Anti-fogging coated transparent articles include anti-fog mirrors used in bathrooms or lavatories and anti-fog windows used in openings of vehicles. Known examples of anti-fog films include films containing a water-absorbent resin such as polyvinyl acetal.
Anti-fog films containing a water-absorbent resin have poor strength properties and are susceptible to surface damage, particularly when they have absorbed water. To address this problem, it has conventionally been proposed to add a layer for surface protection to improve the film strength properties. For example, Patent Literature 1 discloses a two-layered anti-fog film including a water-absorbent layer containing a water-absorbent resin and a water-permeable protective layer formed on the water-absorbent layer. The water-absorbent layer contains polyvinyl acetal and a hydrolysate or partial hydrolysate of alkylsilyl isocyanate. The protective layer is formed of a hydrolysate or partial hydrolysate of alkylsilyl isocyanate. Patent Literature 1 specifies for the water-absorbent layer and the protective layer that the number of carbon atoms in the alkyl group of the alkylsilyl isocyanate is 1 or 2 (claims 1 and 3).
For another example, Patent Literature 2 discloses a two-layered anti-fog film including a water-absorbent layer containing a water-absorbent resin and a water-repellent layer formed on the water-absorbent layer. The water-repellent layer is formed using a compound having a methyl group and an isocyanate group (paragraph [0031]).
Patent Literature 3 discloses a single-layer anti-fog film. This anti-fog film contains a water-absorbent resin, a colloidal silica (fine silica particles), and a silica derived from a hydrolysate or partial hydrolysate of silicon alkoxide, at a predetermined ratio. Tetraalkoxysilane is disclosed as the silicon alkoxide. Despite being a single-layer film, this anti-fog film has improved strength properties by virtue of the addition of the inorganic component such as fine silica particles.