If you don't want your composite film to experience the tunneling effect, you need to be aware of the following seven reasons:
Mismatched tension during lamination: After lamination, different tensions in the films may lead to relative displacement, causing raised wrinkles. Tension matching is crucial and should be adapted to different equipment characteristics.
Issues with the film itself: If the film wrinkles, has uneven thickness, or exhibits loose edges, tunneling issues may arise during the lamination process. The smoothness of the film substrate is of paramount importance.
Improper winding: Adjusting the curl pressure based on the structure of the composite film is necessary to prevent internal slackness and external tightness, which could lead to wrinkles and tunneling.
Adhesive-related problems: Adhesives with low molecular weight, low cohesive strength, or insufficient initial tack can result in film slippage and tunnel formation. Choosing an appropriate adhesive is crucial.
Incorrect adhesive application: Insufficient or uneven adhesive application or excessive adhesive coating can cause localized insufficient bonding strength, resulting in tunneling.
Adhesive ratio and quality issues: Inappropriate adhesive ratios or poor solvent quality, high water content, or excessive alcohol content can lead to slow curing, causing film layers to slide.
Excessive residual solvent: If there is too much residual solvent in the composite film, inadequate drying of the adhesive, and insufficient bonding strength, the film is prone to slippage, resulting in tunneling. Regular solvent checks and ensuring thorough curing of the composite film are essential.