How to control the printability of plastic gravure ink

In the production process, the color of the ink film mainly depends on the concentration and transfer rate of the working ink. For a specific substrate and a specific working ink, the concentration of the working ink is relatively fixed, and the transfer rate of the working ink depends on factors such as its own viscosity, dryness, and the condition of the printing plate, and is also subject to printing. Speed, printing pressure, squeegee pressure, squeegee position, squeegee angle and environmental temperature, humidity and other factors.

(1) The color of the ink

The printing ink color is mainly determined by the color of the selected ink. To solve the problem of the color difference of the plastic gravure printing, first, the ink with stable quality, no deviation in color or small deviation should be selected. It is best to use the same lot of ink for a batch of printed materials, because the colors of different batches of ink may also have some differences. If the ink color deviation is too large, it is difficult to control the consistency of the printing ink by other methods, printing screen tone This is even more so. In the preparation of spot color ink, it is best to modulate a sufficient amount at a time to facilitate the stability of the ink color. During the printing process, the amount of ink added to the ink tray each time is less, and new ink is often added. Especially for some products with low ink consumption, if you add too much ink at a time, the ink will oxidize and become obsolete after being exposed to the air for a long time. For example, the long black ink will be gray, and the new ink will not be black. For a long time, the red ink will turn dark red and not as bright as the new ink.

(2) Viscosity of ink

In the printing process, it is necessary to maintain the consistency and consistency of the ink viscosity. The ideal viscosity of the ink depends on the type of job and the printing conditions, but the color concentration of the ink must be stable, because maintaining the same ink viscosity at different temperatures will cause the ink color density to change, resulting in changes in the ink of the printed matter.

(3) Separation of synthetic colors

In the color mixture in which each of the pale colors and the organic pigments and the inorganic pigments have a large difference in the specific gravity, the separation of the synthesized colors easily occurs. Especially when the ink in the ink tray is not flowing, the precipitation will promote the separation of the synthesized color. Therefore, it is necessary to maintain the ink circulation smoothly. If possible, the ink circulation system is preferably used to ensure the ink has good fluidity. In addition, if the toner is not sufficiently stirred during the color adjustment, the concentration of a certain color tends to increase as printing progresses. Therefore, the ink should be sufficiently stirred before printing.

(4) Printing conditions and drying conditions

The printing speed and the ink drying speed directly affect the ink transfer rate. Therefore, the change of the printing speed and the ink drying speed will inevitably cause the change of the ink color. Squeegee position, blade angle and squeegee pressure have a great influence on the ink color, especially at the shallow level. The ideal condition is that the squeegee is in the same position from beginning to end. However, due to various factors, the squeegee has to be adjusted during the printing process. The position, angle and pressure. Therefore, we must understand the effect of these changes on the color of prints and take appropriate measures. When the print volume is large, as the print volume increases, the degree of wear of the plate cylinder increases, and the printing ink color changes, tending to become lighter as a whole.

(5) Impact of Postpress

Different post-printing processes (such as extrusion compounding and dry compounding) also have a certain influence on the color of the printed matter. For example, the high temperature of the extruded composite may cause changes in the pigment. When heat-sealing at temperatures above 200°C, the hue of the heated area may change. In addition, changes in the post-printing substrate, such as changes in the aluminum layer of the aluminized film, directly affect the overall hue.