A resin frame (2) is disposed on an emission surface (43) side of a light guide plate (4) through at least one optical sheet (3). A protrusion (25) facing an end surface (45) adjacent to the emission surface of the light guide plate is provided upright on the resin frame. The protrusion is elastically deformable towards the opposite side to the light guide plate where the protrusion faces. Since the protrusion elastically deforms to absorb the extension of the light guide plate, the light guide plate does not deform. Therefore, it is possible to prevent, for the long term, deformations of the light guide plate resulting from relative changes in the size of the light guide plate due to changes in temperature and humidity.
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