Dispersion quality measurement and particulate magnetic coating properties

The use of a rheomagnetic instrument which provides an indirect measure of the dispersion quality of a magnetic ink suspension used for coating application in the manufacture of magnetic recording disks is described. The instrument was designed, tested, and put on a pilot line to study the relationship between the dispersion quality measurement and functional characteristics of the magnetic coating. The results of tests performed during pilot production suggest that it is possible to predict some of the disk-coating properties based on the dispersion quality of the magnetic particle suspension measured prior to coating. There is a qualitative correlation between the in situ measurements made on the magnetic particle suspension at the coater with the surface roughness due to flocs, the on-disk orientation ratio, and the signal-to-noise ratio (SNR)