Screen printing due to process adaptability, can be light pressure, thick film, coarse-grained ink printing, it is often used in various types of packaging printed in the decorative means. This article introduces several new types of packaging screen printing decoration technology. Luminous printing The ink used for luminous printing is a light-storing ink containing a luminous material. Luminescent inks are made from luminescent pigments, organic resins, organic solvents, and auxiliaries in certain proportions through special processing techniques. Crystal glue printing The use of crystal glue (the main component is a polymer transparent resin) printed on the gold, silver card paper with a three-dimensional effect of crystal glue droplets called crystal glue printing. The viscosity of the crystal glue is very high, the printing ink layer is very thick, and the printing pressure required is large. Crystalline gloss printing Crystalline gloss printing refers to the fact that the printed surface of the produced product is transparent, and the crystalline layer of glittering material is contained in the ink layer. When the incident angle of sunlight or light changes, a brilliant and colorful decorative effect can be produced. The crystalline flash material is often formed of particles that are colored after the polyester sprayed layer is pulverized or particles that are crushed with special flash fibers. Mirror ink printing Mirror ink is a metallic screen printing ink. It is made of plastic resin mixed with special metal powder. It belongs to solvent evaporation type ink. It is printed on the back of transparent plastic film and can get metallic color mirror printing effect, just like hot stamping. effect. Source: Printing Technology Ningbo Yinzhou Hengxi Winbate Household Product Manufacturer , https://www.nbwinbate.com
1. Luminous pigments (light-storing pigments)
A light-storing pigment is a long-lasting luminescent material, referred to as a long afterglow material, also known as a luminous material. This type of material has structural defects and impurity defects in the lattice of the crystals formed during the synthesis process. The luminescence caused by the material lattice defects is called self-excitation light, and the luminescence caused by impurity defects is called activation luminescence. The actual application of various types of light-emitting materials is mostly the latter.
The glow of luminous materials is based on the principle of photoluminescence. The excitation light source is generally sunlight and an artificial light source (light). It absorbs the excitation light energy and stores it. After the light excitation stops, the stored energy is in the form of light. Release it slowly. Absorb light → light → store → re-light, the process can be repeated indefinitely many times, and the repeated use process of charging, discharging, recharging, and re-discharging of the mobile phone battery is similar.
This luminescent material emits light in a dark environment without an external light source, and its light emission time is called afterglow time. Long afterglow materials with good properties, such as long-lasting phosphors of silicate systems with a variety of luminescent colors, have the best afterglow characteristics of rare earth-activated alkaline earth aluminates and can achieve more than 20 hours of afterglow emission.
2. The application of long afterglow material The long afterglow material involves a wide range of applications, and its product types are many. The long afterglow material is made into luminous paint, luminous ink, luminous plastic, luminous fiber, luminous paper, luminous glass, luminous ceramic, Luminous marble, etc., can be applied to safety emergency, transportation, construction and decoration. In the field of modern printing, it is suitable for the packaging and printing of high-end products such as official documents, securities, documents, and high-grade tobacco, alcohol, pharmaceuticals, and cosmetics.
3. Preparation of Luminous Ink Preparation of the Luminous Ink should pay attention to the following points.
(1) The particle size of the light-storing pigment The particle size of the light-storing pigment should be controlled at 45 to 65 μm so that a practical light-storing ink can be prepared.
(2) Selection of Resin Since the light-storage material is a basic substance, the color of the resin has an influence on its light-emitting brightness, so the following two points should be taken into account when selecting the resin.
1 should use colorless or light color, good transparency resin, varnish.
2 Neutral or slightly acidic resin or varnish should be used.
Resin varieties are epoxy resin (E440), polyurethane resin, amino varnish, polyester resin, acrylic resin, hydroxy acrylic resin, acrylic polyurethane varnish (two-component).
(3) The choice of varnish is usually based on different substrates to choose different types of transparent varnish, such as printing materials for metal materials, metal varnish should be used, the substrate is PVC material, PVC varnish can be used.
(4) Preparation methods 1 Preparation of storage ink should use glass or enamel containers.
2 In order to evenly distribute the light-storage material, a high-speed stirring method may be used, but a grinding method may not be used.
3 The relative density of the light-storage material is between 3.6 and 4.1, and it is easy to sink when preparing the ink. The anti-precipitation agent (fumed silica, commonly known as white carbon black) can be added to the resin to increase the storage period of the light-storing ink. Domestic fumed silicas have No. 2 and No. 4 points, of which No. 4 is better.
4. Storage ink printing screen points (1) The prepared ink viscosity is about 300 ~ 500Pa · s, printing, according to the substrate material and printing speed, with thinner to adjust the ink viscosity.
(2) When printing patterns or logos with light-storing inks, polyester screens of 200 mesh/inch or less should be generally selected, and screens printed with 80 to 120 mesh/inch can achieve better light emission effects.
(3) Print the light-storing ink on the white substrate as much as possible to improve the luminous effect and persistence time of the printed graphic.
(4) When the thickness of the printing ink coating is controlled at 130 to 150 μm, the light emitting effect is the best. Therefore, the screen printing is performed twice with a 80 mesh/inch screen (if a thick plate is used, printing can be performed once), and this can be achieved. thickness.
(5) When the substrate is a transparent object, the white ink should be printed before printing the light-storing ink, which can improve the light-emitting effect.
5. Application Examples (1) Ink Formula (Quality Ratio)
PVC Ink (SS-777): Light Storage Material (PLO-7D) = 50:50
(2) Printing Method 1 A 100 mesh/inch screen was used.
2 printed on copperplate sticker paper twice.
(3) Afterglow Brightness Value of Printing Ink Layer The afterglow brightness value of the printing ink layer is shown in Table 1.
There are two types of crystal glue used in printing: thermosetting and UV-curing. If thermosetting crystal glue is used, the screen should be properly heated during printing. Immediately after the printing, dry it on the infrared heat drying device. The new UV-curable crystal glue currently on the market has a fast film-forming speed and better wear resistance and lightness. In addition, in order to enhance the three-dimensional impression of the crystal glue, the crystal glue is dried and formed into films before the leveling, and a crystal-like three-dimensional effect of droplets can be formed.
In the case of crystal gloss printing using a screen printing method, crystalline glitter particles are incorporated into a binder to produce a screen printing ink, which is directly printed on a printed article to be decorated. It is worth noting that because the flash crystals are contained by the ink layer and the ink transportability factor is taken into consideration, the flash crystals with too coarse particles cannot be selected.
Mirror ink printing points are as follows.
(1) Due to the low viscosity of the mirror ink, a mesh with a higher mesh number should be selected, usually a polyester mesh of 270-300 mesh/inch, the tension of the stretch net should be slightly lower, and the solvent-resistant photosensitive resist should be coated. .
(2) The network distance should be smaller.
(3) Select a relatively high hardness squeegee, usually the hardness of HS80 ~ 85.
(4) Since the relative densities of metal toner, plastic resin, additives, and additives are different, the components in the ink will be layered during storage, so be sure to mix thoroughly before use.
(5) To prevent the occurrence of plugging, care should be taken not to print in places where air flows.
(6) To prevent the decrease of specular gloss caused by the absorption of moisture by the ink, moisture should be avoided during printing and storage, and drying should be performed immediately after printing at a low temperature.