JP2002208178A - Optical information recording medium, manufacturing method therefor and recording method for optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium which can be formed by a simple manufacturing process and on which recording can be performed by using a semiconductor laser beam having 380-430 nm wavelength. SOLUTION: The optical information recording medium has at least a recording layer 2 on a substrate 1. Information recording is performed by irradiating the recording layer with the laser beam having 380-430 nm wavelength. The refractive index n and the extinction coefficient k of the recording layer 2 satisfy the conditions of 3.9<n<5.6 and k>0.4 in the range of 380 nm-430 nm wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical information recording medium for recording / reproducing information by irradiating a laser beam, a method for manufacturing the same, and a method for recording the optical information recording medium.
The present invention relates to a write-once optical information recording medium that can be recorded only once, a method of manufacturing the same, and a method of recording on the medium.

[0002]

2. Description of the Related Art With the recent widespread use of CD-ROMs and DVD-ROMs, the spread of optical information recording media called CD-Rs and DVD-Rs that can be recorded only once by a user is also accelerating. For CD-R and DVD-R,
A photosensitive dye layer is formed on the substrate as a recording layer by spin coating or vapor deposition. In order to realize a reflectance equivalent to that of a CD-ROM, a reflection layer made of a material such as Al or Au is formed on the dye layer. The pigment material is
It is selected so that there is absorption to the extent that recording is possible at the wavelength of the semiconductor laser for recording and reproducing optical information. The wavelength of the semiconductor laser used for recording / reproducing information is around 780 nm for CD-R, and for DVD.
For -R, it is around 650 nm.

On the other hand, in recent years, research and development on blue-violet semiconductor lasers have been rapidly advanced. Thereby, the wavelength 3
The practical use of a blue-violet semiconductor laser with a wavelength of 80 to 430 nm is approaching. The recording density of an optical disk is mainly determined by the size of the focused spot of a light beam used for recording and reproducing information. Since the focused spot size is proportional to the wavelength of the semiconductor laser, it is expected that the recording capacity of the optical disk will be greatly increased by using a blue-violet semiconductor laser having a shorter wavelength than the red semiconductor laser currently in practical use. I have.

However, a dye material suitable for laser light having a wavelength of 380 to 430 nm has not been known so far, and an optical information recording medium using a blue-violet semiconductor laser has not been put to practical use. Further, the process of forming a reflective layer again by sputtering or the like after the dye layer is formed by spin coating is also complicated, and causes an increase in the cost of the optical information recording medium.

[0005] In connection with the above description, an optical recording medium is disclosed in JP-A-10-172180. In this reference,
Information recording and erasing are performed by a phase change between an amorphous phase and a crystalline phase due to light irradiation. At least a first dielectric layer / recording layer / second dielectric layer / reflective layer is laminated on a transparent substrate in this order. The wavelength of the irradiated light is 550 nm or less, and the refractive index n of the first dielectric layer at the wavelength of the irradiated light is 1.4 to 2.1. The wavelength of the irradiated light is 450 nm or less, and the refractive index n of the first dielectric layer at the wavelength of the irradiated light is 1.4 to 1.8.

An optical recording medium is disclosed in Japanese Patent Laid-Open No. 10-2082.
96. In this reference, the optical recording medium is:
An optical recording layer containing at least Te is provided on the substrate. The extinction coefficient ka in the amorphous layer of the optical recording layer is 400 wavelengths.
It is 2.5 or less at 500 nm. Further, the optical recording layer contains 30 ppm or more and 10000 ppm or less of hydrogen.

The optical recording medium is disclosed in Japanese Patent Application Laid-Open No. H11-3970.
9 is disclosed. In this reference, information is recorded and erased by a phase change between an amorphous phase and a crystalline phase due to light irradiation. On a transparent substrate, at least a first dielectric layer / a base dielectric layer / a recording layer / a second dielectric layer / a reflective layer are laminated in this order. 700-630 nm wavelength and 50 wavelength
The refractive index, extinction coefficient, and layer thickness of each layer at 0 to 380 nm have a relationship represented by the following equation. 1.85 ≦ na2, 45 ≦ da55 (nm) 2.1 ≦ nb145 ≦ db155 (nm) 2.4 ≦ nα ≦ 4.5 1.9 ≦ kα ≦ 2.9 1.65 ≦ nc4.5 3.5. 2 ≦ kc4.1 0 <dr20 (nm) 2.1 ≦ nd2.4 10 ≦ dd20 (nm) 0.4 ≦ ne1.4 3.8 ≦ ke6.2 where na is the refraction of the first dielectric layer. Ratio, da is the thickness of the first dielectric layer (nm), nb is the refractive index of the underlying dielectric layer, db is the thickness of the underlying dielectric layer (nm), and nα is the refraction of the recording layer in the amorphous state. Rate, kα is the extinction coefficient of the amorphous state of the recording layer, n
c is the refractive index of the crystalline state of the recording layer, kc is the extinction coefficient of the crystalline state of the recording layer, dr is the thickness (nm) of the recording layer, nd is the refractive index of the second dielectric layer, and dd is the second dielectric layer. Body layer thickness (nm),
ne represents the refractive index of the reflective layer, and ke represents the extinction coefficient of the reflective layer.

An optical recording medium is disclosed in Japanese Patent Application Laid-Open No. H11-3971.
6 is disclosed. In this reference, information is recorded and erased by a phase change between an amorphous phase and a crystalline phase due to light irradiation. At least a first dielectric layer / recording layer / second dielectric layer / reflective layer is laminated on a transparent substrate in this order, and the refractive index, extinction coefficient, and layer thickness of each layer at a wavelength of 390 nm to 450 nm are provided. Has a relationship represented by the following equation. 2.2 ≦ na2.3 30 ≦ da500 2.58 ≦ nα ≦ 3.3 2.6 ≦ kα ≦ 2.9 1.77 ≦ nc2.5 3.2 ≦ kc3.8 7 ≦ dr35 (nm) 25 ≦ nb2.4 0 <db25 (nm) 0.4 ≦ nβ ≦ 0.6 3.8 ≦ kβ ≦ 4.25 where na is the refractive index of the first dielectric layer, and da is the first dielectric layer. , Nα is the refractive index of the amorphous state of the recording layer, kα is the extinction coefficient of the amorphous state of the recording layer, nc is the refractive index of the crystalline state of the recording layer, and kc is the refractive index of the recording layer. Extinction coefficient of the crystalline state, dr is the thickness of the recording layer (nm), nb is the refractive index of the second dielectric layer, db is the thickness of the second dielectric layer (nm), and nβ is the refractive index of the reflective layer. , Kβ represent the extinction coefficient of the reflective layer.

Further, a phase change type optical recording medium is disclosed in
265525. In this reference, the phase change optical recording medium has at least a substrate, a recording layer, and a dielectric layer formed between the recording layer and the substrate. The recording layer is formed on one surface of the substrate, and the phase change between crystal and amorphous is reversibly performed according to the intensity of irradiation light. The dielectric layer is formed between the recording layer and the substrate. Wavelength 4
Overwriting is performed with a single laser beam whose intensity is not less than 00 nm and not more than 500 nm. The dielectric layer is Zn
The recording layer is made of a mixture of S and SiO _2, and the recording layer is made of a material containing at least Ge, Te and Sb. Ag, TiO ₂ , a mixture of Ag and TiO ₂ , A between the substrate and the dielectric layer
A multiple reflection layer made of a mixture containing g as a main component or a mixture containing TiO ₂ as a main component may be provided. A reflective layer is provided on the surface of the recording layer opposite to the substrate, and a second dielectric layer is provided between the reflective layer and the recording layer.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor device which can be formed by a simple manufacturing process and has a wavelength of 380 to 430.
It is an object of the present invention to provide an optical information recording medium that can be recorded only once using a semiconductor laser of nm, a manufacturing method thereof, and a recording method of the optical information recording medium.

[0011]

Means for solving the problem will be described below using the numbers and symbols used in the embodiments of the present invention. These numbers and symbols have been added in order to clarify the correspondence between the description of [Claims] and the description of the embodiment of the invention.
It should not be used for interpreting the technical scope of the invention described in [Claims].

[0012] In order to achieve the above object, the present invention has at least a recording layer (2) on a substrate (1) and has a wavelength of 380.
An optical information recording medium for recording information by irradiating a laser beam of nm to 430 nm, wherein a refractive index n and an extinction coefficient k of the recording layer (2) are 3.9 <in a wavelength range of 380 to 430 nm. It satisfies the conditions of n <5.6 and k> 0.4.

The present invention also relates to an optical information recording medium having at least a recording layer (2) on a substrate (1) and recording information by irradiating a laser beam having a wavelength of 380 nm to 430 nm, wherein the optical information recording medium has a wavelength of 380 to 430 nm. In the range of 430 nm, the recording layer (2) has an absorptance of 20% or more, and the recording layer (2) has a reflectance that is compatible with a read-only optical information recording medium before optical information recording. Are formed so that the reflectance increases after optical information recording.

In the present invention, the thickness of the recording layer (2) is 10 nm or more and 30 nm or less, and the thermal conductivity of the recording layer (2) is 0.5 W / mK or more and 20 W / mK or more.
It is preferably at most W / mK.

Further, in the present invention, the recording layer (2) contains any of Si, Ge, an oxide or nitride containing Si as a main component, and an oxide or nitride containing Ge as a main component. Is preferred.

The method for producing an optical information recording medium according to the present invention comprises:
A method for manufacturing an optical information recording medium, comprising at least a step of forming a recording layer (2) on which information can be recorded by irradiating a laser beam having a wavelength of 380 nm to 430 nm on a substrate, wherein the recording layer (2) is formed of Si. Alternatively, the recording layer (2) is formed by sputtering using Ge as a target under a film forming gas pressure such that the thermal conductivity of the recording layer (2) becomes a desired value.

The recording method of the optical information recording medium of the present invention comprises:
Using a multi-pulse as a recording pulse of the laser light,
When the laser peak power of the multi-pulse is Pw, the laser bottom power of the multi-pulse is Pbw, and the bias power between recording pulses is Pb, 0 <Pbw <0.5 mW,
In addition, recording is performed under conditions satisfying the relationship of 0 <Pb / Pw <0.33.

Further, in the recording method of the present invention, recording is performed at a linear velocity of 10 m / s or more using a rectangular wave as a recording pulse of the laser beam.

An optical information recording medium according to the present invention is an optical information recording medium for recording information by irradiating a laser beam having a wavelength of 380 nm to 430 nm, wherein at least a recording layer (2) is formed on a substrate (1). An optical information recording medium having a layer (7) and recording / reproducing optical information by irradiating a laser beam from the light transmitting layer (7) side, wherein the recording layer (2) and the light transmitting layer (7) A heat deformation suppressing layer (8) is provided between them.

As the thermal deformation suppressing layer (8), SiN, S
iO ₂ , Ta ₂ O ₅ , Al ₂ O ₃ , AlN, SiC, TiC
It is preferable that any one or a plurality of the above is laminated. Alternatively, a metal thin film containing Au or Ag as a main component and having a thickness of 10 nm or less is preferable.

When the thermal deformation inhibiting layer (8) is added,
Si or Ge is particularly suitable for the recording layer (2).

The recording method according to the present invention employs a wavelength of 380 n
Using a laser beam of m to 430 nm, a laser beam is applied from the light transmitting layer (7) side to an optical information recording medium having at least a recording layer (2) and a light transmitting layer (7) on a substrate (1). A recording method for recording / reproducing optical information upon incidence, wherein recording is performed on both flat portions between guide grooves formed in a substrate (1) and between guide grooves.

The optical information recording medium of the present invention comprises a substrate (1) having guide grooves formed at predetermined intervals, and a recording layer (2) formed on the substrate, and has a wavelength of 38.
Information is recorded in a flat region between the adjacent guide grooves by using a laser beam of 0 nm to 430 nm. Information may be recorded in the guide groove.

The optical information recording medium of the present invention comprises a substrate (1) having guide grooves formed at a predetermined interval, and a recording layer (2) formed on the substrate, and has a wavelength of 38.
When information is recorded by using a laser beam of 0 nm to 430 nm, the depth of the guide groove corresponding to a portion where the information is recorded is smaller after recording the information than before recording the information. As a result, the reflectance before recording the information is lower than the reflectance after recording the information. Further, the optical information recording medium of the present invention includes a substrate, and a recording layer formed on the substrate, and a space is formed between the recording layer and the substrate at a position irradiated with laser light. 380nm ~
Information is recorded by irradiating the laser light of 430 nm.

[0025]

Next, an optical information recording medium of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 1 to 9 are cross-sectional views schematically showing an optical disk structure of a phase change type optical information recording medium of the present invention, and FIG. 10 is a view schematically explaining a reproduction signal waveform.

The optical information recording medium of the present invention shown in FIG. 1 employs a simple basic structure in which a recording layer 2 is formed on a substrate 1. The thickness of the substrate 1 is 0.3 mm to 1.2
mm, and a resin such as polycarbonate or glass is used as a material of the substrate 1. The recording layer is
It may be a single layer or a laminate of a plurality of different layers. Normally, as shown in FIG. 1, recording and reproduction of information are performed by irradiating a laser beam from a laser 10 provided on the substrate 1 side and reproducing by receiving a reflected light by a light receiving unit 12.

Since the structure is the simplest, a structure in which the recording layer 2 is formed on the substrate 1 is most desirable. However, in the optical information recording medium of the present invention shown in FIG.
The recording layer 2 may be formed on the substrate 1, and an ultraviolet curable resin 3 may be formed on the recording layer 2 to prevent scratches and dust. Further, as shown in FIG. 3, another substrate 4 may be bonded to improve mechanical characteristics.

In addition, in the optical information recording medium of the present invention shown in FIGS. 4 and 5, a recording layer 2 is formed on a substrate 1, and a dielectric layer 5 or a reflection layer 6 is laminated on the recording layer 2. Is also good. Alternatively, as shown in FIG. 6, a reflective layer 6 may be laminated on a dielectric layer 5 formed on the recording layer 2. Further, as shown in FIG. 7, another substrate 4 may be further bonded with the ultraviolet curing resin 3 in order to improve the mechanical characteristics.

As shown in FIG. 8, in the optical information recording medium of the present invention, a recording layer 2 is formed on a substrate 1,
A light transmitting layer 7 having a thickness of about 0.1 mm may be formed on the recording layer 2. The thickness of the substrate 1 is 0.3 mm to 1.2 m
m, and the substrate 1 is made of a resin such as polycarbonate or glass. Further, as shown in FIG. 9, a thermal deformation suppressing layer 8 may be provided between the recording layer 2 and the light transmitting layer 7. In the case of such a structure, as shown in FIG.
The recording layer 2 is irradiated with laser light from a laser 10 provided on the side, and reproduction is performed by receiving reflected light by a light receiving unit 12.

The thickness of the recording layer 2 is 10 nm or more and 3
It is desirable that the thickness be 0 nm or less. This is because if the film thickness is less than 10 nm, the film quality is deteriorated and a problem occurs in the weather resistance.
This is because it is difficult to obtain a sufficiently high reflectivity, and if it is 30 nm or more, the heat capacity becomes large, so that the recording sensitivity is lowered and good recording cannot be performed. Further, at 30 nm or more, even if recording is performed with high power, thermal interference between marks (influence of temperature rise at the time of recording a mark immediately before a mark to be recorded).
This is because good recording cannot be performed.

Next, the optical characteristics of the optical information recording medium shown in FIGS. 1 to 7 will be described. The reflectance of the optical information recording medium of the present invention is designed to be 30% -70% before recording. This is a read-only type (CD-ROM)
This is because the reflectivity of the optical information recording medium is generally around 60%, and compatibility with a CD-ROM is considered. If the optical information recording medium of the present invention has a reflectance about half that of a CD-ROM, it is possible to reproduce information from the optical information recording medium of the present invention by adding a simple AGC circuit. Because there is.

Further, in the optical information recording medium of the present invention,
As can be seen from the reproduced signal waveform shown in FIG. 10, the reflectance is further increased after recording, so that compatibility with the CD-ROM is more easily achieved. The reason that the reflectivity is increased by recording in this manner corresponds to the region irradiated with the laser beam, where the surface portion of the substrate 1 is melted and flows into the guide groove in the region irradiated with the laser beam. This is because the depth of the guide groove (not shown) becomes shallower than before recording. At this time, a space (gap) is formed between the recording layer and the substrate by the flow at a portion irradiated with the laser beam. In a conventional optical information recording medium, the reflectance decreases after recording,
There was a problem that the servo signal became unstable,
In the optical information recording medium of the present invention, since the reflectance is further increased after recording, the problem that the servo signal becomes unstable does not occur.

Further, although recording can be performed on any of the flat portions (not shown) in the guide grooves and between the guide grooves, an optical information recording medium is formed by using only a single recording layer on a substrate. When formed, recording on a flat portion between the guide grooves can lower the power of the laser beam and improve the signal quality. In addition, when the recording layer is formed as a single layer, the fact that recording is performed in a flat portion between the guide grooves has a lower recording power of the laser beam and a better signal quality. Was found by experiment.

[0035]

The embodiments of the present invention will be described in more detail. For recording and reproducing information, the semiconductor laser 1 is used.
Optical head 20 having light receiving unit 12, objective lens
Is used.

Embodiment 1 First, an optical information recording medium according to a first embodiment of the present invention, a method for manufacturing the same, and a method for recording on the optical information recording medium will be described with reference to FIGS. FIG. 11 is a diagram illustrating a relationship between a recording power and a C / N (carrier-to-noise) ratio of the optical information recording medium according to the first example, and FIG. 12 is a diagram illustrating a laser driving waveform. .

As shown in FIG. 3, a polycarbonate substrate having a thickness of about 0.6 mm is used as the disk-type substrate 1 of the optical information recording medium, and a Si layer having a thickness of about 20 nm is formed thereon as the recording layer 2. The recording layer was formed by a sputtering method using a Si target. Further, in order to secure mechanical properties, a dummy polycarbonate substrate 4 having a thickness of about 0.6 mm
Was pasted together. The substrate 1 has a depth of 30 nm.
A guide groove (not shown) having a pitch of about 0.4 μm was used.

The reflectivity of the optical information recording medium having such a structure with respect to a laser beam having a wavelength of 400 nm is 44% before recording and 57% after recording.
The absorptivity of the laser beam in the i-layer was 43% before recording. Further, (n: refractive index, k: extinction coefficient) for a laser beam having a wavelength of 400 nm was (4.4, 1.9), and the thermal conductivity was 1.5 W / mK.

As shown in FIG. 4, ZnS-SiO ₂ , SiN, AlN, SiO ₂ ,
Al ₂ O _3, Ta ₂ O ₅ or the like dielectric layer even 5 is formed 50
% Can be achieved. As shown in FIG. 6, a metal reflective layer 6 may be formed on the dielectric layer 5 in order to further increase the reflectance, but in this embodiment, only the Si layer is formed.

The optical information recording medium having the above structure has a linear velocity of 3 m /
While rotating at s, an information signal was recorded at a recording frequency of 5 MHz, and the relationship between the recording power of the laser beam and the C / N ratio was examined. For recording / reproduction, a semiconductor laser having a wavelength of 400 nm and an optical head 20 having an objective lens with NA = 0.65 were used, and recording was performed using a flat portion between the guide grooves. The result is shown in FIG. As can be seen from FIG. 11, in the optical information recording medium of this embodiment, when the recording power is about 5 mW or more, the high C of 50 dB or more is obtained.
/ N ratio was obtained. When recording is performed inside the guide groove, the recording power is required to be 6 mW or more.
The C / N ratio was also only about 43 dB.

The recording was performed by using a multi-pulse recording pulse shown in FIG. In FIG.
w is the peak power of the laser beam from the laser 10, Pbw
Is the bottom power of the laser light, and Pb is the bias power between recording pulses. In this embodiment, Pbw = 0.1
mW, Pb = 1.5 mW. FIG. 12 shows 3T
Recording data (recording frequency 5 MHz / clock frequency 30
The recording pulse waveform with respect to (MHz) is shown, but each parameter was set to Td = 1T and Tw = Tbw = 0.5T.

As described above, according to the optical information recording medium of this embodiment, the recording layer 2 formed on the substrate 1
2 for laser light of wavelength 380 to 430 nm from 0
It was formed using a substance having an absorptance of 0% or more and a low thermal conductivity. Thus, it was determined that recording was possible at a high C / N ratio. If the absorptance is lower than 20%, an extremely high recording power is required as a laser beam, which is not preferable. In order to realize a recording layer 2 having a reflectance of 30% or more and an absorption of 20% or more near a wavelength of 400 nm, the recording layer 2 formed on the substrate 1
As a refractive index n and an extinction coefficient k, 3.9 <n <5.6, k>
It was found that the material should be formed of a material satisfying 0.4.

Example 2 A disk-type optical information recording medium was manufactured using the same substrate as in Example 1. Recording layer 2
Is a Si layer, a Ge layer, a (Si + N) nitride layer, or a (Ge + N) nitride layer. During the film formation, the pressure of the film-forming sputter gas was adjusted so that the thermal conductivity of the recording layer 2 became a desired value. The recording layer 2 was formed by sputtering using Si or Ge as a target and an adjusted sputtering gas pressure. Thus, a Si layer or a Ge layer was formed. Alternatively, by adding nitrogen to the sputtering gas, a (Si + N) layer or a (Ge + N) layer was formed. At this time, the optical constant was changed by changing the sputtering power together with the sputtering gas pressure.

When the disk type optical information recording medium has a linear velocity of 3 m /
While rotating at s, an information signal was recorded at a recording frequency of 5 MHz, and the C / N ratio was measured. 4 for recording and playback
An optical head 20 having a semiconductor laser with a wavelength of 05 nm and an objective lens with NA = 0.65 was used, and recording was performed on a flat portion between the guide grooves. The recording pulse waveform is the same as in the first embodiment. Table 1 shows the results.

[0045]

[Table 1] As can be seen from Table 1, 3.9 <n <5.6, k> 0.
4, a high C / N ratio of 50 dB or more was obtained. Recording was attempted on a disk-type optical information recording medium using a semiconductor laser having a wavelength of 660 nm and an optical head 20 having an objective lens with NA = 0.65, but recording could not be performed at all. Was.

Third Embodiment Next, an optical information recording medium according to a third embodiment of the present invention, a method for manufacturing the same, and a method for recording on the optical information recording medium will be described. In this embodiment, an experiment for optimizing the absorptance of the recording layer 2 will be described.

The recording layer 2 was formed on a 1.1 mm thick polycarbonate disk type substrate by a sputtering method. During sputtering, oxygen was added to the sputtering gas, and a (Si + O) oxide layer was formed to a thickness of 15 nm. Then, as the light transmission layer 7, a thickness of 0.1 m
m of the polycarbonate film was adhered. Thus, the optical information recording medium shown in FIG. 8 was created.

When the recording film was formed, the absorptance of the recording layer 2 was changed by changing the amount of oxygen added to the sputtering gas. The guide groove pitch is 0.35 μm and the groove depth is 35
n. Disc type optical information recording medium has a linear velocity of 10m
/ Head rotated at 405 / s and having a semiconductor laser with a wavelength of 405 nm and an objective lens with NA = 0.85
Using 0, the recording layer 2 was irradiated with laser light from the light transmission layer 7 side, and information was recorded / reproduced with a rectangular wave signal having a recording frequency of 5 MHz. Recording was performed on a flat portion between the guide grooves (here, the unevenness of the substrate, which is closer to the laser beam incident side). Table 2 shows the relationship between the absorptance of the recording layer 2, the recording power, and the C / N ratio. The maximum emission power of the laser beam used in this example was 7.5 mW.

As can be seen from Table 2, when the absorption is lower than 20%, a sufficient C / N ratio cannot be obtained. Recording was attempted on each optical information recording medium using an optical head 20 having a semiconductor laser with a wavelength of 660 nm and an objective lens with NA = 0.85, but recording could not be performed at all. Was.

[0050]

[Table 2] Embodiment 4 Next, an optical information recording medium according to a fourth embodiment of the present invention, a method for manufacturing the same, and a method for recording on the optical information recording medium will be described. In the present embodiment, an experiment for optimizing the thickness of the recording layer will be described.

As the substrate 1, the same disk type substrate 1 made of polycarbonate as in the first embodiment was used, and a Si layer was formed as the recording layer 2 by sputtering. Furthermore, in order to secure mechanical characteristics, the thickness of the UV-curable resin layer is set to 0.1 mm.
A 6 mm dummy polycarbonate substrate was bonded. Thus, an optical information recording medium having the structure shown in FIG. 3 was produced. The thickness of the Si layer was changed between 7 nm and 35 nm, and the jitter was measured.

For recording / reproduction, an optical head 20 having a semiconductor laser having a wavelength of 400 nm and an objective lens having an NA of 0.65 was used. Recording was performed at a clock frequency of 33 M while the optical information recording medium was rotated at a linear velocity of 3 m / s.
This was done by recording a random signal (8-16) modulated at Hz. As a recording pulse, a waveform similar to that shown in FIG. 12 is used. For recording data of 3T to 11T,
Td, Tw, and Tbw were set to the same value. The recording was performed using a flat portion between the guide grooves. The results are shown in Table 3. The reproduced signal jitter shown in Table 3 (s / 30 (ns) * 100%: clock frequency 33M)
Hz) is the best value obtained when Pw, Pbw, and Pb are changed.

After the signal was recorded, an environmental test was performed in which each optical information recording medium was exposed to an environment at a temperature of 90 ° C. and a humidity of 90% for 100 hours, and the change in jitter was examined.

[0054]

[Table 3] As can be seen from Table 3, when the film thickness of the recording layer 2 is greater than 30 nm, the jitter sharply worsens. On the other hand, when the film thickness is smaller than 10 nm, the characteristics are greatly deteriorated by an environmental test. Therefore, it is understood that the thickness of the recording layer 2 is preferably 10 nm or more and 30 nm or less.

Fifth Embodiment Next, an optical information recording medium according to a fifth embodiment of the present invention, a method for manufacturing the same, and a method for recording on the optical information recording medium will be described. In this embodiment, an experiment for optimizing the thermal conductivity of the recording layer will be described.

In the optical information recording medium according to the present invention, the laser beam emitted from the semiconductor laser 10 having a recording power during recording is absorbed by the recording layer 2, and the temperatures of the surface of the recording layer 2 and the surface of the substrate 1 rise above the melting point. . Recording layer 2 with low thermal conductivity
Is used, heat diffusion is suppressed, and the surface portion of the substrate 1 is efficiently melted and flown into the guide grooves. Further, a space (gap) is formed between the recording layer 2 and the substrate 1. As a result, the depth of the guide groove becomes shallower than before recording, and the reflectance becomes higher, so that information can be recorded.
Therefore, samples having different thermal conductivity were produced by changing the sputtering conditions of the recording film 2, and a preferable range of the thermal conductivity was examined.

A disc-type polycarbonate substrate is used as the substrate 1, and the recording layer 2 having a thickness of about 20 nm
As a Ge layer was formed by sputtering. Further, a dummy polycarbonate substrate having a thickness of about 0.6 mm was bonded with an ultraviolet curable resin layer to secure mechanical characteristics. Thus, an optical information recording medium having the structure shown in FIG. 3 was produced. When forming the Ge layer, a DC sputtering method is used, and the input power density is 34 KW / m ^2.
Met. Gas pressure (Ar gas) during film formation is 0.05 Pa
The film was formed by changing the pressure between 2.0 Pa and 2.0 Pa. Thereafter, while each optical information recording medium is rotated at a linear velocity of 3 m / s, a signal of a recording frequency of 5 MHz is output by a multi-pulse (P
wb = 0.1 mW, Pb = 2.5 mW)
The relationship between recording power and C / N was examined.

The gas pressure at the time of film formation by sputtering, the thermal conductivity of the recording layer 2 formed under the conditions, and the recording power of the laser beam at which the second harmonic distortion (2ndH / C) of the recording signal is minimized. Table 4 shows the relationship between C / N ratios. Table 4 also shows the values obtained by measuring the thermal conductivity of Ge formed under each condition by a thin wire heating method (for example, Thin Solid Films, 219 (1992) 239).

As shown in Table 4, the thermal conductivity was 20 W
When it is higher than / mK, the C / N ratio sharply decreases.
This is because heat diffusion occurs quickly at 20 W / mK or more, so that the surface portion of the substrate 1 is difficult to melt and recording becomes difficult. From the above viewpoint, the lower the thermal conductivity is, the better. However, if the thermal conductivity is too low, the number of defects in the film increases and the weather resistance is lowered.
It is desirable that this is the case.

[0060]

[Table 4] Embodiment 6 Next, an optical information recording medium according to a sixth embodiment of the present invention, a method for manufacturing the same, and a method for recording on the optical information recording medium will be described. The present embodiment describes an experiment for optimizing the thermal conductivity of the recording layer 2.

A disc type substrate 1 made of polycarbonate was used as the substrate 1, and one (Ge + O) layer was used as the recording layer 2.
The film was formed by a sputtering method so as to have a thickness of 5 nm. Further, a dummy polycarbonate substrate having a thickness of about 0.6 mm was bonded with an ultraviolet curable resin layer to secure mechanical characteristics. Thus, an optical information recording medium having the structure shown in FIG. 3 was produced. The sputtering method was performed by an RF sputtering method using Ar + O2 gas. In order to change the thermal conductivity, the gas pressure during film formation was changed between 0.05 Pa and 2.0 Pa. Each optical information recording medium is recorded at a recording frequency of 5 MHz while being rotated at a linear velocity of 3 m / s (Pwb = 0.1 mW,
Pb = 2.5 mW). Thereafter, an environmental test was performed for 100 hours under the conditions of a temperature of 90 ° C. and a humidity of 90%, and a change in the C / N ratio before and after the environmental test was examined. Table 5 shows the results.

As can be seen from Table 5, the thermal conductivity was 0.5
If it is lower than W / mK, the weather resistance is low and the C / N ratio is significantly reduced by an environmental test. Together with the result of Example 5, it is understood that the thermal conductivity of the recording layer 2 is desirably 0.5 W / mK or more and 20 W / mK or less.

[0063]

[Table 5] [Embodiment 7] Next, a recording method for an optical information recording medium according to a seventh embodiment of the present invention will be described with reference to FIG. FIG. 13 shows Pb of the optical information recording medium according to the present embodiment.
FIG. 4 is a diagram illustrating a relationship between / Pw and C / N.

While the optical information recording medium described in the first embodiment is rotated at a linear velocity of 3 m / s, recording is performed at a recording frequency of 5 MHz, and the relationship between the Pb / Pw ratio and the C / N ratio is examined. Was done. The recording pulse was a multi-pulse as in the first embodiment, and Pw = 6 mW and Pbw = 0.1 mW. For recording, a semiconductor laser of 405 nm wavelength and NA
An optical head 20 having an objective lens of = 0.65 was used. The result is shown in FIG.

As can be seen from FIG. 13, the ratio Pb / Pw>
Under the condition of 0.33, the C / N ratio is reduced. From this, the Pb of the recording pulse of the laser beam (the bias power between the recording pulses) and Pw (the peak power of the laser) are calculated.
It can be seen that the b / Pw ratio is preferably in a range smaller than 0.33.

[Embodiment 8] Next, a recording method for an optical information recording medium according to an eighth embodiment of the present invention will be described with reference to FIG. FIG. 14 is a diagram illustrating a relationship between Pbw and C / N ratio of the optical information recording medium according to the present embodiment.

The recording was performed at a recording frequency of 5 MHz while the optical information recording medium described in the first embodiment was rotated at a linear velocity of 3 m / s, and the relationship between Pbw and the C / N ratio was examined. The recording pulse was a multi-pulse as in the first embodiment, with Pw = 6 mW and Pb = 1.5 mW. For recording, a semiconductor laser having a wavelength of 405 nm and NA = 0.65 were used.
An optical head 20 having an objective lens was used. FIG. 14 shows the result.

As can be seen from FIG. 14, Pbw> 0.5
Under the condition of mW, the C / N ratio is reduced. From this, it is understood that Pbw (bottom power of laser) of the recording pulse of the laser beam is preferably smaller than 0.5 mW.

[Embodiment 9] Next, a recording method for an optical information recording medium according to a ninth embodiment of the present invention will be described. This embodiment describes optimization of a recording method for an optical information recording medium according to the present invention.

For the optical information recording medium described in the first embodiment, a semiconductor laser having a wavelength of 405 nm and NA = 0.
Using an optical head 20 having 65 objective lenses, while changing the rotational linear velocity of the optical information recording medium,
A mark of μm was recorded, and the relationship between the linear velocity and the C / N ratio was examined. At this time, the recording pulse is not a multi-pulse,
A rectangular wave with a duty (duty) = 50% was used. Table 6 shows the results.

As can be seen from Table 6, at a linear velocity of 10 m / s or more, good characteristics can be obtained not only by multi-pulse recording but also by recording using a rectangular wave. Compared with multi-pulse recording, recording using a rectangular wave has advantages such as lower recording power and simplification of a laser driving circuit. The reason why the C / N ratio decreases at a low linear velocity is that noise increases. This is because, when a rectangular wave recording in which heat is more likely to be accumulated at the time of forming a mark is used, the thermal diffusion is slow at a low linear velocity, and the thermal load on the medium increases.

[0072]

[Table 6] [Embodiment 10] Next, a recording method for an optical information recording medium according to a tenth embodiment of the present invention will be described. In this embodiment,
The optimization of the recording method on the optical information recording medium according to the present invention will be described.

An optical head having a semiconductor laser with a wavelength of 400 nm and an objective lens with NA = 0.85 for an optical information recording medium having an absorptance of 40% among the optical information recording media described in the third embodiment. 20 while changing the linear velocity during rotation of the optical information recording medium,
The mark of m was recorded, and the relationship between the linear velocity and the C / N ratio was examined. At this time, the recording pulse is not a multi-pulse, but d.
Uty = 50% rectangular wave. Table 7 shows the results.

[0074]

[Table 7] As in the case of Example 9, it was confirmed that good characteristics could be obtained not only by multi-pulse recording but also by recording with a rectangular wave at a linear velocity of 10 m / s or more.

[Example 11] A 10-nm thick Si layer 2 and a 1-mm thick
A 00 nm SiO ₂ layer 8 was sequentially formed by sputtering. Then, as the light transmission layer 7, a thickness of 0.1 m
m of the polycarbonate film was adhered. Thus, an optical information recording medium having the structure shown in FIG. 9 was produced. The guide groove pitch is 0.35 μm and the groove depth is 35 nm
Met. The optical information recording medium is rotated at a linear velocity of 5 m / s, and a semiconductor laser having a wavelength of 400 nm and NA = 0.
Using an optical head 20 having an objective lens of 85, a laser beam is incident from the light transmitting layer side to record information.
Playback was done.

While changing the recording power of the laser beam, a signal having a frequency of 5 MHz was recorded on the flat portion between the guide grooves, and the C / N ratio was measured. At this time, as shown in FIG. 15, a C / N ratio of 50 dB or more was obtained at a recording power of 5 mW or more.

As a comparison with the above embodiment, a thickness of 1.1 mm
A 10 nm Si layer 2 was formed on the polycarbonate substrate 1 by sputtering, and then a polycarbonate film having a thickness of 0.1 mm was adhered as a light transmitting layer 7. Thus, an optical information recording medium having the structure shown in FIG. 8 was produced. The pitch of the guide grooves was 0.35 μm, and the groove depth was 40 nm. This optical information recording medium has a linear velocity of 5
Optical head 20 rotated at m / s and having a semiconductor laser with a wavelength of 400 nm and an objective lens with NA = 0.85
The recording / reproducing of information was performed by irradiating the recording layer 2 with laser light from the light transmitting layer 7 side using the above.

While changing the recording power of the laser beam, a signal having a frequency of 5 MHz was recorded on the flat portion between the guide grooves, and the C / N ratio was measured. At this time, the same signal amplitude as in the above example was obtained, but the recording noise was high, and as shown in FIG. 15, a C / N ratio of only about 45 dB was obtained.

The reason why the thermal deformation suppressing layer 8 is required when recording is performed by irradiating a laser beam from the light transmitting layer side can be explained as follows. In a write-once optical information recording medium in which a laser beam is incident from the light transmitting layer 7 side, the optical recording medium has a thickness of 0.1.
The very thin film 7 having a thickness of 1 mm is located on the laser light incident surface. In the write-once optical information recording medium according to the present invention, thermal deformation occurs at the time of recording. However, in the case of the cover layer incident type, since the cover layer 7 is very thin, the thermal deformation reaches the surface of the cover layer, thereby increasing noise. Cause it. Therefore, a dielectric layer 8 (SiN, SiO ₂ , Ta ₂ O ₅ ) having a high thermal conductivity is provided between the recording layer 2 and the cover layer 7.
_{Al 2 O 3, AlN, SiC} , TiC , etc.), or by forming a metal layer 8 (Au, Ag, etc.), to suppress the thermal deformation of the cover layer surface, it is possible to increase the recording signal quality.

Example 12 A 10 nm Si layer 2 and a 150 nm SiN layer 8 were sequentially formed on a 1.1 mm thick polycarbonate substrate 1 by sputtering. A 1 mm polycarbonate film was adhered. Thus, an optical information recording medium having the structure shown in FIG. 9 was produced. The pitch of the guide grooves was 0.7 μm, and the groove depth was 40 nm. The optical information recording medium is rotated at a linear velocity of 5 m / s, and the wavelength is 400 n.
m from the light transmitting layer 7 side using the optical head 20 having a semiconductor laser of m and an objective lens of NA = 0.85.
Recording / reproduction of information was performed by injecting a laser beam into the laser beam.

While changing the recording power of the laser beam,
A signal with a frequency of 5 MHz was recorded and the C / N ratio was measured.
As a result, in both the flat portion between the guide grooves and the inside of the guide grooves, the C / N of 50 dB or more at the recording power of 6 mW or more.
A ratio was obtained. When the thermal deformation preventing layer 8 is added,
It was found that a high C / N ratio was obtained even when recording was performed inside the guide groove.

Example 13 A 10 nm Ge layer 2 and a 10 nm A layer were formed on a 1.1 mm thick polycarbonate substrate 1.
The u layer 8 was sequentially formed by sputtering, and then a polycarbonate film having a thickness of 0.1 mm was adhered as the light transmitting layer 7. Thus, an optical information recording medium having the structure shown in FIG. 9 was produced. The pitch of the guide grooves was 0.7 μm, and the groove depth was 40 nm. The optical information recording medium is rotated at a linear velocity of 5 m / s, and the wavelength is 400 nm.
Recording / reproduction of information was performed by injecting a laser beam into the recording layer 2 from the light transmission layer side using the semiconductor laser of No. 1 and an optical head 20 having an objective lens of NA = 0.85.

While changing the recording power of the laser beam, a signal having a frequency of 5 MHz was recorded, and the C / N ratio was measured. As a result, at a recording power of 6.5 mW or more, a C / N ratio of 50 dB or more was obtained in both the flat portion between the guide grooves and inside the guide grooves.

Example 14 A 10-nm thick Ge layer 2 was formed on a 1.1-mm-thick polycarbonate disk-type substrate 1.
And a 3 to 20 nm Ag layer 8 were sequentially formed by sputtering. Then, as the light transmitting layer 7, a thickness of 0.1
mm polycarbonate film was adhered. Thus, an optical information recording medium having the structure shown in FIG. 9 was produced. The pitch of the guide grooves was 0.7 μm, and the groove depth was 40 nm. This optical information recording medium is rotated at a linear velocity of 5 m / s, and has a semiconductor laser having a wavelength of 400 nm and NA = 0.8.
Recording and reproduction of information were performed by irradiating the recording layer 2 with laser light from the light transmitting layer 7 side using an optical head 20 having an objective lens of No. 5.

After a signal having a frequency of 5 MHz is recorded, the optical information recording medium is exposed to an environment having a temperature of 90 ° C. and a humidity of 90%.
An environmental test is performed for 0 hours, and C before and after the environmental test
The change in the / N ratio was examined. As shown in Table 8, A
It was confirmed that the thickness of the g layer is preferably 5 to 20 nm.

[0086]

[Table 8] When the thermal deformation suppressing layer 8 is added, the recording layer 2
When oxides or nitrides of Si and oxides or nitrides of Ge are used, a C / N ratio of about 50 dB was obtained in the flat portion between the guide grooves, but about 40 dB inside the guide grooves. Only the C / N ratio of was obtained. When recording is performed in the flat portion between the guide grooves and inside the guide grooves, the recording layer 2 is preferably a Si layer or a Ge layer.

[0087]

As described above, according to the optical information recording medium of the present invention, the recording layer has a refractive index n and an extinction coefficient k.
Si, G satisfying 3.9 <n <5.6, k> 0.4
e and materials such as oxides and nitrides thereof, and have an appropriate absorption rate (20%) for light having a wavelength of 380 to 430 nm.
Above), a reflectance (30 to 70%), and a layer of a substance having a low thermal conductivity of about 0.5 to 20 W / mK is formed as a recording layer. It is possible to provide an optical information recording medium that can be recorded only once.

The optical information recording medium according to the present invention has a high reflectance near a wavelength of 400 nm.
Another advantage is that compatibility with a read-only optical information recording medium is facilitated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a phase-change optical information recording medium of an optical information recording medium of the present invention when a laser beam is irradiated from a substrate side.

FIG. 2 is a cross-sectional view showing another configuration of the phase-change optical information recording medium of the optical information recording medium of the present invention when laser light is irradiated from the substrate side.

FIG. 3 is a cross-sectional view showing another configuration of the phase-change optical information recording medium of the optical information recording medium of the present invention when laser light is irradiated from the substrate side.

FIG. 4 is a cross-sectional view showing another configuration of the phase-change optical information recording medium of the optical information recording medium of the present invention when a laser beam is irradiated from the substrate side.

FIG. 5 is a cross-sectional view showing another configuration of the phase-change optical information recording medium of the optical information recording medium of the present invention when a laser beam is irradiated from the substrate side.

FIG. 6 is a cross-sectional view showing another configuration of the phase-change optical information recording medium of the optical information recording medium of the present invention when laser light is irradiated from the substrate side.

FIG. 7 is a cross-sectional view showing another configuration of the phase-change optical information recording medium of the optical information recording medium of the present invention when a laser beam is irradiated from the substrate side.

FIG. 8 illustrates a case where laser light is irradiated from the light transmission layer side.
FIG. 2 is a cross-sectional view illustrating a configuration of a phase-change optical information recording medium of the optical information recording medium of the present invention.

FIG. 9 shows a case where laser light is irradiated from the light transmission layer side.
FIG. 11 is a cross-sectional view showing another configuration of the phase-change optical information recording medium of the optical information recording medium of the present invention.

FIG. 10 is a diagram schematically illustrating a reproduction signal waveform of the optical information recording medium of the present invention.

FIG. 11 is a diagram illustrating a relationship between recording power and C / N of the optical information recording medium according to the first example of the present invention.

FIG. 12 is a diagram illustrating a laser drive waveform of the optical information recording medium according to the first embodiment of the present invention.

FIG. 13 is a diagram showing a relationship between Pb / Pw and C / N of an optical information recording medium according to a fourth embodiment of the present invention.

FIG. 14 is a diagram illustrating a relationship between Pbw and C / N of an optical information recording medium according to a fifth embodiment of the present invention.

FIG. 15 is a diagram showing a relationship between recording power and C / N of an optical information recording medium according to an eleventh embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Recording layer 3 Ultraviolet curing resin 4 Substrate 5 Dielectric layer 6 Reflection layer 7 Light transmission layer 8 Thermal deformation suppression layer 10 Laser 12 Light receiving part

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/24 535 G11B 7/24 535D 535H 538 538L B41M 5/26 7/004 Z G11B 7/004 7 / 0045 A 7/0045 7/007 7/007 7/26 531 7/26 531 B41M 5/26 X F term (reference) 2H111 EA03 EA12 EA43 FA23 FA25 FA28 FA29 FB04 FB05 FB25 FB29 5D029 JA01 JB21 JB35 JB47 JC02 JC12 JC05 LA13 LA14 LA16 LB01 LB02 LB07 LC08 LC16 NA13 NA14 5D090 AA01 BB03 CC03 CC12 CC14 DD01 EE02 FF08 GG01 GG10 KK03 KK06 5D121 AA01 EE03 EE16

Claims (21)

[Claims] 1. A substrate comprising: a substrate; and a recording layer formed on the substrate, wherein information is recorded by using a laser beam having a wavelength of 380 nm to 430 nm, and the recording layer has a refractive index n and an extinction coefficient k. 380-43
For a laser beam having a wavelength of 0 nm, 3.9 <n <5.
6. An optical information recording medium satisfying a relationship of k> 0.4. 2. A recording apparatus comprising: a substrate; and a recording layer formed on the substrate, wherein information is recorded using a laser beam having a wavelength of 380 nm to 430 nm, and the recording is performed on the laser beam having a wavelength of 380 to 430 nm. An optical information recording medium in which the layer has an absorptance of 20% or more. 3. The recording layer has a first reflectance before the information is recorded, and has a first reflectivity after the information is recorded.
3. The optical information recording medium according to claim 1, having a second reflectance higher than the reflectance, and having compatibility with a read-only optical information recording medium. 4. The optical information recording medium according to claim 3, wherein said recording layer has said first reflectance of 30 to 70%. 5. The recording layer according to claim 1, wherein said recording layer has a thickness of at least 10 nm and at least 30 nm.
The optical information recording medium according to any one of claims 1 to 4, wherein the optical information recording medium has a thickness of not more than nm. 6. The thermal conductivity of the recording layer is 0.5 W / mK.
The optical information recording medium according to any one of claims 1 to 5, wherein the optical information recording medium has a power of 20 W / mK or less. 7. The recording layer according to claim 1, wherein the recording layer includes at least one selected from the group consisting of Si, Ge, an oxide or nitride of Si, and an oxide or nitride of Ge. An optical information recording medium according to claim 1. 8. A method for manufacturing an optical information recording medium in which information is recorded using a laser beam having a wavelength of 380 nm to 430 nm and a recording layer is formed on a substrate, wherein the recording layer has a desired thermal conductivity. An optical information recording medium comprising: adjusting a gas pressure so as to have a value of; and forming the recording layer on the substrate by sputtering with the adjusted gas pressure using Si or Ge as a target. Manufacturing method. 9. A method for recording information on an optical information recording medium according to claim 1, wherein a multi-pulse is used as a recording pulse of the laser beam,
When the laser peak power of the multi-pulse is Pw, the laser bottom power of the multi-pulse is Pbw, and the bias power between the recording pulses is Pb, 0 <Pbw <
A recording method for an optical information recording medium in which the information is recorded at 0.5 mW and 0 <Pb / Pw <0.33. 10. The optical information recording medium according to claim 9, further comprising guide grooves formed on the substrate at predetermined intervals, wherein the information is recorded in a flat area between the adjacent guide grooves. Recording method for an optical information recording medium. 11. The method for recording information on an optical information recording medium according to claim 1, wherein a rectangular wave is used as a recording pulse of the laser light, and the optical information recording medium is a recording medium. A method for recording an optical information recording medium on which information is recorded while rotating at a linear velocity of 10 m / s or more. 12. A substrate, a recording layer formed on the substrate, a light transmitting layer formed on the recording layer, and a thermal deformation suppressing layer between the recording layer and the light transmitting layer. 380 irradiated to the recording layer via the light transmitting layer
An optical information recording medium on which information is recorded using a laser beam having a wavelength of nm to 430 nm. 13. The thermal deformation suppressing layer is a SiN layer, a SiO
₂ layers, Ta ₂ O ₅ layer, Al ₂ O ₃ layer, AlN layer, SiC layer,
13. The optical information recording medium according to claim 12, wherein the optical information recording medium is a single layer or a stack of a plurality of layers selected from the group consisting of TiC layer and TiC layer. 14. The optical information recording medium according to claim 12, wherein said thermal deformation suppressing layer is a metal layer containing Au or Ag, and has a thickness of 5 nm or more and 15 nm or less. 15. The optical information recording medium according to claim 12, wherein said recording layer is a Si layer or a Ge layer. 16. A method for recording information on an optical information recording medium according to any one of claims 12 to 15, wherein the method comprises the steps of: A recording method of optical information in which the information is recorded. 17. A substrate having guide grooves formed at a predetermined interval, and a recording layer formed on the substrate, wherein a laser beam having a wavelength of 380 nm to 430 nm is used to form adjacent guide grooves. An optical information recording medium on which information is recorded in a flat area between them. 18. The optical information recording medium according to claim 17, wherein information is also recorded in said guide groove. 19. A recording medium comprising: a substrate having guide grooves formed at predetermined intervals; and a recording layer formed on the substrate, wherein information is recorded using laser light having a wavelength of 380 nm to 430 nm. An optical information recording medium, wherein a depth of the guide groove corresponding to a portion where the information is recorded is shallower after recording the information than before recording the information. 20. The optical information recording medium according to claim 19, wherein the reflectance before recording the information is lower than the reflectance after recording the information. 21. A substrate comprising: a substrate; and a recording layer formed on the substrate, wherein a wavelength of 380 nm to 430 nm is formed so that a space is formed between the recording layer and the substrate at a position irradiated with the laser beam.
An optical information recording medium on which information is recorded by irradiating the laser light.