2001 Volume 9 Issue 5 Pages 57-64
Thermal paper is used for a variety of products such as labels, facsimiles, word processors, printers, electric black board printers, handy terminals, etc. Label paper consists of base paper ,under-coating layer, thermal layer (heat sensitive layer), over-coating layer and back-coating layer. The thermal layer which per forms the main function of thermal paper consists of dyes, coloring agents, resins and surface-active agents. It is formed by mixing the suspensions of dyes and coloring agents. The mixture is adjusted, coated then dried. Dye particles can be further milled to be more color sensitive. But super sensitive particles create fog on the non-printed areas. Therefore, the particles must have a certain smaller average diameter and a narrow size distribution. Evaluation of the generic function was made as follows. Dye particles collide with beads, agitator and container wall, becoming finer particles. So the input/output relationship of energy was considered as the generic function. The input energy is proportional to time, and the output (work) is proportional to the surface area per unit weight. Zero-point proportional equation was used. In other words, milling time was considered as the signal factor. No noise factors were assigned. Analysis was also made using dynamic operating window (speed difference method). From the study of the former case, both SN ratio and sensitivity were improved. But the latter case resulted in a poor reproducibility.
