Analysis of the Causes of Bad Flexographic Products

The printing plate is not resistant to printing and bloating, making the print fuzzy and rough

(1) Insufficient exposure and hardening of the photosensitive resin plate during plate making, so the ink is swollen and blurred in pressure and ink infiltration soon after printing, and only re-plating is used to solve the problem.

(2) The ink contains many benzene solvents, which cause the plate to swell, resulting in the use of a good ink solution.

(3) The mixed solvent added during the printing process contains a certain amount of benzenes. Although the amount is small, the plate swells due to a long time, and attention should be paid to it.

Blotting and poor gloss

(1) The volatilization and drying properties of the ink are not balanced, especially when too much ethanol is added during the printing process. The too rapid and unbalanced volatilization make the synthetic resin conjunctiva not smooth, light gloss is bad, and weight is white. If isopropyl alcohol and n-propanol are added, the situation may improve. Ink factory has matching supply of quick-drying and slow-drying thinners, which contain synthetic resin and the appropriate ratio of solvents. In the winter, it is possible to speed up the drying of thinners, and in the summer to slow down the drying of thinners, so that there will be no glare and whitening problems.

(2) If water-containing ethanol is added to the ink, even if the amount is small, water will remain when the ethanol is volatilized, causing the resin conjunctiva to be poor, resulting in loss of light and whitening, and should be avoided. Isopropanol also sometimes contains more water and should also be noted.

(3) Flexographic printing inks are mainly based on alcohol solvents, which are easy to absorb moisture. The humidity in the workshop is too high, and it is easy to make the ink film of printed products lose its light and whiten. The workshop humidity should be reduced to solve.

Print chalking is easy to erase

When printing for a long time, too much solvent is added to the ink, so that the content of synthetic resin is relatively reduced to a certain extent, and the ink layer is poor in conjunctiva, resulting in powdering. Some synthetic resin should be added properly or the ink should be used when adding the solvent

The quick-drying or slow-drying diluent supplied by the factory can prevent powdering from occurring.

Pinhole found in printed products

(1) The wettability between the ink and the surface of the substrate is so poor that the printed ink layer partially shrinks to produce pinholes. Adding glycol ether and other substances to the ink can increase wetting and leveling and improve pinholes.

(2) The surface of plastic film is covered with paraffin, lubricant and other substances, so that the printed ink cannot be wetted, and the ink is imprinted.

The layer produces pinholes. Clean the surface or perform oxidation, corona, or flame treatment to improve pinholes.

Prints are not clear

(1) Imprint patterns are not clear, dots are connected or the edges are fluffy, most of the time the ink is dry too fast, there is a dry phenomenon on the plate; or the ink viscosity is too large, the blotting quantity on the plate is too much, so that the blotting pattern dot Connected or frizzy. Slow-drying diluent should be added to reduce dryness and viscosity.

(2) Thickness of the ink layer on the edge of the printed pattern In most cases, the ink is dried too fast. The viscosity of the ink is increased for a long time on the printer. The ink layer on the edge of the imprinting pattern is thickened, and the slow-drying thinner can be added to solve the problem.

Printing products stick to each other

(1) The workshop temperature is high, the humidity is high, the printing speed is faster, and the ink is not dried and cooled when it is recoiled so that it adheres to the back of the print. Care should be taken to improve the above printing conditions.

(2) Adhesion occurred at one time after bag printing and packaging, and one of the reasons was that the slow-drying and residual solvents were added during the printing process, such as butanol. Should not increase or decrease as much as possible. Another reason is that the ink is mixed with substances having the property of promoting oxidation, and the ink is oxidized and sticky during a long storage period. Absolutely avoid the incorporation of such substances.

(3) The storage condition of the prints is not good. For example, if the temperature of the warehouse is too high, the humidity is too high, and the over-pressing of the prints is too much pressure, it may cause blocking. The above storage conditions should be improved.

Excerpt from: China Packaging News