Method of providing a substrate of an optically readable information disc with an optically detectable structure

• Main Author: PEETERS, HENDRIKUS W. C. M
• Format: Patent
• Language: English; French; German
• Published: 12.11.1986
• Edition: 4
• Subjects: INFORMATION STORAGE; INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORDCARRIER AND TRANSDUCER; PHYSICS

The invention relates to a method of providing a substrate with a centered optically detectable structure, such as a servo structure on a transport substrate of an optical information disc. The method uses a mould (1) having a base (1A) carrying a mould structure (2) which is covered with a reproduction layer (4) of a transparent radiation-curable resin, which after curing is detached from the mould together with the substrate. In its center the base (1A) of the mould is provided with base-centering means (7) relative to which the mould structure is centered accurately. Before it is placed on the mould a substrate (3) is provided with a disc hub (8) comprising separate disc-centering means (9) which serve to center the finished information disc (17) on the drive spindle (27) of a drive apparatus. The intermediate product comprising the substrate (3) and the disc hub (8) is centered on the base (1a) of the mould by cooperation between the base-centering means (17) and the disc-centering means (9). This may be effected by the use of an auxiliary centering means (12) which is in contact with a wall (14) of a central centering hole (11) in the disc hub (8) and with a wall (13) of a central centering recess (10) in the base (1A). Thus, the reproduction layer is cured in the position which is thus centered without any play, after which the substrate together with the disc hub is detached from the mould without the centering of the servo track on the substrate being disturbed.