印刷インキの転移と紙への浸透

抄録

Ink transfer and penetration are of great importance in printing processes. These phenomena were reviewed from a viewpoint of an interaction between the printing ink and the paper stock having a porous structure.
An ink transfer equation can be represented using an amount of fixed ink on paper surface and a coefficient of ink splitting. The amount of fixed ink depends on printing speed, printing pressure, ink viscosity, and the porosity of paper. The coefficient of ink splitting is also affected by the porosity of paper extremely.
The initial setting of printing ink is greatly influenced by the speed of ink penetration which depends on the porosity of the paper. A large part of total pore volume of paper is attributable to an amount of interfibrillar gap. Ink penetration can be monitored by the reflection density of the reverse side of the printed paper using a photoelectric reflectometer as employed by Voet and Brand.
The phenomenon of ink penetration can be predicted by Lucas-Washburn's equation or Olsson-Pihl's equation the penetration depth increases in proportion to square root of time and mean radius of pore.
For a coated paper, the pore structure in the coating layer is different from that in the body stock and the pore size of the former is extremely small. The pore structure in the coating layer behaves as a filter, only ink vehicle penetrates into the coated stock and the penetration speed is not so fast.
The measurement of the time dependence of the penetration depth is an effective method to investigate the capillary structure in paper stocks. We can also evaluate the ink-setting characteristics from the dependence of penetration depth on time.