Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-03-23
2004-05-18
Niebling, John F. (Department: 2812)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S150000, C349S151000, C349S152000
Reexamination Certificate
active
06738121
ABSTRACT:
This application claims the benefit of Korean Patent Application No. P2000-17026, filed on Mar. 31, 2000, which is hereby incorporated by reference for all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an apparatus for mounting an integrated circuit on a liquid crystal display, and more particularly to a tape carrier package with a dummy bending part that is capable of reducing a difference in brightness in a screen. Also, the present invention is directed to a liquid crystal display that is capable of reducing a difference in brightness, using said tape carrier package.
2. Description of the Related Art
Generally, a liquid crystal display with an active matrix driving system uses thin film transistors (TFTs) as switching devices to display a natural moving picture. Since such a liquid crystal display can be made into a smaller-size device than the Brown tube, it is commercially available for a monitor such as a portable television or a lap-top personal computer, etc.
The active matrix liquid crystal display displays a picture corresponding to video signals, such as television signals, on a pixel (or picture element) matrix having pixels arranged at each intersection between gate lines and data lines. Each pixel includes a liquid crystal cell for controlling a transmitted light quantity in accordance with a voltage level of a data signal from a data line. The TFT is installed at an intersection between the gate line and the data line to switch a data signal to be transferred to the liquid crystal cell in response to a scanning signal (i.e., a gate pulse) from the gate line.
Such a liquid crystal display requires a number of driving integrated circuits, each hereinafter referred to as a “D-IC”, connected to the data lines and the gate lines to apply data signals and scanning signals to the data lines and the gate lines, respectively. The D-ICs are installed between the printed circuit board (PCB) and the liquid crystal panel to apply the data signals and the scanning signals to the data lines and the gate lines of the liquid crystal panel in response to a control signal applied from the PCB. A tape automated bonding (TAB) system has generally been used as a mounting method of the D-ICs that is capable of widening an effective area of the panel and has a relatively simple mounting process.
The TAB method may be divided into a bending type as shown in
FIG. 1A
, and a flat type as shown in FIG.
1
B. The bending-type TAB system as shown in
FIG. 1A
has been used for a mounting of source and gate drivers of a monitor or a notebook computer. In the bending-type TAB system, a PCB
6
is folded to the rear side of a liquid crystal panel
2
by bending a tape carrier package (TCP)
10
mounted with a D-IC
8
and connected between a lower glass substrate
3
of the liquid crystal panel
2
and the PCB
6
. A backlight unit
4
is positioned below the liquid crystal display panel
2
. As shown in FIG.
2
and
FIG. 3
, an adhesive
25
is coated on a base film
24
of the TCP
10
, and a lead part
26
is adhered thereon. The lead part
26
made from copper (Cu) is connected to pins of the D-IC
8
. On the lead
26
is coated a solder resistor
27
responsible for providing an insulator. At the upper end and the lower end of the base film
24
, an input pad part
21
and an output pad part
22
extending from each lead of the lead part
26
are provided. The input pad part
21
is connected to an output signal wiring of the PCB while the output pad part
22
is connected to the gate line or the data line formed on a lower glass substrate
3
. Bending parts
10
a
and
10
b
are provided between the input pad part
21
and the D-IC
8
and between the output pad part
22
and the D-IC
8
, respectively. The base film
24
is removed from the bending parts
10
a
and
10
b
. The TCP
10
is easily bent with the aid of these bending parts
10
a
and
10
b.
The flat-type TAB system as shown in
FIG. 1B
is mainly used to mount gate drivers of a 10.4″ or 12.1″ small-size notebook computer or monitor. In the flat-type TAB system, a TCP
12
mounted with a D-IC
8
and connected between a lower glass substrate
3
of a liquid crystal panel
2
and a PCB
6
is arranged in parallel to the liquid crystal panel
2
. Thus, since the TCP
12
connected between the liquid crystal panel
2
and the PCB
6
is not bent, no bending part is formed.
However, the conventional TAB system has a problem in that a brightness difference is generated between an area where the TCP
10
or
12
is adhered onto the liquid crystal panel
2
and an area where the TCP
10
or
12
is not adhered onto the liquid crystal panel
2
. More specifically, as shown in
FIG. 4
, the TCPs
10
c
to
10
j
are adhered to the edge of the lower glass substrate
3
at a desired spacing, having an anisotropic conductive film (ACF) therebetween under a high temperature and high pressure atmosphere. At this time, the TCPs
10
c
to
10
j
are expanded by heat and then contracted while the heat applied thereto is lowered to a normal temperature after their adhesion. A stress is applied to the lower glass substrate
3
by such TCPs
10
c
to
10
j
. As a result, since the lower glass substrate
3
is deformed into a periodical land/groove shape as shown in
FIG. 5
, a cell gap between an upper glass substrate (not shown) and the lower glass substrate
3
has a periodical thickness difference. When an experiment using the gray patterns of ‘7’ and ‘3’ was made with respect to two samples of a 12.1″ liquid crystal panel as shown in
FIG. 4
having SVGA resolution (i.e., 800×600) and a brightness of 300 nit, a brightness difference is periodically generated. As a result of this experiment, a brightness difference between the adhesive areas a, c, e, g, i and k and the non-adhesive areas b, d, f, h and i of the TCPs
10
c
to
10
j
having a difference in the cell gap is indicated in the following Table 1, and in
FIGS. 6 and 7
. As a brightness measuring device, a ‘PR800’ model optical measuring-set is used for sensing a brightness level in accordance with a received light amount.
TABLE 1
Measuring
Sample
Point
a
b
c
d
e
f
g
h
i
j
k
Sample 1
7-Gray
0.577
0.74
0.679
0.879
0.818
0.956
0.801
0.959
0.829
0.957
0.794
3-Gray
0.44
0.538
0.491
0.642
0.577
0.703
0.584
0.707
0.604
0.712
0.596
Sample 2
7-Gray
1.628
2.075
1.892
2.293
1.974
2.165
2.165
2.563
2.217
2.587
2.132
3-Gray
1.925
1.233
1.089
1.369
1.129
1.464
1.258
1.564
1.291
1.549
1.245
As seen from Table 1, a brightness difference is generated between the adhesive areas a, c, e, g, i and k and the non-adhesive areas b, d, f, h and l of the TCPs
10
c
to
10
j
. In two samples, average brightness differences in the 7 gray pattern and the 3 gray pattern have 0.2691 and 0.1957, respectively. Since a stress applied to the lower glass substrate
3
by the TCPs
10
a
to
10
h
becomes larger as the TCPs
10
c
to
10
j
become longer or thicker, a brightness difference between the adhesive areas a, c, e, g, i and k and the non-adhesive areas b, d, f, h and l of the TCPs
10
c
to
10
j
becomes larger. Therefore, a strategy capable of reducing a brightness difference caused by the TCPs
10
c
to
10
j
is required to improve a display quality of the liquid crystal display.
FIG. 6
is a characteristic diagram of a brightness level detected from the liquid crystal panel shown in
FIG. 4
with respect to a 7-gray pattern;
FIG. 7
is a characteristic diagram of a brightness level detected from the liquid crystal panel shown in
FIG. 4
with respect to a 3-gray pattern;
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a tape carrier package with a dummy bending part that is capable of reducing a brightness difference of the screen.
A further object of the present invention is to provide a liquid crystal display that is adaptive for reducing a brightness difference of the screen.
In order to achieve these and other objects of the invention, a tape carrier packag
An Eun Yeong
Yun Sai Chang
Niebling John F.
Roman Angel
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