Polyimide Film Modulus Stability Under High Humidity
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Solution Overview
Problem
Polyimide-based films exhibit significant deformation and changes in optical and mechanical properties under high-temperature and high-humidity conditions, leading to reduced mechanical strength and optical quality, making them unsuitable for durable applications.
Innovation Solution
A polyimide-based film with a modulus of 5 GPa or more, maintained under 60°C and 90% RH for 500 hours, with a rate of change in modulus of 10% or less, and a phase difference change of 5% or less, achieved through heat treatment with a solvent content of 5 wt% or less and controlled humidity, ensuring stability and minimal curling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If polyimide-based film is used for window cover, then lightness and flexibility are improved, but mechanical strength and stability under high-temperature high-humidity conditions deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the polyimide film by incorporating specific cyclic carbonate groups and controlling the ratio of aromatic rings to heteroatoms. This compositional parameter change enables the film to maintain mechanical strength and dimensional stability under high-temperature high-humidity conditions while retaining the lightness and flexibility advantages of plastic films.
Solution Approach 2:
The patent creates a composite polyimide structure by combining specific cyclic carbonate groups with polyimide backbone, forming a new material system that exhibits both the desired mechanical properties and environmental stability. The composite molecular structure resists water penetration and maintains integrity under severe conditions.
2Adaptability or versatility
If polyimide-based film is used for window cover, then flexibility and light weight are improved, but resistance to water penetration and deformation under high-temperature high-humidity conditions worsens
Solution Approach 1:
The patent modifies the molecular structure parameters of polyimide by introducing cyclic carbonate groups and controlling aromatic ring content. This parameter change creates a molecular structure that is both flexible and resistant to water penetration, resolving the contradiction between flexibility and water resistance.
Solution Approach 2:
The patent applies local quality modification by introducing specific functional groups (cyclic carbonate) at specific positions in the polyimide molecular structure. This local structural modification provides water resistance at the molecular level while maintaining overall film flexibility.
3Ease of manufacture
If conventional polyimide film is used, then manufacturing ease is improved, but optical property stability and mechanical property consistency under severe conditions worsen
Solution Approach 1:
The patent establishes specific parameter ranges for the polyimide composition (cyclic carbonate group content, aromatic ring ratio, molecular weight distribution) that ensure consistent optical and mechanical properties. By controlling these parameters within defined ranges, the patent achieves both ease of manufacture and property consistency under severe conditions.
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 film maintains excellent mechanical and optical properties, including high modulus, low curl, and stable phase difference characteristics, even after prolonged exposure to high-temperature and high-humidity conditions, enhancing its durability and suitability for window cover films and display panels.
Implementation Method 1
the rate of change of the modulus being obtained by performing heat treatment on the polyimide-based film in which a content of a solvent is 5 wt % or less using hot air containing a humidity of 1 to 10 wt %
Implementation Method 2
the polyimide-based film has hydrophilic properties, and thus, the above problems occur more seriously in the polyimide-based film in the high-temperature and high-humidity environment
Data Source
AI summary
The present invention relates to a polyimide-based film, a window cover film including the polyimide-based film, and a display panel including the polyimide-based film. More specifically, the present invention relates to a polyimide-based film of which a modulus measured according to ASTM D882 is 5 GPa or more and a rate of change of the modulus, after the polyimide-based film is maintained under a high-temperature and high-humidity condition of 60° C. and 90% RH for 500 hours, is 10% or less.