Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2002-07-30
2004-10-12
Wong, Don (Department: 2821)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C315S169300
Reexamination Certificate
active
06803723
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a plasma display device such as a plasma display panel used for display, and a manufacturing method for the plasma display device. The invention in particular relates to improvements to a sealing process.
BACKGROUND ART
Plasma display panels (PDPs) are a type of plasma display devices. PDPs enable large-screen slimline displays to be produced relatively easily, and so are receiving attention as the coming generation of display panels. Sixty-inch models have already been commercialized.
FIG. 5
is a partially sectional and perspective view showing a main construction of a typical surface discharge AC (alternating current) PDP. In the drawing, the direction z represents the direction along the thickness of the PDP, and the plane xy represents a plane which is parallel with the panel plane of the PDP. As illustrated, the PDP
2
is roughly made up of a front panel
20
and a back panel
26
which are arranged with their major surfaces facing each other.
A front panel glass
21
is a substrate of the front panel
20
. A pair of display electrodes
22
and
23
(an X electrode
22
and a Y electrode
23
) are formed on one of the major surfaces of the front panel glass
21
so that each electrode runs along the direction x. Surface discharge is performed between these electrodes. The display electrodes
22
and
23
are formed by placing bus lines
221
and
231
made of a mixture of Ag and glass, on top of transparent electrodes
220
and
230
formed from ITO (Indium Tin Oxide) and the like.
A dielectric layer
24
made of a dielectric material is formed at the center of the major surface of the front panel glass
21
on which the display electrodes
22
and
23
have been arranged. A protective layer
25
having the same size as the dielectric layer
24
is formed on the dielectric layer
24
.
A back panel glass
27
is a substrate of the back panel
26
. A plurality of address electrodes
28
are formed in stripes on one of the major surfaces of the back panel glass
27
with a predetermined spacing, so that each electrode runs along the direction y. The address electrodes
28
are formed from a mixture of Ag and glass, like the bus lines
221
and
231
. A dielectric layer
29
made of a dielectric material is formed at the center of the major surface of the back panel glass
27
so as to cover the address electrodes
28
. Barrier ribs
30
are arranged on the dielectric layer
29
at the gaps between the adjacent address electrodes
28
. Phosphor layers
31
-
33
corresponding to the colors of red (R), green (G), and blue (B) are applied to the side faces of the adjacent barrier ribs
30
and the surface of the dielectric layer
29
between the adjacent barrier ribs
30
.
Such constructed front panel
20
and back panel
26
are positioned so that the address electrodes
28
cross over the display electrodes
22
and
23
at right angles. The front panel
20
and the back panel
26
are then sealed at their edges to make the inside airtight. In more detail, frit glass as a sealing member
40
is applied to the edges of the front panel glass
21
(more precisely, around the dielectric layer
24
) and the edges of the back panel glass
27
(more precisely, around the dielectric layer
29
), as shown in a top view of FIG.
6
. This sealing member
40
is melted to seal the panels
20
and
26
. Here, the edges
211
and
212
of the front panel glass
21
and the edges
271
and
272
of the back panel glass
27
are outlets for respectively connecting the display electrodes
22
and
23
and the address electrodes
28
to outside drive circuits (not illustrated).
Note that in
FIG. 6
the number of display electrodes
22
and
23
and the number of address electrodes
28
are fewer than in actual PDPs for purposes of illustration. The electrodes are indicated by solid lines. Also, the positions of the sealing member
40
and dielectric layer
24
are indicated by solid lines.
A discharge gas (an enclosed gas) including Xe is introduced between the front panel
20
and the back panel
26
which are sealed together, at a predetermined pressure (typically about 40 kPa-66.5 kPa).
As a result, the spaces which are separated by the dielectric layer
24
, the phosphor layers
31
-
33
, and the adjacent barrier ribs
30
between the front panel
20
and the back panel
26
become discharge spaces
38
. Also, the areas at which the pairs of adjacent display electrodes
22
and
23
cross over the address electrodes
28
with the discharge spaces
38
in between become cells for image display (not illustrated).
To drive the PDP, discharge is started between the address electrode
28
and the display electrode
22
or
23
in each cell. Then ultraviolet light of short wavelength (Xe resonance lines with a wavelength of about 147 nm) is generated from glow discharge between the pair of display electrodes
22
and
23
, and excites the phosphor layers
31
-
33
to emit light. This produces an image display.
The above constructed PDP, however, has the following problem.
FIG. 7
is a sectional view of an edge part of the PDP and its vicinity (taken along an address electrode
28
). The sealing member
40
made of frit glass is melted and fixed between the back panel glass
27
and the dielectric layer
24
, and also melted and fixed between the address electrode
28
and the dielectric layer
24
as shown in the drawing. When melting the sealing member
40
between the address electrode
28
and the dielectric layer
24
, the address electrode
28
is heated together with the sealing member
40
, which causes Ag particles in the address electrode
28
to diffuse and seep into the sealing member
40
.
This diffusion of Ag particles causes the address electrode
28
to partially break and its conductivity to drop. This may even result in shortening of a plurality of address electrodes
28
. Moreover, the seepage of Ag particles in the sealing member
40
degrades the sealing member
40
and reduces its sealing performance.
The same problem may occur between the sealing member
40
and the display electrode
22
(
23
).
FIG. 8
is a sectional view showing an edge part of the PDP and its vicinity (taken along a bus line
221
(
231
)). The drawing shows the state where Ag particles in the bus line
221
has seeped into the sealing member
40
. This causes the bus line
221
(
231
) of the display electrode
22
(
23
) to short out or break, resulting in a decrease in performance of the PDP.
This problem is especially evident with PDPs that have a fine cell structure such as those for use in high-definition television, i.e., PDPs that have very narrow bus lines and address electrodes. An immediate solution is required.
DISCLOSURE OF INVENTION
The present invention was conceived in view of the problem described above, and has a primary object of providing a plasma display device which can exhibit favorable display performance even when the plasma display device has a fine cell structure like those for use in high-definition television, and a manufacturing method for the plasma display device.
The stated object can be achieved by a plasma display device having a first plate and a second plate which face each other with a discharge space in between, and a sealing member which is provided between the first and second plates so as to seal the discharge space at outer edges of the first and second plates, the plasma display device including: a plurality of electrodes which are formed across an inner major surface of one of the first and second plates, and an electrode diffusion preventive layer which is interposed between the sealing member and each of the plurality of electrodes.
With the provision of the electrode diffusion preventive layer, the electrode material is kept from diffusing and seeping into the sealing member, with it being possible to prevent shorting or breaking of the plurality of electrodes. Hence favorable display performance is maintained while the plasma display device is driven.
The present invention is especially effective if eac
Aoki Masaki
Hibino Junichi
Ookawa Masafumi
Sasaki Yoshiki
Yamashita Katuyoshi
A Minh Dieu
Matsushita Electric - Industrial Co., Ltd.
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