Stock material or miscellaneous articles – Composite – Of silicon containing
Reexamination Certificate
2001-03-01
2003-02-25
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Composite
Of silicon containing
C428S421000, C556S436000, C556S465000, C556S471000, C556S466000, C556S484000
Reexamination Certificate
active
06524715
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a chemical adsorption material to be chemically adsorbed on a surface of a substrate to form a thin film thereon and to a producing method thereof. More particularly, the present invention relates to a chemical adsorption material used mainly as liquid crystal alignment film coating material for forming a thin film and to a producing method thereof. Also, the present invention relates to an organic thin film formed by use of the thin film forming chemical adsorption material and to a producing method thereof. Further, the present invention relates to a liquid crystal alignment film and to a producing method thereof. Furthermore, the present invention relate to a liquid crystal display using the same and to a producing method thereof and, further particularly, to a liquid crystal alignment film for use in a plane display panel using liquid crystals to display television (TV) picture, computer picture and the like, to a producing method thereof, and to a liquid crystal display device using it.
BACKGROUND ART
In recent years, liquid crystal elements come into wide use rapidly as means for miniaturization of information technology equipment. A liquid crystal alignment film which is the critical component of the liquid crystal elements is subjected to a rubbing process which can be cited as a typical alignment film treatment process. However, the rubbing process has difficulties of deterioration of display quality caused by generation of fine dusts and rubbing lines and others. To avoid these difficulties, rubbingless alignment film treatments, such as an optical alignment film treatment, are now under study.
Known optical alignment film treatments include the process that an alignment film made of polymer, such as polyimide or polyvinyl alcohol, is irradiated with polarized ultraviolet light for alignment film treatment. Another approach was also reported (by Japanese Patent Application No. Hei 8-224,219), in which the optical alignment film treatment is given to the optical alignment film comprising chemical adsorption monomolecular film, as well as to that of polymer such as polyimide. The optical alignment film treatment is performed under the alignment mechanism that admolecules of the film are irradiated with polarized light so as to be re-aligned, so that the liquid crystal molecules are aligned along the polarization direction.
In the case of the alignment film comprising polymer, it has the molecular structure that polymers are complicated densely and irregularly, except its surface part. Because of this, only a part of a surface of the film from which tip portions of the polymer projects out can contribute to the alignment of the liquid crystal molecules. In addition to this, because of uncertainty of the alignment orientation of the side chain, the functional group contributive to the alignment is not always exposed on the surface. Consequently, the part thereof contributive to the alignment of the liquid crystal molecules is obviously smaller in density than that of the monomolecular film, thus suffering the disadvantage that it is difficult to make an adequate control of alignment of the liquid crystals. Also, since the alignment film comprising polymer has large thickness and thus insulative property, it has the problem that transmission of light and electric field to drive the liquid crystal molecules are hindered.
In contrast to this, in the case of the alignment film comprising chemical adsorption monomolecular film, since the functional group contributive to the alignment of the liquid crystal molecules is fully exposed on the surface of the film, adequate control of alignment of the liquid crystals can be obtained. In addition to this, the alignment film of chemical adsorption monomolecular film is in a monomolecular layer form and thus has small thickness, as compared with the alignment film of polymer. Also, since it is chemically adsorbed on the surface of the substrate, it also has excellent adhesion property.
Thus, the conventional alignment film comprising polymer has the problems that adequate control of alignment cannot be obtained and that it has large thickness and thus insulative property. In view of the problems above, there has been developed and provided an alignment film comprising chemical adsorption monomolecular film.
The alignment film comprising chemical adsorption monomolecular film was rather useful for solving the disadvantages mentioned above. However, the admolecules forming the film are merely aligned and arrayed along the polarization direction, so that when the film is heated to high temperature, the alignment stability falls disadvantageously. Consequently, the development is being desired of a useful alignment film of monomolecular film form that is further excellent in thermal stability of alignment.
Incidentally, the conventional liquid crystal display has the structure wherein a pair of substrates, which have transparent electrodes arranged in a matrix form and liquid crystal alignment films formed on the transparent films, are arranged to confront each other, with a given gap therebetween with their liquid crystal alignment films facing inwards, and liquid crystal is sealed in the gap. Now, taking a color liquid crystal display as an example, a typical producing method will be explained below. A polymer membrane is formed on each of a first glass substrate on which pixel electrodes and thin-film transistor (TFT) array are formed and a second glass substrate on which a number of color filters of red, blue and green are formed and common transparent electrodes are further formed thereon. Then, these polymer-coated surfaces of the substrates are subjected to the rubbing to provide alignment characteristic of liquid crystal. Then, the substrates are so arranged that their coated surfaces can face inward and confront each other in the state in which spacers are interposed therebetween and are adhesive bonded around the margins thereof to form an empty cell (a panel structure).
Liquid crystal material, such as twisted nematic liquid crystal, is filled in and tightly sealed in the empty cell, to form the liquid crystal display element. Further, a polarizing plate is arranged on each outside surface of the element and also a backlight is disposed at the outside of the first glass substrate, to thereby produce the liquid crystal display as the optical display element.
In the liquid crystal display thus structured, the TFT of switching elements controls an interelectrode voltage to change the alignment of liquid crystals, so that the transmission of light is switched on and off in a pixel basis to display any desired image. Consequently, the alignment film that controls the alignment of the liquid crystals at the time of no applied voltage bears a significantly important part in exerting an influence directly on the display performance of the device.
Polyimide films have been widely used hitherto as a coating material of the liquid crystal alignment film, in terms of their excellence in affinity to liquid crystal, heat resistance, and adhesion to the substrate. In general, the polyimide film is produced by using either of the following two processes. One is that after liquid solution obtained by polyamic acid of precursor polymer of polyimide being dissolved in organic solvent such as xylene is rotationally applied on to the substrate, that substrate is baked to imidize the polyamic acid, so as to form the polyimide film. Another is that after liquid solution obtained by polyimide itself being dissolved in organic solvent such as DMF (N,N-dimethylformamide), DMAc (dimethylacetamide), butyl cellosolve acetate and N-methyl-2-pyrrolidone is rotationally applied on to the substrate, the solvent is evaporated to form the coating film. The polyimide film thus produced has the following problems, however.
(1) In the process using the polyamic acid of precursor, the baking at high temperature of 250° C. or more is needed for imidization of the polyamic acid. Also, in the process using polyimide its
Nomura Takaiki
Ogawa Kazufumi
Ootake Tadashi
Takebe Takako
Matsushita Electric - Industrial Co., Ltd.
Parkhurst & Wendel L.L.P.
Pyon Harold
Rhee Jane
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