Introduction: Post-press finishing technology continues to innovate. Hot stamping, as an important process in post-press processing, has attracted more attention and preference due to its unique decorative effect. How to improve the quality of bronzing is often a question of discussion. This article shares several factors that affect the quality of bronzing, and the content is for your reference:

Bronzing process

Hot transfer printing technology is commonly known as hot stamping, hot stamping, and scientific name electrochemical aluminum hot stamping. It is a special printing process that does not use ink. It uses a certain pressure and temperature to use the template installed on the hot stamping machine to make the printed matter and hot stamping foil in Press each other in a short period of time, and transfer the metal foil or pigment foil to the surface of the hot print according to the graphics of the hot stamping template. In terms of specifications, bronzing refers to the hot pad printing process of hot stamping anodized aluminum foil (hot stamping paper) on the surface of the substrate under a certain temperature and pressure.

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Process classification

Hot stamping process
It is a process in which metal foil is transferred to the surface of printed matter or other objects by heat and pressure to increase the decorative effect.

Cold stamping process
It is a process in which metal foil is transferred to the surface of printed matter or other objects without heating, but only through the force of pressure, bonding and peeling, for a decorative effect.

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Influencing factors
From the basic process of bronzing, it can be seen that the three basic elements of bronzing are: temperature, pressure and stamping time. To obtain the ideal hot stamping effect, the hot stamping temperature, hot stamping pressure, hot stamping speed and other process parameters must be reasonably controlled; in addition, the quality of raw materials related to hot stamping must also be guaranteed, such as: the hot stamping suitability of the substrate , The performance of the anodized aluminum material and the quality of the hot stamping plate, etc. If something goes wrong in a certain link, it will definitely affect the final hot stamping effect. Let’s talk about six ways to improve the bronzing process of printed matter:

Choose the right substrate

There are many substrates that can be bronzed, usually paper, such as: coated paper, white paper, white cardboard, cloth paper, offset paper, etc. But not all paper bronzing effects are ideal. If the surface is rough and loose paper, such as book paper, poor offset paper, etc., because the anodized aluminum layer cannot adhere to the surface well, the unique metal The gloss cannot be reflected well, or even cannot be hot stamped. Therefore, the hot stamping substrate should choose paper with dense texture, high smoothness and strong surface strength, so as to obtain a good hot stamping effect, and the unique anodized aluminum The gloss is fully reflected.

Make a good hot stamping plate

Hot stamping plates generally include copper plate, zinc plate and resin plate. Relatively speaking, copper plate is the best, zinc plate is moderate, and resin plate is slightly worse. Therefore, for fine hot stamping, copperplate should be used as much as possible. For the hot stamping plate, it is required to have a smooth surface, clear graphic lines, smooth edges, and no pitting and burrs. If the surface is slightly uneven or slightly scratched or fluffed, use fine charcoal to wipe gently to make it smooth. The corrosion depth of the hot stamping plate should be slightly deeper, at least 0.6mm or more, and the slope should be around 70° to ensure clear hot stamping graphics and text, reduce the appearance of contiguous and stale plates, and improve the printing durability. The design of hot stamping text, lines and patterns is very particular. The graphics and text should be as thick as possible, and the density should be reasonable. If it is too small or too thin, it is easy to miss the strokes; if it is too thick and too dense, it will be easy to paste.

Control the hot stamping temperature

The hot stamping temperature has a great influence on the melting degree of the hot melt silicone resin peeling layer and the adhesive. The hot stamping temperature must not be lower than the lower limit of the anodized aluminum temperature resistance range, which is the minimum temperature to ensure the melting of the anodized aluminum adhesive layer.

If the temperature is too low, the melting will not be sufficient, it will cause the hot stamping or the hot stamping is not strong, and the imprint will not be strong, incomplete, lack of strokes or scratches; while the temperature is too high, the melting will be excessive, resulting in adhesion around the imprint The anodized aluminum also melts and falls off to produce a paste. At the same time, the high temperature will oxidize and polymerize the synthetic resin and dye in the color layer, resulting in blistering or fogging of the print, and oxidation of the surface of the aluminum layer and the protective layer, reducing the hot stamping product Brightness or loss of metallic luster. Generally speaking, the electric heating temperature should be adjusted between 80～180℃. For larger hot stamping area, the electric heating temperature is relatively higher; otherwise, it is lower. The specific situation should be determined according to various factors such as the actual temperature of the printing plate, the type of anodized aluminum, the graphics and text conditions, and usually the most suitable temperature should be found through trial ironing. The temperature should be the lowest and clear graphics and text lines should be printed. As the standard.

Choose the appropriate anodized aluminum model according to the different substrates

The structure of anodized aluminum has 5 layers, namely: polyester film layer, peeling layer, color layer (protective layer), aluminum layer and glue layer. There are many types of anodized aluminum, the common ones are No. 1, No. 2, No. 8, No. 12, No. 15 and so on. In addition to gold, there are dozens of colors, such as silver, blue, brown-red, green, and red. Choosing anodized aluminum should not only choose the right color, but also choose the corresponding model according to the different substrates. Different models have different performance and suitable ironing materials. Normally, No. 8 is the most used hot stamping for paper products, because No. 8 anodized aluminum has moderate adhesion and good gloss, which is more suitable for hot stamping on general printing paper or glazing paper and varnished cloth. If you are hot stamping on hard plastic, you should choose other corresponding models, such as No. 15 anodized aluminum.

The quality of anodized aluminum is mainly checked by visual inspection and hand feel, such as checking the color, brightness and trachoma of anodized aluminum. Good quality anodized aluminum requires uniform color, smooth and clean after hot stamping, and no trachoma. The fastness and tightness of the anodized aluminum can generally be checked by rubbing it by hand or trying to stick the surface layer with transparent tape. If the anodized aluminum does not fall off easily, it means that the fastness and tightness are good, and it is more suitable for hot stamping small text patterns, and it is not easy to paste the plate during hot stamping; if the anodized aluminum falls off after being gently rubbed, it indicates that its tightness is poor. It can be used for hot stamping with sparse graphics and text; in addition, pay attention to the broken ends of anodized aluminum, the less the broken ends, the better.

It is worth noting that the anodized aluminum must be stored properly. It should be stored in a ventilated and dry place. It should not be mixed with acids, alkalis, alcohols and other substances. It must be protected from moisture, high temperature, and sun. Otherwise, the anodized aluminum will shorten Period of use.

To reasonably control the stamping pressure

The hot stamping pressure has a great relationship with the adhesion fastness of anodized aluminum. Even if the temperature is right, if the pressure is not enough, it will not be able to make the anodized aluminum adhere to the substrate firmly, or cause color fading, blotting, etc.; on the contrary, if the pressure is too high, the compression deformation of the liner and the substrate will be too large, resulting in paste The plate or print becomes thicker. Therefore, the hot stamping pressure should be adjusted carefully.

When setting the stamping pressure, the main considerations should be: the properties of anodized aluminum, stamping temperature, stamping speed, substrate, etc. Generally speaking, the paper is strong, smooth, the ink layer of Beijing printing is thick, and the hot stamping temperature is high and the speed of the car is slow, the stamping pressure should be lower; on the contrary, it should be higher. In addition, similar to the hot stamping liner, you should also pay attention to it. For smooth paper, such as: coated paper, glass cardboard, it is best to use hard liner paper, so that the impression obtained is relatively clear; on the contrary, for poor smoothness 2. For rougher paper, the liner should be softer, especially when the hot stamping area is larger. In addition, the hot stamping pressure must be uniform. If you find that the hot stamping is not performed locally or produce fluffing during the trial printing, it may be because the pressure here is not flat. You can pad thin paper on the flat plate at that place and make appropriate adjustments.

The hot stamping speed is as constant as possible

The contact time is directly proportional to the hot stamping fastness under certain conditions, and the hot stamping speed determines the contact time between the anodized aluminum and the substrate. The hot stamping speed is slow, and the contact time between the anodized aluminum and the substrate is long, and the bonding is relatively strong, which is conducive to hot stamping; on the contrary, the hot stamping speed is fast, the hot stamping contact time is short, and the hot-melt silicone resin layer and adhesive of the anodized aluminum If it has not been completely melted, it will cause the hot stamping to fail or the imprint to become blurred. Of course, the hot stamping speed must also be compatible with the pressure and temperature. If the hot stamping speed increases, the temperature and pressure should be increased appropriately.