In the packaging printing industry, the printing resistance of the printing plate refers to the maximum printing quantity that the printing plate can print on the premise of ensuring the printing quality, also known as the printing resistance rate. The number of copies of the printing plate mainly depends on the stability of the graphic part and blank part of the layout. If some of them are damaged, the printing plate will lose its use value.UV Ink And Water-Based Ink Technology
1、 Reduce surface friction of printing plate
In the printing process, the printing plate is rolled and contacted with the water (ink) roller and blanket under a certain pressure to complete the transmission of printed pictures and texts. There are many times of friction in this process, and the greater the printing pressure, the greater the friction. If the ink pigment particles are thick or there is a dry and solid ink cover on the ink roller or the powder and hair of the paper are serious, it will be more intense friction. In addition, the low precision of printing machinery, poor adjustment or improper use of printing machine will cause additional friction.UV Ink And Water-Based Ink Technology
All kinds of friction destroy the surface structure of the printing plate from the beginning of printing. With the increase of the number of printing, the degree of surface damage of the printing plate gradually intensifies.UV Ink And Water-Based Ink Technology
The abrasion of the blank part of the layout gradually smoothes the sand mesh, which weakens the water content of the layout and makes the layout dirty. Especially for the undercut part of the layout, due to the obvious jumping phenomenon of the water (ink) roller and blanket roller when they are in contact with them, the layout is subject to the greatest impact, so it is worn and dirty quickly and seriously.UV Ink And Water-Based Ink Technology
The wear of the graphic part of the layout changes its lipophilic and water-resistant performance. For halftone graphics and text (DOT), the hydrophilic area of its low-cost dot area is greater than the lipophilic area, which is conducive to the expansion of water and is more likely to lead to the flowering of low-cost dot (dot becomes smaller). On the contrary, in the high formation dot area, the lipophilic area is larger than the hydrophilic area, UV Ink And Water-Based Ink Technology.UV Ink And Water-Based Ink Technology
which is conducive to the expansion of oil. When the dot foundation and the sand mesh around it are worn, it is occupied by the polar group in the ink to form the lipophilic foundation, which expands the lipophilic area of the dot and makes it paste. Generally, the phenomenon of printing plate flower and paste occurs at the same time.UV Ink And Water-Based Ink Technology.UV Ink And Water-Based Ink Technology
Therefore, in addition to ensuring the minimum pressure of each part of the printing unit and the level of each drum, pay attention to the following points:
1. Keep the surface speed between the water (ink) roller and the plate cylinder as consistent as possible
2. The shaft core of the water (ink) roller shall be straight and the outer diameter shall be consistent to maintain its uniform speed
3. Control the axial movement of the water (ink) roller within the minimum range
4. Use high-quality ink and paper. If only one sheet is of poor quality, wash the blanket frequently.
2、 Reduce the electrochemical and chemical corrosion to the printing plate
Because the plate material of PS plate is mainly aluminum, and aluminum is easy to react with the electrolyte and inorganic acid in the fountain solution to produce new inorganic salts and replenish the damaged hydrophilic film. UV Ink And Water-Based Ink Technology
The pH value of the fountain solution should be controlled between 5-6. If the pH value of the fountain solution is too high and the ink emulsification is serious, the ink drying time will be delayed and the back of the print will be dirty. UV Ink And Water-Based Ink Technology
Moreover, both of them will cause excessive corrosion to the printing plate. In serious cases, the hydrophilic oil layer of the graphic part of the printing plate will fall off, resulting in “plate dropping” and scrapping of the printing plate.UV Ink And Water-Based Ink Technology.
The temperature of fountain solution is to ensure that the high temperature caused by high-speed friction on the printing plate surface is reduced. Generally, it should be controlled between 10-14 degrees. If the temperature of the fountain solution is too high, it will not only accelerate the chemical reaction between the fountain solution and the plate base, but also cause problems such as dirty layout.UV Ink And Water-Based Ink Technology
2. Ink balance
In the printing process, the moisture of the layout should be controlled within the required minimum, not too large. If the water content of the layout is large, the amount of ink must also be relatively increased, resulting in the virtual and untrue picture and text, which will not only affect the quality of the printed product, but also accelerate the damage of the printing plate. On the contrary, too little moisture in the layout will cause paste, dirty version and other phenomena, which will also accelerate the damage of the printing plate.UV Ink And Water-Based Ink Technology
The ink on the printing plate should be supplied according to the required amount, and ensure that there is a certain residual ink layer on the plate after transfer, which can not only reduce the wear of the graphic part by friction, but also prevent the graphic base from being corroded by direct contact with the fountain solution. On the contrary, too little ink layout will not only make the printing ink light, UV Ink And Water-Based Ink Technology
But also because the Mo layer of the graphic part of the layout is thin, the corrosion resistance of the fountain solution is also poor, which will accelerate the damage of the printing plate. At the same time, there is too little ink on the ink stick, and the water on the layout is easy to transfer to the ink, resulting in the deinking of the ink roller without ink, resulting in the phenomenon of pattern plate. Of course, too much ink will make it paste or cause the disadvantage of dirty version.UV Ink And Water-Based Ink Technology
When the printing is stopped halfway, wipe the Arabic glue solution for the printing plate. The dry and solid adhesive layer after the water in the glue solution evaporates not only reduces the surface free energy of the blank part of the printing plate, but also isolates the contact between the metal surface and air, preventing the reaction between carbon dioxide in humid air and the blank part of the printing plate.UV Ink And Water-Based Ink Technology.