The Cold Foil Technology Principle and Comparison with Traditional Bronzing

Cold stamping technology is a high-tech achievement in the European and American printing industry in recent years. It breaks the traditional process of traditional bronzing relying on heat transfer to transfer electro-aluminum foil. Instead, it uses a new concept, cold-press technology, to transfer the electro-chemical foil. The cold bronzing technology not only solves many of the process problems that were difficult to solve in the printing industry in the past, but more importantly, it saves energy and avoids pollution to the environment during the production of metal plates.

When cold-foil technology is used to print adhesive materials on a narrow-web rotary press, only a few devices can be attached to the original equipment. This article describes the principle of the cold stamping process and its additional equipment.

First, cold stamping process principle

The back of the aluminum foil used in the traditional bronzing process is pre-coated with a hot melt adhesive. When the gold foil is gilded, the adhesive is melted by the pressure of the hot roller to transfer the aluminum foil.

The galvanized aluminum used in cold foiling is a special type of galvanized aluminum. Its back is not glued. The adhesive is directly applied to the required decoration at the time of printing. When transferred, the galvanized aluminum is in contact with the adhesive, and the adhesive is In the role of electro-aluminum is also attached to the surface of the print.

Cold foiling process: First printing UV ink. After drying, special adhesives—UV curing adhesives—are printed on the surface of the ink where gold is to be gilded; then the adhesive can be removed to a certain degree by a UV drying device to form a layer of high viscosity, very thin. The pressure-sensitive adhesive; then, the cold bronzing is started, and the aluminum foil is brought into contact with the adhesive and pressed into one body under the action of a pair of metal rollers. Due to the large adhesive force between the adhesive and the aluminum foil, the parts where the aluminum foil and the adhesive are in contact with the adhesive remain on the surface of the printed matter when being discharged, and become integral with the printed matter, while the other parts of the aluminum foil are discharged as the conventional bronzing. This completes the first part of the bronzing technique.

Since the name foil pattern transferred on the printed matter floats on the surface of the print, the firmness is very poor, so protection must be given. Light or film on the print surface to protect the aluminum foil pattern.

Finally, as with ordinary post-printing post-printing processes, die-cutting, draining, cutting, or rewinding are performed to complete all the adhesive printing process.

Second, additional equipment

Printed cold-foil adhesive printing plates used DuPont Celli. The printed adhesive is dried in an additional UV device to create a high-stick area on the surface of the print that requires gold stamping. A group of metal impression cylinders, which adheres the aluminum foil firmly to the surface of the printed pattern by applying pressure to achieve cold stamping.

Third, the comparison of cold bronzing with the traditional bronzing process

Compared with the traditional bronzing process, the cold bronzing process has many advantages:

1. The speed of cold bronzing is fast, and the fastest speed is up to 50-60 meters per minute, while the average round bronzing speed is only 20-30 meters per minute.

2. The application of cold stamping materials covers a wide range of applications, such as cold stamping on thermal paper and some film materials.

3. Due to the use of general flexo printing plates instead of expensive metal plate cylinders, the production cost of hot stamping plates is greatly reduced. The cost of cold stamping is only about one tenth of that of ordinary stamping.

4. Since no heating roller is used, energy is saved and consumption is reduced.

5. Since the metal plate cylinder is not manufactured, the chemical etching process is abandoned, thereby reducing pollution and favoring environmental protection.

6, using the traditional bronzing process to produce metal plate roller takes a week or two, and cold plated gold plate takes only a short time, so that the production cycle is greatly shortened.

The cold bronzing process is limited by the conditions of adhesives, metal foils, etc. There are also some disadvantages, such as:

1. After the cold stamping of printed materials, it must be glazing or clad wax in order to protect the bronzing pattern, which increases the cost of bronzing and the complexity of the process.

2. Cold-foil gold technology is not suitable for application on film materials with shrinkage characteristics, such as PVC, PE and other materials.

3. Due to poor leveling of the UV adhesive, some of the dried surface is not an absolute flat surface, resulting in poor brightness of the surface of the metal foil transferred to it, and there is diffuse reflection phenomenon. In other words, cold stamping is not as effective as traditional hot stamping.

Cold bronzing process is applicable to various types of narrow-width printing presses. Due to the simple process and convenient installation of the auxiliary equipment, it is a promising new bronzing process.

The key technology of the cold foiling process is UV adhesives and special aluminum foils. At present, imported and domestic UV adhesives have been sold on the market in China, and the production process of anodized aluminum without hot melt adhesives is very simple. We believe that with the development of the printing industry and the needs of various industries, the application of cold bronzing technology in China has also achieved great development.

Source: Printing Technology