日本专利文献

[Detailed Description of the Invention][0001][Industrial Application]By the exposure of a laser beam etc., the present invention relates information to record, elimination, and the refreshable medium for optical information record at high speed and with high density.[0002][Description of the Prior Art]In recent years, the optical disc using laser beams is developed as a recording medium which meets the demand of the high density and improvement in the speed of expansion of the amount of information, and record and playback. There are added type recordable only once of a postscript and an erasable type any number of times can eliminate[ record and ] in an optical disc.[0003]As an erasable optical disc, the optical magnetic recording medium using the photoelectromagnetic effect and the phase change medium using change of the reversible crystallized state are raised. A phase change medium does not need an external magnetic field, but only changes the power of a laser beam, and record and elimination are possible for it. It has the advantage that 1 beam over-writing which performs elimination and re-recording simultaneously by a single beam is possible.[0004]The case where form a recording bit and it eliminates by making it crystallize is common by making record film make it amorphous in the phase change recording method in which 1 beam over-writing is possible. As a recording layer material used for such a phase change recording method, a chalcogen system alloy thin film is used in many cases.[0005]For example, a germanium-Te system, a germanium-Te-Sb system, an In-Sb-Te system, a germanium-Sn-Te system alloy thin film, etc. are raised. An added-a postscript type phase change medium is also realizable by the almost same material and lamination as an erasable type. In this case, it continues for a long period of time more in that there is no reversibility, information can be recorded and saved, and theoretic substantially semipermanent preservation is possible. [0006]When a phase change medium is used as added type of a postscript, since the climax which is called a rim around a bit unlike a perforated type does not arise, it excels in a signal quality, and since the gap is unnecessary, the advantage that it is not necessary to make it air sandwich structure is in the recording layer upper part. Generally, in an erasable phase change recording medium, in order to realize a different crystallized state, two different laser beam power is used. [0007]Taking the case of the case where record and elimination are performed, it describes by elimination and the initial state crystallized with the amorphous bit in this system. Crystallization is made by heating a recording layer to a temperature lower than the melting point sufficiently more highly than the crystallization temperature of a recording layer. In this case, a cooling rate sandwiches a recording layer by a dielectric layer, or uses a long elliptical form beam for the moving direction of a beam so that crystallization may become slow to sufficient degree carried out.[0008]On the other hand, amorphous-ization is performed by heating and quickly cooling a recording layer to a temperature higher than the melting point. In this case, the above-mentioned dielectric layer also has a function as a radiation layer for obtaining sufficient cooling rate (supercooling speed). Also in order to prevent the deformation accompanying melting and the volume change of the recording layer in the above heating and cooling processes, and the thermal damage to a plastic plate or to prevent degradation of the recording layer by humidity, theprotective layer which consists of the above-mentioned dielectric layer is important.[0009]The construction material of the charge of a protective layer material is selected from viewpoints of having optically transparent being a thing, that the melting point, softening temperature, and decomposition temperature are high, that formation is easy, and appropriate thermal conductivity to a laser beam. As a protective layer which has sufficient heat resistance and mechanical strength, dielectric membrane, such as a metaled oxide and a nitride, is raised first. [0010]Since these dielectric membrane and plastic plates differ in a coefficient of thermal expansion or an elastic property largely, while they repeat record and elimination, they become a cause which peels from a substrate and produces a pinhole and a crack. Although a plastic plate tends to produce curvature with humidity, peeling of a protective film may arise also by this. [0011]On the other hand, as a new dielectric protective layer, the main component of the ZnS is carried out and the thing in which SiO2, Y2O3, etc. were made to mix is proposed. These conjugated compound protective films are excellent in the adhesion over chalcogenide type alloy thin films, such as GeTeSb often used as a recording layer, compared with the pure oxide or the nitride dielectric film. For this reason, in addition to the durability to repetition over-writing, the film peeling in an accelerated test is improving the reliability of the phase change medium further few.[0012][Problem to be solved by the invention]However, a conjugated compound does not necessarily exert the characteristic to only mix. Reliability may be made to be deteriorated on the contrary rather than the case where each pure compound is used depending on the physical properties of a composition range and bipolar membrane.[0013]Although much proposals are conventionally made about the protective film which is a compound containing a chalcogenide type element and which made ZnS, ZnSe, etc. mix an oxide, a nitride, fluoride, carbide, etc., It set in part and was only describing the optimal composition range, and even if it used the mixture of the composition, the characteristic superior to the protective layer which consists of the original pure compound simple substance was not necessarily obtained.[0014]Since these differs largely, the compound of them from which the physical properties of the above-mentioned composite constitute it is because ********** [ the change in physical properties by a manufacturing method and others ]. For example, in forming the protective layer which consists of the above-mentioned conjugated compound, the sputtering method is used widely, but the physical properties of the conjugated compound protective film naturally obtained differ by the case where a composite target is used, and the case where a simultaneous sputtering is carried out using each compound target.[0015]It is a well-known fact that physical properties change with the pressures at the time of a sputtering, etc. also by the same manufacturing method. While dispersion in such protective film physical properties existed, it was problem how a compound protective film suitable for a phase change medium is found out.[0016][Means for solving problem]In the medium for optical information record provided with the phase transition type optical recording layer and the dielectric layer at least on the substrate, the summary of the present invention is in the medium for optical information record, wherein a dielectric layer contains a charcogen compound, a zinc oxide and magnesium flux, or calciumfluoride at least.[0017]Chalcogen means four elements of sulfur, selenium, a tellurium, and polonium. Are at least 1 type preferably chosen from the group of ZnS, ZnSe, and ZnTe as a charcogen compound, and preferably, X/Y is more than [ 1/3 or less / 3 ], and the content Z (mol%) of the content X (mol%) of the charcogen compound in a dielectric layer, the content Y of a zinc oxide (mol%), magnesium flux, or calcium fluoride is [ (X+Y)/Z ] 1.5 or less [ 1/4 or more ].[0018]As for a dielectric layer, it is preferable to provide using the compound sputtering target which comprised a mixture of two or more compounds which constitute this dielectric. Next, the composition of the medium for optical record by the present invention is described. At least, the medium for optical record of the present invention has the composition of a substrate / dielectric layer / recording layer / dielectric layer / reflecting layer, and can usually use transparent resin, such as polycarbonate, an acrylic, and polyolefin, or glass for the substrate 1.[0019]The dielectric which fills the above-mentioned characteristic in a substrate surface is usually provided by thickness of 100 to 5000 A. The deformation preventive effect of a substrate or record film is insufficient in the thickness of a dielectric layer being less than 100A, and there is a tendency not to make the task as a protective layer. If it exceeds 5000 A, the difference of the internal stress of the dielectric itself or elasticity with a substrate will become remarkable, and it will become easy to generate a crack.[0020]In the present invention, the mixture of 3 or more type of different compounds is used for a dielectric layer. That is, a zinc oxide, a charcogen compound and magnesium flux, or calcium fluoride is included at least. The above-mentioned charcogen compound is at least 1 type preferably chosen from the group of ZnS, ZnSe, and ZnTe, and preferably, X/Y is more than [ 1/3 or less / 3 ], and the content Z (mol%) of the content X (mol%) of the charcogen compound in a dielectric layer, the content Y of a zinc oxide (mol%), magnesium flux, or calcium fluoride is [ (X+Y)/Z ] 1.5 or less [ 1/4 or more ].[0021]When the content X, Y, and Z of each compound separates from the above-mentioned range, the deformation preventive effect of a substrate or record film is insufficient, and it cannot be said from a protective effect that it is preferable. As for the dielectric layer, the total quantity of a charcogen compound, a zinc oxide and magnesium flux, or calcium fluoride should just be the main ingredients (50-mol% more than preferably 80-mol% more than), and other dielectrics may be mixed.[0022]As other dielectrics, SiO2, ZrO2, BaO, B2O3, etc. are mentioned. When mixing other dielectrics in a dielectric layer, it is necessary to maintain the heat resistance of not less than 1000 degrees C, and an optical property. The heat resistance of not less than 1000 degrees C means not causing decomposition, even if the melting point maintains not less than 1000 degrees C and it heats at 1000 degrees C.[0023]An optical property means that an optical absorption coefficient is 0.02 or less by a thickness of 500 A. As for the above-mentioned dielectric layer, it is preferable that film densities constitute not less than 80% of theoretical density. Here, membranous theoretical density is an integrated value of what was shown by the following formula and multiplied the density in a bulk state of each composition compound by the mol content of the composition compound. Theoretical density =sigma {(density of a composition compound bulk state) x (composition compound mol content)}By carrying out density of a mixture dielectric layer in this way, the durability to repetition recordand aging can be improved remarkably.[0024]It is good to make a degree of vacuum low (it is low about argon gas pressure) for making high film density which can be performed by adjusting the degree of vacuum at the time of sputtering to control film density, and it good to usually make preferably 1 Pa or less of degrees of vacuum into or less 0.8 to 0.1 degree. As for the above-mentioned dielectric layer, it is preferable to provide using the compound sputtering target which comprised a mixture of two or more compounds which constitute a film.[0025]When this forms the dielectric layer consisting of the above-mentioned conjugated compound, the sputtering method is usually used widely, but. Since it becomes what was excellent also in the characteristic as a protective film since the homogeneity of the composing element of the conjugated compound protective film obtained won compared with the direction which uses a composite target carrying out a simultaneous sputtering using each compound target, it is preferable.[0026]The recording layer of the medium of the present invention is a phase change type recording layer, and the thickness has the preferable range of 100 to 1000 A. Sufficient contrast will not be acquired if the thickness of a recording layer is thinner than 100 A. There is a tendency for a crystallization rate to become slow and the record deletion in a short time becomes difficult. Since it will become difficult to acquire too optical contrast and will become easy to produce a crack on the other hand if 1000AA is exceeded, it is not preferable.[0027]The thickness of a recording layer and a dielectric layer also takes into consideration the cross protection accompanying multilayered constitution, its absorption efficiency of a laser beam is good, and it is chosen so that the amplitude of a recording signal, i.e., the contrast of a recorded state and a non-recorded state, may become largely. It is chosen as a material [ over-write / as a recording layer / material / 3 yuan compounds, such as GeSbTe or InSbTe, ].[0028]It is also effective to add a kind or the element beyond it to these 3 yuan compounds, and to improve a crystallization rate, an optical constant, and oxidation resistance to them from the inside of Sn of 0.1-10 atom %, In, Pb, As, Se, Si, Bi, Au, Ti, Cu, Ag, Pt, Pd, Co, nickel, etc. Although the optical reflecting layer and the hard court layer for the prevention from heat deformation are provided on the protective layer, an optical reflecting layer has a preferable substance with large reflectance, and Au, Ag, Cu, aluminum, etc. are used.[0029]Since this reflecting layer has an effect which promotes diffusion of the thermal energy which the recording layer absorbed, it may add a little Ta, Ti, Cr, Mo, Mg, V, Nb(s), Zr, etc. for thermal conductivity control etc. A recording layer, a dielectric layer, and a reflecting layer are formed of sputtering process etc. It is desirable at the target for record film, the target for protective films, and the point that performing film formation with the in-line equipment which installed the target for reflecting layer materials in the same vacuum chamber when required prevents the oxidation and contamination between each layers. It excels also from the surface of productivity.[0030][Working example]The present invention is described in detail with an working example below. As an working-example 1 dielectric-layer material, adjustment mixing of the powder of ZnS, ZnO, and MgF2 was carried out so that it might be set to 20 to 20 to 60 by a mol ratio, and the compound-sintered-compact target obtained in hot pressing was obtained.[0031]****** / recording layer / dielectric layer / reflecting layer was provided on thepolycarbonate resin board, and the recording medium of four layer systems was created. Thickness of each layer was made into 1000 A of lower dielectric layers, 300 A of recording layers, 300 A of upper dielectric layers, and 1000 A of reflecting layers. Composition of a recording layer is germanium(22.2) Sb(22.2)Te(55. 6) .[0032]The reflecting layer used the aluminum alloy. The dielectric layer formed membranes by high frequency (13.56 MHz) sputtering by the Ar gas pressure of 0.7 Pa. Film density was 3.3g/cc, and constituted 84% of theoretical density. The recording layer and the reflecting layer formed membranes by DC sputtering by the Ar gas pressure of 0.7 Pa.[0033]Furthermore, ultraviolet curing resin about 4 micrometers thick was provided. After performing crystallization treatment of initialization, i.e., a recording layer, for this disk using Ar ion laser further, the following conditions estimated the dynamic characteristics of the disk. TheC/N ratio was measured, whenever repeatedly and it reached the predetermined number of times, making it rotate with the linear velocity of 10 m/s. [ using 4 MHz and duty 50% of pulsed light ] [ record power 18mW and base power 9.5mW ] As a result was shown in Fig.1, as compared with the 10th time, deterioration of C/N was about 3 dB repeatedly in 10,000 times.[0034]Except having made ZnS and MgF2 into the mol ratio as a charge of a protective layer material in the comparative example 1 working example 1, and having used by that of 20 to 80, the disk was created similarly and same dynamic-characteristics evaluation was performed. As a result was shown in Fig.2, as compared with the 10th time, deterioration of C/N was about 13 dB repeatedly in 100 times. Film density was 3.0g/cc, and constituted 88% of theoretical density. [0035]the charge of a protective layer material of the working-example 2 working example 1 -- ZrO210-mol% -- except having mixed and used, the disk was created similarly and same dynamic-characteristics evaluation was performed. The result was the same as that of the working example 1 substantially.[0036][Effect of the Invention]utilization of the medium by using the medium for optical record of the present invention which can perform many repetition record and elimination and this kind can eliminate [ repetition record and ] -- many -- it is effective.[Translation done.]。