JP2003154754A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent phase change type optical recording medium, which shows favorable recording and erasing characteristics even in high linear speed recording and has a long storage life. SOLUTION: This phase change type optical recording medium has a recording layer, in which information is recorded through the phase change reversibly developing between a crystalline state and an amorphous state by the irradiation of laser rays and the major components of which are represented by a compositional formula: GeαGaβCuγSbδTeε (wherein α, β, γ, δ and ε represent the compositional ratio (at.%) of respective elements under the conditions that 0<=α<=5, 1<=β<=5, 1<=γ<=10, 65<=δ<=81, 13<=ε<=24 and α+β+γ+δ+ε=100.

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 recording medium.

[0002]

2. Description of the Related Art A phase change type optical recording medium is known as one of mediums capable of recording a large amount of information and capable of reproduction and repetitive recording at a high linear velocity. This phase-change type optical recording medium uses a crystalline state and an amorphous state which are reversibly generated in a recording layer by locally irradiating a laser beam for recording. That is, the fact that the amount of reflected light with respect to light of a specific wavelength differs between the crystalline state and the amorphous state is used as recording, and recording / erasing is possible with a simple optical system, while erasing already recorded information. It has an excellent feature that it is easy to record new information. Generally, in a phase change type optical recording medium capable of repetitive recording, an amorphous state in a recording layer is a recorded state and a crystalline state is an erased state. Information is recorded by irradiating a laser beam to melt and rapidly cool the recording film to form an amorphous recording mark. Then, the recorded signal is reproduced by detecting the change in the amount of light reflected from the disk by utilizing the difference in reflectance between the amorphous portion and the crystalline portion. One of the characteristics required for an optical recording medium that can be repeatedly recorded is high storage reliability. On the other hand, recently, high linear velocity recording, that is, 7-1 which is 2 to 5 times the linear velocity of reproduction of DVD-ROM.
Recording at 7.5 m / s is required, but good erasing characteristics at this linear velocity, that is, fast crystallization, and high storage reliability, that is, stable presence of amorphous marks for a long period of time, are compatible. Was considered difficult.

At present, GeTeSb, AgInSbTe, etc. are known and put to practical use as recording materials for phase-change type optical recording media, but these compositions have good erasing characteristics at high linear velocity of 7 to 17.5 m / s. There is a problem in compatibility of storage reliability. According to Japanese Unexamined Patent Publication No. 2000-132864, when GeSbTe is used for the recording layer and an NZ interface layer is provided, the interface layer may suppress deterioration of the recording layer and reduce increase in jitter during storage. There is. However, the disk linear velocity at the time of recording shown is 8.3 m / s, and there is a problem in recording at a higher linear velocity. Also, the jitter at the first recording is 13
%, Which is not a sufficiently low value.

According to Japanese Patent Laid-Open No. 2000-313170, SbTeGe + M (In and / or Ga) is formed in the recording layer.
Is used, the usable recording linear velocity range is wide and the recording marks are stable for a long period of time. However,
The linear velocity shown is 1.2 to 8.1 m / s, which cannot be said to be sufficiently compatible with high linear velocity recording. Moreover, the data of the shelf life test are not shown. JP-A-6-33
According to Japanese Patent No. 3275, when a recording layer (GeSbTe) or a dielectric layer of an optical information recording medium is formed by sputtering, if at least one kind of gas of Kr and Xe is used as a discharge gas, it is repeatedly overexposed. It is said that the cycle deterioration phenomenon due to the write operation is suppressed, the longevity of the medium and the high reliability are achieved. However, at present, low-cost production is an essential issue, and there is a problem because Kr and Xe are expensive. Also,
Since the recording linear velocity is 10 m / s, it cannot be said that the recording linear velocity is sufficiently high. Furthermore, data for shelf life tests are not shown.

[0005]

DISCLOSURE OF THE INVENTION Presently, DVD-ROM
High-density recording equivalent to or higher than that of DVD-ROM
There is a demand for a phase change type optical recording medium suitable for high linear velocity recording of 7 to 17.5 m / s, which is 2 to 5 times higher than the reproducing linear velocity.
To achieve high linear velocity recording, it is necessary to crystallize the recording material while the light spot passes through one point on the recording medium,
A high crystallization rate is required. Also, at room temperature,
Amorphous marks must exist stably for 10 years or more.
However, when recording is performed on a phase-change optical recording medium using a recording layer having the composition disclosed so far, a recording with a composition that has an appropriate crystallization rate and can form a good recording mark even at high linear velocity recording When a layer is used, there is a problem in storage reliability, and when a recording layer having a composition with good storage reliability is used, the jitter at the time of initial recording exceeds 13% when recording at a high linear velocity, and when recording repeatedly. I couldn't get a low jitter value. Therefore, an object of the present invention is to provide an excellent phase change type optical recording medium which exhibits excellent recording / erasing characteristics even in high linear velocity recording and has a long storage life.

[0006]

The Sb-Sb ₂ Te ₃ pseudo-binary alloy has a eutectic point near Sb ₇₀ Te ₃₀ , and Sb-Te in the vicinity has a phase difference in the recording film even if repeated recording is performed. Separation hardly occurs, and excellent repetitive recording characteristics. The present inventors conducted studies to obtain an excellent recording material for a phase-change optical recording medium by adding various elements based on the Sb-Sb ₂ Te ₃ pseudo-binary eutectic composition. As a result, it has been found that the above problems can be solved by the following inventions 1) to 6) (hereinafter referred to as the inventions 1 to 6). 1) It has a recording layer in which information is recorded by reversible phase change between a crystalline state and an amorphous state upon irradiation with laser light, and the main component of the recording layer is the following composition formula (1) A phase change type optical recording medium characterized by: GeαGaβCuγSbδTeε (1) Here, α, β, γ, δ, and ε in the formula (1) represent the composition ratio (at%) of each element and are in the following ranges. 0 ≦ α ≦ 5 1 ≦ β ≦ 5 1 ≦ γ ≦ 10 65 ≦ δ ≦ 81 13 ≦ ε ≦ 24 α + β + γ + δ + ε = 100 2) The crystallization temperature of the recording layer at a temperature rising rate of 10 ° C./min is 170 to 220. The phase change type optical recording medium as described in 1) above, which is at a temperature of ° C. 3) The phase change type optical recording medium according to 1) or 2), wherein the recording layer has a melting point of 500 to 680 ° C. 4) The phase-change optical recording medium according to any one of 1) to 3), wherein the recording layer has a thickness of 10 to 25 nm. 5) The phase change type optical recording medium according to any one of 1) to 4), in which at least a substrate, a lower protective layer, a recording layer, an upper protective layer, and a reflective layer are provided in this order. 6) The phase-change type according to any one of 1) to 5), which has a recording layer formed by a sputtering method using Ar gas using an alloy target made of a material forming the recording layer. Optical recording medium.

The present invention will be described in detail below. In the first aspect of the invention, the recording layer needs to contain the recording material represented by the composition formula (1) as a main component. here,
The main component means containing 50% or more of the recording material, but it is preferably close to 100%. Explaining the function of each element constituting the composition formula (1), G
Although e has the effect of improving the storage reliability, when α> 5, the crystallization rate becomes slow, and good high linear velocity recording becomes difficult. Cu also has the effect of improving storage reliability,
In the case of γ <1, no effect appears, and in the case of γ> 10, the crystallization speed becomes slow and high linear velocity recording cannot be achieved. Thus, both Ge and Cu have the effect of improving the storage reliability, but Cu also has the negative effect of slowing the crystallization speed. Ge also has a negative effect of slowing the crystallization rate, but the negative effect is smaller than that of Cu. Therefore,
By adding Cu and Ge at the same time for adjustment, it is possible to provide a recording material having both storage reliability and high linear velocity recording.

Ga has the effect of increasing the crystallization rate, but when β <1, it does not appear, and when β> 5, phase separation easily occurs, which causes a problem in repeated recording. S
b is the main component of the alloy. When δ <65, the crystallization speed is slow, so high linear velocity recording cannot be achieved, and when δ> 81, phase separation easily occurs. Te has a tendency of phase separation when ε <13,
If ε> 24, high linear velocity recording cannot be achieved. According to the present invention 1 using the recording material satisfying the various conditions as described above,
Even in recording under high linear velocity, it has good erasing and recording characteristics, and composition segregation does not easily occur even after repeated recording,
It is possible to provide a phase-change optical recording medium that also satisfies storage reliability.

As in the present invention 2, the temperature rising rate of the recording layer is 10
When the crystallization temperature in ° C / min is 170 to 220 ° C, the initial crystallization can be easily and uniformly performed, and the phase change type optical recording medium having good storage reliability can be provided. Crystallization temperature is 1
If it is lower than 70 ° C, storage reliability may be deteriorated, and if it is higher than 220 ° C, initial crystallization becomes difficult. When the melting point of the recording layer is set to 500 to 680 ° C. as in the present invention 3, a phase change type optical recording medium having appropriate sensitivity and storage reliability can be provided. When the crystallization rate is high, a higher cooling rate is required to make the material amorphous, and thus the sensitivity tends to be insufficient. If the melting point is lower than 500 ° C, the storage characteristics and reproduction light stability will deteriorate, and if the melting point is higher than 680 ° C, the sensitivity will deteriorate.

As in the fourth aspect of the present invention, the thickness of the recording layer is 10 to 10.
When the thickness is 25 nm, stable recording can be performed, and a phase change type optical recording medium having good sensitivity can be provided. If the thickness is less than 10 nm, the light absorbing ability is lowered and the temperature of the recording film does not rise sufficiently, so that recording may not be performed in some cases.
If the thickness is thicker, the amount of transmitted light decreases, and it is difficult to expect the interference effect, which is not preferable. As in the present invention 5, by providing at least a substrate, a lower protective layer, a recording layer, an upper protective layer, and a reflective layer in this order, it is possible to perform recording and erasing by utilizing light interference and reflection effect. A changeable optical recording medium can be provided. The protective layer has a function as a heat-resistant protective layer and a function as a light interference layer, and the reflective layer has a function of reflecting light and a function of releasing heat. As in the present invention 6,
Using an alloy target made of the material that constitutes the recording layer,
By forming the recording layer by a sputtering method using Ar gas, it is possible to easily mass-produce a phase-change optical recording medium of low cost and constant quality.

Next, the constitution and manufacturing method of each layer of the phase change type optical recording medium of the present invention will be explained. The phase change type optical recording medium of the present invention is usually formed by sequentially forming a lower protective layer, a recording layer, an upper protective layer, an interface layer and a reflective heat dissipation layer on a substrate by a sputtering method, and further forming an overcoat layer, Created by pasting another substrate on top. As the substrate,
Generally, there is a guide groove for tracking on the surface, and the diameter is 1
A polycarbonate substrate having a disk shape of 2 cm and a thickness of 0.6 mm and having excellent workability and optical characteristics is used. The lower protective layer is required to have good adhesiveness to the substrate and the recording layer and high heat resistance. Further, since it also plays a role as a light interference layer that enables effective light absorption of the recording layer, it is desirable to have optical characteristics suitable for repeated recording at high linear velocity. The preferred material is (Z
nS) ₈₀ (SiO ₂ ) ₂₀ may be mentioned. Film thickness is 20
A thickness of up to 300 nm is suitable. If it is thinner than 20 nm, the function as a heat-resistant protective layer is lost, and if it is thicker than 300 nm, interfacial peeling easily occurs.

The recording layer is provided between the upper protective layer and the lower protective layer. As mentioned above, _Sb-Sb 2 Te ₃ pseudo-binary alloy has a eutectic point to the _Sb 70 _{Te 30} near, Sb-Te composition of the vicinity hardly occurs segregation even if the repetitive recording, repeated Although it has excellent recording characteristics, when an amorphous mark was recorded and then introduced into a constant temperature bath at 80 ° C. for 100 hours, it was found that the mark disappeared and there was a problem in storage reliability. However, the appropriate atomic ratio of GeGaCuSb
By using a recording film containing Te as a main component, a linear velocity of 7 to 17.
Amorphous marks can be reversibly recorded when a laser beam is irradiated at 5 m / s, and a jitter of 10% or less (here, data to clock jitter) is recorded.
The value obtained by normalizing ter σ with the detection window width Tw is called jitter. Further, even after the amorphous mark was recorded, even if the amorphous mark was introduced into a constant temperature bath at 80 ° C., the amorphous mark did not deteriorate much, showing excellent storage reliability.

The upper protective layer is required to have good adhesiveness to the recording layer and the interface layer and high heat resistance. Further, since it also plays a role as a light interference layer that enables effective light absorption of the recording layer, it is desirable to have optical characteristics suitable for repeated recording at high linear velocity. A preferable material is (ZnS) ₈₀ (SiO ₂ ) ₂₀ . A film thickness of 10 to 50 nm is suitable. If it is thinner than 10 nm, the function as a heat resistant protective layer is lost, and if it is thicker than 50 nm, the recording sensitivity is lowered. It is desirable to provide an interface layer between the upper protective layer and the reflective layer. This layer has a function of preventing generation of Ag ₂ S due to a reaction between S contained in the upper protective layer and Ag contained in the reflective layer. SiC is mentioned as a preferable material. Film thickness is 2-10n
m is suitable, and if it is thinner than 2 nm, Ag ₂ S is likely to be generated, and if it is thicker than 10 nm, the recording characteristics deteriorate. A material containing Ag as a main component is used for the reflective layer. Ag has a high thermal conductivity and is suitable for high linear velocity recording. Film thickness is 50-300n
If m is less than 50 nm and the thickness is less than 50 nm, deterioration becomes a problem when recording is repeated, and if more than 300 nm, the heat dissipation efficiency is too good and the sensitivity becomes poor.

[0014]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Examples 1 to 7 and Comparative Examples 1 to 4 Discs of Examples and Comparative Examples were prepared as follows. A lower protective layer, a recording layer, an upper protective layer, and a reflective layer were sequentially formed by sputtering on a polycarbonate substrate having a track pitch of 0.74 μm, a diameter of 12 cm, and a thickness of 0.6 mm. The lower protective layer is (ZnS) ₈₀ (SiO ₂ ).
₂₀ was used as a target and the film thickness was set to 65 nm. For the recording layer, an alloy target having a composition ratio corresponding to the recording material composition shown in Table 1 below was used and the film thickness was set to 18 nm. For the upper protective layer, (ZnS) ₈₀ (SiO ₂ ) ₂₀ was used as a target, and the film thickness was set to 10 nm. The reflective layer uses an Ag target and has a film thickness of 140 nm. Further, an acrylic UV curable resin having a thickness of 5 to 10 μm is formed on the reflective layer by a spinner.
After coating, UV curing was performed to form an organic protective film.
Further thereon, a polycarbonate substrate having a diameter of 12 cm and a thickness of 0.6 μm was attached using an adhesive sheet. Each of the discs created as described above has a diameter of 1 μm × 1
Output 680 mW, feed 3 using a laser of 00 μm
Initial crystallization was performed at 6 μm and a linear velocity of 3 m / s. Recording / reproduction was evaluated using a pickup head with a wavelength of 660 nm and an NA of 0.65, recording density of 0.267 μm / bit, and EFM.
+ Modulation method was used. Recording power is 13-18mW,
Bias power is 0.2mW, erase power is 6-10m
In W, the recording strategy was optimized for each disc. All reproduction is linear speed 3.5m / s, power 0.7
It was performed in mW.

[0016]

[Table 1]

[0017]

[Table 2]

The compositions of the recording layers used for the disks of Examples 1 to 7 and Comparative Examples 1 to 4 are shown in Table 1 above.
Maximum recordable linear velocity (m / s), increase in jitter (%) after repeated recording, increase in jitter (%) after introducing constant temperature bath, crystallization temperature (° C), melting point (° C), initial crystallization The results are shown in Table 2 above. The maximum recordable linear velocity is the recording power,
When the erasing power and the recording strategy are optimized for each of the examples and comparative examples, the linear velocity at which recording is possible with the jitter at the initial recording of 10% or less is possible. The increase in jitter after repetitive recording indicates an increase in jitter after repetitive recording 5000 times based on the initial recording. The increase in jitter after the introduction of the thermostat indicates the amount of increase in the jitter after the introduction after the introduction of the recording mark for 500 hours in the thermostat at 80 ° C. after the introduction. The crystallization temperature is a crystallization temperature measured by a differential scanning calorimeter when the temperature rising rate is 10 ° C / min. The melting point is measured by a differential thermogravimetric simultaneous measurement device. The initial crystallization was evaluated as “◯” when the reflectance after the initial crystallization was uniform in the plane, and as “x” when the reflectance had a distribution.

In Examples 1 to 7, the maximum recordable linear velocity is 1
The recording layer composition was designed so that the crystallization temperature was 7 to 18 m / s, the crystallization temperature was 170 to 220 ° C., and the melting point was 550 to 680 ° C., and a disk was prepared. As a result, although not shown in Table 2, the jitter at the time of initial recording could be suppressed to 10% or less at a high linear velocity. Further, as shown in Table 2, the increase in jitter after repeated recording and the increase in jitter after introduction in a constant temperature bath were low, and good storage characteristics were exhibited. Further, the reflectance after the initial crystallization was also uniform in the plane.

In Comparative Example 1, when the composition of the recording film was evaluated as Ge10 at% and Cu0 at% which are out of the range of the present invention, the maximum recordable linear velocity was as slow as 15 m / s. This is because Ge has the effect of improving the storage reliability, but at the same time has the negative effect of decreasing the crystallization speed.
It is probable that recording at high linear velocity was not possible. In Comparative Example 2, the composition of the recording film is outside the range of the present invention Cu11.
%, The maximum recordable linear velocity was 14 m /
It was slow as s. It is considered that although Cu has an effect of improving the storage reliability, it also has a negative effect of slowing down the crystallization speed, and therefore recording at a high linear velocity could not be performed. Further, it is considered that the addition of Cu had a negative effect of increasing the melting point, and the melting point was raised to 700 ° C. to deteriorate the sensitivity, so that the increase in jitter after repeated recording was large.

In Comparative Example 3, when the composition of the recording film was evaluated as Ga7 at% which is outside the range of the present invention, the increase in jitter after repetitive recording was as large as 8.2%. It is considered that Ga has an effect of increasing the crystallization rate and at the same time has a negative effect of facilitating phase separation, so that deterioration is promoted by repeated recording. Also, Ga
Since it also has a negative effect of increasing the crystallization temperature, it is considered that the crystallization temperature was as high as 228 ° C. and the initial crystallization could not be performed uniformly. In Comparative Example 4, when the composition of the recording film was evaluated as Te10 at% which is out of the range of the present invention, the increase in jitter after repeated recording was as large as 7.5%. It is considered that this is because, when Te is small, phase separation easily occurs, and therefore deterioration is advanced by repeated recording.

Examples 8 and 9 Discs were prepared and evaluated in the same manner as in Example 1 except that the thickness of the recording layer was changed to 13 nm (Example 8) and 22 nm (Example 9). The recording layer thickness (n
m), the jitter (%) at the time of the first recording when recording at a linear velocity of 17 m / s, and the increase (%) of the jitter after repeatedly recording 5000 times based on the time of the first recording. As can be seen from Table 3 below, even at high linear velocity recording, the jitter at the time of initial recording was 10% or less, and there was little deterioration even after repeated recording, and good characteristics were obtained.

[0023]

[Table 3]

Comparative Examples 5 and 6 Discs were prepared and evaluated in the same manner as in Example 1 except that the thickness of the recording layer was changed to 8 nm (Comparative Example 5) and 28 nm (Comparative Example 6). The recording layer thickness (n
m), the jitter (%) at the time of the first recording when recording at a linear velocity of 17 m / s, and the increase (%) of the jitter after repeatedly recording 5000 times based on the time of the first recording. As can be seen from Table 3, in Comparative Examples 5 and 6, even when the recording power, the erasing power and the recording strategy were optimized, the jitter at the initial recording exceeded 12% and the deterioration after the repeated recording was large. It is considered that in Comparative Example 5, since the recording film was thin, the light absorption ability was lowered, and the temperature of the recording film did not rise sufficiently to perform recording, whereas in Comparative Example 6, the recording film was thick. It is considered that recording could not be performed because the transmitted light was reduced and the interference effect was not sufficiently obtained.

[0025]

According to the first aspect of the present invention, it is possible to provide a phase change type optical recording medium which achieves both high linear velocity recording and storage reliability. According to the second aspect of the present invention, it is possible to provide a phase change type optical recording medium in which initial crystallization can be easily and uniformly performed. According to the third aspect of the present invention, it is possible to provide a phase change type optical recording medium having appropriate sensitivity corresponding to a recording linear velocity of 7 to 17.5 m / s. According to the present invention 4, it is possible to provide a phase change type optical recording medium provided with a recording film capable of recording / erasing by further utilizing the light absorption and interference effects. According to the present invention 5, it is possible to provide a phase change type optical recording medium having a layer structure capable of recording / erasing by further utilizing the light absorption and interference effects. According to the present invention 6, it is possible to inexpensively supply a phase change type optical recording medium suitable for mass production with a constant quality.

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[Procedure amendment]

[Submission date] November 30, 2001 (2001.11.
30)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

Examples 1 to 7 and Comparative Examples 1 to 4 Discs of Examples and Comparative Examples were prepared as follows. A lower protective layer, a recording layer, an upper protective layer, and a reflective layer were sequentially formed by sputtering on a polycarbonate substrate having a track pitch of 0.74 μm, a diameter of 12 cm, and a thickness of 0.6 mm. The lower protective layer is (ZnS) ₈₀ (SiO ₂ ).
₂₀ was used as a target and the film thickness was set to 65 nm. For the recording layer, an alloy target having a composition ratio corresponding to the recording material composition shown in Table 1 below was used and the film thickness was set to 18 nm. For the upper protective layer, (ZnS) ₈₀ (SiO ₂ ) ₂₀ was used as a target, and the film thickness was set to 10 nm. The reflective layer uses an Ag target and has a film thickness of 140 nm. Further, an acrylic UV curable resin having a thickness of 5 to 10 μm is formed on the reflective layer by a spinner.
After coating, UV curing was performed to form an organic protective film.
Further thereon, a polycarbonate substrate having a diameter of 12 cm and a thickness of 0.6 mm was attached using an adhesive sheet. Each of the discs created as described above has a diameter of 1 μm × 1
Output 680 mW, feed 3 using a laser of 00 μm
Initial crystallization was performed at 6 μm and a linear velocity of 3 m / s. Recording / reproduction was evaluated using a pickup head with a wavelength of 660 nm and an NA of 0.65, recording density of 0.267 μm / bit, and EFM.
+ Modulation method was used. Recording power is 13-18mW,
Bias power is 0.2mW, erase power is 6-10m
In W, the recording strategy was optimized for each disc. All reproduction is linear speed 3.5m / s, power 0.7
It was performed in mW.

Continued front page    (72) Inventor Masato Hariya             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Hajime Jyohara             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Eiko Suzuki             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Yuji Miura             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Hiroko Tashiro             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Mikiko Abe             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F-term (reference) 2H111 EA04 EA23 EA32 EA36 FA01                       FA12 FA14 FB05 FB09 FB12                       FB17 FB21 FB30 GA03                 5D029 JA01 JB35 JC11 JC17 JC18

Claims (6)

[Claims] 1. A recording layer in which information is recorded by causing reversible phase change between a crystalline state and an amorphous state by irradiation with laser light, and the main component of the recording layer is the following composition formula: (1)
A phase change type optical recording medium characterized by: GeαGaβCuγSbδTeε (1) Here, α, β, γ, δ, and ε in the formula (1) represent the composition ratio (at%) of each element and are in the following ranges. 0 ≦ α ≦ 5 1 ≦ β ≦ 5 1 ≦ γ ≦ 10 65 ≦ δ ≦ 81 13 ≦ ε ≦ 24 α + β + γ + δ + ε = 100 2. The phase change optical recording medium according to claim 1, wherein the crystallization temperature of the recording layer at a temperature rising rate of 10 ° C./min is 170 to 220 ° C. 3. The phase change optical recording medium according to claim 1, wherein the melting point of the recording layer is 500 to 680 ° C. 4. The phase change optical recording medium according to claim 1, wherein the recording layer has a thickness of 10 to 25 nm. 5. A substrate, at least a lower protective layer, a recording layer,
The phase change type optical recording medium according to claim 1, wherein an upper protective layer and a reflective layer are provided in this order. 6. A recording layer formed by a sputtering method using an Ar gas, using an alloy target made of a material forming the recording layer.
6. The phase change type optical recording medium according to any one of 5 to 10.