Characteristics and Uses of UV Metallic Ink (Part 2)

Characteristics and Uses of UV Metallic Ink (Part 2)

Selection of mesh mesh

Different types of UV metal inks need to be printed with different mesh screens. The curing of UV ink is instantaneous. The faster the curing speed, the easier the cured film shrinks; the lower the mesh number, the larger the wire diameter, the thicker the ink layer, and the more obvious the cured film shrinks. 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 can use 300~350 mesh screen, while UV-3000 color sand series ink can only use 180~220 mesh screen The mesh is determined by 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, the mesh should be determined according to the precision and depth of metal etching. The fine pattern can be printed with 300 mesh, and when the etching is deeper, sometimes 120 mesh screen is used.

When printing UV special effect ink, there are curing conditions. For general metallic inks such as UV-MI-20 series, when 300 mesh screen printing, two high-pressure mercury lamp curing machines of 80 W/cm or more can be used for curing, the speed is 5-15 m/min, and the pencil hardness of the cured film is More than 4H, the adhesion is 100%.

UV-MI-25 series light curing metal ink contains a small amount of small molecular additives, which can enhance the wetting of the ink to the mirror metal and improve the penetration of the ink to the metal surface coating. Heating the surface of metal products can effectively improve the adhesion fastness of ink. For surface porous such as anodized aluminum plate, sandblasted or metal products with frosted effect, it can significantly improve ink adhesion and surface hardness. The photo-curing machine in Figure 5, equipped with an infrared heating device and a corrugating device, is specially designed for the curing of these difficult-to-adhere metals.

The UV-MI-105 series elastic metal ink has good elasticity in the cured film and resists the stretching during the stamping process, and the crosslinking density of the cured film will not be very high, so the speed of UV curing should be slower.

Among UV special effect inks, UV-880 ice flower ink has the slowest curing speed. The curing of this ink is divided into two processes: the generation and curing of the ice flower pattern. The generation of the pattern of the ice flower does not require too strong ultraviolet light irradiation, but this process usually takes tens of seconds. After the ice flower is formed, it can be cured by strong light. Many light-solid equipment manufacturing companies do not understand this principle. The ice-flower light-solid machines produced have high power, and most of the light energy is turned into heat energy. In Fig. 6, the lamp distance of the UV ice-flake light-fixing machine can be adjusted up and down.

Selection of UV Metallic Ink

When choosing UV metal ink, it is necessary to prescribe the right medicine. On the one hand, it is necessary to know the performance of the metal substrate, and on the other hand, to understand the characteristics and application scope of different types of UV metal ink, so that high-quality products can be produced, and costs can be reduced and shortened. delivery time. Some metals cannot find a suitable ink for a while, and the metal surface must be treated before printing, or use heat-curing ink instead.

For general metal products such as copper, aluminum, iron, brushed stainless steel, after cleaning the surface oil and dust, UV-MI-20 series light-curable metal ink can be directly screen printed without any treatment on the metal. This type of ink does not contain volatile solvents, has no odor, does not block the screen during screen printing, has fast curing speed, high hardness, high gloss, excellent scrub resistance and high production efficiency. It is an ideal ink for the production of various metal signs. For some products, customers emphasize excellent physical and chemical indicators. For example, for outdoor signs, the ink pattern must have good lightfastness and weather resistance. When purchasing inks, you must pay attention to its lightfastness indicators. Table 2 lists some technical indicators of UV-MI-20 series inks.

UV-MI-25 light-curing special metal ink is specially designed for screen printing various difficult-to-adhere metal substrates. Common metal products can be roughly divided into three categories.

1) Surface-treated metal substrates such as mirror stainless steel, mirror titanium plate, high-gloss aluminum plate, chrome-plated, nickel, silver, nickel/gold and other metal surfaces have high gloss and have a strong decorative effect, but the ink is not easy to adhere after printing. Especially for UV inks, the curing speed is very fast, and the cured film has a certain shrinkage during the curing process. It is not easy to achieve good fastness when printing on high-gloss metal substrates. After printing UV-MI-25 light-curing ink, it is recommended to use a UV oven with an infrared heating device for drying. If your light-curing machine does not have such a device, you can install one yourself.

2) For the surface-coated metal such as the metal substrate that has been sprayed (powder coating) or coated with thermosetting paint, in order to make the small molecule additives in the ink fully penetrate and wet the substrate, print UV-MI-25 After ink, do not light cure immediately, you can park for a few minutes, and then use the above-mentioned UV equipment with hot air device to dry. The usual thermosetting powder coatings include polyester resin and epoxy resin. A large amount of polypropylene, polyethylene wax powder and silicone additives are added to the formula. During the thermal melting process of the powder coating, the wax powder and the auxiliary The agent will float on the surface of the coating, which is the main reason for the poor adhesion of UV ink, and the situation of baking paint is similar.

3) For metal products with uneven or porous surfaces, the reason why the substrate is not easy to adhere to the UV ink is mainly due to the uneven surface, the small contact surface with the ink, and the holes between the ink cured film and the porous substrate. After printing UV-MI-25 ink, the fluidity of the ink must be enhanced with infrared rays or hot air, allowing the ink to flow into the pits before UV curing.

For products that need to be stamped and bent, such as thin aluminum plates, copper plates and other metal decorative plates, in addition to good adhesion, hardness and color, the cured film must also have excellent tensile properties to ensure that the cured layer can be The substrate is deformed and changed without breaking. At this time, it is necessary to choose UV-MI-105 series of anti-stamping elastic UV metal ink, and the printing ink layer should not be too thick.

The main function of UV metal varnish is to increase the surface gloss of metal products and improve the acid and alkali resistance, moisture resistance and scratch resistance of the products. Different types of varnishes also have their own characteristics to meet special needs.

UV-MI-20N does not contain volatile solvents, fast curing, low price, good adhesion to metal substrates such as copper, aluminum, iron, etc. It is the most common UV varnish, suitable for general metal products. . UV-802NS elastic metal varnish, high transparency of cured film, excellent adhesion to mirror aluminum plate, titanium plate, mirror stainless steel plate and other metals, and the cured film has good toughness, and will not crack during embossing.

Special effect UV metal ink belongs to art ink, emphasizing the decorative effect of ink. This type of ink can be divided into two categories. One is that special additives or auxiliaries are added to the ink, which will show special effects after printing, such as UV Frosted, UV frosted, UV matte, UV hammer, UV foam, UV color sand, UV fragrance and other inks; the other is developed according to the characteristics of UV curing, such as UV wrinkles, UV ice flowers, UV crystal, UV Refraction etc. Table 3 lists the technical specifications and effect descriptions of several UV special effect inks from Kewang. Figures 7 to 13 are samples of several special effect UV metallic inks.

Compared with general corrosion-resistant inks, UV-resistant series inks are more resistant to corrosion by strong acids or alkalis. Different types of resist inks have different uses. LPR-800, LPR-820, LPR-811, LPR-812, etc. are used for fine etching, and some are used for special metal etching, which will not be described in detail in this article. It is worth mentioning that the etching of aluminum metal, aluminum is an amphoteric metal, afraid of acid and alkali, so it can be corroded with acid and lye, and it also determines that aluminum cannot be developed and removed with alkali. It is also not possible to develop and remove the film with acid, and can only use a liquid that is not corrosive to aluminum to develop and remove the film. There are two commonly used products at present: 1) LPR-820N liquid photosensitive varnish, colorless and transparent, developed with AL-001 aluminum special developer, after etching, it can be directly electrophoresed for coloring and high temperature baking, no need to use caustic soda to remove the film The final product is obtained; 2) The LPR-805 liquid photosensitive acid and alkali resist ink has the dual functions of acid and alkali resistance. Films such as cyclohexanone, 783, etc., developer and film removal solution can be recycled. It can be used for both acid etching and strong alkali etching. After removing the film, it has no effect on the substrate. It is mainly used for the etching of precision metal aluminum anti-corrosion patterns.