Foldable Substrate Neutral Stress Configuration
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Solution Overview
Problem
Conventional foldable displays and covers with small minimum bend radii suffer from poor impact and puncture resistance, while thicker glass-based sheets with good resistance have large minimum bend radii, necessitating the development of foldable apparatus with low bend radii and enhanced impact and puncture resistance.
Innovation Solution
A foldable substrate with a neutral stress configuration, comprising a glass-based or ceramic-based material with compressive stress regions, is used, which is chemically strengthened to increase density and compressive stresses, allowing for improved impact and puncture resistance while maintaining good folding performance. This substrate is supported by a housing member with a support that contacts the central portion, reducing damage and facilitating compact folding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If plastic displays and covers with small minimum bend radii are used, then good folding performance is achieved, but impact and puncture resistance deteriorate
Solution Approach 1:
The patent changes the material parameter from plastic to glass-based or ceramic-based substrates, and controls the fictive temperature parameter to be substantially equal to the anneal point temperature. This enables the substrate to achieve both small minimum bend radii (good folding performance) and high impact/puncture resistance simultaneously, resolving the contradiction between folding performance and strength.
2Ease of operation
If ultra-thin glass-based sheets with small minimum bend radii are used, then good folding performance is achieved, but impact and puncture resistance deteriorate
Solution Approach 1:
The patent controls the fictive temperature parameter of the glass-based substrate to be substantially equal to the anneal point temperature, and introduces compressive stress regions through chemical strengthening. This enables ultra-thin glass-based sheets to achieve both small minimum bend radii and high impact/puncture resistance, resolving the contradiction between folding performance and strength.
Solution Approach 2:
The patent creates a composite structure within the glass-based substrate by introducing compressive stress regions through ion exchange or chemical strengthening processes. This composite stress distribution enables the substrate to maintain small bend radii while achieving high impact and puncture resistance.
3Strength
If thicker glass-based sheets with good impact and puncture resistance are used, then strength is improved, but minimum bend radii increase
Solution Approach 1:
The patent changes the fictive temperature parameter to be substantially equal to the anneal point temperature and introduces compressive stress regions, enabling thin glass-based sheets to achieve high impact and puncture resistance without increasing thickness. This resolves the contradiction between strength and folding performance.
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 provides a foldable apparatus with increased impact and puncture resistance, reduced fatigue, and improved durability, enabling effective bend-induced stress management and compact configuration without compromising on scratch resistance or folding performance.
Implementation Method 1
chemically strengthening the foldable substrate, for example, because the larger ions exchanged into the foldable substrate create larger stresses in a denser substrate
Implementation Method 2
forming a ribbon (e.g., foldable substrate) at an elevated temperature (e.g., when the ribbon comprises a viscosity in a range from about 104 Pascal-seconds and about 107 Pascal-seconds and/or about an anneal point temperature)
Data Source
AI summary
Foldable apparatus comprise a foldable substrate comprising a substrate thickness. The second major surface of the foldable substrate faces an end portion of a first inner surface area of a first housing member extending along a first plane. The second surface faces an end portion of a second inner surface area of a second housing member extending along a second plane. A support is attached to at least the second housing member. The support contacts the second major surface when an angle between the first plane and the second plane ranges from about 80° to about 135°. The support is spaced from the second major surface when an angle between the first plane and the second plane ranges from about 0° to about 30°. In some embodiments, the foldable substrate comprises a neutral stress configuration at a parallel plate distance ranging from about 20 millimeters to about 200 millimeters.