Luminescence display panel using discharge gas

Details Luminescence display panel using discharge gas Luminescence display panel using discharge gas

1999-02-16

2002-01-01

Patel, Nimeshkumar D. (Department: 2879)

Electric lamp and discharge devices

With luminescent solid or liquid material

With gaseous discharge medium

C313S493000

Reexamination Certificate

active

06335591

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a luminescence display panel using discharge gas for use with television and computer systems, for example.
BACKGROUND OF THE INVENTION
FIG. 6
illustrates a conventional luminescence display panel using discharge gas, generally indicated by reference numeral
20
, for use preferably with a plasma display system. The panel
20
, including transparent front and rear plates,
21
and
22
, spaced apart from each other, is depicted so that one surface
23
of the front plate, away from the rear plate
22
, is oriented upward.
Also,
FIG. 7
illustrates an enlarged partial schematic view of an AC plasma display panel, which is an example of such luminescent display panels. As shown, the panel
20
includes a discharge chamber
3
between the front and rear plates,
21
and
22
. The other surface of the front plate
21
, opposing the rear plate
22
, supports a plurality of pairs of elongated scanning and maintaining electrodes,
6
and
7
, extending in a parallel fashion. The electrodes,
6
and
7
, are covered with a dielectric layer
4
and further with a protection layer
5
, positioned away from the front plate
21
. The rear plate
22
supports a plurality of elongated data electrodes
8
each extending perpendicular to the scanning and maintaining electrodes,
6
and
7
, in a parallel fashion. Also supported on the rear plate
22
are a plurality of elongated partitions
9
each extending in parallel to and spaced a certain distance from the data electrodes
8
, so that the discharge chamber
3
is formed between neighboring partitions
9
. A phosphor
10
is provided between the neighboring partitions
9
so that it covers both data electrode
8
and opposing side surfaces of the partitions
9
in the discharge chamber
3
. For clarity of the drawing, the phosphor
10
is illustrated only in part. Each discharge chamber
3
is filled with a gas mixture having xenon and at least one inert, as such as helium, neon, or argon.
In operation, an electric discharge is generated between the scanning and maintaining electrodes,
6
and
7
, in the discharge chamber
3
. This excites the phosphor
10
to emit visible light, which is used for displaying an image to be viewed on the front plate
21
.
Referring to
FIG. 8
, which is a cross-sectional view taken along lines VIII—VIII in
FIG. 7
, descriptions will be made to the light emission. As shown, three neighboring phosphors
10
construct different color elements of each pixel, red light element
10
R, green light element
10
G and blue light element
10
B for emitting red, green, and blue lights, respectively.
When the electric discharge
1
has occurred in the discharge chamber
3
, the ultraviolet light
2
generated by the discharge
1
excites the phosphor
10
. This allows the color elements
10
R,
10
G, and
10
B to emit red, green, and blue light, respectively, as shown by dotted lines in FIG.
8
. It should be understood that the light passes are provided by dotted lines in
FIG. 8
, as well as in other drawings, only for illustration.
FIG. 9
, which is also a cross-sectional view taken along lines VIII—VIII in
FIG. 7
, illustrates passes of red light emitted only from the color element
10
R. In this instance, the emitted red light RO and R
1
passes through the front plate
21
and then projects out toward a viewer. Simultaneously, the red light R
1
projected obliquely to the front plate
21
is in part reflected at an inner surface
21
a
of the front plate
21
and then at the neighboring green element
10
G. The reflected red light is then projected in part through the front plate
21
, which is shown at R
2
. Remaining red light is reflected at the surface
21
a of the front plate
21
and then at the neighboring blue element
10
B and, afterwards, projected through the front plate
21
. Likewise, the light emitted obliquely is transmitted transversely and reflected on the green and blue elements,
10
G and
10
B, which results in an undesirable halation of the red light being projected through the front plate
21
to the viewer.
Also, the red light emitted from the back surface of the red element
10
R is reflected at the inner surface of the rear plate
22
and then transmitted in part through the neighboring green element
10
G, which is finally projected through the front plate
21
as shown at R
4
. Further, the red light reflected at the green element
10
G is further reflected at the surfaces
22
b
and then
22
a
of the backing and then transmitted through the blue element
10
B, which is finally projected through the front plate
21
as shown at R
5
. As such, another undesirable halation of the red light is projected through the front plate
21
to the viewer. This results in a degradation of a color contrast of the plasma display panel.
In addition, as shown in
FIG. 10
, which is also a cross-sectional view of taken along lines VIII—VIII in
FIG. 7
, when the red and green elements,
10
R and
10
G, simultaneously emit respective lights, the green lights GO and G
1
are merged with the red light halation, R
2
and R
4
, which degrades purity of the green color. At this moment, the red light is also merged with the green light, which also results in a degradation of the red color.
The halation can be evaluated. For example, as shown in
FIG. 11A
, in the evaluation, all the color elements on the left side of the AC plasma display panel are turned on to present a white image and, on the other hand, all the color elements on the right side are turned off to present a black image. Then, measured is a variation of brightness in a boundary zone between the left turned-on and right turned-off regions. When no halation is assumed to occur, the left side region (L<0) would provide 100% brightness in white and the right side region 0% brightness in black (L>0). Contrary to this, practically, as shown in
FIG. 11B
, although in the conventional AC plasma display 100% brightness is obtained in the left side turned-on region (L<0), the brightness in the right side turned-off region decreases gradually from the boundary line and then 0% brightness in black is obtained at a portion spaced a certain distance P away from the boundary line. Also, the distance P in which the brightness decreases from 100% to 0% is significantly large in the conventional AC plasma display panel. Therefore, the boundary line between the white and black regions is unclear due to the halation. This in turn deteriorates a color contrast purity of each color.
SUMMARY OF THE INVENTION
To overcome this problem, a luminescence display panel using discharge gas of the present invention includes dark front and rear plates. Preferably, darkness of each plate is equal to at least about 20%. Instead, transparency of each plate may be equal to at most about 80%. This allows the halation to be decreased considerably in the luminescence display panel of the present invention.


REFERENCES:
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patent: 4224553 (1980-09-01), Hellwig
patent: 4626071 (1986-12-01), Wada et al.
patent: 4692662 (1987-09-01), Wada et al.
patent: 4989953 (1991-02-01), Kirschner
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patent: 4-58436 (1992-02-01), None
patent: 5-121002 (1993-05-01), None
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patent: 10-269950 (1998-10-01), None
Patent Abstracts of Japan, vol. 099, No. 001, Jan. 29, 1999 & JP 10 269950 A (Matsushita Electric Ind. Co. Ltd.), Oct. 9, 1998 * abstract *.
Patent Abstracts of Japan, vol. 018, No. 116 (E-1515), Feb. 24, 1994 & JP 05 314913 A (NEC Corp.), Nov. 26, 1993 * abstract *.

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