网点形状对柔版印刷阶调再现性的影响

How dot shape affect reproductive quality of flexographic printing

为提高柔版印刷的网点再现性，研究了不同形状的网点对柔版印刷网点增大的影响。在相同的印刷条件下，通过柔版印刷机进行印刷实验，测量了方形、圆形、欧几里德形、菱形、椭圆形以及5种Esko专有形状的网点在4种网线数下的网点增大曲线。实验结果表明：网点形状对网点的增大程度是有影响的，在这些形状的网点中，欧几里德形和Esko-CircularS amba36形状的网点增大值相对较小，适合柔版印刷。另外，柔版印刷网点增大较大，在亮调到中间调范围（网点百分比为30％～40％）处的网点增大最严重，且柔版印刷的阶调再现范围较窄。

he paper present a study about how different dot shapes affect dot gain in flexographic printing, which aims at enhancing the capability that halftone dot are reproduced in the printing process. Five popular dot shapes in square, round, euclid, rhombic, elliptic style and five special ones from Esko are used in ripping process for a grayscale with 1% to 100% dot area＇s change. 10 kinds of dot gain curves under four different screening lines are built after printing process and measurement. All the experiments are conducted on one same flexographic press with almost same process control parameters. The result announces that dot shape is truly correlative to the dot＇s change trend. In all the dot shapes above, euclid and one of Esko＇s dot shapes called Circular Samba36 are more suitable for flexography with relative smaller dot gain value. Moreover, flexographic printing has much larger dot gain trend than lithographic offset printing, and the largest change happens between 30% to 40 %, which makes flexography can only reproduce a limited tone region.