Generation and solution of common phenomena after

Production and solution of common phenomena after baking PS plate

with the progress of PS plate processing technology, the printing suitability of PS plate is getting better and better, and the printing resistance is getting higher and higher. However, the printing resistance of the same plate is very different in different models. For example, on the B-B machine, the printing resistance of the PS version is lower. In order to improve the printing resistance of the printing plate, it is necessary to bake the PS plate. The printing resistance of the baked PS plate can be increased by 3~4 times, but in the process of baking, if the operation is improper, it will cause some disadvantages, which will not only save the plate, but also cause waste. 4. Low temperature tank power supply: 220V50Hz below, talk about the causes and solutions through the change of layout color after baking and the inking during printing

1. Abnormal color change of PS plate after baking

ps plate after baking, the color of the photosensitive layer of the plate will change to a certain extent. Under normal circumstances, after the printing plate is baked at a constant temperature of 230~250 ℃ for 5~8min, the photosensitive layer turns from green to reddish brown. However, if any link such as printing, development, baking temperature and baking time is not properly controlled, the quality of baking plate will be affected and the color of the plate will be abnormal

1) the blank part of the layout is light red after baking.

ps version after baking, the normal color of the drug film surface is reddish brown, and the blank part of the layout is the basic color of the layout. If the blank part of the layout is light red, it is because there is a small amount of photosensitive layer after baking. If the light red color disappears after the second development after baking, it will not cause dirt during printing. If the blank part of the page is still light red after the second development, it may cause dirt during printing. In this case, gently wipe it with pumice powder to reduce or eliminate the dirt. If it is serious, it is difficult to save it, and this plate will be scrapped. The micro photosensitive layer of the former is caused by the oxidation between the photosensitive layer and Al2O3 based on the aluminum plate due to the long storage time of the PS plate or the high temperature during coating. This kind of micro substance generally does not cause dirt, and it will not cause dirt after baking. The latter is mostly caused by insufficient exposure or development, so it will also cause dirt. Therefore, the printing plate to be baked should pay more attention to the control of printing time and development

2) after baking the plate, the photosensitive layer of the plate is dark brown or dark brown

such a color shows that the baking temperature is too high or the baking time is too long, which will carbonize the resin in the photosensitive layer. At the same time, the plate base will be deformed, softened and the mechanical strength will be weakened, which will affect the print resistance of the printing plate. The darker the color, the lower the print resistance. The solution is to reduce the baking temperature or the baking time

3) the photosensitive layer of the plate after baking is dark green

the photosensitive layer after baking is in this color, which indicates that the baking temperature is too low or the baking time is too short, the resin in the photosensitive layer is not completely cured, the purpose of baking is not achieved, and the printing resistance is also low. In this case, you can immediately put it back into the baking machine, and the export share to emerging countries will be greatly increased by extending the time, or the temperature will be increased for the second baking, so that the color of the baking version reaches reddish brown

2. The abnormal situation of inking on the plate after baking

although we can see whether the baked printing plate is qualified from the color of the plate, sometimes the color of the plate is normal, but when printing on the machine, there are problems such as dirty and incomplete inking

1) when printing on the machine, there is a phenomenon of incomplete ink on the plate in the form of a channel.

before baking, the PS plate should be coated with protective agent. The main component of the protective agent is emulsifier, which has the property of hydrophilic and oil repellent. When the protective agent coating is too thick, it is more difficult to dissolve in the developer with low concentration (after baking, the protective agent should be washed away with PS plate developer, that is, secondary development). Therefore, there will still be some protective agents left on the layout, resulting in the phenomenon of no inking. This kind of channel like phenomenon is the trace left by the high and uneven concentration of the protective agent smeared. In this case, you can brush once with a developer slightly thicker than the general PS version developer, neutralize the layout with 3% phosphoric acid after brushing, and then lift the ink with PS version developer after washing, or directly repeat with gasoline for 2 Improving the process management level of enterprises, wiping the printing plate can also play the role of ink lifting, so as to eliminate the situation that the road is not inked

2) when printing on the machine, there are generally two cases of local dirt or full plate dirt

one is that if the dirt is washed with gasoline and the bottom layer has a reddish brown baking layer, it indicates that the development is insufficient, and this dirt is generally not easy to remove. Second, if there is no reddish brown baking layer, it means that the concentration of the protective solution is too low, and the protective layer is too thin, which does not protect the layout from pollution. This kind of pollution cannot be found immediately. It can be found only after the printing plate is inked or when printing. Although this kind of dirty situation is difficult to solve, the printing plate can be wiped with PS version repair paste (the repair paste has no effect on the baked film), which can eliminate the dirty phenomenon. If the protective solution used for baking is left standing for a long time, the solute will precipitate, and the concentration of the solution poured out first is low, the protective layer will be too thin, which will cause dirt in serious cases. Therefore, shake or stir it before each use to make it mix evenly, so as to avoid the occurrence of the above disadvantages

3) after printing on the machine, film marks or tape marks gradually appear on the plate

because the dirty spots and film marks on the plate cannot be repaired with revision paste after the plate is baked, the operator generally needs to carefully check and revise the plate before baking, but sometimes the film marks and tape marks are very shallow, which is not easy to be found during revision. After baking, if you carefully check, you can find very light reddish brown marks, After printing on the machine, the film imprint will become more and more obvious. In this case, you can wipe the film imprint on the printing plate with a pumice stick, and then wipe it with a revision paste. You may not know the difference between masks very well about masks? At last, wipe the printing plate with a cloth to remove the above marks

3. Problems that should be paid attention to when coating protective agent and baking version

if some parts are not protected before baking version, some of the originally sealed oxide micropores reopen, and their changes during baking are as follows:

these micropores have strong adsorption, so the blank part is very easy to be polluted, and if the protection is improper, it will cause dirt when printing

1) method of coating protective agent

remove the dirt on the developed printing plate, rinse it with water, scrape off the water on the plate, pour the protective agent on the plate, use about 20~30ml for each folio plate, and then wipe the whole plate evenly with degreasing gauze (pay attention to be even, there must be no water sample trace), and then put it into the baking machine to bake the plate. The baking time is 5~8min. Take it out and wait for the plate to cool. Then use the developer for secondary development, so as to remove the protective agent on the plate. After air drying, rub Arabic gum on it and wait for printing

2) precautions

the photosensitive film after baking is very firmly adsorbed on the layout, and it is difficult to remove it from the layout with revision paste, so the printing plate must be repaired before baking

after revision, be sure to rinse the revision paste with water, otherwise the residual revision paste and the repaired dirt will pollute the layout and cause dirt on the printing plate when baking

the dosage of protective agent should not be too much, too much will appear water like traces, and serious will appear the phenomenon of incomplete ink on the above-mentioned channel, but the dosage should not be too small, otherwise it will lose its protective effect and cause dirt. The dosage is generally controlled in that there is no water like trace after wiping

degreasing gauze should be used when applying protective agent to prevent the fallen fiber from polluting the plate when baking. Do not apply too much force when wiping, so as to avoid the shedding of gauze fiber and affect the quality of baking version

the baking temperature and baking time should be determined according to the curing point of the photosensitive layer: too high baking temperature or too long baking time will cause the photosensitive layer to carbonize and deteriorate, the plate base to deform and soften, and affect the print resistance of the printing plate; Too low temperature or too little time will make the degree of curing insufficient and fail to achieve the effect of baking

after baking, it must be cooled naturally, not forced, so as not to deform the aluminum plate base. After the plate cools naturally, use PS plate developer for secondary development