A. Label Bulging Issues：
Label bulging often occurs in batches and may not be discovered until some time after labeling, sometimes only during the final inspection before shipment. This can cause significant trouble and loss for the end user. The main reasons for label bulging are as follows:
1.Labels Absorbing Water and Swelling
Labels lose a certain amount of moisture during processing. If the ambient humidity increases suddenly during use, the label will absorb moisture and swell after being applied, especially for self-adhesive labels with paper-based surfaces. This problem is more prominent in such labels. Since the label is already affixed to the object, the swollen area can form bubbles or bulges.
To prevent this, it is recommended to glaze or laminate the surface of paper-based self-adhesive labels. This can isolate the label from moisture in the air. If glazing or laminating is not feasible, it is best to leave the label exposed for 24 hours before applying it, allowing the label to balance with the ambient moisture. Also, if the object to be labeled is susceptible to humidity (e.g., corrugated cardboard), it should be treated in the same way.
2.Chemical Reaction Between Glue and the Surface of the Object
Many labeled objects are made from plastics, which often contain various additives, including some from recycled materials. These plastics may have more complex chemical compositions. The adhesive in self-adhesive labels is also a chemical product, and sometimes it reacts chemically with certain components in the plastic, leading to the generation of gas. Since the label is already applied to the surface, the gas cannot escape and results in bubbles or bulges. If the label is removed, the adhesive layer may show signs of change, such as melting.
To solve this issue, it is recommended to use a different self-adhesive material for labeling, ensuring a proper test is conducted before production to confirm there is no chemical reaction between the adhesive and the object.
Additionally, the object's surface may be uneven, or there may be dust, dirt, or particles, preventing the label from adhering properly. This also leads to bubbles. Therefore, before labeling, ensure the object's surface is free from oil, dust, and other contaminants.
B. Labeling Wrinkles
Labeling wrinkles are a common issue during the labeling process. Sometimes wrinkles appear immediately after labeling, and sometimes they become visible after some time. The main causes of labeling wrinkles are as follows:
1.The Shape of the Object Being Labeled
Self-adhesive labels are flat, so the object being labeled must also be flat for a good labeling result. However, in reality, many labeled objects, such as bottles, have a certain curvature. If the curvature is too large, resulting in a nearly spherical shape, the label will inevitably wrinkle because it cannot be fully stretched.
To address this, observe if the wrinkles are concentrated around the edges of the label (sometimes the wrinkles form regularly due to the automatic labeling process, where the label roller presses the area that cannot be fully unfolded). Then, check the object to determine if its curvature is too large. If so, consider redesigning the shape of the object being labeled.
2.Uneven Labeling Pressure
Automatic labeling equipment typically has an adjustable labeling pressure. Some objects have softer surfaces, and if the pressure is too high, it may cause the object's surface to deform, leading to wrinkles. Therefore, it is important to adjust the labeling device pressure to a suitable range, ensuring that the label is firmly applied without excessive force.
3.Label Water Absorption
During the rainy season, the humidity in the air increases. If the label's moisture content is lower than the surrounding air, it may absorb moisture and swell, especially for self-adhesive labels with paper-like surfaces. This effect is particularly noticeable with such materials. As a result, after application, the label may swell and wrinkle.
To prevent this, it is best to open the label package and let the labels rest for 24 hours before labeling, allowing them to equilibrate with the moisture in the air.
4.Transportation or Storage Issues
Improper stacking or squeezing of labels during transportation or storage may cause friction and pressure between layers, resulting in wrinkles. Therefore, when transporting labels, appropriate packaging materials should be used, such as bubble wrap or cardboard, to separate the labels and reduce friction. Additionally, minimize violent vibrations and impacts during transportation to prevent damage to the labels.
