JP2006127657A - Magnetooptical recording medium and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetooptical recording medium suitable for forming a large recording magnetic field at a recording layer, and to provide a manufacturing method thereof. <P>SOLUTION: The magnetooptical recording medium X1 has a laminated structure comprising a substrate S1, the recording layer 11a having a recording function and a soft magnetic part 12 positioned between the substrate S1 and the recording layer 11a. A plane 12a' on the side of the recording layer 11a of the soft magnetic part 12 has a projected and recessed shape. It is preferable that the surface roughness of the plane 12a' is 1 to 5 nm, and that the average height of projecting parts in the projecting and recessed shape is 3 to 30 nm. For example, the manufacturing method of the magnetooptical recording medium comprises a process for forming a soft magnetic film on a base material, a process for forming the soft magnetic part 12 having the projected and recessed shape on its surface by carrying out sputter etching to the exposed surface of the soft magnetic film, and a process for forming the recording layer 11a at the uper part of the soft magnetic part 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magneto-optical recording medium having a soft magnetic layer for enhancing a recording magnetic field and a manufacturing method thereof.

  A magneto-optical recording medium is known as one form of optical media from which information is optically read. A magneto-optical recording medium is a rewritable medium that is thermomagnetically recorded and reproduced using the magneto-optical effect.

  FIG. 10 shows a magneto-optical disk X2 which is an example of a conventional magneto-optical recording medium. The magneto-optical disk X2 has a laminated structure comprising a substrate S2, 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. 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 magnetic films depending on the reproduction method. Become. The magnetic film is a rare earth-transition metal amorphous alloy perpendicular magnetization film. The soft magnetic layer 92 is made of a soft magnetic material having a high magnetic permeability, a large saturation magnetization, and a small coercive force. The pregroove layer 93 is made of a resin material, and an uneven shape (not shown) such as a pregroove is formed on the surface on the recording magnetic portion 91 side. The heat conductive layer 94 is a part for efficiently transmitting heat generated in the recording magnetic part 91 or the like to the substrate S2 side when the laser beam is irradiated, and is made of a high heat conductive material. The dielectric layers 95 and 96 are parts for avoiding an unreasonable magnetic influence from the outside 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 information recording on the magneto-optical disk X2, for example, a recording laser beam is irradiated as a continuous pulse from the protective film 97 side to the recording magnetic part 91 while the disk is rotated. While the recording magnetic unit 91 is locally heated in sequence, a recording magnetic field modulated in a predetermined manner is applied to the temperature rising portion by a magnetic recording head (not shown). In this way, predetermined information or signals are recorded as changes in the magnetization direction in the recording magnetic part 91 or the recording layer included therein.

  In the magneto-optical disk X2, the soft magnetic layer 92 having a high magnetic permeability, a large saturation magnetization, and a small coercive force exists in the vicinity of the recording magnetic part 91. The magnetic flux of the recording magnetic field (represented by the alternate long and short dash line) applied from the magnetic recording head to the recording magnetic part 91 passes through the recording magnetic part 91 so as to bypass the soft magnetic layer 92 as shown in FIG. Thus, the recording magnetic part 91 is concentrated. That is, the recording magnetic field formed by the recording magnetic part 91 is enhanced as compared with the case where the soft magnetic layer 92 is not present. Effective enhancement of the recording magnetic field is preferable for appropriately realizing recording at a higher frequency, that is, high-speed recording, and high-speed recording is important for practical use of a magneto-optical recording medium having a high recording density. A magneto-optical recording medium having a soft magnetic layer such as the magneto-optical disk X2 is described in, for example, Patent Document 1 and Patent Document 2 below.

Japanese Patent Application Laid-Open No. 11-191247 JP 2004-103130 A

  However, in the conventional magneto-optical disk X2, the above-described enhancement of the recording magnetic field due to the presence of the soft magnetic layer 92 may not be sufficient. In the manufacturing process of the magneto-optical disk X2 according to the prior art, the soft magnetic layer 92 is formed on the substrate S2 as a thin film having a substantially flat surface (surface on the recording magnetic portion 91 side). This is probably because the higher the surface flatness of 92, the lower the degree of magnetic flux concentration described above for the recording magnetic field formed in the recording magnetic part 91.

  The present invention has been conceived under such circumstances, and an object thereof is to provide a magneto-optical recording medium suitable for forming a large recording magnetic field in a recording layer and a method for manufacturing the same. To do.

  According to a first aspect of the present invention, a magneto-optical recording medium is provided. This magneto-optical recording medium has a laminated structure including a substrate, a recording layer that bears a recording function, and a soft magnetic portion positioned between the substrate and the recording layer, and the surface of the soft magnetic portion on the side of the recording layer is , Having an uneven shape. The soft magnetic part in the present invention includes a single soft magnetic layer made of a soft magnetic material having a uniform composition. In addition, a soft magnetic layer and a non-soft magnetic layer (for example, a dielectric layer) are alternately arranged, and the side closest to the recording layer has a multilayer structure composed of a soft magnetic layer. A portion exhibiting the function to enhance (recording magnetic field enhancement function) as a whole is also included in the soft magnetic part of the present invention.

  The soft magnetic part in the magneto-optical recording medium according to the first aspect of the present invention has an irregular shape on the surface on the recording layer side, so that the surface on the recording layer side is substantially flatter than the conventional soft magnetic layer. Excellent recording magnetic field enhancement function.

  At the time of recording information on the conventional magneto-optical disk X2, when a recording magnetic field is applied to the recording magnetic part 91 or the recording layer by the magnetic recording head, as described above with reference to FIG. A recording magnetic field is formed so as to bypass the recording magnetic unit 91. At this time, since the surface of the soft magnetic layer 92 on the side of the recording magnetic portion 91 is substantially flat as described above, a magnetic pole appears uniformly on the surface of the soft magnetic layer 92 and passes through the uniform magnetic pole. Magnetic flux is generated. Therefore, the directivity of the generated magnetic flux is low, and the magnetic flux tends to diffuse radially on the surface of the soft magnetic layer 92.

  On the other hand, in the magneto-optical recording medium according to the first aspect of the present invention, when a magnetic field is applied, the magnetic poles are concentrated on the convex portions of the concavo-convex shape on the surface of the soft magnetic portion and pass through the concentrated magnetic poles. Magnetic flux is generated. Therefore, in the magneto-optical recording medium, a highly directional magnetic flux can be generated, and the magnetic flux can be prevented from diffusing radially on the surface of the soft magnetic part. As the diffusion of the magnetic flux on the surface of the soft magnetic part is suppressed, the magnetic flux passing through the recording layer is concentrated, and the recording magnetic field formed in the recording layer is enhanced.

  In addition, in the magneto-optical recording medium according to the first aspect of the present invention, the magnetic poles are concentrated on the convex and concave portions on the surface of the soft magnetic part when a magnetic field is applied. The substantial magnetic pole area occupied is smaller than when the magnetic poles appear uniformly on the surface of the soft magnetic layer 92 in the magneto-optical disk X2. As the magnetic pole area on the surface of the soft magnetic portion is smaller, the density of magnetic flux generated so as to pass through the magnetic pole tends to increase. The larger the magnetic flux density, the larger the recording magnetic field formed in the recording layer.

  As described above, the soft magnetic part in the magneto-optical recording medium according to the first aspect of the present invention has an uneven shape on the surface on the recording layer side, and thus has an excellent recording magnetic field enhancement function. The magneto-optical recording medium of this side is suitable for forming a large recording magnetic field in the recording layer.

  In the first aspect of the present invention, preferably, the surface roughness Ra (arithmetic mean roughness) of the recording layer side surface in the soft magnetic portion is 1 to 5 nm, and the convex portion in the concavo-convex shape of the recording layer side surface is provided. The average height (average of the maximum height Ry) is 3 to 30 nm. Such a configuration is suitable for appropriately realizing both the suppression of the magnetic flux diffusion on the surface of the soft magnetic portion and the increase of the magnetic flux density due to the reduction of the magnetic pole area on the surface of the soft magnetic portion.

  According to a second aspect of the present invention, a method for manufacturing a magneto-optical recording medium is provided. This method includes a step for forming a soft magnetic film on a substrate, and a step for forming a soft magnetic layer having an uneven shape on the surface by performing sputter etching on the exposed surface of the soft magnetic film. And a step for forming a recording layer above the soft magnetic layer. The base material in the present invention includes the substrate itself and a substrate in which a certain layer has already been formed. According to such a method, the soft magnetic part according to the first aspect of the present invention can be appropriately formed, and therefore the magneto-optical recording medium according to the first aspect can be appropriately manufactured.

  According to the third aspect of the present invention, another method for manufacturing a magneto-optical recording medium is provided. In this method, the surface of the substrate is exposed to oxygen plasma and roughened, and a soft magnetic material is formed on the substrate to form a soft magnetic layer having an uneven shape on the growth end face. And a step for forming a recording layer above the soft magnetic layer. Also by such a method, the soft magnetic part according to the first aspect of the present invention can be appropriately formed, and therefore the magneto-optical recording medium according to the first aspect can be appropriately manufactured.

  According to the fourth aspect of the present invention, another method for manufacturing a magneto-optical recording medium is provided. In this method, a process for forming a soft magnetic layer having a concavo-convex shape on the growth end surface by forming a soft magnetic material on the substrate while heating the substrate, and recording on the upper layer of the soft magnetic layer Forming a layer. Also by such a method, the soft magnetic part according to the first aspect of the present invention can be appropriately formed, and therefore the magneto-optical recording medium according to the first aspect can be appropriately manufactured.

  According to the fifth aspect of the present invention, another method of manufacturing a magneto-optical recording medium is provided. This method includes a first step for forming a soft magnetic film by forming a first soft magnetic material on a substrate, and a plurality of protrusions by growing a second soft magnetic material on the soft magnetic film. And a second step for forming a soft magnetic layer comprising the plurality of protrusions and the soft magnetic film, and a third step for forming a recording layer above the soft magnetic layer. Also by such a method, the soft magnetic part according to the first aspect of the present invention can be appropriately formed, and therefore the magneto-optical recording medium according to the first aspect can be appropriately manufactured.

  In a preferred embodiment of the fifth aspect of the present invention, the second soft magnetic material has the same composition as the first soft magnetic material, and conditions for forming the first soft magnetic material in the first step; The conditions for growing the second soft magnetic material in the second step are made different. Alternatively, the second soft magnetic material has a composition different from that of the first soft magnetic material and has a larger surface tension than the first soft magnetic material. These methods are suitable for forming protrusions on the soft magnetic film.

  FIG. 1 is a partial sectional view of a magneto-optical disk X1 according to the present invention. The magneto-optical disk X1 includes a substrate S1, a recording magnetic part 11, a soft magnetic part 12, a pregroove layer 13, a heat conductive layer 14, dielectric layers 15 and 16, and a protective film 17, and a front surface. It is configured as an illumination type magneto-optical disk. The magneto-optical disk X1 has a structure from the soft magnetic part 12 to the protective film 17 only on one side or both sides of the substrate S1.

  The substrate S1 is a part for ensuring the rigidity of the magneto-optical disk X1, and is, for example, a disk substrate made of resin, silicon, aluminum, or glass.

  The recording magnetic part 11 has a laminated structure composed of a recording layer 11a, an intermediate layer 11b, and a reproducing layer 11c, and a magnetic domain expansion system reproducing system (for example, DWDD, MAMMOS, etc.) accompanied by domain wall movement or magnetic domain expansion in the reproducing layer 11c. ) Is configured to be reproducible based on.

  The recording layer 11a is a part responsible for the recording function in the magneto-optical disk X1, is made of an amorphous alloy containing a rare earth element and a transition metal, and has a perpendicular magnetic anisotropy and is perpendicularly magnetized in the perpendicular direction. It is a magnetized film. The vertical direction means a direction perpendicular to the film surface of the magnetic film constituting the layer. Specifically, the recording layer 11a is made of, for example, TbFeCо or TbDyFeCо having a predetermined composition ratio. The thickness of the recording layer 11a is, for example, 40 to 100 nm.

  The intermediate layer 11b is a part for changing the exchange coupling state of the recording layer 11a and the reproducing layer 11c. The intermediate layer 11b changes from the perpendicular magnetization state to the spontaneous magnetization disappearance state at the Curie temperature when the temperature rises, and the Curie temperature when the temperature falls. It is made of a rare earth-transition metal amorphous alloy that transitions from a spontaneous magnetization disappearance state to a perpendicular magnetization state. In the present embodiment, the Curie temperature of the intermediate layer 11b is, for example, 100 to 170 ° C. Therefore, the intermediate layer 11b is a perpendicular magnetization film at room temperature. Specifically, the intermediate layer 11b is made of, for example, TbFe or TbFeCо having a predetermined composition ratio. The thickness of the intermediate layer 11b is, for example, 10 to 30 nm.

  The reproducing layer 11c is a part that bears a reproducing function accompanied by domain wall movement or domain expansion, and is a perpendicular magnetization film made of a rare earth-transition metal amorphous alloy. Specifically, the reproducing layer 11c is made of, for example, GdFeCo or GdDyFeCo having a predetermined composition ratio. The reproducing layer 11c has a thickness of 10 to 50 nm.

  The soft magnetic portion 12 has a laminated structure in which the soft magnetic layers 12a and the dielectric layers 12b are alternately overlapped, and the side closest to the pre-groove layer 13 in the laminated structure (that is, the uppermost layer in the figure) is the soft magnetic layer. 12a. The soft magnetic layer 12a is made of a soft magnetic material having a high magnetic permeability, a large saturation magnetization, and a small coercive force, and is made of, for example, FeCoB, FeCoSiC, or FeCo—AlO. As a constituent material of the dielectric layer 12b, for example, SiN or ZnS can be employed. The soft magnetic portion 12 or the uppermost soft magnetic layer 12a has an uneven surface 12a 'with an uneven shape on the side of the pregroove layer 13 or the recording layer 11a. The surface roughness Ra (arithmetic average roughness) of the uneven surface 12a 'is 1 to 5 nm, and the average height (average of the maximum height Ry) of the convex portions of the uneven surface 12a' is 3 to 30 nm. From the viewpoint of improving the recording magnetic field strength, the uneven surface 12a 'preferably has an uneven shape defined by these ranges. Further, the thickness of the soft magnetic layer 12a is, for example, 50 to 200 nm, the thickness of the dielectric layer 12b is, for example, 1 to 10 nm, and the number of the soft magnetic layers 12a in the soft magnetic portion 12 is appropriately determined as necessary. Is set.

  In the magneto-optical disk X1 according to the present invention, a soft magnetic portion made of a soft magnetic material having a uniform composition may be provided in place of the soft magnetic portion 12 having the laminated structure as described above. Even when a soft magnetic part made of a soft magnetic material having a uniform composition is provided, the soft magnetic part has an uneven surface 12a 'on the pre-groove layer 13 or the recording layer 11a side.

  The pregroove layer 13 is made of a resin material, and an uneven shape (not shown) such as a pregroove is formed on the contact surface with the heat conductive layer 14. The pregroove has a spiral or concentric pattern shape, and a land groove shape in the magneto-optical disk X1 is realized based on the pregroove. A so-called 2P resin can be used as the resin material constituting the pregroove layer. The thickness of such a pregroove layer 13 is, for example, 5 to 25 μm.

  The heat conductive layer 14 is a part for efficiently transferring heat generated in the recording magnetic part 11 and the like to the substrate S1 side when the magneto-optical disk X1 is irradiated with a recording or reproducing laser beam. For example, it is made of a highly heat conductive material such as Ag, Ag alloy (AgPdCuSi, AgPdCu, etc.), Al alloy (AlN, AlSi, AlTi, AlCr, etc.), Au, or Pt. The thickness of the heat conductive layer 14 is, for example, 10 to 50 nm.

The dielectric layers 15 and 16 are parts for avoiding or suppressing an undesired magnetic influence from the outside on the recording magnetic part 11, for example, SiN, SiO ₂ , YSiO ₂ , ZnSiO ₂ , AlO, or AlN. It becomes more. The thickness of the dielectric layers 15 and 16 is, for example, 30 to 100 nm.

  The protective film 17 covers the recording magnetic part 11 in order to protect the recording magnetic part 11 from dust and the like, and is made of a resin material having sufficient permeability to the recording laser beam and the reproducing laser beam of the magneto-optical disk X1. Become. As the resin for forming the protective film 17, for example, an ultraviolet curable transparent resin is employed.

  In information recording on the magneto-optical disk X1, for example, a continuous laser pulse (not shown) is applied to the recording magnetic unit 11 from the protective film 17 side while the disk is rotated. By irradiating as a signal, the recording layer 11a in the recording magnetic part 11 is locally heated in sequence, and a predetermined modulated recording magnetic field is applied to the temperature rising point by a magnetic recording head (not shown). To do. In this way, predetermined information or signals can be recorded on the recording layer 11a as changes in the magnetization direction.

  In the magneto-optical disk X1, when a recording magnetic field is applied by the magnetic recording head, as shown in FIG. 2, the magnetic poles are concentrated on each convex portion of the soft magnetic portion 12 or the uneven surface 12a ′ of the uppermost soft magnetic layer 12a. A magnetic flux (represented by an alternate long and short dash line) is generated so as to pass through the concentrated magnetic pole. Therefore, in the magneto-optical disk X1, a highly directional magnetic flux can be generated, and the magnetic flux can be prevented from diffusing radially on the surface of the soft magnetic portion 12. As the diffusion of the magnetic flux on the surface of the soft magnetic portion 12 is suppressed, the magnetic flux passing through the recording layer 11a is concentrated, and the recording magnetic field formed in the recording layer 11a is enhanced.

  In addition, in the magneto-optical disk X1, when a recording magnetic field is applied by the magnetic recording head, the magnetic poles concentrate on each convex portion in the concave and convex shape of the concave and convex surface 12a ′ in the soft magnetic portion 12 or the uppermost soft magnetic layer 12a. The substantial magnetic pole area occupying the entire recording magnetic field application region on the surface of the soft magnetic portion 12 is smaller than the case where the magnetic pole appears uniformly on the surface of the soft magnetic portion 12. As the magnetic pole area is smaller, the density of magnetic flux generated to pass through the magnetic pole may tend to increase. The larger the magnetic flux density, the larger the recording magnetic field formed in the recording layer 11a.

  As described above, the soft magnetic part 12 in the magneto-optical disk X1 has an uneven surface 12a 'or an uneven shape on the recording layer 11a side, and thus has an excellent recording magnetic field enhancement function. Therefore, in the magneto-optical disk X1, a large recording magnetic field can be formed in the recording layer 11a.

  FIG. 3 shows a first method for manufacturing the magneto-optical disk X1. In this method, first, as shown in FIG. 3A, a soft magnetic portion 12 'is formed on a substrate S1. Specifically, for example, a predetermined material is formed on each of the layers by sputtering, for example, so that the soft magnetic layers 12a and the dielectric layers 12b are alternately formed on the substrate S1, and the soft magnetic layer 12a is provided on the outermost surface. A soft magnetic part 12 'is formed.

  Next, as shown in FIG. 3B, the exposed surface of the soft magnetic part 12 ′ (the outermost soft magnetic layer 12a) is sputter-etched to roughen the exposed surface and thereby provide an uneven surface 12a. 'Form. In this way, the soft magnetic part 12 having the uneven surface 12a 'can be formed on the substrate S1.

  Next, as shown in FIG. 3C, after the pregroove layer 13 is formed on the soft magnetic portion 12, the heat conductive layer 14, the dielectric layer 15, the recording layer 11a, The intermediate layer 11b, the reproduction layer 11c, and the dielectric layer 16 are sequentially formed. As a method for forming the pregroove layer 13, a so-called 2P method can be employed. Moreover, as a film forming method for each layer on the pregroove layer 13, a sputtering method can be employed.

  Next, as shown in FIG. 3D, a protective film 17 is formed on the dielectric layer 16. For example, the protective film 17 can be formed by depositing a transparent ultraviolet curable resin material on the dielectric layer 16 by spin coating and then irradiating the resin material with ultraviolet rays. As described above, the magneto-optical disk X1 can be appropriately manufactured.

  In the process described above with reference to FIG. 3A, a soft magnetic material made of a soft magnetic material having a uniform composition is used in place of the soft magnetic portion 12 ′ having a laminated structure including the soft magnetic layer 12a and the dielectric layer 12b. A magnetic part may be formed. Even in the case where such a soft magnetic part is formed on the substrate S1, by performing the same process as described above with reference to FIG. 3B, unevenness is formed on the exposed surface of the soft magnetic part. A surface 12a 'can be formed.

  FIG. 4 shows a second method for manufacturing the magneto-optical disk X1. In this method, first, as shown in FIG. 4A, a soft magnetic layer 12a and a dielectric layer 12b are alternately formed by depositing a predetermined material on each of them by, for example, a sputtering method. Then, the dielectric layer 12b is formed.

Next, oxygen plasma is applied to the exposed surface of the outermost dielectric layer 12b to roughen the exposed surface. Specifically, using a sputtering apparatus having a substrate heating function, heating is performed from the substrate S1 side to the dielectric layer 12b under the condition that the degree of vacuum in the apparatus chamber is 3 × 10 ⁻⁵ Pa or less. Oxygen plasma is generated in the chamber, and the oxygen plasma acts on the exposed surface of the dielectric layer 12b. In this method, the pressure of the oxygen atmosphere in the chamber is, for example, 0.2 to 1.0 Pa, and the substrate heating temperature is, for example, 150 to 300 ° C.

  Next, as shown in FIG. 4B, a soft magnetic layer 12a is formed on the outermost dielectric layer 12b by depositing a predetermined material, for example, by sputtering. At this time, due to the roughening of the surface of the dielectric layer 12b immediately below the soft magnetic layer 12a as described above, an uneven shape is formed on the growth end face of the soft magnetic layer 12a. In this way, the soft magnetic part 12 having the uneven surface 12a 'can be formed on the substrate S1.

  Next, as shown in FIG. 4C, on the soft magnetic portion 12, the pregroove layer 13, the heat conductive layer 14, the dielectric layer 15, the recording layer 11a, the intermediate layer 11b, the reproducing layer 11c, and the dielectric layer are formed. 16 and the protective film 17 are sequentially formed. The specific formation method is the same as that described above with reference to FIGS. 3C and 3D. The magneto-optical disk X1 can be appropriately manufactured also by the above method.

  FIG. 5 shows a third method for manufacturing the magneto-optical disk X1. In this method, first, as shown in FIG. 5A, a predetermined first soft magnetic material and dielectric material are formed on each of them by, for example, a sputtering method, thereby forming the soft magnetic layer 12a and the dielectric layer 12b. Are alternately formed, and then the soft magnetic film 12c is formed on the outermost surface (soft magnetic film forming step).

  Next, as shown in FIG. 5B, a plurality of protrusions 12d are formed by growing a second soft magnetic material on the soft magnetic film 12c by sputtering (protrusion forming step). In this manner, the soft magnetic portion 12 having the concavo-convex surface 12a 'or the outermost soft magnetic layer 12a is formed.

  When the second soft magnetic material in the protrusion forming step is the same composition as the first soft magnetic material in the soft magnetic film forming step, the conditions for forming the first soft magnetic material in the soft magnetic film forming step And the conditions for growing the second soft magnetic material in the protrusion forming step are made different. For example, a relatively high gas pressure condition is employed in this step. On the other hand, when the second soft magnetic material in the projection forming process adopts a composition different from that of the first soft magnetic material in the soft magnetic film forming process, the second soft magnetic material is selected from the first soft magnetic material. Those having a large surface tension are preferred. For example, FeCoB can be used as the first soft magnetic material, and FeCoSiC can be used as the second soft magnetic material.

  Next, as shown in FIG. 5C, on the soft magnetic portion 12, the pregroove layer 13, the heat conductive layer 14, the dielectric layer 15, the recording layer 11a, the intermediate layer 11b, the reproducing layer 11c, and the dielectric layer are formed. 16 and the protective film 17 are sequentially formed. The formation method is the same as that described above with reference to FIGS. 3C and 3D. The magneto-optical disk X1 can be appropriately manufactured also by the above method.

  FIG. 6 shows a fourth method for manufacturing the magneto-optical disk X1. In this method, for example, an aluminum substrate or a silicon substrate is employed as the substrate S1, and the substrate S1 is heated at a high temperature in a state where a soft magnetic material is not yet formed as shown in FIG. The heating temperature in this process is 400-500 degreeC, for example.

  Next, in a state where the substrate S1 is heated at a high temperature, as shown in FIG. 6B, a predetermined material is deposited on the substrate S1 by, for example, a sputtering method, so that a soft magnetic material having a uniform composition is formed. The magnetic part 12 is formed. At this time, the soft magnetic material grows on the substrate S1 with a relatively large particle size because the substrate S1 is heated at a high temperature (for example, 400 to 500 ° C.). As a result, a predetermined uneven shape is formed on the growth end face of the soft magnetic part 12. In this way, the soft magnetic portion 12 (made of a soft magnetic material having a uniform composition) having the uneven surface 12a 'can be formed on the substrate S1.

  Next, as shown in FIG. 6C, on the soft magnetic portion 12, the pregroove layer 13, the heat conductive layer 14, the dielectric layer 15, the recording layer 11a, the intermediate layer 11b, the reproducing layer 11c, and the dielectric layer are formed. 16 and the protective film 17 are sequentially formed. The specific formation method is the same as that described above with reference to FIGS. 3C and 3D. According to the above method, the magneto-optical disk X1 having the soft magnetic portion 12 made of the soft magnetic material having a uniform composition can be appropriately manufactured.

[Production of magneto-optical disk]
A magneto-optical disk of this example was manufactured as a front-illuminated magneto-optical disk having the laminated structure shown in FIG. The magneto-optical disk manufacturing method of this example corresponds to the first method described above with reference to FIG.

In producing the magneto-optical disk of this example, first, a soft magnetic part was formed on a glass substrate (diameter 120 mm, thickness 1.2 mm). Specifically, first, a soft magnetic layer having a thickness of 100 nm was formed by depositing Fe ₅₄ Co ₃₆ B ₁₀ on a glass substrate by a sputtering method. In this sputtering, an Fe ₅₄ Co ₃₆ B ₁₀ alloy target is used, Ar gas is used as the sputtering gas (the same applies to the following sputtering except reactive sputtering), the sputtering gas pressure is 0.5 Pa, and the sputtering power is 1 0.5 kW. Subsequently, a dielectric layer having a thickness of 5 nm was formed by forming SiN on the soft magnetic layer by a sputtering method. In this sputtering, SiN was formed on the soft magnetic layer by reactive sputtering 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 7: 3, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.8 kW. Thereafter, such soft magnetic layers and dielectric layers are alternately laminated to form a soft magnetic portion comprising a total of nine soft magnetic layers and a total of nine dielectric layers between the soft magnetic layers (the outermost surface is soft). Formed of a magnetic layer).

  Next, the exposed surface of the soft magnetic part (soft magnetic layer) formed as described above was sputter-etched to roughen the exposed surface to form an uneven surface. In this sputter etching, the sputtering gas pressure was 0.5 Pa, the sputtering power was 0.5 kW, and the etching time was 8 minutes. Thus, the soft magnetic part which has an uneven surface on the surface was formed. The surface roughness Ra (arithmetic average roughness) of the uneven surface was 1.5 nm, and the average height (average of the maximum height Ry) of the protrusions in the uneven shape was 8.0 nm. These values are listed in the table of FIG.

  Next, a 10 μm-thick pregroove layer was formed on the soft magnetic part by the 2P method. As the pregroove layer forming material, a resin for 2P method (photopolymer) was employed. Further, the surface irregularity shape of the pregroove layer was a land groove shape with a track pitch of 300 nm and a pregroove depth of 50 nm.

  Next, a 30 nm thick thermal conductive layer was formed by depositing AlSi on the pregroove layer by sputtering. Specifically, AlSi was formed on the substrate by co-sputtering using an Al target and an Si target. In this sputtering, the sputtering gas pressure was 0.6 Pa, and the sputtering power was 0.3 kW (Al target) and 0.2 kW (Si target).

Next, a dielectric layer having a thickness of 15 nm was formed by depositing SiN on the heat conductive layer by 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 7: 3, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.8 kW.

Next, a recording layer having a thickness of 60 nm was formed by depositing Tb ₂₄ Fe ₅₆ Co ₂₀ on the heat conductive layer by sputtering. Specifically, Tb ₂₄ Fe ₅₆ Co ₂₀ was formed on the heat conductive layer by co-sputtering using a Tb target and an FeCo alloy target. In this sputtering, the sputtering gas pressure was 1.5 Pa, and the sputtering power was 0.5 kW (Tb target) and 1.5 kW (FeCo alloy target).

Next, an intermediate layer having a thickness of 15 nm was formed by depositing Tb ₂₂ Fe ₇₈ on the recording layer by sputtering. Specifically, TbFe was formed on the recording layer by co-sputtering using a Tb target and an Fe target. In this sputtering, the sputtering gas pressure was 1.0 Pa, and the sputtering power was 0.3 kW (Tb target) and 0.9 kW (Fe target).

Next, a reproducing layer having a thickness of 25 nm was formed by depositing Gd ₂₅ Fe ₇₀ Co ₅ on the intermediate layer by sputtering. Specifically, Gd ₂₅ Fe ₇₀ Co ₅ was formed on the intermediate layer by co-sputtering using a Gd target and an FeCo alloy target. In this sputtering, the sputtering gas pressure was 0.4 Pa, and the sputtering power was 0.4 kW (Gd target) and 0.8 kW (FeCo alloy target).

Next, a dielectric layer having a thickness of 60 nm was formed by depositing SiN on the reproducing layer by sputtering. Specifically, SiN was formed on the reproduction layer by reactive sputtering 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 7: 3, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.8 kW.

  Next, a protective film having a thickness of 20 μm was formed on the dielectric layer. Specifically, first, an ultraviolet curable transparent resin was applied on the dielectric layer by spin coating. Next, the resin film was cured by ultraviolet irradiation. As described above, the magneto-optical disk of this example was manufactured.

[Measurement of recording magnetic field]
For the magneto-optical disk of this example, the intensity of the recording magnetic field formed in the recording layer when the magnetic field was applied by the magnetic recording head was measured. Specifically, the minimum magnetic field is specified from among the magnetic fields applied by the magnetic recording head that can record information on the magneto-optical disk so that the intensity (CNR) of the reproduction signal is saturated, and the minimum The intensity of the magnetic field formed on the medium surface when a magnetic field was applied was measured with a gauss meter as the intensity of the recording magnetic field formed so as to pass through the recording layer. As a result, the intensity of the recording magnetic field measured in this example was 330 Oe. The measured values are listed in the table of FIG.

[Production of magneto-optical disk]
A magneto-optical disk of this example was manufactured as a front-illuminated magneto-optical disk having the laminated structure shown in FIG. The magneto-optical disk manufacturing method of this example corresponds to the second method described above with reference to FIG.

In producing the magneto-optical disk of this example, first, a soft magnetic part was formed on a glass substrate (diameter 120 mm, thickness 1.2 mm). Specifically, first, a soft magnetic layer having a thickness of 100 nm was formed by depositing Fe ₅₄ Co ₃₆ B ₁₀ on a glass substrate by a sputtering method. In this sputtering, an Fe ₅₄ Co ₃₆ B ₁₀ 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 1.5 kW. Subsequently, a dielectric layer having a thickness of 5 nm was formed by forming SiN on the soft magnetic layer by a sputtering method. In this sputtering, a Si target was used, and SiN was formed on the substrate by reactive sputtering performed using Ar gas and N ₂ gas as sputtering gases. In this sputtering, the flow ratio of Ar gas and N ₂ gas was 7: 3, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 0.8 kW. Thereafter, such soft magnetic layers and dielectric layers are alternately laminated, and a multilayer structure comprising a total of nine soft magnetic layers and a total of nine dielectric layers between soft magnetic layers (the outermost surface is a dielectric layer). Formed).

Next, oxygen plasma was applied to the exposed surface of the outermost dielectric layer to roughen the exposed surface. Specifically, after the degree of vacuum in the chamber of the sputtering apparatus is set to 3 × 10 ⁻⁵ or less, oxygen plasma is generated while heating from the substrate side to the outermost surface dielectric layer in the chamber, thereby forming the outermost surface dielectric. The oxygen plasma was allowed to act on the exposed surface of the body layer. In this step, the pressure of the oxygen atmosphere in the chamber was 0.5 Pa, the substrate heating temperature was 200 ° C., and the oxygen plasma action time was 1 minute.

Next, a soft magnetic layer having a thickness of 100 nm was formed by depositing Fe ₅₄ Co ₃₆ B ₁₀ on the dielectric layer by sputtering. In this sputtering, an Fe ₅₄ Co ₃₆ B ₁₀ alloy target was used, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 1.5 kW. Thus, the soft magnetic part which has an uneven surface on the surface was formed. The surface roughness Ra (arithmetic average roughness) of the uneven surface was 3.0 nm, and the average height of protrusions (average of the maximum height Ry) in the uneven shape was 20.0 nm. These values are listed in the table of FIG.

  Thereafter, a pregroove layer, a heat conductive layer, a dielectric layer, a recording layer, an intermediate layer, a reproducing layer, a dielectric layer, and a protective film were sequentially formed on the soft magnetic portion. The specific formation method is the same as that in the first embodiment. As described above, the magneto-optical disk of this example was manufactured.

[Measurement of recording magnetic field]
For the magneto-optical disk of this example, the intensity of the recording magnetic field formed on the recording layer when a magnetic field was applied was measured in the same manner as in Example 1. As a result, the intensity of the recording magnetic field measured in this example was 380 Oe. The measured values are listed in the table of FIG.

[Production of magneto-optical disk]
The magneto-optical disk of this example was manufactured as a front-illuminated magneto-optical disk having the laminated structure shown in FIG. The magneto-optical disk manufacturing method of this embodiment corresponds to the fourth method described above with reference to FIG.

In the production of the magneto-optical disk of this example, first, an aluminum substrate (diameter 120 mm, thickness 1.2 mm) was heated at a high temperature in a chamber of a sputtering apparatus. In this step, the degree of vacuum in the chamber was set to 3 × 10 ⁻⁵ Pa or less, and the heating temperature was set to 400 ° C.

Next, with the aluminum substrate heated as described above, a Fe ₅₄ Co ₃₆ B ₁₀ film was formed on the substrate by a sputtering method to form a soft magnetic layer having a thickness of 1 μm. In this sputtering, an Fe ₅₄ Co ₃₆ B ₁₀ alloy target was used, the sputtering gas pressure was 0.5 Pa, and the sputtering power was 1.5 kW. Thus, the soft magnetic part which has an uneven surface on the surface was formed. The surface roughness Ra (arithmetic average roughness) of the uneven surface was 2.5 nm, and the average height of protrusions (average of the maximum height Ry) in the uneven shape was 25.0 nm. These values are listed in the table of FIG.

  Thereafter, a pregroove layer, a heat conductive layer, a dielectric layer, a recording layer, an intermediate layer, a reproducing layer, a dielectric layer, and a protective film were sequentially formed on the soft magnetic portion. The specific formation method is the same as that in the first embodiment. As described above, the magneto-optical disk of this example was manufactured.

[Measurement of recording magnetic field]
For the magneto-optical disk of this example, the intensity of the recording magnetic field formed on the recording layer when a magnetic field was applied was measured in the same manner as in Example 1. As a result, the intensity of the recording magnetic field measured in this example was 360 Oe. The measured values are listed in the table of FIG.

Comparative example

[Production of magneto-optical disk]
A soft magnetic part, a pregroove layer, a heat conduction layer, a dielectric layer, a recording layer, an intermediate layer, a reproducing layer, a dielectric layer are formed on a glass substrate in the same manner as in Example 1 except that the surface of the soft magnetic part is not sputter-etched. A body layer and a protective film were sequentially formed. Therefore, the magneto-optical disk of this comparative example has the same structure as the magneto-optical disk of Example 1 except that the soft magnetic part does not have an uneven surface on the recording layer side. In the magneto-optical disk of this comparative example, the surface roughness Ra (arithmetic average roughness) of the surface on the recording layer side in the soft magnetic part was 0.4 nm, and the average convex part height was 1.5 nm. For the magneto-optical disk of this comparative example, the recording magnetic field strength formed on the recording layer when a magnetic field was applied was measured in the same manner as in Example 1. The recording magnetic field strength was 300 Oe. These values are listed in the table of FIG.

Evaluation

  As shown in the table of FIG. 9, in the magneto-optical disks of Examples 1 to 3 according to the present invention, the recording magnetic field formed in the recording layer is larger than that of the magneto-optical disk of the comparative example. Specifically, in the magneto-optical disks of Examples 1 to 3 having a concavo-convex surface in which a concavo-convex shape is positively formed on the recording layer side in the soft magnetic portion, the recording magnetic field formed in the recording layer when a magnetic field is applied. In contrast, in the magneto-optical disk of the comparative example in which the surface on the recording layer side in the soft magnetic portion is substantially flat, the recording magnetic field formed in the recording layer is as small as 300 Oe. Such a difference in recording magnetic field strength between the magneto-optical disks of Examples 1 to 3 and the magneto-optical disk of the comparative example occurs in the magneto-optical disks of Examples 1 to 3 when the magnetic field is applied. Since the magnetic poles are concentrated on each of the convex and concave portions on the surface of the magnetic part, the substantial magnetic pole area in the entire recording magnetic field application area on the surface of the soft magnetic part is uniform on the surface of the soft magnetic layer in the magneto-optical disk of the comparative example. This is probably because the area is smaller than the magnetic pole area when the magnetic pole appears. From the measurement result of the recording magnetic field strength, the substantial magnetic pole area in the magneto-optical disk of Example 1 is considered to be about 0.9 times that in the magneto-optical disk of the comparative example. Similarly, the substantial magnetic pole area in the magneto-optical disks of Examples 2 and 3 is considered to be about 0.8 times and about 0.83 times that of the magneto-optical disk of the comparative example.

  As a summary of the above, the configurations of the present invention and variations thereof are listed below as supplementary notes.

(Additional remark 1) It has a laminated structure containing a board | substrate, the recording layer which bears a recording function, and the soft-magnetic part located between the said board | substrate and the said recording layer,
The magneto-optical recording medium, wherein a surface of the soft magnetic portion on the recording layer side has an uneven shape.
(Supplementary note 2) The magneto-optical recording medium according to supplementary note 1, wherein the surface roughness of the surface of the soft magnetic part is 1 to 5 nm, and the average height of the convex part in the concavo-convex shape is 3 to 30 nm. .
(Additional remark 3) The process for forming a soft-magnetic film | membrane on a base material,
A step for forming a soft magnetic layer having a concavo-convex shape on the surface by performing sputter etching on the exposed surface of the soft magnetic film;
And a step for forming a recording layer above the soft magnetic layer.
(Additional remark 4) The process for exposing and roughening the surface of a base material to oxygen plasma,
A step for forming a soft magnetic layer having a concavo-convex shape on a growth end surface by forming a soft magnetic material on the substrate;
And a step for forming a recording layer above the soft magnetic layer.
(Appendix 5) A step for forming a soft magnetic layer having a concavo-convex shape on a growth end surface by forming a soft magnetic material on the substrate while heating the substrate;
And a step for forming a recording layer above the soft magnetic layer.
(Appendix 6) A first step for forming a soft magnetic film by forming a first soft magnetic material on a substrate;
A second step for forming a plurality of protrusions by growing a second soft magnetic material on the soft magnetic film, and forming a soft magnetic layer comprising the plurality of protrusions and the soft magnetic film;
And a third step for forming a recording layer above the soft magnetic layer.
(Appendix 7) The second soft magnetic material has the same composition as the first soft magnetic material, and the conditions for forming the first soft magnetic material in the first step, and the second soft magnetic material in the second step, The method for manufacturing a magneto-optical recording medium according to appendix 6, wherein the conditions for growing the second soft magnetic material are different.
(Supplementary note 8) The magneto-optical recording medium according to supplementary note 6, wherein the second soft magnetic material has a composition different from that of the first soft magnetic material and has a larger surface tension than the first soft magnetic material. Production method.

1 is a partial cross-sectional view of a magneto-optical disk according to the present invention. The formation mode of the recording magnetic field in the magneto-optical disk of the present invention is schematically shown. 1 represents a method for manufacturing the magneto-optical disk shown in FIG. 2 shows another method for manufacturing the magneto-optical disk shown in FIG. 2 shows another method for manufacturing the magneto-optical disk shown in FIG. 2 shows another method for manufacturing the magneto-optical disk shown in FIG. A common laminated structure is shown for the magneto-optical disks of Examples 1 and 2 and the comparative example. 3 shows a stacked configuration of a magneto-optical disk of Example 3. 4 is a table summarizing the surface roughness and average height of the surface on the recording layer side in the soft magnetic portion and the results of recording magnetic field measurement for the magneto-optical disks of Examples and Comparative Examples. It is a partial sectional view of a conventional magneto-optical disk. The formation mode of the recording magnetic field in the conventional magneto-optical disk is typically represented.

Explanation of symbols

X1, X2 magneto-optical disk S1, S2 substrate 11, 91 recording magnetic part 11a recording layer 11b intermediate layer 11c reproducing layer 12, 12 'soft magnetic part 12a, 92 soft magnetic layer 12a' uneven surface 12b dielectric layer 12c soft magnetic film 12d Protrusion 13, 93 Pregroove layer 14, 94 Thermal conductive layer 15, 16, 95, 96 Dielectric layer 17, 97 Protective film

Claims (5)

A laminated structure including a substrate, a recording layer responsible for a recording function, and a soft magnetic portion located between the substrate and the recording layer;
The magneto-optical recording medium, wherein a surface of the soft magnetic portion on the recording layer side has an uneven shape.   2. The magneto-optical recording medium according to claim 1, wherein the surface roughness of the surface in the soft magnetic part is 1 to 5 nm, and the average height of the convex part in the concavo-convex shape is 3 to 30 nm. A step for forming a soft magnetic film on the substrate;
A step for forming a soft magnetic layer having a concavo-convex shape on the surface by performing sputter etching on the exposed surface of the soft magnetic film;
And a step for forming a recording layer above the soft magnetic layer. A process for roughening the surface of the substrate by exposing it to oxygen plasma;
A step for forming a soft magnetic layer having a concavo-convex shape on a growth end surface by forming a soft magnetic material on the substrate;
And a step for forming a recording layer above the soft magnetic layer. A step for forming a soft magnetic layer having a concavo-convex shape on a growth end surface by forming a soft magnetic material on the substrate while heating the substrate;
And a step for forming a recording layer above the soft magnetic layer.

Images