Factors affecting the reduction of outlets
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Influencing factors and solutions for the reduction of printing technology outlets The basis for print reproduction and color reproduction is the real reflection of the reproduction of prints, levels and colors. The quality of the outlets will directly determine the quality of the printed matter, so controlling the quality of the outlets is of great significance.
Network dot reduction is a major factor affecting dot reproduction and affecting print quality. The maximum density of film, exposure, development conditions, as well as friction during printing, viscosity of the ink, and yield value are the main factors that cause the dot to shrink.
1. The effect of maximum film density
The printing plate is a process of transferring the image on the film to the PS plate by closely bonding the film and the PS plate. In general, the density of the film used for printing is greater than 3.5, preferably around 4.2. At the same time, the dot type of the dot is better, that is, the edge around the dot is required to be clear, and the boundary with the blank is clear. If the density of the field is too low, the small dots of the image will be easily reduced or even lost when printing, and the fine text will be broken. If the edge of the dot on the film is blurred, the dot on the PS plate will change randomly as the exposure and development conditions change, and the dot may increase or decrease.
2. The effect of exposure
Nowadays, the printing machine generally uses the light emitted by a UV lamp as the exposure light source, so that the light is not parallel but scattered. The scattered light is reflected by the film and reflected by the surface of the PS plate to reach the lower part of the film access point. The edge, so that the edge of the corresponding dot formed on the plate is in a half-exposure state. The light directly under the UV lamp is relatively parallel, and the half-exposure of the edge of the dot is lighter, and the phenomenon of the small dot around is more serious. During development, the dot area will shrink or even some small dots will be lost. For different PS versions, the appropriate exposure amount should be selected. If the exposure amount is too large, the dot area will be reduced even if the development conditions are normal.
3. Influence of development conditions
If the developer concentration is too large or the development time is too long, even if the exposure is normal, the developer will excessively corrode the PS plate, which will often dissolve or even completely lose the small dots of the graphic, and the printing plate will also resist printing. decline. In general, outlets below 5% are prone to loss, and 40% midtones are larger. If the PS version is overexposed, the developer concentration is too large, and the development time is too long, which also causes the dot to shrink.
4. The influence of friction during printing
In order to prevent the ink from being absorbed in the blank portion of the printing plate during printing, it is required to wet the printing plate with the dampening solution before the ink is applied. During the high-speed operation of the printing press, the surface of the printing plate is rubbed by the water roller and the rubber roller. The friction causes the sand around the dots to wear, and the dampening solution is then immersed to form a hydrophilic oil-repellent film. For the high-profile part of the printing plate, the area coverage of the mesh is small, the hydrophilic area is larger than the oleophilic area, which is conducive to the expansion of the dampening solution, and the formation of the hydrophilic oil-repellent film due to the abrasion of the sand. Preventing the ink from spreading normally will inevitably cause the dots to shrink.
5. The effect of ink viscosity and yield value
The viscosity of the ink is too large, the yield value is too high, it is easy to cause the ink to flow, the ink is too short, and it is not easy to spread on the PS plate. Even if it is spread under the influence of printing pressure, the ink on the plate dot will be due to the viscosity. Too high and shrink to the center, which will also cause the dot to shrink.
In view of the above situation, if the highest density of the film is insufficient to cause the dot to shrink, then only a set of film of appropriate density is re-outputted to solve the problem.
In the case where the film density is appropriate, the factors causing the dot reduction during the plate making process are mainly the exposure amount and the development condition.
At this time, it can be solved by means of signal bar tracking management. When the plate is printed, the gray ladder is closely combined with the PS plate, and then exposed. After the development, the exposure amount, the developer concentration, and the development speed can be checked by observing the reproduction of the steps, and then adjusted according to the actual situation, so as to avoid the purpose of reducing the dot.
For the dot reduction caused by friction during the printing process, the printing pressure can be reduced as much as possible while ensuring good ink transfer and dot reproduction, thereby avoiding the dot shrinkage caused by the wear of the printing plate caused by the friction.
In short, the quality of the dot directly affects the reproduction of the tone and level of the print, so it must be controlled throughout the entire printing process to avoid dot reduction or to minimize the shrinkage of the dot. Influencing factors and solutions for the reduction of printing technology outlets The basis for print reproduction and color reproduction is the real reflection of the reproduction of prints, levels and colors. The quality of the outlets will directly determine the quality of the printed matter, so controlling the quality of the outlets is of great significance.