During the printing process, we discovered a very strange phenomenon. A large-area halftone printing plate that looks no problem. After the machine appeared, one or two spots of sesame grain size were missing. The suspicion was that the revision had been changed, and the paper was reprinted. During the printing process and the revision process, the operation was strictly performed. The layout was clean and the outlets were even. No problems were found. However, after the machine came up, the same version-off phenomenon appeared. The location is different from the last time. Observed with the magnifying glass off the plate, found that the white point around is very neat, graphic and blank parts without any transition, thus eliminating the possibility of exhaust due to copying caused by the virtual version of the situation. Next, it was reprinted, and the layout was observed after the glue was wiped. There was no occurrence. Then the baking plate was baked. After baking, the plate was placed under the light and carefully observed with a magnifying glass. It was found that one of the outlets was missing and was wiped with a rubbing cloth. There has been a version of the phenomenon.
In view of the above situation, after careful analysis, the judgment is likely to be caused by the developer. The developer is prepared by directly dissolving the purchased developed toner in hot water. When the weather is cold or the preparation time is too long, a small amount of precipitate will be produced. If the developer is not completely washed after development, the developer is developed. The particles of the liquid will stay on the surface of the plate. Under conditions of heat or external pressure, the particles of the developer powder will continue to function, causing the graphic part to be dissolved, resulting in a plate-off phenomenon. In order to confirm whether this judgment is correct, we reprinted the prints. After the development, we thoroughly washed the water and wiped the plate evenly with a wet towel. Then we baked the plate and carefully observed the plate with a magnifying glass. The situation, after printing on the machine, everything is fine. Proved to be a problem with the developer.
Cause of this situation: First, the preparation of the developer solution takes too long, although in the preparation, the developer powder has been fully dissolved, but due to the storage time is too long, there will be precipitation phenomenon; second, the weather becomes cold, the developer will also Precipitation occurred; third, the operator did not completely follow the production process, washed directly after development, did not use 2% to 3% of the phosphoric acid solution for the fixing process, leaving the precipitation particles on the plate after the development, resulting in off version phenomenon.
In fact, the method of avoiding this phenomenon is very simple. First, do not use a developer with a precipitate; secondly, after the development, perform a fixing process and fully perform water washing.
(75719 troops Lu Yaohua)
Source "Printing Technology"