1. Technical Field
The present invention relates to an optical article for use as a lens, such as a spectacle lens, or a like optical material or product, and also to a method for producing the same.
2. Related Art
Optical articles, such as spectacle lenses, have a substrate (optical substrate) with various functions and, on the surface of the substrate, layers (films) that perform various functions for enhancing the functions of the substrate and protecting the substrate. Known examples of such layers are a hard coating layer for securing the durability of a lens substrate, an antireflection layer for preventing ghosting and flickering, and the like. A typical antireflection layer is a so-called multilayer antireflection layer that is formed by alternately laminating oxide films with different refractive indexes on the surface of a lens substrate having laminated thereon a hard coating layer.
JP-A-2004-341052, which is an example of related art, describes the provision of a novel optical element having antistatic performance suitable for substrates with low heat resistance. According to JP-A-2004-341052, in a spectacle lens or a like optical element comprising a plastic optical substrate and a multilayer antireflection film thereon, the antireflection film includes a transparent, electrically conductive layer. The transparent, electrically conductive layer is formed by ion-assisted vacuum deposition, and other layers of the antireflection film are formed by electron-beam vacuum deposition. As materials for the electrically conductive layer, inorganic oxides of one or more of indium, tin, and zinc are mentioned. ITO (Indium Tin Oxide: mixture of indium oxide and tin oxide) is described as particularly preferred.
It is known that a layer of indium tin oxide (ITO) may be inserted in order to impart electrical conductivity to a film or a layer formed on the surface of a substrate for the sake of antistatic performance, electromagnetic shielding, and the like. However, an ITO layer has high transparency and excellent antistatic properties, but is nonresistant to acid, alkali, and like chemicals. Therefore, when such a layer is employed on a spectacle lens, because human sweat is salty and acidic, the durability of the antireflection layer that includes the ITO layer may be of concern.
Meanwhile, a thin layer of metal, such as silver, may be formed to give electrical conductivity. However, an antireflection layer, a hard coating layer, an antifouling layer, and like layers formed on the surface of the substrate of an optical article often primarily consist of a silicon-based compound or oxide, so the compatibility with such a layer is of concern. For example, gold generally has poor adhesion, and film separation may thus occur. Silver may undergo a reduction in electrical conductivity due oxidation.