Article with antifogging film and process for producing same

Details Article with antifogging film and process for producing same Article with antifogging film and process for producing same

2000-11-17

2002-07-16

Nakarani, D. S. (Department: 1773)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

Physical dimension specified

C427S163400, C427S164000, C427S165000, C427S407200, C428S436000, C428S437000, C428S442000, C428S447000, C428S448000, C428S451000, C428S522000, C428S524000, C428S912200

Reexamination Certificate

active

06420020

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an article with an antifogging film, which is useful for windows, mirrors and the like in various fields such as architectural, industrial and automotive ones, and a process for producing the article.
In recent years, there have been proposals of forming photocatalytic films on the substrate surface for providing hydrophilicity and antifogging property.
Japanese Patent Laid-open Publication JP-A-5-253544 discloses a process for producing a plate-like member with deodorizing function by applying a glaze to a substrate and then by spraying an anatase-type TiO
2
powder to the glaze layer.
JP-A-7-232080, which corresponds to U.S. Pat. Nos. 6,027,797 and 5,853,866, discloses a multifunctional material with photocatalytic function, prepared by forming a binder layer on a substrate and then by forming a photocatalytic layer of photocatalytic particles on the binder layer.
JP-A-9-59042 discloses a transparent substrate with an antifogging coating containing photocatalytic titania particles.
JP-A-52-101680 discloses an antifogging agent containing polyacrylic acid, surfactant and a solvent (water and/or alcohol).
Japanese Patent Examined Publication JP-B-5-67330, which corresponds to JP-A-1-38103, discloses a hydrophilic porous film and a process for producing the same. This film is made of a hydrophobic polymer. The external surface and the pore surfaces of the film are coated with a coating of a polyvinyl alcohol/vinyl acetate copolymer and then with a coating of a hydrophilic polymer.
JP-A-10-212471 discloses an antifogging agent containing polyvinyl alcohol, tetramethoxysilane, and hydrochloric acid as a catalyst for polycondensation of these compounds.
JP-A-11-84102 discloses an antifogging coating film and an optical article with this film. This antifogging coating film has (1) a water-absorbing film formed on a substrate and (2) a porous film formed on the water-absorbing film.
JP-A-5-51471 discloses a laminate prepared by forming a curable coating film on a substrate. At least a surface layer portion of the substrate is made of a polymer having —P═N— skeleton.
JP-A-6-157794 discloses an antifogging agent containing a polyvinyl acetal resin.
JP-A-6-158031 discloses a first antifogging article prepared by forming on a substrate an antifogging layer of a polyvinyl acetal resin having a degree of acetalization of 2-40 mol %. This publication further discloses a second antifogging article prepared by forming a water-soluble resin layer on a substrate and then the antifogging layer.
JP-A-9-136374 discloses an antifogging resin article prepared by forming on a resin substrate a first layer containing hydrophilic inorganic fine particles and a coupling agent and then by forming on the first layer a second layer made of a hydrophilic resin and/or a surfactant.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an antifogging article which is superior in antifogging property and abrasion resistance.
It is another object of the present invention to provide a process for producing such antifogging article.
According to a first aspect of the present invention, there is provided a first antifogging article comprising a substrate; and an antifogging film covering said substrate. This antifogging film comprises a water-absorbing organic polymer and an inorganic substance and has a water repellent finishing on a surface of said antifogging film.
According to the first aspect of the present invention, there is provided a first process for producing an antifogging article, comprising:
preparing a first coating solution by dissolving a water-absorbing organic polymer and a silicon-containing compound in a solvent;
applying said first coating solution to a substrate, thereby forming thereon a first precursory film;
drying said first precursory film into an antifogging film;
applying a second coating solution to said antifogging film, thereby forming a second precursory film on said antifogging film; and
drying said second precursory film into a water repellent film.
According to a second aspect of the present invention, there is provided a second antifogging article comprising:
a substrate;
a water-absorbing, antifogging film covering said substrate, said antifogging film comprising:
(a) a polyvinyl acetal resin having a degree of acetalization of not greater than 10 mol %; and
(b) a hydrolysate or partial hydrolysate of an alkylsilylisocyanate represented by the general formula R
2
n
SiR
1
4−n
. where R
1
is an alkyl group having a carbon atom number of 1 or 2, R
2
is an isocyanate group, and n is 1 or 2; and
a water-permeable, protective film covering said antifogging film.
According to the second aspect of the present invention, there is provided a second process for producing an antifogging article, comprising:
(a) providing a substrate;
(b) preparing a first coating liquid by adding a polyvinyl acetal resin and an alkylsilylisocyanate to a solvent, said polyvinyl acetal resin having a degree of acetalization of not greater than 10 mol %, said alkylsilylisocyanate being represented by the general formula R
2
n
SiR
1
4−n
where R
1
is an alkyl group having a carbon atom number of 1 or 2, R
2
is an isocyanate group, and n is 1 or 2;
(c) applying said first coating liquid to said substrate, thereby forming a first precursory film on said substrate;
(d) drying said first precursory film into a water-absorbing, antifogging film;
(e) applying a second coating liquid containing an alkylsilylisocyanate to said antifogging film, said alkylsilylisocyanate being represented by the general formula R
2
n
SiR
1
4−n
where R
1
is an alkyl group having a carbon atom number of 1 or 2, R
2
is an isocyanate group, and n is 1 or 2, thereby forming a second precursory film on said antifogging film; and
(f) drying said second precursory film into a water-permeable, protective film.
The first and second antifogging articles can respectively be produced by the first and second processes.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The above-mentioned first antifogging article of the invention is superior for a long time in antifogging property, durability (particularly abrasion resistance) and transparency, has no image distortion, no defects such as cracks, nor damage to the color tone of its substrate. The first antifogging article can efficiently be produced by the first process with a low production cost and a high productivity. The first antifogging article can be used for various indoor and outdoor glass articles such as architectural window panes, bathroom mirrors, and automotive door mirror and window panes.
The antifogging film of the first antifogging article is superior in antifogging property due to the inclusion of a water-absorbing organic polymer therein. When water drops fall on the antifogging film, they are absorbed by this film until the maximum of the water-absorbing capacity of the organic polymer. With this, it is possible to maintain the antifogging property of this film. Furthermore, even if it exceeds the maximum of the water-absorbing capacity, a uniform water film can be formed on the antifogging film. With this, it is also possible to maintain the antifogging property of the film. However, a film made of only a water-absorbing organic polymer not according to the invention is inferior in water resistance and mechanical strength and can not be expected to have a superior chemical durability. In contrast, according to the first aspect of the present invention, the antifogging film contains an inorganic substance (amorphous silica) in addition to a water-absorbing organic polymer. With this, the antifogging film is unexpectedly substantially improved in water resistance, chemical durability and adhesion to the substrate. Furthermore, according to the first aspect of the invention, it is preferable that the antifogging film is coated with a water repellent film as a protective film. With this, the surface of the antifogging article is lowered in free energy (i.e., considerably lowe

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