Connections to the printing work (4)

Fourth, the quality requirements of the printing plate

The quality of the printing plate has common requirements. According to different printing suitability conditions (comprehensive adaptability of paper, ink, imprinting process, printing environment, blanket, fountain solution, etc.), some indicators allow certain fluctuations.

1. The rules on the layout are complete, and the layout of a set of rules must be consistent.
2. The layout is clean, the graphic is not damaged, the image can not have trachoma or dead spots that should not be connected; the text is complete, there can be no lack of pen strokes; maintain good lipophilicity; the blank part must completely dissolve the decomposed photosensitive layer Drop off, maintain good hydrophilicity. If there is a substance that is completely dissolved in the blank area, it can be removed by removing the dirt, but the operation must be cautious. The dirty agent must not enter the picture and it should be cleaned with clean water.

3. Normal operation, the plate can not be scratched, dirty and horseshoe India and other hard injuries.
4. Complete image adjustment, complete text, in line with the original or printing plate requirements. Different papers, different printing speeds, and indicators of each tone of the image are allowed to fluctuate (see Table 1). The core is that the middle version of the brilliance version must be shallow compared with the original version. If it is not light or dark, the printing plate cannot be used.

It should be pointed out that the same set of original paper and different paper, only rely on exposure and flushing adjustment is limited, should be in the plate when the calibration, the number of lines, the use of color regulation. For example, if newsprint is printed on a high-speed machine, the plate-making scale may be appropriately scaled. The number of screen lines is relatively coarse, and the basic colors are relatively full, while the opposite colors are used less. Table 1

Bright tone dot 50% dottone dark tone dot area area coated paper 2% 47% 97～98%
Offset paper 3 to 4% 46 to 47% 96 to 97%
Newsprint 4 to 5% 45 to 46% 95 to 96%
Paper grade

5. If the stencil is not used right away, a layer of hydrophilic gum arabic or other hydrophilic protective glue should be rubbed to prevent the white parts from being oxidized. At the same time, in order to prevent the dust from contaminating the layout, cleanliness should be avoided. Light.

6. If it is a long-run printing (more than 25,000 printing), in order to enhance the stability of the basis of the graphic, wear resistance, increase the amount of print, reduce the number of printing or changing plate, to maintain the consistency of the printing product, to implement the baking version . The plate layout that needs to be baked must be clean, and the baking temperature and time depend on the amount of printing.