Vehicle Optical Element Nanometric Roughness Anti-Fogging
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Solution Overview
Problem
Optical elements in motor vehicle luminous devices, such as headlights and rear lights, suffer from fogging and dirt adhesion, leading to reduced transparency and maintenance challenges, with existing anti-fogging and self-cleaning coatings not optimizing cleaning properties effectively.
Innovation Solution
A transparent optical element with a surface roughness of at least 20 nm, featuring a polymer first layer and a second layer comprising silicon, titanium, and oxygen, which enhances cleaning and anti-fogging properties through photocatalytic activity and hydrophilicity, reducing contaminant adhesion and promoting easy dirt removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a smooth surface is used for the optical element, then transparency and light transmission are maintained, but fogging and dirt adhesion occur leading to reduced cleaning properties
Solution Approach 1:
The patent applies a local quality change by creating a nanometric roughness layer (Ra between 0.02 and 0.2 μm) only on the outer surface of the optical element, while maintaining the bulk transparency of the material. This localized surface modification enables the surface to exhibit self-cleaning properties through controlled condensation and reduced dirt adhesion, without compromising the overall optical transmission of the element.
Solution Approach 2:
The patent changes the surface parameter from smooth to nanometrically rough (Ra between 0.02 and 0.2 μm), which fundamentally alters the surface's interaction with water and contaminants. This parameter change enables the surface to promote water condensation into large droplets rather than fine fogging, and reduces the adhesion strength of organic and mineral dirt, thereby improving cleaning properties while maintaining optical functionality.
2Object-affected harmful factors
If a superhydrophilic coating is deposited to prevent fogging, then anti-fogging properties are improved, but cleaning properties are not optimized
Solution Approach 1:
The patent creates a localized nanometric roughness structure on the surface that works synergistically with the hydrophilic coating. This local structural modification enables the surface to differentiate between water condensation (promoting large droplet formation for anti-fogging) and dirt adhesion (reducing binding strength for easier cleaning), thereby optimizing both anti-fogging and cleaning properties simultaneously.
Solution Approach 2:
The patent combines a hydrophilic coating material with a nanometric roughness surface structure to create a composite surface treatment. This combination leverages the hydrophilic properties of the coating material for anti-fogging while the nanometric roughness structure provides reduced dirt adhesion and enhanced cleaning properties, achieving a dual-function surface that outperforms either treatment alone.
3Ease of manufacture
If the surface roughness is increased to reduce dirt adhesion, then cleaning properties are improved, but transparency and light transmission may be compromised
Solution Approach 1:
The patent applies partial action by creating a very thin nanometric roughness layer (Ra between 0.02 and 0.2 μm) that is sufficient to provide self-cleaning properties through reduced dirt adhesion and controlled condensation, but thin enough to remain optically transparent. This partial modification achieves the necessary cleaning enhancement without excessive roughness that would scatter light and reduce transmission.
Solution Approach 2:
The patent precisely controls the surface roughness parameter within a narrow range (Ra between 0.02 and 0.2 μm) to optimize the balance between cleaning properties and light transmission. This controlled parameter change ensures that the surface is rough enough to reduce dirt adhesion and promote water drainage, but smooth enough at the macro scale to maintain high optical transparency and light transmission through the element.
Data Source
AI summary
An optical element, which is transparent, for a motor vehicle, including at least one transparent first layer containing a polymer material and at least one second layer including at least silicon, titanium and oxygen. The optical element has a surface roughness defined by a mean square deviation Rq greater than or equal to 20 nm.