Compositions – Inorganic luminescent compositions – Compositions containing halogen; e.g. – halides and oxyhalides
Reexamination Certificate
2000-12-22
2003-05-06
Koslow, C. Melissa (Department: 1755)
Compositions
Inorganic luminescent compositions
Compositions containing halogen; e.g., halides and oxyhalides
C252S30140R, C252S30160R, C428S403000, C428S404000
Reexamination Certificate
active
06558574
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a red phosphor leading to sufficient luminescent at an image display devices driven with low voltages, such as field emission devices (FEDs), which is obtained using a conductive luminescent material, and a method for preparing the same.
2. Description of the Related Art
A conductive layer such as aluminum (Al) layer, which are used in cathode ray tube (CRTs), cannot be employed in FEDs, which are operated with a relatively high current density and low voltage. For this reason, use of commercially available phosphors in FEDs causes accumulation of space charges on the surface of the phosphors, and thus luminescence is lowered. This problem has been considered to be serious in applying phosphors to devices operating with low voltages. In order to avoid formation of potential barriers by space charges, a conductive material such as indium oxide or tin oxide is mixed with a phosphor or is coated on a phosphor to enhance the conductivity. Also, another approach suggests use of a conductive material as a host of phosphor to enable excitation with low voltages.
A technique of adding or coating indium oxide or tin oxide was disclosed in U.S. Pat. Nos. 4,027,192; 4,208,612; and 4,208,613, and JP No. 10212473. These materials have been applied as simple conductive materials in vacuum fluorescent displays (VFDs) after verification. However, the effect of the materials on luminance at FEDs is unclear yet. Reportedly, good results are obtainable only when the driving voltage is 400V or less (H. Kominami et al., “Low Voltage Cathodoluminescent Properties of Phosphors Coated With In
2
O
3
by Sol-gel Method,”
Applied Surface Science
113/114 (1997) 519-522, and R. Durny et al., “Semiconductors,” “Superconductors,” “Magnetism,” “Optics and Quantum Electronics,” “Optical Properties of Condensed Matter,” “Structure and Mechanical and Thermal Properties of Condensed Matter,” “Surfaces, Interfaces, and Films,” and “Instrumentation, Measurement, and Fabrication Technology,”
Japanese J. of Appl. Phys.
Vol. 35 (1996) Pt. 2, No. 12A). Thus, there is a need for further enhancing luminance for FEDs.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a phosphor having effective emission at low voltages, and a method for preparing the same, in which a material having both conductive and luminescent properties is mixed with a red phosphor, or the material is coated on a phosphor, to minimize accumulation of space charges with enhanced conductivity and decreased drop of luminance.
According to an aspect of the present invention, there is provided a red phosphor having effective emission at low voltages, the red phosphor mixed with a conductive luminescent material expressed by (Sn
1-x
Eu
x
)O
2
, in a predetermined concentration.
Preferably, the red phosphor is coated with the conductive luminescent material expressed by (Sn
1-x
Eu
x
)O
2
. Preferably, the concentration of the conductive luminescent material expressed by (Sn
1-x
Eu
x
)O
2
mixed with or coated on the red phosphor is in the range of 5×10
−2
to 5% by weight. Preferably, in the expression of (Sn
1-x
Eu
x
)O
2
, x is a value from 0.0005 to 0.2.
According to another aspect of the present invention, there is provided a method of preparing a red phosphor having effective emission at low voltages, using a conductive luminescent material, the method comprising: (a) synthesizing a red phosphor Y
2
O
3
:Eu as a base phosphor, immersing the red phosphor into an ammonium hydroxide aqueous solution, and adding and stirring a solution containing Eu
3+
and Sn
4+
salts to the solution to form a precipitate on the red phosphor; (b) filtering and drying the precipitate; and (c) firing the dried precipitate at a temperature of 700 to 800° C. to coat SnO
2
:Eu on the red phosphor.
REFERENCES:
patent: 4027192 (1977-05-01), Hanak
patent: 4208612 (1980-06-01), Hase et al.
patent: 4208613 (1980-06-01), Hase et al.
patent: 4303913 (1981-12-01), Tohda et al.
patent: 4314177 (1982-02-01), Matsuoka et al.
patent: 10212473 (1998-08-01), None
H. Kominami, et al., “Low Voltage Cathodoluminescent Properties of Phosphors Coated with In2O3by Sol-gen Method,” Applied Surface Science 113/114 (1997), pp. 519-522.
Hiroko Kominami et al, “Improvement of Low Voltage Cathodoluminescent Properties of Zinc Sulfide Phosphors by Sol-Gel Method”, Jpn. J. Appl. Phys., vol. 35 (1996), pp. L1600-L1602.
Gwak Ji-hye
Jin Yong-wan
Park Shang-hyeun
Vorobyov V. A.
LandOfFree
Red phosphor having effective emission at low voltages and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Red phosphor having effective emission at low voltages and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Red phosphor having effective emission at low voltages and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3082673