Because the heat-shrinkable film is a thermoplastic film that is stretched and oriented during the production process, and is shrinked by heat during use. Therefore, no matter which printing method is used for printing, the horizontal and vertical shrinkage rate of the material and the allowable deformation errors in the decorative graphics after shrinkage must be considered before the design of the surface pattern to ensure that the pattern that shrinks onto the container, Accurate restoration of text and barcode.
1. The direction of the pattern
Regardless of whether the heat shrinkable film adopts gravure printing or flexographic printing, the printing is mainly in the inner printing method, and it should be positive with respect to the pattern direction on the printing plate. There are also shrink films for surface printing. If this happens, the direction of the pattern on the printing plate should be reversed.
2. The level of the pattern
Due to the shortcomings of flexographic printing, if flexo printing is used for the shrink film, the image layer should not be too delicate, while using gravure printing can require a richer image layer.
3. Size design
The heat shrinkable film material used for printing has a lateral shrinkage rate of 50% to 52% and 60% to 62%, and can reach 90% in special cases, and a longitudinal shrinkage rate of 6% to 8%. However, when the film shrinks instantaneously, due to the limitation of the container, the horizontal and vertical directions cannot be completely contracted. To ensure the accurate restoration of the contracted patterns, characters and barcodes, the shape of the container must be taken into consideration, and the correct size and the Deformation rate. For heat-shrinkable labels that need to turn the sheet-like film into a cylindrical shape and use adhesives to seal the overlapping parts together, it should be noted that graphics are not generally designed at the sealing parts to avoid affecting the adhesion fastness.
4. Barcode placement
Generally, the bar code placement direction should be consistent with the printing direction, otherwise the lines of the bar code will be distorted, which will affect the scanning results and cause misreading. In addition, the color selection of label products should be based on spot colors as much as possible, and the production of the white version is necessary. It can be made into a full version or hollowed out according to the actual situation. The color of the bar code should follow the conventional requirements, that is, the color combination of the bar and the space should conform to the principle of bar code color matching. Print material selection. The printing of heat shrinkable labels has been briefly analyzed above. In addition to the quality of the printing process, the material plays a decisive role. Therefore, choosing the right material is the key. The thickness of the film material is determined according to the application field and cost of the heat-shrinkable label, the characteristics of the film, shrinkage performance, printing process and labeling process requirements. In general, the film thickness of shrink film labels should be 30 microns to 70 microns, 50 microns, 45 microns, 40 microns is more commonly used, depending on the labeling performance of the labeling equipment. For the selected label material, the shrinkage of the film material is generally required to be within the range of application, and the shrinkage in the transverse direction (TD) is higher than the shrinkage in the longitudinal direction (MD). The transverse shrinkage rates of commonly used materials are 50% to 52% and 60% to 62%, and can reach 90% in special cases. The longitudinal shrinkage rate is required to be 6% to 8%. In addition, because the shrink film is very sensitive to heat, it is necessary to avoid high temperatures during storage, printing and transportation.
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