Alternating-current-driven-type plasma display

Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device

Reexamination Certificate

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C345S055000, C345S060000, C313S590000, C313S582000

Reexamination Certificate

active

06469451

ABSTRACT:

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a so-called three-electrode-type alternating-current-driven-type plasma display having pairs of sustain electrodes and address electrodes.
As an image display device that can be substituted for a current mainstream cathode ray tube (CRT), flat-screen (flat-panel) displays are studied in various ways. Such flat-panel displays include a liquid crystal display (LCD), an electroluminescence display (ELD) and a plasma display (PDP). Of these, the plasma display has advantages such as a relative easiness to form a larger screen and attain a wider viewing angle, excellent durability against environmental factors such as temperatures, magnetism, vibrations, etc., and a long lifetime. It is therefore expected that the plasma display can be applied not only to a home-use wall-hung television set but also to a public large-sized information terminal.
In the plasma display, a voltage is applied to discharge cells charged with a discharge gas, such as a rare gas, and a phosphor layer in the discharge cell is excited with an ultraviolet ray generated by glow discharge in the discharge gas to emit light. 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 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. AC-type plasma displays are commercially produced and constitute a mainstream in the market.
FIG. 15
shows a typical constitution of a conventional AC-type plasma display. This AC-type plasma display comes under a so-called three-electrode type, and discharge is caused by a pair of sustain electrodes
112
and an address electrode
122
. In the AC type plasma display shown in
FIG. 15
, a first panel
110
corresponding to a front panel and a second panel
120
corresponding to a rear panel are bonded to each other in their circumferential portions. Light emission from a phosphor layer
125
on the second panel
120
is viewed, for example, through the first panel
110
.
The first panel
110
comprises a transparent first substrate
111
, sustain electrodes
112
made of a transparent electrically conductive material and formed in the form of a stripe on the first substrate
111
, bus electrodes
116
made of a material having a lower electric resistivity than the sustain electrodes
112
and provided for decreasing the impedance of the sustain electrodes
112
, and a protective layer
117
made of a dielectric material and formed on the first substrate
111
, the bus electrodes
116
and the sustain electrodes
112
. The protective layer
117
is constituted of two layers such as a dielectric material layer and a covering layer that are positioned in this order from the first substrate side, while it is shown as a single layer.
The second panel
120
comprises a second substrate
121
, address electrodes (also called “data electrodes”)
122
formed in the form of a stripe on the second substrate
121
, a dielectric material film
123
formed on the second substrate
121
and the address electrodes
122
, insulating separation walls
124
which are formed in regions on the dielectric material film
123
between neighboring address electrodes
122
and extend in parallel with the address electrodes
122
, and phosphor layers
125
each of which is formed on the dielectric material film
123
and on side walls of the separation wall
124
. The phosphor layers
125
are composed of a red phosphor layer
125
R, a green phosphor layer
125
G and a blue phosphor layer
125
B, and these phosphor layers
125
R,
125
G and
125
B for corresponding colors are arranged in a predetermined order.
FIG. 15
shows a partial exploded perspective view, and an actual embodiment; and, top portions of the separation walls
124
on the second panel side are in contact with the protective layer
117
on the first panel side. A region where a pair of the sustain electrodes
112
and the address electrode
122
positioned between the two neighboring separation walls
124
overlap corresponds to one discharge cell. And, a rare gas is sealed in each space surrounded by the neighboring separation walls
124
, the phosphor layer
125
and the protective layer
117
.
The extending direction of projection image of the sustain electrode
112
and the extending direction of projection image of the address electrode
122
cross each other at right angles, and a region where a pair of the sustain electrodes
112
and one set of the phosphor layers
125
R,
125
G and
125
B overlap corresponds to one pixel. Since glow discharge takes place between a pair of the sustain electrodes
112
, a plasma display of the above type is called a “surface discharge type”. A pulse voltage lower than the discharge start voltage of the discharge cell is applied to the address electrode
122
immediately before the application of a voltage to a pair of the sustain electrodes
112
, whereby a wall charge is accumulated in the discharge cell (selection of a discharge cell for display), so that the apparent discharge start voltage decreases. Then, discharge that starts between a pair of the sustain electrodes
112
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 rare gas emits light in a color inherent to the phosphor material. The vacuum ultraviolet ray that is generated has a wavelength dependent upon the sealed rare gas.
The light emission state of glow discharge in the discharge cell will be explained below with reference to
FIGS. 13A
,
13
B,
14
A and
14
B.
FIG. 13A
schematically shows a light emission state when DC glow discharge is carried out in a discharge tube with a rare gas sealed therein. From the cathode to the anode, an Aston dark space A, a cathode glow B, a cathode dark space (Crookes dark space) C, a negative glow D, a Faraday dark space E, a positive column F and an anode glow G consecutively appear. In AC-glow discharge, a cathode and an anode are repeatedly altered at a predetermined frequency, so that the positive column F is positioned in a central area between the electrodes and the Faraday dark spaces E, the negative glow D, the cathode dark spaces C, the cathode glow B and the Aston dark spaces A consecutively appear symmetrically on both sides of the positive column F. The state shown in
FIG. 13B
is observed when the distance between the electrodes is sufficiently large like a fluorescent lamp. As the distance between the electrodes is decreased, the length of the positive column F decreases. When the distance between the electrodes is further decreased, the positive column F disappears, the negative glow D is positioned in the central area between the electrodes, and the cathode dark spaces C, the cathode glow B and the Aston dark spaces A appear symmetrically on both sides in this order as shown in FIG.
14
A. The state shown in
FIG. 14A
is observed when the distance between the electrodes is a state that can be attained in a conventional general AC-type plasma display.
Meanwhile, in the conventional AC-type plasma display shown in
FIG. 15
, pairs of the sustain electrodes
112
are formed on one plane. The distance between one sustain electrode
112
and the other sustain electrode
112
of each pair is therefore required to be a predetermined gap (d), for example, for causing the negative glow discharge. The above gap (d) is defined by Paschen's law that a discharge start voltage V
bd
can be expressed by the function of the product d-p of the gap (d) and the gas pressure (p), and it is generally at least 100 &mgr;m in the negative glow discharge. Further, the sustain electrodes
112
are required to

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