JP2002237092A - Optical information recording medium and information recording method therefor, information erasing method therefor, and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium in which the transparency of a phase change recording film is made substantially uniform regardless of whether or not recording is performed and, preferably, information is excellently recorded with high density, reproduced and erased, and a information recording method therefor, information erasing method therefor, and manufacturing method therefor. SOLUTION: This optical information recording medium has a plurality of phase change type optical recording layers stacked to form a phase change recording film 22 where information is recorded and erased by a phase change by irradiation with laser beam. An upper transparent protection film 23 and a lower transparent protection film 21 which protect thermal deformation when the information is recorded and erased are formed on and beneath the phase change recording film 22, respectively. Further, a base interference film 25 which controls the transmissivity of the phase change recording film 22 to the laser beam is formed beneath the lower transparent protection film 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium on which information is recorded, reproduced and erased using a laser beam, an information recording method thereof, and an information erasing method thereof.
In particular, the present invention relates to an optical information recording medium suitable for increasing the density of information, an information recording method thereof, and an information erasing method thereof.

[0002]

2. Description of the Related Art Optical disk recording using laser light is capable of high-capacity recording and can be accessed in a non-contact manner at a high speed.
Optical disks are classified into a read-only type such as a compact disk and a laser disk, a write-once type that can be recorded by the user himself, and a rewritable type that can repeatedly record and erase on the user side. A write-once or rewritable optical disk is used as an external memory of a computer or a recording medium for documents and image files.

In a read-only optical disk, a CD
-Data files typified by ROM have rapidly spread, and are used as high-density recording media in the personal field. Focusing on the large capacity of this CD-ROM, application as a disk for multimedia files including image data by image compression technology such as MPEG2 is being studied. For this purpose, the current capacity of 650 MB per disk is not sufficient, and DVD-ROMs having a capacity eight times the current capacity have begun to be commercialized. On the other hand, DVD players that provide small, high-quality video have begun to be shipped as read-only consumer image file devices, such as laser disks, but further densification of optical disks for high-vision playback is still important. It has become a challenge.

On the other hand, in the write-once optical disc, a certain market is secured in an application field in which the merit that recorded information can be stored stably is utilized to the utmost. Also in this application, it is needless to say that increasing the capacity and increasing the density are important issues to be considered in order to take advantage of economies of scale.

[0005] As rewritable optical disks, there are a phase change optical disk utilizing a phase change of a recording film and a magneto-optical disk utilizing a change in the magnetization direction of a perpendicular magnetization film. Of these, magneto-optical disks have begun to appear as products having four times the capacity of the first generation, and those having eight times or more capacity are being studied. on the other hand,
No external magnetic field is required for phase change optical discs,
Since overwriting can be performed easily, it is expected that rewritable optical disks will become the mainstream along with magneto-optical disks in the future. As for a phase change optical disk, a product equivalent to eight times the capacity of magneto-optics, such as a DVD-RAM having a capacity of 2.6 GB, has begun to be sold. Also in these rewritable optical disks, increasing the capacity and increasing the density are important issues.

Next, the structure of these conventional optical disks will be described. In a read-only optical disk, an Al alloy-based metal reflection film is formed on a concave / convex pit previously formed by injection molding on a substrate, and is used for reproduction. In a write-once optical disc, Te,
An alloy material of a low melting point metal such as Bi, Se or Sn or a dye material having absorption characteristics at a used laser wavelength is thinly applied on a substrate to form a recording film. A rewritable magneto-optical disk employs a structure in which an alloy thin film of a rare earth metal such as Tb, Gd, Dy, and Ho and a transition metal such as Fe, Co, and Ni is sandwiched between transparent protective films such as SiN. In a rewritable phase-change optical disk, a chalcogenide-based thin film made of GeSbTe, InSbTe, or the like is used as a recording film. The recording film of the phase-change optical disk includes an InSe-based thin film, In
Te-based thin film, AsTeGe-based thin film, TeOx-GeSn
System-based thin films, TeSeSn-based thin films, SbSeBi-based thin films, BiSeGe-based thin films, and the like are also used. These thin films are formed by a film forming method such as a resistance heating vacuum evaporation method, an electron beam vacuum evaporation method or a sputtering method, or a spin coating method.

As described above, a large capacity and a high density are required. However, in the conventional read-only, write-once, and rewritable optical disks as described above, a transparent and rigid substrate is provided on a substrate having transparency and rigidity. A so-called single-layer configuration in which uneven pits, a write-once recording film, a magneto-optical recording film, or a phase change recording film are formed is employed.

Further, a partial ROM disk in which a read-only portion, a write-on portion, and a rewrite portion are divided and formed on an inner periphery and an outer periphery on the same substrate has been proposed and manufactured (for example,
"Erasable Optical Disc Technology" p. 249, published by Trikeps Corporation, 1991).

However, since the above-mentioned optical disk and hybrid type disk have a single-layer structure, it is difficult to dramatically improve the recording capacity. In addition, in the case of a double-sided disk in which a single disk is bonded to improve the recording capacity, simultaneous access to both sides using a normal disk drive requires a change in the head and the like, resulting in cost. And it is difficult to implement.

Therefore, as a read-only type optical disk, a read-only type multilayer disk in which two or more multilayer films are accessed from one side has been proposed (for example, K.K.
"Multilayer Volumetric Storage Topic" by Rubin et al.
al Meeting Technical Digest ”, WA3-1, Optical D
ata Storage Topical Meeting Technical Digest (19
94)). Further, the DVD standard for reproduction only specifies a two-layer disc, and employs a method of reproducing information recorded in two layers from one side.

When considering the improvement of the recording density of an optical disk, a rewritable optical disk on which information can be rewritten is extremely useful. Therefore, securing a practical performance with a single-sided multilayer structure has been considered as an issue.

In view of this, an optical information recording medium having a two-layered recording film has been proposed as a rewritable optical disk utilizing a phase change (Japanese Patent Laid-Open No. 3-157830).

[0013] Further, two-layer recording on a phase change optical disk has been reported (for example, Nagata et al., "A rewritable two-layer phase change optical disk" (Preliminary Proceedings of the 59th Autumn Meeting of the Japan Society of Applied Physics 15a-). V-5, p100
8, (1998. 9.15)).

[0014]

However, in the conventional optical information recording medium described in Japanese Patent Application Laid-Open No. 3-157830, recording is not performed on each of the two recording layers, but is simply performed by using a reproduction signal. Only a two-layer structure is employed as a means for adding a desired phase difference to the image data. For this reason, the improvement of the recording capacity is insufficient.

In the optical disk reported by the above-mentioned lecture, the transmittance change between the recording mark portion and the non-recording portion is usually large due to the optical change of the recording film in the first layer. If there is no record in the eyes,
The amount of light transmitted to the second layer is significantly different from the case where recording is performed on the first layer. For this reason, there is a problem that good recording and reproduction cannot be performed unless the power level irradiated during recording and reproduction on the second layer is changed.

The present invention has been made in view of such a problem, and it is possible to make the transmittance of a phase change recording film substantially uniform regardless of the presence or absence of recording, and it is preferable that the film has a high density and a good density. An object of the present invention is to provide an optical information recording medium capable of recording, reproducing, and erasing information, an information recording method thereof, an information erasing method, and a manufacturing method thereof.

[0017]

According to the present invention, there is provided an optical information recording medium comprising a plurality of first layers on at least a transparent substrate.
A phase change optical recording layer and a second phase change optical recording layer are stacked in this order, and a transparent spacer is disposed between the first phase change optical recording layer and the first and second phase change optical recording layers. The first phase-change optical recording layer includes a base interference film, a transparent lower protective film, a phase-change recording film, and a transparent upper protective film, which are arranged at least in this order. A transparent lower protective film, a phase change recording film, a transparent upper protective film, and a metal reflective film are arranged at least in this order, and the base interference film is a film for adjusting light transmittance.

In the present invention, since the base interference film for adjusting the transmittance of the laser light in the phase change recording film is formed in the phase change type optical recording layer, regardless of the presence or absence of recording on the phase change recording film. An almost constant transmittance is obtained. Therefore,
By laminating such a phase change type optical recording layer, it is possible to record, reproduce and erase information at a high density and good.

In particular, in the present invention, the transmittance of the phase change recording film in the area where information is recorded is 0.95 to 1.05 in the area where information is not recorded.
The thickness of the base interference film is set to be twice as large.

In the above configuration, a plurality of first phase change type optical recording layers are provided. However, one first phase change type optical recording layer and one second phase change type optical recording layer 1 are provided. An optical information recording medium in which layers are stacked may be used. In this case, high-density and good recording, reproduction, and erasing can be performed, and the configuration is simple.

Further, in the present invention, a configuration may be adopted in which two optical information recording media having the above configuration are bonded via an adhesive layer such that the second phase change type optical recording layer side faces each other.

Further, the optical information recording medium of the present invention has a third phase change film in which a base interference film, a transparent lower protective film, a phase change recording film, and a transparent upper protective film are arranged in this order on a transparent substrate. A third optical recording layer having a metal reflective film, a transparent lower protective film, a phase change recording film, and a transparent upper protective film arranged in this order on a substrate; And the fourth phase-change optical recording layer are laminated with a transparent spacer interposed therebetween such that the upper transparent protective film located on the top of both recording layers faces each other. Is also good.

As a method of manufacturing an optical information recording medium having this structure, according to the present invention, a base interference film, a transparent lower protective film, a phase change recording film, and a transparent upper protective film are sequentially formed on a transparent substrate. And a second step of sequentially forming a metal reflective film, a transparent lower protective film, a phase change recording film, and a transparent upper protective film on a substrate, and forming the first step. The phase-change optical recording layer and the phase-change optical recording layer formed in the second step are bonded together so that the uppermost transparent upper protective film faces each other. .

Further, in the information recording method according to the present invention, the optical information recording medium having the above-described structure is irradiated with laser light from the transparent substrate side while changing the light condensing position, so that at least one of the phase information is irradiated. Information is recorded by a process of causing a phase change in the change recording film.

Further, in the information erasing method according to the present invention, the optical information recording medium having the above-described structure is irradiated with laser light from the transparent substrate side while changing the light condensing position, so that at least one of the phase information is irradiated. Information is erased by a process of causing a phase change in the change recording film.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an optical information recording medium according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. FIG. 1 is a schematic sectional view showing the structure of the optical information recording medium according to the first embodiment of the present invention.

In the first embodiment, three phase-change optical recording layers 2a to 2c are laminated on a transparent rigid substrate 1 via transparent spacers 3a and 3b. Further, a transparent spacer 3 is formed on the third phase-change optical recording layer 2c.
The phase-change optical recording layer 2d is formed via the layer c. Recording, reproduction, or erasure of information is performed on the phase-change optical recording layers 2a to 2d by irradiating laser light.

As the transmissive rigid substrate 1, a transparent resin substrate and a glass substrate conventionally used for optical disks can be used. The thickness of the optical disc may be any thickness as long as the rigidity of the optical disc is ensured. Depending on the design value of the condenser lens of the optical disc head to be used, the thickness of 1.2 mm usually used for compact discs (CDs) is used. The thickness may be other than that, for example, 0.4 mm, 0.6 mm, or 0.8 mm. It is also possible to make the substrate thicker than 1.2 mm.

Each of the phase-change optical recording layers 2a to 2c includes a base interference film, a transparent lower protective film, a phase-change recording film, and a transparent upper protective film. FIG. 2 is a sectional view showing the structure of the first-layer phase-change optical recording layer 2a.

The phase change type optical recording layer 2 a is provided with a base interference film 25 formed on the transparent rigid substrate 1.
The base interference film 25 is formed of a material having a high refractive index to extract an interference effect, and a Si film or a Ge film can be used. Also, an oxide film containing Si as a main component, S
A nitride film containing i as a main component, an oxide film containing Ge as a main component, or a nitride film containing Ge as a main component can also be used. Of course,
Needless to say, a high refractive index dielectric film other than these films can be used as long as the interference effect is obtained. The transmittance of laser light in the phase change recording film 22 is adjusted by the base interference film 25.

Further, on the base interference film 25, a transparent lower protective film 21 for protecting the phase change recording film 22 mainly from thermal deformation at the time of recording and erasing information is formed. As the transparent lower protective film 21, a protective film containing ZnS and SiO ₂ as main components is used.

Further, on the transparent lower protective film 21, a phase change recording film 22 is formed. The phase change recording film 22 includes
A thin film mainly composed of Ge, Sb and Te is used.
Specifically, a Ge ₂ Sb ₂ Te ₅ film, a Ge ₁ Sb ₂ Te ₄ film,
Ge ₁ Sb ₄ Te ₇ film, a film to which Ge, Sb or Te is added in a small amount, and Pd, Pt, A as the fourth element
A film to which a small amount of u, Ag, Ti or Cu is added is used as the phase change recording film 22. The thickness of the phase change recording film 22 is about 5 to 30 nm, and high transmitted light can be obtained.

Further, on the phase change recording film 22, a transparent upper protective film 23 for protecting the phase change recording film 22 mainly from thermal deformation at the time of recording and erasing of information is formed. Like the transparent lower protective film 21, the transparent upper protective film 23
A protective film containing ZnS and SiO ₂ as main components is used.

The structure of the phase-change optical recording layers 2b and 2c is the same as that of the first embodiment except that a base interference film is formed not on the transparent rigid substrate 1 but on the transparent spacer 3a or 3b.
This is the same as the phase change type optical recording layer 2a.

In these phase-change optical recording layers 2a to 2c, by making the thickness of the base interference film appropriate, it is possible to remarkably suppress the difference in transmittance due to the presence or absence of recording marks. . FIGS. 4A and 4B are graphs showing the relationship between the thickness of the underlying interference film on the horizontal axis and either the transmittance or the reflectance on the vertical axis.
In FIG. 4, a solid line indicates an area where a recording mark exists, that is, an area where recording is performed, and a broken line indicates an area where no recording mark exists, that is, an area where recording is not performed. ing.

The optical characteristics shown in FIG. 4 are those of the following phase change type optical recording layer. The base interference film is a Si film,
Its optical constant is Si (4.52, 0.15i).
The transparent lower protective film and the transparent upper protective film are ZnS-SiO ₂
And the optical constant is ZnS—SiO
₂ (2.10, 0.0i), and its film thickness is 150 nm. The phase change recording film is a film made of GeSbTe, and its optical constant is GeSbTe (3.9) in a crystalline state.
1, 4.22i), GeSb in the amorphous state
Te (4.13, 1.89i), the thickness of which is 16 nm. The wavelength of the laser light is 660 nm.

As shown in FIG. 4A, when the thickness of the Si film as the base interference film is 100 nm, the transmittance for GeSbTe in the amorphous state corresponding to the recording mark becomes 37.2%, and the unrecorded state. Has a transmittance of 36.4% with respect to GeSbTe in the crystalline state corresponding to the erased state. Thus, the transmittance of the amorphous phase change recording film is 1.03 times that of the crystalline phase change recording film. Accordingly, the difference between these transmittances is extremely small, and it is possible to record, reproduce, and erase good information. The transmittance of the phase change recording film in the area where the information is recorded is:
0.95 of transmittance in an area where no information is recorded
Desirably, it is about 1.05 times.

As described above, the phase change type optical recording layers 2a to 2a
In c, it is possible to design so that 30 to 50% of transmitted light is generated.

The transparent spacer 3 has a thickness of 5 to 30 μm.
It is composed of a photocurable resin such as a photopolymer of m. The thickness of the transmissive spacer 3 is set sufficiently thicker than the depth of focus determined by the characteristics of the condenser lens used and the laser wavelength. Here, by making the condensing position of the incident condensed laser light variable, the phase-change optical recording layer 2 is formed.
It becomes possible to perform recording, reproduction and erasure on a to 2d.

The fourth phase change type optical recording layer 2d is composed of a transparent lower protective film, a phase change recording film, a transparent upper protective film, and a metal reflection film. FIG. 3 is a sectional view showing a fourth phase-change optical recording layer 2d.

In the fourth phase change type optical recording layer 2d, a transparent lower protective film 21a, a phase change recording film 22a and a transparent upper protective film 23a are formed on the transparent spacer 3c. It is formed similarly to the phase change type optical recording layer. These materials are the same as those of the first to third phase-change optical recording layers.

In the fourth phase change type optical recording layer 2d, a metal reflective film 24a is further formed on the transparent upper protective film 23a.
Is formed. Al, Ag,
A metal film containing Au or Pt as a main component is used.

The metal reflection film 24a may not be provided. In this case, light is transmitted through the uppermost phase-change optical recording layer. However, when it is not necessary to transmit light, it is desirable to provide a metal reflective layer on the uppermost phase-change optical recording layer in order to enable the reflected light to be efficiently used for signal reproduction.

In recording, reproducing or erasing information on the optical information recording medium according to the first embodiment configured as described above, as shown in FIG. 1, a laser used for recording, reproducing or erasing information is used. Light 10 is condensed by a condenser lens 11 and is incident from the outside through the transparent rigid substrate 1.

For this reason, when recording / reproducing on the upper phase change type optical recording layer, the laser light transmitted through the lower phase change type optical recording layer is used. It is necessary to set the thickness of each film so that the transmittance is not less than a predetermined value at the wavelength of the laser to be used.

In the first to third phase-change optical recording layers 2a to 2c, if the transmittance is significantly different between the case where the recording mark is present and the case where the recording mark is not present, the transmittance in that region is different. , And there is also a difference between the amount of light reaching the layer and the amount of reflected light and the amount of reflected light. For this reason, a shift in recording sensitivity and a change in reproduction characteristics are caused.

In this embodiment, by adjusting the thickness of the base interference film as described above, the phase change type optical recording layer 2 is formed.
Since the transmittance in a to 2c can be controlled and the transmittance difference due to the presence or absence of the recording mark can be suppressed, it is possible to record and reproduce good information.

Next, a second embodiment of the present invention will be described. In the second embodiment, two optical information recording media according to the first embodiment are bonded. FIG. 5 is a sectional view showing the structure of the optical information recording medium according to the second embodiment of the present invention. In the second embodiment shown in FIG. 5, the same components as those in the first embodiment shown in FIG.
The same reference numerals are given and the detailed description is omitted.

In the second embodiment, the two optical information recording media according to the first embodiment have their fourth phase-change type optical recording layer 2d bonded together by an adhesive layer 4. .

In the second embodiment constructed as described above, not only the effect of the first embodiment but also the rewriting of information on both sides is possible, so that the recording capacity is the same as that of the first embodiment. Double.

[0051]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples that fall outside the scope of the claims.

First, the diameter is 120 mm and the thickness is 0.6 m.
m, polycarbonate base with track pitch of 1.0μm
The plate is used as a transparent rigid substrate, and
The underlying interference film shown was formed. Then, a film is formed on the base interference film.
ZnS-SiO with a thickness of 150 nm_TwoTransparent lower cover made of
A protective film was formed by a sputtering method. In addition, transparent lower protection
16 nm thick Ge on the film_TwoSb_TwoTe_FivePhase change
A recording film was formed by a sputtering method. And phase change
ZnS-SiO with a thickness of 150 nm on the recording film _TwoFrom
A transparent upper protective film was formed by a sputtering method. This
Thus, the first phase-change optical recording layer was formed.

Next, an ultraviolet curable resin was applied to a thickness of 25 μm on the transparent upper protective film by spin coating. Next, after that, the transparent stamper in which the tracking groove was previously formed was brought into close contact with the ultraviolet curable resin, the ultraviolet curable resin was cured by irradiating ultraviolet rays, and the stamper was removed, whereby a good tracking groove having a track pitch of 1.0 μm was obtained. Was transferred to an ultraviolet curable resin. Thus, a transparent spacer was formed.

Next, a film thickness of 170 is formed on the transparent spacer.
a second transparent lower passivation layer consisting nm of ZnS-SiO ₂ was formed by sputtering. Thereafter, a second phase-change recording film made of Ge ₂ Sb ₂ Te ₅ having a thickness of 14 nm was formed on the second transparent lower protective film by a sputtering method. Further, on the second phase change recording film, a ZnS-
A _second transparent upper protective film made of SiO ₂ was formed by a sputtering method. Then, a metal reflective film shown in Table 1 below was formed on the second transparent upper protective film by a sputtering method. Thus, the second (uppermost) phase-change optical recording layer was formed.

The Si underlayer interference films in Examples 1, 2 and 8 were formed by sputtering, and the Ge underlayer interference film in Example 3 was formed by Ar gas sputtering using a Ge target. The SiO film in Example 4 was formed by reactive sputtering using a Si target in a mixed gas atmosphere of Ar and O ₂ , and the SiN underlayer interference film in Example 5 was Ar
And a reactive sputtering using a Si target in a mixed gas atmosphere of N ₂ and N ₂ . Further, the GeO base interference film in Example 6 was formed by reactive sputtering using a Ge target in a mixed gas atmosphere of Ar and O ₂ , and the GeN base interference film in Example 7 was a mixed gas of Ar and N ₂ . It was formed by reactive sputtering using a Ge target in an atmosphere.

In the second embodiment, based on the second embodiment, two disks of the first embodiment are bonded together with a metal reflective film by an adhesive layer.

Further, in the production of Example 8, the following method was employed. FIG. 6 is a sectional view showing the structure of the eighth embodiment. First, a first phase-change optical recording layer including a base interference film 55, a transparent lower protective film 51, a phase-change recording film 52, and a transparent upper electrode 53 was formed on a first transparent rigid substrate 56a. . Thereafter, the second transparent rigid substrate 5 having a spiral tracking guide groove with a track pitch of 1.0 μm opposite to the first transparent rigid substrate 56a is formed.
6b, a metal reflective film 54a from the lower layer and a thickness of 18 nm
, A phase change recording film 52a having a thickness of 14 nm, and a transparent upper protection film 51a having a thickness of 170 nm.
Was formed. That is, the second phase-change optical recording layer was formed upside down on the second transparent rigid substrate 56b.

Next, an ultraviolet curable resin was spread and applied to a thickness of 40 μm by a spin coating method between the film forming surfaces of the two substrates on which the film formation was completed, and the first transparent rigid substrate side was coated. UV light was applied to cure the UV-curable resin. Thus, the transparent spacer 57 was formed, and the two substrates were bonded together. The optical disk manufactured in this manner has the following features, except that the second permeable rigid substrate is formed and the thickness of the permeable spacer.
It has a structure similar to that of the first embodiment.

[0059]

[Table 1]

As Comparative Example 9, the diameter was 120 m.
m, using a polycarbonate substrate having a plate thickness of 0.6 mm and a track pitch of 1.0 μm as a transparent rigid substrate,
A transparent lower passivation layer having a thickness thereon made of ZnS-SiO ₂ of 230nm was formed by sputtering. Further, a phase change recording film made of Ge ₂ Sb ₂ Te ₅ having a thickness of 10 nm was formed on the transparent lower protective film by a sputtering method. Furthermore, a ZnS-Si film having a thickness of 18 nm is formed on the phase change recording film.
A transparent upper protective film made of O ₂ was formed by a sputtering method. Then, a Si film having a thickness of 60 nm is formed on the transparent upper protective film.
A transparent reflection film was formed. Thus, the first phase-change optical recording layer was formed.

Next, an ultraviolet curable resin was applied on the Si transparent reflective film to a thickness of 25 μm by spin coating. Next, after that, the transparent stamper in which the tracking groove was previously formed was brought into close contact with the ultraviolet curable resin, the ultraviolet curable resin was cured by irradiating ultraviolet rays, and the stamper was removed, whereby a good tracking groove having a track pitch of 1.0 μm was obtained. Was transferred to an ultraviolet curable resin. Thus, a transparent spacer was formed.

Next, a thickness of 230 is formed on the transparent spacer.
a second transparent lower passivation layer consisting nm of ZnS-SiO ₂ was formed by sputtering. Thereafter, a second phase change recording film made of Ge ₂ Sb ₂ Te ₅ having a thickness of 10 nm was formed on the second transparent lower protective film by a sputtering method. Further, on the second phase change recording film, a ZnS-
A second transparent upper protective film made of SiO2 was formed by a sputtering method. Then, Al is formed on the second transparent upper protective film.
Was formed by a sputtering method. Thus, the second (uppermost) phase-change optical recording layer was formed.

For each of the examples and comparative examples, the transmittance was measured and the characteristics of recording, reproduction and erasing were evaluated.

The transmittance of the first phase-change optical recording layer is
In Example 1, at a laser beam wavelength of 660 nm, 40% when the recording film is in a crystalline state, and 3% when the recording film is in an amorphous state.
8%. In Example 4, it was 43% when the recording film was in a crystalline state and 41% when the recording film was in an amorphous state. In Example 5, it was 37% when the recording film was in a crystalline state and 39% when the recording film was in an amorphous state. In Example 7, 38% when the recording film is in a crystalline state, and 39% when the recording film is in an amorphous state.
Met. In Example 8, when the recording film is in a crystalline state,
0% and 38% in the amorphous state. On the other hand, in Comparative Example 9, when the recording film was in a crystalline state, it was 40%, and when the recording film was in an amorphous state, it was 68%, and the difference was extremely large.

The characteristics of recording, reproducing and erasing of information were evaluated as follows.

First, the first and second phase change type optical recording layers in the optical disk are initialized, and the optical disk is set at 3600 rpm.
After rotating at a rotation speed of m, a signal of 8.4 MHz (duty ratio: 50%) was recorded on a track having a radius of 30 mm of the first phase-change optical recording layer. Thereafter, a signal of 2.2 MHz (duty ratio: 50%) was overwritten (overwritten) on the same track. For recording, reproducing and erasing information, an optical head equipped with a semiconductor laser having a wavelength of 660 nm was used, and the aperture ratio of the condenser lens was set to 0.6.

In the first embodiment, the recording power and the erasing power are set to 8 mW and 4 mW, respectively, so that the second harmonic distortion of the reproduction signal is minimized, and when this track is reproduced, a good reproduction signal is obtained. Obtained.

Next, an offset was applied to the focus servo circuit of the optical head, and the focus position of the laser light was moved to the position of the second phase change type optical recording layer of the optical disk. When the optical disk was rotated at 3600 rpm, the recording power and the erasing power were set to 14 mW and 7 mW, respectively, and recording and reproduction were performed on the optical disk, a good reproduction signal was obtained.

In the second embodiment, as in the first embodiment,
The recording power and the erasing power were set to 8 mW and 4 mW, respectively, so that the second harmonic distortion of the reproduction signal was minimized, and when this track was reproduced, a good reproduction signal was obtained.

Next, the focus servo circuit of the optical head was offset, and the focus position of the laser beam was moved to the position of the second phase change type optical recording layer of the optical disk. Then, the optical disk is rotated at a rotation speed of 3600 rpm, a signal of 8.0 MHz (duty ratio: 50%) is recorded on a track having a radius of 31 mm, and 1.9 is recorded on the same track.
MHz (duty ratio: 50%) signal was overwritten. The recording power and the erasing power were set to 14 mW and 7 mW, respectively, so that the second harmonic distortion of the reproduced signal was minimized. When this track was reproduced, a good reproduced signal was obtained. In addition, good recording / reproduction was confirmed regardless of the presence / absence of recording in the first phase-change optical recording layer. When the same recording and reproduction were performed on the opposite surface, it was confirmed that the operation was good.

In the third embodiment, the recording power and the erasing power are set to 8.8 mW and 4.4 mW, respectively, so that the second harmonic distortion of the reproduced signal is minimized. Reproduction signal was obtained.

Next, the focus servo circuit of the optical head was offset, and the focus position of the laser beam was moved to the position of the second phase change type optical recording layer of the optical disk. Then, the optical disk is rotated at a rotation speed of 3600 rpm, and the recording power and the erasing power are reduced to 14.2 mW and 7.6, respectively.
When recording and reproduction were performed on this optical disk at mW, a good reproduction signal was obtained.

In the fourth embodiment, the recording power and the erasing power were set to 7.7 mW and 3.8 mW, respectively, so that the second harmonic distortion of the reproduced signal was minimized. Reproduction signal was obtained.

Next, an offset was applied to the focus servo circuit of the optical head, and the focus position of the laser beam was moved to the position of the second phase change type optical recording layer of the optical disk. Then, the optical disk is rotated at a rotation speed of 3600 rpm, and the recording power and the erasing power are reduced to 13.5 mW and 7 mW, respectively.
After recording and reproducing on this optical disc,
A good reproduction signal was obtained.

In the fifth embodiment, the recording power and the erasing power are set to 7.8 mW and 4 mW, respectively, so that the second harmonic distortion of the reproduced signal is minimized. A signal was obtained.

Next, the focus servo circuit of the optical head was offset, and the focus position of the laser light was moved to the position of the second phase change type optical recording layer of the optical disk. Then, the optical disk is rotated at a rotation speed of 3600 rpm, and the recording power and the erasing power are respectively 14.3 mW and 7.3 mW.
When recording and reproduction were performed on this optical disk at mW, a good reproduction signal was obtained.

In the sixth embodiment, the recording power and the erasing power are set to 8.3 mW and 4 mW, respectively, so that the second harmonic distortion of the reproduced signal is minimized. A signal was obtained.

Next, the focus servo circuit of the optical head was offset, and the focus position of the laser beam was moved to the position of the second phase change type optical recording layer of the optical disk. Then, the optical disk is rotated at a rotation speed of 3600 rpm, and the recording power and the erasing power are respectively 14.6 mW and 8.0.
When recording and reproduction were performed on this optical disk at mW, a good reproduction signal was obtained.

In the seventh embodiment, the recording power and the erasing power are set to 8.1 mW and 4 mW, respectively, so that the second harmonic distortion of the reproduction signal is minimized. A signal was obtained.

Next, the focus servo circuit of the optical head was offset, and the focus position of the laser beam was moved to the position of the second phase change type optical recording layer of the optical disk. Then, the optical disk is rotated at a rotation speed of 3600 rpm, and the recording power and the erasing power are respectively 13.9 mW and 7.3 mW.
When recording and reproduction were performed on this optical disk at mW, a good reproduction signal was obtained.

In the eighth embodiment, the recording power and the erasing power were set to 8 mW and 4 mW, respectively, so that the second harmonic distortion of the reproduction signal was minimized, and when this track was reproduced, a good reproduction signal was obtained. Obtained.

Next, the focus servo circuit of the optical head was offset, and the focus position of the laser beam was moved to the position of the second phase change type optical recording layer of the optical disk. When the optical disk was rotated at 3600 rpm, the recording power and the erasing power were set to 14 mW and 7 mW, respectively, and recording and reproduction were performed on the optical disk, a good reproduction signal was obtained.

In Examples 1 and 3 to 8, the first-layer phase-change optical recording layer has the first-layer phase-change optical recording layer that matches the recorded area and the non-recorded area, respectively. When trying to record / reproduce the area of the variable optical recording layer,
In each case, the same signal quality was obtained without changing the recording / erasing power and the reproducing power.

In Comparative Example 9, the recording power and the erasing power were set to 8 mW and 4 mW, respectively, so that the second harmonic distortion of the reproduction signal was minimized, and this track was reproduced. Obtained.

Next, the focus servo circuit of the optical head was offset, and the focus position of the laser beam was moved to the position of the second phase change type optical recording layer of the optical disk. Then, the optical disk is rotated at a rotation speed of 3600 rpm, and the recording power and the erasing power are each 14 mW in the area where the recording of the first phase-change optical recording layer is not performed.
Recording and reproduction were performed on the second phase-change optical recording layer of the optical disk at 7 mW, and a good reproduction signal was obtained.

However, the recording power and the erasing power are each 14 m in the area of the second phase change type optical recording layer which matches the area where the recording of the first phase change type optical recording layer is performed.
When recording was performed with W and 7 mW, recording could not be performed. Further, first, recording is performed on the second phase change type optical recording layer, and then recording is performed on the first phase change type optical recording layer, and subsequently, the second phase change type optical recording layer is recorded. Was regenerated, the regenerated power increased to the original 0.8m
Unless it was increased from W to 1.5 mW, good reproduction could not be performed.

[0087]

As described in detail above, according to the present invention,
Since the phase change type optical recording layer is provided with a base interference film for adjusting the transmittance of the laser light in the phase change recording film, it is possible to obtain a substantially constant transmittance regardless of the presence or absence of recording of the phase change recording film. it can. Therefore, it is not necessary to change the recording condition or the reproduction condition depending on the presence or absence of the recording, so that the operability on the drive can be improved. Further, by laminating and using such a phase-change type optical recording layer, it becomes possible to perform high-density and good information recording, reproduction and erasing.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the structure of an optical information recording medium according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a structure of a first-layer phase-change optical recording layer 2a.

FIG. 3 is a cross-sectional view showing a fourth-layer phase-change optical recording layer 2d.

FIGS. 4A and 4B are graphs showing the relationship between the thickness of a base interference film and transmittance or reflectance.

FIG. 5 is a sectional view showing a structure of an optical information recording medium according to a second embodiment of the present invention.

FIG. 6 is a sectional view showing a structure of an eighth embodiment.

[Explanation of symbols]

 1, 56a, 56b; transmissive rigid substrates 2a, 2b, 2c, 2d; phase-change optical recording layers 3a, 3b, 3c, 57; transmissive spacers 4: adhesive layer 10; laser light 11; 21a, 51, 51a; transparent lower protective film 22, 22a, 52, 52a; phase change recording film 23, 23a, 53, 53a; transparent upper protective film 24a, 54a; metal reflective film 25, 55;

Claims (10)

[Claims] 1. A plurality of first phase change type optical recording layers and a plurality of second phase change type optical recording layers are laminated in this order on at least a transmissive substrate, and said first phase change type optical recording layer and A transmissive spacer is disposed between the first and second phase change type optical recording layers, and the first phase change type optical recording layer comprises a base interference film, a transparent lower protective film, a phase change recording film, and a transparent upper protective film. Are arranged at least in this order, and the second phase change type optical recording layer comprises:
A transparent lower protective film, a phase change recording film, a transparent upper protective film, and a metal reflective film are arranged at least in this order, and the base interference film is a film that adjusts the transmittance of laser light in the phase change recording film. An optical information recording medium characterized by the above-mentioned. 2. A first phase-change optical recording layer in which a base interference film, a transparent lower protective film, a phase change recording film, and a transparent upper protective film are arranged in this order on at least a transparent substrate, and a transparent lower protective film. A phase change recording film, a transparent upper protective film, and a second phase change type optical recording layer in which a metal reflection film is arranged in this order, with a transparent spacer interposed therebetween, and the base interference film is formed of the phase change recording film. An optical information recording medium, wherein the optical information recording medium is a film that adjusts a transmittance of a laser beam in the film. 3. The phase change recording film is a phase change recording film in which information is recorded and erased by a phase change by irradiation of a laser beam, and a transmittance of the phase change recording film in a region where the information is recorded. The thickness of the base interference film is set so that the thickness of the base interference film is 0.95 to 1.05 times the transmittance in an area where no information is recorded.
Or the optical information recording medium according to 2. 4. An optical information recording medium according to claim 1, wherein two optical information recording media are bonded together via an adhesive layer such that the second phase-change type optical recording layer side faces each other. An optical information recording medium, comprising: 5. A plurality of third phase-change optical recording layers in which a base interference film, a transparent lower protective film, a phase-change recording film, and a transparent upper protective film are arranged in this order on at least a transparent substrate. And a fourth phase-change optical recording layer in which a metal reflective film, a transparent lower protective film, a phase-change recording film, and a transparent upper protective film are arranged in this order on the substrate. The transparent upper protective film located on the top of the third phase-change optical recording layer and the transparent upper protective film located on the top of the fourth phase-change optical recording layer face each other. An optical information recording medium which is laminated and arranged with a spacer interposed therebetween, and wherein the base interference film is a film for adjusting the transmittance of laser light in the phase change recording film. 6. A third phase-change optical recording layer in which a base interference film, a transparent lower protective film, a phase-change recording film, and a transparent upper protective film are arranged in this order on at least a transparent substrate; A fourth phase-change optical recording layer in which a metal reflective film, a transparent lower protective film, a phase-change recording film, and a transparent upper protective film are arranged in this order; And a phase change type optical recording layer is disposed with a transparent spacer interposed therebetween such that a transparent upper protective film located at the uppermost part of both recording layers faces each other. An optical information recording medium, wherein the optical information recording medium is a film that adjusts a transmittance of a laser beam in the film. 7. The phase change recording film is a phase change recording film in which information is recorded and erased by a phase change due to laser light irradiation, and a transmittance of the phase change recording film in a region where information is recorded. 7. The optical device according to claim 5, wherein the thickness of the base interference film is set to be 0.95 to 1.05 times the transmittance in an area where no information is recorded. Information recording medium. 8. The at least one phase change by irradiating the optical information recording medium according to claim 1 with a laser beam from the transparent substrate side while changing a focusing position thereof. An information recording method for an optical information recording medium, comprising a step of causing a phase change in a recording film. 9. The at least one phase change by irradiating the optical information recording medium according to claim 1 with laser light from the transparent substrate side while changing its focusing position. An information erasing method for an optical information recording medium, comprising a step of causing a phase change in a recording film. 10. A first step of sequentially forming a base interference film, a transparent lower protective film, a phase change recording film, and a transparent upper protective film on a transparent substrate, and a metal reflective film, a transparent lower protective film on the substrate. A second step of sequentially forming a protective film, a phase-change recording film, and a transparent upper protective film, wherein the phase-change optical recording layer formed in the first step and the second
A method for producing an optical information recording medium, wherein the optical information recording medium is produced by bonding the phase-change optical recording layer formed in the step (1) to the transparent upper protective film located on the uppermost side.