Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-01-22
2001-08-07
Dudek, James A. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S111000, C349S141000
Reexamination Certificate
active
06271903
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device in which alignment of liquid crystal can be controlled by applying an electric field along the substrate face, and relates to a structure in which in addition to a wider angle of view, a higher aperture ratio can be achieved.
2. Description of the Prior Art
Recent TN mode liquid crystal display devices have a problem of high dependency on the angle of view, since the visibility in the vertical direction is inferior in spite of excellent visibility in the lateral direction. The applicant of this application claimed liquid crystal display devices having a structure by which the above problem can be solved in Japanese Patent Application Nos. 7-1579, 7-306276, and the like.
According to the techniques described in such Patent Applications, instead of providing liquid crystal driving electrodes for each of the upper and lower substrates sandwiching the liquid crystal layer, two types of linear electrodes
12
and
13
having different polarity from each other are provided only on the lower substrate
11
at a distance from each other, as is shown in
FIG. 10
, and no electrode is formed on the upper substrate
10
shown in the upper side of
FIG. 10
so that liquid crystal molecules
36
are aligned in the direction of the transverse electric field (in the substrate-face direction) which is generated between the linear electrodes
12
and
13
by applying a voltage.
In more detail, as is shown in
FIG. 9
, the linear electrodes
12
are connected by a base line
14
to form a comb-shaped electrode
16
, the linear electrodes
13
are connected by a base line
15
to form a comb-shaped electrode
17
, the comb-shaped electrodes
16
and
17
are engaged with each other such that the linear electrodes
12
and
13
are alternately positioned without being in contact with each other, and a switching element
19
and a power source
18
are connected to the base lines
14
and
15
.
As is shown in
FIG. 11A
, an alignment film is formed on the liquid-crystal side of the upper substrate
10
to align the liquid crystal molecules
36
in the &bgr; direction, another alignment film is formed on the liquid-crystal side of the lower substrate
11
to align the liquid crystal molecules
36
in the &ggr; direction parallel to the &bgr; direction, and a polarizing plate polarizing light in the &bgr; direction shown in
FIG. 11A and a
polarizing plate polarizing light in the &agr; direction are provided for the substrates
10
and
11
, respectively.
According to the above structure, the liquid crystal molecules
36
are homogeneously aligned in the same direction when no voltage is applied between the linear electrodes
12
and
13
, as is shown in
FIGS. 11A and 11B
. In this state, a light beam transmitted through the lower substrate
11
is polarized in the &agr; direction by the polarizing plate, passes through a layer of the liquid crystal molecules
36
, and then reaches the polarizing plate of the upper substrate
10
, which polarizing plate has a polarization direction &bgr; different from the direction &agr;. The light beam is thereby shaded by the polarizing plate of the upper substrate
10
and is unable to pass through the liquid crystal display device, thereby rendering the liquid crystal display device in a dark state.
When a voltage is applied between the linear electrodes
12
and
13
, among the liquid crystal molecules
36
, those adjacent to the lower substrate
11
are aligned perpendicular to the longitudinal direction of the linear electrodes
12
and
13
. The nearer a liquid crystal molecule is located to the lower substrate
11
, the more strongly this phenomenon is observed. In other words, lines of electric force perpendicular to the longitudinal direction of the linear electrodes
12
and
13
are generated by the transverse electric field (an electric field in the substrate-face direction) produced by the linear electrodes
12
and
13
. Thus, the major axes of the liquid crystal molecules
36
aligned in the &ggr; direction by the alignment film formed on the lower substrate
11
are altered to the &agr; direction, i. e., perpendicular to the &ggr; direction, by the force of the electric field which is stronger than that of the alignment film, as is shown in FIG.
12
A.
Therefore, twisted alignment is achieved in the liquid crystal molecules
36
by applying a voltage between the linear electrodes
12
and
13
, as is shown in
FIGS. 12A and 12B
. In this state, the polarization direction of the polarized light beams, which have been transmitted through the lower substrate
11
and polarized in the &agr; direction, is converted by the twisted liquid crystal molecules
36
so that the polarized light beams are allowed to pass through the upper substrate
10
having a polarizing plate whose polarization direction &bgr; is different from the &agr; direction. The liquid crystal display device thereby exhibits a bright state.
FIGS. 13 and 14
are an enlarged fragmentary view of the structure of an actual active-matrix liquid crystal driving circuit to which a liquid crystal display device equipped with the linear electrodes
12
and
13
is applied.
The structure shown in
FIGS. 13 and 14
corresponds to only one pixel. On a transparent substrate
20
such as a glass substrate, a gate electrode
21
and linear common electrodes
22
both made of a conductive layer are separately provided parallel to each other. A gate insulating film
24
is formed to cover these electrodes. A thin-film transistor T is formed such that a source electrode
27
and a drain electrode
28
are formed on a portion of the gate insulating film
24
corresponding to the gate electrode
21
, and a semiconductor film
26
is provided on a portion of the gate insulating film
24
between the source electrode
27
and the drain electrode
28
. A linear pixel electrode
29
made of a conductive layer is formed on a portion of the gate insulating film
24
between the common electrodes
22
.
FIG. 13
is a plan view of these electrode. Gate lines
30
and signal lines
31
are formed on the transparent substrate
20
according to a matrix pattern. The gate electrode
21
which is a part of the gate line
30
is provided at a corner of each pixel region formed by the gate lines
30
and the signal lines
31
. Via a capacitor electrode
33
, the drain electrode
28
above the gate electrode
21
is connected to the pixel electrode
29
which is provided between the common electrodes
22
in parallel with the signal line
31
and the common electrodes
22
.
The ends, near the gate line
30
, of the common electrodes
22
are connected by a connecting line
34
, provided in the pixel region in parallel with the gate line
30
, and the other ends of the common electrodes
22
are connected by a common line
35
, provided in the pixel region in parallel with the gate line
30
. The common line
35
is provided over numerous pixel regions in parallel with the gate line
30
so as to apply a common voltage to the common electrodes
22
provided for each pixel region.
As is shown in
FIG. 14
, on the surface, opposing the substrate
20
, of the substrate
37
, a light shielding matrix
38
is formed with an opening
38
a
corresponding to a pixel region, and a color filter
39
is also provided to cover the opening
38
a.
In the above structure shown in
FIGS. 13 and 14
, lines of electric force generated by a transverse electric field can be obtained along the directions of the arrows a shown in FIG.
14
. Thus, the liquid crystal molecules
36
are aligned by the transverse electric field in a manner shown in FIG.
14
. The dark and bright states are thereby switchable by controlling the alignment of the liquid crystal molecules
36
similarly to the above description made with reference to
FIGS. 11 and 12
.
However, according to liquid crystal display devices having the above structure, the aperture ratio is disadvantageously reduced in spite of a wide angle of view. In other words, al
Shin Hyunho
Sung Chae Gee
Takashina Kouji
Dudek James A.
LG. Philips LCD Co. Ltd.
Long Aldridge & Norman
LandOfFree
Liquid crystal display device having a light shielding matrix does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Liquid crystal display device having a light shielding matrix, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display device having a light shielding matrix will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2447145