Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified... – Alignment layer of specified composition
Reexamination Certificate
1998-03-04
2002-04-09
Thomas, Alexander S. (Department: 1772)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
Alignment layer of specified composition
C349S124000
Reexamination Certificate
active
06368681
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an image display apparatus employing liquid crystal and a method for producing such an image display apparatus. More specifically, the present invention relates to a liquid crystal alignment film used for a flat display panel employing liquid crystal for displaying images on television (TV) and computers or the like, and a method for producing such a liquid crystal alignment film, and also relates to a liquid crystal display apparatus employing the same and a method for producing such a liquid crystal display apparatus.
BACKGROUND ART
Conventionally, an apparatus used as a color liquid crystal display panel generally includes liquid crystal that is injected between two substrates provided with counter electrodes arranged in a matrix via a liquid crystal alignment film formed by rotary-coating a polyvinyl alcohol or a polyimide solution with a spinner or the like.
For example, the following device was proposed. Thin film transistor (TDF) arrays having pixel electrodes are formed on a first glass substrate beforehand. A plurality of color filters of red, blue and green are formed on a second glass substrate, and common transparent electrodes are further formed thereon. The surfaces provided with the respective electrodes are coated with a polyvinyl alcohol or a polyimide solution with a spinner so as to form films. Then, rubbing is performed so as to form liquid crystal alignment films, and the substrates are opposed and attached to each other via spacers with an arbitrary gap. Thereafter, liquid crystal (twist nematic (TN) or the like) is injected therebetween so as to form a panel structure. Then, polarizing plates are provided on the front and the back of the panel. While the panel is irradiated with back light from the back side, TFTs are operated. In this manner color images are displayed.
However, in the conventional method for producing an alignment film, polyvinyl alcohol or polyimide is dissolved in an organic solvent and the resultant solution is applied by rotary-coating or the like. Then, rubbing is performed with a felt cloth or the like. Therefore, there is a serious problem in that uniformity in the alignment film is poor in surface step portions or for a large area panel (such as a 14 inch display). Moreover, since rubbing is performed, defects are generated in the TFTs, and debris generated by rubbing causes defects in display.
DISCLOSURE OF INVENTION
The present invention was carried out in order to solve the above-mentioned conventional problems, and thus has the object of providing a method for forming an alignment film used in a liquid crystal display panel highly efficiently, uniformly and thinly without performing a rubbing treatment as conventionally performed, and providing a method for producing a display panel employing the same.
A first liquid crystal alignment film of the present invention for achieving the object is characterized in that a silane-based surfactant having linear carbon chains and Si is chemically adsorbed via a resin film sensitive to energy beams for generating functional groups containing active hydrogen by energy beam irradiation formed on a predetermined surface of a substrate, and that the linear carbon chains are aligned in a specific direction.
In the above-mentioned liquid crystal alignment film, a film formed of the surfactant is preferably fixed to an energy beam sensitive resin film via covalent bonds on the surface of the substrate in a striped pattern. Thus, a liquid crystal alignment film having excellent uniaxial alignment can be obtained.
In the above-mentioned liquid crystal alignment film, the fixed film formed of the surfactant is preferably fixed to the energy beam sensitive resin film via a film having siloxane bonds. This is advantageous because peeling resistance, namely adhesiveness is improved.
In the above-mentioned liquid crystal alignment film, the silane-based surfactant is preferably a chlorosilane-based surfactant containing a linear hydrocarbon group and a chlorosilyl group. As the silane-based surfactant, a substance comprising a chlorosilyl group (SiCl), an alkoxysilyl group (SiOA, A represents an alkyl group), or an isocyanate silyl group (SiNCO) at the terminal of the molecule can be used. Above all, when a chlorosilane-based surfactant is used, an alignment film covalently bonded to the substrate via siloxane bonds can be produced easily and efficiently.
In the above-mentioned liquid crystal alignment film, a part of the hydrogen of the linear hydrocarbon group of the chlorosilane-based surfactant is preferably substituted with at least a fluorine atom. This is advantageous because the critical surface energy as the alignment film can be reduced, thereby improving a response performance of liquid crystal.
In the above-mentioned liquid crystal alignment film, a plurality of chlorosilane-based surfactants each having a different molecular length are preferably mixed and used as the chlorosilane-based surfactant containing a linear hydrocarbon group and a chlorosilyl group. Thus, a film having concavities and convexities on the molecular level on its surface can be formed, thus obtaining a liquid crystal alignment film with which the alignment angle (pre-tilt angle) of liquid crystal can be controlled on the molecular level.
A second liquid crystal alignment film of the present invention is a monomolecular film formed on a surface of a substrate provided with desired electrodes. The molecules constituting the film have a desired tilt, and are bonded and fixed to the surface of the substrate at one end while being aligned uniformly in a specific direction.
In the above-mentioned liquid crystal alignment film, the desired tilt of the molecules is preferably formed by fixing the molecules constituting the film to the substrate by covalent bonds, washing the molecules with an organic solvent, and tilting the substrate in a desired direction so as to drain off the solvent.
In the above-mentioned liquid crystal alignment film, the molecules constituting the film preferably contain carbon chains or siloxane bond chains. This is advantageous because the alignment property of the film can be improved.
In the above-mentioned liquid crystal alignment film, a carbon of a part of the carbon chain preferably has an optical activity. This is advantageous because the alignment property of the film can be improved by irradiation of light.
In the above-mentioned liquid crystal alignment film, the molecules constituting the film preferably have Si at both ends. This is advantageous because the film can be bonded to the substrate firmly.
In the above-mentioned liquid crystal alignment film, the molecules constituting the film are preferably formed by mixing a plurality of types of chemisorption molecules each having a different molecular length, and the fixed film preferably has concavities and convexities on the molecular length level. This is advantageous because the tilt angle of liquid crystal can be controlled.
A third liquid crystal alignment film of the present invention is a monomolecular film formed on a surface of a substrate provided with desired electrodes. The molecules constituting the film have carbon chains or siloxane bond chains, and at least a part of the carbon chain or the siloxane bond chain contains at least a functional group for controlling a surface energy of the film. The production of such a liquid crystal alignment film can provide an alignment film that has functions of controlling the critical surface energy of the alignment film and thus controlling the pre-tilt angle of injected liquid crystal, and aligning the liquid crystal in an arbitrary direction, without performing conventional rubbing.
In the above-mentioned liquid crystal alignment film, a plurality of types of silane-based surfactants each having a different critical surface energy are preferably mixed and used as the molecules constituting the film, so as to control the fixed film to have a desired critical surface energy value. This is advantageous because the pre-tilt angle can
Hon Sow-Fun
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P,C,
Thomas Alexander S.
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