1. Field of the Invention
The present invention relates to a dielectric material for use in a transducer such as an actuator and a speaker, and a method for manufacturing the dielectric material. Furthermore, the present invention relates to a transducer including a dielectric layer made of the dielectric material.
2. Description of Related Art
Transducers are known that perform conversion between mechanical energy and electric energy such as actuators and sensors, or that perform conversion between acoustic energy and electric energy such as speakers and microphones. In order to constitute a highly flexible, compact and lightweight transducer, polymer materials such as dielectric elastomers are useful.
For example, an actuator can be constituted by arranging a pair of electrodes on both sides in the thickness direction of a dielectric layer made of an elastomer. In the actuator of this type, when a higher voltage is applied between the electrodes, an electrostatic attraction between the electrodes increases. This compresses the dielectric layer interposed between the electrodes in the thickness direction, and the thickness of the dielectric layer decreases. When the dielectric layer becomes thinner, it extends accordingly in the direction parallel to the surfaces of the electrodes. On the contrary, when a lower voltage is applied between the electrodes, the electrostatic attraction between the electrodes decreases. This decreases a compressive force to the dielectric layer in the thickness direction, and the thickness of the dielectric layer increases due to its elastic restoring force. When the dielectric layer becomes thicker, it contracts accordingly in the direction parallel to the surfaces of the electrodes. In such a manner, the actuator drives a member to be driven by the expansion and contraction of the dielectric layer.
In order to increase a force and displacement output from the actuator by applying a high voltage, the dielectric layer preferably has high volume resistivity and high dielectric breakdown resistance. For example, Patent Document 1 describes a dielectric material in which metal oxide nanoparticles are chemically bound to an elastomer and are dispersed in the elastomer. Patent Document 2 describes a dielectric material that is manufactured by using a rubber polymer and an alkoxysilane-modified epoxy resin. In the dielectric material described in Patent Document 2, silica is produced from alkoxysilane of the alkoxysilane-modified epoxy resin during manufacture, and epoxy groups are bound to the rubber polymer. The dielectric material thereby has a structure in which the epoxy resin and silica are incorporated in a cross-linked structure of the rubber polymer.
[Patent Document 1] Japanese Patent Application Publication No. 2013-72063 (JP 2013-72063 A)
[Patent Document 2] Japanese Patent Application Publication No. 2012-72268 (JP 2012-72268 A)
[Patent Document 3] Japanese Patent Application Publication No. 2008-034189 (JP 2008-034189 A)
[Patent Document 4] Japanese Patent Application Publication No. 2004-111400 (JP 2004-111400 A)
[Patent Document 5] Japanese Patent Application Publication No. 2007-027101 (JP 2007-027101 A)