Polyamic Acid Composite for Low Thermal Expansion
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Solution Overview
Problem
Current polyimide films used in display substrates face challenges in achieving high transparency and low thermal expansion, with existing fluorinated polyimide films exhibiting high thermal expansion coefficients, which are not suitable for flexible displays requiring coefficients of 20 ppm/°C or less and glass transition temperatures of 350°C or higher.
Innovation Solution
A polyamic acid polymer composite is developed, comprising 50-99 wt% of a polyamic acid polymer with a specific repeating unit and 1-50 wt% of silica-based particles, where the silica particles are chemically bonded to the polymer via ether, amide, or ester bonds, forming a network structure, to create a polyimide film with improved thermal properties and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a fluorinated polyimide is used to improve transparency, then light transmittance increases, but thermal expansion coefficient increases
Solution Approach 1:
The patent combines fluorinated polyimide with inorganic particles (silica, alumina, or titania) to create a composite material that achieves both high transparency and low thermal expansion. The inorganic particles have low thermal expansion coefficients that compensate for the high thermal expansion of the fluorinated polyimide, while the fluorinated groups maintain optical transparency. This composite approach allows the film to achieve thermal expansion coefficients of 20 ppm/°C or less while maintaining light transmittance of 80% or more.
Solution Approach 2:
The patent modifies the chemical structure of polyimide by introducing fluorinated groups at specific positions in the polymer chain, which changes the physical parameters of the material. The fluorination increases transparency but also increases thermal expansion, so this parameter change is combined with the addition of inorganic particles to balance the thermal expansion coefficient while maintaining the transparency improvement.
2Weight of moving object
If plastic substrates are used to achieve lightweight and flexible displays, then weight decreases, but thermal expansion control becomes more difficult
Solution Approach 1:
The patent creates a composite film structure where plastic substrate is coated with a polyimide layer containing inorganic particles. This composite structure allows the lightweight plastic substrate to achieve the thermal expansion properties of glass (20 ppm/°C or less) through the thermally stable polyimide coating with low-expansion inorganic particles, enabling flexible displays with glass-level thermal stability.
3Ease of operation
If polyimide film thickness is reduced to achieve flexibility, then flexibility increases, but maintaining glass transition temperature becomes more difficult
Solution Approach 1:
The patent uses a composite structure with polyimide and inorganic particles to maintain high glass transition temperature (350°C or higher) even in thin film form. The inorganic particles provide thermal stability that prevents the polyimide from softening at lower temperatures, allowing the film to remain flexible and processable at reduced thickness while maintaining the required glass transition temperature for display applications.
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 high transparency (>80% at 550 nm), low thermal expansion (≤20 ppm/K from 100 to 300°C), and a glass transition temperature of 350°C or higher, making it suitable for flexible display substrates.
Implementation Method 1
the silica particles are chemically bonded to the polymer via ether, amide, or ester bonds, forming a network structure
Data Source
AI summary
The present invention relates to a polyamic acid polymer composite and a method for producing the same, and more specifically, a polyamic acid polymer composite, which can be applied to display substrate production due to its high transparency and low thermal expansion of glass-level, and a method for producing same. The polyamic acid polymer composite comprises 50 to 99 wt % of a polyamic acid polymer having a repeating unit of Chemical Formula 1; and 1 to 50 wt % of a silica-based particle:wherein, R1 to R3, m and n have the same meanings as defined in the specification.