Backlight device and transmissive liquid crystal display device

A transmission liquid crystal display device using a backlight device for supplying display light emitted from a large number of light emission diodes to a transmission display panel. The transmission liquid crystal display device has an optical sheet block (10) between a liquid crystal panel (5) and a light source unit (7) having a large number of LEDs (12) and has a light diffusion plate (15), which has light transmission properties and is made of resin, for controlling the incidence of display light emitted from each of the LEDs (12). On the light diffusion plate (15) are formed vertically long light modulation patterns (18) by using light reflective ink. Each pattern (18) faces each LED (12) and has a size equal to the size of each LED (12) including its external shape. The light modulation patterns (18) make the light uniformly emitted from the LEDs (12) and realize an image display of high brightness where color irregularity and horizontal stripes are suppressed.