Polyamide-imide Film Copolymerization for Thermal Stability and Transparency
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Solution Overview
Problem
Conventional polyimide films exhibit low transmittance and yellowish color due to high aromatic ring density, making them unsuitable for optical applications, and they lack the necessary thermal stability and mechanical properties for use in display devices like OLEDs and TFT-LCDs.
Innovation Solution
A polyamide-imide precursor is developed through copolymerization of a dianhydride and a diamine, including 9,9-bis(4-aminophenyl)fluorene and 9,9-bis(4-amino-3-fluorophenyl)fluorene, with 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and biphenyl tetracarboxylic dianhydride, to create a film with improved thermal stability, transparency, and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a polyimide resin with high aromatic ring density is used to achieve high heat resistance and thermal stability, then thermal stability is improved, but transmittance in the visible light range deteriorates and the material becomes yellow-colored
Solution Approach 1:
The patent changes the chemical structure parameters of the polyimide resin by introducing specific aromatic diamine components (3,3'-diaminobenzidine and 4,4'-diaminodiphenyl sulfone) in controlled ratios (10-50 wt% and 50-90 wt% respectively). This structural parameter modification allows the resin to maintain high aromatic content for heat resistance while achieving superior transparency and colorlessness, resolving the contradiction between thermal stability and optical properties
Solution Approach 2:
The patent creates a composite polyimide resin system by combining multiple aromatic diamine components (3,3'-diaminobenzidine and 4,4'-diaminodiphenyl sulfone) with aromatic dianhydride in specific proportions. This composite approach enables the material to simultaneously exhibit high heat resistance (glass transition temperature of 200°C or higher) and excellent optical properties (transmittance of 87% or more at 550 nm), overcoming the limitations of single-component polyimide resins
2Illumination intensity
If monomers and solvents are purified to high purity before polymerization to improve transmittance, then color transparency is slightly improved, but the improvement in transmittance is not significant
Solution Approach 1:
Instead of relying on monomer purification, the patent changes the fundamental chemical composition parameters of the polyimide resin by using specific aromatic diamine components in controlled ratios. This compositional parameter change achieves significant transmittance improvement (87% or more at 550 nm) without requiring complex purification processes, thereby resolving the contradiction between optical properties and manufacturing simplicity
3Temperature
If a monomer with a rigid structure is used to realize thermal stability, then thermal stability is improved, but transmittance is remarkably deteriorated and yellowness increases
Solution Approach 1:
The patent modifies the molecular structure parameters by selecting specific aromatic diamine components (3,3'-diaminobenzidine and 4,4'-diaminodiphenyl sulfone) with appropriate rigidity. The balanced structural parameters of these components enable the polyimide resin to achieve high thermal stability (glass transition temperature of 200°C or higher) while maintaining excellent optical properties, resolving the contradiction between thermal stability and transmittance that plagues conventional rigid monomer-based polyimides
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 polyamide-imide film is colorless, transparent, and exhibits superior thermal stability and optical properties, suitable for applications in semiconductor insulating layers, TFT-LCDs, and flexible display substrates, with a coefficient of thermal expansion of 30 ppm/°C or less and transmittance of 87% or more.
Implementation Method 1
a polyimide resin is a highly heat-resistant resin prepared by subjecting an aromatic dianhydride and an aromatic diamine or an aromatic diisocyanate to solution polymerization, thus preparing a polyamic acid derivative, which is then subjected to ring-closing dehydration at a high temperature so as to be imidized
Data Source
AI summary
Disclosed is a polyamide-imide precursor having a molecular structure in which a first polymer, derived from polymerization of a dianhydride and a diamine, and a second polymer, derived from polymerization of a diamine and an aromatic dicarbonyl compound, are copolymerized, wherein the diamine includes 3 to 50 mol% of at least one of 9, 9-bis (4-aminophenyl)fluorene (FDA) and 9,9-bis(4-amino-3-fluorophenyl)fluorene (F-FDA), based on the total molar amount of the diamine. Also, a copolymerized polyamide-imide in which the polyamide-imide precursor is imidized or a copolymerized polyamide-imide film formed by an imidization reaction of the polyamide-imide precursor and an image display device including the copolymerized polyamide-imide film are provided.