Analysis of the Factors Affecting the Quality of Electrochemical Aluminum Hot Stamping
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With the continuous improvement of people's living standards, people's requirements for the quality of printed matter are getting higher and higher. The flourishing development of the printing industry has prompted the widespread application of hot stamping processes, especially holographic positioning, in the printing and packaging industry. It not only has good sensory effect on gloss, three-dimensionality, color and metal sense, but also has unique anti-counterfeiting function, so it is more and more favored by consumers. In addition, the unique hot stamping highlights the individuality, environmental protection and safety of the product packaging. Many high-end packagings use the bronzing process. Therefore, it is very meaningful to study what is the bronzing process and the factors affecting the hot stamping process.
First, the principle and process of hot stamping
Anodized aluminum hot stamping refers to a post-press process for hot stamping, hot stamping or hot stamping. For ease of discussion, the following description of electro-aluminized hot stamping is referred to as bronzing. There are two main functions of bronzing: first, surface decoration, promotion of sales, and can be combined with the embossing process to show 3D effect; second, high anti-counterfeiting performance, using holographic positioning hot stamping trademark logo, anti-counterfeiting, brand protection .
1. Structural characteristics of anodized aluminum
The basic structure of the electrochemical aluminum foil is divided into 4 to 5 layers: a base layer, a release layer, a protective layer, a colored layer, a plating layer, and an adhesive layer (see FIG. 1). The silver anodized aluminum has no colored layer, and the main functions of each layer are as follows:
1.1 Base layer: Generally, a biaxially stretched polyester film with a thickness of 12 μm to 25 μm is used, and the main function is to support the respective coatings attached thereto to facilitate continuous hot stamping during processing.
1.2 Release layer: The electro-aluminized aluminum foil is peeled off from the base layer, and this layer determines the transfer property of the electrochemical aluminum; it is generally coated with a silicone resin or the like. The main function is to make the color material, aluminum and rubber layer quickly disengage from the polyester film after hot stamping and transfer and bond on the surface of the object to be stamped.
1.3 coloring layer: There are two main functions: one is to display the color; the other is to protect the image of the aluminized layer printed on the surface of the article from being oxidized. The color of the electrochemical aluminum foil is golden, orange, gray, red, blue, green, and the like. The color of the color layer is imparted with gloss after passing through the aluminized layer, and the color has a certain change, such as yellow gold after cobalt plating, silver after gray plating, and the like. The coating requirements for the colored layer are fine without any small particles to avoid dull eyes and uniform coating.
1.4 plating layer: the main role is to reflect light, change the color of the color layer to make it metallic luster.
1.5 Adhesive layer: The main function is to bond the hot stamping material to the object to be burnt.
Figure 1 Basic structure of anodized aluminum foil
2. The principle of hot stamping
Figure 2 Principles and elements of hot stamping process
2.1. Flat pressing hot stamping machine 2.2. Hot stamping template 2.3. Hot stamping foil 2.4. Hot material
Hot stamping is a special printing process that does not use ink. A process of transferring a material to be stamped onto a substrate under the action of a certain temperature and pressure. The specific operation procedure is to apply the template mounted on the hot stamping machine under appropriate pressure and temperature, so that the substrate and the hot stamping foil are pressed against each other instantaneously, and the hot stamping material is transferred to the substrate according to the image of the hot stamping template. Surface process. Among them, the hot stamping process has four elements: hot stamping foil, hot stamping stencil, hot stamping machine and substrate (Figure 2).
3. Hot stamping process
There are two kinds of hot stamping methods: pressing method and hot stamping method. The general operation process is as follows:
Prepress preparation → plate loading → pad version → initial value of application process parameters → test hot → signing → official hot stamping
The hot stamping pattern is clear, beautiful, colorful, and wear resistant. Widely used in cigarette packaging applications, it has extraordinary value in graphic design, especially in trademarks and registration names.
Second, the main factors affecting the quality of hot stamping
The factors affecting the quality of hot stamping are mainly the hot stamping suitability of the substrate, the performance of the electrochemical aluminum material, the hot stamping temperature, the hot stamping pressure, and the hot stamping speed. The perfect graphic bronzing effect depends on how well each other fits. Therefore, in the hot stamping process, temperature, pressure and speed should be strictly controlled to ensure the quality of hot stamping.
1. Temperature
Proper temperature is one of the guarantees of hot stamping quality. If the temperature is too high, the melting is excessive, the electro-chemical aluminum around the hot stamping image is easy to fall off and cause paste, and at the same time, the high temperature will cause chemical changes in the electro-aluminized dyeing resin and the aluminum layer, so that the brightness of the hot stamping product is lowered and the metallic luster is lost. Even the blotting is foggy or blistering; on the contrary, if the temperature is too low, the melting is insufficient, which may result in poor hot stamping, weak imprinting, easy peeling or lack of stroke, and imprinting.
2. Pressure
Whether the pressure and temperature are properly matched is also an important guarantee for the quality of hot stamping. When the temperature is constant, if the pressure is insufficient, the electrochemical aluminum can not be transferred to the substrate very well, resulting in problems such as embossing, stenciling, etc. On the contrary, if the pressure is too large, the compression deformation of the liner and the substrate Large, the print will be thick, even sticky, paste. Usually the hot stamping pressure should be adjusted from small to large, so as not to fade, the edge is smooth.
3. Speed
The hot stamping speed actually reflects the contact time of the substrate with the hot stamping foil during hot stamping, which directly affects the hot stamping fastness. If the hot stamping speed is too fast, it will cause hot stamping or imprinting. On the contrary, if the speed is too slow, the gold foil will lose its metallic luster, affecting the quality of the printed product, and will affect the production efficiency.
4. Anodized aluminum
In the hot stamping process of tipping paper products, the quality of anodized aluminum is closely related to the quality of hot stamping. If the tightness of the anodized aluminum is too tight (too loose and too tight), it will cause the hot stamping to be untrue; if the hot melt hue is not correct or unstable, it will directly affect the quality of the printed product. To some extent, good quality aluminum is the premise of hot stamping quality. Grasping the quality of anodized aluminum is equivalent to controlling half of the quality of printed products.
5. Hot materials
The influence of the hot material on the quality of the hot stamping of the tipping paper is mainly reflected on the ink layer on the surface of the hot material. The temperature resistance and thickness of the ink layer directly affect the quality of the hot stamping print, especially if the temperature of the glue is improper, which will cause the hot stamping paste; when printing the anodized aluminum with pearlescent ink, it is necessary to pay attention to the curing time and tension control.
Third, the conclusion
The bronzing process is a complicated process technology, and may encounter various problems in actual production. The common problems and solutions after sorting are shown in Table 1 below. In short, only a strict control of the factors affecting the hot stamping process, in order to get a satisfactory hot stamping effect. In the hot stamping process, only these problems can be grasped in order to obtain a satisfactory hot stamping effect.