How to realize the first hot printing process

At present, the post-press processing methods in the packaging field are increasingly diversified. Each post-press processing method has its own characteristics, but none of the finishing methods is omnipotent. Therefore, in many cases, people often use a variety of surface finishing processes in combination, such as the current hot stamping and postprinting process. This process is to print and polish after printing on paper, cardboard or plastic film. The demand for packaging products for the process is growing. Here's how to implement the first hot post-printing process.

In the implementation of the first hot post-printing process, it should first determine which printing method is more appropriate. Commonly used printing methods are offset printing and flexographic printing, and sometimes screen printing, depending on whether the ink used is a conventional drying ink or a UV-curable ink.

1. Ordinary offset printing

When ordinary offset printing inks are used to print on hot stamping foils, since the surface of the stamping foils is smooth and poor in ink permeability and absorption, special components of ink should be selected so as not to affect the drying of the ink. To this end, ink manufacturers have developed oxide conjunctiva drying inks, also known as hot stamping foil printing inks, that dry by chemically reacting with oxygen in the air. This type of ink is often used in conjunction with an on-line water-based glazing process, and its products achieve excellent dirt and scratch resistance after 24 hours, and have a very attractive appearance.

When printing on hot stamping foils, one of the prerequisites for achieving the desired effect is to ensure that the hot stamping foil is firmly stamped on paper or cardboard. Otherwise, when the ink is transferred from the blanket of the offset press to the hot stamp foil, if the viscosity of the ink is high, the hot stamp foil will be pulled back. The hot stamped foil powder that is pulled down quickly accumulates on the blanket, reducing print quality. In some cases, the addition of an ungreaser in the ink can reduce or even completely eliminate this failure.

Another prerequisite is that the edge of the hot stamping pattern should be as clear and sharp as possible, otherwise the hot stamping foil particles scattered on the hot stamping edge will be bounced down by the rubber and quickly pile up on the blanket, thus affecting the printing quality.

2.UV offset printing

When using UV offset printing on hot stamping foils, UV glazing is usually combined with the connection. At this point, care must be taken to ensure the adhesion between the ink and the hot stamp foil. One of the reasons that affect the fastness of adhesion is the residue of hot stamping foil spacers. When the hot stamping pattern is peeled from the hot stamping foil, there is inevitably residue in the material in the barrier layer. When printing with an oxidized conjunctiva dry ink, these residual substances can be gradually absorbed during the drying process due to the longer drying time. However, if printing with UV inks, due to the very short curing time, these residual substances are too late to be absorbed, which will affect the curing of the ink on the surface of the hot stamping foil.

Another problem with UV offset printing is that shrinkage occurs when the UV ink cures quickly, which of course affects the quality of the stamp foil layer. If a high-gloss finish is to be applied to a hot stamping foil, this will be aggravated by the thicker coating of the UV light oil layer. In this case, the scratch resistance of the ink layer is poor regardless of whether it is stuck with tape or nails. In order to improve this situation, the only way is to pre-treat the surface of the stamping foil to improve the adhesion of the UV ink on the surface of the stamping foil and improve the adhesion fastness.

3.UV flexo printing

UV flexo printing is usually achieved with a narrow flexographic printing press, which is much more economical than UV offset printing. However, to obtain a satisfactory result, it must be ensured that the ink used matches the hot stamp foil and printing equipment. This requires hot stamping foil suppliers to work closely with ink suppliers to provide tailored solutions.