UV Cold Stamping Technology

Cold stamping technology refers to the use of UV adhesive to transfer the stamping foil to the printing material. The cold stamping process can be further divided into dry film cold stamping and wet film cold stamping.

The dry film-covering cold stamping process is to cure the applied UV adhesive before the stamping. Ten years ago, when the cold stamping technology was just introduced, the dry film-covering cold stamping process was used. The main process steps are as follows:

(1) The cationic UV adhesive is printed on the roll printing material.

(2) Curing UV adhesives.

(3) Compress the cold foil with the printing material by means of a pressure roller.

(4) The excess hot stamping foil is peeled off from the printing material, and the desired hot stamping image is left only on the part coated with the adhesive.

It is worth noting that the use of dry film cold stamping process, the UV adhesive curing should be fast, but can not be completely cured, to ensure that it still has a certain viscosity after curing, so that it can be very hot stamping foil Bonding together well.

The wet film-covering cold stamping process is after the UV adhesive is applied, the first hot stamping and then the UV adhesive curing, the main process steps are as follows:

(1) Print free radical UV adhesive on web printing materials.

(2) Composite cold stamping foils on printing materials.

(3) Curing the radical-type UV adhesive, since the adhesive is sandwiched between the cold-stamped foil and the printing material, the UV light must pass through the hot-stamping foil to reach the adhesive layer.

(4) The hot stamp foil is peeled off from the printing material, and a stamping graphic is formed on the printing material.

It should be noted that: First, the wet film-covering cold stamping process replaces the traditional cationic UV adhesive with a free radical UV adhesive; second, the UV adhesive has a strong initial adhesive force and cannot be cured after curing. Adhesive; Third, the aluminum foil of the stamping foil should have a certain light transmission, so as to ensure that the UV light can pass through and trigger the UV adhesive curing reaction.

The wet film-covering cold stamping process can connect hot stamping metal foils or holographic foils on a printing press, and its application range is also becoming wider and wider. At present, many narrow-width paper boxes and label flexographic printing presses already have such cold hot stamping capability.

1. The advantages and disadvantages of cold stamping technology

The outstanding advantages of cold stamping technology mainly include the following aspects.

(1) There is no need for special hot stamping equipment, and the prices of these equipment are usually relatively expensive.

(2) It is not necessary to make a metal hot stamping plate, and an ordinary flexible plate can be used. Not only the plate making speed is high, but also the cycle time is short, and the production cost of the hot stamping plate can also be reduced.

(3) Fast hot stamping, up to 450fpm.

(4) No need for heating devices and energy savings.

(5) The use of a photosensitive resin plate can be used to simultaneously finish the registration of the halftone image and the on-site color patch, ie, the halftone image and the field patch to be hot stamped can be formed on the same hot stamping plate. Of course, just like the reconciliation of the real-world color block system to the same printing plate, both the hot stamping effect and the quality may have a certain loss.

(6) The hot stamping substrate has a wide range of applications. Hot stamping can also be performed on heat-sensitive materials, plastic films, and in-mold labels.

However, cold stamping technology also has certain deficiencies, mainly including the following two points:

(1) Cold-printing graphics usually require film or glazing for secondary processing protection, which increases the cost of stamping and the complexity of the process.

(2) The coated high-viscosity adhesive has poor leveling and is not smooth, which causes diffuse reflection on the surface of the cold stamping foil, which affects the color and gloss of the hot stamping graphic, thereby reducing the appearance of the product.

J. Michael Rivera, deputy general manager of sales for AMAGICHologrphics, said that although the cold stamping process cannot achieve the high precision and high definition of the hot stamping process, the cold stamping technology can bring many advantages to flexographic printers, including: Lower initial equipment investment, lower platemaking cost, faster hot stamping, online on the press, and on materials that are not suitable for hot stamping (such as films without substrates, PET and plastic bags, etc.) Hot stamping, etc.

Cold foil stamping technology can achieve the best hot stamping effect on film and non-absorbent paper materials. On the contrary, when cold stamping on porous materials with high permeability, the effect is not ideal. However, Mr. Rivera pointed out that some AMAGIC customers had hot stamped Raflatac Raflasilk's matte PSA material, and the feedback was quite good. In addition, some customers can obtain better cold stamping results by applying primers and gluing on matt paper materials.

Cold stamping technology has become a strong competitor of hot stamping technology, and cold stamping technology is expanding from narrow flexographic printing to other printing processes, such as wide flexographic printing, embossing, web offset and single printing. Sheet offset printing and so on. For example, at Drupa 2004, a Roland 700 sheet-fed offset press equipped with Manroland's new PrindorInLine cold stamping device was exhibited.

Cold stamping technology has provided new opportunities for printing companies. Its greatest advantage is less investment, or even no investment at all. Another outstanding advantage is the high cost performance, which is also the biggest selling point of cold stamping technology. As some industry insiders have said: “For customers, the cost-effectiveness of cold stamping technology is higher, which can help customers increase the added value of the products and is very cost-effective.” In addition, since cold stamping technology does not require the production of expensive hot stamping, So it is very suitable for short-lived, low-quality labeling and proofing production. However, compared with the hot stamping technology, the cold stamping technology still has certain defects in quality and needs to be further improved. Therefore, the cold stamping technology is not suitable for the processing of high quality packaging and label products.

Here, I would also like to mention here that although gold and silver ink printing can also produce metallic gloss decorative effects similar to those of hot stamping, and gold and silver ink printing technology has made great progress in recent years, it still cannot be achieved. Hot stamping or cold stamping technology brought about by the kind of strong visual impact.