Compositions – Inorganic luminescent compositions – Compositions containing halogen; e.g. – halides and oxyhalides
Reexamination Certificate
2000-09-19
2002-08-27
Koslow, C. Melissa (Department: 1755)
Compositions
Inorganic luminescent compositions
Compositions containing halogen; e.g., halides and oxyhalides
C252S30160F
Reexamination Certificate
active
06440329
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phosphor having efficient emission at a low voltage, and more particularly, to a SrTiO
3
:Pr, Al based phosphor applicable for driving displays at a low voltage, which is a kind of oxide phosphor emerging as a very likely substitute for sulfide based phosphors.
2. Description of the Related Art
Field emission displays (FEDs) need a phosphor with high luminescent efficiency to be driven with low voltages of 1 kV or less. An existing sulfide based phosphor applied to FEDs has problems in terms of chemical stability and charge build-up during operation. To avoid these problems, research has been conducted into oxide based phosphors.
Oxide based phosphors have a luminance which is 30 to 40% of that of sulfide based phosphors. The sulfide based phosphor used in FEDs has effective emission at a high voltage (5 to 10 kV). However, in FEDs operated with a driving voltage as low as 1 kV or less, the luminance is lowered due to the problem of charge-build up. For this reason, there is a need for a novel phosphor with high luminescent efficiency at a low voltage, especially for a high-efficiency oxide based phosphor capable of replacing the existing sulfide phosphor.
One kind of oxide based phosphor that has been developed is SrTiO
3
:Pr phosphor. However, the SiTiO
3
:Pr phosphor shows low luminance at a low voltage. To improve this problem, U.S. Pat. No. 5,619,098 taught SrTiO
3
:Pr, Al based phosphors with increased luminance. However, further development of phosphors for FEDs having effective emission and stability at a driving voltage as low as 1 kV or less, is needed.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a SrTiO
3
:Pr, Al based phosphor having high luminance, applicable to display devices such as field emission displays (FEDs) operating with a voltage as low as 1 kV or less.
The objective of the present invention is achieved by a SrTiO
3
:Pr, Al based phosphor having effective emission at a low voltage, having the composition of (Me
I
Me
II
Me
III
)TiO
3
. A
2
O
3
obtained by adding Me
II
to a phosphor having the composition of (Me
I
Me
III
)TiO
3
. A
2
O
3
, where Me
I
is a metal selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba); Me
II
is a metal of zinc (Zn) or cadmium (Cd), Me
III
is a metal selected from the group consisting of praseodymium (Pr), europium (Eu), terbium (Tb), erbium (Er), cerium (Ce) and thulium (Tm), and A is a metal selected from the group consisting of aluminum (Al), gallium (Ga), indium (In) and thallium (Tl).
Preferably, in the above composition of (Me
I
Me
II
Me
III
)TiO
3
. A
2
O
3
, Me
II
is Zn and A. Preferably, Me
II
is added in an amount of 0.01 to 15 mole %, and at least one flux selected from the group consisting of SrCl
2
, ZnCl
2
, Srl
2
, Znl
2
and Cdl
2
is used. If the flux is used, the amount of flux may be in the range of 0.5 to 60 mole %. Preferably, in the composition of (Me
I
Me
II
Me
III
)TiO
3
. A
2
O
3
, Me
III
is added in an amount of 0.05 to 5 mole %, and A is added in an amount of 0.5 to 80 mole %.
REFERENCES:
patent: 5619098 (1997-04-01), Toki et al.
patent: 5650094 (1997-07-01), Royce et al.
patent: 2001-0011735 (2001-02-01), None
Gwak Ji-hye
Park Shang-hyeun
Burns Doane Swecker & Mathis L.L.P.
Koslow C. Melissa
Samsung SDI & Co., Ltd.
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