Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2000-02-18
2002-11-19
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C313S582000
Reexamination Certificate
active
06482062
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma display panel (hereinafter referred to as a “PDP”) and a method of forming barrier ribs (partition walls) for the same. More particularly, the invention relates to a method of forming barrier ribs for the PDP that is suitable for a high-definition color display apparatus having a reduced thickness and larger display area. The present invention also relates to a method of forming discharge cells for a plasma display panel. Further, the present invention relates to a phosphor material sheet which is used in the method of forming the discharge cells in the plasma display panel and relates to manufacturing method thereof.
2. Description of the Related Art
A PDP is a display device which serves as flat panel display in large and high-definition color display. The general construction of the PDP includes front and rear glass substrates facing each other with minute spacing and peripherally sealed. Pairs of electrodes are regularly arranged on these two glass substrates, respectively, and a discharge gas mixture containing Ne as a main component is hermetically sealed in the space defined by the two substrates. On the rear glass substrate, a large number of small discharge spaces called discharge cells are formed by line barrier ribs (partition walls). A phosphor is applied to the internal side of each discharge cell. On the opposite front substrate, electrodes facing the discharge cell are provided. By applying a suitable voltage between electrodes, the plasma discharge is induced locally in the discharge gas. ultraviolet ray generated by the plasma discharge induces luminescence of the neighboring phosphors. That is, the discharge cells are used as light emitting elements of the display.
As a method of manufacturing the barrier ribs (partition walls) forming the discharge cells of the PDP, a print laminating method and a sandblasting method are generally known. According to the print laminating method, a the barrier ribs are formed by repeating a step of printing a glass paste onto the rear glass substrate by a screen printing method and drying it until the paste has a height which is required for the barrier rib.
According to the sandblasting method, a thick film made of a barrier rib material (glass paste) is formed on the rear substrate, a subtractive resist. pattern is formed on the thick film by lithography, and the barrier rib material exposed in opening portions of the resist is removed by sandblasting (spraying fine particles mixed into a compressed air at a high speed to physically etch). The resist pattern is removed after the formation of the barrier ribs.
The barrier rib pattern formed by such various methods is fired at a high temperature to form glass barrier ribs. A phosphor material layer (thickness is 20 to 30 &mgr;m) is formed in each discharge cell in the next phosphor forming step. The formation of the phosphor material layer employs the screen printing method so far. According to the conventional screen printing method, a phosphor material paste obtained by mixing and kneading a phosphor, an organic binder, a solvent, and the like is supplied to the internal wall of each discharge cell partitioned by the fired barrier ribs.
It is a matter of course that the phosphor material paste of a color corresponding to the color of the pixel of the PDP is supplied to the corresponding discharge cell. Each of R (red), G (green), and B (blue) phosphor material pastes is applied to the inside of-the corresponding discharge cells by the different screen printing step. Namely, there is required to conduct three times printing steps in total in order to supply three different color phosphor material pastes to the corresponding discharge cells.
A technique of photolithography employing photosensitive phosphor material pastes is also examined in place of the screen printing method. According to the method, R/G, and B phosphor material pastes are sequentially applied and procedures such as exposure, development, cleaning, and the like are repeated every phosphor material paste.
The conventional methods of forming the barrier ribs have the following problems. First in the print laminating method, since the thickness of the rib material layer which can be formed in one printing operation is tens of &mgr;m at maximum, in order to obtain a height of 100 to 200 &mgr;m required for the barrier ribs, it is necessary to repeat printing and drying a large number of times, generally, about ten times. Consequently, there is a problem that the productivity is remarkably low. In an addition, the rib material layer formed by the screen printing has a declined peripheral portion and the raised center portion. When the layers are stacked by printing many times over, the peripheral portions in a sagging form in section are accumulated, so that the bottom of the barrier rib is widened. Consequently, the realization of a high density formation of the barrier ribs is restricted. Further, pitch precision is also limited because of distortion or life of a screen (printing plate), so that it is difficult to realize the large size, high definition, and mass production of the PDP.
As for the sandblasting method, the procedures of formation, elimination, and the like of the resist pattern are complicated. Particularly, when the large-sized display is realized, the scale of an exposing apparatus or a sandblasting apparatus is enormously enlarged, resulting in a sharp increase in cost of equipment. Further, the loss of a material due to sandblast etching is large. Consequently, there is a problem that the manufacturing cost is increased.
Both of the print laminating method and the sandblasting method have the common problem that the shape of the uncured barrier rib is easily deformed due to shrinkage upon firing in a post process. Generally, the shrinkage upon firing can be reduced at a certain degree by raising the content of glass powders contained in the barrier rib material. In this case, however, the flowability of the barrier rib material is contrarily deteriorated. Consequently, it becomes hard to form the fine structures of the barrier ribs, so that there is a problem that formability of the uncured freestanding structures which will be fired to Dorm the barrier ribs, namely, fidelity of the finished barrier ribs is deteriorated.
In order to solve the above-mentioned problems existing in the conventional print laminating method and sandblasting method, it is considered to use a pressure molding method of pressurizing a plane mold onto a thick film made of a barrier rib material formed on a substrate. Also it is considered that a method of photolithography widely used for formation of a-thin film pattern is used for forming the barrier ribs.
The pressure molding method employing the plane mold is excellent because it solves the problems of the printing method and the sandblasting method. Fundamentally, however, the method has a problem that the glass paste is easily partially peeled off from the substrate when the plane mold is separated from the substrate. Therefore, various means for raising adhesive properties of the glass paste to the glass substrate are needed. Selection of the material is restricted and addition of a new process is required. It is difficult to manufacture a large-sized precision mold corresponding to the large size of the substrate, so that a stupendous increase in cost of the apparatus is also conceived as a problem.
The photolithography method employs a photosensitive glass paste and has characteristics such that a precise pattern of barrier ribs can be realized at a high resolution. According to the method, however, processes such as coating/drying of a photo resist, exposure by ultraviolet rays, development, cleaning, and drying are complicated and it takes much time. Surplus materials such as photo resist and developer are required. Expensive apparatuses having a large floor area such as exposing apparatus, developing apparatus, and cleaning apparatus are also needed. Further, t
Kanezawa Akihiro
Kubo Tooru
Utsumi Takashi
Yamazaki Nobuya
Yao Yasunori
Fuji Photo Film Co. , Ltd.
Ramsey Kenneth J.
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