US 4,785,444 A · Optical recording disc

Abstract

An optical recording disc in which a disc substrate made of a synthetic resin having a light transmittance and a hub made of a synthetic resin, fixed to a center part of the disc substrate by means of a predetermined technique such as a supersonic wave expansion molding and on which a circular magnetic metal plate is installed by means of an insert molding and so on are provided and a circular groove which is continuous at an outer peripheral side of a fixing part between the disc substrate and hub is furthermore installed on at least either of the disc substrate or hub. The groove is provided for absorbing a stress generated due to a difference in thermal expansion rates between the disc substrate made of the snythetic resin and magnetic metal plate.

Claims43

Dependent claims

An optical recording disc on which information is optically recorded or reproduced, the optical recording disc comprising:

(a) a disc substrate made of a synthetic resin and having a light transmittance;
(b) a hub fixed to a substantially center part of the disc substrate and having a magnetic metal plate;
and
(c) a groove for absorbing a stress imposed on the optical recording disc and generated due to a difference in thermal expansion rates between the disc substrate made of the synthetic resin and magnetic metal plate, which is located at least at a periphery outside of a part at which the disc substrate and hub are fixed together and is extended on at least either of the disc substrate or hub.

1 more element

Dependencies are inferred from the claim text.

Optical recording disc

Life of this patent

Optical recording disc

Life of this patent

Abstract

Claims43