JP2006155896A - Optical information recording medium, its production method, recording and reproducing method for the same, and optical recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium which suppresses cross-erasures and is suitable for recording and reproducing high density information and to provide an optical information recording medium which ensures a high erasure rate, even in high density and high linear velocity overwriting and can record and reproduce information with small jitters. <P>SOLUTION: The optical information recording medium includes a transparent substrate (31) and a multilayered film (32-36) formed on the transparent substrate (31). The multilayered film (32-36) comprises a lower protective layer (32), a recording layer (33) reversibly changing between different two states which can be optically detected by irradiation with a light beam, an upper protective layer (34), a light absorption layer (35) and a reflection layer (36) sequentially from a side near the transparent substrate (31). The difference Δn=n<SB>1</SB>-n<SB>2</SB>between a refractive index n<SB>1</SB>of the light absorption layer (35) and a refractive index n<SB>2</SB>of the reflection layer (36) is 2 to 6 and the film thickness of the reflection layer (36) is larger than that of the light absorption layer (35). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical information recording medium capable of recording and reproducing information signals with high signal quality by irradiating a thin film formed on a substrate with a high-energy light beam such as a laser beam, and its manufacture The present invention relates to a method, a recording / reproducing method thereof, and an optical recording / reproducing apparatus.

  When a thin film such as a chalcogen material formed on a substrate is irradiated with a laser beam while adjusting the irradiation conditions and locally heated, the irradiated portion is amorphous with different optical constants (refractive index n, extinction coefficient k). It is possible to change the phase between the crystalline phase and the crystalline phase. A medium for performing high-speed and high-density information recording that detects a difference in the amount of reflected light or transmitted light with respect to light of a specific wavelength as a signal using such a phase change and a method for using the medium have been developed.

  In phase change recording, only a single laser beam is used and the laser output is modulated between the recording level and the erasing level according to the information signal and irradiated onto the information track. A signal can be recorded (for example, cited document 1). This method is advantageous in that the magnetic circuit parts required for magneto-optical recording are not required and the head can be simplified, and the rewriting time can be shortened because erasing and recording can be performed simultaneously.

  In order to increase the density of phase change recording, a smaller recording mark is formed by shortening the wavelength of the light source used for recording, increasing the NA (numerical aperture) of the objective lens, and the like. A technique for improving the linear density in the direction and the track density in the radial direction is employed. Further, in order to improve the density in the circumferential direction, mark edge recording which gives information to the length of the recording mark is a groove which is a laser beam guiding groove provided on the substrate in order to improve the density in the radial direction. Land and groove recording, in which both the land between the guide groove and the land between the guide grooves, is proposed.

  In addition to increasing the density, it is also important to improve the information processing speed, that is, the speed of recording / reproducing information. For this reason, even if the disk is rotated at a high rotational speed even at the same radial position, the recording / reproducing speed is high. Studies are also underway on increasing the linear velocity.

  Furthermore, a plurality of recordable information layers are stacked via a separation layer, and a recording medium (for example, cited document 2) in which the capacity is doubled and any one of such a plurality of information layers is selected for recording / reproduction. Layer recognition means and layer switching means (for example, cited document 3) have been proposed.

  As recording density increases, overwriting distortion and repetitive degradation also become a problem. Especially, when recording marks are recorded on a track, the recording mark on the adjacent track is partially erased. (Hereinafter referred to as “cross erase”) is a problem. Cross erase becomes more prominent as the track interval is shortened in order to improve the recording density in the radial direction. In particular, in the land & groove recording, the radial distance between the recording marks is approximately halved as compared with the case of recording only in one of the groove and the land.

  The cross erase occurs because the spot of the laser beam narrowed down during recording affects the track adjacent to the track to be recorded. Specifically, it is considered that the direct heating of the adjacent track by the laser beam and the indirect heating of the adjacent track by the heat conduction from the track to be recorded cause the cross erase.

  In addition, in the case of overwriting with a single beam, the light absorption rate is different between the amorphous part and the crystal part, and the crystal part requires latent heat of fusion. A difference in temperature reached when irradiated occurs, and the mark edge position is uneven due to the influence of the signal before overwriting at the time of overwriting. As a result, the error (jitter) in the time axis direction of the reproduction signal increases and the erasure rate decreases. This phenomenon becomes a serious problem when the recording linear velocity and density are increased, especially when the mark edge recording method is introduced.

  In order to solve this problem, it is necessary to equalize the ultimate temperatures when the beam of the same power is irradiated in the crystal part and the amorphous part. For that purpose, when the laser beam of wavelength λ is irradiated, the absorptance of the crystal part is Acry, the amorphous part is Aamo, and the light absorptivity ratio is used to compensate for the latent heat of fusion of the crystal part. Acry / Aamo must be greater than 1.0. In addition, the reflectance difference ΔR = Rcry−Ramo is obtained in order to obtain a high C / N ratio, where Rcry is the reflectance of the crystal part when the laser beam of wavelength λ is irradiated and Ramo is that of the amorphous part. Larger is desirable.

  Conventionally, as a technique for increasing both Acry / Aamo and ΔR as described above, a three-layer structure without a reflective layer (cited documents 4 to 5), a reflective layer using a material with low reflectivity, or a film thickness of A four-layer configuration (cited documents 6 to 7) having a sufficiently thin reflective layer has been proposed.

However, even if Acry / Aamo and ΔR are both increased using the above-described means, sufficient recording / reproducing characteristics are not always obtained. For example, when the thickness of the reflective layer is thin or the thermal conductivity of the reflective layer is low, the so-called cooling ability that releases heat generated from the light absorption of the recording layer to the reflective layer becomes insufficient, and the amorphous layer becomes amorphous. Hinder. This phenomenon is particularly noticeable in the front end portion of the mark that is amorphous, and an imbalance occurs in which the width of the front end portion of the mark is smaller than the width of the rear end portion of the mark. In addition, the mark edge position is not only physically deviated from the desired position, but the mark width is not uniform, so the edge position as an electric signal is further deviated, resulting in an increase in jitter. End up. This is a big problem in high density and high linear velocity recording.
JP-A-56-145530 JP-A-9-212917 Japanese National Patent Publication No. 10-505188 Japanese Patent Laid-Open No. 3-113844 JP-A-5-298748 JP-A-4-102243 JP-A-5-298747

  The present invention provides an optical information recording medium suitable for recording and reproducing high-density information with small cross erase. The present invention also provides an optical information recording medium capable of recording and reproducing information with a high erasure rate and low jitter even in high-density / high linear velocity overwrite. Furthermore, the present invention provides a manufacturing method and a recording / reproducing method of these optical information recording media, and an optical information recording / reproducing apparatus using the optical information recording medium.

The first optical information recording medium of the present invention includes a transparent substrate and a multilayer film formed on the transparent substrate, and the multilayer film, in order from the side close to the transparent substrate, a lower protective layer, Refraction of the light-absorbing layer at a wavelength λ of the light beam, comprising a recording layer, an upper protective layer, a light-absorbing layer, and a reflecting layer that reversibly change between two different states that are optically detectable by light beam irradiation The difference Δn = n ₁ −n ₂ between the refractive index n ₁ and the refractive index n ₂ of the reflective layer is 2 or more and 6 or less, and the thickness of the reflective layer is equal to or greater than the thickness of the light absorption layer. It is characterized by.

  By using such an optical information recording medium, heat conduction from the recording layer in the thickness direction of the multilayer film is promoted, and cross erase can be reduced. The film thickness of the recording layer is preferably 6 nm or more and 14 nm or less.

In the first optical information recording medium, the film thickness d ₁ of the light absorption layer is 0.1λ / (n ₁ · k ₁ ) ≦ d ₁ ≦ where the extinction coefficient of the light absorption layer is k _1. It is preferably in the range of 1.0λ / (n ₁ · k ₁ ). According to this preferred example, good values can be obtained for the C / N ratio, the erasure rate, and the jitter.

The second optical information recording medium of the present invention includes a transparent substrate and a multilayer film formed on the transparent substrate, and the multilayer film, in order from the side close to the transparent substrate, a lower protective layer, recording layer that changes reversibly between optically detectable two different states by irradiation of light beams, an upper protective layer includes an optical absorption layer and a reflective layer, the thickness d ₁ of the light absorbing layer, the light Assuming that the wavelength of the beam is λ and the refractive index and extinction coefficient of the light absorption layer at the wavelength λ are n ₁ and k ₁ , respectively, 0.1λ / (n ₁ · k ₁ ) ≦ d ₁ ≦ 1.0λ / ( n ₁ · k ₁ ).

  By using such an optical information recording medium, both Acry / Aamo and ΔR can be increased, and a sufficient cooling effect can be obtained. As a result, it is possible to realize an optical information recording medium capable of recording / reproducing information with a high erasure rate and small jitter even in high-density / high linear velocity overwrite.

  The optical information recording medium of the present invention may include a plurality of recording layers, or may include two or more information layers composed of a multilayer film including the recording layers. In this case, it is preferable that two or more information layers are laminated via a separation layer. Such an optical information recording medium includes, for example, a transparent substrate and a first information layer, a separation layer, and a second information layer formed on the transparent substrate in this order from the side close to the transparent substrate.

  In the case where two information layers are provided as described above, the structure of the multilayer film described above is preferably applied to the second information layer, although not particularly limited. It is important that the second information layer far from the transparent substrate side on which the laser light is incident has high sensitivity. In the multilayer film, the intermediate layer or the light absorption layer absorbs the laser beam as in the case of the recording layer, so that the temperature of the recording layer is easily raised and good sensitivity is obtained. Moreover, in the multilayer film, heat generation is eliminated by rapid cooling by the reflective layer having high thermal conductivity. For this reason, thermal diffusion in the recording layer does not increase, and deterioration of the cross erase characteristic can be suppressed.

The first manufacturing method of the optical information recording medium of the present invention is such that, on the transparent substrate, in order from the side close to the transparent substrate, the lower protective layer, between two different states optically detectable by light beam irradiation. Forming a multilayer film including a recording layer, an upper protective layer, a light absorption layer, and a reflection layer that reversibly change, and the refractive index n ₁ of the light absorption layer at the wavelength λ of the light beam and the reflection layer The difference Δn = n ₁ −n ₂ with respect to the refractive index n ₂ is 2 or more and 6 or less, and the thickness of the reflective layer is equal to or greater than the thickness of the light absorption layer. With this manufacturing method, an optical information recording medium that has a high erasure rate and can record and reproduce information with low jitter even in high-density and high linear velocity overwriting can be obtained.

The second manufacturing method of the optical information recording medium of the present invention is such that, on the transparent substrate, in order from the side close to the transparent substrate, the lower protective layer, between two different states optically detectable by light beam irradiation. Forming a multilayer film including a recording layer, an upper protective layer, a light absorption layer, and a reflection layer that reversibly change, wherein the film thickness of the light absorption layer is d ₁ , the wavelength of the light beam is λ, When the refractive index and extinction coefficient of the light absorption layer at the wavelength λ are n ₁ and k ₁ , respectively, 0.1λ / (n ₁ · k ₁ ) ≦ d ₁ ≦ 1.0λ / (n ₁ · k ₁ ) The light absorption layer is formed so as to be established.

The third manufacturing method of the optical information recording medium of the present invention includes a step of forming a first information layer on a transparent substrate, a step of forming a second information layer on a protective substrate, the transparent substrate and the protection Forming the first information layer, the separation layer, and the second information layer in this order on the transparent substrate by attaching the substrate to the transparent substrate, and the second information layer includes: From the side close to the transparent substrate, the lower protective layer, the recording layer, the upper protective layer, the light absorbing layer, and the reflective layer that reversibly change between two different states that can be detected optically by irradiation with a light beam. The difference Δn = n ₁ −n ₂ between the refractive index n ₁ of the light absorbing layer and the refractive index n ₂ of the reflective layer at the wavelength λ of the light beam is 2 or more and 6 or less, and the reflection The second information layer is placed on the protective layer so that the thickness of the layer is equal to or greater than the thickness of the light absorption layer. It is formed on a protective substrate.

The fourth method for producing an optical information recording medium of the present invention includes a step of forming a first information layer on a transparent substrate, a step of forming a second information layer on a protective substrate, the transparent substrate and the protection Forming the first information layer, the separation layer, and the second information layer in this order on the transparent substrate by attaching the substrate to the transparent substrate, and the second information layer includes: In order from the side closer to the transparent substrate, a lower protective layer, a recording layer that reversibly changes between two different states that can be detected optically by irradiation with a light beam, an upper protective layer, a light absorbing layer, and a reflective layer. In this order, the thickness of the light absorption layer is d ₁ , the wavelength of the light beam is λ, and the refractive index and extinction coefficient of the light absorption layer at the wavelength λ are n ₁ and k ₁ , respectively. / (N ₁ · k ₁ ) ≦ d ₁ ≦ 1.0λ / (n ₁ · k ₁ ) In addition, the second information layer is formed on the protective substrate.

  Each of the above manufacturing methods can also be applied to an optical information recording medium having two or more information layers. In this case, the step of forming the first information layer on the transparent substrate, the step of forming the second information layer on the protective substrate, and bonding the transparent substrate and the protective substrate through the separation layer, Preferably, the manufacturing method includes a step of forming the first information layer, the separation layer, and the second information layer in this order on the transparent substrate. In this case, the protective substrate functions as a layer that protects the information layer. Also in this case, it is preferable to form the second information layer on the protective substrate so that each configuration of the multilayer film described above is applied to the second information layer.

The optical information recording medium recording / reproducing method of the present invention is a method for recording and reproducing information by making a light beam incident on the optical information recording medium of the present invention described above from the transparent substrate side, wherein the light beam The power level P ₁ that can instantaneously melt the irradiated portion, power levels P ₂ and P ₃ that cannot instantaneously melt the irradiated portion (where P ₁ > P ₂ ≧ P ₃ ≧ 0), and When the display is performed at a power level P ₀ (where P ₁ > P ₀ > 0) in which the optical state of the recording mark of the recording layer does not change and the reflection sufficient to reproduce the recording mark is obtained by irradiation, wherein at least one of recording marks recorded on the recording layer, a light beam is formed by a recording pulse train consisting of a group of pulses were generated by modulating between a power level P ₁ and P _3, forming a recording mark Holding the optical beam power level P ₂ in the absence,
Information recorded on the recording layer is reproduced by irradiating a light beam with a power level P ₀ .

  Thus, by forming a recording mark with a pulse train generated by modulating the intensity, for example, when the first optical information recording medium is used, information can be recorded and reproduced while suppressing cross erase. Become. Further, for example, when the second or third optical information recording medium is used, the mark width can be made uniform except for excessive heat when a long mark is formed.

  Each of the above recording / reproducing methods can also be applied to an optical information recording medium having two or more information layers. In this case, it is preferable to change the state of the recording layer included in the first information layer and the second information layer by making a light beam incident from the transparent substrate side.

The optical information recording medium recording / reproducing apparatus of the present invention comprises the above-described optical information recording medium of the present invention, a light beam generating means for generating a light beam applied to the optical information recording medium, A light beam intensity modulating means for modulating the intensity of the light beam, and the power level P ₁ that can instantaneously melt the irradiated portion and the power level P ₂ that cannot instantaneously melt the irradiated portion. And P ₃ (where P ₁ > P ₂ ≧ P ₃ ≧ 0), and the power level at which the optical state of the recording mark of the recording layer does not change and the reflection sufficient for reproduction of the recording mark is obtained by irradiation. When the light beam intensity modulation means records information by forming a recording mark when displayed by P ₀ (where P ₁ > P ₀ > 0), the light beam is set to the power level P ₁ . At least one of the recording marks is formed by a recording pulse train composed of a group of pulses generated by modulation with P _3, and when the recording mark is not formed, the intensity of the light beam is maintained at the power level P _2. When reproducing information recorded on the recording layer, the intensity of the light beam is maintained at the power level P ₀ .

  The recording / reproducing apparatus can also be applied to an optical information recording medium having two or more information layers. In this case, it is preferable to arrange the light beam generating means on the transparent substrate side of the recording medium so that the laser light is incident from the transparent substrate side.

  According to the present invention, it is possible to provide an optical information recording medium that is small in cross erase and suitable for recording and reproducing high-density information. Further, according to the present invention, it is possible to provide an optical information recording medium capable of recording / reproducing information with a high erasure rate and low jitter even in high-density / high linear velocity overwrite. In addition, according to the present invention, there are provided an optical information recording medium recording / reproducing method and an optical information recording medium reproducing apparatus suitable for the medium as well as a method for producing such an optical information recording medium. is there.

  Hereinafter, preferred embodiments of the present invention will be described.

(First embodiment)
In the present embodiment, the first optical information recording medium of the present invention will be mainly described. As a result of studying various layer configurations of the multilayer film formed on the substrate, the present inventor has found that the film thickness of the recording layer and the heat of the layer on the air side (opposite side of the substrate) from the recording layer are included in the cross erase. It was found that the relationship of conductivity has a great influence, and this type of medium was completed.

  In the optical information recording medium, the upper protective layer preferably has a thickness of 10 nm or more. If the upper protective layer is too thin, the distance between the recording layer and the intermediate layer becomes too short, and as a result, heat conduction from the recording layer to the intermediate layer is suppressed due to the heat of the intermediate layer itself. It is. The upper protective layer preferably has a thickness of 200 nm or less.

  The optical information recording medium preferably further includes an interface layer formed so as to be in contact with the recording layer. The interface layer is formed at least one interface between the upper protective layer and the recording layer and between the lower protective layer and the recording layer. The interface layer is preferably a layer containing Ge. This is because interdiffusion of atoms between the upper protective layer and / or the lower protective layer and the recording layer can be suppressed. The interface layer preferably contains at least one selected from Ge, Si, Cr, Ti, and Al.

  In the optical information recording medium, the recording layer preferably contains Ge, Sb, and Te. This is because it is suitable as a material when erasing and recording are simultaneously performed in the recording layer. More preferably, the recording layer contains Ge, Sb, and Te as main components and further contains N of 6.0 atomic% or less. This is because it is effective in improving the repetition characteristics.

Further, in the optical information recording medium, the upper protective layer and / or the lower protective layer is 60 to 100 mol% of ZnS, preferably contains SiO ₂ 40 to 0 mol%. This is because such a protective layer is excellent in heat resistance, has an appropriate thermal conductivity, and further has an appropriate refractive index for adjusting the optical characteristics of the medium.

  In the optical information recording medium, the reflective layer preferably contains at least one selected from Au, Ag, Cu, and Al. You may use the alloy containing these metals.

  In the optical information recording medium, the intermediate layer includes Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Os, Al, Ga, In, C, Si, Ge, Sn. It is preferable that it contains at least one element selected from Pb, Sb and Bi. More specifically, it preferably comprises at least one compound selected from oxides, nitrides, carbides, sulfides, fluorides, selenides and tellurides containing at least one selected from the above elements. The intermediate layer is made of a material whose thermal conductivity has a value between the thermal conductivity of the upper protective layer and the thermal conductivity of the reflective layer.

  Moreover, it is preferable that an intermediate | middle layer consists of an interelement compound of the said element like Ge-Cr, Si-W, for example. In the present specification, a compound composed of two or more elements is referred to as an inter-element compound.

  In the optical information recording medium, when the recording layer is a crystalline phase, the reflectance, which is the ratio at which the light beam is reflected by the recording medium, and the absorption ratio, which is the ratio at which the light beam is absorbed by the recording layer. When Rcry and Acry and the recording layer is in an amorphous phase, the difference in reflectance (Rcry-Ramo) is 5% or more (5 points or more in%) as Ramo and Aamo, and the absorption ratio (Acry / Aamo) is preferably 1.0 or more.

  In this method for producing an optical information recording medium, it is preferable to form the recording layer in the thickness direction at a rate of 200 nm / min or less. This is to ensure the film thickness accuracy of the recording layer.

  Further, the recording layer may be formed in an atmosphere containing an inert gas and a nitrogen gas, and the content of the nitrogen gas adjusted so that the recording layer contains not more than 6.0 atomic% of nitrogen atoms. preferable.

  In this optical information recording medium recording / reproducing method, it is preferable that at least a part of the recording pulse train is generated so that the pulse width and the interval between the pulses are substantially the same.

In the recording / reproducing method of the optical information recording medium, it is preferable to provide a cooling section of power level P ₄ (where P ₂ > P ₄ ≧ 0) immediately after the last pulse of the recording pulse train.

  Hereinafter, the present embodiment will be specifically described with reference to the drawings.

  1 and 2 are a partial cross-sectional view and a partial perspective view, respectively, of the optical disk of the present embodiment. As shown in FIG. 1, on this optical disk, a lower protective layer 2, a recording layer 3, an upper protective layer 4, an intermediate layer 5, and a reflective layer 6 are sequentially laminated on a transparent disk substrate 1 and further overcoated. A coat layer 7 is provided. Further, as shown in FIG. 2, since the groove 8 having a depth D is formed on the substrate 1, the concave and convex portions parallel to each other are also formed on the surface of the laminated film 10 composed of the above layers. The land 9 is formed. The recording layer 3 is irradiated with laser light as a light beam from the substrate 1 side to form a recording mark 11. As shown in FIG. 2, it is preferable to form recording marks on both the groove 8 and the land 9 for high density recording (land and groove recording).

  As the substrate 1, transparent materials such as polycarbonate resin, polymethyl methacrylate resin, polyolefin resin, arton resin, glass and the like can be used. The thickness of the substrate 1 is not particularly limited, but is preferably 0.1 mm to 2.0 mm.

  The lower protective layer 2 and the upper protective layer 4 are used for suppressing noise increase due to thermal damage of the substrate 1 or the recording layer 3 during laser light irradiation, and for adjusting the reflectance, absorption rate, and phase of reflected light with respect to the laser light. Formed for. Examples of the protective layers 2 and 4 include Sc, Y, Ce, La, Ti, Zr, Hf, V, Nb, Ta, Zn, Al, Si, Te, and other oxides, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Zn, B, Al, Ga, In, Si, Ge, Sn, Pb, and other nitrides, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Carbides such as Zn, B, Al, Ga, In, Si, sulfides such as Zn, Cd, Ga, In, Si, Ge, Sn, Pb, Sb, Bi, selenides or tellurides, Mg, Ca, etc. A dielectric material made of a simple substance such as fluoride, C, Si, or Ge, or a mixture thereof can be used.

  The film thickness of the upper protective layer 4 is preferably 10 nm or more and 200 nm or less. If the upper protective layer 4 is too thin, heat escape from the recording layer 3 to the intermediate layer 5 becomes worse due to the influence of the heat of the intermediate layer 5 itself as described above. As described above, when the heat conduction in the thickness direction of the layer is lowered, the thermal diffusion in the surface of the recording layer 3 is increased, so that the cross erase may be increased. When the upper protective layer 4 is 10 nm or more, for example, the track pitch (average of the width of a pair of adjacent lands and grooves (1/2 of the groove pitch), the same as the groove pitch when recording only on the groove) is 0. Even if it is 6 μm, the cross erase is within the allowable range. The thicker the upper protective layer 4, the smaller the cross erase. However, since the optical characteristics repeat with a period of the film thickness λ / 2n (λ is the wavelength of the laser beam and n is the refractive index of the upper protective layer 4), the film thickness is necessary to obtain the desired optical characteristics of the medium. It is industrially disadvantageous to make it thicker. Therefore, although it depends on the wavelength λ and the refractive index n, the film thickness is preferably 200 nm or less. For the reasons described above, the thickness of the upper protective layer 4 is preferably 10 nm or more and 200 nm or less, and particularly preferably 20 nm or more and 200 nm or less.

  On the other hand, the thickness of the lower protective layer 2 is not particularly limited, but is preferably 10 nm or more and 200 nm or less. If the thickness of the lower protective layer is less than 10 nm, the substrate may be thermally deformed. The reason why the lower protective layer is preferably 200 nm or less is the same as that described above, where the upper protective layer is preferably 200 nm or less.

  As the recording layer 3, a chalcogenide based on Te or Se, for example, Ge—Sb—Te, Ge—Te, Pd—Ge—Sb—Te, In—Sb—Te, Sb—Te, Ag—In—Sb is used. -Te, Ge-Sb-Bi-Te, Ge-Sb-Se-Te, Ge-Sn-Te, Ge-Sn-Te-Au, Ge-Sb-Te-Cr, In-Se, In-Se-Co An alloy whose main component is etc. can be used. Alternatively, a material obtained by adding oxygen, nitrogen, or the like to these alloys may be used.

  The film thickness of the recording layer 3 is suitably 4 nm or more and 16 nm or less. Conventionally, in the case where the track pitch is so large that cross-erasing is not a problem, a film thickness of 20 nm or more has been advantageous in order to increase the optical contrast. However, when the recording layer is thick in this way, the heat conduction in the in-plane direction of the recording layer is large, and therefore, as the track pitch becomes shorter (for example, 0.6 μm or less), the cross erase becomes conspicuous. In order to reduce cross erase, it is advantageous that the recording layer is thin. By reducing the thickness of the recording layer, heat conduction in the in-plane direction of the layer can be reduced. For example, when the film thickness of the recording layer is 16 nm or less, the cross erase is within the allowable range even if the track pitch is 0.6 μm. However, if the film thickness of the recording layer is less than 4 nm, the optical contrast cannot be secured, and the influence of the film thickness fluctuation due to repeated recording becomes large and tracking becomes unstable, so that the cross erase becomes large. . Therefore, the film thickness of the recording layer is preferably 4 nm to 16 nm, and more preferably 6 nm to 14 nm.

  As the intermediate layer 5, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Al, Ga, In, C, Si, Ge, Sn, Pb, At least one element selected from Sb and Bi (in particular, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Os, Al, Ga, In, C, Si, Ge, Sn, Pb , At least one element selected from Sb and Bi), or at least one compound selected from oxides, nitrides, carbides, sulfides, fluorides, selenides, tellurides, and interelement compounds of these elements More specifically, Cr, Mo, W, Ti, Zr, Nb, Ta, Ge—Cr, Ge—Mo, Ge—W, Si—Cr, Si—Mo, Si are preferable. Use -W etc. It can be.

  Although it does not specifically limit as a film thickness of the intermediate | middle layer 5, 5 nm or more and 100 nm or less are preferable.

  The reflective layer 6 is formed for the purpose of adjusting the reflectance, absorption rate, and phase of reflected light with respect to laser light, and reducing the thermal load on the recording thin film. As described above, a metal material having a relatively high thermal conductivity such as Al, Au, Ag, or Cu, or an alloy material based on these can be used as the reflective layer.

  The thickness of the reflective layer 6 is not particularly limited, but is preferably 10 nm or more and 200 nm or less.

  The material used for each layer may be selected from materials exemplified above, but the reflective layer 6, the intermediate layer 5, and the upper protective layer 4 have a higher thermal conductivity in this order. select. By setting the heat conductivity in this way, heat conduction from the recording layer 3 in the film thickness direction of the multilayer film is accelerated. Accordingly, the heat conduction in the in-plane direction of the recording layer 3 is relatively suppressed, and the adjacent tracks are hardly affected.

  The optical information recording medium can be provided with an interface layer 12 as shown in FIG. The interface layer 12 may be provided on both sides of the recording layer 3 as shown in FIG. 3, but may be provided only on one of them. When the interface layer 12 is provided, the atomic diffusion between the protective layers 2 and 4 and the recording layer 3 is suppressed, so that the repetitive characteristics of the recording medium can be improved. As the interface layer 12, a material having an anti-diffusion effect with respect to the material used for the protective layers 2 and 4 can be used, but a material containing Ge is preferable, and a material mainly containing a nitride of Ge is particularly preferable. Are better.

  The film thickness of the interface layer 12 is not particularly limited, but is preferably 1 nm or more and 50 nm or less.

  Each of the layers 2 to 6 and 12 can be formed by vapor phase thin film deposition methods such as vacuum deposition, sputtering, ion plating, CVD (Chemical Vapor Deposition), and MBE (Molecular Beam Epitaxy). . However, the sputtering method has the best balance from the viewpoint of the film formation rate, the manufacturing cost, the quality of the obtained film, and the like. Each layer is generally formed while flowing an inert gas into a high vacuum chamber, but may be formed while oxygen, nitrogen, or the like is mixed in the inert gas. Thereby, O atoms, N atoms, etc. are mixed in the film, and the characteristics of the film can be adjusted. In particular, in the recording layer 3, mixing of these atoms (for example, mixing of nitrogen atoms of 6.0 atomic% or less) may be effective for improving the repetition characteristics of the medium and reducing cross erase.

  In addition, it is industrially advantageous for the optical information recording medium to sequentially form the layers 2 to 6 and 12 in parallel in separate chambers using a single-wafer film forming apparatus. When such a film forming method is employed, the recording layer does not affect the overall film forming efficiency even if the recording layer is formed at a relatively low speed. This is because the film thickness of the recording layer 3 is preferably 4 nm or more and 16 nm or less, and is, for example, about one digit thinner than the normal film thickness (100 nm or more) of the lower protective layer 2. Since accurately controlling the film thickness of the recording layer 3 is important for reducing cross erase as described above, it is preferable to secure a minimum film formation time of about 5 seconds. Accordingly, the recording layer deposition rate is preferably 200 nm / min or less.

  An overcoat layer 7 may be further provided on each layer formed as described above as shown in FIG. This layer 7 is preferably formed by applying an ultraviolet curable resin.

  However, the optical information recording medium of the present invention is not limited to a single-sided single-sided disk as shown in FIG. 1, and a recording layer is formed in the same manner as described above by using an ultraviolet curable resin and / or a hot melt type adhesive. It is good also as a double-sided disk by sticking together so that the board | substrate in which the multilayer film containing was formed and film surfaces oppose. In this case, it is preferable that the substrates are bonded via the separation layer so that the multilayer films, each of which serves as an information layer, do not directly contact each other. Alternatively, the surface on which the multilayer film is formed may be bonded to a dummy substrate with the adhesive to form a single-sided disk.

  FIG. 4 is a diagram showing an outline of an example of an apparatus for recording / reproducing an optical information recording medium. The laser beam 10 emitted from the semiconductor laser 13 in accordance with the input signal is condensed by the collimator lens 14 to become a parallel beam, and sequentially passes through the beam splitter 15, the quarter wavelength plate 16, and the objective lens 17. The light is irradiated onto the optical disk 18. The laser beam 10 is focused by moving the voice coil 19 up and down. The optical disk 18 is fixed on the turntable 20. Information signals are recorded and reproduced by irradiating the optical disk 18 rotating at a predetermined speed by the motor 21 with laser light.

FIG. 5 is an example of a pulse waveform of laser light when recording an information signal. As shown in FIG. 5, the intensity of the laser light is modulated between P ₁ , P ₂ , P ₃ and P ₄ . Here, P ₁ can instantaneously melt the irradiated portion, and preferably can instantaneously melt the irradiated portion even when irradiation is performed while modulating the intensity below the power level as shown in FIG. Power level. P ₂ and P ₃ are power levels at which the irradiated portion cannot be instantaneously melted, and preferably the irradiated portion cannot be instantaneously melted even when irradiated without modulation. P ₄ is a power level for cooling the recording layer immediately after the last recording pulse train. FIG. 5 shows an example in which each power level is set so that P ₁ > P ₂ ≧ P ₃ ≧ P ₄ ≧ 0. In order to modulate the intensity of the laser beam as described above, the drive current of the semiconductor laser may be modulated, but means such as an electro-optic modulator or an acousto-optic modulator may be used.

However, it is not necessary to form a recording pulse train as shown all of the recording marks in FIG. 5, for the mark length is short pulses may be formed by a single rectangular pulse of power level P _1. However, when forming a long mark, excessive heat can be suppressed by forming a pulse train including the power level P ₁ as a power peak in order to improve repetition characteristics and reduce cross erase. preferable.

P ₂ is a power level at which a recording mark cannot be formed even when the light beam is held at its intensity as shown in FIG. This power level may be a power level at which the recording mark cannot be formed but the recording mark can be erased. In this case, in a portion where the light beam of power level P ₂ is irradiated, the recording mark is erased.

For example, in a phase change type optical disk, when the recording state is used corresponding to the amorphous state and the erased state corresponds to the crystalline state, P ₁ is a power level that can reversibly change the recording layer from the crystalline state to the amorphous state, P ₂ may be set as a power level that can reversibly change the recording layer from the amorphous state to the crystalline state.

Immediately after the recording pulse train shown in FIG. 5, a cooling section with a power level P ₄ is provided. Providing such a power level for cooling can remove heat of the mark rear end portion that is likely to be excessive in heat, and is effective in suppressing cross erase.

  Further, if the pulse width and the length between each pulse are constant except for the first and last pulses as in the recording pulse train shown in FIG. 5, the modulation means can be simplified because modulation can be performed at a single frequency. Can do.

  Note that each pattern such as the length of the recording mark, the length of the space before and after it, and the length of the adjacent mark may cause unevenness in the mark edge position, which may increase jitter. In the recording / reproducing method of the optical information recording medium, in order to prevent this and improve the jitter, the pulse position of the pulse train or the length of the pulse is adjusted as necessary so that the edge position is aligned for each pattern. It is preferable to compensate.

When reproducing the information signal thus recorded, the optical disk is irradiated with laser light (unmodulated light) having a power level P ₀ that does not change the phase of the recording layer 3, and the reflected light is incident on the detector 22. The reflected light amount change is detected as the reproduction signal 23.

  The change of the laser light power level as described above can be performed by controlling the drive current of the laser diode. Further, an electro-optic modulator or an acousto-optic modulator may be used as the light beam intensity modulating means.

(Second Embodiment)
In the present embodiment, mainly the second and third optical information recording media of the present invention will be described.

  In the optical information recording medium, it is preferable that an interface layer is further provided at at least one interface between the lower protective layer and the recording layer and between the recording layer and the upper protective layer. According to this preferable example, the erasing characteristics can be improved. The interface layer preferably contains at least one selected from Ge, Si, Cr, Ti, and Al.

  In the optical information recording medium, the thickness of the recording layer is preferably 4 nm or more and 16 nm or less. This is because if the recording layer is too thin, the optical contrast and the signal amplitude are reduced, and if it is too thick, thermal diffusion in the inner surface direction of the recording layer is increased and thermal interference between the marks is increased.

  In the optical information recording medium, the upper protective layer preferably has a thickness of 10 nm to 200 nm. If the upper protective layer is too thin, the heat generated by the light absorption of the light absorbing layer will affect the recording layer, increasing the thermal interference between the marks, and if it is too thick, the cooling effect by the reflective layer will be reduced. This is because the front and rear ends become unbalanced. Although not particularly limited, also in the present embodiment, the thickness of the lower protective layer is preferably 10 nm or more and 200 nm or less.

  In the optical information recording medium, the recording layer preferably contains Ge, Sb and Te, and further preferably contains Ge, Sb and Te as main components and further contains 6.0 atomic% N. .

Further, in the optical information recording medium, the upper protective layer and / or the lower protective layer preferably contains 60 to 100 mol% of ZnS and 40 to 0 mol% of SiO _2.

  In the optical information recording medium, it is preferable that the reflective layer contains at least one selected from Au, Ag, and Cu.

  In the optical information recording medium, the light absorption layer includes Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Al, Ga, In, At least one element selected from C, Si, Ge, Sn, Pb, Sb and Bi (in particular, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Os, Al, Ga, In) , C, Si, Ge, Sn, Pb, Sb and Bi). More specifically, it is preferably composed of at least one compound selected from oxides, nitrides, carbides, sulfides, fluorides, selenides, and tellurides containing at least one selected from the above elements. It is preferably an inter-element compound consisting of at least two selected from

  In the optical information recording medium, when the recording layer is a crystalline phase, the reflectance, which is the ratio at which the light beam is reflected by the recording medium, and the absorption ratio, which is the ratio at which the light beam is absorbed by the recording layer. When Rcry and Acry and the recording layer is in an amorphous phase, the difference in reflectance (Rcry-Ramo) is 5% or more (5 points or more in%) as Ramo and Aamo, and the absorption ratio (Acry / Aamo) is preferably 1.0 or more. According to this preferable example, the unevenness of the mark edge position at the time of overwriting can be eliminated.

  In the method for producing an optical information recording medium, the recording layer is preferably formed at a speed of 200 nm / min or less. This is to ensure the film thickness accuracy of the recording layer.

  Further, the recording layer may be formed in an atmosphere containing an inert gas and a nitrogen gas, and the content of the nitrogen gas adjusted so that the recording layer contains not more than 6.0 atomic% of nitrogen atoms. preferable.

  In this optical information recording medium recording / reproducing method, it is preferable that at least a part of the recording pulse train is generated so that the pulse width and the interval between the pulses are substantially the same.

In the recording / reproducing method of the optical information recording medium, it is preferable to provide a cooling section of power level P ₄ (where P ₂ > P ₄ ≧ 0) immediately after the last pulse of the recording pulse train. According to this preferable example, the heat at the rear end portion of the mark, which is likely to be excessive in heat, can be removed, which is effective.

  Hereinafter, the present embodiment will be specifically described with reference to the drawings.

  FIG. 6 is a partial sectional view showing the optical information recording medium of the present embodiment, and FIG. 7 is a partial sectional view of another example of the optical information recording medium of the present embodiment.

  As shown in FIG. 6, a lower protective layer 32, a recording layer 33, an upper protective layer 34, a light absorbing layer 35, and a reflective layer 36 are sequentially stacked on the substrate 31. Further, an overcoat layer 37 is provided. The disk is irradiated with a laser beam 38 from the substrate 31 side, whereby recording / reproduction of the disk is performed.

  As the material for the substrate 31, the lower protective layer 32, the recording layer 33, and the upper protective layer 34, the materials described in the first embodiment can be applied.

  The light absorption layer 35 is formed for the purpose of adjusting the reflectivity, the absorptance, and the phase of the reflected light with respect to the laser beam 38. Examples of the material constituting this layer include Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Al, Ga, In, C, Si, Ge, A material containing at least one selected from Sn, Pb, Sb, and Bi, or at least one selected from oxides, nitrides, carbides, sulfides, fluorides, selenides, tellurides, and interelement compounds of these elements A material comprising one compound is preferred. More specifically, Cr, Mo, W, Si, Ge, Te, Ge—Cr, Ge—Mo, Ge—W, Si—Cr, Si—Mo, Si—W, Ge—Te, Sn—Te, Pb-Te, Sb-Te, Bi-Te, or the like can be used.

  In addition, the said compound material may use the thing of the stoichiometric composition vicinity, and may use the thing of the composition shifted | deviated from the stoichiometric composition as needed. This also applies to the intermediate layer and the like in the first embodiment.

  The reflective layer 36 is formed for the purpose of adjusting the reflectance, absorption rate, and phase of reflected light with respect to the laser beam 38, reducing the thermal load on the recording thin film, and the like. As a material of the reflective layer, for example, a metal material having a relatively high thermal conductivity such as Al, Au, Ag, Cu, etc., in particular, Au, Ag, Cu, or these having a refractive index smaller than 0.5 at a wavelength of 600 nm. An alloy material based on is preferred. Especially, Ag alloy is excellent in terms of thermal conductivity and optical constant, and is cheaper than Au or the like having equivalent characteristics. In particular, a material in which an element such as Pd, Cu, Ti or the like is added to Ag within a range of 10 atomic% or less hardly corrodes, and is preferable from the viewpoint of environmental resistance and reliability.

  In the optical information recording medium, as shown in FIG. 7, the recording layer 33 is interposed between the lower protective layer 32 and the recording layer 33 and / or between the recording layer 33 and the upper protective layer 34. The interface layer 39 is preferably provided for the purpose of promoting crystallization. As the interface layer 39, there are several dielectric materials that play a role in the materials that can be used as the lower protective layer 32 and the upper protective layer 34, and these can be used. Is the most excellent. Further, by providing such an interface layer 39, the erasing characteristics can be improved.

  The lower protective layer 32, the recording layer 33, the upper protective layer 34, the light absorbing layer 35, the reflective layer 36, and the interface layer 39 can be formed by the same method as in the first embodiment.

  Further, as shown in FIG. 6, the optical information recording medium can be used as a single-sided single-sided disk by overcoating with an ultraviolet curable resin. Further, as described in the first embodiment, it can also be used as a double-sided disk. Furthermore, it can also be used as a single-sided disk by bonding the film surface facing the dummy substrate.

The optical information recording medium of this embodiment includes a light absorption layer 35 (refractive index n ₁ , extinction coefficient k ₁ , film thickness d ₁ ) and reflective layer 36 (refractive index n ₂ , extinction coefficient k ₂ , film thickness). It is characterized by a combination of the material and film thickness of d ₂ ). Hereinafter, the role and effect of each layer will be described.

Optically, by making the refractive index n ₁ of the light absorbing layer 35 appropriately larger than the refractive index n ₂ of the reflective layer 36, both Acry / Aamo and ΔR can be increased. The refractive index difference Δn = n ₁ −n ₂ is preferably 2 or more and 6 or less, and more preferably 3 or more and 5 or less.

The above range is supported by the following optical calculations. That is, the refractive index, extinction coefficient, and film thickness of each layer of the multilayer film are determined, and simultaneous equations for the optical energy balance at each interface are established and solved for all interfaces based on the energy conservation law. Thus, the reflectivity / transmittance of the entire multilayer film and the absorptance of each layer can be obtained. This technique itself is known, for example, as a matrix method (for example, Hiroshi Kubota et al. “Wave Optics” Iwanami Shoten, 1971). Here, substrate 31 / lower protective layer 32 (arbitrary film thickness) / recording layer 33 (10 nm) / upper protective layer 34 (arbitrary film thickness) / arranged in order from the incident side of the light beam (wavelength 660 nm) / Acry / Aamo and ΔR values were calculated for the multilayer structure medium of the light absorption layer 35 (film thickness d ₁ ) / reflection layer 36 (80 nm).

At that time, the refractive index n and the extinction coefficient k of each layer are set such that the substrate 31 has n = 1.6, k = 0.0, the lower protective layer 32 has n = 2.1, k = 0.0, and the recording layer. In the amorphous state, n = 4.1, k = 1.6, in the crystalline state, n = 3.9, k = 4.2, and the upper protective layer 34 is n = 2.1, k = 0.0. The light absorption layer 35 is calculated as n = n ₁ , k = k ₁ , and the reflection layer 36 is calculated as n = n ₂ , k = k ₂ .

For various combinations of n ₁ and n ₂ , k ₁ , k ₂ , and d ₁ were arbitrarily changed, and the maximum value of ΔR in the range of Acry / Aamo ≧ 1.0 was obtained. The results are shown in (Table 1). In the following (Table 1), “A” and “B” are expected to have sufficient characteristics as a practical recording medium, and “C” is not sufficient, but density, linear velocity, recording / reproducing method, etc. Depending on the specifications, “D” indicates a material that may be used as a practical recording medium, and “D” indicates a material that is not suitable for practical use. More specifically, “A” indicates a case where there is a configuration in which the maximum value of ΔR satisfying the condition of Acry / Aamo ≧ 1.0 is 15% or more, and “B” indicates the same condition. The case where there is a configuration in which the maximum value of ΔR that satisfies the condition is 10% or more and less than 15% exists, and “C” indicates the case where there is a configuration in which the maximum value of ΔR that satisfies the condition satisfies 5% or more and less than 10%. “D” indicates a case where there is no configuration in which the maximum value of ΔR satisfying the same condition is 5% or more.

（表１）の結果からも、Δｎ＝ｎ₁−ｎ₂は２以上が好ましく、３以上がより好ましいことがわかる。

From the results of (Table 1), it is understood that Δn = n ₁ −n ₂ is preferably 2 or more, and more preferably 3 or more.

Moreover, when the film thickness of the light absorption layer 35 is too thin, the optical effect of the light absorption layer 35 will become small, and when the film thickness of the light absorption layer 35 is too thick, the optical effect of the reflection layer 36 will become small. For this reason, the film thickness of the light absorption layer 35 needs to be a film thickness that allows appropriate transmission and absorption of incident light. The film thickness d ₁ of the light absorption layer 35 is 0.1λ / (n ₁ · k ₁ ) ≦ d ₁ ≦ 1.0λ / (n, where λ is the wavelength of the incident light, based on experimental results such as examples described later. is preferably in the range of _{1 · k 1), 0.2λ /} (n 1 · k 1) the range of _{≦ d 1 ≦ 0.8λ / (n} 1 · k 1) is more preferably confirmed.

In order to obtain sufficient cooling ability, a material having a high thermal conductivity is used for the reflective layer 36, and the mark width is made uniform to reduce jitter. The thermal conductivity of the reflective layer is, for example, preferably 50 W / m · K or more, more preferably 100 W / m · K or more, and more preferably 150 W / m · K or more under a temperature condition in the vicinity of 300K. To further obtain a sufficient cooling effect, the film thickness d ₂ of the reflective layer 36, from the experimental results, such as the examples described below, is preferably the thickness d ₁ or more light absorbing layer 35, the d ₁ It was confirmed that 1.5 times or more, more preferably 2 times or more is more preferable.

  The optical information recording medium manufacturing method, recording / reproducing method, and recording / reproducing apparatus of the present embodiment may be the same as those of the first embodiment.

  In the above description, the thickness of the recording layer is set to 10 nm, but the thickness of the recording layer is not necessarily limited to this thickness.

(Third embodiment)
In this embodiment, an optical information recording medium in which two or more multilayer films including a recording layer are formed will be described. Here, a description will be given of a form in which two multilayer films (information layers) each including a recording layer are arranged via a separation layer.

  As shown in FIG. 8, in the optical information recording medium of the present embodiment, the first information layer 42, the separation layer 43, the second information layer 44, and the protective layer 45 are formed in this order on the transparent substrate 41. Yes. Each of the first information layer 42 and the second information layer 43 includes a recording layer. Information is recorded and reproduced on these recording layers by laser light irradiated from the transparent substrate side.

  The multilayer film described in the above embodiment is applied to the second information layer 44 of this embodiment. The first information layer 42 is preferably a multilayer film including at least a recording layer and a lower protective layer and an upper protective layer arranged on both sides of the recording layer. Each layer and transparent substrate included in these multilayer films can be formed using the materials described in the above embodiment. Note that the first information layer may be a reproduction-only layer that reproduces information stored in advance as a concavo-convex pattern on the surface of the transparent substrate.

  In addition, in order to record and reproduce information in the second information layer 44, the first information layer 42 preferably transmits at least 30% of the irradiated laser light.

  The separation layer 43 is preferably a material that is transparent at the wavelength λ of the laser beam and is excellent in heat resistance and adhesiveness. Specifically, an adhesive resin (for example, an ultraviolet curable resin), a double-sided tape, A dielectric film or the like can be used. The thickness of the separation layer 43 is set to 2 μm or more so that the information in the other information layer does not leak when information is recorded / reproduced in either the first information layer 42 or the second information layer 44. It is preferable. On the other hand, the thickness of the separation layer 43 is 100 μm or less so that the sum of the substrate thickness and the first information layer 42 and the second information layer 44 is within the substrate thickness tolerance range in order to focus the laser light on both. It is preferable.

  The protective layer 45 may be used as a substrate (protective substrate) for forming the second information layer 44. In this case, the transparent substrate 41 on which the first information layer 42 is formed and the protective substrate on which the second information layer 44 is formed are bonded together via the separation layer 43 to manufacture an optical disc. As the material of the protective substrate, the same material as that of the transparent substrate 41 can be used, but it is not necessarily transparent and other materials may be used. Also, the shape of the substrate surface need not be the same as the shape of the transparent substrate surface. For example, the shape of the guide groove forming the groove and the land may be different, and the spiral direction of the guide groove is reversed. Also good. Furthermore, if the guide groove is provided on the surface of the separation layer on the second information layer side by, for example, the 2P method (photo-polymerization method), the surface of the protective substrate may be flat. The protective layer 45 may be a layer formed on the second information layer 44 formed on the transparent substrate. Such a protective layer can be formed by, for example, resin spin coating or pasting a resin plate with an adhesive.

  An example of the manufacturing method of this embodiment is demonstrated. A first information layer and a second information layer are formed on the surfaces of the transparent substrate and the protective substrate, each having a guide groove, by the sputtering method described above. Next, an ultraviolet curable resin is applied on the surface of the first information layer or the second information layer to form a separation layer. Further, the transparent substrate and the protective substrate are pressed to face each other so that the first information layer and the second information layer face each other through the separation layer, and the separation layer is cured by irradiating ultraviolet rays.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, a following example does not limit this invention.

Example 1
As the substrate, a polycarbonate resin having a thickness of 0.6 mm was used. On this substrate, lands and grooves each having a width of 0.6 μm were formed. The groove depth was about 70 nm.

On this substrate, a lower protective layer of about 1200 nm, Ge—Sb—Te (atomic ratio Ge: Sb: Te = 22) using a ZnS—SiO ₂ (molecular number ratio ZnS: SiO ₂ = 80: 20) target. : 25: 53) recording layer of various thickness using a target, ZnS-SiO ₂ (the number of molar ratio _{ZnS: SiO 2 = 80: 20} ) the upper protective layer of various thickness using a target, various materials An intermediate layer having a thickness of about 40 nm using a target of No. 4 and a reflective layer having a thickness of about 40 nm using targets of various materials were sequentially stacked by sputtering. Each layer uses a sputtering target having a diameter of 10 cm and a thickness of 6 mm, except for the recording layer, in Ar gas, and the recording layer is a mixed gas of Ar and N ₂ (total pressure 2 mTorr, N ₂ gas partial pressure is about 5%). The film was formed inside.

  The optical disk thus obtained was overcoated with an ultraviolet curable resin, and then annealed with laser light, whereby the entire surface was initially crystallized to obtain No. 1 to No. 21 optical disks. These were produced by intentionally changing the thickness of the recording layer, the upper protective layer, and the materials of the intermediate layer and the reflective layer in order to investigate the dependency of the cross erase on the material and the film thickness configuration.

  Table 2 shows the film thickness of the recording layer / upper protective layer and the material of the intermediate layer / reflection layer of each optical disc.

  Mark edge recording was performed on these optical discs using an optical system with a wavelength of 660 nm and NA of 0.6 at a linear velocity of 6.0 m / s (radius position: about 32 mm, rotation speed: about 1800 rpm), and cross erase was measured. .

Specifically, first, a 9.7 MHz 3T signal is recorded in the groove, this track is reproduced, and the 3T signal amplitude A ₀ is measured with a spectrum analyzer. Next, an 11T signal of 2.6 MHz is recorded on both lands adjacent to the groove, the groove is reproduced again, and the 3T signal amplitude A ₁ is measured with a spectrum analyzer. The amount of decrease 3A signal amplitude ΔA = A ₁ −A ₀ measured in this way is used as an index for cross erase evaluation. The same thing is performed by reversing the land and the groove, and the 3T signal amplitude decrease amount ΔA ′ is measured in the same manner.

  Table 2 lists the superiority or inferiority of each disk according to the value of ΔA. However, as a result of the above measurement, when the measurement track was a groove in any sample, the amount of decrease in the 3T signal amplitude was large (ΔA> ΔA ′). Therefore, the determination was made based only on the result (ΔA) in that case. A value of ΔA of less than 1 dB is indicated by “A”, 1 B or more and less than 2 dB is “B”, 2 dB or more and less than 5 dB is indicated by “C”, and 5 dB or more is indicated by “D”.

The laser modulation waveform for recording a signal is a single rectangular pulse having a pulse width of 51.3 ns (power level P ₁ ) for a 3T signal, and a pulse train (power) of 9 pulses for an 11T signal. Level P ₁ ), the top of which is 51.3 ns, the second and subsequent pulses are all 17.1 ns wide, the width between each pulse is also 17.1 ns (power level P ₃ ), and 34 immediately after the last pulse. A cooling section (power level P ₄ ) of 2 ns was provided. In the portion where no mark is recorded, continuous light (unmodulated light) of power level P ₂ is used.

The recording power level P ₁ is 1.5 times the lower limit value of the power with a C / N ratio exceeding 45 dB when a 3T signal is recorded, and the power level P ₂ is an erasure ratio, that is, after recording a 3T signal. The 3T signal amplitude attenuation ratio when the 11T signal was overwritten was set to the median value of the power range exceeding 25 dB, and the power levels P ₃ and P ₄ were set to 1 mW, the same as the reproduction power level.

中間層及び反射層に用いた各材料の熱伝導率は温度依存性があるが、おおよその値の範囲は以下のように特定できる。熱伝導率の大きい順に、Ａｌ（３０〜６００℃における熱伝導率は、約１５０〜２５０Ｗ／ｍ・ｋ）、Ｃｒ（５０〜１００Ｗ／ｍ・ｋ）、Ｔｉ（２０〜５０Ｗ／ｍ・ｋ）、ＷＳｉ₂（５〜２０Ｗ／ｍ・ｋ）、ＰｂＴｅ（１．０〜３．０Ｗ／ｍ・ｋ）、ＺｎＳ−ＳｉＯ₂（０．１〜０．５Ｗ／ｍ・ｋ）である。

The thermal conductivity of each material used for the intermediate layer and the reflective layer is temperature-dependent, but the approximate value range can be specified as follows. In descending order of thermal conductivity, Al (the thermal conductivity at 30 to 600 ° C. is about 150 to 250 W / m · k), Cr (50 to 100 W / m · k), Ti (20 to 50 W / m · k) , WSi ₂ (5 to ₂₀ W / m · k), PbTe (1.0 to 3.0 W / m · k), ZnS—SiO ₂ (0.1 to 0.5 W / m · k).

  According to Table 2, first, No. 1 to No. 5 optical discs having different recording layer thicknesses are compared. No. 5 has a large cross erase, No. 1 and No. 4 have improved cross erase to some extent, In 3 and No. 4, the cross erase was small enough. Accordingly, from the viewpoint of reducing cross erase, the film thickness of the recording layer is required to be 4 nm to 16 nm, and preferably 6 nm to 14 nm.

  Next, comparing No. 3 and No. 6 to No. 11 optical discs having different upper protective layer thicknesses, it can be seen that the thicker the upper protective layer thickness, the smaller the cross erase. From this, it can be seen that the film thickness of the upper protective layer is preferably 10 nm or more, and more preferably 20 nm or more, from the viewpoint of reducing cross erase.

  Further, No. 3 and No. 12 to No. 21 optical discs having different materials for the intermediate layer and the reflective layer will be compared. Among these, except for No. 3, No. 12 to No. 14 have small cross erase. All of them use Al having the highest thermal conductivity among the materials used this time as the reflective layer, and the intermediate layer is a material having thermal conductivity between the upper protective layer and the reflective layer. On the other hand, the other No. 15 to No. 21 have large cross erase.

  No.15 to No.19 all have higher thermal conductivity of the intermediate layer than that of the reflective layer, especially No.17 is the one in which the materials of the No.3 intermediate layer and the reflective layer are interchanged. There was a big difference in terms of erasing. Nos. 20 and 21 have a configuration in which either the intermediate layer or the reflective layer is omitted, but both have large cross erase.

  From the above, when multiple layers are stacked on the recording layer, cross-erase can be suppressed by adopting a configuration that gradually changes from a material with low thermal conductivity to a material with high thermal conductivity in order from the recording layer. Was confirmed. This is because heat transfer from the recording layer to the reflective layer through the upper protective layer and the intermediate layer is accelerated, so that the heat conduction in the surface of the recording layer is reduced and adjacent to it. This is because the influence on the track is also suppressed.

Further, for the configuration shown as No. 3, an optical disk was fabricated in which an interface layer of about 10 nm made of Ge, O, and N was formed in contact with the upper and lower sides of the recording layer as shown in FIG. The GeON film was formed by reactive sputtering in Ar, N ₂ and O ₂ gases using a Ge target. In order to investigate the repetitive characteristics of this optical disc, 3T and 11T signals were alternately recorded 10,000 times or 100,000 times, and the amplitude change of the 3T signal was measured as compared to after 10 times recording.

  As a result, after recording 10,000 times, both the No. 3 optical disc and the optical disc with the interface layer inserted therein had an amplitude drop of 0.5 dB or less, but after recording 100,000 times, the No. 3 optical disc While the amplitude was reduced by about 3 dB, the optical disc with the interface layer inserted therein still had an amplitude reduction of 0.5 dB or less. From this, it was confirmed that by inserting the interface layer, it is possible to further improve the repeated recording characteristics in addition to the reduction of the cross erase.

As a result of analyzing the composition of the recording layer of the optical disk by Auger electron spectroscopy, the proportion of N atoms was about 2.2 atomic%. Here, when a plurality of optical disks having the same configuration as No. 3 were formed by changing the N ₂ gas partial pressure at the time of forming the recording layer, the proportion of N atoms in the recording layer was determined as a result of the analysis. About 0.0, 0.2, 0.8, 4.0, and 7.6 atomic% were obtained.

  In order to investigate the repetitive characteristics of these optical discs, 3T and 11T signals were alternately recorded 10,000 times or 100,000 times, and the change in amplitude of the 3T signal compared to after 10 times recording was measured. As a result, after 10,000 recordings, the amplitude drop of each disk was within an error range of 0.5 dB or less, but after 100,000 recordings, the ratio of N atoms in the recording layer was about 0.0 atomic%. However, only about 0.2 atomic% was about 1 dB, and others were about 0.5 dB within the error range. Also, record the 3T signal on these discs and measure the amplitude of the 3T signal, and then store for 100 hours in an environment of 90 ° C. and 80% relative humidity, and then measure the amplitude of the 3T signal to examine the amplitude change. As a result, the disk in which the proportion of N atoms in the recording layer was 7.6 atomic% had an amplitude decrease of 5 dB or more, while that of 4.0 atomic% was about 2 dB, and the others were hardly decreased. . From these results, it is preferable that the ratio of N atoms in the recording layer is 0.0 to 6.0 atom%, more preferably 0.5 to 4.0 atom%, from the viewpoints of repeatability and moisture resistance. confirmed.

(Example 2)
As the substrate, a substrate made of polycarbonate resin having a thickness of 0.6 mm, a groove and a land width of 0.6 μm, and a groove depth of about 70 nm was used. On this substrate, using a ZnS—SiO ₂ (ZnS: SiO ₂ = 80: 20) target, a lower protective layer having a film thickness of about 150 nm, Ge—Sb—Te (atomic ratio Ge: Sb: Te = 22). : 25:53) Recording layer with a thickness of about 10 nm using a target, ZnS-SiO ₂ (molecular number ratio ZnS: SiO ₂ = 80: 20) Upper protective layer with a thickness of about 30 nm using a target, various materials For example, by using a PbTe (atomic ratio Pb: Te = 50: 50) target, a light absorption layer with various film thicknesses, and with various materials, for example, a reflective layer with various film thicknesses using an Au target, by sputtering. Laminated sequentially. In any case, a target having a diameter of 10 cm and a thickness of 6 mm was used, the recording layer was in Ar gas, and the recording layer was a mixed gas of Ar and N ₂ (total pressure of 1 mTorr, N ₂ gas partial pressure was about 5%. ) Was sputtered.

  After forming an overcoat layer using an ultraviolet curable resin on the reflective layer of the disk thus obtained, the entire surface was initially crystallized by annealing with a laser beam, and No. 31 to 47 I got a disc. These discs were produced by intentionally changing the materials and film thicknesses of the light absorption layer and the reflection layer in order to investigate the dependency of the recording / reproducing characteristics on the material and the film thickness structure. The following (Table 3) shows materials and film thicknesses of the light absorption layer and the reflection layer of each disk.

Here, the optical constants (refractive index n, extinction coefficient k) of each layer at a wavelength of 660 nm obtained by actual measurement are as follows: the substrate is n = 1.6, k = 0.0, the lower protective layer and the upper protective layer. ZnS—SiO ₂ is n = 2.1, k = 0.0, Ge—Sb—Te as a recording layer is n = 4.1 in the amorphous state, k = 1.6, and n = 3 in the crystalline state. .9, k = 4.2, PbTe as light absorption layer and reflection layer is n = 5.0, k = 3.2, Au is n = 0.3, k = 3.6, Al is n = 1 .4, k = 6.4, Pd n = 2.2, k = 4.4, Cr n = 3.6, k = 3.4, TiN n = 2.5, k = 1.2 PdTe is n = 3.2, k = 2.2, Ge ₈₀ Cr ₂₀ is n = 4.5, k = 2.5, Ag ₉₈ Pd ₁ Cu ₁ is n = 0.3, k = 4.0 Met. Optical calculation is performed based on this value, and the calculated values of Acry / Aamo and ΔR are also shown in (Table 3).

Using these optical systems with a wavelength of 660 nm and a numerical aperture (NA) of 0.6 on these disks, mark edge recording was performed under the conditions of a linear velocity of 6.0 m / s (radius position: about 32 mm, rotation speed: about 1800 rpm), The following measurements were made. First, a 9.7 MHz 3T signal and a 2.6 MHz 11T signal are alternately recorded 11 times on the groove and land, and this track is reproduced with the 3T signal recorded, and its C / N ratio and erasure rate are recorded. Was measured using a spectrum analyzer. Here, the erasing rate was defined as the difference between the amplitude A ₁₁ of the amplitude A ₃ and 11T residual signal of the 3T signal (A ₃ -A _11).

A random signal of (8-16) modulation was recorded 11 times, and the jitter was measured using a time interval analyzer. Here, the jitter is a deviation on the time axis between the recording original signal and the reproduction signal, and the sum (σsum) of jitter standard deviations of each signal of 3T to 11T is taken, and this is used as the window width of the signal detection. It is expressed as a value (σsum / T) divided by (T). For example, it is known that a jitter of 12.8% or less corresponds to a bit error rate of 10 ⁻⁴ or less, assuming that the deviation on the time axis is a normal distribution. .

The laser modulation waveform at the time of recording a signal is a pulse train (power level P ₁ ) composed of (n−2) pulses in the case of an nT (n is an integer, 3 ≦ n ≦ 11) signal, and its head. 51.3 ns, the second and subsequent pulses all have a pulse width of 17.1 ns, the width between each pulse is also 17.1 ns (power level P ₃ ), and a cooling interval of 34.2 ns (power level immediately after the last pulse) P ₄₎ was the arranged. In a portion where no mark is recorded, continuous light having a power level P ₂ is used. The recording power level P ₁ is 1.5 times the lower limit value of the power with a C / N ratio exceeding 45 dB when a 3T signal is recorded, and the power level P ₂ is the power at which the erasure rate is maximized. P ₃ and P ₄ were set to 1 mW which is the same as the reproduction power level.

  The results measured under the above conditions are shown in the above (Table 3). The measurement results in the table are “B”, which is sufficient as a practical recording medium, and “A”, which is particularly excellent, and is insufficient, but the density, linear velocity, recording Depending on the specifications of the reproduction method, etc., those that may be usable are represented as “C”, and those that are not likely to be used are represented as “D”. More specifically, regarding the C / N ratio, “A” corresponds to 53 dB or more, “B” corresponds to 50 dB or more and less than 53 dB, “C” corresponds to 47 dB or more and less than 50 dB, and “D” corresponds to less than 47 dB. Regarding the erasure rate, “A” corresponds to 24 dB or more, “B” corresponds to 20 dB or more and less than 24 dB, “C” corresponds to 16 dB or more and less than 20 dB, and “D” corresponds to less than 16 dB. With respect to jitter, “A” corresponds to less than 8%, “B” corresponds to 8% or more and less than 10%, “C” corresponds to 10% or more and less than 13%, and “D” corresponds to 13% or more.

ディスクNo.31〜No.38は、光吸収層としてｎの大きいＰｂＴｅ、反射層としてｎが小さく熱伝導率の大きいＡｕを用いたディスクであり、ディスクNo.31〜No.34は、反射層の膜厚を変化させたディスクであり、ディスクNo.34〜No.38は、光吸収層の膜厚を変化させたディスクである。

Discs No. 31 to No. 38 are discs using PbTe having a large n as a light absorption layer and Au having a small n and a large thermal conductivity as a reflection layer. Discs No. 31 to No. 34 are reflection layers. The disks No. 34 to No. 38 are disks in which the film thickness of the light absorption layer is changed.

  When comparing disks No. 31 to No. 34, the cooling performance increases as the Au film thickness of the reflective layer increases, so the jitter is good, and the reflective layer thickness is greater than or equal to the thickness of the light absorbing layer. Jitter is 10% or less from around.

When comparing disks No. 34 to No. 38, the film thickness of the light absorbing layer is too thin as in disk No. 35, or the film thickness of the light absorbing layer is too thick as in disks No. 37 and No. 38. In the case of a disc, both optical characteristics and evaluation results are worse. On the other hand, in the case of the disks No. 34 and No. 36, since the film thickness of the light absorption layer is appropriate, good values are obtained for the C / N ratio, the erasure rate, and the jitter. Thus, appropriate thickness of the light absorbing _{layer, 0.1λ / (n 1 · k} 1) or _{1.0λ / (n 1 · k 1} ) is less.

  Disks No. 39 to No. 47 are disks in which the materials of the light absorption layer and the reflection layer are changed. While disk No. 34 is Δn = 4.7, disk No. 40 (Δn = 1.4), disk No. 41 (Δn = 1.1), disk No. 42 (Δn = 1.9) ), Disc No. 44 (Δn = 1.4), disc No. 45 (Δn = −4.7), etc. have a poor optical characteristic because the value of Δn is smaller than 2, and the C / N ratio and erasure The rate is also low, and of course the jitter is also large. Disc No. 39 (Δn = 2.8), Disc No. 43 (Δn = 3.3), Disc No. 46 (Δn = 2.2), Disc No. 47 (Δn = 2.9), etc. Although Δn is 2 or more and each characteristic is good, it is understood that the smaller the Δn is, the worse the recording / reproduction characteristic is, and Δn is 2.5 or more, and more preferably 3 or more.

As for the configuration of the disk No. 34, an interface layer 39 having a film thickness of about 5 nm made of a GeON film is formed on the surface of the recording layer 33 on the substrate 31 side and / or on the opposite side of the substrate 31 as shown in FIG. A disc was made. The GeON film was formed by reactive sputtering in Ar, N ₂ and O ₂ gases using a Ge target. Measurements similar to those of the disk No. 34 were performed on these disks. As a result, although the C / N ratio of each of the disks is not different from that of the disk No. 34, the interface layer 39 (GeON film) is formed only on the substrate 31 side of the recording layer 33, only on the opposite side of the substrate 31, on the substrate 31 side and For each of the disks provided on the opposite side of the substrate 31, the erasure rate is improved by about 2 dB, about 4 dB, and about 5 dB with respect to the disk No. 34, and a good jitter value of less than 8% is obtained. It was. From this, it became clear that the erasing characteristics of the optical information recording medium of this embodiment are further improved by inserting the interface layer 39.

It is a fragmentary sectional view of one form (1st Embodiment) of the optical information recording medium of this invention. It is a fragmentary perspective view of one form of the optical information recording medium of this invention. It is a fragmentary sectional view of another form (1st Embodiment) of the optical information recording medium of this invention. It is a figure which shows the structure of one form of the optical information recording / reproducing apparatus of this invention. It is a wave form diagram which shows an example of the pulse waveform applied to the recording / reproducing method of the optical information recording medium of this invention. It is a fragmentary sectional view of another form (2nd Embodiment) of the optical information recording medium of this invention. It is a fragmentary sectional view of another form (2nd Embodiment) of the optical information recording medium of this invention. It is a fragmentary sectional view of another form (3rd Embodiment) of the optical information recording medium of this invention.

Explanation of symbols

1, 31 Transparent substrate 2, 32 Lower protective layer 3, 33 Recording layer 4, 34 Upper protective layer 5 Intermediate layer 35 Light absorbing layer 6, 36 Reflecting layer 7, 37 Overcoat layer 8 Groove 9 Land 10 Laser beam 11 Recording Marks 12, 39 Interface layer 13 Semiconductor laser 14 Collimating lens 15 Beam splitter 16 λ / 4 wavelength plate 17 Objective lens 18 Optical disk 19 Voice coil 20 Turntable 21 Motor 22 Detector 23 Reproduction signal 41 Transparent substrate 42 First information layer 43 Separation Layer 44 Second information layer 45 Protective layer (protective substrate)

Claims (26)

A transparent substrate, and a multilayer film formed on the transparent substrate,
The multilayer film, in order from the side close to the transparent substrate, a lower protective layer, a recording layer that reversibly changes between two different states that can be detected optically by irradiation with a light beam, an upper protective layer, and a light absorbing layer And a reflective layer,
The difference Δn = n ₁ −n ₂ between the refractive index n ₁ of the light absorbing layer and the refractive index n ₂ of the reflective layer at the wavelength λ of the light beam is 2 or more and 6 or less,
The optical information recording medium is characterized in that the thickness of the reflective layer is equal to or greater than the thickness of the light absorption layer. Thickness d ₁ of the light absorption layer, the extinction coefficient of the light absorbing layer as _{k 1, 0.1λ / (n 1} · k 1) ≦ d 1 ≦ 1.0λ / (n 1 · k 1) The optical information recording medium according to claim 1, which is in the range described above. A transparent substrate, and a multilayer film formed on the transparent substrate,
The multilayer film, in order from the side close to the transparent substrate, a lower protective layer, a recording layer that reversibly changes between two different states that can be detected optically by irradiation with a light beam, an upper protective layer, and a light absorbing layer And a reflective layer,
The film thickness d ₁ of the light absorbing layer is 0.1λ / (when the wavelength of the light beam is λ and the refractive index and extinction coefficient of the light absorbing layer at the wavelength λ are n ₁ and k ₁ , respectively. n ₁ · k ₁ ) ≦ d ₁ ≦ 1.0λ / (n ₁ · k ₁ )   The optical information recording medium according to claim 1, wherein the reflective layer contains at least one selected from Au, Ag, and Cu.   The light absorption layer is selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Os, Al, Ga, In, C, Si, Ge, Sn, Pb, Sb and Bi. The optical information recording medium according to claim 1, comprising at least one element.   The optical recording information recording medium according to claim 5, wherein the light absorption layer is made of at least one compound selected from oxides, nitrides, carbides, sulfides, fluorides, selenides, and tellurides.   The optical information recording medium according to claim 5, wherein the light absorption layer is made of an inter-element compound.   The optical information recording medium according to claim 1, wherein the recording layer has a thickness of 4 nm to 16 nm.   9. The optical information recording according to claim 1, further comprising an interface layer at at least one interface between the lower protective layer and the recording layer and between the recording layer and the upper protective layer. Medium.   The optical information recording medium according to claim 9, wherein the interface layer includes at least one selected from Ge, Si, Cr, Ti, and Al.   The optical information recording medium according to claim 1, wherein the upper protective layer has a thickness of 10 nm to 200 nm.   The optical information recording medium according to claim 1, wherein the recording layer contains Ge, Sb, and Te.   The optical information recording medium according to claim 12, wherein the recording layer contains Ge, Sb, and Te as main components and further contains N of 6.0 atomic% or less. At least one layer selected from the upper protective layer and a lower protective layer, optical information recording according to any one of claims 1 to 13 containing 60 to 100 mol% of ZnS and 40 to 0 mol% of SiO ₂ Medium.   The reflectance, which is the ratio at which the light beam is reflected by the recording medium, and the absorption ratio, which is the ratio at which the recording layer is absorbed, are Rcry and Acry when the recording layer is in a crystalline phase, respectively, and the recording layer is amorphous. When it is a phase, as Ramo and Aamo, a reflectance difference (Rcry-Ramo) is 5% or more and an absorptance ratio (Acry / Aamo) is 1.0 or more. An optical information recording medium according to claim 1. A transparent substrate, and a first information layer, a separation layer, and a second information layer, which are sequentially formed on the transparent substrate from the side close to the transparent substrate,
Each of the first information layer and the second information layer includes a recording layer that reversibly changes between two different states that are optically detectable by irradiation with a light beam,
The optical information recording medium, wherein the second information layer is a multilayer film according to any one of claims 1 to 15. On the transparent substrate, in order from the side close to the transparent substrate, the lower protective layer, the recording layer that reversibly changes between two different states that can be detected optically by irradiation with a light beam, the upper protective layer, and the light absorbing layer And a step of forming a multilayer film including a reflective layer, and the difference Δn = n ₁ −n ₂ between the refractive index n ₁ of the light absorbing layer and the refractive index n ₂ of the reflective layer at the wavelength λ of the light beam is A method for producing an optical information recording medium, wherein the thickness is 2 or more and 6 or less, and the thickness of the reflective layer is equal to or greater than the thickness of the light absorption layer. On the transparent substrate, in order from the side close to the transparent substrate, the lower protective layer, the recording layer that reversibly changes between two different states that can be detected optically by irradiation with a light beam, the upper protective layer, and the light absorbing layer And a step of forming a multilayer film including a reflection layer, wherein the film thickness of the light absorption layer is d ₁ , the wavelength of the light beam is λ, and the refractive index and extinction coefficient of the light absorption layer at the wavelength λ are respectively as n ₁ and k _1, characterized in that _{0.1λ / (n 1 · k 1} ) ≦ d 1 ≦ 1.0λ / (n 1 · k 1) to form the light-absorbing layer to stand A method for manufacturing an optical information recording medium. A step of forming a first information layer on a transparent substrate; a step of forming a second information layer on a protective substrate; and bonding the transparent substrate and the protective substrate through a separation layer to thereby form the transparent substrate And forming the first information layer, the separation layer, and the second information layer in this order,
The second information layer has a lower protective layer, a recording layer that reversibly changes between two different states that can be detected optically by irradiation with a light beam, an upper protective layer, and light absorption from the side close to the transparent substrate. comprising a layer and a reflective layer in this order, the difference [Delta] n = n ₁ -n ₂ between the refractive index n ₂ of the reflective layer and the refractive index n ₁ of the light absorption layer at the wavelength λ of the light beam 2 to 6 Yes,
In addition, the method for manufacturing an optical information recording medium, wherein the second information layer is formed on the protective substrate so that the thickness of the reflective layer is equal to or greater than the thickness of the light absorption layer. A step of forming a first information layer on a transparent substrate; a step of forming a second information layer on a protective substrate; and bonding the transparent substrate and the protective substrate through a separation layer to thereby form the transparent substrate And forming the first information layer, the separation layer, and the second information layer in this order,
The second information layer, in order from the side close to the transparent substrate, a lower protective layer, a recording layer that reversibly changes between two different states that can be detected optically by irradiation with a light beam, an upper protective layer, and light An absorption layer and a reflection layer are included in this order. The thickness of the light absorption layer is d ₁ , the wavelength of the light beam is λ, and the refractive index and extinction coefficient of the light absorption layer at the wavelength λ are n ₁ and k, respectively. ₁ , the second information layer is formed on the protective substrate so that 0.1λ / (n ₁ · k ₁ ) ≦ d ₁ ≦ 1.0λ / (n ₁ · k ₁ ) is satisfied. A method for producing an optical information recording medium characterized by the above.   21. The method for producing an optical information recording medium according to claim 17, wherein the recording layer is formed in the thickness direction at a rate of 200 nm / min or less.   The recording layer is formed in an atmosphere containing an inert gas and a nitrogen gas, wherein the content of the nitrogen gas is adjusted so that the recording layer contains 6.0 atom% or less of nitrogen atoms. The manufacturing method of the optical information recording medium in any one of 17-21. A method for recording and reproducing information by making a light beam incident on the optical information recording medium according to any one of claims 1 to 16 from the transparent substrate side,
The intensity of the light beam is set to a power level P ₁ that can instantaneously melt the irradiated portion, and power levels P ₂ and P ₃ that cannot instantaneously melt the irradiated portion (where P ₁ > P ₂ ≧ P ₃ ≧ 0). ), And the power level P ₀ (where P ₁ > P ₀ > 0) where the optical state of the recording mark of the recording layer does not change and the reflection sufficient for reproduction of the recording mark is obtained by irradiation. sometimes,
At least one recording mark to be recorded on the recording layer is formed by a recording pulse train composed of a group of pulses generated by modulating a light beam between power levels P ₁ and P _3, and no recording mark is formed. In that case the light beam is held at power level P ₂ ,
A recording / reproducing method for an optical information recording medium, wherein information recorded on the recording layer is reproduced by irradiating a light beam having a power level P ₀ . 24. The recording / reproducing method for an optical information recording medium according to claim 23, wherein a cooling section having a power level P ₄ (where P ₂ > P ₄ ≧ 0) is provided immediately after the recording pulse train.   25. The recording / reproducing method for an optical information recording medium according to claim 23 or 24, wherein at least a part of the recording pulse train is generated so that a pulse width and an interval between the pulses are substantially the same. 17. The optical information recording medium according to claim 1, a light beam generating means for generating a light beam irradiated on the optical information recording medium, and a light beam intensity for modulating the intensity of the light beam. Modulation means,
The intensity of the light beam is set to a power level P ₁ that can instantaneously melt the irradiated portion, and power levels P ₂ and P ₃ that cannot instantaneously melt the irradiated portion (where P ₁ > P ₂ ≧ P ₃ ≧ 0). ), And the power level P ₀ (where P ₁ > P ₀ > 0) where the optical state of the recording mark of the recording layer does not change and the reflection sufficient for reproduction of the recording mark is obtained by irradiation. sometimes,
When the light beam intensity modulating means records information by forming a recording mark, the recording is made of a group of pulses generated by modulating the light beam between power levels P ₁ and P _3. the pulse train to form at least one of the recording mark, holding the intensity of the light beam at the power level P ₂ when not forming a recording mark,
When reproducing the information recorded on the recording layer, the optical information recording medium recording / reproducing apparatus is characterized in that the intensity of the light beam is maintained at the power level P ₀ .

Images