JP2002285121A - Pressure-sensitive adhesive composition and sheet produced using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive, pressure-sensitive adhesive composition having excellent electrical insulation, flame retardance, adhesive force, and flexibility and keeping the high adhesive force. SOLUTION: The pressure-sensitive adhesive composition contains a (meth) acrylate polymer composed of a toluene insoluble component and a toluene soluble component and a metal hydroxide. The ratio of the toluene insoluble component to the (meth)acrylate polymer is 5-90 wt.%, the weight-average molecular weight of the toluene soluble component of the (meth)acrylate polymer is 30,000-250,000, the metal hydroxide is hydroxide of a group 2 or group 13 metal of the periodic table and the amount of the metal hydroxide is 80-160 pts.wt. based on 100 pts.wt. of the (meth)acrylate polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a heat conductive pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet. For more information,
The present invention relates to a thermally conductive pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet having excellent adhesiveness, electrical insulation, thermal conductivity, flame retardancy and flexibility.

[0002]

2. Description of the Related Art Some electric and electronic components generate heat during operation, and if the heat is not removed quickly, their performance and life will be reduced. Therefore, in the CPU, the light emitting element, and the like, a heat radiation heat sink is attached in order to prevent performance degradation due to heat generation. For attaching the heat sink to the heat generating component, an adhesive or an adhesive sheet having high heat conduction efficiency is used. Adhesives and adhesive sheets for this purpose need to have adhesiveness, thermal conductivity, electrical insulation and flame retardancy, and it is also important that the bonding operation is easy. U.S. Pat. No. 4,722,960 discloses a heat-conducting adhesive for attaching heat-generating electrical and electronic components to a heat sink. However, the method using the adhesive has a disadvantage that the workability is poor because the adhesive needs to be cured while the component and the heat sink are fixed. JP-A-6-88061 proposes a pressure-sensitive adhesive containing a polar group-containing acrylic polymer and an oxide or nitride of aluminum or titanium. However, the adhesive has the disadvantage that it is not flame-retardant. Japanese Patent Application Laid-Open No. H11-269438 teaches a pressure-sensitive adhesive tape containing a tackifying resin in order to enhance the adhesiveness, but has a problem that the adhesive strength decreases at high temperatures.
Japanese Patent Application Laid-Open No. 2000-281997 proposes a pressure-sensitive adhesive containing a flame retardant. However, contamination due to migration of inorganic ions due to the addition of the flame retardant and a problem that adhesion persistence decreases after a long period of time. There is.

On the other hand, conventionally known heat conductive adhesives and adhesive sheets are all used in a thin state having a thickness of 200 μm or less. This is because when the distance between the heating element and the heat sink is short, heat is efficiently transmitted. In recent years, in order to simplify the work of the bonding process, instead of flattening the surface of the heating element as in the past and then bonding it to the heat sink, the surface of the heating element having irregularities of several hundred μm or the surface of the heating element having distortion has been used. It has become necessary to adhere the heat sink to the heat sink as it is, or to apply a leveling process to a surface having a large distortion so as not to flatten the surface and adhere the heat sink to the heat sink. Therefore, there is a demand for an adhesive or an adhesive sheet having a sufficient thermal conductivity and adhesive durability even with a thick film.

[0004]

SUMMARY OF THE INVENTION The present invention provides a pressure-sensitive adhesive composition which exhibits excellent thermal conductivity, electrical insulation, adhesive strength, and flame retardancy, and has flexibility and continuous adhesion. An object and a pressure-sensitive adhesive sheet are provided. The present inventors have conducted intensive studies to solve the above-mentioned problems, and have found that a composition containing a (meth) acrylic polymer having both a crosslinked structure and a low molecular weight and aluminum hydroxide achieves the above object. And completed the present invention based on this finding.

[0005]

That is, the present invention provides:
(1) A pressure-sensitive adhesive composition comprising a (meth) acrylate-based polymer composed of a toluene-insoluble component and a toluene-soluble component, and a metal hydroxide, wherein the toluene-insoluble component relative to the (meth) acrylate-based polymer is Is 5 to 90
% By weight, and the weight-average molecular weight of the toluene-soluble component of the (meth) acrylate polymer is 30,000 to 25.
000, and the metal hydroxide is a hydroxide of a metal belonging to Group 2 or Group 13 of the periodic table, and the compounding ratio of the metal hydroxide to 100 parts by weight of the (meth) acrylate-based polymer is (2) a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive composition according to (1) is applied on a base material; A) a heat-dissipating sheet for a heat-generating electronic product, wherein the pressure-sensitive adhesive composition according to (1) is applied on a substrate;
Is provided. In a preferred embodiment, the present invention provides the pressure-sensitive adhesive composition according to any one of the above (1) to (3),
(4) The pressure-sensitive adhesive sheet or the heat-dissipating sheet for heat-generating electronic products, wherein (4) the metal hydroxide has an average particle size of 0.5 to 2;
A pressure-sensitive adhesive composition having a durometer of 10 to 55;

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION (Meth) acrylate used in the present invention (meaning acrylate or methacrylate)
The acrylate or methacrylate unit having an alkyl group having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms, is usually 50% by weight or more, preferably 60% by weight or more of the total structural units of the polymer. More preferably, it is a polymer occupying 70% by weight or more, and is a polymer having a toluene-insoluble component and a toluene-soluble component. The toluene-insoluble matter is contained in the (meth) acrylate polymer 0.1.
A solution obtained by immersing 2 g of the mixture in 20 ml of toluene at a temperature of 60 ° C. for 72 hours is 177 μm (80 mesh).
Through the sieve, and the non-passing components remaining on the sieve are cooled to 25 ° C.
And expressed as a percentage of the weight of the polymer after dissolution in vacuum for 24 hours relative to the weight of the polymer before dissolution. In the present invention, the toluene insoluble content is 5 to 90% by weight, preferably 10 to 90% by weight.
-60% by weight, more preferably 13-40% by weight. If the amount of the toluene insolubles is too small, the adhesive strength at high temperatures may be reduced. Conversely, if the amount is too large, the adhesive strength at room temperature may be reduced. The weight-average molecular weight (hereinafter, sometimes referred to as “Mw”) of the toluene-soluble component is 30,000 to 30,000 in terms of standard polystyrene in gel permeation chromatography (GPC) using tetrahydrofuran as a solvent. 250,000, preferably 50,000 to 250,000, more preferably 8
It is between 000 and 200,000. If the Mw is too small, the adhesive strength at high temperatures may be reduced.
Is too large, the adhesive strength at room temperature may decrease. In the present invention, two or more (meth) acrylate-based polymers having different ratios of the toluene-insoluble portion and the toluene-soluble portion are combined, and the above-mentioned composition, toluene-insoluble content, and toluene-soluble It is also possible to show the minute Mw.

A preferred monomer for producing the above (meth) acrylate polymer is an alkyl (meth) acrylate having usually 4 to 18, preferably 4 to 12, and more preferably 4 to 8 carbon atoms in the alkyl group. Specifically, butyl (meth) acrylate, hexyl (meth)
Does not have a ring structure in an alkyl group such as acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, and n-dodecyl (meth) acrylate Alkyl (meth) acrylate is mentioned. An adhesive composition using a polymer containing 20% by weight or more of an alkyl (meth) acrylate having a ring structure such as isobornyl methacrylate or cyclohexyl methacrylate has a durometer greater than 55,
It is not preferable because it gives an adhesive layer having too high hardness.

The above (meth) acrylate polymer is
In addition to the above (meth) acrylates, copolymers of monomers copolymerizable with them may be used. Examples of the copolymerizable monomer include carboxylic acids and anhydrides such as acrylic acid and anhydride thereof, methacrylic acid and anhydride thereof, itaconic acid and anhydride thereof, maleic acid and anhydride thereof; And a polar group-containing monomer such as hydroxyalkyl (meth) acrylate having an alkyl group of 8; glycidyl (meth) acrylate; and polyethylene glycol (meth) acrylate. The amount of these copolymerizable monomers used is usually 30% by weight or less, preferably 25% by weight, based on the total amount of monomers.
% By weight, more preferably 20% by weight or less.

The (meth) acrylate-based polymer may be copolymerized with a crosslinkable monomer in order to have a toluene-insoluble component by a polymerization reaction. Examples of the crosslinking monomer include divinyl compounds such as divinylbenzene; dimethacrylates such as ethylene dimethacrylate, diethylene glycol dimethacrylate, and ethylene glycol dimethacrylate; trimethacrylates such as trimethylolpropane trimethacrylate;
Diacrylates such as polyethylene glycol diacrylate and 1,3-butylene glycol diacrylate; triacrylates such as trimethylolpropane triacrylate; and dienes such as butadiene and isoprene. The amount of the crosslinking monomer used is preferably 0.3 to 10% by weight, more preferably 0.5 to 6% by weight, based on the total amount of the monomers used.
It is good to be.

In order to control the weight-average molecular weight of the toluene-soluble component of the (meth) acrylate-based polymer within the above range, a method of adjusting the concentration of a radical initiator described below and a method of adding a molecular weight modifier are used. and so on. Examples of the molecular weight modifier include t-dodecyl mercaptan, 2
-Mercaptans such as mercaptoethanol; halogenated hydrocarbons such as carbon tetrachloride and the like. These molecular weight regulators can be added before the start of polymerization or during the polymerization. The relationship between the concentration of the radical initiator or the molecular weight modifier and Mw is determined by the monomer composition,
Since the type of the initiator or the type of the molecular weight modifier, the polymerization temperature, and the like are related, it is preferable to grasp them by preliminary experiments.

As a polymerization method of the (meth) acrylate polymer used in the present invention, known polymerization methods such as emulsion polymerization, dispersion polymerization, suspension polymerization, solution polymerization, bulk polymerization and the like can be adopted. Further, Mw is 30,000 to 2 due to bulk polymerization.
A crosslinked polymer containing a fluid polymer is obtained by generating a 50,000 fluid polymer, adding a monomer, a crosslinkable monomer, and a polymerization initiator thereto and performing the second-stage polymerization. A method is also possible. This method is preferable because a uniform pressure-sensitive adhesive composition of the present invention can be produced by charging a metal hydroxide together with the second-stage monomer. As a polymerization initiation method, a method of starting by heating using a radical initiator, a method of starting by irradiating low intensity ultraviolet rays using a photopolymerization initiator, a method of electron beam irradiation, and the like can be arbitrarily selected. Although the polymerization reaction temperature is not limited, it is usually 30 to 180 ° C.

Known radical initiators can be used. For example, persulfates such as potassium persulfate and ammonium persulfate; hydrogen peroxide; lauroyl peroxide, benzoyl peroxide, di-2-ethylhexylperoxydicarbonate, t-butylperoxypivalate, cumene hydroperoxide and the like Of organic peroxides and the like, alone or in combination,
Alternatively, it can be used as a redox system in combination with a reducing agent such as sodium acid sulfite, sodium thiosulfate, ascorbic acid and the like. Further, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), Azo compounds such as dimethyl 2,2′-azobisisobutyrate and 4,4′-azobis (4-cyanopentanoic acid);
2,2′-azobis (2-aminodipropane) dihydrochloride, 2,2′-azobis (N, N′-dimethyleneisobutylamidine), 2,2′-azobis (N,
Amidine compounds such as (N'-dimethyleneisobutylamidine) dihydrochloride can also be used.

Examples of photopolymerization initiators include acyloin ethers (eg, benzoin ethyl ether, benzoin isopropyl ether, anisoin ethyl ether and anisoin isopropyl ether), substituted acyloin ethers (eg, α-hydroxymethylbenzoin ethyl). Ether), Michael ketone (4,4'-tetramethyldiaminobenzophenone), 2,2-dimethoxy-2
-Phenylacetophenone (e.g., KB-1 from Sartomer or "Irgacure" 651 from Ciba-Geigy) and the like. The mixing amount of the radical initiator and the photopolymerization initiator is 0.01 to 5 parts by weight per 100 parts by weight of the total amount of the monomers.

The emulsifier and dispersant used in the emulsion polymerization and suspension polymerization of the (meth) acrylate polymer may be those used in a usual emulsion polymerization method, suspension polymerization method, dispersion polymerization method and the like. Are alkyl aryl sulfonates such as sodium dodecylbenzene sulfonate and sodium dodecyl phenyl ether sulfonate; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecyl sulfate; sulfosuccinates such as sodium dioctyl sulfosuccinate and sodium dihexyl sulfosuccinate Fatty acid salts such as sodium laurate; alkoxysulfate salts such as sodium polyoxyethylene lauryl ether sulfate and sodium polyoxyethylene nonylphenyl ether sulfate;
Alkyl sulfonates such as sodium lauryl sulfonate; alkyl ether phosphates and sodium salts thereof; polyoxyethylene nonylphenyl ether, polyoxyethylene sorbitan lauryl ester,
Nonionic emulsifier such as polyoxyethylene-polyoxypropylene block copolymer; gelatin, maleic anhydride-styrene copolymer, polyvinylpyrrolidone, sodium polyacrylate, polyvinyl having a polymerization degree of 700 or more and a saponification degree of 75% or more Examples thereof include water-soluble polymers such as alcohols, and these may be used alone or in combination of two or more. The addition amount of the emulsifier and the dispersant is usually about 0.01 to 10 parts by weight based on 100 parts by weight of the total amount of the monomers.

As a method of retaining toluene-insoluble components in the (meth) acrylate polymer, instead of using a crosslinkable monomer at the time of the above polymerization reaction, a method of subjecting the polymer after the polymerization reaction to ionic crosslinking may be employed. Good.
In the ionic crosslinking method, an acid group such as a carboxyl group is introduced into a polymer by a polymerization reaction or a post-polymerization treatment. This is a method of adding an agent. Examples of the ionic crosslinking agent include monovalent ions such as potassium, sodium, lithium, and ammonium ions; tin,
An ionic compound that generates a divalent ion such as copper, chromium, calcium, magnesium, zinc, or strontium ion; a trivalent ion such as an aluminum ion; preferably an ionic compound that generates a divalent ion or a trivalent ion It is.

When the polymerization of the (meth) acrylate polymer is carried out by a polymerization reaction in an aqueous dispersion such as emulsion polymerization, dispersion polymerization or suspension polymerization, the polymerization is followed by steam coagulation, alcohol coagulation, salting out and the like. After filtration, the resultant is dried with a band dryer, a rotary kiln, an expansion dryer, or the like to obtain a (meth) acrylate-based polymer. In the case of a polymer having no tackiness, such as polymer 1 when two types of (meth) acrylate-based polymer are polymerized, ie, polymer 1 insoluble in toluene and polymer 2 soluble in toluene, spray drying, fluid drying, flashing A dryer such as drying can also be used. Even in the case of solution polymerization, crumbs can be formed by steam coagulation, methanol coagulation or the like.

The (meth) acrylate polymer used in the present invention includes a toluene-insoluble component formed by the use of a crosslinking monomer during polymerization or formed by adding an ionic crosslinking agent after polymerization, and a molecular weight. And a small amount of toluene-soluble matter are contained in a well-balanced manner. The toluene-insoluble component has an effect of exhibiting structural strength for the adhesive composition to fix the object, and the toluene-soluble component controls the effect of exhibiting adhesive force. The (meth) acrylate-based polymer has both shape fluidity and structural strength because it absorbs a flowable toluene-soluble component in a network structure of a toluene-insoluble component, and has flexibility as a whole. And toughness. When this (meth) acrylate polymer is used in a pressure-sensitive adhesive composition, the composition can flexibly follow the shape of the bonding surface of the object to be bonded, change its shape, and adhere to it. When the shape is determined, the structural strength is developed in that state, so that a large adhesive force can be maintained even after a long period of time or even at a high temperature.

The pressure-sensitive adhesive composition of the present invention (hereinafter sometimes referred to as "adhesive") is prepared by adding a (meth) acrylate-based polymer to a metal of Group 2 or 13 of the periodic table. It is prepared by blending substances. The metals of the second group of the periodic table include magnesium, calcium, strontium,
Barium and the like, and Group 13 metals include aluminum, gallium, indium and the like, with aluminum being preferred. The average particle size of such metal hydroxides by centrifugal sedimentation turbidity method is usually 0.5 to 250.
μm, preferably 1 to 100 μm, more preferably 10 μm
７０70 μm. If the metal hydroxide is too small, the thermal conductivity may decrease, and if it is too large, the flame retardancy may decrease. Further, the particle shape may be spherical, needle-like or flake-like, or amorphous.
Further, in order to improve the dispersibility of the metal hydroxide, the surface of the particles may be appropriately treated with a coupling agent, a stearic acid, or the like.

The metal hydroxide has a function of imparting flame retardancy and thermal conductivity to the adhesive. The compounding amount of the metal hydroxide is 80 to 160 parts by weight, preferably 90 to 140 parts by weight, more preferably 100 to 120 parts by weight per 100 parts by weight of the (meth) acrylate-based polymer. If the amount of the metal hydroxide is too small, the flame retardancy and the thermal conductivity of the pressure-sensitive adhesive composition may decrease. Conversely, if the amount is too large, the adhesive strength may decrease.

The pressure-sensitive adhesive composition of the present invention may contain an epoxy crosslinking agent, if necessary, for the purpose of improving its cohesion.
A cross-linking agent such as an isocyanate-based cross-linking agent, an aziridine-based cross-linking agent, or a chelate-based cross-linking agent can be blended.
Further, the pressure-sensitive adhesive composition of the present invention may optionally contain a modifying polymer for the purpose of improving flexibility and tackiness. Examples of such modifying polymers include dicyclopentadiene resin, hydrogenated dicyclopentadiene resin, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, and styrene-ethylene-butylene-styrene block copolymer. And a modified product thereof. The addition amount of these modified polymers is less than 100 parts by weight per 100 parts by weight of the (meth) acrylate-based polymer.
If it is added in an amount of 100 parts by weight or more, the adhesive strength may be reduced at a high temperature of 100 ° C. or more.

The method of mixing the (meth) acrylate polymer with the metal hydroxide for preparing the pressure-sensitive adhesive composition of the present invention is not particularly limited. Roll, Henschel,
A dry mixing method of mixing a (meth) acrylate polymer dried with a kneader or the like with a metal hydroxide, or a wet mixing method of mixing in a vessel having a stirrer in the presence of an organic solvent may be used. When preparing the pressure-sensitive adhesive composition, the above, if necessary, a crosslinking agent, a modifying polymer, and the like,
Add at this time.

The pressure-sensitive adhesive sheet of the present invention has the above-mentioned pressure-sensitive adhesive composition applied on a substrate. As a method for producing the pressure-sensitive adhesive sheet, a substrate made of a synthetic resin film such as polyester, polyimide, or polycarbonate or an aluminum foil is treated with a release agent, and the pressure-sensitive adhesive composition is rolled thereon. Coater, apply with a doctor blade, etc., if the pressure-sensitive adhesive composition contains a solvent, remove the solvent and, if necessary, cross-link by heating or irradiating with energy rays such as light. . When the polymer does not substantially contain a solvent, a method is also possible in which the pressure-sensitive adhesive composition is formed into a sheet by an extruder, and the sheet is wound together with a substrate subjected to a release agent treatment.

The thickness of the adhesive layer of the pressure-sensitive adhesive sheet is usually 0.5 to 5 mm, preferably 1 to 3 mm. If the adhesive layer is too thin, it may not be possible to follow the shape when the surface of the heating element has undulations, and if it is too thick, the heat conduction efficiency may be reduced and sufficient heat dissipation may not be possible. In the pressure-sensitive adhesive sheet of the present invention, the hardness of the adhesive layer is preferably from 10 to 55 as durometer, and from 15 to 55.
It is more preferably 45 and particularly preferably 20 to 40. If the durometer of the adhesive layer is less than 10, the adhesive layer is easily deformed greatly when the heat sink and the heat generating element are attached, and the heat generating element may be greatly deformed accordingly, which is not preferable. On the other hand, if the durometer is greater than 55, the flexibility of the adhesive is lacking, the adhesive cannot follow the shape of the object to be bonded, and the contact between the heat sink and the electronic component may be insufficient.

The pressure-sensitive adhesive composition of the present invention can be used for a hybrid package, a multi-chip module, a ceramic integrated circuit package, a plastic integrated circuit package,
When a heat-generating electric / electronic component such as a metal integrated circuit package is attached to a heat sink, the heat-generating electric / electronic component can be easily fixed by applying pressure between the heat sink and the heat sink. In the above-mentioned application, as a method of fixing by an easier operation, the adhesive surface of the pressure-sensitive adhesive sheet of the present invention is brought into contact with one side, for example, a heat sink, and the other side is attached to the surface where the base material of the sheet is peeled off On the other hand, for example, there is a method in which a hybrid package is brought into contact with and pressed to adhere. Therefore, the sheet is suitable as a heat dissipation sheet for heat-generating electronic products. By using the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet of the present invention, the heating element and the heat sink can be easily fixed. These adhesive layers have excellent electrical insulation and thermal conductivity, and are flexible and have good shape following properties of the bonding surface. Force is developed.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.
"Parts" and "%" are based on weight unless otherwise specified. Test methods were as follows. (1) Weight average molecular weight (Mw) Mw was determined by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent in terms of standard polystyrene. (2) Surface Hardness The hardness of the adhesive layer is determined by durometer hardness (JIS K62) by stacking three 2 mm thick sheets to a thickness of 6 mm.
53).

(3) Thermal conductivity Measured at room temperature by a rapid thermal conductivity meter (QTM-500, manufactured by Kyoto Electronics Industry Co., Ltd.). When this value is 0.3 W / m · K or more, it is determined that the thermal conductivity is good. (4) Electrical insulation The sample box was measured with an electrometer (R8340, manufactured by Advantest) using TR42. (5) Adhesive force A 20 mm × 100 mm tape sample adhered to an aluminum plate is placed on the PET film, and JIS Z02 is placed on the PET film.
Using a test piece bonded by reciprocating a roller having a load of 2 kg five times with a pressure device described in No. 37, the sample was peeled off in a 180 ° direction at a peeling speed of 50 mm / min, and the adhesive force was measured. The test pieces were placed in a thermostat at normal temperature and 100 ° C. for 30 minutes before measurement, respectively.

(6) Flame Retardancy Test was conducted in accordance with UL standard [UL94 "Testing method for combustion of plastic materials for equipment parts". "VTM-0" and "VTM-1" are based on the following criteria. The sheet-like adhesive material was put in a cylinder, and a flame contact for 3 seconds was performed twice, and the following evaluation was performed. Five samples of the same sample type were tested. Combustion class classification VTM-0 VTM-1 Afterflame burning time of each material ≦ 30 seconds ≦ 10 seconds Total burning time of 5 samples ≦ 250 seconds ≦ 50 seconds Afterflame time and flameless combustion after the second flame contact Sum of time ≤60 seconds ≤30 seconds Ignition of cotton by dripping None None Afterflame or flameless combustion up to clamp None None

Polymer Production Example 1 80 parts of 2-ethylhexyl acrylate, n
20 parts of -butyl acrylate, 0.2 parts of 2,2'-azobisisobutyronitrile and 200 parts of ethyl acetate were added and uniformly dissolved, and after purging with nitrogen, a polymerization reaction was carried out at 80 ° C for 6 hours. The polymerization conversion was 97%. Pouring the obtained polymer into a large amount of methanol to precipitate the polymer,
After filtration, the polymer was dried under reduced pressure at 90 ° C. for 24 hours to obtain a polymer A having fluidity. Mw of polymer A is 150,000
0 and Mw / Mn were 4.3.

Polymer Production Example 2 The procedure of Polymer Production Example 1 was repeated except that the amount of 2,2′-azobisisobutyronitrile was reduced to 0.02 parts, the polymerization temperature and the polymerization time were changed to 75 ° C. and 24 hours. In the same manner as in Example 1, a viscous solid polymer B was obtained at a polymerization conversion of 98%. Mw of polymer B is 450,00
0 and Mw / Mn were 5.6.

(Examples 1 to 5 and Comparative Examples 1 to 4) The second stage polymerization by bulk polymerization was carried out using the components and amounts shown in Table 1.
A sheet was prepared according to the following procedure. First, aluminum hydroxide (aluminum oxide in Comparative Example 3) was added to polymer A or polymer B in a container and mixed uniformly.
To this, 2-ethylhexyl acrylate (2EHA),
n-Butyl acrylate (nBA), ethylene glycol dimethacrylate (EGDM) and benzoyl peroxide (BPO) were added and mixed well (in Comparative Example 1, all components were mixed together). The resulting fluid mixture is
P on the bottom of a 30 mm long, 30 mm wide, 2 mm deep mold
An ET film was laid and filled, and the ET film was covered with a PET film and pressed at 5 MPa to flatten the surface, and then heated to 150 ° C. and polymerized for 2 hours to obtain an adhesive sheet. Table 1 shows the test results of the sheet.

[0031]

[Table 1]

As shown in Table 1, the pressure-sensitive adhesive composition of the present invention has thermal conductivity, sufficient electric insulation, flame retardancy and adhesive strength, and has a moderate surface hardness and is flexible. And high-temperature adhesive strength (adhesion persistence) (Example 1)
~ 5). On the other hand, if the toluene-insoluble content of the acrylate-based polymer was too small (absent), the surface hardness was too large, and the adhesive strength and high-temperature adhesive strength were significantly reduced (Comparative Example 1). When the Mw of the acrylate polymer was too large, the adhesive strength and the high-temperature adhesive strength were reduced (Comparative Example 2). In addition, even when the amount of aluminum hydroxide was reduced to 50 parts, even when aluminum hydroxide was replaced with aluminum oxide, combustion occurred in the flame retardancy test (Comparative Examples 4 and 3).

[0033]

According to the present invention, there is provided a heat-conductive pressure-sensitive adhesive composition having excellent electrical insulation properties, flame retardancy and adhesive strength, and having flexibility and good adhesive durability.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Koichiro Maeda 2-4-1 Shiba Park, Minato-ku, Tokyo ZEON Kasei Co., Ltd. F-term (reference) 4J004 AA07 AA10 AB01 AB05 AB06 CA04 CA06 CA08 FA05 4J040 DF041 DF051 GA01 GA05 GA07 GA11 HA136 HD02 JB09 KA03 KA16 KA18 KA42 LA02 LA06 LA08 LA09 MA10 NA19 NA20 PA30 PA32

Claims (3)

[Claims] 1. A pressure-sensitive adhesive composition comprising a (meth) acrylate-based polymer comprising a toluene-insoluble component and a toluene-soluble component, and a metal hydroxide, wherein toluene is used for the (meth) acrylate-based polymer. The proportion of the insoluble component is 5 to 90% by weight, the weight average molecular weight of the toluene-soluble component of the (meth) acrylate polymer is 30,000 to 250,000, and the metal hydroxide is the second component of the periodic table. A pressure-sensitive adhesive composition, which is a hydroxide of a Group III or Group 13 metal, wherein the mixing ratio of the metal hydroxide is 80 to 160 parts by weight based on 100 parts by weight of the (meth) acrylate-based polymer. 2. A pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive composition according to claim 1 is applied on a substrate. 3. The pressure-sensitive adhesive composition according to claim 1,
Heat-dissipating sheet for heat-generating electronic products applied on a substrate.