Abstract: A polyolefin resin drawn sheet 4 is laminated on at least one face of a sheet-form core material 6 having a density of 30 to 300 kgf/m3. At this time, a sheet or film 5 made of a bonding synthetic resin or rubber having a flow starting temperature lower than the thermal deformation temperature of the core material 6 and the melting point of the drawn sheet 4 is interposed between the core material 6 and the drawn sheet 4. The resultant stack product is heated to not less than the flow starting temperature of the synthetic resin or the rubber and not more than the thermal deformation temperature of the core material 6 and the melting point of the drawn sheet 4. At the same time of or after the heating, the stack product is pressed to apply a compression strain of 0.01 to 10% to the core material 6.

Abstract: A magnetic disk comprises a magnetic layer and a protective layer sequentially formed on a disk-shaped substrate and has a principal surface to which data is recorded, and a side surface portion both of which are coated with the protective layer. The protective layer on the side surface portion is thinner than the protective layer on the principal surface. Preferably, the side surface portion includes a side wall surface, and a chamfered surface lying between the side wall surface and the principal surface, and at least the protective layer on the chamfered surface is thinner than the protective layer on the principal surface.

Abstract: In a magnetic disk having a magnetic layer, a protection layer, and a lubrication layer formed on a substrate in this order, a surface free energy ?S of a surface of the magnetic disk derived by an extended Fowkes equation is greater than 0 and no greater than 24 mN/m. ?Sd (dispersion force component of surface free energy) forming the surface free energy ?S is greater than 0 and no greater than 17 mN/m, ?Sp (dipole component of surface free energy) forming the surface free energy ?S is greater than 0 and no greater than 1 mN/m, and ?Sh (hydrogen bonding force component of surface free energy) forming the surface free energy ?S is greater than 0 and no greater than 6 mN/m.

Abstract: A polyolefin resin drawn sheet 4 is laminated on at least one face of a sheet-form core material 6 having a density of 30 to 300 kgf/m3. At this time, a sheet or film 5 made of a bonding synthetic resin or rubber having a flow starting temperature lower than the thermal deformation temperature of the core material 6 and the melting point of the drawn sheet 4 is interposed between the core material 6 and the drawn sheet 4. The resultant stack product is heated to not less than the flow starting temperature of the synthetic resin or the rubber and not more than the thermal deformation temperature of the core material 6 and the melting point of the drawn sheet 4. At the same time of or after the heating, the stack product is pressed to apply a compression strain of 0.01 to 10% to the core material 6.

Abstract: In a method of evaluating surface tension of a solid body surface, selection is made of at least three liquid samples having different surface tensions, and contact angles between the respective liquid samples and the solid body surface are measured. Thereby, a correlation between cosines (Y) of the contact angles and surface tensions (X) of the liquid samples is derived as a logarithmic function. Surface tension of the solid body surface is evaluated by the use of a value of X that is calculated by substituting 1 for Y in the correlation. When evaluated by the foregoing evaluation method, a magnetic disk has a surface where the value of X, when 1 is substituted for Y, is greater than 0 and no greater than 17 mN/m.

Abstract: In a magnetic recording medium which comprises a substrate (1), a magnetic layer (3) formed on the substrate, a carbon-based protection layer (4) comprising carbon and formed on the magnetic layer, and a lubrication layer (5) formed on the carbon-based protection layer, the carbon-based protection layer comprises a hydrogenated carbon protection layer (4a) facing the magnetic layer and a nitrogenated carbon protection layer (4b) facing the lubrication layer. The hydrogenated carbon protection layer (4a) comprises carbon and hydrogen. The nitrogenated carbon protection layer (4b) includes no hydrogen but comprises carbon and nitrogen.

Abstract: In a magnetic recording medium which comprises a substrate (1), a magnetic layer (3) formed on the substrate, a carbon-based protection layer (4) comprising carbon and formed on the magnetic layer, and a lubrication layer (5) formed on the carbon-based protection layer, the carbon-based protection layer comprises a hydrogenated carbon protection layer (4a) facing the magnetic layer and a nitrogenated carbon protection layer (4b) facing the lubrication layer. The hydrogenated carbon protection layer (4a) comprises carbon and hydrogen. The nitrogenated carbon protection layer (4b) includes no hydrogen but comprises carbon and nitrogen.

Abstract: A protection layer containing carbon as a major component is deposited by plasma CVD. The protection layer has film quality such that, when a spectrum is obtained by excluding photoluminescence from a Raman spectrum in a wavenumber band from 900 cm?1 to 1800 cm?1 obtained by exciting the protection layer with an argon ion laser beam having a wavelength of 514.5 nm and the spectrum is subjected to waveform separation by the Gaussian function to split a D peak appearing around 1350 cm?1 and a G peak appearing around 1520 cm?1, the ratio Dw/Gw between a half width Dw of the D peak and a half width Gw of the G peak exceeds 0 and is not greater than 2.7.

Abstract: A magnetic disk includes a substrate on which a nonmagnetic metal layer, a magnetic layer, a carbon-based protection layer, an alcohol-based coupling layer, and a lubrication layer successively formed thereon. The lubrication layer contains a hydroxyl- or a carboxyl-modified compound as a lubricating material. The alcohol-based coupling layer contains, for example, lower alcohol as a main component and is deposited on the carbon-based protection layer, for example, by vapor deposition. The alcohol-based coupling layer may be replaced by a layer containing lower alcohol. The carbon-based protection layer may be deposited by plasma CVD.

Abstract: Disclosed is a method of manufacturing magnetic disks, comprising a magnetic layer, a protective layer, and a lubricating layer on a substrate.

Abstract: After at least a magnetic layer is formed on a disk substrate, a carbon-based protection layer is formed by plasma CVD using a mixed gas of a hydrocarbon-based gas and a nitrogen gas under the condition that the temperature of the disk substrate with the magnetic layer formed thereon is higher than 200° C.

Abstract: In a magnetic recording medium which comprises a substrate (1), a magnetic layer (3) formed on the substrate, a carbon-based protection layer (4) comprising carbon and formed on the magnetic layer, and a lubrication layer (5) formed on the carbon-based protection layer, the carbon-based protection layer comprises a hydrogenated carbon protection layer (4a) facing the magnetic layer and a nitrogenated carbon protection layer (4b) facing the lubrication layer. The hydrogenated carbon protection layer (4a) comprises carbon and hydrogen. The nitrogenated carbon protection layer (4b) includes no hydrogen but comprises carbon and nitrogen.

Abstract: A polyolefin resin drawn sheet 4 is laminated on at least one face of a sheet-form core material 6 having a density of 30 to 300 kgf/m3. At this time, a sheet or film 5 made of a bonding synthetic resin or rubber having a flow starting temperature lower than the thermal deformation temperature of the core material 6 and the melting point of the drawn sheet 4 is interposed between the core material 6 and the drawn sheet 4. The resultant stack product is heated to not less than the flow starting temperature of the synthetic resin or the rubber and not more than the thermal deformation temperature of the core material 6 and the melting point of the drawn sheet 4. At the same time of or after the heating, the stack product is pressed to apply a compression strain of 0.01 to 10% to the core material 6.