In the process of pasting self-adhesive labels , in addition to configuring high-quality label printing equipment, a reasonable selection of self-adhesive label materials is also a very important link. Self-adhesive label materials are usually composed of three parts: liner, face material, and adhesive. Among them, the surface of the liner has release agent, which has an isolation effect on the adhesive and can ensure that the face material with adhesive is easily peeled off from the liner;
The face material can be divided into coated paper, thermal paper , PP, PET , PE, PVC, etc. according to its material.
Self-adhesive labels often have problems such as labeling warping, wrinkling, air bubbles, and backing paper breakage during the labeling process, and are complained by customers.
Among them, warping is the most common in the labeling process.
1. The roughness of the surface of the object to be attached has a great influence on the labeling effect. The rougher the surface of the object to be attached, the easier it is for the label to warp. In addition, if there are oil stains, water droplets, dust and other impurities on the surface of the sticker, it is equivalent to glue sticking to these impurities instead of sticking to the surface of the sticker, and it is easy to cause the label to warp. In addition, whether the surface of the object to be pasted has been treated by a special process may also affect the final labeling effect.
2. Influence of labeling environment on label warping. Under normal circumstances, the labeling temperature requirements generally include four aspects: label temperature, object temperature, labeling ambient temperature, and storage temperature after labeling. The technical parameters of each self-adhesive label material are clearly marked with the minimum application temperature and service temperature range. When labeling, the ambient temperature must meet the minimum labeling temperature of the label. Only in this way can the glue on the label flow normally and exert normal viscosity. The surface temperature of the object to be pasted must be above the minimum labeling temperature, so that the originally fluid glue will not become less fluid or stop flowing after being attached to a low-temperature surface, resulting in a decrease in viscosity. The temperature of the storage environment after labeling is also very important. In order to maintain the fluidity of the glue and convert the glue after labeling from the initial viscosity to the final viscosity, it needs to be completed in an environment above the minimum labeling temperature.
3. The material of the object to be attached will affect the labeling effect. Because the material of the object to be attached is different, the surface energy will be different, so the effect of the same self-adhesive label after labeling will also be different. Normally, the surface energy of different materials to be pasted is compared as follows: stainless steel > glass > PET > PP > PE. In addition, the surface energy of the same material will be different due to different processing techniques, such as frosted glass bottles, plastic bottles with different surface roughness, etc. Therefore, for objects or bottles with different surface energies, self-adhesive labels with different glues need to be selected for matching.
4. In order to achieve the ideal labeling effect, the labeling surface of the object to be labeled should be a plane after unfolding. If the labeling surface of the object to be labeled is curved in both directions (spherical labeling surface) after unfolding, it is difficult to achieve the ideal labeling effect. Therefore, such a shape should be avoided when designing the bottle body, or such a position should be avoided when labeling. If the curved surface of the object to be attached or small-bore bottle, the label needs to be equipped with a soft and followable surface material and a strong adhesive.
In addition, due to the pressure of production costs, bottle blowing factories often reduce the weight of the bottle body and make the bottle body thinner, resulting in large deformation of the bottle body before and after filling, and cannot apply a large labeling pressure, such as hot filling after labeling When the liquid is at around 35℃, the bottle body will protrude and deform, and the bottle body will shrink after cooling, resulting in the unfavorable phenomenon that the label is warped.
5. For self-adhesive label materials, the smoothness of the self-adhesive label surface material is a key factor affecting the smoothness of the overall material, and the smoothness of the overall material is an important indicator to ensure printing quality. Therefore, during the labeling process, you must pay attention to check whether the surface material of the self-adhesive label is flat, especially when the label is covered with a film, you must pay attention to the tension of the film not too high, otherwise the excessive tension will cause the label to curl upwards, causing the label to warp.
6. When the label uses the varnish process, if there is no gap in the middle after the label is wrapped around the object in the design, and the two sides are stacked together, since the varnish itself contains a certain release agent, the label is also easy to warp after sticking. Therefore, it is not recommended to use the glazing process for labels using the lapping process, and it is best to change to the lamination process.
7. The influence of labeling equipment on labeling warping，According to different surface and labeling requirements, different labeling mechanisms should be selected. The commonly used ones are sponge wheel, belt pulley, labeling plate, etc. The labeling machine should apply appropriate labeling pressure to ensure that the label is consistent with the label. Covered objects can be a perfect fit.
When the labeling pressure is insufficient, such as using a soft brush, too soft labeling board, or the distance between the sponge wheel, the pulley and the bottle body is too large, etc., the label will warp due to insufficient labeling pressure question. In addition, if the labeling mechanism is aging, it will affect the pressure of the labeling, which may cause the problem of labeling warping.