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Screen printing ink performance introduction.


1. Viscosity:
Viscosity, also known as internal friction, is the pressure caused by the corresponding movement of one layer of liquid against another. This is a characteristic of the internal structure of a liquid that prevents it from flowing. Printing ink viscosity is generally indicated by "poisons" and "centipoisons". The viscosity of the printing ink is about 4000 to 12000 cm.

The viscosity of the printing ink is too large, and the lubrication of the substrate is poor, and it is not easy to migrate to the substrate according to the screen printing ink. It leads to difficult packaging printing and inking.

The viscosity is too small, which will lead to the expansion of the impression, causing the printing wire frame to join and become scrap.

The viscosity index value requires accurate measurement with a viscometer.

The relationship between viscosity change and packaging printability is: the more stable the viscosity of the printing ink on the screen screen, the better, but the faster the viscosity increases after it is transferred to the copy. Compressibility is bad for the front and beneficial for the back, so moderate compressibility is available, and cutting variation is harmful to packaging and printing.

Add organic solvent, paint thinner or viscosifier to reduce viscosity; Add filler, color paste, silicide, can improve the viscosity.

2. Compressibility:
Compressibility refers to the ability of a liquid to recover its original viscosity after its viscosity is reduced due to ground stress. In the case of screen printing ink, the main performance is that the printing ink thickens after standing still for a certain time, the viscosity increases, and becomes thinner after stirring, and the viscosity is also reduced. Because the appearance design of the pigment particles in the printing ink is irregular, although it adsorbs a layer of interconnecting material, it is also an irregular sphere. Therefore, after standing still for a certain period of time, the pigment particles will touch or be very close to each other, resulting in mutual attraction, blocking the free movement of particles, and the printing ink will become thick and sticky.

However, this kind of temporary stable structure, after being stirred by external force, is quickly affected, lifting the mutual attraction between the particles, the random fitness movement of the particles is repaired, the circulation is improved, the printing ink becomes thinner, and the viscosity is reduced. The smaller the compressibility of screen printing ink, the better. In order to solve these adverse conditions, before printing, it is necessary to completely mix the printing ink, normalize the repair, and then carry out packaging printing.

The more irregular the pigment particles in the printing ink, the more porous the multi-foot worm structure, such as black ink, its compressibility is large. On the contrary, such as yellow ink, its compressibility is small. The interconnecting material in the printing ink is more, the color paste is less, and the compressibility is small, on the contrary, the compressibility is large. In addition, the interconnecting material is not the same as the harm to compressibility is also large, such as the printing ink made of converged edible oil, its compressibility is small, such as the polymer material epoxy resin as the interconnecting material, its compressibility is large.