Electret

Patent metadata

Field	Value
Publication number	US-2021183584-A1
Application number	US-202017116204-A
Country	US
Kind code	A1
Filing date	Dec 9, 2020
Priority date	Dec 13, 2019
Publication date	Jun 17, 2021
Grant date	—

Abstract

An electret includes an electret layer. The electret layer is formed by subjecting a composite film in which inorganic dielectric particles are dispersed and held in a base film to a polarization treatment. The inorganic dielectric particles are mainly composed of an inorganic dielectric material having a bandgap energy of 4 eV or more.

First claim

What is claimed is:

1 . An electret comprising an electret layer, wherein
the electret layer is formed by subjecting a composite film in which inorganic dielectric particles are dispersed and held in a base film to a polarization treatment, and the inorganic dielectric particles are mainly composed of an inorganic dielectric material having a bandgap energy of 4 eV or more.

2 . The electret according to claim 1 , further comprising a substrate, wherein
the electret layer is formed above a surface of the substrate.

3 . The electret according to claim 1 , wherein
the inorganic dielectric material is a composite oxide having an ABO 3 type perovskite structure containing two different metal elements A and B.

4 . The electret according to claim 3 , wherein
in the composite oxide, an A site of the perovskite structure is occupied by a rare earth element R selected from the group consisting of La, Y, Pr, Sm and Nd, and a B site of the perovskite structure is occupied by Al.

5 . The electret according to claim 4 , wherein
in the composite oxide, at least one of the metal elements A and B is partially substituted with a dopant element composed of a different metal element, the dopant element that substitutes for the metal element A is an alkaline earth metal element, and the dopant element that substitutes for the metal element B is one or more element selected from the group consisting of alkaline earth metal elements and Zn.

6 . The electret according to claim 5 , wherein
a substitution ratio of the dopant element that substitutes for the metal element A is 0.5 atomic % to 20 atomic %, and a substitution ratio of the dopant element that substitutes for the metal element B is 0.5 atomic % to 20 atomic %.

7 . The electret according to claim 1 , wherein
the inorganic dielectric material is an inorganic compound having an apatite structure containing phosphate ions and hydroxide ions.

8 . The electret according to claim 1 , wherein
the base film has a dielectric breakdown electric field strength higher than an electric field strength during the polarization treatment and is made of a material that is stable at a temperature during the polarization treatment.

9 . The electret according to claim 1 , wherein
a content of the inorganic dielectric particles in the composite film is 30% by volume or more and 75% by volume or less.

Assignees

• Denso Corp
• Univ Tokyo Science Found

Inventors

• Matsushita Noriyuki
• Kozawa Yoshihiro
• Kanoh Kazuhiko
• Tanaka Yumi
• Otsuka Hirotoshi
• Kotaka Yuki

Classifications

• H01G7/021

  having an organic dielectric · CPC title

• H01G7/026

  with ceramic dielectric · CPC title

• H01G7/028

  having a heterogeneous dielectric · CPC title

• C01P2004/61

  Micrometer sized, i.e. from 1-100 micrometer · CPC title

• C01F17/34

  Aluminates, e.g. YAlO3 or Y3-xGdxAl5O12 · CPC title