The commonly used printing methods for self-adhesive labels are as follows:
The letterpress printing is used for self-adhesive labels. The printing plate is photosensitive resin letterpress. The printed labels have the advantage of full ink color, but now the grades of letterpress printing equipment are quite different. Some are still using circular embossing presses, and some are ordinary Some rotary embossing machines have adopted professional oblique-back, satellite-type or unit-type adhesive label printers, so they cannot be generalized during the transformation. Professional self-adhesive printers, mainly embossing, have the ability to print film labels, but they need to contact the supplier to replace some related parts, such as adding a tension control system controlled by a servo motor, adding a film surface treatment unit, high-end Some machines can also add a precise registration system.
Self-adhesive offset printing
Offset printing is the main way for label printing factories in my country to print paper stickers. Offset printing is characterized by fine graphics, rich layers, 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 films with non-absorbent surfaces, because film labels are mostly roll-to-roll printing and require volatile dry inks. Offset printing can print thicker plastic materials, such as in-mold labels and tag tags, but the machine must be equipped with a UV curing device, which requires a lot of expense.
The quality of flexographic printing is no less than that of offset printing, and even has its own unique features. The advantages of this printing process are 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. Flexo printing uses water-based ink and uv ink, which does not pollute the environment. However, due to the greater flexibility of the flexographic plate, the tone reproducibility is different from that of the intaglio and ordinary letterpress. The dots from the highlights to the midtones of the flexographic printing are larger, the printing contrast is small, and the high-gloss levels are prone to faults. In the printing of fine graphics When labeling, in order to make up for the defects of the level, the highlight part can use frequency modulation dots, dark adjustment or mid-call amplitude modulation screening to improve the quality.
Gravure printing uses a short ink path inking system to supply ink, web printing, with a high degree of automation, using solvent-based inks, the ink layer dries quickly, and is the first choice for film printing. Generally, the speed of gravure printing presses is relatively high, and the back end of many gravure printing presses is also equipped with a cylinder die cutting device, which can perform die cutting and indentation, and is suitable for printing various labels. However, due to the long cycle of gravure plate-making and the high cost of plate-making, it is only suitable for mass label production.
Self-adhesive screen printing
Screen printing is the most widely adaptable printing method for substrates. At present, many screen printing factories use low-cost screen printing equipment to undertake the printing business of self-adhesive labels and film labels. Screen printing labels are characterized by strong ink color and strong three-dimensional effect. UV ink can be used to print film products. Except for a handful of rotary screen printing equipment capable of roll-to-roll label printing, most of the screen printing equipment are semi-automatic flat screen printers, which can only print single products, and the overprinting accuracy is not high, so they are not suitable for matching with the production line. Film label production equipment.
Mass printing is mostly based on offset printing, gravure printing, letterpress resin printing or flexographic printing. However, the demand for personalized and small-volume self-adhesive labels on the market is increasing. There are tens of thousands of small labels. For single sheets of six or eight sheets, some thousands or hundreds of copies, the waste of web label printers in printing this kind of job is a bit large and not cost-effective.
In terms of printing products, small batch jobs require low cost and short delivery time; and product quality often requires bright colors, and most of the hierarchical layouts composed of dots. According to this situation, many small printing companies have adopted six-carriage monochromatic offset printing presses for four-color overprinting, which also achieved very good results.
In offset printing, embossing, gravure printing, etc., offset printing is undoubtedly the lowest cost printing method. In the pre-press process, compared to the complicated plate making process of the flexographic plate, the production, filming, and printing process of the PS plate are familiar to the printing factory. From a technical point of view, all printing plants have switched to offset printing after eliminating lead printing. Therefore, there is no additional burden.
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