Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-04-16
2004-07-20
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S043000
Reexamination Certificate
active
06765641
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device such as a liquid crystal display device which is used, for example, for office automation equipment (e.g., a word processor, a personal computer, or the like) or a television set.
2. Description of the Related Art
FIG. 19
shows a configuration of an active matrix substrate which is a part of a conventional liquid crystal display device.
This liquid crystal display device is of the active matrix type in which the active matrix substrate and a counter substrate are disposed so as to face each other with a display medium made of liquid crystals or the like interposed therebetween. The active matrix substrate includes thin-film transistors (hereinafter, referred to as “TFTs”)
2
serving as switching elements and pixel capacitances
1
disposed in a matrix.
Gate signal lines
3
each serving as a scanning line for controlling the TFTs
2
are connected to a gate electrode of the respective TFTs
2
, thereby driving the TFTs
2
by a signal input thereto. Source signal lines
5
each serving as a signal line for supplying a data signal to the TFTs
2
are connected to a source electrode of the respective TFTs
2
, allowing a video signal or the like to be input therefrom. The gate signal lines
3
and the source signal lines
5
are provided so as to cross each other in the vicinity of the TFTs
2
.
A pixel electrode
6
and one terminal (i.e., an electrode) of the pixel capacitance
1
are connected to a drain electrode of the TFT
2
. The other terminal (i.e., an electrode) of the pixel capacitance
1
is connected to a pixel capacitance line
4
. The pixel capacitance lines
4
are electrically connected to a counter electrode formed on the counter substrate in the completed configuration of the liquid crystal display device.
FIG. 20
is a cross-sectional view illustrating the conventional active matrix substrate.
The active matrix substrate includes a gate electrode
12
, which is a part of the gate signal line
3
, provided on a transparent insulating substrate
11
, and a gate insulating film
13
provided so as to cover the gate electrode
12
. On the gate insulating film
13
, a semiconductor layer
14
is provided so as to overlap the gate electrode
12
. A channel protecting layer
15
is provided above a center portion of the semiconductor layer
14
. Furthermore, n
+
-Si layers
16
a
and
16
b
to be a source electrode and a drain electrode, respectively, are provided so as to cover edge portions of the channel protecting layer
15
and parts of the semiconductor layer
14
and so as to be separated from each other on the channel protecting layer
15
.
An ITO (Indium Tin Oxide) film
9
a
and a metal layer
17
a
to be a source signal line
5
are sequentially provided on a part of the n
+
-Si layer
16
a
. An ITO film
9
b
and a metal layer
17
b
to be a connecting electrode for connecting a drain electrode and a pixel electrode
20
(not shown) are sequentially provided on a part of the n
+
-Si layer
16
b.
A passivation film
18
made of an inorganic thin film is provided on the resultant substrate, and an interlayer insulating film
19
, formed of an organic thin film having a high transparency, is provided thereon so as to cover the TFT
2
, the gate signal line
3
, and the source signal line
5
. The pixel electrode
6
is formed on the interlayer insulating film
19
. The pixel electrode
6
is connected to the n
+
-Si layer
16
b
, i.e., the drain electrode of the TFT
2
, by the ITO film
9
b
which functions as the connecting electrode via a contact hole
7
penetrating through the passivation film
18
and the interlayer insulating film
19
.
However, in the case where the gate insulating film
13
and the passivation film
18
made of the inorganic thin film are present between the transparent insulating substrate
11
and the interlayer insulating film
19
made of the organic thin film having a high transparency as in the above, light reflection occurs due to differences in refractive indexes at the interface of the substrate
11
and the gate insulating film
13
and at the interface of the passivation film
18
and the interlayer insulating film
19
.
As a result of such reflection, there arises a problem of reduced light transmittance.
SUMMARY OF THE INVENTION
A display device of the present invention has a pair of substrates provided so as to face each other with a display medium interposed therebetween, and further includes, on a first substrate of the pair of substrates: switching elements disposed in a matrix; scanning lines and signal lines disposed so as to cross each other; and an interlayer insulating film provided so as to have the switching elements, the scanning lines and the signal lines on one surface thereof and pixel electrodes on the other surface thereof. Each of the pixel electrodes is electrically connected to a drain electrode of one of the switching elements via a contact hole which penetrates through the interlayer insulating film. The interlayer insulating film is made of an organic thin film having a high transparency and covers at least the switching elements, the scanning lines and the signal lines. Furthermore, the interlayer insulating film is provided so as to contact directly with the first substrate in a light-transmitting area which is not shaded at least by the switching elements, the scanning lines and the signal lines.
In one embodiment, the display device further includes: a gate insulating film at least covering a gate electrode of each of the switching elements; and a passivation film, made of an inorganic thin film, at least covering the switching elements. The gate insulating film and the passivation film are provided between the first substrate and the interlayer insulating film in a region excluding the light-transmitting area. The gate insulating film is a first patterned film which is provided to cover both the light-transmitting area and the region excluding the light-transmitting area on the first substrate and then partially removed in the light-transmitting area. The passivation film is a second patterned film which is provided to cover both the light-transmitting area and the region excluding the light-transmitting area on the first substrate and then partially removed in the light-transmitting area.
In another embodiment, the display device further includes a gate insulating film at least covering a gate electrode of each of the switching elements. The gate insulating film is provided between the first substrate and the interlayer insulating film in a region excluding the light-transmitting area. The gate insulating film is a patterned film which is provided to cover both the light-transmitting area and the region excluding the light-transmitting area on the first substrate and then partially removed in the light-transmitting area.
Preferably, a refractive index of the interlayer insulating film is in the range of about 1.5 to about 2.0.
In one embodiment, the display device further includes a gate insulating film provided on the gate electrodes of each of the switching elements and the scanning lines and under the signal lines between the first substrate and the interlayer insulating film in a region excluding the light-transmitting area. The gate insulating film is a first patterned film which is provided to cover both the light-transmitting area and the region excluding the light-transmitting area on the first substrate and then partially removed in the light-transmitting area while retained on the gate electrodes and the scanning lines and under the signal lines.
Preferably, the display device further includes a passivation film made of an inorganic thin film. The passivation film is provided on the switching elements and the scanning lines and under the signal lines between the first substrate and the interlayer insulating film in the region excluding the light-transmitting area. The passivation film is a second patterned film which is provided to cover both the light-tr
Katayama Mikio
Kubo Masumi
Maekawa Kazuhiro
Maruyama Yuko
Narutaki Yozo
Nixon & Vanderhye P.C.
Parker Kenneth
Sharp Kabushiki Kaisha
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