1. Material type and color
Some types and colors of materials have the property of being able to absorb ultraviolet rays, and the curing of these materials will be slow. In addition, the same type of material may vary depending on the level of curing.
2. The nature of the pigment
Ultraviolet absorbing pigments, in particular, slow down the cure. The more the content of the pigments, the stronger the tendency. In particular, various primary color inks do not have a curing problem when they are toned, but the color inks have a problem of poor curing. Especially when using high concentrations of white and dark (black, blue, and other) components, care must be taken.
3. Photo-curing initiator
The addition of a photo-curing initiator is an effective method for improving the curability. However, excessive addition of photo-curing initiators will hinder the curing, and attention should be paid to the amount added (within 4% or less).
4. Print film thickness
The thinner the printed film, the better the curing property. The general colored ink can obtain sufficient curing performance in a film thickness range of 10 to 12 Î¼m. When the film thickness exceeds 15 Î¼m or more, poor adhesion due to poor curing occurs. Even if the varnish ink exceeds 100 Î¼m or more, it has no problem in curability.
5. Lamp intensity and accumulated light
The standard for determining the hardening is the intensity and totalization of the lamp. The intensity of the lamp (W/cm2) is determined by the output of the lamp and the shape of the lamp house. The data for integrating the ultraviolet intensity and the irradiation time is the accumulated light quantity U/cm2). Although the overall judgment of the hardening property is determined by the amount of accumulated light, the most important factor in the hard internal hardening of the printed film thickness is ultraviolet light. When the ultraviolet light intensity is low, increasing the irradiation time and increasing the ratio of the light quantity cannot improve the internal hardening of the printed film bottom. In this case, the height of the lamp can be reduced or the lamp output can be converted to a higher output.
6. Irradiation temperature
The ambient temperature during UV irradiation has a great influence on the curing of the UV ink. The higher the temperature, the better the curability. Therefore, if the preheating is performed, the curability of the ink will be enhanced and the adhesion will be better.
7. Obstacles to the development of UV inks
There are currently three main factors that hinder the widespread use of UV technology.
One is that UV inks are harmful to the human body. Many printing factories have used some domestic and imported UV inks, especially UV imitation metal etching inks, and found that some printing workers have red, swollen skin, pimples, and itchiness on the ink. During the research work, the author tried the imitation metal etching ink produced by a certain domestic unit. There was no indication that the ink would damage the skin on the packaging of the product, and the author's index finger was not cleaned in time after being stained with ink. The index finger was severely peeled off and almost muscles were seen. He recovered only three months later. Therefore, the issue of the safety of UV-curable ink must be given enough attention.
The use of UV-curable inks poses two major hazards to the human body: the first is the harm caused by the radiation to the human body; the second is the harm caused by the ink to the human body. Ultraviolet light, X-rays, and Y-rays are electromagnetic waves, but they have different wavelengths and different energies. The human body is exposed to intense ultraviolet light for a long time and causes dermatitis, cataracts, leukopenia and other diseases, and may even cause skin cancer. However, the ultraviolet light has low energy and weak transmissivity, and it can be shielded by coating a layer of opaque material. For this reason, the protection against ultraviolet light is much simpler than that of x-rays. As long as the use of lead and other materials to seal the UV lamp, ultraviolet light can not leak. At present, most automatic printing machines with UV light sources have good shielding effects and do not cause any harm to the human body. Some of the more primitive equipment, due to poor shielding, the operator should put on work clothes, wear protective gloves (mirrored gloves can be) and protective glasses (sunglasses), so that the skin and eyes are not exposed to ultraviolet light. In addition, when the air is exposed to ultraviolet light, a large amount of ozone is generated, which is harmful to the human body and must be discharged outdoors.
The second is insufficient understanding of the tremendous achievements made in the field of UV ink chemistry. Since UV inks cost slightly more than solvent-based inks, some printers believe that switching to UV inks will increase their overall cost. However, a study published by the International Screen Printing and Imaging Association showed that the use of UV inks can increase productivity and work efficiency, reduce the rate of ink scrap, which can greatly save the higher ink costs, and the results prove that the purchase of new curing The equipment is cost-effective.
Third, UV inks have disadvantages such as poor layer performance and creases.
Eight, UV ink market forecast
The use of UV-curable inks and coatings began in the 1970s and currently holds a large market share in the printing industry, including applications in lithography, styrene printing, and letterpress printing. It is predicted that by 2005, the market for UV-curable inks will increase from US$1.1 billion in 2001 to US$1.5 billion. In the United States, the output value of the printing industry using UV inks and coatings is approximately 1.5 to 200 million U.S. dollars per year, and the amount of ink and coating is approximately equal. Of course, the growth rate depends on the development of the branch market. The annual growth range is between 4% and 20%. The growth rate of most companies can reach 7% to 12%. Some areas, such as inkjet printing, screen printing In areas such as printing and flexo printing, due to the current low market share, the growth rate is relatively large and can reach 20%.
For the moment, web offsets account for the largest share of the market. They can use UV-curable inks in the production of direct mail, business forms, folding cartons and credit cards. Narrow flexo printing has been used in a large number of UV inks and coatings. In packaging printing, the application of UV inks and coatings is growing, both in offset printing and flexo printing.
Energy-curing products are entering every corner of the market and are of great economic importance. Electron beam EB curing market share of about 30 million to 50 million US dollars, accounting for almost 13% of the entire energy curing market. Compared with UV curing drying systems, EB equipment is expensive and covers an area that is relatively large, so the growth rate is relatively slow. Although the price of equipment has been reduced, the chemical materials used are still relatively expensive.
Source: Shandong Printing Network