Fluoropolymer Anti-Reflective Coating for Durable IR Optics
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Solution Overview
Problem
Conventional anti-reflection coatings for organic wavelength converters and IR devices face issues such as peeling and cracking due to mismatched thermal expansion and viscoelasticity, leading to reflection loss and durability problems.
Innovation Solution
Utilizing an amorphous fluoropolymer coating with a refractive index of 1.3 to 1.4, which matches the thermal expansion of organic matrices, providing an anti-reflective layer that reduces reflection loss and enhances durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an inorganic anti-reflection coating such as dielectric oxide layers is applied to organic wavelength converters, then reflection loss is reduced, but the coating peels and cracks due to mismatched thermal expansion and viscoelasticity
Solution Approach 1:
The patent changes the material parameters of the anti-reflection coating from inorganic dielectric oxides to organic fluoropolymers, matching the thermal expansion coefficient and viscoelasticity of the organic wavelength converter matrix. This parameter matching eliminates the mechanical stress causing peeling and cracking while maintaining the anti-reflection function.
Solution Approach 2:
The patent uses organic fluoropolymer materials that are chemically and mechanically homogeneous with the organic wavelength converter matrix, creating a compatible interface that prevents coating failure. The matching thermal expansion coefficients ensure homogeneous stress distribution under thermal cycling.
2Loss of energy
If the refractive index contrast between wavelength converter and air is minimized, then reflection loss is reduced, but the coating material must be precisely selected to match thermal expansion properties
Solution Approach 1:
The patent establishes specific parameter ranges for the fluoropolymer coating (refractive index 1.3-1.4, thermal expansion coefficient matching the organic matrix) to simultaneously achieve low reflection loss and high durability. This parameter specification simplifies material selection and manufacturing.
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 amorphous fluoropolymer coating effectively reduces reflection loss across a wide wavelength range, maintains high transmittance in the visible and IR regions, and offers protection against humidity, while being cost-effective and durable.
Implementation Method 1
The optical performance of an anti-reflection coating is found be critical for wavelength converters. By minimizing the index of refraction contrast between the wavelength converter and the air, the reflection loss (RL) could be minimized.
Implementation Method 2
the refractive index differences of the wavelength converters and the air. For normal incidence, the surface reflection loss of the emitted rays from the wavelength converters can be written as: where n0 is the refractive index of the air and n1 is the refractive index of the wavelength converters.
Implementation Method 3
One key difference for this invention is the thermal expansion. In general, the coefficient of linear expansion is low for inorganic materials and higher for organic materials. For example, the coefficient of thermal expansion (CTE) for fused silica is 100 ppm/K. Such large mismatches in thermal expansion can lead to warpage, cracking, and/or delamination when such materials are used together in the same device.
Data Source
AI summary
The present invention concerns an optoelectronic device, in particular an optical wavelength-converter or an infrared (IR) emitting or IR photodiode device, comprising an organic matrix-based material, wherein the organic matrix-based material is coated with at least one layer comprising an amorphous fluoropolymer. The invention also pertains to a method for the production of such an optoelectronic device.