Analysis on the principle and process conditions o

2022-07-23
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In recent years, improving the packaging and decoration of commodities has become an important means to promote the sales of commodities. From cigarettes, wine, drugs, food to clothing, fruits, liquid drinks, cosmetics, etc., all areas of daily life have reflected the rapid development of packaging and decoration printing. As an important finishing process of packaging and printing, hot stamping plays a key role in commodity packaging, meets people's psychological needs, and has a promising future

the main material for hot stamping is electrochemical aluminum, also known as hot stamping foil. It is mainly composed of two thin layers, namely polyester film substrate and transfer layer. During hot stamping, the transfer layer is pressed on all or part of the surface of the substrate by virtue of heat and pressure. After hot stamping, the polyester film is pulled away together with the part that has not been transferred

the hot stamping process is divided into four steps:

(1) the hot stamping foil is in contact with the substrate

(2) by virtue of heat and pressure, the transfer layer is transferred to the substrate surface

(3) remove the pressure and peel off the polyester film

(4) feed the hot stamping foil and replace the substrate to be hot stamped

perfect and important driving factor the hot stamping effect mainly depends on the level of cooperation among hot stamping temperature, hot stamping pressure and hot stamping time. In addition, consider whether the substrate, hot stamping machine, hot stamping plate, fixture and pad plate are appropriate. Finally, it is necessary to study the environmental conditions, including indoor temperature, substrate temperature, indoor air cleanliness (dust content), humidity, etc., which are described below

1. Hot stamping foil

hot stamping foil has two categories: roll foil and sheet foil. The roll foil can be divided into different models according to the ironing materials, such as 1 \812 1518general type, etc. it can also be divided into gold, silver, brown red, light blue, black, bright red, green, etc. according to its color

different types of anodized aluminum have different properties and are suitable for different ironing materials. For example, 11anodized aluminum is suitable for hot stamping on paper, leather, varnished cloth, silk, plexiglass and hard plastics with light ink background and loose texture; 8electrochemical aluminum is suitable for hot stamping on paper, varnished cloth and leather; Anodized aluminum is suitable for hot stamping on plexiglass, hard plastic and some polished paper; Electrochemical aluminum is suitable for hot stamping on plastic films and soft plastic products; Electrochemical aluminum is suitable for hot stamping on paper and leather with dark ink and thick lines. Although some anodized aluminum products are of the same model, they are produced in different places, and the suitable ironing materials are also different

single pure gold foil is used for hot stamping of lacquer cloth, silk, leather and other materials; Gold foil (red, green and medium red) and silver foil are suitable for cloth (including lacquer cloth), paper and silk, while silver foil is suitable for hot stamping of cloth, ethylene, leather and other materials

2. Hot stamping temperature

if the hot stamping temperature is too high, the hot stamping imprint will lose its metallic luster, blister, unclear edge or even paste; Hot stamping temperature is too low, which will lead to poor hot stamping or hairy hot stamping impression

various types of anodized aluminum are suitable for different hot stamping temperatures, 1is 80 ~ 95 ℃, 8is 75 ~ 90 ℃, 12is 75 ~ 90 ℃, 15is 60 ~ 70 ℃, while pure gold foil is 80 ~ 130 ℃, and color foil, gold powder foil and silver powder foil are 70 ~ 120 ℃

3. Hot stamping pressure

too much hot stamping pressure will cause the paste or imprint to become thicker; The hot stamping pressure is too small, and the hot stamping foil cannot adhere to the substrate, and the hot stamping part of the hot stamping foil cannot be cut

the installation of hot stamping foil shall not be too tight or too loose. If it is too tight, the handwriting will be missing and broken. If it is too loose, the handwriting will be unclear and the version will be pasted

4. Hot stamping speed

hot stamping speed actually reflects the contact time between the substrate and the hot stamping foil during hot stamping, which directly affects the hot stamping fastness. Hot stamping speed is too fast, which will lead to hot stamping failure or blotting; The hot stamping speed is too slow, which not only affects the hot stamping quality, but also affects the production efficiency. The suitable hot stamping speed for various types of anodized aluminum is different, for example, the suitable hot stamping speed for 8 # and 12 anodized aluminum is 18 ~ 30 sheets/minute, the suitable hot stamping speed for 15 anodized aluminum is 18 ~ 22 sheets/minute, and 1 anodized aluminum is suitable for fast hot stamping, such as about 40 sheets/minute

in the process of hot stamping, the hot stamping speed, pressure and temperature restrict each other, and the process parameters are always determined in the order of hot stamping speed, pressure and temperature. First, determine the hot stamping speed. In general, treat it as a constant, not easy to change, and then find out the corresponding hot stamping pressure and temperature, which can simplify the operation procedure and easily control the hot stamping quality

5. Hot stamping machine

according to the hot stamping method, the hot stamping machine can be divided into flat pressing, round pressing and round pressing; According to the placement mode of the hot stamping plate, the hot stamping machine can be divided into two types: discrete and horizontal rapid prototyping thermosetting automotive composite materials: characteristic types balanced for mass production

6. Hot stamping materials

offset paper, coated paper, white board paper (paperboard), cloth paper, lacquer cloth, plastic, etc. can be used as hot stamping materials

(1) hot stamping of coated paper prints

① for the field version containing wax, when the hot stamping quantity is small, use 5 layers of gauze wrapped with rosin powder to wipe the hot stamping part; When the quantity is large, first use the washing ink plus 3% adhesive and 3% white dry oil printing. After this treatment, the hot stamping effect is good

② for reverse pulling, corresponding measures shall be taken according to different conditions. The first reason for the reverse pull is that the bottom ink of the printed matter is not completely dry. The solution is to put the printed matter in a ventilated and dry place to make the ink layer completely dry. Second, white ink is excessively used as the washing agent on the light color ink layer. Due to the coarse particles of white ink pigment and the poor binding force between the binders, the hot stamping surface is powdered. The solution is to use the brightening agent and dry oil to cover the printing first, and then hot stamping. You can also use electrochemical aluminum with low separation force for hot stamping

(2) hot stamping of gold card paper. However, gold card paper is difficult to print, easy to get dirty, ink can be removed at one touch, and hot stamping is difficult. These factors limit its development. Here, combined with practice, we will talk about some problems that should be paid attention to in gold card printing and hot stamping

① from the cross section, gold card paper is divided into surface coating, aluminum foil layer, bonding layer and paper base. The surface coating is equivalent to pre printing a layer of metal color. The surface is smooth, with poor permeability. The ink is not easy to adhere, and it is difficult to dry even if printed. Therefore, it is best to use synthetic paper special ink for printing, and the ink volume should be small. Try to thin print, and do not spray too much powder. Hot stamping can be carried out only after the imprint is completely dry. Another way to solve the problem of hot stamping is to print a thin layer of background color at the place to be hot stamping before hot stamping, so that the hot stamping foil can be firmly adhered to the ink

② select appropriate hot stamping temperature, pressure and speed; The bronzing plate shall be copper plate. Because it has good heat transfer performance, pressure resistance, wear resistance and is not easy to deform, the height difference between the graphic part and the blank part shall be widened as much as possible to prevent it from being connected or pasted

in addition, the resin version can also be used for hot stamping. Some manufacturers are unable to make copper and zinc plates locally. Considering the cost of making copper and zinc plates in other places, they try to use resin plates instead of copper and zinc plates for hot stamping. As long as the hot stamping temperature and pressure match perfectly, good products can also be hot printed. The following points should be paid attention to when using resin version hot stamping:

enterprises need to accelerate the pace of transformation and upgrading.

① if the hot stamping temperature is too high, the resin version will be scorched, and the hot stamping foil will also have adhesion under the influence of temperature

② due to the toughness of the resin version, there is no need to use too much pressure, and the hot stamping handwriting will be very clear

③ double sided adhesive tape shall be used to fix the resin plate as far as possible. This kind of adhesive tape is not insulated, so it is easy to control the hot stamping temperature

source: printing technology

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