In a liquid crystal display, a side light system shown in Patent Document 1 is widely known since it has advantages that it is low-profile and can illuminate uniformly. This side light system refers to a system in which the light of a cold cathode tube is illuminated from an edge of a transparent plate such as an acrylic plate having a certain thickness, and illuminated light is uniformly distributed by virtue of dot print provided for the transparent plate and a screen with uniform brightness can be attained. In this case, it is necessary to install a reflector on the rear side of the screen in order to prevent the illuminated light from escaping toward the rear side of the screen. High reflectiveness and high diffusing property of light are required of this reflecting plate.
As a method for obtaining a polyester film suitable for a reflector of a liquid crystal display in line with this object, a method for allowing the polyester film to contain inorganic fine particles of barium sulfate or the like is known. This method can be performed at relatively low cost. This method is described in, for example, Patent Document 2. However, in this method, since some distinction is made in temperatures of stretching in a longitudinal direction between both surfaces of the film in order to adjust a diffusing property of light, i.e., a gloss level, stretching irregularities are apt to occur and the stability of film forming is low.
Further, when inorganic fine particles of titanium dioxide or the like are added to the polyester film in a high concentration, an improvement in the reflection efficiency can be expected, but since the concentration of inert particles is very high, for example, in the case of adding the inert particles to the polyester film in an amount of 50% by weight, a break of the film often takes place and film forming is very difficult.
Furthermore, the polyester film has a static-prone defect, and when it is charged, dirt and dust adhere to its surface to cause troubles of quality. This has also become a very big problem with a polyester film for the reflector. Accordingly, it is necessary to impart an antistatic property to the polyester film for the reflector. There is a description about the technique of imparting the antistatic property in, for example, Patent Document 3.    [Patent Document 1] Japanese Unexamined Patent Publication No. 63-62104    [Patent Document 2] Japanese Unexamined Patent Publication No. 2005-125700
[Patent Document 3] Japanese Unexamined Patent Publication No. 2004-149653