technological innovation

Tips for using cold bronzing paper

Application range of cold foil paper
In general, any operation performed on a flexo printing machine can use the cold foiling process. However, the specific cold stamping function of the flexo printing machine must also be considered. For information about this, please contact the equipment supplier. As mentioned in the explanation of the cold foiling process, this wet laminating process requires gluing, foiling and peeling units. According to the glue, substrate, ink roller and printing plate used, the cold stamping process can be used to achieve the gradient cold stamping effect.

Cold-pressing glue

There are a variety of glues on the market (see process description), which must be tested carefully to choose the right glue. Manufacturers should state in their product specifications whether their products are suitable for free radical curing UV inks or coatings, and whether they can be used for solvent-based inks or water-soluble inks.

What kind of substrate can be hot stamped?

In fact, all substrates suitable for flexible printing (such as PP, PE and non-absorbent paper) can be cold-ironed. If adhesion problems occur, the customer should contact the glue supplier.

Ink roller:

The average amount of glue applied to the ink roller depends on the design pattern used on the hot stamping substrate. Depending on the pattern, the correct ink roller must be selected. At the beginning, 120 lines / cm and 10cm3 / m2 ink rollers are used. High-line ink rollers should be used for hot stamping of fine patterns. Low-line ink rollers should be used for hot stamping of large-area patterns.

For all non-absorbent materials and plastics, the typical sizing amount is 2-5 g / m2, and the required ink roller is 180 lines / cm, 6 cm3 / m2.

For highly absorbent materials, such as paper, you should initially use an ink roller of 100 lines / cm and 14m3 / m2 for gluing, but we do not recommend directly on the rough, untreated paper surface UV glue. For this type of material, it is recommended that you apply primer first.

Foil unit

We recommend that after applying the wet UV glue, use a silicone roller with a Shore hardness of 80-95 to cover the cold foil. The lower the tension of the feeding and rewinding unit, the better. If the Shore hardness of the nip roller is too low, the transfer effect of the cold foil will be poor. The roller used in the foil coating process must be completely clean and free of dust. Proper pressure of the foil coating unit is essential to avoid air bubbles. The air in the air bubbles will cause the cold foil foil to have a poor transfer effect.

Applicable UV lamp

For UV curing, medium or high pressure mercury lamps should be used. The power of the lamp should be adjustable according to the operating speed. The faster the operation speed, the greater the power of the mercury lamp. A typical power range is approximately 120-200 watts / cm. Color cold foils require higher power than UV lamps for silver or light gold foils.

The distance between the units for glue coating, hot stamping, UV lamp curing and peeling

In order to avoid wrinkling, the distance between each process should be as short as possible, and there should be no idler between the foil coating and the peeling unit. In the general process arrangement, the distance from the glue application to the peeling process should not exceed 1 meter at most.

The standard hot stamping speed for cold stamping is generally 45 to 120 meters per minute.