Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-06-08
2004-02-03
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S150000, C349S152000
Reexamination Certificate
active
06686987
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display (“LCD”) device in which TCPs are mounted on a liquid crystal panel.
Conventionally, the mounting architecture between a liquid crystal panel and driver ICs in an LCD device adopts a TCP (Tape Carrier Package) method chiefly. An LCD device mounted using the TCP method is shown in
FIGS. 7A and 7B
.
FIG. 7A
is a schematic perspective view of the LCD device, and
FIG. 7B
is a schematic enlarged view of a source TCP (or a gate TCP) used in FIG.
7
A.
Referring to
FIGS. 7A and 7B
, the LCD device
500
has, on peripheries of a liquid crystal panel
501
, gate TCPs
502
and source TCPs
503
for feeding signals to gate signal lines and source signal lines, respectively, of the liquid crystal panel
501
, and external circuit boards
504
for feeding external signals to those TCPs
502
,
503
.
As shown in
FIG. 7B
, the gate TCP
502
and the source TCP
503
each have, on a flexible substrate
506
, a liquid crystal driver IC
505
, signal input lines
507
for feeding external signals (image data signal, IC driving power supply voltage, counter-electrode driving power supply voltage, etc.) to the liquid crystal driver IC
505
, and signal-output lines
508
for feeding signals output from the liquid crystal driver IC
505
to the liquid crystal panel
501
.
The signal input lines
507
of each TCP
502
,
503
are electrically connected to terminals on the circuit boards
504
located outside the liquid crystal panel
501
, by which external signals are led from the terminals on the circuit boards
504
to the liquid crystal drivers IC
505
.
In this LCD device
500
adopting the TCP method, since signals are supplied directly and individually from the external circuit board
504
to the TCPs
502
,
503
, a very large number of wirings are necessitated on the external circuit board
504
. This has caused hitherto such disadvantages as complicated fabrication process, cost increase and lowered reliability.
Thus, for the TCP method, there has been introduced in recent years a so-called “signal propagation method” in which a signal, after once input to one TCP, is propagated to adjacent TCPs one after another. This method is disclosed in, for example, Japanese Patent Laid-Open Publication HEI 4-313731, Japanese Utility Model Laid-Open Publication HEI 3-114820, and Japanese Patent Laid-Open Publication HEI 10-214858.
A detailed structure of a gate TCP or source TCP mounted on an LCD device adopting the signal propagation method is as follows. That is, on a flexible substrate are mounted a liquid crystal driver IC, signal input lines for inputting external signals to the liquid crystal driver IC, signal-output lines for feeding image signals from the liquid crystal driver IC to the liquid crystal panel, and lines (hereinafter, referred to as “relay lines”) for outputting a liquid crystal driving signal to the adjacent TCP.
Meanwhile, connecting lines for connecting adjacent TCPs to each other are provided on peripheral portions of a substrate of the liquid crystal panel, between regions where the TCPs are mounted.
Signal propagation paths between adjacent two TCPs (designated as a first TCP and a second TCP) are explained below.
First, when external signals are fed from the circuit board to a first liquid crystal driver IC via the signal input lines, image signals responsive to these signals are sent to the liquid crystal panel via the liquid crystal driver IC and the signal-output lines.
Meanwhile, part of the external signals inputted to the first TCP are led to the relay lines of the first TCP and then fed to the input signal lines of the second TCP via the connecting lines provided on the liquid crystal panel between these first and second TCPs.
Accordingly, once signals are input from the circuit board to one TCP, part of the signals are supplied to pixels of the liquid crystal panel via the liquid crystal driver IC of the TCP, while the rest of the signals are propagated to adjacent TCPs sequentially via the relay lines of the TCPs and the connecting lines of the liquid crystal panel.
As shown above, the signal propagation method allows the number of wirings, which are necessary for input from the external circuit board to the TCPs, to be considerably reduced, as compared with the TCP method. Thus, this method is effective for cost reduction of circuit boards.
Aforementioned Japanese Patent Laid-Open Publication HEI 4-313731 and Japanese Utility Model Laid-Open Publication HEI 3-114820 suggest that the need of external circuit boards can be eliminated by providing bus lines, which run longitudinally over the entire peripheral part of the liquid crystal panel while bending again and again, in order to propagate signals to the individual TCPs sequentially.
In this manner, the two publications disclose a method for dispensing with the external circuit boards. However, the technique disclosed in these two publications incurs high wiring resistance because of the bus lines being very long. Also, since the wirings of the liquid crystal panel generally need to be provided on a glass substrate, it is inevitable to use wirings much higher in resistance value than those of the external circuit boards or TCPs, resulting in further increase of the wiring resistance. This in return causes problems such as propagation delay of signals. Besides, the publications make no mention of signals that are to be introduced. So, there may occur problems in practical use. In particular, a large voltage drop due to wiring resistance in the power supply voltage for driving the liquid crystal driver IC of the TCP, the power supply voltage for driving counter-electrodes, and the like, may cause operational problems. For prevention of this, signals need to be propagated under low resistance. Thus, for those signals, actually, circuit boards
504
would inevitably be provided as shown in
FIG. 8A
, where signals are inputted from the circuit boards
504
to the TCPs separately and individually.
Japanese Patent Laid-Open Publication HEI 10-214858 discloses that a power supply voltage line for driving the liquid crystal driver IC extends from one end to the other end of the TCP. In such a case, connecting the power supply voltage lines of the adjacent TCPs to each other makes it possible to dispense with the external circuit boards shown in FIG.
8
A. Also, since the connection of the adjacent TCPs to each other is only required, it is unnecessary to form such a long bus line as runs over the entire peripheral part of the liquid crystal panel, as would be involved in the technique disclosed in the foregoing two publications. However, because the third publication does not at all disclose a wiring structure for propagating on the TCP a signal which does not need to be input to the liquid crystal driver IC but which is to be output to the pixel section of the liquid crystal panel, such as for counter-electrode voltage lines, use of such signals would incur inconvenience in the implementation of the technique of this publication. Further, the TCP disclosed in the third publication has a structure that connecting terminals are not arranged along just one side edge of the TCP but a plurality of side edges thereof. On this account, there is a problem that an application process of an anisotropic conductive tape involved in the bonding of the TCPs to the liquid crystal panel is complicated.
SUMMARY OF THE INVENTION
The present invention having been accomplished to solve these and other problems, an object of the invention is to provide an LCD device which dispenses with the external circuit boards to thereby realize reduction in module size and weight at low costs and without incurring any disadvantages or inconveniences.
According to an aspect of the invention, there is provided a liquid display device (LCD) comprising:
a liquid crystal panel having a plurality of electrode terminals provided in a peripheral part thereof and a pixel section provided in a central part thereof; and
a plurality of wiring boards each provided with
Kawaguchi Hisao
Nagata Katsunori
Sakaki Yoichiro
Kim Robert H.
Nguyen Hoan
Nixon & Vanderhye PC
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