Magneto-optical disk having lands and grooves for recording information
AssigneeTDK Corporation
InventorsHajime Utsunomiya, Masanori Shibahara
Life of this patent
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Abstract
A magneto-optical disk is made up of a disk form of substrate including on its surface a recessed area having at least one of a groove and pits, and a recording layer provided such that it covers the recessed area. The geometry of at least one of the groove and pits is designed to conform to .theta..sub.10 .gtoreq..theta..sub.50 and .theta..sub.50 >.theta..sub.90 where .theta..sub.10, .theta..sub.50 and .theta..sub.90 are respectively the angles that tangential lines make with horizontal lines at 10%, 50% and 90% depth positions of a side wall of the recess in the diametrical direction of the substrate. This magneto-optical disk is improved in terms of the push-pull signal level, radial contrast, skew margin and C/N.
Claims28
A magneto-optical disk, comprising:
- a disk-shaped substrate including a recessed region on the surface thereof and a recording layer provided such as to cover said recessed region;
- said recessed region having alternately arranged grooves and lands, each of said grooves having a cross-sectional geometry defined by curvilinear side walls and a base, each groove having a width between the side walls and each land having a width between the adjacent grooves;
- the ration of groove width to land width is at least one;
- and the geometry of said grooves conforms to:
- .theta..sub.10 .gtoreq..theta..sub.50
- .theta..sub.50 .gtoreq..theta..sub.90,
- and
- .theta..sub.50 -.theta..sub.90 .gtoreq.5 degrees,
- wherein
- .theta..sub.10, .theta..sub.50 and 74 .sub.90 are respectively angles that tangential lines make with horizontal lines 10%, 50% and 90%-depth positions of the side wall of the recess in the diametrical direction of the substrate.
A method of making a magneto-optical disk using a substrate in the form of a disk, comprising the steps of:
- forming a recessed region having at least one groove for recording information therein and pits on the surface of said disk;
- covering said recessed region with a recording layer;
- conforming the geometry of said at least one groove and pits to:
- .theta..sub.10 .gtoreq..theta..sub.50
- .theta..sub.50 >.theta..sub.90
- where .theta..sub.10, .theta..sub.50 and .theta..sub.90 are respectively the angles that tangential lines make with horizontal lines at. 10%, 50% and 90% depth positions of a side wall of the recess in the diametrical direction of the substrate;
- controlling the formation of tracks by a push-pull technique;
- and
- detecting a track by using a radial contrast technique.
Dependencies are inferred from the claim text.