Silicon-Modified Polyimide Film for Flexible Displays
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Solution Overview
Problem
Flexible display substrates face challenges in maintaining restorability after repeated bending and require a balance between flex resistance and surface hardness to prevent damage to touch sensors and display panels.
Innovation Solution
A polyimide film with a specific molecular structure, containing 10-50 mol% diamine residues with one or two silicon atoms and 50-90 mol% diamine residues without silicon atoms, offering high tensile elastic modulus, improved light transmittance, and controlled glass transition temperature, is developed to enhance flex resistance and surface hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a resin film is used to replace glass plate for flexible display, then weight is reduced and processability is improved, but surface hardness decreases making it vulnerable to damage
Solution Approach 1:
The patent uses a composite polyimide structure combining rigid aromatic diamine units with flexible aliphatic diamine units containing silicon atoms. This composite molecular structure provides both the hardness needed for surface protection and the flexibility required for bending, resolving the contradiction between surface hardness and flexibility in resin films replacing glass.
Solution Approach 2:
The patent modifies the molecular structure parameters of polyimide by incorporating specific ratios of aromatic to aliphatic diamine units (5:95 to 45:55 mol ratio). This parameter change optimizes the balance between tensile strength (surface hardness) and flexibility, allowing the resin film to maintain surface durability while enabling repeated bending without damage.
2Temperature
If polyimide resin is used for transparent applications, then heat resistance is improved, but transparency deteriorates due to yellow or brown color
Solution Approach 1:
The patent changes the chemical composition parameters by using specific aromatic diamines (like p-phenylenediamine) combined with aliphatic diamines containing silicon atoms. This compositional parameter change maintains the high heat resistance of polyimide while significantly improving optical transparency by reducing the yellow-brown discoloration typical of conventional polyimide resins.
3Ease of operation
If a resin film is made more flexible for bending, then flex resistance is improved, but surface hardness decreases reducing protection against damage
Solution Approach 1:
The patent applies local quality by having different regions of the polymer chain serve different functions: aromatic diamine units provide rigid segments for surface hardness and protection, while aliphatic diamine units with silicon atoms provide flexible segments for bending. This local differentiation within the molecular structure allows simultaneous optimization of both surface hardness and flex resistance.
Solution Approach 2:
The patent employs a composite molecular structure combining rigid aromatic polyimide segments with flexible aliphatic polyimide segments containing silicon atoms. This composite architecture allows the material to exhibit both high surface hardness for protection and high flexibility for repeated bending, resolving the contradiction between these two properties.
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 achieves increased flex resistance and surface hardness, allowing for repeated bending and improved protection against damage, while maintaining transparency and heat resistance.
Implementation Method 1
polyimide resin is a highly heat resistant resin obtained by a dewatering cyclization reaction of a polyamide acid obtained by a condensation reaction between an aromatic tetracarboxylic anhydride and an aromatic diamine
Implementation Method 2
a flexible display mounted on the mobile device is required to be able to return to the original state when it is unfolded and flattened
Data Source
AI summary
A polyimide film includes a polyimide in which a specific amount of molecular framework containing one or two silicon atoms in its main chain, wherein a total light transmittance measured in accordance with JIS K7361-1 is 85% or more; wherein a yellowness index calculated in accordance with JIS K7373-2006 is 30 or less; wherein a glass transition temperature is in a temperature range of from 150° C. to 400° C.; and wherein a tensile elastic modulus at 25° C. obtained by measuring a 15 mm×40 mm test piece at a tensile rate of 10 mm/min and a chuck distance of 20 mm in accordance with JIS K7127, is 1.8 GPa or more.