US5023015A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of phosphor preparation
Assignee: Osram Sylvania Inc
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Filing: 1989-12-19
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Granted: 1991-06-11
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Expires: 2009-12-19
Abstract
Abstract An improved method for preparing a phosphor is disclosed. The method of the invention includes preparing a solution comprising the non-oxygen elements of the phosphor in molar proportions equal to the respective molar proportions of the non-oxygen elements in the phosphor; precipitating the non-oxygen elements from the solution through the addition of a precipitating agent; spray drying the solution including the precipitate to form a spray dried powder; and firing the spray dried powder in a single firing step. The single firing step of the method comprises (a) increasing the temperature of the spray dried powder at an even and controlled rate from room temperature to a firing temperature sufficiently high to convert the spray dried powder to the phosphor; and (b) maintaining the temperature of the spray dried powder at the firing temperature for a period of time sufficient to produce the phosphor. The method is particularly useful in the preparation of Eu 2+ -activted strontium borate phosphor.
Inventors
- 👤 Costas C. Lagos
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 10:50
CPC Classifications
C; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7728; C09K11/774
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
169 words
A method for preparing divalent europium doped strontium orthoborate phosphor having the empirical formula: Sr.sub.1-x B.sub.4 O.sub.7 :Eu.sub.x.sup.+2 wherein x is from about 0.005 to about 0.05, the method comprising: preparing a solution comprising europium (3+) and strontium in molar proportions equal to their respective molar proportions in the phosphor and boron in a molar proportion of about 4 to about 4.2: precipitating the europium (3+), strontium, and boron from the solution by adding a precipitating agent to the solution; spray drying the solution, including the precipitate, to form a spray dried powder; and firing the spray dried powder in a single firing step in a reducing atmosphere comprising: (a) increasing the temperature of the spray dried powder at an even rate no faster than about 5.5° C./minute from room temperature to a firing temperature of from about 920 to about 942° C.; and (b) maintaining the temperature of the spray dried powder at the firing temperature for a period of at least 4 hours to produce the phosphor.
Claim 2
Independent Claim
169 words
A method for preparing divalent europium doped strontium orthoborate phosphor having the empirical formula: Sr.sub.1-x B.sub.4 O.sub.7 :Eu.sub.x.sup.+2 wherein x is from about 0.005 to about 0.05, the method comprising: preparing a solution comprising europium (3+) and strontium in molar proportions equal to their respective molar proportions in the phosphor and boron in a molar proportion of about 4 to about 4.2: precipitating the europium (3+), strontium, and boron from the solution by adding a precipitating agent to the solution; spray drying the solution, including the precipitate, to form a spray dried powder; and firing the spray dried powder in a single firing step in a reducing atmosphere comprising: (a) increasing the temperature of the spray dried powder at an even rate no faster than about 5.5° C./minute from room temperature to a firing temperature of from about 920 to about 942° C.; and (b) maintaining the temperature of the spray dried powder at the firing temperature for a period of at least 4 hours to produce the phosphor.
Claim 3
Dependent Claim
19 words
A method in accordance with claim 1 wherein the firing step is carried out in a flowing reducing atmosphere.
Claim 4
Dependent Claim
31 words
A method in accordance with claim 1 wherein the single firing step is carried out in a furnace equipped with a microprocessor programmed to increase the temperature at the specified rate.
Claim 5
Dependent Claim
24 words
A method in accordance with claim 3 wherein the firing step further comprises permitting the phosphor to cool to room temperature within the furnace.
Claim 6
Dependent Claim
19 words
A method in accordance with claim 4 wherein the firing step is carried out in a flowing reducing atmosphere.
Claim 7
Dependent Claim
15 words
A method in accordancd with claim 1 wherein the rate is from about 4.2°-5.5° C./min.
Claim 8
Dependent Claim
15 words
A method in accordance with claim 1 wherein the rate is from about 5.1°-5.2° C./minute.
Claim 9
Dependent Claim
14 words
A method in accordance with claim 1 wherein the firing temperature is 942° C.
Claim 10
Dependent Claim
15 words
A method in accordance with claim 1 wherein the precipitating agent is an aqueous base.
References Cited (Backward Citations)
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US3923682A
Cited
US3709826A
Cited
GB1509119A
Cited
US4719033A
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-06-10 | 1994-12-10 | 1995-06-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-06-10 | 1998-12-10 | 1999-06-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-06-10 | 2002-12-10 | 2003-06-11 | $7700.00 | Window Closed / Lapsed |