Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2002-11-01
2004-08-17
Williams, Joseph (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S582000
Reexamination Certificate
active
06777874
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel and more particularly to a plasma display panel having a pair of substrates facing each other with a discharge space held therebetween, the surrounding areas of the substrates being sealed up with sealing material.
2. Description of the Related Art
A typical conventional plasma display panel (PDP) is provided with a plurality of discharge spaces formed by sectioning an airtight space between a pair of substrates, in a striped or matrix form and selectively causing an electric discharge in the plurality of discharge spaces whereby to display an image.
The structure of a conventional plasma display panel will be described by reference to
FIGS. 1
,
2
and
4
.
FIG. 1
is a plan view of the plasma display panel;
FIG. 2
is a partial sectional view taken on line V—V of
FIG. 1
; and
FIG. 4
is a partial sectional view depicting characteristic of the conventional plasma display panel taken on line W—W of FIG.
1
.
As shown in
FIGS. 1
,
2
and
4
, a conventional plasma display panel
20
has transparent electrodes
12
laid on the inner surface of a front substrate
11
and narrow bus electrodes
13
laid on the respective transparent electrodes
12
; further, line electrode pairs (display electrodes)
14
forming display lines, a dielectric layer
15
for covering the line electrode pairs
14
, and an MgO layer
16
are provided thereon in this order.
On the other hand, on the inner surface of a back substrate
17
facing the front substrate
11
via the discharge spaces lie column electrodes
18
as discharge cells formed in a direction perpendicular to the line electrode pairs
14
and in the intersecting portions with the respective line electrode pairs
14
, a column electrode protective layer (white dielectric layer)
19
for covering the column electrodes
18
, partition walls
21
for use in sectioning the space between the two substrates into the discharge spaces on a discharge cell-basis, and phosphor layers
22
of R, G and B colors for covering the side wall of the column electrode protective layer
19
between the partition walls and the side walls of each partition wall
21
.
A discharge gas containing neon and xenon gases is encapsulated in the discharge spaces. Each partition wall
21
is provided between the column electrodes to form striped partition walls
21
such that the space between the two substrates is sectioned into the discharge spaces in the direction of the line electrodes or to form matrix discharge cells (partition walls in the form of a well curb) in the directions of the line and column electrodes.
The dielectric layer
15
covering the line electrode pairs
14
has a bulk raising portion
15
a
above and between the bus electrodes
13
a
, the bulk raising portion having a film thickness greater than the rest of it and protruding toward the discharge space. The bulk raising portion
15
a
is used for preventing the discharge induced between the line electrodes from scattering in the column direction and spreading out into the adjoining cells in the line direction, thus preventing error discharging.
The dielectric layer
15
is formed by screen printing using low-melting glass paste or transferring a low-melting glass layer in the form of a film for patterning, which is then subjected to calcination. Although the bulk raising portion
15
a
, of the dielectric, layer
15
is provided by patterning above the bus electrodes
13
and among the bus electrodes
13
a
in the display area of the panel, the bulk raising portion thereof is also formed uniformly by solid coating in a non-display area
32
outside the display area
31
excluding the peripheral portion where a sealing layer
23
is formed.
A method of producing the conventional plasma display panel
20
will be described below.
First, the component elements of the plasma display panel
20
including line electrode pairs
14
, a dielectric layer
15
, the bulk raising portion
15
a
of the dielectric layer
15
and an MgO layer
16
are successively formed on one side of the front substrate
11
, whereas column electrodes
18
, a column electrode protective layer
19
, partition walls
21
, phosphor layers
22
and the like are successively formed on one side of the back substrate
17
.
Then there follows a sealing process including the steps of applying a sealing material of low-melting fritted glass
27
containing glass beads (granular substance)
28
by screen printing to the peripheral portion of the back substrate
17
and also applying a lead-in passage forming material of low-melting fritted glass
27
containing glass beads (granular substance)
28
so that a lead-in passage
41
for exhausting and introducing the discharge gas from and into an exhaust/lead-in port
25
provided in the end portion of the back, substrate
17
.
After the formation of the sealing layer
23
and a lead-in rib
24
through tentative calcination, the front-substrate
11
and the back substrate
17
are stacked up and then final calcination is carried out while the end portions of both the substrates are fixed with clips. The sealing layer
23
is softened during the final calcination and fused, so that the space between both the substrates (the front substrate
11
and the back substrate
17
) is sealed up.
Both the substrates are sealed up and then a chip pipe
26
is fixed to the exhaust/lead-in port
25
of the back substrate
17
with low-melting fritted glass
27
whereby to exhaust the air in the inner space between both the substrates via the chip pipe
26
. Then the discharge gas containing neon and xenon gases is encapsulated in the inner space with a predetermined pressure, which is followed by fusion-sealing the chip pipe
26
.
As the discharge gas is introduced from the exhaust/lead-in port
25
into the discharge spaces of the display area
31
via the lead-in passage
41
defined by the lead-in rib
24
, any impurity gas is absorbed by the side wall of the lead-in rib
24
in the lead-in passage
41
and the MgO layer
16
of the front substrate
11
and prevented from flowing into the display area
31
.
During the sealing process in the method of producing the plasma display panel, the bulk raising portion
15
a
of the dielectric layer
15
is formed on a portion opposite to the portion to which the lead-in passage forming material is applied rather than the portion to which the sealing material is applied.
Consequently, because the height of a lead-in rib
24
to be formed is made greater by the thickness (10 &mgr;m-12 &mgr;m) of the bulk raising portion
15
a
than that of the sealing layer
23
, the space
42
between both the substrates (i.e., between the MgO layer
16
and the column electrode protective layer
19
) is not uniformized in the display area
31
as shown in FIG.
2
. Therefore, a gap
33
is produced between the partition wall
21
and the MgO layer
16
.
Moreover, there has been a problem arising from being unable to obtain desired display characteristics as interference with the discharging of adjoining discharge cells via the gap
33
may develop error discharging.
The gap
33
may also be produced in case where the bulk raising portion
15
a
exists in a portion corresponding to the lead-in rib
24
even when the glass beads (granular substance)
28
are not contained in the fritted glass.
SUMMARY OF THE INVENTION
An object of the invention made to solve the foregoing problems is to provide a plasma display panel from which desired display characteristics and quality are obtained by uniformizing the space between both substrates in order to close the gap between a partition wall and an MgO layer.
To achieve the above object, a plasma display panel according to a first aspect of the invention comprises a front substrate and a back substrate facing each other with a discharge space held therebetween, the surrounding areas of the substrates being sealed up with a sealing layer, and partition walls for sectioning the discharge space in a display area into a plur
Nakatani Tomoyuki
Okamoto Sota
Pioneer Corporation
Sughrue & Mion, PLLC
Williams Joseph
LandOfFree
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