Liquid crystal apparatus and production process thereof

Details Liquid crystal apparatus and production process thereof Liquid crystal apparatus and production process thereof

1999-01-12

2001-07-24

Dudek, James A. (Department: 2871)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

C349S151000

Reexamination Certificate

active

06266119

ABSTRACT:

FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a liquid crystal apparatus including a liquid crystal device provided with drive devices and a process for producing the liquid crystal apparatus.
There have hitherto been utilized liquid crystal apparatus for displaying various data or information by the use of a liquid crystal in various fields.
FIG. 1
shows a schematic plan view of an embodiment of a structure of such a conventional liquid crystal apparatus.
Referring to
FIG. 1
, a liquid crystal apparatus
1
comprises a liquid crystal panel P
1
including a pair of glass substrates
2
and
3
disposed opposite to each other with a gap and a liquid crystal (not shown) sandwiched between these glass substrates
2
and
3
. On the (inner) surfaces of the substrates
2
and
3
, data electrodes
5
and scanning electrodes
6
are formed, respectively (as partially shown in FIG.
1
).
At a periphery of the liquid crystal panel P
1
, (peripheral) print-circuit boards or driver boards (hereinafter, simply referred to as “PCB(s)”)
7
,
8
and
9
are disposed and connected to the electrodes
5
and
6
on the liquid crystal panel side via a plurality of tape carrier packages (referred to as “TCP(s)”)
10
.
FIG. 2
is an enlarged plan view of an embodiment of the TCP
10
.
As shown in
FIG. 2
, the TCP
10
includes a flexible film
10
a
of, e.g., polyimide and a driver IC (integrated circuit)
10
b
mounted on the flexible film
10
a
by the tape automated bonding (TAB). On the flexible film
10
a
, a plurality of output leads
10
c
are formed from the driver IC
10
b
to a side (edge) of the flexible film
10
a
(as partially shown in
FIG. 2
) and are electrically connected to the liquid crystal panel-side electrodes
5
and
6
(not shown). Similarly, a plurality of input leads
10
d
are formed from the driver IC
10
b
to an opposite side of the flexible film
10
a
to be connected to the PCBs
7
,
8
and
9
.
However, in the case where an external force is exerted on the above-mentioned TCP
10
including the driver IC
10
b
being rigid mounted on the flexible sheet
10
a
, stress concentration is liable to occur at an electrode-connecting portion of the driver IC
10
b
. As a result, the TCP
10
is required to adopt various means in order to obviate the stress concentration.
For that purpose, there has been proposed a liquid crystal apparatus
20
having a structure as shown in FIG.
3
.
Referring to
FIG. 3
, in the liquid crystal apparatus
20
, driver ICs
21
are directly attached to (mounted on) a glass substrate
22
without using the above-mentioned and a PCB (driver board)
23
is also directly connected to the glass substrate
22
with, e.g., an anisotropic conductive adhesive. More specifically, many electrodes (panel-side electrodes)
21
a
are formed with a certain pitch at a periphery of the glass substrate
22
between the driver ICs
21
and the PCB
23
. On the other hand, on the PCB
23
, many electrodes (board-side electrodes)
23
a
are formed with an identical pitch (to that of the panel-side electrodes
21
a
) so that respective opposite electrodes
21
a
and
23
a
are electrically connected to each other between the glass substrate
22
(or the driver ICs
21
) and the PCB
23
.
According to this liquid crystal apparatus
20
, the driver ICs
21
are attached to the glass substrate
22
which is not readily deformed, so that it becomes possible to alleviate the above-described stress concentration at an electrode-connecting portion of the driver ICs
21
.
However, in the case of the liquid crystal apparatus
20
, when positions of the board-side electrodes
23
a
are deviated from normal positions therefor and a degree (amount) of the positional deviation is larger than a width of the panel-side electrodes
21
a
, electrical connection between the board-side electrodes
23
a
and the panel-side electrodes
21
a
cannot be ensured. For this reason, the PCB
23
(driver board) of the liquid crystal apparatus
20
is required to be controlled in terms of a positional error during its production and a position of attachment so that the degree of the positional deviation of the board-side electrodes
23
a
is smaller than an electrode width of the panel-side electrodes
21
a.
In that regard, however, with a longer PCB
23
, a degree of a (positional) production error becomes larger, thus requiring a sufficient control of the attachment position of the PCB
23
in order to ensure an electrical connection between the board-side electrodes
23
a
and the panel-side electrodes
21
a
. As a result, there arises a problem of a lowering in production yields. Further, when the length of the PCB
23
is further longer, the positional deviation degree of the board-side electrodes
23
a
exceeds the electrode width of the panel-side electrodes
21
a
, thus resulting in a failure of production. Particularly, a liquid crystal panel in recent years tends to become a larger size (have a larger picture area), thus leading to a longer PCB
23
. As a result, the above-mentioned problem becomes noticeable.
For example, when a flexible printed circuit (FPC) board (referred to as “FPC”) is liable to cause a dimensional change of its base film due to, e.g., heat treatment during the production of the FPC, thus resulting in a dimensional error (tolerance) a to a dimensional accuracy of an electrode pattern. The dimensional error of the electrode pattern on the FPC s larger than that on the glass substrate
22
and is generally ca. ±0.1%. Even when the dimensional error is decreased by finely adjusting a size of a mask used in the electrode pattern formation, the resultant dimensional error is ca. ±0.05%.
When the FPC providing a dimensional error of ca. ±0.1% is used as the PCB in combination with a liquid crystal panel having a display area of 17 in., the FPC has a length of ca. 340 mm, thus causing a dimensional error of ca. ±0.34 mm as a maximum error. In this case, if a positional alignment is effected on the basis of a central electrode of the FPC, both terminal-side electrodes are (positionally) deviated by ca. 0.17 mm (a half of the dimensional error).
On the other hand, the panel-side electrodes
21
a
generally have a width of 0.15-0.2 mm, so that it is theoretically possible to ensure an electrical connection between the panel-side electrodes
21
a
and the (FPC) board-side electrodes
23
a
but is difficult to perform the positional alignment, thus lowering a production yield. In the case where the width of the panel-side electrodes
21
a
is below 0.17 mm, even the production of the liquid crystal apparatus becomes impossible.
This problem becomes more noticeable when a dissolution of the liquid crystal panel is increased or motion picture images are displayed since electrodes employed are required to be arranged in a smaller pitch to increase the number thereof.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a liquid crystal apparatus capable of ensuring an electrical connection between a liquid crystal device and a PCB.
Another object of the present invention is to provide a liquid crystal apparatus capable of preventing a lowering in production yield.
A further object of the present invention is to provide a process for producing the liquid crystal apparatus.
According to the present invention, there is provided a liquid crystal apparatus, comprising:
a liquid crystal device including a pair of substrates at least one of which is provided with first electrodes, and a liquid crystal disposed between the substrates,
a plurality of driver devices disposed on the at least one substrate at a periphery thereof and electrically connected to the first electrodes,
a driver board for supplying signals to the driver devices, disposed in parallel with the driver devices,
second electrodes disposed on the at least one substrate and electrically connected to the driver devices, and
a plurality of connection sheets disposed between the driver board and the at least one substrate and each elec

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