Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2002-09-26
2004-06-01
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S587000
Reexamination Certificate
active
06744201
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma information display element such as a plasma display panel (PDP) and a plasma addressed liquid crystal display device (PALC), and a method for producing the same.
2. Description of the Background Art
In recent years, a plasma information display element such as a plasma display panel (PDP) and a plasma addressed liquid crystal display device (PALC) has been attracting public attention.
PDPs are generally classified into those of DC type and those of AC type. At present, AC-type PDPs are the mainstream in view of the discharge stability and the long-term reliability, and AC-type PDPs have already been commercially available.
A structure of a conventional AC-type PDP
300
will be described with reference to FIG.
8
.
FIG. 8
is a cross-sectional view schematically illustrating the PDP
300
. Note that
FIG. 8
shows a front substrate
310
in a schematic cross-sectional view taken in a direction that is parallel to the direction in which discharge channels
350
extend, and shows a rear substrate
320
in a schematic cross-sectional view taken in a direction that is perpendicular to the direction in which the discharge channels
350
extend.
The PDP
300
includes the front substrate
310
and the rear substrate
320
provided so as to oppose each other, and a plurality of barrier ribs
340
provided between the front substrate
310
and the rear substrate
320
.
The barrier ribs
340
are arranged in a stripe pattern, and the discharge channels
350
, which are also arranged in a stripe pattern, are defined each as a space surrounded by the front substrate
310
, the rear substrate
320
and the barrier rib
340
. This space, i.e., the discharge channel
350
, is filled with a discharge gas that can be ionized by a discharge.
The front substrate
310
includes a transparent substrate
312
, display electrodes
314
provided on the transparent substrate
312
, a dielectric layer
316
provided so as to cover the display electrodes
314
, and a protective layer
318
provided on the dielectric layer
316
.
The display electrodes
314
of the front substrate
310
are arranged in a stripe pattern and in pairs. One of each pair of display electrodes
314
functions as an anode
314
A and the other as a cathode
314
C. Moreover, each display electrode
314
includes a transparent electrode
314
a
and a bus electrode
314
b
provided on the transparent electrode
314
a.
The rear substrate
320
includes an insulative substrate
322
, address electrodes
324
provided on the insulative substrate
322
, and a dielectric layer
326
provided so as to cover the address electrodes
324
. The address electrodes
324
are arranged in a stripe pattern so as to cross the display electrodes
314
, with the barrier rib
340
described above being formed between each pair of adjacent address electrodes
324
.
Phosphor layers
328
are formed each in a “U” shape on the side surface of the barrier ribs
340
and the upper surface of the dielectric layer
326
. Typically, the phosphor layer
328
is a red phosphor layer
328
R (e.g., a (Y,Ga)BO
3
:Eu layer), a green phosphor layer
328
G (e.g., a Zn
2
SiO
4
:Mn layer) or a blue phosphor layer
328
B (e.g., a BaMgAl
14
O
23
:Eu layer).
The operation of the PDP
300
having such a structure will be described with reference to FIG.
9
.
FIG. 9
schematically illustrates the operation of the PDP
300
. Note that the PDP
300
has a plurality of picture element regions arranged in a matrix pattern, and a pair of one display electrode
314
and one address electrode
324
intersect each other in each of the picture element regions. Moreover, in a write operation to be described later, one of each pair of display electrodes
314
functions as a scanning electrode.
First, a write discharge is caused selectively in a predetermined picture element region by applying a voltage that exceeds a discharge threshold between one scanning electrode (one of a pair of display electrodes
314
) and one address electrode
324
. Through the write discharge, a charge is induced/stored around the surface of the dielectric layer
316
above the scanning electrode. Note that such induction/storage of a charge is also referred to as the formation of a wall charge.
Next, a voltage that does not exceed the discharge threshold is applied between a pair of display electrodes
314
. At this time, in the predetermined picture element region in which the write discharge has been caused, this voltage is superimposed on a wall voltage that occurs due to the wall charge formed in the write operation, whereby the effective voltage in the region exceeds the discharge threshold, thus initiating a sustain discharge. A predetermined picture element region can be brought into an illuminated state by illuminating the phosphor layer
328
using ultraviolet rays that are generated by the sustain discharge.
In the PDP
300
, which operates as described above, the protective layer
318
is provided for the purpose of protecting the display electrodes
314
and the dielectric layer
316
from a discharge (plasma discharge). Typically, an MgO layer is used as the protective layer
318
.
Japanese Laid-Open Patent Publication No. 5-234519 discloses a PDP in which the discharge voltage is reduced by using a (111)-oriented MgO layer as the protective layer. Moreover, Japanese Laid-Open Patent Publication No. 10-106441 discloses a PDP in which the anti-sputtering property (the resistance against sputtering due to a plasma discharge) of the protective layer is improved by using a (220)-oriented MgO layer (disclosed as a (110)-oriented MgO layer in the publication) as the protective layer.
However, a (111)-oriented MgO layer, which is provided as the protective layer in the PDP disclosed in Japanese Laid-Open Patent Publication No. 5-234519, does not have a sufficient anti-sputtering property though it has a desirable property for reducing the discharge voltage.
Moreover, a (220)-oriented MgO layer, which is provided as the protective layer in the PDP disclosed in Japanese Laid-Open Patent Publication No. 10-106441 does not have a sufficient property for reducing the discharge voltage though it has a sufficient anti-sputtering property.
SUMMARY OF THE INVENTION
The present invention has been made in view of these problems in the art, and has an object to provide a plasma information display element that includes a protective layer with a desirable anti-sputtering property and has a reduced discharge voltage, and a method for producing the same.
A plasma information display element of the present invention includes: a first substrate; a second substrate opposing the first substrate; a plurality of barrier ribs provided between the first substrate and the second substrate; a plurality of discharge channels defined by the first substrate, the second substrate and the barrier ribs; an anode and a cathode provided on one side of the first substrate that is closer to the second substrate; and a protective layer provided so as to cover the anode and the cathode, wherein the protective layer is a layer that contains (220)-oriented MgO and (200)-oriented MgO. Thus, the object set forth above is achieved. Note that “(220)-oriented MgO” refers to an MgO crystal in which the crystal plane parallel to the layer plane is the (220) plane, and “(200)-oriented MgO” refers to an MgO crystal in which the crystal plane parallel to the layer plane is the (200) plane.
The protective layer may be provided directly on the anode and the cathode.
The plasma information display element may further include a dielectric layer provided between the anode and the cathode and the protective layer.
It is preferred that the protective layer is a layer that is substantially made only of (220)-oriented MgO and (200)-oriented MgO.
The plasma information display element may further include: a third substrate provided so as to oppose the second substrate; and a liquid crystal layer provided between the second substrate and the third substrate.
Nakayama Junichiro
Tanaka Masanobu
Nixon & Vanderhye P.C.
Patel Vip
Sharp Kabushiki Kaisha
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