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The characteristics of 7 kinds of soft package printing substrates!
When printing on flexible packaging printing substrates, gravure printing should pay attention to the characteristics of the film's surface tension, heat shrinkage, surface smoothness, deformation, high temperature resistance and solvent solubility to the film. The control of these characteristics is an important factor that affects the quality of film printing.
The following are the printability of several films:
1.BOPP
For the most common flexible packaging printing substrates, pay attention to surface tension, heat shrinkage and surface smoothness, and there must be no fine pits, otherwise it will affect the shallow mesh part, the printing tension and embossing force are moderate, and the drying temperature is below 80 ℃.
2.BOPET
Because PET is usually thin, 12μm, it is easy to wrinkle, it needs a lot of tension when printing, and it has certain selectivity to ink. It is best to use special ink. It is easy to peel off with general printing ink, the film is static electricity, and it is easy to block. Plates, fluff, and scratch marks (filaments). In addition, the high humidity in the workshop during printing has certain advantages, and it can withstand higher drying temperatures.
3.BOPA
The biggest feature of BOPA film is that it is easy to absorb moisture and deform. This key point should be grasped when printing.
(1). The size of BOPA changes after moisture absorption, so it should be unpacked and used, and the moisture-proof packaging should be sealed immediately with the remaining film.
(2). One to two-color preheating and dehumidification can be carried through in air during production, and the temperature is 60 ～ 90 ℃.
(3). It is best not to print nylon film when the relative ambient temperature is greater than 85%.
(4). The printed BOPA should be immediately transferred to the next process for compounding. If the country cannot compound immediately, it should be sealed and packaged. The storage time is generally not more than 24 hours.
(5). The printing tension and printing pressure are appropriate.
4.K coating film
Key points for K-coated film printing: Because the K-coated film is either roll-coated or spray-coated, its thickness uniformity is not very good, the surface is uneven, and the PVDC is just brittle, the printing tension and printing pressure should not be too great during printing Large, difficult to overprint, and poor ink transferability. It is easy to produce dots when printing a light screen (some dots are lost). A high hardness pressure roller is required for printing. In addition, it is selective for the solvent. The improper use of the solvent may dissolve the layer. The residual solvent of the printed film is large and it is easy to stick. Therefore, special attention should be paid to drying and cooling.
5. Matting film
The printing of matting film can be carried out by OPP process on its glossy surface, but because the matting layer on its surface cannot withstand high temperatures, it is necessary to control the drying temperature.
6. Pearlescent film
The pearlescent film uses surface printing ink for surface printing, and try to use surface printing ink with good transparency. When the heat shrinkable film is printed, a very low drying temperature should be used. A special heat shrinkable ink should be selected (the printed ink should be able to shrink by heat without falling). If the PVC heat shrinkable film also needs to consider the solubility of the solvent in the film.
7. CPP, CPE
The unstretched PP and PE films have very little tension during printing, which makes it difficult to overprint. When designing a pattern, the printing deformation must be fully considered.