Oriented Polyester Film Thermal Stability
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Solution Overview
Problem
Current polyester films used in flexible electronics face challenges with dimensional stability at high temperatures and temperature changes, leading to issues like thermal shrinkage and cracks, which affect the functionality of laminated products.
Innovation Solution
An oriented polyester film with polyethylene-2,6-naphthalene dicarboxylate as a major component, stretched in at least one direction, achieving a coefficient of linear thermal expansion between 0 to 15 ppm/°C and a thermal shrinkage rate of 0.5% or less at 100°C, ensuring stability and flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a polymer film is used as a substrate for flexible electronics, then the device achieves light weight and flexibility, but the film suffers thermal expansion and shrinkage at high temperatures, leading to poor dimensional stability
Solution Approach 1:
The patent applies parameter changes by controlling the coefficient of linear thermal expansion through specific processing conditions and material composition. The polyester film is processed to achieve a coefficient of linear thermal expansion of 50 ppm/°C or less at 50°C, which is a critical parameter change that enables the film to maintain dimensional stability while remaining lightweight and flexible for flexible electronics applications
Solution Approach 2:
The patent uses composite materials by combining polyester resin with specific additives and controlling the molecular structure to create a film that exhibits both flexibility and exceptional thermal stability. The composite structure allows the material to achieve a coefficient of linear thermal expansion of 50 ppm/°C or less, resolving the contradiction between light weight and dimensional stability
2Stability of the object's composition
If the coefficient of linear thermal expansion of the polymer film is reduced to improve dimensional stability, then thermal shrinkage decreases, but the film may become more prone to cracking when laminated with functional layers
Solution Approach 1:
The patent applies parameter changes by precisely controlling the coefficient of linear thermal expansion to 50 ppm/°C or less at 50°C, which optimizes the balance between dimensional stability and crack resistance. This specific parameter range ensures the film is stable at high temperatures while remaining flexible enough to accommodate functional layers without cracking
Solution Approach 2:
The patent directly addresses thermal expansion by designing the polyester film to have a coefficient of linear thermal expansion of 50 ppm/°C or less at 50°C. This controlled thermal expansion behavior prevents both excessive shrinkage and stress-induced cracking during lamination and high-temperature processing, simultaneously improving dimensional stability and reliability
3Ease of manufacture
If a polyester film is used to replace polyimide film for flexible printed circuits, then cost is reduced, but the film exhibits large dimensional change upon absorbing moisture
Solution Approach 1:
The patent applies parameter changes by controlling the water absorption rate to 0.3% or less and the coefficient of linear thermal expansion to 50 ppm/°C or less at 50°C. These parameter changes enable the polyester film to achieve dimensional stability comparable to polyimide film while maintaining the cost advantage of polyester materials, making it suitable for flexible printed circuit applications
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The film provides excellent dimensional stability and transparency, reducing thermal distortion and enabling the use of flexible electronics devices with improved functionality and durability.
Implementation Method 1
a coefficient of linear thermal expansion at 50°C of 50 ppm/°C or less, as measured in both longitudinal and width directions
Implementation Method 2
a thermal shrinkage rate in the width direction at 150°C for 30 minutes of 2% or less
Data Source
AI summary
An object of the invention is to provide such an oriented polyester film that has a constant thickness, and is excellent in dimensional stability at a high temperature and dimensional stability to temperature change in a working temperature range. The invention relates to an oriented polyester film containing as a major component of a substrate layer polyethylene -2,6-naphthalene dicarboxylate, being stretched at least in one direction, and having a film thickness of from 12 to 250 μm, wherein(1) a coefficient of linear thermal expansion αt at a temperature of from 30 to 100° C. is from 0 to 15 ppm/° C. in both longitudinal and width directions of the film, and(2) a thermal shrinkage rate at 100° C. for 10 minutes is 0.5% or less in both longitudinal and width directions of the film.