Durable antireflective film

Abstract

Antireflective films are described having a surface layer comprising a the reaction product of a polymerizable low refractive index composition comprising at least one fluorinated free-radically polymerizable material and surface modified inorganic nanoparticles. A high refractive index layer is coupled to the low refractive index layer. In one emboidiment, the high refractive index layer comprises surface modified inorganic nanoparticles dispersed in a crosslinked organic material. The antireflective film is preferably durable, exhibiting a haze of less than 1.0% after 25 wipes with steel wool using a 3.2 cm mandrel and a mass of 1000 grams.

Description

RELATED APPLICATION DATA[0001]This application is a Continuation-In-Part of application Ser. No. 11 / 423,781, filed Jun. 13, 2006.BACKGROUND[0002]Various antireflective polymer films (“AR films”) have been described. The physical principles by which anti-reflection films and coatings function are well known. Several overviews can be found, for example, in Optical Engineering, S. Muskiant Ed, Vol. 6., Optical Materials, Chap. 7, p 161, 1985 and as shown in U.S. Pat. No. 3,833,368 to Land, et al. AR films are often constructed of alternating high and low refractive index (“RI”) polymer layers of the correct optical thickness. With regards to visible light, this thickness is on the order of one-quarter of the wavelength of the light to be reflected. The human eye is most sensitive to light around 550 nm. Therefore it is desirable to design the low and high index coating thicknesses in a manner that minimizes the amount of reflected light in this optical range (e.g. 2.5% or lower).[0003]...

AI Technical Summary

Benefits of technology

[0007]In one embodiment, the antireflective film surface exhibits a haze of less than 1.0% after 25 wipes with steel wool using a 3.2 cm mandrel and a mass of 1000 grams.

[0008]The high refractive index layer preferably has a refractive index of at least 1.60 and preferably comprises 15 vol-% to 40 vol % surface modified zirconia nanoparticles. The surface modified nanoparticles preferably comprise free-radically polymerizable groups.

[0009]The low refractive index composition typically comprises one or more fluorinated free-radically polymerizable monomers, oligomers, polymers, and mixtures thereof, having a fluorine content of at least 25 wt-%. The proportion of such material in the low refractive index layer is typically at least 25 wt-% or greater. The fluorinated free-radically polymerizable material is preferably multi-functional. The low refractive index layer composition typically further comprises at least one non-fluorinated crosslinker having at least three multi-acrylate groups. In preferred embodiments, the fluorinated free-radically polymerizable material comprises at least one fluoropolymer.

[0010]In one embodiment, the low refractive index layer comprises the reaction product of a polymerizable composition comprising a free-radically polymerizable fluorinated polymeric intermediate, at least one fluorinated free-radically polymerizable (e.g. monomeric and/or oli

Problems solved by technology

Although increased fluorine content decreases the refractive index of the low refractive index coating composition, the concurrent decrease in surface energy can result in poor coating and optical cosmetic properties as well as a loss in interfacial adhesion with the adjacent high refractive index layer.

Also, highly fluorinated materials have been known to reduce the hardness and durability of the coating.

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