Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2002-02-26
2003-11-18
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C313S485000, C313S509000, C313S586000
Reexamination Certificate
active
06650063
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel, and an image display device using the same, particularly to a plasma display panel, which may be abbreviated to a PDP hereinafter, suitable for making display images highly minute, and an image display device using the same.
2. Description of the Related Prior Art
An AC plane-discharge type PDP is a display device wherein a great number of minute discharge spaces (discharge cells) airtightly closed between two glass panel plate are set up. Referring to a drawing, this AC plane-discharge type PDP will be briefly described hereinafter.
FIG. 2
is a perspective exploded view illustrating a part of an ordinary PDP structure. The PDP illustrated in
FIG. 2
is a panel wherein a front panel plate
21
made of glass and a back panel plate
28
made of glass are adhered to and integrated with each other, and is a reflection type PDP wherein phosphor layers
32
emitting red (R), green (G) and blue (B) rays are formed on the side of the back panel plate
28
.
The front panel plate
21
has a pair of sustaining electrodes, which are also called display electrodes, formed on its face opposite to the back panel plate
28
and in parallel to have regular intervals.
The pair of sustaining electrodes is composed of transparent common electrodes (hereinafter referred to merely as X electrodes)
22
-
1
,
22
-
2
, . . . , and transparent independent electrodes (hereinafter referred to merely as Y electrodes or scanning electrodes)
23
-
1
,
23
-
2
, . . . .
In the X electrodes
22
-
1
,
22
-
2
, . . . , non-transparent X bus electrodes
24
-
1
,
24
-
2
, . . . for compensating for the conductivity of the transparent electrodes are set up to extend in the direction shown by an arrow D
2
in
FIG. 2
, and in the Y electrodes
23
-
1
,
23
-
2
, . . . , Y bus electrodes
25
-
1
,
25
-
2
, . . . are set up to extend in the same direction.
The X electrodes
22
-
1
,
22
-
2
, . . . , the Y electrodes
23
-
1
,
23
-
2
, . . . , the X bus electrodes
24
-
1
,
24
-
2
, . . . , and the Y bus electrodes
25
-
1
,
25
-
2
, . . . are insulated from the discharge spaces, in order to be AC-driven. In other words, these electrodes are covered with a dielectric layer
26
composed of a low melting point glass layer which generally has a thickness of several tens of microns. This dielectric layer
26
is covered with a metal oxide layer
27
.
As the metal oxide layer
27
, there is generally used a magnesium oxide (MgO) layer formed by EB vapor deposition and having a thickness of about 1 &mgr;m. This magnesium oxide layer has a high secondary electron emission factor and excellent resistance against sputtering by ions, and functions so as to cause an improvement in discharge characteristics.
The above-mentioned metal oxide layer is generally called “protective layer”. An example thereof is a single layer composed of a magnesium oxide layer which is directly formed on a display electrode by chemical vapor deposition (CVD), as disclosed in JP-A-10-261362.
The back panel plate
28
has, on its face opposite to the front panel plate
21
, address electrodes (hereinafter referred to merely as A electrodes) crossing three-dimensionally and perpendicularly to the X electrodes
22
-
1
,
22
-
2
, . . . , and the Y electrodes
23
-
1
,
23
-
2
, . . . of the front panel plate
21
.
The A electrodes
29
are set up to extend in the direction shown by an arrow D
1
in FIG.
2
. Barrier ribs
31
for separating the A electrodes
29
from each other are set up in order to prevent the expanding of discharge (regulate the region of discharge). The pair of sustaining electrodes composed of the X electrode and the Y electrode may also be separated from each other by means of the barrier rib along the direction shown by the arrow D
2
. The respective phosphor layers
32
emitting red, green and blue light rays are successively applied in the form of stripes so as to cover groove faces between the barrier ribs
31
.
FIG. 3
is a view showing the structure of a main cross section of the PDP, as is viewed along the direction shown by the arrow D
2
in
FIG. 2
, and illustrates a single discharge cell, which is the smallest unit of a cell. In
FIG. 2
, the boundaries of the discharge cell are roughly shown by broken lines. The inside of a discharge space
33
is filled with a discharge gas (e.g., a mixed rare gas such as helium, neon, argon, krypton or xenon) for generating plasma.
When a voltage is applied between the X display electrodes and the Y display electrodes, plasma
10
is generated by electrolytic dissociation of the discharge gas.
FIG. 3
schematically illustrates a situation in which the plasma
10
is generated. Ultraviolet rays from this plasma excite the phosphors
32
to emit fluorescent rays. The fluorescent rays from the phosphors
32
are emitted through the front panel plate
21
outside the discharge cells. The rays emitted from the respective discharge cells constitute images on a display screen.
In the case of attempting to make the PDP highly minute, the gap distance (discharge gap) between the X-Y display electrodes must be made narrow with an improvement in the minuteness of the discharge cells. When the discharge gap is made narrow, the electric field intensity between the electrodes increases. As a result, sputtering is promoted with an increase in ion impact against the protective layer. By the sputtering, the protective layer is stricken off and the dielectric is made naked so that the discharge becomes unstable. Consequently, the panel cannot be driven. In other words, a problem that the lifetime of the panel becomes short arises.
In order to prevent the reduction in the lifetime of the panel, the protective layer should be made thick. According to the prior art, however, as the protective layer is made thicker, a large number of cracks are generated. It is therefore impossible to make the thickness of the protective layer sufficiently thick.
Since the protective layer cannot be easily made thick in the prior art as described above, it is indispensable to form the dielectric layer for insulating the electrodes from discharge. It is difficult to cut off this step of forming the dielectric layer.
Furthermore, with an improvement in the minuteness of the discharge cells (reduction in the cell pitch), the ratio of the luminescent area in the PDP is reduced; therefore, a drop in display brightness thereof is also caused.
SUMMARY OF THE INVENTION
Therefore, in order to overcome the above-mentioned problems in the prior art, a first object of the present invention is to provide a plasma display panel wherein a drop in the brightness thereof with an improvement in the minuteness thereof can be prevented and the luminescent efficiency thereof to applied electric power can be improved by making a high-quality and thick protective layer. A second object of the present invention is to provide a plasma display device having this plasma display panel.
In the case that a metal oxide layer such as a MgO layer is formed as a protective layer on a glass panel plate or a dielectric layer, the linear thermal expansion coefficient of this metal oxide layer is generally larger that of the glass panel plate or the dielectric layer as an undercoat. Therefore, with a drop in temperature after the formation of the layer, tensile stress acts on the formed metal oxide layer so that cracks are generated in the metal oxide layer.
The number of the generated cracks becomes larger as the thickness of the metal oxide layer becomes larger. Incidentally, in order to reduce the number of the generated cracks, it is advisable to decrease the difference in linear thermal expansion coefficient between the above-mentioned glass panel plate or dielectric layer and the above-mentioned metal oxide layer. In this way, the metal oxide layer can be made so as to have a larger thickness and higher-quality.
Therefore, the above-mentioned object of the present invention can be attained in the way that a protective layer coverin
Kajiyama Hiroshi
Suzuki Keizo
Tsuji Kazutaka
Uemura Norihiro
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Tran Thuy Vinh
Wong Don
LandOfFree
Plasma display panel and image display device using the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plasma display panel and image display device using the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plasma display panel and image display device using the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3178335