Abstract: The invention discloses a photopolymerizable composition comprising at least one, ethylenic unsaturated bond-containing compound, a hexaaryl-biimidazole compound, and an organoboron compound represented by a specific general formula; and discloses a photosensitive thermal recording material having a recording layer that contains the photopolymerizable composition. The photopolymerizable composition and the photosensitive thermal recording material of the invention are highly sensitive to UV rays and visible to IR rays falling within a wavelength range that includes wavelengths not longer than 450 nm, and are effective for decoloring a dye component that absorbs the rays falling within the wavelength range.

Abstract: An optical disk and a method of fabricating the optical disk capable of improving the signal quality and the productivity are disclosed. The optical disk includes a plurality of reflective layers stacked on a substrate, amorphous layers formed among the reflective layers which include a small amount of oxide therein, a recording layer, formed on the reflective layer, for recording information, and a cover layer formed on the recording layer.

Abstract: In an apparatus for fabricating a carbon coating, an object such as a magnetic recording medium is disposed on a side of an electrode connected to a high-frequency power supply. Ultrasonic vibrations are supplied to the object. Discharge is generated between the electrode connected to the high-frequency power supply and a grounded electrode to fabricate a carbon coating on the surface of the object. Also, an electrode interval is set to 6 mm or less, pressure between the electrodes is set to 15 Torr to 100 Torr, whereby high-density plasma is generated to form an ion sheath on an anode side. Therefore, a coating is fabricated on the surface of the object by bombardment of ions.

Abstract: An input is ciphered in at least one of a sector forming circuit 13, a scrambling circuit 14, a header appendage circuit 15, an error correction encoding circuit 16, a modulation circuit 18 and a synchronization appendage circuit 18, used for processing input data for forming a recording signal. Not only the key for ciphering itself in the circuits but also the information as to which of the circuits has been used for ciphering becomes the key for ciphering. This realizes ciphering difficult to decode by a simplified structure.

Abstract: There are provided a method of manufacturing a glass substrate for information recording media that allows the inner and outer peripheral edge surfaces of the glass substrate for information recording media to be smoothed easily and inexpensively, a glass substrate for information recording media manufactured using this method, and an information recording medium using this glass substrate. A donut-shaped glass disk for information recording media having an outer peripheral edge surface and an inner peripheral edge surface is prepared. At least one of the outer peripheral edge surface and the inner peripheral edge surface of the glass disk is smoothed by melt-heating to a temperature at or above the softening point of the glass by irradiating with at least one laser beam.

Abstract: A process for producing a fluoroalkanol of high purity containing little evaporation residue, which can be industrially easily carried out with high selectivity, is provided. In the process, a radial initiator and CF2═CFR3 (formula 3) are continuously added to CHR1R2—OH (Formula 2) to react them to form H—(CFR3CF2)n—CR1R2—OH (formula 1). In the formulae, n is an integer of from 1 to 4, each of R1 and R2 is a hydrogen atom or a C1-3 alkyl group, and R3 is a fluorine atom or a C1-4 perfluoroalkyl group.

Abstract: Light-readable information-recording media are fabricated according to a method wherein the back of a production stamper is laser-scribed, diamond-scribed, etched, or marked by other means to produce an image. This production stamper is then used to form a substantially transparent substrate having information recorded on it by means of pits and lands. During the formation of the substrate, the image is transferred from the back of the stamper to the surface of the substrate. The resulting watermark may be visible under normal light conditions. Information-recording media bearing indelible watermarks according to the present invention are also disclosed.

Abstract: An optical information medium comprises a supporting substrate, an information recording surface 4 on the supporting substrate and a light-transmitting layer of resin on the information recording surface. Recording light and/or reproducing light are incident on the information recording surface through the light-transmitting layer. The light-transmitting layer is obtained by curing a resin layer containing an ultraviolet-curing cationic resin. If the light-transmitting layer is formed by repeating the cycle of resin coating and curing or drying a plurality of times, the uniformity of thickness of the light-transmitting layer can be much more improved and the amount of warpage can be much more reduced. Repetition of the cycle of resin coating and curing or drying is also effective for resins other than the ultraviolet-curing cationic resin.

Abstract: A glass for a data storage medium substrate, which consists essentially of the following components as represented by mol %: SiO2 60 to 72, Al2O3  2 to 9 MgO  3 to 9, CaO  2 to 10, SrO  0 to 15, ZnO  0 to 4, TiO2  0 to 8, ZrO2  0 to 4, Li2O  1 to 12, Na2O  0 to 8, K2O  0 to 5, Y2O3  0 to 5, La2O3  0 to 5, and Li2O + Na2O + K2O  4 to 15, and which has a Young's modulus of at least 85 GPa.

Abstract: An optical disk which operates which two of more different wavelengths, comprising a disk substrate on which tracks are formed at a track pitch of not more than 0.5 &mgr;m corresponding to light with a short wavelength, a super-resolution film whose transmittance changes due to irradiation of light, and a recording layer, wherein the transmittance of the super-resolution film changes due to the irradiation of light with a long wavelength. In this optical disk, information recorded by light with a short wavelength can be reproduced by light with a long wavelength.

Abstract: An optical storage element capable of writing and/or erasing information by irradiation with light, which element comprises a first unit composed of a first photo-induced phase-transition substance that gets stable in a first state, and a second unit composed of a second photo-induced phase transition substance that gets stable in a second state, the first and second units being arrayed in a superlattice-like form.

Abstract: A U-shaped groove is formed in a glass sheet along a cutting line and the sheet is cut by breaking along the groove. The groove is formed by heating a sheet portion including the cutting line by a laser beam, cooling it to lower its density, and etching that portion to dissolve it. Every surface exposed by cutting the sheet has a pair of edges which are properly beveled and rounded.

Abstract: A substrate disk consists of a first and a second substrate connected to one another wherein the first and second substrates have center holes. The first substrate has at least one projection positioned at the circumference of the center hole and projecting from the face of the substrate. In a preferred embodiment an annular projection surrounding the center hole is provided.

Abstract: A glass, glass-ceramic, or ceramic body having a textured pattern over at least a portion of its surface, the pattern comprising depressed, conical areas at spaced intervals on the surface, and a method of producing the depressed conical areas that employs laser radiation.

Abstract: An information recording medium which includes at least a recording layer, and first and second metallic layers disposed on an opposite side of an energy beam incident side of the recording layer and having different compositions, and in which the first one of the first and second metallic layers located closer to the recording layer contains Al, Ag, Au, Pt and Pd as its main components and a sum of contents of these atoms is 60% or more. Thereby recording and reproducing of information can be realized with a high reliability.

Abstract: A glass composition is disclosed which has a high modulus of elasticity (Young's modulus) and a high rigidity (modulus of elasticity/specific gravity) and is capable of being effectively inhibited from bending or vibrating. Also disclosed is a substrate for information recording media, which comprises the glass composition. The glass composition comprises the following components in terms of mol %: 40 to 60% SiO2, 8 to 25% Al2O3, 2 to 20% Li2O, 0 to 5% Na2O; provided that the content of R2O (R2O=Li2O+Na2O) is from 2 to 20%, 0 to 10% TiO2, 0 to 10% ZrO2, 5 to 25% MgO, 0 to 25% CaO and 0 to 6% SrO, provided that the content of RO (RO=MgO+CaO+SrO) is from more than 15 to 40%.

Abstract: Master discs and similar devices used in the production of digital data storage and recording discs and the like are produced with a substrate member which is provided with a layer of material which is applied to the substrate member in liquid form of a thickness greater than the surface roughness of the substrate member and of a thickness greater than any particulates present on the substrate member. The material layer is preferably a polymer such as epoxy, acrylic or styrene and is hardenable by exposure to UV light, heat, air circulation or catalytic reaction to provide a substantially smooth flat surface for receiving a data bearing film. The film may be treated to generate bumps or pits representing digital signals, for example, which are free of any defects resulting from surface roughness or contamination of the substrate member.

Abstract: A glass composition is disclosed which has a high modulus of elasticity (Young's modulus) and a high rigidity (modulus of elasticity/specific gravity) and is capable of being effectively inhibited from bending or vibrating. Also disclosed is a substrate for information recording media which comprises the glass composition. The glass composition comprises the following components, in terms of mol %: 55 to 65% SiO2, 0.5 to less than 6% Al2O3, 12 to 22% Li2O, 0 to 5% Na2O, 0 to 10% TiO2, 0 to 3% ZrO2, 0 to 8% MgO, 0 to 18% CaO, and 0 to 6% SrO, provided that the content of RO (RO=MgO+CaO+SrO) is 5 to 18%.

Abstract: An improved substrate and stamper holder and method of forming substrates are disclosed. According to a preferred embodiment of the invention, a substrate for a DVD has a moat with a capillary barrier shape. Under one embodiment, the moat has a region with an abrupt outer diameter transition. One embodiment has the outer diameter transition at approximately at a right angle relative to a registering surface of the substrate. Another embodiment of the invention provides a wider moats. The improvements reduce the likelihood of resin wicking past the moats.

Abstract: The present invention is related to flexible information-carrying substrates, such as optical media discs, which can withstand the stresses of being handled, processed and deformed, yet maintain enough integrity and properties such that it can still be read without the use of a rigid adapter.

Abstract: A multilayer optical disk having an information storage layer which can as well as be reproduced by a general purpose reproducing apparatus, for example, a compact disk player, and from which information can be read from other information storage layers by using an exclusive reproducing apparatus. The method of manufacturing a multilayer disk comprises the steps of forming a first substrate having a first information storage area enabling reproduction of information therein with a first light beam having a wavelength of 770 nm to 830 nm; forming a second substrate having a second information storage area enabling reproduction of information therein with a second light beam having a wavelength of 615-655 nm but which is relatively transparent with respect to said first light beam; and bonding said first substrate to said second substrate together without said first and second said information areas facing each other.

Abstract: Composition and use of polymers in appropriate solvent(s) with or without addition of selected dye combinations are proposed for developing a thin-layer coating on the transparent layer of optical storage media such as audio and video CDs, laser discs (LD) and DVDs for improvement of the sound and/or video quality during either recording and/or playback of the encoded digital information. The invention can also be incorporated in manufacture of recordable (CD-R) and re-writeable CD (CD-RW) media. In that case, the proposed composition is applied on the polycarbonate transparent surface of optical storage media at the final stages of recordable media manufacturing.

Abstract: Information is recorded on or reproduced from an optical recording medium (10) with irradiation of light from the opposite side of a substrate (2). In this optical recording medium (10), a reflection layer (6) is deposited on the substrate (2). This reflection layer (6) is made of an AgPdCu alloy thin layer or an AgPdCuAl alloy thin layer. A surface roughness (Ra) of this reflection layer (6) is less than 0.75 nm. A dielectric layer (3) is deposited on this reflection layer (6), and a heat control layer (1) is deposited on this dielectric layer (3). This heat control layer (1) is made of an AgPdCu alloy thin layer. A surface roughness (Ra) of this heat control layer (1) is less than 0.75 nm. A recording layer (4), a dielectric layer (5) and an organic protection layer (7) are deposited on this heat control layer (1). This optical recording medium can improve heat characteristics and reduce a disk noise.

Abstract: A glass substrate for a highly reliable information-recording medium in which stiction is reduced because of a small diameter of each protuberance, the CSS durability is good, and a head is prevented from being damaged, is provided. A method capable of stably manufacturing such a glass substrate for a highly reliable information-recording medium with a good controllability, is also provided. In a method of making protuberances 1a by irradiation to a glass substrate 1 with a laser light, a glass substrate having a coefficient of thermal expansion of 75×10−7/° C. or more is used as the glass substrate 1.

Abstract: An optical recording medium incorporating a supporting body; a recording portion which is formed on either main surface of the supporting body and on which a signal is recorded; and a light permeable layer formed on the recording portion, wherein light is applied from a position adjacent to the light permeable layer to record/reproduce a signal, and carboxylic acid amine salt expressed by general formula (1) and/or general formula (2) is held on the surface which is irradiated with light where n is an integer from 1 to 3, each of R1 and R2 is hydrogen or a hydrocarbon group, R3 is a hydrocarbon group and Rf is a perfluoroalkyl group having three or more carbon atoms, where at least either of R1 and R2 is perfluoroalkyl group having three or more carbon atoms, at least any one of R1, R2, R3, R4 and R5 is hydrocarbon group having 12 or more carbon atoms and the rest of them are hydrogen or hydrocarbon group.

Abstract: A protective layer is applied to the surface of a compact disc precursor that must be protected from dust during manufacture. The layer is removable and preferably made of ethylene vinyl acetate.

Abstract: An optical recording layer of an optical recording medium comprises a dye material represented by the formula (I), wherein R1 is a hydrogen atom, a methyl group, or an ethyl group, R2 and R3 each is, independent from each other, a substituted or unsubstituted C1 to C12 alkyl group, A⊖ is an anion selected from the group consisting of halogen atoms, ClO4⊖, BF4⊖, PF6⊖, SbF6⊖, CF3SO2⊖, C2F5SO3⊖, CF3COO⊖, and CH3C6H4SO3⊖, X is hydrogen, alkyl, alkoxy, halogen, nitro, or fused benzene, Y is hydrogen, alkoxy, halogen, alkyl, aryl, alkoxycarbonyl, aryloxycarbonyl, alkylamine, arylamine, alkylamide, arylamide, alkylsulfonyl, aryl sulfonyl, alkoxysulfonyl, aryloxysulfonyl, nitro, or cyano groups.

Abstract: A glass composition is disclosed which has a high modulus elasticity (Young's modulus) and a high rigidity (modulus of elasticity/specific gravity) and is capable of being effectively inhibited from bending or vibrating. Also disclosed is a process for producing the glass composition. The glass composition comprises, in terms of mol %, 40 to 65% SiO2, 5 to 25% Al2O3, 2 to 20% Li2O, 0 to 9% Na2O, 0 to 10% TiO2, 0 to 10% ZrO2, 0 to 25% MgO, 0 to 25% CaO, and 0 to 10% SrO, provided that the content of RO (RO=MgO+CaO+SrO) is from 2 to 40% and the sum of (Li2O)/2 and Na2O is from 1 to 10 mol %, said glass composition further containing, as clarifiers, from 0.01 to 5 mol % SnO2 and up to 0.1 mol % sulfur (S) in terms of the amount of SO3.

Abstract: The glasses used for making rigid disk substrates have the following composition (in % by weight based on oxides): SiO2, 40 to 50.8; Al2O3, 5 to 20; B2O3, 0 to 5; Li2O, 0 to 10; Na2O, 0 to 12, with the proviso that Li2O+Na2O, 5 to 12; K2O, 0 to 5; MgO, 0 to 20; CaO, 0 to 6, with the proviso that MgO+CaO, 4 to 20; SrO+BaO, 0 to 10; ZrO2, 0 to 5; TiO2,0 to 5; CeO2, 0 to 1; La2O3, 0 to 10; Fe2O3, 0 to 10; Nb2O5, 0 to 10; V2O5, 0 to 15, with the proviso that TiO2+ZrO2+La2O3+Fe2O3+Nb2O5+V2O5≧18.7; As2O3+Sb2O3+F. 0,1 to 1. These glasses also fulfill the following inequality formulae (1): (E/&rgr;)·+3,500 R>38.5 and 1000 R>1  (1), wherein R represents the relaxation rate of the glass and E/&rgr; represents specific elasticity modulus of the glass measured in GPA*cm3/g.

Abstract: In an apparatus for fabricating a carbon coating, an object such as a magnetic recording medium is disposed on a side of an electrode connected to a high-frequency power supply. Ultrasonic vibrations are supplied to the object. Discharge is generated between the electrode connected to the high-frequency power supply and a grounded electrode to fabricate a carbon coating on the surface of the object. Also, an electrode interval is set to 6 mm or less, pressure between the electrodes is set to 15 Torr to 100 Torr, whereby high-density plasma is generated to form an ion sheath on an anode side. Therefore, a coating is fabricated on the surface of the object by bombardment of ions.

Abstract: An ultraviolet-curable adhesive composition comprising a photopolymerization initiator whose molar absorption coefficient at a wavelength of 360-450 nm is at least 400 and an ultraviolet-curable compound. The adhesive composition of this invention can bond substrates which show transmittances of 0.01-20% to all of energy beams of a wavelength of 280-380 nm, to one another.

Abstract: An optical information recording medium includes a first substrate; at least a first dielectric layer and a recording layer for signal recording provided on a surface of the first substrate; and a second substrate. The first substrate and the second substrate are assembled together in the state of being warped in planar symmetry and flattened. The first dielectric layer and the recording layer is interposed between the first substrate and the second substrate.

Abstract: An optical information recording medium having a recording layer comprising a dye layer containing a trimethine-based cyanine dye having nitro group attached to a benzene ring or to a naphthalene ring, both being bonded to indole ring, is capable of minimizing the second peak in relative to the main peak shown in FIG. 1, thus enabling the spectrum consisting of a main peak and a second peak to become sharp. The recording layer is capable of performing the recording and reading with a laser beam having a wavelength falling within a range of 620 nm to 690 nm.

Abstract: An optical data recording medium in which the shape of the dye spectrum of a dye film having a thin film thickness per unit absorbance is controlled so as to enable improvements in the recording speed during high speed recording, jitter, and modulation, wherein the optical data recording medium is characterized in that 0<D/C≦100, and 80≦D/B, where D (nm) is the mean film thickness of the light-absorbing layer, C (Abs) is the maximum absorbance (based on molecular absorption) of the light-absorbing substance, B (Abs) is the maximum absorbance (based on association absorption) of the light-absorbing substance, D/C is the unit absorbance thickness based on the molecular absorption, and D/B is the unit absorbance thickness based on the association absorption.

Abstract: An ultraviolet-curable adhesive composition comprising a photopolymerization initiator whose molar absorption coefficient at a wavelength of 360-450 nm is at least 400 and an ultraviolet-curable compound. The adhesive composition of this invention can bond substrates which show transmittances of 0.01-20% to all of energy beams of a wavelength of 280-380 nm, to one another such as base boards for an optical disk.

Abstract: A copper-based or silver-based alloy thin film is provided for the highly reflective or semi-reflective layer of optical discs. Alloy additions to silver include gold, palladium, copper, rhodium, ruthenium, osmium, iridium, beryllium and platinum. Alloy additions to copper include silver, cadmium, gold, magnesium, aluminum, beryllium, zirconium, and nickel. These alloys have moderate to high reflectivity and reasonable corrosion resistance in the ambient environment.

Abstract: Disclosed is an apparatus for formation of high quality plastic sheet in a continuous fashion. Also disclosed are a variety of optical and electronic display applications for high quality plastic sheet produced in a continuous fashion.

Abstract: A high-density information recording medium free from lowering the reflectance by over-write of a large number of times and exfoliation defect in a structure for suppressing cross-erase. This medium includes, over a substrate having a groove shape, a recording layer, and three-layered thin films of a first interference layer, a second interference layer and an interface layer having mutually different compositions and disposed on a laser beam incidence side of the recording layer in order named from the laser beam incidence side. The first interference layer has a smaller refractive index and a larger thermal conductivity than the second interference layer, the interface layer is interposed between the second interference layer and the recording layer, and a distance between the first interference layer and the recording layer is greater than at least a groove depth.

Abstract: There is provided an optical recording medium provided with at least an optical recording layer, further comprising a cured layer provided on/over outer surface of the optical recording layer and a receiving layer provided on at least a part of the cured layer. It is possible to provide an optical recording medium which allows post-processing such as printing on the cured layer which has been very difficult to be carried out so far, without degrading the reliability of the information of the optical recording medium.

Abstract: The invention relates to a process for preparing molded discs suitable for use in optical information recording carriers and to the optical information recording carriers thereby obtainable. The process comprises plasticating a homopolymer or a copolymer of methyl methacrylate, injecting the plasticated homopolymer or copolymer into a mold to form a disc and removing the molded disc in a very short cycle time. Good quality discs which are particularly suitable for use in optical information recording carriers may thereby be obtained.

Abstract: An optical information recording medium comprising a thin plastic substrate of 0.6 mm or thinner, wherein the substrate is protected against strain without being limited by a film structure and a film formation condition. A single-layer or multilayer thin film (70) is formed on a plastic disk-like substrate having a center hole (10). This thin film (70) has a strain relief area (72) inside a recording area (71). This strain relief area (72) is formed by setting an outer diameter of an undeposited inner portion (5) to a value satisfying the following formula (1), for example: A0≦AX≦−0.172P+0.163 where A0: diameter of center hole, AX: outer diameter of undeposited inner portion, P: total strain occurring in thin film when film depositing.

Abstract: An information recording medium and a supporter used for the information recording medium capable of recording a land/groove recording by using a high density recording technique such as a super-resolution, resulting in a high density recording. An information recording medium B has a supporter 1A, on which a recording layer 5 is formed. On the supporter 1A, lands 2 and groove 3 are alternately formed as a minute track pattern. A crevice 4 having a depth Dc larger than a depth Dg of the respective grooves 3 is formed in the respective grooves 3 at one end of the respective grooves 3 in a width direction of the respective grooves.

Abstract: The present invention aims to develop a photosensitive resin composition which exhibits a rapid ink absorption rate, which has an excellent water resistance, and which is appropriate for providing an ink receiving layer forming a sharp ink dot shape and having an excellent color formability of ink. A photosensitive resin composition forming an excellent ink receiving layer is obtained by incorporating at least one selected from an ethylenically unsaturated group-containing compound having quaternary nitrogen and a grain flour (filler) such as a wheat flour or the like in a photosensitive resin composition containing a quaternary nitrogen-free ethylenically unsaturated group-containing compound, a photopolymerization initiator etc.

Abstract: A glass composition is disclosed which has a high modulus of elasticity (Young's modulus) and a high rigidity (modulus of elasticity/specific gravity) and is capable of being effectively inhibited from bending or vibrating. Also disclosed is a substrate for information recording media, which comprises the glass composition. The glass composition comprises the following components in terms of mol %: 50 to 64% SiO2, 6 to 18% Al2O3, 7 to 15% Li2O, 3 to 12% Na2O, 0 to 2% K2O, 0 to 10% TiO2, 0 to 4% ZrO2, 0 to 6% MgO, 0 to 9% CaO, and 0 to 6% SrO, provided at the content of RO (RO=MgO+CaO+SrO) is from 2 to 15%.

Abstract: The invention relates to an optical storage medium comprising a substrate and a storage layer, wherein the storage layer comprises a compound of the formula (I) or (II) in which A and A′, independently of one another, are unsubstituted or mono- or di-halo-, -hydroxy-, —C1-C6alkyl-, —C1-C6alkoxy-, -cyano- or -nitro-substituted phenyl, pyridyl, pyrrolyl, imidazolyl, furyl or thienyl, which can, if desired, be fused to a benzene ring, are halide, tetrafluoroborate or unsubstituted or with one or more halogen substituted C1-C6alkane-sulfonate, benzenesulfonate, C1-C6alkylbenzenesulfonate, C1-C6alkylsulfate or di-C1-C6alkyl-phosphonate of N—C1-C6alkyl-pyridiniumyl, or are unsubstituted or mono- or di-hydroxy-substituted C2-C6alkyl or C2-C6alkenyl, whose chain may be uninterrupted or interrupted by one or two oxygen atoms, B and B′, independently of one another, are 2 H, S, S2 or SO2, and n and n′, independently of one another, are each a number from 1 to 4.

Abstract: The present invention provides an optical disc capable of effectively reducing a reproduction signal jitter value and obtaining a wider record power margin assuring a reproduction limit jitter value to obtain a preferable recording/reproduction characteristic even after a number of times of recording repeated. The optical disc includes the following films successively formed on a substrate 2: a first dielectric film 3; a phase change recording film 4 whose phase is changed between a crystalline state and an amorphous state thereby to record an information signal; a second dielectric film 5; and a light reflection film formed on the phase change recording film 4 and constituted by an Al alloy containing Cu in a range from 0.1 to 1.0 atomic %.

Abstract: A rewritable optical recording disk has an increased thickness that is greater than or equal to approximately 1.5 mm. In particular, the disk may have a substrate with a thickness that is greater than or equal to approximately 2.3 mm and less than or equal to approximately 2.6 mm. The increased thickness of the substrate enhances the flatness of the recording disk relative to a recording plane. In particular, the increased thickness reduces process-induced surface variations such as warpage and tilt, and provides the disk with increased stiffness to resist deflection during use. The enhanced flatness enables data to be recorded on the disk in a consistent manner with greater spatial densities using techniques such as near-field, air-incident recording. The resulting disk thereby yields greater spatial density and data storage capacity.

Abstract: An optical information recording disc of DVD (Digital Video Disc) type having an information recordable layer(s) between a pair of substrates (i.e., sandwich structure) shows an improved mechanical strength and an improved storage stability when the substrate has an exposed area on its outer peripheral edge and the exposed area is placed in contact with a resin layer, or the substrate has an enlarged surface area (preferably it is exposed) on its outer peripheral edge and the enlarged surface area is placed in contact with a resin layer. An apparatus for preparing an optical information recording disc of DVD type having an improved mechanical strength and an improved storage stability is further disclosed.

Abstract: There is disclosed an optical data storage medium in which the weather resistance of the semitransparent reflective film is improved and the adhesive property between the semitransparent reflective film and a substrate is enhanced, and which has a higher reliability. In an optical data storage medium (6), on the side on which a reproduction light (8) is incident, a first information layer (9) is located while on the side opposite to the side on which the reproduction light (8) is incident, a second information layer (10) is located. A semitransparent reflective film (3) of first information layer (9) is AgPdCu alloy thin films containing 0.5 to 3.0 weight % Pd and 0.1 to 3.0 weight % Cu or AgPdTi alloy thin films containing 0.5 to 3.0 weight % Pd and 0.1 to 3.0 weight % Ti. At the wavelength 650 nm, the optimum film thickness of AgPdCu alloy thin film is 5 to 18 nm and the optimum film thickness of AgPdTi alloy thin film is 10 to 25 nm.

Abstract: A high-density optical disk includes reflective layers respectively formed at both information-recorded surfaces of a first substrate, and semitransparent layers respectively formed at one information-recorded surface of each of second and third substrates. The second and third substrates are respectively bonded at both sides of the first substrate.