UV ink

What is UV ink? How is it different from traditional ink? Compared with traditional inks, what are the advantages?
Traditional inks can be divided into two categories: (a) oil-soluble inks - commonly known as inks; (b) water-soluble inks - commonly known as ink. The mechanism of film formation and drying of the two inks depends on the volatilization of the solvent (organic solvent or water) in the ink in the air, or the partial absorption by the substrate (SUBSTRATES). However, this mechanism not only contaminates the air, but also reduces the production rate, and it is difficult to achieve the high quality requirements for future printing.
UV ink, as the name implies, is a specially formulated ink that uses ultraviolet (ULTRAVIOLET) light-wave sensitization to make the ink film and dry. Its characteristics are: (i) Fast drying, film-forming speed, and it takes only a few tenths of a second, and printing productivity is also relatively high. (b) The resulting color film can act as a cross-linking agent on the substrate, so the adhesion force is particularly strong. (C) color film brightness is very high, water resistance and chemical resistance. (d) To reduce air pollution and the VOC content is almost zero.
The mechanism of UV ink drying and film formation is a chemical change. Different UV spectra were used to generate different energy and different prepolymers (Oligomers) and different monomers (MONOMER) were polymerized into polymers (POLYMER). Therefore, the UV ink film has good mechanical and chemical properties.
If we compare the composition of UV ink with the composition of traditional ink, we will find that there are similarities between the two. The difference is that the film formation of the UV ink is a chemical action, from the monomer to the polymer, while the traditional ink filming is a physical function, the resin is a polymer, and the solvent is a polymer that dissolves the solid polymer into a liquid state. Helps to adapt the print to the substrate, and then the solvent is volatilized or absorbed, allowing the liquid polymer to revert back to its original solid state. The following is a comparison of the composition of the two inks:

The composition of UV ink is now described separately.
(I) Pigments Many types of pigments are suitable for the coloring of UV inks; however, care must be taken when selecting them. First of all, many pigments promote the natural polymerization of the vehicle (VEHICLE) in the dark; this natural polymerization does not take place immediately, but it takes a long time to occur, thus reducing the UV ink inventory time. In addition, different colors have different speeds to absorb ultraviolet light waves, which often affects the polymerization of UV inks. In other words, the speed of printing is affected by the speed of drying, thereby reducing the mechanical and chemical properties of the color film. Furthermore, the acrylic salt (ACRYLATES) used in the vehicle of the UV ink is not a good wetting agent (WETTING AGENT), which often makes the grinding of the pigment difficult and affects the smoothness and evenness of the color film in the future.
In general, to successfully deploy a good UV ink, an ink chemist must not only have experience with pigments, but also have some knowledge of physics and chemistry.
(B) Prepolymers (OLIGOMER)
Is a high molecular weight and high viscosity (HIGHVISCOSITY) monomer, it is like the resin in the traditional ink combination, is the main chemical film; also determines the various properties of UV ink, such as mechanical, chemical, physical Sex and so on. The resin used in traditional ink is a compound that has been polymerized, and may be a solid or a liquid; and this prepolymer is a non-polymerized liquid compound that needs to be polymerized by the action of ultraviolet light waves. There are three main types of prepolymers commonly used, (a) epoxy acrylates (EPOXY ACRYLATES), (b) URETHANE ACRYLATES, (c) polyester acrylates (POLYESTER ACRYLATES).
(a) Epoxy acrylate Epoxy resin and acrylic acid produce epoxy acrylate.
UV inks made with epoxy acrylates are extremely fast drying, glossy and chemically resistant. At the same time, they are inexpensive and are very popular with UV ink manufacturers. If used to formulate UV varnish, coated on paper or cardboard, the paper or board can have good chemical and mechanical properties.
After the epoxy acrylate is polymerized by UV light waves, it often exhibits the unique properties of the acrylic resin, and also shows the strong chemical resistance of the epoxy resin. Its biggest drawback is poor wettability of the pigment and high viscosity. For example, the film-forming agent used alone as a UV ink tends to make the RHEOLOGY and DISPERSING worse.
(b) Amine ester acrylates The amine ester acrylates are produced when isocyanates (ISOCYANATE) and hydroxy (HYDROXYL) in acrylic acid.
The amine ester acrylate is polymerized by ultraviolet light and has the characteristics of polyurethane resin. The color film has high lightness, high flexibility, strong elasticity, and good adhesion. UV inks composed of amine ester acrylates are particularly suitable for printing various plastics and foils.
(c) Polyester Acrylate After the hydroxyl and acrylic acid in the polyester are reacted, a polyester acrylate is obtained.
Polyester acrylates have a low molecular weight and therefore have a low viscosity. Its price is very cheap, wet and flexible. Commonly used as a carrier for grinding pigments. It can sometimes be used as a thinner for UV inks to adjust the viscosity of epoxy acrylates and urethane acrylates. It has strong surface adhesion to non-porous substrates, tantalum sheets, aluminum sheets and plastic sheets, and is often used as a printing UV ink for such articles.
Its biggest drawback is its poor chemical resistance. Many alkaline chemicals can erode it. Because the molecular weight is low, the polymerization time is longer, in other words, the drying is slower.