DESCRIPTION POLYESTER COMPOSITION FOR SOLAR BATTERY AND METHOD FOR PRODUCING SAME TECHNICAL FIELD [0001] The present invention relates to a polyester composition. More particularly, the present invention relates to a polyester composition suitable as a solar battery film, which contains only small amount of terminal carboxy groups and terminal methoxy groups and has excellent hydrolysis resistance and heat resistance; and a method of producing the polyester composition. BACKGROUND ART [0002] In general, polyesters such as polyethylene terephthalate have excellent mechanical and chemical characteristics and are, therefore, used in a wide range of applications such as those films for magnetic recording media, general industry, heat-sensitive stencil plates, ribbons, reflecting plates, optics, food packings, paper alternatives, mold-release, electric insulation and capacitors. [0003] Particularly, in recent years, attention has been drawn to photovoltaic power generation which is expected to contribute to CO2 reduction; and, in a film for solar battery, there is a demand for an improvement in the hydrolysis resistance, which is one of the required properties, and a reduction in the cost. [0004] As a method of improving the hydrolysis resistance, it is known to perform solid phase polymerization so as to reduce the amount of terminal carboxyl groups. In Patent Document 1, it is described that an electrical insulating film is subjected to solid phase polymerization so as to reduce the cyclic trimer content. [0005] Further, in Patent Documents 2 and 3, it is proposed to further add ethylene glycol during or after esterification reaction. [0006] Moreover, Patent Document 4 proposes a polyester for lamination to a metal plate in which the amount of terminal methoxy groups is reduced. PRIOR ART DOCUMENTS PATENT DOCUMENTS [0007] [Patent Document 1] JP H02-296860A [Patent Document 2] JP 2002-47340A [Patent Document 3] JP 2010-163613A [Patent Document 4] JP 2000-86875A SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION [0008] However, in the polyester described as an electrical insulating film in Patent Document 1, in which the cyclic trimer content is reduced by solid phase polymerization, since the polyester is subjected to a polycondensation reaction at a high temperature prior to the solid phase polymerization, the amount of terminal carboxyl groups is increased due to thermal decomposition and the high amount of terminal carboxyl groups cannot be adequately reduced even with solid phase polymerization, so that it cannot be said that the amount of terminal carboxyl groups is sufficiently low. In addition, in a conventional DMT method where a polyester is produced by using dimethyl terephthalate and ethylene glycol as starting materials, the amount of terminal methoxy groups is high after a polycondensation reaction; therefore, consequently, the time required for solid phase polymerization becomes long and the method is not adequate also from the cost standpoint. [0009] Further, Patent Documents 2 and 3 propose polyesters in which the amount of terminal carboxyl groups is reduced by further adding ethylene glycol during or after esterification reaction. These polyesters contain only a small amount of terminal carboxyl groups; however, since the phosphorus content is also small, the polyesters have poor heat resistance and are thus not appropriate for a solar battery used in harsh environment such as outdoor environment. Furthermore, since the polyesters have a low haze value, when they are made into films, the resulting films have a low surface roughness, making it difficult wind up the films. [0010] Moreover, Patent Document 4 proposes a polyester for lamination to a metal plate in which the amount of terminal methoxy groups is reduced. However, in the polyester, although the amount of terminal methoxy groups is small, since the amount of terminal carboxyl groups is high and the phosphorus content is low, the polyester cannot be used as a film for solar battery. [0011] In view of the above, an object of the present invention is to provide a polyester composition for a solar battery which solves the above-described problems in prior art and is excellent in the hydrolysis resistance and heat resistance and cost for which properties the demand has become increasingly stringent in recent years. MEANS FOR SOLVING THE PROBLEMS [0012] The above-described object of the present invention is achieved by a polyester composition for a solar battery which comprises a dicarboxylic acid component having terephthalic acid as a main component and a diol component having ethylene glycol as a main component, the polyester composition being characterized by satisfying the following Formulae (1) to (5). [0013] 0.65 < intrinsic viscosity < 0.90 (1) 0.7