JP6729380B2 - Adhesive sheet, method for producing laminated body with adhesive layer, laminated body with adhesive layer, image display device and touch panel - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive sheet, a method for manufacturing a pressure-sensitive adhesive layer-carrying laminate, a pressure-sensitive adhesive layer-carrying laminate, an image display device, and a touch panel. The present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer that is well balanced in terms of pressure-sensitive adhesive properties and wet heat resistance.

In recent years, display devices such as liquid crystal displays (LCD) and input devices such as touch panels used in combination with the display devices have been widely used in various fields. A transparent adhesive sheet is used for application.
For example, a transparent double-sided pressure-sensitive adhesive sheet is used to attach a touch panel to various display devices and optical members (protective plates, etc.). In such applications, it is necessary to follow various steps due to the recent changes in the configuration of the touch panel. (Hereinafter referred to as step followability) is required. Furthermore, when a plastic material such as a polycarbonate resin, an acrylic resin, or a (cyclic) olefin resin is used as a member forming the touch panel, the adherend (member) and the pressure-sensitive adhesive layer are caused by gas or moisture generated from the member. Foaming and peeling may occur between and, and blister resistance that can suppress these is also required.

As a means for imparting the step followability, there is a method of using a soft pressure-sensitive adhesive layer, but in the above method, the step followability is improved by softening the pressure-sensitive adhesive layer, but deformation and distortion easily occur. However, there was a problem that the durability was poor.

Focusing on the above-mentioned problems, as a pressure-sensitive adhesive sheet that can easily secure the step followability and prevent the deformation/distortion of the film, for example, in Patent Document 1, cross-linking of an acrylic resin with a heat-crosslinking cross-linking agent and ethylenic A pressure-sensitive adhesive sheet of a type which also uses curing of an unsaturated monomer by irradiation with active energy rays, comprising a base polymer, a monomer having at least one polymerizable unsaturated group, a cross-linking agent which reacts with the base polymer by heat, and a polymerization. A pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive that is semi-cured by heating an pressure-sensitive adhesive composition containing an initiator and a solvent has been proposed.

Further, as a means for imparting blister resistance, a method of increasing the cohesive force of the pressure-sensitive adhesive layer by using a polymer containing an acid-based or nitrogen-based monomer as a polymerization component in the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer There has been proposed a method in which the product is pressure-bonded to an adherend and then heated at high temperature.

International Publication No. 2013/061938

However, in recent years, it has been required to follow various steps due to the change in the structure of the adherend (member) as described above, and the usage environment also varies. Therefore, depending on the adherend, the usage environment, the application, etc. However, there is still a demand for improvements in adhesives. Although the pressure-sensitive adhesive sheet disclosed in Patent Document 1 is also excellent in step followability, it is not sufficient in terms of blister resistance, and a pressure-sensitive adhesive sheet excellent in step followability and blister resistance is required.

Therefore, in the present invention, under such a background, the pressure-sensitive adhesive sheet is excellent in step-following property and blister resistance, and has a well-balanced adhesive property (adhesive strength, holding power) and moist heat resistance, and a high level of reliability. The purpose is to provide a pressure-sensitive adhesive sheet.

However, the present inventor, as a result of repeated intensive studies in view of such circumstances, in a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which an acrylic resin is cross-linked by a cross-linking agent, the glass transition temperature is usually an acrylic resin used as a pressure-sensitive adhesive. By using an acrylic resin having a glass transition temperature higher than that of (1), the obtained pressure-sensitive adhesive sheet exhibits excellent step-following properties when bonded to a substrate having irregularities, and also when bonded to a plastic substrate. The present invention has been completed by finding that it has excellent blister resistance without causing foaming or peeling between the base material and the pressure-sensitive adhesive layer, and also has excellent adhesive physical properties (adhesive strength, holding power) and wet heat resistance. ..

That is, the gist of the present invention is the following (1) to (9).
(1) A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a cross-linked product of a functional group-containing acrylic resin (A) and a cross-linking agent (B), and an ethylenically unsaturated compound (C) having one ethylenically unsaturated group. And a glass transition temperature of the functional group-containing acrylic resin (A) is -35°C or higher.
(2) The functional group-containing acrylic resin (A) is an acrylic resin obtained by polymerizing a monomer component containing an alkyl group-containing methacrylic acid alkyl ester monomer having 1 to 8 carbon atoms. (1) The pressure-sensitive adhesive sheet described.
(3) The pressure-sensitive adhesive sheet according to (1) or (2), wherein the pressure-sensitive adhesive layer has a thickness of 5 to 300 μm.
(4) The pressure-sensitive adhesive sheet according to any one of (1) to (3), which is a double-sided pressure-sensitive adhesive sheet in which a release sheet is laminated on both sides of the pressure-sensitive adhesive layer.
(5) A pressure-sensitive adhesive that adheres the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet according to any one of (1) to (4) to an adherend and performs at least one of active energy ray irradiation and heating. A method for producing a layered laminate.
(6) The method for producing a laminate with a pressure-sensitive adhesive layer according to (5), wherein the surface of the adherend has a step of 1 to 100 μm.
(7) A laminate with an adhesive layer obtained by the method for producing a laminate with an adhesive layer according to (5) or (6) above.
(8) An image display device having the pressure-sensitive adhesive layer-provided laminate according to (7).
(9) A touch panel having the laminate with the pressure-sensitive adhesive layer described in (7) above.

The present invention is most characterized by using an acrylic resin having a high glass transition temperature, which is usually difficult to use for pressure-sensitive adhesives required to have step-following properties. The ethylenically unsaturated compound contained therein is contained in the pressure-sensitive adhesive layer. With this configuration, when the pressure-sensitive adhesive sheet of the present invention is bonded to an adherend, it exhibits good step followability and adhesive strength, and after being bonded to the adherend, it is cured by active energy rays and/or heat. In this case, since the adherend and the pressure-sensitive adhesive layer are very firmly fixed to each other, foaming between the adherend and the pressure-sensitive adhesive layer can be suppressed.

The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having excellent step followability and also excellent in blister resistance, and has excellent balance in adhesive physical properties (adhesive strength, holding power), wet heat resistance, and excellent reworkability. In particular, it is useful as an adhesive sheet used for laminating a touch panel or an image display device.

Hereinafter, the present invention will be described in detail.
In the present invention, (meth)acrylic means acryl or methacryl, (meth)acryloyl means acryloyl or methacryloyl, and (meth)acrylate means acrylate or methacrylate.
The acrylic resin is a resin obtained by polymerizing a monomer component containing at least one (meth)acrylic monomer.

The pressure-sensitive adhesive sheet of the present invention comprises a cross-linked product of a functional group-containing acrylic resin (A) having a specific glass transition temperature and a cross-linking agent (B), and an ethylenically unsaturated compound (C having one ethylenically unsaturated group). And a pressure-sensitive adhesive layer containing a).

<Functional group-containing acrylic resin (A)>
The pressure-sensitive adhesive sheet of the present invention is most characterized by using the functional group-containing acrylic resin (A) having a glass transition temperature of −35° C. or higher. The glass transition temperature of the functional group-containing acrylic resin (A) is preferably −35° C. to 30° C., more preferably −35° C. to 0° C., particularly preferably −35° C. to −10° C., particularly preferably Is -30°C to -10°C. If the glass transition temperature of the functional group-containing acrylic resin (A) is too low, the blister resistance deteriorates and the object of the present invention cannot be achieved. Further, even if the glass transition temperature is too high, the step followability tends to decrease.

In order to keep the glass transition temperature of the functional group-containing acrylic resin (A) within the above range, the kind and blending ratio of the monomer components constituting the functional group-containing acrylic resin (A) may be adjusted appropriately. ..

The above glass transition temperature is calculated from the following Fox equation.

In the above formula,
Tg: glass transition temperature (K) of copolymer
Tga: glass transition temperature (K) of homopolymer of monomer A
Wa: Weight fraction of monomer A Tgb: Glass transition temperature (K) of homopolymer of monomer B
Wb: Weight fraction of monomer B Tgn: Glass transition temperature (K) of homopolymer of monomer N
Wn: Weight fraction of monomer N (however, Wa+Wb+...+Wn=1)
Is.

The functional group-containing acrylic resin (A) contains a functional group that can serve as a crosslinking point by reacting with a crosslinking agent (B) described later. Examples of the functional group include a hydroxyl group, a carboxyl group, and an amino group. , Acetoacetyl group, isocyanate group, glycidyl group and the like.
Among these, it is preferable to contain a hydroxyl group and a carboxyl group from the viewpoint of efficient crosslinking reaction, and it is preferable to contain a hydroxyl group from the viewpoint of improving wet heat resistance.

The functional group-containing acrylic resin (A) used in the present invention contains a functional group-containing monomer (a1) as an essential component as a monomer component, and a (meth)acrylic acid alkyl ester-based monomer (a2) is necessary. According to the above, it is obtained by further polymerizing a monomer component containing other polymerizable monomer (a3).

The functional group-containing monomer (a1) may be any monomer containing a functional group capable of forming a crosslinking point by reacting with a crosslinking agent (B) described later, and examples thereof include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and an amino group. Examples thereof include a group-containing monomer, an acetoacetyl group-containing monomer, an isocyanate group-containing monomer and a glycidyl group-containing monomer.
Among these, it is preferable to use a hydroxyl group-containing monomer and a carboxyl group-containing monomer from the viewpoint of efficient crosslinking reaction, and it is preferable to use a hydroxyl group-containing monomer from the viewpoint of improving wet heat resistance.
When the adherend is a metal or its oxide, it is easily corroded, and therefore it is preferable not to use a carboxyl group-containing monomer.

As the hydroxyl group-containing monomer, for example,
(Meth)acryl such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate Acid hydroxyalkyl ester, caprolactone-modified monomer such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, oxyalkylene-modified monomer such as diethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, and 2-acryloyloxyethyl-2 A primary hydroxyl group-containing monomer such as hydroxyethylphthalic acid;
Secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate;
Mention may be made of tertiary hydroxyl group-containing monomers such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate.

Among the above-mentioned hydroxyl group-containing monomers, primary hydroxyl group-containing monomers are preferable in terms of excellent reactivity with the crosslinking agent, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferable.

As the hydroxyl group-containing monomer used in the present invention, it is also preferable to use one having a content ratio of di(meth)acrylate as an impurity of 0.5% or less, particularly 0.2% or less, and further preferably 0% or less. It is preferable to use 0.1% or less, and specifically, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferable.

Examples of the carboxyl group-containing monomer include (meth)acrylic acid, acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide-N-glycolic acid, and cinnamon bark. Examples thereof include acids, and among them, (meth)acrylic acid is preferably used.

Examples of the amino group-containing monomer include t-butylaminoethyl (meth)acrylate, ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and the like.

Examples of the acetoacetyl group-containing monomer include 2-(acetoacetoxy)ethyl (meth)acrylate and allyl acetoacetate.

Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate and their alkylene oxide adducts.

Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and allylglycidyl (meth)acrylate.

These functional group-containing monomers (a1) may be used alone or in combination of two or more.

The content ratio of the functional group-containing monomer (a1) in the monomer component is preferably 0.01 to 70% by weight, particularly preferably 0.1 to 50% by weight, further preferably 1 to 35% by weight, It is particularly preferably 10 to 30% by weight. If the content ratio of the functional group-containing monomer (a1) is too small, the cohesive force of the acrylic resin becomes insufficient, so that the durability performance tends to decrease. If it is too large, the viscosity of the acrylic resin becomes high, Stability tends to decrease.

When a hydroxyl group-containing monomer is used as the functional group-containing monomer (a1), the content ratio of the hydroxyl group-containing monomer is preferably 5 to 50% by weight, particularly preferably 7 to 40% by weight, based on the whole copolymerization component. %, more preferably 10 to 35% by weight, particularly preferably 15 to 30% by weight. If the content of the hydroxyl group-containing monomer is too small, the adhesive strength tends to decrease or the moist-heat resistance tends to decrease, and if it is too large, the viscosity of the acrylic resin becomes high and a good coating film may be formed. Tends to be difficult.

Examples of the (meth)acrylic acid alkyl ester-based monomer (a2) include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl ( (Meth)acrylate, n-propyl(meth)acrylate, n-hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, iso-octyl(meth)acrylate, isodecyl(meth)acrylate, Lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, n-stearyl (meth)acrylate, iso-stearyl (meth)acrylate, behenyl (meth)acrylate, 2-decyltetradecanyl (meth)acrylate. Etc.

These (meth)acrylic acid alkyl ester-based monomers (a2) may be used alone or in combination of two or more kinds.

In the present invention, it is preferable to use a methacrylic acid alkyl ester monomer (a2-1) having an alkyl group having 1 to 8 carbon atoms, such as methyl methacrylate, ethyl methacrylate, and tert-butyl methacrylate, from the viewpoint of increasing cohesive force, More preferably, the carbon number of the alkyl group is 4 to 8 from the viewpoint that the rigidity of the main chain can be efficiently increased, the blister resistance can be improved, and the copolymerizability with the monomer (polymerization stability) is excellent. It is preferable to use a methacrylic acid alkyl ester-based monomer, particularly tert-butyl methacrylate.

From the viewpoint of imparting hydrophobicity to the adhesive layer, a (meth)acrylic acid alkyl ester-based monomer (a2) having a glass transition temperature of −20° C. or higher when formed into a homopolymer and having an alkyl group having 8 or more carbon atoms -2) (however, excluding (a2-1)) is preferably used.

Examples of the (meth)acrylic acid alkyl ester-based monomer having a glass transition temperature of −20° C. or higher when a homopolymer is formed and an alkyl group having 8 or more carbon atoms include lauryl acrylate (Tg=−3° C.; carbon). Number 12), cetyl acrylate (Tg=35° C.; carbon number 16), n-stearyl acrylate (Tg=30° C., carbon number 18), isostearyl acrylate (Tg=−18° C.; carbon number 18), behenyl acrylate ( Tg=46° C.; carbon number 22), 2-decyltetradecanyl acrylate (Tg=9° C.; carbon number 24), 2-ethylhexyl methacrylate (Tg=−10° C.; carbon number 8), cetyl methacrylate (Tg=23) 0.5° C.; carbon number 16), n-stearyl methacrylate (Tg=38° C.; carbon number 18), behenyl methacrylate (Tg=44° C.; carbon number 22), 2-decyltetradecanyl methacrylate (Tg=10° C.; C24) etc. are mentioned.
Among these, 2-ethylhexyl methacrylate and isostearyl acrylate are preferably used because they are excellent in polymerization stability and hydrophobicity.

The content ratio of the (meth)acrylic acid alkyl ester monomer (a2) in the monomer component is preferably 5 to 99% by weight, particularly preferably 20 to 80% by weight, further preferably 40 to 70% by weight. Is. If the content of the (meth)acrylic acid alkyl ester-based monomer (a2) is too low, the blister resistance and cohesive force tend to decrease, and if it is too high, the adhesive property when used as an adhesive tends to decrease. It is in.

When the methacrylic acid alkyl ester monomer (a2-1) having 1 to 8 carbon atoms of the alkyl group is used, the content ratio in the monomer component is preferably 10 to 70% by weight, particularly preferably 15 -60% by weight, more preferably 20-50% by weight. If the content ratio is too small, the blister resistance tends to decrease due to the decrease in cohesive force, and if it is too large, the step followability tends to deteriorate.

Monomer component in the case of using (meth)acrylic acid alkyl ester-based monomer (a2-2) having a glass transition temperature of −20° C. or higher when the above homopolymer is used and an alkyl group having 8 or more carbon atoms The content ratio in the whole is preferably 1 to 70% by weight, particularly preferably 5 to 60% by weight, further preferably 7 to 55% by weight, and particularly preferably 10 to 50% by weight. If the content ratio of the (meth)acrylic acid alkyl ester-based monomer (a2-2) is too small, the blister resistance performance tends to decrease, and if it is too large, the viscosity of the acrylic resin becomes high and the handling becomes difficult. However, when used as an adhesive, the adhesive properties tend to decrease.

As the other polymerizable monomer (a3), for example,
Alicyclic (meth)acrylic acid ester-based monomers such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate;
One fragrance such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, styrene and α-methylstyrene. A monomer containing a ring;
Biphenyloxy structure-containing (meth)acrylic acid ester-based monomers such as biphenyloxyethyl (meth)acrylate;
2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-butoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth) Acrylate, methoxytriethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, octoxypolyethylene glycol-polypropylene glycol-mono(meth)acrylate, lauro Ether chain-containing (meth)acrylic acid ester-based monomers such as xypolyethylene glycol mono(meth)acrylate and stearoxypolyethylene glycol mono(meth)acrylate;
Acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinylpyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride , Methyl vinyl ketone, N-acrylamidomethyl trimethyl ammonium chloride, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone, (meth)acryloylmorpholine and the like can be used.
These may be used alone or in combination of two or more.

The content ratio of the other polymerizable monomer (a3) in the monomer component is preferably 0 to 40% by weight, particularly preferably 0 to 30% by weight, and further preferably 0 to 25% by weight. If the amount of the other polymerizable monomer (a3) is too large, the adhesive property tends to deteriorate.

The functional group-containing acrylic resin (A) can be produced by polymerizing the above monomer components. As the method for polymerizing the functional group-containing acrylic resin (A), for example, conventionally known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization and emulsion polymerization can be used. Polymerization can be carried out according to specific polymerization conditions, but solution polymerization is preferable in that the functional group-containing acrylic resin (A) can be safely and stably produced with an arbitrary monomer composition.
In such solution polymerization, for example, the monomer components (a1) to (a3) and the polymerization initiator are mixed or added dropwise to an organic solvent, and polymerization is carried out under reflux or at 50 to 98° C. for 0.1 to 20 hours. Good.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, N-propyl alcohol, isopropyl alcohol. Examples thereof include aliphatic alcohols such as acetone, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Among these solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl ketone are used from the viewpoints of easiness of polymerization reaction, chain transfer effect, easy drying at the time of coating the adhesive, and safety. Are preferred, and ethyl acetate, acetone, and methyl ethyl ketone are more preferred.

Examples of such a polymerization initiator include azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, which are usual radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, and di-t-butyl peroxide. Specific examples include peroxide type polymerization initiators such as cumene hydroperoxide and the like. These can be appropriately selected and used according to the monomer to be used, and are used alone or in combination of two or more kinds.

The weight average molecular weight of the functional group-containing acrylic resin (A) is usually 50,000 to 2,000,000, preferably 200,000 to 1,000,000, and particularly preferably 300,000 to 800,000. If the weight average molecular weight is too small, the durability performance tends to decrease, and if it is too large, the step followability tends to decrease.

The degree of dispersion (weight average molecular weight/number average molecular weight) of the functional group-containing acrylic resin (A) is preferably 20 or less, particularly preferably 15 or less, further preferably 10 or less, particularly 7 or less. Is preferred. If the dispersity is too high, the durability of the pressure-sensitive adhesive layer tends to decrease. The lower limit of the dispersity is usually 1.1 from the viewpoint of manufacturing limit.

In addition, the weight average molecular weight is a weight average molecular weight based on standard polystyrene molecular weight conversion, and in high performance liquid chromatography (manufactured by Japan Waters, "Waters 2695 (main body)" and "Waters 2414 (detector)"), column: Shodex. GPC KF-806L (Exclusion limit molecular weight: 2×10 ⁷ , separation range: 100 to 2×10 ⁷ , theoretical plate number: 10,000 plates/piece, filler material: styrene-divinylbenzene copolymer, filler particle size : 10 μm), and the number average molecular weight can be measured by the same method. The dispersity is calculated from the weight average molecular weight and the number average molecular weight.

The functional group-containing acrylic resin (A) used in the present invention is a functional group-containing acrylic resin having an active energy ray-reactive structure site, that is, a functional group-containing acrylic resin containing an ethylenically unsaturated group. It is preferred to use (ethylenically unsaturated group-containing acrylic resin) from the viewpoint that the pressure-sensitive adhesive layer after irradiation with active energy rays can have a higher elastic modulus.

The ethylenically unsaturated group-containing acrylic resin is obtained by reacting the functional group of the functional group-containing acrylic resin (A) with an ethylenically unsaturated compound having a functional group that reacts with the functional group. Can be done. Examples of the ethylenically unsaturated compound include the carboxyl group-containing unsaturated monomer, the hydroxyl group-containing unsaturated monomer, the glycidyl group-containing unsaturated monomer, the isocyanate group-containing unsaturated monomer, the amide group-containing unsaturated monomer, and the amino group-containing unsaturated monomer. Examples thereof include monomers and sulfonic acid group-containing unsaturated monomers.

For example, when the functional group in the acrylic resin is a carboxyl group, a glycidyl group-containing unsaturated monomer or an isocyanate group-containing unsaturated monomer, when the functional group is a hydroxyl group, an isocyanate group-containing unsaturated monomer, the functional group is In the case of a glycidyl group, a carboxyl group-containing unsaturated monomer or an amide group-containing unsaturated monomer is selected and when the functional group is an amino group, a glycidyl group-containing unsaturated monomer is selected and used. Among them, when the functional group in the acrylic resin is a hydroxyl group, it is preferable that the ethylenically unsaturated compound is an isocyanate group-containing unsaturated compound in terms of excellent reactivity of the functional group.

Further, in the present invention, the adhesive sheet has a corrosion resistance when used in transparent electrodes and other electronic members for touch panels and other electronic members, particularly information label applications where they are attached to precision electronic members, and electronic member fixing applications. Therefore, in this case, it is preferable that the functional group-containing acrylic resin (A) does not contain an acidic group.

<Crosslinking agent (B)>
The cross-linking agent (B) used in the present invention exhibits excellent adhesive strength mainly by reacting with a functional group contained in the functional group-containing acrylic resin (A), and is, for example, an isocyanate-based cross-linking agent. , Epoxy-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, aldehyde-based crosslinking agents, amine-based crosslinking agents, metal chelate-based crosslinking agents, and the like. Among these, the isocyanate cross-linking agent is preferably used from the viewpoint of improving the adhesion to the substrate and the reactivity with the functional group-containing acrylic resin (A).

Examples of the isocyanate-based cross-linking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and hexamethylene. Diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof Examples thereof include adducts of trimethylolpropane and other polyol compounds, and burettes and isocyanurates of these polyisocyanate compounds.

Examples of the epoxy cross-linking agent include bisphenol A/epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin 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.

Examples of the aziridine-based crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, and N,N′-diphenylmethane-4,4. Examples include ′-bis(1-aziridinecarboxamide) and N,N′-hexamethylene-1,6-bis(1-aziridinecarboxamide).

Examples of the melamine-based cross-linking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resin. ..

Examples of the aldehyde cross-linking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardialdehyde, formaldehyde, acetaldehyde, benzaldehyde and the like.

Examples of the amine-based cross-linking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resin, and polyamide.

Examples of the metal chelate-based cross-linking agent include acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium. Can be mentioned.

Further, these cross-linking agents (B) may be used alone or in combination of two or more kinds.

The amount of the cross-linking agent (B) to be compounded is usually preferably 0.001 to 10 parts by weight, more preferably 0.01 to 10 parts by weight, based on 100 parts by weight of the functional group-containing acrylic resin (A). 5 parts by weight, particularly preferably 0.1 to 2 parts by weight. If the amount of the cross-linking agent (B) used is too small, the cohesive force tends to be insufficient and sufficient durability tends not to be obtained, and if it is too large, the flexibility tends to decrease and the step followability tends to decrease. Seen.

The reaction temperature at the time of cross-linking the acrylic resin (A) and the cross-linking agent (B) to form a cross-linked product may be room temperature, or may be heating at 20 to 60° C., for example.

<Ethylene unsaturated compound (C) containing one ethylenically unsaturated group>
The ethylenically unsaturated compound (C) containing one ethylenically unsaturated group used in the present invention (hereinafter sometimes referred to as a monofunctional unsaturated compound (C)) is an ethylenically unsaturated group. A (meth)acrylic acid ester compound (C1) (excluding (C2) described below. Hereinafter, it may be referred to as “monofunctional (meth)acrylic acid ester compound (C1)”) or The use of an ethylenically unsaturated compound (C2) having one ethylenically unsaturated group containing a nitrogen atom (hereinafter sometimes referred to as "nitrogen-containing monofunctional unsaturated compound (C2)"). Is preferred.

Examples of the monofunctional (meth)acrylate compound (C1) include long-chain aliphatic (meth)acrylate (C1-1), alicyclic (meth)acrylate (C1-2), and aromatic (meth)acrylate. (C1-3), and oxyalkylene structure-modified compounds of these (meth)acrylates (C1-4).

Examples of the long-chain aliphatic (meth)acrylate (C1-1) include decane (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, isotridecyl (meth)acrylate, isomyristyl. (Meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, 2-decyltetradecanyl (meth)acrylate and the like can be mentioned.

Examples of the alicyclic (meth)acrylate (C1-2) include isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate and the like.

Examples of the aromatic (meth)acrylate (C1-3) include biphenyl (meth)acrylate, naphthalene (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl ( Examples thereof include (meth)acrylate.

Examples of the oxyalkylene structure-modified compound (C1-4) of (C1-1) to (C1-3) include the following.
Examples of the oxyalkylene structure-modified compound (C1-1) include 2-ethylhexyldiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, alkyl polyethylene glycol (meth)acrylate, methoxydi Examples include propylene glycol (meth)acrylate, alkylene glycol monoalkyl ester (meth)acrylate, and alkylene glycol mono(meth)acrylate.
Examples of the (C1-2) oxyalkylene structure-modified compound include t-butylcyclohexyloxyethyl (meth)acrylate, cyclohexyloxyalkyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyloxyethyl. (Meth)acrylate etc. are mentioned.
Examples of the (C1-3) oxyalkylene structure-modified compound include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenyltriethylene glycol (meth)acrylate, and phenyltetraglycol (meth). Examples thereof include acrylate, biphenyloxyethyl (meth)acrylate, nonylphenol ethylene oxide modified (repeated 4) (meth)acrylate, nonylphenol ethylene oxide modified (repeated 8) (meth)acrylate and the like.

Among these monofunctional (meth)acrylate compounds (C1), long-chain aliphatic (meth)acrylate (C1-1), alicyclic (meth)acrylate (C1-2) and aromatic (meth) It is preferable to use an oxyalkylene structure-modified compound (C1-4) of acrylate (C1-3) from the viewpoint of obtaining a stable adhesive force, and particularly preferably isomyristyl acrylate, isotridecyl acrylate, isostearyl acrylate, Phenyldiethylene glycol acrylate and dicyclopentenyloxyethyl acrylate.

The nitrogen-containing monofunctional unsaturated compound (C2) can improve the adhesive strength of the pressure-sensitive adhesive by using, for example, acrylamide, methacrylamide, butoxymethyl acrylamide, hydroxyethyl acrylamide, dimethylaminopropyl acrylamide, dye. (Meth)acrylamide unsaturated monomers such as acetone acrylamide, N-acryloyloxyethylhexahydrophthalimide, acryloylmorpholine, oxazolidone acrylate and the like can be mentioned. Among them, (meth)acrylamide unsaturated monomers should be used. Is preferred because it is excellent in balance in volatility and adhesive performance, and butoxymethyl acrylamide and diacetone acrylamide are particularly preferred.

Among them, in the present invention, the long-chain aliphatic acrylate (C1-1) is used because it is possible to obtain an optically transparent pressure-sensitive adhesive layer that is difficult to be colored, and can impart hydrophobicity to the pressure-sensitive adhesive layer. Is particularly preferable, and isomyristyl acrylate, isotridecyl acrylate, isostearyl acrylate, and 2-decyl tetradecanyl acrylate are particularly preferable.

The monofunctional unsaturated compound (C) is present as a polymer in the pressure-sensitive adhesive layer by being cured with at least one of active energy rays and heat as described below. The monofunctional unsaturated compound (C) is preferably selected so that the glass transition temperature of the polymer is −80 to 80° C.

The glass transition temperature is particularly preferably −60 to 40° C., further preferably −55 to 10° C., and particularly preferably −20 to 0° C. If the glass transition temperature is too high, the adhesive performance tends to be difficult to be exhibited, and if it is too low, the cohesive force tends to decrease.
The glass transition temperature is calculated from the above Fox equation.

Further, the monofunctional unsaturated compound (C) has the effects of softening the pressure-sensitive adhesive and improving the drying property at the time of coating using an organic solvent, and at the time of coating drying (especially for thick film coating). A material that is less likely to volatilize and stays in the pressure-sensitive adhesive layer than an organic solvent is used.

The flash point of the monofunctional unsaturated compound (C) is preferably 40° C. or higher, particularly preferably 80° C. or higher, further preferably 100° C. or higher, and particularly preferably 140° C. or higher. If the flash point is too low, it tends to evaporate during the drying process. The upper limit of the flash point is usually 350°C.

The weight average molecular weight of the monofunctional unsaturated compound (C) is preferably 100 to 2,000, particularly preferably 120 to 1,000, further preferably 160 to 600, and particularly preferably 200 to 400. is there.
If the molecular weight is too high, the pressure-sensitive adhesive property tends to decrease, and if it is too low, it tends to volatilize in the drying step.

<Adhesive sheet>
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer containing a crosslinked product of a functional group-containing acrylic resin (A) having a specific glass transition temperature and a crosslinking agent (B), and a monofunctional unsaturated compound (C). It is an adhesive sheet.

In the pressure-sensitive adhesive layer, the content ratio of the monofunctional unsaturated compound (C) is preferably 5 to 70% by weight, particularly 9 to 50% by weight, and further 12 to 10% by weight based on the whole pressure-sensitive adhesive layer. It is preferably 40% by weight, particularly preferably 15 to 30% by weight.
If the content ratio of the monofunctional unsaturated compound (C) is too small, the step followability tends to be lowered, and if it is too large, the elastic modulus at the time of forming the sheet becomes too low, so that the handleability and the stability of the coating film are deteriorated. Tends to decline.

The content ratio of the monofunctional unsaturated compound (C) is calculated as the content ratio of the monofunctional unsaturated compound (C) to the entire pressure-sensitive adhesive composition after the organic solvent forming the pressure-sensitive adhesive layer is dried and removed. It is a value that can be.

The pressure-sensitive adhesive layer may be obtained by crosslinking the functional group-containing acrylic resin (A) and the crosslinking agent (B) and then blending the monofunctional unsaturated compound (C), or the monofunctional unsaturated compound ( C) may be blended and the functional group-containing acrylic resin (A) and the cross-linking agent (B) are cross-linked in the presence of the monofunctional unsaturated compound (C), but the step followability is excellent. It is preferable that the functional group-containing acrylic resin (A) and the cross-linking agent (B) are cross-linked in the presence of the monofunctional unsaturated compound (C) from the viewpoint that a pressure-sensitive adhesive sheet can be easily obtained.

Blending of the functional group-containing acrylic resin (A) when the pressure-sensitive adhesive sheet of the present invention is produced using the functional group-containing acrylic resin (A), the cross-linking agent (B) and the monofunctional unsaturated compound (C). The amount and the blending amount of the monofunctional unsaturated compound (C) are preferably 50:50 to 95:5 (weight ratio), particularly 65:35 to 90:9, and further 70:30 to 85:. It is preferably 15.
If the blending amount of the monofunctional unsaturated compound (C) with respect to the functional group-containing acrylic resin (A) is too large, the stability of the coating film tends to decrease, and if it is too small, the step followability tends to decrease.

The blending amount of the cross-linking agent (B) and the blending amount of the monofunctional unsaturated compound (C) are preferably 0.1:99.9 to 20:80 (weight ratio), and particularly 0.3:99. It is preferably from 0.7 to 2:98, more preferably from 0.5:99.5 to 1:99.0.
If the blending amount of the monofunctional unsaturated compound (C) with respect to the blending amount of the crosslinking agent (B) is too large, the stability of the coating film tends to decrease, and if it is too small, the step followability tends to decrease.

In the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention, in addition to the monofunctional unsaturated compound (C) and the crosslinked product of the functional group-containing acrylic resin (A) and the cross-linking agent (B) in the pressure-sensitive adhesive layer, The inclusion of an ethylenically unsaturated compound (D) containing two or more saturated groups (hereinafter, may be abbreviated as "polyfunctional unsaturated compound (D)") adjusts the cohesive force of the entire pressure-sensitive adhesive layer. It is preferable that the polymerization initiator (E) is further contained, and it is preferable that the polymerization initiator (E) is contained in the reaction during irradiation of active energy rays and/or heating.

Examples of the polyfunctional unsaturated compound (D) include an ethylenically unsaturated monomer containing two or more ethylenically unsaturated groups in one molecule, for example, a bifunctional monomer, a trifunctional or more functional monomer, and urethane. A (meth)acrylate compound, an epoxy (meth)acrylate compound, and a polyester (meth)acrylate compound can be used. Among these, it is preferable to use an ethylenically unsaturated monomer and a urethane (meth)acrylate-based compound in terms of excellent curing rate and stability of ultimate physical properties.

The bifunctional monomer may be a monomer containing two ethylenically unsaturated groups, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene. Glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene Oxide modified bisphenol A type di(meth)acrylate, propylene oxide modified bisphenol A type di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,6-hexanediol ethylene oxide modified di(meth)acrylate, Glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid Examples include modified neopentyl glycol di(meth)acrylate, isocyanuric acid ethylene oxide-modified diacrylate, and 2-(meth)acryloyloxyethyl acid phosphate diester.

The trifunctional or higher functional monomer may be a monomer containing three or more ethylenically unsaturated groups, and examples thereof include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth). ) Acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, Glycerin polyglycidyl ether poly(meth)acrylate, isocyanuric acid ethylene oxide modified tri(meth)acrylate, ethylene oxide modified dipentaerythritol penta(meth)acrylate, ethylene oxide modified dipentaerythritol hexa(meth)acrylate, ethylene oxide modified pentaerythritol Examples thereof include tri(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, and succinic acid-modified pentaerythritol tri(meth)acrylate.

The urethane (meth)acrylate compound is a (meth)acrylate compound having a urethane bond in the molecule, and a (meth)acrylic compound having a hydroxyl group and a polyvalent isocyanate compound (polyol, if necessary). The compound obtained by reacting the (system compound) by a known general method may be used. The weight average molecular weight of the urethane (meth)acrylate compound may be usually 300 to 4000.

In the pressure-sensitive adhesive layer, the content ratio of the polyfunctional unsaturated compound (D) is preferably 20 to 0.1% by weight, particularly 10 to 0.2% by weight, based on the whole pressure-sensitive adhesive layer. Further, it is preferably 5 to 0.3% by weight, particularly preferably 1 to 0.5% by weight.
If the content of the polyfunctional unsaturated compound (D) is too small, the reliability when cured by irradiation with active energy rays tends to decrease, and if it is too large, the cohesive force when cured by irradiation with active energy rays is increased. If the temperature rises too much, curing shrinkage occurs, and the adhesive performance tends to decrease.

The content ratio of the polyfunctional unsaturated compound (D) is calculated as the content ratio of the polyfunctional unsaturated compound (D) to the entire pressure-sensitive adhesive composition after the organic solvent forming the pressure-sensitive adhesive layer is dried and removed. It is a value that can be.

The content of the polyfunctional unsaturated compound (D) in the pressure-sensitive adhesive layer is preferably 0.01 to 50 parts by weight, particularly preferably 100 parts by weight of the monofunctional unsaturated compound (C). Is 0.5 to 20 parts by weight, more preferably 1 to 5 parts by weight. If the content of the polyfunctional unsaturated compound (D) is too large, the cohesive force will be excessively increased in the post-curing step, and curing shrinkage will occur to lower the adhesive performance. If it is too small, the holding power will be insufficient. Tend.

When a polyfunctional unsaturated compound (D) is further used for the functional group-containing acrylic resin (A), the cross-linking agent (B), the monofunctional unsaturated compound (C), and when the pressure-sensitive adhesive sheet of the present invention is produced, The compounding amount of the polyfunctional unsaturated compound (D) is preferably 0.01 to 50 parts by weight, and particularly preferably 0.1 to 30 parts by weight, based on 100 parts by weight of the functional group-containing acrylic resin (A). It is preferably 0.5 to 20 parts by weight, more preferably 1 to 5 parts by weight. If the blending amount of the polyfunctional unsaturated compound (D) is too large, cohesive force will be excessively increased in the post-curing step, and curing shrinkage will occur to lower the adhesive performance. If it is too small, the holding force will be insufficient. Tend.

As the polymerization initiator (E), for example, various polymerization initiators such as a photopolymerization initiator (e1) and a thermal polymerization initiator (e2) can be used, but in particular, the photopolymerization initiator ( It is preferable to use e1) because it can be cured by irradiation with active energy rays such as ultraviolet rays for a very short time.
Moreover, it is also preferable to use both in combination, if necessary.

As the photopolymerization initiator (e1) and the thermal polymerization initiator (e2), known general polymerization initiators may be used.
Examples of the photopolymerization initiator (e1) include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, and 4-(2-hydroxyethoxy)phenyl-(2. -Hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenylketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4- Acetophenones such as morpholinophenyl)butanone and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer; benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl Benzoins such as ethers; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3',4,4'-tetra(t-butylperoxycarbonyl) ) Benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, (4-benzoylbenzyl ) Benzophenones such as trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-(3-dimethylamino-). 2-Hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one thioxanthones such as mesochloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2. , 4,4-trimethyl-pentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and other acylphosphine oxides; and the like. In addition, as for these photoinitiators (e1), only 1 type may be used independently and 2 or more types may be used together.

Further, as these auxiliary agents, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, 4-dimethylaminobenzoic acid Ethyl, 4-dimethylaminobenzoic acid (n-butoxy)ethyl, 4-dimethylaminobenzoic acid isoamyl, 4-dimethylaminobenzoic acid 2-ethylhexyl, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone It is also possible to use the above together.
Among these, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoyl isopropyl ether, 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone, 2-hydroxy-2-methyl-1- Preference is given to using phenylpropan-1-one.

Examples of the thermal polymerization initiator (e2) include methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl cyclohexanone peroxide, methyl acetoacetate peroxide, acetyl acetate peroxide, 1,1-bis(t-hexylperoxy). )-3,3,5-Trimethylcyclohexane, 1,1-bis(t-hexylperoxy)-cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1, 1-bis(t-butylperoxy)-2-methylcyclohexane, 1,1-bis(t-butylperoxy)-cyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, 1,1- Bis(t-butylperoxy)butane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3. 3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t-butyl hydroperoxide, α,α′-bis(t-butylperoxy)diisopropylbenzene, dicumyl peroxide, 2 ,5-Dimethyl-2,5-bis(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butylperoxide, 2,5-dimethyl-2,5-bis(t-butylperoxide) (Oxy)hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinic acid peroxide, m-toluoylbenzoyl peroxide, benzoyl Peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethoxyhexyl Peroxydicarbonate, di-3-methoxybutylperoxydicarbonate, di-s-butylperoxydicarbonate, di(3-methyl-3-methoxybutyl)peroxydicarbonate, α,α′-bis(neo Decanoylperoxy)diisopropylbenzene, cumylperoxy neodecanoate, 1,1,3,3- Tetramethylbutylperoxy neodecanoate, 1-cyclohexyl-1-methylethylperoxy neodecanoate, t-hexylperoxy neodecanoate, t-butylperoxy neodecanoate, t-hexylperoxy Pivalate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanooate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylper) (Oxy)hexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t- Hexylperoxyisopropyl monocarbonate, t-butylperoxyisobutyrate, t-butylperoxymalate, t-butylperoxy-3,5,5-trimethorhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-butylperoxyacetate, t-butylperoxy-m-toluylbenzoate, t-butylperoxybenzoate, bis(t- Butylperoxy)isophthalate, 2,5-dimethyl-2,5-bis(m-toluylperoxy)hexane, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis(benzoylperoxy) Hexane, t-butylperoxyallyl monocarbonate, t-butyltrimethylsilyl peroxide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 2,3-dimethyl-2,3-diphenyl Organic peroxide initiators such as butane; 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 1-[(1-cyano-1-methylethyl)azo]formamide, 1,1'-azobis (Cyclohexane-1-carbonitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile) ), 2,2'-azobis(2-methylpropionamidine)dihydrochloride, 2,2'-azobis(2-methyl-N-phenylpropionamidine)dihydrochloride, 2,2'-azobis[N-(4- Chlorophenyl)-2-methylpropionamidine ] Dihydrido chloride, 2,2'-azobis[N-(4-hydrophenyl)-2-methylpropionamidine] Dihydrochloride, 2,2'-azobis[2-methyl-N-(phenylmethyl)propionamidine] Dihydrochloride, 2,2'-azobis[2-methyl-N-(2-propenyl)propionamidine]dihydrochloride, 2,2'-azobis[N-(2-hydroxyethyl)-2-methylpropionamidine]dihydro Chloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydro Chloride, 2,2'-azobis[2-(4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(3 ,4,5,6-Tetrahydropyrimidin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(5-hydroxy-3,4,5,6-tetrahydropyrimidin-2-yl)propane] Dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis[2-(2-imidazoline-2 -Yl)propane], 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis{2-methyl- N-[1,1-bis(hydroxymethyl)ethyl]propionamide},2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],2,2'-azobis(2- Methylpropionamide), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), dimethyl-2,2-azobis(2-methylpropionate) , 4,4′-azobis(4-cyanopentanoic acid), 2,2′-azobis[2-(hydroxymethyl)propionitrile] and the like; and the like. In addition, as for these thermal-polymerization initiators (e2), only 1 type may be used independently and 2 or more types may be used together.

Regarding the content of the above-mentioned polymerization initiator (E) in the pressure-sensitive adhesive layer, 100 parts by weight of the monofunctional unsaturated compound (C) (when using the polyfunctional unsaturated compound (D), (C) and ( It is preferably 0.01 to 50 parts by weight, particularly preferably 0.1 to 20 parts by weight, further preferably 0.3 to 12 parts by weight, particularly preferably 100 parts by weight of D). Is 0.5 to 5 parts by weight. If the content of the polymerization initiator (E) is too small, the curability is poor and the physical properties tend to be unstable, and if it is too large, no further effect tends to be obtained.

The pressure-sensitive adhesive sheet of the present invention does not have a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer provided on a base material sheet, a double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer provided on a release sheet, and a base material sheet at the time of bonding an adherend. Examples of the baseless double-sided pressure-sensitive adhesive sheet used in the state include a substrateless double-sided pressure-sensitive adhesive sheet, which is excellent in transparency and has a high adhesive force with respect to the thickness of the component.

The method for producing the pressure-sensitive adhesive sheet of the present invention includes, for example, a functional group-containing acrylic resin (A), a cross-linking agent (B), and a monofunctional unsaturated compound (C) as essential components, and ethylene as necessary. Of a pressure-sensitive adhesive composition containing an ethylenically unsaturated compound (D) containing two or more polyunsaturated groups and a polymerization initiator (E) onto a base sheet or a release sheet and drying the composition, if necessary. By curing, the pressure-sensitive adhesive sheet of the present invention having the pressure-sensitive adhesive layer containing the crosslinked product of the functional group-containing acrylic resin (A) and the cross-linking agent (B) and the monofunctional unsaturated compound (C) is obtained.
In the case of a substrateless double-sided PSA sheet, for example, after the PSA composition is applied onto a release sheet to form a PSA layer obtained by drying, the PSA layer does not have a release sheet. It can be manufactured by further adhering another release sheet to the side and curing if necessary.

Examples of the base sheet include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate/isophthalate copolymers; polyolefin resins such as polyethylene, polypropylene and polymethylpentene, and trade names " Examples include cyclic olefin resins such as ARTON (cyclic olefin polymer; manufactured by JSR Co.) and trade name "Zeonor (cyclic olefin polymer; manufactured by Nippon Zeon Co., Ltd.)"; polyvinyl fluoride, polyvinylidene fluoride, polyfluoroethylene. Polyfluorinated ethylene resins such as; polyamides such as nylon 6, nylon 6,6; polyvinyl chloride, polyvinyl chloride/vinyl acetate copolymers, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, polyvinyl alcohol , Vinyl polymers such as vinylon; cellulose resins such as cellulose triacetate and cellophane; acrylic resins such as polymethylmethacrylate, polyethylmethacrylate, ethylpolyacrylate, and polybutylacrylate; polystyrene; polycarbonate; polyarylate A synthetic resin sheet such as polyimide, a metal foil of aluminum, copper or iron, a paper such as high quality paper or glassine paper, a woven fabric or a non-woven fabric made of glass fiber, natural fiber, synthetic fiber or the like. These base sheets can be used as a single layer or as a multi-layer body in which two or more kinds are laminated.

In addition, as the base material sheet, an ITO (acid-valued indium tin) electrode film, a transparent electrode film such as Cu mesh, Ag mesh, Ag nanofiber, or an organic conductive curtain such as polythiophene, or the above-mentioned various electrode film-attached An optical member such as a substrate, a polarizing plate, a retardation plate, an elliptically polarizing plate, an optical compensation film, a brightness enhancement film, an electromagnetic wave shielding film, a near infrared ray absorbing film, an AR (antireflection) film may be used.

As the release sheet, it is possible to use various synthetic resin sheets exemplified by the base material sheet, paper, cloth, non-woven fabric or the like subjected to a release treatment. For example, a silicone-based release sheet, an olefin-based release sheet. Examples thereof include a release sheet, a fluorine-based release sheet, a long-chain alkyl-based release sheet, and an alkyd-based release sheet.

As a method for applying the pressure-sensitive adhesive composition, for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater or the like may be used.

Regarding the drying conditions, the drying temperature is usually 50°C to 250°C, preferably 60°C to 120°C, and more preferably 65°C to 95°C. The drying time is usually 10 seconds to 10 minutes.

As conditions for the above-mentioned curing treatment, the temperature is usually room temperature to 70° C., and the time is usually 1 day to 30 days, specifically, for example, 23° C. for 1 day to 20 days, preferably 23° C. for 3 days. It may be carried out for 10 days at 40° C. for 1 to 7 days.

The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention is usually preferably 5 to 300 μm, particularly preferably 10 to 250 μm, further preferably 25 to 200 μm, and particularly preferably 50 to 175 μm.
If the thickness of the pressure-sensitive adhesive layer is too thin, the step followability tends to deteriorate, and if it is too thick, the thickness of the entire optical member tends to increase too much.

Further, particularly when a thick film pressure-sensitive adhesive layer is obtained, it is preferable to apply a film having a thickness of 10 μm or more, particularly preferably 50 μm or more, further preferably 100 μm or more, and the upper limit of the film thickness is The film thickness at the time of coating is usually 800 μm.

In addition, the said film thickness is the value calculated|required by subtracting the measured value of the thickness of a structural member other than an adhesive layer from the measured value of the thickness of the whole adhesive sheet using "ID-C112B" by Mitutoyo. ..

The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention (before curing by irradiation with active energy rays and/or heating) is preferably 5 to 60% from the viewpoint of adhesive force and step followability, and further, It is preferably 10 to 50%, particularly preferably 20 to 45%. If the gel fraction is too low, the pressure-sensitive adhesive sheet tends to be marked by foreign matter due to a decrease in cohesive force, or the pressure-sensitive adhesive sheet tends to sag. Further, if the gel fraction is too high, there is a tendency that the step followability is lowered due to an increase in cohesive force, the adhesion to the adherend is lowered, and the blister resistance is deteriorated.

The gel fraction of the pressure-sensitive adhesive layer after curing of the pressure-sensitive adhesive sheet of the present invention by irradiation with active energy rays and/or heating is preferably 10 to 95% from the viewpoint of durability and adhesive strength, and particularly preferably 20 to 90% is preferable, and 30 to 80% is particularly preferable. If the gel fraction is too low, the durability of the adhesive layer tends to deteriorate due to a decrease in cohesive force. On the other hand, if the gel fraction is too high, the cohesive force increases and the adhesion with the interface tends to decrease.

The gel fraction is a measure of the degree of crosslinking (degree of curing) and is calculated, for example, by the following method. That is, an adhesive sheet (without a separator) formed by forming an adhesive layer on a polymer sheet (for example, polyethylene terephthalate film) serving as a base material is wrapped with a 200-mesh SUS wire mesh, and then placed in The gel fraction is defined as the weight percentage of the insoluble pressure-sensitive adhesive component remaining in the wire mesh after being immersed at 24° C. for 24 hours. However, the weight of the base material is subtracted.

The pressure-sensitive adhesive sheet of the present invention thus obtained is a monofunctional unsaturated compound in addition to a crosslinked product of a functional group-containing acrylic resin (A) having a specific glass transition temperature in the pressure-sensitive adhesive layer and a crosslinking agent (B). Since it contains (C), the monofunctional unsaturated compound (C) imparts a plasticizing effect to the pressure-sensitive adhesive, whereby the elastic modulus of the pressure-sensitive adhesive layer becomes low, and thus the step (unevenness) of the adherend Demonstrate excellent followability to. Further, since the glass transition temperature of the functional group-containing acrylic resin (A) is higher than usual, the content of the cross-linking agent can be reduced, and therefore the deterioration of the adhesiveness due to the thermal cross-linking of the acrylic resin can be suppressed to the minimum. can do.
Then, after sticking the adherend, the monofunctional unsaturated compound (C) contained in the pressure-sensitive adhesive layer is polymerized by irradiating the adhesive layer with active energy rays and/or heating to form an adherend. It becomes possible to adhere more firmly to.

As a method for sticking the pressure-sensitive adhesive sheet to the adherend, for example, after sticking the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet to the adherend, heat and pressure treatment (eg, 50° C./0.5 MPa) in an autoclave or the like X 30 minutes).

In the present invention, when the pressure-sensitive adhesive layer is cured by irradiation with active energy rays, at least one of the substrate sheet and the adherend may be transparent, and the active energy ray may be irradiated from the transparent surface.

In the irradiation of the active energy rays, rays such as deep ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, electromagnetic waves such as X-rays and γ-rays, electron rays, proton rays, neutron rays, etc. can be used. Curing by ultraviolet irradiation is advantageous because of the availability of the equipment and the price. In the case of performing electron beam irradiation, it can be cured without using the photopolymerization initiator (e1).

A high pressure mercury lamp, an electrodeless lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, an LED lamp, or the like is used as a light source when performing the ultraviolet irradiation. For the high-pressure mercury lamp, for example, 5~3000mJ / cm ^2, preferably at the conditions of 50~2000mJ / cm ^2. In the case of the above electrodeless lamp, for example, it is performed under the conditions of ^{2 to} 2000 mJ/cm ² , preferably 10 to 1000 mJ/cm ² . The irradiation time varies depending on the type of the light source, the distance between the light source and the coating surface, the coating thickness, and other conditions, but it is usually several seconds to several tens of seconds, and in some cases, may be a fraction of a second. On the other hand, in the case of the electron beam irradiation, for example, an electron beam having an energy in the range of 50 to 1000 Kev is used, and the irradiation amount of 2 to 50 Mrad is preferable.

When the pressure-sensitive adhesive layer is cured by heat, the thermal polymerization initiator (e2) is used as the above-mentioned polymerization initiator (E), and the polymerization reaction is started and progressed by heating. The treatment temperature and the treatment time at the time of curing by heating differ depending on the type of the thermal polymerization initiator (e2) used and are usually calculated from the half-life of the initiator, but the treatment temperature is usually The temperature is preferably 70 to 170° C., and the treatment time is preferably 0.2 to 20 minutes, particularly preferably 0.5 to 10 minutes.

Thus, by sticking the pressure-sensitive adhesive sheet of the present invention to an adherend and performing at least one of irradiation with active energy rays and heating, the pressure-sensitive adhesive layer of the present invention after curing is laminated on the adherend. A laminate with an agent layer ([adherent/adhesive layer/base sheet] or [adhesive/adhesive layer/adhesive] when used as a baseless double-sided adhesive sheet) can be obtained. it can.

The adherend is not particularly limited, but includes, for example, an ITO film, a Cu mesh, a transparent electrode film such as an organic conductive screen such as Ag nanofibers and polythiophene, a polarizing plate, a retardation plate, and an elliptically polarized light. Examples include optical members such as a plate, an optical compensation film, a brightness enhancement film, an electromagnetic wave shielding film, a near infrared ray absorbing film, and an AR (antireflection) film. In particular, an adherend having a step on the surface is preferable because the effect of the pressure-sensitive adhesive sheet excellent in followability of the present invention is remarkably exhibited, and for example, 1 to 100 μm, particularly 3 to 50 μm, and further, Even an adherend having a level difference of 5 to 30 μm on the surface exhibits good followability.

The adhesive sheet of the present invention has a storage elastic modulus of the adhesive layer of 1.0×10 ^{3 to} 1.0×10 ⁵ at 23° C. and 1 Hz, and a tan δ at 50° C. and 1 Hz of 0.5 to 10. It is preferably 0.7.
In addition, the storage elastic modulus of the pressure-sensitive adhesive layer after curing with active energy rays and/or heat is 1.0×10 ⁴ or more at 23° C. and 1 Hz, and tan δ at 50° C. and 1 Hz is less than 0.5. Is preferred.

The pressure-sensitive adhesive sheet of the present invention is an optical sheet such as glass or ITO transparent electrode sheet, polyethylene terephthalate (PET), polycarbonate (PC), polymethylmethacrylate (PMMA), polarizing plate, retardation plate, optical compensation film, and brightness enhancement. It is useful for attaching optical members such as films. Further, it can be suitably used for an image display device such as a touch panel including these optical members.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, “part” and “%” mean weight basis.

First, various functional group-containing acrylic resin (A) solutions were prepared as follows. The weight average molecular weight, dispersity, and glass transition temperature of the functional group-containing acrylic resin (A) were measured according to the methods described above.

Regarding the measurement of the solid content concentration, 1 to 2 g of the functional group-containing acrylic resin (A) solution was taken on an aluminum foil, dried by heating with a ket (infrared dryer, 185 W, height 5 cm) for 45 minutes, before and after drying. The weight change was measured, and the viscosity was measured according to JIS K5400 (1990) 4.5.3 rotational viscometer method.

[Production of functional group-containing acrylic resin (A) solution]
[Functional group-containing acrylic resin (A-1)]
29 parts of 2-ethylhexyl acrylate (a2), 30 parts of 2-hydroxyethyl acrylate (a1), and 2-ethylhexyl were placed in a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas blowing port and a thermometer. Charge 15 parts of methacrylate (a2-2), 15 parts of isostearyl acrylate (a2-2), 11 parts of tert-butyl methacrylate (a2-1), and 8 parts of acetone, 41 parts of methyl ethyl ketone and 5 parts of ethyl acetate, and heat to reflux. After the initiation, 0.04 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and after reacting for 3 hours at the methylethylketone reflux temperature, 0.02 part of azobisisobutyronitrile (AIBN) and 3 parts of ethyl acetate were added. Was added, and the mixture was further reacted for 4 hours and diluted with ethyl acetate to obtain an acrylic resin solution. 100 parts (resin content) of the resulting acrylic resin solution was charged with 0.03 part of 2-methacryloyloxyethyl isocyanate and reacted at 50° C. for 12 hours to give an ethylenically unsaturated group in the side chain to hydroxyethyl acrylate. 0.13 mol% added functional group-containing acrylic resin (A-1) solution (weight average molecular weight 296,000, dispersity 3.72, glass transition temperature −25.4° C., solid content 60%, viscosity 12,000 mPa*s (25 degreeC)) was obtained.

[Functional group-containing acrylic resin (A-2)]
In a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 50 parts of 2-ethylhexyl acrylate (a2), 30 parts of 2-hydroxyethyl acrylate (a1), tert-butyl. Charge 20 parts of methacrylate (a2-1) and 76 parts of ethyl acetate, and after heating under reflux, add 0.04 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator, and react at ethyl acetate reflux temperature for 3 hours. Then, 0.02 parts of azobisisobutyronitrile (AIBN) and 3 parts of ethyl acetate were added, and the reaction was further continued for 3 hours, followed by dilution with ethyl acetate to obtain an acrylic resin solution. 100 parts (resin content) of the resulting acrylic resin solution was charged with 0.03 part of 2-methacryloyloxyethyl isocyanate and reacted at 50° C. for 12 hours to give an ethylenically unsaturated group in the side chain to hydroxyethyl acrylate. 0.08 mol% added functional group-containing acrylic resin (A-2) solution (weight average molecular weight 622,000, dispersity 4.95, glass transition temperature -32.2°C, solid content 49.1%). , Viscosity 16,000 mPa·s (25° C.)) was obtained.

[Functional group-containing acrylic resin (A'-1)]
70 parts of 2-ethylhexyl acrylate (a2), 30 parts of 2-hydroxyethyl acrylate (a1), and ethyl acetate were placed in a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas blowing port, and a thermometer. After charging 150 parts and starting heating under reflux, 0.04 parts of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and after reacting for 3 hours at the ethyl acetate reflux temperature, it was diluted with ethyl acetate to prepare an acrylic resin. A solution was obtained. 100 parts (resin content) of the resulting acrylic resin solution was charged with 0.03 part of 2-methacryloyloxyethyl isocyanate and reacted at 50° C. for 12 hours to give an ethylenically unsaturated group in the side chain to hydroxyethyl acrylate. 0.17 mol% added functional group-containing acrylic resin (A′-1) solution (weight average molecular weight 69,10,000, dispersity 4.99, glass transition temperature −56.1° C., solid content 51.7). %, a viscosity of 20,000 mPa·s (25° C.)) was obtained.

Regarding the functional group-containing acrylic resins (A-1), (A-2), and (A'-1) produced as described above, the content of the raw material monomer components, and when each raw material monomer component is a homopolymer, The glass transition temperature, the weight average molecular weight of the functional group-containing acrylic resin, the degree of dispersion, and the viscosity are shown in Table 1 below.

The abbreviations in Table 1 represent the following compounds.
HEA: 2-hydroxyethyl acrylate 2EHA: 2-ethylhexyl acrylate tBMA: tert-butyl methacrylate 2EHMA: 2-ethylhexyl methacrylate ISTA: isostearyl acrylate

[Crosslinking agent (B)]
The following were prepared as a crosslinking agent (B-1).
55% ethyl acetate solution of tolylene diisocyanate adduct of trimethylol propane ("Coronate L-55E" manufactured by Nippon Polyurethane Co., Ltd.)

[Monofunctional unsaturated compound (C)]
The following were prepared as a monofunctional unsaturated compound (C).
-(C1-1a) isotridecyl acrylate ("FA-113A" manufactured by Hitachi Chemical Co., Ltd.)
-(C1-1b) 2-decyl tetradecanyl acrylate ("DTD-A" manufactured by Kyoeisha Chemical Co., Ltd.)
・(C1-1c) Isostearyl acrylate (“ISTA” manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[Polyfunctional unsaturated compound (D)]
The following were prepared as the polyfunctional unsaturated compound (D-1).
・Trimethylolpropane triacrylate (TMPTA)

[Polymerization initiator (E)]
The following were prepared as the polymerization initiator (E-1).
・1:1 mixture of 1-hydroxycyclohexyl phenyl ketone and benzophenone (“Irgacure 500” manufactured by Ciba Japan)

<Example 1>
0.2 part of crosslinking agent (B-1), 40 parts of monofunctional unsaturated compound (C-1), polyfunctional unsaturated compound in 100 parts (resin content) of the functional group-containing acrylic resin (A-1) (D-1) 1 part and a photopolymerization initiator (E-1) 1 part were blended to prepare a pressure-sensitive adhesive composition solution.
The pressure-sensitive adhesive composition solution was applied to a polyester release sheet so that the thickness after drying was 100 μm, and dried at 90° C. for 5 minutes to form a pressure-sensitive adhesive layer. The obtained pressure-sensitive adhesive layer was sandwiched between polyester-based release sheets and aged at 40° C. for 3 days to obtain a substrateless double-sided pressure-sensitive adhesive sheet [I-1].
Further, the release sheet on one surface was peeled off from the pressure-sensitive adhesive layer of the substrateless double-sided pressure-sensitive adhesive sheet obtained above, and pressed against a 125 μm-thick easily-adhesion-treated polyethylene terephthalate (PET) sheet to obtain a film thickness of the pressure-sensitive adhesive layer. To obtain a PET sheet [II-1] with an adhesive layer having a thickness of 100 μm.
Further, the release sheet on one side is peeled off from the pressure-sensitive adhesive layer of the substrateless double-sided pressure-sensitive adhesive sheet and pressed against a polyethylene terephthalate (PET) sheet having a thickness of 50 μm, and the pressure-sensitive adhesive layer has a pressure-sensitive adhesive layer having a thickness of 100 μm. A PET sheet [III-1] was obtained.

<Example 2, Comparative Examples 1 and 2>
A substrateless double-sided pressure-sensitive adhesive sheet [I-2], [I′-1], in the same manner as in Example 1 except that the mixing ratios of the components (A) to (E) were changed to the mixing ratios shown in Table 2. [I'-2] and PET sheet with adhesive layer [II-2], [II'-1], [II'-2], [III-2], [III'-1], [III'-]. 2] was obtained.

<Example 3>
The film of the pressure-sensitive adhesive layer was prepared in the same manner as in Example 1 except that the mixing ratios of the components (A) to (E) were changed to the mixing ratios shown in Table 2 and the coating was performed so that the thickness after drying was 160 μm. A substrateless double-sided pressure-sensitive adhesive sheet [I-3] and a pressure-sensitive adhesive layer-attached PET sheet [II-3] and [III-3] having a thickness of 160 μm were obtained.

Using the above-mentioned substrateless double-sided pressure-sensitive adhesive sheets [I-1] to [I-3], [I'-1], and [I'-2], the gel fraction of the pressure-sensitive adhesive layer, the optical characteristics of the pressure-sensitive adhesive layer, and The blister resistance was measured. Further, the adhesive force of the pressure-sensitive adhesive layer was measured using the above-mentioned pressure-sensitive adhesive layer-attached PET sheets [II-1] to [II-3], [II'-1], and [II'-2], and the step followability was measured. Was evaluated. Furthermore, the PET sheet [III-1] to [III-3], [III'-1], and [III'-2] with the pressure-sensitive adhesive layer were used to evaluate the moist heat resistance of the pressure-sensitive adhesive layer. The results are shown in Table 3 below.

[Gel fraction before UV irradiation]
After cutting the above-mentioned substrateless double-sided pressure-sensitive adhesive sheets [I-1] to [I-3], [I'-1], and [I'-2] into 40 mm x 40 mm, respectively, 23°C x 50% R.I. H. It was left to stand for 30 minutes under the conditions. After that, one release sheet is peeled off, the pressure-sensitive adhesive layer side is stuck to a SUS mesh sheet of 50 mm x 100 mm (200 mesh), the other release sheet is peeled off, and the longitudinal direction of the SUS mesh sheet is measured. After wrapping the sample by folding back from the central part, the gel fraction (%) was measured by the weight change when immersed in a sealed container containing 250 g of toluene for 24 hours.

[Gel fraction after UV irradiation]
Each of the above-mentioned substrateless double-sided pressure-sensitive adhesive sheets [I-1] to [I-3], [I'-1], and [I'-2] was cut into a size of 40 mm x 40 mm, and then the high pressure mercury UV irradiation device was used. At a peak illuminance of 150 mW/cm ² and an integrated exposure dose of 1000 mJ/cm ² (500 mJ/cm ² ×2 passes), and 23° C.×50% R. H. It was left to stand for 30 minutes under the conditions. After that, one release sheet is peeled off, the pressure-sensitive adhesive layer side is stuck to a SUS mesh sheet of 50 mm x 100 mm (200 mesh), the other release sheet is peeled off, and the longitudinal direction of the SUS mesh sheet is measured. After wrapping the sample by folding back from the central part, the gel fraction (%) was measured by the weight change when immersed in a sealed container containing 250 g of toluene for 24 hours.

[Adhesive strength (initial adhesive strength)]
The PET films with adhesive layers [II-1] to [II-3], [II'-1], and [II'-2] were cut into a width of 25 mm and a length of 100 mm, respectively, and the release sheet was peeled off. Then, the pressure-sensitive adhesive layer side was pressure-bonded to the non-alkali glass at 23° C. and 50% relative humidity in two round trips of a 2 kg rubber roller, and left for 30 minutes in an atmosphere of 23° C. and 50% relative humidity, The 180-degree peel strength (N/25 mm) was measured at a peeling speed of 300 mm/min at room temperature.

[Adhesive strength (adhesive strength after curing)]
The PET films with adhesive layers [II-1] to [II-3], [II'-1], and [II'-2] were cut into a width of 25 mm and a length of 100 mm, respectively, and the release sheet was peeled off. Then, the pressure-sensitive adhesive layer side is pressure-bonded to the non-alkali glass at 23° C. and 50% relative humidity in two round trips of a 2 kg rubber roller, and is pressure-heated at 50° C. and 0.5 MPa×20 minutes in an autoclave. I went. After that, UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW/cm ² and an integrated exposure amount of 1000 mJ/cm ² (500 mJ/cm ² ×2 passes), and 23° C.×50%R. ． H. After being left for 30 minutes under the above condition, the 180-degree peel strength (N/25 mm) was measured at a peeling speed of 300 mm/min at room temperature.

[Step followability]
25 μm, 38 μm, 50 μm, 70 μm, and 100 μm PET films were fixed on cell-free glass with cellophane tape to prepare glass with steps. The above-mentioned pressure-sensitive adhesive layer-attached PET sheets [II-1] to [II-3], [II'-1], and [II'-2] were each at 23°C and a relative humidity of 50% with respect to the stepped glass. It was pressure-bonded with a 2 kg rubber roller reciprocating twice under an atmosphere, and pressure-heated at 50° C. and 0.5 MPa×20 minutes in an autoclave. After that, UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW/cm ² and an integrated exposure amount of 1000 mJ/cm ² (500 mJ/cm ² ×2 passes), and 23° C.×50%R. ． H. After being left for 30 minutes under the conditions described above, the followability to the step was visually evaluated as follows.
(Evaluation)
◎・・・No air entrapment or floating could be confirmed in the step.
○: Air was slightly trapped in a part of the step, but floating was not confirmed.
B: Air entrapment and floating could be confirmed in part of the step.
×: Large floating was confirmed at the step.

[Measurement of optical properties of adhesive layer]
[Preparation of sample for optical measurement]
The above-mentioned substrateless double-sided pressure-sensitive adhesive sheets [I-1] to [I-3], [I'-1], and [I'-2] were each cut into a size of 25 mm x 25 mm, and a high pressure mercury UV irradiation device was used. UV irradiation was performed at a peak illuminance: 150 mW/cm ² and an integrated exposure amount: 1000 mJ/cm ² (500 mJ/cm ² ×2 passes). After that, the release sheet on one surface was peeled from the adhesive layer, the adhesive layer side was attached to a slide glass (Eagle XG, manufactured by Corning Incorporated), and then autoclaved (50°C, 0.5 MPa, 20 minutes). And 23° C.×50% R. H. It was left to stand for 30 minutes under the conditions. Finally, the other release sheet was peeled off to prepare a test piece having a constitution of "slide glass/adhesive layer".

The haze value and the color difference b* value were measured using the obtained test piece.
[Haze value]
The haze value was measured by measuring the diffuse transmittance and the total light transmittance using Haze MATER NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and substituting the obtained values of the diffuse transmittance and the total light transmittance into the following formulas. Then, the haze was calculated. This machine complies with JIS K7361-1.
Haze value (%)=(diffuse transmittance (%)/total light transmittance (%))×100
[Color difference]
The color difference b* value was measured according to JIS K7105, and the measurement was performed under a transmission condition using a spectral color difference meter (SE6000: manufactured by Nippon Denshoku Industries Co., Ltd.).
In the present invention, the haze, the total light transmittance, and the color difference b* value were measured using only the adhesive layer without alkali glass (total light transmittance=93, haze=0.06, b* value=0. It is a value measured by sticking to 16).

[Moisture and heat resistance]
The PET films [III-1] to [III-3], [III'-1], and [III'-2] with the pressure-sensitive adhesive layer were cut into 25 mm x 25 mm, and the release sheet was peeled off. After sticking the pressure-sensitive adhesive layer side to a slide glass (Eagle XG, manufactured by Corning Incorporated), autoclave treatment (50° C., 0.5 MPa, 20 minutes) was performed. After that, UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW/cm ² and an integrated exposure amount of 1000 mJ/cm ² (500 mJ/cm ² ×2 passes), and 23° C.×50%R. ． H. The sample was left for 30 minutes under the condition of 1 to prepare a test piece having a constitution of "slide glass/adhesive layer/PET film".

Using the obtained test piece, 85° C.×85% R. H. A moist-heat resistance test was performed for 168 hours in the atmosphere, and the haze value was measured before the start of the moist-heat resistance test and after the moist-heat resistance test, and evaluated according to the following criteria. The haze value was measured by the same method as the optical property measurement of the pressure-sensitive adhesive layer.
(Evaluation)
Good: The haze value after the moist-heat resistance test is less than 2.0%, and the rate of increase in the haze value before and after the moist-heat resistance test is 1.2 times or less.
B: The haze value immediately after the moist-heat resistance test is less than 2.0%, and the increase rate of the haze value before and after the moist-heat resistance test is more than 1.2 times.
X... The haze value immediately after the moist heat resistance test is 2.0% or more.

[Blister resistance]
The PET films with adhesive layers [II-1] to [II-3], [II'-1], and [II'-2] were cut into 25 mm x 50 mm, and the release sheet was peeled off. Then, the pressure-sensitive adhesive layer side was attached to an untreated polycarbonate plate having a thickness of 2 mm and subjected to autoclave treatment (50° C., 0.5 MPa, 20 minutes). Then, UV irradiation was performed from the PET film side with a high-pressure mercury UV irradiation device at a peak illuminance of 150 mW/cm ² and an integrated exposure amount of 1000 mJ/cm ² (500 mJ/cm ² ×2 passes), and 23° C.×50% R. ． H. The sample was left for 30 minutes under the condition of 1 to prepare a test piece having a structure of "polycarbonate plate/acrylic pressure-sensitive adhesive layer/PET film".
Then, 85° C.×85% R. H. It was left standing for 24 hours under the atmosphere described above, and the degree of blister generation before and after the standing was visually observed. The evaluation criteria are as follows.
(Evaluation)
A: No foaming.
B: Foaming with a diameter of 0.5 mm or less was observed, but no foaming with a diameter of more than 0.5 mm was observed.
Δ: Foaming exceeding φ0.5 mm occurred in less than 1/3 of the entire sticking surface.
×...Bubbling exceeding φ0.5 mm occurred on 1/3 or more of the entire pasting surface.

From the above results, the pressure-sensitive adhesive sheets of Examples 1 and 2 in which the thickness of the pressure-sensitive adhesive layer was 100 μm showed extremely excellent followability to steps of 25 μm and 38 μm, and the pressure-sensitive adhesive sheet of Example 1 was 50 μm. It can be seen that sufficient followability is exhibited even for the step.
In addition, the pressure-sensitive adhesive sheet of Example 3 having a pressure-sensitive adhesive layer having a thickness of 160 μm exhibits excellent followability with respect to steps of 25 μm, 38 μm, and 50 μm, and also has sufficient followability with steps of 75 μm. It turns out that it shows sex. This shows sufficient followability with respect to a step difference of about 47% with respect to the thickness of the pressure-sensitive adhesive layer, and shows sufficient followability with respect to a step difference of 50% with respect to the thickness of the adhesive layer. It can be seen that the pressure-sensitive adhesive sheet according to Example 1 has the same excellent step followability as that of the pressure-sensitive adhesive sheet.
Furthermore, the pressure-sensitive adhesive sheets of Examples 1 to 3 have physical properties required when the pressure-sensitive adhesive sheets are used for laminating optical members such as touch panels, such as strong adhesive strength, resistance to moist heat and whitening, and blister resistance. Also proves to be excellent.

On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2 using the functional group-containing acrylic resin (A) having a glass transition temperature lower than −35° C. are inferior in step followability and blister resistance.

Although the present invention has been described in detail and with reference to particular embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on the Japanese patent application filed on Aug. 3, 2015 (Japanese Patent Application No. 2015-153476), the contents of which are incorporated herein by reference.

The pressure-sensitive adhesive sheet of the present invention is excellent in step-following property, has high adhesiveness, has high light transmittance, and is unlikely to generate haze, and is therefore glass, ITO transparent electrode sheet, polyethylene terephthalate (PET). ), polycarbonate (PC), polymethylmethacrylate (PMMA), and other optical sheets, polarizing plates, retardation plates, optical compensation films, and brightness enhancement films. Furthermore, it can be suitably used for a touch panel including these optical members.

Claims (8)

A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a cross-linked product of a functional group-containing acrylic resin (A) and a cross-linking agent (B), and an ethylenically unsaturated compound (C) having one ethylenically unsaturated group,
The functional group-containing acrylic resin (A) is an acrylic resin obtained by polymerizing a monomer component containing a hydroxyl group-containing monomer and an alkyl group-containing methacrylic acid alkyl ester-based monomer having 4 to 8 carbon atoms, The content ratio of the hydroxyl group-containing monomer is 10 to 40% by weight based on the whole monomer components,
An adhesive sheet in which the functional group-containing acrylic resin (A) has a glass transition temperature of −35° C. or higher. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 5 to 300 µm. The release sheet on each side of the adhesive layer is a double-sided pressure-sensitive adhesive sheet obtained by laminating, pressure-sensitive adhesive sheet according to claim 1 or 2. The pressure-sensitive adhesive layer surface of the adhesive sheet according to any one of claims 1 to 3, the bonding to the adherend, the manufacture of pressure-sensitive adhesive layer-carrying laminated body for performing at least one of the active energy ray irradiation and heat Method. The method for producing a laminate with a pressure-sensitive adhesive layer according to claim 4 , wherein the surface of the adherend has a step of 1 to 100 μm. A laminate with an adhesive layer obtained by the method for producing a laminate with an adhesive layer according to claim 4 or 5 . An image display device comprising the laminate with the pressure-sensitive adhesive layer according to claim 6 . A touch panel comprising the laminate with the pressure-sensitive adhesive layer according to claim 6 .