JP2017208458A - Thermally conductive composite sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally conductive composite sheet which reduces the temperature of a heat source effectively, does not exfoliate even if placed vertically but can keep adhesion state, and is very effective for reducing the temperature of an electrical heating element.SOLUTION: A thermally conductive composite sheet has a thermally conductive adhesive layer having a thickness of 100 μm or less, a thermal resistance of 1.2 cm-K/W or less, and an adhesive strength of 8 N/cmor more, on one side of a heat conduction layer having an in-plane heat conductivity of 200 W/mK or more, and has a heat radiation layer having a thickness of 10-100 μm and an emittance of 0.80 or more on another side.SELECTED DRAWING: None

Description

  The present invention relates to a heat conductive composite sheet suitable for mounting on an electronic device in which a cooling member such as a heat sink cannot be used.

  Electronic devices such as televisions, computers, communication devices, and industrial devices are becoming smaller, thinner, and higher in performance, and the amount of heat generated by chips such as CPUs and driver ICs mounted on these devices is increasing. Chip temperature rise causes chip malfunction and destruction. 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, 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 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.

  However, as described above, there are increasing cases in which a heat sink cannot be mounted due to downsizing, thinning, and high performance of devices. For example, you cannot use a heat sink due to size or weight problems, such as smartphones and digital video cameras that are supposed to be carried, LED lighting that is installed on the ceiling, or LED lighting that is supposed to be suspended from the ceiling, There is a need to lose. For this reason, some heat dissipation countermeasure parts using thermal radiation have been reported.

  A method of dissipating heat from the heating element as radiant heat by molding ceramic materials obtained by firing cordierite particles with high infrared radiation rate and using it for substrates or replacing heat sinks has been proposed. (Patent Document 1: Japanese Patent Laid-Open No. 2006-298703). However, this has a problem that the ceramic material cannot be attached when the rigidity of the ceramic material is high and molding is difficult, or when the surface of the heat-generating component to be attached is curved rather than flat.

  In addition, it is called thermal radiation paint, and a composition containing particles with high thermal emissivity in a curable resin diluted with an appropriate organic solvent is applied to or sprayed on a heating element and dried and cured. In addition, a technique has been proposed in which a heat radiation layer is directly laminated on a heating element to dissipate heat from the heating element to the outside of the system (Patent Documents 2 and 3: JP 2004-43612 A and JP 2013-144747 A). Issue gazette). However, for coating or spraying on the heating element, it is necessary to introduce equipment for that purpose, it is difficult to manage the coating amount and spraying amount, and a process for curing the paint is required. There was a drawback that the process was complicated.

  Further, there has been proposed a heat radiation sheet in which a heat radiation film is formed on one surface of a metal thin plate and an adhesive layer is bonded to the other surface of the metal thin plate (Patent Document 4: Japanese Patent Application Laid-Open No. 2004-200199). However, according to the embodiment, the thickness of the adhesive layer is as large as about 180 μm, which hinders the flow of heat.

  Further, there has been proposed a heat conductive composite sheet having a heat radiation layer on one side of a metal thin plate and a heat conductive silicone layer having a thickness of 0.2 mm or more laminated on the other side (Patent Document 5: Japanese Patent Laid-Open No. 2015). -119173). However, this method is not a good idea when the thermal conductivity is important.

JP 2006-298703 A JP 2004-43612 A JP 2013-144747 A JP 2004-200199 A JP2015-119173A

  The present invention has been made in view of the above circumstances, and can effectively reduce the temperature of the heat source, and can maintain a close contact state without being peeled even when placed vertically, and is extremely useful for reducing the temperature of the heating element. It is an object of the present invention to provide a heat conductive composite sheet that is effective for the above.

As a result of intensive studies to achieve the above object, the inventors of the present invention have a thickness of 100 μm or less and a thermal resistance of 1.2 cm ^{2 on} one side of the heat conduction layer having an in-plane heat conductivity of 200 W / mK or more. −K / W or less and a heat conductive adhesive layer having an adhesive strength of 8 N / cm ² or more are laminated, and the other surface has a thickness of 10 μm or more and 100 μm or less and an emissivity of 0.80 or more. It has been found that the heat conductive composite sheet laminated with the heat radiation layer can effectively reduce the temperature of the heat source and can maintain a close contact state without being peeled even when placed vertically. It was.

Accordingly, the present invention provides a thermally conductive composite sheet.
[1]
On one side of the thermal conductive layer having an in-plane thermal conductivity of 200 W / mK or more, a thickness of 100 μm or less, a thermal resistance of 1.2 cm ² -K / W or less, and an adhesive force of 8 N / cm ² or more. The heat conductive composite sheet which has the heat conductive adhesive layer which is these, and also has the heat radiation layer whose thickness is 10 micrometers or more and 100 micrometers or less, and whose emissivity is 0.80 or more on the other surface.
[2]
The heat conductive composite sheet according to [1], wherein the heat conductivity of the heat conductive adhesive layer is 0.5 W / mK or more.
[3]
Thermally conductive adhesive layer
(A) Organopolysiloxane having an alkenyl group: 100 parts by mass,
(B) Thermally conductive filler: 300 to 900 parts by mass,
(C) Organohydrogenpolysiloxane: an amount of 0.5 to 3 in terms of a molar ratio of hydrogen atoms directly bonded to silicon atoms of component (c) to alkenyl groups of component (a),
(D) platinum group metal catalyst: 0.1 to 1,000 ppm of component (a) in terms of platinum element mass,
(F) Silicone resin: The thermally conductive composite sheet according to [1] or [2], comprising a cured product of a thermally conductive silicone composition containing 50 to 300 parts by mass as an essential component.
[4]
The heat conductive composite sheet according to [3], wherein the heat conductive filler is alumina.
[5]
The heat conductive composite sheet according to [3] or [4], wherein the heat conductive filler has an average particle size of 0.5 to 10 μm and coarse particles of 30 μm or more are 1% by mass or less.

As described above, on one side of the thermal conductive layer having an in-plane thermal conductivity of 200 W / mK or more, a thickness of 100 μm or less, a thermal resistance of 1.2 cm ² −K / W or less, and 8 N Heat conduction adhesive layer having an adhesive force of / cm ² or more is laminated, and heat radiation layer having a thickness of 10 μm to 100 μm and an emissivity of 0.80 or more is laminated on the other surface. The composite sheet effectively reduces the temperature of the heat source, and can maintain a close contact state without being peeled even when placed vertically, so there are many places where it can be used, which is extremely useful for reducing the temperature of the heating element. It is effective for.

Hereinafter, the present invention will be described in detail.
The heat conductive composite sheet of the present invention has a thickness of 100 μm or less and a thermal resistance of 1.2 cm ² −K / W or less on one side of a heat conductive layer having an in-plane heat conductivity of 200 W / mK or more. In addition, a heat conductive adhesive layer having an adhesive strength of 8 N / cm ² or more is laminated, and a heat radiation layer having a thickness of 10 μm to 100 μm and an emissivity of 0.80 or more is laminated on the other surface. It has been made.

《Heat conduction layer》
In the thermally conductive composite sheet of the present invention, the thermal conductive layer has an in-plane thermal conductivity of 200 W / mK or more, and a thermal conductive adhesive layer, which will be described later, is laminated on one side, and on the other side. A heat radiation layer to be described later is laminated.

[In-plane thermal conductivity of thermal conductive layer]
The thermal conductivity in the surface direction of the heat conductive layer is 200 W / mK or more, preferably 230 W / mK or more, more preferably 280 W / mK or more, and 2,000 W / mK or less. Is preferred. This is because if the thermal conductivity in the surface direction of the thermal conductive layer is low, the thermal diffusibility of the thermal conductive composite sheet of the present invention cannot be obtained sufficiently. The amount of heat dissipated when considering heat dissipation measures using thermal radiation depends on the area and thermal emissivity. Therefore, it is advantageous to increase the area of the heat conductive composite sheet within a range where there is no problem in mounting. At this time, heat from the heating element can be efficiently radiated by the heat conduction layer quickly diffusing. Without the heat conductive layer, the heat from the heating element is difficult to diffuse, so the advantage of increasing the area of the heat conductive composite sheet cannot be fully utilized. In the present invention, the thermal conductivity in the surface direction of the thermal conductive layer can be measured by measuring the thermal diffusivity with a thermowave analyzer and calculating the thermal conductivity from the thermal diffusivity.

[Material of heat conduction layer]
As a heat conductive layer, a graphite sheet, aluminum foil, copper foil, etc. are mentioned, for example. The graphite sheet is very excellent in in-plane heat conduction, but is weak against bending and pulling and has poor workability. Further, there is a risk of dropping off the graphite powder, and the cost is high. Aluminum foil and copper foil are suitable because they are lower in cost and higher in strength than graphite sheets.

[The thickness of the heat conduction layer]
The thickness of the heat conductive layer is preferably 10 to 100 μm. More preferably, it is 20-100 micrometers, More preferably, it is 20-80 micrometers. If the thickness of the heat conductive layer is too thin, the heat conductive composite sheet may have poor rigidity and may be difficult to handle. On the other hand, if it exceeds 100 μm, the flexibility as the heat conductive composite sheet is impaired, and there is a possibility that it becomes unsuitable when mounting is considered.

《Thermal radiation layer》
In the heat conductive composite sheet of the present invention, the heat radiation layer is laminated on the surface opposite to the surface on which the heat conductive adhesive layer described later of the heat conductive layer described above is laminated, and has a thickness of 10 μm or more and 100 μm or less. The emissivity is 0.80 or more.

[Thermal emissivity of the thermal radiation layer]
The thermal emissivity of the thermal radiation layer is 0.80 or more, preferably 0.83 to 0.99. When it is less than 0.80, a sufficient heat dissipation effect cannot be obtained.
In the present invention, the emissivity is a value measured using a thermal emissivity meter (manufactured by A & D).

[Thickness of heat radiation layer]
The thickness of the heat radiation layer is not less than 10 μm and not more than 100 μm, preferably 20 to 80 μm. If the thickness is less than 10 μm, the thickness of the heat radiation layer is too thin to sufficiently exhibit the heat radiation performance, and if it exceeds 100 μm, the efficiency of heat transfer inside the heat conductive composite sheet is deteriorated.

[Material of heat radiation layer]
The thermal radiation layer is an organic resin layer containing ceramic powder such as silica, alumina, titanium oxide, boron nitride, and aluminum nitride, cordierite powder, particles having high thermal emissivity such as graphite, or a combination of two or more kinds. Although it is preferable to have sufficient flexibility, it is not particularly limited as long as the thermal emissivity can be secured to 0.80 or more when particles having high thermal emissivity are dispersed in the organic resin. Examples of the organic resin include, but are not limited to, an acrylic resin, a silicone resin, an epoxy resin, and a urethane resin.

  In addition, as a thermal radiation layer, what is marketed can be used, for example, shellac alpha (Ceramission Co., Ltd., thermal emissivity 0.96), Percool (Pernox Co., Ltd., powder) Containing acrylic resin).

<Heat conductive adhesive layer>
In the heat conductive composite sheet of the present invention, the heat conductive adhesive layer is stacked on one side of the heat conductive layer described above (the surface opposite to the surface on which the heat radiation layer is stacked), and has a thickness of 100 μm or less. The thermal resistance is 1.2 cm ² -K / W or less, and the adhesive strength is 8 N / cm ² or more.

[Thermal resistance of heat conductive adhesive layer]
The heat resistance of the heat conductive adhesive layer is 1.2 cm ² -K / W or less, preferably 1.0 cm ² -K / W. If it exceeds 1.2 cm ² -K / W, heat from the heating element cannot be efficiently transferred. Although a minimum in particular is not restrict | limited, Usually, it is 0.4 cm < ² > -K / W or more. This thermal resistance can be obtained by reducing the thickness of the heat conductive adhesive layer and increasing the filling amount of the heat conductive filler.
In the present invention, the thermal resistance is a value measured using a laser flash method with a heat conductive adhesive layer sandwiched between aluminum plates.

[Adhesive strength of heat conductive adhesive layer]
Adhesion of the thermally conductive adhesive layer is 8N / cm ² or more, preferably 10 N / cm ² or more. If the adhesive force is less than 8 N / cm ² , the sheet will be peeled off when the application location is vertical. This adhesive force can be obtained by increasing the thickness of the heat conductive adhesive layer and reducing the filling amount of the heat conductive filler.
In the present invention, the adhesive force was measured by using a bond tester (manufactured by Nordson) after sandwiching a thermally conductive adhesive layer of 10 mm × 10 mm size between two aluminum plates and pressing for 1 kg for 1 minute. It is stress.

[Thermal conductivity of heat conductive adhesive layer]
The thermal conductivity of the thermally conductive adhesive layer is preferably 0.5 W / mK or more, more preferably 0.6 W / mK or more. If it is less than 0.5 W / mK, the desired thermal resistance may not be obtained. The upper limit is not particularly limited, but is usually 2 W / mK or less. This heat conductivity can be obtained by blending a predetermined amount of heat conductive filler in the heat conductive silicone composition used for the heat conductive adhesive layer.
In the present invention, the thermal conductivity is a value measured using a thermal conductivity meter (TPA-501, trade name, manufactured by Kyoto Electronics Industry Co., Ltd.).

[Thickness of heat conductive adhesive layer]
The thickness of the heat conductive adhesive layer is 100 μm or less, preferably 60 μm or less. When it exceeds 100 μm, the heat conductive adhesive layer becomes thick, and the flow of heat from the heating element is hindered. Although a minimum in particular is not restrict | limited, It is preferable that it is 20 micrometers or more.

[Material of heat conductive adhesive layer]
As the thermally conductive adhesive layer, a layer formed by filling an organic resin polymer matrix with a thermally conductive filler can be used. The organic resin polymer matrix is not particularly limited, and examples thereof include acrylic, silicone, epoxy, and urethane. Silicone is preferable in view of heat resistance and hardness resistance.

In the present invention, the thermally conductive adhesive layer is
(A) an organopolysiloxane having an alkenyl group,
(B) a thermally conductive filler,
(C) organohydrogenpolysiloxane,
(D) a platinum group metal catalyst,
(F) What consists of hardened | cured material of the heat conductive silicone composition which used silicone resin as an essential component is preferable.
Below, each component is explained in full detail.

<(A) Organopolysiloxane>
The alkenyl group-containing organopolysiloxane which is component (a) of the thermally conductive silicone composition is the main component (base polymer) of the thermally conductive silicone composition, and has two alkenyl groups bonded to silicon atoms in one molecule. As described above, an organopolysiloxane having 2 to 5 is preferable. Usually, the main chain portion is basically composed of repeating diorganosiloxane units, and this organopolysiloxane may contain a branched structure as part of the molecular structure. Moreover, although it may be a cyclic body, linear diorganopolysiloxane is preferable 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 that does not contain an aliphatic unsaturated bond. 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, cyclodecyl group such as cyclopentyl group, cyclohexyl group, cycloheptyl group, etc. Aryl group such as alkyl group, phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group, aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group, and carbon atoms of these groups are bonded. Some or all of the hydrogen atoms are halogen atoms such as fluorine, chlorine, bromine, etc. Groups substituted with a cyano group, 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, typical ones having 1 to 10 carbon atoms, particularly typical ones having 1 to 6 carbon atoms. Preferably, it is unsubstituted or substituted with 1 to 3 carbon atoms such as methyl group, ethyl group, propyl group, chloromethyl group, bromoethyl group, 3,3,3-trifluoropropyl group, cyanoethyl group, etc. And an unsubstituted or substituted phenyl group such as a phenyl group, a chlorophenyl group, and 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. A lower alkenyl group such as an allyl group, particularly preferably a vinyl group. This alkenyl group may be bonded to a silicon atom at the end of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain, or may be bonded to both.

Kinematic viscosity at 25 ° C. This organopolysiloxane is generally preferably in the range of 10~100,000mm ² / s, more preferably in the range of 500~50,000mm ² / s. When the kinematic viscosity is too low, the storage stability of the resulting composition may be deteriorated, and when it is too high, the extensibility of the obtained composition may be deteriorated. In the present invention, the kinematic viscosity is measured by an Ostwald viscometer.

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

<(B) Thermally conductive filler>
Examples of the thermally conductive filler that is the component (b) of the thermally conductive silicone composition include nonmagnetic metals such as copper and aluminum, metals such as alumina, silica, magnesia, bengara, beryllia, titania, zirconia, and zinc oxide. A material generally used as a thermally conductive filler such as oxide, aluminum nitride, silicon nitride, metal nitride such as boron nitride, metal hydroxide such as magnesium hydroxide, artificial diamond, or silicon carbide can be used. You may use a heat conductive filler individually by 1 type or in combination of 2 or more types. Considering the use in particular, metal oxide, aluminum nitride, boron nitride and the like are preferable because the heat conductive silicone adhesive tape needs insulation. More preferred is alumina.

Moreover, as a heat conductive filler, the thing whose average particle diameter is 0.5-10 micrometers and whose coarse particle of 30 micrometers or more is 1 mass% or less is preferable. More preferably, the average particle size is 0.5 to 5 μm, and the coarse particles of 30 μm or more are 0.5% by mass or less. When the average particle size is larger than 10 μm, or the coarse particles of 30 μm or more exceed 1% by mass, the surface smoothness of the heat conductive adhesive layer may be impaired, and the thermal resistance may be deteriorated.
In the present invention, the average particle diameter is a volume-based measurement value by a Microtrac particle size distribution measuring device MT3300EX (Nikkiso Co., Ltd.). Moreover, the measurement of the coarse particle | grains 30 micrometers or more is measured from the mass which remained on the sieve when the water slurry of a heat conductive filler is prepared and passed through a sieve with a mesh size of 30 micrometers.

  As a filling amount of a heat conductive filler, it is preferable that it is 300-900 mass parts with respect to 100 mass parts of (a) component, More preferably, it is 300-700 mass parts. If it is less than 300 parts by mass, sufficient thermal conductivity may not be obtained, and if it exceeds 900 parts by mass, a desired shear stress may not be obtained.

<(C) Organohydrogenpolysiloxane>
The organohydrogenpolysiloxane which is the component (c) of the thermally conductive silicone composition is a crosslinking agent for the thermally conductive silicone composition, and includes three hydrogen atoms (SiH groups) bonded to silicon atoms in one molecule. In particular, 3 to 10 are provided. This SiH group may be bonded to a silicon atom at the end of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain, or may be bonded to both.

  Examples of the organic group other than the hydrogen atom bonded to the silicon atom include those similar to the unsubstituted or substituted monovalent hydrocarbon group not containing the aliphatic unsaturated bond exemplified in the component (a). Among these, a methyl group, an ethyl group, and a phenyl group are preferable.

  The degree of polymerization of the organohydrogenpolysiloxane is preferably 10-50, and more preferably 10-30. When the degree of polymerization is within this range, a high adhesive force can be obtained. In the present invention, this degree of polymerization can be measured as a weight average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC) analysis.

  Preferable specific examples of the organohydrogenpolysiloxane include methylhydrogenpolysiloxane having both molecular chain ends blocked with trimethylsiloxy groups, and dimethylsiloxane / methylhydrogen having both molecular chain ends blocked with trimethylsiloxy groups. Siloxane copolymer, dimethylsiloxane / methylhydrogensiloxane / methylphenylsiloxane copolymer blocked at both molecular chain ends with trimethylsiloxy groups, dimethylpolysiloxane blocked at both molecular chain ends with dimethylhydrogensiloxy groups, Dimethylsiloxane / methylhydrogensiloxane copolymer with both ends of the molecular chain blocked with dimethylhydrogensiloxy groups, dimethylsiloxane / methyl with both ends of the molecular chain blocked with dimethylhydrogensiloxy groups E vinylsiloxane copolymer, both molecular chain terminals with dimethylhydrogensiloxy methylphenyl polysiloxane blocked with group. The (c) component organohydrogenpolysiloxane may be used alone or in combination of two or more.

  Component (c) is added in an amount such that the SiH group in component (c) is 0.5 to 3 moles, preferably 0.8 to 3 moles per mole of alkenyl group in component (a). This is the amount to make a mole. When the amount of SiH groups in the component (c) is less than 0.5 mol relative to 1 mol of the alkenyl groups in the component (a), the composition does not cure or the molded product has insufficient strength. Problems such as inability to handle as a complex may occur. On the other hand, when the amount exceeding 3 moles is used, there is a risk that the tackiness of the surface of the cured product will be insufficient.

<(D) Platinum group metal-based catalyst>
The platinum group metal catalyst that is the component (d) of the thermally conductive silicone composition promotes the addition reaction between the alkenyl group in the component (a) and the hydrogen atom bonded to the silicon atom in the component (c), It is a component blended for converting a heat conductive silicone composition into a crosslinked cured product having a three-dimensional network structure.

The component (d) can be appropriately selected from known catalysts used in ordinary hydrosilylation reactions. 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. , KHPtCl 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 (wherein n is an integer of 0 to 6, preferably 0 or 6.), etc.), such as platinum chloride, chloroplatinic acid and chloroplatinate, alcohol-modified chloroplatinic acid, chloroplatinic acid and olefin complex, platinum black , Platinum group metals such as palladium supported on alumina, silica, carbon, etc., rhodium-olefin complex, chlorotris (triphenylphosphine) rhodium (Wilkin) Son catalyst), platinum chloride, chloroplatinic acid, or a complex of chloroplatinate and a vinyl group-containing siloxane. These platinum group metal catalysts may be used singly or in combination of two or more.

  (D) The compounding quantity of a component should just be an effective quantity required in order to harden a heat conductive silicone composition, and is not restrict | limited in particular. Usually, it is 0.1 to 1,000 ppm, preferably 0.5 to 500 ppm in terms of mass of the platinum group metal element with respect to the component (a).

<(E) Reaction control agent>
A reaction control agent can be mix | blended with a heat conductive silicone composition as (e) component. The reaction control agent is for adjusting the rate of the hydrosilylation reaction that is an addition reaction of the component (a) and the component (c) that proceeds in the presence of the component (d). Such a reaction control agent of the component (e) can be appropriately selected from known addition reaction inhibitors used in ordinary addition reaction curable silicone compositions.
Specific examples thereof include acetylene compounds such as 1-ethynyl-1-cyclohexanol, 3-butyn-1-ol, ethynylmethylidenecarbinol, nitrogen compounds, organic phosphorus compounds, sulfur compounds, oxime compounds, organic chloro compounds, and the like. Is mentioned. These addition reaction inhibitors can be used singly or in combination of two or more.

  Since the blending amount of the component (e) varies depending on the amount of the component (d) used, it cannot be determined unconditionally. Any effective amount that can adjust the progress of the hydrosilylation reaction to a desired reaction rate is sufficient. (E) When mix | blending a component, it is good normally to set it as about 10-50,000 ppm with respect to the mass of (a) component. If the amount of component (e) is too small, the storage stability of the thermally conductive silicone composition may be insufficient, and sufficient usable time may not be ensured. The curability of the silicone composition may be reduced.

<(F) Silicone resin>
The silicone resin that is the component (f) of the thermally conductive silicone composition has an action of imparting tackiness to the cured product surface obtained by curing the thermally conductive silicone composition.
An example of such a component (f) is a copolymer of R ¹ ₃ SiO _1/2 units (M units) and SiO _4/2 units (Q units), wherein the ratio of M units to Q units ( Molar ratio) M / Q is 0.5 to 1.5, preferably 0.6 to 1.4, more preferably 0.7 to 1.3. A desired adhesive strength can be obtained when the M / Q is in the range of 0.5 to 1.5.

R ¹ in the general formula representing the M unit is an unsubstituted or substituted monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond. Examples of such R ¹ include, 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, alkyl group such as dodecyl group, cyclopentyl group, cyclohexyl group, cycloalkyl group such as cycloheptyl group, phenyl group, tolyl group, xylyl group, naphthyl group, aryl group such as biphenylyl group, benzyl group, Aralkyl groups such as phenylethyl group, phenylpropyl group and methylbenzyl group, and part or all of hydrogen atoms bonded to carbon atoms of these groups are halogen atoms such as fluorine, chlorine and bromine, cyano groups, etc. A group substituted with, for example, a chloromethyl group, a 2-bromoethyl group, a 3-chloropropyl group, , 3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, etc., having 1 carbon atom To 10 or preferably 1 to 6 carbon atoms.

In the present invention, among these, an unsubstituted or substituted group 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, a cyanoethyl group, etc. A substituted alkyl group and an unsubstituted or substituted phenyl group such as a phenyl group, a chlorophenyl group and a fluorophenyl group are preferred. R ¹ may all be the same or different. Unless special characteristics such as solvent resistance are required, R ¹ is preferably all methyl groups from the viewpoints of cost, availability, chemical stability, environmental burden, and the like.

  The component (f) itself is a solid or viscous liquid at room temperature (25 ° C.), but it can also be used in a state dissolved in a solvent such as toluene or xylene. In that case, the amount added to the composition is determined by the amount excluding the solvent.

The silicone resin preferably has a kinematic viscosity at 25 ° C. in 70 wt% toluene solution is 5 to 100 mm ² / s, particularly 5 to 35 mm ² / s, especially 5 to 20 mm ² / s. If the kinematic viscosity is too higher than the above range, it may be necessary to add toluene during molding. If it is too low, it may be difficult to mold during molding. The viscosity can be measured with a cup viscometer.

  (F) It is preferable that the compounding quantity of a component is 50-300 mass parts with respect to 100 mass parts of (a) component, More preferably, it is 100-200 mass parts. If the amount is too small or too large, sufficient adhesive strength may not be obtained.

<(G) Surface treatment agent>
In the thermally conductive silicone composition, as a surface treatment agent (g) for improving wettability and adhesion to the thermally conductive layer, an organoxysilane compound such as alkoxysilane, or a molecular chain fragment. Hydrolyzable group-containing organosilicon compounds such as linear diorganopolysiloxanes whose ends are blocked with triorganoxysilyl groups such as trialkoxysilyl groups are used in an amount of 1 to 40 masses per 100 mass parts of component (a). Can be blended in part.

  Moreover, you may add additives, such as another heat resistance imparting agent and a flame retardance imparting agent, to the heat conductive silicone composition as long as the object of the present invention is not impaired.

Although a heat conductive silicone composition can be prepared using kneading apparatuses, such as a planetary mixer and a kneader, it is not specifically limited.
In addition, the curing conditions of the thermally conductive silicone composition for use as the thermally conductive adhesive layer are not particularly limited, but 80 to 150 ° C., particularly 100 to 150 ° C., particularly 110 to 130 ° C. for 3 to 15 minutes, In particular, it is preferably 3 to 10 minutes.

<< Method for Producing Thermal Conductive Composite Sheet >>
The heat conductive composite sheet of this invention is obtained by laminating | stacking a heat conductive adhesion layer with respect to the laminated body of a heat conductive layer and a heat radiation layer. A method of laminating the heat radiation layer on the heat conductive layer includes a coating method and a spray method, but is not limited to this method. Moreover, the method of laminating | stacking a heat conductive adhesion layer includes the bonding method, the coating method, and the press method, However, It is not limited to these.

  The heat conductive composite sheet of the present invention is effective for reducing the temperature of the heating element, and is suitably used for portable electronic terminals such as smartphones and digital video cameras, LED lighting, motors, converters, and the like.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1-7, Comparative Examples 1-5]
The manufacturing method of the heat conductive composite sheet of an Example and a comparative example is described below.
(Thermal conduction layer)
Aluminum foil: 50 μm thick, thermal conductivity in the plane direction 236 W / mK
Aluminum foil: 20 μm thickness, thermal conductivity in the plane direction 236 W / mK
Copper foil: 30 μm thick, thermal conductivity in the plane direction 398 W / mK

(Laminate of heat conduction layer and heat radiation layer)
A-1: Thermal radiation sheet array in which shellac α (thermal radiation layer; thermal emissivity: 0.96, manufactured by Ceramission Co., Ltd.) is laminated on a 50 μm aluminum foil (thermal conductive layer) with a thickness of 50 μm 2: Thermal radiation sheet A-3 in which shellac α (thermal radiation layer; thermal emissivity: 0.96, manufactured by Ceramission Co., Ltd.) was laminated on a 30 μm copper foil (thermal conductive layer) with a thickness of 30 μm: Thermal radiation sheet in which Pelcourt (thermal radiation layer; thermal emissivity: 0.86, manufactured by Pernox Co., Ltd.) is laminated on a 20 μm aluminum foil (thermal conductive layer) with a thickness of 30 μm. A-1 to A-3, which are laminates of a heat conductive layer and a heat radiation layer, use a comma coater for the paint (shellac α or percool) on the aluminum foil or copper foil that is the heat conductive layer. Coating to the above thickness, and 8 It was obtained by heat curing at 0 ° C./10 minutes and then at 120 ° C./10 minutes.

(Thermal conductive adhesive layer)
A-1 to A-6: Thermally conductive adhesive layer comprising a cured product of a thermally conductive silicone composition comprising the components shown in Table 1 below. For comparison, the following thermal resistance and adhesive force deviate from the present invention. The heat conductive adhesive layer of was used.
A-7: TC-50CAT-20 (thermal resistance 1.7 cm ² -K / W, adhesive strength 2 N / cm ² )
B-8: TC-50CAS-10 (thermal resistance 4.2 cm ² -K / W, adhesive strength 3 N / cm ² )
In addition, a thermal resistance and adhesive force are the values measured by the method mentioned later.

（ｍは２５℃における動粘度が３０，０００ｍｍ²／ｓとなる数） Each component used for the said heat conductive silicone composition is shown below.
(A) Component:
Organopolysiloxane represented by the following formula (1) and having a kinematic viscosity of 30,000 mm ² / s at 25 ° C., wherein X is a vinyl group

(M is the number at which the kinematic viscosity at 25 ° C. is 30,000 mm ² / s)

(B) Component:
(B-1) Component:
Aluminum oxide powder (b-2) component having an average particle diameter of 1 μm and 0.5% by mass of coarse particles of 30 μm or more:
Zinc oxide powder with an average particle size of 0.6 μm and coarse particles of 30 μm or more of 0.1% by mass

（平均重合度：ｏ＝１６．８、ｐ＝６．３） (C) Component:
The average degree of polymerization represented by the following formula (2) is as follows, and the methyl hydrogen polysiloxane whose side chain is blocked with a hydrogen atom:

(Average polymerization degree: o = 16.8, p = 6.3)

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

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

(F) Component:
Substantially a toluene solution of a silicone resin (M unit / Q unit molar ratio: 1.15) composed of (CH ₃ ) ₃ SiO _0.5 unit (M unit) and SiO ₂ unit (Q unit) (non-volatile content: 70 mass) %; Kinematic viscosity at 25 ° C. 30 mm ² / s)

(G) Component:
Dimethylpolysiloxane in which one end of average polymerization degree 30 represented by the following formula (3) is blocked with a trimethoxysilyl group

(H) Component:
2-ethylhexyl acrylate

(I) Component:
Acrylic acid

(J) Component:
Hexanediol acrylic acid

[Method for Preparing Thermally Conductive Silicone Composition]
The heat conductive silicone composition was prepared by mixing the above components in the blending amounts shown in Table 1 at 25 ° C. for 60 minutes using a planetary mixer.

[Method for producing thermally conductive adhesive layer]
The heat conductive silicone composition obtained above is coated on a fluorine-treated PET film using a comma coater and heated at 80 ° C. for 3 minutes and then at 120 ° C. for 5 minutes, as shown in Table 1. A heat conductive adhesive layer having a thickness was obtained.

[Evaluation of heat conductive adhesive layer]
The thermal resistance, adhesive strength and thermal conductivity of the thermally conductive adhesive layer were evaluated by the methods shown below. The results are shown in Table 1.
·Thermal resistance:
The 12.7 mmφ × 1 mm thick aluminum plate was sandwiched between the 12.7 mmφ × thick thermal conductive adhesive layer described in Table 1 and a pressure of 137.9 kPa (20 psi) was applied. After leaving at room temperature (25 ° C.) for 60 minutes, the thermal resistance of the thermal conductive adhesive layer was measured with a thermal resistance measuring instrument (trade name Flash Analyzer, manufactured by NETZSCH) based on a laser flash method.
・ Adhesive strength (shear stress):
10 mm × 10 mm obtained by curing the thermally conductive silicone composition at 120 ° C. for 10 minutes, each of the samples having the thickness shown in Table 1 between two aluminum plates of 10 mm × 10 mm × 1 mm thickness A 1 kg load was applied at room temperature (25 ° C.), and after 1 minute, the shear stress was measured with a bond tester (trade name: 4000 Plus, manufactured by Nordson).
·Thermal conductivity:
Measured by hot disk method. That is, the above heat conductive silicone composition was cured into a sheet of 60 mm × 60 mm × 6 mm thickness at 120 ° C. for 10 minutes, and a thermal conductivity meter (TPA-501, Kyoto Electronics Industry) was used using the two sheets. The thermal conductivity of the sheet was measured according to the product name of the product.

[Method for producing thermally conductive composite sheet]
As shown in Tables 2 and 3 below, the thermally conductive adhesive layer is laminated on the thermally conductive layer side of the laminate of the thermally conductive layer and the thermally radiant layer, and is allowed to stand at room temperature (25 ° C.) for 5 minutes. Lamination was performed using a laminator apparatus at a pressure of 5 MPa to obtain a heat conductive composite sheet. About the obtained heat conductive composite sheet, the thermal radiation test and the vertical placement test were done by the evaluation method shown below. The results are also shown in Tables 2 and 3.

[Evaluation method]
-Thermal radiation test A 400 mm load is applied to a 15 mm x 15 mm surface of a 15 mm x 15 mm x 100 mm heat source, and the center of the heat source composite sheet overlaps the center of the 100 mm x 100 mm heat conductive composite sheet. Pasted like so. A power of 4 W was applied to the heat source, and the temperature of the heat source after 2 hours was measured. The measurement environment was 25 ° C. and humidity 50%.

-Vertical placement test A heat conductive composite sheet of 200 mm x 300 mm is attached to an aluminum plate sufficiently larger than this by reciprocating a 1 kg rubber roller once to make a vertical placement. After 10 days, if the heat conductive composite sheet was not peeled off, it was accepted.

As shown in Table 2, on one side of the thermal conductive layer having an in-plane thermal conductivity of 200 W / mK or more, a thickness of 100 μm or less, a thermal resistance of 1.2 cm ² −K / W or less, and 8 N A heat conductive adhesive layer having an adhesive force (shear stress) of / cm ² or more is laminated, and a heat radiation layer having a thickness of 10 μm to 100 μm and an emissivity of 0.80 or more is laminated on the other surface. The heat conductive composite sheets of Examples 1 to 7 can effectively reduce the temperature of the heat source, and can maintain a close contact state without being peeled even when placed vertically.
As shown in Table 3, the heat conductive composite sheets of Comparative Examples 1, 2, and 3 have excellent adhesive strength of the heat conductive adhesive layer, so there is no fear of peeling even when placed vertically. Since the thermal resistance of the layer is high, the temperature reduction effect is small. In addition, since the heat conductive composite sheets of Comparative Examples 4 and 5 use a heat conductive adhesive layer having a low adhesive force, the heat conductive composite sheet does not maintain an adhesive state with the aluminum plate when placed vertically. The sheet peels off.

Claims (5)

On one side of the thermal conductive layer having an in-plane thermal conductivity of 200 W / mK or more, a thickness of 100 μm or less, a thermal resistance of 1.2 cm ² -K / W or less, and an adhesive force of 8 N / cm ² or more. The heat conductive composite sheet which has the heat conductive adhesive layer which is these, and also has the heat radiation layer whose thickness is 10 micrometers or more and 100 micrometers or less, and whose emissivity is 0.80 or more on the other surface.   The heat conductive composite sheet according to claim 1, wherein the heat conductivity of the heat conductive adhesive layer is 0.5 W / mK or more. Thermally conductive adhesive layer
(A) Organopolysiloxane having an alkenyl group: 100 parts by mass,
(B) Thermally conductive filler: 300 to 900 parts by mass,
(C) Organohydrogenpolysiloxane: an amount of 0.5 to 3 in terms of a molar ratio of hydrogen atoms directly bonded to silicon atoms of component (c) to alkenyl groups of component (a),
(D) platinum group metal catalyst: 0.1 to 1,000 ppm of component (a) in terms of platinum element mass,
(F) Silicone resin: It consists of the hardened | cured material of the heat conductive silicone composition which used 50-300 mass parts as an essential component, The heat conductive composite sheet of Claim 1 or 2 characterized by the above-mentioned.   The heat conductive composite sheet according to claim 3, wherein the heat conductive filler is alumina.   The heat conductive composite sheet according to claim 3 or 4, wherein the average particle diameter of the heat conductive filler is 0.5 to 10 µm, and the coarse particles of 30 µm or more are 1 mass% or less.