Screen Printing 1000 Question (73-78)

â–¼73. What is a two-fluid reactive ink and what are its characteristics?

The ink that is mixed with a resin and a curing agent at the time of printing is called a two-liquid reactive ink. Epoxy-based resins are used in many of these inks, and curing agents use more ammonia. The advantages are: the solvent composition is very small, the adhesion to various materials is better, the ink film is hard and tough, with strong oil resistance, solvent resistance, heat resistance and so on. The disadvantage is that since the two solutions start to react after being mixed, the viscosity of the ink gradually increases during the printing process, and the ink after mixing cannot be preserved.

â–¼74. What is a heat curable ink and what are its characteristics?

The resin and curing agent are preliminarily mixed and then heated after printing so that the resin reacts to form an ink film. This ink is called a heat-curable ink. Although the characteristics of the film formed by the single-liquid type epoxy resin used for the resin of the ink are almost the same as those of the two-component type ink, the flexibility of the film is much different, since the ink is hardly at room temperature. Since the reaction is performed, it is easier to perform than the two-component type ink at the time of printing. But must use the high temperature above 150 °C barbecue, the ink is also difficult to save for a long time.

â–¼75. What is UV curable ink? What are its characteristics?

During the drying process, the ink is irradiated with ultraviolet rays to cause polymerization of the resin to form an ink film. This ink is called an ultraviolet curable ink (ie, UV ink). Ultraviolet ink is composed of a colorant, a prepolymer, a cross-linking agent, a photoinitiator, and an auxiliary agent. This ink mainly uses a photopolymerized photosensitive resin of a modified acrylic system prepolymer, and a photosensitive monomer, The photopolymerization initiator, the pigment and the auxiliary agent are mixed together so that the photosensitive resin forms the ink skin and the film according to the photopolymerization principle. Advantages: UV ink does not use any solvent, does not produce solvent volatilization in the printing process, is conducive to environmental protection and the health of workers, has good stability in the printing process, fast drying speed, saves heat, the film is shiny, color density Reproducibility is better than ordinary inks, with excellent abrasion resistance, water resistance, oil resistance and solvent resistance. Ultraviolet ink has a high flash point (above 100°C) and is not flammable. It is safe to use. Disadvantages: The UV light does not cure at the end, and the black part of the light absorption and the self part of the reflected light cure slowly. It is not the kind of material that can be bonded, and the cost of the ink is high.

â–¼76. What are the characteristics of the base ink?

An ink using water as a solvent is called a water-based ink. This kind of ink uses the water in the ink to evaporate during the drying process, so that the dissolved resin helps to cure and form a film. This ink is also called water-based ink. Water based inks are formulated from aqueous resins, pigments, adjuvants, and water-based system additives.
The advantages of water-based inks are: Since most of the solvent is water, the pollution is less conducive to environmental protection, and the ink has better passability and reproducibility of the screen. The disadvantages are: poor ink luster, low precision, poor adhesion, and must use a water-resistant version. When printing paper, it is easy to cause the paper to curl and bend, which affects the quality of overprinting. In addition, the evaporation rate of water in the ink is slower, so the drying time is longer.

â–¼77. What is the composition of foam ink and what are its characteristics?

The foaming ink is formed by blending a water-based resin and a water-based water solvent, a microsphere foam, and other auxiliary agents. As the foaming ink is used in the water-based connection material, it is easy to use, no pollution, and the ink on the screen through the good and reproducible, ink layer has good solvent resistance, drug resistance, abrasion resistance And no deformation under heavy load and other characteristics.
Emulsions used in foamed inks are generally crosslinked synthetic resin emulsions, crosslinked propylene emulsions, and crosslinked reactive propylene emulsions or bad oxygen emulsions and urethane emulsions.
The microsphere foam in the foamed ink is a thermoplastic polymer particle, which is in the form of "hollow" and is generally formed by polymerization of polyvinylidene chloride or vinylidene chloride and acrylonitrile, or methyl acrylate and acrylonitrile. The hollow part contains a volatile expansion agent, and the expansion agent is mostly a carbon compound such as ethane, propane, butane, and the like. Microspheres are generally between 5 and 150 microns in diameter. The content of the microsphere foam in the ink is generally 5-50%, the content of the microsphere foam is low, and the foaming effect is not good. If the content is too high, the fluidity of the ink is reduced, making the ink layer uneven.
The ink uses a variety of dyes, pigments, and colorants to adjust the ink to achieve the desired color.
Other additives used in the ink include stabilizers, tackifiers, defoamers, oxidation inhibitors, ultraviolet absorbers, and the like. Formulations for making foamed inks are described below.
Crosslinked Epoxy Emulsion 50%
Epoxy glycol 8%
Microsphere foam 25%
Defoamer 0.2%
Water-dispersed pigment 1.8%
Crosslinking agent 10%
Water 5%

â–¼78. What is a fluorescent ink and what should you watch out for when using it?

Fluorescent inks for screen printing use inks made from fluorescent pigments as a coloring material. Fluorescent pigments are made from fluorescent dyes and synthetic resins. The ink particle size is between 5-15 microns.
Fluorescent inks for screen printing are suitable for the printing of paper and vinyl films. There are two types of paper-based fluorescent inks: oxidative drying and evaporation drying. The fluorescent film for the ethylene film is an evaporation-drying type.
The following points should be noted when using fluorescent inks.
1 Since the fluorescent ink has poor light resistance, it is not suitable for long-term outdoor use. Therefore, screen printing used outdoors should not use fluorescent ink.
2 Fluorescent inks are suitable for screens up to 200 mesh.
3 The ink volume after printing is 50-60 g/m2, which is ideal for hair color and light fastness.
4 When the substrate is a transparent object, white ink should be printed before printing fluorescent ink, which can improve the fluorescence effect.
In general, fluorescent inks are easily confused with luminous inks and can generally be distinguished by comparing the characteristics of the two inks.

---Qi Lu Graphic Arts