Optical information recording medium, method of manufacturing the optical information recording medium, and method of and apparatus for recording/reproducing optical information

FIELD OF THE INVENTION

The present invention relates to a phase change type optical information recording medium capable of recording/reproducing information and capable of rewriting information, by generating a phase change in a recording layer material through the irradiation of a laser beam onto this recording medium. This invention particularly relates to a phase change type optical information recording medium capable of recording information at high speed. This invention further relates to a method of manufacturing the optical information recording medium according to the present invention, a method of and an apparatus for recording/reproducing optical information onto/from the optical information recording medium according to the present invention.

BACKGROUND OF THE INVENTION

As one of optical information recording media capable of recording information ("recording"), reproducing information ("reproducing"), and erasing information ("erasing") based on an irradiation of a laser beam, what is called a phase change type optical information recording medium has been known well. The phase change type optical information recording medium make use a phenomenon of phase transition between a crystalline and an amorphous phases or between the crystalline and the crystalline phases. Particularly, because of easiness in overwriting information ("overwriting") by using a single laser beam, that is difficult to achieve in case of the optical magnetic recording, and because of a simple optical system of the apparatus used for recording/reproducing, the demand for the phase change type optical information recording medium has been increasing. As a result, CD-RWs, DVD-RWs, and DVD-RAMs have already been commercialized.

In general, if more information is to be recorded at a faster speed, then it becomes necessary to develop recording media having higher density and higher linear velocity.

Likewise, the linear velocity at which information can be recorded ("recording velocity" or "recording liner velocity") with an optical information recording apparatus has also been increasing day-by day. At present, maximum recording linear velocities of different media belonging to the CD family are as follows. In case the CD-R, the maximum recording linear velocity is twelve times faster than that of the CD. In case the CD-RW, the maximum recording linear velocity is ten times faster than that of the CD. Moreover, the recording liner velocity of the CD-RW has always been higher than that of the CD-RW. For example, when the CD-RW had the recording velocity that is four times faster than that of the CD, the CD-R had a recording velocity of eight, ten or twelve times faster than that of the CD.

As a result, although a spindle, a semiconductor laser, and a control system that meet high recording velocity have been installed on the optical information recording apparatus, this optical information recording apparatus has recorded at a low velocity onto a CD-RW. This is mainly for the following reasons. The CD-RW stores information that indicates the standard recording linear velocity or the maximum recording linear velocity of the CD-RW; see, e.g. EP-A-852 796. The optical information recording apparatus recognizes this information and then performs the recording based on a linear velocity that is in line with the read information. There fore, it was not possible to achieve a higher recording velocity than the maximum recording linear velocity indicated by the information stored in the CD-RW.

Furthermore, the CD-RW disk also stores information indicating the minimum recording linear velocity. Recording on the CD-RW is performed at a recording linear velocity that is determined in such a manner that the recording linear velocity is between the minimum and the maximum recording linear velocities. Consequently, it is difficult in the optical information recording apparatus to perform matching at high-velocity recording. Therefore, such matching has never been realized.

In a phase change type optical information recording medium, usually, it is necessary to optimize a dislocation linear velocity of the medium so that it matches the recording linear velocity.

The dislocation linear velocity is defined as follows. As shown in Fig. 5, the optical information recording medium is rotated at various linear velocities. A semiconductor laser beam is traces a guide groove formed on the optical information recording medium. Because of the irradiation of the laser beam, a material of a recording layer in the optical information recording medium is heated to a melting point or above of that material. Reflectivity, i.e. the light intensity of the light reflected from the optical information recording medium, is measured. An example of the result of such a measurement are shown in Fig. 6. The linear velocity (shown by an arrow mark in Fig. 6) at which the reflectivity starts declining when the linear velocity is increased is called as the dislocation linear velocity.

As disclosed in detail in Japanese Patent Application Laid-open Publication No. 11-115313, it is important to control the dislocation linear velocity of the phase change type optical information recording medium, in order to the maintain the quality. Further, it has been disclosed in this publication, that the optimum dislocation linear velocity at two times to four times the linear velocity of the CD-RW (i.e. 2.4 to 5.6 m/s) is 2.5 to 5.0 m/s.

However, when the groove of the optical information recording medium has been narrowed, when the laser beam wavelength has been decreased, and when NA (number of apertures) have been increased for the purpose of increasing the density, the thermal properties of the optical information recording medium change drastically. Therefore, in order to carry out recording onto a phase change type optical information recording medium in a high-density and high-linear velocity area like two or more times the linear velocity of the DVD and eight or more times the linear velocity of the CD, the following becomes necessary. That is, it becomes necessary to examine the material of the recording layer, the layer structure of the medium, and conditions under which the medium is manufactured once more, and redesign the dislocation linear velocity that satisfies the factors such as the recording linear velocity, track pitch of the guide groove, wavelength of the laser beam, and NA.

Under the above circumstances, conventionally, the recording linear velocity of the CD-RW disk has been designed so as to be between the minimum and the maximum recording linear velocities. Moreover, the dislocation linear velocity is designed so as to be smaller than 0.85 times the maximum recording linear velocity. Thus, conventionally, it was not possible to increase the speed of recording.

As the material ("phase change recording material") for forming the recording layer in the optical information recording medium, there are materials like GeTe, GeTeSe, GeTeS, GeSeS, GeSeSb, GeAsSe, InTe, SeTe, SeAs, Ge-Te-(Sn, Au, Pd), GeTeSeSb, GeTeSb, and AgInSbTe. Particularly, AgInSbTe has high sensitivity and has clear outline at an amorphous portion, and has been developed as a recording layer for a mark edge recording (refer to Japanese Patent Application Laid-open Publication No. 3-231889, Japanese Patent Application Laid-open Publication No. 4-191089, Japanese Patent Application Laid-open Publication No. 4-232779, Japanese Patent Application Laid-open Publication No. 4-267192, Japanese Patent Application Laid-open Publication No. 5-345478, and Japanese Patent Application Laid-open Publication No. 6-166266.)

Japanese Patent Application Laid-open Publication No. 3-231889 discloses a recording layer that is expressed by a general composition expression of a I · (III_1-rV_r) · VI₂ type, where I represents a I-group element, III represents a III-group element, V represents a V-group element, and VI represents a VI-group element. However, according to this recording layer, a repetitive recording characteristic is not always sufficiently satisfactory.

Further, in the recording layer used in the optical information recording medium disclosed in Japanese Patent Application Laid-open Publication No. 4-191089, an improvement in erasing ratio and a high-speed recording can be achieved. However, there was a problem, in the disclosed technology, that when recording is performed repeatedly the recording characteristic ("repetitive recording characteristic") gets degraded. Further, regarding an information recording medium disclosed in Japanese Patent Application Laid-open Publication No. 1-303643, it has been reported that it is possible to provide a medium having a high C/N ratio and repetitive recording characteristic and excellent preservation characteristic by employing a new crystalline structure. However, there is a drawback that the recording sensitivity and repetitive recording characteristic are not sufficient.

The portion where no information is recorded (i.e. the portion that is crystalline) of the recording layer used in an information recording medium disclosed in Japanese Patent Application Laid-open Publication No. 4-232779 has a structure that a stable phase (AgSbTe₂) and an amorphous phase existing around this stable phase coexist. Therefore, although the disclosed medium had improved repetitive recording characteristic, a boundary of fine crystals is generated around the crystalline portion that became a cause of an occurrence of noise.

Existence of the boundary of fine crystals does not produce a seriously bad effect on the recording characteristic of an optical information recording medium that has a relatively low recording density like the CD-RW that uses a laser beam having a recording/reproduction wavelength of about 780 nm. However, the boundary of fine crystals becomes a hindrance in realizing a high-density recording of the DVD that uses a laser beamhaving a wavelength of 680 nm or below and has a recording density of about four times that of the CD-RW or the DVD-RW that have higher densities. Moreover, the problem of the repetitive recording characteristic remains unsolved.

A crystalline portion of the recording layer used in a recording medium disclosed in Japanese Patent Application Laid-open Publication No. 4-267192 has a structure that a phase of AgSbTe₂ isolated from a uniform amorphous phase and other phase (a stable phase or an amorphous phase) coexist. When other phase is an amorphous phase, a problem similar to that of the information recording medium disclosed in Japanese Patent Application Laid-open Publication No. 4-232779 occurs. On the other hand, when the other phase is a stable crystalline phase, there is a problem that it is not possible to obtain satisfactory recording characteristic, as described later.

The technologies disclosed in Japanese Patent Application Laid-open Publication No. 5-345478 and Japanese Patent Application Laid-open Publication No. 6-166268 have problems similar to those described above. Namely, in an optical information recording medium that has a phase change recording material of an AgInSbTe system or this system with an expanded Ib group element, IIIb group element, Vb group element, and the VIb group element as a recording layer, there is no knowledge about a recording medium that prescribes coordination numbers of elements that constitute the recording layer. Therefore, there is no conventional techniques that make clear the roles of functions as a recording material of each constituent element. As a result, there is no detailed improvement carried out, based on a particular theory, in the repetitive recording characteristic of the AgInSbTe recording layer and information recording and erasing sensitivities.

Further, as phase change recording materials for forming the recording layer of the optical information recording medium, there are what are called chalcogen system alloy materials like GeTe, GeTeSn, GeTeS, GeSeS, GeSeSb, GeAsSe, InTe, SeTe, and SeAs, as disclosed in the specification of US Patent No. 3,530,441.

Further, for the purpose of improving stability and high-speed crystallization, there has been proposed a material having a GeTe system that is added with Au (Japanese Patent Application Laid-open Publication No. 61-219692), Sn and Au (Japanese Patent Application Laid-open Publication No. 61-270190), and Pd (Japanese Patent Application Laid-open Publication No.62-19490) respectively. Further, for the purpose of improving repetitive performance of recording/erasing, there have been proposed materials having specified composition ratios of GeTeSeSb, and GeTeSb (Japanese Patent Application Laid-open Publication No. 62-73438, and Japanese Patent Application Laid-open Publication No. 63-228433).

None of the above-described technologies has been able to satisfy all the characteristics required for a phase change type optical information recording medium. Particularly, there are important problems to be solved, such as the improvement in recording sensitivity and erasing sensitivity, the prevention of a reduction in an erasing ratio due to a remaining of a portion not erased at the time of an overwriting, and the increase in the life of a recorded portion and an unrecorded portion.

In the mean time, in Japanese Patent Application Laid-open Publication No. 63-251290, there has been proposed a recording medium that is equipped with a recording layer consisting of a multi-dimensional compound single layer having a crystalline state in substantially three or more dimensions. In this case, the multi-dimensional compound single layer having a crystalline state in substantially three or more dimensions is defined as a one that has a compound (for example, In₃SbTe₂) having a stoichiometric composition of three or more dimensions by 90 atom % or more in a recording layer. It has been disclosed that it is possible to improve the recording and erasing characteristics by using such a recording layer. However, this has a drawback in that the erasing ratio is small, and laser power required for erasing a recording has not yet been lowered sufficiently.

Further, in Japanese Patent Application Laid-open Publication No. 1-277338, there has been proposed an optical information recording medium that has a recording layer consisting of an alloy of a composition as represented by (Sb_aTe_1-a)_1-yM_y. Here, 0.4 ≤ a ≤ 0.7, and Y ≤ 0.2, and M is at least one element selected from a group consisting of Ag, Al, As, Au, Bi, Cu, Ga, Ge, In, Pb, Pt, Se, Si, Sn, and Zn. The base of this system is Sb₂Te₃. By adding Sb as a surplus, high-speed erasing and repetitive recording characteristic are improved. Moreover, by adding M, the high-speed erasing is further promoted. In addition, it has been disclosed that the erasing ratio due to a DC light is large. However, in this document, there is no description about the erasing ratio at the time of overwriting. Moreover, the recording sensitivity is insufficient. Inventors of the present invention carried out a study on the erasing ratio at the time of overwriting of the disclosed medium, and they found that non-erased portions were disadvantageously remaining.

Japanese Patent Application Laid-open Publication No. 60-177446 discloses a recording layer that uses an alloy of (In_1-x Sb_x)_1-yM_y. Here, 0.55 ≤ x ≤ 0.80, and 0 ≤ y ≤ 0.20, and M is at least one element selected from a group consisting of Au, Ag, Cu, Pd, Pt, Al, Si, Ge, Ga, Sn, Te, Se, and Bi. Japanese Patent Application Laid-open Publication No. 63-228433 discloses a recording layer that uses an alloy of GeTeSb₂Te₃Sb (where Sb is surplus). However, none of the disclosed media posses satisfactory sensitivity and erasing ratio characteristics.

In addition, Japanese Patent Application Laid-open Publication No. 4-163839 discloses an optical information recording medium in which a recording thin film is formed by including N in a TeGeSb alloy. Japanese Patent Application Laid-open Publication No. 4-52188 discloses an optical information recording medium in which a recording thin film is formed by including at least one of components of a TeGeSe alloy as an a nitride in this alloy. Japanese Patent Application Laid-open Publication No. 4-52189 discloses an optical information recording medium in which a recording thin film is formed by making a TeGeSe alloy adsorb N. However, none of the disclosed optical information recording media posses satisfactory characteristics.

As mentioned above, it is required in case of the conventional optical information recording media to solve important problems such as the improvement in the recording sensitivity and the erasing sensitivity, the prevention of a reduction in an erasing ratio due to a remaining of a non-erased portion at the time of an overwriting, and the increase in the life of a recorded portion and an unrecorded portion.

In the mean time, in recent years, along a rapid popularization of the CD, there has been developed a compact disk into which data can be written only once (i. e. the CD-R) . Such CD-Rs have already appeared in the market. However, in case of the CD-R, it is not possible to edit once the data is written. Therefore, when there is an input error in this CD-R, this disk cannot be used, and it has to be abandoned. Consequently, there has been desired a rewritable compact disk that can solve all these problems.

As a result of researches and developments to obtain such a disk, there has been developed a rewritable compact disk that utilizes an optical magnetic disk. However, the optical magnetic disk has drawbacks in that it is difficult to overwrite and that it is difficult to obtain compatibility between the optical magnetic disk and the CD-ROM or the CD-R. Therefore, the phase change type optical information recording medium is being researched because it has an advantage in securing compatibility in principle.

As researches made into a rewritable compact disk that uses the phase change type optical information recording medium, there are examples that have been announced by Furuya and others in the lecture draft at the fourth phase change recording study symposium, 70 (1992), Jinno and others in the lecture draft at the fourth phase change recording study symposium, 76 (1992), Kawanishi and others in the lecture draft at the fourth phase change recording study symposium, 82 (1992), T. Handa and others in Jpn. J. Appl. Phys., 32 (1993), Yoneda and others in the lecture draft at the fifth phase change recording study symposium, 9 (1993), and Tominaga and others in the lecture draft at the fifth phase change recording study symposium, 5 (1993). However, none of them have sufficiently satisfied a total performance including a securing of compatibility with the CD-ROM or the CD-R, recording and erasing performance, recording sensitivity, possible repetitive number of rewriting, number of reproduction, preservation stability, etc. These drawbacks are mainly due to a composition of recording materials and a low erasing ratio attributable to a structure.

Because of the above reasons, it has been expected to develop phase change recording materials that are suitable for high-sensitivity recording and erasing, and to develop a phase change type compact optical information recording medium having high performance and capable of rewriting.

The present inventors have found and proposed that an AgInSbTe system recording material is the material that solves almost all the drawbacks. As representative examples of the publication by the present inventor there are: Japanese Patent Application Laid-open Publication No. 4-78031, Japanese Patent Application Laid-open Publication No. 4-123551, H. Iwasaki and others in Jpn. J. Appl. Phys, 31 (1992) 461, Ide and others in the lecture draft at the third phase change recording study symposium, 102 (1991), and H. Iwasaki and others in Jpn. J. Appl. Phys, 32 (1993) 5241.

The Orange Book part III (version 1.0) was published in October 1996 as a standard of a rewritable compact disk (CD-RW). As the Orange Book part III (version 1.0) is a standard of a CD-RW two-time linear velocity recording (2.4 to 2.8 m/s), a recording time becomes too long based on this low linear velocity. Therefore, an advent of a high-speed recording rewritable compact disk has been expected.

In the mean time, various kinds of recording compensation systems have been disclosed as systems for improving the quality of recording signals in the phase change type recording system.

For example, Japanese Patent Application Laid-open Publication No. 63-266632 discloses, that a system for recording an amorphous mark by using a pulse string is effective in a PWM recording using a recording film having a high crystallization speed.

Further, Japanese Patent Application Laid-open Publication No. 63-266633 and US Patent No. 5150351 disclose, that jitter is improved by restricting a positional fluctuation of a mark edge, by increasing laser energy at the head or tail of a pulse string or by increasing an irradiation time. Further, as described in Japanese Patent Application Laid-open Publication No. 63-29336, there has been known a method of scanning while irradiating an optical spot like a laser beam onto an optical disk in an optical disk recording apparatus, and recording an information signal onto the optical disk by strongly or weakly modulating the optical spot like a laser beam with the information signal. There has also been known a method of reproducing an information signal recorded on an optical disk, and monitoring an amplitude of a reproduction signal and a length of a recording mark, thereby to adjust recording conditions like recording optical power and a width of a recording optical pulse in an optimum state, and set these conditions.

Further, Japanese Patent Application Laid-open Publication No. 9-138946, Japanese Patent Application Laid-open Publication No. 9-138947, and Japanese Patent Application Laid-open Publication No. 9-219021 have disclosed the following. In the case of recording information onto an information recording medium according to a PWM recording system, a recording wave at the time of recording or rewriting a 0 signal having a signal width n × T after modulation (where T is a clock time) is a continuous electromagnetic wave having a power level e. Then, a recording wave pulse string at the time of recording or rewriting a 1 signal having a signal width n × T after modulation is an electromagnetic wave pulse string that has a pulse portion fp having a time width × and a power level 'a', a multi-pulse portion mp in which a low-level pulse of a power level b having a time width T in total and a high-level pulse having a power level c alternately continue by (n - n') times in total at a duty ratio y, and a pulse portion op having a time width z and a power level d, where x, y, and z.are in relationships of T × 0.5 ≤ x ≤ T × 2.0, 0.4 ≤ y ≤ 0.6, and T × 0.5 ≤ z ≤ T, n' is a positive integer of n' ≤ n, and a & c ≥ e ≥ b & d.

Based on the conventional techniques, there have been substantial improvement in the quality of a recording signal and the stability at the time of repeating an overwriting, and improvement in reliability and general applicability. However, in recent years, a technique for making it possible to record at a plurality of linear velocities (a multi-speed recording) in one information recording medium has been required in a rewritable information recording medium, particularly, in the phase change type optical information recording medium.

Further, a high-speed recording has also been required, and a CAV recording that is advantageous in a high-speed recording has also been required. The technologies in the above-described Japanese Patent Application Laid-open Publication No. 9-138946, Japanese Patent Application Laid-open Publication No. 9-138947, and Japanese Patent Application Laid-open Publication No. 9-219021 have not been able to meet these technical requirements. For example, it has been tried to carry out a recording at an eight-time linear velocity and at a ten-time linear velocity respectively, based on the recording strategy having fp, mp, and op where it is possible to record at four times the linear velocity of the CD. In this case, it has not been possible to obtain sufficient signal quality in the recording at the eight-time linear velocity and at the ten-time linear velocity respectively. Furthermore, there has been a problem of degradation in the signal quality in the overwriting at a different recording linear velocity. For example, there has been a problem of degradation in the signal quality in the case of overwriting at ten times the linear velocity of the CD on a portion recorded at four times the linear velocity of the CD, and overwriting at four times the linear velocity of the CD on a portion recorded at ten times the linear velocity of the CD. Moreover, there has also been a problem of degradation in the signal quality in the overwriting based on a different recording system, such as overwriting in a CAC recording at a CLV recorded portion, and an overwriting in a CLV recording at a CAV recorded portion.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an optical information recording medium capable of recording at a high speed, and a method of and an apparatus for recording/reproducing optical information capable of recording at a high speed that can sufficiently exhibit the capability of the optical information recording medium.

It is another object of this invention to provide an optical information recording medium that is excellent in a repetitive recording characteristic, recording and erasing sensitivities, and a preservation characteristic, and a method of manufacturing such optical information recording medium.

It has been a conventional subject to obtain an optical information recording medium that can perfectly satisfy the above total performance, and can secure both a recording at a higher speed and preservation and using reliability at high temperatures. In addition, it has been a conventional subject to improve the stability of an overwriting signal quality in a multi-speed CLV recording and a CAV recording, and to make it possible to record based on a general-purpose recording strategy.

In other words, it is still another object of this invention to provide an optical information recording medium that is optimum in recording and erasing at high linear velocity. It is still another object of this invention to provide an optical information recording medium that has satisfactory reliability in high-speed recording and erasing. It is still another object of this to provide an optical information recording medium capable of executing multi-speed CLV recording and CAV recording.

The optical information recording medium according to one aspect of the present invention as claimed in claim 1, at least stores information that indicates a standard recording linear velocity Vr and/or a maximum recording linear velocity Vh. Moreover, the optical information recording medium comprises a transparent substrate having a concentric circular guide groove or a spiral guide groove, the guide grove having land portions and groves portions; and at least a phase change type recording layer on the transparent substrate. When reflectivity of the optical information recording medium is measured, while irradiating energy on the guide groove such that the energy melts the material of the phase change type recording layer and while rotating the optical information recording medium and increasing a linear velocity of gradually, and when the linear velocity at which the reflectivity of the optical information recording medium decreases, in comparison to the state when the energy is not radiated, is defined as dislocation linear velocity V, then the dislocation linear velocity V satisfies a relation V ≥ Vr × 0.85 or V ≥ Vh × 0.85.

The method of recording/reproducing optical information according to another aspect of the present invention as claimed in claim 15, includes following steps. That is, setting a phase change type of optical information recording medium to an optical information recording/reproducing apparatus, the optical information recording medium recording in advance specific information indicating that a dislocation linear velocity V corresponding to the optical information recording medium satisfies a specific relation; reproducing the specific information from the optical information recording medium; deciding from the specific information, whether it is possible or not to record at a recording linear velocity higher than a maximum recording linear velocity of the optical information recording medium; and recording and reproducing at a recording linear velocity higher than the maximum recording linear velocity, when it is decided in the deciding step that it is possible to record at a higher recording linear velocity than the maximum recording linear velocity.

The apparatus for recording/reproducing optical information according to still another aspect of the present invention as claimed in claim 16, comprises following units. That is, a specific information reproduction unit which reproduces a specific information from a phase change type of optical information recording medium, wherein the optical information recording medium recording in advance the specific information indicating that a dislocation linear velocity V corresponding to the optical information recording medium satisfies a specific relation; a deciding unit which decides from the specific information, whether it is possible or not to record at a recording linear velocity higher than a maximum recording linear velocity of the optical information recording medium; and a data reproduction/recording unit which reproduces or records at a linear velocity higher than the maximum recording linear velocity, when the deciding unit decides that it is possible to record at a higher recording linear velocity than the maximum recording linear velocity.

Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

• Fig. 1 is a diagram showing an example of a structure of an optical information recording medium according to a first embodiment of the present invention.
• Fig. 2 is a diagram showing a dislocation linear velocity dependency of a two-recording jitter.
• Fig. 3 is a diagram showing examples of a recording pulse waveform according to the first embodiment.
• Fig. 4 is a diagram showing an example of recording and reproduction according to the first embodiment of the invention.
• Fig. 5 is an evaluation system diagram of a dislocation linear velocity.
• Fig. 6 is a diagram showing a result of an evaluation of a dislocation linear velocity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the optical information recording medium, method of manufacturing the optical information recording medium, method of and apparatus for recording/reproducing optical information onto/from the optical information recording medium will be explained below with reference to the accompanying drawings.

Fig. 1 shows an example of a layer structure of the phase change type optical information recording medium according to the first embodiment of the present invention. As a basic structure, on a transparent substrate 1 having a guide groove, there are disposed the first protection layer 2, recording layer 3, second protection layer 4, reflection layer 6, overcoat layer 7, and preferably with the third protection layer 25. Further, there may be disposed the print layer 8 on the overcoat layer 7, and there maybe disposed the hard-coat layer on the other surface of the substrate 1. A single-plate disk or a transparent substrate may be adhered via the adhesive layer 10 to the print layer 8. If the single-plate disk or the transparent substrate is such that it is not provided with any print layer, then the print layer 8' may be formed on the other surface of this single-plate disk or the transparent substrate.

The substrate 1 may be made from glass, ceramics or resin. However, from the viewpoint of the moldability and the cost, it is preferable to make the substrate 1 from resin.

Examples of resins that may be used to make the substrate 1 are the polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluororesin, ABS resin, and the urethane resin. From the viewpoint of the moldability, optical characteristic, and the cost, the polycarbonate resin or the acrylic resin are most preferable.

However, in the case of applying an optical information recording medium of the first embodiment to a rewritable disk compatible with a DVD-ROM, it is desirable to meet a condition that a guide groove formed on the substrate 1 has a width between 0.10 and 0.40 µm, and preferably between 0.15 and 0.30 µm, and has a depth between 15 and 65 nm, and preferably between 25 and 50 nm.

While there is no particular limitation on the thickness of the substrate 1, thickness of 0.6 nm is preferable. Moreover, there is no particular limitation on the thickness of the disk after the adhesion, however, the thickness between 1.1 and 1.3 mm is preferable.

Further, in the case of applying an optical information recording medium of the first embodiment to a CD-RW, it is desirable to meet a condition that the guide groove has a width between 0.25 and 0.65 µm, an preferably between 0.30 and 0.55 µm, and has a depth between 25 and 65 nm, and preferably between 30 and 55 nm. While there is no particular limitation on the thickness of the substrate 1, the thickness of 1.2 nm is preferable.

For the recording layer 3, it is preferable to use a phase change type recording material including Sb and Te that generate a phase change between the crystalline phase and the amorphous phase and that can take a stabilized state and a semi-stabilized state respectively, and a composition expression of which is Sb_χTe 100 - χ (40 ≤ χ ≤ 80, where χ is atomic percentage), because of its satisfactory recording (amorphous) sensitivity/speed, erasing (crystallization) sensitivity/speed, and erasing ratio respectively.

When elements such as Ga, Ge, Ag, In, Bi, C, N, O, Si, and S are added to SbTe, it is possible to improve the recording/erasing sensitivities, signal characteristic, and reliability. Thus, it is possible to control the characteristics of the optical information recordingmedium based on which elements are added ("added element" or "additive element") in what proportion.

The proportion of the added element should be between 0.1 and 20 atomic percentage, and preferably between 1 and 15 atomic percentage. When the proportion of the added element is as mentioned here, initialization can be performed satisfactorily.

Depending on the composition ratio, a dislocation linear velocity of the above material changes, and an optimum recording linear velocity is also different. Therefore, it is necessary to adjust a composition ratio of the material and control the dislocation linear velocity, based on a target recording linear velocity and a target linear velocity area. The study of the present inventors showed that a composition ratio of Te has high correlation with a dislocation linear velocity.

As the quality of the phase change type optical information recording medium used in the first embodiment, reproduction stability of a signal when it has been recorded in the high-density high linear velocity area, and the life (reliability) of the signal are required, as well as the recording/erasing capability.

The above material is excellent for the recording layer 3 that can satisfy almost all the conditions. Particularly, a material expressed by the following composition expression is excellent in the reproduction stability and the life of the signal. Further, this material is preferable, as it is possible to execute the initialization satisfactorily:

• (Ag, Ge)_α (In, Ga, Bi)_β Sb_γTe_δ, wherein
• (Ag, Ge) and (In, Ga, Bi) mean respectively that they include at least one kind of elements enclosed by the brackets, α, β, γ, and δ represent atomic percentages respectively. The atomic percentages α, β, γ, and δ satisfy the following relationship: 0.1 ≤ α ≤ 7, 1 ≤ β ≤ 15, 61 ≤ γ ≤ 85, and 20 ≤ δ ≤ 30.

Further, a material having a cubic lattice crystal structure of an isotropic crystal structure in an un-recorded state after the initialization, preferably, the NaCl type crystal structure, can generate a phase change having small variation with an amorphous phase that is similarly considered to be highly isotropic. This material is preferable as this can perform recording (transformation to amorphous state) and erasing (transformation to crystalline state) uniformly at a high speed.

It is desirable that the recording layer 3 has a thickness between 10 and 50 nm, and preferably between 12 and 30 nm. Further, considering the initial characteristic such as jitter, overwriting characteristic, and the mass-production efficiency, it is preferable that the recording layer 3 has a thickness between 14 and 25 nm. If the recording layer 3 is thicker than 10 nm, the light absorptance is improved, and the characteristic of the recording layer 3 are improved. If the recording layer 3 is thinner than 50 nm, it becomes possible to generate a uniform phase change even at a high speed.

This recording layer 3 can be formed using any of the conventionally known vapor deposition methods. Examples of such methods are the vacuum deposition method, sputtering method, plasma CVD method, optical CVD method, ion-plating method, and the electronic beam deposition method. Among others, the sputtering method is excellent from a viewpoint of mass-production efficiency and film quality.

The first protection layer 2 and the second protection layer 4 may be formed from material such as metal oxides like SiO, SiO₂, ZnO, SnO₂, Al₂O₃, TiO₂, In₂O₃, MgO, and ZrO₂, nitrides like Si₃N₄, A1N, TiN, BN, and ZrN, a sulfide like ZnS, In₂S₃, and TaS₄, carbides like SiC, TaC, B₄C, WC, TiC, and ZrC, and diamond carbon. It should be notated that the material listed here may be used singularly or in combination. Moreover, if required, an impurity may be added. However, it is necessary that the melting point of the first protection layer 2 and the second protection layer 4 is higher than that of the recording layer 3.

The first protection layer 2 and the second protection layer 4 can be formed using any of the conventionally known vapor deposition methods. Examples of such methods are the vacuum deposition method, sputtering method, plasma CVD method, optical CVD method, ion-plating method, and electronic beam deposition method. Among others, the sputtering method is excellent from a viewpoint of mass-production efficiency and film quality.

The thickness of the first protection layer 1 produces large influence on the reflectivity, modulation level, and the recording sensitivity. In order to obtain a satisfactory signal characteristic, it is required that the thickness of the first protection layer 2 should be between 60 and 120 m. It is desirable that the second protection layer 4 has a thickness between 5 and 45 nm, and preferably between 7 and 40 nm. If the second protection layer 4 is thicker than 5 nm, then it functions as a perfect heat-resisting protection layer, and thereby the recording density is improved. On the other hand, if the second protection layer 4 is thinner 45 nm, the interface separation does not occur so easily, and the repetitive recording performance is also improved.

The reflection layer 6 is possibly made from metals like Al, Au, Ag, Cu, Ta, Ti, and W, or an alloy that includes these elements. For improving corrosion-proof characteristic, and thermal conductivity, element like Cr, Si, or Pd may be added to the above mentioned metals. It is preferable that the elements listed here are added in a proportion between 0.3 and 2 atomic percentage. If the proportion in which these elements are added is greater than 0.3 atomic percentage, then the corrosion-proof characteristic are improved. On the other hand, if proportion is smaller than 2 atomic percentage, the thermal conductivity is improved, and it becomes easy to form the amorphous state.

The reflection layer 6 can be formed using the any conventionally know vapor deposition method. Examples of such methods are the vacuum deposition method, sputtering method, plasma CVD method, optical CVD method, ion-plating method, and the electronic beam deposition method.

It is desirable that the reflection layer 6 has a thickness between 50 and 200 nm, and preferably between 70 and 160 nm. The reflection layer 6 may have a multi-layer structure. If the reflection layer 6 has the multi-layer structure, each layer of the multi-layer structure needs to have a thickness of at least 10 nm. Moreover, it is desirable that a total thickness of such multi-layer reflection layer 6 to be between 50 and 160 nm.

The overcoat layer 7 is formed on the reflection layer 6 in order to prevent the reflection layer 6 from being oxidized. As the overcoat layer 7, an ultraviolet-ray-cured resin manufactured by spin coating is general. It is desirable that the overcoat layer 7 has a thickness between 3 and 15 µm. If the overcoat layer 7 is thicker than 3 µm, then signal error does not occur even if the print layer 8 is disposed above the overcoat layer 7. On the other hand, if the overcoat layer 7 is thinner than 15 µm, then the internal stress is reduced whereby the mechanical characteristic of the disk are not affected.

As the hard-coat layer 9, an ultraviolet-ray-cured resin manufactured by spin coating is general. It is desirable that the hard-coat layer 9 has a thickness between 2 and 6 µm. If the hard-coat layer 9 is thicker than 2 µm, then sufficient friction damage-proof characteristic can be obtained. If the hard-coat layer 9 is thinner than 6 µm, then the internal stress is reduced whereby the mechanical characteristic of the disk are not affected. The hard-coat layer 9 should be harder to the extent that is not hurt when the layer is rubbed with cloth. For example, the hard-coat layer 9 should be harder than H on the hardness scale for pencils.

It may be effective to mix a conductive material into the material of the hard-coat layer 9. By mixing such material it is possible prevent the hard-coat layer 9 from getting charged and thereby preventing dust from getting adhered to the hard-coat layer 9.

The print layer 8 has been provided to protect the underplaying layer from getting damaged due to friction. Moreover, a label may or the brand name of the manufacturer may be printed on the print layer 8. Moreover, an ink reception layer for an inkjet printer may be formed on the print layer 8. It is general that the print layer is formed from an ultraviolet-ray-cured resin using the screen printing method.

It is desirable that the print layer 8 has a thickness between 3 and 50 µm. If the print layer 8 is thicker than 3 µm, then variation are not generated at the time of formation of the layer. If the print layer 8 is thinner than 50 µm, then the internal stress is reduced whereby the mechanical characteristic of the disk are not affected.

The adhesive layer 10 may be made from the ultraviolet-ray-cured resin, hot-melt adhesive, and the silicone resin. The adhesive layer 10 is formed on the overcoat layer 7 or the print layer 8 using the spin coating method, roll coating method, or the screen printing method, depending upon the material with which the later is to be formed. The disk of the other side may be adhered to the adhesive layer 10 by irradiating the surface with ultraviolet rays, or heating, or pressing.

The disk of the other side may be a single-plate disk or just a transparent substrate. When this disk is to be adhered to the adhesive layer 10, an adhesive may or may not be coated on the surface of the disk that is to be adhered to the adhesive layer 10. Moreover, the adhesive layer 10 may be an adhesive sheet.

There is no particular limitation on the thickness of the adhesive layer 10. However, it is preferable that the adhesive layer 10 has a thickness between 5 and 100 µm, considering the easiness of coating the material, curability, and influence to a mechanical characteristic of the disk.

There is no particular limitation on where the adhesive layer 10 is formed. However, in the case of applying this to a rewritable disk having compatibility with a DVD and/or a CD, in order to achieve a high-speed recording of the first embodiment, it is desirable that the adhesive layer 10 is formed in a region between 15 to 40 mm from the inner periphery, and preferably between 15 to 30 mm from the inner periphery, for securing the adhesive strength.

The third protection layer 5 may be provided in between each of the transparent substrate 1, first protection layer 2, recording layer 3, second protection layer 4, reflection layer 6, overcoat layer 7, print layer 8, and the adhesive layer 10. The third protection layer 5 is provided in order to improve adhesion between the corresponding layers, preventing chemical reaction between the corresponding, adjusting the optical characteristic, and adjusting the thermal property. It should be noted that, the third protection layer 5 in between the second protection layer 4 and the reflection layer 6 has only been shown in Fig. 1.

Particularly, if the third protection layer 5 is formed in between the second protection layer 4 and the reflection layer 6, it is desirable that the layer is formed using at least one substance selected from a group consisting of C, Si, SiC, SiN, SiO, and SiO₂.

It is desirable that the third protection layer 5 has a thickness between 1 and 40 nm, and preferably between 2 and 30 nm. If the third protection layer 5 is thicker than 1 nm, then it easier to form the stable interface layer. On the other hand, if the third protection layer 5 is thinner than 40 nm, then the interface separation does not occur so easily, whereby the inter-layer adhesion is improved.

The third protection layer 5 may be formed using any of the conventionally known vapor deposition methods. Examples of such methods are the vacuum deposition method, sputtering method, plasma CVD method, optical CVD method, ion-plating method, and the electronic beam deposition method. Particularly, considering a mass-production efficiency, the DC-sputtering method is desirable as it is possible to utilize a general-purpose sputtering apparatus.

In order to carry out a mass production of the optical information recording medium in good quality that meets a high linear velocity according to the first embodiment, it is necessary to adjust the dislocation linear velocity as it is required to take a large margin of a recording linear velocity.

The dislocation linear velocity is influenced by the thermal property, and is different depending on a track pitch of the optical information recording medium, wavelength of the laser beam, NA, and laser power. In the case of a phase change type optical information recording medium having a track pitch between 0.2 and 1.4 µm, it has been found that it is important to set the dislocation linear velocity to 6 to 24 m/s when a DC irradiation has been carried out by focusing a semiconductor laser beam to a groove or a land of the guide groove.

When the dislocation linear velocity is higher than 6 m/s, it is possible to achieve the recording in a high linear velocity area like two or more times the linear velocity of the DVD (7.0 m/s) or eight or more times the linear velocity of the CD (9.6 to 11.2 m/s). On the other hand, when the dislocation linear velocity is slower than 24 m/s, the recording sensitivity in an area of a recording linear velocity suitable for recording is not lowered so easily; whereby it becomes possible to execute recording in good quality based on a pulse strategy to be described later.

In general, in the case of overwriting on a phase change type optical information recording medium, there is observed such a phenomenon that jitter increases at the time of overwriting two times, jitter decreases at the time of overwriting three or more times, and jitter is stabilized after overwriting for ten or more times. Since the object of the first embodiment is to achieve high-speed recording, the above mentioned phenomenon becomes sever. Therefore, amount of jitter at the time of recording two times is practically the most important factor in the phase change type optical information recording medium that decided the quality.

Fig. 2 shows jitter when recording is carried out two times using recording power and a recording strategy that the jitter at the time of recording two times becomes smaller than the jitter at the time of recording 1,000 times. Phase change type optical information recording media having different dislocation linear velocities were used for the study. These optical information recording media were manufactured by using a substrate that has information that a minimum recording linear velocity is four times (i.e. 4.8 m/s) the speed of the CD ("CD four-time speed") and a maximum recording linear velocity is ten times (i.e. 12.0 m/s) the speed of the CD ("CD ten-time speed"). The jitter is a value at the time of reproducing at one times the speed of the CD. The value of 35 ns (nanosecond) corresponds to the jitter for the speed of CD and this value satisfies the standard.

It can be understood from Fig. 2, that basically the dislocation linear velocity at which jitter becomes small when the recording linear velocity is four times the speed of a CD and ten times the speed of a CD respectively is 12 m/s.

However, the commercially available CD-RW recording medium that has the minimum recording linear velocity as the CD four-time speed and the maximum recording linear velocity as the CD ten-time speed has the dislocation linear velocity of 9 m/s. This dislocation linear velocity is about 0.75 times the maximum recording linear velocity, and it is matched with the minimum recording linear velocity, i.e. CD four-time speed. In other words, the dislocation linear velocity of the commercially available CD-RW recording medium does not match with the maximum recording linear velocity, i.e. CD ten-time speed.

In order to make it possible to achieve a higher-speed recording which is the object of the first embodiment, particularly in order for a user to sense a high speed, it is necessary to realize a recording linear velocity that is 20% or higher than the maximum recording linear velocity of the CD ten-time speed (that is, 14.4 m/s). In order to suppress the jitter to 35 ns or below as the standard, it can be understood from Fig. 2 that the dislocation linear velocity should be 9.5 m/s or above. In other words, the dislocation linear velocity should be 0.8 times the maximum recording linear velocity or above.

Also it can be understood from Fig. 2, that if recording is to be performed at still higher speed, such as, for example, CD sixteen-time speed (i.e. 19.2 m/s), CD twenty-time speed (i.e. 24 m/s), or CD twenty-four time speed (i.e. 28.8 m/s), the dislocation linear velocity should respectively be 12, 16, or 19 m/s or above.

Moreover, it can be understood from Fig. 2, that in order to have the jitter suppressed to 35 ns or below even at the recording at the minimum recording linear velocity 4.8 m/s, it is necessary that the dislocation linear velocity is below 25 m/s. In other words, a linear velocity that is approximately two times or less than the maximum recording linear velocity becomes an upper limit of the recording linear velocity at which it is possible to execute a recording.

In the above explanation, a CD-RW recording medium has been taken as an example. In the case of other phase change type optical information recording medium, in order to realize a higher-speed recording, it is desirable that the dislocation linear velocity is set to a speed at least 0.8 times the maximum recording linear velocity of the recording medium, preferably, 0.85 times or above, or more preferably, 0.9 times or above.

The CD-RW recording medium having various kinds of dislocation linear velocities shown in Fig. 2 has been manufactured by suitably selecting the composition and thickness of the recording layer 3, selecting impurity to be mixed in the recording layer 3, the material of the reflection layer 6, composition of the dielectric material, and the conditions of the initialization process.

It is possible to adjust the dislocation linear velocity by changing the composition and thickness of each constituent layer, and the processing condition.

For example, the dislocation linear velocity can be decreased by increasing the proportion of Ag and Ge in the material for forming the recording layer 3. On the other hand, the dislocation linear velocity can be increased by decreasing the proportion of In and Ga in the material for forming the recording layer 3. Similarly, the dislocation linear velocity can be decreased by increasing the thickness of the recording layer 3. On the other hand, the dislocation linear velocity can be increased by decreasing the thickness of the recording layer 3.

Moreover, the dislocation linear velocity can be decreased by increasing the thermal conductivity of the second protection layer 4 and the reflection layer 6. On the other hand, the dislocation linear velocity can be increased by decreasing the thermal conductivity of the second protection layer 4 and the reflection layer 6.

Regarding processing conditions, when the recording layer 3, first protection layer 2, second protection layer 4, and the third protection layer 5 are formed using the sputtering method, the dislocation linear velocity decreased by lowering the temperature of the substrate to be input. On the other hand, the dislocation linear velocity can be increased by raising the temperature of the substrate to be input.

Furthermore, the dislocation linear velocity decreased by adding gasses such as N₂ and O₂ as coexisting gases to Ar at the time of the sputtering. In this case, the dislocation linear velocity becomes fast at an initial stage of the target life, and the dislocation linear velocity becomes slow during a latter half of the target life.

It is also possible to adjust a dislocation linear velocity based on factors such as the linear velocity of the initialization, and the laser power.

Thus, it is possible to determine a value of a dislocation linear velocity based on a combination of various kinds of conditions. Accordingly, the dislocation linear velocity may be adjusted to a desired value by adjusting the conditions in best manner.

It is desirable that the linear velocity for initialization is slower than the dislocation linear velocity. If the initialization linear velocity is faster than the dislocation linear velocity, a rise in the temperature of the recording layer tends to be insufficient whereby it becomes impossible to achieve uniform crystallization. If crystallization is not achieved uniformly, then there occurs variations in the initialization, which generates a disturbance in the RF signal.

Moreover, it is desirable that the initialization linear velocity Vi is 0.5 times or above and 1.6 times or below of the standard recording linear velocity Vr and/or the maximum recording linear velocity Vh. If the initialization linear velocity Vi is above 0.5 times, the good initialization can be performed, moreover, the overwriting performance is good. If the initialization linear velocity Vi less that 1.6 times, the temperature of the recording layer rises insufficient whereby uniform crystallization can be achieved and disturbance in the RF signal is not generated.

Fig. 4 shows one example of the apparatus for recording/reproducing optical information that uses the method according to the first embodiment. As shown in Fig. 4, the driving section includes the spindle motor that drives and rotates the phase change type optical information recording medium according to the present invention. The laser driving circuit drives a power source consisting of a semiconductor laser of the recording/reproducing pick-up. When the recording/reproducing pick-up is drives, it irradiates a laser beam of a pulse strategy having fp, mp, and ep as shown in Fig. 3. With this arrangement, recording is carried out by generating a phase change in the recording layer 3 of the optical information recording medium. The recorded information is reproduced by receiving a reflection beam from the optical information recording medium that has been irradiated with the reproduction beam, with the recording/reproducing pick-up.

Next, a recording of a signal as a width of a mark on the recording layer 3 of the optical information recording medium according to the first embodiment will be explained. In other words, a recording of information based on what is called a PWM recording system will be explained.

When recording information, a signal to be recorded is modulated by using a clock in a modulator based on, for example, the EFM (Eight-to-Fourteen Modulation) system that is suitable for recording the information on a rewritable compact disk, or an improved modulation system of this system.

At the time of carrying out a recording according to the PWM recording system, a recording beam at the time of recording or rewriting a 0 signal having a signal width n × T after modulation (where n represents a positive integer, and T represents a clock time, that is a time corresponding to a period of a clock used for modulating the signal) is a continuous beam having a power level e, and a recording beam pulse string at the time of recording or rewriting a 1 signal having a signal width n × T after modulation is a laser wave pulse string that has a pulse portion fp having a time width × and a power level a, a multi-pulse portion mp in which a low-level pulse of a power level b having a time width T in total and a high-level pulse having a power level c alternately appear and continue by (n - n') times in total at a duty ratio y, and a pulse portion ep having a time width z and a power level d, where x, y, and z are in relationships of T × 0.125 ≤ × ≤ T × 2.0, 0.125 ≤ y ≤ 0.875, and T × 0.125 ≤ z ≤ T, a & c ≥ e ≥ b & d.

Fig. 3 shows an example when n is equal to 3, and n' is equal to 2.

The apparatus for recording/reproducing optical information from the optical information recording medium according to the first embodiment has means for reading information that indicates a maximum recording linear velocity of the disk set in the apparatus, means for reading other specific information from the disk, and deciding whether it is possible to record at a linear velocity higher than the maximum recording linear velocity or not.

One example of the operations performed by the apparatus according to the present invention are as follows:

1. 1. The optical information recording medium according to the present invention is set on a tray of a drive of the apparatus.
2. 2. The drive reproduces ID information or discrimination information from the set optical information recording medium according.
3. 3. The drive collates the same ID information or discrimination information from the optical information recording medium stored in advance in the drive with the ID information or the discrimination information reproduced in 2 above.
4. 4. The drive recognizes the property and characteristic of the set optical information recording medium based on the collation of the ID information or the discrimination information.
5. 5. The drive selects a recording method that is optimal to the set optical information recording medium from a list of recording methods stored in advance, and starts the recording onto the set optical information recording medium.

Examples of the first embodiments will be explained in detail below. However, the invention of the first embodiment is not limited to these examples.

Example 1:

A polycarbonate substrate 1 having a guide groove with a width of 0.55 µm and depth of 30 nm was prepared by injection molding. On this substrate 1, the first protection layer 2, recording layer 3, second protection layer 4, and the reflection layer 6 were laminated in this order using the sputtering method. The substrate 1 was put into the sputtering unit by keeping the substrate at 55°C. Information that the maximum recording linear velocity is ten times (i.e. 12 m/s) the speed of the CD was recorded onto the substrate 1.

The first protection layer 2 and the second protection layer 4 were made from ZnS · SiO₂. The first protection layer 2 had a thickness of 90 nm and the second protection layer had a thickness of 30 nm. The recording layer 3 was made from Ge₂In₈Sb₆₈Te₂₂. The recording layer 3 was made 16 nm thick. The reflection layer 6 was made from AlTi (with Ti content of 0.5 weight percent). The reflection layer 6 had a thickness of 140 nm.

As a result, a laminate having a layer structure as follows was formed. That is, the substrate 1 (composition: polycarbonate), first protection layer 2 (composition: ZnS·SiO₂, thickness: 90 nm), recording layer 3 (composition: Ge₂In₈Sb₆₈Te₂₂, thickness: 16 nm), second protection layer 4 (composition: ZnS·SiO₂, thickness: 30 nm), and the reflection layer 6 (composition: AlTi, thickness: 140 nm). Finally, the overcoat layer 7 was formed'by spin coating an ultraviolet-ray-cured type resin on the reflection layer 6 to obtain a single-plate disk of the optical information recording medium.

Next, the entire surface of this optical information recording medium was crystallized at a constant linear velocity of 7.0 m/s, from the inner periphery toward the outer periphery, at electric power 850 mW, and feed 120µm, with an initializing unit having a large diameter LD (a beam diameter 200 × 1µm).

The dislocation linear velocity of the optical information recording medium obtained in this way was measured by DC irradiation, by focusing a semiconductor laser beam of a wavelength 780 nm onto a groove portion of the guide groove. The dislocation linear velocity was found to be 12.8 m/s, that is 1.1 times the maximum recording linear velocity.

Next, the optical information recording medium was set into an apparatus for recording optical information that has a list that it is possible to record at a sixteen-time faster a code string of a combination of code information including a read-in time and a read-out time of this optical information recording medium, an optimum recording power code, and a disk type.

This optical information recording apparatus was made to read first the read-in time, the read-out time, the optimum recording power code, and the disk type. Then, the optical information recording apparatus decided whether it is possible or not to achieve a recording at a recording linear velocity equal to or faster than the maximum recording linear velocity based on the combination of this read information. The optical information recording apparatus decided that it is possible to record onto this optical information recording medium at a recording linear velocity of CD sixteen-time speed that is faster than the maximum recording linear velocity.

Next, information was recorded onto this the optical information recording medium in a format capable of being reproduced with a CD-ROM at the recording linear velocity of CD sixteen-time speed. It was found that the jitter characteristic at the initial stage of a recording and even after 1,000 times of overwriting was satisfactory.

Further, a preservation test on the optical information recording medium was carried out by leaving the disk for 500 hours in an environment at a temperature 80 °C and humidity 85%. The optical information recording medium did not show any signs of oxidization of the recording layer 3 or a change in the signal characteristics. Thus, the optical information recording medium can be preserved with great satisfaction for a long time.

As explained above, it possible to realize a high-speed recording at the CD sixteen-time speed on the optical information recording medium that had the maximum recording linear velocity of only ten times that of the CD.

Example 2:

A polycarbonate substrate 1 having a guide groove with a width of 0.2 µm and depth of 27 nm was prepared by injection molding. On this substrate 1, the first protection layer 2, recording layer 3, second protection layer 4, third protection layer 5, and the reflection layer 6 were laminated in this order using the sputtering method. The substrate 1 was put into the sputtering unit by keeping the substrate at 55°C. Information that the maximum recording linear velocity is 8.44 m/s the speed of the CD was recorded onto the substrate 1.

The first protection layer 2 and the second protection layer 4 were made from ZnS · SiO₂. The first protection layer 2 had a thickness of 75 nm and the second protection layer had a thickness of 10 nm. The third protection layer 5 was made from SiC. The third protection layer 5 had a thickness of 3 nm. The recording layer 3 was made from Ag_0.5Ge_1.5Ga₈Sb₆₈Te₂₂. The recording layer 3 had a thickness of 14 nm. The reflection layer 6 was made from AlTi (with Ti content of 0.5 weight percent). The reflection layer 6 had a thickness of 140 nm.

As a result, a laminate having a layer structure as follows was formed. That is, the substrate 1 (composition: polycarbonate), first protection layer 2 (composition: ZnS·SiO₂, thickness: 75 nm), recording layer 3 (composition: Ag_0.5Ge_1.5Ga₈Sb₆₈Te₂₂, thickness: 14 nm), second protection layer 4 (composition: ZnS·SiO₂, thickness: 10 nm), third protection layer 5 (composition: SiC, thickness: 3 nm), and the reflection layer 6 (composition: AlTi, thickness: 140 nm). Finally, the overcoat layer 7 was formed by spin coating an ultraviolet-ray-cured type resin on the reflection layer 6 to obtain a single-plate disk of the optical information recording medium.

Next, the entire surface of this optical information recording medium was crystallized at a constant linear velocity of 10.0 m/s, from the inner periphery toward the outer periphery, at electric power 850 mW, and feed 120µm, with an initializing unit having a large diameter LD (a beam diameter 200 × 1µm).

The dislocation linear velocity of the optical information recording medium obtained in this way was measured by DC irradiation, by focusing a semiconductor laser beam of a wavelength 660 nm onto a groove portion of the guide groove. The dislocation linear velocity was found to be 14.4 m/s, that is 1.7 times the maximum recording linear velocity.

Next, the optical information recording medium was set into an apparatus for recording optical information that has a list that it is possible to record at a DVD four-time fast speed a code string of a combination of code information including a read-in time and a read-out time of this optical information recording medium, an optimum recording power code, and a disk type.

This optical information recording apparatus was made to read first the read-in time, the read-out time, the optimum recording power code, and the disk type. Then, the optical information recording apparatus decided whether it is possible or not to achieve a recording at a recording linear velocity equal to or faster than the maximum recording linear velocity based on the combination of this read information. The optical information recording apparatus decided that it is possible to record onto this optical information recording medium at a recording linear velocity of DVD four-time speed that is faster than the maximum recording linear velocity.

Next, information was recorded onto this the optical information recording medium in a format capable of being reproduced with a DVD-ROM at the recording linear velocity of DVD four-time speed. It was found that the jitter characteristic at the initial stage of a recording and even after 1,000 times of overwriting was satisfactory.

Further, a preservation test on the optical information recording medium was carried out by leaving the disk for 500 hours in an environment at a temperature 80 °C and humidity 85%. The optical information recording medium did not show any signs of oxidization of the recording layer 3 or a change in the signal characteristics. Thus, the optical information recording medium can be preserved with great satisfaction for a long time.

As explained above, it possible to realize a high-speed recording at a DVD four-time speed on the optical information recording medium that had the maximum recording linear velocity of only 8.44 m/s.

Examples 3 to 14:

A polycarbonate substrate 1 was prepared by injection molding. On this substrate 1, the first protection layer 2, recording layer 3, second protection layer 4, third protection layer 5, and the reflection layer 6 were laminated in this order using the sputtering method.

The first protection layer 2 and the second protection layer 4 were made from ZnS · SiO₂. The first protection layer 2 had a thickness of 80 nm and the second protection layer had a thickness of 10 nm. The third protection layer 5 was made from SiC. The third protection layer 5 had a thickness of 5 nm. The recording layer 3 was made frommaterial having a composition shown in Table 1 to obtain Examples 3 to 14. The recording layer 3 had a thickness of 15 nm. The reflection layer 6 was made from Ag. The reflection layer 6 had a thickness of 140 nm.

As a result, a laminate having a layer structure as follows was formed. That is, the substrate 1 (composition: polycarbonate), first protection layer 2 (composition: ZnS · SiO₂, thickness: 80 nm), recording layer 3 (composition: as shown in Table 1, thickness: 15 nm), second protection layer 4 (composition: ZnS · SiO₂, thickness: 10 nm), third protection layer 5 (composition: SiC, thickness: 5 nm), and the reflection layer 6 (composition: Ag, thickness: 140 nm). Finally, the overcoat layer 7 was formed by spin coating an ultraviolet-ray-cured type resin on the reflection layer 6 to obtain a single-plate disk of the optical information recording medium.

Next, the recording layer 3 of the optical information recording medium was crystallized with an initializing unit having a large diameter LD (a beam diameter 200 × 1µm).

Thereafter, a single-plate disk having a polycarbonate substrate thickness of 0.6 mm was adhered onto the overcoat layer 7 via an adhesive (i.e. the adhesive layer 10). Then, the print layer 8' was formed on the other surface of this polycarbonate substrate. Thus, a adhesion-type disk was obtained.

Table 1 shows the parameters of the optical information recording/reproducing media according to'Example 3 to 14. These parameters include: the polycarbonate substrate thickness, disk structure of either the single plate or the adhesion-type disk, track pitch, various conditions for manufacturing a composition of the recording layer 3, wavelength of a pick-up of an apparatus used for recording and reproducing on/from thus obtained the optical information recording/reproducing media, dislocation linear velocity, recording linear velocity, and the result of evaluation.

Jitter characteristic in the result of evaluation has been defined as σ/T (%) standardized in the clock time T.

As can be seen from the evaluation result shown in Table 1, in all the Examples 3 to 14, jitter characteristics at the initial stage and even after overwriting 1,000 times are satisfactory.

Further, a preservation test on the optical information recording medium was carried out by leaving the disk for 500 hours in an environment at a temperature 80°C and humidity 85%. The optical information recording medium did not show any signs of oxidization of the recording layer 3 or a change in the signal characteristics. Thus, the optical information recording medium can be preserved with great satisfaction for a long time.

As explained above, according to the present invention, it is possible to provide an optical information recording medium capable of recording at linear velocity that is higher than the even the maximum recording linear velocity of the optical information recording medium.

Moreover, it is possible distinguish whether the optical information recording medium is according to the conventional technology or it is according to the present invention. Therefore, it is possible to provide an optical information recording medium capable of avoiding a recording on a conventional disk at a speed faster than a maximum recording linear velocity by error.

Furthermore, it is possible to provide an optical information recording medium having good signal quality, excellent overwriting characteristic. Moreover, it is possible to provide an optical information recording medium that is very reliable and can be mass-produced efficiently.

Furthermore, it is possible to provide an optical information recording medium capable of recording at a faster linear velocity than a maximum recording linear velocity, based on a fine adjustment of a currently-available general-purpose optical information recording apparatus.

According to the method of recording/reproducing optical information according to the present invention, it is decided whether it is possible or not to record at a recording linear velocity higher than a maximum recording linear velocity, and recording is carried out at a recording linear velocity higher than a maximum recording linear velocity, only when it is decided that it is possible to do so. Therefore, it is possible to provide an optical information recording medium and an optical information recording/reproducing method having no recording error.

Furthermore, it is possible to provide an optical information recording medium that is excellent in power margin and that has satisfactory repetitive recording characteristic, recording and erasing sensitivities, and preservation characteristic. Moreover, when manufacturing the optical information recording medium, it is possible to efficiently form a recording layer having desired characteristics.