Optical disk

摘要

Opposed faces of disk substrates 1a and 1b or disk substrates 1a and 1a are bonded by an adhesive layer 3 whose characteristic values are set in predetermined ranges, particularly in the values of a product of Young's modulus and the film thickness in a range of 1.0 x 10<-2>kg/mm to 3.0 kg/mm, a product of Young's module and the thermal expansion coefficient in a range not larger than 1.5 x 10<-2>kg.mm<-2>. DEG C<-1>, or a product of the thermal expansion coefficient and the film thickness in a range not larger than 2.0 x 10<-5> mm / DEG C. Preferably, the glass transition point of the used adhesive is set to a value in a range of 20 DEG C to 80 DEG C, and the film thickness is set to a value in a range of 10 mu m to 100 mu m.