Screen printing 1000 questions (100-114)

â–¼100. How many lines can be reached in screen printing?
Generally can reach 80 lines, up to 100 lines, from the print definition, 80 lines and 65 lines of visual effects are better, the number of lines is high, the network is easy to paste.

â–¼101. How to control the stretch netting screen
Such as making red, blue, yellow, black, four sets of color plus screen, stretch angle can be 0 degrees, 4 degrees, 0 degrees, 12 degrees.

▼102. Screen printing, how to prevent the occurrence of moiré?
First, we must choose a uniform weaving screen, some visually uneven screen can not be used for screen printing, and the other according to the angle of the screen, generally do not produce moire.

â–¼103. After the number of screen lines is determined, what is the corresponding number of line screens?
In general, the number of screens is 3.5 times the number of lines and not more than 6 times. If the number of lines is 80, the minimum number of lines is 80*3.5=280 mesh.

â–¼104. The same photographic film, the line thickness difference is too large, how to choose the printing time?
In the case of large differences in line thickness, thin lines should be the main choice for printing time.

â–¼105. When the screen printing ink surface is sticky and has paste-like substances, how does it happen? How to overcome?
The sticky material is an uncross-linked film that dissolves in water and becomes sticky. The ink surface layer should not be overcoated and the printing time should be extended.

â–¼106. What is the cause of the loss of the printed adhesive layer when it is visible?
Speaking first of the film paper, if it is apparently peeled off on the polyester mesh, it is likely that the mesh is not good, that is, the screen coarsening treatment is not good enough, and the attached fastness is poor and it falls off. Another possibility is that the printing time is too short. After the membrane swells and falls off, the first is to increase the grinding time, and the second is to increase the printing time. If the film is detached when the sensitized adhesive is visible, it may be caused by a short printing time, so long as the printing time is increased, the delamination problem can be solved.

â–¼107. When the shape is visible, use the finger surface to rub the rubber surface hair on the film machine several times and produce pinholes. What is the reason?
Similar situations are caused by insufficient time for printing (with other conditions unchanged).

â–¼108. When the image is displayed, the center image of the screen is very good and the film is very firm. What is the reason why the film is easily peeled off at the edge of the image?
This shows that the printing time is moderate and the edges are partially stripped. There are three possibilities. First, the marginal light is weak, the printing plate is insufficient, the second is that the edge of the local coating is too thick, the third is not partially dried, the general printing lamp tube layout is greater than the screen version of the film surface. Makes the entire screen plate evenly dry to the light.

â–¼109. Can a screened version be reheated, cured, or reprinted? (Solvent-resistant photopolymer). Does it have any effect on film release?
Solvent-based photosensitive adhesive screen version, the general use of secondary printing does not use heating curing. Otherwise it will be more difficult to remove the film.

â–¼110. Why is it difficult to remove the edges of the image lines?
Around the image, the adhesive layer is often too thin, resulting in excessive overprinting and difficulty in film removal. The edges of the lines are often in contact with the ink. Each time the printing is completed, the ink on the edges cannot be cleaned. The components of some inks will undergo chronic hardening of the film. The longer the time, the harder it is to remove the film. Therefore, each time it is completed, it must be Thoroughly clean the ink with a hole-opener (ink cleaner).

â–¼111. After degumming, most of the film is removed, and very few can't be removed. How should it be removed?
If there is a small amount of residual film that can not be removed, dry rub with dimethyl amide. Note that rubbing can not be washed with water. Only dry towels, dry cotton yarn, wipe clean.

â–¼112. Why is the yellow screen better than the white screen?

Yellow screen printing, the reflective effect is poor, absorb light energy, light cross-linking is sufficient, while the white screen printing when the reflective light, light cross-linking is relatively poor, and therefore more difficult to film.

â–¼113. How is the ghost image on the screen generated and how can it be removed?
Turtle shadow is mainly the color of the adhesive layer and the color of ink is formed on the screen. It can be soaked with turtle shadow cleaner for about 10 minutes and then washed with tap water.

â–¼114. Turtle shadow has no effect on the second plate?
Strictly speaking, there should be an influence, which will make it difficult to locate the printing plate. The line of sight is blurred, and it is necessary to wash it out and remake the plate.

---Qi Lu Graphic Arts