抄録
In offset lithography, the ink picks up significant quantities of dampening solution as emulsified droplets. Good printability of lithographic ink depends on the balance between the ink and water content. In this study, the rheological properties of emulsifying inks are measured and dynamics of ink splitting and transfer in a roll nip are investigated. The values of yield stress and storage modulus are increased with emulsification. The acoustic study of the ink splitting is performed using a sound analyzing system consisting of a microphone with sensitivity at higher frequencies and a FFT analyzer. The ink splitting sound can be characterized by the power density in the frequency region between 15 to 35kHz and the magnitude of power density decreases with increasing the water content in ink. Growth and rupturing of ink filaments between rollers are observed using a video system which consists of a microscope. CCD video camera and a personal computer with an image processing board. The length of ink filaments also decreases with proceeding emulsification. The relations between these rheological properties and lithographic printability are discussed using three kinds of litho-inks with different formulations.
