XIAMEN SUNBOO PACKAGING

As a part of product packaging, unique and beautiful printing and decoration effects can help grab customers' attention and attract their attention, becoming an important means to add value to packaging products.

Among them, the environmentally friendly cold stamping process has received more and more attention. Today, we will learn about the cold stamping process~

01

Process introduction

Cold stamping is a technology that uses a printing plate to transfer hot stamping foil to the substrate using UV curable adhesive.

Compared with traditional hot stamping technology, the whole process does not require heating or a special metal stamping plate, so it can save a lot of energy. It is a new technology that meets the requirements of green environmental protection. Cold stamping technology can be divided into dry stamping and dry stamping according to the process. There are two types: lamination type and wet lamination type.

[Dry lamination type]

The coated UV adhesive is cured first and then hot stamped. Its main process steps are as follows:

1) Print UV adhesive on roll printing materials;

2) Curing UV adhesive;

3) The hot stamping foil and the printing material are combined together with the help of a pressure roller;

4) The excess hot stamping foil is peeled off from the printing material, and only the areas coated with adhesive are transferred to the printing material to obtain the required hot stamping graphics and text.

It is worth noting:

When using the dry lamination cold stamping process, the UV adhesive should be cured quickly, but it cannot be completely cured. It is necessary to ensure that it still has a certain viscosity after curing, so that it can bond well with the stamping foil. .

[Wet lamination type]

After applying the UV adhesive, stamp it first and then cure the UV adhesive. The main process steps are as follows:

1) Print free radical UV adhesive on roll printing materials.

2) Composite cold stamping foil on the printing material.

3) Curing the free radical UV adhesive. Since the adhesive is sandwiched between the cold stamping foil and the printing material, the UV light must pass through the stamping foil to reach the adhesive layer.

4) Peel off the hot stamping foil from the printing material and form hot stamping graphics and text on the printing material.

It should be noted:

The wet laminating cold stamping process uses free radical UV adhesives to replace traditional cationic UV adhesives;

The initial adhesion of UV adhesive must be strong, and it should no longer be sticky after curing;

The aluminum-plated layer of the hot stamping foil should have a certain degree of light transmittance to ensure that UV light can pass through and trigger the curing reaction of the UV adhesive.

The wet-laminated cold stamping process can hot stamp metal foil or holographic foil in-line on the printing press, and its application range is becoming wider and wider. Currently, many narrow-web carton and label flexographic presses already have this in-line cold stamping capability.

02

Advantages and disadvantages of cold stamping

Compared with traditional hot stamping technology, cold stamping technology has outstanding advantages, but due to the inherent process characteristics of cold stamping, this technology must have shortcomings.

【advantage】

1) Cold stamping does not require special stamping equipment and can be produced in-line with offset printing, flexo printing, gravure printing and other equipment.

2) Cold hot stamping does not require expensive metal hot stamping plates like hot stamping, and it also avoids environmental pollution during the production of metal hot stamping plates.

Cold hot stamping can use ordinary flexographic plates, which not only has fast plate making speed and short cycle, but also reduces the production cost of hot stamping plates.

In this way, cold stamping technology can be fully utilized to actively develop the plate making and stamping business by taking advantage of the cost advantages of short-run printing parts. At the same time, with the advantages of environmental protection and energy saving, replacing traditional hot stamping technology with cold stamping technology is also a good choice for enterprises to implement green printing and reform production methods.

3) Compared with hot stamping, cold stamping technology has the advantages of fast stamping speed and high stamping accuracy.

The back of the electrochemical aluminum hot stamping foil used in the traditional hot stamping process is coated with hot melt adhesive. During hot stamping, the temperature and pressure of the hot stamping plate are used to melt the hot melt adhesive and realize the transfer of the hot stamping foil. The adhesive in cold stamping uses the UV curing principle, and the curing time is significantly shortened, so it has a faster stamping speed.

4) A wide range of printing substrates.

Cold hot stamping can realize the transfer of hot stamping foil by relying on adhesive and pressure at normal temperature. It does not require special adjustment and control of the hot stamping temperature like hot stamping. Therefore, cold stamping technology is not only suitable for hot stamping on ordinary substrates such as paper and cardboard, but also on film materials that are easily deformed by heat, heat-sensitive materials, in-mold labels, etc. This makes cold stamping technology unique in various label application fields such as daily chemical labels, wine labels, and food labels.

5) It is easier to iron first and then print.

The process of hot stamping first and then printing is to hot stamp paper, cardboard or plastic film before printing and varnishing. The cold stamping process has a lighter and more uniform pressure, and the surface of the cold stamping pattern is smooth.

At the same time, cold stamping has low difficulty and high efficiency, and can realize online production. Therefore, after printing with highly transparent ink on the surface of the cold stamping pattern, colorful and ever-changing gold effects can be obtained.

【shortcoming】

1) The process is complex and there are technical obstacles.

Cold stamping uses printing adhesive to transfer the stamping foil. The adhesion fastness of the stamping pattern to the surface of the printing material is not high. The stamped products usually need to be coated or glazed for secondary processing protection, making the process complicated. change.

Moreover, due to the poor leveling properties of UV adhesive, if it is not spread evenly and evenly, it may cause diffuse reflection on the surface of the hot stamping foil, affecting the color and gloss of the hot stamping graphics and text, thereby reducing the aesthetics of the product.

For a long time, a key factor that restricts printing companies from investing in cold stamping equipment is that the stamping speed after connection must be consistent with the printing speed. It is impossible to use skip steps to save stamping foil like hot stamping equipment, which will inevitably cause stamping foil to be saved. This is a huge waste of printing, which leads to increased costs.

Although some printing equipment manufacturers have introduced cold stamping modules with skip functions in recent years, most of them have been at the expense of printing speed and have not maximized the utilization of hot stamping foil.

2) The quality of hot stamping needs to be improved.

Compared with hot stamping, cold stamping is not as good as hot stamping in terms of the metallic effect of graphics and text and the flatness of the stamping surface.

This is mainly determined by the principles of these two technologies: the hot stamping process is similar to the ironing of an electric iron, and the hot stamping surface is naturally bright and flat; the cold stamping technology mainly relies on the adhesion and peeling of the adhesive. The effect on the surface of the post-hot stamping foil is the final result.

As you can imagine, the flatness of its surface is naturally not as good as hot stamping. Moreover, when cold stamping products are subjected to other subsequent processing, the hot stamping pattern will usually appear to be blooming, smeared, the image and text gradient is not smooth, or small dots are lost. The hot stamping pattern is easy to fall off after being rubbed due to insufficient fastness. Printed patterns are prone to quality defects such as linear wrinkles.