Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-06-09
2002-09-24
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S139000
Reexamination Certificate
active
06456352
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, in particular, to an orientation division type liquid crystal display device of which the manufacturing process is simplified.
2. Description of the Related Art
Conventional liquid crystal display devices are widely known in which a twisted nematic system or a vertical orientation system are adopted. However, liquid crystal display devices of those systems have the problem that the tint differs according to the viewing angle, since the orientation direction of the liquid crystal molecules of the intermediate layer of the liquid crystal layer at the time of voltage application is uniform within pixels and, therefore as a method to improve this viewing angle characteristic, an orientation division type liquid crystal display device is introduced. Here, the orientation division type liquid crystal display device is a technology for gaining broad sight angle characteristics by dividing one pixel into a plurality of regions and by making the orientation direction of the liquid crystal molecules of the intermediate layer in each region different, so that the visual characteristic of each region compensate for each other.
FIG. 1
is a sectional view showing an orientation division type liquid crystal display device according to a prior art (conventional example 1: for example Japanese Laid-open Patent publication No. Hei-10-20323) and
FIG. 2
is a plan view of the same.
As shown in
FIG. 1
, a switching element comprises a gate electrode
403
, a gate insulation film
404
, a semiconductor layer
405
, a drain electrode
406
and a source electrode
407
. The switching element and a pixel electrode
408
which is electrically connected to the source electrode
407
are arranged on a substrate
401
. An opening
409
is provided to the pixel electrode
408
which becomes the border of the regions for orientation division. Under the opening
409
, a control electrode
411
is provided. The numeral
424
shows a passivation film and the
425
shows a color layer. Also, the numerals
426
and
427
show optical films.
On the opposite substrate
402
, a common electrode
412
is provided. This common electrode
412
doesn't need an opening. Orientation films
413
and
414
are formed on the respective substrate
401
and
402
, as the top layers of the respective substrates, and the orientation films
413
and
414
sandwich liquid crystal molecules
415
. By applying a voltage onto the control electrode
411
, a diagonal electric field is generated across the edge of the opening
409
and the edge of pixel electrode
408
. The orientation direction of the liquid crystal molecules
415
is divided by the diagonal electric field of which the direction of the generation differs with the border of the opening
409
.
The orientation direction of the liquid crystal molecules as shown in
FIG. 1
exhibits the orientation direction of the liquid crystal molecules
415
existing mainly in the central layer of the liquid crystal molecule layer. At this time by carrying out ultraviolet irradiation, a small amount of ultraviolet curing monomer or oligomer, which has been added to the liquid crystal molecules
415
in advance, is polymerized to become a polymer
416
.
The polymer
416
follows the orientation direction of the liquid crystal molecules
415
at the time of ultraviolet irradiation so as to secure its form even in the case when no voltage is applied to the control electrode
411
. In addition, since the polymer
416
is small in quantity, the liquid crystal molecules
415
are regulated only in the rising direction at the time of voltage application while the gradient changes according to the applied voltage. Accordingly, it is not necessary to apply a voltage to the control electrode
411
at the time of driving and the display can be made performed by only applying voltage to the pixel electrode
408
, with the result in that application only to the pixel electrode
408
makes display possible.
In the plan view as shown in
FIG. 2
, an example is disclosed in which the structure is formed in a Y shape configured by the opening
503
and the control electrode
501
arranged side by side. When carrying out a predetermined rubbing and when performing the process of the above described orientation division, a TN orientation divided into four pieces is formed by this configuration.
In an example with respect to the control electrode in this disclosed technology there are descriptions in which the control electrode is formed in the same layer as the gate electrode, in which a different voltage from that of the pixel part can be applied to from the outside, and in which a voltage is applied to the control electrode at the time when the device is manufactured. However, there are no descriptions with respect to its wiring method and how to draw out terminals.
Technologies where the control electrode is added in order to carry out an orientation control of the liquid crystal molecules such as the technology described in the Japanese Laid-open Patent publication No.Hei-10-20323 of the conventional example 1 are also disclosed in the Japanese Laid-open Patent publication No.Hei-7-13164, the Japanese Laid-open Patent publication No.Hei-7-199190, the Japanese Laid-open Patent publication No.Hei-7-230097 and the Japanese Laid-open Patent publication No.Hei-8-76125. The particular points of difference between these technologies and the technology of conventional example 1 is that a predetermined voltage is applied not at the time when the device is manufactured but at the time the display is driven.
FIG. 3
is a plan view showing a technology disclosed in the Japanese Laid-open Patent publication No.Hei-7-199190 (conventional example 2).
Referring to
FIG. 3
, the control electrode
601
(referred to as an orientation control electrode in the above described publication) has a structure which surrounds the periphery of the pixel electrode
602
so as to control the orientation direction of the liquid crystal molecules by generating a specific diagonal electrical field between each edge of the pixel electrode
602
and the control electrode
601
. There are mainly two types of settings with respect to the positional relationships of each electrode and an applied voltage. The first setting is an electrode arrangement where the control electrode is arranged as the lower layer of the pixel electrode and an X type opening
603
is arranged in the common electrode on the opposite substrate. In this structure, the control electrode is connected in parallel to the input terminal of the common electrode and is set to be at the same potential as the common electrode. The second setting is an example where the X type electrode opening
603
is arranged in the pixel electrode
602
so that the control electrode
601
is arranged as a layer above the pixel electrode.
Regarding the applied voltage settings in this structure, there is a description in which the effective potential difference between the control electrode and the common electrode is set to be larger than the effective potential difference between the display electrode and the common electrode without any description relating to its wiring or the way the terminal are drawn out. That is to say, there is no description with respect to the connection structure in the case where a different potential independent of the pixel electrode or the common electrode is applied to the control electrode. With respect to this point the situation is the same as that in the Japanese Laid-open Patent publication No.Hei-7-13164 and the Japanese Laid-open Patent publication No.Hei-8-76125.
Next, referring to
FIG. 4
, a technology described in the Japanese Laid-open Patent publication No.Hiei-7-230097 (conventional example 3) is explained. Referring to
FIG. 4
the control electrode
701
arranged in each pixel is connected to the gate wiring
704
. By this structure, the same potential as that of the gate wiring
704
and the gate electrode
70
Hirai Yoshihiko
Ishii Toshiya
Kobayashi Kazumi
Matsuyama Hiroaki
Murai Hideya
Foley & Lardner
NEC Corporation
Nguyen Hoan
Ton Toan
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