To maintain a hydrophilic nature of a front surface for a long time which has not been known in prior art, and which can be restored even in having been lost.

A solution prepared by adding trimethoxymethyl silane after silicasol is addeed to anatase type titansol (having solute concentration of 10wt.%, a nitric acid dispersion type and a pH value of 0.8) having an averaged particle size of 0.01μm and is diluted with ethanol, is applied over the surface of a transparent plastic substrate 1 which has been previously formed on its back surface with a reflective layer 2 and a protecting layer 3, and thereafter, is heated and solidified at a temperature of 100°C in order to form an outer surface layer 4 having a film thickness of 0.1μm. The outer surface layer 4 exhibits a hydrophilic nature due to reaction of titanium oxide.