OPTICAL MOUNTING SUBSTRATE

PROBLEM TO BE SOLVED: To provide an optical mounting substrate for preventing dust and dirt from being attached to a substrate and a light transmission plate and further having a function for electrification prevention, electromagnetic wave prevention or heat dissipation. SOLUTION: This optical mounting substrate 1 is provided with: a substrate 3 provided with a light emitting element 4a and a light receiving element 5a; and a light guide plate 2 being a transmission path of signal light 9. The substrate 1 is further provided with a dustproof wall 8 such as to surround the circumferential part of a space part 10 between the substrate 3 and the light guide plate 2. A resin layer 11 is also formed on the surface of the light guide plate 2, and an electrification prevention layer 12 is formed on the resin layer 11. A spacer 14 is further formed on the surface of the light guide plate 2, and a function layer 15 having additional functions for electromagnetic wave absorption, electromagnetic wave reflection, an electrostatic shield, electrification prevention, heat dissipation, light leakage prevention, the reinforcement of a light transmission layer, etc., is provided on the surface of the spacer.