JP2011060339A - Method for manufacturing magnetic recording medium and magnetic recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a magnetic recording medium which achieves a high-speed smoothing process of a magnetic layer which comprises a clear magnetic recording pattern. <P>SOLUTION: While pressing a rotating polishing pad 101 onto the surface of a nonmagnetic substrate 1, a polishing solution S is supplied between the surface of the nonmagnetic substrate 1 and the polishing pad 101, and the nonmagnetic substrate is rotated or swung, in a polishing process. The polishing solution S includes monocrystal diamond particles and a polishing auxiliary agent. The diamond particles have 1-10 nm primary particle diameters and 50-100 nm secondary particle diameters. The auxiliary agent contains an organic polymer which comprises a sulfonic acid group or a carboxylic acid group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a magnetic recording medium used in a hard disk drive (HDD) and the like, and a magnetic recording / reproducing apparatus.

  In recent years, the application range of magnetic recording devices such as magnetic disk devices, flexible disk devices, and magnetic tape devices has been remarkably increased, and the importance has increased, and the recording density of magnetic recording media used in these devices has been significantly improved. Is being planned. In particular, since the introduction of MR heads and PRML technology, the increase in surface recording density has become even more intense. In recent years, GMR heads, TMR heads, etc. have been introduced and have continued to increase at a rate of about 1.5 times a year. ing.

  These magnetic recording media are required to achieve higher recording densities in the future. For this reason, it is required to achieve a high coercivity of the magnetic layer, a high signal-to-noise ratio (SNR), and high resolution. In recent years, efforts have been made to increase the surface recording density by increasing the track density as well as improving the linear recording density.

  In the latest magnetic recording apparatus, the track density has reached 110 kTPI. However, as the track density is increased, magnetic recording information between adjacent tracks interferes with each other, and the problem that the magnetization transition region in the boundary region becomes a noise source and the SNR is easily lost. This leads to a deterioration of the bit error rate, which is an obstacle to improvement of the recording density.

  In order to increase the surface recording density, it is necessary to make the size of each recording bit on the magnetic recording medium finer and ensure as much saturation magnetization and magnetic film thickness as possible for each recording bit. On the other hand, when the recording bit is miniaturized, the minimum magnetization volume per bit is reduced, and there arises a problem that the recording data is lost due to magnetization reversal due to thermal fluctuation.

  In addition, as the track density increases, the distance between tracks becomes closer, so magnetic recording devices require extremely accurate track servo technology. At the same time, recording is performed widely and playback is affected by adjacent tracks. In order to eliminate as much as possible, a method of executing narrower than the recording is generally used. However, this method can minimize the influence between tracks, but has a problem that it is difficult to obtain a sufficient reproduction output, and as a result, it is difficult to ensure a sufficient SNR.

  As one of the methods for achieving such problems of thermal fluctuation, ensuring SNR, and ensuring sufficient output, by forming irregularities along the tracks on the recording medium surface and physically separating the recording tracks from each other Attempts have been made to increase track density. Such a technique is generally called a discrete track method, and a magnetic recording medium manufactured by the technique is called a discrete track medium. There is also an attempt to manufacture a so-called patterned medium in which the data area in the same track is further divided.

  As an example of a discrete track medium, a magnetic recording medium is known in which a magnetic recording medium is formed on a non-magnetic substrate having a concavo-convex pattern formed on a surface, and a magnetic recording track and a servo signal pattern that are physically separated are formed. (For example, refer to Patent Document 1).

  In this magnetic recording medium, a ferromagnetic layer is formed on a surface of a substrate having a plurality of irregularities on the surface via a soft magnetic layer, and a protective film is formed on the surface. In this magnetic recording medium, a magnetic recording area physically separated from the periphery is formed in the convex area.

  According to this magnetic recording medium, the occurrence of a domain wall in the soft magnetic layer can be suppressed, so that the influence of thermal fluctuation is difficult to occur, and there is no interference between adjacent signals, so that a high-density magnetic recording medium with less noise can be formed. ing.

  The discrete track method includes a method of forming a track after forming a magnetic recording medium consisting of several thin films, and a magnetic pattern after forming a concavo-convex pattern directly on the substrate surface in advance or on a thin film layer for track formation. There is a method of forming a thin film of a recording medium (see, for example, Patent Documents 2 and 3).

  Among these, the former method is called a magnetic layer processing type. However, in this method, since the surface is physically processed after the medium is formed, there is a disadvantage that the medium is easily contaminated in the manufacturing process and the manufacturing process becomes very complicated. On the other hand, the latter method is called an embossing die. However, in this method, although the medium is not easily contaminated during the manufacturing process, the uneven shape formed on the substrate is inherited by the film formed thereon, so that recording is performed while floating on the medium. There is a problem that the flying posture of the recording / reproducing head for performing reproduction and the flying height become unstable.

  Also, the magnetic track area of the discrete track medium is formed by injecting ions such as nitrogen and oxygen into a previously formed magnetic layer or by irradiating a laser to change the magnetic characteristics of the portion. A method is disclosed (for example, see Patent Documents 4 to 6).

  Further, after forming a concavo-convex pattern on the surface of the magnetic layer, a nonmagnetic layer is formed to cover the surface, and the surface of the nonmagnetic layer is smoothed by oblique ion beam etching or CMP (Chemical Mechanical Polishing). A method of forming a magnetic recording pattern is disclosed (see, for example, Patent Document 7).

JP 2004-164692 A JP 2004-178793 A JP 2004-178794 A Japanese Patent Laid-Open No. 5-205257 JP 2006-209952 A JP 2006-309841 A JP 2005-135455 A

  By the way, in order to fly the magnetic head in a stable state on the surface of the magnetic recording medium, high smoothness on the surface of the magnetic recording medium is required. For example, when manufacturing a discrete track medium, the magnetic layer is physically roughened, and then the processed portion is filled with a nonmagnetic material. It is necessary to remove from the surface of the substrate or to smooth the surface.

  As the smoothing process, oblique ion beam etching is generally used. However, the oblique ion beam etching (dry etching) has a problem that productivity of the magnetic recording medium is lowered because the etching takes time. Further, in Patent Document 7 described above, CMP is described as a smoothing process. However, a wet smoothing process such as CMP has a high polishing speed, but is difficult to precisely polish and requires high smoothness. It was not suitable for surface polishing of magnetic recording media. There is also a problem that the magnetic layer is corroded after polishing.

  The present invention has been proposed in view of such a conventional situation, and performs a smoothing process of a magnetic layer having a clear magnetic recording pattern at a high speed and further improves the productivity. It is an object of the present invention to provide a method for manufacturing a recording medium, and a magnetic recording / reproducing apparatus using a magnetic recording medium manufactured by such a manufacturing method, which can further improve electromagnetic conversion characteristics.

  In order to achieve the above object, the present inventor has conducted intensive research, and as a result, when polishing the surface of the nonmagnetic layer covering the processed surface of the magnetic layer until the magnetic layer is exposed, a specific diamond is used. Using a diamond slurry containing particles and a polishing aid and supplying the diamond slurry to the surface of the nonmagnetic layer, a rotating polishing pad is pressed against the surface of the nonmagnetic layer, thereby providing a magnetic film having a clear magnetic recording pattern. The present inventors have found that the layer smoothing process can be performed at high speed and productivity can be improved, and the present invention has been completed.

That is, the present invention provides the following means.
(1) A method of manufacturing a magnetic recording medium having magnetically separated magnetic recording patterns,
Forming a magnetic layer on a non-magnetic substrate;
Forming a resist layer patterned in a shape corresponding to the magnetic recording pattern on the magnetic layer;
Partially removing the magnetic layer using the resist layer;
Forming a nonmagnetic layer covering the surface from which the magnetic layer has been removed;
Polishing the nonmagnetic layer until the magnetic layer is exposed,
The polishing process supplies diamond slurry between the surface of the nonmagnetic layer and the polishing pad while pressing the rotating polishing pad against the surface of the nonmagnetic layer to rotate or swing the nonmagnetic substrate. By doing
The diamond slurry includes single crystal diamond particles and a polishing aid,
The diamond particles have a primary particle size in the range of 1 to 10 nm and a secondary particle size in the range of 50 to 100 nm.
The method for producing a magnetic recording medium, wherein the polishing aid contains an organic polymer having a sulfonic acid group or a carboxylic acid group.
(2) The method for producing a magnetic recording medium as described in (1) above, wherein the polishing aid is an organic polymer having an average molecular weight of 4000 to 10,000 having sodium sulfonate or sodium carboxylate.
(3) The diamond slurry further includes an anticorrosive agent,
The method for producing a magnetic recording medium according to (1) or (2), wherein the anticorrosive is benzotriazole or a derivative thereof.
(4) The above-mentioned item, wherein the benzotriazole derivative is obtained by substituting one or more hydrogen atoms of benzotriazole with any of a carboxyl group, a methyl group, an amino group, and a hydroxyl group. The method for producing a magnetic recording medium according to (3).
(5) a magnetic recording medium manufactured by the method according to any one of (1) to (4) above;
A medium driving unit for driving the magnetic recording medium in a recording direction;
A magnetic head for performing a recording operation and a reproducing operation on the magnetic recording medium;
Head moving means for moving the magnetic head relative to a magnetic recording medium;
A magnetic recording / reproducing apparatus comprising: a recording / reproducing signal processing means for inputting a signal to the magnetic head and reproducing an output signal from the magnetic head.

  As described above, according to the present invention, it is possible to perform a smoothing process of a magnetic layer having a clear magnetic recording pattern at high speed, so that a magnetic recording medium having a high recording density can be manufactured with high productivity. Is possible. Further, in a magnetic recording / reproducing apparatus using such a magnetic recording medium, it is possible to further improve electromagnetic conversion characteristics.

FIG. 1 is a cross-sectional view for explaining a method of manufacturing a magnetic recording medium to which the present invention is applied. FIG. 2 is a side view showing an example of a polishing apparatus used in the present invention. FIG. 3 is a cross-sectional view showing an example of a magnetic recording medium manufactured by applying the present invention. FIG. 4 is a perspective view showing a configuration example of the magnetic recording / reproducing apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

(Method of manufacturing magnetic recording medium)
First, a method for manufacturing a magnetic recording medium to which the present invention is applied will be described.
The present invention relates to a method of manufacturing a magnetic recording medium having magnetically separated magnetic recording patterns. For example, as shown in FIGS. 1A to 1F, a magnetic layer is formed on a nonmagnetic substrate 1. 2, a step of forming a resist layer 3 patterned in a shape corresponding to the magnetic recording pattern MP on the magnetic layer 2, and a step of partially removing the magnetic layer 2 using the resist layer 3. A step of forming a nonmagnetic layer 4 covering the surface from which the magnetic layer 2 has been removed, a step of polishing the nonmagnetic layer 4 until the magnetic layer 2 is exposed, and a surface subjected to the polishing process It includes a step of forming the protective layer 5 thereon and a step of forming the lubricating film 6 on the protective layer 5.

  Specifically, when manufacturing such a magnetic recording medium, first, as shown in FIG. 1A, a magnetic layer 2 is formed on a nonmagnetic substrate 1 and then the magnetic layer 2 is formed. For example, the resist layer 3 patterned into a shape corresponding to the magnetic recording pattern MP is formed by using, for example, a photolithography method or a nanoimprint method.

  Here, when patterning the resist layer 3, it is preferable to use a nanoimprint method. In this nanoimprint method, a material that is cured by irradiation with radiation is used for the resist layer 3, and a pattern is transferred to the resist layer 3 using a stamp (not shown).

  Moreover, in this invention, it is preferable to irradiate the resist layer 3 with a radiation after the process of transferring such a pattern. Thereby, the shape of the stamp can be transferred to the resist layer 3 with high accuracy, and the formation characteristics of the magnetic recording pattern MP can be improved.

  In particular, when a pattern is transferred to the resist layer 3 using a stamp, the resist layer 3 is pressed in a state where the fluidity of the resist layer 3 is high, and the resist layer 3 is irradiated with radiation in the pressed state. By irradiating, the resist layer 3 is cured, and then the stamp is separated from the resist layer 3 so that the shape of the stamp can be transferred to the resist layer 3 with high accuracy.

  As a method of irradiating the resist layer 3 with radiation while the stamp is pressed against the resist layer 3, for example, a method of irradiating radiation from the opposite side of the stamp, that is, the non-magnetic substrate 1 side, or radiation as a stamp material. A material that can pass through, a method of irradiating radiation from the stamp side, a method of irradiating radiation from the side of the stamp, a radiation that is highly conductive to solids such as heat rays, or a stamp or a non-magnetic substrate 1 A method of irradiating radiation by heat conduction from the substrate can be used.

  In addition, the radiation in this invention means the electromagnetic waves of wide concepts, such as a heat ray, visible light, an ultraviolet-ray, X-ray | X_line, a gamma ray. Examples of the material that is cured by irradiation with radiation include a thermosetting resin for heat rays and an ultraviolet curable resin for ultraviolet rays.

  Among these materials, in particular, the resist layer 3 is made of an ultraviolet curable resin such as a novolak resin, an acrylate ester, or an alicyclic epoxy, and the stamp material is a glass that is highly permeable to ultraviolet rays. Alternatively, it is preferable to use a resin.

  In the above-described pattern transfer process, a stamper in which a fine track pattern is formed on a metal plate by using a method such as electron beam drawing can be used as the stamp. Further, since the stamper is required to have hardness and durability that can withstand the above process, for example, Ni or the like is used. However, the material is not particularly limited as long as it meets the above purpose. . Further, in addition to the track for recording normal data, a servo signal pattern such as a burst pattern, a gray code pattern, and a preamble pattern can be formed on the stamp.

  Further, as shown in FIG. 1B, the resist layer 12 is removed by ion milling or the like until the magnetic layer 11 is exposed after the pattern is transferred.

  Next, as shown in FIG. 1C, portions of the magnetic layer 2 that are not covered with the resist layer 3 are partially removed by ion milling or the like. As a result, the surface of the nonmagnetic substrate 1 is exposed from between the resist layers 3 remaining on the magnetic layer 2.

  Next, as shown in FIG. 1D, a nonmagnetic layer 4 covering the surface from which the magnetic layer 2 has been removed is formed. The nonmagnetic layer 4 is formed with a thickness sufficient to be embedded in the portion where the magnetic layer 2 is removed.

  Next, as shown in FIG. 1E, the nonmagnetic layer 4 is polished by CMP (Chemical Mechanical Polishing) until the magnetic layer 2 is exposed. As a result, the magnetic layer 2 serving as the magnetic recording pattern MP is exposed from between the flattened nonmagnetic layers 4.

  Next, as shown in FIG. 1 (f), a protective layer 5 is formed on the magnetic layer 2 and the nonmagnetic layer 4 that have been subjected to polishing, and then a lubricant is applied on the protective layer 5. Thus, the lubricating film 6 is formed.

  Incidentally, when polishing the surface of the nonmagnetic substrate 1 on which the nonmagnetic layer 4 is formed, for example, a polishing apparatus 100 as shown in FIG. 2 is used.

  As shown in FIG. 2, the polishing apparatus 100 is polished from a flat surface plate 102 having a polishing pad 101 attached to the upper surface, a spindle 103 that rotationally drives the flat surface plate 102, and a rotation center of the flat surface plate 102. A nozzle 104 that supplies the polishing liquid S to the surface of the pad 101, a pressing tool 105 that presses the nonmagnetic layer 4 side of the nonmagnetic substrate 1 against the polishing pad 101, and a spindle 106 that rotationally drives the pressing tool 105 are provided. .

  In the polishing apparatus 100, the nonmagnetic substrate 1 can be swung in the radial direction of the flat surface plate 102 via the pressing tool 105. Further, an elastic sheet 107 made of rubber or the like is disposed on the pressing surface of the pressing tool 105. In the polishing apparatus 100, the nonmagnetic substrate 1 is pressed against the polishing pad 101 via the elastic sheet 107, whereby the pressure applied to the nonmagnetic substrate 1 can be made uniform and the occurrence of uneven polishing can be suppressed. ing.

  In the polishing apparatus 100 having the above-described structure, the nonmagnetic substrate 1 is nonmagnetically bonded to the surface of the polishing pad 101 rotating together with the flat surface plate 102 via the pressing tool 105 while rotating the flat surface plate 102. Press the layer 4 side. At this time, the polishing liquid S is supplied between the surface of the nonmagnetic substrate 1 and the polishing pad 101 through the nozzle 104. Then, the surface of the nonmagnetic substrate 1 (nonmagnetic layer 4) is wet-polished by rotating or swinging the nonmagnetic substrate 1 on the polishing pad 101 via the pressing tool 105.

  Thereby, the surface of the nonmagnetic substrate 1 on which the nonmagnetic layer 4 is formed can be smoothed until the magnetic layer 2 is exposed.

  By the way, in the manufacturing method of the magnetic recording medium to which the present invention is applied, a diamond slurry containing specific diamond particles (abrasive grains) and a polishing aid (polishing accelerator) is used as the polishing liquid S. The smoothing process of the magnetic layer 2 having the magnetic recording pattern MP can be performed at high speed.

  Specifically, the diamond slurry is obtained by dispersing diamond particles and a polishing aid in a dispersion medium such as water or alcohol, and the single crystal diamond particles are in the range of 0.001 to 0.05 mass%, A polishing aid is contained in the range of 10 to 100 times the diamond particles.

  The diamond particles preferably have a primary particle size in the range of 1 to 10 nm and a secondary particle size in the range of 50 to 100 nm. By using such diamond particles, the surface of the nonmagnetic substrate 1 can be further smoothed in the polishing step.

  The polishing aid contains at least an organic polymer having a sulfonic acid group or a carboxylic acid group, and among them, an organic polymer having an average molecular weight of 4000 to 10,000 having sodium sulfonate or sodium carboxylate is preferably used. . Thereby, the surface of the nonmagnetic substrate 1 can be further smoothed in the polishing step.

  Examples of the organic polymer containing sodium sulfonate or sodium carboxylate include GEROPON SC / 213 (trade name / Rhodia), GEROPON T / 36 (trade name / Rhodia), GEROPON TA / 10 (trade name / Rhodia), GEROPON TA / 72 (brand name / Rhodia), New Calgen WG-5 (brand name / Takemoto Yushi Co., Ltd.), Agrisol G-200 (brand name / Kao Corporation), Demall EP Powder (brand name / Kao Corporation) Co., Ltd.), Demall RNL (trade name / Kao Corporation), Isoban 600-SF35 (trade name / Kuraray Co., Ltd.), Polystar OM (trade name / Nippon Yushi Co., Ltd.), Sokalan CP9 (trade name / BA) SF Japan Co., Ltd.), Sokalan PA-15 (trade name / BSF Japan ( )), Toxanone GR-31A (trade name / Sanyo Chemical Industry Co., Ltd.), Solpol 7248 (trade name / Toho Chemical Co., Ltd.), Charol AN-103P (trade name / Daiichi Kogyo Seiyaku Co., Ltd.), Aron T-40 (trade name / Toagosei Chemical Co., Ltd.), Panacayak CP (trade name / Nippon Kayaku Co., Ltd.), Disrol H12C (trade name / Nippon Emulsifier Co., Ltd.) . Among them, it is particularly preferable to use Demol RNL (trade name / Kao Co., Ltd.) and Polystar OM (trade name / Nippon Yushi Co., Ltd.) as the polishing aid.

  The diamond slurry preferably further contains an anticorrosive agent. In the polishing step, the magnetic layer 2 to be the magnetic recording pattern MP is exposed from between the polished nonmagnetic layers 4, but the magnetic layer 2 generally contains a corrosive substance such as Co, Ni, and Fe. It is out. Therefore, by adding an anticorrosive to the diamond slurry, it is possible to prevent corrosion of the magnetic layer 2 during polishing and to obtain a magnetic recording medium having excellent electromagnetic conversion characteristics.

  As the anticorrosive agent, it is preferable to use benzotriazole or a derivative thereof. Moreover, as a derivative of benzotriazole, for example, one obtained by substituting one or two or more hydrogen atoms of benzotriazole with a carboxyl group, a methyl group, an amino group, a hydroxyl group, or the like can be used. Furthermore, as a derivative of benzotriazole, 4-carboxylbenzotriazole or a salt thereof, 7-carboxybenzotriazole or a salt thereof, benzotriazole butyl ester, 1-hydroxymethylbenzotriazole, 1-hydroxybenzotriazole, or the like can be used. . The addition amount of the anticorrosive agent is preferably 1% by mass or less, more preferably 0.001 to 0.1% by mass with respect to the total amount when the diamond slurry is used.

  When the polishing apparatus 100 shown in FIG. 2 is used to polish the surface of the non-magnetic substrate 10, the rotational speed of the flat surface plate 102 by the spindle 103 is in the range of 10 to 100 rpm. Is more preferable, and a range of 15 to 50 rpm is more preferable. If the rotational speed of the flat surface plate 102 is less than 10 rpm, it takes a very long time to smooth the surface of the nonmagnetic substrate 1. On the other hand, when the rotational speed of the flat surface plate 102 exceeds 100 rpm, the polishing liquid S supplied from the nozzle 104 does not stay between the surface of the non-magnetic substrate 1 and the polishing pad 101 and is scattered around. Absent.

  The flow rate of the polishing liquid S supplied from the nozzle 104 is preferably 10 to 100 ml / min. The polishing liquid S may be supplied continuously between the surface of the nonmagnetic substrate 1 and the polishing pad 101, may be supplied at intervals, or may be supplied discontinuously.

  As the polishing pad 101, for example, a foamed urethane-based polishing pad such as a foamed urethane sheet, a nonwoven fabric-based polishing pad in which a nonwoven fabric such as polyester is impregnated with a urethane resin, a suede-based polishing pad, etc. can be generally used. It is not necessarily limited to these.

  The pressing tool 105 can rotate the nonmagnetic substrate 1 in the same direction as the rotation direction of the flat surface plate 102 or in the opposite direction. At this time, the rotational speed of the nonmagnetic substrate 1 by the pressing tool 105 is preferably in the range of 5 to 60 rpm, more preferably in the range of 20 to 40 rpm. Thereby, generation | occurrence | production of a scratch etc., and the diamond particle in polishing liquid S can suppress that the surface of the nonmagnetic board | substrate 1 is stabbed or embedded. In addition, when the rotational speed of the nonmagnetic substrate 1 is less than 5 rpm, the uniformity of the polishing amount on the polishing surface decreases. On the other hand, if the rotational speed of the nonmagnetic substrate 1 exceeds 60 rpm, the polishing amount becomes too high and it is difficult to control the polishing amount.

  Further, the pressing tool 105 can be swung in the radial direction of the flat surface plate 102 at the same time as rotating the non-magnetic substrate 1. The rocking speed at that time is preferably 10 to 100 times / minute in a reciprocating manner, and more preferably 30 to 50 times / second. As a result, a sufficient amount of grinding can be obtained, and a surface with a uniform grinding state in which generation of scratches and the like is suppressed can be obtained.

The pressing pressure of the nonmagnetic substrate 1 against the polishing pad 101 by the pressing tool 105 is preferably in the range of 0.5 × 9.8 × 10 ^{4 to} 1.5 × 9.8 × 10 ⁴ Pa, and 0.8 × 9. More preferably, the range is from 8 × 10 ^{4 to} 1.2 × 9.8 × 10 ⁴ Pa. Thereby, generation | occurrence | production of a scratch etc. can be suppressed and a smooth polished surface can be formed.

  In addition, after performing the said grinding | polishing process, it is preferable to perform the cleaning process by a pure water or neutral detergent. Thereby, the residue by the said grinding | polishing process can be removed from the surface of the nonmagnetic board | substrate 1. FIG.

  In addition, the surface average roughness Ra of the nonmagnetic substrate 1 after passing through the polishing step is preferably as low as possible. Specifically, it is preferably 2.5 mm (0.25 nm) or less, and more preferably 1.5 mm or less. Here, when the surface average roughness Ra of the nonmagnetic substrate 1 exceeds 2.5 mm, the smoothness of the surface of the magnetic recording medium is lowered, the glide height characteristic is lowered, and the flying height of the magnetic head is lowered during recording and reproduction. It becomes difficult to do.

  In the polishing apparatus 100 shown in FIG. 2, the polishing process is performed on one surface of the nonmagnetic substrate 1. However, the present invention is not limited to such a configuration, and both surfaces of the nonmagnetic substrate 1 are used. At the same time, it is possible to have a configuration in which polishing is performed.

  When the polishing apparatus 100 shown in FIG. 2 is used, the entire surface of the nonmagnetic substrate 1 can be simultaneously polished, and the surface of the nonmagnetic substrate 1 can be polished in a random direction. Is possible. Therefore, when such a polishing apparatus 100 is used, it is possible to suppress the occurrence of uneven polishing on the surface of the nonmagnetic substrate 1, and a plurality of nonmagnetic substrates 1 can be simultaneously attached to one unit. Since it is also possible to polish, productivity can be improved.

  As described above, according to the present invention, it is possible to perform a smoothing process of a magnetic layer having a clear magnetic recording pattern at high speed, so that a magnetic recording medium having a high recording density can be manufactured with high productivity. Is possible. Further, in a magnetic recording / reproducing apparatus using such a magnetic recording medium, it is possible to further improve electromagnetic conversion characteristics.

(Magnetic recording medium)
Next, a specific configuration of the magnetic recording medium manufactured by applying the present invention will be described in detail by taking, for example, a discrete magnetic recording medium 30 shown in FIG.
Note that the magnetic recording medium 30 exemplified in the following description is only an example, and the magnetic recording medium manufactured by applying the present invention is not necessarily limited to such a configuration. It is possible to carry out by appropriately changing within a range not changing.

  As shown in FIG. 3, the magnetic recording medium 30 has a soft magnetic layer 32, an intermediate layer 33, a recording magnetic layer 34 having a magnetic recording pattern 34a, and a protective layer 35 on both surfaces of a nonmagnetic substrate 31. It has a structure in which layers are sequentially laminated, and further has a structure in which a lubricating film 36 is formed on the outermost surface. The soft magnetic layer 32, the intermediate layer 33, and the recording magnetic layer 34 constitute a magnetic layer 37. In FIG. 3, only one surface of the nonmagnetic substrate 31 is illustrated.

  As the nonmagnetic substrate 31, for example, an Al alloy substrate mainly composed of Al such as an Al—Mg alloy, a glass substrate such as soda glass, aluminosilicate glass, or crystallized glass, a silicon substrate, a titanium substrate, a ceramic substrate, Various substrates such as a resin substrate can be mentioned, and among them, an Al alloy substrate, a glass substrate, and a silicon substrate are preferably used. Further, the average surface roughness (Ra) of the nonmagnetic substrate 31 is preferably 1 nm or less, more preferably 0.5 nm or less, and further preferably 0.1 nm or less.

The magnetic layer 37 may be a horizontal magnetic layer for an in-plane magnetic recording medium or a perpendicular magnetic layer for a perpendicular magnetic recording medium, but a perpendicular magnetic layer is preferable in order to realize a higher recording density. The magnetic layer 37 is preferably formed from an alloy mainly composed mainly of Co, for example, CoCrPt system, CoCrPtB based magnetic layer and the CoCrPtTa system, these and SiO _2, the oxidation of such _Cr 2 _{O 3} A magnetic layer having a granular structure to which an object is added can be used.

In the case of a perpendicular magnetic recording medium, for example, a soft magnetic FeCo alloy (FeCoB, FeCoSiB, FeCoZr, FeCoZrB, FeCoZrBCu, etc.), FeTa alloy (FeTaN, FeTaC, etc.), Co alloy (CoTaZr, CoZrNB, CoB, etc.), etc. available soft magnetic layer 32, an intermediate layer 33 made of Ru or the like, a material obtained by laminating a recording magnetic layer 34 made of 60Co-15Cr-15Pt alloy or 70Co-5Cr-15Pt-10SiO ₂ alloy. Further, an orientation control film made of Pt, Pd, NiCr, NiFeCr or the like may be laminated between the soft magnetic layer 32 and the intermediate layer 33.

  On the other hand, in the case of an in-plane magnetic recording medium, a non-magnetic CrMo underlayer and a ferromagnetic CoCrPtTa magnetic layer can be used as the magnetic layer 37.

  The thickness of the magnetic layer 37 is 3 nm or more and 20 nm or less, preferably 5 nm or more and 15 nm or less, and may be formed so as to obtain sufficient head input / output according to the type of magnetic alloy used and the laminated structure. In addition, the magnetic layer 37 needs to have a film thickness of a certain level or more in order to obtain an output of a certain level or more during reproduction, while parameters indicating recording / reproduction characteristics usually deteriorate as the output increases. Therefore, it is necessary to set an optimum film thickness. The magnetic layer 37 is usually formed as a thin film by sputtering.

  The granular magnetic layer 37 includes at least Co and Cr as magnetic particles, and at least Si oxide, Cr oxide, Ti oxide, W oxide, Co oxide, Ta oxide at the grain boundary portion of the magnetic particles. And those containing at least one or two or more selected from Ru oxides. Specifically, for example, CoCrPt—Si oxide, CoCrPt—Cr oxide, CoCrPt—W oxide, CoCrPt—Co oxide, CoCrPt—Cr oxide—W oxide, CoCrPt—Cr oxide—Ru oxide , CoRuPt—Cr oxide—Si oxide, CoCrPtRu—Cr oxide—Si oxide, and the like.

  The average grain size of the magnetic crystal grains having a granular structure is preferably 1 nm or more and 12 nm or less. The total amount of oxides present in the magnetic layer is preferably 3 to 15 mol%. Examples of the magnetic layer not having a granular structure include a layer using a magnetic alloy containing Co and Cr, and preferably containing Pt.

The magnetic recording medium 30 is a so-called discrete type magnetic recording medium in which a magnetic recording pattern 34 a formed in the recording magnetic layer 34 is magnetically separated by a nonmagnetic layer 38. For the nonmagnetic layer 38, for example, in addition to a Cr alloy, a nonmagnetic CoCr alloy having a large Cr content, a Ti alloy, or the like, SiO ₂ using spin-on glass or the like, a resin material, or the like can be used. .

  Also, in the discrete magnetic recording medium 30, in order to increase the recording density, in the recording magnetic layer 34, the width L1 of the magnetic recording pattern 34a is 200 nm or less, and the width L2 of the nonmagnetic layer 38 is 100 nm or less. Is preferred. The track pitch P (= L1 + L2) of the magnetic recording medium 30 is preferably 300 nm or less, and is preferably as narrow as possible in order to increase the recording density.

The protective layer 35 may be made of a material usually used in a magnetic recording medium. Examples of such a material include carbon (C), hydrogenated carbon (HXC), nitrogenated carbon (CN), and alumocarbon. Examples thereof include carbonaceous materials such as silicon carbide (SiC), SiO ₂ , Zr ₂ O ₃ , and TiN. The protective layer 35 may be a laminate of two or more layers. If the thickness of the protective layer 35 exceeds 10 nm, the distance between the magnetic head and the magnetic layer 37 increases, and sufficient input / output characteristics cannot be obtained.

  The lubricating film 36 can be formed, for example, by applying a lubricant made of a fluorine-based lubricant, a hydrocarbon-based lubricant, a mixture thereof, or the like on the protective layer 35. The film thickness of the lubricating film 36 is usually about 1 to 4 nm.

  The discrete magnetic recording medium 30 as described above can be manufactured with high productivity by using the magnetic recording medium manufacturing method to which the present invention is applied.

(Magnetic recording / reproducing device)
Next, a magnetic recording / reproducing apparatus (HDD) to which the present invention is applied will be described.
A magnetic recording / reproducing apparatus to which the present invention is applied includes, for example, as shown in FIG. 4, the magnetic recording medium 30, a rotational drive unit 51 that rotationally drives the magnetic recording medium 30, A magnetic head 52 that performs a reproducing operation, a head drive unit 53 that moves the magnetic head 52 in the radial direction of the magnetic recording medium 30, and a signal input to the magnetic head 52 and an output signal from the magnetic head 52 are reproduced. And a recording / reproducing signal processing system 54.

  In this magnetic recording / reproducing apparatus, by using the discrete track type magnetic recording medium 30, it is possible to eliminate writing blur when performing magnetic recording on the magnetic recording medium 30 and to obtain a high surface recording density. That is, by using the magnetic recording medium 30, a magnetic recording / reproducing apparatus having a high recording density can be configured. In addition, by processing the recording track of the magnetic recording medium 30 magnetically discontinuously, conventionally, the reproducing head width is made narrower than the recording head width in order to eliminate the influence of the magnetization transition region at the track edge portion. What was supported can be operated with both of them approximately the same width. As a result, sufficient reproduction output and high SNR can be obtained.

  Furthermore, by configuring the reproducing unit of the magnetic head 52 with a GMR head or a TMR head, a sufficient signal intensity can be obtained even at a high recording density, and a magnetic recording / reproducing apparatus having a high recording density can be realized. it can. Further, when the flying height of the magnetic head 52 is within the range of 0.005 μm to 0.020 μm, and the flying height is lower than the conventional height, the output is improved and a high device SNR is obtained, and the large capacity and the high reliability are obtained. The magnetic recording / reproducing apparatus can be provided.

  Further, when the signal processing circuit based on the maximum likelihood decoding method is combined, the recording density can be further improved. For example, the track density is 100 k tracks / inch or more, the linear recording density is 1000 k bits / inch or more, and the recording density is 100 G bits or more per square inch. A sufficient SNR can also be obtained when recording / reproducing.

  The present invention can be widely applied to a magnetic recording medium having a magnetically separated magnetic recording pattern MP. As a magnetic recording medium having a magnetic recording pattern, the magnetic recording pattern is 1 bit. Examples thereof include so-called patterned media arranged with a certain regularity, media with magnetic recording patterns arranged in a track shape, and other magnetic recording media including servo signal patterns. Among these, the present invention is preferably applied to a so-called discrete type magnetic recording medium in which magnetically separated magnetic recording patterns are magnetic recording tracks and servo signal patterns, from the viewpoint of simplicity in manufacturing.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
In Example 1, first, the vacuum chamber in which the glass substrate for HD was set was evacuated to 1.0 × 10 ⁻⁵ Pa or less in advance. The glass substrate used here is composed of Li ₂ Si ₂ O ₅ , Al ₂ O ₃ —K ₂ O, Al ₂ O ₃ —K ₂ O, MgO—P ₂ O ₅ , and Sb ₂ O ₃ —ZnO. The material is crystallized glass, and the outer diameter is 65 mm, the inner diameter is 20 mm, and the average surface roughness (Ra) is 2 angstroms (unit: Å, 0.2 nm).

Next, using a DC sputtering method on this glass substrate, a FeCoB film having a thickness of 60 nm as a soft magnetic layer, a Ru film having a thickness of 10 nm as an intermediate layer, and a 70Co-5Cr-15Pt— layer having a thickness of 15 nm as a recording magnetic layer. A 10SiO ₂ alloy film and a 70Co-5Cr-15Pt alloy film having a layer thickness of 14 nm were laminated in this order.

Next, a resist was applied thereon by a spin coating method to form a resist layer having a layer thickness of 100 nm. Note that a novolac resin, which is an ultraviolet curable resin, was used as the resist. Then, using a glass stamp having a positive pattern of the magnetic recording pattern, UV light having a wavelength of 250 nm is applied to the resist layer in a state where the stamp is pressed against the resist layer at a pressure of 1 MPa (about 8.8 kgf / cm ² ). The resist layer was cured by irradiating from the top of a glass stamp having a transmittance of 95% or more for 10 seconds. Thereafter, the stamp was separated from the resist layer, and an uneven pattern corresponding to the magnetic recording pattern was transferred to the resist layer.

  The concavo-convex pattern transferred to the resist layer corresponds to a magnetic recording pattern of 271 k tracks / inch, the convex portion has a circumferential shape with a width of 64 nm, and the concave portion has a circumferential shape with a width of 30 nm. The thickness was 65 nm, and the depth of the concave portion of the resist layer was about 5 nm. The angle of the recess with respect to the substrate surface was approximately 90 degrees.

Next, the concave portions of the resist layer were removed by dry etching. The dry etching conditions were O ₂ gas of 40 sccm, pressure of 0.3 Pa, high frequency plasma power of 300 W, DC bias of 30 W, and etching time of 10 seconds.

Next, a portion of the recording magnetic layer not covered with the mask layer was processed with an ion beam. The ion beam was generated using a mixed gas of nitrogen gas 40 sccm, hydrogen gas 20 sccm, and neon 20 sccm. The amount of ions was 5 × 10 ¹⁶ atoms / cm ² , the acceleration voltage was 20 keV, the etching rate was 0.1 nm / second, and the etching time was 90 seconds. The processing depth of the recording magnetic layer was 15 nm, and the recording magnetic layer having a thickness of about 14 nm below the processing position became amorphous by ion beam implantation, and the coercive force was reduced by about 80%.

  Next, a silsesquioxane skeleton-containing organic compound film was formed on this surface by spin coating. Spin coating was performed by dropping 0.5 ml of the composition onto a substrate set in a spin coater and rotating the substrate at 500 rpm for 5 seconds, then at 3000 rpm for 2 seconds, and further at 5000 rpm for 20 seconds. And after apply | coating the organic compound film | membrane to the substrate surface, this organic compound film | membrane was irradiated and irradiated with the ultraviolet-ray, and was hardened.

  Next, using the polishing apparatus 100 shown in FIG. 2, the surface of this nonmagnetic substrate was polished. The polishing conditions are as follows. That is, for the abrasive grains contained in the polishing liquid S, cluster-like single crystal diamond particles having primary particles of 5 nm, secondary particles of 70 nm, and a concentration of 1% by mass were used. To this, 5% by mass of sodium paratoluenesulfonate and 0.1% by mass of benzotriazole were added as polishing aids. Note that pure water was used as a solvent for the polishing liquid. The polishing liquid was dropped for 2 seconds before the processing was started at a dropping rate of 1 cc / min.

In addition, a polishing pad made of urethane foam having a thickness of 2 mm is used, the rotation speed of the flat surface plate 102 is 100 rpm, the rotation speed of the nonmagnetic substrate by the pressing tool 105 is 60 rpm, and the swing speed of the nonmagnetic substrate by the pressing tool 105 The oscillation width was 2 cm and the cycle was 2 times / second. The pressing load of the pressing tool 105 against the non-magnetic substrate was 0.5 kgf / cm ² and the polishing time was 60 seconds.

  Next, after spin cleaning the nonmagnetic substrate using pure water, the surface of the nonmagnetic substrate is etched by about 1 nm using ion beam etching, a DLC film is formed to a thickness of 4 nm by CVD, and a lubricant is applied. A magnetic recording medium was prepared by applying 2 nm.

(Comparative Example 1)
In Comparative Example 1, the average primary particle diameter of diamond particles was 20 nm, the average secondary particle diameter was 80 nm, and other conditions were the same as in Example 1.

  The electromagnetic conversion characteristics of the magnetic recording media of Example 1 and Comparative Example 1 manufactured by the above method were evaluated. Specifically, the electromagnetic conversion characteristics were evaluated using a spin stand. The evaluation head uses a perpendicular recording head for recording and a TuMR head for reading, and measures 3T-squash when a 750 kFCI signal is recorded at the innermost and outermost circumferences. The variation of 3T-squash between the inner periphery and the outermost periphery was determined.

  As a result, in the magnetic recording medium of Example 1, the average of 3T-squash was 90%, and the variation of 3T-squash between the innermost periphery and the outermost periphery was ± 2%. On the other hand, in the magnetic recording medium of Comparative Example 1, although the average of 3T-squash was 90%, the variation of 3T-squash between the innermost periphery and the outermost periphery was ± 4%.

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic substrate 2 ... Magnetic layer 3 ... Resist layer 4 ... Nonmagnetic layer 5 ... Protective layer 6 ... Lubricating film MP ... Magnetic recording pattern 30 ... Magnetic recording medium 31 ... Nonmagnetic substrate 32 ... Soft magnetic layer 33 ... Intermediate layer 34 ... Recording magnetic layer 34a ... Magnetic recording pattern 35 ... Protective layer 36 ... Lubricating film 37 ... Magnetic layer 38 ... Nonmagnetic layer 51 ... Rotation drive unit 52 ... Magnetic head 53 ... Head drive unit 54 ... Recording / reproduction signal processing system 100 ... Polishing apparatus 101 ... Polishing pad 102 ... Flat surface plate 103 ... Spindle 104 ... Nozzle 105 ... Pushing tool 106 ... Spindle 107 ... Elastic sheet S ... Polishing liquid

Claims (5)

A method for producing a magnetic recording medium having a magnetically separated magnetic recording pattern, comprising:
Forming a magnetic layer on a non-magnetic substrate;
Forming a resist layer patterned in a shape corresponding to the magnetic recording pattern on the magnetic layer;
Partially removing the magnetic layer using the resist layer;
Forming a nonmagnetic layer covering the surface from which the magnetic layer has been removed;
Polishing the nonmagnetic layer until the magnetic layer is exposed,
The polishing process supplies diamond slurry between the surface of the nonmagnetic layer and the polishing pad while pressing the rotating polishing pad against the surface of the nonmagnetic layer to rotate or swing the nonmagnetic substrate. By doing
The diamond slurry includes single crystal diamond particles and a polishing aid,
The diamond particles have a primary particle size in the range of 1 to 10 nm and a secondary particle size in the range of 50 to 100 nm.
The method for producing a magnetic recording medium, wherein the polishing aid contains an organic polymer having a sulfonic acid group or a carboxylic acid group.   2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the polishing aid is an organic polymer having sodium sulfonate or sodium carboxylate and an average molecular weight of 4000 to 10,000. The diamond slurry further includes a corrosion inhibitor,
The method for manufacturing a magnetic recording medium according to claim 1, wherein the anticorrosive is benzotriazole or a derivative thereof.   The benzotriazole derivative is obtained by substituting one or more hydrogen atoms of benzotriazole with any of a carboxyl group, a methyl group, an amino group, and a hydroxyl group. A method for producing the magnetic recording medium according to claim. A magnetic recording medium manufactured by the method according to any one of claims 1 to 4,
A medium driving unit for driving the magnetic recording medium in a recording direction;
A magnetic head for performing a recording operation and a reproducing operation on the magnetic recording medium;
Head moving means for moving the magnetic head relative to a magnetic recording medium;
A magnetic recording / reproducing apparatus comprising: a recording / reproducing signal processing means for inputting a signal to the magnetic head and reproducing an output signal from the magnetic head.

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