Method for manufacturing mold and method for manufacturing molded article having fine uneven structure on surface

Patent metadata

Field	Value
Publication number	US-9797059-B2
Application number	US-201314403908-A
Country	US
Kind code	B2
Filing date	May 28, 2013
Priority date	May 30, 2012
Publication date	Oct 24, 2017
Grant date	Oct 24, 2017

Abstract

A method for manufacturing a mold includes (a) anodizing an aluminum substrate at a voltage of 60 V to 120 V in an electrolytic solution in which two or more species of acid are mixed, and forming an oxide film having a plurality of minute holes on a surface of the aluminum substrate; and (b) removing at least a portion of the oxide film. The electrolytic solution used in (a) satisfies the relation (D1)/2<D2, where D1 is the current density when the aluminum substrate is anodized under the same conditions as in (a) in an electrolytic solution of only the acid (A) having the highest acid dissociation constant (Ka) of the two or more species of acid, and D2 is the current density when the aluminum substrate is anodized under the same conditions (a) in the same electrolytic solution as that of (a).

First claim

The invention claimed is:

1. A method for manufacturing a mold which has an oxidized coating film having a plurality of micropores formed on a surface of an aluminum substrate, the method comprising:
(a) performing anodic oxidation of an aluminum substrate at a voltage of 70 V but less than 120 V in an electrolytic solution having three or more kinds of acid mixed therein to form an oxidized coating film having a plurality of micropores on a surface of the aluminum substrate,
wherein, as the electrolytic solution having three or more kinds of acid mixed therein for use in (a), a solution satisfying the following condition (α) is used, wherein in condition (α)
D 1 is the current density when the aluminum substrate is subjected to anodic oxidation under the same conditions as in (a) in an electrolytic solution of only the acid A having the highest acid dissociation constant Ka of the three or more kinds of acid,
D 2 is the current density when the aluminum substrate is subjected to anodic oxidation under the same conditions as in (a) in the same electrolytic solution as that of (a), and
D 1 and D 2 satisfy the following formula (1):
(D1)/2>D2  (1), and

the solution used as the electrolytic solution in (a) further satisfying the following condition (β), wherein in
condition (β)
the ratio of the volume molar concentration of the acids other than the acid A to the volume molar concentration of the acid A (x=other acids/acid A×100) satisfies the following formula (2):
0.85V−60< x< 140  (2),

wherein in the formula (2), V represents the voltage applied during anodic oxidation in (a);
(b) removing at least a portion of the oxidized coating film which has been formed in (a);
(c) comprising (c)(1) subjecting the aluminum substrate to anodic oxidation after (b) or (c)(2) subjecting the aluminum substrate to anodic oxidation after the following (d) so as to form an oxidized coating film having a plurality of micropores,
(d) removing a portion of the oxidized coating film is removed after (c) and the pore diameter of the micropores is enlarged, and
(e) alternately repeating (c)(2) and (d).

2. The method for manufacturing a mold according to claim 1 , wherein the anodic oxidation of the aluminum substrate is performed at a voltage of 75 V to 110 V in (a).

3. The method for manufacturing a mold according to claim 1 , wherein the initial temperature of the electrolytic solution for use in (a) is 6° C. or higher.

4. The method for manufacturing a mold according to claim 1 , wherein the acid A used in (a) is oxalic acid.

5. The method for manufacturing a mold according to claim 1 , wherein one of the acids other than the acid A for use in (a) is phosphoric acid.

6. The method for manufacturing a mold according to claim 1 , wherein the electrolytic solution for use in (a) comprises a mixture solution including oxalic acid and phosphoric acid.

7. The method for manufacturing a mold according to claim 1 , wherein
the aluminum substrate is subjected to anodic oxidation in (c) at a voltage of 70 V but less than 120 V in an electrolytic solution having three or more kinds of acid mixed therein, and
a solution satisfying the following condition (α′) is used as the electrolytic solution, wherein the electrolytic solution has three or more kinds of acid mixed therein for use in (c), wherein in
condition (α′)
D 1 ′ is the current density when the aluminum substrate is subjected to anodic oxidation under the same conditions as in (c) in an electrolytic solution of only the acid A′ having the highest acid dissociation constant Ka of the three or more kinds of acid,
D 2 ′ is the current density when the aluminum substrate is subjected to anodic oxidation under the same conditions as in (c) in the same electrolytic solution as that of (c), and
D 1 ′ and D 2 ′ satisfy the following formula (1′):
(D1′)/2>D2′  (1′).

8. The method for manufacturing a mold according to claim 7 ,
the solution further satisfying the following condition (β′) is used as the electrolytic solution for use in (c), wherein in
condition (β′)
the ratio of the volume molar concentration of the acids other than the acid A′ to the volume molar concentration of the acid A′ (x′=other acids/acid A′×100) satisfies the following formula (2′):
0.85V′−60< x′< 140  (2′),

wherein in the formula (2), V′ represents the voltage applied during anodic oxidation in (c).

9. The method for manufacturing a mold according to claim 8 , wherein the anodic oxidation of the aluminum substrate is performed at a voltage of 75 V to 110 V in (c).

10. The method for manufacturing a mold according to claim 7 , wherein the initial temperature of the electrolytic solution for use in (c) is 6° C. or higher.

11. The method for manufacturing a mold according to claim 1 , wherein one of the acids other than the acid A for use in (a) is malonic acid or tartaric acid.

12. The method for manufacturing a mold according to claim 5 , wherein the electrolytic solution having two or more kinds of acid mixed therein for use in (a) further comprises malonic acid as a third acid.

13. The method for manufacturing a mold according to claim 12 , wherein in (a) the anodization is conducted at 80 V and the electrolytic solution includes malonic acid at a concentration of 0.05 mol/L to 0.1 mol/L.

14. The method for manufacturing a mold according to claim 1 , wherein in (a) and in (c) the anodic oxidation of an aluminum substrate is conducted at a voltage of 80 V to 120 V.

15. The method for manufacturing a mold according to claim 1 , wherein in (a) the oxidized coating film is 0.5 to 10μm thick.

16. The method for manufacturing a mold according to claim 12 , wherein in (a) the electrolytic solution includes malonic acid at a concentration of 0.05 mol/L or 0.1 mol/L.

17. A method for manufacturing a mold which has an oxidized coating film having a plurality of micropores formed on a surface of an aluminum substrate, the method comprising:
performing anodic oxidation of an aluminum substrate at a voltage in a range from 70 V up to less than 120 V in an electrolytic solution having three or more kinds of acid mixed therein to form an oxidized coating film having a plurality of micropores on a surface of the aluminum substrate,
wherein, as the electrolytic solution having three or more kinds of acid mixed therein for use in (a), a solution satisfying the following condition (α) is used, wherein in condition (α)
D 1 is the current density when the aluminum substrate is subjected to anodic oxidation under the same conditions as in (a) in an electrolytic solution of only the acid A having the highest acid dissociation constant Ka of the three or more kinds of acid,
D 2 is the current density when the aluminum substrate is subjected to anodic oxidation under the same conditions as in (a) in the same electrolytic solution as that of (a), and
D 1 and D 2 satisfy the following formula (1):
(D1)/2>D2  (1), and

wherein the solution used as the electrolytic solution in (a) further satisfying the following condition (β), wherein in
condition (β)
the ratio of the volume molar concentration of the acids other than the acid A to the volume molar concentration of the acid A (x =other acids/acid A ×100) satisfies the following formula (2):
0.85V-60< x< 140  (2),

wherein in the formula (2), V represents the voltage applied during anodic oxidation in (a).

18. The method according to claim 17 , wherein electrolytic solution has three kinds of acid mixed therein.

Assignees

• Mitsubishi Chem Corp
• Kanagawa Acad Of Science And Tech
• Kanagawa Inst Of Ind Science And Tech

Inventors

• IKAWA Masashi
• Okamoto Eiko
• Masuda Hideki

Classifications

• B29C33/38 Primary

  characterised by the material or the manufacturing process (B29C33/44 takes precedence) · CPC title

• C25D11/10

  containing organic acids · CPC title

• G02B1/118

  having sub-optical wavelength surface structures designed to provide an enhanced transmittance, e.g. moth-eye structures · CPC title

• B29C33/42

  characterised by the shape of the moulding surface, e.g. ribs or grooves · CPC title

• B29C59/046

  for layered or coated substantially flat surfaces · CPC title