Siloxane Polyimide Film Thermal Expansion Mismatch
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Solution Overview
Problem
Polyimide films used in display devices face issues with curling due to thermal expansion differences when coated on ultra-thin tempered glass, which affects their mechanical properties and optical clarity.
Innovation Solution
A polyimide precursor composition is developed, comprising a polyimide precursor with a specific siloxane structure and a solvent having a negative partition coefficient, which minimizes curling by introducing a stress relaxation segment, thereby improving thermal compatibility and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polyimide film is coated on ultra-thin tempered glass to replace tempered glass, then the film can be applied to display devices with improved flexibility, but the film curls due to thermal expansion differences between the film and the glass substrate
Solution Approach 1:
The patent modifies the thermal expansion characteristics of the polyimide film by changing the chemical structure of the diamine component. Specifically, it uses a diamine with a siloxane backbone (Formula 1) where the Si-O-Si linkage provides flexibility and altered thermal expansion properties, matching the thermal expansion coefficient of ultra-thin tempered glass to prevent curling while maintaining flexibility
Solution Approach 2:
The patent creates a composite polyimide structure by incorporating siloxane groups into the polymer backbone. This composite approach combines the mechanical properties of polyimide with the thermal stability and flexibility of siloxane, resulting in a material that simultaneously achieves flexibility and thermal compatibility with glass substrates
2Length of stationary object
If the polyimide film is made thinner to achieve ultra-thin characteristics, then the film can be applied to advanced display devices, but the mechanical strength and resistance to breaking during bending or folding deteriorate
Solution Approach 1:
The patent employs the siloxane-containing polyimide structure to create an inherently flexible and tough thin film. The Si-O-Si bonds in the polymer chain provide rotational freedom and flexibility, allowing the film to maintain high mechanical strength and fracture resistance even at ultra-thin thicknesses suitable for flexible display applications
Solution Approach 2:
The patent changes the molecular structure parameters of the polyimide by incorporating siloxane groups, which fundamentally alter the mechanical properties. This structural modification enables the film to achieve both ultra-thin thickness and high mechanical strength, overcoming the inverse relationship between thickness and strength
3Illumination intensity
If the polyimide film is made colorless and transparent with improved intrinsic yellow index characteristics, then the optical clarity is enhanced, but the complexity of the composition formulation increases
Solution Approach 1:
The patent achieves excellent optical clarity by changing the chemical parameters of the polyimide composition, specifically using the siloxane-containing diamine (Formula 1) with appropriate aromatic groups. This structural parameter change inherently reduces yellowing and improves transparency, eliminating the need for complex additives or post-processing treatments to achieve colorless and transparent 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 composition produces a polyimide film with reduced curling and enhanced transparency, maintaining mechanical integrity and optical clarity even when coated on ultra-thin tempered glass, addressing the thermal expansion mismatch.
Implementation Method 1
minimizes curling by introducing a stress relaxation segment
Implementation Method 2
curling due to thermal expansion differences
Implementation Method 3
a polyimide film comprising a cured product of the polyimide precursor composition
Data Source
AI summary
Provided is a polyimide precursor composition including a polyimide precursor including a siloxane structure and a solvent having a negative partition coefficient (log P). The polyimide precursor composition may be used to alleviate thermal expansion-contraction behavior, thereby producing a polyimide film with minimal curling.