Stock material or miscellaneous articles – Structurally defined web or sheet – Physical dimension specified
Patent
1991-12-24
1993-12-28
Ryan, Patrick J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Physical dimension specified
428409, 4284111, 1562737, 156247, B32B 900
Patent
active
052738124
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a non-fogging sheet and its production. More particularly, it concerns a non-fogging sheet whose surface is in good condition and which has excellent durability in retaining fogging-preventive property over an extended period of time and its production.
BACKGROUND ART
When automotive windows and side mirrors, bathroom mirrors and windows, etc. are exposed to moisture, their surfaces become cloud and so require frequent wiping, which is inconvenient. Accordingly, various measures are being taken to impart non-fogging property to the surfaces of such articles.
Heretofore, non-fogging layers designed to impart non-fogging to the surfaces of articles have typically included:
(i) layers caused to exhibit fogging-preventiveness by incorporating surface active agents in resins by kneading,
(ii) layers to which such inorganic salts as colloidal silica and phosphites are added to extend their non-fogging life, and
(iii) layers whose surfaces are made hydrophilic by modification of polymers such as saponification of acetyl cellulose.
However, a problem with the layers (i) and (ii) is that their non-fogging life is short due to the exudation of the surfactants, and the layers (iii) have low film strength during wetting so that when laid out, there are apt to be damaged and become degraded in terms of non-fogging.
In order to solve the above described problems of the prior art, we have already proposed a non-fogging sheet including a backing film and a non-fogging layer, characterized in that the non-fogging layer is obtained by exposure of a polymer and a hydrophilic monomer to electron beams for their crosslinking (e.g., Japanese Patent Laid-Open (Kokai) Publication Nos. 63-273668, 63-251401, 63-258905, 63-258904 and 63-278840).
Incidentally, non-fogging sheets including relatively thick, non-fogging layers (hydrophilic films) have recently been in great demand due to requirement for non-fogging to be much more improved and retained over a much longer period of time. However, it has now been found that when it is intended to form thicker non-fogging layers with a solvent-containing coating solution, not only do solvent residues pose another problem, but the resulting non-fogging layers suffer surface roughening as well, thus making them unsuitable for non-fogging sheets to be applied over mirrors or windowpanes.
DISCLOSURE OF THE INVENTION
Therefore, it is an object of this invention to provide a non-fogging sheet including a thick hydrophilic film so as to retain non-fogging property over a long period and a method for producing the same.
With the above-mentioned object in mind, we have made study after study and have found as a result that it is possible to obtain a thick hydrophilic film whose surface is in good condition by applying on a backing or support film a hydrophilic film-forming composition comprising specific components and having a specific viscosity, in the form of a non-solvent type of coating solution, by means of a specific process and crosslinking it by exposure to ionizing radiation.
More particularly, the present invention provides a method for producing a thick film type of non-fogging sheet of 30 .mu.m or more in thickness, characterized by comprising the steps of:
preparing a solvent-free composition comprising (a) a polymer, (b) a hydrophilic monomer, and (c) a surface active agent and having a viscosity of 50,000 cP,
applying said composition on a backing film without recourse to any solvent, and
crosslinking the thus coated composition by exposure to ionizing radiations, thereby forming a hydrophilic film of 30 .mu.m or more in thickness.
In a preferable mode of carrying out this invention, in carrying out the coating of the backing film with the above described composition and the forming of the hydrophilic film:
the backing film and the laminating film are prepared;
both films are placed one upon the other between a pair of rolls;
the above-mentioned composition is fed and carried under pressure in between the two films, thereby fo
REFERENCES:
patent: 4470858 (1984-09-01), McMaster
patent: 4605574 (1986-08-01), Yonehara
patent: 5037668 (1991-08-01), Nagy
R. Takiguchi et al., "Anti-Fogging Sheet", Patent Abstracts of Japan, JP-A-63 278 840 Nov. 16, 1988.
Takiguchi, Chemical Abstracts, vol. 110, No. 22, 194270w May 29, 1989.
Doi Tomio
Oguchi Kiyoshi
Takekoh Osamu
Ueda Kenji
Yamamoto Masahiro
Dai Nippon Insatsu Kabushiki Kaisha
Jewik Patrick R.
Ryan Patrick J.
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