Cold press technology innovation in flexographic printing

The new printing technology of flexo printing has the characteristics of wide range of printing materials, efficient post-connection processing, simple operation, etc. It has been rapidly and steadily developed in the country, especially in the field of cigarette marking printing. The newly developed high-grade cigarette label adopts flexo printing technology and has achieved good economic benefits.

At the beginning of our company's establishment in 2002, we purchased the more advanced Juras [M 41 0 nine-color flexographic printing machine at the time, mainly used for the production of two kinds of Torch Labels, Red River Boutique Soft Bag and Treasure White Sand Soft Bag. In January of this year, our company re-introduced the Tess [M51 0 eight-color flexo printing machine, in addition to the increase in printing format, it also added a cold stamping group for cold transfer printing. Only five years have passed since the development of the cold transfer technology. The EMSl 0 purchased by our company is the first device that has been sold by the company on the mainland.

The principle of cold transfer technology is to use a flexographic printing plate to apply UV glue partially or full-print onto a paper tape and compound it with a transfer film. After being irradiated with an uV lamp, the glue cures instantaneously. After peeling, the laser layer on the film is transferred. Will be in accordance with the pattern on the plate transferred to the tape, forming a gorgeous packaging effect. It is called cold (cold transfer) because it does not require heating. Unlike traditional hot stamping, this technology was first applied to telephone cards and pharmaceutical packaging.

Compared with traditional blanching, cold blanching offers the following advantages:

1 Low cost. Its structure is simple, it only occupies a printing color group for gluing and a group of spaces for compounding. The materials used are also relatively inexpensive. The rotary bronzing equipment is expensive, and the sheet-foil bronzing machine is slow and cannot be connected. Hot stamping.

2 pressure is small. Extruded rubber roller hardness of 80 ~ 90 Shore hardness, while the general hot stamping machine pressure, mechanical strength requirements are also high.
3 speed. In the case of the printing color group, it can reach 90m/min, and the speed of the line blanching on a flexo machine is generally only 60m/min or less.
4 not affected by the printing format. The size of the cold-iron design pattern does not affect the printing operation. If the hot-scalding area is too large, it will cause difficulty in starting the machine.

The lines of the cold-ironing pattern are smooth, and there are no broken lines or stencils, but the edges are jagged and the hot-stamped pattern is prone to pinholes. In this regard, it can be designed to cover up the jagged edges of the graphic; or to design a trap to cover the edge of the jagged with ink. The use of smooth substrates and good quality UV glue can avoid pinholes.

The shorter the distance between the color set of the glue and the squeeze roller is, the better, and the peeling angle between the film and the paper should be as large as possible, so that the adhesion of the laser layer after the transfer is better. To cover the ink on the transfer layer, apply a layer of varnish (water-based acrylic) over it to increase the surface tension.

Cold stamping can be directly printed on single-sided coated paper or white card paper, resulting in a laser effect comparable to composite laser paper or transferable laser paper. Our company used the full version of the transfer printing on the single copper when proofing the “alcohol” white sand cigarette label. The printing effect was good. A laser pattern can also be made on transfer paper. For example, the "Five-leaf God" of Meizhou Cigarette Factory adopts a holographic pattern, but this will place high demands on the opening and printing of overprinting. Moreover, the composite laser paper has OPP or PET film, and the product is not easy to recycle, causing environmental pollution. Laser paper also has a fatal flaw, that is, there is a large color difference, which is inevitable in its current production process. When printing a clear, real-world ink, it is difficult to control the consistency of the hue, and cold lapping does not cause these problems.

With the maturity of domestic flexo printing technology, flexo printing will account for an increasing share in the domestic printing market. With its numerous advantages, cold press technology will also develop rapidly.

(Author/Australian Color Printing Co., Ltd. Liu Zhe)

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