| 摘要 |
PURPOSE:To permit production of a knife mold for forming slits of a seal which is seamless and can be mounted to a cylindrical barrel by etching the surface of a steel sheet to a knife edge shape by using a resist agent, then removing the resist agent and injecting an etching soln. under the pressure higher than in the preceding stage thereto. CONSTITUTION:The steel sheet 20 formed with lines of a photoresist film 78 corresponding to the shape of the desired knife mold on the surface is mounted to a mounting plate 22 in an etching chamber 18 and the etching soln. is injected under the prescribed 1st high pressure toward the steel sheet 20. The part where there is no film 78 is then etched. On the other hand, the liquid injected onto the etched surface is reflected and is projected again to the side faces of the steel sheet part 20a left in the film 78, by which the part 20a is formed to a peak shape in section; in addition, a constriction 20b is formed right under the surface part where the film 78 remains. The film 78 is removed and the etching soln. is injected to the steel sheet under the 2nd high pressure higher than the 1st high pressure to etch the part upper than the constriction 20b. The knife mold 88 made of the iron or steel having the knife edge 84 sharpened at the peak is obtd.
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