JP2005093012A - Phase change type optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase change type optical information recording medium which facilitates the management of the lower limit of reflectivity by constituting the information recording medium in such a manner that the reflectivity in a recorded state is higher than the reflectivity in an unrecorded state, i.e. the reflectivity is made higher and the reflectivity in an unrecorded portion is made lowest by accumulation of recording and which has good reproduction interchangeability simply by regulating the reflectivity in the unrecorded state or simply by checking the reflectivity above a standard, makes a stable reproduction signal obtainable and permits the condition of recording/reproducing with high accuracy. <P>SOLUTION: The optical information recording medium has at least a phase change recording layer on a substrate having concentrical circle or spiral guide grooves and performs recording and/or writing of information by causing a phase change in the recording layer by irradiation with a semiconductor laser beam. When the reflectivity Rb in the unrecorded portion of the guide groove section and the reflectivity Ra(m) at the time of performing overwrite recording (direct overwriting, DOW) m times (m is a natural number) are compared, Ra(m)/Rb≥1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a phase change optical information recording medium that records, reproduces, and rewrites information by causing a phase change in a recording layer material by irradiating a laser beam.

As an optical information recording medium for recording / reproduction by laser light irradiation, in addition to a reproduction-only optical information recording medium, a write-once optical information recording medium capable of writing information only once and information can be rewritten. There are various rewritable optical information recording media.
Among the rewritable optical information recording media, CD-RW, DVD + RW, DVD-RW, DVD-RAM, etc. are so-called phases that utilize a transition between crystal-amorphous phase or crystal-crystal phase as a recording layer material. Change material is used.
In general, in the case of a phase change type optical information recording medium, the recording layer is once crystallized (initialized) by continuous light to obtain a uniform crystal state, and then used as a medium for recording information. Then, the optical information recording medium after the initialization is irradiated with pulsed light in which the power level of the laser light is modulated in three stages, and the recording layer is made of crystal (high reflectance state) and amorphous (low reflectance state). Information is recorded and / or rewritten by setting the state.

At this time, the crystal state after initialization and before recording (unrecorded) differs from the crystal after recording laser light irradiation, and there may be a difference in the amount of reflected light with respect to the laser light. . In such a case, the reflectivity changes abruptly at the boundary from the unrecorded state to the recorded state, so the tracking servo becomes unstable during recording / playback, and the servo comes off and causes a problem. Sometimes.
Further, when the reflectivity is lowered by recording, the reflectivity necessary for reproducing the phase change type optical information recording medium by the reproduction-only device (for example, 18% or more for DVD, 15% or more for CD, etc.) May not be able to be secured, and this is considered to be a factor in reducing reproduction compatibility. As shown in FIG. 1, in a general conventional phase change optical information recording medium, the reflectivity decreases when recording (FIG. 1A), or the reflectivity occurs when recording is performed in an unrecorded state. However, when recording is repeated, the reflectance gradually decreases (FIG. 1-B).
Therefore, in order to reduce the decrease in reflectance, the present applicant, as a prior application (Japanese Patent Application No. 2002-57669, filed on Mar. 4, 2002), describes the reflectance Ra in the recording state in the optical information recording medium and the unapplied reflectance Ra. An invention was filed in which the ratio Ra / Rb of the reflectance Rb in the recording state was specified as Ra / Rb = 0.95 to 1.05 (FIG. 1-C).
However, even in the prior invention, since the reflectivity is lowered by repeating the recording, and the reflectivity necessary for reproducing the optical information recording medium may be lowered, it has not been completely solved.

  In the present invention, the reflectivity in the recorded state is higher than the reflectivity in the unrecorded state, that is, the reflectivity increases each time recording is repeated, and the reflectivity is the lowest in the unrecorded portion. By doing this, the lower limit of reflectance is easy to manage, and it is possible to obtain a stable reproduction signal with good reproduction compatibility simply by adjusting the reflectance of the unrecorded state or confirming that it is above the level. An object of the present invention is to provide a phase change optical information recording medium that can be recorded and reproduced with high accuracy.

As a result of diligent studies to achieve the above object, a phase change type optical information recording medium that meets this requirement has been found. That is, the above problems are solved by the following inventions 1) to 8).
1) At least a phase change recording layer is formed on a substrate having concentric or spiral guide grooves, and a phase change is caused in the recording layer by irradiating a semiconductor laser beam, thereby recording and / or rewriting information. In the optical information recording medium to be performed, the reflectance Rb of the unrecorded portion of the guide groove was compared with the reflectance Ra (m) when overwriting (direct overwriting, DOW) was performed m times (m is a natural number). Ra (m) / Rb ≧ 1 is a phase change optical information recording medium.
2) When 10 ≦ m ≦ 2000, the phase change optical information recording medium according to 1), wherein Ra (m) /Rb≧1.05.
3) At least a phase change recording layer is formed on a substrate having concentric or spiral guide grooves, and a phase change is caused in the recording layer by irradiating a semiconductor laser beam, thereby recording and / or rewriting information. In the optical information recording medium to be performed, the reflectance Ra (m) when the overwriting (direct overwrite, DOW) is performed m times (m is a natural number) in the guide groove, and the reflectance Ra when the DOW is performed m + 1 times. A phase change optical information recording medium, wherein Ra (m + 1) / Ra (m) ≧ 1 when compared with (m + 1).
4) The phase-change optical information recording medium according to any one of 1) to 3), wherein Rb ≧ 18% and Ra (m) ≧ 18% at a laser beam wavelength λ = 640 to 670 nm.
5) The phase change optical information recording medium according to any one of 1) to 3), wherein Rb ≧ 15% and Ra (m) ≧ 15% at a laser beam wavelength λ = 770 to 800 nm.
6) The phase change light according to any one of 1) to 5), wherein a lower protective layer, an intermediate layer, a phase change recording layer, an upper protective layer, and a reflective layer are sequentially formed on the substrate. Information recording medium.
7) The phase change optical information recording medium according to 6), wherein the material constituting the intermediate layer is a material having higher crystallinity than the material constituting the lower protective layer.
8) The phase change type optical information recording medium according to 6) or 7), wherein the material constituting the intermediate layer is a ceramic material made of a simple substance of oxide or carbide, or a mixture thereof.

Hereinafter, the present invention will be described in detail.
In the present invention, by adopting the above configuration, each time recording is performed on the guide groove portion, the reflectance of the recording portion increases, and the unrecorded portion of the guide groove portion can have the lowest reflectance (for example, FIG. 1-D).
An example of the layer structure of the optical information recording medium of the present invention is shown in FIG. Basically, it has a lower protective layer 2, an intermediate layer 3, a phase change recording layer 4, an upper protective layer 5, a reflective layer 6, and an overcoat layer 7 on a transparent substrate 1 having guide grooves. The printed layer 9 may be provided on the overcoat layer, and the hard coat layer 8 may be provided on the mirror surface side of the substrate.
Further, a structure in which the above single plate disk and a transparent substrate or another similar single plate disk are bonded to each other through an adhesive layer 10 may be used. Alternatively, the single-layer disc may be bonded without forming a print layer, and the print layer 9 ′ may be formed on the opposite side after the bonding.

  The material of the substrate is usually one of glass, ceramics, and resin, and the resin substrate is preferable in terms of moldability and cost. Examples of the resin include polycarbonate resin, acrylic resin, epoxy resin, polystyrene resin, acrylonitrile-styrene copolymer resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Polycarbonate resins and acrylic resins that are excellent in terms of moldability, optical characteristics, and cost are preferred.

As a material for the recording layer, a phase change type recording material containing Sb and Te that causes a phase change between a crystal and an amorphous phase, and each of which can be in a stabilized or metastable state, has a recording (amorphization) sensitivity / Suitable for speed, erasure (crystallization) sensitivity / speed, and erasure ratio.
By adding elements such as Ga, Ge, Ag, In, Bi, C, N, O, Si, and S to the SbTe material, recording / erasing sensitivity, signal characteristics, reliability, and the like can be improved. . Therefore, the optimum recording linear velocity is controlled by adjusting the composition ratio of the elements and materials to be added according to the target recording linear velocity and linear velocity region, and at the same time, the reproduction stability of the recorded signal and the life of the signal (reliability) It is desirable to ensure
The phase change optical information recording medium of the present invention contains Ag and / or Ge, Ga and / or In, Sb, and Te as constituent elements as a recording layer material that can satisfy these characteristics comprehensively. When the composition formula is (Ag and / or Ge) _α (Ga and / or In) _β Sb _γ Te _δ (α, β, γ, δ are atomic%, α + β + γ + δ = 100), the following relationship is satisfied The material to be used is preferable because it has excellent signal reproduction stability and signal life.
0 <α ≦ 6
2 ≦ β ≦ 10
60 ≦ γ ≦ 85
15 ≦ δ ≦ 27

The film thickness of the phase change recording layer is preferably 5 to 40 nm. Furthermore, considering initial characteristics such as jitter, overwrite characteristics, and mass production efficiency, the thickness is preferably 10 to 25 nm. If it is thinner than 5 nm, the light absorption ability is remarkably lowered, and the role as a recording layer cannot be achieved. On the other hand, if it is thicker than 40 nm, uniform phase change is difficult to occur at high speed.
Such a phase change recording layer can be formed by various vapor phase growth methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, electron beam deposition, and the like. Among these, the sputtering method is preferable because it is excellent in mass productivity and film quality.

A protective layer is formed below and above the phase change recording layer.
Examples of the material for the protective layer include nitrides such as Si ₃ N ₄ , AlN, TiN, BN, and ZrN; sulfides such as ZnS, In ₂ S ₃ , and TaS ₄ ; or a mixture thereof, or the nitrides and sulfides. And oxides such as SiO, SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, and ZrO ₂ ; carbides such as SiC, TaC, BC, WC, TiC, and ZrC; diamond A mixture with carbon-like carbon may be mentioned, and impurities may be included if necessary. Further, not a single layer but a structure in which two or more layers are stacked may be employed. However, the melting point of the protective layer needs to be higher than that of the phase change recording layer.

Such a protective layer can be formed by various vapor phase growth methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, and electron beam deposition. Among these, the sputtering method is preferable because it is excellent in mass productivity and film quality.
The film thickness of the protective layer greatly affects the reflectivity, modulation degree, and recording sensitivity. In order to satisfy these characteristics, the thickness of the lower protective layer needs to be 30 to 200 nm. In order to obtain better signal characteristics, the thickness is preferably 40 to 100 nm.
The film thickness of the upper protective layer is 5 to 40 nm, preferably 7 to 30 nm. When the thickness is less than 5 nm, the function as a heat-resistant protective layer is not achieved. Further, the recording sensitivity is lowered. On the other hand, if it is thicker than 40 nm, interfacial peeling is likely to occur, and the repeated recording performance also decreases.

An intermediate layer is formed between the lower protective layer and the phase change recording layer. As the material for the intermediate layer, it is desirable to use a material having a hardness higher than that of at least the lower protective layer. In general, a hard material often has a dense crystal structure, and the molecular fluidity is low, so that the chemical influence on adjacent layers is reduced. By including such an intermediate layer, it is possible to suppress physical or chemical alteration at the interface between the lower protective layer and the phase change recording layer due to thermal load caused by repeated recording. The decline in rate can be suppressed. In addition, since the layer having a dense crystalline state is adjacent, the crystalline state after recording of the phase change recording layer material changes to a denser state, thereby increasing the reflectivity of the phase change recording layer. Can do.
When an intermediate layer is formed between the phase change recording layer and the upper protective layer, the effect of promoting the change in the crystalline state of the phase change recording layer material is the same, but on the incident side of the laser beam. Since physical or chemical alteration at the interface between a certain lower protective layer and the phase change recording layer cannot be suppressed, a decrease in reflectance cannot be suppressed.

Specifically, the material of the intermediate layer is a hard material such as a ceramic material. For example, SiO, SiO ₂ , ZnO, SnO ₂ , Al ₂ O ₃ , TiO ₂ , In ₂ O ₃ , MgO, ZrO _From oxides such as ₂ ; carbides such as SiC, TaC, BC, WC, TiC, ZrC; diamond-like carbon; or a mixture thereof, a material having higher hardness than the material used for the lower protective layer is selected. . For example, when ZnS (Knoop hardness of about 200) is used for the lower protective layer, Al ₂ O ₃ (Knoop hardness of about 2000), SiC (Knoop hardness of about 2500) or the like is used as the intermediate layer.
In order to form a layer of these materials, known methods such as various vapor deposition methods (vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method, electron beam deposition method, etc.) are used. That's fine. Among these, the sputtering method is preferable because it is excellent in mass productivity and film quality. At this time, since it is preferable to form a denser film (a film having a higher density) than the lower protective layer, the sputtering conditions are such that the sputtering rate is as low as possible (reducing the gas flow rate, reducing the power, etc.) )
The thickness of the intermediate layer may be set to a thickness that has a small effect on the recording quality. If it is too thick, the recording layer material has a great influence on the change in crystal state, and it becomes difficult to ensure recording quality. If it is too thin, the function of the intermediate layer cannot be fully exhibited. Moreover, since it is a hard film | membrane, when too thick, since the adhesiveness to an adjacent layer becomes low and it will become easy to peel, it is unpreferable. The appropriate film thickness varies depending on the material, but a range of 2 to 20 nm is preferable.

As the reflective layer, a metal material such as Al, Au, Ag, Cu, Ta, Ti, W, or an alloy containing these elements can be used. In addition, in order to improve the corrosion resistance and the thermal conductivity, elements such as Cr, Ti, Si, Cu, Ag, Pd, and Ta may be added to the above materials. The addition ratio is suitably 0.3 to 2 atomic%. If it is less than 0.3 atomic%, the effect of corrosion resistance is inferior. If it exceeds 2 atomic%, the thermal conductivity will be too low and it will be difficult to form an amorphous state.
Such a reflective layer can be formed by various vapor phase growth methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, and electron beam deposition.
The thickness of the reflective layer made of the metal or alloy is 50 to 200 nm, preferably 70 to 160 nm. In addition, the metal or alloy layer can be multi-layered. The thickness of each layer in the case of multilayering is required to be at least 10 nm or more, and the total thickness of the multilayered film is preferably 50 to 160 nm.

An overcoat layer is formed on the reflective layer to prevent oxidation. As the overcoat layer, an ultraviolet curable resin produced by spin coating is generally used. The thickness is suitably 3 to 15 μm. If the thickness is less than 3 μm, an increase in errors may be observed when a printed layer is provided on the overcoat layer. On the other hand, if it is thicker than 15 μm, the internal stress increases, which greatly affects the mechanical properties of the disk.
As the hard coat layer, an ultraviolet curable resin produced by spin coating is generally used. The thickness is suitably 2 to 6 μm. If it is thinner than 2 μm, sufficient scratch resistance cannot be obtained. If it is thicker than 6 μm, the internal stress increases, which greatly affects the mechanical properties of the disk. The hardness must be H or higher, which is a pencil hardness that does not cause large scratches even when rubbed with a cloth. If necessary, it is also effective to mix a conductive material to prevent electrification and prevent adhesion of dust and the like.

  The printed layer is used for the purpose of ensuring scratch resistance, label printing such as a brand name, and forming an ink receiving layer for an ink jet printer, and an ultraviolet curable resin is generally formed by a screen printing method. The thickness is suitably 3 to 50 μm. If it is thinner than 3 μm, unevenness will occur during layer formation. If it is thicker than 50 μm, the internal stress increases, which greatly affects the mechanical properties of the disk.

As the adhesive layer, an adhesive such as an ultraviolet curable resin, a hot melt adhesive, or a silicone resin can be used. The material of such an adhesive layer is applied on the overcoat layer or the print layer by a method such as spin coating, roll coating, or screen printing, depending on the material, and subjected to treatment such as ultraviolet irradiation, heating, and pressurization. Line up and paste the disc on the opposite side. The disk on the opposite surface may be a single-plate disk similar to the above-described layers or a transparent substrate alone, and the adhesive layer material may or may not be applied to the bonding surface of the disk on the opposite surface. Moreover, as an adhesive layer, an adhesive sheet can also be used.
The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 100 μm in view of the effects of material applicability, curability, and disk mechanical properties. The range of the adhesive surface is not particularly limited, but when applied to an optical information recording medium capable of DVD and / or CD compatibility, the position of the inner peripheral edge is 15 to 40 mm in diameter to ensure adhesive strength. The diameter is preferably 15 to 30 mm.

As an initialization method of the phase change type optical information recording medium of the present invention, after the recording medium is configured to a single plate disk or a bonded structure, the apparatus shown in FIG. This is performed by irradiating a continuous laser beam to crystallize the entire recording layer.
As a laser light source, a semiconductor laser (LD) having a large diameter (on the order of 100 μm) is used even if a semiconductor laser (LD) having a small beam diameter (on the order of 0.1 to 1 μm) used in a recording / reproducing apparatus is used. May be used.
The unrecorded reflectance Rb after initialization is 15% or more at the laser light wavelength λ = 770 to 800 nm, and λ = 640 by adjusting the laser light irradiation condition according to the configuration of the optical information recording medium. It is desirable to set it to 18% or more at ˜670 nm. When the reflectance is lower than this, it is not preferable because a trouble may occur when the optical information recording apparatus recognizes the optical information recording medium.

As a recording / reproducing method for a phase change type optical information recording medium according to the present invention, an optical information recording medium is rotated by a driving means comprising a spindle motor by means of an apparatus as shown in FIG. The semiconductor laser light source is driven by the laser driving circuit, and the laser light of the pulse pattern having the front pulse part, the multi-pulse part, and the end pulse part as shown in FIGS. Irradiation causes an optical change in the recording layer of the optical information recording medium, and reflected light from the optical information recording medium is received by a recording / reproducing pickup to record and reproduce information on the optical information recording medium. Is.
The recording means uses a so-called PWM recording (mark edge recording) method in which a signal is recorded as the mark width on the recording layer of the optical information recording medium of the present invention, and the signal to be recorded is used by the clock of the modulator. Thus, for example, recording is performed by modulating with an EFM (Eight-to-Fourteen Modulation, 8-14) modulation method used for information recording on a compact disc or an improved modulation method thereof.

When recording by the PWM recording method, recording or rewriting of a 0 signal whose modulated signal width is nT (n is a predetermined value, T is a clock time: a time corresponding to a clock period used for signal modulation). The recording pulse in the case of performing is assumed to be continuous light of power level Pe (erasing pulse).
Some examples of recording pulse patterns when recording or rewriting one signal whose signal width after modulation is nT are given. As a first example, a time width xT (x is a positive real number). And the front pulse part which is the power level Pw for the heating pulse, the high level pulse of the power level Pw ′ with the total time (n−n ′) time width yT (y is a positive real number of 1 or less) and its high level A multi-pulse part of 1T period having a low level pulse of a power level Pb for a cooling pulse with a time width (1-y) T between pulses, and a power level Pb ′ with a time width zT (z is a positive real number) It is composed of a certain end pulse part, and n and n ′ are positive integers of n ′ ≦ n, and a pulse pattern of recording light having a power level of (Pw and Pw ′)>Pe> (Pb and Pb ′). A method is mentioned. 4 shows a case where n = 6 and n ′ = 2 in the first example, and FIG. 5 shows a case where n = 6 and n ′ = 3.

  As a second example, when n is an odd number and an even number, different patterns are combined. When n is an even number, the power for the heating pulse with the time width x′T (x ′ is a positive real number) is used. The front pulse part at level Pw, the high level pulse of power level Pw 'and its high level with a total time interval of {(n / 2) -1} times y'T (y' is a positive real number less than 2) Multi-pulse part of 2T period having a low level pulse of power level Pb for cooling pulse with time width (2-y ′) T between pulses, and power with time width z′T (z ′ is a positive real number) When n is an odd number, the pulse pattern of the multi-pulse part has a total power of [{(n-1) / 2} -1] time width y'T. The time between the high level pulse of level Pw 'and the high level pulse (2-y ′) T is composed of a 2T period pulse pattern having a low level pulse of power level Pb, where n and n ′ are positive integers of n ′ ≦ n, and the power levels are (Pw and Pw There is a method of forming a pulse pattern of recording light that is ')> Pe> (Pb and Pb'). FIGS. 6 and 7 respectively show the case of n = 6 (even number) and n = 7 (odd number) in the second example.

  As a third example, in the same pulse pattern, the multi-pulse part when n is an odd number has a total time width y′T (y ′ is [{(n−1) / 2} −1] times). A positive real number of 5/2 or less) and a power level with a time width [[n / {(n−1) / 2}] − y ′] T between the high level pulse of the power level Pw ′ and the high level pulse. A method comprising a pulse pattern of [n / {(n-1) / 2}] T period having a low level pulse of Pb is also mentioned. FIG. 8 shows a case where n = 7 in the third example.

The optical information recording medium has a post-recording reflectance Ra of 15% or more at a reproduction laser beam wavelength λ = 770 to 800 nm and 18% or more at λ = 640 to 670 nm when recording is performed by such a method. It is desirable to devise the layer structure.
Specifically, materials and film thicknesses of the phase change recording layer, the upper and lower protective layers, and the reflective layer are mainly selected. That is, among the preferred layer configurations mentioned above, materials having a large reflectance at the laser light wavelength λ = 770 to 800 nm and / or λ = 640 to 670 nm are used, or the thickness of these materials is increased. In addition, in order to increase the reflected light due to interference, the reflectance as a medium can be increased by adjusting the optical path length by increasing / decreasing the film thickness of the protective layer. In the case of a medium used under special recording conditions (different recording power and recording linear velocity region), the appropriate layer structure is different, and accordingly, the phase change recording layer, the upper and lower protective layers, the reflective layer What is necessary is just to change material and film thickness. If the reflectance is lower than the above value, a problem may occur during signal reproduction, and reproduction compatibility may be lowered.
Further, the post-recording reflectance Ra here refers to the maximum reflectance when a recorded signal is reproduced. For example, when a CD compatible signal is recorded, the reflectance of an 11T long space signal is Ra, and when a DVD compatible signal is recorded, the reflectance of a 14T long space signal is Ra.

The ratio Ra (m) / Rb between the reflectance Ra (m) when m times (m is a natural number) direct overwrite (DOW) and the reflectance Rb when not recorded is 1 or more. That is, it is necessary that Ra (m) / Rb ≧ 1. When Ra (m) / Rb <1, the reflectance decreases as the number of times of recording is increased. Therefore, the reflectance necessary for reproducing the optical information recording medium may not be ensured.
Further, when the number of DOWs is 10 times or more and 2000 times or less, that is, when 10 ≦ m ≦ 2000, if Ra (m) /Rb≧1.05, the optical information recording medium can be more easily reproduced. It is possible to ensure the reflectivity necessary to do this. Here, the reason why the upper limit of the number of DOWs is set to 2000 is that the practically required number of DOWs is about 1000, and there is no problem as long as the characteristics of DOW 2000 times that are significantly higher are guaranteed.
Furthermore, Ra (m) / Rb ≧ 1, and the ratio of the reflectance Ra (m) when m times DOW is performed to the reflectance Ra (m + 1) when DOW is performed m + 1 times is as follows. If it is 1 or more, that is, R (m + 1) / R (m) ≧ 1, the reflectivity increases or remains the same as the recording is repeated, so the necessary reflectivity is ensured in the unrecorded state. By doing so, it is more preferable because a necessary reflectance can always be secured after recording.

  According to the present invention, the lower limit of the reflectance is easy to manage, and it is possible to obtain a stable reproduction signal with good reproduction compatibility simply by adjusting the reflectance of the unrecorded state or confirming that it is above the level. Therefore, it is possible to provide a phase change optical information recording medium capable of recording / reproducing with high accuracy.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples.

<Example 1>
A polycarbonate substrate having a thickness of 0.6 mm was prepared by injection molding, and a lower protective layer, an intermediate layer, a phase change recording layer, an upper protective layer, and a reflective layer were sequentially laminated on the substrate by a sputtering method.
The lower and upper protective layers are made of (ZnS) ₈₀ (SiO ₂ ) ₂₀ , the intermediate layer is made of SiC that is harder than (ZnS) ₈₀ (SiO ₂ ) ₂₀ , and the recording layer is made of Ag ₂ Ge ₂ In _4. Ag was used for the Sb ₇₀ Te ₂₂ phase change recording material and the reflective layer, and the film thickness was 80 nm, 3 nm, 20 nm, 15 nm, and 140 nm in order from the substrate side.
Further, an overcoat layer by spin coating of an ultraviolet curable resin was formed on the reflective layer, and a single disk of a phase change type optical information recording medium having DVD-ROM reproduction compatibility was produced.
Next, a polycarbonate substrate was bonded onto the overcoat layer via an adhesive layer, a printing layer was formed on the surface of the polycarbonate substrate (opposite to the bonding surface), and a bonded disk was obtained.
Thereafter, the recording layer of the phase change optical information recording medium was crystallized on the entire surface by an initialization apparatus having a large aperture LD (beam diameter 200 × 1 μm).
The optical information recording medium having DVD-ROM compatibility obtained as described above is recorded with a recording linear velocity of 8.5 m / s and a recording power Pw (MP5125A manufactured by Ricoh Co., Ltd.). = Pw ′) = 15 mW, 1 time recording, 2 times, 3 times, 4 times, 5 times, 10 times, 11 times, 100 times, 101 times, 1000 times, 1001 times, 2000 times, 2001 times Direct overwrite (DOW) was performed.
With respect to each of these recorded portions and unrecorded portions, the reflectance was measured by a DVD playback evaluation apparatus (DDU-1000 manufactured by Pulstec Industrial Co., Ltd.) using a laser beam wavelength λ = 650 nm. As shown in the results, the unrecorded reflectance Rb = 19.2%, the reflectance Ra (1) after one recording = 19.6%, and the reflectance Ra (2) after two recordings = 11.9. 8%, reflectance Ra (3) after 3 times recording = 20.0%, reflectance Ra (4) after 4 times recording = 20.2%, reflectance Ra (5) after 5 times recording = 20 .3% Reflectance Ra (10) after 10 times DOW = 20.4%, Reflectance Ra (11) after 11 times recording = 20.4%, Reflectance Ra (100) after 100 times DOW = 20.8%, reflectance Ra (101) after 101 recordings = 20.8%, 1000 times DO Reflectance Ra (1000) = 21.3% after, Reflectance Ra (1001) after recording 1001 times = 11.3%, Reflectance Ra (2000) after 2000 times DOW = 21.4%, 2001 times The reflectance Ra after recording (2001) = 21.4%, and the reflectance ratio after unrecorded / recorded is Ra (1) /Rb=1.02 and Ra (2) /Rb=1.03, respectively. , Ra (3) /Rb=1.04, Ra (4) /Rb=1.05, Ra (5) /Rb=1.06, Ra (10) /Rb=1.06, Ra (11) / Rb = 1.06, Ra (100) /Rb=1.08, Ra (101) /Rb=1.08, Ra (1000) /Rb=1.11, Ra (1001) /Rb=1.11, Ra (2000) /Rb=1.11 and Ra (2001) /Rb=1.11.
When this optical information recording medium was reproduced by a DVD-ROM reproducing device (MP9120A manufactured by Ricoh Co., Ltd.), it could be reproduced without any problem.

<Example 2>
A polycarbonate substrate having a thickness of 1.2 mm was prepared by injection molding, and a lower protective layer, an intermediate layer, a phase change recording layer, an upper protective layer, and a reflective layer were sequentially laminated on the substrate by a sputtering method.
The lower and upper protective layers are made of (ZnS) ₈₀ (SiO ₂ ) ₂₀ , the intermediate layer is made of SiO ₂ that is harder than (ZnS) ₈₀ (SiO ₂ ) ₂₀ , and the recording layer is made of Ag ₂ In ₈ Sb. ₆₅ Te ₂₅ phase change recording material, Al ₉₈ Ti ₂ was used for the reflective layer, and the film thickness was 90 nm, 10 nm, 20 nm, 30 nm and 140 nm in order from the substrate side.
Further, an overcoat layer formed by spin coating of an ultraviolet curable resin was formed on the reflective layer to produce a phase change optical information recording medium having CD-ROM reproduction compatibility.
Thereafter, the recording layer of the phase change optical information recording medium was crystallized on the entire surface by an initialization apparatus having a large aperture LD (beam diameter 100 × 1 μm).
With respect to the CD-ROM compatible optical information recording medium obtained in this way, a recording linear velocity of 12.0 m / s and a recording power Pw (recording power Pw (MP7120A manufactured by Ricoh Co., Ltd.)) can be used. = Pw ′) = 20 mW, 1 time recording, 2 times, 3 times, 4 times, 5 times, 10 times, 11 times, 100 times, 101 times, 1000 times, 1001 times, 2000 times, 2001 times DOW recording was performed.
With respect to each of these recorded portions and unrecorded portions, the reflectance was measured by a CD reproduction evaluation apparatus (DDU-1000 manufactured by Pulstec Industrial Co., Ltd.) using a laser beam wavelength λ = 780 nm. As shown in FIG. 4, the unrecorded reflectance Rb = 17.6%, the reflectance Ra (1) after one recording = 17.8%, and the reflectance Ra (2) after two recordings = 18.0. 0%, reflectance Ra (3) after 3 times recording = 18.1%, reflectance Ra (4) after 4 times recording = 18.3%, reflectance Ra (5) = 5 times after recording .3%, reflectance Ra (10) after 10 times DOW = 18.5%, reflectance Ra (11) after 11 times recording = 18.5%, reflectance Ra (100) after 100 times DOW = 18.8%, reflectance Ra (101) after recording 101 times = 18.8%, 1000 times DOW Reflectance Ra (1000) = 19.3%, reflectance Ra (1001) after 1001 recording = 19.3%, reflectance Ra (2000) after 2000 times DOW = 19.4%, recording 2001 times The subsequent reflectance Ra (2001) = 19.4%, and the reflectance ratio after unrecorded / recorded is Ra (1) /Rb=1.01, Ra (2) /Rb=1.02, Ra (3) /Rb=1.03, Ra (4) /Rb=1.04, Ra (5) /Rb=1.04, Ra (10) /Rb=1.05, Ra (11) / Rb = 1.05, Ra (100) /Rb=1.07, Ra (101) /Rb=1.07, Ra (1000) /Rb=1.10, Ra (1001) /Rb=1.10, Ra (2000) /Rb=1.10 and Ra (2001) /Rb=1.10.
When this optical information recording medium was reproduced by a CD-ROM reproducing device (MP9120A manufactured by Ricoh Co., Ltd.), it could be reproduced without any problem.

<Example 3>
A polycarbonate substrate having a thickness of 0.6 mm was formed by injection molding, and a lower protective layer, an intermediate layer, a phase change recording layer, an upper protective layer, and a reflective layer were sequentially laminated on the substrate by a sputtering method.
The lower and upper protective layers are (ZnS) ₈₀ (SiO ₂ ) ₂₀ , the intermediate layer is Al ₂ O ₃ , which is harder than (ZnS) ₈₀ (SiO ₂ ) ₂₀ , and the recording layer is Ag ₂ Ge. ₂ In ₄ Sb ₇₂ Te ₂₀ phase change recording material, Ag was used for the reflective layer, and the film thickness was 70 nm, 5 nm, 15 nm, 15 nm, and 120 nm in order from the substrate side.
Further, an overcoat layer by spin coating of an ultraviolet curable resin was formed on the reflective layer, and a single disk of a phase change type optical information recording medium having DVD-ROM reproduction compatibility was produced.
Next, a polycarbonate substrate was bonded onto the overcoat layer via an adhesive layer, a printing layer was formed on the surface of the polycarbonate substrate (opposite to the bonding surface), and a bonded disk was obtained.
Thereafter, the recording layer of the phase change type optical information recording medium was crystallized on the entire surface by an initialization apparatus having a large aperture LD (beam diameter 75 × 1 μm).
The optical information recording medium having DVD-ROM compatibility obtained in this manner is recorded with a DVD-compatible optical information recording apparatus (MP5240A, manufactured by Ricoh Co., Ltd.) with a recording linear velocity of 14.0 m / s and a recording power Pw ( = Pw ′) = 20 mW, 1 time recording, 2 times, 3 times, 4 times, 5 times, 10 times, 11 times, 100 times, 101 times, 1000 times, 1001 times, 2000 times, 2001 times DOW recording was performed.
With respect to each of these recorded portions and unrecorded portions, the reflectance was measured by a DVD playback evaluation apparatus (DDU-1000 manufactured by Pulstec Industrial Co., Ltd.) using a laser beam wavelength λ = 650 nm. As shown in the graph, the unrecorded reflectance Rb = 18.4%, the reflectance Ra (1) after one recording is 18.7%, and the reflectance Ra (2) after two recordings is 18.2. 9% Reflectance Ra (3) after 3 times recording = 19.1% Reflectance Ra (4) after 4 times recording = 19.2% Reflectance Ra (5) after 5 times recording 19 .3%, reflectance Ra (10) after 10 times DOW = 19.4%, reflectance Ra (11) after 11 times recording = 19.4%, reflectance Ra (100) after 100 times DOW = 20.0%, reflectance Ra (101) after recording 101 times = 20.0%, 1000 times DO Reflectance Ra (1000) = 20.8% after recording, Reflectance Ra (1001) after recording 1001 times = 20.8%, Reflectance Ra (2000) after 2000 times DOW = 21.0%, 2001 times The reflectance Ra (2001) after recording is 21.0%, and the reflectance ratio after unrecorded / recorded is Ra (1) /Rb=1.02 and Ra (2) /Rb=1.03, respectively. , Ra (3) /Rb=1.04, Ra (4) /Rb=1.04, Ra (5) /Rb=1.05, Ra (10) /Rb=1.05, Ra (11) / Rb = 1.05, Ra (100) /Rb=1.09, Ra (101) /Rb=1.09, Ra (1000) /Rb=1.13, Ra (1001) /Rb=1.13, Ra (2000) /Rb=1.14 and Ra (2001) /Rb=1.14.
When this optical information recording medium was reproduced by a DVD-ROM reproducing device (MP9120A manufactured by Ricoh Co., Ltd.), it could be reproduced without any problem.

<Example 4>
A polycarbonate substrate having a thickness of 0.6 mm was formed by injection molding, and a lower protective layer, an intermediate layer, a phase change recording layer, an upper protective layer, and a reflective layer were sequentially laminated on the substrate by a sputtering method.
The lower and upper protective layer _{(ZnS) 80 (SiO 2)} 20, the intermediate layer is a material having higher hardness than _{(ZnS) 80 (SiO 2)} 20 (ZrO 2) 80 (TiO 2) 20, a recording Ag ₂ Ge ₂ In ₄ Sb ₇₂ Te ₂₀ phase change recording material was used for the layer, Ag was used for the reflective layer, and the film thickness was 70 nm, 5 nm, 15 nm, 15 nm, and 120 nm in order from the substrate side.
Further, an overcoat layer by spin coating of an ultraviolet curable resin was formed on the reflective layer, and a single disk of a phase change type optical information recording medium having DVD-ROM reproduction compatibility was produced.
Next, a polycarbonate substrate was bonded onto the overcoat layer via an adhesive layer, a printing layer was formed on the surface of the polycarbonate substrate (opposite to the bonding surface), and a bonded disk was obtained.
Thereafter, the recording layer of the phase change type optical information recording medium was crystallized on the entire surface by an initialization apparatus having a large aperture LD (beam diameter 75 × 1 μm).
The optical information recording medium having DVD-ROM compatibility obtained in this way is recorded with a recording linear velocity of 3.5 m / s and a recording power Pw (recording power Pw (MP5240A manufactured by Ricoh Co., Ltd.) compatible with DVD). = Pw ′) = 16 mW, 1 time recording, 2 times, 3 times, 4 times, 5 times, 10 times, 11 times, 100 times, 101 times, 1000 times, 1001 times, 2000 times, 2001 times DOW recording was performed.
With respect to each of these recorded portions and unrecorded portions, the reflectance was measured by a DVD playback evaluation apparatus (DDU-1000 manufactured by Pulstec Industrial Co., Ltd.) using a laser beam wavelength λ = 650 nm. As shown in the results, the unrecorded reflectance Rb = 18.5%, the reflectance Ra (1) after one recording = 19.7%, and the reflectance Ra (2) after two recordings = 11.9. Reflectivity Ra (3) after 3 times recording 8% = 19.9% Reflectance Ra (4) after 4 times recording = 19.9% Reflectance Ra (5) after 5 times recording 19 .9%, reflectance Ra (10) after 10 times DOW = 20.0%, reflectance Ra (11) after 11 times recording = 20.0%, reflectance Ra (100) after 100 times DOW = 20.2%, reflectance Ra (101) after recording 101 times = 20.2%, 1000 times DO Reflectance Ra (1000) = 20.4% after, Reflectance Ra (1001) after recording 1001 times = 20.4%, Reflectance Ra (2000) after 2000 times DOW = 20.5%, 2001 times The reflectance Ra after recording (2001) = 20.5%, and the reflectance ratio after unrecorded / recorded is Ra (1) /Rb=1.06 and Ra (2) /Rb=1.07, respectively. , Ra (3) /Rb=1.08, Ra (4) /Rb=1.08, Ra (5) /Rb=1.08, Ra (10) /Rb=1.08, Ra (11) / Rb = 1.08, Ra (100) /Rb=1.09, Ra (101) /Rb=1.09, Ra (1000) /Rb=1.10, Ra (1001) /Rb=1.10, Ra (2000) /Rb=1.11 and Ra (2001) /Rb=1.11.
When this optical information recording medium was reproduced by a DVD-ROM reproducing device (MP9120A manufactured by Ricoh Co., Ltd.), it could be reproduced without any problem.

<Example 5>
A polycarbonate substrate having a thickness of 1.2 mm was prepared by injection molding, and a lower protective layer, an intermediate layer, a phase change recording layer, an upper protective layer, and a reflective layer were sequentially laminated on the substrate by a sputtering method.
The lower and upper protective layer _{(ZnS) 80 (SiO 2)} 20, the intermediate layer is a material having higher hardness than _{(ZnS) 80 (SiO 2)} 20 (ZrO 2) 80 (TiO 2) 20, a recording The layer was made of Ag ₂ In ₈ Sb ₆₅ Te ₂₅ phase change recording material, the reflective layer was made of Al ₉₈ Ti ₂ , and the film thicknesses were set to 80 nm, 5 nm, 18 nm, 25 nm, and 140 nm in this order from the substrate side.
Further, an overcoat layer formed by spin coating of an ultraviolet curable resin was formed on the reflective layer to produce a phase change optical information recording medium having CD-ROM reproduction compatibility.
Thereafter, the recording layer of the phase change optical information recording medium was crystallized on the entire surface by an initialization apparatus having a large aperture LD (beam diameter 100 × 1 μm).
With respect to the CD-ROM compatible optical information recording medium obtained in this way, a recording linear velocity of 12.0 m / s and a recording power Pw (recording power Pw (MP7120A manufactured by Ricoh Co., Ltd.)) can be used. = Pw ′) = 20 mW, 1 time recording, 2 times, 3 times, 4 times, 5 times, 10 times, 11 times, 100 times, 101 times, 1000 times, 1001 times, 2000 times, 2001 times DOW recording was performed.
With respect to each of these recorded portions and unrecorded portions, the reflectance was measured by a CD reproduction evaluation apparatus (DDU-1000 manufactured by Pulstec Industrial Co., Ltd.) using a laser beam wavelength λ = 780 nm. As shown in FIG. 4, the unrecorded reflectance Rb = 17.2%, the reflectance Ra (1) after one recording = 17.5%, and the reflectance Ra (2) after two recordings = 17.7. Reflectance Ra (3) after 3 times recording 6% = 17.6% Reflectance Ra (4) after 4 times recording = 17.7% Reflectance Ra (5) after 5 times recording 17 .7%, reflectance Ra (10) after 10 times DOW = 17.9%, reflectance Ra (11) after 11 times recording = 17.9%, reflectance Ra (100) after 100 times DOW = 18.2%, reflectance Ra (101) after 101 recordings = 18.2%, 1000 DOWs Reflectance Ra (1000) = 18.5%, reflectance Ra (1001) after 1001 recording = 18.5%, reflectance Ra (2000) after 2000 times DOW = 18.6%, recording 2001 times The subsequent reflectance Ra (2001) = 18.6%, and the reflectance ratio after unrecorded / recorded is Ra (1) /Rb=1.02, Ra (2) /Rb=1.02, Ra (3) /Rb=1.02, Ra (4) /Rb=1.03, Ra (5) /Rb=1.03, Ra (10) /Rb=1.04, Ra (11) / Rb = 1.04, Ra (100) /Rb=1.06, Ra (101) /Rb=1.06, Ra (1000) /Rb=1.08, Ra (1001) /Rb=1.08, Ra (2000) /Rb=1.08 and Ra (2001) /Rb=1.08.
When this optical information recording medium was reproduced by a CD-ROM reproducing device (MP9120A manufactured by Ricoh Co., Ltd.), it could be reproduced without any problem.

The figure which shows the relationship between the frequency | count of recording of a phase change type optical information recording medium, and a reflectance ratio. The figure which shows an example of the layer structure of the phase change type | mold optical information recording medium of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a recording / reproducing apparatus for a phase change optical information recording medium according to the present invention. Explanatory drawing of a recording pulse strategy (when 1T period: n = 6, n ′ = 2). Explanatory drawing of a recording pulse strategy (when 1T period: n = 6, n '= 3). Explanatory drawing of a recording pulse strategy (2T period: n = 6, that is, even number). Explanatory drawing of a recording pulse strategy (2T period: n = 7, ie, odd number). Explanatory drawing of a recording pulse strategy [n / {(n-1) / 2}]: n = 7).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Lower protective layer 3 Intermediate layer 4 Phase change recording layer 5 Upper protective layer 6 Reflective layer 7 Overcoat layer 8 Hard coat layer 9 Print layer 9 'Print layer 10 Adhesive layer T Clock time Pw Power level for heating pulse Pw ′ Power level for heating pulse Pe Power level for erasing pulse Pb Power level for cooling pulse Pb ′ Power level for cooling pulse x Positive real number x ′ Positive real number y Positive real number less than 1 y ′ Less than 2 (In the case of FIG. 6, FIG. 7) or 7/3 or less (in the case of FIG. 8) positive real number z positive real number z ′ positive real number

Claims (8)

  Light that has at least a phase change recording layer on a substrate having concentric or spiral guide grooves, and causes recording and / or rewriting of information by causing a phase change in the recording layer by irradiation with a semiconductor laser beam. In the information recording medium, when the reflectance Rb of the unrecorded portion of the guide groove is compared with the reflectance Ra (m) when overwriting (direct overwrite, DOW) is performed m times (m is a natural number), Ra (m) / Rb ≧ 1 Phase change optical information recording medium   2. The phase change optical information recording medium according to claim 1, wherein Ra (m) /Rb≧1.05 when 10 ≦ m ≦ 2000.   Light that has at least a phase change recording layer on a substrate having concentric or spiral guide grooves, and causes recording and / or rewriting of information by causing a phase change in the recording layer by irradiation with a semiconductor laser beam. In the information recording medium, the reflectance Ra (m) when the overwrite recording (direct overwrite, DOW) is performed m times (m is a natural number) in the guide groove, and the reflectance Ra (m + 1) when DOW is performed m + 1 times. ) And Ra (m + 1) / Ra (m) ≧ 1, a phase change optical information recording medium characterized in that   4. The phase change optical information recording medium according to claim 1, wherein Rb ≧ 18% and Ra (m) ≧ 18% at a laser light wavelength λ = 640 to 670 nm.   4. The phase change optical information recording medium according to claim 1, wherein Rb ≧ 15% and Ra (m) ≧ 15% at a laser light wavelength λ = 770 to 800 nm.   6. The phase change optical information recording according to claim 1, wherein a lower protective layer, an intermediate layer, a phase change recording layer, an upper protective layer, and a reflective layer are sequentially formed on the substrate. Medium.   7. The phase change optical information recording medium according to claim 6, wherein the material constituting the intermediate layer is a material having higher crystallinity than the material constituting the lower protective layer. 8. The phase change optical information recording medium according to claim 6, wherein the material constituting the intermediate layer is a ceramic material made of a single substance of oxide or carbide, or a mixture thereof.

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