Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-08-28
2002-05-28
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C257S676000
Reexamination Certificate
active
06396557
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tape carrier package which is attached to the periphery of a liquid crystal panel of a liquid crystal display device and accommodates a semiconductor chip for driving the liquid crystal panel on a tape carrier, and a liquid crystal display device provided with tape carrier packages.
2. Description of the Related Art
Conventional liquid crystal display devices, as shown in
FIG. 10
, have been known. This liquid crystal display device
150
is mainly composed of a liquid crystal panel
100
, a plurality of tape carrier packages (TCPs)
117
, and a common printed wiring board
118
. The liquid crystal panel
100
is mainly composed of an upper glass substrate
110
, a lower glass substrate
111
, and a liquid crystal layer (not shown) interposed therebetween. Reference numeral
122
denotes a flexible substrate.
In this liquid crystal display device, as shown in
FIG. 13
, the semiconductor chips
104
for driving the liquid crystal are mounted onto the liquid crystal panel
100
as follows: a tape carrier with semiconductor chips
104
placed thereon is cut to a predetermined size to obtain TCPs
117
; each TCP
117
is supplied onto the liquid crystal panel
100
; and a conductive pattern portion (e.g., outer leads) of each TCP
117
and electrodes on the lower glass substrate
111
of the liquid crystal panel
100
are crimped onto each other by heating with an anisotropic conductive film
140
interposed therebetween, whereby each TCP
117
is mounted onto the liquid crystal panel
100
.
As shown in
FIG. 13
, outer leads (not shown) of the TCPs
117
are connected to wiring (not shown) of the printed wiring board
118
. A signal for driving the liquid crystal is supplied to each semiconductor chip
104
through each TCP
117
from the printed wiring board
118
. The printed wiring board
118
also has a region
118
a
for accommodating components, such as a chip capacitor, which cannot be incorporated into the circuit of each semiconductor chip
104
.
FIG. 11
is a cross-sectional view of another liquid crystal display device
160
with a TCP
117
′ attached to the periphery of a liquid crystal panel
100
. The TCP
117
′ is attached to the liquid crystal panel
100
as follows: an output terminal
117
a
of the TCP
117
′ for driving the liquid crystal is connected to the liquid crystal panel
100
via an anisotropic conductive film
140
; thereafter, an input signal terminal
117
b
of the TCP
117
′ is connected to a printed wiring board
118
by soldering or via an anisotropic conductive film
140
′; and the TCP
117
′ is bent along the contour of a module, whereby the attachment of the TCP
117
′ to the liquid crystal panel
100
is complete. In
FIG. 11
, reference numeral
119
denotes a backlight unit;
120
denotes a polarizing plate; and
116
denotes a bezel.
It is also known that a semiconductor chip is attached to a liquid crystal panel by a Chip-On-Glass (COG) method. According to the COG method, as shown in
FIG. 12
, a semiconductor chip
104
having metal bumps
104
a
is directly connected to wiring (not shown) on a lower glass substrate
111
by face down bonding. Regarding the COG method, the following two processes are known.
Firstly, a semiconductor chip having solder bumps is directly attached to a glass substrate of a liquid crystal panel, and then, a gap between the semiconductor chip and the glass substrate is filled with a resin (Japanese Laid-Open Patent Publication No. 4-105331). Secondly, a semiconductor chip having gold bumps is connected to wiring on a glass substrate of a liquid crystal panel via an anisotropic conductive film
121
(Japanese Laid-Open Patent Publication Nos. 4-76929, 4-71246, and 4-317347). In the case of the second process, a gap between the semiconductor chip and the glass substrate is filled with a resin (binder) of the anisotropic conductive film. According to the second process, repairs are easily conducted, and it is not required to fill a resin in the gap between the semiconductor chip and the glass substrate; therefore, this process has been mainly used.
In recent years, there is a tendency to secure a larger display area with the same module size by decreasing the width of the portion of a liquid crystal display device that extends off a glass substrate. Furthermore, there is a great demand for a reduction in costs for liquid crystal panels in light of the generally, higher production costs compared with those of CRTs (Cathode Ray Tube).
Under such circumstances, in order to decrease the width of a TCP which extends off a glass substrate, the following two methods using TCPs have been proposed: (1) A slim-type TCP
117
with a narrow semiconductor chip formed thereon is used, as shown in
FIG. 13
(Japanese Design Patent Application No. 2-40145); and (2) as described with reference to
FIG. 11
, a portion of a TCP
117
′ which extends off a glass substrate is bent (Japanese Laid-Open Patent Publication No. 2-132418).
According to the method shown in
FIG. 13
, a material used for a TCP itself is also reduced, which contributes to a reduction in costs. However, it is necessary to decrease the width of a printed wiring board in accordance with the width of a portion of a TCP which extends off a glass substrate. When the width of the printed wiring board is decreased without changing the wiring density, it is necessary to increase the number of layers of the printed wiring board. This results in an increase in costs. In addition, since the width of a connected portion of the printed wiring board and the TCP is very small, it is difficult to mount the TCP onto the printed wiring board. This may adversely influence the yield and reliability of the semiconductor device. These problems become serious in circumstances where liquid crystal panels are increasing in size.
As shown in
FIG. 13
, even when the above-mentioned slim-type TCP is used, a portion with a width of about 5 mm necessarily extends off the glass substrate.
FIG. 10
is a schematic plan view (the bezel
116
is omitted) of a liquid crystal panel constructed as illustrated in FIG.
13
.
In the case where the bent TCP
117
′ is used, as shown in
FIG. 11
, the printed wiring board
118
may be provided either on the upper surface or on the lower surface of the lower glass substrate
111
. In the case where the printed wiring board is provided on the lower surface of the lower glass substrate
111
, the wiring of the liquid crystal panel
100
can be connected to the printed wiring board
118
via the bent TCP
117
′. Therefore, the printed wiring board
118
need not extend beyond the liquid crystal panel
100
. Accordingly, the problem associated with large size devices can be solved to some degree. In the case shown in
FIG. 11
, the width of a portion of the TCP which extends off the glass substrate is only 2 mm (which is much smaller than that in the case as shown in FIG.
13
).
However, in the case of using the bent TCP
117
′, there are the following problems: the length of the TCP
117
′ must be larger by the bent portion thereof, so that the costs for a tape carrier portion of the TCP
117
′ are higher; it is easier to connect the printed wiring board
118
to the TCP
117
′ compared with the case where the above-mentioned slim-type TCP
117
is used, however, the TCP
117
′ must be bent to a predetermined shape after the TCP
117
′ is connected to the printed wiring board
118
, so that the TCP
117
′ is fixed to the printed wiring board
118
, so that the TCP
117
′ is fixed to the printed wiring board
118
; and the thickness of a liquid crystal module becomes larger by the total thickness of the printed wiring board
118
and the TCP
117
′ (i.e., about 2.5 mm to 3 mm), compared with the case where the slim-type TCP
117
, as shown in
FIG. 13
, is used.
According to the COG method, a semiconductor chip is directly mounted onto a glass substrate,
Duong Tai V.
Sharp Kabushiki Kaisha
Sikes William L.
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