Guide: self-adhesive labels can be seen everywhere in our lives. With the change of packaging concept and technological innovation, labels have become an important part of commodity packaging. Label is an important embodiment of company image and brand, which plays an important role in reflecting product quality and arousing consumers' desire to buy. As a kind of label, the printing method of adhesive label needs to be understood. This article shares the printing method of adhesive label for reference by friends in the industry:

Self adhesive printing method

Self adhesive refers to a kind of composite material printed with paper, film or other special materials as the fabric, adhesive coated on the back, and silicon coated protective paper as the backing paper. In terms of product form, it is composite material single page printed with adhesive coated on the back, which can be bonded to the place where customers need to bond. The so-called self-adhesive printing is the process of transferring ink and other substances through the printing plate to the surface of the printing material with a pre coated adhesive layer on the back under a certain pressure.

01 Embossing

Embossed printing is used to print self-adhesive labels. The printing plate is a light-sensitive resin relief plate. The printing label has the advantage of full ink color. However, the level of relief printing equipment now varies greatly. Some still use a round flat embossing machine, some use an ordinary rotary embossing machine, and some have used a professional slant back, satellite or unit type self-adhesive label printing machine, so it cannot be generalized in the transformation.

02 Offset printing

Offset printing is the main way for label printing plants to print paper stickers. Offset printing is characterized by fine graphics and text, rich levels, suitable for mass printing, and the printing equipment can be used for multiple purposes, which is suitable for the characteristics of the Chinese label market. However, sheet fed offset printing is not suitable for printing without absorbent film on the surface, because film labels are mostly roll to roll printing, requiring volatile dry ink

03 Flexographic printing

At present, the quality of flexographic printing is not inferior to offset printing, and even has its unique features. This printing process has the advantages of simple machine structure, low cost, printing quality comparable to offset printing and gravure printing, and has the advantage of thicker ink layer than offset printing products. Flexographic printing uses water-based ink and UV ink, which does not pollute the environment.

However, due to the flexibility of flexography, the gradient reproducibility is different from that of intaglio and ordinary relief. The dot from highlight to middle tone of flexography printing increases greatly, the printing contrast is small, and the highlight layer is prone to be broken. When printing fine graphic labels, in order to make up for the layer defects, FM dot can be used for highlight part, and AM screening can be used for darkening or middle call to improve the quality. Label printing plants without flexographic printing machines can introduce a laminated narrow width flexographic printing machine dedicated to the printing of self-adhesive labels, which is suitable for film label printing. Since flexographic printing presses all use circular die cutting, the die cutting roller is expensive and has a long production cycle, which is only suitable for long version, but not suitable for domestic adhesive labels with large demand for short version. However, it is a label printing equipment that is easy to transform and can work online with film cutting, sewing and sealing processes.

04 Gravure printing

The intaglio printing adopts the short ink path ink conveying system for ink supply, and the roll printing has a high degree of automation. With solvent based ink, the ink layer dries rapidly, and is the first choice for film printing. Generally, the speed of intaglio printing machines is high. Many intaglio printing machines are also equipped with cylinder die cutting devices at the rear end, which can perform die cutting and indentation, and are suitable for printing various labels. However, because of the long cycle and high cost of gravure plate making, it is only suitable for label production in large quantities.

05 Gluing

The glue of self-adhesive labels is divided into water glue and hot melt adhesive. Because the hot melt adhesive equipment has the advantages of small size and low price, and the hot melt adhesive has the advantages of environmental protection, intensive, repeated bonding, recyclability and easy operation in the process of operation, it is more and more widely used in the field of labels. The process of hot melt adhesive equipment is composed of several parts, such as unwinding, coating, cooling, laminating and winding.

06 Hot stamping

As an important metal effect surface finishing method, hot stamping is an effective way to enhance the visual effects of trademarks, cartons, labels and other products, and is widely used. The two main hot stamping methods, hot stamping and cold stamping, have their own advantages and disadvantages. In practical application, appropriate hot stamping methods should be selected according to the specific situation, mainly based on cost and quality. Hot stamping technology refers to the transfer of hot stamping foil to the substrate surface by heating and pressurizing the special metal hot stamping plate

The advantages of hot stamping technology mainly include the following: good quality, high precision, clear and sharp edges of hot stamping images. High surface gloss, bright and smooth hot stamping pattern. A wide selection of hot stamping foils, such as hot stamping foils with different colors, different gloss effects, and hot stamping foils suitable for different substrates. The three-dimensional hot stamping method is used to make the three-dimensional hot stamping plate, so that the images and texts processed by hot stamping have obvious three-dimensional layers, form relief effect on the surface of the printed matter, and produce a strong visual impact effect. Stereoscopic hot stamping can make the package have a unique touch. It is precisely because the hot stamping process has many of the advantages mentioned above that it has been favored by the majority of users and consumers, and has been widely used. However, the hot stamping process requires special equipment, heating devices and hot stamping plates. Therefore, obtaining high-quality hot stamping results also means paying higher costs.

07 Post process editor

In order to protect the printing pattern of adhesive labels and improve the quality of labels, many adhesive labels have chosen surface finishing treatment such as film covering, glazing and gilding after printing. The stamping method is divided into sheet fed stamping and web paper stamping according to the processing method of adhesive labels. The sheet fed gilding process is the same as the traditional gilding process, which is processed on a special gilding machine. Web bronzing is completed on the label linkage machine, which is the most widely used processing method.

There are several ways to gild drum materials:

① Scaling on label machine

② Multi station flat stamping

③ Flattening and stamping on the processing machine

④ Rotary stamping on rotary machine

⑤ Cold stamping on rotary machine

This is a new gilding process. Instead of using the heated metal printing plate, the method of printing adhesive is used to transfer the metal foil to achieve gilding.

The process flow is: UV pressure-sensitive adhesive is printed at the place where the printed matter needs to be gilded, the adhesive is dried by the UV drying device, then special metal foil is used to compound with the pressure-sensitive adhesive, and then the metal foil is stripped, so the part of the metal foil that needs to be transferred is transferred to the surface of the printed matter to achieve cold gilding. Cold stamping process has low cost, energy saving and high production efficiency. It can use existing equipment components without adding additional devices. It is a new process with great development prospects.

The glazing process is mainly applied to the surface coating of mirror coated paper and coated paper labels, in order to increase the surface glossiness, and achieve the functions of antifouling, moisture prevention and pattern protection. According to the processing method, the glazing of self-adhesive label materials can be divided into sheet paper glazing and web paper glazing, of which web paper glazing is the most commonly used method in the self-adhesive label printing process. The glazing of web paper self-adhesive labels is carried out on the wheel transformation label machine, and the UV glazing process is generally adopted, that is, a layer of UV glazing oil is evenly coated on the printed image surface. For water-based ink flexographic labels, glazing is an essential process.

Film covering: laminating with backing paper composite film - it is carried out on the label machine, using the special composite film with backing paper, and laminating under the action of the composite device. This is a traditional film covering method, which has been replaced by the process of using a bottomless paper composite film. Lamination of paperless composite film -- It is carried out on the label machine, and the film covering principle is basically similar to that of paper-based composite film. The backing paper free film replaces the backing paper after rewinding based on the surface smoothness (surface tension) of its own material. After the adhesive is bonded with its surface, it can be peeled off without leaving adhesive traces. The material used for the bottomless film is BOPP film with low surface tension. Backless paper film is the most widely used film covering material due to its low cost.