US3858307A - Electrostatic transducer - Google Patents

Electrostatic transducer Download PDF

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Publication number
US3858307A
US3858307A US337843A US33784373A US3858307A US 3858307 A US3858307 A US 3858307A US 337843 A US337843 A US 337843A US 33784373 A US33784373 A US 33784373A US 3858307 A US3858307 A US 3858307A
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US
United States
Prior art keywords
vibratile
film
polarizing
saturation
electrode
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US337843A
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English (en)
Inventor
Hisashi Yoshimura
Nobuhisa Atoji
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Panasonic Holdings Corp
Original Assignee
Matsushita Electric Industrial Co Ltd
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Filing date
Publication date
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Application granted granted Critical
Publication of US3858307A publication Critical patent/US3858307A/en
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Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/01—Electrostatic transducers characterised by the use of electrets
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49005—Acoustic transducer

Definitions

  • This invention relates to electrostatic type transducers and particularly to a method of polarizing vibratile films of electrostatic type transducers, the vibratile films being permanently polarized after assembly into housings of the transducers.
  • the electrostatic type speaker which is a typical example of the electrostatic type transducer, is usually of a construction as shown in FIG. 1 of the accompanying drawing. It comprises a vibratile film 1 of a dielectric material, a vibratile electrode 2 formed by depositing or applying a thin film of such material as aluminum and silver on one surface of the dielectric film l and vibrating therewith, and a stationary electrode 3 of a punched or perforate metal plate extending parallel to the vibratile film 1 to form a capacitor therewith.
  • the stationary electrode 3 and vibrating film 1 are spaced apart a certain distance conforming to the required acoustic characteristics of the speaker by a spacer 5 defining an air layer 6 between them.
  • the speaker unit should include a high voltage generator and an amplifier as well as requiring a signal input terminal and a bias voltage terminal, which imposes restriction on the speaker design and leads to increased manufacturing cost.
  • the high d-c bias voltage will cause ionization of the air layer between the electrodes, thus rendering the speaker sensitivity unstable resulting in various practical problems. Further, the use of high d-c voltage is quite hazardous to the user.
  • an object of the invention is to provide an electrostatic type transducer, which is free from the drawbacks inherent in the conventional transducers of these types and can be readily manufactured.
  • Another object of the invention is to provide an electro-static transducer for use in speakers, microphones, pickups and the like, which uses a vibratile film of a dielectric material such as a plastic film capable of readily undergoing permanent polarization by the forced induction and charge attraction phenomena therein and does not require any d-c bias voltage for operation.
  • a vibratile film of a dielectric material such as a plastic film capable of readily undergoing permanent polarization by the forced induction and charge attraction phenomena therein and does not require any d-c bias voltage for operation.
  • a permanent electrostatic charge can be built up on the vibratile film by applying a saturation polarizing voltage thereto for several seconds, so that it is possible to manufacture an electrostatic transducer without requiring any d-c bias voltage for its operation.
  • a saturation polarizing voltage thereto for several seconds, so that it is possible to manufacture an electrostatic transducer without requiring any d-c bias voltage for its operation.
  • the ionization of the air layer between the electrodes can be eliminated to greatly improve the sensitivity and other characteristics of the transducer.
  • the saturation polarizing voltage maybe applied after the vibrating film is assembled into a housing of the transducer such as a speaker, microphone and the like. By so doing, the initially built-up charge may be prevented from being otherwise neutralized during the assemblage.
  • FIG. 1 is a schematic representation of a prior-art electrostatic transducer
  • FIG. 2 is a schematic representation of the principles underlying the invention.
  • FIG. 3 is a graph representing a hysteresis characteristic showing the relationship between the polarizing voltage E applied on the vibrating film and the residual sound pressure after the removal of the polarizing voltage E,,, which is obtained when the vibratile film according to the invention is applied to a speaker.
  • Aluminum was deposited on one surface of an unpolarized film of polyethylene terephthalate known commercially by the trademark Tetron" and assembled, as a vibratile film, into a housing of an electrostatic speaker, opposite to a stationary electrode and spaced therefrom so as to define an air layer. It was found that a capacitor consisting of the deposited aluminum layer, Tetron film, air layer and the stationary electrode exhibits a hysteresis phenomenon due to absorbed surface charges. This phenomenon is thought to correspond to a ferroelectric phenomenon of a ferroelectric substance and is called a hysteresis of the condenser speaker with absorbed surface charges.
  • reference numeral 7 designates a vibratile dielectric thin film made of such plastic material as Tetron and Mylar trademarks for polyethylene terephthalate, polymide or a fluorine compound resin, for instance ethylene tetrafluoride'or polyvinylidene fluoride, capable of readily undergoing permanent polarization.
  • the vibratile film initially undergoes no polarization.
  • the vibratile film is provided on one side with a vibratile electrode 8 as in the conventional transducer. It faces a stationary electrode 9 formed with a plurality of small pores 10.
  • the stationary electrode 9 and the vibrating film 7 define an air layer 11 therebetween.
  • a capacitor consisting of the electrodes 8 and 9 in between which the vibratile film 7 and the air layer 11 are sandwiched is formed.
  • a saturation polarizing voltage E is applied between the electrodes 8 and 9 such that the residual charge on the vibratile film 7 is maximum, thereby causing the ferroelectric phenomenon in the vibratile film 7 due to absorbed surface charges and thereby polarizing permanently the vibratile film 7.
  • the direction of polarization when the polarizing voltage E is applied between the electrodes 8 and 9 is shown in FIG. 2. Even when the polarizing voltage E is removed, the vibratile film 7 still remains polarized. This is thought to be due to spontaneous polarization for permanent superficial charge attraction. That is, spontaneous polarization is induced in the vibratile film 7 and permanent superficial charge attraction consequently occurs in opposite surfaces of the vibratile film 7.
  • FIG. 3 shows a hysteresis of the output residual sound pressure p, which is obtained by using a Tetron film 15 microns thick as the vibratile film 7 and applying input signal e after the application of polarizing voltage E for several seconds without heating the vibratile film 7.
  • the sound pressure would follow the dashed plot in FIG. 3. Actually, the plastic film usually bears a slight negative charge. Due to the natural charging of the film and the application of the polarizing voltage, the output sound pressure will start to follow segment 1 of the plot and then follow through segments 2, 3, 4, 5 and 6 of the hysteresis curve in the mentioned order back to segment 2 as the polarizing voltage on the non-polarized film is increased in small steps to a positive maximum, then reduced to a negative maximum and back to the positive maximum.
  • the saturation polarizing voltage E is determined by the speaker construction, the thickness of the air layer 11 and the material of the vibratile film 7. After removal of the saturation polarizing voltage a residual sound pressure of about 98 db may be obtained, so that the bias voltage becomes unnecessary.
  • plastic material is selected from a group consisting of polyethylene terephthalate, a polyimide resin and fluorine compound resin.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
US337843A 1969-12-11 1973-03-05 Electrostatic transducer Expired - Lifetime US3858307A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP44099939A JPS5220851B1 (enExample) 1969-12-11 1969-12-11

Publications (1)

Publication Number Publication Date
US3858307A true US3858307A (en) 1975-01-07

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ID=14260671

Family Applications (1)

Application Number Title Priority Date Filing Date
US337843A Expired - Lifetime US3858307A (en) 1969-12-11 1973-03-05 Electrostatic transducer

Country Status (5)

Country Link
US (1) US3858307A (enExample)
JP (1) JPS5220851B1 (enExample)
CA (1) CA944473A (enExample)
DE (1) DE2061210A1 (enExample)
FR (1) FR2070812B1 (enExample)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3945112A (en) * 1975-03-21 1976-03-23 Bell Telephone Laboratories, Incorporated Technique for fabrication of foil electret
US4062105A (en) * 1976-12-20 1977-12-13 The United States Of America As Represented By The Secretary Of The Navy Method for fabricating ferroelectric ultrasonic transducers
US4191193A (en) * 1976-02-29 1980-03-04 Mitsubishi Petrochemical Co. Ltd. Catheter head-type transducer
US5267076A (en) * 1988-06-10 1993-11-30 Thomson-Csf Process for obtaining a structure generating non-linear electrooptical effects, structure obtained and applications thereof
US20020131228A1 (en) * 2001-03-13 2002-09-19 Potter Michael D. Micro-electro-mechanical switch and a method of using and making thereof
US20020182091A1 (en) * 2001-05-31 2002-12-05 Potter Michael D. Micro fluidic valves, agitators, and pumps and methods thereof
EP1282339A3 (en) * 2001-07-31 2004-01-14 Matsushita Electric Industrial Co., Ltd. Condenser microphone and production method thereof
US6688179B2 (en) 2001-10-26 2004-02-10 Nth Tech Corporation Electrostatic pressure transducer and a method thereof
US20040145271A1 (en) * 2001-10-26 2004-07-29 Potter Michael D Electrostatic based power source and methods thereof
US20050044955A1 (en) * 2003-08-29 2005-03-03 Potter Michael D. Methods for distributed electrode injection and systems thereof
US20050205966A1 (en) * 2004-02-19 2005-09-22 Potter Michael D High Temperature embedded charge devices and methods thereof
US20070074731A1 (en) * 2005-10-05 2007-04-05 Nth Tech Corporation Bio-implantable energy harvester systems and methods thereof
US7211923B2 (en) 2001-10-26 2007-05-01 Nth Tech Corporation Rotational motion based, electrostatic power source and methods thereof
US7217582B2 (en) 2003-08-29 2007-05-15 Rochester Institute Of Technology Method for non-damaging charge injection and a system thereof
US20090086613A1 (en) * 2007-10-02 2009-04-02 Seagate Technology Llc Non-Destructive Readback For Ferroelectric Material
EP2019298A4 (en) * 2006-04-27 2016-03-02 Univ Saitama Nat Univ Corp DEVICE FOR CONVERTING MECHANICAL IN ELECTRICAL AND MANUFACTURING METHOD THEREFOR
US20170170674A1 (en) * 2015-12-09 2017-06-15 Nth Tech Corporation Methods for trapping electrons at an interface of insulators each having an arbitrary thickness and devices thereof

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2330800C3 (de) * 1973-06-16 1981-10-01 Sennheiser Electronic Kg, 3002 Wedemark Elektroakustischer Wandler nach dem elektrostatischen Prinzip und Verfahren zu dessen Herstellung
GB2079056B (en) * 1980-06-30 1985-04-17 Tokyo Shibaura Electric Co Electret device
DE4115221C2 (de) * 1991-05-10 1994-09-01 Sennheiser Electronic Elektroakustischer Wandler nach dem elektrostatischen Prinzip

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3705312A (en) * 1970-11-02 1972-12-05 Bell Telephone Labor Inc Preparation of electret transducer elements by application of controlled breakdown electric field

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3705312A (en) * 1970-11-02 1972-12-05 Bell Telephone Labor Inc Preparation of electret transducer elements by application of controlled breakdown electric field

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3945112A (en) * 1975-03-21 1976-03-23 Bell Telephone Laboratories, Incorporated Technique for fabrication of foil electret
US4191193A (en) * 1976-02-29 1980-03-04 Mitsubishi Petrochemical Co. Ltd. Catheter head-type transducer
US4062105A (en) * 1976-12-20 1977-12-13 The United States Of America As Represented By The Secretary Of The Navy Method for fabricating ferroelectric ultrasonic transducers
US5267076A (en) * 1988-06-10 1993-11-30 Thomson-Csf Process for obtaining a structure generating non-linear electrooptical effects, structure obtained and applications thereof
US20020131228A1 (en) * 2001-03-13 2002-09-19 Potter Michael D. Micro-electro-mechanical switch and a method of using and making thereof
US7280014B2 (en) 2001-03-13 2007-10-09 Rochester Institute Of Technology Micro-electro-mechanical switch and a method of using and making thereof
US7195393B2 (en) 2001-05-31 2007-03-27 Rochester Institute Of Technology Micro fluidic valves, agitators, and pumps and methods thereof
US20020182091A1 (en) * 2001-05-31 2002-12-05 Potter Michael D. Micro fluidic valves, agitators, and pumps and methods thereof
EP1282339A3 (en) * 2001-07-31 2004-01-14 Matsushita Electric Industrial Co., Ltd. Condenser microphone and production method thereof
US6731766B2 (en) 2001-07-31 2004-05-04 Matsushita Electric Industrial Co., Ltd. Condenser microphone and production method thereof
US20040145271A1 (en) * 2001-10-26 2004-07-29 Potter Michael D Electrostatic based power source and methods thereof
US7211923B2 (en) 2001-10-26 2007-05-01 Nth Tech Corporation Rotational motion based, electrostatic power source and methods thereof
US6688179B2 (en) 2001-10-26 2004-02-10 Nth Tech Corporation Electrostatic pressure transducer and a method thereof
US7378775B2 (en) 2001-10-26 2008-05-27 Nth Tech Corporation Motion based, electrostatic power source and methods thereof
US20050044955A1 (en) * 2003-08-29 2005-03-03 Potter Michael D. Methods for distributed electrode injection and systems thereof
US7217582B2 (en) 2003-08-29 2007-05-15 Rochester Institute Of Technology Method for non-damaging charge injection and a system thereof
US20070152776A1 (en) * 2003-08-29 2007-07-05 Nth Tech Corporation Method for non-damaging charge injection and system thereof
US7287328B2 (en) 2003-08-29 2007-10-30 Rochester Institute Of Technology Methods for distributed electrode injection
US7408236B2 (en) 2003-08-29 2008-08-05 Nth Tech Method for non-damaging charge injection and system thereof
US8581308B2 (en) 2004-02-19 2013-11-12 Rochester Institute Of Technology High temperature embedded charge devices and methods thereof
US20050205966A1 (en) * 2004-02-19 2005-09-22 Potter Michael D High Temperature embedded charge devices and methods thereof
US20070074731A1 (en) * 2005-10-05 2007-04-05 Nth Tech Corporation Bio-implantable energy harvester systems and methods thereof
EP2019298A4 (en) * 2006-04-27 2016-03-02 Univ Saitama Nat Univ Corp DEVICE FOR CONVERTING MECHANICAL IN ELECTRICAL AND MANUFACTURING METHOD THEREFOR
US7876661B2 (en) * 2007-10-02 2011-01-25 Seagate Technology Llc Non-destructive readback for ferroelectric material
US20090086613A1 (en) * 2007-10-02 2009-04-02 Seagate Technology Llc Non-Destructive Readback For Ferroelectric Material
US20170170674A1 (en) * 2015-12-09 2017-06-15 Nth Tech Corporation Methods for trapping electrons at an interface of insulators each having an arbitrary thickness and devices thereof

Also Published As

Publication number Publication date
FR2070812A1 (enExample) 1971-09-17
DE2061210A1 (de) 1971-06-24
FR2070812B1 (enExample) 1974-02-15
JPS5220851B1 (enExample) 1977-06-07
CA944473A (en) 1974-03-26

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