JP2016011322A - Heat-conductive composite silicone rubber sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive composite silicone rubber sheet excellent in high heat conductivity, low hardness, good restoration property and workability under high temperature, thermal conductivity, rework property, insulation assurance property, and long term reliability.SOLUTION: A thermal conductive silicone composition contains (a) organopolysiloxane containing 2 to 9 alkenyl groups bonded to a silicon atom at a non-terminal part, (b) organohydrogenpolysiloxane where at least both terminals are blocked with a hydrogen atom bonded to the silicon atom, (c) a heat-conductive filler and (d) a platinum group metal-based curing catalyst, and in the thermal conductive silicone composition, assuming that an average number of siloxane bond among silicon atoms of the non-terminal moiety, to each of which the alkenyl group is bonded in the organosiloxane of the (a) component is L, and that an average degree of polymerization of the organohydrogenpolysiloxane of the (b) component is L', L'/L=0.6 to 3.0 is satisfied. A heat-conductive silicone sheet is molded by curing the heat-conductive silicone composition in a heating process at 90 to 130°C and then, further adding a post-curing process at 140 to 180°C.

Description

  The present invention relates to a thermally conductive molded article useful as a heat transfer material for interposing an interface between a heat generating electronic component and a heat dissipating member such as a heat sink or a circuit board to cool the electronic component by heat conduction, and a method for manufacturing the same. About.

  LSI chips such as CPUs, driver ICs, and memories used in electronic devices such as personal computers, digital video discs, 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 an aluminum plate or a copper plate 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, the heat sink needs to be in close contact with the chip, but because there is a difference in the height of each chip and tolerance due to assembly processing, a flexible sheet or grease should be 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 Patent Document 1, 100 to 800 parts by weight of at least one metal oxide selected from beryllium oxide, aluminum oxide, hydrated aluminum oxide, magnesium oxide and zinc oxide is blended with 100 parts by weight of a synthetic rubber base such as silicone rubber. Insulating compositions having excellent electrical insulation and thermal conductivity are disclosed.

  In addition, as a heat dissipation material used in a place where insulation is not required, Patent Document 2 discloses that finely pulverized fine particles made of silica fine particles and heat conductive powders such as silver, gold and silicon are added to an addition curable silicone rubber. A composition containing 500 parts by weight 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 increases, and there is a problem that the moldability becomes very poor.

  Therefore, as a heat conductive material for solving this, Patent Document 3 discloses that alumina particles having an average particle diameter of 5 μm or less are 10 to 30% by weight, and the balance is a single particle having an average particle diameter of 10 μm or more and a cutting edge. A highly thermally conductive rubber / plastic composition is disclosed which is filled with alumina composed of spherical corundum particles having a shape that does not have. Patent Document 4 includes 100 parts by weight of a base in which a gum-like organopolysiloxane having an average degree of polymerization of 6,000 to 12,000 and an oily organopolysiloxane having an average degree of polymerization of 200 to 2,000 are used in combination. A thermally conductive silicone rubber composition containing 500 to 1,200 parts by mass of spherical aluminum oxide powder is disclosed.

  However, even when these thermally conductive materials are used, for example, when the aluminum oxide powder is highly filled with 1,000 parts by weight or more (70% by volume or more of aluminum oxide) with respect to 100 parts by weight of the base, the combination of particles and There is a limit to the improvement of molding processability only by adjusting the viscosity of the silicone base.

  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 a resin having poor thermal conductivity such as glass-reinforced epoxy resin or polyimide resin is used as the material of the board. Heat cannot be released to the substrate through the sheet.

  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 by the element is transmitted to the heat dissipating part. However, even if the element and the heat dissipation component are in direct contact with this method, heat transfer is poor due to the unevenness of the surface, and even if the element and the heat dissipation component are attached via a heat dissipation insulating sheet, the flexibility of the heat dissipation insulating sheet However, since the thermal expansion causes a stress between the element and the substrate, the element may be damaged.

  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. . At this time, since a BGA type CPU used in a notebook personal computer is lower in height than other elements and generates a large amount of heat, it is necessary to sufficiently consider a cooling method.

  Therefore, a low-hardness highly heat-conductive material that can fill various gaps caused by different heights for each element is required. In order to solve such a problem, there is a demand for a thermally conductive sheet that is excellent in thermal conductivity, flexible, and can accommodate various gaps. Further, as the driving frequency increases year by year and the performance of the CPU improves, the amount of heat generation increases, so a material with higher thermal conductivity is required.

  For example, Patent Document 5 discloses a silicone resin having a strength required for handling in a heat transfer sheet formed by molding a silicone resin mixed with a heat conductive material such as a metal oxide into a sheet shape. A heat transfer sheet is disclosed in which a soft and easily deformable silicone resin layer is laminated on a layer and configured as a single sheet. Patent Document 6 discloses heat conduction in which a silicone rubber layer containing a thermally conductive filler and having an Asker C hardness of 5 to 50 is combined with a porous reinforcing material layer having a diameter of 0.3 mm or more. A functional composite sheet is disclosed. Patent Document 7 discloses a sheet in which a skeleton lattice surface of a flexible three-dimensional network or foam is coated with a heat conductive silicone rubber. Patent Document 8 discloses a thermally conductive composite silicone sheet having a thickness of 0.4 mm or less having a built-in reinforcing sheet or cloth, at least one surface having adhesiveness, and an Asker C hardness of 5 to 50. Is disclosed. Patent Document 9 contains an addition reaction type liquid silicone rubber and a heat conductive / insulating ceramic powder, and the cured product has an Asker C hardness of 25 or less and a thermal resistance of 3.0 ° C./W or less. And a heat dissipation spacer made of a cured product of the composition.

  These thermal conductive sheets are required to have high thermal conductivity and low hardness in order to improve adhesion to the chip and the heat sink, and low hardness thermal conductive sheets with Asker C hardness of 20 or less are used. It is becoming. Since the low-hardness heat conductive sheet can relieve stress, it achieves high adhesion to the heating element and the heat radiating member, and can be applied to a low thermal resistance and step structure. However, since it is inferior in recoverability, it is disadvantageous in that once it is deformed, it does not return to its original shape, and subsequent molding such as cutting is difficult, and handling properties at the time of pasting and reworkability are poor. On the other hand, in order to improve handleability and reworkability, it is necessary to increase the hardness of the heat conductive sheet, and there has been an incompatible relationship between low hardness, handleability and reworkability.

In order to solve this problem, for example, Patent Document 10 discloses a composition capable of improving restorability by homogenizing a crosslinked structure of a silicone resin and achieving both low hardness and reworkability, and the composition. A thermally conductive silicone cured product comprising a cured product of the composition is disclosed.
However, in in-vehicle applications, there is a concern that the recoverability is insufficient even with the above-described thermally conductive silicone cured product. In recent years, there is a case where an electronic device is disposed in an engine room or the like under a high temperature due to a space saving problem. In this case, there is a case where the environmental temperature rises to about 150 ° C. to 180 ° C. In addition, in the case of in-vehicle use, the heat conductive silicone sheet is exposed to vibration for a long period of time. The molding temperature of the thermosetting heat conductive silicone sheet is often around 100 ° C., and the restorability is lost by the reaction of the unreacted components gradually proceeding at a temperature exceeding the molding temperature. When vibration is applied in a state where the restorability is lost, in general screw fixing, there is a problem that the heat conductive silicone sheet and the heating element or the heat radiating member are peeled off, and the thermal resistance is remarkably increased. Arise.

  By adding a post-cure process, the resilience at high temperatures can be improved. However, in silicone materials, post-cure is generally performed at around 200 ° C, so a large amount of thermally conductive filler is filled. However, in such a system, there is a problem that a compressibility is lowered due to an increase in hardness and a restoration property is lowered due to deterioration of cracking of silicone. Moreover, it is necessary to use a highly heat-resistant polyimide as a protective film for the sheet, and there is a problem that costs increase. When the filling amount of the heat conductive filler is decreased in order to suppress the hardness increase and the cracking deterioration of the silicone, the thermal conductivity is lowered as a contradiction. That is, it has been extremely difficult to achieve both excellent thermal conductivity (heat dissipation), high compression characteristics due to low hardness, and high temperature resilience.

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 JP 2011-16923 A

  Accordingly, an object of the present invention is to provide a thermally conductive silicone sheet suitable for in-vehicle use, which has high thermal conductivity and low hardness, and has high resilience at high temperatures. .

In view of such a situation, the present inventor has intensively studied, and as a result, has found that the following thermally conductive silicone sheet solves the above problems, and has completed the present invention.
That is, this invention provides the following heat conductive silicone sheet and its manufacturing method.

<1>
(a) Organopolysiloxane containing at least an alkenyl group bonded to a silicon atom in a non-terminal part and having 2 to 9 alkenyl groups bonded to a silicon atom in a non-terminal part: 100 parts by mass
(b) Organohydrogenpolysiloxane having at least both ends blocked with hydrogen atoms bonded to silicon atoms: The number of moles of hydrogen atoms bonded to silicon atoms in this component is 1.0 mol of alkenyl groups in component (a). In an amount of 0.1 to 1.5 mol,
(c) Thermally conductive filler: 500-4000 parts by weight, and
(d) Platinum group metal-based curing catalyst: 0.1 to 1000 ppm in terms of mass of platinum group metal element with respect to component (a)
Comprising
In the organopolysiloxane of component (a), the average number of siloxane bonds between the silicon atoms of the non-terminal portion to which the alkenyl group is bonded is L,
When the average degree of polymerization of the organohydrogenpolysiloxane of component (b) is L ′, a thermally conductive silicone composition satisfying L ′ / L = 0.6 to 3.0 was cured in a heating process at 90 to 130 ° C. Then, a heat-conductive silicone sheet formed by adding a post-cure process at 140 to 180 ° C.

<2>
(e) The thermally conductive silicone composition according to <1>, further comprising 0.1 to 100 parts by mass of dimethylpolysiloxane having one end blocked with a trialkoxysilyl group.

<3>
<1> or <2>, wherein the hardness is 5 to 30 in terms of Asker C hardness.

<4>
(c) Any one of <1> to <3>, wherein the thermally conductive filler contains the following amount with respect to 100 parts by mass of component (a), and the thermal conductivity exceeds 1.5 W / m · K: A thermally conductive silicone sheet according to claim 1.
(C-1) 300-1500 parts by mass of amorphous alumina with a center particle size of 0.5-5um
(C-2) 300-1500 parts by mass of spherical alumina with a center particle size of 7-25um
(C-3) 300-1500 parts by mass of spherical alumina with a center particle size of 30-50um
(C-4) 300-1500 parts by mass of spherical alumina with a central particle size of 60-90um

<5>
(a) Organopolysiloxane containing at least an alkenyl group bonded to a silicon atom in a non-terminal part and having 2 to 9 alkenyl groups bonded to a silicon atom in a non-terminal part: 100 parts by mass
(b) Organohydrogenpolysiloxane having at least both ends blocked with hydrogen atoms bonded to silicon atoms: The number of moles of hydrogen atoms bonded to silicon atoms in this component is 1.0 mol of alkenyl groups in component (a). In an amount of 0.1 to 1.5 mol,
(c) Thermally conductive filler: 500-4000 parts by weight, and
(d) Platinum group metal-based curing catalyst: 0.1 to 1000 ppm in terms of mass of platinum group metal element with respect to component (a)
Comprising
In the organopolysiloxane of component (a), the average number of siloxane bonds between the silicon atoms of the non-terminal portion to which the alkenyl group is bonded is L,
When the average degree of polymerization of the organohydrogenpolysiloxane of component (b) is L ′, a thermally conductive silicone composition satisfying L ′ / L = 0.6 to 3.0 was cured in a heating process at 90 to 130 ° C. Thereafter, a post-cure process at 140 to 180 ° C. is further added to form the heat conductive silicone sheet.

<6>
After curing, the cover film on one side of the sheet produced by coating or press molding is peeled off at a temperature of 90 to 130 ° C so that both sides of the sheet are finally protected by the cover film, <1> The method for producing a thermally conductive silicone sheet according to <5>, wherein one post-cure process is added and a second post-cure process at 140 to 180 ° C. is added, and then a cover film is laminated on the exposed sheet surface.

  The thermally conductive silicone sheet of the present invention has high thermal conductivity and low hardness, so it deforms along the shape of the object to be radiated and exhibits good heat dissipation characteristics without applying stress to the object to be radiated. On the other hand, since it has good recoverability at high temperature, it can exhibit excellent long-term reliability even in harsh environments such as high temperature and vibration. It is also excellent in handling and reworkability, and is used as a heat transfer material to cool electronic components by heat conduction by interposing them at the interface between heat-generating electronic components such as in-vehicle use and heat dissipation members such as heat sinks or circuit boards. Useful.

Hereinafter, the present invention will be described in detail.
[(a) Organopolysiloxane]
The alkenyl group-containing organopolysiloxane as component (a) contains at least an alkenyl group bonded to a silicon atom at the non-terminal portion (that is, contains at least an alkenyl group at the side chain), and has a non-terminal portion silicon atom. An organopolysiloxane having 2 to 9 bonded alkenyl groups. The organopolysiloxane of component (a) is generally a straight chain in which the main chain is basically composed of repeating diorganosiloxane units and both ends of the molecular chain are blocked with triorganosiloxy groups. However, a part of the polysiloxane structure composed of a chain of siloxane bonds may include a branched structure, or may be a cyclic body. The alkenyl group may be bonded only to the silicon atom of the non-terminal part or may be bonded to both the silicon atom of the non-terminal part and the terminal silicon atom. In view of physical properties such as mechanical strength of the cured product, the component (a) is preferably a linear diorganopolysiloxane.
Component (a) can be used alone or in combination of two or more.

An example of the component (a) is an organopolysiloxane represented by the following general formula (1).

（式中、Ｒ^１は独立に脂肪族不飽和結合を有しない非置換又は置換の１価炭化水素基であり、Ｘはアルケニル基であり、ｎは０又は１以上の整数であり、ｍは２〜９の整数である。）

(Wherein R ¹ is an unsubstituted or substituted monovalent hydrocarbon group independently having no aliphatic unsaturated bond, X is an alkenyl group, n is 0 or an integer of 1 or more, and m is It is an integer from 2 to 9.)

In the general formula (1), R ¹ is, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group. Alkyl groups such as heptyl group, octyl group, nonyl group, decyl group, dodecyl group; cycloalkyl groups such as cyclopentyl group, cyclohexyl group, cycloheptyl group; phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group, etc. An aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group; and a part or all of hydrogen atoms bonded to carbon atoms of these groups are fluorine atom, chlorine atom, A group substituted with a halogen atom such as a bromine atom, a cyano group or a combination thereof, such as a 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 etc. are mentioned. R ¹ is an unsubstituted or substituted, typically 1 to 12 carbon atoms, more typically 1 to 10 carbon atoms, and most typically carbon atoms, that does not contain an aliphatic unsaturated bond. It is a monovalent hydrocarbon group having a number of 1 to 6. R ¹ is preferably an unsubstituted or substituted alkyl having 1 to 3 carbon atoms such as a methyl group, an ethyl group, a propyl group, a chloromethyl group, a bromoethyl group, a 3,3,3-trifluoropropyl group or a cyanoethyl group. Group and an unsubstituted or substituted phenyl group such as a phenyl group, a chlorophenyl group, and a fluorophenyl group. In addition, R ¹ does not have to be all the same, and may be different from each other.

  In the general formula (1), as X, for example, an alkenyl group having about 2 to 8 carbon atoms such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, a hexenyl group, and a cyclohexenyl group. Among them, a lower alkenyl group such as a vinyl group and an allyl group is preferable, and a vinyl group is particularly preferable.

  In the general formula (1), n is 0 or an integer of 1 or more, and m is an integer of 2 to 9. Further, n and m are preferably 10 ≦ n + m ≦ 10,000, more preferably An integer that satisfies 50 ≦ n + m ≦ 2,000, more preferably 100 ≦ n + m ≦ 500, and satisfies 0 <m / (n + m) ≦ 0.05.

[(b) Organohydrogenpolysiloxane]
The component (b) is an organohydrogenpolysiloxane blocked at least at both ends with hydrogen atoms bonded to silicon atoms (that is, Si—H groups), and is usually linear. The component (b) may have Si—H groups only at both ends, or may have both ends and non-terminal portions (that is, side chains). Component (b) has at least two Si-H groups in one molecule because at least both ends are blocked with Si-H groups, but has an average of 2 to 4 Si-H groups. Those are preferred. When the number of Si—H groups in the component (b) is less than 2, the resulting composition may not be cured. Component (b) can be used alone or in combination of two or more.

An example of the component (b) is an organohydrogenpolysiloxane represented by the following average structural formula (2).

（式中、Ｒ^１は独立に脂肪族不飽和結合を有しない非置換又は置換の１価炭化水素基であり、oは0以上の正数であり、pは0以上2未満の正数である。）

(In the formula, R ¹ independently represents an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, o is a positive number of 0 or more, and p is a positive number of 0 or more and less than 2. is there.)

  In the above average structural formula (2), o is a positive number of 0 or more, preferably 10 to 250, and p is a positive number of 0 or more and less than 2, but preferably 0 or more and less than 1. Is a positive number. The numerical values of o and p indicate the average number of siloxane units in the average structural formula (2), and each organohydropolysiloxane constituting the organohydrogenpolysiloxane represented by the average structural formula (2). The number of siloxane units in the genpolysiloxane molecule is not limited to the range represented by o and p.

  The amount of component (b) added is such that the number of moles of Si-H groups in this component is 0.1 to 1.5 mol, preferably 0.3 to 1.0 mol, relative to 1.0 mol of alkenyl groups in component (a). Is the amount. When component (b) is added such that the number of moles of Si-H groups in this component is less than 0.1 mol or more than 1.5 mol relative to 1.0 mol of alkenyl groups in component (a), the desired low hardness It is difficult to obtain a molded product.

  In the composition of the present invention, the average number of siloxane bonds between silicon atoms in the non-terminal portion to which the alkenyl group is bonded in the organopolysiloxane of component (a) is L, and the organohydrogenpolysiloxane of component (b) When the average degree of polymerization is L ′, it is necessary to satisfy L ′ / L = 0.6 to 3.0, preferably L ′ / L = 0.7 to 2.3, and satisfies L ′ / L = 0.8 to 2.0. It is more preferable. When L ′ / L is less than 0.6 or greater than 3.0, the crosslinked structure tends to be non-uniform in the cured product of the resulting composition, and the thermally conductive silicone molded product made of the cured product has good restorability. It is hard to become a thing. Thus, the ratio L ′ / L indicates the uniformity of the cross-linked structure in the cured product of the composition of the present invention, and serves as an indicator of the resilience possessed by the thermally conductive silicone molded product of the present invention.

In addition, in the component (a), the average number L of siloxane bonds between the silicon atoms of the non-terminal portion to which the alkenyl group is bonded is determined as follows, for example. First, (a) component is an organopolysiloxane composed of siloxane units M at both ends and n types of non-terminal siloxane units D1 to Dn, and (a) a non-terminal having an alkenyl group bonded thereto Assume that the number of silicon atoms in the portion is N. When ²⁹ Si-NMR of component (a) is measured and the integrated area of the peak derived from the silicon atom in M units at both ends is 2, the D1 to Dn units in each non-terminal part are present. Integral areas S1 to Sn of peaks derived from silicon atoms are obtained. As a result, component (a) has an average structural formula:
_{M-D1 S1 -D2 S2 - ···} -Dn Sn -M
It is represented by L is the formula:
L = (S1 + S2 + ... + Sn) / (N + 1)
It is requested from. L is a silicon atom of the non-terminal part to which the alkenyl group is directly bonded in the average structure where the silicon atom of the non-terminal part to which the alkenyl group is directly bonded is present in the molecule of the component (a). Represents the number of siloxane bonds between The value of L corresponds to the average value of the number of oxygen atoms between the silicon atoms of the non-terminal portion to which the alkenyl group is bonded.

Specifically, for example, when the component (a) is a trimethylsiloxy group-blocked dimethylsiloxane / methylalkenylsiloxane copolymer, when ²⁹ Si-NMR of the component (a) is measured, the terminal trimethylsiloxy group is around 8 ppm. Peak 1 derived from silicon atom is detected, peak 2 derived from silicon atom in dimethylsiloxane unit is detected around -22 ppm, and peak 3 derived from silicon atom in methylalkenylsiloxane unit is detected around -36 ppm The When the integrated area of peak 1 is 2, assuming that the integrated areas of peaks 2 and 3 are t and u, respectively, this (a) component is the average structural formula:
(H ₃ C) ₃ SiO-[(CH ₃ ) ₂ SiO] _t -[(CH ₃ ) (Alk) SiO] _u -Si (CH ₃ ) ₃
(In the formula, Alk represents an alkenyl group)
L is the formula:
L = (t + u) / (u + 1)
It is requested from.

On the other hand, the average degree of polymerization L ′ of the component (b) is obtained, for example, as follows. First, it is assumed that the component (b) is an organohydrogenpolysiloxane composed of siloxane units M ′ at both ends and n types of siloxane units D′ 1 to D′ n at non-terminal portions. The ²⁹ Si-NMR of this component (b) was measured, and when the integrated area of the peak derived from the silicon atom in the M ′ units at both ends was taken as 2, the D′ 1 to D′ n units of the non-terminal portion The integrated areas S′1 to S′n of peaks derived from silicon atoms present in each are obtained. As a result, component (b) has an average structural formula:
_{M'-D'1 S'1 -D'2 S'2 - ···} -D'n S'n -M '
The average polymerization degree L ′ of the component (b) is represented by the formula:
L '= S'1 + S'2 + ... + S'n
It is requested from.

Specifically, for example, when the component (b) is a dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, when ²⁹ Si-NMR of the component (b) is measured, the terminal dimethylhydrogensiloxy group is in the vicinity of -8 ppm. A silicon atom-derived peak 1 'is detected, and a silicon atom-derived peak 2' in the dimethylsiloxane unit is detected at around -22 ppm. When the integrated area of peak 1 'is 2, and the integrated area of peak 2' is t ', this (b) component is the average structural formula:
H (H ₃ C) ₂ SiO-[(CH ₃ ) ₂ SiO] _{t '} -Si (CH ₃ ) ₂ H
And L ′ = t ′.

[(c) Thermally conductive filler]
As the thermally conductive filler as component (c), any material that is generally regarded as a thermally conductive filler can be used without any particular limitation. Examples of the component (c) include non-magnetic metals such as copper and aluminum; metal oxides such as alumina, silica, magnesia, bengara, beryllia, titania and zirconia; metal nitrides such as aluminum nitride, silicon nitride and boron nitride. A metal hydroxide such as aluminum hydroxide and magnesium hydroxide; artificial diamond; silicon carbide and the like.

As the component (c) filler, one kind may be used alone, or a plurality of kinds may be mixed and used. Two or more kinds of particles having different average particle diameters can be used.
For example, when the (c) thermally conductive filler contains the following, the filler of the thermally conductive filler becomes good and exhibits a particularly excellent restoring effect.
(C-1) 300-1500 parts by mass of amorphous alumina with a center particle size of 0.5-5um
(C-2) 300-1500 parts by mass of spherical alumina with a center particle size of 7-25um
(C-3) 300-1500 parts by mass of spherical alumina with a center particle size of 30-50um
(C-4) 300-1500 parts by mass of spherical alumina with a central particle size of 60-90um
[To 100 parts by mass of component (a)]
The average particle diameter is obtained as a volume-based cumulative average diameter by, for example, a laser diffraction method.

  (C) The compounding quantity of a component needs to be 500-4000 mass parts with respect to 100 mass parts of (a) component, Preferably it is 700-3500 mass parts. When the blending amount is less than 500 parts by mass, the thermal conductivity of the composition tends to be poor and the storage stability may be poor. On the other hand, when the blending amount exceeds 4000 parts by mass, the resulting composition may be poor in extensibility, and the resilience of the obtained molded product is lowered.

[(d) Platinum group metal-based curing catalyst]
The platinum group metal-based curing catalyst of component (d) is a catalyst for promoting the addition reaction between the alkenyl group in component (a) and the Si—H group in component (b), and is used for the hydrosilylation reaction. A well-known catalyst can be used as the catalyst to be produced. Component (d) can be used alone or in combination of two or more.

Specific examples of component (d) include platinum group metals such as platinum (including platinum black), rhodium, palladium, etc .; 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 (in each formula , N is an integer from 0 to 6, preferably 0 or 6), such as platinum chloride, chloroplatinic acid and chloroplatinate; alcohol-modified chloroplatinic acid (see US Pat. No. 3,220,972); Complex of platinum acid and olefin (see US Pat. Nos. 3,159,601, 3,159,662, and 3,775,452); platinum group metals such as platinum black and palladium are supported on alumina, silica, carbon and the like Rhodium-olefin complex; Chlorotris (triphenylphosphine) rhodium (Wilkinson's catalyst) Medium); and a complex of platinum chloride, chloroplatinic acid or chloroplatinate and a vinyl group-containing siloxane, particularly a vinyl group-containing cyclic siloxane.

  The amount of the component (d) used may be a so-called catalytic amount, and is usually about 0.1 to 1000 ppm in terms of the mass of the platinum group metal element with respect to the component (a).

[(e) Surface treatment agent]
The dimethylpolysiloxane in which one end of the component (e) is blocked with a trialkoxysilyl group is an optional component used as a surface treatment agent. The dimethylpolysiloxane of component (e) is usually blocked at one end with a trialkoxysilyl group and at the other end with a trimethylsilyl group. Component (e) can be used alone or in combination of two or more.

  An example of the component (e) is dimethylpolysiloxane represented by the following general formula (3).

（式中、Ｒ^２は独立に非置換または置換の炭素原子数1〜6のアルキル基であり、qは5〜200の整数である。）

(In the formula, R ² is independently an unsubstituted or substituted alkyl group having 1 to 6 carbon atoms, and q is an integer of 5 to 200.)

In the general formula (3), as R ² , for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group And some or all of the hydrogen atoms bonded to the carbon atoms of these alkyl groups are substituted with halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, cyano groups, or combinations thereof. Groups such as chloromethyl, 2-bromoethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, cyanoethyl, 3,3,4,4,5,5,6,6, Examples include 6-nonafluorohexyl group.

  The amount of the component (e) added is preferably 0.1 to 100 parts by mass, more preferably 5 to 80 parts by mass with respect to 100 parts by mass of the component (a). When the ratio of this component increases too much, oil separation may be induced in the resulting composition.

[Other ingredients]
In addition, the composition of the present invention includes, as an optional component, an addition reaction control agent for adjusting the curing rate, a pigment / dye for coloring, a flame retardant, as long as the object and effects of the present invention are not impaired. Various for improving functions, such as a property-imparting agent, an internal release agent for improving mold release from a mold or a separator film, a viscosity of a composition, a plasticizer for adjusting the hardness of a molded product, or both. Effective amounts of these additives can be added.
In the following, an addition reaction control agent and a plasticizer are listed as examples, but the optional components used in the present invention are not limited to these.

<Addition reaction control agent>
As the addition reaction control agent, all known addition reaction control agents used in usual addition reaction curable silicone compositions can be used. Examples thereof include acetylene compounds such as 1-ethynyl-1-hexanol, 3-butyn-1-ol, ethynylmethylidenecarbinol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. The amount used is preferably about 0.01 to 1 part by mass with respect to 100 parts by mass of component (a).

<Plasticizer>
Examples of the plasticizer include dimethylpolysiloxane represented by the following general formula (4).

（式中、rは1〜200の整数である。）

(In the formula, r is an integer of 1 to 200.)

[Preparation of thermally conductive silicone composition]
The thermally conductive silicone composition of the present invention is prepared by mixing the above components (a) to (d) and, if necessary, the component (e) and other optional components with a mixing device such as a planetary mixer. Can do.

[Heat conductive silicone molding]
The thermally conductive silicone molded article of the present invention is a sheet-like thermally conductive silicone molded article made of a cured product of the thermally conductive silicone composition of the present invention. The molded product of the present invention can be produced by molding the composition of the present invention into a sheet and curing it.

The thermally conductive silicone sheet molded article of the present invention needs to be molded by adding a post-cure process at 140 to 180 ° C. after being cured in a heating process at 90 to 130 ° C.
The curing molding method in the heating step at 90 to 130 ° C. is not particularly limited, but press molding or coating molding is preferable from the viewpoint of simplicity. Since the heat-conductive silicone sheet molding after curing has adhesiveness on both sides, it is preferable to stick a cover film on both sides. For example, in the case of press molding, it is possible to obtain a sheet having a PET film as a cover film on both sides of the sheet by discharging the composition onto the PET film and further pressing the PET film from above the composition. it can. In the case of coating molding, for example, the composition is continuously discharged onto a PET film, cured through a heating oven, and then laminated with a PE film to be a cover film. The provided sheet can be molded.

The reaction of unreacted functional groups remaining in the sheet can be promoted by a post-cure process at 140 to 180 ° C., which is performed after curing in a heating process at 90 to 130 ° C. Usually, since the heat-resistant temperature required for in-vehicle use is 150 ° C., it is possible to suppress a reduction in restoration property at high temperature use by taking a post-cure process of 140 to 180 ° C. In the case of a post-cure temperature exceeding 180 ° C., the thermal degradation of the thermally conductive silicone sheet may progress and the restorability may decrease. Moreover, since a heat-resistant film will be needed as a cover film when post-curing temperature exceeds 150 degreeC, more preferable post-curing temperature is 140 to 150 degreeC. Within this temperature range, an inexpensive PET film can be used as the cover film.
The post-cure method is not particularly limited, but as an example, the sheet may be put into an oven set at a temperature of 140 ° C. to 180 ° C. for a certain period of time. At this time, if post-cure is performed by removing one surface of the cover film, the remaining volatile matter in the sheet is lost, which is more effective in improving the restoring property. In this case, the cover film is laminated again on the exposed surface of the post-cured sheet. In view of cost, the post cure time is preferably about 1 to 3 hours.

  When post-cure is performed in two stages, low-temperature post-cure and high-temperature post-cure, it is possible to suppress the generation of voids due to rapid volatilization of the volatile components contained in the sheet. In this case, the cover film on one side of the sheet is peeled off, a first post-curing step is added at a temperature of 90 to 130 ° C, and a second post-curing step of 140 to 180 ° C is further added to the exposed sheet surface. A cover film may be laminated. By performing such two-stage post-cure, post-cure can be performed with high yield.

<Hardness of molded body>
The Asker C hardness of the molded product of the present invention, that is, the hardness at 25 ° C. measured with an Asker C hardness meter in accordance with SRIS 0101 is preferably 30 or less, and more preferably 25 or less. A molded product having a hardness exceeding 30 may be deformed to conform to the shape of the heat radiating object, and it may be difficult to exhibit good heat radiation characteristics without applying stress to the heat radiating material.

<Thermal conductivity of the molded body>
The thermal conductivity of the molded article of the present invention is preferably 1.5 W / m · K or more, and more preferably 2.0 W / m · K or more. A molded body having a thermal conductivity of less than 1.5 W / m · K may not be applicable to a heating element having a large calorific value. In the present specification, the thermal conductivity of the molded article of the present invention is the thermal conductivity at 25 ° C. measured by the hot disk method in accordance with ISO 22007-2: 2008.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[Preparation of thermally conductive silicone composition]
The components (a) to (g) used in the following examples and comparative examples are shown below.
(a) Component:
(A-1) Organopolysiloxane represented by the following general formula (1a) in which n + m = 300 and m = 2 (a-2) n + m = 240 and m = 2 in the following general formula (1a ) The organopolysiloxane (a-3) represented by) is dimethylpolysiloxane having a viscosity of 600 mm ² / s at 25 ° C. sealed at both ends with dimethylvinylsilyl groups.

In the general formula (1a), n + m represents an average degree of polymerization, and m represents an average number of side chain vinyl groups. Here, regarding the above (a-1), the average number of siloxane bonds L between the silicon atoms of the non-terminal portion to which the alkenyl group is bonded was calculated as follows. First, by measuring ²⁹ Si-NMR of (a-1), a peak A derived from a silicon atom in the terminal trimethylsiloxy group was detected at around 8 ppm, and derived from a silicon atom in the dimethylsiloxane unit at around -22 ppm. Peak B was detected, and a peak C derived from a silicon atom in the methylvinylsiloxane unit was detected at around -36 ppm. When the integrated area of peak A was 2, the integrated areas of peaks B and C were 298 and 2, respectively. That is, (a-1) is the average structural formula:

It was represented by. L is the silicon of the non-terminal part to which the vinyl group is directly bonded in the average structure when the silicon atom of the non-terminal part to which the vinyl group is directly bonded is present in the molecule of (a-1). Represents the number of siloxane bonds between atoms and has the formula:
L = (298 + 2) / (2 + 1)
It was calculated as 100. The value of L was similarly calculated for the above (a-2).

(b) Component:
(B-1) Hydrogen polysiloxane represented by the following general formula (2a) where o = 18 (b-2) Hydrogen polysiloxane represented by the following general formula (2a) where o = 80 (b -3) Hydrogen polysiloxane represented by the following general formula (2a) in which o = 100 (b-4) Hydrogen polysiloxane represented by the following general formula (2a) in which o = 120 (b-5) ) Hydrogen polysiloxane represented by the following general formula (2a) where o = 250 (b-6) Me ₃ SiO (Me ₂ SiO) ₂₇ (HMeSiO) ₂ SiMe ₃

In the general formula (2a), o represents the average degree of polymerization L ′. The value of o was obtained as follows. That is, ²⁹ Si-NMR of each of (b-1) to (b-6) was measured, and a peak A ′ derived from a silicon atom in the terminal dimethylhydrogensiloxy group was detected in the vicinity of −8 ppm, and −22 ppm A peak B ′ derived from a silicon atom in the dimethylsiloxane unit was detected in the vicinity, and the integrated area of peak B ′ when the integrated area of peak A ′ was set to 2 was determined, and the value was taken as the value of o.

(c) Component:
(C-1) Amorphous aluminum hydroxide with an average particle diameter of 1 μm (c-2) Amorphous aluminum hydroxide with an average particle diameter of 10 μm (c-3) Amorphous alumina with an average particle diameter of 2 μm (c-4) Spherical alumina with diameter 10μm (c-5) Spherical alumina with average particle diameter 45μm (c-6) Spherical alumina with average particle diameter 70μm

(d) Component:
5 mass% chloroplatinic acid 2-ethylhexanol solution

(e) Component:
Dimethylpolysiloxane having one end of average polymerization degree 30 represented by the following formula (3a) blocked with a trimethoxysilyl group

(f) Component:
Ethinylmethylidenecarbinol as an addition reaction control agent

(g) component:
As a plasticizer, dimethylpolysiloxane represented by the following formula (4a)

  Components (a), (c), (e) and (g) were charged in a planetary mixer in the amounts shown in Table 1 and kneaded for 60 minutes. The components (d) and (f) were added in the amounts shown in Table 1 to the obtained kneaded product, and an effective amount of an internal additive releasing agent for promoting release from the cover film was further added, and the mixture was further kneaded for 30 minutes. Component (b) was added to the obtained kneaded material in the amount shown in Table 1, and kneaded for 30 minutes to obtain a composition.

[Molding method]
The obtained composition was poured into a 200 mm × 300 mm × 3 mm thick mold and molded and cured at 120 ° C. for 10 minutes using a press molding machine. A PI film was used as the cover film. Thereafter, the PI film on one side was peeled off, and post-curing was performed in an oven at the temperature and time shown in Table 1 below. After the post cure, a PI film was laminated on the exposed surface of the sheet, and a thermally conductive silicone sheet was provided with the PI film as a cover film on both sides.
The post cure conditions are summarized in Table 1.

[Evaluation method]
Hardness: 4 sheets of the obtained sheet-like molded product were stacked and measured with an Asker C hardness meter.
-Thermal conductivity: Using the obtained sheet-like molded product as a sample, the thermal conductivity of the molded product was measured with a thermal conductivity meter (TPA-501 (trade name), manufactured by Kyoto Electronics Industry Co., Ltd.). .
・ Restoration rate: A 20 mm square test piece was punched from the obtained sheet-like molded product, compressed in the thickness direction by 50% (up to 1.5 mm), and aged in a 150 ° C. oven for 50 hours and 500 hours while being compressed. did. Thereafter, the test piece was released from compression, and the thickness of the test piece after 60 minutes was measured.
The results of the above evaluation are shown in Table 1.
-Void: The surface state of the obtained sheet-like molded product was observed, and the presence or absence of a void was confirmed.
The results of the above evaluation are shown in Table 1.

[Evaluation]
When Examples 1-6 were compared with Comparative Examples 1-3, it became clear that long-term restoring property will become favorable by giving a 140-180 degreeC postcure. Further, as in Comparative Example 3, under conditions where the post-cure temperature exceeded 180 ° C., it was confirmed that there was a decrease in resilience due to thermal deterioration and the generation of voids.
As in Comparative Examples 4 and 5, long-term recovery was significantly reduced when outside the range satisfying L ′ / L = 0.6 to 3.0. In view of the result of Comparative Example 6, the side chain is more than the sheet-like molded product using a combination of dimethylpolysiloxane blocked at both ends with vinyl groups and hydrogen polysiloxane having Si-H groups in the side chains. It was clarified that a sheet-like molded article using a combination of dimethylpolysiloxane having a vinyl group and hydrogenpolysiloxane having both ends blocked with hydrogen atoms exhibits better restoring properties.

Claims (6)

(a) Organopolysiloxane containing at least an alkenyl group bonded to a silicon atom in a non-terminal part and having 2 to 9 alkenyl groups bonded to a silicon atom in a non-terminal part: 100 parts by mass
(b) Organohydrogenpolysiloxane having at least both ends blocked with hydrogen atoms bonded to silicon atoms: The number of moles of hydrogen atoms bonded to silicon atoms in this component is 1.0 mol of alkenyl groups in component (a). In an amount of 0.1 to 1.5 mol,
(c) Thermally conductive filler: 500-4000 parts by weight, and
(d) Platinum group metal-based curing catalyst: 0.1 to 1000 ppm in terms of mass of platinum group metal element with respect to component (a)
Comprising
In the organopolysiloxane of component (a), the average number of siloxane bonds between the silicon atoms of the non-terminal portion to which the alkenyl group is bonded is L,
When the average degree of polymerization of the organohydrogenpolysiloxane of component (b) is L ′, a thermally conductive silicone composition satisfying L ′ / L = 0.6 to 3.0 was cured in a heating process at 90 to 130 ° C. Then, a heat-conductive silicone sheet formed by adding a post-cure process at 140 to 180 ° C.   The thermally conductive silicone composition according to claim 1, further comprising (e) dimethylpolysiloxane having one end blocked with a trialkoxysilyl group: 0.1 to 100 parts by mass.   The thermally conductive silicone sheet according to claim 1 or 2, which has an Asker C hardness of 5 to 30. The heat conductive filler (c) contains the following amount with respect to 100 parts by mass of the component (a), and the heat conductivity exceeds 1.5 W / m · K. The heat conductive silicone sheet which concerns on a term.
(C-1) 300-1500 parts by mass of amorphous alumina with a center particle size of 0.5-5um
(C-2) 300-1500 parts by mass of spherical alumina with a center particle size of 7-25um
(C-3) 300-1500 parts by mass of spherical alumina with a center particle size of 30-50um
(C-4) 300-1500 parts by mass of spherical alumina with a central particle size of 60-90um (a) Organopolysiloxane containing at least an alkenyl group bonded to a silicon atom in a non-terminal part and having 2 to 9 alkenyl groups bonded to a silicon atom in a non-terminal part: 100 parts by mass
(b) Organohydrogenpolysiloxane having at least both ends blocked with hydrogen atoms bonded to silicon atoms: The number of moles of hydrogen atoms bonded to silicon atoms in this component is 1.0 mol of alkenyl groups in component (a). In an amount of 0.1 to 1.5 mol,
(c) Thermally conductive filler: 500-4000 parts by weight, and
(d) Platinum group metal-based curing catalyst: 0.1 to 1000 ppm in terms of mass of platinum group metal element with respect to component (a)
Comprising
In the organopolysiloxane of component (a), the average number of siloxane bonds between the silicon atoms of the non-terminal portion to which the alkenyl group is bonded is L,
When the average degree of polymerization of the organohydrogenpolysiloxane of component (b) is L ′, a thermally conductive silicone composition satisfying L ′ / L = 0.6 to 3.0 was cured in a heating process at 90 to 130 ° C. Thereafter, a post-cure process at 140 to 180 ° C. is further added to form the heat conductive silicone sheet.   After curing, the cover film on one side of the sheet produced by coating or press molding is peeled off at a temperature of 90 to 130 ° C so that both sides of the sheet are finally protected by the cover film, The manufacturing method of the heat conductive silicone sheet | seat of Claim 5 which laminates | stacks a cover film on the exposed sheet | seat surface after adding one post-cure process and adding the 2nd post-cure process of 140-180 degreeC further.