Hot stamping is the use of heating method to melt the adhesive, the metal foil or color sheet stamping to the surface of paper or other materials, thereby forming a special decorative effect of the technical process, is one of the most commonly used post-printing process . Electro-chemical aluminum stamping is still the mainstream of hot stamping process because of its low price, rich color, stable nature and relatively simple process.
Electrochemical aluminum foil consists of five layers of different materials, namely polyester film film base layer, isolation layer, dyed layer, aluminized layer and adhesive layer. During the process of transfer of electro-aluminum foil to the substrate, the base layer of the film is peeled off, and the high temperature is finally obtained. The dyed layer, aluminized layer, and adhesive layer are transferred to the surface of the printing material so as to show a metallic luster image.
In the hot stamping process, due to different environments, processes, and materials, it will have a certain impact on the final product quality. In this regard, the common problems in the hot stamping process are analyzed and explained.
1, hot stamping is not strong
Insufficient hot stamping is one of the most common failures in electro-aluminum hot stamping. And stamping temperature, stamping pressure, ink formulations, printing surface properties, the choice of electrochemical aluminum and other factors have a certain relationship.
The main reasons and solutions: 1 low stamping temperature, light pressure or high lead speed lead to hot stamping is not strong, you can re-adjust the stamping temperature, pressure and speed. 2 Ink layer surface crystallization or excessive dusting. The solution is to prevent the crystallization of the ink as much as possible during the printing process. If the crystallization occurs once, the hot stamping foil can be removed, and the printed product can be air-pressed under heating to destroy the crystallization layer first, and the surface is cleaned before hot stamping. After removing dust, hot stamping is performed again. 3 The surface of printed matter contains waxes (such as releasant and bright paste additives), which hinders the adsorption of aluminum and paper, and must be solved in the printing process. 4 Prints The undercoat ink layer is too thick, which causes the undercoat ink layer to close the capillary pores of the paper fibers, hindering the adsorption of the electrochemical aluminum and the paper, and thus resulting in poor hot stamping. The solution is that the printed parts of the printed product must be printed with as little printing as possible, and the method of dark ink thin printing (that is, making the ink slightly darker than the standard proofs when the colors are matched and the ink layer being thin and even when printed) can be improved. 5 The improper use of anodized aluminum directly affects the fastness of hot stamping. Based on the size of the bronzing area and the characteristics of the hot stamped material, which type of galvanized aluminum is selected should be taken into consideration.
For the most commonly used hot stamping materials - the selection of the main aluminum can refer to the following categories: Hot stamping on ordinary products General Ink electro-aluminum type 88-l, KURZ PM type; cigarette packs, cosmetics and other ink-colored prints include There are 88-2 gold foil stamping and silver stamping foils for aluminum foil stamping, and 88-3, 88-4 and PM288 stamping stamping foils for fine pencils and cosmetics packaging; suitable for OPP or PET lamination. Paper and paperboards with UV inks, glazing papers and other products are stamped with electroformed aluminum 88-4 type, K series, LK series, and SP series.
2, pull back
In the overlapped hot stamping, the phenomenon of the sticking of the printing ink or the varnish on the printed matter by the hot stamping material is called reverse pulling. Reasons for causing such failures and solutions: (1) The ink layer on the surface of the printed product is not dry, resulting in the ink on the surface of the printed product not being firmly bonded to the surface of the paper. Should be dried after the print and then gold, can also use fast-drying ink or add the right amount of desiccant in the ink. In addition, electrified aluminum foil with low separation power and excellent heat transferability can be used. 2 Excessive use of white ink as diluting agent. The binding force between the ink and the linking material is poor. After the printing, the linking material in the ink is easily absorbed by the paper surface, so that the pigment is suspended on the paper surface to cause powdering phenomenon. In this way, the galvanized aluminum foil layer cannot be peeled off smoothly at the time of hot stamping, but instead it will pull back the ink layer on the printed product. Therefore, it is necessary to dilute the use of titanium white ink as little as possible or use a mixture of a light diffusing agent and white ink. In addition, when designing, full consideration should be given to avoid large-area hot stamping on a light-colored ink plate surface. 3 The viscosity of the ink itself is too low and less than that of the electro-aluminum foil layer.
Pay attention to the use of fast-fixing inks that meet the requirements for viscosity printing. Pay attention to controlling the amount of anti-sticking agent added in the ink and ensuring that the viscosity of the ink meets the requirements.
3, hot stamping hair
If the result of the roughing of the hot stamping substrate is eliminated, the temperature of the hot stamping is mainly due to the low temperature, and the hot plate temperature should be raised before hot stamping. If the hairiness is still adjusted, the pressure may be insufficient, and the pressure of the platen or the pad may be increased. It is also possible that the surface of the hot stamping plate is uneven, and the hot stamping plate area should be reduced (single-spindle machining) or the local gasket thickness of the printing plate should be increased.
4, exposed
When hot stamping, the graphic or the hot stamp is not displayed.
The main reasons and solutions: 1 hot stamping temperature is too low or hot stamping pressure is small, resulting in hot stamping, anodized aluminum stamping transfer layer is not completely transferred, resulting in the text flowers, bare bottom or hot stamping is not on. When this quality problem is discovered, the temperature of the hot plate must be adjusted in a timely and appropriate manner or by observing the severity of the embossed marks to appropriately increase the hot stamping pressure. 2 The background is too dry and the surface is crystallized. The underlying ink layer on the surface of the substrate is too thick and excessively dry, and crystallization will occur, so that the galvanized aluminum foil will not be hot stamped. When hot stamping, the dryness of the background color is printed immediately within the printable range. When the background color is printed, the ink layer should not be too thick. When the printing volume is large, it is necessary to print in batches, and the production cycle is appropriately shortened. Once the crystallization phenomenon is found, the printing should be stopped immediately, and the printing should be continued after searching for defects. 4 The type of galvanized aluminum foil is incorrect or of poor quality. At this time, it should replace the type of aluminum foil with good quality, good adhesion and strong adhesion. Stamping larger area of ​​the substrate, can be hot stamping twice, you can avoid hair, exposed bottom and hot stamping is not on.
5, luster or hot stamping discoloration
Main reasons and solutions: This is mostly because the hot stamping temperature is too high. The temperature of the hot plate should be properly reduced. Empty cars should be used as little as possible to reduce unnecessary parking. Because the empty car and parking will increase the temperature of the hot plate. , to proofread the actual operating temperature and instrument display error. In addition, it is also possible that the ink is not dry and the influence of the volatilization of the binder. In addition, due to the improper arrangement of the process, the surface luster of the aluminum can be destroyed. For example, when a printed product requires lamination and bronzing, people often worry that the gold foil will be easily wiped off and then hot stamped and then laminated, which will cause the film, especially the matte film, to destroy the surface luster of the anodized aluminum. Therefore, it is not appropriate to use water-soluble glue coating, otherwise it will cause blackening of the surface of the electrodeposited aluminum, and at the same time, it may easily cause the adhesion of gold powder to the edge of the picture and cause hair-dappling. The correct process is to apply the film first and then apply gold.
6, the picture issued by virtual, faint
The main reasons and solutions: 1 stamping temperature is too high, so that more than the limit can withstand the electrochemical foil, hot stamping, the expansion of the aluminum foil around, resulting in dizziness, hair false phenomenon. To find this fault, the temperature must be adjusted to the proper range based on the characteristics of the electrochemical foil. 2 Electrochemical aluminum foil coking. If the machine is shut down too long during the hot stamping process, a certain part of the electro-aluminum foil will come into contact with the electrothermal high-temperature printing plate and the phenomenon of heat coking will occur, and the graphic will be dizzy after hot stamping. During the production process, in case of shutdown, the temperature should be lowered, or the electro-aluminum foil should be removed. A thick paper can also be placed in front of the higher-temperature plate to isolate the electro-aluminum foil from the plate.
7, text flowers
Main reasons and solutions: There are many reasons for this failure. For example, the pressure of stamping is not enough and the force is uneven. It is not enough to completely peel off and attach the printed aluminum foil to the printed product. Pay attention to controlling the pressure and ensure the leveling of the printing plate. The temperature is too low, so that the adhesive layer of the aluminum is not fully or unevenly melted, and a suitable stamping temperature is to be pre-tested; the hot stamping speed is too fast, so that the foil separation force and the peeling force of the aluminum foil do not match. Adjust the hot stamping speed; the lining is uneven or too soft, so that the pressure foil is not completely separated in the area where the stamping pressure is insufficient. Pay attention to check the quality of the lining, replace the lining and its cushioning material, and make the lining have a good leveling. Degree; the use of the aluminum foil model is not consistent or poor quality, so that the foil layer is difficult to completely peel and transfer, should replace the appropriate quality of the good quality of aluminum.
8, paste version
This is one of the more prominent issues in hot stamping. The main reasons for this failure are the high stamping temperature, the excessive thickness of the electro-aluminum aluminizing layer, the excessive hot stamping pressure, the looseness of the electro-aluminum installation, the inaccuracy of the electro-aluminum foil, and the poor production of hot stamping. Excessive hot stamping temperature is the main cause of unclear writing and stencil. During the hot stamping of galvanized aluminum, if the printing plate temperature is too high, melting occurs when the galvanized aluminum foil layer is separated, resulting in transfer and stickiness of the film base layer and other film layers. As a result, the writing is unclear and the stencils are blurred. At this time, the stamping temperature should be appropriately lowered. In addition, there are obvious slopes on the edge of the printing plate or the plate is too thin, or the over-hot stamping of the printing plate wears down, so that the difference between the hot printing plate surface and the blank space is too small, the cushion material is too soft, and blank areas and electroplating of the plate are caused. For aluminum foil contact, etc., the edge of the plate should be made to a right angle of approximately 90°. If engraving is used for plate making, the edge of the plate will have almost no slope. According to the features of the hot plate, a plate with a larger thickness will be used. Corrosion of the blank part is deeper, and a hard lining is used for hot stamping; in addition, a thin aluminum aluminized layer should be selected to adjust the appropriate printing pressure, and the pressure of the pressure roller and the tension of the winder roller should be properly adjusted.
9, hot stamping picture is not complete
The main reason and solution: (1) The tension of the galvanized aluminum foil is too tight. At this time, the tension of the galvanized aluminum foil should be adjusted so that the feeding rolling tension is moderate. 2 The hot stamping production is not fine enough, and the hot stamping version should be trimmed. 3 The surface of the substrate is rough and uneven, and the surface can be purified, or the stamping pressure and temperature can be appropriately increased. 4 The hot stamping pressure is too light or the pressure of the printing plate is not equal. The stamping pressure should be appropriately increased, or the printing plate gasket should be adjusted to keep the pressure of the plate balanced.
10, the same version of the hot stamping effect is different
The main reason for this phenomenon is that the area of ​​the hot stamping graphic is too large, and the uneven heat or pressure of the printing plate is generated. Try to mark or adjust the thickness of the printing plate in batches so that the heat and pressure are uniform in all parts.
11, the same material hot stamping, good and bad
Main reasons and solutions: 1 If the quality of materials is not stable, use stable quality materials. 2 The control of the feeding speed of the stamping machine is unstable, so that when the aluminum foil is loosened tightly, the discharge roll of the aluminum foil should be inspected, and the roller is pressed to make the operation smooth and the pressure is balanced. 3 If the pressure adjustment nut of the stamping machine is loose and the pressure is unstable, the pressure fixing device should be overhauled and adjusted. 4 electric heating plate control failure, must be troubleshooting to eliminate the hot plate failure.
12, flying gold
The main reason is that the adhesion of the anodized aluminum is poor, and the electrified aluminum foil with strong adhesion can be replaced.
13. Slippage when printing velvet materials
Mainly due to hairiness, it can be solved by the second hot stamping method. For the first time, the viscous material will be pressed down to stick with the help of the adhesive material, and the second time the stamping will use the electrochemical foil.
Electrochemical aluminum foil consists of five layers of different materials, namely polyester film film base layer, isolation layer, dyed layer, aluminized layer and adhesive layer. During the process of transfer of electro-aluminum foil to the substrate, the base layer of the film is peeled off, and the high temperature is finally obtained. The dyed layer, aluminized layer, and adhesive layer are transferred to the surface of the printing material so as to show a metallic luster image.
In the hot stamping process, due to different environments, processes, and materials, it will have a certain impact on the final product quality. In this regard, the common problems in the hot stamping process are analyzed and explained.
1, hot stamping is not strong
Insufficient hot stamping is one of the most common failures in electro-aluminum hot stamping. And stamping temperature, stamping pressure, ink formulations, printing surface properties, the choice of electrochemical aluminum and other factors have a certain relationship.
The main reasons and solutions: 1 low stamping temperature, light pressure or high lead speed lead to hot stamping is not strong, you can re-adjust the stamping temperature, pressure and speed. 2 Ink layer surface crystallization or excessive dusting. The solution is to prevent the crystallization of the ink as much as possible during the printing process. If the crystallization occurs once, the hot stamping foil can be removed, and the printed product can be air-pressed under heating to destroy the crystallization layer first, and the surface is cleaned before hot stamping. After removing dust, hot stamping is performed again. 3 The surface of printed matter contains waxes (such as releasant and bright paste additives), which hinders the adsorption of aluminum and paper, and must be solved in the printing process. 4 Prints The undercoat ink layer is too thick, which causes the undercoat ink layer to close the capillary pores of the paper fibers, hindering the adsorption of the electrochemical aluminum and the paper, and thus resulting in poor hot stamping. The solution is that the printed parts of the printed product must be printed with as little printing as possible, and the method of dark ink thin printing (that is, making the ink slightly darker than the standard proofs when the colors are matched and the ink layer being thin and even when printed) can be improved. 5 The improper use of anodized aluminum directly affects the fastness of hot stamping. Based on the size of the bronzing area and the characteristics of the hot stamped material, which type of galvanized aluminum is selected should be taken into consideration.
For the most commonly used hot stamping materials - the selection of the main aluminum can refer to the following categories: Hot stamping on ordinary products General Ink electro-aluminum type 88-l, KURZ PM type; cigarette packs, cosmetics and other ink-colored prints include There are 88-2 gold foil stamping and silver stamping foils for aluminum foil stamping, and 88-3, 88-4 and PM288 stamping stamping foils for fine pencils and cosmetics packaging; suitable for OPP or PET lamination. Paper and paperboards with UV inks, glazing papers and other products are stamped with electroformed aluminum 88-4 type, K series, LK series, and SP series.
2, pull back
In the overlapped hot stamping, the phenomenon of the sticking of the printing ink or the varnish on the printed matter by the hot stamping material is called reverse pulling. Reasons for causing such failures and solutions: (1) The ink layer on the surface of the printed product is not dry, resulting in the ink on the surface of the printed product not being firmly bonded to the surface of the paper. Should be dried after the print and then gold, can also use fast-drying ink or add the right amount of desiccant in the ink. In addition, electrified aluminum foil with low separation power and excellent heat transferability can be used. 2 Excessive use of white ink as diluting agent. The binding force between the ink and the linking material is poor. After the printing, the linking material in the ink is easily absorbed by the paper surface, so that the pigment is suspended on the paper surface to cause powdering phenomenon. In this way, the galvanized aluminum foil layer cannot be peeled off smoothly at the time of hot stamping, but instead it will pull back the ink layer on the printed product. Therefore, it is necessary to dilute the use of titanium white ink as little as possible or use a mixture of a light diffusing agent and white ink. In addition, when designing, full consideration should be given to avoid large-area hot stamping on a light-colored ink plate surface. 3 The viscosity of the ink itself is too low and less than that of the electro-aluminum foil layer.
Pay attention to the use of fast-fixing inks that meet the requirements for viscosity printing. Pay attention to controlling the amount of anti-sticking agent added in the ink and ensuring that the viscosity of the ink meets the requirements.
3, hot stamping hair
If the result of the roughing of the hot stamping substrate is eliminated, the temperature of the hot stamping is mainly due to the low temperature, and the hot plate temperature should be raised before hot stamping. If the hairiness is still adjusted, the pressure may be insufficient, and the pressure of the platen or the pad may be increased. It is also possible that the surface of the hot stamping plate is uneven, and the hot stamping plate area should be reduced (single-spindle machining) or the local gasket thickness of the printing plate should be increased.
4, exposed
When hot stamping, the graphic or the hot stamp is not displayed.
The main reasons and solutions: 1 hot stamping temperature is too low or hot stamping pressure is small, resulting in hot stamping, anodized aluminum stamping transfer layer is not completely transferred, resulting in the text flowers, bare bottom or hot stamping is not on. When this quality problem is discovered, the temperature of the hot plate must be adjusted in a timely and appropriate manner or by observing the severity of the embossed marks to appropriately increase the hot stamping pressure. 2 The background is too dry and the surface is crystallized. The underlying ink layer on the surface of the substrate is too thick and excessively dry, and crystallization will occur, so that the galvanized aluminum foil will not be hot stamped. When hot stamping, the dryness of the background color is printed immediately within the printable range. When the background color is printed, the ink layer should not be too thick. When the printing volume is large, it is necessary to print in batches, and the production cycle is appropriately shortened. Once the crystallization phenomenon is found, the printing should be stopped immediately, and the printing should be continued after searching for defects. 4 The type of galvanized aluminum foil is incorrect or of poor quality. At this time, it should replace the type of aluminum foil with good quality, good adhesion and strong adhesion. Stamping larger area of ​​the substrate, can be hot stamping twice, you can avoid hair, exposed bottom and hot stamping is not on.
5, luster or hot stamping discoloration
Main reasons and solutions: This is mostly because the hot stamping temperature is too high. The temperature of the hot plate should be properly reduced. Empty cars should be used as little as possible to reduce unnecessary parking. Because the empty car and parking will increase the temperature of the hot plate. , to proofread the actual operating temperature and instrument display error. In addition, it is also possible that the ink is not dry and the influence of the volatilization of the binder. In addition, due to the improper arrangement of the process, the surface luster of the aluminum can be destroyed. For example, when a printed product requires lamination and bronzing, people often worry that the gold foil will be easily wiped off and then hot stamped and then laminated, which will cause the film, especially the matte film, to destroy the surface luster of the anodized aluminum. Therefore, it is not appropriate to use water-soluble glue coating, otherwise it will cause blackening of the surface of the electrodeposited aluminum, and at the same time, it may easily cause the adhesion of gold powder to the edge of the picture and cause hair-dappling. The correct process is to apply the film first and then apply gold.
6, the picture issued by virtual, faint
The main reasons and solutions: 1 stamping temperature is too high, so that more than the limit can withstand the electrochemical foil, hot stamping, the expansion of the aluminum foil around, resulting in dizziness, hair false phenomenon. To find this fault, the temperature must be adjusted to the proper range based on the characteristics of the electrochemical foil. 2 Electrochemical aluminum foil coking. If the machine is shut down too long during the hot stamping process, a certain part of the electro-aluminum foil will come into contact with the electrothermal high-temperature printing plate and the phenomenon of heat coking will occur, and the graphic will be dizzy after hot stamping. During the production process, in case of shutdown, the temperature should be lowered, or the electro-aluminum foil should be removed. A thick paper can also be placed in front of the higher-temperature plate to isolate the electro-aluminum foil from the plate.
7, text flowers
Main reasons and solutions: There are many reasons for this failure. For example, the pressure of stamping is not enough and the force is uneven. It is not enough to completely peel off and attach the printed aluminum foil to the printed product. Pay attention to controlling the pressure and ensure the leveling of the printing plate. The temperature is too low, so that the adhesive layer of the aluminum is not fully or unevenly melted, and a suitable stamping temperature is to be pre-tested; the hot stamping speed is too fast, so that the foil separation force and the peeling force of the aluminum foil do not match. Adjust the hot stamping speed; the lining is uneven or too soft, so that the pressure foil is not completely separated in the area where the stamping pressure is insufficient. Pay attention to check the quality of the lining, replace the lining and its cushioning material, and make the lining have a good leveling. Degree; the use of the aluminum foil model is not consistent or poor quality, so that the foil layer is difficult to completely peel and transfer, should replace the appropriate quality of the good quality of aluminum.
8, paste version
This is one of the more prominent issues in hot stamping. The main reasons for this failure are the high stamping temperature, the excessive thickness of the electro-aluminum aluminizing layer, the excessive hot stamping pressure, the looseness of the electro-aluminum installation, the inaccuracy of the electro-aluminum foil, and the poor production of hot stamping. Excessive hot stamping temperature is the main cause of unclear writing and stencil. During the hot stamping of galvanized aluminum, if the printing plate temperature is too high, melting occurs when the galvanized aluminum foil layer is separated, resulting in transfer and stickiness of the film base layer and other film layers. As a result, the writing is unclear and the stencils are blurred. At this time, the stamping temperature should be appropriately lowered. In addition, there are obvious slopes on the edge of the printing plate or the plate is too thin, or the over-hot stamping of the printing plate wears down, so that the difference between the hot printing plate surface and the blank space is too small, the cushion material is too soft, and blank areas and electroplating of the plate are caused. For aluminum foil contact, etc., the edge of the plate should be made to a right angle of approximately 90°. If engraving is used for plate making, the edge of the plate will have almost no slope. According to the features of the hot plate, a plate with a larger thickness will be used. Corrosion of the blank part is deeper, and a hard lining is used for hot stamping; in addition, a thin aluminum aluminized layer should be selected to adjust the appropriate printing pressure, and the pressure of the pressure roller and the tension of the winder roller should be properly adjusted.
9, hot stamping picture is not complete
The main reason and solution: (1) The tension of the galvanized aluminum foil is too tight. At this time, the tension of the galvanized aluminum foil should be adjusted so that the feeding rolling tension is moderate. 2 The hot stamping production is not fine enough, and the hot stamping version should be trimmed. 3 The surface of the substrate is rough and uneven, and the surface can be purified, or the stamping pressure and temperature can be appropriately increased. 4 The hot stamping pressure is too light or the pressure of the printing plate is not equal. The stamping pressure should be appropriately increased, or the printing plate gasket should be adjusted to keep the pressure of the plate balanced.
10, the same version of the hot stamping effect is different
The main reason for this phenomenon is that the area of ​​the hot stamping graphic is too large, and the uneven heat or pressure of the printing plate is generated. Try to mark or adjust the thickness of the printing plate in batches so that the heat and pressure are uniform in all parts.
11, the same material hot stamping, good and bad
Main reasons and solutions: 1 If the quality of materials is not stable, use stable quality materials. 2 The control of the feeding speed of the stamping machine is unstable, so that when the aluminum foil is loosened tightly, the discharge roll of the aluminum foil should be inspected, and the roller is pressed to make the operation smooth and the pressure is balanced. 3 If the pressure adjustment nut of the stamping machine is loose and the pressure is unstable, the pressure fixing device should be overhauled and adjusted. 4 electric heating plate control failure, must be troubleshooting to eliminate the hot plate failure.
12, flying gold
The main reason is that the adhesion of the anodized aluminum is poor, and the electrified aluminum foil with strong adhesion can be replaced.
13. Slippage when printing velvet materials
Mainly due to hairiness, it can be solved by the second hot stamping method. For the first time, the viscous material will be pressed down to stick with the help of the adhesive material, and the second time the stamping will use the electrochemical foil.
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