JP4439325B2 - Phase change recording material and information recording medium - Google Patents

Description

  The present invention relates to a phase change recording material and an information recording medium using the same.

  As a recording method using phase change, a method of reversibly changing the crystal structure of a metal or semiconductor by applying an energy beam or energy flow such as light or current (Joule heat) is known (for example, Non-Patent Document 1 and Patent Document 1).

  As a recording technique for an information recording medium using a phase change recording material, a technique that utilizes a reversible change between a crystalline phase and an amorphous phase (amorphous phase) is currently in practical use. Specifically, this is a technique in which the crystal state is set to an unrecorded / erased state, and an amorphous mark is formed during recording. Usually, the recording layer is locally heated to a temperature higher than the melting point and rapidly cooled to form an amorphous mark. On the other hand, recrystallization is performed by heating the recording layer to approximately the melting point or lower and the crystallization temperature or higher and gradually cooling the recording layer to maintain the recording layer or higher for a predetermined time. That is, generally utilizing a reversible change between a stable crystalline phase and an amorphous phase, physical parameters in crystalline and amorphous states, such as refractive index, electrical resistance, volume, Information is recorded and reproduced by detecting a difference in density change or the like.

  Among information recording media, optical information recording media utilize the change in reflectivity associated with the reversible change between a crystalline state and an amorphous state that are locally generated by irradiation with a focused light beam. Recording / reproduction is performed. An optical information recording medium having such a phase change recording layer has been developed and put into practical use as an inexpensive large-capacity recording medium excellent in portability, weather resistance, impact resistance and the like. For example, a rewritable phase change type optical information recording medium (hereinafter referred to as “rewritable phase change type optical information recording medium”) such as CD-RW, DVD-RW, DVD + RW, DVD-RAM, etc. Phase change optical discs, optical discs, and discs may be used). Furthermore, developments such as high density recording by using a blue laser, increasing the density of the objective lens by increasing the NA, and improving the recording pulse waveform are being carried out.

As a material of the phase change recording layer, a chalcogen alloy is often used. Examples of the chalcogen-based alloy include GeSbTe-based, InSbTe-based, GeSnTe-based, and AgInSbTe-based alloys. These alloys are also usually overwritable materials.
Overwriting is a method of overwriting as it is without erasing before recording, that is, a method of recording while erasing, when recording on an optical information recording medium that has already been recorded. In an optical information recording medium having a phase change recording layer, since recording is usually performed by overwriting, recording while erasing (that is, overwriting) may be simply referred to as recording.

Among the chalcogen alloys, the composition based on the Sb ₇₀ Te ₃₀ alloy containing excess Sb based on the Sb ₇₀ Te ₃₀ eutectic point composition is used for the recording layer, so that the crystallization speed can be increased to 10 times faster. Thus, an optical information recording medium capable of high-speed recording can be obtained. In particular, a composition containing Ge in the Sb ₇₀ Te ₃₀ eutectic point composition containing excess Sb in the recording layer is preferable (Patent Document 2).

Appl. Phys. Lett., 18, 254-257, 1971 US Pat. No. 3,530,441 JP 2001-229537 A (paragraph 0031)

  In recent years, with the increase in the amount of information, it has been desired to develop an optical information recording medium capable of recording / erasing / reproducing at higher speed. That is, it is necessary to use a phase change recording material capable of further high-speed crystallization for the recording layer. However, the above phase change recording material has excellent jitter characteristics (recording signal quality) due to the reason that the noise of the signal of the optical information recording medium becomes high when the composition allows sufficiently high crystallization. It tends to be difficult to satisfy both the storage stability characteristics of the amorphous mark. This problem is particularly noticeable in an optical information recording medium that performs high-speed recording / erasing of an information signal at a reference clock period of 15 ns or less.

For example, when the composition containing Ge in the Sb ₇₀ Te ₃₀ eutectic point composition containing excess Sb is expressed as (Sb _c Te _1-c ) _1-d Ge _d , the value of c is increased to 0.9 It is possible to increase the crystallization speed by reducing the Te content ratio to Sb close to. However, the noise of the optical information recording medium tends to increase at this time, and good jitter characteristics cannot be obtained. Further, if the Ge content is decreased, the storage stability of the amorphous mark is lowered although the increase in noise tends to be suppressed.

  The present invention has been made to solve the above problems, and its purpose is to enable recording erasure at high speed, excellent recording signal characteristics such as reflectance, signal amplitude or jitter characteristics, and storage of recorded signals. An object of the present invention is to provide a highly stable phase change recording material and an information recording medium using the material. Furthermore, even when the information recording medium is stored for a long period of time, the change in the reflectance of the recorded signal is small, and the recording signal characteristics when the information recording medium on which the signal is recorded is overwritten again after long-term storage. It is an object to provide an excellent phase change recording material and an information recording medium using the material. In particular, it is an object of the present invention to provide an optical information recording medium which is one form of application of the information recording medium.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the recording signals such as jitter characteristics can be obtained even when recording / erasing is performed at a high speed by satisfying a predetermined relational expression of the composition of Sb, In, Sn, Te, and Ge. The present invention has been achieved by finding that both the quality and the stability of the amorphous mark can be achieved, and that excellent recording signal characteristics can be maintained even when overwriting again after long-term storage.

  That is, the present invention provides a phase change recording material characterized in that, as described in claim 1, a main component is a composition represented by the following general formula (1).

_{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z (1)
(However, the Sb content is higher than any of the Ge content, the In content, the Sn content, and the Te content, and x, y, z, and w representing the atomic ratio are as follows. Satisfy (i) to (vi).
(I) 0 ≦ x ≦ 0.30
(Ii) 0.13 ≦ yz
(Iii) w × yz ≦ 0.10
(Iv) 0 <z
(V) (1-w) × y ≦ 0.35
(Vi) 0.35 ≦ 1-xyz)
The phase-change recording material of the present invention has excellent recording signal characteristics even when recording and erasing at high speed by having the composition represented by the general formula (1) as a main component, and the storage stability of the recording signal Even after long-term storage, the recorded signal has a small decrease in reflectance, and excellent recording signal characteristics can be exhibited even when overwriting is performed again.

The present invention provides the phase change recording material according to claim 1, wherein x in the general formula (1) further satisfies 0 <x as described in claim 2.
Further, according to the present invention, as set forth in claim 3, x in the general formula (1) further satisfies x ≦ 0.07. I will provide a.
Further, according to the present invention, as described in claim 4, w in the general formula (1) further satisfies 0 <w. Provide material.
Further, according to the present invention, as described in claim 5, in the general formula (1), z further satisfies 0.08 ≦ z. Provide change recording material.
Further, according to the present invention, as described in claim 6, the information recording material has a crystalline state in an unrecorded state and an amorphous state in a recorded state. A phase change recording material as described above is provided.

In addition, the present invention provides an information recording medium having a recording layer as described in claim 7, wherein the recording layer has a composition represented by the following general formula (1) as a main component. An information recording medium is provided.
_{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z (1)
(However, the Sb content is higher than any of the Ge content, the In content, the Sn content, and the Te content, and x, y, z, and w representing the atomic ratio are as follows. Satisfy (i) to (vi).
(I) 0 ≦ x ≦ 0.30
(Ii) 0.13 ≦ yz
(Iii) w × yz ≦ 0.10
(Iv) 0 <z
(V) (1-w) × y ≦ 0.35
(Vi) 0.35 ≦ 1-xyz)
In addition, as described in claim 8, the present invention provides the information recording medium according to claim 7, wherein x in the general formula (1) further satisfies 0 <x.
Further, according to the present invention, as described in claim 9, x in the general formula (1) further satisfies x ≦ 0.07. I will provide a.

Further, according to the present invention, as described in claim 10, in the general formula (1), w further satisfies 0 <w . Provide media.
Further, according to the present invention, as described in claim 11, z in the general formula (1) further satisfies 0.08 ≦ z . Information according to any one of claims 7 to 10 A recording medium is provided.
Further, according to the present invention, as described in claim 12, the information recording medium has a crystalline state in an unrecorded state and an amorphous state in a recorded state. An information recording medium according to any one of the above is provided.

Further, according to the present invention, as described in claim 13, the information recording medium is an optical information recording medium for recording with a laser beam. An information recording medium as described is provided.
According to the present invention, the optical information recording medium has a protective layer A in contact with the recording layer, and the protective layer A is a metal oxysulfide and / or metal nitride. The information recording medium according to claim 13, further comprising an object.
Further, according to the present invention, the metal oxysulfide is an yttrium oxysulfide, and the metal nitride is a nitride of an alloy containing germanium as a main component. An information recording medium according to claim 14 is provided.
Further, according to the present invention, as described in claim 16, the information recording medium according to claim 14 or 15, wherein the protective layer A is provided in contact with both surfaces of the recording layer. provide.

According to the present invention, the protective layer A is provided in contact with the surface of the recording layer on the side where the laser beam is incident, and the thickness of the protective layer A is 50 nm. The information recording medium according to claim 14, wherein the information recording medium is provided as follows.
Further, according to the present invention, the protective layer A is provided in contact with the surface of the recording layer on the side on which laser light is incident, and further in contact with the protective layer A, as described in claim 18. The protective layer B is provided on the surface opposite to the recording layer, and the total thickness of the protective layer A and the protective layer B is 50 nm or less. An information recording medium according to any one of 1 to 16 is provided.
Further, according to the present invention, as described in claim 19, the information recording medium according to any one of claims 14 to 18, wherein the film thickness of the recording layer is 5 nm or more and 15 nm or less. provide.
Furthermore, according to the present invention, as described in claim 20, the optical information recording medium further includes a reflective layer, and the reflective layer contains Ag as a main component. An information recording medium described in any of the above is provided.

  According to the present invention, it is possible to obtain a phase change recording material capable of erasing at a high speed, having excellent recording signal characteristics, and high recording signal storage stability, and an information recording medium using the material. Can do.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist of the present invention.
[1] Phase change recording material [1-1] General description The phase change recording material of the present invention is characterized by having a composition represented by the following general formula (1) as a main component.

_{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z (1)
(However, the Sb content is higher than any of the Ge content, the In content, the Sn content, and the Te content, and x, y, z, and w representing the atomic ratio are as follows. Satisfy (i) to (vi).
(I) 0 ≦ x ≦ 0.3
(Ii) 0.07 ≦ yz
(Iii) w × y−z ≦ 0.1
(Iv) 0 <z
(V) (1-w) × y ≦ 0.35
(Vi) 0.35 ≦ 1-xyz)
In the present invention, “having a predetermined composition as a main component” means that the content of the predetermined composition is 50 atomic% or more in the entire material or the entire layer containing the predetermined composition. In order to effectively exert the effects of the present invention, the composition represented by the general formula (1) in the entire phase change recording material is preferably 80 atomic% or more, more preferably 90 atomic% or more, particularly Preferably it contains 95 atomic% or more.

  In the present invention, a composition mainly composed of Sb is used for the phase change recording material in order to increase the crystallization speed and enable recording erasure at a high speed. For this reason, the content of Sb is made higher than the content of any other atom. The reason why Sb is mainly used is that the amorphous mark of Sb can be crystallized at a very high speed, so that the amorphous mark can be crystallized in a short time. That is, by using Sb as a main component, the amorphous recording mark can be easily erased.

  In the present invention, an additive element for promoting amorphous formation and improving the temporal stability of the amorphous state is used together with Sb, rather than using Sb alone. For this reason, Ge is used together with Sb. That is, when the Ge content is large, amorphous formation is facilitated, and amorphous stability over time is increased. According to the study by the present inventors, it has been found that the recording signal characteristic when overwriting is performed after the recorded medium is stored for a long period of time is also related to the Ge content.

  In the Sb-based phase change recording material according to the present invention, the total amount of In and / or Sn and the total amount of Te have a predetermined relationship.

Here, as a phase change recording material using Sb as a main component, a composition containing excess Sb in the above-described Sb ₇₀ Te ₃₀ eutectic point composition and further containing about 10 atomic% Ge is known. In the present invention, it can be considered as a material in which a large amount of In and / or Sn is added so as to satisfy a predetermined relationship with respect to the above-described conventional composition (hereinafter sometimes referred to as a conventional SbTe eutectic composition). In the conventional SbTe eutectic composition to which In or Sn is added, there is a tendency that the deterioration of jitter and the like due to crystal grain boundary noise can be suppressed to some extent, but the reflectivity of the crystal and the amorphous state decreases as the reflectivity of the crystal state decreases. The difference (signal amplitude) tends to be small. In particular, when the content of In is large, a phenomenon in which the reflectance in the crystalline state decreases with time is observed. This is considered to indicate that when the In content increases, the crystal state, which should be stable originally, may form an unstable metastable phase.

  In addition, in the conventional SbTe eutectic composition containing In and Sn, the performance of amorphization (easiness of formation of amorphous state, preservation of formed amorphous state) is increased by increasing the number of repeated overwriting. Stability and the like) and crystallization speed (hereinafter sometimes referred to as phase change performance change) tended to change. The cause of this is that In or Sn and Te are repeatedly melted and cooled in the process of repeated overwriting, forming an intermetallic compound (Te compound), causing segregation, and changing the properties of the alloy. Presumed to be. This change in phase change performance becomes a more serious problem when overwriting recording at higher density and higher recording linear velocity is realized. For this reason, in the conventional SbTe eutectic composition, it was thought that In or Sn could be added only in a trace amount (about 10 atomic% at most). In particular, it was thought that In or Sn could be added only about half or less of Te. In fact, as can be seen from the description of Examples in JP-A-10-326436 and JP-A-2002-79757, the amount of In and Sn added in the conventional SbTe eutectic composition is less than 10 atomic%. It has become. In addition, the content of In and Sn is significantly less than Te.

As described above, the conventional addition of In, Sn, etc. in the SbTe eutectic composition has the purpose of further improving the SbTe eutectic composition, which is the main component. Was done. For this reason, the content of In and Sn has been studied only up to the point where the harmful effects of various species appearing when approaching the same content as Te are confirmed, and the In and Sn contents are positively exceeded beyond the Te content. It is considered that there was no need for inclusion in.
However, according to the study by the present inventors, when the content of In and / or Sn with respect to Te is significantly increased, the reflectance in the crystalline state becomes larger, and the difference in reflectance between the crystal and the amorphous state is increased. It was found that (signal amplitude) increased again. Then, it was found that when the content of In and / or Sn is significantly increased with respect to Te, the change in reflectance with time is small. Moreover, it has been found that at this time, it is possible to achieve both high-speed recording signal characteristics and stability in the amorphous state.

That is, when the Sb / Te ratio is increased (especially when the Sb / Te ratio exceeds 4) for the purpose of increasing the crystallization speed in order to realize high-speed overwrite, the crystal grain boundary noise increases and jitter is increased. The tendency of the signal quality to deteriorate and the deterioration of the temporal stability of the amorphous state (the amorphous state crystallizes after long-term storage at room temperature) are observed. However, when the content of In and / or Sn is significantly increased with respect to Te, it is expected that any of the above problems can be solved. For example, regarding the stability of the amorphous state, it has been found that the stability of the amorphous state becomes very high under normal storage conditions near room temperature.
In addition, the change in the phase change performance that occurs during repeated overwriting is presumed to be due to segregation of the Te compound that occurs during repeated overwriting. For this reason, it is generally considered that the addition of a large amount of In and Sn further exacerbates the problem of segregation of the Te compound. However, according to the study by the present inventors, contrary to this idea, when the content of In and / or Sn is significantly increased with respect to Te, the change in phase change performance due to repeated overwriting is suppressed. I understood that.

The phase change recording material of the present invention in which In, Sn, Sb, Te and Ge each satisfy a predetermined relationship cannot be considered as a simple addition of an additive element to the SbTe eutectic composition. This is because the phase state of the phase change recording material is expected to be very complicated, and it is not clear whether segregation occurs in the repeated overwriting. However, stabilization of crystallization speed (suppression of change in crystallization speed) when repeated overwriting is performed on the phase change recording material of the present invention is achieved by one of the following two mechanisms. It is considered a thing. That is, the first mechanism is that, in the phase change recording material of the present invention, a relatively stable solid solution state is formed although it is metastable in a specific composition range. This is a mechanism in which the change in phase change performance is suppressed by being less likely to occur. Further, the second mechanism is that even if segregation occurs, the phase to be segregated is limited to a phase having a specific composition ratio. It is a mechanism that changes are suppressed.
From the above, in the present invention, it is important to control the Te content and the In and / or Sn content within a predetermined range.

  In the present invention, there is another reason why it is important to control the Te content and the In and / or Sn content. That is, the central composition of the present invention can be considered as a material in which Te is added to a GeSbSn-based material or GeInSb-based material mainly composed of Sb. In and Te are elements that facilitate the formation of an amorphous mark and reduce the fluctuation of the end of the formed amorphous mark shape. Therefore, by using these elements, it is possible to reduce the jitter in mark length recording when the present invention is applied to an optical information recording medium. Te also increases the durability of repeated recording. However, the addition of Te tends to reduce the reflectance in the crystalline state and the reflectance difference (signal amplitude) between the crystal and the amorphous state. Therefore, it is important to control the amount of Te added. According to the study by the present inventors, the reflectance of the crystalline state and the signal amplitude decrease due to the addition of Te by setting the relationship between the Te content and the total amount of the In content and the Sn content within a predetermined range. Was found to be suppressed. Then, by setting the relationship between the Te content and the total amount of In content and Sn content within a predetermined range, an amorphous mark (recording signal) by recrystallization in a short time when recording at high speed Erasure and stability of the amorphous mark (recording signal) during storage can be achieved. Furthermore, by setting the relationship between the Te content and the total amount of In content and Sn content within a predetermined range, noise due to fluctuations in the mark shape (mark length recording when applied to an optical information recording medium) It is possible to form amorphous marks with less jitter.

Further, when the In content is large, the reflectance of the crystal state of the phase change disk tends to decrease due to long-term storage. This is presumably because a metastable crystal state is formed and the crystal structure slightly changes. The amount of decrease in the reflectance may reach 10% or more of the reflectance in the initial crystalline state. Such a change in the crystalline state over time is considered to change not only the optical characteristics but also other physical characteristics such as electrical characteristics. Therefore, the change in the crystalline state with time causes a decrease in the storage stability of the recorded information.
However, according to the study by the present inventors, it has been found that even if the In content is large to some extent, the decrease in reflectance due to long-term storage can be reduced by defining the relationship between the In and Te contents. .

  That is, by adjusting the recording layer composition, an information recording medium having excellent recording signal characteristics at high speed and excellent stability in the crystalline state and the amorphous state can be obtained. For this reason, it is excellent in stability such as optical characteristics and electrical characteristics derived from the physical characteristic difference between both states, and also in recording signal characteristics when overwriting after storing the recorded medium for a long time. A recording medium can be obtained.

In the present invention, it is preferable that the phase change recording material has a crystalline state in an unrecorded state and an amorphous state in a recorded state. This is because it is presumed that there are not many crystal nuclei in the amorphous state of the phase change recording material of the present invention. That is, when an amorphous state is not recorded and a crystal state mark is formed in the amorphous state, it is preferable to use a phase change recording material having many crystal nuclei. This is because if there are many crystal nuclei in the phase change recording material, the shape of the mark in the crystalline state will not be affected by the position of the crystal nuclei. On the other hand, as described above, since many crystal nuclei are not present in the phase change recording material of the present invention, the amorphous state is set to the unrecorded state, and the crystalline state recording mark is formed in the amorphous state. In this case, it is easier to perform good recording when the crystalline state is set to the unrecorded state and the amorphous state recording mark is formed in the crystalline state.
Hereinafter, the relationship between the content of each element and the characteristics will be described in detail.
In the following description, the effect of adding each element (particularly In and Sn) is described mainly from the viewpoint of optical characteristics. However, the difference in reflectivity between the crystalline state and the amorphous state observed as optical characteristics, and the stability over time of this difference in reflectivity, at the same time, the crystalline state and the amorphous state viewed from the electrical characteristics etc. It is considered that this also affects the characteristic difference and stability of the recording medium (and therefore the amplitude of the recording signal, the size of the SN ratio, and its stability). Further, it is considered that noise due to scattering at the crystal grain boundary, which is grasped as optical characteristics, is electrically observed as noise due to electron scattering at the crystal grain boundary. For this reason, it is considered that the following description from the viewpoint of the optical characteristics can be similarly applied to the electrical characteristics.

(Sb, formula (vi))
The Sb content is higher than any of the Ge content, the In content, the Sn content, and the Te content. That is, the recording material of the present invention is mainly composed of Sb. Sb itself is effective for crystallizing the amorphous state in a short time, but has a low ability to form an amorphous state and tends to be unstable, so that it can be combined with an additive element described later. Need to be used. If there is much content of Sb, the crystallization speed will increase. In particular, in high-speed recording that requires crystallization in a short time, the Sb content is relatively increased. Specifically, the Sb content is 35 atomic% or more, which is higher than any of the other contained elements. In order to sufficiently obtain the effects of the present invention, the Sb content is preferably 40 atomic% or more, and more preferably 45 atomic% or more.
In the present invention, it is also important to control the Sb / Te ratio. From the viewpoint of performing high-speed recording, the Sb / Te ratio is usually 2.3 or more, preferably 3 or more, more preferably 4 or more. On the other hand, the Sb / Te ratio is usually 9.5 or less, preferably 9 or less, from the balance between the high-speed recording characteristics and characteristics other than the high-speed recording characteristics.

(Sn, formula (ii), (v))
The influence of Sn content on the reflectivity in the crystalline state and the difference in reflectance between the crystal and the amorphous phase (signal amplitude), and the In content on the reflectance in the crystalline state and the difference in reflectance between the crystalline and amorphous phase (signal amplitude) ) Has almost the same effect. For this reason, the phase change recording material contains either Sn or In. And the reflectance of a crystal | crystallization and a signal amplitude can be enlarged by making the sum total of Sn content and In content within the range of fixed amount from Te amount. On the other hand, when the Te content increases, the reflectance and signal amplitude of the crystal decrease. Therefore, in order to obtain a desired crystal state reflectance and signal amplitude, it is important to control the relationship between the Sn and / or In content and the Te content.

  For this reason, the value of (yz) in the general formula (1) is 0.07 or more, preferably 0.1 or more, more preferably 0.13 or more, and particularly preferably 0.15 or more. A larger value of y is preferable because the optimum power decreases.

  Further, when Sn is too much, the boundary shape of the amorphous mark particularly when applied to an optical information recording medium tends to fluctuate, or the jitter characteristic which seems to be due to the crystal grain boundary deteriorates. Because of this tendency, the value of (1-w) × y in the general formula (1) is set to 0.35 or less, preferably 0.3 or less. Therefore, in the case where a large amount of Te is contained, it is necessary to increase the sum of the In content and the Sn content from the viewpoint of controlling the signal amplitude. However, considering the jitter characteristics, Sn cannot be increased so much. When the content of is increased, it is preferable to contain In in addition to Sn. Specifically, in the case where the Te content is increased so that the decrease in reflectance and signal amplitude of crystals due to Te cannot be suppressed unless Sn is contained in excess of 35 atomic%, In may be included. .

(In, formula (iii))
By using In, the reflectance in the crystalline state and the difference in reflectance (signal amplitude) between the crystal and the amorphous can be increased. Therefore, in the present invention, In is used as an element to be included in the recording layer. Is preferred.
By using In, it is possible to increase the reflectivity in the crystal state and the difference in reflectivity between the crystal and the amorphous material (signal amplitude), and to reduce the influence on the jitter characteristics compared to Sn. In is presumed to have a function of reducing crystal grain boundary noise than Sn and Te. On the other hand, In causes a decrease in reflectance due to long-term storage, which seems to be derived from a metastable crystalline state. In contrast, Te tends to suppress a decrease in reflectance due to long-term storage. Therefore, it is important that the In content and the Te content have a predetermined relationship from the viewpoint of suppressing a decrease in the reflectance of the optical information recording medium during long-term storage. As a result of producing and investigating optical information recording media having various recording layer compositions, the present inventors have found that if the In content is excessively increased with respect to the Te content, the reflectance decreases due to long-term storage. I found out. That is, in the above general formula (1), by setting the value of (In content−Te content) within a predetermined range, it is possible to suppress a decrease in reflectance due to long-term storage. Specifically, if the value of w × yz in the above general formula (1) is small, the rate of decrease in reflectance due to long-term storage is small, so the value of w × yz is preferably 0.1 or less, 0.05 or less is more preferable, and 0 or less is more preferable. Here, w × yz = 0 means that the In content and the Te content are the same. Therefore, it is more preferable in the present invention that the In content is the same as the Te content or the In content is smaller than the Te content.

In order to reduce the reflectivity decrease due to long-term storage as much as possible, In cannot be contained excessively with respect to Te. Therefore, in order to satisfy the above-described relational expression 0.07 ≦ yz, The phase change recording material of the invention preferably contains Sn in addition to In. Specifically, when w × yz <0.07, 0.07 ≦ yz cannot be satisfied unless Sn is contained in addition to In. In addition, it is preferable to contain both In and Sn from the viewpoint that increasing the contents of In and Te without containing Sn makes it difficult to obtain a crystallization speed suitable for high-speed recording. That is, 0 <w <1 is preferable.
If In is excessively large, the signal quality of the information recording medium during long-term storage tends to deteriorate (for example, the reflectance during long-term storage tends to decrease when the information recording medium is used as an optical information recording medium). )It is in. Further, when In is increased without containing Sn, a stable crystal layer with a low reflectance, which is seen in the In—Sb system, may appear. For this reason, the In content, that is, the value of w × y is preferably set to 0.35 or less.

(Te, formula (iv))
The phase change recording material of the present invention contains Te.
Since the phase change material of the present invention exhibits its phase change performance based on the SbTe eutectic system containing Sb in excess of Sb ₇₀ Te ₃₀ , Te is an essential element.
Te can combine with Sb to stabilize the phase change performance in repeated recording and improve repeated recording durability. Further, Te is effective in maintaining the erasing performance (maintaining the crystallization speed) and improving the repeated recording durability accompanying the storage of the information recording medium using the phase change recording material of the present invention for a long time. There is.
When Te is contained, if In, Sn, or the like is added for the purpose of improving other characteristics, In or Sn may form a compound with Te and segregation may occur. However, in order to maintain basic phase change performance, Te is an essential element together with Sb. That is, even when In or Sn is used for the phase change recording material of the present invention, Te cannot be excluded, and in order to further improve the characteristics in the SbTe binary composition, In or Sn is contained. I have to do it. Therefore, there is one of the important meanings of the present invention in that the adverse effects of segregation are suppressed to a negligible level by including the amounts of In and Sn in a specific range with respect to Te.
For this reason, the Te content is preferably increased to some extent, but as described above, the relationship between In and / or Sn and Te and the relationship between In and Te must be controlled within a predetermined range. Specifically, z representing the Te content in the general formula (1) is 0 <z, preferably 0.01 ≦ z, more preferably 0.05 ≦ z, and still more preferably 0.8. 08 ≦ z, particularly preferably 0.1 ≦ z, and most preferably 0.1 <z.

  Although z representing Te content is usually less than 0.29, this is a value inevitably determined by another relational expression defined in the above general formula (1). As described above, it is preferable to increase the content of In and Te to some extent. However, since Te has a function of slowing down the crystallization speed, the Te content is required to obtain a crystallization speed suitable for high-speed recording. Z represented is preferably 0.25 or less, and more preferably 0.20 or less.

(Ge, formula (i))
In the present invention, Ge can be used to adjust the crystallization speed. That is, Ge is not greatly related to characteristics such as reflectivity, signal amplitude (reflectance difference between crystal and amorphous), and reflectivity decrease due to long-term storage of the medium. For this reason, Ge can be used to obtain a crystallization rate suitable for the recording conditions to be used. Since the crystallization speed decreases as the Ge content increases, for example, in an information recording medium for higher speed recording, the Ge content can be reduced and the crystallization speed can be adjusted. However, the crystallization rate is also related to the content of other elements, and the crystallization rate increases as Sb and Sn increase, and the crystallization rate decreases as In and Te increase. Therefore, it is preferable to adjust the crystallization speed according to the recording conditions by adjusting the Ge content after determining the content ratio of elements other than Ge in consideration of the above-mentioned characteristics. If the Ge content is too high, the crystallization rate becomes too slow, so x in the above general formula (1) is 0.3 or less, preferably 0.25 or less, more preferably 0.2 or less. The influence of the content on the crystallization rate is particularly large for Ge and Te.

  Further, when the Ge content is large, when the recorded amorphous mark is stored for a long time, it tends to be harder to crystallize than immediately after recording before storage. When this phenomenon becomes remarkable, when overwriting is performed after the recorded information recording medium is stored for a long period of time, the signal quality of the overwritten recording signal becomes insufficient. That is, the old mark after long-term storage does not disappear sufficiently, so that the signal quality of the new recording mark is deteriorated. This phenomenon of difficulty in crystallization becomes a problem only in the first recording after long-term storage, and an amorphous mark newly recorded after long-term storage has a normal crystallization speed. In any case, this phenomenon is alleviated by reducing the Ge content. In this sense, the Ge content is preferably small, and the value of x in the general formula (1) is particularly preferably 0.1 or less, and most preferably 0.07 or less. The present invention succeeded in reducing this phenomenon while satisfying the various characteristics.

  As described above, Te and In have the effect of slowing down the crystallization speed. Therefore, in order to obtain the same crystallization speed when the crystallization speed is slowed down, the content of Te and In is higher when the content of Te and In is higher. Can be reduced. In this sense, the Te content, that is, the value of z is preferably 0.05 or more, more preferably 0.08 or more, and most preferably 0.1 or more. Further, at this time, the In content, that is, the value of w × y is preferably 0.05 or more, and more preferably 0.08 or more. Moreover, when there is much Te content as mentioned above, it becomes preferable to contain both In and Sn. That is, the most preferable composition contains all of Ge, In, Sb, Sn, and Te.

  On the other hand, when the Ge content is too small, the storage stability of the amorphous mark is deteriorated and tends to be crystallized by long-term storage. The storage stability of the amorphous mark tends to be improved by increasing In, but the influence of Ge tends to be stronger. On the other hand, due to the influence of other elements, the storage stability of amorphous marks may be relatively good even when the Ge content is zero. Therefore, the value of x in the general formula (1) is 0 or more, but is preferably larger than 0, more preferably 0.01 or more, and further preferably 0.02 or more.

[1-2] Content of each of Ge, In, Sn, Te, and Sb in the phase change recording material of the present invention In the present invention, the condition in the general formula (1), that is, (a) the content of Sb is (B) 0 ≦ x ≦ 0.3 (c) 0.07 ≦ y−z (d) w, which is higher than any of the Ge content, the In content, the Sn content, and the Te content. Xy-z ≦ 0.1 (e) 0 <z (f) (1-w) × y ≦ 0.35 (g) 0.35 ≦ 1-xyz From the seven conditions of the present invention, The maximum and minimum contents that can be taken by the Ge, In, Sn, Te, and Sb elements constituting the phase change recording material are inevitably determined.

  Specifically, a computer that determines whether or not the above seven conditions are satisfied when the values of x, y, z, and w are independently changed from 0 to 1 in increments of 0.001. By creating a program and executing it, the maximum and minimum contents of Ge, In, Sn, Te, and Sb can be determined. Of course, the total number ratio of Ge, In, Sn, Te, and Sb is 1. Further, by reducing the interval for changing the value in increments of 0.0001 and 0.00001, the detailed range of each atom of Ge, In, Sn, Te, and Sb can be obtained. Table 1 shows an example of the computer program created using Visual Basic.

When the computer program shown in Table-1 is executed, the ranges that Ge, In, Sn, Te, and Sb can take are as follows:
Ge is 0.000 to 0.300.
In is 0.000 to 0.366.
Sn is 0.000 to 0.350
Te is 0.001 to 0.290.
Sb is 0.350 to 0.929.
It is.

  Further, according to the above program, the range of yz that is the difference between the total In content and / or the Sn content and the Te content is 0.070 to 0.449, and the In content and The possible range of w × yz, which is the difference from the Te content, is −0.279 to 0.100.

In addition, the number indicating the range of the content of each element by the program varies somewhat depending on how significant numbers are taken when the program is executed.
In addition, as described in [1-1] above, each of the conditions (a) to (g) can be changed by changing conditions such as a preferable range and a more preferable range, but the conditions have changed. In this case, the computer program is executed again using new conditions, and the upper limit and the lower limit of each element of Ge, In, Sn, Te, and Sb may be obtained.
In addition, it cannot be said that a composition can be freely changed independently within the composition range of each element alone, and it goes without saying that the conditions of the formulas (a) to (g) are given priority.

[1-3] Other Elements In the phase change recording material of the present invention, Au, Ag, Al, Ga, Zn, Si, Cu, Pd, Pt, Rh are optionally added to improve various characteristics. Pb, Cr, Mo, W, Mn, Co, O, N, Se, V, Nb, Ta, Ti, Bi, B, and rare earth elements such as Tb, Dy, and Gd may be added. In order to obtain the effect of improving the characteristics, the addition amount is 0.1 at. % (Atomic%) or more is preferable. However, in order not to impair the preferable characteristics of the phase change recording material of the present invention, 10 at. % Or less is preferable. Particularly preferred is the addition of N (nitrogen), and by adding 0.1 atomic% or more and 5 atomic% or less of the total composition, there is an effect of improving repeated overwrite durability.
Ag, Cu, Si, Pb, Cr, Mo, W, Mn, Nb, Ta, V, B, and rare earth elements can be used for further fine adjustment of the crystallization temperature and the crystallization speed.
Al, Ga, Zn, Bi, Pd, Pt, and Rh show that the phase change recording material of the present invention exhibits a crystallization process mainly of crystal growth, but can function as a crystal nucleus. Can be fine-tuned. The other additive elements may also function as crystal nuclei.
O and Se can be used for fine adjustment of optical characteristics.
The rare earth element (rare earth metal element) refers to a group 3B element of the periodic table, and specifically refers to Sc, Y, a lanthanoid element, and an actinoid element.

[2] Information Recording Medium Next, the information recording medium of the present invention will be described.
The information recording medium of the present invention is an information recording medium having a recording layer, wherein the recording layer is mainly composed of a composition represented by the following general formula (1).

_{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z (1)
(However, the Sb content is higher than any of the Ge content, the In content, the Sn content, and the Te content, and x, y, z, and w representing the atomic ratio are as follows. Satisfy (i) to (vi).
(I) 0 ≦ x ≦ 0.3
(Ii) 0.07 ≦ yz
(Iii) w × y−z ≦ 0.1
(Iv) 0 <z
(V) (1-w) × y ≦ 0.35
(Vi) 0.35 ≦ 1-xyz)
In the present invention, it is preferable that the information recording medium has a crystal state in an unrecorded state and an amorphous state in a recorded state. This is because it is presumed that there are not many crystal nuclei in the recording layer composition of the present invention. That is, in the case where the amorphous state is not recorded and a crystalline mark is formed in the amorphous state, it is preferable to use a recording layer composition in which many crystal nuclei exist. This is because if there are many crystal nuclei in the recording layer, the shape of the mark in the crystalline state is not affected by the position of the crystal nuclei. On the other hand, as described above, since a large number of crystal nuclei are not present in the recording layer composition in the present invention, the amorphous state is set to the unrecorded state, and the crystalline state recording mark is formed in the amorphous state. If the crystal state is set to the unrecorded state and an amorphous state recording mark is formed in the crystal state, it becomes easier to perform good recording.

  By using the composition represented by the general formula (1) as the recording layer, the recording layer has excellent recording signal characteristics such as reflectance, signal amplitude, and jitter characteristics even when recording is erased at high speed. The storage stability of the mark (recording signal) can also be improved. Even when the information recording medium of the present invention is stored for a long period of time, the change in the reflectance of the recorded signal is small, and excellent recording signal characteristics can be maintained even if overwriting is performed again. The information recording medium of the present invention can also exhibit excellent repeated recording durability by using the above composition. In addition, since description about General formula (1) is the same as what was described in said [1], description here is abbreviate | omitted.

Such an information recording medium is not particularly limited as long as it records and reproduces information by detecting a physical parameter difference between a crystalline state and an amorphous state. An information recording medium that detects differences in electrical resistance, volume, density change, and the like can be given. Among them, the information recording medium using the phase change recording material of the present invention is suitable for application to an optical information recording medium for recording with laser light. In particular, it is suitable for application to a phase change type optical information recording medium using a change in reflectance accompanying a reversible change in crystal state caused by laser light irradiation.
The specific configuration and recording / reproducing method of the optical information recording medium of the present invention will be described below.

[2-1] Optical information recording medium (layer structure)
As the optical information recording medium, a medium having a multilayer structure as shown in FIG. 1 (a) or FIG. 1 (b) is usually used. That is, as is clear from FIGS. 1A and 1B, the substrate has a recording layer mainly composed of the composition represented by the general formula (1), and further has a protective layer. It is preferable to do.

  A more preferable layer configuration of the optical information recording medium is a configuration in which a first protective layer, a recording layer, a second protective layer, and a reflective layer are provided in order along the incident direction of the reproduction light. That is, when the reproduction light is incident from the substrate side, the layer structure includes a substrate, a first protective layer (lower protective layer), a recording layer, a second protective layer (upper protective layer), and a reflective layer (FIG. 1A). In the case where the reproduction light is incident from the recording layer side, the substrate, the reflective layer, the second protective layer (lower protective layer), the recording layer, the first protective layer (upper protective layer), and the cover layer are configured. (See FIG. 1B).

  Of course, each of these layers may be formed of two or more layers, and an intermediate layer may be provided between them. For example, a translucent extremely thin metal, semiconductor, or dielectric having absorption on a substrate / protective layer when reproducing light is incident from the substrate side, or on a protective layer when reproducing light is incident from the opposite side of the substrate It is also possible to provide a layer or the like to control the amount of light energy incident on the recording layer.

As described above, a reflective layer is often provided on the side opposite to the incidence of the recording / reproducing light beam (recording / reproducing light), but this reflective layer is not essential. In addition, in the protective layer that is preferably provided on at least one surface of the recording layer, materials having different characteristics may be multilayered.
Hereinafter, each layer will be described in detail.

(A) Recording layer (A-1) Material and amount contained in recording layer The material contained in the recording layer contains the composition represented by the general formula (1) as a main component. Since the detailed explanation about this composition has already been given, the explanation here is omitted. In order to effectively exhibit the effects of the present invention, the composition represented by the general formula (1) in the entire recording layer is usually 50 atom% or more, preferably 80 atom% or more, more preferably 90 atoms. % Or more, particularly preferably 95 atomic% or more. The higher the content is, the more the effect of the present invention is exhibited. However, even if other components such as O and N are contained during the formation of the recording layer, it is several atomic percent to 20 atomic percent. If it is within the range, the effects of the present invention such as high-speed recording and erasure are surely exhibited.

(A-2) Film thickness of recording layer The thickness of the recording layer is usually 1 nm or more, preferably 5 nm or more. By doing so, the difference in reflectance (contrast) between the crystal and the amorphous is sufficient, the crystallization speed is sufficient, and recording and erasing can be performed in a short time. Also, the reflectance itself is a sufficient value. On the other hand, the thickness of the recording layer is usually 30 nm or less, preferably 25 nm or less, more preferably 20 nm or less, and particularly preferably 15 nm or less. In this way, sufficient optical contrast can be obtained, and cracks are less likely to occur in the recording layer. In addition, the deterioration of recording sensitivity due to an increase in heat capacity is less likely to occur. Furthermore, if the film thickness is within the above range, the volume change accompanying the phase change can be moderately suppressed, and when recording is repeated, the recording layer itself or a protective layer that can be provided above and below that causes noise The microscopic and irreversible deformations are difficult to accumulate. Since accumulation of such deformation tends to decrease the durability of repeated recording, this tendency can be suppressed by setting the film thickness of the recording layer within the above range.

  An optical information recording medium for high-density recording that performs recording and reproduction with a focused light beam of an LD (laser diode) with a wavelength of about 650 nm and an objective lens with a numerical aperture of about 0.6 to 0.65, such as a rewritable DVD In optical information recording media for high-density recording in which recording / reproduction is performed with a focused light beam of a blue LD having a wavelength of about 400 nm and an objective lens having a numerical aperture of about 0.7 to 0.85, the requirements for noise are more severe. . For this reason, in such a case, a more preferable recording layer thickness is 25 nm or less.

(A-3) Further preferred embodiment relating to recording layer film thickness In the present invention, an optical system provided with a recording layer mainly composed of a predetermined Ge—In—Sb—Sn—Te based composition capable of high-speed recording / erasing. In a typical information recording medium, by making the recording layer very thin, the recording characteristics of the second time after the optical information recording medium is stored for a long time and the reflectance drop after long-term storage are improved. It is considered possible. Specifically, by setting the thickness of the recording layer to preferably 11 nm or less, the optical information recording medium using the recording layer having the predetermined Ge—In—Sb—Sn—Te composition can be stored for a long time. It seems that there is a tendency that the recording characteristics at the later second recording are improved, and a decrease in reflectivity during long-term storage is improved.

In the optical information recording medium using the recording layer having the predetermined Ge—In—Sb—Sn—Te composition, the jitter in the second recording after long-term storage (storage) may be slightly inferior.
Here, the recording characteristics at the time of the second recording after long-term storage (storage) refer to the characteristics in the following two cases (shelf second recording, archival second recording).
First, recording on a medium stored for a long time in an unrecorded state after initial crystallization is referred to as the first shelf recording, and the subsequent overwriting is referred to as the second shelf recording. When the shelf second recording is performed when the storage period is relatively short, the jitter is hardly increased, but the jitter increase may be significant in the second shelf recording when the storage period is long. . This increase in jitter is reduced if the overwrite is repeated several times as it is, and the overwrite recording characteristic before storage is restored. The reason for this is not necessarily clear, but it seems to be related to the tendency that the signal intensity in the first shelf recording after long-term storage tends to be small. That is, when recording is performed after the optical information recording medium is stored for a long time, the signal amplitude in the first shelf recording tends to be small. Since the signal amplitude is recovered by recording several more times, the decrease in the signal amplitude during the first recording of the shelf increases the recording mark when the crystal part after long-term storage becomes amorphous for the first time. The cause is thought to be difficult. The reason why the jitter is likely to deteriorate during the second recording on the shelf after long-term storage is that the portion that becomes amorphous after the long-term storage (the portion where the recording beam was not irradiated in the first recording on the shelf) and again (the second time) This is presumably due to the presence of a portion where amorphization is performed. In other words, in the second shelf recording, it is considered that the size of amorphous marks varies due to the mixture.

Although the cause of the tendency of the amorphous mark to become difficult to increase during the first recording on the shelf after long-term storage is not clear, the characteristics return after recording several times. It is thought that this happened. By making the recording layer very thin (preferably 11 nm or less), the characteristics at the time of the second shelf recording after long-term storage are improved. This is because the change in the crystal part of the recording layer tends to be suppressed. Seem.
On the other hand, in the overwritable information recording medium for forming an amorphous mark, the second recording after other long-term storage (storage) means that the information once recorded (state in which the amorphous mark is formed) is stored for a long time. This is a record when information is rewritten by overwriting again after storage.
Recording performed for the first time after long-term storage on an information recording medium on which recording has been performed before storage will be referred to as archival second recording. In this case, when the second archival recording is performed in a state where the storage period is relatively short, an increase in jitter is hardly observed. However, in the second archival recording when the storage period is long, a phenomenon in which the increase in jitter is noticeable may be observed. This increase in jitter decreases if the overwrite is repeated several times as it is. Then, the overwrite recording characteristic before storage is restored.

The above phenomenon occurs because the amorphous mark recorded before storage changes to a stable amorphous state by long-term storage, and even after recording (overwriting), erasing in recrystallization becomes insufficient. Then you can think. Since the amorphous state is a metastable state, the amorphous state can be changed to a more stable amorphous state by being stored for a long period of time. In general, a stable amorphous mark tends to be difficult to disappear, and thus noise due to unerased is generated.
In view of this, it can be explained that the fact that jitter is reduced when overwriting is performed after the second archival recording is performed. In other words, if the second archival recording is performed, the formed amorphous mark is in the “newly formed” amorphous state, and thus returns to the initial relatively erasable amorphous state. .
When the recording layer is made very thin, it is easily affected by the interface of other layers in contact with the recording layer. For this reason, it can be considered that the improvement in stability of the amorphous state occurs because the amorphous state is maintained in a certain metastable state by the effect of the interface.
It should be noted that it is not clear whether one of the two second recordings (the second shelf recording or the second archival recording) is the main problem, and both may have an influence at the same time.

In any case, the long-term storage stability of a mere recorded amorphous mark is considered to depend on the subtle changes in the crystalline state and / or amorphous state of the recording layer as described above. In addition, the first recording in the unrecorded state that has been stored for a long time is also considered to depend on the subtle change in the crystalline state and / or amorphous state of the recording layer as described above. Further, the storage stability of the recording medium including the shelf and archival second recording on the medium stored for a long time after recording is also a slight change in the crystalline state and / or the amorphous state of the recording layer as described above. Is also considered to depend.
The above phenomenon becomes particularly remarkable when the phase change recording material of the present invention is used particularly for high-speed recording (generally a linear velocity of 20 m / s or more during recording). Conventionally, the above phenomenon has not been regarded as a problem in information recording media used for low linear velocity recording. This is because the recording linear velocity has conventionally been slow. Since the phase change recording material of the present invention can be applied to high-speed recording, the above phenomenon is considered to be a newly discovered problem.
In the phase change recording material of the present invention, compared with the conventional eutectic material in the vicinity of Sb ₇₀ Te ₃₀ and the eutectic material in the vicinity of Sb ₈₅ Ge _{15, the} second shelf recording and the archival 2 in the high linear velocity recording. The increase in jitter in the second recording can be suppressed low. Further, the increase in the jitter can be more effectively suppressed by reducing the film thickness of the recording layer.
Furthermore, a reduction in reflectance due to long-term storage tends to be suppressed by making the recording layer very thin (preferably 11 nm or less). The reason for this is not clear, but the change in the recording layer during long-term storage may be suppressed as in the case of improvement in recording characteristics in the second recording after long-term storage.

In the recording layer having the predetermined Ge—In—Sb—Sn—Te composition, when the In content is high and the Te content is low, the optical information recording medium is subjected to an environmental resistance test (optical In some cases, the reflectivity may decrease in the same state as after a long-term storage of the target information recording medium. For this reason, it is preferable that the content of In and the content of Te have a specific relationship (in the general formula (1), w × yz ≦ 0.1). However, since the recording layer tends to be able to suppress a decrease in reflectance after the environmental resistance test (after long-term storage) by making the recording layer very thin, In and Te need not be in the predetermined relationship. May also improve. This means that the usable recording layer composition range is expanded by making the recording layer very thin. In this respect as well, it is preferable to reduce the recording layer thickness.
However, if the recording layer is very thin, recording characteristics such as signal amplitude may be impaired. In this regard, the recording characteristics such as the signal amplitude can be made sufficiently good by adjusting the layer configuration and the film thickness of the optical information recording medium.

That is, in the case of an optical information recording medium in which a protective layer, a Ge—In—Sb—Sn—Te recording layer having a predetermined composition, a protective layer, and a reflective layer are provided on the substrate in this order or reverse order, When the film thickness is very thin (for example, thinner than about 12 nm), the signal intensity tends to decrease. For this reason, when the recording layer is very thin (for example, 11 nm or less), it is necessary to devise to obtain a large signal intensity.
For example, one method is to change the film thickness of the protective layer located on the side where the laser light enters the recording layer. That is, the thickness of the protective layer is made thinner than the thickness of the protective layer at which the reflectance of the optical information recording medium is minimized. The minimum film thickness depends on the laser wavelength to be used, but for example, the film thickness near 650 nm for DVD is about 50 nm. By doing so, the signal intensity is optically increased.

  However, it is generally known that when the thickness of the protective layer on the light incident side is reduced, the thermal effect on the substrate and the like tends to increase and the recording durability tends to deteriorate repeatedly. The above method of reducing the thickness as described above (for example, around 50 nm) is difficult to use. Against this tendency, even when the thickness of the protective layer on the side where the laser beam enters the recording layer is reduced (for example, 50 nm or less), the entire protective layer is protected later. By using layer A (a protective layer containing a metal oxysulfide and / or metal nitride) or by forming a protective layer region in a portion in contact with the recording layer of this protective layer as a protective layer A described later, It is considered that the repeated recording durability of the target information recording medium is improved. Details of the protective layer A will be described later.

Based on the above, the thickness of the recording layer in this embodiment is preferably 15 nm or less, more preferably 14 nm or less, further preferably 13 nm or less, particularly preferably 12 nm or less, and 11 nm. The following is most preferable.
On the other hand, as described above, even when the recording layer thickness is very thin in order to improve the recording characteristics after long-term storage, if the recording layer thickness is excessively thin, the layers other than the recording layer are adjusted. However, sufficient signal strength cannot be obtained. The lower limit value of the signal intensity depends on the performance of the reproducing apparatus. For example, in a rewritable DVD, if the recording layer thickness is less than 3 nm, the signal intensity tends to be small and difficult to use. For this reason, for example, in a rewritable DVD, the recording layer thickness is set to 3 nm or more. In general, it is preferable that the film thickness of the recording layer is 5 nm or more.

(A-4) Recording Layer Manufacturing Method The recording layer can be obtained by DC or RF sputtering of a predetermined alloy target in an inert gas, particularly Ar gas.
The density of the recording layer is usually 80% or more, preferably 90% or more of the bulk density. As the bulk density ρ here, an approximate value according to the following general formula (2) is usually used, but it is also possible to actually measure an alloy composition lump constituting the recording layer.

ρ = Σm _i ρ _i (2)
(Here, _mi is the molar concentration of each element i, and ρ _i is the atomic weight of element i.)
In the sputtering film formation method, the pressure of a sputtering gas (usually a rare gas such as Ar, which will be described below as an example of Ar) during film formation is reduced, or a substrate is disposed close to the front of the target. Thus, the density of the recording layer can be increased by increasing the amount of high energy Ar irradiated to the recording layer. The high energy Ar is usually one in which Ar ions irradiated to the target for sputtering are partially rebounded and reach the substrate side, or Ar ions in the plasma are accelerated by the sheath voltage across the substrate and reach the substrate. Either.

  The irradiation effect of such a high energy rare gas is referred to as an atomic peening effect, but in sputtering with Ar gas that is generally used, Ar is mixed into the sputtered film due to the atomic peening effect. Therefore, the atomic peening effect can be estimated from the amount of Ar in the film. That is, if the amount of Ar is small, it means that the effect of high energy Ar irradiation is small, and a film with a low density is likely to be formed.

On the other hand, if the amount of Ar is large, irradiation with high energy Ar becomes intense and the density of the film becomes high, but Ar taken in the film precipitates as void during repeated recording, deteriorating repeated recording durability. Cheap. Therefore, discharge is performed at an appropriate pressure, usually in the order of 10 ⁻² to 10 ⁻¹ Pa.

  Next, another component of the structure of the optical information recording medium, which is a preferred embodiment of the present invention, will be described.

(B) Substrate As a substrate used in the present invention, a resin such as polycarbonate, acrylic resin or polyolefin, or a metal such as glass or aluminum can be used. Since a guide groove having a depth of about 20 to 80 nm is usually provided on the substrate, a resin substrate capable of forming the guide groove by molding is preferable. In addition, in the case of so-called substrate surface incidence (see FIG. 1A) where a focused light beam for recording / erasing / reproducing is incident from the substrate side, the substrate is preferably transparent.

  The thickness of the substrate is usually 0.05 mm or more and 1.5 mm or less, but about 1.2 mm for CD and about 0.6 mm for DVD are used. Further, in order to increase the density, when the laser optical head has a high NA and a short wavelength, a thin one of about 0.1 mm is used.

(C) Protective layer (C-1) General description of the protective layer used in the present invention In order to prevent evaporation / deformation associated with the phase change of the recording layer and to control the thermal diffusion at that time, one side of the normal recording layer Alternatively, a protective layer is formed on both, preferably both. The material of the protective layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. In general, a metal having high transparency and a high melting point, or a dielectric such as oxide, sulfide, nitride, carbide, fluoride of Ca, Mg, Li or the like can be used.

In this case, these oxides, sulfides, nitrides, carbides, and fluorides do not necessarily have to have a stoichiometric composition, and the composition may be controlled or mixed for controlling the refractive index and the like. Is also effective. In consideration of repetitive recording characteristics, a mixture of dielectrics is preferable. More specifically, a mixture of a chalcogen compound such as ZnS or rare earth sulfide and a heat-resistant compound such as oxide, nitride, carbide, or fluoride can be used. For example, a mixture of a heat-resistant compound containing ZnS as a main component and a mixture of a heat-resistant compound containing rare-earth sulfate, particularly Y ₂ O ₂ S as a main component are examples of a preferable protective layer composition.

  As a material for forming the protective layer, a dielectric material can be generally used. Examples of the dielectric material include Sc, Y, Ce, La, Ti, Zr, Hf, V, Nb, Ta, Zn, Al, Cr, In, Si, and Ge oxides, Ti, Zr, and Hf. , V, Nb, Ta, Cr, Mo, W, Zn, B, Al, Si, Ge, and Sn nitrides, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and Si And the like, or a mixture thereof. Dielectric materials include sulfides such as Zn, Y, Cd, Ga, In, Si, Ge, Sn, Pb, Sb, and Bi, selenides or tellurides, and oxysulfides such as Y and Ce. , Fluorides such as Mg and Ca, or a mixture thereof.

Further Examples of dielectric _materials include _{ZnS-SiO 2, SiN, SiO} 2, TiO 2, CrN, and TaS _2, Y _{2 O 2} S or the like. Among these materials, ZnS—SiO ₂ is widely used because of its high deposition rate, low film stress, low volume change rate due to temperature change, and excellent weather resistance. When using a ZnS-SiO _2, ZnS and the composition ratio of SiO ₂ ZnS: SiO ₂ is generally 0: 1 to 1: 0, preferably from 0.5: 0.5 to 0.95: 0.05, more Preferably, the ratio is 0.7: 0.3 to 0.9: 0.1. Most preferably, ZnS: SiO _{2 is set} to 0.8: 0.2.

  Considering repeated recording characteristics, it is desirable from the viewpoint of mechanical strength that the film density of the protective layer is 80% or more of the bulk state. When a dielectric mixture is used, the theoretical density of the above general formula (2) is used as the bulk density.

  The thickness of the protective layer is generally 1 nm or more and 500 nm or less. By setting the thickness to 1 nm or more, the effect of preventing deformation of the substrate and the recording layer can be secured, and the role as a protective layer can be achieved. Further, when the thickness is 500 nm or less, it is possible to prevent the occurrence of cracks due to a significant difference in internal stress of the protective layer itself and elastic properties with the substrate while serving as a protective layer. .

  In particular, when the first protective layer is provided, the thickness of the first protective layer is usually 1 nm or more, preferably 5 nm or more, particularly preferably, because it is necessary to suppress substrate deformation (cover layer deformation) or the like due to heat. 10 nm or more. In this way, accumulation of microscopic substrate deformation during repetitive recording is suppressed, and reproduction noise is not scattered and noise rises significantly.

  On the other hand, the thickness of the first protective layer is preferably 200 nm or less, more preferably 150 nm or less, and still more preferably 100 nm or less, in view of the time required for film formation. In this way, there is no change in the groove shape of the substrate when viewed in the plane of the recording layer. For example, the phenomenon that the depth and width of the groove become smaller than the intended shape on the substrate surface is less likely to occur.

  On the other hand, when the second protective layer is provided, the thickness of the second protective layer is usually 1 nm or more, preferably 5 nm or more, particularly preferably 10 nm or more in order to suppress deformation of the recording layer. Further, in order to prevent accumulation of microscopic plastic deformation inside the second protective layer that occurs with repeated recording, and to suppress an increase in noise due to scattering of reproduction light, preferably 200 nm or less, more preferably 150 nm or less, More preferably, it is 100 nm or less, Most preferably, it is 50 nm or less.

The thickness of the recording layer and the protective layer is not limited in terms of mechanical strength and reliability. It is selected so that the contrast between the recorded state and the unrecorded state is large.
The protective layer may be usually produced by a known sputtering method.
The protective layer may be composed of a plurality of layers made of different materials as described above. In particular, it is preferable to provide an interface layer that does not contain sulfur or has a low sulfur content at the interface in contact with the recording layer and / or the interface in contact with the reflective layer containing Ag as a main component.
Here, the interface layer provided at the interface on the side in contact with the reflective layer containing Ag as a main component is usually used to suppress the reaction between Ag and sulfur (corrosion of Ag) when the protective layer contains sulfur. Used.

Examples of the material for the interface layer include Ta, Nb, and Mo. Of these materials, Nb and Mo are preferable. The atomic weight of Nb and Mo is relatively close to Ag contained in the reflective layer, and the emission angle of each element from the target is almost the same as Ag during film formation by the sputtering method. The film thickness distribution can be secured, and there is an advantage that uniformity can be easily secured. In addition, Nb and Mo are very inexpensive at a price of 1/10 to 1/100 of the raw material, and there is an advantage that the target can be manufactured at a low cost.
The content of the material of the interface layer is preferably 80 atomic% or more, more preferably 90 atomic% or more, particularly preferably 95 atomic% or more, most preferably 100 atomic% (Nb in the interface layer). In the example of using N, the interface layer is made of pure Nb).

  If necessary, the interface layer may contain other elements to the extent that the characteristics of the layer are not impaired. When other elements are included, the content of the elements is preferably 20 atomic% or less, more preferably 10 atomic% or less, particularly preferably 5 atomic% or less, and most preferably 2 atomic% or less. Examples of the element include Ni, Pd, Pt, Si, O, Se, V, Ti, and Ta.

In addition to this, the interface layer may be a dielectric containing no sulfur. Specifically, it is a metal or semiconductor oxide, nitride, carbide or the like, and SiC, Si ₃ N ₄ , SiC, GeN, Ta ₂ O ₅ , ZrO ₂ AlN, Al ₂ O ₃ or the like is used. These do not necessarily have a stoichiometric composition or may be a mixture.
The film thickness of the interface layer is preferably 1 nm or more, more preferably 2 nm or more. If the film thickness of the interface layer is too thin, the reaction between the protective layer and the reflective layer may not be effectively suppressed. Even in the reliability test under such a severe environment, the reliability of the optical information recording medium can be secured satisfactorily.
On the other hand, the thickness of the interface layer is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 6 nm or less. If it is the said range, it will become possible to suppress reaction with Ag in a reflective layer, and S in a protective layer, ensuring the transmittance | permeability of an interface layer favorably.
The interface layer is usually formed by a sputtering method.

(C-2) Preferred Mode of Protective Layer In the information recording medium used in the present invention, the protective layer A is in contact with the recording layer using a predetermined Ge—In—Sb—Sn—Te-based material, The protective layer A preferably contains a metal oxysulfide and / or a metal nitride.
When the information recording medium of the present invention is used as a phase change optical information recording medium, (ZnS) ₈₀ (SiO ₂ ) ₂₀ is usually used as the material of the protective layer. This is because this material is excellent in transparency, adhesion to a conventional recording layer, sputtering rate, price, and the like.

However, when the protective layer (ZnS) ₈₀ (SiO ₂ ) ₂₀ is used for a recording layer having a predetermined Ge—In—Sb—Sn—Te composition that enables high-speed recording / erasing, repeated recording durability is achieved. There is a case where there is a problem of improving the sex. This is because, in comparison with the case of an optical information recording medium for low-speed recording, recording erasure with an optical information recording medium for high-speed recording is accompanied by a rapid temperature change. One is considered. For example, when the recording linear velocity is doubled, the time for heating the recording layer by irradiating the laser beam is halved and the cooling rate tends to be abrupt. This is because the temperature distribution in the molten region of the recording layer tends to be gentle when recording at a low linear velocity, but steep when recording at a high linear velocity. Furthermore, the positional relationship between the melted region and the laser beam tends to be relatively farther in recording at a high linear velocity than in the case of recording at a low linear velocity. Of course, the reason why the repeated recording durability is not sufficient has been reported in relation to the recording layer material itself, such as the difference in properties related to mass transfer due to melting and solidification, and when it is combined with conventional recording materials. It is also possible that atomic diffusion such as sulfur is more likely to occur.

In the present invention, in contact with the recording layer containing the Ge—In—Sb—Sn—Te recording layer material, for example, GeN is contained as a metal nitride, and, for example, Y ₂ O ₂ S is contained as a metal oxysulfide. By providing the protective layer A, further improvement in the repeated recording durability of the information recording medium is expected. The reason why repeated recording durability is expected to be improved by providing the protective layer A containing a metal nitride such as GeN or a metal oxysulfide such as Y ₂ O ₂ S is not necessarily clear, but compared with the conventional case. This is because the effect of suppressing the deformation due to a rapid temperature change of the recording layer, the mass transfer of the recording layer, the atomic diffusion between layers, etc. due to the high speed recording is exhibited.

  As described above, when the protective layer A in contact with the recording layer contains a metal oxysulfide or a metal nitride, the repeated recording characteristics (repeated overwrite characteristics) tend to be improved. For this reason, it is considered that the protective layer A has high affinity with Sb, Ge, In, and Sn constituting the phase change recording material of the present invention.

(1) Protective layer A
In the present invention, the protective layer A in contact with the recording layer preferably contains a metal oxysulfide and / or a metal nitride. Of course, a metal oxysulfide and a metal nitride may be used in combination. This will be described in more detail below.
(1-1) Protective layer A containing metal oxysulfide
In the present invention, it is preferable to use a protective layer A containing a metal oxysulfide. Containing metal oxysulfide means that this constituent element exists while maintaining the form of metal oxysulfide.

In the present invention, by providing the recording layer having a specific composition in contact with the protective layer A containing a metal oxysulfide, it is expected that the durability when the information recording medium is repeatedly recorded is further improved. The Although this reason is not yet clear, it is considered that the protective layer A containing a metal oxysulfide has high thermal conductivity and hardness and high uniformity of constituent element distribution. That is, the protective layer A in the present invention has a thermal conductivity as compared with a protective layer using a composite dielectric containing ZnS as a main component, as represented by a conventionally used ZnS—SiO ₂ film. High rate and hardness. On the other hand, although the refractive index of the protective layer A depends on the composition ratio, it is usually about 1.7 to 2.4, which is almost the same as that of a protective layer using a composite dielectric composed mainly of ZnS.

Then, since the protective layer A containing the metal oxysulfide has a high thermal conductivity, the deformation due to the thermal expansion of the recording layer is considered to be small. That is, since the thermal conductivity of the protective layer A is high, it is possible to quickly release the heat of the recording layer that has been heated when the recording mark is formed by the laser. For this reason, the temperature difference between the interface region in contact with the recording layer of the protective layer A and the region of the protective layer A away from the recording layer or the temperature difference between the mark forming region and the surrounding region can be quickly eliminated. As a result, the occurrence of film peeling and cracks due to temperature differences are suppressed. In other words, it is considered that the overwrite deterioration can be delayed. The thermal conductivity can be indirectly known from the value of the laser power when the amorphous mark is formed on the produced disk. That is, the greater the thermal conductivity, the greater the laser power required to raise the temperature of the recording layer. For example, when the protective layer A containing a metal oxysulfide is used, the power required for mark formation is higher than when a protective layer of ZnS: SiO ₂ = 80: 20 (mol%) is used. Although there is a tendency, this is because the protective layer A functions more as a heat dissipation layer due to its high thermal conductivity.

The JIS Knoop hardness of the protective layer using ZnS: SiO ₂ = 80: 20 (mol%) is 280, whereas the JIS of the protective layer A using, for example, Y ₂ O ₂ S as the metal oxysulfide. Knoop hardness is 520. The protective layer A having high hardness is important for preventing deformation of the recording layer. When the hardness is low, it is difficult to appropriately suppress the volume change of the recording layer accompanying recording / erasing, that is, deformation due to the volume difference between the amorphous and the crystal. Leads to a decrease in signal strength.

Furthermore, since the protective layer A containing a metal oxysulfide has metal atoms bonded to both sulfur and oxygen, the mixing property of sulfur and oxygen is a sulfide such as ZnS—SiO ₂ or ZnS—Y ₂ O ₃ . And a protective layer using a mixture of oxides are incomparably high. Therefore, the protective layer A is considered to exhibit stable and high characteristics because the dispersibility of metal atoms such as sulfur, oxygen, and selenium atoms is higher than that of conventional ZnS—SiO ₂ . For this reason, it is presumed that the phenomenon in which sulfur diffuses from the protective layer to the recording layer during repeated overwriting to cause a decrease in reflectance and a change in crystallization speed is also suppressed.

Further, when the protective layer A containing a metal oxysulfide such as Y ₂ O ₂ S is provided in contact with the predetermined Ge—In—Sb—Sn—Te recording layer used in the present invention, the protective layer Compared with the case where A contains a metal nitride such as GeN, the signal amplitude of the information recording medium tends to increase. The reason for this is not clear, but it is conceivable that the crystal growth property of the recording layer varies somewhat depending on the protective layer A in contact with the recording layer, and the size of the formed amorphous mark is different. Such properties are considered to be determined by the combination of the recording layer material and the protective layer A material. However, in the conventional recording layer material, attention has been paid to changes in signal intensity due to the protective layer A material. There wasn't.

Examples of the metal element used for the metal oxysulfide include Sc, yttrium, and rare earth metal elements such as lanthanoid elements such as La and Ce; transition metal elements such as Ti. Among these, rare earth metal elements are preferred, yttrium and rare earth metal elements selected from the group consisting of La, Ce, Nd, Sm, Eu, Gd, Tb, Dy are particularly preferred, and most preferred are yttrium, Ce. It is. Since yttrium oxysulfide (Y ₂ O ₂ S) is thermochemically more stable than Y ₂ O ₃ and Y ₂ S ₃ up to about 1000 ° C., the most preferred element is yttrium.
The content of the metal oxysulfide in the protective layer A is preferably 5 mol% or more, more preferably 10 mol% or more, and most preferably 15 mol% or more. If the content of the metal oxysulfide is too small, the overwrite characteristics may not be sufficient. On the other hand, from the viewpoint of repetitive overwriting characteristics and the like, it is preferable that the content of the metal oxysulfide in the protective layer A is larger, and the content of the metal oxysulfide in the protective layer A is 100 mol% or less. Good.

The content of the metal element constituting the metal oxysulfide in the protective layer A is usually 10 atomic% or more, preferably 20 atomic% or more, more preferably 25 atomic% or more. Since the content of the metal element constituting the metal oxysulfide serves as an index indicating the content of the metal oxysulfide in the protective layer A, if the amount of the metal element is too small, the effect of further improving the overwrite characteristics may be obtained. It may not be enough. On the other hand, from the viewpoint of repeated overwrite characteristics, etc., the higher the content of the metal oxysulfide in the protective layer A, the better. Therefore, the upper limit of the content of the metal element constituting the metal oxysulfide is the protection This is the content of the metal element when the layer A is entirely composed of a metal oxysulfide.
Further, the protective layer A may be used in combination with a metal oxysulfide and other materials. The other material is not particularly limited as long as it is a material generally used for the protective layer. For example, the materials exemplified in the above “General description of the protective layer used in the present invention” may be used as appropriate.
As other materials, more specifically, represented by zinc sulfide, zinc oxide, silicon oxide, silicon nitride, aluminum nitride, aluminum oxide, rare earth oxide, rare earth sulfide, rare earth fluoride, magnesium fluoride, etc. Metal or semiconductor oxides, sulfides, nitrides, carbides or fluorides can be exemplified. Among these, particularly preferred are zinc compounds such as zinc sulfide and zinc oxide, which are excellent in adhesion to the recording layer. As a result, more stable and high durability can be obtained.

When other materials are contained in the protective layer A in addition to the metal oxysulfide, the content of this material is usually 99 mol% or less, preferably 90 mol% or less. On the other hand, it is usually 1 mol% or more, preferably 5 mol% or more.
However, the appropriate content varies depending on the type of material to be mixed. For example, when zinc sulfide is used as the material, there is no problem even if the content thereof is large, and it is usually 20 mol% or more, preferably 30 mol% or more, more preferably 50 mol% or more, and most preferably 60 mol% or more.
On the other hand, when zinc oxide is used as the material, an excessively large content tends to be unfavorable, and is usually 30 mol% or less, preferably 20 mol% or less, and more preferably 10 mol% or less. Moreover, it is more preferable that the molar content of zinc oxide is not more than half the molar content of metal oxysulfide.
A particularly preferable composition of the protective layer A is a mixed composition containing Y ₂ O ₂ S and ZnS. In this case, particularly excellent overwrite characteristics can be obtained. In this case, the molar ratio of ZnS to Y ₂ O ₂ S is usually 1% or more, preferably 5% or more, more preferably 10% or more, and usually 1000% or less, preferably 700% or less, more preferably Is 500% or less.

Note that metallic zinc can be present in the protective layer A. However, it is preferable to contain it in the form of a zinc compound such as zinc oxide or zinc sulfide.
The purity of the protective layer A in the present invention (the content of the metal oxysulfide in the protective layer A or the content of the mixture of the metal oxysulfide and other materials) is preferably 90 mol% or more. The higher the purity, the better. However, the influence of impurities of less than 10 mol% on the characteristics of the protective layer A is so small that it can be ignored. In particular, if the impurity is a stable compound, the adverse effect is small, but if the impurity exceeds 10 mol%, the physical property values such as the hardness and stress of the film are likely to change, and the characteristics of the protective layer A may be deteriorated. There is.

The protective layer A containing a metal oxysulfide can be formed by forming a film by a sputtering method using a target containing a metal oxysulfide. Usually, a target having a composition range substantially the same as the composition preferred for the protective layer A is used.
That is, it is preferable to use a target containing a metal oxysulfide as a sputtering target. The type of metal element of the metal oxysulfide used for the target is appropriately selected according to the composition of the protective layer A.
When the protective layer A contains a metal oxysulfide and another protective layer material, a target of a mixture of the metal oxysulfide and the other material is used according to the composition of the other material to be used. can do. It is also possible to prepare a metal oxysulfide target and the target of the other material separately and to sputter them simultaneously.

  The content of the metal oxysulfide in the target is usually 10 mol% or more, preferably 30 mol% or more, more preferably 50 mol% or more. If the content of the metal oxysulfide in the target is excessively small, the metal oxysulfide may be decomposed in the target and the protective layer A may not be able to contain the metal oxysulfide. On the other hand, the content of the metal oxysulfide in the target varies depending on the content of the other material used. However, when using a target made of a metal oxysulfide alone, the content of the metal oxysulfide in the target is usually 100 mol%.

Whether or not a metal oxysulfide is contained in the target can be confirmed by measuring the X-ray diffraction of the target.
In addition, a target containing a metal oxysulfide is usually manufactured using a metal oxysulfide powder or a mixed powder of the same metal oxide and sulfide using a known method such as a hot press method. Is done. Here, a rare earth metal element is preferable as the metal element to be used.
Known conditions may be used for sputtering.
The analysis of the composition of the protective layer A can be generally identified by combining Auger electron spectroscopy (AES), Rutherford back scattering method (RBS), inductively coupled radio frequency plasma spectroscopy (ICP), and the like.

(1-2) Protective layer A containing metal nitride
In the present invention, it is preferable to use a protective layer A containing a metal nitride.
Metal nitrides tend to have high thermal conductivity like metal oxysulfides. For this reason, as described in the case of containing the metal oxysulfide, the thermal conductivity of the protective layer A is increased, thereby suppressing the occurrence of film peeling and cracking due to the temperature difference. It is considered that overwriting deterioration can be delayed.
Examples of the metal used for the metal nitride include at least one element selected from the group consisting of Si, Ge, Al, Ti, Ta, Cr, Mo, Sb, Sn, Nb, Y, Zr, and Hf. be able to. Since nitrides of these elements are stable, the storage stability of the optical information recording medium tends to be improved. The element is preferably Si, Ge, Al, or Cr, which has higher transparency and excellent adhesion. A plurality of the above elements can be used. In the case of using an alloy nitride containing a plurality of the above elements, it is preferable to use an alloy nitride containing Ge as a main component. Here, “mainly comprising Ge” means that the content of Ge in the alloy is usually 50 atomic% or more, preferably 70 atomic% or more, more preferably 80 atomic% or more, particularly preferably 90 atomic% or more, Most preferably, it is 95 atomic% or more.

In the case of using one kind of the element, a nitride of the element alone can be cited as a material formed by the element and nitrogen. More specifically, Si—N, Ge—N, Cr—N, Al—N, and the like are included in the vicinity, and among these, from the viewpoint that the diffusion preventing effect on the recording layer is higher, Si— N (silicon nitride), Ge—N (germanium nitride), and Al—N (aluminum nitride) are preferably used, and Ge—N (germanium nitride) is more preferably used. In this case, a nitride of an alloy containing Ge as a main component in which a part of Ge is replaced with Cr or the like may be used. However, the substitution amount is preferably 50% or less, more preferably 30% or less of Ge in terms of atomic ratio.
When two or more of the above elements are used, examples of a material formed by the above elements and nitrogen include composite nitrides of the above elements. Examples of such compounds typically using Ge-N are Ge-Si-N, Ge-Sb-N, Ge-Cr-N, Ge-Al-N, Ge-Mo-N, Ge. As in Ti-N, together with Ge, Al, B, Ba, Bi, C, Ca, Ce, Cr, Dy, Eu, Ga, In, K, La, Mo, Nb, Ni, Pb, Pd, Examples include those containing Si, Sb, Sn, Ta, Te, Ti, V, W, Yb, Zn, and Zr.

The content of the metal nitride in the protective layer A is preferably 5 mol% or more, more preferably 10 mol% or more, and most preferably 15 mol% or more. If the content of metal nitride is too small, the overwrite characteristics may deteriorate. On the other hand, from the viewpoint of repetitive overwriting characteristics and the like, it is preferable that the content of the metal nitride in the protective layer A is as large as possible. Good.
Further, the content of the metal element constituting the metal nitride in the protective layer A is usually 10 atomic% or more, preferably 20 atomic% or more, more preferably 25 atomic% or more. If the content of the metal oxysulfide is too small, the effect of further improving the overwrite characteristics may not be sufficient. On the other hand, from the viewpoint of repeated overwrite characteristics and the like, the higher the content of the metal nitride in the protective layer A, the better. Therefore, the upper limit of the content of the metal element constituting the metal nitride is the protective layer A Is the content of the metal element when all are made of metal nitride.
The protective layer A may be used in combination with a metal oxynitride and another material. Other materials and their contents may be the same as those described in the protective layer A containing the metal oxysulfide.

The purity of the protective layer A in the present invention (the content of the metal nitride in the protective layer A or the content of the mixture of the metal nitride and other materials) is preferably 90 mol% or more. The higher the purity, the better. However, the influence of impurities of less than 10 mol% on the characteristics of the protective layer A is so small that it can be ignored. In particular, when the impurity is a stable compound, the adverse effect is small, but if the impurity exceeds 10 mol%, the physical property values such as the hardness and stress of the film are likely to change and the characteristics of the protective layer A may be deteriorated. .
The protective layer A containing metal nitride can be formed by sputtering using a target containing metal nitride. In addition, the protective layer A is made by flowing a small amount of Ar, N ₂ mixed gas in a vacuum chamber to a predetermined vacuum pressure, and a predetermined metal (a metal element alone or a metal in the metal nitride contained in the protective layer A). It may be formed by a reactive sputtering method in which a voltage is applied to a target made of a composite of elements) and a metal element alone or a composite of metal elements that is released by reacting with N ₂ is reacted with N ₂ to form a nitride. The matters to be noted here are that if the nitrogen content in the protective layer A is excessively small, it becomes difficult to ensure the transparency of the protective layer A, and if the nitrogen content is excessively large, the optical information recording medium The improvement in the repeated recording durability is insufficient. For this reason, adjustment of the nitrogen flow rate is important when the reactive sputtering method is used. Moreover, the pressure during sputtering also affects the film quality. Usually, the protective layer A can be densely formed by lowering the pressure.
The analysis of the composition of the protective layer A can be generally identified by combining Auger electron spectroscopy (AES), Rutherford back scattering method (RBS), inductively coupled radio frequency plasma spectroscopy (ICP), and the like.

(1-3) Film thickness of the protective layer A The preferable range of the film thickness of the protective layer A differs depending on the position where the protective layer A is used.
That is, when the protective layer A is provided as the first protective layer, the thickness of the first protective layer is usually 1 nm or more, preferably 5 nm or more, particularly preferably 10 nm because it is necessary to suppress deformation of the substrate due to heat. That's it. In this way, accumulation of microscopic substrate deformation during repetitive recording is suppressed, and reproduction noise is not scattered and noise rises significantly.
On the other hand, the thickness of the first protective layer is preferably 200 nm or less, more preferably 150 nm or less, and still more preferably 100 nm or less, in view of the time required for film formation. In this way, the substrate groove shape as seen on the recording layer plane is not changed. For example, a phenomenon that the depth or width of the groove becomes smaller than the intended shape on the substrate surface is less likely to occur.
When the protective layer A is provided as the second protective layer, the thickness of the second protective layer is usually 1 nm or more, preferably 5 nm or more, and particularly preferably 10 nm or more in order to suppress deformation of the recording layer. Moreover, in order to prevent the accumulation of microscopic plastic deformation inside the second protective layer that occurs with repeated recording, and to suppress the increase in noise due to scattering of the reproduction light, preferably 200 nm or less, more preferably 150 nm or less, More preferably, it is 100 nm or less, Most preferably, it is 50 nm or less.

  However, in the present invention, since the protective layer A having high thermal conductivity and high hardness is generally provided in contact with the recording layer, the film thickness of the protective layer A located on the side where the laser beam is incident on the recording layer is set. As already explained, it can be thinned. That is, when the protective layer A is provided in contact with the recording layer surface on which the laser beam is incident, the thickness of the protective layer A is preferably 50 nm or less.

Note that the sputtering rate of a material mainly composed of a metal oxysulfide such as Y ₂ O ₂ S is higher than that of a conventionally used material such as (ZnS) ₈₀ (SiO ₂ ) ₂₀ . It tends to be slow. Therefore, from the viewpoint of increasing the productivity of the information recording medium, the protective layer A containing a metal oxysulfide may be provided relatively thin in contact with the recording layer, and the protective layer B may be provided in contact with the protective layer A. Good. Further, a conventionally used material (for example, (ZnS) ₈₀ (SiO ₂ ) ₂₀ ) may be used for the protective layer B. Details of a specific aspect of such an information recording medium will be described later.
Thus, when multilayering is performed using the protective layer A and the protective layer B, the thickness of the protective layer A in the present invention is usually 0.1 nm or more, preferably 1 nm or more, more preferably 5 nm or more. On the other hand, the thickness of the protective layer A is usually 100 nm or less, preferably 50 nm or less, more preferably 25 nm, and still more preferably 10 nm or less.

(1-4) Position of Protective Layer A and Recording Layer In the present invention, it is preferable that the protective layer A containing a metal oxysulfide and / or a metal nitride is provided in contact with the recording layer. More preferably, the predetermined protective layer A is provided on both sides of the recording layer. This is because by providing the predetermined protective layer A on both sides of the recording layer, it is possible to further improve the overwrite characteristics repeatedly. Generally, by providing the predetermined protective layer A on both surfaces of the recording layer, the recording layer and the protective layer A tend to be peeled off easily. However, the predetermined Ge—In—Sb—Sn—Te in the present invention is used. In the recording layer using the system composition, the above-mentioned peeling problem is unlikely to occur.
For example, when a protective layer A containing a metal oxysulfide such as Y ₂ O ₂ S is provided in contact with a recording layer having a conventional SbTe eutectic composition, film peeling tends to occur in an environmental resistance test. This tendency becomes more prominent when the protective layer A is provided on both sides of the recording layer. For example, in a conventional recording layer using an SbTe eutectic composition, an environmental resistance test with high humidity is performed by providing a protective layer A containing a metal oxysulfide such as Y ₂ O ₂ S in contact with both surfaces of the recording layer. As a result, film peeling occurs, and the adhesion and weather resistance of the film tend not to be sufficient.

On the other hand, when the protective layer A containing a metal oxysulfide such as Y ₂ O ₂ S is provided in contact with the recording layer using the predetermined Ge—In—Sb—Sn—Te-based composition of the present invention, the recording layer Even when it is provided on both sides, film peeling does not occur in the environmental resistance test, and the repeated recording durability tends to hardly change before and after the environmental resistance test.
Further, when a protective layer A containing a metal oxysulfide such as Y ₂ O ₂ S is provided in contact with a recording layer using a conventional SbTe eutectic composition, the stability of the amorphous mark tends to deteriorate. . On the other hand, the predetermined Ge—In—Sb—Sn—Te-based composition used in the present invention can increase the stability of the amorphous mark by adjusting the composition. For this reason, even when the protective layer A containing a metal oxysulfide such as Y ₂ O ₂ S is provided in contact with the recording layer, the deterioration of the stability of the amorphous mark can be suppressed. Become.

(2) Protective layer B
Another example of a preferable layer structure of the optical information recording medium is that one or both of the first protective layer and the second protective layer have a two-layer structure of a protective layer A and a protective layer B. From the viewpoint of repeated overwriting and the like, it is preferable that the first protective layer positioned on the laser light incident side has a two-layer structure (FIGS. 5A and 5B). It is more preferable that both of the protective layers have a two-layer structure of a protective layer A and a protective layer B (see FIGS. 6A and 6B).
In the preferred layer configuration, the first protective layer and the second protective layer have a two-layer structure of the protective layer A and the protective layer B. However, as long as the protective layer A is provided in contact with the recording layer, It is not necessarily limited to such an aspect. For example, by providing a protective layer formed of another material in contact with the protective layer B, the first protective layer and the second protective layer can be appropriately multi-layered into three or more layers.

(2-1) Material of protective layer B, production method, etc. As a material of protective layer B, a material generally used for the protective layer may be appropriately used. Since such a material has already been described, a description thereof is omitted here. The protective layers A and B may be two layers made of different materials, or may have a gradient composition in which each component gradually changes.
Moreover, the manufacturing method generally used for a protective layer should just be used also about the manufacturing method of a protective layer.

(2-2) Film thickness of the protective layer B The protective layer B is in contact with the protective layer A and serves as a protective layer in a two-layer structure of the protective layer A and the protective layer B. For this reason, the film thickness of the protective layer B is a film thickness obtained by subtracting the film thickness of the protective layer A from the film thickness generally required for the protective layer.
However, in the present invention, since the protective layer A having a high thermal conductivity and a high hardness is generally provided in contact with the recording layer, the thickness of the protective layer positioned on the side where the laser beam is incident on the recording layer (for example, When the protective layer is formed of only the protective layer A, the film thickness of the protective layer A, and when the protective layer is formed by laminating the protective layer A and the protective layer B, the total film of the protective layer A and the protective layer B As described above, the thickness can be reduced.
That is, when the protective layer A is provided in contact with the recording layer surface on which the laser beam is incident, and the protective layer B is provided in contact with the protective layer A, the thickness of the protective layer A The total film thickness with the film thickness of the protective layer B is preferably 50 nm or less.
As described above, when multilayering is performed using the protective layer A and the protective layer B, the thickness of the protective layer A in the present invention is usually 0.1 nm or more, preferably 1 nm or more, more preferably 2 nm or more, and further preferably. Is 3 nm or more, particularly preferably 5 nm or more. On the other hand, the thickness of the protective layer A is usually 100 nm or less, preferably 50 nm or less, more preferably 25 nm, and still more preferably 10 nm or less. For this reason, what is necessary is just to let the film thickness of the protective layer B be the remainder except the protective layer A among the total film thickness of a protective layer.
The thickness of the recording layer and the protective layer is not limited in terms of mechanical strength and reliability. It is selected so that the contrast between the recorded state and the unrecorded state is large.

(D) Reflective layer In the optical information recording medium, a reflective layer can be further provided. In the present invention, it is preferable that the optical information recording medium further has a reflective layer from the viewpoint of improving the heat dissipation of the recording layer.
The position where the reflective layer is provided usually depends on the incident direction of the reproduction light, and is provided on the opposite side of the recording layer with respect to the incident side. That is, when reproducing light is incident from the substrate side, it is usual to provide a reflective layer on the opposite side of the recording layer with respect to the substrate. When reproducing light is incident from the recording layer side, the recording layer and the substrate Usually, a reflective layer is provided between them (see FIGS. 1A and 1B).
In addition to the reflective layer that completely reflects light, a very thin reflective layer material layer that transmits more than half of the light may be provided on the incident side of the recording layer. Used separately from the layer. The purpose of providing the translucent reflective layer is usually to promote the adjustment of the phase of incident light or reflected light and the heat radiation from the protective layer on the incident light side.

  The material used for the reflective layer is preferably a substance having a high reflectance, and in particular, a metal such as Au, Ag, or Al, which can be expected to have a heat dissipation effect. Although the heat dissipation is determined by the film thickness and the thermal conductivity, the thermal conductivity of these metals is almost proportional to the volume resistivity, so that the heat dissipation performance can be expressed by the area resistivity. The sheet resistivity is usually 0.05Ω / □ or more, preferably 0.1Ω / □ or more, and usually 0.6Ω / □ or less, preferably 0.5Ω / □ or less, more preferably 0.4Ω / □ or less. More preferably, it is 0.2Ω / □ or less.

This guarantees particularly high heat dissipation, and the competition between amorphization and recrystallization is significant in the formation of amorphous marks as in the recording layer used for optical information recording media. In some cases, this is necessary to suppress recrystallization to some extent. A small amount of Ta, Ti, Cr, Mo, Mg, V, Nb, Zr, Si, or the like may be added to the above metal for controlling the thermal conductivity of the reflective layer itself or improving the corrosion resistance. The addition amount is usually 0.01 atomic percent or more and 20 atomic percent or less. An aluminum alloy containing at least one of Ta and Ti of 15 atomic% or less, particularly an alloy of Al _α Ta _1-α (0 ≦ α ≦ 0.15) has excellent corrosion resistance and is used for optical information recording. This is a particularly preferable reflective layer material for improving the reliability of the medium.

  In particular, when the thickness of the second protective layer is set to 40 nm or more and 50 nm or less, it is preferable that the contained additive element is 2 atomic% or less in order to make the reflective layer have high thermal conductivity.

Particularly preferred as the material of the reflective layer is that Ag is the main component. “Containing Ag as a main component” means that 50 atomic% or more of Ag is contained in the entire reflective layer. The content of Ag with respect to the entire reflective layer is preferably 70 atomic% or more, more preferably 80 atomic% or more, further preferably 90 atomic% or more, and 95 atomic% or more. Particularly preferred. From the viewpoint of improving heat dissipation, it is most preferable that the material of the reflective layer is pure Ag.
The reason why Ag is the main component is as follows. In other words, when a recording mark that has been stored for a long time is recorded again, there may be a phenomenon in which the recrystallization speed of the phase change recording layer increases only for the first recording immediately after storage. The reason why such a phenomenon occurs is unknown, but due to the increase in the recrystallization speed of the recording layer immediately after the storage, the size of the amorphous mark formed in the first recording immediately after the storage is desired. It is presumed that it will be smaller than the size of the mark. Therefore, when such a phenomenon occurs, the recording layer is re-recorded during the first recording immediately after storage by increasing the cooling rate of the recording layer by using Ag having a very high heat dissipation property for the reflective layer. Crystallization is suppressed, and the size of the amorphous mark can be maintained at a desired size.
Ag alloy containing any one of Mg, Ti, Au, Cu, Pd, Pt, Zn, Cr, Si, Ge, Bi, and rare earth elements in an amount of 0.01 atomic% to 10 atomic% in Ag is also reflective and heat conductive. The rate is high and heat resistance is excellent, which is preferable.

  The thickness of the reflective layer is usually 10 nm or more in order to completely reflect incident light without transmitted light, but is preferably 20 nm or more, and more preferably 40 nm or more. Moreover, even if it is too thick, there is no change in the heat dissipation effect, and the productivity is worsened and cracks are easily generated. Therefore, it is usually 500 nm or less, but preferably 400 nm or less, preferably 300 nm or less. More preferably.

The recording layer, protective layer, and reflective layer are usually formed by sputtering or the like.
In order to prevent oxidation and contamination between layers, it is desirable to form a film with an in-line apparatus in which a target for a recording layer, a target for a protective layer, and, if necessary, a target for a reflective layer material are installed in the same vacuum chamber. It is also excellent in terms of productivity.

(E) Protective coat layer (cover layer)
On the outermost surface side of the optical information recording medium, it is preferable to provide a protective coating layer made of an ultraviolet curable resin or a thermosetting resin in order to prevent direct contact with air or damage due to contact with foreign matter. . The protective coat layer is usually 1 μm to several hundred μm thick. Further, a dielectric protective layer having high hardness can be further provided, and a resin layer can be further provided thereon.

(Initial crystallization method of optical information recording medium)
The recording layer is usually formed by a physical vapor deposition method in vacuum such as sputtering. However, in the state immediately after the film formation (as-deposited state), the recording layer is usually amorphous. It is preferable to crystallize to an unrecorded erase state. This operation is referred to as initialization (or initial crystallization). Examples of the initial crystallization operation include oven annealing in a solid phase at a crystallization temperature (usually 150 to 300 ° C.) or higher and a melting point or lower, annealing by irradiation with light energy such as laser light or flash lamp light, and melting initialization. And the like. In the present invention, since a phase change recording material with less crystal nucleation is used, it is preferable to use melt initialization among the above initial crystallization operations.

  In the melt initialization, if the recrystallization rate is too slow, there is a time margin for achieving thermal equilibrium, so that another crystal phase may be formed. Therefore, it is preferable to increase the cooling rate to some extent. In addition, holding in a molten state for a long time is not preferable because the recording layer flows, a thin film such as a protective layer peels off due to stress, or a resin substrate or the like is deformed, leading to destruction of the medium.

  For example, the time for maintaining the melting point or more is usually 10 μs or less, preferably 1 μs or less.

  In addition, it is preferable to use laser light for melt initialization, and in particular, initial crystallization is performed using an elliptical laser light having a minor axis substantially parallel to the scanning direction (hereinafter, this initialization method is referred to as “bulk”). It is sometimes referred to as “erase”.). In this case, the length of the major axis is usually 10 to 1000 μm, and the length of the minor axis is usually 0.1 to 5 μm.

  Here, the lengths of the major axis and the minor axis of the beam are defined from the half width when the light energy intensity distribution in the beam is measured. In order to make it easy to realize local heating and rapid cooling in the short axis direction, the beam shape is more preferably 5 μm or less, and more preferably 2 μm or less.

  Various laser light sources such as a semiconductor laser and a gas laser can be used. The power of the laser light is usually about 100 mW to 10 W. Other light sources may be used as long as the same power density and beam shape can be obtained. Specific examples include Xe lamp light.

  In initialization by bulk erase, for example, when using a disk-shaped optical information recording medium, the minor axis direction of the elliptical beam is substantially coincident with the circumferential direction, the disk is rotated and scanned in the minor axis direction, The entire surface can be initialized by moving in the major axis (radius) direction every round (one rotation). By doing so, it is possible to realize a polycrystalline structure oriented in a specific direction with respect to the recording / reproducing focused light beam scanned along the track in the circumferential direction.

  It is preferable that the moving distance in the radial direction per rotation is shorter than the long axis of the beam so as to be overlapped so that the same radius is irradiated with the laser beam multiple times. As a result, reliable initialization is possible, and non-uniformity of the initialization state derived from the energy distribution in the beam radial direction (usually 10 to 20%) can be avoided. On the other hand, if the amount of movement is too small, other undesirable crystal phases are likely to be formed. Therefore, the amount of movement in the normal radial direction is usually set to 1/2 or more of the long axis of the beam. The scanning speed of the initialization energy beam is usually in the range of about 3 to 20 m / s.

  At least whether or not the optical information recording medium of the present invention can be obtained by melt initialization depends on the reflectance R1 in the unrecorded state after initialization and the actual focused light beam for recording (for example, the diameter of the beam). It is possible to determine whether or not the reflectance R2 in the erased state by recrystallization after recording an amorphous mark with a focused light beam of about 1 μm is substantially equal. Here, R2 is the reflectance of the erased portion after 10 times recording.

  Therefore, the optical information recording medium of the present invention satisfies the following relational expression (3) when the reflectance R1 of the unrecorded portion after initial crystallization is 10 and the reflectance of the erased portion after 10 times recording is R2. It is preferable.

ΔR = 2 | R1-R2 | / (R1 + R2) × 100 (%) ≦ 10 (3)
Here, the reason why the reflectivity R2 of the erased portion after 10 times of recording is used as a judgment index is that the effect of the reflectivity of the crystal state that can remain in an unrecorded state only after one time of recording is performed. This is because the entire surface of the optical information recording medium can be recrystallized at least once by recording and erasing. On the other hand, if the number of recordings greatly exceeds 10, conversely, factors other than changes in the crystal structure of the recording layer, such as microscopic deformation of the recording layer due to repeated recording, diffusion of foreign elements from the protective layer to the recording layer, etc. This is because it causes a change in reflectance, making it difficult to determine whether or not a desired crystal state has been obtained.

  In the relational expression (3), ΔR is set to 10% or less, but is preferably set to 5% or less. If it is 5% or less, an optical information recording medium with lower signal noise can be obtained.

  For example, in the case of an optical information recording medium having R1 of about 17%, R2 may generally be in the range of 16 to 18%.

  The erased state can also be obtained by irradiating recording power in a direct current to melt the recording layer and resolidifying it without necessarily modulating the recording focused laser beam in accordance with the actual recording pulse generation method. .

  In order to obtain a desired initial crystal state for the phase change recording material used for the recording layer in the present invention, the setting of the scanning speed of the initialization energy beam with respect to the recording layer plane is particularly important. Basically, since it is important that the crystal state after the initial crystallization is similar to the crystal state of the erased portion after recording, the focused light beam with respect to the recording layer surface when actually recording using the focused light beam is important. It is desirable to be close to the relative scan line speed. Specifically, the initialization energy beam is scanned at a linear velocity of about 20 to 80% of the maximum linear velocity for recording on the optical information recording medium.

  Here, the maximum linear velocity of recording means, for example, a linear velocity at which the erasure ratio is 20 dB or more when the erasing power Pe is applied in a direct current at the linear velocity.

  The erasure ratio is generally defined as the difference between the carrier level of the signal of the amorphous mark recorded at a single frequency and the carrier level after erasure by direct current irradiation of Pe. The erasure ratio is measured as follows, for example. First, in a recording condition where a sufficient signal characteristic (that is, a characteristic in which reflectivity, signal amplitude, jitter, etc. satisfy a specified value) is obtained, a condition with a high frequency is selected from the modulated signals to be recorded, and a single frequency is set to 10 times. An amorphous mark is formed by recording, and the carrier level (CL during recording) is measured. Thereafter, direct current irradiation is performed once on the amorphous mark while changing the erasing power Pe, and the carrier level (CL after erasing) at this time is measured. L. And after erasure C.I. L. Difference, that is, the erasure ratio is calculated. When the power Pe of direct current irradiation is changed, the erasure ratio generally tends to increase once, decrease, and increase, but here, the peak value at the beginning of the erasure ratio seen when the power Pe starts to increase is shown for the sample. The erase ratio.

  The scanning speed of the initialization energy beam is such that when the initialization energy beam is scanned at a speed lower than about 20% of the maximum linear velocity defined above, phase separation occurs and it is difficult to obtain a single phase. Even in the phase, the crystallites particularly grow in the initializing beam scanning direction and become giant or are oriented in an unfavorable direction. Preferably, the initialization energy beam may be scanned at a speed of 30% or more of the maximum recordable linear speed.

  On the other hand, when the initialization energy beam is scanned at a speed equal to the maximum recordable linear velocity, that is, generally higher than 80%, the region once melted by the initialization scan becomes amorphous again, which is not preferable. This is because if the scanning line speed is increased, the cooling rate of the melted portion is increased and the time until re-solidification is shortened. With a focused light beam having a diameter of about 1 micron for recording, recrystallization by crystal growth from the crystal region around the molten region can be completed in a short time. However, when scanning with an initialized elliptical light beam, the area of the melted area in the major axis direction becomes wider, so the scanning linear velocity is lower than during actual recording, and recrystallization during resolidification is performed in the melted area. It is necessary to spread the entire area. From such a viewpoint, the scanning linear velocity of the initialization energy beam is preferably 70% or less of the maximum linear velocity of recording, more preferably 60% or less, and most preferably lower than 50%. .

  The optical information recording medium of the present invention is characterized in that when initial crystallization is performed by laser light irradiation, the moving speed of the medium relative to the laser light can be increased. This is preferable in that the initial crystallization can be performed in a short time, and the productivity can be improved and the cost can be reduced.

(Recording / reproducing method of optical information recording medium)
The recording / reproducing light that can be used in the optical information recording medium of the present invention is usually a laser beam such as a semiconductor laser or a gas laser, and its wavelength is usually about 300 to 800 nm, preferably about 350 to 800 nm. In particular, in order to achieve a high surface recording density of 1 Gbit / inch ² or more, it is necessary to reduce the diameter of the focused light beam, a blue to red laser beam having a wavelength of 350 to 680 nm, and a numerical aperture NA of 0.5 or more. It is desirable to obtain a focused light beam using an objective lens.

  In the present invention, the amorphous state is preferably used as the recording mark as described above. In the present invention, it is effective to record information by the mark length modulation method. This is particularly noticeable in mark length recording where the shortest mark length is 4 μm or less, particularly 1 μm or less.

  When forming a recording mark, it is possible to perform recording by a method in which the conventional recording power is modulated at two levels of high level (recording power) and low level (erasing power). In the present invention, the following recording is performed. It is particularly preferable to employ a recording method based on modulation of three or more levels of recording power, such as providing an off-pulse period sufficiently lower than the erasing power when forming a mark.

FIG. 2 is a schematic diagram showing a power pattern of recording light in the recording method of the optical information recording medium. When forming an amorphous mark with a mark length modulated to a length nT (T is a reference clock period, n is a mark length that can be taken in mark length modulation recording and is an integer value), m = n−k ( However, k is an integer equal to or greater than 0) and is divided into individual recording pulse widths α _i T (1 ≦ i ≦ m), and β _i T (1 ≦ i ≦ m) for each recording pulse. An off pulse (cooling pulse) period of time is accompanied. In the divided recording pulse of FIG. 2, the reference clock synchronization T is omitted from the viewpoint of easy viewing. That is, in FIG. 2, what should be described as α _i T, for example, is simply described as α _i . Here, it is preferable that α _i ≦ β _i or α _i ≦ β _i-1 (2 ≦ i ≦ m or m−1). Note that Σα _i + Σβ _i is usually n, but Σα _i + Σβ _i = n + j (j is a constant satisfying −2 ≦ j ≦ 2) may be used to obtain an accurate nT mark.

During recording, recording light with an erasing power Pe that can crystallize amorphous is irradiated between the marks. In addition, in α _i T (i = 1 to m), recording light having a recording power Pw sufficient to melt the recording layer is irradiated, and in a time of β _i T (1 ≦ i ≦ m−1). , Pb <Pe, preferably recording light of bias power (cooling power, off-pulse power) Pb satisfying Pb ≦ (1/2) Pe is irradiated.

Note that the power Pb of the recording light irradiated in the period β _m T is normally Pb <Pe, preferably Pb ≦ 1 / 2Pe, as in the period β _i T (1 ≦ i ≦ m−1). , Pb ≦ Pe may be satisfied.

By adopting the above recording method, it is possible to widen the power margin and the linear velocity margin during recording. This effect is particularly remarkable when the bias power Pb is sufficiently low so that Pb ≦ 1 / 2Pe.
In FIG. 2, the switching period (α _i + β _i ) T or (β _i−1 + α _i ) T between the recording pulse (section α _i T) and the off-pulse (section β _i T) is substantially equal to T. That is, (α _i + β _i ) or (β _i-1 + α _i ) is set to approximately 1, but this switching cycle can be made larger than 1T, and in particular, 2T or 3T can also be set. It is.

The above recording method is particularly suitable for an optical information recording medium using the phase change recording material of the present invention for the recording layer. As described above, the phase change recording material of the present invention has few crystal nuclei in the amorphous mark and is recrystallized mainly by crystal growth from the crystal region around the amorphous mark (erasing of the amorphous mark). Is done. For this reason, in recording at a high linear velocity, the crystallization rate is increased by increasing the crystal growth rate. This is one of the characteristics of the phase change recording material of the present invention containing Sb as a main component. In particular, when the amount of Sb is increased and Ge and Te are decreased, the crystal growth rate can be selectively increased. it can. Such a composition adjustment promotes recrystallization from the peripheral crystal portion of the amorphous mark and also increases the crystal growth rate during melt resolidification. When the recrystallization speed from the periphery of the amorphous mark is increased to some extent, recrystallization from the peripheral portion of the molten region proceeds at the time of resolidification of the molten region formed for recording the amorphous mark. For this reason, the tendency to recrystallize without amorphizing the region which should be amorphized originally becomes strong. Therefore, it is important to sufficiently reduce the bias power Pb, or to ensure a sufficient cooling section with α _i ≦ β _i or α _i ≦ β _i−1 (2 ≦ i ≦ m to m−1).

  Further, when the linear velocity at the time of recording is increased, the clock cycle is shortened, so that the off-pulse period is shortened and the cooling effect tends to be impaired. In such a case, it is effective to divide the recording pulse at the time of nT mark recording, and set the cooling interval by the off pulse to 1 nsec or more, more preferably 5 nsec or more in real time.

[2-2] Use of the information recording medium of the present invention other than the optical information recording medium The information recording medium of the present invention is capable of at least reversible phase change recording by light irradiation. As described above, it can be used as a recording medium. However, the rewritable information recording medium used in the present invention can also be applied to phase change recording, for example, by passing a current through a very small area. This point will be described below.

FIG. 3 is a conceptual diagram of a temperature history (curve a) at the time of recording an amorphous mark and a temperature history (curve b) at the time of erasing by recrystallization. At the time of recording, the temperature of the recording layer is raised to a melting point Tm or more in a short time by heating with a high voltage and short pulse current or a high power level light beam, and after the current pulse or light beam irradiation is turned off, It becomes amorphous by being rapidly cooled by heat dissipation to the periphery. If the cooling rate of the temperature at the time τ ₀ from the melting point Tm to the crystallization temperature Tg is larger than the critical cooling rate for amorphization, the film is amorphized. On the other hand, at the time of erasing, by applying a relatively low voltage or irradiating light energy at a low power level, it is heated to a crystallization temperature Tg or higher, generally about a melting point Tm or lower, and held for a certain time or more, so that a substantially solid state. Thus, recrystallization of the amorphous mark proceeds. That is, if the holding time τ ₁ is sufficient, crystallization is completed.

  Here, regardless of the state of the recording layer before application of energy for recording or erasing, if the temperature history of curve a is given to the recording layer, the recording layer becomes amorphous, and the recording layer If the temperature history of curve b is given to, the recording layer is crystallized.

  The reason why the rewritable information recording used in the present invention can be used not only as an optical information recording medium but also for phase change recording by passing a current through a minute region is as follows. That is, it is the temperature history as shown in FIG. 3 that causes the reversible phase change. The energy source that causes the temperature history is either a focused light beam or current heating (Joule heat by energization). But that's fine.

The resistivity change accompanying the phase change between the crystal and the amorphous phase change recording material used in the present invention is a GeTe-Sb ₂ Te ₃ pseudo binary alloy that is currently being developed as a nonvolatile memory, in particular, Ge. ₂ Sb ₂ Te ₅ compound stoichiometric alloy, which is sufficiently comparable to a resistivity change of two orders of magnitude or more (J. Appl. Phys., 87, 4130-4133, 2000) ). Actually, the resistivity in the as-deposited amorphous state of the rewritable information recording medium using the phase change recording material whose main component is the composition represented by the general formula (1), and annealing When the resistivity after crystallization was measured, a change of 3 digits or more was confirmed. It is considered that the amorphous state obtained by current pulse, the amorphous state obtained by crystallization, and the crystalline state are slightly different from the as-deposited amorphous state and the crystalline state obtained by annealing. However, since the resistivity change of 3 digits or more can be obtained, even when the phase change recording material used in the present invention is phase-shifted by a current pulse, a large resistivity change of about 2 digits can sufficiently occur. Be expected.

FIG. 4 is a cross-sectional view showing the structure of one cell of such a nonvolatile memory. In FIG. 4, a voltage is applied between the upper electrode 1 and the lower electrode 2, and a phase change recording layer 3 containing a phase change recording material (hereinafter sometimes simply referred to as phase change recording layer 3) and a heater unit 4. And are energized. The phase change recording layer 3 is covered with an insulator 10 such as SiO ₂ . The phase change recording layer 3 is crystallized in the initial state. The initial crystallization in this case is performed by heating the entire system of FIG. 4 to the crystallization temperature of the recording layer (usually about 100-300 ° C.). In the formation of an integrated circuit, this level of temperature rise is normally performed.

  In particular, the thinned portion 4 (heater portion) in FIG. 4 functions as a local heater because heat generation due to Joule heat is likely to occur due to energization between the upper electrode 1 and the lower electrode 2. The reversible change part 5 adjacent thereto is locally heated to become amorphous through a temperature history as shown by a curve a in FIG. 3, and a temperature history as shown by a curve b in FIG. It is recrystallized after that.

  In reading, a low current is passed to such an extent that the heat generation of the heater unit 4 can be ignored, and a potential difference generated between the upper and lower electrodes is read. Note that since there is a difference in electric capacity between the crystalline and amorphous states, the difference in electric capacity may be detected.

  Actually, a further integrated memory using a semiconductor integrated circuit formation technique has been proposed (US Pat. No. 6,3114014), and its basic configuration is shown in FIG. In addition, if the phase change recording material used in the present invention is contained, an exactly equivalent function can be realized.

  As an energy source that causes a temperature change as shown in FIG. As an example of a recording device using an electron beam, a method of causing a phase change in a phase change recording material by locally irradiating an electron beam emitted from a field emitter as disclosed in US Pat. No. 5,557,596 is disclosed. There is.

  In addition, this invention is not limited to the said embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same function and effect. It is included in the technical scope.

In the following, the phase change recording material used in the present invention will be described with reference to an example in which the material is applied to an optical information recording medium. It is not limited to.
In the following embodiments, the optical information recording medium may be simply referred to as “disk”, “optical disk”, “phase-change optical disk”, or the like.

(Examples 1-6, Comparative Examples 1-4)
For measurement of the composition of the phase change recording material used in the recording layer of the optical information recording medium, acid-dissolved ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) and X-ray fluorescence analysis A device was used. Regarding the acid-dissolved ICP-AES, JY 38 S manufactured by JOBIN YVON was used as the analyzer, and the recording layer was dissolved in dil-HNO ₃ and quantified by a matrix matching calibration curve method. As the X-ray fluorescence analyzer, RIX3001 manufactured by Rigaku Corporation was used.

  The disk characteristics were measured using Pulse Tech DDU1000, with a reproduction power of 0.8 mW and applying focus servo and tracking servo in the groove. This apparatus is an optical disk evaluation apparatus having a pickup with a laser wavelength of 780 nm and NA of 0.5.

A first to fifth layers are sequentially sputtered onto a disc-shaped polycarbonate substrate having a diameter of 120 mm and a thickness of 1.2 mm having guide grooves having a groove width of 0.5 μm, a groove depth of 40 nm, and a groove pitch of 1.6 μm as follows. Provided. The first layer is a (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, the second layer is a Ge—In—Sb—Sn—Te recording layer, the third layer is a (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, and the fourth layer. The layer is a Ta or GeN interface layer, and the fifth layer is an Ag reflective layer (200 nm). The fourth layer is a thin interface layer for preventing diffusion of S into the Ag reflecting layer, and there is almost no difference in disk characteristics between Ta and GeN. A protective layer made of an ultraviolet curable resin was further provided on these layers to produce a phase change optical disc. Shows the thickness of each layer, the recording layer composition _{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z in the case of representation in x, y, z, the value of w in Table 2 . For the fourth layer, GeN was used only for the disks of Comparative Examples 2 and 3, and Ta was used for the other disks. Each disk has a slightly different film thickness for adjustment of reflectivity, signal amplitude, recording sensitivity, repeated recording durability, etc., but it is considered that there is no significant influence on the experimental results shown here. . Further, the recording layer composition was adjusted so as to have a crystallization speed suitable for the recording conditions described later except for the disks of Comparative Examples 1 and 4 in which the initial crystallization or recording erasure could not be satisfactorily performed.

These disks were initially crystallized as follows.
As a laser beam for initial crystallization, a laser beam having a width of about 1 μm and a length of about 75 μm and having a wavelength of 810 nm / power of 800 mW was used. Then, while rotating the disk at 12 m / s, the disk was irradiated such that the long axis of the laser beam was perpendicular to the guide groove formed on the substrate. Then, initialization was attempted by continuously moving the laser beam in the radial direction of the disk at a feed amount of 50 μm per rotation of the disk.
The disks other than Comparative Example 4 were capable of uniform initial crystallization. However, the disk of Comparative Example 4 did not crystallize under these conditions. Although initial crystallization was attempted in the same manner at a linear velocity of 2 m / s and a laser power of 400 mW to 1000 mW, a uniform crystal state could not be obtained. This is probably because the crystallization rate is too slow. Therefore, it seems that the disk of Comparative Example 4 is substantially difficult to use as a phase change optical disk.

  Although the initial crystallization was possible with the disc of Comparative Example 1, the reflectivity was as low as about 11%. There was no change in the reflectance even after about 10 attempts of recording and erasing. When the value of yz is small, the reflectivity and signal amplitude are small, making it difficult to use as a phase change optical disk. When a part or all of Sn is replaced with In, the relationship between the value of yz and the reflectance has the same tendency.

  Each disk was subjected to an environmental resistance test (acceleration test) maintained at 105 ° C. for 3 hours, and the crystal state reflectance was measured before and after that. The accelerated test is considered to correspond to long-term storage of the medium. The results are shown in Table-2. Every disk has a tendency to decrease the reflectivity by the acceleration test, but the degree of decrease varies depending on the disk. It can be seen that the degree of decrease in reflectance by the accelerated test is correlated with (In content−Te content), that is, the value of w × yz. Decrease rate of reflectivity by accelerated test (indicated in the column of “Reflected rate of decrease after accelerated test” in Table-2) is ((reflected before accelerated test) − (reflected after accelerated test)) / (accelerated test (Pre-reflectance), but if the reduction rate is to be kept smaller than about 0.15, w × yz needs to be about 0.1 or less. Of course, the smaller the decrease rate, the better.

  For the disks of Examples 1 to 6, before performing the acceleration test, the optical disk evaluation apparatus was used to record an EFM random signal at a linear velocity of 28.8 m / s as described later, and then the acceleration test was performed. The disk characteristics described below before and after the acceleration test were measured. The pulse strategy, recording power Pw, and erasing power Pe were selected in the vicinity where the jitter characteristics of the respective disks were as good as possible.

  Recording was performed on the disks of Examples 1 to 5 as follows. Marks having a length of 3T to 11T (T is a reference clock cycle of 9.6 nsec) included in the EFM signal were formed by irradiating a pulse train in which the following laser pulses were sequentially connected.

  An erasing power Pe was irradiated between the above-described pulse forming pulse trains, and Pb was set to 0.8 mW. The recording power Pw and erasing power Pe are shown in Table-2. Overwriting (overwriting) was performed 10 times.

  The disk of Example 6 was recorded as follows. Marks having a length of 3T to 11T (T is a reference clock cycle of 9.6 nsec) included in the EFM signal were formed by irradiating a pulse train in which the following laser pulses were sequentially connected.

  An erasing power Pe was irradiated between the above-described pulse forming pulse trains, and Pb was set to 0.8 mW. The recording power Pw and erasing power Pe are shown in Table-2. Also, the irradiation position of the 3T mark formation pulse is shifted by 0.2 T before the original start position of the 3T mark length signal in the EFM random signal (irradiation time is earlier than the original time), and the 4T mark formation pulse The irradiation position was shifted 0.05T before the original start position of the 4T mark length signal in the EFM random signal. By doing so, the mark formed becomes close to the original random signal. Overwriting (overwriting) was performed 10 times.

  The recording part of each disk was reproduced at a linear velocity of 1.2 m / s, and the characteristics of the recording signal were evaluated. Evaluation items are jitter between 3T marks and crystal state reflectance. The results are shown in Table-2. The 3T mark-to-mark jitter has a value of 40 ns or less, which is a characteristic that can be aimed at practical use. Particularly, in the disks of Examples 1 to 5, a value of 30 ns or less is obtained, which is preferable. In the disk of Example 6, the jitter characteristics are somewhat inferior, but this is thought to be due to the high Sn content.

  After performing the above acceleration test on these discs, the portion recorded before the acceleration test was reproduced, and the jitter between 3T marks was measured again. The results are shown in Table-2. Any disk has a 3T mark-to-mark jitter of 40 ns or less, which is a characteristic that can be put to practical use. In particular, the disks of Examples 1, 2, 4, and 5 are preferable because values of 30 ns or less are obtained. In these disks, the amorphous marks are sufficiently stable. In the disk of Example 3, the jitter value was slightly degraded by the acceleration test. It was thought that the crystallization of the 3T mark was progressing by observing the reproduced waveform with an oscilloscope. When Ge is contained, the amorphous mark is particularly stable.

  Next, the signal recorded before the acceleration test was erased after the acceleration test, and it was observed with an oscilloscope whether or not the disappearance was observed. In the case where unerased residue is observed, there is a possibility that the signal quality when the recorded medium is overwritten after long-term storage is not sufficiently good. The erasing operation is to irradiate each disk once with DC light having the erasing power Pe shown in Table-2. As a result, it was observed that the discs of Examples 4 and 5 had unerased residues, whereas the discs of Examples 1, 2, and 3 showed good erasing conditions. It appears that the erasure status is improved due to the low Ge content.

  In addition, when the recording part of the disk substantially equivalent to Example 4 was observed with the transmission electron microscope (TEM), it was confirmed that the amorphous mark was recorded in the crystalline state. For this reason, it is considered that an amorphous mark is recorded in the crystalline state on the disks of all the examples in which recording was performed.

(Comparative Example 5)
The disc of Comparative Example 5 was produced as follows.
On the disk-shaped polycarbonate substrate having a groove width of 0.5 μm, a groove depth of 40 nm, a groove pitch of 1.6 μm and a diameter of 120 mm and a thickness of 1.2 mm, the first to fifth layers are as follows: Were sequentially provided by a sputtering method. The first layer is a (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, the second layer is a recording layer, the third layer is a (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, the fourth layer is a GeN interface layer, and the fifth layer Is an Ag reflective layer. A protective layer made of an ultraviolet curable resin was further provided on these layers to produce a phase change optical disc. Shows the thickness of each layer, the recording layer composition _{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z in the case of representation in x, y, z, the value of w in Table 2 . Thereafter, initial crystallization was performed under the same conditions as in Example 1.
Using a disk evaluation apparatus having a laser wavelength of 780 nm and an NA of 0.5, repeated overwriting durability of the disk of Example 1 and the disk of Comparative Example 5 was measured.
The evaluation conditions for repeated overwrite durability are as follows.
That is, the recording linear velocity was 28.8 m / s, and an EFM random signal was recorded on the disc. The recording pulse used for recording was the same as in Example 1, the recording power Pw was 33 mW, and the erasing power Pe was 9 mW.
Reproduction was performed at a linear velocity of 1.2 m / s. The 3T mark-to-mark jitter after 10 overwrites was 25.6 ns for the disk of Example 1 and 27.1 ns for the disk of Comparative Example 5. The jitter between 3T marks after overwriting 2000 times was 32.1 ns for the disk of Example 1 and 58.4 ns for the disk of Comparative Example 5, and the disk of Comparative Example 5 was inferior in repeated recording durability.
The main cause of jitter deterioration in the disk of Comparative Example 5 seemed to be that erasing of marks was incomplete due to a decrease in crystallization speed due to repeated overwriting. On the other hand, in the disk of Example 1 containing Te, a decrease in crystallization speed due to repeated recording was suppressed.

(Reference Example 1)
The disc of Reference Example 1 was produced as follows.
On the disk-shaped polycarbonate substrate having a groove width of 0.5 μm, a groove depth of 40 nm, a groove pitch of 1.6 μm and a diameter of 120 mm and a thickness of 1.2 mm, the first to fifth layers are as follows: Were sequentially provided by a sputtering method. The first layer is a (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, the second layer is a recording layer, the third layer is a (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, the fourth layer is a Ta interface layer, and the fifth layer Is an Ag reflection layer. A protective layer made of an ultraviolet curable resin was further provided on these layers to produce a phase change optical disc. Shows the thickness of each layer, the recording layer composition _{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z in the case of representation in x, y, z, the value of w in Table 2 . Thereafter, initial crystallization was performed under the same conditions as in Example 1.
The disc of Reference Example 1 was subjected to an environmental resistance test (acceleration test) that was maintained at 105 ° C. for 3 hours, and the crystal state reflectance was measured before and after the test. The crystal state reflectances before and after the acceleration test were 27.8% and 23.4%, respectively. When the rate of decrease in reflectance by the accelerated test was defined as ((reflectance before accelerated test) − (reflected after accelerated test)) / (reflected before accelerated test), the decreased rate was 0.158.
In each of the disks of Examples 1 to 6, Comparative Examples 2 and 3, and Reference Example 1, the rate of decrease in reflectance after the acceleration test with respect to the (In-Te) amount (((reflectance before acceleration test) − (after acceleration test)) FIG. 7 is a graph in which the value defined by “reflectance) / (reflectance before the acceleration test) and plotted as“ data representing the reflectance reduction rate after the acceleration test ”in Table-2 is shown in FIG. . From FIG. 7, it can be seen that when In—Te ≦ 0.1 (10 atomic%), the decrease in the reflectance during acceleration is suppressed within 0.15 (15%).

(Examples 7 to 12, Comparative Example 6)
[Example 7]
A polycarbonate resin substrate having a track pitch of 0.74 μm and a thickness of 0.6 mm was formed by injection molding and used in the following experimental examples. The groove width formed on the substrate was about 0.31 μm, and the groove depth was about 28 nm. The groove shape was determined by an optical diffraction method approximating a U groove using He-Cd laser light having a wavelength of 441.6 nm.
Subsequently, a 65 nm (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, 2 nm Y ₂ O ₂ S layer, 12 nm Ge ₇ In ₆ Sb ₅₆ Sn ₂₄ Te ₇ recording layer, 2 nm Y ₂ O on the substrate. _{A 2} S layer, a 12 nm (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, a 2 nm Ta interface layer, a 200 nm Ag reflecting layer, and an approximately 4 μm UV-curing resin layer were formed in this order. The Ta layer is an interface layer for preventing diffusion of S into the Ag reflection layer.
Each layer was laminated on the substrate by sputtering in order without releasing the vacuum. However, the ultraviolet curable resin layer was applied by spin coating. Thereafter, a similar non-film-formed 0.6 mm thick substrate was bonded with an adhesive so that the recording layer surface was on the inside.

[Example 8]
Similarly, a 60 nm (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, 2 nm Y ₂ O ₂ S layer, 12 nm Ge ₇ In ₆ Sb ₅₆ Sn ₂₄ Te ₇ recording layer, 14 nm Y ₂ on the substrate. An O ₂ S layer, a 2 nm Ta interface layer, a 200 nm Ag reflective layer, and a UV curable resin layer of about 4 μm were formed in this order. The Ta layer is an interface layer for preventing diffusion of S into the Ag reflection layer.
Each layer was laminated on the substrate by sputtering in order without releasing the vacuum. However, the ultraviolet curable resin layer was applied by spin coating. Thereafter, a similar non-film-formed 0.6 mm thick substrate was bonded with an adhesive so that the recording layer surface was on the inside.
[Example 9]
Similarly, a 70 nm (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, a 13 nm Ge ₇ In ₆ Sb ₅₆ Sn ₂₄ Te ₇ recording layer, and a 14 nm (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer are formed on the substrate. A 2 nm Ta interface layer, a 200 nm Ag reflecting layer, and an ultraviolet curable resin layer of about 4 μm were formed in this order. The Ta layer is an interface layer for preventing diffusion of S into the Ag reflection layer.
Each layer was laminated on the substrate by sputtering in order without releasing the vacuum. However, the ultraviolet curable resin layer was applied by spin coating. Thereafter, a similar non-film-formed 0.6 mm thick substrate was bonded with an adhesive so that the recording layer surface was on the inside.

[Example 10]
Similarly, a disk using a GeN layer instead of the Y ₂ O ₂ S layer in Example 7 was produced.
[Example 11]
Similarly, a disk using a ZnO layer instead of the Y ₂ O ₂ S layer in Example 7 was produced.
[Example 12]
Similarly, a disk using a (ZnS) ₈₀ (CeO ₂ ) ₂₀ layer instead of the Y ₂ O ₂ S layer in Example 7 was produced.
[Comparative Example 6]
Similarly, a disk using a Ge ₅ Sb ₇₂ Te ₂₃ layer instead of the Ge ₇ In ₆ Sb ₅₆ Sn ₂₄ Te ₇ layer in Example 7 was produced.

[Evaluation]
The film thickness of each layer was controlled by the sputtering film formation time after measuring the film formation rate. As the recording layer composition, a value obtained by calibrating the fluorescence intensity of each element by the fluorescent X-ray method with an absolute composition separately obtained by chemical analysis (atomic absorption analysis) was used.
Next, initial crystallization was performed. As the laser beam used for the initial crystallization, a laser beam having an elliptical shape with a wavelength of 810 nm focused on a major axis of about 75 μm and a minor axis of about 1 μm was used. Then, while rotating the disk, the laser beam is irradiated so that the long axis of the laser beam is perpendicular to the guide groove formed on the substrate, and the laser is fed in the radial direction of the disk with a feed amount of 50 μm per rotation of the disk. Initial crystallization was performed by moving the light continuously.

The disks of Examples 7 and 9-12 have a linear velocity of 30 m / s and a laser power of 1500 mW, the disk of Example 8 has a linear velocity of 30 m / s and a laser power of 1800 mW, and the disk of Comparative Example 6 has a linear velocity of 3 m / s. The laser power was 500 mW.
For recording / reproduction evaluation, a DDU1000 tester (wavelength: about 650 nm, NA = 0.65, spot shape: a circle of 1 / e ² intensity and 0.86 μm) was used for recording / reproduction evaluation. The standard linear velocity of 3.49 m / s for DVD was set to 1 × speed, and the recording characteristics at 10 × speed were evaluated.
The reference clock cycle of data at each linear velocity is inversely proportional to the reference clock cycle of data at 1 × speed of 38.2 nsec.
Reproduction was performed at 1 × speed unless otherwise specified. The output signal from the DDU 1000 was passed through a high-frequency pass filter having a cutoff of 5 to 20 kHz, and then jitter was measured with a time interval analyzer (manufactured by Yokogawa Electric Corporation). The reproduction power Pr was 0.6 mW.
An arbitrary signal generator (AWG710, manufactured by Sony Tektronix) was used to generate a logic level for controlling the recording pulse dividing method. From the same signal generator, a logic signal of ECL level was inputted as a gate signal to the laser driver of the tester.

On the disks of Examples 7 to 12, EFM + random data was overwritten and recorded up to 2000 times at a linear velocity of 10 ×, and the data-to-clock jitter (Data to clock jitter, hereinafter referred to as a reference) What was normalized by the clock period T and expressed as a% value was simply referred to as jitter.
The pulse train for recording each mark length was set as follows. The light exposure time for recording a mark of _{nT, α 1 T, β 1} T, α 2 T, β 2 T, ···, α i T, β i T, ···, α m T, β _It is divided in the order of _m T (m is the number of pulse divisions, T is the reference clock period), and within the time of α _i T (1 ≦ i ≦ m), the recording light of recording power Pw is irradiated, and β _i T (1 Within the time of ≦ i ≦ m), the recording light with the bias power Pb was irradiated. These values were selected so that the jitter value was improved in each disk, and the values were as shown in Table 3 for the disks of Examples 7 and 9 to 12 and Table 4 for the disks of Example 8. Depending on the mark length, the irradiation timing of the pulse train was delayed by a certain time from the original start time of the mark length in the EFM + signal. This time is described in the “delay time” column. The case where the irradiation timing is delayed is defined as +, and the case where the irradiation timing is advanced is defined as-. The value was normalized by the clock period T. A mark formed by providing a delay time approaches an ideal EFM + random signal and improves jitter. The erasing power Pe was applied to the part between marks (the part other than those described in the table). In the disks of Examples 7 and 10 to 12, Pw was 23 mW, Pb was 0.5 mW, and Pe was 6.6 mW. In the disk of Example 8, Pw was 28 mW, Pb was 0.5 mW, and Pe was 8 mW. In the disk of Example 9, Pw was 23 mW, Pb was 0.5 mW, and Pe was 6.2 mW. The laser power was chosen to be optimal for each disc.

The results of repeated durability tests on the disks of Examples 7 to 10 are shown in FIG. In FIG. 8, the horizontal axis represents the number of overwrites. Actually, the first time is recording on a disk in an unrecorded initial crystal state, and the second time and thereafter are overwritten. (Hereafter, the same applies to FIGS. 9, 10, and 12) In any of the examples, the deterioration of jitter up to 1000 times is good at about 2% or less. With 2000 overwrites, the disk of Example 9 increased the jitter value to 12.5%, but the disks of Examples 7 and 8 had a jitter value of 10% or less, and the deterioration due to repeated recording was small. That is, when Y ₂ O ₂ S is provided in contact with the Ge—In—Sb—Sn—Te-based recording layer, repeated recording durability tends to be greatly improved. Even in the disk of Example 10, the jitter value after overwriting 2000 times was 10% or less, and the repeated recording durability was improved. On the other hand, in the disks of Examples 11 and 12 not shown in FIG. 8, the repeated recording durability was inferior to that of the disk of Example 9, but it was still stable at least several hundred times. Is practical enough. In these discs, the jitter can be stabilized 1000 times or more by further optimizing the protective layer and the layer structure.
Next, the signal amplitude after overwriting 10 times with the disks of Example 7 and Example 10 was measured. In all cases, Pw was 23 mW, Pb was 0.5 mW, and Pe was 6.6 mW. When the signal amplitude was defined by (inter-mark part reflectance) − (14T mark part reflectance), the values of the signal amplitudes were different between 0.151 and 0.144 in Example 7 and Example 10, respectively. That is, it can be seen that the Ge—In—Sb—Sn—Te-based recording layer is superior in that Y ₂ O ₂ S has a larger signal amplitude than GeN. These values are the results of recording and reproduction with the optimum tilt of the disk and laser head. The difference in signal amplitude seems to have a large effect on signal quality when recording under more severe conditions.

Next, an environmental resistance test (hereinafter referred to as environmental resistance test 1) was performed for the disks of Example 7 and Example 8 which were maintained in an environment of 100 ° C. for 1 hour. 9 and 10 show measurement results of repeated recording durability before and after the environmental resistance test 1. FIG. “Archival” in the figure is a result of repeated recording endurance test recorded before the environmental resistance test 1 and only reproducing the signal repeatedly recorded a predetermined number of times after the environmental resistance test 1. It can be seen that the disks of Examples 7 and 8 have no problems with the stability of the amorphous mark and the temporal change of the repeated recording durability.
The disks of Examples 7 and 8 and Comparative Example 6 were subjected to an environmental resistance test (hereinafter referred to as an environmental resistance test 2) for 90 hours in an environment of a temperature of 80 ° C. and a humidity of 85% RH. No film peeling occurred in the disks of Examples 7 and 8, but film peeling was observed in the disk of Comparative Example 6. In the disk of Comparative Example 6, the portion irradiated with laser after the environmental resistance test 2 was observed with an oscilloscope. As a result, a large number of portions where the reflectance was reduced due to film peeling appeared. Specifically, for example, when 8 mW DC light is irradiated at a linear velocity of 4 ×, a large number of portions with reduced reflectivity appear. This was not the case with the disks of Examples 7 and 8. That is, when Y ₂ O ₂ S is provided in contact with a material having a conventional SbTe eutectic composition, there may be a problem in interlayer adhesion, but Y in contact with a Ge—In—Sb—Sn—Te-based material. _{When 2} O ₂ S is provided, no problem is observed in the adhesion between the layers. Although the environmental resistance test was continued for 250 hours at the same temperature and humidity as the environmental resistance test 2 on the disk of Example 8, there were no problems such as film peeling. Thereafter, the same measurement as in the environmental resistance test 1 was performed on the disk of Example 8, and there was almost no difference from the case of the environmental resistance test 1.

(Examples 13 and 14)
[Example 13]
A polycarbonate resin substrate having a track pitch of 0.74 μm and a thickness of 0.6 mm was formed by injection molding and used in the following experimental examples. The groove width formed on the substrate was about 0.31 μm, and the groove depth was about 28 nm. The groove shape was determined by an optical diffraction method approximating a U groove using He-Cd laser light having a wavelength of 441.6 nm.
Subsequently, a 40 nm (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, 2 nm (Y ₂ O ₂ S) ₉₀ (ZnO) ₁₀ layer, 10 nm Ge ₇ In ₆ Sb ₅₆ Sn ₂₄ Te ₇ recording on the substrate. A layer, 14 nm (Y ₂ O ₂ S) ₉₀ (ZnO) ₁₀ layer, 2 nm Ta interface layer, 200 nm Ag reflection layer, and about 4 μm UV curable resin layer were formed in this order. The Ta layer is an interface layer for preventing diffusion of S into the Ag reflection layer.
Each layer was laminated on the substrate by sputtering in order without releasing the vacuum. However, the UV curable resin layer was applied by spin coating. Thereafter, a similar non-film-formed 0.6 mm thick substrate was bonded via an adhesive so that the recording layer surface was on the inside.
[Example 14]
Similarly, a 60 nm (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, 2 nm (Y ₂ O ₂ S) ₉₀ (ZnO) ₁₀ layer, 12 nm Ge ₇ In ₆ Sb ₅₆ Sn ₂₄ Te ₇ on the substrate. A recording layer, 10 nm (Y ₂ O ₂ S) ₉₀ (ZnO) ₁₀ layer, 2 nm Ta interface layer, 200 nm Ag reflecting layer, and about 4 μm UV curable resin layer were formed in this order. Thereafter, a similar non-film-formed 0.6 mm thick substrate was bonded with an adhesive so that the recording layer surface was on the inside.

[Evaluation]
The film thickness of each layer was controlled by the sputtering film formation time after measuring the film formation rate. As the recording layer composition, a value obtained by calibrating the fluorescence intensity of each element by the fluorescent X-ray method with an absolute composition separately obtained by chemical analysis (atomic absorption analysis) was used.
Next, initial crystallization was performed. As the laser beam used for the initial crystallization, an elliptical laser beam having a wavelength of 810 nm / power of 1800 mW focused on a major axis of about 75 μm and a minor axis of about 1 μm was used. Then, while rotating the disk at 30 m / s, the laser beam is irradiated so that the long axis of the laser beam is perpendicular to the guide groove formed on the substrate, and the radius of the disk is 50 μm per disk rotation. Initial crystallization was performed by continuously moving the laser beam in the direction.
For recording / reproduction evaluation, a DDU1000 tester (wavelength: about 650 nm, NA = 0.65, spot shape: a circle of 1 / e ² intensity and 0.86 μm) was used for recording / reproduction evaluation. The standard linear velocity of 3.49 m / s for DVD was set to 1 × speed, and the recording characteristics at 10 × speed were evaluated.
The reference clock cycle of data at each linear velocity is inversely proportional to the reference clock cycle of data at 1 × speed of 38.2 nsec.
Reproduction was performed at 1 × speed unless otherwise specified. The output signal from the DDU 1000 was passed through a high-frequency pass filter having a cutoff of 5 to 20 kHz, and then jitter was measured with a time interval analyzer (manufactured by Yokogawa Electric Corporation). The reproduction power Pr was 0.6 mW.

An arbitrary signal generator (AWG710, manufactured by Sony Tektronix) was used to generate a logic level for controlling the recording pulse dividing method. From the same signal generator, a logic signal of ECL level was inputted as a gate signal to the laser driver of the tester.
The disks of Example 13 and Example 14 were subjected to an environmental resistance test 1 that was maintained in an environment of 100 ° C. for 1 hour, and the recording characteristics before and after the environmental resistance test 1 were measured. EFM + random data was recorded at a linear velocity of 10 times, and the jitter of the recorded data was measured.
The pulse train for recording each mark length was set as follows. The light exposure time for recording a mark of _{nT, α 1 T, β 1} T, α 2 T, β 2 T, ···, α i T, β i T, ···, α m T, β _It is divided in the order of _m T (m is the number of pulse divisions, T is the reference clock period), and within the time of α _i T (1 ≦ i ≦ m), the recording light of recording power Pw is irradiated, and β _i T (1 Within the time of ≦ i ≦ m), the recording light with the bias power Pb was irradiated. These values were set as shown in Table-5. Depending on the mark length, the irradiation timing of the pulse train was delayed by a certain time from the original start time of the mark length in the EFM + signal. This time is described in the “delay time” column. The case where the irradiation timing is delayed is defined as +, and the case where the irradiation timing is advanced is defined as-. The value was normalized by the clock period T. A mark formed by providing a delay time approaches an ideal EFM + random signal and improves jitter. The erasing power Pe was applied to the part between marks (the part other than those described in the table).

The jitter characteristic when overwriting was recorded twice after the environmental resistance test 1 was measured by changing the recording power Pw. Pb was 0.5 mW, and Pe was 8 mW. The results are shown in FIG. The disk of the thirteenth embodiment has a power with a jitter of 10% or less, but the disk of the fourteenth embodiment does not have a power of 10% or less. In the overwriting up to about 1000 times before and after the environmental resistance test 1, the jitter deteriorates most in the second recording (second recording on the shelf) in the repeated overwriting test after the environmental resistance test 1, and when the overwriting is repeated further, the jitter Is once lowered (see FIG. 12 described later), it is preferable that the jitter of the second recording is kept low. Therefore, it can be said that Example 13 has higher performance than the disk of Example 14.
Further, in the disk of Example 13, the deterioration of jitter at the first overwriting (second archival recording) when overwriting after the environmental resistance test 1 on the signal recorded before the environmental resistance test 1 is the same. Was kept low. Such a disk can be said to be more reliable in long-term use.
Further, the signal intensity after overwriting 10 times before the environmental resistance test 1 was compared between the disks of Example 13 and Example 14. When Pw is 28 mW, Pe is 8 mW, and Pb is 0.5 mW, the signal amplitude, ie, ((inter-mark part reflectivity) − (mark part reflectivity)) is 0.161 in Example 13 and 0.161 in Example 14. Yes, it was the same. If the recording layer is only thinned, the signal intensity is reduced, but the recording characteristics after the environmental resistance test 1 can be improved without reducing the signal intensity by reducing the thickness of the recording layer and the incident side protective layer at the same time.

Further, FIG. 12 shows the repeated recording durability of the disk of Example 13 up to 2000 times when Pw is 28 mW, Pe is 8 mW, and Pb is 0.5 mW. The jitter is 10 at all overwriting times. It can be seen that it exhibits a highly reliable characteristic in repeated overwriting after long-term use. Further, when the portion recorded once before the environmental resistance test 1 was reproduced after the environmental resistance test 1, the jitter was 7% and was not deteriorated at all. That is, the storage stability of the amorphous mark is sufficient.
Next, the reflectance of the portion overwritten 10 times before the environmental resistance test 1 was measured before and after the environmental resistance test 1. As a result, the reflectance of the disk of Example 13 was 0.234 and 0.229, respectively. On the other hand, the reflectance of the disk of Example 14 was 0.246 and 0.234, respectively. When the reflectance reduction rate according to the environmental resistance test 1 is defined by (((reflectance before the environmental resistance test 1) − (reflectance after the environmental resistance test 1)) / (reflectance before the environmental resistance test 1)) The rate of decrease was about 0.021 in Example 13 and about 0.049 in Example 14, and the rate of decrease in reflectance was smaller in Example 13. That is, it can be seen that the reduction rate of the reflectance in the environmental resistance test 1 is reduced by making the recording layer thinner.

(Example 15)
The following experiment was conducted to show the possibility of recording due to a change in electrical resistance for the phase change recording material used in the present invention.
That is, in the _Ge-In-Sn-Te- Sb (Ge x (In w Sn 1-w) y Te z Sb 1-x-y-z having a thickness of 50nm on a polycarbonate substrate having a diameter of 120 mm, w = 0 189, x = 0.056, y = 0.301, z = 0.073) An amorphous film was formed by sputtering.
After measuring the resistivity of the amorphous film, the amorphous film was crystallized, and the resistivity of the crystallized film was measured.
For the initial crystallization, laser light having a shape with a width of about 1 μm / length of about 75 μm, a wavelength of 810 nm, and a power of 1040 mW was used. Then, while rotating the Ge—In—Sn—Te—Sb amorphous film formed on the substrate at a linear velocity of 12 m / s, the long axis of the laser beam is formed in the guide groove formed on the substrate. The amorphous film was irradiated with the laser beam so as to be vertical. Further, initial crystallization was performed by continuously moving the laser beam in the radial direction at a feed amount of 50 μm per rotation.
For resistivity measurement, a resistivity measuring device Loresta MP (MCP-T350) manufactured by Dia Instruments was used.
The resistivity before crystallization was 1.36 × 10 ⁻¹ Ωcm. The resistivity after crystallization was 0.95 × 10 ⁻⁴ Ωcm. From this result, it was found that a resistivity change of nearly three orders of magnitude occurs between the amorphous state and the crystalline state. Therefore, the phase change recording material used in the present invention has a large difference in resistivity between the phase change between the amorphous state and the crystalline state, and can be applied to a rewritable information recording medium for recording by electric resistance change. I know that there is.

(Example 16)
A polycarbonate resin substrate having a track pitch of 0.74 μm and a thickness of 0.6 mm was formed by injection molding and used in the following experimental examples. The groove width formed on the substrate was about 0.31 μm, and the groove depth was about 28 nm. The groove shape was determined by an optical diffraction method approximating a U groove using He-Cd laser light having a wavelength of 441.6 nm.
Subsequently, a 65 nm (ZnS) ₈₀ (SiO ₂ ) ₂₀ protective layer, 2 nm Y ₂ O ₂ S layer, 15 nm Ge ₅ In _8.5 Sb ₅₂ Sn ₂₄ Te _10.5 recording layer, 17 nm on the substrate. Y ₂ O ₂ S layer, 2 nm Mo interface layer, 200 nm Ag reflection layer, and about 4 μm UV curable resin layer were formed in this order. The Mo layer is an interface layer for preventing diffusion of S into the Ag reflection layer.
Each layer was laminated on the substrate by sputtering in order without releasing the vacuum. However, the UV curable resin layer was applied by spin coating. Thereafter, a similar non-film-formed 0.6 mm thick substrate was bonded via an adhesive so that the recording layer surface was on the inside.
The film thickness of each layer was controlled by the sputtering film formation time after measuring the film formation rate. The recording layer composition is the composition of the sputtering target.

Next, initial crystallization was performed. As the laser beam used for the initial crystallization, an elliptical laser beam having a wavelength of 810 nm / power of 1200 mW focused on a major axis of about 75 μm and a minor axis of about 1 μm was used. Then, while rotating the disk at 16 m / s, the laser beam is irradiated so that the long axis of the laser beam is perpendicular to the guide groove formed on the substrate, and the radius of the disk is set at a feed amount of 50 μm per rotation of the disk. Initial crystallization was performed by continuously moving the laser beam in the direction.
For recording / reproduction evaluation, an ODU-1000 tester (wavelength: about 650 nm, NA = 0.65, spot shape: a circle of 1 / e ² intensity and 0.86 μm) was used for evaluation of recording and reproduction. The standard linear velocity of 3.49 m / s for DVD was set to 1 × speed, and the recording characteristics at 8 × speed were evaluated.
The reference clock cycle of data at each linear velocity is inversely proportional to the reference clock cycle of data at 1 × speed of 38.2 nsec.
Reproduction was performed at 1 × speed unless otherwise specified. The output signal from ODU-1000 was passed through a high-frequency pass filter having a cutoff of 5 to 20 kHz, and then jitter was measured with a time interval analyzer (manufactured by Yokogawa Electric Corporation). The reproduction power Pr was 0.6 mW.

An arbitrary signal generator (AWG710, manufactured by Sony Tektronix) was used to generate a logic level for controlling the recording pulse dividing method. From the same signal generator, a logic signal of ECL level was inputted as a gate signal to the laser driver of the tester.
The disk of Example 16 was overwritten with EFM + random data 10 times at a linear velocity of 8 ×, and the jitter of the recorded data was measured.
The pulse train for recording each mark length was set as follows. The light exposure time for recording a mark of _{nT, α 1 T, β 1} T, α 2 T, β 2 T, ···, α i T, β i T, ···, α m T, β _It is divided in the order of _m T (m is the number of pulse divisions, T is the reference clock period), and within the time of α _i T (1 ≦ i ≦ m), the recording light of recording power Pw is irradiated, and β _i T (1 Within the time of ≦ i ≦ m), the recording light with the bias power Pb was irradiated. These values were set as shown in Table-6. Depending on the mark length, the irradiation timing of the pulse train was delayed by a certain time from the original start time of the mark length in the EFM + signal. This time is described in the “delay time” column. The case where the irradiation timing is delayed is defined as +, and the case where the irradiation timing is advanced is defined as-. The value was normalized by the clock period T. A mark formed by providing a delay time approaches an ideal EFM + random signal and improves jitter. The erasing power Pe was applied to the part between marks (the part other than those described in the table). Pe was 7.6 mW and Pb was 0 mW.

The results are shown in FIG. There is a power range in which the jitter is 10% or less, and this is a characteristic that can be put into practical use.

  According to the present invention, recording erasure at high speed is possible, recording signal characteristics such as jitter characteristics are excellent, recording signal storage stability is high, and recording signal quality changes over time due to long-term storage (for example, reflectance reduction) ), And an information recording medium using the material can be obtained. Further, excellent recording signal characteristics can be obtained even if overwriting is performed after the recorded information recording medium is stored for a long period of time.

It is a schematic diagram which shows the layer structure of the optical information recording medium. It is a schematic diagram which shows the power pattern of the recording light in the recording method of the optical information recording medium. It is a conceptual diagram which shows the temperature history at the time of recording or erasing of rewritable information recording. It is a schematic diagram which shows the structure of 1 cell of a non-volatile memory. It is a schematic diagram which shows the layer structure of the optical information recording medium. It is a schematic diagram which shows the layer structure of the optical information recording medium. It is a graph which shows the reflectance fall at the time of acceleration with respect to the quantity of (In-Te). Repetitive overwrite characteristics of optical information recording media Repetitive overwrite characteristics of optical information recording media Repetitive overwrite characteristics of optical information recording media Repetitive jitter characteristics of optical information recording media. Repetitive overwrite characteristics of optical information recording media Repetitive jitter characteristics of optical information recording media.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper electrode 2 Lower electrode 3 Phase change recording layer 4 Heater part 5 Reversible change part 10 Insulator

Claims (20)

A phase change recording material comprising a composition represented by the following general formula (1) as a main component.
_{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z (1)
(However, the Sb content is higher than any of the Ge content, the In content, the Sn content, and the Te content, and x, y, z, and w representing the atomic ratio are as follows. Satisfy (i) to (vi).
(I) 0 ≦ x ≦ 0.30
(Ii) 0.13 ≦ yz
(Iii) w × yz ≦ 0.10
(Iv) 0 <z
(V) (1-w) × y ≦ 0.35
(Vi) 0.35 ≦ 1-xyz) The phase change recording material according to claim 1, wherein x in the general formula (1) further satisfies 0 <x. The phase change recording material according to claim 1, wherein x in the general formula (1) further satisfies x ≦ 0.07. The phase change recording material according to claim 1, wherein w in the general formula (1) further satisfies 0 <w. The phase change recording material according to claim 1, wherein z in the general formula (1) further satisfies 0.08 ≦ z. 6. The phase change recording material according to claim 1, wherein the information recording material has a crystalline state in an unrecorded state and an amorphous state in a recorded state. An information recording medium having a recording layer, wherein the recording layer contains a composition represented by the following general formula (1) as a main component.
_{Ge x (In w Sn 1-} w) y Te z Sb 1-x-y-z (1)
(However, the Sb content is higher than any of the Ge content, the In content, the Sn content, and the Te content, and x, y, z, and w representing the atomic ratio are as follows. Satisfy (i) to (vi).
(I) 0 ≦ x ≦ 0.30
(Ii) 0.13 ≦ yz
(Iii) w × yz ≦ 0.10
(Iv) 0 <z
(V) (1-w) × y ≦ 0.35
(Vi) 0.35 ≦ 1-xyz) 8. The information recording medium according to claim 7, wherein x in the general formula (1) further satisfies 0 <x. The information recording medium according to claim 7, wherein x in the general formula (1) further satisfies x ≦ 0.07. In the general formula (1) w is further 0 <information recording medium according to any one of claims 7 to 9, characterized in that meet w. 11. The information recording medium according to claim 7, wherein z in the general formula (1) further satisfies 0.08 ≦ z. 12. The information recording medium according to claim 7, wherein the information recording medium has a crystalline state as an unrecorded state and an amorphous state as a recorded state. 13. The information recording medium according to claim 7, wherein the information recording medium is an optical information recording medium for recording with a laser beam. The optical information recording medium has a protective layer A in contact with the recording layer, and the protective layer A contains a metal oxysulfide and / or a metal nitride. Information recording medium. 15. The information recording medium according to claim 14, wherein the metal oxysulfide is an yttrium oxysulfide, and the metal nitride is a nitride of an alloy containing germanium as a main component. 16. The information recording medium according to claim 14, wherein the protective layer A is provided in contact with both surfaces of the recording layer. The protective layer A is provided in contact with the surface of the recording layer on the side where the laser beam is incident, and the thickness of the protective layer A is 50 nm or less. An information recording medium according to any one of the above. The protective layer A is provided in contact with the surface of the recording layer on the side where the laser light is incident, and the protective layer B is provided on the surface opposite to the recording layer in contact with the protective layer A. The information recording medium according to claim 14, wherein the total thickness of the protective layer A and the protective layer B is 50 nm or less. 19. The information recording medium according to claim 14, wherein the recording layer has a thickness of 5 nm or more and 15 nm or less. 20. The information recording medium according to claim 13, wherein the optical information recording medium further includes a reflective layer, and the reflective layer contains Ag as a main component.

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