In a liquid crystal substrate in which a matrix of reflecting electrodes is formed on a substrate, a transistor is formed corresponding to each reflective electrode and a voltage is applied to the reflective electrode through the transistor. A silicon oxide film having a thickness of 500 to 2,000 angstroms is used as the passivation film and the thickness is set to a value in response to the wavelength of the incident light to maintain a substantially constant reflectance.