UV offset printing process main problems and solutions

UV offset printing products have advantages over traditional offset printing products in terms of surface texture, protection, abrasion resistance, and production efficiency, and are particularly useful for non-absorbent materials such as plastic sheets and gold and silver cardboard. These advantages make printing companies that use UV offset technology stand out from the competition. However, the UV offset printing process is more complicated. How do package printing companies deal with the problems in the process of UV offset printing? How should packaging and printing companies planning to adopt UV offset printing be prepared?

For UV offset printing to work better, the main issues that need to be addressed are the following.

1. Designing plate

The design draft for producing UV printing must determine the output format according to the work order, such as the film surface swept forward or reverse sweep, the number of output network lines, the angle of the network cable and so on. Some special printing requirements are higher, such as 3D printing, the resolution must be very high, the network line angle must match with the printing materials to avoid hitting the net; transparent plastic sheet and aluminized paper often need to add white ink, should pay attention to the printing material stretching Impact, pre-correction of film to achieve the best quality.

2. Adhesion

Since the permeability of substrates such as plastic sheets or gold-silver cardboard is poor, the adsorption of ink is weak, so even if UV ink printing is used, the ink adhesion is poor and the printing quality is not high. It can be solved by surface treatment of the material.

3. Ink emulsification

UV ink ink balance tolerance is very narrow, easy to cause ink emulsification, dirty version, affect the printing quality.

Solution: Reduce the printing speed and control the printing speed at 5000 to 8000 prints/hour.

4. Curing degree

In order to improve the color saturation of printed products, when printing on the surface of a substrate such as a plastic sheet, the printing pressure is large, the ink layer is thick, and the dots are enlarged so that the ink is not easily cured. In order to ensure print quality, printing pressure cannot be greatly adjusted.

The solution is to first moderately reduce the printing speed, so that the UV lamp irradiation time is properly lengthened, so that the ink is completely cured; followed by adjusting the distance between the UV lamp and the substrate, increase the UV light irradiation intensity, so that the ink curing. The effective wavelength range of UV curing is 200-400nm. The wavelength of some light sources in the printing shop is also within this range, which will cause the ink surface to be slightly cured. Therefore, the influence of ambient light on UV ink should be taken into consideration.

5. Color order arrangement

UV offset color arrangement problem is more complicated. Due to the limitations of the inking principle, the ink layer on the substrate is relatively thin. When a relatively thick ink layer is needed, it is difficult for the printing product to achieve the desired reproduction effect. For example, in the case of four-color overprinting, the commonly used printing sequence is black, cyan, magenta, and yellow. Since black fills almost all the space, the ink strength of cyan, magenta, and yellow is lower, and the total amount of ink is insufficient. The color is not full.

Solution: Change the color sequence, first print the ink with a smaller amount of color, and then black with a larger amount of ink, so that you can get the highest amount of ink and the fuller color.

6. Print registration

UV offset printing uses UV light irradiation for ink curing. The main problem caused by curing is that the substrate is thermally expanded, resulting in misprints. This is inconsistent with the UV ink curing, because the UV curing requires a longer time for the ink to cure, and the printing sleeve guidelines require a shorter UV lamp irradiation time.

Solution: After the last color is printed, perform UV curing. Even if the substrate expands, lowering the temperature for a period of time can minimize the deformation of the substrate. Under special circumstances, the middle color group can also be exposed to UV light, but the shorter the irradiation time, the better. Or you can use cold UV technology.