Improving the quality of bronzing process is not as difficult as you think, look here!

Improving the quality of bronzing process is not as difficult as you think, look here!

At present, due to the continuous development of science and technology, the post-press finishing process has been constantly innovating, and many new processes such as holographic positioning hot stamping and cold hot stamping have emerged. However, traditional hot stamping is an important process in post-press processing, in view of its unique luxurious decoration The effect has not been neglected, but has received more attention and preference from customers. Therefore, how to improve the quality of bronzing has often become a problem that people discuss. The following will explain the operation of some bronzing processes from several aspects.

　　 One, the basic process of bronzing

　　The main material of hot stamping is anodized aluminum, so hot stamping is also called anodized aluminum hot stamping. Hot stamping is to transfer the aluminum layer in the anodized aluminum to the surface of the substrate by using the principle of heat and pressure transfer.

　　Basic craft:

First of all, in the state where the anodized aluminum is pressed by the hot stamping plate and the substrate, the anodized aluminum is heated to melt the hot-melt silicone resin layer and the adhesive. At this time, the viscosity of the heated and melted silicone resin changes However, the viscosity of the special heat-sensitive adhesive increases after being heated and melted, so that the aluminum layer and the anodized aluminum base film are peeled off and transferred to the substrate at the same time.

　　 As the pressure is removed, the adhesive quickly cools and solidifies, and the aluminum layer is firmly attached to the substrate, completing a hot stamping process.

　　 Process flow:

　　 Hot stamping preparation-loading plate-pad plate-adjusting hot stamping process parameters-trial hot stamping-signing sample-formal hot stamping.

　　 2. Ways to improve the quality of bronzing

　　 From the basic process of bronzing, it can be seen that the three basic elements of bronzing are: temperature, pressure and stamping time.

In order to obtain the ideal hot stamping effect, the hot stamping temperature, hot stamping pressure, hot stamping speed and other process parameters must be reasonably mastered; 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.

　　 1. 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 the paper is loose, such as book paper, poor offset paper, etc., because the anodized aluminum layer cannot adhere to the surface well, the unique metal The gloss is not well reflected, and it may even fail to be hot-stamped.

　　 Therefore, the hot stamping substrate should choose paper with dense texture, high smoothness and high surface strength, so as to obtain a good hot stamping effect and fully reflect the unique gloss of anodized aluminum.

　　2, 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 is not only to choose the right color, but also to choose the corresponding model according to the different substrates. Different models have different performances and the range of materials suitable for ironing.

　　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 the 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 scotch tape.

If the anodized aluminum does not fall off easily, it indicates 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 cannot be mixed with acids, alkalis, alcohols and other substances. It must be protected from moisture, high temperature, and sun. Otherwise, the aluminum will shorten Period of use.

　　 3. Make a good hot stamping plate

　　 Hot stamping plates generally include copper plate, zinc plate and resin plate. Relatively speaking, the copper plate is the best, the zinc plate is moderate, and the 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 graphics and text lines, smooth edges, and no pitting and burrs.

　　 If the surface is slightly uneven or slightly scratched or fluffy, wipe it gently with fine charcoal 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 images 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 texts should be as thick as possible, and the density should be reasonable. If it is too small or too thin, it will be easy to miss the strokes; if it is too thick and too dense, it will be easy to paste.

　　4, 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 range, which is the minimum temperature to ensure the melting of the anodized aluminum adhesive layer.

　　If the temperature is too low and the melting is insufficient, it will cause the hot stamping or the hot stamping to be weak, which will make the imprints not strong, incomplete, missing pens, broken marks or flowers;

If the temperature is too high, the melting will be excessive, causing the anodized aluminum attached around the print to melt and fall off to produce a paste. At the same time, high temperature will also oxidize and polymerize the synthetic resin and dye in the color layer, causing the print to bubble or appear foggy The surface of the aluminum layer and the protective layer are oxidized, which reduces the brightness of the hot stamping product or loses its 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 the most suitable temperature is usually found through trial ironing. The temperature should be the lowest and clear graphics and text lines can be imprinted. As the standard.

　　 5. 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, the anodized aluminum will not stick firmly to the substrate, or cause color fading, imprinting, 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, when the paper is strong, smooth, the ink layer printed is thick, and the hot stamping temperature is high and the vehicle speed is slow, the stamping pressure should be lower; on the contrary, it should be higher.

In addition, similar to printing, you should also pay attention to the liner for hot stamping. For smooth paper, such as coated paper and glass cardboard, it is best to use hard liner paper, so that the print will be clearer; on the contrary, for smoothness For poor, rough paper, the liner should be softer, especially when the hot stamping area is large.

　　Finally, the hot stamping pressure must be even. If it is found that the hot stamping cannot be performed locally or tingling occurs during the trial printing, it may be that the pressure here is not flat. You can pad thin paper on the flat plate there and make appropriate adjustments.

　　6, the hot stamping speed is as constant as possible

　　The contact time is 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 be 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 also be increased appropriately.

　　 In addition, the performance of the anodized aluminum itself has a greater impact on the hot stamping speed. High-quality anodized aluminum can realize fast hot stamping. This is a big difference between domestically made anodized aluminum and imported anodized aluminum.

　　 Domestic anodized aluminum is usually only suitable for low-speed hot stamping, the speed is about 2000 sheets/h, and the highest is generally not more than 3000 sheets/h; imported ones can reach 8000 sheets/h, or even higher. Regardless of the speed, the important point is: the hot stamping speed should be kept as relatively stable as possible, and should not be changed easily.

　　 Under the premise of stable hot stamping speed, the hot stamping temperature and pressure should be adjusted appropriately to optimize the hot stamping effect, which can reduce the variable factors, make the operation stable, and easily control the hot stamping quality.

　　 The above are just a few of the main factors that affect the quality of bronzing, and these factors are not isolated from each other, they are mutually restricted.

　　The determination of these factors should be based on the hot stamping suitability of the anodized aluminum and the characteristics of the substrate, and the graphic structure, area and hot stamping speed of the hot stamping plate to determine the best pressure, and finally adjust the appropriate hot stamping temperature.

The basic starting point is to perform hot stamping with as uniform and moderate pressure as possible, low temperature and relatively stable hot stamping speed to achieve clear and clean graphics, smooth and firm, high gloss, no dirty spots, and no blisters. The good results.

　　 Three, other issues that should be paid attention to in hot stamping

　　The quality of bronzing is affected by many factors, especially since bronzing is done after printing, its printing effect, ink layer thickness, ink properties, etc. will directly affect the bronzing effect. Therefore, the following issues should be paid attention to:

　　01. Hot stamping should be done after the ink is dry. If the ink layer is not completely dry, start hot stamping, because the ink is not firmly attached, it is easy to cause the failure of pulling off the ink layer, so that the hot stamping cannot be performed.

02. If hot stamping on the background color, the background color ink layer should not be too thick or too thick, try to make deep ink thin printing, avoid 3 colors, 4 colors overprinting, lest the ink layer is too thick and the ink adhesion is not strong enough. Bad phenomenon such as poor hot stamping, smutting, or even pulling off the ink layer. In addition, when hot-stamping solid background colors, the hot-stamping temperature should be appropriately lowered, so that the hot-stamping effect is ideal.

03. If you are hot stamping on spot colors, you must control the amount of ink additives when printing spot colors. For example, if the amount of desiccant is too much, it will cause the ink layer to crystallize and cause the hot stamping of anodized aluminum to fail; in addition, printing Try to avoid mixing non-drying oils, such as motor oil, kerosene, slow-drying agents, and corn flour, to avoid hot stamping.

　　 If the hot stamping is not possible due to the addition of ink additives, you can wipe the surface of the printed matter with anhydrous alcohol to destroy the oil layer or wax, so as to enhance the adhesion of the anodized aluminum and improve the hot stamping effect.

　　04. If you are hot stamping on glazing and laminating printed matter, you should choose the corresponding anodized aluminum model.

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