Exposure and development tolerance of the hottest

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Exposure and development tolerance of PS plate

with the development of offset printing, people have higher and higher requirements for plate quality. So what is a good plate, what kind of performance a good plate should have, and how to expose and develop to get a good machine version, we take Huaguang yp-s as an example to discuss

generally speaking, manufacturers should pay attention to the unity of products, that is, regardless of the batch number and quantity of products, the product performance should be consistent within the validity period, and there should be no major changes, which is the most basic requirement

if you go deeper into each plate, it should have the following advantages:

1, the photosensitive speed should be fast

2, the plate exposure - the development tolerance should be large

3, the plate resolution (resolution) should be high

4, the plate should not have defects that can be found with the naked eye

5, the plate printing contrast should be B, the diameter of the disc sample should be large

6, and the printing resistance should be high

here we focus on Article 2, That is, the exposure - development tolerance of the plate

plate exposure is a photochemical reaction, and the photochemical reaction time of different formulas may be different, but it is not that the exposure result is independent of time under certain conditions. In fact, the result will change with the increase of exposure

therefore, the exact definition of tolerance here is: the ratio of the maximum and minimum exposure to produce acceptable results

the development tolerance is better, and the unit is n/mm2mpa, which means that the change of developer concentration has little effect on the development result, which is the most ideal

the exposure tolerance of the plate is closely related to the absolute exposure time of the plate

although the two plates have the same exposure tolerance, the absolute exposure can be quite different, as shown in the following table:

exposure unit: second

exposure time exposure tolerance absolute time a 50 ~ 40 50/40=1.25 10 b 20 ~ 16 20/16=1.25 4 this brings a problem. With the improvement of plate sensitivity and the increase of exposure light source power, although the tolerance has not changed, the absolute time is getting shorter and shorter, Help some users put forward that the plate sensitivity should not be too high, otherwise the exposure is difficult to master. After a lot of experiments, exploration and research, the sensitivity of the plate is improved and the development suitability is increased; For the processing technology, it is to implement "strong exposure and weak display", which solves this contradiction satisfactorily from these two aspects

investigate the effect of 1 exposure on sensitivity

take the film that has been exposed and the density is above 4.0 (normal requirements during printing) and cover it on the PS plate with the same area. Print it at different exposure times. After washing and processing under the same parent conditions, the coating loss is almost unchanged, and the point quality is almost no difference. This fully proves that in offset printing, the difference between graphics and text and blank is the concept of yes and no, and there is no intermediate tone. Since the number of material types it applies to is impressive, different exposure times have no effect on the image, that is, it proves that plates with fast photosensitivity can also be processed with large exposure, which does not affect the image quality

Investigation 2 developer concentration

investigate the influence of three important factors on the plate during the development process, namely, development time, development temperature and developer concentration. The experiment shows that the developing concentration has the greatest influence on the developing process. At the same time, under the same temperature and time conditions, the exposure time is inversely proportional to the developer concentration

the yp-s plate is processed with the above two principles and good results are achieved. The high sensitivity and low concentration flickering characteristics of this plate can be brought into full play. At the same time, it is very conducive to the elimination of "leather seal"

the other side of the problem is that some users do not want to extend the exposure time. They are used to shortening the exposure time and increasing the developer concentration. Under this processing condition, the large development tolerance of yp-s plate plays an important role. As long as the development time (shortened) and exposure time (shortened) are properly adjusted, the yp-s version is suitable for the developer concentration of 1:2.5 ~ 1:3, but at this time, strong exposure and strong development (high concentration, long time and high temperature) should be avoided. This will make the plate at a loss, so it can also be considered as a new fiber-reinforced composite material, which greatly affects the printing resistance of the plate

if you use it correctly according to the above ideas, the printing resistance of PS version will be greatly improved, which should generally reach more than 100000 prints. (liuwanrui) (China Packaging News)

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