Method for forming anodized layer and mold production method

A method for manufacturing a mold which has an inverted moth-eye structure over its surface, the inverted moth-eye structure having a plurality of minute recessed portions whose two-dimensional size viewed in a direction normal to the surface is not less than 10 nm and less than 500 nm, the method, comprising the steps of:

• providing an aluminum film provided on a support or an aluminum base;
• a step of forming a porous alumina layer which has minute recessed portions by means of anodization by applying a voltage between an anode which is electrically coupled to a surface of the aluminum film or the aluminum base and a cathode which is provided in an electrolytic solution with the surface of the aluminum film or the aluminum base being in contact with the electrolytic solution;
• and
• an etching step after the porous alumina layer is formed, in which the porous alumina layer is brought into contact with an etching solution such that the minute recessed portions are enlarged,
• wherein the step of forming the porous alumina layer by means of anodization includes
• increasing the voltage to a target value, and
• before the voltage is increased to the target value, increasing the voltage to a first peak value which is lower than the target value and thereafter decreasing the voltage to a value which is lower than the first peak value.