Biaxially Oriented Polyester Film Adhesion and Drawability
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Solution Overview
Problem
Conventional polyester films exhibit low lamination strength and moldability issues when laminated with a metal layer, particularly due to high crystallinity, which limits their suitability for deep drawing applications.
Innovation Solution
A biaxially oriented polyester film with a base layer and adhesive layer, where the reversible heat capacity difference between the two layers is within a specific range, and the molecular orientation ratio and stress at 10% elongation are optimized, enhancing adhesiveness and deep drawability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a crystalline polyester film is used to provide high productivity and dimensional stability, then the film has good mechanical properties and chemical resistance, but the lamination strength with metal layer decreases and moldability deteriorates
Solution Approach 1:
The invention changes the crystallinity parameter of the polyester film from high (conventional) to low (5% or less), which fundamentally alters the film's properties. This parameter change enables both good lamination strength with metal layers and excellent moldability while maintaining dimensional stability, resolving the contradiction between productivity and adhesion strength
Solution Approach 2:
The invention creates a composite structure by laminating the low-crystallinity polyester film with a metal layer (such as aluminum foil). This composite material combines the dimensional stability and chemical resistance of polyester with the barrier properties and structural integrity of metal, achieving both strong adhesion and good moldability
2Strength
If an easily adhesive coat is provided on the polyester film to increase adhesiveness to metal layer, then lamination strength improves, but blocking occurs when made into film roll and transparency deteriorates
Solution Approach 1:
The invention extracts and removes the easily adhesive coat (including lubricants and additives) from the polyester film structure. Instead of adding an adhesive layer, the invention achieves adhesion through the base polyester film itself by controlling its crystallinity to be 5% or less, thereby avoiding blocking and transparency deterioration while maintaining good lamination strength
Solution Approach 2:
The invention replaces the complex easily adhesive coat system with a simple low-crystallinity polyester film structure. This simpler solution achieves the same adhesion function without the side effects of blocking and transparency loss, effectively substituting a complicated system with a more elegant simple solution
Data Source
AI summary
Disclosed is a biaxially oriented polyester film that is excellent in adhesiveness with a metal layer etc. and excellent in deep drawability for an isotropic shape, such as a square shape. A biaxially oriented polyester film having at least a base layer and an adhesive layer each of which contains a polyester as a main component, the film satisfying the following requirements (1) to (3): (1) a difference between reversible heat capacity difference (ΔCp) at around glass transition temperatures of the adhesive layer and the base layer is not smaller than 0.10 and not larger than 0.45; (2) a molecular orientation ratio measured by using a molecular orientation meter is not lower than 1.0 and not higher than 1.2; and (3) a stress at 10% elongation (F10) in each of a machine and transverse direction is not lower than 90 MPa and not higher than 160 MPa.