JP4109255B2 - Magneto-optical recording medium and manufacturing method thereof - Google Patents

Description

  The present invention relates to a magneto-optical recording medium having a soft magnetic layer and a method for producing such a magneto-optical recording medium.

  In recent years, magneto-optical recording media have attracted attention. The magneto-optical recording medium is a rewritable recording medium that is configured using various magnetic properties of a magnetic material and has two functions of thermomagnetic recording and reproduction using a magneto-optical effect. The magneto-optical recording medium has a recording magnetic part composed of one or more perpendicular magnetization films, and a signal is recorded on the recording layer in the recording magnetic part. When recording, a predetermined magnetic field is applied to the recording layer while the temperature of the recording layer is increased by irradiating a laser beam condensed through the objective lens. In this way, a predetermined signal is recorded as a change in the magnetization direction in the recording layer. At the time of reproduction, this recording signal is read by a predetermined optical system.

  As one of the techniques for improving the recording density of the magneto-optical recording medium, it is known to reduce the size, that is, the spot diameter, of the region where the laser is irradiated onto the medium during the recording process. By reducing the spot diameter, the track pitch of the medium can be designed to be short, the recording mark length can be shortened, and the recording density can be improved. The spot diameter can be reduced by shortening the wavelength of the irradiation laser or increasing the numerical aperture NA of an objective lens (lens facing the medium) for condensing the irradiation laser.

  As the numerical aperture NA of the lens increases, the focal length of the lens decreases. However, in the field of magneto-optical recording technology, front illumination is used instead of the conventional back illumination method in order to apply a lens having a large numerical aperture NA. There is a high demand for practical application of the method.

  In the back illumination type magneto-optical recording medium, the laser is irradiated from the transparent substrate side to the recording magnetic part in the recording process and the reproducing process. Since the transparent substrate requires a considerable thickness in order to ensure the rigidity of the medium, for a back-illumination type magneto-optical recording medium, a lens having a shorter focal length, that is, a larger numerical aperture NA. Lenses are harder to adopt.

  On the other hand, in the front illumination type magneto-optical recording medium, in the recording process and the reproducing process, the recording magnetic part from the side of the transparent protective film provided on the side opposite to the substrate is applied to the recording magnetic part. A laser is irradiated. Since the transparent protective film can be formed to be considerably thin, a lens having a short focal length, that is, a lens having a large numerical aperture NA can be employed for the front illumination type magneto-optical recording medium.

  In the front illumination type magneto-optical recording medium, the recording layer included in the recording magnetic part is formed between the substrate and the recording magnetic part for the purpose of improving the sensitivity to the magnetic field from the magnetic recording head (electromagnet) during recording. A soft magnetic layer may be provided. Such magneto-optical recording media are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 3-105741 and 3-137837.

  FIG. 15 shows a laminated configuration of a magneto-optical recording medium X4 which is an example of a conventional magneto-optical recording medium. The magneto-optical recording medium X4 is a laminated layer composed of a substrate S3, a recording magnetic part 91, a soft magnetic layer 92, a pregroove layer 93, a heat conductive layer 94, dielectric layers 95 and 96, and a protective film 97. It has a structure and is configured as a front-illuminated magneto-optical disk.

  The recording magnetic part 91 has a magnetic structure capable of performing two functions of thermomagnetic recording and reproduction utilizing the magneto-optical effect, and is composed of one or more perpendicular magnetization films depending on the reproduction method. . One of the perpendicular magnetization films is a recording layer. The soft magnetic layer 92 is composed of a magnetic film having a high magnetic permeability, and is an in-plane magnetization film that is magnetized with an easy magnetization axis in a direction parallel to the film surface of the magnetic film (in-plane direction). The pre-groove layer 93 is a layer made of a resin material and having an uneven shape for forming land grooves on the contact surface with the heat conductive layer 94. The heat conductive layer 94 is for efficiently conducting heat generated in the recording magnetic part 91 to the substrate side. The dielectric layers 95 and 96 are for avoiding external physical and chemical influences on the recording magnetic part 91. The protective film 97 is a part for protecting the recording magnetic part 91 particularly from dust, and is made of a light transmissive resin material.

  In manufacturing the conventional magneto-optical recording medium X4, first, the soft magnetic layer 92 is formed on the substrate S3 by forming a soft magnetic material by sputtering. Next, a pregroove layer 93 made of a resin material is formed on the soft magnetic layer 92 by a so-called 2P method. Next, a predetermined material is deposited on the pre-groove layer 93 by sputtering, whereby a heat conductive layer 94, a dielectric layer 95, a recording magnetic part 91, and a dielectric layer 96 are sequentially formed. Thereafter, an ultraviolet curable resin is formed on the dielectric layer 96 by spin coating, and the protective film 97 is formed by curing the resin film by ultraviolet irradiation.

  In the magneto-optical recording medium X4, since the soft magnetic layer 92 having a high magnetic permeability exists, the magnetic flux of the recording magnetic field applied from the magnetic recording head to the recording magnetic unit 91 is diffused by the recording magnetic unit 91 during recording. There is a tendency to concentrate. Therefore, the recording magnetic field sensitivity of the recording layer included in the recording magnetic part 91 is improved as compared with the case where the soft magnetic layer 92 is not present.

  In the conventional magneto-optical recording medium X4, a glass substrate or an aluminum substrate is often employed as the substrate S3. Since glass substrates and aluminum substrates are relatively expensive, it is desirable to put a relatively inexpensive resin substrate into practical use instead. However, in the conventional technique, a sputtering method is employed as a method for forming the soft magnetic layer 92. When the substrate S3 is made of resin, the soft magnetic layer 92 is appropriately formed on the substrate S3 by the sputtering method. There are many cases where this is not possible.

  In forming the soft magnetic layer 92 by the sputtering method, it is necessary to heat the substrate S3 to a relatively high temperature when the soft magnetic material is formed. When the substrate S3 is made of resin, if the substrate S3 and the soft magnetic layer 92 are cooled and contracted after the soft magnetic material is formed, the difference in thermal expansion coefficient between the resin material and the soft magnetic material is large. An unreasonable stress acts on the soft magnetic layer 92 having a smaller shrinkage than that. Therefore, when the soft magnetic layer 92 is formed on the resin substrate S3 by the sputtering method, cracks and peeling are likely to occur in the soft magnetic layer 92.

  On the other hand, from the viewpoint of realizing good throughput in the industrial production of the conventional magneto-optical recording medium X4, the soft magnetic layer 92 that requires a considerable thickness is not formed by a sputtering method. It is preferable to employ an electrolytic plating method. However, when a resin substrate is employed as the substrate S3 and a soft magnetic material is directly formed on the resin substrate by an electroless plating method, the magneto-optical layer is formed between the formed soft magnetic plating layer and the resin substrate. In the recording medium, sufficient bondability to withstand practical use cannot be obtained.

  The present invention has been conceived under such circumstances, and a front illumination type magneto-optical recording medium having good bonding properties between a soft magnetic plating layer formed by a plating method and a resin substrate. It is an object of the present invention to provide a method for manufacturing such a magneto-optical recording medium.

  According to a first aspect of the present invention, a magneto-optical recording medium is provided. This magneto-optical recording medium includes a resin substrate having a pre-groove surface on which a pre-groove is formed, a recording magnetic unit that performs a recording function and a reproducing function, and a soft magnetic layer provided between the resin substrate and the recording magnetic unit. A plating layer and an adhesion layer interposed between the resin substrate and the soft magnetic plating layer for improving the bondability of the resin substrate and the soft magnetic plating layer. The magneto-optical recording medium has a soft magnetic layer between the resin substrate and the recording magnetic part. Therefore, in the recording process and the reproducing process of the magneto-optical recording medium, the recording magnetic part is started from the side opposite to the substrate. On the other hand, a front illumination method in which laser irradiation is performed is adopted.

In the manufacture of a magneto-optical recording medium having such a configuration, after an adhesion layer is formed on a resin substrate, a soft magnetic plating layer is laminated on the adhesion layer by plating. The adhesion layer is made of a material having excellent adhesion to a substrate made of a resin material and excellent adhesion to a plating film made of a soft magnetic material. Examples of such materials include AlCr, Al, Cr, Ti, FeCo, Ni, NiP, Pd, SiN, and SiO ₂ . Since such an adhesion layer is interposed between the soft magnetic plating layer and the resin substrate, the present magneto-optical recording medium can obtain good bondability between the soft magnetic plating layer and the resin substrate. It is.

  In the magneto-optical recording medium according to the first aspect of the present invention, since the resin substrate itself functions as a pre-groove layer for forming the land groove shape in the recording magnetic part, the soft magnetic plating layer and the recording magnetic part It is not necessary to separately provide a pregroove layer between the two. Therefore, the soft magnetic plating layer and the recording magnetic part can be brought close to each other, and the function of the soft magnetic plating layer to improve the recording magnetic field sensitivity of the recording layer included in the recording magnetic part can be efficiently exhibited.

  In the magneto-optical recording medium according to the first aspect of the present invention, a relatively inexpensive resin substrate is employed in place of the glass substrate or aluminum substrate employed in conventional media. Therefore, this magneto-optical recording medium is suitable for reducing the manufacturing cost.

  In the magneto-optical recording medium according to the first aspect of the present invention, the soft magnetic layer for increasing the recording magnetic field sensitivity of the recording layer has a good throughput instead of the sputtering method conventionally employed in the production of the medium. Can be formed by an electroless plating method capable of realizing the above. Therefore, the magneto-optical recording medium is suitable for improving the production efficiency.

  According to the second aspect of the present invention, another magneto-optical recording medium is provided. The magneto-optical recording medium includes a resin substrate, a recording magnetic part that performs a recording function and a reproducing function, a soft magnetic plating layer provided between the resin substrate and the recording magnetic part, and a recording magnetic property from the soft magnetic plating layer. A pre-groove layer provided between the resin substrate and the soft magnetic plating layer, and an adhesion layer interposed between the resin substrate and the soft magnetic plating layer for improving the bondability between the resin substrate and the soft magnetic plating layer. The magneto-optical recording medium has a soft magnetic layer between the resin substrate and the recording magnetic part. Therefore, in the recording process and the reproducing process of the magneto-optical recording medium, the recording magnetic part is started from the side opposite to the substrate. On the other hand, a front illumination method in which laser irradiation is performed is adopted.

  In the manufacture of a magneto-optical recording medium having such a configuration, after an adhesion layer is formed on a resin substrate, a soft magnetic plating layer is laminated on the adhesion layer by plating. The adhesion layer is made of a material having excellent adhesion to a substrate made of a resin material and excellent adhesion to a plating film made of a soft magnetic material. Therefore, in the magneto-optical recording medium, good bondability can be obtained between the soft magnetic plating layer and the resin substrate, similarly to the magneto-optical recording medium according to the first aspect.

  In the magneto-optical recording medium according to the second aspect of the present invention, the pre-groove layer to which the concave / convex shape of the pre-groove forming stamper is directly transferred and the recording magnetic portion are close to each other. Such a configuration is suitable for realizing a land groove shape having high dimensional accuracy in the recording magnetic part.

  In the magneto-optical recording medium according to the second aspect of the present invention, since a relatively inexpensive resin substrate is employed, the magneto-optical recording medium is suitable for reducing the manufacturing cost. In the magneto-optical recording medium, the soft magnetic layer for increasing the recording magnetic field sensitivity of the recording layer can be formed by an electroless plating method capable of realizing a good throughput. The medium is suitable for improving the production efficiency.

In the first and second aspects of the present invention, preferably, the adhesion layer is made of a material selected from the group consisting of AlCr, Al, Cr, Ti, FeCo, Ni, NiP, Pd, SiN, and SiO _2. Including. Such a configuration is suitable for obtaining an adhesion layer having excellent adhesion to the resin substrate and excellent adhesion to the soft magnetic plating layer.

  Preferably, the adhesion layer has a thickness of 5 to 30 nm. The function of the adhesion layer, which is to improve the bondability between the soft magnetic plating layer and the resin substrate, tends to be sufficiently exhibited when the thickness is 5 nm or more. On the other hand, for example, when the adhesion layer is formed by a sputtering method, an adhesion layer exceeding a thickness of 30 nm tends not to be properly formed on the resin substrate.

  Preferably, the soft magnetic plating layer is made of CoNiFe. CoNiFe is an amorphous soft magnetic alloy and is suitable for improving the recording magnetic field sensitivity of the recording layer in the magneto-optical recording medium.

  In the second aspect of the present invention, preferably, the pregroove layer is made of a resin material, and the magneto-optical recording medium includes the soft magnetic plating layer and the pregroove layer between the soft magnetic plating layer and the pregroove layer. An adhesion layer for further improving the bonding property of the groove layer is further provided. When the pregroove layer is made of a resin material, if the pregroove layer is directly provided on the soft magnetic plating layer, sufficient bonding may not be obtained between the two layers. This configuration is suitable for avoiding such a problem.

According to a third aspect of the present invention, a method for manufacturing a magneto-optical recording medium is provided. In this method, a resin substrate having a pregroove surface on which a pregroove is formed is formed on the pregroove surface from the group consisting of AlCr, Al, Cr, Ti, FeCo, Ni, NiP, Pd, SiN, and SiO _2. A process for forming an adhesion layer by depositing the selected material by sputtering, and a soft magnetic plating layer is formed by depositing a soft magnetic material on the adhesion layer by electroless plating And a step for forming a recording magnetic part that bears a recording function and a reproducing function. The recording magnetic part is formed after forming a heat radiating part, a dielectric layer, etc. on the soft magnetic plating layer.

According to such a method, the magneto-optical recording medium according to the first aspect of the present invention can be appropriately manufactured. Therefore, according to the third aspect of the present invention, the effects described above with respect to the first aspect can be achieved in the produced magneto-optical recording medium. Further, according to a third aspect, the method of forming the Ki Tsu soft Me contained in the recording magnetic unit layer, since the electroless plating method is used, is possible to achieve good throughput in the formation of the soft magnetic layer it can.

According to the fourth aspect of the present invention, another method for manufacturing a magneto-optical recording medium is provided. In this method, a material selected from the group consisting of AlCr, Al, Cr, Ti, FeCo, Ni, NiP, Pd, SiN, and SiO ₂ is deposited on a resin substrate by sputtering. A step for forming a layer, a step for forming a soft magnetic plating layer by depositing a soft magnetic material on the adhesion layer by an electroless plating method, and a pull groove layer on the soft magnetic plating layer And a step for forming a recording magnetic part that bears a recording function and a reproducing function. The pregroove layer has a pregroove surface on which the pregroove is formed on the side opposite to the substrate. The recording magnetic part is formed after a heat radiating part, a dielectric layer, etc. are formed on the pre-groove layer.

According to such a method, the magneto-optical recording medium according to the second aspect of the present invention can be appropriately manufactured. Therefore, according to the fourth aspect of the present invention, the effect described above with respect to the second aspect can be achieved in the produced magneto-optical recording medium. Further, in the fourth aspect, as the formation method of Ki Tsu soft Me contained in the recording magnetic unit layer, since the electroless plating method is used, is possible to achieve good throughput in the formation of the soft magnetic layer it can.

According to the fifth aspect of the present invention, another method for manufacturing a magneto-optical recording medium is provided. In this method, a material selected from the group consisting of AlCr, Al, Cr, Ti, FeCo, Ni, NiP, Pd, SiN, and SiO ₂ is formed on a resin substrate by sputtering. A step for forming an adhesion layer, a step for forming a soft magnetic plating layer by depositing a soft magnetic material on the adhesion layer by an electroless plating method, and a step on the soft magnetic plating layer. Forming a second adhesion layer by depositing a material selected from the group consisting of AlCr, Al, Cr, Ti, FeCo, Ni, NiP, Pd, SiN, and SiO ₂ by sputtering. A step, a step for forming a pull groove layer made of a resin material on the second adhesion layer, and a step for forming a recording magnetic part that bears a recording function and a reproducing function. Including. The pregroove layer has a pregroove surface on which the pregroove is formed on the side opposite to the substrate. The recording magnetic part is formed after a heat radiating part, a dielectric layer, etc. are formed on the pre-groove layer.

According to such a method, the magneto-optical recording medium according to the second aspect of the present invention can be appropriately manufactured. Therefore, according to the fifth aspect of the present invention, the effect described above with respect to the second aspect is exerted in the produced magneto-optical recording medium. Further, according to the fifth aspect, as the formation method of Ki Tsu soft Me contained in the recording magnetic unit layer, since the electroless plating method is used, is possible to achieve good throughput in the formation of the soft magnetic layer it can.

  In the third to fifth aspects of the present invention, preferably, the adhesion layer is formed to a thickness of 5 to 30 nm. Preferably, the soft magnetic plating layer is formed by depositing CoNiFe.

  FIG. 1 shows a magneto-optical recording medium X1 according to the first embodiment of the present invention. The magneto-optical recording medium X1 includes a resin substrate S1, a recording magnetic part 11, a soft magnetic layer 12, an adhesion layer 13, a heat radiating part 14, a dielectric layer 15, and a protective film 16, and includes a front illumination system. It is configured as a magneto-optical disk.

  The resin substrate S1 is a part for ensuring the rigidity of the magneto-optical recording medium X1, and has a pregroove surface 1a on which the pregroove 1b is formed with a desired dimension. Such a resin substrate S1 is made of, for example, polycarbonate (PC) resin, polymethyl methacrylate (PMMA) resin, epoxy resin, or polyolefin resin.

  In this embodiment, the recording magnetic part 11 includes a recording layer 11a and a recording auxiliary layer 11b as shown in FIG.

  The recording layer 11a is a part having two functions of a land portion and / or a groove portion used as an information track, namely, thermomagnetic recording and reproduction using a magneto-optical effect, and includes a rare earth element and a transition metal. A perpendicular magnetization film made of an amorphous alloy and magnetized in the perpendicular direction with perpendicular magnetic anisotropy. The vertical direction means a direction perpendicular to the film surface of the magnetic film constituting the layer. As the rare earth element contained in the amorphous alloy constituting the recording layer 11a, Tb, Gd, Dy, Nd, Pr, or the like can be used. As the transition metal, Fe, Co, or the like can be used. More specifically, the recording layer 11a is made of, for example, TbFeCо, DyFeCо, or TbDyFeCо having a predetermined composition. The thickness of the recording layer 11a is, for example, 25 to 65 nm.

  The recording auxiliary layer 11b has a function of generating an exchange coupling force with the recording layer 11a to improve the recording magnetic field sensitivity of the recording layer 11a. The recording auxiliary layer 11b is a perpendicular magnetization film made of a rare earth-transition metal amorphous alloy.

In the present invention, the recording magnetic part 11 may be composed of only a single recording layer having both a recording function and a reproducing function, instead of the above-described structure. Alternatively, the recording magnetic part 11 includes a recording layer having a relatively large coercive force and performing a recording function, and a reproducing layer having a relatively large Kerr rotation angle in the reproducing laser and performing a reproducing function. It may have a structure. Alternatively, the recording magnetic unit 11 may have a three-layer structure including a recording layer, a reproducing layer, and an intermediate layer between them in order to realize MSR reproduction, MAMMOS reproduction, or DWDD reproduction. Good.

When the recording magnetic part 11 having such a magnetic structure is provided, each layer in each structure that the recording magnetic part 11 can take is made of an amorphous alloy of a rare earth element and a transition metal, and has perpendicular magnetic anisotropy. It is a perpendicular magnetization film magnetized in the perpendicular direction. As the rare earth element, Tb, Gd, Dy, Nd, Pr, or the like can be used. As the transition metal, Fe, Co, or the like can be used. More specifically, as described above, the recording layer is made of, for example, TbFeCо, DyFeCо, or TbDyFeCо having a predetermined composition. When the reproduction layer is provided, the reproduction layer is made of, for example, GdFeCо, GdDyFeCо, GdTbDyFeCо, NdDyFeCо, NdGdFeCо, or PrDyFeCо having a predetermined composition. In the case of providing the intermediate layer, the intermediate layer is made of, for example, GdFe, TbFe, GdFeCо, GdDyFeCо, GdTbDyFeCо, NdDyFeCо, NdGdFeCо, or PrDyFeCо having a predetermined composition. The thickness of each layer is determined according to the magnetic structure desired for the recording magnetic part 11 .

  The soft magnetic layer 12 is a part for increasing the recording magnetic field sensitivity of the recording layer 11a included in the recording magnetic part 11, and is formed by forming a soft magnetic material having a high magnetic permeability by an electroless plating method. It is. Examples of the soft magnetic material include CoNiFe, FeCo, and FeNi. The thickness of the soft magnetic layer 12 is, for example, 200 to 1000 nm.

  During recording on the magneto-optical recording medium X1, the magnetic flux of the recording magnetic field applied to the recording layer 11a by the magnetic recording head from the protective film 16 side is due to the presence of the soft magnetic layer 12 below the recording layer 11a. Therefore, the recording layer 11a tends to concentrate without being diffused. Therefore, the recording magnetic field sensitivity of the recording layer 11a is improved as compared with the case where the soft magnetic layer 12 is not present.

The adhesion layer 13 is a part for interposing between the soft magnetic layer 12 formed by the electroless plating method and the resin substrate S1, and for improving the bondability between them, and is made of a resin base material (resin substrate It is made of a material having excellent adhesion to S1) and excellent adhesion to a plating film (soft magnetic layer 12) made of a soft magnetic material. Examples of such materials include AlCr, Al, Cr, Ti, FeCo, Ni, NiP, Pd, SiN, and SiO ₂ . The thickness of the adhesion layer 13 is 5 to 30 nm.

  The heat dissipating part 14 is a part for appropriately transmitting heat generated in the recording magnetic part 11 and the like by laser irradiation during recording and reproduction to the substrate S1. In the present embodiment, the heat radiating portion 14 has a laminated structure including heat conductive layers 14a and 14b and a heat distribution adjusting layer 14c, as shown in FIG.

The heat conductive layers 14a and 14b are made of a high heat conductive material. As the high heat conductive material, for example, Ag, Ag alloy, Al alloy (AlTi, AlCr, etc.), Au, or Pt can be adopted. The heat distribution adjusting layer 14c has a lower thermal conductivity than the heat conductive layers 14a and 14b, and is made of, for example, SiN. The heat distribution adjustment layer 14c made of SiN also functions as a dielectric layer between the substrate S1 and the recording magnetic part 11 . The thickness of the heat conductive layers 14a and 14b is, for example, 20 to 50 nm, and the thickness of the heat distribution adjusting layer 14c is, for example, 2 to 10 nm.

  In this invention, it may replace with such a structure about the thermal radiation part 14, and may be comprised by a single heat conductive layer, and may employ | adopt the two-layer structure of a heat conductive layer and a heat distribution adjustment layer.

The dielectric layer 15 is a part for avoiding or suppressing an external magnetic influence on the recording magnetic part 11 and is made of, for example, SiN, SiO ₂ , YSiO ₂ , ZnSiO ₂ , AlO, or AlN. The thickness of the dielectric layer 15 is, for example, 30 to 60 nm.

  The protective film 16 is made of a resin that is sufficiently transmissive to the recording laser and the reproducing laser of the magneto-optical recording medium X1, and has a thickness of, for example, 10 to 40 μm. Examples of the resin for forming the protective film 16 include acrylic resin, polycarbonate (PC) resin, epoxy resin, and polyolefin resin.

  3 and 4 show a method for manufacturing the magneto-optical recording medium X1. In manufacturing the magneto-optical recording medium X1, first, a resin substrate S1 having a pregroove surface 1a on which a pregroove 1b is formed as shown in FIG. 3A is prepared. The resin substrate S1 is formed by resin injection molding in which a Ni stamper manufactured through a conventional optical disk master manufacturing process is disposed in a mold. The Ni stamper has an uneven shape for forming the pregroove 1b on the resin substrate S1.

  Next, as shown in FIG. 3B, the adhesion layer 13 is formed on the pre-groove surface 1a of the resin substrate S1. The adhesion layer 13 can be formed by depositing the above-described material for forming the adhesion layer 13 on the pre-groove surface 1a by sputtering.

  Next, as shown in FIG. 3C, the soft magnetic layer 12 is formed on the adhesion layer 13 by electroless plating. Specifically, first, the resin substrate S1 having the adhesion layer 13 formed on the surface thereof is immersed in a tin chloride aqueous solution (1 to 5 wt%, room temperature), and then sufficiently washed with water. Tin chloride contained in the aqueous solution is adsorbed on the surface of the adhesion layer 13 and functions as a palladium adsorption nucleus described later. Next, the resin substrate S1 is immersed in an aqueous palladium chloride solution (0.01 to 0.1 wt%, room temperature), and then sufficiently washed with water. Palladium contained in the aqueous solution is adsorbed on the surface of the adhesion layer 13 using tin chloride as a nucleus, and functions as a catalyst nucleus in the subsequent plating growth. Next, the substrate S1 is immersed in a plating bath having a predetermined composition, and a soft magnetic plating film is grown by an electroless plating method. The plating bath contains a predetermined concentration of Co, Ni, Fe or the like according to the composition of the soft magnetic layer 12 to be formed. The plating bath preferably contains a predetermined concentration of B.

  In the manufacture of the magneto-optical recording medium X1, next, as shown in FIG. 4A, the heat radiating portion 14 (the heat conducting layer 14a, the heat distribution adjusting layer 14c, the heat conducting layer 14b) and the recording magnetic portion are formed on the soft magnetic layer 12. 11 (recording auxiliary layer 11b, recording layer 11a) and dielectric layer 15 are sequentially formed. Each layer can be formed by a sputtering method.

  Next, as shown in FIG. 4B, a protective film 16 is formed on the dielectric layer 15. In forming the protective film 16, first, a liquid resin composition is formed on the dielectric layer 15. As a film forming method, a spin coating method can be employed. As the resin composition, an ultraviolet curable resin having the above-described resin as a constituent material of the protective film 16 as a main component is used. Next, the resin film is cured by ultraviolet irradiation. In this way, the protective film 16 can be formed.

  As described above, the magneto-optical recording medium X1 shown in FIGS. 1 and 2 can be manufactured.

  In the magneto-optical recording medium X1, since the soft magnetic layer 12 having high permeability exists, the magnetic flux of the recording magnetic field applied from the magnetic recording head to the recording layer 11a does not diffuse in the recording layer 11a during recording. There is a tendency to concentrate. Therefore, the recording magnetic field sensitivity of the recording layer 11a is improved as compared with the case where the soft magnetic layer 12 is not present.

  In the recording process and the reproducing process of the magneto-optical recording medium X1, when the laser irradiation is performed on the recording magnetic part 11 from the protective film 16, the soft magnetic layer 12 protects the recording magnetic part 11 (recording layer 11a). Since it is provided on the side opposite to the film 16, it does not hinder such front illumination type recording processing and reproducing processing.

  In the manufacture of the magneto-optical recording medium X1, after the adhesion layer 13 is formed on the resin substrate S1, the soft magnetic layer 12 is laminated on the adhesion layer 13 by electroless plating. The adhesion layer 13 is made of a material having excellent adhesion to the substrate made of a resin material (resin substrate S1) and excellent adhesion to the plating film made of the soft magnetic material (soft magnetic layer 12). Since such an adhesion layer 13 is interposed between the resin substrate S1 and the soft magnetic layer 12, in the magneto-optical recording medium X1, a good bonding property is provided between the resin substrate S1 and the soft magnetic layer 12. Can be achieved.

  In the magneto-optical recording medium X1, since the resin substrate S1 itself functions as a pregroove layer for forming the land groove shape in the recording magnetic part 11, the pregroove layer is interposed between the soft magnetic layer 12 and the recording magnetic part 11. Need not be provided separately. Therefore, the soft magnetic layer 12 and the recording magnetic part 11 can be brought close to each other to effectively exhibit the function of the soft magnetic layer 12 to improve the recording magnetic field sensitivity of the recording layer 11a.

  In the magneto-optical recording medium X1, a relatively inexpensive resin substrate is employed instead of the glass substrate or aluminum substrate employed in conventional media. Therefore, the magneto-optical recording medium X1 is suitable for reducing the manufacturing cost.

  In the magneto-optical recording medium X1, the soft magnetic layer 12 for increasing the recording magnetic field sensitivity of the recording layer 11a is not capable of realizing a good throughput in place of the sputtering method employed in the manufacture of conventional media. It is formed by electrolytic plating. Therefore, the magneto-optical recording medium X1 is suitable for improving the manufacturing efficiency.

  5 and 6 show a magneto-optical recording medium X2 according to the second embodiment of the present invention. The magneto-optical recording medium X2 includes a resin substrate S2, a recording magnetic part 11, a soft magnetic layer 12, an adhesion layer 13, a heat dissipation part 14, a dielectric layer 15, a protective film 16, and a pregroove layer 17. And is configured as a front-illuminated magneto-optical disk.

  The resin substrate S2 is a part for ensuring the rigidity of the magneto-optical recording medium X2, and is a flat disk substrate. Such a resin substrate S2 is made of, for example, polycarbonate (PC) resin, polymethyl methacrylate (PMMA) resin, epoxy resin, or polyolefin resin.

  The configurations of the recording magnetic part 11, the soft magnetic layer 12, the adhesion layer 13, the heat radiation part 14, the dielectric layer 15, and the protective film 16 of the magneto-optical recording medium X2 are the same as those described above regarding the magneto-optical recording medium X1. is there.

  The pregroove layer 17 is made of a resin material and has a pregroove surface 17a on which a pregroove 17b is formed with a desired dimension. The pregroove layer 17 is made of, for example, an acrylic resin, a polycarbonate (PC) resin, an epoxy resin, or a polyolefin resin.

7 to 9 show a method for manufacturing the magneto-optical recording medium X2. In manufacturing the magneto-optical recording medium X2, first, a flat resin substrate S2 as shown in FIG. 7A is prepared. The resin substrate S2 is formed by resin injection molding in which a Ni stamper manufactured through a conventional optical disk master manufacturing process is disposed in a mold. The Ni stamper is flat so that the surface of the resin substrate S2 to be molded is flat.

  Next, as shown in FIG. 7B, the adhesion layer 13 is formed on the resin substrate S2. The formation method of the adhesion layer 13 is the same as that described above with reference to FIG. 3B regarding the first embodiment.

  Next, as shown in FIG. 7C, the soft magnetic layer 12 is formed on the adhesion layer 13 by electroless plating. The specific formation method is the same as that described above with reference to FIG. 3C regarding the first embodiment.

  Next, as shown in FIGS. 8A and 8B, a stamper 21 is bonded to the soft magnetic layer 12 via an ultraviolet curable resin 17 '. The stamper 21 is transparent and has a concavo-convex shape corresponding to the pregroove 17b to be formed of the ultraviolet curable resin 17 '. Thereafter, the ultraviolet curable resin 17 ′ is irradiated with ultraviolet rays from the stamper 21 side in a state where the stamper 21 is bonded to the soft magnetic layer 12. Thereby, the resin is cured and the pre-groove layer 17 is formed. Next, as shown in FIG. 8C, the stamper 21 is peeled from the pregroove layer 17.

  Next, as shown in FIG. 9A, on the pre-groove layer 17, the heat radiating portion 14 (the heat conducting layer 14a, the heat distribution adjusting layer 14c, the heat conducting layer 14b), the recording magnetic portion 11 (the recording auxiliary layer 11b, the recording layer 11a). ) And the dielectric layer 15 are sequentially formed. Each layer can be formed by a sputtering method.

  Next, as shown in FIG. 9B, a protective film 16 is formed on the pre-groove layer 17. The formation method of the protective film 16 is the same as that described above with reference to FIG. 4B regarding the first embodiment.

  As described above, the magneto-optical recording medium X2 shown in FIGS. 5 and 6 can be manufactured.

  In the magneto-optical recording medium X2, as in the magneto-optical recording medium X1, the recording magnetic field sensitivity of the recording layer 11a is improved as compared with the case where the soft magnetic layer 12 is not present.

  The magneto-optical recording medium X2 employs the front illumination method. Since the soft magnetic layer 12 is provided on the side opposite to the protective film 16 with respect to the recording magnetic portion 11 (recording layer 11a), the front illumination method recording is performed. Does not interfere with processing and regeneration processing.

In the manufacture of the magneto-optical recording medium X2, after the adhesion layer 13 is formed on the resin substrate S2, the soft magnetic layer 12 is laminated on the adhesion layer 13 by electroless plating. The adhesion layer 13 is made of a material that is excellent in adhesion to a substrate made of a resin material (resin substrate S2 ) and excellent in adhesion to a plating film (soft magnetic layer 12) made of a soft magnetic material. Since such an adhesion layer 13 is interposed between the resin substrate S2 and the soft magnetic layer 12, in the magneto-optical recording medium X2, a good bonding property is provided between the resin substrate S2 and the soft magnetic layer 12. Can be achieved.

  In the magneto-optical recording medium X2, the pregroove layer 17 and the recording layer 11a to which the uneven shape of the stamper for forming the pregroove is directly transferred are close to each other. Such a configuration is suitable for realizing the land groove shape having high dimensional accuracy in the recording magnetic unit 11.

  Since the magneto-optical recording medium X2 employs a relatively inexpensive resin substrate, the magneto-optical recording medium X2 is suitable for reducing the manufacturing cost.

  In the magneto-optical recording medium X2, the soft magnetic layer 12 for increasing the recording magnetic field sensitivity of the recording layer 11a is formed by an electroless plating method capable of realizing a good throughput. This is suitable for improving the production efficiency.

  10 and 11 show a magneto-optical recording medium X3 according to the third embodiment of the present invention. The magneto-optical recording medium X3 includes a resin substrate S2, a recording magnetic part 11, a soft magnetic layer 12, adhesion layers 13 and 18, a heat radiating part 14, a dielectric layer 15, a protective film 16, and a pregroove layer. 17 and configured as a front illumination type magneto-optical disk. The magneto-optical recording medium X3 has the same configuration as that of the magneto-optical recording medium X2, except that an adhesion layer 18 is further provided between the soft magnetic layer 12 and the pregroove layer 17.

The adhesion layer 18 is interposed between the soft magnetic layer 12 and the pregroove layer 17 formed by an electroless plating method, and is a part for improving the bonding property between them. The adhesion layer 18 is made of a material having excellent adhesion to the resin pregroove layer 17 and excellent adhesion to the soft magnetic layer 12 formed by an electroless plating method. Examples of such materials include AlCr, Al, Cr, Ti, FeCo, Ni, NiP, Pd, SiN, and SiO ₂ . The thickness of the adhesion layer 18 is 5 to 30 nm.

  The magneto-optical recording medium X3 having such a structure is formed after the soft magnetic layer 12 is formed and the adhesion layer 18 is further formed on the soft magnetic layer 12 before the pregroove layer 17 is formed. It is manufactured through the same process as the magneto-optical recording medium X2. As a method for forming the adhesion layer 18, a sputtering method is employed.

  The magneto-optical recording medium X3 can enjoy the same benefits as described above for the magneto-optical recording medium X2.

  In addition, in the magneto-optical recording medium X3, the adhesion layer 18 having excellent adhesion to the soft magnetic layer 12 and excellent adhesion to the pregroove layer 17 made of a resin material is included in the soft magnetic layer 12 and the pregroove layer 17. Therefore, good bondability can be achieved between the soft magnetic layer 12 and the pregroove layer 17.

[Example 1]
A magneto-optical recording medium of this example was manufactured as a front-illuminated magneto-optical disk having the laminated structure shown in FIG.

  In producing the magneto-optical recording medium of this example, first, a polycarbonate substrate having a spiral pre-groove on its surface (diameter: 86 mm, thickness: 1.2 mm, land width: 0.275 μm, groove width: 0.275 μm, groove depth: 50 nm). Specifically, the substrate was formed by resin injection molding in which a Ni stamper having a spiral pattern with a depth of 50 nm and a track pitch of 0.275 μm on the surface was placed in a mold.

  Next, an adhesion layer having a thickness of 30 nm was formed on the pregroove surface of the substrate by depositing Ti by a DC sputtering method using a DC magnetron sputtering apparatus. In this sputtering, a Ti target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the discharge power was 400 W.

  Next, a 1000 nm thick soft magnetic layer was formed on the adhesion layer by electroless plating. Specifically, first, the substrate on which the adhesion layer was formed as described above was immersed in a 3 wt% tin chloride aqueous solution (35 ° C.) for 1 minute, and then washed with pure water. Next, the substrate was immersed in a 0.05 wt% palladium chloride aqueous solution (35 ° C.) for 1 minute and then washed with pure water. Next, the substrate was immersed in an electroless plating bath (55 ° C.) for a predetermined time, and then washed with pure water. The electroless plating bath is an aqueous solution containing 0.1 wt% dimethylamine borane, 0.3 wt% nickel sulfate, 0.3 wt% iron sulfate, and 3 wt% cobalt sulfate. In this way, a 1000 nm thick soft magnetic layer (CoNiFe) was formed by electroless plating.

  Next, an AgPdCuSi alloy film was formed on the soft magnetic layer by DC sputtering to form a first heat conductive layer having a thickness of 10 nm. Specifically, co-sputtering using an AgPdCu alloy target and a Si target is performed, Ar gas is used as a sputtering gas, the sputtering gas pressure is 0.5 Pa, the discharge power for the AgPdCu alloy target is 500 W, and the Si target The discharge power for was set to 40W.

Next, a 5 nm thick heat distribution adjusting layer was formed by depositing SiN on the first heat conductive layer by DC sputtering. Specifically, SiN was formed on the substrate by reactive sputtering performed using an Si target and using Ar gas and N ₂ gas as sputtering gas. In this sputtering, the flow ratio of Ar gas and N ₂ gas was 3: 1, the sputtering gas pressure was 1.5 Pa, and the discharge power was 800 W.

  Next, an AgPdCuSi alloy film was formed on the heat distribution adjusting layer by DC sputtering to form a second heat conductive layer having a thickness of 30 nm. Specific sputtering conditions are the same as those described above regarding the formation of the first heat conductive layer. In this way, a heat dissipation portion composed of the first heat conductive layer (AgPdCuSi, thickness 10 nm), the heat distribution adjustment layer (SiN, thickness 5 nm), and the second heat conductive layer (AgPdCuSi, thickness 30 nm) is provided. Formed.

In the production of the magneto-optical recording medium of the present example, a GdFeCo amorphous alloy (Gd ₂₅ Fe ₄₉ Co ₂₆ ) was then formed on the second heat conductive layer by DC sputtering to have a thickness of 5 nm. The recording auxiliary layer was formed. In this sputtering, a GdFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 500 W.

Next, a TbFeCo amorphous alloy (Tb ₂₃ Fe ₆₁ Co ₁₆ ) was formed on the recording auxiliary layer by DC sputtering to form a recording layer having a thickness of 25 nm. In this sputtering, a TbFeCo alloy target was used, Ar gas was used as the sputtering gas, the sputtering gas pressure was 1.5 Pa, and the discharge power was 500 W. In this way, a recording magnetic part composed of the recording layer (Tb ₂₃ Fe ₆₁ Co ₁₆ , thickness 25 nm) and the recording auxiliary layer (Gd ₂₅ Fe ₄₉ Co ₂₆ , thickness 5 nm) was formed, which bears the recording function and the reproducing function. .

Next, a dielectric layer having a thickness of 50 nm was formed by depositing SiN on the recording layer. Specifically, SiN was formed on the substrate by reactive sputtering performed using an Si target and using Ar gas and N ₂ gas as sputtering gas. In this sputtering, the flow ratio of Ar gas and N ₂ gas was 3: 1, the sputtering gas pressure was 1.5 Pa, and the discharge power was 800 W.

  Next, a transparent protective film having a thickness of 15 μm was formed on the dielectric layer. Specifically, first, an ultraviolet curable resin (trade name: Dicure Clear, manufactured by Dainippon Ink) was formed to a thickness of 15 μm on the dielectric layer by spin coating. Next, the ultraviolet curable resin film was cured by ultraviolet irradiation to form a protective film on the dielectric layer. As described above, the magneto-optical recording medium of this example was produced.

  For the magneto-optical recording medium of this example, the recording magnetic field dependence of the bit error rate (BER) in the reproduction signal was examined. Specifically, first, a random signal having a shortest mark length of 0.15 μm was recorded on information tracks (groove track and land track) on a magneto-optical recording medium (magneto-optical disk). The recording process was performed by a magnetic field modulation recording method using a predetermined optical disk evaluation apparatus. The numerical aperture NA of the objective lens in this evaluation apparatus is 0.85, and the laser wavelength is 405 nm. In the recording process, the laser scanning speed was 7.5 m / s, and a predetermined applied magnetic field (recording magnetic field) was modulated while continuously irradiating a laser (laser power of 18 mW) for each information track.

  Next, by reproducing only the groove track or only the land track on the magneto-optical recording medium, and comparing the modulation signal at the time of recording with the demodulated signal at the time of reproduction, the error rate of the reproduced demodulated signal with respect to the recorded modulation signal is bit Calculated as error rate (BER). The reproduction process was performed using the same evaluation apparatus as the recording process, the laser power was 18 mW, and the laser scanning speed was 7.5 m / s.

  Such recording processing and subsequent reproduction processing were performed for each recording magnetic field by changing the applied magnetic field (recording magnetic field) in the recording processing, and the BER in each recording magnetic field was measured. The dependence of the BER on the recording magnetic field in each magneto-optical recording medium is shown in the graph of FIG. In the graph of FIG. 14, the recording magnetic field (Oe) generated by the magnetic recording head is represented on the horizontal axis, and the BER is represented on the vertical axis. Line G shows the recording magnetic field dependence of BER in the groove track. A line L indicates the recording magnetic field dependency of BER in the land track.

  From the graph of FIG. 14, it can be understood that a relatively high recording magnetic field sensitivity is achieved in the magneto-optical recording medium of the present embodiment. It can also be seen that the recording layer sensitivity in the groove track is higher than the recording layer sensitivity in the land track.

[Comparative Example 1]
A magneto-optical device having the same layered structure as that of the magneto-optical recording medium of Example 1 except that a soft magnetic layer is directly provided on the resin substrate without a Ti adhesion layer interposed between the resin substrate and the soft magnetic layer. An attempt was made to produce a recording medium.

  First, in the same manner as in Example 1, a polycarbonate substrate having a spiral pregroove on its surface (diameter: 86 mm, thickness: 1.2 mm, land width: 0.275 μm, groove width: 0.275 μm, groove Depth: 50 nm).

Next, a soft magnetic material was grown on the pregroove surface of the substrate by the same electroless plating method as in Example 1. However, the soft magnetic plating layer could not be formed with good reproducibility. Even if it was possible to form a soft plating layer, in the step that follows, the material film had peeled from the substrate surface. Therefore, a magneto-optical recording medium could not be produced.

[Example 2]
A magneto-optical recording medium of this example was manufactured as a front-illuminated magneto-optical disk having the laminated structure shown in FIG.

  In the production of the magneto-optical recording medium of this example, first, a polycarbonate substrate (diameter: 86 mm, thickness: 1.2 mm) having a flat surface on which the adhesion layer is to be laminated was produced. Specifically, the substrate was formed by resin injection molding in which a flat Ni stamper having no pregroove pattern was disposed in a mold.

  Next, an adhesion layer (Ti, thickness: 30 nm) and a soft magnetic layer (CoNiFe, thickness: 1000 nm) were sequentially formed on the flat surface of the substrate in the same manner as in Example 1.

  Next, after applying an ultraviolet curable resin (trade name: Iupimer, manufactured by Mitsubishi Chemical) on the soft magnetic layer, a transparent stamper was bonded to the soft magnetic layer. This transparent stamper has a spiral pattern with a depth of 50 nm and a track pitch of 0.275 μm on the contact surface with the resin. After the resin was cured by ultraviolet irradiation, the stamper was peeled off from the resin. Thus, a pre-groove layer (thickness: 10 μm, land width: 0.275 μm, groove width: 0.275 μm, groove depth: surface having a spiral pre-groove formed by transferring the spiral pattern of the stamper. 50 nm) was formed.

  In the production of the magneto-optical recording medium, the first heat conductive layer (AgPdCuSi, thickness: 10 nm), the heat distribution adjustment layer (Si, thickness) are then formed on the pregroove layer in the same manner as in Example 1. Thickness: 5 nm), second heat conductive layer (AgPdCuSi, thickness: 30 nm), recording auxiliary layer (GdFeCo, thickness: 5 nm), recording layer (TbFeCo, thickness: 25 nm), dielectric layer (SiN, thickness) Thickness: 50 nm) and a protective layer (ultraviolet curable transparent resin, thickness: 15 μm) were sequentially formed. As described above, the magneto-optical recording medium of this example was produced.

  Regarding the magneto-optical recording medium of this example, the recording magnetic field dependency of BER was examined in the same manner as in Example 1. As a result, substantially the same characteristics as those of the magneto-optical recording medium of Example 1 were obtained.

FIG. 1 is a partial sectional view of a magneto-optical recording medium according to the first embodiment of the present invention. FIG. 2 shows a stacked structure in the information track of the magneto-optical recording medium shown in FIG. 3A to 3C show some steps in the method of manufacturing the magneto-optical recording medium shown in FIG. 4A and 4B represent the process following FIG. 3C. FIG. 5 is a partial sectional view of a magneto-optical recording medium according to the second embodiment of the present invention. FIG. 6 shows a stacked structure in the information track of the magneto-optical recording medium shown in FIG. 7A to 7C show some steps in the method of manufacturing the magneto-optical recording medium shown in FIG. 8A to 8C show a process subsequent to FIG. 7C. 9A and 9B represent the process that follows FIG. 8C. FIG. 10 is a partial cross-sectional view of a magneto-optical recording medium according to the third embodiment of the present invention. FIG. 11 shows a stacked structure in the information track of the magneto-optical recording medium shown in FIG. FIG. 12 shows a stacked structure in the information track of the magneto-optical recording medium of Example 1. FIG. 13 shows a stacked structure in the information track of the magneto-optical recording medium of the second embodiment. FIG. 14 shows the dependence of the bit error rate on the recording magnetic field for the groove track and land track in the magneto-optical recording medium of Example 1. FIG. 15 shows a laminated structure of a conventional magneto-optical recording medium having a soft magnetic layer.

Claims (2)

Forming a first adhesion layer on the resin substrate by depositing Ti by a sputtering method;
A step for forming a soft magnetic plating layer by depositing CoNiFe on the adhesion layer by an electroless plating method;
Forming a second adhesion layer on the soft magnetic plating layer by depositing Ti by a sputtering method;
Forming a pull groove layer made of a resin material on the second adhesion layer;
And a step for forming a recording magnetic part that bears a recording function and a reproducing function. A resin substrate;
A first adhesion layer located on the resin substrate and formed of Ti ;
A soft magnetic plating layer formed of CoNiFe on the first adhesion layer;
A second adhesion layer located on the soft magnetic plating layer and formed of Ti ;
A pregroove layer located on the second adhesion layer and formed of a resin material;
A magneto-optical recording medium comprising: a recording magnetic unit that is located on the pre-groove layer and performs a recording function and a reproducing function .

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