Flexible Backplane Substrate Crack Propagation Control
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Solution Overview
Problem
Flexible display devices face reliability issues due to cracks at the edge of flexible substrates, which can propagate to the active area, causing lighting faults or malfunctions when folded or bent, as they are weak in physical properties compared to glass substrates.
Innovation Solution
A backplane substrate with a flexible base film and interlayer insulating film featuring connection holes in columns that intersect when the substrate is folded, preventing crack propagation by distributing stress and blocking crack paths through the interlayer insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible substrate is used to enable folding or bending motion, then flexibility and thin profile are improved, but crack resistance and reliability deteriorate
Solution Approach 1:
The patent divides the flexible substrate into multiple segments by introducing folding lines with different folding forces. The substrate includes a first flexible substrate and a second flexible substrate connected via a folding line, where each segment has optimized thickness and structural properties to prevent crack propagation while maintaining flexibility
Solution Approach 2:
The patent applies different thicknesses and material properties to different regions of the flexible substrate. Specifically, the first flexible substrate has a first thickness and the second flexible substrate has a second thickness different from the first, creating localized structural optimization at the folding line to enhance crack resistance while preserving overall flexibility
2Length of moving object
If the flexible substrate is made thinner to reduce space occupancy, then device thickness is improved, but mechanical strength and crack resistance worsen
Solution Approach 1:
The patent implements non-uniform thickness distribution across the flexible substrate. The first flexible substrate has a first thickness while the second flexible substrate has a second thickness different from the first, with the folding line region specifically optimized to provide enhanced mechanical strength locally without increasing the overall device thickness
Solution Approach 2:
The patent uses composite flexible substrate structures with different material compositions and thicknesses in different regions. The first and second flexible substrates are made with different thickness specifications to create a composite structure that optimizes both mechanical strength and thin profile characteristics
3Manufacturing precision
If scribing is performed to define the effective area, then manufacturing precision is improved, but crack initiation at edges worsens
Solution Approach 1:
The patent introduces folding lines that segment the flexible substrate into distinct regions. These folding lines are positioned to prevent cracks initiated at scribed edges from propagating into the effective area, as the folding line acts as a barrier that redirects crack propagation away from critical regions
Data Source
AI summary
A backplane substrate and a flexible display having the same are provided. The backplane substrate includes a flexible base film having an active area with a plurality of sub-pixels and a non-display area around the active area; and an interlayer insulating film on flexible base film and including a plurality of connection holes provided in first columns and second columns with each of the first and second columns arranged in a first direction of the flexible base film. When the flexible base film is folded along a folding axis in a direction intersecting the first and second columns, the folding axis intersects at least one connection hole of the first and second columns.