Float Glass Chemical Strengthening Warpage Control
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Solution Overview
Problem
Conventional methods for chemical strengthening of float glass to enhance scratch resistance often result in warpage due to differences in chemical strengthening behavior between the top and bottom surfaces, requiring cumbersome dipping in mixed inorganic salts or grinding/polishing treatments, which compromise strength and productivity.
Innovation Solution
The solution involves controlling the difference in weathering degrees between the top and bottom surfaces by managing the Na2O concentration and ion exchange amounts, using specific formulas to ensure the difference in normalized Na2O surface concentrations and ion exchange amounts are within certain limits, thereby equalizing the strengthening degree and reducing warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If chemical strengthening is performed on float glass to enhance scratch resistance, then the strength and scratch resistance are improved, but warpage occurs due to difference in strengthening behavior between top and bottom surfaces
Solution Approach 1:
The patent applies different weathering treatments to different surfaces of the float glass. The bottom surface (contacted with molten tin) receives one level of weathering control while the top surface receives another, creating local quality differences that compensate for the inherent asymmetry in chemical strengthening behavior. This allows uniform strengthening without warpage.
Solution Approach 2:
The patent controls specific chemical parameters - particularly the Na2O concentration and ion exchange amounts - at different surfaces through weathering treatment. By adjusting these parameters before chemical strengthening, the patent equalizes the strengthening degree between top and bottom surfaces, preventing warpage while maintaining strength enhancement.
2Manufacturing precision
If grinding or polishing treatment is applied to remove surface heterogeneous layer before chemical strengthening, then warpage is reduced, but productivity decreases and strength is compromised
Solution Approach 1:
The patent performs weathering treatment as a preliminary action before chemical strengthening. This pre-treatment controls the Na2O concentration and ion exchange amounts at the surfaces, preparing the glass for uniform strengthening without requiring subsequent grinding or polishing. The preliminary weathering control eliminates the need for time-consuming mechanical removal of heterogeneous layers.
3Manufacturing precision
If strengthening stress is decreased to reduce warpage, then flatness is improved, but the strength of the float glass becomes insufficient
Solution Approach 1:
The patent changes the chemical parameters (Na2O concentration, ion exchange amounts) at the glass surfaces through controlled weathering. This parameter change equalizes the chemical composition at top and bottom surfaces, allowing uniform ion exchange during strengthening. As a result, high strengthening stress can be applied without causing warpage, maintaining both flatness and strength.
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 effectively suppresses warpage in float glass after chemical strengthening, allowing for excellent flatness without the need for polishing treatments and maintaining sufficient strength, thus improving the productivity and effectiveness of the chemical strengthening process.
Implementation Method 1
a compressive stress layer is formed on the surface by chemically strengthening a float glass
Implementation Method 2
the difference in the weathering degree between the top surface and the bottom surface, namely, the difference in the degree of hydration-dealkalization
Data Source
AI summary
The present invention relates to a float glass for chemical strengthening, containing a bottom surface coming into contact with a molten metal at the time of forming and a top surface opposing the bottom surface, in which a difference Δ(N—Na2O2) determined by subtracting a square of a normalized Na2O surface concentration of the bottom surface which is a value obtained by dividing an Na2O concentration in the bottom surface by an Na2O concentration at a depth position of 100 μm therefrom, from a square of a normalized Na2O surface concentration of the top surface which is a value obtained by dividing an Na2O concentration in the top surface by an Na2O concentration at a depth position of 100 μm therefrom, is 0.040 or less.