| 摘要 |
PURPOSE:To develop an etching soln. which has short etching time and has long holding time for etching power by using a soln. prepd. by mixing a concd. hydrochloric acid and a concd. nitric acid at a specific ratio for the etching soln. to be used for measuring the thickness of a magnetic recording medium formed of a thin alloy film cnsisting principally of Co and Cr. CONSTITUTION:A magnetic material for a magnetic recording medium consisting of a Co-Cr alloy is etched with solns. 2, 3, 4 prepd. by mixing a concd. hydrochloric acid (10N) and concd. nitric acid (10N) at 50:50-25:75 and the thickness of the magnetic material is measured by a stylus method in the stage of measuring the layer thickness of the Co-Cr alloy powder as the magnetic material when the Co-Cr alloy is used as said magnetic material. The mixed soln. composed of the concd. hydrochloric acid and concd. nitric acid at the above-mentioned ratio has short etching time and maintains etching power for long time without increasing the etching time even if the time elapsed after prepn. of the mixed soln. is long. |
