Plastic screen printing ink classification and necessary conditions

1. Classification of plastic screen printing inks

(1) Classification by substrate

According to the chemical name of the substrate, it can be divided into: polyethylene, polypropylene (non-polar) ink. Polyvinyl chloride, polystyrene, ABS polycarbonate (polar) ink. According to the shape of the substrate, it can be divided into soft plastic ink and hard plastic ink.

(2) Classification by drying method

There are volatile drying ink, ultraviolet curing ink, and oxidation drying ink.

â‘  Volatile dry ink: It is the most used ink in screen printing. The composition of the ink film is mainly a polymer substance, and the solvent volatilizes after printing, and the polymer substance forms an ink film. This volatile drying process is reversible, that is, the dried ink film can be re-dissolved using a solvent.

After the ink is transferred to the substrate, there will be a solvent ink film, and the solvent will evaporate first. The solvent in the ink diffuses in the atmosphere due to the effect of vapor pressure, forming a liquid film on the surface of the ink film, and then volatilizing through the liquid film. In this drying process, the internal drying is generally slow, and sometimes a blower is required to accelerate the drying.

Volatile inks are easy to use and generally dry faster, so they are widely used.

â‘¡Ultraviolet curing ink (UV ink): Ultraviolet ink can produce photochemical reaction, which can be completely cured in a few seconds, and it is used more and more in plastic printing. The main components of the ink are photopolymerizable resins, initiators, colorants and additives. In principle, no organic solvents are used.

â‘¢ Oxidation drying ink: The ink contains a polymer with a small molecular weight, which is oxidized in the air and forms a polymer film through the chemical reaction of heat, light or reactive substances. After this ink is printed on the surface of the substrate, it generally needs to be heated to promote hardening.

2. Requirements for plastic screen printing inks

â‘  The ink should not dry the conjunctiva on the printing plate, and when printed on the surface of the substrate, it can be quickly fixed and dried, and has good adhesion fastness.

â‘¡ The ink should have the characteristics of loose, short, thin and slippery, to ensure that the ink is easy to spread evenly on the printing plate. It is easy to cross the net under the condition of small stress. It is required that the printed pictures and graphics are clear and free from sticking.

â‘¢When the ink is coated on the printing plate, the viscosity, viscosity and consistency of the ink should have a certain stability to ensure the consistency of the printing quality and the smooth progress of the printing.

â‘£ After printing, the ink on the printing plate should be easy to clean to ensure that the printing plate can be reused.

⑤ Make sure that the printed matter has a certain color density. For color patterns, make sure that they have a normal hue.

3. The main components of plastic screen printing ink

(1) Color

Including pigments and dyes. In addition to the color development effect of the pigment in the ink, the ink has a hiding power. In addition, it also affects the light resistance, heat resistance, solvent resistance, and chemical resistance of the ink.

(2) Link material

The binder is the fluid component in the ink. It plays a connecting role, dispersing solid materials such as pigments and fillers in it, which facilitates the uniform transfer of ink during printing. Another important role is to make the ink dry, fix and form a film on the surface of the substrate.

The binder is the key factor that determines the performance of the ink. Different types of inks usually require different binder materials. The binder includes resin, grease, solvent, etc.

(3) Auxiliaries

Auxiliary agents are various auxiliary agents added in order to improve various printing suitability of the ink, and mainly include defoamers, thinners, plasticizers, ultraviolet absorbers, drying regulators and the like. Usually only need to be added when printing.

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