Seiko Epson Corporation

Hirokazu Deguchi

Kenji Kojima

Takao Mogami

A synthetic resin lens having a refractive index of at least 1.55 and an antireflection coating thereon is provided. The antireflection coating includes at least a hard coat layer formed of a dielectric substance having a refractive index n.sub.h disposed on the lens having a refractive index n.sub.s (n.sub.s .noteq.n.sub.h) and at least one antireflection layer of a dielectric or metallic material disposed between the lens and the hard coat layer. The antireflection layer has a refractive index n in the range represented by the formula: ##EQU1## and an optical film thickness of 4 (where denotes a wavelength in the range between about 450 nm to 650 nm) or two or more plies optically equivalent to a single layer of the antireflection material. The synthetic resin lens may be prepared by radical polmerization of a mixed monomer solution of styrene, 2,2-bis[3,5-dibromo-4-(2-methacryloloxyethoxy)phenyl]propane, and ultraviolet absorber and a light stabilizer. Such synthetic resin lenses generally have a refractive index of about 1.6 and a surface hardening layer usually SiO.sub.2 has a refractive index of about 1.46. It is desirable to provide an antireflection layer having a refractive index of about 1.52 which may be provided by a first layer of silicon dioxide and another layer of an oxide selected from the group of oxides of ZrO.sub.2, HfO.sub.2, Ti.sub.2 O.sub.3 TiO.sub.2, Ta.sub.2 O.sub.5, Si.sub.3 N.sub.4, Yb.sub.2 O.sub.3, Y.sub.2 O.sub.3 or Al.sub.2 O.sub.3. An outer antireflection layer is then disposed on the outer surface of the surface hardening layer.

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Suwa, Japan

Hirokazu Deguchi