Discussion on Surface Printing Methods of Paper Mold Sales Packaging Products (in Chinese)

3, paper packaging products surface printing method

According to the printability of the paper moulding material and the structural characteristics of the paper moulded product (printing technology can be used to complete the decoration of the surface of the printing. A printing machine can print 8000-10000 times in 8 hours (4-6 times) This is a small printing product with a small print area and a varied geometry, such as sales of paper packaging (pad printing is an ideal printing method.)

3,1 principle of printing technology

Pad printing belongs to indirect printing. It uses a gravure plate, which is pressed into the plate by silicone rubber hemispherical printing heads. The graphic on the plate is transferred to the substrate to complete the graphic reproduction. That is, first apply the ink on the corroded copper or steel gravure or photosensitive gravure, scrape off the excess ink with a squeegee, leaving only the ink in the concave graphics part, and then give the silicone rubber print head Pressure sticking ink, transfer to the multi-faceted, multi-curved surface, multi-angle plane on the substrate, the uneven surface of the irregular multi-color printing. The printing principle can be expressed as Figure 1:

In Fig. 1(a), the printing and wiping device is moved to the right, and the ink is scraped by a doctor blade to scrape the ink on the blank portion of the gravure. (b) Move the print head downwards to exert a certain pressure on the gravure, transferring the ink in the gravure part to the print head. In (e) the head is raised and the printing squeegee moves to the left. On the one hand, the ink is applied to the layout by the ink brush, on the other hand, the printing head moves downwards, and a certain pressure is applied to the surface of the printing material to enter the state (d) to complete the printing. Then the printing head moves upwards and returns from the (a) state to the working state of a.

The gravure used is generally made of steel or copper plates. The production is divided into two stages: the pre-processing of plates and the production of gravure plates. The gravure is produced by gravure etching (the roughness of the surface of the substrate determines the concave depth of the gravure image. Generally, the depth of the concave surface is 0.015--0.035mm. If the printing surface is rough, the concave depth of the image is 0.04. -0.15mm is suitable.The metal plate has a high resistance to printing force, up to 1 million printing.Also can choose the lower cost resin gravure, its resistance to printing force 5000-10000 India.

The transfer head is made of elastic material such as silicon rubber and polyurethane (is an important part of the pad printer. The pad is the carrier of the ink image, and the surface is achieved by embracing the surface of the substrate. Printing, it directly affects the transfer rate and printing quality of inks.The surface tension of silicone rubber is low (Incorporation of phenyl and vinyl groups in the polymer chain, increase the surface tension, improve the adsorption of ink and its own Resistance and aging resistance: The printing head is required to have good elasticity (elastic modulus parameter 0.005) and certain softness (about 50 Shore hardness), which can be divided into soft-type printing head and hard-type printing In practice, soft-type printing heads are used for curved printing (hard-type printing heads are used for flat printing. Squeegee is another important part of the pad printing machine (requires good straightness and reasonable elasticity. Different thickness, the squeegee can be divided into thin 0.2mm, thick 0.5mm, special thickening, printing according to the printing requirements of the substrate to be selected.

Pad printing ink belongs to the category of screen printing ink (fast-drying solvent type. It requires fast solvent evaporation, high viscosity, strong coloring power, good fluidity and filling performance. This is an important condition for ensuring printing quality. Its drying speed is very high. Fast (The time is generally no more than 15 seconds, multi-color overprinting is possible.
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