Light irradiation device, image reading device, and image forming apparatus

A light irradiation device comprising:

• a light source that is an elongated light source or a plurality of light emitting elements linearly arranged in a main scanning direction on a board;
• a light guide member including a transparent material to guide light from the light source;
• and
• a holding member to hold the light source and the light guide member,
• the light guide member including:
• an incident surface on which the light exiting from the light source is incident, the incident surface having an elongated shape in the main scanning direction and being disposed to face a light emitting surface of the light source;
• an exit surface from which the light incident from the incident surface is to exit toward an irradiation area of an irradiation target;
• a held surface disposed in contact with the holding member to be pressed against and secured to the holding member;
• and
• a securing structure in each of both end portions in the main scanning direction, which are out of a light guide area of the light guide member,
• the securing structure in one end portion that is an engagement lug structure protruding to penetrate into a through-hole of the holding member, including a lug on a leading end, and engaging the holding member,
• the securing structure on another end portion that is a fastening structure having a fastening hole penetrated with a fastening member and being secured to the holding member with the fastening member.