Low-Emissivity Coating Segmentation for Thermal Stability
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Solution Overview
Problem
Existing low-emissivity glass coatings face challenges in achieving high visible transmittance and light to solar gain while maintaining color neutrality and thermal stability, especially during heat treatment processes.
Innovation Solution
The use of multiple infrared reflective layers with separation layers, such as zinc tin oxide and nickel niobium titanium oxide, is implemented to reduce interference and enhance thermal stability, along with a Ni-Nb alloy barrier layer to protect the reflective layers from oxidation and maintain conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a single Ag layer is used to achieve high visible transmittance and low emissivity, then light transmission is improved, but light to solar gain ratio deteriorates
Solution Approach 1:
The patent divides a single Ag layer into multiple thinner Ag layers separated by dielectric layers. This segmentation allows each Ag layer to contribute to infrared reflection while the dielectric spacers prevent excessive absorption, achieving both high visible transmittance and high light to solar gain ratio simultaneously
2Use of energy by moving object
If the Ag layer is made thicker to reduce solar heat gain, then light to solar gain is improved, but visible light transmission deteriorates
Solution Approach 1:
Instead of using one thick Ag layer, the patent uses multiple thin Ag layers separated by dielectric layers. This segmentation distributes the infrared reflection function across multiple interfaces, achieving effective solar heat rejection while maintaining high visible light transmission through constructive interference effects
Solution Approach 2:
The patent creates a nested structure where thin Ag layers are embedded within dielectric layers forming a multilayer stack. Each Ag layer is nested between dielectric spacers, creating a compact structure that achieves high performance in both visible transmission and solar heat rejection
3Use of energy by moving object
If multiple Ag layers are used to improve light to solar gain, then solar heat gain is reduced, but visible light transmission deteriorates
Solution Approach 1:
The patent introduces dielectric spacers as intermediary layers between Ag layers. These spacers have optimized refractive indices and thicknesses that mediate the optical interaction between Ag layers, enabling constructive interference for visible light transmission while maintaining infrared reflection
4Use of energy by moving object
If standard low-emissivity coating is used, then infrared reflection is achieved, but color neutrality deteriorates after heat treatment
Solution Approach 1:
The patent uses composite material structures combining Ag layers with specific dielectric materials (such as SiO2, TiO2, ZnO) in alternating layers. This composite structure provides thermal stability during heat treatment while maintaining color neutrality through controlled optical interference effects
5Use of energy by moving object
If standard low-emissivity coating is used, then infrared reflection is achieved, but thermal stability during heat treatment deteriorates
Solution Approach 1:
The patent employs composite structures with thermally stable dielectric materials (SiO2, TiO2, ZnO) alternating with Ag layers. These dielectric materials have high melting points and thermal stability, protecting the Ag layers during glass heat treatment processes while maintaining the low-emissivity property
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
This configuration achieves high visible light transmission, improved light to solar gain, and minimal color change after heat treatment, ensuring consistent performance and appearance before and after thermal exposure.
Implementation Method 1
IR radiation is mostly reflected with minimum absorption and emission, thus reducing the heat transferring to and from the low emissivity surface
Implementation Method 2
a Ni-Nb alloy barrier layer to protect the reflective layers from oxidation
Implementation Method 3
by adding appropriate separation layers between the infrared reflective layers, the interference between the coatings can be reduced
Implementation Method 4
forming a fourth layer on the third layer, wherein the fourth layer comprises silver, wherein the fourth layer is operable as an infrared reflective layer
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
Low emissivity panels can include a separation layer of Zn2SnOx between multiple infrared reflective stacks. The low emissivity panels can also include NiNbTiOx as barrier layer. The low emissivity panels have high light to solar gain, color neutral, together with similar observable color before and after a heat treatment process.