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Patent US3705312A successfully refreshed from Google Patents.
US3705312A
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Preparation of electret transducer elements by application of controlled breakdown electric field
Assignee: AT&T Inc
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Filing: 1970-11-02
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Granted: 1972-12-05
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Expires: 1990-11-02
Abstract
Abstract A thin film electret with excellent surface charge properties is produced by placing a thin polymer film between two electrodes together with a dielectric plate and by applying a voltage of about 30 keV across the resulting sandwich of elements for about 1 minute. The process is carried out at room temperature and at atmospheric pressure. By using an auxiliary dielectric plate that is much thicker than the film and has the proper resistivity, a high voltage drop can be applied across the film without a resulting destructive breakdown. Charge-densities of up to 1.5 X 10 6 C/cm2, which are greater by a factor of 3 than those previously reported, are produced.
Inventors
- 👤 Gerhard Martin Sessler
- 👤 James Edward West
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 20:13
CPC Classifications
H; H01; H01G; H01G7/00; H01G7/02; H01G7/025; H01G7/026; H01G7/021; H01G7/023; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49005; Y10T428/00; Y10T428/12; Y10T428/12431; Y10T428/12438
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
30 words
Apparatus for electrically charging a thin polymer foil, as defined in claim 1, wherein, said auxiliary dielectric insert comprises at least one sheet of soda-lime glass approximately 0.1 cm thick.
Claim 2
Dependent Claim
49 words
Apparatus for electrostatically charging a thin polymer foil, as defined in claim 1, wherein, the thickness of said polymer foil and the thickness of said auxiliary dielectric insert are proportioned to establish a steady state current density within the critical range of about 10 8 to 10 6 A/cm2.
Claim 3
Dependent Claim
36 words
Apparatus for electrostatically charging a thin polymer foil, as defined in claim 1, wherein, said auxiliary dielectric insert has a resistance in the range 109 to 1012 ohms for an area of 10 to 100 cm2.
Claim 4
Dependent Claim
45 words
Apparatus for electrostatically charging a thin polymer foil, as defined in claim 1, wherein, said auxiliary dielectric insert has a resistance sufficiently high to induce breakdown of said foil but low enough to allow a relatively high voltage to be developed across said polymer foil.
Claim 5
Dependent Claim
25 words
Apparatus for electrostatically charging a thin polymer foil, as defined in claim 1, wherein, said voltage applied between said electrodes is of approximately 30 kV.
Claim 6
Independent Claim
124 words
The method of fabricating a foil electret characterized by a charge density in excess of 0.5 X 10 6 C/cm2, which comprises the steps of: sandwiching a foil of polymer material and an auxiliary dielectric plate having a resistance sufficiently high to permit nondestructive breakdown of said foil, together between a pair of plane conductive electrodes, compressing said electrodes to hold said sandwich of foil and dielectric in close contact, applying a sufficiently high voltage between said electrodes to cause said foil to break down in localized channels, but not sufficiently high to cause said dielectric plate to break down, and maintaining said voltage between said electrodes for an interval of about one minute to charge areas of said foil remote from said channels.
Claim 7
Dependent Claim
26 words
A foil electret characterized by a charge density in excess of 0.5 X 10 6 C/cm2 prepared in accordance with the method defined in claim 7.
Claim 8
Independent Claim
88 words
The method of fabricating an electret transducer, which comprises the steps of: preparing an electret diaphragm from a thin polymer film metallized on one of its surfaces by supporting said film between two electrodes, inserting a dielectric plate having a resistance sufficiently high to permit nondestructive breakdown of said film between the nonmetallized surface of said film and one of said electrodes, and supplying a voltage of approximately 30 keV between said electrodes for about 1 minute; and supporting said electret diaphragm in juxtaposition to a conductive backplate.
Claim 9
Dependent Claim
22 words
The method of fabricating an electret transducer, as defined in claim 9, wherein, said vibratile diaphragm is prepared at normal room temperature.
Claim 10
Dependent Claim
45 words
The method of fabricating an electret transducer as defined in claim 9, wherein, said dielectric plate employed in preparing said vibratile diaphragm comprises at least two sheets of soda-lime glass, each approximately 0.1 cm thick and each exhibiting a resistance of at least 1010 ohms.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-12-05 | 1976-06-05 | 1976-12-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-05 | 1980-06-05 | 1980-12-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-05 | 1984-06-05 | 1984-12-05 | $7700.00 | Window Closed / Lapsed |