Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Field effect device in non-single crystal – or...
Reexamination Certificate
1999-08-20
2001-10-02
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Field effect device in non-single crystal, or...
C257S059000, C349S042000, C349S043000
Reexamination Certificate
active
06297520
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an active matrix substrate forming a liquid crystal panel, and to a correcting method of a structural defect thereof caused during the fabrication sequence.
BACKGROUND OF THE INVENTION
A liquid crystal panel of an active matrix type liquid crystal display device is composed of two substrates placed in parallel to keep a predetermined space and a liquid crystal filled in the space. One of the two substrates is called an active matrix substrate and the other is called an opposing substrate. In some cases, a 3-color filter of RGB or YMC is provided on the opposing substrate.
As shown in
FIG. 9
, provided atop of the active matrix substrate are a plurality of gate wires
101
aligned in rows to serve as scanning lines, a plurality of source wires
102
aligned in columns to serve as signal lines, and a plurality of pixels
103
formed in a matrix area of the wires
101
and
102
which intersect at right angles with each other. Also, provided atop of the opposing substrate is a common electrode
104
.
Each pixel
103
mainly comprises a pixel electrode
105
and a switching element
106
, such as a thin film transistor (TFT). The pixel
103
used herein further comprises an additional capacity
107
. Also, a leading terminal
108
and a leading terminal
109
are provided to each gate wire
101
and each source wire
102
, respectively.
Recently, there has been an increasing demand for an active matrix substrate with higher definition, and to meet such a demand, a numerical aperture of the pixel
103
has been increasing. One possible method of increasing a numerical aperture is to narrow a space between the pixel electrodes
105
in adjacent pixels
103
, but this method poses problems as specified below.
That is, the shorting of the pixel electrodes
105
in two adjacent pixels
103
occurs if the patterning during the fabrication sequence of the active matrix substrate is defective and the pixel electrodes
105
are not separated completely. Or even when the pixel electrodes
105
in two adjacent pixels
103
are separated completely, the shorting occurs if scraps of electrode conductive films of the switching element
106
fall in the space between the pixel electrodes
105
during the pattering step.
When this kind of shorting occurs in a longitudinal direction of the gate wire
101
, two kinds of source signals written into the pixel electrodes at the timing of the same gate signal are mixed, and a potential of each shorted pixel
103
is brought to an intermediate potential, whereby a display defect occurs. The display defect becomes noticeable when the liquid crystal panel is driven by providing a display signal having alternating polarities to a plurality of source wires
102
, because two source signals having different polarities are impressed on the adjacent pixel electrodes, respectively. On the other hand, when the shorting occurs in a longitudinal direction of the source wire
102
, two shorted pixels
103
are driven by the writing action of the switching element
106
in either pixel
103
whichever has the later gate signal input timing. Thus, a source signal written by the switching element
106
in the other pixel
103
having the earlier gate signal input timing must be cancelled. However, this makes the writing action by the switching element
106
in the pixel
103
having the later input timing difficult, which results in a display defect.
Incidentally, the fabricated active matrix substrate is subject to inspection, and if any shorting is discovered, a laser beam is irradiated to the shorting spot to remove a material causing the shorting. However, since such a short-causing material is in an extremely narrow space between the pixel electrodes
105
, it is tedious and inefficient to set an irradiation point and only a quite low success rate is achieved. Moreover, the fragments of the removed material may fall in the space between the pixel electrodes
105
again and cause the shorting at a different spot. Therefore, the above conventional method needs improvement.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide (1) an active matrix substrate which can make a display defect resulted from the shorting of adjacent pixels less noticeable to upgrade display quality, and (2) a correcting method of a structural defect of such an active matrix substrate.
To fulfill the above object, an active matrix substrate of the present invention having thereon a matrix of pixels each of which includes a pair of switching element and a pixel electrode is characterized in that it has a cut-off portion where an electrical connection between the pixel electrode and the switching element of a matching pair is cut in one of adjacent pixels having a shorting between their respective pixel electrodes.
According to the above arrangement, when the shorting of the pixel electrodes in the adjacent pixels occurs, an electrical connection between the pixel electrode and the switching element of a matching pair is cut in either of the shorted pixels. Under these conditions, the other pixel is restored to resume a normal operation while the above pixel in which the electrical connection is cut is driven together with the restored pixel. Thus, even when the shorting of the pixel electrodes in the adjacent pixels occurs, the mixing of source signals and the writing of the resulting mixed signal can be prevented. Since only one kind of source signal is written into the pixel electrodes, the display defect becomes less noticeable, thereby enabling a high-quality liquid crystal display.
When the shorting of the pixel electrodes in the adjacent pixels occurs, the electrical connection is cut in any of the following manners:
(1) a connection between the pixel electrode and the drain electrode of the switching element is fused;
(2) a connection between the gate electrode of the switching element and scanning line is fused; and
(3) a connection between the source electrode of the switching element and signal line is fused.
Therefore, every time the shorting of the pixel electrodes in the adjacent pixels occurs, the electrical connection is cut in any of the above manners to prevent the mixing of more than one source signal and the writing of the resulting mixed signal into the pixel electrodes in a reliable manner, thereby suppressing the display defects.
In particular, when the pixel electrode and the drain electrode of the switching element of a matching pair is connected through a connecting electrode, such as a transparent conductive film, a connection between the pixel electrode and the drain electrode of the switching element can be cut using a laser beam or the like. In this case, a success ratio increases because a larger cut-off region is secured.
Also, to fulfill the above object, a method of the present invention for correcting a structural defect of an active matrix substrate that includes an insulating substrate; a plurality of parallel scanning lines provided on the insulating substrate; a plurality of signal lines provided to intersect at right angles with the plurality of scanning lines; a plurality of switching elements, each switching element being a thin film transistor connected to a portion near each intersection of the scanning lines and signal lines, respectively; a transparent insulating film covering the scanning lines, signal lines, and switching elements to make a surface of the active matrix substrate flat; and a matrix of pixel electrodes provided on the transparent insulating film, each pixel electrode being connected to a drain electrode of each switching element via a contact hole made through the transparent insulating film, thereby to form a pixel with each switching element as a matching pair. The method is characterized in that an electrical connection between the pixel electrode and the switching element of a matching pair is cut in one of adjacent pixels having a shorting between their respective electrodes instead of correcting a shorting spot directly.
According to
Kubo Masumi
Tajima Yoshimitsu
Yamashita Toshihiro
Forde Remmon R.
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
Williams Alexander O.
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