UV metal ink classification and characteristics

UV metal inks are photocurable inks that can be printed directly on metal surfaces (including surface-treated metal substrates and surface-coated metals), rather than inks that contain metal or metal effect inks. Commonly used metals in printing such as copper, aluminum, iron, stainless steel, mirror stainless steel, titanium mirror plate, surface treated metal such as anodized porous aluminum plate, iron phosphide plate, galvanized iron, nickel, chrome plating, surface finish Metals such as sprayed powder coatings or thermoset painted metal sheets.
Different metals, different surface properties, the choice of UV ink varieties should also be different, otherwise there will be such as the adhesion is not strong, the ink layer when the metal bending and embrittlement crack phenomenon.

UV metal ink classification, characteristics

Kewang's UV inks are divided into the following categories: General metal UV ink UVMI-20 series, special metal UV ink UV-MI-25 series, elastic UV metal ink UV-MI-105 series, high temperature UV metal ink UV-MI-28 series, special decorative effect UV metal ink, UV etching ink for metal etching and UV metal varnish series. Table 1 lists the properties and range of use of non-type UV metal inks for reference.

Metal properties and pre-press surface treatment

Different metals have different physical and chemical properties. Some are high in polarity and some are low in polarity; some are easily oxidized, such as copper, and some are afraid of acids and are afraid of alkalis such as aluminum; some have high hardness, and some are soft and can be stamped. Different types of metals should be selected to match the UV metal ink, such as flexible metal to choose UV elastic metal ink UV-MI-105 series.

Different metals have different surface states and require different methods for surface treatment. Some have high gloss, some are porous, such as alumina plates, and some have a passivation film on the surface, some have a coating layer, some have a spray paint, and some have a powder coating. For high-gloss difficult-to-attach metal, such as mirror titanium gold plate, mirror stainless steel, you need to first print a layer of UV varnish such as UV-802N on the metal surface full screen, after the light curing other UV color ink printing, the effect is very obvious; Can also be used Ke Wang 20 # surface treatment water rubbed the metal surface, in 100 ~ 120 °C / 5 ~ 10min conditions, drying and then printing UV metal ink, greatly improved the fastness. Some metal coatings, for which inks are not sticky, such as fluorocarbon coating, polypropylene coating, can only print UV inks after being treated with special treatment agent such as PP. Coatings of different compositions are treated with different surface treatments.

The same kind of metal materials, different use environments, the requirements of UV inks printed on the surface are not the same. Some require high temperature resistance, some require water resistance and moisture resistance, and some require resistance to freezing.

Different metals, different decorative effects, need to use different UV effect inks. Some want to ice effect, some to scrub, some to matte effect, some to sand effect, some to colorful crystal effect, and some to wrinkle or hammer effect. High-gloss metal is suitable for printing UV metal ice, hammer, matte, frosted ink, if printed on other metal substrates will not achieve the desired effect.

Different metals have different chemical compositions. Etching solutions and anti-corrosion inks used in etching are also different. Some require fine etching, some require deep etching, some metals must be removed before the titanium layer etching, some etching can be diluted with alkaline water, after the metal aluminum etching can only be neutral to remove the ink layer, The protective ink EPR-400BL used in aluminum anodizing can only be washed off with xylene, petroleum solvents, etc. after it is acid and alkali resistant.
UV metal ink printing and curing

Printing color sequence

Each UV metal ink has an optimal printing sequence. UV inks of different colors have different photocuring speeds. Some cures are slow, some are fast curing, and unlike self-drying solvent inks, any color can be printed first. When screen printing UV metallic ink, especially multi-color printing, generally follow the dark color ink printing, light ink printing.

Different colors of UV metal inks have an optimal curing sequence. UV metal ink curing sequence is gold, silver → black → blue → red → yellow → colorless transparent varnish. Dark ink requires large UV light energy, drying is slow, and UV light is not easy to penetrate the ink layer, the bottom layer is more difficult to cure, it must be printed dark; light-colored ink is easy to cure, only need to light once. If you first print light-colored ink, it will inevitably lead to light-colored curing, ink layer crisp, poor adhesion, and dark ink layer curing is not enough, the surface hardness is low, abrasion resistance, poor resistance and other shortcomings. After the UV ink is printed, it can be cured immediately and printed in one color. Once the second color ink is cured, the first color ink has been irradiated twice. If it is a four-color pattern, the bottom layer ink is cured when the fourth color ink is cured. Four times.

The choice of screen mesh number

Different types of UV metal inks require the use of different mesh screens for printing. The curing of UV inks is instantaneous. The faster the curing speed, the more easily the cured film shrinks. The lower the mesh number, the larger the wire diameter, the thicker the ink layer, the more pronounced the shrinkage of the cured film, and the ink layer and the metal substrate. When the shrinkage cannot be synchronized, it will inevitably lead to a decrease in adhesion.

General color ink such as UV-MI-20, UV-MI-25, UV-MI-105 series available 300 ~ 350 mesh screen, and UV-3000 color sand series ink can only use 180 ~ 220 mesh screen, this is Due to the size of the metal particles contained in the ink, the mesh is too high and the sand cannot leak.

When printing UV resist ink, it is necessary to determine the mesh according to the precision and depth of the metal etching. The fine pattern can be printed with 300 mesh. When the etching is deep, 120 mesh mesh is sometimes used.
UV-MI-105 series of elastic metal inks in order to make the cured film has good elasticity, resistance to stretching during the stamping process, the cross-linking density of the cured film will not be very high, so the UV curing speed should be slower.

Among the UV special effects inks, UV-880 ice printing inks have the slowest curing speed. This type of ink curing is divided into two processes: the generation and curing of ice flower patterns. The production of the ice flower pattern does not require too strong UV light irradiation, but this process usually takes several tens of seconds. After the ice flower is formed, it can be cured with strong light. Many light-solid equipment manufacturing companies do not understand this principle, and the power produced by the light-solid machine is very large. Most of the light energy becomes heat energy. Not only does it cost electricity, heat is hard to discharge, and the effect is not good. Figure 6 UV ice light machine adjustable lamp height adjustable low.