Chemically Strengthened Glass Surface Roughness and Hydrogen Profile
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Solution Overview
Problem
The strength of chemically strengthened glass is compromised due to moisture penetration during the chemical strengthening process, leading to reduced surface strength and potential appearance failures, particularly when conventional polishing or etching methods are used.
Innovation Solution
A chemically strengthened glass with a controlled hydrogen concentration profile and surface roughness (Ra ≥ 0.20 nm) is developed, ensuring the hydrogen concentration in the surface layer follows a specific relational equation, thereby enhancing surface strength without the need for polishing or hydrofluoric acid etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If polishing treatment is performed after chemical strengthening, then surface smoothness is improved, but surface strength is reduced due to scratching
Solution Approach 1:
Instead of polishing after chemical strengthening (conventional sequence), the invention performs chemical strengthening first and then applies a specific surface treatment that increases roughness to 0.20 nm or more. This inverted approach prevents the strength reduction that occurs with conventional polishing while still achieving acceptable surface quality.
Solution Approach 2:
The invention changes the surface roughness parameter from the conventional smooth finish (Ra < 0.20 nm) to a controlled rough finish (Ra ≥ 0.20 nm). This parameter change prevents moisture penetration and hydrogen concentration increase that would otherwise occur with smoother surfaces, thereby maintaining surface strength.
2Strength
If etching treatment with hydrofluoric acid is performed, then surface strength is improved by removing defective layers, but appearance failures occur due to pit formation and safety concerns arise
Solution Approach 1:
The invention replaces the expensive and hazardous hydrofluoric acid etching process with a simpler, safer surface treatment method. The new method achieves the same strength improvement goal without the appearance failures (pits) and safety concerns associated with hydrofluoric acid handling.
Solution Approach 2:
The invention substitutes the chemical etching process with hydrofluoric acid with a different surface treatment approach that controls surface roughness. This replacement eliminates the need for hazardous chemicals while achieving the desired strength improvement through controlled surface morphology rather than chemical removal.
3Stress or pressure
If chemical strengthening is performed, then surface compressive stress is increased, but surface strength is reduced due to moisture penetration and hydrogen concentration increase
Solution Approach 1:
The invention applies a surface treatment after chemical strengthening that creates a rough surface morphology (Ra ≥ 0.20 nm) as a preliminary protective measure. This rough surface structure prevents subsequent moisture penetration and hydrogen concentration increase, counteracting the strength-reducing effect that would otherwise occur after chemical strengthening.
Solution Approach 2:
The invention converts the potentially harmful effect of chemical strengthening (which creates a smooth surface prone to moisture penetration) into a benefit by subsequently creating a controlled rough surface. The roughness, which might seem counterintuitive, actually prevents moisture ingress and hydrogen accumulation, thereby maintaining the strength benefits of chemical strengthening.
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
This approach significantly improves and stabilizes the surface strength of chemically strengthened glass, preventing strength reduction and appearance failures, while ensuring safety and cost-effectiveness in production.
Implementation Method 1
a chemically strengthened glass having a compressive stress layer formed in a surface layer thereof according to an ion exchange method
Implementation Method 2
the glass has a surface roughness (Ra) of 0.20 nm or higher
Data Source
AI summary
A chemically strengthened glass having a compressive stress layer formed in a surface layer thereof according to an ion exchange method, in which the glass has a surface roughness (Ra) of 0.20 nm or higher, a hydrogen concentration Y in a region to a depth X from an outermost surface of the glass satisfies the following relational equation (I) at X=from 0.1 to 0.4 (μm), a surface strength F (N) measured by a ball-on-ring test under the following conditions is (F≥1500×t2) relative to a sheet thickness t (mm) of the glass, and a surface of the glass has no polishing flaw:Y=aX+b (I)in which meanings of respective symbols in the equation (I) are as follows: Y: hydrogen concentration (as H2O, mol/L); X: depth from the outermost surface of the glass (μm); a: −0.270 to −0.005; and b: 0.020 to 0.220.