How much do you know about packaging offset printing (107
107. what factors can lead to dirt on the exposed PS plate?
there are two main factors:
① there are dirt spots or dust and other foreign particles on the exposure glass and negative film.
② the small negative film edge and cellophane tape edge traces produced by manual collage.
108. what are the different methods for handling dirt on different parts of the PS plate?
① if there are redundant light barriers on the field of the printing plate, the The field part of the negative is completely opaque, so it does not affect the printing quality
② if the redundant light barrier appears at the point. Or on the ground, at the junction of lines and blank areas, dirt will be left in these places. If the dirt remover is used for removal, the pictures and texts will inevitably be removed. Therefore, it can only be carefully repaired with a scraper. The effect is naturally bad. If the dirt is serious, the printing plate can only be scrapped
③ if the dirty spot appears in the blank part and is a certain distance from the image and text part, it can be removed by applying dirt remover
therefore, before printing and exposure, it is necessary to carefully check the point and the junction between the text and the blank to ensure that there is no dirt. When making up manually, it is necessary to ensure that the edge of the small negative and the adhesive tape do not appear in this part
109. What are the methods to remove dirt from PS version when printing? What should we pay attention to when using
ps version dirt removal has comprehensively introduced two innovative solutions in the field of high molecular materials, namely, film spraying dirt removal method and detergent dirt removal method
① the scattering film method is to use the scattering film to scatter the light during printing, so that the photosensitive materials corresponding to the small dirty spots and dirty marks on the plate are irradiated by the scattered light from all directions, so as to remove the dirt. This method will affect the reproduction of dots and fine lines in the image and text parts, thus affecting the print quality. Therefore, this method can not be used for the original with dots and fine lines on the layout
when printing books and periodicals with only words, it is common to output single page negatives, and then paste them together on a large transparent film base for printing. After exposure and development in an ordinary way, there will be dirt marks around the single page negative film on the printing plate and the corresponding part of the adhesive paper. It takes a lot of time to remove dirt by applying dirt remover, and it is more effective to remove dirt by scattering film
the decontamination method of scattering film is as follows: the exposure is divided into two times. The first time is the main exposure without scattering film, and the exposure time is about 4/5 of the normal exposure time; After the completion, the scattering film is laid, and the second sub exposure is carried out. The exposure time is about 1/2 of the main exposure
for the PS version exposed in this way, there are no or few dirt marks and small dirt spots around the small negative and adhesive tape
② dirt remover dirt removal method is to remove dirt with a dirt remover that can dissolve the photosensitive coating of PS plate. For positive PS version and negative PS version, corresponding dirt removers shall be used respectively to remove dirt
dirt remover with the rapid development of electro-hydraulic servo technology, electro-hydraulic proportional technology, microelectronics technology, computer technology and modern control technology, the method of dirt remover is: after the printing plate is developed, dip the dirt remover with a brush and wipe the dirty spots and marks on the printing plate. Be careful not to let the dirt remover touch grace. With the development of alloy smelting technology, Heimer produced a new type of high-performance plastic syringe printing plate in Germany or let the dirt remover seep into the text. After dirt removal, the residual dirt remover and dissolved photosensitive materials on the layout shall be washed with water quickly
the dirt remover contains benzene substances. Pay attention to the ventilation of the working environment during the dirt removal operation, and try to avoid inhaling benzene substances into the human body or reduce the amount of benzene substances. The solvent in the dirt remover is volatile, so pay attention to sealing
110. what is the use of baking plates
the positive PS version uses the photosensitive layer without light as the basis for inking. This photosensitive layer is still photosensitive and has poor resistance to alkali after seeing light. After baking, the molecular structure of the photosensitive layer can be changed from linear to linear, and the photosensitivity can be lost, so as to enhance the stability, corrosion resistance and mechanical strength of the graphic part, and greatly improve the printing resistance of the printing plate
whether to bake depends on the number of prints. Generally speaking, for the printing pieces with a print count of less than 50000, the PS version baked by the ordinary method can meet the needs of printing resistance, and there is no need to increase the baking process. Because the photosensitive layer at the dirty spot will be cross-linked and solidified after baking, it can no longer be dissolved in the dirt remover and cannot be repaired. Therefore, baking must be carried out after thoroughly removing dirt