Silicone composition, heat dissipation member, and electronic device

Abstract

A silicone composition comprising (a) a specific organopolysiloxane, (b) an organohydrogenpolysiloxane having Si-H at both ends of a molecular chain and at both side chains and having 4-15 Si-H in the molecular chain side chain, (c) a thermally conductive filler, and (d) a curing catalyst, the silicone composition being obtained by combining a first agent and a second agent, the first agent contains component (a), component (c) and component (d) and does not contain component (b), the second agent contains component (a), component (b) and component (c) and does not contain component (d), the viscosity difference between component (a) and component (b) in the second agent at 23 DEG C is 400 mPa.s or less, and the ratio (H / Vi) of the number of Si-H to the number of alkenyl groups is in the range of 0.5-1.5.

Description

Technical Field

[0001] The present invention relates to a silicone composition, a heat dissipation member formed from the composition, and an electronic component including the heat dissipation member. Background Art

[0002] In the past, electronic components integrated in electronic devices generated heat and became the cause of failure. Therefore, heat dissipation components for dissipating the heat generated by electronic components to the outside of the device were widely used. The heat dissipation components are, for example, arranged between a heat generating body such as an electronic component and a heat dissipation body such as a housing or a radiator. As heat dissipation components, for example, as disclosed in Patent Documents 1 to 6, most of them are formed by curing a silicone composition containing a silicone resin and a thermally conductive filler.

[0003] In recent years, as electric devices become smaller and more powerful, it is necessary to improve the thermal conductivity of heat dissipating components in order to efficiently diffuse the heat generated by driving. In order to improve the thermal conductivity, studies have been conducted to increase the filling rate of the thermally conductive filler.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2019 / 181713

[0007] Patent Document 2: Japanese Patent Application Publication No. 2009-179714

[0008] Patent Document 3: Japanese Patent Application Publication No. 2016-53140

[0009] Patent Document 4: Japanese Patent Application Publication No. 2016-79204

[0010] Patent Document 5: International Publication No. 2019 / 021824

[0011] Patent Document 6: International Publication No. 2019 / 021826 Summary of the invention

[0012] Problems to be solved by the invention

[0013] However, if the filling rate of the thermally conductive filler is increased, the viscosity of the composite before curing may increase and the fluidity may decrease, or the hardness may increase after curing, and the stress on the surrounding electronic components may increase, thereby damaging the electronic components. In addition, there is also the problem that the reliability during long-term use, the so-called long-term reliability, may become insufficient. Specifically, if used for a long time in a high temperature environment, the following problems may sometimes occur: the hardness increases, and the heat dissipation component may be peeled off from the heating element due to vibration or impact, thereby deteriorating the thermal resistance value.

[0014] In addition, silicone compositions are sometimes used as two-component curing types. In the two-component curing type, each component is divided into a first component and a second component in advance, and the first component and the second component are mixed and cured before use, thereby obtaining a cured product. In a two-component curing silicone composition, usually, an alkenyl-containing organopolysiloxane is contained in the first component and an organohydrogenpolysiloxane is contained in the second component, but in order to make the mass ratio of the first component and the second component equal, an alkenyl-containing organopolysiloxane is sometimes also contained in the second component. However, if the second component contains an alkenyl-containing organopolysiloxane in addition to the organohydrogenpolysiloxane, oil bleeding sometimes occurs during storage and the storage stability becomes insufficient.

[0015] On the other hand, various studies have been conducted in the past to eliminate the disadvantages of highly filling thermally conductive fillers in silicone compositions. For example, in Patent Document 1, an attempt was made to improve fluidity by making the silicone composition containing an organopolysiloxane, an organohydrogenpolysiloxane, a thermally conductive filler, etc., further contain a slightly volatile isoparaffin compound with a boiling point of 160 to 360°C. However, in the past silicone compositions, it was difficult to improve the thermal conductivity while also improving the flexibility, long-term reliability, and oil permeability.

[0016] Therefore, an object of the present invention is to provide a two-component curable silicone composition that can improve the thermal conductivity of a heat dissipating member while also improving flexibility, long-term reliability, and oil permeability.

[0017] Means for solving problems

[0018] The inventors of the present application have conducted intensive research and have found that the above-mentioned problems can be solved by using a specific organohydrogenpolysiloxane while keeping the ratio of Si-H to alkenyl groups in the composition to a certain value and keeping the viscosity difference of the specific components to a certain value or less, thereby completing the following invention. That is, the present invention provides the following [1] to

[26] .

[0019] [1] An organosilicon composition comprising (a) an organopolysiloxane, (b) an organohydrogenpolysiloxane, (c) a thermally conductive filler, and (d) a curing catalyst, wherein the (a) organopolysiloxane has at least two alkenyl groups in one molecule, and the (b) organohydrogenpolysiloxane has hydrogen atoms directly bonded to silicon atoms at both ends of the molecular chain and in the side chains of the molecular chain, and the number of hydrogen atoms contained in the side chains of the molecular chain is 4 to 15.

[0020] The silicone composition is a combination of a first agent and a second agent, wherein the first agent comprises the component (a), the component (c), and the component (d) but does not comprise the component (b), and the second agent comprises the component (a), the component (b), and the component (c) but does not comprise the component (d).

[0021] The difference in viscosity between the component (a) and the component (b) in the second agent at 23° C. is 400 mPa·s or less,

[0022] In the silicone composition, a ratio (H / Vi) of the number of hydrogen atoms directly bonded to silicon atoms to the number of alkenyl groups is in a range of 0.5 to 1.5.

[0023] [2] The organosilicon composition according to [1] above, comprising an organosilicon compound having a hydrolyzable silyl group at a molecular chain terminal.

[0024] [3] The silicone composition according to [1] or [2] above, comprising at least one component selected from the group consisting of (e) an organopolysiloxane having no addition reactive group and (f) a silane coupling agent.

[0025] [4] The silicone composition according to [3] above, wherein each of the first agent and the second agent contains at least one component selected from the component (e) and the component (f).

[0026] [5] The silicone composition according to [3] or [4] above, comprising, as the component (e), (e-1) an organopolysiloxane having a hydrolyzable silyl group at a molecular chain terminal.

[0027] [6] The silicone composition according to any one of [3] to [5] above, comprising, as the component (e), at least one compound selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2).

[0028]

[0029] In formulas (1) and (2), R 1 Each independently represents any group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. 1 Each may be the same or different. 2 Each independently represents an alkyl group having 1 to 4 carbon atoms, wherein R 2 In the case of multiple R 2 Each may be the same or different. 3Each independently represents any group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 2 to 4 carbon atoms, and an acyl group having 2 to 4 carbon atoms, wherein R 3 In the case of multiple R 3 Can be the same or different. 4 Each independently represents an alkyl group having 1 to 8 carbon atoms. 5 Each independently represents a divalent hydrocarbon group having 2 to 20 carbon atoms, and a plurality of R 5 Each may be the same or different. In formula (2), R 6 is an oxygen atom or a divalent hydrocarbon group having 2 to 20 carbon atoms. In formula (1) and (2), a is an integer of 0 to 2. In formula (1), n ​​is an integer of 4 to 150, and in formula (2), m is an integer of 15 to 315.

[0030] [7] The silicone composition according to any one of [1] to [6] above, wherein the viscosity of the component (a) at 23° C. is 20 m·Pa or more and 100,000 m·Pa or less.

[0031] [8] The silicone composition according to any one of [1] to [7] above, wherein the content of the (c) thermally conductive filler is 1000 parts by mass or more and 4000 parts by mass or less per 100 parts by mass of the organopolysiloxane contained in the silicone composition.

[0032] [9] The silicone composition according to any one of [1] to [8] above, wherein the content of the (d) curing catalyst is 0.1 ppm by mass or more and 500 ppm by mass or less.

[0033]

[10] The silicone composition according to any one of [1] to [9] above, wherein the second agent contains (g) a curing inhibitor.

[0034]

[11] The silicone composition according to any one of [1] to

[10] above, wherein the organohydrogenpolysiloxane contained in the silicone composition comprises only an organohydrogenpolysiloxane having hydrogen atoms directly bonded to silicon atoms at both ends of the molecular chain and at side chains of the molecular chain.

[0035]

[12] The silicone composition according to any one of [1] to

[11] above, wherein the (c) thermally conductive filler is at least one material selected from oxides, nitrides, carbides, carbon-based materials and metal hydroxides.

[0036]

[13] The silicone composition according to any one of [1] to

[12] above, wherein the (c) thermally conductive filler is at least one material selected from the group consisting of alumina, diamond, and aluminum nitride.

[0037]

[14] The silicone composition according to any one of [1] to

[13] above, wherein the average particle size of the primary particles of the (c) thermally conductive filler is 0.1 μm or more.

[0038]

[15] The silicone composition according to any one of [1] to

[14] above, wherein the (c) thermally conductive filler contains two or more types of particles having different primary particle average diameters.

[0039]

[16] The silicone composition according to any one of [1] to

[15] above, wherein a cured product obtained by curing the silicone composition has an E-type hardness of less than 70.

[0040]

[17] The silicone composition according to any one of [1] to

[16] above, wherein the viscosity of the component (a) in the second agent at 23° C. is 20 m·Pa or more and 100,000 m·Pa or less.

[0041]

[18] The silicone composition according to any one of [1] to

[17] above, wherein the viscosity of the component (b) in the second agent at 23° C. is 20 m·Pa or more and 100,000 m·Pa or less.

[0042]

[19] According to the silicone composition described in any one of [1] to

[18] above, the mass ratio ((a2+b2) / a1) of the total content of the components (a) and (b) in the second agent to the content of the component (a) in the first agent is greater than 0.8 and less than 1.2.

[0043]

[20] The silicone composition according to any one of [1] to

[21] above, wherein the mass ratio (c2 / c1) of the content of the component (c) in the second agent to the content of the component (c) in the first agent is 0.8 or more and 1.2 or less.

[0044]

[21] The silicone composition according to any one of [1] to

[20] above, wherein the content of the component (a) in the silicone composition is 30% by mass or more and 92% by mass or less relative to the total amount of the organopolysiloxane, and the content of the component (b) is 3% by mass or more and 40% by mass or less.

[0045]

[22] The silicone composition according to any one of [1] to

[21] above, wherein the component (a) contains alkenyl groups at both ends of the molecular chain.

[0046]

[23] The silicone composition according to any one of [1] to

[22] above, wherein the curing catalyst (d) is a platinum-based catalyst.

[0047]

[24] The silicone composition according to any one of [1] to

[23] above, wherein the average particle size of the primary particles of the (c) thermally conductive filler is 200 μm or less.

[0048]

[25] A heat dissipation member formed from the silicone composition according to any one of [1] to

[24] above.

[0049]

[26] An electronic device comprising an electronic component and the heat dissipation member described in

[25] above, wherein the heat dissipation member is arranged on the electronic component.

[0050] Effects of the Invention

[0051] By using the two-component curable silicone composition of the present invention, it is possible to obtain a heat dissipation member having improved flexibility, long-term reliability, and oil permeability while improving thermal conductivity. DETAILED DESCRIPTION

[0052] [Silicone composition]

[0053] Hereinafter, the silicone composition of the present invention will be described in detail.

[0054] The silicone composition of the present invention comprises the following components (a), (b), (c) and (d). In addition, the silicone composition of the present invention preferably comprises at least one of the following components (e) and (f). Each component is described in detail below.

[0055] <(a)Component>

[0056] The component (a) is an organopolysiloxane having at least two alkenyl groups in one molecule. Since the organosilicon composition contains the component (a), the organosilicon composition can be cured by an addition reaction with the organohydrogenpolysiloxane (component (b)) described later.

[0057] The organopolysiloxane used as the component (a) may be linear, branched, or a mixture of linear and branched ones, but is preferably linear.

[0058] The alkenyl group in the component (a) may be contained at any of the terminal or side chain of the molecular chain of the polysiloxane structure of the component (a), or may be contained at both the terminal and the side chain. However, it is preferably contained at least at the terminal, more preferably contained at both terminals of the molecular chain, and even more preferably contained only at both terminals.

[0059] The alkenyl group is not particularly limited, and examples thereof include alkenyl groups having 2 to 8 carbon atoms, such as vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, etc. Among them, vinyl is preferred from the viewpoints of ease of synthesis and reactivity. In addition, the alkenyl group may be an alkenyl group directly bonded to a silicon atom.

[0060] The number of alkenyl groups in one molecule of the component (a) is not particularly limited as long as it is 2 or more, and is, for example, 2 to 8, preferably 2 to 4, and more preferably 2.

[0061] In the organopolysiloxane of the component (a), as the remaining group bonded to the silicon atom other than the alkenyl group, there can be mentioned a hydrocarbon group which may have a substituent. As the hydrocarbon group which may have a substituent, there can be mentioned a hydrocarbon group having about 1 to 20 carbon atoms, specifically, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms.

[0062] The alkyl group may be straight chain, branched chain or have a cyclic structure. More specifically, examples include straight chain alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl, branched chain alkyl groups such as isopropyl, tert-butyl, isobutyl, 2-methylundecyl and 1-hexylheptyl, and cyclic alkyl groups such as cyclopentyl, cyclohexyl and cyclododecyl.

[0063] Examples of the haloalkyl group include chloromethyl, 3,3,3-trifluoropropyl, and 3-chloropropyl. Examples of the aryl group include phenyl, tolyl, and xylyl. Examples of the aralkyl group include benzyl, phenethyl, and 2-(2,4,6-trimethylphenyl)propyl.

[0064] Among them, an alkyl group is preferred, and a methyl group is preferred from the viewpoint of ease of synthesis. In addition, among the residual groups bonded to silicon atoms, preferably 80 mol% or more are methyl groups, more preferably 90 mol% or more are methyl groups, and further preferably 100 mol% are methyl groups. It should be noted that component (a) may not have a hydrogen atom as a residual group bonded to a silicon atom, that is, component (a) may not contain a hydrosilyl group.

[0065] Specific examples of the component (a) include compounds represented by the following formula (A).

[0066]

[0067] In formula (A), R 11 Each independently represents a hydrocarbon group which may have a substituent other than an alkenyl group.12 Each is independently an alkenyl group. The details of the hydrocarbon group and alkenyl group which may have a substituent are as described above. 11 , preferably an alkyl group, more preferably a methyl group, R of formula (A) 11 Among them, preferably 80% or more are methyl groups, more preferably 90% or more are methyl groups, and even more preferably 100% are methyl groups. 12 Vinyl is preferred.

[0068] In formula (A), p is the number of repeating units, for example, an integer of 0 to 8, preferably 0 to 2, and more preferably 0. In addition, q is the number of repeating units, which is an integer greater than 1 and may be such a number of repeating units that the viscosity at 23° C. is within the range described below, for example, about 20 to 1500.

[0069] In formula (A), -SiR 11 R 12 O-represented structural unit and -SiR 11 R 11 The structural unit represented by O- may be polymerized randomly or in blocks.

[0070] The organopolysiloxane of the component (a) may be used alone or in combination of two or more.

[0071] The viscosity of component (a) at 23°C is not particularly limited, but is preferably 20 mPa·s or more and 100,000 mPa·s or less. By making the viscosity of component (a) above the above lower limit, the crosslinking density in the cured product is prevented from becoming too high, and the flexibility after curing is easily maintained. In addition, by setting it below the above upper limit, the silicone composition can be prevented from becoming highly viscous. In addition, by making the viscosity within the above range, it is easy to make the viscosity difference between it and the later-described component (b) less than a certain value, and it is easy to make the molecular weight of component (a) of an appropriate size and make the reactivity appropriate.

[0072] The viscosity of the component (a) at 23° C. is more preferably 40 mPa·s to 10,000 mPa·s, further preferably 60 mPa·s to 1,000 mPa·s, and still more preferably 80 mPa·s to 500 mPa·s.

[0073] The viscosity of the component (a) at 23° C. can be measured using a Brookfield B viscometer. In the Brookfield B viscometer, the spindle can be appropriately selected so that the torque is 10 to 80%. The same applies to the viscosity of the component (b) described later.

[0074] The content of the component (a) in the silicone composition may be appropriately selected so as to adjust the ratio (H / Vi) described later, etc., within a desired range. The content is not particularly limited and is, for example, 30% by mass to 92% by mass, preferably 40% by mass to 87% by mass, and more preferably 50% by mass to 84% by mass, relative to the total amount of the organopolysiloxane contained in the silicone composition.

[0075] <(b) Components>

[0076] The component (b) is an organohydrogenpolysiloxane having hydrogen atoms directly bonded to silicon atoms (hereinafter sometimes referred to as "Si-H") at both ends of the molecular chain and at the side chains of the molecular chain, and having 4 to 15 Si-H atoms contained in the side chains of the molecular chain.

[0077] Since the silicone composition of the present invention contains an organohydrogenpolysiloxane having Si-H at both ends of the molecular chain and at the side chains of the molecular chain, it can be cured while performing chain extension and crosslinking. Moreover, by making the number of Si-H in the side chain within a certain range, a certain crosslinking density can be ensured and chain extension and curing can be appropriately performed. Therefore, even if the (c) thermally conductive filler material is highly filled, the softness after curing can be ensured, and even if it is heated at high temperature for a long time after curing, the hardness increase can be suppressed and long-term reliability can be ensured. That is, even if it is heated for a long time, the hardness increase can be suppressed, so even if vibration and impact are applied to the cured product of the silicone composition, it can be suppressed from peeling off from the heating element, etc., thereby maintaining good thermal resistance for a long time.

[0078] In addition, when an organohydrogen polysiloxane having Si-H at both ends of the molecular chain is mixed with an organopolysiloxane containing an alkenyl group, oil bleeding is likely to occur, but by making the number of Si-H contained in the side chain of the molecular chain within a certain range, the compatibility with the component (a) is improved. Therefore, it is also coordinated with the point of adjusting the viscosity difference as described later, so that oil bleeding becomes less likely to occur.

[0079] The organohydrogenpolysiloxane used as the component (b) may be linear, branched, or a mixture of linear and branched, but is preferably linear. The component (b) may contain one Si-H group at each end of the linear molecular chain and 4 to 15 Si-H groups in the side chain.

[0080] In the component (b), the number of Si-H groups present in one molecule of the side chain is 4 to 15 as described above, but is preferably 4 to 14, and more preferably 4 to 12. For the component (b), by making the number of Si-H groups in the side chain an appropriate number, flexibility can be easily ensured and long-term reliability can also be improved.

[0081] In the component (b), as the residual group other than Si-H bonded to the silicon atom, a hydrocarbon group which may have a substituent can be mentioned. As the hydrocarbon group which may have a substituent, a hydrocarbon group having about 1 to 20 carbon atoms can be mentioned, and specifically, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms can be mentioned. The details of the alkyl group, the halogenated alkyl group, the aryl group, and the aralkyl group are as described in the above-mentioned component (a).

[0082] The residual groups are preferably alkyl groups, and are preferably methyl groups from the viewpoint of ease of synthesis, etc. In addition, of the residual groups bonded to silicon atoms, preferably 80 mol% or more are methyl groups, more preferably 90 mol% or more are methyl groups, and further preferably 100 mol% are methyl groups.

[0083] It should be noted that the component (b) may not have an alkenyl group as a residual group bonded to a silicon atom, that is, the component (b) may not contain an alkenyl group.

[0084] Specific examples of the component (b) include compounds represented by the following formula (B).

[0085]

[0086] In formula (B), R 13 Each independently represents a hydrocarbon group which may have a substituent other than an alkenyl group. The details of the hydrocarbon group which may have a substituent are as described above. 13 , preferably an alkyl group, more preferably a methyl group. 13 Among them, preferably 80% or more are methyl groups, more preferably 90% or more are methyl groups, and further preferably 100% are methyl groups.

[0087] In formula (B), r is the number of repeating units, which is an integer selected from 4 to 15, preferably 4 to 14, and more preferably 4 to 12. s is the number of repeating units, which is an integer greater than 1, and may be such a number that the viscosity at 23° C. is within the range described below, for example, about 20 to 1500.

[0088] In formula (B), -SiHR 13 O-represented structural unit and -SiR 13 R 13 The structural unit represented by O- may be polymerized randomly or in blocks.

[0089] The organohydrogenpolysiloxane of the component (b) may be used alone or in combination of two or more.

[0090] The viscosity of the component (b) at 23°C is not particularly limited, but is preferably 20 mPa·s or more and 100,000 mPa·s or less. By setting the viscosity of the component (b) within the above range, it is possible to prevent the crosslinking density from becoming too high, maintain the flexibility after curing, and prevent the silicone composition from becoming highly viscous. In addition, by setting the viscosity within the above range, it is easy to make the viscosity difference between the component (b) and the component (a) less than a certain value, and it is easy to make the molecular weight of the component (b) moderate and the reactivity appropriate. The viscosity of the component (b) at 23°C is more preferably 20 mPa·s or more and 10,000 mPa·s or less, more preferably 30 mPa·s or more and 1,000 mPa·s or less, and even more preferably 40 mPa·s or more and 500 mPa·s or less. Typically, the viscosity of the component (b) at 23°C is lower than the viscosity of the component (a) at 23°C, but it may be greater than the viscosity of the component (a) at 23°C.

[0091] The content of the component (b) in the silicone composition may be appropriately selected so as to adjust the ratio (H / Vi) described later, etc., within a desired range. The content is not particularly limited and is, for example, 3% by mass to 40% by mass, preferably 4% by mass to 35% by mass, and more preferably 7% by mass to 30% by mass, relative to the total amount of the organopolysiloxane contained in the silicone composition.

[0092] <(c) Ingredients>

[0093] Component (c) is a thermally conductive filler. Since the silicone composition contains a thermally conductive filler, the thermal conductivity of the silicone composition and a cured product (heat dissipating member) formed by curing the silicone composition is improved.

[0094] The (c) thermally conductive filler is not particularly limited, but is preferably at least one material selected from oxides, nitrides, carbides, carbon-based materials, and metal hydroxides.

[0095] Examples of the oxide include metal oxides such as iron oxide, zinc oxide, aluminum oxide, magnesium oxide, titanium oxide, cerium oxide, and zirconium oxide, and oxides other than metal oxides such as silicon oxide (silicon dioxide).

[0096] Examples of the nitride include metal nitrides such as aluminum nitride, gallium nitride, chromium nitride, tungsten nitride, magnesium nitride, molybdenum nitride, and lithium nitride, and nitrides other than metal nitrides such as silicon nitride and boron nitride.

[0097] Examples of the carbide include metal carbides such as aluminum carbide, titanium carbide, and tungsten carbide, and carbides other than metal carbides such as silicon carbide and boron carbide.

[0098] Examples of the carbon-based material include diamond particles, carbon black, graphite, graphene, fullerene, carbon nanotubes, and carbon nanofibers.

[0099] Examples of the metal hydroxide include aluminum hydroxide, calcium hydroxide, and magnesium hydroxide.

[0100] These thermally conductive fillers may be used alone or in combination of two or more.

[0101] As the thermally conductive filler, among the above, at least one material selected from the group consisting of alumina, diamond, and aluminum nitride is preferred from the viewpoint of easily improving thermal conductivity.

[0102] The average particle size of the primary particles of the thermally conductive filler (c) is not particularly limited, but is preferably 0.1 μm or more. By setting it to 0.1 μm or more, the thermal conductivity of the silicone composition can be easily improved and the viscosity of the silicone composition can be easily reduced. The average particle size of the primary particles of the thermally conductive filler (c) is more preferably 0.2 μm or more, and further preferably 0.5 μm or more.

[0103] The average particle size of the primary particles of the thermally conductive filler (c) is preferably 200 μm or less. By setting it to 200 μm or less, it can be appropriately dispersed in the silicone composition and contain the thermally conductive filler (c) at a high filling rate. The average particle size of the primary particles of the thermally conductive filler (c) is more preferably 150 μm or less, and further preferably 100 μm or less.

[0104] The average particle size of the primary particles can be measured using, for example, a "laser diffraction particle size distribution analyzer" manufactured by Horiba, Ltd., and the particle size (d50) when the cumulative volume is 50% can be taken as the average particle size of the primary particles.

[0105] (c) The thermally conductive filler preferably comprises two or more particles having different average primary particle sizes. If two or more particles having different average primary particle sizes are used, particles having a smaller average particle size enter between particles having a larger average particle size, so that the thermally conductive filler is appropriately dispersed in the organopolysiloxane, and the filling rate of the thermally conductive filler is also easily increased. It should be noted that the presence of two or more peaks in the particle size distribution of the thermally conductive filler can be used to determine that the organosilicon composition has two or more particles having different average primary particle sizes.

[0106] When the thermally conductive filler (c) includes two or more particles having different average primary particle sizes, the specific particle size can be selected according to the type of the thermally conductive filler. For example, a thermally conductive filler having an average primary particle size of 10 μm or more and 200 μm or less and a thermally conductive filler having an average primary particle size of 0.1 μm or more and less than 10 μm can be used in combination.

[0107] In addition, for example, a thermally conductive filler having an average primary particle size of 1 μm or more and 100 μm or less (large-particle-diameter thermally conductive filler) and a thermally conductive filler having an average primary particle size of 0.1 μm or more and less than 1 μm (small-particle-diameter thermally conductive filler) may be used together. In this case, the average primary particle size of the large-particle-diameter thermally conductive filler is preferably 2 μm or more and 80 μm or less, and more preferably 2 μm or more and 50 μm or less. In addition, the average primary particle size of the small-particle-diameter thermally conductive filler is preferably 0.1 μm or more and 0.8 μm or less.

[0108] The content of the thermally conductive filler (c) in the silicone composition is, for example, 500 parts by mass or more, preferably 800 parts by mass or more, and more preferably 1000 parts by mass or more, relative to 100 parts by mass of the organopolysiloxane contained in the silicone composition. When the content of the thermally conductive filler (c) is 500 parts by mass or more, the thermal conductivity can be improved, and when the content of the thermally conductive filler (c) is 1000 parts by mass or more, the thermal conductivity can be sufficiently improved.

[0109] The content of the thermally conductive filler (c) is, for example, 4000 parts by mass or less, preferably 3000 parts by mass or less, and more preferably 2500 parts by mass or less, relative to 100 parts by mass of the organopolysiloxane. By setting the content of the thermally conductive filler (c) to be below these upper limits, the thermally conductive filler can be appropriately dispersed in the silicone composition. In addition, the viscosity of the silicone composition can be prevented from increasing more than necessary.

[0110] The thermally conductive filler (c) can be a surface-treated thermally conductive filler using an organosilicon compound having a hydrolyzable silyl group at a molecular chain terminal, such as the component (e-1) or the component (f) described later. Among them, the thermally conductive filler (c) is preferably surface-treated with the component (e-1).

[0111] The surface-treated thermally conductive filler can be obtained by mixing an organosilicon compound having a hydrolyzable silyl group at the molecular chain terminal, such as the component (e-1) or the component (f) described later, with the thermally conductive filler (c). In addition, when mixing, a wet treatment method, a dry treatment method, etc. are preferably used from the viewpoint of facilitating the surface treatment.

[0112] In the wet treatment method, for example, the (c) thermally conductive filler is added to a solution in which the (e-1) component or (f) component described later is dispersed or dissolved, and the mixture is mixed, and then heat-treated, thereby allowing the (e-1) component or (f) component to bond or adhere to the surface of the thermally conductive filler.

[0113] The dry treatment method is a method of performing surface treatment without using a solution, and specifically, is a method in which the (c) thermally conductive filler is mixed with the (e-1) component or the (f) component, stirred using a mixer or the like, and then subjected to a heat treatment, thereby bonding or adhering the (e-1) component or the (f) component to the surface of the thermally conductive filler. It should be noted that the surface treatment performed by mixing the (c) thermally conductive filler with the (e-1) component or the (f) component may also be performed in the presence of the above-mentioned (a) component, (b) component, or the (e-2) component described later.

[0114] <(d) Component>

[0115] Component (d) is a curing catalyst. Since the silicone composition contains a curing catalyst, the addition reaction between the alkenyl-containing organopolysiloxane (component (a) etc.) and the organohydrogenpolysiloxane (component (b) etc.) can be accelerated, thereby appropriately curing the silicone composition.

[0116] As the curing catalyst, platinum catalysts, palladium catalysts, rhodium catalysts, etc. can be cited, among which platinum catalysts are preferred. As the platinum catalyst, there is no particular limitation, and chloroplatinic acid, complexes of chloroplatinic acid and olefins, vinyl siloxanes or acetylenic compounds, etc. can be cited.

[0117] The content of the curing catalyst in the silicone composition is not particularly limited as long as it is an amount that can promote the addition reaction, and is preferably 0.1 mass ppm to 500 mass ppm, more preferably 0.5 mass ppm to 200 mass ppm, and further preferably 1 mass ppm to 100 mass ppm, based on the total amount of the silicone composition.

[0118] <<Ingredients (e) and (f)>>

[0119] The organosilicon composition of the present invention preferably contains an organosilicon compound having no addition reactive group, and specifically, preferably contains at least one of an organopolysiloxane having no addition reactive group (component (e)) and a silane coupling agent (component (f)), and more preferably contains component (e).

[0120] As the organosilicon compound having no addition reaction group, more specifically, the component (e) and the component (f), an organosilicon compound having a hydrolyzable silyl group, especially an organosilicon compound having a hydrolyzable silyl group at the molecular chain terminal is preferred. More specifically, an organopolysiloxane having a hydrolyzable silyl group at the molecular chain terminal described later (component (e-1)) or a silane coupling agent (component (f)) is preferred. By using an organosilicon compound having a hydrolyzable silyl group at the molecular chain terminal, the filler can be easily dispersed, and as a result, the (c) thermally conductive filler can be highly filled, and the thermal conductivity becomes high.

[0121] <(e) Ingredients>

[0122] The component (e) is an organopolysiloxane having no addition reaction group. By making the organosilicon composition of the present invention contain the component (e), in the cured product, more than a certain amount of the component will not be incorporated into the cross-linked structure, and the flexibility is easily improved. In addition, the viscosity of the organosilicon composition is easily reduced, and the operability is easily improved. It should be noted that the addition reaction group refers to a functional group that reacts through an addition reaction, and representative examples include alkenyl, methacryloyl, acryloyl, hydrosilyl, etc.

[0123] As the component (e), there can be mentioned (e-1) an organopolysiloxane having a hydrolyzable silyl group at the end of the molecular chain and (e-2) a silicone oil. The component (e) may contain any one of the components (e-1) or (e-2), but preferably contains at least the component (e-1). By containing the component (e-1), it is easy to further reduce the viscosity of the silicone composition. In addition, it is easy to disperse the filler, and as a result, it becomes possible to highly fill the (c) thermally conductive filler, thereby increasing the thermal conductivity.

[0124] It should be noted that the component (e-1) may be subjected to a surface treatment on the thermally conductive filler (c) as described above. By subjecting the component (e-1) to a surface treatment on the thermally conductive filler (c), the dispersibility of the filler can be further improved.

[0125] When the silicone composition contains the component (e-1), it may further contain the component (e-2).

[0126] The component (e-1) may be linear, branched, or a mixture of linear and branched, but is preferably linear. In addition, the component (e-1) is preferably an organopolysiloxane having at least one hydrolyzable silyl group at a molecular chain terminal, more preferably an organopolysiloxane having at least one hydrolyzable silyl group only at one terminal, and further preferably an organopolysiloxane having three hydrolyzable silyl groups at one terminal. Here, the hydrolyzable silyl group is preferably an alkoxysilyl group, more preferably a methoxysilyl group.

[0127] It is inferred that the component (e-1) having a hydrolyzable silyl group at the end makes it easy to react or interact with the functional group or the like present on the surface of the thermally conductive filler, and that the component (e-1) also has a polysiloxane structure, thereby improving the dispersibility of the filler and making it easy to reduce the viscosity of the silicone composition. In addition, the filler has good dispersibility, and as a result, the thermally conductive filler (c) can be highly filled, making it easy to improve thermal conductivity.

[0128] Component (e-1) specifically includes compounds represented by the following formula (1) and compounds represented by the following formula (2). Among them, the compound represented by the following formula (1) is preferred. The compound represented by the following formula (1) can suppress the change in the physical properties of the silicone composition at high temperatures and can also improve the dispersibility. This is presumably due to the ester structure of the compound represented by the following formula (1).

[0129]

[0130] In formulas (1) and (2), R 1 Each independently represents any group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. 1 Each may be the same or different. 2 Each independently represents an alkyl group having 1 to 4 carbon atoms, wherein R 2 In the case of multiple R 2 Each may be the same or different. 3 Each independently represents any group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 2 to 4 carbon atoms, and an acyl group having 2 to 4 carbon atoms, wherein R 3 In the case of multiple R 3 Can be the same or different. 4 Each independently represents an alkyl group having 1 to 8 carbon atoms. 5 Each independently represents a divalent hydrocarbon group having 2 to 20 carbon atoms, and a plurality of R 5 Each may be the same or different. In formula (2), R6 is an oxygen atom or a divalent hydrocarbon group having 2 to 20 carbon atoms. In formula (1) and (2), a is an integer of 0 to 2. In formula (1), n ​​is an integer of 4 to 150, and in formula (2), m is an integer of 15 to 315.

[0131] In the above formulas (1) and (2), R 1 , examples include alkyl groups having 1 to 20 carbon atoms, halogenated alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 20 carbon atoms. 1 Each may be the same or different.

[0132] The alkyl group may be straight chain, branched chain or have a cyclic structure. More specifically, examples include straight chain alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl and eicosyl, branched chain alkyl groups such as isopropyl, tert-butyl, isobutyl, 2-methylundecyl and 1-hexylheptyl, and cyclic alkyl groups such as cyclopentyl, cyclohexyl and cyclododecyl.

[0133] Examples of the haloalkyl group include chloromethyl, 3,3,3-trifluoropropyl, and 3-chloropropyl. Examples of the aryl group include phenyl, tolyl, and xylyl. Examples of the aralkyl group include benzyl, phenethyl, and 2-(2,4,6-trimethylphenyl)propyl.

[0134] Among them, R 1 An alkyl group having 1 to 20 carbon atoms is preferred, an alkyl group having 1 to 4 carbon atoms is more preferred, and a methyl group is further preferred.

[0135] In the above formulas (1) and (2), R 2 Each is an alkyl group having 1 to 4 carbon atoms, R 2 When there are multiple R 2 Each of them may be the same or different. In addition, the alkyl group may be a straight chain or a branched chain. 2 It is preferably an alkyl group having 1 to 2 carbon atoms, and more preferably a methyl group. In addition, a is an integer of 0 to 2, and a is preferably 0 or 1, and more preferably 0.

[0136] In the above formulas (1) and (2), R 3 Each of them is an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 2 to 4 carbon atoms, or an acyl group having 2 to 4 carbon atoms, and R 3 When a is 0 or 1, the multiple R 3 They can be the same or different. 3The alkyl, alkoxyalkyl and acyl groups in the formula (A) may be straight-chain or branched. 3 An alkyl group having 1 to 4 carbon atoms is preferred, and a methyl group is more preferred.

[0137] In the above formulas (1) and (2), R 4 Each is an alkyl group having 1 to 8 carbon atoms, preferably an alkyl group having 2 to 6 carbon atoms, and more preferably a butyl group.

[0138] In the above formula (1), R 5 is a divalent hydrocarbon group having 1 to 20 carbon atoms, and multiple R 5 Each of them may be the same or different. The divalent hydrocarbon group is preferably an alkylene group, which may be a straight chain or a branched chain. 5 An alkylene group having 2 to 10 carbon atoms is preferred, an alkylene group having 2 to 8 carbon atoms is more preferred, an alkylene group having 2 to 4 carbon atoms is further preferred, and an alkylene group represented by -CH2-CH2-CH2- or -CH(CH3)-CH2- is further preferred.

[0139] In the above formula (2), R 6 is an oxygen atom or a divalent hydrocarbon group having 1 to 20 carbon atoms, preferably a divalent hydrocarbon group. The divalent hydrocarbon group is preferably an alkylene group, which may be a linear or branched chain. 6 The alkylene group is preferably an alkylene group having 2 to 10 carbon atoms, more preferably an alkylene group having 2 to 8 carbon atoms, and still more preferably an alkylene group having 2 to 4 carbon atoms. Examples thereof include methylene, ethylene, propylene, butylene, and methylethylene, and among them, ethylene is preferred.

[0140] In formula (1), n ​​represents the number of repetitions, and is an integer of 4-150, preferably an integer of 5-120, and more preferably an integer of 5-50.

[0141] In formula (2), m represents the number of repetitions, and is an integer of 15 to 315, preferably an integer of 18 to 280, and more preferably an integer of 20 to 220.

[0142] Among the compounds represented by the above formulas (1) and (2), from the viewpoint of improving the dispersibility of the thermally conductive filler and obtaining a silicone composition with little change in physical properties at high temperatures, the compound represented by the following formula (1-1) or formula (2-1) is preferred, and the compound represented by the following formula (1-1) is particularly preferred.

[0143]

[0144] It should be noted that n is as described above.

[0145]

[0146] It should be noted that m is as described above.

[0147] The component (e-1) may be used alone or in combination of two or more.

[0148] As (e-2) silicone oil, in addition to straight-chain silicone oils such as dimethyl silicone oil and benzyl silicone oil, non-reactive modified silicone oils obtained by introducing non-reactive organic groups into the main chain having a polysiloxane structure, the side chain bonded to the main chain, or the end of the main chain can also be cited. The so-called non-reactive organic group is an organic group that does not have an addition reaction group. As non-reactive modified silicone oils, for example, polyether modified silicone oils, aralkyl modified silicone oils, fluoroalkyl modified silicone oils, long-chain alkyl modified silicone oils, higher fatty acid ester modified silicone oils, higher fatty amide modified silicone oils and phenyl modified silicone oils can be cited. Among the above, as silicone oil, preferably straight-chain silicone oil, among the straight-chain silicone oils, more preferably dimethyl silicone oil.

[0149] (e-2) The silicone oil may be used alone or in combination of two or more.

[0150] The content of component (e) in the silicone composition is based on the total amount of organopolysiloxane contained in the silicone composition, for example, from 1 mass % to 50 mass %. By making the content of component (e) above the above lower limit, it is easy to improve the softness of the cured product obtained from the silicone composition, and it is also easy to use component (e) to reduce the viscosity of the silicone composition. In addition, by making the content of component (e) below the above upper limit, it is possible to impart a certain curability to the silicone composition, it is easy to obtain a cured product with desired physical properties, and it is also easy to prevent exudation after curing. The content of component (e) in the silicone composition is preferably from 2 mass % to 45 mass %, more preferably from 4 mass % to 40 mass %, and further preferably from 6 mass % to 35 mass %.

[0151] <(f) ingredient>

[0152] The silicone composition of the present invention may further contain (f) a silane coupling agent. As the silane coupling agent, known silane coupling agents may be used without particular limitation, and examples thereof include dimethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, n-decyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, and 3-phenylaminopropyltrimethoxysilane.

[0153] The silane coupling agents may be used alone or in combination of two or more.

[0154] By making the silicone composition of the present invention contain (f) a silane coupling agent, it is easy to disperse the filler, and as a result, it becomes possible to highly fill the (c) thermally conductive filler, and the thermal conductivity becomes high. In addition, the (f) component may be surface-treated on the above-mentioned (c) thermally conductive filler, and by making the (f) component surface-treat the (c) thermally conductive filler, the dispersibility of the filler can be further improved.

[0155] The content of the (f) silane coupling agent in the silicone composition is, for example, 0.1 to 10 parts by mass, or preferably 0.5 to 5 parts by mass, per 100 parts by mass of the organopolysiloxane contained in the silicone composition.

[0156] The (f) silane coupling agent may be used together with the above-mentioned component (e), but it does not have to be used together with the above-mentioned component (e).

[0157] <(g) Curing Inhibitor>

[0158] The silicone composition may contain (g) a curing inhibitor. (g) The curing inhibitor may be a known addition reaction control agent that can be used in an addition reaction curing silicone composition, without particular limitation. Examples thereof include acetylene compounds such as 1-ethynyl-1-hexanol, 1-ethynyl-2-cyclohexanol, 3-butyn-1-ol, 2-methyl-3-butyn-2-ol, ethynyl methylene methanol, 3,5-dimethyl-1-hexyn-3-ol, various nitrogen compounds, organophosphorus compounds, oxime compounds, organochlorine compounds, organosulfur compounds, etc. Among them, acetylene compounds are preferred.

[0159] The content of the curing inhibitor (g) in the silicone composition is not particularly limited, but is preferably 1 mass ppm to 5000 mass ppm, more preferably 10 mass ppm to 2000 mass ppm, and further preferably 20 mass ppm to 1000 mass ppm, based on the total amount of the silicone composition.

[0160] In the silicone composition of the present invention, the total content of components (a), (b) and (e) is preferably 2% by mass or more and 40% by mass or less relative to the total amount of the silicone composition. By making the total amount of components (a), (b) and (e) more than a certain amount, these components can properly function as a binder resin, and these components can be used to properly retain the (c) thermally conductive filler. In addition, by making the above-mentioned total content less than a certain amount, a large amount of (c) thermally conductive filler can be contained. The total content of components (a), (b) and (e) is more preferably 3% by mass or more and 30% by mass or less, more preferably 3.5% by mass or more and 20% by mass or less, and even more preferably 4% by mass or more and 12% by mass or less relative to the total amount of the silicone composition.

[0161] The organopolysiloxane in the silicone composition of the present invention may be composed of components (a) and (b) or components (a), (b) and (e), but may contain organopolysiloxane other than components (a), (b) and (e) within a range not impairing the effects of the present invention.

[0162] Examples of the organopolysiloxane other than the components (a), (b) and (e) include alkenyl group-containing organopolysiloxane other than the component (a) and organohydrogenpolysiloxane other than the component (b).

[0163] Examples of the organohydrogenpolysiloxane other than the component (b) include organohydrogenpolysiloxanes other than the component (b) having Si-H at both ends of the molecular chain and at the side chains (hereinafter also referred to as component (b2)). Specifically, examples of the component (b2) include organohydrogenpolysiloxanes having Si-H at both ends of the molecular chain and at the side chains of the molecular chain, wherein the number of Si-H contained in the side chains of the molecular chain is 3 or less or 16 or more.

[0164] However, component (b2) is preferably not included in the silicone composition, or even if included, it is in a small amount. Relative to 100 mass % of component (b), the content of component (b2) in the silicone composition is, for example, 30 mass % or less, preferably 20 mass % or less, more preferably 10 mass % or less, and even more preferably 0 mass %.

[0165] In addition, the silicone composition may contain an organohydrogenpolysiloxane (hereinafter also referred to as component (b3)) other than the organohydrogenpolysiloxane having Si-H at both ends of the molecular chain and at the side chains of the molecular chain (i.e., components (b) and (b2)). Examples of the component (b3) include an organohydrogenpolysiloxane having Si-H only at both ends of the molecular chain, an organohydrogenpolysiloxane having Si-H only at one end of the molecular chain, and an organohydrogenpolysiloxane having Si-H at one end of the molecular chain and at the side chains.

[0166] However, the organosilicon composition of the present invention preferably does not contain organohydrogenpolysiloxanes other than organohydrogenpolysiloxanes having Si-H at both ends of the molecular chain and at the side chains of the molecular chain, or, even if it contains organohydrogenpolysiloxanes other than organohydrogenpolysiloxanes having Si-H at both ends of the molecular chain and at the side chains of the molecular chain, it is a small amount. With such a composition, the effect of the present invention can be easily achieved. Specifically, it is preferred that the organohydrogenpolysiloxane of the organosilicon composition preferably contains organohydrogenpolysiloxanes having Si-H at both ends of the molecular chain and at the side chains of the molecular chain at a ratio of 70% by mass or more, more preferably contains organohydrogenpolysiloxanes having Si-H at both ends of the molecular chain and at the side chains of the molecular chain at a ratio of 80% by mass or more, further preferably contains organohydrogenpolysiloxanes having Si-H at both ends of the molecular chain and at the side chains of the molecular chain at a ratio of 90% by mass or more, and most preferably contains organohydrogenpolysiloxanes having Si-H at both ends of the molecular chain and at the side chains of the molecular chain at a ratio of 100% by mass. That is, the organohydrogenpolysiloxane contained in the silicone composition preferably contains only organohydrogenpolysiloxane having Si—H at both ends of the molecular chain and at the side chains of the molecular chain.

[0167] In addition, examples of alkenyl-containing organopolysiloxanes other than component (a) include organopolysiloxanes having one alkenyl group in one molecule. However, the silicone composition of the present invention preferably does not contain alkenyl-containing organopolysiloxanes other than component (a), or, even if it contains alkenyl-containing organopolysiloxanes other than component (a), it is a small amount. Specifically, of the alkenyl-containing organopolysiloxanes contained in the silicone composition, preferably 70% by mass or more is component (a), more preferably 80% by mass or more is component (a), further preferably 90% by mass or more is component (a), and preferably 100% by mass is component (a). That is, the alkenyl-containing organopolysiloxanes contained in the silicone composition preferably contain only component (a).

[0168] In addition to the above, the silicone composition of the present invention may also contain various additives. Examples of additives include dispersants, flame retardants, plasticizers, antioxidants, colorants, etc. It should be noted that each additive may be included in either the first agent or the second agent, or in both. One or more additives may be appropriately selected from these additives and used.

[0169] <Comparison (H / Vi)>

[0170] Regarding the silicone composition of the present invention, the ratio (H / Vi) of the number of Si-H contained in the composition to the number of vinyl groups is in the range of 0.5 or more and 1.5 or less. In the silicone composition, if the ratio (H / Vi) is less than 0.5, the curability of the silicone composition decreases, and it is difficult to cure the silicone properly. In addition, if the ratio (H / Vi) is greater than 1.5, the curing proceeds excessively, the hardness of the cured product after curing becomes high, and there is a concern that the flexibility of the cured product decreases. In addition, if the ratio (H / Vi) is outside the above range, the long-term reliability is impaired. If it is used for a long time in a high-temperature environment after curing, the hardness becomes high, the cured product peels off from a heating element, a heat sink, etc., and there is a concern that the thermal resistance value becomes large.

[0171] From the viewpoint of ensuring flexibility and suppressing the increase in hardness when used in a high-temperature environment to improve long-term reliability, the ratio (H / Vi) is preferably 0.55 or more and 1.3 or less, more preferably 0.65 or more and 1.2 or less, and even more preferably 0.75 or more and 1.1 or less.

[0172] It should be noted that the number of vinyl groups in the ratio (H / Vi) is the total of the number of vinyl groups of all components contained in the silicone composition. The number of vinyl groups of each component can be calculated from the amount of functional groups (mmol / g) in each component and the content of each component. The same applies to the number of Si-H.

[0173] <E-type hardness>

[0174] Regarding the silicone composition of the present invention, the E-type hardness of the cured product obtained by curing the silicone composition is preferably less than 70. If the above E-type hardness is less than 70, the cured product obtained from the silicone composition becomes soft. Therefore, it is possible to suppress the case where the obtained cured product peels off from a heat sink, a heating element, etc., and the thermal resistance becomes high or the stress on surrounding electronic components becomes high. The E-type hardness of the cured product obtained by curing the silicone composition is more preferably less than 60, and further preferably less than 50.

[0175] In addition, the E-type hardness of the cured product obtained by curing the silicone composition is preferably 10 or more. By making the above E-type hardness a certain value or more, it is possible to sufficiently support the weight of a member provided on the upper part of the cured product, and it is possible to prevent the cured product from being compressed in the thickness direction during use.

[0176] It should be noted that the E-type hardness can be measured for the cured product obtained by curing the silicone composition by the method described in the examples.

[0177] <Two-component curable type>

[0178] In the present invention, the silicone composition is a two-component curing type composed of a first component and a second component. The two-component curing type silicone composition can be obtained by mixing the first component and the second component.

[0179] In a two-component curable silicone composition, the mass ratio of the first component to the second component (second component / first component) is preferably 1 or a value close to 1, preferably 0.8 or more and 1.2 or less, more preferably 0.9 or more and 1.1 or less, and more preferably 0.95 or more and 1.05 or less. As described above, by making the mass ratio of the first component to the second component 1 or a value close to 1, it becomes easy to prepare the silicone composition.

[0180] The first and second agents can be stored in different containers, taken out from the containers and mixed immediately before use. The container is not particularly limited and may be a syringe or the like. If a syringe is used, the first and second agents ejected from each syringe can be easily mixed. In addition, as described above, the first and second agents can be easily mixed at a mass ratio of 1 or a mass ratio close to 1. The first and second agents can have fluidity at room temperature (23°C). If they have fluidity at room temperature, operability becomes good.

[0181] In the two-component curable silicone composition, the first component and the second component can be prepared so that they do not substantially react before the first component and the second component are mixed. Specifically, in the two-component curable silicone composition, the first component contains the component (a) which is an organopolysiloxane having an alkenyl group (alkenyl-containing organopolysiloxane), and the curing catalyst (d), but does not contain the component (b) which is an organohydrogenpolysiloxane. In addition, the second component contains the component (b) which is an organohydrogenpolysiloxane, but does not contain the curing catalyst (d).

[0182] Furthermore, in the present invention, the (c) thermally conductive filler is contained in both the first agent and the second agent, and the (a) component is also contained in the second agent.

[0183] The first agent having the above-mentioned structure contains the curing catalyst (d) that accelerates the addition reaction, but does not contain the component (b), and thus, the addition reaction can be prevented from proceeding before being mixed with the second agent. On the other hand, the second agent contains the components (a) and (b), but does not contain the curing catalyst (d) that accelerates the addition reaction, and thus, the addition reaction can be prevented from proceeding before being mixed with the first agent.

[0184] In addition, in the present invention, by making the first agent and the second agent both contain (a) and (c) components, the specific gravity and viscosity of the first agent and the second agent can be made the same, thereby improving the miscibility of the first agent and the second agent. In addition, it is easy to make the mass ratio of the first agent to the second agent 1 or approximately 1. The details of the (a) and (c) components contained in the first agent and the second agent are as described above, but the (a) component contained in the first agent can use the same component as the (a) component contained in the second agent, or a different component can be used. The same applies to the (c) component, and the (e), (f), and (g) components described later.

[0185] (Difference in viscosity between component (a) and component (b))

[0186] In the present invention, the difference in viscosity between the component (a) and the component (b) at 23°C in the second agent is 400 mPa·s or less. If the viscosity difference is greater than 400 mPa·s, the component (a) and the component (b) are difficult to be compatible, and oil seepage occurs in the second agent during storage, thereby reducing storage stability. From the perspective of being less likely to cause oil seepage, the above viscosity difference is preferably 350 mPa·s or less, and more preferably 300 mPa·s or less. In addition, from the perspective of reducing oil seepage, the lower the viscosity difference, the better, and it can be 0 mPa·s or more. It should be noted that the so-called viscosity of the component (a), when the second agent contains two or more components (a) with different viscosities, is the viscosity of these mixtures. The same applies to the viscosity of the component (b).

[0187] In a two-component curable silicone composition, the total content of the components (a) and (b) in the second agent can be adjusted to be approximately the same as the content of the component (a) in the first agent. If these contents are made approximately the same, it is also coordinated with the fact that the viscosity difference between the above-mentioned components (a) and (b) is small, so that it is easy to make the viscosity of the first agent and the second agent the same. In addition, the specific gravity of the first agent and the second agent is also more likely to become the same, which can improve the miscibility of the first agent and the second agent. In addition, it is easy to make the mass ratio of the first agent to the second agent 1 or approximately 1.

[0188] Specifically, the mass ratio of the total content of component (a) and component (b) in the second agent to the content of component (a) in the first agent ((a2+b2) / a1) is preferably greater than 0.8 and less than 1.2, more preferably greater than 0.9 and less than 1.1, and further preferably greater than 0.95 and less than 1.05.

[0189] In order to make the mass ratio ((a2+b2) / a1) 1 or close to 1 as described above, the component (a) may be contained in the second agent in an amount greater than or equal to a certain amount. Specifically, the component (a) may be formulated in the first agent and the second agent in such a manner that the ratio (a2 / a1) of the content of the component (a) in the second agent to the content of the component (a) in the first agent is, for example, 0.1 or greater, preferably 0.2 or greater, and more preferably 0.35 or greater. As described above, even if the component (a) is contained in the second agent in an amount greater than or equal to a certain amount, in the present invention, the occurrence of oil seepage can be suppressed by adjusting the viscosity of the components (a) and (b), and therefore, the reduction in storage stability due to the formulation of the component (a) in the second agent can be suppressed.

[0190] The ratio (a2 / a1) is not particularly limited, and is, for example, 2 or less, but is preferably less than 1, and more preferably 0.95 or less.

[0191] The mass ratio (a2 / b2) of the component (a) to the component (b) in the second agent is not particularly limited, and is, for example, 0.4 to 15, but is preferably 0.5 to 10, and more preferably 0.75 to 8.

[0192] The (c) thermally conductive filler is preferably contained approximately equally in the first agent and the second agent for forming the silicone composition. Specifically, the mass ratio (c2 / c1) of the content of the (c) thermally conductive filler in the second agent to the content of the (c) thermally conductive filler in the first agent is preferably 0.8 or more and 1.2 or less, more preferably 0.9 or more and 1.1 or less, and further preferably 0.95 or more and 1.05 or less. As described above, by distributing the (c) thermally conductive filler approximately equally in the first agent and the second agent, it is easy to reduce the difference in specific gravity and viscosity between the first agent and the second agent, and the mass ratio of the first agent to the second agent is also easy to approach 1.

[0193] The silicone composition may contain organohydrogenpolysiloxane in addition to the component (b), and in this case, the organohydrogenpolysiloxane may be entirely contained in the second agent, and not contained in the first agent. With such a configuration, it is possible to prevent the addition reaction from proceeding in the first agent.

[0194] On the other hand, the silicone composition may contain an alkenyl group-containing organopolysiloxane in addition to the component (a). The alkenyl group-containing organopolysiloxane other than the component (a) may be contained in the first agent, in the second agent, or in both the first agent and the second agent.

[0195] The silicone composition preferably contains component (e), and component (e) may be contained in at least one of the first agent and the second agent, but is more preferably contained in both the first agent and the second agent. If component (e) is contained in both the first agent and the second agent, the viscosity of the first agent and the second agent can be adjusted by component (e), and the viscosity of both the first agent and the second agent can be made low.

[0196] The silicone composition may contain component (f) (silane coupling agent). Component (f) may be contained in at least one of the first agent and the second agent, but is preferably contained in both the first agent and the second agent because it is more effective.

[0197] That is, when the silicone composition contains the component (f) (silane coupling agent) or the component (e-1), each of the first agent and the second agent preferably contains at least one of the component (f) or the component (e-1) in addition to the thermally conductive filler (c).

[0198] The organosilicon composition may contain component (g) (curing inhibitor), and component (g) may be contained in one of the first agent and the second agent, or in both of the first agent and the second agent, but it is preferred that the curing inhibitor be contained in at least the second agent. The second agent contains both an organohydrogenpolysiloxane (e.g., component (b)) and an alkenyl-containing organopolysiloxane (e.g., component (a)), but by further containing a reaction control agent (g), the reaction between them can be prevented from proceeding in the second agent.

[0199] When preparing a two-component curable silicone composition, all the components constituting the first agent or the second agent can be mixed to prepare the first agent and the second agent respectively. In this case, the mixing order of the components constituting the first agent and the second agent is not particularly limited. However, when the (c) thermally conductive filler is surface-treated with an organosilicon compound having a hydrolyzable silyl group such as the (e-1) component or the (f) component, when preparing the first agent and the second agent respectively, the organosilicon compound having a hydrolyzable silyl group such as the (e-1) component or the (f) component can be first mixed with the (c) thermally conductive filler, so that the above-mentioned (e-1) component or the (f) component adheres to the surface of the (c) thermally conductive filler or reacts with the surface, and then other components are further mixed.

[0200] In the second agent, it is preferred that the component (c) which has been subjected to surface treatment as required is stirred with the component (a) to be sufficiently dispersed as described above, and then the component (b) is added after cooling. When the component (c) is stirred, the temperature rises, and heating and stirring are sometimes performed to improve dispersibility. However, as described above, by mixing the components (a) and (c) before mixing the component (b), it is possible to prevent the component (b) from reacting due to heat or heating when the component (c) is stirred.

[0201] [Heat dissipation component]

[0202] The silicone composition of the present invention can be used as a raw material to produce a heat dissipation component formed of the silicone composition. For example, after the silicone composition is formed into a specified shape, it can be appropriately heated and cured to produce a heat dissipation component formed into a specified shape. The heat dissipation component can be interposed between the heating element and the radiator, and the heat generated by the heating element can be transferred to the radiator by heat conduction, and the heat can be dissipated from the radiator. Here, as the heating element, various electronic components such as CPU, power amplifier, power supply, etc. used in electronic equipment can be cited. In addition, the radiator can be a radiator, a heat pump, a metal housing of an electronic device, etc.

[0203] The heat dissipation component can be used inside an electronic device, for example, an electronic device can be made that includes an electronic component and a heat dissipation component disposed on the electronic component. Specifically, the heat dissipation component can be disposed between an electronic component such as a semiconductor element and a heat dissipation body such as a radiator to effectively dissipate heat generated by the electronic component.

[0204] Example

[0205] The present invention will be clarified below by listing specific examples and comparative examples of the present invention. It should be noted that the present invention is not limited to the following examples.

[0206] The measuring methods and evaluation methods of various physical properties are as follows.

[0207] [Viscosity]

[0208] The viscosity was measured at 23°C using a Brookfield B-type viscometer. As a measuring device, the measurement was performed using "HB DVE" manufactured by Eiko Seiki Co., Ltd. The rotation speed was set to 10 rpm, and the value 3 minutes after the start of rotation was taken as the viscosity. In the measurement using the B-type viscometer, the spindle was appropriately selected so that the torque became 10 to 80%.

[0209] [Thermal conductivity]

[0210] The thermal conductivity of the silicone composition before curing was measured in accordance with ASTM D5470 at 23° C. The thermal conductivity was measured using “T3Ster DynTIM Tester” manufactured by Mentor, a Siemens Business, as a measuring device, and was evaluated based on the following evaluation criteria.

[0211] OK: 3W / m·K or above

[0212] NG: less than 3W / m·K

[0213] [Hardness measurement]

[0214] The hardness was measured using an automatic hardness tester, "GX-02E" manufactured by TECHLOCK CO., LTD., at 25° C. using a type E. The initial hardness of the cured product obtained in each example and comparative example was measured and evaluated based on the following evaluation criteria.

[0215] A: Hardness is 10 or more and less than 50

[0216] B: Hardness is 50 or more and less than 70

[0217] C: Hardness 70 or above

[0218] [Oil seepage (separability during storage)]

[0219] The first and second agents of the silicone composition were filled into 30 ml syringes, respectively, and stored in an oven set at 50° C. After 2 weeks, the presence of oil seepage from each liquid was checked.

[0220] [Long-term reliability]

[0221] The silicone composition obtained in each embodiment and comparative example is applied to a copper block of 25.4 mm × 25.4 mm in size, clamped by another copper block, and set to a uniform thickness using a 1 mm gasket. Place at room temperature (23°C) for 24 hours to cure the silicone composition. The thermal resistance value after curing is measured as the initial thermal resistance value. Then, heat in an oven at 150°C for 250 hours, measure the thermal resistance value, and calculate the rate of change of the thermal resistance value using the following formula. The rate of change of the thermal resistance value is evaluated according to the evaluation criteria described later.

[0222] Thermal resistance change rate (%) = [thermal resistance after heating / initial thermal resistance] × 100

[0223] It should be noted that the thermal resistance value was measured according to the following method. A heater was grounded on one side of the copper block, and a radiator with a fan was grounded on the other side. The heater was used to generate heat, and the temperature (T1) of one side, the temperature (T2) of the other side, and the calorific value (Q) were measured when the temperature reached a certain temperature, and the thermal resistance value was calculated using the following formula.

[0224] Thermal resistance = (T1-T2) / Q

[0225] A: 100% or more and less than 125%

[0226] B: 125% or more and less than 150%

[0227] C: 150% or more

[0228] The components used in the examples and comparative examples are as follows. The vinyl content of the alkenyl-containing organopolysiloxane and the SiH content of the organohydrogenpolysiloxane are as described in the functional group amount column of Tables 1 and 2. The viscosity of each component at 23° C. is also shown in Tables 1 and 2.

[0229] [Alkenyl-containing organopolysiloxane]

[0230] <(a)Component>

[0231] A-1: an organopolysiloxane having vinyl groups only at both ends of the molecular chain and represented by formula (A), the number of vinyl groups in one molecule = 2

[0232] A-2: an organopolysiloxane having vinyl groups only at both ends of the molecular chain and represented by formula (A), the number of vinyl groups in one molecule = 2

[0233] A-3: an organopolysiloxane having vinyl groups only at both ends of the molecular chain and represented by formula (A), the number of vinyl groups in one molecule = 2

[0234] A-4: an organopolysiloxane having vinyl groups only at both ends of the molecular chain and represented by formula (A), the number of vinyl groups in one molecule = 2

[0235] A-5: an organopolysiloxane having vinyl groups only at both ends of the molecular chain and represented by formula (A), the number of vinyl groups in one molecule = 2

[0236] [Organohydrogenpolysiloxane]

[0237] <(b) Components>

[0238] B-1: an organohydrogenpolysiloxane having Si—H at both ends of the molecular chain and at the side chains of the molecular chain and represented by formula (B), the number of Si—H in one molecule = 6 (2 at the ends, 4 at the side chains)

[0239] B-2: an organohydrogenpolysiloxane having Si—H at both ends of the molecular chain and at the side chains of the molecular chain and represented by formula (B), the number of Si—H in one molecule = 12 (2 at the ends, 10 at the side chains)

[0240] B-3: an organohydrogenpolysiloxane having Si—H at both ends of the molecular chain and at the side chains of the molecular chain and represented by formula (B), the number of Si—H in one molecule = 17 (2 at the ends, 15 at the side chains)

[0241] B-4: an organohydrogenpolysiloxane having Si—H at both ends of the molecular chain and at the side chains of the molecular chain and represented by formula (B), the number of Si—H in one molecule = 12 (2 at the ends, 10 at the side chains)

[0242] <(b2) ingredient>

[0243] B2-1: Organohydrogen polysiloxane having Si-H groups at both ends of the molecular chain and at the side chains of the molecular chain, the number of Si-H groups in one molecule = 22 (2 at the ends, 20 at the side chains)

[0244] <(b3)Component>

[0245] B3-1: Organohydrogen polysiloxane having Si-H only in the side chains of the molecular chain, the number of Si-H in one molecule = 10 (10 side chains)

[0246] [Thermal conductive filler]

[0247] C-1: Alumina 1 (average particle size of primary particles: 3 μm)

[0248] C-2: Alumina 2 (average particle size of primary particles: 0.5 μm)

[0249] C-3: Aluminum nitride (average particle size of primary particles: 10 μm)

[0250] C-4: Diamond (average particle size of primary particles: 12 μm)

[0251] [Curing catalyst]

[0252] D-1: Platinum catalyst

[0253] [Organopolysiloxane containing addition reaction groups]

[0254] E-1: A compound represented by formula (1-1) wherein n is 10 to 11.

[0255] [Curing Inhibitor]

[0256] G-1: Curing inhibitor 3,5-dimethyl-1-hexyn-3-ol

[0257] [Examples 1 to 11, Comparative Examples 1 to 5]

[0258] The first and second agents were prepared according to the formulation shown in Table 1. The first and second agents were mixed using a stirring device to obtain a silicone composition, and the silicone composition was cured at room temperature for 24 hours to obtain a cured product. The initial hardness and oil penetration of the cured product were evaluated. In addition, the thermal conductivity and long-term reliability of the silicone composition were evaluated. The evaluation results are shown in Table 1.

[0259] [Table 1]

[0260]

[0261] [Table 2]

[0262]

[0263] ※ In Tables 1 and 2, the amounts (ppm) of the platinum catalyst and the curing inhibitor are ppm by mass relative to the silicone composition. The amounts other than these are parts by mass of each component relative to 100 parts by mass of the organopolysiloxane contained in the silicone composition.

[0264] The silicone compositions of Examples 1 to 11 above contain components (a) to (d), and the ratio of the number of SiH to the number of alkenyl groups (H / Vi) is within the specified range. Therefore, although the thermal conductivity is high and the thermal conductivity is good, the initial hardness is low and the flexibility is good. In addition, even if heated for a long time at 150°C after curing, the increase in thermal resistance is small, and the long-term reliability is good. In addition, although the second agent contains components (a) and (b), since the viscosity difference between components (a) and (b) is less than 400mPa·s, oil leakage does not occur in the second agent during storage.

[0265] In contrast, the silicone compositions of Comparative Examples 1 and 2 did not contain the specific component (b), so the flexibility could not be improved and the long-term reliability was low. In Comparative Example 3, the viscosity difference between the components (a) and (b) was greater than 400 mPa·s, so oil bleeding occurred in the second agent. In Comparative Example 4, the ratio (H / Vi) was too low, so poor curing occurred, while in Comparative Example 5, the ratio (H / Vi) was too high, so the curing was excessively performed, the hardness became high, and the long-term reliability was also deteriorated.

Claims

1. An organosilicon composition comprising (a) an organopolysiloxane, (b) an organohydrogenpolysiloxane, (c) a thermally conductive filler, and (d) a curing catalyst, wherein the (a) organopolysiloxane has at least two alkenyl groups in one molecule, and the (b) organohydrogenpolysiloxane has hydrogen atoms directly bonded to silicon atoms at both ends of the molecular chain and at side chains of the molecular chain, and the number of hydrogen atoms contained in the side chains of the molecular chain is 4 to 15. The silicone composition is a combination of a first agent and a second agent, wherein the first agent comprises the component (a), the component (c), and the component (d) but does not comprise the component (b), and the second agent comprises the component (a), the component (b), and the component (c) but does not comprise the component (d). The difference in viscosity between the component (a) and the component (b) in the second agent at 23° C. is 400 mPa·s or less, In the silicone composition, the ratio of the number of hydrogen atoms directly bonded to silicon atoms to the number of alkenyl groups, that is, H / Vi, is in a range of 0.5 to 1.

5. 2 . The organosilicon composition according to claim 1 , comprising an organosilicon compound having a hydrolyzable silyl group at a molecular chain terminal. 3 . The organosilicon composition according to claim 1 , comprising at least one component selected from the group consisting of (e) an organopolysiloxane having no addition reactive group and (f) a silane coupling agent. 4 . The silicone composition according to claim 3 , wherein each of the first agent and the second agent contains at least one component selected from the group consisting of the component (e) and the component (f). 5 . The silicone composition according to claim 3 , comprising, as the component (e), (e-1) an organopolysiloxane having a hydrolyzable silyl group at a molecular chain terminal.

6. The silicone composition according to claim 3, comprising, as the component (e), at least one compound selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2), In formulas (1) and (2), R 1 Each independently represents any group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms. 1 They can be the same or different, R 2 Each independently represents an alkyl group having 1 to 4 carbon atoms, wherein R 2 In the case of multiple R 2 They can be the same or different, R 3 Each independently represents any group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 2 to 4 carbon atoms, and an acyl group having 2 to 4 carbon atoms, wherein R 3 In the case of multiple R 3 Can be the same or different, R 4 Each independently represents an alkyl group having 1 to 8 carbon atoms, wherein R 5 Each independently represents a divalent hydrocarbon group having 2 to 20 carbon atoms, and a plurality of R 5 They can be the same or different. In formula (2), R 6 It is an oxygen atom or a divalent hydrocarbon group having 2 to 20 carbon atoms. In formulas (1) and (2), a is an integer of 0 to 2, n in formula (1) is an integer of 4 to 150, and m in formula (2) is an integer of 15 to 315. 7 . The silicone composition according to claim 1 , wherein the component (a) has a viscosity of 20 m·Pa or more and 100,000 m·Pa or less at 23° C. 8 . The silicone composition according to claim 1 , wherein the content of the (c) thermally conductive filler is 1000 parts by mass or more and 4000 parts by mass or less relative to 100 parts by mass of the organopolysiloxane contained in the silicone composition. 9 . The silicone composition according to claim 1 , wherein a content of the (d) curing catalyst is 0.1 ppm by mass or more and 500 ppm by mass or less. 10 . The silicone composition according to claim 1 , wherein the second agent contains (g) a curing inhibitor. 11 . The silicone composition according to claim 1 , wherein the organohydrogenpolysiloxane contained in the silicone composition comprises only an organohydrogenpolysiloxane having hydrogen atoms directly bonded to silicon atoms at both ends of the molecular chain and at side chains of the molecular chain. 12 . The organosilicon composition according to claim 1 , wherein the (c) thermally conductive filler is at least one material selected from oxides, nitrides, carbides, carbon-based materials, and metal hydroxides. 13 . The organosilicon composition according to claim 1 , wherein the (c) thermally conductive filler is at least one material selected from the group consisting of aluminum oxide, diamond, and aluminum nitride. 14 . The silicone composition according to claim 1 , wherein the average particle size of primary particles of the (c) thermally conductive filler is 0.1 μm or more. 15 . The silicone composition according to claim 1 , wherein the thermally conductive filler (c) comprises two or more types of particles having different primary particle average diameters. 16 . The silicone composition according to claim 1 , wherein a cured product obtained by curing the silicone composition has an E-type hardness of less than 70. 17 . A heat dissipation member formed from the silicone composition according to claim 1 or 2. 18 . An electronic device comprising an electronic component and the heat dissipation member according to claim 17 , wherein the heat dissipation member is disposed on the electronic component.

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