Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
1999-03-11
2002-01-29
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S040000, C349S055000
Reexamination Certificate
active
06342931
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an active-matrix substrate and an inspecting method thereof, more specifically, relates to the active-matrix substrate which is used for a device such as an active-matrix liquid crystal display device in which driving voltage is applied to a pixel electrode via a switching element and liquid crystal is driven in accordance with a potential difference between the pixel electrode and an opposing electrode so as to provide a display, and concerns the inspecting method thereof.
BACKGROUND OF THE INVENTION
Conventionally, an active-matrix liquid crystal display device has been arranged in a state in which individual pixel portions are independently disposed in a matrix form, and each pixel portion is provided with a pixel electrode and a switching element.
In the above-mentioned active-matrix liquid crystal display device, driving voltage is applied to the pixel electrode via the switching element, liquid crystal is driven in accordance with a potential difference between the pixel electrode and an opposing electrode which is disposed in a manner so as to oppose the pixel electrode via the liquid crystal, and transmitted light or reflected light is subjected to an optical modulation so as to display an image on the liquid crystal display panel.
In the above-mentioned liquid crystal display device, an MIM(Metal Insulator Metal) element or TFT(Thin Film Transistor) element has been used as the switching element. Especially, a liquid crystal panel using the TFT element has been most widely used as the active-matrix liquid crystal display device thanks to its quality and cost efficiency.
In the above-mentioned liquid crystal display device in which the TFT element is used, with regard to the pixel portions arranged in a matrix form, scanning lines for inputting a scanning signal which controls the switching element and signal lines for inputting a signal of an image which is to be displayed on the liquid crystal panel are vertically and horizontally disposed. Further, a between layer insulating film is formed between the scanning and signal lines and the pixel electrode.
In the liquid crystal display device having the above-mentioned construction, the between-layer insulating film allows the pixel electrode to be stacked on the scanning lines and the signal lines. Further, for example, Japanese Published Unexamined Patent Application No. 172685/1983 (Tokukaisho 58-172685, published on Oct. 11, 1983) discloses a liquid crystal display device which has the above-mentioned construction so as to improve an aperture rate of each pixel, and furthermore, so as to allow the insulating film to shield from electric field induced by a signal line, thereby reducing defects in alignment of liquid crystal.
Incidentally, a switching element such as the TFT element is generally weak against strong electric field. Therefore, static electricity appearing during a manufacturing process of the liquid crystal display device tends to destroy the TFT element. For example, the liquid crystal display device is provided with an alignment film made of polyimide that determines the alignment direction of the liquid crystal on the substrate. Further, the alignment film is rubbed with a cloth in one direction so as to determine the aligning direction of a liquid crystal molecule. At this time, static electricity appears by the rubbing operation.
When the scanning lines and signal lines on the substrate become charged by the static electricity, an influence is given on a crystal structure of a semiconductive layer within the TFT element. Therefore, the threshold of the TFT element is shifted by several volts. As a result, the switching operation of the switching element is not normally performed so that a portion which has received static electricity is recognized as a defected pixel.
In order to prevent the above-mentioned problem, in the manufacturing process of the substrate, each input terminal of the scanning lines and the signal lines is generally short-circuited by a metal pattern referred to as a short ring. However, after the active-matrix substrate and an opposing substrate have been bonded to each other so as to form the liquid crystal panel, the short ring is removed before peripheral circuits such as a driver have been installed on the input terminals. Therefore, the input terminal of the short ring is not appropriate for a measure against static electricity appearing during the installing process.
For this reason, in the vicinity of the input terminals of the scanning lines and/or the signal lines, protecting circuits are provided so as to connect the adjacent scanning lines and/or the adjacent signal lines.
FIG. 9
is a plan view schematically showing the construction of a conventional active-matrix substrate
51
. The liquid crystal panel has a construction in which an active-matrix substrate
51
and an opposing substrate
52
are bonded to each other with a sealing member(not shown), and liquid crystal(not shown) is sealed into a gap between the substrates
51
and
52
.
On the active-matrix substrate
51
, a plurality of scanning lines
53
and a plurality of signal lines
54
are vertically and horizontally disposed. Each of the areas divided by the scanning lines
53
and the signal lines
54
is referred to as a pixel portion
55
, and an effective display area
56
is constituted by the pixel portions
55
which are disposed in a matrix form.
Furthermore, on the active-matrix substrate
51
, a plurality of spare wires
57
are disposed on the input side and the non-input side of the signal lines
54
.
Additionally, on the active-matrix substrate
51
, a scanning-line input terminal
58
and a signal-line input terminal
59
are respectively formed on each end of the scanning lines
53
and each end of the signal lines
54
. And protecting circuits
60
are formed so as to connect the adjacent scanning lines
53
and to connect the adjacent signal lines
54
on the active-matrix substrate
51
.
The protecting circuit
60
is, for example, formed by using a switching element adopting a diode. Namely, as shown in
FIG. 10
, the two switching elements are arranged in parallel in the opposite direction from each other so as to form a diode ring structure, which serves as the protecting circuit
60
. The protecting circuits
60
are arranged in a manner so as to connect the adjacent scanning lines
53
and to connect the adjacent signal lines
54
.
For example, Japanese Published Unexamined Patent Application No. 106788/1988 (Tokukaisho 63-106788, published on May 11, 1988) discloses the above-mentioned construction. With this arrangement, even in the case when an electric field exceeding a certain value is concentrated on a certain portion, the electric charge can be released to the adjacent scanning line
53
and the adjacent signal line
54
; thus, it is possible to prevent defects caused by the aforementioned electrostatic destruction.
Moreover, as shown in
FIG. 9
, the active-matrix substrate
51
is provided with a plurality of terminals
61
for a lighting inspection. The active-matrix substrate
51
is cut along a division line
62
upon completion of the lighting inspection so that the terminals
61
are removed.
As shown in
FIG. 9
, the spare wires
57
are normally disposed outside the effective display area
56
so as to intersect the end portions of the signal lines
54
and/or the scanning lines
53
. Therefore, in many cases, terminal portions
63
of the spare wires
57
are placed closer to the corners of the liquid crystal panel as compared with the terminals
58
,
59
, and
60
of the scanning lines
53
and the signal lines
54
. Hence, upon handling the panel, the terminal portions
63
of the spare wires
57
tend to come into contact with static electricity prior to other portions. Thus, in the case when the panel comes into contact with an object which is electrostatically charged, or in the case when the panel has been electrostatically charged and the terminal portions
63
of the spare wires
57
come into contact
Nagata Hisashi
Shimada Takayuki
Tajima Yoshimitsu
Nguyen Dung
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
Sikes William L.
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