Most plate-making personnel have experienced continuous exposure, and feel that most continuous exposure operations are not difficult, but continuous exposure to films with very full graphics (such as full-color background dots) is more difficult. Because of this kind of film, the adjacent distance is required to be less than 2cm after continuous exposure, and even few gaps or seamless connections are required, so that the dots along the edge of the cover sometimes shrink or even become virtual. Why is this?
In addition to the PS version and film, a glass plate, cover, and rubber film are also used in the printing, and the positional relationship is shown in the figure.
The closeness between the PS version and the film will greatly affect the printing quality. During continuous exposure, it must be covered with a cover at least twice. The fuller the picture and text, the closer the edge of the cover is to the edge of the picture and text, or even close to the edge of the picture and text. Because there is an additional layer of cover between the film and the glass plate, there is a gap between the film and the glass plate at the edge of the cover, and the film and the PS version are not tight enough here, resulting in the shrinking of the dots and making them false. It is not difficult to see from the figure that the thicker the cover and the wider the gap, the wider the area where the dots shrink, and vice versa.
In order to solve the above problems, the thinnest cover should be used, especially the cover near the text. The author's experience is: if the gap between the images after the continuous exposure is less than 5mm, ink can be used; if the gap is 5-10mm, the red film on the red film can be used; if the gap is 10-15mm, the black paper can be used ; If the gap is greater than 15mm, thinner cardboard can be used. Among the above covers, the front one can replace the back one, and vice versa. Instead of using the above-mentioned coverings, it is also possible to use opaque materials of corresponding thickness, but it is better to use less or no cardboard. The specific approach is as follows.
(1) Ink cover: use ink to apply an ink ribbon wider than 15mm to the back side of the film at a distance of 3 to 4mm from the graphic. There is overlap.
It should be noted that the ink should not contain small solid particles, and the ink should be thin and uniform, and the blackness should be sufficient. After the ink has dried and the inspection meets the above requirements, you can paste the film on the PS version as required, and cover it with black paper (no cardboard, too thick) where there is no need to cover and no ink ribbon. After confirming that there is no gap between the black paper and the ink ribbon, and the distance between the edge of the black paper and the image is greater than 10mm, the first exposure can be carried out by pasting the black paper on the PS plate.
During the second exposure, if there is ink on the photosensitive area reserved for the PS version, wipe it off and dry it, apply ink to the corresponding area as needed, and then paste the film on the PS version as required to check the reserved Is the photosensitive area of â€‹â€‹the PS version large enough (re-exposure if not enough, add ink or increase black paper when re-exposure), and then do it according to the requirements of the first exposure.
(2) Cover with red film: Cut a red film with a sufficient length and a width greater than 10mm. Carefully remove the red film and immediately stick it on the reverse side of the film. If the sticking is not firm, you can use cotton dipped in a little water to moisten the reverse side of the film, and then stick the red film on it. After drying, you can expose it. If the white edge of the film is less than 8-9mm wide, the red film should be attached to the PS version. The red film is 8 to 9mm from the edge of the text. The following work is similar to covering with ink, and will not be repeated here.
(3) Cover with black paper or cardboard: it can be covered directly without special treatment, but it should be noted that the edge is not less than 10mm (black paper) or 15mm (cardboard) from the edge of the graphic. Try to use black paper instead of cardboard.
The above is just different from the general operation of continuous printing, other steps and methods must still be implemented as required to ensure the quality of the printing.
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