Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-04-16
2001-02-20
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S043000, C349S110000, C349S138000
Reexamination Certificate
active
06191835
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a technique of a liquid crystal display, and more particularly to a thin film transistor liquid crystal display having an improved hue and a simple process thereof and a method for manufacturing the same.
2. Description of the Related Art
In general, a thin film transistor liquid crystal display includes a lower substrate, a thin film transistor, as a switching device, formed on the lower substrate, an upper substrate opposite to the lower substrate, a color filter of red, green and blue formed on the upper substrate and a liquid crystal sealed within a cavity defined by both substrates.
FIG. 1
is a view showing a cross sectional view of the conventional thin film transistor liquid crystal display(TFT LCD).
On a portion of a lower substrate
1
an etch stopper inverse staggered type thin film transistor
15
(E/S inverse staggered TFT) and on the other portion of the lower substrate
1
a pixel electrode
8
is disposed. The pixel electrode is of ITO. A passivation layer
9
for protecting the E/S inverse staggered TFT
15
is arranged on the E/S inverse staggered TFT
15
. The TFT
15
has a gate
2
a
, a source
7
a
and a drain
7
b
. A storage electrode
2
b
on the same plane as the gate
2
a
, the pixel electrode
8
and a insulating layer
3
interposed between the storage electrode
2
b
and the pixel electrode
8
, form a capacitor
17
. On a portion of the upper substrate
11
is disposed a black matrix
12
for preventing a cross talk of the liquid crystal display. The black matrix
12
is formed on a portion of the upper substrate corresponding to the TFT
15
and the capacitor
17
. On another portion of the upper substrate which corresponds to the pixel electrode, the color filter layer
13
of red, green and blue is disposed. A common electrode
14
is arranged on the black matrix
12
and the color filter
13
. The common electrode
14
is of ITO. A numeral
4
indicates an active region, a numeral
5
indicates an etch stopper and a numeral
6
indicates an ohmic resistance contact layer.
In order to manufacture such TFT LCD, in one production line, the TFT
15
is formed on the portion of the lower substrate
1
. During the formation of the TFT
15
before forming the source
7
a
and the drain
7
b
, the pixel electrode
8
is formed on the other portion of the lower substrate
1
. Thereafter, the passivation layer
9
, for protecting the TFT
15
is formed thereon. On the other hand, in another production line, the black matrix
12
is formed on a portion of the upper substrate
11
corresponding to the TFT
15
and the capacitor
17
. The color filter layer
13
is formed on another portion of the upper substrate
11
corresponding to the pixel electrode
8
. Then the common electrode
14
is formed over the resultant in which the black matrix
12
and the color filter
13
are provided.
According to the above described manufacturing method, a process for the passivation layer
9
is independently carried out from a process for the color filter layer
13
. Accordingly, the process for the LCD is considered complicate.
In addition, two production lies are required so as to make the TFT LCD; one line for formation of both the TFT
15
and the passivation layer
9
on the lower substrate
1
and the other line for formation of the color filter layer
13
on the upper substrate
11
. An investment cost on a setting-up of additional production line is much high.
SUMMARY OF THE INVENTION
An object of the present invention is to simplify a manufacturing process of a liquid crystal display.
In a view of a present invention, the liquid crystal display has a first substrate, a switching device formed on a portion of an opposing surface of the first substrate, a color filter layer formed on the entire opposing surface of the first substrate provided with the switching device and a first electrode formed on the color filter layer positioned on the other portion of the opposing surface of the first substrate and electrically connected to the switching device. In addition, the liquid crystal display further includes a second substrate opposite to the first substrate, a black matrix formed on a portion of an opposing surface of the second substrate corresponding to the switching device and a second electrode formed on the entire opposing surface of the second substrate provided with the black matrix. Among the color filter layer a portion over the switching device serves a protection layer of the switching device.
In another view of a present invention, in order to manufacture a liquid crystal display, a first substrate and a second substrate are prepared. The switching device is formed on a portion of an opposing surface of the first substrate. The color filter layer is formed on the entire opposing surface of the first substrate with the switching device. After formation of the color filter layer, a contact hole is made in the color filter layer to expose a portion of the switching device. So as to electrically connect to the switching device and a first electrode, the first electrode is formed on the color filter layer including the contact hole. On the other hand, a black matrix is formed on a portion of an opposing surface of the second substrate corresponding to the switching device and then a second electrode is formed on the entire opposing surface of the second substrate with the black matrix. Here, among the color filter layer, a portion over the switching device is for protecting the switching device.
In a specific case, the first electrode is a pixel electrode, the second electrode is a common electrode, the first substrate is a lower substrate and the second substrate is a upper substrate. The switching device is of an etch stopper inverse staggered type TFT. The thickness of the color filter layer is substantially 1 to 3 &mgr;m in thickness.
A process for a passivation layer, a protection layer of a switching device, is simultaneously carried out with a process for a color filter layer. So, the total process number for LCD is decreased in comparison with the conventional art and then the process for the LCD is more simple. Further, since the switching device and the color filter layer are formed in the same production line, no separate production line for the color filter layer is required. Therefore, we can reduce the investment cost for setting-up the production line.
On the other hand, owing to the color filter layer formed on the lower substrate, an incident light from a backlight is successively transmitted through the color filter layer and the liquid crystal layer and therefore an improvement of the hue can be obtained.
REFERENCES:
patent: 5499124 (1996-03-01), Vu et al.
patent: 5933208 (1999-08-01), Kim
patent: 5943107 (1999-08-01), Kadota et al.
patent: 6008872 (1999-12-01), den Boer et al.
patent: 6118505 (2000-09-01), Nagata et al.
patent: 64-3604 (1989-01-01), None
patent: 3-85529 (1991-04-01), None
patent: 5-72561 (1993-03-01), None
Hyundai Electronics Industries Co,. Ltd.
Jacobson Price Holman & Stern PLLC
Sikes William L.
Ton Toan
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