Because the heat shrinkable film is a thermoplastic film that is stretched and oriented during the production process and contracted by heat during use. Therefore, no matter what kind of printing method is used for printing, before the design of the surface pattern, the horizontal and longitudinal shrinkage rate of the material should be taken into account, as well as the deformation error allowed in each direction of the decorative text after the contraction, in order to ensure the accurate restoration of the pattern, text and bar code on the container.
1, the direction of the heat shrink label pattern
Whether the heat shrink film adopts gravure printing or flexographic printing, its printing is mainly in the printing mode, and the direction of the pattern on the printing plate should be positive. Now there is also a shrink film printed, in this case, the pattern on the plate should be reversed.
2, the level of heat shrink film label design pattern
Limited by the shortcomings of flexographic printing, if the shrink film is flexographic, the level of the image should not be too delicate, and the use of gravure can require the level of the image to be richer.
3, the size of the shrink film label design
The horizontal shrinkage rate of the heat shrink film material used for printing is 45% ~ 52% and 70% ~ 78%, and it can reach 90% in special cases, and the longitudinal shrinkage rate is required to be 1% ~ 8%. However, when the film is contracted instantaneously, it is limited by the container, and the horizontal and vertical cannot be completely contracted. In order to ensure the accurate restoration of the pattern, text and bar code after the contraction, it is necessary to take into account the shape of the container and calculate the correct size and deformation rate according to the actual situation. For the heat shrink label that needs to turn the sheet film into a cylinder and seal the composite part together with an adhesive, it should be noted that the graphic is generally not designed in the sealing part, so as not to affect the bonding fastness.
4, heat shrink film label bar code placement
Usually, the direction of placement of the bar code should be consistent with the direction of printing, otherwise it will cause the line of the bar code to be distorted, which will affect the scanning results and cause misreading. The location of the bar code symbol should be determined in accordance with the principle of non-deformation, easy to read and plate making. That is, it is required to be set on the right side of the main display surface of the commodity packaging or the plane connected on the main display surface, and the back of the main display surface of the commodity packaging. Taking into account the characteristics of the printing process, the bar code direction should be corresponding to the printing direction, so that the printing deformation can only be displayed in the vertical position of the bar code, so as not to affect the accurate reading. Due to the differences in packaging methods and characteristics, the barcode printing position is also different. It is best to print the barcode on one side of the label, but the surface curvature of the barcode symbol should not exceed 30°; Bar code is usually the original large direct printing, and to enlarge or reduce printing according to the technical requirements of EAN organization, can not be carried out at will, generally stipulated that the zoom ratio should be controlled at 80% ~ 200%. Barcode scaling ratio has a great impact on the printing pass rate, when the scaling ratio is 100%, the printing pass rate is 97.3%; When the zoom ratio is 90%, the printing qualification rate is 95.7%; When the zoom ratio is 85%, the printing qualification rate is 25%; When the zoom ratio is less than 80%, the printing qualification rate is only 10%. Therefore, scaling printing is best done by the bar code film provider, if there is not enough place to place the bar code, the height of the bar code can be appropriately truncated, but the remaining height is not less than 2/3 of the original height. For printing heat shrink packaging materials, it is necessary to consider the position of the bar code after the shrinkage of the film, and calculate the vertical and horizontal contraction multiple in advance, so as to adjust it during plate making.