Glazing Stack with Absorbent Layer for Thermal Selectivity
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Solution Overview
Problem
Existing thermal insulation and solar protection glazings face challenges in achieving high selectivity while maintaining excellent color neutrality and stability across different angles of incidence, particularly for glazings with light transmission in the range of 25 to 75%. Additionally, there is a difficulty in maintaining consistent production quality due to the complexity of functional coatings.
Innovation Solution
A novel two-functional-layer stack is developed, comprising two silver-based functional metal layers sandwiched between dielectric coatings, with an absorbent layer in the intermediate dielectric coating to absorb solar radiation in the visible spectrum. The stack is designed to have a specific thickness ratio for the metal and dielectric layers to optimize color neutrality and thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single functional metal layer is used in the stack, then the device complexity is reduced, but the thermal insulation performance and solar protection performance cannot be simultaneously optimized
Solution Approach 1:
The single functional layer is segmented into two separate metal layers with different functions: the first metal layer (closer to exterior) provides solar radiation reflection, while the second metal layer (closer to interior) provides thermal radiation reflection. This segmentation allows independent optimization of each layer's properties to achieve both solar control and thermal insulation performance.
Solution Approach 2:
The two functional metal layers are nested between dielectric layers in a sandwich structure: dielectric layer - first metal layer - dielectric layer - second metal layer - dielectric layer. This nested arrangement allows both functional layers to work synergistically while being protected and optically integrated through the dielectric layers.
2Loss of energy
If the light transmission is reduced to improve thermal insulation, then the solar factor decreases, but the light reflection increases excessively affecting aesthetic appearance
Solution Approach 1:
Different regions of the coating system are assigned different optical properties: the first metal layer is optimized for solar radiation reflection with specific thickness and material composition, while the second metal layer is optimized for thermal radiation reflection. The dielectric layers are designed with specific refractive indices to control overall light transmission and reflection characteristics, achieving a balance between energy performance and aesthetic appearance.
3Loss of energy
If the functional coating design is optimized for high selectivity, then the thermal performance improves, but the color neutrality and stability across different angles of incidence deteriorate
Solution Approach 1:
The optical parameters of the coating system are carefully adjusted: metal layer thicknesses are optimized to control reflection bands, dielectric layer thicknesses are tuned for anti-reflective properties, and material compositions are selected to achieve desired refractive indices. These parameter changes enable high selectivity while maintaining neutral color appearance and angular stability.
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 proposed stack achieves a light transmission of less than 40%, a solar factor between 25 and 34%, and a high selectivity while maintaining a neutral color in reflection, which is stable across different angles of incidence. This results in laminated glazings with improved thermal performance and aesthetic appearance.
Implementation Method 1
an absorbent layer in the intermediate dielectric coating to absorb solar radiation in the visible spectrum
Implementation Method 2
a functional metal layer having properties of reflection in the infrared range and/or in the solar radiation range
Implementation Method 3
the aim of these coatings which surround the functional metal layer is to antireflect this functional metal layer
Data Source
AI summary
A substrate which is coated on one of its faces with a stack of thin layers having reflection properties in the infrared and/or in solar radiation, including two metallic functional layers, in particular based on silver. Each of the metallic functional layers is disposed between two dielectric coatings. The dielectric coating Di2 situated between the two functional layers includes at least one absorbent layer which absorbs solar radiation in the visible part of the spectrum. It has been found that for a stack for laminated glazing, some symmetry at the functional metal layers and the dielectric layers 1 and 3 is favorable.