JP7256809B2 - Adhesive composition and adhesive tape - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition and an adhesive tape provided with an adhesive layer comprising the adhesive composition.

BACKGROUND ART Conventionally, adhesive tapes have been widely used for fixing parts of OA equipment and electronic equipment. In recent years, OA equipment and electronic equipment have become lighter, thinner, shorter, and smaller, and adhesive tapes used for fixing these parts are also required to be thinner.

However, the adhesive strength of the adhesive tape generally decreases as the thickness of the adhesive layer decreases. Especially in a region where the thickness of the pressure-sensitive adhesive layer is 10 µm or less, the pressure-sensitive adhesive strength is significantly reduced. For this reason, it is difficult to develop a sufficiently strong adhesive force even under thin film conditions, and there is a strong demand for the development of an adhesive tape that is thin but has a high adhesive force.

Patent Document 1 discloses an adhesive composition for thin films in which 40% by mass to 60% by mass of a tackifying resin is added to the adhesive, forming an adhesive layer of 2 to 10 μm.
However, the tackifying resin used in the examples of Patent Document 1 is a rosin-based resin. Generally, rosin-based resins are yellow to orange, and the color of the sheet may be a problem. In addition, since the compatibility with the acrylic pressure-sensitive adhesive is poor, the adhesive strength cannot be greatly improved, and haze may become a problem.
Moreover, many rosin-based resins have carboxyl groups and hydroxyl groups in their structures, which may inhibit cross-linking between adhesives. For this reason, if a large amount of rosin-based resin is used, the holding power and constant-load peelability may deteriorate.

Patent Document 2 discloses a pressure-sensitive adhesive composition containing a (meth)acrylic polymer derived from n-butyl acrylate, a tackifying resin, and a cross-linking agent. Since the average molecular weight is 500,000, the adhesive strength is not high, and since the tackifying resin used is a rosin-based resin, it is presumed that the color is not preferable.

JP 2007-169327 A JP 2012-162703 A

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a pressure-sensitive adhesive composition that has high adhesive strength and exhibits high adhesiveness even when the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape used is thin.

That is, the present invention includes the following.
[1] A pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) having a weight average molecular weight of 700,000 or more and a synthetic hydrocarbon-based tackifying resin (B),
(Meth)acrylic polymer (A) is a polymer obtained by polymerizing a monomer containing 60% by mass or more of n-butyl (meth)acrylate (a1),
The content of the synthetic hydrocarbon-based tackifying resin (B) is 40% by mass or more and 60% by mass or less with respect to the total mass of the (meth)acrylic polymer (A) and the synthetic hydrocarbon-based tackifying resin (B). A pressure-sensitive adhesive composition characterized by:
[2] The pressure-sensitive adhesive composition according to [1], wherein the synthetic hydrocarbon-based tackifying resin (B) is a styrene-based resin.
[3] The pressure-sensitive adhesive composition according to [1] or [2], which contains a cross-linking agent.
[4] The (meth)acrylic polymer (A) is a polymer obtained by polymerizing a monomer containing a (meth)acrylic monomer containing 80% by mass or more of n-butyl (meth)acrylate, [1] to [ 3], the pressure-sensitive adhesive composition according to any one of items.
[5] Any one of [1] to [4], containing 0.01 to 3.0 parts by mass of a silane coupling agent with respect to 100 parts by mass of the resin solid content of the adhesive composition The adhesive composition described.
[6] A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of [1] to [5].
[7] The pressure-sensitive adhesive tape according to [6], wherein pressure-sensitive adhesive layers are provided on both sides of the substrate.
[8] The pressure-sensitive adhesive tape of [6] or [7], which has a total thickness of 25 μm or less excluding the release film.
[9] The pressure-sensitive adhesive tape according to any one of [6] to [8], wherein the pressure-sensitive adhesive layer accounts for 40% or more of the total thickness excluding the release film.
[10] The pressure-sensitive adhesive tape according to any one of [6] to [9], which is for fixing members of electronic equipment.

ADVANTAGE OF THE INVENTION The adhesive composition of this invention can provide an adhesive tape with high adhesiveness. Furthermore, since even a thin adhesive tape exhibits high adhesiveness, it can be used for small OA equipment and electronic equipment.

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

[Adhesive composition]
The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) having a weight average molecular weight of 700,000 or more and a synthetic hydrocarbon-based tackifying resin (B), The (meth)acrylic polymer (A) is a polymer obtained by polymerizing a monomer containing 60% by mass or more of n-butyl (meth)acrylate (a1), and the (meth)acrylic polymer (A) and a synthetic hydrocarbon The content of the synthetic hydrocarbon-based tackifying resin (B) is 40% by mass or more and 60% by mass or less with respect to the total mass of the tackifying resin (B).
The configuration will be specifically described below.

<(Meth) acrylic polymer (A)>
The pressure-sensitive adhesive composition of the present invention contains a (meth)acrylic polymer (A). The (meth)acrylic polymer (A) is obtained by polymerizing at least n-butyl (meth)acrylate (a1) and, if necessary, a monomer copolymerizable therewith. Here, the (meth)acrylate monomer is a monomer having a (meth)acryloyl group.
Examples of monomer components forming the (meth)acrylic polymer (A) include, in addition to n-butyl (meth)acrylate (a1), monomer (a2) and monomer (a3) described later.

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

<n-Butyl (meth)acrylate (a1)>
Among the monomer components forming the (meth)acrylic polymer (A), n-butyl (meth)acrylate (a1) is 60% by mass or more, preferably 70% by mass, from the viewpoint of the heat resistance and adhesiveness of the pressure-sensitive adhesive composition. % or more, more preferably 80 mass % or more.

<Monomer (a2)>
A monomer (a2) may be further included as a monomer forming the (meth)acrylic polymer (A).
Examples of the monomer (a2) include alkyl (meth)acrylates other than n-butyl (meth)acrylate, alicyclic (meth)acrylates, aryl (meth)acrylates, aralkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, alkoxy Polyalkylene glycol mono(meth)acrylates and aryloxyalkyl(meth)acrylates can be mentioned.

Examples of alkyl (meth)acrylates other than n-butyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and 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 , and isostearyl (meth)acrylate.

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. be done.

Aryl (meth)acrylates include, for example, phenyl (meth)acrylate, and aralkyl (meth)acrylates include, for example, benzyl (meth)acrylate.

Alkoxyalkyl (meth)acrylates include, for example, methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl ( meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate.

Examples of alkoxypolyalkylene glycol mono(meth)acrylates 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.

Aryloxyalkyl (meth)acrylates include, for example, phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-tolyloxyethyl (meth)acrylate, xylyloxymethyl (meth)acrylate, naphthyloxymethyl (Meth)acrylates are mentioned.

The monomer (a2) may be used alone or in combination of two or more.

Among the monomer components forming the (meth)acrylic polymer (A), the total amount of n-butyl (meth)acrylate (a1) and monomer (a2) is preferably 70% by mass or more, more preferably 80% by mass. or more, more preferably 85% by mass.

<Monomer (a3)>
The monomer forming the (meth)acrylic polymer (A) preferably contains the monomer (a3). Monomer (a3) is a crosslinkable group-containing monomer. Examples of crosslinkable group-containing monomers include carboxyl group-containing monomers and hydroxyl group-containing monomers.

Examples of carboxyl group-containing monomers 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, 2- Hydroxy-3-phenoxypropyl (meth)acrylate can be mentioned.

The monomer (a3) may be used alone or in combination of two or more.

In the monomer component used to form the (meth)acrylic polymer (A), the amount of the monomer (a3) used is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, and further It is preferably 1 to 8% by mass. In such a mode, an appropriate crosslinked structure can be formed by the reaction between the (meth)acrylic polymer (A) and the crosslinking agent described below.

<Other monomers (a4)>
The copolymerizable monomer may further contain a monomer (a4) other than (a1) to (a3).

Other monomers (a4) 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, N -ethyl (meth)acrylamide; glycidyl group-containing monomers include, for example, glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether; vinyl group-containing monomers, such as vinyl acetate , ethylene, propylene, isobutylene, vinyl chloride, styrene, α-methylstyrene, butadiene, isoprene, and chloroprene.

Examples of polymerizable macromonomers include macromonomers in which the main chain-constituting monomer is methyl methacrylate (product names: 45% AA-6 (AA-6S), AA-6; manufactured by Toagosei Co., Ltd.), main chain-constituting monomers. is butyl acrylate (product name: AB-6; manufactured by Toagosei Co., Ltd.). mentioned.

Other monomers (a4) may be used singly or in combination of two or more.

In 100% by mass of the monomer component used to form the (meth)acrylic polymer (A), the amount of the other monomer (a4) used is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably It is 10% by mass or less.

The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) measured by gel permeation chromatography (GPC) is 700,000 or more, preferably 800,000 or more, and more Preferably it is 900,000 or more.

The (meth)acrylic polymer (A) has a molecular weight distribution (Mw/Mn) of preferably 20 or less, more preferably 1.5-18, still more preferably 1.8-15.

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

<Production of (meth)acrylic polymer (A)>
The (meth)acrylic polymer (A) can be produced by polymerizing or copolymerizing the above monomer components. The copolymer may be a random copolymer, a block copolymer or a graft copolymer, preferably a random copolymer. The (meth)acrylic polymer (A) can be produced by conventionally known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. Among these, solution polymerization is preferred. .

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

Examples of polymerization initiators 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-carbo nitrile), 2-(carbamoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′- azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) dihydrate, 4 ,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionate) and the like.

Peroxide-based polymerization initiators include, for example, t-butyl hydroperoxide, cumene hydroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propylperoxydicarbonate. , di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 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-cumylperoxycyclohexyl) ) 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 the production of the (meth)acrylic polymer (A), the amount of the polymerization initiator used is usually 0.001 to 5 parts by mass, preferably 0.005 to 3 parts by mass, with respect to 100 parts by mass of the total monomer components. 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, cyclo 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 and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethylsulfoxide and sulfolane.
One type of polymerization solvent may be used alone, or two or more types may be used.

<Synthetic hydrocarbon-based tackifying resin (B)>
The pressure-sensitive adhesive composition of the present invention contains a synthetic hydrocarbon-based tackifying resin (B). The synthetic hydrocarbon-based tackifying resin (B) is not particularly limited as long as it is a petroleum-based resin and can impart tackiness to the pressure-sensitive adhesive composition.

From the viewpoint of heat resistance, the molecular weight of the synthetic hydrocarbon-based tackifier resin (B) is preferably 800 or more, more preferably 1000 or more, and even more preferably 1100 or more. In addition, when petroleum-based adhesive resin is a polymer, it represents the weight average molecular weight (Mw).

From the viewpoint of heat resistance, the softening point of the synthetic hydrocarbon-based tackifier resin (B) is preferably 80°C or higher, more preferably 85°C or higher, and even more preferably 90°C or higher.

Examples of synthetic hydrocarbon-based tackifying resins (B) include petroleum resins, styrene-based resins, and coumarone-indene resins. Among them, a styrene resin is preferable from the viewpoint of compatibility (appearance) with an acrylic polymer containing n-butyl (meth)acrylate as a main component.

<Petroleum resin>
Petroleum resins include aliphatic (C5) petroleum resins, aromatic (C9) petroleum resins, aliphatic/aromatic copolymer (C5/C9) petroleum resins, hydrogenated products thereof (e.g., aromatic alicyclic petroleum resin obtained by hydrogenating a family petroleum resin) and the like. Specific examples of petroleum resins include, for example, Quinton A, B, R, CX series (manufactured by Nippon Zeon Co., Ltd.), Alcon P-90, Alcon P-100, Alcon P-115, Alcon P-125, Alcon P-135, Alcon M-90, Alcon M-100, Alcon M-115 (manufactured by Arakawa Chemical Industries, Ltd.), Nisseki Neopolymer L-90, 120, 130, 140, 150, 170S, S, T - REZ HA085, HA103, HA105, HA125 (manufactured by JXTG Nippon Oil & Energy Corporation).

<Styrene resin>
Styrene-based tackifying resins include, for example, styrene-based polymers, α-methylstyrene-based polymers, styrene-(α-methylstyrene)-based copolymers, styrene-aliphatic hydrocarbon-based copolymers, styrene-(α -methylstyrene)-aliphatic hydrocarbon copolymers, styrene-aromatic hydrocarbon copolymers, and the like. More specifically, for example, FMR-0150, FTR-0100, FTR-2120, FTR-2140, FTR-6100, FTR-6110, FTR-6125, FTR-7100, FTR-8100, FTR-8120 (above, Mitsui Chemicals, Inc.). YS resin SX-100 (manufactured by Yasuhara Chemical Co., Ltd.) is also included.

<Cumarone-indene resin>
Specific examples of coumarone-indene resins include coumarone G-90, V-120, and L-5 (manufactured by Nichinuri Kagaku Co., Ltd.).

The synthetic hydrocarbon-based tackifying resin (B) may be used singly or in combination of two or more, but preferably contains at least one styrene-based resin.

A tackifying resin other than the synthetic hydrocarbon-based tackifying resin (B) can be used as long as the properties are not impaired. Examples of tackifying resins other than synthetic hydrocarbon-based tackifying resins include rosin-based tackifying resins, terpene-based tackifying resins, and terpene-phenol-based tackifying resins.

In the pressure-sensitive adhesive composition of the present invention, the lower limit of the content of the synthetic hydrocarbon-based tackifying resin (B) is relative to the total amount of the (meth)acrylic polymer (A) and the synthetic hydrocarbon-based tackifying resin (B). and 40% by mass or more. In addition, the upper limit of the content of the synthetic hydrocarbon-based tackifying resin (B) is 60% by mass or less with respect to the total amount of the (meth)acrylic polymer (A) and the synthetic hydrocarbon-based tackifying resin (B). Yes, preferably 55% by mass or less. If it is 40% by mass or more, it is possible to develop physical properties such as a predetermined adhesive force, and if it is 60% by mass or less, the uniformity of the adhesive component can be maintained. When using a plurality of synthetic hydrocarbon-based tackifying resins (B), the composition of the pressure-sensitive adhesive composition may be adjusted so that the total of the tackifying resins falls within the above range.

<Crosslinking agent>
The cross-linking agent contained in the pressure-sensitive adhesive composition is reactive with the cross-linkable groups of the (meth)acrylic polymer (A).

Examples of cross-linking agents include isocyanate compounds, epoxy compounds, and metal chelate compounds.

As the isocyanate compound, an isocyanate compound having 2 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 from the viewpoint of efficiency of the cross-linking reaction between the (meth)acrylic polymer (A) and the isocyanate compound and the flexibility of the pressure-sensitive adhesive layer.

Diisocyanate compounds having two isocyanate groups per molecule include, for example, 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 Aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate can be mentioned. The alicyclic diisocyanate includes alicyclic compounds 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 can be mentioned. Examples of aromatic diisocyanates include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenylether diisocyanate, diphenylmethane diisocyanate and diphenylpropane diisocyanate.

Examples of isocyanate compounds having 3 or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples include 2,4,6-triisocyanatotoluene, 1,3,5-triisocyanatobenzene, and 4,4',4''-triphenylmethane triisocyanate.

Examples of isocyanate compounds include polymers (e.g. dimers or trimers, biuret forms, isocyanurate forms) and derivatives (e.g., polyhydric alcohols and addition reaction products with diisocyanate compounds having two or more molecules) and polymers. Examples of polyhydric alcohols in the derivatives include low-molecular-weight polyhydric alcohols, such as trimethylolpropane, glycerin, pentaerythritol, and other trihydric or higher alcohols; high-molecular-weight polyhydric alcohols, such as polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, and polyisoprene polyols.

Examples of such isocyanate compounds include trimers of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, biuret or isocyanurate of hexamethylene diisocyanate or tolylene diisocyanate, trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate. (e.g. trimolecular adducts of tolylene diisocyanate or xylylene diisocyanate), reaction products of trimethylolpropane with hexamethylene diisocyanate (e.g. trimolecular adducts of hexamethylene diisocyanate), polyether polyisocyanates, Polyester polyisocyanates are mentioned.

Among isocyanate compounds, xylylene diisocyanate-based and hexamethylene diisocyanate-based cross-linking agents are preferable from the viewpoint of yellowing resistance, and tolylene diisocyanate-based cross-linking agents are preferable from the viewpoint of stress relaxation. Xylylene diisocyanate-based cross-linking agents include, for example, xylylene diisocyanate, polymers and derivatives thereof, and polymers; Examples of tolylene diisocyanate-based cross-linking agents include tolylene diisocyanate, its polymers, derivatives, and polymers.

Epoxy compounds include compounds having two or more epoxy groups in the molecule, and examples thereof include 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, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'- diamine glycidylaminomethyl).

As metal chelate compounds, for example, polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium are coordinated with alkoxides, acetylacetone, ethyl acetoacetate, and the like. compound. Specific examples include aluminum isopropylate, aluminum secondary butyrate, aluminum ethylacetoacetate/diisopropylate, aluminum trisethylacetoacetate, and aluminum trisacetylacetonate.

The cross-linking agents may be used singly or in combination of two or more.

In the pressure-sensitive adhesive composition of the present invention, the cross-linking agent is preferably 0.01 to 5 parts by mass with respect to a total of 100 parts by mass of the (meth)acrylic polymer (A) and the synthetic hydrocarbon-based tackifying resin (B). More preferably 0.05 to 3 parts by mass, more preferably 0.1 to 2.5 parts by mass. With such an aspect, excellent adhesive properties can be realized.

<Additive>
The adhesive composition of the present invention may contain various additives such as silane coupling agents, organopolysiloxane compounds, pigments, flame retardants, plasticizers, antistatic agents, lubricants and fillers. The content of the additive is not particularly limited, but should be within a range that does not impair the properties of the double-sided PSA sheet and the PSA composition used in the double-sided PSA sheet of the present invention.
Among them, by appropriately containing a silane coupling agent in the pressure-sensitive adhesive composition of the present invention, it is possible to impart adhesion to polar adherends (glass, SUS, etc.), so that curved surface adhesion and the like can be improved. be able to. When a silane coupling agent is added, it can be contained in an amount of more than 0% by mass and 3% by mass or less, preferably 2% by mass or less, more preferably 0.01 to 1 mass with respect to the entire pressure-sensitive adhesive composition. % or less. A flame retardant may also be included, but it is preferably less than 24 parts by mass with respect to a total of 100 parts by mass of the (meth)acrylic polymer (A) and the synthetic hydrocarbon-based tackifying resin (B).

<Organic solvent>
The pressure-sensitive adhesive composition of the present invention may contain an organic solvent in order to adjust coatability. As the organic solvent, for example, the polymerization solvent described in the section of the manufacturing conditions of the (meth)acrylic polymer (A) can be used. The content of the organic solvent in the pressure-sensitive adhesive composition is generally 30-90% by mass, preferably 40-90% by mass.

[Adhesive tape]
The adhesive tape of the present invention comprises a substrate and an adhesive layer formed on at least one of both surfaces of the substrate. Therefore, the pressure-sensitive adhesive tape of the present invention has at least a two-layer structure of a substrate and an adhesive layer, and has at least a three-layer structure when pressure-sensitive adhesive layers are formed on both sides of the substrate. there is A release film may be attached to the surface of the pressure-sensitive adhesive layer that is not in contact with the substrate.

<Base material>
The adhesive tape of the present invention contains a substrate. The thickness of the base material used for the adhesive tape of the present invention is not particularly limited, but a thickness of 1 to 12 μm is preferable for thinning the adhesive tape. If the thickness is 1 μm or more, appropriate sheet strength can be obtained, and if the thickness is 12 μm or less, adhesion enhancement can be suppressed.
In applications where the total thickness of the pressure-sensitive adhesive tape is preferred to be thin, the substrate is preferably thin. In that case, the thickness of the substrate is preferably 10 µm or less, and particularly preferably 6 µm or less.

Substrates and release films include polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), Plastic films such as ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, acrylonitrile-butadiene-styrene copolymer (ABS), polyamide (nylon), polyimide, and polyvinyl chloride (PVC) can be mentioned. Moreover, glass, paper, a nonwoven fabric, etc. are mentioned as a base material. When the pressure-sensitive adhesive tape is to be made thin, the substrate is preferably a plastic film because it is smooth, and more preferably PET from the viewpoint of strength and ease of handling.
When the pressure-sensitive adhesive tape of the present invention is used as a light-shielding tape, a substrate in which a black colorant such as a black pigment or a white colorant such as a white pigment is dispersed may be used.

<Adhesive layer>
The pressure-sensitive adhesive layer provided on at least one surface of the substrate can be formed from the pressure-sensitive adhesive composition of the present invention. When the pressure-sensitive adhesive layers are provided on both sides of the substrate, they may be the same or different.
The thickness of the pressure-sensitive adhesive layer is not particularly limited, but a thickness of 1 to 12 μm is preferable for thinning the pressure-sensitive adhesive tape. If the thickness is 1 μm or more, a pressure-sensitive adhesive tape having an appropriate adhesive strength can be obtained, and if the thickness is 12 μm or less, the increase in adhesion can be suppressed.
When a thin adhesive tape is required as a tape for fixing electrical members, the total thickness of the adhesive tape excluding the release film is preferably 25 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less. be.
Furthermore, it is preferable that the pressure-sensitive adhesive layer accounts for 40% or more of the total thickness of the pressure-sensitive adhesive tape excluding the release film. By doing so, it is possible to ensure sufficient adhesive strength of the adhesive tape.

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

[Use]
As described above, the pressure-sensitive adhesive tape of the present invention can be used for various purposes because it has a strong adhesive force despite being a thin film. For example, the adhesive tape of the present invention can be used to attach a heat-dissipating sheet or a light-shielding tape to a target article. The heat-dissipating sheet and the light-shielding tape will be described below.

・Heat-dissipating sheet Heat-dissipating sheets can dissipate heat over the entire surface of OA equipment and electronic equipment by installing them in localized high-temperature areas. The graphite sheet used for the heat dissipation sheet includes, for example, a natural graphite sheet obtained by sheeting natural graphite powder, an artificial graphite sheet obtained by heat-treating a polymer film, and the like.
Examples of the polymer film include polyimide, polyamide, polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polyparaphenylene vinylene, polybenzimidazole, polybenzobisimidazole, poly A film made of thiazole or the like can be mentioned.
The thickness of the graphite sheet is preferably 10-100 μm, more preferably 15-50 μm. By setting the thickness of the graphite sheet within the above range, it can be suitably used for fixing parts of OA equipment and electronic equipment.

Light-shielding tape Light-shielding tape can prevent problems caused by leaked light by using the light-shielding tape, for example, for attaching a non-self-luminous display unit such as a liquid crystal display module unit and a backlight unit.

<Method for manufacturing adhesive tape>
The adhesive tape of the invention can be produced as follows. The case where adhesive layers are provided on both sides will be described as an example.
The pressure-sensitive adhesive composition of the present invention is coated on one side of the release film so that the thickness after drying becomes a predetermined thickness, and dried at 60 to 100° C. for 1 to 10 minutes to remove the solvent. After that, the obtained pressure-sensitive adhesive layer is attached to one side of the substrate (which is defined as the first side of the substrate).

Next, the pressure-sensitive adhesive composition is coated on one side of another release film so that the thickness after drying becomes a predetermined thickness. Then, the adhesive layer obtained by drying at 60 to 100 ° C. for 1 to 10 minutes to remove the solvent is the side of the substrate on which the adhesive layer is not bonded (as the second surface of the substrate). to produce a double-sided adhesive tape.
The coating method is not particularly limited, and conventionally known methods can be used. Examples of the coating method of the pressure-sensitive adhesive composition include a method using a roll coater, fountain coater, lip coater, knife coater, die coater, gravure coater, reverse coater, lip coater, curtain coater, slit die coater, and the like. .
The pressure-sensitive adhesive layer formed on the first surface and the pressure-sensitive 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 1: Production of (meth)acrylic polymer (A-1))
80 parts by mass of n-butyl acrylate (n-BA), 17.9 parts by mass of 2-ethylhexyl acrylate (2EHA) and 2-hydroxyethyl acrylate were placed in a reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube. 0.1 part by mass of (2-HEA), 2 parts by mass of acrylic acid (AA), and 150 parts by mass of ethyl acetate were charged, and the temperature was raised to 70° C. while introducing nitrogen gas. Next, 0.03 part by mass of 2,2'-azobis(methyl isobutyrate) was added, and the reaction was carried out for 6 hours while repeating heating and cooling so that the temperature of the contents in the flask could be maintained at 70 to 71°C. rice field. After completion of the reaction, 20 parts by mass of ethyl acetate was further added to obtain a (meth)acrylic polymer (A-1) having a weight average molecular weight (Mw) of 1,000,000.

(Production Example 2: Production of (meth)acrylic polymer (A-2))
A (meth)acrylic polymer (A-2) having a weight average molecular weight (Mw) of 700,000 was prepared in the same manner as in Production Example 1, except that 2,2'-azobis(methyl isobutyrate) was changed to 0.06 parts. Obtained.

(Production Example 3: Production of (meth)acrylic polymer (A-3))
A (meth)acrylic polymer (A-3) having a weight average molecular weight (Mw) of 1,000,000 was obtained in the same manner as in Production Example 1 except that n-BA was changed to 70 parts by mass and 2EHA was changed to 27.9 parts by mass. .

(Production Example 4: Production of (meth)acrylic polymer (A-4))
A (meth)acrylic polymer (A-4) having a weight average molecular weight (Mw) of 1,000,000 was obtained in the same manner as in Production Example 1 except that n-BA was changed to 90 parts by mass and 2EHA was changed to 7.9 parts by mass. .

(Production Example 5: Production of (meth)acrylic polymer (A-5))
A (meth)acrylic polymer (A-5) having a weight average molecular weight (Mw) of 500,000 was prepared in the same manner as in Production Example 1, except that 2,2′-azobis(methyl isobutyrate) was changed to 0.08 parts. Obtained.

(Production Example 6: Production of (meth)acrylic polymer (A-6))
A (meth)acrylic polymer (A-6) having a weight average molecular weight (Mw) of 1,000,000 was obtained in the same manner as in Production Example 1 except that n-BA was changed to 50 parts by mass and 2EHA was changed to 47.9 parts by mass. .

(Example 1)
(Meth) per 100 parts by mass of the solid content of the acrylic polymer (A-1), synthetic hydrocarbon-based tackifying resin (B) (FTR-6100: manufactured by Mitsui Chemicals, Inc.) 80 parts by mass ((A) and ( The ratio of (B) to the total of B): 44% by mass), an isocyanate cross-linking agent (L-45: manufactured by Soken Chemical Co., Ltd.) (meth) acrylic polymer (A-1) and a synthetic hydrocarbon-based tackifying resin ( 1.5 parts by mass (solid content) was mixed with the total of B) to obtain a pressure-sensitive adhesive composition 1.

The pressure-sensitive adhesive composition 1 was coated on a release-treated polyethylene terephthalate (PET) release film so as to have a thickness of 2 μm after drying. The coated sheet was dried at 80°C for 3 minutes, transferred to both sides of a 2 µm thick PET film substrate, and aged for 7 days at room temperature of 23°C and humidity of 50% to obtain a double-sided tape. rice field.
Various properties of the obtained adhesive tape were measured and shown in Table 1.

(Examples 2 to 4, Examples 6 to 8 and Comparative Examples 1 to 5)
The same procedure as in Example 1 was performed except that the type of (meth)acrylic polymer (A), the type of synthetic hydrocarbon-based tackifying resin (B), and the amount used were changed as shown in Table 1. Products 2-4, 6-13 were obtained.
Various properties of the obtained adhesive tape were measured and shown in Table 1.

(Example 5)
A pressure-sensitive adhesive composition 5 was obtained in the same manner as in Example 1 except that 0.2 parts by mass of a silane coupling agent (KBM-403: manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 100 parts of the resin solid content. rice field.
Various properties of the obtained adhesive tape were measured and shown in Table 1.

(Example 9)
The pressure-sensitive adhesive composition 1 was coated on a release-treated PET release film so as to have a thickness of 25 μm after drying. The coated sheet was dried at 80° C. for 3 minutes, transferred to a 25 μm thick PET film substrate, and aged for 7 days at room temperature of 23° C. and humidity of 50% to obtain a single-sided tape.
Various properties of the obtained adhesive tape were measured and shown in Table 2.

(Comparative Example 6)
A single-sided tape was obtained in the same manner as in Example 9, except that the pressure-sensitive adhesive composition was changed to 13.
Various properties of the obtained adhesive tape were measured and shown in Table 2.

<Measurement/Evaluation>
The measurement method is described below.
(Weight average molecular weight (Mw))
For the (meth)acrylic polymer (A), 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-column column (all manufactured by Tosoh Corporation)
(1) TSK-GELHXL-H (guard column)
(2) TSK-GELG7000HXL
(3) TSK-GELGMHXL
(4) TSK-GELGMHXL
(5) TSK-GELG2500HXL
・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°C

(Adhesive force)
In the case of the double-sided adhesive tape, after peeling off one PET release film, the exposed one adhesive layer surface was lined with a PET film having a thickness of 6 μm and cut into a size of 25 mm×70 mm to obtain a test piece. In the case of a single-sided tape, it was cut into a size of 25 mm×70 mm and used as a test piece. The remaining PET release film was peeled off from this test piece under conditions of 23° C. and 50% RH, and stainless steel (SUS) was bonded to the exposed adhesive layer surface using a 2 kg roller (bonding area 25 mm × 70 mm). .
Twenty minutes after the bonding, the test piece was peeled off from the SUS plate in the direction of 180° at a rate of 300 mm/min, and the adhesive strength of the adhesive layer was measured.

(Holding force)
In the case of a double-sided adhesive tape, the PET release film on one side was peeled off, and the exposed adhesive layer surface was lined with a PET film having a thickness of 100 μm, and cut into a width of 20 mm to obtain a test piece. In the case of the single-sided tape, it was used as a test piece by simply cutting it to 20 mm. Thereafter, the PET release film on the other side was peeled off, and the other exposed pressure-sensitive adhesive layer side was adhered to a SUS plate and pressed with a 2 kg roller. The pasting area was 20 mm×20 mm. Twenty minutes after application, a load of 1 kg was applied in a direction parallel to the surface of the adhesive layer under dry conditions at 80° C., and the distance (mm) of displacement from the original position after one hour was measured. In the table, "n.c." means that the amount of deviation is equal to or less than the lower limit of measurement.

(Constant load peelability)
In the case of the double-sided adhesive tape, after removing one PET release film, the exposed one adhesive layer surface was lined with a PET film having a thickness of 6 μm and cut into a size of 20 mm × 50 mm to prepare a test piece. In the case of a single-sided tape, a test piece was prepared by simply cutting it into a size of 20 mm×50 mm. The PET release film remaining on the test piece was peeled off, and the surface was polished and bonded to a SUS plate cleaned with a solvent. (mm) or the time to drop was measured. In addition, "X'↓" in the table means that it fell within 60 minutes, and means that it fell in "X" minutes.

(exterior)
In the case of the double-sided adhesive tape, after removing one PET release film, the exposed one adhesive layer surface was lined with a PET film having a thickness of 6 μm and cut into a size of 20 mm × 50 mm to prepare a test piece. In the case of a single-sided tape, a test piece was prepared by simply cutting it into a size of 20 mm×50 mm. A test piece was produced by peeling off the PET release film of the test piece and bonding it to glass. After the specimens were autoclaved (50° C., 5 atm, 20 minutes), the appearance of the specimens was visually evaluated. A colorless and transparent sample was rated as ◯, a yellow transparent or cloudy sample was rated as Δ, and a clear color was rated as x.

(Curved surface adhesion)
After peeling off one PET release film of the double-sided adhesive tape, the exposed one adhesive layer surface was lined with a PET film having a thickness of 100 μm and cut into a size of 20 mm×60 mm to prepare a test piece. The PET release film remaining on the test piece was peeled off, and the surface was polished and cleaned with a solvent. held for time. After 24 hours, the average distance of peel length from both ends was measured. ◯ indicates that no peeling was observed, Δ indicates that peeling is 5 mm or less, and x indicates that peeling exceeds 5 mm.

Comparative Examples 1 and 2 used a rosin-based tackifying resin, and compared to Examples 1, 6, 7, and 8, the adhesive strength, holding power, and constant load peelability were lowered. Furthermore, in Comparative Example 2, since the amount of the tackifying resin added was the same as in Examples 1, 6, 7 and 8, the compatibility was poorer, the appearance of the sheet was poor, and the curved surface adhesiveness was also reduced.
In Comparative Example 3, the same synthetic hydrocarbon-based tackifying resin as in Example 1 was used, but the content of the synthetic hydrocarbon-based tackifying resin was the same as the (meth)acrylic polymer (A) and the synthetic hydrocarbon-based tackifying resin. Since it is less than 40% by mass with respect to the total amount of (B), the constant load peelability is superior to that of Example 1, but the adhesive strength and the curved surface adhesiveness are lowered.
Compared to Examples 1 and 2 in which the (meth)acrylic polymer (A) had a molecular weight of less than 700,000, Comparative Example 4 exhibited lower adhesive strength and constant load peelability, as well as lower curved surface adhesiveness.
Comparative Example 5 had an n-butyl acrylate content of less than 70% by mass, and was inferior to Examples 1, 3, and 9 in adhesive strength, holding power, and constant load peelability.
In Example 9 and Comparative Example 6, the pressure-sensitive adhesive composition used in Example 1 and Comparative Example 5 was applied to a single-sided tape. Compared to Example 9, the adhesive strength, holding power, and constant load peelability were lowered.

Claims (9)

A pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) having a weight average molecular weight of 700,000 or more and a synthetic hydrocarbon-based tackifying resin (B),
(Meth)acrylic polymer (A) is a polymer obtained by polymerizing a monomer containing 60% by mass or more of n-butyl (meth)acrylate (a1),
The content of the synthetic hydrocarbon-based tackifying resin (B) is 40% by mass or more and 60% by mass or less with respect to the total mass of the (meth)acrylic polymer (A) and the synthetic hydrocarbon-based tackifying resin (B). and the synthetic hydrocarbon-based tackifying resin (B) is a styrene-based resin having a softening point of over 90°C . The pressure-sensitive adhesive composition according to claim 1 , further comprising a cross-linking agent. 3. The polymer according to claim 1 or 2 , wherein the (meth)acrylic polymer (A) is a polymer obtained by polymerizing a monomer containing a (meth)acrylic monomer containing 80% by mass or more of n-butyl (meth)acrylate. Adhesive composition. The adhesive composition according to any one of claims 1 to 3 , which contains 0.01 to 3.0 parts by mass of a silane coupling agent with respect to 100 parts by mass of the resin solid content of the adhesive composition. thing. A pressure-sensitive adhesive tape comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 4 . The pressure-sensitive adhesive tape according to claim 5 , wherein the pressure-sensitive adhesive layer is provided on both sides of the substrate. 7. The pressure-sensitive adhesive tape according to claim 5 , wherein the total thickness excluding the release film is 25 [mu]m or less. The pressure-sensitive adhesive tape according to any one of claims 5 to 7, wherein the pressure-sensitive adhesive layer accounts for 40% or more of the total thickness excluding the release film. The pressure-sensitive adhesive tape according to any one of claims 5 to 8 , which is for fixing members of electronic equipment.