Kaplanmış ve Kaplanmamış Kağıtların Baskı Kalitesine Etkisini Belirleyen Parametrelerin Analizi

Abstract

Both paper and ink are the two main raw materials in the manufacture of printed materials. The visual quality of the printed product is very important. Printing an image on paper with ink in high resolution is dependent on the quality of the interfacial relationship between paper and ink. Newsprint, book paper, and pure cellulose-based high-grade paper pulp where the mechanical wood pulp is intensively utilized have porous structures. Coldset offset printing is used for printing on these papers. The coldset offset printing is a printing process where drying occurs late by evaporation of the liquid portion of the ink and absorption into the paper. The ink can sometimes take several days to dry completely (solidify). During this drying process, the ink penetrates the cellulose capillaries in the paper in the vertical direction and behaves the same in the horizontal direction. The dot diameter, which mechanically grows due to the printing pressure (dot gain), grows even larger by spontaneous micro-steps during the drying process. It tends to cross to the back surface of the paper in a vertical direction. For this reason, the paper-ink interfacial behavior is a critical parameter that should be maintained under control as much as possible. The rough surface, porous structure and humidity of the paper, the viscosity and amount of ink printed on the paper surface, the printing pressure at the NIP point, and the physical conditions of the printing room are influential in this interfacial relationship. In this study, the factors that affect the image quality in printing on uncoated and coated papers were investigated by test printing. The CMYK test scale, which was specially prepared for the examination of print quality, was printed with Coldset Offset Printing on smooth papers coated with woodfree coated paper and woodfree uncoated paper, which are the best examples of uncoated papers and are widely used especially in book production. After printing, the surface of the papers was measured with a spectrophotometer and the dot growth and trapping values were determined. Surface and interfacial images of the prints were taken with a stereoscopic microscope and visual examinations were undertaken.