A lens film with small warpage even when a transparent base is thin is provided. Pole prisms made of a hardening resin are arranged along the extending direction on a transparent base made of a flexible material. The transparent base has a depression according to a valley between the pole prisms adjacent to each other. The pole prism has a sloping face extending to an inner wall of the depression. The transparent base is in contact with the valley. A layer not functioning as a prism, that is, a so-called skirt layer does not exist between the transparent base and the pole prisms.
1. An optical sheet having pole prisms made of a hardening resin arranged along an extending direction on a transparent base made of a flexible material, wherein
the transparent base is adjacent to a valley between the pole prisms adjacent to each other and has a depression corresponding to the valley.
2. The optical sheet according to claim 1 , wherein the pole prisms have a sloping face extending to an inner wall of the depression.
3. The optical sheet according to claim 1 , wherein the transparent base has a convex curved face between the valleys adjacent to each other.
4. The optical sheet according to claim 1 , wherein the depression has a depth of about 10% or less of a thickness of the transparent base.
5. The optical sheet according to claim 1 , wherein the depression has a depth of 4.31 μm or less.
6. An optical sheet having pole prisms made of a hardening resin arranged along an extending direction on a transparent base made of a flexible material, wherein
the transparent base has a depression corresponding to a valley of the pole prisms, and
where a depth of the valley is D 1 and a thickness of the transparent base is D 2 , D 1 and D 2 satisfy the following relation:
0.3 ≦D 1 /D 2.
7. The optical sheet according to claim 6 , wherein the thickness of the transparent base D 2 is 50 μm or less.
8. The optical sheet according to claim 6 , wherein a height of the optical sheet is 65.3 μm or less.
9. An optical sheet having pole prisms made of a hardening resin arranged along an extending direction on a transparent base made of a flexible material, wherein
the transparent base is adjacent to a valley of the pole prisms and
where a thickness of the transparent base is D 2 , a height of the pole prism is D 3 and a height of the optical sheet is H, D 2 , D 3 and H satisfy the following relation:
H≦65.2 μm,
0.3 ≦D 3 /D 2.