<p>PURPOSE: A display device is provided to provide sound without a speaker. CONSTITUTION: A liquid crystal display device (100) includes a liquid crystal display panel assembly (70) and a back light unit (20). The liquid crystal display panel assembly includes a liquid crystal display panel (75), an integrated circuit chip (77) and a flexible printed circuit board (79). The back light unit includes an optical sheet (24) including a diffusion sheet (25), a reflective sheet (26) and a light source (12). The optical sheet is located in the rear of the liquid crystal display panel assembly and provides a light to the liquid crystal display panel assembly. The optical sheet or the reflective sheet includes a vibration material layer which provides sound by being applied with at least one electric field.</p>
