Thermochromic Substrate Manufacturing with Refractive Index Matching
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Solution Overview
Problem
Existing methods for manufacturing thermochromic substrates result in low visible light transmittance due to the thermochromic thin film's metal characteristics and nonuniform phase transition, and the formation of multilayer film structures leads to VO2 phase changes, causing loss of thermochromic characteristics.
Innovation Solution
A method involving the formation of a first and second thin film with different refractive indices on a glass substrate, followed by heat-treating the stack to convert pure vanadium into VO2, using reactive sputtering deposition and controlling oxygen exposure to maintain thermochromic properties while increasing transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of the thermochromic thin film is decreased to increase visible light transmittance, then the transmittance is improved, but the phase transition characteristic becomes nonuniform
Solution Approach 1:
The patent applies composite materials by creating a multilayer film structure consisting of a thermochromic thin film (VO2) combined with low-refractivity and high-refractivity thin films. This composite structure increases visible light transmittance while maintaining uniform phase transition characteristics through the synergistic interaction of different material layers with varying refractive indices.
Solution Approach 2:
The patent employs parameter changes by adjusting the thickness, refractive index, and material composition of multiple thin film layers. By optimizing these parameters, the system achieves enhanced visible light transmittance while preserving uniform phase transition characteristics across the thermochromic film.
2Illumination intensity
If a multilayer film structure is formed to increase visible light transmittance, then the transmittance is improved, but oxygen diffuses into the VO2 thin film causing phase change and loss of thermochromic characteristics
Solution Approach 1:
The patent uses intermediary layers (low-refractivity and high-refractivity thin films) that act as barriers to oxygen diffusion. These intermediary layers protect the VO2 thermochromic thin film from oxygen exposure during the formation process, preventing unwanted phase changes while still allowing the multilayer structure to enhance visible light transmittance.
Solution Approach 2:
The patent creates an inert environment by carefully controlling the deposition process and selecting materials with low oxygen permeability for the low-refractivity and high-refractivity thin films. This inert environment prevents oxygen diffusion into the VO2 layer, maintaining thermochromic characteristics while achieving the desired transmittance enhancement through the multilayer structure.
3Stability of the object's composition
If heating to high temperature is used to transform vanadium oxides into VO2 crystalline phase, then the thermochromic phase is achieved, but the transmittance remains low due to metal characteristics
Solution Approach 1:
The patent resolves this contradiction by creating a composite multilayer film structure where the VO2 thermochromic layer is combined with low-refractivity and high-refractivity thin films. This composite structure maintains the VO2 crystalline phase for thermochromic functionality while the additional layers with optimized refractive indices enhance visible light transmittance, overcoming the inherent low transmittance of pure VO2 films.
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 method achieves increased visible light transmittance while preserving thermochromic characteristics by stabilizing the VO2 phase, outperforming traditional multilayer film structures in maintaining thermochromic functionality.
Implementation Method 1
using reactive sputtering deposition
Implementation Method 2
controlling oxygen exposure to maintain thermochromic properties
Implementation Method 3
heat-treating the stack to convert pure vanadium into VO2
Implementation Method 4
convert pure vanadium into VO2
Implementation Method 5
an oxide or a sulfide of a transition metal undergoes a change in its crystal structure below and above a specific temperature (i.e. a transition temperature (Tc)), so that its physical properties (electrical conductivity and infrared (IR) transmittance) suddenly change
Data Source
AI summary
A method of manufacturing a thermochromic substrate, with which transmittance can be increased. The method includes the steps of forming a first thin film as a coating on a base substrate, the refractive index of the first thin film being different from that of a VO2 thin film; forming a pre-thermochromic thin film by coating the first thin film with pure vanadium; forming a second thin film as a coating on the pre-thermochromic thin film, the refractive index of the second thin film being different from that of a VO2 thin film; and heat-treating a resultant stack that includes the base substrate, the first thin film, the pre-thermochromic thin film and the second thin film.