(3) Dirty protection agent
PS version of the baking protector is easy to precipitate, and the solute is deposited on the bottom of the bottle and the protective agent poured out is thin. The use of such a protective agent to wipe the plate will cause the plate surface protection film to be too thin or have a leaky area, causing the PS plate to become dirty. So be sure to shake it evenly before using it. Also wipe the protective agent must be rubbed evenly.
(4) Poor performance of the protective agent, and the baking plate is dirty.
The performance of the protective agent used in the PS plate baking directly affects the quality of the baking plate. Many manufacturers are self-made, should pay attention to whether the formula is appropriate, whether the performance of the drug used is standard, the preparation method is not appropriate. No matter which part of the link goes wrong, the performance of the protective agent will be affected and the protective agent will not be protected. In particular, when certain medicines are not available and they are replaced with infrequent pharmaceuticals, special attention must be paid to the quality of the protective agent. In order to prevent the loss of media, it is possible to try it out first, and you can put it into formal production only if there is no problem with it.
(Baking version of the liquid formula: water 1000ml; ammonium tetraborate (or ammonium hexaborate) 50g; flat plus 20 (or OP-10) 10g; sodium dodecylbenzenesulfonate 10ml.) Note that under normal circumstances baking solution The dosage should be 20-30ml/(block split version).
Third, there will be such problems in the operation of the baking machine.
(1) Surface scratches
The high temperature in the roasting press causes the PS plate to deform and bend, often scraping the plate and causing scratches when it is taken, and it is dirtier during printing. Slight scratches can be removed by using a plate cleaner or a dirt remover without damaging the image. If there is a serious scratch, destroying the photosensitive film cannot be recovered. (2) Light brown or dark brown after baking
Under normal circumstances, the photosensitive layer is reddish brown after baking. If the color is dark brown, the baking temperature is too high or the baking time is too long. This version is over-baked, so that the photosensitive layer of the resin has a different degree of carbonization, darkening and brittle, the result will reduce the print version of the printing capacity and ink affinity. (3) Dark green after baking
This version of the color, indicating low baking temperature or short time, the photosensitive resin is not completely polymerized, its stability, corrosion resistance and mechanical strength have not been maximized, can be re-bake once, to achieve the best results .
(Usually the curing point of the phenolic resin is 200-300°C, and the recrystallization temperature of the aluminum plate is 250°C. Therefore, the temperature of the baking plate should generally be controlled at 200-230°C for a time of five minutes.)
Fourth, there are many other aspects that affect the quality of baking plates:
(1) The fabric of the wipe protector is not clean. The fabric on the layout or the cloth is peeled off on the surface of the plate. If this happens, be careful to change the cloth. Wiping cloths should pay attention to the selection of long fiber cotton fabrics, or special cloth.
(2) The printer did not wipe the glue in time during the stoppage of the printing. After turning on the machine, it did not discharge the water roller first, but the ink roller or the roller with oil on the surface was put down without running water, resulting in a large number of layouts. Some ink. If the ink is washed with gasoline, the surface is clean, and it will be dirty when it is turned on. In this case, you can use a clean cloth, a cleaning solution, or a correction paste (the graphic base on the plate is already tight and tight, so it will not be removed by the correction paste). Scrub slowly until all the ink is dissolved. , And then wash with the fountain solution in time, you can completely remove the stains.
Fifth, pay attention to:
(1) The printed plate must be thoroughly cleaned before it is printed on the machine to avoid the phenomenon that the graphic part is not inked. Because the baking solution contains emulsifiers, and has a strong hydrophilic and oil-resistant, if you can not timely clean the baking version, it will easily accelerate the emulsification of the ink, and will also reduce the graphic basis of the lipophilicity.
(2) In normal circumstances, the recycled PS plate is not suitable for baking, and it is prone to severe deformation of the printing plate and printing on the machine, resulting in a fee. The temperature, time, amount, etc., given above for baking are not absolute. Different brands of baking solutions generally use different production processes and will use slightly different in the production process. In the middle of the experiment, we must first do a good job of the preliminary experimental work, get more accurate data, and then start the formal production and use, to avoid the waste of media and production time
Source: "Packaging and Printing Online"
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