Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-04-20
2004-02-10
Chawdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S156000, C349S157000
Reexamination Certificate
active
06690445
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display apparatus provided with a support spacer for holding a cell gap for a liquid crystal layer.
2. Description of the Related Art
Various kinds of liquid crystal display apparatuses using thin-film transistors (TFTs) are known in accordance with forms. For one of the forms, a liquid crystal display apparatus using an inverted stagger type thin-film transistor is exemplified. The liquid crystal display apparatus will be described referring to the liquid crystal display apparatus using the inverted stagger type thin-film transistor.
When the cell gap for a liquid crystal layer is formed between transparent substrates, spacers are used. By the spacers, the uniformity of the cell gap can be improved in the liquid crystal display apparatus with the large size substrates.
FIG. 1
shows a concept of the spacer in a conventional example of the liquid crystal display apparatus. In
FIG. 1
, support spacers
500
c
and
500
d
are used. The supporting spacers
500
c
and
500
d
are located in regions corresponding to light shielding layers (black matrix)
12
. A color filter (color layer)
13
is arranged between the light shielding layers
12
in a lateral direction. A transparent substrate
14
is located above the color filter
13
and the light shielding layers
12
.
FIG. 2
is a schematic cross sectional view of an in-phase switching type liquid crystal display apparatus in a first conventional example. A display cell
501
is composed of a polarizing plate
17
and an electric conducting layer
16
formed on the front surface of a transparent substrate
14
, a color filter
13
and flattening films or light shielding layers
12
formed on the back surface of the transparent substrate
14
and the supporting spacers
500
c
and
500
d
extending from the light shielding layers
12
. The display cell
501
is composed of a passivation film
22
, an interlayer insulating film
10
, a gate electrode
3
and a common electrode
4
formed on the front surface of a transparent substrate
9
, and a polarizing plate
18
formed on the back surface of the transparent substrate
9
. The supporting spacers
500
c
and
500
d
are adhered to the light shielding layers
12
and the passivation film
22
. The adhesion of the supporting spacer to the light shielding layer
12
on the side of the transparent substrate
14
is higher than that of the supporting spacer to the passivation film
22
on the side of the transparent substrate
9
. Consequently, when an external pressure is applied to the display cell
501
, the supporting spacers
500
c
and
500
d
are moved from specified positions on the side of the passivation film
22
because of the external pressure. The movement of the supporting spacers
500
c
and
500
d
induces color irregularity.
FIG. 3
is a plan view of the display cell of a second conventional example of the in-phase switching type liquid crystal display apparatus. A display cell
502
is composed of an amorphous silicon film
1
, a pixel electrode
2
, a gate electrode
3
, a common electrode
4
, data line
5
, source electrode
6
, a drain electrode
7
, and a supporting spacer
500
.
FIG. 4
is a cross sectional view of the display cell
502
in a region of the supporting spacer
500
along the line X-X′ of FIG.
3
. In
FIG. 4
, the upper substrate section of the display cell is composed of a polarizing plate
17
and an electric conducting layer
16
formed on the front surface of a transparent substrate
14
, and a black matrix layer
12
, a color layer (color filter)
13
, a flattening film
15
, and an orientation film
11
formed on the back surface of the transparent substrate
14
. A part of the flattening film
15
functions as the supporting spacer
500
. The surface of the supporting spacer
500
is covered by the orientation film
11
. In
FIG. 4
, the lower substrate section of the display cell
500
is composed of an orientation film
11
, a passivation film
22
, an interlayer insulating film
10
and a gate electrode
3
formed on the front surface of a transparent substrate
9
, and a polarizing plate
18
formed on the back surface of the transparent substrate
9
. A liquid crystal layer
20
is formed in the cell gap supported by the supporting spacer
500
. The supporting spacer
500
has the low adhesion on the side of the lower substrate section of the display cell
500
. Accordingly, when the display cell is pressed, the supporting spacer
500
may be moved. If the supporting spacer
500
moves, color irregularity is caused.
FIG. 5
is a plan view of a display cell in a third conventional example of an in-phase switching type liquid crystal display apparatus. A display cell
503
is composed of an amorphous silicon film
1
, a pixel electrode
2
, a gate electrode
3
, a common electrode
4
, a data line
5
, a source electrode
6
, a drain electrode
7
, and a supporting spacer
500
. In the display cell
503
, the supporting spacer
500
is arranged on the gate electrode
1
.
FIG. 6
is a cross sectional view of the display cell
503
in a region of the supporting spacer
500
along the line Y-Y′ in FIG.
5
. In
FIG. 6
, the upper substrate section of the display cell is composed of a polarizing plate
17
and an electric conducting layer
16
formed on the front surface of a transparent substrate
14
, and a black matrix layer
12
, a color layer (color filter)
13
, a flattening film
15
, and an orientation film
11
formed on the back surface of the transparent substrate
14
. A part of the flattening film
15
functions as the supporting spacer
500
. On the other hand, the lower substrate section of the display cell
503
is composed of the orientation film
11
, a passivation film
22
, an interlayer insulating film
10
and a gate electrode
3
formed on the front surface of a transparent substrate
9
, and a polarizing plate
18
formed on the back surface of the transparent substrate
9
. The passivation film
22
is formed to have a concave section. The supporting spacer
500
is loaded in the concave section. The liquid crystal layer
20
is formed in the cell gap formed by the supporting spacer
500
.
Because the supporting spacer
500
is loaded on the concave section, the resistance against the movement in the lateral direction is higher than in the supporting spacer shown in
FIGS. 3 and 4
. However, since the depth of the concave section is extremely shallow, the improvement of the strength of a great extent cannot be expected. Consequently, when the display cell is externally pressed, the supporting spacer
500
may be moved. If the supporting spacer
500
moves, color irregularities result.
FIG. 7
shows a plan view of the display cell of a fourth conventional example of the in-phase switching type liquid crystal display apparatus. The display cell
504
is composed of an amorphous silicon film
1
, a pixel electrode
2
, a gate electrode
3
, a common electrode
4
, a data line
5
, a source electrode
6
, a drain electrode
7
, and supporting spacers
500
a
and
500
b.
In the display cell
504
, the supporting spacers
500
a
and
500
b
are located on the data lines
5
.
FIG. 8
is a cross sectional view of the display cell
504
in the region of the supporting spacers
500
a
and
500
b
along the line Z-Z′ in FIG.
7
. In
FIG. 8
, the upper substrate section of the display cell
504
is composed of a polarizing plate
17
, an electric conducting layer
16
formed on the front surface of a transparent substrate
14
, and a black matrix layer
12
, a color layer (color filter)
13
, a flattening film
15
, and an orientation film
11
formed on the back surface of the transparent substrate
14
. A part of the flattening film
15
is formed to have the supporting spacers
500
a
and
500
b.
In
FIG. 8
, the lower substrate section of the display cell
504
is composed of an orientation film
11
, s passivation film
22
, data lines
5
and
5
′, pixel electrodes
2
, an interlayer in
Chawdhury Tarifur R.
Choate Hall & Stewart
NEC LCD Technologies Ltd.
Qi Mike
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