Screen Printing 150 Questions (101-125)

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–¼ 104. 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–¼ 107. 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–¼ 114. 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.

â–¼115. Is there a screen-free version that can be dried, can it be coated with sensitized adhesive, and is it film-coated?

Wet screen version can not be immediately coated with sensitized adhesive, nor can it be sensitized immediately. The reason is that the surface of the wet screen has water, and when the sensitized adhesive is applied, the latex does not dissolve well with the surface floating water. The coating is severely uneven and even coated. When sensitized to the film, the floating surface will reduce the sensitization effect. Therefore, it must be dried and then coated or filmed.

â–¼116 . Do the sensitized powder pour into the latex and can it be mixed even after a while?

The photosensitive powder is poured into the latex and should be mixed immediately. Otherwise, the sensitized plutonium that accumulates on the surface of the latex will absorb moisture and solidify the agglomerate, and then it will not stir evenly after stirring.

â–¼117. Just stirred a diazo photosensitive adhesive, can be immediately coated? Do you want to apply after the bubbles disappear?

Just with a good sensitized adhesive, you can't apply it immediately, because bubbles are produced in the stirring process, and coating is performed again in two hours.

â–¼118. In the application of sensitized adhesive, from the second coating after drying, only coating on the printing surface, not on the ink surface!

â–¼119. When using glue, how to use photosensitive powder correctly?

When using glue, it is best to use a small amount of distilled water, about 50 or so milliliters, first dissolve the photosensitive powder into a solution, then add it to the emulsion, so that it is easy to mix evenly, and the photosensitive powder will not be solidified due to uneven mixing.

â–¼120. When coating sensitized adhesive, sometimes a yellow trace is drawn on the screen, what causes it?

The yellow or yellowish-green traces drawn on the screen plate are not completely dissolved by the photosensitive powder. In fact, they are the photosensitive powder that absorbs moisture and condenses and should be mixed for a while to make the photosensitive powder completely. Dissolved.

â–¼ 121. Photosensitive powder and dichromate, can be dissolved with hot water?

Photosensitive powder can not generally be dissolved with hot water, should use cold water, high temperature, easy to make photosensitive materials change.

â–¼122 . How long can I store the diazo photosensitive paste after it has been prepared?

Protected from light at 20 degrees Celsius, it can be stored for two months. If it is stored in a frosty place, it can be stored for six months without deterioration.

â–¼123. Can the brushing solution be applied to the wet film and will it affect it?

Generally should be painted on a film without floating water. Otherwise it will reduce the concentration of the stripping solution, stripping effect.

â–¼ 124. Does the unwashed ink screen affect the film release?

The ink has not been cleaned, the surface of the film has had water, the molecules of the releasing agent do not penetrate into the layer, and it is difficult to remove the film. Therefore, the ink must be cleaned before the film is removed.

â–¼125. With one kind of screen, the same sensitive adhesive, the same kind of liquid stripping, stripping Why not the same effect?

This situation is often encountered, one is the control of process conditions, temperature - drying temperature, time - drying time and printing time, high temperature, long time, difficult to remove film, and second, ink performance, some types Screen printing ink will occur with the film, chronic dark reaction, the use of hydrophilic layer -OH gradually reduced, resulting in difficulty in film removal, the third is the screen is stored too long, the film aging dehydration, therefore, should try to avoid unfavorable The occurrence of membrane factors.