# US 8,542,852 B2 · Electro-mechanical transducer, an electro-mechanical converter, and manufacturing methods of the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,542,852 B2 - Document ID: US8542852B2 - Status: Granted - Kind: B2 - Application number: 12/936,770 - Filed: 2009-04-07 - Published: 2011-05-12 - Granted: 2013-09-24 - Earliest claimed: 2008-04-07 - Assignees: National University Corporation Saitama University - Applicants: Kensuke Kageyama - Inventors: Kensuke Kageyama - Web page: https://patentgrep.com/patent/US8542852B2 ## CPC - H04R 19/016: {for microphones} - B06B 1/0292: {Electrostatic transducers, e.g. electret-type} - H04R 19/005: {using semiconductor materials} - 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) - B06B: METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, {e.g.} FOR PERFORMING MECHANICAL WORK IN GENERAL (for particular applications, see the relevant subclasses, e.g. B07B1/40, B23Q17/12, B24B31/06; measurement of mechanical vibrations G01H; in direction finding, locating, distance or velocity measuring G01S; {generating seismic energy G01V1/02}; control of mechanical vibrations in general G05D; sound-producing devices, e.g. bells, sirens, whistles G10K, {e.g. methods or devices for transmitting, conducting, or directing sound in general G10K11/00}; generation of electrical oscillations H03B; electromechanical resonators in general H03H; electromechanical transducers {for communication techniques, e.g. microphones, speakers} H04R) ## Abstract An electro-mechanical transducer contains a vibrating electrode (15b), a vibrating-electrode-insulating film (15a) disposed at a bottom surface of the vibrating electrode (15b), an electret layer (13) facing to the vibrating electrode (15b), an electret-insulating layer (14e) joined to a top surface of the electret layer (13), and a back electrode 17 in contact with a bottom surface of the electret layer (13). A microgap between ten nanometers and 100 micrometers is established between the vibrating-electrode-insulating film (15a) and electret-insulating layer (14e). A central line average roughness Ra of the vibrating electrode (15b), including a bending, is 1/10 or less of a gap width measured between the bottom surface of the vibrating electrode (15b) and the top surface of the electret layer (13). ## Claims ### Claim 1 An electro-mechanical transducer comprising: a vibrating electrode having a flat vibration surface under no load condition; a vibrating-plate-insulating layer disposed at a bottom surface of said vibrating electrode; an electret layer facing to the vibrating electrode; and a back electrode in contact with a bottom surface of the electret layer, wherein a microgap between ten nanometers and 100 micrometers is established between the vibrating-plate-insulating layer and the electret layer, and a central line average roughness Ra of the vibrating electrode, including a bending under a loaded condition, is 1/10 or less of a gap width measured between the bottom surface of the vibrating electrode and a top surface of the electret layer. ### Claim 2 An electro-mechanical transducer comprising: a vibrating electrode having a flat vibration surface under no load condition; an electret layer facing to the vibrating electrode; an electret-insulating layer joined to a top surface of the electret layer; and a back electrode in contact with a bottom surface of the electret layer, wherein a microgap between ten nanometers and 100 micrometers is established between the vibrating electrode and the electret-insulating layer, and a central line average roughness Ra of the vibrating electrode, including a bending under a loaded condition, is 1/10 or less of a gap width measured between a bottom surface of the vibrating electrode and the top surface of the electret layer. ### Claim 3 An electro-mechanical transducer comprising: a vibrating electrode having a flat vibration surface under no load condition; a vibrating-plate-insulating layer disposed at a bottom surface of the vibrating electrode; an electret layer facing to the vibrating electrode; an electret-insulating layer joined to a top surface of the electret layer; and a back electrode in contact with a bottom surface of the electret layer, wherein a microgap between ten nanometers and 100 micrometers is established between the vibrating-plate-insulating layer and the electret-insulating layer, and a central line average roughness Ra of the vibrating electrode, including a bending under a loaded condition, is 1/10 or less of a gap width measured between the bottom surface of the vibrating electrode and the top surface of the electret layer. ### Claim 4 (depends on 1) The electro-mechanical transducer according to claim 1, wherein the microgap is controlled by a height of a protrusion, which is provided as a spacer at a bottom surface of the vibrating-plate-insulating layer. ### Claim 5 (depends on 2) The electro-mechanical transducer according to claim 2, wherein the microgap is controlled by a height of a protrusion, which is provided as a spacer at a top surface of the electret-insulating layer. ### Claim 6 (depends on 1) The electro-mechanical transducer according to claim 1, wherein the microgap is controlled by a diameter of a particle, which is provided as a spacer between the vibrating-plate-insulating layer and the electret layer. ### Claim 7 (depends on 2) The electro-mechanical transducer according to claim 2, wherein the microgap is controlled by a diameter of a particle, which is provided as a spacer between the vibrating electrode and the electret-insulating layer. ### Claim 8 (depends on 3) The electro-mechanical transducer according to claim 3, wherein the microgap is controlled by a diameter of a particle, which is provided as a spacer between the vibrating-plate-insulating layer and the electret-insulating layer. ### Claim 9 (depends on 3) The electro-mechanical transducer according to claim 3, wherein the microgap is controlled by a thickness of a spacer layer that has a plurality of penetration holes, the spacer layer is inserted between the vibrating-plate-insulating layer and the electret-insulating layer. ### Claim 10 (depends on 1) The electro-mechanical transducer according to claim 1, further comprising a spacer ring that surrounds the microgap, the spacer ring is inserted between the vibrating-plate-insulating layer and the electret layer in a periphery of the microgap. ### Claim 11 (depends on 2) The electro-mechanical transducer according to claim 2, further comprising a spacer ring that surrounds the microgap, the spacer ring is inserted between the vibrating electrode and the electret-insulating layer in a periphery of the microgap. ### Claim 12 (depends on 3) The electro-mechanical transducer according to claim 3, further comprising a spacer ring that surrounds the microgap, the spacer ring is inserted between the vibrating-plate-insulating layer and the electret-insulating layer in a periphery of the microgap. ### Claim 13 (depends on 1) The electro-mechanical transducer according to claim 1, further comprising a matching layer configured to increase matching characteristics of acoustic impedance, the matching layer is provided on a top surface of the vibrating electrode. ### Claim 14 (depends on 1) The electro-mechanical transducer according to claim 1, wherein the electret layer is a single crystalline ferroelectric material, a polycrystalline ferroelectric material or a crystalline polymer film.