Effect of Surface Properties of Base Paper on Print Quality, 2006 TAPPI Advanced Coating Fundamentals Symposium

The uniformity of coating layer is one of the most important properties of coated paper in terms of the print quality. If the coating layer is not uniform, poor print qualities such as mottling in offset printing might be occurred. The uniformity of coating layer is affected by surface properties of base paper such as roughness and porosity, and penetration of coating color into base paper. Pre-calendering is used to improve these properties of base paper, which leads to better coverage and uniformity of coating layer. As the pre-calendering of coated paper, hard nip calender have been widely used. On the other hand, hot soft nip calender (HSNC) has been used as post-calender for coated paper. Comparing with conventional method like supercalender or soft nip calender (SNC), HSNC has advantages as followings, 1) increase of paper density is relatively small, 2) smoothness is higher at the same calendering linear load. In this study, the effect of HSNC for pre-calendering was investigated by comparing with/without pre-calendering using SNC (the temperature was different from HSNC). As a result of this comparison, mottling of LWC was improved by pre-calendering using HSNC. The base paper pre-calendered with HSNC has smaller pore diameter on the surface than supercalender or SNC. As a consequent, the coating coverage of base paper was improved by HSNC.