Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2001-07-20
2003-10-21
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S042000, C349S139000
Reexamination Certificate
active
06636279
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to a display device, a method of manufacturing the same and a wiring board for a display device. More particularly, the invention relates to a display device with a short-circuit wiring representing a short circuit due to the electrostatic breakdown between the wirings by short-circuiting with another wiring, a method of manufacturing the same and a wiring board.
As an image display device for a personal computer or other various monitors, a liquid crystal display (LCD) device has been remarkably widespread. In general, the liquid crystal display device includes a liquid crystal display panel with a drive circuit, and a backlight unit disposed on a back surface thereof. The display panel displays an image by controlling light transmitted therethrough. The display panel includes a display area made from a plurality of sub-pixels disposed in the form of matrix, and an outer peripheral area formed in an outer periphery thereof. Among the liquid crystal display devices, there is an active matrix LCD in which each sub-pixel has a switching element such as a Thin Film Transistor (TFT) and a Metal Insulator Metal (MIM).
Since the active matrix LCD is able to perform a subtle gray-scale display and has a high contrast, it is widely adopted for a high-definition display device or a color LCD device. The color LCD device is typically formed by sealing liquid crystal between an array substrate and a color filter substrate with color filters, the array substrate having switching elements, pixel electrodes and the like formed in the form of array. The color LCD has a color filter, each of R, G and B for each sub-pixel, and performs a color display by controlling a quantity of light from each sub-pixel. Three sub-pixels of R, G and B form one pixel. Note that, in a monochrome LCD, each sub-pixel corresponds to the pixel.
FIG. 1
is a conventional view schematically showing a sub-pixel with a TFT as a switching element. Only a sub-pixel that is formed on the TFT substrate side is shown. In
FIG. 1
, a bottom gate type TFT is shown which uses amorphous silicon (a-Si) as a semiconductor. Besides this, there exist a bottom gate type TFT using polysilicon as a semiconductor, or a top gate type TFT and the like. The bottom gate type TFT is a TFT in which a gate of the TFT is disposed in a lower layer than a layer of a drain/source.
In the drawing, a reference numeral
11
denotes a TFT as a switching element; a numeral
12
a gate electrode; a numeral
13
a gate insulating layer; a numeral
14
an amorphous silicon (a-Si) layer; a numeral
15
an ohmic layer improving an ohmic contact between the a-Si layer and electrodes; a numeral
16
a source electrode; a numeral
17
a drain electrode; and a numeral
18
a pixel electrode applying an electric field to liquid crystal. The ohmic layer
15
is doped with P or As as a donor. The gate electrode
12
is connected to a Y axis side driver IC (not shown) via a gate line
19
, and the source electrode
16
is connected to an X-axis side driver IC (not shown) via a signal line
20
. Note that, since the TFT
11
is driven by an alternating current, the polarities of the source electrode
16
and the drain electrode
17
are inverted with the passage of time.
An operation of the sub-pixel will now be described. A signal is sent from the Y-axis driver IC via the gate line
19
to each gate electrode
12
. By this signal, a gate voltage of the TFT
11
is manipulated to turn on/off the TFT
11
. Moreover, a signal is sent from the X-axis driver IC via the signal line
20
to the source electrode
16
. Whether or not the signal is transmitted from the source electrode
16
to the drain electrode
17
is controlled by the gate electrode
12
. An amplitude of a signal voltage to the drain electrode
17
is controlled by changing a signal voltage value from the X-axis driver IC to the source electrode
16
. The pixel electrode
18
having the signal voltage sent from the drain electrode
17
applies a voltage to the liquid crystal, between the pixel electrode
18
and a common electrode (not shown) formed on an opposing substrate. The gray-scale display can be performed by changing the voltage applied to the liquid crystal.
FIG. 2
is a constructional view schematically showing a TFT array substrate. In the drawing, a reference numeral
21
denotes a display area; reference numeral
22
is an outer peripheral area; reference numeral
23
are signal lines; reference numeral
24
are gate lines; and reference numeral
25
are short rings. In manufacturing the TFT array substrate, wirings
25
called short rings are formed at the outside of the display area
21
. Each short ring is a wiring in which end terminals of each signal line and gate line are short-circuited with each other in order to prevent electrostatic breakdown in an active matrix wiring.
However, each short ring
25
functions only after completing the gate line
24
and the signal line
23
. Therefore, particularly in the case where the signal line
23
has a plurality of layers, there has been a problem that a short circuit occurs between the signal line
23
and the gate line
24
before an uppermost layer of the signal line
23
is attached. Moreover, it has been known that the electrostatic breakdown frequently occurs particularly between the most external signal line of the display area
21
and a gate line thereunder. This is because an electric charge causing the electrostatic breakdown is apt to accumulate on a substrate end since the substrate end is grasped or contacts with a device when the substrate is carried, and thus it is conceived that the electrostatic breakdown is apt to occur between the external electric conductors.
As means for preventing such electrostatic breakdown before the completion of the signal line, a dummy signal line is formed on the outer peripheral area. This is a wiring formed at the further outside of the most external signal line in the display area in an electrically floating state. This dummy line has the same construction as that of the signal line, and is formed at the same time when the signal line is formed. By forming such a dummy signal line, a short circuit due to the electrostatic breakdown may occur between the gate line and the dummy signal line, thus the defect due to the short circuit between the signal line and the gate line can be prevented.
However, even in the case where the dummy line is formed in the above-described manner, there has been a problem that the dummy line causes a short circuit with two or more of the gate lines. In such a case where short circuits occur at two or more spots, two gate lines are electrically connected to each other thus causing a defect called an inter-gate-line short circuit. In order to prevent such a short circuit therebetween, it is conceived that the dummy line between the gate lines is previously cut. However, when the dummy line is disconnected in such a manner as described above, since capacitance of each of the cut dummy lines is decreased, there has been a problem that the electrostatic breakdown occurs not between the dummy line and the gate line but between the most external signal line and gate line.
SUMMARY OF INVENTION
In order to solve the foregoing problems, the feature of the present invention is to obtain a display device, a method of manufacturing the same and a wiring board for a display device, which are capable of preventing the short circuit between the wirings.
Another feature of the present invention is to obtain a display device, a method of manufacturing the same and a wiring board for a display device, which are capable of, even in the case where the dummy line and other two or more wirings are short-circuited, for eliminating a short circuit between the two or more wirings. Still another feature of the present invention is to obtain a display device, a method of manufacturing the same and a wiring board for a display device, which are capable of, even in the case where the dummy line and other two or more wirings are short-cir
Iiyori Hideo
Takasugi Shinji
Dudek James
Duong Tai
International Business Machines - Corporation
Jennings Derek S.
LandOfFree
Display device and method of manufacturing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Display device and method of manufacturing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Display device and method of manufacturing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3136337