Effect of Coating Material of Ink Jet Printing Paper on Printing Quality and Stability (Part 2)

2.3 Effect on Printing Performance

The performance of an ink jet pigment is good for its printed image. The test pattern was printed on coated and calendered paper. FIG. 2 shows the ink density values ​​of the four colors of blue, red, yellow, and black (CMYB). The performance of all three SiO2 particles was compared. It can be seen from FIG. 2 that the concentration of the colloidal SiO2 and the sintered SiO2 black pigment ink is slightly higher.

Figure 2 Ink Concentration - Epson Press

In addition to cationic mordants, these pigments showed poor water resistance in the tests. Particle structure and pH have no effect on water resistance, which is controlled by the surface chemistry of SiO2. The addition of a cationic polymer such as poly DADMAC can improve the water resistance of these three particles, however, the colloidal SiO2 and sintered SiO2 particles reduce their surface gloss.

The study of print characteristics by image analysis techniques further illustrates the differences among the three SiO2 particles. Table 2 shows the image analysis results of the Epson printer.

Table 2 Black Dot Characteristics - Epson Presses

From Table 2, it can be seen that the area of ​​the dot from top to bottom is significantly reduced. The smaller area is better, and the print resolution can be improved without losing the ink density. The test results of the dot roundness values ​​show that the sintered SiO2 coating has a more uniform coating structure. In contrast, the smoke SiO2 has a lower dot area due to its higher porosity, but irregular smoke particles produce a higher dot roundness value resulting in uneven coating.

Figure 3 shows the porosity of the three SiO2 particles. The porosity of colloidal SiO2 and sintered SiO2 is lower than that of smoke SiO2. This data is consistent with the observed dot area results.

Fig. 3 Coating porosity

The porosity of the colloidal SiO2-based coating is created by the interstitial porosity created by the spherical particles during the filling process. Sintered SiO2 with intercellular particle porosity is expected to have more porosity, but its porosity is only about 10% higher than that of colloidal SiO2. This may be due to the degradation of certain sintered SiO2 to its colloidal raw material.

Smoke SiO2 exhibits the highest coating porosity. The final image quality requires a balance between coating porosity and coating uniformity. Although the print quality of colloidal SiO2 and sintered SiO2 coatings is acceptable, their lower porosity limits their effectiveness.

3 Conclusion

Colloidal SiO2 and sintered SiO2 particles have more advantages in the rheology, percentage of solid content, gloss, ink concentration, and dot roundness of the coating formulation than smoke SiO2. However, its coating exhibits a lower porosity. In contrast, smoke SiO2 with a rigid, irregular shape can produce more porous layers. However, it also reduces the gloss and the solids content of the coating formulation. In order to obtain a low-cost, high-gloss ink-jet paint, all factors must be balanced.

Author: Ma Xin
Source: "International Paper"