Analysis of the causes of the bad phenomenon of flexo printing
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The printing plate is not resistant to printing and swelling, making the print blurred and rough
(1) Insufficient exposure and hardening during the photosensitive resin plate making, so shortly after printing, the film is swollen under pressure and ink infiltration, and only re-plate is solved.
(2) The ink contains more benzene solvents, which causes the plate to swell and only replace it with good ink.
(3) The mixed solvent added during the printing process contains a certain amount of benzene, although the amount is small, the length of time makes the plate
Swelling should be noted.
Imprinting whitening and poor gloss
(1) The evaporation and drying properties of the ink are unbalanced, especially when too much ethanol is added during the printing process, and the volatilization is too fast and unbalanced, so that the synthetic resin conjunctiva is not smooth, the gloss is poor, and the white is heavy. If isopropyl alcohol and n-propanol are added, the situation may improve. The ink factory has a supply of fast drying and slow drying diluents, which contain synthetic resins and a suitable solvent. In winter, the thinner can be accelerated, and in the summer, the thinner is added slowly, so that the bad gloss and whitening defects do not occur.
(2) If aqueous ethanol is added to the ink, even if the amount is not large, moisture will be left behind due to evaporation of the ethanol, resulting in poor resin conjunctiva, resulting in loss of light and whitening, and should be avoided. Isopropyl alcohol sometimes contains more water and should be noted.
(3) The flexographic ink is mainly based on alcohol solvent, which is easy to absorb moisture. The humidity in the workshop is too high, and the ink film of the printed product is also lost and whitened. Should reduce the humidity of the workshop to solve.
Imprinting powder is easy to erase
When printing for a long period of time, too much solvent is added to the ink, so that the content of the synthetic resin is relatively reduced to a certain extent, and the film of the ink layer is poor, so as to be powdered. Appropriately add some synthetic resin when adding solvent, or use ink
The factory supplies quick-drying or slow-drying thinner to avoid powdering.
Printed pinhole
(1) The wettability between the ink and the surface of the substrate is too poor, so that the printed ink layer partially shrinks to cause pinholes. Adding glycol ether and other substances to the ink can increase the wetting and leveling properties and improve the pinhole phenomenon.
(2) The surface of the plastic film is stained with paraffin, lubricant, etc., so that the printed ink cannot be wetted, and the imprinted ink layer generates pinholes. The surface must be cleaned or oxidized, corona, and flame treated to improve pinholes.
The print pattern is not clear
(1) The printed pattern is not clear, the dots are connected or the edges are fluffed. In most cases, the ink is too dry and has a dry phenomenon on the plate; or the viscosity of the ink is too large, and the amount of ink absorbed on the plate is too large, so that the blotting pattern dots Connected or raised at the edges. Slow drying diluents should be added to reduce dryness and viscosity.
(2) Thickness of the ink layer at the edge of the printed pattern In most cases, the ink is dried too fast, and the viscosity increases when running on the printing machine for a long time, so that the ink layer on the edge of the printed pattern is thickened, and slow-drying diluent can be added to solve the problem.
Prints stick to each other
(1) The workshop has high temperature, high humidity, fast printing speed, and the ink is not dry and cold through after re-rolling after printing, so as to adhere to the back of the printing. Care should be taken to improve the above printing conditions.
(2) One of the reasons for the adhesion of the printed bag after the stacking is that the slow drying and the residual amount of solvent, such as butanol, are added during the printing process. Should be added as little or as little as possible. Another reason is that a substance having an oxidizing property is mixed in the ink to cause the ink to be oxidized and become sticky during a long storage period. The incorporation of such substances should be absolutely avoided.
(3) The storage conditions of the printed products are not good. For example, if the warehouse temperature is too high, the humidity is too high, and the printed matter is too much pressure, it will cause adhesion. The above storage conditions should be improved.