Compared with traditional labels, self-adhesive labels do not need glue, no paste, no water, no pollution, save labeling time, and are convenient and quick to use in various situations. Different types of labels for different fabrics, adhesives, and backing papers can be applied to materials that are not suitable for general paper labels. It can be said that stickers are a universal label. The printing of self-adhesive labels is very different from traditional printing. Self-adhesive labels are usually printed on the label coupler and multi-processes are completed at one time, such as graphic printing, die-cutting, waste disposal, cutting, or reworking. Volume and so on. That is, one end of the raw material for the entire volume is input, and the other end is the finished product. Finished products are divided into single-sheet or roll labels, and finished labels can be directly applied to goods. Therefore, the label printing process is more complex and the requirements for equipment performance and printing staff quality are also higher.
Compared with ordinary paper, film material has many advantages. Film material printing is the direction of future adhesive printing. We briefly describe the structural characteristics of the film material, printability and post-printing process:
1, the film material printing process
The basic printing methods include gravure printing: gravure ink printing and gravure water ink printing; offset printing: UV offset ink printing; embossing: common resin ink printing and UV embossing ink printing; flexo printing: water-based printing Ink printing, solvent ink printing and UV ink printing; silk screen: divided into UV ink printing and solvent ink printing; combination printing: divided into embossing + screen printing, embossing + flexo, flexo + screen printing, offset + embossing four Printing method. Here are some more specific printing methods used:
A, ordinary resin ink printing
This is the most common method currently used. Due to the problem of drying, there are two kinds of drying methods: cutting leaflets and drying on shelves. This method has a long drying time, covers a large area and is easy to pick up. Laminated film. The undried ink is wrapped in the film, and care must be taken to avoid overlaminating the film and preventing film failure.
B, UV ink printing
This method has good printing quality and high efficiency. It is a printing process that has the most development in China and is most suitable for the country. Since the domestic embossing equipment generally does not have UV devices, the printing of the film is limited, so the equipment is renewed and transformed is a necessary condition for the printing film.
C. Solvent ink flexo printing
This is a traditional printing method with good quality. Due to the low surface tension of the solvent ink, the surface tension of the film is not as strict as that of other inks, so the ink layer is strong and the process is relatively simple. However, solvents affect environmental protection and are harmful to the human body. It is a printing method that is about to be eliminated.
D. Water-based ink flexo
This is the most advanced printing method in the world today, with low cost, good quality, and no pollution. However, the process requirements are strict, and the surface tension of the film must be above 40 dyne. There are strict requirements on the PH value and viscosity of the ink. This process is a process that has been vigorously developed in China, but it has been slow to develop due to equipment limitations.
E, UV ink flexo
Features with UV embossing, high cost, but the film surface tension requirements are relatively unrestricted. Most manufacturers use water-based ink printing. UV coating can reduce the cost and increase the printing effect.
F, UV ink screen printing
This new process can be single-sheet or reel-printed, with high cost and good quality. Single-page printing does not need to be racked and the reel printing can be performed at high speed.
G, solvent ink screen printing
This is a traditional process, in which sheets are printed by hand and reel materials are printed by a linkage engine. More than 95% are leaflets, with good results and low costs. However, solvent screen printing inks are harmful to the human body and pollute the environment. H, UV offset ink. Since the adhesive uses resin ink, ordinary offset printing cannot print films. Some manufacturers use a single sheet of overprinting when printing PVC, put it on a shelf to dry, and finally make a film. However, because the ink is not easy to dry, it is easy to pick up the dirt, resulting in waste and low productivity. The use of UV offset printing eliminates all of the above problems and allows printing of high-level, horizontal-format film products.
I, gravure printing
Gravure printing is rarely printed stickers, but printing quality is the best of all printing methods, is a potential printing method. In the country as long as the post-press processing, the existing equipment can fully print high-quality self-adhesive labels.
J, combination printing
Also called compound printing, it is the most advanced printing method in the packaging and printing industry in the world. According to different pattern designs, several methods are printed on the same pattern to achieve the best visual effect. Such equipment abroad is very common. There are two types in China: SR-520B of LINTEC in Japan and F-330 of SHIKY. The former is embossing and screen printing, and the latter is offset+embossing.
2, ink drying method
The ink on the film is classified according to drying characteristics: oxidative polymerization drying (tree ink), volatile conjunctiva drying (solvent ink), evaporation conjunctiva drying (water-based ink) and light curing drying (UV ink).
Drying methods are divided into: hot air drying, electric drying (far infrared), UV curing and drying.
Requirements for drying: The ink is fully dried; it does not affect the physical and chemical properties of the film; it does not affect the properties of the adhesive; it has no effect on the backing paper.
Ways to improve the effect of ink drying:
A, use additives to improve the ink drying speed. Such as resin ink plus dry oil; water-based ink plus special additives, solvent ink and low boiling point solvents. However, it should be noted that the additive will change the brightness and brightness of the ink and cannot affect the bond strength of the ink to the film due to the additives.
B. Change the running speed of the film material.
C. Change the temperature in the drying oven or change the intensity of the UV light source.
D, use a suitable film material.
3, post-press processing
The post-press processing of film materials is generally the same as the post-print processing of paper labels. Such as hot stamping, laminating, punching, folding, cutting, rewinding, discharging, and die-cutting are all used for the post-press processing of film adhesive labels.