Self-adhesive labels and traditional labels have the advantages of no need to brush glue, no paste, no dipping water, no pollution, save labeling time, etc., a wide range of applications, convenient and fast. Self-adhesive is a kind of material, also called self-adhesive label material. It is a composite material with paper, film or other special materials as the fabric, the back side is coated with adhesive, and the silicon coated protective paper is used as the bottom paper. And after printing, die cutting and other processing, it becomes a finished label.
Selection of raw materials
When selecting raw materials, be sure to use high-quality self-adhesive materials that meet all physical and chemical indicators, rather than products that have expired or have unstable physical and chemical indicators. Although the latter is low in price, due to the unstable quality of such materials, it consumes a large number of processes and even causes the equipment to be unable to be processed normally. While wasting raw materials, it also wastes a lot of manpower and material resources. It is not necessarily low, and more seriously, it may be returned by customers, or even lose customers.
Printing and processing characteristics of stickers
① Consistency of surface gloss and color of surface material, uniformity of density
These indicators determine the uniformity of the ink absorption of the self-adhesive materials, and also determine the color difference of the same batch of label prints. The coating strength of the face material determines whether a large amount of paper dust will be generated during printing, and it is also an important indicator to determine the printing quality.
②The uniformity and strength indication of the thickness of the backing paper and face material
These indexes are not only related to printing performance, but also important indexes that determine the uniformity of die cutting and the speed and paper edge breakage when discharging.
③The flatness of the material or the uniformity of the rewinding tension
Whether it is single-sheet printing or web printing, the flatness of the material determines whether the paper can be correctly fed, run and registered, and received during printing. For the roll material, the rewinding tension will play an important role in the flatness of the end surface of the roll material, whether there is glue leakage, and whether it can be correctly registered.
④ Uniformity and correct coating amount of adhesive and silicone oil coating
These indicators directly affect the peeling force (release force) between the label and the backing paper, and the size of the peeling force directly affects the die-cutting waste discharge and the speed of the machine. The peeling force also determines the label’s output status, that is, application. In addition, the amount of glue applied will also affect the material’s end-face penetration. Therefore, when purchasing adhesive materials, we should carefully check and choose the materials with the appropriate amount of glue and silicon.
The choice of ink is mainly considered from the aspects of the ink’s own quality, hue, and ink wetting to the substrate—that is, the adhesion of the ink. Although there are many types of self-adhesive materials, the surface materials can be basically divided into three types: paper, aluminum foil and film. At present, in China, the printing of self-adhesive labels is mainly based on relief printing (reel printing) and offset printing (single sheet printing). Among them, relief printing and offset printing are divided into ordinary resin ink printing and UV ink printing.
In general, paper-based surface materials do not have the problem of ink adhesion fastness, so the requirements for inks are not high, and different brands of inks have certain interchangeability and versatility. However, due to the influence of surface tension and different physical properties, aluminum foil and film materials have very strict requirements on inks. When selecting inks, the following principles should be followed:
① A kind of self-adhesive material can only use inks produced by one ink supplier at a time, and can not mix and use similar inks produced by other manufacturers at the same time.
② In principle, each kind of self-adhesive material can only use the matching and corresponding ink.
③ The additives used must be matched with the ink, and cannot be replaced with other types of additives.
④Pay attention to the expiration date of ink, and it is strictly prohibited to use expired ink.
Equipment configuration and adjustment
Different types of label printing equipment have different hardware configurations and different functions. They can be printed with different types, different materials, and different formats of label products. In order to ensure the printing and processing quality of self-adhesive labels, after the selection of raw materials and inks, the reasonable selection of equipment and adjustment of equipment is one of the keys to ensure the quality of label printing.
The labeling machine is a multi-function device. Only when the printing and processing stations coordinate and coordinate with each component with high precision can qualified labels be produced. Pay attention to the following adjustments when using labeling equipment:
1) Inking system
Care should be taken to maintain the accuracy of each rubber roller, especially the inking roller. The rubber roller should be replaced and cleaned regularly to make the system uniform ink distribution and printing plate ink uniformity.
2) Imprinting device
Imprint cylinders and imprinting platforms should be cleaned frequently to keep them flat and smooth. The gears and chains between the impression cylinder and the impression platform must be kept in good mesh. Only in this way can the correct closing pressure, separating pressure and printing register be guaranteed.
3) Traction system
Regardless of whether the labeling machine feeds continuously or intermittently, the accuracy of the traction device determines the accuracy of label overprinting. The rotary labeling machine must guarantee the accuracy of the transmission gear, and the intermittent labeling machine must guarantee the accuracy of the unidirectional traction roller.
4) Precision of die cutting device
The accuracy of the die-cutting device includes the accuracy of the die-cutting knife and the accuracy of the die-cutting parts. The accuracy of the die-cutting device not only affects the discharge of the label, but also directly affects the application of the label, such as the accuracy of labeling when labeling and the speed of the labeling machine. Therefore, the state of the die-cutting device of the labeling device must be adjusted.
Determining the label printing process is a comprehensive issue. It should be considered from the customer’s requirements, label samples, equipment, materials and inks, and the specific situation of the printing plant. The formulation of the process route includes the following contents:
Bronzing or bronzing first; glazing or lamination;
Field printing or screen printing; automatic labeling or manual labeling;
Independent printing or mixed printing; large layout printing or small layout printing;
Whether the double-sided label is printed on the back or single-sided; whether the label is printed once or twice;
Large format die cutting or small format die cutting; automatic waste discharge or manual waste discharge;
There are many problems involved in determining the process route, and using a reasonable process route will get twice the result with half the effort. Determining the process route should proceed from reality, and if necessary, process tests should be conducted to check the printing and processing suitability of the label.
Analysis of label application
The determination of a label production process route and the determination of raw materials are related to the customer’s label application effect. Keeping track of the application status and problems of labels in a timely manner is of great importance for improving the process route and the overall quality of the self-adhesive labels, so it is necessary for material suppliers and printing plants to visit end customers regularly.
The following points should be noted in understanding the application of labels:
① The firmness and abrasion of the label ink layer;
②The corrosion resistance, shrinkage and expansion of the label;
③The working condition of the label on the labeling machine;
④The weather resistance of the label, whether the ink layer and blank space are faded;
⑤Whether the label has warpage and surrounding glue leakage;
⑥The application of labels on printers or electronic scales.
According to the situation learned, first analyze the cause of the problem, and then you can further improve the printing and processing technology of the label by modifying the label’s production process or changing the material type.