(1) The type, grade, and quality of the object to be labeled, the characteristics of the surface to be applied, the usage environment, and the user's requirements should be considered comprehensively. Using highly transparent polypropylene self-adhesive labels on transparent bottles can create a fashionable, label-free look, enhancing the product's perceived quality and stimulating consumer purchasing desire. Polyvinyl chloride (PVC) film, on the other hand, offers excellent flexibility, shrinkage, opacity, processing characteristics, and labeling properties, along with vibrant colors, making it effective for promotional purposes.
(2) The surface of film-type self-adhesive labels must be smooth, dense, uniform in density, consistent in color, and have good light transmittance to ensure even ink absorption and minimal color difference within the same batch of prints.
(3) The thickness of the self-adhesive labels must be uniform, and their strength indicators must meet standards. The printing pressure applied during the printing process is related to the thickness of the self-adhesive label. Uneven thickness results in uneven printing pressure, leading to variations in the depth of the printed text or ink. Poor film strength makes it difficult to control film tension during printing, significantly impacting die-cutting and waste removal.
(4) Self-adhesive labels should be relatively flat, and the rewinding tension should be uniform. Good flatness ensures correct feeding, operation, registration, and rewinding during printing. The rewinding tension of the film should be uniform and appropriate. If the tension is too low, the film substrate will be loose, resulting in inaccurate registration in both the longitudinal and transverse directions; if the tension is too high, the substrate will shrink laterally, leading to unstable color registration and making normal printing difficult.
(5) Film-based self-adhesive labels should also possess characteristics such as corrosion resistance, aging resistance, colorfastness, and low shrinkage and expansion ratios. Poor corrosion resistance, easy aging, and fading will result in labels that are not durable and will affect the sale and use of the goods. If the shrinkage and expansion ratios are high, it will not only affect the registration accuracy during printing but also cause the label to deform during use, affecting the sale and use of the goods. Especially for labels of high-end goods, the embarrassing situation of the label aging before the product expires should be avoided as much as possible (label aging includes plastic aging and ink fading, etc.). If necessary, aging resistance tests should be conducted on the plastic or label to test its performance.