Thermosoftening thermally conductive composition

Abstract

Provided is a thermosoftening thermally conductive composition having excellent pump-out resistance, heat resistance, and flame retardancy.　The present invention provides a thermosoftening thermally conductive composition containing the following components (A), (B), and (C). (A) a phenyl-modified silicone resin that contains R1SiO3 / 2 units (in the formula, R1 is a group selected from an alkyl group having 1-10 carbon atoms and a phenyl group) and R2 2SiO2 / 2 units (in the formula, R2 is a group selected from an alkyl group having 1-10 carbon atoms, an alkenyl group having 2-10 carbon atoms, and a phenyl group), and that has a phenyl modification rate of 30-60 mol%; (B) a linear aryl-modified organopolysiloxane that has one or more aryl groups having 6-10 carbon atoms in one molecule, and that has an aryl modification rate of 20-60 mol%; and (C) a thermally conductive filler that has a thermal conductivity of 10 W / (m•K) or greater, and that has an average particle diameter of 0.3-20 μm

Description

Heat-softening thermally conductive composition

[0001] The present invention relates to a heat-softenable thermally conductive composition.

[0002] In recent years, numerous thermosoftening materials have been disclosed that possess the advantages of both thermally conductive sheets and thermally conductive greases. These materials are non-fluid at room temperature but soften or melt when heated, becoming fluid. However, thermosoftening materials with organic base oils (Patent Documents 1 to 4) have poor heat resistance, raising concerns about deterioration at high temperatures when used in automotive applications. To improve heat resistance, numerous silicone-based thermosoftening materials have also been disclosed (e.g., Patent Documents 5 and 6), including sheet-formed products and paste-like thermally conductive materials (using a curing reaction). However, when rapidly applying a thermally conductive material over a large area, sheet-formed products can have the problem of air bubbles forming between the contact surfaces. Furthermore, when using a thermally conductive material on electronic components, applying the thermally conductive material by screen printing or other methods is the fastest and most efficient method. However, when using screen-printed sheets, the curing reaction proceeds from the surface of the sheet during the drying process after application, which can result in solvent remaining within the sheet. In response to this, a paste-like heat-softenable composition suitable for application by screen printing, etc. has been disclosed (Patent Document 7). However, because this composition uses a modified silicone wax, it has the drawback of being inferior in fluidity, flame retardancy, and heat resistance to unmodified silicone, and its pump-out resistance at high temperatures is insufficient.

[0003] Japanese Patent Application Laid-Open No. 2021-106283 International Publication No. 2016 / 185936 International Publication No. 2015 / 035575 Japanese Patent Application Laid-Open No. 2021-80316 Japanese Patent Application Laid-Open No. 2016-76678 Japanese Patent Application Laid-Open No. 2021-147591 Japanese Patent Application Laid-Open No. 2017-061613

[0004] Therefore, an object of the present invention is to provide a heat-softenable thermally conductive composition that is used as a thermally conductive material to be interposed at the thermal boundary between a heat-generating electronic component and a heat-dissipating component such as a heat sink or metal housing for cooling the electronic component, that is in a paste form with excellent fluidity and can be applied by screen printing or the like, that reduces in viscosity, softens, or melts at temperatures within the operating temperature range of the electronic component, so that the thermally conductive material (coating) adheres closely to the thermal boundary, and that has better pump-out resistance than conventional products.

[0005] As a result of intensive research aimed at solving the above-mentioned problems, the inventors discovered that a heat-softening thermally conductive composition capable of reducing thermal resistance can be obtained by blending a heat-softening phenyl-modified silicone resin with a linear aryl-modified organopolysiloxane and a thermally conductive filler, leading to the completion of the present invention. Furthermore, a heat-softening thermally conductive composition containing a specific amount of isoparaffin with a boiling point of 80 to 360°C, which is capable of dissolving or dispersing the following components (A) and (B), is in a paste form when applied, allowing for easy and rapid screen printing, thereby facilitating efficient operation. Furthermore, the inventors discovered that the composition, upon volatilization of the solvent contained therein, becomes a thermally conductive coating that is non-fluid at room temperature, resulting in improved pump-out resistance and reliability compared to conventional thermal greases, leading to the completion of the present invention.

[0006] That is, the present invention aims to provide a heat-softenable thermally conductive composition containing the following components (A) to (C), and a paste-like heat-softenable thermally conductive composition obtained by dissolving the heat-softenable thermally conductive composition with the following component (D). Here, heat-softening refers to the ability to be thermally softened, reduced in viscosity, or melted by heat (at 40°C or higher), and a composition that is thermally softened, reduced in viscosity, or melted to fluidize the surface of the coating can be considered to have "heat-softening" properties.

[0007] [1] A heat-softenable thermally conductive composition comprising the following components (A), (B), and (C): (A)R 1 SiO 3 / 2 Units (wherein R 1 is a group selected from an alkyl group having 1 to 10 carbon atoms or a phenyl group), and R 2 2SiO 2 / 2 Units (wherein R2 (B) a linear aryl-modified organopolysiloxane having one or more aryl groups having 6 to 10 carbon atoms per molecule and an aryl modification rate of 20 to 60 mol %: 20 to 40 parts by mass; and (C) a thermally conductive filler having a thermal conductivity of 10 W / (m K) or more and an average particle size of 0.3 to 20 μm: 800 to 1,300 parts by mass. [2] The heat-softening thermally conductive composition according to [1], further comprising, as component (D), 10 to 300 parts by mass of an isoparaffin-based solvent having a boiling point of 80 to 360°C per 100 parts by mass of component (A). [3] The thermosoftenable thermally conductive composition according to [1] or [2], further comprising a surface treatment agent as component (E) in an amount of 5 to 40 parts by mass per 100 parts by mass of component (A). [4] A cured product of the thermosoftenable thermally conductive composition according to any one of [1] to [3].

[0008] The heat-softenable thermally conductive composition of the present invention has superior pump-out resistance, heat resistance, and flame retardancy compared to conventional products, and is useful as a heat-dissipating material. Furthermore, the heat-softenable thermally conductive composition of the present invention is disposed between a heat-generating electronic component and a heat-dissipating component, has no fluidity at room temperature, and becomes less viscous, softens, or melts due to heat generated during operation of the electronic component, thereby substantially filling the boundary between the electronic component and the heat-dissipating component. Furthermore, the heat-softenable thermally conductive composition of the present invention can be made into a paste-like material with excellent fluidity, allowing it to be easily applied by screen printing or the like.

[0009] The present invention will be described in detail below.

[0010] (A) Phenyl-Modified Silicone Resin Component (A) is a heat-softenable phenyl-modified silicone resin that forms the matrix of the composition (heat dissipation member) of the present invention. Component (A) is a silicone resin that allows the composition (heat dissipation member) of the present invention to be substantially non-fluid at room temperature, but which heat-softens, reduces viscosity, or melts to become fluid upon heat generation from a heat-generating electronic component, specifically within a temperature range of 40 to 80°C. Component (A) also functions as a binder that thermally softens the composition (heat dissipation member) of the present invention and provides processability and workability to the filler that imparts thermal conductivity. In the present invention, "room temperature" refers to a temperature range of 10 to 30°C. Here, the temperature at which heat softening, viscosity reduction, or melting occurs refers to the temperature required for the heat dissipation member, and the melting point of the silicone resin itself is preferably 40 to 80°C, and particularly preferably 50 to 70°C. If the melting point of the silicone resin itself is below 40°C, the surface of the composition may become tacky when applied, resulting in poor handling. Furthermore, if the melting point of the silicone resin itself is higher than 80° C., the temperature during thermocompression bonding must be high, which may make the mounting process difficult.

[0011] The component (A) is R 1 SiO 3 / 2 unit (hereinafter referred to as T unit), and R 2 2SiO 2 / 2 In addition to these T units and D units, R 2 3SiO 1 / 2 It may have a small amount of R units (hereinafter referred to as M units). 1 is a group selected from an alkyl group having 1 to 10 carbon atoms and a phenyl group. 1 Specific examples of R include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl, and phenyl groups. 1 is preferably a methyl group or a phenyl group. 2 is the above R 1In addition to the alkyl groups and phenyl groups, R is a group selected from alkenyl groups having 2 to 10 carbon atoms. 2 Specific examples of 1 In addition to the above, specific examples include alkenyl groups such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group, and octenyl group. Among these, from the viewpoint of flame retardancy, R 2 is preferably a methyl group, a phenyl group, a vinyl group, or an allyl group.

[0012] The silicone resin of component (A) will now be described in more detail. The silicone resin of component (A) must contain T units and D units to be non-fluid at room temperature. A typical example of such a silicone resin is a silicone resin composed of a combination of T units, D units, and a small amount of M units. Introducing T units can increase toughness and improve brittleness when solid at room temperature, preventing breakage during handling. Introducing D units can also improve toughness at room temperature. M units form terminal groups. In silicone resins composed of a combination of M units / T units / D units, the ratio of T units to D units is preferably 10:90 to 90:10, and particularly preferably 20:80 to 80:20. The ratio of M units to the total of T units and D units is preferably 0.2:100 to 4:100.

[0013] The phenyl modification rate of the silicone resin of component (A) is 30 to 60 mol%, preferably 40 to 60 mol%, and particularly preferably 50 to 60 mol%. If the phenyl modification rate is less than 30 mol%, the adhesiveness of the resin may be weakened, and pump-out resistance may be reduced. If the phenyl modification rate exceeds 60 mol%, the compatibilizer component (B) may not dissolve even when added, and may separate. The phenyl modification rate is the ratio of units containing phenyl groups among M units, D units, and T units, expressed as a mole percentage.

[0014] Specific examples of component (A) include silicone resins having a specific composition of bifunctional structural units (D units) and trifunctional structural units (T units) as shown below. The bonding order of the siloxane units listed below may be block or random. D m Tφ p D Vi n (where D is a dimethylsiloxy unit (i.e., (CH)SiO 2 / 2 ), Tφ is a phenylsiloxy unit (i.e., (C6H5)SiO 3 / 2 ), D Vi represents a methylvinylsiloxy unit (i.e., (CH3)(CH2=CH)SiO 2 / 2 ), where p / (m+p+n) (molar ratio) is 0.3 to 0.6, and n / (m+n) (molar ratio) is 0.7 to 1.0.

[0015] Specific examples of component (A) include silicone resins having a specific composition of monofunctional structural units (M units), difunctional structural units (D units), and trifunctional structural units (T units), such as those shown below. L D m Tφ p D Vi n (where M is a trimethylsiloxy unit (i.e., (CH3)3SiO 1 / 2 ), and D, Tφ and D Vi are as described above, and p / (m+p+n+L) (molar ratio) = 0.3 to 0.6, n / (m+n) (molar ratio) = 0.7 to 1.0, L / (m+n) (molar ratio) = 0.001 to 0.1.

[0016] Method for measuring the ratio of M units, D units, and T units In the present invention, the monofunctional R units of the organopolysiloxane resin with a three-dimensional network (resinous) structure are 1 3SiO 1 / 2 Unit (M unit), bifunctional R 2 SiO 2 / 2 unit (D unit) and trifunctional R 1 SiO 3 / 2 The ratio of units (T units) is 29 This is a value determined by Si-NMR. 29The method for preparing a sample for Si-NMR is not particularly limited, but for example, a sample can be prepared by dissolving 1 part by mass of organopolysiloxane resin in 3 parts by mass of deuterated chloroform. The average degree of polymerization of the silicone resin, i.e., the total amount of M units, D units, T units, and Q units, is preferably 30 to 300, and more preferably 50 to 150. In the present invention, the average degree of polymerization is the value determined as the polystyrene-equivalent number-average degree of polymerization (number-average molecular weight) by GPC (gel permeation chromatography) analysis using toluene as a developing solvent.

[0017] The component (A) may be used alone or in combination of two or more types. The content of component (A) in the composition of the present invention is preferably 6.9 to 9.1 mass%, more preferably 7.2 to 8.6 mass%.

[0018] (B) Linear Aryl-Modified Organopolysiloxane Component (B) is a linear aryl-modified organopolysiloxane. The heat-softenable thermally conductive composition of the present invention can be formed into a paste-like form with excellent fluidity, allowing for easy application by screen printing or the like. After applying the heat-softenable thermally conductive composition of the present invention to a heat-generating electronic component and / or a heat-dissipating component by screen printing or the like, if the composition contains the component (D) described below, the isoparaffin of component (D) is air-dried or heated to volatilize, resulting in a non-fluid state at room temperature. Subsequently, due to heat generated during operation of the electronic component, the composition reduces viscosity, softens, or melts, fluidizing at least the surface of the coating. Component (B) is a necessary component for dissolving component (A), the base polymer, in component (D), and also has the effect of increasing the fluidity of the coating surface when it fluidizes due to heat generation.

[0019] Component (B) is a linear organopolysiloxane having one or more aryl groups having 6 to 10 carbon atoms per molecule for compatibility with component (A), and the aryl modification ratio is 20 to 60 mol%, preferably 30 to 50 mol%. If the aryl modification ratio is less than 20 mol% or more than 60 mol%, the function as a compatibilizer decreases, and component (A) may not dissolve and may separate. The aryl modification ratio is the ratio of units having aryl groups or aralkyl groups to all siloxane units, expressed as a mole percentage.

[0020] Specific examples of the component (B) include those represented by the following formula (1).

[0021] In formula (1), R 3 is an aryl group having 6 to 10 carbon atoms or an aralkyl group having 7 to 10 carbon atoms, and specific examples include aryl groups such as a phenyl group, a tolyl group, a xylyl group, and a naphthyl group, and aralkyl groups such as a benzyl group. 3 is preferably a phenyl group. 4 is a monovalent hydrocarbon group selected from an alkyl group having 1 to 10 carbon atoms, preferably 1 to 6, or an alkenyl group having 2 to 10 carbon atoms, preferably 2 to 4. Examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, and octyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; and alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl. Among these, R 4 is preferably a methyl group or a vinyl group. The siloxane units bounded by a and b may be bonded in a block or random fashion. In formula (1), the ratio of each siloxane unit is preferably within the ranges 0.1<a<0.7 and 0.3<b<0.9, where a+b=1.

[0022] The component (B) may be used alone or in combination of two or more types.

[0023] The organopolysiloxane of component (B) has a kinematic viscosity at 25°C of 200 to 5,000 mm 2 / s, and particularly 300 to 4,000 mm 2 / s. 2 If it is lower than 5,000mm / s, oil bleeding will occur easily. 2 If the kinematic viscosity is greater than 1 / s, the viscosity may become low and the fluidity upon softening or melting may become poor. The kinematic viscosity of the organopolysiloxane is the value measured at 25°C using an Ostwald viscometer.

[0024] Specific examples of component (B) include organopolysiloxanes having the following structures:

[0025] The blend amount of component (B) is in the range of 20 to 40 parts by mass, and preferably in the range of 25 to 35 parts by mass, per 100 parts by mass of component (A). If the blend amount is less than 20 parts by mass, the function of the compatibilizer will be weakened and the viscosity will be reduced and the fluidity after softening or melting will be poor. If the blend amount is more than 40 parts by mass, the composition will not become non-fluid at room temperature, and pump-out resistance may be reduced.

[0026] (C) Thermally conductive filler The thermally conductive filler of component (C) must have a thermal conductivity of 10 W / (m K) or more. If the thermal conductivity is less than 10 W / (m K), the thermal conductivity of the heat-softening thermally conductive composition itself will be low. The upper limit of the thermal conductivity varies depending on the material used for the thermally conductive filler, but there is no particular upper limit. Examples of thermally conductive fillers having a thermal conductivity of 10 W / (m K) or more include powders and granules such as aluminum powder, copper powder, silver powder, nickel powder, gold powder, alumina powder, zinc oxide powder, magnesium oxide powder, aluminum nitride powder, boron nitride powder, silicon nitride powder, diamond powder, and carbon powder. These may be used alone or in combination of two or more.

[0027] When a powder or granule is used as the thermally conductive filler, the shape may be any shape, such as amorphous or spherical, but the average particle size is 0.3 to 20 μm, preferably 1 to 15 μm. If the average particle size is less than 0.3 μm, the compoundability of the composition decreases and extensibility becomes poor, while if it exceeds 20 μm, it may not be possible to reduce the thickness after thermocompression bonding. The average particle size is determined by measuring the cumulative volume average diameter D 50 Specifically, the cumulative 50% particle diameter (D) on a volume basis measured by a particle size distribution measuring device MT3000II manufactured by Microtrac Bell Co., Ltd. 50 ) (the same applies hereinafter). The amount of the thermally conductive filler blended is in the range of 800 to 1,300 parts by mass, and preferably in the range of 900 to 1,200 parts by mass, per 100 parts by mass of component (A). If the blended amount is less than 800 parts by mass, the required thermal conductivity cannot be obtained, and if it exceeds 1,300 parts by mass, the blendability of the composition decreases and extensibility may become poor.

[0028] (D) Isoparaffin-Based Solvent The heat-softenable thermally conductive composition of the present invention preferably further contains, as component (D), an isoparaffin-based solvent capable of dissolving or dispersing components (A) and (B). Other volatile solvents can also dissolve the composition, but are difficult to use during packaging due to safety and health concerns. On the other hand, isoparaffin-based solvents pose no safety or health concerns and offer excellent workability during printing.

[0029] In the present invention, "isoparaffinic solvent" refers to a solvent containing 80 mass percent or more of isoparaffin, which is an aliphatic hydrocarbon having 10 or more carbon atoms. The boiling point of component (D) is preferably 80 to 360°C, and more preferably 150 to 350°C. If the boiling point is less than 80°C, evaporation may be too rapid, causing an increase in viscosity during printing, which may result in problems. If the boiling point exceeds 360°C, it may easily remain in the heat-softenable thermally conductive composition of the present invention, which may result in a decrease in thermal properties.

[0030] In the present invention, the term "dissolved or dispersible" means that when component (A) and component (B) are placed in the isoparaffinic solvent, they are uniformly mixed together or uniformly suspended as fine particles.

[0031] When component (D) is blended, the blending amount is preferably in the range of 10 to 300 parts by mass, more preferably in the range of 50 to 200 parts by mass, per 100 parts by mass of component (A). If the added amount of component (D) is less than 10 parts by mass per 100 parts by mass of component (A), the viscosity of the heat-softenable thermally conductive composition of the present invention at room temperature cannot be sufficiently reduced, and printability may also be impaired. If the added amount is more than 300 parts by mass, the filler will settle quickly, and the storage stability of the heat-softenable thermally conductive composition may be impaired.

[0032] The component (D) may be used alone or in combination of two or more types.

[0033] (E) Surface Treatment Agent The heat-softenable thermally conductive composition of the present invention can be blended with a surface treatment agent (E). Component (E) hydrophobizes component (C) during composition preparation, improving the wettability of component (A) with component (B), and enabling component (C) to be uniformly dispersed in the matrix formed by component (A) and component (B). Component (E) is preferably at least one selected from the following components (E-1) and (E-2).

[0034] The component (E-1) is an alkoxysilane compound represented by the following formula (3): (In formula (3), R 5 are independently alkyl groups having 6 to 15 carbon atoms, and R 6 are independently selected from alkyl groups having 1 to 5 carbon atoms, aryl groups having 6 to 12 carbon atoms, and aralkyl groups having 7 to 12 carbon atoms; R 7 are independently an alkyl group having 1 to 6 carbon atoms, b is a number from 1 to 3, c is a number from 0 to 2, and b+c is a number from 1 to 3.

[0035] In the above formula (3), R 5Examples of the alkyl group represented by R include a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, and a tetradecyl group. 5 When the alkyl group represented by the formula (I) has 6 to 15 carbon atoms, the wettability of component (A) is improved sufficiently, the composition is easy to handle, and the low-temperature properties of the composition are excellent.

[0036] In the above formula (3), R 6 Examples of alkyl groups having 1 to 5 carbon atoms represented by the formula (I) include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, and neopentyl groups. Examples of aryl groups having 6 to 12 carbon atoms include phenyl, tolyl, xylyl, naphthyl, and biphenylyl groups. Examples of aralkyl groups having 7 to 12 carbon atoms include benzyl, phenylethyl, phenylpropyl, and methylbenzyl groups. Of these, preferred are alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, and propyl groups, and phenyl groups. R 6 Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group.

[0037] In the above formula (3), R 7 Examples of the alkyl group having 1 to 6 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group.

[0038] Component (E-2) is a dimethylpolysiloxane represented by the following formula (4) in which one molecular chain end is blocked with a trialkoxysilyl group. (In formula (4), R 8 are independently alkyl groups having 1 to 6 carbon atoms, and specifically, 7 Examples of the alkyl group include the same alkyl groups as those exemplified in the above. d is a number from 5 to 100, preferably from 5 to 70, and particularly preferably from 10 to 50.

[0039] The surface treatment agent for component (E) may be either component (E-1) or component (E-2), or a combination of both. When component (E) is used, the amount of component (E) added is preferably 5 to 40 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of component (A). If the amount of component (E) added is more than 40 parts by mass, oil separation may occur.

[0040] Other Additives The heat-softenable thermally conductive composition of the present invention may further contain additives or fillers as optional components, provided that the purpose of the present invention is not impaired. Specifically, the following may be added: a release agent such as silicone oil or a fluorine-modified silicone surfactant; a colorant such as carbon black, titanium dioxide, or red iron oxide; a flame retardant such as a platinum catalyst, iron oxide, titanium oxide, or cerium oxide, or a metal hydroxide; or a process oil, a reactive titanate catalyst, or a reactive aluminum catalyst as a processability improver. Furthermore, it is optional to add finely powdered silica such as precipitated silica or pyrogenic silica, a thixotropy improver, or the like, as an anti-settling agent for the thermally conductive filler.

[0041] The heat-softenable thermally conductive composition used in the heat dissipation member of the present invention can be easily produced by blending and kneading the above-mentioned components (A), (B), and (C), as well as other components (component (D) and / or (E)) as needed, using a rubber kneader such as a kneader, gate mixer, or planetary mixer. Heating may be performed as needed.

[0042] Properties after heat compression When the obtained heat-softening thermally conductive composition is heat-compressed under a pressure of 0.7 kPa at 50°C for 30 minutes after drying, it can be compressed to a thickness of 60 μm or less. The heat resistance of the obtained heat-softening thermally conductive composition after drying is 20 to 60 μm and 10 mm 2 Preferably K / W or less, more preferably 7 mm 2 The effective thermal resistance was calculated from the thermal conductivity determined by the laser flash method and the thickness of the sample using the following formula:

[0043] The heat-softenable thermally conductive composition of the present invention can be applied to a heat-generating electronic component and / or a heat-dissipating component by screen printing or the like, and then air-dried or heated. If an isoparaffinic solvent (D) is added, the component (D) can be volatilized to form a heat-conductive coating that is non-fluid at room temperature. Furthermore, the present invention can provide a heat-dissipating structure that includes a heat-generating electronic component that generates heat and reaches a temperature higher than room temperature when in operation, a heat-dissipating component, and a heat-conductive coating formed from the heat-softenable thermally conductive composition interposed between these two components. The heat-softenable thermally conductive composition is non-fluid at room temperature before the electronic component operates, but becomes less viscous, softens, or melts due to heat generated during operation of the electronic component, causing at least the surface of the coating to become fluid, thereby filling the space between the electronic component and the heat-dissipating component with substantially no voids.

[0044] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0045] The components (A) to (E) constituting the heat-softenable thermally conductive materials used in the following examples and comparative examples are as follows: M represents a trimethylsiloxy unit (i.e., (CH3)3SiO 1 / 2 ), D is a dimethylsiloxy unit (i.e., (CH3)2SiO 2 / 2 ), Dφ is a diphenylsiloxy unit (i.e., (C6H5)2SiO 2 / 2 ), D Vi represents a methylvinylsiloxy unit (i.e., (CH3)(CH2=CH)SiO 2 / 2 ), Tφ is a phenylsiloxy unit (i.e., (C6H5)SiO 3 / 2 )

[0046] Component (A): Phenyl-modified silicone resin (A-1) A silicone resin (average degree of polymerization: 100) represented by the following formula, with a phenyl modification rate of 55 mol%. 25 Tφ 55 D Vi 20 (A-2) Silicone resin (average polymerization degree: 100) (for comparison) represented by the following formula and having a phenyl modification rate of 73 mol% 15 D 12(Dφ) 22 Tφ 51 (A-3) Silicone resin represented by the following formula, with a phenyl modification rate of 20 mol% (average polymerization degree: 100) (for comparison) D 80 Tφ 20

[0047] Component (B): Linear aryl-modified organopolysiloxane (B-1) An organopolysiloxane having an aryl modification rate of 26.7 mol %, as represented by the following formula (5): (B-2) Organopolysiloxane (for comparison) having an aryl modification rate of 5.6 mol%, represented by the following formula (6): (B-3) Organopolysiloxane (for comparison) having an aryl modification rate of 100 mol% represented by the following formula (7):

[0048] (C) Component: Thermally conductive filler (C-1) Zinc oxide powder: average particle size 1.0 μm (thermal conductivity: 54 W / (m·K)) (C-2) Alumina powder: average particle size 0.3 μm (thermal conductivity: 27 W / (m·K)) (C-3) Aluminum powder: average particle size 2 μm (thermal conductivity: 236 W / (m·K)) (C-4) Aluminum powder: average particle size 10 μm (thermal conductivity: 236 W / (m·K)) (C-5) Aluminum powder: average particle size 30 μm (thermal conductivity: 236 W / (m·K)) (for comparison)

[0049] Component (D): Isoparaffinic solvent (D-1) IP Solvent 1620 (Idemitsu Kosan Co., Ltd., boiling point: 170 to 200°C)

[0050] Component (E): Surface treatment agent (E-1) Silane C represented by the following formula 10 H 21 Si(OCH3)3

[0051] The above components (A), (B), (C), (D), and (E) were charged into a planetary mixer in the amounts shown in Tables 1 and 2 below and mixed for 60 minutes to produce paste-like thermosoftenable thermally conductive compositions of Examples 1 to 6 and Comparative Examples 1 to 7. The paste-like thermosoftenable thermally conductive compositions were then dried to a constant volume and thickness, volatilizing the solvent in the composition and obtaining thermosoftenable thermally conductive compositions. The properties of the obtained thermosoftenable thermally conductive compositions are also shown in Tables 1 and 2.

[0052] [Evaluation Method] Tests related to the present invention were performed as follows. [Pump-out Resistance] 0.3 g of a paste-like heat-softening thermally conductive composition was applied to an aluminum plate, and the solvent in the composition was evaporated in an oven at 120°C for 30 minutes. Then, before cooling, a 0.5 mm spacer was provided, and a glass slide was placed over the plate, sandwiching the heat-softening thermally conductive composition. The test specimen was placed vertically from the ground and placed in a thermal shock tester (model number: TSE-11-A) manufactured by Espec Corporation, set to alternate between 0°C and 125°C (30 minutes each), and a 500-cycle test was performed. After 500 cycles, the extent to which the heat-softening thermally conductive composition had shifted from its original position was measured. [Thickness and Thermal Resistance After Heat-Compression Bonding] A paste-like heat-softening thermally conductive composition was applied to a PET light-release separator film, and the solvent in the composition was evaporated in an oven at 120°C for 10 minutes to produce a 200 μm-thick heat-softening thermally conductive composition (hereinafter referred to as a sheet). The sheet was attached to an aluminum plate, the separator film was peeled off, and then an aluminum plate was attached on top of the sheet that was on the peeled film side. Next, the two aluminum plates were heated at 50°C for 30 minutes while applying a pressure of 0.7 kPa using clips or the like. The thickness of the two aluminum plates was then measured, and the actual thickness of the sheet was determined by subtracting the thickness of the aluminum plate, whose thickness was previously known. A micrometer (Mitutoyo Corporation, Model: M802-25VA) was used to measure the thickness. The thermal resistance of the sheet was measured using a laser flash measuring instrument (LFA467HyperFlash, manufactured by NETZSCH).

[0053] Examples 1 to 6: Sheet-shaped heat-softenable thermally conductive compositions were obtained using compositions (a) to (f) by the method described above. Comparative Example 1: Composition (g) was applied to an aluminum plate or a separator film, and after drying, a heat-softenable thermally conductive composition was obtained. In the pump-out resistance test, there was significant slippage and poor pump-out resistance. Comparative Example 2: Composition (h) was applied to an aluminum plate or a separator film, and after drying, a heat-softenable thermally conductive composition was obtained. In the pump-out resistance test, there was significant slippage and poor pump-out resistance. Comparative Example 3: Composition (i) was applied to an aluminum plate or a separator film, and after drying, a heat-softenable thermally conductive composition was obtained. Even after hot pressing, the thickness did not decrease and the thermal resistance was high. Comparative Example 4: Composition (j) was applied to an aluminum plate or a separator film, and after drying, a heat-softenable thermally conductive composition was obtained. Even when heated and pressed, the thickness did not decrease and the thermal resistance was large. Comparative Example 5: The oil separated from composition (k) during compounding, and the composition did not become grease-like, so the physical properties could not be evaluated. Comparative Example 6: The oil separated from composition (l) during compounding, and the composition did not become grease-like, so the physical properties could not be evaluated. Comparative Example 7: The oil separated from composition (m) during compounding, and the composition did not become grease-like, so the physical properties could not be evaluated.

[0054]

[0055]

Claims

1. A heat-softenable thermally conductive composition comprising the following components (A), (B), and (C): (A)R 1 SiO 3 / 2 Units (wherein R 1 is a group selected from an alkyl group having 1 to 10 carbon atoms or a phenyl group), and R 2 2SiO 2 / 2 Units (wherein R 2 (B) a linear aryl-modified organopolysiloxane having one or more aryl groups having 6 to 10 carbon atoms per molecule and having an aryl modification rate of 20 to 60 mol%: 20 to 40 parts by mass; (C) a thermally conductive filler having a thermal conductivity of 10 W / (m K) or more and an average particle size of 0.3 to 20 μm: 800 to 1,300 parts by mass; 2. The heat-softenable, thermally conductive composition according to claim 1, further comprising, as component (D), 10 to 300 parts by mass of an isoparaffinic solvent having a boiling point of 80 to 360°C per 100 parts by mass of component (A).

3. The heat-softenable, thermally conductive composition according to claim 1, further comprising a surface treatment agent as component (E) in an amount of 5 to 40 parts by mass per 100 parts by mass of component (A).

4. A cured product of the heat-softenable thermally conductive composition according to any one of claims 1 to 3.

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