# US 5,702,643 A · ZnS:Cu electroluminescent phosphor and method of making same

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- Number: US 5,702,643 A
- Document ID: US5702643A
- Status: Granted
- Kind: A
- Application number: 08/637,146
- Filed: 1996-04-24
- Granted: 1997-12-30
- Earliest claimed: 1996-04-24
- Assignees: Osram Sylvania Inc.
- Inventors: Vaddi Butchi Reddy; Kenneth T. Reilly
- Web page: https://patentgrep.com/patent/US5702643A

## CPC

- C09K 11/642: {with zinc or cadmium}
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE

## Abstract

A improved ZnS:Cu electroluminescent phosphor having a halflife of at least about 900 hours. The halflife improvement is made by doping the phosphor with minor amounts of gold and substantially increasing the amount of low intensity milling between firing steps. The improved phosphor has a dramatically longer halflife without sacrificing brightness or exhibiting large shifts in emission color.

## Claims

### Claim 1

An electroluminescent phosphor having the general formula ZnS:Cu,Cl,Au, a halflife of at least about 900 hours, and x and y color coordinates where the x color coordinate is from about 0.156 to about 0.196 and the y color coordinate is from about 0.370 to about 0.430.

### Claim 2 (depends on 1)

The electroluminescent phosphor of claim 1 wherein the phosphor has a halflife of at least about 1100 hours.

### Claim 3 (depends on 1)

The electroluminescent phosphor of claim 1 wherein the phosphor has a halflife of at least about 1300 hours.

### Claim 4 (depends on 1)

The electroluminescent phosphor of claim 1 wherein the phosphor has an initial brightness of at least about 28 fL.

### Claim 5 (depends on 1)

The electroluminescent phosphor of claim 1 wherein the phosphor has a y color coordinate of about 0.422.

### Claim 6 (depends on 1)

The electroluminescent phosphor of claim 1 wherein the amount of gold in the phosphor is about 0.5 .+-.0.2 ppm.

### Claim 7 (depends on 1)

The electroluminescent phosphor of claim 1 wherein the phosphor has a copper concentration of about 0.06 wt. % and a chlorine concentration of about 0.03 wt. %.

### Claim 8 (depends on 1)

The electroluminescent phosphor of claim 1 wherein the x color coordinate is from about 0.162 to about 0.202 and the y color coordinate is from about 0.425 to about 0.485.

### Claim 9 (depends on 8)

The electroluminescent phosphor of claim 8 wherein the phosphor has a halflife of at least about 1200 hours.

### Claim 10 (depends on 8)

The electroluminescent phosphor of claim 8 wherein the phosphor has a halflife of at least about 1400 hours.

### Claim 11

A method for increasing the halflife of a ZnS:Cu electroluminescent phosphor comprising:
blending amounts of zinc sulfide, a copper source, a gold source and a chloride flux to form a mixture;
firing the mixture at a temperature from about 900.degree. C. to about 1400.degree. C. for about 2 hours to about 8 hours to form a zinc sulfide material containing copper, chlorine and gold;
subjecting the zinc sulfide material to a low intensity milling for between about 190 minutes to about 280 minutes to form a milled material;
blending the milled material with an amount of zinc sulfate and an amount of copper sulfate; and
refiring the blended milled material at a temperature from about 500.degree. C. to about 1000.degree. C. for about 1 to 5 hours to form an electroluminescent phosphor.

### Claim 12 (depends on 11)

The method of claim 11 wherein the amount of gold in the mixture is from about 15 to 88 ppm.

### Claim 13 (depends on 11)

The method of claim 11 wherein the phosphor contains copper and chlorine.

### Claim 14 (depends on 11)

The method of claim 11 wherein an amount of a manganese source is added to the mixture in order to produce a manganese and copper coactivated phosphor.

### Claim 15

An electroluminescent lamp comprising:
a first electrode, a first layer of dielectric material adjacent to the first electrode, a second layer of a dielectric material adjacent to the first layer;
the second layer containing an electroluminescent phosphor having a general formula ZnS:Cu,Cl,Au, a halflife of at least about 900 hours, and x and y color coordinates where the x color coordinate is from about 0.156 to about 0.196 and the y color coordinate is from about 0.370 to about 0.430; and
a second electrode adjacent to the second layer of dielectric material.

### Claim 16 (depends on 15)

The electroluminescent lamp of claim 15 wherein the phosphor has a halflife of at least about 1100 hours.

### Claim 17 (depends on 15)

The electroluminescent lamp of claim 15 wherein the phosphor has a halflife of at least about 1300 hours.

### Claim 18 (depends on 15)

The electroluminescent lamp of claim 15 wherein the phosphor has an initial brightness of at least about 28 fL.

### Claim 19 (depends on 15)

The electroluminescent lamp of claim 15 wherein the phosphor has a y color coordinate of about 0.422.

### Claim 20 (depends on 15)

The electroluminescent lamp of claim 15 wherein the amount of gold in the phosphor is about 0.5 .+-.0.2 ppm.

### Claim 21 (depends on 15)

The electroluminescent lamp of claim 15 wherein the phosphor has a copper concentration of about 0.06 wt. % and a chlorine concentration of about 0.03 wt. %.

### Claim 22 (depends on 15)

The electroluminescent lamp of claim 15 wherein the x color coordinate is from about 0.162 to about 0.202 and the y color coordinate is from about 0.425 to about 0.485.

### Claim 23 (depends on 22)

The electroluminescent lamp of claim 22 wherein the phosphor has a halflife of at least about 1200 hours.

### Claim 24 (depends on 22)

The electroluminescent lamp of claim 22 wherein the phosphor has a halflife of at least about 1400 hours.