Lighting apparatus and light-emitting element mounting substrate having stress absorbing means

A lighting apparatus comprising:

• an apparatus main body;
• a substrate comprising a front surface on which a plurality of light-emitting elements are mounted, and a back surface which contacts the apparatus main body;
• a plurality of fasteners configured to fasten and fix the substrate to the apparatus main body at a plurality of fastening positions so as to bring the back surface of the substrate into intimate contact with the apparatus main body and provide thermal coupling;
• stress absorbing means arranged on the substrate on imaginary straight lines connecting the plurality of fastening positions with each other, wherein the stress absorbing means includes a hole which penetrates through the substrate;
• a light directing member comprising a plurality of openings which respectively surround the plurality of light-emitting elements, and a plurality of reflective surfaces which open wider on a light retrieval side corresponding to each opening, the light directing member contacting the front surface of the substrate;
• a heat transfer layer provided on the front surface of the substrate;
• a heat radiation layer provided on the back surface of the substrate;
• and
• a metal layer provided on an inner surface of the hole so as to thermally couple the heat transfer layer and the heat radiation layer.