Conventionally, a hard coat is widely provided to a desired site such as a surface of a molded body made from resin, in order to confer abrasion resistance to a surface of various products similar to that of a glass surface.
One of methods for forming such hard coat, is a method for transferring a hard coat layer.
This is a method comprising using a so-called transfer foil, and there is an advantage that by using a transfer foil comprising a hard coat layer on the substrate, a hard coat with a uniform film thickness can be formed with a relatively simple process to a desired site of various substances. However, there is a problem for a hard coat transfer foil, that when the hardness of the hard coat layer is very high, cracks are generated to the hard coat layer when wrapped in a roll state. There is a transfer foil for hard coat by two-step curing, comprising wrapping around a hard coat layer in a roll state when it is in a semi-cured state, transferring the layer to the adherend, and performing further curing to complete a final hard coat on the adherend (Patent Document 1).
As an alternative method, there is a method comprising coating and drying a resin solution to be a hard coat layer in a later step, to a surface of a thermoplastic resin sheet that has been adjusted to a certain size, to provide a semi-cured resin layer, and subjecting the thermoplastic resin sheet to heat molding such as vacuum molding (Patent Documents 2, 3). The semi-cured resin layer has a hardness of a level that there is no difficulty for handling, and changes its shape by sufficiently following the prescribed shape of molding. A hard coat covering the surface of the molded product is made by completely curing the semi-cured resin layer after semi-curing and molding.
Each of these methods uses a sheet (foil) having a hard coat precursor layer in a semi-cured state on the substrate. However, these sheets had also drawbacks in that it cannot be stored for a long period in a semi-cured state as the semi-cured state is not stable, and that it was necessary to put a release resin film or the like between the sheets in order to avoid adhesion (blocking) of the sheets, when wrapping a long sheet in a roll state.
On the other hand, it is known to use acrylate series resin and the like as UV curable resin for a hard coat film. For example, Patent Document 3 describes a hard coat film comprising meth(acrylic)ester mixture (A), photopolymerization initiator (B), ethylene unsaturated group-containing urethane origomer (C), colloidal silica sol (D), and diluent (E), and that the obtained film has a good pencil hardness, curl and adherence to the substrate.
Moreover, Patent Document 4 describes to use a curable composition comprising (A) a particle made by binding an oxide particle of at least one element selected from the group consisting of silicon, aluminum, zirconium, titanium, zinc, germanium, indium, tin, antimony and cerium, and an organic compound comprising a polymerizable unsaturated group; (B) a compound having a urethane bound and 2 or more polymerizable unsaturated groups in the molecule; and (C) a curable composition comprising a photopolymerization initiator, and describes that a film (layer) having an excellent coating ability, can be formed on the surface of various substrates with a high hardness and high refractive index as well as an excellent abrasion resistance and an excellent adherence between the substrate and layer with low refractive index.
Further, Patent Document 5 describes an ultraviolet ray curable-hard coat resin composition made by compounding (A) a mixture of a hydrolysate of an organosilicon compound and fine particles of a metal oxide, (B) multifunctional acrylate or methacrylate, and (C) a photopolymerization initiator, which bleed to the surface of antistatic agent, decrease of transparency, degradation of humidity resistance and the like can be set within a substantially acceptable range, and can satisfy the functions as a hard coat (abrasion resistance, surface hardness, humidity resistance, resistance to solvents and chemicals, etc.).
However, as hard coat films using these acrylate series resins are inferior to inorganic films in the point of wear resistance, they are improved by adding metal oxide sols. Thus, while the hardness was improved, they had drawbacks in the decrease of transparency and flexibility.
Against this problem, the present inventors had found out that a thin film comprising a polysiloxane composition and an ultraviolet ray curable compound had a significantly high hardness as the surface is mineralized, and thus excellent in abrasion resistance, and also had an excellent adhesion with the adherend (Patent Document 6).    Patent Document 1: Japanese Laid-Open Patent Application No. 2005-206778    Patent Document 2: Japanese Laid-Open Patent Application No. 2004-1350    Patent Document 3: Japanese Laid-Open Patent Application No. 2006-150949    Patent Document 4: Japanese Laid-Open Patent Application No. 2005-272702    Patent Document 5: Japanese Laid-Open Patent Application No. 2001-214092    Patent Document 6: WO2008/069217