JP2010144022A - Heat-conductive pressure-sensitive adhesive composition and heat-conductive pressure-sensitive adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-conductive pressure-sensitive adhesive sheet containing expanded graphite and suppressing ununiformness of a physical property, and a heat-conductive pressure-sensitive adhesive composition used as a basis of the heat-conductive pressure-sensitive adhesive sheet. <P>SOLUTION: The heat-conductive pressure-sensitive adhesive composition (E) contains at least one kind of polymer (S) selected from the group consisting of a rubber, an elastomer and a resin, an expanded graphite powder (B), and a silane coupling agent (C) or a polyglycerine fatty acid ester (D). The heat-conductive pressure-sensitive adhesive sheet (F) is obtained by heating and molding the heat-conductive pressure-sensitive adhesive composition (E) to a sheet-like form. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat conductive pressure-sensitive adhesive composition and a heat conductive pressure-sensitive adhesive sheet formed from the heat conductive pressure-sensitive adhesive composition.

  In recent years, electronic components such as plasma display panels (PDP), integrated circuit (IC) chips, and the like have increased in heat generation as their performance has increased. As a result, there is a need to take measures against functional failures due to temperature rise. In general, a method of diffusing and radiating heat is adopted by attaching a heat sink such as a metal heat sink, heat radiating plate, or heat radiating fin to a heat generating body such as an electronic component. On the other hand, in small electronic devices such as notebook computers, mobile phones, and personal digital assistants (PDAs), countermeasures against functional failures due to temperature rise are more important. However, as a result of progress in thinning, there is no space for heat countermeasures. Therefore, it has been difficult to dissipate heat using conventional fans and fins. In this case, as a general method for efficiently removing heat from a heating element such as an electronic component, heat diffusion and thermal radiation can be performed using a sheet member such as a graphite sheet for the heating element. However, in general, graphite is difficult to process into a sheet because of its poor processability, and the graphite sheet itself is not sticky. Therefore, it is necessary to provide a separate pressure-sensitive adhesive layer. There is a risk that the conductivity is lowered.

For the purpose of improving the performance of the heat conductive pressure sensitive adhesive sheet as described above, various fillers are added to the composition that is the basis of the heat conductive pressure sensitive adhesive sheet, and the heat conductive pressure sensitive adhesive property is added. May get a sheet. Moreover, some techniques for highly filling the filler added to the composition have been disclosed so far (for example, Patent Document 1).
JP 2003-137627 A

  As one of the fillers added to the heat conductive pressure-sensitive adhesive composition that is the basis of the heat conductive pressure-sensitive adhesive sheet, there is expanded graphite powder. A heat conductive pressure-sensitive adhesive sheet obtained from a heat conductive pressure-sensitive adhesive composition highly filled with expanded graphite powder has high heat conductivity. However, the heat conductive pressure-sensitive adhesive composition highly filled with the expanded graphite powder has poor dispersibility and has a large variation in physical properties. Therefore, development of a technique capable of uniformly dispersing the expanded graphite powder contained in the heat conductive pressure-sensitive adhesive composition has been desired. Generally, as disclosed in Patent Document 1 above, A silane coupling agent or the like used as a dispersant has been thought to be ineffective against graphite.

  Accordingly, the present invention includes a thermally conductive pressure-sensitive adhesive sheet containing expanded graphite powder, in which variation in physical properties is suppressed, and a thermally conductive pressure-sensitive adhesive composition that is the basis of the thermally conductive pressure-sensitive adhesive sheet The purpose is to provide.

  As a result of continual research on the heat conductive pressure-sensitive adhesive sheet containing expanded graphite powder, the present inventors have found that some of the dispersants that have been thought to have no effect on graphite are expanded. The present inventors have found that there is an effect on graphitized graphite powder and have solved the above-mentioned problems and completed the present invention.

  Thus, according to the first aspect of the present invention, at least one polymer (S) selected from the group consisting of rubber, elastomer and resin, expanded graphite powder (B), silane coupling agent (C) or poly There is provided a heat conductive pressure-sensitive adhesive composition (E) characterized by containing glycerin fatty acid ester (D).

  In the heat conductive pressure-sensitive adhesive composition (E) of the first invention, the expanded graphite powder (B) of 30 parts by mass or more and 400 parts by mass or less and 1 part by mass with respect to 100 parts by mass of the polymer (S). It is preferable to contain silane coupling agent (C) or polyglycerin fatty acid ester (D) in an amount of 150 parts by weight or more and 150 parts by weight or less.

  In the heat conductive pressure-sensitive adhesive composition (E) of the first invention, the polymer (S) is preferably a (meth) acrylic acid ester polymer (A1). In the present invention, “(meth) acryl” means “acryl and / or methacryl”. By using the polymer (S) as a (meth) acrylic acid ester polymer (A1), the heat conductive pressure-sensitive adhesive composition (E) is used as the heat conductive pressure-sensitive adhesive sheet (F). It is easy to impart adhesiveness and flexibility to the heat conductive pressure-sensitive adhesive sheet (F).

  The heat conductive pressure-sensitive adhesive composition (E) of the first aspect of the present invention comprises (meth) acrylic acid ester polymer (A1) and (meth) acrylic acid ester monomer (A2m). Further preferred. By setting it as this form, the moldability at the time of making a heat conductive pressure sensitive adhesive composition (E) into a heat conductive pressure sensitive adhesive sheet (F) can be improved.

  Moreover, according to 2nd this invention, the heat conductive pressure sensitive adhesive sheet (F) formed by shape | molding the heat conductive pressure sensitive adhesive composition (E) of 1st this invention in a sheet form is provided. The

  The heat conductive pressure-sensitive adhesive sheet (F) of the second aspect of the present invention is preferably a first containing a (meth) acrylic acid ester polymer (A1) and a (meth) acrylic acid ester monomer (A2m). While the heat conductive pressure-sensitive adhesive composition (E) of the present invention is formed into a sheet shape or after being formed into a sheet shape, the (meth) acrylate polymer (A1) is present in the presence of the (meta) ) A sheet-like molded product of the solidified product (E ′) of the thermally conductive pressure-sensitive adhesive composition (E) obtained by polymerizing the acrylate monomer (A2m).

  When a device using a heat conductive pressure sensitive adhesive sheet is commercialized, the amount of heat generated from a heating element such as an electronic component incorporated in the device, and the amount of heat that can be dissipated by the heat conductive pressure sensitive adhesive sheet, etc. Calculated and designed. Therefore, the performance of the heat conductive pressure-sensitive adhesive sheet is required to be the same at any part. ADVANTAGE OF THE INVENTION According to this invention, the heat conductive pressure-sensitive-adhesive composition used as the origin of the heat conductive pressure-sensitive-adhesive sheet in which the dispersion | variation in physical property was suppressed, and this heat-conductive pressure-sensitive adhesive sheet can be obtained.

1. Thermally conductive pressure sensitive adhesive composition (E)
The heat conductive pressure sensitive adhesive composition (E) of the present invention comprises at least one polymer (S) selected from the group consisting of rubber, elastomer and resin, expanded graphite powder (B), and silane coupling agent. (C) or polyglycerol fatty acid ester (D). Hereinafter, each of these substances will be described in detail.

<Silane coupling agent (C)>
As the silane coupling agent (C) that can be used in the present invention, a known silane coupling agent can be used. Specific examples include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyl. Methyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminop Pyrtrimethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3 -Dimethyl-butylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane , 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatopropyltriethoxysilane, and the like. Among these, 3-glycidoxypropyltriethoxysilane and 3-methacryloxypropyltriethoxysilane are preferable.

  The amount of the silane coupling agent (C) contained in the heat conductive pressure-sensitive adhesive composition (E) is preferably 100 parts by mass of the polymer (S) and the lower limit is preferably 1 part by mass. 2 parts by mass is more preferable, and 1.5 parts by mass is even more preferable. On the other hand, the upper limit is preferably 150 parts by mass, more preferably 120 parts by mass, and even more preferably 100 parts by mass. If the amount of the silane coupling agent (C) contained in the heat conductive pressure-sensitive adhesive composition (E) is less than the lower limit (1 part by mass) of the above range, the silane coupling agent (C) is contained. When the heat conductive pressure sensitive adhesive composition (E) is used as the heat conductive pressure sensitive adhesive sheet (F), the heat conductive pressure sensitive adhesive property is not obtained. The thermal conductivity of the sheet (F) tends to decrease.

  <Polyglycerin fatty acid ester (D)>

  The amount of the polyglycerol fatty acid ester (D) contained in the heat conductive pressure-sensitive adhesive composition (E) is preferably 100 parts by mass of the polymer (S) and the lower limit is preferably 1 part by mass. 2 parts by mass is more preferable, and 1.5 parts by mass is even more preferable. On the other hand, the upper limit is preferably 150 parts by mass, more preferably 50 parts by mass, and even more preferably 30 parts by mass. If the amount of the polyglycerol fatty acid ester (D) contained in the heat conductive pressure-sensitive adhesive composition (E) is less than the lower limit (1 part by mass) of the above range, the polyglycerol fatty acid ester (D) is included. When the heat conductive pressure sensitive adhesive composition (E) is used as the heat conductive pressure sensitive adhesive sheet (F), the heat conductive pressure sensitive adhesive property is not obtained. The thermal conductivity of the sheet (F) tends to decrease.

<Expanded graphite powder (B)>
The thermally conductive pressure-sensitive adhesive composition (E) of the present invention contains expanded graphite powder (B). As an example of the expanded graphite powder that can be used in the present invention, a process including heat-treating acid-treated graphite at 500 ° C. to 1200 ° C. to expand it to 100 ml / g to 300 ml / g and then pulverizing it. Can be mentioned. More preferably, the graphite is treated with a strong acid, sintered in an alkali, and then again treated with a strong acid at 500 ° C. to 1200 ° C. to remove the acid and to 100 ml / g to 300 ml / g. What was obtained through the process including expanding and then crushing can be mentioned. The temperature of the heat treatment is particularly preferably 800 ° C to 1000 ° C.

  The average particle size of the expanded graphite powder (B) used in the present invention is preferably 30 μm to 500 μm, more preferably 50 μm to 400 μm, and still more preferably 80 μm to 300 μm. When the average particle diameter of the expanded graphite powder (B) is less than the lower limit of the above range, when the heat conductive pressure sensitive adhesive composition (E) is used as the heat conductive pressure sensitive adhesive sheet (F), the heat conductive feeling is obtained. The effect of improving the thermal conductivity of the pressure-adhesive sheet (F) tends to be low. On the other hand, when the average particle size of the expanded graphite powder (B) exceeds the upper limit of the above range, when the heat conductive pressure sensitive adhesive composition (E) is used as the heat conductive pressure sensitive adhesive sheet (F), Since the expanded graphite powder (B) exists in a large domain on the surface of the heat conductive pressure-sensitive adhesive sheet (F), voids are easily formed at the interface with the adherend, and the heat conductive pressure-sensitive adhesive sheet. There is a possibility that the thermal conductivity and adhesiveness of (F) may be lowered, and the moldability may be deteriorated.

  The average particle size of the expanded graphite powder (B) is measured using a laser-type particle size measuring machine (manufactured by Seishin Enterprise Co., Ltd.) and a micro-sorting control method (measuring particles are allowed to pass only within the measurement region to ensure measurement reliability. (Measure to improve). In this measurement method, 0.01 g to 0.02 g of the expanded graphite powder (B) to be measured is flowed into the cell, so that the expanded graphite powder (B) flowing into the measurement region has a semiconductor with a wavelength of 670 nm. By irradiating the laser beam and measuring the scattering and diffraction of the laser beam at that time, the average particle size and particle size distribution are calculated from the Franhofer diffraction principle, and the results are displayed.

  The amount of the expanded graphite powder (B) contained in the heat conductive pressure-sensitive adhesive composition (E) is preferably 30 parts by mass with respect to 100 parts by mass of the polymer (S), 35 More preferably, it is 40 parts by mass. The upper limit is preferably 400 parts by mass, more preferably 300 parts by mass, and even more preferably 200 parts by mass. If the amount of expanded graphite powder (B) contained in the heat conductive pressure sensitive adhesive composition (E) is less than the lower limit (30 parts by mass) of the above range, the heat conductive pressure sensitive adhesive composition (E). When the heat conductive pressure sensitive adhesive sheet (F) is used, the effect of improving the thermal conductivity of the heat conductive pressure sensitive adhesive sheet (F) tends to be low. On the other hand, when the upper limit (400 parts by mass) of the above range is exceeded, the viscosity of the heat conductive pressure-sensitive adhesive composition (E) increases, and the heat conductive pressure-sensitive adhesive composition (E) increases the heat conductive pressure-sensitive adhesive property. Besides reducing the productivity when obtaining the sheet (F), the thermal conductivity of the thermally conductive pressure-sensitive adhesive sheet (F) increases so much even if the number of added parts of the expanded graphite powder (B) is increased. It disappears and it becomes uneconomical.

<Polymer (S)>
The heat conductive pressure sensitive adhesive composition (E) of the present invention contains a polymer (S). As what comprises a polymer (S), at least 1 type arbitrarily selected from rubber | gum, an elastomer, and resin can be mentioned. And in order to shape | mold the heat conductive pressure-sensitive-adhesive composition (E) of this invention in a sheet form, and to use as a heat conductive pressure-sensitive-adhesive sheet (F), adhesiveness or adhesion to a polymer (S). It is preferable to provide the property. In order to make the polymer (S) have adhesiveness or tackiness, the rubber, elastomer and resin are preferably selected from those having adhesiveness or tackiness. However, an adhesive agent can be used in combination with rubber, elastomer, and resin that do not have adhesiveness or tackiness.

  Specific examples of rubbers, elastomers and resins that can be used in the present invention are listed below.

  Conjugated diene polymers such as natural rubber, polybutadiene rubber, polyisoprene rubber; butyl rubber; styrene-butadiene random copolymer, styrene-isoprene random copolymer, styrene-butadiene-isoprene random copolymer, styrene-butadiene block copolymer Polymers, styrene-isoprene block copolymers, styrene-butadiene-isoprene block copolymers, styrene-isoprene-styrene block copolymers, aromatic vinyl-conjugated diene copolymers; styrene-butadiene copolymers Hydrogenated aromatic vinyl-conjugated diene copolymer, such as hydrogenated product; Vinyl cyanide compound-conjugated diene copolymer, such as acrylonitrile-butadiene copolymer rubber, acrylonitrile-isoprene copolymer rubber; acrylonitrile- Hydrogenates of vinyl cyanide compounds-conjugated diene copolymers, such as hydrogenates of tadiene copolymers; vinyl cyanide-aromatic vinyl-conjugated diene copolymers; vinyl cyanide compounds-aromatic vinyl-conjugated Hydrogenated diene copolymer; vinyl cyanide compound-mixture of conjugated diene copolymer and poly (vinyl halide); polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polymethyl methacrylate, polyacrylic Ethyl acetate, polyethyl methacrylate, poly (n-butyl acrylate), poly (n-butyl methacrylate), poly (2-ethylhexyl acrylate), poly (2-ethylhexyl methacrylate), poly [acrylic acid- ( N-butyl acrylate)], poly [acrylic acid- (2-ethylhexyl acrylate)], poly [acrylic acid Acid- (n-butyl acrylate)-(2-ethylhexyl acrylate)], poly [methacrylic acid- (n-butyl acrylate)], poly [methacrylic acid- (2-ethylhexyl acrylate)], poly [methacryl Acid- (n-butyl acrylate)-(2-ethylhexyl acrylate)], poly [acrylic acid-methacrylic acid- (n-butyl acrylate)], poly [acrylic acid-methacrylic acid- (2-ethylhexyl acrylate) )], Poly [acrylic acid-methacrylic acid- (n-butyl acrylate)-(2-ethylhexyl acrylate)], poly (stearyl acrylate), poly (stearyl methacrylate), (meth) acrylic polymers; polyepichloro Polyepihalohydrin rubbers such as hydrin rubber and polyepibromohydrin rubber; polyethylene oxide , Polypropylene oxide, polyalkylene oxide; ethylene-propylene-diene copolymer (EPDM); silicone rubber; silicone resin; fluororubber; fluororesin; polyethylene; ethylene-propylene copolymer, ethylene-1-butene copolymer Ethylene-α-olefin copolymers such as coalescence; α-olefin polymers such as polypropylene, poly-1-butene, poly-1-octene; polyhalogens such as polyvinyl chloride resin and polyvinyl bromide resin Polyvinylidene resin; Polyvinylidene chloride resin, Polyvinylidene bromide resin, Polyhalogenated vinylidene resin; Epoxy resin; Phenol resin; Polyphenylene ether resin; Nylon-6, Nylon-6, 6, Nylon-6, 12, etc. , Polyamide; polyurethane; polyester Polyvinyl acetate; poly (ethylene-vinyl alcohol); and the like.

  Among the specific examples of the rubber, elastomer and resin described above, styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, polyethyl acrylate, poly (n-butyl acrylate), poly (acrylic acid 2 -Ethylhexyl), poly [acrylic acid- (n-butyl acrylate)], poly [acrylic acid- (2-ethylhexyl acrylate)], poly [acrylic acid- (n-butyl acrylate)-(acrylic acid 2- Ethylhexyl)], poly [methacrylic acid- (n-butyl acrylate)], poly [methacrylic acid- (2-ethylhexyl acrylate)], poly [methacrylic acid- (n-butyl acrylate)-(acrylic acid 2- Ethylhexyl)], poly [acrylic acid-methacrylic acid- (n-butyl acrylate)], poly [acrylic acid] Acid - methacrylic acid - (2-ethylhexyl acrylate)], poly [acrylic acid - methacrylic acid - (n-butyl acrylate) - (2-ethylhexyl acrylate)] is, adhesion, preferred because of its excellent adhesiveness.

  More preferably, poly (n-butyl acrylate), poly (2-ethylhexyl acrylate), poly [acrylic acid- (n-butyl acrylate)], poly [acrylic acid- (2-ethylhexyl acrylate)], Poly [acrylic acid- (n-butyl acrylate)-(2-ethylhexyl acrylate)], poly [methacrylic acid- (n-butyl acrylate)], poly [methacrylic acid- (2-ethylhexyl acrylate)], Poly [methacrylic acid- (n-butyl acrylate)-(2-ethylhexyl acrylate)], poly [acrylic acid-methacrylic acid- (n-butyl acrylate)], poly [acrylic acid-methacrylic acid- (acrylic acid) 2-ethylhexyl)], poly [acrylic acid-methacrylic acid- (n-butyl acrylate)-(2-ethylhexyl acrylate) ], And the like.

  More preferable examples include poly [acrylic acid- (2-ethylhexyl acrylate)], poly [methacrylic acid- (2-ethylhexyl acrylate)], and poly [acrylic acid-methacrylic acid- (2-ethylhexyl acrylate)]. It is done.

  The said substance quoted as a specific example of rubber | gum, an elastomer, and resin may be used individually by 1 type, and may use 2 or more types together. As what constitutes the polymer (S), as will be described in detail later, a (meth) acrylic acid ester polymer (A1) is preferable, and in the presence of the (meth) acrylic acid ester polymer (A1) ( Those obtained by polymerizing the (meth) acrylic acid ester monomer (A2m) are particularly preferred.

  Various known agents can be used as the tackifier imparted to the polymer (S) as desired. For example, petroleum resin, terpene resin, phenol resin and rosin resin can be mentioned, and among these, petroleum resin is preferable. These may be used individually by 1 type and may use 2 or more types together.

  Specific examples of petroleum resins include C5 petroleum resins obtained from pentene, pentadiene, isoprene, etc .; C9 petroleum resins obtained from indene, methylindene, vinyltoluene, styrene, α-methylstyrene, β-methylstyrene, etc .; C5-C9 copolymerized petroleum resins obtained from monomers; petroleum resins obtained from cyclopentadiene and dicyclopentadiene; hydrides of these petroleum resins; maleic anhydride, maleic acid, fumaric acid, (meth) of these petroleum resins And modified petroleum resins modified with acrylic acid, phenol, and the like.

  Examples of terpene resins include α-pinene resins, β-pinene resins, and aromatic-modified terpene resins obtained by copolymerizing terpenes such as α-pinene and β-pinene with aromatic monomers such as styrene. .

  As the phenol resin, a condensate of phenols and formaldehyde can be used. Examples of the phenols include phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcin, and the like. These phenols and formaldehyde are subjected to an addition reaction with an alkali catalyst, or an acid catalyst is used for a condensation reaction. The novolak obtained by this can be illustrated. Moreover, the rosin phenol resin etc. which are obtained by adding phenol to an rosin with an acid catalyst and heat-polymerizing can also be illustrated.

  Examples of rosin resins include gum rosin, wood rosin or tall oil rosin, stabilized rosin or polymerized rosin disproportionated or hydrogenated using the rosin, maleic anhydride, maleic acid, fumaric acid, (meth) acrylic acid, Examples thereof include modified rosin modified with phenol and the like, and esterified products thereof.

  The alcohol used for esterification to obtain the esterified product is preferably a polyhydric alcohol, and examples thereof include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol and neopentyl glycol, glycerin, trimethylolethane, Examples include trihydric alcohols such as trimethylolpropane, tetrahydric alcohols such as pentaerythritol and diglycerin, and hexahydric alcohols such as dipentaerythritol. These may be used alone or in combination of two or more. You may use together.

  The softening point of these adhesiveness-imparting agents is not particularly limited, and liquids at room temperature can be appropriately selected from those having a high softening point of 200 ° C. or lower.

((Meth) acrylic acid ester polymer (A1))
A viewpoint that when the heat conductive pressure-sensitive adhesive composition (E) is used as the heat conductive pressure-sensitive adhesive sheet (F), it is easy to impart adhesion and flexibility to the heat conductive pressure-sensitive adhesive sheet (F). The polymer (S) is preferably a (meth) acrylic acid ester polymer (A1). Hereinafter, the (meth) acrylic acid ester polymer (A1) will be described in detail.

  The (meth) acrylic acid ester polymer (A1) is not particularly limited, but the unit (a1) of the (meth) acrylic acid ester monomer that forms a homopolymer having a glass transition temperature of −20 ° C. or lower, and It is preferable to contain a monomer unit (a2) having an organic acid group.

  The (meth) acrylate monomer (a1m) that gives the unit (a1) of the (meth) acrylate monomer that forms a homopolymer having a glass transition temperature of −20 ° C. or lower is not particularly limited. However, for example, ethyl acrylate (glass transition temperature of homopolymer is -24 ° C), propyl acrylate (-37 ° C), butyl acrylate (-54 ° C), sec-butyl acrylate (same as above) -22 ° C), heptyl acrylate (-60 ° C), hexyl acrylate (-61 ° C), octyl acrylate (-65 ° C), 2-ethylhexyl acrylate (-50 ° C), acrylic acid 2 -Methoxyethyl (at -50 ° C), 3-methoxypropyl acrylate (at -75 ° C), 3-methoxybutyl acrylate (at -56 ° C), 2-ethoxymethyl acrylate (at -50) ), Octyl methacrylate (same -25 ° C.), and the like decyl methacrylate (same -49 ° C.).

  These (meth) acrylic acid ester monomers (a1m) may be used individually by 1 type, and may use 2 or more types together.

  These (meth) acrylic acid ester monomers (a1m) are such that the monomer unit (a1) derived therefrom is preferably 80% by mass or more and 99.9% by mass in the (meth) acrylic acid ester polymer (A1). % Or less, more preferably 85% by mass or more and 99.5% by mass or less. When the amount of the (meth) acrylic acid ester monomer (a1m) is within the above range, the heat-sensitive pressure-sensitive adhesive sheet (F) obtained therefrom is excellent in pressure-sensitive adhesiveness around room temperature.

  The monomer (a2m) that gives the monomer unit (a2) having an organic acid group is not particularly limited, and representative examples thereof include organic acid groups such as a carboxyl group, an acid anhydride group, and a sulfonic acid group. In addition to these, monomers containing sulfenic acid groups, sulfinic acid groups, phosphoric acid groups, and the like can also be used.

  Specific examples of the monomer having a carboxyl group include, for example, α, β-ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, α, such as itaconic acid, maleic acid, and fumaric acid. In addition to β-ethylenically unsaturated polyvalent carboxylic acid, α, β-ethylenically unsaturated polyvalent carboxylic acid partial esters such as monomethyl itaconate, monobutyl maleate and monopropyl fumarate can be exemplified. Moreover, what has group which can be induced | guided | derived to a carboxyl group by hydrolysis etc., such as maleic anhydride and itaconic anhydride, can be used similarly.

  Specific examples of the monomer having a sulfonic acid group include allyl sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, α, β-unsaturated sulfonic acid such as acrylamide-2-methylpropane sulfonic acid, And salts thereof.

  Among these monomers having an organic acid group, monomers having a carboxyl group are more preferable, and acrylic acid and methacrylic acid are particularly preferable. These are industrially inexpensive and can be easily obtained, have good copolymerizability with other monomer components, and are preferable in terms of productivity. These monomers (a2m) having an organic acid group may be used alone or in combination of two or more.

  The monomer (a2m) having these organic acid groups is such that the monomer unit (a2) derived therefrom is 0.1% by mass or more and 20% by mass or less in the (meth) acrylic acid ester polymer (A1), Preferably, it is used for the polymerization in such an amount that it is 0.5 mass% or more and 15 mass% or less. In use within the above range, the viscosity of the polymerization system during polymerization can be maintained within an appropriate range.

  The monomer unit (a2) having an organic acid group is introduced into the (meth) acrylic acid ester polymer by polymerization of the monomer (a2m) having an organic acid group as described above. Although simple and preferable, an organic acid group may be introduced by a known polymer reaction after the (meth) acrylic acid ester polymer is formed.

  The (meth) acrylic acid ester polymer (A1) may contain a polymer unit (a3) derived from a monomer (a3m) containing a functional group other than an organic acid group.

  Examples of the functional group other than the organic acid group include a hydroxyl group, an amino group, an amide group, an epoxy group, and a mercapto group.

  Examples of the monomer having a hydroxyl group include (meth) acrylic acid hydroxyalkyl esters such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate.

  Examples of the monomer containing an amino group include N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and aminostyrene.

  Examples of monomers having an amide group include α, β-ethylenically unsaturated carboxylic acid amide monomers such as acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, and N, N-dimethylacrylamide. Can be mentioned.

  Examples of the monomer having an epoxy group include glycidyl (meth) acrylate and allyl glycidyl ether.

  The monomer (a3m) containing a functional group other than the organic acid group may be used alone or in combination of two or more.

  The monomer (a3m) having a functional group other than these organic acid groups is such that the monomer unit (a3) derived therefrom is 10% by mass or less in the (meth) acrylate polymer (A1). It is preferred to be used in the polymerization in an appropriate amount. By using 10 mass% or less of monomer (a3m), the viscosity at the time of superposition | polymerization can be kept appropriate.

  The (meth) acrylic acid ester polymer (A1) is a unit of (meth) acrylic acid ester monomer (a1) that forms a homopolymer having a glass transition temperature of −20 ° C. or lower, and an organic acid group. In addition to the monomer unit (a2) and the monomer unit (a3) containing a functional group other than the organic acid group, it is derived from a monomer (a4m) copolymerizable with these monomers. The monomer unit (a4) may be contained. A monomer (a4m) may be used individually by 1 type, and may use 2 or more types together.

  The amount of the monomer unit (a4) derived from the monomer (a4m) is preferably 10% by mass or less, more preferably 5% by mass or less of the acrylate polymer (A1).

  Although a monomer (a4m) is not specifically limited, As a specific example, (meth) acrylic acid ester monomers (a1m) other than (meth) acrylate monomer (a1m) that form a homopolymer having a glass transition temperature of −20 ° C. or lower are used. ) Acrylic acid ester monomer, α, β-ethylenically unsaturated polyvalent carboxylic acid complete ester, alkenyl aromatic monomer, conjugated diene monomer, non-conjugated diene monomer, vinyl cyanide monomer Carboxylic acid unsaturated alcohol ester, olefinic monomer and the like.

  Specific examples of the (meth) acrylate monomer other than the (meth) acrylate monomer (a1m) that forms a homopolymer having a glass transition temperature of −20 ° C. or lower include methyl acrylate (single The glass transition temperature of the polymer is 10 ° C., methyl methacrylate (105 ° C.), ethyl methacrylate (63 ° C.), propyl methacrylate (25 ° C.), butyl methacrylate (20 ° C.), and the like. be able to.

  Specific examples of the α, β-ethylenically unsaturated polyvalent carboxylic acid complete ester include dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate and dimethyl itaconate.

  Specific examples of the alkenyl aromatic monomer include styrene, α-methylstyrene, methyl α-methylstyrene, vinyl toluene, and divinylbenzene.

  Specific examples of the conjugated diene monomer include 1,3-butadiene, 2-methyl-1,3-monobutadiene (synonymous with isoprene), 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene. Examples include 2-chloro-1,3-butadiene and cyclopentadiene.

  Specific examples of the non-conjugated diene monomer include 1,4-hexadiene, dicyclopentadiene, ethylidene norbornene and the like.

  Specific examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like.

  Specific examples of the carboxylic acid unsaturated alcohol ester monomer include vinyl acetate.

  Specific examples of the olefin monomer include ethylene, propylene, butene, pentene and the like.

  The weight average molecular weight (Mw) of the (meth) acrylic acid ester polymer (A1) is preferably in the range of 100,000 to 400,000 as measured by gel permeation chromatography (GPC method). It is more preferable that it is in the range of 300 to 300,000.

  The (meth) acrylic acid ester polymer (A1) is a (meth) acrylic acid ester monomer (a1m) that forms a homopolymer having a glass transition temperature of −20 ° C. or lower, a monomer having an organic acid group (A2m), a monomer containing a functional group other than an organic acid group (a3m) used as required, and a monomer copolymerizable with these monomers used as needed ( a4m) can be obtained particularly preferably by copolymerization.

  The polymerization method is not particularly limited, and may be any of solution polymerization, emulsion polymerization, suspension polymerization, bulk polymerization and the like, and may be other methods. Solution polymerization is preferred, and among them, solution polymerization using a carboxylic acid ester such as ethyl acetate or ethyl lactate or an aromatic solvent such as benzene, toluene or xylene as the polymerization solvent is more preferred.

  In the polymerization, the monomer may be added in portions to the polymerization reaction vessel, but it is preferable to add the whole amount at once.

  The method for initiating the polymerization is not particularly limited, but it is preferable to use a thermal polymerization initiator as the polymerization initiator. The thermal polymerization initiator is not particularly limited, and may be either a peroxide or an azo compound.

  Peroxide polymerization initiators include hydroperoxides such as t-butyl hydroperoxide, peroxides such as benzoyl peroxide and cyclohexanone peroxide, and persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate. Can be mentioned. These peroxides can also be used as a redox catalyst in appropriate combination with a reducing agent.

  As azo compound polymerization initiators, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile) And so on.

  Although the usage-amount of a polymerization initiator is not specifically limited, It is preferable that it is the range of 0.01 mass part or more and 50 mass parts or less with respect to 100 mass parts of monomers.

  Other polymerization conditions (polymerization temperature, pressure, stirring conditions, etc.) of these monomers are not particularly limited.

  After completion of the polymerization reaction, the obtained polymer is separated from the polymerization medium as necessary. The separation method is not particularly limited, but in the case of solution polymerization, the (meth) acrylic acid ester polymer (A1) can be obtained by placing the polymerization solution under reduced pressure and distilling off the polymerization solvent.

  The weight average molecular weight of the (meth) acrylic acid ester polymer (A1) can be controlled by appropriately adjusting the amount of the polymerization initiator used in the polymerization and the amount of the chain transfer agent.

((Meth) acrylic acid ester monomer (A2m))
From the viewpoint of improving the formability of the heat conductive pressure sensitive adhesive sheet (F) when the heat conductive pressure sensitive adhesive composition (E) is used as the heat conductive pressure sensitive adhesive sheet (F), It is particularly preferred that the coalescence (S) is obtained by polymerizing the (meth) acrylic acid ester monomer (A2m) in the presence of the (meth) acrylic acid ester polymer (A1). When the heat conductive pressure-sensitive adhesive composition (E) of the present invention is formed into a heat conductive pressure-sensitive adhesive sheet (F), (meth) in the heat conductive pressure-sensitive adhesive composition (E). The acrylate monomer (A2m) is polymerized and converted to a (meth) acrylate polymer.

  The (meth) acrylic acid ester monomer (A2m) is not particularly limited as long as it contains a (meth) acrylic acid ester monomer, but a homopolymer having a glass transition temperature of −20 ° C. or lower. It is preferable to contain the (meth) acrylic acid ester monomer (a5m) to form.

  As an example of the (meth) acrylic acid ester monomer (a5m) that forms a homopolymer having a glass transition temperature of −20 ° C. or lower, it is used for the synthesis of a (meth) acrylic acid ester polymer (A1) (meta ) The same (meth) acrylate monomer as the acrylate monomer (a1m) can be mentioned. A (meth) acrylic acid ester monomer (a5m) may be used individually by 1 type, and may use 2 or more types together.

  The (meth) acrylate monomer (A2m) may be used as a mixture of the (meth) acrylate monomer (a5m) and a monomer copolymerizable therewith.

  Particularly preferred (meth) acrylate monomer (A2m) is a (meth) acrylate monomer (a5m) that forms a homopolymer having a glass transition temperature of −20 ° C. or lower, and an organic acid group. It consists of a monomer (a6m) having

  As an example of the monomer (a6m) having an organic acid group, a monomer having an organic acid group similar to that exemplified as the monomer (a2m) used for the synthesis of the (meth) acrylic acid ester polymer (A1). A polymer can be mentioned. As the monomer having an organic acid group (a6m), one type may be used alone, or two or more types may be used in combination.

  The ratio of the (meth) acrylate monomer (a5m) in the (meth) acrylate monomer (A2m) is preferably 70% by mass or more and 99.9% by mass or less, more preferably 75% by mass or more. 99% by mass or less. When the ratio of the (meth) acrylic acid ester monomer (a5m) is in the above range, the pressure-sensitive adhesiveness and flexibility of the heat conductive pressure-sensitive adhesive sheet (F) are excellent.

  The ratio of the monomer (a6m) having an organic acid group in the (meth) acrylic acid ester monomer (A2m) is preferably 0.1% by mass or more and 30% by mass or less, more preferably 1% by mass or more and 25%. It is below mass%. When the ratio of the monomer having an organic acid group (a6m) is in the above range, the hardness of the heat conductive pressure sensitive adhesive sheet is appropriate, and the pressure sensitive adhesive property at high temperature (100 ° C.) is good. It becomes.

  The (meth) acrylic acid ester monomer (A2m) is a monomer capable of copolymerizing with the (meth) acrylic acid ester monomer (a5m) and the monomer having an organic acid group (a6m). A body (a7m) can be contained in 20 mass% or less.

  Examples of the monomer (a7m) include a monomer (a3m), a monomer (a4m) used in the synthesis of the (meth) acrylic acid ester polymer (A1), or a polyfunctional monomer shown below. The monomer similar to what is illustrated as a body can be mentioned.

  As the copolymerizable monomer (a7m), as described above, a polyfunctional monomer having two or more polymerizable unsaturated bonds can also be used. By copolymerizing the polyfunctional monomer, intramolecular and / or intermolecular crosslinking can be introduced into the copolymer to increase the cohesive force as a pressure-sensitive adhesive.

  As polyfunctional monomers, 1,6-hexanediol di (meth) acrylate, 1,2-ethylene glycol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, polyethylene glycol di (meth) ) Acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pen erythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, ditrimethylolpropane tri Multifunctional (meth) acrylates such as (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and 2,4-bis (trichloromethyl) Other substituted triazines, such as 6-p-methoxystyrene-5-triazine, etc. monoethylenically unsaturated aromatic ketones such as 4-acryloxy benzophenone can be used. Among these, pen erythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, and pentaerythritol tetra (meth) acrylate are preferable. These can be used alone or in combination of two or more.

  The (meth) acrylic acid ester monomer (A2m) preferably contains the above polyfunctional monomer. The polyfunctional monomer is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.5% by mass or more and 3% by mass with respect to 100% by mass of the (meth) acrylic acid ester monomer (A2m). It is desirable to contain it by mass% or less.

  The amount of the (meth) acrylate monomer (A2m) contained in the heat conductive pressure-sensitive adhesive composition (E) is the lower limit with respect to 100 parts by weight of the (meth) acrylate polymer (A1). Is preferably 20 parts by mass, more preferably 40 parts by mass, and even more preferably 60 parts by mass. The upper limit is preferably 170 parts by mass, more preferably 150 parts by mass, and even more preferably 130 parts by mass. When the amount of the (meth) acrylic acid ester monomer (A2m) contained in the heat conductive pressure-sensitive adhesive composition (E) is less than the lower limit (20 parts by mass) or exceeds the upper limit (170 parts by mass) of the above range. When the heat conductive pressure-sensitive adhesive composition (E) is used as the heat conductive pressure-sensitive adhesive sheet (F), the pressure-sensitive adhesive retention of the heat conductive pressure-sensitive adhesive sheet (F) may be inferior. .

  When forming the heat conductive pressure sensitive adhesive sheet (F), it is preferable to polymerize the (meth) acrylic acid ester monomer (A2m) in the heat conductive pressure sensitive adhesive composition (E). While forming the thermally expanded pressure-sensitive adhesive composition (E) containing a predetermined amount of the expanded graphite powder (B) and the silane coupling agent (C) or the polyglycerol fatty acid ester (D) into a sheet, Or after shape | molding in a sheet form, in this heat conductive pressure sensitive adhesive composition (E) in presence of the (meth) acrylic acid ester polymer (A1) in this heat conductive pressure sensitive adhesive composition (E). From the solidified product (E ′) of the heat conductive pressure-sensitive adhesive composition (E) obtained by polymerizing the (meth) acrylic acid ester monomer (A2m) of (5), a heat conductive pressure-sensitive adhesive sheet (F) The surface state of the heat conductive pressure sensitive adhesive sheet (F) can be improved.

  In order to promote the polymerization, the heat conductive pressure-sensitive adhesive composition (E) is added to the (meth) acrylic acid ester polymer (A1) and the (meth) acrylic acid ester monomer (A2m), It preferably contains a polymerization initiator.

  Examples of the polymerization initiator include a photopolymerization initiator, an azo thermal polymerization initiator, an organic peroxide thermal polymerization initiator, and the like. From the viewpoint of the adhesive strength of the obtained heat conductive pressure-sensitive adhesive sheet (F). Therefore, an organic peroxide thermal polymerization initiator is preferably used.

  Various known photopolymerization initiators can be used as the photopolymerization initiator. Among these, a phosphine oxide compound is preferable. Examples of the phosphine oxide compound that is a preferred photopolymerization initiator include bis (2,4,6-trimethylbenzyl) phenylphosphine oxide and 2,4,6-trimethylbenzyldiphenylphosphine oxide.

  As azo thermal polymerization initiators, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile) ) And the like.

  Examples of organic peroxide thermal polymerization initiators include hydroperoxides such as t-butyl hydroperoxide, benzoyl peroxide, cyclohexanone peroxide, 1,6-bis (t-butylperoxycarbonyloxy) hexane, 1,1-bis ( Examples thereof include peroxides such as t-butylperoxy) -3,3,5-trimethylcyclohexanone, but it is preferable not to release volatile substances that cause odor during thermal decomposition. Among organic peroxide thermal polymerization initiators, those having a one-minute half-life temperature of 100 ° C. or more and 170 ° C. or less are preferable.

  The amount of the polymerization initiator such as the organic peroxide thermal polymerization initiator used is preferably 0.1 parts by mass, more preferably 100 parts by mass with respect to 100 parts by mass of the (meth) acrylic acid ester monomer (A2m). 0.3 mass part, More preferably, it is 0.5 mass part, and an upper limit becomes like this. Preferably it is 10 mass parts, More preferably, it is 5 mass parts, More preferably, it is 3 mass parts.

  The polymerization conversion rate of the (meth) acrylic acid ester monomer (A2m) is preferably 95% by mass or more. If the polymerization conversion rate is too low, a monomer odor remains in the obtained heat conductive pressure-sensitive adhesive sheet (F), which is not preferable.

<Other ingredients>
The heat-conductive pressure-sensitive adhesive composition (E) of the present invention further includes various known additions such as a foaming agent, an external cross-linking agent, a pigment, other fillers, an anti-aging agent, and a thickener, if necessary. An agent can be contained in the range which does not impair the effect of this invention.

(Foaming agent)
A foaming agent can also be added to the heat conductive pressure sensitive adhesive composition (E) of the present invention in order to foam the heat conductive pressure sensitive adhesive sheet (F) obtained therefrom. As the foaming agent, a thermally decomposable organic foaming agent is preferable. Furthermore, as a thermally decomposable organic foaming agent, what has a decomposition start temperature of 80 degreeC or more and 200 degrees C or less is preferable.

  Specific examples of such thermally decomposable organic foaming agents include 4,4'-oxybis (benzenesulfonyl hydrazide). Similarly, a foaming system in which a certain amount of a foaming aid described later is mixed with an organic foaming agent having a thermal decomposition starting temperature higher than 200 ° C., such as azodicarboxamide, and the thermal decomposition starting temperature is set to 100 ° C. or higher and 200 ° C. or lower. It can be a thermally decomposable organic foaming agent.

  Examples of the foaming aid include zinc stearate, a mixture of stearic acid and zinc white (zinc oxide), zinc laurate, a mixture of lauric acid and zinc white, zinc palmitate, a mixture of palmitic acid and zinc white, stearin Examples include sodium acid, sodium laurate, sodium palmitate, potassium stearate, potassium laurate, and potassium palmitate.

(External crosslinking agent)
In addition, an external cross-linking agent is added to the heat conductive pressure-sensitive adhesive composition (E) of the present invention in order to increase the cohesive force as a pressure-sensitive adhesive and improve heat resistance, and (meth) A crosslinked structure can be introduced into the polymer obtained by polymerizing the (meth) acrylate monomer (A2m) in the presence of the acrylate polymer (A1).

  Examples of external crosslinking agents include polyfunctional isocyanate crosslinking agents such as tolylene diisocyanate, trimethylolpropane diisocyanate, diphenylmethane triisocyanate; epoxy crosslinking such as diglycidyl ether, polyethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether Melamine resin crosslinking agent; amino resin crosslinking agent; metal salt crosslinking agent; metal chelate crosslinking agent; peroxide crosslinking agent;

  The external crosslinking agent is obtained by polymerizing the (meth) acrylic acid ester monomer (A2m) in the presence of the (meth) acrylic acid ester polymer (A1), and then added to this. By performing heat treatment or radiation irradiation treatment, a cross-link is formed within and / or between the molecules of the copolymer.

(Other)
The pigment can be used regardless of organic type or inorganic type such as carbon black and titanium dioxide. Examples of other fillers include inorganic compounds such as clay. You may add nanoparticles, such as fullerene and a carbon nanotube. Antioxidants such as polyphenols, hydroquinones, and hindered amines can be used as the anti-aging agent because they are likely to inhibit radical polymerization and are not usually used. As the thickener, inorganic polymer fine particles such as acrylic polymer particles and fine silica, and reactive inorganic compounds such as magnesium oxide can be used.

2. Thermally conductive pressure sensitive adhesive sheet (F)
The heat conductive pressure sensitive adhesive sheet (F) of the present invention is formed by molding a heat conductive pressure sensitive adhesive composition (E) into a sheet shape. When forming into a sheet, it is preferable to heat.

  In the heat conductive pressure-sensitive adhesive sheet (F) of the present invention, preferably, the heat conductive pressure-sensitive adhesive composition (E) is composed of a (meth) acrylate polymer (A1) and a (meth) acrylate ester. Containing a monomer (A2m), expanded graphite powder (B), silane coupling agent (C) or polyglycerin fatty acid ester (D), and thermally conductive pressure-sensitive adhesive composition (E) Obtained by polymerizing the (meth) acrylic acid ester monomer (A2m) in the presence of the (meth) acrylic acid ester polymer (A1) while being molded into a sheet shape or after being molded into a sheet shape. A sheet-like molded body of the solidified product (E ′) of the thermally conductive pressure-sensitive adhesive composition (E).

  However, when the content of the monomer in the heat conductive pressure-sensitive adhesive composition (E) is 5% by mass or less, the heat conductive pressure-sensitive adhesive composition (E) is a solidified product (E '). In fact, the heat conductive pressure-sensitive adhesive composition (E) substantially not containing the (meth) acrylic acid ester monomer (A2m) can be considered to be equivalent to the solidified product (E ′). .

  In the heat conductive pressure sensitive adhesive composition (E), when the monomer content in the heat conductive pressure sensitive adhesive composition (E) is 5% by mass or less, the heat conductive pressure sensitive adhesive composition The agent composition (E) can be molded as it is without polymerizing the monomer to obtain the heat conductive pressure-sensitive adhesive sheet (F) of the present invention.

  The heat conductive pressure-sensitive adhesive sheet (F) of the present invention may be composed of only the heat conductive pressure-sensitive adhesive composition (E) or its solidified product (E ′). It may be a composite comprising a thermally conductive pressure-sensitive adhesive composition (E) or a solidified product (E ′) layer formed on both sides.

  The thickness of the layer of the heat conductive pressure-sensitive adhesive composition (E) or its solidified product (E ′) in the heat conductive pressure-sensitive adhesive sheet (F) of the present invention is not particularly limited, but is usually 50 μm to 3 mm. is there. If it is thinner than 50 μm, air is likely to be involved when affixing to the heat generator and the heat radiating body, and as a result, sufficient thermal conductivity may not be obtained. On the other hand, if it is thicker than 3 mm, the thermal resistance in the thickness direction of the heat conductive pressure-sensitive adhesive sheet (F) becomes large, and there is a possibility that the heat dissipation is impaired.

  When the layer of the heat conductive pressure-sensitive adhesive composition (E) or its solidified product (E ′) is formed on one side or both sides of the substrate, the substrate is not particularly limited.

  Specific examples of the substrate include metals having excellent thermal conductivity such as aluminum, copper, stainless steel, and beryllium copper, and foils of alloys and polymers having excellent thermal conductivity such as thermal conductive silicone. A sheet-like material, a heat conductive plastic film containing a heat conductive filler, various nonwoven fabrics, glass cloth, a honeycomb structure, or the like can be used.

  Plastic films include polyimide, polyethylene terephthalate, polyethylene naphthalate, polytetrafluoroethylene, polyether ketone, polyethersulfone, polymethylpentene, polyetherimide, polysulfone, polyphenylene sulfide, polyamideimide, polyesterimide, aromatic polyamide, etc. A film made of a heat-resistant polymer can be used.

  The method for forming the heat conductive pressure-sensitive adhesive composition (E) or the solidified product (E ′) thereof into a sheet is not particularly limited. Suitable methods include, for example, a casting method in which the heat conductive pressure-sensitive adhesive composition (E) is applied onto process paper such as a polyester film subjected to a release treatment, the heat conductive pressure-sensitive adhesive composition (E) or The solidified product (E ′) is sandwiched between two exfoliated process papers if necessary and passed between rolls, and the thickness is controlled through a die when extruding using an extruder. And the like.

  While forming into a sheet or after forming into a sheet, for example, the heat conductive pressure-sensitive adhesive composition (E) is suitably obtained by heating the heat conductive pressure-sensitive adhesive composition (E) with hot air, an electric heater, infrared rays, or the like. be able to. The heating temperature at this time is preferably such that the organic peroxide thermal polymerization initiator decomposes efficiently and the polymerization of the (meth) acrylic acid ester monomer (A2m) proceeds. Although a temperature range changes with kinds of organic peroxide thermal-polymerization initiator to be used, 100 to 200 degreeC is preferable and 130 to 180 degreeC is more preferable.

  The heat conductive pressure-sensitive adhesive sheet (F) is obtained by forming the heat conductive pressure-sensitive adhesive composition (E) into a sheet shape and heating it to a temperature of 100 ° C. or higher and 200 ° C. or lower. It is a sheet-like molded body obtained by forming a sheet of the pressure-sensitive adhesive composition (E) and polymerizing the (meth) acrylic acid ester monomer (A2m) in the heat conductive pressure-sensitive adhesive composition (E). It is preferable.

  The heat conductive pressure-sensitive adhesive sheet (F) of the present invention can be directly formed on a base material such as a radiator and provided as a part of an electronic component.

  Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the examples. The “parts” and “%” used here are based on mass unless otherwise specified.

  The following measurements were performed using a heat conductive pressure-sensitive adhesive sheet (F) having a size of 30 mm width × 150 mm length as a sample.

<Measurement of thickness of heat conductive pressure sensitive adhesive sheet>
The thickness of the release paper attached to the sample was corrected to zero, and the sample with the release paper attached was placed on a thickness measuring instrument, and the thickness was measured. The results are shown in Table 2.

<Measurement of specific gravity>
The sample was divided into about 5 equal parts in the length direction, and five test pieces of about 30 mm × 50 mm were prepared from one sample. The five test specimens are named “right end”, “right side”, “center”, “left side”, and “left end” in order from one end of the sample, the specific gravity is measured for each, and the average and standard deviation thereof are measured. Asked. The results are shown in Table 2. The specific gravity was measured using an automatic hydrometer “DENSIMTER-H” manufactured by Toyo Seiki Seisakusho Co., Ltd.

Example 1
A reactor was charged with 100 parts of a monomer mixture composed of 94% 2-ethylhexyl acrylate and 6% acrylic acid, 0.03 parts 2,2′-azobisisobutyronitrile and 700 parts ethyl acetate. Then, after substitution with nitrogen, a polymerization reaction was carried out at 80 ° C. for 6 hours. The polymerization conversion rate was 97%. The obtained polymer was dried under reduced pressure to evaporate ethyl acetate to obtain a viscous solid (meth) acrylate polymer (A1). The weight average molecular weight (Mw) of the (meth) acrylic acid ester polymer (A1) was 270,000, and the weight average molecular weight (Mw) / number average molecular weight (Mn) was 3.1. The weight average molecular weight (Mw) and the number average molecular weight (Mn) were determined in terms of standard polystyrene by gel permeation chromatography using tetrahydrofuran as an eluent.

  Next, using an electronic balance, 0.2 part of a polyfunctional monomer obtained by mixing pentaerythritol triacrylate, pentaerythritol tetraacrylate and pentaerythritol diacrylate in a ratio of 60: 35: 5, 2-ethylhexyl acrylate (Hereinafter abbreviated as “2EHA”) 35.4 parts, methacrylic acid (hereinafter abbreviated as “MAA”) 2.7 parts, 1,6-bis (organic peroxide thermal polymerization initiator) t-butylperoxycarbonyloxy) hexane (hereinafter abbreviated as “tBCH”) [1 minute half-life temperature is 150 ° C. ] 1.8 parts were weighed and mixed to obtain a liquid raw material.

Next, 61.9 parts of the (meth) acrylic acid ester polymer (A1) and expanded graphite powder (B) (trade name “EC-50”, manufactured by Ito Graphite Industries Co., Ltd., average particle size: 250 μm) 44.2 parts, 1.8 parts of silane coupling agent (C) (trade name “KBM-503”, manufactured by Shin-Etsu Chemical Co., Ltd.), and the above liquid raw materials are put in a Hobart container in the order listed. The mixture was defoamed with stirring and mixing under reduced pressure to obtain a heat conductive pressure-sensitive adhesive composition (E1). The raw materials used are shown in Table 1. The mixing was performed according to the following conditions using a Hobart mixer (trade name “ACM-5LVT type, capacity: 5 L”) manufactured by Kodaira Seisakusho.
Mixing conditions:
Using a thermostatic bath (trade name “Viscomate 150III”, manufactured by Toki Sangyo Co., Ltd.), the temperature control of the Hobart container was set to 40 ° C.
1. 1. Mix in the rotation speed memory 3 × 10 minutes 2. Mix in rotation speed memory 5 x 20 minutes Rotation speed memory 3 × 10 minutes, mixing while vacuum degassing at -0.1 MPa

Thereafter, a polyester film with a release agent is laid on the bottom surface of the mold, and then the above heat conductive pressure-sensitive adhesive composition (E1) is poured into the mold, and the polyester film with a release agent is placed thereon. Covered with.
This was taken out of the mold and polymerized in a hot air oven at 155 ° C. for 30 minutes to obtain a heat conductive pressure sensitive adhesive sheet (F1) whose both surfaces were covered with a polyester film with a release agent.
The polymerization conversion rate of the (meth) acrylic acid ester monomer mixture (A2m) was calculated from the residual monomer amount in the heat conductive pressure-sensitive adhesive sheet (F1) and found to be 99.9%.
Each characteristic was evaluated about this heat conductive pressure sensitive adhesive sheet (F1). The results are shown in Table 2.

(Examples 2-7, Comparative Examples 1-2)
As shown in Table 1, the heat conductive pressure-sensitive adhesive compositions (E2) to (E7) and (EC1) to (EC2), similar to Example 1, except that each compound type and its amount were changed. And heat conductive pressure-sensitive-adhesive sheet (F2)-(F7) and (FC1)-(FC2) were obtained. Each characteristic was evaluated about the said heat conductive pressure-sensitive-adhesive sheet (F2)-(F7) and (FC1)-(FC2), respectively. The results are shown in Table 2.
However, those not shown in Example 1 were used as shown below.
Limpen-like graphite used in Comparative Example 2: (trade name “W-5”, manufactured by Ito Graphite Industries, Ltd., average particle size: 5 μm)
Silane coupling agent (C) used in Example 6: (trade name “KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd.)
Polyglycerin fatty acid ester (D) used in Example 7: (trade name “Tirabazole H-818”, manufactured by Taiyo Chemical Co., Ltd., average molecular weight: 4000)

  From the above results, it is considered that the thermal conductive pressure-sensitive adhesive sheets (F1) to (F7) of Examples 1 to 7 have small variations in specific gravity, and the expanded graphite powder (B) is dispersed almost uniformly. On the other hand, the heat conductive pressure-sensitive adhesive sheet (FC1) of Comparative Example 1 that does not contain the silane coupling agent (C) or the polyglycerin fatty acid ester (D) has a large variation. The expanded graphite powder (B) contained in the heat conductive pressure-sensitive adhesive sheets (F1) to (F7) of Examples 1 to 7 was dispersed almost uniformly by C) or the polyglycerol fatty acid ester (D). Conceivable. In addition, since the thermal conductive pressure-sensitive adhesive sheet (FC2) of Comparative Example 2 containing limpen-like graphite instead of the expanded graphite powder (B) had a large variation in specific gravity, a silane coupling agent ( C) is considered to have no effect on limpen-like graphite.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. Rather, the heat conductive pressure-sensitive adhesive composition and the heat conductive pressure-sensitive adhesive can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. The sheet must also be understood as being included in the technical scope of the present invention.

Claims (6)

Contains at least one polymer (S) selected from the group consisting of rubber, elastomer and resin, expanded graphite powder (B), and silane coupling agent (C) or polyglycerol fatty acid ester (D). A heat-conductive pressure-sensitive adhesive composition (E) characterized by the above. 30 parts by mass or more and 400 parts by mass or less of the expanded graphite powder (B) and 1 part by mass or more and 150 parts by mass or less of the silane coupling agent (C) or the above-mentioned polymer (S) The heat conductive pressure-sensitive adhesive composition (E) according to claim 1, comprising a polyglycerin fatty acid ester (D). The heat conductive pressure-sensitive-adhesive composition (E) of Claim 1 or 2 whose said polymer (S) is a (meth) acrylic acid ester polymer (A1). The heat conductive pressure-sensitive adhesive composition (E) according to claim 3, further comprising a (meth) acrylic acid ester monomer (A2m). The heat conductive pressure sensitive adhesive sheet (F) formed by shape | molding the heat conductive pressure sensitive adhesive composition (E) in any one of Claims 1-4 in a sheet form. While forming the heat conductive pressure sensitive adhesive composition (E) according to claim 4 into a sheet shape or after forming into a sheet shape, (meth) in the heat conductive pressure sensitive adhesive composition (E). The thermal conductive feeling obtained by polymerizing the (meth) acrylic ester monomer (A2m) in the thermal conductive pressure-sensitive adhesive composition (E) in the presence of the acrylic ester polymer (A1). The heat conductive pressure-sensitive-adhesive sheet (F) which is a sheet-like molded object of the solidified material (E ') of a pressure-sensitive adhesive composition (E).