Perpendicular Magnetic Field Orientation of Acicular Particles: Oblique Orientation with Field Gradient and Viscosity Gradient in Coating

The LIPS (longitudinally oriented inside layer, perpendicularly oriented surface layer) method of film orientation was improved in order to enable preparation of obliquely oriented tapes with a definite orientation angle. The permanent magnet pairs previously used in LIPS perpendicular orientation were replaced by an electromagnet with long iron plates for extension of the magnetic poles. Obliquely oriented tapes are easily prepared by appropriately choosing the coating speed and drying conditions. Coatings dried in a perpendicular magnetic field with an intensity gradient were found to be oriented not perpendicularly, but obliquely. It is thought that inner-layer particles are more easily displaced by the field gradient force than surface particles because of the effect of the viscosity gradient in the coating drying process.