Low-Emissivity Glazing Coating with Thermal Stability
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Solution Overview
Problem
Existing glazing systems face challenges in achieving a balance between low-emissivity, anti-solar properties, and mechanical reinforcement, particularly during heat treatments, which can degrade the optical and energy performance of the coatings, and require separate production lines for toughened and non-toughened glazing units.
Innovation Solution
A glazing unit with a specific stack of thin layers comprising alternating infrared radiation reflecting functional layers and dielectric coatings, including a barrier layer based on zinc oxide or indium oxide, with silicon nitride or oxide layers for enhanced chemical stability and self-matchability, allowing for high light transmission and low emissivity while withstanding heat treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the glazing undergoes heat treatment for mechanical reinforcement, then the resistance to mechanical stresses is improved, but the optical and energy properties of the coating are degraded
Solution Approach 1:
The patent applies parameter changes by carefully controlling the deposition thicknesses of each layer and selecting specific materials with appropriate thermal stability. The dielectric layers are deposited with precise thickness control to ensure they can withstand heat treatment temperatures while maintaining optical properties. The functional layers are designed with sufficient thickness and protective overcoatings to survive thermal processing without significant degradation of infrared reflective properties.
Solution Approach 2:
The patent uses composite materials by combining multiple dielectric layers with different properties (e.g., silicon nitride, silicon oxide, zinc oxide, indium oxide) in a specific sequence. Each material is selected for its thermal stability and optical characteristics, creating a composite coating structure that collectively withstands heat treatment while maintaining the required optical and energy performance.
2Reliability
If separate production lines are used for toughened and non-toughened glazing units, then the optical properties are maintained, but the device complexity and production cost increase
Solution Approach 1:
The patent achieves universality by designing a coating structure that serves dual purposes: it provides the required optical and energy properties for both toughened and non-toughened glazing units. The coating is designed to be universally applicable, eliminating the need for separate production lines while maintaining performance through the inherent thermal stability of the multi-layer structure.
3Reliability
If the functional layer is made thinner to reduce emissivity, then the low-emissivity property is improved, but the resistance to heat treatment deteriorates
Solution Approach 1:
The patent protects thin functional layers by surrounding them with multiple dielectric protective layers. The functional layer can be made thin to achieve low emissivity, but it is encased in a composite structure where the dielectric layers provide thermal protection during heat treatment. This allows the functional layer to remain thin for optimal optical performance while the composite structure ensures heat treatment resistance.
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 glazing units with high light transmission, low solar factor, and thermal insulation, maintaining optical and energy properties post-heat treatment, and ensuring self-matchability and chemical stability, reducing the need for separate production lines.
Implementation Method 1
a system of thin layers comprising at least two functional layers based on an infrared radiation reflecting material
Implementation Method 2
barrier layers that are capable of either oxidising in place of the silver by trapping free oxygen or blocking the free oxygen migrating towards the silver during the heat treatment
Implementation Method 3
heating the glass sheet to a temperature higher than 560° C. in air, e.g. between 560° C. and 700° C., and in particular around 640° C. to 670° C.
Implementation Method 4
The toughening treatment then consists of abruptly cooling the surface of the flat or bent glass sheet by air jets or cooling fluid to obtain a mechanical reinforcement of the sheet
Data Source
AI summary
The invention relates to low-emissivity and anti-solar glazing systems that change only very little in properties when they are subjected to a heat treatment. They comprise a stack of thin layers comprising an alternating arrangement of n infrared radiation reflecting functional layers and n+1 dielectric coatings, and a barrier layer directly superposed on the last functional layer furthest away from the substrate, characterized in that: (i) the first dielectric coating closest to the substrate comprises a layer made from an oxide, in direct contact with the substrate, (ii) the internal dielectric coating or coatings surrounded by two functional layers comprise a layer made from a silicon nitride or a silicon oxide with a thickness greater than 5 nm surrounded on both sides by layers made from an oxide other than silicon oxide with thicknesses greater than 5 nm, (iii) the barrier layer is based on zinc oxide or consists of an indium oxide possibly doped with tin, and (iv) the last dielectric coating furthest away from the substrate comprises, in order starting from the substrate: a layer made from an oxide other than silicon oxide with a thickness greater than 3 nm and a layer made from a silicon nitride or a silicon oxide with a thickness greater than 10 nm.