloxy polyethylene glycol mono (meth)acrylate, and the like; acrylic acid dimers such as (meth)acrylic acid, β-carboxyethyl acrylate, and the like; carboxyl group-containing monomers such as crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, N-glycolic acid, cinnamic acid, and the like; benzophenone-containing monomers such as 4-(meth)acryloyloxybenzophenone; and acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyltoluene, vinylpyridine, vinylpyrrolidone, dialkyl itaconate, dialkyl fumarate, acryloyl chloride, methyl vinyl ketone, N-acrylamide methyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, and the like.

[0101] In addition, as the above-mentioned ethylenically unsaturated monomer having 2 or more ethylenically unsaturated groups, for example, there can be mentioned ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, divinylbenzene, and the like.

[0102] These other polymerizable monomers (a4) can be used singly or in combination of two or more.

[0103] Composition of the acrylic resin (A)

[0104] The content of the structural unit derived from the (meth) acrylic acid alkyl ester (al) having an alkyl group having a carbon number of 5 or more in the acrylic resin (A) is preferably 20 to 70 mass%, more preferably 25 to 65 mass%, particularly preferably 30 to 55 mass%, with respect to the entire acrylic resin (A) (100 mass%). If the content of the structural unit derived from the (meth) acrylic acid alkyl ester (al) is too small, there is a tendency that the active energy ray curability decreases, and if the content is too large, there is a tendency that the adhesive properties such as tackiness at the time of primary curing when the adhesive is produced, and the shape stability after curing decrease.

[0105] Further, when the acrylic resin (A) contains the structural unit derived from the branched (meth) acrylic acid alkyl ester (al-2), the content thereof is usually 50 mass% or more, preferably 80 mass% or more, particularly preferably 90 mass% or more, in the structural unit derived from the (meth) acrylic acid alkyl ester (al). By setting the content to the above range, there is a tendency that the active energy ray curability at the time of producing the adhesive, and the adhesive properties after final curing are excellent.

[0106] When the acrylic resin (A) contains the structural unit derived from the (meth) acrylic acid alkyl ester (a2) having an alkyl group having a carbon number of 1 to 4, the content thereof is usually 15 to 70 mass%, preferably 20 to 60 mass%, further preferably 25 to 55 mass%, particularly preferably 30 to 50 mass%, with respect to the entire acrylic resin (A) (100 mass%). If the content is too small, there is a tendency that the adhesive properties such as tackiness at the time of primary curing when the adhesive is produced decrease, and if the content is too large, there is a tendency that the active energy ray curability decreases.

[0107] The content of the structural unit derived from the ethylenically unsaturated monomer (a3) containing an amide group in the acrylic resin (Al) is preferably 5 to 40 mass%, more preferably 10 to 35 mass%, particularly preferably 15 to 30 mass%, with respect to the entire acrylic resin (Al) (100 mass%). If the content is too small, there is a tendency that the active energy ray curability at the time of producing the adhesive, the adhesive properties such as tackiness at the time of primary curing, and the shape stability after curing decrease, and if the content is too large, there is a tendency that the adhesive force decreases due to the decrease in adhesion.

[0108] When the acrylic resin (A2) has a structural unit derived from the amide group-containing ethylenically unsaturated monomer (a3), the content thereof is preferably 5 to 40 mass%, more preferably 10 to 35 mass%, particularly preferably 15 to 30 mass%, relative to the entire acrylic resin (A2) (100 mass%). When the content is too small, there is a tendency that the active energy ray-curing property at the time of producing an adhesive, the adhesive properties such as tackiness at the time of primary curing, and the shape stability after curing are reduced, and when the content is too large, there is a tendency that the adhesive force is reduced with the decrease in adhesion.

[0109] When the acrylic resin (A) has a structural unit derived from the other polymerizable monomer (a4), the content of the structural unit derived from the other polymerizable monomer (a4) is usually 20 mass% or less, preferably 10 mass% or less, more preferably 5 mass% or less, relative to the entire acrylic resin (A) (100 mass%). When the content of the other polymerizable monomer (a4) is too large, there is a tendency that the balance of the adhesive properties is deteriorated.

[0110] The mass ratio of the content of the structural unit derived from the alkyl (meth)acrylate (a2) to the content of the structural unit derived from the amide group-containing ethylenically unsaturated monomer (a3) in the acrylic resin (A) is usually 75:25 to 25:75, preferably 70:30 to 35:65, particularly preferably 65:35 to 45:55. By setting the mass ratio of the contents to the above range, there is a tendency that the active energy ray-curing property at the time of producing an adhesive and the shape stability after final curing are excellent.

[0111] [Physical properties of the acrylic resin (A)]

[0112] The glass transition temperature (Tg) based on dynamic viscoelasticity of the acrylic resin (A), that is, the temperature at which the loss tangent of dynamic viscoelasticity reaches a maximum, is 12 to 40°C, preferably 14 to 35°C, more preferably 16 to 30°C, particularly preferably 18 to 27°C.

[0113] When the glass transition temperature of the acrylic resin (A) is too high, there is a tendency that the adhesive force is reduced with the decrease in adhesion at the time of producing an adhesive. In addition, when the glass transition temperature of the acrylic resin (A) is too low, there is a tendency that the adhesive properties such as tackiness at the time of primary curing in the low crosslinking state after producing an adhesive, and the shape stability after curing are reduced.

[0114] The above glass transition temperature (Tg) based on dynamic viscoelasticity is obtained by the following measurement method.

[0115] An acrylic resin solution containing only the acrylic resin (A) and the organic solvent was prepared by adding an appropriate organic solvent to the acrylic resin (A). The acrylic resin solution was applied to a release sheet in such a manner that the thickness after drying became 50 μm. Then, it was dried by heating treatment at 90°C to 105°C for 5 minutes to 10 minutes, and the like, whereby the organic solvent was removed, and it was attached to the release sheet, to prepare an acrylic resin sheet containing 99 mass% or more of the acrylic resin (A). Then, a plurality of the acrylic resin sheets were laminated, to prepare an acrylic resin sheet having a thickness of about 800 μm.

[0116] The dynamic viscoelasticity of the prepared acrylic resin sheet was measured under the following conditions, and the temperature at which the tangent of the loss angle (loss modulus G" / storage modulus G' = tan δ) reached a maximum was read as the glass transition temperature of the acrylic resin (A) based on the dynamic viscoelasticity.

[0117] (Measurement conditions of dynamic viscoelasticity)

[0118] Measurement device: dynamic viscoelasticity measuring device (trade name: DVA-225, IT Measurement Control Co., Ltd.)

[0119] Deformation mode: shear

[0120] Strain: 0.1%

[0121] Measurement temperature: -100°C to 60°C

[0122] Measurement frequency: 1 Hz

[0123] On the other hand, the glass transition temperature (calculated Tg) was calculated by the Fox formula described below. The "glass transition temperature (Tg) of the acrylic resin (A) based on the dynamic viscoelasticity" in the present application is different from the calculated Tg.

[0124]

[0125] Tg: glass transition temperature (K) of the copolymer

[0126] Tga: glass transition temperature (K) of the homopolymer of monomer A

[0127] Wa: mass fraction of the structural unit derived from monomer A in the copolymer

[0128] Tgb: glass transition temperature (K) of the homopolymer of monomer B

[0129] Wb: mass fraction of the structural unit derived from monomer B in the copolymer

[0130] Tgn: glass transition temperature (K) of the homopolymer of monomer N

[0131] Wn: mass fraction of structural units derived from monomer N in the copolymer

[0132] (Wa + Wb + ··· + Wn = 1)

[0133] The weight average molecular weight (Mw) of the acrylic resin (A) is preferably from 500,000 to 6,000,000, more preferably from 1,000,000 to 5,000,000, and particularly preferably from 1,500,000 to 4,000,000. When the weight average molecular weight of the acrylic resin (A) is too large, the viscosity becomes too high, and there is a tendency for the coatability and handleability to decrease. In addition, when the weight average molecular weight of the acrylic resin (A) is too small, there is a tendency for the cohesive force to decrease, the adhesion properties to decrease, or the durability after final curing to decrease.

[0134] The weight average molecular weight of the acrylic resin (A) described above is the weight average molecular weight at the time of completion of production. The weight average molecular weight is measured for the acrylic resin (A) after production without heating or the like.

[0135] The weight average molecular weight of the acrylic resin (A) is the weight average molecular weight converted on the basis of the standard polystyrene molecular weight, and is measured by using three Shodex GPC KF-806L columns (exclusion limit molecular weight: 2 x 10 7 , separation range: 100 to 2 x 10 7 , theoretical plate number: 10,000 per column, filler material: styrene-divinylbenzene copolymer, filler particle diameter: 10 μm) connected in series in a high-performance liquid chromatograph (manufactured by Japan Waters Co., Ltd., "Waters 2695 (main body)" and "Waters 2414 (detector)").

[0136] In addition, the number average molecular weight of the acrylic resin (A) can also be measured using the same method. In addition, the dispersity is calculated from the weight average molecular weight and the number average molecular weight.

[0137] The dispersity (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 15 or less, more preferably 10 or less, further preferably 7 or less, and particularly preferably 5 or less. When the dispersity of the acrylic resin (A) is too high, there is a tendency for the durability of the adhesive layer to decrease, and for foaming to easily occur. When the dispersity of the acrylic resin (A) is too low, there is a tendency for the handleability to decrease. From the viewpoint of the limit of production, the lower limit of the dispersity is usually 1.1.

[0138] [Method for producing acrylic resin (A)]

[0139] The acrylic resin (A1) can be produced by polymerizing the above-mentioned (meth) acrylic acid alkyl ester (a1) having an alkyl group having a carbon number of 5 or more, the ethylenically unsaturated monomer (a3) containing an amido group, the (meth) acrylic acid alkyl ester (a2) preferably having an alkyl group having a carbon number of 1 to 4, and the other polymerizable monomer (a4) as needed [copolymerization component].

[0140] In addition, the acrylic resin (A2) can be produced by polymerizing the above-mentioned (meth) acrylic acid alkyl ester (a1) having an alkyl group having a carbon number of 5 or more, the (meth) acrylic acid alkyl ester (a2) preferably having an alkyl group having a carbon number of 1 to 4, and the ethylenically unsaturated monomer (a3) containing an amido group, and the other polymerizable monomer (a4) as needed [copolymerization component].

[0141] As the polymerization method of the acrylic resin (A), for example, conventionally known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and the like can be exemplified. From the viewpoint of safety and stability of the reaction, and the fact that the acrylic resin (A) can be produced with an arbitrary monomer composition, solution polymerization is preferred.

[0142] Hereinafter, an example of a preferred production method of the acrylic resin (A) will be shown.

[0143] First, the copolymerization component and the polymerization initiator are mixed or added dropwise in an organic solvent, and solution polymerization is performed.

[0144] As the organic solvent used in the polymerization reaction, for example, aromatic hydrocarbons such as toluene, xylene, and the like; aliphatic hydrocarbons such as n-hexane and the like; esters such as methyl acetate, ethyl acetate, butyl acetate, and the like; aliphatic alcohols such as methanol, ethanol, n-propanol, isopropanol, and the like; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and the like; aliphatic ethers such as dimethyl ether, diethyl ether, and the like; aliphatic halogenated hydrocarbons such as dichloromethane, chloroethylene, and the like; cyclic ethers such as tetrahydrofuran, and the like can be exemplified.

[0145] Among these organic solvents, esters and ketones are preferred, and ethyl acetate, acetone, and methyl ethyl ketone are particularly preferred.

[0146] The organic solvent can be used alone as one kind, or two or more kinds in combination.

[0147] As the polymerization initiator used in the polymerization reaction, an azo-based polymerization initiator, a peroxide-based polymerization initiator, and the like, which are generally used as radical polymerization initiators, can be used.

[0148] As the azo-based polymerization initiator, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(isobutyronitrile), (1-phenylethyl)azobisphenylmethane, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and the like can be exemplified.

[0149] As the peroxide-based polymerization initiator, for example, benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, lauryl peroxide, t-butyl peroxypivalate, t-hexyl peroxypivalate, t-hexyl peroxynonadecanoate, diisopropyl peroxydicarbonate, diisobutyryl peroxide, and the like can be exemplified.

[0150] Among them, the azo-based polymerization initiator is preferred, and 2,2'-azobis(isobutyronitrile) and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) are more preferred.

[0151] The polymerization initiator can be used alone or in combination of two or more.

[0152] The amount of the polymerization initiator is usually 0.001 parts by mass to 10 parts by mass, preferably 0.1 parts by mass to 8 parts by mass, more preferably 0.5 parts by mass to 6 parts by mass, particularly preferably 1 part by mass to 4 parts by mass, further preferably 1.5 parts by mass to 3 parts by mass, and most preferably 2 parts by mass to 2.5 parts by mass, relative to 100 parts by mass of the copolymerization component. When the amount of the polymerization initiator is too small, there is a tendency that the polymerization rate of the acrylic resin (A) decreases and the residual monomer increases. In addition, there is a tendency that the weight average molecular weight of the acrylic resin (A) becomes high. When the amount of the polymerization initiator is too large, there is a tendency that the acrylic resin (A) is gelled.

[0153] The polymerization conditions for solution polymerization are not particularly limited, and the polymerization can be performed according to the conventionally known polymerization conditions. For example, the copolymerization component and the polymerization initiator can be mixed or added dropwise in an organic solvent to perform the polymerization.

[0154] The polymerization temperature in the polymerization reaction is usually 40°C to 120°C, but in the present application, it is preferably 50°C to 90°C from the viewpoint of being able to stably react. When the polymerization temperature is too high, there is a tendency that the acrylic resin (A) is easily gelled, and when it is too low, the activity of the polymerization initiator decreases, and thus there is a tendency that the polymerization rate decreases and the residual monomer increases.

[0155] The polymerization time in the polymerization reaction is not particularly limited, and it is 0.5 hours or more, preferably 1 hour or more, and more preferably 2 hours or more, particularly preferably 5 hours or more, from the addition of the polymerization initiator.

[0156] From the viewpoint of easy heat removal, it is preferable to perform the polymerization reaction while refluxing the solvent.

[0157] [Photopolymerization initiator (B)]

[0158] The present adhesive composition contains a photopolymerization initiator (B) in addition to the acrylic resin (A). The photopolymerization initiator (B) can be used alone or in combination with two or more kinds.

[0159] Hereinafter, the photopolymerization initiator (B) used in the present adhesive composition 1 or the present adhesive composition 2 will be described.

[0160] The photopolymerization initiator (B) contained in the present adhesive composition 1 preferably contains a hydrogen abstraction type photopolymerization initiator (b).

[0161] As the above hydrogen abstraction type photopolymerization initiator (b), intramolecular hydrogen abstraction type photopolymerization initiator (bl) and intermolecular hydrogen abstraction type photopolymerization initiator (b2) can be exemplified, and further, intramolecular hydrogen abstraction type photopolymerization initiator (bl) is preferable.

[0162] The photopolymerization initiator (B) can further contain other photopolymerization initiator (b3) than the intramolecular hydrogen abstraction type photopolymerization initiator (bl) and the intermolecular hydrogen abstraction type photopolymerization initiator (b2) as long as the effect of the present application is not impaired.

[0163] [Intramolecular hydrogen abstraction type photopolymerization initiator (bl)]

[0164] The intramolecular hydrogen abstraction type photopolymerization initiator (bl) has a structure capable of generating a radical by abstracting hydrogen of the photopolymerization initiator itself, and specifically has a phenyl glyoxylic acid ester structure or the like.

[0165] As the intramolecular hydrogen abstraction type photopolymerization initiator (bl), for example, oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetyloxy-ethoxy]-ethyl ester, [4-(4-methoxy-oxalyl-phenoxy)-phenyl]-oxo-acetic acid methyl ester, [4-(4-butoxy-oxalyl-phenoxy)-phenyl]-oxo-acetic acid butyl ester, [4-(4-methoxy-oxalyl-phenylsulfanyl)-phenyl]-oxo-acetic acid methyl ester, [4-(4-ethoxy-oxalyl-phenylsulfanyl)-phenyl]-oxo-acetic acid methyl ester, [4-(4-butoxy-oxalyl-phenylsulfanyl)-phenyl]-oxo-acetic acid methyl ester, [4-(4-methoxy-oxalyl-benzyl)-phenyl]-oxo-acetic acid methyl ester, phenyl glyoxylic acid methyl ester, or the like can be exemplified.

[0166] Among them, from the viewpoint of crosslinking efficiency at the time of final curing, oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetyloxy-ethoxy]-ethyl ester in which a plurality of crosslinking points exist in the molecule is preferable.

[0167] In addition, as a commercially available product of the intramolecular hydrogen abstraction type photopolymerization initiator (b1), "Omnirad MBF", "Omnirad 754" manufactured by IGM RESINS B.V. can be exemplified.

[0168] The intramolecular hydrogen abstraction type photopolymerization initiator (b1) can be used alone or in combination with two or more.

[0169] [Intermolecular hydrogen abstraction type photopolymerization initiator (b2)]

[0170] The intermolecular hydrogen abstraction type photopolymerization initiator (b2) has a structure capable of generating a radical by abstracting hydrogen from other than the photopolymerization initiator itself, and specifically has a benzophenone structure, a thioxanthone structure, or the like.

[0171] As the intermolecular hydrogen abstraction type photopolymerization initiator (b2), for example, benzophenone, 4-methyl-benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(meth)acryloyloxybenzophenone, 4-[2-((meth)acryloyloxy)ethoxy]benzophenone, 4-(meth)acryloyloxy-4'-methoxybenzophenone, carboxymethoxymethoxybenzophenone-polyethylene glycol 250 diester, 2-benzoylbenzoic acid methyl ester, 4-(1,3-acryloyl-1,4,7,10,13-pentaoxatridecyl)benzophenone, and the like benzophenones; 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2,4-diisopropylthioxanthone, 1-chloro-4-propoxythioxanthone, 2-acryloyloxythioxanthone, 2-(2-acryloyloxyethoxy)thioxanthone, and the like thioxanthones can be exemplified.

[0172] Among them, from the viewpoint of being able to crosslink highly, 4-(meth)acryloyloxybenzophenone, 4-[2-((meth)acryloyloxy)ethoxy]benzophenone, 4-(meth)acryloyloxy-4'-methoxybenzophenone, carboxymethoxymethoxybenzophenone-polyethylene glycol 250 diester, in which multiple crosslinking points exist in the molecule, are preferable.

[0173] In addition, as a commercially available product of the intermolecular hydrogen abstraction type photopolymerization initiator (b2), "MBP" manufactured by Shin-Nakamura Chemical Co., Ltd., "Omnirad BP", "Omnirad 4MBZ", "Esacure TZT", "Omnipol BP" manufactured by IGM RESINS B.V. can be exemplified.

[0174] The intermolecular hydrogen abstraction type photopolymerization initiator (b2) can be used alone or in combination with two or more.

[0175] [Other photopolymerization initiator (b3)]

[0176] As the other photopolymerization initiator (b3), for example, acetophenone-based compounds such as diethoxyacetophenone, 2-hydroxy-2-methyl-l-phenylpropan-l-one, benzildimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, l-hydroxycyclohexyl phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-l-one, 2-benzyl-2-dimethylamino-l-(4-morpholinophenyl)butanone, 2-hydroxy-2-methyl-l-[4-(l-methylethenyl)phenyl]propanone oligomer, and the like; benzoin-based compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and the like; acyloxyphosphine-based compounds such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and the like.

[0177] The other photopolymerization initiator (b3) can be used alone as one kind or in combination with two or more kinds.

[0178] The photopolymerization initiator (B) contained in the present adhesive composition 2 contains a photopolymerization initiator (β1) having a molar absorption coefficient of 30 to 5,000 (L / mol-cm) in a wavelength range of 380 nm to 450 nm (hereinafter referred to as "photopolymerization initiator (β1)").

[0179] As the photopolymerization initiator (β1), intramolecular hydrogen abstraction type photopolymerization initiators (β1-1) having a molar absorption coefficient of 30 to 5,000 (L / mol-cm) in a wavelength range of 380 nm to 450 nm (hereinafter referred to as "intramolecular hydrogen abstraction type photopolymerization initiators (β1-1)"), intermolecular hydrogen abstraction type photopolymerization initiators (β1-2) having a molar absorption coefficient of 30 to 5,000 (L / mol-cm) in a wavelength range of 380 nm to 450 nm (hereinafter referred to as "intermolecular hydrogen abstraction type photopolymerization initiators (β1-2)"), and intramolecular cleavage type photopolymerization initiators (β1-3) having a molar absorption coefficient of 30 to 5,000 (L / mol-cm) in a wavelength range of 380 nm to 450 nm (hereinafter referred to as "intramolecular cleavage type photopolymerization initiators (β1-3)"), further preferably intramolecular hydrogen abstraction type photopolymerization initiators (β1-1) can be exemplified.

[0180] [intramolecular hydrogen abstraction type photopolymerization initiator (β1-1)]

[0181] The intramolecular hydrogen abstraction type photopolymerization initiator (β1-1) has a structure capable of generating a radical by abstracting hydrogen from the photopolymerization initiator itself using active energy rays having a wavelength of 380 nm to 450 nm, and specifically has a phenyl glyoxylic acid ester structure or the like.

[0182] As the intramolecular hydrogen abstraction type photopolymerization initiator (β1-1), for example, [4-(4-methoxyoxalyl-phenylsulfanyl)-phenyl]-oxoacetic acid methyl ester, [4-(4-ethoxyoxalyl-phenylsulfanyl)-phenyl]-oxoacetic acid methyl ester, [4-(4-butoxyoxalyl-phenylsulfanyl)-phenyl]-oxoacetic acid methyl ester, or the like can be exemplified, of which [4-(4-methoxyoxalyl-phenylsulfanyl)-phenyl]-oxoacetic acid methyl ester is preferred.

[0183] The intramolecular hydrogen abstraction type photopolymerization initiator (β1-1) can be used alone or in combination with two or more kinds.

[0184] [Intermolecular hydrogen abstraction type photopolymerization initiator (β1-2)]

[0185] The intermolecular hydrogen abstraction type photopolymerization initiator (β1-2) has a structure capable of generating a radical by abstracting hydrogen from other than the photopolymerization initiator itself using active energy rays having a wavelength of 380 nm to 450 nm, and specifically has a benzophenone structure, a thioxanthone structure, or the like.

[0186] As the intermolecular hydrogen abstraction type photopolymerization initiator (β1-2), for example, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2,4-diisopropylthioxanthone, 1-chloro-4-propoxythioxanthone, or the like can be exemplified.

[0187] The intermolecular hydrogen abstraction type photopolymerization initiator (β1-2) can be used alone or in combination with two or more kinds.

[0188] [Intramolecular cleavage type photopolymerization initiator (β1-3)]

[0189] The intramolecular cleavage type photopolymerization initiator (β1-3) has a structure capable of generating a radical by cleaving the photopolymerization initiator itself using active energy rays having a wavelength of 380 nm to 450 nm, and specifically has an acyl phosphine oxide structure, an α-aminoacetophenone structure, or the like.

[0190] As the above-mentioned intramolecular cleavage type photopolymerization initiator (β1-3), for example, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-ethoxyphenylphosphine oxide, 2-(N,N-dimethylamino)-2-(4-methylbenzyl)-1-(4-morpholinophenyl)butan-1-one, 2-benzyl-2-(dimethylamino)-1-(4-morpholinophenyl)-1-butanone, and the like can be exemplified.

[0191] The above-mentioned intramolecular cleavage type photopolymerization initiator (β1-3) can be used alone one kind, or two or more kinds can be used in combination.

[0192] The above-mentioned photopolymerization initiator (B) can further contain other photopolymerization initiator (β2) than the photopolymerization initiator (β1) having a molar absorption coefficient of 30 to 5,000 (L / mol·cm) in the range of wavelength of 380 nm to 450 nm, as long as the effect of the present application is not impaired.

[0193] [Other photopolymerization initiator (β2)]

[0194] As the other photopolymerization initiator (β2), for example, oxyl-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetyloxy-ethoxy]-ethyl ester, phenylglyoxalic acid methyl ester, benzophenone, 4-methyl-benzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(meth)acryloyloxybenzophenone, 4-[2-((meth)acryloyloxy)ethoxy]benzophenone, 4-(meth)acryloyloxy-4'-methoxybenzophenone, carboxymethoxymethoxybenzophenone-polyethylene glycol 250 diester, diethoxyphenylethanone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzil dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and the like can be exemplified. The other photopolymerization initiator (β2) can be used alone one kind, or two or more kinds can be used in combination.

[0195] In addition, as the aid of the photopolymerization initiator (B) used in the present adhesive composition, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethyl benzoic acid, 4-dimethylaminobenzoic acid ethyl ester, 4-dimethylaminobenzoic acid (n-butoxy) ethyl ester, 4-dimethylaminobenzoic acid isopentyl ester, 4-dimethylaminobenzoic acid 2-ethylhexyl ester, and the like can be used in combination.

[0196] The photopolymerization initiator (B) can be used alone or in combination with two or more kinds.

[0197] <crosslinking agent (C)>

[0198] The present adhesive composition preferably contains a crosslinking agent (C) in addition to the acrylic resin (A) and the photopolymerization initiator (B).

[0199] As the crosslinking agent (C), active energy ray crosslinking agents (cl), thermal crosslinking agents (c2) can be exemplified. The crosslinking agent (C) can be used alone or in combination with two or more kinds.

[0200] In the case where only an active energy ray crosslinking agent (cl) is contained as the crosslinking agent (C), multi-stage curing can be performed by controlling only the active energy ray amount. In addition, in the case where an active energy ray crosslinking agent (cl) and a thermal crosslinking agent (c2) are contained as the crosslinking agent (C), multi-stage curing can also be performed by combining thermal curing and active energy ray curing.

[0201] By thus controlling the crosslinking reaction, the cohesive force of the adhesive layer as a whole can be adjusted, and stable adhesive properties can be obtained after the first curing and after the final curing.

[0202] [active energy ray crosslinking agent (cl)]

[0203] As the active energy ray crosslinking agent (cl), multifunctional crosslinking agents containing two or more ethylenically unsaturated groups in one molecule can be exemplified.

[0204] For example, hexanediol di(meth)acrylate, butanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, (poly)ethylene glycol mono(meth)acrylate, (poly)butanediol mono(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, (poly)pentamethylene glycol di(meth)acrylate, (poly)hexamethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, EO-modified glycerol tri(meth)acrylate, isocyanuric acid ethylene oxide-modified tri(meth)acrylate, multifunctional urethane (meth)acrylate, and the like can be exemplified.

[0205] Among them, from the viewpoint of the balance between the adhesion properties after curing and shape stability, a (meth)acrylate ester containing 2 to 6 ethylenic unsaturated groups is preferred, and a (meth)acrylate ester containing 2 to 4 ethylenic unsaturated groups is further preferred. Particularly preferred are (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate.

[0206] The active energy ray crosslinking agent (c1) can be used alone or in combination with two or more kinds.

[0207] [Thermal crosslinking agent (c2)]

[0208] The thermal crosslinking agent (c2) can exert excellent adhesion by mainly reacting with the functional group derived from the functional group-containing monomer as a constituent monomer of the acrylic resin (A).

[0209] As the thermal crosslinking agent (c2), for example, isocyanate-based crosslinking agents (c2-1), epoxy-based crosslinking agents (c2-2), aziridine-based crosslinking agents (c2-3), melamine-based crosslinking agents (c2-4), aldehyde-based crosslinking agents (c2-5), amine-based crosslinking agents (c2-6), metal chelate-based crosslinking agents (c2-7) can be exemplified. Among them, from the viewpoint of improving the adhesion to the substrate and the reactivity with the acrylic resin (A), the use of the isocyanate-based crosslinking agent (c2-1) is preferred.

[0210] The thermal crosslinking agent (c2) can be used alone or in combination with two or more kinds.

[0211] As the isocyanate-based crosslinking agent (c2-1), for example, toluene diisocyanate compounds such as 2,4-toluene diisocyanate and 2,6-toluene diisocyanate; xylylene diisocyanate compounds such as 1,3-xylylene diisocyanate and 1,4-xylylene diisocyanate, and tetramethylxylylene diisocyanate; aromatic isocyanate compounds such as 1,5-naphthalene diisocyanate and triphenylmethane triisocyanate; hexamethylene diisocyanate compounds such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; aliphatic isocyanate compounds such as lysine diisocyanate; alicyclic isocyanate compounds such as isophorone diisocyanate; and adducts of these isocyanate compounds with polyol compounds such as trimethylolpropane; biuret bodies of these isocyanate compounds, isocyanurate bodies; and the like can be exemplified.

[0212] Among the isocyanate-based crosslinking agents (c2-1), from the viewpoint of excellent reactivity, aromatic isocyanate-based compounds are preferred, and tolylene diisocyanate-based compounds are particularly preferred. In addition, from the viewpoint of suppressing yellowing, aliphatic isocyanate-based compounds are preferred, and hexamethylene diisocyanate-based compounds are particularly preferred.

[0213] As the epoxy-based crosslinking agent (c2-2), for example, bisphenol A-epichlorohydrin type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, and the like can be exemplified.

[0214] As the aziridine-based crosslinking agent (c2-3), for example, tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(l-aziridinylcarboxamide), N,N'-hexamethylene-l,6-bis(l-aziridinylcarboxamide), and the like can be exemplified.

[0215] As the melamine-based crosslinking agent (c2-4), for example, hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexabutoxymethyl melamine, hexapentoxymethyl melamine, hexahexyoxymethyl melamine, melamine resin, and the like can be exemplified.

[0216] As the aldehyde-based crosslinking agent (c2-5), for example, glyoxal, malondialdehyde, butanedial, crotonaldehyde, glutaraldehyde, formaldehyde, acetaldehyde, benzaldehyde, and the like can be exemplified.

[0217] As the amine-based crosslinking agent (c2-6), for example, hexamethylenediamine, triethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophorone diamine, amino resins, polyamides, and the like can be exemplified.

[0218] As the metal chelate-based crosslinking agent (c2-7), for example, acetylacetone, acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, palladium, chromium, zirconium, and the like can be exemplified.

[0219] <Silane Coupling Agent (D)>

[0220] From the viewpoint of improving durability, the present adhesive composition preferably further contains a silane coupling agent (D) as a compound other than the acrylic resin (A), the photopolymerization initiator (B), and the crosslinking agent (C).

[0221] The silane coupling agent (D) is an organosilicon compound containing 1 or more reactive functional groups and alkoxyl groups bonded to silicon atoms in its structure, respectively. As the silane coupling agent (D), monomeric and oligomeric types can be cited.

[0222] As the reactive functional group in the silane coupling agent (D), for example, an epoxy group, a (meth)acryloyl group, a mercapto group, a hydroxyl group, a carboxyl group, an amino group, an amide group, an isocyanate group, and the like can be cited. Among these, from the viewpoint of excellent durability and reworkability, an epoxy group and a mercapto group are preferred.

[0223] The content ratio of the reactive functional group in the silane coupling agent (D) is usually 3,000 g / mol or less, preferably 1,500 g / mol or less, and more preferably 1,000 g / mol or less. Note that the lower limit is 200 g / mol. When the content ratio of the reactive functional group is within the above numerical range, there is a tendency that the balance between durability and reworkability improves. The lower limit of the content ratio of the reactive functional group in the silane coupling agent (D) is 200 g / mol.

[0224] As the alkoxyl group bonded to a silicon atom in the silane coupling agent (D), from the viewpoints of durability and storage stability, an alkoxyl group having a carbon number of 1 to 8 is preferred, and a methoxyl group and an ethoxyl group are more preferred.

[0225] In addition, the silane coupling agent (D) can have an organic functional group other than the reactive functional group and the alkoxyl group bonded to a silicon atom, such as an alkyl group, a phenyl group, and the like.

[0226] As the silane coupling agent (D), for example, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, methyltris(glycidyl)silane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and the like can be cited. Among these, from the viewpoint of heat resistance, γ-glycidoxypropyltrimethoxysilane is preferred.

[0227] The silane coupling agent (D) can be used alone as one kind or in combination with two or more kinds.

[0228] <Optional Components>

[0229] The present adhesive composition can contain, as other optional components, an adhesive as needed. The present adhesive composition can contain a carbodiimide, an antioxidant, an ultraviolet absorber, a crosslinking accelerator, an antistatic agent, an adhesion-improving agent, a functional pigment, and the like, which are conventionally known additives.

[0230] <Composition of the adhesive composition>

[0231] The content of the acrylic resin (A) in the present adhesive composition is usually 80% by mass or more, preferably 90% by mass to 99.9% by mass, and further preferably 92% by mass to 99.9% by mass, relative to the entire adhesive composition. When the content of the acrylic resin (A) is within the above numerical range, there is a tendency that an excellent adhesive property can be obtained in a low crosslinked state after primary curing.

[0232] The content of the photopolymerization initiator (B) in the present adhesive composition 1 is usually 0.1 parts by mass to 5 parts by mass, preferably 0.5 parts by mass to 4 parts by mass, and further preferably 1.0 parts by mass to 3 parts by mass, relative to 100 parts by mass of the acrylic resin (Al). When the content of the photopolymerization initiator (B) is within the above numerical range, there is a tendency that sufficient curing property can be obtained when curing is performed.

[0233] When a hydrogen abstraction type photopolymerization initiator (b) is used as the photopolymerization initiator (B) in the present adhesive composition 1, the content thereof is usually 0.1 parts by mass to 5 parts by mass, preferably 0.5 parts by mass to 4 parts by mass, and further preferably 1.0 parts by mass to 3 parts by mass, relative to 100 parts by mass of the acrylic resin (Al). When the content of the photopolymerization initiator (b) is within the above numerical range, there is a tendency that sufficient curing property can be obtained when curing is performed.

[0234] When an intramolecular hydrogen abstraction type photopolymerization initiator (bl) is used as the photopolymerization initiator (B) in the present adhesive composition 1, the content thereof is usually 0.1 parts by mass to 5 parts by mass, and preferably 0.5 parts by mass to 3 parts by mass, relative to 100 parts by mass of the acrylic resin (Al). When the content of the intramolecular hydrogen abstraction type photopolymerization initiator (bl) is too much, there is a tendency that discoloration is easily caused after heat and humidity resistance. In addition, when the content of the intramolecular hydrogen abstraction type photopolymerization initiator (bl) is too little, since the crosslinking degree does not increase, there is a tendency that the adhesive property at the time of primary curing and the durability after final curing decrease.

[0235] When an intermolecular hydrogen abstraction type photopolymerization initiator (b2) is used as the photopolymerization initiator (B) in the present adhesive composition 1, the content thereof is usually 0.1 parts by mass to 5 parts by mass, and preferably 0.5 parts by mass to 3 parts by mass, relative to 100 parts by mass of the acrylic resin (Al). When the content of the intermolecular hydrogen abstraction type photopolymerization initiator (b2) is too much, there is a tendency that the durability is deteriorated due to bleeding. In addition, when the content of the intermolecular hydrogen abstraction type photopolymerization initiator (b2) is too little, since the crosslinking degree does not increase, there is a tendency that the adhesive property at the time of primary curing and the durability after final curing decrease.

[0236] In addition, when the intramolecular hydrogen-abstracting photopolymerization initiator (b1) and the intermolecular hydrogen-abstracting photopolymerization initiator (b2) are used in this adhesive composition 1, the proportion of them in the mass ratio [(b1) / (b2)] is generally 1 / 9 to 9 / 1, preferably 5 / 5 to 8 / 2.

[0237] In addition, when the photopolymerization initiator (B) in this adhesive composition 1 contains other photopolymerization initiators (b3), the content of the other photopolymerization initiators (b3) is generally 2 parts by mass or less, preferably 1 part by mass or less, relative to 100 parts by mass of acrylic resin (A1).

[0238] The content of photopolymerization initiator (B) in this adhesive composition 2 is typically 0.1 to 5 parts by weight relative to 100 parts by weight of acrylic resin (A2), preferably 0.5 to 4 parts by weight, and more preferably 1.0 to 3 parts by weight. When the content of photopolymerization initiator (B) is within the above-mentioned range, there is a tendency to obtain sufficient curability during curing.

[0239] The content of photopolymerization initiator (β1) in this adhesive composition 2 is typically 0.1 to 5 parts by weight relative to 100 parts by weight of acrylic resin (A2), preferably 0.5 to 4 parts by weight, and more preferably 1.0 to 3 parts by weight. When the content of photopolymerization initiator (β1) is within the above-mentioned range, there is a tendency to obtain sufficient curability during curing.

[0240] When an intramolecular hydrogen-abstraction photopolymerization initiator (β1-1) is used as the photopolymerization initiator (β1) in this adhesive composition 2, its content is typically 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight, relative to 100 parts by weight of the acrylic resin (A2). Excessive content of the intramolecular hydrogen-abstraction photopolymerization initiator (β1-1) tends to reduce durability due to exudation. Conversely, insufficient content of the intramolecular hydrogen-abstraction photopolymerization initiator (β1-1) tends to reduce the adhesive properties during primary curing and the durability after final curing, as the degree of crosslinking does not increase.

[0241] When an intermolecular hydrogen-abstraction photopolymerization initiator (β1-2) is used as the photopolymerization initiator (β1) in this adhesive composition 2, its content is typically 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight, relative to 100 parts by weight of the acrylic resin (A2). Excessive content of the intermolecular hydrogen-abstraction photopolymerization initiator (β1-2) tends to reduce durability due to exudation. Conversely, insufficient content of the intermolecular hydrogen-abstraction photopolymerization initiator (β1-2) tends to reduce the adhesive properties during primary curing and the durability after final curing, as the degree of crosslinking does not increase.

[0242] In the present adhesive composition 2, when the intramolecular cleavage type photopolymerization initiator (β1-3) is used as the photopolymerization initiator (β1), the content thereof is usually 0.1 parts by mass to 5 parts by mass, preferably 0.5 parts by mass to 3 parts by mass, relative to 100 parts by mass of the acrylic resin (A2). When the content of the intramolecular cleavage type photopolymerization initiator (β1-3) is too large, there is a tendency that the durability is reduced due to bleeding. In addition, when the content of the intramolecular cleavage type photopolymerization initiator (β1-3) is too small, since the crosslinking degree is not improved, there is a tendency that the adhesive properties at the time of primary curing and the durability after final curing are reduced.

[0243] In the present adhesive composition 2, when the photopolymerization initiator (B) contains another photopolymerization initiator (β2), the content of the other photopolymerization initiator (β2) is preferably 2 parts by mass or less, more preferably 1 part by mass or less, relative to 100 parts by mass of the acrylic resin (A2).

[0244] When the present adhesive composition contains the crosslinking agent (C), the content of the crosslinking agent (C) is usually 30 parts by mass or less, preferably 0.001 parts by mass to 10 parts by mass, further preferably 0.1 parts by mass to 7.5 parts by mass, relative to 100 parts by mass of the acrylic resin (A). When the content of the crosslinking agent (C) is too large, there is a tendency that the adhesive force is reduced. In addition, when the content of the crosslinking agent (C) is too small, there is a tendency that the durability is reduced.

[0245] When the active energy ray crosslinking agent (c1) is used as the crosslinking agent (C), the content of the active energy ray crosslinking agent (c1) is usually 0.1 parts by mass to 20 parts by mass, preferably 0.5 parts by mass to 15 parts by mass, further preferably 1.0 parts by mass to 10 parts by mass, relative to 100 parts by mass of the acrylic resin (A). When the content of the active energy ray crosslinking agent (c1) is too small, the cohesive force is reduced, and there is a tendency that sufficient durability cannot be obtained. In addition, when the content of the active energy ray crosslinking agent (c1) is too large, there is a tendency that the adhesive properties at the time of primary curing are reduced.

[0246] When the thermal crosslinking agent (c2) is used as the crosslinking agent (C), the content of the thermal crosslinking agent (c2) is usually 0.001 parts by mass to 5 parts by mass, preferably 0.02 parts by mass to 1 part by mass, further preferably 0.05 parts by mass to 0.5 parts by mass, relative to 100 parts by mass of the acrylic resin (A). When the content of the thermal crosslinking agent (c2) is too small, the cohesive force is reduced, and there is a tendency that the adhesive properties at the time of primary curing are reduced. In addition, when the content of the thermal crosslinking agent (c2) is too large, there is a tendency that the adhesive force at the time of final curing is reduced.

[0247] When the adhesive composition of the present application contains the silane coupling agent (D), the content of the silane coupling agent (D) is usually 0.001 parts by mass or more and 3 parts by mass or less, preferably 0.005 parts by mass or more and 1 part by mass or less, further preferably 0.01 parts by mass or more and 0.5 parts by mass or less, and particularly preferably 0.015 parts by mass or more and 0.3 parts by mass or less, relative to 100 parts by mass of the acrylic resin (A). When the content of the silane coupling agent (D) is too small, there is a tendency that the effect of improving the durability cannot be obtained. In addition, when the content of the silane coupling agent (D) is too large, there is a tendency that the adhesive force is decreased due to bleeding or the like.

[0248] When the adhesive composition of the present application contains other adhesives or additives, the content of the other adhesives or additives is usually 10 parts by mass or less, and preferably 5 parts by mass or less, relative to 100 parts by mass of the acrylic resin (A).

[0249] <Preparation of the adhesive composition>

[0250] The adhesive composition of the present application can be obtained by mixing the acrylic resin (A), the photopolymerization initiator (B), the crosslinking agent (C) as needed, the silane coupling agent (D), and other arbitrary components. The mixing method is not particularly limited, and various methods such as a method in which all the components are mixed together, a method in which arbitrary components are mixed and then the remaining components are mixed together or sequentially, and the like can be employed.

[0251] <Use>

[0252] The adhesive composition 1 of the present application can be suitably used as an adhesive for an adhesive sheet exhibiting multi-stage curing in which curing is performed in a plurality of stages. The above-described adhesive is low in tackiness even in a low crosslinked state after primary curing, high in constant load retention, can be efficiently cured even with a small amount of active energy rays at the time of curing, and further excellent in adhesive properties, reliability, and shape stability after final curing. Therefore, a laminate obtained by bonding using a multi-stage curing adhesive sheet formed of the adhesive is excellent in mechanical strength.

[0253] In addition, the adhesive composition 2 of the present application can be suitably used as an adhesive for an adhesive sheet exhibiting multi-stage curing in which curing is performed in a plurality of stages. The above-described adhesive can be efficiently cured using active energy rays in the visible region even in a low crosslinked state after primary curing, and is excellent in adhesive properties. After final curing, the adhesive is excellent in adhesive properties, reliability, and shape stability. Therefore, a laminate obtained by bonding using a multi-stage curing adhesive sheet formed of the adhesive is excellent in mechanical strength.

[0254] The adhesive composition 2 of the present application is excellent in adhesive properties such as low tackiness and high constant load retention even in a low crosslinked state after primary curing, and therefore is improved in workability and reliability.

[0255] Thus, the present adhesive composition is particularly suitable for use in adhesives, adhesive sheets, and the like used in touch panels, image display devices, and the like.

[0256] <Adhesive>

[0257] The adhesive of one embodiment of the present application (hereinafter referred to as "the present adhesive") is obtained by crosslinking the present adhesive composition described above. By crosslinking (curing) the present adhesive composition, at least one of the acrylic resin (A) contained in the present adhesive composition forms a crosslinked structure within a molecule and between molecules. As a result, the present adhesive composition is crosslinked to become the present adhesive.

[0258] In addition, in the case where the acrylic resin (A) has a site having a crosslinking property with respect to active energy rays, a crosslinked structure can be formed by irradiation with active energy rays.

[0259] The present adhesive exhibits a multi-stage curing property capable of being cured in multiple stages. The present adhesive becomes a low crosslinked state by primary curing, and further reaches final curing by crosslinking (curing). The final curing and the primary curing are not necessarily clearly distinguishable, but can be distinguished based on differences in gel fraction and dynamic viscoelasticity.

[0260] The means for performing the primary curing and the final curing are not particularly limited, and can be, for example, any of heating and irradiation with active energy rays. The primary curing described above can be performed in multiple stages, and in addition, the final curing can be performed in multiple stages.

[0261] The present adhesive has excellent adhesive properties after primary curing, and is thus suitable for use in bonding of optical members constituting touch panels, image display devices, and the like.

[0262] The present adhesive can also be said to include a crosslinked product of at least the acrylic resin (A). The crosslinked product can be a partially crosslinked product in which at least a part of the acrylic resin (A) is partially crosslinked, or a completely crosslinked product in which the entire acrylic resin (A) is completely crosslinked. In addition, the present adhesive can include both a partially crosslinked product and a completely crosslinked product of the acrylic resin (A).

[0263] <Adhesive sheet>

[0264] The adhesive sheet of one embodiment of the present application (hereinafter referred to as "the present adhesive sheet") has an adhesive layer formed of the present adhesive. The adhesive layer of the present adhesive sheet can exhibit a multi-stage curing property of being cured in multiple stages.

[0265] An adhesive sheet can be produced by providing an adhesive layer formed of the present adhesive on a base sheet. In addition, the present adhesive sheet can be produced as a double-sided adhesive sheet by providing an adhesive layer on a release sheet. Furthermore, instead of a base sheet, an adhesive layer of the present adhesive sheet can be formed on a release sheet, and a release sheet can be attached to the surface of the adhesive layer on the opposite side, thereby producing a baseless double-sided adhesive sheet. In addition, the present adhesive sheet can be produced to have a large thickness by further forming an adhesive layer on the formed adhesive layer.

[0266] The obtained adhesive sheet, double-sided adhesive sheet is used by peeling the release sheet from the adhesive layer.

[0267] As a method for producing the present adhesive sheet, for example, the following (i), (ii), and the like can be listed.

[0268] (i) A method in which the present adhesive composition is dissolved in a solvent to be coated to produce an adhesive sheet.

[0269] (ii) A method in which the present adhesive composition is melted by heating to produce an adhesive sheet.

[0270] The method of (i) will be described.

[0271] When the present adhesive composition is dissolved in a solvent to be coated to produce an adhesive sheet, the concentration of the coating liquid containing the present adhesive composition is adjusted using an appropriate organic solvent, and it is directly coated on a base sheet. Then, it is dried by, for example, heating treatment at 80°C to 105°C for 0.5 minutes to 10 minutes, or the like, and it is attached to a base sheet or a release sheet. Then, the adhesive composition is crosslinked (cured) by active energy ray irradiation or aging, and an adhesive sheet having an adhesive layer formed of an adhesive can be produced.

[0272] As the organic solvent used in the concentration adjustment, the organic solvents listed as the organic solvents used in the polymerization of the acrylic resin (A) can be used. The concentration of the adhesive composition is usually 20 mass% to 60 mass%, and preferably 30 mass% to 50 mass% in terms of solid content.

[0273] The method of (ii) will be described.

[0274] In the case where the present adhesive composition is melted by heating to produce an adhesive sheet, the adhesive layer is formed on one side or both sides of a base sheet in such a manner that the desired thickness is obtained by a method in which the present adhesive composition is coated on one side or both sides of a base sheet in a molten state and then cooled, a method in which the present adhesive composition is extrusion laminated on a base sheet by a T-die or the like, or the like. Next, a release sheet is attached to the surface of the adhesive layer as necessary, and thereby an adhesive sheet can be produced.

[0275] In addition, after forming the adhesive layer on the base sheet, the active energy ray irradiation treatment is performed as necessary, and then the curing is performed, whereby an adhesive sheet having an adhesive layer cured (crosslinked) by the adhesive composition can be produced.

[0276] Further, by forming the adhesive layer on the release sheet and adhering the release sheet to the surface of the adhesive layer on the opposite side, a double-sided adhesive sheet without a base sheet can also be produced.

[0277] As the above-mentioned base sheet, for example, polyester-based resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate / polyethylene isophthalate copolymer, and the like; polyolefin-based resins such as polyethylene, polypropylene, polymethylpentene, and the like; polyvinyl fluoride resins such as polyvinyl fluoride, polyvinylidene fluoride, polyvinylidene chloride, and the like; polyamides such as nylon 6, nylon 6,6, and the like; vinyl polymers such as polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, vinylon, and the like; cellulose-based resins such as cellulose triacetate, cellophane, and the like; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polybutyl acrylate, and the like; polystyrene; polycarbonate; polyarylate; synthetic resin sheets such as polyimide and the like; metal foils such as aluminum, copper, iron, and the like; paper such as high-quality paper, glassine paper, and the like; fabrics and nonwoven fabrics composed of glass fibers, natural fibers, synthetic fibers, and the like. These base sheets can be used in the form of a single layer or in the form of a multilayer in which two or more layers are stacked. Among them, from the viewpoint of light weight and the like, synthetic resin sheets are preferred.

[0278] As the above-mentioned release sheet, for example, a sheet subjected to a release treatment on various synthetic resin sheets, paper, fabrics, nonwoven fabrics, and the like exemplified as the base sheet can be used. As the release sheet, for example, a release sheet of silicon is preferably used.

[0279] The method of applying the present adhesive composition is not particularly limited, and for example, methods such as roll coating, die coating, gravure coating, comma coating, slit coating, screen printing, and the like can be exemplified.

[0280] As the above-mentioned active energy ray, light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, and the like; electromagnetic waves such as X-rays, γ-rays, and the like; electron beams; proton rays; neutron rays, and the like can be used. From the viewpoints of the curing speed, the ease of obtaining the irradiation device, the price, and the like, curing using ultraviolet rays is preferred.

[0281] The gel fraction after the primary curing of the adhesive layer of the present adhesive sheet is generally 0.1 mass% to 60 mass%, preferably 0.5 mass% to 55 mass%, and particularly preferably 1 mass% to 50 mass% from the viewpoint of the ease of adhesion regardless of the shape of the adherend and the viewpoint of the ability of the adhesive layer to hold the adherend after adhesion.

[0282] The gel fraction of the adhesive layer of the present adhesive sheet after final curing is preferably 60 to 90 mass%, more preferably 65 to 87 mass%, and particularly preferably 70 to 85 mass% from the viewpoint of durability and adhesive strength. If the gel fraction is too low, there is a tendency for durability to decrease due to a decrease in cohesive force. Note that if the gel fraction is too high, there is a tendency for adhesive strength to decrease due to an increase in cohesive force.

[0283] The above gel fraction can be appropriately adjusted, for example, by the following methods.

[0284] (1) A method of adjusting the amount of irradiation of active energy rays.

[0285] (2) A method of adjusting the content of active energy ray-crosslinkable structural sites in the acrylic resin (A).

[0286] (3) A method of adjusting the types and amounts of the photopolymerization initiator (B) and the crosslinking agent (C).

[0287] The above gel fraction is a reference for the degree of crosslinking (degree of curing) and is calculated, for example, by the following method. That is, an adhesive sheet (an adhesive sheet without a release sheet) in which an adhesive layer is formed on a high-molecular sheet (for example, a polyethylene terephthalate (PET) film or the like) as a base material is wrapped with a 200-mesh SUS metal mesh, immersed in toluene maintained at 23°C for 24 hours, and the mass percentage of the insoluble adhesive component remaining in the metal mesh is taken as the gel fraction. Here, the mass of the base material is subtracted from the mass before and after toluene dissolution.

[0288] The thickness of the adhesive layer of the present adhesive sheet is generally preferably 50 to 3000 μm, more preferably 75 to 1000 μm, and particularly preferably 100 to 350 μm. If the thickness of the adhesive layer is too thin, there is a tendency for impact absorbability to decrease. If the thickness of the adhesive layer is too thick, for example, the overall thickness increases when attached to an optical member, and there is a tendency for practicality to decrease.

[0289] The thickness of the adhesive layer in the present adhesive sheet is a value obtained by subtracting the measured value of the thickness of the constituent members other than the adhesive layer from the measured value of the overall thickness of the laminate containing the adhesive layer, using "ID-C112B" manufactured by Mitutoyo Corporation.

[0290] Further, the storage modulus G' of the adhesive layer of the present adhesive sheet obtained using the present adhesive composition 1 after final curing is usually 400 kPa or greater, preferably 600 kPa or greater, further preferably 700 kPa or greater, and particularly preferably 800 kPa or greater at 25°C. When the storage modulus G' is within the above range, there is a tendency that the shape stability of the adhesive layer is excellent, and the mechanical strength of a laminate formed by bonding using the adhesive sheet containing the adhesive layer is excellent. Note that the upper limit value is usually 5000 kPa.

[0291] The above storage modulus G' is obtained by measuring the adhesive layer using a dynamic viscoelasticity device at a frequency of 1 Hz.

[0292] Further, the storage modulus G' of the adhesive layer of the present adhesive sheet obtained using the present adhesive composition 2 after final curing is usually 400 kPa or greater, preferably 600 kPa or greater, further preferably 700 kPa or greater, and particularly preferably 800 kPa or greater at 25°C. When the storage modulus G' is within the above range, there is a tendency that the shape stability of the adhesive layer is excellent, and the mechanical strength of a laminate formed by bonding using the adhesive sheet containing the adhesive layer is excellent. Note that the upper limit value is usually 5000 kPa.

[0293] The tensile modulus of the adhesive layer of the present adhesive sheet obtained using the present adhesive composition 1 after final curing is usually 0.35 MPa or greater, preferably 0.40 MPa or greater, and further preferably 0.45 MPa or greater at 23°C, 50% RH. When the tensile modulus is within the above range, the shape stability of the adhesive layer is excellent, and there is a tendency that the mechanical strength of a laminate formed by bonding using the adhesive sheet containing the adhesive layer is excellent. Note that the upper limit value is usually 10 MPa.

[0294] The above tensile modulus is obtained by measuring the adhesive layer using a tensile testing machine at a tensile speed of 10 mm / min, and deriving from the ratio of the change in tensile strain to tensile stress.

[0295] Further, the tensile modulus of the adhesive layer of the present adhesive sheet obtained using the present adhesive composition 2 after final curing is usually 0.45 MPa or greater, preferably 0.55 MPa or greater, and further preferably 0.70 MPa or greater at 23°C, 50% RH. When the tensile modulus is within the above range, the shape stability of the adhesive layer is excellent, and there is a tendency that the mechanical strength of a laminate formed by bonding using the adhesive sheet containing the adhesive layer is excellent. Note that the upper limit value is usually 10 MPa.

[0296] The haze value of the adhesive layer (100 μm thick) of the present adhesive sheet is usually 2% or less, preferably 0 to 1.5%, and particularly preferably 0 to 1%. When the haze value is too high, there is a tendency for the adhesive layer to whiten and for the transparency to decrease.

[0297] The haze value is calculated by substituting the values of the diffuse transmittance (DT) and the total light transmittance (TT) obtained by measuring the diffuse transmittance and the total light transmittance using a HAZE MATER NDH4000 (manufactured by Nippon Denshoku Industries Co., Ltd.) into the following [Formula 1]. The host is in accordance with JIS K7361-1.

[0298] Haze value (%) = (DT / TT) x 100 [Formula 1]

[0299] In the present application, by using the present adhesive composition to form an adhesive layer on an optical member, an optical member with an adhesive layer can be obtained. For example, after attaching the adhesive layer surface of the present adhesive sheet having an adhesive layer formed on a release sheet to an optical member, the release sheet is peeled off, whereby an optical member with an adhesive layer can be obtained. Alternatively, the optical members can be attached to each other using the above-described double-sided adhesive sheet.

[0300] As the optical member, members constituting a touch panel, an image display device can be given. For example, a display (organic EL, liquid crystal), a transparent conductive film substrate (ITO substrate), a protective film (glass), a transparent antenna (film), a transparent wiring, and the like can be given.

[0301] EXAMPLE

[0302] Hereinafter, the present application will be specifically described by citing examples, but the present application is not limited to the following description. In the examples, "parts", "%" refer to mass basis. In addition, the weight average molecular weight of the acrylic resin (A), the glass transition temperature based on dynamic viscoelasticity, the thickness of the adhesive layer, and the haze value (%) are measured according to the methods described in the above-described embodiments.

[0303] Prior to the examples, the following raw materials were prepared.

[0304] <Acrylic Resin (A)>

[0305] 〔(Meth)Acrylic Acid Alkyl Ester (a1) Having an Alkyl Group with a Carbon Number of 5 or More〕

[0306] • 2EHA: Acrylic acid 2-ethylhexyl ester (Tg of homopolymer: -70°C)

[0307] • IDMA: Methacrylic acid isodecyl ester (Tg of homopolymer: -41°C)

[0308] 〔(Meth)Acrylic Acid Alkyl Ester (a2) Having an Alkyl Group with a Carbon Number of 1 to 4〕

[0309] • MA: methyl acrylate (Tg of homopolymer: 8°C)

[0310] • MMA: methyl methacrylate (Tg of homopolymer: 105°C)

[0311] [Amide group-containing ethylenically unsaturated monomer (a3)]

[0312] • DMAA: dimethyl acrylamide (Tg of homopolymer: 119°C)

[0313] • ACMO: acryloyl morpholine (Tg of homopolymer: 145°C)

[0314] [Other polymerizable monomer (a4)]

[0315] • HEMA: 2-hydroxyethyl methacrylate (Tg of homopolymer: 55°C)

[0316] • HEA: 2-hydroxyethyl acrylate (Tg of homopolymer: -15°C)

[0317] [Polymerization initiator]

[0318] • ADVN: 2,2'-azobis(2,4-dimethylvaleronitrile) (10-hour half-life temperature: 52°C)

[0319] [Photopolymerization initiator (B)]

[0320] [Intramolecular hydrogen abstraction type photopolymerization initiator (bl)]

[0321] • bl-1: blend of 2-[2-oxo-2-phenyl-acetyloxy-ethoxy]-ethyl oxypheylacetate and 2-[2-hydroxy-ethoxy]-ethyl oxypheylacetate, "Omnirad 754" by IGM Resins B.V.

[0322] [Intermolecular hydrogen abstraction type photopolymerization initiator (b2)]

[0323] • b2-1: 4-methacryloyloxybenzophenone, "MBP" by New Mills Co.

[0324] [Intramolecular hydrogen abstraction type photopolymerization initiator (β1-1)]

[0325] • β1-1(1): methyl [4-(4-methoxyoxalyl-phenylsulfanyl)-phenyl]-oxoacetate

[0326] [Intramolecular cleavage type photopolymerization initiator (β1-3)]

[0327] • β1-3 (1): 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, product "Omnirad TPO" of IGM Resins B.V.

[0328] <crosslinking agent (C)>

[0329] • c1-1: polypropylene glycol #400 diacrylate, "NK Ester APG400" of Shin Nakamura Chemical Co., Ltd.

[0330] • c1-2: trimethylolpropane triacrylate, "ARONIX M-309" of Toagosei Co., Ltd.

[0331] <silane coupling agent (D)>

[0332] • D-1: 3-glycidoxypropyltrimethoxysilane, "KBM403" of Shin-Etsu Chemical Co., Ltd.

[0333] <Manufacturing Example: Manufacturing of acrylic resin (A1-1)>

[0334] In a 2L flask with a condenser, ethyl acetate: 24 parts (boiling point 77°C), methyl ethyl ketone: 16 parts (boiling point 80°C), ADVN: 0.01 part, 2EHA: 4.5 parts, MA: 1.7 parts, MMA: 1.8 parts, DMAA: 2 parts as a polymerization solvent were put in, after heating to reflux in the flask, a mixture of ethyl acetate: 10 parts, ADVN: 0.18 part, 2EHA: 40.5 parts, MA: 15.3 parts, MMA: 16.2 parts, DMAA: 18 parts was added dropwise over 3 hours. Further, after dropping for 30 minutes, a mixture of ethyl acetate: 10 parts, ADVN: 0.13 part was added dropwise over 1 hour, and the reaction was allowed to proceed, to obtain a solution of acrylic resin (A-1). The polymer composition, weight average molecular weight (Mw), glass transition temperature based on dynamic viscoelasticity, storage modulus at 25°C of the acrylic resin (A1-1) are shown in Table 1 below.

[0335] <Manufacturing Example 2: Manufacturing of acrylic resins (A1-2), (A1-3)>

[0336] The acrylic resins (A1-2), (A1-3) were manufactured in the same manner as in Manufacturing Example 1 except that the copolymerization components of the acrylic resins were as shown in Table 1 below. The physical properties of the obtained acrylic resins (A1-2), (A1-3) are shown in Table 1 below.

[0337] <Comparative Manufacturing Example: Manufacturing of acrylic resin (A'1-1)>

[0338] In a 2L flask with a condenser, ethyl acetate: 33.3 parts (boiling point 77°C), methyl ethyl ketone: 6.7 parts (boiling point 80°C) were put as a polymerization solvent, and after heating to reflux in the flask, ethyl acetate: 10 parts, ADVN: 0.2 parts, 2EHA: 40 parts, MA: 52 parts, DMAA: 8 parts were added dropwise over 3 hours. Further, after dropping for 60 minutes, a mixture of ethyl acetate: 5 parts, ADVN: 0.07 parts was added, and the reaction was allowed to proceed, and then, after 60 minutes, a mixture of ethyl acetate: 5 parts, ADVN: 0.07 parts was added, to obtain a solution of acrylic resin (A'1-1). The polymer composition, weight average molecular weight (Mw), glass transition temperature based on dynamic viscoelasticity, and storage modulus at 25°C of the acrylic resin (A'1-1) are shown in Table 1 below.

[0339] <Manufacture of Comparative Examples: Acrylic Resins (A'1-2) ~ (A'1-4)>

[0340] The copolymer components of the acrylic resins were as shown in Table 1 below, and otherwise, the acrylic resins (A'1-2) ~ (A'1-4) were manufactured similarly to Comparative Production Example 1. The physical properties of the obtained acrylic resins (A'1-2) ~ (A'1-4) are shown in Table 1 below.

[0341] [Table 1]

[0342]

[0343] <Manufacture of Comparative Examples: Acrylic Resins (A'1-2) ~ (A'1-4)>

[0344] In a 2L flask with a condenser, ethyl acetate: 33.3 parts (boiling point 77°C), methyl ethyl ketone: 6.7 parts (boiling point 80°C) were put as a polymerization solvent, and after heating to reflux in the flask, ethyl acetate: 10 parts, ADVN: 0.2 parts, 2EHA: 40 parts, MA: 52 parts, DMAA: 8 parts were added dropwise over 3 hours. Further, after dropping for 60 minutes, a mixture of ethyl acetate: 5 parts, ADVN: 0.07 parts was added, and the reaction was allowed to proceed, and then, after 60 minutes, a mixture of ethyl acetate: 5 parts, ADVN: 0.07 parts was added, to obtain a solution of acrylic resin (A'1-1). The polymer composition, weight average molecular weight (Mw), glass transition temperature based on dynamic viscoelasticity, and storage modulus at 25°C of the acrylic resin (A'1-1) are shown in Table 1 below.

[0345] <Manufacture of Comparative Examples: Acrylic Resins (A'1-2) ~ (A'1-4)>

[0346] The acrylic resin (A2-2), (A2-3) was produced in the same manner as in Production Example 1 except that the copolymerization components of the acrylic resin were as shown in Table 2 below. The physical properties of the obtained acrylic resins (A2-2), (A2-3) are shown in Table 2 below.

[0347] [Production of Comparative Acrylic Resin (A'2-1)]

[0348] Into a 2L flask equipped with a condenser was placed ethyl acetate: 50 parts (boiling point 77°C), ADVN: 0.01 part, 2EHA: 7 parts, MA: 1 part, HEA: 2 parts as a polymerization solvent, and after heating to reflux in the flask, a mixture of ethyl acetate: 10 parts, ADVN: 0.16 part, 2EHA: 63 parts, MA: 9 parts, HEA: 18 parts was added dropwise over 3 hours. Further, after dropwise addition for 30 minutes, a mixture of ethyl acetate: 10 parts, ADVN: 0.15 part was added dropwise over 1 hour, and the reaction was allowed to proceed, to obtain a solution of the acrylic resin (A'2-1). The polymer composition, weight average molecular weight (Mw), glass transition temperature based on dynamic viscoelasticity, and storage modulus at 25°C of the acrylic resin (A'2-1) are shown in Table 2 below.

[0349] [Production of Comparative Acrylic Resin (A'2-2)]

[0350] Into a 2L flask equipped with a condenser was placed ethyl acetate: 32 parts (boiling point 77°C), methyl ethyl ketone: 8 parts (boiling point 80°C), ADVN: 0.01 part, 2EHA: 5 parts, MA: 2.5 parts, MMA: 1 part, DMAA: 1.5 parts as a polymerization solvent, and after heating to reflux in the flask, a mixture of ethyl acetate: 10 parts, ADVN: 0.17 part, 2EHA: 45 parts, MA: 22.5 parts, MMA: 9 parts, DMAA: 13.5 parts was added dropwise over 3 hours. Further, after dropwise addition for 55 minutes, a mixture of ethyl acetate: 5 parts, ADVN: 0.07 part was added, and after 120 minutes, a mixture of ethyl acetate: 5 parts, ADVN: 0.07 part was added, and the reaction was allowed to proceed, to obtain a solution of the acrylic resin (A'2-2). The polymer composition, weight average molecular weight (Mw), glass transition temperature based on dynamic viscoelasticity, and storage modulus at 25°C of the acrylic resin (A'2-2) are shown in Table 2 below.

[0351] [Table 2]

[0352]

[0353] [Example 1-1]

[0354] To 100 parts (solid content basis) of a solution of the acrylic resin (Al-1), b1-1: 2 parts (solid content basis), b2-1: 1 part (solid content basis), c1-1: 1.5 parts (solid content basis), and D-1: 0.1 part (solid content basis) were mixed to obtain an adhesive composition. The obtained adhesive composition was adjusted to a solid content concentration of 45% with toluene, and was applied to a polyester release sheet in a manner such that the dried thickness was about 50 μm, and was dried at 100°C for 5 minutes to form an adhesive composition layer.

[0355] Two pieces of the adhesive sheet on which the adhesive composition layer was formed on a polyester release sheet as described above were prepared, and the two adhesive composition layers were stacked opposite each other. In a state in which both sides of the stacked adhesive composition layers were sandwiched with polyester release sheets (release sheet / stacked adhesive composition layers / release sheet), ultraviolet irradiation was performed using a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 2000 mJ / cm 2 (1000 mJ / cm 2 x 2 times) to thereby form an adhesive layer (primary curing), and a substrate-free double-coated adhesive sheet having an adhesive layer thickness of 100 μm was obtained.

[0356] Next, the release sheet on one side of the adhesive layer of the obtained substrate-free double-coated adhesive sheet was peeled off, and the exposed adhesive layer side was pressed against an easily-adhesive-treated polyethylene terephthalate (PET) sheet (thickness 125 μm) to obtain a PET sheet with an adhesive layer having an adhesive layer thickness of 100 μm.

[0357] [Examples 1-2, 1-3, Comparative Examples 1-1 to 1-4]

[0358] As shown in Table 2, the adhesive compositions of each example were prepared in the same manner as in Example 1-1, except that the acrylic resin (Al-1) was changed. Next, the substrate-free double-coated adhesive sheet having an adhesive layer thickness of 100 μm, and the PET sheet with an adhesive layer were sequentially produced in the same manner as in Example 1-1. The composition of the adhesive composition of each example is shown in Table 3 below.

[0359] [Table 3]

[0360]

[0361] [Measurement method, evaluation method]

[0362] Using the substrate-free double-coated adhesive sheet, and the PET sheet with an adhesive layer of the examples and comparative examples, the following evaluations were performed. The results are shown in Tables 4 to 6 below.

[0363] (Gel fraction: after primary curing)

[0364] Each of the double-coated adhesive sheets without a substrate was cut into a size of 40 mm x 40 mm, and after standing for 30 minutes under conditions of 23°C x 50% RH, one of the release sheets was peeled off, and the exposed adhesive layer side was attached to a 50 mm x 100 mm SUS mesh (200 mesh). The remaining release sheet was peeled off, and the adhesive layer was wrapped with the SUS mesh, with the SUS mesh being folded back from the center portion with respect to the length direction of the SUS mesh. The gel fraction (%) was calculated from the change in mass when the adhesive layer was immersed in a sealed container containing 250 g of toluene maintained at 23°C for 24 hours.

[0365] (Permanent load holding power (40°C): after primary curing)

[0366] Each of the PET sheets with an adhesive layer was cut into a size of 25 mm in width x 75 mm in length (25 mm in width x 50 mm in length of the adhesive layer portion + 25 mm in width x 25 mm in length of the non-adhesive layer portion), and the release sheet was peeled off. The exposed adhesive layer side was attached (attached area: 25 mm x 50 mm) to a stainless steel plate (SUS304) by reciprocating and pressing a 2 kg roller, and the sample was left to stand for 20 minutes in a 40°C atmosphere. Then, a 50 g weight was hung from the end portion in the length direction of the non-attached portion (area: 25 mm x 25 mm), a load of 50 g was applied in the direction of 90° with respect to the plane of the stainless steel plate, and the sample was left to stand for 60 minutes in this state, and the distance of the PET sheet peeled off was measured. The evaluation criteria are described below.

[0367] ◎ (Excellent) ••• The distance of the peeled-off PET sheet was less than 5 mm.

[0368] O (Very good) ••• The distance of the peeled-off PET sheet was 5 mm or more and less than 10 mm.

[0369] X (Poor) ••• The distance of the peeled-off PET sheet was 10 mm or more, or the PET sheet was completely peeled off and fell down.

[0370] (Probe tack: after primary curing)

[0371] For each of the PET sheets with an adhesive layer, the sheet was cut into a size of 12 mm in width x 12 mm in length, the release sheet was peeled off, and the probe tack (unit: N) was measured using a probe tack tester (TESTER SANGYO CO., LTD., probe tack tester TE-6001) under conditions of a pressing time of 5 seconds, an attached pressure of 1000 gf, a pressure-in speed of 600 mm / min, a lift-off speed of 600 mm / min, and a probe diameter of 5.1 mm (diameter). The evaluation criteria are described below.

[0372] ◎ (Excellent) ••• The probe tack (unit: N) was less than 5.

[0373] O (Good) ••• Probe tackiness (unit: N) was 5 or more and less than 7.5.

[0374] X (Poor) ••• Probe tackiness (unit: N) was 7.5 or more.

[0375] (Gel fraction: after final curing)

[0376] Each of the examples of the double-coated adhesive sheet without a substrate was subjected to ultraviolet irradiation using a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 3000 mJ / cm 2 (1000 mJ / cm 2 x 3 times), cut into 40 mm x 40 mm, and left to stand for 30 minutes under conditions of 23°C x 50% RH. Then, one of the release sheets was peeled off, and the exposed adhesive layer side was attached to a 50 mm x 100 mm SUS mesh sheet (200 mesh). The remaining release sheet was peeled off, folded back from the center with respect to the length direction of the SUS mesh sheet, and the adhesive layer was wrapped with the SUS mesh sheet. The gel fraction (%) was calculated from the change in mass when the same was immersed in a sealed container containing 250 g of toluene maintained at 23°C for 24 hours.

[0377] (180-degree peel strength (23°C): after final curing)

[0378] Each of the examples of the PET sheet with an adhesive layer was cut into a size of 25 mm in width x 100 mm in length, subjected to ultraviolet irradiation using a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 3000 mJ / cm 2 (1000 mJ / cm 2 x 3 times), and then the release sheet was peeled off. The exposed adhesive layer side was attached to an alkali-free glass ("EAGLE XG" manufactured by Corning Inc., thickness 1.1 mm) using a 2-kg rubber roll under an atmosphere of 23°C, 50% RH, and then autoclave treatment (0.5 MPa x 50°C x 20 minutes) was performed, and left to stand for 24 hours under an atmosphere of 23°C, 50% RH. Then, the 180-degree peel strength (N / 25 mm) was measured at room temperature (23°C) at a peel rate of 60 mm / min.

[0379] The evaluation criteria for the 180-degree peel strength are described below.

[0380] O (Good) ••• The peel strength was 30 (N / 25 mm) or more, and peeling occurred at the interface with the adherend.

[0381] Δ (Good) ••• The peel strength was 30 (N / 25 mm) or more, and peeling occurred outside the interface with the adherend.

[0382] × (poor)... The peeling strength is less than 30 (N / 25 mm).

[0383] (Shape stability: storage modulus G' and tensile modulus: after final curing)

[0384] Each of the baseless double-coated adhesive sheets was subjected to ultraviolet irradiation using a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 3000 mJ / cm 2 (1000 mJ / cm 2 x 3 times), and then only 8 adhesive layers were laminated, whereby a baseless double-coated adhesive sheet having an adhesive layer thickness of about 800 μm was produced.

[0385] The release sheets on both sides of the produced baseless double-coated adhesive sheet were peeled off, and the exposed adhesive layers were measured for the storage modulus G' under the following conditions to obtain the storage modulus G' at 25°C.

[0386] (Measurement conditions for the storage modulus G')

[0387] Measurement device: dynamic viscoelasticity measuring device (trade name: DVA-225, IT Measurement Control Co., Ltd.)

[0388] Deformation mode: shear

[0389] Strain: 0.1%

[0390] Measurement temperature: -80°C to 80°C

[0391] Measurement frequency: 1 Hz

[0392] In addition, each of the baseless double-coated adhesive sheets was subjected to ultraviolet irradiation using a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 3000 mJ / cm 2 (1000 mJ / cm 2 x 3 times), and then only 2 adhesive layers were laminated, whereby a baseless double-coated adhesive sheet having an adhesive layer thickness of about 200 μm was produced.

[0393] Then, the release sheets on both sides of the produced baseless double-coated adhesive sheet were peeled off, and the exposed adhesive layers were measured for the tensile modulus under the following conditions.

[0394] (Measurement conditions for the tensile modulus)

[0395] Measurement device: tensile testing machine (trade name: Autograph AG-X, Shimadzu Corporation)

[0396] Measurement environment: 23°C, 50% RH

[0397] Stretching speed: 10 mm / min

[0398] Distance between chucks: 20 mm

[0399] Sample width: 10 mm

[0400] Here, the tensile modulus is calculated from the ratio of the change in the tensile strain (strain at displacement 1% ~ strain at displacement 2%) to the tensile stress (tensile stress at displacement 1% ~ tensile stress at displacement 2%).

[0401] From the values of the storage modulus G' and the tensile modulus obtained by the measurement, the evaluation of the shape stability is performed by the following evaluation criteria.

[0402] ◎ (Excellent) ··· The storage modulus G' at 25°C is 700 kPa or more, and the tensile modulus is 0.70 MPa or more.

[0403] O (Very good) ··· The storage modulus G' at 25°C is 700 kPa or more, and the tensile modulus is 0.45 MPa or more and less than 0.70 MPa.

[0404] O (Very good) ··· The storage modulus G' at 25°C is 400 kPa or more and less than 700 kPa, and the tensile modulus is 0.70 MPa or more.

[0405] O (Very good) ··· The storage modulus G' at 25°C is 400 kPa or more and less than 700 kPa, and the tensile modulus is 0.45 kPa or more and less than 0.70 kPa.

[0406] X (Poor) ··· The storage modulus G' at 25°C is less than 400 kPa or the tensile modulus is less than 0.45 kPa.

[0407] (Retention (80°C): after final curing)

[0408] For each of the PET sheets with the adhesive layer, a 25 mm x 50 mm size was cut out, and after ultraviolet irradiation was performed using a high-pressure mercury UV irradiation device at a peak luminance: 150 mW / cm 2 , cumulative exposure: 3000 mJ / cm 2 (1000 mJ / cm 2 x 3 times), the release sheet was peeled off. A stainless steel plate (SUS304) was placed on the exposed adhesive layer side, and a 2 kg roller was reciprocated to press and attach (attachment area 25 mm x 25 mm). Using a creep testing machine (BE-501, a retention testing machine with a constant humidity tank manufactured by TESTER SANGYO CO., LTD.), a 1 kg load was applied for 24 hours in an 80°C atmosphere, and the retention was measured. The evaluation criteria are described below.

[0409] ◎ (Excellent) ··· No shift (N.C.).

[0410] O (Good) ··· Shift is less than 0.1 mm.

[0411] X (Poor) ··· Shift is 0.1 mm or more or PET sheet falls.

[0412] (Optical properties: after final curing)

[0413] The substrate-free double-coated adhesive sheet of each example was cut into a size of 30 mm x 50 mm, and after ultraviolet irradiation was performed using a high-pressure mercury UV irradiation device at a peak luminance of 150 mW / cm 2 , a cumulative exposure of 3000 mJ / cm 2 (1000 mJ / cm 2 x 3 times), one release sheet was peeled off. The exposed adhesive layer side was attached to an alkali-free glass ("EAGLE XG" manufactured by Corning, Inc., thickness 1.1 mm). Then, autoclave treatment was performed at 50°C, 0.5 MPa, for 20 minutes, and the remaining release sheet was peeled off after standing for 30 minutes in an atmosphere of 23°C, 50% RH, thereby producing a test piece having a layer configuration of "alkali-free glass / adhesive layer".

[0414] The haze value and the color difference b value were measured using the obtained test piece.

[0415] [Haze value]

[0416] The haze value (%) was calculated by substituting the values of the diffuse transmittance (DT) and the total light transmittance (TT) obtained using a HAZE MATER NDH4000 (manufactured by Nippon Denshoku Industries Co., Ltd.) into the following formula 2. The main machine is based on JIS K7361-1.

[0417] Haze value (%) = (DT / TT) x 100 [Formula 2]

[0418] [Color difference]

[0419] The color difference b value is a value measured according to JIS K7105, and the measurement was performed under transmission conditions using a spectrophotometer (SE6000: manufactured by Nippon Denshoku Industries Co., Ltd.).

[0420] Note that the haze value and the color difference b value in the present application were measured by attaching only the adhesive layer to an alkali-free glass (haze = 0.06, b value = 0.16).

[0421] (wet heat resistance: after final curing)

[0422] For each of the PET sheets with the adhesive layer, a 30 mm x 50 mm size was cut out, and after ultraviolet irradiation was performed using a high-pressure mercury UV irradiation device at a peak luminance: 150 mW / cm 2 , a cumulative exposure: 3000 mJ / cm 2 (1000 mJ / cm 2 x 3 times), the release sheet was peeled off. The exposed adhesive layer side was attached to an alkali-free glass ("EAGLE XG" manufactured by Corning, Inc., thickness 1.1 mm). Then, autoclave treatment was performed at 50°C, 0.5 MPa, for 20 minutes, and the test piece was left to stand for 30 minutes in an atmosphere of 23°C, 50% RH, to produce a test piece having a layer configuration of "alkali-free glass / adhesive layer / PET".

[0423] Using the obtained test piece, a wet heat resistance test was performed for 7 days (168 hours) in an atmosphere of 85°C, 85% RH, and the haze value before the wet heat resistance test (initial haze value) and the haze value after the wet heat resistance test (post-durability haze value) were measured.

[0424] Note that the post-durability haze value was measured after the wet heat test, after leaving to stand for 2 hours in an atmosphere of 23°C, 50% RH.

[0425] The haze value (%) was measured using HAZE MATER NDH4000 (manufactured by Nippon Denshoku Industries Co., Ltd.) to measure the diffuse transmittance and total light transmittance, and the obtained values of the diffuse transmittance (DT) and total light transmittance (TT) were substituted into the following Equation 3 to calculate the haze value. Further, the haze value difference (%) was calculated from the following Equation 4. The main machine was in accordance with JIS K7361-1.

[0426] Haze value (%) = (DT / TT) x 100 [Equation 3]

[0427] Haze value difference (%) = post-durability haze value - initial haze value [Equation 4]

[0428] The evaluation criteria for the wet heat resistance test are as follows.

[0429] ◎ (excellent)... the haze value difference is less than 2.0%.

[0430] O (very good)... the haze value difference is 2.0% or more and less than 3.5%.

[0431] X (poor)... the haze value difference is 3.5% or more.

[0432] (polarizing plate durability: after final curing)

[0433] For each of the double-coated adhesive sheets without a substrate, one release sheet was peeled off, and the exposed adhesive layer was pressure-bonded to one TAC film surface of a polarizing plate on which a TAC film was laminated on both surfaces of the polarizing plate. Next, the other release sheet was peeled off, and the exposed adhesive layer was bonded to an alkali-free glass ("EAGLE XG" manufactured by Corning Inc., thickness: 1.1 mm), and autoclave treatment (50°C, 0.5 MPa, 20 minutes) was performed. Then, using a high-pressure mercury UV irradiation device, ultraviolet irradiation was performed from the alkali-free glass side at a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 3000 mJ / cm 2 (1000 mJ / cm 2 x 3 times) to produce a sample for durability evaluation of a polarizing plate.

[0434] After the sample for durability evaluation of a polarizing plate was left to stand in an atmosphere of 23°C, 50% RH for 1 day, a durability test was performed in an atmosphere of 60°C, 90% RH for 7 days (168 hours), and evaluation was performed in accordance with the following criteria. Note that, in the durability evaluation, evaluation of lifting and bubbles generated in the durability test was excluded from bubbles mixed in when bonded to the alkali-free glass.

[0435] O (very good) • • • Neither lifting nor bubbles with a diameter of 1 mm or more were observed on the polarizing plate.

[0436] X (poor) • • • Either or both of lifting and bubbles with a diameter of 1 mm or more were observed in the polarizing plate.

[0437] [Table 4]

[0438]

[0439] [Table 5]

[0440]

[0441] [Table 6]

[0442]

[0443] Examples 1-1 to 1-3 in which the adhesive composition of the present application was used were able to obtain an adhesive that, in a low crosslinked state after one curing, has excellent adhesive properties, that, even with a small amount of active energy rays at the time of curing, is able to efficiently perform multistage curing, and that, after final curing, has excellent shape stability, an adhesive that is able to obtain adhesive properties and reliability, and an adhesive sheet having an adhesive layer formed of the above adhesive.

[0444] On the other hand, in Comparative Examples 1-1 to 1-4 not using the acrylic resin (A) defined in the present application, the adhesive properties at the time of primary curing, the shape stability after final curing, and the adhesive properties were poor.

[0445] [Example 2-1]

[0446] To 100 parts (solid content basis) of a solution of the acrylic resin (A2-1), β1-1 (1): 2.5 parts (solid content basis), c1-1: 2 parts (solid content basis), and D-1: 0.1 part (solid content basis) were mixed to obtain an adhesive composition. The obtained adhesive composition was adjusted to a solid content concentration of 45% with toluene, and was applied to a polyester release sheet in a manner such that the dried thickness was about 50 μm, and was dried at 100°C for 5 minutes to form an adhesive composition layer.

[0447] Two pieces of the adhesive sheet on which the adhesive composition layer was formed on the polyester release sheet were prepared, and the two adhesive composition layers were stacked opposite each other. In a state in which the two sides of the stacked adhesive composition layers were sandwiched with polyester release sheets (release sheet / stacked adhesive composition layers / release sheet), ultraviolet irradiation was performed using a high-pressure mercury UV irradiation device with a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 2000 mJ / cm 2 (1000 mJ / cm 2 x 2 times) through a glass of a sticking UV cutoff film (transmittance: 1% or less in the range of wavelengths of 200 nm to 380 nm, 80% or more in the range of wavelengths of 410 nm to 500 nm), whereby an adhesive layer (primary curing) was formed, and a non-substrate double-sided adhesive sheet having an adhesive layer thickness of 100 μm was obtained.

[0448] Next, the release sheet on one side of the obtained non-substrate double-sided adhesive sheet was peeled off, and the exposed adhesive layer side was pressed against an easily-adhesive-treated polyethylene terephthalate (PET) sheet (thickness: 125 μm) to obtain a PET sheet with an adhesive layer having an adhesive layer thickness of 100 μm.

[0449] [Examples 2-2 to 2-4, Comparative Examples 2-1 to 2-3]

[0450] The composition of the adhesive composition was changed as shown in Table 7 below, and otherwise, the adhesive composition of each example was prepared in the same manner as in Example 2-1. Next, the non-substrate double-sided adhesive sheet having an adhesive layer thickness of 100 μm, and the PET sheet with an adhesive layer were sequentially produced in the same manner as in Example 2-1. The composition of the adhesive composition of each example is shown in Table 7 below.

[0451] [Table 7]

[0452]

[0453] Measurement method, evaluation method

[0454] The following evaluations were performed using the double-coated adhesive sheets without a substrate and the PET sheets with an adhesive layer of the Examples and Comparative Examples. The results are shown in Tables 8 to 10 described later.

[0455] (Gel fraction: before final curing (after first curing))

[0456] Each of the double-coated adhesive sheets without a substrate was cut into 40 mm x 40 mm, and after standing for 30 minutes under conditions of 23°C x 50% RH, one release sheet was peeled off, and the exposed adhesive layer side was attached to a 50 mm x 100 mm SUS mesh sheet (200 mesh). The remaining release sheet was peeled off, and the adhesive layer was wrapped with the SUS mesh sheet with the central portion folded back with respect to the length direction of the SUS mesh sheet. The gel fraction (%) was calculated from the change in mass when the same was immersed in a sealed container containing 250 g of toluene maintained at 23°C for 24 hours.

[0457] (Constant load holding force (40°C): before final curing (after first curing))

[0458] Each of the PET sheets with an adhesive layer was cut into a size of 25 mm in width x 75 mm in length (25 mm in width x 50 mm in length of the adhesive layer portion + 25 mm in width x 25 mm in length of the non-adhesive layer portion), and a release sheet was peeled off. The exposed adhesive layer side (attached area 25 mm x 50 mm) was attached to a stainless steel plate (SUS304) by reciprocating and pressing a 2 kg roller, and the same was left to stand for 20 minutes in a 40°C atmosphere. Then, a 50 g weight was hung from the end portion in the length direction of the non-attached portion (area 25 mm x 25 mm), a 50 g load was applied in the direction of 90° with respect to the plane of the stainless steel plate, and the same was left to stand for 60 minutes in this state, and the distance of the PET sheet peeled off was measured. The evaluation criteria are described below.

[0459] ◎ (Excellent) ••• The distance of peeling off was less than 5 mm.

[0460] O (Very good) ••• The distance of peeling off was 5 mm or more and less than 10 mm.

[0461] X (Poor) ••• The distance of peeling off was 10 mm or more, or the PET sheet was completely peeled off and fell down.

[0462] (Probe tack: after first curing)

[0463] For each of the PET sheets with the adhesive layer, a piece was cut to a size of 12 mm in width x 12 mm in length, the release sheet was peeled off, and the probe tackiness was measured using a probe tackiness tester (TESTER SANGYO CO., LTD., TE-6001) under conditions of a pressurization time of 5 seconds, an adhering pressure of 1000 gf, a press-in speed of 600 mm / min, a lift-off speed of 600 mm / min, and a probe diameter of 5.1 mm (diameter). The evaluation criteria are described below.

[0464] ◎ (Excellent)... Probe tackiness (unit: N) is less than 5.

[0465] O (Very good)... Probe tackiness (unit: N) is 5 or more but less than 7.5.

[0466] X (Poor)... Probe tackiness (unit: N) is 7.5 or more.

[0467] (Gel fraction: after final curing)

[0468] After each of the double-coated adhesive sheets without a substrate was irradiated with ultraviolet rays through a glass to which a UV cut film was attached using a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW / cm 2 and a cumulative exposure of 8000 mJ / cm 2 (1000 mJ / cm 2 x 8 times), a piece was cut to 40 mm x 40 mm, and left to stand for 30 minutes under conditions of 23°C x 50% RH. Then, one release sheet was peeled off, and the exposed adhesive layer side was attached to a 50 mm x 100 mm SUS mesh sheet (200 mesh). The remaining release sheet was peeled off, folded back from the center with respect to the length direction of the SUS mesh sheet, and the adhesive layer was wrapped with the SUS mesh sheet. The gel fraction (%) was calculated from the change in mass when the same was immersed in a sealed container containing 250 g of toluene maintained at 23°C for 24 hours.

[0469] (180-degree peel strength (23°C): after final curing)

[0470] For each of the PET sheets with the adhesive layer, a piece was cut to a size of 25 mm in width x 100 mm in length, and the 180-degree peel strength was measured using a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW / cm 2 and a cumulative exposure of 8000 mJ / cm 2 (1000 mJ / cm 2After ultraviolet irradiation through a glass to which a UV cut film was attached, the release sheet was peeled off. The exposed adhesive layer was attached to an alkali-free glass ("EAGLE XG" manufactured by Corning, Inc., thickness 1.1 mm) using a 2 kg rubber roll at 23°C in an atmosphere of 50% RH, and then autoclave treatment (0.5 MPa x 50°C x 20 minutes) was performed, and the sample was left to stand at 23°C in an atmosphere of 50% RH for 24 hours. Then, the 180-degree peeling strength (N / 25 mm) was measured at room temperature (23°C) at a peeling rate of 60 mm / min.

[0471] The evaluation criteria for the 180-degree peeling strength are described below.

[0472] O (very good) ··· The peeling strength was 30 (N / 25 mm) or more, and peeling occurred at the interface with the adherend.

[0473] Δ (good) ··· The peeling strength was 30 (N / 25 mm) or more, and peeling occurred outside the interface with the adherend.

[0474] X (poor) ··· The peeling strength was less than 30 (N / 25 mm).

[0475] (Shape stability: storage modulus G' and tensile modulus: after final curing)

[0476] Using a high-pressure mercury UV irradiation device, ultraviolet irradiation was performed on the adhesive layer of each of the examples at a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 8000 mJ / cm 2 (1000 mJ / cm 2 x 8 times) through a glass to which a UV cut film was attached, and then only 8 pieces of the adhesive layer were laminated, thereby producing a double-coated adhesive sheet without a substrate having an adhesive layer thickness of about 800 μm.

[0477] The release sheet was peeled off from both surfaces of the double-coated adhesive sheet without a substrate produced, and the storage modulus G' of the exposed adhesive layer was measured under the following conditions to obtain the storage modulus G' at 25°C.

[0478] (Measurement conditions for the storage modulus G')

[0479] Measurement device: dynamic viscoelasticity measuring device (trade name: DVA-225, manufactured by IT Corporation)

[0480] Deformation mode: shear

[0481] Strain: 0.1%

[0482] Measurement temperature: -80°C to 80°C

[0483] Measurement frequency: 1 Hz

[0484] In addition, each of the base material-free double-coated sheets was irradiated with ultraviolet rays through a glass to which a UV cut film was attached, using a high-pressure mercury UV irradiation device, at a peak illuminance of 150 mW / cm 2 , a cumulative exposure of 8000 mJ / cm 2 (1000 mJ / cm 2 x 8 times), and then, only two adhesive layers were laminated, thereby producing a base material-free double-coated sheet having an adhesive layer thickness of about 200 μm.

[0485] Then, the release sheets on both sides of the produced base material-free double-coated sheet were peeled off, and the tensile modulus was measured for the exposed adhesive layer under the following conditions.

[0486] (Measurement conditions for tensile modulus)

[0487] Measurement device: Tensile tester (trade name: Autograph AG-X, manufactured by Shimadzu Corporation)

[0488] Measurement environment: 23°C, 50% RH

[0489] Tensile speed: 10 mm / min

[0490] Distance between chucks: 20 mm

[0491] Sample width: 10 mm

[0492] Here, the tensile modulus was calculated from the change ratio of the tensile strain (strain at displacement of 1% ~ strain at displacement of 2%) and the tensile stress (tensile stress at displacement of 1% ~ tensile stress at displacement of 2%).

[0493] From the values of the storage modulus G' and the tensile modulus obtained by the measurement, the shape stability was evaluated by the following evaluation criteria.

[0494] ◎ (Excellent) ··· The storage modulus G' at 25°C is 700 kPa or more, and the tensile modulus is 0.70 MPa or more.

[0495] O (Very good) ··· The storage modulus G' at 25°C is 700 kPa or more, and the tensile modulus is 0.45 MPa or more and less than 0.70 MPa.

[0496] O (Very good) ··· The storage modulus G' at 25°C is 400 kPa or more and less than 700 kPa, and the tensile modulus is 0.70 MPa or more.

[0497] O (Very good) ··· The storage modulus G' at 25°C is 400 kPa or more and less than 700 kPa, and the tensile modulus is 0.45 MPa or more and less than 0.70 MPa.

[0498] X (poor) ··· The storage modulus G' at 25°C is less than 400 kPa, or the tensile modulus is less than 0.45 MPa.

[0499] (Retention (80°C): after final curing)

[0500] For each of the PET sheets with an adhesive layer, a size of 25 mm x 50 mm was cut out, and after ultraviolet irradiation through a glass to which a UV cut film was attached, using a high-pressure mercury UV irradiation device at a peak luminance: 150 mW / cm 2 , a cumulative exposure: 8000 mJ / cm 2 (1000 mJ / cm 2 x 8 times), a release sheet was peeled off. A stainless steel plate (SUS304) was left on the exposed adhesive layer side, and the 2 kg roller was reciprocated to press and attach (attachment area 25 mm x 25 mm). Using a creep testing machine (a retention testing machine BE-501 manufactured by TESTER SANGYO CO., LTD., with a constant humidity tank), a load of 1 kg was applied for 24 hours in an atmosphere of 80°C, and the retention was measured. The evaluation criteria are described below.

[0501] X (poor) ··· The storage modulus G' at 25°C is less than 400 kPa, or the tensile modulus is less than 0.45 MPa.

[0502] O (very good) ··· The shift is less than 0.1 mm.

[0503] X (poor) ··· The shift is 0.1 mm or more or the PET sheet falls.

[0504] (Optical properties: after final curing)

[0505] Each of the base material-free double-coated adhesive sheets was cut out to a size of 30 mm x 50 mm, and after ultraviolet irradiation through a glass to which a UV cut film was attached, using a high-pressure mercury UV irradiation device at a peak luminance: 150 mW / cm 2 , a cumulative exposure: 8000 mJ / cm 2 (1000 mJ / cm 2 x 8 times), one release sheet was peeled off. The exposed adhesive layer side was attached to an alkali-free glass ("EAGLE XG" manufactured by Corning, Inc., thickness 1.1 mm). Then, autoclave treatment was performed at 50°C, 0.5 MPa, for 20 minutes, and left to stand for 30 minutes in an atmosphere of 23°C, 50% RH, and the remaining release sheet was peeled off, thereby producing a test sheet having a layer configuration of "alkali-free glass / adhesive layer".

[0506] The haze value was measured using the obtained test sheet.

[0507] [Haze value]

[0508] The haze value (%) was calculated by substituting the values of the diffuse transmittance (DT) and the total light transmittance (TT) obtained by measuring the diffuse transmittance and the total light transmittance using a HAZE MATER NDH4000 (manufactured by Nippon Denshoku Industries Co., Ltd.) into the following Formula 5. The host was in accordance with JIS K7361-1.

[0509] Haze value (%) = (DT / TT) x 100 [Formula 5]

[0510] Note that the haze value in the present application was a value measured by attaching only the adhesive layer to an alkali-free glass (haze = 0.06).

[0511] (Resistance to moist heat: after final curing)

[0512] The adhesive-layer-equipped PET sheet of each example was cut into a size of 30 mm x 50 mm, and, using a high-pressure mercury UV irradiation device, ultraviolet rays were irradiated through a glass to which a UV cut film was attached, with a peak luminance of 150 mW / cm 2 , a cumulative exposure of 8000 mJ / cm 2 (1000 mJ / cm 2 x 8 times), and then the release sheet was peeled off. The adhesive layer side that was exposed was attached to an alkali-free glass ("EAGLE XG" manufactured by Corning, thickness 1.1 mm). Then, autoclave treatment was performed at 50°C, 0.5 MPa, for 20 minutes, and the test piece was left to stand in an atmosphere of 23°C, 50% RH for 30 minutes, to produce a test piece having a layer configuration of "alkali-free glass / adhesive layer / PET".

[0513] Using the obtained test piece, a moist heat resistance test was performed for 7 days (168 hours) in an atmosphere of 85°C, 85% RH, and the haze value before the moist heat resistance test (initial haze value) and the haze value after the moist heat resistance test (post-durability haze value) were measured.

[0514] Note that the post-durability haze value was measured after the moist heat test, after leaving to stand for 2 hours in an atmosphere of 23°C, 50% RH.

[0515] The haze value (%) was calculated by substituting the values of the diffuse transmittance (DT) and the total light transmittance (TT) obtained by measuring the diffuse transmittance and the total light transmittance using a HAZE MATER NDH4000 (manufactured by Nippon Denshoku Industries Co., Ltd.) into the following Formula 6. Furthermore, the haze value difference (%) was calculated from the following Formula 7. The host was in accordance with JIS K7361-1.

[0516] Haze value (%) = (DT / TT) x 100 [Formula 6]

[0517] Difference in haze value (%) = haze value after durability - initial haze value [Formula 7]

[0518] The evaluation criteria for the moisture heat resistance test are described below.

[0519] ◎ (Excellent) • The difference in haze value is less than 2.0%.

[0520] O (Very good) • The difference in haze value is 2.0% or more and less than 3.0%.

[0521] X (Poor) • The difference in haze value is 3.0% or more.

[0522] (Polarizing plate durability: after final curing)

[0523] For each of the examples of the double-coated adhesive sheet without a substrate, one release sheet was peeled off after cutting to a size of 60 mm x 100 mm. The exposed adhesive layer side was pressure-bonded to one TAC film surface polarizing plate of a polarizing plate on which a TAC film was laminated on both surfaces. Next, the other release sheet was peeled off, and the exposed adhesive layer side was bonded to an alkali-free glass ("EAGLE XG" manufactured by Corning Inc., thickness 1.1 mm), and autoclave treatment (50°C, 0.5 MPa, 20 minutes) was performed. Then, using a high-pressure mercury UV irradiation device, ultraviolet rays were irradiated through a glass on which a UV cut film was bonded, at peak luminance: 150 mW / cm 2 , cumulative exposure: 8000 mJ / cm 2 (1000 mJ / cm 2 x 8 times), to produce a sample for polarizing plate durability evaluation.

[0524] After the sample for polarizing plate durability evaluation was left to stand in an atmosphere of 23°C, 50% RH for 1 day, a durability test was performed for 7 days (168 hours) in an atmosphere of 60°C, 90% RH, and evaluation was performed in accordance with the following criteria. Note that, in the durability evaluation, the occurrence of floating and bubbles during the durability test was evaluated excluding bubbles mixed in when bonded to the alkali-free glass.

[0525] O (Very good) • Neither floating nor bubbles with a diameter of 1 mm or more were found on the polarizing plate.

[0526] X (Poor) • Either or both of floating and bubbles with a diameter of 1 mm or more were observed in the polarizing plate.

[0527] [Table 8]

[0528]

[0529] [Table 9]

[0530]

[0531] [Table 10]

[0532]

[0533] Examples 2-1 to 2-4 using the adhesive composition of the present invention can obtain adhesives that have excellent adhesion in a low crosslinking state after one-time curing, can be cured efficiently even under visible light, and have excellent shape stability after final curing. The adhesives can produce adhesives with good adhesion and reliability, as well as adhesive sheets having an adhesive layer formed by the adhesives.

[0534] On the other hand, in Comparative Examples 2-1 to 2-3, which did not use the acrylic resin (A) specified in this invention, the adhesive properties during the first curing, the shape stability after final curing, and the adhesive properties were poor.

[0535] It should be noted that the above embodiments illustrate specific aspects of the present invention, but these embodiments are merely illustrative and not intended to be limiting. Various modifications that are obvious to those skilled in the art are intended to be within the scope of the present invention.

[0536] Industrial availability

[0537] The adhesive made using this adhesive composition exhibits excellent adhesion in a low-crosslinked state after single-stage curing, can efficiently perform multi-stage curing even with low levels of active energy radiation during curing or under visible light, and maintains excellent shape stability after final curing. This adhesive achieves excellent adhesion and reliability. Furthermore, the adhesive made using this adhesive composition is particularly useful as an adhesive for bonding optical components in touch panels, image display devices, etc., and for sealing organic EL displays.

Claims

1. An adhesive composition comprising an acrylic resin (Al) and a photopolymerization initiator (B), wherein, the acrylic resin (Al) has a glass transition temperature calculated from dynamic viscoelasticity of 12°C to 40°C, the acrylic resin (Al) contains a structural unit derived from an alkyl (meth)acrylate (al) having an alkyl group with a carbon number of 5 or more and a structural unit derived from an ethylenically unsaturated monomer (a3) containing an amide group.

2. The adhesive composition of claim 1, wherein, the content of the structural unit derived from the alkyl (meth)acrylate (al) having an alkyl group with a carbon number of 5 or more is 20% to 70% by mass relative to the entire acrylic resin (Al).

3. The adhesive composition of claim 1, wherein, the content of the structural unit derived from the ethylenically unsaturated monomer (a3) containing an amide group is 5% to 40% by mass relative to the entire acrylic resin (Al).

4. The adhesive composition of claim 1, wherein, the acrylic resin (Al) contains a structural unit derived from an alkyl (meth)acrylate (a2) having an alkyl group with a carbon number of 1 to 4.

5. The adhesive composition of claim 1, wherein, the acrylic resin (Al) has a weight average molecular weight of 50,000 to 600,000.

6. The adhesive composition of claim 1, wherein, the photopolymerization initiator (B) contains a hydrogen abstraction type photopolymerization initiator (b).

7. The adhesive composition according to claim 1, further comprising a crosslinking agent (C).

8. An adhesive obtained by crosslinking the adhesive composition according to any one of claims 1 to 7.

9. The adhesive of claim 8, wherein, The crosslinking is performed by irradiation of active energy rays.

10. An adhesive sheet having an adhesive layer formed of the adhesive according to claim 8, the adhesive layer showing a multi-stage curing property of curing in multiple stages.

11. An adhesive sheet having an adhesive layer formed of the adhesive according to claim 9, the adhesive layer showing a multi-stage curing property of curing in multiple stages.

12. An adhesive composition comprising an acrylic resin (A2) and a photopolymerization initiator (B), wherein, the acrylic resin (A2) has a glass transition temperature calculated from dynamic viscoelasticity of 12°C to 40°C, the acrylic resin (A2) contains a structural unit derived from an alkyl (meth)acrylate (al) having an alkyl group with a carbon number of 5 or more, the photopolymerization initiator (B) contains a photopolymerization initiator (βl) having a molar absorption coefficient of 30 to 5,000 L / mol-cm in a range of wavelengths of 380 nm to 450 nm.

13. The adhesive composition of claim 12, wherein, the content of the structural unit derived from the alkyl (meth)acrylate (al) having an alkyl group with a carbon number of 5 or more is 20% to 70% by mass relative to the entire acrylic resin (A2).

14. The adhesive composition of claim 12, wherein, the acrylic resin (A2) contains a structural unit derived from an alkyl (meth)acrylate (a2) having an alkyl group with a carbon number of 1 to 4.

15. The adhesive composition of claim 12, wherein, the acrylic resin (A2) has a structural unit derived from an ethylenically unsaturated monomer (a3) containing an amide group.

16. The adhesive composition of claim 12, wherein, the acrylic resin (A2) has a weight average molecular weight of 50,000 to 600,000.

17. The adhesive composition according to claim 12, further comprising a crosslinking agent (C).

18. An adhesive which is obtained by cross-linking the adhesive composition according to any one of claims 12 to 17.

19. The adhesive of claim 18, wherein, The cross-linking is performed by irradiation with active energy rays.

20. An adhesive sheet having an adhesive layer formed of the adhesive according to claim 18, the adhesive layer showing a multi-stage curability which cures in a plurality of stages.

21. An adhesive sheet having an adhesive layer formed of the adhesive according to claim 19, the adhesive layer showing a multi-stage curability which cures in a plurality of stages.

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