# US 8,785,555 B2 · Process for producing electret, and electrostatic induction conversion device

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- Number: US 8,785,555 B2
- Document ID: US8785555B2
- Status: Granted
- Kind: B2
- Application number: 13/176,690
- Filed: 2011-07-05
- Published: 2011-10-27
- Granted: 2014-07-22
- Earliest claimed: 2009-02-20
- Assignees: Asahi Glass Company, Limited
- Applicants: Kimiaki Kashiwagi
- Inventors: Kimiaki Kashiwagi
- Web page: https://patentgrep.com/patent/US8785555B2

## CPC

- H01G 7/023: {of macromolecular compounds}
- H04R 19/01: characterised by the use of electrets
- H01G: CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE (selection of specified materials as dielectric H01B3/00; capacitors having potential barriers H10D1/62, H10K10/10)
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)

## Abstract

The present invention provides a process for producing an electret which has high thermal stability of retained electric charge and which has excellent charge retention performance. This is accomplished by a process for producing an electret which includes a step of thermally treating a fluorinated polymer and a silane coupling agent, where the fluorinated polymer has an alicyclic structure in its main chain and has a carboxy group or an alkoxycarbonyl group as its terminal group; the silane coupling agent has an amino group; and the weight average molecular weight of the fluorinated polymer is at least 200,000.

## Claims

### Claim 1

A process for producing an electret, which comprises a step of thermally treating a composition comprising a fluorinated polymer and a silane coupling agent, wherein the fluorinated polymer has an alicyclic structure in its main chain and has a carboxy group or an alkoxycarbonyl group as its terminal group; the silane coupling agent has an amino group; and the weight average molecular weight of the fluorinated polymer is from 200,000 to 600,000.

### Claim 2 (depends on 1)

The process for producing an electret according to claim 1, wherein the fluorinated polymer has, as the alicyclic structure, a fluorinated alicyclic structure in its main chain.

### Claim 3 (depends on 1)

The process for producing an electret according to claim 1, wherein the silane coupling agent is at least one member selected from the group consisting of γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldiethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane and aminophenyltrimethoxysilane.

### Claim 4 (depends on 1)

The process for producing an electret according to claim 1, wherein the content of the silane coupling agent is from 0.1 to 20 mass %, based on the total amount of the fluorinated polymer and the silane coupling agent.

### Claim 5 (depends on 1)

The process for producing an electret according to claim 1, which includes the following (1) to (4) in the order of (1), (2), (3) and (4):
(1) a step of obtaining a coating fluid having the fluorinated polymer and the silane coupling agent dissolved in a solvent (a coating fluid-preparation step),
(2) a step of coating a substrate with the coating fluid to form a coating layer comprising the fluorinated polymer and the silane coupling agent (a coating step),
(3) a step of thermally treating the coating layer to obtain a coating film (a thermal treatment step), and
(4) a step of injecting an electric charge to the coating film after the thermal treatment (an electric charge-injection step).

### Claim 6 (depends on 5)

The process for producing an electret according to claim 5, wherein the solvent is a fluorinated organic solvent.

### Claim 7 (depends on 1)

An electrostatic induction conversion device comprising the electret obtained by the process as defined in claim 1.