WO2015098072A1

WO2015098072A1 - Curable organopolysiloxane composition, member for transducers

Info

Publication number: WO2015098072A1
Application number: PCT/JP2014/006358
Authority: WO
Inventors: Takuya Ogawa; Sawako Inagaki
Original assignee: Dow Corning Toray Co., Ltd.
Priority date: 2013-12-27
Filing date: 2014-12-20
Publication date: 2015-07-02
Also published as: TW201533167A

Abstract

To provide a curable organopolysiloxane composition having excellent mechanical characteristics and/or electrical characteristics, and particularly one capable of producing a silicone elastomer cured product capable of being used as a member for transducers. A curable organopolysiloxane composition comprising an organopolysiloxane and at least one type of inorganic microparticles having an average primary particle diameter of not less than 50 nm, wherein the mass fraction of monovalent aromatic hydrocarbon groups having from 6 to 10 carbons (Z) in the total of organopolysiloxanes is not less than 0.2% by mass and not greater than 50% by mass, and the mass fraction of straight-chain organopolysiloxanes having a certain chain length range and a group capable of a curing reaction (W) in the total of organopolysiloxanes is not less than 50% by mass.

Description

CURABLE ORGANOPOLYSILOXANE COMPOSITION, MEMBER FOR TRANSDUCERS

The present invention relates to a curable organopolysiloxane composition capable of use with advantage in electrical and/or electronics applications, especially in transducers. In particular, the present invention provides a curable organopolysiloxane composition of which the organopolysiloxane cured product formed by curing can be advantageously used as an electrically active silicone elastomer material capable of use as a dielectric layer or electrode layer of a transducer. The present invention particularly relates to a curable organopolysiloxane composition of which the organopolysiloxane cured product has electrical characteristics and mechanical characteristics suitable for a material used as a dielectric material, and more particularly for use as a dielectric layer of a transducer. The present invention further relates to a production method of an electrically active polymer material formed using a curable organopolysiloxane composition, and to a member for transducers containing this electrically active polymer material. Priority is claimed on Japanese Patent Application No.2013-272971, filed on December 27, 2013, the content of which is incorporated herein by reference.

A.G. Benjanariu, et al., indicated that dielectric polymers are potential materials for artificial muscles (A.G. Benjanariu, et al., "New elastomeric silicone based networks applicable as electroactive systems," Proc. of SPIE vol. 7976 79762V-1 to 79762V-8 (2011)). Here, they showed the physical characteristics of a material having a unimodal or bimodal network formed with an addition-curable silicone rubber. To form this silicone rubber, a linear chain poly(dimethylsiloxane) (PDMS) polymer having vinyl groups is crosslinked using a short chain organohydrogensiloxane having 4 silicon-bonded hydrogen atoms as the crosslinking agent. Moreover, in B. Kussmaul et al., Actuator 2012, 13th International Conference on New Actuators, Bremen, Germany, 18-20 June 2012, pp. 374 to 378, there is mention of an actuator in which an organopolydimethylsiloxane that has been chemically modified by bonding a group functioning as an electrical dipole to polydimethylsiloxane using a crosslinking agent is sandwiched between electrodes as a dielectric elastomer actuator material.

However, no specific composition is disclosed for the curable organopolysiloxane composition in either of the aforementioned references, and furthermore, in practice, the physical properties of the curable organopolysiloxane compositions are insufficient for materials for various types of transducers in industrial use. Thus an electrically active polymer material is needed that achieves both mechanical characteristics and electrical characteristics capable of being satisfactory in actual use as a material for various types of transducers. In particular, there is strong need for a curable organopolysiloxane composition that cures and provides an electrically active polymer material having excellent physical characteristics.

On the other hand, blending inorganic microparticles such as thermally conductive filler, fluorescent filler and reinforcing filler in a curable organopolysiloxane composition in electrical and/or electronic applications is well known. For example, Patent Documents 1 to 3 disclose addition-curable organopolysiloxanes having a phenyl group-containing siloxane and describe that inorganic microparticles can be added.

However, these addition-curable organopolysiloxanes are sealants lacking rubber elasticity, and there is no description whatsoever regarding a curable organopolysiloxane composition that provides an elastic body having tensile breaking elongation of not less than 200%. Furthermore, these documents neither describe nor suggest providing rubber elasticity or adding inorganic microparticles, particularly dielectric inorganic microparticles, to a curable siloxane matrix having a prescribed high aromatic content.

Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-159670A
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2010-084118A
Patent Document 3: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2012-507582A

Non-patent Document 1: "New elastomeric silicone based networks applicable as electroactive systems," Proc. of SPIE vol. 7976 79762V-1 to 79762V-8 (2011)
Non-patent Document 2: Actuator 2012, 13th International Conference on New Actuators, Bremen, Germany, 18-20 June 2012, pp. 374 to 378

The present invention solves the problems of conventional curable polyorganosiloxane compositions, and an object thereof is to provide a curable organopolysiloxane composition having excellent mechanical characteristics and/or electrical characteristics, and particularly having capability of producing a silicone elastomer cured product capable of being used as a member for transducers.

Another object of the present invention is to provide a curable organopolysiloxane composition capable of realizing a high energy density by providing excellent mechanical characteristics and/or electrical characteristics, and particularly a high specific dielectric constant, high dielectric breakdown strength, and low Young's modulus; able to achieve durability and a practical displacement amount due to excellent mechanical strength (i.e., tensile strength, tear strength, elongation, and the like) when used as a dielectric layer of a transducer; and able to produce a cured product capable of use as a material for use in transducers. Furthermore, various types of fillers (including fillers that have been surface-treated) may be blended with the curable organopolysiloxane composition of the present invention in order to attain desired electrical characteristics, and the curable organopolysiloxane composition of the present invention may comprise a mold release additive in order to prevent breakage when molded into a thin sheet, and also may comprise an additive for improvement of dielectric breakdown characteristics.

Other objects of the present invention are to provide a production method of the curable organopolysiloxane composition, to provide a curable silicone elastomer material capable of use as an electrically active polymer material for use in transducers, to provide a method of production for such a curable silicone elastomer material, and to provide various types of transducers using the curable silicone elastomer material.

The object of the present invention is achieved by
a curable organopolysiloxane composition comprising an organopolysiloxane represented by formula (I) below:
R^a _aR^b _bSiO_(4-a-b)/2 (I)
(wherein R^a is a monovalent aromatic hydrocarbon group having from 6 to 10 carbons, and
R^b is at least one type of monovalent functional group (however, R^b is a group other than a monovalent aromatic hydrocarbon group having from 6 to 10 carbons), wherein at least part of R^b is a group capable of a curing reaction, and 0 < a, 0 < b, 1.9 < a+b < 2.1), and
one or more types of inorganic microparticles having an average primary particle diameter of not less than 50 nm,
wherein,
the mass fraction of the monovalent aromatic hydrocarbon groups having from 6 to 10 carbons (Z) in the total of organopolysiloxanes is not less than 0.2% by mass and not greater than 50% by mass,
and
the mass fraction of the straight-chain organopolysiloxanes represented by formula (II) below (W) in the total of organopolysiloxanes is not less than 50% by mass:
R¹R² ₂Si(OSiR³R⁴)_n(OsiR³R¹)_mOsiR¹R² ₂ (II)
(wherein R¹ is a group capable of a curing reaction, R², R³, and R⁴ represent each independently, the same or different, a hydrogen atom, monovalent aliphatic hydrocarbon groups having from 1 to 10 carbons, and monovalent aromatic hydrocarbon groups having from 6 to 10 carbons; n and m are numbers respectively satisfying the conditions 200 < n and 0 =< m =< (n/20)).

Here, the mass fraction of the monovalent aromatic hydrocarbon groups (Z) is preferably not less than 0.5% by mass and not greater than 30% by mass. Also, the mass fraction of the straight-chain organopolysiloxanes (W) is preferably not less than 75.0% by mass and not greater than 99.9% by mass. Additionally, the curable organopolysiloxane composition more preferably has these preferred aspects of "Z" and "W" simultaneously. Furthermore, the monovalent aromatic hydrocarbon group having from 6 to 10 carbons is preferably a phenyl group. Additionally, the one or more types of inorganic microparticles having an average primary particle diameter of not less than 50 nm preferably include dielectric inorganic microparticles having a specific dielectric constant at 1 kHz at room temperature of not less than 10, and, more preferably, part or all of the inorganic microparticles are surface-treated by one or more types of surface treatment agent.

The curing mechanism of the curable organopolysiloxane composition of the present invention is not particularly limited, but the group capable of a curing reaction may be a group capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction, and is preferably a group capable of an addition curing reaction typified by a hydrosilylation reaction (particularly a silicon-bonded unsaturated hydrocarbon group such as an alkenyl group, or a silicon atom-bonded hydrogen atom). Other compositional features advantageous for realizing better mechanical characteristics and/or electrical characteristics will be described later.

By the present invention, it is possible to produce a silicone elastomer cured product having excellent mechanical characteristics and/or electrical characteristics, and particularly having capability of being used as a member for transducers.

Furthermore, the present invention can provide a curable organopolysiloxane composition by which durability and a practical displacement can be achieved by excellent mechanical characteristics and/or electrical characteristics, in particular, high energy density being achieved due to a high specific dielectric constant, high dielectric breakdown strength, and low Young's modulus, and by excellent mechanical strength (specifically, tensile strength, tear strength, elongation, and the like) when used as a dielectric layer of a transducer; therefore, the curable organopolysiloxane composition can produce a cured product capable of use as a material for use in transducers.

The present invention can also provide a production method of the curable organopolysiloxane composition, a curable silicone elastomer material capable of use as an electrically active polymer material for use in transducers, a method of production for such a curable silicone elastomer material, and various types of transducers using the curable silicone elastomer material.

FIG. 1 illustrates a cross-sectional view of an actuator 1 of the present invention in which dielectric layers are stacked. FIG. 2 illustrates a cross-sectional view of an actuator 2 of the present invention in which dielectric layers and electrode layers are stacked. FIG. 3 illustrates the configuration of a sensor 3 of the present invention. FIG. 4 illustrates a cross-sectional view of an electricity generating element 4 of the present invention in which dielectric layers are stacked.

As a result of diligent investigation, the present inventors discovered that a silicone elastomer cured product having excellent mechanical characteristics and/or electrical characteristics is obtained by a curable organopolysiloxane composition comprising: an organopolysiloxane represented by formula (I) below:
R^a _aR^b _bSiO_(4-a-b)/2 (I)
wherein, R^a is a monovalent aromatic hydrocarbon group having from 6 to 10 carbons, and
R^b is at least one type of monovalent functional group (however, R^b is a group other than a monovalent aromatic hydrocarbon group having from 6 to 10 carbons), wherein at least part of R^b is a group capable of a curing reaction, and 0 < a, 0 < b, 1.9 < a+b < 2.1; and
one or more types of inorganic microparticles having an average primary particle diameter of not less than 50 nm,
wherein
the mass fraction of the monovalent aromatic hydrocarbon groups having from 6 to 10 carbons (Z) in the total of organopolysiloxanes is not less than 0.2% by mass and not greater than 50% by mass,
and
the mass fraction of the straight-chain organopolysiloxanes represented by formula (II) below (W) in the total of organopolysiloxanes is not less than 50% by mass:
R¹R² ₂Si(OSiR³R⁴)_n(OSiR³R¹)_mOSiR¹R² ₂ (II)
wherein, R¹ is a group capable of a curing reaction, R², R³, and R⁴ represent each independently, the same or different, a hydrogen atom, monovalent aliphatic hydrocarbon groups having from 1 to 10 carbons, and monovalent aromatic hydrocarbon groups having from 6 to 10 carbons; n and m are numbers respectively satisfying the conditions 200 < n and 0 =< m =< (n/20). Therefore, the present inventors have completed the present invention.

<Organopolysiloxane>
The organopolysiloxane represented by general formula (I): R^a _aR^b _bSiO_(4-a-b)/2 used in the present invention contains one or a plurality of organopolysiloxanes, which, as a whole, have curability, and contain a monovalent aromatic hydrocarbon having from 6 to 10 carbons in a mass fraction (Z) of not less than 0.2% by mass and not greater than 50% by mass relative to the total of organopolysiloxanes, and the mass fraction of the straight-chain organopolysiloxanes represented by formula (II) above (W) relative to the total of organopolysiloxanes is not less than 50% by mass. Furthermore, because the monovalent aromatic hydrocarbon R^a is a mandatory substituent, a > 0, and more specifically, the value of a must be a number in a range that results in the mass fraction of the monovalent aromatic hydrocarbons having from 6 to 10 carbons (Z) being not less than 0.2% by mass and not greater than 50% by mass relative to the total of organopolysiloxanes. Here, the organopolysiloxane containing a monovalent aromatic hydrocarbon having from 6 to 10 carbons may be the same as or different from the straight-chain organopolysiloxane represented by formula (II) above, but the organopolysiloxane represented by formula (I) above preferably contains a plurality of curable organopolysiloxanes, in which case the mass fraction of the monovalent aromatic hydrocarbons (Z) satisfies the aforementioned range relative to the total of organopolysiloxanes, and the mass fraction of the straight-chain organopolysiloxanes represented by formula (II) above (W) is not less than 50% by mass relative to the total of organopolysiloxanes. Provided that the mass fraction of the monovalent aromatic hydrocarbons (Z) satisfies the aforementioned range in the total of organopolysiloxanes, the monovalent aromatic hydrocarbon having from 6 to 10 carbons may be contained in any curable or non-curable organopolysiloxane constituting the organopolysiloxane.

First, the monovalent aromatic hydrocarbon group R^a having from 6 to 10 carbons will be described. This monovalent aromatic hydrocarbon group is exemplified by a phenyl group, a naphthyl group, a substituted phenyl group, and a substituted naphthyl group, and specific examples include a phenyl group, a naphthyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a xylyl group, an ethylphenyl group, and the like. On the other hand, although aromatic hydrocarbon group-substituted aliphatic hydrocarbon groups (i.e. arylalkyl group) are not aromatic hydrocarbon groups strictly speaking, they are treated as monovalent aromatic hydrocarbon groups in the present invention. Such groups are exemplified by a benzyl group, a phenethyl group, and the like. Among these groups, a phenyl group is preferred from the standpoints of economics and industrial productivity.

The content of the monovalent aromatic hydrocarbon groups (mass fraction relative to the total of organosiloxane components in the curable organopolysiloxane composition: Z) is not less than 0.2% by mass and not greater than 50% by mass. If Z is less than 0.2% by mass, the dielectric breakdown strength improvement effect is not sufficiently exhibited in the obtained cured product, while on the other hand, if it exceeds 50% by mass, the elastic modulus of the obtained cured product is too high and the molded product is inadequate because it is too brittle. A preferred range of Z is not less than 0.5% by mass and not greater than 30% by mass, and a more preferred range is not less than 0.5% by mass and not greater than 10% by mass.

These monovalent aromatic hydrocarbon groups are contained in a monovalent aromatic hydrocarbon group-containing organopolysiloxane constituting part or all of the organosiloxane components. These monovalent aromatic hydrocarbon group-containing organopolysiloxanes are exemplified by dimethylsiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups, dimethylsiloxane/methylvinylsiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups, polymethylphenylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups, dimethylsiloxane/diphenylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups, dimethylsiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with dimethylhydrogensiloxy groups, polymethylphenylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups, dimethylsiloxane/diphenylsiloxane copolymer capped at both molecular terminals with dimethylhydrogensiloxy groups, diphenylsiloxane/methylvinylsiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, diphenylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, methylphenylsiloxane/methylvinylsiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, methylphenylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, polymethylphenylsiloxane capped at both molecular terminals with methylphenylvinylsiloxy groups, polydiphenylsiloxane capped at both molecular terminals with methylphenylvinylsiloxy groups, and the like.

The organopolysiloxanes represented by general formula (I): R^a _aR^b _bSiO_(4-a-b)/2 used in the present invention, as a whole, have curability, and in formula (I), R^b is at least one type of monovalent functional group (however, R^b is a group other than a monovalent aromatic hydrocarbon group having from 6 to 10 carbons), and at least part of R^b has a group capable of a curing reaction. Here, the substituent R^b may be one type or two or more types of functional group provided that at least part is a group capable of a curing reaction and that the substituent R^b is not R^a, and part of the substituent R^b is preferably a reactive group capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction.

Additionally, part of the substituent R^b is particularly preferably a non-reactive functional group. Furthermore, the reactive group capable of a curing reaction that is part of the substituent R^b may be one type or two or more types of reactive group (for example, a combination of an addition reactive functional group and a photoreactive functional group).

The substituent R^b that is a non-reactive group is specifically exemplified by alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and the like. A methyl group is preferred from the standpoint of economics.

The substituent R^b that is a reactive group is the reactive group capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction. It is particularly preferable if part of R^b is a reactive group capable of curing by an addition reaction. Examples of a reactive group capable of an addition reaction include: a styryl group, (meth)acrylic group, vinylether group, and the like, which are addition polymerizable functional groups; combinations of a thiol group-containing organic group, which is a group active in a thiol-ene reaction, and an alkenyl group; combinations of a BH group-containing organic group, which is a group active in a hydroboration reaction, and an alkenyl group; combinations of a silicon atom-bonded hydrogen atom-containing organic group, which is a group active in a hydrosilylation reaction, and an alkenyl group; combinations of a diene group-containing organic group, which is a group active in a Diels-Alder reaction, and an alkenyl group; and the like. When these two types of reactive groups are combined, it is particularly preferable if a compound having only one type of reactive group and a compound having another type of reactive group are used in combination.

Other reactive groups capable of a curing reaction are exemplified by a hydroxyl group and alkoxy groups having from 1 to 4 carbons, specifically a methoxy group, an ethoxy group, a propoxy group, and the like, but are not limited thereto.

The organopolysiloxanes represented by general formula (I): R^a _aR^b _bSiO_(4-a-b)/2 used in the present invention are, as a whole, preferably organopolysiloxanes curable by an addition reaction, and the aforementioned group capable of a curing reaction is preferably a group capable of an addition reaction. Groups capable of an addition reaction are as described above.

In particular, R^b in formula (I) is a group selected from the group consisting of optionally substituted monovalent hydrocarbon groups having from 1 to 10 carbons (however, R^b is a group other than a monovalent aromatic hydrocarbon group having from 6 to 10 carbons), a hydrogen atom, alkenyl groups having from 2 to 8 carbons, alkoxy groups having from 1 to 4 carbons, and a hydroxyl group, and at least part of R^b is preferably a group capable of an addition reaction selected from the group consisting of a hydrogen atom and alkenyl groups having from 2 to 8 carbons.

Among these groups, in consideration of high reaction rate and low side reactions, at least part of R^b is preferably a group active in a hydrosilylation reaction, i.e., a silicon atom-bonded hydrogen atom and an alkenyl group. Here, a vinyl group is preferred as the alkenyl group from the standpoint of economy.

In the organopolysiloxanes represented by general formula (I): R^a _aR^b _bSiO_(4-a-b)/2 used in the present invention, as a whole, the proportion of substituents on silicon atoms (mass fraction relative to silicon atoms of total number of substituents on silicon atoms; a+b) is in the range of 1.9 < a+b < 2.1. If the proportion of substituents is outside this range, the silicone elastomer that is the obtained cured product has insufficient mechanical characteristics (particularly tensile breaking elongation and elastic modulus), and is inadequate. Furthermore, since 1.9 < a+b < 2.1, it means that the organopolysiloxanes used in the present invention, as a whole, contain numerous chain polysiloxane structures having diorganosiloxane units.

The organopolysiloxanes represented by general formula (I): R^a _aR^b _bSiO_(4-a-b)/2 used in the present invention also contain a straight-chain organopolysiloxane represented by formula (II) below in an amount not less than 50% by mass. The content of such straight-chain organopolysiloxanes is not less than 50% by mass. If the content is outside this range, the mechanical characteristics (particularly breaking elongation) of the silicone elastomer that is the cured product do not reach a satisfactory range. The preferred tensile breaking characteristics are elongation at tensile breaking of not less than 200% as measured according to JIS K 6249, and the preferred content of straight-chain organopolysiloxanes for realizing this is in the range of not less than 70% by mass and not greater than 99.9% by mass.
R¹R² ₂Si(OSiR³R⁴)_n(OSiR³R¹)_mOSiR¹R² ₂ (II)
(In the formula, R¹ is a group capable of a curing reaction, R², R³, and R⁴ represent each independently, the same or different, monovalent aliphatic hydrocarbon groups having from 1 to 10 carbons and monovalent aromatic hydrocarbon groups having from 6 to 10 carbons; n and m are numbers that satisfy the conditions 200 < n and 0 =< m =< (n/20))

In formula (II), R¹ is a group capable of a curing reaction, and may be the same group as the reactive group of R^b, but for the reasons described above, a reactive group capable of an addition reaction is preferred. In particular, it is preferably a group active in a hydrosilylation reaction, i.e., a silicon atom-bonded hydrogen atom or a vinyl group. R², R³, and R⁴ are each independently, the same or different, monovalent aliphatic hydrocarbon groups having from 1 to 10 carbons and monovalent aromatic hydrocarbon groups having from 6 to 10 carbons, and are exemplified by a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, a phenyl group, a naphthyl group, a substituted phenyl group, a substituted naphthyl group, a benzyl group, a phenethyl group, and the like, but from the standpoint of economy, a methyl group and a phenyl group are preferred. Furthermore, needless to say, the monovalent aromatic hydrocarbon group in the straight-chain organopolysiloxane represented by formula (II) is also included in the mass fraction of the monovalent aromatic hydrocarbon groups (Z) in the organopolysiloxanes represented by formula (I).

In formula (II), n is a number exceeding 200. If it is a number not greater than 200, the mechanical characteristics (particularly breaking elongation) of the obtained cured product are low, and therefore are inadequate in the present invention. In consideration of molding processability, a number not greater than 20,000 is preferred. On the other hand, there is no distinct upper limit on the value of m, but it must be a value not greater than (n/20) in consideration of breaking elongation of the obtained cured product, similar to above. Furthermore, this condition is closely associated with advantageous improvement upon the problem of the present invention due to the fact that the total of siloxane components in the curable organopolysiloxane composition to be described later satisfy the specified compositional features.

Specific examples of reactive organopolysiloxanes constituting the curable organopolysiloxane composition used in the present invention include polydimethylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups, dimethylsiloxane/methylvinylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups, dimethylsiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups, dimethylsiloxane/methylvinylsiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups, polymethylphenylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups, dimethylsiloxane/diphenylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups, polydimethylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups, dimethylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with dimethylhydrogensiloxy groups, dimethylsiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with dimethylhydrogensiloxy groups, polymethylphenylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups, dimethylsiloxane/diphenylsiloxane copolymer capped at both molecular terminals with dimethylhydrogensiloxy groups, dimethylsiloxane/methylhydrogensiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with dimethylhydrogensiloxy groups, polymethylvinylsiloxane capped at both molecular terminals with trimethylsiloxy groups, polymethylhydrogensiloxane capped at both molecular terminals with trimethylsiloxy groups, dimethylsiloxane/methylvinylsiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, dimethylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, diphenylsiloxane/methylvinylsiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, diphenylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, methylphenylsiloxane/methylvinylsiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, methylphenylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, dimethylsiloxane/methylvinylsiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, dimethylsiloxane/methylhydrogensiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, dimethylhydrogen functional MQ resin, dimethylvinyl functional MQ resin, polydimethylsiloxane capped at both molecular terminals with diphenylvinylsiloxy groups, polymethylphenylsiloxane capped at both molecular terminals with diphenylvinylsiloxy groups, polydiphenylsiloxane capped at both molecular terminals with diphenylvinylsiloxy groups, polydimethylsiloxane capped at both molecular terminals with methylphenylvinylsiloxy groups, polymethylphenylsiloxane capped at both molecular terminals with methylphenylvinylsiloxy groups, polydiphenylsiloxane capped at both molecular terminals with methylphenylvinylsiloxy groups, copolymer containing a dimethylvinylsiloxy group ((CH₃)₂(CH₂=CH)SiO_1/2) and a phenylsiloxy group (C₆H₅SiO_3/2), copolymer containing a dimethylhydrogensiloxy group ((CH₃)₂HSiO_1/2) and a phenylsiloxy group (C₆H₅SiO_3/2), copolymer containing a dimethylvinylsiloxy group ((CH₃)₂(CH₂=CH)SiO_1/2), a dimethylsiloxy group ((CH₃)₂SiO_2/2), and a phenylsiloxy group (C₆H₅SiO_3/2), copolymer containing a dimethylhydrogensiloxy group ((CH₃)₂HSiO_1/2), a dimethylsiloxy group ((CH₃)₂SiO_2/2), and a phenylsiloxy group (C₆H₅SiO_3/2), copolymer containing a methylvinylsiloxy group ((CH₃)(CH₂=CH)SiO_2/2) and a phenylsiloxy group (C₆H₅SiO_3/2), copolymer containing a methylhydrogensiloxy group ((CH₃) HSiO_2/2) and a phenylsiloxy group (C₆H₅SiO_3/2), and the like. Among these, it is particularly preferable if a silicon atom-bonded hydrogen atom-containing organopolysiloxane and a silicon atom-bonded unsaturated hydrocarbon group-containing organopolysiloxane in combination are used as the organopolysiloxane or the components constituting the organopolysiloxane of the invention of the present application.

The number average molecular weight (Mw) of the reactive organopolysiloxane is preferably in the range of 250 to 100,000. Moreover, no particular limitation is placed on viscosity of the reactive organopolysiloxane measured under conditions of shear rate 10 (1/s) at 25C using a rheometer equipped with a cone plate of 20 mm diameter, although this viscosity is preferably in the range of 1 to 50,000 mPa s, and particularly preferably in the range of 5 to 10,000 mPa s.

Furthermore, the siloxane components of the curable organopolysiloxane composition of the present invention may be constituted by appropriately combining the various reactive organopolysiloxanes described above such that the mass fraction of the monovalent aromatic hydrocarbon groups (Z) and the mass fraction of the straight-chain organopolysiloxanes having reactive groups at both terminals of the molecular chain (W) are within the designated ranges.

<Inorganic microparticles having an average primary particle diameter of not less than 50 nm>
The curable organopolysiloxane composition of the present invention is further characterized by being a composition containing an organopolysiloxane having the above features and at least one type of inorganic microparticles having an average primary particle diameter of not less than 50 nm. As a result, it is possible to obtain a silicone elastomer cured product having excellent mechanical characteristics and/or electrical characteristics which are difficult to obtain with a conventional curable organopolysiloxane composition.

The average primary particle diameter of the microparticles is not less than 50 nm. The microparticles may be a mixture of microparticles of different particle diameters. Average particle diameter may be measured by a measurement method commonly used in the field. For example, if the average particle diameter is not less than 50 nm and not greater than approximately 500 nm, average primary particle diameter can be measured by averaging the particle diameter measured by microscope observation using a transmission electron microscope (TEM), field emission-type transmission electron microscope (FE-TEM), scanning electron microscope (SEM), field emission-type scanning electron microscope (FE-SEM), or the like. On the other hand, if the average particle diameter is not less than approximately 500 nm, the value of average primary particle diameter can be directly determined by a laser diffraction-scattering type particle size distribution measurement device or the like.

The function and type of these inorganic microparticles are not particularly limited, but examples include electrically conductive inorganic microparticles, insulating inorganic microparticles, thermally conductive inorganic microparticles, and dielectric inorganic microparticles. It is preferable if one or more types selected from these microparticles is used in the composition of the present invention. In particular, it is preferable to use dielectric inorganic microparticles, and it is particularly preferable if the dielectric inorganic microparticles are dielectric inorganic microparticles in which at least part of the one or more types of inorganic microparticles having an average primary particle diameter of not less than 50 nm has a specific dielectric constant at 1 kHz at room temperature of not less than 10. Furthermore, the upper limit on the preferred size (average primary particle diameter) of the inorganic microparticles is 20,000 nm (20 maicrometers), but considering processability into a thin film for transducers to be described later, 10,000 nm (10 maicrometers) is more preferable.

<Dielectric inorganic microparticles (C)>
The dielectric inorganic microparticles (C) are, advantageously, dielectric inorganic microparticles (C1) having a specific dielectric constant at 1 kHz at room temperature of not less than 10. By the dielectric inorganic microparticles being carried in the cured product comprising the curable organopolysiloxane, the physical characteristics and electrical characteristics required for a transducer are both satisfied.

The dielectric inorganic microparticles, for example, may be selected from metal oxides (hereinafter, also referred to as "metal oxide (C2)") represented by formula (C2) below:
M^a _naM^b _nbO_nc (C2)
(In the formula,
M^a is a group 2 metal element of the periodic table;
M^b is a period 4 metal element of the periodic table;
na is a number ranging from 0.9 to 1.1;
nb is a number ranging from 0.9 to 1.1; and
nc is a number ranging from 2.8 to 3.2)

Preferred examples of the group 2 metal element M^a of the periodic table in the metal oxide (C2) include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Titanium (Ti) is cited as a preferred example of a period 4 metal element M^b of the periodic table. In the particles of metal oxides represented by the Formula (C2), M^a and M^b may each be a single element, or may be two or more elements.

Specific examples of the metal oxide (C2) include barium titanate, calcium titanate, and strontium titanate.

The dielectric inorganic microparticles, for example, may be selected from metal oxides (hereinafter, also referred to as "metal oxide (C3)") represented by formula (C3) below:
M^a _naM^b' _nb'O_nc (C3)
(in the formula,
M^a is a group 2 metal element of the periodic table;
M^b' is a period 5 metal element of the periodic table;
na is a number ranging from 0.9 to 1.1;
nb' is a number ranging from 0.9 to 1.1; and
nc is a number ranging from 2.8 to 3.2)

Preferred examples of the group 2 metal element M^a of the periodic table in the metal oxide (C3) include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Preferred examples of the period 5 metal element M^b' of the periodic table include tin (Sn), antimony (Sb), zirconium (Zr), and indium (In). In the particles of the metal oxide represented by the formula (C3), M^a and M^b' may each be a single type of element, or may be two or more elements.

Specific examples of the metal oxide (C3) include magnesium stannate, calcium stannate, strontium stannate, barium stannate, magnesium antimonate, calcium antimonate, strontium antimonate, barium antimonate, magnesium zirconate, calcium zirconate, strontium zirconate, barium zirconate, magnesium indate, calcium indate, strontium indate, and barium indate.

Furthermore, in combination with such metal oxide particles, it is permissible to use particles of other metal oxides such as lead titanate zirconate, zinc titanate, lead titanate, titanium oxide, or the like (particularly titanium oxide composite oxides other than those previously listed). Moreover, solid solutions comprising other metal elements may be used as the dielectric inorganic microparticles (C). In this case, other metal elements are exemplified by La (lanthanum), Bi (bismuth), Nd (neodymium), Pr (praseodymium), and the like.

Of these, preferred examples of the dielectric inorganic microparticles (C) include one or more types of inorganic microparticles selected from the group consisting of titanium oxide, barium titanate, strontium titanate, lead titanate zirconate, and composite metal oxides in which the barium and titanium positions of barium titanate are partially substituted with an alkaline earth metal such as calcium or strontium; zirconium; or rare earth metals such as yttrium, neodymium, samarium, and dysprosium. Titanium oxide, barium titanate, barium calcium titanate zirconate, and strontium titanate are more preferred, and titanium oxide and barium titanate are most preferred.

The morphology of the dielectric inorganic microparticles (C) may be any morphology, such as spherical, tabular, needle-like, fibrous, or the like. The average primary particle diameter thereof is not less than 50 nm, but in consideration of molding processability, particularly thin film formability, of the curable organopolysiloxane composition, the range of 50 to 5,000 nm is preferable. If the inorganic microparticles are anisotropic microparticles in which the morphology is tabular, needle-like, fibrous, or the like, although no limitation is placed on the aspect ratio of such microparticles, the aspect ratio may normally be not less than 5.

No particular limitation is placed on the particle size distribution of the dielectric inorganic microparticles (C), and the dielectric inorganic microparticles may be mono-dispersed, or alternatively, it is possible to produce a distribution in the particle diameters so as to improve mechanical strength by filling at higher density by lowering the void fraction between microparticles. As a measure of the particle size distribution, the ratio (D₉₀/D₁₀) of the particle diameter at 90% cumulative area (D₉₀) to the particle diameter at 10% cumulative area (D₁₀) of the cumulative particle size distribution curve measured by the laser light diffraction method is preferably not less than 2. Moreover, no limitation is placed on the particle size distribution shape (relationship between particle diameter and particle concentration). It is possible to have a so-called plateau shaped distribution, or a particle size distribution that is multi-modal, i.e., bimodal (i.e., having two hill-shaped distributions), tri-modal, or the like.

In order to make particle size distributions of the dielectric inorganic microparticles (C) similar to those described above, methods may be adopted, for example, such as combined use of two or more types of microparticles having different average diameters or particle size distributions, and blending of particles of particle diameter fractions obtained by sieving or the like to produce a desired particle size distribution, or the like.

Furthermore, these dielectric inorganic microparticles (C) may be treated using various types of the below described surface treatment agents.

In consideration of mechanical characteristics and dielectric characteristics of the obtained cured product, the blended amount (filling ratio) of the dielectric inorganic microparticles (C) in the curable organopolysiloxane composition of the present invention, relative to the entire volume of the composition, may be not less than 10%, preferably not less than 15%, and further preferably not less than 20%. Moreover, this blended amount relative to the total volume of the composition is preferably not greater than 70%, and further preferably not greater than 60%.

In the curable organopolysiloxane composition of the present invention, the one or more types of inorganic microparticles having an average primary particle diameter of not less than 50 nm are preferably the dielectric inorganic microparticles (C), but they may also include the following electrically conductive inorganic microparticles, insulating inorganic microparticles, and thermally conductive inorganic microparticles.

The electrically conductive inorganic microparticles that may be used here are not particularly limited provided that they can impart electrical conductivity to the cured product of the organopolysiloxane composition. Specific examples of the electrically conductive inorganic microparticles include: electrically conductive carbon such as electrically conductive carbon black, graphite, vapor phase-grown carbon (VGCF), or the like; and metal powders such as platinum, gold, silver, copper, nickel, tin, zinc, iron, aluminum, or the like; as well coated pigments such as antimony-doped tin oxide, phosphorous-doped tin oxide, needle-shaped titanium oxide surface-treated using tin oxide/antimony, tin oxide, indium oxide, antimony oxide, zinc antimonate, and graphite or carbon whiskers surface-treated by tin oxide or the like; pigments coated by at least one type of electrically conductive metal oxide selected from the group consisting of tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), and phosphorous-doped tin oxide and phosphorous-doped nickel oxide; pigments having electrical conductivity and containing tin oxide and phosphorous in the surface of titanium dioxide particles; these electrically conductive inorganic microparticles being optionally surface-treated using various types of the below described surface treatment agents. Such electrically conductive inorganic microparticles may be used as one type or as a combination of two or more types.

Furthermore, the electrically conductive inorganic microparticles may be fibers such as glass fibers, silica alumina fibers, alumina fibers, carbon fibers, or the like, or needle-like reinforcing materials such as aluminum borate whiskers, potassium titanate whiskers, or the like; or an inorganic filler material such as glass beads, talc, mica, graphite, wollastonite, dolomite, or the like that has been surface-coated by an electrically conductive substance such as a metal or the like.

By blending the electrically conductive inorganic microparticles in the composition, it is possible to increase the specific dielectric constant of the organopolysiloxane cured product. The blended amount of such electrically conductive inorganic microparticles relative to the curable organopolysiloxane composition is, depending on the application thereof, preferably in the range of 0.01 to 10% by mass, and more preferably in the range of 0.05 to 5% by mass. When the blended amount of the electrically conductive inorganic microparticles departs from the aforementioned preferred range, the effect of blending is not obtained, or there may be a lowering of the dielectric breakdown strength of the cured product.

The insulating inorganic microparticles that can be used in the present invention are not particularly limited provided that they are generally known insulating inorganic microparticles, i.e., particles of inorganic material having volume resistivity of from 10¹⁰ to 10¹⁸ OHM cm, and may be used in any morphology of granules, flakes, and fibers (including whiskers). Preferred specific examples include spherical particles, tabular particles, and fibers of ceramics, particles of metal silicates such as alumina, iron oxide, copper oxide, mica, and talc, and particles such as quartz, amorphous silica, and glass. Moreover, such insulating inorganic microparticles may be surface-treated using the various types of below described surface treatment agents. Such electrically insulating inorganic microparticles may be used as one type or as a combination of two or more types.

By blending the insulating inorganic microparticles into the composition, it becomes possible to increase the mechanical strength and dielectric breakdown strength of the organopolysiloxane cured product, and the specific dielectric constant may sometimes be observed to increase. The blended amount of such insulating inorganic particles relative to the curable organopolysiloxane composition is, depending on the application thereof, preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.1 to 5% by mass. When the blended amount of the insulating inorganic particles deviates from the aforementioned preferred range, the effect of blending is not obtained, or there may be a lowering of the mechanical strength of the cured product.

Examples of the thermally conductive inorganic microparticles that can be used in the present invention include metal oxide particles such as magnesium oxide, zinc oxide, nickel oxide, vanadium oxide, copper oxide, iron oxide, silver oxide, and the like, and inorganic compound particles such as aluminum nitride, boron nitride, silicon carbide, silicon nitride, boron carbide, titanium carbide, diamond, diamond-like carbon, and the like. Zinc oxide, boron nitride, silicon carbide, and silicon nitride are preferred. By blending one or more types of these thermally conductive inorganic microparticles into the composition, it becomes possible to increase the thermal conductivity of the organopolysiloxane cured product. The blended amount of such thermally conductive inorganic microparticles relative to the curable organopolysiloxane composition is, depending on the application thereof, preferably in the range of 0.1 to 30% by mass.

The curable organopolysiloxane composition of the present invention contains the organopolysiloxane and at least one type of inorganic microparticles having an average primary particle diameter of not less than 50 nm, but more advantageously, it is preferable if the organopolysiloxane composition satisfies the compositional features of items [1], [2], and [3] below.

[1] The curable organopolysiloxane composition contains an organopolysiloxane represented by the general formula: M_aM^R _bD_cD^R _dT_eT^R _fQ_g wherein the value of (a + c)/(b + d + e + f + g) is less than 3, in an amount not less than 0.1% by mass and not greater than 10% by mass relative to the total of organopolysiloxane components in the curable organopolysiloxane composition. Here, in the above general formula, M is a triorganosiloxy unit; D is a diorganosiloxy unit; T is a monoorganosiloxy unit; Q is a siloxy unit represented by SiO_4/2; and substituent R on each of the siloxy units is a group capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction.

[2] The curable organopolysiloxane composition contains a reactive organopolysiloxane having only at both molecular terminals a group capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction, in an amount not less than 75% by mass and not greater than 99.9% by mass relative to the total of siloxane components in the curable organopolysiloxane composition.

[3] The curable organopolysiloxane composition at least contains (S) a reactive organopolysiloxane having in a molecule at least two groups capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction, the reactive organopolysiloxane S having an average molecular weight less than 10,000 between the two groups capable of the curing reaction; and
(L) a reactive organopolysiloxane having in a molecule at least two groups capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction, the reactive organopolysiloxane L having a molecular weight not less than 10,000 and not greater than 150,000 between the two groups; and the blending ratio of component (S) and component (L) being from 1:99 to 20:80.

The above features [1] to [3] will be described in further detail below. It is particularly preferable if the organopolysiloxane of the present invention satisfies all of these conditions.

With regard to feature [1], the mass fraction of reactive organopolysiloxanes represented by M_aM^R _bD_cD^R _dT_eT^R _fQ_g wherein the value of (a + c)/(b + d + e + f + g) is less than 3 is preferably not less than 0.1% by mass and not greater than 10% by mass, and particularly preferably not less than 0.1% by mass and not greater than 5% by mass, relative to the total of siloxane components in the curable organopolysiloxane composition of the present invention. When the proportion is less than 0.1% by mass, the number of crosslink points in the polysiloxane component is excessively low, and thus there is the risk that mechanical strength and dielectric breakdown strength after the curing reaction will be insufficient. Conversely, a proportion in excess of 10% by mass is unsuitable since the number of crosslink points is excessive, and thus post-curing elastic modulus is high and breaking elongation is low.

With regard to feature [2], the weight fraction of reactive organopolysiloxanes having a group capable of a curing reaction only at both molecular terminals relative to the total of organopolysiloxane components in the curable organopolysiloxane composition is preferably not less than 75% by mass and not greater than 99.9% by mass. If this proportion is outside the above range, it is unsuitable because high breaking elongation of the silicone elastomer that is a cured product cannot be achieved or the dielectric breakdown strength is insufficient. Here, as the group capable of a curing reaction, a group capable of a condensation reaction, addition reaction, peroxide reaction, or photoreaction may be used. However, for reasons similar to those described above, this group is preferably capable of an addition reaction. Among such groups capable of an addition reaction, the group is preferably active in a hydrosilylation reaction, i.e., a silicon atom-bonded hydrogen atom-containing group or an aliphatic unsaturated bond-containing group (for example, an alkenyl group having from 2 to 20 carbons, or the like). Specific examples thereof include polydimethylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups, and polydimethylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups. For further suitability with respect to material characteristics (e.g., mechanical characteristics, dielectric characteristics, heat resistance characteristics, or the like) of these polymers, it is possible for part of the methyl groups of such polymers to be substituted with an ethyl group, propyl group, butyl group, hexyl group, or phenyl group.

The number average molecular weight (Mw) of the reactive organopolysiloxane having groups capable of a curing reaction only at both molecular terminals is in the range of 250 to 100,000. Moreover, no particular limitation is placed on viscosity of the reactive organopolysiloxanes measured under conditions of shear rate 10 (1/s) at 25C using a rheometer equipped with a cone plate of 20 mm diameter; however, this viscosity is preferably in the range of 1 to 100,000 mPa s, and particularly preferably in the range of 5 to 10,000 mPa s.

With regard to feature [3], in the present invention, it is preferable if a reactive organopolysiloxane (S), which is a reactive organopolysiloxane having at least two groups capable of a curing reaction in a molecule, having an average molecular weight between the two groups capable of a curing reaction of less than 10,000, and a reactive organopolysiloxane (L), which is a reactive organopolysiloxane having at least two groups capable of a curing reaction in a molecule, having a molecular weight between the two groups capable of a curing reaction of not less than 10,000 and not greater than 150,000, are used. These are contained in the molecule as a short-chain non-reactive polymer portion and a long-chain non-reactive polymer portion, respectively. Here, the molecular weight between these two groups capable of the crosslinking reaction, in the case of a chain type organopolysiloxane that has reactive functional groups only at both terminals of the molecular chain, is defined as the molecular weight of the non-reactive polysiloxane part (not including the siloxy units at both terminals). In the case of molecular weight between multiple groups capable of a crosslinking reaction, this is the molecular weight of the longest part.
When the component (S) and component (L) are used together in the aforementioned blending ratio as raw materials for curable organopolysiloxane, it is possible to introduce portions of different chain lengths in the silicone chain components constituting the silicone elastomer obtained by the curing reaction. By this means, it is possible to reduce permanent strain of the obtained silicone elastomer, and it is possible to decrease the mechanical energy conversion loss. In particular, when the silicone elastomer of the present invention is used in the dielectric layer of a transducer, this combined use of the component (S) and component (L) has the practical advantage of increasing the energy conversion efficiency.

As mentioned previously, it is possible to use a group capable of a condensation reaction, addition reaction, peroxide reaction, or photoreaction as the groups capable of a curing reaction of these components. However, for reasons similar to those described above, this is preferably a group capable of an addition reaction. Among groups capable of an addition reaction, the group is preferably a group active in a hydrosilylation reaction, i.e., a silicon atom-bonded hydrogen atom or an aliphatic unsaturated bond-containing group (for example, an alkenyl group having from 2 to 20 carbons, or the like). Specific examples of the reactive organopolysiloxanes (S) and (L) are the examples cited as the reactive organopolysiloxanes represented by M_aM^R _bD_cD^R _dT_eT^R _fQ_g and the examples cited as the reactive organopolysiloxanes having a group capable of a curing reaction only at both molecular chain terminals. For further suitability with respect to mechanical characteristics and thermal characteristics after curing, it is possible for part of the methyl groups to be substituted with an ethyl group, propyl group, butyl group, hexyl group, or phenyl group.

The preferred range of values of the blending ratio (mass ratio) S:L of component (S) and the following component (L) is from 1:99 to 40:60. If the value of the blending ratio is outside this range, the cured product obtained by curing the curable organopolysiloxane composition of the present invention cannot satisfy at least one characteristic including high breaking elongation, high mechanical strength, high dielectric breakdown strength, and low elastic modulus.

<SiH/Vi ratio>
The curable organopolysiloxane composition is advantageously cured by a hydrosilylation reaction, and the blending ratio (molar ratio) of silicon-bonded hydrogen atoms (H) to silicon-bonded unsaturated hydrocarbon groups (Vi) in the organopolysiloxane of the present invention is preferably in the range of 0.5 to 3.0. When this value is outside the aforementioned range, the residual functional groups after curing by the hydrosilylation reaction may adversely affect material physical properties of the cured product.

The curable organopolysiloxane composition of the present invention preferably contains a curing catalyst (B) for curing the organopolysiloxane components.
The component (B) used in the present invention is preferably one generally known as a hydrosilylation reaction catalyst, and is not particularly limited provided that it is a substance capable of promoting a hydrosilylation reaction. Examples include platinum-based catalysts, rhodium-based catalysts, and palladium-based catalysts. Of these, due to high catalytic activity, particularly platinum group element catalysts and platinum group element compound catalysts are cited as the component (B). Without particular limitation, platinum-based catalysts are exemplified by platinum fine powder, platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid, chloroplatinic acid-diolefin complex, olefin-platinum complexes; platinum-carbonyl complexes such as platinum bis(acetoacetate), platinum bis(acetylacetonate), or the like; chloroplatinic acid-alkenyl siloxane complexes such as chloroplatinic acid-divinyltetramethyldisiloxane complex, chloroplatinic acid-tetravinyltetramethylcyclotetrasiloxane complex, or the like; platinum-alkenylsiloxane complexes such as platinum-divinyltetramethyldisiloxane complex, platinum-tetravinyltetramethylcyclotetrasiloxane complex, or the like; and complexes between chloroplatinic acid and acetylene alcohols. Due to high catalytic activity with respect to hydrosilylation reactions, recommended examples of the component (B) are platinum-alkenylsiloxane complexes, and particularly platinum 1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex.

Moreover, for further improvement of stability of the platinum-alkenylsiloxane complex, these platinum-alkenylsiloxane complexes may be dissolved in an organosiloxane oligomer such as alkenylsiloxane oligomers of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3-diallyl-1,1,3,3-tetramethyldisiloxane, 1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane, 1,3-divinyl-1,1,3,3-tetraphenyldisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, or the like; or dimethylsiloxane oligomers; or the like. In particular, the use of a platinum-alkenylsiloxane complex dissolved in an alkenylsiloxane oligomer is preferred.

The utilized amount of the component (B) may be any amount capable of promoting an addition reaction of the organopolysiloxane components of the present composition, without particular limitation. Relative to the total mass of the organopolysiloxane components, the concentration of platinum group metal atoms contained in the component (B) (e.g., platinum atoms) is normally in the range of 0.01 to 500 ppm, preferably in the range of 0.1 to 100 ppm, and particularly preferably in the range of 0.1 to 50 ppm.

An example of a preferred embodiment of the curable organopolysiloxane composition of the present invention is
a composition comprising, as mandatory ingredients, at least one type of reactive organohydrogenpolysiloxane (A1) having at least two silicon atom-bonded hydrogen atoms in a molecule, the weight fraction of hydrogen atoms being from 0.01 to 2.0% by weight, at least one type of reactive organopolysiloxane (A2) having a number of repeating units exceeding 200 and having alkenyl groups at both molecular terminals, the weight fraction of alkenyl groups being from 0.05 to 5.0% by weight, a hydrosilylation reaction catalyst (B), and dielectric inorganic microparticles (C1) having a specific dielectric constant at 1 kHz at room temperature of not less than 10.
Here, preferred examples of (A1) are polydimethylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups, dimethylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with trimethylsiloxy groups, and dimethylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with dimethylhydrogensiloxy groups. On the other hand, examples of (A2) are polydimethylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups, polymethylphenylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups, dimethylsiloxane/methylvinylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups, and dimethylsiloxane/methylphenylsiloxane copolymer capped at both molecular terminals with dimethylvinylsiloxy groups. In order to further optimize material characteristics such as mechanical characteristics, dielectric characteristics, heat resistance, and the like, part of the methyl groups of the polymers may be substituted with an ethyl group, propyl group, butyl group, hexyl group, or phenyl group.
No particular limitation is placed on the molecular weights of (A1) and (A2), as long as the weight fraction of the hydrogen atoms and the weight fraction of the alkenyl groups are in the aforementioned ranges. However, the number of siloxane units is preferably from 5 to 1,500.

The curable organopolysiloxane composition of the present invention may be further provided with the below described characteristics.

The curable organopolysiloxane composition of the present invention may also contain at least one type of inorganic microparticles having an average primary particle diameter of less than 50 nm.

The at least one type of inorganic microparticles having an average primary particle diameter of less than 50 nm is not particularly limited in its function and the like, provided that the average primary particle diameter is less than 50 nm, and even so-called nanocarbon materials such as single-layer, double-layer and multi-layer carbon nanotubes, fullerenes, metal-encapsulated fullerenes, single-layer and multi-layer graphene, carbon nanofibers, and the like may be used as the dielectric inorganic particles.

A preferred example of the at least one type of inorganic microparticles having an average primary particle diameter of less than 50 nm is reinforcing inorganic microparticles, exemplified by fumed silica, wet silica, ground silica, calcium carbonate, diatomaceous earth, finely ground quartz, various types of metal oxide powders other than alumina-zinc oxide, glass fibers, carbon fibers, and the like. Moreover, they may be used after treatment using the below described various types of surface treatment agents. Among them, silica is recommended.
A preferred example, from the standpoint of mechanical strength improvement, is partially aggregated fumed silica having an average primary particle diameter of not greater than 10 nm, a specific surface area of not less than 50 m²/g and not greater than 300 m²/g. Furthermore, from the standpoint of dispersibility improvement, fumed silica that has been treated with the below-described silane coupling agent is preferred. However, if the curable organopolysiloxane (A) is addition-curable, fumed silica surface-treated with silazane is not used as reinforcing inorganic particles. These reinforcing inorganic particles may be used as a single type, or may be used as a combination of two or more types.

By blending the reinforcing inorganic microparticles into the composition, it becomes possible to increase the mechanical strength and dielectric breakdown strength of the organopolysiloxane cured product. The blended amount of such reinforcing inorganic microparticles relative to the curable organopolysiloxane composition is preferably in the range of 0.1 to 30% by mass, and more preferably in the range of 0.1 to 10% by mass. When the blended amount deviates from the aforementioned preferred range, the effect of blending the inorganic microparticles is not obtained or molding processability of the curable organopolysiloxane composition may decrease.

Part or all of the inorganic microparticles (regardless of particle diameter, function, or the like) used in the curable organopolysiloxane composition of the present invention may be surface-treated using one or more types of surface treatment agent. The type of surface treatment may be hydrophilizing treatment or hydrophobizing treatment without particular limitation, but hydrophobizing treatment is preferred. When inorganic microparticles that have undergone hydrophobizing treatment are used, it is possible to disperse the inorganic microparticles at a high filling ratio in the organopolysiloxane composition. Moreover, increase of viscosity of the composition is suppressed, and molding processability is improved.

The surface treatment may be performed by treatment (or coating treatment) of the inorganic microparticles using a surface treatment agent. The surface treatment agent used for hydrophobizing is exemplified by at least one type of surface treatment agent selected from the group consisting of organic titanium compounds, organosilicon compounds, organic zirconium compounds, organic aluminum compounds, and organic phosphorous compounds. The surface treatment agent may be used as a single type or as a combination of two or more types.

The organic titanium compound is exemplified by coupling agents such as alkoxy titanium, titanium chelates, titanium acylate, or the like. Preferred coupling agents among such compounds are exemplified by alkoxy titanium compounds such as tetraisopropyl titanate or the like, and titanium chelates such as tetraisopropyl bis(dioctylphosphate) titanate or the like.

The organosilicon compound is exemplified by low molecular weight organosilicon compounds such as silanes, silazanes, siloxanes, or the like; and organosilicon polymers or oligomers such as polysiloxanes, polycarbosiloxanes, or the like. Preferred silanes are exemplified by so-called silane coupling agents. Representative examples of such silane coupling agents include alkyltrialkoxysilanes (such as methyltrimethoxysilane, vinyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, or the like), organic functional group-containing trialkoxysilane (such as glycidoxypropyltrimethoxysilane, epoxycyclohexylethyltrimethoxysilane, methacryloxypropyltrimethoxysilane, aminopropyltrimethoxysilane, or the like). Preferred siloxanes and polysiloxanes include hexamethyldisiloxane, 1,3-dihexyl-tetramethyldisiloxane, polydimethylsiloxane capped at a molecular terminal with trialkoxysilyl, polydimethylsiloxane capped at a molecular terminal with trialkoxysilyl and another molecular terminal with dimethylvinyl, polydimethylsiloxane capped at a molecular terminal with trialkoxysilyl and capped at another molecular terminal with organic functional group, polydimethylsiloxane capped at both molecular terminals with trialkoxysilyl, polydimethylsiloxane capped at both molecular terminals with organic functional group, or the like. The number n of siloxane bonds in this case is preferably from 2 to 150. Preferred examples of silazanes include hexamethyldisilazane, 1,3-dihexyl-tetramethyldisilazane, and the like. Preferred polycarbosiloxanes are exemplified by polymers that have Si-C-C-Si-O bonds in the polymer main chain.

The organic zirconium compound is exemplified by alkoxy zirconium compounds such as tetraisopropoxy zirconium or the like and zirconium chelates.

The organic aluminum compound is exemplified by alkoxy aluminum and aluminum chelates.

The organic phosphorous compound is exemplified by phosphite esters, phosphate esters, and phosphorous acid chelates.

Among these surface treatment agents, organosilicon compounds are preferred. Among such organosilicon compounds, silanes, siloxanes, and polysiloxanes are preferred. As described previously, the use of alkyltrialkoxysilanes and polydimethylsiloxanes capped at a molecular terminal with trialkoxysilyl is most preferred.

The proportion of the surface treatment agent to the total amount of the inorganic microparticles is preferably not less than 0.1% by mass and not greater than 10% by mass, and more preferably not less than 0.3% by mass and not greater than 5% by mass. Furthermore, the treatment concentration is the ratio of the fed inorganic particles to the fed surface treatment agent, and the excess surface treatment agent is preferably removed after treatment.

The curable organopolysiloxane composition of the present invention may further comprise an additive for improvement of mold releasability or dielectric breakdown characteristics. The electrically active silicone elastomer sheet obtained by curing this organopolysiloxane composition as a thin sheet may be used with advantage as an electrically active film (dielectric layer or electrode layer) constituting a transducer. However, when mold releasability of the silicone elastomer sheet is poor during molding of the thin film, and particularly when a dielectric film is produced at high speed, the dielectric film may be damaged due to demolding. However, the curable organopolysiloxane composition of the present invention has excellent mold releasability, and thus the curable organopolysiloxane composition is advantageous in that it is possible to improve speed of production of the film without damaging the film. This additive further improves these features of the curable organopolysiloxane composition of the present invention, and this additive may be used as a single type or as a combination of two or more types. On the other hand, an additive for improvement of dielectric breakdown characteristics, as per the name of the additive, is used for improvement of dielectric breakdown strength of the silicone elastomer sheet obtained by the curing.

Mold release improvement additives (i.e., mold release agents) that can be used are exemplified by carboxylic acid-based release agents, ester-based release agents, ether-based release agents, ketone-based release agents, alcohol-based release agents, fluorine-based release agents, and the like. Such release agents may be used alone as a single type or may be used as a combination of two or more types. Moreover, although the release agents do not contain silicon atoms, it is also possible to use a release agent that contains silicon atoms, or it is possible to use a mixture of such release agents.

The release agent that does not contain silicon atoms may be selected, for example, from the group consisting of saturated or unsaturated aliphatic carboxylic acids such as palmitic acid, stearic acid, or the like; alkali metal salts of such aliphatic carboxylic acids (such as sodium stearate, magnesium stearate, calcium stearate, or the like); esters of aliphatic carboxylic acids and alcohols (such as 2-ethylhexyl stearate, glycerin tristearate, pentaerythritol monostearate, or the like), aliphatic hydrocarbons (liquid paraffin, paraffin wax, or the like), ethers (distearyl ether or the like), ketones (distearyl ketone or the like), higher alcohols (2-hexadecyloctadecanol or the like), and mixtures of such compounds.

The silicon atom-containing release agent is preferably a non-curable silicone-based release agent. Specific examples of such silicone-based release agents include non-organic modified silicone oils such as polydimethylsiloxane, polymethylphenylsiloxane, poly(dimethylsiloxane-methylphenylsiloxane) copolymers, poly(dimethylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymers, or the like; and modified silicone oils such as amino-modified silicones, amino polyether-modified silicones, epoxy-modified silicones, carboxyl-modified silicones, polyoxyalkylene-modified silicones, or the like. Such silicone-based release agents may have any structure, such as linear, partially-branched linear, or ring shaped. Moreover, no particular limitation is placed on the viscosity at 25C of such silicone oils. This viscosity is preferably in the range of 10 to 100,000 mPa s, and particularly preferably is in the range of 50 to 10,000 mPa s.

Although no particular limitation is placed on the blended amount of the mold release improvement additive, this amount is preferably not less than 0.1% by mass and not greater than 30% by mass, relative to the total amount of the curable organopolysiloxane composition.

On the other hand, the dielectric breakdown characteristic improvement agent is preferably an electrical insulation improvement agent. The dielectric breakdown characteristic improvement agent is exemplified by aluminum or magnesium hydroxides or salts, clay minerals, and mixtures of such. Specifically, the dielectric breakdown characteristic improvement agent may be selected from the group consisting of aluminum silicate, aluminum sulfate, aluminum hydroxide, magnesium hydroxide, calcined clays, montmorillonite, hydrotalcite, talc, and mixtures of such agents. Moreover, as may be required, this insulation improvement agent may be surface-treated by the surface treatment method.

Although no particular limitation is placed on the blended amount of the insulation improvement additive, this amount is preferably not less than 0.1% by mass and not greater than 30% by mass, relative to the total amount of the curable organopolysiloxane composition.

The curable organopolysiloxane composition of the present invention may comprise other organopolysiloxanes having highly dielectric functional groups that differ from the reactive organopolysiloxanes.

In the same manner, in the molecule, the curable organopolysiloxane composition of the present invention may further comprise a compound that has highly dielectric functional groups and at least one group capable of reacting by condensation curing reaction, addition curing reaction, peroxide curing reaction, or photo-curing reaction. This highly dielectric functional group is introduced to the obtained cured product (i.e., electrically active silicone elastomer) by the curing reaction.

For the curable organopolysiloxane composition of the present invention, part or the entire reactive organopolysiloxane may be a reactive organopolysiloxane further having a highly dielectric functional group.

If a silicone elastomer obtained by curing the curable organopolysiloxane composition of the present invention is used for a dielectric layer, the specific dielectric constant of the dielectric layer is preferably high, and highly dielectric functional groups may be introduced in order to improve the specific dielectric constant of the elastomer.

Specifically, dielectric properties may be increased for the curable organopolysiloxane composition and cured silicone elastomer obtained by curing the curable organopolysiloxane composition, by a method such as adding to the curable organopolysiloxane composition a component for imparting high dielectric properties, a method of introducing a group for imparting high dielectric properties to the organopolysiloxane component constituting the curable organopolysiloxane composition, or a combination of such methods. Such specific embodiments and highly dielectric functional groups capable of introduction will be explained below.

In a first embodiment, the curable organopolysiloxane composition is a curable organopolysiloxane composition that comprises an organosilicon compound that has a highly dielectric group. In this curable composition, part or all of the reactive organopolysiloxanes contained in the curable composition are reactive organopolysiloxanes further having a highly dielectric functional group, and the specific dielectric constant of the silicone elastomer obtained by curing is increased.

In a second embodiment, by adding an organosilicon compound having highly dielectric groups to the curable organopolysiloxane composition, specific dielectric constant of a silicone elastomer that is obtained by curing is increased. An organosilicon compound having highly dielectric groups may be added separately from the component used for curing in this curable composition.

In a third embodiment, an organic compound having highly dielectric groups and functional groups reactive with the reactive organopolysiloxane contained in the curable composition is added to the curable organopolysiloxane composition, thereby increasing specific dielectric constant of the silicone elastomer obtained by curing. As a result of formation of bonds between the organic compound and the organopolysiloxane due to the functional groups of the organic compound that are reactive with the reactive organopolysiloxane in this curable composition, highly dielectric groups are introduced into the silicone elastomer obtained by curing.

In a fourth embodiment of the present invention, by adding an organic compound miscible with the curable organopolysiloxane composition and having highly dielectric groups to the curable organopolysiloxane composition, the specific dielectric constant of the silicone elastomer obtained by curing is increased. Due to miscibility between the organic compound and the organopolysiloxane in this curable composition, an organic compound having these highly dielectric groups is incorporated in the matrix of the silicone elastomer obtained by curing.

No particular limitation is placed on the highly dielectric group in the present invention, and the highly dielectric group may be any group capable of increasing dielectric properties of the obtained cured product obtained by curing the curable organopolysiloxane composition of the present invention in comparison to the dielectric properties when the group is not contained. Without limitation, examples of the highly dielectric group used in the present invention are listed below.
a) Halogen Atoms and Halogen Atom-containing Groups
No particular limitation is placed on the halogen atom, and the halogen atom is exemplified by the fluorine atom and chlorine atom. The halogen atom-containing group may be selected as an organic group having one or more atoms of one or more types selected from fluorine atom and chlorine atom, as exemplified by halogen-substituted alkyl groups, halogen-substituted aryl groups, and halogen-substituted aryl alkyl groups. Specific examples of halogen-containing organic groups include the chloromethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, and perfluoroalkyl group, without limitation. By introduction of such groups, it is possible to anticipate also an improvement of mold releasability of the composition the present invention and the cured product obtained from the composition.
b) Nitrogen Atom-containing Groups
Nitrogen atom-containing groups are exemplified by the nitro groups, cyano groups (e.g., cyanopropyl group and cyanoethyl group), amido groups, imido groups, ureido groups, thioureido groups, and isocyanate groups.
c) Oxygen Atom-containing Groups
The oxygen atom-containing group is exemplified by ether groups, carbonyl groups, and ester groups.
d) Heterocyclic Groups
The heterocyclic group is exemplified by an imidazole group, pyridine group, furan group, pyran group, thiophene group, phthalocyanine group, and complexes of such.
e) Boron-containing Groups
The boron-containing group is exemplified by borate ester groups and boric acid salt groups.
f) Phosphorous-containing Groups
The phosphorous-containing group is exemplified by the phosphine group, phosphine oxide group, phosphonate ester group, phosphite ester group, and phosphate ester group.
g) Sulfur-containing Groups
The sulfur-containing group is exemplified by the thiol group, thioether group, sulfoxide group, sulfone group, thioketone group, sulfonate ester group, and sulfonamide group.

The curable organopolysiloxane composition of the present invention may comprise additives normally blended in organopolysiloxane compositions. As long as the object of the curable organopolysiloxane composition of the present invention is not impaired, it is possible to blend any additives, such as a curing retardant (curing suppression agent), flame retardant, heat resistance improvement agent, colorant, solvent, or the like. If the curable organopolysiloxane composition is an addition reaction curable type organopolysiloxane composition, the curing retardant (curing suppression agent) is exemplified by alkyne alcohols such as 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, 2-phenyl-3-butyn-2-ol, or the like; enyne compounds such as 3-methyl-3-penten-1-yne, 3,5-dimethyl-3-hexen-1-yne, or the like; and benzotriazole; without limitation. The utilized concentration of the curing retardant (curing suppression agent), relative to the total composition by mass, is preferably in the range of 1 to 50,000 ppm.

As long as the object of the present invention is not impaired, hybridization is possible by combining the curable organopolysiloxane composition for transducers of the present invention with a polymer other than the organopolysiloxane. By hybridization with a polymer having a higher dielectric constant than that of the organopolysiloxane with the organopolysiloxane, it may be possible to increase the dielectric constant of the composition of the present invention and of the cured product obtained from the composition. Hybridization embraces the so-called polymer blend of the organopolysiloxane with a non-organopolysiloxane polymer, and a fused polymer (i.e., so-called copolymer) formed by covalent bonding of the organopolysiloxane and the other polymer together.

The type of curing of the curable organopolysiloxane composition of the present invention may be condensation curable, addition-curable, peroxide curable, or photo-curable; however, an addition-curable organopolysiloxane composition is preferred. To this curable system, an acrylic group, methacrylic group, epoxy group, or thiol group may be introduced to an organopolysiloxane molecule chain of the curable organopolysiloxane composition in accordance with the method of introducing the dielectric functional group described above. By use of this photo-curable part or electron beam curable part, in addition to the addition curing reaction, it is possible to also use a photo-curing reaction or electron beam curing reaction. If such combined reactions are used, a compound known as a monomer and/or oligomer capable of curing by light or electron beam (such as (meth)acrylate esters and multi-functional (meth)acrylate compounds) may be further added to the curable composition. Moreover, a so-called photosensitizer may be added.

When the dielectric silicone elastomer that is the member for transducers obtained by at least partially curing the curable organopolysiloxane composition of the present invention is thermally molded into a sheet of 2.0 mm thickness, it has the below listed mechanical properties as measured based on JIS K 6249.
(1) Young's modulus (MPa) at room temperature may be set in the range of 0.1 to 10 MPa, and the particularly preferred range is 0.1 to 2.5 MPa.
(2) Tear strength (N/mm) at room temperature may be set to not less than 1 N/mm, and particularly preferably not less than 2 N/mm.
(3) Tear strength (MPa) at room temperature may be set to not less than 1 MPa, and particularly preferably not less than 2 MPa.
(4) Breaking elongation (%) may be set to not less than 200%, and from the standpoint of displacement amount of the transducer, is particularly preferably in the range of 200 to 1,000%.

The dielectric silicone elastomer that is the member for transducers obtained by curing of the curable organopolysiloxane composition of the present invention has the below listed dielectric characteristics.
(1) When the curable organopolysiloxane composition is thermally molded into a sheet of 0.07 mm thickness, the dielectric breakdown strength (V/maicrometers) may be set not less than 20 V/maicrometers. Although the preferred dielectric breakdown strength will vary according to the application of the transducer, the dielectric breakdown strength is particularly preferably in the range of not less than 30 V/maicrometers.
(2) When the curable organopolysiloxane composition is thermally molded into a sheet of 1 mm thickness, the specific dielectric constant measured at 1 MHz measurement frequency and 23C measurement temperature may be set to not less than 3.0. Although the preferred specific dielectric constant will change according to the required form of the dielectric layer and the type of the transducer, a particularly preferred range of specific dielectric constant under the aforementioned measurement conditions is not less than 5.0.

The curable organopolysiloxane composition of the present invention can be produced by kneading the curable organopolysiloxane component, a curing catalyst, dielectric inorganic microparticles having a specific dielectric constant at 1 kHz at room temperature of not less than 10, and optionally at least one type of inorganic microparticles and other additive, in an extruder or kneader (more specifically, at least one type of mechanical means selected from the group consisting of twin screw extruders, twin screw kneaders, and single blade extruders). In particular, in the present invention, by using a twin screw extruder having a free volume of at least 5,000 (L/h) to knead the reactive organopolysiloxane component, dielectric inorganic microparticles, and a surface treatment agent, it is possible and preferable to produce the curable organopolysiloxane composition by forming a silicone rubber compound (master batch) comprising a high concentration (e.g., at least 80% by mass) of inorganic microparticles and then forming the curable organopolysiloxane composition by adding and kneading other reactive organopolysiloxane components, curing catalyst, and other components.

Inorganic microparticles are dispersed well and at high concentration in the curable organopolysiloxane composition obtained by the aforementioned production method, and it is thus possible to produce a member for transducers that has good electrical characteristics and mechanical characteristics. Moreover, it is possible to obtain a uniform film-like cured product during production of the member for transducers, the electrical characteristics and mechanical characteristics of the obtained film-like cured product are excellent, and handling ability is excellent for lamination or the like.

In the aforementioned kneading process, no particular limitation is placed on the temperature during formation of the silicone rubber compound (master batch) that does not contain a curing catalyst. However, this temperature is set in the range of 40C to 200C, and may be set in the range of 100C to 180C. In a continuous process using a twin screw extruder or the like, the residence time during treatment may be set to about 30 seconds to 5 minutes.

Due to the dielectric characteristics and mechanical characteristics of the electrically active silicone elastomer obtained by curing or semi-curing of the curable organopolysiloxane composition of the present invention, use is possible with particular advantage as a member for transducers selected from the group consisting of artificial muscles, actuators, sensors, and electricity generating elements. Specifically, after molding the curable organopolysiloxane composition into a sheet-like or film-like shape, the member may generally be cured by heating, irradiation by a high energy beam, or the like. Although no particular limitation is placed on the method of molding the curable organopolysiloxane composition into a film-like shape, the method is exemplified by a method of forming a coating film by coating of the curable organopolysiloxane composition on a substrate using conventionally known coating methods, a method of molding by passing the curable organopolysiloxane composition through an extruder equipped with a slot of the desired shape, or the like.

Thickness of this type of film-like curable organopolysiloxane composition may be set in the range of 0.1 to 5,000 maicrometers, for example. Depending on the coating method and the absence or presence of a volatile solvent, thickness of the obtained cured product may be made thinner than thickness at the time of application of the composition.

After production of the film-like curable organopolysiloxane composition by the aforementioned method, thermal curing, room temperature curing, or curing by high energy beam irradiation may be performed on the curable organopolysiloxane composition, while applying an electrical field or magnetic field in a target orientation direction for the dielectric inorganic microparticles, or after orienting of the filler by application of a magnetic field or electrical field for a fixed time period. Although no particular limitation is placed on each curing operation or the conditions during each curing operation, if the curable organopolysiloxane composition is an addition-curable organopolysiloxane composition, curing is preferably performed in the temperature range of 90C to 180C by retention in this temperature range for 30 seconds to 30 minutes.

No particular limitation is placed on the thickness of the silicone elastomer for transducers, and the thickness may be from 1 to 2,000 maicrometers, for example. The silicone elastomer for transducers of the present invention may be stacked as one layer or two or more layers. Furthermore, an electrode layer may be provided at both tips of the dielectric elastomer layer, and a configuration may be used in which the transducer itself is composed of multiple stacked electrode layers and the dielectric elastomer layers. Thickness of the silicone elastomer for transducers per single layer for such a configuration may be from 0.1 to 1,000 maicrometers. If such layers are stacked as at least 2 layers, the thickness per single layer may be from 0.2 to 2,000 maicrometers.

Although no particular limitation is placed on the forming method of the two or more types of silicone elastomer cured layers, any of the following methods can be used: (1) after obtaining a silicone elastomer cured layer by coating and curing the curable organopolysiloxane composition on the substrate, applying the curable organopolysiloxane composition on the same cured layer to repeatedly coat and cure to stack layers; (2) coating the curable organopolysiloxane composition in a stacked manner on the substrate in an uncured or semi-cured state, and curing all of the various curable organopolysiloxane compositions that have been coated in a stacked manner; or (3) a method that combines the (1) and (2) methods.

For example, in the invention of the present application, the production can be performed by coating the curable organopolysiloxane composition on the substrate by die coating, curing to form the two or more stacked silicone elastomer cured layers, and then adhering the obtained silicone elastomer cured layers to an electrode. For this configuration, the two or more stacked silicone elastomer cured layers are preferably dielectric layers, and the electrode is preferably an electrically conductive layer.

High speed coating is possible by die coating, and this coating method is highly productive. The transducer having the multilayered configuration of the present invention, after coating of a single layer containing the organopolysiloxane composition, may be produced by coating a layer that comprises a different organopolysiloxane composition. Moreover, production is possible by simultaneously coating multiple layers containing each organopolysiloxane composition.

The thin film-like silicone elastomer that is the member for transducers may be obtained by coating the curable organopolysiloxane composition on the substrate, and then curing the assembly at room temperature and by heating, or by curing using high energy beam irradiation such as ultraviolet radiation or the like. Moreover, when the thin film-like dielectric silicone elastomer is stacked, uncured curable organopolysiloxane composition may be applied on the cured layer and then cured sequentially, or the uncured curable organopolysiloxane composition may be stacked in layers, and then the layers may be cured simultaneously.

The thin film-like silicone elastomer is particularly useful as a dielectric layer for a transducer. It is possible to form a transducer by arranging electrode layers at both ends of the thin film-like silicone elastomer. Furthermore, by blending electrically conductive inorganic particles into the curable organopolysiloxane composition of the present invention, it is possible to impart functionality as an electrode layer. Furthermore, the "electrode layer" in the specification of the present invention is sometimes simply referred to as the "electrode."

One embodiment of the member for transducers is a thin film, and is sheet-like or film-like. Film thickness is generally from 1 to 2,000 maicrometers, and the film may have a structure that is a single layer, two or more layers, or a greater number of stacked layers. Moreover, as may be desired, the stacked electrically active silicone elastomer layers, when used as dielectric layers, may be used with a film thickness of from 5 to 10,000 maicrometers, or such layers may be stacked to obtain greater thickness.

The thin film-like silicone elastomer layer that is the member for transducers may be formed by stacking the same thin film-like silicone elastomer, or by stacking two or more types of thin film-like silicone elastomers having different physical characteristics or pre-curing compositions. Moreover, the function of the thin film-like silicone elastomer layer may be a dielectric layer or an electrode layer. In particular, in a preferred member for transducers, thickness of the dielectric layer is from 1 to 1,000 maicrometers, and thickness of the electrode layer is from 0.05 to 100 maicrometers.

The transducer of the present invention is characterized by having this member for transducers produced by curing of the curable organopolysiloxane composition of the present invention, and the transducer of the present invention may have a structure that particularly comprises a highly stacked layer structure, i.e. two or more dielectric layers. The transducer of the present invention further may have a structure that comprises 3 or more dielectric layers. The transducer that has this type of highly stacked structure is able to generate greater force by comprising multiple layers. Moreover, by stacking of layers, it is possible to obtain greater displacement than would be obtained by using a single layer.

An electrode may be comprised at both ends of the dielectric layer for transducers of the present invention. The utilized electrode material is exemplified by metals and alloys of metals such as gold, platinum, silver, palladium, copper, nickel, aluminum, titanium, zinc, zirconium, iron, cobalt, tin, lead, indium, chromium, molybdenum, manganese, or the like; metal oxides such as indium-tin compound oxide (ITO), antimony-tin compound oxide (ATO), ruthenium oxide, titanium oxide, zinc oxide, tin oxide, and the like; carbon materials such as carbon nanotubes, carbon nano-horns, carbon nanosheets, carbon fibers, carbon black, or the like; and electrically conductive resins such as poly(ethylene-3,4-dioxythiophene) (PEDOT), polyaniline, polypyrrole, or the like. Electrically conductive elastomer and electrically conductive resin having electrically conductive fillers dispersed in the resin may be used.

The electrode may comprise one substance alone from among the electrically conductive substances, or may comprise two or more such electrically conductive substances. If the electrode comprises two or more types of electrically conductive substances, at least one type of the electrically conductive substances may function as the active substance, and may function as a conductive material for lowering resistance of the other electrode.

The total thickness of the dielectric layer for transducers of the present invention may be set in the range of 10 to 2,000 maicrometers (2 mm), although this total thickness may be particularly set to a value not less than 200 maicrometers. In particular, thickness per single layer of the dielectric silicone elastomer layer forming the dielectric layer is preferably from 0.1 to 500 maicrometers, and this thickness is particularly preferably from 0.1 to 200 maicrometers. By stacking two or more layers of these thin silicone elastomer layers, it is possible to improve characteristics such as dielectric breakdown voltage, dielectric constant, and displacement amount in comparison to the use of a single layer.

The term "transducer" in the present invention is taken to mean an element, machine, or device for conversion of a certain type of energy to a different type of energy. This transducer is exemplified by artificial muscles and actuators for conversion of electrical energy into mechanical energy; sensors and electricity generating elements for conversion of mechanical energy into electrical energy; speakers, microphones, and headphones for conversion of electrical energy into sound energy; fuel cells for conversion of chemical energy into electrical energy; and light emitting diodes for conversion of electrical energy into light energy.

The transducer of the present invention is capable of use particularly as an artificial muscle, actuator, sensor, or electricity generating element due to the dielectric and mechanical characteristics of the transducer of the present invention. An artificial muscle is anticipated to be used for applications such as robots, nursing equipment, rehabilitation training equipment, or the like. An embodiment as an actuator will be explained below as an example of the present invention.

FIG. 1 shows a cross sectional view of an actuator 1 of the present embodiment in which dielectric layers are stacked. In this embodiment, the dielectric layer is composed of 2 dielectric layers, for example. The actuator 1 is equipped with

dielectric layers

10a and 10b, electrode layers 11a and 11b, a wire 12, and an electrical power source 13. The electrode layers 11a and 11b cover a respective contacting surface of the dielectric layer, and these are connected to the electrical power source 13 through respective wires 12.

The actuator 1 may be driven by application of a voltage between the electrode layer 11a and the electrode layer 11b. By application of voltage, the

dielectric layers

10a and 10b become thinner due to dielectric properties, and this results in elongation parallel to the faces of the electrode layers 11a and 11b. That is to say, it is possible to convert electrical energy into force or mechanical energy of movement or displacement.

FIG. 2 shows a cross sectional view of an actuator 2 of the present embodiment in which the dielectric layer and electrode layer are stacked. According to the present embodiment, the dielectric layer is composed of 3 layers, and the electrode layer is composed of 4 layers, for example. The actuator 2 is equipped with

dielectric layers

20a, 20b, and 20c,

electrode layers

21a, 21b, 21c and 21d; the wire 22; and the electrical power source 23. The electrode layers 21a, 21b, 21c, and 21d each cover a respective contacting surface of dielectric layer, and these are connected to the electrical power source 23 through respective wires 22. The electrode layers are connected alternatingly to sides of different voltage, and the electrode layers 21a and 21c are connected to a different side from that of the electrode layers 21b and 21d.

By application of voltage between the electrode layer 21a and electrode layer 21b, application of voltage between the electrode layer 21b and electrode layer 21c, and application of voltage between the electrode layer 21c and electrode layer 21d, it is possible to drive the actuator 2. By application of voltage, the

dielectric layers

20a, 20b, and 20c become thinner due to dielectric properties, and this results in elongation parallel to the faces of the

electrode layers

21a, 21b, 21c, and 21d. That is to say, it is possible to convert electrical energy into force or mechanical energy of movement or displacement.

Although the embodiment of an actuator was described as an example of the transducer of the present invention, when mechanical energy (such as pressure or the like) is applied from outside to the transducer of the present invention, it is possible to generate an electrical potential difference as electrical energy between the mutually insulated electrode layers. That is to say, use is possible as a sensor for the conversion of mechanical energy into electrical energy. This embodiment of a sensor will be described below.

FIG. 3 shows structure of the sensor 3 of the present embodiment. The sensor 3 has a structure in which the dielectric layer 30 is disposed between

upper electrode layers

31a, 31b, and 31c and

lower electrode layers

32a, 32b, and 32c arranged in a matrix-like pattern. According to the present embodiment, for example, the electrode layers are disposed in a matrix pattern of three rows in the vertical direction and horizontal direction, respectively. The face of each electrode layer not contacting the dielectric layer 30 may be protected by an insulating layer. Moreover, the dielectric layer 30 may comprise two or more layers of the same dielectric layer containing organopolysiloxane.

When an external force is applied to the surface of this sensor 3, the thickness of the dielectric layer 30 between the upper electrode layer and the lower electrode layer changes at the applied location, and there is a change in static capacity between the electrode layers due to this change. By measurement of the electrical potential difference between the electrode layers due to this change of static capacity between these electrode layers, it is possible to detect the external force. That is to say, this embodiment may be used as a sensor for conversion of mechanical energy into electrical energy.

Furthermore, although the opposing electrode layers sandwiching the dielectric layer were formed as 3 pairs in the sensor 3 of the present embodiment, the number, sizes, placement, or the like of electrode layers may be selected appropriately according to application.

An electricity generating element is a transducer for conversion of mechanical energy into electrical energy. This electricity generating element may be applied for devices that generate electricity, beginning with electricity generation by natural energy such as wave power, water power, water power, or the like, as well as generation of electricity due to vibration, impact, pressure change, or the like. An embodiment of this electricity generating element will be described below.

FIG. 4 shows a cross sectional view of the electricity generating element 4 of the present embodiment, in which dielectric layers are stacked. In this embodiment, the dielectric layer is composed of 2 dielectric layers, for example. The electricity generating element 4 is composed of the

dielectric layers

40a and 40b and the electrode layers 41a and 41b. The electrode layers 41a and 41b are arranged covering one face of the respective contacted dielectric layer.

The electrode layers 41a and 41b are connected electrically to a non-illustrated load. This electricity generating element 4 may generate electrical energy by change of the static capacity by change of the distance between the electrode layers 41a and 41b. That is to say, due to change in the shape of the element between the electrode layers 41a and 41b in the electrostatic charge-induced state due to electrostatic field formed by the

dielectric layers

40a and 40b, the charge distribution becomes biased, the static capacity between electrode layer changes due to such bias, and an electrical potential difference arises between the electrode layers.

In the present embodiment, due to change from a state (upper drawing) of applied compression force in the direction parallel to the faces of the electrode layers 41a and 41b of the electricity generating element 4 shown in FIG. 4 to a state (lower drawing) of non-application of compression as shown in the same figure, an electrical potential difference arises between the electrode layers 41a and 41b, and it is possible to realize the function of an electricity generating element by output of this change of electrical potential difference as electrical power. That is to say, it is possible to convert mechanical energy into electrical energy. Moreover, multiple elements may be arranged on a substrate, and it is possible to construct an electricity generating device that generates a greater amount of electricity by series or parallel connection of such multiple elements.

The transducer of the present invention may operate in air, water, vacuum, or organic solvent. Moreover, the transducer of the present invention may be sealed appropriately according to the environment of use of the transducer. No particular limitation is placed on the sealing method, and this sealing method is exemplified by sealing using a resin material or the like.

The curable organopolysiloxane composition of the present invention can be advantageously used in applications requiring an elastomer with excellent mechanical characteristics and electrical characteristics, such as the production of transducers, for example. The curable organopolysiloxane composition of the present invention, rather than simply an uncured curable composition, may comprise a so-called B stage material in a state in which the reactive organopolysiloxane is partially reacted and curing is incomplete. A B stage material of the present invention is exemplified by a material in a state that is gel-like or has fluidity. Therefore, the embodiments of the present invention also comprise a member in a state where the curing reaction of the curable organopolysiloxane composition has partially progressed, and in which the member for transducers is in a state that is gel-like or fluid. Moreover, the member for transducers in this type of semi-cured state may be composed of a single layer or stacked layers of the thin film-like silicone elastomer.

Examples

In order to exemplify the present invention, practical examples will now be given. However, it should be understood that these practical examples do not limit the scope of the present invention. Furthermore, "%" below represents percent by mass.

Practical Example 1
To 14.22% of dimethylpolysiloxane (A₂₁) (0.23% vinyl content) having a viscosity of 2,000 mPa s at 25C and capped by dimethylvinylsiloxy groups at both terminals were added 85.35% spherical barium titanate of 1.0 maicrometers average particle diameter (produced by Fuji Titanium Industry Co., Ltd., HPBT-1B), 0.356% polysiloxane capped at a molecular terminal with trimethoxysilyl and capped at another molecular terminal with dimethylvinyl (average degree of polymerization 25), and 0.071% of 1,1,3-trimethyl-3,3-diphenyl-1-carboxydecyldisiloxane. After mixing uniformly using a Ross mixer, the mixture was further heated and mixed at 150C for 30 minutes to obtain a silicone elastomer base.

To this silicone rubber base, polydimethylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups (A₁₁; SiH content: 0.015%), a copolymer containing dimethylhydrogensiloxy groups ((CH₃)₂HSiO_1/2) and phenylsiloxy groups (C₆H₅SiO_3/2) (A₁₆; SiH content: 0.66%), a solution of dimethylpolysiloxane with dimethylvinylsiloxy groups at both terminals containing 0.67% (as platinum) 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane platinum complex, and tetramethyltetravinylcyclotetrasiloxane as a reaction control agent were added so as to result in the blending ratios shown in Table 1. The mixture was mixed until uniform (approximately 10 minutes) to obtain a silicone elastomer composition. Here, the molar ratio of all SiH functional groups to all vinyl groups (SiH groups/vinyl groups) in this silicone elastomer composition was 1.3.
Here, the mass fraction of the monovalent aromatic hydrocarbon groups having from 6 to 10 carbons (Z) relative to the total of siloxane components in the curable silicone elastomer composition is 0.49%; the mass fraction of organopolysiloxanes having reactive groups at both molecular terminals and having more than 200 repeating units (W) is 85.2%; the mass fraction of reactive organopolysiloxanes (X) represented by M_aM^R _bD_cD^R _dT_eT^R _fQ_g, wherein the value of (a + c)/(b + d + e + f + g) is less than 3, relative to the total of siloxane components in the curable organopolysiloxane composition, is 1.6%; the mass fraction of organopolysiloxanes having reactive groups at both molecular terminals (Y) relative to the total of siloxane components in the curable organopolysiloxane composition is 98.4%; the blending ratio (mass ratio: S/L) of reactive organopolysiloxanes (S) having at least two groups capable of a curing reaction in a molecule and having an average molecular weight between the two groups capable of a curing reaction of less than 10,000 to the reactive organopolysiloxanes (L) having at least two groups capable of a curing reaction in a molecule and having a molecular weight between the two groups capable of a curing reaction of not less than 10,000 and not greater than 150,000 is 1.6/98.4.

This silicone elastomer composition was press cured for 15 minutes at 150C, and then was post-cured in an oven for 60 minutes at 150C. Based on JIS K 6249, Young's modulus, tensile strength, breaking elongation, and tear strength were measured for the obtained cured product. In order to measure mechanical strength, a sheet of 2 mm thickness was made. Durometer A hardness of a 6 mm thick sheet was measured based on JIS K 6253.
Moreover, this silicone elastomer composition was press cured for 15 minutes at 150C to produce a 0.07 mm thick sheet, and dielectric breakdown strength was measured using an electrical dielectric breakdown voltage oil tester, i.e., PORTATEST 100A-2 manufactured by Soken Electric Co., Ltd. Similarly, the silicone elastomer composition was press cured for 15 minutes at 150C to produce a 1 mm thick sheet, and dielectric constant was measured in the measurement frequency range of 100 Hz to 30 MHz at measurement temperature 23C using an LCR meter 6530P/D2 manufactured by Wayne Kerr Electronics. Among these, the value measured at 1 MHz was used in the practical examples and comparative examples. These results are shown in Table 4.1 and 4.2

Practical Examples 2 to 16 and Comparative Examples 1 to 2
The same procedure as that of Practical Example 1 was performed except for changing the added amounts and chemical structures of the crosslinking agent and the polymer, or as may have been required, using the microparticles listed in Tables 1 to 3, to obtain silicone rubber compositions. The aforementioned Z, X, Y, and S/L values were calculated in the same manner. The obtained composition was heated and cured in the same manner, and mechanical strength and electrical characteristics were evaluated. The results are shown in Tables 4.1, 4.2 and 5. Moreover, in the tables, the chemical structures of the crosslinking agents and polymers not described above are as follows.

A₂₂: Polydimethylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups
A₂₃: Polymethylphenylsiloxane capped at both molecular terminals with dimethylvinylsiloxy groups
A₂₄: Polymethylphenylsiloxane capped at both molecular terminals with diphenylvinylsiloxy groups
A₁₂: Dimethylmethylhydrogensiloxane copolymer capped at both molecular terminals with trimethylsilylsiloxy groups
A₁₃: Polydimethylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups
A₁₄: Dimethylsiloxane/methylhydrogensiloxane copolymer capped at both molecular terminals with trimethylsilylsiloxy groups
A₁₅: Polydiphenylsiloxane capped at both molecular terminals with dimethylhydrogensiloxy groups
Reaction control agent: Tetramethyltetravinylcyclotetrasiloxane
Pt catalyst (hydrosilylation reaction catalyst): 1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex

Table 1 (Compositions of Practical Examples 1 to 8)

Table 2 (Compositions of Practical Examples 9 to 16)

Table 3 (Compositions of Comparative Examples 1 to 2)

Table 4.1 Compositions, Structural Factors, and Physical Property Values of Practical Examples 1 to 11

Table 4.2 Compositions, Structural Factors, and Physical Property Values of Practical Examples 1 to 11 (Continued)

Table 5 Compositions, Structural Factors, and Physical Property Values of Practical Examples 12 to 16 and Comparative Examples 1 to 2

As illustrated in Tables 4.1, 4.2 and 5, a curable organopolysiloxane composition having constituent components of a curable organopolysiloxane containing an organopolysiloxane having reactive groups at both molecular terminals and having more than 200 repeating units and containing a prescribed quantity of monovalent aromatic hydrocarbon groups, and inorganic microparticles having an average primary particle diameter of not less than 50 nm, provides a silicone elastomer having excellent mechanical characteristics represented by breaking elongation and electrical characteristics represented by dielectric breakdown strength. Furthermore, using dielectric inorganic microparticles as the inorganic microparticles enables both a reduction in the elastic modulus and an increase in the dielectric breakdown strength of the cured product, and enables the design of a silicone elastomer advantageously used in transducer applications.
On the other hand, as shown in Table 5, the silicone elastomers obtained by curing substances other than the curable organopolysiloxane of the present invention, as a whole, hardly achieved the reduction in elastic modulus and increase in dielectric breakdown strength of the cured product at the same time that were realized in the practical examples.

1, 2 Actuator
10a, 10b, 20a, 20b, 20c Dielectric layer
11a, 11b, 21a, 21b, 21c, 21d Electrode layer (electrically conductive layer)
12, 22 Wire
13, 23 Electrical power source
3 Sensor
30 Dielectric layer
31a, 31b, 31c Upper electrode layer
32a, 32b, 32c Lower electrode layer
4 Electricity generating element
40a, 40b Dielectric layer
41a, 41b Electrode layer

Claims

A curable organopolysiloxane composition comprising an organopolysiloxane represented by formula (I) below:
R^a _aR^b _bSiO_(4-a-b)/2 (I)
wherein R^a is a monovalent aromatic hydrocarbon group having from 6 to 10 carbons, and
R^b is at least one type of monovalent functional group, provided that R^b is a group other than a monovalent aromatic hydrocarbon group having from 6 to 10 carbons, wherein at least part of R^b is a group capable of a curing reaction, and 0 < a, 0 < b, 1.9 < a+b < 2.1; and
at least one type of inorganic microparticles having an average primary particle diameter of not less than 50 nm;
wherein
the mass fraction of the monovalent aromatic hydrocarbon groups having from 6 to 10 carbons (Z) in the total of organopolysiloxanes is not less than 0.2% by mass and not greater than 50% by mass;
and
the mass fraction of a straight-chain organopolysiloxanes represented by formula (II) below (W) in the total of organopolysiloxanes is not less than 50% by mass:
R¹R² ₂Si(OSiR³R⁴)_n(OSiR³R¹)_mOSiR¹R² ₂ (II)
wherein R¹ is a group capable of a curing reaction, R², R³, and R⁴ are each independently, the same or different, a hydrogen atom, monovalent aliphatic hydrocarbon groups having from 1 to 10 carbons, and monovalent aromatic hydrocarbon groups having from 6 to 10 carbons; n and m are numbers respectively satisfying the conditions 200 < n and 0 =< m =< (n/20).
The curable organopolysiloxane composition according to claim 1, wherein the mass fraction of the monovalent aromatic hydrocarbon groups (Z) is not less than 0.5% by mass and not greater than 30% by mass.
The curable organopolysiloxane composition according to claim 1 or 2, wherein the mass fraction of the straight-chain organopolysiloxanes (W) is not less than 75.0% by mass and not greater than 99.9% by mass.
The curable organopolysiloxane composition according to any one of claims 1 to 3, wherein the monovalent aromatic hydrocarbon group having from 6 to 10 carbons is a phenyl group.
The curable organopolysiloxane composition according to any one of claims 1 to 4, wherein the at least one type of inorganic microparticles having the average primary particle diameter of not less than 50 nm include dielectric inorganic microparticles having a specific dielectric constant at 1 kHz at room temperature of not less than 10.
The curable organopolysiloxane composition according to any one of claims 1 to 5, wherein the group capable of a curing reaction is a group capable of a curing reaction in a condensation reaction, an addition reaction, a peroxide reaction, or a photoreaction.
The curable organopolysiloxane composition according to any one of claims 1 to 6, further satisfying all of the compositional features described in [1], [2], and [3] below:
[1] the curable organopolysiloxane composition contains an organopolysiloxane represented by a general formula: M_aM^R _bD_cD^R _dT_eT^R _fQ_g, wherein a value of (a + c)/(b + d + e + f + g) is less than 3, in an amount not less than 0.1% by mass and not greater than 10% by mass relative to the total of organopolysiloxane components in the curable organopolysiloxane composition; wherein, in the above general formula, M is a triorganosiloxy unit; D is a diorganosiloxy unit; T is a monoorganosiloxy unit; Q is a siloxy unit represented by SiO_4/2; and substituent R on each of the siloxy units is a group capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction;
[2] the curable organopolysiloxane composition contains a reactive organopolysiloxane having only at both molecular terminals a group capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction, in an amount not less than 75% by mass and not greater than 99.9% by mass relative to the total of siloxane components in the curable organopolysiloxane composition;
[3] the curable organopolysiloxane composition contains (S) a reactive organopolysiloxane having in a molecule at least two groups capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction, the reactive organopolysiloxane S having an average molecular weight of less than 10,000 between the two groups capable of the curing reaction, and
(L) a reactive organopolysiloxane having in a molecule at least two groups capable of a curing reaction in a condensation reaction, addition reaction, peroxide reaction, or photoreaction, the reactive organopolysiloxane L having a molecular weight of not less than 10,000 and not greater than 150,000 between the two groups capable of a curing reaction, and a blending ratio (mass ratio) of component (S) and component (L) being from 1:99 to 20:80.
The curable organopolysiloxane composition according to claim 7, wherein a weight fraction of the reactive organopolysiloxanes represented by the general formula M_aM^R _bD_cD^R _dT_eT^R _fQ_g of [1] above is not greater than 5% by mass relative to the total of organopolysiloxane components in the curable organopolysiloxane composition.
The curable organopolysiloxane composition according to any one of claims 1 to 8, wherein the group capable of a curing reaction is a group capable of an addition reaction, R^b in formula (I) is a group selected from the group consisting of optionally substituted monovalent hydrocarbon groups having from 1 to 10 carbons (provided that, R^b is a group other than a monovalent aromatic hydrocarbon group having from 6 to 10 carbons), a hydrogen atom, alkenyl groups having from 2 to 8 carbons, alkoxy groups having from 1 to 4 carbons, and a hydroxyl group, and at least part of R^b is a group capable of an addition reaction selected from a hydrogen atom and alkenyl groups having from 2 to 8 carbons.
The curable organopolysiloxane composition according to any one of claims 1 to 9, wherein the organopolysiloxane contains an organopolysiloxane having a silicon-bonded hydrogen atom and an organopolysiloxane having a silicon-bonded unsaturated hydrocarbon group, wherein a blending ratio (molar ratio) of the silicon-bonded hydrogen atoms and the silicon-bonded unsaturated hydrocarbon groups in the organopolysiloxane is from 0.5:1.0 to 3.0:1.0 (silicon-bonded hydrogen atoms:silicon-bonded unsaturated hydrocarbon groups).
The curable organopolysiloxane composition according to any one of claims 1 to 10, comprising at least one type of reactive organohydrogenpolysiloxane in which the organopolysiloxane has at least two silicon-bonded hydrogen atoms in a molecule, a weight fraction of hydrogen atoms being from 0.01 to 2.0% by weight, and
at least one type of reactive organopolysiloxane in which the number of repeating units exceeds 200, having an alkenyl group at both terminals of the molecular chain, a weight fraction of alkenyl groups being from 0.05 to 5.0% by weight;
the composition further comprising:
a hydrosilylation reaction catalyst; and
dielectric inorganic microparticles having a specific dielectric constant at 1 kHz at room temperature of not less than 10.
The curable organopolysiloxane composition according to any one of claims 1 to 11, wherein at least a part of the organopolysiloxane is an organopolysiloxane having a highly dielectric functional group.
The curable organopolysiloxane composition according to any one of claims 1 to 12, further comprising a compound having a highly dielectric functional group (with an exception of an organopolysiloxane participating in the curing reaction).
The curable organopolysiloxane composition according to any one of claims 1 to 13, further comprising at least one type of inorganic microparticles having an average primary particle diameter of less than 50 nm.
The curable organopolysiloxane composition according to claim 14, wherein the at least one type of inorganic microparticles having the average primary particle diameter of less than 50 nm further contain reinforcing inorganic microparticles.
The curable organopolysiloxane composition according to any one of claims 1 to 15, wherein part or all of the inorganic microparticles are surface-treated by one or more types of surface treatment agent.
The curable organopolysiloxane composition according to any one of claims 1 to 16, further comprising an additive for improvement of mold releasability or dielectric breakdown characteristics.
An organopolysiloxane cured product having tensile breaking elongation measured according to JIS K 6249 of not less than 200%, the product being formed by at least partially curing the curable organopolysiloxane composition described in any one of claims 1 to 17.
A member for transducers, the member being formed by at least partially curing the curable organopolysiloxane composition described in any one of claims 1 to 17.
A transducer comprising a silicone elastomer intermediate layer disposed between at least one pair of electrodes, the silicone elastomer intermediate layer being formed by a curing reaction or partial curing reaction of the curable organopolysiloxane composition described in any one of claims 1 to 17.
The transducer according to claim 20, wherein at least two silicone elastomer layers are stacked.
A method of producing the curable organopolysiloxane composition described in any one of claims 1 to 17, the method comprising a step of blending at least two components constituting the curable organopolysiloxane composition using at least one mechanical means selected from the group consisting of twin screw extruders, twin screw kneaders, and single screw blade-type extruders.