Method for coating phosphor particles using aluminum isopropoxide precursors and an isothermal fluidized bed
US5049408A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 24, 1990 |
| Grant date | Sep 17, 1991 |
| Priority date | — |
| Expiry date | Aug 24, 2010 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB01J2/006
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
Abstract
Disclosed is a method for applying a continuous protective coating to the surface of individual phosphor particles. The method involves chemical vapor deposition of an aluminum oxide coating on individual particles of a phosphor powder while the particles are suspended in a fluidized bed. The particles in the fluidized bed are exposed to vaporized coating precursor material, preferably aluminum isopropoxide at a temperature above 300.degree. C. The bed is kept at as nearly an isothermal condition as possible. Prior to entering the fluidized bed the aluminum isopropoxide is vaporized and kept at a temperature less than the decomposition temperature of aluminum isopropoxide. Mechanical means are used to help increase the fluidization efficiency of the fluidized bed. After coating the phosphor particles for approximately 30 minutes the vaporized precursor material is shut off from the bed entrance and the oxygen flow rate to the fluidized bed is increased. This carbon reduction step lasts for approximately 15 minutes. The coating step and carbon reduction step can be repeated to increase the thickness of the aluminum oxide coating on the phosphor particles.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.