Transparent Aromatic Copolyamide Films for Flexible Substrates
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Solution Overview
Problem
Current polymer films for flexible substrates lack thermal stability, high transparency, low coefficient of thermal expansion, and sufficient barrier properties, making them unsuitable for high-temperature processing and robust flexible displays.
Innovation Solution
Development of transparent aromatic copolyamide films with a glass transition temperature greater than 300°C and a coefficient of thermal expansion less than 20 ppm/°C, achieved by forming a mixture of aromatic diamines with free carboxyl groups, dissolving in polar solvents, and curing at elevated temperatures, eliminating the need for inorganic salts and resulting in solvent-resistant films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional polymer films are used for flexible substrates, then flexibility and transparency are achieved, but thermal stability and dimensional stability are insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer by incorporating aromatic polyamide units with specific glass transition temperatures (>300°C) and controlling the coefficient of thermal expansion to less than 20 ppm/°C. This parameter modification enables the film to maintain dimensional stability at high processing temperatures while remaining suitable for flexible substrate applications.
2Stability of the object's composition
If aromatic polyamide films are made with high thermal stability, then dimensional stability is improved, but transparency and flexibility deteriorate
Solution Approach 1:
The patent creates a composite polymer structure combining aromatic polyamide units with flexible chains and specific side groups. This composite approach allows the film to achieve both high dimensional stability (CTE < 20 ppm/°C) and high optical transparency (transmittance >80% from 400-750 nm) by balancing the rigid aromatic backbone with flexible components.
3Weight of moving object
If polymer films are made thinner and lighter, then weight and flexibility are improved, but barrier properties against oxygen and moisture deteriorate
Solution Approach 1:
The patent modifies the polymer's chemical parameters by incorporating aromatic polyamide units with specific glass transition temperatures and controlled CTE, which inherently provide better barrier properties. This allows thinner films to achieve sufficient oxygen and moisture barrier performance without sacrificing the lightweight and flexible characteristics.
4Temperature
If polymer films are made more robust and thermally stable, then processing temperature range is expanded, but solvent resistance and chemical stability deteriorate
Solution Approach 1:
The patent changes the polymer's chemical composition by using aromatic polyamide units with high glass transition temperatures (>300°C) and specific side groups that provide inherent solvent resistance. This parameter modification enables the film to maintain both high thermal stability for expanded processing temperature ranges and resistance to common organic solvents like NMP, DMAc, and DMSO.
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 films exhibit high thermal and dimensional stability, maintaining transparency and resistance to solvents, enabling their use as flexible substrates for high-temperature fabrication of thin film transistors and OLED displays, expanding the application of AMOLEDs in portable devices.
Implementation Method 1
curing the film at a temperature, wherein the temperature is at least 90% of the glass transition temperature of the film
Implementation Method 2
a rigid backbone with a glass transition temperature higher than 300° C.
Data Source
AI summary
The present invention is directed toward transparent films prepared from soluble aromatic copolyamides with glass transition temperatures greater than 300° C. The copolyamides, which contain pendant carboxylic groups are solution cast into films using N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP), or other polar solvents. The films are thermally cured at temperatures near the copolymer glass transition temperature. After curing, the polymer films display transmittances >80% from 400 to 750 nm, have coefficients of thermal expansion of less than 20 ppm, and are solvent resistant. The films are useful as flexible substrates for microelectronic devices.