Research on the Technology of Benzene-free Solvents and Inks in Food Package Printing (2)

Through investigation and research, we found that the following factors affect the quality of packaged intaglio prints:

1, the hue of the ink. Each batch of ink is required to have the same hue.

2, the coloring power of ink. The coloring power is the color intensity of the ink, commonly known as the ink concentration. The coloring power depends on the nature of the pigment, which is determined by the content of the pigment and the method of manufacture. The greater the degree of dispersion of the pigment, the stronger its coloring power; but as the dispersion of the pigment particles increases, the increase in coloring power will gradually slow down.
The coloring power of the ink has a great influence on the quality of the printed matter and is closely related to the cost. In general, the coloring power of the ink is strong, the amount of use is small, and the printing performance is good. The coloring power of inks made with organic pigments is strong, showing a bright color and saturation.

3, the transparency of the ink. The transparency of ink is expressed by hiding power. The transparency with low hiding power is good, but the transparency is poor.

4, the fineness of the ink. The technical personnel of the ink production company all know that the fineness of the ink depends on the size of the pigment particles in the ink. The finer the pigment particles in the ink, the more stable the performance of the ink. The pigment particles in the ink are fine, so that the dots are saturated with ink and the product quality is also better. If the ink particles are too thick, they will not be transferred within the mesh and will not be blocked, causing plate jamming, especially for gradation printing. Plastic gravure inks generally require a fineness of 10 μm or less, and the transfer effect will be better.

5, the viscosity of the ink. General use of Zahn -3 cup measuring viscosity, viscosity is generally required in the 16S-18S, it refers to the ink under the influence of the force, the ink inside to hinder the ability of the relative motion between molecules, the greater the ability, this ink The higher the viscosity, the smaller the viscosity. The viscosity of the ink is closely related to the smooth progress of production and product quality. When the viscosity of the ink is high, the dot transfer is not true, and the evacuation phenomenon occurs. After the printing, the hue will become lighter; when the viscosity is low, the dot transfer will be delayed. Shadow, the ink saturation is reduced, the ink with suitable viscosity has good transmission performance, and is an important condition for improving the print fastness, drying speed and gloss.

There are many factors that affect the viscosity, generally the effect of temperature is greater, the temperature increases the viscosity decreases, the temperature decreases the viscosity of the ink increases.

6, ink fluidity. It is the nature of the ink flowing to the surroundings under the effect of its own gravity or external force. It is closely related to the viscosity of the ink.

7, the drying of the ink. It has a great relationship with the quality of printed matter, and there are many factors that affect ink drying. The adjustment of the drying performance of the ink can be achieved by adjusting the temperature, humidity, heat, air volume, etc. at the production site. The food packaging gravure printing ink is Volatile drying, drying speed is not appropriate, there will be sticky, non-dry, deinking, word line pattern incomplete defects and other ills. Therefore, the evaporation speed of the ink is controlled by the selection of the drying temperature and the solvent during printing.

8, ink ratio and adjustment. In the printing process, the plastic gravure printing ink is generally composed of a raw ink and a solvent (also called diluent), and the solvent is the main component of the plastic gravure printing ink. The solvent dissolves the resin to dilute the ink; it also adjusts the ink to increase its fluidity and gloss, as well as to improve the fineness of the ink, but it must be selected for proper solvent and control of the amount of care.

9, the control of the amount of plastic gravure printing ink, the rational arrangement of the printing color sequence, multi-color product overprint control.

10, printing speed. When the printing speed is too fast, air holes and wire drawing will occur, causing white spots on the printed products, affecting the appearance of the printed products; when the printing speed is too low, the ink transfer will be affected, showing poor leveling. The hue is shallow and uneven. Therefore, the printing speed should meet the printing material's adaptation scope.

11, plate making. The shape, width, and depth of the mesh produced by different plate making processes have a great influence on the effect of ink transfer. In plastic gravure, the depth of printing and the number of screens should be determined according to the nature of the printing material. If the cell site is too shallow, it will be polished for a long time without printing, thereby reducing the amount of ink in the cell site and affecting the ink transfer effect. Therefore, under the premise of ensuring quality, the network cave sculpture should be deeper.

12, squeegee. The angle and type of squeegee will affect the squeegee effect and the amount of ink in the plate mesh. Adjusting the blade pressure, using a soft blade, and appropriately reducing the angle of the blade can improve the ink transfer effect. In addition, if the squeegee is far away from the printing line of the printing plate, the ink in the small cell is easy to dry and the phenomenon of “dry printing” occurs. Therefore, the squeegee should be pushed forward and the printing ink should be closer to the printing line. Helps the squeegee to scrape the excess ink so that the ink in the mesh is well transferred to the substrate.

13, printing pressure. Compared to letterpress and lithography, gravure printing requires more pressure. The printing pressure of the embossing roller has a great influence on the transfer of the plastic gravure ink. Increasing the printing pressure can increase the relative force between the printing material and the printing plate, thereby increasing the transfer rate of the gravure printing ink. But the pressure can not be too big, because a long time will have an impact on the impression cylinder, severe cracks will occur, it should be reasonable to adjust the printing pressure.

14, electrostatic effects. The use of an electrostatic process helps to improve the transfer of ink in the finer portions of the printing plate, and can prevent the occurrence of dots missing. Therefore, in the process of plastic gravure printing, the electrostatic ink-absorbing device is installed, and the effect of attracting the opposite charges on each other can be used to absorb more ink on the printing plate mesh to the printing material, thereby improving the ink transfer effect.

15, the environment temperature and humidity. If the ambient temperature is too high, the solvent volatilizes too quickly, and is easily dried, resulting in a "dry" phenomenon, resulting in poor transfer; if the ambient humidity is too high, the moisture in the air will enter the ink tank, making the ink solubility worse , affect the ink transfer effect.

16. Solvent (diluent). It has the ability to dissolve substances and volatilize itself, and its volatilization rate is an important factor that determines the dry condition of the plastic gravure ink ink layer and affects the printing quality. Therefore, the choice of solvent is a prerequisite for ensuring the quality of the ink.