Tempered Glass Plate Bending Strain and Compressive Stress Control
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Solution Overview
Problem
Tempered glass sheets used in foldable displays experience reduced visibility and increased breakage risk due to bending strain and compressive stress issues when held in a bent state.
Innovation Solution
A tempered glass sheet with a compressive stress value of 200 MPa or higher on the outermost surface and a bending strain of 30×10−4 or less, achieved through ion-exchange treatment and specific glass composition, to maintain visibility and prevent breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cover member is held in a bent state for a certain period of time, then the bendability is maintained, but the visibility of the bent portion increases (image quality deteriorates)
Solution Approach 1:
The patent applies parameter changes by controlling the bending strain to be 30×10^-4 or less and the compressive stress value on the outermost surface to be 200 MPa or higher. By adjusting these physical parameters through ion-exchange treatment and specific glass composition, the glass maintains bendability while minimizing visibility degradation in the bent portion.
2Strength
If the compressive stress value on the outermost surface is increased to prevent breakage, then the strength increases, but the bending strain increases causing visibility reduction
Solution Approach 1:
The patent resolves this contradiction by precisely controlling multiple parameters: compressive stress value (≥200 MPa), bending strain (≤30×10^-4), and ion-exchange treatment conditions. By optimizing the ion-exchange treatment parameters and glass composition, the patent achieves sufficient compressive stress for breakage prevention while maintaining bending strain within acceptable limits for visibility.
Solution Approach 2:
The patent uses composite material approach by combining specific glass composition (containing SiO2, Al2O3, B2O3, and other oxides in controlled proportions) with ion-exchange treatment to create a glass structure that simultaneously achieves high compressive stress and low bending strain.
3Reliability
If the compressive stress value on the outermost surface is increased to prevent breakage, then the reliability increases, but the manufacturing complexity increases
Solution Approach 1:
The patent achieves breakage resistance by controlling the compressive stress value to be 200 MPa or higher through ion-exchange treatment. This parameter control ensures reliability while using established manufacturing processes (ion-exchange treatment and conventional glass forming) to avoid excessive manufacturing complexity.
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 effectively reduces bending strain and enhances compressive stress, maintaining visibility and preventing breakage in foldable displays by controlling the glass sheet's compressive stress and strain levels.
Implementation Method 1
a tempered glass sheet including a compressive stress layer on a surface
Data Source
AI summary
A tempered glass sheet according to an embodiment of the present invention has a compressive stress layer on a surface of the tempered glass sheet, in which a compressive stress value on the outermost surface of the compressive stress layer is 200 MPa or higher, and a bending strain is 30×10−4 or less.