A light guide includes a main body and a curved refracting face formed in the main body. As light enters the main body, a bright zone and a secondary bright zone less brighter than the bright zone are formed in the main body. The curved refracting face can be an inner wall face of a curved groove or a cavity disposed in the main body. Through the formation of the curved refracting face, the light in the secondary bright zone can be directed such that, when the light guide is disposed in a thin film keyboard, the brightness of a portion of the keyboard that corresponds to the secondary bright zone has improved brightness.