Variable Thickness Optical Coating for Angle-Independent Color
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Solution Overview
Problem
Optical coatings with variable thickness on substrates with planar and non-planar portions exhibit changes in optical properties such as color and reflectance due to differences in surface angles, leading to quality and aesthetic issues, and inadequate transmission of visible and infrared radiation.
Innovation Solution
An optical coating comprising alternating layers of low and high refractive index materials, with a total thickness between 320 nm to 1000 nm, where the high refractive index material makes up at least 40% of the top 250 nm, ensuring a uniform appearance and improved optical properties across different angles and wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional optical coating process is used on substrates with planar and non-planar portions, then the coating can be applied to the entire surface, but the coating thickness varies due to different surface angles, causing changes in optical properties such as color and reflectance
Solution Approach 1:
The patent applies different thickness specifications for different regions of the coating. The first portion (planar) has a thickness of 320-1000 nm while the second portion (curved/faceted) has a reduced thickness of 160-500 nm. This local differentiation compensates for the geometric variations and maintains consistent optical properties across the entire substrate surface.
Solution Approach 2:
The patent changes the coating thickness parameter based on the surface geometry. By reducing the thickness in areas where the coating would naturally be thinner due to angle effects, the patent compensates for variations and maintains uniform optical characteristics across different surface orientations.
2Reliability
If the optical coating thickness is increased to improve optical properties, then transmittance and reflectance characteristics improve, but the coating becomes more sensitive to thickness variations caused by surface angle differences
Solution Approach 1:
The patent specifies different thickness ranges for different portions of the substrate. The planar portion receives a thicker coating (320-1000 nm) while the curved/faceted portions receive a thinner coating (160-500 nm). This local differentiation ensures that each region achieves optimal optical properties while compensating for geometric variations, resulting in consistent appearance across different viewing angles.
3Adaptability or versatility
If the optical coating is made thinner to reduce sensitivity to angle variations, then viewing angle independence improves, but the optical properties such as color stability and reflectance control deteriorate
Solution Approach 1:
The patent implements region-specific thickness control where the planar portion maintains a thicker coating (320-1000 nm) for optimal optical properties, while curved/faceted portions have reduced thickness (160-500 nm) for angle insensitivity. This localized approach allows each region to be optimized for its specific geometric characteristics.
Solution Approach 2:
The patent adjusts the coating thickness parameter based on local surface geometry. By implementing a thickness gradient that accounts for surface orientation, the patent maintains both color stability and viewing angle independence simultaneously through parameter optimization.
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 solution provides a stable reflected color and high transmittance across visible to infrared wavelengths, maintaining optimal optical properties regardless of viewing angle and coating thickness variations, while also imparting hardness to the substrate.
Implementation Method 1
an optical coating disposed on both portions of the external surface... comprising alternating layers of a low refractive index material and a high refractive index material
Data Source
AI summary
An article is described herein that includes an optical coating on both a first portion and a second portion of a first major surface of a substrate. The first portion and the second portion face in different directions. The optical coating forms an anti-reflective surface, has a total thickness of less than 1000 nm, and is thicker over the first portion than over the second portion. The optical coating exhibits a first surface reflected color characterized by International Commission on Illumination (“CIE”) L*a*b* color space values of: (i) a*, from −6.0 to +4.5, and (ii) b*, from −11.0 to +6.0 at all viewing angles within a range of from 0 degrees to 10 degrees relative to a normal of the first major surface at both (i) the first portion and (ii) the second portion where the total thickness of the optical coating is 75% to 90% of the maximum value of the total thickness.