When arranging the printing color sequence, the matte ink should be arranged in the last color printing. For example, when printing a cigarette label containing white, red, pattern hot stamping and matte effect, the general color sequence is to print white and red ink first, then hot stamping, and finally print matte ink. Because the matte ink is colorless and transparent, printed on the surface of gold and silver cardboard, it can transmit the inherent metallic luster of the printing material to achieve the printing effect of imitation metal etching. Moreover, the final printing of matte ink can also reveal the ink color of the previous printing.
(5) Curing method
Use a high-pressure mercury lamp to cure. The lamp life is generally 1500 to 2000 hours, and it needs to be replaced frequently. The price of domestic lamps is about 1,000 yuan each; the price of imported lamps is about 3000-4000 yuan.
(6) Printing pressure
When printing matte ink, the pressure of the squeegee should be slightly higher than that of printing ordinary color ink, and the pressure should be kept the same.
(7) Printing speed
The particles of the matte ink are large. In order to make the matte ink fully penetrate the mesh during the printing, the printing speed should be lower than that of other inks. Generally, the printing speed of other color inks is 2500 ± 100 sheets / hour; the printing speed of matte inks is generally 2300 ± 100 sheets / hour.
(8) Online version requirements
Imported plain weave nylon mesh with a mesh size of about 300 mesh is generally used, and the tension of the stretched mesh is uniform, and the deformation of the printing plate must be strictly controlled during the printing process.
5. Common faults and solutions
(1) Poor metal texture
Cause: The thinner added in the ink is not suitable; the power of the UV lamp is insufficient; the quality of the printing material is poor.
Solution: Add the thinner matched with the matte ink before printing; the amount of thinner is accurate and the stirring is sufficient. In the curing process, the power range of the light source should be selected according to the thickness of the ink layer and the speed of the light curing machine. The power of the light source should be 0.08 ~ 0.4kW. In addition, the printing material with high metallic luster should be selected, the surface must not be scratched, and it has appropriate tensile strength and high temperature resistance.
(2) The matte surface of the tobacco standard is rough and the particles are unevenly distributed
Cause: Inconsistent printing pressure.
Solution: The length of the scraper should be slightly larger than the width of the printed substrate. Right angle scraper can be selected for cigarette label printing, but the hardness of rubber scraping should not be too high, the general hardness is HS65.
(3) The ink dries on the screen
Cause: Natural light direct screen. Because natural light contains a large amount of ultraviolet light, it is easy to cause the curing reaction of the photosensitizer in the ink. The paper surface or ink contains impurities.
Solution: Avoid direct sunlight on the printing plate; choose paper with high surface strength; keep the printing environment clean.
(4) Printed matter adhesion
Cause: The ink layer on the printed matter is not completely cured.
Solution: Increase the power of the light tube of the light curing machine; reduce the running speed of the light curing machine; reduce the thickness of the ink layer on the premise of meeting the printing requirements.
(5) Sticky version
Cause: Incorrect positioning of the paper, improper adjustment of the gripper of the impression cylinder.
Solution: calibrate the paper positioning system, adjust the position of the gripper to prevent the paper from rotating with the roller.
(6) Cracked printing plate
Cause: Excessive printing pressure and uneven tension on the stretched web.
Solution: Adjust the pressure of the scraper evenly; keep the tension of the stretched net uniform; it is best to choose imported net cloth.
(7) Hair on the edges of the text
Cause: The viscosity of the ink is too large.
Solution: Add appropriate thinner to adjust the viscosity of the ink; avoid ink drawing.
Shaanxi University of Science and Technology, Guo Linghua, Xi'an University of Engineering Science and Technology, An Xiaoyan
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