Heat Treatable Solar Control Coating via Tungsten Nitride Barrier
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Solution Overview
Problem
Solar control coatings with metal-based or oxidizable metal compound functional layers are not heat treatable, as they tend to oxidize and lose their solar control function during thermal processing, necessitating dielectric layers that protect against oxidation and diffusion during heat treatments.
Innovation Solution
A solar control coating comprising a lower dielectric layer, a functional layer with tungsten-based nitrides or carbides, and an upper dielectric layer, where the functional layer has a tungsten to nitrogen atomic ratio between 10:1 and 1:2, providing stability and minimizing degradation during heat treatments, and the dielectric layers act as anti-reflection and diffusion barriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal-based functional layers are used in solar control coatings, then solar control function is improved, but heat treatability deteriorates due to oxidation during thermal processing
Solution Approach 1:
The patent introduces dielectric intermediary layers (silicon nitride, silicon oxynitride, aluminium nitride, or aluminium oxynitride) between the metal-based functional layer and the environment. These intermediary layers act as diffusion barriers that prevent oxygen from reaching the metal functional layer during heat treatment, thereby protecting it from oxidation while allowing the coating to withstand thermal processing temperatures of 590-690°C
Solution Approach 2:
The patent creates a composite coating structure consisting of multiple materials with complementary properties: metal-based functional layers (providing solar control through absorption and reflection), dielectric barrier layers (providing oxidation protection during heat treatment), and optionally additional dielectric layers for anti-reflection. This composite structure combines the advantages of different materials to achieve both solar control functionality and heat treatability
2Adaptability or versatility
If dielectric layers are added to protect functional layer during heat treatment, then heat treatability is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by positioning dielectric barrier layers specifically where they are most needed - adjacent to the metal-based functional layer that requires protection during heat treatment. The dielectric layers are strategically located to provide oxidation protection at the critical metal-coating interface, while other parts of the coating structure can be optimized for different functions such as anti-reflection or mechanical protection
Solution Approach 2:
The dielectric layers serve multiple functions simultaneously: they act as diffusion barriers protecting the metal functional layer from oxidation during heat treatment, provide mechanical protection to improve corrosion and scratch resistance, and can contribute to anti-reflection properties through optical interference. This multi-functionality reduces the need for additional separate layers
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 coating maintains its optical and mechanical properties, achieving high light and solar energy transmittance while remaining heat treatable, with minimal changes in appearance and haze value after heat treatment, allowing for the use of heat-treated and non-heat-treated glass panes side by side.
Implementation Method 1
the dielectric layers embedding the functional layer need to be well selected to protect it against oxidisation during the heat treatment and to stabilize it against diffusion effects
Implementation Method 2
reduced visible light and solar energy transmittance, such reduction taking place partially by absorption and partially by reflection
Implementation Method 3
reduced visible light and solar energy transmittance, such reduction taking place partially by absorption and partially by reflection
Implementation Method 4
anti-reflection of the functional layer by optical interference
Data Source
AI summary
The invention relates to a coated glass pane with a solar control coating comprising in sequence at least the following transparent layers: a lower dielectric layer, a functional layer comprising at least one metal or metal compound, and an upper dielectric layer, the functional layer comprising at least one of tungsten, molybdenum, a tungsten-based alloy, a molybdenum-based alloy, their nitrides, carbides and/or borides.