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.
â–¼79. What are the drying methods of ink?
The ink drying method can be divided into natural drying, heat drying, ultraviolet drying, electron beam irradiation drying, infrared drying, microwave drying and other forms.
In addition to the drying method described above, two types of physical drying and chemical drying may be used depending on the type of ink contained in the ink. Second, according to the different properties of ink can be divided into infiltration drying, oxidation and conjunctiva drying, volatile drying and other forms.
The inks with special properties in the dry form include photopolymerization drying and UV drying. Most ink drying methods usually use only one drying method, but some of the inks are dried in a certain dry form, and they are also dried together with other auxiliary drying forms. The drying type of ink is shown on the previous page.
Under normal circumstances, volatile drying inks, water-based inks, oxidative polymerization inks, and two-liquid reaction inks are dried by natural drying, hot-air drying, or infrared irradiation. The heat-curable ink is dried by infrared irradiation. Ultraviolet curing inks are dried using ultraviolet radiation.
Which drying method is used in actual printing production depends on the actual conditions of the used ink, drying equipment, and site.
â–¼80. There are several ways to dry glass after printing.
After printing, glass products are dried differently from other substrates by two methods, namely, natural drying and forced drying. Natural drying is to place the printed glass product in a proper place and allow it to dry naturally. Because of the different conditions of air temperature and air circulation, the speed of drying is also slow, sometimes to speed up drying, and it can also be dried by cold and warm air. After the glass products are printed, they must be fully dried before firing. The firing temperature should not exceed 120 °C. And the firing temperature should be gradually increased from low to high. This must be noticed.
When printing in high-volume multicolor glass products, forced drying methods are often used. The most commonly used is electrothermal drying. For multi-color printing, dry one time for each color of the ink, only after four colors are printed, can the firing be performed. The firing temperature should not exceed 120°C.
â–¼81. Which lamp source is ideal in silk screen platemaking?
Ultraviolet cold light is an ideal light source. If there is a strong ultraviolet light, the effect is better. Domestic mainly by 20W/A, 30W/A
Branches, 40W/A branch, 80W/A branch, 8W/branch, followed by high-pressure mercury lamps, high-pressure xenon lamps, high-pressure mercury lamps are not common small sun lamps, and are special plate-making lamps.
Use these two kinds of lamp plates, pay attention to the temperature of the glass surface in the hot season, if necessary, add fan cooling to prevent cross-linking caused by overheating and photoresist.
And can not be started continuously, that is, after the lamp is turned off, it can not be restarted after at least 5 minutes.
â–¼82. With ultraviolet light exposure, how long should the printing time be? What is the high pressure mercury lamp and high pressure xenon lamp?
Ultraviolet light cold light printing time is generally controlled between 3-6 minutes (referring to 1000W- mercury lamp or xenon lamp), thick glue layer, long time, glue layer book, shorter time, slightly longer winter, summer Shorter, for high-pressure mercury lamps and high-pressure xenon lamps, the grid voltage is high and the light is strong, and the printing time can be shorter, and vice versa. Specifically, the correct time can be calculated.
â–¼83. What are the advantages of the external cold light ?
Ultraviolet cold light, using electronic rectifier, the light intensity emitted is not affected by the level of the grid voltage, only 130 volts can start. The range of light it emits is exactly what the photosensitive material needs. The lamp can run continuously, start continuously, and has low heat output and low investment at one time. Silk screen printing is the best light source.