Foldable Glass Substrate Structure for Small Bend Radius and Impact Resistance
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Solution Overview
Problem
Existing foldable displays and covers face challenges in achieving small minimum bend radii while maintaining good impact and puncture resistance, with conventional glass-based substrates failing to meet these requirements due to mechanical instabilities and strain issues.
Innovation Solution
The development of foldable substrates with a central portion having a thickness less than the overall substrate thickness, featuring recessed surfaces and compressive stress regions, along with controlled transition regions, enhances impact and puncture resistance and reduces mechanical instabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If glass-based substrates are made thinner to reduce minimum bend radius, then foldability is improved, but impact resistance and puncture resistance deteriorate
Solution Approach 1:
The substrate is designed with non-uniform thickness, featuring a thinner central portion (50-120 μm) for flexibility and a thicker peripheral portion (125-200 μm) for strength. This local variation in thickness allows the substrate to achieve both small minimum bend radius in the center while maintaining good impact and puncture resistance at the edges.
Solution Approach 2:
The substrate is divided into distinct functional regions: a central portion optimized for bending flexibility and peripheral portions optimized for mechanical strength. This segmentation allows each region to be optimized independently for its specific function, resolving the contradiction between thinness for foldability and thickness for strength.
2Strength
If glass-based substrates are made thicker to improve impact resistance, then strength is improved, but minimum bend radius increases
Solution Approach 1:
The substrate employs local thickness variation where the peripheral regions are thicker (125-200 μm) to provide impact resistance, while the central region is thinner (50-120 μm) to enable small minimum bend radius. This local quality differentiation allows simultaneous achievement of strength and foldability.
Solution Approach 2:
By segmenting the substrate into central and peripheral portions with different thicknesses, the design allows the peripheral regions to bear impact loads while the central region facilitates bending, thus resolving the contradiction between overall strength and local flexibility.
3Ease of manufacture
If uniform thickness is used throughout the substrate, then manufacturing is simplified, but mechanical instabilities occur during folding
Solution Approach 1:
The substrate is designed with deliberately varied local thickness to optimize mechanical stability during folding. The thinner central portion reduces stress concentration while the thicker peripheral portions maintain structural integrity, preventing mechanical instabilities that would occur in uniform thickness designs.
Solution Approach 2:
The substrate thickness parameter is changed spatially across the substrate, transitioning from thinner regions in the center to thicker regions at the periphery. This parameter variation optimizes the stress distribution during bending and folding operations, enhancing mechanical stability.
Data Source
AI summary
Foldable substrates comprise a first portion, a second portion, and a central portion positioned therebetween. The first portion comprises a substrate thickness and a first depth of compression. The central portion comprises a central thickness and a first central depth of compression. In aspects, a ratio of the first depth of compression to the substrate thickness is greater than a ratio of the first central depth of compression to the central thickness. In aspects, a ratio of a first depth of layer associated with the first depth of compression to the substrate thickness is greater than a ratio of a first central depth of layer associated with the first central compressive stress region to the central thickness. Methods comprise chemically strengthening a foldable substrate, etching a portion of the first major surface to form a first central surface area, and further chemically strengthening the foldable substrate.