Mixed ink for efficient on-line uv coating

Mixed ink production background

1. The adhesion of UV varnish to common ink is poor

Since the beginning of the 1960s, due to its advantages of high gloss, instant fixation and good resistance, UV Varnish has gradually become the material of choice for glazing products. However, in the early applications, the UV coating on the ordinary printing ink layer is not easy, because the chemical properties of the UV varnish and common ink are very different. The incompatibility between the two causes the UV varnish layer and the common The adhesion between ink layers is poor.

2. Glossiness fades

After UV polishing, the high gloss retention time of the finished product is not long. This phenomenon is called “glossiness fade” and the result is that the gloss of the printed product is reduced by 30%, resulting in uneven glossiness on the surface of the printed product. The degree of dry discoloration is related to factors such as ink hiding power, ink formulation, substrate and printing conditions. However, the gloss fade phenomenon is more serious in the dark color printing area, while in the light color printing area and the blank area directly covered by the coating oil (no printing ink), the UV gloss oil can still maintain a high gloss after drying.

3. Process attempts and improvements

In practical applications, printing houses have found that if the general ink layer is sufficiently dried before UV glazing, the gloss and various resistances of the printed products will be greatly improved. In general, dusting is required to prevent back-scratching during ink drying. When UV glazing is performed, the dusting will affect the appearance quality of the printed sheets, which will make the printing surface that should be smooth and smooth and high gloss appear frosted, which affects the glazing effect of printed products.

For this reason, the printing factory came up with a way to perform off-press water-based coating of prints, and to minimize the amount of printing and dusting. Doing so can achieve the desired quality, but it requires the paper to go twice on the printing press, or it needs to be detached from the machine for glazing, which increases the equipment use time and material consumption, resulting in an increase in the printing price. This led to the new concept of double glazing, and printer manufacturers have developed a double glazing press. The basic principle is to run paper twice to polish. First, a water-based coating is applied to a common ink layer to cover the normal ink layer, followed by UV coating. The processed product has a high gloss.

However, there are still some problems that cannot be solved, namely the drying of water-based base coats. Water-based coating oils need to be completely dried, and acrylic resins need to be agglomerated into macromolecules. Therefore, the drying speed of this process is limited. If the speed is increased, it will have a negative effect. Although double-swather printing presses have been used in some printing plants, the profitability of these machines is relatively lower than that of off-machine coating, especially for large-volume printing jobs. Double-glazing technology is ineffective. Now.

Mixed ink features

While improving the printing press and installing the double coater, the varnish and ink manufacturer is also trying to develop a new technology: to achieve on-line UV coating on the common ink layer, and later the UV ink and the common The ink was mixed and the new ink was formulated. This attempt was successful. However, there are still some problems: poor ink adaptability, unstable performance during storage, uneven gloss after coating, special coating rollers, etc. In this regard, ink manufacturers have developed a new ink - mixed ink, and has matured.

1. Good glazing effect

Take Sun Chemical's Hy-Bryte blended ink as an example, it combines the components of ordinary inks with UV-curing ingredients. The curing lamps installed at the end of the printing press and before the UV coating unit can cure the mixed ink. As long as the curing mode is correct, the printing product can maintain a uniform high gloss after polishing. The gloss effect of printed products is related to the factors such as UV varnish, printing materials, and coating units. The mixed ink is used for printing and then UV glazing. The gloss can reach 90%.

After the mixed ink is printed, it can also be painted with an aqueous coating. After the mixed ink is dried, the adhesion to the aqueous coating oil is good; the gloss is not as good as the UV coating, but it is better than the coating effect of the aqueous coating oil on the ordinary ink; the flatness is also good.

2. No special equipment required

The use of mixed inks is not much different from ordinary inks. First of all, the glue stick and blanket used by it are exactly the same as ordinary ink, so the printing factory is very flexible to use. When mixing with UV, you can choose mixed ink printing, and you can print with ordinary ink when you do not need to polish. Of course, this does not mean that every roller and blanket is an ideal choice for mixed inks. Also, mixed ink printing does not require special fountain solution, but it can be cleaned with general cleaning agents.

Reprinted from: Longjiang Printing Network