For a surface layer used for a display and the like, (1) those obtained by a method generally referred to as a dry method, i.e., making a dielectric multilayer film in a vapor phase process and realizing a low reflectance with an optical interference effect and (2) those obtained by a method generally referred to as a wet method, i.e., coating a low refractive index material on a substrate film have been used. As a technology which is quite different principally from (1) and (2), (3) it has been known that the low reflectance can be realized by providing a fine structure to the surface (Patent Documents 1 to 10).
In general, such a surface layer has required not only an antireflection performance of light and an improved performance of the light permeability, but also a certain mechanical strength to withstand abrasion and scratches in practical use.
However, for the surface layer having the surface fine structure described in the above (3), the good antireflection performance is obtained while the mechanical strength such as surface scratch resistance is insufficient. Thus, the surface layer easily abrades away and is easily scratched. Therefore, it has not come in practical use yet.
For example, in Patent Documents 1 to 10, materials for such an antireflection film are listed, and a (meth)acrylate compound is described therein to be used as a polymerizable resin. However, the materials listed there are quite usual materials for forming ordinary polymer films, and they are not the materials which are discussed from the aspect of the present invention. Namely, Patent Documents 1 to 10 do not describe the surface layer having the special surface fine structure described in (3), which is made practical for the mechanical strength such as surface scratch resistance by selecting these materials.
Furthermore, the antireflection film having the fine structure on the surface in the above described (3) has the special fine structure on the surface so as to suitably prevent the reflection. Thus, for the materials to be selected for the antireflection film, a special physical property is required. However, what kind of physical property is required has been scarcely known.
Patent Document 1: JP Sho-50-070040-A
Patent Document 2: JP Hei-9-193332-A
Patent Document 3: JP 2003-162205-A
Patent Document 4: JP 2003-215314-A
Patent Document 5: JP 2003-240903-A
Patent Document 6: 2004-004515-A
Patent Document 7: 2004-059820-A
Patent Document 8: 2004-059822-A
Patent Document 9: 2005-010231-A
Patent Document 10: 2005-092099-A