Optical information recording medium

#1. Field of the Invention

#The present invention relates to an optical information recording medium, and in particular, to an optical information recording medium having a high recording density, such as a Blu-ray Disc in which a dye is used in a recording layer.

#2. Description of the Related Art

#FIG. 1 is a schematic enlarged view of a cross section of an optical information recording medium according to a first embodiment of the present invention.

#FIG. 2 is a schematic enlarged view of a cross section of the optical information recording medium after recording according to the first embodiment of the present invention.

#FIG. 3 is a schematic enlarged view of a cross section of an optical information recording medium according to a second embodiment of the present invention.

#An optical information recording medium according to a first embodiment of the present invention will now be described with reference to FIGS. 1 and 2. An optical information recording medium 1 shown in FIG. 1 includes a disc-shaped substrate 2 that has a through-hole (not shown) provided at the central portion thereof and a spiral guiding groove 3 provided on a surface thereof; a reflective layer 4 provided on the guiding groove 3 of the substrate 2; a recording layer 5 that is provided on the reflective layer 4 and that is made of an organic substance containing a dye; and a light-transmissive cover layer 6 provided on the recording layer 5.

#The substrate 2 is a resin substrate having a thickness t of 1.1 mm and a diameter of 120 mm in the case of BD-R or CD-R. The described embodiments, however, can be used with media of different sizes. Various types of materials that are used for a substrate of known optical information recording media can be selected and used as the substrate 2. Specific examples thereof include polycarbonate, acrylic resins such as polymethylmethacrylate, vinyl chloride resins such as polyvinyl chloride and polyvinyl chloride copolymers, epoxy resins, amorphous polyolefins, polyester resins, metals such as aluminum, and glass. These materials may be used in combination or as a mixture, as needed. Among these materials, thermoplastic resins are preferable, and polycarbonate is particularly preferable from the standpoint of moldability, moisture resistance, dimensional stability, low cost, and the like. The substrate 2 may be formed by injection molding. When injection molding, a stamper is provided in a mold, and the spiral guiding groove 3 due to the stamper is formed on the substrate 2. This guiding groove 3 is formed at a pitch of 0.35 or 0.32 μm in the case of BD-R or CD-R, and pits are formed in this guiding groove 3. Other pitches may also be used, depending on the media.

#The reflective layer 4 is composed of a thin film of a metal having a high reflectance, such as a silver (Ag) alloy or an aluminum (Al) alloy. The reflective layer 4 is formed by, for example, sputtering. The recording layer 5 is made of an organic substance containing a dye. The recording layer 5 is formed by, for example, applying a solution prepared by dissolving a dye such as an azo dye or a cyanine dye in tetrafluoropropanol (TFP) by spin coating.