JP2024087720A - Conductive silicone composition and method for producing the same, and adhesive and conductive silicone cured product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive silicone composition that produces a highly conductive cured product, even when only small amounts of carbon black are added.

SOLUTION: A conductive silicone composition comprises an addition-curable silicone composition with a post-curing loss modulus of 0.25 MPa or less: 100 pts.mass, and carbon black: 1-50 pts.wt.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a conductive silicone composition and its manufacturing method, as well as an adhesive and a conductive silicone cured product.

Addition-curing silicone compositions have traditionally been used in a wide range of applications, including potting materials, coating materials, adhesives, and molding materials, due to their excellent heat, weather, and cold resistance. Silicones are also widely used in applications where they are made conductive by blending conductive materials such as carbon black, metals, and conductive metal oxides with silicone, which is inherently insulating.

Carbon black is an inexpensive conductive filler that is widely used in antistatic materials, roll materials, contact materials, and the like. To impart high conductivity to an addition-curing silicone composition, it is generally necessary to incorporate more carbon black, but this also has undesirable effects such as a significant increase in viscosity and a decrease in curability and adhesion. Carbon black, which can exhibit conductivity in small amounts, in particular, has a highly developed structure that is prone to increase viscosity and decrease fluidity. In addition, carbon with a large specific surface area can inhibit the curing of addition-curing silicone compositions and impair the adhesive properties of adhesives by adsorbing adhesive-imparting components.

For these reasons, when using an addition-curing silicone composition as a conductive adhesive, it is desirable to incorporate as little carbon black as possible. One method known for achieving high conductivity with a small amount of carbon is to add nanocarbons such as graphene and carbon nanotubes (Patent Document 1), but this causes an extremely large increase in the viscosity of the composition, making it unsuitable for use as an adhesive that requires a liquid state. Another practical problem is that it is very expensive compared to carbon black.

In addition, a conductive silicone composition has been proposed that gives a cured product with high conductivity even with a small amount of carbon black, in which a specific amount of carbon black is filled into an addition-curable silicone containing a crosslinker with a specific structure (Patent Document 2).

JP 2013-245329 A JP 2022-137416 A

The present invention has been made in consideration of the above circumstances, and aims to provide a conductive silicone composition that gives a cured product with high electrical conductivity even when a small amount of carbon black is added.

In order to achieve the above object, the present invention provides
The present invention provides a conductive silicone composition comprising: 100 parts by mass of an addition-curable silicone composition having a loss modulus of elasticity of 0.25 MPa or less after curing; and 1 to 50 parts by weight of carbon black.

A conductive silicone composition specified in this way can be made to give a cured product with high electrical conductivity even with a small amount of carbon black added.

In this case, the addition-curable silicone composition is
(A) an organopolysiloxane having at least two groups having a hydrosilylation reactive carbon-carbon unsaturated bond in each molecule;
It is preferable that the composition contains: (B) an organohydrogenpolysiloxane having at least two SiH groups per molecule: the number of SiH groups in component (B) is in an amount such that there are 0.5 to 10.0 SiH groups per hydrosilylation reactive carbon-carbon unsaturated bond in component (A); and (C) a platinum group metal catalyst: the amount of platinum group metal contained in the addition-curable silicone composition is 0.01 to 500 ppm by mass.

By using such an addition-curing silicone composition, it is possible to more effectively produce a conductive silicone composition that gives a cured product with high electrical conductivity even with a small amount of carbon black added.

Furthermore, in this case, it is preferable that the component (B) is an organohydrogenpolysiloxane having an average structure represented by the following formula (1).
( ^R13SiO1 _{/ 2} ) _a ( _R12HSiO1 / _{2 ) b} (R1HSiO) _c ( ^R12SiO ) _d (HSiO3 ^/ ₂ ) _e ( ^R1SiO3 / ₂ ) _f (SiO4 _/ ² ) _g (1)
(In formula (1), each R ¹ may be the same or different, and is a substituted or unsubstituted monovalent hydrocarbon group that does not contain a hydrosilylation reactive carbon-carbon unsaturated bond. a, b, c, d, e, f, and g are numbers that satisfy a≧0, b≧0, c>0, d≧0, e≧0, f≧0, and g≧0, and 20<b+c+e<40 and a+b+c+d+e+f+g≦100. The order of arrangement of the siloxane units is arbitrary.)

By using such a compound as component (B) in a conductive silicone composition, it is possible to more effectively produce a conductive silicone composition that gives a cured product with high electrical conductivity even with a small amount of carbon black added.

The carbon black preferably has a BET specific surface area of 50 to 200 m ² /g and a DBP oil absorption of 100 to 280 ml/100 g.

Carbon black in this range of BET specific surface area has excellent electrical conductivity, is easy to blend with low-viscosity polysiloxane, and can suppress a decrease in adhesion due to adsorption of adhesive components. In addition, the use of carbon black in this range of DBP oil absorption results in a conductive silicone composition with better electrical conductivity and fluidity.

The present invention also provides an adhesive comprising any one of the conductive silicone compositions described above.

Even with a small amount of carbon black, such adhesives produce cured products with high electrical conductivity, making them adhesives that are free from the risk of increased viscosity or reduced curing and adhesive properties caused by carbon black.

The present invention also provides a conductive silicone cured product, which is a cured product of any of the above conductive silicone compositions.

Such conductive silicone cured products can have high electrical conductivity even with a small amount of carbon black.

In this case, it is preferable that the conductive silicone cured product of the present invention has a durometer type A hardness of 30 or more.

Such conductive silicone cured products have a sufficient degree of crosslinking and are easy to develop electrical conductivity.

The conductive silicone cured product of the present invention preferably has a volume resistivity of 1 to 50 Ω·cm.

Such a conductive silicone cured product will have sufficient conductivity.

The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of:
an addition-curable silicone composition having a loss modulus of 0.25 MPa or less after curing: 100 parts by mass;
preparing carbon black: 1 to 50 parts by weight;
and kneading the addition-curable silicone composition and the carbon black to produce a conductive silicone composition.

This method for producing a conductive silicone composition makes it possible to produce a conductive silicone composition that gives a cured product with high electrical conductivity even when a small amount of carbon black is added.

The conductive silicone composition of the present invention gives a cured product with high electrical conductivity even when a small amount of carbon black is blended, so there is no risk of an increase in viscosity or a decrease in curability or adhesion due to carbon black. The conductive silicone composition of the present invention, which has such properties, is useful as a conductive adhesive or conductive paste for bonding electronic components or elements to substrates. Furthermore, the method for producing the conductive silicone composition of the present invention is capable of producing such a conductive silicone composition.

The present invention is described in detail below, but is not limited to these.

As mentioned above, there was a need to develop a conductive silicone composition that would give a cured product with high electrical conductivity even with a small amount of carbon black added.

After extensive research into the above problems, the inventors discovered that a conductive silicone composition can be obtained by filling an addition-curing silicone composition with a specific amount of carbon black, and by using an addition-curing silicone composition that has a loss modulus of elasticity below a certain level when cured, a conductive silicone composition that gives a cured product with excellent electrical conductivity can be obtained, and thus completed the present invention.

That is, the present invention provides:
The conductive silicone composition comprises: 100 parts by mass of an addition-curable silicone composition having a loss modulus of elasticity after curing of 0.25 MPa or less; and 1 to 50 parts by weight of carbon black.

The addition-curable silicone composition used in the conductive silicone composition of the present invention preferably contains the following components (A) to (C).
(A) an organopolysiloxane having at least two groups having a hydrosilylation reactive carbon-carbon unsaturated bond in each molecule;
(B) an organohydrogenpolysiloxane having at least two SiH groups per molecule: an amount such that the number of SiH groups in component (B) is 0.5 to 10.0 per hydrosilylation reactive carbon-carbon unsaturated bond in component (A); and (C) a platinum group metal catalyst: an amount such that the content of the platinum group metal in the addition-curable silicone composition is 0.01 to 500 ppm by mass.

The components of the conductive silicone composition of the present invention are described in more detail below.

[Component (A)]
The above-mentioned component (A) is an organopolysiloxane having at least two groups containing hydrosilylation reactive carbon-carbon unsaturated bonds in each molecule.

As the component (A), for example, an organopolysiloxane represented by the following average formula (2) can be used.
( ^R33SiO1 _{/ 2} ⁾ _h (R2R32SiO1 _/2 ⁾ _i ( ^R2R3SiO _{) j} ( ^{R32SiO )} _k ( ^R2SiO3 _/2 ) _l ( ^R3SiO3/ ₂ ) _m ( _SiO4 / ₂ ) _n ... (2)

In formula (2), ^R2 is a group having a hydrosilylation reactive carbon-carbon unsaturated bond, and ^R3 is a substituted or unsubstituted monovalent hydrocarbon group that does not contain a hydrosilylation reactive carbon-carbon unsaturated bond and may be the same or different, where h, i, j, k, l, m, and n are numbers that satisfy h≧0, i≧0, j≧0, k≧0, l≧0, m≧0, and n≧0, with the proviso that i+j+l>0 and h+i+j+k+l+m+n=1. The order of arrangement of the siloxane units is arbitrary.

Examples of the group having a hydrosilylation reactive carbon-carbon unsaturated bond for ^R2 include a vinyl group, an allyl group, a propenyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a dodecenyl group, a norbornyl group, an isonorbornyl group, an acryloyl group, and a methacryloyl group. An alkenyl group having 2 to 10 carbon atoms, preferably 2 to 6 carbon atoms, is particularly preferably a vinyl group.

The organopolysiloxane of component (A) contains at least two, and preferably two to six, groups with hydrosilylation-reactive carbon-carbon unsaturated bonds per molecule. These groups may be located either at the molecular chain terminals or molecular side chains (non-terminal) of component (A), or may be located at both.

^R3 is not particularly limited as long as it does not contain a hydrosilylation reactive carbon-carbon unsaturated bond, and examples thereof include unsubstituted or halogen-substituted monovalent hydrocarbon groups preferably having 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 8 carbon atoms, such as alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, s-butyl, isobutyl, t-butyl, n-pentyl, neopentyl, isopentyl, s-pentyl, 2-pentyl, hexyl, heptyl, octyl, and 2-ethylhexyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; aryl groups such as phenyl, tolyl, xylyl, mesityl, and naphthyl; aralkyl groups such as benzyl and phenethyl; and halogenated alkyl groups such as chloromethyl, 3-chloropropyl, trifluoromethyl, and 3,3,3-trifluoropropyl. Methyl is particularly preferred.

Specific examples of component (A) include dimethylsiloxane capped at both ends with dimethylvinylsiloxy groups, methylvinylsiloxane capped at both ends with trimethylsiloxy groups, dimethylvinylsiloxane-cyclic methylvinylsiloxane copolymer, cyclic methylvinylsiloxane, dimethylsiloxane-cyclic diphenylsiloxane copolymer capped at both ends with dimethylvinylsiloxy groups, dimethylsiloxane-cyclic methylphenylsiloxane copolymer capped at both ends with dimethylvinylsiloxy groups, dimethylsiloxane capped at both ends with methylphenylvinylsiloxy groups, diphenylsiloxane capped at both ends with methylphenylvinylsiloxy groups, methylphenylsiloxane capped at both ends with methylphenylvinylsiloxy groups, dimethylsiloxane-cyclic diphenylsiloxane copolymer capped at both ends with methylphenylvinylsiloxy groups, (CH ₂ ═CH)(CH ₃ ) ₂ SiO _1/2 units and (CH ₃ ) ₃ SiO _1/2 units and SiO _4/2 units, etc. The component (A) may be used alone or in combination of two or more types.

The kinetic viscosity of component (A) is not particularly limited, but is preferably in the range of 10 to 100,000 mm ² /s, and more preferably 100 to 10,000 mm ² /s. The kinetic viscosity can be, for example, a value measured at 25°C using an Ubbelohde viscometer or a Cannon-Fenske viscometer. If the viscosity is in this range, the composition will have excellent handleability.

[Component (B)]
The component (B) in the conductive silicone composition of the present invention is a crosslinking agent that crosslinks with the hydrosilylation-reactive carbon-carbon unsaturated bonds contained in the component (A) through a hydrosilylation reaction. The component (B) is an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms (SiH groups) per molecule, preferably more than 20 and less than 40 on average, more preferably more than 30 and less than 40 on average. When the number of SiH groups per molecule is within this range, the crosslinking points are sufficiently dispersed, and a cured product having good hardness and electrical conductivity can be obtained. If the number of SiH groups per molecule is less than two on average, the curability of the composition may be insufficient.

As the component (B), it is preferable to use an organohydrogenpolysiloxane having an average structure represented by the following formula (1).
( ^R13SiO1 _{/ 2} ) _a ( _{R12HSiO1 /2 ) b} (R1HSiO) _c ( ^R12SiO ) _d (HSiO3 ^/ ₂ ) _e ( ^R1SiO3/ ₂ ) _f (SiO4 _/ ² ) _g ... (1)

In formula (1), each R ¹ may be the same or different, and is a substituted or unsubstituted monovalent hydrocarbon group that does not contain a hydrosilylation reactive carbon-carbon unsaturated bond. Here, a, b, c, d, e, f, and g are numbers that satisfy a≧0, b≧0, c>0, d≧0, e≧0, f≧0, and g≧0. Also, 20<b+c+e<40, and preferably 30<b+c+e<40. Also, a+b+c+d+e+f+g is 100 or less, and preferably 50 or less. Also, the order of arrangement of each siloxane unit is arbitrary.

Specific examples of ^R1 include the same groups as ^R3 above, preferably an unsubstituted or halogen-substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 8 carbon atoms, and a methyl group is particularly preferred.

When the organohydrogenpolysiloxane of component (B) has a linear structure, the SiH groups may be located either at the molecular chain terminals or at the molecular chain side chains (non-terminal), or at both.

Specific examples of the (B) component include dimethylsiloxanes blocked at both ends with dimethylhydrogensiloxy groups, methylhydrogensiloxane-dimethylsiloxane copolymers blocked at both ends with trimethylsiloxy groups, dimethylsiloxane-cyclic methylhydrogensiloxane copolymers blocked at both ends with dimethylhydrogensiloxane, cyclic methylhydrogensiloxanes, methylphenylhydrogensiloxane-dimethylsiloxane cyclic copolymers blocked at both ends with dimethylphenylsiloxy groups, diphenylsiloxane-methylhydrogensiloxane copolymers blocked at both ends with dimethylphenylsiloxy groups, diphenylpolysiloxanes blocked at both ends with methylphenylhydrogensiloxy groups, dimethylsiloxane-diphenylsiloxane-methylhydrogensiloxane copolymers blocked at both ends with methylphenylhydrogensiloxy groups, and dimethylsiloxane-diphenylsiloxane-methylhydrogensiloxane copolymers blocked at both ends with diphenylhydrogensiloxy groups.

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

The kinetic viscosity of component (B) is not particularly limited, but is preferably in the range of 10 to 1,000 mm ² /s, and more preferably 10 to 100 mm ² /s. The kinetic viscosity can be, for example, a value measured at 25°C using an Ubbelohde viscometer or a Cannon-Fenske viscometer. If the viscosity is in this range, the composition will have excellent handleability.

The amount of component (B) to be blended is such that the number of SiH groups in component (B) per hydrosilylation reactive carbon-carbon unsaturated bond in component (A) is within the range of 0.5 to 10.0, preferably 1.0 to 5.0. If the amount of component (B) is too small, the curing properties may be insufficient, and if the amount is too large, the physical properties of the cured product may deteriorate.

[Component (C)]
Component (C) in the conductive silicone composition of the present invention is a platinum group metal catalyst which acts as a hydrosilylation reaction catalyst for promoting the addition reaction between the hydrosilylation-reactive carbon-carbon unsaturated bonds in component (A) above and the SiH groups in component (B).

The platinum group metal catalyst is not particularly limited as long as it accelerates the addition reaction, and a known platinum group metal catalyst can be used. Specifically, platinum group metals such as platinum (including platinum black ₎ , rhodium, and _{palladium are} used as the catalyst; _{H2PtCl4.nH2O , H2PtCl6.nH2O , NaHPtCl6.nH2O , KHPtCl6.nH2O , Na2PtCl6.nH2O} , _{K2PtCl4.nH2O , PtCl4.nH2O , PtCl2 , Na2HPtCl4.nH2O} , _{and the like} . O (wherein n in the chemical formula is an integer of 0 to 6, preferably 0 or 6); alcohol-modified chloroplatinic acid; complexes of chloroplatinic acid and olefins; catalysts in which platinum group metals such as platinum black and palladium are supported on carriers such as alumina, silica, and carbon; rhodium-olefin complexes; Wilkinson's catalyst [chlorotris(triphenylphosphine)rhodium]; complexes of platinum chloride, chloroplatinic acid or chloroplatinate with vinyl group-containing siloxanes, and the like. These platinum group metal catalysts may be used alone or in combination of two or more. Among these platinum group metal catalysts, platinum and platinum compounds are preferred.

The amount of component (C) is preferably in the range of 0.01 to 500 ppm by mass, more preferably 0.05 to 100 ppm by mass, and even more preferably 0.05 to 50 ppm by mass, calculated as the platinum group metal in component (C) relative to the total mass of the conductive silicone composition of the present invention. If the amount of component C) is within the above range, the reaction can be sufficiently promoted and there is no need to add a large amount of a reaction inhibitor, which is preferable.

The addition-curable silicone composition used in the conductive silicone composition of the present invention has a loss modulus of 0.25 MPa or less when cured. If the loss modulus of the addition-curable silicone composition after curing is greater than 0.25 MPa, the carbon black network is not sufficiently fixed in the conductive silicone cured product after curing the conductive silicone composition, making it difficult to obtain good conductivity.

The loss modulus of the cured product after curing of the addition-curing silicone composition can be measured, for example, as follows. During curing, the cured product is molded into a sheet with a thickness of 2 mm. The sheet is then cut into a size of 10 cm length x 1 cm width. The loss modulus of this 2 mm sheet is then measured in tension mode using a Hitachi High-Tech Science viscoelasticity measuring device DMA7100. In this measurement, the measured value at 23°C and a frequency of 1 Hz can be used as the loss modulus of the addition-curing silicone composition after curing that constitutes the conductive silicone composition of the present invention.

[Carbon black]
The carbon black in the conductive silicone composition of the present invention is a component that imparts electrical conductivity to the silicone composition and its cured product.

Carbon black includes acetylene black, furnace black, ketjen black, channel black, etc., depending on the manufacturing method. Of these, acetylene black is suitable because it contains few impurities and has high conductivity due to its developed structure. These carbon blacks may be used alone or in combination of two or more types.

The BET specific surface area of the carbon black is preferably 50 to 200 m ² /g, and more preferably 50 to 100 m ² /g. Carbon black with a large BET specific surface area is likely to exhibit electrical conductivity in small amounts but has poor dispersibility, but carbon black with a BET specific surface area in this range is excellent in electrical conductivity, can be easily blended with low-viscosity polysiloxane, and can suppress a decrease in adhesiveness due to adsorption of adhesive components. The BET specific surface area of carbon black can be measured in accordance with JIS K6217.

The DBP (dibutyl phthalate) oil absorption of carbon black is preferably 100 to 280 ml/100 g, and more preferably 120 to 200 ml/100 g. Carbon black with a high DBP oil absorption has a developed structure and is prone to exhibiting electrical conductivity with a small amount, but has poor fluidity. Within this range, however, a composition with better electrical conductivity and fluidity will be obtained. The DBP oil absorption of carbon black can be measured in accordance with JIS K6217.

The amount of carbon black to be blended is 1 to 50 parts by weight, preferably 5 to 30 parts by weight, and more preferably 10 to 20 parts by weight, per 100 parts by weight of the addition-curable silicone composition. If the amount of carbon black blended is too high, this may result in a significant increase in viscosity and a decrease in adhesion, and if the amount of carbon black blended is too low, the conductivity will be insufficient.

[Other ingredients]
If necessary, the conductive silicone composition of the present invention may contain components other than the above-mentioned components (A) to (C) and carbon black. Specific examples of such components include adhesion promoters, reaction regulators, reinforcing materials, fillers, dispersants, colorants, heat resistance promoters, and flame retardant promoters.

<Adhesive assistant>
An adhesive aid may be added to the conductive silicone composition of the present invention in order to improve adhesion to resins.As the adhesive aid, from the viewpoint of imparting self-adhesiveness to the conductive silicone composition of the present invention, which is of the addition reaction curing type, an organosilicon compound such as silane or siloxane containing a functional group that imparts adhesiveness, or a non-silicone organic compound, etc., is used.

Specific examples of functional groups that impart adhesive properties include polymerizable groups having a carbon-carbon unsaturated bond bonded to a silicon atom, epoxy groups bonded to a silicon atom via a carbon atom (e.g., γ-glycidoxypropyl group, β-(3,4-epoxycyclohexyl)ethyl group, etc.), and alkoxysilyl groups (e.g., trimethoxysilyl group, triethoxysilyl group, methyldimethoxysilyl group, etc.).

The adhesive aid may contain SiH groups, and it is preferable that the number of SiH groups contained per molecule is 2 or more and 20 or less.

An example of a compound containing at least one of the above functional groups and an organosiloxane skeleton is represented by the following structural formula. In the formula, Me represents a methyl group.

Examples of non-silicone organic compounds include organic acid allyl ester compounds and allyl ether compounds represented by the following structural formulas.

Other non-silicone adhesive aids include organotitanium compounds, organozirconium compounds, organoaluminum compounds, etc.

Examples of organic titanium compounds include tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, titanium tetraacetylacetonate, and diisopropoxytitanium bis(acetylacetonate).

Examples of organic zirconium compounds include zirconium tetraethoxide, zirconium propoxide, zirconium butoxide, zirconium acetylacetonate, and bisacetatooxozirconium.

Examples of organoaluminum compounds include aluminum ethoxide, aluminum propoxide, aluminum butoxide, aluminum isopropoxide, and aluminum acetylacetonate.

<Reaction control agent>
The composition of the present invention may contain a known reaction inhibitor that has a reaction inhibitor effect on the addition reaction catalyst of component (C). Examples of reaction inhibitors include phosphorus-containing compounds such as triphenylphosphine, nitrogen-containing compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole, sulfur-containing compounds, acetylene compounds, hydroperoxy compounds, and maleic acid derivatives.

<Reinforcing materials/fillers>
The conductive silicone composition of the present invention may contain finely powdered silica such as fumed silica (dry silica) or precipitated silica (wet silica) as a reinforcing material to improve tensile strength, elongation, tear strength, etc. Finely powdered silica may be used as is, but in order to impart good fluidity to the composition, it is preferable to use silica treated with an organosilicon compound such as methylchlorosilanes such as trimethylchlorosilane, dimethyldichlorosilane, and methyltrichlorosilane, dimethylpolysiloxane, hexamethyldisilazane, divinyltetramethyldisilazane, and hexaorganodisilazanes such as dimethyltetravinyldisilazane. The reinforcing silica may be used alone or in combination of two or more kinds.

In addition, inorganic fillers such as crystalline silica, diatomaceous earth, aluminum oxide, and calcium carbonate may be used as known fillers. In addition to metals such as Cu, Ni, Ag, Al, and alloys thereof, various conductive fillers such as metal-coated particles in which a metal film is formed on various insulating particles and conductive metal oxides may also be used in combination.

The conductive silicone composition of the present invention can be a one-part type in which components (A) to (C), carbon black and other components are premixed, a two-part type in which each component is optionally divided into two parts and mixed before use, or other multi-component systems.

[glue]
The conductive silicone composition of the present invention can be used as an adhesive. Even with a small amount of carbon black blended, such an adhesive gives a cured product with high electrical conductivity, and therefore can be an adhesive that is free from the risk of increased viscosity or reduced curability and adhesiveness caused by carbon black.

[Conductive silicone cured product]
The present invention provides a conductive silicone cured product, which is a cured product of the above-mentioned conductive silicone composition.

The hardness of the conductive silicone cured product of the present invention is preferably 30 or more, more preferably 35 or more, in terms of durometer type A hardness as specified in JIS K6253-3:2012. Such a conductive silicone cured product has a sufficient degree of crosslinking in the cured product, and is likely to exhibit electrical conductivity.

The conductive silicone cured product of the present invention preferably has a volume resistivity of 1 to 50 Ω·cm. Such a conductive silicone cured product will have sufficient conductivity.

[Method of producing conductive silicone composition]
The conductive silicone composition can be produced by the following method. First, an addition-curable silicone composition having a loss modulus of 0.25 MPa or less after curing and carbon black are prepared (step S11). At this time, the carbon black is prepared in an amount of 1 to 50 parts by weight per 100 parts by mass of the addition-curable silicone composition. An addition-curable silicone composition having a loss modulus of 0.25 MPa or less after curing can be easily selected by a person skilled in the art, for example, by an experiment in which an addition-curable silicone composition is actually cured, and can be used in the method for producing the conductive silicone composition of the present invention.

More specifically, for example, the above components (A) to (C) are mixed to prepare an addition-curable silicone composition, which is then actually cured, so that the loss modulus after curing can be measured. The mixing ratio of the above components (A) to (C) can be adjusted so that the loss modulus after curing is 0.25 MPa or less, and an addition-curable silicone composition can be prepared.

Next, the addition-curable silicone composition and the carbon black are kneaded to produce a conductive silicone composition (step S12). In this way, a conductive silicone composition can be produced.

The present invention will be explained in more detail below with reference to Preparation Examples, Comparative Preparation Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. The kinetic viscosity at 25°C was measured using an Ubbelohde viscometer or a Cannon-Fenske viscometer. The BET specific surface area and DBP oil absorption of carbon black were measured in accordance with JIS K6217.

[Preparation Examples 1 and 2, Comparative Preparation Examples 1 to 3]
An addition-curable silicone composition was obtained by kneading the following components (A) to (C), component d-1, and component e-1 in the amounts shown in Table 1 using a planetary mixer, and then processing once with a three-roll mill. The numerical values for each component in Table 1 indicate parts by mass.

[Component (A)]
a-1: Dimethylpolysiloxane capped at both ends with dimethylvinylsilyl groups (kinematic viscosity at 25° C.: 10,000 mm ² /s)

ｂ－２：平均構造が下記式（４）で表されるオルガノハイドロジェンポリシロキサン

（式中、括弧内のシロキサン単位の配列順は不定である。） [Component (B)]
b-1: Organohydrogenpolysiloxane having an average structure represented by the following formula (3):

b-2: Organohydrogenpolysiloxane having an average structure represented by the following formula (4):

(In the formula, the order of the siloxane units in parentheses is not specified.)

[Component (C)]
c-1: A solution of a reaction product of hexachloroplatinic acid and 1,3-divinyltetramethyldisiloxane in dimethylpolysiloxane (viscosity 600 mPa·s) (platinum concentration 1.0% by mass)

[Other ingredients]
d-1: 1-ethynyl-1-methyldecylcarbinol (reaction regulator)
e-1: Hydrophobically treated fine silica powder (reinforcement material) having a BET specific surface area of 130 m ² /g

[Loss modulus]
The obtained addition curing silicone composition was press molded into a test sheet. After heating at 120°C/10 minutes under a molding pressure of 2 MPa, post curing at 120°C/50 minutes was performed, and the loss modulus of the obtained 2 mm thick sheet was measured in tension mode using a Hitachi High-Tech Science viscoelasticity measuring device DMA7100. The measured values at 23°C and 1 Hz are shown in Table 1.

[Examples 1 and 2, Comparative Examples 1 to 3]
A conductive silicone composition was prepared by mixing 100 parts by mass of the addition-curable silicone composition obtained in Preparation Examples 1 and 2, and Comparative Preparation Examples 1 to 3 above, and 12.4 parts by mass of carbon black (ENSACO 260G, manufactured by IMERYS, BET specific surface area: 70 ^m2 /g, DBP oil absorption: 190 ml/100 g) using a planetary mixer.

The obtained conductive silicone composition was used to prepare a test sheet by press molding. After heating at 120°C for 10 minutes at a molding pressure of 2 MPa, the sheet was post-cured at 120°C for 50 minutes, and the obtained sheet was evaluated as follows. The results are shown in Table 2.

[Durometer A hardness]
Durometer A hardness was measured in accordance with JIS K6253-3:2012.

[Volume resistivity]
The volume resistivity was measured by the parallel terminal electrode method specified in JIS K6271-2:2015.

The results in Table 2 show that the sheets obtained by curing the conductive silicone composition of the present invention (Examples 1 and 2) have a lower volume resistivity and are more conductive than the sheets obtained using base materials with relatively high loss modulus of the cured product (Comparative Examples 1 to 3).

The present specification includes the following aspects.
[1]: An electrically conductive silicone composition comprising: 100 parts by mass of an addition-curable silicone composition having a loss modulus of 0.25 MPa or less after curing; and 1 to 50 parts by weight of carbon black.
[2]: The addition-curable silicone composition is
(A) an organopolysiloxane having at least two groups having a hydrosilylation reactive carbon-carbon unsaturated bond in each molecule;
The conductive silicone composition of item [1] above, comprising: (B) an organohydrogenpolysiloxane having at least two SiH groups per molecule: the number of SiH groups in component (B) is 0.5 to 10.0 per hydrosilylation reactive carbon-carbon unsaturated bond in component (A); and (C) a platinum group metal catalyst: the content of the platinum group metal in the addition-curable silicone composition is 0.01 to 500 ppm by mass.
[3]: The conductive silicone composition of the above [2], wherein the component (B) is an organohydrogenpolysiloxane having an average structure represented by the following formula (1):
( ^R13SiO1 _{/ 2} ) _a ( _R12HSiO1 / _{2 ) b} (R1HSiO) _c ( ^R12SiO ) _d (HSiO3 ^/ ₂ ) _e ( ^R1SiO3 / ₂ ) _f (SiO4 _/ ² ) _g (1)
(In formula (1), each R ¹ may be the same or different, and is a substituted or unsubstituted monovalent hydrocarbon group that does not contain a hydrosilylation reactive carbon-carbon unsaturated bond. a, b, c, d, e, f, and g are numbers that satisfy a≧0, b≧0, c>0, d≧0, e≧0, f≧0, and g≧0, and 20<b+c+e<40 and a+b+c+d+e+f+g≦100. The order of arrangement of the siloxane units is arbitrary.)
[4]: The conductive silicone composition of any one of the above [1] to [3], wherein the carbon black has a BET specific surface area of 50 to 200 m ² /g and a DBP oil absorption of 100 to 280 ml/100 g.
[5]: An adhesive comprising the conductive silicone composition according to any one of [1] to [4] above.
[6]: A conductive silicone cured product, which is a cured product of the conductive silicone composition according to any one of [1] to [4] above.
[7]: The conductive silicone cured product according to the above [6], having a durometer type A hardness of 30 or more.
[8]: The conductive silicone cured product according to the above [6] or [7], having a volume resistivity of 1 to 50 Ω·cm.
[9]: 100 parts by mass of an addition-curable silicone composition having a loss modulus of 0.25 MPa or less after curing;
preparing carbon black: 1 to 50 parts by weight;
and kneading the addition-curable silicone composition and the carbon black to produce a conductive silicone composition.

The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention.

Claims (9)

An electrically conductive silicone composition comprising: 100 parts by mass of an addition-curable silicone composition having a loss modulus of elasticity of 0.25 MPa or less after curing; and 1 to 50 parts by weight of carbon black. The addition-curable silicone composition is
(A) an organopolysiloxane having at least two groups having a hydrosilylation reactive carbon-carbon unsaturated bond in each molecule;
2. The conductive silicone composition according to claim 1, comprising: (B) an organohydrogenpolysiloxane having at least two SiH groups per molecule: the number of SiH groups in component (B) is in an amount such that 0.5 to 10.0 groups per hydrosilylation reactive carbon-carbon unsaturated bond in component (A); and (C) a platinum group metal catalyst: the content of the platinum group metal in the addition-curable silicone composition is in an amount of 0.01 to 500 ppm by mass. 3. The conductive silicone composition according to claim 2, wherein the component (B) is an organohydrogenpolysiloxane having an average structure represented by the following formula (1):
( ^R13SiO1 _{/ 2} ) _a ( _R12HSiO1 / _{2 ) b} (R1HSiO) _c ( ^R12SiO ) _d (HSiO3 ^/ ₂ ) _e ( ^R1SiO3/ ₂ ) _f (SiO4 _/2 ⁾ _g (1)
(In formula (1), each R ¹ may be the same or different, and is a substituted or unsubstituted monovalent hydrocarbon group that does not contain a hydrosilylation reactive carbon-carbon unsaturated bond. a, b, c, d, e, f, and g are numbers that satisfy a≧0, b≧0, c>0, d≧0, e≧0, f≧0, and g≧0, and 20<b+c+e<40 and a+b+c+d+e+f+g≦100. The order of arrangement of the siloxane units is arbitrary.) 2. The conductive silicone composition according to claim 1, wherein the carbon black has a BET specific surface area of 50 to 200 m ² /g and a DBP oil absorption of 100 to 280 ml/100 g. An adhesive comprising the conductive silicone composition according to any one of claims 1 to 4. A conductive silicone cured product, which is a cured product of the conductive silicone composition according to any one of claims 1 to 4. The conductive silicone cured product according to claim 6, characterized in that it has a durometer type A hardness of 30 or more. The conductive silicone cured product according to claim 7, characterized in that it has a volume resistivity of 1 to 50 Ω·cm. an addition-curable silicone composition having a loss modulus of 0.25 MPa or less after curing: 100 parts by mass;
preparing carbon black: 1 to 50 parts by weight;
and kneading the addition-curable silicone composition and the carbon black to produce a conductive silicone composition.