Influence of Coating Pore Structure on Optical Properties of Low Gloss Coated Paper, 2006 TAPPI Advanced Coating Fundamentals Symposium

Coating pore structure of low gloss coated paper based on different pigment blends was analyzed using mercury intrusion porosimetry. Optical properties and printability such as brightness, light scatter, sheet gloss and print gloss can be related to coating pore structure. Brightness and opacity depend strongly on the pore diameter of coating structure because coatings with larger pore diameter can enhance light scatter. Brightness increases 0.8 units when pore size varies from 350 nm to 650 nm. Print gloss and delta gloss are affected by sheet gloss and coating pore structure. Only the combination of optimal pigment blends and supercalender conditions can achieve ideal coating pore structure for low gloss coated paper; 60/20/20 blends of coarse ground calcium carbonate/ultra-fine ground calcium carbonate/no. 2 kaolin are found to be optimal. The pore size distribution of ideal coating structure is mainly in the range of 30~2500 nm and its average pore size diameter is about 510 nm.