UV ink requirements for printing equipment and printing equipment

When changing from ordinary ink printing to UV ink printing, the following aspects need to be prepared.

1, drying equipment

Different types of inks have different drying characteristics. To make the UV ink sufficiently dry, a UV light source that matches the ink needs to be selected. The commonly used UV light sources are high-pressure mercury lamps, ozone-free lamps, and metal halide lamps. The output power is 80W/cm, 120W/cm, and 160W/cm. Lamp cooling methods are ventilation cooling and water cooling. The installation of the drying device is divided into a type (printer modification type, no modification type) and conveyor belt type installation.

When selecting a UV light source, it is necessary to compare the irradiation efficiency of the UV lamp according to the drying conditions of the UV ink and the UV light oil. Different UV lamps have different irradiation efficiencies.

UV Ink Printing: Metal Halide Lamps> High Pressure Mercury Lamps> No Ozone Lamps; UV Varnish: High Pressure Mercury Lamps> Metal Halide Lamps> No Ozone Lamps.

There are other factors to consider when choosing a UV lamp. For example, when using a high-pressure mercury lamp, the lamp cannot be replaced with a metal halide lamp because of the high voltage. Metal halide lamps can be replaced with high-pressure mercury lamps or ozone-free lamps. From this point of view, metal halide lamps are recommended.

Compared with the 80 W/cm lamp, the irradiation efficiency of 120 W/cm is twice that of the former, and 160 W/cm is 2.5 times of 80 W/cm. In general, 120W/cm is used for ventilation cooling and 160W/cm for water cooling.

From the cooling effect, the ventilation cooling method is better than the water cooling, and the water cooling curing efficiency is lower by 20% to 25% than the ventilation cooling due to the influence of the jacket. Especially when printing UV Varnish, short-wave UV light is blocked by the jacket, causing the print to dry slowly. In addition, the water cooling method is expensive, and the lamp life is only 50% to 70% of the ventilation cooling, and the odor generated during the operation is also large, so it is not suitable for use.

UV light absorbed by the ink when dry, 30% from the light source, 70% from the reflector launch. Nowadays, aluminum reflectors are used more often. Due to different processing technologies, the reflectivity of the reflectors varies greatly. Therefore, when detecting UV light energy, not only the lamps but also all ultraviolets including reflected light must be measured. The amount of light. Such as printing special materials (PET film, PP film, synthetic paper, etc.), the need for cold reflective panels, only the reflection of ultraviolet light and infrared transmission, so that the printed surface temperature dropped by 10 °C.

In summary, ventilation cooling is better than water cooling in both curing efficiency and economy. The method of installing the UV lamp is preferably by using a printing machine and then incorporating the UV lamp. Conveyor belts are not used due to the impact of paper neatness and are not used except for special purposes. In addition, the length of the lamp tube must be 10-20 cm longer than the print, otherwise it will cause poor drying at both ends of the printed matter.

Installation example - four-color machine installed UV drying device

In order to achieve printing speeds of 8,000 to 10,000 sheets per hour, considering the use of UV inks and UV varnish, it is best to install ventilated and cooled 120W/cm or 160W/cm metal halide lamps behind each unit. It can also hold 5. If the maximum printing speed is only 8000 sheets/hour, and the drying requirement is not very high, install only 3 tubes. If you want to balance the drying effect of UV inks and UV varnish, you can also use a combination of metal halide lamps and high-pressure mercury lamps.

3, preparation of printing equipment

1 Replace the rubber roller

Need to replace the rubber roller UV ink special roller. Even for the special roller for UV inks, due to different materials, there are differences in the viscosity of the machine, so the choice of rubber is also very important.

Generally choose to increase the viscosity of the resin roller.
2 Replacement of gripper teeth

After the UV offset device is installed on the sheet-fed offset press, the gripper will generate shadows when exposed to UV radiation, making it impossible for the gripper to fully irradiate the UV light. To avoid this phenomenon, replace the UV-friendly grippers during printing.

3PS version

In addition to UV ink positive positive PS version, if other positive type PS version is not subjected to baking treatment, the printing resistance is low. Therefore, baking treatment is required. The baking condition is 250°C for 6-8 minutes.

4 fountain solution

There is no special fountain solution for UV inks. Avoid excessive gum arabic in the fountain solution when printing UV inks, because gum arabic reacts with UV inks, causing ink stacker plates and pile blankets to malfunction.

5 substrates

UV inks have poor adhesion on some substrates, and it should be noted that the printed substrates should not be suitable for printing with UV inks.