Special ink printing color decoration--troubleshooting (2)

5. Floating color, color layering

Due to the difference in size, shape, density, dispersibility, and cohesion of the pigments in the ink, the pigments on the surface and the underlying layer of the ink film are unevenly distributed, resulting in a phenomenon in which the hue of each layer is different.

the reason:
In the process of formation of floating color and ink film, the distribution of the pigment in the solvent is inconsistent, and the ink formulation and the ink distribution process are unreasonable.
(1) When the ink with two or more pigments is blended, since the solvent volatilizes in the interior of the ink layer and the surface is inconsistent, convection is likely to occur and a floating color phenomenon occurs;
(2) The density of pigments in the ink varies greatly;
(3) The operating method and equipment are not suitable for use.

Prevention:
(1) Improve the ink formulation and manufacturing process (such as selecting pigments that are not easily floatable, easily dispersible, and improving the pigment dispersion process);
(2) Adding anti-floating agents, such as silicone oil, has a significant effect on preventing floating color;
(3) Select the appropriate modulation method and equipment.

6. Color uneven (color hair flowers)

The color of the ink film is locally uneven, and the phenomenon of spot printing, stripes, and hue appears. It is generally caused by improper printing operations of the ink and the effects of ink components and certain substances.

the reason:
(1) Insufficient dispersion of the pigment in the ink or insufficient mixing of two or more color paints when mixed with each other;
(2) Insufficient solvent strength or inappropriate working viscosity of the solvent used;
(3) It is printed too thickly so that the pigment in the ink film produces "convection" in the surface;
(4) Gases (such as ammonia, sulfur dioxide, etc.) and acids, alkalis, and other substances that have come into contact with the ink film at the job site.

Prevention:
(1) Use pigments with good dispersibility and mutual solubility;
(2) Select the appropriate solvent and use printing viscosity and film thickness that meet the process requirements;
(3) The same type of ink should be used when formulating the multicolor paint, using the same type of ink produced by the same manufacturer.

7. Bad gloss

The ink layer did not reach the desired gloss after drying, and the ink layer showed a drop in gloss soon after printing.

the reason:
(1) Improper choice of pigment, poor miscibility of the resin, improper solvent selection;
(2) The surface of the printing ink absorption, uneven;
(3) The surface of printing is rough and uneven;
(4) Insufficient ventilation during drying of the ink layer;
(5) Printing under high temperature, high humidity, or extremely low temperature.

Prevention:
(1) Select the appropriate ink and solvent through the test;
(2) Printing primer ink to improve the roughness of the surface of the printing surface, ie roughness;
(3) Strictly control the ink layer drying conditions, and the ventilation in the drying room should be appropriate;
(4) Pay attention to the control of the printing process to ensure uniform thickness of the ink layer;
(5) Polishing after the ink layer has dried and matured;
(6) Control the environmental conditions of the printing job.


Author: Pengming Gang Source: special screen printing 2005.10