Polyimide Film Transparency Thermal Resistance Balance
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Solution Overview
Problem
Conventional polyimide films face challenges in achieving both excellent thermal resistance and transparency, as improvements in transparency often compromise thermal resistance, and vice versa, limiting their application in transparent conductive films and other electronic materials.
Innovation Solution
A polyimide powder and film with a specific refractive index increment (dn/dc) of 0.100 to 0.180, achieved through the polymerization of diamine and acid dianhydride, ensuring a balance between thermal resistance and transparency, with an imidization degree of not less than 80% for storage stability and controlled molecular weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If general polyimide resin is used to achieve high thermal resistance, then thermal resistance is improved, but transparency is worsened due to browning and yellowing
Solution Approach 1:
The patent changes the chemical composition parameters of the polyimide resin by using specific aromatic diamines (ODA, 2,2'-BDAF, 3,3'-BDAF, 4,4'-BDAF) and aromatic acid dianhydrides (PMDA, 6FDA, ODPA, BPDA) in controlled molar ratios. This compositional parameter adjustment allows the resin to maintain high thermal resistance while achieving transparency by reducing yellowing and browning through optimized molecular structure
Solution Approach 2:
The patent creates a composite polyimide system by combining multiple diamine and dianhydride components in specific ratios. This composite approach allows synergistic effects where different monomer units contribute different properties - some providing thermal stability while others enhance transparency, thus resolving the contradiction between thermal resistance and transparency
2Illumination intensity
If efforts are made to improve color and transmittance of polyimide film, then transparency is improved, but thermal resistance is worsened
Solution Approach 1:
The patent optimizes the imidization degree parameter to a specific range (80-95%) and controls the molar ratios of diamine to dianhydride (0.95:1 to 1:1.05). These parameter changes ensure that the polyimide film achieves high transparency through reduced yellowing while maintaining thermal resistance by preventing excessive degradation that would occur at higher imidization levels
3Reliability
If high imidization degree is achieved to improve storage stability, then storage stability is improved, but molecular weight distribution becomes uncontrolled
Solution Approach 1:
The patent employs controlled imidization processes with specific temperature profiles and reaction time parameters that provide feedback control over the imidization degree. By monitoring and controlling the imidization process to achieve 80-95% conversion, the system maintains storage stability while preventing excessive crosslinking that would cause uncontrolled molecular weight distribution
Solution Approach 2:
The patent changes the imidization degree parameter to an optimized range (80-95%) rather than pursuing complete imidization. This parameter adjustment balances storage stability requirements with molecular weight control, as complete imidization (100%) would cause excessive crosslinking and uncontrolled molecular weight distribution
Data Source
AI summary
The present invention provides a polyimide film having a good transparency and also an excellent thermal resistance so that it is useful in a transparent conductive film, TFT substrate, a flexible printing circuit substrate, and the like.