Solvents are indispensable materials in screen printing and have a crucial influence on the quality of screen printing and quality of printed matter. In screen printing, solvents and screen printing inks are closely related and must be given full attention. Here are some simple explanations.

1. The function of solvent in screen printing

(1) Dissolve resin: Dissolve in different solvents (polar, non-polar) according to different resin requirements.

(2) Liquidity: Different manufacturers produce similar products with different solvency, which directly affects the viscosity of the ink.

(3) Gloss: The same or different solvents with different volatilization speeds will cause fog and whitening of the ink film when it is released in the printing ink film, thereby affecting the gloss of the printed surface.

(4) Drying time: Since different printing methods are selected during the printing operation, as well as the differences in the printing environment, climatic conditions, and formulation requirements, the boiling point of the solvent is different to provide an appropriate drying time.

(5) Residual of the solvent: The low-viscosity solvent partially contributes to the long open time of the ink film and reduces the residual solvent.

2. Setting of Screen Printing Ink Characteristics by Solvent

(1) Solvent: The solvent used to dissolve the stable viscosity of the resin in accordance with the basic conditions of the ink quality when the ink is produced.

(2) Co-solvent: Solvents with good solvent power in the main solvent, but with some disadvantages in other conditions.

(3) Diluent: The resin of the ink itself does not have a dissolving power, and it has a dissolving function after being mixed with the main solvent to reduce the ink viscosity. Diluted ink effect.

3. Solubility of solvents and the relationship between screen printing

(1) For the ink itself, the good dissolving power makes the appearance of the ink uniform, so that the ink has a stable viscosity and fluidity, is not easy to gel, and the effect of dilution and dispersion can be fully obtained by adding an appropriate cosolvent.

(2) For printing equipment: Adding improper solvent can increase the friction of the equipment and make the printing equipment depreciate faster; at the same time, it may cause the ink plug to cause frequent downtime. Start-up operation to accelerate the wear of parts and reduce production efficiency.

(3) Relationship with printing ink film: The choice of solvent must fully consider the glossiness, flatness, residual property, fastness, ductility and adhesion of the printing ink film.

4, select the solvent considerations

(1) The solvents commonly used in screen printing inks are roughly classified into ketones, alcohols, benzene, esters, alkanes, and five types. The main function of the solvent is to dissolve the resin and dilute the ink. Various inks should be carefully selected with appropriate solvents. For example, in PVC systems, ketones can be dissolved, benzene can be slightly swollen, alcohol can be gelled, and care must be taken when selecting.

(2) Dissolving power of cosolvent: The function of the cosolvent is similar to that of the main solvent, so be sure to use the correct cosolvent so as not to cause gelation, loss of fluidity, and stickiness of the ink.

(3) Solvent original specification purity (percentage): The original specification and purity of the solvent directly affect the degree of ink dissolution and dilution. If it is not the original solvent, it may contain a small amount of water or impurities, and it will have a very bad effect on the quality of the printed matter, which may cause the printing surface to lose its luster, the adhesion becomes worse and the phenomenon of stencil printing and the like.

(4) The evaporation rate of the solvent directly affects the drying speed of the ink. Due to the rapid development of printing technology and printing speed, it is necessary to carefully select the appropriate solvent, otherwise it will affect the printing workability, causing the ink to print too quickly, too slow, it is easy to stick back and so on.

(5) The dispersibility of the solvent to the colorant: The choice of the solvent has a close relationship with the dispersion of the pigment contained in the ink. If the wrong solvent is used, the pigment in the ink will also agglomerate (anti-coarse) and affect the color rendering power. , To reduce the color density, or even normal printing.

(6) Solubility of the Solvent to the Resin: In practical use for printing, if the solvent is poor in dissolving power, the resin or the ink will be solidified and the fluidity will be deteriorated.

(7) Solvent separation of colorants: In the use of color matching inks, if the wrong solvent is selected, the different colors in the ink will be dispersed inconsistently, resulting in color separation, floating color separation and other phenomena.

(8) When a cosolvent is used, if the dissolving power is too poor, the ink tends to lose its viscosity (poor fluidity), and wrinkles, adhesion, and deterioration of gloss tend to occur during printing.

(9) Drying speed of solvent Cost: The volatilization rate of the solvent during printing is too fast, which not only affects the normal printing process, but also causes the solvent to be used quickly and increases the cost. If the solvent is too slow, the production speed will be slowed down and the man-hour cost will be increased.

(10) Solvent preparation: The proportion of the solvent has a great influence on the dissolving power and speed. When the preparation is required, the main solvent and co-solvent components must be controlled according to specific requirements, so that the dissolving power and the drying speed can be adjusted according to the ink requirements.

(11) The relationship between the use of solvent and air humidity: If using a fast-drying solvent with printing ink, when the temperature is above 90%, the solvent will volatilize too quickly and absorb a large amount of water in the air, resulting in deterioration of the ink flowability and the printed matter. Lost gloss and poor adhesion.

(12) The appearance of the solvent: If the appearance of the solvent is poor (unclear or colored), it will directly affect the hue of the printed matter and the occurrence of color variation phenomenon. (Trancy)

Source: China Ink Technology Network