In recent years, the use of silver salt CTP plates in press printing has been increasing. Moreover, the daily usage of silver salt plates is also very large. Users are also more concerned about the problems during use. The author summarizes many years of production experience and believes that the preservation of silver salt CTP plates and related production conditions are closely related to the printing quality, especially the printing quality of newspapers. Sometimes the unfavorable factors in the process may even cause catastrophic printing. as a result of.
We analyzed some easily overlooked issues of silver salt CTP plates from both storage and use.
1. Problems with Silver Salt CTP Plate Storage
In general, the silver salt CTP plates we are concerned about are generally stored under conditions of temperature and humidity. The storage temperature is required to be less than 30°C and the humidity is 30% to 70%. The best storage temperature is 23°C and the humidity is 50%. The shelf life of silver salt plates is usually 36 months. For newspaper printing, due to the large amount of plates used, it can basically be stored and used as required. In addition to the general preservation requirements, we must also pay attention to the following issues:
1 We usually notice that the temperature and humidity cannot be too high. If the temperature is higher than 30°C, the photographic performance of the film will be greatly reduced. But at the same time, the humidity temperature should not be too low.
The storage humidity is too low and it is easy for the PS plate to accumulate static electricity. Under the action of static electricity, the PS plate easily generates sparks when it is separated, causing the PS plate to partially degrade. In addition, due to the electrostatic adsorption, the offset paper sticks to the PS plate, and the CTP automatic paper removal device malfunctions, resulting in a card plate. What's more, the stencil paper enters the plate processor, causing the circulation pump of the plate processor to become clogged. Caused a lot of time loss. For newspapers that are pragmatic, the time loss is enormous and cannot be compensated.
In addition, if the storage temperature is too low, the temperature difference between the storage environment and the use environment will be too large, moisture will condense on the PS plate, destroy the photosensitive layer, and cause the PS plate material to fail.
2 When you save the PS version, be sure to pay attention to the formation of the stack. Due to the heavy weight of the plate, when stacking too much, the shelves of stacked plates sometimes deform under the influence of gravity, causing deformation of the bottom PS plate. In use, these plates are often jammed in the plate processor, causing interruptions in production. In severe cases, the platen rollers may even be damaged.
3 storage location problem. The use of PS editions in newspaper printing is huge, and there are often multiple batches of PS editions in the warehouse. Attention must be paid during storage. First of all, different batches of PS plates should be stored separately, do a good job of identification, so as not to mix, resulting in expired PS version. Second, pay attention to the stacking sequence. The new version is in and the old version is out. Otherwise, because the weight of the piled PS plate is huge, it is a very difficult task to bypass the new version and use the old version.
2. Problems with silver salt CTP plate use
Silver salt CTP plate is a mature plate material with stable process. But sometimes there are some unexpected situations.
1 blank part of the plate is dirty. In the case of plate and syrup quality and correct exposure, it was caused by insufficient washing of the plate processor. At this time, we should check whether the nozzles of the washing machine washing part are blocked. In addition, the aging of the rubber roller and insufficient pressure between the rubber rollers will lead to the above situation.
2 printing plate graphic part is not inked. Such issues are highly concealed and often cannot be discovered during the process of plate making. It is not until the printing on the machine can be revealed that it will cause a great deal of waste of the PS plate material. At the same time, it will cause irreparable loss of time for newspaper publishing.
There are several factors that can cause such problems. First of all, the current plate processor is an automatic and regular replenishment of potions. Excluding human factors such as adding wrong potions, it is necessary to check whether the automatic filling of the plate dispenser is normal or not. In particular, it is necessary to pay attention to whether or not the plate dispensing pump is operating normally. Secondly, the silver salt CTP plate has a protective layer. If this layer is not cleaned in the plate cleaner, it will remain on the PS plate. When printing, it will also cause the plate to not be inked. This is caused by the clogging of the nozzles in the washing section of the processor.
3 Printing plate printing rate decreased. Silver salt CTP plate can generally reach 200,000 or so. Sometimes, if the imprint rate falls sharply and less than tens of thousands of grades are milled, in addition to considering whether the corrugator roll is clean, the potion is normal, the press is in normal condition, and the fountain solution used during printing is correct. There is also a problem that is not noticed, that is, whether the pH of the tap water used in the washing machine is normal. I have encountered such a problem, in the production of CTP printing rate fell sharply, printing less than 20,000 to a large number of grinding. Check the CTP, the plate processor, and the printer are all in the normal state. The syrup during the printing and the fountain solution during the printing are all normal. Finally excluding various factors, it was found that the problem was caused by the tap water used. Since the reservoir was cleaned on that day, it was found that the pH exceeded the normal range. It was estimated that the cleaning agent had not been rinsed clean. After the property department replaced the water in the reservoir, everything was normal.
In summary, the silver salt CTP plate has been used for a large scale for ten years and is already a fairly mature plate. This kind of CTP plate process is stable, but in the production, if we can pay attention to the following points or can reduce the occurrence of the use of failure, reduce the rate of rejection.
Pay attention to the status of storing CTP plates, such as proper temperature and humidity, whether the support is flat when stacked, the order of the other old and new plates, etc. It is necessary to strengthen the maintenance of the offset machine. After cleaning the plate processor, it is necessary to carefully check whether the rubber roller is worn, whether the nozzle is smooth, and whether the respective circulating pump and the supplementary pump are operating normally. Try to find faults in advance so as not to cause loss of time and benefits.