Thermally conductive silicone composition

Abstract

Provided is a thermally conductive silicone composition capable of both satisfying weight reduction and storage stability even when an aluminum hydroxide filler is used. The thermally conductive silicone composition includes: (A) a diorganopolysiloxane containing an alkenyl group bonded to a silicon atom; (B) an organopolysiloxane having a hydrogen atom bonded to a silicon atom; (C) a first thermally conductive filler contained in an amount of 30 parts by mass or more and 220 parts by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B), the first thermally conductive filler being at least one thermally conductive filler selected from the group consisting of aluminum oxide (C1) that contains less than 300 ppm of hot water-extractable sodium oxide, as determined by atomic absorption spectrometry, and that has an average particle diameter of less than 5 μm, and aluminum hydroxide (C2) that contains less than 70 ppm of hot water-extractable sodium oxide, as determined by atomic absorption spectrometry, and that has an average particle diameter of less than 5 μm; and (D) a second thermally conductive filler contained in an amount of 400 parts by mass or more and 950 parts by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B), the second thermally conductive filler being an aluminum hydroxide filler that contains less than 70 ppm of hot water-extractable sodium oxide, as determined by atomic absorption spectrometry, and that has an average particle diameter of 5 μm or more and 100 μm or less; and (E) an addition reaction catalyst contained in an amount of 0.2 parts by mass or more and 1.0 part by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B).

Description

THERMALLY CONDUCTIVE SILICONE COMPOSITIONTechnical Field

[0001] The present invention relates to a thermally conductive silicone composition .Background Art

[0002] A thermally conductive silicone composition, such as , a gap filler for example , is applied directly to a heatgenerating body or a heat-dissipating body, such as a battery of an electric vehicle or a semiconductor in an electronic device , and has a function of transmitting the heat emitted from these bodies to a heat-dissipating member such as a heat sink . In recent years , with the spread of environmentally friendly electric vehicles , the development of high- performance batteries has been progressing . At the same time , the development of many heat-dissipating silicone products for trans ferring heat generated by heat-generating bodies such as electronic components , batteries , and the like to a heatdissipating member such as a heat sink has been progressing . In addition, since automobiles are required to be lightweight , it is desirable for members mounted on automobiles to have a low speci fic gravity .The thermally conductive silicone composition for a gap filler in PTL 1 uses only an aluminum hydroxide filler . However, since an alkoxy catalyst having Si bonds is used as a condensation catalyst in PTL 1 , the adhesive properties are insuf ficient .

[0003] PTL 2 discloses a silicone composition for a gap filler having improved adhesive properties . In this silicone composition, a Ti-Zr alkoxy compound as a condensation catalyst and an addition reaction catalyst are used in combination . In gap filler applications , further weight reduction, while maintaining thermal conductivity and adhesive properties , is desired .Citation ListPatent Literature

[0004] PTL 1 : Japanese Patent No . 6339761

[0005] PTL 2 : WO 2023 / 053760Summary of Invention Technical Problem

[0006] In a thermally conductive silicone composition having adhesive properties , an aluminum hydroxide filler having a low speci fic gravity may be used for the purpose of weight reduction . However, use of such an aluminum hydroxide filler may impair the storage stability . Thus , there may be concerns that the cured state of the silicone composition may be compromised after the silicone composition is stored for a certain period of time and also that the adhesive properties or hardness of a cured product obtained by curing the silicone composition may deteriorate . I t is considered that such undesirable ef fects are caused by the basicity being increased by the Na2<3 component contained in the aluminum hydroxide filler and a hydrolysis reaction that breaks apart the Si— H bond in the silicone chain being promoted by moisture in the air or OH bonds in the silicone chain or on the filler surface . It is considered that the same is true when aluminum oxide is used .

[0007] The present invention provides a thermally conductive silicone composition capable of suppressing a reduction in hardness and adhesive properties during storage and achieving a satis factory storage stability even when an aluminum oxide or aluminum hydroxide filler is used . In particular, the present invention provides a thermally conductive silicone composition capable of achieving weight reduction by using aluminum hydroxide .The present invention also provides a thermally conductive silicone composition that has a low speci fic gravity and yet has good storage stability, that is capable ofmaintaining good adhesion to a heat-generating body or a heatdissipating body even when subj ected to vibrations , that has moderate fluidity, and that provides a thermally conductive member ( gap filler ) that exhibits excellent heat dissipation properties due to high thermal conductivity . Solution to Problem

[0008] The thermally conductive silicone composition of the present invention includes : a component (A) that is a diorganopolysiloxane containing an alkenyl group bonded to a silicon atom; a component (B ) that is an organopolysiloxane having a hydrogen atom bonded to a silicon atom; a component ( C ) that is a first thermally conductive filler contained in an amount of 30 parts by mass or more and 220 parts by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B ) , the first thermally conductive filler being at least one thermally conductive filler selected from the group consisting of aluminum oxide ( Cl ) that contains less than 300 ppm of hot water-extractable sodium oxide (Na20) , as determined by atomic absorption spectrometry, and that has an average particle diameter of less than 5 m, and aluminum hydroxide ( C2 ) that contains less than 70 ppm of hot water-extractable sodium oxide (Na20) , as determined by atomic absorption spectrometry, and that has an average particle diameter of less than 5 pm; and a component ( D) that is a second thermally conductive filler contained in an amount of 400 parts by mass or more and 950 parts by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B ) , the second thermally conductive filler being an aluminum hydroxide filler that contains less than 70 ppm of hot water-extractable sodium oxide (Na2<3) , as determined by atomic absorption spectrometry, and that has an average particle diameter of 5 pmor more and 100 m or less; and a component (E) that is an addition reaction catalyst contained in an amount of 0.2 parts by mass or more and 1.0 part by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B) .

[0009] The hot water-extractable sodium oxide (Na2O) is derived from, for example, an aqueous sodium hydroxide solution used in the production process of aluminum oxide or aluminum hydroxide.The amount of hot water-extractable sodium oxide (Na20) is determined as follows. For example, aluminum oxide (Cl) or aluminum hydroxide (C2) is put in hot water at a temperature of 80°C to 150°C in a pressure-resistant container for 4 to 30 hours. Then, sodium oxide (Na20) dissolved in the hot water is quantified by atomic absorption spectrometry.In the thermally conductive silicone composition (first liquid or second liquid) , the hot water-extractable sodium oxide (Na20) is thought to elute over time.

[0010] The first thermally conductive filler of the component (C) ( (Cl) or (C2) ) and / or the second thermally conductive filler of the component (D) may be subjected to a surface treatment.

[0011] A ratio SiH / SiVi as a ratio of the component (A) to the component (B) may fall within a range of 0.5 or more and 1.5 or less .

[0012] The component (A) may contain an organopolysiloxane having a viscosity, at 25°C, of 10 mPa-s or more and 7, 000 mPa-s or less.

[0013] The component (B) may contain an organopolysiloxane having two or more hydrogen atoms in one molecule and having a viscosity, at 25°C, of 10 mPa-s or more and 7, 000 mPa-s or less.

[0014] The thermally conductive silicone composition or a cured product thereof may have a thermal conductivity of 2.0 W / m-k or more.

[0015] The cured product of the thermally conductive silicone composition preferably has an initial tensile shear bond stress of 0 . 1 MPa or more .The rate of decrease in tensile shear bond stress of the cured product of the thermally conductive silicone composition may be 30% or less , preferably 29% or less , and more preferably 28 % or less .Rate of decrease in tensile shear bond stress = ( ( initial tensile shear bond stress ) - ( tensile shear bond stress after 1 month storage at 50°C and 50% relative humidity) ) / ( initial tensile shear bond stress ) x 100A test piece for tensile shear bond test is subj ected to a tensile shear bond test in accordance with JIS K6850 to obtain an S-S curve graph . In the S-S curve graph, the maximum stress value for each test piece in the tensile shear bond test is defined as the tensile shear bond stress of the cured product of the corresponding silicone composition .

[0016] The cured product of the thermally conductive silicone composition preferably has an initial Asker C hardness in a range of 50 or more and 70 or less .The rate of decrease in the Asker C hardness of the cured product of the thermally conductive silicone composition may be less than 20% .Rate of decrease in hardness = ( ( initial hardness ) - (hardness after 1 month storage at 50°C and 50% relative humidity) ) / ( initial hardness ) x 100The hardness can be measured in accordance with the Asker C method of the Society of Rubber Industry and Technology, Japan Standard ( SRIS 0101 ) .

[0017] The thermally conductive silicone composition described above may be a two-liquid type thermally conductive silicone composition including a first liquid and a second liquid that are packaged separately from each other . Here , the first liquid and the second liquid are mixed ( for example ,under pressure in a discharge device) at the time of use to produce the thermally conductive silicone composition.The first liquid may contain the components (A) , (C) ( (Cl) or (C2) ) , (D) , and (E) .The second liquid may contain the components (A) , (B) , (C) ( (Cl) or (C2) ) , and (D) .

[0018] First liquid:The first liquid may contain: the component (A) in an amount of 5 parts by mass or more and 20 parts by mass or less; the component (C) ( (Cl) or (C2) in an amount of 3 parts by mass or more and 22 parts by mass or less; the component (D) in an amount of 60 parts by mass or more and 100 parts by mass or less; and the component (E) in an amount of 0.4 parts by mass or less, relative to 100 parts by mass of the total amount of the first liquid.The first liquid may further contain, as optional components, a silane coupling agent, a reaction inhibitor, an adhesion condensation catalyst, and / or a pigment.

[0019] Second liquid:The second liquid may contain: the component (A) in an amount of 1 part by mass or more and 10 parts by mass or less; the component (B) in an amount of 3 parts by mass or more and 15 parts by mass or less; the component (C) ( (Cl) or (C2) in an amount of 3 parts by mass or more and 22 parts by mass or less; and the component (D) in an amount of 60 parts by mass or more and 100 parts by mass or less, relative to 100 parts by mass of the total amount of the second liquid.The second liquid may further contain, as optional components, a silane coupling agent, a reaction inhibitor, and / or a pigment.

[0020] The two-liquid type thermally conductive silicone composition may include the first liquid in an amount of 40 parts by mass or more and 60 parts by mass or less, and a second liquid in an amount of 60 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the total amount of the thermally conductive silicone composition.

[0021] A method for producing the thermally conductive silicone composition according to the present invention includes : a first liquid production step of mixing the component (A) , the component (E) , and an optional component, and then mixing the component (C) ( (Cl) or (C2) ) and the component (D) to obtain a first liquid; and a second liquid production step of mixing the component (A) , the component (B) , and an optional component, and then mixing the component (C) ( (Cl) or (C2) ) and the component (D) to obtain a second liquid.Examples of the optional components include a silane coupling agent, a reaction inhibitor, an adhesion condensation catalyst, and a pigment.

[0022] The method for producing the thermally conductive silicone composition according to the present invention may include : a first liquid packaging step of filling a predetermined first packaging material with the first liquid obtained in the first liquid production step; and a second liquid packaging step of filling a predetermined second packaging material with the second liquid obtained in the second liquid production step.

[0023] The method for discharging the thermally conductive silicone composition according to the present invention may include : introducing a first liquid from a first packaging material into a first liquid flow path of a dispenser;introducing a second liquid from a second packaging material into a second liquid flow path of the dispenser ; introducing the first liquid and the second liquid at a predetermined ratio into a merging flow path where the first liquid flow path and the second liquid flow path merge ; and discharging a mixed liquid of the first liquid and the second liquid, which have been brought into contact with each other in the merging flow path, from a noz zle of the dispenser to a substrate .The "predetermined ratio" is a mixing ratio of the first liquid and the second liquid, and can be set according to speci fications of the thermally conductive silicone composition . The predetermined ratio is , for example , of 1 : 1 .

[0024] The method for producing a thermally conductive member according to the present invention may include : discharging the first liquid from a first liquid storage section to a mixing section; discharging the second liquid from a second liquid storage section to the mixing section; mixing the first liquid and the second liquid in the mixing section to obtain the thermally conductive silicone composition; discharging and applying the thermally conductive silicone composition to a substrate ; and curing the thermally conductive silicone composition applied to the substrate to obtain a thermally conductive member .

[0025] In the method for producing a thermally conductive member and the method for discharging a thermally conductive silicone composition, discharge pressures at which the first liquid, the second liquid, and the thermally conductive silicone composition are discharged onto a substrate vary depending on the dispenser, but may be , for example , a lower limit value of 0 . 1 MPa, and preferably 0 . 2 MPa to 0 . 8 MPa .Advantageous Ef fects of Invention

[0026] In a mode in which an aluminum oxide filler or aluminum hydroxide filler having a fine particle diameter such as an average particle diameter of less than 5 m, and an aluminum hydroxide filler having a particle diameter that is larger than the fine particle diameter are used in combination, even when a high-purity filler of a reduced Na20- content grade is not used, use of a filler having a hot water- extractable sodium oxide (Na20) the amount of which falls within a speci fic range can provide a gap filler that has good thermal conductivity, adhesion, and fluidity and a low speci fic gravity, and also can provide a silicone composition having satis factory storage stability .The above-described thermally conductive silicone composition can serve as a gap filler having excellent heat dissipation properties due to its high thermal conductivity . Even when the thermally conductive silicone composition includes an aluminum hydroxide filler having a low speci fic gravity as a filler component , the thermally conductive silicone composition can have good gapless contact and adhesion to a substrate such as a heat-dissipating body, moderate fluidity, and good storage stability all at the same time .Brief Description of Drawings

[0027] FIG . 1A is a table showing blending ratios of respective components of each of a first liquid and a second liquid in each of Examples .FIG . IB is a table showing the amounts (unit : parts by mass ) of respective components relative to the amount of a component (A- l ) in the first liquid and the amounts (unit : parts by mass ) of respective components relative to the total amount of components (A- l ) , (A-2 ) , and (B- l ) in the second liquid in each of Examples .FIG . 1C is a table showing the respective components interms of their blending ratios and the results of tensile shear bond stress, hardness, and thermal conductivity in each of Examples.FIG. ID is a table showing the respective components in terms of parts by mass and the results of tensile shear bond stress, hardness, and thermal conductivity in each of Examples .FIG. 2A is a table showing blending ratios of respective components of each of a first liquid and a second liquid in each of Comparative Examples.FIG. 2B is a table showing the amounts (unit: parts by mass) of respective components relative to the amount of the component (A-l) in the first liquid and the amounts (unit: parts by mass) of respective components relative to the total amount of the components (A-l) , (A-2) , and (B-l) in the second liquid in each of Comparative Examples.FIG. 2C is a table showing the respective components in terms of their blending ratios and the results of tensile shear bond stress, hardness, and thermal conductivity in each of Comparative Examples.FIG. 2D is a table showing the respective components in terms of parts by mass and the results of tensile shear bond stress, hardness, and thermal conductivity in each of Comparative Examples. Description of Embodiments

[0028] Hereinafter, details of a thermally conductive silicone composition and a method for producing the thermally conductive silicone composition according to the present invention will be described.

[0029] Thermally conductive silicone composition:The thermally conductive silicone composition may be any composition for forming thermally conductive members. Examples of the thermally conductive members include constituting elements that are cured and formed on a heat-generating bodysuch as a car battery or on members such as a substrate , a circuit chip, a heat-dissipating member, or the like that are used in an electrical device or an electronic device .The thermally conductive silicone composition may be applied to a substrate in a liquid state before curing and may be cured after application to provide the thermally conductive member . Alternatively, the thermally conductive silicone composition may be first cured to obtain a thermally conductive member, and the resulting thermally conductive member may be applied to a substrate afterwards .

[0030] The temperature , procedure , and the like for curing the thermally conductive silicone composition are not limited to particular ones and can be appropriately selected depending on the use application or other factors related to the cured product to be obtained .

[0031] A curing method of the thermally conductive silicone composition is preferably an addition reaction type . The main reasons for this are , for example , as follows : curing can be controlled over a wide temperature range of room temperature to approximately 150°C, volume change and the amount of desorption gas are low, and in general good compatibility with a thermally conductive filling agent is achieved . In general , the higher the curing temperature , the faster the curing process . The present invention assumes that some or all steps , namely the step of applying the thermally conductive silicone composition, the curing step, and the subsequent steps are required to be performed at room temperature because of various restrictions depending on the use application . The addition reaction type allows the curing temperature to be set appropriately according to the restrictions .

[0032] Assuming that the curing method of the thermally conductive silicone composition according to the present invention is of the addition reaction type , respectivecomponents of the thermally conductive silicone composition will be described in detail below.

[0033] Component (A) :The component (A) , which is the main component of the thermally conductive silicone composition, is a diorganopolysiloxane containing an alkenyl group bonded to a silicon atom. The alkenyl group-containing diorganopolysiloxane preferably has a terminal Vi (vinyl group) in order to have a moderate hardness after curing. The alkenyl group-containing diorganopolysiloxane may have an OH group at its terminal.The viscosity and the degree of polymerization of the component (A) are not particularly limited, and can be selected according to the required mixing viscosity and the like of the thermally conductive silicone composition, and the viscosity at 25°C may be, for example, 10 mPa-s or more and 7, 000 mPa-s or less.As the diorganopolysiloxane, one type thereof may be used alone, or two or more types thereof may be used in combination as appropriate. The diorganopolysiloxane is the main component of the thermally conductive silicone composition and has, on average, at least two alkenyl groups bonded to silicon atoms within one molecule, preferably 2 to 50 alkenyl groups, and more preferably 2 to 20 alkenyl groups.The amount of the component (A) is in the range of 3.0 part by mass or more and 15.0 parts by mass or less, preferably 5.0 parts by mass or more and 11.0 parts by mass or less, relative to 100 parts by mass of the entirety of the thermally conductive silicone composition. The component (A) is preferably contained in both the first liquid and the second liquid.

[0034] The molecular structure of the component (A) is not particularly limited, and may be, for example, a linear structure, a partially branched linear structure, a branchedchain structure , a cyclic structure , or a branched cyclic structure . Among these , the component (A) is preferably a substantially linear diorganopolysiloxane . Speci fically, the component (A) can be a linear diorganopolysiloxane in which the molecular chain is mainly composed of a diorganosiloxane repeat unit and of which both terminals of the molecular chain are blocked with a triorganosiloxy group . Some or all of the terminals of the molecular chain or a part of the side chain may be a silanol group .

[0035] The position of the alkenyl group bonded to a silicon atom in the component (A) is not particularly limited, and the component (A) may be a diorganopolysiloxane having an alkenyl group bonded to a silicon atom at both molecular chain terminals . The diorganopolysiloxane having one alkenyl group at each terminal of the molecular chain has an advantage in that the content of the alkenyl groups serving as the reaction point of the cross-linking reaction is small and the flexibility of the cured product , e . g . , gap filler, obtained after curing is enhanced .

[0036] The alkenyl group may be bonded to the silicon atom at the molecular chain terminal , to the silicon atom at a nonterminal molecular chain site ( in the middle of the molecular chain) , or to both .The component (A) may be a polymer composed of a single type of siloxane unit or a copolymer composed of two or more types of siloxane units .

[0037] The viscosity, at 25°C, of the component (A) is 10 mPa-s or more and 7 , 000 mPa-s or less , preferably 20 mPa-s or more and 5 , 000 mPa-s or less , more preferably 30 mPa-s or more and 3 , 000 mPa-s or less , even more preferably 40 mPa-s or more and 2 , 000 mPa-s or less , and still more preferably 50 mPa-s or more and 1 , 000 mPa-s or less .When the viscosity falls within the above-described range , an appropriate fluidity of the resulting thermallyconductive silicone composition can be obtained, and thus the discharge performance becomes high and the productivity can thus be improved. In addition, it is possible to increase the flexibility of the resulting thermally conductive member obtained by curing the thermally conductive silicone composition .

[0038] In order to adjust the viscosity (mixing viscosity) , before curing, of the thermally conductive silicone composition that is obtained by mixing the liquid compositions, two or more types of diorganopolysiloxanes having an alkenyl group and having different viscosities can also be used in combination.

[0039] Specifically, the component (A) is represented by the following general formula (1) as an average composition formula :R1aS 10 ( 4-a ) / 2 ... (1)(In the formula (1) , Rxs are the same as or different from each other and each are an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, a is 1.7 to 2.1, preferably 1.8 to 2.5, and more preferably 1.95 to 2.05. ) .

[0040] In one embodiment, at least two or more of the monovalent hydrocarbon groups represented by the aforementioned R1are selected from alkenyl groups such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, an isobutenyl group, a hexenyl group, and a cyclohexenyl group. Groups other than these groups are substituted or unsubstituted monovalent hydrocarbon groups having 1 to 18 carbon atoms. Specifically, the aforementioned R1is selected from the group consisting of an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tertbutyl group, a pentyl group, a neopentyl group, a hexyl group, a 2-ethylhexyl group, a heptyl group, an octyl group, a nonylgroup, a decyl group, and a dodecyl group ; a cycloalkyl group such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group ; an aryl group such as a phenyl group, a tolyl group, a xylyl group, a biphenyl group, and a naphthyl group ; an aralkyl group such as a benzyl group, a phenylethyl group, a phenylpropyl group, and a methylbenzyl group ; and a halogen-substituted or cyano-substituted alkyl group in which a part or all of hydrogen atoms in the above-described hydrocarbon groups have been substituted with a halogen atom, a cyano group, or the like , such as a chloromethyl group, a 2 - bromoethyl group, a 3 , 3 , 3-tri f luoropropyl group, a 3- chloropropyl group, and a cyanoethyl group .

[0041] Examples of Rxs to be selected preferably include , as the two or more alkenyl groups required, a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a 2 - methyl- l-propenyl group, a 2 -methylallyl group, and a 2 - butenyl group . A vinyl group is particularly preferable . Examples of preferable R1other than the alkenyl group include a methyl group and a phenyl group, with a methyl group being particularly preferable . In addition, it is preferable that 70 mol% or more of Rxs be a methyl group, in consideration of physical properties and economic ef ficiency of the cured product , and normally, it is preferable that 80 mol% or more of Rxs be a methyl group .

[0042] Speci fic examples of the molecular structure of the component (A) include a dimethylpolysiloxane with both molecular chain terminals blocked with a dimethylvinylsiloxy group, a dimethylsiloxane-methylphenylsiloxane copolymer with both molecular chain terminals blocked with a dimethylvinylsiloxy group, a dimethylsiloxane- methylvinylsiloxane copolymer with both molecular chain terminals blocked with a dimethylvinylsiloxy group, a dime thyl s il oxane -methyl vinyl si 1 oxane -me thylphyenyl siloxane copolymer with both molecular chain terminals blocked with adimethylvinylsiloxy group, a dimethylsiloxane- methylvinylsiloxane copolymer with both molecular chain terminals blocked with a trimethylsiloxy group, an organopolysiloxane composed of a siloxane unit represented by the formula : ( CH3 ) 2ViSiOi / 2 , a siloxane unit represented by the formula : ( CH3 ) 3S1O1 / 2 , and a siloxane unit represented by the formula : S1O4 / 2 (Vi in the formula represents a vinyl group ) , an organopolysiloxane in which part or all of the methyl groups in the above-mentioned organopolysiloxanes are substituted by an alkyl group such as an ethyl group or a propyl group, an aryl group such as a phenyl group or a tolyl group, and a halogenated alkyl group such as a 3 , 3 , 3- tri f luoropropyl group, and mixtures of two or more of these organopolysiloxanes . From the viewpoint of enhancing stretchability at the time of breakage of the cured product due to increased molecular chain length, a linear diorganopolysiloxane with one vinyl group at each molecular chain terminal is preferable .

[0043] The component (A) may include an alkenyl group- containing diorganopolysiloxane having at least one silanol group at the molecular chain terminal in an amount of 1 . 0 part by mass or more and 9 . 0 parts by mass or less .When the thermally conductive silicone composition of the present invention is stored as a two-component composition, the alkenyl group-containing diorganopolysiloxane having a silanol group may be contained in the first liquid and / or the second liquid .

[0044] These diorganopolysiloxanes may be commercially available or prepared by methods known to those skilled in the art .

[0045] Component (B ) :The component (B ) is an organopolysiloxane having a hydrogen atom bonded to a silicon atom .The viscosity and degree of polymeri zation of thecomponent (B) are not particularly limited, and can be selected according to the required mixing viscosity and the like of the thermally conductive silicone composition. For example, the component (B) may include an organopolysiloxane that has a viscosity, at 25°C, of 10 mPa-s or more and 7,000 mPa-s or less and contains two or more hydrogen atoms within one molecule.

[0046] The SiH / SiVi ratio as the ratio of the component(A) to the component (B) may fall within a range of 0.5 or more and 1.5 or less. The molar ratio [Si-H group / alkenyl group] of the sum of Si-H groups contained in the entire thermally conductive silicone composition to the sum of alkenyl groups bonded to silicon atoms in the component (A) may fall within a range of 0.5 or more and 1.5 or less.

[0047] The number of the hydrogen atoms bonded to silicon atoms may be 2 or more, and the bonding sites are not particularly limited.The hydrogen content (H content) of the component (B) is not particularly limited. In order to impart a practically sufficient stretchablity to a thermally conductive member that is obtained by curing the thermally conductive silicone composition, the hydrogen content (H content) of the component(B) is preferably 0.01 mmol / g or more and 4.0 mmol / g or less, more preferably 0.1 mmol / g or more and 2.0 mmol / g or less, and even more preferably 0.4 mmol / g or more and 1.0 mmol / g or less .

[0048] As the component (B) , an organohydrogenpolysiloxane can be used. The component (B) forms a cured product by an addition reaction with an alkenyl group, and may have a hydrogen atom (hydrosilyl group) bonded to at least one or more silicon atoms in a side chain in the molecule.The component (B) may function as a cross-linking agent. The component (B) that serves as the cross-linking agent preferably has three or more hydrosilyl groups within onemolecule and may have at least one hydrosilyl group in a side chain in the molecule . The component (B ) that serves as the cross-linking agent is more preferably an organohydrogenpolysiloxane having 5 or more hydrosilyl groups , and may have 10 or more and 18 or less hydrosilyl groups . The organohydrogenpolysiloxane that serves as the cross-linking agent has at least two hydrosilyl groups in its side chain . The number of hydrosilyl groups at a molecular chain terminal may be zero or more and two or less , and is , from an economic perspective , preferably two . The molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures . The position of the silicon atom to which a hydrogen atom is bonded is not particularly limited, and may be a molecular chain terminal , a non-terminal molecular chain site ( in the middle of the molecular chain) , or a side chain . Other conditions , the type of the organic group other than a hydrosilyl group, the bonding position, the degree of polymeri zation, the structure , and the like in the organohydrogenpolysiloxane are not particularly limited . Two or more types of organohydrogenpolysiloxanes may be used in combination .

[0049] In the thermally conductive silicone composition described above , the amount of the component (B ) is preferably in such a range that the ratio of the number of hydrogen atoms (hydrosilyl groups ) in the component (B ) to that of the alkenyl group in the component (A) falls within the range of 0 . 2 to 7 , more preferably within the range of 0 . 3 to 2 , and still more preferably within the range of 0 . 4 to 1 . 5 . When the amount of the component (B ) falls within the aforementioned range , the thermally conductive silicone composition is suf ficiently cured and the hardness of the entire cured product obtained by curing the composition falls within a more preferable range . As a result , cracks are less likely to occurwhen the cured product of the composition is used as a gap filler. In addition to these, there is an advantage that the cured product achieves both a desired certain degree of flexibility and adhesion.

[0050] The hydrogen atom (hydrosilyl group) in the component (B) may be present at the molecular chain terminals, may be present in side chains, or may be present both at the molecular chain terminals and in the side chains. It is preferable to use a mixture of an organohydrogenpolysiloxane having one hydrogen atom (hydrosilyl group) only at each molecular chain terminal and an organohydrogenpolysiloxane having hydrogen atoms (hydrosilyl groups) only in the side chain of the molecular chain.

[0051] From the viewpoint of improving heat resistance, the component (B) may include an organohydrogenpolysiloxane having at least one aromatic group within the molecule. For economic reasons, the aromatic group is more preferably a phenyl group. An aromatic group-containing organohydrogenpolysiloxane and an aromatic group-free organohydrogenpolysiloxane may be used in combination.

[0052] The viscosity, at 25°C, of the component (B) is 10 mPa-s or more and 7, 000 mPa-s or less, preferably 20 mPa-s or more and 5, 000 mPa-s or less, and more preferably 30 mPa-s or more and 500 mPa-s or less.In order to adjust the viscosity of the thermally conductive silicone composition, which is the final product, it is also possible to use two or more types of organopolysiloxanes having a hydrogen atom and having different viscosities. The mixing viscosity of the thermally conductive silicone composition may be in the range of 10 Pa-s or more and 1,000 Pa-s or less, more preferably in the range of 20 Pa-s or more and 500 Pa-s or less, and even more preferably in the range of 30 Pa-s or more and 200 Pa-s or less.

[0053] Component (C) :The component (C) is a first thermally conductive filler and is a filler component for improving the thermal conductivity of the thermally conductive silicone composition. In order to obtain a gap filler having excellent electrical insulation properties for application to electronic substrates or the like, the thermally conductive filler is preferably a material having not only excellent thermal conductivity but also excellent electrical insulation properties.The first thermally conductive filler of the component (C) is at least one thermally conductive filler selected from the group consisting of aluminum oxide (Cl) and aluminum hydroxide (C2 ) .In the thermally conductive silicone composition, the amount of the first thermally conductive filler as the component (C) is 30 parts by mass or more and 220 parts by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B) .

[0054] Component (Cl) :The component (Cl) , i.e., aluminum oxide, contains less than 300 ppm of hot water-extractable sodium oxide (Na2O) , as determined by atomic absorption spectrometry, and has an average particle diameter of less than 5 m.The amount of aluminum oxide as the component (Cl) is 30 parts by mass or more and 220 parts by mass or less, preferably 40 parts by mass or more and 200 parts by mass or less, and more preferably 60 parts by mass or more and 180 parts by mass or less, relative to 100 parts by mass of the total amount of the component (A) and the component (B) .Even when only one type of aluminum oxide is used, it is more preferable to combine two or more types of different shapes. For example, spherical aluminum oxide and amorphous aluminum oxide may be combined.

[0055] Note that an average particle diameter is defined by D50, which is the 50% particle diameter in a volume-basedcumulative particle size distribution measured by a laser diffraction particle size measuring device. Herein, the same measurement method is used unless otherwise specified. Note that a median diameter may also be used.

[0056] Component (C2) :The component (C2) , i.e., aluminum hydroxide, contains less than 70 ppm of hot water-extractable sodium oxide (Na20) , as determined by atomic absorption spectrometry, and has an average particle diameter of less than 5 m.The amount of aluminum hydroxide as the component (C2) is 30 parts by mass or more and 220 parts by mass or less, preferably 40 parts by mass or more and 210 parts by mass or less, relative to 100 parts by mass of the total amount of the component (A) and the component (B) .Even when only one type of aluminum hydroxide is used, it is more preferable to combine two or more types of different shapes. For example, spherical aluminum hydroxide and amorphous aluminum hydroxide may be combined.

[0057] The aluminum hydroxide filler may be subjected to a surface treatment.Examples of the surface treatment include a treatment with a long-chain alkyl fatty acid, a silane coupling treatment, and a titanium coupling agent treatment.

[0058] Component (D) :The component (D) , i.e., a second thermally conductive filler, is a filler component for improving the thermal conductivity of the thermally conductive silicone composition. In order to obtain a gap filler having excellent electrical insulation properties for application to electronic substrates or the like, it is preferable to use a material having not only excellent thermal conductivity but also excellent electrical insulation properties as the second thermally conductive filler as the component (D) .The second thermally conductive filler as the component(D) is an aluminum hydroxide filler that contains less than 70 ppm of hot water-extractable sodium oxide sodium oxide (Na20) , as determined by atomic absorption spectrometry, and that has an average particle diameter of 5 pm or more and 100 m or less .

[0059] The amount of the aluminum hydroxide filler as the second thermally conductive filler of the component ( D) is 400 parts by mass or more and 950 parts by mass or less , preferably 400 parts by mass or more and 750 parts by mass or less , and more preferably 400 parts by mass or more and 600 parts by mass or less , relative to 100 parts by mass of the total amount of the component (A) and the component (B ) .Even when only one type of aluminum hydroxide filler is used, it is more preferable to combine two or more types of di f ferent shapes . For example , spherical aluminum hydroxide filler and amorphous aluminum hydroxide filler may be combined .

[0060] The aluminum hydroxide filler may be subj ected to a surface treatment .Examples of the surface treatment include a treatment with a long-chain alkyl fatty acid, a silane coupling treatment , and a titanium coupling agent treatment .

[0061] The shape of the thermally conductive fillers of the components ( C ) and ( D) is not particularly limited and may be , for example , a spherical shape , an amorphous shape , a fine powder, a fibrous shape , a scaly shape , or the like . In order to blend the amount of the thermally conductive filler required to enhance the thermal conductivity of the thermally conductive member, the thermally conductive filler preferably has a spherical shape , and the average particle diameter thereof may be 1 to 100 m . Herein, the spherical shape may be not only a true spherical shape but also an oval sphere shape .

[0062] When spherical aluminum oxide is used, a-alumina obtained by high-temperature thermal spraying or hydrothermaltreatment of alumina hydrate may be used .

[0063] In order to improve the filling rate of the thermally conductive filler, it is more preferable to use a spherical thermally conductive filler and a thermally conductive filler other than a spherical filler . When at least two or more types of thermally conductive fillers having di f ferent shapes are used in combination, the fillers can be packed in a state that is almost the closest packed, so that the ef fect of increasing the thermal conductivity can be obtained . When the spherical thermally conductive filler is used in combination with a thermally conductive filler other than spherical fillers ( for example , an amorphous thermally conductive filler ) , thermal conductivity can be further increased .

[0064] The thermally conductive filler preferably has a thermal conductivity of 10 W / m-K or more . When the thermal conductivity is less than 10 W / m-K, the thermal conductivity itsel f of the thermally conductive silicone composition may be reduced .In particular, i f the thermally conductive member requires electrical insulation properties , it is conceivable to select a non-electroconductive thermally conductive filler .

[0065] The thermally conductive filler may be blended in an amount required to increase the thermal conductivity of the thermally conductive member ( e . g . , 2 . 0 W / m-K or higher ) . For example , the amount of the thermally conductive filler may be 70 parts by mass or more and 95 parts by mass or less relative to 100 parts by mass of the entire thermally conductive silicone composition .When the amount of the thermally conductive filler falls within the above-mentioned range , the thermally conductive silicone composition as a whole has suf ficient thermal conductivity, is easy to mix at the time of blending, and maintains flexibility even after curing . In addition, sincethe thermally conductive filler contained in such an amount does not excessively increase the speci fic gravity, the resulting thermally conductive silicone composition is more suitable for forming a thermally conductive member that is required to have high thermal conductivity and reduced weight . I f the amount of the thermally conductive filler is too small , it becomes di f ficult to suf ficiently increase the thermal conductivity of the cured product obtained from the thermally conductive silicone composition, whereas i f the amount of the thermally conductive filler is too large , the resulting thermally conductive silicone composition becomes highly viscous , and there is a possibility that it becomes di f ficult to uni formly apply the thermally conductive silicone composition . Thus , such cases result in problems such as an increase in the thermal resistance value of the cured product of the composition and a decrease in flexibility of the cured product .

[0066] Component (E ) :The component (E ) is an addition reaction catalyst , and promotes an addition-curing reaction between an alkenyl group bonded to a silicon atom in the component (A) described above and a hydrogen atom bonded to a silicon atom in the component (B ) described above .Such addition reaction catalysts are known to those skilled in the art . Examples of the component (E ) include a platinum group metal such as platinum, rhodium, palladium, osmium, iridium, and ruthenium, and catalysts in which any of the aforementioned metals is supported by a fine particulate carrying material ( for example , activated carbon, aluminum oxide , and silicon oxide ) .Furthermore , speci fic examples of the component (E ) include a platinum halide , a platinum-olef in complex, a platinum-alcohol complex, a platinum-alcoholate complex, a platinum-vinylsiloxane complex, dicyclopentadiene-platinumdichloride, cyclooctadiene-platinum dichloride, and cyclopentadiene-platinum dichloride .

[0067] In addition, from an economic viewpoint, a metal compound catalyst other than platinum group metals as described above may be used as the component (E) . Examples of the iron catalyst for hydrosilylation include an iron-carbonyl complex catalyst, an iron catalyst having a cyclopentadienyl group as a ligand, an iron catalyst having a terpyridine-based ligand or a combination of a terpyridine-based ligand and a bistrimethylsilylmethyl group, an iron catalyst having a bisiminopyridine ligand, an iron catalyst having a bisiminoquinoline ligand, an iron catalyst having an aryl group as a ligand, an iron catalyst having a cyclic or acyclic olefin group with an unsaturated group, and an iron catalyst having a cyclic or acyclic olefinyl group with an unsaturated group. Other examples of the catalyst for hydrosilylation include a cobalt catalyst, a vanadium catalyst, a ruthenium catalyst, an iridium catalyst, a samarium catalyst, a nickel catalyst, and a manganese catalyst.

[0068] The blending amount of the component (E) is generally, in terms of the concentration of the catalyst metal element, in the range of preferably 0.5 ppm or more and 1,000 ppm or less, more preferably 1 ppm or more and 500 ppm or less, and still more preferably 1 ppm or more and 100 ppm or less, relative to the total mass of the thermally conductive silicone composition, although an effective amount thereof according to the curing temperature and curing time desired depending on the use applications is used. If the blending amount is less than 0.5 ppm, the addition reaction will become remarkably slow. If the blending amount exceeds 1,000 ppm, it is not economically preferable because of cost increase.

[0069] The addition reaction catalyst of the component (E) is 0.2 parts by mass or more and 1.0 part by mass or less, preferably 0.25 parts by mass or more and 0.9 parts by mass orless, and more preferably 0.3 parts by mass or more and 0.8 parts by mass or less, relative to 100 parts by mass of the total amount of the components (A) and (B) .

[0070] Optional components:In the thermally conductive silicone composition, as an additional optional component other than the aforementioned components (A) to (F) , conventionally known additives for use in a silicone rubber or gel can be used as long as the object of the present invention is not impaired. Examples of such additives include an organosilicon compound, a cross-linking agent, an adhesive aid, a pigment, a dye, a reaction inhibitor, a curing inhibitor, a heat-resistance imparting agent, a flame retardant, an antistatic agent, a conductivity imparting agent, an airtightness improving agent, a radiation shielding agent, an electromagnetic wave shielding agent, a preservative, a stabilizer, an organic solvent, a plasticizer, a fungicide, an organopolysiloxane that contains one hydrogen atom or alkenyl group bonded to a silicon atom within one molecule and that contains no other functional groups, and a silicon atom-bonded hydrogen atom. As these optional components, one type thereof may be used alone, or two or more types thereof may be used in combination as appropriate.The thermally conductive silicone composition of the present invention may contain any one or more selected from the group consisting of octamethylcyclotetrasiloxane (D4) , decamethylcyclopentasiloxane (D5) , dodecamethylcyclohexasiloxane (D6) , tetradecamethylcycloheptasiloxane (D7) , and hexadecamethylcyclooctasiloxane (D8) . The total content of (D4) , (D5) , (D6) , (D7) , and (D8) may be less than 0.1 parts by mass (i.e., less than 1,000 ppm) relative to 100 parts by mass of the total blending amount of the first liquid and / or the total blending amount of the second liquid.

[0071] The coupling agent of the optional componentincludes , for example , a silane coupling agent . Examples of the silane coupling agent include an organosilicon compound and an organosiloxane having an organic group with 3 or more carbon atoms and a silicon atom-bonded alkoxy group within one molecule . Examples of the organic group with 3 or more carbon atoms include an epoxy group, an alkyl group, an aryl group, a vinyl group, a styryl group, a methacryl group, an acryl group, an amino group, an isocyanurate group, a ureide group, a mercapto group, an isocyanate group, and an acid anhydride , all of which have 3 or more carbon atoms . An example of the silane coupling agent is a silane compound such as octyl trimethoxysilane , octyl triethoxysilane , de cyl trimethoxysilane , de cyl triethoxysilane , dodecyl trimethoxysilane , dodecyl triethoxysilane , vinyltrimethoxysilane , 3-glycidoxypropyltrimethoxysilane , p- styryl trimethoxysilane , 3 -methacryl oxypropyl trimethoxysilane , 3 -acryl oxypropyl trimethoxysilane , 3- aminopropyl trimethoxysilane , 3 -aminopropyl triethoxysilane , tris- ( trimethoxysilylpropyl ) isocyanurate , 3- ureidopropyltrialkoxysilane , 3- mercaptopropylmethyldimethoxysilane , 3- isocyanatopropyltriethoxysilane , and 3-trimethoxysilylpropyl succinic anhydride . The silane compound may be a compound having no hydrosilyl group . One type thereof may be used alone , or two or more types thereof may be used in combination as appropriate . When the surface of the thermally conductive filler is treated with the above-mentioned silane coupling agent , the af finity with the silicone polymer can be improved, the viscosity of the composition can be decreased, and the filling properties of the thermally conductive filler can be improved . Therefore , when a larger amount of the thermally conductive filler is added, thermal conductivity can be improved .

[0072] The reaction inhibitor as the optional componenthas the ability to adj ust the curing rate of the addition reaction . Examples of the reaction inhibitor include an acetylene-based compound, hydrazines , triazoles , phosphines , and mercaptans . Any curing inhibitor conventionally known in the art as a compound having a curing inhibitory ef fect can be used . Examples of such compounds include a phosphorus- containing compound such as triphenylphosphine , a nitrogencontaining compound such as tributylamine , tetramethylethylenediamine , and benzotriazole , a sul fur- containing compound, an acetylene-based compound, compounds containing 2 or more alkenyl groups , a hydroperoxy compound, and a maleic acid derivative . S ilane and silicone compounds having an amino group may also be used .The blending amount of the reaction inhibitor may be an ef fective amount according to the desired curing temperature and curing time depending on the use application . Generally, the blending amount thereof is desirably in the range of 0 . 1 parts by mass to 15 parts by mass , preferably in the range of 0 . 2 parts by mass to 10 parts by mass , and more preferably in the range of 0 . 3 parts by mass to 5 parts by mass , relative to 100 parts by mass of the total amount of components (A) and (B ) . When the amount is less than 0 . 1 parts by mass , the addition reaction becomes too fast , and the curing reaction proceeds during the coating operation, which may deteriorate the workability . On the other hand, when the amount exceeds 10 parts by mass , the addition reaction is slowed down, and there is a possibility that pump-out occurs .

[0073] An organohydrogenpolysiloxane can be used as the optional cross-linking agent . The cross-linking agent forms a cured product by an addition reaction with an alkenyl group, and may have a hydrogen atom (hydrosilyl group ) bonded to at least one or more silicon atoms in a side chain in the molecule .The cross-linking agent preferably has three or morehydrosilyl groups within one molecule and may have at least one hydrosilyl group in a side chain in the molecule . The cross-linking agent is more preferably an organohydrogenpolysiloxane having 5 or more hydrosilyl groups , and may be those having 10 or more and 15 or less hydrosilyl groups . The organohydrogenpolysiloxane that serves as the cross-linking agent has at least two hydrosilyl groups in its side chain . The number of hydrosilyl groups at a molecular chain terminal may be zero or more and two or less , and is , from an economic perspective , preferably two . The molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures . The position of the silicon atom to which a hydrogen atom is bonded is not particularly limited, and may be at a molecular chain terminal , at a non-terminal molecular chain site ( in the middle of the molecular chain) , or in a side chain . Other conditions , the type of the organic group other than a hydrosilyl group, the bonding position, the degree of polymeri zation, the structure , and the like in the organohydrogenpolysiloxane are not particularly limited . Two or more types of organohydrogenpolysiloxanes may be used in combination .The cross-linking agent may be contained in an amount necessary to form a matrix containing the components (A) and (B ) by cross-linking . The blending amount of the cross-linking agent may be 0 . 1 parts by mass or more and 10 parts by mass or less , preferably 0 . 2 parts by mass or more and 6 parts by mass or less , and more preferably 0 . 4 parts by mass or more and 4 parts by mass or less , relative to 100 parts by mass of the total amount of the components (A) and (B ) .

[0074] The adhesion condensation catalyst as one of the optional components is an alkoxy compound that serves as a condensation catalyst , for example , an alkoxy compoundcontaining Ti or Zr.The blending amount of the adhesion condensation catalyst may be 0.1 parts by mass or more and 1.5 parts by mass or less, preferably 0.2 parts by mass or more and 1.2 parts by mass or less, and more preferably 0.3 parts by mass or more and 1.0 part by mass or less, relative to 100 parts by mass of the total amount of the components (A) and (B) .

[0075] Substrate:Here, the substrate may be at least one selected from glass, metals, ceramics, and resins.Examples of the preferable metal substrate to which the thermally conductive silicone composition is bonded include those made of aluminum, magnesium, iron, nickel, titanium, stainless steel, copper, lead, zinc, molybdenum, and silicon.Examples of the preferable ceramic substrate to which the thermally conductive silicone composition is bonded include those made of an oxide, a carbide, and a nitride, such as aluminum oxide, aluminum nitride, alumina zirconia, zirconium oxide, zinc oxide, barium titanate, lead zirconate titanate, beryllium oxide, silicon nitride, and silicon carbide.Examples of the preferable resin substrate to which the cured thermally conductive silicone composition is bonded include resin substrates made of a polyester, an epoxy resin, a polyamide, a polyimide, an ester-based resin, a polyacrylamide, an acrylonitrile-butadiene-styrene (ABS) resin, a styrene-based resin, a polypropylene, a polyacetal, an acrylic resin, a polycarbonate (PC) , a polyethylene terephthalate (PET) , a polybutylene terephthalate (PBT) , a polyether-ether ketone (PEEK) , a polymethyl methacrylate (PMMA) , and a silicone resin.In a case where the thermally conductive member obtained by curing the thermally conductive silicone composition is used as a gap filler for battery units, a battery unit housing, which is a substrate to be bonded, may have an ironsurface at least partially coated with a cationic electrodeposition coating on the substrate surface, and a heat sink may have an aluminum surface.The thermally conductive silicone composition is injected and cured to fill a space between the aluminum surface and the iron surface coated by cationic electrodeposition coating therewith to provide a gap filler.

[0076] The electric apparatus and the electronic apparatus are not particularly limited, and examples thereof include a mobile phone, a smart phone, a tablet computer, a smart watch, a computer, a semiconductor package substrate, an electronic circuit substrate, an LED package substrate, a sensor substrate, an imaging device substrate, a liquid crystal substrate, and an organic EL substrate.

[0077] Example:The present invention will be described using examples, but the present invention is not limited to the following examples. Note that the viscosity described herein refers to a value measured at 25°C and at a shear rate of 10 / s using a rotational viscometer (in accordance with JIS K 7117-2) .

[0078] A first liquid and a second liquid for each of Examples and Comparative Examples were produced. FIG. 1A is a table showing blending ratios of respective components of the first liquid and the second liquid of each of Examples 1 to 12, and FIG. IB is a table showing data of the amounts (unit: parts by mass) of respective components relative to the amount of the component (A) in the first liquid and the amounts (unit: parts by mass) of respective components relative to the total amount of the components (A) and (B) in the second liquid in each of Examples 1 to 12. FIG. 2A is a table showing blending ratios of respective components of each of a first liquid and a second liquid in each of Comparative Examples 1 to 8, and FIG. 2B is a table showing the amounts (unit: parts by mass) of respective components relative to the amount ofthe component (A) in the first liquid and the amounts (unit: parts by mass) of respective components relative to the total amount of the components (A) and (B) in the second liquid in each of Comparative Examples 1 to 8.

[0079] First liquid:A diorganopolysiloxane having an alkenyl group as the component (A) , a platinum-divinyltetramethyldisiloxane complex as the component (E) , hexadecyltrimethoxysilane as the optional silane coupling agent (hereinafter referred to as a "component (Fl)") , a condensation catalyst (hereinafter referred to as a "component (F4)") , and a pigment (hereinafter referred to as a "component (F5)") were respectively weighed and placed in a planetary mixer and kneaded at room temperature for 30 minutes.The component (A) is a linear dimethylpolysiloxane having one alkenyl group at each terminal and a viscosity of 120 mPa-s (hereinafter referred to as a "component (A-l)") .After that, a half of the blending amount of the component (C) and a half of the blending amount of the component (D) relative to the total amount of the composition were added thereto and the entirety was kneaded at room temperature for 15 minutes using the planetary mixer to prepare a first liquid.

[0080] Second liquid:The diorganopolysiloxane of the component (A-l) having an alkenyl group, which was the same as that in the first liquid, and a linear dimethylpolysiloxane having a viscosity of 1,000 mPa-s (hereinafter referred to as a "component (A-2)") as the component (A) ; a linear diorganopolysiloxane having one hydrogen atom at each terminal (two hydrogen atoms in total) and having a viscosity of 70 mPa-s (hydrogen content: 0.5 mmol / g) as the component (B) ; and, as optional components, an oligomer that was a hydrolyzate of tetraethoxysilane, the silane coupling agent (component (Fl) ) , a diorganosiloxanehaving 2 or more alkenyl groups and a viscosity of 50 mPa-s as a reaction inhibitor (hereinafter referred to as a "component (F2)") , and a cross-linking agent (hereinafter referred to as a "component (F3)") were respectively weighed and placed in a planetary mixer and kneaded at room temperature for 30 minutes .The silane coupling agent, the component (Fl) , was the same component as that in the first liquid.The cross-linking agent, the component (F3) , was dimethylpolysiloxane having 12 to 18 hydrogen atoms bonded to silicon atoms in side chains and having a viscosity of 200 mPa-s. After that, the component (C) and the component (D) that were the same first thermally conductive filler and the same second thermally conductive filler as those used in the first liquid were added thereto and kneaded at room temperature for 15 minutes using the planetary mixer to prepare a second liquid.The component (C) and the component (D) that were aluminum oxide or aluminum hydroxide described below, were subjected to a hydrophobizing treatment with a long-chain alkyl fatty acid as a surface treatment.

[0081] Method for measuring tensile shear bond stress: A thermally conductive silicone composition was sandwiched between an aluminum test piece and an iron test piece having a cationic electrodeposition coating such that the coating area was 25 mm in length x 25 mm in width and the thickness was 0.8 mm, and this composition was cured at a temperature of 23°C for 24 hours to obtain a test piece for a tensile shear bond test.Each test piece for the tensile shear bond test was subjected to a tensile shear bond test in accordance with JIS K6850 to obtain an S-S curve graph. In the S-S curve graph, the maximum stress value for each test piece in the tensile shear bond test was defined as the tensile shear bond stressof the cured product of the corresponding silicone composition .

[0082] Measurement method of thermal conductivity:The first liquid and the second liquid shown in each of Examples and Comparative Examples were weighed at a ratio of 1:1, mixed thoroughly with a stirrer, and then degassed with a vacuum pump. The mixture was press-molded into a columnar shape with a diameter of 30 mm and a height of 6 mm, and then was cured at 100°C for 60 minutes to produce a columnar cured product. The thermal conductivity of the cured product was measured by the hot disk method in accordance with ISO 22007-2 using a measuring apparatus named TPS-500 manufactured by Kyoto Electronics Manufacturing Co., Ltd. A sensor was sandwiched between the two columnar cured products produced as above, and the thermal conductivity was measured by the measuring apparatus .The thermal conductivity is preferably 2.0 W / m-K or higher .

[0083] Measurement method of viscosity:A viscosity of a sample (first liquid, second liquid, or composition) was measured at 25°C and at a shear rate of 10 / s with a gap of 0.5 mm using a rotational viscometer (in accordance with JIS K7117-2) .

[0084] Method of measuring Asker C hardness:The first liquid and the second liquid shown in each of Examples and Comparative Examples were weighed at a ratio of 1:1, mixed thoroughly with a stirrer, and then degassed with a vacuum pump. The mixture was press-molded into a columnar shape with a diameter of 30 mm and a height of 6 mm, and then was cured at 100°C for 60 minutes to produce a columnar cured product. The Asker C hardness was measured at a temperature of 23°C using a hardness meter (product name "ASKER CL-150LJ" manufactured by Kobunshi Keiki Co., Ltd.) in accordance withthe Asker C method of the Society of Rubber Industry andTechnology, Japan Standard (SRIS 0101) . Specifically, the damper height was adjusted so that the distance between the obtained cylindrical cured product and the pointer was 15 mm, and the damper falling speed was adjusted so that the time required for the pointer to reach the surface of the test specimen was 5 seconds. The maximum value when the pointer collided with the test specimen was taken as a measured value of the Asker C hardness. The measurement was performed three times using the hardness meter, and the average value of the measurement results was used as the Asker C hardness. In general, a smaller Asker C hardness indicates higher flexibility. The Asker C hardness of the cured product is preferably in the range of 50 or more and 70 or less.

[0085] Components (A) and (B) :Component (A-l) : a linear dimethylpolysiloxane having one alkenyl group at each terminal and a viscosity of 120 mPa-sComponent (A-2) : a linear dimethylpolysiloxane having at least one alkenyl group and a viscosity of 1,000 mPa-sComponent (B-l) : a linear diorganopolysiloxane having one hydrogen atom at each terminal (two hydrogen atoms in total) and a viscosity of 70 mPa-s

[0086] Component (Cl) :Component (Cl-1) : aluminum oxide that contains less than 300 ppm of hot water-extractable sodium oxide (Na20)Component (Cl-2) : aluminum oxide that contains less than 300 ppm of hot water-extractable sodium oxide (Na20)Component (Cl-3) : aluminum oxide that contains equal to or more than 300 ppm of hot water-extractable sodium oxide (Na20)

[0087] Component (C2) :Component (C2-1) : aluminum hydroxide that contains less than 700 ppm of hot water-extractable sodium oxide (Na20)Component (C2-2) : aluminum hydroxide that contains lessthan 700 ppm of hot water-extractable sodium oxide (Na20)Component (C2-3) : aluminum hydroxide that contains less than 700 ppm of hot water-extractable sodium oxide (Na20)Component (C2-4) : aluminum hydroxide that contains equal to or more than 700 ppm of hot water-extractable sodium oxide (Na20)Component (C2-5) : aluminum hydroxide that contains equal to or more than 700 ppm of hot water-extractable sodium oxide (Na20)

[0088] Component (D) :Component (Dl-1) : aluminum hydroxide that contains less than 700 ppm of hot water-extractable sodium oxide (Na20)Component (Dl-2) : aluminum hydroxide that contains less than 700 ppm of hot water-extractable sodium oxide (Na20)Component (Dl-3) : aluminum hydroxide that contains less than 700 ppm of hot water-extractable sodium oxide (Na20)Component (Dl-4) : aluminum hydroxide that contains less than 700 ppm of hot water-extractable sodium oxide (Na2O)Component (Dl-5) : aluminum hydroxide that contains less than 700 ppm of hot water-extractable sodium oxide (Na2O)Component (Dl-6) : aluminum hydroxide that contains equal to or more than 700 ppm of hot water-extractable sodium oxide (Na2O)Component (Dl-7) : aluminum hydroxide that contains equal to or more than 700 ppm of hot water-extractable sodium oxide (Na2O)

[0089] Component (E) and optional components:Component (E) : platinum-divinyltetramethyldisiloxane complexComponent (Fl) : silane coupling agent (hexade cyl trimethoxysilane )Component (F2) : reaction inhibitor (diorganosiloxane having 2 or more alkenyl groups and a viscosity of 50 mPa-s)Component (F3) : cross-linking agent (dimethylpolysiloxanehaving 12 to 18 hydrogen atoms bonded to silicon atoms in side chains and having a viscosity of 200 mPa-s)Component (F4) : alkoxy group-containing titanium chelate compoundComponent (F5) : pigment

[0090] Evaluation:FIG. 1C is a table showing the respective components in terms of their blending ratios and the respective measurement results in each of Examples 1 to 12, in the table where both the first liquid and the second liquid were gathered, and FIG. ID is a table showing the respective components in terms of parts by mass relative to the components (A) and (B) and the respective measurement results. FIG. 2C is a table showing the respective components in terms of their blending ratios and the respective measurement results in each of Comparative Examples 1 to 8, in the table where both the first liquid and the second liquid were gathered, and FIG. 2D is a table showing the respective components in terms of parts by mass relative to the components (A) and (B) and the respective measurement results.As the measurement results, the tensile shear bond stress (initial) , the rate of decrease in the tensile shear bond stress, the hardness (initial) , the rate of decrease in the hardness, the thermal conductivity, and the viscosity (when the first liquid and the second liquid before curing were mixed) were shown.In the measurement items, the following were evaluated as good results.Tensile shear bond stress (initial) : 0.1 MPa or more Rate of decrease in tensile shear bond stress: 30% or lessAsker C hardness (initial) : 50 to 70Rate of decrease in Asker C hardness: 20% or lessThermal conductivity: 2.0 W / m-k or moreViscosity : 50 to 200 mPa-s

[0091] Table 1 shows the particle diameter of the filler, the conditions of the concentration range of hot water- extractable sodium oxide (Na20) , and the evaluation results in Examples 1 to 12 , and Table 2 shows these in Comparative Examples 1 to 8 . Examples 1 to 12 were good in all of the evaluation items . On the other hand, in Comparative Examples 1 to 8 , both the rate of decrease in tensile shear bond stress and the rate of decrease in hardness were higher than the evaluation criteria . In Comparative Examples 7 and 8 , the viscosities were out of the evaluation criteria .

[0092] [Table 1]

[0093] [Table 2]

Claims

Claims

1. A thermally conductive silicone composition comprising : a component (A) that is a diorganopolysiloxane containing an alkenyl group bonded to a silicon atom; a component (B ) that is an organopolysiloxane having a hydrogen atom bonded to a silicon atom; a component ( C ) that is a first thermally conductive filler contained in an amount of 30 parts by mass or more and 220 parts by mass or less relative to 100 parts by mass of a total amount of the component (A) and the component (B ) , the first thermally conductive filler being at least one thermally conductive filler selected from the group consisting of aluminum oxide ( Cl ) that contains less than 300 ppm of hot water-extractable sodium oxide , as determined by atomic absorption spectrometry, and that has an average particle diameter of less than 5 m, and aluminum hydroxide ( C2 ) that contains less than 70 ppm of hot water-extractable sodium oxide , as determined by atomic absorption spectrometry, and that has an average particle diameter of less than 5 m; and a component ( D) that is a second thermally conductive filler contained in an amount of 400 parts by mass or more and 950 parts by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B ) , the second thermally conductive filler being an aluminum hydroxide filler that contains less than 70 ppm of hot water-extractable sodium oxide , as determined by atomic absorption spectrometry, and that has an average particle diameter of 5 pm or more and 100 pm or less ; and a component (E ) that is an addition reaction catalyst contained in an amount of 0 . 2 parts by mass or more and 1 . 0 part by mass or less relative to 100 parts by mass of the total amount of the component (A) and the component (B ) .

2. The thermally conductive silicone composition according to claim 1 , wherein a ratio SiH / SiVi as a ratio of the component (A) to the component (B ) falls within a range of 0 . 5 or more and 1 . 5 or less .

3. The thermally conductive silicone composition according to claim 1 , wherein the component (A) contains an organopolysiloxane having a viscosity, at 25°C, of 10 mPa-s or more and 7 , 000 mPa-s or less .

4. The thermally conductive silicone composition according to claim 1 , wherein the component (B ) contains an organopolysiloxane having two or more hydrogen atoms in one molecule and having a viscosity, at 25°C, of 10 mPa-s or more and 7 , 000 mPa-s or less .

5. The thermally conductive silicone composition according to claim 1 , comprising an adhesion condensation catalyst that is an alkoxy compound containing Ti or Zr .

6. The thermally conductive silicone composition according to claim 1 , wherein the thermally conductive silicone composition or a cured product thereof has a thermal conductivity of 2 . 0 W / m-k or more .

7. The thermally conductive silicone composition according to claim 1 , wherein a rate of decrease in tensile shear bond stress of a cured product of the thermally conductive silicone composition is 30% or less .

8. The thermally conductive silicone composition according to claim 1 , wherein a rate of decrease in hardness of a cured product of the thermally conductive silicone composition is 20% or less .

9. The thermally conductive silicone composition according to claim 1 , wherein the thermally conductive silicone composition is a two-liquid type thermally conductive silicone composition including a first liquid and a second liquid that are packaged separately from each other, and the first liquid and the second liquid are mixed at a time of use to produce the thermally conductive silicone composition .

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