Chemically Strengthened Glass Substrate with Low Potassium Ion Concentration
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Solution Overview
Problem
Conventional glass substrates for mobile terminal devices, such as cellular phones, face challenges in achieving high strength while maintaining a thin form factor due to the limitations of acrylic resin protective plates and existing glass strengthening methods, which often result in increased thickness and susceptibility to bending.
Innovation Solution
A chemically strengthened glass substrate with a compressive stress layer having a potassium ion concentration of 500 ppm or less, formed through an ion exchange process using molten salt, and subsequent removal of the ion exchange layer to prevent tensile stress formation, is developed. This process enhances the glass substrate's strength and allows for a thinner, more robust design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a chemically strengthened glass substrate with a compressive stress layer is used, then the strength of the glass substrate is enhanced, but the standard deviation in breaking loads increases due to tensile stress formation
Solution Approach 1:
The patent removes the ion exchange layer from the surface of the chemically strengthened glass substrate. This extraction eliminates the source of tensile stress that causes high standard deviation in breaking loads, while preserving the compressive stress layer beneath that provides high strength.
Solution Approach 2:
The patent creates a non-uniform ion concentration distribution where the surface layer has low potassium ion concentration (after removal) and the subsurface layer maintains high potassium ion concentration. This local differentiation allows the surface to be free of tensile stress while the subsurface provides compressive stress reinforcement.
2Strength
If the mobile terminal device is designed with a wide distance between the protective plate and the display, then the acrylic resin protective plate can accommodate bending deflection, but the device thickness increases
Solution Approach 1:
The patent changes the material parameters of the protective plate from acrylic resin to chemically strengthened glass with specific ion concentration distribution. This material transformation enables the plate to resist bending forces while maintaining a thin profile, eliminating the need for large spacing.
3Length of stationary object
If a thin glass substrate is used, then the device can be thinned, but the glass substrate lacks sufficient strength to receive great external stress
Solution Approach 1:
The patent creates a composite structure within the glass substrate through chemical strengthening, forming a compressive stress layer beneath the surface. This internal composite structure provides high strength to thin substrates, enabling them to withstand great external stress despite minimal thickness.
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 achieves a glass substrate with significantly higher breaking strength and reduced standard deviation in breaking loads, even when formed in a thin shape, effectively addressing the need for high-strength, lightweight cover glasses for mobile terminal devices.
Implementation Method 1
chemically strengthening the glass substrate by immersing the glass substrate in heated molten salt such that ions of the glass substrate are ion-exchanged for ions of the molten salt
Implementation Method 2
removing an ion exchange layer formed in an uppermost surface layer of a primary surface of the glass substrate in the step of chemically strengthening the glass substrate
Data Source
Figure 1A~1B
Figure 1C
Figure 2
AI summary
A glass substrate chemically strengthened (1), includes a primary surface that has a compressive stress layer (1a) formed in an uppermost surface layer thereof. The compressive stress layer is configured to enhance strength of the glass substrate due to a compressive stress generated in the compressive stress layer. The compressive layer consists of a layer of a potassium ion concentration equal to or less than 5000 parts per million (ppm).