Method of manufacturing mold, and molded article having fine relief structure on surface and method of manufacturing the same

1. A method of manufacturing a mold having an oxide film with a plurality of pores formed on a surface of an aluminum substrate, the method comprising:

(a) a process of applying a voltage to a machined aluminum substrate and anodizing a surface of the aluminum substrate to form an oxide film; and

(b) a process of removing at least a part of the oxide film formed in the process (a), wherein a voltage (V a [V]) immediately before the process (a) is terminated and a time (t a [sec]) required to reach the voltage (V a [V]) after starting the application of voltage satisfy the following Equation (i) in the process (a):

0.01 <V a /t a <0.088  (i),

wherein (a) comprises conducting an initial anodization at a voltage; and conducting a final anodization at a final voltage that is higher than the voltage in the initial anodization in (a) such that the final voltage applied in (a) is 60 V or more; and

wherein in (a) a current density immediately after the application of voltage is 20 mA/cm 2 or less.

2. The method of manufacturing a mold according to claim 1 , wherein a current density immediately after the application of voltage is 10 mA/cm 2 or less in the process (a).

3. The method of manufacturing a mold according to claim 1 , wherein an electrolytic solution used in the anodization of the process (a) contains an organic acid.

4. The method of manufacturing a mold according to claim 3 , wherein a main component of the electrolytic solution is oxalic acid.

5. The method of manufacturing a mold according to claim 1 , wherein (a) comprises conducting the initial anodization at 50 V or less.

6. The method of manufacturing a mold according to claim 5 , wherein in (a) the voltage is raised in a stepwise manner from the initial anodization voltage to the final voltage in the final anodization.

7. The method of manufacturing a mold according to claim 5 , wherein an electrolytic solution used in the anodization of the process (a) contains an organic acid.

8. The method of manufacturing a mold according to claim 7 , wherein a main component of the electrolytic solution is oxalic acid.

9. The method of manufacturing a mold according to claim 1 , wherein the method further comprises:

(c) a process of anodizing the aluminum substrate to form an oxide film with a plurality of pores after the process (b) or the following process (d);

(d) a process of removing a part of the oxide film formed in the process (c); and

(e) a process of alternately repeating the process (c) and the process (d), wherein

a voltage (V c [V]) immediately before the process (c) is terminated and a time (t c [sec]) required to reach the voltage (V c [V]) after applying a voltage satisfy the following Equation (ii) in the process (c):

2 <V c /t c <14  (ii).

10. The method of manufacturing a mold according to claim 9 , wherein a current density immediately after the application of voltage is 20 mA/cm 2 or less in the process (c).

11. The method of manufacturing a mold according to claim 10 , wherein a current density immediately after the application of voltage is 10 mA/cm 2 or less in the process (c).

12. The method of manufacturing a mold according to claim 9 , wherein (a) comprises conducting an initial anodization at 40 V or less; and an electrolytic solution used in the anodizing in (c) contains an organic acid.

13. The method of manufacturing a mold according to claim 12 , wherein a main component of the electrolytic solution used in the anodization of the process (c) is oxalic acid.

14. A method for suppressing cloudiness of a mold surface in the manufacture of a mold having a fine relief surface composed of an oxide film with a plurality of pores that is formed on a surface of an aluminum substrate, the method comprising:

(a) a process of applying a voltage to a machined aluminum substrate and anodizing a surface of the aluminum substrate to form an oxide film,

wherein (a) comprises the steps of

(1) conducting an initial anodization at 50 V or less; and

(2) conducting a final anodization at a final voltage that is higher voltage than the voltage in the initial anodization in (a)(1),

in which the voltage is raised in a stepwise manner from the voltage in the initial anodization in (a)(1) to the final voltage in (a)(2),

provided a voltage (V a [V]) immediately before the process (a) is terminated and a time (t a [sec]) required to reach the voltage (V a [V]) after starting the application of voltage satisfy the following Equation (i) in the process (a)

0.010 <V a /t a <0.088  (i),

provided in (a) a current density immediately after the application of voltage is 20 mA/cm 2 or less while avoiding a jump in current and in voltage immediately after the voltage is applied, and

step (a) is conducted using an electrolytic solution comprising oxalic as a main acid at an oxalic acid concentration of 0.7M or less, and the electrolytic solution has a temperature of 60° C. or less; and

(b) a process of removing at least a part of the oxide film formed in the process (a),

whereby the mold having a fine relief on the mold surface with an oxide film having a plurality of pores formed on the mold surface and having suppressed cloudiness of the mold surface is obtained.