Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2000-05-18
2003-06-17
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S584000, C313S587000, C313S586000, C445S024000, C445S033000
Reexamination Certificate
active
06580216
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This present invention relates to a display and a method for making the same, and in particular relates to a high contrast plasma display panel (PDP) and a method for making the same.
2. Description of the Prior Art
PDP uses the UV light emitted by a gas arc to excite red, green and blue phosphorous materials and generate visible light when the excited phosphorous materials return to ground state.
FIG. 1A
is a schematic view of the traditional PDP with electrodes, and
FIG. 1B
illustrates the cross-sectional view of a discharge cell of the PDP shown in FIG.
1
A. As shown in
FIGS. 1A and 1B
, the electrodes are arrayed on a matrix consisting of vertical and horizontal stripes set on the glass substrates
1
and
2
. One set of the electrodes is the address electrode
3
for the display data to write therein. Another set of the electrodes is the display electrodes
4
, which is used to discharge and display. Between the display electrodes is discharge region. The region which is not covered by the discharge region is a non-discharge region. The address electrodes
3
are separated by ribs
5
, and the red, green, blue phosphorous materials are coated on the glass substrate
1
to cover the address electrodes
3
. The display panel is formed by joining the rear glass substrate
1
with the front glass substrate
2
, and the space between the glass substrates
1
and
2
are filled with a mixing gas consisting of Ne and Ar. Each intersection of an address electrode
3
and a pair of display electrodes
4
is a discharge cell. The data written into the address electrode
3
are transformed and transferred to the display panel by discharging between the display electrodes
4
. By controlling the discharge intensity of the display electrodes
4
, the intensity of the emission light can be controlled and the display panel can show true color symbols, drawings and images.
The brightness and the contrast are both important properties for PDP. The definition of contrast is the ratio of the brightness level to the darkness level. As shown in
FIG. 2
, during operation, the PDP has a little background radiation even in full dark state. Therefore, the definition of contrast in a dark room (dark-room contrast) is the ratio of intensity of display light (Ld) over the intensity of background radiation (Lb):
Dark-room contrast=
Ld/Lb
Next, consider a light environment (such as indoor illumination). Let the intensity of incident light be Lin, and the reflection coefficient of the glass substrate be &agr;. Let the the intensity of reflecting light be Lref, then Lref=&agr;Lin. The contrast in a light room (light-room contrast) is amended as the following formula:
Light-room contrast=(
Ld+Lref
)/(
Lb+Lref
)
Therefore, decreasing the intensity of the reflecting light is necessary to enhance light-room contrast.
To reduce the intensity of reflection and improve the contrast in a light room, a non-transparent black matrix (BM) is introduced to the front panel of the PDP to cover the non-discharge region of PDP.
FIGS.
3
A~
3
G are cross-sectional views showing one process in the prior art for improving the light-room contrast by introducing black matrices onto the front panel of the PDP. In this example, black matrices are introduced into to the front panel of the PDP to improve the light-room contrast.
As shown in
FIG. 3A
, a glass substrate
10
is provided first. Then, transparent electrodes
12
are formed on the discharge region of the glass substrate
10
as shown in FIG.
3
B. The transparent electrodes
12
usually consist of indium tin oxide (ITO). Then, display electrodes
14
are formed on top of the transparent electrode
12
as shown in FIG.
3
C. The display electrodes usually consist of Cr/Cu/Cr or Cr/Al/Cr. A planarized dielectric layer
16
is deposited as shown in FIG.
3
D. Then, black matrices
18
are formed on top of the dielectric layer
16
in areas corresponding to non-discharge region of PDP as shown in FIG.
3
E. The black matrices
18
usually consist of black low melting-point glass. Then, a sealing frit
20
is formed on top of the dielectric layer
16
in the peripheral PDP. For illustration purpose, the sealing frit is shown next to the black matrix in FIG.
3
F. Afterwards, a MgO layer
22
is formed as shown in FIG.
3
G.
FIGS.
4
A~
4
F are cross-sectional views showing another process for improving the light-room contrast by introducing a black matrix onto the front panel of the PDP.
As shown in
FIG. 4A
, a glass substrate
30
is provided first. Then, transparent electrodes
32
are formed on the discharge region of the glass substrate
30
as shown in FIG.
4
B. The transparent electrodes
32
usually consist of indium tin oxide (ITO). Then, display electrodes
34
are formed on top of the transparent electrodes
32
, and black matrices
36
are formed on the non-discharge region of the PDP as shown in FIG.
4
C. Then, a planarized dielectric layer
38
is deposited as shown in FIG.
4
D. Then, a sealing frit
40
is formed on top of the dielectric layer
38
in the peripheral PDP as shown in FIG.
4
E.
Afterwards, a MgO layer
42
is formed on the exposed dielectric layer
38
as shown in FIG.
4
F.
Similarly, FIGS.
5
A~
5
F shows another example, wherein black matrices are introduced into to the front panel of PDP to improve the light-room contrast.
As shown in
FIG. 5A
, a glass substrate
50
is provided first. Then, transparent electrodes
52
are formed on the discharge region of the glass substrate
50
as shown in FIG.
5
B. The transparent electrodes
52
usually consist of indium tin oxide (ITO). Then, display electrodes
54
are formed on top of the transparent electrodes
52
, as shown in FIG.
5
C. The display electrodes usually consist of Cr/Cu/Cr or Cr/Al/Cr. Then, a planarized dielectric layer
56
is deposited as shown in FIG.
5
D. Black matrices
58
are formed on top of the dielectric layer
56
which corresponds to non-discharge region of PDP as shown in
FIG. 5E
, wherein the black matrices
58
usually consists of black low melting-point glass. Then, another dielectric layer
60
is deposited as shown in FIG.
5
F. Then, a sealing frit
62
is formed on top of the dielectric layer
60
in the peripheral PDP as shown in FIG.
5
G. Afterwards, a MgO layer
64
is formed on the exposed dielectric layer
60
as shown in FIG.
5
H.
In the above-mentioned examples, the surface reflectance of the black matrices (
18
,
36
,
58
) consisting of either Cr/Cu/Cr or Cr/Al/Cr may reach as high as 60%.
SUMMARY OF THE INVENTION
One object of this present invention is to provide a high contrast PDP and a method for making the same to reduce the surface reflectance of the black masks, thus the intensity of the reflection can be reduced. Consequently, the light-room contrast is improved.
Another object of this invention is to provide a high contrast PDP and a method for making the same, which is characterized by that shielding masks formed of black matrix material below the display electrodes. Compared with the traditional PDP, the area covered by the black matrix material within this present PDP is increased, thereby the reflection intensity of PDP is reduced.
Another object of this invention is to provide a high contrast PDP, and a method for making the same. The reflection intensity can be reduced and the light-room contrast can be improved without extra processes or cost.
REFERENCES:
patent: 5818168 (1998-10-01), Ushifusa et al.
patent: 5952782 (1999-09-01), Nanto et al.
patent: 6410214 (2002-06-01), Kim
Huang Chun-Chin
Lee Ta-Yuan
Lu Jin-Yuh
Sung Wen-Fa
Au Optronics Corp.
Colón German
Patel Nimeshkumar D.
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