Zinc Stannate Layer Reduces Mottling in Low-E Coatings
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Solution Overview
Problem
Coated articles used in vehicle windshields and insulating glass window units suffer from mottling damage and reduced optical and thermal performance when subjected to high degrees of heat bending, limiting their bendability and durability.
Innovation Solution
Incorporating a zinc stannate based layer between tin oxide and silicon nitride layers in the low-E coating layer stack, which reduces mottling and enhances mechanical durability, allowing for greater bendability without fatal mottling damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If high degrees of heat bending are applied to achieve desired windshield shape, then the windshield can be formed to specification, but mottling damage occurs in the coating
Solution Approach 1:
The patent applies composite materials by creating a multi-layer coating structure where a zinc stannate layer is integrated between tin oxide and silicon nitride layers. This composite structure reduces mottling damage during heat bending while maintaining the desired windshield shape, resolving the contradiction between achieving proper shape and preventing coating failure.
Solution Approach 2:
The patent changes the chemical composition parameters of the coating by incorporating zinc stannate (ZnSnO3) in specific quantities (0.1-10 nm thickness) between the dielectric layers. This parameter modification alters the coating's mechanical properties to reduce mottling during heat bending processes, allowing the windshield to be formed to specification without coating damage.
2Reliability
If the coating structure is modified to reduce mottling, then coating durability improves, but optical and thermal performance may deteriorate
Solution Approach 1:
The patent applies local quality by placing the zinc stannate layer specifically between the tin oxide and silicon nitride layers, rather than uniformly throughout the coating. This localized modification improves durability against mottling while preserving the optical and thermal performance characteristics of the overall coating structure.
Solution Approach 2:
The zinc stannate layer acts as an intermediary between the tin oxide and silicon nitride layers, improving the interface properties and reducing stress concentrations that cause mottling. This intermediary layer enhances coating durability while maintaining the optical and thermal functions of the adjacent layers.
3Shape
If zinc stannate layer is added to reduce mottling, then bendability improves, but layer stack complexity increases
Solution Approach 1:
The patent merges the functions of multiple layers by integrating zinc stannate into the existing dielectric layer structure. The zinc stannate layer combines dielectric functionality with mottling resistance, allowing the coating to achieve improved bendability without proportionally increasing overall structural complexity.
Solution Approach 2:
By creating a composite dielectric layer structure incorporating zinc stannate, the patent achieves improved bendability through enhanced mechanical properties at the material level, rather than requiring additional structural elements that would increase device complexity.
Data Source
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AI summary
A coated article is provided which may be heat treated (e.g., thermally tempered) and/or heat bent in certain example instances. In certain example embodiments, a zinc stannate based layer is provided between a tin oxide based layer and a silicon nitride based layer, and this has been found to significantly reduce undesirable mottling damage upon heat treatment/bending. This results in significantly improved bendability of the coated article in applications such as vehicle windshields and the like.