PI Substrate Edge Thickness Control via Separable Film Masking
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Solution Overview
Problem
Flexible display substrates with uneven polyimide (PI) film thicknesses at the edges lead to defects such as residual solvents, incomplete curing, and holes, affecting the yield rate of PI substrates during the manufacturing process.
Innovation Solution
A method involving the formation of separable films and inorganic layers at the edge regions of the substrate, followed by the application and stripping of polyamic acid (PAA) films to achieve even PI film thickness through imidization, eliminating edge region thickness issues and improving substrate yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If PI coating is performed on the entire substrate including edge regions, then complete substrate coverage is achieved, but uneven PI film thickness occurs at the edges
Solution Approach 1:
The substrate is divided into a central region and an edge region. The edge region is further segmented by forming a separable film that extends from the edge toward the center. This segmentation allows different coating strategies to be applied to different regions, with the separable film serving as a mask to prevent PI coating on the edge region, thereby achieving uniform thickness control while maintaining complete coverage of the functional central area.
Solution Approach 2:
Different regions of the substrate are assigned different functional qualities. The central region receives the PI coating for its intended function, while the edge region is treated differently by being covered with a separable film that prevents coating. This local differentiation ensures that the PI film achieves uniform thickness in the functional area without the edge thickness problems that would occur with uniform coating across the entire substrate.
2Manufacturing precision
If edge regions are excluded from PI coating to ensure uniform thickness, then manufacturing precision is improved, but substrate coverage is reduced
Solution Approach 1:
A separable film is introduced as an intermediary element between the substrate and the PI coating process. This separable film serves as a temporary mask that prevents PI deposition on the edge region during coating, ensuring uniform thickness in the functional area. After coating, the separable film is removed, and the edge region can be subsequently processed or left as-is, thus achieving both uniform thickness and maintaining the option for complete substrate utilization.
Solution Approach 2:
The separable film is formed on the substrate before the PI coating process. This preliminary action prepares the substrate by defining which regions should be coated and which should be protected. By establishing this protective layer in advance, the subsequent PI coating can proceed uniformly across the intended area without edge effects, and the separable film can be removed afterward to reveal the properly coated substrate.
3Manufacturing precision
If separable films and PAA films are formed and stripped at edge regions, then PI film thickness uniformity is improved, but process complexity increases
Solution Approach 1:
The formation of the separable film and the PI coating process are merged into a single operational sequence. The separable film is applied first, then the PI coating is performed in one continuous process flow. This merging reduces the need for separate, complex operations and allows the edge protection and functional coating to be achieved in an integrated manner, thereby managing process complexity while maintaining precision.
Solution Approach 2:
The separable film serves multiple functions: it acts as a mask during PI coating to prevent edge deposition, provides a release layer for easy removal after coating, and can potentially serve as part of the final structure or be completely removed. This multi-functionality reduces the need for additional specialized components or processes, thereby managing overall process complexity while achieving the desired thickness uniformity.
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 method ensures even PI film thickness, reducing defects and enhancing the yield of PI substrates by stripping and imidizing the PAA films at the edge regions, resulting in improved manufacturing efficiency and quality.
Implementation Method 1
performing imidization on the first-layer PAA film on the substrate with the edge region exposed, to enable the first-layer PAA film to be transformed into a first-layer PI film
Implementation Method 2
stripping the first separable film and the first-layer PAA film that covers the first separable film to expose the edge region of the substrate
Data Source
AI summary
There are provided a PI substrate, a preparation method thereof and a display device. The preparation method includes: forming a first separable film at an edge region of a substrate; forming a first-layer polyamic acid (PAA) film on the first separable film and the substrate; stripping the first separable film and the first-layer PAA film that covers the first separable film to expose the edge region of the substrate; and performing imidization on the first-layer PAA film on the substrate with the edge region exposed, to enable the first-layer PAA film to be transformed into a first-layer PI film, thereby avoiding uneven film thicknesses at edges of the first-layer PI substrates.