Surface illuminant device

A surface illuminant device comprising:

• a light source;
• a light transmitter having an incident end face disposed in a vicinity of said light source;
• a holder accommodating said light source and serving for condensing rays emitted from said light source onto said incident end face of said light transmitter;
• a light diffusing sheet mounted on an upper side surface of said light transmitter;
• and
• a reflecting sheet disposed on a lower side surface of said light transmitter,
• wherein a layered structure .consisting of said light transmitter, said light diffusing sheet and said reflecting sheet, is integrally fixed by fixing means at a portion of a first end zone of said layered structure opposite to said incident end face, and
• wherein said holder is attached to said layered structure by a plurality of attaching means in such a manner that a second end zone of said layered structure opposite to said first end zone and including said incident end face of said light transmitter is enclosed between an upper end portion and a lower end portion of said holder, with end edges of said light diffusing sheet and said reflecting sheet located in said second end zone being laid respectively underneath said upper end portion and said lower end portion, with respective minimum spaces kept between said upper end portion of said holder and said light diffusing sheet and between said lower end portion of said holder and said reflecting sheet for allowing movement of said light diffusing sheet and said reflecting sheet relative to said light transmitter in directions along the upper side and lower side surfaces of said light transmitter except at said portion fixed by said fixing means.