Patent ID: 8882280

Claim:
An optical substrate comprising: a tone-adjustment antireflection film which adjusts a reflected color and effects a small change in the reflected color depending on an incident angle; and an antifouling layer formed on the antireflection film in order to minimize fingerprint adhesion, wherein the antireflection film includes at least nine layers, wherein in the antireflection film a D65 white light source is used, and a* and b* values in the CIELAB color space expressing the reflected color of an antireflection film employed meet −5≦a*<5 and −5<b*<5 respectively, wherein: the antireflection film includes nine layers; assuming that λ 0 is a design center wavelength n 1 , n 2 , n 3 , n 4 , n 5 , n 6 , n 7 , n 8 , and n 9 denote the refractive indices of the nine layers at λ 0 beginning with a layer on a side of the antireflection film furthest from a reinforcement layer, and d 1 , d 2 , d 3 , d 4 , d 5 , d 6 , d 7 , d 8 , and d 9 denote the optical film thicknesses of the respective layers beginning with the layer on side of the antireflection film furthest from the reinforcement layer, the antireflection film satisfies conditions below: n2≦1.40, (a) n3=n5=n7=n9>n1=n4=n6=n8>n2, (b) 0.0225λ0≦d1≦0.0525λ0, (c) 0.1453λ0≦d2≦0.3389λ0, (d) 0.0733λ0≦d3≦0.1710λ0, (e) 0.0307λ0=d4≦0.0716λ0, (f) 0.2096λ0≦d4≦0.4892λ0, (g) 0.0315λ0≦d6≦0.0735λ0, (h) 0.0810λ0≦d7≦0.1889λ0, (i) 0.0798λ0≦d8≦0.1863λ0, (j) 0.0258λ0≦d9≦0.0602λ0. (k)