JPH10312585A5 - - Google Patents

Description

[0002]
2. Description of the Related Art
In optical recording media, such as ROM (Read Only Memory) type optical disks or rewritable optical disks having a phase change recording layer, pits and/or grooves, i.e., fine concave-convex patterns, are formed in a required format.
This fine uneven pattern can be formed by injection molding using a stamper on which an uneven pattern that is the reverse of the fine uneven pattern is formed, thereby forming the fine uneven pattern at the same time as molding the optical disk, or by using the 2P method (photopolymerization method), in which an ultraviolet-curable resin is applied to a substrate, the above-mentioned stamper is pressed against it to transfer and form the fine uneven pattern, and then ultraviolet light is irradiated.

[0009]
In the present invention, it is possible to improve the variation in pit width and also to improve the degradation of RF signals even in optical recording media having a fine uneven pattern including extremely short pits of less than 0.40 μm , which are approximately 85% or less of the recording spot diameter at the aforementioned recording wavelength of 351 nm.

[0010]
Furthermore, the present invention provides a stamper for producing an optical recording medium, a master disk for the stamper, and a method for producing an optical recording medium that are useful even when the fine uneven pattern is, for example, a fine uneven pattern consisting only of grooves, and does not include extremely short pits less than 0.40 μm, having a length of approximately 85% or less as described above, provided that the groove width is made sufficiently smaller than the spot diameter of the recording exposure described above.

[0014]
Furthermore, in the method for manufacturing an optical recording medium according to the present invention, an optical recording medium is obtained by a photopolymer method or an injection molding method using a stamper obtained through the process according to each of the above-described present inventions, i.e., the process of depositing a thin film along the concave-convex surface of the concave-convex pattern to form a reduced concave-convex pattern.

[0015]
According to the above-described method of the present invention, a reduced concave-convex pattern is formed by depositing a thin film on the concave-convex pattern of a master or mother disk that forms a stamper for obtaining an optical recording medium. This allows the width of the concave-convex pattern to be increased during exposure recording for master formation. That is, even when obtaining an optical recording medium using a format that includes a pit length of less than 0.40 μm, which corresponds to less than 85% of the exposure spot diameter at a recording wavelength of 351 nm , the width of the concave-convex pattern can be increased during exposure recording for master formation. This allows the exposure intensity to be sufficiently increased, thereby improving the width variation of the concave-convex pattern, as explained in FIG. 23 . Furthermore, since the exposure intensity can be sufficiently increased, a so-called "clear" pattern can be formed. Therefore, the fine concave-convex pattern in the final optical recording medium has reduced width variation and is formed as a so-called "clear" fine concave-convex pattern, thereby improving RF characteristics.

[0020]
Furthermore, in the method for manufacturing an optical recording medium according to the present invention, an optical recording medium is obtained by a photopolymer method or an injection molding method using a stamper obtained through the process according to each of the above-described present inventions, i.e., the process of depositing a thin film along the concave-convex surface of the concave-convex pattern to form a reduced concave-convex pattern.

[0029]
The stamper 9 obtained in this manner is placed in an injection molding die (not shown), and a resin such as polycarbonate is injected into it to obtain the desired optical recording medium 10, such as an optical disk, on which a fine concave-convex pattern 34 is formed by transferring the concave-convex pattern 24 of the stamper 9.

[0039]
The stamper 70 obtained in this manner is placed in an injection molding die (not shown), and a resin such as polycarbonate is injected into it to obtain an optical recording medium 10, such as an optical disk, on which the desired fine concave-convex pattern 34 is formed by transferring the concave-convex pattern 74 of the stamper 70.