Liquid crystal (LC) materials doped with non-mesomorphic or chiral substances are used for the matrix-addressed LC displays based on electro-thermo-optical effect. The influence of phase-transition temperature on driving condition and contrast ratio is investigated. Non-mesomorphic dopants which decrease greatly the thermal stability of LC phase expands the allowance of the driving condition and increases the contrast ratio. The chiral dopants also cause similar effects. However, the effects are not caused by the decrease of the thermal stability but by the twist force of chiral dopants. The minimum signal voltage to make a transparent state is not changed by non-mesomorphic dopant, whereas it increases with increasing the concentration of the chiral dopant. On the basis of our investigation, LC blends with the non-mesomorphic or chiral dopants have been developed. They have not only a wide allowance of driving condition and a high contrast ratio but also a high writing speed.