Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2001-10-25
2003-09-30
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S582000, C313S586000
Reexamination Certificate
active
06628077
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an alternating current driven type plasma display.
Flat type (flat panel type) displays are studied in various ways as image displays that will replace cathode ray tubes (CRTS) constituting a mainstream at present. As such flat type displays, for example, there are a liquid crystal display (LCD), an electroluminescence display (ELD) and a plasma display (PDP). Of these, a plasma display has advantages that it permits a larger screen and a wider viewing angle relatively easily, that it has excellent durability against environmental factors such as temperature, magnetism and vibrations and that it has a long lifetime. It is expected that a plasma display can be applied not only to a television set of a hanging-up-on-the-wall fashion, but also to a large-scale public information terminal unit.
In the plasma display, a voltage is applied to discharge cells formed by charging discharge spaces with discharge gas consisting of a rare gas, and a phosphor layer in each discharge cell is excited with vacuum ultraviolet ray generated by glow discharge in the discharge gas to give light emission. That is, each discharge cell is driven according to a principle similar to that of a fluorescent lamp, and generally, the discharge cells are put together on the order of hundreds of thousands to constitute a display screen. The plasma display is largely classified into a direct current driven type (DC type) and an alternating current driven type (AC type) according to methods of applying a voltage to the discharge cells, and each type has advantages and disadvantages. The AC type plasma display is suitable for attaining a higher fineness, since separation walls which work to separate the discharge cells individually within a display screen can be formed, for example, in the form of stripes. Further, it has an advantage that electrodes are less worn out and have a long lifetime since the surfaces of the electrodes for discharge are covered with a dielectric layer.
FIG. 11
shows a partial schematic exploded perspective view of a typical constitution of a conventional AC type plasma display. This AC type plasma display comes under a so-called tri-electrode type, and discharging takes place mainly between a pair of sustain electrodes
512
. In the AC type plasma display shown in
FIG. 11
, a first panel
10
corresponding to a front panel and a second panel
20
corresponding to a rear panel are bonded to each other in their circumferential portions.
The first panel
10
comprises a transparent first substrate
11
, a plurality of pairs of sustain electrodes
512
made of a transparent electrically conductive material and formed on the first substrate
11
in the form of stripes, bus electrodes
13
made of a material having a lower electric resistivity than the sustain electrodes
512
and formed on the sustain electrodes
512
for decreasing the impedance of the sustain electrodes
512
, a dielectric layer
14
formed on the first substrate
11
and also on the bus electrodes
13
and the sustain electrodes
512
, and a protective layer
15
made of MgO and formed on the dielectric layer
14
.
The second panel
20
comprises a second substrate
21
, a plurality of address electrodes (also called data electrodes)
22
formed on the second substrate
21
in the form of stripes, a dielectric material layer
23
formed on the second substrate
21
and also on the address electrodes
22
, insulating separation walls
24
formed in regions on the dielectric material layer
23
between neighboring address electrodes
22
and which extend in parallel with the address electrodes
22
, and phosphor layers
25
which are formed on the dielectric material layer
23
and are also formed on the side walls of the separation walls
24
. When the AC type plasma display is used for display in colors, each phosphor layer
25
is constituted of a red phosphor layer
25
R, a green phosphor layer
25
G and a blue phosphor layer
25
B, and the phosphor layers
25
R,
25
G and
25
B of these colors are formed in a predetermined order.
FIG. 11
is an exploded perspective view, and in an actual embodiment, top portions of the separation walls
24
on the second panel side are in contact with the protective layer
15
on the first panel side. A region where a pair of the sustain electrodes
512
and the address electrode
22
positioned between two of the separation walls
24
overlap corresponds to a discharge cell. A discharge gas is charged in a discharge space surrounded by mutually neighboring two separation walls
24
, the phosphor layer
25
and the protective layer
15
. The first panel
10
and the second panel
20
are bonded to each other with a frit glass in their circumferential portions.
The extending direction of projection image of the sustain electrodes
512
and the extending direction of projection image of the address electrodes
22
cross each other at right angles, and a region where a pair of the sustain electrodes
512
and one combination of the phosphor layers
25
R,
25
G and
25
B for emitting light in three primary colors overlap corresponds to one pixel. Since glow discharge is caused between the sustain electrodes
512
that are forming a pair, the AC type plasma display of the above type is called “surface discharge type”. For example, a pulse voltage lower than the discharge start voltage of the discharge cell is applied to the address electrode
22
immediately before the application of a voltage between a pair of the sustain electrodes
512
. In this case, a wall charge is accumulated in the discharge cell (selection of a discharge cell for display), and an apparent discharge start voltage decreases. Then, the discharge that has started between a pair of the sustain electrodes
512
can be sustained at a voltage lower than the discharge start voltage. In the discharge cell, the phosphor layer excited by irradiation with vacuum ultraviolet ray generated by glow discharge in the discharge gas emits light in a color characteristic of a phosphor material. Vacuum ultraviolet ray having a wavelength according to a type of the charged discharge gas is generated. Light emission of the phosphor layer
25
on the second panel
20
is viewed, for example, through the first panel
10
.
Generally, the discharge gas charged in the discharge space is composed of a mixture prepared by mixing approximately 4% by volume of xenon (Xe) gas with an inert gas such as neon (Ne) gas, helium (He) gas or argon (Ar) gas. The gas mixture has a total pressure of approximately 6×10
4
Pa to 7×10
4
Pa, and the xenon (Xe) gas has a partial pressure of approximately 3×10
3
Pa. The distance between the sustain electrodes
512
forming each pair is approximately 100 &mgr;m.
FIGS. 12A and 12B
and
FIGS. 13A and 13B
show plane forms of a pair of conventional sustain electrodes
512
. For clearly showing the electrodes in
FIGS. 12A and 12B
and
FIGS. 13A and 13B
, the electrodes are provided with slanting lines. In these Figures, further, showing of the dielectric layer
14
and the protective layer
15
is omitted.
In an example shown in
FIG. 12A
, a pair of the sustain electrodes
512
have a plane form consisting of two stripes and have two sides (two edges) extending straight and being opposite to each other. Each bus electrode
13
is in contact with one straightly extending side (one edge) of the sustain electrode
512
. The other side (other edge) of one sustain electrode
512
forming a pair and the other side (other edge) of the other sustain electrode
512
forming the pair face each other at a constant interval (distance). For accomplishing a higher fineness of an alternating current driven type plasma display, it is required to decrease the discharge cells in size. When the discharge cells are decreased in size, however, the sustain electrodes constituted as shown in
FIG. 12A
have a problem that a portion of each sustain electrode that serves for discharging comes to have a smaller length.
FIG. 12B
s
Colón German
Kananen, Esq. Ronald P.
Patel Nimeshkumar D.
Rader & Fishman & Grauer, PLLC
Sony Corporation
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