Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2001-05-31
2004-03-30
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S582000, C313S585000
Reexamination Certificate
active
06713960
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a structure of an AC surface discharge type color plasma display panel of matrix display and a plasma display device comprising the plasma display panel (hereinafter referred to as “PDP”).
2. Description of the Background Art
FIG. 13
is a perspective view showing a cell structure of an AC surface discharge type PDP.
FIG. 14
is a schematic view showing an arrangement of a scan electrode
102
, a sustain electrode
103
and barrier ribs
108
viewed from the X direction shown in FIG.
13
. In general, an AC surface discharge type PDP of matrix display consists of a front panel on the side of display surface and a rear panel opposed to the front panel with a discharge space interposed therebetween. On a main surface of a glass substrate
101
in the front panel (a surface on the side opposed to the rear panel), a plurality of pairs of scan electrodes
102
and sustain electrodes
103
(only a pair is shown in
FIGS. 13 and 14
) are each arranged parallelly and symmetrically with a discharge gap which is a core of discharge in each discharge cell interposed therebetween with a spacing of pixel pitch in the Z direction of these figures.
Referring to
FIG. 14
, the scan electrode
102
is constituted of a bus electrode
102
a
which extends in the Y direction of the figure and transparent electrodes
102
b
(
102
b
R
1
,
102
b
G,
102
b
B and
102
b
R
2
in
FIG. 14
) which are connected to the bus electrode
102
a
and protrude in the Z direction of the figure. Further, the sustain electrode
103
is constituted of a bus electrode
103
a
which extends in the Y direction and transparent electrodes
103
b
(
103
b
R
1
,
103
b
G,
103
b
B and
103
b
R
2
in
FIG. 14
) which are connected to the bus electrode
103
a
and protrude in the Z direction to define the discharge gaps between themselves and the transparent electrodes
102
b.
The lengths of the transparent electrodes
102
b
and
103
b
(L
102
b
0
and L
103
b
0
) in the Z direction are equal and the widths thereof (WR
0
, WG
0
and WB
0
) in the Y direction are equal among all the discharge cells. Further, the spacings (G
0
) of the discharge gaps in the Z direction are equal among all the discharge cells.
The transparent electrodes
102
b
and
103
b
are made of materials having a relatively high transmissivity of visible rays, such as ITO (Indium Tin Oxide) or SnO
2
(NESA), and formed by thin film processing such as evaporation or CVD in many cases. Further, the bus electrodes
102
a
and
103
a
are made of materials having relatively low resistance, such as silver, aluminum, copper or multilayer film of chromium and copper, and formed by thick film processing using printing process or thin film processing using photosensitive paste.
Furthermore, on the main surface of the glass substrate
101
, a dielectric layer
104
is formed covering the scan electrode
102
and the sustain electrode
103
. A surface of the dielectric layer
104
(exposed to the discharge space) is covered with a protection film
105
made of MgO and the like having relatively high secondary emission ratio and excellent sputtering resistance against ions, electrons and the like generated from the discharge.
On a main surface of a glass substrate
106
in the rear panel (a surface on the side opposed to the front panel), a plurality of barrier ribs
108
having a predetermined height are formed extending in the Z direction between adjacent discharge cells in the Y direction, to define a discharge space between the front panel and the rear panel. Further, on the main surface of the glass substrate
106
, a plurality of write electrodes
107
(
107
R,
107
G and
107
B in
FIG. 13
) are formed extending in the Z direction between the adjacent barrier ribs
108
.
On a surface of a concave portion made by side surfaces of the barrier ribs
108
and the main surface of the glass substrate
106
, predetermined phosphors
109
(
109
R,
109
G and
109
B in
FIG. 13
) corresponding to red (R), green (G) and blue (B), respectively, are coated, to cover the write electrodes
107
. Further, in some times, an insulating layer is provided between the write electrode
107
and the phosphor
109
.
The front panel and the rear panel are sealed to each other by a sealing member (not shown) provided on rims of the panels, bringing tops of the barrier ribs
108
and the protection film
105
into contact with each other. The discharge space of the PDP formed by the front panel, the rear panel and the sealing member and defined by the barrier ribs
108
is filled with a noble gas such as xenon which generates ultraviolet ray from a discharge and a dischargeable gas such as nitrogen or oxygen. The phosphors
109
are excited by the ultraviolet ray generated from the discharge to cause luminescence in respective colors.
FIG. 15
is a schematic view briefly illustrating a process for luminescence of the discharge cell in the background-art PDP. In the discharge cell to be lighted, a predetermined voltage is applied between the scan electrode
102
and the write electrode
107
to cause a discharge between these electrodes. This is termed writing discharge, and positive ions and electrons ionized by the writing discharge are accumulated as wall charges on surfaces of the phosphors
109
and the protection film
105
.
In the discharge cell in which the wall charges are accumulated, when a voltage is applied to the sustain electrode
103
, a creepage discharge starts through the discharge gap between the scan electrode
102
and the sustain electrode
103
. After that, an alternating electric field is further produced in the scan electrode
102
and the sustain electrode
103
, and a discharge is thereby repeatedly caused in the scan electrode
102
and the sustain electrode
103
. This discharge, repeatedly occurring in the scan electrode
102
and the sustain electrode
103
, is termed sustain discharge, and the ultraviolet rays generated from the sustain discharge excites the phosphors
109
and becomes visible rays to be radiated outside through the front panel.
In order to make a tone display in the PDP, generally adopted is the time division toning system in which the number of sustain discharges in one field period of an image is controlled to control the luminance. One field period is divided into some small time units called subfields (SF), and pulse voltages to cause the sustain discharge, the number of which is weighted on the binary basis, are inserted in each subfield. For example, when one field is divided into eight subfields (SF
0
to SF
7
) and sustain pulses are inserted in the respective subfields at a ratio of 1:2:4:8:16:32:64:128, combination of any subfields allows representation of 256-level luminance. Such a control is made on the discharge cells for all the colors, to represent about 16,700,000 colors.
If white is displayed by using the PDP which adopts this time division toning system, when gains of respective input signals of red, green and blue are mixed at a ratio of 1:1:1, 256-level white can be displayed. When all the colors are displayed by the maximum gains, in particular, white of maximum luminance can be displayed theoretically. Herein, white refers to a color whose normal state is at a point of color temperature of 6500 K in the Planckian locus of CIE xy chromaticity diagram.
When white is actually displayed in the PDP, however, even if the phosphors
109
R,
109
G and
109
B are irradiated with the same amount of ultraviolet rays at a mixture ratio of 1:1:1, white can not be displayed or the color temperature is lowered in some cases. These phenomena are caused by bad balance of obtained visible lights of colors or affected by the visible lights of discharge gas itself other than the those from the phosphors
109
. Particularly, low color temperature is largely affected by luminescence characteristics of the blue phosphor
109
B. For this reason, when white is displayed in the PDP, the gains of the input signals are controlled, with the gains for
Mitsubishi Denki & Kabushiki Kaisha
Patel Vip
Phinney Jason
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