US4727004A
Expired / Lapsed
US
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Thin film electroluminescent device
Assignee: Sharp Corp
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Filing: 1986-11-18
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Granted: 1988-02-23
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Expires: 2006-11-18
Abstract
Abstract A thin film EL device having a double-insulated structure and comprising an emitting layer made of an alkaline-earth sulfide as its host material and doped with Eu 2+ for providing luminescent centers. The emitting layer has a Eu concentration of 0.15 to 0.75 atm. % and a controlled thickness of at least 1.3 μm to impart hysteresis to the brightness vs. applied voltage characteristics of the device.
Inventors
- 👤 Koichi Tanaka
- 👤 Takashi Ogura
- 👤 Koji Taniguchi
- 👤 Akiyoshi Mikami
- 👤 Masaru Yoshida
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:57
CPC Classifications
H; H05; H05B; H05B33/00; H05B33/12; H05B33/20; C; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7728; C09K11/7729; C09K11/7731; H05B33/14
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
73 words
A thin film EL device which exhibits a memory effect comprising an emitting layer made of an alkaline-sulfide as a host material, doped with 0.15 to 0.75 atm. % of Eu for providing luminescent centers and having a controlled thickness of at least 1.3 μm, insulating layers sandwiching the emitting layer, and a pair of electrodes provided on the outer surfaces of the insulating layers, at least one of the electrodes being transparent.
Claim 2
Dependent Claim
73 words
A thin film EL device which exhibits a memory effect comprising an emitting layer made of an alkaline-sulfide as a host material, doped with 0.15 to 0.75 atm. % of Eu for providing luminescent centers and having a controlled thickness of at least 1.3 μm, insulating layers sandwiching the emitting layer, and a pair of electrodes provided on the outer surfaces of the insulating layers, at least one of the electrodes being transparent.
Claim 3
Dependent Claim
19 words
A device as defined in claim 1 wherein the sulfide of alkaline earth metal is CaS, SrS or BaS.
Claim 4
Dependent Claim
18 words
A device as defined in claim 1 wherein the amount of Eu is 0.3 to 0.5 atm. %.
Claim 5
Dependent Claim
18 words
A device as defined in claim 1 wherein the emitting layer is 1.3 to 5 μm in thickness.
Claim 6
Dependent Claim
83 words
A device as defined in claim 1 wherein each of the insulating layers is a film of a oxide or nitride selected from among Al 2 O 3 , SiO 2 , Y 2 O 3 , TiO 2 , HfO 2 , Ta 2 O 5 , Si 3 N 4 and AlN, a film of a highly dielectric material selected from among BaTiO 3 , PbTiO 3 , SrTiO 3 , PZT and PLZT, or a composite film comprising these films.
Claim 7
Dependent Claim
20 words
A device as defined in claim 1 wherein the transparent electrode comprises a film of ITO or SnO 2 .
Claim 8
Dependent Claim
20 words
A device as defined in claim 1, wherein the emitting layer further comprises ZnS:Mn dopant to provide a multi-color display.
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) | 1991-02-22 | 1991-08-24 | 1992-02-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-02-22 | 1995-08-24 | 1996-02-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-02-22 | 1999-08-24 | 2000-02-23 | $7700.00 | Window Closed / Lapsed |