Low-Emissivity Coating Refractive Index Control for Durability
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Solution Overview
Problem
Existing window and door materials lack improved heat, moisture, and abrasion resistances while maintaining excellent optical performance.
Innovation Solution
A functional building material with a low-emissivity coating comprising a sequential stack of dielectric and low-emissivity protective layers on a transparent substrate, including silicon aluminum nitride and oxide layers, which enhances refractive index control for improved durability and optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low-emissivity layer containing silver is deposited on glass substrate, then infrared radiation reflection is improved, but the silver layer is oxidized when exposed to air reducing durability
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the silver low-emissivity layer and the external environment. This dielectric layer serves as a protective barrier that prevents oxidation of the silver while maintaining the infrared reflection capability. The dielectric material is specifically selected to be transparent to infrared radiation, allowing the silver layer to function effectively without direct exposure to air.
Solution Approach 2:
The patent creates a composite structure combining multiple materials: the glass substrate, the silver low-emissivity layer, and the dielectric protective layer. This composite approach allows each material to contribute its specific properties - the silver provides infrared reflection, the dielectric provides oxidation protection, and the glass provides structural support - achieving both energy efficiency and durability.
2Reliability
If dielectric layers are deposited on low-emissivity layer to prevent oxidation, then oxidation resistance is improved, but visible light transmittance decreases
Solution Approach 1:
The patent optimizes the parameters of the dielectric layer, specifically its thickness and refractive index, to achieve a balance between protection and transparency. By carefully controlling these parameters, the dielectric layer provides sufficient oxidation protection while minimizing its impact on visible light transmission. The refractive index is specifically selected to reduce optical interference effects that would otherwise reduce visibility.
3Reliability
If multiple protective layers are added to low-emissivity coating, then durability and resistance are improved, but manufacturing complexity increases
Solution Approach 1:
The protective coating is segmented into functionally distinct layers: a dielectric layer for oxidation protection and low-emissivity protective layers for mechanical and chemical protection. This segmentation allows each layer to be optimized for its specific function while maintaining overall system performance. The clear functional division simplifies the design process despite the multiple layers present.
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 material achieves excellent optical performance, heat resistance, moisture resistance, and abrasion resistance, effectively reflecting solar radiation and maintaining indoor heat while allowing high visible light transmittance.
Implementation Method 1
a low-emissivity layer containing a metal with a high reflectance in an infrared region such as silver (Ag) is deposited as a thin film. This low-emissivity glass is a functional material to reflect radiation in the infrared region
Implementation Method 2
a dielectric layer as an oxidation-preventive layer is deposited on each of top and bottom faces of the low-emissivity layer. This dielectric layer also serves to increase a visible light transmittance
Data Source
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AI summary
Provided is a functional building material for a door and a window, comprising a transparent substrate and a low-emissivity coating formed on one surface of the transparent substrate, wherein the low-emissivity coating comprises a first dielectric layer, a second dielectric layer, a third dielectric layer, a first low-emissivity protection layer, a low-emissivity layer, a second low-emissivity protection layer, a fourth dielectric layer, a fifth dielectric layer and a sixth dielectric layer which are stacked sequentially from the transparent substrate, wherein the refractive index of the first dielectric layer and the refractive index of the third dielectric layer are each lower than the refractive index of the second dielectric layer, and the refractive index of the fourth dielectric layer and the refractive index of the sixth dielectric layer are each lower than the refractive index of the fifth dielectric layer.