Special glossy printing technology (2)

3 pearl printing process

(1) Pearlescent printing requirements for paper

Pearlescent printed substrates can be paper and plastic film, but the amount of paper is large. The paper used for pearlescent printing should have a tight texture, good surface gloss, high smoothness, and poor ink absorption. Therefore, cellophane, coated paper and calendered white paperboard are generally preferred, followed by offset paper. For letterhead, writing paper, and newsprint paper with loose texture, poor surface gloss and smoothness, and strong ink absorption, it should not be used.

(2) Pearl ink printing method requirements for ink

The formulated pearlescent ink can in principle be applied to various printing methods, such as lithographic offset printing, flexo printing, gravure printing and screen printing. However, different printing methods have different requirements for pearlescent inks.

Offset offset printing. Choose pearlescent pigment particle size in the 10 ~ 12μm, particle size of 800 mesh; added in the ink is about 30%. The viscosity of the prepared pearlescent ink is preferably 5 to 30 Pa·s.

Flexo printing. The pearlescent pigments are selected to have a particle size of 20-40 μm, ie a particle size of 400 mesh; the addition ratio in the ink is approximately 10% to 20%. The viscosity of the prepared pearlescent ink is preferably 50 to 300 Pa·s.

When water-based pearlescent ink flexographic printing is used, it is better to use a laser-engraved ceramic anilox roller, and the mesh wall hole ratio should not be lower than 4:1. Whether it is printing on coated paper or film, when the printing speed is 50 to 100 m/min, the printing viscosity of pearlescent ink should be controlled between 40 and 60 seconds. The content of the corresponding pearlescent pigment in the ink should be ink. The content of 15% to 25%, if you need to adjust the ink viscosity during printing, you can use water in isopropanol (weight ratio of 2:1) or distilled water. The following table shows the relationship between the number of screens, printing materials, and printing methods. When printing with Iriodin pearlescent pigment inks, a 1.16 mm thin plate such as Du Pont "Cyrel PLS" should be used. Table 2-28 Number of Screens, Printing Materials, and Printing Methods

Table 2-28 Number of Screens, Printing Materials, and Printing Methods

Number of screen printing materials Printing method Iriodin pearl pigment grade 80 to 120 (1/cm) Smooth material Fine words and patterns, halftone version Particle size 5 to 25 μm 119, 120, 123, 201, 211, 223, 231, 302, 323 , 326, 520, 522, 52460-80 (1/cm) smooth material, coated paper and film full version, halftone version fine character and pattern particle size of 10 ~ 60μm 100,103,205,215,219,225, 235,300,303,306,309,500,502,50440～60(1/cm) Rough, easy-absorbing material Full-size particle size larger than 60μm153,163,249,259,289,299,351,355,530 532,534

Gravure printing. When gravure is printed, it is recommended to use 75 lines/inch or more of network cable with a corrosion depth of 25 μm or more, so that the pearlescent pigment can be filled into the gravure plate without dragging, weak printing, or unprinting.

Choose pearlescent pigment particle size size of 35 ~ 55μm, that is, the size of the particle size of 300 mesh; added in the ink is about 10% to 20%. If 30 to 40 lines/cm are used, it is better to use a plate with a depth of 35 to 40 μm. The viscosity of the prepared pearlescent ink is preferably 2 to 6 Pa·s. To achieve a good pearlescent printing effect, the proportion of pearlescent pigments should account for 15% to 25% of the finished ink.

It is recommended that the opening angle of the engraving is 120o, and the etching plate is used, and the engraving depth of the ink hole of the solvent ink is controlled to 50 [mu]m. For pearlescent pigments with particle sizes between 5 and 25 μm, it is recommended to use 70 line/cm engraving parameters; for high pearlescent pigments with particle sizes between 10 and 55 μm, it is advisable to use 60 lines/cm or more sparse engraving parameters.

The larger the pearlescent pigment particles, the coarser the network lines should be, and the deeper the corrosion depth should be. Table 2-29 shows the matching of pearl powder and roller engraving depth.

Table 2-29 Mixing depth of pearl powder and roller

Table 2-30 Causes and countermeasures of prints without pearlescent effect

(to be continued)