The quality of the bottom paper is the key to the quality of die-cutting. The thickness of the bottom paper. Flatness, fiber structure and strength directly affect die-cutting quality. The commonly used bottom paper is divided into two major categories, namely opaque backing paper and semi-transparent backing paper. Opaque paper-backed self-adhesive materials generally have a ration of more than 90g/m2, and have a certain degree of stiffness. They are suitable for sheet-fed printing and web-fed printing. Finished labels are mostly used for manual labeling. Transparent backing paper type self-adhesive material is generally weighed 60-70g/m2, the bottom paper fiber has a certain density or tightness, mainly used for web printing, not suitable for single-sheet printing, finished label for automatic labeling. Self-adhesive materials require a good flatness of the backing paper, a uniform thickness, a uniform light transmittance, and a higher density, so that the surface material can be completely die-cut.
1. Opaque backing paper
The commonly used opaque backing paper is distinguished by color, and is divided into yellow and white. In terms of structure, it is divided into pre-coated PE coating and without PE coating. Coating PE coating has two purposes. One is to seal the surface of the paper pores to make it smooth and smooth, apply silicone oil, reduce the amount of coating, can reduce the cost; Another role is to improve the cutting characteristics, because the PE coating has a certain toughness and elasticity, can reduce the bottom paper breaks .
Since thick-bottom paper labels are mainly used for manual labeling, continuous die-cutting, and manual removal of waste labels, they will be peeled off together with the labels; if the bottom paper is cut through half or cut through, it is very difficult to uncover the labels. When the opaque backing paper is die-cut on a flat die-cutting die-cutting machine, the common fault is the bottom paper breakage. Therefore, to ensure the precision of the die-cutting knife and the flatness of the liner, a flat paper with good flatness, large fiber tension, and uniform thickness is used to improve die cutting. quality.
2. Translucent paper
Translucent bottom paper, also known as thin-bottomed paper, is used for label printing with commonly used glassine paper (glass bottom paper). There are two indicators of the glassine base paper will affect die-cutting quality: one is the thickness uniformity, and the second is the fiber structure. The thickness uniformity of the bottom paper is the most important, especially when circular die cutting, because the size of the die cutter roller is determined by the thickness of the bottom paper. If the thickness of the bottom paper is not uniform, the cutting edge will cut or not cut to the bottom paper.
The fiber structure of the glassine substrate mainly affects the die cutting speed for round die cutting, because the fiber strength directly influences the speed of waste scrapping and breaking, and the speed is faster. The greater the pull force, the easier it is to waste. If the material itself is strong, the cutting speed can be increased. However, for slower flattened die-cuts, the fiber structure has little effect on die-cut quality. If the bottom paper has brittle fiber and poor toughness, it can only be die-cut on equipment with high precision and good die-cutting quality. This shows that the accuracy of the equipment is also one of the factors that affect the quality of die-cutting.