Factors Affecting Plastic Gravure Ink Transfer

In the process of plastic gravure printing, improving the transfer of ink is the key to controlling the quality of printed products. The transfer of plastic gravure ink refers to the physical inking process from the plate cylinder mesh to the printing material. The mechanism can be described as follows: the surface of the plate cylinder is immersed in the ink tank. When the ink roller rotates, the squeegee will be unnecessary. The ink is scraped off, and the ink in the mesh is transferred to the plastic film under the pressure of the impression cylinder. Below I will analyze some of the factors that affect the transfer of plastic gravure ink and hope to help everyone.

1. The characteristics of the ink itself

1) The fineness of the ink: If the ink particles are too thick, they will not be able to transfer inside the mesh and will not be able to transfer, resulting in the phenomenon of blockage, especially for the lithography printing. Plastic gravure inks generally require a fineness of 10 μm or less, and the transfer effect will be better.

2) Viscosity of the ink: When the viscosity of the ink is high, the dot shift is not true, and the evacuation phenomenon occurs. After the printing, the hue will become lighter; when the viscosity is low, smears appear in the dot transfer, and the ink saturation decreases. Therefore, the ink viscosity should be adjusted, usually black and white ink for the 16sî—¤3# Zahn Cup î—¥, blue, magenta, yellow for the 18sî—¤3# Zahn Cup.

3) Ink drying performance: If the initial drying speed is too fast, “dry” phenomenon is likely to occur, causing ink transfer difficulties and poor transfer stability. Slow-drying solvents such as xylene and butyl acetate should be used. For example, they can be mixed in toluene. Toluene or xylene alone.

2. 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.

3. Platemaking

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 substrate. 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.

4. 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 up, and the phenomenon of “dry printing” appears. Therefore, the squeegee should be pushed forward and be closer to the printing line. Helps the squeegee to scrape excess ink, allowing the ink in the mesh to transfer well to the substrate.

5. 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.

6. Electrostatic effect

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 missing dots. 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.

7. Ambient temperature and humidity

If the ambient temperature is too high, the solvent volatilizes too quickly, and is easily dried, resulting in a "dry plate" 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. Therefore, the temperature should be controlled at 18 to 23°C and the relative humidity should be 50% to 60%. Conditional workshops can be equipped with central air conditioning. When the humidity is high, some desiccant can be placed near the printing plate. This will help improve the transfer of ink.

8. Other aspects

In order to improve the transfer effect of the plastic gravure ink, we can adjust the position of the ink tray properly so that the printing plate is immersed in the ink to the utmost so that the printing surface remains moist. And can often clean the printing plate, use the copper wire brush to clean the net hole carefully, wash away the ink that blocks in the inside, it is better to use the special edition plate cleaner or decontamination powder when cleaning.

Reprinted from: Shenzhen Printing Network