Printing technology: Analysis of bronzing process of self-adhesive anti-counterfeiting labels

Printing technology: Analysis of bronzing process of self-adhesive anti-counterfeiting labels

Self-adhesive label material is called self-adhesive label material in the industry. It is a composite material with paper, film or special material as the fabric, adhesive on the back, and silicon-coated protective paper as the backing paper. Today, the demand for self-adhesive labels in my country is growing rapidly at a rate of more than 20 percent every year. The size of the self-adhesive label market is about 450 million to 500 million square meters per year. Therefore, the current application of self-adhesive is more and more extensive, and it is widely used in commercial label printing and screen printing. Among them, bronzing technology is the most important process of self-adhesive printing.

In general, self-adhesive includes a variety of bronzing processes: cold bronzing, round bronzing, flat bronzing and other processes. According to the processing method of self-adhesive labels, its bronzing methods are divided into single-sheet bronzing and roll-fed bronzing. Sheet-fed hot stamping is the same as the traditional hot stamping process, and it is processed on a special hot stamping machine. Roll paper bronzing is done on a label linkage machine, which is the most widely used processing method. At present, there are several ways to bronze roll material:

1. Cold bronzing on a rotary machine

This is a new process of hot stamping. Instead of using heated metal printing plates, the method of printing adhesive is used to transfer the metal foil to achieve hot stamping. The technological process is: first print UV pressure-sensitive adhesive on the position where the printed product needs to be stamped, and then dry the adhesive by a UV drying device, then use special metal foil to compound the pressure-sensitive adhesive, and then peel off the metal foil, so that the metal The part of the foil that needs to be transferred is transferred to the surface of the printed matter to achieve cold bronzing. The cold bronzing process has low cost, energy saving, high production efficiency, and can utilize existing equipment components without adding additional devices. It is a promising new process.

2. Round pressing and hot stamping on the rotary machine

The hot stamping plate used for round pressing and round hot stamping is in the shape of a cylinder, and it is in contact with the imprinting cylinder during hot stamping to achieve hot stamping. Round press round bronzing is suitable for continuous paper feeding rotary labeling machines, but it has certain requirements on paper feeding speed, that is to say, it has an impact on printing speed. But compared with flat pressing and bronzing, the efficiency is greatly improved. The manufacturing cost of the round stamping roll is high, so it is only suitable for long version live stamping.

3. Flat stamping on the labeling machine

Whether the letterpress label printing machine is a flat flattening or a circular flattening equipment, due to the intermittent feeding of the roll paper, the bronzing method is all flattened. Under normal circumstances, the bronzing station is an independent unit, and some models share a unit for bronzing and die-cutting and are used separately.

4. Multi-station flat pressing and bronzing

Some models have two-station hot stamping units, such as the SMHC-45-MWL label machine from Shiki in Japan. One unit is close to the printing plate to complete horizontal hot stamping, and the other unit is an independent unit to complete vertical hot stamping. This model can perform two-color bronzing at the same time.

5. Flatten bronzing on the processing machine

The processing machine is specially designed for processing printed roll labels and labels that do not need to be printed. Hot stamping is a function of the processing machine. The hot stamping device on the processing machine generally adopts the flat pressing method, and its working principle is the same as that of the above-mentioned labeling machine.

According to the order of self-adhesive bronzing, it can also be divided into first bronzing process and post bronzing process. First bronzing refers to first bronzing on the labeling machine, and then printing; then bronzing refers to printing first, and then bronzing last. The key to first bronzing and later bronzing is the drying of the ink. Different inks are used, and two different processes of first bronzing and post bronzing are used for label printing:

1. First bronzing process

When the label machine with the intermittent paper feeding bronzing part installed in the front uses the ordinary ink to print the label, the first bronzing process is adopted. Since the ink used is of the oxidative polymerization drying type, it takes a certain time for the ink layer after printing to completely dry, so bronzing is required. Patterns must avoid ink. The best way to avoid ink is to pre-stamp the web material before printing.

The use of the first bronzing process requires that the printing pattern and the bronzing pattern are separated (juxtaposed), because the surface of the anodized aluminum is smooth, not inked, and cannot be printed. First bronzing can prevent ink from smudging and ensure the quality of label printing.

2. Post bronzing process

The post-gilding process is applied to the labeling machine where the hot-stamping parts are installed on the back door, and UV ink is used for printing. The roll material is first printed, and the ink is dried instantly by a UV drying device, and then the surface of the material or the surface of the ink after the ink is dried is stamped. Since the ink has been dried, the hot stamping pattern and the printed pattern can be side-by-side or superimposed, and the phenomenon of ink smearing will not occur.

Among the two bronzing methods, post bronzing is the ideal method, which also brings convenience to the label pattern design and expands the application range of the bronzing pattern. However, due to the limitation of equipment functions, the cost of label printing is relatively high. The first bronzing process is suitable for the processing of small labels with simple patterns, with low cost and wide application range. It is a commonly used method in small and medium-sized printing plants.

Summary: Doing good self-adhesive bronzing is an important factor to seize the label printing market. Therefore, it is necessary to master the self-adhesive bronzing process.

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