A hydrophobic and abrasion-resistant MgF2 coating with an ultralow refractive index for double-layer broadband antireflective coatings

An ultralow-index top layer is a prerequisite to preparing high-performance broadband AR coatings. When coupled with hydrophobicity and the abrasion-resistance required in practical applications, the challenge becomes even greater. In this work, a MgF2 AR coating was studied because of the low refra...

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Bibliographic Details
Published in:Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2017-03, Vol.5 (12), p.3088-3096
Main Authors: Cui, Xinmin, Ding, Ruimin, Wang, Mengchao, Wang, Conghui, Zhang, Jing, Wang, Jing, Dong, Wensheng, Xu, Yao
Format: Article
Language:English
Subjects:
Assembly
Broadband
Coating
Contact angle
Heat treatment
Hydrophobicity
Refractive index
Refractivity
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Summary:An ultralow-index top layer is a prerequisite to preparing high-performance broadband AR coatings. When coupled with hydrophobicity and the abrasion-resistance required in practical applications, the challenge becomes even greater. In this work, a MgF2 AR coating was studied because of the low refractive index of MgF2 and its easily realized strong adhesion through low-temperature heat treatment. In order to obtain an ultralow refractive index and endow the coating with hydrophobicity, we designed several experimental routes and finally adopted MTES/TEOS co-precursors to direct MgF2 particles to form a honeycomb-like network structure without a template. A final refractive index of 1.15 and good hydrophobicity, with a water contact angle of 122 degree , were obtained using the MgF2-SiO2(CH3) coating. These superior properties were attributed to the incorporation of methyl groups, which not only endowed the coating with hydrophobicity, but also changed the original linear assembly of MgF2 particles to a circular assembly. Using this hydrophobic ultralow-index coating as a top layer, a high-performance double-layer AR coating was fabricated with a high average transmittance of 99.43% in the wavelength range of 400-1000 nm, good abrasion-resistance, and damp heat resistance after a low-temperature heat treatment of 250 degree C. This MgF2 double-layer AR coating may be used in display devices or lenses.
ISSN:2050-7526
2050-7534
DOI:10.1039/c6tc05307f