UV technology and printing features

In recent years, due to the increasing demand for packaging in the tobacco and alcohol industry, and more emphasis on the use of non-absorbent materials such as gold/silver cardboard and plastics, domestic printing companies have been rushing to introduce and install UV curing equipment related to these technologies. . After nearly 10 years of sharpening in the market, the complexity of domestic adoption of UV technology in packaging and printing has far exceeded that of similar foreign products.

However, foreign experts believe that although we are more sophisticated than UV in the application of UV technology, the understanding and application of UV technology is still not thorough enough. For example, although it is known that UV ink printing requires special rubber rollers, blankets, plates, and cleaning agents, it is not known that the ink may dry or fly on the ink roller. This may be due to improper use of the ink or cleaning agent. For this reason, in the spirit of "pursuing refinement and improvement," we must re-understand UV technology and printing characteristics, and it is necessary for those who have adopted UV printing and are preparing to introduce UV technology. This article will briefly describe the problems existing in domestic UV printing, and introduce foreign co-cured inks developed for traditional UV printing and their applications.

UV printing with joy and worries

At present, UV printing is mainly used for the packaging and printing of non-absorbent materials such as gold/silver cardboard, aluminized paper, and plastics. UV inks give prints high quality and high gloss, but also bring a lot of trouble to the operation.

(1) UV inks are highly corrosive and require very high demands on the rubber rollers. EPDM or dual ink rollers are required. However, EPDM and Dual Ink Rollers are particularly sensitive to benzene ring-containing cleaners and can easily harden to change ink roller performance.

(2) The conversion time between common ink printing and UV printing is too long and the process is cumbersome. If the conversion and cleaning time is too long, the printer needs to be shut down for a long time, which will affect the production progress.

(3) UV ink ink balance tolerance is very narrow, easy to cause ink emulsification in the printing, affecting the stability of the printing quality, and improper control, there will also be dirty version of the failure. Due to the high viscosity and lack of leveling properties after UV ink printing, the ink film surface may be rough and the hue may not be sufficiently transparent.

(4) Due to the poor overprint performance of UV inks, it is necessary to add an intermediate seat for curing between the printing color groups in order to improve the overprinting effect; installing multiple sets of intermediate seats increases hardware investment.

At present, the domestic UV printing market is mainly concentrated in the field of packaging and printing. In the packaging printing, the color printing is more and the printing volume is larger, the problems such as longer conversion and cleaning time, difficult control of ink and ink balance, and high hardware investment are still negligible, but if these problems occur in commercial or publishing printing, etc. Markets based on short-run printing are absolutely unacceptable.

The origin of UV co-curing process

In order to perfect the UV printing process, Grafix, a German UV system manufacturer, cooperated with INX ink company to develop a new UV co-curing process. The process is the use of a new ink technology to break the incompatibility of traditional UV inks and common inks, and then combined with high-power UV curing device to improve the UV ink curing quality, solve some problems in UV printing, and reduce The technical threshold for printers to enter the special printing field.

1. Characteristics of UV Co-curing Process

(1) It can be cleaned with general cleaning agent, and the cleaning time is short, avoiding the problem of long downtime in the printing process.

(2) The time required for the conversion between ordinary ink printing and co-curing ink printing is the same as that for normal ink printing, and the operation is simple.

(3) Co-curing inks have the same ink balance in printing as ordinary offset inks. Therefore, problems such as ink emulsification and dirty printing are easily controlled, and the stability of printing quality is improved.

(4) The printing dot is more sharp than the ordinary UV printing, and the surface of the printing ink film is delicate and has the effect of color transparency.

(5) Co-curing ink does not require expensive UV-specific roller.

(6) The overprintability between inks is excellent. Only a set of intermediate seats can be cured to enhance the overprint effect and reduce hardware investment.

2. The views of foreign counterparts

INX Ink Company UV/EB Product Manager - Gale Waller

Co-cured inks are superior to conventional UV inks in controlling dot gain, overprint performance, and color contrast.

Compared with traditional UV inks, co-cured inks have wider ink emulsification space and can reduce waste in printing.

Editor-in-Chief of American Print Magazine - Cheno Adams

The cost of co-curing ink is higher than that of traditional UV inks, but the other benefits it brings, such as UV glazing, simple cleaning operations, less waste, faster delivery, etc., can completely offset this A disadvantage.

However, before investing in UV technology or converting services, manufacturers must determine whether the curing system and consumables suppliers can provide adequate technical support.

John Stout, President of Saint Louis Printing Company

This technology has expanded our range of services to our customers and widened the distance between us and our competitors.

American Ink magazine editor David Satano

Co-cured inks provide great flexibility for print manufacturers.

Inverted light

In China, the main substrates for UV printing are non-absorbent materials. In Europe and the United States, printing companies not only use the co-curing process to print the same quality prints as traditional UV inks, but also do not satisfy their high-gloss mirror effects or transparency effects, and further improve this process to achieve more. High printing contrast. To this end, an early version of the so-called "back-lighting process" was developed. At that time, however, some details were not solved, such as adhesion, so they were not really implemented. After several years of improvement, this process has matured. The following section describes the local glazing process using this technique.

Pro-Cure is relative to traditional local glazing. In the past, regardless of the type of glazing (flexographic printing, screen printing, or gravure printing) used for local glazing, the last glazing process must use partial glazing printing in order to achieve high contrast in local graphics. , Polishing and printing accuracy of the key to the glazing process. The inverse light process broke through the above laws and solved the problem of registering.

Before glazing, it is necessary to complete conventional printing and determine that the ink has been completely dried or cured; then, the non-high-light areas on the design draft are printed with transparent reverse ink by offset printing in a wired or offline manner; The printing method applies UV varnish to the printing surface and cures.

At this time, the optical oil forms a small-particle-like ink film by forming a cohesive reaction with the reverse-light-up ink contact region, and forms a mirror surface in the counter-light-up region.

Obviously, with the retro-reflective process, both high-gloss and non-high-gloss effects will be present on the same print. Moreover, because the non-highlighted part is an offset printing, overprinting is accurate, and at the same time, the accuracy of the graphic part of the high light part is also guaranteed.

Source: 21st Century Fine Chemicals Network