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High-durability hydrophilic coating technology for lens surfaces

Ensuring a clear view for cameras free from water droplets even in rainy weather

High-durability hydrophilic coating technology

High-durability hydrophilic coating for clear view

In recent years, sensing, driver assistance, and monitoring cameras have become widely used for autonomous driving. Along with this trend, high-durability hydrophilic coating has become crucial to keep a clear view in the rain. Many conventional hydrophilic coatings gradually lose their affinity for water over time even though they are hydrophilic immediately after fabrication. In particular, it is difficult to fully meet environmental durability requirements under all high-temperature, high-temperature and high-humidity, and abrasive conditions. To address this challenge, Konica Minolta selected a hard, inorganic abrasion-resistant material to form a controlled nanostructure on its surface, and added sodium atoms to the material to enhance the durabilty against high-temperature and high-himidity environement. Moreover, the photocatalytic effect provided to the surface decomposes contamination and keeps the surface clean. This innovative hydrophilic coating ensures a clear view unaffected by rain droplets.

Technology Overview

The highly durable hydrophilicity is attributable to the coating feature of sodium atoms added to a SiO2 layer and to the nanostructure etched on the surface. When forming the coating, nanosized holes, which reach the photocatalytic TiO2 layer below the hydrophilic layer, are created. The holes guide the photocatalytic effect to the surface to remove contamination. While normal etching process requres lithography technique to form a mask, this coating product only uses a self-assembled silver mask. This eliminates lithography process to each piece and enables a mask to be formed not only on a flat surface but also on a lens or other curved surfaces. In contrast to ordinary two-dimensional antireflective coatings, the three-dimensional configuration allows three features (antireflection, photocatalyst, and super hydrophilic effects) to be imparted simultaneously.

<p>Microscopic hole pattern on lens surface</p>
<p>Results of high-temperature high-humidity durability test</p>

Microscopic hole pattern on lens surface

Results of high-temperature high-humidity durability test

Photocatalytic effects (double-speed video)

Disappearance of applied methylene blue ink from surfaces owing to photocatalytic effects

Technology awards/oral presentations

1. 2019 Outstanding Achievements Award from MEXT Nanotechnology Platform

“Antireflection Multilayer Dielectric Coating with Photocatalytic Effects and Super Hydrophilicity”

2. DTIP2020, Antireflection coating with both super-hydrophilicity and photocatalytic effect

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