Application of a New Evaluation Method of Sheet Appearance to Various Coated Papers, 2003 Spring Technical Conference Proceedings

Coated paper should have excellent sheet appearance. Further, it is well known that sheet appearance is affected by gloss profile. Evaluation of sheet appearance is generally determined by visual inspection. However, this evaluation method is subjective and not quantitative; therefore the evaluation of sheet appearance is difficult. A few methods have been reported for the purpose of quantitative evaluation of sheet appearance.

We developed a new method for evaluating the sheet appearance of coated paper using a scanning white-light interferometer. We found that the standard deviation of the slope angle area ratio (SDS), with the optimal threshold of |3°|, was strongly related to sheet appearance. The narrower the distribution of the slope angle area ratio (SAAR) becomes, the better the sheet appearance. Moreover, we measured the ultra fine surface profiles of various commercial coated papers, and studied the influence of SDS on sheet appearance.

As a result, we found that the optimal threshold for binary transformation of the average of surface slope angles (ASSA) changes depending upon the kind of coated papers, and that the optimal threshold is |7°| for A2 coated paper and |10°| for A3 coated paper. We also found that correlation with sheet appearance is best when it is not concerned with the kind of coated papers but SAAR after binary thresholding becomes 70%. This method can accurately evaluate sheet appearance of a variety of papers.