Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2000-12-29
2003-04-01
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C313S582000
Reexamination Certificate
active
06541922
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an alternating current driven type plasma display device and a method for the production thereof.
As an image display device that can be substituted for a currently mainstream cathode ray tube (CRT), flat-screen (flat-panel) display devices are studied in various ways. Such fat-panel display devices include a liquid crystal display (LCD), an electroluminescence display (ELD) and a plasma display device (PDP). Of these, the plasma display device has advantages that it is relatively easy to form a larger screen and attain a wider viewing angle, it has excellent durability against environmental factors such as temperatures, magnetism, vibrations, etc., and it has a long lifetime. The plasma display device is therefore expected to be applicable not only to a home-use, wall-hung television set but also to a large-sized public information terminal.
In the plasma display device, a voltage is applied to discharge cells charged with a rare gas, and a fluorescence layer in each discharge cell is excited with vacuum ultraviolet ray generated by glow discharge in the rare 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 device is largely classified into a direct-current driven type (DC type) and an alternate-current driven type (AC type) according to the methods of applying a voltage to the discharge cells, and each type has advantages and disadvantages. The AC type plasma display device is suitable for attaining a higher fineness, since separation walls which work to separate the discharge cells 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 are covered with a dielectric material.
FIG. 2
shows a typical constitution of a conventional AC type plasma display device. This AC type plasma display device comes under a so-called tri-electrode type, and discharging takes place mainly between the first electrodes
12
A and
12
B, which are a pair of discharge sustain electrodes (see FIG.
12
B). In the AC type plasma display device shown in
FIG. 2
, a front panel
10
and a rear panel
20
are bonded to each other in their circumferential portions. Light emission from fluorescence layers
24
on the rear panel is viewed through the front panel
10
.
The front panel
10
comprises a transparent first substrate
11
, pairs of first electrodes
12
A and
12
B composed of a transparent, electrically conductive material and formed on the first substrate
11
in the form of stripes, bus electrodes
13
composed of a material having a lower electric resistivity than the first electrodes
12
A and
12
B and provided for decreasing the impedance of the first electrode
12
A and
12
B, and a protective layer
14
formed on the first substrate
11
, the first electrodes
12
A and
12
B and bus electrodes
13
. The protective layer
14
works as a dielectric film and is provided for protecting the first electrodes
12
A and
12
B.
The rear panel
20
comprises a second substrate
21
, second electrodes (also called address electrodes or data electrodes)
22
formed on the second substrate
21
in the form of stripes, a dielectric film
23
formed on the second substrate
21
and on the second electrodes
22
, insulating separation walls
25
, which are formed in regions on the dielectric film
23
between neighboring second electrodes
22
and which extend in parallel with the second electrodes
22
, and fluorescence layers
24
which are formed on, and extend from, the surfaces of the dielectric film
23
and which also are formed on side walls of the separation walls
25
. The second electrodes
22
are provided for decreasing a discharge starting voltage. The separation walls
25
are provided for preventing an optical crosstalk, a phenomenon in which plasma discharge leaks to a neighboring discharge cell and allows a fluorescence layer of the neighboring discharge cell to emit light. Each fluorescence layer
24
is constituted of a red fluorescence layer
24
R, a green fluorescence layer
24
G and a blue fluorescence layer
24
B, and the fluorescence layers
24
R,
24
G and
24
B of these colors are formed in a predetermined order.
FIG. 2
is an exploded perspective view, and in an actual embodiment, top portions of the separation walls
25
on the rear panel side are in contact with the protective layer
14
on the front panel side. A region where a pair of the first electrodes
12
A and
12
B and a pair of the separation walls
25
overlap corresponds to one discharge cell. A rare gas is sealed in each space surrounded by two neighboring separation walls
25
, the fluorescence layers
24
and the protective layer
14
.
The extending direction of the first electrodes
12
A and
12
B and the extending direction of the second electrodes
22
make an angle of 90°, and the region where a pair of the neighboring first electrodes
12
A and
12
B and one set of the fluorescence layers
24
R,
24
G and
24
B for emitting light of three primary colors overlap corresponds to one pixel. Glow discharge takes place between the pair of the facing first electrodes
12
A and
12
B, so that a plasma display device of this type is called “surface discharge type”. In each discharge cell, the fluorescence layers excited by irradiation with vacuum ultraviolet ray generated by glow discharge in the rare gas emit light of colors characteristic of kinds of fluorescent materials. A vacuum ultraviolet ray having a wavelength depending upon the kind of the sealed rare gas is generated.
FIG. 19
shows a schematic layout of a pair of the first electrodes
12
A and
12
B, the bus electrode
13
and the separation walls
25
in the conventional plasma display device shown in FIG.
2
. The region surrounded by dotted lines corresponds to one pixel. For clarification of each region, slanting lines are added. In general, each pixel has the form of a square. Each pixel is divided into three sections (discharge cells) with the separation walls
25
, and each section emits light of one of three primary colors (R, G, B). When one pixel has an outer dimension L
0
, one side of each discharge cell has a length of L
0
/3=L
1
, and the other side has a length of L
0
. In a pair of the first electrodes
12
A and
12
B, therefore, those portions of the first electrodes
12
A and
12
B that contribute to discharging have a length slightly smaller than L
1
each.
Meanwhile, in the plasma display device, it is increasingly demanded to increase the density and fineness of pixels. For complying with such demands, it is inevitable to decrease the length L
1
of one side of each discharge cell. Suppose a case where one discharge cell having a side length L
1
as shown in a conceptual view of
FIG. 16A
, is modified to a discharge cell having a side length L
1
/2=L
2
as shown in a conceptual view of FIG.
16
B. In this connection, a subscript “1” is added when the state shown in
FIG. 16A
is explained, and a subscript “2” is added when the state shown in
FIG. 16B
is explained. In the above case, the thickness of each separation wall
25
is changed from W
1
to W
2
. Since, however, the separation walls
25
are required to have certain strength for preventing failures, such as chipping during the formation of the separation walls, it involves some difficulty that the value of W
2
equals ½ of W
1
. Therefore, a discharge space interposed between the separation walls
25
has a volume V
2
which is less than ½ of a volume V
1
of an original discharge space.
As the volume of the discharge cell decreases as described above, the number of metastable particles (the rare gas atoms, molecules, dimers, etc., in a metastable state in the discharge space) required for st
A Minh D
Kananen, Esq. Ronald P.
Rader & Fishman & Grauer, PLLC
Sony Corporation
Wong Don
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