An Optical Method for Evaluating Printing Smoothness of Paper

抄録

When a paper surface is in contact with a prism surface, the fractional contact area in the paper surface is measured by the total reflection method and discussed. Variation of the fractional area depends on wavelength of incident light, and has the function F(λ) well expressed as a Gaussian distribution of the logarithm of wavelength. The dominant cause for the variation of the fractional contact area is th light transmission, known as frustrated total reflection, from the prism surface to non-contact areas in the paper surface. The topographical structure of the paper surface is closely related to the variation of the fractional area with the change of wavelength. Then, for the evaluation of printing smoothness, a new measure R_p is introduced and obtained from the values of F(λ) on a probability-logarithm graph. From comparison with other testing methods, it is shown that R_p has a considerably good correlation (Spearman's correlation coefficient of 0.97) with ‘ink covering resistance’, which is reported to be one of the most reliable measures in printing smoothness tests.