Traditional hot stamping anodized aluminum is generally composed of 5 layers of materials, including base film layer (sheet base), separation layer (separation layer), dyeing layer (protective layer), aluminum plating layer, adhesive layer, etc.
During hot stamping, the electrochemical aluminum separation layer and adhesive layer are heated and melted. Under the action of pressure, the separation layer and the base film layer are separated to realize the transfer of aluminum foil pigment layer.
The structure of anodized aluminum used in cold stamping gold is basically the same as that of traditional anodized aluminum.
The back is not coated with glue, and the adhesive is directly printed or coated on the predetermined position of the substrate to be decorated during printing. During the transfer, the anodized aluminum contacts and dries with the adhesive under the action of pressure, and completes the transfer of the anodized color layer under the action of the adhesive.
For traditional anodized hot stamping, it is necessary to make hot stamping templates by means of corrosion method or electronic engraving in advance according to the designed pictures and texts. Generally, the templates are mostly one metal relief plate or two templates with Yin and Yang engaged. The metal relief plate is mostly copper plate or copper zinc alloy plate, and there are also a small amount of other materials. The other is mostly made of polymer materials. Considering that it is easy to wear during hot stamping, Therefore, the number of plate making is relatively large. During hot stamping, the hot stamping template is installed on the hot stamping equipment, and the melting and transfer of electrochemical aluminum separation layer and adhesive layer are completed through heating system and pressure. At present, the process is relatively mature, there are many types of equipment and high production efficiency.
The hot stamping process includes preparation before hot stamping, plate loading, plate pad, determination of hot stamping process parameters (temperature, pressure, time), trial ironing, sample signing, formal hot stamping and so on.
Combined with the principle of electrochemical aluminum cold hot stamping process, the hot stamping process is designed, as shown in Figure 5. It can be clearly seen from the flow chart that the cold hot stamping process mainly includes product multi-color printing, adhesive printing, proper drying, cold hot stamping, composite protective layer, etc. The principle is that the adhesive is printed on the substrate in advance, and the part required by cold hot anodized aluminum (i.e. picture and text part) is transferred to the substrate surface under pressure through the adhesion performance of the adhesive to form a picture and text. Considering the poor picture and text adhesion effect, the adhesion effect on the substrate surface is improved through subsequent surface polishing, film coating and other post printing processing technologies, Improve product hot stamping quality.
The common process steps of cold stamping gold are generally as follows: first, print ∪ V ink. After drying, the special adhesive UV curing adhesive shall be printed on the necessary bronzing part of the ink surface; Then, the moisture of the adhesive is removed to a certain extent through the UV drying device to form a layer of high viscosity and very thin pressure-sensitive adhesive layer; Start cold hot stamping. Under the pressure of a pair of metal rollers, the aluminum foil is in close contact with the adhesive and pressed into one. Due to the large adhesive force between the adhesive and the aluminum foil, when discharging, the contact part between the aluminum foil and the adhesive remains on the surface of the printed substrate to form a predetermined picture and text, while other parts of the aluminum foil are discharged like traditional hot stamping. In the production process, it is found that the pigment layer transferred by this process has poor adhesion on the surface of the printed matter, and corresponding processes must be taken to protect it, otherwise it is easy to wear. General printing enterprises adopt processes such as polishing or coating on the surface of printed products to protect cold hot stamping.
The quality of traditional hot stamping products is mainly determined by processing equipment, hot stamping materials, technical parameters of hot stamping process and human operation. After the extensive use of traditional anodized hot stamping in recent years and the continuous improvement of process and technical personnel, the process maturity has been relatively mature, especially the processing equipment and hot stamping materials. As long as the hot stamping process parameters are effectively controlled and adjusted in the actual production process, high-quality hot stamping products can generally be produced.
Influencing factors of cold hot stamping quality
Generally speaking, the main factors affecting the quality of cold hot stamping products are basically the same as the traditional process, but the specific processing process parameters are quite different, mainly due to the different processing materials of the equipment, including the selection and moderate drying of adhesive, hot stamping pressure, winding speed, UV drying and subsequent surface protection process, Will seriously affect the hot stamping quality and hot stamping effect. The cold stamping process is limited by the conditions such as adhesive and metal foil, and has the following disadvantages and deficiencies.
Printed matter must be polished or covered with film after cold stamping to protect the bronzing pattern, which increases the bronzing cost and process complexity.
Some hot stamping materials are inappropriate
Cold stamping process is not suitable for film materials with shrinkage characteristics, such as PVC, PE and other materials.
The gloss effect is slightly poor
Due to the poor leveling of UV adhesive, some of the dried surface is not flat, resulting in poor brightness and slow reflection on the surface of the metal foil transferred on it. The effect of cold bronzing is not as good as that of traditional hot bronzing.
It takes one to two weeks to make a metal plate cylinder using the traditional bronzing process. Cold stamping plate making takes only a short time, which greatly shortens the production cycle.
Cold stamping materials have a wide range of applications, such as cold stamping on thermal paper and some film materials. The use of general flexo printing plate instead of expensive metal plate cylinder greatly reduces the production cost of bronzing plate.
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