Abstract: An optical recording medium has a mask layer of a non-linear optical material and a phase change recording layer, and an intermediate dielectric layer disposed therebetween wherein an optical aperture is formed in the mask layer upon exposure to a reading light beam. A recording light beam is irradiated to the recording layer from the side away from the mask layer, and a reading light beam is irradiated to the recording layer from the mask layer side. Microscopic recorded marks below the diffraction limit are readable.

Abstract: In a phase change optical recording medium, time required for recording the unrecorded area as well as jitter produced are reduced. Provided is an optical recording method for recording an optical recording medium having a phase change recording layer, wherein the recording is conducted such that: VW/Vo>1, and 0.

Abstract: An optical recording medium having at least a light-transmitting substrate, a recording layer recorded by heat mode recording, and a reflective layer comprising a metal or a semimetal disposed in this order exhibiting reduced signal noise in the reading and improved recording characteristics are provided. A method for producing such optical recording medium is also provided, and this method includes the step of changing bonding state of the element(s) constituting the reflective layer at least in the area to be recorded.

Abstract: Noise of the read-out signal is reduced in an optical information medium comprising a supporting substrate and a reflective layer disposed on the supporting substrate wherein the reading beam irradiates the medium from the side where the reflective layer is formed. In addition, noise of the read-out signal is reduced without adversely affecting the recording properties in an optical information medium comprising a supporting substrate, and a reflective layer and a recording layer disposed on the supporting substrate in this order wherein the recording beam irradiates the medium from the side where the reflective layer is formed. In the medium, the reflective layer has a crystallite size of up to 30 nm.

Abstract: In an optical recording medium of land/groove recording system, a sufficient tilt margin and a reduced cross talk are realized simultaneously with a sufficiently increased output.

Abstract: High temperature reliability, and in particular, the high temperature reliability after repeated overwriting operations is improved in an optical recording medium wherein a material of Ag—In—Sb—Te system is used for the recording layer. Provided is an optical recording medium having a recording layer of phase change type, wherein said recording layer contains Ag, In, Sb, and Te as its main components, and Ge as its sub-component such that, when molar ratio of the elements constituting the main and sub-components is represented by formula (I): (AgaInbSbcTed) (1-e/100)Gee, 2≦a≦20, 2≦b≦20, 35≦c≦80, 8≦d≦40, a+b+c+d=100, and 1≦e≦15.

Abstract: The invention provides an optical disc comprising a circular glass substrate (2) having information-carrying means (3) on one major surface. A protective member (4) of a resin includes a circular flat portion (42) and an annular rim (41) extending perpendicular from the periphery of the flat portion (42). The glass substrate (2) is integrally joined to the protective member (4) such that the information-carrying means (3) of the glass substrate (2) may face the covering portion (42) of the protective member (4). The outer side of the glass substrate (2) is surrounded by the protective member rim (41) to leave a shock absorbing space therebetween. The invention prevents the glass substrate from failure at its corner when impact is applied to the disc.

Abstract: Formation of a synchronization mark pattern of excellent readability is enabled in an optical recording disc wherein track jump is required once per one disc rotation in a convenient manner. The optical recording disc comprises a disc substrate 2 and a recording layer 4 on the disc substrate 2, and at least one surface-irregularity region 2b having an irregularity pattern formed therein is provided on the substrate in its non-recording region and circumferentially adjacent to a smooth region. The surface-irregularity region is preferably in the shape of an arc concentric with the substrate, and the surface-irregularity region preferably comprises a plurality of circumferentially extending grooves or a plurality of projections.

Abstract: In a phase change-type optical recording medium of absorption coefficient control structure used by land/groove recording system, difference in reproduction characteristics between the land and the groove is minimized while ensuring sufficient output of the tracking signal. In the optical recording medium of the present invention, light absorption coefficient at the wavelength of said recording/reproducing beam is such that: Ac/Aa≧0.8 when light absorption coefficient in crystalline region is Ac and light absorption coefficient in amorphous region is Aa; relation between groove width WG and land width WL is such that: 0.97≦2WG/(WL+WG)<1.

Abstract: Formation of small record marks at high shape and dimensional precision is enabled in an optical recording medium of phase change type adapted for formation of small record marks. Thermal stability of such small record marks with high shape and dimensional precision is also improved to provide a highly reliable optical recording medium of phase change type. The optical recording medium of the invention has a recording layer of phase change type, and record marks with minimum length of up to 350 nm are formed in the recording layer. The recording layer contains Ag, In, Sb and Te as its main components. Also provided is an optical recording medium wherein the recording layer also contains Ge and/or N as its sub-component.

Abstract: In the phase change type optical recording medium of the present invention, loss of reliability by high-temperature storage is prevented, and self-erasure (a phenomenon of partial erasure of the record mark by heat diffusion in the lateral direction during the irradiation of the recording laser beam) is suppressed. There is thus provided an optical recording medium designed for use in a drive system wherein overwriting is conducted at a linear velocity V.sub.0 which satisfies the relation:0.6<V.sub.2nd /V.sub.0 <1.25when V.sub.2nd is the overwriting linear velocity at which the frequency component corresponding to the second harmonic of the frequency of the recording signal used for the overwriting is minimized when the record marks formed by the overwriting are reproduced and measured for such frequency component. Also provided is an optical recording medium adapted for use in a drive system wherein overwriting is conducted at a linear velocity V.sub.

Abstract: A phase change type optical recording medium comprises a dielectric layer 1a, a dielectric layer 1b, a phase change type recording layer and a second dielectric layer in the described order. The recording layer satisfies Ac/Aa.gtoreq.0.8 where Ac is an absorption coefficient of the recording layer in a crystalline region and Aa is an absorption coefficient of the recording layer in an amorphous region. The dielectric layer 1a comprises ZnS--SiO.sub.2 as main components and the dielectric layer 1b comprises a metal nitride or ZnS--SiO.sub.2 having an SiO.sub.2 content of 40 to 80 mol % as main components. At least an area of the second dielectric layer that is in contact with the recording layer comprises a metal nitride, a rare earth oxide, silicon oxide or ZnS--SiO.sub.2 having an SiO.sub.2 content of at least 40 mol% as main components. However, an optical recording medium comprising a dielectric layer 1a having an SiO.sub.

Abstract: Deterioration of properties associated with high-density recording is suppressed in the recording of a phase change optical recording medium wherein a land or groove is used for the recording track. A method for recording an optical recording medium having a substrate having grooves formed thereon and a recording layer of phase change type on the substrate wherein a groove or a land between two adjacent grooves is used for the recording track is provided. In this method, the record marks are formed such that:M.sub.W /T.sub.W >1when T.sub.W is width of the recording track, and M.sub.W is width of the record mark.

Abstract: Prevented is the reliability loss in phase change optical recording media during high-temperature storage, and also prevented is the phenomenon of self-erase by which a part of record marks having been formed in the media are erased due to the lateral heat diffusion into the recording layer while recording laser beams are irradiated to the media. The optical recording medium disclosed has a recording layer of a phase change type and is applied to driving units for overwriting it at a linear velocity of V.sub.0. The medium is so designed as to satisfy the requirement of 1<V.sub.max /V.sub.0 <1.5, where V.sub.max indicates the linear velocity at which the medium being overwritten has a highest C/N ratio.

Abstract: The invention provides a method of fabricating an optical recording medium comprising a phase change type recording layer containing at least one element selected from In, Ag, Te and Sb. The recording layer is formed by a sputtering technique wherein sputtering is carried out while an inert gas and an oxygen gas are introduced in a vacuum chamber in a sputtering system, so that the number of overwritable cycles can be increased by simple means.

Abstract: In a phase change-type optical recording medium of absorption coefficient control structure used by land/groove recording system, difference in reproduction characteristics between the land and the groove is minimized while ensuring sufficient output of the tracking signal. In the optical recording medium of the present invention, light absorption coefficient at the wavelength of said recording/reproducing beam is such that: Ac/Aa.gtoreq.0.8 when light absorption coefficient in crystalline region is Ac and light absorption coefficient in amorphous region is Aa; relation between groove width W.sub.G and land width W.sub.L is such that: x=2W.sub.G /(W.sub.L +W.sub.G).gtoreq.1.03; and the relation: .lambda.max.sup.i <.lambda.u.ltoreq..lambda.min.sup.i, and -100x+123.ltoreq.t.sub.R .ltoreq.-100x+126 are satisfied when the wavelength of a local minimum in reflectance spectrum is .lambda.min.sup.i ; the wavelength of the local maximum in the reflectance spectrum nearest to the .lambda.min.sup.

Abstract: An optical recording medium of phase change type, and in particular, a dual side medium prepared by adhering two single side media is provided. In this medium, deformation of record marks generated in the overwriting due to difference in light absorption between the record marks and the region other than the record marks is prevented by providing a reflective layer of high light transmission, and increase in jitter and failure of track servo and focus servo caused by uneven coating of the adhesive layer and the resin protective layer are prevented. The optical recording medium comprises a substrate, a recording layer of phase change type on the surface side of the substrate, and a reflective layer and a light absorption layer disposed in this order on the surface side of the recording layer.

Abstract: A method for preparing an optical recording medium of phase change type is provided. This recording medium comprises a substrate, a recording layer, and a lower and an upper dielectric layers provided in direct contact with the recording layer. In this method, a step of an exposure treatment wherein the surface of the lower dielectric layer is exposed to an oxidative atmosphere is conducted after forming the lower dielectric layer on the substrate and before forming the recording layer on the lower dielectric layer. A step of a heat treatment wherein said lower dielectric layer is heat treated may be carried out in addition to the exposure treatment.

Abstract: A method for recording/reproducing an optical recording medium of phase change type is provided. The method enables a high density recording while increase in the cross erase is suppressed. The method also enables an accurate tracking while increase in the crosstalk is suppressed. The method is adapted for use with an optical recording medium of phase change type comprising a substrate having a thickness of up to 0.8 mm wherein lands and grooves on opposite sides of the land are formed on the surface, and both the lands and the grooves are used as recording tracks, and the medium is overwritten at a recording power Pw (mW) and an erasing power Pe (mW) which meet the relation: (Pw/Pe).times.k.sup.2 .ltoreq.8.5, when the medium has a recording track pitch P (.mu.m), the recording/reproducing optical system has a numerical aperture NA, and the recording/reproducing light has a wavelength .lambda. (.mu.m) which meet the relation: k=(.lambda./NA)/P.gtoreq.1.78.

Abstract: An optical recording medium comprises a substrate and a multilayer structure on the substrate. The multilayer structure comprises a phase change type recording layer and a pair of dielectric layers, at least one of which contains zinc sulfide optionally with silicon oxide. When a depth profile of the multilayer structure in a thickness direction thereof is found by Auger electron spectroscopy, a region having an intensity ratio S/Zn of 2 or lower exists across a thickness of at least 6.0 nm, calculated as SiO.sub.2, from the vicinity of an interface between the dielectric layer and the recording layer into the recording layer. In the vicinity of the interface between the dielectric layer and the recording layer, there is also a region having an intensity ratio S/Zn vs. O/Si relation that satisfies S/Zn<O/Si.