Victor Company of Japan, Limited

Toyohito Asanuma

Kenichi Shimomai

Tsutomu Matsumoto

Takayuki Deno

Takeo Kojima

Fumitaka Tsuji

An optical disk includes a reflective layer, a recording layer, an optical-transparent bonding layer and an optical transparent sheet laminated on a substrate in this order. The total thickness of the optical-transparent bonding layer and the optical transparent sheet is 0.1 mm. The peak-to-peak height of wrinkles formed on the sheet is 2.5 &#x3bc;m or lower. The optical disk is produced as follows: A first ultraviolet ray is radiated to an optical transparent sheet at a first energy level in the range from 500 mJ/cmto 3000 mJ/cm, a wavelength of the first ultraviolet ray being in the range from 250 nm to 300 nm. Prepared next is a substrate laminated on which are a reflective layer and a recording layer in this order. Ultraviolet hardened resin is applied on the recording layer to form an optical-transparent bonding layer thereon. An optical transparent sheet is provided on the optical-transparent bonding layer. A second ultraviolet ray is radiated to the optical transparent sheet at a second energy level the same as or lower than the first energy level, to harden the optical-transparent bonding layer, thus the optical transparent sheet being bonded on the substrate via the optical-transparent bonding layer.

Optical disk and method of producing the same

When an LPP (land pre-pit) is formed between shallow grooves or shallow pits, the LPP is formed on a land existing between the shallow grooves or the shallow pits. Further, the LPP is formed in a position displaced from a centerline of the land in the radial direction by a predetermined amount. Furthermore, a laser beam power utilized for forming a shallow groove or a shallow pit adjacent to the LPP is reduced so as to be lower than a regular laser beam power.

Optical disc having land pre-pits and variable groove depths

A method for manufacturing a disk substrate for mass production of a phase change optical disk, wherein an original disk substrate is having a resist layer ( ) applied on a glass substrate ( ), composed of the steps of forming a depression (pit &ldquo;p &rdquo; and groove &ldquo;g &rdquo;) having a first and a second depth by cutting laser to be exposed on the surface of the resist layer ( ), etching the depression having the first depth and the second depth from the surface of the resist layer ( ) of the disk substrate in atmosphere mixed with Argon and Oxygen in ratio of 10 to 90% under gas pressure of 0.1 to 1.5 Pa, wherein the first and the second depth of the depression (pit &ldquo;p &rdquo; and groove &ldquo;g &rdquo;) become predetermined value respectively, and ashing the resist layer ( ) from the glass substrate ( ).

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Yokohama, Japan

Toyohito Asanuma