The causes and elimination methods of gradation screen printing moiré

The dot moiré is caused by the uneven distribution of density caused by the uneven arrangement of two colors in dot printing on the Internet. This uneven distribution is between full weight and complete juxtaposition. Obviously, the density of heavy dots is less than the density of parallel dots. If the density difference is too large and appears regularly alternately, moire appears.

Because the silk screen weaving structure is also arranged in the same way as the dots, there is a possibility that the silk screen and the film will have a moire. In addition, the printing control of silk screens has more variable factors than offset printing, so the control of the moiré of the screen printing is more complex. The old screen printer worker Liu Yusheng is proficient in color tonality and screen printing process, and has a lot of research on color tones and four-color screening technology. Recently, at the request of the majority of users, as a special expert of HC Screen Special Printing Network, Liu Yusheng specially compiled his valuable experience in platemaking with the theme of “the causes and elimination methods of moiré”, and delivered it to HC Screen Special Printing Network. Published in the 2009 "Encyclopedia."

Screen printing uses the dots to reproduce the tonality of originals, as well as plain printing and lead printing. Y, M, C, and K versions of each dot print interfere with each other, and various types of interference patterns and patterns appear to vary with the size of the dot difference. All patterns appear within an angle of 45° and repeat within a 90° range. The normal pattern is dense and dense, looks comfortable, and has a normal gradation reproduction performance. Unusual patterns, dots accumulate according to specific rules, evacuation, thick patterns, uneven colors, look uncomfortable, destroy the performance of the dot reproduction color, is a taboo printing, therefore, how to eliminate moire becomes all Screen printing practitioners must master the experience. Professor Liu Yusheng started from his own experience to analyze the causes of overprinting moiré and screen moiré. The overprinting of the tortoise was mainly caused by the mutual interference between two or more pictures whose spatial periods differed less; The pattern is caused by the interference of the mesh weft and weft threads.

Understand the causes of different moirés, carefully analyze how to eliminate moire through six aspects: how to correctly select the number of manuscript screens to match the number of screen meshes, correct plate making technology, screen angle selection, and correct operation of the process. In practice, there is a large amount of actual data as an illustration. I believe that readers will be able to intuitively understand moiré and quickly master the elimination of moire.

In order to better help the industry to improve the screen printing process, HC Screen Special Printing Co., Ltd. has opened a special topic “Screen Printing Process” in the “Technical Articles” column of 09 Daquan, aiming to start with the pre-press process and guide the industry. People concerned about the prepress, do the first step to ensure high-quality screen printing products.