Process for providing hydrolysis resistant phosphors

Details Process for providing hydrolysis resistant phosphors Process for providing hydrolysis resistant phosphors

1986-12-09

1987-09-01

Cooper, Jack

Coating processes

Electrical product produced

Fluorescent or phosphorescent base coating

2523014F, 2523014S, 2523016F, 2523016S, 427 68, 427219, 4273722, 428404, C09K 11475

Patent

active

046908323

ABSTRACT:
A process is disclosed for making a rare earth oxysulfide phosphor resistant to hydrolysis. The process involves adding to a water slurry of the phosphor a sufficient amount of a source of silicon dioxide and a water soluble salt which can be an alkaline earth metal salt or a transition group IIB metal salt with agitation for a sufficient time to form a silicate coating on the phosphor with the cation of the water soluble salt becoming the cation of the silicate coating, the amount of the coating being sufficient to impart hydrolysis resistance thereto. The resulting silicate coated phosphor is then separated from the resulting liquor and heated at a sufficient temperature for a sufficient time in ambient atmosphere to remove essentially all of the water therefrom and to produce the final hydrolysis resistant phosphor.
A hydrolysis resistant rare earth oxysulfide phosphor is disclosed consisting essentially of a host which can be gadolinium oxysulfide, yttrium oxysulfide, gadolinium-yttrium oxysulfide, and lanthanum oxysulfide, from about 0.001 to about 0.10 moles of terbium per mole of host as an activator, and a sufficient amount of a silicate coating on the phosphor to impart hydrolysis resistance thereto.

REFERENCES:
patent: 4473634 (1984-09-01), Dodds et al.
patent: 4544605 (1985-10-01), Miyazaki et al.
patent: 4624861 (1986-11-01), Yale et al.

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