Compositions – Liquid crystal compositions – Containing nonchiral aligning agents
Patent
1998-07-16
1999-12-14
Wu, Shean C.
Compositions
Liquid crystal compositions
Containing nonchiral aligning agents
349123, 349134, 349135, 349136, 428 12, C09K 1956, G02F 11337
Patent
active
060012773
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a liquid-crystal alignment film, a treatment process for the liquid-crystal alignment film, a liquid-crystal sandwiched panel, a liquid-crystal display device, process for fabricating the liquid-crystal display device, and a material for the liquid-crystal alignment film.
BACKGROUND ART
Liquid-crystal display devices are conventionally constituted of a pair of transparent electrode substrates provided opposite to each other at a certain distance, a liquid-crystal alignment film of polyimide or the like coming into contact on each side with liquid crystal, and a liquid crystal hermetically sealed between the electrode substrates. One liquid-crystal display device has a large number of pixels, and images are displayed by utilizing changes in the direction of alignment of liquid-crystal molecules at the pixel portions, the changes being caused upon application of a voltage to the liquid-crystal layer through transparent electrodes. In recent years, liquid-crystal display devices have become available that incorporate switching devices such as thin-film transistors (TFT) on the electrode substrates at the pixel portions. These are known as active matrix type liquid-crystal display devices. The active matrix type liquid-crystal display devices commonly employ a twisted nematic (TN) type liquid-crystal display system in which the alignment direction of liquid-crystal molecules is twisted by about 90 degrees from one electrode substrate toward the other electrode substrate at the time the voltage is not applied across the electrodes. In the liquid-crystal display devices of the TN type liquid-crystal display system, the application of a voltage across the electrodes causes liquid-crystal molecules to incline to make it possible to perform gradational display. However, since this inclination of liquid-crystal molecules has a directionality, a visual angle dependence comes into question such that display colors or contrast ratios vary depending on the direction in which liquid-crystal display devices are viewed.
Some methods for improving this visual angle dependence to broaden the visual angle are disclosed as a pixel division method in which display electrodes constituting one pixel are divided and the voltage applied thereto is changed for each electrode (Japanese Patent Application Laid-open No. 2-12) and an alignment division method in which the insides of pixels are divided to change pretilt angles (Japanese Patent Application Laid-open No. 62-159119) or to change the alignment direction of liquid-crystal molecules (Japanese Patent Application Laid-open No. 63-106624), for each region.
In liquid-crystal display devices, the liquid-crystal alignment film formed on an electrode substrate on the side coming into contact with the liquid crystal has the function to align the liquid-crystal molecules in a certain direction on the film surface. For this purpose, treatment called rubbing is prevalent. Rubbing is a process in which a high-molecular film of polyimide or the like formed on the substrate is rubbed with a cloth covered with a large number of fibers like velvet to thereby furnish the film with the ability to cause liquid-crystal alignment, and is a simple and inexpensive process.
As liquid-crystal alignment control processes other than the rubbing, proposed are an oblique deposition process making use of an obliquely deposited film of SiO or the like (Japanese Patent Application Laid-open No. 56-66826, etc.), a photolithographic process in which irregularities are formed in gratings on the surface of an alignment film by a process such as photolithography (Japanese Patent Application Laid-open No. 60-60624, etc.), an LB film process in which high-molecular chains are aligned in the draw-up direction when built up on the substrate (Japanese Patent Application Laid-open No. 62-195622, etc.), an ion irradiation process in which ions are obliquely shed (Japanese Patent Application Laid-open No. 3-83017, etc.), a high-velocity fluid jet process in which a fluid is o
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Fukuchi Iwao
Honda Yutaka
Ichimura Kunihiro
Johar Perminder Singh
Miyadera Nobuo
Hitachi Chemical Company Ltd.
Wu Shean C.
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