Plastic film substrates are currently commonly used for in-mold labels, which are printed in a traditional manner. The surface is coated with a layer of UV or EB cured varnish for protection, and the back of the label is coated with a solid chemical adhesive. In-mold label materials are suitable for a variety of printing processes and different inks, including: screen printing, UV relief printing, flexographic printing, gravure printing, and offset printing. Before selecting the ink, the adhesion, scratch resistance, chemical resistance and other properties of the ink on the in-mold label material should be tested according to the requirements of the final application.
There are two printing processing methods for in-mold labels: web printing and sheet printing.
1. Web printing processing: divided into on-line one-time processing and extension multiple-time processing. These two processing methods are related to the factory's own equipment and label design requirements. If printing a label with a bronzing pattern, and the printing machine has a round-pressing bronzing and die-cutting device, the processed label can be formed at one time; if there is only a separate bronzing machine and die-cutting machine, the label can only be processed multiple times carry out. The characteristics are fast production speed and high efficiency, but due to the high cost of roll making, it is more suitable for mass production.
2. Sheet paper printing process: usually silk screen and offset offset printing. This method is completed by multiple processes on multiple devices. The printing process is related to process design. The processing is more flexible and the plate making cost is lower than the reel method. It is suitable for small batch production; the printing effect is good, the screen printing is on-site and the offset printing is layered. Both are better than web printing.
Offset printing process
1. Features of offset printing
A. The printing quality of fine dots is better than other printing methods,
B. The printing effect of line and field and the saturation of color are inferior to other printing methods,
C. It is more difficult to control the color difference than other printing methods,
D. For short-run business, the production cost of offset printing is lower than other printing methods,
E. It has the advantages of flexible production and rich printing levels. It is suitable for in-mold labels with small batches, multiple varieties, and high printing quality requirements. It is more suitable for the current status of the label printing market in China.
2. Offset printing process
A. The amount of powder sprayed is moderate, and the accumulation of printed products should not be too high.
B. After printing, it should be fully aged to dry the ink. After printing, it needs to be coated with varnish to ensure the quality of the printing.
C. In printing, the amount of fountain solution should be reduced by 10% to 15% (based on the non-dry plate) compared to printed paper products due to the poor hygroscopicity of the substrate. Too much fountain solution will cause false drying and ink emulsification during printing. The pH value of fountain solution is controlled between 6 and 6.5.
3. Offset printing equipment: Most domestic printing companies use Heidelberg sheet-fed offset printing machine series
Features of Speedmaster CD74-Medium Format Sheetfed Offset Press
* A wide range of substrates, from thin paper to cardboard to plastic film,
* Suitable for high-speed long-form jobs, fully automatic feed preparation and easy-to-control paper feeding system,
* The digital CP2000 printing control system supports the rapid replacement of paper format and stack.
Flexo process
Flexo printing is the mainstream packaging and label printing method in Europe and the United States. However, due to the imperfect domestic supporting facilities such as flexo plate making and knife molds, the current market share is small.
However, the rapid development of flexo printing in recent years is an important development direction for label printing.
1. Features of flexo printing
A. Cooperate with the CDI platemaking technology of computer direct platemaking, which can obtain better dot quality and saturated printing color,
B. It has the advantages of one-time molding and multi-process combination that other printing methods cannot compare with,
C. UV ink printing is used to make the printing color more gorgeous, fast drying, high molding efficiency, suitable for medium and large batch production,
D. Poor adhesion of ink and poor gradation effect, generally need to be polished after UV printing.
2. Flexo printing equipment
The foreign models are mainly Gellas and McAndy; the domestic models are mainly Shanghai Ziguang.
(1) GullasEM280 narrow width flexo printing machine is an ideal model for high-quality, low-cost and medium-length label production. Its main features are:
A. Easy operation, easy cleaning, short preparation time for job adjustment,
B. Quick conversion platform and quick ink replacement, the printing method can be converted within a few minutes, the printing process combination is flexible and diverse,
C. Units can be added at any time, which is the ideal model for flexo and UV printing,
(2) Shanghai Ziguang
YR420 / 450 series is a flexographic printing machine, using water-based ink, suitable for packaging printing of food and medicine. Among them, the main features of YR420 web flexo printing machine:
A. It has functions such as quantitative paper feeding, UV coating, waste rewinding, longitudinal slitting, etc.
B. Equipped with PLC controller, coil deviation correction device, static elimination device, UV curing device, etc.
C. Can increase the functions of UV printing, self-adhesive printing, flip printing, bronzing, punching, etc.
D. It is suitable for printing materials such as stickers, coated paper, cardboard, aluminum foil paper and plastic film, etc. It is an ideal equipment for printing medium and high-end packaging boxes, bottle stickers and labels.
Gravure process: The number of gravure products in North America is absolutely dominant.
1. Features of gravure
A. The field printing effect and color saturation are better than offset printing, the ink is thicker, the color of the printed product is natural, but the text is not as expressive as offset printing.
B. It is better than offset printing and embossing in color difference control.
C. The paper path is the longest, which is more likely to generate static electricity than other printing methods.
D. The plate making time is long and the cost is high, which is not suitable for the medium and short version label printing business.
E. The ink layer is thick and has the best scratch resistance, and the printing speed is fast, which is especially suitable for printing large batches of long jobs.
F. Continuous web printing, high output, low cost,
2. Gravure printing equipment
Domestic manufacturers such as Shaanxi Beiren and Zhongshan Songde.
Shaanxi Beiren gravure printing machine is suitable for printing packaging materials such as plastic film and tipping paper.
Resin letterpress printing
1. Characteristics of resin relief printing
A. The quality of the printed fine dots is worse than other methods,
B. The printing resistance of the printing plate is lower than that of the intaglio and flexible plates,
C. It is easier to control the printing color difference than offset printing, but not as good as gravure printing and flexo printing.
D. The cost and cycle time of plate making is lower than that of gravure printing and flexo printing,
E. UV ink printing is used to make the printing color more dazzling, fast drying, high forming efficiency at one time, suitable for medium and large batch production.
2. Letterpress equipment
Foreign countries are mainly Ko-Pack and Luotie
The Class series central embossing cylinder printing machine manufactured by Ko-Pack Company in Japan is the representative model of CID high-speed label printing machine. Its advantages are that the transmission error of the substrate is small and the overprint is accurate; the printing speed can reach 100m / min; Small, low-cost venues, very suitable for the Chinese market.
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