Influencing Factors and Failure Analysis of Electrochemical Foil Hot Stamping Quality

With the increasingly fierce competition in commodities, commodity packaging and decoration has become an important means to promote the circulation of commodities. Novel and exquisite packaging can reflect the value of goods more concretely, vividly and vividly, and it is highly appreciated by consumers. This has greatly promoted the development of packaging printing. Electrochemical aluminum foil hot stamping is an important process for packaging, decorating and printing. It plays a crucial role in trademark printing and has become increasingly widely used. However, since hot stamping is different from general packaging and decoration printing, its process technology has greater specificity. Therefore, it is necessary to fully grasp its technical characteristics and constantly sum up experience in order to be able to stamp out exquisite products and add icing on packaging and decoration printing.

Electrochemical aluminum foil hot stamping features

Anodized aluminum is also called hot stamping foil. It is the main material for hot stamping. It is mainly composed of two thin layers, a polyester film substrate and a transfer layer. The basic structure of the sub-layer film, alcohol-soluble dyed resin layer, aluminized layer, adhesive layer. Electro-aluminum is available in roll foil and leaflet foils. The roll foil can be divided into different types depending on the material used for the ironing, mainly including No.1, No.8, No.12, No.15 and No.18, and general-purpose type, such as gold, silver, brown and red, and light blue. , black, red, green, etc. Different types of aluminum have different properties, and the suitable materials are different. For example, No. 1 anodized aluminum is suitable for hot stamping on the background of light-colored ink, loose texture of paper, leather, linoleum, silk and plexiglass, hard On plastics, No. 8 galvanized aluminum is suitable for hot stamping on paper, varnished cloth, and leather; No. 18 galvanized aluminum is suitable for hot stamping on paper products and leather with dark ink and thick lines. The single sheet of pure gold foil is suitable for hot stamping on the cover of materials such as linoleum, satin, and leather; gold foil (three kinds of red, green, and middle red) and silver powder are applicable to cloth (including linoleum), paper, and other materials. Cover stamping; silver foil is suitable for cloth, vinyl, leather and other materials of the book cover stamping. During hot stamping, the hot stamping foil is in contact with the substrate. The transfer layer is fused and transferred to the surface of the substrate by virtue of heat and pressure. After the hot stamping is completed, the polyester film is taken together with the untransferred portion. Peel off.

The main factors that affect hot stamping

The main factors affecting the quality of hot stamping are temperature, pressure and hot stamping time, as well as the level of cooperation among the three. In addition, stampability, speed, substrate, stamping machine, hot stamp quality, plate loading and hot plate technology, anodized aluminum tensioning, fixtures and pads, environmental conditions, indoor, substrate temperature, indoor The degree of air cleanliness (dust content), humidity, etc. are also important factors that affect hot stamping. The adjustment of major factors should pay attention to the following issues.

First, the hot stamping temperature: hot stamping temperature is too high, will make hot stamping prints lose the metallic luster, blistering, the edge is not clear or even paste version; and hot stamping temperature is too low, there will be hot stamping is not strong or writing hair and even will Can't hot stamp. Various types of aluminum foil suitable for different stamping temperature, 1 is 80 ~ 95 °C, 8 is 75 ~ 90 °C, 12 is 75 ~ 90 °C, 15 is 60 ~ 75 °C, while the pure gold foil is 80 ~ 130 °C, color foil, gold foil, silver foil is 70 ~ 120 °C, so according to the actual situation, pay attention to debugging.

Second, the hot stamping pressure: stamping pressure is too large, will lead to paste or imprint thicker; hot stamping pressure is too small, hot stamping foil and substrate can not adhere, and can not hot stamping foil hot stamping parts cut. In addition, the installation of hot stamping foil can not be too tight or too loose, when the writing is too short, the handwriting will be cut off; if it is too loose, the writing will be unclear and the paste will be dirty.

Third, the hot stamping speed: Hot stamping speed actually reflects the contact time between the substrate and the hot stamping foil during hot stamping, directly affecting the hot stamping fastness. Hot stamping speed is too fast, it will lead to hot stamping or imprinting; Hot stamping speed will not only affect the quality of hot stamping, but also affect the production efficiency. Different types of aluminum foil suitable for different hot stamping speeds, according to practice, No. 1 anodized aluminum suitable for fast hot stamping, about 40 sheets / min or so, No. 8 and No. 12 anodized aluminum suitable hot stamping speed of 18 to 30 sheets /min, 15 is 18-22 shots/min. In addition, the speed, pressure, temperature and other factors in the hot stamping process are mutually restricted, and the process parameters are always determined in the order of stamping speed, pressure, and temperature. Under normal circumstances, the hot stamping speed should be determined first, and treated as a constant, not to be easily changed; then the corresponding stamping pressure and hot stamping temperature can be found out, which can simplify the operation procedure and also can easily control the quality of the stamping. .

Fourth, hot stamping materials. Various hot stamping substrates are available. Printed materials include offset paper, coated paper, whiteboard paper (cardboard), textured paper, lacquer cloth, plastics, etc. Hot stamping process and precautions for different substrates vary. For example, hot stamping of coated paper products, such as hot at various temperatures are not up, or there is a lack of pen strokes, edge hair and other phenomena, generally can be hot stamping on the back of the plate, the effect is ideal. Sometimes the ground color is found, the ink layer is not thick, and the ink film surface is slightly shiny. This is caused by the addition of detackifiers containing wax substances to the ink in order to overcome certain process failures when printing in the field version. The processing method is: For the field version containing wax materials, a small number of hot stamping uses five layers of gauze wrapped in rosin powder to wipe in the hot stamping area, a large number to dilute the ink plus 3% adhesive and 3% white dry oil cover Once printed, after this treatment, the hot stamping results are better; for reverse pulling, corresponding measures are taken according to different situations. The reason for the back-pulling is that the printed ink color is not dry, and the printed product should be placed in a ventilated and dry place to make the ink layer dry; second, the white ink is used excessively on the light-colored ink layer as a diluting agent. The white ink pigment is coarse, and the bonding force between the binders is poor, which causes the hot stamping surface to be powdered. The light dipping agent and the drying oil can be used to cover the ink first, then the hot stamping is performed, and the aluminum foil with low separation force can also be used. Hot stamping. Want to achieve a colorful, glossy, and moisture-resistant, wear-resistant hot stamping effect on gold paper, pay attention to the following issues: The best choice for synthetic paper ink, ink volume should be small, as thin as possible, can not spray Excessively, the prints are completely dry before they can be hot stamped. If hot stamping is not possible, a thin layer of background color may be printed on the hot stamping area before printing so that the hot stamping foil can be firmly adhered to the ink. When hot stamping, choose the right stamping temperature, pressure and speed, hot stamping version to use copper plate, because of its good heat transfer performance, pressure wear resistance, not easy to deformation, the height difference between graphic and blank parts should be as possible to pull Large, so that it does not contiguous or paste version.

Analysis of Graphical Quality Faults of Common Stamping Materials

First, hot stamping is not strong. There are many reasons why hot stamping is not strong, and there are differences in processing methods. To sum up, there are mainly the following three types: (1) When the hot stamping temperature is low or the pressure is light, the hot stamping temperature and pressure can be readjusted. (2) In the printing process, due to the excessive dry oil added in the ink, the surface of the ink layer is dried too quickly to cause crystallization, so that the hot stamping foil is not hot stamped. The solution is to prevent crystallization from occurring when printing first, and secondly, after the crystallization occurs, the stamping foil can be removed, and the printed product can be air-compressed under heating to destroy the crystallized layer first and then proceed. Hot stamping. (3) Adding an appropriate amount of a wax-containing lighter, anti-sticking agent, or non-drying oily substance to the ink may also result in poor hot stamping. The solution is: First, a layer of highly absorbent paper is pressed on the printing plate to press it again, and the wax and non-drying oil on the ink layer will be adsorbed, and the hot stamping operation will be performed.

Second, the hot stamping of the picture is fat, faint. This is due to the high stamping temperature and the coking aluminum foil. If the hot stamping temperature of the printing plate is too high and the galvanized aluminum foil exceeds the limit that can be tolerated, hot stamping will cause the galvanized aluminum foil to expand around and cause haziness and hair deficiency. At this time, according to the characteristics of the galvanized aluminum foil, The temperature is adjusted to the proper range. For galvanized aluminum foil coking, the main reason is that the shutdown during the hot stamping process is too long, so that a certain part of the galvanized aluminum foil comes into contact with the electrothermal high-temperature printing plate for a period of time and the phenomenon of heat coking occurs, and the graphic and text will become dizzy after hot stamping. Therefore, in case of shutdown in the production process, the temperature should be reduced or the electro-aluminum foil should be removed. Alternatively, a thick paper can be placed in front of the higher-temperature plate to isolate the electro-aluminum foil from the plate.

Third, the writing is vague and pastes. The main reasons for this failure are the high stamping temperature, the excessive thickness of the electro-aluminum aluminizing layer, the excessive embossing force, and the looseness of the electro-aluminum installation. According to the specific circumstances to take appropriate measures to resolve. Excessive hot stamping temperature is the main cause of illegible writing and stencil. During the hot stamping of galvanized aluminum, if the printing plate temperature is too high, the film base layer and other film layers will be transferred and sticked, resulting in illegible writing and stencil. Hot stamping should be based on the temperature of the application of aluminum foil, the appropriate reduction in the stamping temperature. In addition, we should choose a thin aluminum aluminized layer, adjust the appropriate pressure, and properly adjust the pressure of the pressure roller and the winding roller tension.

Fourth, the edges of the picture and text are not smooth and unclear. The main performance is that when the electro-aluminum hot stamping occurs, the edges and edges of the picture and text appear flashing, which affects the printing quality. The main reasons for this phenomenon are: uneven pressure in the printing plate, which is mainly due to uneven layout during plate loading, causing uneven pressure on various areas of the plate, some pressure is too large, and some are too small, thus making the graphic Uneven stress, the surface of the stamping foil is not clean, the adhesion of the various parts and the substrate is not the same, resulting in uneven printing. Therefore, the printing plate of the electro-foiled aluminum foil must be flat and solid to ensure that the stamping pressure is even and the graphic image can be avoided. In addition, if the pressure of the printing plate is too large during hot stamping, it may cause the image printing to be uneven. During the hot stamping process, the hot stamping pressure must be adjusted to a suitable level. Make sure that the pad of the embossing mechanism adheres exactly to the area of ​​the pattern without shifting or making a hole. In this way, it can be ensured that the graphic and pad overlays are matched during hot stamping and the hair around the graphic is avoided. Also, the pressure of the same plate after stamping is uneven. This is because the size of the graphic area is very different, and it is necessary to increase the pressure of the large-scale graphic text. The pressure of the size and area can be corrected and adjusted by the pad-sheet method to make it equal. Finally, if the temperature is too high during hot stamping, the image imprinting will be uneven. Therefore, according to the characteristics of the aluminum foil, reasonable control of the printing temperature of the printing plate, in order to ensure that the four sides of the picture is smooth, smooth, not hairy.

5. The imprints are incomplete and lack of strokes. This failure is mainly caused by the delivery of electro-aluminum foil, printing plates and other reasons. For example, the printing plate is damaged or deformed, which is one of the important reasons for the incompleteness of the graphic print. Therefore, if the plate is found to be damaged, the plate should be repaired or replaced immediately. The deformation of the printing plate does not allow the printing plate to withstand the applied stamping pressure, and the printing plate should be replaced and the pressure adjusted. If the electro-aluminum foil cutting and conveying deviation, when the electro-aluminum foil is cut horizontally when the margin is too small or when the skew occurs when the skew is unrolled and conveyed, the electro-aluminum foil will not coincide with the plate and the graphic and text will be partially exposed. incomplete. In order to prevent such problems, it should be neat and tidy when cutting electro-aluminum foil, and the margin size should be appropriately increased. Improper speed and tightness of the electro-aluminum foil can also cause such failure. The galvanized aluminum foil feeding and receiving device is loosely displaced, or the galvanized aluminum foil core is loosened from the winding shaft, the unwinding speed is changed, the degree of tightness of the electro-aluminum foil is changed, the position of the hot stamping position is deviated, and the image is incomplete. . At this time, the winding and unwinding devices should be adjusted. However, if the hot stamping foil is too tight, the pressure of the rewinding roller and the tension of the winding roller should be properly adjusted to ensure that the electrified aluminum foil has suitable speed and tightness. If hot stamping materials and hot stamping materials are not suitable or if excessive dusting during printing may cause such failures, adjustments should be made. In addition, when the printing plate part is moved or dropped at the position of the bottom plate, the pressure of the pad of the embossing mechanism or the normal hot stamping pressure is changed or uneven, the incompleteness of the graphic printing may be caused, for example, the pressure may be too light. Increase pressure. Found that the printing plate moves or the pad shifts, adjusts in time, puts the printing plate and the padding back in place to fix.

Six, hot stamping or text flowers. The main reasons are: (1) The hot stamping temperature is too low, and the hot stamping temperature of the printing plate is too low to reach the minimum temperature required for the electro-deposited aluminum foil to separate from the substrate and transfer to the substrate. When hot stamping, the electro-aluminum foil does not completely Transferred, resulting in text flowers, exposed or hot stamping. When this quality problem is discovered, the temperature of the hot plate must be adjusted properly in time until it is printed. (2) Small hot stamping pressure. During the hot stamping process, if the platen stamping pressure is too small, the pressure applied to the electrodeposited aluminum foil will be too light, and the galvanic aluminum foil will not be transferred smoothly, making the hot stamping artwork incomplete. Found that this situation should first analyze whether it belongs to the hot stamping pressure, and observe the severity of imprint marks, such as the hot stamping pressure is small, the stamping pressure should be increased.