Mold, process for producing mold, and process for producing sheet

1. A large area alumina mold having a microscopic pattern, the mold prepared by a process comprising steps of:

preparing a pre-mold by polishing an aluminum plate free from a rolling mark or by forming an aluminum film on a substrate surface;

forming a first oxide film by subjecting surface aluminum of the pre-mold to a first anodic oxidation for a time adjusted to provide said first oxide film with a thickness of 10 μm or less;

removing the first oxide film so as to leave regular pore originating points on a surface of remaining pre-mold aluminum;

forming pores from the originating points by subjecting the surface of remaining pre-mold aluminum to a second anodic oxidation forming a second oxide film;

removing a part of the second oxide film so as to enlarge pore diameter; and

repeating the second anodic oxidation and the pore diameter enlargement so as to form regularly arranged tapered pores decreasing in diameter from a top surface thereof,

wherein relative distances between adjacent pores of the alumina mold are not longer than a wavelength of visible light.

2. The large area mold according to claim 1 , wherein the alumina mold comprises pre-mold aluminum remaining beneath an alumina surface.

3. The large area mold according to claim 2 , wherein a height or depth of a crystal grain boundary of the remaining aluminum is 300 nm or less.

4. The large area mold according to claim 3 , wherein the crystal grain boundary height or depth is determined over an average of 10 bumps arbitrarily selected in a 10-mm square observation area of the mold.

5. The large area mold according to claim 2 , wherein a height or depth of a crystal grain boundary of the remaining aluminum is 250 nm or less.

6. The large area mold according to claim 2 , wherein a height or depth of a crystal grain boundary of the remaining aluminum is 180 nm or less.

7. The large area mold according to claim 1 , wherein a standard deviation of respective barycentric distances between an arbitrary pore and 6 pores adjacent thereto is 6.0 to 12.0.

8. The large area mold according to claim 1 , wherein a standard deviation of respective barycentric distances between an arbitrary pore and 6 pores adjacent thereto is 6.0 to 9.6.

9. The large area mold according to claim 1 , wherein a standard deviation of respective barycentric distances between an arbitrary pore and 6 pores adjacent thereto is 7.5 to 9.6.

10. The large area mold according to claim 1 , wherein the pre-mold is an aluminum rod.

11. The large area mold according to claim 10 , wherein the alumina mold is a roll mold.

12. The large area mold according to claim 10 , wherein aluminum purity of the pre-mold is 99.5% or higher.

13. The large area mold according to claim 1 , wherein aluminum purity of the pre-mold is 99.8% or higher.

14. The large area mold according to claim 1 , wherein aluminum purity of the pre-mold is 99.99% or higher.

15. The large area mold according to claim 1 , wherein a height or depth of the microscopic pattern is 50 nm or larger.

16. The large area mold according to claim 1 , wherein a height or depth of the microscopic pattern is 100 nm or larger.

17. The large area mold according to claim 1 , wherein the first oxide film has a thickness of 1 to 5 μm.

18. The large area mold according to claim 1 , wherein the first oxide film has a thickness of 1 to 3 μm.

19. The large area mold according to claim 1 , wherein the mold is used to transcribe the microscopic pattern so as to form an optical article.

20. The large area mold according to claim 19 , wherein the optical article is an antireflection film, antireflection coat, antireflection part, optical waveguide, relief hologram, lens, or polarization splitting element.

21. The large area mold according to claim 1 , wherein said removing of the first oxide film comprises removing the entire first oxide film.