PS plate exposure and development latitude

With the development of offset printing, people have higher and higher requirements for the quality of media. So what is a good plate, a good plate should have what kind of performance, how to exposure and development to get a good version, we use Huaguang YP-S as an example to discuss.
On a large scale, manufacturers should pay attention to the unity of the product, that is, regardless of the batch number and quantity of the product, the performance of the product should remain consistent within the validity period, and there should not be major changes. This is the most basic requirement.
If you go deeper into each plate then it should have the following advantages:
1, the photosensitive speed should be faster, 2 exposure plate - the development tolerance should be large 3, plate resolution (resolution) should be high 4, the layout should not have the naked eye can be found in the shortcomings 5, plate material contrast should be Big 6, India and India should be high We will focus here on the second article, the exposure of the plate - the development latitude.
The exposure of the plate is a photochemical reaction. The photochemical reaction time of different formulations may be different, but it is not that the exposure result is independent of time under certain conditions. In fact, as the exposure decreases, the result will be a certain change.
So the exact definition of latitude here is: the ratio of the maximum and minimum exposures that produce acceptable results.
The development latitude is better understood, that is, the change in the concentration of developer solution has little effect on the development results.
Plate exposure latitude and plate absolute exposure time have a great relationship.
Although both plates have the same exposure latitude, the absolute exposure can be quite different, as shown in the following table:
Exposure unit: second

There is a problem here. With the increase in the sensitivity of the media, the power of the exposure light source has increased. Although the latitude has not changed, the absolute time is getting shorter and shorter. To help some users suggest that the sensitivity of the media should not be too high. Otherwise, exposure is hard to grasp. After a lot of trials, explorations, and researches, the plate material has improved its sensitivity and increased its applicability to the development. For the processing technology, it has implemented the “strong exposure and weak display,” and has successfully solved this contradiction in both aspects.
Examine the impact of 1 exposure on the sensitivity of the exposure to light and the density of 4.0 or more films (normal requirements when printing) cover the same area of ​​the PS plate, with different exposure time for printing, under the conditions of the same relative to the processing After that, the coating loss was almost unchanged, and there was almost no difference in the dot quality. This fully proves that the difference between graphic and blank in offset printing is the concept of presence and absence, there is no intermediate tone, since the different exposure time has no effect on the image, that is to say, it can also be used for printing materials with fast speed. Large exposures are processed without affecting image quality.
Investigation 2 Developer Concentrations There are three important factors that influence the plate during the development process: development time, development temperature, and developer concentration. Tests have shown that the development density has the greatest impact on the development 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 was processed with the above two principles and achieved good results. The high sensitivity of the plate and the ability to perform shading at low concentrations were fully exploited. At the same time, it is extremely beneficial to the elimination of "leather printing."
The other side of the problem is that some users do not want to extend the exposure time, they are used to shorten the exposure time, increase the developer concentration. Under this processing condition, the large development latitude of the YP-S plate plays an important role. As long as the development time (shortening) and the exposure time (shorten) are adjusted appropriately, the YP-S version is suitable for a developer concentration of 1:2.5 to 1:3, but strong exposure and strong development (high concentration and long time) should not be avoided at this time. , high temperature, this will make the plate at a loss, which will greatly affect the printing plate resistance to force.
In accordance with the above ideas for correct use, the PS version of the printing resistance will be greatly improved, generally should be more than 100,000 prints. (Liu Wanrui) ("China Packaging News")