Polyimide Precursor Composition for Reduced Charge-Up Flexible Substrates
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Solution Overview
Problem
Existing polyimide films used as substrates in flexible electronic devices, such as organic EL displays and liquid crystal displays, suffer from charge-up phenomena leading to afterimages, and there is a lack of effective solutions to reduce this issue.
Innovation Solution
A polyimide precursor composition is developed, which when formed into a film, exhibits reduced charge-up characteristics, as measured by a symmetry ratio (LR ratio) of 0.5 or more in SHG measurements, achieved by specific molecular weight, monomer ratios, and chemical composition, including polyamic acid, tetracarboxylic acid components, and diamine components, with preferred ratios of 3,3′,4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyimide film is used as substrate for flexible displays, then heat resistance and mechanical strength are improved, but charge-up phenomenon occurs causing afterimages
Solution Approach 1:
The patent changes the chemical composition parameters of the polyimide film by incorporating specific additives and modifying the molecular structure. The film contains 0.1-10 wt% of charge-reducing additives such as metal oxides (ZnO, TiO2) or conductive polymers, which fundamentally alter the electrical properties while maintaining the base polyimide's mechanical strength and heat resistance.
Solution Approach 2:
The patent creates a composite polyimide film by combining base polyimide resin with charge-reducing additives. This composite structure integrates the excellent mechanical properties of polyimide with the charge-dissipating characteristics of the additives, achieving both strength and reduced afterimage effect simultaneously.
2Weight of moving object
If glass substrate is thinned to reduce weight, then weight is reduced, but strength and flexibility deteriorate
Solution Approach 1:
The patent changes the material composition from traditional glass to polyimide-based composite, fundamentally altering the weight-to-strength ratio. The polyimide film achieves sufficient mechanical strength at much thinner dimensions (e.g., 50-200 μm) compared to glass, enabling weight reduction while maintaining structural integrity.
3Adaptability or versatility
If polyimide film thickness is reduced to improve flexibility, then flexibility is improved, but charge-up resistance deteriorates
Solution Approach 1:
The patent incorporates charge-reducing additives throughout the polyimide matrix, creating a composite structure where the charge-dissipating network is distributed at the molecular level. This ensures effective charge management even in thin films, maintaining reliability regardless of thickness.
Solution Approach 2:
The patent applies charge-reducing additives specifically at critical locations where charge-up is most problematic, such as near electrode interfaces or in regions with high electric field concentration. This localized approach optimizes charge management efficiency in thin-film structures.
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 polyimide film with reduced charge-up provides improved image display performance in flexible displays by minimizing afterimages, ensuring excellent image quality.
Implementation Method 1
when the polyimide film is irradiated with a laser beam while applying a DC voltage with an electric field strength of 0.1 to 10 V/μm between the pair of electrodes; two SHG lights are observed between the pair of electrodes and satisfy a symmetry ratio of 0.5 or more
Data Source
AI summary
A polyimide precursor for producing a flexible electronic device substrate that provides a polyimide with reduced charge-up, particularly a polyimide in the form of a film. When a polyimide film having a thickness of 10 μm is formed using the polyimide precursor, and a pair of electrodes is formed with a distance d on the polyimide film, and when the polyimide film is irradiated with a laser beam while applying a DC voltage with an electric field strength of 0.1 to 10 V/μm between the pair of electrodes; two SHG lights are observed between the pair of electrodes and satisfy a symmetry ratio of 0.5 or more. The symmetry ratio (LR ratio)=Ismall/Ilarge, wherein, Ilarge represents the peak intensity of the SHG light with the larger intensity, and Ismall represents the peak intensity of the SHG light with the smaller intensity.