Cycloolefin Polyimide Sacrificial Layer for UV Laser Delamination
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Solution Overview
Problem
Current methods for manufacturing flexible substrates face challenges in achieving low coefficient of thermal expansion, high solubility, transparency, and thermal stability, while also requiring efficient delamination techniques that minimize energy density and ash generation during the laser lift-off process.
Innovation Solution
A laminate comprising a carrier substrate, an organic sacrificial layer with a polyimide resin containing an amide bond, and a flexible substrate layer, where the polyimide is prepared by polymerizing specific diamines and tetracarboxylic anhydrides, allowing for reduced adhesion to the carrier substrate using a UV laser, thereby facilitating easy delamination with low energy density and minimizing ash generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aromatic polyimide is used to achieve high thermal stability and mechanical properties, then thermal stability and mechanical strength are improved, but color transparency deteriorates due to deep brown color from charge transfer complex
Solution Approach 1:
The patent changes the chemical structure parameters of polyimide by introducing cycloolefin units (non-aromatic rings) instead of aromatic benzene units in the main chain. This structural parameter change reduces the charge transfer complex formation that causes brown coloring, thereby improving color transparency while maintaining thermal stability through the rigid cycloolefin structure.
Solution Approach 2:
The patent creates a composite polymer structure by combining cycloolefin units with imide linkages in a single polyimide chain. This composite molecular structure integrates the thermal stability of imide with the optical clarity of cycloolefin, achieving both high thermal stability and color transparency simultaneously.
2Temperature
If polyimide is used to achieve excellent heat resistance and chemical resistance, then thermal stability and chemical resistance are improved, but coefficient of thermal expansion remains too high for display applications
Solution Approach 1:
The patent modifies the molecular structure parameters by incorporating cycloolefin units with rigid six-membered rings that have lower thermal expansion coefficients than aromatic benzene rings. This structural parameter change reduces the overall coefficient of thermal expansion of the polyimide while preserving heat resistance through the stable imide linkage and rigid cyclic structure.
3Strength
If conventional polyimide is used as sacrificial layer to achieve good adhesion to carrier substrate, then adhesion strength is improved, but laser delamination requires high energy density causing ash generation
Solution Approach 1:
The patent changes the optical parameters of the sacrificial layer by selecting polyimide formulations with specific UV absorption characteristics. The modified polyimide contains structural features that enhance UV absorption at wavelengths suitable for laser delamination, enabling effective adhesion during processing while requiring lower laser energy density for delamination, thus reducing ash generation.
Solution Approach 2:
The patent converts the potential harm of high UV absorption (which could cause excessive heating and ash) into a benefit by carefully selecting the absorption spectrum. The polyimide is designed to absorb UV at specific wavelengths that promote controlled delamination rather than uncontrolled decomposition, transforming the absorption characteristic from a potential harm into a beneficial control mechanism for low-energy delamination.
4Strength
If polyimide is used to achieve high-performance properties, then mechanical strength and electrical properties are improved, but solubility deteriorates making solution molding difficult
Solution Approach 1:
The patent modifies the molecular structure parameters by introducing cycloolefin units with different steric and electronic properties compared to aromatic units. These parameter changes can enhance intermolecular spacing and reduce pi-pi stacking interactions that typically reduce solubility in aromatic polyimides, thereby improving solubility while maintaining mechanical strength through the rigid cyclic structure.
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 solution enables efficient delamination of the flexible substrate with reduced energy density and ash generation, improving process efficiency and reliability by utilizing a polyimide with high UV absorbance and controlled thermal expansion, thus addressing the requirements for flexible substrate manufacturing.
Implementation Method 1
the polyimide is prepared by polymerizing at least one diamine selected from the following formulas 3a to 3c and at least one tetracarboxylic anhydride... the adhesion of the organic sacrificial layer to the carrier substrate is reduced by a UV laser... the polyimide contained in the organic sacrificial layer may have a coefficient of thermal expansion (CTE) of 0 to 20 ppm/°C
Data Source
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AI summary
According to the present invention, a laminate for manufacturing a flexible substrate uses, as an organic sacrificial layer for separation of a flexible substrate and a carrier substrate, a polyimide having a high absorption rate for a UV laser so as to enable laser energy density (E/D) necessary during a laser separation process to be reduced and the generation of ash caused by the separation process to be remarkably reduced, thereby enabling process efficiency during a display manufacturing process to improve and reliability of an element to increase by improving the permeability of the flexible substrate.