JP2009245533A - Master carrier for magnetic transfer and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a master carrier for magnetic transfer and a magnetic recording medium for suppressing magnetization inversion on an initialization side and drastically improving transfer signal quality. <P>SOLUTION: The master carrier for the magnetic transfer has a rugged pattern formed by arraying a plurality of projections with the surface of a base material as a reference on the surface and at least a magnetic layer formed on the surface of the projections, wherein the ratio (A/B) of the protruding amount A of the magnetic layer in the projection and the thickness B of the magnetic layer in the projection satisfies 1/10 to 1/6. The protruding amount A means (the maximum width X of the magnetic layer in a direction vertical to the thickness direction of the magnetic layer in the projection)-(the maximum width Y of the projection in the direction vertical to the thickness direction of the magnetic layer in the projection). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a master carrier for magnetic transfer and magnetic recording that can suppress the magnetization reversal on the initialization side by optimizing the amount of protrusion of the magnetic layer at the convex portion, and can greatly improve the quality of the transfer signal. It relates to the medium.

  2. Description of the Related Art In recent years, magnetic recording / reproducing apparatuses tend to have a higher recording density in order to realize a small size and a large capacity, and in particular, in the field of hard disk drives (HDDs), which are typical magnetic storage devices, The progress is rapid.

  With such an increase in the amount of information, high-density magnetic recording capable of recording a large amount of information, high-capacity, inexpensive, and preferably capable of reading a required portion in a short time, so-called high-speed access A medium is desired. In these high-density magnetic recording media, the information recording area is composed of narrow tracks, and so-called tracking servo technology is used to reproduce signals with high S / N by accurately scanning the magnetic head in a narrow track width. It plays a big role. In order to perform this tracking servo, a sector servo system is widely adopted.

  The sector servo system is a servo field that is correctly arranged at a certain angle on the data surface of a magnetic recording medium such as a magnetic disk, a servo signal for track positioning, an address information signal of the track, a reproduction clock signal, etc. This servo information is recorded, and the magnetic head scans this servo field, reads the servo information, and corrects it while checking its own position.

  The servo information needs to be recorded on the magnetic recording medium in advance as a preformat at the time of manufacturing the magnetic recording medium, and is currently preformatted using a dedicated servo recording device. Currently used servo recording devices include a magnetic head having a head width of about 75% of the track pitch, for example, and while the magnetic head is in close proximity to the magnetic disk, the magnetic disk is rotated and ½ track is rotated. Each time a servo signal is recorded while moving from the outer periphery to the inner periphery of the magnetic disk. For this reason, it takes a long time to perform preformat recording on one magnetic disk, which is problematic in terms of production efficiency, which causes an increase in cost.

  For this reason, as a method for accurately and efficiently performing preformatting, a method of magnetically transferring information on a master recording medium on which a pattern corresponding to servo information is formed to a magnetic recording medium has been proposed (Patent Document 1). To 4).

  This magnetic transfer uses a master carrier having a magnetic layer pattern corresponding to information (for example, servo information) to be transferred to a magnetic recording medium (slave medium) such as a magnetic disk for transfer, and the master carrier and the magnetic recording medium (slave) The magnetic pattern corresponding to the magnetic layer pattern of the master carrier is magnetically transferred to the magnetic recording medium by applying a recording magnetic field in close contact with the medium. In this method, recording can be performed statically without changing the relative positions of the master carrier and the magnetic recording medium, accurate preformat information can be recorded, and the time required for recording is extremely high. It has the advantage of being short.

Patent Document 4 discloses a perpendicular magnetic recording magnetic transfer technique in which the direction of magnetization to be recorded is perpendicular to the medium surface.
Since this perpendicular magnetic recording method can be expected to greatly improve the recording density compared to the in-plane magnetic recording method, the development of perpendicular magnetic recording technology has been advanced in response to the recent demand for higher recording density. It has reached practical use.

  In the case of magnetic transfer to a perpendicular magnetic recording medium, first, a DC magnetic field is applied to the perpendicular recording medium to be a transfer target (slave disk) in a direction perpendicular to the disk surface, and the magnetic layer (recording layer) of the disk is initially magnetized. . After this initial magnetization, the information corresponding to the concavo-convex pattern on the surface of the transfer master is transferred to the slave disk by bringing the transfer master (master disk) into close contact with the slave disk and applying a DC magnetic field in the direction opposite to the initial magnetization. The

By the way, when a perpendicular magnetic layer is formed on a magnetic transfer master carrier having a concavo-convex pattern, if the protruding amount A of the magnetic layer at the convex portion is large as shown in FIG. It will be reversed. As a result, the goodness of the perpendicular magnetic layer that originally exhibits excellent magnetic transfer characteristics is lost. For this reason, it is preferable to suppress the protrusion of the magnetic layer in the convex portion as much as possible.
However, when the magnetic layer is formed using the most common sputtering method, the oblique component increases due to scattering of the sputtered particles, and in FIG. 1, about 1/4 to 1/5 of the thickness of the magnetic layer. There is a “projection amount”. This phenomenon becomes more conspicuous when the width of the concavo-convex portion (bit length) becomes narrower, and it is currently desired to solve this phenomenon.

JP 2003-203325 A JP 2000-195048 A U.S. Pat. No. 7,218,465 JP 2001-297435 A

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, according to the present invention, by optimizing the protruding amount of the magnetic layer at the convex portion, the magnetization reversal on the initialization side can be suppressed, and the master carrier for magnetic transfer that can greatly improve the quality of the transfer signal and An object is to provide a magnetic recording medium.

Means for solving the above problems are as follows. That is,
<1> In a magnetic transfer master carrier having a concavo-convex pattern formed by arranging a plurality of convex portions on the surface of a base material with reference to the surface, and at least the convex portion surface having a magnetic layer. ,
The magnetic transfer master carrier, wherein the ratio (A / B) between the protruding amount A of the magnetic layer at the convex portion and the thickness B of the magnetic layer at the convex portion satisfies 1/10 to 1/6. It is.
However, the protrusion A is (the maximum width X of the magnetic layer in the direction perpendicular to the thickness direction of the magnetic layer in the convex portion) − (the convex portion in the direction perpendicular to the thickness direction of the magnetic layer in the convex portion). Represents the maximum width Y).
<2> The magnetic transfer master carrier according to <1>, wherein the ratio (A / B) satisfies 1/8 to 1/7.
<3> The magnetic transfer master carrier according to any one of <1> to <2>, wherein the magnetic layer has perpendicular magnetic anisotropy.
<4> A magnetic recording medium produced by a magnetic transfer method using the magnetic transfer master carrier according to any one of <1> to <3>.

  According to the present invention, it is possible to solve the conventional problems, and by optimizing the amount of protrusion of the magnetic layer at the convex portion, it is possible to suppress the magnetization reversal on the initialization side and greatly improve the quality of the transfer signal. It is possible to provide a magnetic transfer master carrier and a magnetic recording medium.

(Master carrier for magnetic transfer)
The master carrier for magnetic transfer of the present invention has a concavo-convex pattern formed by arranging a plurality of convex portions on the surface of a base material with reference to the surface, and at least the convex portion surface has a magnetic layer. And other layers as necessary.

In the present invention, the ratio (A / B) between the protruding amount A of the magnetic layer at the convex portion and the thickness B of the magnetic layer at the convex portion satisfies 1/10 to 1/6, and 1/8 to It is preferable to satisfy 1/7.
When the ratio (A / B) is less than 1/10, the magnetic film continuously formed on the uneven surface of the master surface is divided, so that the magnetic film is peeled off due to the adhesion impact during magnetic transfer. If it exceeds 1/6, the signal on the initialization side may be inverted due to the influence of an external magnetic field applied during magnetic transfer.
Here, as shown in FIG. 2, the protruding amount A is the maximum width X of the magnetic layer in the direction perpendicular to the thickness direction of the magnetic layer in the convex portion-vertical to the thickness direction of the magnetic layer in the convex portion. The maximum width Y of the convex part in the direction is represented. The direction perpendicular to the thickness direction of the magnetic layer at the convex portion is the same as the radial direction of the concentric circles of the disk-shaped substrate (the direction in which the convex portions are arranged).
The protruding amount A can be measured, for example, by preparing an ultrathin section using FIB (focused ion beam) and observing a cross section using a TEM (transmission electron microscope).

The thickness B of the magnetic layer in the convex portion is preferably 5 nm to 100 nm, and more preferably 10 nm to 40 nm.
The thickness B of the magnetic layer can be measured by, for example, a stylus type surface shape measuring instrument (DEKTAK6M, manufactured by ULVAC).

For adjusting the protrusion amount of the magnetic layer in the convex portion, a method of selectively cutting by Ar etching after sputtering is effective. However, in order to further increase the effect, divided formation of the magnetic layer [(1) Sputtering, (2) A method of forming a predetermined film thickness by Ar etching, (3) sputtering, (4) Ar etching, (5) sputtering, etc.] is preferable.
When forming the perpendicular magnetic layer in the initial stage, it is also effective to suppress the protruding amount of the magnetic layer before the Ar etching by using an ion gun method instead of the sputtering method.

-Base material-
The substrate is not particularly limited in its shape, structure, size, material, and the like, and can be appropriately selected according to the purpose. For example, when the shape is an information recording medium, It is disk-shaped. The structure may be a single layer structure or a laminated structure. The material can be appropriately selected from those known as base materials, and examples thereof include nickel, aluminum, glass, silicon, quartz, and transparent resin. These board | substrate materials may be used individually by 1 type, and may use 2 or more types together.
The base material may be appropriately synthesized or a commercially available product may be used.
There is no restriction | limiting in particular as thickness of the said base material, According to the objective, it can select suitably, 50 micrometers or more are preferable and 100 micrometers or more are more preferable.

As a specific example of a magnetic layer having a concavo-convex pattern formed by arranging a plurality of convex portions on the surface of the base material with reference to the surface, and at least the convex portion surface is made of a magnetic material, Examples thereof include a perpendicular magnetic recording film in a perpendicular magnetic recording medium.
As a configuration and manufacturing method of the perpendicular magnetic recording film in the perpendicular magnetic recording medium, conventionally known methods described in, for example, Japanese Patent Application Laid-Open No. 2007-335034, Japanese Patent Application Laid-Open No. 2005-285275, Japanese Patent Application Laid-Open No. 2008-10088, and the like. Can be used as appropriate.

-Magnetic layer patterning method-
Examples of a method for forming a patterned concavo-convex structure on the magnetic layer include those described in Japanese Patent No. 1888363, Japanese Patent Laid-Open No. 9-97419, Japanese Patent Laid-Open No. 2001-110050, US Pat. No. 6,518,189, and the like. At least a part of the method can be used. Specifically, the existing photolithography method, etching method, vacuum film forming method, and lift-off method are appropriately combined.
The method of making the perpendicular magnetic layer into a patterned concavo-convex structure is a method of patterning only the perpendicular magnetic layer by the method, a method of patterning the surface side from the underlayer for promoting orientation, a method of patterning from the soft magnetic layer, Etc. can be appropriately selected.
The method for forming the magnetic layer is not particularly limited and may be appropriately selected depending on the purpose. For example, vacuum deposition methods such as vacuum deposition, sputtering, and ion plating, plating, and coating The film can be formed by, for example.

A protective film such as diamond-like carbon (DLC) or sputtered carbon is preferably provided on the magnetic layer, and a lubricant layer may be further provided on the protective film. In this case, a configuration in which a DLC film having a thickness of 3 to 30 nm and a lubricant layer are used as the protective film is preferable. Further, an adhesion reinforcing layer such as Si may be provided between the magnetic layer and the protective film. The lubricant has an effect of improving the deterioration of durability such as the occurrence of scratches due to friction when correcting the deviation caused in the contact process with the slave disk.
Examples of the transfer information include a tracking servo signal, a clock signal, and an address information signal.

Hereinafter, a magnetic transfer technique of perpendicular magnetic recording to which the magnetic transfer master carrier of the present invention is applied will be described with reference to the drawings.
FIG. 3 is a schematic diagram showing the steps of a magnetic transfer method for perpendicular magnetic recording. In FIG. 3, reference numeral 10 denotes a slave disk (corresponding to a “perpendicular magnetic recording medium”) as a magnetic disk for transfer, and reference numeral 20 denotes a master disk as a master carrier.

  First, as shown in FIG. 3 (a), a perpendicular direct current magnetic field (Hi) is applied to the slave disk 10 to perform initial magnetization (initial magnetization step), and then, as shown in FIG. 3 (b), the master disk 20 and slave disk 10 are brought into close contact (contact process), and a magnetic field (Hd) in the direction opposite to that at the time of initial magnetization is applied as shown in FIG. Thus, magnetic transfer is performed (transfer process).

[Description of magnetic disk for transfer (slave disk)]
The slave disk 10 used in this example is one in which a magnetic layer made of a perpendicular magnetization film is formed on one side or both sides of the surface of a disk-shaped substrate, and specifically includes a high-density hard disk or the like.

  FIG. 4 is a schematic sectional view of the slave disk 10. As shown in FIG. 4, the slave disk 10 includes a soft magnetic layer (soft magnetic underlayer; SUL) 13, a nonmagnetic layer (intermediate layer) 14, and a magnetic layer (perpendicular magnetic) on a nonmagnetic substrate 12 such as glass. Recording layer) 16 is sequentially laminated, and the magnetic layer 16 is further covered with a protective layer 18 and a lubricating layer 19. Although an example in which the magnetic layer 16 is formed on one surface of the substrate 12 is shown here, an embodiment in which the magnetic layer is formed on both the front and back surfaces of the substrate 12 is also possible.

  The disk-shaped substrate 12 is made of a nonmagnetic material such as glass or Al (aluminum). After the soft magnetic layer 13 is formed on the substrate 12, the nonmagnetic layer 14 and the magnetic layer 16 are formed. .

  The soft magnetic layer 13 is useful for stabilizing the perpendicular magnetization state of the magnetic layer 16 and improving the sensitivity during recording and reproduction. The material used for the soft magnetic layer 13 is preferably a soft magnetic material such as CoZrNb, FeTaC, FeZrN, FeSi alloy, FeAl alloy, FeNi alloy such as permalloy, and FeCo alloy such as permendur. The soft magnetic layer 13 has a magnetic anisotropy in a radial direction (radially) from the center of the disk to the outside.

  The thickness of the soft magnetic layer 13 is preferably 50 nm to 2000 nm, and more preferably 80 nm to 400 nm.

  The nonmagnetic layer 14 is provided for reasons such as increasing the magnetic anisotropy in the perpendicular direction of the magnetic layer 16 to be formed later. The material used for the nonmagnetic layer 14 is preferably Ti (titanium), Cr (chromium), CrTi, CoCr, CrTa, CrMo, NiAl, Ru (ruthenium), Pd (palladium), Ta, Pt, or the like. The nonmagnetic layer 14 is formed by depositing the above material by a sputtering method. The thickness of the nonmagnetic layer 14 is preferably 10 nm to 150 nm, and more preferably 20 nm to 80 nm.

The magnetic layer 16 is formed of a perpendicular magnetization film (with the easy axis of magnetization in the magnetic film oriented mainly perpendicular to the substrate), and information is recorded in the magnetic layer 16. The material used for the magnetic layer 16 is Co (cobalt), Co alloy (CoPtCr, CoCr, CoPtCrTa, CoPtCrNbTa, CoCrB, CoNi, etc.), Co alloy-SiO ₂ , Co alloy-TiO ₂ , Fe, Fe alloy (FeCo, FePt, FeCoNi, etc.) are preferred.
These materials have a large magnetic flux density and have perpendicular magnetic anisotropy by adjusting film forming conditions and composition. The magnetic layer 16 is formed by depositing the above material by a sputtering method. The thickness of the magnetic layer 16 is preferably 10 nm to 500 nm, and more preferably 20 nm to 200 nm.

In the present embodiment, a disk-shaped glass substrate having an outer diameter of 65 mm is used as the substrate 12 of the slave disk 10, and the glass substrate is installed in the chamber of the sputtering apparatus to obtain 1.33 × 10 ⁻⁵ Pa (1.0 × ^10-7 Torr), Ar (argon) gas was introduced into the chamber, the CoZrNb target in the chamber was used, and the temperature of the substrate in the chamber was set to room temperature. Sputter film formation. Next, a 0.8 nm thick Ru layer is formed by sputtering using a Ru target in the chamber. Further, a SUL second layer having a thickness of 80 nm is formed by sputtering using a CoZrNb target. The SUL thus formed by sputtering is heated to room temperature and cooled to room temperature with a magnetic field of 50 Oe or more applied in the radial direction.

  Next, sputtering film formation is performed by using a Ru target and discharging the substrate at a room temperature. Thereby, the nonmagnetic layer 14 made of CrTi is formed to a thickness of 60 nm.

Thereafter, Ar gas is introduced in the same manner as described above, and sputtering film formation is performed by using a CoCrPt target in the same chamber and discharging the substrate at the same room temperature. Thus, the magnetic layer 16 having a granular structure made of CoCrPt—SiO ₂ is formed to a thickness of 25 nm.

  Through the above-described process, a transfer magnetic disk (slave disk) 10 in which a soft magnetic layer, a nonmagnetic layer, and a magnetic layer were formed on a glass substrate was produced.

[Initial magnetization of slave disk]
Next, initial magnetization of the formed slave disk 10 is performed. As described with reference to FIG. 3A, the initial magnetization (DC magnetization) of the slave disk 10 is initially performed by a device (magnetic field applying means (not shown)) that can apply a DC magnetic field perpendicular to the surface of the slave disk 10. This is performed by generating the activating magnetic field Hi. Specifically, the initialization magnetic field Hi is generated by generating a magnetic field having a strength equal to or greater than the coercive force Hc of the slave disk 10. By this initial magnetization step, as shown in FIG. 9, the magnetic layer 16 of the slave disk 10 is initially magnetized Pi in one direction perpendicular to the disk surface. This initial magnetization step may be performed by rotating the slave disk 10 relative to the magnetic field applying means.

[Form of master disk]
Next, the master disk 20 which is a master carrier will be described. FIG. 6 shows an example of the form of the master disk 20. As the shape of the master disk 20, as shown in FIG. 6A, the magnetic layer 204 is formed on the uneven surface of the base material 202, or as shown in FIG. A form in which the magnetic layer 214 is formed only on the bit portion corresponding to the transfer signal on the surface (the portion that reverses the initial magnetization and corresponds to the “transfer portion”) is preferable.

  In the form of FIG. 6A, the magnetic layer 204 formed on the upper surface of the convex portion 206 of the base material 202 becomes a bit portion (portion where the initial magnetization is reversed) corresponding to the transfer signal. In FIG. 6A, the magnetic layer 208 is also formed in the concave portion 207 (corresponding to the “non-transfer portion”) of the base material 202, but the magnetic layer 208 may be omitted from the concave portion 207. Considering the ease of manufacturing, the magnetic layers 204 and 208 are provided on the surfaces of the convex portions 206 and the concave portions 207 as shown in FIG. 6A rather than the magnetic layer 204 selectively provided only on the convex portions 206. Is more convenient.

  6 (a) and 6 (b), the place where the magnetic layers 204 and 214 corresponding to the transfer signal (bit part) are provided is the highest position in the master disk 20 (however, the protective layer). And a portion other than the bit portion are relatively lower than the magnetic layers 204 and 214 in the bit portion. That is, the master disk 20 has a shape in which the magnetic layers 204 and 214 in the bit part are the uppermost layers (however, a protective layer and a lubricating layer may be further provided on the magnetic layers 204 and 214), and the non-bits. The disk surface has an uneven surface because the part forms a relatively low recess.

[Manufacturing method of master disk]
Next, an example of a master disk manufacturing method will be described with reference to FIG.
First, as shown in FIG. 7A, an original plate (Si substrate) 30 which is a silicon wafer having a smooth surface is prepared, and an electron beam resist solution is applied onto the original plate 30 by a spin coating method or the like. Then, a resist layer 32 is formed (FIG. 7B), and a baking process (pre-baking) is performed.

  Next, an original plate 30 is set on a stage of an electron beam exposure apparatus (not shown) equipped with a high-precision rotary stage or an XY stage, and an electron beam modulated in accordance with a servo signal is rotated while the original plate 30 is rotated. A predetermined pattern 33, for example, a pattern corresponding to a servo signal extending linearly from the center of rotation to each track in a radial direction on each track is drawn and exposed on a portion corresponding to each frame on the circumference (subject to irradiation). (Electron beam drawing) (FIG. 7C).

  Next, as shown in FIG. 7D, the resist layer 32 is developed to remove the exposed (drawn) portion, and a coating layer having a desired thickness is formed from the remaining resist layer 32. This coating layer becomes a mask for the next process (etching process). The resist applied on the substrate 30 can be either a positive type or a negative type, but the exposure (drawing) pattern is reversed between the positive type and the negative type. After this development process, a baking process (post-bake) is performed to increase the adhesion between the resist layer 32 and the original plate 30.

  Next, as shown in FIG. 7E, the original plate 30 is removed (etched) by a predetermined depth from the surface through the opening 34 of the resist layer 32. In this etching, anisotropic etching is preferable in order to minimize undercut (side etching). As such anisotropic etching, reactive ion etching (RIE) can be preferably employed.

  Next, as shown in FIG. 7F, the resist layer 32 is removed. As a method for removing the resist layer 32, ashing can be adopted as a dry method, and a removal method using a stripping solution can be adopted as a wet method. Through the above ashing process, the master disk 36 on which a reverse type of a desired concavo-convex pattern is formed is produced.

  Next, as shown in FIG. 7G, a conductive layer 38 is formed on the surface of the master 36 with a uniform thickness. As a method for forming the conductive layer 38, various metal film forming methods including PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), sputtering, and ion plating can be applied. Thus, if one layer of the conductive film (reference numeral 38) is formed, the effect that the electrodeposition of the metal in the next process (electroforming process) can be performed uniformly can be obtained. The conductive layer 38 is preferably a film containing Ni as a main component. Such a film containing Ni as a main component is easy to form and is suitable as a conductive film. Although there is no restriction | limiting in particular as the thickness of this conductive layer 38, about several dozen nm is generally employable.

  Next, as shown in FIG. 7 (h), a metal plate 40 made of metal (here, Ni) having a desired thickness is laminated on the surface of the master disk 36 by electroforming (reverse plate forming step). This process is performed by immersing the master 36 in the electrolytic solution of the electroforming apparatus, using the master 36 as an anode, and energizing between the cathode and the electrolyte. At this time, the concentration of the electrolyte, pH, and how to apply the current Are required to be performed under optimum conditions without distortion on the laminated metal plates 40 (that is, the master substrate corresponding to the base material 202 described in FIG. 6).

  Then, the master 36 on which the metal plate 40 is laminated as described above is taken out from the electrolytic solution of the electroforming apparatus and immersed in pure water in a peeling tank (not shown).

  Next, in the peeling tank, the metal plate 40 is peeled from the master 36 (peeling step), and a master substrate 42 having an uneven pattern inverted from the master 36 as shown in FIG.

Next, as shown in FIG. 7J, a magnetic layer 48 made of a soft magnetic film is formed on the uneven surface of the master substrate 42. At this time, the amount of protrusion of the magnetic layer at the convex portion is adjusted by adjusting the film forming conditions for sputtering and the Ar etching conditions. Examples of the material of the magnetic layer 48 include Co ₄ Pt ₁ (atomic ratio). The thickness of the magnetic layer 48 is preferably in the range of 10 nm to 320 nm, particularly preferably in the range of 20 nm to 300 nm, and more preferably 40 to 100 nm.

  Thereafter, the inner diameter and the outer diameter of the master substrate 42 are punched into a predetermined size. Through the above process, as shown in FIG. 7J, the master disk 20 having a concavo-convex pattern provided with the magnetic layer 48 (corresponding to the magnetic layer 204 in FIG. 6) is manufactured. The concavo-convex pattern on the master disk 20 formed in this way is the ratio of the width Sa in the track direction (circumferential direction) of the concave region (space portion) to the width La in the track direction (circumferential direction) of the convex region (land portion). (Sa / La) is made to be 1.3 to 1.9 times, preferably 1.45 to 1.75 times.

  FIG. 8 is a top view of the master disk 20. As shown in the figure, a servo pattern 52 composed of a concavo-convex pattern is formed on the surface of the master disk 20. Although not shown in the drawing, a protective film such as diamond-like carbon may be provided on the magnetic layer 48 (see FIG. 7J) on the surface of the master disk 20, and a lubricant layer may be provided on the protective film. Good.

  The master disk 20 is in close contact with the slave disk 10, but this prevents the magnetic layer 48 from being easily damaged when the master disk 20 is in close contact so that it cannot be used as the master disk 20. In addition, the lubricant layer has an effect of preventing the occurrence of scratches due to friction generated when contacting the slave disk 10 and improving durability.

  Specifically, a structure in which a carbon film having a thickness of 2 nm to 30 nm is formed as a protective film and a lubricant layer is further formed thereon is preferable. Further, in order to reinforce the adhesion between the magnetic layer 48 and the protective film, an adhesion reinforcing layer such as Si may be formed on the magnetic layer 48 and then the protective film may be formed.

[Contact process in magnetic transfer]
Next, the master disk 20 produced by the above process and the slave disk 10 after the initial magnetization process are superposed as shown in FIG.

  As shown in FIG. 3B, in the adhesion process, a predetermined pressing is performed between the surface of the master disk 20 on which the projection pattern (uneven pattern) is formed and the surface of the slave disk 10 on which the magnetic layer 16 is formed. Adhere with pressure.

  Before being brought into close contact with the master disk 20, the slave disk 10 is subjected to a cleaning process (burnishing or the like) for removing minute projections or adhering dust on the surface by a glide head, a polishing body, or the like as necessary.

  As shown in FIG. 3 (b), in the contact process, the master disk 20 is attached to only one side of the slave disk 10 and the transfer magnetic disk in which the magnetic layer is formed on both sides. May stick. The latter case has an advantage that both sides can be transferred simultaneously.

[Magnetic transfer process]
Next, the magnetic transfer process will be described with reference to FIG.

  In the case where the slave disk 10 and the master disk 20 are brought into close contact with each other in the contact step, a recording magnetic field Hd is generated in a direction opposite to the direction of the initialization magnetic field Hi by a magnetic field applying means (not shown). Magnetic transfer is performed by the magnetic flux generated by generating the recording magnetic field Hd entering the slave disk 10 and the master disk 20.

  In this embodiment, the magnitude of the recording magnetic field Hd is substantially the same value as Hc of the magnetic material constituting the magnetic layer 16 of the slave disk 10.

  In the magnetic transfer, a recording magnetic field Hd is applied by a magnetic field applying means while rotating a close contact of the slave disk 10 and the master disk 20 by a rotating means (not shown), and the protruding shape recorded on the master disk 20 is applied. Information consisting of the pattern is magnetically transferred to the magnetic layer 16 of the slave disk 10. In addition to this configuration, a mechanism for rotating the magnetic field applying unit may be provided to rotate the slave disk 10 and the master disk 20 relatively.

  FIG. 9 shows a cross-sectional state of the slave disk 10 and the master disk 20 in the magnetic transfer process. As shown in the figure, when the recording magnetic field Hd is applied in a state where the master disk 20 having a concavo-convex pattern is in close contact with the slave disk 10, the magnetic flux G causes the convex area of the master disk 20 and the slave disk 10 to contact each other. The recording magnetic field Hd causes the magnetization direction of the magnetic layer 48 of the master disk 20 to be aligned with the direction of the recording magnetic field Hd, and the magnetic information is transferred to the magnetic layer 16 of the slave disk 10. On the other hand, in the concave area of the master disk 20, the magnetic flux G generated by the application of the recording magnetic field Hd is weaker than that of the convex area, and the magnetization direction of the magnetic layer 16 of the slave disk 10 does not change and maintains the initial magnetization state. It remains.

  FIG. 10 shows in detail a magnetic transfer apparatus used for magnetic transfer. The magnetic transfer device has a magnetic field applying means 60 composed of an electromagnet having a coil 63 wound around a core 62, and a master disk 20 and a slave disk that are brought into close contact with each other in a gap 64 by passing an electric current through the coil 63. The structure is such that a magnetic field is generated perpendicular to the ten magnetic layers 16. The direction of the generated magnetic field can be changed depending on the direction of the current flowing through the coil 63. Therefore, it is possible to perform the initial magnetization of the slave disk 10 and the magnetic transfer by this magnetic transfer device.

  When magnetic transfer is performed after the initial magnetization by the magnetic transfer device, a current having a direction opposite to the direction of the current flowing in the coil 63 when the initial magnetization is performed is supplied to the coil 63 of the magnetic field applying unit 60. As a result, the recording magnetic field can be generated in a direction opposite to the magnetization direction during the initial magnetization. Magnetic transfer is performed by applying a magnetic field for recording Hd by the magnetic field applying means 60 while rotating the disk in which the slave disk 10 and the master disk 20 are in close contact with each other, so that information consisting of a protruding pattern recorded on the master disk 20 is obtained. Rotating means (not shown) is provided for magnetic transfer to the magnetic layer 16 of the slave disk 10. In addition to this configuration, a mechanism that rotates the magnetic field applying unit 60 and rotates the slave disk 10 and the master disk 20 relatively may be used.

  In the present embodiment, the recording magnetic field Hd is a magnetic field having a strength of 60% to 125%, preferably 70% to 115%, of the coercive force Hc of the magnetic layer 16 of the slave disk 10 used in the present embodiment. Magnetic transfer is performed by applying.

  As a result, information on the magnetic pattern such as a servo signal is recorded on the magnetic layer 16 of the slave disk 10 as the recording magnetization Pd having the magnetization opposite to the initial magnetization Pi (see FIG. 11).

  In carrying out the present invention, the protruding pattern formed on the master disk 20 may be a negative pattern opposite to the positive pattern described in FIG. In this case, the same magnetization pattern can be magnetically transferred to the magnetic layer 16 of the slave disk 10 by reversing the direction of the initialization magnetic field Hi and the direction of the recording magnetic field Hd. In the present embodiment, the magnetic field applying unit has been described as an electromagnet, but a permanent magnet that similarly generates a magnetic field may be used.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1-2 and Comparative Examples 1-4)
-Preparation of master carrier for magnetic transfer-
A magnetic transfer master carrier was prepared by the method shown in FIGS. 7 (a) to 7 (j).
Specifically, in the magnetic layer formation step of FIG. 7 (j), using the following sputtering film formation conditions and Ar etching conditions, the film transfer conditions shown in Table 1 and the convex portions (width = 100 nm), a perpendicular magnetic recording layer material (Fe ₇₀ —Co ₃₀ at%) was formed to a thickness of 50 nm.

<Sputtering film formation conditions>
Deposition pressure = 0.05 to 0.2 Pa, substrate-target distance = 200 mm, DC power = 1000 W

<Ar etching conditions (basic conditions)>
Plasma pressure = 0.16 Pa, substrate-target distance = 75 mm, DC power = 1500 W

  Each magnetic transfer master carrier produced as described above was measured for the amount of protrusion of the magnetic layer, measured for the thickness of the magnetic layer, and evaluated for inversion on the initialization side as follows. The results are shown in Table 1.

<Measurement of protrusion A of magnetic layer>
The amount A of protrusion of the magnetic layer was determined by preparing an ultrathin slice using FIB (focused ion beam) and observing it with a TEM (transmission electron microscope). Since it is a method of observing the cross section of the formed thin film, a difference in nano order was confirmed.

<Measurement of magnetic layer thickness B>
The magnetic layer thickness B was measured by a stylus type surface shape measuring instrument (DEKTAK6M, manufactured by ULVAC).

<Initialization inversion evaluation>
The waveform was taken into the oscilloscope in the preamble portion of the transferred servo signal, and the pulses whose output on the initialization side was inverted by 30% were counted. When a portion exceeding 30% exists even with one pulse, it was determined as an NG frame. Of 190 frames, the number of frames that became NG was counted.

* For a sputtering method formed by using Ar etching together, the total thickness of the magnetic layers was adjusted to be the same in consideration of the magnetic layer that can be removed by etching.

  From the results in Table 1, when the perpendicular magnetic layer is formed on the magnetic transfer master carrier having the concavo-convex pattern, the amount of protrusion of the magnetic layer is suppressed as much as possible, and the amount of protrusion A of the magnetic layer at the convex portion It was found that the signal inversion on the initialization side can be suppressed when the ratio (A / B) with the thickness B of the magnetic layer in the portion satisfies 1/10 to 1/6.

  The magnetic transfer master carrier of the present invention is particularly suitable for magnetic transfer of a perpendicular magnetic recording medium because it can suppress magnetization reversal on the initialization side and can greatly improve the quality of a transfer signal.

FIG. 1 is a schematic view for explaining the protrusion amount of a convex portion of a conventional magnetic transfer master carrier. FIG. 2 is a schematic diagram for explaining the protrusion amount of the convex portion of the magnetic transfer master carrier of the present invention. FIG. 3 is a schematic diagram of the steps of the magnetic transfer method according to the embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of the slave disk. FIG. 5 is a schematic cross-sectional view showing the magnetization direction of the magnetic layer (recording layer) after the initial magnetization step. FIG. 6 is a cross-sectional view showing a form example of the master disk. FIG. 7 is a process diagram showing a method for manufacturing a master disk. FIG. 8 is a plan view of the master disk. FIG. 9 is an explanatory diagram of the magnetic transfer process. FIG. 10 is a schematic configuration diagram of a magnetic field application device used in the magnetic transfer process. FIG. 11 is a schematic cross-sectional view showing the magnetization direction of the magnetic layer after the magnetic transfer process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Slave disk 20 Master disk 12 Board | substrate 13 Soft magnetic layer 16 Magnetic layer 60 Magnetic field application means 62 Core 63 Coil 80 Magnetic field application apparatus 202,212 Base material 204,214 Magnetic layer 206 Convex part 207 Concave part

Claims (4)

In the master carrier for magnetic transfer having a concavo-convex pattern formed by arranging a plurality of convex portions on the surface of the base material with reference to the surface, and at least the convex portion surface has a magnetic layer,
The magnetic transfer master carrier, wherein the ratio (A / B) between the protruding amount A of the magnetic layer at the convex portion and the thickness B of the magnetic layer at the convex portion satisfies 1/10 to 1/6. .
However, the protrusion A is (the maximum width X of the magnetic layer in the direction perpendicular to the thickness direction of the magnetic layer in the convex portion) − (the convex portion in the direction perpendicular to the thickness direction of the magnetic layer in the convex portion). Represents the maximum width Y).   The master carrier for magnetic transfer according to claim 1, wherein the ratio (A / B) satisfies 1/8 to 1/7.   The magnetic transfer master carrier according to claim 1, wherein the magnetic layer has perpendicular magnetic anisotropy.   A magnetic recording medium produced by a magnetic transfer method using the magnetic transfer master carrier according to claim 1.