UV screen printing metal ink characteristics and printing elements

Screen printing metal inks, due to the application of UV curing drying system, there are many differences in the actual printing operation compared with ordinary solvent-based screen printing metal inks. The following is a brief introduction to the characteristics and printing elements of UV screen printing metallic inks.

First, the characteristics of UV screen printing metal ink

UV Screen Printing Metallic inks are mainly composed of photosensitive resins, photosensitizers, pigments, and additives. They do not contain harmful volatile substances such as solvents. Therefore, UV screen printing metal ink is an ink that meets the concept of environmental protection. In the UV curing process, when the ink layer is exposed to ultraviolet radiation, cross-linking between the photosensitive resin molecules contained in the ink rapidly occurs, thereby achieving curing. This process is very fast, usually only 0.5 ~ 3s time. Therefore, the UV screen printing metal ink in the application process, has the characteristics of saving energy and space, improve work efficiency, in the printing process, because the screen printing ink can not touch the ultraviolet radiation, so it will never block the network, This brings great convenience to print-accurate graphics and continuity operations.

Second, printing elements and operating methods

1. The printing material must be fully deoiled and dust-removed.

2. Stir the ink thoroughly before use. As the temperature changes, the state of the ink will become thicker or thinner. At this time, the viscosity of the ink should be adjusted by a special UV thinner. Under normal circumstances, the amount of release agent should not exceed 5% of the weight of the ink, otherwise it may reduce the curing speed of the ink.

3, when the need for stacked color printing, should pay attention to weakening the background of the UV light intensity or reduce the illumination time, in order to avoid over-curing due to the underlying color resulting in poor adhesion adhesion phenomenon.

4, the open cans of ink should be careful to avoid blind irradiation of ultraviolet light or sunlight, yellow light is safe light.

5, the choice of screen. When printing solvent-based screen printing metallic inks, there are no special requirements for screens and squeegees. For UV metal screen printing inks, the choice of screens and squeegees is crucial. Because it is correct or not, it is directly related to the curing speed and adhesion of the ink. When printing black and white ink, the mesh size should not be less than 420 mesh. When printing other colored systems, the screen should be above 350 mesh. Scrapers should use a sharp PU blade with a hardness of 70 or more. When the blades of the scraper have worn out, it should be immediately reground or replaced with a new scraper. In the production of screen, the photosensitive adhesive should not be too thick, usually in the front, second time is appropriate. As mentioned above, the purpose of this selection is to control the thickness of the ink layer. We know that the UV metal screen printing ink needs to absorb the energy of UV light during the curing process. The entire ink layer is from the surface to the deep layer. The intensity of the received UV light is gradually decreasing, and the UV light received is deeper and the UV is accepted. The weaker the light, the harder it is to cure. If the printed ink layer is too thick, the UV light can hardly penetrate the ink layer and reach the bottom of the ink layer due to the hiding property of the ink itself. This will result in deep penetration of the ink and cause the adhesion to decrease. On the contrary, if the thickness of the ink layer can be controlled, the UV light can easily penetrate to the bottom of the ink layer and rapidly solidify.

6, UV lamp power selection. UV lamp power can choose 3 ~ 8kW, this power is generally sufficient to meet the UV-5000 screen printing metal ink curing requirements, it is worth noting that the reflector should choose a semi-circular arc with light focusing function to increase UV The density of light.

7, the curing time control. There are many factors that can affect the UV screen printing metal ink curing time. First of all, the color of the ink is different, and the curing time is not the same. In general, due to the high hiding power of white and black, the curing time is longer than other colored inks, and the power requirement for the lamp is also relatively high. Therefore, when the printing plant is operating, the white and black curing time is relatively slow compared to other colored inks, and the UV curing machine's transmission speed should be adjusted more slowly. Secondly, the size of printed graphics also affects the length of curing time. Some small texts and thin lines cure faster, because UV light can be received in front, rear, left, right, and upper five directions. The radiated energy is greater. For some larger color blocks, the middle part can only receive UV light from the upper direction and receive less radiation energy. Therefore, the curing speed is relatively slow and the time is longer. In the applied printing factory, many will find such a phenomenon, in the same pattern, small text and lines, UV adhesion is high after curing, and the larger color, the middle part of the adhesion can not. This phenomenon is often caused by the above reasons. The solution is to increase the cure time. Third, the thickness of the ink layer will also affect the curing time. Due to the gradual decrease of the UV light intensity during penetration of the ink layer, the UV light is weaker toward the bottom layer of the ink film. Therefore, if the ink layer is thicker, the curing speed is slower, and the faster is the opposite.

In summary, to embody the advantages of UV screen printing metallic inks in application, it is necessary to cooperate closely with the screen, scraper, UV lamp, and various elements of the operator. As long as you understand the characteristics and curing mechanism of UV metal screen printing ink and control the thickness of the ink layer, applying UV metal screen printing ink will bring you unexpected printing effects and convenience.

UV screen printing metal ink has obvious advantages compared with common solvent metal inks because of its environmental protection, cost, and efficiency. Therefore, its application prospects must be very broad.

Source: China Ink Technology Network