Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2000-01-11
2003-03-11
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S585000
Reexamination Certificate
active
06531819
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plasma display panel of a surface discharge type having a plurality of display electrodes constituting sustain discharge electrode pairs arranged adjacent to each other.
The plasma display panel is attracting attention as a display device of wall type, and a vigorous effort is under way for improving the image quality by improving the resolution and suppressing the power consumption.
First, an explanation will be given of the structure of an AC-driven 3-electrode plasma display panel of a surface discharge type (hereinafter referred to as PDP).
FIG. 1
is a perspective view showing a part of the PDP. As shown in
FIG. 1
, display electrodes (also called sustain electrodes) X, Y for generating the surface discharge along the surface of a substrate are arranged, at the rate of a pair on each row L of the matrix display, on the inner surface of a front substrate
100
of a transparent glass material. The display electrodes X, Y, are formed by photolithography and, as described in detail later, are each configured with a transparent electrode
102
and a bus electrode
103
of a metal thin film of a multilayer structure. In order to cover the display electrodes X, Y and the discharge space, a dielectric layer
104
for AC drive is formed by screen printing. A protective film
105
of MgO (magnesium oxide) is deposited by evaporation on the surface of the dielectric layer
104
.
On the other hand, a plurality of address electrodes
106
for generating the address discharge are arranged at a predetermined pitch at right angles to the display electrodes X, Y on the inner surface of the back substrate
101
. The address electrodes
106
are also formed by photolithography and are made of a metal film of a multilayer structure like the bus electrodes
103
. A dielectric layer
107
is formed by screen printing over the whole surface of the back substrate
101
including the address electrodes
106
. Linear partitioning walls
108
about 150 &mgr;m tall, one each between each pair of the address electrodes
106
, are formed on the dielectric layer
107
. Phosphor bands
110
of the three primary colors R (red), G (green), B (blue) for full color display are formed, by screen printing, in such a manner as to cover the surface of the dielectric layer
107
and the sides of the partitioning walls
108
above the address electrodes
106
. Also, a discharge gas such as Ne—Xe (a mixed gas of Ne and Xe) for exciting the phosphor material by radiating ultraviolet light at the time of discharge is sealed in the discharge space
109
under the pressure of about several tens of KPa (several hundred torr). A seal member
111
is formed along the peripheral edge of the substrates for sealing the discharge space
109
. The front substrate
100
and the back substrate
101
are formed separately from each other, are attached to each other and are fixed by the seal member
111
, thus completing the PDP.
FIGS. 2A and 2B
are a plan view and a sectional view, respectively, showing the structure of the display electrodes of the conventional PDP. The same component parts as the corresponding parts in
FIG. 1
are designated by the same reference numerals, respectively. As explained with reference to
FIG. 1
, the display electrodes X, Y constitute a pair, and are each comprised of a wide transparent electrode
102
and a narrow transparent electrode
103
as seen from FIG.
2
A.
The bus electrode
103
is made of a multilayer metal such as Cr—Cu—Cr taking the conductivity and the matching with the surrounding film into consideration. The transparent electrode
102
is adapted to transmit light to prevent a reduction in luminous efficacy. The bus electrodes of the multilayer metal compensate for the insufficient conductivity of the transparent electrode
102
. The bus electrode
103
is arranged on the outside of each transparent electrode
102
thereby to form a luminous area
112
between the two bus electrodes
103
. Each luminous area
112
is defined by the partitioning walls
108
indicated by dashed lines formed on the back substrate in opposed relation to the address electrode
106
indicated by one-dot chains in FIG.
2
A.
FIG. 2B
is a cross sectional view of the display electrode taken along the arrow in FIG.
2
A. To complement the foregoing description with reference to
FIG. 1
, as shown in
FIG. 2B
, the transparent electrodes
102
are formed in contact with the inner surface of the front substrate
100
, and the bus electrodes
103
are deposited on a part of the transparent electrodes
102
, respectively. Also, though not shown in
FIG. 2A
, the dielectric member
104
is formed in such a manner as to cover the transparent electrodes
102
and the bus electrodes
103
, and a protective film
105
is formed on the dielectric member
104
.
In this structure, the main discharge is generated between the display electrodes X and Y to emit light from the portion selected by the address electrodes
106
. In the light emission, the ultraviolet light generated by the discharge excites the phosphor member
110
(
FIG. 1
) and appears as visible light on the front substrate
100
.
In recent years, the trend has been toward an increased number of pixels, to meet an HDTV requirement, at the sacrifice of increased power consumption. Specifically, a higher definition of the screen of the same size increases the number of electrodes and hence the area occupied by the electrodes, resulting in a correspondingly increased power consumption. Japanese Unexamined Patent Publication No. 8-22772 discloses a PDP in which the power consumption is suppressed by changing the pattern of the wide transparent electrode and thus the area thereof is reduced.
FIG. 3
is a plan view showing the display electrode pattern for reducing the power consumption disclosed in the same publication. As shown in
FIG. 3
, each transparent electrode
122
of the display electrodes X, Y includes a plurality of protrusions
122
a
extending in the direction perpendicular to the main pattern and each having, at the forward end thereof, a discharge unit
122
b
of a width required for discharge. This pattern shape can reduce the area of the transparent electrodes
122
remarkably. The bus electrodes
123
are formed on the outside of the transparent electrodes
122
, respectively, in the same manner as explained with reference to FIG.
2
.
The discharge is generated at the opposed portions of the adjacent transparent electrodes
122
. The portions defined by the partitioning walls
128
opposed to the address electrodes
126
on the back substrate constitute a luminous area
129
. Therefore, the opposed portions of the transparent electrodes
122
, as long as they are in a predetermined spaced relation with each other in the luminous area
129
, can generate the desired discharge. In view of this, as shown in
FIG. 3
, a pattern formed with the discharge potions
122
b
having a predetermined width through the protrusions
122
a
, respectively, can generate a discharge without any problem. Thus, the power consumption can be reduced by reducing the area of the transparent electrodes
122
.
In spite of this, it has been found that the pattern described above for reducing the area is accompanied by another problem. Specifically, in view of the fact that the transparent electrode film as thin as several thousand A may cause a disconnected portion
130
at the time of patterning under the effect of the dust or a scratch or other damage on the surface of the substrate. The disconnected portion
130
of the protrusion
122
a
cuts off the conduction to the discharge unit
122
b
and thus naturally prevents the discharge.
U.S. Ser. No. 5640068, on the other hand, discloses a PDP with the brightness increased by reducing the shielding area of the luminous area.
FIG. 4
is a plan view showing a display electrode pattern for reducing the shielding area disclosed by the well-known reference. As shown in
FIG. 4
, each transparent electrode
142
of the display electrodes X, Y extends in
Kanazawa Yoshikazu
Miyazaki Yukinori
Moriyama Mitsuhiro
Nakahara Masahiro
Nomura Shin-ichi
Clove Thelma Sheree
Fujitsu Limited
Patel Nimeshkumar D.
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