Five Key Factors of Adhesion Fastness of Screen Printing Inks (Bottom)

In the ink production and formulation process, the solvent also affects the adhesion effect. We know that the solubility parameters of the resin and the solvent used are similar, and the solubility parameters of the substrate must be considered simultaneously. However, for plastic screen printing inks, it must be considered from other screen printing effects.

● Solubility parameters of resin and solvent are similar, which is conducive to dissolution.

● The solubility parameters of plastics and plasticizers are similar to those for increasing plasticity.

● The solvent of the ink is similar to the solubility parameter of the plastic, which is favorable for the attachment effect, but it is necessary to prevent the plastic surface from being excessively eroded by the ink solvent (even causing the plastic to deform).

● The use of excessively high-boiling solvents will reduce the adhesion effect.

● Improper use of solvents has poor adhesion. The use of solvents must be considered from a variety of factors, so the solvent used for printing inks should use more than three kinds of mixed solvents.

● The solvent and binder in the ink (high molecular polymer) are in contact with the substrate, and the surface of the substrate is dissolved and dissolved, so that the substrate and the binder in the ink are mutually diffused to form a layer of mixed unbounded line. The layer causes the disappearance of the interface, forming a strong bond between the ink and the substrate.

Third, the impact of additives in the ink

The variety of additives in the ink is mainly used to improve the performance of the ink. Additives that have an effect on the adhesion are as follows:

Cross-linking agent: The cross-linking agent can not only improve the adhesion of the ink, but also can greatly improve the hardness, solvent resistance, water resistance and drying speed of the ink.

Coupling agent: Coupling agent to promote the coupling of resin and macromolecule printing materials in the ink, can improve the adhesion of the ink.

Plasticizers: Plasticizers can improve the softness of the ink film and at the same time have an advantageous effect on the adhesion.

Fourth, the impact of ink performance

Screen printing ink has good wettability and is beneficial to the adhesion effect. If the substrate has not been wetted, the ink has dried or has been cured, the adhesion effect is poor, which involves the problem of ink fluidity. Flow performance is also closely related to other factors of screen printing. Here only ink adhesion problems are discussed.

● The ink must be formulated to control the volatilization rate of the solvent. The presence of a high-boiling solvent is beneficial to leveling.

● Use an appropriate molecular weight of the resin to formulate the ink, the higher the viscosity of the resin, the more unfavorable the ink leveling.

● Add appropriate leveling agent to the screen printing ink.

Fifth, the influence of substrates on the fastness of adhesion in the printing process

The material of the screen printing substrate directly affects the adhesion of the ink. Designing special inks for different substrates is a good way to overcome this effect. Plastic inks, paper inks, textile inks, wood inks, metal inks, leather inks, printed circuit board inks, ceramics, and glass inks are commonly used. For different printing materials, the ink of the corresponding adaptability is selected, and the fastness of the ink on the printing material can also be improved by means of changing properties of the screen printing material, surface treatment and the like.

● When printing on printed materials, it is very important that the printed materials are subjected to strict degreasing and pre-press inspection before printing. When the surface of the substrate adheres to oils, adhesives, dust, etc., the adhesion between the ink and the substrate is not firm. Inadequate surface treatment of plastic products prior to printing can also result in ink adhesion problems. Therefore, cleaning the surface of the screen printing substrate can also improve the adhesion of the ink on the surface, and the presence of dust, grease, and dirt on the substrate makes it difficult for the ink to adhere and must be removed.

●The screen printing material is a polyethylene film. In order to improve the adhesive performance with the ink during printing, surface flame treatment must be performed; if it is a metal material, it must be degreasing and dust removal before it can be printed. Since the metal cannot absorb ink after printing Membrane, only the use of oxidized conjunctiva, volatile drying methods, and in accordance with the required temperature of the ink drying process Caixing. Improper drying can also cause the ink film to fall off. In addition, in order to make the textile waterproof in the textile printing, silicon processing is generally required in order to ensure good ink adhesion during printing.

● The surface of the substrate will be oxidized and the surface state of the substrate will be changed. This will greatly increase the adhesion of the ink. Generally, for substrates that are difficult to screen, such as olefins, screen printing can be performed smoothly after chemical treatment, flame treatment, and electronic impact.

● Items such as glass and ceramics must be cooked at high temperatures after screen printing. Therefore, as long as the temperature is properly treated, the adhesion of the ink layer will be good. A simple method to check the adhesion of the ink film is good and bad: glass and ceramic prints are exposed to the rain, to see if the ink is easy to peel off. When the printed material is paper, in order to test the fastness of the ink, the printed surface can be repeatedly bent to see if the ink layer at the fold is peeled off. If the ink is peeled off, then the fastness of the ink is poor, and vice versa.