Screen printing due to the strong adaptability of the process of Photoluminescent film, can be light pressure, thick film, thick granule ink printing, so it is often used in all kinds of packaging printing decorative means. This paper introduces several new packaging screen printing decoration technology.
Luminous printing ink is a luminous material containing light storage ink. Light storage ink is made of luminescent pigments, organic resins, organic solvents and additives in a certain proportion, through special processing technology.
- Luminous pigment
Light storage pigment is a long afterglow luminous material, referred to as long afterglow material, also known as luminous material. Only when structural defects and impurity defects occur in the crystal lattice formed by such materials in the synthesis process can they have luminescence properties. The luminescence caused by lattice defects of materials is called self-excitation light, while the luminescence caused by impurity defects is called activation luminescence.
Luminous material luminescence is based on the principle of photoluminescence, its excitation light source is generally daylight and artificial light source, it absorbs the excitation light energy and stored, light excitation stop, and then the stored energy in the form of light slowly released. Absorption light luminescence storage re-luminescence, the process can be repeated infinitely many times, and the phone battery charging discharge recharging re-discharge of the repeated use of the process is similar.
This luminescent material glows in the dark environment without external light source, and its luminescence time is called afterglow time. Long-afterglow materials with better properties, such as silicate system long-afterglow materials with diverse colors, etc., the rare earth activated alkaline soil aluminate has the most excellent afterglow characteristics, which can achieve more than 20 hours of afterglow.
- Application of long afterglow materials
Long afterglow materials are widely used in a wide range of products, such as luminescent paint, luminescent ink, luminescent plastic, luminescent fiber, luminescent paper, luminescent glass, luminescent ceramics, luminescent marble, etc., which can be used in safety emergency, transportation, construction and decoration, etc. In the field of modern printing, it is suitable for the packaging and printing of official documents, securities, certificates and high-grade commodities such as cigarettes, wines, medicines and cosmetics.
- Preparation of storage ink
The following points should be noted when preparing light-storing ink:
(1) particle size of light-storing pigment
Storage pigment particle size should be controlled in 45 to 65um, so as to produce a practical storage ink.
(2) selection of resin
As the light storage material is alkaline, the color of the resin has an effect on its luminance, so the following two points should be paid attention to when selecting the resin.
Should choose colorless or light color, transparency good resin, varnish.
Should choose neutral or weak acid resin, varnish.
Resin varieties are epoxy resin (E440), polyurethane resin, amino varnish, polyester resin, acrylic resin, hydroxyl acrylic resin, acrylic polyurethane varnish (two components).
(3) the choice of ink
Usually according to different substrate to choose different types of transparent ink, such as substrate is a metal material, should choose metal ink, substrate is PVC material, can choose PVC ink.
(4) preparation method
(1) make storage ink should use glass or enamel containers.
(2) in order to make the light storage material evenly distributed, can use high-speed mixing method, but can not use the means of grinding.
(3) the relative density of light storage material is between 3.6 and 4.1, ink is easy to sink, can be added in the resin anti-precipitation agent, improve the storage life of light storage ink. There are no. 2 and no. 4 in domestic gas phase silica, among which no. 4 is better.
- Storage ink screen printing points
(1) the prepared ink viscosity is about 300-500pa ·s. In printing, the ink viscosity should be adjusted with diluent according to the substrate material and printing speed.
(2) when printing patterns or labels with light-storing ink, a polyester silk mesh with 200 mesh/inch or less should be generally selected. 80-120 mesh/inch silk mesh printing can achieve a better luminous effect.
(3) as far as possible in the white substrate printing light storage ink, so as to improve the printing graphics and text luminous effect and afterglow time.
(4) printing ink coating thickness is controlled at 130-150um, its luminous effect is the best, so 80 mesh/inch screen printing twice (if using thick version, printing once), you can achieve this thickness.
(5) when the substrate is a transparent object, printing light storage ink should be printed all over the white ink, so as to improve the luminous effect.
- Examples of application
(1) ink formula (mass ratio) ink: light storage material = 50:50
(2) printing method
(1) use 100 mesh/inch screen seihan.
(2) in copperplate printing on adhesive paper twice.
(3) value of the afterglow brightness of the printing ink layer.
Use crystal glue (main composition is high polymer transparent colophony) the method that gives the crystal glue droplet effect that has stereo feeling to print on gold, silver card paper calls crystal glue printing. The viscosity of the crystal glue is very high, printing ink layer is very thick, the printing pressure is large.
There are two kinds of crystal glue for printing: thermosetting type and UV curing type. If thermosetting type crystal glue is used, the screen should be properly heated during printing, and the printing should be dried immediately on the infrared hot drying device. Now the market launched a new UV curing type of crystal salt film fast, wear resistance, brightness is also better. In addition, in order to enhance the stereoscopic effect of the printing of the crystal gum, the crystal gum is dried into the crystal drop shape before leveling.
Crystal gloss printing
Surface transparent crystal gloss printing refers to the production of print, ink layer of crystal flash material, or the sun light incidence Angle changes, can produce a colorful and sparkled special adornment effect, crystal flash material with polyester coating layer after coloring crushed into particles or with special flash fiber crushed into particles.
In the process of crystal luster printing with screen printing method, the crystal glitter particles are mixed into the linker to produce screen printing ink, which is directly printed to the parts that need to be decorated on the printed matter. It is worth noting that, because the flash crystal is contained in the ink layer, while taking into account the ink transfer factor, so you can not choose the flash crystal particles too thick.
Mirror ink printing
Mirror ink is metallic screen printing ink, is made of plastic resin mixed with special metal toner, is a solvent volatile ink, it is printed on the back of transparent plastic sheet, can get the metallic mirror printing effect, as hot stamping effect.
The main points of mirror ink printing are as follows:
(1) due to the viscosity of the mirror ink is low, should choose mesh number of higher screen, usually choose 270-300 mesh/inch polyester screen, tension should be slightly lower, coating solvent-based sensitive adhesive.
(2) the net distance should be smaller.
(3) choose a scraping knife with high hardness, whose hardness is usually hs80-85.
(4) as a result of the metal toner, plastic resin and additives, the relative density of different, storage ink components will be layered, so before use must be thoroughly stirred evenly.
(5) in order to prevent the occurrence of blocking network, should pay attention not to print in the air circulation.
(6) in order to prevent the ink absorption of water caused by the decline in the gloss of the mirror, in the printing and storage should avoid moisture, immediately after printing should be dry in a low temperature environment.