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Red-emitting superlinear phosphor
| Details |
Inventors: Ohtani, Hiroko; Toyokawa, Kazuharu;
Assignee: International Business Machines Corporation (Armonk, NY)
Primary Examiner:
Assistant Examiner:
Attorney, Agent or Firm:
In a red-emitting phosphor which includes ZnSe as a host material, copper (Cu) as an activator and aluminum (Al) as a coactivator, the improvement comprising the inclusion of a small amount of cobalt (Co) to provide superlinear characteristics to said phosphor in combination with said Cu and Al. A preferred range of concentration of said Co is 10.sup.-6 -2.times.10.sup.-5 g atom/mol. A specific application of said red-emitting superlinear phosphor is as a phosphor screen for a current density sensitive, single gun color CRT, when mixed with a green-emitting sublinear phosphor. |
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DETAILED DESCRIPTION OF THE INVENTION The invention proposs to add cobalt Co to a red-emitting phosphor which includes ZnSe as a host material, Cu as an activator, Al as a coactivator.
It has been found that ZnSe: Cu, Al which has been known as a red-emitting linear phosphor of high color purity changes its luminance-current density behavior to superlinear behavior by addition of a small amount of Co while substantially maintaining its original red-emitting spectral characteristics.
Therefore, it is possible to get a wide chromaticity gamut ranging from green to yellow to orange to red by mixing the phosphor with a sublinear green-emitting phosphor.
Now, preferred embodiments in accordance with the present invention are described.
The superlinear red-emitting phosphor of the invention is easily obtainable by the addition of Co in the production of the already publicly known red-emitting linear phosphor ZnSe: Cu, Al.
As is well known, ZnSe: Cu, Al can be produced, for example, as follows: ZnSe powder of high purity, say, about 99.
9999%, copper sulfate (II), aluminium sulfate and a suitable crystallization promoter (flux) are mixed in a solution and dried.
After drying, the mixture is fired at about 1,030.
degree.
C.
in a H.
sub.
2 S atmosphere.
Concentrations of Cu and Al to be added to 1 mol of ZnSe are generally selected from the viewpoint of emission efficiency in the following relationship: X.
ltoreq.
X' (1) 10.
sup.
-4 .
ltoreq.
X.
ltoreq.
5.
times.
10.
sup.
-3 (2) where X is the Cu concentration (g atom/mol) and X' is the Al concentration (g atom/mol).
To improve emission efficiency, the concentration of Al as a coactivator should be higher than the concentration of Cu as an activator.
ZnSe: Cu, Al has its peak emission efficiency at about 10.
sup.
-3 mol of Cu concentration, and it is not desirable to put Cu concentration lower than 10.
sup.
-4 mol or higher than 5.
times.
10.
sup.
-3 mol because in these cases the emission efficiency drops to below 50%.
ZnSe: Cu, Al obtained in such manner exhibits red-emitting spectrum characteristics with its peak value at wave length 620 nm and half-value width of 90 nm
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Manufacturing Materials 
