Talking about the Process and Precautions of the Stamping and Stamping Process
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The essence of hot stamping is heat transfer, which is the process of transferring the electrochemical aluminum to the surface of the substrate by the action of temperature and pressure. The perfect hot stamping effect depends on the temperature, pressure and hot stamping time. The constant of the three parameters is the continuous stamping and the guarantee of its quality. The process of hot stamping is: the aluminum foil is heated by the hot stamping plate, the peeling layer is melted, and then the adhesive layer is bonded to the substrate, the colored layer is separated from the base layer of the polyester sheet, and the aluminized layer and the colored layer are left on the substrate.
Type and basic characteristics of hot stamping process
The type of hot stamping process is mainly divided into lithographic hot stamping, engraving hot stamping + bump, hot stamping + embossing. The surface of the hot stamping process is flat, and the plate is mainly made of zinc plate or red copper plate, and the thickness is generally 2mm; the surface of the hot stamping + bump hot stamping pattern is three-dimensional, and the main plate is copper plate and resin. The thickness of the plate is generally 7mm; the surface of the hot stamping + embossed substrate has obvious grain, and the plate is generally made of copper plate, and the thickness is generally 2mm or 7mm.
After hot printing, a large area of anodized aluminum is usually printed on a spot color ink or an unprinted paper surface, and then a UV ink is printed on the anodized aluminum. It has high requirements for printing materials, printing inks, printing equipment and printing personnel.
Production process and process control of hot stamping products
According to the actual requirements of the sample and production work orders, understand the production requirements according to the corresponding samples and production work orders, and determine the corresponding plates and auxiliary materials (including anodized aluminum, hot stamping plates, film and other auxiliary materials) according to the sample. The key monitoring items are as follows.
1. Set: Set hot stamping or specific testing tools, such as film.
2. Hot stamping effect: pattern integrity, edge uniformity, surface gloss.
3. The surface of the printed matter is printed with indentation, scratches, nozzles, ink on the edge of the hot stamping pattern, gold on the edge of the hot stamping, and direction of the anodized aluminum.
Problems that are prone to hot stamping
During the hot stamping process, pay attention to the choice of the type of anodized aluminum and the matching between hot stamping speed, temperature, pressure and other factors. In the case of fixed hardware such as equipment, correct mastering of hot stamping is the most important means to improve the quality of hot stamping.
1. Hot stamping is not possible or hot stamping is not true: this is related to the surface characteristics of the print, the nature of the electrochemical aluminum, hot stamping temperature and pressure. 1 The surface of the printed matter is too dusty or the surface contains additives such as detacking agent and brightening paste, which will hinder the adsorption of the electrochemical aluminum and the paper. Solution: Surface de-powder treatment or solution in the printing process. 2 improper use of electrochemical aluminum directly affects the hot stamping fastness. According to the size of the hot stamping area and the characteristics of the hot stamping material, it should be considered which type of anodized aluminum is selected. The domestically produced anodized aluminum is mainly Guangzhou Leibao and Wuhan Huagong Technology; the imported electro-aluminized aluminum is mainly the German Kurz series and the Taiwan Guangqun series; 3 does not correctly grasp the hot stamping equipment and the matching between the hot pressing time and the hot stamping temperature, affecting The sharpness of the hot stamping and the sharpness of the graphic outline. Due to the different materials and hot stamping materials, the hot pressing time and hot stamping temperature are not the same. For example, the high-speed circular pressing machine is fast, the embossing line is in contact, and the hot stamping temperature is higher than the round flat or flat flat. Under normal circumstances, the round stamping temperature is 190 ~ 220 ° C, the round flat is about 130 ~ 150 ° C, the flat pressure is about 100 ~ 120 ° C. Of course, the hot pressing time, hot stamping temperature and production efficiency are also largely restricted by the transfer performance of the electrochemical aluminum.
2. Reverse pulling: refers to the removal of printing ink or printing varnish after the hot stamping. The main reason is that the ink on the surface of the printed product is not dried or the UV processing on the surface of the printed product is improperly processed, resulting in the ink surface of the printed product and the UV oil combined with the surface of the paper. Solution: After the printed products are dried, hot stamping is applied. In addition, an electrochemical aluminum with low separation force and excellent thermal transferability can be selected.
3. Paste plate and hot stamping aluminum after discoloration: Paste plate is mainly caused by poorly produced hot stamping plate, slack of electrified aluminum installation or incorrect aluminum foil. After the hot stamping, the discoloration of the anodized aluminum is mainly caused by the excessive hot stamping temperature. In addition, the wrinkling of the anodized aluminum is also likely to cause discoloration and discoloration of the hot stamping, which can be solved by appropriately lowering the temperature. For the round flattening machine type, a fan can be installed at the foil feeding position to keep the foil fluttering up, avoiding the scorching of the electroplated aluminum before the hot stamping.
4. The process arrangement is not proper, destroying the gloss of the surface of the electrochemical aluminum, the contour of the graphic is faint: the hot stamping of the film processing is required, people often worry that the gold foil is easy to be rubbed and the hot stamping and then the film, which is easy to cause: 1 film especially It is the matt film that will destroy the surface gloss of the electrochemical aluminum. It is not suitable to use water-soluble glue film. Otherwise, the surface of the electrochemical aluminum will be black, and it will easily cause the gold powder to stick to the edge of the image to cause fading. 2 After hot stamping, it is sunken by pressure, and the glue is not easy to penetrate the surface of the electrochemical aluminum. It is easy to cause the separation of OPP and paper in the hot stamping area and affect the product quality. The correct process is to first film and then hot stamp, choose the electrochemical aluminum that matches OPP.
The main factors affecting the hot stamping process
1. Pressure. The lightness and uniformity of the pressure depend on the softness of the material and the texture of the surface. The smooth surface of the substrate can use lighter pressure, and the rough stripes can use heavier pressure. During the hot stamping process, it can be adjusted to just press it out, and the pressure is too heavy, which will cause the paste or damage the electrotype.
2. Temperature. In the hot stamping operation, it is necessary to select a suitable temperature and emboss a clear pattern at the lowest temperature. The optimum temperature can be found through experiments. If the temperature is too high, the paste will be burned, the anodized aluminum will be burnt, and the light will become dumb or become dumb. color.
3. Hot stamping speed. Determine the peeling complete and the dissolution rate of the glue layer (ie the integrity of the hot stamping).
How to choose anodized aluminum
For hot stamping, the most important auxiliary material is hot stamping paper, which is what we call anodized aluminum. The types of electrochemical aluminum are roughly divided into ordinary and laser. The laserized aluminum has the characteristics of beautiful, bright and rich in color, and the temperature is between 110 and 150 °C. There is also laser holographic positioning of hot aluminum, mainly used in cigarette labels, wine boxes, cosmetics packaging, etc., is the most popular anti-counterfeiting method in the hot stamping industry, the applicable temperature is between 110 ~ 150 °C.
When selecting, according to the size of the hot stamping pattern, the selection should pay attention to the adhesion performance (ie, hot stamping adhesion) separability, tolerance to hot stamping patterns and adaptability to ink.
Identification of the tightness of the electrified aluminum primer, simple method: stick with transparent adhesive tape, or rub it by hand. If the color layer is easy to fall off, it means that the adhesive layer is loose and easy to stamp, suitable for hot stamping, otherwise it is suitable for hot Small text, lines. But not absolute, the choice after trial is more reliable. The hot stamping suitability of anodized aluminum includes surface finish, brightness, sharpness, hot stamping suitability for graphics and small texts, surface flying gold and flashing problems, etc., according to different printing materials, the level of packaging products, anodized aluminum Price and hot stamping trade-offs are chosen.
The high-quality anodized aluminum should conform to the uniform color of the color layer, and there is no visible color flower after ironing; the color is good, no black spots; the adhesive coating is uniform, smooth and has no obvious stripes.
The second important material for hot stamping is hot stamping, which is usually made of aluminum-zinc-magnesium-copper alloy or brass. The hot stamping pattern surface and the non-embossed surface have a depth of 1 to 1.5 mm and an inclination angle of between 15 and 30 degrees.
The layout must be clean and the tiny spot scratches will be reflected on the printed stamp.
The hot stamping process is formed: heat is applied during hot stamping, the adhesive changes to a liquid state, and the anodized aluminum is embossed on the printed matter by an electric plate, and then the base is separated from the aluminum layer and the color layer to complete the hot stamping.
Hot stamping process precautions
1. Product design should consider matters
(1) The hot stamping part should be fully considered, that is, the matching of the color of the hot stamped text or pattern with the printing color and the effect of hot stamping on hot stamping.
(2) Consider the overall effect of hot stamping and the cost of hot stamping. For example, some products often only stamp the outline and text of the pattern, and do not directly stamp the pattern to achieve the effect of point lining; for some aluminum-plated cigarette packets, the printing design can be printed by transparent yellow and then pressed Instead of hot stamping, it reduces costs.
2. The effect of printing before hot stamping and hot stamping
Generally, hot stamping products must be printed before hot stamping, with monochromatic printing and multicolor printing; after hot stamping, press embossing, UV glazing, laminating, reprinting and die cutting.
Some points to be noted before printing: hot dark printing, using ink with strong tinting strength, as little as possible to add anti-adhesive agent and de-adhesive agent in the ink, try not to spray powder, printing ink, varnish and anodized aluminum The printability of hot stamping is matched, and the effect of ink crystallization on hot stamping should also be prevented.