US4248808A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Technique for removing surface and volume charges from thin high polymer films
Assignee: AT&T Inc
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Filing: 1978-12-29
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Granted: 1981-02-03
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Expires: 1998-12-29
Abstract
Abstract A technique for removing surface charges from thin film electret foils involves subjecting the foil to penetrating radiation of a dosage ranging from 1-25 krad and, subsequently, annealing the foil at a temperature ranging from 80°-150° C.
Inventors
- 👤 James E. West
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 21:56
CPC Classifications
G; G11; G11C; G11C11/00; G11C11/21; G11C11/24; G11C11/34
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
94 words
A technique for reducing surface charges on a fluorinated polymer thin film having a surface charge density greater than 10 -9 C/cm 2 characterized by steps comprising (a) subjecting said film to penetrating radiation of a dosage ranging from 1 to 25 krad, in order to increase the conductivity of the film, and (b) annealing the film at a temperature ranging from 80° to 150° C. in order to substantially restore the low conductivity of the film, thereby producing a film having a residual surface charge density less than 10 -9 C/cm 2 .
Claim 2
Dependent Claim
94 words
A technique for reducing surface charges on a fluorinated polymer thin film having a surface charge density greater than 10 -9 C/cm 2 characterized by steps comprising (a) subjecting said film to penetrating radiation of a dosage ranging from 1 to 25 krad, in order to increase the conductivity of the film, and (b) annealing the film at a temperature ranging from 80° to 150° C. in order to substantially restore the low conductivity of the film, thereby producing a film having a residual surface charge density less than 10 -9 C/cm 2 .
Claim 3
Dependent Claim
16 words
Technique in accordance with claim 1 wherein the source of radiation is a cobalt 60 cell.
Claim 4
Dependent Claim
13 words
Technique in accordance with claim 1 wherein the source of radiation is x-radiation.
Claim 5
Dependent Claim
17 words
Technique in accordance with claim 1 wherein the duration of annealing ranges from 0.5 to 10 hours.
Claim 6
Dependent Claim
12 words
Technique in accordance with claim 1 wherein the fluorinated polymer is polytetrafluoroethylene.
Claim 7
Dependent Claim
14 words
Technique in accordance with claim 1 wherein the fluorinated polymer is an ethylene-propylene copolymer.
Claim 8
Independent Claim
140 words
A method for making a thin film electret comprising the steps of injecting charge into a fluorinated polymer thin film having a thin layer of a metal deposited upon at least one surface thereof in order to produce a film having an intercepted charge density greater than 10 -9 C/cm 2 , and annealing the charged film, characterized by steps prior to said step of injecting charge comprising subjecting the film to penetrating radiation of a dosage ranging from 1 to 25 krad, in order to increase the conductivity of the film, and annealing the film at a temperature ranging from 80° to 150° C. in order to substantially restore the low conductivity of the film, thereby producing prior to said step of injecting charge a film having a residual surface charge density less than 10 -9 C/cm 2 .
Claim 9
Independent Claim
140 words
A method for making a thin film electret comprising the steps of injecting charge into a fluorinated polymer thin film having a thin layer of a metal deposited upon at least one surface thereof in order to produce a film having an intercepted charge density greater than 10 -9 C/cm 2 , and annealing the charged film, characterized by steps prior to said step of injecting charge comprising subjecting the film to penetrating radiation of a dosage ranging from 1 to 25 krad, in order to increase the conductivity of the film, and annealing the film at a temperature ranging from 80° to 150° C. in order to substantially restore the low conductivity of the film, thereby producing prior to said step of injecting charge a film having a residual surface charge density less than 10 -9 C/cm 2 .
Claim 10
Dependent Claim
18 words
The method of claim 7 further characterized in that the source of said penetrating radiation is cobalt 60.
Claim 11
Independent Claim
20 words
The method of claims 7 or 8 further characterized in that the fluorinated polymer is polytetrafluoroethylene or an ethylene-propylene copolymer.
Claim 12
Dependent Claim
36 words
The method of claim 9 further characterized in that the step of annealing the film at a temperature ranging from 80 to 150 degrees C. has a duration in the range from 0.5 to 10 hours.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-02-03 | 1984-08-04 | 1985-02-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-02-03 | 1988-08-04 | 1989-02-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-02-03 | 1992-08-04 | 1993-02-03 | $7700.00 | Window Closed / Lapsed |