Zinc Stannate Layer for Low-E Coating Thermal Stability
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Solution Overview
Problem
Existing low-emissivity (low-E) coatings in window applications face challenges with thermal stability during heat treatment, leading to unpredictable color changes and performance degradation, making it difficult to match heat-treated and non-heat-treated products in terms of color and performance.
Innovation Solution
Incorporating a zinc stannate based layer between silver-based infrared reflecting layers, along with silicon nitride and nickel-chromium oxide layers, to enhance thermal stability and maintain color consistency during heat treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high temperature heat treatment (at least 580°C, preferably 600-620°C) is applied to low-E coatings, then thermal stability and strength are improved, but coating breakdown and unpredictable color changes occur
Solution Approach 1:
A zinc stannate based layer is introduced as an intermediary between the silver-based infrared reflecting layer and the silicon nitride based layer. This intermediate layer acts as a protective buffer that prevents direct harmful interactions between the silver layer and the silicon nitride layer during high temperature heat treatment, thereby maintaining coating integrity while allowing thermal stability to be achieved
Solution Approach 2:
The patent employs a composite multi-layer structure combining zinc stannate, silicon nitride, and silver-based materials. This composite approach creates a synergistic system where each material contributes specific properties: zinc stannate provides thermal stability and protective characteristics, silicon nitride offers structural support and barrier properties, and silver provides infrared reflection. The composite structure enables the coating to withstand heat treatment temperatures of at least 580°C without breakdown
2Strength
If heat treatment is applied to coated glass articles, then tempered glass strength is improved, but color match between heat-treated and non-heat-treated products deteriorates (high ΔE* value)
Solution Approach 1:
The zinc stannate based layer serves as a mediator that stabilizes the optical properties of the coating during heat treatment. It prevents excessive color changes by acting as a buffer between the heat treatment process and the silver-based infrared reflecting layer, ensuring that the ΔE* value remains at or below 5.0, and preferably at or below 4.0
Solution Approach 2:
The patent utilizes controlled parameter changes during heat treatment, specifically maintaining heat treatment temperatures of at least 580°C (preferably 600-620°C) for controlled durations. The zinc stannate layer enables these parameter changes to occur without causing unacceptable color shifts, allowing the coating to achieve thermal stability while maintaining color consistency
3Reliability
If zinc stannate based layer is added between silver layers, then thermal stability upon heat treatment is improved, but device complexity increases
Solution Approach 1:
The zinc stannate based layer performs multiple functions simultaneously: it provides thermal stability during heat treatment, prevents coating breakdown, reduces color changes (keeping ΔE* ≤ 5.0), and maintains the structural integrity of the multi-layer coating. This multi-functionality justifies the added layer by delivering several benefits from a single component
Solution Approach 2:
The zinc stannate layer is strategically positioned in specific locations within the coating structure - between the silicon nitride based layer and the silver-based infrared reflecting layer, and in some embodiments between two silver-based layers. This localized placement optimizes thermal stability where it is most needed while minimizing the overall complexity of the coating structure
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 zinc stannate based layer improves thermal stability, ensuring a low ΔE* value of no greater than 5.0, maintaining color consistency and performance across various heat treatment times, and allowing for the production of heat-treated products that match non-heat-treated versions in terms of color and performance.
Implementation Method 1
a zinc stannate based layer provided over a silver-based infrared (IR) reflecting layer
Implementation Method 2
the provision of the zinc stannate based layer results in a coated article having improved thermal stability upon heat treatment (HT)
Data Source
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AI summary
A coated article is provided which may be heat treated (e.g., thermally tempered) in certain example instances. In certain example embodiments, the coated article includes a low-emissivity (low-E) coating having a zinc stannate based layer provided over a silver-based infrared (IR) reflecting layer, where the zinc stannate based layer is preferably located between first and second silver based IR reflecting layers. The zinc stannate based layer may be provided between and contacting (i) an upper contact layer of or including Ni and/or Cr (or Ti, or TiOx), and (ii) a layer of or including silicon nitride.