The selection of printing plate and ink should be considered when printing Cigarette Packaging Boxes

The selection of printing plate and ink should be considered when printing Cigarette Packaging Boxes

The printing plates used in flexographic printing are divided into rubber plates and photosensitive resin plates. The ink is mainly divided into solvent inks, water-based inks and UV inks. Solvent-based ink is similar to intaglio printing ink. This paper mainly explains the selection of water-based ink from the quality parameters of water-based ink, such as fineness, viscosity and pH value.

The selection of printing plate

Flexible printing plates are mainly divided into two categories:

Rubber plate and photosensitive resin version, and photosensitive resin version is divided into liquid photosensitive resin version and solid photosensitive resin version. Rubber edition is mainly hand-carved rubber edition, casting rubber edition and laser engraving rubber edition, its plate-making cost is lower, but the printing quality is not as good as photosensitive resin edition, more suitable for printing image requirements simple print.

The thickness of solid resin version is relatively uniform, and the expansion rate is much smaller than the rubber version and liquid resin version. Due to the plate has good surface inking, higher printing resistance, and plate tolerance is better, can reproduce the finer highlight dot and fine text, lines, etc., however, the plate price is more expensive.

The general solid version is more suitable for printing fine lines, high resolution hierarchical dot points and anti - white text. In addition, from the perspective of cost, the printing quantity of the product should be larger to be cost-effective. And liquid photosensitive resin edition is based on liquid photosensitive resin material, go through the back flow, the front of the monitor's mask exposure, exposure, exposure, no hardening of recycled resin, development comprehensive and dry again after the exposure, plate-making are relatively long time, usually need 1 h or so, however, the raw material cost is about half of the solid resin version.

In addition, because the accuracy of the liquid plate thickness is not as high as the solid version, and the deformation coefficient is relatively large, the printing quality is not as good as the solid version. Therefore, it is generally suitable for printing a small number of products, as well as relatively simple layout.

Flexo printing ink selection

The correct use of ink, in fact, is to control the quality of ink. Flexographic printing mainly has solvent ink, water ink and UV ink three categories. Solvent-based ink is similar to intaglio printing ink. The selection of water-based ink is mainly explained here. The quality parameters of water-based ink are mainly fineness, viscosity and pH value.

1, the fineness

Fineness of water-based ink, the pigment, packing particles are relatively fine, good color effect, printing ink relative coating amount is less, you can obtain a satisfactory color effect.

Control the fineness of flexo printing waterborne ink, can be used to detect the fineness of the scraper, generally flexo printing waterborne ink fineness within 20µm is appropriate, the lower the value of the ink color concentration is stronger, the amount of ink can be relatively reduced, you can obtain the ideal color, printing is not easy to paste and other shortcomings.

2, viscosity

Viscosity is also one of the main indicators of water-based ink, printing product quality has a greater impact, if the viscosity is too high, ink advection is not good, affect the ink uniform coating, and prone to dirty version, paste version and other shortcomings. On the contrary, if the viscosity is too low, the printing color quality is not good.

Usually high-grade waterborne ink viscosity, you can control the ink temperature and diluent dosage, so that the ink viscosity to meet the requirements of printing. For the viscosity test of water-based ink, the viscosity coating No. 4 cup is generally used to fill the ink, and then the time from the release hole to the ink flow in the cup is the test result.

3, pH value

PH value is also an important control index can not be ignored, and the change of PH value will change the viscosity of ink. Usually, the PH value of water-based ink is controlled in the range of 8.5-9.5, then the printing performance of ink is relatively good, and the printing quality is relatively stable.

When the PH value is higher than 9.5, due to the strong alkaline ink, its viscosity will decrease, drying speed is slow, water resistance is worse. When the pH value is lower than 8.5, due to the alkalinity of the ink is weak, its viscosity is higher, the ink is prone to dry phenomenon, so that the printing plate or roller blocked, resulting in the layout dirty. Therefore, the printing process should pay attention to the control of pH value. Generally, the PH stabilizer is used to adjust the PH value of ink, when used, the pH stabilizer is added to the ink stirring evenly or directly into the circulating ink pump.