Float Glass Warpage Reduction via Fluorine Surface Treatment
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Solution Overview
Problem
The existing methods for manufacturing thin cover glasses for flat panel displays face challenges such as warpage after chemical strengthening, which affects their flatness and suitability for use in touch panels and LCDs, leading to issues like luminance unevenness and transport failures, and require costly preprocessing treatments like grinding or polishing.
Innovation Solution
A method involving fluorine treatment of the glass surface during the float glass manufacturing process, where a gas containing fluorine is blown onto the glass ribbon to control the viscosity and reduce the difference in chemical strengthening between surfaces, thereby minimizing warpage without compromising strength or requiring preprocessing treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the cover glass is reduced to make devices lightweight and thinned, then the weight and thickness are improved, but the strength lowers and the cover glass may be broken
Solution Approach 1:
The patent applies chemical strengthening by immersing the glass in a molten salt bath to exchange sodium ions with potassium ions, creating compressive stress in the surface layer. This changes the mechanical properties of the glass, enabling thin glass (0.1-1.0mm) to achieve sufficient strength for display protection while maintaining the weight reduction benefit.
2Strength
If chemical strengthening is performed to enhance scratch resistance and strength, then the strength and scratch resistance are improved, but warpage occurs due to heterogeneity between top and bottom surfaces
Solution Approach 1:
The patent introduces a fluorine-containing layer on the glass surface before chemical strengthening. This creates a localized modification where fluorine concentrates in the surface region, suppressing ion exchange in this area. The result is that the top surface (with fluorine layer) experiences less compressive stress than the bottom surface, balancing the stress distribution and preventing warpage while maintaining high scratch resistance.
Solution Approach 2:
The fluorine-containing layer acts as an intermediary substance that mediates the chemical strengthening process. By introducing fluorine ions that preferentially occupy surface positions, it controls the ion exchange kinetics and creates a gradient in compressive stress distribution, thereby preventing the uniform stress buildup that causes warpage.
3Strength
If surface compressive stress is increased to 600 MPa or more for high scratch resistance, then the scratch resistance is improved, but warpage becomes more obvious
Solution Approach 1:
The patent modifies the chemical composition of the glass surface by introducing fluorine, which changes the ion exchange characteristics. The fluorine-containing layer suppresses sodium-potassium ion exchange in the surface region, creating a non-uniform compressive stress distribution where the surface has lower stress (preventing warpage) while the subsurface maintains high stress (providing scratch resistance).
4Shape
If grinding treatment or polishing treatment is performed before chemical strengthening to reduce warpage, then the flatness is improved, but productivity decreases and manufacturing complexity increases
Solution Approach 1:
The patent applies fluorine treatment to the glass surface during or before the float glass manufacturing process, before the chemical strengthening step. This preliminary action of introducing fluorine creates a stress-balancing layer that prevents warpage during subsequent strengthening, eliminating the need for post-manufacturing grinding or polishing operations and thereby maintaining high productivity.
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 method effectively reduces warpage in chemically strengthened glass sheets while maintaining high strength and scratch resistance, ensuring excellent flatness and reducing the need for preprocessing treatments, thus improving the glass sheets' suitability for display applications.
Implementation Method 1
a fluid containing a molecule having a fluorine atom present therein is blown to the glass ribbon
Implementation Method 2
a float glass is chemically strengthened to form a compressive stress layer on the surface thereof
Data Source
AI summary
A method for manufacturing a float glass includes a step of melting a glass raw material, a step of forming the glass melted in the melting step into a glass ribbon while floating the glass on a molten metal, and a step of annealing the glass ribbon. In the forming step, a gas or a liquid containing a molecule having a fluorine atom present therein is blown to the glass ribbon having a viscosity of from 1.0×104 to 2.5×1010 Pa·s.