Walter Crooks

Uniformity of radial and circumferential orientation ratio of particulate disks

In magnetic recording on hard disks, coated with particulate media, the maietic panicles are oriented circumferentially to provide a higher signal amplitude for the read/write head. The degree of anisotropy is termed the orientation ratio. It is the value of the magnetic remanence measured in the easy axis direction or circumferential direction, divided by the rnaietic remanence measured in the hard axis direction or radial direction. It is preferred that this ratio he uniform from the inner-most recording track of the disk (ID) to the outermost recording track of the disk (01)). Additionally, it is preferred that this ratio be uniform circumlerentially around the disk surface. Magnetic performance in terms of uniform signal modulation is more satisfactory when the orientation ratio is uniform radially and circumlerentially compared to when this ratio varies someway in either or both of these directions. j\ nondestructive optical technique, which allows the radial and circumferential orientation uniformity to be rapidly measured on a disk after coating application and orientation, is described. The methods make use of a Cross Polarizing Microscope. This rapid measuring technique allows parameters to be changed quickly, should the orientation ratio he nonuniform in any way during disk development. This convenient method ensures that disks tested at sinJe disk test do not tini because of particle orientation problems.

Nonimpact printers as low end hardcopy printout devices

Low-end nonimpact printers are either impulse ink-jet or thermal printers. The impulse printers are either piezoelectric impulse or the thermal-bubble types. The thermal printers also fall into two categories. In one type heating occurs in one or more of a matrix of heating elements in a head and the head in term contacts a ribbon which contains a thermally sensitive ink in contact with paper. Alternatively the thermal head may be in direct contact with a thermally sensitive paper. In the second type of thermal printer the head is an array of electrodes which inject current into a resistive ribbon. The ribbon is the transducer which heats a thermally sensitive ink which is in contact with paper. The paper describes the principles of operation of these technologies, and their capabilities as well as their advantages and disadvantages.<<ETX>>

An Ink Transfer Mechanism,Hardware And Material Considerations For A Resistive-Ribbon High Quality Thermal-Transfer Printing Process

This report describes R2T2, a dynamic thermal printing process. Print quality is dependent on many printing parameters interacting with each other during ink transfer. The entire transfer process can be divided into five stages: heat, melt, adhesion, separation, and solidification. The report deals with the ink and printing parameters most pertinent to print quality. The ink transfer temperature determines the printing power as well as the ribbon stability. The viscoelasticity and adhesive property of the ink-melt influences the actual print quality. Contact pressure, heat transfer, ink adhesion, and separation also play important roles. The effects of all these factors and the limitations of print speed arc discussed as well.