Issues To Consider When Choosing Screen Printing Inks

In industrial screen printing ink applications, ink selection is not only based on color requirements, but must also be compatible with equipment characteristics, substrate types, environmental conditions, and production speed. From an engineering perspective, a suitable screen printing ink system must achieve a balance between printability and functional performance.

1. Drying Performance (Ink Drying Behavior)

The requirements for drying performance in screen printing are: the ink should not dry and form a film on the screen for a relatively long time, but after printing, it should dry as dry as possible on the substrate. For multi-color continuous printing, the requirements for the drying performance of screen printing inks are even higher.

2. Tackiness / Stringing Property (Ink Drawback Control)

Because the binder in the ink has a large molecular weight and strong viscosity, many fine ink threads appear on the back of the screen when the printing plate is lifted; this phenomenon is called stringing. This is a highly undesirable phenomenon in screen printing, as it not only easily causes the printed material and the screen to stick together, but can even make screen printing impossible. Therefore, screen printing inks are required to have the basic property of not exhibiting stringing during the printing process.

3. Particle Size (Fineness of Dispersion)

Particle Size	Result
Too large (>45 μm)	Mesh clogging, incomplete transfer
Too fine (<10 μm)	Excess flow, loss of sharpness

Design Rule: Particle size should be ≤ 1/4 of mesh opening size.

Fineness refers to the size of pigment and other solid particles in the ink, and also indicates the uniformity of their distribution in the binder. The fineness of screen printing inks is generally between 15 and 45 μm. If the fineness is too high, it will cause smudging during printing, preventing the pattern from being printed. If the screen mesh is coarser, the fineness can be increased accordingly. Generally, coarser particles should be less than one-quarter of the mesh area.

4. Plasticity

Plasticity refers to the property of a material that, after being deformed by external force, can completely or partially retain its deformation. Screen printing ink is a viscous suspension colloid between a fluid and a semi-solid, thus possessing both fluidity and plasticity. The lower the content of pigments and other solid materials, the thinner the ink and the lower its plasticity. Printing inks require a certain degree of plasticity to ensure printing accuracy; otherwise, printed lines are prone to enlargement.

5. Thixotropy

Thixotropy refers to the property of a fluid to change its flow properties under the influence of external forces. For example, in screen printing, the reversible phenomenon of ink thickening after standing for a certain period and thinning again after stirring can be explained by the concept of thixotropy. The lower the thixotropy of screen printing ink, the better. To eliminate this adverse factor, the ink should be thoroughly stirred before printing.

6. Viscosity (Flow Resistance Control)

Viscosity is the resistance to fluid flow, also known as the coefficient of internal friction or viscosity coefficient. If the ink viscosity is too high, it will not easily transfer to the substrate through the screen, causing printing difficulties and incomplete prints; if the viscosity is too low, it will cause the print to expand, affecting the printing quality and even resulting in defective products.

System-Level Insight: Interdependence

Parameters are not independent: drying rate affects viscosity stability, and particle size influences flow behavior. Selection must be treated as a system-level engineering decision.

Only when these parameters are properly matched can stable, high-quality printing be achieved.