Optical disc and method of producing the same

摘要

An optical disc has a first transparent substrate and a second substrate. The first substrate has a first surface and an opposing second surface. The first surface is a beam incidence surface for a laser beam in recording or reproduction of data. The second surface has first concave sections and first convex sections alternately formed thereon. The first concave sections are closer than the first convex sections to the beam incidence surface. The first convex sections have first top portions and first bottom portions closer than the first top portions to the beam incidence surface. First pre-pits carrying auxiliary information related to the data is formed on the first top portions. Each first top portion has a first width orthogonal to a direction of tracks on the first substrate. A second width orthogonal to the above direction between two first top portions of adjacent first convex sections having a first concave section therebetween is narrower than the first width. The second substrate has second concave sections and second convex sections alternately formed thereon. The second concave sections are closer than the second convex sections to the beam incidence surface. The second convex sections have second top portions and second bottom portions closer than the second top portions to the beam incidence surface. Second pre-pits carrying auxiliary information related to the data is formed on the second top portions. Each second top portion has a third width orthogonal to the above direction on the second transparent substrate. A fourth width orthogonal to the direction of tracks between two second top portions of adjacent second convex sections having a second concave section therebetween is narrower than the third width. Recording layers are formed on the first concave and second concave sections. The recording layers are formed in order between the substrates.