Cause analysis of the most popular phenomenon that

It is reported that with the continuous development of printing technology, the Yangtu PS version developed and produced by China has been widely used in China. Compared with offset printing plates such as gravure plate, PS plate has the characteristics of simple printing process, clear dots and high printing resistance, but sometimes it will lose its due efficiency due to various adverse factors. Due to the regeneration of PS version, the author has visited some printing manufacturers and found that many manufacturers have experienced the failure of PS version inking, and most of the failure occurred by purchasing the original PS version. This paper wants to analyze the causes of this fault from the following aspects for your reference

I. storage environment and shelf life of PS version

so far, there are nearly 20 PS version manufacturers in China, and some recycled PS version manufacturers also purchase aluminum version base to produce PS version. The standardized management and production scale of each manufacturer are different, and the sales progress and inventory period are also different. Due to the market economy, printing manufacturers have a wide channel to purchase PS version, and sometimes purchase some P3 versions with a storage period of more than one year. It is the main reason for the failure of PS version inking. In addition, some printing factories' warehouses or printing workshops for storing PS plates are not suitable for the storage requirements of PS plates, such as too wet indoor, too strong light, high temperature, acid and alkali erosion, etc. These conditions will cause the PS version to lose its due efficiency, make the exposure and development abnormal, and the inkability is extremely poor, so it is bound to be difficult to ink or not to ink on the machine printing

II. The sand mesh condition of PS plate and the quality of photosensitive layer

some printing manufacturers purchase PS plates for a short storage period, and the storage and use environment also meet the requirements of degrading organic substances, but there will also be non inking faults. Analyzing the reasons, I think it is mainly caused by the poor shape of electrolytic sand mesh of PS plate and the quality of photosensitive layer. The specific reasons are as follows:

1. PS plate needs to go through the production process of surface treatment of aluminum plate base before coating photosensitive wave. Among them, electrolytic grit process is very important. If it is not handled well, it will affect the next process, plate printing and printing quality. The sand orders of Banji are composed of numerous convex peaks and concave valleys. The concave valleys of sand orders are deep, most of the valley bottoms are on the same plane, and the side walls from peak to valley are steep. Such a structure can store enough water in the layout, and the blank part of the printing plate is not easy to get dirty during printing. However, if the convex peak is too high, the concave Valley is too deep, and the side wall is too steep, it is not easy to evenly coat the photosensitive solution. After exposure and development of PS plate, the protruding peak of sand eye is often difficult to go up and down because there is no photosensitive layer

2. Less denier is used in the photosensitive solution, which makes the alkali resistance and inkiness of the synthetic resin extremely poor, and the alkali resistance of the photosensitive adhesive prepared with photosensitive agent and other materials is poor, resulting in the erosion of the developing solution after the development, the fine dots, thin words and thin lines of the graphic part are first dissolved and reduced. If the development time is extended, not only the dot area of the high-profile area and the middle tone area will be reduced, but also the ink absorption performance and printing resistance of the PS version will be reduced

3. the storage place of the photosensitive solution used for coating is high in temperature, high in air humidity, and the storage period is too long. If it is used to coat the photosensitive layer, the inkability is extremely poor

4. the maturity of the photosensitive solution is too low, the photosensitive coating is too thin, the coating surface is too smooth for various reasons, and the developing plate is not coated with developing ink, so the PS plate is not easy to be inked for machine printing

III. printing and printing

in addition to the reasons for the quality and storage of PS version, the improper operation of printing technicians all night and printing will also cause poor inking or non inking failure

1. The density of the original image and text is too low. This "super glue" can be applied to materials with different surface characteristics, which is easy to cause poor alkali resistance of image and text parts and loss of photosensitive layer after exposure and development

2. Overexposure, developing too much skin, and the high concentration of sodium hydroxide in the developing solution will make the photosensitive layer of the developed image and text thinner

3. The PS version was not inked after exposure and development, and the light exposure time was too long, which made the photosensitive layer of the image and text decompose, and the color became light blue

4. The protective agent on the baking plate was not completely removed during the second development. Because the protective agent contains emulsifier, if it is left on the layout, it will cause ink emulsification, reduce the ink absorption performance of the graphic part, and will not absorb ink in serious cases. The concentration of the protective agent

5. Because the room temperature is low in winter, the ink becomes thick, and the ink must be thinned with ink blending oil. In this way, the water volume of the layout also needs to be increased (because the ink has high fluidity and oiliness, it is easy to get dirty). Especially in the early stage of proofreading, the amount of water is easy to be too large. Large water and thin ink will cause ink emulsification and reduce the ink absorption performance of the image and text part. If the photosensitive layer of the image and text part is too thin and the density is poor, it will also cause the failure of not adsorbing ink

6. Due to the guarantee for printing or stopping printing and sealing, the specified creep limit is usually adopted to protect the glue from deterioration, so that the glue film on the surface before printing can not be removed, and there is a problem of no inking when inking

7. the printing plates that are out of the machine but still available should generally be retained in case of replenishment. However, because the sealing glue or glue is not evenly wiped before the layout is cleaned after falling off the machine, the layout will not be inked or dirty if it is not wiped clean during reuse

8. Under the repeated friction of the water roller, inking roller, rubber roller, paper powder and paper wool, the photosensitive layer of the printing plate is gradually destroyed, the lipophilicity is weakened, and the hydrophilicity is enhanced. When the wetting solution given to the printing plate is excessive, the wetting solution will adhere to the image and text part, forming a water retaining film, resulting in the failure of inking