High brightness green-emitting phosphor

Details High brightness green-emitting phosphor High brightness green-emitting phosphor

2003-05-09

2004-10-19

Koslow, C. Melissa (Department: 1755)

Compositions

Inorganic luminescent compositions

Compositions containing halogen; e.g., halides and oxyhalides

Reexamination Certificate

active

06805813

ABSTRACT:

TECHNICAL FIELD
This invention is related generally to phosphors for plasma display panels. More particularly, this invention is related to green-emitting borate phosphors.
BACKGROUND OF THE INVENTION
In order to achieve full color reproduction, a plasma display panel (PDP) is composed of pixels which emit light corresponding to the three primary colors of red, green and blue. The pixels are formed from red-, green-, and blue-emitting phosphors which have been deposited in a paste or ink form on an inner wall of the device. The binder materials are then burned out at a high temperature (about 400° C.). The tri-color emission is achieved by stimulating the phosphors with vacuum ultraviolet (VUV) radiation generated by Xe-Ne gas discharges (172 nm). The luminous efficiency, color chromaticity, afterglow, and stability of the phosphors have significant roles in the PDP performance. Typical phosphors used in PDP applications include a red-emitting (Y,Gd)BO
3
:Eu phosphor (YOB), a green-emitting Zn
2
SiO
4
:Mn phosphor, and a blue-emitting BaMgAl
10
O
17
:Eu.
The conventional green-emitting Zn
2
SiO
4
:Mn phosphor suffers from a long decay time and a decreasing luminous efficiency which negatively affects panel characteristics. A potentially more effective green-emitting phosphor is yttrium gadolinium terbium borate, (Y,Gd,Tb)BO
3
. The luminescence properties of a Y
0.95-x
Gd
x
Tb
0.05
BO
3
phosphor system in the VUV region have been described by Kwon et al.
J. Luminescence
87-89 (2000) 1039-1041. Japanese Patent Application 11-071581 to Ohto describes a green-emitting (Y,Gd,Tb)BO
3
for use in plasma display panels. The (Y,Gd,Tb)BO
3
phosphor exhibits a higher VUV absorption at 172 nm and experiences a smaller decrease in brightness after binder burnout.
SUMMARY OF THE INVENTION
It has been discovered that substituting a small amount of lanthanum for yttrium improves the brightness of the (Y,Gd,Tb)BO
3
phosphor under VUV excitation. The substituted phosphor has the general formula:
(Y
(1-x-y-z)
Gd
x
Tb
y
La
z
)BO
3
where
0.01≦x≦0.4,
0.01≦y≦0.1, and
0<z≦0.2.
Preferably, 0.2≦x≦0.3, 0.03≦y≦0.07 and 0.05≦z≦0.15. More preferably, 0.05≦z≦0.1. The phosphor exhibits a bright green emission (CIE color coordinates; x=0.323, y=0.610) under VUV excitation. However, increasing the amount of lanthanum above the specified range causes a decrease in the VUV brightness.


REFERENCES:
patent: 11-071581 (1999-03-01), None
Kwon et al.,Luminescence properties of borate phosphors in the UV/VUV region,J. Luminescence 87-89 (2000) 1039-1041.

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