Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2000-05-18
2003-02-11
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C427S352000, C427S353000, C427S162000, C427S553000, C427S379000
Reexamination Certificate
active
06517401
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods of forming monomolecular chemisorption films obtained by chemisorbing adsorbate molecules on a surface of a base material. More particularly, the invention relates to methods of forming monomolecular chemisorption films used for antifouling films, liquid crystal alignment layers, polarizing films, retardation films, conductive films for molecular devices or the like. The invention further relates to methods of manufacturing liquid crystal display devices utilizing such thin films.
BACKGROUND OF THE INVENTION
Monomolecular thin films (also referred to as “monomolecular chemisorption films”) have conventionally been produced by the methods comprising the steps of immersing a base material in a chemisorption solution containing a nonaqueous organic solvent and an adsorbate at a relatively low concentration for a predetermined time, thereafter react the adsorbate with the surface of the base material, and thereafter washing the unadsorbed molecules away from the surface of the base material. In such conventional methods, since the chemisorption solution contains the adsorbate at a low concentration, the adsorbate is not excessively adsorbed to the surface of the base material. Therefore, uniform monomolecular films can be readily obtained. In addition, since the adsorbate is lost little in the step of washing, the adsorbate can be efficiently used, leading to high cost efficiency in production.
However, in such conventional methods, it takes a long time to react the adsorbate with the base material, and therefore the base material needs to be immersed in the solution for a long time, leading to poor production efficiency. For example, in the case where the chemisorption solution contains a silane-based surface active agent (an adsorbate) having a linear hydrocarbon chain group and Si at a concentration of 1% by weight, the base material needs to be immersed in the solution for approximately two hours.
In view of such a drawback in the conventional methods, various attempts to improve the production efficiency have been made, but heretofore no such attempts have been successful in achieving a simple and effective method. For example, by heating the chemisorption solution, it is possible to improve the reactivity and thereby to reduce the time for immersing the base material to a certain extent. However, when the chemisorption solution is heated, such disadvantageous effects are incurred that the solvent is evaporated or boiled in the immersing reaction and that the decomposition or side reaction of the adsorbate molecules is caused, and thus it is difficult to produce good uniform monomolecular chemisorption films. In addition, by heating the solution, the amount of evaporating solvent increases, and this requires a consideration for providing special explosion-proof facilities. Due to such drawbacks, it is generally undesirable to heat the chemisorption solution to a temperature higher than 80° C., but heating the solution up to such a temperature only reduces the reaction time by about 10-20%.
It is, on the other hand, also possible to reduce the time for immersing the base material by increasing the concentration of the adsorbate in the solution. However, the increase of the concentration of the adsorbate induces such a drawback that the adsorbate is excessively attached onto the substrate surface, which results in a difficulty in forming uniform monomolecular films and a poor utilization efficiency of the adsorbate.
DISCLOSURE OF THE INVENTION
In view of the foregoing and other drawbacks in prior art, it is a primary object of the present invention to provide methods of forming monomolecular chemisorption films that are excellent in uniformity and molecular alignment property and usable for liquid crystal alignment layers. More specifically, it is a first object of the present invention to provide methods of forming extremely thin monomolecular films which is formed to have a thickness at the nanometer level within a short production time.
It is a second object of the invention to provide methods of forming such monomolecular films capable of controlling an alignment of liquid crystal molecules in a predetermined direction (for example, liquid crystal alignment layers).
It is a third object of the invention to provide methods of manufacturing liquid crystal display devices utilizing such liquid crystal alignment layers.
In order to accomplish the foregoing and other objects, the present invention provides the following methods:
(1) The present invention provides methods of forming a monomolecular chemisorption film comprising at least the steps of: forming a solution layer on a surface of a base material by contacting the chemisorption solution with the surface of the base material in a dry atmosphere, the chemisorption solution including a silane-based surface active agent and a nonaqueous organic solvent; and chemisorbing molecules of the surface active agent onto the surface of the base material by evaporating the organic solvent contained in the solution layer in the dry atmosphere.
In the above-described method, the chemisorption solution is applied onto the base material sufficiently but not excessively to form the solution layer formed of the chemisorption solution, and thereafter the chemisorption solution is concentrated on the surface of the base material. By employing this method, the chemisorption reaction proceeds in a remarkably efficient manner. Accordingly, a monomolecular thin film can be formed within a short time.
Now, the technical significance of the above-described constitution of the invention is explained below. Ideally, in a monomolecular chemisorption film formed on the surface of the base material, the adsorbate molecules are bonded to the surface of the base material at one end of the molecules, and are arrayed along the surface of the base material in a monolayer-like manner. In order to form such an ideal chemisorption film, the chemical adsorbate molecules need to be bonded sufficiently but not exceedingly to all the possible positions on the surface where the molecules can be adsorbed. For this purpose, it is preferable that the concentration of the chemisorption solution should be made low so that the adsorbate molecules can move freely. However, when the concentration of the solution is low, it takes a long time to adsorb the molecules to all the possible positions, and therefore the production efficiency is poor. Nevertheless, by employing the above-described method, since the solution is concentrated after applied onto the base material, the adsorbing reaction can be completed within a short time even in the case of the solution having a low concentration. In addition, since the solution has a low initial concentration, the affinity of the solution with the base material is good, and a thin, uniform coating layer (solution layer) can be formed on the base material. As a result, excessive use of the chemisorption solution is eliminated and uniform thin films are readily formed. Moreover, the concentration of the adsorbate molecules on the base material gradually increases corresponding to the evaporation of the solvent, resulting in a smooth chemisorption reaction. Consequently, in comparison with the case of the solution having a high initial concentration, it is possible to form a chemisorption film with a higher quality in which unadsorbed molecules remaining on the base material is less, and a density of the adsorbed molecules is higher. According to the experiments by the present inventors, by employing the above-described method, the reaction time was reduced to approximately 1 to 11 minutes, whereas in conventional methods (immersing reaction methods) the time was approximately 1 to 2 hours.
(2) The above-described method (1) may be such a method comprising the steps of: accelerating a chemisorption reaction by evaporating the organic solvent and concentrating a silane-based surface active agent contained in the solution layer; aging to complete the chemisorption reaction for a p
Nomura Takaiki
Ogawa Kazufumi
Ohtake Tadashi
Parkhurst & Wendel L.L.P.
Ramsey Kenneth J.
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