At present, flexo printing has developed rapidly. Some data indicate that in the United States, total flexo printing accounted for 33% of total print output in 2000, only after offset printing (35% for lithographic printing and 17% for gravure printing). In the packaging and printing industry, flexographic printing has become the dominant printing process and has played a greater role in the printing of newspapers and periodicals. Flexographic printing can adapt to a wide range of printing materials, can print smooth, smooth, absorbing paper, rough surface, corrugated cardboard, textiles, and non-absorbent ceramics and plastic films. , aluminum foil and other substrates. Flexo printing not only has wide adaptability, low cost, fast printing speed, multi-color overprinting, but also the process of cutting, forming, laminating, etc. can be connected into a line, which gives higher requirements for flexo printing inks. . Flexo inks are required to have low viscosity, fast drying and many varieties, and adhere to the substrates firmly. The solvent in the ink cannot affect the printing plates and the rollers. Printing inks for food packaging should be non-toxic, odorless, non-polluting, and should meet environmental protection requirements.
Flexo inks can be divided into solvent inks, water inks and UV inks. The more widely used are solvent-based inks.
Solvent inks can be divided into solvent dye inks and solvent pigment inks depending on the colorant used.
The solvent dye ink has good transparency and can see the substances in the printed matter package, which can increase the perception of the package. When the ink is printed on metallic glossy paper (such as aluminum foil), special gloss color can be printed and the printing is greatly increased. The vividness of the product. Dye ink has better rheological properties, because the solubility of the dye is better, so the viscosity of the ink is relatively low, can control the drying speed. Mainly used for printing absorbent paper, such as kraft paper bags, wrapping paper, cellophane and other cardboard.
Solvent dye inks have a wide range of substrates, including paper, plastic film, and aluminum foil. The binder in the ink plays a role in the adhesion of the ink and the substrate. Therefore, the choice of solvents and resins in the binders is affected and limited by the printing materials and printing conditions. That is to say, different substrates, the choice of resin and solvent are also different, so the solvent pigment ink can be divided into paper pigment ink, cellulose film ink, polypropylene film ink, polyvinyl chloride (PVC) film ink. , polyester film (PET) ink, nylon film ink, aluminum foil ink and so on.
Flexo-based water-based inks and UV inks are inks that are being developed, which are discussed later. It is not necessary to repeat them here.
3, gravure printing ink
A gravure is a type of printing plate for printing (graphics) partially concave (non-graphic) portions. Generally divided into engraving gravure and gravure (abbreviation edition). The ink used for engraved gravure printing is thick and short, mainly oxidized conjunctiva drying, and the imprint of the print (ink film) is protruding from the surface of the paper. It is easy to feel it by touching it. The ink is mainly used to print valuable securities, such as currency, stamps, and a few important documents, because it is not easy to duplicate the imitation of the intaglio. And play a role in security. Such as the new version of the fifth set of hundred RMB below the back with a magnifying glass to see the engraving gravure printing "RMB100" and "RMB" abbreviation text. The engraving gravure is also used for the printing of stamps. The patterns printed on the stamps are printed with intaglio ink. The lines are clear, the ink layer is thick, and they are slightly raised on the paper. The fine dots and lines are clear and definable, and the color and luster remain unchanged. Good for stamp security.
It should be noted that the name of the engraving gravure is due to the fact that the original printing gravure was hand-engraved, and the thick and short oxide conjunctiva drying ink used for engraving gravure printing is called an engraving gravure ink. Nowadays, engraving and gravure platemaking methods include mechanical plate printing, electroplating, and etching. So the name of the engraving gravure is not very strict.
Photogravure printing is commonly known as photocopying, and photogravure is also called photocopying. This is the customary name in our country. It was because of the original photographic etching method. Photographic gravure printing used a very thin, mainly volatile, dry ink called photographic. Gravure ink, photogravure ink is a typical liquid ink, and it is a kind of ink close to Newtonian fluid like a flexible letterpress ink. It has good fluidity and belongs to solvent type ink. Drying and drying are volatile drying.
Photogravure inks can be divided into benzene type, gasoline type, mixed solvent type, alcohol type and water type according to the solvent classification. If classified by purpose, it can be divided into paper gravure ink and plastic gravure ink.
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