The quality of the finished printing plate is also closely related to time. The control of time is the same as the temperature, and the requirements are relatively strict, mainly including: 1. Drying time in the oven; 2. Exposure time; 3. Development time.
1. Time in the oven
This time should first be determined by the dryness of the layout, and secondly, the prescribed range of drying.
For D and N, because the squeegee is a manual operation, the thickness of the squeegee cannot be completely controlled. In general, the scraped adhesive layer is thicker, and the drying time is longer. The glue applied each time is not too thick, but should be thin and uniform. Thirdly, the glue scraping should be carried out on the basis of sufficient drying last time, otherwise the surface drying degree will be inconsistent.
For the F version, you should also pay attention to the appropriate amount when applying the sensitizer. Otherwise, the layout is difficult to dry. If plates F and D are not sufficiently dried, it will cause the film or adhesive layer to loose and fall off during development; and if the drying time is too long, it may also lead to the phenomenon that development is difficult or not obvious.
For the N version, because it has no drying restrictions, but only depends on the degree of drying. Therefore, under the control of normal drying temperature, it can be stored in the oven for a long time to ensure that the plate surface is fully dried. If it is not sufficiently dried, the layout is likely to be thinned and frosted when developing.
2. Exposure time
The process of exposure is a process of photochemical reaction. Regardless of the type of material, although the exposure time has a specified value, it must be tested multiple times. In the process of plate making, you should be able to know the whole process, estimate the problems that will occur after development, and finally determine the appropriate exposure time.
It is necessary to judge from the situation at the time of development: whether the exposure time is appropriate.
Fast development, clear patterns and straight lines, proving proper exposure time;
Difficult or undevelopable development proves that the exposure time is too long;
The exposure time is not enough. For the F and D versions, the surface of the film or adhesive layer is loose or easily peeled off during development. For the N version, the layout is blank and there is glue on the non-pattern parts during development.
3. Development time
The most obvious expression of a successfully produced printing plate is the relatively short development time. This means that the adhesive layer has good adhesion and development needs to be fast. If the development time is long, it not only indicates that there are problems in the production process, but also affects the service life of the printing plate, and even leads to production failure. Because during the exposure process, the photochemical reaction is not sufficient, the developer dissolves the film of the non-light-transmitting part, and also affects the part where the reaction is insufficient. Therefore, the development time will affect the fastness of the printing plate. The development time is too long. For the F and o versions, the following problems will occur:
â‘ The edges of the pattern swell and the lines are unclear;
â‘¡The surface of the film or glue layer is loose, and the adhesion to the wire mesh is reduced;
â‘¢The film layer and adhesive layer are easy to fall off.
The development time is too long. For the N version, the following problems will occur:
â‘ The layout is thinned and trachoma appears;
â‘¡The edges of the pattern are hairy and the lines are not straight.
The process of making a printing plate is a complex physical and chemical process involving many factors. In addition to the above factors, there are the luminosity at the time of exposure, the humidity during the plate making process, etc. Especially in the plate-making process, many processes are manual operations, and many factors are directly controlled by people. Therefore, in the production process, many factors cannot be measured accurately. For example, the thickness of the squeegee is difficult to measure during operation. Therefore, how long it can be dried can not be specifically determined; for example, how thick the film layer after squeegee is, how long the exposure time should be, and not proportional Increasing, but through trial and error. However, because of the other preparation factors involved in the pre-plate making process, the conclusions drawn are only a reference. In short, to make the production process of screen printing as perfect and reasonable as possible, it takes a long time of practice, continuous summary, continuous exploration, and find out some laws.
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