JP7070320B2 - Thermally conductive silicone composition - Google Patents

Description

The present invention relates to a thermally conductive silicone composition in which the hardness after curing does not increase even when exposed to a high temperature for a long time, and no outflow occurs after mounting.

It is widely known that electronic components such as LSIs and IC chips generate heat during use and the performance deteriorates with it, and various heat dissipation techniques are used as means for solving this. For example, by arranging a member for cooling purposes such as a heat sink near the heat generating part and bringing them into close contact with each other, efficient heat transfer to the cooling member is promoted and the cooling member is cooled to efficiently dissipate heat from the heat generating part. It is known to do so. At that time, if there is a gap between the heat generating member and the cooling member, the temperature of the heat generating member cannot be sufficiently lowered because heat transfer becomes inefficient due to the presence of air having low thermal conductivity. In order to prevent the intervention of air between the heat generating member and the cooling member in order to prevent such a phenomenon, a heat radiating material, a heat radiating sheet or a heat radiating grease having good thermal conductivity and following the surface of the member is used. (Patent No. 2938428, Japanese Patent No. 2938429, Japanese Patent No. 3952184: Patent Documents 1 to 3). Among them, thermal paste exhibits high performance from the viewpoint of thermal resistance because it can be used with a thin thickness at the time of mounting.

There is also a type of thermal paste that is sandwiched between members and then heat-cured before use. Since the heat-cured thermal paste is further heated during operation of the element, its hardness may increase during use. If the hardness increases, the material becomes inflexible, and there is a concern that it will not be able to follow the “warp” during operation. If it cannot follow, a gap will be generated between the member and the heat-dissipating grease, and the heat-dissipating characteristics will deteriorate.

Japanese Patent No. 29384428 Japanese Patent No. 2938429 Japanese Patent No. 3952184

The present invention has been made in view of the above circumstances, and provides a thermally conductive silicone composition in which the hardness after curing does not increase even when exposed to a high temperature for a long time and the outflow does not occur after mounting. The purpose.

As a result of diligent studies to achieve the above object, the present inventor (A) has an alkenyl group directly bonded to at least two silicon atoms in one molecule, and has a kinematic viscosity at 25 ° C. of 10 to 100. 000 mm ² / s organopolysiloxane, (B) one-terminal trifunctional hydrolyzable methylpolysiloxane represented by the general formula (1) described later, (C) heat having a thermal conductivity of 10 W / m ° C. or higher. Conductive filler, (D) Organohydrogenpolysiloxane containing at least one hydrogen atom directly connected to a silicon atom at the terminal site and side chain site, respectively, 1 other than the components (E) and (D) Thermally conductive silicone composition containing a specific amount of an organohydrogenpolysiloxane containing a hydrogen atom directly connected to at least two silicon atoms in the molecule and a catalyst selected from the group consisting of (F) platinum and platinum compounds. We have found that the hardness of an object does not increase after curing even when it is exposed to a high temperature for a long time, and that no outflow occurs after mounting, which led to the present invention.

（式中、Ｒ¹は炭素数１～６のアルキル基であり、ａは５～１００の整数である。）
で表される片末端３官能の加水分解性メチルポリシロキサン： （Ａ）成分１００質量部に対して１０～４００質量部、
（Ｃ）１０Ｗ／ｍ℃以上の熱伝導率を有する熱伝導性充填材： （Ａ）成分と（Ｂ）成分の合計１００質量部に対して５００～３，０００質量部、
（Ｄ）末端部位と側鎖部位にそれぞれ少なくとも１個のケイ素原子に直結した水素原子を１分子中に含有するオルガノハイドロジェンポリシロキサン、
（Ｅ）（Ｄ）成分以外の１分子中に少なくとも２個のケイ素原子に直結した水素原子を含有するオルガノハイドロジェンポリシロキサン、
但し、｛（Ｄ）成分と（Ｅ）成分のケイ素原子に直結した水素原子の個数｝／｛（Ａ）成分のアルケニル基の個数｝が０．５～１．５となる量、及び
（Ｆ）白金及び白金化合物からなる群より選択される触媒： 白金原子の質量として（Ａ）成分の質量に対して０．１～５００ｐｐｍ
を含有する熱伝導性シリコーン組成物。
２． （Ｅ）成分が、分子鎖末端のみ又は分子鎖側鎖のみにＳｉ－Ｈ基を有する直鎖状構造又は分岐状構造のオルガノハイドロジェンポリシロキサン、及び環状構造のオルガノハイドロジェンポリシロキサンから選ばれるものである１に記載の熱伝導性シリコーン組成物。
３． さらに、（Ｇ）アセチレン化合物、窒素化合物、有機りん化合物、オキシム化合物及び有機クロロ化合物より選択される制御剤を（Ａ）成分に対して０．１～５質量％含む１又は２に記載の熱伝導性シリコーン組成物。
４． 硬化物を１２５℃で１，０００時間エージングした後の硬度がアスカーＣで４０以下である１～３のいずれかに記載の熱伝導性シリコーン組成物。
５． １５０℃で加熱して硬化させた硬化物を角速度１．０ｒａｄ／ｓで振動させながら歪を大きくしていった際に貯蔵弾性率が損失弾性率を下回る歪が５％以上である１～４のいずれかに記載の熱伝導性シリコーン組成物。 Therefore, the present invention provides the following thermally conductive silicone compositions.
1. 1. (A) Organopolysiloxane having an alkenyl group directly bonded to at least two silicon atoms in one molecule and having a kinematic viscosity of 10 to 100,000 mm ² / s at 25 ° C.
(B) The following general formula (1)

(In the formula, R ¹ is an alkyl group having 1 to 6 carbon atoms, and a is an integer of 5 to 100.)
Hydrolyzable methylpolysiloxane with one-ended trifunctionality represented by: (A) 10 to 400 parts by mass with respect to 100 parts by mass of the component,
(C) Thermally conductive filler having a thermal conductivity of 10 W / m ° C. or higher: 500 to 3,000 parts by mass with respect to 100 parts by mass of the total of the components (A) and (B).
(D) Organohydrogenpolysiloxane, which contains at least one hydrogen atom directly connected to a silicon atom at the terminal site and the side chain site in one molecule.
(E) An organohydrogenpolysiloxane containing a hydrogen atom directly linked to at least two silicon atoms in one molecule other than the components (D).
However, the amount in which {the number of hydrogen atoms directly connected to the silicon atoms of the component (D) and the component (E)} / {the number of alkenyl groups of the component (A)} is 0.5 to 1.5, and (F). ) Platinum and catalyst selected from the group consisting of platinum compounds: 0.1 to 500 ppm as the mass of platinum atom with respect to the mass of component (A)
A thermally conductive silicone composition containing.
2. 2. The component (E) is selected from an organohydrogenpolysiloxane having a linear structure or a branched structure having a Si—H group only at the end of the molecular chain or only the side chain of the molecular chain, and an organohydrogenpolysiloxane having a cyclic structure. The heat conductive silicone composition according to 1.
3. 3. The heat according to 1 or 2, wherein the control agent selected from (G) an acetylene compound, a nitrogen compound, an organic phosphorus compound, an oxime compound and an organic chloro compound is contained in an amount of 0.1 to 5% by mass based on the component (A). Conductive silicone composition.
4. The thermally conductive silicone composition according to any one of 1 to 3, wherein the cured product has a hardness of 40 or less in Asker C after aging at 125 ° C. for 1,000 hours.
5. When the strain is increased while vibrating the cured product cured by heating at 150 ° C. at an angular speed of 1.0 rad / s, the strain with a storage elastic modulus lower than the loss modulus is 5% or more. The thermally conductive silicone composition according to any one of.

According to the present invention, an organohydrogenpolysiloxane containing a hydrogen atom (Si—H group) directly connected to a silicon atom at the end of the molecular chain and the side chain of the molecular chain is combined with another organohydrogenpolysiloxane. By blending, it is possible to provide a thermally conductive silicone composition in which the hardness after curing does not increase even when exposed to a high temperature for a long time and the outflow does not occur after mounting.

The thermally conductive silicone composition of the present invention will be described in detail below.
The component (A) constituting the present invention is an organopolysiloxane having an alkenyl group directly bonded to at least two silicon atoms in one molecule and having a kinematic viscosity of 10 to 100,000 mm ² / s at 25 ° C. This organopolysiloxane has at least two, preferably 2 to 8, more preferably 2 to 5 alkenyl groups directly linked to a silicon atom in one molecule, and may be linear or branched, and may be linear or branched. A mixture of these two or more kinds having different viscosity may be used.

Examples of the alkenyl group directly linked to the silicon atom include those having 2 to 6 carbon atoms such as a vinyl group, an allyl group, a 1-butenyl group and a 1-hexenyl group, but from the viewpoint of ease of synthesis and cost. Vinyl groups are preferred.
The residual organic group bonded to the silicon atom is preferably an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, particularly a monovalent hydrocarbon group having 1 to 6 carbon atoms and which does not contain an aliphatic unsaturated bond. Examples thereof include an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group and a dodecyl group, an aryl group such as a phenyl group, and an aralkyl group such as a 2-phenylethyl group and a 2-phenylpropyl group. Further, halogen-substituted hydrocarbon groups such as a chloromethyl group and a 3,3,3-trifluoropropyl group are also mentioned as examples. Of these, a methyl group is preferable from the viewpoint of ease of synthesis and cost.
The alkenyl group bonded to the silicon atom may be present at either the end or the middle (side chain) of the molecular chain of the organopolysiloxane, but it is preferably present at least at the end.

The kinematic viscosity of the component (A) at 25 ° C. is in the range of 10 to 100,000 mm ² / s, preferably 100 to 100,000 mm ² / s. If the kinematic viscosity is too low, oil bleeding from the composition will occur, and if it is too high, the viscosity of the composition will be too high and the material will have poor extensibility. In the present invention, the kinematic viscosity can be measured by an Ostwald viscometer (hereinafter, the same applies).

As the component (A), for example, dimethylpolysiloxane having both ends of the molecular chain sealed with a dimethylvinylsiloxy group, and dimethylpoly having one end of the molecular chain sealed with a dimethylvinylsiloxy group and the other end of the molecular chain closed with a trimethylsiloxy group. Siloxane / methylvinylpolysiloxane copolymer, trimethylsiloxy group blockade at both ends of the molecular chain dimethylsiloxane / methylvinylsiloxane copolymer, trimethylsiloxy group blockage at both ends of the molecular chain, methylvinylpolysiloxane, dimethylvinylsiloxy group blockade at both ends of the molecular chain Examples thereof include a dimethylsiloxane / methylvinylpolysiloxane copolymer, but the present invention is not limited to these, and two or more of these may be mixed and used.

（式中、Ｒ¹は炭素数１～６のアルキル基であり、ａは５～１００の整数である。） The component (B) is a hydrolyzable methylpolysiloxane represented by the following general formula (1), which is trifunctional at one end.

(In the formula, R ¹ is an alkyl group having 1 to 6 carbon atoms, and a is an integer of 5 to 100.)

In the above formula (1), R ¹ is an alkyl group having 1 to 6 carbon atoms, and is a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, and the like. A hexyl group or the like can be exemplified.
Further, if a is smaller than 5, the oil bleeding of the composition becomes severe and the reliability becomes poor, and if it is larger than 100, the wettability is not sufficient, so it is an integer of 5 to 100, preferably an integer of 10 to 60. be.

If the amount of the hydrolyzable methylpolysiloxane added at one end trifunctional is less than 10 parts by mass with respect to 100 parts by mass of the component (A), sufficient wettability cannot be exhibited, and if it is more than 400 parts by mass, the oil Since bleeding becomes severe and reliability deteriorates, the amount is 10 to 400 parts by mass, preferably 20 to 350 parts by mass.

The component (C) is a thermally conductive filler having a thermal conductivity of 10 W / m ° C. or higher.
The thermally conductive filler of the component (C) has a thermal conductivity of 10 W / m ° C. or higher, preferably 20 W / m ° C. or higher. When the thermal conductivity is smaller than 10 W / m ° C., the thermal conductivity itself of the thermally conductive silicone composition becomes small.
Examples of the heat conductive filler include aluminum powder, copper powder, silver powder, iron powder, nickel powder, gold powder, tin powder, metallic silicon powder, aluminum nitride powder, boron nitride powder, alumina powder, diamond powder and carbon powder. , Indium powder, gallium powder, zinc oxide powder and the like, but any filler may be used as long as it has a filler temperature of 10 W / m ° C. or higher, and one type or a mixture of two or more types may be used.

The average particle size of the heat conductive filler of the component (C) is preferably in the range of 0.1 to 100 μm, particularly preferably 0.1 to 90 μm. If the average particle size is smaller than 0.1 μm, the obtained composition may not be in the form of a paste and may have poor extensibility, and if it is larger than 100 μm, the thermal resistance of the heat-dissipating grease increases and the performance deteriorates. May be done. In the present invention, the average particle size can be measured by Microtrac MT3300EX manufactured by Nikkiso Co., Ltd., and is a volume-based volume average diameter.
The shape of the component (C) may be irregular, spherical, or any shape.

If the filling amount of the component (C) is less than 500 parts by mass with respect to 100 parts by mass of the total of the components (A) and (B), the thermal conductivity of the composition will be low and 3,000 mass by mass. If the amount is more than the part, the viscosity of the composition increases and the extensibility becomes poor. Therefore, it is in the range of 500 to 3,000 parts by mass, preferably in the range of 500 to 2,800 parts by mass, and more preferably. It is in the range of 500 to 2,500 parts by mass.

The component (D) is an organohydrogenpolysiloxane containing at least one hydrogen atom directly linked to a silicon atom at the terminal site and the side chain site in one molecule. The organohydrogenpolysiloxane having a hydrogen atom (Si—H group) directly connected to the silicon atom has at least one, preferably 1 to 4 and a side chain at the terminal site in order to network the composition by cross-linking. It is necessary to have at least one, preferably 1 to 6, more preferably 2 to 4 at the site, and further, Si—H groups in one molecule (that is, Si—H at the terminal site and the side chain site). It is preferable to have at least two, preferably 2 to 8 (as a total of groups).

The component (D) contains at least one Si—H group at the end of the molecular chain and the side chain of the molecular chain. By including the Si—H group at the end of the molecular chain, the reaction proceeds sufficiently during the initial heat curing, so that the excess reaction does not proceed after high temperature aging, and the increase in hardness can be suppressed. If the hardness increases during aging, the followability will decrease during mounting, and the heat dissipation characteristics will deteriorate. Further, by including the Si—H group in the side chain of the molecular chain, the composition can be sufficiently reticulated, the strain (crossoverstrain%) in which the storage elastic modulus is lower than the loss elastic modulus is sufficiently increased, and the grease flows out at the time of mounting. It does not occur, and the thermal characteristics are good.

The residual organic group other than the Si—H group bonded to the silicon atom is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, particularly a monovalent hydrocarbon group having 1 to 6 carbon atoms and not containing an aliphatic unsaturated bond. Specifically, there are an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group and a dodecyl group, an aryl group such as a phenyl group, a 2-phenylethyl group and a 2-phenylpropyl group. Aralkyl groups such as, chloromethyl group, halogen-substituted hydrocarbon groups such as 3,3,3-trifluoropropyl group, 2-glycidoxyethyl group, 3-glycidoxypropyl group, 4-glycidoxybutyl. Examples include an epoxy-substituted hydrocarbon group such as a group and a trialkoxysilyl-substituted hydrocarbon group such as a trimethoxysilylethyl group. Among these, an alkyl group such as a methyl group, a phenyl group and the like are preferable.

The molecular structure of the organohydrogenpolysiloxane of the component (D) is preferably linear or linear with some branches. The number of silicon atoms (or degree of polymerization) in one molecule is preferably 6 to 200, particularly 8 to 180, and particularly preferably 8 to 150.

（式中、ｂは１～１０の整数、ｃは１～１０の整数、ｄは１～１９７の整数、ｅは１～２０の整数で、ｂ＋ｃ＋ｄ＋ｅは４～１９８の整数である。） Examples of the organohydrogenpolysiloxane of the component (D) include a dimethylhydrogensiloxy group-blocked methylhydrogenpolysiloxane at both ends, a dimethylhydrogensiloxy group-blocked methylhydrogensiloxane / dimethylsiloxane copolymer at both ends, and both ends. Examples thereof include dimethylhydrogensiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, both-terminal dimethylhydrogensiloxy group-blocked methylhydrogensiloxane / dimethylsiloxane / diphenylsiloxane copolymer, and compounds represented by the following formulas. ..

(In the formula, b is an integer of 1 to 10, c is an integer of 1 to 10, d is an integer of 1 to 197, e is an integer of 1 to 20, and b + c + d + e is an integer of 4 to 198.)

As for the blending amount of the component (D), if {the number of Si—H groups of the component (D)} / {the number of alkenyl groups of the component (A)} is smaller than 0.1, the composition cannot be sufficiently reticulated, so that the grease is used. May pump out, and if it is larger than 0.9, the crosslink density may become too high and peeling may occur during the reliability test, so it is preferably in the range of 0.1 to 0.9. It is more preferably in the range of 0.1 to 0.8.

The component (E) is an organohydrogenpolysiloxane containing a hydrogen atom (Si—H group) directly linked to at least two silicon atoms in one molecule other than the component (D). This organohydrogenpolysiloxane having a Si—H group has at least two Si—H groups in at least one molecule, preferably 2 to 10, and more preferably 2 to 8 in order to network the composition by cross-linking. It is necessary to have.

The residual organic group other than the Si—H group bonded to the silicon atom is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, particularly a monovalent hydrocarbon group having 1 to 6 carbon atoms and not containing an aliphatic unsaturated bond. Specifically, there are an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group and a dodecyl group, an aryl group such as a phenyl group, a 2-phenylethyl group and a 2-phenylpropyl group. Aralkyl groups such as, chloromethyl group, halogen-substituted hydrocarbon groups such as 3,3,3-trifluoropropyl group, 2-glycidoxyethyl group, 3-glycidoxypropyl group, 4-glycidoxybutyl. Examples include an epoxy-substituted hydrocarbon group such as a group and a trialkoxysilyl-substituted hydrocarbon group such as a trimethoxysilylethyl group. Among these, an alkyl group such as a methyl group, a phenyl group and the like are preferable.

The organohydrogenpolysiloxane having such a Si—H group may be linear, branched or cyclic, or may be a mixture thereof. The organohydrogenpolysiloxane of the component (E) has a linear structure or a branched structure having a Si—H group only at the end of the molecular chain or only the side chain of the molecular chain, or has a cyclic structure. It is preferable to have. The number of silicon atoms (or degree of polymerization) in one molecule is preferably 2 to 80, more preferably 2 to 50, particularly 2 to 40, and particularly preferably 2 to 35.
This organohydrogenpolysiloxane may be used alone or in combination of two or more.

Examples of the organohydrogenpolysiloxane as the component (E) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, and methylhydrogensiloxane cyclic polymers. Tris (dimethylhydrogensiloxy) methylsilane, Tris (dimethylhydrogensiloxy) phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, both-terminal dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, Both-ended trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both-ended trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both-ended trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, both-ended trimethylsiloxy Examples thereof include a base-sealed methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer and a compound represented by the following formula.

As for the blending amount of the component (E), if {the number of Si—H groups of the component (E)} / {the number of alkenyl groups of the component (A)} is smaller than 0.1, the composition cannot be sufficiently reticulated, so that the grease is used. May pump out, and if it is larger than 0.9, the crosslink density may become too high and peeling may occur during the reliability test, so it is preferably in the range of 0.1 to 0.9. It is more preferably in the range of 0.1 to 0.8.

Further, as for the blending amount of the component (D) and the component (E), {the number of Si—H groups of the component (D) and the component (E)} / {the number of alkenyl groups of the component (A)} is 0.5. If it is smaller than 1.5, the composition cannot be sufficiently reticulated and the grease will be pumped out. If it is larger than 1.5, the crosslink density will be too high and it will peel off during the reliability test, so 0.5 to 1 It is in the range of .5, preferably in the range of 0.7 to 1.3.

The blending ratio of the component (D) and the component (E) is the ratio of the number of Si—H groups to [the number of Si—H groups of the component (D): the number of Si—H groups of the component (E)]. Is preferably 20: 1 to 1:20, particularly preferably 10: 1 to 1:10. If the ratio of the Si—H group of the component (D) is too small, the pot life at room temperature may be shortened.

The catalyst selected from the group consisting of platinum as a component (F) and a platinum compound is a component that promotes an addition reaction between an alkenyl group in the component (A) and a Si—H group in the component (D) and the component (E). Is. Examples of the component (F) include a simple substance of platinum, platinum chloride acid, a platinum-olefin complex, a platinum-alcohol complex, a platinum coordination compound and the like.

If the blending amount of the component (F) is less than 0.1 ppm as the mass of the platinum atom with respect to the mass of the component (A), there is no effect as a catalyst, and if it exceeds 500 ppm, the effect does not increase, which is not good. Since it is economical, it is in the range of 0.1 to 500 ppm, preferably 0.1 to 400 ppm.

In the heat conductive silicone composition of the present invention, a control agent can be further added as the component (G) for the purpose of suppressing the catalytic activity of the component (F). The control agent for the component (G) suppresses the progress of the hydrosilylation reaction at room temperature and prolongs the shelf life and the pot life. As the reaction control agent, known ones can be used, and acetylene compounds, various nitrogen compounds, organic phosphorus compounds, oxime compounds, organic chloro compounds and the like can be used.

If the blending amount of the component (G) is less than 0.1% by mass with respect to the component (A), sufficient shelf life and pot life may not be obtained, and if it is more than 5% by mass, the curing rate decreases. Therefore, the range of 0.1 to 5% by mass, particularly 0.1 to 4% by mass is preferable.
These may be diluted with a solvent such as toluene and used in order to improve the dispersibility in the thermally conductive silicone composition.

Further, in the heat conductive silicone composition of the present invention, in addition to the above-mentioned components (A) to (G), if necessary, an antioxidant, a heat resistance improving agent and the like are used to prevent deterioration. May be blended within a range that does not impair.

In order to produce the heat conductive silicone composition of the present invention, a predetermined amount of the above-mentioned components (A) to (G) is applied to a trimix, a twin mix, and a planetary mixer (all of which are mixers manufactured by Inoue Seisakusho Co., Ltd.). Manufactured by mixing with a mixer such as (registered trademark), Ultra Mixer (registered trademark of Mizuho Kogyo Co., Ltd. mixer), Hibis Dispermix (registered trademark of Mizuho Kogyo Co., Ltd. mixer), etc. be able to.

The absolute viscosity of the obtained thermally conductive silicone composition at 25 ° C. measured by a rotational viscometer is preferably 10 to 1,000 Pa · s, particularly preferably 10 to 800 Pa · s.

Further, the obtained thermally conductive silicone composition can be made into a cured product by heating at 80 to 180 ° C., particularly 90 to 170 ° C. for 30 to 150 minutes, particularly 40 to 140 minutes.

The hardness (initial hardness) of this cured product at 25 ° C. is preferably 25 or less, particularly 1 to 25 in Asker C, and the hardness of this cured product after aging at 125 ° C. for 1,000 hours is , 40 or less in Ascar C, particularly preferably 1 to 39. If it is harder than the above hardness, the material may become hard during the operation of the element when it is actually mounted on the heat generating element, and peeling may occur. In order to keep the hardness after aging at 125 ° C. for 1,000 hours within the above range, the organohydrogenpolysiloxane used as a cross-linking agent in the composition of the present invention is applied to the terminal site and the side chain site. This can be achieved by including a structure having a hydrogen atom directly connected to a silicon atom.

Further, the obtained thermally conductive silicone composition was applied between two parallel plates having a diameter of 2.5 cm so as to have a thickness of 2 mm, and the applied plates were heated at 150 ° C. for 90 minutes to prepare the composition. After curing, the strain was increased and the storage elastic modulus and the loss elastic modulus were measured while shearing at an angular velocity of 1.0 rad / s. The strain whose storage modulus was lower than the loss modulus was 5%. Above, it is particularly preferable that it is 8% or more. The storage elastic modulus and the loss elastic modulus can be measured by using a viscoelasticity measuring device (manufactured by TA Instruments, type ARES-G2). In order to make the strain 5% or more, the composition of the present invention has a structure in which an organohydrogenpolysiloxane used as a cross-linking agent has a hydrogen atom directly bonded to a silicon atom at a terminal portion and a side chain portion. It can be achieved by including the ones.

Since the thermally conductive silicone composition of the present invention does not increase in hardness after curing even when exposed to a high temperature for a long time and does not flow out after mounting, for example, heat dissipation of a semiconductor element, It can be suitably used for heat dissipation of parts mounted on automobiles and heat dissipation of a substrate of a light emitting element.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

The test for the effect of the present invention was carried out as follows.
〔viscosity〕
The absolute viscosity of the thermally conductive silicone composition was measured at 25 ° C. using a viscometer (type PC-1TL) manufactured by Malcolm Co., Ltd.

〔Thermal conductivity〕
Each heat-conducting silicone composition was poured into a mold having a thickness of 3 cm, covered with a kitchen wrap, and measured with a Model QTM-500 manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[Crossoverstrain evaluation]
A thermally conductive silicone composition was applied between two parallel plates having a diameter of 2.5 cm to a thickness of 2 mm. The coated plate was heated at 150 ° C. for 90 minutes to cure the thermally conductive silicone composition. Then, while shearing at an angular velocity of 1.0 rad / s, the strain was increased and the storage elastic modulus G'and the loss elastic modulus G'were measured. The strain in which the value of the storage elastic modulus G'was less than the loss elastic modulus G'was defined as the Crossoverstrain and used as an index of curing. The measurement was performed using a viscoelasticity measuring device (Type ARES-G2 manufactured by TA Instruments).

[Evaluation of increased hardness]
The thermally conductive silicone composition was poured into a 6 cm × 6 cm × 6 mm mold and heated at 150 ° C. for 90 minutes to cure the thermally conductive silicone composition to prepare a sheet-shaped sample. The hardness of a stack of two of these was measured using an Asker C hardness tester and used as the initial hardness. After that, aging was performed at 125 ° C. for 1,000 hours, and the hardness was measured.

[Measurement of thermal resistance]
A heat conductive silicone composition is sandwiched between a 15 mm × 15 mm × 1 mmt Si chip and a 15 mm × 15 mm × 1 mmt Ni plate so as to have a thickness of 40 μm, and placed in an oven at 150 ° C. for 90 minutes to conduct heat. The sex silicone composition was heat-cured to prepare a test piece for measuring heat resistance, and the heat resistance was measured. After that, a heat cycle test (-55 ° C ⇔ 125 ° C) was carried out for 500 cycles and changes in thermal resistance were observed. This thermal resistance measurement was performed by nanoflash (manufactured by Nitsche, LFA447).

The following components for preparing the thermally conductive silicone composition of the present invention were prepared.
(A) Component A-1: Didimethylpolysiloxane having both ends sealed with a dimethylvinylsilyl group and having a kinematic viscosity of 600 mm ² / s at 25 ° C. (vinyl group content: 0.015 / 100 g)

A-2: Didimethylpolysiloxane having both ends sealed with dimethylvinylsilyl group and kinematic viscosity at 25 ° C. of 30,000 mm ² / s (vinyl group content: 0.0036 / 100 g)

(B) Component B-1: One-ended trimethoxysilyl group-blocking methylpolysiloxane represented by the following formula

(C) Ingredients The following aluminum powder or alumina powder and zinc oxide powder are mixed at room temperature (25 ° C) for 15 minutes at room temperature (25 ° C) at the mass mixing ratio shown in Table 1 below using a 5 liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.). And C-1 or C-2 was obtained.
Aluminum powder with an average particle size of 20 μm (thermal conductivity: 236 W / m ° C)
Alumina powder with an average particle size of 10 μm (thermal conductivity: 27 W / m ° C)
Zinc oxide powder with an average particle size of 0.6 μm (thermal conductivity: 25 W / m ° C)

(D) Component D-1: Organohydrogenpolysiloxane represented by the following formula

D-2: Organohydrogenpolysiloxane represented by the following formula

(E) Component E-1: Organohydrogenpolysiloxane represented by the following formula

E-2: Organohydrogenpolysiloxane represented by the following formula

E-3: Organohydrogenpolysiloxane represented by the following formula

(F) Component F-1: A-1 solution of platinum-divinyltetramethyldisiloxane complex (containing 1% by mass as platinum atom)

(G) Component G-1: 1-ethynyl-1-cyclohexanol

Heat resistance improver:
Benzotriazole derivative represented by the following formula

[Examples 1 to 6, Comparative Examples 1 to 6]
The components (A) to (G) and the heat resistance improver were mixed as follows to obtain the heat conductive silicone compositions of Examples 1 to 6 and Comparative Examples 1 to 6.
That is, the component (A) was taken in a 5 liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) in the blending amounts shown in Tables 2 and 3, and the component (B) and (C) were taken in the blending amounts shown in Tables 2 and 3. ) Ingredients were added and mixed at 170 ° C. for 1 hour. Cool to room temperature (25 ° C), then add (D), (E), (F), (G) components and heat resistance improver in the blending amounts shown in Tables 2 and 3 to make them uniform. Was mixed with.

Claims (5)

(A) Organopolysiloxane having an alkenyl group directly bonded to at least two silicon atoms in one molecule and having a kinematic viscosity of 10 to 100,000 mm ² / s at 25 ° C.
(B) The following general formula (1)

(In the formula, R ¹ is an alkyl group having 1 to 6 carbon atoms, and a is an integer of 5 to 100.)
Hydrolyzable methylpolysiloxane with one-ended trifunctionality represented by: (A) 10 to 400 parts by mass with respect to 100 parts by mass of the component,
(C) Thermally conductive filler having a thermal conductivity of 10 W / m ° C. or higher: 500 to 3,000 parts by mass with respect to a total of 100 parts by mass of the components (A) and (B).
(D) Organohydrogenpolysiloxane, which contains at least one hydrogen atom directly linked to a silicon atom at the terminal site and the side chain site in one molecule.
(E) An organohydrogenpolysiloxane containing a hydrogen atom directly linked to at least two silicon atoms in one molecule other than the components (D).
However, the amount in which {the number of hydrogen atoms directly connected to the silicon atoms of the component (D) and the component (E)} / {the number of alkenyl groups of the component (A)} is 0.5 to 1.5, and (F). ) Platinum and catalyst selected from the group consisting of platinum compounds: 0.1 to 500 ppm as the mass of platinum atom with respect to the mass of component (A)
A thermally conductive silicone composition containing
A thermally conductive silicone composition having an Asker C hardness of 25 or less at 25 ° C. of the cured product. The component (E) is selected from an organohydrogenpolysiloxane having a linear structure or a branched structure having a Si—H group only at the end of the molecular chain or only the side chain of the molecular chain, and an organohydrogenpolysiloxane having a cyclic structure. The heat conductive silicone composition according to claim 1. Further, according to claim 1 or 2, a control agent selected from (G) an acetylene compound, a nitrogen compound, an organic phosphorus compound, an oxime compound and an organic chloro compound is contained in an amount of 0.1 to 5% by mass based on the component (A). Thermally conductive silicone composition. The heat conductive silicone composition according to any one of claims 1 to 3, wherein the cured product has a hardness of 40 or less in Asker C after aging at 125 ° C. for 1,000 hours. Claim 1 in which the strain in which the storage elastic modulus is lower than the loss elastic modulus is 5% or more when the strain is increased while vibrating the cured product cured by heating at 150 ° C. at an angular speed of 1.0 rad / s. The thermally conductive silicone composition according to any one of 4 to 4.