Abstract: A curable resin composition for a hard coat layer capable of forming a hard coat layer having high hardness even with thin thickness and/or excellent in abrasion resistance and hardness, and a hard coat film using the curable resin composition.

Abstract: The present invention is to provide an optical sheet having excellent abrasion resistance and hardness, and a method for producing the same. The object of the present invention was accomplished by an optical sheet in which a hard coat layer is provided on one surface of a substrate, wherein the hard coat layer comprises a cured product of a curable resin composition for a hard coat layer, which composition comprising reactive, irregularly shaped silica fine particles and a binder component, and wherein at least part of the irregularly shaped silica fine particles have a specific three-dimensional configuration and are present on an interface on the side opposite to the substrate side of the hard coat layer.

Abstract: The main object of the present invention is to provide an optical sheet having excellent abrasion resistance and hardness, and a method for producing the same. The present invention provides an optical sheet in which a hard coat layer is provided on one surface of a substrate, wherein the hard coat layer comprises a cured product of a curable resin composition for a hard coat layer, which comprises reactive inorganic fine particles and a binder component, and wherein fine protrusions are provided on an interface on the side opposite to the substrate side of the hard coat layer, in which the minimum angle of each of the fine protrusions making angles with a virtual plane that is parallel to the hard coat layer is an acute angle.

Abstract: A curable resin composition for a hard coat layer capable of forming a hard coat layer having high hardness even with thin thickness and/or excellent in abrasion resistance and hardness, and a hard coat film using the curable resin composition are provided. A hard coat film in which a hard coat layer is provided on one side of a transparent substrate film, wherein the hard coat layer comprises a matrix in a crosslinked state and an aggregate in which 3 to 100 silica fine particles having an average primary particle diameter of 1 to 100 nm are aggregated, and wherein the aggregate is cross-linked to the matrix, and an irregularly shaped silica fine particle constituted with 3 to 20 silica fine particles having an average primary particle diameter of 1 to 100 nm connected to each other by inorganic chemical bonding is contained as a part of the aggregates. The hard coat layer further contains a silica fine particle preferably.

Abstract: A propanol sol of silica having a specific surface area of 25 to 550 m.sup.2 /g, the sol having an SiO.sub.2 concentration of 10 to 50% by weight of SiO.sub.2 and a residual content of a medium containing 7.5% by weight or less of water based on the SiO.sub.2 content and 90% by weight or more of propanol, is prepared by an improved process involving replacing the aqueous medium in an acidic aqueous sol of silica containing 5 to 50% by weight of SiO.sub.2 and a medium having a water content of 15% by weight or more with propanol by an atmospheric distillation method in which a concentration of 5 to 50% by weight of SiO.sub.2 in the sol and 1 to 85% by weight of methanol in the medium in the sol is maintained when the medium in the sol during the replacement contains 15 to 0.5% by weight of water.

Abstract: Binders for manufacture of precision casting molds are provided, which are highly stable and are advantageous in that these may impart a high strength to the green molds as obtained by forming an accumulative refractory coat layer on a water-soluble pattern and then taking off the pattern from the coat layer, that no interlayer cleavage occurs in the accumulative coat layer when the pattern is taken off in the formation of the green mold, that the binders may impart a high strength to fired molds, that the castings as obtained by the use of the present fired molds are free from the surface roughness and other surface faults and that the dimension accuracy of the castings is not deteriorated at all by the use of the present binders.The binders of the present invention are characterized by containing the following components (a), (b) and (c) and optionally (d):(a) an organo-silicasol capable of providing 5-50 parts by weight of SiO.sub.

Abstract: A binder for manufacture of a precision casting mold comprising a transparent solution containing an alkyl orthosilicate or an alkyl polysilicate having a polymerization degree of 2 to 10, and an amino-alkoxide of a metal selected from a group consisting of titanium, zirconium, tin and aluminum or a mixture thereof in the mol ratio (Si/N) of 0.01 to 1.0 calculated in terms of the silicon atom contained in the silicate and the basic nitrogen atom contained in the amino-alkoxide. This binder is excellent in preservation stability and workability and does not dissolve the surface of a water-soluble pattern.