JP7390281B2 - Double-sided adhesive sheet and its uses - Google Patents

Description

The present invention relates to a double-sided pressure-sensitive adhesive sheet, a method for manufacturing the same, and uses thereof.

2. Description of the Related Art Adhesive sheets (adhesive tapes) have been widely used for fixing parts of OA equipment and electronic equipment. In recent years, office automation equipment and electronic equipment have become lighter, thinner, and smaller, and adhesive sheets used for fixing these parts are also required to be thinner.

It is generally believed that the thinner the adhesive sheet, the weaker the adhesive strength, but the market is demanding thinner and stronger adhesive sheets. On the other hand, as parts become lighter, thinner, shorter and smaller, their strength decreases, and parts breakage during re-adhesion has become an issue, and there is a need for tapes that have strong adhesion and are suitable for re-application.

As an adhesive sheet for fixing parts of OA equipment and electronic equipment, for example, Patent Document 1 discloses an adhesive tape having an adhesive layer on at least one surface of a base material, which has a thickness of 25 mm in the thickness direction of the base material. An adhesive tape is described which has a % compressive strength of 300 kPa or less, a total thickness of 250 μm or less, and a probe tack of 2.0 N/cm ² or more.

Further, Patent Document 2 describes a double-sided adhesive sheet for fixing members constituting portable electronic devices, which is an acrylic adhesive sheet having as a base polymer an acrylic polymer containing 9 to 30% by mass of structural units derived from polar monomers. A double-sided pressure-sensitive adhesive sheet is disclosed that includes a acrylic pressure-sensitive adhesive layer, and the thickness of the acrylic pressure-sensitive adhesive layer is 280 μm or more.

JP2016-89145A Japanese Patent Application Publication No. 2015-147873

However, in both Patent Documents 1 and 2, although they are thin films, they do not mention the characteristics of having strong adhesiveness and being able to be reattached.

The present invention has been made in view of the above problems, and by applying an adhesive layer obtained from an adhesive composition having a predetermined composition to a double-sided adhesive sheet having on both sides of a core material, a thin film can be obtained. However, it has been found that the above-mentioned problems can be solved by having a strong adhesive force, suppressing adhesion acceleration, and being suitable for re-adhesion.

That is, the present invention includes the following.
[1] An adhesive consisting of an adhesive composition containing 100 parts by mass of a (meth)acrylic copolymer, 40 to 70 parts by mass of a tackifying resin, and 0.01 to 5 parts by mass of a crosslinking agent. A double-sided adhesive sheet having layers on both sides of a core material, wherein the thickness of the core material is 1 to 12 μm, and the thickness of the adhesive layers on both sides of the core material is 1 to 12 μm, A double-sided adhesive sheet that satisfies the following conditions (i) and (ii).
(i) The adhesive force A of the adhesive layer is 1000 to 1600 g/25 mm when measured after the adhesive surface of the adhesive layer is attached to a SUS plate and left in an environment of 25° C./50% RH for 20 minutes.
(ii) Adhesive force B/adhesive force A when the adhesive surface of the adhesive layer is attached to a SUS board and the adhesive force is measured after being left in a 25°C/50% RH environment for 24 hours. The value is 1.00 or more and 1.25 or less.
[2] The double-sided pressure-sensitive adhesive sheet according to item [1], wherein the tackifying resin contains a styrene-based tackifying resin and a rosin-based tackifying resin.
[3] The double-sided pressure-sensitive adhesive sheet according to item [2], wherein the content of the styrene-based tackifying resin is greater than the content of the rosin-based tackifying resin.
[4] The double-sided adhesive according to item [3] above, wherein the content of the styrene-based tackifying resin is 20 to 35 parts by mass, and the content of the rosin-based tackifying resin is 18 to 32 parts by mass. sheet.
[5] The double-sided adhesive according to item [4] above, wherein the content of the styrene-based tackifying resin is 27 to 35 parts by mass, and the content of the rosin-based tackifying resin is 26 to 30 parts by mass. sheet.
[6] The double-sided pressure-sensitive adhesive sheet according to any one of [1] to [5] above, which is a double-sided pressure-sensitive adhesive sheet for a heat dissipation sheet.
[7] The double-sided adhesive sheet according to any one of [1] to [5] above, which is a double-sided adhesive sheet for light-shielding tape.

Although the double-sided adhesive sheet of the present invention is a thin film, it has strong adhesive strength, suppresses adhesion acceleration, and is suitable for repositioning. Therefore, the double-sided adhesive sheet of the present invention can contribute to the miniaturization of electronic devices, and when used for electronic components, it can firmly connect components to each other, and when it needs to be reattached, it can be peeled off from the component without causing damage. be able to.

The present invention will be described in detail below, but the present invention is not limited to the description of the embodiments of the invention.

The double-sided pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive composition containing 100 parts by mass of a (meth)acrylic copolymer, 40 to 70 parts by mass of a tackifying resin, and 0.01 to 5 parts by mass of a crosslinking agent. A double-sided adhesive sheet having adhesive layers on both sides of a core material, wherein the thickness of the core material is 1 to 12 μm, and the thickness of the adhesive layers on both sides of the core material is 1 to 12 μm, respectively. It is a double-sided pressure-sensitive adhesive sheet characterized by having a thickness of 12 μm and satisfying the following conditions (i) and (ii).
(i) The adhesive force A of the adhesive layer is 1000 to 1600 g/25 mm when measured after the adhesive surface of the adhesive layer is attached to a SUS plate and left in an environment of 25° C./50% RH for 20 minutes.
(ii) Adhesive force B/adhesive force A when the adhesive surface of the adhesive layer is attached to a SUS board and the adhesive force is measured after being left in a 25°C/50% RH environment for 24 hours. The value is 1.00 or more and 1.25 or less.
The configuration will be specifically explained below.

[(meth)acrylic copolymer]
A (meth)acrylic copolymer is a monomer in which at least one of the monomers constituting the copolymer has a (meth)acryloyl group, such as (meth)acrylate, etc. It means a copolymer obtained by polymerizing a monomer having a (meth)acryloyl group and a monomer component having copolymerizability with the monomer.
Examples of monomer components forming the (meth)acrylic copolymer include (meth)acrylate, which will be described later, and a crosslinkable group-containing monomer copolymerizable therewith.

In addition, in this specification, "(meth)acrylic" means to include both "acrylic" and "methacrylic", and "(meth)acrylate" includes both "acrylate" and "methacrylate". "(meth)acryloyl" is meant to include both "acryloyl" and "methacryloyl".

(Meth)acrylates include alkyl (meth)acrylates, alicyclic (meth)acrylates, aryl (meth)acrylates, aralkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, alkoxypolyalkylene glycol mono(meth)acrylates, Examples include aryloxyalkyl (meth)acrylates.

Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl ( meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, undecyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate, Isostearyl (meth)acrylate is mentioned.

Examples of alicyclic (meth)acrylates include cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate and 4-tert-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate. It will be done.

Examples of aryl (meth)acrylate include phenyl (meth)acrylate, and examples of aralkyl (meth)acrylate include benzyl (meth)acrylate.

Examples of alkoxyalkyl (meth)acrylates include methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, and 3-ethoxypropyl (meth)acrylate. Examples include meth)acrylate, 4-methoxybutyl(meth)acrylate, and 4-ethoxybutyl(meth)acrylate.

Examples of the alkoxy polyalkylene glycol mono(meth)acrylate include methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, ethoxytriethylene glycol mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, Methoxytriethylene glycol mono(meth)acrylate is mentioned.

Examples of the aryloxyalkyl (meth)acrylate include phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-tolyloxyethyl (meth)acrylate, xyloxymethyl (meth)acrylate, and naphthyloxymethyl. (Meth)acrylates are mentioned.

One type of (meth)acrylate may be used alone, or two or more types may be used.

The amount of (meth)acrylate used in 100% by mass of the monomer components used to form the (meth)acrylic copolymer is preferably 65% by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass. ~99% by mass. Such an embodiment is preferable from the viewpoint of the adhesive strength of the resulting pressure-sensitive adhesive layer and the suppression of adhesion acceleration. Further, it is preferable that 60% by mass or more of the 100% by mass of (meth)acrylate is alkyl (meth)acrylate.

Examples of the crosslinkable group-containing monomer include carboxyl group-containing monomers and hydroxyl group-containing monomers.

Examples of the carboxyl group-containing monomer include (meth)acrylic acid, β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, crotonic acid, maleic acid, and fumaric acid.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Hydroxy-3-phenoxypropyl (meth)acrylate is mentioned.

The crosslinkable group-containing monomers may be used alone or in combination of two or more.

The amount of the crosslinkable group-containing monomer used in 100% by mass of the monomer components used to form the (meth)acrylic copolymer is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass. % by mass, more preferably 1 to 8% by mass. In this embodiment, an appropriate crosslinked structure can be formed by the reaction between the (meth)acrylic copolymer and the crosslinking agent described below.

The monomer component may further contain other monomers than the (meth)acrylate and the crosslinkable group-containing monomer.

Other monomers include, for example, amino group-containing monomers, amide group-containing monomers, glycidyl group-containing monomers, vinyl group-containing monomers, and polymerizable macromonomers.

Examples of amino group-containing monomers include dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; examples of amide group-containing monomers include (meth)acrylamide, N-methyl(meth)acrylamide, and N-methyl(meth)acrylamide. -ethyl (meth)acrylamide; examples of glycidyl group-containing monomers include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether; examples of vinyl group-containing monomers include, for example, vinyl acetate , ethylene, propylene, isobutylene, vinyl chloride, styrene, α-methylstyrene, butadiene, isoprene, and chloroprene.

As the polymerizable macromonomer, for example, a macromonomer whose main chain constituent monomer is methyl methacrylate (product name: 45% AA-6 (AA-6S), AA-6; manufactured by Toagosei Co., Ltd.), a main chain constituent monomer A macromonomer whose main chain is butyl acrylate (product name: AB-6; manufactured by Toagosei Co., Ltd.) and a macromonomer whose main chain is a copolymer of styrene/acrylonitrile (product name: AN-6S; manufactured by Toagosei Co., Ltd.) Can be mentioned.

Other monomers may be used alone or in combination of two or more.

The amount of other monomers used in 100% by mass of the monomer components used to form the (meth)acrylic copolymer is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass. It is as follows.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer measured by gel permeation chromatography (GPC) is not particularly limited, but is preferably 100,000 to 1,500,000, more preferably 20,000 to 1,500,000. It is from 1,200,000 to 1,200,000, more preferably from 300,000 to 1,000,000.

The molecular weight distribution (Mw/Mn) of the (meth)acrylic copolymer is preferably 20 or less, more preferably 1.5 to 18, even more preferably 1.8 to 15.

The glass transition temperature (Tg) of the (meth)acrylic copolymer is preferably less than 0°C, more preferably -80 to -10°C, even more preferably -70 to -20°C. The Tg of a (meth)acrylic copolymer can be determined by the Fox formula, and the Tg of a homopolymer formed from each monomer in the Fox formula is described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003). value can be adopted.

[Production of (meth)acrylic copolymer]
The (meth)acrylic copolymer can be produced by copolymerizing the above monomer components, and may be any of random copolymers, block copolymers, and graft copolymers. The (meth)acrylic copolymer can be produced by conventionally known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization, among which solution polymerization is preferred. .

Specifically, in the solution polymerization method, monomer components, a polymerization initiator, and other components such as a chain transfer agent and a polymerization solvent as necessary are charged into a reaction vessel, and the reaction initiation temperature is set at 40 to 100°C. , the reaction system is maintained at a temperature of 50 to 90° C. and reacted for 2 to 20 hours. The reaction is carried out under an inert gas atmosphere such as nitrogen gas. Further, during the polymerization reaction, at least one selected from monomer components, polymerization initiators, chain transfer agents, and polymerization solvents may be additionally added.

Examples of the polymerization initiator include thermal polymerization initiators such as azo initiators and peroxide polymerization initiators.
Examples of azo initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2- cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carboxylic acid), nitrile), 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'- Azobis(N,N'-dimethyleneisobutyramidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutyramide) dihydrate, 4 , 4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-cyanopropanol), and dimethyl-2,2'-azobis(2-methylpropionate).

Examples of peroxide-based polymerization initiators include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, and di-i-propyl peroxide. carbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxybivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-bis(4,4 -di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxy) cyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane.

One type of polymerization initiator may be used alone, or two or more types may be used in combination.

In the production of (meth)acrylic copolymers, the amount of polymerization initiator used is usually 0.001 to 5 parts by weight, preferably 0.005 to 3 parts by weight, based on a total of 100 parts by weight of monomer components. It is.

Examples of the polymerization solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; cyclopentane, cyclohexane, cycloheptane, and cyclopentane; Alicyclic hydrocarbons such as octane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, diphenyl ether; chloroform, carbon tetrachloride, 1,2- Halogenated hydrocarbons such as dichloroethane and chlorobenzene; Esters such as ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; Ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; N,N-dimethylformamide, N , N-dimethylacetamide, N-methylpyrrolidone; nitriles such as acetonitrile, benzonitrile; and sulfoxides such as dimethyl sulfoxide and sulfolane.
One type of polymerization solvent may be used alone, or two or more types may be used.

[Tackifying resin]
The adhesive composition used in the double-sided adhesive sheet of the present invention contains a tackifier resin. The tackifying resin is not particularly limited as long as it is a material that can impart tackiness to the adhesive composition. Examples of the tackifier resin include styrene tackifier resins, rosin tackifier resins such as rosin ester resins, terpene tackifier resins such as terpene phenol resins, and alicyclic saturated hydrocarbon resins.

[Styrenic tackifier resin]
The styrenic tackifier resin contained in the adhesive composition is not particularly limited. Examples of the styrene-based tackifying resin include styrene-based and substituted styrene-based petroleum resins.

Specific examples of styrene-based tackifying resins include FMR-0150, FTR-0100, FTR-2120, FTR-2140, FTR-6100, FTR-6110, FTR-6125, FTR-7100, FTR-8100, FTR -8120 is mentioned. The above products are manufactured by Mitsui Chemicals, Inc. Another example is YS Resin SX-100 (manufactured by Yasuhara Chemical Co., Ltd.).

[Rosin-based tackifier resin]
The rosin-based tackifying resin contained in the pressure-sensitive adhesive composition is not particularly limited, but a rosin ester-based tackifying resin is usually used.

Specific examples of rosin ester resins include Super Ester A75, Super Ester A100, Super Ester A115, Super Ester A125, Pine Crystal KE-100, Pine Crystal KE-311, Pine Crystal KE-359, Pine Crystal KE- 604, Ester Gum AT, Ester Gum H, Ester Gum HP, Pencel D-125, Pencel D-135, and Pencel D-160. The above products are manufactured by Arakawa Chemical Industry Co., Ltd.

Further examples include Harriestar TF, Harriestar S, Harrietac 8LJA, Harrietac ER95, Harrietac SE10, Harrietac PH, Harrietac F85, Harrietac F105, Harrietac FK100, and Harrietac PCJ. The above products are manufactured by Harima Kasei Co., Ltd.

[Terpene-based tackifier resin]
Examples of terpene-based tackifying resins include YS Resin PX800, YS Resin PX1000, YS Resin PX1150, YS Resin PX1250, YS Polyster U115, YS Polyster U130, YS Polyster UH115, YS Polyster T80, YS Polyster T100, YS Polyster T115, Examples include YS Polyster T130, YS Polyster T145, and YS Polyster T160. The above products are manufactured by Yasuhara Chemical Co., Ltd. Also included are Tamanol 803L and Tamanol 901 (manufactured by Arakawa Chemical Industry Co., Ltd.).

[Alicyclic saturated hydrocarbon resin]
Examples of the alicyclic saturated hydrocarbon resin include Alcon P-90, Alcon P-100, Alcon P-115, Alcon P-125, Alcon P-135, Alcon M-90, Alcon M-100, Alcon M- 115 is mentioned. The above products are manufactured by Arakawa Chemical Industry Co., Ltd.

The tackifier resin may be used alone or in combination of two or more, but it is preferable that at least one of the styrene tackifier resin and the rosin tackifier resin is included. It is more preferable to use the imparting resin and the rosin-based tackifying resin together.

In the adhesive composition of the present invention, the tackifying resin is preferably contained in an amount of 40 to 70 parts by weight, more preferably 45 to 65 parts by weight, based on 100 parts by weight of the (meth)acrylic copolymer. If it is 40 parts by mass or more, a predetermined adhesive layer strength can be obtained, so that physical properties such as adhesive force can be exhibited, and if it is 70 parts by mass or less, the uniformity of the adhesive component can be maintained. When using a plurality of tackifier resins, the composition of the adhesive composition may be adjusted so that the total number of tackifier resins falls within the above range.

The content of the styrene-based tackifying resin when using the styrene-based tackifying resin and the rosin-based tackifying resin together is not particularly limited, but is based on 100 parts by mass of the (meth)acrylic copolymer. The amount is preferably 20 to 38 parts by weight, more preferably 23 to 35 parts by weight, and still more preferably 27 to 35 parts by weight. If it is 20 parts by mass or more, it is possible to suppress component breakage during reattachment, and if it is 38 parts by mass or less, the styrenic tackifier resin, which is relatively poorly compatible, can be uniformly dissolved in the adhesive composition. In addition, dullness of the adhesive layer made of the resulting adhesive composition can be prevented.

The content of the rosin tackifier resin is not particularly limited, but is preferably 18 to 32 parts by mass, more preferably 20 to 30 parts by mass, based on 100 parts by mass of the (meth)acrylic copolymer. Parts by weight, more preferably 26 to 30 parts by weight. If it is 18 parts by mass or more, strong adhesiveness can be achieved, and if it is 32 parts by mass or less, it is possible to suppress component breakage during reattachment.

Further, the content of the styrene-based tackifying resin relative to the content of the rosin-based tackifying resin is not particularly limited, but the content of the styrene-based tackifying resin is greater than the content of the rosin-based tackifying resin. It is preferable. If the amount of the styrene-based tackifier resin is greater than the rosin-based tackifier resin, it becomes easier to maintain the relationship of adhesive force B/adhesive force A described below while maintaining strong adhesive force.

[Crosslinking agent]
The crosslinking agent contained in the adhesive composition is reactive with the crosslinkable group that the (meth)acrylic copolymer has.

Examples of the crosslinking agent include isocyanate compounds, epoxy compounds, and metal chelate compounds.

As the isocyanate compound, an isocyanate compound having two or more isocyanate groups in one molecule is usually used, preferably 2 to 8, more preferably 3 to 6. When the number of isocyanate groups is within the above range, it is preferable in terms of the crosslinking reaction efficiency between the (meth)acrylic copolymer and the isocyanate compound and in maintaining the flexibility of the adhesive layer.

Examples of the diisocyanate compound having two isocyanate groups in one molecule include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl Examples include aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate. Examples of alicyclic diisocyanates include alicyclic diisocyanates having 7 to 30 carbon atoms, such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate. Diisocyanates are mentioned. Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms, such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.

Examples of the isocyanate compound having three or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4',4''-triphenylmethane triisocyanate.

Examples of the isocyanate compound include multimers (e.g., dimer, trimer, biuret, isocyanurate), derivatives (e.g., polyhydric alcohol and addition reaction products with two or more molecules of diisocyanate compounds) and polymers. Examples of the polyhydric alcohol in the derivative include low molecular weight polyhydric alcohols such as trihydric or higher alcohols such as trimethylolpropane, glycerin, and pentaerythritol; high molecular weight polyhydric alcohols such as polyether polyol, Examples include polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

Such isocyanate compounds include, for example, trimer of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, biuret or isocyanurate of hexamethylene diisocyanate or tolylene diisocyanate, trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate. reaction products of trimethylolpropane and hexamethylene diisocyanate (e.g. trimolecular adducts of hexamethylene diisocyanate), polyether polyisocyanates, Examples include polyester polyisocyanates.

Among the isocyanate compounds, xylylene diisocyanate-based and hexamethylene diisocyanate-based crosslinking agents are preferred from the viewpoint of resistance to yellowing, and tolylene diisocyanate-based crosslinking agents are preferred from the viewpoint of stress relaxation properties. Examples of xylylene diisocyanate-based crosslinking agents include xylylene diisocyanate and its multimers, derivatives, and polymers; examples of hexamethylene diisocyanate-based crosslinking agents include hexamethylene diisocyanate and its multimers, derivatives, and polymers. Examples of tolylene diisocyanate-based crosslinking agents include tolylene diisocyanate, polymers, derivatives, and polymers thereof.

Examples of epoxy compounds include compounds having two or more epoxy groups in the molecule, such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexane. Diol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidyl aminomethyl) Examples include cyclohexane and 1,3-bis(N,N-diglycidylaminomethyl)benzene.

Examples of metal chelate compounds include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium, coordinated with alkoxides, acetylacetone, ethyl acetoacetate, etc. Examples include compounds. Specific examples include aluminum isopropylate, aluminum secondary butyrate, aluminum ethyl acetoacetate diisopropylate, aluminum tris ethyl acetoacetate, and aluminum tris acetylacetonate.

One type of crosslinking agent may be used alone, or two or more types may be used.

In the adhesive composition of the present invention, the crosslinking agent is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably contains 1 to 2.5 parts by mass. With such an embodiment, excellent adhesive properties can be achieved.

[Additive]
The adhesive composition used in the double-sided adhesive sheet of the present invention contains various additives such as a silane coupling agent, an organopolysiloxane compound, a pigment, a flame retardant, a plasticizer, an antistatic agent, a lubricant, and a filler. Good too. The content of the additive is not particularly limited, but the content should be within a range that does not impair the properties of the double-sided pressure-sensitive adhesive sheet of the present invention and the pressure-sensitive adhesive composition used in the double-sided pressure-sensitive adhesive sheet.

[Organic solvent]
The adhesive composition used in the double-sided adhesive sheet of the present invention may contain an organic solvent in order to adjust coating properties. Examples of the organic solvent include the polymerization solvents described in the section on manufacturing conditions for (meth)acrylic copolymers. The content of the organic solvent in the adhesive composition is usually 30 to 90% by weight, preferably 40 to 90% by weight.

[Adhesive composition]
The adhesive composition used in the double-sided adhesive sheet of the present invention contains 40 to 65 parts by mass of a tackifying resin and 0.01 to 5 parts by mass of a crosslinking agent, based on 100 parts by mass of a (meth)acrylic copolymer. It can be prepared by mixing these. In addition, the adhesive composition may contain other components.

[Double-sided adhesive sheet]
The double-sided pressure-sensitive adhesive sheet of the present invention includes a core material and pressure-sensitive adhesive layers (a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer) formed on both sides of the core material. Therefore, the double-sided adhesive sheet of the present invention has a structure of at least three layers. Furthermore, a release film may be attached to the surface of the adhesive layer that is not in contact with the core material.

[Core material]
The double-sided adhesive sheet of the present invention includes a core material. The core material used in the double-sided adhesive sheet of the present invention has a thickness of 1 to 12 μm. If it is 1 μm or more, appropriate sheet strength can be obtained, and if it is 12 μm or less, adhesion enhancement can be suppressed.

The core material and release film include polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), Examples include plastic films such as ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer (ABS), polyamide (nylon), polyimide, and polyvinyl chloride (PVC). Further, examples of the core material include glass, paper, and nonwoven fabric. In addition, from the viewpoint of strength and ease of handling, it is preferable that the core material is PET.
When the double-sided pressure-sensitive adhesive sheet of the present invention is used as a light-shielding tape, a core material in which a black coloring material such as a black pigment or a white coloring material such as a white pigment is dispersed may be used.

[Adhesive layer]
The adhesive layers provided on both sides of the core material can be formed from an adhesive composition. The adhesive layers on both sides of the core material may be the same or different.
One adhesive layer has a thickness of 1 to 12 μm. If it is 1 μm or more, a double-sided pressure-sensitive adhesive sheet with appropriate adhesive strength can be obtained, and if it is 12 μm or less, adhesion enhancement can be suppressed.

In addition, the gel fraction of the adhesive layer is preferably 10 to 98% by mass, more preferably 20 to 90% by mass, and even more preferably 30 to 85% by mass, from the viewpoint of cohesive force, adhesive strength described below, and suitability for reattachment. %.

[Adhesive strength A]
The double-sided adhesive sheet of the present invention has an adhesive strength A of 1000 to 1600 g/25 mm when measured after the adhesive side of the adhesive layer is attached to a SUS board and left in an environment of 25°C/50% RH for 20 minutes. has. Having such characteristics indicates that the double-sided adhesive sheet has strong initial adhesive strength. Details of the measurement conditions are described in Examples.

[Adhesive force B/Adhesive force A]
The double-sided pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive force B when the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer is attached to a SUS plate and is measured after being left in an environment of 25°C/50%RH for 24 hours. It has a characteristic that the ratio of adhesive force A (adhesive force B/adhesive force A) is 1.00 or more and 1.25 or less. The conditions for measuring the adhesive force B are described in Examples.

Adhesive force B is the adhesive force measured after being left for 24 hours after application, and therefore is usually higher than adhesive force A. However, in the double-sided pressure-sensitive adhesive sheet of the present invention, since the adhesive force B/adhesive force A is 1.00 or more and 1.25 or less, the rate of increase in adhesive force is not high and adhesion acceleration can be suppressed. That is, the double-sided pressure-sensitive adhesive sheet of the present invention has high repositioning properties and can suppress component breakage due to repositioning.

[Application]
As described above, the double-sided pressure-sensitive adhesive sheet of the present invention has strong adhesive strength despite being a thin film, suppresses adhesion acceleration, and is suitable for repositioning, and can be used for various purposes. For example, a heat dissipation sheet or a light-shielding tape can be attached to a target article using the double-sided pressure-sensitive adhesive sheet of the present invention. The heat dissipation sheet and light shielding tape will be explained below.

- Heat dissipation sheet By installing a heat dissipation sheet in a localized high temperature area, heat can be dissipated to the entire surface of OA equipment or electronic equipment. Examples of the graphite sheet used for the heat dissipation sheet include a natural graphite sheet obtained by forming natural graphite powder into a sheet, and an artificial graphite sheet obtained by heat-treating a polymer film.
Examples of the polymer film include polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene vinylene, polybenzimidazole, polybenzobisimidazole, poly Examples include films made of thiazole and the like.
The thickness of the graphite sheet is preferably 10 to 100 μm, more preferably 15 to 50 μm. By setting the thickness of the graphite sheet within the above range, it can be suitably used for fixing parts of office automation equipment and electronic equipment.

- Light-shielding tape A light-shielding tape can be used, for example, to attach a non-self-luminous display unit such as a liquid crystal display module unit to a backlight unit, thereby preventing problems caused by leakage of light.

[Method for manufacturing double-sided adhesive sheet]
The double-sided adhesive sheet of the present invention can be manufactured as follows.
The adhesive composition is coated on one side of the release film so that the thickness after drying is 1 to 12 μm, and the solvent is removed by drying, usually at 60 to 100° C., for 1 to 10 minutes. Thereafter, the obtained adhesive layer is attached to one side of a core material having a thickness of 1 to 12 μm (referred to as the first surface of the core material).

Next, a pressure-sensitive adhesive composition is applied to one side of another release film so that the thickness after drying is 1 to 12 μm. Then, the adhesive layer obtained by drying at 60 to 100°C for 1 to 10 minutes and removing the solvent is placed on the side of the core material to which the adhesive layer is not attached (the second side of the core material). A double-sided adhesive sheet is manufactured by laminating the two sheets together.
The coating method is not particularly limited, and conventionally known methods can be used. Examples of methods for applying the adhesive composition include methods using a roll coater, fountain coater, lip coater, knife coater, die coater, gravure coater, reverse coater, curtain coater, slit die coater, and the like.
Note that the adhesive layer formed on the first surface and the adhesive layer formed on the second surface may be the same or different.

Examples will be described below, but the present invention is not limited to the examples.

(Production example: Preparation of adhesive composition)
97 parts by mass of n-BA (n-butyl acrylate), 2 parts by mass of AA (acrylic acid), and 1 part by mass of 2HEA (2-hydroxyethyl acrylate) were placed in a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube. Parts by mass and 80 parts by mass of ethyl acetate were charged, and the temperature was raised to 75° C. while introducing nitrogen gas. Next, 0.3 parts by mass of azobisisobutyronitrile was added, and the reaction was carried out for 4 hours while heating and cooling were repeated so that the temperature of the contents in the flask could be maintained at 75 to 76°C. After the reaction was completed, 20 parts by mass of ethyl acetate was further added to obtain a (meth)acrylic copolymer having a weight average molecular weight (Mw) of 850,000.
For 100 parts by mass of the solid content of the (meth)acrylic copolymer, 35 parts by mass of styrene tackifier resin (FTR-6100: manufactured by Mitsui Chemicals, Inc.), rosin tackifier resin (D-135: Arakawa) 30 parts by mass (manufactured by Kagaku Kogyo Co., Ltd.) and 1.5 parts by mass (solid content) of an isocyanate-based crosslinking agent (L-45: manufactured by Soken Kagaku Co., Ltd.) were mixed to obtain an adhesive composition.

(Example 1: Double-sided adhesive sheet and its production)
The adhesive composition was coated on a release film so that the thickness after drying was 5 μm, dried at 90°C for 3 minutes, and bonded to a 2 μm thick PET film (core material) (first surface adhesive). agent layer formation). Furthermore, a sheet with an adhesive layer, which was coated with the adhesive composition on a release film to a dry thickness of 5 μm and dried at 90°C for 3 minutes, was coated with the adhesive layer on the first side of the PET film. A double-sided pressure-sensitive adhesive sheet (Example 1) was produced by bonding it to the unbonded side (second side pressure-sensitive adhesive layer formation).

(Examples 2 to 6 and Comparative Examples 1 to 3)
Various double-sided adhesive sheets (Examples 2 to 6 and comparative Examples 1 to 3) were obtained.

<Measurement/Evaluation>
The conditions for measuring the weight average molecular weight, adhesive force A, and adhesive force B of the (meth)acrylic copolymers used in Examples 1 to 6 and Comparative Examples 1 to 3 are described below.
(Weight average molecular weight (Mw))
Regarding the (meth)acrylic copolymer, the weight average molecular weight (Mw) in terms of standard polystyrene was determined by gel permeation chromatography (GPC) under the following conditions.
・Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)
・GPC column configuration: The following 5 columns (all manufactured by Tosoh Corporation)
(1) TSK-GEL HXL-H (guard column)
(2) TSK-GEL G7000HXL
(3) TSK-GEL GMHXL
(4) TSK-GEL GMHXL
(5)TSK-GEL G2500HXL
・Sample concentration: Diluted with tetrahydrofuran to 1.0 mg/cm ³・Mobile phase solvent: Tetrahydrofuran ・Flow rate: 1.0 cm ³ /min
・Column temperature: 40℃

(Adhesive force A and adhesive force B)
The release film on the first adhesive layer side of the double-sided adhesive sheets obtained in Examples and Comparative Examples was peeled off, the exposed entire surface of the adhesive layer was bonded to a 50 μm thick PET film, and cut into 25 mm x 150 mm. A test piece was prepared. Next, the release film on the second adhesive layer side was peeled off, and the exposed adhesive layer was bonded to an SUS plate, and a roller weighing 2 kg was moved back and forth three times to press it. After crimping, the test piece was left in an environment of 25° C./50% RH for 20 minutes, and then the end of the test piece was pulled at a speed of 300 mm/min in a 180° direction with respect to the PET film surface, and the adhesive force A was measured.
In addition, the adhesive force B was measured in the same manner as the adhesive force A measurement except that the adhesive force was left in a 25° C./50% RH environment for 24 hours after pressure bonding.

Although the double-sided pressure-sensitive adhesive sheets of the examples were all thin films, they had high initial adhesive strength and were able to suppress adhesion acceleration, indicating that they were suitable for reapplying. The double-sided adhesive sheets of Comparative Example 1, in which the amount of tackifying resin used was less than 40 parts by mass, and Comparative Example 2, in which the thickness of the core material exceeded 12 μm, had low initial adhesive strength, and the adhesive layer thickness was 12 μm. The double-sided pressure-sensitive adhesive sheet of Comparative Example 3 in which the adhesive strength was exceeded was unable to suppress adhesion.

Claims (5)

100 parts by mass of (meth)acrylic copolymer, 23 to 35 parts by mass of styrene tackifying resin, 18 to 32 parts by mass of rosin tackifying resin, and 0.01 to 5 parts by mass of crosslinking agent. A double-sided adhesive sheet having adhesive layers on both sides of a core material made of an adhesive composition containing,
The (meth)acrylic copolymer is a copolymer of monomer components containing 92 to 97% by mass of n-butyl acrylate and 3 to 8% by mass of a carboxyl group-containing monomer and a hydroxyl group-containing monomer, and n - the total content of butyl acrylate, carboxyl group-containing monomers and hydroxyl group-containing monomers is 100%,
The thickness of the core material is 1 to 12 μm, the thickness of the adhesive layer on both sides of the core material is 1 to 12 μm, and the following conditions (i) and (ii) are satisfied. Double-sided adhesive sheet.
(i) The adhesive force A of the adhesive layer is 1000 to 1600 g/25 mm when measured after the adhesive surface of the adhesive layer is attached to a SUS plate and left in an environment of 25° C./50% RH for 20 minutes.
(ii) Adhesive force B/adhesive force A when the adhesive surface of the adhesive layer is attached to a SUS board and the adhesive force is measured after being left in a 25°C/50% RH environment for 24 hours. The value is 1.00 or more and 1.25 or less. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the content of the styrene-based tackifying resin is greater than the content of the rosin-based tackifying resin. The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the content of the styrene-based tackifying resin is 27 to 35 parts by mass, and the content of the rosin-based tackifying resin is 26 to 30 parts by mass. The double-sided adhesive sheet according to any one of claims 1 to 3, which is a double-sided adhesive sheet for a heat dissipation sheet. The double-sided adhesive sheet according to any one of claims 1 to 3, which is a double-sided adhesive sheet for light-shielding tape.