Factors Affecting the Quality of Self-adhesive Label Flexography (2)

The corona discharge is completed between the electrodes at the short distance. One end of the two electrodes is connected to a high frequency and high voltage, and the end of the array is grounded. For example, the corona treatment frequency range of a typical narrow web press is between 9-30 KHz, and the output is squeezing - 15,000 volts. In the case of large print speeds and high speeds, higher voltages are required. In corona discharge treatment, the discharge process releases electrons, ions, and protons contained therein, some of which impinge on the surface of the polymer and add to the free proton reaction sequence. The functional groups can be introduced on the surface. Most of these functional groups contain carbon and oxygen. Usually, the surface and force of the film after corona should reach 40 dyne or more will not cause the ink to fall off.
6. Ink color matching

The color of the ink directly affects the color quality of the printed product, especially for the spot color ink, which is usually modulated in the ink chamber first and detected using a colorimeter. The naked eye can no longer see the discernment, and factories that require more extensive use sometimes require it. The color density meter of a professional supplier is now more complete, and the instrument can provide recommended ink color formulae while measuring the sample according to the ink database provided by the ink manufacturer, which greatly improves work efficiency.

7. Printing press and its operation and adjustment

This factor clearly determines the quality of printed products. For example, the gear bars in flexo printing, which are the periodic bars formed by a certain gear in the printing unit drive system trapped on the prints, are affected by the defects of the printing press itself. Product quality. The tension control ability and manufacturing accuracy of the printing press also affect the registration and printing accuracy.

8. Die cutting

As a feature of self-adhesive label printing, label die cutting has always been a significant component. The quality of die-cutting processes directly affects the labeling and use of labels. At present, the common die-cutting methods are round-pressing rounding and production flattening. The flat-pressing flat die-cutting speed is slow and the precision is slightly poor, while the round-pressing round die-cutting is not only fast and accurate, but also the machine adjustment loss is very small. . At present, the labeling of the product has been more and more using the automatic labeling method, and the labeling speed has become more and more reminiscent. Now, the speed of 250-300 Label/Min is not uncommon for medium and small labels. Therefore, the high-quality die-cutting processing of China's adhesives has become the market's development needs. At present, more and more various types of round-circular die cutters are seen as a product of the times. The medium-solid round die cutter has a long service life, high die-cutting precision, and quick operation, and is suitable for medium-to-long live work; and the thin-plate type round die cutter with h-magnetic roller cooperates with the magnetic roller to have a shorter service life than one Die cutter, but die-cutting accuracy, running speed is also excellent, suitable for short-lived version. Moreover, round-circular die cutters have been steadily declining in prices in Europe and the United States in the past decade, and so far they have dropped by 30-50%. The development of die-cutting knives is a great impetus for the flexographic printing of adhesive labels, including flexographic printing.

9. Static electricity

Static electricity is often overlooked, but static electricity is often a very important factor in actual production. Electrostatic charges are formed by friction and induction and are more pronounced on the film. Therefore, the entire adhesive manufacturing and printing process will generate electrostatic charges that will occur on the materials and the machine. If they are not removed in time, they will cause a lot of troubles and quality problems with the adhesive tape. Problems that may be caused by static electricity in label processing :

1) Print quality (all printing methods): The needles or nets are missing on the label, and each defect is caused by partial discharge of a certain amount of charge (which can be considered as a small explosion);

2) Ink build-up or repulsion: Static electricity on the material or machine can cause uneven distribution of the ink on the material, appearing to be deep and shallow;

3) Die-cutting/effluent quality; the label is discharged along with the waste, so operators often mistakenly believe that the pressure of the die-cutting knife is insufficient and apply more pressure to the die-cutting knife so that the hair-cutting tool is easily worn out. Or destroy it to reduce its service life.