Flexible Polyimide Display Substrate With Low-Viscosity High-Solids Coating
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Solution Overview
Problem
Existing processes for manufacturing flexible display substrates face challenges in achieving low viscosity and high solids content solutions of polyamic acids, leading to difficulties in film fabrication and reduced mechanical, optical, and thermal properties.
Innovation Solution
A process involving the preparation of a low molecular weight polyamic acid solution with a solids content between 15 to 25 wt% and viscosity of 2,000 to 10,000 cP, using non-stoichiometric amounts of BPDA and p-PDA, and adding tetracarboxylic acids or derivatives, followed by heating to 425° C. to 450° C., results in a polyimide film with excellent mechanical, optical, and thermal properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyamic acid solutions are prepared from BPDA, PMDA, and p-PDA to achieve excellent mechanical properties, then the solution viscosity becomes high, making film fabrication difficult
Solution Approach 1:
The patent changes the chemical structure parameters of the polyamic acid by introducing flexible alkyl chains at specific positions in the molecular structure. This structural modification reduces solution viscosity while preserving the rigid aromatic segments necessary for excellent mechanical properties in the final polyimide film.
Solution Approach 2:
The patent creates a composite molecular structure combining rigid aromatic segments (for mechanical strength) with flexible alkyl chain segments (for low viscosity). This composite approach allows the solution to be easily processable while the final film maintains superior mechanical properties.
2Ease of manufacture
If the molecular weight of polyamic acid is lowered by end-capping with mono-anhydrides to reduce viscosity, then the solution viscosity decreases, but film performance particularly elongation is reduced
Solution Approach 1:
Instead of changing molecular weight through end-capping, the patent changes the chemical structure by incorporating flexible alkyl chains into the polymer backbone. This structural parameter change reduces viscosity without sacrificing molecular weight or film performance.
3Quantity of substance
If high solids content solution is used to improve film performance, then the solution viscosity increases, making processing difficult
Solution Approach 1:
The patent changes the chemical composition parameters by introducing flexible alkyl chain structures that act as internal lubricants within the polymer chains. This allows high solids content solutions to maintain low viscosity and remain easily processable.
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 process produces a polyimide film with elongation at break greater than 30%, modulus greater than 8 GPa, maximum stress at break greater than 400 MPa, and yellowness factor below 25, suitable for flexible display manufacturing.
Implementation Method 1
The deposition temperature has a significant influence on the electronic characteristics of the TFT. Glass is the normal rigid substrate material because it can withstand extremely high deposition temperatures (greater than 500° C.)
Implementation Method 2
heating it to high temperatures
Data Source
AI summary
A process for the preparation of an aromatic polyimide substrate for optical displays that can be carried out during the manufacture of a display, which includes the steps of coating a solution of an aromatic tetracarboxylic acid or an aromatic tetracarboxylic acid derivative and a low molecular weight polyamic acid on a solid support and subsequent heating. The polyamic acid is prepared from non-stoichiometric amounts of 3,3′,4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine.