In order to achieve better flat screen printing effect in flexographic printing , the author summed up some practical experiences based on actual production and shared it with peers.

1. Reduce the number of screen lines in the flat network part

Generally, if the number of screen lines on the flat screen portion of the printing plate is smaller than the number of screen lines in the graphic portion, a better printing effect can be obtained. With the support of existing flexographic plates and supporting technologies, especially when the printing width exceeds 380mm, it is recommended Do not add more than 160 lines/inch to the screen after the color separation . The flexo plate is a flexible material. When the number of screens on the plate exceeds 160 lines/inch, the dots on the plate become very fragile, especially when the dot area ratio is less than 10%, once the viscosity is large. UV ink, the dot on the printing plate may be tripped by the ink, and a dirty spot will be formed at the corresponding position, thereby affecting the quality of the printed product.

Therefore, in order to make the flat screen printing smooth, no ink bar, and the printing plate has good printing durability, and the printing process is stable, the dots on the printing plate need to be strong and without defects. Our company adopts the method of reducing the number of screen lines in the flat net to obtain high-quality flat screen printing effect. If the number of screen lines in the graphic part of the printing plate is 160 lines/inch, the number of screen lines in the flat net part is generally set to 100 to 120 lines / inch, while using chain-type mesh points, the screen angle is 30 ° ~ 45 °. In this way, while obtaining a solid dot, the dot enlargement rate, the dirty spot and the joint point of the printing plate are also more controllable, and the ink inking and the printing mechanical properties of the printing plate dot point are also more excellent. However, the reduction in the number of screen lines is not fixed, it is recommended that each According to its actual situation, the label printing enterprise optimizes the parameters such as the number of screen lines, the type of outlets, and the angle of the screen in the flat screen, so as to screen out better process parameters, and regularly improve the parameters and correct the work because of production. condition, Printing equipment and printed materials will vary with time.

2. Anti-white text or anti-white pattern processing

Reducing the number of screen lines in the flat screen has little effect on the visual evaluation of the printed products, but if there are anti-white text or reverse white patterns in the flat screen printing, the reduction of the number of screen lines will make the edge of the reverse white text or the reverse white pattern It appears rough and the recognition is reduced. Therefore, when the anti-white text or the reverse white pattern is encountered in the flat screen printing, it is recommended to use the "edge-adding" process. As shown in Fig. 1, the edge of the reverse white text that has not been edged is jagged, which affects the recognizability of the text. After the edge processing, the edge of the reverse white text becomes clearer.

figure 1

According to the daily production experience, the author summarizes the following rules for the width of the edge: when the area ratio of the flat mesh portion is 60% to 80%, the width of the edge is 0.04 to 0.06 mm; when the area of ​​the flat mesh is 40. When the ratio is from 5% to 60%, the width of the edge is 0.02 to 0.04 mm; when the area of ​​the dot of the flat mesh is 20% to 50%, the width of the edge is 0.01 to 0.02 mm; when the area of ​​the flat portion is 5 When %~20%, the edge width is 0.01mm. After such a simulation process, the anti-white text or the reverse white pattern in the flat screen printing can be visually and objectively clear and fine, and the recognition effect is good.

The above content is selected from the " Printing Technology" of Science and Technology Media , Volume 1, 2012. For more journal content, please pay attention to the journal channel. The latest journal content is clicked into the electronic journal channel of Keyin.com.