JP2009138019A - Silicone rubber composition for acf pressure bonding sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure bonding sheet capable of achieving a smaller sheet thickness and higher thermal conduction and excellent also in releasability from an ACF (Anisotropic Conductive Film). <P>SOLUTION: The silicone rubber composition for the ACF pressure bonding sheet having a thermal conductivity of ≥0.5 W/mK comprises (A) 100 pts.wt. of a silicone rubber composition prepared by mixing a silicone rubber composition containing the following components (a-1) to (a-5) at a temperature lower than a decomposition temperature of the component (a-5) and heat-treating the mixture at the decomposition temperature of the component (a-5) or above and (B) such an amount of a curing agent as to be required to cure the component (A). Component (a-1): 100 pts.wt. of a polyorganosiloxane having an average polymerization degree of 4,000-20,000 represented by an average unit formula: R<SB>a</SB>SiO<SB>(4-a)/2</SB>(wherein R and a have predetermined meanings), (a-2): 0.1-20 pts.wt. of a hydroxy or alkoxy end-blocked polyorganosiloxane having a polymerization degree of 6-700 represented by an average unit formula: R<SP>1</SP><SB>b</SB>SiO<SB>(4-b)/2</SB>(wherein R<SP>1</SP>and b have predetermined meanings), (a-3): 1-50 pts.wt. of fine powdered fumed silica, (a-4): such an amount of a thermally conductive filler as to make the volume ratio of (a-4)/(a-1) (50-200)/100, (a-5) 0.001-10 pts.wt. of a thermally decomposable catalyst represented by an average unit formula: M<SP>1</SP>O(R<SP>2</SP><SB>c</SB>SiO)<SB>z</SB>M<SP>2</SP>(wherein M<SP>1</SP>, M<SP>2</SP>, R<SP>2</SP>, c and z have predetermined meanings). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a silicone rubber composition used as a pressure-sensitive adhesive sheet for ACF (anisotropic conductive adhesive film).

  In recent years, flat display panels such as liquid crystal panels and plasma display panels are increasingly used as displays for personal computers, thin-screen TVs, mobile phones and the like. The electrodes connected to the flat display panel and the lead electrodes of the flexible printed circuit board on which the driving LSI is mounted are thermocompression bonded via an ACF (anisotropic conductive adhesive film) to be electrically and mechanically connected. Things have been done.

  In this case, a thermocompression bonding sheet is used for the purpose of transferring heat from the thermocompression bonding jig to the ACF and applying a uniform pressure between the thermocompression bonding jig and the flexible printed circuit board. The thermocompression bonding sheet is required to be peelable from the ACF so that it can be used repeatedly.

  As such a thermocompression bonding sheet, a silicone rubber sheet having low elasticity, flexibility, and good thermal conductivity has come to be used, and various sheets have been proposed (Patent Document 1, etc.).

The sheet for thermocompression bonding includes a single layer of silicone rubber and a multilayer layer (a layer of heat-resistant resin film laminated on silicone rubber to improve physical strength, a thin release layer on the silicone rubber sheet. However, in the case of multiple layers, the thermal conductivity of the entire sheet is reduced. To compensate for this, it is necessary to increase the temperature of the thermocompression bonding jig. Problems such as thermal deformation of the thermocompression bonding jig may occur. In particular, with the recent increase in the size of flat display panels, the problem of productivity due to the necessity of increasing the temperature of the thermocompression bonding jig has become more prominent. In addition, the multilayer sheet has a problem that the manufacturing cost itself is remarkably increased.
JP 2006-281670 A

  The present invention has been devised in view of the above-mentioned problems of the prior art, and provides a pressure-sensitive adhesive sheet that can be thinned and has high thermal conductivity and is excellent in releasability from ACF. Objective.

  As a result of intensive investigations to achieve the above object, the present inventors have found that polyorganosiloxane containing finely powdered fumed silica and a thermally conductive filler is blocked with a hydroxyl group or an alkoxy group at the end. And a specific heat-decomposable catalyst are combined and heated to a temperature above the decomposition temperature of the catalyst, and a silicone rubber composition containing a curing agent has a high thermal conductivity and good The present inventors have found that a thin layer sheet can be produced with good workability and can be a pressure-bonding sheet excellent in releasability from ACF, and the present invention has been completed.

That is, the present invention
(A) After mixing a silicone rubber composition containing the following (a-1) to (a-5) at a temperature lower than the decomposition temperature of the component (a-5), Heat-treated silicone rubber composition 100 parts by weight (a-1) Average unit formula: R _a SiO _{(4-a) / 2}
(Wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, a represents a number in the range of 1.98 to 2.02) 100 parts by weight of polyorganosiloxane having an average degree of polymerization of 4000 to 20000 (a- 2) Average unit formula: R ¹ _b SiO _{(4-b) / 2}
(Wherein R ¹ represents a substituted or unsubstituted monovalent hydrocarbon group, b represents a number in the range of 1.98 to 2.02), and the degree of polymerization is blocked with a hydroxyl group or an alkoxy group. 0.1 to 20 parts by weight of polyorganosiloxane being 6 to 700 (a-3) 1 to 50 parts by weight of finely powdered fumed silica (a-4) thermally conductive filler, with respect to volume 100 of (a-1) Amount of (a-4) volume 50-200 (a-5) Average unit formula: M ¹ O (R ² _c SiO) _z M ²
(Wherein M ¹ is a tetraalkylammonium group or a tetraalkylphosphonium group, M ² is the same or hydrogen as M ¹ , R ² is a substituted or unsubstituted monovalent hydrocarbon group, and c is 1.98. 0.001-10 parts by weight of a thermally decomposable catalyst represented by a number in the range of -2.02 and z is a number of 1-1000)
(B) A silicone rubber composition for an ACF pressure-bonded sheet having a thermal conductivity of 0.5 W / mK or more, comprising a curing agent and an amount necessary to cure the component (A).

  Hereinafter, the present invention will be described in detail. The component (A) used in the present invention is composed of a polyorganosiloxane containing finely powdered fumed silica and a thermally conductive filler, a polyorganosiloxane whose end is blocked with a hydroxyl group or an alkoxy group, and a specific thermal decomposability. It is a silicone rubber composition obtained by combining a catalyst and heating it to a temperature equal to or higher than the decomposition temperature of the catalyst.

Average unit formula of component (a-1): R _a SiO _{(4-a) / 2}
The polyorganosiloxane represented by the formula (wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, and a represents a number in the range of 1.98 to 2.02) is a base polymer of the curable silicone composition. In general, a straight chain is used, but a part thereof may form a branched chain or a three-dimensional structure, and may be a homopolymer, a copolymer or a mixture thereof. Good. Examples of the substituted or unsubstituted monovalent hydrocarbon group bonded to the silicon atom of the polyorganosiloxane include an alkyl group such as a methyl group, an ethyl group and a propyl group; a vinyl group, an allyl group and a butadienyl group. An alkenyl group; an aryl group such as a phenyl group, a xenyl group, and a naphthyl group; a cycloalkyl group such as a cyclohexyl group; a cycloaryanyl group such as a cyclohexenyl group; an aralkyl group such as a benzyl group; a tolyl group, and a xylyl group Examples thereof include alkylaryl groups. As the monovalent hydrocarbon group bonded to these silicon atoms, a methyl group is mainly used. For example, in the case of a vinyl group, 0 to 5 with respect to the total number of organic groups from the viewpoint of mechanical strength and crosslinkability. % May be contained, and the range of 0.05 to 3% is particularly preferable. In addition, as a molecular chain terminal of polyorganosiloxane, a hydroxyl group, an alkoxy group, or a triorganosilyl group is illustrated, and a triorganosilyl group is more preferable. Examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, and a methyldiphenylsilyl group. The average degree of polymerization of the component (a-1) is in the range of 4000 to 20000, preferably 600 to 10,000. If the degree of polymerization is too small, it is difficult to obtain sufficient mechanical strength. Conversely, if the degree of polymerization is too large, blending into the system becomes difficult.

The component (a-2) used in the present invention has an average unit formula: R ¹ _b SiO _{(4-b) / 2}
(Wherein R ¹ represents a substituted or unsubstituted monovalent hydrocarbon group, b represents a number in the range of 1.98 to 2.02), and the degree of polymerization is blocked with a hydroxyl group or an alkoxy group. The polyorganosiloxane is 6 to 700, preferably 10 to 300, more preferably 15 to 200, and a linear one is mainly used. A part of the polyorganosiloxane forms a branched chain and a three-dimensional structure. May be. Examples of the substituted or unsubstituted monovalent hydrocarbon group used in the polyorganosiloxane include an alkyl group such as a methyl group, an ethyl group, and a propyl group; an alkenyl group such as a vinyl group, an allyl group, and a butadienyl group; Aryl groups such as phenyl, xenyl and naphthyl groups; cycloalkyl groups such as cyclohexyl groups; cycloalkyl groups such as cyclohexenyl groups; aralkyl groups such as benzyl groups; alkylaryls such as tolyl groups and xylyl groups Examples include groups such as the monovalent hydrocarbon group used in component (a-1), considering compatibility with the polyorganosiloxane of component (a-1) that is the base polymer. It is desirable to be. Furthermore, the molecular chain terminal of the polyorganosiloxane is either a hydroxyl group or an alkoxy group. Further, when the molecular weight of the component (a-2) is high, the effect as a treating agent is reduced, and when the molecular weight is too low, the roll workability of the obtained compound is deteriorated, so that the degree of polymerization is 6 to 700, preferably The range is 10 to 300, more preferably 15 to 200. If the compounding amount of component (a-2) is too large, the resulting compound will be sticky, and if it is too small, the surface treatment effect of the filler will be inadequate, and good workability and releasability will be the original purpose. Since it cannot be obtained, it is used in the range of 0.1 to 20 parts by weight per 100 parts by weight of component (a-1).

  The fine powder fumed silica of the component (a-3) may be a known one generally blended with silicone rubber or the like. The preferred particle size of these fumed silicas is 20 μm or less. These fumed silicas may be not surface-treated, or may be surface-treated with organosilane, organochlorosilane, organosiloxane, organosilazane, or the like. Wet silica is not preferred because it has a high water content and reduces the catalytic action of the component (a-5). If the blending amount of this component (a-3) is too large, the compound becomes hard and it becomes difficult to blend a sufficient amount of the heat conductive filler, and the necessary heat conductivity cannot be obtained. If the amount is too small, the mechanical properties are lowered.

  As the (a-4) thermally conductive filler used in the present invention, those having a thermal conductivity of 1 W / mK or more are preferable, and metal oxides such as alumina, quartz and zinc oxide; aluminum nitride, boron nitride and silicon nitride Metal carbides such as silicon carbide; metal powders such as aluminum powder and silver powder; diamond powders; carbon black such as carbon graphite, acetylene black and furnace black, etc., particularly zinc oxide and quartz are preferred. Used.

  Further, zinc oxide having an average particle diameter of 0.1 to 20 μm is preferable, and quartz having an average particle diameter of 0.1 to 10 μm is particularly preferable.

  In addition, a thermally conductive filler that has been subjected to a surface treatment with a silane coupling agent or the like in advance in order to facilitate blending may be used.

  Furthermore, it is particularly preferable to use (a-4) a thermally conductive filler in combination with zinc oxide having an average particle diameter of 0.1 to 20 μm and quartz having an average particle diameter of 0.1 to 10 μm. It is preferable that the volume of quartz relative to the total volume of the thermally conductive filler is 30% or more.

  Further, the blending amount of the (a-4) thermally conductive filler is an amount such that the volume of (a-4) is 50 to 200 with respect to the volume 100 of (a-1) polyorganosiloxane. The silicone rubber composition for ACF pressure-bonding sheets is appropriately selected so that the thermal conductivity is 0.5 W / mK or more.

The component (a-5) used in the present invention has an average unit formula: M ¹ O (R ² _c SiO) _z M ²
(Wherein M ¹ is a tetraalkylammonium group or a tetraalkylphosphonium group, M ² is the same or hydrogen as M ¹ , R ² is a substituted or unsubstituted monovalent hydrocarbon group, and c is 1.98. The number is in the range of -2.02, and z is a number of 1-1000). As the component (a-5), those having a polymerization degree z in the range of 1 to 1000 are used, and preferably 5 to 100. When the polymerization degree z exceeds 1000, the viscosity becomes high, handling becomes difficult, and workability is lowered. This component (a-5) can be obtained by reacting tetraalkylammonium hydroxide, tetraalkylphosphonium hydroxide and polyorganosiloxane by a known method. Here, it is conceivable to use these hydroxides for this purpose, but these are usually present in an aqueous solution of 50% by weight or less, and thus dispersibility in the silicone rubber compound becomes very poor. The target kneading time cannot be shortened, and even if dispersed, water that lowers the catalytic action is contained in the composition, making it difficult to control the reaction, and the silicone rubber compound is not collected. It is very difficult to obtain stable characteristics because it may be scattered and become unmanufacturable. In addition, an aqueous solution exceeding 50% by weight cannot be prepared, and in this case, it becomes a solid form, which is also very difficult to disperse. On the other hand, the component (a-5) of the present invention has very good dispersibility in the silicone rubber compound, and since it does not contain moisture, the reaction can be easily controlled, and the silicone rubber composition of the present purpose can be easily and quickly. Can be obtained. From the standpoint of catalyst stability, tetraalkylammonium silanolate is preferred. This component (a-5) is obtained by polycondensing the hydroxyl group or alkoxy group of the component (a-2) with the hydroxyl group on the component (a-3) and (a-4) and performing filler treatment, It is considered that the condensation polymerization of the components a-2) occurs, and further, the silicone rubber composition is slightly equilibrated at the same time due to the trace amount of water contained in the components (a-3) and (a-4). As a result, there are very few residual hydroxyl groups and alkoxy groups in the silicone rubber composition, and the familiarity between the components (a-1) and (a-3) and (a-4) is very good. A silicone rubber composition excellent in moldability and moldability and excellent in releasability for ACF can be obtained. The amount of component (a-5) is preferably 0.001 to 10 parts by weight with respect to 100 parts by weight of component (a-1). If the amount is less than 0.001 part by weight, the reaction does not proceed sufficiently. The odor of the catalytic decomposition substance becomes a problem. The decomposition temperature of the component (a-5) is not particularly limited, but is preferably 70 ° C. or higher from the viewpoint of stability, and 130 ° C. or lower is preferable from the viewpoint of reaction temperature.

  The component (A) silicone rubber composition comprises (a-1) a high-molecular-weight polyorganosiloxane, (a-2) a low-viscosity polyorganosiloxane whose end is blocked with a hydroxyl group or an alkoxy group, and (a-3) a fume. It can be obtained simply by adding the above-described (a-5) thermally decomposable catalyst to a silicone rubber composition containing silica, and (a-4) a thermally conductive filler. In the production of the silicone rubber composition of the component (A), the components (a-1) to (a-5) may be mixed together or the components (a-1) to (a-4) may be mixed. Thereafter, the component (a-5) may be added. However, the component (a-5) needs to be added below the decomposition temperature, and after the addition, it needs to be above the decomposition temperature. However, the manufacturing process shown here is the one in which the component (a-5) is added to the normal method for manufacturing a silicone rubber composition, and those skilled in the art may introduce a special manufacturing apparatus. And can be manufactured easily.

  The silicone rubber composition of the present invention can be obtained by applying a known silicone rubber curing mechanism, and is generally cured by crosslinking with an organic peroxide or by addition reaction. It is. The curing agent as component (B) is as follows.

  As the curing agent used for crosslinking of the organic peroxide, commercially available organic peroxides can be used, such as benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide. , Dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, di-t-butyl peroxide, and other organic peroxide vulcanizing agents are used. .

  These organic peroxide vulcanizing agents can be used as one kind or a mixture of two or more kinds. The compounding amount of the organic peroxide as the curing agent is generally in the range of 0.05 to 10 parts by weight with respect to 100 parts by weight of the silicone base polymer of component (A).

  On the other hand, as a curing agent when crosslinking by addition reaction is applied, a platinum catalyst such as chloroplatinic acid, platinum olefin complex, platinum vinylsiloxane complex, platinum black, platinum triphenylphosphine complex is used as a curing catalyst. As the crosslinking agent, a polydiorganosiloxane having an average number of hydrogen atoms bonded to silicon atoms exceeding at least two per molecule is used. Of the addition reaction curing agent, the amount of the curing catalyst is preferably in the range of 0.1 to 1000 ppm in terms of platinum element with respect to the base polymer of component (A). If the blending amount of the curing catalyst is less than 0.1 ppm as the amount of platinum element, curing does not proceed sufficiently, and if it exceeds 1000 ppm, no improvement in the curing rate can be expected. The amount of the crosslinking agent is preferably such that the number of hydrogen atoms bonded to silicon atoms in the crosslinking agent is 0.5 to 20 per alkenyl group in component (A). The amount is preferably 1 to 10. When the amount of hydrogen atoms is less than 0.5, the curing of the composition does not proceed sufficiently, the hardness of the composition after curing becomes low, and when the amount of hydrogen atoms exceeds 20 The physical properties and heat resistance of the cured composition are reduced.

  In addition to the above components, the silicone rubber composition used in the present invention may contain a semi-reinforcing or non-reinforcing filler as long as the effects of the present invention are not impaired. Examples of the semi-reinforcing or non-reinforcing filler include diatomaceous earth, metal carbonate, clay, talc, mica, and titanium oxide. Further, heat-resistant additives, flame retardants, antioxidants, processing aids and the like conventionally used in the silicone rubber composition can be blended.

The thickness of the layer made of the cured product of the silicone rubber composition constituting the pressure-bonding sheet is usually 10 to 10,000 μm, preferably 30 to 1,000 μm, more preferably 50 to 500 μm. If this range is satisfied, the strength of the pressure-bonding sheet becomes good and there is no risk of breakage, and the temperature of the thermocompression bonding jig is sufficiently transmitted to the ACF.
The thermocompression-bonding sheet according to the present invention can be produced by forming the composition into a sheet by pressing, calendering, or the like as necessary, followed by curing.

  Next, examples of the present invention will be described, but the present invention is not limited to the following examples. Moreover, the part in an example represents a weight part.

Example 1
(CH _{3) 2} SiO units 99.8 _{mol%, (CH 3) (CH} 2 = CH) of SiO units 0.2 mol%, terminals blocked with dimethyl vinyl silyl group, a polyorganosiloxane 100 parts of polymerization degree 6000 , 1.5 parts of polydiorganosiloxane with terminal terminated by silanol group and polymerization degree of 50, 3.5 parts of polydiorganosiloxane with terminal closed by methoxy group and degree of polymerization of 20, surface treated with octamethylcyclotetrasiloxane 25 parts of fumed silica (AEROSIL 200) and 460 parts of zinc oxide (average particle size 8 μm) were kneaded with a kneader mixer until uniform, and 0.1 part of tetramethylammonium silanolate (z = 20) was added and kneaded. The temperature at this time was 60 ° C. Thereafter, heat treatment was performed at 150 ° C. for 3 hours to obtain a silicone rubber composition.

  For 100 parts by weight of this silicone rubber composition, 0.5 part of TC-25 (A) (made by Momentive Performance Materials Japan) as an addition reaction type catalyst and TC25- (B) (momentive performance as a crosslinking agent) (Materials Japan) 2.0 parts was blended to obtain a silicone rubber compound.

  Next, this silicone rubber compound is dispensed using a calendering machine so that the thickness is 0.5 mm on the PET film, and this is first cured at 150 ° C. for 1 hour, and then the PET film is removed. Secondary curing was performed at 200 ° C. for 4 hours to produce a pressure-bonded sheet.

  In addition, this silicone rubber compound having a thickness of 2 mm was subjected to press molding at 170 ° C. for 15 minutes, and then taken out from the die and subjected to secondary curing at 200 ° C. for 4 hours to measure mechanical properties. Created a sheet.

  Furthermore, after press molding at 170 ° C. for 15 minutes using this silicone rubber compound 20 mm thick mold, it was taken out from the mold and subjected to secondary curing at 200 ° C. for 4 hours to measure the thermal conductivity. A test specimen was created.

Example 2
As a thermally conductive filler, a pressure-sensitive adhesive sheet, a sheet for measuring mechanical properties, and a sheet for measuring mechanical properties were obtained in the same manner as in Example 1 except that zinc oxide having an average particle diameter of 8 μm and quartz having an average particle diameter of 4 μm were used in the ratio shown in Table 1. A test specimen for measuring thermal conductivity was prepared.

Example 3
A pressure-sensitive adhesive sheet, a sheet for measuring mechanical properties, and a test for measuring thermal conductivity were performed in the same manner as in Example 1 except that quartz having an average particle diameter of 4 μm was used as the thermally conductive filler in the ratio shown in Table 1. The body was made.

Comparative Examples 1-6
As shown in Table 1, when fumed silica is not blended or when a thermally decomposable catalyst is not blended, etc., in the same manner as in Example 1, a pressure-bonded sheet, a sheet for measuring mechanical properties, and for measuring thermal conductivity The test body was prepared.

About the crimping | compression-bonding sheet obtained in Examples 1-2 or Comparative Examples 1-6, it evaluated on the following references | standards.
<Mechanical properties>
In accordance with JIS K6249, hardness, tensile strength, and elongation were measured.
<Thermal conductivity>
It measured with the Kyoto Electronics Industrial Co., Ltd. product thermal conductivity meter QTM-500.
<Processability>
The workability (roll workability) when a 0.5 mm thick sheet was calendered was evaluated in the following three stages.
○: Good calendar formability (ear crack less than 5mm)
Δ: Calendar formability is poor (ear crack 5mm or more)
×: Inability to calendar molding <ACF releasability>
(Number of times)
Repeatedly pressing the pressure-bonded sheet on ACF with width of 1mm ("ANISOLM AC" manufactured by Hitachi Chemical Co., Ltd.) at 180 ° C and 4Mpa for 30 seconds. evaluated.
◎: 20 times or more ○: 10 times or more and less than 20 times Δ: 5 times or more and less than 10 times ×: Less than 5 times (after fixing)
When the sheet adhered in the above (number of times) test, the adhered sheet was peeled off to confirm the presence or absence of cohesive failure, and evaluated in the following three stages.
◯: No cohesive failure Δ: Partial cohesive failure ×: Rubber rupture These results are shown in Table 1.

Claims (4)

(A) After mixing a silicone rubber composition containing the following (a-1) to (a-5) at a temperature lower than the decomposition temperature of the component (a-5), Heat-treated silicone rubber composition 100 parts by weight (a-1) Average unit formula: R _a SiO _{(4-a) / 2}
(Wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, a represents a number in the range of 1.98 to 2.02) 100 parts by weight of polyorganosiloxane having an average degree of polymerization of 4000 to 20000 (a- 2) Average unit formula: R ¹ _b SiO _{(4-b) / 2}
(Wherein R ¹ represents a substituted or unsubstituted monovalent hydrocarbon group, b represents a number in the range of 1.98 to 2.02), and the degree of polymerization is blocked with a hydroxyl group or an alkoxy group. 0.1 to 20 parts by weight of polyorganosiloxane being 6 to 700 (a-3) 1 to 50 parts by weight of finely powdered fumed silica (a-4) thermally conductive filler, with respect to volume 100 of (a-1) Amount of (a-4) volume 50-200 (a-5) Average unit formula: M ¹ O (R ² _c SiO) _z M ²
(Wherein M ¹ is a tetraalkylammonium group or a tetraalkylphosphonium group, M ² is the same or hydrogen as M ¹ , R ² is a substituted or unsubstituted monovalent hydrocarbon group, and c is 1.98. 0.001-10 parts by weight of a thermally decomposable catalyst represented by a number in the range of -2.02 and z is a number of 1-1000)
A silicone rubber composition for an ACF pressure-bonded sheet having a thermal conductivity of 0.5 W / mK or more, comprising (B) a curing agent and an amount necessary for curing the component (A).   (A-4) The silicone rubber composition for an ACF pressure-bonded sheet according to claim 1, wherein the thermally conductive filler is zinc oxide having an average particle size of 0.1 to 20 μm.   (A-4) The silicone rubber composition for an ACF pressure-bonded sheet according to claim 1, wherein the thermally conductive filler is quartz having an average particle size of 0.1 to 10 μm.   (A-4) The silicone rubber composition for an ACF pressure-bonded sheet according to claim 1, wherein zinc oxide having an average particle size of 0.1 to 20 μm and quartz having an average particle size of 0.1 to 10 μm are used in combination as the thermally conductive filler. .