UNDERLAYER POWDER FOR COATING-TYPE MAGNETIC RECORDING MEDIA AND PROCESS FOR PRODUCING THE SAME

摘要

A powder for use in the lower layer of a coating type magnetic recording medium, comprising acicular particles with a mean major axis length in a range of from 0.01 to 0.5 mu m and a mean minor axis length in a range of from 0.01 to 0.05 mu m, 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 DEG C is in a range of from 0.1 to 2.0 % by weight. <IMAGE>