Porous Ceramic-Like Decorative Coating for Glass Cooktops
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Solution Overview
Problem
Decorative coatings for glass and glass-ceramic surfaces, particularly in high-temperature applications like cooktops, face challenges in maintaining strength and opacity while resisting thermal cycling, as existing solutions either compromise substrate strength or exhibit discoloration under heat.
Innovation Solution
A method involving a sol-gel binder with a high pigment content, forming a porous, ceramic-like structure that compensates for thermal expansion differences and maintains substrate strength, achieved by mixing pigments with a small amount of sol-gel binder and curing to create a layer with a predominantly polycrystalline structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a vitreous layer is formed with low pigment content to achieve density and impermeability, then the layer becomes dense and prevents penetration of foreign substances, but thick layers are required to achieve desired optical effects, which can cause flaking or cracking under thermal cycling due to different coefficients of thermal expansion
Solution Approach 1:
The patent applies a porous ceramic-like structure instead of a dense vitreous layer. The porous structure is formed by using a sol-gel binder with high pigment content that creates a network where pigment particles and fillers are connected by cured sol-gel binder, leaving void spaces. This porous structure reduces the layer thickness needed for optical effects while maintaining flexibility to accommodate thermal expansion differences, preventing flaking and cracking.
2Shape
If glass flow-based layers are used for marking cooking zones, then the production process is established, but such layers cannot achieve sufficient opacity while maintaining glass strength sufficient for technical applications
Solution Approach 1:
The patent uses a composite material system consisting of pigment particles, filler particles, and sol-gel binder. This composite structure allows high pigment content (up to 90 wt% or more) to achieve sufficient opacity while the sol-gel binder matrix maintains the mechanical strength required for technical applications like glass ceramic cooktops. The composite nature enables both opacity and strength to coexist.
3Strength
If silicone-based coatings are used to maintain glass strength, then the required high glass strength is not significantly impaired, but discoloration occurs when exposed to heat which is unacceptable for decorative layers
Solution Approach 1:
The patent changes the chemical composition parameters of the binder system from silicone-based to sol-gel based. The sol-gel binder, formed from organometallic compounds through hydrolysis and condensation, provides heat stability that prevents discoloration while maintaining adhesion and mechanical strength. This parameter change in the binder chemistry resolves the discoloration issue while preserving the strength benefits.
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 provides a decorative layer that is thermally stable, resistant to cracking, and maintains the strength of the glass or glass-ceramic substrate, allowing for high-temperature use without significant strength reduction, while also achieving desired optical effects like metallic appearances.
Implementation Method 1
a composition is used for producing the layers which is formed by hydrolysis and polycondensation of silanes, organosilanes
Implementation Method 2
hydrolysis and polycondensation of silanes, organosilanes
Implementation Method 3
due to the generally different coefficients of thermal expansion of substrate and coating. If the substrate is used in a high-temperature environment, the solid vitreous layer can flake off or crack under the thermal cycling that occurs
Data Source
Figure 1~4
Figure 2~3
Figure 5~6
AI summary
In order to produce a decorative coating (9) that exhibits an improved strength and thermal resistance on glass and glass ceramics while not or at least no longer significantly reducing the strength of the substrate (3), the invention provides a method for producing glass or glass-ceramic articles with a decorative layer, during which at least one decorative pigment (13) is mixed with a sol gel binder (11), and the pigment mixed with the sol gel binder is hardened on the glass or glass-ceramic substrate by tempering while forming a decorative layer having a porous ceramic-like structure.