Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-07-19
2002-12-31
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S156000, C349S187000
Reexamination Certificate
active
06501526
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat panel display apparatus and a method for manufacturing the same, and more particularly to a field emission display (FED) apparatus including high aspect ratio spacers which have improved structures for maintaining a gap between an upper substrate and a lower substrate and to a method for manufacturing the same.
2. Description of the Prior Art
As the recent trend in the field of display apparatus is to make a large-sized display apparatus with a high definition, the main emphasis of the research and development has been turned from a cathode ray tube (CRT) to new flat panel display devices such as a liquid crystal display (LCD), an electroluminescent display (ELD), a plasma display panel (PDP) or a vacuum fluorescent display (VFD). The new flat panel display devices have many advantages and disadvantages in comparison with the CRT.
However, the FED, one of the new flat panel display devices, has been anticipated to resolve most of all the disadvantages of the above devices. The FED has such advantages as a simple structure of electrodes therein, a reduced power consumption, a high operation speed, a capability of a multiplexed addressing, a high definition, a wide viewing angle and a perfect color expression. Also, the FED can have a big size display panel since it adopts inner supporters.
The FED generally comprises a lower substrate on which cathode electrodes with emitter tips and gate electrodes are formed, an upper substrate on which anode electrodes and fluorescent materials are formed, and spacers formed between both substrates. The spacers maintain the space between the upper substrate and the lower substrate and the space has the highly vacuumed condition. As an intense electric field is developed among the cathode, the gate and the anode electrodes when the space is maintained in the high vacuum condition, electrons are emitted from the emitter tips by an electric field emission and a tunneling effect.
In the conventional FED, the spacer is generally formed according as a sealant is accumulated to a predetermined height and then sintered by a screen printing technique. Also, the spacer is formed by arranging pre-manufactured glass balls by a predetermined interval, by growing optical fiber between both substrates or by standing bar-shaped glass or ceramic material between the two substrates. Furthermore, the spacer is formed by a plating method using a photoresist pattern or the spacer is mounted by inserting into a groove formed on the upper substrate or on the lower substrate.
The screen printing technique is limited because the width of the spacer becomes substantially wide when the spacer has a height of above 200 &mgr;m. When the spacer is made of the glass ball, the spacer has a low aspect ratio of about 1 due to the low aspect ratio of the glass ball with reference to U.S. Pat. No. 5,562,517.
In the method using the optical fiber, it is difficult to cut and fix the fiber for forming the spacer. The manufacturing process is very complicated in the plating method.
In the method that the spacer having a bar shape or a “T” shape is inserted into the groove as disclosed in U.S. Pat. Nos., 5,578,325 and 5,708,325, it is difficult to form the groove on the upper substrate or the lower substrate where the spacer is inserted. Further, it is more difficult to expose the electrodes and to coat the fluorescent material on the electrodes. When the spacer is made of the bar-shaped glass, the spacer may be bent during the sintering process or the emitter tip may be damaged by the falling of the spacer.
In general, the spacer of the FED preferably has not only a sufficient strength for maintaining the space between both substrates against an external pressure (that is, the atmospheric pressure) but also a minimized area for maximizing the active region of the FED. If the width of the spacer increases to maintain the space against the external pressure, the active region decreases due to the increased area of the spacer. However, the strength of the spacer is lowered if the width of the spacer decreases. In particular, the spacer should have a height of about 1,000 &mgr;m when the fluorescent materials for a high voltage are coated on the electrodes so that the aspect ratio of the spacer (that is, the ratio of height over width) must be more than 10.
SUMMARY OF THE INVENTION
Considering the above-mentioned problems, it is a first object of the present invention to provide a flat panel display apparatus comprising high aspect ratio spacers having supporting walls and supporting legs which are integrally formed by exposing and etching processes and by using a photosensitive material.
It is a second object of the present invention to provide a method for manufacturing a flat panel display apparatus comprising high aspect ratio spacers having supporting walls and supporting legs integrally formed by exposing and etching processes and by using a photosensitive material.
It is a third object of the present invention to provide a flat panel display apparatus comprising a latticed spacer having supporting posts and connecting walls whose heights are lower than those of the supporting posts thereby accomplishing smooth evacuation of a space between an emitter panel and a display panel.
It is a forth object of the present invention to provide a method for manufacturing a flat panel display apparatus comprising a latticed spacer having supporting posts and connecting walls whose heights are lower than those of the supporting posts thereby accomplishing smooth evacuation of a space between an emitter panel and a display panel.
To accomplish the first object of the present invention, a flat panel display apparatus comprises an emitter panel, a display panel, a plurality of spacers and a sealing member. The emitter panel has a lower substrate, cathode electrodes formed on the lower substrate and gate electrodes formed on the cathode electrodes. The display panel has an upper substrate, transparent anode electrodes formed on the upper substrate and fluorescent materials coated on the anode electrodes. The spacers maintains the emitter panel and the display panel by a predetermined gap. The spacers comprises supporting walls having high aspect ratio and supporting legs respectively protruded from the supporting walls.
Preferably, the supporting legs protruded from the supporting walls in a first perpendicular direction and in a second perpendicular direction in order to support the supporting walls. The sealing member keeps vacuum sealing peripheral regions of the emitter panel and the display panel.
The spacers are formed by exposing and etching a photosensitive material. The cross sections of the supporting walls have rectangular shapes, hexagonal shapes or trapezoid shapes and the cross sections of the supporting legs have triangular shapes by a tilt exposure method or rectangular shapes by a vertical exposure method. If the cross sections of the supporting walls have the trapezoid shapes, the upper ends of the supporting walls are attached to the display panel. The heights of the supporting legs are lower than heights of the supporting walls.
According to one embodiment of the present invention, the lengths of the supporting walls are longer than a display region of the display panel and the supporting legs are formed at both lateral portions of the supporting walls which lie at the peripheral region of the display panel so that the spacers have bar shapes which are longer than the display region of the display panel.
According to another embodiment of the present invention, the lengths of the supporting walls are shorter than the display region of the display panel and the supporting legs are formed at lateral portions of the supporting walls which lie at the peripheral region of the display panel so that the spacers have half bar shapes which are shorter than the display region of the display panel.
According to other embodiment of the present invention, the lengths of the supporting walls are
Institute for Advanced Engineering
Jacobson & Holman PLLC
Qi Mike
Ton Toan
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