Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-10-04
2003-02-18
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S146000
Reexamination Certificate
active
06522379
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a liquid crystal display element, a substrate for the liquid crystal display element, a liquid crystal display, a method for fabricating the liquid crystal display element, and a method for driving the liquid crystal display element, which have a display capability of a high-speed response and a wide viewing angle. More particularly, the present invention relates to a liquid crystal display element, a substrate for the liquid crystal display element, a liquid crystal display, a method for fabricating the liquid crystal display element, and a method for driving the liquid crystal display element, which are of an optically self-compensated birefringence mode cell type and facilitate spray to bend transition.
BACKGROUND OF THE INVENTION
With advance of multimedia technologies, image information has greatly occupied a position in multimedia. In recent years, a liquid crystal display with high contrast and a wide viewing angle has been developed and put to practical use, with development of liquid crystal technologies. Now, the liquid crystal display is equal to a CRT (Cathode Ray Tube) display in performance.
However, in the current liquid crystal display, an image is blurred due to image retention because of a low response speed in display of a moving image. In this respect, the current liquid crystal display is inferior to the CRT display.
In the past, many attempts have been made to provide a high-speed responsive liquid crystal display. While various liquid crystal display systems of the high-speed response are arranged by Wu et al. (C. S. Wu and S. T. Wu, SPIE, 1665, 250 (1992)), a system and method that realizes a response characteristic required for display of a moving image is limited.
Specifically, in the current NTSC (National Television Standard Committee) system, it is required that a liquid crystal follow a video signal in one frame (16.7 msec). While the current liquid crystal display has satisfactorily high-speed responsiveness between white and black values, it has responsiveness as slow as not less than 100 msec in a response between gray scales in multiple gray scale display. In particular, the response between gray scales in an area where a driving voltage is low is noticeably slow.
Currently, as potential liquid crystal displays having high-speed responsiveness suitable for display of the moving image, there are an OCB (Optically Compensated Birefringence) mode liquid crystal display element, a ferroelectric liquid crystal display element, and an antiferroelectric liquid crystal display element.
In actuality, however, the ferroelectric liquid crystal display element and the antiferroelectric liquid crystal display element having a layer structure have many problems associated with their practical use: low shock resistance, a limited range of available temperatures, high temperature dependency of property, and so forth. Hence, the OCB mode liquid crystal display element using a nematic liquid crystal is considered to be promising as the liquid crystal display element suitable for display of the moving image.
The OCB mode liquid crystal display element is a display system, the responsiveness of which was demonstrated by J. P. Bos in 1983. Thereafter, it was demonstrated that combination of the OCB mode liquid crystal display element and a film retardation film brought about a display with a wider viewing angle and a high-speed responsiveness, and the OCB mode liquid crystal display element has been studied and developed actively.
Referring to
FIG. 14
, the OCB mode liquid crystal display element comprises a glass substrate
1
on which a transparent electrode
2
is formed, a glass substrate
8
on which a transparent electrode
7
is formed, and a liquid crystal layer
4
disposed between the substrates
1
and
8
. Alignment layers
3
,
6
are formed on the electrodes
2
and
7
, respectively, and have been subjected to alignment treatment to orient liquid crystal molecules in parallel with one another and in the same direction. Polarizers
13
and
16
are provided in cross nicol on the outsides of the substrates
1
and
8
, respectively. A retardation film
17
is interposed between the polarizer
13
and the substrate
1
and a retardation film
18
is interposed between the polarizer
16
and the substrate
8
.
A liquid crystal cell so structured is characterized in that bend orientation or bend orientation including twist orientation is induced in a central portion of the cell by application of a voltage and the retardation films
17
and
18
are provided for driving a low voltage and enlarging a viewing angle. The cell has a capability of a high-speed response in a medium gray scale display area and a wide viewing angle characteristic.
In a normal state, the OCB mode liquid crystal display element is operated at a voltage at which a liquid crystal in a liquid crystal panel maintain the bend orientation. Below a given voltage, since the spray orientation state is more stable than the bend orientation state, transition to the spray orientation takes place. This transition is irreversible. A pixel with the spray orientation is thereafter left on the liquid crystal display element as a display defect (luminescent spot), which impedes its normal display operation.
In the OCB mode, an initialization process for transitioning from an initial spray orientation state
4
a
to a bend orientation state
4
b
by application of a voltage is essential.
However, the application of the voltage at approximately several volts requires some minutes for the initialization process, which is one of the problems with the OCB mode. Accordingly, there is a need for a liquid crystal display element with a high transition speed in which the bend orientation is easily formed by applying a voltage at several volts.
Japanese Patent Application Publication No. 11-7018 discloses techniques for high-speed transition from the spray orientation to the bend orientation (hereinafter referred to as “spray to bend transition”) in the OCB liquid crystal display mode. The techniques are a technique for adding a chiral agent to a liquid crystal, a technique for uniformly forming twist over the entire surface of a liquid crystal panel at an angle of 180 degrees, and a technique for uniformly forming twist over the entire surface of the liquid crystal panel at an angle of 10 degrees. However, these techniques are not useful in achieving the high-speed spray to bend transition. When the spray to bend transition unreliably takes place and thereby an area of the spray orientation is locally left, the area becomes a luminescent spot, which looks like a spot defect.
SUMMARY OF THE INVENTION
The present invention is directed to solving aforesaid problems and an object of the present invention is to provide a liquid crystal display element, a substrate for the liquid crystal display element, a liquid crystal display, a method for fabricating the liquid crystal display element, and a method for driving the liquid crystal display element, which are capable of high-speed and reliable transition of spray orientation to bend orientation.
To solve the aforesaid problem, the inventors observed the behavior of the spray to bend transition. The observation result is that a nucleus of the bend orientation is generated from a specific portion and is grown. After intensive study, the inventors discovered that a twist orientation locally formed becomes a nucleus, from which bend transition occurs.
A first aspect of the present invention is based on this knowledge. According to a first aspect of the present invention, there is provided a liquid crystal display element comprising at least one substrate and a liquid crystal layer, wherein a different orientation direction area of an orientation direction locally different from an orientation direction of the other area is present on the liquid crystal layer. More specifically, the liquid crystal display element comprises a pair of substrates and a liquid crystal layer, wherein the pair of substrates have been
Hattori Katsuji
Ishihara Shoichi
Kobayashi Jun'ichi
Nakao Kenji
Takubo Yoneharu
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
Rude Timothy
LandOfFree
Liquid crystal display element with zigzag data or scan... 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 element with zigzag data or scan..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display element with zigzag data or scan... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3145309