Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-06-05
2002-06-18
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C361S749000
Reexamination Certificate
active
06407796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, or the like, used for a computer, word processor, etc., and also to a tape carrier package mounted on the display device which package includes a semiconductor chip for driving a display medium such as for example a liquid crystal material.
2. Description of the Related Art
FIG. 23
illustrates an example of a liquid crystal display device, which includes: a liquid crystal panel including an upper glass plate
15
and a lower glass plate
16
provided so as to interpose a liquid crystal material (not shown); a backlight unit
21
as a light source; a semiconductor chip
5
for driving the liquid crystal material; a tape carrier package (TCP)
7
connecting the semiconductor chip
5
to the wiring (or lines) provided on the lower glass plate
16
; a printed board
23
for connecting a plurality of TCPs
7
together; and a vessel
22
for covering the liquid crystal panel.
Known methods for mounting a semiconductor chip for driving a liquid crystal material include: mounting the semiconductor chip directly on the liquid crystal panel; and mounting the semiconductor chip supplied in the form of a tape carrier package (TCP) on the liquid crystal panel.
In the latter method, as shown in
FIG. 23
, an electrode provided on the lower glass plate
16
and a patterned portion of a conductive material on the TCP
7
are attached together via an anisotropic conductive film (not shown) by thermo compression bonding, so as to provide a plurality of TCPs along the periphery of the liquid crystal panel. The plurality of TCPs
7
mounted around the liquid crystal panel are connected to the common printed board
23
which is provided with printed lines. Signals for conducting a display via the liquid crystal material are supplied to the TCPs
7
through the printed board
23
. Moreover, conventionally, some chip components (e.g., a chip capacitor), are mounted on the printed board
23
if they cannot be included in the semiconductor chip
5
. The vessel
22
is provided so as to surround the periphery of the liquid crystal panel.
The assembly steps for the liquid crystal display device include: connecting a liquid crystal driving output terminal of the TCP
7
to an electrode provided on the lower glass plate
16
via the anisotropic conductive film (not shown); and thereafter connecting an input signal terminal of the TCP
7
to the printed board
23
by soldering or via the anisotropic conductive film.
When a bendable TCP
25
is used, as shown in
FIG. 24
, the TCP
25
is bent after the above steps so that the printed board
23
matches the shape of the module.
On the other hand, the former method includes a Chip On Glass (COG) method, where the semiconductor chip
5
having metal bumps is mounted facing down directly onto the lines provided on the lower glass plate
16
. There are different ways for making connections in this COG method such as: one described in Japanese Laid-open Publication No. 4-105331, etc., where connections are directly made by solder bumps after which the gap between the semiconductor chip and the glass plate is filled with a resin; and one described in Japanese Laid-open Publication Nos. 4-76929, 4-71246, 4-317347, etc., where, as shown in
FIG. 25
, the metal bumps of the semiconductor chip
5
are connected to the lines on the lower glass plate
16
via an anisotropic conductive film (ACF)
20
made of a resin (binder)
20
b
including conductive particles
20
a.
In the latter method, the resin (binder)
20
b
of the anisotropic conductive film
20
is used in place of the filling resin in the former method. Recently, the COG method using the anisotropic conductive film which can be easily repaired and which dose not require the resin filling has been widely used.
To each semiconductor chip used in the method where the printed board is used or in the COG method, input signals and power voltages are parallelly input through the lines provided on the printed board or by the ITO lines provided on the liquid crystal panel. However, chip select signals are synchronized with the clock signals parallelly input so that signals are transferred among the semiconductor chips.
In recent years, a prevailing technique is to ensure a larger display area for a certain module size by reducing the width by which the liquid crystal panel extends beyond the glass plate (i.e., the frame size). Moreover, the cost of a liquid crystal panel is higher than that of a CRT, and great cost reduction has been demanded for the liquid crystal panels.
Under such circumstances, as a method using a TCP, it has been proposed (Japanese Design Patent Application No. 2-40145) to use a slim-type TCP which is obtained by shaping a semiconductor chip into an elongated shape in order to reduce the width by which the TCP extends beyond the glass plate. Moreover, it has also been proposed (Japanese Laid-open Publication No. 2-132418, etc.) to reduce the frame size by bending a portion of the TCP which extends beyond the glass plate, as described above.
However, both of the proposed methods require the printed board, the TCP and the liquid crystal panel, and the assembly process thereof requires two connection steps, i.e., one for connecting the glass plate of the liquid crystal panel with the TCP, and another for connecting the TCP with the printed board. This increases material cost and the number of steps to be performed, thereby presenting a bottleneck in reducing the cost of a liquid crystal module.
Moreover, another method has been proposed (Japanese Laid-Open Publication No. 5-297394, Japanese Laid-Open Publication No. 6-258653, etc.) in which a liquid crystal display device includes the liquid crystal panel (reference numeral
15
in
FIG. 26A
denotes the upper glass plate of the liquid crystal panel) and the TCP
7
but does not include a printed board, as shown in FIG.
26
A. In this method, as shown in
FIG. 26B
, adjoining two TCPs
7
are directly connected to each other, whereby input signals are transmitted/received through only the TCPs
7
.
In the case of this proposed method, although it is possible to reduce the material cost for the printed board, two connection steps are required; one for connecting the glass plate of the liquid crystal panel with the TCP
7
; and another for connecting the TCPs
7
together, thereby providing no cost reduction in terms of the number of steps to be performed. Moreover, in this proposed method, if one of the continuously connected TCPs
7
becomes defective, the defective one of the TCPs
7
has to be removed. Such a removal may give some mechanical damage to the adjacent TCPs
7
, and may also present a burden on the process in terms of the number of steps to be performed, requiring disconnection at three positions (at the right and left input terminals and at an output terminal of the defective TCP
7
). Moreover, since transmission/reception of input signals is all performed between the TCPs
7
, the input terminals thereof need to be arranged respectively on the left and right sides, perpendicular to the side on which the output terminal thereof is provided. The input lines connected respectively to the input terminals will also have to be arranged, thereby increasing the width of the TCP
7
, which may then conflict with the frame size limitation of the liquid crystal panel. Moreover, the increased area of the TCP
7
will result in an increased material cost. Thus, the proposed method has some difficulty in repair, does not reduce the number of connection steps; and increases the TCP size.
On the other hand, in the COG method, since the semiconductor chip is directly mounted on the glass plate, the packaging cost thereof is lower than that in a method using a TCP. Moreover, when input signals can be supplied to the semiconductor chip via the lines on the glass plate, the printed board may also be eliminated, thereby presenting a significant advantage in terms of cost. In such a case, there is another advantage that the mounting
Chikawa Yasunori
Gyouten Seijirou
Murahashi Shun-ichi
Tajima Naoyuki
Nixon & Vanderhye P.C.
Parker Kenneth
Sharp Kabushiki Kaisha
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