Thermal conductive composite silica rubber sheet

Abstract

The present invention is a thermally conductive composite silicone rubber sheet characterized by comprising: a thermally conductive silicone rubber sheet; and a heat-softening silica resin layer which is disposed on one surface or both surfaces of the heat-conducting silica rubber sheet, has a thickness of 0.5-10 [mu] m, and has an absolute viscosity at 70 DEG C of 10-700 Pa * s. The heat-softening silica resin layer contains: (A) 75-95% by mass of a heat-softening silica resin in which the ratio of phenyl groups to the number of all substituents directly bonded to silicon atoms is 20 mol% or more; and (B) 5-25 mass% of a diphenylsiloxy group-containing organopolysiloxane represented by formula (1) (in formula (1), m is an integer of 3-5, and n is an integer of 5-12). As a result, it is possible to provide a thermally conductive composite silicone rubber sheet which is capable of suppressing oil bleeding and which exhibits adhesiveness by instantaneous contact. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a thermally conductive composite silicone rubber sheet which is disposed between a heat generating component and a heat dissipating component in an electronic device, for example, and is used for heat dissipation. Background Art

[0002] Conventionally, in electronic devices and the like, in order to suppress the temperature rise of a semiconductor during operation, a heatsink using a metal plate having a relatively high thermal conductivity such as aluminum and copper has been used. It is known that electrical insulation must be provided between the semiconductor and the heatsink, and by using a thermally conductive silicone rubber sheet obtained by filling a polymer such as polysiloxane with a thermally conductive filler and imparting thermal conductivity, both insulation and thermal conductivity can be achieved.

[0003] Moreover, when a thermally conductive silicone rubber sheet is installed between a heat generating body such as a semiconductor and a cooling plate such as a heatsink, a thermally conductive silicone rubber sheet is fixed using, for example, screws or spring clip members. However, due to problems in the installation steps, at least one surface of the thermally conductive silicone rubber sheet requires adhesiveness. This is because it is necessary to align the installation location of the thermally conductive silicone rubber sheet during installation. If there is no adhesive layer, it may deviate from the desired installation location during fixation. In addition, sometimes due to the installation steps, the thermally conductive silicone rubber sheet must be attached vertically.

[0004] Coating an adhesive layer on a thermally conductive silicone rubber sheet is a known technique, and by coating the adhesive layer, countermeasures in the installation steps are sought (Patent Documents 1, 2, and 3). However, the thickness of the adhesive layer coated on the thermally conductive silicone rubber sheet so far is about 10 to 50 μm, and since the thickness of the adhesive layer is relatively thick, the thermal conductivity is significantly deteriorated. If the thickness of the adhesive layer is made thinner in order to improve the thermal conductivity, the thermal conductivity will indeed be improved, but the adhesive force will decrease. In addition, although there is also an idea of imparting thermal conductivity to the adhesive layer itself, in order to impart thermal conductivity to the adhesive layer, it is necessary to add a thermally conductive filler, which also causes a decrease in the adhesive force. Therefore, in order to ensure the adhesive force, it is possible to consider making the thickness of the adhesive layer relatively thick, but if the thickness of the adhesive layer is made thick, the thermal conductivity will be sacrificed. In this way, the adhesive force and the thermal conductivity are in a trade-off relationship, and there has long been a need for a method of imparting adhesive force in a manner that sacrifices as little thermal conductivity as possible.

[0005] Patent Document 4 proposes a thermally conductive composite silicone rubber sheet which achieves both adhesive force, heat dissipation performance, and its long-term reliability by providing a thermally softening silicone resin layer having a thickness of 0.5 to 10 μm. However, in order to sufficiently adhere the thermally conductive silicone rubber sheet and prevent peeling or falling off from the adherend, a step of crimping for several seconds to several tens of seconds during attachment is indispensable. In order to shorten these steps during the assembly operation, it is indispensable to improve the adhesive force, which is generally expressed as the adhesiveness manifested by instantaneous contact. Prior art documents Patent documents

[0006] Patent document 1: Japanese Patent Application Laid-Open No. 2014-193598 Patent document 2: Japanese Patent Application Laid-Open No. 2018-193491 Patent document 3: International Publication No. 2018 / 070351 Patent document 4: Japanese Patent Application Laid-Open No. 2020-203457 Summary of the invention

Problems to be solved by the invention

[0007] The present invention has been completed in view of such circumstances, and an object thereof is to provide a thermally conductive composite silicone rubber sheet in which a thermally softening silicone resin layer is provided on one or both surfaces of a thermally conductive silicone rubber sheet, and the thermally conductive composite silicone rubber sheet can suppress oil bleeding and exhibit adhesiveness by instantaneous contact.

Means for solving the problems

[0008] In order to solve the above problems, the present invention provides a thermally conductive composite silicone rubber sheet, characterized by having: a thermally conductive silicone rubber sheet; and a thermally softening silicone resin layer disposed on one or both surfaces of the thermally conductive silicone rubber sheet, having a thickness of 0.5 to 10 μm and an absolute viscosity of 10 to 700 Pa·s at 70°C; The thermally softening silicone resin layer contains: (A) 75 to 95% by mass of a thermally softening silicone resin, in which the proportion of phenyl groups relative to the total number of all substituents directly bonded to silicon atoms is 20 mol% or more; and (B) 5 to 25% by mass of an organopolysiloxane containing a diphenylsiloxy group represented by the following formula (1), In formula (1), m is an integer of 3 to 5, and n is an integer of 5 to 12.

[0009] In the case of a thermally conductive composite silicone rubber sheet having such a thermally softening silicone resin layer, the compatibility between the silicone rubber component of the thermally conductive silicone rubber sheet and the resin component ((A) component) of the thermally softening silicone resin layer is not too high, so that a decrease in the adhesive force during storage due to the dispersion of the resin component of the thermally softening silicone resin layer in the thermally conductive silicone rubber sheet can be suppressed. Thus, adhesiveness can be exhibited by instantaneous contact. Further, the organopolysiloxane containing a diphenylsiloxy group as the component (B) can be appropriately retained in the resin layer, suppressing oil bleeding to the outside.

[0010] Furthermore, preferably, the component (A) is a heat-softenable silicone resin represented by the following formula (2) or (3): D p T φ q D Vi r (2) wherein D represents a dimethylsiloxane unit (CH3)2SiO 2 / 2 , T φ represents a phenylsiloxane unit (C6H5)SiO 3 / 2 , D Vi represents a methylvinylsiloxane unit (CH3)(CH2=CH)SiO 2 / 2 , and p, q, and r satisfy (p + r) / q (molar ratio) = 0.25 to 4.0 and (p + r) / r (molar ratio) = 1.0 to 4.0; M L D p T φ q D Vi r (3) wherein M represents a trimethylsiloxane unit (CH3)3SiO 1 / 2 , D, T φ and D Vi As described above, p, q, r, and L satisfy (p + r) / q (molar ratio) = 0.25 to 4.0, (p + r) / r (molar ratio) = 1.0 to 4.0, and L / (p + r) (molar ratio) = 0.001 to 0.1.

[0011] If the heat-softenable silicone resin of the component (A) is the above heat-softenable silicone resin, more excellent adhesiveness can be exhibited by instant contact.

[0012] Preferably, the adhesive force of the heat-softenable silicone resin layer measured by the probe tack test described in ASTM D2979 is 2.0 N / cm 2 or more.

[0013] If the adhesive force is 2.0 N / cm 2 or more, it can be fixed to the adherend without applying pressure again.

[0014] Furthermore, preferably, the silicone rubber component of the thermally conductive silicone rubber sheet contains a dimethylsiloxane unit.

[0015] Thus, preferably, the thermally conductive silicone rubber sheet: its silicone rubber component contains a dimethylsiloxane unit, that is, its silicone rubber component is dimethyl silicone rubber. If it is such a thermally conductive silicone rubber sheet, diffusion of the diphenylsiloxy group-containing organopolysiloxane as the component (B) of the thermoplastic silicone resin layer can be suppressed.

[0016] Furthermore, preferably, the thermally conductive silicone rubber sheet contains a glass cloth and / or a plastic film.

[0017] If it contains a glass cloth, the strength is excellent. Furthermore, if it contains a plastic film, the electrical insulation is excellent.

[0018] At this time, preferably, the A-type hardness of the thermally conductive silicone rubber sheet measured by the method described in JIS K6253:2012 is 50 to 100.

[0019] If it is within this range, change in the thickness or cracking of the thermally conductive silicone rubber sheet can be suppressed, and stable insulation can be maintained.

Effects of the Invention

[0020] As described above, if it is the thermally conductive composite silicone rubber sheet of the present invention, oil bleeding can be suppressed, and adhesiveness is exhibited by instant contact. For example, when it is installed at the interface between a heating element and a cooling member, it can adhere to an adherend only by contact, so the process time can be shortened, and the production efficiency can be significantly improved. Detailed Description of the Invention

[0021] As described above, there is a demand for developing a thermally conductive composite silicone rubber sheet formed by providing an adhesive layer on one or both sides of a thermally conductive silicone rubber sheet, which can suppress oil bleeding and exhibit adhesiveness by instant contact.

[0022] The present inventors repeatedly and intensively studied the above problems, and as a result, found a thermally conductive composite silicone rubber sheet formed by disposing a thermoplastic silicone resin layer on one or both sides of a thermally conductive silicone rubber sheet. The thermoplastic silicone resin layer contains: (A) 75 to 95% by mass of a thermoplastic silicone resin, in which the proportion of phenyl groups relative to the total number of all substituents directly bonded to silicon atoms is 20 mol% or more; and (B) 5 to 25% by mass of a diphenylsiloxy group-containing organopolysiloxane represented by the above formula (1); the thickness of the thermoplastic silicone resin layer is 0.5 to 10 μm, and the absolute viscosity at 70°C is 10 to 700 Pa·s; if it is such a thermally conductive composite silicone rubber sheet, oil bleeding can be suppressed, and adhesiveness is exhibited by instant contact, thereby completing the present invention.

[0023] That is, the present invention is a thermally conductive composite silicone rubber sheet, characterized by having: a thermally conductive silicone rubber sheet; and A thermoplastic silicone resin layer, which is disposed on one or both sides of the thermally conductive silicone rubber sheet, has a thickness of 0.5 to 10 μm, and an absolute viscosity at 70 °C of 10 to 700 Pa·s; The thermoplastic silicone resin layer contains: (A) 75 to 95% by mass of a thermoplastic silicone resin, in which the proportion of phenyl groups relative to the total number of all substituents directly bonded to silicon atoms is 20 mol% or more; and, (B) 5 to 25% by mass of an organopolysiloxane containing a diphenylsiloxy group represented by the following formula (1), In formula (1), m is an integer from 3 to 5, and n is an integer from 5 to 12.

[0024] In the case of the thermally conductive composite silicone rubber sheet of the present invention, the compatibility between the silicone rubber component of the thermally conductive silicone rubber sheet and the resin component ((A) component) of the thermoplastic silicone resin layer is not too high. Therefore, it is possible to suppress the decrease in adhesion during storage caused by the dispersion of the resin component of the thermoplastic silicone resin layer in the thermally conductive silicone rubber sheet. Thus, the adhesiveness can be exhibited by instant contact. Further, the organopolysiloxane containing a diphenylsiloxy group as component (B) can be appropriately retained in the resin layer, suppressing oil bleeding to the outside.

[0025] Hereinafter, the present invention will be described in detail, but the present invention is not limited to these descriptions.

[0026] [Thermally Conductive Silicone Rubber Sheet] The thermally conductive silicone rubber sheet of the thermally conductive composite silicone rubber sheet of the present invention is obtained, for example, by molding a thermally conductive silicone rubber composition into a sheet by any method and curing it. The thermally conductive silicone rubber composition is obtained by adding a thermally conductive filler, a curing agent, etc. to a silicone polymer and kneading them. However, the thermally conductive silicone rubber sheet of the thermally conductive composite silicone rubber sheet of the present invention is not particularly limited as long as it is a thermally conductive silicone rubber sheet.

[0027] Preferably, the kneading is carried out by a kneading method having a shearing force such as a planetary mixer, a kneader, a two-roll mill, etc., and there is no particular limitation. Examples of the method of molding the thermally conductive silicone rubber composition into a sheet include calendering, coating, extrusion molding, etc.; there is no particular limitation.

[0028] The cured form of the thermally conductive silicone rubber composition is not particularly limited, and examples thereof include: addition-cured silicone rubber obtained by a hydrosilylation reaction, peroxide-cured silicone rubber obtained by a peroxide catalyst, condensation-cured silicone rubber obtained by a condensation reaction of silanols, etc. Among them, from the aspect of the time required for curing, addition-cured silicone rubber or peroxide-cured silicone rubber is preferred.

[0029] In addition, the silicone polymer can be arbitrarily selected according to the physical properties of the desired cured product, etc. It is preferably a dimethylsiloxane polymer in which all substituents other than reactive points such as alkenyl, silanyl, and hydroxyl groups in the substituents directly bonded to silicon atoms of the silicone polymer are methyl groups. That is, preferably, the silicone rubber component of the thermally conductive silicone rubber sheet contains dimethylsiloxane units. If it is such a silicone polymer, the diffusion of the diphenylsiloxy group-containing organopolysiloxane contained in the following thermally softenable silicone resin layer can be suppressed, so it is preferred.

[0030] The thermal conductivity of the thermally conductive silicone rubber sheet is preferably 0.8 W / mK or more, more preferably 1.2 W / mK or more. If the thermal conductivity is 0.8 W / mK or more, the heat of the heating element can be sufficiently transferred to the cooling part. There is no specific upper limit for the thermal conductivity. If it can be formed into a sheet, those with higher thermal conductivity can transfer the heat from the heating element to the cooling part more efficiently, so it is preferred.

[0031] The thickness of the thermally conductive silicone rubber sheet is preferably 0.08 mm or more and 1.2 mm or less. If it is 0.08 mm or more, sufficient insulation can be ensured. In addition, if it is 1.2 mm or less, insulation can be ensured, and the heat from the heating element can be sufficiently transferred to the cooling part.

[0032] The thermally conductive silicone rubber sheet may contain a glass cloth and / or a plastic film. Examples include: containing a glass cloth for reinforcement effect, or containing a plastic film for insulation effect, etc. For example, the thermally conductive silicone rubber sheet can be made to include two silicone rubber layers and an intermediate layer between these silicone rubber layers, and the above materials can be contained as this intermediate layer.

[0033] If it contains a glass cloth, the strength is excellent. In addition, if it contains a plastic film, the electrical insulation is excellent.

[0034] Preferably, the hardness of the thermally conductive silicone rubber sheet containing a glass cloth and / or a plastic film is such that the type A hardness measured by the method described in Japanese Industrial Standard (JIS) K6253:2012 is 50 or more and 100 or less. If the type A hardness is 50 or more, it is possible to suppress the destabilization of insulation caused by a change in thickness due to the fixing pressure of a screw or a clip during the installation of the thermally conductive composite silicone rubber sheet. In addition, if the type A hardness is 100 or less, it is possible to suppress the breakage of the sheet due to bending or flexing.

[0035] Various products of thermally conductive silicone rubber sheets are already on the market, and examples include: TC-20CG (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-30BG (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-15TAP-2 (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-20TAG-8 (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-20TA-1 (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-20TAG-2 (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-20TAP-2 (manufactured by Shin-Etsu Chemical Co., Ltd.), etc. These products are only examples and are not limited to these products.

[0036] [Thermally softening silicone resin layer] The thermally softening silicone resin layer contains a thermally softening silicone resin ((A) component). Thermally softening means that it is solid at room temperature (25°C), but it becomes fluid when heated. That is, when the thermally conductive composite silicone rubber sheet obtained by laminating the thermally softening silicone resin layer as an adhesive layer on the thermally conductive silicone rubber sheet is installed at the interface between a heating element and a cooling member, for example, due to the heat from the heating element, the thermally softening silicone resin layer softens and becomes fluid, thereby improving the contact state with the adherend and increasing the thermal conductivity.

[0037] More specifically, the thermally softening silicone resin layer contains the following (A) component and (B) component: (A) 75 to 95% by mass of a thermally softening silicone resin, the ratio of phenyl groups to the total number of all substituents directly bonded to silicon atoms (hereinafter sometimes referred to as the phenyl modification rate) being 20 mol% or more; and, (B) 5 to 25% by mass of an organopolysiloxane containing a diphenylsiloxy group represented by the following formula (1), In formula (1), m is an integer from 3 to 5, and n is an integer from 5 to 12. In addition, the absolute viscosity of the thermally softening silicone resin layer at 70°C is 10 to 700 Pa·s.

[0038] (A) The phenyl modification rate of the component is 20 mol% or more, preferably 30 to 70 mol%. When the phenyl modification rate is 20 mol% or more, the compatibility between the thermally conductive silicone rubber component mainly composed of dimethylsiloxane units and the resin component of the thermally softening silicone resin layer will not become too high, and the diffusion of the resin component of the thermally softening silicone resin layer into the thermally conductive silicone rubber sheet can be suppressed.

[0039] As the thermally softening silicone resin of the (A) component, preferably, it is a silicone polymer having a bifunctional structural unit (D unit) and a trifunctional structural unit (T unit) represented by the following formula (2) or (3), and a monofunctional structural unit (M unit) with a specific composition.

[0040] D p T φ q D Vi r (2) Wherein, D represents a dimethylsiloxane unit (i.e., (CH3)2SiO 2 / 2 ), T φ represents a phenylsiloxane unit (i.e., (C6H5)SiO 3 / 2 ), D Vi represents a methylvinylsiloxane unit (i.e., (CH3)(CH2=CH)SiO 2 / 2 ), and p, q, and r satisfy (p + r) / q (molar ratio) = 0.25 to 4.0 and (p + r) / r (molar ratio) = 1.0 to 4.0.

[0041] M L D p T φ q D Vi r (3) Wherein, M represents a trimethylsiloxane unit (i.e., (CH3)3SiO 1 / 2 ), D, T φ and D Vi As described above, p, q, r, and L satisfy (p + r) / q (molar ratio) = 0.25 to 4.0, (p + r) / r (molar ratio) = 1.0 to 4.0, and L / (p + r) (molar ratio) = 0.001 to 0.1.

[0042] In addition, as the thermally softening silicone resin, one kind can be used alone, or two or more kinds can be mixed.

[0043] The thermally softening silicone resin layer contains an organopolysiloxane containing a diphenylsiloxy group represented by the following formula (1) as the (B) component.

[0044] In the formula (1), m is an integer of 3 to 5, preferably an integer of 4 to 5. n is an integer of 5 to 12, preferably an integer of 6 to 12. Furthermore, m + n is preferably in the range of 8 to 17, more preferably in the range of 10 to 15.

[0045] This diphenylsiloxy group-containing organopolysiloxane can be incorporated into the soft silicone resin layer without oil bleeding, and can maintain the adhesion of the soft silicone resin layer for a long time.

[0046] The content of the (B) diphenylsiloxy group-containing organopolysiloxane in the thermoplastic silicone resin layer is 5% by mass or more and 25% by mass or less, preferably 10% by mass or more and 20% by mass or less of the whole thermoplastic silicone resin layer. When the content of the diphenylsiloxy group-containing organopolysiloxane is less than 5% by mass, sufficient adhesion is difficult to obtain. When it is more than 25% by mass, oil bleeding may occur from the thermoplastic silicone resin layer.

[0047] The absolute viscosity of the thermoplastic silicone resin layer at 70 °C is 10 Pa·s or more and 700 Pa·s or less. When the absolute viscosity of the thermoplastic silicone resin layer at 70 °C is higher than 700 Pa·s, it is difficult to sufficiently fill the gap with the adherend. When it is lower than 10 Pa·s, the fluidity is too high, and thus there is a possibility of flowing out, etc.

[0048] The absolute viscosity can be measured using a HAAKE RotoVisco 1 (trade name, RotoVisco) rotational viscometer. Specifically, the silicone resin of the sample can be sandwiched between a lower planar circular plate (diameter 20 mm) and an upper conical circular plate (diameter 20 mm, cone angle 2 degrees, stem 0.1 mm) that are respectively horizontally arranged on the upper and lower sides of a vertical central axis, and the planar circular plate is fixed, and the conical circular plate is rotated around it at a rotational speed of 10 s －1 to perform the measurement.

[0049] The thickness of the thermoplastic silicone resin layer is 0.5 to 10 μm. Preferably it is 1 to 5 μm. If it is thinner than 0.5 μm, it cannot follow the unevenness of the adherend surface and sufficient adhesion cannot be obtained. In addition, if it is thicker than 10 μm, the thermal resistance of the thermally conductive composite silicone rubber sheet will increase.

[0050] The adhesion of the soft silicone rubber resin layer of the thermally conductive composite silicone rubber sheet is preferably 2.0 N / cm 2 or more, more preferably 2.5 N / cm 2 or more, further preferably 3.0 N / cm 2 or more. If the adhesion is 2.0 N / cm2 Above, sufficient adhesive force can be obtained when contacting the adherend, and position deviation or dropping can be prevented. The upper limit of the adhesive force is not particularly limited. For example, it can be set to 30 N / cm 2 or less.

[0051] Furthermore, the adhesive force can be measured by the probe tack test method according to ASTM D2979. This method can make a stainless steel (SUS) probe contact the soft silicone rubber resin layer of the fixed thermally conductive composite silicone rubber sheet, and measure the adhesive force according to the maximum load required to peel it off. [Examples]

[0052] Hereinafter, the present invention will be specifically described using examples and comparative examples, but the present invention is not limited to these examples.

[0053] [Thermally Conductive Silicone Rubber Sheet] Regarding the thermally conductive silicone rubber sheet, any one of the following 1 or 2 was used. 1. Glass cloth-reinforced thermally conductive silicone rubber sheet made of dimethyl silicone rubber (trade name: TC-20TAG-2, manufactured by Shin-Etsu Chemical Co., Ltd., thickness 0.2 mm, thermal conductivity 2.0 W / mK, Shore A hardness 88, peroxide curing) 2. Glass cloth-reinforced thermally conductive silicone rubber sheet made of dimethyl silicone rubber (trade name: TC-20TAG-3, manufactured by Shin-Etsu Chemical Co., Ltd., thickness 0.2 mm, thermal conductivity 3.0 W / mK, Shore A hardness 88, peroxide curing)

[0054] [Thermally Softenable Silicone Resin Layer] 85% xylene solution of (Component A) in the following formula (4) was added with (Component B-1) in the following formula (5) or (Component B-2) in the following formula (6) and fed into a planetary mixer, and stirred at room temperature for 30 minutes to obtain a thermally softenable silicone resin composition. This composition was coated on one side of the thermally conductive silicone rubber sheet using a comma coater, and the xylene was removed by drying at 80°C for 10 minutes to form a thermally softenable silicone resin layer. The ratios of (Component A) to (Component B-1) or (Component B-2) in the thermally softenable silicone resin layer in each example and each comparative example are shown in Table 1 and Table 2.

[0055] (Component A) Thermally Softenable Silicone Resin D 25 T Φ 55D Vi 20 (4) (Absolute viscosity at 70 °C: 20 Pa·s)

[0056] (Component B-1) Organopolysiloxane containing diphenylsiloxy group (phenyl content: 25 mol%)

[0057] (Component B-2) Dimethylpolysiloxane

[0058] [Examples 1 - 9] In Examples 1 - 9, a thermoplastic silicone resin layer with the content (proportion) of (Component B-1) in the thermoplastic silicone resin layer varied between 5 - 25 mass% was formed on one side of the thermally conductive silicone rubber sheet 1 or 2, and the thermally conductive composite silicone rubber sheets of Examples 1 - 9 were obtained. Table 1 shows the proportions of (Component A) and (Component B-1) in the thermoplastic silicone resin layer of each of Examples 1 - 9, and the thickness of the thermoplastic silicone resin layer.

[0059] [Comparative Examples 1 - 5] In Comparative Examples 1 and 2, a thermoplastic silicone resin layer containing neither (Component B-1) nor (Component B-2) was formed on one side of the thermally conductive silicone rubber sheet 1 or 2, and the thermally conductive composite silicone rubber sheets of Comparative Examples 1 and 2 were obtained.

[0060] In addition, in Comparative Examples 3 and 4, a thermoplastic silicone resin layer with the content of (Component B-1) in the thermoplastic silicone resin layer set to 30 mass% was formed on one side of the thermally conductive silicone rubber sheet 1 or 2, and the thermally conductive composite silicone rubber sheets of Comparative Examples 3 and 4 were obtained.

[0061] Furthermore, in Comparative Example 5, (Component B-1) was not added to the thermoplastic silicone resin, and 10 mass% of (Component B-2) was added instead to form the thermoplastic silicone resin layer, and the thermally conductive composite silicone rubber sheet of Comparative Example 5 was obtained.

[0062] Table 2 shows the proportions of (Component A), (Component B-1) and (Component B-2) in the thermoplastic silicone resin layer of each of Comparative Examples 1 - 5, and the thickness of the thermoplastic silicone resin layer.

[0063] [Evaluation Method] [Thermal Resistance Measurement] Using a TIM-Tester (trade name, manufactured by Analysistech) in accordance with ASTM D 6470, at a measurement temperature of 50 °C and 0.69 N / mm 2The thermal conductivity of the silicone rubber sheets of Examples 1 to 9 and Comparative Examples 1 to 5 obtained in the above manner was measured under pressure.

[0064] [Adhesion measurement] Using a TACKINESS TESTER TK-1 (trade name, manufactured by malcom Co., Ltd.) based on ASTM D 2979, the adhesion of the thermally softened silicone resin layer of the thermally conductive composite silicone rubber sheets prepared in Examples 1 to 9 and Comparative Examples 1 to 5 was measured at a measurement temperature of 25°C.

[0065] [Confirmation of oil bleeding] A 100-μm polyethylene film was attached to the thermally softened silicone resin layer of the thermally conductive composite silicone rubber sheets prepared in Examples 1 to 9 and Comparative Examples 1 to 5 as a protective film, and left standing at 25°C for 24 hours. Then, the protective film was peeled off, and it was visually confirmed whether there was any oil component attached to the protective film side.

[0066] [Absolute viscosity of thermally softened silicone resin layer] An HAAKE RotoVisco 1 (trade name, RotoVisco) rotational viscometer was used to measure the absolute viscosity of the thermally softened silicone resin layer of the thermally conductive composite silicone rubber sheets prepared in Examples 1 to 9 and Comparative Examples 1 to 5.

[0067] These measurement results are shown in Tables 1 and 2.

[0068] [Table 1]

[0069] [Table 2]

[0070] As shown in Comparative Examples 1 and 2, when the organopolysiloxane containing diphenylsiloxy group was not added, the adhesion was 2.0 N / cm 2 or less. On the other hand, as shown in Comparative Examples 3 and 4, when the organopolysiloxane containing diphenylsiloxy group in the thermally softened silicone resin layer was more than 25% by mass, although the adhesion was high, oil bleeding occurred from the organopolysiloxane containing diphenylsiloxy group in the resin layer and adhered to the protective film. The exuded oil may cause contamination of electronic devices or contact failures. In addition, as shown in Comparative Example 5, when dimethylpolysiloxane was added to the thermally softened silicone resin layer with a phenyl modification rate of 20 mol% or more, the compatibility was poor, and even when the addition amount was 10% by mass, oil adhesion to the protective film was still observed.

[0071] On the other hand, the thermally conductive composite silicone rubber sheets of Examples 1 to 9 exhibited an adhesion of 2.0 N / cm 2 or more, and no oil adhesion to the protective film was observed.

[0072] As described above, by providing a specific thermoplastic silicone resin layer with a thickness of 0.5 to 10 μm on one or both sides of the thermally conductive silicone rubber sheet, a thermally conductive composite silicone rubber sheet capable of suppressing oil bleeding and having excellent adhesion can be obtained. The thermoplastic silicone resin layer contains a thermoplastic silicone resin in which the proportion of phenyl groups relative to the total number of all substituents directly bonded to silicon atoms is 20 mol% or more at a proportion of 75 to 95% by mass, and contains an organopolysiloxane containing diphenylsiloxy groups at a proportion of 5 to 25% by mass.

[0073] In addition, it can be seen that the thermally conductive composite silicone rubber sheets of Examples 1 to 9 have a thermal resistance of 2.0 cm 2 ·K / W or less, and therefore, by being disposed between the heating element and the cooling part, the heat of the heating element can be sufficiently transferred to the cooling part.

[0074] Furthermore, the present invention is not limited to the above-described embodiments. The above-described embodiments are examples, and any configuration that has substantially the same technical idea as that described in the claims of the present invention and exhibits the same effects is included in the technical scope of the present invention.

Claims

1. A thermally conductive composite silicone rubber sheet, characterized in that, Comprising: A heat-conductive silicone rubber sheet; and A heat-softening silicone resin layer disposed on one or both sides of the heat-conductive silicone rubber sheet, having a thickness of 0.5 to 10 μm and an absolute viscosity at 70°C of 10 to 700 Pa·s; The heat-softening silicone resin layer contains: (A) 75 to 95% by mass of a heat-softening silicone resin, in which the proportion of phenyl groups relative to the total number of all substituents directly bonded to silicon atoms is 20 mol% or more; and (B) 5 to 25% by mass of an organopolysiloxane containing a diphenylsiloxy group represented by the following formula (1), In formula (1), m is an integer from 3 to 5, and n is an integer from 5 to 12.

2. The thermally conductive composite silicone rubber sheet according to claim 1, wherein Component (A) is a heat-softening silicone resin represented by the following formula (2) or (3): D p T φ q D Vi r (2) wherein, D represents a dimethylsiloxane unit (CH3)2SiO 2 / 2 , T φ represents a phenylsiloxane unit (C6H5)SiO 3 / 2 , D Vi represents a methylvinylsiloxane unit (CH3)(CH2=CH)SiO 2 / 2 , p, q and r satisfy (p+r) / q (molar ratio) = 0.25 to 4.0, and (p+r) / r (molar ratio) = 1.0 to 4.0; M L D p T φ q D Vi r (3) Among them, M represents a trimethylsiloxane unit (CH3)3SiO 1 / 2 , D, T φ and D Vi As described above, p, q, r and L satisfy (p + r) / q (molar ratio) = 0.25 to 4.0, (p + r) / r (molar ratio) = 1.0 to 4.0, and L / (p + r) (molar ratio) = 0.001 to 0.

1.

3. The thermally conductive composite silicone rubber sheet according to claim 1, characterized in that, The adhesive force of the thermoplastic silicone resin layer measured by the probe tack test described in ASTM D2979 is 2.0 N / cm 2 or more.

4. The thermally conductive composite silicone rubber sheet according to claim 1, wherein The silicone rubber component of the heat-conductive silicone rubber sheet contains dimethylsiloxane units.

5. The thermally conductive composite silicone rubber sheet according to claim 1, characterized in that, The heat-conductive silicone rubber sheet contains a glass cloth and / or a plastic film.

6. The heat-conductive composite silicone rubber sheet according to claim 5, wherein, The A-type hardness of the heat-conductive silicone rubber sheet measured by the method described in JIS K6253:2012 is 50 to 100.

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