Coating apparatus – With heat exchange – drying – or non-coating gas or vapor... – With housing surrounding or engaging coating means
Reexamination Certificate
1999-04-19
2001-02-06
Cameron, Erma (Department: 1762)
Coating apparatus
With heat exchange, drying, or non-coating gas or vapor...
With housing surrounding or engaging coating means
C118S244000, C118S249000, C118S262000, C118S326000
Reexamination Certificate
active
06183558
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for producing a molecular film in which silane-based compounds are covalently bonded to a substrate surface via siloxane bonds.
BACKGROUND OF THE INVENTION
A method for producing a molecular film by coating the surface of a glass or the like having active hydrogen atoms on its surface with chlorosilane-based compounds having chlorosilyl groups at the end of the molecules comprising alkyl groups or fluoroalkyl groups so as to form covalent bonds by a dehydrochlorination reaction already has been proposed.
In the prior art, a substrate is dipped into a coating solution containing chlorosilane-based compounds to form a molecular film, as disclosed in Japanese Laid-Open Patent Publication No. 1-70917 and EP 0492545A. Another example of the proposed methods is to contact the chlorosilane-based compounds in a vapor phase onto the surface of a substrate for effecting a reaction.
However, the conventional dip method is excellent in the case where a film is to be formed not on a flat plate, but instead on a rough surface, because the liquid reacts along the rough surface, so that a film can be formed along the surface of the unusual shaped object. On the other hand, this method requires a large amount of the liquid for dipping and a troublesome operation of putting in and withdrawing the substrate, which takes a long time. Consequently, this method adversely results in a high cost. Furthermore, since the chlorosilane-based compounds readily react with water, the pot life is short. In addition, in the dip method, the chlorosilane-based compounds are in contact with the entire substrate and a reaction is effected all over the surface of the substrate. Therefore, this method is disadvantageous in the case where a prescribed portion is not desired to be coated with the chlorosilane-based compounds.
Furthermore, a method of contacting the chlorosilane-based compound in a vapor phase with the surface of the substrate for effecting a reaction is disadvantageous in that it is difficult to form a molecular film uniformly.
SUMMARY OF THE INVENTION
A method for forming a molecular film of the present invention includes the steps of: coating a surface of a substrate having active hydrogen atoms on its surface with a coating solution containing a silane-based compound having at least one reactive group selected from the group consisting of a chloro group, an alkoxy group and an isocyanate group; and effecting an elimination reaction between the active hydrogen atoms on the surface of the substrate and the reactive groups of the silane-based compounds, thereby covalently bonding the silane-based compounds to the surface of the substrate. The substrate is supplied to a chamber in which an atmosphere is maintained at a low water vapor density, the surface of the substrate is coated with a coating solution containing the silane-based compound and a solvent by using a transfer element. An elimination reaction is effected between the active hydrogen atoms and the reactive groups of the silane-based compounds. Thereafter, any coating solution containing unreacted silane-based compounds that remains after coating is removed inside or outside the chamber.
In the above mentioned step, in the case where a chlorosilane compound is used as the silane-based compound, a dehydrochlorination reaction is effected as the elimination reaction. In the case where an alkoxysilane compound is used, a dealcoholization reaction is effected.
In one embodiment according to the above-mentioned method of the present invention, the transfer element comprises an inner chamber enclosing at least a portion where a coating solution is present in the transfer element. In this manner, hydrolysis of the silane-based compound in the coating solution can be prevented.
In another embodiment according to the above-mentioned method of the present invention, air curtains for shutting off outside air are provided at an inlet and an outlet of the chamber through which the substrate is introduced and withdrawn, respectively. In this manner, hydrolysis of the silane-based compound in the coating solution can further be prevented.
In still another embodiment according to the above-mentioned method of the present invention, the transfer element performs at least the steps of applying the coating solution onto a support, and transferring the solution applied to the support to the substrate on which a -film is to be formed. In this manner, the substrate can be uniformly coated with the coating solution.
In yet another embodiment according to the above-mentioned method of the present invention, the transfer element is a roller coating element. This is most inexpensive. Furthermore, this method makes it possible to deal with a wide substrate having, for example, 1 to 10 m.
In another embodiment according to the above-mentioned method of the present invention, the silane-based compound comprises an alkyl group or a fluoroalkyl group. In particular, it is preferable to comprise an fluoroalkyl group, because a water-repelling property, an oil-repelling property and an antifouling property are improved.
In still another embodiment according to the above-mentioned method of the present invention, the solvent contains no active hydrogen atoms. This is preferable because a solvent having active hydrogen atoms reacts with the silane-based compound.
In yet another embodiment according to the above-mentioned method of the present invention, the solvent containing no active hydrogen atoms is at least one selected from the group consisting of a hydrocarbon compound, a siloxane-based compound and hydrocarbon halide.
In another embodiment according to the above-mentioned method of the present invention, the mixing ratio of the silane-based compound to the solvent in the coating solution is such that the silane-based compound is present at an amount of 0.05 to 20% by weight, and the kinematic viscosity of the coating solution is 0.5 to 5000 cst (at 25° C.).
In still another embodiment according to the above-mentioned method of the present invention, the substrate is a glass sheet, and a face other than a face that is to be coated with the coating solution is masked with a resin film prior to coating. This is preferable because masking perfectly protects the surface which is not to be coated, although the surface which is not to be coated hardly reacts with the silane-based compound.
According to another aspect of the present invention, an apparatus for forming a molecular film includes a chamber including an element for transporting a substrate from an inlet to an outlet, a transfer element for coating a surface of the substrate with a coating solution containing silane-based compounds and a solvent, and an element for maintaining the atmosphere in the chamber at a low water vapor density. The apparatus further includes an element for removing any remaining coating solution containing unreacted silane-based compounds after the process of coating inside or outside the chamber.
In one embodiment according to the above-mentioned apparatus of the present invention further includes an inner chamber enclosing at least a portion where a coating solution is present in the transfer element.
In another embodiment according to the above-mentioned apparatus of the present invention, air curtains for shutting off outside air are provided at the inlet and the outlet of the chamber through which the substrate is introduced and withdrawn, respectively.
In still another embodiment according to the above-mentioned apparatus of the present invention, the element for maintaining the atmosphere at a low water vapor density is an element for introducing a gas having a water vapor density in the range from 0 to 0.0076 kg/m
3
.
In yet another embodiment according to the above-mentioned apparatus of the present invention, the transfer element performs at least the steps of applying the coating solution onto a support, and transferring the solution applied to the support to the substrate on which a film is to
Mino Norihisa
Nakagawa Tohru
Nomura Takaiki
Ogawa Kazufumi
Otake Tadashi
Cameron Erma
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
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