图像处理法分析纸张表面孔隙对胶印质量的影响

Effect of Paper Surface Porous on Off-set Image Quality

目的得到纸张表面孔隙的相对深度与平均孔半径,并探讨表面孔隙的相对深度以及平均孔半径与纸张表面特征之间的关系。最后,使用IGT印刷适性仪模拟胶印方式对其中3种牛皮纸进行印刷。方法使用扫描电子显微镜（SEM）对5种非涂布纸样的印刷面进行扫描,然后,采用Image J图像处理法对各纸样的SEM图进行定量分析。结果结果表明,纸张表面孔隙的相对深度介于107～133之间,平均孔半径介于36.06～45.71μm之间,且纸张表面孔隙的相对深度越浅,其平滑度越高,反之亦然。平均孔半径越小,其光泽度越高,反之亦然。结论采用图像处理的方法,可以快捷、高效的测定纸张表面的粗糙程度与对入射光镜面反射的情况。在纸张表面孔隙平均孔半径相当的情况下,其值越小的,胶印图像的密度、饱和度、光泽度就越高,相反就越差,但是,如果平均孔半径太小,油墨颗粒不能很好的渗入到孔隙当中,图像的耐摩擦性就会差。

This experiment aimed to obtain the relative depth of the porous and the average aperture of the paper surface and investigate the relationship of the porous relative depth and the average aperture with the paper surface characteristics. The IGT printability tester was used to simulate the offset printing approach to do printing on three kinds of brown paper. The Image J image processing method was used to quantitatively analyze the scanning electron microscopy（SEM） image of printing surface of five kinds of non-coated paper. The results showed that the porous relative depths were between 107 and 133, and the average apertures were between 36.06 μm and 45.71 μm. The shallower the porous relative depth was, the higher the smoothness of paper surface would be, vice versa; the smaller the average aperture was, the higher the glossiness of paper would be, vice versa. In conclusion, the method of image processing can quickly and efficiently determine the roughness and the reflection of incident light of paper surface. Under the case of little difference of average aperture, the smaller the value was, the higher the density, saturation, glossiness of the offset printing image were. But if the average aperture was too small, the particle of the ink can not permeate to the porous successfully. Given that, the abrasion resistance of the image would be disappointing.