De, Sucheta and Jana, Debrina and Medda, Samar Kumar and De, Goutam (2013) Wavelength selective antireflective coatings on plastics with hydrophobic surfaces. Industrial & Engineering Chemistry Research, 52 (23). pp. 7737-7745. ISSN 0888-5885

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Wavelength selective antireflective (AR) coatings have been deposited on hard-coated CR-39 ophthalmic lenses and polycarbonate (PC) sheets following a two-layer (high and low index) quarter wavelength (lambda/4) optical design. Covalently bonded SiO2-poly(ethylene oxide) (PEO)-TiO2 and SiO2-PEO inorganic organic composite based coatings were used as high and low index coatings, respectively. Transmissions of 99% (reflection loss minimized to similar to 1%) have been achieved in the visible wavelength regions after deposition of such AR coatings on hard-coated CR-39. The predetermined reflection minima/transmission maxima can be tuned over the entire visible wavelength region by changing simply the physical/optical thickness of the two layers (lambda/4 design), thereby generating different reflection colors. The AR-coated CR-39 lenses showed a surface hardness of 3H (ASTM D 3363). Applying a thin (<= 50 nm) hydrophobic layer on top, the surface hardness value can be increased to 5H due to decrease of the frictional coefficient. Deposition of such a thin hydrophobic layer (lambda/4 in the UV region) does not alter any AR property in the visible region. In the case of PC the surface hardness value can be close to 4H after application of such a hydrophobic coating. Coated CR-39 and PC substrates have passed all the standard tests related to adhesion, abrasion, surface hardness, and chemical endurance. These AR coatings with hard and hydrophobic surfaces (static water contact angle 102 +/- 3 degrees) can find a wide range of applications starting from visual comfort in optical related appliances to antireflective covers on solar cells with a modest self-cleanable property.

Item Type: Article
Subjects: Engineering Materials
Divisions: Nano-Structured Materials
Depositing User: Bidhan Chaudhuri
Date Deposited: 09 Sep 2013 11:07
Last Modified: 05 Mar 2014 14:04

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