The characteristics of paper-based label materials, also known as pressure-sensitive labels, involve an adhesive that forms a bond with the substrate upon application of pressure. The paper facestock, a component of the pressure-sensitive label, is composed of fibers, resins, fillers, and pigments. The fibers themselves have strong water-absorbing properties and create gaps between them, as well as capillary action that absorbs moisture. After absorbing moisture, the paper's dimensional stability and printing performance are significantly affected. Therefore, maintaining a stable moisture content during the application process of paper-based label materials is crucial.
Storage Precautions for Paper-Based Label Materials
Adhesive labels should be stored in a dry environment to avoid negative effects such as adhesive seepage, moisture damage, and curling caused by high temperatures and humidity. The recommended storage conditions for adhesive labels are: 22℃ ± 2℃ and 50% ± 5% relative humidity. Label suppliers typically seal the labels for packaging, creating a small, moisture-proof environment. The humidity control in the storage environment can be slightly relaxed. However, due to variations in packaging materials, the isolation effect and shelf life may differ. It is recommended to follow the "first in, first out" principle when applying labels, and keep unused materials sealed and intact.
1. Effective Temperature and Humidity Control in the Printing Workshop: Most printing processes currently use UV drying methods, where paper materials release noticeable moisture due to high temperatures when passing through UV lamps. Excessive humidity in the environment at this time can affect the moisture balance of labels, leading to leaf edges and impacting the labeling effect. Generally, paper materials after printing reach humidity balance and maintain stable performance when the humidity environment is 50% ± 5%. 2. Surface Protection Processes for Post-Printing Materials: 1) UV Coating: Applying a layer of coating on the ink surface aims to protect the ink layer, prevent moisture and water damage, and enhance surface luster. Many applications indicate that the thickness of UV coating and the hydrophilic properties of the coating can affect its waterproof performance. 2) Lamination: Applying a film to paper materials to protect the ink, prevent moisture and water damage, and increase label strength. Lamination processes effectively provide waterproof protection for labels, but due to the increased thickness of materials and the difficulty in controlling lamination tension, labeling can easily lead to label翘起 or small bellows-like bulges. 3. Selection of Paper Materials: Different types of paper materials and adhesive characteristics have varying stability in moisture content. Generally speaking: Moisture content stability: Optimal Mirror Copper Plate > Mirror Copper Plate > Water-Soluble Adhesive Copper Plate Products > Thermal Melt Adhesive Products
When labeling, the moisture content of the label and the item being labeled should be balanced: The labeling action ensures a flat combination of the label and the item in the labeling environment. After labeling, if there are significant changes in temperature and humidity, especially during the rainy season, the different degrees of impact on the label and the item can cause changes in the labeling state, leading to issues like creases and bubbles on the label. To avoid these problems, it is crucial to control the labeling and storage environment to prevent drastic changes in temperature and humidity. Additionally, the moisture content of the label and the item should be as balanced as possible during labeling. According to our experience, it is ideal to have the label exposed to the labeling process for more than 24 hours. This way, when the label and the item are exposed to different environments after labeling, their changes are relatively synchronized, which can reduce the occurrence of creases and bubbles.
