| abstract |
(57) [Summary] [Problem] A conventional photomask for forming a dynamic pressure generation groove has a poor circularity, poor dimensional accuracy, and a large dimensional variation among products. Since it is impossible to form a pattern, it is impossible to form a dynamic pressure generation groove having a pattern faithful to the design pattern. By using an electroforming method, it is possible to fit an exposed portion 11 in which a photoresist layer 10 is applied and formed on a surface of a processed portion 91 of a dynamic pressure generation groove forming object 9 and to obtain a desired dynamic pressure. The metal cylindrical photomask 7 in which the through holes 8 having the pattern of the generation groove is formed is manufactured. |