Future advances in mass production technologies and the implementation of market creation ideas based on technological convergence can be expected in the lighting sector of the information display market, allowing the development of high-value-added products. The challenges faced, with regard to conventional lighting systems, in achieving an increased manufacturing efficiency via simple processing techniques by utilizing minimal light sources are identified. Consequently, a performance evaluation was conducted for an improvement in the optical characteristics. This was achieved by optimizing the shapes of geometric scattering patterns and the positions of the light sources near the light guide plate (LGP). Based on the results, an effective structure of an LGP for large-area, flat-type lighting systems is proposed. To evenly distribute the incident light, a light-emitting diode (at a beam angle of 60 deg) is placed at each corner of the LGP. Moreover, it was confirmed that the optimum condition for improving the optical characteristics of the applied light is a curved pattern starting from each corner. To increase the illuminance efficiency, this curved pattern is inclined toward the center. Further, the illuminance is approximately doubled (592 lux) when the pattern spacing is reduced, creating an optimal design approach for improving the optical characteristics of a large-area, flat-type lighting system.