1. Classification of plastic screen printing inks
(1) Classification by Sheet
According to the chemical name of the substrate can be divided into: polyethylene, polypropylene (non-polar) ink. Polyvinyl chloride, polystyrene, ABS polycarbonate (polar) ink. According to the form of the substrate can be divided into soft plastic ink and hard plastic ink.
(2) Classification by Drying
There are volatile drying ink, UV curing ink, and oxidation drying ink.
1 Volatile drying ink: It is the most used ink in screen printing. The composition of the ink film is mainly a polymer material, and the solvent is volatilized after printing, and the polymer material forms an ink film. This volatilization drying process is reversible, ie the dried ink film can be redissolved with a solvent.
After the ink is transferred to the substrate, there will be a solvent ink ink film, and the solvent volatilizes first. The solvent in the ink diffuses in the atmosphere due to the effect of vapor pressure, forms a liquid film on the surface of the ink film, and then volatilizes through the liquid film. In this drying process, the internal drying is generally slower, and it is sometimes necessary to accelerate the drying by blowing.
Volatile inks are widely used due to their ease of use and dryness.
2 UV curable inks (UV inks): UV inks can produce photochemical reactions that can be completely cured in a matter of seconds, and are increasingly used in plastic printing. The main components of inks are photopolymer resins, initiators, colorants, and additives. In principle, organic solvents are not used.
3 Oxidation-drying type ink: The ink contains a polymer with a relatively small molecular weight and oxidizes in the air to form a polymer film through a chemical reaction of heat, light or a reactive material. This type of ink generally requires heat to promote hardening after it is printed on the substrate surface.
2. Plastic screen printing ink must have the conditions
1 The ink should not dry the conjunctiva on the plate, but the requirement of printing on the surface of the substrate can be quickly fixed and dry, and it has good adhesion fastness.
2 ink should have a loose, short, thin, slippery characteristics, in order to ensure that the ink on the plate easily coated evenly. It is easy to pass through the net under low stress conditions. The printed artwork is required to be clear and there is no stickiness.
3 When the ink is coated on the printing plate, the viscosity, viscosity, and consistency of the ink should have a certain degree of stability, so as to ensure the consistency of the quality of the printed product and the smooth progress of the printing.
4 After printing, the ink on the plate should be easily cleaned to ensure that the plate can be reused.
5 To ensure that the printed product has a certain color concentration. For color patterns, ensure that they have a normal hue.
3. The main component of plastic screen printing ink
(1) Color
Includes pigments and dyes. In addition to the color development of the pigment in the ink, it also provides the hiding power of the ink. In addition, the light resistance, heat resistance, solvent resistance, and chemical resistance of the ink are also affected.
(2) Binder
The binder is a fluid component in the ink. It acts as a link, allowing solids such as colorants and fillers to be dispersed therein, facilitating the even transfer of ink during printing. Its other important function is to allow the ink to dry, fix and film on the surface of the substrate.
The linking material is a key factor in determining ink performance. Different types of inks usually use different types of linking materials. Links include resins, greases, solvents, etc.
(3) Additives
Auxiliaries are various additives added to improve various printability of the ink, and include defoamers, diluents, plasticizers, ultraviolet absorbers, and drying conditioners. Usually only added when printing.
