Application of Water-based UV Ink in Outdoor Large-scale Advertising Screen Printing (I)

Screen printing has been widely used in the advertising industry, especially for outdoor large-scale advertisements. It is also a unique advantage of screen printing, which is difficult to match with other printing. However, the traditional petroleum-based solvent-based inks still occupy a large share in the advertising screen printing inks. Solvent-based ink solvents are volatile, which not only affects the health of the printing staff, but also pollutes the air and water environment. In today's rising environmental protection voice, the selection of excellent environmental protection ink has become an important factor for the company's long-term stable production.

In view of the environmental pollution caused by the emission of solvent-based ink VOCs, especially outdoor large-scale advertising, the pollution is even worse. Therefore, the search for pollution-free environmentally friendly ink has become an important issue. Water-based inks and UV inks are commonly used today.

First, water-based ink

Water-based ink is based on water-soluble resin and a certain amount of water as the main body, together with organic pigments, surfactants, defoamers, etc. It utilizes the evaporation of water in the ink during the drying process to cure the dissolved water-based resin and form a film. Water-based inks have the following characteristics:

1. Because it does not contain or contain a very small amount of organic solvents, there is basically no emission of VOCs, which avoids VOC pollution, improves the printing operation environment, is conducive to human health, and meets the requirements of green printing.

2. The water-soluble resin in the ink can uniformly disperse the pigment particles, so the ink has good dispersibility, fluidity, strong adhesion, and a uniform film layer can be formed after printing.

3. Printed products using water-based inks have good color rendering and fastness to rubbing, and along with the development of water-soluble polymer resins, the printing effect, water-resistance, and rub resistance of inks have been greatly improved. Greatly improved, it can be widely applied to four-color overprinting and spot color printing on a variety of substrates, whether it is printing non-woven fabric, PE film, BOPP film, PA film, PVC soft film, PVC hard film, aluminum foil or vacuum aluminum plating. Membrane, you only need to purchase a water-based ink, and can be printed, printed, composite printing.

4. Water-based inks have low ink consumption, and the amount of ink used per square meter for full-size printing is only about 50% of that for solvent-based inks, and has gradually become a major printing ink. For example, 95% of flexographic prints in the United States use water-based inks, and 80% of gravure prints use water-based inks. 40% of water-based inks are used in plastic printing.

However, water-based inks also have some deficiencies, such as poor ink gloss, low accuracy, poor adhesion, must use water-resistant version. In addition, the evaporation rate of water in the ink is slower, so the drying time is longer.

Second, UV ink

UV inks have the reputation of energy saving and environmental protection. Its main advantages are:

1. energy saving. Since the ink does not contain VOC, it is beneficial to the health of the employees, no pollution to the environment, and meets the requirements of environmental protection and green printing. In addition, the ink has a high flash point (above 100°C), which makes it hard to burn, saves heat, and is safe to use.

2. Drying fast. The stability during the printing process is good. It can be dried and solidified instantaneously (only a fraction of a second) after being irradiated with UV light. The middle part of the online printing can be dried, and the post-processing can be carried out immediately after printing to save the finished product cycle.

3. The equipment has a small footprint. Compared with thermal drying, the drying device has a small footprint. Relative to other inks (except natural evaporation drying ink), it can save energy. Printing can be streamlined, saving manpower and economical benefits.

4. Small ink particles can print fine text. The friction resistance of the ink is very good, the gloss of the printed matter is good, the color is colorful, the reproducibility of the color density is better than the common ink, and it has excellent abrasion resistance, water resistance, oil resistance and solvent resistance.

Third, water-based UV ink

The viscosity of the prepolymer in the UV ink is generally very large, and it needs to be diluted with a reactive diluent. However, the currently used diluent acrylate compounds have different degrees of skin irritation and toxicity, so in addition to developing low viscosity prepolymers In addition to the low-toxic reactive diluents, water-based UV inks that use water (partially ethanol) as a diluent can not only make alcohol-soluble inks have good compatibility and excellent adhesion properties, but also can be used in VOCs. Lower toxicity is still achieved with very low emissions.

At present, water-based UV inks have been successfully developed and applied in some printing.

For example, the United States NAZDAR company developed, developed and produced a special advertising UV ink - water based HU000 series UV ink, it can solve the problem of ordinary UV ink in the process of color overprint dot enlargement, image color reproduction is difficult. In order to meet the requirements of rich outdoor advertising color, the four-color advertising screen printing inks of the HU000 series water-based UV inks are equipped with two kinds of outlet dots (a kind of bluish, a kind of red), and two kinds of dots (a type of bias). Green, a reddish, and dot blue and dot black. The user can choose according to the color of the color picture, can achieve better visual effect. Water-based UV ink is a new research direction in the UV ink field.

Water-based UV inks are favored by the advertising industry in the market. To sum up, there are mainly the following technical characteristics:

1. Water based UV inks are single component photocurable inks that do not contain NVP or heavy metal contamination. In addition, due to the addition of a certain amount of moisture and 5% of environmental protection solvents in the UV ink, the moisture evaporates after curing, and the ink layer is thinned. Therefore, it has both the advantages of thin ink layer after drying of the solvent ink, and quick drying of the UV ink. The advantages of environmental protection.

2. Water-based UV inks are suitable for use in modern printing equipment such as continuously produced fully automatic roller screen printers. Because the ink requires low curing energy, it can reduce the cost and avoid overprinting due to thermal deformation of the substrate. At the same time, the surface of the ink is hard after curing, with high dot density, bright colors, high definition, and no shadow on the periphery of the dot. The phenomenon that the viscosity of the solvent-type ink in the printing process, such as the blocking of the net and the loss of the fine dots and the color distortion caused by the increased volatilization of the solvent, is avoided, and the printing accuracy is improved. In particular, four-color printing has a very good sharpness of the outlets, which is more suitable for large-scale indoor and outdoor advertising fields, such as back-lighting advertisements and front-end advertisements.

3. Water-based UV inks have high color density and can be used to change the printing effect. When printing with water-based UV inks, it must be fully stirred and printed directly from the ink tank. According to the printing equipment materials and the use of good ink viscosity control, if found too much viscosity, can add less than 10% thinner, and found that the ink viscosity is too low, you need to increase the viscosity before printing, then you can mix in matt varnish (high viscosity ) or add powder matting agent, after the use of a good mix of printing. Before printing, the ink should be tested for printing conditions. After the printing, the ink should be placed for 24 hours before testing the performance of the ink. The ink density can be adjusted by adding a transparent varnish or a colorless concentration adjuster.