2-DIMENSIONAL CHARACTERIZATION OF THE SUR FACE-STRUCTURE OF PAPER WITH REFERENCE TO ITS PRINTABILITY

The Microfocus optical measuring system enables two-dimensional surfac e measurements to be carried out. Microfocus works in accordance with the dynamic focusing measuring principle. Comparative tests were carri ed out with standard air flow and stylus smoothness measuring equipmen t. The standardised roughness measurement coefficients recorded with t he Microiocus sensor correlate to a large degree with the results obta ined with other measuring instruments. Within a product group, the int errelation between Microfocus and PPS instrument is not statistically proven. There is a low degree oi correlation with the other air flow m easuring instruments as well as the Hommel tester. The surface structu re of a print substrate influences printing quality. But it is necessa ry to take a differentiated view of the interrelation between the surf ace structure and print image reproduction within a product group (e.g . SC papers). With a wide quality spectrum of the papers, there is a h igh degree of correlation between the roughness values in the z-direct ion (average roughness R(a)) and the printed reproduction of halfetone s. Within a narrow quality spectrum, no assertions can be made concern ing the dependency of the number of missing dots on the average roughn ess. For this, horizontal descriptors that provide information on roug hness variations in the x-, y-direction must be referred to. Relevant parameters for characterising the two-dimensional surface structure of paper in the x-, y-direction can be calculated from the gradients mat rix.