Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
1999-01-20
2001-07-10
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S149000, C349S152000, C257S059000
Reexamination Certificate
active
06259495
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to liquid crystal display panels for liquid crystal displays and, more particularly, the structure of and method of preparing terminal or connecting electrodes for connecting such a display panel to an external drive circuit.
Up to date, liquid crystal displays which feature small thickness and light weight, particularly active matrix liquid crystal displays which have switching elements each provided for each pixel, have been extensively used. The extensive use of active matrix liquid crystal displays is attributable to their general features that they are capable of readily providing gradations, quickly responsive and suited for displaying moving images. As the switching element are used thin film transistors (TFT) and MIM elements.
FIG. 14
is a sectional view showing an active matrix liquid crystal display. The illustrated active matrix liquid crystal display comprises an active matrix substrate
1
having switching elements, another substrate
2
parallel to and spaced apart by about 50 &mgr;m from the substrate
1
, and liquid crystal
4
filling a space defined by the substrates
1
and
2
and a seal
3
. Polarizing sheets
5
are each bonded to the outer surface of each of the substrates
1
and
2
.
FIG. 15
is a view showing the electric configuration of an active matrix liquid crystal display panel using TFTs. The illustrated active matrix liquid crystal display panel using the TFTs, comprises pluralities of scan lines
12
and signal lines
13
, which are formed in crossing relation to one another on a transparent substrate
11
, and the TFTs
14
provided at the intersections of the lines
12
and
13
. The TFT
4
is a three-terminal element, which comprises a switching semiconductor layer and a gate, a source and a drain electrodes. Pixel electrodes
15
, each connected to each TFT
14
, are provided in a matrix array. For connecting the display panel to an external drive circuit, scan line terminals
16
are provided on the leading ends (i.e., one side) of the scan lines
12
, and signal line terminals
17
are provided on the leading ends (i.e., one side) of the signal lines
13
. The external drive circuit is usually electrically connected to the display panel by press bonding the two via a tape carrier package (TCP) and an isotropic conductive film (ACF), the TCP being provided on the circuit side, the ACF being provided on the terminal surface side.
Referring to
FIG. 15
, for instance, when a scan line Xi among the scan lines
12
is selected and activated by voltage pulse application, the TFTS
14
connected to this scan line are simultaneously turned on with a resultant increase of their gate voltage beyond a threshold voltage, and signal voltage corresponding to image data is transmitted from each signal line
13
through the source of each “on” TFT
14
to the drain thereof. The signal voltage transmitted to the drain produces a voltage difference between the pixel electrode
15
, which is connected to the drain, and the opposed electrode
19
facing the pixel electrode
15
via the intervening liquid crystal layer
18
, thus changing the light permeability thereof for image display.
In a liquid crystal display of lateral electric field type, the opposed electrode
19
is provided on the TFT substrate side. In this display, when the selected scan line Xi is restored to the non-selected state so that the gate voltage becomes lower than the threshold voltage, the gates of all the TFTs
14
connected to this scan line are turned off at a time, and then the next scan line Xi+
1
is selected, and the gates of the TFTs
14
connected to this scan line are turned on, thus bringing about an operation like that described above.
After the gates have been turned off, the voltage difference between the pixel electrode
15
and the opposed electrode
19
is accumulated in the inter-electrode electrostatic capacitance and held in the liquid crystal layer
18
until the same scan line is selected and activated afresh by voltage pulse application.
In the active matrix substrate which uses amorphous silicon (a-Si) for the semiconductor layer and utilizes TFTs or MIM elements, connecting terminals (i.e., scan line terminals
16
and signal line terminals
17
) are provided on the leading ends of the scan lines and signal lines for connecting the display panel to the external drive circuit. In the case of utilizing TFTs, the above operation is brought about.
Requirements for the connecting terminals are that the connection resistance at the terminal part is low and stable, that high reliability can be ensured against intrusion of water or the like from the outside and that a press bonding process can be readily carried out afresh.
By way of example, Japanese Patent Laid-Open No. 60-260920 discloses a method, in a liquid crystal display of thermal write type, of forming an aluminum hydroxide cover film on heating electrodes by using aluminum or an alloy thereof.
FIG. 17
shows the method described in the Japanese Patent Laid-Open No. 60-260920. In this method, after formation on a transparent substrate
11
of stripe-like heating electrodes
171
of aluminum or an alloy thereof, the resultant substrate is hot water treated in pure water at
50
to
100
degrees C, and then an aluminum hydroxide cover film is formed to a thickness of 0.1 to 1 &mgr;m on the surface of the heating electrodes
171
. In the hot water treatment, on the terminal electrode was formed the photo resist pattern and the aluminum hydroxide is not formed thereon.
Japanese Patent Laid-Open No. 3-280021 discloses an electro-optical apparatus, which uses aluminum or like corrosion-resistant metal for the terminal electrode part.
FIG. 18
shows the discloses electro-optical apparatus. As shown in the Figure, on a transparent substrate
11
are formed a pixel electrode (not shown), a non-linear resistance layer
181
, an upper electrode (not shown) of chromium, a column electrode
182
, a terminal electrode
184
of aluminum.
Aluminum and its alloys is usually readily subject to corrosion. However, even by directly forming the terminal electrode in this way, relatively satisfactory reliability can be maintained against external water intrusion.
As a further example, Japanese Patent Laid-Open No. 8-12282 discloses a technique concerning a thin film transistor substrate, which has scan lines and gate electrodes formed by using aluminum or an alloy thereof and covered by an anodic oxidization film. This technique features satisfactory anodic oxidization film boundary controllability with respect to the gate terminal part.
FIG. 19
illustrates this technique. As shown in the Figure, on a transparent substrate
11
are formed a scan line
12
, a signal line
13
, a TFT
14
and a pixel electrode
15
. The scan line
12
and the gate of the TFT
14
are formed by using aluminum or an alloy thereof. Scan line terminal part
16
is formed by laminating aluminum or an alloy thereof, titanium or tantalum and indium tin oxide (ITO). The scan line
12
and gate electrode are covered by an anodic oxidization film of aluminum, which is formed by an anodic oxidization process in the presence of a titanium layer having been formed.
Japanese Patent Laid-Open No. 43-232274 also discloses a method, which is used for a thin film transistor substrate using aluminum or an alloy thereof for scan lines and gate electrodes for covering these desired parts with an anodic oxidization film.
The prior art techniques disclosed in the Japanese Patent Laid-Opens No. 60-260920 and No. 3-280021, however, have a problem that an additional photo-lithographic process is necessary for the following reasons. According to the Japanese Patent Laid-Open No. 60-260920, it is necessary to carry out the hot water process by forming a photo-resist pattern on the terminal electrode part. According to the Japanese Patent Laid-Open No. 3-280021 it is necessary to convert chromium low electrodes in the terminal electrode part to aluminum.
Another problem posed in these techniques is that th
Chowdhury Tarifur R.
NEC Corporation
Sikes William L.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Liquid crystal display panel and method of manufacturing the... 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 panel and method of manufacturing the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display panel and method of manufacturing the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2480083