Biaxially Oriented Film Laminate for Cold-Forming Accuracy
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Solution Overview
Problem
Conventional laminate materials for cold forming suffer from issues such as pinholes, delamination, reduced physical properties, and inadequate resistance to springback and warpage, which affect dimensional accuracy and productivity.
Innovation Solution
A laminate comprising a biaxially oriented polyester film as the base layer and a biaxially oriented polyamide film as the intermediate layer, with specific mechanical characteristics and stretching conditions to enhance cold formability, inhibit springback, and improve warp resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the resin film has low flexibility, then the metal foil is protected better, but pinholes or delamination occur during cold forming
Solution Approach 1:
The invention uses a composite laminate structure consisting of a polyethylene terephthalate film layer and a polyamide film layer. The polyethylene terephthalate film provides flexibility and formability, while the polyamide film provides strength and protection. This composite structure resolves the contradiction by combining materials with complementary properties, allowing the laminate to both protect the metal foil and withstand cold forming without pinholes or delamination.
2Ease of operation
If the resin film has excessively high flexibility, then cold formability is improved, but the protection effect on metal foil is reduced and physical properties degrade
Solution Approach 1:
The laminate combines a flexible polyethylene terephthalate film with a stronger polyamide film. The polyethylene terephthalate layer provides the necessary flexibility for cold forming, while the polyamide layer maintains structural integrity and protection effects. This composite approach allows the laminate to achieve both high flexibility for forming and sufficient strength for protection.
3Ease of operation
If conventional laminate structures are used for cold forming, then formability is achieved, but springback occurs reducing dimensional accuracy
Solution Approach 1:
The invention specifies precise parameter ranges for the film layers, including thickness ratios (polyamide film 5-20 μm, polyethylene terephthalate film 20-50 μm), strength ratios, and elongation characteristics. By controlling these parameters within specific ranges, the laminate achieves optimal balance between formability and springback resistance, maintaining dimensional accuracy after cold forming.
4Strength
If the base layer has high strength, then pinhole resistance is improved, but formability during cold forming is reduced
Solution Approach 1:
The laminate uses a composite structure where the polyethylene terephthalate film provides formability and the polyamide film provides pinhole resistance. The specific thickness ratio and material properties are optimized so that the overall laminate maintains both good formability during cold forming and sufficient pinhole resistance, resolving the contradiction between these two properties.
Data Source
AI summary
Provided is a polyamide film that not only has excellent cold formability regardless of the film's position in the width direction, but also has excellent warpage resistance with less deterioration in dimensional accuracy after forming due to springback. In particular, the invention provides a biaxially oriented polyamide film containing 60% by mass or more of polyamide 6, (a) having a piercing strength of 0.5 N/μm or more and 1.0 N/μm or less measured in accordance with JIS Z 7102, (b) having a heat shrinkage rate at 160° C. of 3.0% or less in each of the MD direction and the TD direction, and (c) having a stress attenuation rate of 12.0% or more in each of the MD direction and the TD direction in the tensile stress relaxation test at 25° C.