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What are the categories of inks?
Release time:
2022-06-23 17:54
Printing plate type
Modern inks are mainly divided into four categories according to the plate type.
Letterpress ink: a type of ink used to print books, newspapers, picture albums, documents, account books, etc. in letterpress printing. The main feature of letterpress printing is that the inked part of the printing plate protrudes from the non-inked part. Letterpress ink is divided into lead printing ink, copperplate ink, letterpress rotary ink, and flexible letterpress ink according to the type of printing machine and the purpose of the printed product.
Lithographic ink: a type of ink suitable for lithographic printing. The various parts of the lithographic printing plate are basically on the same plane, the pattern is oleophilic, and the non-pattern is hydrophilic. Printing is based on the principle of oil-water repulsion, so lithographic ink must have water resistance. According to the process, it is divided into offset ink, web offset ink, flat offset ink, waterless offset ink, iron printing ink, lithographic ink, and collotype ink.
Gravure ink: a type of ink suitable for gravure printing. When printing, the part of the pattern recessed in the plate is inked, and the ink of the non-pattern part is wiped or scraped off before printing. There are carved gravure inks and photogravure inks.
Mesh plate ink: a type of ink that is printed through the mesh of the printing plate onto the printing surface. Mesh plate ink is further divided into copying ink and screen ink.
Solvent
The ink has different properties depending on the binder used. There are mainly resin-based inks, solvent-based inks, water-based inks and UV-curing inks. The use of organic solvents as ink binders will have a negative impact on the environment. In order to make the ink meet environmental protection requirements, environmentally friendly materials should be used as ink binders. Environmentally friendly inks mainly include water-based inks, UV inks, water-based UV inks and some alcohol-soluble inks.
Water-based ink: The biggest difference between water-based ink and solvent-based ink is that the solvent used in water-based ink is water instead of organic solvent, which significantly reduces VOC emissions, can prevent air pollution, does not affect human health, is not easy to burn, has stable ink properties, bright colors, does not corrode the plate, is easy to operate, is cheap, has good adhesion after printing, strong water resistance, and dries quickly. Therefore, it is particularly suitable for packaging and printing of food, beverages, medicines, etc. It is recognized as an environmentally friendly printing material in the world and is also the only ink approved by the US Food and Drug Association among all printing inks.
UV-curable ink: UV-curable (UV) ink refers to an ink that uses ultraviolet light of different wavelengths and energies to form a film and dry the ink under ultraviolet irradiation. Different ultraviolet spectra can generate different energies to polymerize the monomers in different ink binders into polymers, so the color film of UV ink has good mechanical and chemical properties. The main advantages of UV ink are: (1) no solvent is required; (2) fast drying speed and low energy consumption; (3) good gloss and bright colors; (4) water resistance, solvent resistance, and good wear resistance. The photoinitiator in UV ink is a compound that is easily excited by light. After absorbing light, it is excited into free radicals, and the energy is transferred to photosensitive molecules or photocrosslinkers, causing the UV ink to undergo a photocuring reaction. UV ink has become a more mature ink technology, and its pollutant emissions are almost zero. In addition to being solvent-free, UV ink also has advantages such as not easy to paste the plate, clear dots, bright and bright ink color, excellent chemical resistance, and low dosage.
Water-based UV ink: Water-based UV ink is a new research direction in the field of UV ink. The viscosity of the prepolymer in ordinary UV ink is generally very large, and active diluents need to be added to dilute it. The diluent acrylate compounds used have different degrees of skin irritation and toxicity. Therefore, while developing low-viscosity prepolymers and low-toxic active diluents, another development direction is to study water-based UV inks, that is, using water and ethanol as diluents. Water-based UV inks have been successfully developed and applied in some printing.
Alcohol-soluble ink: Alcohol-soluble ink, which mainly plays a role in flexographic printing, is also a kind of ink with very little pollution. It is mainly used in packaging and printing of food, medicine, beverage, tobacco, alcohol and daily necessities that come into contact with the human body.
Color
Standard color ink: Printing inks are generally standard color inks of the same type produced by various ink factories. In addition to color, the main difference in ink tone is the different gloss of the ink film, which has shiny gloss type and matte type, and the semi-bright type ink is between the two.
Spot color ink: Spot color ink is a special color ink formulated using existing color ink and auxiliary agents according to the color standard designed for the original manuscript. Color continuous tone image originals are all reproduced by overprinting with yellow, magenta, cyan and black four-color dot printing plates, and do not require spot color ink. However, in color printed products such as packaging, advertisements, and book covers, most of the colors used are solid flat coatings with spot colors.
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