Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-05-30
2004-08-03
Nguyen, Dung T. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S149000, C349S150000, C349S151000, C174S258000, C174S259000, C174S260000, C174S262000, C174S263000, C174S265000, C174S266000, C361S751000, C361S760000, C361S761000, C361S762000
Reexamination Certificate
active
06771348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device (hereinafter referred to as “LCD”), and more particularly to a displaying substrate formed with a pad portion capable of enhancing contact characteristics with a circuit substrate for applying electric signals to the displaying substrate, and an LCD having the same.
2. Description of the Related Art
Information-processing appliances have been rapidly developed to have a variety of shapes and functions and much faster information processing speed. Information in the form of an electrical signal processed in such an information-processing appliance requires a displaying device serving as an interface.
Compared with a CRT-type display device, a flat type display device has various advantages such as lighter weight and smaller size. Moreover, the flat type display device is able to realize full colorization and high resolution. The LCD is one of currently available flat-type display devices, which is provided with a liquid crystal display panel including two sheets of substrates formed with electrodes and a liquid crystal layer injected between the two substrates. Images are displayed in such a manner that the quantity of light transmitted is adjusted by applying a voltage to the electrodes of the liquid crystal display panel to rearrange the liquid crystal molecules of the liquid crystal layer.
Generally, in order to precisely display the detailed images on the liquid crystal display panel of the LCD, an image data generated from an external information processing apparatus should be converted into driving signals which are suitable for driving the liquid crystal display panel. The driving signals are applied to the liquid crystal display panel at proper timing.
For embodying such an operation, the LCD requires a process of signal processing upon the image data on a driving printed circuit substrate prior to being applied to the liquid crystal display panel.
In order to allow the LCD to carry out the full-color display, signal lines including gate lines and data lines are densely formed within a certain area of the TFT substrate. Also, a pad formed to be wider than the area occupied by the signal lines is connected to one end of the signal lines.
A medium for transmitting signals are required so as to apply the driving signals generated from the driving printed circuit substrate to the densely formed signal lines at an accurate timing. Chip On Glass (COG), Chip On Film (COF), Flexible Printed Circuit film (FPC) or Tape Carrier Package (TCP) are mainly employed as the medium. One end of the medium is connected to the driving printed circuit substrate while the other end thereof is electrically connected to the pad to be firmly fixed.
An interval between the pad and adjacent pad is too narrow as described above to utilize a method such as a fine welding typically employed for connecting the pad with the medium. For this reason, the pad is electrically and mutually connected with the medium by interposing an Anisotropic Conductive Film (ACF).
The ACF includes an adhesive tape and conductive particles regularly arranged in the adhesive tape. The conductive particle is smaller than several micrometers in diameter. That is, the conductive layer having an adhesive material and conductive particles and a passivation layer form the ACF. The conductive particles serve for applying the signal transmitted via the medium to the liquid crystal display panel via the pad. The conductive particles have one directional orientation in transmitting the signal. In other words, the signal from the medium can be applied to the liquid crystal display panel; on the contrary the signal from the liquid crystal display panel cannot be transmitted to the medium.
Additionally, the ACF is thermally compressed under the state of being interposed between the liquid crystal display panel and medium to be adhesively bonded therewith. The pad of the liquid crystal display panel and the medium are bonded with each other by means of the adhesive material, and further they are firmly attached to each other by a restoring force originated from an elastic deformation of the conductive particles.
FIG. 1
is a plan view for explaining a structure of a conventional pad, and
FIGS. 2A
to
2
D are sectional views showing the manufacturing process of the pad shown in FIG.
1
.
FIGS. 1
to
2
D show a gate pad structure which is extended from a gate line of an LCD. TCP is used as a medium. Referring to
FIGS. 1 and 2A
, a metal such as aluminum (Al) or chrome (Cr) is deposited on a substrate
60
generally formed of an insulating material, and is patterned to form a gate pad
10
. Then, as shown in
FIG. 2B
, a silicon nitride layer is deposited on the entire surface of the substrate
60
formed with the gate pad
10
thereon via a plasma chemical vapor deposition (LPCVD) method, thereby forming a gate insulating layer
20
.
As shown in
FIG. 2C
, an organic resist layer is coated on the entire surface of the gate pad
10
and a peripheral region thereof to form an organic insulating layer
30
. In order to form an opening
11
in the gate insulating layer
20
to expose a portion of the gate pad
10
, a mask
31
is placed over the organic insulating layer
30
. Thereafter, the opening
11
for exposing the gate pad
10
is formed in the organic insulating layer
30
by an exposure and development process. The gate insulating layer
20
underlying the organic insulating layer
30
is also removed together to form the opening
11
that partially exposes the gate pad
10
.
Then, as shown in
FIG. 2D
, a conductive layer
40
is formed along an inner surface of the opening
11
and organic insulating layer
30
at the periphery of the opening
11
. The conductive layer
40
includes a metallic material such as aluminum or a transparent conductive material such as Indium Tin Oxide (ITO) or Indium Zinc Oxide (IZO).
Referring to
FIG. 3
, an anisotropic conductive film
70
includes conductive particles
71
and an adhesive material
72
is placed over the conductive layer
40
formed on the gate pad
10
, and aligned with an output port
81
of a gate-side TCP
80
. Then, a compressing operation is performed, to make an electrical connection between the conductive layer
40
and the output port
81
of the gate-side TCP
80
by means of the conductive particles
71
.
The conductive particle
71
include a first conductive particle
71
a
, a seconds conductive particle
71
b
. The first conductive particle
71
a
is placed in the opening
11
and the seconds conductive particle
71
b
is placed on the surrounding portions of the opening
11
. At this time, the difference in thickness of the second conductive particle
71
b
and the orgarnic insulating layer
30
is not large enough to transfer a sufficient compressing force upon the second conductive particle
71
b
when compressing the second conductive particle
71
b
onto the gate pad
10
. Therefore, the height difference between the organic insulating layer
30
and the gate pad
10
induces a problem that the gate-side TCP
80
is poorly bonded to the gate pad
10
or detached therefrom even after being adhered thereto.
Furthermore, if the gate-side TCP
80
is mistakenly bonded onto the gate pad
10
, the gate-side TCP
80
should be detached from the gate pad
10
, and correctly bonded again thereto. For re-attachment, the substrate is wiped by means of a cotton swab and so on for eliminating foreign materials remaining on the gate pad
10
. The organic insulating layer
30
is, liable to be detached from the gate insulating layer
20
because of weak adhesive strength between them and the step between the organic insulating layer
30
and the gate pad
10
. As a result, the conductive layer
40
formed on the organic insulating layer
30
is detached together with the organic insulating layer
30
and placed between adjacent pads, thereby causing a short between the pads.
However, the organic insulating layer
30
functions to prevent an electrical shor
Cho Won-Gu
Oh Weon-Sik
Yoo Hyeong-Suk
Yoon Ju-Young
Caley Michael H.
Cantor & Colburn LLP
Nguyen Dung T.
Samsung Electronics Co,. Ltd.
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