Tinplate printing
1. Selection of ink printing:
After the tinplate has been treated by the inner coating and outer coating process, it can be printed on the machine. Because the tinplate surface is smooth, the adhesion performance is low, and it has a certain hardness and thickness, offset printing is generally used for tinplate printing. The printing principle: oil and water are incompatible. , Dot conformation and color formation, selective adsorption. Tinplate lithographic printing is basically the same as sheetfed offset printing, but due to the particularity of tinplate, tinplate printing is also different from ordinary offset printing, mainly in the following aspects:
1) Printing ink
(1) The drying and heat resistance of the printing ink, the curing of the printing ink must be heated and dried, so the white ink after heating is required to remain unchanged, not yellow, the color ink will not fade or change color, and the varnish will not lose its gloss. Iron printing ink generally needs to be fixed at 150 degrees Celsius for 10 to 12 minutes. Therefore, the heat resistance of the ink is more important.
(2) Process resistance, tinplate products need to go through processes such as stamping, punching, bending, flanging, and sealing, so the ink layer on the surface of the tinplate should have a strong structure, and the printing ink is required to have good adhesion and flexibility. properties, surface hardness and impact strength.
2) Varnish
After the tinplate printing is completed, a layer of varnish needs to be applied to increase the gloss and scratch resistance of the tinplate surface, and at the same time increase a certain hardness, so that the printing surface coating film has certain flexibility and corrosion resistance. The varnish should have the following functions:
(1) It has high hardness and strong adhesion, and can withstand the processing deformation of the subsequent process.
(2) The color retention performance is good, and the solvent in the varnish cannot cause the ink to bleed or fade.
(3) Matching with white paint or primer, can not corrode white paint or primer.