Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1998-04-29
2001-09-04
Malinowski, Walter J. (Department: 2164)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06285427
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an optical aligning apparatus of liquid crystals (LCs), and more particularly to an apparatus and a method for optically aligning LCs in a desired direction through control of the polarization direction of light.
To fabricate liquid crystal displays (LCDs) having uniform brightness and high contrast ratio, it should align LC molecules injected between upper and lower glass substrates in a constant direction. It is in general LCDs that LC molecules has been aligned in a constant direction through alignment films which are respectively formed on opposite surfaces of the upper and lower glass substrates. There have been used a conventional rubbing method and an UV alignment method as LC alignment techniques using alignment films. The conventional rubbing method which now is the most widely used as alignment techniques, aligns LCs with linear grooves formed in alignment films in a constant direction. In rubbing methods, polyimide as alignment films is coated on a transparent glass substrate of LCD and rubbed with a rubbing cloth in a constant direction, resulting in inducing physical defects on the surface of the polyimide to form linear grooves.
The UV alignment technique which utilizes polarized light differently from the mechanical rubbing technique, forms polyvinyl resin on a transparent glass substrate of an LCD and irradiates UV light to it, resulting in aligning LCs.
The conventional rubbing method has difficulties in adjusting a pretilt angle and achieving the reproducibility of process. Because the conventional rubbing method forms and rubs with a rubbing cloth polyimide on the surface of the glass substrate where TFT arrays or color filter arrays are arranged, it causes electrical and mechanical damages to the underlying TFT arrays and reduces the life time of LCDs due to particles and static electricity generated in rubbing. The UV alignment methods have difficulties in controlling residuum in polymerization by irradiation of UV light and fabricating uniform alignment films.
In Korean Patent Application No. 96-42514, there is disclosed an alignment method of “Method for aligning polymeric film, LC alignment method using the same, LC cell and fabrication thereof” to solve the problems of the conventional rubbing method and the UV alignment method.
To briefly speaking, the polymeric film alignment method forms the polymeric film doped with the photosensitive compound on a transparent glass substrate and irradiates the circularly polarized light to the polymeric film, resulting in tiltly aligning photosensitive compound with respect to the substrate surface. By using the polymeric alignment film, it is able to tiltly align LCs injected between two glass substrates with tilt alignment of the photosensitive compound contained within the polymeric alignment film. In the polymeric film alignment method, azo dye doped-polymeric alignment film was used for the photosensitive compound and circularly polarized beam was used for the irradiating light to the polymeric film instead of linearly polarized beam.
In order to align LCs using the above polymeric alignment film, there is a urgent need for an optical apparatus that polarizes beam from the light source into circularly polarized beam or elliptically polarized beam and irradiates the polarized light to the polymeric alignment film.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an apparatus and method for optically aligning polymeric alignment films by controlling polarization direction of beam irradiated to the polymeric alignment films.
An another object of the present invention is to provide an apparatus and method for optically aligning LCs without rubbing.
A further object of the present invention is to provide an optical alignment apparatus and method capable of obtaining alignment films of excellent reproducibility and uniformity.
A still another object of the present invention is to provide an optical alignment apparatus and method capable of readily fabricating alignment films on LCD substrates of large area.
A still another object of the present invention is to provide an optical alignment apparatus and method capable of readily fabricating alignment films having a multi-domain structure with separate control of optical paths.
A still another object of the present invention is to provide an optical alignment apparatus and method capable of simply fabricating alignment films having a multi-domain structure on LCD substrates of large area.
According to the present invention, there is provided an optical alignment apparatus for aligning an alignment film on one sided surface of a LCD substrate, comprising: a light unit for generating a parallel beam; a beam-splitter for beam-splitting the parallel beam; and a beam regulator for changing the beam spilt from the beam-splitter into a polarized beam and irradiating the polarized beam to the LCD substrate.
In the optical alignment apparatus, the light unit includes a light source for generating a beam such as an Ar laser; and a parallel beam generating mean for changing the beam from the light source into the parallel beam such as a collimator. The LCD substrate is any one of a TFT substrate, color filter, or a LCD module. The polarized beam from the beam regulator of a polarizer irradiated to the LCD substrate is any one of a circularly polarized beam or an elliptically polarized beam. The alignment film is comprised of methyl orange-contained polyvinylalcohol.
The optical alignment apparatus may be any one of a substrate-rotated type that the light unit, the beam-splitter and the beam regulator are fixed and the LCD substrate is rotated on the light unit, beam-splitter and beam regulator or a substrate-fixed type that the LCD substrate is fixed and the light unit, beam-splitter and beam regulator are rotated on the LCD substrate.
The optical alignment apparatus further comprises an alignment mask arranged between the LCD substrate and the beam modulator, for selectively providing the polarized beam from the beam regulator to form multi domains. The alignment mask has a plurality of windows and parts of a plurality of windows are open with the domain number.
According to the present invention, there is provided an optical alignment apparatus for aligning an alignment film having multi domain on a LCD substrate, comprising: a light unit for generating a parallel beam; a beam-splitter for beam-splitting the parallel beam; a polarizer for polarizing the beam split from the beam-splitter into a polarized beam and irradiating the polarized beam to the alignment film on the LCD substrate; and an alignment mask arranged between the polarizer and the LCD substrate, for selectively irradiating the polarized beam to the LCD substrate.
According to the present invention, there is provided an optical alignment apparatus for aligning alignment films formed on one-sided surface of a plurality of LCD substrates, comprising: a light unit for generating a parallel beam; a plurality of beam-splitters for beam-splitting the parallel beam, respectively; and a plurality of polarizers for polarizing the beams split from the respective beam-splitters into polarized beams, respectively; wherein the alignment films on one-sided surface of the LCD substrates are simultaneously optically aligned.
According to the present invention, there is provided an optical alignment apparatus for aligning front alignment films and rear alignment films formed on front and rear surfaces of a plurality of LCD substrates, comprising: a light unit for generating a first parallel beam; a front alignment optical system for polarizing the first parallel beam received from the light unit into a first plurality of polarized beams having the same polarization direction, respectively and irradiating the plurality of polarized beams to the front alignment films on the plurality of LCD substrates; a beam reflection system for reflecting the first parallel beam to generate a second parallel beam which travels in the opposite direction to the first
Choi Sang Un
Lee Si Hyoung
Hyundai Electronics Industries Co,. Ltd.
Malinowski Walter J.
Selitto Behr & Kim
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