Powder for use in lower layer of coating type magnetic recording medium
AssigneeDowa Mining Co., Ltd.
InventorsSeiichi Hisano, Kazuhisa Saito, Kazushi Sano, Yoshichika Horikawa
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Abstract
A powder for use in the lower layer of a coating magnetic recording medium, comprising acicular particles with a mean major axis length in a range of from 0.01 to 0.5 μm and a mean minor axis length in a range of from 0.01 to 0.05 μm, provided that the acicular particles are flat acicular particles which, when cut in a direction perpendicular to the major axis, uniformly exhibit a cross section having a larger width to smaller width ratio of greater than 1, and that the quantity of discharged H2O at 100° C. is in a range of from 0.1 to 2.0% by weight.
Claims11
A powder for use in the lower layer of a magnetic recording medium, comprising acicular particles with a mean major axis length in a range of from 0.01 to 0.5 μm and a mean minor axis length in a range of from 0.01 to 0.05 μm, provided that the acicular particles are flat acicular particles which, when cut in a direction perpendicular to the major axis, exhibit a cross section having a larger width WL and a smaller width WS, wherein the ratio WL/WS is not less than 1.4, and that the quantity of discharged H2O at 100° C. is in a range of from 0.1 to 2.0% by weight.
In a method for producing a powder for use in the lower layer of a magnetic recording medium, the method is characterized in that a flat acicular iron oxyhydroxide particles for use in the lower layer of a magnetic recording medium is produced by a process comprising:
- adding an alkali hydroxide to an aqueous solution of a ferric salt at an amount equivalent value of 1.0 to 3.5 with respect to Fe3+ ion to form neutralized precipitate at a temperature of 5° C. or higher;
- allowing a flat acicular iron oxyhydroxide to precipitate by holding the resulting suspension containing the neutralized precipitate at a temperature higher than the former temperature;
- and
- separating the resulting precipitated flat acicular iron oxyhydroxide from the suspension.
Dependencies are inferred from the claim text.