Active matrix liquid crystal display and method of...

Details Active matrix liquid crystal display and method of... Active matrix liquid crystal display and method of...

1996-12-20

2001-06-12

Dudek, James A. (Department: 2871)

Liquid crystal cells, elements and systems

Particular excitation of liquid crystal

Electrical excitation of liquid crystal

C349S151000, C349S153000, C349S187000

Reexamination Certificate

active

06246454

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active matrix liquid crystal display and, more particularly, to a miniaturized active matrix liquid crystal display having high reliability.
2. Description of the Related Art
An active matrix liquid crystal display uses a liquid crystal as a display medium. A pixel is disposed at each intersection in a matrix construction. Every pixel is equipped with a switching device. Information about the pixels is represented by turning on and off the switching devices. Three-terminal devices which are thin-film transistors having gate, source, and drain are most often used as the switching devices. The thin-film transistors are hereinafter often abbreviated as TFTs.
In the matrix construction, scanning lines (gate lines) extending parallel to a row are connected with the gate electrodes of the TFTs in this row. Signal lines (source lines) running parallel to a column are connected with the source (or drain) electrodes of the TFTs in this column. A circuit for driving the scanning lines and a circuit for driving the signal lines are also provided.
FIG. 2
shows one conventional active matrix liquid crystal display. A signal line driver circuit
221
for driving signal lines is mounted above the pixel matrix
220
of this active matrix liquid crystal display. A scanning line driver circuit
222
for driving scanning lines is disposed to the left. Indicated by
223
is a sealant material region.
FIG. 3
is a cross section of FIG.
2
. Pixel TFTs
311
are covered by a liquid crystal material
304
. A liquid crystal material
304
is held between a TFT substrate
301
and a counter substrate
302
. On the other hand, the signal line driver circuit
221
and scanning line driver circuit
222
are protected only by a thin film
309
of oxide or nitride. Therefore, TFTs forming these driver circuits are placed in a harsher environment than the pixel TFTs
311
located inside the liquid crystal material.
In an attempt to solve the foregoing problems and to obtain long-term reliability, a display device structure having improved reliability has been devised. In this structure, both signal line driver circuit and scanning line driver circuit are placed within a liquid crystal material, as well as pixel TFTs.
FIG. 4
shows a known device of this improved structure. In this known structure, a region of a sealant material or sealing material
423
is located outside both a signal line driver circuit
421
and a scanning line driver circuit
422
. Therefore, the driver circuit TFTs are covered by the liquid crystal material, as well as the pixel TFTs. Furthermore, to miniaturize the liquid crystal display, three end surfaces (in
FIG. 4
, the top end surface, bottom end surface, and right end surface) of the counter substrate are made to conform to three end surfaces of the TFT substrate. Indicated by
420
is a pixel matrix.
These two conventional structures suffer from the following problems.
As shown in
FIG. 5
, in the conventional active matrix liquid crystal display, a short ring
506
is formed around the pixel matrix to protect the TFT devices from static charges. Since the signal lines
530
and scanning lines
531
connected with pixel TFTs
511
are all shorted, static charges produced during manufacturing steps, especially during rubbing steps, for the liquid crystal display are prevented from being applied across the terminals of each pixel TFT
511
.
In the first-mentioned conventional structure shown in
FIGS. 2 and 3
, it is common practice to cut the short ring together with the glass substrate with a laser beam or the like in the final manufacturing step for the liquid crystal display.
However, in the second-mentioned conventional structure, in an attempt to minimize the size of the liquid crystal display, the counter substrate and the TFT substrate are preferably cut along common planes (in
FIG. 4
, the top end surface, bottom end surface, and right end surface of each substrate) from which no terminals are brought out. Accordingly, it is difficult to cut the short ring with a laser beam in the final step. In particular, the short ring is cut together with the substrate along a common plane. As shown in
FIG. 6
, after the cutting, the end surface of the TFT substrate
101
is exposed. If static charges are produced on the exposed end surfaces after the cutting, the internal pixel TFTs will be destroyed, thus making the display device defective.
SUMMARY OF THE INVENTION
A method of fabricating an active matrix liquid crystal display according to the present invention comprises the steps described hereinafter to solve the foregoing problem.


REFERENCES:
patent: 4394067 (1983-07-01), Spruijt et al.
patent: 5148301 (1992-09-01), Sawatsubashi et al.
patent: 5504348 (1996-04-01), Yoshida et al.
patent: 5610742 (1997-03-01), Hinata et al.
patent: 57-99615 (1982-06-01), None
patent: 47-99615 (1982-06-01), None
patent: 59-166984 (1984-09-01), None
patent: 4-355720 (1992-09-01), None
patent: 6-123882 (1994-05-01), None
patent: 6-186578 (1994-07-01), None
patent: 6-258659 (1994-09-01), None
patent: 6-258660 (1994-09-01), None

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