Method for manufacturing magnetic recording media

Abstract

The present invention provides a method for manufacturing a magnetic recording medium that can efficiently remove foreign matter from the surface of the magnetic recording medium and has a high coverage rate by the lubricating layer. [Solution] The present invention relates to a method for manufacturing a magnetic recording medium, which involves forming a lubricating layer on a laminate obtained by laminating a magnetic recording layer and a protective layer on a substrate in that order, and comprises the steps of: applying a first lubricant and a second lubricant to the laminate; burning the surface of the laminate to which the first lubricant and the second lubricant have been applied with an abrasive; and removing the second lubricant from the laminate, wherein a spin coating method is used for applying the second lubricant, the burning step includes pressing a tape containing an abrasive onto the surface of the laminate and rubbing it, and the step of removing the second lubricant includes at least one of the steps of irradiating the laminate to which the first lubricant and the second lubricant have been applied with ultraviolet light and heat treating the laminate to which the first lubricant and the second lubricant have been applied.

Description

Technical Field

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

Background Art

[0002] In recent years, magnetic storage devices have been mounted in various products such as personal computers, video recorders, and data servers, and their importance has been increasing. A magnetic storage device is a device having a magnetic recording medium that stores electronic data by magnetic recording. For example, there is a hard disk drive (HDD).

[0003] A general magnetic recording medium has a multilayer film laminated structure 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 applied to the surface of the protective layer. The protective layer and the lubricating layer are provided to prevent the durability of the magnetic recording medium from deteriorating due to wear damage caused by contact sliding with a magnetic head. As the protective layer, a hard carbon film is generally used, and the lubricating layer is formed by applying a liquid perfluoropolyether compound or the like to the surface.

[0004] For the purpose of increasing the bonding strength of the lubricating layer to the protective layer, it is known to perform various treatments on the lubricating layer. For example, Patent Document 1 discloses a method in which a heat treatment is performed on the applied lubricating layer, and further a light irradiation treatment using an ultraviolet lamp is performed.

[0005] In addition, in order to remove foreign matters and protrusions on the surface of the protective layer, the surface of the magnetic recording medium is tape burnished with a polishing tape. At this time, it is known to perform tape burnishing after forming the lubricating layer in order to prevent scratches from occurring on the surface of the protective layer by tape burnishing.

[0006] Furthermore, Patent Document 2 discloses a method for manufacturing a magnetic recording medium, in which, after forming a protective layer, a first lubricant without end groups is applied to its surface, tape varnish is performed, the first lubricant is removed with a solvent, and a second lubricant having end groups is applied. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 11-25452 [Patent Document 2] Japanese Patent Publication No. 2002-222519 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] In the manufacturing of magnetic recording media, tape varnishing after the formation of a lubricating layer can reduce the occurrence of scratches due to the lubricity of the layer. However, depending on the lubricant used in the lubricating layer and the thickness of the lubricating layer, tape varnishing may not be suitable in some cases.

[0009] As described in Patent Document 2 for the manufacturing method of magnetic recording media, it is conceivable to perform processing using a first lubricant suitable for tape varnish, then remove the first lubricant, and apply a second lubricating layer suitable for magnetic recording media. However, in this case, the following problems arise. Specifically, contaminants and lubricants dissolved in the solvent used to remove the lubricant re-adhere to the processed substrate, causing foreign matter on the surface of the magnetic recording media. Furthermore, it is difficult to completely remove the lubricant bonded to the protective layer using a solvent, and the remaining solvent causes foreign matter on the surface of the magnetic recording media, reducing the coverage rate of the magnetic recording media surface by the lubricating layer and complicating the manufacturing process of the magnetic recording media.

[0010] One aspect of the present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a magnetic recording medium that can efficiently remove foreign matter from the surface of the magnetic recording medium and has a high coverage rate by a lubricating layer. [Means for solving the problem]

[0011] The present invention comprises the following configuration. [1] A method for manufacturing a magnetic recording medium, comprising forming a lubricating layer on a laminate in which a magnetic recording layer and a protective layer are stacked on a substrate in this order, A step of applying a first lubricant and a second lubricant onto the laminate, A step of burning the surface of the laminate to which the first lubricant and the second lubricant have been applied with an abrasive, A step of removing the second lubricant from the laminate, Includes, The second lubricant is applied using the spin coating method. The burning step includes pressing the tape containing the abrasive material against the surface of the laminate and rubbing it, A method for manufacturing a magnetic recording medium, wherein the step of removing the second lubricant includes at least one of the steps of irradiating the laminate coated with the first lubricant and the second lubricant with ultraviolet light and heat-treating the laminate coated with the first lubricant and the second lubricant. [2] The average molecular weight of the first lubricant is higher than the average molecular weight of the second lubricant. The method for manufacturing a magnetic recording medium according to [1], wherein the polarity of the first lubricant is higher than the polarity of the second lubricant. [3] The method for manufacturing a magnetic recording medium according to [1] or [2], wherein the second lubricant has an average molecular weight of 300 to 1000 and contains two or fewer polar groups, or does not contain any. [4] The method for manufacturing a magnetic recording medium according to any one of [1] to [3], wherein the first lubricant has an average molecular weight of 900 to 3000 and contains 4 to 8 polar groups. [5] The film thickness of the first lubricant applied to the laminate is 5 to 10 Å. A method for manufacturing a magnetic recording medium according to any one of [1] to [4], wherein the film thickness of the second lubricant is 5 to 20 Å. [6] The step of irradiating the ultraviolet rays is performed in an inert gas atmosphere or in a vacuum, and is the method for manufacturing a magnetic recording medium according to any one of [1] to [5]. [7] The step of performing the heat treatment is performed in an inert gas atmosphere, and is the method for manufacturing a magnetic recording medium according to any one of [1] to [6].

Advantages of the Invention

[0012] According to one aspect of the present invention, foreign substances on the surface of the magnetic recording medium can be efficiently removed, and the coating rate by the lubricating layer can be increased.

Brief Description of the Drawings

[0013] [[ID=B15]] [Figure 1] It 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 an embodiment of the present invention. [Figure 2] It is a diagram for explaining an example of the outline of the method for manufacturing a magnetic recording medium according to an embodiment of the present invention. [Figure 3A] It is a diagram for explaining an example of a lubricant coating apparatus by the dip method, and shows a state in which the laminate 11 is immersed in the solution 52. [Figure 3B] It is a diagram for explaining an example of a lubricant coating apparatus by the dip method, and shows a state in which the laminate 11 is pulled up from the solution 52. [Figure 4] It is a diagram for explaining an example of a lubricant coating apparatus by the spin coating method. [Figure 5] It is a diagram for explaining an example of a lubricant coating apparatus by the vapor method. [Figure 6] It is an enlarged cross-sectional view showing an example of a tape containing an abrasive used when burnishing. [Figure 7] It is a diagram showing an example of a burnishing apparatus used in the step of burnishing the surface of the laminate with an abrasive.

Embodiments for Carrying Out the Invention

[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. For ease of understanding, the same reference numerals are used for identical components in each drawing, and redundant explanations are omitted as appropriate. The scale of each component in the drawings may differ from the actual scale. In this specification, the "~" indicating a numerical range means that the values ​​before and after it are included as the lower and upper limits, respectively, unless otherwise specified. Furthermore, if only the upper limit of a numerical range represented by "~" has a unit specified, it means that the lower limit also has the same unit.

[0015] The following describes a 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.

[0016] <Magnetic recording medium> Figure 1 is a cross-sectional view showing an example of a magnetic recording medium manufactured by the manufacturing method of the magnetic recording medium according to this embodiment. As shown in Figure 1, the magnetic recording medium 1 has a lubricating layer 12 on both sides of a laminate (also referred to as a laminated body) 11.

[0017] The laminate 11 is provided with a magnetic recording layer 112 and a protective layer 113 laminated on both sides of the substrate 111 in that order, starting from the substrate 111 side.

[0018] The substrate 111 is made of a non-magnetic material. The substrate 111 may be a metal substrate made of a metallic material such as an aluminum alloy, or a non-metallic substrate made of a non-metallic material such as glass. Furthermore, an NiP alloy layer may be formed on the surface of these metal or non-metallic substrates using methods such as plating or sputtering.

[0019] The magnetic recording layer 112 is a layer provided for recording and reproducing information. For example, it is provided for storing data by reversing the direction of magnetization using magnetic energy supplied from the magnetic head of the HDD and maintaining that magnetization state.

[0020] The magnetic recording layer 112 uses FePt-based alloys having an L10 structure, CoPt-based alloys having an L10 structure, and CoCrPt-based alloys having an hcp structure, among others.

[0021] For forming the magnetic recording layer 112, known methods such as sputtering and ion beam deposition can be used.

[0022] 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 improve the corrosion resistance of the magnetic recording medium 1.

[0023] The protective layer 113 can be formed from well-known materials, such as hard carbon films or diamond-like carbon (DLC).

[0024] For forming the protective layer 113, known methods such as sputtering and ion beam deposition can be used.

[0025] The protective layer 113 may have its surface hydrogenated or nitrogenated. By hydrogenating or nitrogenating its surface, the protective layer 113 can increase its bonding strength with the lubricating layer 12 formed on top of it. That is, since the first lubricant applied on the protective layer 113 has polarity, it forms a strong bond with the hydrogen and nitrogen atoms on the surface of the protective layer 113. In particular, it is preferable that the surface of the protective layer 113 be nitrogenized.

[0026] The lubricating layer 12 is provided to suppress wear on the surface of the magnetic head and the magnetic recording medium 1 when the magnetic head comes into contact with the magnetic recording medium 1, thereby improving the corrosion resistance of the magnetic recording medium 1.

[0027] The thickness of the lubricating layer 12 is preferably 5 to 10 Å. By setting the thickness of the lubricating layer 12 to 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 improved, and the distance between the magnetic head and the magnetic recording medium 1 in the HDD can be shortened to achieve high recording density.

[0028] In this embodiment, the magnetic recording medium 1 may include one or more of the following between the substrate 111 and the magnetic recording layer 112: an adhesion layer, a soft magnetic underlayer, a seed layer, and an orientation control layer. One or more of these layers may be laminated.

[0029] In this embodiment, the magnetic recording medium 1 may include a plurality of magnetic recording layers 112 stacked together. In this case, non-magnetic recording layers may be stacked between the magnetic recording layers 112.

[0030] <Method for manufacturing magnetic recording media> Figure 2 shows an example of the outline of the manufacturing method for a magnetic recording medium according to this embodiment. As shown in Figure 2, the manufacturing method for a magnetic recording medium according to this embodiment includes the steps of: forming a laminate 11 by stacking a magnetic recording layer 112 and a protective layer 113 in that order on both sides of a substrate 111 (laminated body formation step); applying a first lubricant 121 and a second lubricant 122 onto the laminate 11 (coating step); burning the surface of the laminate 11 to which the first lubricant 121 and the second lubricant 122 have been applied with an abrasive (burnishing step); and removing the second lubricant 122 (see Figure 2) from the laminate 11 (removal step). In the coating process, a spin coating method is used for applying the second lubricant; the burnishing process includes a step of pressing a tape containing an abrasive material against the surface of the laminate and rubbing it (rubbing process); and the removal process includes at least one of the following steps: irradiating the laminate coated with the first and second lubricants with ultraviolet light (ultraviolet irradiation process) and heat treating the laminate coated with the first and second lubricants (heat treatment process).

[0031] Furthermore, the method for manufacturing a magnetic recording medium according to this embodiment may include other steps, 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. Also, if the method for manufacturing a magnetic recording medium according to this embodiment is provided by stacking multiple magnetic recording layers 112, it may include steps such as forming a non-magnetic recording layer between the magnetic recording layers 112.

[0032] In the manufacturing method of the magnetic recording medium according to this embodiment, a first lubricant 121 and a second lubricant 122 are applied to the surface of the laminate 11, and then the surface of the laminate 11 is burnished with an abrasive. Subsequently, the second lubricant 122 on the laminate 11 is removed by applying ultraviolet irradiation treatment 31 or heat treatment 32. As a result, the first lubricant 121 remains on the surface of the protective layer 113 of the laminate 11, and the remaining first lubricant 121 becomes the lubricating layer 12 of the magnetic recording medium 1, thus forming the lubricating layer 12.

[0033] In this embodiment, ultraviolet irradiation treatment 31 or heat treatment 32 is used to remove the second lubricant 122. As mentioned above, conventionally, the lubricant used in the burnishing process was removed by cleaning with a solvent. However, according to the inventors' investigation, the solvent used for cleaning contained not only the lubricant to be removed but also contaminants generated during burnishing, and it was found that the solvent remained on the surface of the protective layer 113, which was the surface to be cleaned, for some time. It was found that the re-adhesion of these remaining contaminants and lubricant to the protective layer 113 was the cause of foreign matter on the surface of the magnetic recording medium 1. Furthermore, it was found that it is difficult to completely remove the lubricant bonded to the protective layer 113 by solvent cleaning, and that the small amount of remaining lubricant is the cause of foreign matter on the surface of the magnetic recording medium 1.

[0034] In this embodiment, the removal of the second lubricant 122 on the laminate 11 is performed by a dry process, which involves ultraviolet irradiation 31 or heat treatment 32. Therefore, the second lubricant 122 or contaminants dissolved in it rapidly gasify and leave the surface of the laminate 11, so they do not cause foreign matter on the surface of the magnetic recording medium 1. Furthermore, by setting the conditions of the ultraviolet irradiation 31 or heat treatment 32 to conditions that allow the second lubricant 122 to gasify, the second lubricant 122 on the laminate 11 can be completely removed. In addition, since the process of forming the lubricating layer 12 is simple, a highly productive method for manufacturing a magnetic recording medium can be provided.

[0035] [Laminate formation process] In the method for manufacturing a magnetic recording medium according to this embodiment, first, a laminate 11 is formed by stacking a magnetic recording layer 112 and a protective layer 113 in that order on both sides of a prepared substrate 111, as shown in Figure 1 (laminated body formation step).

[0036] The laminate 11 can be formed using a general method for depositing the magnetic recording layer 112 and the protective layer 113.

[0037] First, a magnetic recording layer 112 is formed on both sides of the substrate 111. A general film deposition method such as sputtering can be used to form the magnetic recording layer 112.

[0038] In the sputtering method, a target containing the material for forming the magnetic recording layer 112 can be used.

[0039] As a target containing the material for forming the magnetic recording layer 112, for example, an FePt-based alloy having an L10 structure, a CoPt-based alloy having an L10 structure, or a CoCrPt-based alloy having an hcp structure can be used.

[0040] Sputtering methods that can be used include DC sputtering, DC magnetron sputtering, and RF sputtering.

[0041] When forming the magnetic recording layer 112, RF (Radio Frequency) bias, DC bias, pulsed DC, and pulsed DC bias may be used as needed.

[0042] O2 gas, H2O gas, N2 gas, etc., may be used as the reactive gas.

[0043] The sputtering gas pressure is adjusted as needed to optimize the characteristics of each layer, but it is usually within the range of 0.1 to 30 Pa.

[0044] Next, a protective layer 113 is formed on the magnetic recording layer 112. The method for forming the protective layer 113 is not particularly limited, but general deposition methods such as the RF-CVD (Radio Frequency-Chemical Vapor Deposition) method, which decomposes a source gas consisting of hydrocarbons with a high-frequency plasma to form a film, the IBD (Ion Beam Deposition) method, which ionizes the source gas with electrons emitted from a filament to form a film, and the FCVA (Filtered Cathodic Vacuum Arc) method, which uses a solid carbon target to form a film without using a source gas, can be used.

[0045] [Coating process] Next, as shown in Figure 2, the first lubricant 121 and the second lubricant 122 are applied to both sides of the laminate 11 in that order (application step).

[0046] Note that "both sides of the laminate 11" refers to both main surfaces of the laminate 11 to which the first lubricant 121 and the second lubricant 122 are applied. The first lubricant 121 and the second lubricant 122 may be applied to one main surface of the laminate 11 and then to the other main surface of the laminate 11, or they may be applied to both main surfaces of the laminate 11 simultaneously.

[0047] When the first lubricant 121 is applied to the protective layer 113, it is ideally preferable that the entire surface of the protective layer 113 is covered by the first lubricant 121, but a portion of the surface of the protective layer 113 may remain uncovered. In that case, the second lubricant 122 may be applied to the portion not covered by the first lubricant 121.

[0048] Preferably, the average molecular weight of the first lubricant 121 is higher than that of the second lubricant 122, and the polarity of the first lubricant 121 is higher than that of the second lubricant 122. This makes it easier to remove the second lubricant 122 from the laminate 11 while leaving the first lubricant 121 in the laminate 11 when applying ultraviolet irradiation treatment 31 or heat treatment 32 to the laminate 11 in the removal process described later.

[0049] The organic compounds used as the first lubricant 121 and the second lubricant 122 contain functional groups such as hydroxyl groups, amino groups, amide groups, carbonyl groups, carboxyl groups, cyano groups, phenyl groups, and methyl groups. Among these, the polar functional groups (polar groups) are the hydroxyl group, amino group, amide group, carbonyl group, carboxyl group, and cyano group.

[0050] The average molecular weight of the first lubricant 121 is preferably 900 to 3000, and the structural formula of the first lubricant 121 preferably contains 4 to 8 polar groups. This makes it easy to select between ultraviolet irradiation treatment 31 and heat treatment 32, which gasify the second lubricant 122 without gasifying the first lubricant 121, when removing the second lubricant 122 by ultraviolet irradiation treatment 31 or heat treatment 32 in the removal step described later.

[0051] The average molecular weight of the second lubricant 122 is preferably 300 to 1000, and the number of polar groups in the structural formula of the second lubricant 122 is preferably two or less, or none at all. This makes it easy to select between the ultraviolet irradiation treatment 31 and the heat treatment 32 that gasify the second lubricant 122 without gasifying the first lubricant 121 when removing the second lubricant 122 by ultraviolet irradiation treatment 31 or heat treatment 32 in the removal step described later.

[0052] The polar groups of the first lubricant 121 and the second lubricant 122 are preferably hydroxyl groups, amide groups, and cyano groups, with hydroxyl groups being particularly preferred among these. By having the above-mentioned preferred polar groups, the first lubricant 121 can be made suitable for the lubrication layer 12 of the magnetic recording medium 1, and the second lubricant 122 can be made suitable for varnishing the surface of the laminate 11. Furthermore, when performing the above-mentioned ultraviolet irradiation treatment 31 or heat treatment 32, the effect of quickly removing the second lubricant 122 or contaminants dissolved in it is enhanced. In addition, by leaving the first lubricant 121 on the laminate 11 and increasing the bonding force between the protective layer 113 and the first lubricant 121, surface foreign matter can be further reduced and the coverage rate of the magnetic recording medium 1 by the lubrication layer 12 can be further increased.

[0053] The first lubricant 121 forms a lubricating layer 12 on the magnetic recording medium 1. Therefore, a film thickness of 5 to 10 Å for the first lubricant 121 is preferable, as it suppresses wear on the surface of the magnetic recording medium 1, improves the corrosion resistance of the magnetic recording medium 1, and shortens the distance between the magnetic head and the magnetic recording medium 1 in an HDD to achieve high recording density.

[0054] The film thickness of the second lubricant 122 is preferably 5 to 20 Å. A film thickness of 5 to 20 Å for the second lubricant 122 makes it suitable for varnishing the surface of the laminate 11. Furthermore, the second lubricant 122 can be removed in a short time by ultraviolet irradiation treatment 31 or heat treatment 32, thereby increasing the productivity of the magnetic recording medium 1.

[0055] For applying the first lubricant 121, known methods such as the dipping method, the spin coating method, and the vapor coating method can be used.

[0056] The dipping method is a method of forming a film of the first lubricant 121 on the surface of the laminate 11 by immersing the laminate 11 in a solution containing a dissolved lubricant and then pulling the laminate 11 up at a constant speed. The spin coating method is a method of forming a film of the first lubricant 121 on the laminate 11 by applying a solution containing a dissolved lubricant to the surface of the laminate 11 and then rotating the laminate 11 at high speed for a certain period of time. The vapor coating method is a method of forming a film of the first lubricant 121 on the laminate 11 by placing the laminate 11 in a vacuum chamber and introducing a lubricant that has been gasified by heating into the vacuum chamber.

[0057] An example of the formation of a film of the first lubricant 121 by the dipping method will be explained using Figures 3A and 3B.

[0058] As shown in Figure 3A, a solution 52 containing the first lubricant 121 is placed in a solution tank 51, and an arm 53 to which the laminate 11 is fixed is lowered vertically at a constant speed into the solution 52 to immerse the laminate 200 in the solution 52. Then, the arm 53 is raised vertically at a constant speed to the state shown in Figure 3B, thereby forming a film of the first lubricant 121 on the surface of the laminate 11. Here, the laminate 11 is held by the arm 53 so that its inner circumference is caught in a V-shaped groove provided on the arm 53. The arm 53 is mounted so that it can move vertically relative to the support column 54. The thickness of the film of the first lubricant 121 can be controlled by the raising speed of the arm 53.

[0059] An example of forming a film of the first lubricant 121 by the spin coating method will be explained using Figure 4. As shown in Figure 4, the spin coating lubricant application apparatus 60 prepares a solution of dissolved lubricant in a tank 61. After spraying this solution from nozzles 63 onto both surfaces of a laminate 11 chucked to a spindle 62, the laminate 11 is rotated at high speed for a certain period of time by a motor 64, thereby forming a film of the first lubricant 121 on the laminate 11 by centrifugal force. Excess solution is discharged outside the apparatus from a drain port 65. The thickness of the film of the first lubricant 121 can be controlled by the rotation speed of the spindle 62.

[0060] An example of forming a film of the first lubricant 121 by the vapor method will be explained using Figure 5. As shown in Figure 5, the vapor method lubricant application apparatus 70 places the laminate 11 on the mounting stand 72 in the processing chamber 71, and then evacuates the processing chamber 71 with a vacuum pump 73. After this, a lubricant film is formed on the laminate 11 by introducing a gasified lubricant 74 into the processing chamber 71. Subsequently, the processing chamber 71 is evacuated, then the pressure inside the processing chamber 71 is increased to atmospheric pressure, and the processed substrate is removed from the processing chamber 71. The thickness of the film of the first lubricant 121 can be controlled by the amount of gasified lubricant introduced.

[0061] The second lubricant 122 is applied using the spin coating method. The following effects can be obtained by using the spin coating method for applying the second lubricant 122. When applying the second lubricant 122, it is necessary to avoid dissolving the already formed film of the first lubricant 121. The spin coating method can apply the second lubricant 122 on top of the first lubricant 121 at a higher speed than other methods, thus reducing the impact on the film of the first lubricant 121 during application. Furthermore, using the spin coating method makes it less likely for the in-plane film thickness distribution of the applied film of the second lubricant 122 to become large, and since an immersion tank for the second lubricant 122 is not used as in the dip method, there are advantages such as being able to reduce fluctuations in the liquid composition of the second lubricant 122.

[0062] [Burning process] Next, the surface of the laminate 11 is burnished with an abrasive (burnishing process).

[0063] The burning process includes a scraping step in which an abrasive tape 20 is pressed against the surface of the laminate 11 and scraped, as shown in Figure 2. In the burning process, a method can be used in which an abrasive tape 20 is pressed against the surface of the laminate 11 and scraped. The burning method and burning apparatus will be described in detail with reference to the figures.

[0064] Figure 6 is an enlarged cross-sectional view showing an example of a polishing tape 20 used during varnishing. As shown in Figure 6, the polishing tape 20 polishes the laminate 11 by sliding its polishing surface S against the surface of the laminate 11.

[0065] 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 binds the abrasive grains 221 together and also binds the abrasive grains 221 to the support 21, thereby fixing the abrasive grains 221 to the abrasive layer 22.

[0066] The material constituting the support 21 is not particularly limited, and various resins such as polyethylene terephthalate can be used.

[0067] The abrasive grains 221 can be used as an abrasive material contained in the polishing tape 20. Examples of abrasive grains 221 include particles having chromium oxide, α-alumina, silicon carbide, nonmagnetic iron oxide, diamond, γ-alumina, α,γ-alumina, fused alumina, corundum, and artificial diamond. The abrasive grains 221 may also be particles made from these materials. These may be used individually or in appropriate combinations of two or more types.

[0068] The binder 222 is not particularly limited, and for example, thermosetting resins, thermoplastic resins, and photosensitive resins can be used. The resin used as the binder 222 may be used alone or in combination of two or more types.

[0069] Alternatively, a lubricating film 23 may be provided on the surface of the polished surface S.

[0070] Figure 7 shows an example of a burnishing apparatus used in the process of burnishing the surface of a laminate 11 with an abrasive material. As shown in Figure 7, the burnishing apparatus 80 has a pair of abrasive tapes 20 (abrasive tapes 20A and 20B) arranged opposite each other so as to sandwich the laminate 11 from both sides, a rotating support means 81, and a tape moving means 82. In the burnishing apparatus 80, the abrasive tapes 20A and 20B are arranged opposite each other so as to sandwich the laminate 11 from both sides, allowing for efficient burnishing of both sides of the laminate 11 simultaneously.

[0071] The rotational support means 81 rotates the laminated body 11 in the circumferential direction (direction of arrow r) while supporting the central opening of the laminated body 11.

[0072] The tape moving means 82 presses the polishing tapes 20A and 20B against both surfaces of the rotated laminate 11 in the direction of arrow F, and moves the polishing tapes 20A and 20B relative to each other in the radial direction of the laminate 11.

[0073] Furthermore, the tape moving means 82 includes a pair of abrasive tape pressing means 821 and a pair of abrasive tape running systems 822, which are positioned opposite each other so as to sandwich the laminate 11 from both sides via the abrasive tapes 20A and 20B.

[0074] The pair of abrasive tape pressing means 821 comprises a first abrasive tape pressing means 821A and a second abrasive tape pressing means 821B. The pair of abrasive tape running systems 822 comprises a first abrasive tape running system 822A and a second abrasive tape running system 822B.

[0075] In other words, the tape moving means 82 includes a first polishing tape pressing means 821A and a first polishing tape running system 822A arranged on one side of the laminate 11, and a second polishing tape pressing means 821B and a second polishing tape running system 822B arranged on the other side.

[0076] The first abrasive tape transport system 822A includes a supply roll and a winding roll (not shown), and first guide rolls 823A-1 to 823A-4 arranged below the supply roll and winding roll, and transports the abrasive tape 20A in the direction of arrow Ra.

[0077] The second abrasive tape transport system 822B includes a supply roll and a winding roll (not shown), and second guide rolls 823B-1 to 823B-4 arranged below the supply roll and winding roll, and transports the abrasive tape 20B in the direction of arrow Rb.

[0078] [Removal process] Next, as shown in Figure 2, the second lubricant 122 on the laminate 11 is removed (removal step).

[0079] The removal process includes at least one of two steps: an ultraviolet irradiation step, which involves irradiating the laminate 11 coated with the first lubricant 121 and the second lubricant 122 with ultraviolet light, and a heat treatment step, which involves heat treating the laminate 11 coated with the first lubricant 121 and the second lubricant 122. By performing at least one of the ultraviolet irradiation treatment 31 and the heat treatment 32 on the laminate 11, the second lubricant 122 on the laminate 11 is removed. As a result, the first lubricant 121 remains on the surface of the protective layer 113 of the laminate 11, and the remaining first lubricant 121 becomes the lubricating layer 12 of the magnetic recording medium 1.

[0080] In the removal process, it is preferable that the second lubricant 122 is completely removed by ultraviolet irradiation treatment 31 or heat treatment 32, but some of it may remain.

[0081] A known irradiation source can be used in the ultraviolet irradiation process, and known irradiation sources include, for example, ultraviolet lamps or LED lamps. The emission wavelength, emission output, and irradiation time of the ultraviolet light from these lamps may be appropriately selected under treatment conditions that can remove the second lubricant 122, and it is also preferable to consider treatment conditions that enhance the bonding strength of the first lubricant 121 to the protective layer 113. Specifically, for ultraviolet lamps, the peak wavelength is preferably appropriately selected from 100-280 nm, 280-315 nm, or 315-400 nm. For LED lamps, since the emission wavelength can be easily controlled, it is preferable to design the LED lamp according to the type of lubricant used.

[0082] Since the ultraviolet irradiation time is preferably within 1 minute from the perspective of the productivity of the magnetic recording medium 1, it is preferable to adjust the light emission output so that the processing is completed within 1 minute.

[0083] Furthermore, if the ultraviolet irradiation process is carried out in the atmosphere, ozone may be generated, which may adversely affect the manufacturing of the magnetic recording medium 1. Therefore, in order to suppress the generation of ozone, it is preferable to carry out the ultraviolet irradiation process in an inert gas atmosphere or in a vacuum.

[0084] The heat treatment process can use known heat sources. Examples of known heat sources include halogen lamp heaters, ceramic heaters, resistance heaters, and LED lamp heaters. The heating temperature and heating time using these heat sources may be appropriately selected under treatment conditions that allow for the removal of the second lubricant 122, and it is also preferable to consider treatment conditions that enhance the bonding strength of the first lubricant 121 to the protective layer 113.

[0085] Since the heating time is preferably 15 minutes or less from the perspective of the productivity of the magnetic recording medium, it is preferable to adjust the heating time so that the process is completed within 15 minutes.

[0086] The heating temperature is preferably 120°C or lower, from the standpoint of ease of designing the heating device.

[0087] Furthermore, depending on the heat source, a large amount of degassing may occur, and this degassing may be incorporated into the laminate 11, potentially adversely affecting the manufacturing of the magnetic recording medium 1. To minimize the effects of degassing, it is preferable to perform the heat treatment process in an inert gas atmosphere.

[0088] As described above, the method for manufacturing a magnetic recording medium according to this embodiment includes a coating step, a burnishing step, and a removal step. In the coating step, a spin coating method is used for coating the second lubricant 122, and the burnishing step includes a scraping step in which an abrasive tape 20 is pressed against the surface of the laminate 11. The removal step includes an ultraviolet irradiation step in which ultraviolet light is irradiated onto the laminate 11 coated with the first lubricant 121 and the second lubricant 122, or a heat treatment step in which heat treatment is performed on the laminate 11 coated with the first lubricant 121 and the second lubricant 122. In the removal step, the second lubricant 122 is removed by the ultraviolet irradiation treatment 31 or the heat treatment 32, and the first lubricant 121 is formed as a lubricating layer 12, thereby increasing the coverage rate of the lubricating layer 12 on the laminate 11 and reducing the amount of foreign matter generated on the surface of the lubricating layer 12. Therefore, according to the method for manufacturing a magnetic recording medium according to this embodiment, foreign matter on the surface of the magnetic recording medium 1 can be efficiently removed, and a magnetic recording medium with a high coverage rate by the lubricating layer 12 can be manufactured.

[0089] As described above, the magnetic recording medium 1 manufactured using the manufacturing method for magnetic recording media according to this embodiment has fewer foreign matter on its surface and a high coverage rate by the lubricating layer 12, thus suppressing wear damage due to contact sliding with the magnetic head and improving durability. The magnetic recording medium 1 can maintain excellent electromagnetic conversion characteristics and have a stable high recording density, making it suitable for use in magnetic recording and playback devices. The form of the magnetic recording and playback device is not particularly limited as long as it has a magnetic recording medium manufactured using the manufacturing method for magnetic recording media according to this embodiment, and may be a magnetic recording and playback device that records magnetic information on a magnetic recording medium using a heat-assisted recording method.

[0090] As described above, embodiments have been explained, but these embodiments are presented as examples only, and the present invention is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Examples]

[0091] The embodiments will be described in detail below based on examples, but the embodiments are not limited to these examples.

[0092] <Example 1> [Manufacturing of magnetic recording media] A cleaned glass substrate (manufactured by HOYA, 2.5 inches in diameter) is placed in the deposition chamber of a DC magnetron sputtering system (Anelva C-3040), and the ultimate vacuum level is 1 × 10⁻¹⁰. -5 The deposition chamber was evacuated until the temperature dropped to Pa. Then, a 10 nm thick adhesion layer was formed on the glass substrate using a Cr target via sputtering.

[0093] 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 sequence. First, a first soft magnetic recording layer with a thickness of 25 nm was deposited using a target of Co-20Fe-5Zr-5Ta (Fe content 20 atoms, Zr content 5 atoms, Ta content 5 atoms, remainder Co) at a substrate temperature of 100°C or less. Next, an intermediate layer made of Ru with a thickness of 0.7 nm was formed. After that, a second soft magnetic recording layer made of Co-20Fe-5Zr-5Ta with a thickness of 25 nm was deposited.

[0094] Next, a seed layer with a thickness of 5 nm was formed on the soft magnetic underlayer using a Ni-6W {W content of 6 atoms, remainder Ni} target by sputtering.

[0095] Subsequently, a Ru layer with a thickness of 10 nm was deposited on the seed layer as a first orientation control layer by sputtering at a sputtering pressure of 0.8 Pa. Next, a Ru layer with a thickness of 10 nm was formed on the first orientation control layer by sputtering at a sputtering pressure of 1.5 Pa as a second orientation control layer.

[0096] Next, a first magnetic recording layer consisting of 91(Co15Cr16Pt)-6(SiO2)-3(TiO2){an alloy with 15 atomic% Cr content, 16 atomic% Pt content, and the remainder being Co, comprising 91 mol%, 6 mol% SiO2, and 3 mol% TiO2} was formed on the second orientation control layer by sputtering, with a layer thickness of 9 nm. The sputtering pressure used here was 2 Pa.

[0097] Next, a non-magnetic recording layer consisting of 88(Co30Cr)-12(TiO2){an alloy with a Cr content of 30 atoms, the remainder being Co, and 88 mol% TiO2} was formed on the first magnetic recording layer by sputtering, with a layer thickness of 0.3 nm.

[0098] Subsequently, a second magnetic recording layer consisting of 92(Co11Cr18Pt)-5(SiO2)-3(TiO2){92 mol% of an alloy with 11 atomic% Cr, 18 atomic% Pt, and the remainder being Co, 5 mol% SiO2, and 3 mol% TiO2} was formed on the non-magnetic recording layer by sputtering to a thickness of 6 nm. The sputtering pressure used here was 2 Pa.

[0099] Subsequently, a non-magnetic recording layer made of Ru with a thickness of 0.3 nm was formed on the second magnetic recording layer using a sputtering method.

[0100] Next, a third magnetic recording layer was formed on the non-magnetic recording layer using a sputtering method with a thickness of 7 nm, using a target made of Co-20Cr-14Pt-3B {Cr content 20 atoms%, Pt content 14 atoms%, B content 3 atoms%, remainder Co}, at a sputtering pressure of 0.6 Pa.

[0101] A carbon hydride film was formed on the surface of the third magnetic recording layer using ion beam deposition with gasified toluene as the source gas. To deposit the carbon hydride film, the gas flow rate of the source gas supplied to the deposition chamber was set to 2.9 SCCM, and the reaction pressure to 0.2 Pa. Furthermore, the cathode power, which is the excitation source for the source gas, was set to 225 W (AC 22.5 V, 10 A). Then, the voltage between the cathode electrode and the anode electrode covering it 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 1.5 seconds, resulting in a carbon hydride film with a thickness of 3.5 nm. After the formation of the carbon hydride film, the supply of the source gas was stopped, and the deposition chamber was evacuated for 2 seconds.

[0102] Next, nitrogen gas was supplied to the deposition chamber at a gas flow rate of 2 SCCM and a reaction pressure of 5 Pa. Then, the cathode power was set to 128 W (AC 16V, 8A), the voltage between the cathode and anode electrodes was 75 V, the current was 1000 mA, the ion acceleration voltage was 200 V, the current was 90 mA, and the processing time was 1 second. Nitrogen ions formed from nitrogen gas were irradiated onto the surface of the carbon hydride film, exposing it to nitrogen plasma. This dehydrogenated and nitrogenized the surface of the carbon hydride film, forming a nitrogenized carbon film as a protective layer.

[0103] Next, D5OH(XS) (trade name, manufactured by MORESCO Corporation), with the following structural formula (i), was dissolved in Bartlell XF (trade name, manufactured by Mitsui DuPont Fluorochemicals) to obtain the first lubricating layer forming solution. The concentration of the compound in the first lubricating layer forming solution was 0.3% by mass.

[0104] [ka] (In structural formula (i), m is a positive integer.)

[0105] Next, the first lubrication layer forming solution was applied to the protective layer using the dip method. Specifically, the laminate, with each layer up to the protective layer formed, was immersed in the first lubrication layer forming solution placed in the immersion tank of the dip coating apparatus, and then the laminate was withdrawn from the immersion tank at a constant speed. In this way, the first lubrication layer forming solution was applied to the surface on the protective layer so that the thickness of the first lubrication layer was 7 Å. Subsequently, the first lubrication layer was formed on the surface of the laminate by drying the surface to which the first lubrication layer forming solution had been applied.

[0106] Next, the second lubricant, represented by the following structural formula (ii), was dissolved in HFE7200 (trade name, manufactured by 3M Corporation) to obtain a second lubricating layer forming solution. The concentration of the compound in the second lubricating layer forming solution was 0.3% by mass. Note that HFE7200 can dissolve the second lubricant represented by the following structural formula, but it cannot dissolve the first lubricant, D5OH(XS).

[0107] [ka] (In structural formula (ii), m is a positive integer.)

[0108] Next, a second lubricant was applied to the surface of the laminate where the first lubricating layer had been formed, using a spin-coating method. The thickness of the second lubricating layer was set to 7 Å. Subsequently, the second lubricating layer was formed on the surface of the laminate where the first lubricating layer had been formed by drying the surface to which the second lubricating layer-forming solution had been applied.

[0109] Next, the surface of the laminate, on which the first and second lubrication layers were formed, was varnished using a polishing tape. The polishing tape used was Sumitomo 3M Co., Ltd.'s model DQ3, which uses Al2O3 with a particle size of 0.3 μm as the abrasive material. The varnishing conditions were a rotation speed of 1000 rpm for the laminate and a processing time of 3 seconds.

[0110] Next, the surface of the laminate on which the first and second lubricating layers were formed was irradiated with ultraviolet light. An ultraviolet lamp manufactured by Ushio Inc. was used for the irradiation, and the irradiation time was 10 seconds in a nitrogen gas atmosphere.

[0111] Next, the surface of the laminate on which the first and second lubricating layers were formed was heat-treated. The heat treatment was performed in a nitrogen gas atmosphere at 120°C for 1200 seconds. By heat-treating the surface of the laminate on which the first and second lubricating layers were formed, the second lubricating layer was removed from the surface of the first lubricating layer, and a new lubricating layer was formed from the first lubricating layer.

[0112] As a result, a magnetic recording medium was manufactured by laminating an adhesion layer, a soft magnetic underlayer, a seed layer, a first orientation control layer, a second orientation control layer, a first magnetic recording layer, a non-magnetic recording layer, a second magnetic recording layer, a non-magnetic recording layer, a third magnetic recording layer, a nitrogenized carbon film (protective layer), and a lubricating layer on both sides of a glass substrate in this order.

[0113] [Evaluation of the lubrication layer] The laminated material, after UV irradiation and heat treatment, was analyzed using ESCA and confirmed that the first lubricating layer with a thickness of 7 Å remained, while the second lubricating layer had been removed.

[0114] (Coverage of the lubricating layer) The coverage of the lubricating layer on the fabricated magnetic recording medium was measured. The coverage was determined by immersing the magnetic recording medium, after the lubricating layer had formed, in a fluorocarbon solvent for 5 minutes. The absorbance at approximately 1270 cm⁻¹ at the same location on the same medium before and after immersion was measured using ESCA, and the percentage of the ratio ((absorbance after immersion / absorbance before immersion) × 100) was used. Bartrell XF (trade name, manufactured by Mitsui DuPont Fluorochemicals) was used as the fluorocarbon solvent. The coverage of the lubricating layer on the fabricated magnetic recording medium was 80%.

[0115] (TA (Thermal Asperity) Glide Evaluation) TA glide evaluation was performed on the fabricated magnetic recording media. An MR head (manufactured by TDK Corporation) was used as the inspection head for the TA glide evaluation. TA glide evaluation is a method that detects thermal asperities (TA), which are phenomena in which the signal waveform reproduced by the MR head fluctuates due to frictional heat generated when the MR head collides with protrusions on the surface of the magnetic recording media. The smoothness of the surface of the magnetic recording media is evaluated from the number of such signals (TA count). A smaller TA count indicates higher surface smoothness of the magnetic recording media. The average TA count for 100 fabricated magnetic recording media was 7 per surface.

[0116] Table 1 shows the conditions for preparing the first and second lubricants, and Table 2 shows the processing conditions for the first and second lubricants and the evaluation results of the lubricating layer.

[0117] <Examples 2-11, Comparative Examples 1-11> A magnetic recording medium was fabricated in the same manner as in Example 1, except that the fabrication conditions for the first and second lubricants and the processing conditions for the first and second lubricants were changed to the values ​​shown in Tables 1 and 2, respectively, and the lubricating layer was evaluated. The fabrication conditions for the first and second lubricants are shown in Table 1, and the processing conditions for the first and second lubricants and the evaluation results of the lubricating layer are shown in Table 2.

[0118] In Examples 2-11 and Comparative Examples 1-11, the D4OH and D4OH(s) (both trade names, manufactured by MORESCO Corporation) used as the first and second lubricants have the following structural formula (iii) and structural formula (iv) is as shown below. The average molecular weight of D4OH was adjusted to be 2000, and the average molecular weight of D4OH(s) was adjusted to be 1600. As with Example 1, HFE7200 (trade name, manufactured by 3M Corporation) was used as the solvent for the second lubricant. HFE7200 can dissolve the second lubricant, but not the first lubricant.

[0119] Structural formulas of D4OH and D4OH(s): CH2(OH)CH(OH)CH2OCH2CF2CF2(OCF2CF2CF2) mOCF2CF2CH2OCH2CH(OH)CH2OH ···(iii) (In structural formula (iii), m is a positive integer.)

[0120] Structural formula (iv): [ka]

[0121] [Table 1]

[0122] [Table 2]

[0123] From Tables 1 and 2, Examples 1 to 11 showed improved lubrication layer coverage and lower TA counts compared to Comparative Examples 1 to 11, which correspond to Examples 1 to 11. Therefore, it can be said that by using the manufacturing method of the magnetic recording medium according to this embodiment, applying the spin coating method to the second lubricant, removing the second lubricant by subjecting it to at least one of ultraviolet irradiation and heat treatment, and forming a lubricating layer consisting of the first lubricant, foreign matter on the surface of the magnetic recording medium can be efficiently removed, and a magnetic recording medium with a high lubrication layer coverage can be obtained. [Explanation of Symbols]

[0124] 1 Magnetic recording medium 11 Laminated body (laminated body) 12 Lubricating layer 20, 20A, 20B Tapes containing abrasive material (abrasive tapes) 21 Support 22 Abrasive layer 31. UV irradiation treatment 32 Heat treatment 51 Solution tank 52 Solution 53 Arm 54 Post 60 Lubricant application apparatus using spin coating method 61 A solution containing lubricant is placed in a tank. 62 spindles 63 nozzles 64 motors 70. Lubricant application apparatus using the vapor method 71 Processing Room 72 Installation stand 73 Vacuum pump 74 Lubricant 80 Burnishing Machine 111 circuit board 112 Magnetic recording layer 113 Protective layer 121 First Lubricant 122 Second lubricant 221 abrasive grains 222 Binder 821 Pair of abrasive tape pressing means 822 Pair of abrasive tape transport systems 821A First polishing tape pressing means 821B Second polishing tape pressing means 822A First polishing tape transport system 822B Second polishing tape transport system S polished surface

Claims

1. A method for manufacturing a magnetic recording medium, comprising forming a lubricating layer on a laminate in which a magnetic recording layer and a protective layer are stacked on a substrate in that order, The process involves applying a first lubricant and a second lubricant onto the laminate, A step of burning the surface of the laminate to which the first lubricant and the second lubricant have been applied with an abrasive, A step of removing the second lubricant from the laminate, Includes, The second lubricant is applied using the spin coating method. The burning step includes pressing the tape containing the abrasive material against the surface of the laminate and rubbing it, A method for manufacturing a magnetic recording medium, wherein the step of removing the second lubricant includes at least one of the steps of irradiating the laminate coated with the first lubricant and the second lubricant with ultraviolet light and heat-treating the laminate coated with the first lubricant and the second lubricant.

2. The average molecular weight of the first lubricant is higher than the average molecular weight of the second lubricant. The method for manufacturing a magnetic recording medium according to claim 1, wherein the polarity of the first lubricant is higher than the polarity of the second lubricant.

3. The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the second lubricant has an average molecular weight of 300 to 1000 and contains two or fewer polar groups, or does not contain any.

4. The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the first lubricant has an average molecular weight of 900 to 3000 and contains 4 to 8 polar groups.

5. The film thickness of the first lubricant applied to the laminate is set to 5 to 10 Å. A method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the film thickness of the second lubricant is 5 to 20 Å.

6. The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the step of irradiating with ultraviolet light is performed in an inert gas atmosphere or in a vacuum.

7. The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the heat treatment step is performed in an inert gas atmosphere.

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