Low-E Coating Color Stability Using Crystalline Zinc Oxide
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Solution Overview
Problem
Existing low-E coating systems struggle to maintain color matchability and durability before and after heat treatment, often requiring separate layer systems and compromising on visible transmission characteristics and thermal stability.
Innovation Solution
A low-E coating system incorporating a multi-layer absorber film with silver and partially or fully oxidized NiCr, along with crystalline zinc oxide and dielectric layers, which improves thermal stability and matchability by reducing ΔE* values and eliminating the need for silicon nitride layers, thereby enhancing manufacturability and optical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a low-E coating system uses traditional layer structures (e.g., without silver or with high nitrogen flow rates), then manufacturing is simpler, but color stability upon heat treatment deteriorates (high ΔE* values)
Solution Approach 1:
The patent changes the chemical composition parameters of the absorber film by incorporating silver and controlling the oxidation state of NiCr, and by using crystalline zinc oxide instead of amorphous forms. These parameter changes in material composition and crystal structure enable color stability (low ΔE*) upon heat treatment while maintaining a manageable coating structure.
Solution Approach 2:
The patent employs composite material structures by combining multiple layers with different functions: silver-containing absorber film for optical properties, crystalline zinc oxide for thermal stability, and dielectric layers for protection. This composite approach achieves both color stability and durability without excessive complexity.
2Stability of the object's composition
If a low-E coating system incorporates silver and crystalline zinc oxide for improved thermal stability, then color matchability improves (low ΔE* values), but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by forming the crystalline zinc oxide layer in a specific crystal structure during deposition, and by pre-oxidizing the NiCr layer to controlled extents before final assembly. These preliminary structural preparations ensure that the layers are pre-configured to maintain stability during subsequent heat treatment, reducing the need for post-manufacturing adjustments and improving color matchability.
3Ease of manufacture
If a low-E coating system eliminates silicon nitride layers to improve manufacturability, then production cost and complexity decrease, but durability may be compromised
Solution Approach 1:
The patent extracts and eliminates the silicon nitride layer from the coating structure, removing the material and process steps associated with it. This simplification improves manufacturability by reducing the number of deposition steps and material handling requirements, while the remaining layers are optimized to provide necessary durability functions.
Solution Approach 2:
The patent changes the material parameters by substituting crystalline zinc oxide and optimized dielectric layers to replace the protective functions previously provided by silicon nitride. These parameter changes in material selection and structural configuration maintain durability while improving ease of manufacture.
4Illumination intensity
If a low-E coating system optimizes for visible transmission characteristics, then optical performance improves, but thermal stability deteriorates
Solution Approach 1:
The patent applies local quality by assigning different functional optimizations to different layers: the silver-containing absorber film is optimized for visible transmission and optical properties, while the crystalline zinc oxide and dielectric layers are optimized for thermal stability and protection. This localized functional distribution allows the overall system to achieve both high visible transmission and excellent thermal stability simultaneously.
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 system achieves color stability with low ΔE* values, maintaining desirable visible transmission and durability both before and after heat treatment, while improving thermal stability and manufacturability by using silver in the absorber film and crystalline zinc oxide under infrared reflecting layers.
Implementation Method 1
crystalline or substantially crystalline layer of or including zinc oxide...immediately under an infrared (IR) reflecting layer
Implementation Method 2
The silver based layer in the absorber film is preferably sufficiently thin so that its primary function is to absorb visible light and provide desirable coloration
Implementation Method 3
a second layer of or including NiCr which may be partially or fully oxided (NiCrOx)
Implementation Method 4
an as-deposited crystalline or substantially crystalline...layer of or including zinc oxide
Data Source
AI summary
A low-E coating has good color stability (a low ΔE* value) upon heat treatment (HT). Thermal stability may be improved by the provision of an as-deposited crystalline or substantially crystalline layer of or including zinc oxide, doped with at least one dopant (e.g., Sn), immediately under an infrared (IR) reflecting layer of or including silver; and/or by the provision of at least one dielectric layer of or including at least one of: (a) an oxide of silicon and zirconium, (b) an oxide of zirconium, and (c) an oxide of silicon. These have the effect of significantly improving the coating's thermal stability (i.e., lowering the ΔE* value). An absorber film may be designed to adjust visible transmission and provide desirable coloration, while maintaining durability and/or thermal stability.