Magnetic recording medium and method of producing the same

Abstract

A magnetic recording medium, which comprises: a nonmagnetic support; and a magnetic layer comprising a ferromagnetic powder and a binder, wherein an average surface roughness (Ra) at a center of a surface of the magnetic layer measured by using an atomic force microscope (AFM) is 2 nm or less, the maximum height (Rmax) thereof is 50 nm or less, and an arithmetic average of phase difference between a drive signal and a response signal of a probe measured with the atomic force microscope in a tapping mode is from 2 to 20°, and a method of producing the same.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates to a magnetic recording medium and a method of producing the same. More specifically, it relates to a magnetic recording medium of the coated type which has smooth surface properties, has small spacing between head and the medium, enables high-density recording, shows favorable running performance and causes little head wear, and a method of producing a magnetic recording medium whereby the above-described characteristics can be established while achieving a high productivity.[0003]2. Description of the Related Art[0004]In the field of magnetic recording, recording wavelength becomes shorter with the recent increases in the recording density. With the tendency toward using MR heads as reproduction heads, attempts have been made to finely divide a magnetic material and thus increase the number of magnetic particles per unit volume thereby reducing medium noises. To magnetically separate magnetic pa...

AI Technical Summary

Benefits of technology

The invention is a magnetic recording medium that has smooth surface properties, can achieve high-density recording, and has favorable running performance and causes little head wear. The medium comprises a nonmagnetic support and a magnetic layer comprising a ferromagnetic powder and a binder. The average surface roughness of the magnetic layer measured by AFM is 2 nm or less, and the maximum height of the magnetic layer is 50 nm or less. The arithmetic average of the phase difference between the drive signal and the response signal measured with the AFM is from 2 to 20°. The magnetic recording medium can be produced using a method that involves separately dispersing a magnetic solution and an abrasive solution, and then mixing them to form a coating solution for the magnetic layer. The resulting medium has smooth surface properties, small spacing between the head and the medium, and high-density recording capabilities. The amount of diamond particles added to the magnetic layer is from 0.05 to 5% by mass based on the ferromagnetic powder. The average surface roughness of the medium is from 0.5 to 1.5 nm, and the maximum height of the medium is from 10 to 50 nm.

Problems solved by technology

When a magnetic solution is high-dispersed, however, there arises a problem that the exposure of abrasive particles from a magnetic layer is inhibited or the projection height on the magnetic layer surface is lowered and thus the durability is worsened.

However, this method suffers from a problem that the diamond causes abrasion of media beads (for example, glass beads or ZrO2 beads) or the inner wall (mainly made of stainless steel) of the disperser in the course of the dispersion and thus abrasion dusts contaminate the magnetic solution.

However, it has been found out that, in the case where the surface roughness is extremely elevated by using the technique disclosed in JP-A-2005-228369, there arise troubles such as sticking of a medium to a head and stripping of a magnetic layer due to sliding with a guide.