JP2000298874A - Phase-change optical disk and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the rapid increase in jitter when repeated recording is made from several times to several tens of times. SOLUTION: A first dielectric layer 3, a signal-recording layer 4, a second dielectric layer 5, a light reflection layer 6, and a protection film layer 7 are successively laminated on a substrate 2 for formation. The signal-recording layer 4 is formed by GeSbTe material, and at the same time the diameter of a crystal particle being generated at the rear end part of a recording mark formed according to a recording signal for the signal-recording layer 4 is set to 50 nm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change type optical disk on which recording signals are recorded and / or reproduced by a phase change recording method, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A phase-change optical disk is a type of optical recording medium in which signal recording and / or reproduction (hereinafter referred to as recording / reproduction) is performed by irradiating a signal recording layer with laser light. Yes, the signal recording layer is made of a phase change material.

In a phase-change optical disk, when a recording / reproducing device irradiates a laser beam, a phase-change material constituting a signal recording layer reversibly changes between a crystalline state and an amorphous state at a laser beam irradiation position. I do. The recording / reproducing apparatus performs recording / reproducing on a phase-change optical disc by detecting a change in the reflectance of the signal recording layer due to a difference in optical constant between these two states.

[0004] In a phase change optical disk, the initial state of the signal recording layer is generally in a crystalline state. When a recording signal is recorded on a phase-change optical disk, a laser beam having a predetermined output is applied to a signal recording layer by a recording / reproducing device. As a result, the temperature of the signal recording layer is raised to a temperature equal to or higher than the melting point at the irradiation position of the laser beam. After that, the signal recording layer is cooled and becomes an amorphous state at this position. In a phase change optical disk, a recording signal is recorded by forming an amorphous portion (hereinafter referred to as a recording mark) on a signal recording layer in accordance with the recording signal.

When a recording signal recorded on the signal recording layer is erased, the phase-change type optical disk is irradiated with a laser beam having a lower output than that at the time of recording. In addition, the temperature is raised to the melting point temperature or lower. Thus, the signal recording layer becomes a crystalline state at the irradiation position of the laser beam irrespective of the state before the irradiation.

[0006] When reproducing a recording signal recorded in the signal recording layer, the phase-change type optical disk is irradiated with a laser beam having a weaker output than when erasing the recording signal. At this time,
The recording / reproducing apparatus detects return light that is reflected by the laser light and returns to the signal recording layer, and the reflectivity differs depending on whether the signal recording layer is in a crystalline state or an amorphous state at the irradiation position of the laser light. That is, the recorded signal is reproduced.

[0007] As described above, the phase change optical disk is
Rewriting of the recording signal is possible. Unlike a magneto-optical disk, for example, there is no need for a means for generating an external magnetic field for recording and reproduction. Therefore, the phase-change optical disk can contribute to downsizing of the recording / reproducing device and can easily perform overwriting.

[0008]

By the way, as a phase change material constituting a signal recording layer of a phase change type optical disk,
Mainly, GeSbTe-based materials and AgInSbTe-based materials are used. Among them, GeSbTe-based materials are:
It is known that repeated durability is excellent. However, the phase change type optical disc has a problem that, when a signal recording layer is formed of a GeSbTe-based material, signal characteristics when repeated recording is performed several to several tens of times are deteriorated.

More specifically, in a phase-change type optical disk having a signal recording layer formed of a GeSbTe-based material, when repeated recording is performed, the jitter of a reproduced signal after the second recording is rapidly increased. I will. Until the jitter was stabilized at 10% or less, about 100 repetitive recordings were required. As described above, in the conventional phase-change type optical disk, when the repetitive recording is performed several to several tens times (hereinafter, referred to as an initial recording stage), a sharp increase in jitter is observed.

Therefore, the conventional phase-change type optical disk requires a step of repeatedly performing recording about 100 times after its manufacture in order to secure stable recording / reproducing characteristics, and it is difficult to improve the production efficiency. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a phase-change type optical disc having a stable recording / reproducing characteristic in which an increase in jitter in an initial recording stage is suppressed, and a method for manufacturing the same.

[0012]

Means for Solving the Problems As a result of studying to achieve the above object, the present inventor has found the following facts by observing recording marks with a transmission electron microscope (TEM). . That is, when a new recording mark is formed on the recording mark or on the crystal after the recording mark has been formed once, the crystal penetrates into the rear end of the recording mark, and the mark shape is distorted. It is considered that the increase in jitter at the initial recording stage is caused by the distortion of the mark shape. In the conventional phase-change type optical disk, the average grain size of the crystal penetrating the rear end of the recording mark was about 80 nm.

The phase-change type optical disk according to the present invention based on the above-mentioned knowledge has at least a signal recording layer formed on a substrate, and records and records a recording signal on this signal recording layer by a phase-change recording method. And / or a recording medium on which reproduction is performed. The signal recording layer is made of a GeSbTe-based material, and when irradiated with laser light, reversibly changes between a crystalline state and an amorphous state at an irradiation position, and its initial state is changed to a crystalline state. The average grain size of crystal grains generated at the rear end of the recording mark formed by changing the signal recording layer from the crystalline state to the amorphous state in the moving direction of the laser beam is 5%.
0 nm or less.

In the phase-change type optical disk constructed as described above, even if a new recording mark is formed on a recording mark or on a crystal after the recording mark has been formed, the recording mark is The distortion of the mark shape is reduced.

Further, in the method for manufacturing a phase change optical disk according to the present invention, at least a signal recording layer is formed on a substrate, and recording and / or recording of a recording signal on the signal recording layer by a phase change recording method. This is a method for manufacturing a phase-change optical disc on which reproduction is performed. When forming the signal recording layer, the target material is sputtered in a mixed atmosphere of a rare gas and an additive gas containing at least one selected from a hydrocarbon gas, a nitrogen gas, an oxygen gas, and a carbon dioxide gas. By forming the film, the average grain size of the crystal grains generated at the rear end portion of the recording mark formed by changing the signal recording layer from the crystalline state to the amorphous state in the moving direction of the laser beam becomes 50 nm or less. To do.

Thus, even when a new recording mark is formed on a recording mark or on a crystal after the recording mark has been formed, a phase change type recording medium in which the distortion of the mark shape of the recording mark is reduced. An optical disk can be manufactured, and the manufacturing process of a phase change optical disk can be simplified.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, as a phase-change optical disk according to the present invention, a so-called double-sided recording / reproducing type having two signal recording layers, two substrates on which signal recording layers are formed and bonded together on a protective film layer side. The phase change type optical disk is described as an example. However, the present invention is not limited to this example.
The optical disk may be a phase-change optical disk in which a plurality of substrates are bonded on the substrate side, or a single-sided recording / reproducing-type phase-change optical disk having only one signal recording layer.

In the following description, a phase change type optical disc 1 as shown in FIG. 1 will be described. A phase-change type optical disc 1 has a first dielectric layer 3 on a substrate 2.
, A signal recording layer 4, a second dielectric layer 5, and a light reflecting layer 6
And a protective film layer 7 are sequentially laminated, and the two substrates 2 on which these layers are formed have a structure in which the protective film layers 7 are bonded to each other with an adhesive 8. That is, the phase change optical disk 1 has two signal recording layers 4 formed on two substrates 2 respectively. FIG. 1 is a cross-sectional view of the phase-change optical disc 1, showing only each layer formed on one of the two substrates 2 bonded together, and formed on the other substrate. Illustration of each layer is omitted.

The phase-change type optical disk 1 has a substantially disk shape as a whole, and has, for example, a diameter of 120 mm and a thickness of 1.2 mm. Also, the phase change optical disc 1
For example, it is housed in a disk cartridge (not shown) and is used detachably with respect to a recording / reproducing device (not shown). The phase-change optical disk 1 may be used without being housed in a disk cartridge, or may be configured integrally with a recording / reproducing device.

The substrate 2 is made of a hard material having a light-transmitting property with respect to a laser beam irradiated by a recording / reproducing apparatus.
The whole is formed in a substantially disk shape. As a material for forming the substrate 2, for example, various resin materials such as a polycarbonate resin, an acrylic resin, a polyolefin resin, and an epoxy resin, and a glass material such as quartz glass are used. In addition, a groove-shaped groove is formed on the substrate 2 in a predetermined concavo-convex pattern, and a recording track is formed along the groove.

The first dielectric layer 3 is made of, for example, Si ₃ N ₄ ,
SiN, AlN, Al ₂ O ₃ , AlSiNO, HfO ₂ ,
ZnS, ZrO ₂ , Y ₂ O ₃ , MgO, SiO ₂ , Mg
It is formed in a thin film form on the substrate 2 by using a material such as F ₂ and LiF by a thin film forming technique such as various sputtering methods. Note that in this embodiment, ZnS-Si
It was formed by O ₂ . The thickness of the first dielectric layer 3 is, for example, 80 nm to 140 nm.

The signal recording layer 4 is made of GeS which is a phase change material.
A thin film is formed on the first dielectric layer 3 using a bTe-based material. The signal recording layer 4 is reversibly changed between a crystalline state and an amorphous state at the irradiation position of the laser beam by being irradiated with the laser beam from the main surface 2a facing the outside of the substrate 2 by the recording / reproducing apparatus. It is configured to be. In addition, the signal recording layer 4 has different reflectivities between a portion in a crystalline state and a portion in an amorphous state.

The second dielectric layer 5 is formed in a thin film on the signal recording layer 4 in the same manner as the first dielectric layer 3. The second dielectric layer 5 is made of, for example, ZnS—SiO ₂
To a thickness of 10 nm to 30 nm.

The phase-change type optical disc 1 has a structure in which a signal recording layer 4 is sandwiched between a first dielectric layer 3 and a second dielectric layer 5. Thereby, the signal recording layer 4
Is prevented from being degraded by moisture, oxygen, carbon dioxide and the like contained in the atmosphere. Also, the first
The dielectric layer 3 and the second dielectric layer 5 have a function of causing multiple interference in a laser beam irradiated at the time of recording / reproducing and amplifying the laser beam.

The light reflecting layer 6 is formed on the second dielectric layer 5 in a thin film shape. The light reflection layer 6 has a function as a reflection layer that reflects the laser light transmitted through the signal recording layer 4 and the second dielectric layer 5. Accordingly, in the phase-change type optical disc 1, since the light reflection layer 6 has a function as a reflection layer, the use efficiency of the laser light at the time of recording and reproduction can be improved.

The light reflecting layer 6 has a function as a heat sink for preventing heat from being stored in the signal recording layer 4 by the laser beam irradiated toward the signal recording layer 4. As a result, in the phase-change type optical disc 1, the cooling speed of the signal recording layer 4 is increased, the amorphization by the laser beam is promoted, and the recording characteristics can be improved. In addition, in the phase-change optical disc 1, the temperature distribution of the signal recording layer 4 when the laser beam is irradiated becomes gentle, and the power margin at the time of recording and at the time of signal erasing can be widened.

As a material for forming the light reflecting layer 6, a non-ferrous metal element or a compound thereof which is a thermally good conductor is used alone.
Alternatively, it is desirable to use them in combination, for example, A
It is formed with a film thickness of 50 nm to 300 nm from u, Al or the like.

The protective film layer 7 is formed as a thin film on the light reflecting layer 6 by, for example, curing an ultraviolet curable resin applied by a spin coater or the like. The phase change optical disk 1 includes the protective film layer 7 so that
The signal recording layer 4 and the light reflection layer 6 are prevented from being deteriorated by oxidation or the like. Further, it is possible to prevent each layer formed on the substrate 2 from being damaged.

In the phase-change type optical disk 1 configured as described above, the initial state of the signal recording layer 4 is a crystalline state. The phase-change optical disk 1 is mounted on a recording / reproducing apparatus, and records, erases, and records recording signals on the signal recording layer 4 in a state where rotation is controlled to a predetermined linear velocity or a predetermined rotation speed. Alternatively, reproduction is performed.

Specifically, for example, the linear velocity is 4.8 m /
The optical system is controlled so that the rotation becomes s, and the relationship between the wavelength λ of the laser beam used for recording and reproduction and the lens numerical aperture NA satisfies the following equation 1.

[0031]

(Equation 1)

When recording signals are recorded on the phase-change type optical disc 1, a laser beam of a predetermined output is incident on the signal recording layer 4 from the main surface 2 a facing the outside of the substrate 2 by the recording / reproducing device. Irradiated. Thereby, the signal recording layer 4
Is heated to a temperature equal to or higher than the melting point at the irradiation position of the laser beam.
Thereafter, the signal recording layer 4 is cooled and becomes amorphous at this position. In a phase-change optical disc, a portion that is made amorphous according to a recording signal, that is,
By forming a recording mark on the signal recording layer 4,
Record the recording signal.

The phase-change type optical disk 1 is irradiated with a laser beam with the same output as described above, so that the signal recording layer 4 can be irradiated irrespective of whether the irradiation position is in a crystalline state or an amorphous state. Rewriting the recorded signal,
So-called overwriting can be performed.

When the recording signal recorded on the signal recording layer 4 is erased, the phase-change type optical disk 1 is irradiated with a laser beam having an output lower than that at the time of recording. The temperature is raised to a temperature higher than the formation temperature and lower than the melting point.
As a result, the signal recording layer 4 is in a crystalline state at this irradiation position irrespective of the state before irradiation. It should be noted that the phase-change type optical disc 1 uses the signal recording layer 4 to erase such a recording signal.
Is carried out over the entire surface, so that the entire surface of the signal recording layer 4 is initialized to a crystalline state.

When reproducing the recording signal recorded on the signal recording layer 4, the phase-change type optical disk 1 is irradiated with a laser beam having a weaker output than when erasing the recording signal. At this time, the recording / reproducing device detects the returning light reflected by the laser light on the signal recording layer 4, and determines whether the signal recording layer 4 is in a crystalline state or an amorphous state at the irradiation position of the laser light. The recording signal is reproduced by utilizing the fact that the reflectivity is different.

Meanwhile, in the phase change type optical disk 1, the signal recording layer 4 is formed of a GeSbTe-based material as described above. It is generally known that a GeSbTe-based material has excellent repetition durability when used for a signal recording layer of a phase-change optical disc. However, in the conventional phase-change type optical disc, when a signal recording layer is formed of a GeSbTe-based material, the jitter at the initial recording stage increases rapidly when repeated recording is performed several to several tens of times, that is, at the initial recording stage. There was a problem.

In order to solve this problem, the present inventor has observed the recording marks formed on the signal recording layer 4 with a transmission electron microscope (TEM) to find out the fact described below. Hereinafter, description will be made with reference to FIG. FIG. 2 is a schematic diagram showing a new recording mark 10 formed on a recording mark or on a crystal after the recording mark has been formed once. Arrow A in FIG.
Indicates the moving direction of the spot of the laser beam. In the following description, for the sake of convenience, the end where the recording mark 10 is first amorphized by the laser beam is referred to as the tip 10.
a and the opposite end is referred to as a rear end 10b.

The recording mark 10 is formed by making the signal recording layer 4 amorphous, but according to observations by the present inventors, crystal grains 11 are formed so as to penetrate the rear end 10b. It was confirmed that. Thereby, the recording mark 10 is formed with a distorted mark shape at the rear end portion 10b. It is considered that the above-mentioned rapid increase in jitter is caused by the fact that the distortion of the mark shape is not easily averaged during repeated recording. The average grain size of the crystal grains 11 in the conventional phase-change optical disc was about 80 nm.

Therefore, the present inventors have found that by reducing the average grain size of the crystal grains 11, the distortion at the rear end portion 10b of the recording mark 10 can be reduced and the increase in jitter can be suppressed. I got In order to obtain a crystal phase having a small grain size, it is effective to increase the number of crystal nuclei. In order to increase the number of crystal nuclei in the signal recording layer 4, a method of mixing impurities into the signal recording layer 4, a method of forming a layer that generates nuclei at an interface between the signal recording layer 4 and the dielectric layer, and the like are given. Can be

In the phase-change type optical disc 1 according to the present invention, since the signal recording layer 4 is formed by a method described later, the signal recording layer 4 is formed by mixing impurities. Thus, in the phase-change optical disc 1, the impurities mixed into the signal recording layer 4 function as crystal nuclei, and the average grain size of the crystal grains 11 penetrating into the rear end portion 10b of the recording mark 10 is set to 50 nm or less. .

Therefore, in the phase change type optical disk 1, distortion generated in the mark shape of the recording mark 10 is reduced, and a sharp increase in jitter in the initial recording stage is suppressed. As a result, the phase-change optical disc 1 has excellent repetition durability due to the signal recording layer 4 being formed of the GeSbTe-based material, and has stable recording / reproducing characteristics due to the suppression of a sharp increase in jitter. It can be used as an optical recording medium provided. Specifically, the phase-change optical disc 1 can obtain a good reproduction signal even when recording and reproduction are repeated tens of thousands of times or more.

Hereinafter, the phase change type optical disk according to the present invention will be described based on experimental examples. Hereinafter, first, a plurality of phase change optical disks were manufactured in the same manner as the above-described phase change optical disk 1.

Experimental Example 1 In Experimental Example 1, the diameter was 120 mm, the thickness was 0.6 mm,
Each layer was formed on a substrate having a track pitch of about 0.8 μm, and the two substrates were bonded together on the protective film layer side via an adhesive, thereby producing a phase-change optical disk similar to the conventional one. The materials and film thicknesses used for forming each layer on the substrate are shown below.

Layer Configuration of Phase Change Optical Disk of Experimental Example 1 First dielectric layer: ZnS—SiO ₂ (film thickness: 120 nm) Signal recording layer: GeSbTe-based material (film thickness: 25 nm) Second dielectric layer: ZnS -SiO ₂ (film thickness: 15 nm) Light reflection layer: Al alloy (film thickness: 150 nm) Protective film layer: UV curable resin (film thickness: 10 μm) In this phase change optical disk, about 3.0 GB is provided for each signal recording layer. Recording capacity. In producing the phase-change optical disk, the signal recording layer was formed by sputtering in an Ar gas atmosphere using Ge ₂ Sb ₂ Te ₅ as a target material in the same manner as before.

Experimental Examples 2 to 6 In Experimental Examples 2 to 6, when forming the signal recording layer,
A phase change optical disk was manufactured in the same manner as in Experimental Example 1 except that the film was formed by sputtering in an Ar gas atmosphere mixed with CH ₄ gas.

Table 1 shows the ratio of the CH ₄ gas to the Ar gas in the sputter gas used for forming the signal recording layer when producing the phase change type optical disc of each experimental example.

[0047]

[Table 1]

Next, as described above, the phase change type optical discs of Experimental Examples 1 to 5 are subjected to an initialization process on the entire surface of the signal recording layer, and thereafter, are subjected to the recording / reproducing apparatus shown in FIG.
Then, a laser beam having a wavelength of 650 nm was irradiated with a light emission pattern as shown in FIG. FIG. 3A shows an emission pattern of a laser beam when a recording mark (11T signal) having a length 11 times the unit length is formed, and FIG. 4 shows a light emission pattern of laser light when forming a recording mark (3T signal) having a length three times as long. At this time, the linear velocity of the disk is 4.8 m / s, and the channel clock is 2
7.7 MHz. The recording / reproducing apparatus has a recording power Ph of 14.5 mW, an erasing power Pl of 5.8 mW, and a cooling power Pc of 1.5 mW.
Was used.

With respect to the phase change type optical disk of Experimental Example 1,
FIG. 4 shows the result of measuring the jitter of the reproduced signal when recording was repeatedly performed up to 10,000 times with the above-described light emission pattern. FIG. 4 shows the jitter at the leading end and the trailing end of the recording mark as shown in FIG. 2, and the jitter obtained by averaging the jitter at the leading end and the trailing end. As is clear from FIG. 4, the jitter of the reproduced signal is highest when the recording operation is repeated several times at the beginning, that is, at the initial recording stage, and decreases as the number of recordings increases. Also, it can be seen that the jitter at the rear end is higher than the jitter at the front end of the recording mark.

The phase-change type optical discs of Experimental Examples 1 to 5 have a light emission pattern of 100
FIG. 5 shows the result of measuring the average jitter of the reproduced signal when recording was repeatedly performed up to 00 times. Further, at this time, the signal recording layers of these phase-change optical disks were observed with a transmission electron microscope (TEM), and as shown in FIG. FIG. 6 shows the result of measuring the average particle size of the sample. When obtaining the average particle size, a photograph near the recording mark obtained by TEM was taken as image data into a computer using a scanner. Then, after calculating the area of each crystal grain by a computer, the diameter was determined assuming that the crystal shape was a circle, and this was defined as the average grain size of the crystal grains.

From the results shown in FIG. 5, in the case of the phase change type optical disc, CH ₄ was used as the sputtering gas when forming the signal recording layer.
It can be seen that as the ratio of mixing is increased, the occurrence of abrupt jitter in the initial recording stage is suppressed, and stable recording and reproduction can be performed from the stage where the number of recordings is small. Specifically, in the case of Experimental Example 1 in which the signal recording layer was formed without mixing CH ₄ with the sputtering gas, the jitter was 1 at the maximum.
Becomes 2.5% as high, in the case of Experimental Example 3 Experimental Example 5 formed a signal recording layer by using the sputtering gas mixed with CH ₄ 5% or more, jitter became a value below 9% .

Therefore, the method of manufacturing a phase change optical disk according to the present invention does not require a step of repeatedly performing recording about 100 times after manufacturing the disk in order to secure stable recording and reproduction characteristics. Efficiency can be improved. Further, as is clear from the results shown in FIG. 5, according to the method for manufacturing a phase change optical disk according to the present invention, the phase change optical disk manufactured with the conventional manufacturing method has a reduced jitter compared to the phase change optical disk. Optical discs can be manufactured.

In a phase change optical disk, good recording and reproduction can be generally performed when the jitter is 9% or less. Therefore, as in the case of Experimental Examples 3 to 5, it is desirable that the ratio of mixing CH ₄ with the sputtering gas be 5% or more.

Further, from the results shown in FIG. 6, it can be seen from the results shown in FIG. 6 that as the ratio of mixing CH ₄ into the sputter gas when forming the signal recording layer is increased, the crystal grains formed by penetrating into the rear end of the recording mark are increased. It can be seen that the average particle size becomes smaller. The average grain size of the crystal grains hardly changes even after repeated recording up to 10,000 times. Further, considering the results shown in FIG. 5, in the case of Experimental Examples 3 to 5, that is, when the average grain size of the crystal grains formed by penetrating the rear end of the recording mark is 50 nm or less. In addition, the phase change optical disk can perform good recording and reproduction.

Next, FIG. 7 shows the results of measuring the reflectivity of the phase-change optical discs of Experimental Examples 1 to 6 with respect to laser light at the positions where the grooves were formed. From this result, it is understood that the reflectivity monotonously decreases as the ratio of mixing CH ₄ with the sputtering gas increases. In general, in the case of a phase change optical disk, when the reflectance with respect to laser light is 11% or less, it is not possible to secure a sufficient signal modulation degree for performing good recording and reproduction.
Therefore, from the results shown in FIG.
It is desirable that the mixing ratio of ₄ is 10% or less.

From the above results, when manufacturing a phase change optical disk, when forming a signal recording layer by sputtering, the ratio of CH _{4 to} Ar gas should be 5% or more and 10% or more.
It can be said that the following is desirable.

In this experimental example, CH ₄ gas was mixed as an additional gas with Ar gas as a sputtering gas when forming the signal recording layer. However, the present invention is not limited to this example. Absent. As a sputter gas used in the present invention, a gas having an effect of increasing the number of crystal nuclei by mixing impurities into the signal recording layer may be mixed with a rare gas as an additional gas. As the additive gas, for example, ethane (C ₂ H ₆ ) or propane (C ₃ H ₈ ) which is a paraffinic hydrocarbon similar to CH ₄ may be used. Further, the same effect as described above can be obtained even when the signal recording layer is formed by sputtering using a gas such as oxygen, nitrogen or carbon dioxide as an additional gas. Alternatively, a plurality of these gases may be mixed with the rare gas.

[0058]

As described above, the phase-change type optical disk according to the present invention can be used for recording a new recording mark on a recording mark or on a crystal after the recording mark has been formed. The distortion of the mark shape of the mark is reduced. As a result, it is possible to suppress a sudden increase in jitter at the initial recording stage. Therefore, the phase-change optical disk according to the present invention has an optical recording layer having a signal recording layer formed of a GeSbTe-based material and having excellent repetition durability, and having a stable recording / reproducing characteristic by suppressing a sharp increase in jitter. It can be used as a medium.

Further, the method for manufacturing a phase-change optical disc according to the present invention can be applied to a method for manufacturing a recording mark even if a new recording mark is formed on a recording mark or on a crystal after the recording mark has been formed. A phase-change optical disk in which intrusion of crystals into the rear end of the optical disk is suppressed.
Therefore, a step of repeating recording about 100 times to stabilize the generation of jitter becomes unnecessary, and the production efficiency of the phase change optical disk can be improved.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part showing a phase change optical disk according to the present invention.

FIG. 2 is a diagram for explaining recording marks formed on a signal recording layer of the in-phase change optical disk.

3A and 3B are diagrams illustrating a pattern of a laser beam applied to an in-phase change type optical disc, wherein FIG. 3A illustrates an 11T signal, and FIG. 3B illustrates a 3T signal.

FIG. 4 is a diagram showing a relationship between the number of times of repetitive recording and jitter in a phase change optical disk of Experimental Example 1 manufactured similarly to a conventional phase change optical disk.

FIG. 5 is a diagram showing the relationship between the number of times of repetitive recording and jitter in the phase change optical discs of Experimental Examples 1 to 5.

FIG. 6 is a diagram showing the relationship between the number of repetitive recordings and the average grain size of crystal grains formed at the rear end of a recording mark in the phase change optical disks of Experimental Examples 1 to 5.

FIG. 7 is a diagram showing the relationship between the mixing ratio of CH ₄ and the reflectance with respect to laser light in the phase change optical disks of Experimental Examples 1 to 6.

[Explanation of symbols]

Reference Signs List 1 phase change optical disk, 2 substrate, 3 first dielectric layer, 4 signal recording layer, 5 second dielectric layer, 6 light reflection layer, 7 protective film layer, 8 adhesive

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shiminori Takase 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Yoshihiro Saito 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo No. Sony Corporation F term (reference) 5D029 JA01 JC09 JC18 5D121 AA01 EE03 EE14 EE17

Claims (3)

[Claims] 1. A phase-change type optical disc, wherein at least a signal recording layer is formed on a substrate, and recording and / or reproduction of a recording signal is performed on the signal recording layer by a phase-change recording method. The signal recording layer is made of a GeSbTe-based material, and when irradiated with laser light, reversibly changes between a crystalline state and an amorphous state at an irradiation position, and its initial state is changed to a crystalline state. A phase-change optical disc, characterized in that the recording mark formed by changing from a crystalline state to an amorphous state has an average grain size of crystal grains generated at a rear end portion in a moving direction of a laser beam of 50 nm or less. 2. A method for manufacturing a phase-change optical disc, comprising forming at least a signal recording layer on a substrate, and recording and / or reproducing a recording signal on the signal recording layer by a phase-change recording method. When forming the signal recording layer, the target material is sputtered in a mixed atmosphere of a rare gas and an additive gas containing at least one selected from a hydrocarbon gas, a nitrogen gas, an oxygen gas, and a carbon dioxide gas. By forming a film, the signal recording layer is irradiated with a laser beam, so that the signal recording layer changes from a crystalline state to an amorphous state, and a trailing end of a recording mark formed in the moving direction of the laser beam. A method for manufacturing a phase-change optical disk, characterized in that the average grain size of crystal grains generated in a portion is 50 nm or less. 3. The method according to claim 2, wherein, when forming the signal recording layer, the ratio of the additional gas is set to 5% or more and 10% or less.