Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2000-09-20
2003-02-18
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S491000, C313S584000, C313S586000
Reexamination Certificate
active
06522072
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel (hereinafter referred to also as “PDP”), and more particularly, it relates to a technique of improving display quality such as luminance of an alternating current PDP (hereinafter referred to also as “AC-PDP”).
2. Description of the Background Art
FIG. 30
is an exploded perspective view showing a conventional AC-PDP
101
P. As shown in
FIG. 30
, the AC-PDP
101
P is roughly classified into a front panel
101
FP and a rear panel
101
RP.
In the front panel
101
FP, a transparent dielectric thin film layer
55
P containing no alkaline metal such as sodium (Na) is formed on a main surface of a glass substrate
51
made of soda-lime glass, for example. The dielectric thin film layer
55
P is formed through a thin film forming process such as CVD method, for example. In general, the insulation resistance of soda-lime glass or the like is reduced when the temperature is increased, and hence inconvenience may result in operations of the AC-PDP
101
P due to heat generated in operation. The dielectric thin film layer
55
P is provided for ensuring insulation of sustain electrodes
10
P and
20
P described later.
Strip-shaped sustain electrodes
10
P and
20
P forming sustain electrode pairs
30
P are formed in parallel with each other through prescribed gaps (discharge gaps) g on the surface of the dielectric thin film layer
55
P opposite to glass substrate
51
. A plurality of such sustain electrodes
10
P and
20
P are alternately formed in the form of stripes. The sustain electrodes
10
P and
20
P consist of transparent electrodes
11
P and
21
P formed on the aforementioned surface of the dielectric thin film layer
55
P and metal electrodes (referred to also as “bus electrodes”)
12
P and
22
P formed on surfaces of the transparent electrodes
11
P and
21
P opposite to the glass substrate
51
.
As described later, display emission is taken out from the side of the glass substrate
51
. Therefore, the transparent electrodes
11
P and
21
P are employed for increasing discharge areas, i.e., electrode areas while not screening visible light converted/generated in fluorescent materials
75
R,
75
G and
75
B described later.
The transparent electrodes
11
P and
21
P have high electrode resistance, and hence these transparent electrodes
11
P and
21
P are combined with the metal electrodes
12
P and
22
P thereby reducing the resistance of the sustain electrodes
10
P and
20
P.
The transparent electrodes
11
P and
21
P are prepared from ITO or SnO
2
, for example, while the metal electrodes
12
P and
22
P are formed by thick films of Ag or the like or thin films having a three-layer structure of Cr/Cu/Cr or a two-layer structure of Al/Cr, for example.
A black pattern (hereinafter referred to also as “in-electrode black layer”) of the same size or shape as the metal electrodes
12
P and
22
P is formed between the metal electrodes
12
P and
22
P and the transparent electrodes
11
P and
21
P, although
FIG. 30
omits illustration of such an in-electrode black layer in order to avoid complication. The in-electrode black layer, which must electrically connect the metal electrodes
12
P and
22
P with the transparent electrodes
11
P and
21
P, is made of a conductive material.
On the aforementioned surface of the dielectric thin film layer
55
P, a stripe-shaped black pattern (the so-called black stripe pattern)
76
P is formed between adjacent sustain electrode pairs
30
P in parallel with the sustain electrodes
10
P and
20
P. In order to avoid complication of illustration,
FIG. 30
shows the black stripe pattern
76
P only in the fragmented portion. Dissimilarly to the aforementioned in-electrode black layer, the black stripe pattern
76
P is made of an insulating material. If made of a conductive material, the black stripe pattern
76
P disadvantageously serves as an electrode to readily induce discharge (false discharge) between the same and the sustain electrode pairs
30
P.
According to the in-electrode black layer and the black stripe pattern
76
P, reflection of external light can be more reduced as viewed from the side of the front panel
101
FP forming the display surface of the AC-PDP
101
P, thereby consequently improving the contrast. The reason for this is as follows: Under light environment, the contrast, decided by the ratio of (i) reflection intensity of external light when the PDP emits no light to (ii) luminous intensity when the PDP emits light, is increased as the reflection intensity of external light is reduced under constant luminous intensity. Therefore, reflection of external light is preferably minimized, as enabled by the in-electrode black layer and the black stripe pattern
76
P.
At this time, light generated in a discharge space, defined by the front panel
101
FP and the rear panel
101
RP, is screened by the opaque metal electrodes
12
P and
22
P arranged closer to the discharge space than the in-electrode black layer when taken out from the AC-PDP
10
P. In addition, the in-electrode black layer is identical in size to the metal electrodes
12
P and
22
P as described above. In consideration of these points, the numerical aperture, i.e., luminous intensity is not reduced due to provision of the in-electrode black layer.
The black stripe pattern
76
P is provided between adjacent discharge cells in the direction perpendicular to the sustain electrodes
10
P and
20
P. In other words, the black stripe pattern
76
P is provided on a region irrelevant to display emission, and hence reduction of luminance is small despite provision of the black stripe pattern
76
P.
A transparent dielectric layer
52
is formed to cover the dielectric thin film layer
55
P and the sustain electrodes
10
P and
20
P. The dielectric layer
52
has a role of isolating the sustain electrodes
10
P and
20
P from each other while isolating the sustain electrodes
10
P and
20
P from the discharge space defined by the front panel
101
FP and the rear panel
101
RP or discharge formed in the discharge space. A protective film
53
of MgO, for example, is formed on the dielectric layer
52
. The protective film
53
has a role of protecting the dielectric layer
52
from the discharge formed in the discharge space while serving as a secondary-electron emission film for reducing a (discharge) firing voltage.
In the rear panel
101
RP, on the other hand, a plurality of strip-shaped write electrodes
72
are formed in the form of stripes on a main surface of a glass substrate
71
. A dielectric layer
73
is formed on the aforementioned main surface of the glass substrate
71
to cover the write electrodes
72
. Further, barrier ribs (also simply referred to as “ribs”)
74
are formed on regions corresponding to those between adjacent two write electrodes
72
on a surface of the dielectric layer
73
opposite to the glass substrate
71
. End portions or top portions of the barrier ribs
74
separated from the glass substrate
71
are blackened by a black material, for example. Such black portions
74
T, referred to as black stripe or black matrix, act to improve the contrast of display emission. Fluorescent materials or fluorescent layers
75
R,
75
G and
75
B for emitting light of red (R), green (G) and blue (B) are arranged on inner surfaces of U-shaped trenches defined by adjacent two barrier ribs
74
and the dielectric layer
73
respectively. There is also a rear panel having no dielectric layer
73
.
The front panel
101
FP and the rear panel
101
RP are so arranged that the aforementioned main surfaces of the glass substrates
51
and
71
face each other in such a direction that the sustain electrodes
10
P and
20
P and the write electrodes
72
three-dimensionally intersect with each other, while the peripheries thereof are airtightly sealed. The striped discharge space defined between the front panel
101
FP and the rear panel
101
RP and divided by the fluorescent layers
75
R,
75
G and
75
B (may be grasped as divided by the barrier ribs
74
) is
Harada Shigeki
Hashimoto Takashi
Kawabe Kazuya
Yura Shinsuke
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Patel Ashok
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