Polyester Film for High-Temperature Transparent Conductive Applications
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Solution Overview
Problem
Biaxially-oriented PET films lack temperature dimensional stability and durability for high-temperature applications in electronic devices, such as flat panel displays and photovoltaic devices, due to their low melting temperature and oligomer migration issues during annealing processes.
Innovation Solution
A blend of semi-crystalline and amorphous polyester components based on terephthalic acid, isophthalic acid, and 1,4-cyclohexanedimethanol is used to create a high-temperature polyester film with improved crystallization rates and dimensional stability, allowing for biaxial orientation and heat-setting at elevated temperatures without oligomer migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If biaxially-oriented PET films are used as substrates for high-temperature applications, then the films can be processed and coated, but the films lack temperature dimensional stability and suffer from oligomer migration during annealing processes
Solution Approach 1:
The patent modifies the chemical composition parameters of the polyester by incorporating cyclic diol units (1,4-cyclohexanedimethanol) at 10-40 mole percent and adjusting the ratio of terephthalic acid to isophthalic acid. These parameter changes raise the glass transition temperature above 80°C and improve dimensional stability at elevated temperatures, allowing annealing at higher temperatures without substrate deformation or oligomer migration.
Solution Approach 2:
The patent creates a composite polyester material by blending different polyester components with specific chemical structures. The composite contains semi-crystalline polyester (providing mechanical strength and processability) and amorphous polyester (providing optical clarity and reduced oligomer migration). This composite structure achieves both high-temperature stability and processing compatibility.
2Reliability
If higher annealing temperatures are used to reduce ITO coating thickness and improve conductivity, then the substrate must maintain dimensional stability, but PET substrates deform and migrate oligomers at these temperatures
Solution Approach 1:
The patent changes the chemical structure parameters by incorporating cyclic diol units and adjusting acid component ratios, which fundamentally alters the thermal behavior of the polyester. The modified structure reduces oligomer formation and migration tendency while maintaining mechanical integrity at annealing temperatures up to 150°C or higher, enabling reliable high-temperature processing without substrate degradation.
3Temperature
If PCT polyester is used to achieve higher heat resistance, then the film becomes brittle due to fast crystallization on the chill drum, but this brittleness causes problems for stretching and end use
Solution Approach 1:
The patent carefully controls the crystallization kinetics by adjusting the cyclic diol content (10-40 mole percent) and the ratio of TPA to IPA. This parameter optimization slows down the crystallization rate during extrusion, preventing brittle film formation on the chill drum, while still achieving sufficient crystallinity for heat resistance. The balanced composition allows the film to remain flexible for stretching operations and end-use 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 resulting polyester film exhibits superior transparency, conductivity, flexibility, and hydrolytic stability, enabling higher annealing temperatures with shorter times and increased ITO deposit rates, while maintaining low haze and high visual light transparency.
Implementation Method 1
A blend of semi-crystalline and amorphous polyester components based on terephthalic acid, isophthalic acid, and 1,4-cyclohexanedimethanol is used to create a high-temperature polyester film with improved crystallization rates and dimensional stability, allowing for biaxial orientation and heat-setting at elevated temperatures without oligomer migration.
Implementation Method 2
A blend of semi-crystalline and amorphous polyester components based on terephthalic acid, isophthalic acid, and 1,4-cyclohexanedimethanol is used to create a high-temperature polyester film with improved crystallization rates and dimensional stability
Data Source
AI summary
Described are polymer compositions that include a blend of copolyester polymers based on monomers that include on terephthalic acid (TPA), isophthalic acid (IPA) and 1,4-cyclohexanedimethanol (CHDM), wherein the blend includes a first copolyester that is semi-crystalline and a second copolyester that is amorphous; and films made from the polymer compositions useful for transparent high temperature conductive film applications.