Light emitting unit, illumination apparatus, reading apparatus, and recording system

Alight emitting unit comprising a substrate, a light emitting element placed on a first surface of the substrate, a front panel covering the first surface, and a back panel placed on a second surface of the substrate, which is opposite to the first surface,

• wherein the back panel has a thermal conductivity higher than that of the front panel,
• an opening for extracting light emitted by the light emitting element is formed in the front panel,
• an inner wall of the front panel, which includes a circumferential wall of the opening, has a ventilation portion including at least one of a trench or a through hole extending from the inner wall to an outer edge of the front panel, and
• an area of the ventilation portion formed in the circumferential wall of the opening is 1% (inclusive) to 20% (inclusive) of an area of the circumferential wall of the opening.