Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2000-06-26
2003-04-01
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
Reexamination Certificate
active
06540576
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a plasma display panel used for display devices and the like and a method for producing the same, and more specifically to a plasma display panel having a partition wall formed by a thermal spraying technique and a method for producing the same, especially a process for forming a partition wall by the thermal spraying technique.
BACKGROUND ART
A plasma display panel, which has recently been a target of attention as being suitable for a thin display device, has, for example, a structure shown in FIG.
1
. The plasma display device shown in
FIG. 1
includes a front substrate
300
and a rear substrate
301
which are located to face each other. Display electrodes
302
and
303
, a dielectric layer
304
, and a MgO dielectric protective layer
305
are sequentially formed on the front substrate
300
. An address electrode
306
and a dielectric layer
307
are formed on the rear substrate
301
, and partition walls
308
are formed thereon. A fluorescent layer
309
is applied to a side surface of each partition wall
308
.
Discharge gas
310
(for example, a Ne-Xe mixture gas) is sealed between the front substrate
300
and the rear substrate
301
at a pressure of 500 to 600 Torr. The discharge gas
310
is discharged between the display electrodes
302
and
303
to generate ultraviolet rays, and the fluorescent layer
309
is irradiated with the ultraviolet rays to realize image display including color image display.
The partition walls
308
are provided for forming a microscopic discharge space for each of pixel element colors (G, B, R), thus to form discharge cells. The partition walls
308
allow discharge to be controlled on a cell-by-cell basis. Thus, erroneous discharge and erroneous display can be prevented. The sizes of the partition walls
308
are typically as follows in a 40-inch NTSC panel: the partition wall pitch per color is 360 &mgr;m; the width of a top end of the partition wall is 50 &mgr;m to 100 &mgr;m; and the height of the partition wall is 100 &mgr;m to 150 &mgr;m.
Conventional methods for forming a partition wall include (1) a printing technique, (2) a sand-blasting technique, (3) a photo-pasting technique, and (4) a photo-burying technique (or a lift-off technique). By the printing technique, the partition wall is formed using a screen printing technology. By the sand-blasting technique, a partition wall material is applied on the entire surface of the rear substrate, then a photosensitive film layer is formed on the partition wall material to form a prescribed pattern by a photography technique. An unnecessary portion of the partition wall material is removed by sand-blasting to remove the photosensitive film layer, thereby forming the partition wall. By the photo-pasting technique, a photosensitive paste is applied, and then an unnecessary portion is removed by a photography technique to form the partition wall. By the photo-burying technique (or a lift-off technique), a photosensitive film layer is formed on a substrate, and then a prescribed pattern is formed by a photography technique. A paste is buried in a groove of the pattern, the photosensitive film layer is removed, and then the paste is solidified by baking.
However, these conventional methods have the following problems.
By the printing technique, a partition wall having a height of only about 10 &mgr;m can be formed by one cycle of printing. Thus, the printing cycle and the drying cycle need to be repeated in order to form a partition wall having a height of about 100 &mgr;m. Such a repetition increases the number of steps and raises the cost. Moreover, as the screen becomes larger, the non-linear expansion and contraction of the screen plate becomes conspicuous, which results in a larger dispersion in the position, thickness and shape of the partition walls.
The sand-blasting technique has the problems that a large amount of material needs to be removed, and that the amount of the material to be removed is difficult to be controlled and thus the substrate and the electrodes are likely to be damaged. The photo-pasting technique has the problem of the expensive pasting material. The photo-burying technique realizes a high precision plasma display panel but cannot realize low-cost production due to the baking step required for forming the partition wall.
DISCLOSURE OF THE INVENTION
The invention described herein made for overcoming the above-described problems of the conventional art makes possible the advantages of (1) providing a method for producing a plasma display panel realizing high quality display by forming a partition wall by a thermal spraying technique at a high precision at low cost; and (2) providing a plasma display panel which has a partition wall produced at a high precision at low cost and thus can realize high quality display.
According to a plasma display panel of the present invention, a partition wall for defining a discharge space is formed of a thermal-sprayed film formed by thermal spraying of a partition wall material. Thus, the above-described objectives are achieved.
In one embodiment, the plasma display panel includes a pair of substrates; and an electrode, a dieleetric layer and a fluorescent layer located between the pair of substrates. The partition wall is located between the pair of substrates. A gas medium is a sealed in the discharge space, and ultraviolet rays generated by discharge of the gas medium are converted into visible light when the fluorescent layer is irradiated, and thus the plasma display panel is lit.
The partition wall may be formed of a partition wall material of a first color from a bottom thereof to a prescribed height and is formed of a partition wall material of a second color from the prescribed height to a top end of the partition wall. For example, the first color is white and the second color is black. The partition wall material of the first color may be aluminum oxide or spinel and the partition wall material of the second color may be chromium oxide, titanium oxide, or a mixture or a melt of aluminum oxide and titanium oxide.
The thermal spraying may be plasma thermal spraying.
A method for producing a plasma display panel according to the present invention includes a partition wall formation process of forming a partition wall defining a discharge space of a thermal-sprayed film formed by thermal spraying of a partition wall material. Thus, the above-described objectives are achieved.
In one embodiment, the partition wall formation process includes the steps of forming a photosensitive coating layer on a substrate; forming an opening having a prescribed pattern in the photosensitive coating layer; depositing the partition wall material to a prescribed height at least inside the opening by the thermal spraying technique, thereby forming the thermal-sprayed film; removing a portion of the thermal-sprayed film bulging out from a surface of the photosensitive coating layer by polishing; and removing the photosensitive coating layer to obtain the partition wall having a prescribed shape.
The thermal spraying may be plasma thermal spraying.
In one embodiment the opening having a prescribed pattern formed on the photosensitive coating layer has a trapezoidal cross-section in which a bottom end is wider than a top end, and the base angle of the cross-section is 60 degrees or more and less than 90 degrees.
A width of the top end of the opening having the prescribed pattern formed on the photosensitive coating layer may be 100 &mgr;m or less.
In one embodiment, the partition wall has a multiple-layer structure including at least a first layer formed by depositing a first partition wall material at a plasma energy quantity A and a second layer formed by depositing a second partition wall material on the first layer to a prescribed height at a plasma energy quantity smaller than the plasma energy quantity A, where A is the plasma energy quantity at the time of thermal spraying in an area where at least thermal spray particles tightly adhere to the substrate.
The thermal spraying may be
Aoki Masaki
Suzuki Shigeo
Takada Yuusuke
Watanabe Taku
Matsushita Electric - Industrial Co., Ltd.
Ramsey Kenneth J.
Renner Otto Boisselle & Sklar
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