Tempered Glass Softening Point Control via Beta-OH Parameter
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Solution Overview
Problem
Tempered glass with a specific shape, such as a curved shape, faces challenges in achieving a low softening point while maintaining high mechanical strength, as increasing compression stress and thickness of the compression stress layer requires the introduction of components like Al2O3, which raises the softening point.
Innovation Solution
Control of the β-OH value through methods such as using high water content raw materials, adjusting the addition of components like Cl or SO3, and employing specific melting processes to achieve a β-OH value of 0.3 to 1/mm, allowing for a glass composition of 45 to 75% SiO2, 0 to 30% Al2O3, and 0 to 30% Li2O+Na2O+K2O, with a compression stress layer of 50 MPa or more and 10 μm or more in thickness, while keeping the softening point at 900°C or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the compression stress value and thickness of the compression stress layer are increased to enhance mechanical strength, then the mechanical strength is improved, but the softening point is raised due to the introduction of Al2O3 and other components
Solution Approach 1:
The patent applies parameter changes by precisely controlling the β-OH value (a parameter related to water content and hydroxyl groups in the glass) within the range of 0.3 to 1.0 mm⁻¹, along with specific glass composition ratios (SiO2: 45-75 mass%, Al2O3: 0-30 mass%, Li2O+Na2O+K2O: 0-30 mass%). This parameter optimization enables the glass to achieve both high mechanical strength through ion exchange and low softening point for thermal processability, resolving the contradiction between strength enhancement and softening point elevation.
Solution Approach 2:
The patent creates a composite structure within the glass by forming a compression stress layer through ion exchange, where alkali metal ions are exchanged between the glass and molten salt. The controlled β-OH value and specific composition ratios create a composite material system that simultaneously achieves high compression stress (500-2000 MPa) and low softening point (below 900°C), enabling both mechanical strength and thermal processability.
2Strength
If Al2O3 and other components are introduced to enhance ion exchange performance and increase compression stress layer thickness, then the mechanical strength is improved, but the softening point is raised
Solution Approach 1:
The patent optimizes the β-OH value parameter within 0.3 to 1.0 mm⁻¹ and controls the composition ratios of SiO2, Al2O3, and Li2O+Na2O+K2O to achieve both high ion exchange performance and low softening point. This parameter control enables thermal processing at lower temperatures while maintaining high mechanical strength, resolving the contradiction between strength enhancement and ease of manufacturing through thermal processing.
Solution Approach 2:
The patent creates a composite glass structure with controlled β-OH value and specific composition ratios that enables simultaneous achievement of high compression stress layer thickness and low softening point. The ion-exchanged compression stress layer combined with the specific glass composition creates a composite material that is both mechanically strong and thermally processable, resolving the manufacturing contradiction.
3Temperature
If the β-OH value is controlled to lower the softening point, then the thermal processability is improved, but the compression stress value and thickness of compression stress layer may be reduced
Solution Approach 1:
The patent simultaneously optimizes multiple parameters: β-OH value (0.3-1.0 mm⁻¹), SiO2 content (45-75 mass%), Al2O3 content (0-30 mass%), and Li2O+Na2O+K2O content (0-30 mass%). This multi-parameter optimization ensures that the low softening point achieved through β-OH control does not compromise the compression stress value and thickness, as the composition ratios are specifically tuned to maintain high ion exchange performance while enabling thermal processing.
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 approach effectively lowers the softening point while securing high mechanical strength and thermal processability, enabling the production of tempered glass with specific shapes like curved shapes for exterior parts, such as mobile PC components, with improved thermal expansion coefficients and liquidus viscosity.
Implementation Method 1
a glass tempered by an ion exchange or the like (so-called tempered glass) tends to be used for the cover glass of mobile phones
Implementation Method 2
modifying the shape of the glass to a specific shape by thermal processing
Implementation Method 3
the appropriate control of a β-OH value results in lowering of softening point, while securing an appropriate compression stress value and thickness of compression stress layer
Data Source
AI summary
A tempered glass of the present invention includes, as a glass composition, in terms of mass %, 45 to 75% of SiO2, 0 to 30% of Al2O3, and 0 to 30% of Li2O+Na2O+K2O and has a β-OH value of 0.3 to 1/mm.