Lead-Free Glass Flux Coating for Low Expansion Substrates
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Solution Overview
Problem
Conventional glass flux materials are not suitable for applying opaque coatings on substrates with low thermal expansion coefficients, as they require high firing temperatures and often result in thin layer thicknesses, poor chemical resistance, and increased manufacturing costs, especially for lead-free materials.
Innovation Solution
A lead-free glass flux material with a specific composition, including silicon oxide, aluminum oxide, bismuth oxide, and alkali oxides, is developed to create a printable paste that can be fired at temperatures below 750°C, achieving opaque, scratch-resistant, and chemically resistant coatings with a coefficient of linear thermal expansion suitable for low-expansion glass and glass ceramic substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional glass flux materials are used for coating low thermal expansion glass substrates, then the coating can be applied, but the layer thickness is limited to thin layers and the coating is not opaque
Solution Approach 1:
The patent modifies the chemical composition parameters of the glass flux material by incorporating specific oxide combinations (Bi2O3, B2O3, SiO2, ZnO, Al2O3) in controlled proportions. This compositional parameter change enables the coating to achieve both sufficient thickness (5-20 μm) and complete opacity while maintaining adhesion to low thermal expansion substrates during firing at 600-750°C.
2Object-affected harmful factors
If lead-free glass flux materials are used to avoid toxicity, then environmental safety is improved, but the softening point increases and firing temperature must be raised above 750°C
Solution Approach 1:
The patent creates a composite glass flux system combining multiple oxide components (Bi2O3 as flux, B2O3 for low melting point, SiO2 for structural framework, ZnO and Al2O3 for stability) that work synergistically. This composite approach achieves lead-free status while maintaining a low softening point that allows firing at 600-750°C, avoiding the need for high-temperature processing.
3Temperature
If high bismuth oxide content is used to lower softening point and enable lower firing temperature, then firing temperature is reduced, but manufacturing costs increase
Solution Approach 1:
The patent optimizes the bismuth oxide content to a specific range (10-30 wt%) rather than using excessive amounts. This parameter optimization balances the softening point reduction effect with cost considerations, achieving sufficient low-temperature processing capability (600-750°C) while controlling raw material costs through precise compositional control.
4Reliability
If the coating layer is made thick to achieve opacity, then opacity is improved, but the coating becomes prone to cracking and peeling due to thermal expansion mismatch
Solution Approach 1:
The patent adjusts multiple compositional parameters simultaneously to match the thermal expansion characteristics of the coating with the substrate. The specific oxide ratios (Bi2O3: 10-30 wt%, B2O3: 20-40 wt%, SiO2: 20-40 wt%, ZnO: 5-20 wt%, Al2O3: 5-15 wt%) create a thermal expansion coefficient that accommodates thicker layers (5-20 μm) without causing cracking or peeling, while ensuring complete opacity.
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 allows for the application of a single-layer opaque coating with high layer thickness and excellent chemical resistance, suitable for heat-resistant glass and glass ceramic substrates, while maintaining mechanical stability and cost-effectiveness, even on substrates prone to deformation during firing.
Implementation Method 1
it has to be fired at more than 750° C.
Implementation Method 2
The material to be fused in particular contains the ground glass frits.
Data Source
AI summary
A glass flux material for applying an opaque coating is provided. The glass flux material includes at least one pigment and a glass component with the following composition:SiO2 55-70 mol %,Al2O3 2.5-8 mol %,Bi2O3 0.5-<4 mol %,B2O3 14-27 mol %,with at least 2.5 mol % of at least one oxide of the group Li2O, Na2O, and K2O, wherein the ratio of alkali oxides to aluminum oxide ΣR2O/Al2O3 is less than 6.