Improvement of the method of even covering
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Most plate-making people have had the experience of continuous drying. I feel that most of the continuous drying operations are not difficult, but it is more difficult for the film to be full (such as full-color background dots). Because of such film, even if the adjacent spacing is less than 2cm, even a small gap or seamless connection is required, so that the dots along the edge of the covering sometimes shrink or even become virtual. Why is this?
In addition to the PS plate and the film, the glass plate, the cover, and the rubber film are used in the printing, and the positional relationship is as shown in the drawing.
The tightness between the PS version and the film will greatly affect the quality of the printing plate. Cover the cover at least twice with the cover. The more the picture is, the closer the edge of the cover is to the edge of the image, or even the edge of the image. Because there is a layer of cover between the film and the glass plate, there is a gap between the film at the edge of the cover and the glass plate. Here, the combination of the film and the PS plate is not tight enough, resulting in shrinkage and fading of the dots. It is not difficult to see from the figure that the thicker the cover, the wider the gap, and the wider the area where the dots are narrowed, and vice versa.
In order to solve the above problems, the cover should be as thin as possible, especially the cover close to the graphic. The author's experience is: if the gap between the graphic and the image after drying 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, black paper can be used. If the gap is larger than 15mm, thinner cardboard can be used. In the above cover, the front can be replaced by the latter, and vice versa. It is also possible to use an opaque material of a corresponding thickness without using the above-mentioned covering, but it is preferable to use less or no cardboard. The specific approach is as follows.
(1) Ink cover: Apply ink to the ink tape wider than 15mm from the reverse side of the film with ink. If the film blank is less than 15mm wide, the PS plate should be coated and the PS plate and the ink ribbon on the film should be applied. 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 is dry, after checking the above requirements, the film can be attached to the PS plate as required, and covered with black paper (unusable cardboard, too thick) where it needs to be covered without ink ribbon. After determining 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 edge of the image is greater than 10 mm, the black paper can be attached to the PS plate for the first exposure.
For the second time, if there is ink on the PS plate reserved for the photosensitive area, wipe it off and dry it, then apply ink to the corresponding area as needed, then paste the film on the PS plate as required, check the reserved Is the PS version of the photosensitive area large enough (to re-dry when not enough, add ink or heavy black paper when re-drying), and then do it according to the first exposure requirement.
(2) Cover with red film: Cut a red film of sufficient length and width greater than 10mm, carefully remove the red film and immediately attach it to the reverse side of the film. If the sticker is not strong, use the cotton dipped in a little water to wet the film on the reverse side and stick the red film. After drying, it can be exposed. If the white side of the film is less than 8 to 9 mm wide, the red film should be attached to the PS plate. The red film is 8 to 9 mm away from the edge of the image. The next work is similar to covering with ink, and will not be described 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 replace cardboard with black paper.
The above is just different from the practice of continuous drying. Other steps and methods should still be implemented as required to ensure the quality of the printing.