Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
2000-02-03
2001-10-30
Kopec, Mark (Department: 1751)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S053000, C501S073000, C106S712000
Reexamination Certificate
active
06309992
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a dielectric forming material and a dielectric forming paste, each of which is for use as a transparent dielectric layer formed onto an inside surface of a front glass substrate in a plasma display panel.
An AC type plasma display panel (which may also be referred to as “PDP” hereunder) to which this invention is applicable comprises a front glass substrate for displaying a video image and a rear glass substrate opposed to the front glass substrate with a predetermined gap.
On one hand, the front glass substrate has a plurality of display electrodes and a transparent dielectric layer formed on its inside surface facing the rear glass substrate. The display electrodes are buried in the transparent dielectric layer. An MgO film is formed on a surface of the transparent dielectric layer. On the other hand, the rear glass substrate has a plurality of address electrodes formed on its inside surface facing the front glass substrate.
Between the MgO film on the front glass substrate and the inside surface of the rear glass substrate, a plurality of barrier ribs vertically protrude from the rear glass substrate to be erected thereon to define a plurality of inner spaces between adjacent ones of the barrier ribs. Each of the barrier ribs has a surface covered with a phosphor. An inner space or cavity surrounded by the front and the rear glass substrates is filled with a rare gas. As the glass substrate, use is generally made of a soda lime glass or a high-strain-point glass which has a strain point of 570° C. or more.
With this structure, when an electric voltage is applied to drive the PDP, electric discharge occurs between a selected one of the display electrodes and a selected one of the address electrodes so that ultraviolet rays are emitted from the rare gas. The ultraviolet rays excite the phosphor to emit visible light. The wavelength range of visible light is 620 nm for red, 550 nm for green, and 460 nm for blue.
The light emitted from the phosphor is transmitted through the front glass substrate and the transparent dielectric layer formed thereon. However, a part of the light is scattered on the inside surfaces of the front glass substrate and the transparent dielectric layer and repeatedly reflected on the inside and the outside surfaces thereof. In this event, the light undesiredly leaks into adjacent spaces beyond the barrier ribs. This results in a phenomenon that the video image becomes unclear because of occurrence of glow around a shining point or bright spot. Such phenomenon is generally called a halation.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a plasma display panel material which enables manufacture of a plasma display panel (PDP) suppressed in possibility of occurrence of halation.
As a result of various extensive studies, the present inventors have found that the above-mentioned object is achieved by forming a transparent dielectric layer capable of decreasing a transmittance within the wavelength range of visible light, and hereby proposes this invention.
According to this invention, there is provided a dielectric forming material which is for use as a transparent dielectric layer formed on an inside surface of a front glass substrate in a plasma display panel, and which comprises powder of colored glass.
According to this invention, there is also provided a dielectric forming paste which is for use as a transparent dielectric layer formed on an inside surface of a front glass substrate in a plasma display panel and which is characterized by including powder of colored glass as a solid component.
The transparent dielectric layer is formed on the front glass substrate to the thickness of about 30-40&mgr;m in order to keep the discharge of the display electrodes. As a matter of course, the transparent dielectric layer is required to have a high breakdown voltage, an excellent transparency, and so on. For this purpose, use has generally been made of powder of a transparent glass such as a PbO—B
2
O
3
—SiO
2
glass or a ZnO—B
2
O
3
—SiO
2
glass.
On the other hand, the dielectric forming material according to this invention comprises powder of a so-called colored glass containing a base glass and coloring ingredients added thereto. Use of the colored glass decreases the transmittance of the light passing through the transparent dielectric layer within the wavelength range of visible light and enhances absorption of the scattered light. Accordingly, it is possible to suppress occurrence of halation. In addition, it is possible to improve the contrast in the video image.
Proposal is also made of a technique of coloring the transparent dielectric layer by adding pigment powder. However, this technique is not preferable because the transmittance of the transparent dielectric layer is significantly decreased.
As a result of the inventors' studies, it has been confirmed that the coloring ingredients preferably comprise CoO and NiO different in light absorption within the wavelength range of visible light. It has also been confirmed that, as the base glass, a PbO—B
2
O
3
—SiO
2
glass or a ZnO—B
2
O
3
—SiO
2
glass is preferable.
Moreover, it has been confirmed that the appropriate dielectric forming material provides a glass film having a spectral transmittance T%
(460 nm)
of 50-75% at the wavelength of 460 nm or which is higher than a spectral transmittance T%
(550 nm)
at the wavelength of 550 nm and a spectral transmittance T%
(620 nm)
at the wavelength of 620 nm. Herein, the glass film is prepared from the dielectric forming material in the following manner. Specifically, the dielectric forming material is applied to a soda lime glass plate having a thickness of 1.7 mm and then baked or fired to form a baked film having a thickness of 20-40 &mgr;m thickness as the glass film. Thereafter, the transmittance of the glass film is measured together with the glass plate.
REFERENCES:
patent: 5089444 (1992-02-01), Hattori et al.
patent: 5565388 (1996-10-01), Krumwiede et al.
patent: 5688727 (1997-11-01), Shelestak et al.
patent: 5942331 (1999-08-01), Miyauchi et al.
patent: 5952255 (1999-09-01), Seto et al.
patent: 03285841 (1991-12-01), None
patent: 11260272 (1999-09-01), None
Hadano Kazuo
Morita Yoshiro
Ohji Masahiko
Oshita Hiroyuki
Collard & Roe P.C.
Kopec Mark
Nippon Electric Glass Co. Ltd.
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