网点扩大的原因及控制方法

Dot Gain:Reason and Control

在印刷中,总会发生网点扩大,但扩大量超过一定范围时会产生质量问题。文章分析了由于网点的形状;曝光的不彻底;显影药液疲劳或是显影药液的pH值过低,显影的时间短或是显影的温度过低;润版液的pH值过低;橡皮布的弹性变形;纸张的吸收性、平整度以及不同的类型;油墨粘度;印刷压力偏大等因素对网点扩大的影响。并提出了具体解决措施:用灰梯尺,晒版信号条进行数据化控制掌握好曝光,显影时间;合理选择包衬材料,通过对胶印机的包衬厚度的调整调节印刷压力;使用尽量少的版面水分,减少油墨的乳化现象和纸张的伸缩变形,控制好水墨平衡。从而有效地控制网点扩大,提高印制质量。

Dot gain is inevitable in painting process excessive gain may result from the dot shape, insufficient , but an excessive gain will be harmful to the quality. An exposal , fatigue or low PH value of the developer, insufficient developing time or low temperature of developer, low PH value of dampening solution, elastic deformation of mackintosh, absorbency, level and type of paper, viscidity of printing ink and excessive printing pressure. To solve the problem, we can digitally control exposing and developing time with gray scale or signal strip of plate burning, properly choose lining material and modulate printing pressure by adjusting the thickness of lining material, minimize the amount of water on the plate, reduce the emulsification of printing ink and the deformation of paper, balance the printing ink and water.