A valve for regulating the flow of fluids using two flexible diaphragms in which an additional element is added to promote rolling contact between the diaphragms. A first horizontal line image signal is written in a write memory, read in parallel from a read memory during a horizontal blanking period next to the horizontal image signal period, and amplified to thereafter perform modulation. The display device includes a display screen, a dimension of the display screen in a vertical direction being larger than that in a horizontal direction.