Low voltage blue emitting phosphor and method of preparing same

Details Low voltage blue emitting phosphor and method of preparing same Low voltage blue emitting phosphor and method of preparing same

1999-11-22

2001-04-17

Koslow, C. Melissa (Department: 1755)

Compositions

Inorganic luminescent compositions

Zinc or cadmium containing

Reexamination Certificate

active

06217795

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a low voltage blue emitting phosphor with improved brightness and a method of preparing the same.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,478,499 discloses a blue emitting phosphor that can be used in a vacuum fluorescent display, a field emission display, a write head of a printer, a back light for a liquid crystal display, etc. The phosphor of the '499 patent is capable of emitting a blue luminous color at a voltage of 100V or less. The phosphor is a ZnO—Ga
2
O
3
matrix doped with Li (lithium) and P (phosphorus).
FIG. 2
shows a flow chart of a method for preparing the above blue emitting phosphor of the '499 patent. First, ZnO, Ga
2
O
3
, and Li
3
PO
4
are mixed. Next, the resulting mixture is subjected to a first sintering step for approximately 3 hours at a temperature of 1200° C. and in a normal air atmosphere. The matrix is then milled, preferably with a ball mill, such that lumped matrix particles are evenly dispersed. To remove excess Li
3
PO
4
, the dispersed matrix particles are washed with nitric acid. Subsequently, the washed matrix is subjected to a second sintering step for 1 to 3 hours at a temperature of 1100° C. under a reducing atmosphere. Subsequently, the matrix is classified using a sieve, thereby obtaining the phosphor. The phosphor has an x value of 0.08 to 0.20 and a y value of 0.05 to 0.25 in a CIE chromaticity diagram. However, the blue emitting phosphor produced as described above has a low brightness, i.e., a low light emitting efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a low voltage blue emitting phosphor having improved brightness, i.e., an improved light emitting efficiency. It is another object of the present invention to provide a method of preparing the low voltage blue emitting phosphor.
To achieve the above objects, the present invention provides a low voltage blue emitting phosphor and a method of preparing the same. The method includes the steps of mixing ZnO, Ga
2
O
3
and an Na-based compound to obtain a mixture; sintering the mixture at a temperature of 1100 to 1300° C.; milling the material; washing the milled material using hydrochloric acid; sintering the washed material at a temperature of 800 to 1100° C.; and classifying the material.
The low voltage blue emitting phosphor produced according to the inventive method described above has an x value of 0.18±0.05 and a y value of 0.17±0.05 in a CIE chromaticity diagram.


REFERENCES:
patent: 5478499 (1995-12-01), Satoh et al.

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