Fluorinated Diamine Polyimide for Transparent Flexible Displays
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Solution Overview
Problem
Conventional polyimides used in display applications suffer from yellowing due to charge transfer complexes, which affects their transparency and thermal expansion properties, making them unsuitable for flexible displays requiring high solubility, transparency, and thermal stability.
Innovation Solution
A novel diamine compound with specific fluoroalkyl and cyano groups is introduced to the polyimide main chain, inhibiting charge transfer and reducing crystallinity, thereby enhancing transparency and mechanical properties, and a method for manufacturing this compound and its subsequent polymerization into transparent films is developed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional polyimide structure is used, then thermal stability and mechanical properties are maintained, but transparency deteriorates due to yellowing from charge transfer complexes
Solution Approach 1:
The patent introduces fluorinated aromatic diamine units with specific local chemical structures (containing F atoms and aromatic rings) into the polyimide main chain. These localized structural modifications create regions with reduced electron density and altered electronic properties that suppress charge transfer complexes, thereby improving transparency while maintaining the overall thermal stability provided by the polyimide backbone structure.
Solution Approach 2:
The patent changes the chemical composition parameters of the polyimide by incorporating diamine units with fluorine atoms and aromatic groups. This parameter change modifies the electronic structure and HOMO-LUMO energy gap of the polymer, reducing the tendency to form charge transfer complexes and thus improving optical transparency while preserving thermal properties through the rigid aromatic structure.
2Strength
If aromatic structure is used in polyimide, then mechanical strength is improved, but color transparency deteriorates due to charge transfer complex formation
Solution Approach 1:
The patent introduces fluorinated aromatic diamine units with specific local chemical structures (containing F atoms and aromatic rings) into the polyimide main chain. These localized structural modifications create regions with reduced electron density and altered electronic properties that suppress charge transfer complexes, thereby improving transparency while maintaining the overall thermal stability provided by the polyimide backbone structure.
Solution Approach 2:
The patent creates a composite molecular structure within the polyimide chain by combining fluorinated aromatic diamine units with the polyimide backbone. This composite structure at the molecular level integrates the mechanical strength benefits of aromatic structures with the transparency benefits of fluorinated groups, achieving both properties simultaneously in the final polymer material.
3Temperature
If polyimide is used for flexible display, then thermal resistance is achieved, but solubility and processingability are insufficient
Solution Approach 1:
The patent changes the chemical composition parameters of the polyimide by incorporating diamine units with fluorine atoms and aromatic groups. This parameter change modifies the electronic structure and HOMO-LUMO energy gap of the polymer, reducing the tendency to form charge transfer complexes and thus improving optical transparency while preserving thermal properties through the rigid aromatic structure.
Solution Approach 2:
The patent introduces fluorinated aromatic diamine units with specific local chemical structures (containing F atoms and aromatic rings) into the polyimide main chain. These localized structural modifications create regions with reduced electron density and altered electronic properties that suppress charge transfer complexes, thereby improving transparency while maintaining the overall thermal stability provided by the polyimide backbone structure.
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 polymer exhibits improved mechanical properties, heat resistance, and transparency, with a haze of 2 or less and a yellowness index of 20 or less, suitable for applications in flexible displays and optical films.
Implementation Method 1
aromatic polyimide has a unique color of dark brown. The reason for this is that electrons can be excited due to a σ electron, a π electron, a nonbonding unshared electron pair within the imide structure, and it can be explained by the theory of charge transfer complex (hereinafter, called CT-complex) induced by π electrons of benzene within a main chain of the polyimide.
Implementation Method 2
a method of introducing an electron-withdrawing functional group having relatively strong electronegativity such as trifluoromethyl (—CF3), sulfone (—SO2) and ether (—O—) to the main chain of the polyimide is used to lower resonance effect by limiting the movement of π electron.
Implementation Method 3
Polyimide (PI) is a polymer having relatively low crystallinity or amorphous structure, and it has advantages such as easy manufacturing process, easy process to make a thin film and no crosslinkable moieties necessary for curing, as well as polymeric properties such as high transparency, excellent thermal and chemical resistance, excellent mechanical and electrical properties, and dimensional stability due to its rigid chain structure.
Data Source
AI summary
The present invention provides a novel diamine compound capable of producing a polymer which exhibits greatly enhanced mechanical properties and heat resistance while maintaining transparency. A film including a polymer produced using the diamine compound has excellent transparency, heat resistance, mechanical strength and flexibility, and thus can be used in various fields, such as in a device substrate, a display cover substrate, an optical film, an Integrated circuit (IC) package, an adhesive film, a multi-layer flexible printed circuit (FPC), a tape, a touch panel and an optical disc protection film, and the like.