Polyimide Varnish with Trace Metals for Flexible Displays
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Solution Overview
Problem
Conventional polyimide films used in flexible optical devices, such as flexible displays and organic EL light-emitting devices, face challenges with low bending resistance and light transmittance, making them unsuitable for repeated bending applications.
Innovation Solution
A polyimide varnish containing specific transition metal elements like Zn, Zr, Cu, Cr, Mn, Co, Pd, Ni, Rh, Al, and Fe, at concentrations between 0.05 to 500 ppm, is used to create a polyimide film with enhanced bending resistance and high transparency, achieved through improved polymerization reactivity and molecular weight increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyimide films are used, then heat resistance and chemical resistance are improved, but bending resistance against multiple bending is worsened
Solution Approach 1:
The patent changes the chemical composition parameters of the polyimide film by incorporating specific metal elements (Fe, Co, Ni, Cu, Zn, Al, Mn, Mo, or Ti) at controlled concentrations (0.01-1000 ppm). This parameter modification allows the film to maintain heat resistance while improving bending resistance through enhanced molecular structure and intermolecular interactions provided by the metal elements.
Solution Approach 2:
The patent creates a composite polyimide material by combining conventional polyimide resin with trace amounts of metal elements. This composite approach allows the film to inherit the excellent heat resistance of polyimide while gaining improved bending resistance from the metal elements that reinforce the polymer structure without compromising thermal stability.
2Reliability
If polyimide films with rigid skeleton monomers are used to improve surface adhesion, then adhesion is improved, but light transmittance is worsened
Solution Approach 1:
The patent modifies the polyimide composition by adding metal elements at very low concentrations (0.01-1000 ppm), which is sufficient to improve surface adhesion through enhanced intermolecular forces while maintaining high light transmittance. The low concentration ensures that the metal elements do not form light-absorbing aggregates that would reduce transparency.
Solution Approach 2:
The patent applies the metal element modification locally at the molecular level rather than using rigid skeleton monomers throughout the entire polymer structure. This localized modification of specific regions with metal elements provides improved adhesion at the interface while the bulk polymer structure remains transparent, resolving the contradiction between adhesion and light transmittance.
3Strength
If metal elements are added to improve bending resistance, then bending resistance is improved, but light transmittance may be worsened due to light absorption
Solution Approach 1:
The patent optimizes the concentration parameter of metal elements to a specific range (0.01-1000 ppm) that provides sufficient bending resistance through structural reinforcement while remaining below the threshold for significant light absorption. This precise parameter control allows simultaneous achievement of both improved mechanical strength and maintained optical transparency.
Solution Approach 2:
The patent uses a partial amount of metal elements (trace concentrations) that is excessive for providing adhesion improvement but insufficient to cause significant light absorption. This partial action approach achieves the necessary bending resistance without reaching the concentration level where metal particles would absorb visible light and reduce transmittance.
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 polyimide film exhibits improved bending resistance against multiple bending cycles while maintaining high transparency, suitable for flexible optical devices.
Implementation Method 1
the varnish contains at least one metal element(s) that is a typical metal element(s) having an atomic weight of from 26 to 201 except alkali metals and alkaline earth metals, or a transition metal element(s) having an atomic weight of from 26 to 201, and wherein at least one of the metal element(s) contained in the varnish is present in an amount of from 0.05 to 500 ppm relative to the polymer (α)
Data Source
AI summary
The purpose of the present invention is to provide a, polyimide film having high transparency and improved bending resistance against multiple times of bending, and a varnish capable of providing such a polyimide film. The varnish according to the present invention contains a polymer (α) and a solvent (β). The polymer (α) is polyimide or a polyimide precursor. The varnish further contains a typical metal element having an atomic weight of 26-201 except alkali metals and alkaline earth metals, or at least one metal element among transition metal elements having an atomic weight of 26-201 or less. At least one of the metal elements contained in the varnish is present in an amount of 0.05-500 ppm relative to the polymer (α).