Electric lamp and discharge devices – With gas or vapor – Three or more electrode discharge device
Reexamination Certificate
2001-01-25
2003-11-11
Beatty, Robert (Department: 2852)
Electric lamp and discharge devices
With gas or vapor
Three or more electrode discharge device
C313S584000, C313S609000, C445S024000
Reexamination Certificate
active
06646376
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel (PDP) used such as for a display device, and to a PDP production method.
2. Description of the Prior Art
A plasma display panel (PDP) has recently received much attention as a flat panel display used in computers and televisions.
A PDP is classified as one of two major types, namely a DC-type and an AC-type, of which the latter has become mainstream because it is suitable for use in a large display.
To illuminate discharge cells of an AC-type PDP, an AC pulse voltage is applied to electrodes covered by a dielectric layer that sustains a discharge. With an AC-type PDP, a surface-discharge type and an opposed-discharge type are widely known. For the surface-discharge type, pairs of sustained electrodes are placed in parallel on a front panel. For the opposed-discharge type, pairs of sustained electrodes are placed on both the front panel and the back panel, and so the pairs of sustained electrodes face one another.
FIG. 10
shows a standard AC surface-discharge PDP as one example.
For this PDP, a front panel
110
and a back panel
120
face each other, and outer parts (not shown in the figure) of their facing surfaces are bonded with a sealing material made of low-melting glass.
For the front panel
110
, pairs
112
a
-
112
b
of display electrodes are formed on a front substrate
111
on a side facing the back panel
120
. A dielectric layer
113
made of dielectric glass, and a protecting layer
114
made of magnesium oxide (MgO) cover the display electrode pairs
112
a
and
112
b.
For the back panel
120
, address electrodes
122
are formed in parallel at certain intervals on a back substrate
121
on a side facing the front panel
110
. A back dielectric layer
123
covers the address electrodes
122
, and partitions
130
are formed in parallel at certain intervals on the back dielectric layer
123
along the address electrodes
122
. Phosphor layers
140
for respective colors (red, green, and blue) are formed in channels between the partitions
130
.
With the above construction, the display electrode pairs
112
a
and
112
b
are placed perpendicular to the address electrodes
122
. At intersections of the display electrode pairs
112
a
-
112
b
and the address electrodes
122
, discharge cells are formed.
Based on image data to be displayed, an address pulse voltage is first placed between the address electrodes
122
and the display electrode pair
112
a.
After this, a sustain pulse voltage is placed between the display electrode pair
112
a
and
112
b
. This causes a sustained discharge to occur selectively in the discharge cells, so that ultraviolet rays are emitted from the discharge cells where the sustained discharge occurs. The emitted ultraviolet rays excite the RGB phosphor layers
140
, which then emit visible light, so that images are displayed on the PDP.
Adjacent discharge cells are separated by the partitions
130
, which prevent a crosstalk phenomenon, i.e., a state in which discharges at different discharge cells mix, from occurring.
The partitions
130
are usually produced by having a partition material such as a glass material formed into a partition pattern (i.e., stripes) and baking the formed partition material at a temperature higher than a softening point of the glass material contained in the partition material. There are three major partition forming methods as follows. The first one is called a “printing method”, with which a partition pattern is printed using a paste containing the partition material, such as by the screen printing. The second method is called a “sandblasting method”. For this method, the above paste is applied onto the entire surface of the back substrate, and then a photosensitive film layer is formed on this paste. The predetermined partition pattern is then formed using photography. After this, unnecessary paste is removed by sandblasting. The third method is called a “photo-paste method”. In this method, a photosensitive paste containing the partition material is applied onto the entire surface of the back substrate, and then unnecessary portions are removed using photography.
When a partition material is formed into a partition pattern using any of the above three partition forming methods and then baked, an end part
130
a
of a resulting partition
130
swells and becomes higher than other parts, such as a part
130
a
. When compared with the part
130
b
, this end part
130
a
becomes high by ten to twenty percent.
A swelling such as in the end part
130
a
is likely to be generated especially when the partitions
130
are formed on the back dielectric layer
123
on the back substrate
121
.
The swellings in the end parts of the partitions
130
, however, make it difficult to join a back substrate and a front substrate together without leaving any gaps between the partitions
130
and the front substrate during an assembly of a PDP. When this PDP with gaps is driven, an improper discharge or an abnormal discharge is likely to occur in adjacent cells. In addition, due to the above gaps, the front panel vibrates, so that noise is likely to be generated.
SUMMARY OF THE INVENTION
The present invention is therefore made in view of the above problems, and aims to provide a technique for easily producing partitions whose end parts do not swell, thereby providing a PDP capable of displaying a high-quality image.
To solve the above problems, the partitions of a PDP according to the present invention include a plurality of main parts that extend parallel to either first electrodes or second electrodes. Each main part contains an end part and a central part, and the end part is wider than the central part.
When the above partitions are baked, no swellings are produced in their end parts.
Note that for forming a partition patter, standard processes such as the “sandblasting method” and the screen printing method can be used.
The following describes reasons why the partitions of the present invention prevent swellings from being produced in the end parts of the partitions.
Usually, a partition material tries to contract during baking, so that large tension is exerted parallel to the longitudinal direction of main parts. A central part of a main part is pulled toward two opposite directions that are parallel to the longitudinal direction of the main part. On the other hand, an end part of the main part is pulled toward the center, but not pulled toward the direction opposite to the center.
A swelling is therefore considered to be produced when the partition material making up a portion near the surface of the end part moves due to the pulling force exerted to the end part toward the center.
When a main part has an end part that is wider than a central part, the pulling force is distributed over the wide end part so that the movement of the partition material can be suppressed. Moreover, when the end part of the main part extends parallel to the direction of the main part's width in this way, tension is exerted parallel to the width direction as well as toward the center. This tension parallel to the width direction is also considered to suppress swellings.
To make a width of the end part larger than that of the central part, the end part may have a shape whose cross section is similar to either a letter “T” or a letter “L”.
In order to allow each partition to have ends that are wider than a center of the partition, a sub part is provided to each main part for the present invention. This sub part extends from an end part of the main part parallel to a direction of a width of the main part.
When end parts of every two adjacent main parts are connected with one another by such a sub part, large tension is exerted parallel to the direction in which the sub part extends. This construction is effective in suppressing swellings in the end parts.
It is desirable that a sub part has a larger width than a main part, preferably at least 1.5 times as large as a main part, so as to have sufficiently large tension exerted pa
Akata Yasuyuki
Ashida Hideki
Fujiwara Shinya
Suzuki Shigeo
Uemura Sadao
LandOfFree
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