Three factors that affect the exposure of photosen

Factors affecting the exposure of photosensitive plate making (3)

this paper introduces a method to correctly determine the exposure time. First, use the same photosensitive adhesive to coat several plates respectively. The operation methods and conditions of these plates must be strictly consistent, and then exposure with the same light source at the same distance, but with different exposure time. The exposure time starts from 15 seconds and is doubled, i.e. 30, 60, 120, 240 and 480 seconds. Through development, we can see that the photosensitive adhesive layer on each plate has different expansion, as shown in Figure 4. In this way, we can take the point without expansion as the exposure time. In the future, if the exposure distance is required, we can calculate the new exposure time according to the following formula. The calculation method is as follows:

if the light source is changed, the new exposure time can be calculated according to the following formula:

many factors affect the exposure. The surface roughness of the metal surface before electroplating has an impact on the quality after plating. In addition to the main factors such as light intensity and distance, we should also consider the sensitivity of photosensitive colloid, the hardening process of colloid, the coating thickness of adhesive layer, the spectral sensitivity of photosensitive colloid, the spectral scattering rate of exposure, and the loss of light caused by light absorption

in the actual production operation, in order to determine whether the exposure time is correct, you can also observe that the color of the photosensitive adhesive layer on the plate changes only under the same experimental conditions. The color of photosensitive adhesives from different manufacturers may be different. The color of most diazo photosensitive adhesives currently used is green. Through exposure, the color of photosensitive adhesives will gradually turn light blue, and then the exposure can be stopped. Overexposure will affect development. Insufficient exposure will cause development difficulties

4.2 determination of distance between light and plate

light distance affects exposure time and image quality. The short distance between the lamp and the plate will shorten the exposure time but affect the resolution. The different distance between the lamp tube and the plate will produce "bright spots" in the center of the image and serious sidewall corrosion around it. Increasing the distance between the lamp and the plate will reduce this effect and improve the resolution, but the exposure time is greatly prolonged

in order to estimate the minimum light distance corresponding to producing good definition with the best exposure time, measure the diagonal of the image area on the plate, and place the exposure equipment so that the light source and the vacuum printer are separated by the measured distance. If you want to expose images of various sizes, you should try to standardize one or two distances, because changing the distance between the lamp and the version will cause confusion. There is an empirical method recommended to you; If the standard distance mentioned above is doubled, the exposure time will be tripled. Conversely, if this distance is halved, the exposure time will be reduced to one quarter of the original

if several plates are exposed at the same time, you must remember to measure the diagonal of the whole image and determine the distance between the light and the plate. Because one plate is exposed at a time, changing the exposure distance is faster and more applicable than increasing the exposure time

5 humidity of photoresist

complete drying of plate material is very important for effective exposure. The more thoroughly the plate is dried, the shorter the exposure time will be. On the contrary, the exposure time will be extended accordingly. Therefore, pay attention to the consistency of the drying degree of each batch of the same version when printing. Residual water will hinder the crosslinking of diazo sensitizer and polyvinyl alcohol in photosensitive adhesive. In fact, the low cost and function of moisture all affect the exposure. Even if the optical integrator has received an appropriate amount of light, the version will show various signs of insufficient exposure

the plate drying oven, which controls heat and removes moisture, is the most effective drying equipment before and after plate exposure. Strong hot air dehumidification is another method. The coated version should be dried under the yellow safety light in the dark, and should not be exposed to high temperature for a long time

6 supplementary instructions on post exposure

it is not a good idea to replace the first correct exposure with this method by placing the version in the exposure equipment after development and development. Although the exposure of some double nitrogen templates will be improved after adoption, their water resistance will be affected. If the exposure is obviously insufficient, it is vulnerable to solvent etching

the post exposure method has almost no effect on diazo photosensitive template materials, because the residual diazo sensitizer is washed away during the development process without additional cross-linking reaction. The only advantage that can be obtained is the rapid drying of template materials

it is necessary for every plate maker to determine the correct exposure parameters. Before each exposure with a brand of photoresist, it is best to conduct exposure experiments to master the exposure tolerance and relevant exposure parameters of the product. Version exposure requires only a little experience and assurance to control some variables. It is often easier to make a correct version exposure than to take shortcuts and guess

source: China porcelain trade

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