Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-11-24
2001-01-23
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S126000, C349S130000, C349S141000
Reexamination Certificate
active
06177973
ABSTRACT:
BACKGROUND
The present invention relates to a technique of an electrically controlled birefringence(ECB)-in plane switching (IPS) mode liquid crystal display(LCD), and more particularly to the LCD for improving a response speed thereof by treating an alignment film such as the rubbing.
Many study for solving a narrow viewing angle of a twisted Nematic(TN) mode LCD has developed. As one of the researches, a double ECB mode LCD had been produced using a vertical alignment film and a liquid crystal with negative dielectric anisotropy by Fujitsu Co., Ltd in Japan. In the double ECB mode LCD, two domains in which liquid crystal molecules are arranged in a given direction and each domain is symmetrical to each other, thus realizing a wide viewing angle. However, for forming the two domains of the double ECB mode LCD, two-time mask rubbing and optical alignment should be performed, so the manufacturing process for two domains is complicated. In addition, the two-time mask rubbing can result in the destruction of an element underlying the vertical alignment film and further in the difficulty of an application of mass production line for the LCD.
Therefore, the present applicant had been invented a new ECB-IPS mode LCD having a pixel electrode and a counter electrode both formed in a lower substrate and further having a phase compensation film, which was filled in a patent application to Korean Industrial Patent and Trademark Office(KIPO) on May 30, 1997. As shown in
FIG. 2A
, the liquid crystal molecules over the vertical alignment films formed on the entire surface of the lower substrate on which the pixel electrode and the counter electrode are disposed and the entire surface of a upper substrate, form a given tile angle &thgr; with respect to the both substrates when no voltage is applied. The tilt angle &thgr; is about 85 to about 90 degree, and each liquid crystal molecule has a different tilt angle &thgr; and thus all liquid crystal molecules are randomly arranged at the tilt angle range of about 85 to about 90 degree. Accordingly, a random arrangement of the liquid crystal molecules is made at “on”/“off” of the voltage, and one liquid crystal molecule collide against adjacent liquid crystal molecule after the application of voltage, thus slowing down a response speed of the LCD.
SUMMARY
Accordingly, an aim of a present invention is to increase the response speed of the LCD.
In order to accomplish the aim of the present invention, a liquid crystal display(LCD) comprising: a first substrate; a pixel electrode as a first electrode formed on a front surface of the first substrate; a counter electrode as a second electrode, spaced from the first electrode on the front surface of the first substrate; a first vertical alignment film formed on a surface of a resultant in which the first electrode and the second electrode are formed and rubbed in a length direction of the second electrode; a first polarization film disposed on a back surface of the first substrate opposite to the front surface of the first substrate; a second substrate having a surface opposite to the first substrate; a second vertical alignment film formed on the opposite surface of the second substrate and rubbed in a length direction of the second electrode; a liquid crystal layer interposed between the first vertical alignment film and the second vertical alignment film so that all the liquid crystal molecules in the liquid crystal layer have a single uniform tilt angle with respect to the first substrate when no voltage is applied; and a second polarization film formed on a back surface of the second substrate opposite to the opposite surface of the second substrate.
Here, a rubbing direction of the first vertical alignment film and a rubbing direction of the second vertical alignment film form about 0 to about 30 degree from the length of the second electrode toward a right or left direction. The single uniform tilt angle is about 85 to about 90 degree. The liquid crystal molecule has a positive or negative dielectric anisotropy.
The LCD further has a phase compensation film formed between the counter electrode and the second polarization film for making an index of refraction anisotropy isotropic in order to prevent an optical leakage when no voltage is applied.
The vertical alignment film is rubbed so that all the liquid crystal molecules have a single uniform tilt angle over the vertical alignment film, so the collision between the liquid crystal molecules are prevented between the “on” of the voltage and the “off” of the voltage, thus increasing a response speed of the LCD.
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Kim Hyang Yul
Lee Seung Hee
Lee Yun Hee
Park In Cheol
Chowdhury Tarifur R.
Hyundai Electronics Industries Co,. Ltd.
Ladas & Parry
Sikes William L.
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