JP6651855B2 - Pressure-sensitive adhesive composition, pressure-sensitive adhesive, pressure-sensitive adhesive sheet, double-sided pressure-sensitive adhesive sheet, pressure-sensitive adhesive for transparent electrode, touch panel, and image display device - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, a double-sided pressure-sensitive adhesive sheet, a pressure-sensitive adhesive for a transparent electrode, a touch panel, and an image display device, and more particularly to a pressure-sensitive adhesive used for an active energy ray-curable pressure-sensitive adhesive. It relates to compositions and the like.

  An adhesive used for a touch panel or the like is mainly used for bonding a support plate having an ITO (indium tin oxide) surface to a cover panel or a liquid crystal (LCD) module. The conventional touch panel has a glass / adhesive / glass structure, and the adhesive has excellent shock absorption and visibility, and prevents accurate detection and malfunction due to touch (finger touch). Therefore, a low dielectric constant is required, and various pressure-sensitive adhesives have been developed. For example, it has been studied to satisfy these requirements by increasing the thickness of the pressure-sensitive adhesive layer.

  The present applicant has developed a pressure-sensitive adhesive composition containing an acrylic resin, an organic solvent having a specific flash point, and an ethylenically unsaturated compound having a specific flash point as an acrylic pressure-sensitive adhesive suitable for thick coating. Has developed and proposed an acrylic pressure-sensitive adhesive (Patent Document 1).

  The pressure-sensitive adhesive sheet provided with a low dielectric constant and high transparency includes a pressure-sensitive adhesive layer containing stearyl (meth) acrylate and N, N-dialkyl (meth) acrylamide of a lower alkyl group as a monomer or a monomer unit. A pressure-sensitive adhesive sheet has been proposed (Patent Document 2).

JP 2012-111939 A JP 2014-152225 A

  Since the acrylic pressure-sensitive adhesive of Patent Document 1 is suitable for increasing the thickness of the pressure-sensitive adhesive layer, the ability to follow steps has been improved by increasing the film thickness, but there is still room for improvement. In addition to lowering the dielectric constant, there is a need for further improvements in terms of adhesive properties and good handleability at a low viscosity.

  Further, Patent Document 2 described above is still unsatisfactory in terms of low dielectric constant, good adhesive properties and good handleability at low viscosity, and further improvement is required as in Patent Document 1. Was something.

  Under such a background, the present invention provides a pressure-sensitive adhesive composition, a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, a double-sided pressure-sensitive adhesive sheet, a double-sided pressure-sensitive adhesive sheet, which exhibits a low dielectric constant under such a background and can satisfy both of the pressure-sensitive adhesive properties and the low viscosity. The purpose of the present invention is to provide a pressure-sensitive adhesive, a touch panel, and an image display device.

  That is, the present inventor has conducted intensive studies in view of such circumstances, and as a result, by using (meth) acrylate (b1) having a dioxane skeleton and one (meth) acryloyl group as diluent monomers, it is possible to obtain an adhesive as an adhesive. They have found that low viscosity can be achieved while maintaining good adhesive properties, and have reached the present invention.

<Summary of the present invention>
The present invention provides a pressure-sensitive adhesive composition containing a (meth) acrylic resin (A) and an ethylenically unsaturated compound (B) containing one ethylenically unsaturated group, wherein the ethylenically unsaturated group is One containing ethylenically unsaturated compound (B) contains a (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group , and contains an organic solvent in the pressure-sensitive adhesive composition. the amount is to first aspect of the der Ru adhesive composition below 1 wt%.

  Further, the present invention provides a pressure-sensitive adhesive comprising a crosslinked body of the pressure-sensitive adhesive composition of the first aspect as a second aspect, and a pressure-sensitive adhesive sheet containing an adhesive layer containing the pressure-sensitive adhesive of the second aspect. The double-sided pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to the second aspect is referred to as a fourth point, and the transparent electrode pressure-sensitive adhesive using the pressure-sensitive adhesive according to the second point is referred to as a fourth point. A touch panel containing the pressure-sensitive adhesive layer containing the transparent electrode pressure-sensitive adhesive according to the fifth aspect, wherein the touch panel has a sixth aspect, and an image display containing the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to the second point. The device is referred to as a seventh aspect.

  The pressure-sensitive adhesive composition of the present invention comprises an ethylenically unsaturated group containing (meth) acrylic resin (A) and (meth) acrylate (b1) each having one dioxane skeleton and one (meth) acryloyl group as essential components. And an ethylenically unsaturated compound (B) containing one. For this reason, low viscosity is realized while maintaining good adhesive properties as an adhesive.

  When the ethylenically unsaturated compound (B) containing one ethylenically unsaturated group contains an alkyl (meth) acrylate (b2) having an alkyl group having 8 to 30 carbon atoms, the dielectric constant can be reduced. The effect of improvement is achieved.

Hereinafter, the present invention will be described in detail, but these show one example of a preferred embodiment.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

  The pressure-sensitive adhesive composition of the present invention is obtained by using a (meth) acrylic resin (A) and an ethylenically unsaturated compound (B) containing one ethylenically unsaturated group containing a specific monomer component. Can be

<(Meth) acrylic resin (A)>
As the (meth) acrylic resin (A) used in the present invention, for example, a (meth) acrylic acid alkyl ester-based monomer (a1) is used as a polymerization component, and if necessary, a crosslinking agent (E) described below is further used. (Meth) acrylic resin obtained by polymerizing a functional group-containing monomer (a2) which can become a cross-linking point by reacting as a copolymer component is exemplified. An active energy ray-reactive (meth) acrylic resin having a reactive structural part capable of reacting with a part of the (meth) acrylic resin or other curing components contained in the pressure-sensitive adhesive composition by irradiation with the active energy ray. Resins can also be used.

  The (meth) acrylic resin contains a (meth) acrylic acid alkyl ester-based monomer (a1) as a polymerization component, and further contains a functional group-containing monomer (a2) as a copolymerization component, if necessary. Further, if necessary, another copolymerizable monomer (a3) can be contained as a copolymerization component. When the (meth) acrylic resin uses a functional group-containing monomer (a2) as a copolymer component, it serves as a cross-linking point of the (meth) acrylic resin and adheres to a substrate or an adherend. Sex can be further increased.

  As the alkyl (meth) acrylate monomer (a1), the number of carbon atoms of the alkyl group is usually 1 to 20, especially 1 to 12, further preferably 1 to 8, particularly 4 to 8. Preferably, specifically, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) A) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, iso-octyl acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, Stearyl (meth) acrylate, iso-stearyl acrylate Rate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and the like. These can be used alone or in combination of two or more.

  Among the above (meth) acrylic acid alkyl ester-based monomers (a1), n-butyl (meth) acrylate and 2-ethylhexyl (meth) are preferable in terms of copolymerizability, adhesive properties, ease of handling and availability of raw materials. Acrylates are preferably used.

  The content of the (meth) acrylic acid alkyl ester-based monomer (a1) in the copolymer component is preferably 10 to 100% by weight, particularly preferably 30 to 95% by weight, more preferably 50 to 90% by weight, The content is particularly preferably 60 to 85% by weight. When the content of the (meth) acrylic acid alkyl ester-based monomer (a1) is too small, the adhesive strength when used as an adhesive tends to decrease.

  The functional group-containing monomer (a2) may be any monomer containing a functional group that can become a cross-linking point by reacting with a cross-linking agent (E) described below. Examples thereof include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and an amino acid. Examples include a group-containing monomer, an acetoacetyl group-containing monomer, an isocyanate group-containing monomer, and a glycidyl group-containing monomer. Among these, a hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferably used in that a crosslinking reaction can be performed efficiently.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl ( Hydroxyalkyl acrylates such as meth) acrylates; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth) acrylate and polyethylene glycol (meth) acrylate; Primary hydroxyl group-containing monomers such as acryloyloxyethyl-2-hydroxyethylphthalic acid; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) Acrylate, secondary hydroxyl group-containing monomers such as 3-chloro-2-hydroxypropyl (meth) acrylate; can be mentioned 2,2-dimethyl-2-hydroxyethyl (meth) tertiary hydroxyl group-containing monomers such as acrylates.

  Among the above hydroxyl group-containing monomers, it is particularly preferable to use 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate in terms of excellent reactivity with a crosslinking agent.

  As the hydroxyl group-containing monomer used in the present invention, it is preferable to use a monomer having a content of di (meth) acrylate of 0.5% by weight or less, more preferably 0.2% by weight or less, especially Is preferably 0.1% by weight 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 silicic acid. And citric acid. 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, and diethylaminoethyl (meth) acrylate.

  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 alkylene oxide adducts thereof.

Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl (meth) acrylate.
These functional group-containing monomers (a2) may be used alone or in combination of two or more.

  The content of the functional group-containing monomer (a2) in the copolymer component is preferably 0 to 90% by weight, particularly preferably 5 to 60% by weight, more preferably 10 to 55% by weight, and particularly preferably 15 to 55% by weight. ５０50% by weight. If the content of the functional group-containing monomer (a2) is too small, the wet heat whitening resistance and the cohesive strength tend to decrease, and if it is too large, the viscosity tends to increase and the stability of the resin tends to decrease. .

  Examples of the other copolymerizable monomer (a3) include, for example, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenyldiethylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl ( A monomer containing one aromatic ring such as meth) acrylate, styrene, α-methylstyrene; a biphenyloxy structure-containing (meth) acrylate-based monomer such as biphenyloxyethyl (meth) acrylate; ethoxymethyl (meth) acrylamide; n-butoxymethyl (meth) acrylamide, (meth) acryloylmorpholine, dimethyl (meth) acrylamide, diethyl (meth) acrylamide, dimethylaminopropylacrylamide, (meth) acryl (Meth) acrylamide-based monomers such as mid-N-methylol (meth) acrylamide; 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxy Monomers containing an alkoxy group or an oxyalkylene group such as polyethylene glycol (meth) acrylate and polypropylene glycol mono (meth) acrylate; acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, Alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, dialkyl itaconate, dialkyl fumarate , Allyl alcohol, acryl chloride, methyl vinyl ketone, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone and the like. These may be used alone or in combination of two or more.

  The content of the other copolymerizable monomer (a3) in the copolymer 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 copolymerizable monomer (a3) is too large, the adhesive properties tend to be reduced.

  Thus, in the present invention, the (meth) acrylic acid alkyl ester-based monomer (a1), preferably the functional group-containing monomer (a2), and if necessary, the other copolymerizable monomer (a3) is polymerized as a copolymer component. By this, the (meth) acrylic resin (A) is produced. In such polymerization, production by solution polymerization can be carried out safely and stably with an arbitrary monomer composition using the (meth) acrylic resin (A). This is preferable in that A) can be produced.

  In the above solution polymerization, for example, a monomer component such as a (meth) alkyl acrylate monomer (a1), a functional group-containing monomer (a2), and other copolymerizable monomers (a3) in an organic solvent, a polymerization initiator May be mixed or added dropwise, and polymerization may be carried out at reflux or at 50 to 98 ° C. for 0.1 to 20 hours.

  Examples of the polymerization initiator include azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, which are ordinary radical polymerization initiators, benzoyl peroxide, lauroyl peroxide, and di-t-butyl peroxide. And peroxide-based polymerization initiators such as cumene hydroperoxide.

  Examples of the organic solvent include alcohols such as methanol, ethanol, propanol, n-butanol and i-butanol; ketones such as acetone, methyl isobutyl ketone, methyl ethyl ketone and cyclohexanone; cellosolves such as ethyl cellosolve; toluene and xylene. And propylene glycol monomethyl ether, glycol ethers such as propylene glycol monomethyl ether acetate, acetates such as ethyl acetate and butyl acetate, and diacetone alcohol. These may be used alone or in combination of two or more.

  In the present invention, when producing the (meth) acrylic resin (A) by solution polymerization, it is preferable to produce the (meth) acrylic resin (A) through a step of distilling off the organic solvent after the polymerization. Examples of the distillation method include a method of distilling the organic solvent by heating, a method of distilling the organic solvent by reducing the pressure, and the like. It is preferable to reduce the pressure while heating in consideration of efficiency.

  In the present invention, it is preferable to use a solvent-free (meth) acrylic resin that does not substantially contain an organic solvent as the (meth) acrylic resin (A) in that a thick film of an adhesive sheet can be formed. . "Substantially free of an organic solvent" means that the content of the organic solvent in the (meth) acrylic resin (A) is usually 1% by weight or less, preferably 0.1% by weight or less, particularly preferably 0% by weight or less. 0.01% by weight or less, and the lower limit is usually 0.0001% by weight.

  The weight average molecular weight of the (meth) acrylic resin (A) is usually 50,000 to 5,000,000, preferably 100,000 to 1,500,000, and particularly preferably 200,000 to 1,000,000. If the weight average molecular weight is too small, the durability tends to decrease, and if it is too large, the production tends to be difficult.

  The dispersity (weight average molecular weight / number average molecular weight) of the (meth) acrylic resin (A) is preferably 20 or less, particularly preferably 10 or less, more preferably 7 or less, and particularly preferably Is preferably 5 or less. If the degree of dispersion is too high, the durability of the pressure-sensitive adhesive layer is reduced, and foaming or the like tends to occur. The lower limit of the degree of dispersion is usually 1.1 from the viewpoint of the production limit.

  Further, the (meth) acrylic resin (A) preferably has a glass transition temperature of -80 to 10C, particularly preferably -60 to -10C, and more preferably -50 to -20C. If it is too high, the tack tends to be insufficient, and if it is too low, the heat resistance tends to decrease.

  The weight average molecular weight, the degree of dispersion and the glass transition temperature of the (meth) acrylic resin (A) can be determined by the following methods.

The weight average molecular weight is a weight average molecular weight in terms of standard polystyrene molecular weight. The column is Shodex GPC KF in high performance liquid chromatography (“Waters 2695 (body)” and “Waters 2414 (detector)” manufactured by Waters Japan). -806 L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / unit, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm ) Is measured by using three series, and the same method can be used for the number average molecular weight. The degree of dispersion is determined from the weight average molecular weight and the number average molecular weight.

The glass transition temperature is calculated from the Fox equation shown below.

  In addition, when the pressure-sensitive adhesive composition of the present invention is used for an information label or an electronic member fixing application in which the pressure-sensitive adhesive composition of the present invention is attached to a transparent electrode or other electronic member for a touch panel or the like, particularly a precision electronic member, it has corrosion resistance. In this case, it is preferable that the (meth) acrylic resin (A) does not contain an acidic group.

<Ethylenically unsaturated compound (B)>
The pressure-sensitive adhesive composition of the present invention comprises, in addition to the (meth) acrylic resin (A), an ethylenically unsaturated compound (B) containing one ethylenically unsaturated group containing a specific monomer component (B) , Simply referred to as “ethylenically unsaturated compound (B)”) as a diluent monomer.

  The ethylenically unsaturated compound (B) used in the present invention contains, as essential components, a (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group.

As each have one of the above dioxane skeleton and (meth) acryloyl group-containing (meth) acrylate (b1), for example, trimethylolpropane formal acrylated preparative like represented by the following structural formula (1). These can be used alone or in combination of two kinds.
Above all, it is preferable to use trimethylolpropane formal acrylate represented by the following structural formula (1) in terms of imparting good adhesive properties and having a high glass transition temperature (Tg).

Specific examples of the (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group include “Biscoat # 200 ” manufactured by Osaka Organic Chemical Industry Co., Ltd.

  The weight average molecular weight of the (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group is preferably 100 to 500, more preferably 150 to 400, and particularly preferably 150 to 300. It is. If the weight average molecular weight is too small, heat resistance tends to decrease, and if the weight average molecular weight is too large, photopolymerizability tends to decrease. The weight average molecular weight of (b1) is determined by the same method as for the (meth) acrylic resin (A).

  Further, (b1) exists as a polymer in the pressure-sensitive adhesive layer by being cured by at least one of active energy ray irradiation and heating as described later. The glass transition temperature (Tg) in this case is preferably −20 to 50 ° C., more preferably −15 to 40 ° C., and particularly preferably −10 to 30 ° C.

  In the present invention, the blending amount of the (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group is based on 100 parts by weight of the (meth) acrylic resin (A) from the viewpoint of viscosity. It is preferably 15 to 150 parts by weight, particularly preferably 20 to 125 parts by weight, further preferably 20 to 100 parts by weight, particularly preferably 20 to 80 parts by weight. If the amount is too small, the viscosity tends to be high, and if it is too large, the adhesive performance tends to decrease.

  In the present invention, the ethylenically unsaturated compound (B) preferably contains an alkyl (meth) acrylate (b2) having 8 to 30 carbon atoms in the alkyl group from the viewpoint of lowering the dielectric constant. . Along with the above dioxane skeleton and (meth) acrylate (b1) each having one (meth) acryloyl group as a diluting monomer, in particular, a long-chain alkyl (meth) acrylate (b2) having an alkyl group having 8 to 30 carbon atoms. By using the composition, it becomes easier to obtain a pressure-sensitive adhesive composition that achieves both low viscosity and low dielectric constant while maintaining good pressure-sensitive adhesive properties as a pressure-sensitive adhesive.

The alkyl group of the alkyl (meth) acrylate (b2) preferably has 10 to 26 carbon atoms, particularly preferably 13 to 24 carbon atoms. If the carbon number is too small, the dielectric constant of the pressure-sensitive adhesive composition tends to increase, and if it is too large, the adhesive strength tends to decrease. Specific examples include, for example, decane (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, myristyl (meth) acrylate, pentadecyl (meth) acrylate, cetyl (meth) acrylate, and n-stearyl (meth) acrylate Aliphatic (meth) acrylate having a linear alkyl chain such as isodecyl (meth) acrylate, isotridecyl (meth) acrylate, isomyristyl (meth) acrylate, isopentadecyl (meth) acrylate, isocetyl (meth) acrylate; Isostearyl (meth) acrylate, isotetracosyl (meth) acrylate, 2-dodecyl-hexadecanyl (meth) acrylate, 2-tetradecyl-octadecanyl (meth) acrylate, isobehenyl ( Data) acrylate, 2-decyl tetradecanyl (meth) long chain aliphatic having a branched chain containing alkyl chains such as acrylates (meth) acrylate; and the like.
These can be used alone or in combination of two or more.
Above all, it is preferable to use isostearyl (meth) acrylate, isotridecyl (meth) acrylate, isotetracosyl (meth) acrylate, or the like from the viewpoint that the relative permittivity of the pressure-sensitive adhesive layer can be efficiently reduced.

  In the present invention, the amount of the alkyl (meth) acrylate (b2) in which the alkyl group has 8 to 30 carbon atoms is based on 100 parts by weight of the (meth) acrylic resin (A) from the viewpoint of the dielectric constant. , Preferably from 10 to 200 parts by weight, more preferably from 25 to 175 parts by weight, even more preferably from 50 to 150 parts by weight. If the amount is too small, the dielectric constant tends to increase, and if it is too large, the adhesion tends to decrease.

  An ethylenically unsaturated compound (B) containing one ethylenically unsaturated group is a (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group, respectively, and the alkyl group has 8 to 30 carbon atoms. In the case of containing the alkyl (meth) acrylate (b2), the (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group, respectively, and the alkyl group has 8 to 30 carbon atoms. The content ratio (b1: b2) of the alkyl (meth) acrylate (b2) is preferably b1: b2 = 5: 100 to 100: 100 by weight, more preferably b1: b2 = 10: 100 to. 90: 100, particularly preferably b1: b2 = 15: 100 to 80: 100. If the proportion of (b1) is too small, the viscosity tends to be low and coating tends to be difficult. If the proportion of (b1) is too large, the adhesive performance tends to decrease.

  The ethylenically unsaturated compound (B) may contain other ethylenically unsaturated compounds other than the above (b1) and (b2) as long as the effects of the present invention are not impaired. .

  Examples of the other ethylenically unsaturated compounds include alicyclic (meth) acrylates and aromatic (meth) acrylates.

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

Examples of the aromatic (meth) acrylate include benzyl (meth) acrylate, biphenyl (meth) acrylate, naphthalene (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and 3-chloro-2-hydroxy. Propyl (meth) acrylate and the like.
These can be used alone or in combination of two or more.

  Specifically, it is preferable that the mixing ratio when the other ethylenically unsaturated compound is compounded is set to 50% by weight or less of the whole ethylenically unsaturated compound (B).

  The ethylenically unsaturated compound (B) is present as a polymer in the pressure-sensitive adhesive layer by being cured by at least one of irradiation with active energy rays and heating as described below. It is preferable to select (b1) and (b2), which are essential components constituting the ethylenically unsaturated compound (B), such that the glass transition temperature (Tg) is -80 to 80 ° C.

The glass transition temperature (Tg) of the above polymer is particularly preferably -60 to 40C, more preferably -30 to 20C, and particularly preferably -10 to 10C. If it is too high, the adhesive performance tends to be difficult to appear, and if it is too low, the cohesive strength tends to decrease.
The glass transition temperature is calculated from the above Fox equation.

  In the present invention, the content of the ethylenically unsaturated compound (B) is preferably from 50 to 300 parts by weight, particularly preferably from 60 to 250 parts by weight, per 100 parts by weight of the (meth) acrylic resin (A). Parts by weight, particularly preferably 70 to 200 parts by weight, more preferably 110 to 180 parts by weight. If the content of the ethylenically unsaturated compound (B) is too small, the viscosity tends to be high and the handleability tends to decrease. If the content is too large, the viscosity is too low and it is difficult to coat to a desired thickness. Tends to decrease the reliability of the pressure-sensitive adhesive.

The content ratio of the (meth) acrylic resin (A) in the entire pressure-sensitive adhesive composition of the present invention is usually 5 to 70% by weight, preferably 10 to 60% by weight, particularly preferably 25 to 50% by weight. Tend to content is too high too much the viscosity is the coating applied is lowered in the (A), coatability is lowered too low is too low viscosity, more reliable pressure-sensitive adhesive Tends to decrease.

  The pressure-sensitive adhesive composition of the present invention preferably has a viscosity of 40,000 (mPa · s / 25 ° C.) or less from the viewpoint of handleability, particularly preferably 30,000 (mPa · s / 25 ° C.) or less, more preferably It is at most 20,000 (mPa · s / 25 ° C.), particularly preferably at most 10,000 (mPa · s / 25 ° C.). Usually, the lower limit of the viscosity is 100 (mPa · s / 25 ° C.). If the viscosity is too high, the coating tends to be difficult due to easy formation of coating streaks when applied. The viscosity (25 ° C.) of the pressure-sensitive adhesive composition of the present invention is measured at 25 ° C. using a Brookfield viscometer.

In the present invention, it is preferable that the pressure-sensitive adhesive composition does not substantially contain an organic solvent, since a thick film of the pressure-sensitive adhesive sheet can be formed. "Substantially contains no organic solvent" means that the content of the organic solvent in the pressure-sensitive adhesive composition is 1 % by weight or less, preferably 0.1% by weight or less, particularly preferably 0.01% by weight or less. The lower limit is usually 0.0001% by weight.

  Further, the pressure-sensitive adhesive composition of the present invention comprises, after producing the (meth) acrylic resin (A), simultaneously adding the (meth) acrylic resin (A) and the ethylenically unsaturated compound (B), or It is preferred to add one to the other and stir to produce.

<Adhesive>
In the present invention, after the pressure-sensitive adhesive composition containing the (meth) acrylic resin (A) and the ethylenically unsaturated compound (B) is applied, the pressure-sensitive adhesive is cured and cross-linked to form a pressure-sensitive adhesive. Can be.

  As the curing / crosslinking method, [α] a method of curing by at least one of active energy ray irradiation and heating, [β] a method of curing by at least one of irradiation and heating of active energy ray, and a method of crosslinking using a crosslinking agent And the like.

  When performing the curing by at least one of the above-mentioned [α] active energy ray irradiation and heating, as the pressure-sensitive adhesive composition, an ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated groups (hereinafter referred to as “C”) The polyfunctional unsaturated compound (C) may be abbreviated in that the cohesive force of the entire pressure-sensitive adhesive layer can be adjusted. Further, the polymerization initiator (D) preferably contains a polymerization initiator (D). This is preferable in that at least one of the reactions during energy beam irradiation and heating can be stabilized.

  In the above curing, the ethylenically unsaturated compound (B) and the polyfunctional unsaturated compound (C) are polymerized (polymerized) by at least one of irradiation with active energy rays and heating to be cured.

  Further, when crosslinking is performed using a crosslinking agent in the above [β], a crosslinking reaction can be performed by adding a crosslinking agent (E) to the pressure-sensitive adhesive composition. When the crosslinking agent (E) is used, the (meth) acrylic resin (A) preferably has a functional group, and the functional group reacts with the crosslinking agent (E) to form a crosslink ( Curing) is performed.

  In the present invention, in view of the fact that the aging time is not required and the gel fraction of the pressure-sensitive adhesive layer can be increased in a short time, it is preferable to carry out curing by at least one of the above-mentioned [α] active energy ray irradiation and heating. preferable.

  Further, in terms of increasing the crosslink density of the pressure-sensitive adhesive and increasing the cohesive force to obtain more excellent durability, a method of curing by at least one of irradiation with active energy ray and heating using a crosslinking agent is used. The method of combining with the method of cross-linking is preferred.

  Examples of the polyfunctional unsaturated compound (C) include an ethylenically unsaturated monomer containing two or more ethylenically unsaturated groups in one molecule, for example, a bifunctional monomer, a trifunctional or higher monomer, Urethane (meth) acrylate compounds, epoxy (meth) acrylate compounds, and polyester (meth) acrylate compounds can be used. Among them, it is preferable to use an ethylenically unsaturated monomer or a urethane (meth) acrylate compound in terms of excellent curing speed and stability of the reached properties.

  The bifunctional monomer may be any 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, diglycidyl phthalate di (meth) acrylate, neopentyl glycol di (meth) acrylate modified with hydroxypivalic acid, diacrylate modified with ethylene oxide isocyanurate, 2- (meth) acryloyloxyethyl acid phosphate diester, and the like. Can be These may be used alone or in combination of two or more.

  The trifunctional or higher functional monomer may be a monomer containing three or more ethylenically unsaturated groups, such as trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol tetra (meth) acrylate. ) 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 (Meth) acrylate, ethylene oxide-modified dipentaerythritol hexa (meth) acrylate, ethylene oxide-modified pentaerythritol tri (meth) acrylate, ethylene oxide-modified pentaerythritol tetra (meth) acrylate, succinic acid-modified pentaerythritol tri (meth) acrylate And the like. These may be used alone or in combination of two or more.

  The urethane (meth) acrylate-based compound is a (meth) acrylate-based compound having a urethane bond in a molecule, and includes a hydroxyl-containing (meth) acryl-based compound and a polyvalent isocyanate-based compound (if necessary, a polyol And a compound obtained by reacting the compound according to a known general method with a weight-average molecular weight of usually 300 to 4000.

  The content of the polyfunctional unsaturated compound (C) is desirably 0.01 to 100 parts by weight, preferably 0.05 to 100 parts by weight, based on 100 parts by weight of the (meth) acrylic resin (A). It is 10 parts by weight, more preferably 0.1 to 5 parts by weight. If the content of the polyfunctional unsaturated compound (C) is too large, the cohesive strength tends to be too high, so that the adhesive performance tends to decrease, and if too small, the holding power tends to be insufficient.

  The content of the polyfunctional unsaturated compound (C) is preferably 0.01 to 99 parts by weight, and more preferably 0.05 to 99 parts by weight, based on 100 parts by weight of the ethylenically unsaturated compound (B). It is 10 parts by weight, more preferably 0.1 to 5 parts by weight. If the content of the polyfunctional unsaturated compound (C) is too large, the cohesive strength of the pressure-sensitive adhesive will be too high, and the adhesive performance will tend to be reduced. Tends to decrease.

  As the polymerization initiator (D), for example, various polymerization initiators such as a photopolymerization initiator (d1) and a thermal polymerization initiator (d2) can be used. Use of d1) is preferable in that it can be cured by irradiating active energy rays such as ultraviolet rays for a very short time.

  When the photopolymerization initiator (d1) is used, the pressure-sensitive adhesive composition is cured by irradiation with active energy rays, and when the thermal polymerization initiator (d2) is used, the pressure-sensitive adhesive composition is cured by heating. However, if necessary, it is preferable to use both.

  Examples of the photopolymerization initiator (d1) 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 Ben such as ether Benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenylsulfide, 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) trimethylammonium Benzophenones such as chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino-2-hydroxy ) -3 Thioxanthones such as 4-dimethyl-9H-thioxanthone-9-one mesochloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl- Acyl phosphine oxides such as pentyl phosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenyl phosphine oxide; and the like. These photopolymerization initiators (d1) are used alone or in combination of two or more.

Moreover, as these aids, triethanolamine, triisopropanolamine, 4,4'-dimethylamino benzophenone (Michler's ketone), 4,4'-diethylamino benzophenone, 2-dimethylaminopyridine Roh weaker Ikikosan ethyl, 4-dimethylaminopyridine ethyl benzoate, 4-dimethylamino-benzoic acid (n- butoxy) ethyl, 4-dimethylamino benzoic acid isoamyl, 4-dimethylaminobenzoic acid 2-ethylhexyl, 2,4-diethyl thioxanthone tons, 2,4-diisopropyl it is also possible to use a thioxane tons, and the like.

  Among these, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoin isopropyl ether, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 2-hydroxy-2-methyl-1- It is preferred to use phenylpropan-1-one.

Examples of the thermal polymerization initiator (d2) include methyl ethyl ketone peroxide, cyclohexanone peroxide, methyl cyclohexanone peroxide, methyl acetoacetate peroxide, acetyl acetate peroxide, and 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-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, -Di-t-butylperoxycyclohexyl) propane, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroper Oxide, 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-butyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexa Noil peroxide, octanoyl par Oxide, lauroyl peroxide, stearoyl peroxide, succinic acid peroxide, m-toluoylbenzoyl peroxide, benzoyl peroxide, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, bis (4-t-butyl Cyclohexyl) peroxydicarbonate, di-2-ethoxyethylperoxydicarbonate, di-2-ethoxyhexylperoxydicarbonate, di-3-methoxybutylperoxydicarbonate, di-s-butylperoxydicarbonate, Di (3-methyl-3-methoxybutyl) peroxydicarbonate, α, α'-bis (neodecanylperoxy) diisopropylbenzene, cumylperoxyneodecanate, 1,1,3,3-te Lamethylbutyl peroxy neodecanoate, 1-cyclohexyl-1-methylethyl peroxy neodecanoate, t-hexyl peroxy neodecanoate, t-butyl peroxy neodecanoate, t-hexyl peroxy Pivalate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanooate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperpate Oxy) hexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t- Hexyl peroxyisopropyl monocarbonate, t-butyl peroxyisobutyrate t-butylperoxy maleate, t- butyl peroxy-3,5,5-trimethyl Ji Ruhekisanoeto, t- butyl peroxy laurate, t- butyl peroxy isopropyl monocarbonate, t- butyl peroxy-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) organic peroxide initiators such as benzophenone and 2,3-dimethyl-2,3-diphenylbutane; 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, [(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] Hydrate B chloride, 2,2'-azobis [N-(4-hydro-phenyl) -2-methylpropionamidine] dihydrochloride, 2,2'-azobis [2-methyl -N- (phenylmethyl) propionamidine] dihydro Chloride, 2,2'-azobis [2-methyl-N- (2-propenyl) propionamidine] dihydrochloride, 2,2'-azobis [N- (2-hydroxyethyl) -2-methylpropionamidine] dihydrochloride 2,2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride , 2,2'-azobis [2- (4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl) p Pan] 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-imidazolin-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], etc .; These thermal polymerization initiators (d2) are used alone or in combination of two or more.

  Regarding the content of the polymerization initiator (D), 100 parts by weight of the ethylenically unsaturated compound (B) [when the polyfunctional unsaturated compound (C) is used, the content of (B) and (C) To 100 parts by weight], preferably 0.01 to 50 parts by weight, particularly preferably 0.1 to 20 parts by weight, more preferably 0.3 to 12 parts by weight, particularly preferably 0.1 to 20 parts by weight. It is preferably 5 to 3 parts by weight. If the content of the polymerization initiator (D) is too small, the curability tends to be poor and the physical properties tend to be unstable, and if it is too large, no further effect tends to be obtained.

  When irradiating the active energy ray, far-ultraviolet rays, ultraviolet rays, near-ultraviolet rays, rays such as infrared rays, X-rays, electromagnetic waves such as γ-rays, electron beams, proton rays, neutron rays, etc. can be used. Curing by ultraviolet irradiation is advantageous from the standpoint of availability of the apparatus and cost. When electron beam irradiation is performed, curing is possible without using the photopolymerization initiator (d1).

As a light source for performing the ultraviolet irradiation, a high-pressure mercury lamp, an electrodeless lamp, an ultra-high-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, an LED lamp, and the like are used. 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-mentioned electrodeless lamp, for example, it is performed under the condition of ^{2 to} 2000 mJ / cm ² , preferably 10 to 1000 mJ / cm ² . The irradiation time varies depending on the type of light source, the distance between the light source and the application surface, the coating thickness, and other conditions, but is usually several seconds to several tens of seconds, and in some cases, 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 preferably used, and the irradiation amount is preferably 2 to 50 Mrad. In the case of electron beam irradiation, the polymerization initiator (D) may not be blended.

  When a thermal polymerization initiator (d2) is used as the polymerization initiator (D), the polymerization reaction is started and advanced by heating. The processing temperature and the processing time at the time of curing by heating differ depending on the type of the thermal polymerization initiator (d2) used, and are usually calculated from the half-life of the initiator. The temperature is preferably from 70 ° C to 170 ° C, and the treatment time is usually preferably from 0.2 to 20 minutes, particularly preferably from 0.5 to 10 minutes.

  The crosslinking agent (E) exhibits excellent adhesive strength by reacting with a functional group derived from the functional group-containing monomer (a2), which is a constituent monomer of the (meth) acrylic resin (A). Examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, aldehyde-based crosslinking agents, amine-based crosslinking agents, and metal chelate-based crosslinking agents. Among these, an isocyanate-based crosslinking agent is preferably used from the viewpoint of improving the adhesion to the base material and the reactivity with the (meth) acrylic resin (A).

  Examples of the isocyanate-based crosslinking 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-naphthalenediisocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof Adducts of a polyisocyanate with a polyol compound such as trimethylolpropane; and burettes and isocyanurates of these polyisocyanate compounds.

  Examples of the epoxy crosslinking agent include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexanediol diglycidyl ether. And 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. '-Bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like.

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

  Examples of the aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleic dialdehyde, glutardialdehyde, formaldehyde, acetaldehyde, benzaldehyde and the like.

As the amine-based crosslinking agents, for example, hexamethylenediamine, triethyl Ren diamine, polyethylene imine, hexamethylene tetraamine, diethylene triamine, triethylene Ren tetraamine, isophorone diamine, amino resins, polyamides, and the like.

  Examples of the metal chelate crosslinking agent include, for example, aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as zirconium. can give.

  These crosslinking agents (E) may be used alone or in combination of two or more.

  Usually, the content of the crosslinking agent (E) is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 10 parts by weight, based on 100 parts by weight of the (meth) acrylic resin (A). It is 5 parts by weight, particularly preferably 0.1 to 2 parts by weight. If the amount of the crosslinking agent (E) is too small, the cohesive strength tends to decrease, and sufficient durability tends not to be obtained. If the amount is too large, the flexibility and the adhesive strength decrease, the durability decreases, and Tends to occur, so that it tends to be difficult to use it as an optical member.

  Further, in the pressure-sensitive adhesive composition of the present invention, a silane coupling agent, an antistatic agent, other acrylic pressure-sensitive adhesives, other pressure-sensitive adhesives, urethane resins, rosin, rosin ester, as long as the effects of the present invention are not impaired. Tackifiers such as hydrogenated rosin esters, phenolic resins, aromatic modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene resins, xylene resins, coloring agents, fillers, antiaging agents Conventionally known additives such as ultraviolet absorbers and functional dyes, and compounds which cause coloration or discoloration by irradiation with ultraviolet rays or radiation can be blended. The compounding amount of these additives is preferably 30% by weight or less, particularly preferably 20% by weight or less of the whole pressure-sensitive adhesive composition, and low molecular components having a molecular weight lower than 10,000 are included as additives as much as possible. It is preferable that there is no such material in terms of excellent durability.

  Further, in addition to the above-mentioned additives, those containing a small amount of impurities or the like contained in the raw materials for producing the components of the pressure-sensitive adhesive composition may be used.

  In the present invention, the pressure-sensitive adhesive composition obtained above is cured or crosslinked to obtain a (meth) acrylic pressure-sensitive adhesive.

<Adhesive sheet>
And the pressure-sensitive adhesive of the present invention is preferably used as a pressure-sensitive adhesive layer-containing laminate containing a pressure-sensitive adhesive layer comprising the above pressure-sensitive adhesive, and a base sheet, a release sheet, or an optical member. Is used as an adhesive sheet having an adhesive layer provided on a base sheet, a double-sided adhesive sheet having an adhesive layer provided on a release sheet, and an optical member with an adhesive layer having an adhesive layer provided on an optical member. Is preferred.

  As the method for producing the pressure-sensitive adhesive sheet, it can be produced according to a known general method for producing a pressure-sensitive adhesive sheet, for example, by forming the pressure-sensitive adhesive composition layer by applying the pressure-sensitive adhesive composition on a base sheet. After that, a treatment by at least one of irradiation with active energy rays and heating is performed, and curing is performed if necessary, whereby a pressure-sensitive adhesive layer can be formed.

The base sheet provided with the adhesive composition, for example, polyethylene naphthalate over preparative, polyethylene terephthalate, polybutylene terephthalate, polyester resins such as polyethylene terephthalate / isophthalate copolymer, polyethylene, polypropylene, polymethylpentene, etc. Polyolefin resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyfluoroethylene; polyamides such as nylon 6, nylon 6,6; polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene- Vinyl polymers such as vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol and vinylon; cellulose resins such as cellulose triacetate and cellophane; polymethyl methacrylate, polymethacrylic acid Acrylic resins such as chill, polyethyl acrylate and polybutyl acrylate; polystyrene; polycarbonate; polyarylate; synthetic resin sheets such as polyimide, aluminum, copper, iron metal foil, woodfree paper, glassine paper and other paper, glass Fabrics and nonwoven fabrics made of fibers, natural fibers, synthetic fibers, and the like can be given. These base sheets can be used as a single-layer body or as a multilayer body in which two or more kinds are laminated. Among these, a synthetic resin sheet is preferable in terms of weight reduction and the like.

  Further, the double-sided pressure-sensitive adhesive sheet may be a double-sided pressure-sensitive adhesive sheet having a known general structure using the (meth) acrylic pressure-sensitive adhesive, and is particularly excellent in transparency and has an adhesive force to a configured thickness. It is preferable to use a substrate-less double-sided pressure-sensitive adhesive sheet because of its high point.

  The substrate-less double-sided pressure-sensitive adhesive sheet, for example, after coating the pressure-sensitive adhesive composition on a release sheet, to form a pressure-sensitive adhesive composition layer, on the side of the pressure-sensitive adhesive composition layer without a release sheet, Further, another pressure-sensitive adhesive sheet is pasted, and a treatment by at least one of irradiation with active energy rays and heating is performed, and if necessary, curing is performed, whereby a pressure-sensitive adhesive layer can be formed. The method of use may be such that after one release sheet is peeled off and bonded to an adherend, the other release sheet is peeled off and bonded to an adherend.

  Furthermore, in the present invention, the pressure-sensitive adhesive is preferably used as a pressure-sensitive adhesive for an optical member, and the pressure-sensitive adhesive layer made of the (meth) acrylic pressure-sensitive adhesive is laminated on an optical member to form the pressure-sensitive adhesive layer. Thus, an optical member can be obtained.

  Examples of the optical member include an ITO electrode film and an organic conductive film such as polythiophene, a transparent electrode film such as a metal mesh such as copper and silver, a polarizing plate, a retardation plate, an elliptically polarizing plate, an optical compensation film, and a brightness enhancement. Films, electromagnetic wave shielding films, near infrared absorbing films, AR (anti-reflection) films, and the like. Among these, when the optical member is a transparent electrode film, the effects of the present invention can be remarkably exhibited and a high adhesive strength is obtained, and an ITO electrode film is particularly preferable. Note that the ITO electrode film is often formed as a thin film on a substrate such as glass or PET.

  Here, when the pressure-sensitive adhesive composition of the present invention is used for the optical member, the (meth) acrylic resin (A) and the ethylenically unsaturated compound (B) preferably do not contain an acidic group. Further, it is more preferable that the entire pressure-sensitive adhesive composition does not contain an acidic group.

  In addition, that it does not contain an acidic group specifically, an acid value is preferably 10 mgKOH / g or less, particularly preferably 1 mgKOH / g or less, more preferably 0.1 mgKOH / g or less.

  In the optical member with the pressure-sensitive adhesive layer, it is preferable to further provide a release sheet on the surface opposite to the optical member surface of the pressure-sensitive adhesive layer, and when practically used, after releasing the release sheet, The adhesive layer and the adherend will be bonded. As the release sheet, it is preferable to use a silicon release sheet.

  The method for producing the optical member with the pressure-sensitive adhesive layer to which the release sheet is bonded is as follows: [1] After applying the pressure-sensitive adhesive composition onto the optical member, bonding the release sheet, and irradiating with an active energy ray. And [2] a method of applying a pressure-sensitive adhesive composition onto a release sheet, bonding an optical member thereto, and performing at least one of active energy ray irradiation and heating. [3] a method of applying a pressure-sensitive adhesive composition on an optical member, performing a treatment by at least one of irradiation with active energy rays and heating, and then laminating a release sheet; [4] A method of applying the pressure-sensitive adhesive composition, performing a treatment by at least one of irradiation with active energy rays and heating, and then bonding the optical member. Among these, the case where only the active energy ray irradiation is performed by the method [2] is preferable in terms of not damaging the substrate, workability and stable production.

  Up to here, after manufacturing the optical member with the pressure-sensitive adhesive layer to which the release sheet is once bonded, the pressure-sensitive adhesive for peeling the release sheet and then bonding the pressure-sensitive adhesive layer and the adherend (other optical members) Has been described, but a method of bonding optical members together using the above-described double-sided pressure-sensitive adhesive sheet may be used.

  The pressure-sensitive adhesive layer included in the pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet, and the optical member with a pressure-sensitive adhesive layer will be described. The pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive composition on a substrate sheet, a release sheet, or an optical member to form a pressure-sensitive adhesive composition layer, and then performing treatment by at least one of active energy ray irradiation and heating. And, if necessary, aging.

  The application of the pressure-sensitive adhesive composition is performed by a conventional method such as roll coating, die coating, gravure coating, comma coating, and screen printing.

  The pressure-sensitive adhesive composition layer thus obtained is subjected to at least one of active energy ray irradiation and heating, and the pressure-sensitive adhesive layer is formed by performing an aging treatment in order to balance pressure-sensitive adhesive properties as necessary. The pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet, and the optical laminate (optical member) with the pressure-sensitive adhesive layer of the present invention are manufactured.

  The active energy ray irradiation conditions are as described above.

  The aging treatment is preferably performed particularly when a crosslinking agent (E) is used in the pressure-sensitive adhesive composition. The conditions for the aging treatment are as follows: temperature is usually room temperature (25 ° C.) to 70 ° C .; 30 to 30 days, specifically, for example, at 23 ° C. for 1 to 20 days, preferably at 23 ° C. for 3 to 10 days, and at 40 ° C. for 1 to 7 days.

  The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet, and the optical member with a pressure-sensitive adhesive layer is preferably 30 to 100%, particularly preferably 40 to 95%, from the viewpoint of durability and adhesive strength. Is preferable, and particularly preferably 50 to 90%. If the gel fraction is too low, the cohesive strength tends to decrease, which tends to cause a decrease in durability. On the other hand, if the gel fraction is too high, the adhesive strength tends to decrease due to an increase in cohesive force.

  In adjusting the gel fraction to the above range, for example, it is achieved by adjusting the type and amount of the crosslinking agent (E) or the type and amount of the polyfunctional acrylate or the like.

  The gel fraction is a measure of the degree of crosslinking (degree of curing) and is calculated by the following method. That is, a pressure-sensitive adhesive sheet (without a separator) formed by forming a pressure-sensitive adhesive layer on a polymer sheet (for example, polyethylene terephthalate (PET) film or the like) serving as a base material is wrapped with a 200-mesh SUS wire mesh, and toluene The gel was immersed in a metal mesh at 23 ° C. for 24 hours, and the weight percentage of the insoluble adhesive component remaining in the wire mesh was defined as the gel fraction. However, the weight of the substrate is subtracted.

  The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet, and the optical member with a pressure-sensitive adhesive layer is usually preferably 50 to 3000 μm, more preferably 80 to 1000 μm, and particularly preferably 100 to 1000 μm. It is preferably 350 μm. If the thickness of the pressure-sensitive adhesive layer is too small, the shock absorption tends to decrease. If the thickness is too large, the thickness of the entire optical member tends to increase too much.

  The thickness of the pressure-sensitive adhesive layer in the present invention is obtained by measuring the thickness of the components other than the pressure-sensitive adhesive layer from the measured value of the thickness of the entire pressure-sensitive adhesive layer-containing laminate using “ID-C112B” manufactured by Mitutoyo Corporation. This is a value obtained by subtracting the value.

  The pressure-sensitive adhesive force of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention, the double-sided pressure-sensitive adhesive sheet, and the optical member with a pressure-sensitive adhesive layer is appropriately determined according to the material of the adherend, for example, glass substrate, polycarbonate plate, poly When sticking to a methyl methacrylate plate or a PET sheet on which an ITO layer is deposited, it is preferable to have an adhesive strength of 5 N / 25 mm to 500 N / 25 mm, and more preferably 10 N / 25 mm to 100 N / 25 mm.

  In addition, the said adhesive force is calculated as follows. The release sheet on one side is peeled off from the pressure-sensitive adhesive layer (thickness: 80 μm) of a substrate-less double-sided pressure-sensitive adhesive sheet using a polyester release sheet (polyethylene terephthalate sheet), and a 125 μm-thick easily-adhesive PET (polyethylene terephthalate) film To produce a PET film with an adhesive layer. The PET film with the pressure-sensitive adhesive layer is cut into a width of 25 mm and a length of 100 mm, the release sheet is peeled off, and the pressure-sensitive adhesive layer side is brought into close contact with the adherend, under an atmosphere of 23 ° C. and a relative humidity of 50%. After applying pressure with two reciprocations of 2 kg rubber roller and leaving it in the same atmosphere for 30 minutes, a 180 degree peel strength (N / 25 mm) is measured at a normal temperature (23 ° C.) at a peel rate of 300 mm / min.

  The total light transmittance of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet, and the optical member with a pressure-sensitive adhesive layer of the present invention is preferably 85% or more, particularly preferably 90% or more, and further preferably. Preferably it is at least 92%. If the total light transmittance is too low, it tends to be difficult to use in display applications due to low light transmittance. The upper limit of the total light transmittance is usually 95%.

  The haze value of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet, and the optical member with a pressure-sensitive adhesive layer of the present invention is preferably 10% or less, particularly preferably 2% or less, more preferably 2% or less. 1% or less. If the haze value is too high, the image tends to be unclear when used for a display. The lower limit of the haze value is usually 0.00%.

  Here, the above-mentioned total light transmittance and haze value are values measured using a haze meter based on JIS K7361-1.

  The color difference b * value of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet, and the optical member with a pressure-sensitive adhesive layer of the present invention is preferably 1 or less, particularly preferably 0.5 or less. If the color difference b * value is too high, the original color tends to be difficult to appear when used for a display. The lower limit of the color difference b * value is usually -1.

  Here, the color difference b * value is measured according to JIS K7105, and the measurement is performed under a predetermined transmission condition using a spectral color difference meter (SE6000: manufactured by Nippon Denshoku Industries Co., Ltd.).

  In the present invention, the measurement of the haze, the total light transmittance, and the color difference b * value was performed by measuring only the pressure-sensitive adhesive layer with an alkali-free glass (total light transmittance = 93%, haze = 0.06%, color difference b * value). = 0.16).

  The pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition of the present invention includes glass, ITO transparent electrode sheets, optical sheets such as polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PMMA), polarizing plates, retardation plates, It is useful for attaching optical members such as optical compensation films and brightness enhancement films. Furthermore, 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 more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In the examples, “parts” and “%” mean on a weight basis.

  First, various (meth) acrylic resin (A) solutions were prepared as described below. The weight average molecular weight, glass transition temperature, and degree of dispersion of the (meth) acrylic resin (A) were measured in accordance with the above-described methods.

[Preparation of (meth) acrylic resin (A) solution]

[Acrylic resin (A-1)]
A four-necked round-bottomed flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet, and a thermometer was charged with 300 parts of acetone, and 2,2'-azobis (2,4-dimethylvaleronitrile was used as a polymerization initiator. ) (ADVN) (0.15 parts) was added, the mixture was heated while stirring, and at reflux temperature, a mixture of 70 parts of 2-ethylhexyl acrylate (2EHA) and 30 parts of 2-hydroxyethyl acrylate (HEA) was added dropwise over 2 hours. . After reacting at the reflux temperature of acetone for 15 hours, the mixture is diluted with acetone, and 0.5 parts of pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] is added as a stabilizer. An acrylic resin solution was obtained. Acetone in 400 parts (resin content: 100 parts) of the obtained acrylic resin solution was distilled off to obtain a solvent-free acrylic resin (A-1) (weight-average molecular weight (Mw): 220,000; glass transition temperature ( Tg) -56.1 ° C; dispersity 3.40).

[Acrylic resin (A-2)]
A four-necked round-bottomed flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet, and a thermometer was charged with 300 parts of acetone, and 2,2'-azobis (2,4-dimethylvaleronitrile was used as a polymerization initiator. ) (ADVN) (0.15 parts) was added, the mixture was heated while stirring, and at reflux temperature, a mixture of 70 parts of 2-ethylhexyl acrylate (2EHA) and 30 parts of 2-hydroxyethyl acrylate (HEA) was added dropwise over 2 hours. . After reacting at the reflux temperature of acetone for 7 hours, the mixture was diluted with acetone, and 1 part of 3,5-dibutyl-4-hydroxytoluene (BHT) was added as a stabilizer to obtain an acrylic resin solution. Acetone was distilled off from 400 parts (resin content: 100 parts) of the obtained acrylic resin solution to obtain a solvent-free acrylic resin (A-2) (weight average molecular weight (Mw) 400,000, glass transition temperature ( Tg) -56.1 ° C; dispersity 4.00).

[Acrylic resin (A-3)]
A four-necked round-bottomed flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet, and a thermometer was charged with 400 parts of acetone, and 2,2'-azobis (2,4-dimethylvaleronitrile was used as a polymerization initiator. ) (ADVN) (0.15 parts), the mixture was heated while stirring, and at reflux temperature 50 parts of 2-ethylhexyl acrylate (2EHA), 30 parts of 2-hydroxyethyl acrylate (HEA) and t-butyl methacrylate (tBMA) 20 parts of the mixture were added dropwise over 2 hours. After reacting at the reflux temperature of acetone for 15 hours, the mixture is diluted with acetone, and 0.5 parts of pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] is added as a stabilizer. An acrylic resin solution was obtained. Acetone was distilled off from 500 parts (resin content: 100 parts) of the obtained acrylic resin solution to obtain a solvent-free acrylic resin (A-3) (weight average molecular weight (Mw) 300,000; glass transition temperature ( Tg) -32.0 ° C; dispersity 2.88).

  Table 1 shows the monomer components, the weight average molecular weight (Mw), the glass transition temperature (Tg), and the degree of dispersion of the acrylic resins (A-1) to (A-3) produced as described above. .

The components shown below were prepared.
[Ethylenically unsaturated compound (B)]
B1-1: Trimethylolpropane formal acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., “Biscoat # 200”, molecular weight 200.3) (V # 200)
B1-2: (2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl acrylate ("MEDOL-10", manufactured by Osaka Organic Chemical Industry Co., Ltd., molecular weight 200.2)
B2: isostearyl acrylate (Osaka Organic Chemical Industry Co., Ltd., “ISTA”, molecular weight 324)

[Other ethylenically unsaturated compounds (B ')]
B'-1: methoxyethyl acrylate (MEA)
B'-2: acryloyl morpholine (ACMO)
B'-3: ethyl carbitol acrylate (CBA)
B'-4: 2-ethylhexyl acrylate (2EHA)

[Polyfunctional unsaturated compound (C)]
・ Trimethylolpropane triacrylate (TMPTA)

[Photopolymerization initiator (D)]
-2-hydroxy-2-methyl-1-phenyl-propan-1-one ("DAROCURE 1173", manufactured by BASF Japan)

[Example 1]
Acrylic resin (A-1) was charged with 100 parts (resin content) in a four-necked round-bottomed flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet, and a thermometer. As B), 100 parts of isostearyl acrylate ("ISTA", manufactured by Osaka Organic Chemical Industry Co., Ltd.) (b2), and trimethylolpropane formal acrylate ("Biscoat # 200", manufactured by Osaka Organic Chemical Industry Co., Ltd.) (b1-1) 40 Parts, 2 parts of trimethylolpropane triacrylate (TMPTA) as the polyfunctional unsaturated compound (C), and 2-hydroxy-2-methyl-1-phenyl-propan-1-one as the photopolymerization initiator (D) ( 2 parts of “Darocur 1173” manufactured by BASF Japan Ltd.) were simultaneously charged and mixed to obtain a pressure-sensitive adhesive composition.

[Examples 2 to 6 , Reference Examples 1 and 2, Comparative Examples 1 to 5]
The components prepared and prepared as described above were blended at the ratios shown in Table 2 below, and otherwise the procedure of Example 1 was repeated to prepare a pressure-sensitive adhesive composition solution.

Then, the pressure-sensitive adhesive composition solution obtained above was applied to a polyester release sheet to form a pressure-sensitive adhesive composition layer. The obtained pressure-sensitive adhesive composition layer is sandwiched between polyester-based release sheets, and irradiated with ultraviolet light by 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 a pressure-sensitive adhesive layer (film thickness 80 μm: film thickness of 185 μm only in Example 8) was obtained to obtain a substrate-less double-sided pressure-sensitive adhesive sheet. The thickness of the pressure-sensitive adhesive layer was determined by measuring the thickness of the entire substrate-less double-sided pressure-sensitive adhesive sheet on which the pressure-sensitive adhesive layer was formed using “ID-C112B” manufactured by Mitutoyo Corporation. This is a value obtained by subtracting the measured value of the thickness of the member.

  Using the substrate-less double-sided pressure-sensitive adhesive sheet obtained above, the gel fraction, the pressure-sensitive adhesive strength, and the relative dielectric constant were measured and evaluated according to the following methods. In addition, the viscosity of the pressure-sensitive adhesive composition obtained above and the optical properties (optical measurement) of the pressure-sensitive adhesive layer were measured and evaluated according to the following methods. The results are shown in Table 3 below.

[Viscosity (adhesive composition)]
The temperature of the pressure-sensitive adhesive composition was adjusted to 25 ° C., and the viscosity at 25 ° C. was measured using a Brookfield viscometer. The evaluation criteria are as follows.
(Evaluation criteria)
◎ ... less than 10000mP a · s / 25 ℃.
○ ... 10000mP a · s / 25 ℃ more than 40000mP · s / 25 less than ℃.
× ... 40000mP a · s / 25 ℃ or more.

[Optical measurement (only glue)]
Optical measurements (haze value, color difference b * value, total light transmittance) of the obtained pressure-sensitive adhesive layer (paste only) were measured according to the above-mentioned method. That is, the total light transmittance and the haze value were measured using a haze meter based on JIS K7361-1. The color difference b * value was measured according to JIS K7105, and the measurement was performed using a spectral color difference meter (SE6000: manufactured by Nippon Denshoku Industries Co., Ltd.) under predetermined transmission conditions.
In the measurement of the haze value, the total light transmittance, and the color difference b * value, only the pressure-sensitive adhesive layer was coated with an alkali-free glass (total light transmittance = 93%, haze = 0.06%, b * value = 0. 16) is a value measured after sticking.

[Moisture and heat resistance]
The release sheet on one side was peeled off from the pressure-sensitive adhesive layer of the substrate-less double-sided pressure-sensitive adhesive sheet, and pressed against an easily adhesive PET (polyethylene terephthalate) film having a thickness of 125 μm to obtain a PET film with a pressure-sensitive adhesive layer. The PET film with the pressure-sensitive adhesive layer was cut into a width of 25 mm x a length of 25 mm, the release sheet was peeled off, and the pressure-sensitive adhesive layer side was placed on an optical glass ("Corning EagleXG") at 23 ° C under an atmosphere of 50% relative humidity After applying pressure with two reciprocations of 2 kg rubber roller, the autoclave treatment was performed at 0.5 MPa at 50 ° C. for 20 minutes, and then the haze value was measured (optical measurement before endurance). Subsequently, a durability test was performed at 85 ° C. and 85% RH × 100 hours, and a haze value immediately after the durability (within 5 minutes) was measured (optical measurement after the durability). The evaluation criteria are as follows.
(Evaluation criteria)
…: Haze change before and after endurance is 1.0% or less.
X: Haze change before and after endurance is greater than 1.0%.

[Gel fraction]
After cutting the substrate-less double-sided pressure-sensitive adhesive sheet to 40 mm × 40 mm, the release sheet on one side was peeled off, and the pressure-sensitive adhesive layer side was bonded to a 50 mm × 100 mm SUS mesh sheet (200 mesh). After lightly adapting to the SUS mesh sheet, the other release sheet was peeled off, the sample was wrapped around the center of the SUS mesh sheet in the longitudinal direction, and the sample was wrapped. The gel fraction (%) was measured by determining the change in weight of the pressure-sensitive adhesive layer when immersed for 24 hours.

[Adhesive force]
The release sheet on one side was peeled off from the pressure-sensitive adhesive layer of the substrate-less double-sided pressure-sensitive adhesive sheet, and pressed against a 125 μm-thick easily-adhesive PET (polyethylene terephthalate) film to obtain a PET film with a pressure-sensitive adhesive layer. The PET film with the pressure-sensitive adhesive layer was cut into a width of 25 mm x a length of 100 mm, the release sheet was peeled off, and the pressure-sensitive adhesive layer side was placed on soda glass at 23 ° C under a 50% relative humidity atmosphere with a 2 kg rubber roller. Using two reciprocations, pressure-bonding was performed, and the mixture was allowed to stand for 30 minutes in the same atmosphere, and then a 180-degree peel strength (N / 25 mm) was measured at a normal temperature (23 ° C.) at a peel speed of 300 mm / min. The evaluation criteria are as follows.
(Evaluation criteria)
◎: 30 N / 25 mm or more.
…: 15 N / 25 mm or more and less than 30 N / 25 mm.
×: less than 15 N / 25 mm.

[Relative permittivity]
After peeling off the release sheet on one side from the pressure-sensitive adhesive layer of the substrate-less double-sided pressure-sensitive adhesive sheet and pressing it on an untreated polyethylene terephthalate (PET) film, the other release sheet is further peeled off and untreated polyethylene terephthalate (PET) film To obtain a PET film with a pressure-sensitive adhesive layer having a structure of PET film (thickness: 50 μm) / pressure-sensitive adhesive layer (thickness: 80 μm: film thickness in Example 8: 185 μm) / PET film (thickness: 50 μm).
The PET film with the pressure-sensitive adhesive layer was cut into a 7 cm × 7 cm square test piece, and the test piece was sandwiched between electrodes using an HP4284A Precision LCR meter (manufactured by Agilent) under an atmosphere of 23 ° C. and a relative humidity of 50%. The electric capacity was measured by applying an electric field at a frequency of 1 MHz, and the relative dielectric constant of the pressure-sensitive adhesive layer was calculated from the change in the electric capacity between the electrodes. The evaluation criteria are as follows.
(Evaluation criteria)
…: 3.5 or less.
×: greater than 3.5

From the above results, as the ethylenically unsaturated compound (B), trimethylolpropane formal acrylate (V # 200 ), which is (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group, is used. The products of Examples have low viscosity, have excellent adhesive properties with high adhesive strength, and have further reduced the dielectric constant. Further, as shown in the product of Example 6 , even when the thickness of the pressure-sensitive adhesive layer was as very large as 185 μm, there was no problem in coating properties, and the film had particularly excellent pressure-sensitive adhesive properties and low dielectric constant. Met.

  On the other hand, Comparative Examples 1 to 5 in which the ethylenically unsaturated compound (B) does not contain a (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group, respectively, are in a cohesive failure state (adhesion failure). The adhesive layer had high adhesive strength, but high viscosity (Comparative Example 1), low viscosity and low dielectric constant, but low adhesive strength and poor adhesive physical properties (Comparative Examples 2 to 2). 5).

  Although the specific embodiments of the present invention have been described in the above embodiments, the above embodiments are merely examples and are not to be construed as limiting. Various modifications apparent to those skilled in the art are contemplated to be within the scope of the present invention.

  The pressure-sensitive adhesive comprising the pressure-sensitive adhesive composition of the present invention can be suitably used as a pressure-sensitive adhesive sheet, particularly a double-sided pressure-sensitive adhesive sheet, particularly a double-sided pressure-sensitive adhesive sheet having no substrate (substrate-less). Glass and ITO transparent electrode sheet, optical sheets such as polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polarizing plate, retarder, etc. It is useful for attaching optical members such as optical compensation films and brightness enhancement films. Furthermore, it can be suitably used for a touch panel including these optical members.

Claims (14)

A pressure-sensitive adhesive composition containing a (meth) acrylic resin (A) and an ethylenically unsaturated compound (B) containing one ethylenically unsaturated group, which contains one of the above ethylenically unsaturated groups. The ethylenically unsaturated compound (B) contains (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group , and the content of the organic solvent in the pressure-sensitive adhesive composition is 1% by weight. % adhesive composition, characterized in der Rukoto below.   The ethylenically unsaturated compound (B) having one ethylenically unsaturated group contains an alkyl (meth) acrylate (b2) having an alkyl group having 8 to 30 carbon atoms. The pressure-sensitive adhesive composition according to the above.   The pressure-sensitive adhesive composition according to claim 2, wherein the alkyl (meth) acrylate (b2) having an alkyl group having 8 to 30 carbon atoms is an aliphatic alkyl (meth) acrylate.   The pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group has a weight average molecular weight of 100 to 500. Composition. (Meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group is (meth) acrylate having a glass transition temperature of −20 to 50 ° C. when formed into a homopolymer. The pressure-sensitive adhesive composition according to any one of claims 1 to 4 . The content of the ethylenically unsaturated compound (B) containing one ethylenically unsaturated group is 50 to 300 parts by weight based on 100 parts by weight of the (meth) acrylic resin (A). The pressure-sensitive adhesive composition according to any one of claims 1 to 5 . The content ratio (b1: b2) of the (meth) acrylate (b1) having one dioxane skeleton and one (meth) acryloyl group to the alkyl (meth) acrylate (b2) having 8 to 30 carbon atoms in the alkyl group, respectively. The pressure-sensitive adhesive composition according to any one of claims 2 to 6 , wherein b1: b2 = 5: 100 to 100: 100 in weight ratio. Adhesive characterized by comprising the crosslinked product of the pressure-sensitive adhesive composition according to any one of claims 1-7. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to claim 8 . The pressure-sensitive adhesive sheet according to claim 9 , wherein the pressure-sensitive adhesive layer has a thickness of 50 to 3000 µm. A double-sided pressure-sensitive adhesive sheet, comprising a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to claim 8 . A pressure-sensitive adhesive for a transparent electrode, comprising the pressure-sensitive adhesive according to claim 8 . A touch panel comprising a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive for a transparent electrode according to claim 12 . An image display device comprising an adhesive layer containing the adhesive according to claim 8 .