Abstract: An optical disc with a first recording layer has first data pits that include 14T data pits formed thereon in compliance with DVD-ROM specifications. A first reflective film is formed on the first recording layer, whereby the first reflective film has the relationship of 2.3?Pw/Tf?14 between the 14T pit width and the first reflective film thickness. The disc also includes a second recording layer having a first surface and an opposed second surface, whereupon second data pits are formed on the first surface in compliance with BD-ROM specifications. A second semi-transparent reflective film is formed on the second recording layer, while a transparent layer having opposed third and fourth surfaces is formed over the second reflective film at the third surface, such that the fourth surface allows a laser beam to pass therethrough in reproduction from either the first or second data pits.

Abstract: An optical disc includes a first substrate having a first surface having a first recording layer formed thereon, a first reflective film formed on the first recording layer, a second substrate having a second surface and a third surface on both sides with a second recording layer and a third recording layer formed thereon, respectively, a second semi-transparent reflective film formed on the second recording layer, a third semi-transparent reflective film formed on the third recording layer, an adhesive layer provided between the first and second reflective films, and a transparent cover layer having a fourth surface and a fifth surface on both sides, formed on the third semi-transparent reflective film at the fourth surface. The first recording layer is capable of storing first data in compliance with first specifications. The second recording layer is capable of storing second data in compliance with the first specifications.

Abstract: An optical disc is produced. A first recording layer is formed on a first substrate having a thickness of 0.6 mm±30 ?m, so that the first recording layer has first data pits formed concentrically or spirally in compliance with the DVD-ROM specifications, the first data pits including 14T pits, T being a reference clock cycle. A first reflective film is formed on the first recording layer, so that the first reflective film has a thickness in the range from 30 nm to 140 nm and has a relationship of 2.3?Pw /Tf?14 with the first reflective film, wherein Pw is a pit width of each 14T pit at a middle section of the first substrate and Tf is a thickness of the first reflective film, the middle section being located between a top section and a bottom section of the first substrate in a thickness direction thereof, a distance from the top section to the middle section and another distance from the middle section to the bottom section being equal to each other.

Abstract: An optical disc includes a first substrate having a first surface having a first recording layer formed thereon, a first reflective film formed on the first recording layer, a second substrate having a second surface and a third surface on both sides with a second recording layer and a third recording layer formed thereon, respectively, a second semi-transparent reflective film formed on the second recording layer, a third semi-transparent reflective film formed on the third recording layer, an adhesive layer provided between the first and second reflective films, and a transparent cover layer having a fourth surface and a fifth surface on both sides, formed on the third semi-transparent reflective film at the fourth surface. The first recording layer is capable of storing first data in compliance with first specifications. The second recording layer is capable of storing second data in compliance with the first specifications.

Abstract: An optical disc includes a first substrate and a second substrate. The first substrate has a thickness of 0.6 mm±30 ?m, with a first recording layer formed thereon. The first recording layer has a string of first data pits concentrically or spirally formed in compliance with the DVD-ROM specifications. The second substrate has a thickness of 0.5 mm±30 ?m, with a first surface and a second surface on both sides. A second recording layer is formed on the first surface, as having a string of second data pits concentrically or spirally formed in compliance with the DVD-ROM specifications. A third recording layer is formed on the second surface, as having a string of third data pits concentrically or spirally formed in compliance with the BD-ROM specifications. A first reflective film is formed on the first recording layer. A second semi-transparent reflective film is formed on the second recording layer.

Abstract: This invention provides a manufacturing method for an optical disc master, in which a photoresist layer is formed on a substrate, and then a laser beam having a wavelength of 200 to 300 nm is exposed to the photoresist layer to form thereon a latent image corresponding to an information signal, and then the latent image is developed with an alkaline aqueous solution to form a convex-concave pattern. Particularly, in the manufacturing method for the optical disc master, a value obtained by multiplying a value A with a film thickness is set in a range of 0.02 to 0.06. The value A is a change amount of a light transmittance per unit depth under a wavelength of light for exposure of the photoresist layer. Further, in the manufacturing method, a value obtained by multiplying a value B with the film thickness is set to be equal to or less than 0.3. The value B is an optical density of a base resin and a photoproduct per unit depth under the wavelength of light for exposure of the photoresist layer.

Abstract: An information recording medium in higher quality of which pit deformation is suppressed by setting film strength of a photoresist within a predetermined range is provided. A positive photoresist utilized for manufacturing the information recording medium, which is recorded with an information signal formed as a pit or a groove on a disc, is constituted such that a modulus of compression elasticity of a solid component of the photoresist after removing a solvent component is set within a range of 8.0×10−3 to 5.0×10−1 MPa at 100° C.

Abstract: An optical disc used for information recording capable of suppressing an increase of birefringence of the light-transmitting layer at the minimum, resulting in an optical disc having a high quality without a degradation of signal characteristics. The optical disc has a substrate having a group of pits/grooves representing information signal on a surface thereof, a reflecting layer formed on the substrate, and a resin film formed on the reflecting layer through an adhesive layer, wherein a thickness of the adhesive layer is made to be not more than 100 &mgr;m, and a product value of a photoelasticity constant, a modulus of tension elasticity and a thickness with respect to the resin film is established within −0.2 to 0.2 mm.