Method of manufacturing magnetic recording medium

Abstract

To provide a manufacturing method of a magnetic recording medium capable of enhancing productivity of the magnetic recording medium.SOLUTION: A method for manufacturing a magnetic recording medium according to the present invention includes a burnishing step of burnishing, with an abrasive, a surface of a laminate in which a magnetic recording layer and a protective layer are laminated in this order on a substrate, the burnishing step includes a step of using a long polishing tape in which abrasive grains are fixed as the polishing material on a support in a state of being wound in a roll shape, and pressing the polishing tape supplied from the state of being wound in a roll shape against the surface of the laminate to rub the surface, in which the polishing tape in which free abrasive grains are reduced by performing a vacuum treatment in advance is used as the polishing tape in the state of being wound in a roll shape.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a magnetic recording medium. [Background technology]

[0002] In recent years, magnetic storage devices have become increasingly important as they are installed in a variety of products, such as personal computers, video recorders, and data servers. A magnetic storage device is a device that has a magnetic recording medium that stores electronic data by magnetic recording, and an example of such a device is a hard disk drive (HDD).

[0003] A typical magnetic recording medium has a multilayer film in which, for example, an underlayer, an intermediate layer, a magnetic recording layer, and a protective layer are formed in this order on a non-magnetic substrate, and a lubricating layer is formed on the surface of the protective layer.

[0004] When manufacturing a magnetic recording medium, a burnishing process using an abrasive tape is carried out to remove foreign matter and protrusions on the surface of the protective layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2-10486 Summary of the Invention [Problem to be solved by the invention]

[0006] 1, a polishing tape 100 is used in the burnishing process, in which abrasive grains 102 such as alumina are fixed to a resin film 101 with resin, as shown in Fig. 1. The polishing tape 100 is long, measuring several centimeters wide and about 100 meters long, and is supplied wound in a roll around a core material 110.

[0007] If foreign matter or loose abrasive grains are mixed into the polishing tape 100, circumferential scratches will occur on the surface of the multilayer film during the burnishing process, making it more susceptible to contamination. Therefore, the polishing tape 100 is manufactured under quality control to prevent the inclusion of foreign matter or loose abrasive grains during the manufacturing process. However, there remains a problem in the manufacture of magnetic recording media: scratches or stains that are thought to be caused by the burnishing process may still occur. Magnetic recording media with scratches and stains on the surface of the multilayer film are treated as defective products, which reduces the productivity of magnetic recording media.

[0008] An object of one aspect of the present invention is to provide a method for manufacturing a magnetic recording medium that can increase productivity of the magnetic recording medium. [Means for solving the problem]

[0009] The inventors of the present invention noticed a correlation between the incidence of defective products due to circumferential scratches and stains on the surface of magnetic recording media and the position of the abrasive tape roll used in the burnishing process. They discovered that the incidence of defective products due to the burnishing process is higher on the outer side of the abrasive tape roll than on the inner side, i.e., the core material side. Investigation into the cause of this finding revealed that loose abrasive grains are generated by the pressure caused by the tightening of the abrasive tape when it is rolled, and these loose abrasive grains are the cause of the defective products. The pressure caused by the tightening of the roll differs between the inner and outer sides of the roll, resulting in a difference in the amount of loose abrasive grains generated on the inner and outer sides of the roll. Therefore, the inventors of the present invention discovered that the productivity of magnetic recording media can be improved by vacuum-treating the abrasive tape in a rolled state before use to reduce the amount of loose abrasive grains.

[0010] The present invention has the following configuration. [1] A burnishing step of burnishing the surface of a laminate in which a magnetic recording layer and a protective layer are laminated in this order on a substrate, using an abrasive; The burnishing step includes a step of using a long abrasive tape having abrasive grains fixed to a support as the abrasive material, wound up in a roll, and pressing the abrasive tape supplied from the rolled up state against the surface of the laminate to rub it; A method for manufacturing a magnetic recording medium, characterized in that the abrasive tape wound into a roll is an abrasive tape in which the amount of free abrasive grains has been reduced by vacuum treatment in advance. [2] The method for manufacturing a magnetic recording medium according to [1], wherein after the vacuum treatment, the abrasive tape wound into a roll is rewound. [3] The method for producing a magnetic recording medium according to [1] or [2], wherein the vacuum treatment is performed by holding the abrasive tape in a rolled state at 50 kPa or less for one hour or more. [4] The method for producing a magnetic recording medium according to any one of [1] to [3], wherein the loose abrasive grains are loose abrasive grains from the support of the abrasive tape. [5] The method for producing a magnetic recording medium according to any one of [1] to [4], wherein the free abrasive grains are removed by blowing them away with a gas. [6] A method for manufacturing a magnetic recording medium according to any one of [1] to [5], in which the free abrasive grains are removed by contacting another tape with the surface of the abrasive tape and adsorbing the free abrasive grains onto the other tape. [7] A lubricating layer forming step of forming a lubricating layer on the surface of the laminate, The method for producing a magnetic recording medium according to any one of [1] to [6], wherein the burnishing step involves burnishing the surface of the laminate on which the lubricating layer is formed, with the abrasive material. [Effects of the Invention]

[0011] According to one aspect of the present invention, the productivity of magnetic recording media can be improved. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 2 is a schematic diagram showing an example of a polishing tape wound into a roll. [Figure 2] 1 is a cross-sectional view showing an example of a magnetic recording medium manufactured by a method for manufacturing a magnetic recording medium according to an embodiment of the present invention. [Figure 3] FIG. 1 is a diagram illustrating a burnishing process. [Figure 4] FIG. 2 is an enlarged cross-sectional view showing an example of a polishing tape used in burnishing. [Figure 5] FIG. 2 is a schematic diagram showing an example of a state in which the polishing tape is placed in a vacuum pack bag. [Figure 6] FIG. 10 is a schematic diagram showing an example of a method for removing loose abrasive grains. [Figure 7] FIG. 10 is a schematic diagram showing another example of a method for removing loose abrasive grains. [Figure 8] FIG. 2 is a diagram showing an example of a burnishing device used in a process of burnishing the surface of a lubricating layer formed on the surface of a laminate with an abrasive tape. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. To facilitate understanding of the description, the same components in each drawing will be assigned the same reference numerals, and duplicate descriptions will be omitted where appropriate. Furthermore, the scale of each member in the drawings may differ from the actual scale. In this specification, unless otherwise specified, "to" indicating a numerical range means that the numerical values ​​before and after it are included as the lower and upper limits. Furthermore, when only the upper limit value in a numerical range expressed by "to" is specified in units, it means that the lower limit value is also in the same units.

[0014] Before describing the method for manufacturing a magnetic recording medium according to an embodiment of the present invention, a magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to this embodiment will be described below.

[0015] [Magnetic recording media] 2 is a cross-sectional view showing an example of a magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to this embodiment. As shown in FIG. 2, the magnetic recording medium 1 has a laminate 11 and lubricating layers 12 provided on both sides of the laminate 11.

[0016] The laminate 11 includes a magnetic recording layer 112 and a protective layer 113 laminated on both sides of a substrate 111 in this order from the substrate 111 side.

[0017] The substrate 111 is made of a non-magnetic material. For example, a metal substrate made of a metal material such as an aluminum alloy may be used as the substrate 111, or a non-metal substrate made of a non-metal material such as glass may be used. Furthermore, a NiP alloy layer may be formed on the surface of such a metal substrate or non-metal substrate by, for example, plating or sputtering.

[0018] The magnetic recording layer 112 is a layer provided for recording and reproducing information, and is provided, for example, for storing data by reversing the direction of magnetization using magnetic energy supplied from the magnetic head of the HDD and maintaining that state of magnetization.

[0019] For the magnetic recording layer 112, an FePt-based alloy having an L10 structure, a CoPt-based alloy having an L10 structure, a CoCrPt-based alloy having an hcp structure, or the like can be used.

[0020] The magnetic recording layer 112 can be formed by known methods such as sputtering and ion beam deposition.

[0021] The protective layer 113 is provided to suppress corrosion of the magnetic recording layer 112, to prevent and protect the surface of the magnetic recording medium 1 from damage when the magnetic head comes into contact with the magnetic recording medium 1, and to increase the corrosion resistance of the magnetic recording medium 1.

[0022] The protective layer 113 can be formed of a known material, for example, a hard carbon film and diamond-like carbon (DLC).

[0023] The protective layer 113 can be formed by a known method such as sputtering or ion beam deposition.

[0024] The surface of the protective layer 113 may be hydrogenated or nitrogenated. By hydrogenating or nitrogenating the surface of the protective layer 113, the bonding strength with the lubricating layer 12 formed on the surface can be increased.

[0025] The lubricating layer 12 is provided to suppress wear on the surfaces of the magnetic head and the magnetic recording medium 1 when the magnetic head comes into contact with the magnetic recording medium 1, and to enhance the corrosion resistance of the magnetic recording medium 1.

[0026] The lubricating layer 12 is formed using a lubricant, which may be any lubricant commonly used in the manufacture of magnetic recording media.

[0027] The thickness of the lubricating layer 12 is preferably 5 to 10 Å. By making the thickness of the lubricating layer 12 5 to 10 Å, wear on the surface of the magnetic recording medium 1 is suppressed, the corrosion resistance of the magnetic recording medium 1 is increased, and the distance between the magnetic head and the magnetic recording medium 1 in the HDD can be shortened, thereby achieving high recording density.

[0028] [Magnetic recording medium manufacturing method] The method for manufacturing a magnetic recording medium according to this embodiment includes a step of forming a laminate 11 by stacking a magnetic recording layer 112 and a protective layer 113 in this order on the surfaces of both major surfaces of a substrate 111 (laminate formation step), a step of applying a lubricant to the surface of the laminate 11 (application step), and a step of burnishing the surface of the laminate 11 to which the lubricant has been applied using an abrasive (burnishing step).

[0029] In the method for manufacturing a magnetic recording medium according to this embodiment, the burnishing step may be carried out before the application step, and the surface of the laminate 11 before the lubricant is applied may be burnished with an abrasive.

[0030] In addition, in the method for manufacturing a magnetic recording medium according to this embodiment, the laminate formation process may include other processes such as forming an adhesion layer, a soft magnetic underlayer, a seed layer, or an orientation control layer between the substrate 111 and the magnetic recording layer 112.

[0031] Furthermore, in the method for manufacturing a magnetic recording medium according to this embodiment, when the stack 11 comprises multiple stacked magnetic recording layers 112, the stack formation process may include a process of forming a non-magnetic recording layer between the magnetic recording layers 112.

[0032] In the method for manufacturing a magnetic recording medium according to this embodiment, first, a laminate 11 is formed by laminating a magnetic recording layer 112 and a protective layer 113 in this order on the surfaces of both major surfaces of a prepared substrate 111 (laminate formation process).

[0033] The stack 11 can be formed by using a general method for forming the magnetic recording layer 112 and the protective layer 113.

[0034] First, magnetic recording layers 112 are formed on the surfaces of both main surfaces of substrate 111. As a method for forming magnetic recording layers 112, a general film formation method such as sputtering (also called "sputtering method") can be used.

[0035] In the sputtering method, a target containing the material for forming the magnetic recording layer 112 can be used.

[0036] As a target containing a material for forming the magnetic recording layer 112, for example, an FePt-based alloy having an L10 structure, a CoPt-based alloy, or a CoCrPt-based alloy having an L10 structure can be used.

[0037] As the sputtering method, DC sputtering, DC magnetron sputtering, RF sputtering, and the like can be used.

[0038] When depositing the magnetic recording layer 112, an RF (Radio Frequency) bias, a DC bias, a pulsed DC bias, or the like may be used as needed.

[0039] As the reactive gas, O2 gas, H2O gas, N2 gas, or the like may be used.

[0040] The sputtering gas pressure is adjusted appropriately to optimize the properties of each layer, but is usually within the range of about 0.1 to 30 Pa.

[0041] Next, the protective layer 113 is formed on the magnetic recording layer 112. The method for forming the protective layer 113 is not particularly limited, but can be a general film formation method such as RF-CVD (Radio Frequency-Chemical Vapor Deposition), which forms a film by decomposing a source gas made of hydrocarbon with high frequency plasma, IBD (Ion Beam Deposition), which forms a film by ionizing a source gas with electrons emitted from a filament, or FCVA (Filtered Cathodic Vacuum Arc), which forms a film using a solid carbon target without using a source gas.

[0042] In this embodiment, the stack formation step may include forming an adhesion layer, a soft magnetic underlayer, a seed layer, an orientation control layer, and the like between the substrate 111 and the magnetic recording layer 112.

[0043] In this embodiment, when the stack 11 includes a plurality of stacked magnetic recording layers 112, the stack formation step may include a step of forming a non-magnetic recording layer between the magnetic recording layers 112, and the like.

[0044] Next, a lubricant is applied to the surface of the laminate 11 to form a lubricant layer 12, which is a film made of the lubricant (application step). This results in a magnetic recording medium 1, which is a multilayer body with the lubricant layer 12 formed on the surface of the laminate 11.

[0045] The lubricant can be applied by a common application method such as a dipping method, a spin coating method, or a vapor method.

[0046] 3, the surface of the lubricating layer 12 formed on the surface of the laminate 11 is burnished with a polishing tape 20 (burnishing step). This allows the burnished lubricating layer 12 to be laminated on the surface of the laminate 11.

[0047] Burnishing is performed using abrasive tape 20 wound in a roll, and the abrasive tape 20 supplied from the roll is pressed against the surface of the lubricating layer 12 formed on the surface of the laminate 11 and rubbed.

[0048] In this embodiment, the polishing tape 20 wound into a roll for use in the burnishing process is a polishing tape that has been vacuum-treated in advance to reduce the amount of loose abrasive grains. As mentioned above, when the polishing tape 20 is rolled, the pressure caused by the tight winding generates loose abrasive grains, and these loose abrasive grains cause defective products. In this embodiment, the roll-shaped polishing tape 20 is vacuum-treated before use, thereby reducing the amount of loose abrasive grains. This reduces the occurrence of defective magnetic recording media 1 due to loose abrasive grains, thereby improving the productivity of the magnetic recording media 1.

[0049] 4 is an enlarged cross-sectional view showing an example of a polishing tape 20 used for burnishing. As shown in FIG. 4, the polishing tape 20 can polish the surface of the lubricating layer 12 formed on the surface of the laminate 11 by sliding the polishing surface S against the surface of the lubricating layer 12.

[0050] The polishing tape 20 has an abrasive layer 22 on a support 21. The abrasive layer 22 has abrasive grains 221 and a binder 222 that bonds the abrasive grains 221 to each other and to the support 21, thereby fixing the abrasive grains 221 to the abrasive layer 22.

[0051] The material that constitutes the support 21 is not particularly limited, and examples of the material that constitutes the support 21 include various resins such as polyethylene terephthalate.

[0052] The abrasive grains 221 can be used as the abrasive material contained in the polishing tape 20. Examples of the abrasive grains 221 include particles containing chromium oxide, α-alumina, silicon carbide, non-magnetic iron oxide, diamond, γ-alumina, α,γ-alumina, fused alumina, corundum, and artificial diamond. The abrasive grains 221 may be particles made of these materials. These may be used alone or in appropriate combinations of two or more types.

[0053] The binder 222 is not particularly limited, and examples of the binder 222 that can be used include thermosetting resins, thermoplastic resins, and photosensitive resins. The resin used as the binder 222 may be one type used alone or two or more types used in combination.

[0054] As described above, the polishing tape 20 is long, and therefore is supplied in a rolled state as shown in FIG. 1, and is used by being set on the reel of a burnishing device in the rolled state.

[0055] As described above, when the polishing tape 20 is rolled, the pressure caused by the tight winding causes loose abrasive grains to form within the roll. Here, if the pressure caused by the tight winding is very large, the abrasive grains 221 bound to the support 21 may themselves become loose, but it is generally thought that the loose abrasive grains 221 are those that are loosely bound to the support 21 or those that are attached to the bound abrasive grains 221. It is difficult to completely remove such loose abrasive grains 221 during the manufacturing process of the polishing tape 20, and it is thought that most of them are generated after the polishing tape 20 is manufactured, i.e., after the polishing tape 20 is wound into a roll.

[0056] In this embodiment, by vacuum-treating the roll-shaped polishing tape 20 before use, the amount of loose abrasive grains 221 can be reduced, thereby suppressing the occurrence of defective products due to loose abrasive grains 221. The following reasons are thought to be the reason why loose abrasive grains 221 are reduced by vacuum treatment. That is, the vacuum treatment degasses the gas inside the polishing tape 20, reducing the tightness of the tape, which in turn reduces the loosening of the abrasive grains 221. Furthermore, degassing increases the adhesion between the polishing tapes 20, which causes the loose abrasive grains 221 to move from the abrasive layer 22 to the back surface of the polishing tape 20. Furthermore, degassing increases the adhesion between the polishing tapes 20, which causes the abrasive grains 221 that are likely to loosen to be pressed against the abrasive layer 22 by the back surface of the polishing tape 20, thereby suppressing the loosening of the abrasive grains 221.

[0057] In this embodiment, the vacuum treatment is performed by subjecting the polishing tape 20 in a rolled state to as low a pressure as possible, preferably 50 kPa or less, more preferably 10 kPa or less, and most preferably 1 kPa or less, and holding the tape for as long as possible, preferably 1 hour or more, more preferably 10 hours or more, and most preferably 1 week or more.

[0058] This vacuum treatment is preferably carried out by holding the rolled polishing tape 20 in a vacuum container, but as shown in Fig. 5, it is also possible to hold the rolled polishing tape 20 in a vacuum packing bag 2. In this case, it is preferable to use, for example, a metal-deposited bag or a multi-layer resin film bag with high gas barrier properties as the vacuum packing bag 2.

[0059] In this embodiment, it is preferable to rewind the roll-shaped polishing tape 20 after vacuum processing, thereby removing the loose abrasive grains 221, thereby suppressing the occurrence of defective magnetic recording media 1 due to the loose abrasive grains 221. Here, by rewinding the polishing tape 20, it becomes roll-shaped again, but because pressure has already been applied to the polishing tape 20 by tightening the winding, it is possible to suppress the re-occurrence of loose abrasive grains 221 even when rewinding.

[0060] The rewinding speed of the polishing tape 20 is preferably about 1 to 20 m / min. When the polishing tape 20 is rewound, the surface of the polishing tape 20 is subjected to wind pressure, which can remove loose abrasive grains 221 from the surface of the polishing tape 20.

[0061] In this embodiment, it is preferable to remove the abrasive grains 221 that have become loose within the roll-shaped polishing tape 20 by blowing them away with gas, as shown in Fig. 6. By using such a method, the loose abrasive grains 221 can be removed more efficiently and reliably.

[0062] 6, the polishing tape 20 is set on a supply reel 31, and is taken up onto a take-up reel 33 while being guided by a guide roller 32. Then, while the polishing tape 20 is running, both sides of the polishing tape 20 are cleaned by gas ejected from a pair of gas ejection nozzles 34. The removal of the free abrasive grains 221 is preferably carried out in a static-neutral atmosphere to prevent the free abrasive grains 221 from re-adhering due to static electricity.

[0063] 7, in this embodiment, it is preferable to remove the free abrasive grains 221 by bringing another tape 44 into contact with the surface of the polishing tape 20, thereby causing the free abrasive grains 221 to be adsorbed onto the other tape 44. By using such a method, the free abrasive grains 221 can be removed more efficiently and reliably.

[0064] In Figure 7, the polishing tape 20 is set on a polishing tape supply reel 41, and the polishing tape 20 is guided by a guide roller 42 and wound onto a polishing tape take-up reel 43. The surface of the polishing tape 20 then comes into contact with another tape 44 as it travels, thereby removing any loose abrasive grains 221. The contact surface of the other tape 44 is preferably charged and made adhesive so that the loose abrasive grains can be easily attracted. The other tape 44 is set on another tape supply reel 45, and is guided by a guide roller 42 so that it comes into contact with the surface of the polishing tape 20, and is then wound onto another tape take-up reel 46.

[0065] In the burnishing step, a method can be used in which a tape containing an abrasive (abrasive tape 20) is pressed against and rubbed against the surface of the lubricating layer 12 formed on the surface of the laminate 11. The burnishing method and burnishing device will be described in detail with reference to the drawings.

[0066] Fig. 8 is a diagram showing an example of a burnishing device used in a process of burnishing the surface of the lubricating layer 12 formed on the surface of the laminate 11 with a polishing tape 20. As shown in Fig. 8, the burnishing device 50 has a pair of polishing tapes 20 (hereinafter also referred to as "a pair of polishing tapes 20A and 20B") arranged opposite each other so as to sandwich the laminate 11 having the lubricating layer 12 formed on its surface from both sides, a rotation support means 51, and a tape moving means 52.

[0067] A pair of polishing tapes 20A and 20B are supplied in a rolled state from a first polishing tape supply reel 53A and a second polishing tape supply reel 53B, respectively, and are then taken up in a rolled state by a first polishing tape take-up reel 54A and a second polishing tape take-up reel 54B.

[0068] In the burnishing device 50, a pair of polishing tapes 20A and 20B are arranged opposite each other so as to sandwich the laminate 11 having a lubricating layer 12 formed on its surface from both sides, thereby enabling efficient burnishing to be performed simultaneously on the lubricating layer 12 formed on both sides of the laminate 11.

[0069] The rotation support means 51 supports the central opening of the laminate 11 having the lubricating layer 12 formed on its surface and rotates the laminate 11 having the lubricating layer 12 formed on its surface in the circumferential direction (direction of arrow r).

[0070] The tape moving means 52 presses a pair of polishing tapes 20A and 20B against the lubricating layers 12 formed on both surfaces of the rotating laminate 11 in the direction of arrow F, and moves the pair of polishing tapes 20A and 20B relative to each other in the radial direction of the laminate 11.

[0071] The tape moving means 52 also has a pair of polishing tape pressing means 521 and a pair of polishing tape running systems 522 arranged opposite each other so as to sandwich the laminate 11 having the lubricating layer 12 formed on its surface from both sides via a pair of polishing tapes 20A and 20B.

[0072] The pair of polishing tape pressing means 521 includes a first polishing tape pressing means 521A and a second polishing tape pressing means 521B. The pair of polishing tape running systems 522 includes a first polishing tape running system 522A and a second polishing tape running system 522B.

[0073] That is, the tape moving means 52 has a first polishing tape running system 522A and a first polishing tape pressing means 521A arranged on one side of the laminate 11 having a lubricating layer 12 formed on its surface, and a second polishing tape running system 522B and a second polishing tape pressing means 521B arranged on the other side.

[0074] The first polishing tape running system 522A has first guide rolls 523A-1 to 523A-6, and runs the polishing tape 20A in the direction of the arrow Ra.

[0075] The second polishing tape running system 522B has second guide rolls 523B-1 to 523B-6, and runs the polishing tape 20B in the direction of arrow Rb.

[0076] As described above, the method for manufacturing a magnetic recording medium according to this embodiment includes a burnishing process. In this burnishing process, the abrasive tape 20, which is supplied in a rolled state, is pressed against and rubbed against the surface of the laminate 11 having the lubricating layer 12 formed on its surface. The rolled abrasive tape 20 is previously vacuum-treated to remove any loose abrasive grains. This prevents the loose abrasive grains from causing circumferential scratches on the surface of the lubricating layer 12 formed on both sides of the laminate 11, and prevents the loose abrasive grains from adhering as contaminants such as foreign matter. Therefore, according to the method for manufacturing a magnetic recording medium according to this embodiment, the rate of defective magnetic recording media 1 can be reduced in the burnishing process, thereby increasing the productivity of the magnetic recording media 1.

[0077] As described above, the magnetic recording medium 1 manufactured using the method for manufacturing a magnetic recording medium according to this embodiment has fewer circumferential scratches and stains on the surface of the magnetic recording medium 1, thereby improving the reliability of its quality. The magnetic recording medium 1 can suppress defects in recording and reading and maintain a high recording density, making it suitable for use in magnetic recording and reproducing devices. The magnetic recording and reproducing device is not particularly limited in form as long as it has a magnetic recording medium manufactured using the method for manufacturing a magnetic recording medium according to this embodiment, and may be a magnetic recording and reproducing device that records magnetic information on the magnetic recording medium using a thermally assisted recording method.

[0078] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims. [Example]

[0079] The present embodiment will be specifically described below based on examples, but the present embodiment is not limited to these examples.

[0080] Example 1 [Preparing the polishing tape] The polishing tape used 0.2 μm grain size Al2O3 (manufactured by Mipox) as abrasive grains. The polishing tape was 12.6 mm wide and 100 m long, and wound into a roll. This polishing tape was subjected to a vacuum treatment at 10 kPa for 10 hours. The polishing tape was then rewound using the apparatus shown in FIG. 6 as an additional treatment to remove loose abrasive grains. During this process, the polishing tape was run at 10 m / min without gas injection from the gas injection nozzle 34. The rewounding was performed in a static-free environment.

[0081] Table 1 shows the vacuum treatment conditions and additional treatment details used in preparing the polishing tape.

[0082] [Magnetic recording medium fabrication] A cleaned glass substrate (HOYA, 2.5-inch diameter) was placed in the deposition chamber of a DC magnetron sputtering device (Anelva C-3040) and the ultimate vacuum was 1×10 -5 The film formation chamber was evacuated until the pressure reached 1 Pa. Thereafter, an adhesive layer having a thickness of 10 nm was formed on the glass substrate by sputtering using a Cr target.

[0083] Next, a soft magnetic underlayer was formed on the adhesion layer by sputtering. The soft magnetic underlayer consisted of a first soft magnetic recording layer, an intermediate layer, and a second soft magnetic recording layer, formed in that order. First, a 25-nm-thick first soft magnetic recording layer was deposited at a substrate temperature of 100°C or less using a target of Co-20Fe-5Zr-5Ta (Fe content 20 atomic %, Zr content 5 atomic %, Ta content 5 atomic %, balance Co). Next, a 0.7-nm-thick intermediate layer made of Ru was formed. Then, a 25-nm-thick second soft magnetic recording layer made of Co-20Fe-5Zr-5Ta was deposited.

[0084] Next, a seed layer having a thickness of 5 nm was formed on the soft magnetic underlayer by sputtering using a Ni-6W {W content 6 atomic %, balance Ni} target.

[0085] After that, a 10 nm thick Ru layer was formed on the seed layer as a first orientation control layer by sputtering at a sputtering pressure of 0.8 Pa. Next, a 10 nm thick Ru layer was formed on the first orientation control layer by sputtering at a sputtering pressure of 1.5 Pa as a second orientation control layer.

[0086] Next, a first magnetic recording layer was formed on the second orientation control layer by sputtering to a thickness of 9 nm. The layer consisted of 91(Co15Cr16Pt)-6(SiO2)-3(TiO2) (Cr content 15 atomic %, Pt content 16 atomic %, the remainder an alloy of Co 91 mol %, SiO2 6 mol %, TiO2 3 mol %). The sputtering pressure here was 2 Pa.

[0087] Next, a non-magnetic recording layer consisting of 88(Co30Cr)-12(TiO2) {Cr content 30 atomic %, the remainder an alloy of Co 88 mol %, TiO2 12 mol %} was formed on the first magnetic recording layer by sputtering to a layer thickness of 0.3 nm.

[0088] Then, a second magnetic recording layer was formed on the non-magnetic recording layer by sputtering to a thickness of 6 nm. The layer consisted of 92(Co11Cr18Pt)-5(SiO2)-3(TiO2) (Cr content 11 atomic %, Pt content 18 atomic %, the remainder an alloy of Co 92 mol %, SiO2 5 mol %, TiO2 3 mol %). The sputtering pressure was 2 Pa.

[0089] Thereafter, a non-magnetic recording layer made of Ru was formed on the second magnetic recording layer by sputtering to a thickness of 0.3 nm.

[0090] Next, a third magnetic recording layer was formed on the non-magnetic recording layer by sputtering with a target consisting of Co-20Cr-14Pt-3B (Cr content 20 atomic %, Pt content 14 atomic %, B content 3 atomic %, remainder Co) at a sputtering pressure of 0.6 Pa to a thickness of 7 nm.

[0091] A hydrogenated carbon film was formed as a protective layer on the surface of the third magnetic recording layer by ion beam deposition using gasified toluene as the source gas. The flow rate of the source gas supplied to the deposition chamber was set to 2.9 SCCM, and the reaction pressure was set to 0.2 Pa. The cathode power, which is the excitation source for the source gas, was set to 225 W (AC 22.5 V, 10 A). The voltage between the cathode electrode and the covering anode electrode was set to 75 V, the current to 1650 mA, the ion acceleration voltage to 200 V, the current to 180 mA, and the deposition time to a thickness of 3.5 nm. After the hydrogenated carbon film was formed, the supply of source gas was stopped, and the deposition chamber was evacuated for 2 seconds.

[0092] Next, nitrogen gas was supplied into the film formation chamber with a gas flow rate of 2 SCCM and a reaction pressure of 5 Pa. Then, the cathode power was set to 128 W (AC 16 V, 8 A), the voltage between the cathode electrode and the anode electrode was set to 75 V, the current was set to 1000 mA, the ion acceleration voltage was set to 200 V, the current was set to 90 mA, and the treatment time was set to 1 second. Nitrogen ions formed from the nitrogen gas were irradiated onto the surface of the hydrogenated carbon film, exposing it to nitrogen plasma. This dehydrogenated and nitrogenated the surface of the hydrogenated carbon film.

[0093] Next, a lubricant (D5OH(XS), manufactured by Matsumura Oil Research Institute) was applied onto the surface of the protective layer by dipping to form a lubricating layer made of the lubricant to a thickness of about 7 Å.

[0094] Next, the surface of the laminate on which the lubricating layer was formed was burnished using the abrasive tape vacuum-treated by the method described above. The burnishing conditions were a rotation speed of the laminate of 2000 rpm and a processing time of 7 seconds. By performing the burnishing, a magnetic recording medium was obtained in which a burnished lubricating layer was laminated on the surface of the laminate.

[0095] [Measurement of TA counts] The magnetic recording media fabricated were optically inspected to remove any large scratches or particles. Next, they were treated with a burnishing head to remove any foreign matter, and then a glide evaluation was performed using a glide head. The glide evaluation is an evaluation method in which an AE sensor attached to the glide head detects vibrations that occur when the head collides with a protrusion on the surface. The TA count was evaluated for magnetic recording media that passed the glide evaluation. An MR head was used to evaluate the TA count. The TA count is a method of detecting thermal asperities (TA), a phenomenon in which the signal waveform reproduced by the MR head fluctuates due to frictional heat generated when the MR head collides with a protrusion on the surface of the magnetic recording medium. The number of occurrences of these signals (TA count) is used to evaluate the surface smoothness of the magnetic recording medium. A lower TA count indicates a smoother magnetic recording medium surface. The TA count was calculated by taking the average value per surface of 100 magnetic recording media burnished with a 100m long abrasive tape approximately 20m from the end where the abrasive tape is wound out, and the average value per surface of 100 magnetic recording media burnished with abrasive tape approximately 80m from the end where the abrasive tape is wound out. Note that the area from the end where the abrasive tape is wound out to approximately 20m is the outside of the abrasive tape, and the area from 20m to 100m in the longitudinal direction of the abrasive tape is the inside of the abrasive tape. The evaluation results are shown in Table 1.

[0096] <Examples 2 and 3, Comparative Examples 1 and 2> A magnetic recording medium was manufactured and the TA count was measured in the same manner as in Example 1, except that the preparation of the abrasive tape was changed as follows. The evaluation results are shown in Table 1. [Example 2] Nitrogen gas was sprayed from the gas spray nozzle 34 of the device shown in FIG. 6, and other procedures were carried out in the same manner as in Example 1 to prepare an abrasive tape. [Example 3] The loose abrasive grains were removed by rewinding the tape using the device shown in Figure 7. A charged polyethylene tape was used as another tape to be brought into contact with the polishing tape, and the tape running speed was set to 10 m / min. The polishing tape was then de-charged and rewound. Other than that, the same procedures as in Example 1 were carried out to prepare the polishing tape. [Comparative Examples 1 and 2] Abrasive tapes were prepared in the same manner as in Example 1, except that the vacuum treatment and rewinding were changed as shown in Table 1.

[0097] [Table 1]

[0098] As can be seen from Table 1, in Comparative Example 1, the TA count differed between the inside and outside of the burnished abrasive tape roll. This is thought to be because the pressure caused by the tight winding of the abrasive tape inside the roll caused a difference in the amount of abrasive grains released between the inside and outside of the roll. On the other hand, in Examples 1 to 3, the TA count was the same between the inside and outside of the abrasive tape roll, and was low at 7 or less. This is thought to be because the abrasive tape was previously vacuum-treated, removing the abrasive grains released between the inside and outside of the roll.

[0099] Therefore, by vacuum treating the roll of abrasive tape when preparing the abrasive tape, it is possible to reduce the rate of defective products produced in the burnishing process of the magnetic recording media, thereby increasing the productivity of the magnetic recording media. [Explanation of symbols]

[0100] 1. Magnetic recording media 11 Laminate 12 Lubricating layer 20, 20A, 20B Polishing Tape 21 Support 22 Abrasive layer 31 Supply reel 32 Guide roller 33 Take-up reel 34 Gas injection nozzle 41 Polishing tape supply reel 42 Guide roller 43 Polishing tape take-up reel 44 Another Tape 45 Separate tape supply reel 46 Another tape take-up reel 50 Burnishing equipment 53A First Polishing Tape Supply Reel 53B Second polishing tape supply reel 54A First Polishing Tape Take-Up Reel 54B Second abrasive tape take-up reel 111 Substrate 112 Magnetic Recording Layer 113 Protective layer 221 Abrasive grain 222 Binder 521 Pair of polishing tape pressing means 522 Pair of polishing tape running systems 521A First polishing tape pressing means 521B Second abrasive tape pressing means 522A First polishing tape running system 522B Second polishing tape transport system S polished surface

Claims

1. a burnishing step of burnishing the surface of a laminate in which a magnetic recording layer and a protective layer are laminated in this order on a substrate, using an abrasive; The burnishing step includes a step of using a long abrasive tape having abrasive grains fixed to a support as the abrasive material, wound up in a roll, and pressing the abrasive tape supplied from the rolled up state against the surface of the laminate to rub it; A method for manufacturing a magnetic recording medium, characterized in that the abrasive tape wound into a roll is an abrasive tape that has been subjected to a vacuum treatment in advance to reduce the amount of free abrasive grains.

2. 2. The method for manufacturing a magnetic recording medium according to claim 1, wherein after the vacuum treatment, the abrasive tape wound in a roll is rewound.

3. 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the vacuum treatment comprises holding the abrasive tape in the rolled state at 50 kPa or less for one hour or more.

4. 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the loose abrasive grains are loosened from the support of the abrasive tape.

5. 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the free abrasive grains are removed by blowing them away with a gas.

6. 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the removal of the loose abrasive grains is carried out by bringing another tape into contact with the surface of the polishing tape so that the loose abrasive grains are adsorbed onto the other tape.

7. a lubricating layer forming step of forming a lubricating layer on the surface of the laminate, 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the burnishing step involves burnishing the surface of the laminate on which the lubricating layer is formed, with the abrasive material.

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