Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
1999-09-02
2004-11-23
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S043000, C349S192000
Reexamination Certificate
active
06822701
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to liquid crystal display apparatus for use as display units in computers, audio-visual equipment and the like.
2. Description of the Related Art
Generally a liquid crystal display apparatus with switching elements is provided with an auxiliary capacitance electrode which comprises an auxiliary capacitor, as well as pixel electrodes for use in driving pixels of a liquid crystal layer. In the case where such pixel-driving pixel electrode is disposed via an interlayer insulating film on the pixels, an underlying auxiliary capacitance electrode is provided due to the fact that thickness of the interlayer insulating film is large.
FIG. 28A
is a view showing a plan view of one example of the liquid crystal display apparatus mentioned above, whereas
FIG. 28B
is a partial sectional view showing a thin-film transistor (TFT) for use as a switching element in the liquid crystal display apparatus as shown in FIG.
28
A. The liquid crystal display apparatus of such a constitution has been disclosed for example, in Japanese Unexamined Patent Publication JP-A 9-152625.
In
FIGS. 28A and 28B
a TFT
124
is provided on a substrate
131
, and an underlying electrode
125
is formed so as to connect to a drain electrode
136
b
of this TFT
124
. This underlying electrode
125
may sometimes be called a “drain electrode” in the case where it is made integral with the drain electrode
136
b.
An interlayer insulating film
138
is so formed as to overlay this structure, and pixel electrodes
121
formed thereon are electrically connected to the underlying electrode
125
via a contact hole
126
that is provided in the interlayer insulating film
138
.
In addition, the underlying electrode
125
is designed so as to extend up to the center of the pixel electrode
121
while an auxiliary capacitor electrode
125
a
is so formed as to oppose an auxiliary capacitance line
127
which is formed under a gate insulation film
133
which covers a gate electrode
132
which constitutes part of the TFT
124
. An auxiliary capacitor section is formed at a portion at which this auxiliary capacitance line
127
opposes the auxiliary capacitor electrode
125
a.
Since the underlying electrode
125
is aimed to fabricate the intended auxiliary capacitor section, this electrode is formed to be partly narrowed in width in regions other than a region for the auxiliary capacitor section.
In the active matrix substrate having the switching element formed thereon, defects may be generated during manufacturing processes. The defects may result in creation of unwanted display defects or image visualization failures including, but not limited to, line defects, inadvertent bright dots, and flicker. For this reason, there have been proposed and developed a variety of defect repairing techniques in order to increase production yields, and one or a combination of a plurality of defect repairing techniques has been implemented.
As a typical repairing technique, for example, Japanese Examined Patent Publication JP-B2 3-55985 (1991) discloses a line defect repairing technique in the case of short circuit between a data signal transmission line
401
and a transmission line
402
in a MOS transistor
408
, as shown in
FIGS. 29A-29B
.
More specifically, as shown in
FIGS. 29A
,
29
B, suppose a gate electrode
420
has been cut and thus separated from the scan signal transmission line
402
, by use of a laser beam. Thereafter, as the repairing technique laser irradiation is aimed at specified positions shown by arrows Y, Z, from either the top surface or bottom surface of a substrate. The irradiation permits a source electrode
421
and drain electrode
422
to be electrically shorted together via the gate electrode
420
that has experienced the laser-cutting process. This electrical shorting results in application of an average voltage potential of data signals to the pixel electrode
406
, which in turn reduces or minimizes recognizability of defects.
The conventional defect repairing technique above is inherently for use with liquid crystal display apparatus of the transmission type. The applicants named herein have proposed in Japanese Patent Application 9-355824 a defect repairing technique adapted for use in liquid crystal display apparatus of the reflection type as typically shown in FIG.
30
.
However, this reflection type defect repairing technique, which is designed for repair of defects occurring in the manufacturing processes, irradiates a substrate
430
shown in
FIG. 30
with laser light or beam at a portion to be corrected, from the bottom surface of the substrate, thereby cutting and blowing the to-be-corrected portion away from the substrate. This approach is inherently faced with a problem that cracks or “infractions” can occur in the interlayer insulating film
434
during the laser irradiation. Such cracks would result, when the pixel electrode
435
overlies the to-be-corrected portion, in undesired projection of such overlying pixel electrode
435
toward a liquid crystal layer
454
together with the cracked interlayer insulating film
434
. This projected pixel electrode
435
badly behaves to deform and come into contact with an opposed or “counter” electrode
451
and/or the cross-section of the to-be-corrected portion thus letting different signal transmission lines be electrically shorted together, which leads to creation of secondary defects.
Another problem encountered with the approach is that fragments of the interlayer insulating film
434
with the conductive pixel electrode
435
attached thereto reside and float inside of the liquid crystal layer
454
, which would result in inadvertent conduction with the counter electrode
451
and other associative electrodes—in particular, the pixel electrode
435
—thereby causing creation of defects therein.
Especially, as shown in
FIG. 31
, in the case of reflective liquid crystal display apparatus which make use of a pixel electrode
435
made typically of aluminum (Al) or other conductive materials equivalent thereto, fuzz- or fluff-like irregular portions
500
can readily take place at edge faces of a cut-off portion of the pixel electrode
435
resulting in such fluffs
500
coming into contact with the counter electrode
451
and/or pixel electrode
435
, thus leading to creation of re-leakage phenomena.
A further problem lies in association with many disadvantages when compared to transmission-type liquid crystal display apparatus which make the requisite, accurate and reliable defect repairing procedures unavailable, one of which disadvantages is such that the presence of the pixel electrode
435
or else overlying the to-be-corrected portion necessitates laser irradiation at increased power, which can result in destruction in structure of the peripheral section and also in disturbance of an orientation or “alignment” film
453
leading to irregularity in realignment of liquid crystals resulted therefrom, which in turn causes display defects.
SUMMARY OF THE INVENTION
The present invention has been made to solve the problems faced with the prior art, and a primary object of the invention is to provide an improved liquid crystal display apparatus capable of increasing the defect repairing success rate to thereby eliminate reduction of the aperture ratio while increasing manufacturing efficiencies thereof.
To attain the foregoing object the invention provides a liquid crystal display apparatus comprising a pair of substrates disposed opposing each other; a liquid crystal layer sandwiched therebetween; a data signal transmission line for supplying data signals, laid out on one of the substrates; a scan signal transmission line for supplying timing signals, laid out on the one of the substrates, the data signal transmission line and scan signal transmission line being arranged to intersect each other; a thin-film transistor including a gate electrode which is diverted from the scan signal transmission line, electrically connected to the data and scan signal-
Irie Katsumi
Kasahara Touko
Nakamura Hisakazu
Shimokawa Hiroshi
Tanaka Kyoushi
Chowdhury Tarifur R.
Duong Tai
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
LandOfFree
Liquid crystal display apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3324575