蛍光Ｘ線元素分析による紙面インキ量の定量法

Abstract

With a view to quantify ink on nip-printed paper, the amount of which is unknown, a newly developed technique using an X-ray fluorescence method was applied. In this technique, the content of copper included in a cyan ink printed on paper was measured as an intensity of its peak in the X-ray fluorescence spectrum. Several kinds of paper were subjected to solid-printing using a universal printability tester with a cyan ink, and then the transferred ink amount was measured by weighing the ink roll before and after printing. The proportional relationship between the so measured copper content and the transferred ink amount measured gravimetrically was confirmed irrespective of the kinds of printing paper. This result suggests that the printed cyan ink amount can be determined by measuring the copper intensity in an X-ray fluorescence spectrum. Further, papers having several levels of smoothness were prepared with a supercalender. The transferred ink amount was found to decrease with increasing the smoothness of paper.The X-ray fluorescence method was compared with the method of print density calculated from lightness (L *). The coated papers containing the hollow or filled sphere pigments were prepared and solid-printings were conducted on the coated paper by an RI printing tester with a cyan ink. Lightness (L *) of printed surfaces of the coated papers was measured with a spectrophotometer. The print density was not proportional to the transferred ink amount measured by the X-ray fluorescence method, and was influenced by the lightness of unprinted surfaces. In application, the X-ray intensities of copper and coating components of the print with print mottle were measured and mapped using an X-ray fluorescence microanalyzer. For the poor print with print mottle, binder and pigment in the coating were distributed unevenly. This finding suggests that the print mottle may have been caused by the uneven distribution of binder and/or pigment in the coating.