# US 4,393,118 A · Method of preparing a dark body phosphor

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- Number: US 4,393,118 A
- Document ID: US4393118A
- Status: Granted
- Kind: A
- Application number: 06/322,330
- Filed: 1981-11-18
- Granted: 1983-07-12
- Earliest claimed: 1981-11-18
- Assignees: GTE Products Corporation
- Inventors: Harry L. Marshall; Alan R. Schwartz
- Web page: https://patentgrep.com/patent/US4393118A

## CPC

- C09K 11/025: {non-luminescent particle coatings or suspension media}
- Y10T 428/2991: Coated
- Y10T 428/2993: Silicic or refractory material containing [e.g., tungsten oxide, glass, cement, etc.]
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A pigmented phosphor is prepared by coating phosphor particles with a coating of finely powdered carbon and colloidal silica.

## Claims

### Claim 1

A method of making pigmented phosphor comprising the steps of: preparing an aqueous suspension of phosphor particles and finely powdered carbon; adding colloidal silica to the suspension; agitating the suspension; removing the liquid and drying the phosphor particles.

### Claim 2 (depends on 1)

The method of claim 1 wherein the pH of the phosphor-carbon suspension is adjusted to 8-9 prior to the addition of the colloidal silica.

### Claim 3 (depends on 1)

The method of claim 1 wherein the phosphor-carbon suspension is prepared by preparing an aqueous suspension of the phosphor particles, adjusting the pH thereof to 4-5, and then adding thereto a colloidal dispersion of graphite.

### Claim 4 (depends on 1)

The method of claim 1 wherein the phosphor is a data display tube phosphor.

### Claim 5 (depends on 1)

Phosphor made in accordance with claim 1.

### Claim 6

A pigmented phosphor comprising a core of a phosphor particle having a black coating thereon wherein the black coating is finely powdered carbon.

### Claim 7 (depends on 6)

A phosphor of claim 6 wherein the phosphor is a data display tube phosphor.

### Claim 8 (depends on 7)

The phosphor of claim 7 wherein the phosphor is copper-silver-activated zinc sulfide.