JP5664563B2 - Thermally conductive silicone composition and cured product thereof - Google Patents

Description

  The present invention relates to a thermally conductive silicone composition useful as a heat transfer material interposed at the interface between a heat boundary surface of a heat-generating electronic component and a heat-dissipating member such as a heat sink or a circuit board, particularly for cooling of the electronic component by heat conduction. Product and its cured product.

  LSI chips such as CPUs, driver ICs, and memories used in electronic devices such as personal computers, digital video disks, and mobile phones are becoming more and more themselves as performance, speed, size, and integration increase. Heat is generated, and the temperature rise of the chip due to the heat causes malfunction and destruction of the chip. Therefore, many heat dissipating methods for suppressing the temperature rise of the chip during operation and heat dissipating members used therefor have been proposed.

  Conventionally, in an electronic device or the like, a heat sink using a metal plate having a high thermal conductivity such as aluminum or copper is used in order to suppress a temperature rise of a chip during operation. The heat sink conducts heat generated by the chip and releases the heat from the surface due to a temperature difference from the outside air.

In order to efficiently transfer the heat generated from the chip to the heat sink, it is necessary to closely attach the heat sink to the chip.However, because there is a difference in the height of each chip and tolerance due to assembly processing, a flexible sheet or grease is used. It is interposed between the chip and the heat sink, and heat conduction from the chip to the heat sink is realized through this sheet or grease.
Sheets are superior in handling properties compared to grease, and heat conductive sheets (heat conductive silicone rubber sheets) formed of heat conductive silicone rubber or the like are used in various fields.

In JP-A-47-32400 (Patent Document 1), at least one selected from beryllium oxide, aluminum oxide, hydrated aluminum oxide, magnesium oxide, and zinc oxide is added to 100 parts by mass of a synthetic rubber such as silicone rubber. An insulating composition containing 100 to 800 parts by mass of a metal oxide is disclosed.
Japanese Patent Application Laid-Open No. 56-1009009 (Patent Document 2) discloses a heat-dissipating material used in a place that does not require insulation, and includes addition-curable silicone rubber compositions such as silica, silver, gold, and silicon. A composition containing 60 to 500 parts by mass of conductive powder is disclosed.

  However, all of these thermally conductive materials have low thermal conductivity, and when a large amount of thermally conductive filler is filled to improve thermal conductivity, liquid silicone rubber compositions have fluidity. In the case of a millable type silicone rubber composition, the plasticity increased, and there was a problem that all of the moldability became very poor.

  Therefore, as a method for solving this, Japanese Patent Laid-Open No. 1-66961 (Patent Document 3) discloses that 10 to 30% by mass of alumina particles having an average particle size of 5 μm or less and the average particle size of 10 μm or more of the remaining single particles. And a highly thermally conductive rubber / plastic composition filled with alumina composed of spherical corundum particles having a shape having no cutting edge. JP-A-4-328163 (Patent Document 4) discloses a gum-like organopolysiloxane having an average degree of polymerization of 6,000 to 12,000 and an oil-like organopolysiloxane having an average degree of polymerization of 200 to 2,000. A thermally conductive silicone rubber composition comprising a base combined with 500 and 1,200 parts by mass of spherical aluminum oxide powder is disclosed.

  However, even when these methods are used, for example, when aluminum oxide powder is highly filled with 1,000 parts by mass or more (aluminum oxide is 70% by volume or more), molding processability can be achieved only by combining particles and adjusting the viscosity of the silicone base. There was a limit to improvement.

  On the other hand, as electronic devices such as personal computers, word processors, and CD-ROM drives have become highly integrated, the amount of heat generated by integrated circuit elements such as LSIs and CPUs in the apparatus has increased, so conventional cooling methods may not be sufficient. is there. In particular, in the case of a portable laptop personal computer, a large heat sink or cooling fan cannot be attached because the space inside the device is narrow. Furthermore, in these devices, an integrated circuit element is mounted on a printed circuit board, and glass reinforced epoxy resin or polyimide resin having poor thermal conductivity is used as the material of the circuit board. Heat cannot escape to the substrate.

  Therefore, a system is used in which a natural cooling type or forced cooling type heat dissipating part is installed in the vicinity of the integrated circuit element and the heat generated in the element is transmitted to the heat dissipating part. If the element and the heat dissipation component are brought into direct contact with this method, the heat transfer will be worse due to the unevenness of the surface, and the heat dissipation insulation sheet will be slightly less flexible even if it is attached via a heat dissipation insulation sheet. There is a risk of stress being applied between the substrate and the substrate.

In addition, if a heat dissipation component is attached to each circuit element, an extra space is required, which makes it difficult to reduce the size of the device. Therefore, a cooling method may be adopted in which several elements are combined into one heat dissipation component. .
In particular, a BGA type CPU used in a notebook personal computer has a low height and a large amount of heat generation compared to other elements, and thus a cooling method must be sufficiently considered.

  Therefore, a low-hardness and high-heat conductive material that can fill various gaps caused by different heights for each element is required. There is a need for a thermal conductive sheet that is excellent in thermal conductivity, flexible, and can cope with various gaps. In addition, as the driving frequency is increased year by year, the CPU performance is improved and the amount of heat generation is increased. Therefore, a material having higher thermal conductivity is demanded.

  In this case, Japanese Patent Laid-Open No. 2-196453 (Patent Document 5) discloses a silicone sheet having a strength required for handling, which is a sheet formed by mixing a silicone resin with a heat conductive material such as a metal oxide. A sheet in which a soft and easily deformable silicone layer is laminated on a resin layer is disclosed. Japanese Patent Laid-Open No. 7-266356 (Patent Document 6) discloses a porous material containing a heat conductive filler and having a silicone rubber layer having an Asker C hardness of 5 to 50 and pores having a diameter of 0.3 mm or more. A thermally conductive composite sheet combining a reinforcing material layer is disclosed. Japanese Patent Application Laid-Open No. 8-238707 (Patent Document 7) discloses a sheet in which the surface of a skeleton lattice of a flexible three-dimensional network or foam is covered with a heat conductive silicone rubber. Japanese Patent Application Laid-Open No. 9-1738 (Patent Document 8) has a thickness 0 in which a reinforcing sheet or cloth is incorporated, at least one surface is adhesive, and Asker C hardness is 5 to 50. A thermally conductive composite silicone sheet of 4 mm or less is disclosed. Japanese Patent Application Laid-Open No. 9-296114 (Patent Document 9) contains an addition reaction type liquid silicone rubber and a heat conductive insulating ceramic powder. The cured product has an Asker C hardness of 25 or less and a thermal resistance of 3.0. A heat dissipating spacer having a temperature of ℃ / W or less is disclosed.

  Since these thermally conductive silicone cured products often require insulating properties, aluminum oxide (alumina) is mainly used as the thermally conductive filler in the range of thermal conductivity of 0.5 to 6 W / mK. It is often done. In general, amorphous alumina has a higher effect of improving thermal conductivity than spherical alumina, but has a drawback that the filling property to silicone is poor, the viscosity of the material is increased by filling, and the workability is deteriorated. . Alumina is very hard with a Mohs hardness of 9 as used in abrasives. Therefore, the heat conductive silicone composition using amorphous alumina having a particle diameter of 10 μm or more has a problem that the inner wall of the reaction kettle and the stirring blades are scraped off when the production takes a share. Then, the components of the reaction kettle and the stirring blade are mixed into the heat conductive silicone composition, and the insulation properties of the heat conductive silicone composition and the cured product using the same are lowered. In addition, the clearance between the reaction kettle and the stirring blade is widened, the stirring efficiency is lowered, and a certain quality cannot be obtained even if manufactured under the same conditions. In addition, in order to prevent this, there is a problem that parts must be frequently replaced.

  In order to solve this problem, there is also a method using only spherical alumina powder, but in order to achieve high thermal conductivity, it is necessary to fill in a large amount compared to amorphous alumina, the viscosity of the composition increases, Workability deteriorates. Moreover, since the amount of silicone present in the composition and its cured product is relatively reduced, the hardness is increased and the compressibility is inferior. Furthermore, since alumina has a very high theoretical specific gravity of 3.98, the specific gravity of the composition and the cured product increases as much alumina is filled. In recent years, electronic devices have been reduced in size and weight, and in order to reduce the weight of the entire electronic device, there is a demand for lighter weight while maintaining performance in units of grams or milligrams in terms of members. . Mass filling of alumina is disadvantageous from the viewpoint of weight reduction.

JP 47-32400 A JP-A-56-100849 JP-A-1-69661 JP-A-4-328163 Japanese Patent Laid-Open No. 2-196453 JP-A-7-266356 JP-A-8-238707 Japanese Patent Laid-Open No. 9-1738 JP-A-9-296114

  The present invention has been made in view of the above circumstances, and has excellent compressibility, insulation, thermal conductivity, and workability, and particularly has a thermal conductivity of 3.0 W / mK or more, for example, a heat generating component in an electronic device. An object of the present invention is to provide a thermally conductive silicone composition and a cured product thereof, which are preferably used as a thermally conductive resin molded body that is installed between a heat radiating component and used for heat dissipation.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors use an amorphous alumina having an average particle diameter of 10 to 30 μm and a spherical alumina having an average particle diameter of 30 to 85 μm in combination at a specific ratio. And found that the above problem can be solved. That is, by using amorphous alumina having an average particle size of 10 to 30 μm, it is possible to effectively improve thermal conductivity, an increase in specific gravity is suppressed, and the proportion of silicone in the composition is increased. To promote the development of rubber properties. Further, by using a spherical alumina having an average particle size equal to or larger than that of the amorphous alumina, the fluidity of the composition is improved and the workability is improved. In addition, wear of the reaction kettle and stirring blade is suppressed, and insulation is improved.

  That is, spherical alumina compensates for the defects of amorphous alumina, and irregular alumina compensates for the defects of spherical alumina, so that it has excellent compressibility, insulation, thermal conductivity, and workability, particularly 3.0 W / mK or more. It has been found that a thermally conductive silicone composition having a thermal conductivity and a cured product can be provided, and has led to the present invention.

（式中、Ｒ⁴は独立に炭素原子数１〜６のアルキル基であり、ｃは５〜１００の整数である。）
で表される分子鎖片末端がトリアルコキシシリル基で封鎖されたジメチルポリシロキサン
からなる群から選ばれる少なくとも１種：（Ａ）成分１００質量部に対し０．０１〜３００質量部を含有する〔１〕記載の熱伝導性シリコーン組成物。
〔３〕
更に、（Ｇ）成分として、下記一般式（３）

（式中、Ｒ⁵は独立に炭素原子数１〜１２の脂肪族不飽和結合を含まない１価炭化水素基、ｄは５〜２，０００の整数である。）
で表される２３℃における動粘度が１０〜１００，０００ｍｍ²／ｓのオルガノポリシロキサンを（Ａ）成分１００質量部に対し０．１〜１００質量部含有する〔１〕又は〔２〕に記載の熱伝導性シリコーン組成物。
〔４〕
２３℃における粘度が８００Ｐａ・ｓ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〕
〔１〕〜〔４〕のいずれかに記載の熱伝導性シリコーン組成物を硬化させてなる熱伝導性シリコーン硬化物。
〔６〕
熱伝導率が３．０Ｗ／ｍＫ以上である〔５〕記載の熱伝導性シリコーン硬化物。
〔７〕
硬度がアスカーＣ硬度計で６０以下である〔５〕又は〔６〕記載の熱伝導性シリコーン硬化物。
〔８〕
絶縁破壊電圧が１０ｋＶ／ｍｍ以上である〔５〕〜〔７〕のいずれかに記載の熱伝導性シリコーン硬化物。 Accordingly, the present invention provides the following thermally conductive silicone composition and cured product thereof.
[1]
(A) Organopolysiloxane having at least two alkenyl groups in one molecule: 100 parts by mass
(B) Organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: The number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to the number of moles of alkenyl groups derived from component (A). 5.0 times the amount,
(C) Thermally conductive filler: 1,200 to 6,500 parts by mass,
(D) Platinum group metal-based curing catalyst: 0.1 to 2,000 ppm in terms of platinum group metal element mass relative to component (A)
Including
The thermally conductive filler of component (C)
(Ci) 500 to 1,500 parts by mass of amorphous alumina having an average particle size of 10 to 30 μm,
(C-ii) 150 to 4,000 parts by mass of spherical alumina having an average particle size of 30 to 85 μm,
(C-iii) A thermally conductive silicone composition comprising 500 to 2,000 parts by mass of an insulating inorganic filler having an average particle size of 0.1 to 6 μm.
[2]
Furthermore, as component (F),
(F-1) The following general formula (1)
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)
And (F-2) the following general formula (2)

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.)
At least one selected from the group consisting of dimethylpolysiloxanes whose molecular chain fragment ends are blocked by trialkoxysilyl groups: 0.01 to 300 parts by mass per 100 parts by mass of component (A) [ 1] The heat conductive silicone composition of description.
[3]
Further, as the component (G), the following general formula (3)

(In the formula, R ⁵ is independently a monovalent hydrocarbon group not containing an aliphatic unsaturated bond having 1 to 12 carbon atoms, and d is an integer of 5 to 2,000.)
[1] or [2] containing 0.1-100 parts by mass of organopolysiloxane having a kinematic viscosity of 10-100,000 mm ² / s represented by the formula (A) with respect to 100 parts by mass of the component (A). Thermally conductive silicone composition.
[4]
The heat conductive silicone composition in any one of [1]-[3] whose viscosity in 23 degreeC is 800 Pa * s or less.
[5]
A thermally conductive silicone cured product obtained by curing the thermally conductive silicone composition according to any one of [1] to [4].
[6]
The thermally conductive silicone cured product according to [5], wherein the thermal conductivity is 3.0 W / mK or more.
[7]
The heat-conductive silicone cured product according to [5] or [6], wherein the hardness is 60 or less with an Asker C hardness meter.
[8]
The thermally conductive silicone cured product according to any one of [5] to [7], wherein the dielectric breakdown voltage is 10 kV / mm or more.

  The heat conductive silicone composition of the present invention has the disadvantage of amorphous alumina by using amorphous alumina having an average particle size of 10 to 30 μm and spherical alumina having an average particle size of 30 to 85 μm in a specific ratio. Spherical alumina compensates, and irregular alumina compensates for the disadvantages of spherical alumina, so it has excellent compressibility, insulation, thermal conductivity, and workability, especially thermal conductivity with a thermal conductivity of 3.0 W / mK or more. A silicone cured product can be provided.

The thermally conductive silicone composition of the present invention is
(A) an alkenyl group-containing organopolysiloxane,
(B) organohydrogenpolysiloxane,
(C) a thermally conductive filler,
(D) A platinum group metal-based curing catalyst is contained as an essential component.

[Alkenyl group-containing organopolysiloxane]
The alkenyl group-containing organopolysiloxane as component (A) is an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule, and becomes the main component of the thermally conductive silicone cured product of the present invention. It is. Usually, the main chain part is generally composed of repeating diorganosiloxane units, but this may be a part of the molecular structure containing a branched structure or cyclic. However, linear diorganopolysiloxane is preferred from the viewpoint of physical properties such as mechanical strength of the cured product.

  The functional group other than the alkenyl group bonded to the silicon atom is an unsubstituted or substituted monovalent hydrocarbon group, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl. Group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group and other alkyl groups, cyclopentyl group, cyclohexyl group, cycloheptyl group and other cycloalkyl groups, phenyl group, tolyl group Aryl groups such as xylyl group, naphthyl group, biphenylyl group, aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group, and part of hydrogen atoms having carbon atoms bonded to these groups Or a group in which all or a halogen atom such as fluorine, chlorine or bromine, a cyano group or the like is substituted, eg For example, chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5, 6,6,6-nonafluorohexyl group and the like are mentioned, typical ones having 1 to 10 carbon atoms, particularly typical ones having 1 to 6 carbon atoms, preferably methyl group An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as ethyl group, propyl group, chloromethyl group, bromoethyl group, 3,3,3-trifluoropropyl group, cyanoethyl group, and phenyl group, chlorophenyl group , An unsubstituted or substituted phenyl group such as a fluorophenyl group. Further, the functional groups other than the alkenyl group bonded to the silicon atom are not limited to being the same.

  Examples of the alkenyl group include those having usually about 2 to 8 carbon atoms such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group, etc. And lower alkenyl groups such as an allyl group are preferable, and a vinyl group is particularly preferable. In addition, although it is preferable that two or more alkenyl groups exist in the molecule, it is preferable that the alkenyl group is bonded only to the silicon atom at the end of the molecular chain in order to make the obtained cured product flexible.

Kinematic viscosity at 23 ° C. This organopolysiloxane is usually, 10~100,000mm ² / s, particularly preferably from 500~50,000mm ² / s. If the viscosity is too low, the storage stability of the resulting composition will be poor, and if it is too high, the extensibility of the resulting composition may be poor. The kinematic viscosity is a value when an Ostwald viscometer is used (hereinafter the same).

  This organopolysiloxane of component (A) may be used alone or in combination of two or more having different viscosities.

[Organohydrogenpolysiloxane]
The organohydrogenpolysiloxane of component (B) is an organohydrogenpolysiloxane having a hydrogen atom (Si-H group) directly bonded to 2 or more, preferably 2 to 100 silicon atoms on average in one molecule. It is a component that acts as a crosslinking agent for component (A). That is, the Si—H group in the component (B) and the alkenyl group in the component (A) are added by a hydrosilylation reaction promoted by the platinum group metal-based curing catalyst of the component (D) described later, and crosslinked. A three-dimensional network structure having a structure is given. In addition, when the number of Si-H groups is less than 2, it does not harden.

（式中、Ｒ⁶は独立に水素原子又は脂肪族不飽和結合を含有しない非置換又は置換の１価炭化水素基であるが、少なくとも２個、好ましくは２〜１０個は水素原子であり、ｅは１以上の整数、好ましくは１０〜２００の整数である。） As the organohydrogenpolysiloxane, one represented by the following average structural formula (4) is used, but is not limited thereto.

Wherein R ⁶ is independently a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond, but at least 2, preferably 2 to 10 are hydrogen atoms, e is an integer of 1 or more, preferably an integer of 10 to 200.)

In the formula (4), examples of the unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond other than the hydrogen atom of R ⁶ include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. , Alkyl groups such as isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, cycloalkyl such as cyclopentyl group, cyclohexyl group, cycloheptyl group, etc. Group, phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group and other aryl groups, benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group and other aralkyl groups, and carbon atoms of these groups are bonded. Some or all of the hydrogen atoms are substituted with halogen atoms such as fluorine, chlorine and bromine, cyano groups, etc. Groups such as chloromethyl, 2-bromoethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, chlorophenyl, fluorophenyl, cyanoethyl, 3,3,4,4,5 5,6,6,6-nonafluorohexyl group and the like, typical examples having 1 to 10 carbon atoms, especially typical ones having 1 to 6 carbon atoms, preferably An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as methyl group, ethyl group, propyl group, chloromethyl group, bromoethyl group, 3,3,3-trifluoropropyl group, cyanoethyl group, and phenyl group; An unsubstituted or substituted phenyl group such as a chlorophenyl group and a fluorophenyl group. Further, R ⁶ is not limited to being all the same.

  Component (B) is added in an amount such that the Si-H group derived from component (B) is 0.1 to 5.0 moles per mole of alkenyl group derived from component (A), preferably 0.3. The amount is -2.0 mol, more preferably 0.5-1.0 mol. When the amount of the Si-H group derived from the component (B) is less than 0.1 mol relative to 1 mol of the alkenyl group derived from the component (A), the cured product does not have sufficient strength or the molded product has insufficient strength. The shape may not be retained and may not be handled. On the other hand, if it exceeds 5.0 mol, the cured product becomes inflexible and the cured product becomes brittle.

[Thermal conductive filler]
The thermally conductive filler as the component (C) mainly contains alumina and is composed of the following components (Ci) to (C-iii).
(Ci) amorphous alumina having an average particle size of 10 to 30 μm,
(C-ii) spherical alumina having an average particle size of 30 to 85 μm,
(C-iii) Insulating inorganic filler having an average particle size of 0.1 to 6 μm In the present invention, the average particle size is a volume standard measured by Microtrac MT3300EX, which is a particle size analyzer manufactured by Nikkiso Co., Ltd. Is the value of the cumulative average particle diameter (median diameter).

  The amorphous alumina as the component (Ci) can improve the thermal conductivity. The average particle size of the amorphous alumina is 10 to 30 μm, and preferably 15 to 25 μm. When the average particle size is less than 10 μm, the effect of improving the thermal conductivity is lowered, the composition viscosity is increased, and the processability is deteriorated. On the other hand, if the average particle size is larger than 30 μm, the reaction kettle and the stirring blade are significantly worn, and the insulation of the composition is lowered. As the amorphous alumina of component (Ci), one type or two or more types may be used in combination. As the amorphous alumina, a normal commercial product can be used.

  The spherical alumina as the component (C-ii) improves the thermal conductivity of the composition, and suppresses the contact between the amorphous alumina, the reaction kettle and the stirring blade, and provides a barrier effect to suppress wear. The average particle size is 30 to 85 μm, preferably 40 to 80 μm. When the average particle size is less than 30 μm, the barrier effect is lowered, and wear of the reaction kettle and stirring blade due to the irregular shaped particles becomes remarkable. On the other hand, when the average particle size is larger than 85 μm, alumina tends to settle in the composition, and the uniformity of the composition is impaired. As the spherical alumina as the component (C-ii), one kind or a combination of two or more kinds may be used. In addition, a normal commercial item can be used for spherical alumina.

  The insulating inorganic filler of component (C-iii) also plays a role of improving the thermal conductivity of the composition, and its main roles are viscosity adjustment of the composition, prevention of sedimentation, improvement of smoothness, and improvement of filling properties. . It also plays roles such as coloring, improving flame retardancy, improving strength, and improving compression set. In order to ensure insulation of the composition, the filler needs to have insulation. (C-iii) The average particle diameter of a component is 0.1-6 micrometers, and it is more preferable for it to be 0.5-4 micrometers because of the above-mentioned characteristic expression. When the average particle size is less than 0.1 μm, the viscosity of the composition is remarkably increased, and the moldability is greatly impaired. On the other hand, if the average particle size is larger than 6 μm, the smoothness of the composition is impaired, and the sedimentation of the filler proceeds rapidly, so that the thermal conductivity of the molded body and the moldability of the composition are impaired.

  Examples of the insulating inorganic filler of the component (C-iii) include metal oxides such as alumina, silica, magnesia, bengara, beryllia, titania, zirconia other than the components (C-i) and (C-ii), Metal nitrides such as aluminum nitride, silicon nitride, and boron nitride, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, artificial diamond, and the like can be used, and these shapes are irregular even if spherical. Further, one or more of these may be used in combination. In addition, a normal commercial item can be used for an insulating inorganic filler.

  (Ci) The compounding quantity of a component is 500-1,500 mass parts with respect to 100 mass parts of (A) component, Preferably it is 700-1,200 mass parts. If the amount is too small, it is difficult to improve the thermal conductivity. If the amount is too large, the fluidity of the composition is lost and the moldability is impaired. In addition, wear of the reaction kettle and stirring blade becomes remarkable, and the insulation of the composition is lowered.

  (C-ii) The compounding quantity of a component is 150-4,000 mass parts with respect to 100 mass parts of (A) component, Preferably it is 200-3,000 mass parts. If the amount is too small, it is difficult to improve the thermal conductivity. If the amount is too large, the fluidity of the composition is lost and the moldability is impaired.

  (C-iii) The compounding quantity of a component is 500-2,000 mass parts with respect to 100 mass parts of (A) component, Preferably it is 600-1,800 mass parts. If the amount is too small, the smoothness of the composition is impaired, and the sedimentation of the filler proceeds rapidly, so that the thermal conductivity of the molded body and the moldability of the composition are impaired. When the amount is too large, the viscosity of the composition is remarkably increased, and the moldability is greatly impaired.

Furthermore, the blending amount of the component (C) (that is, the total blending amount of the components (Ci) to (C-iii)) is 1,200 to 6,500 masses per 100 parts by mass of the component (A). Part, preferably 1,500 to 5,500 parts by mass. When the blending amount is less than 1,200 parts by mass, the resulting composition has poor thermal conductivity, the composition viscosity becomes extremely low, and the storage stability becomes poor, and 6,500 parts by mass. When exceeding, the extensibility of a composition is scarce, and it becomes a molding with high hardness and weak intensity | strength.
By using the component (C) at the above blending ratio, the above-described effects of the present invention can be achieved more advantageously and reliably.

[Platinum group metal curing catalyst]
The (D) component platinum group metal-based curing catalyst is a catalyst for accelerating the addition reaction of the (A) component-derived alkenyl group and the (B) component-derived Si—H group, and is used for the hydrosilylation reaction. Well-known catalysts are mentioned as the catalyst to be used. Specific examples thereof include platinum group metals such as platinum (including platinum black), rhodium and palladium, H ₂ PtCl ₄ · nH ₂ O, H ₂ PtCl ₆ · nH ₂ O, NaHPtCl ₆ · nH ₂ O. , KaHPtCl ₆ · nH ₂ O, Na ₂ PtCl ₆ · nH ₂ O, K ₂ PtCl ₄ · nH ₂ O, PtCl ₄ · nH ₂ O, PtCl ₂ , Na ₂ HPtCl ₄ · nH ₂ O (where, n is an integer of 0 to 6, preferably 0 or 6.) Chlorine chloroplatinic acid and chloroplatinic acid salt, alcohol-modified chloroplatinic acid (US Pat. No. 3,220,972) ), Complex of chloroplatinic acid and olefin (see US Pat. Nos. 3,159,601, 3,159,662, and 3,775,452), platinum black Platinum group gold such as palladium Genus supported on a support such as alumina, silica, carbon, rhodium-olefin complex, chlorotris (triphenylphosphine) rhodium (Wilkinson catalyst), platinum chloride, chloroplatinic acid or chloroplatinate and vinyl group-containing siloxane In particular, a complex with a vinyl group-containing cyclic siloxane may be mentioned.

  (D) The usage-amount of a component is 0.1-2,000 ppm in conversion of the mass of the platinum group metal element with respect to (A) component, Preferably it is 50-1,000 ppm.

[Reaction control agent]
In the thermally conductive silicone composition of the present invention, an addition reaction control agent can be further used as the component (E). As the addition reaction control agent, all known addition reaction control agents used in ordinary addition reaction curable silicone compositions can be used. Examples thereof include acetylene compounds such as 1-ethynyl-1-hexanol, 3-butyn-1-ol, and ethynylmethylidenecarbinol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds.
(E) As a usage-amount in the case of mix | blending a component, 0.01-1 mass part with respect to 100 mass parts of (A) component, Especially about 0.1-0.8 mass part is desirable. If the amount is too large, the curing reaction may not proceed and the molding efficiency may be impaired.

[Surface treatment agent]
In the thermally conductive silicone composition of the present invention, the thermally conductive filler as component (C) is hydrophobized during composition preparation to improve wettability with organopolysiloxane as component (A), For the purpose of uniformly dispersing the thermally conductive filler as the component (C) in the matrix composed of the component (A), a surface treatment agent as the component (F) can be blended. As the component (F), the following components (F-1) and (F-2) are particularly preferable.

The component (F-1) is an alkoxysilane compound represented by the following general formula (1).
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)

In the general formula (1), examples of the alkyl group represented by R ¹ include a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, and a tetradecyl group. When the number of carbon atoms of the alkyl group represented by R ¹ satisfies the range of 6 to 15, the wettability of the component (A) is sufficiently improved, the handleability is good, and the low temperature characteristics of the composition are good. Become.
Examples of the unsubstituted or substituted monovalent hydrocarbon group represented by R ² include 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, Hexyl, heptyl, octyl, nonyl, decyl, dodecyl and other alkyl groups, cyclopentyl, cyclohexyl, cycloheptyl and other cycloalkyl groups, phenyl, tolyl, xylyl, naphthyl, biphenylyl Aryl groups such as benzyl groups, aralkyl groups such as benzyl groups, phenylethyl groups, phenylpropyl groups, and methylbenzyl groups, and some or all of the hydrogen atoms to which the carbon atoms of these groups are bonded are fluorine, chlorine, Groups substituted with halogen atoms such as bromine, cyano groups, etc., for example, chloromethyl group, 2-bromoethyl 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group Typical examples are those having 1 to 10 carbon atoms, particularly typical ones having 1 to 6 carbon atoms, preferably methyl, ethyl, propyl, chloromethyl groups. , Unsubstituted or substituted alkyl groups having 1 to 3 carbon atoms such as bromoethyl group, 3,3,3-trifluoropropyl group, and cyanoethyl group, and unsubstituted or substituted phenyl group, chlorophenyl group, fluorophenyl group, etc. Of the phenyl group. Examples of R ³ include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group.

（式中、Ｒ⁴は独立に炭素原子数１〜６のアルキル基であり、ｃは５〜１００、好ましくは５〜７０、特に好ましくは１０〜５０の整数である。） The component (F-2) is dimethylpolysiloxane in which a molecular chain fragment end represented by the following general formula (2) is blocked with a trialkoxysilyl group.

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100, preferably 5 to 70, and particularly preferably 10 to 50.)

In the general formula (2), examples of the alkyl group represented by R ⁴ include the same alkyl groups represented by R ³ in the general formula (1).

As the surface treatment agent for the component (F), either the component (F-1) or the component (F-2) may be combined in combination.
(F) As a compounding quantity in the case of mix | blending a component, it is preferable that it is 0.01-300 mass parts with respect to 100 mass parts of (A) component, especially 0.1-200 mass parts. Increasing the proportion of this component can induce oil separation.

（式中、Ｒ⁵は独立に炭素原子数１〜１２の脂肪族不飽和結合を含まない１価炭化水素基、ｄは５〜２，０００の整数である。）
で表される２３℃における動粘度が１０〜１００，０００ｍｍ²／ｓのオルガノポリシロキサンを添加することができる。（Ｇ）成分は、１種単独で用いても、２種以上を併用してもよい。 [Organopolysiloxane]
The thermal conductive silicone composition of the present invention has the following general formula (3) as the component (G) for the purpose of imparting properties such as viscosity adjustment of the thermal conductive silicone composition.

(In the formula, R ⁵ is independently a monovalent hydrocarbon group not containing an aliphatic unsaturated bond having 1 to 12 carbon atoms, and d is an integer of 5 to 2,000.)
It is possible to add an organopolysiloxane having a kinematic viscosity at 23 ° C. of 10 to 100,000 mm ² / s. (G) A component may be used individually by 1 type, or may use 2 or more types together.

In the above general formula (3), R ⁵ is independently an unsubstituted or substituted monovalent hydrocarbon group containing no C1-C12 aliphatic unsaturated bond. Examples of R ⁵ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group. Alkyl groups such as dodecyl group, cycloalkyl groups such as cyclopentyl group, cyclohexyl group and cycloheptyl group, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group and biphenylyl group, benzyl group, phenylethyl group, phenylpropylene Groups in which some or all of the hydrogen atoms to which the carbon atoms of these groups are bonded are substituted with halogen atoms such as fluorine, chlorine and bromine, cyano groups, etc. For example, chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-to Fluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, etc. are mentioned. 1 to 10, especially typical ones having 1 to 6 carbon atoms, preferably methyl group, ethyl group, propyl group, chloromethyl group, bromoethyl group, 3,3,3-trifluoropropyl group , An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as a cyanoethyl group, and an unsubstituted or substituted phenyl group such as a phenyl group, a chlorophenyl group, and a fluorophenyl group. Is preferred.
From the viewpoint of the required viscosity, d is preferably an integer of 5 to 2,000, and particularly preferably an integer of 10 to 1,000.

Moreover, kinematic viscosity at 23 ° C. of component (G) is preferably 10~100,000mm ² / s, it is preferable in particular 100~10,000mm ² / s. When the kinematic viscosity is lower than 10 mm ² / s, the cured product of the resulting composition tends to generate oil bleeding. If the kinematic viscosity is greater than 100,000 mm ² / s, the flexibility of the resulting heat conductive silicone composition tends to be poor.

  (G) When adding a component to the heat conductive silicone composition of this invention, the addition amount is not specifically limited, What is necessary is just the quantity from which a desired effect is acquired, (A) With respect to 100 mass parts of component The amount is preferably 0.1 to 100 parts by mass, more preferably 1 to 50 parts by mass. When the addition amount is within this range, it is easy to maintain good fluidity and workability in the thermally conductive silicone composition before curing, and the composition is filled with the thermally conductive filler of component (C). Easy to do.

[Other ingredients]
The heat conductive silicone composition of the present invention may further contain other components as long as the objects and effects of the present invention are not impaired. For example, optional components such as a heat resistance improver such as iron oxide and cerium oxide; a viscosity modifier such as silica; a colorant; and a release agent can be blended.

[Preparation of thermally conductive silicone composition]
The heat conductive silicone composition of this invention can be prepared by mixing each component mentioned above uniformly according to a conventional method.

[Viscosity of composition]
The viscosity of the heat conductive silicone composition of the present invention is 800 Pa · s or less, preferably 700 Pa · s or less at 23 ° C. If the viscosity is too high, moldability may be impaired. In the present invention, this viscosity is based on measurement with a B-type viscometer.

[Method for producing thermally conductive silicone cured product]
The curing conditions for molding the thermally conductive silicone composition may be the same as those of a known addition reaction curable silicone rubber composition. For example, it is sufficiently cured at room temperature, but may be heated as necessary. Preferably, the addition curing is performed at 100 to 120 ° C. for 8 to 12 minutes. Such a cured silicone of the present invention is excellent in thermal conductivity.

[Thermal conductivity of molded body]
As for the thermal conductivity of the molded product (heat conductive silicone cured product) in the present invention, the measured value at 25 ° C. measured by the hot disk method is preferably 3.0 W / mK or more, particularly 4.0 W / mK or more. . If the thermal conductivity is less than 3.0 W / mK, application to a heating element having a large calorific value may be impossible. Note that such thermal conductivity can be adjusted by adjusting the combination of the type and particle size of the thermally conductive filler.

[Dielectric breakdown voltage of molded body]
The dielectric breakdown voltage of the molded body in the present invention is preferably 10 kV or more, more preferably 13 kV or more when the dielectric breakdown voltage of a 1 mm-thick molded body is measured in accordance with JIS K 6249. In the case of a sheet having a dielectric breakdown voltage of 10 kV / mm or less, it is difficult to stably secure insulation during use. Such a breakdown voltage can be adjusted by adjusting the type and purity of the filler.

[Hardness of molded body]
Regarding the hardness of the molded product in the present invention, the measured value at 25 ° C. measured with an Asker C hardness meter is 60 or less, preferably 40 or less, more preferably 30 or less, and preferably 5 or more. When the hardness exceeds 60, it may be difficult to exhibit good heat dissipation characteristics without applying stress to the heat radiating body due to deformation along the shape of the heat radiating body. Such hardness can be adjusted by changing the ratio of the component (A) and the component (B) to adjust the crosslinking density.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. The kinematic viscosity was measured with an Ostwald viscometer at 23 ° C. The average particle diameter is a volume-based cumulative average particle diameter (median diameter) measured by Microtrac MT3300EX, a particle size analyzer manufactured by Nikkiso Co., Ltd.

（式中、Ｘはビニル基であり、ｆは下記粘度を与える数である。）
（Ａ−１）動粘度：６００ｍｍ²／ｓ
（Ａ−２）動粘度：３０，０００ｍｍ²／ｓ The components (A) to (F) used in the following examples and comparative examples are shown below.
(A) component:
Organopolysiloxane represented by the following formula (5).

(In the formula, X is a vinyl group, and f is a number giving the following viscosity.)
(A-1) Kinematic viscosity: 600 mm ² / s
(A-2) Kinematic viscosity: 30,000 mm ² / s

（式中、ｇは２８、ｈは２である。） (B) component:
Organohydrogenpolysiloxane represented by the following formula (6).

(In the formula, g is 28 and h is 2.)

(C) component:
Amorphous alumina, spherical alumina, and amorphous aluminum hydroxide whose average particle size is as follows.
(C-1) Amorphous aluminum hydroxide having an average particle diameter of 1 μm (C-2) Amorphous alumina having an average particle diameter of 1.5 μm (C-3) Spherical alumina having an average particle diameter of 1.5 μm (C- 4) Amorphous alumina (C-5) with an average particle size of 3.6 μm Amorphous alumina (C-6) with an average particle size of 18 μm Amorphous alumina (C-7) with an average particle size of 50 μm 17 μm spherical alumina (C-8) Spherical alumina having an average particle diameter of 45 μm (C-9) Spherical alumina having an average particle diameter of 70 μm

(D) component:
5 mass% chloroplatinic acid 2-ethylhexanol solution.

(E) component:
Ethynylmethylidenecarbinol as an addition reaction control agent.

(F) component: (F-2) component The dimethylpolysiloxane by which the one terminal of the average polymerization degree 30 shown by following formula (7) was blocked with the trimethoxysilyl group.

（式中、ｊは８０である。） (G) Component Dimethylpolysiloxane represented by the following formula (8) as a plasticizer.

(Where j is 80)

[Examples 1-3, Comparative Examples 1-3]
In Examples 1 to 3 and Comparative Examples 1 to 3, the above-mentioned components (A) to (G) were prepared as described below using predetermined amounts shown in Table 1 and molded and cured. Thus, the viscosity of the composition, the thermal conductivity of the cured product, the hardness, the dielectric breakdown voltage, the specific gravity, and the wear of the reaction kettle were measured or observed. The results are also shown in Table 1.

[Preparation of composition]
Components (A), (C), (F), and (G) were added in predetermined amounts shown in Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1 below, and kneaded for 60 minutes with a planetary mixer.
Therein, (D) and (E) are added in the predetermined amounts shown in Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1 below, and Shin-Etsu is used as an internal release agent that further promotes release from the separator. An effective amount of KF-54, which is a phenyl-modified silicone oil manufactured by Chemical Industry Co., Ltd., was added and kneaded for 30 minutes.
The component (B) was further added in predetermined amounts shown in Examples 1 to 3 and Comparative Examples 1 to 3 in Table 1 below, and kneaded for 30 minutes to obtain a composition.

[Molding method]
The compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were poured into a 60 mm × 60 mm × 6 mm mold and molded using a press molding machine at 120 ° C. for 10 minutes.

[Evaluation method]
Viscosity of the composition:
The viscosities of the compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were measured with a B-type viscometer in a 23 ° C. environment.

Thermal conductivity:
The compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were cured into a 6 mm thick sheet using a press molding machine at 120 ° C. for 10 minutes, and two sheets of the sheets were used. The thermal conductivity of the sheet was measured with a thermal conductivity meter (trade name: TPA-501, manufactured by Kyoto Electronics Industry Co., Ltd.).

hardness:
The compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were cured into a 6 mm thick sheet in the same manner as described above, and the two sheets were stacked and measured with an Asker C hardness meter.

Dielectric breakdown voltage:
The compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were cured into a 1 mm thick sheet using a press molding machine at 120 ° C. for 10 minutes, and insulated in accordance with JIS K 6249. The breakdown voltage was measured.

specific gravity:
The compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were cured into a 1 mm thick sheet using a press molding machine under the conditions of 120 ° C. and 10 minutes, and the specific gravity of the cured product was replaced in water. It was measured by.

Reaction kettle wear:
According to the above preparation method, when the composition was prepared, the reaction kettle was shaved and “Yes” was indicated if the black component was visually confirmed, and “None” if not confirmed. Since the alumina and aluminum hydroxide used in the examples and comparative examples are white powder, the composition is inherently white, so that it is easy to understand the black component.

  When the total mass part of the thermally conductive filler exceeds 6,500 parts by mass as in Comparative Example 1, the wettability of the composition is insufficient, and a grease-like uniform composition cannot be obtained. When the amorphous alumina having an average particle diameter of 10 to 30 μm as the component (Ci) was not included as in Comparative Example 2, a decrease in thermal conductivity and an increase in hardness were observed. When an amorphous alumina having an average particle size exceeding 30 μm as in Comparative Example 3 (that is, a heat conductive filler other than the components (Ci) to (C-iii)) is used, the wear of the reaction kettle is remarkable. As a result, the dielectric breakdown voltage of the molded sheet was significantly reduced.

Like an Example, the compounding quantity of (C) component is the range of 1,200-6,500 mass parts with respect to 100 mass parts of (A) component, and (C) component is,
(Ci) 500 to 1,500 parts by mass of amorphous alumina having an average particle size of 10 to 30 μm,
(C-ii) 150 to 4,000 parts by mass of spherical alumina having an average particle size of 30 to 85 μm,
(C-iii) When composed of 500 to 2,000 parts by mass of an insulating inorganic filler having an average particle size of 0.1 to 6 μm, the viscosity of the composition, the thermal conductivity, hardness, specific gravity, and dielectric breakdown voltage of the cured product The results were good and no reaction kettle was observed.

Claims (8)

(A) Organopolysiloxane having at least two alkenyl groups in one molecule: 100 parts by mass
(B) Organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: The number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to the number of moles of alkenyl groups derived from component (A). 5.0 times the amount,
(C) Thermally conductive filler: 1,200 to 6,500 parts by mass,
(D) Platinum group metal-based curing catalyst: 0.1 to 2,000 ppm in terms of platinum group metal element mass relative to component (A)
Including
The thermally conductive filler of component (C)
(Ci) 500 to 1,500 parts by mass of amorphous alumina having an average particle size of 10 to 30 μm,
(C-ii) 150 to 4,000 parts by mass of spherical alumina having an average particle size of 30 to 85 μm,
(C-iii) A thermally conductive silicone composition comprising 500 to 2,000 parts by mass of an insulating inorganic filler having an average particle size of 0.1 to 6 μm. Furthermore, as component (F),
(F-1) The following general formula (1)
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)
And (F-2) the following general formula (2)

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.)
And at least one selected from the group consisting of dimethylpolysiloxanes whose molecular chain fragment ends are blocked with trialkoxysilyl groups: Claims containing 0.01 to 300 parts by weight per 100 parts by weight of component (A) Item 2. A thermally conductive silicone composition according to item 1. Further, as the component (G), the following general formula (3)

(In the formula, R ⁵ is independently a monovalent hydrocarbon group not containing an aliphatic unsaturated bond having 1 to 12 carbon atoms, and d is an integer of 5 to 2,000.)
The heat according to claim 1 or 2, comprising 0.1 to 100 parts by mass of an organopolysiloxane having a kinematic viscosity of 10 to 100,000 mm ² / s represented by the formula (A) with respect to 100 parts by mass of the component (A). Conductive silicone composition.   The heat conductive silicone composition according to any one of claims 1 to 3, which has a viscosity at 23 ° C of 800 Pa · s or less.   The heat conductive silicone hardened | cured material formed by hardening | curing the heat conductive silicone composition of any one of Claims 1 thru | or 4.   The thermally conductive silicone cured product according to claim 5, which has a thermal conductivity of 3.0 W / mK or more.   The thermally conductive silicone cured product according to claim 5 or 6, which has a hardness of 60 or less as measured by an Asker C hardness meter.   The thermally conductive silicone cured product according to any one of claims 5 to 7, wherein a dielectric breakdown voltage is 10 kV / mm or more.