Temperature-Stable Surface Reflector Layer System
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Solution Overview
Problem
Existing surface reflector technologies face challenges in achieving high, uniform reflection across the visible and solar radiation range of 300 to 2700 nm while maintaining temperature stability and resistance to oxidation, diffusion, and agglomeration, especially at high temperatures.
Innovation Solution
A layer system comprising a metallic substrate with a reflector layer made of high-purity metals like silver or aluminum, combined with a specific sequence of substoichiometric titanium oxide, nickel-vanadium, and dielectric layers to enhance adhesion, prevent diffusion, and improve corrosion resistance, applied using PVD and electron beam evaporation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a metallic reflector layer is used to achieve high reflectivity, then reflectance is improved, but temperature stability deteriorates due to diffusion and agglomeration at high temperatures
Solution Approach 1:
A substoichiometric titanium oxide layer is introduced as an intermediary between the metallic reflector layer and the dielectric layers. This intermediate layer acts as a diffusion barrier that prevents atom diffusion between the reflector and substrate while also suppressing agglomeration of the metallic layer at high temperatures, thereby maintaining both high reflectance and temperature stability.
Solution Approach 2:
The patent employs a composite layer structure combining metallic materials (silver, aluminum, or aluminum alloy) with substoichiometric titanium oxide and dielectric materials. This composite approach allows the system to leverage the high reflectance of metals while the titanium oxide and dielectric layers provide thermal stability and diffusion protection.
2Illumination intensity
If pure aluminum is used to achieve high reflectivity, then reflectance is improved, but mechanical strength deteriorates due to softness
Solution Approach 1:
The patent uses composite layering where pure aluminum or aluminum alloy serves as the reflective base layer, combined with substoichiometric titanium oxide and dielectric overlay layers. This composite structure provides the high reflectance of pure aluminum while the additional layers contribute mechanical durability and environmental protection.
3Reliability
If an anodization process is applied to protect the aluminum surface, then corrosion resistance is improved, but optical performance deteriorates due to light interference and absorption
Solution Approach 1:
The patent extracts or omits the anodization process entirely, replacing it with a vacuum-deposited substoichiometric titanium oxide layer that provides corrosion protection without the optical interference problems of anodized aluminum oxide. This alternative approach achieves both protection and optical performance.
Solution Approach 2:
The substoichiometric titanium oxide layer serves as an intermediary protective coating that replaces the problematic anodization layer. It provides corrosion resistance and diffusion protection while maintaining optical transparency and avoiding the light interference effects associated with thick anodized layers.
4Reliability
If multiple protective layers are added to improve temperature stability, then reliability is improved, but device complexity increases
Solution Approach 1:
The substoichiometric titanium oxide layer is designed to perform multiple functions simultaneously: it acts as a diffusion barrier, suppresses agglomeration, provides adhesion between layers, and maintains optical transparency. This multi-functionality reduces the need for separate dedicated layers for each protective function, thereby limiting complexity increase while achieving high reliability.
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 layer system achieves a total reflection of at least 94% in the visible range and 89% in the solar range with improved temperature stability up to 250°C, maintaining reflectivity and resistance to corrosion and mechanical damage.
Implementation Method 1
a metallic mirror layer or reflector layer (6) having a reflection-enhancing 'alternating layer system' (9, 10) arranged above that
Implementation Method 2
a dielectric LI layer (low-index layer) having a refractive index n1 and a dielectric HI layer (high-index layer) arranged thereon having a higher refractive index n2 than n1
Implementation Method 3
a dielectric LI layer (low-index layer) having a refractive index n1 and a dielectric HI layer (high-index layer) arranged thereon having a higher refractive index n2 than n1
Implementation Method 4
which is provided for improving the adhesion of said metallic layer of the mirror and also as a diffusion barrier and which inhibits the diffusion of atoms from the substrate into the reflector layer
Implementation Method 5
which can be deposited using a suitable combination of metallic and transparent—primarily dielectric—layers by means of well-known thin film coating processes, such as PVD, CVD or PECVD
Implementation Method 6
applied using PVD and electron beam evaporation processes
Data Source
AI summary
The present invention relates to a layer system, comprising a metallic substrate (1) having the following layers applied on a side (A) thereof from the inside to the outside in the specified order: 4) a layer composed of a material selected from among substoichiometric oxides and oxynitrides of titanium and zirconium or from among metals, selected from among titanium, zirconium, molybdenum, platinum, and chromium or an alloy using one of these metals or of at least two of these metals, 5a) a layer composed of a nickel alloy having chromium, aluminum, vanadium, molybdenum, cobalt, iron, titanium, and/or copper as an alloying partner, or composed of a metal selected from among copper, aluminum, chromium, molybdenum, tungsten, tantalum, titanium, platinum, ruthenium, rhodium, and alloys using one of these metals, or of at least two of these metals, or composed of iron, steel or stainless steel, provided the layer may only consist of aluminum if the reflector layer 6) is formed of aluminum and that, in this case, the aluminum of layer 5a) has been sputtered, 6) an optically dense, high-purity metal reflector layer, 7) a layer selected from among substoichiometric oxides of titanium, zirconium, hafnium, vanadium, tantalum, niobium or chromium and from among metals selected from among chromium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, tungsten, molybdenum, rhodium, and platinum and alloys using one of these metals or at least two of these metals, 9) a layer having a low refractive index (“LI layer”) in relation to a directly adjoining layer 10) (“HI layer”), and 10) a layer directly adjoining layer 9) and having a higher refractive index (“HI layer”) in relation to layer 9) (“LI layer”). The layer system can be used, e.g. as a surface reflector, preferably in applications with LEDs, particularly MC-COB for LEDs, as a solar reflector or as a laser mirror, in particular for color wheels in DLP laser projectors.