Non-pollution UV ink in flexographic printing

UV ink, also known as UV ink, is the use of ultraviolet radiation of a certain wavelength, through the instantaneous photochemical reaction, so that the liquid UV ink becomes a solid ink.

UV ink has developed rapidly in the past 10 years, has entered a mature stage, and is recognized by the world as a pollution-free ink type. At the 7th International Conference on Radiation Curing in Asia, a lot of information has shown that the world's most important application area for radiation curing (including EB curing and UV curing) materials is the printing industry. Its main varieties include: UV Varnish, UV screen printing inks, UV offset printing inks, UV flexo printing inks, UV metal printing inks, and UV electronic circuit inks. According to information, the amount of UV flexo printing ink consumed in the United States in 1997 reached 3,000 tons, and it is also increasing at a rate of 9-12% per year.

In recent years, the development of domestic printing UV materials is also relatively fast. According to statistical data, in 1998, the domestic consumption of UV printing materials has exceeded 2,000 tons (including domestic and imported materials), which is mainly used for UV coating, printed circuit board ink And UV screen printing ink, in addition, there are some UV offset printing inks, UV embossing inks, etc., UV flexo printing ink usage is very small, is still in its infancy.

UV flexo printing ink has received universal attention and favor in foreign countries, mainly because it has the following characteristics:

1. UV flexo printing ink is safe, reliable, solvent-free, non-flammable, and non-polluting. It is suitable for packaging materials with high sanitary requirements such as food, beverages, alcohol and tobacco, and pharmaceuticals. Flexo-UV inks have been used in foreign food packaging for many years without any problems.

2. UV flexo printing inks have good printability, high printing quality, no change in physical properties during the printing process, no volatile solvent, stable viscosity, and are not easy to paste plate, can use higher viscosity printing, strong ink, high dot definition, reproduction of tone It is good in nature, bright and light in ink, and firmly attached, suitable for printing fine products.

3. UV flexo printing inks can be instantaneously dried, have high production efficiency and wide application range. They have good adhesion on different printing carriers such as paper, aluminum foil and plastics. Products can be stacked immediately after printing, and adhesion will not occur.

4. UV flexo ink has excellent physical and chemical properties. The process of UV curing and drying is the photochemical reaction of UV ink, ie, the process of changing from a linear structure to a network structure. Therefore, it has many excellent physical and chemical properties such as water resistance, alcohol resistance, alcohol resistance, abrasion resistance, and aging resistance. This type of ink is not as good as it is.

5. UV flexo ink consumption. Because there is no solvent volatilization, the effective composition is high, nearly 100% can be converted into ink film, its amount is less than half of the ink or solvent ink, and the cleaning times of the printing plate and the anilox roller can be greatly reduced, so the comprehensive cost is relatively low. Based on the above characteristics, UV flexo printing ink has obvious advantages and development prospects in terms of environmental protection, quality, and technology development.

The promotion and application of UV flexo printing technology in the country has a process from the current point of view. On the one hand, it is a further understanding and understanding of UV flexo printing technology. On the other hand, it is necessary to improve and perfect the equipment, light sources, supporting equipment, and process technologies. The following comprehensive domestic and international information discusses some issues that should be noted in the application of UV flexo technology.

First, UV light source: UV flexo printing needs to be equipped with a UV light source for each color group. Different colors of UV flexo inks have different UV absorption capabilities. For example, yellow and magenta have low absorption capacity, they are easy to cure and dry, and blue and black have strong UV absorption ability and are less likely to dry. The power of UV lamps can be assigned according to different colors to ensure proper drying of various colors of UV inks, and also to save energy. Pay attention to the aging of the UV light source and replace the UV lamp in time to prevent incomplete curing and adhesion. UV lamps have a typical life of 1000 hours. Frequent start-up will significantly reduce lamp life.

Second, the anilox roller: When using UV flexo ink, the anilox roller mesh angle is preferably 30 ° or 60 °. The following are several common specifications of ceramic anilox roller.

2O0 line 9.5-11.0 BCM Anilox: Printable opaque solid pattern.

360 line 4.5-6.5 BCM Anilox: Printable field and line patterns.

550 line 3.OBCM anilox: Printable continuous tone image product.

650 line 2.5BCM anilox roller: can print continuously adjusted image products.

800 line 2.0BCM anilox roller: Printable fine continuous tone image product.

Third, the rubber roller: The roller must be able to resist UV ink, usually used rubber roller EPDM rubber (EPDM) or silicone rubber.

Fourth, the media: Although the current use of flexo printing plate can basically be used for UV flexo ink, but it is best to use UV ink resistance better plate, such as DuPont's UVP-67 open plate Wait.

Fifth, the viscosity of ink UV flexo ink use slightly larger viscosity than water-based ink or solvent-based flexographic ink, and a wide range, can be in the range of 200 ~ 1000CPS, the general use of the viscosity of 30O-500CPS.

Six, storage: UV flexo ink should be strictly avoid light, avoid heat storage. Storage temperature should be controlled at 5 °C -30 °C, storage shelf life is generally six months.

Seven, additives: UV flexo printing ink commonly used additives are mainly three kinds: 1. UV reactive diluent; 2. UV curing accelerator; 3. UV ink cleaner.

VIII. Security Protection: There are two main points for prevention. One is the harm of UV radiation to the human body and the other is the harm of UV ink to the human body. The former needs to use lightproof materials to shield and seal the light source and enhance venting. The latter should be operated with gloves to prevent UV inks from coming into direct contact with the skin. For example, UV ink splashes on the skin and should be wiped dry and then soaped immediately. Wash with water.

UV flexo printing ink and its process technology are still continuously improving, new varieties and new equipment are emerging. All of these will promote the improvement of UV printing technology.

At present, flexographic presses equipped with a UV ink curing system are continuously increasing in foreign countries, and the existing flexographic presses are constantly being modified into UV ink curing systems. Replacing water-based inks and solvent-based inks with UV flexo inks has become a development trend, and has been widely applied to wide-width and narrow-width flexo printing machines. There is no doubt that the development prospect of UV flexo printing technology is very good. The promotion and application of domestic UV flexo technology needs to be based on our national conditions and the needs of products, as well as the perfection of domestic equipment and equipment. With the increasingly stringent environmental protection requirements and quality requirements, we believe that in the near future, domestic UV flexo technology There must also be a larger development.