The cold gilding printed anodized aluminum foil, working principle and process flow are different from the traditional hot gilding. The back of the galvanized aluminum foil used in the traditional gilding process is pre-coated with hot-melt adhesive. Aluminum foil transfer.
The cold bronzing is made of special anodized aluminum, the back of which is not coated with glue, and the adhesive is directly applied to the location where decoration is needed during printing. Adopt cold-pressing new technology to transfer anodized aluminum foil.
The cold bronzing technology solves the process problems that are difficult to solve in hot bronzing printing, and avoids the pollution caused to the environment during the production of metal printing plates, and can also save a lot of energy.
When printing anodized aluminum, the anodized aluminum is in contact with the adhesive, and under the effect of the adhesive, the anodized aluminum foil is attached to the surface of the printed matter. Its technological process is:
First print the UV ink, after drying, print a special adhesive-UV curing adhesive on the area where the ink surface needs to be gilded. The printed adhesive is dried in the additional UV device, and the moisture in the adhesive is dried by the UV drying device To a certain extent, a very thin high-viscosity pressure-sensitive adhesive layer is formed, so that the surface of the printed matter that needs to be gilded forms a high-viscosity area.
Next, start cold bronzing. Under the action of a pair of metal rollers, the anodized aluminum foil is in contact with the adhesive. By applying pressure, the anodized aluminum foil is firmly bonded to the surface of the printed pattern, and then the anodized aluminum foil is peeled off. Part of it was transferred to the surface of the printed matter to realize cold bronzing printing. Due to the large adhesive force between the adhesive and the aluminum foil, when waste is discharged, the part where the electrochemical aluminum foil contacts the adhesive remains on the surface of the printed product and becomes integrated with the printed product, and the other parts of the electrochemical aluminum foil are discharged like the traditional bronzing. Complete the front part of the bronzing technique.
Since the pattern of anodized aluminum foil transferred on the printed matter floats on the surface of the printed matter, the firmness is very poor, so it must be protected. Polishing or coating on the surface of printed matter can protect the pattern of anodized aluminum foil. Finally, other processes for post-press processing, such as die-cutting, waste discharge, cutting or rewinding, etc., complete the entire printing process.
Cold stamping is a method that uses glue to transfer foil to the substrate. Compared with the traditional hot stamping process, cold stamping technology has the following characteristics:
Fast printing speed
The cold bronzing speed can reach 50 ～ 60m / min, while the general traditional round pressing round bronzing speed is only 20 ～ 30m / min.
Short production cycle
It takes about two weeks to make a metal plate cylinder using the traditional hot bronzing process, and the time required for cold bronzing plate making is very short, which greatly shortens the production cycle.
Wide range of materials
Cold bronzing can be operated on a variety of materials, such as cold bronzing printing on heat-sensitive paper and some film materials.
High printing accuracy and good anti-counterfeiting effect
Compared with the traditional hot stamping, because the cold stamping technology uses printing registration, its registration accuracy is high. In printing anti-counterfeiting, holographic image bronzing has very good counterfeiting and decorative effects, so it can be combined with holographic image technology, laser transparent material technology, or combined with other anti-counterfeiting technologies to highlight changes in printing design and produce metallic inks The effect of anti-counterfeiting is achieved in printing of securities and packaging and decoration.
Because cold stamping uses general flexographic printing plates instead of expensive metal plate cylinders, the production cost of hot stamping plates is greatly reduced. The cost of cold stamping is only about one tenth of the cost of traditional hot stamping and can be suitable for small batch production. In addition, since the heating roller is not used, energy consumption is reduced.
Can make full use of the original equipment to improve production efficiency
The cold stamping technology can make full use of the original printing machinery when it is applied. For example, when the cold stamping technology is used to print the self-adhesive materials on a narrow-web rotary printing machine, only some devices need to be added to the original equipment. In addition, cold bronzing can also be combined with front-end printing, completed in one machine, the operation speed is fast, which can greatly improve production efficiency.
Meet the requirements of environmental protection printing
Because cold bronzing does not require the production of metal plate rollers, it eliminates the chemical corrosion process, so it reduces pollution and is beneficial to environmental protection.
Cold bronzing technology can be widely used in a variety of printing industries and is suitable for proofing. At present, cold bronzing printing is mainly used in narrow-width flexographic printing machines, narrow-width relief printing machines, label linkage machines, rotary printing machines and waterless offset printing machines. In the printing method, the current cold bronzing printing is mainly done by two methods of wet lamination and dry lamination.
The printing process is as follows: print the image on the substrate → use the pressing wheel to attach the cold foiled aluminum foil to the substrate → use a UV lamp to dry the UV glue on the substrate to make the image sticky → remove the excess aluminum foil .
Pay attention to the following issues when printing in wet lamination:
①Glue can be printed on the surface of water-based ink and UV ink;
②Restriction of printing speed;
③ Tension control of electrochemical aluminum foil and substrate;
④A hard roller must be installed before and behind the UV lamp;
⑤It can print thin lines, cutouts and thin dots.
Wet lamination printing is mainly suitable for printing large area images. It can be used for cold bronzing printing on the surface of water-based inks and UV inks. The more suitable substrates are films. Post-drying procedures are not required after printing. Control the speed.
The printing process is as follows: print the image on the substrate → dry the UV glue on the substrate with a UV lamp to make the image sticky → immediately turn the anodized aluminum foil onto the adhered image with a pressing wheel and remove the excess anodized aluminum foil .
Pay attention to the following issues when printing in dry lamination:
①Glue should not be printed on the surface of water-based or solvent-based inks that have not been dried;
② The glue should not be too dry or insufficiently dry;
③ It should be attached within 12cm behind the UV lamp;
④ High-pressure roller and high pressure must be used for the bonding of foil and substrate;
⑤ The treatment and storage of glue is the same as that of general UV ink.
Dry lamination printing is suitable for printing dots, thin lines, etc., and can be used for cold bronzing printing on the UV surface. The suitable substrate is the substrate of the paper. After printing, post drying treatment is required. During printing, it is necessary to control the appropriate printing speed. .
The cold bronzing process is limited by the conditions of adhesives, anodized aluminum foil, etc. There are still some shortcomings, so pay attention to when applying cold bronzing printing.
1. Because the pattern of anodized aluminum foil printed by cold bronzing is embossed on the surface of the printed matter, its firmness is very poor and must be covered with protection. Therefore, after the cold stamping of the printed matter, the surface of the printed matter must be polished or waxed to protect the pattern of the electrochemical aluminum foil, which increases the cost of cold stamping and the complexity of the process.
Second, due to the poor leveling of the UV adhesive used in cold bronzing printing, some of the dried surface is not an absolute plane, resulting in poor brightness of the surface of the anodized aluminum foil transferred on it, and even diffuse reflection phenomenon. In addition, cold bronzing printing is currently not suitable for film materials with shrinkage characteristics (such as PVC, PE, etc.). In these two points, the effect of cold bronzing is not as good as traditional hot bronzing.
Third, since the quality of cold bronzing printing depends on the quality of the glue being printed, it is necessary to pay attention to the quality of the glue and the suitability of printing, and pay special attention to observe and summarize the printing experience in order to better operation in the future.
Fourth, the requirements of the cold bronzing printing on the substrate can only be printed on the substrate with a smooth surface, and the glue on the rough substrate will be absorbed, resulting in insufficient glue on the substrate surface for cold bronzing printing. Therefore, the cold bronzing technology needs to be improved for printing on substrates with rough surfaces (such as leather, etc.). Therefore, pay attention to the smoothness of the surface when selecting the substrate.
5. Cold bronzing technology is currently mainly used for printing on roll substrates.