Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1999-06-01
2001-11-06
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S040000
Reexamination Certificate
active
06313900
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to the configuration of a substrate on the side of reflecting electrodes which constitutes a reflective-type liquid crystal panel and to a liquid crystal panel using the substrate, and further to an electrode apparatus using the liquid crystal panel.
2. Description of Related Art
Use of transmissive-type liquid crystal panels has been implemented as microminiature a high-definition active matrix liquid crystal panels which are suitable for light valves for projectors or the like, in which thin film transistors (TFTs) are formed on a quartz substrate using polysilicon, and transparent electrodes are formed thereon as pixel electrodes. In the transmissive-type liquid crystal panel using the TFT, since TFT regions provided for the individual pixels, gate electrodes for driving the TFTs, and wiring regions constituting source and drain electrodes are not transmissive regions for transmitting liquid, as the panel resolution increase such as XGA and SXGA, the aperture ratio decreases, which is a fatal detect.
Accordingly, as active matrix liquid crystal panels which can be easily fabricated with a high aperture ratio in comparison with the transmission-type active matrix liquid crystal panels, reflective-type active matrix liquid crystal panels have been proposed, in which pixel electrodes are made as reflecting electrodes and transistors are arranged thereunder.
FIG. 9
is a sectional view of a conventional reflective-type active matrix liquid crystal panel, around a scribe line surrounding the exterior of the pixel and peripheral circuit regions. In
FIG. 9
, numeral
101
represents a p-type semiconductor substrate such as single crystal silicon and numeral
102
represents a p-type well region, having a higher impurity concentration than that of the substrate, formed on the surface of the semiconductor substrate
101
. Numeral
102
represents a field oxide film for isolating elements formed on the surface of the semiconductor substrate
101
, and numeral
114
represents a gate oxide film formed by thermal oxidation of the surface of the silicon substrate. A first interlayer insulating film
104
is formed on the field oxide film
103
and the gate insulating film
114
. On the first interlayer insulating film
104
, a first conductive layer
10
a,
which has been formed simultaneously with a source electrode, is formed. A second interlayer insulating film
108
is formed on the first conductive layer
107
a,
a second conductive layer
120
is formed as a guard ring on the second interlayer insulating film
108
, and the guard ring
120
is connected to the first conductive layer
107
a
through a via opening formed in the second interlayer insulating film
108
. A third interlayer insulating film
110
is formed on the second conductive layer
120
, and a third conductive layer
113
formed on the third interlayer insulating film
110
is connected to the second conductive layer
120
through a via opening formed in the third interlayer insulating film
110
. An oxide film
111
and a silicon nitride film
121
are formed further thereon.
In the conventional reflective-type active matrix liquid crystal panel described above, a device substrate on which reflecting electrodes are formed must be provided with a passivation film as a protection film having moisture resistance in order to ensure reliability of transistors and wiring metals on the element substrate.
Therefore, is most cases, as shown in
FIG. 9
, as a passivation film for a element substrate, a silicon nitride film
121
formed by a reduced pressure CVD method or the like is used. As shown in
FIG. 9
, since the side is exposed when the element substrate is diced, a guard ring
120
which connects all the metal wiring layers is often provided in the periphery of the element. Moisture penetration from the surface of the element substrate can be prevented by the passivation film, and moisture penetration from the dicing side can be prevented by the guard ring.
With respect to the passivation film formed by a CVD method, current techniques cannot prevent the occurrence of uneven thickness of approximately 10%. In the reflective-type liquid crystal panel, if a silicon nitride film forming by a CVD method is used as a passivation film, since the silicon nitride film has a larger refractive index than that of a liquid crystal, because of the inconsistency of the thickness of the silicon nitride film, the reflectivity in the visible light range may vary greatly, which is disadvantageous. Therefore, in the reflective-type liquid crystal panel, the passivation film must be nonexistent or must have a thickness of at most several tons of nanometers.
In a typical liquid crystal panel, a flexible printed circuit (FPC) is used for connecting an element substrate to an external circuit. The FPC contains conductive particles, and the terminal of the element substrate and the terminal of the FPC are connected to each other through the conductive particles. However, if a passivation film is nonexistent on a guard ring of the element substrate or if it is thin, the conductive particles are connected to the guard ring, resulting in short-circuiting between adjacent terminals through the guard ring, which is disadvantageous.
SUMMARY OF THE INVENTION
It is as object of the present invention to provide a high reliable reflective-type liquid crystal panel substrate and a liquid crystal panel having a passivation structure is which reflectivity does not vary greatly.
In order to achieve the object described above, in accordance with the present invention, a liquid crystal panel substrate includes reflecting electrodes formed in a matrix on a substrate and a switching element formed corresponding to each of the reflecting electrodes. A guard ring composed of a conductive layer is disposed in a periphery of the substrate, and the guard ring is directly covered with a moisture resistant insulating film.
Consequently, moisture penetration from the surface and the side of the substrate can be prevented, and thus the reliability of the liquid crystal panel substrate can be improved. Additionally, since a thick insulating film is placed on the guard ring, short-circuiting between terminals will be effectively prevented during mounting after the substrate is fabricated into a liquid crystal panel.
In accordance with the present invention, a liquid crystal panel substrate includes reflecting electrodes formed in a matrix on a substrate and a transistor formed corresponding to each of the reflecting electrodes. A guarding is disposed in a peripheral of the substrate, a first conductive layer of the guard ring is composed of a same material as that of source and drain electrodes of the transistor, a second conductive layer of the guard ring is composed of a same material as that of a shading film formed on the transistor, and the guard ring including the first and second conductive layers is directly covered with a moisture resistant insulating film.
Consequently, moisture penetration from the surface and the side of the substrate is presented, and thus the reliability of the liquid crystal panel substrate is improved. Furthermore, since a thick insulating film exists on the guard ring, short-circuiting between terminals is effectively prevented during mounting after the substrate is fabricated into a liquid crystal panel.
In accordance with the present invention, in the liquid crystal panel substrate, the guard ring may be formed by directly connecting the first conductive layer to the second conductive layer through a via opening. Consequently, the structure can be implemented without increasing the number of steps related to the guard ring, resulting in reductions is cost.
In accordance with the present invention, in a liquid crystal panel substrate, the guarding ring may be formed by connecting the first conductive layer to the second conductive layer through a connecting plug embedded in a via opening. Consequently, the area required for the guard ring can be reduc
Dudek James A.
Oliff & Berridg,e PLC
Schechter Andrew
Seiko Epson Corporation
LandOfFree
LCD with anti-moisture conductive guard ring does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with LCD with anti-moisture conductive guard ring, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and LCD with anti-moisture conductive guard ring will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2592445