In recent years, transparent conductive coatings such as indium tin oxide (ITO) thin coatings have found a wide variety of applications. For example, it is known that a transparent conductive coating is formed as an antistatic layer on one side of the transparent substrate of a liquid crystal cell opposite to its side in contact with the liquid crystal layer in a liquid crystal display device using a liquid crystal cell of an in-plane switching (IPS) type or the like. A transparent conductive coating is also formed on a transparent resin film to form a transparent conductive film, which is used as an electrode substrate to form a touch panel. For example, such a touch panel is used in combination with a liquid crystal display device or image display device for cellular phones, portable music players, or other devices to form an input device, which has become widely spread.
A widely-spread conventional input device including a combination of a touch panel and an image display device is of an out-cell type, in which a transparent conductive film including a transparent substrate made of a glass sheet or a transparent resin film and a transparent conductive layer formed thereon is provided on a liquid crystal display device (above the viewer-side polarizing film of the liquid crystal display device). In recent years, however, various other structures have become known, such as an on-cell type, in which a transparent conductive coating electrode is formed on the upper glass substrate of a liquid crystal cell, and an in-cell type, in which a transparent conductive coating electrode is incorporated in a liquid crystal cell. It is also known that an ITO layer as an antistatic layer for an image display device is used to form a touch sensor, which is patterned to provide a touch panel function.
In some cases, an optical film such as a polarizing film is disposed on such a transparent conductive coating with a pressure-sensitive adhesive layer interposed therebetween. A common pressure-sensitive adhesive is produced using a carboxyl group-containing monomer as a pressure-sensitive adhesive component for increasing the cohesive strength of the pressure-sensitive adhesive. Unfortunately, it is difficult to use such an acid component-containing pressure-sensitive adhesive layer for the above applications because the acid can corrode the transparent conductive layer when the acid component-containing pressure-sensitive adhesive layer comes directly into contact with the transparent conductive layer.
For the solution of the problem of such metal corrosion, there are proposed various pressure-sensitive adhesive compositions having the ability to prevent metal corrosion. Specifically, there are proposed a pressure-sensitive adhesive composition with its acid component content reduced by the addition of a specific amount of a nitrogen atom-containing component (see, for example, Patent Document 1), a pressure-sensitive adhesive composition containing an acidic group-free acrylic resin as a main component (see, for example, Patent Document 2), and a pressure-sensitive adhesive containing a (meth)acryl-based polymer substantially free of any acidic group (see, for example, Patent Document 3).
Now, the liquid crystal display devices and image display devices mentioned above are strongly required to be lighter and thinner, and polarizing films for use in the liquid crystal display devices and so on are also required to be lighter and thinner. Known methods for reducing the weight and thickness of polarizing films include, for example, a method of providing a transparent protective film on only one side of a polarizer to form a one-side-protected polarizing film, and a method of producing a thin polarizing film with a thinner polarizer.
A known method of producing a thin polarizing film includes producing an optical film laminate including: an amorphous ester-based thermoplastic resin substrate in the form of a continuous web; and a thin polarizing coating that is formed on the substrate and includes a polyvinyl alcohol-based resin containing oriented iodine (see, for example, Patent Documents 4 and 5).