Method for manufacturing magnetic recording medium

Abstract

The purpose of the present invention is to provide a method for manufacturing a magnetic recording medium, wherein foreign matter on the surface of the magnetic recording medium can be efficiently removed, and the coating rate by a lubricating layer is high. A method for manufacturing a magnetic recording medium according to the present invention is a method for manufacturing a magnetic recording medium in which a lubricating layer is formed on a laminate in which a magnetic recording layer and a protective layer are laminated in this order on a substrate, the method comprising: a step for applying a first lubricant and a second lubricant on the laminate, and a polishing step for polishing the surface of the laminate to which the first lubricant and the second lubricant have been applied with a polishing material, and a step for removing the second lubricant from the laminate, the polishing step including: a step for pressing and rubbing a tape containing the polishing material against the surface of the laminate; the step of removing the second lubricant includes a step of irradiating the laminate coated with the first lubricant and the second lubricant with light emitted from an LED light source.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of a magnetic recording medium. BACKGROUND

[0002] In recent years, magnetic storage devices are mounted on various products such as personal computers, moving image recorders, and data servers, and their importance is increasing. The magnetic storage device is a device having a magnetic recording medium that stores electronic data by magnetic recording, and for example, has a hard disk drive (HDD).

[0003] A general magnetic recording medium has a multilayer film laminated structure in which a base layer, an intermediate layer, a magnetic recording layer, and a protective layer are sequentially formed on a non-magnetic substrate, and a lubricating layer is coated on the surface of the protective layer. The protective layer and the lubricating layer are provided to prevent the durability from deteriorating due to wear damage caused by contact sliding of the magnetic recording medium with a magnetic head. As the protective layer, a hard carbon film is generally used, and the lubricating layer is formed by coating a liquid perfluoropolyether compound or the like on the surface.

[0004] To improve the adhesion of the protective layer to the lubricating layer, various treatments for the lubricating layer are known. For example, in Patent Literature 1, a method is disclosed in which a heat treatment is applied to the coated lubricating layer, and further, a light irradiation treatment using an ultraviolet lamp is performed.

[0005] Further, to remove foreign matter and protrusions on the surface of the protective layer, the surface of the magnetic recording medium is belt polished by a polishing belt. At this time, to prevent the surface of the protective layer from being damaged by belt polishing, it is known that the belt polishing is performed after the formation of the lubricating layer.

[0006] Further, in Patent Literature 2, a manufacturing method of a magnetic recording medium is disclosed in which, after the formation of the protective layer, a first lubricant having no terminal group is coated on the surface thereof, and after the belt polishing, the first lubricant is removed using a solvent, and a second lubricant having a terminal group is coated.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: Japanese Patent Application Laid-Open No. 11-25452

[0010] Patent Literature 2: Japanese Patent Application Laid-Open No. 2002-222519 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] In the production of a magnetic recording medium, polishing is performed after the formation of a lubricating layer, so that the occurrence of scratches and the like is reduced by the lubricity of the lubricating layer. However, depending on the lubricant used for the lubricating layer and the film thickness of the lubricating layer, the polishing is not always suitable.

[0013] In the production method of the magnetic recording medium of Patent Document 2, after processing using the first lubricant suitable for polishing is performed, the first lubricant is removed, and a second lubricating layer suitable for the magnetic recording medium is applied. However, in this case, the following problems occur. That is, contaminants dissolved in a solvent used for the removal of the lubricant and the like are reattached to the processed substrate, and become a cause of foreign matter on the surface of the magnetic recording medium. In addition, it is difficult to completely remove the lubricant combined with the protective layer using a solvent, and the remaining solvent becomes a cause of foreign matter on the surface of the magnetic recording medium, and the manufacturing process of the magnetic recording medium becomes complicated while the coverage of the surface of the magnetic recording medium using the lubricating layer is reduced.

[0014] One embodiment of the present application is made in view of the above-described circumstances, and aims to provide a production method of a magnetic recording medium capable of efficiently removing foreign matter from the surface of the magnetic recording medium and having a high coverage using a lubricating layer.

[0015] Method for solving the problem

[0016] The present application has the configuration shown below.

[0017] [1] A production method of a magnetic recording medium, which is a production method of a magnetic recording medium in which a lubricating layer is formed on a laminate in which a magnetic recording layer and a protective layer are sequentially stacked on a substrate, the production method comprising:

[0018] a step of applying a first lubricant and a second lubricant on the laminate,

[0019] a step of polishing the surface of the laminate on which the first lubricant and the second lubricant are applied by an abrasive,

[0020] a step of removing the second lubricant on the laminate,

[0021] the step of polishing includes a step of pressing a belt including the abrasive against the surface of the laminate and rubbing it,

[0022] the step of removing the second lubricant includes a step of irradiating light emitted from an LED light source to the laminate on which the first lubricant and the second lubricant are applied.

[0023] [2] The production method of a magnetic recording medium according to [1], wherein the center wavelength of the light emitted from the LED light source is less than 500 nm, and does not include a wavelength region in which the center wavelength is 170 to 190 nm.

[0024] [3] The method for manufacturing a magnetic recording medium according to [1] or [2], wherein the step of irradiating the light emitted from the LED light source is performed at a pressure near atmospheric pressure.

[0025] [4] The method for manufacturing a magnetic recording medium according to any one of [1] to [3], wherein the average molecular weight of the first lubricant is higher than the average molecular weight of the second lubricant,

[0026] the polarity of the first lubricant is higher than the polarity of the second lubricant.

[0027] [5] The method for manufacturing a magnetic recording medium according to [4], wherein the average molecular weight of the second lubricant is 300 to 1000, and the number of polar groups is 2 or less, or the second lubricant does not contain a polar group.

[0028] [6] The method for manufacturing a magnetic recording medium according to [4], wherein the average molecular weight of the first lubricant is 900 to 3000, and the number of polar groups is in the range of 4 to 8.

[0029] [7] The method for manufacturing a magnetic recording medium according to any one of [1] to [6], wherein the film thickness of the first lubricant applied to the laminate is the film thickness of the second lubricant is

[0030] Effects of the Invention

[0031] According to one embodiment of the present application, a method for manufacturing a magnetic recording medium having a high coverage ratio of a lubricating layer, which can efficiently remove foreign matter from the surface of the magnetic recording medium, can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A cross-sectional view showing an example of a magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to the embodiment of the present application.

[0033] Figure 2 A view showing an example of an outline of the method for manufacturing a magnetic recording medium according to the embodiment of the present application.

[0034] Figure 3 An enlarged cross-sectional view showing an example of a tape including an abrasive used at the time of polishing.

[0035] Figure 4 A view showing an example of a polishing device used in the step of polishing the surface of the laminate by the abrasive.

[0036] Figure 5 A cross-sectional view showing an example of an LED light irradiation device used for manufacturing a magnetic recording medium.

[0037] Figure 6 This is a slanted view schematic diagram illustrating an example of a light source in an LED illumination device. Detailed Implementation

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, for ease of understanding, the same symbols are used to denote the same constituent elements in each drawing, and repetitive descriptions are omitted where appropriate. Additionally, the scale of each component in the drawings may sometimes differ from the actual scale. In this specification, the tilde “~” indicating a numerical range means that, unless otherwise stated, the values ​​described before and after it include both the lower and upper limits. In a numerical range indicated by “~”, where only the unit of the upper limit is described, the lower limit is also described in the same unit.

[0039] The following describes a method for manufacturing a magnetic recording medium according to an embodiment of the present invention. A magnetic recording medium manufactured using the method described in this embodiment will also be explained.

[0040] <Magnetic Recording Media>

[0041] Figure 1 This 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. Figure 1 As shown, the magnetic recording medium 1 has a lubricating layer 12 on both sides of the laminate (also called the laminated body) 11.

[0042] The laminate 11 is stacked on both sides of the substrate 111, and has a magnetic recording layer 112 and a protective layer 113 stacked sequentially from the substrate 111 side.

[0043] The substrate 111 is formed of a non-magnetic material. For example, the substrate 111 can be a metal substrate formed of a metallic material such as aluminum alloy, or a non-metallic substrate formed of a non-metallic material such as glass. Furthermore, the surface of these metal or non-metallic substrates can be formed with a NiP alloy layer, for example, using a plating or sputtering method.

[0044] The magnetic recording layer 112 is a layer provided for recording and reproducing information, for example, by using magnetic energy supplied by the magnetic head of the HDD to reverse the direction of magnetization and maintain its magnetized state, thereby being provided for storing data.

[0045] The magnetic recording layer 112 uses FePt alloys with an L10 structure, CoPt alloys with an L10 structure, and CoCrPt alloys with an hcp structure, etc.

[0046] In the formation of the magnetic recording layer 112, known methods such as sputtering and ion beam deposition can be used.

[0047] The protective layer 113 is provided to inhibit the corrosion of the magnetic recording layer 112 and to protect the surface of the magnetic recording medium 1 from damage when the magnetic head contacts the magnetic recording medium 1, thereby improving the corrosion resistance of the magnetic recording medium 1.

[0048] The protective layer 113 can be formed from known materials, such as hard carbon film or diamond-like carbon (DLC).

[0049] In the formation of the protective layer 113, known methods such as sputtering and ion beam deposition can be used.

[0050] The protective layer 113 can be hydrogenated or nitrided. Hydrogenating or nitriding the surface of the protective layer 113 improves its adhesion to the lubricating layer 12 formed thereon. Specifically, the first lubricant applied to the protective layer 113 is polar, thus forming a strong bond between the hydrogen and nitrogen atoms on the surface of the protective layer 113. In particular, nitriding is preferably performed on the surface of the protective layer 113.

[0051] The lubricating layer 12 is provided to suppress the wear of the magnetic head and the surface of the magnetic recording medium 1 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.

[0052] The thickness of the lubricating layer 12 is preferably... The thickness of lubrication layer 12 is This allows for the suppression of surface wear of the magnetic recording medium 1, improvement of its corrosion resistance, and shortening of the distance between the magnetic head and the magnetic recording medium 1 in the HDD, thereby achieving high recording density.

[0053] <Methods for Manufacturing Magnetic Recording Media>

[0054] An example of a summary of the method for manufacturing a magnetic recording medium according to this embodiment is shown in Figure 2 . Figure 2 As shown, the method for manufacturing a magnetic recording medium according to this embodiment includes: a step of forming a laminate 11 (laminate forming step), a step of coating a first lubricant 121 and a second lubricant 122 onto the laminate 11 (coating step), a step of polishing the surface of the laminate 11 coated with the first lubricant 121 and the second lubricant 122 using an abrasive material (polishing step), and a step of removing the second lubricant 122 from the laminate 11 (removal step). The polishing step includes: a step of pressing a strip containing an abrasive material (abrasive strip) 20 onto the surface of the laminate 11 and rubbing it (rubbing step), and the removal step includes a step of irradiating the laminate 11 coated with the first lubricant 121 and the second lubricant 122 with light emitted by an LED light source (also called "LED light") 30 (LED light irradiation step).

[0055] Furthermore, the method for manufacturing the magnetic recording medium according to this embodiment may include other steps such as forming an adhesive layer, a soft magnetic substrate layer, a seed layer, or an orientation control layer between the substrate 111 and the magnetic recording layer 112. Additionally, when the method for manufacturing the magnetic recording medium according to this embodiment includes multiple magnetic recording layers 112 stacked together, it may include steps such as forming non-magnetic recording layers between the magnetic recording layers 112.

[0056] The method for manufacturing a magnetic recording medium according to this embodiment involves coating the surface of a laminate 11 with a first lubricant 121 and a second lubricant 122, and then polishing the surface of the laminate 11 with an abrasive. Then, the second lubricant 122 on the laminate 11 is removed by irradiating it with LED light 30 emitted by an LED light source. 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, forming the lubricating layer 12.

[0057] In this embodiment, the removal of the second lubricant 122 is performed using LED light 30 emitted by an LED light source. As described above, the lubricant used in the polishing process is removed by conventional solvent washing. However, according to the research of the inventors, in addition to the removed lubricant, contaminants generated during polishing are also dissolved in the solvent used for washing, and this solvent temporarily remains on the surface of the protective layer 113, which is the surface being washed. It is known that these residual contaminants and lubricant re-adhere to the protective layer 113, becoming foreign matter on the surface of the magnetic recording medium 1. Furthermore, it is difficult to completely remove the lubricant bonded to the protective layer 113 by solvent washing, and it is known that slightly residual lubricant becomes a cause of foreign matter on the surface of the magnetic recording medium 1.

[0058] In this embodiment, the removal of the second lubricant 122 on the laminate 11 is performed by dry treatment with LED light 30 emitted by an LED light source. Therefore, the second lubricant 122, or any contaminants dissolved therein, rapidly vaporizes and leaves the surface of the laminate 11, thus preventing them from becoming foreign matter on the surface of the magnetic recording medium 1. Furthermore, the irradiation conditions of the LED light 30 emitted by the LED light source are such that the second lubricant 122 is vaporized, thereby completely removing the second lubricant 122 from the laminate 11. In addition, the formation process of the lubricating layer 12 is simple, thus providing a highly productive method for manufacturing magnetic recording media.

[0059] [Laminated body formation process]

[0060] In the method for manufacturing a magnetic recording medium according to this embodiment, firstly, in Figure 1A laminate 11 is formed on both sides of a substrate 111 prepared as shown, wherein a magnetic recording layer 112 and a protective layer 113 are sequentially stacked (laminate formation process).

[0061] The laminate 11 can be formed using conventional film-forming methods for the magnetic recording layer 112 and the protective layer 113.

[0062] First, magnetic recording layers 112 are formed on both sides of the substrate 111. As a method for forming the magnetic recording layers 112, general film formation methods such as sputtering can be used.

[0063] In sputtering, a target containing a material that forms the magnetic recording layer 112 can be used.

[0064] As a target for the material comprising the magnetic recording layer 112, for example, FePt alloys with an L10 structure, CoPt alloys with an L10 structure, CoCrPt alloys with an hcp structure, etc., can be used.

[0065] As a sputtering method, DC sputtering, DC magnetron sputtering, and RF sputtering can be used.

[0066] When forming the magnetic recording layer 112, RF (Radio Frequency) bias, DC bias, pulsed DC bias, and pulsed DC bias can be used as needed.

[0067] As reactive gases, O2, H2O, N2, etc. can be used.

[0068] The sputtering gas pressure is adjusted appropriately to optimize the properties of each layer, typically within the range of 0.1 Pa to 30 Pa.

[0069] 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; for example, it can be formed using RF-CVD (Radio Frequency-Chemical Vapor Deposition), which decomposes a hydrocarbon-containing feed gas using high-frequency plasma; IBD (Ion Beam Deposition), which ionizes the feed gas using electrons emitted from a filament and forms a film; or FCVA (Filtered Cathodic Vacuum Arc), which forms a film using a solid carbon target without a feed gas.

[0070] [Coating Process]

[0071] Next, Figure 2As shown, a first lubricant 121 and a second lubricant 122 are sequentially applied to both sides of the laminate 11 (coating process).

[0072] Furthermore, the two sides of the laminate 11 refer to the two main surfaces of the laminate 11 coated with the first lubricant 121 and the second lubricant 122. The first lubricant 121 and the second lubricant 122 can be applied to the other main surface of the laminate 11 after being applied to one main surface, or they can be applied to both main surfaces of the laminate 11 simultaneously.

[0073] When the first lubricant 121 is applied to the protective layer 113, ideally, the entire protective layer 113 is covered by the first lubricant 121, but a portion of the surface of the protective layer 113 may remain uncoated. In this case, the second lubricant 122 may be applied to the areas not covered by the first lubricant 121.

[0074] 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. Therefore, in the light irradiation step of the removal process described later, when the second lubricant 122 is removed by LED light 30 emitted from the LED light source, the first lubricant 121 can be prevented from vaporizing, and the irradiation conditions of the LED light 30 that would vaporize the second lubricant 122 can be easily selected.

[0075] The organic compounds used as the first lubricant 121 and the second lubricant 122 include functional groups such as hydroxyl, amino, amide, carbonyl, carboxyl, cyano, phenyl, and methyl. Among these, the functional groups (polar groups) that are polar include hydroxyl, amino, amide, carbonyl, carboxyl, and cyano.

[0076] Preferably, the average molecular weight of the first lubricant 121 is 900 to 3000, and the structural formula of the first lubricant 121 contains 4 to 8 polar groups. Therefore, in the light irradiation step of the removal process described later, when the second lubricant 122 is removed by LED light 30 emitted by the LED light source, the first lubricant 121 can be prevented from vaporizing, and the irradiation conditions of the LED light that vaporize the second lubricant 122 can be easily selected.

[0077] Preferably, the average molecular weight of the second lubricant 122 is 300 to 1000, and the structural formula of the second lubricant 122 contains two or fewer polar groups, or none at all. Therefore, in the light irradiation step of the removal process described later, when the second lubricant 122 is removed by LED light 30 emitted from the LED light source, the first lubricant 121 can be prevented from vaporizing, and the irradiation conditions of the LED light that vaporize the second lubricant 122 can be easily selected.

[0078] The polar groups of the first lubricant 121 and the second lubricant 122 are preferably hydroxyl, amide, or cyano groups, with hydroxyl being particularly preferred. By having the aforementioned preferred polar groups, the first lubricant 121 can be applied to the lubrication layer 12 of the magnetic recording medium 1, and the second lubricant 122 can be suitable for polishing the surface of the laminate 11. Furthermore, when irradiated with light emitted by the LED light source, the effect of rapidly removing contaminants dissolved in the second lubricant 122 is improved. In addition, by leaving the first lubricant 121 on the laminate 11, the adhesion between the protective layer 113 and the first lubricant 121 can be improved, thereby further reducing surface foreign matter and further improving the coverage of the magnetic recording medium 1 utilizing the lubrication layer 12.

[0079] The coating of the first lubricant 121 and the second lubricant 122 can be performed using known methods such as immersion coating, spin coating, and vapor coating. Immersion coating involves immersing the laminate 11 in a liquid containing lubricant, then lifting the laminate 11 at a certain speed to form a lubricant film on the surface of the laminate 11. Spin coating involves applying a liquid containing lubricant to the surface of the laminate 11, then rotating the laminate 11 at high speed for a certain period to form a lubricant film on the laminate 11. Vapor coating involves placing the laminate 11 in a vacuum container, introducing a lubricant that has been vaporized by heating into the vacuum container, and thus forming a lubricant film on the laminate 11.

[0080] When the second lubricant 122 is coated using either an immersion method or a spin coating method, the solvent for dissolving the second lubricant needs to be selected from any of the following: a solvent that does not dissolve the first lubricant 121, a solvent that is difficult to dissolve, or a solvent that leaves a certain film thickness even if dissolved.

[0081] The first lubricant 121 forms a lubricating layer 12 of the magnetic recording medium 1. Therefore, the film thickness of the first lubricant 121 is... This is preferable in terms of suppressing surface wear of the magnetic recording medium 1, improving the corrosion resistance of the magnetic recording medium 1, shortening the distance between the magnetic head and the magnetic recording medium 1 in the HDD, and achieving high recording density.

[0082] The preferred film thickness of the second lubricant 122 is... If the film thickness of the second lubricant 122 is This is suitable for polishing the surface of the laminate 11. In addition, the removal of the second lubricant 122 by irradiation with light emitted by an LED light source can also be carried out in a short time, thereby improving the productivity of the magnetic recording medium 1.

[0083] [Polishing process]

[0084] Next, the surface of the laminate 11 is polished using an abrasive material (polishing process).

[0085] Polishing process such as Figure 2 As shown, the polishing process includes a rubbing step in which the abrasive belt 20 is pressed against the surface of the laminate 11 and rubbed. The polishing process can also utilize a method of pressing the abrasive belt 20 against the surface of the laminate 11 and rubbing it. The polishing method and polishing apparatus will be described in detail using the accompanying drawings.

[0086] Figure 3 An enlarged cross-sectional view showing an example of the abrasive belt 20 used during polishing. Figure 3 As shown, the abrasive belt 20 abrades the laminate 11 by sliding the abrasive surface S relative to the surface of the laminate 11.

[0087] The abrasive belt 20 has an abrasive layer 22 on the support 21. The abrasive layer 22 has abrasive grains 221 and an adhesive 222 that bonds the abrasive grains 221 together with each other and bonds the abrasive grains 221 to the support 21, so that the abrasive grains 221 are adhered to the abrasive layer 22.

[0088] The material constituting the support 21 is not particularly limited, and various resins such as polyethylene terephthalate can be used.

[0089] Abrasive grains 221 can be used as abrasive materials included in the abrasive belt 20. Examples of abrasive grains 221 include particles of chromium oxide, α-alumina, silicon carbide, non-magnetic iron oxide, diamond, γ-alumina, α,γ-alumina, fused alumina, corundum, and synthetic diamond. Abrasive grains 221 can be particles formed from these materials. These can be one type or a suitable combination of two or more types.

[0090] There are no particular limitations on the adhesive 222; for example, thermosetting resins, thermoplastic resins, and photosensitive resins can be used. One type of resin can be used alone, or two or more types can be used in combination as the adhesive 222.

[0091] In addition, a lubricating film 23 can be provided on the surface of the grinding surface S.

[0092] Figure 4 This figure shows an example of a polishing apparatus used in the process of polishing the surface of the laminate 11 with an abrasive material. Figure 4As shown, the polishing apparatus 50 includes a set of polishing belts 20 (polishing belts 20A and 20B) arranged opposite each other to hold the laminate 11 from both sides, a rotation support mechanism 51, and a belt moving mechanism 52. In the polishing apparatus 50, the polishing belts 20A and 20B can be arranged opposite each other to hold the laminate 11 from both sides, allowing for efficient simultaneous polishing of both sides of the laminate 11.

[0093] With the central opening of the laminate 11 supported by the rotation support mechanism 51, the laminate 11 is rotated in the circumferential direction (arrow r direction).

[0094] The moving mechanism 52 presses the grinding belts 20A and 20B on the surfaces of the rotating laminate 11 in the direction of arrow F, while simultaneously moving the grinding belts 20A and 20B relative to each other in the radial direction of the laminate 11.

[0095] In addition, the belt moving mechanism 52 has a pair of grinding belt pressing mechanisms 521 and a pair of grinding belt moving systems 522, which are arranged opposite each other to clamp the laminate 11 from both sides via grinding belts 20A and 20B.

[0096] A pair of grinding belt pressing mechanisms 521 includes a first grinding belt pressing mechanism 521A and a second grinding belt pressing mechanism 521B. A pair of grinding belt moving systems 522 includes a first grinding belt moving system 522A and a second grinding belt moving system 522B.

[0097] That is, the belt moving mechanism 52 has: a first grinding belt pressing mechanism 521A and a first grinding belt moving system 522A disposed on one side for holding the laminate 11, and a second grinding belt pressing mechanism 521B and a second grinding belt moving system 522B disposed on the other side.

[0098] The first grinding belt moving system 522A has a supply roller and a winding roller (not shown), and a first guide roller 523A-1 to 523A-4 arranged below the supply roller and the winding roller, so that the grinding belt 20A moves in the direction of arrow Ra.

[0099] The second grinding belt moving system 522B has a supply roller and a winding roller (not shown), and a second guide roller 523B-1 to 523B-4 arranged below the supply roller and the winding roller, so that the grinding belt 20B moves in the direction of arrow Rb.

[0100] [Removal process]

[0101] Next, Figure 2 As shown, the second lubricant 122 is removed from the laminate 11 (removal process).

[0102] The removal process includes an LED light irradiation process, in which light emitted by an LED light source is irradiated onto the laminate 11, on which the surface is coated with the first lubricant 121 and the second lubricant 122. By irradiating the second lubricant 122 on the laminate 11 with LED light emitted by the LED light source, 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.

[0103] In addition, during the LED light irradiation process, it is preferable that the second lubricant 122 is completely removed, but a portion of it may remain.

[0104] The LED light 30 emitted by the LED light source is easily parallel light, which can suppress diffusion to the surroundings. Thus, the second lubricant 122 on the laminate 11 is efficiently heated and decomposed, and can be removed as a condition that allows the second lubricant 122 to be vaporized.

[0105] Preferably, the center wavelength of the LED light 30 is less than 500 nm. LED light 30 with a center wavelength less than 500 nm readily vaporizes and decomposes commonly used organic compounds used as lubricants. Therefore, by making the center wavelength of the LED light 30 less than 500 nm, conditions for vaporizing the second lubricant 122 can be easily selected without vaporizing the first lubricant 121.

[0106] The LED light 30 preferably does not contain a wavelength range with a center wavelength of 170–190 nm. Light in the 170–190 nm wavelength range typically decomposes oxygen to produce ozone. During the manufacture of the magnetic recording medium 1, ozone sometimes decomposes environmental substances, which become pollutants and adhere to the surface of the magnetic recording medium 1. The LED light 30 does not contain a wavelength range with a center wavelength of 170–190 nm, thereby suppressing the generation of ozone.

[0107] Furthermore, by using an LED light source that irradiates LED light 30 with the aforementioned center wavelength, the LED light irradiation process can be carried out in the atmosphere, i.e., under pressure near atmospheric pressure or in an atmospheric atmosphere. At the same time, the LED light irradiation device becomes simple, thus reducing the manufacturing cost of the magnetic recording medium 1 and the LED light irradiation device.

[0108] In the manufacturing method of the magnetic recording medium according to this embodiment, it is preferable to perform the LED light irradiation process within 60 seconds, and more preferably within 20 seconds. By shortening the processing time in this way, the manufacturing cost of the magnetic recording medium 1 is reduced, while the risk of contamination of the magnetic recording medium 1 during processing is also reduced.

[0109] (LED light illumination device)

[0110] This embodiment describes an example of an LED light irradiation device used in the removal process of a method for manufacturing magnetic recording media. Figure 5 This is a cross-sectional schematic diagram illustrating an example of an LED light irradiation device used in the removal process of the manufacturing method of the magnetic recording medium according to this embodiment. Figure 5 As shown, the LED light irradiation device 60 includes: a first LED light source 62 that emits (irradiates) LED light (first LED light) to one side (processing surface) 61a of the substrate 61 to process the substrate 61; a second LED light source 63 that emits LED light (second LED light) to the other side (processing surface) 61b of the substrate 61 to heat the substrate 61; and a mechanism 65 that supports the outer peripheral end 61c of the substrate 61 by means of a support member 64 and removes and places the substrate 61 between the first LED light source 62 and the second LED light source 63. Figure 5 In the middle, the mechanism 65 for taking out and putting in the substrate 61 and the support member 64 has the function of lifting and lowering the substrate 61 as shown by the arrow.

[0111] A slanted schematic diagram showing an example of the light source of the LED light irradiation device 60 is shown in Figure 6 . Figure 6 As shown, the LED light source 70 constituting the first LED light source 62 and the second LED light source 63 is composed of a plurality of LED elements 72 mounted on the main body 71 of the LED light source 70. Furthermore, the plurality of LED elements 72 mounted on the main body 71 of the LED light source 70 are connected to... Figure 5 The substrate 61 shown has two processed surfaces 61a and 61b arranged opposite each other.

[0112] Each LED element 72 is configured such that the emitted light has a directional orientation with a central axis perpendicular to the main surface 71a of the main body 71 of the LED light source 70. Preferably, the central axis of the directional orientation of the LED element 72 is ±60° or less.

[0113] Here, the directional angle of the LED element 72 is defined as an angle with an illuminance of 50% relative to the central axis, assuming the position of the brightest light from the LED element 72 is the central axis and the illuminance of the central axis is 100%. Furthermore, Figure 5 The substrate 61 shown has an opening in the center, so the LED light source 70 can be installed without LED elements 72 near the center of the main body 71.

[0114] As described above, the LED light illumination device 60 uses a first LED light source 62 and a second LED light source 63, wherein the first LED light source 62 and the second LED light source 63 have... Figure 6The LED light source 70 shown can perform high-speed processing on both surfaces (processing surfaces 61a, 61b) of the substrate 61. Therefore, in the LED light irradiation device 60, the substrate 61 uses the magnetic recording medium 1, which enables high-speed processing on both surfaces of the magnetic recording medium, thereby improving the productivity of the magnetic recording medium 1.

[0115] In the LED light irradiation device 60, more than 50% of the LED light from the first LED light source 62 and the second LED light source 63 preferably directly irradiates the substrate 61. The LED light irradiation device 60 is configured in such a way that the LED light emitted by the first LED light source 62 and the second LED light source 63 can be concentrated on the substrate 61, and components other than the substrate 61 do not come into contact with the LED light, thereby improving the processing speed while suppressing the generation of impurities.

[0116] In the LED light irradiation device 60, the distance L between the substrate 61 and the first LED light source 62 and the second LED light source 63 is preferably 50 mm or less. The LED light irradiation device 60 is configured in such a way that the LED light emitted by the first LED light source 62 and the second LED light source 63 can be concentrated on the substrate 61, thereby improving the processing speed.

[0117] In the preferred LED light irradiation device 60, the center wavelength of the LED light emitted by the first LED light source 62 and the second LED light source 63 is less than 500 nm, excluding the wavelength range of 170–190 nm. Because the center wavelength of the LED light emitted by the first LED light source 62 and the second LED light source 63 is less than 500 nm, it is easy to select conditions that only vaporize the second lubricant 122. Furthermore, since the LED light emitted by the first LED light source 62 and the second LED light source 63 does not include the wavelength range of 170–190 nm, it can decompose oxygen and suppress ozone generation.

[0118] In the LED light irradiation device 60, the substrate 61 preferably includes a control device that causes the first LED light source 62 and the second LED light source 63 to emit light when it is disposed only between the first LED light source 62 and the second LED light source 63. Furthermore, the substrate 61 refers to the substrate 61 that, when disposed between the first LED light source 62 and the second LED light source 63, becomes... Figure 5 When shown in the state.

[0119] The LED light irradiation device 60 is configured such that the heat generated when LED light from one of the LED light sources 62 and 63 irradiates the other LED light source can be reduced, thereby minimizing the degradation of the other LED light source. Furthermore, the LED light irradiation device 60 only emits light from the first LED light source 62 and the second LED light source 63 during processing, thereby extending the lifespan of the first LED light source 62 and the second LED light source 63 while reducing the power consumption of the LED light irradiation device 60.

[0120] Thus, the method for manufacturing a magnetic recording medium according to this embodiment includes a coating process, a polishing process, and a removal process. The polishing process includes a rubbing process in which an abrasive belt 20 is pressed against the surface of the laminate 11 and rubbed. The removal process includes an LED light irradiation process in which LED light is irradiated onto the laminate 11 coated with a first lubricant 121 and a second lubricant 122. The removal process removes the second lubricant 122 while simultaneously forming the first lubricant 121 as a lubricating layer 12 using LED light 30 emitted from an LED light source. This increases the coverage of the lubricating layer 12 on the laminate 11 while 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 removed efficiently and effectively, and a magnetic recording medium with a high coverage of the lubricating layer 12 can be manufactured.

[0121] As described above, the magnetic recording medium 1 manufactured using the manufacturing method of the magnetic recording medium according to this embodiment has fewer foreign matter on its surface and a high coverage of the lubricating layer 12, thus suppressing wear damage caused by contact sliding with the magnetic head and improving durability. The magnetic recording medium 1 maintains excellent electromagnetic conversion characteristics and can stably have a high recording density, therefore it is suitable for use in magnetic recording playback devices. If a magnetic recording playback device includes a magnetic recording medium manufactured using the manufacturing method of the magnetic recording medium according to this embodiment, its form is not particularly limited, and it can be a magnetic recording playback device that uses a heat-assisted recording method to record magnetic information onto the magnetic recording medium, etc.

[0122] In addition, in this embodiment, the magnetic recording medium may have one or more of the following: an adhesive layer, a soft magnetic substrate layer, a seed layer, and an orientation control layer, between the substrate 111 and the magnetic recording layer 112. More than one of these layers may be stacked.

[0123] In this embodiment, the magnetic recording medium can be stacked and include multiple magnetic recording layers. In this case, non-magnetic recording layers can be stacked between the magnetic recording layers.

[0124] As described above, embodiments have been presented as examples and are not intended to limit the invention. These 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. These embodiments and their variations are included within the scope and spirit of the invention, and are also included within the scope of the invention as described in the claims and their equivalents.

[0125] Example

[0126] The following describes this embodiment in detail based on the examples, but this embodiment is not limited to these examples.

[0127] <Example 1>

[0128] [Manufacturing of magnetic recording media]

[0129] The washed glass substrate (HOYA, 2.5-inch) was placed in the film deposition chamber of a DC magnetron sputtering apparatus (ANELVA C-3040), and the film deposition chamber was evacuated until a vacuum of 1×10⁻⁶ was achieved. -5 Pa. Then, a 10 nm thick adhesive layer was formed on the glass substrate using a Cr target by sputtering.

[0130] Next, a soft magnetic substrate layer is formed on the bonding layer by sputtering. As the soft magnetic substrate layer, a first soft magnetic recording layer, an intermediate layer, and a second soft magnetic recording layer are formed sequentially. First, using a target of Co-20Fe-5Zr-5Ta {Fe content 20 atomic%, Zr content 5 atomic%, Ta content 5 atomic%, with the remainder Co}, a first soft magnetic recording layer with a thickness of 25 nm is formed at a substrate temperature below 100 °C. Next, an intermediate layer of Ru with a thickness of 0.7 nm is formed. Then, a second soft magnetic recording layer of Co-20Fe-5Zr-5Ta with a thickness of 25 nm is formed.

[0131] Next, a seed layer with a thickness of 5 nm is formed on the soft magnetic substrate by sputtering using a Ni-6W target (W content 6 atomic%, the remainder Ni).

[0132] Then, on the seed layer, a Ru layer with a thickness of 10 nm is formed by sputtering at a sputtering pressure of 0.8 Pa as the first orientation control layer.

[0133] Next, on the first orientation control layer, a Ru layer with a thickness of 10 nm is formed by sputtering as the second orientation control layer at a sputtering pressure of 1.5 Pa.

[0134] Next, by sputtering, a first magnetic recording layer containing an alloy of 91(Co15Cr16Pt)-6(SiO2)-3(TiO2) {Cr content 15 atomic%, Pt content 16 atomic%, and the remaining portion of Co 91 mol%, SiO2 6 mol%, TiO2 3 mol%} is formed on the second orientation control layer with a layer thickness of 9 nm. The sputtering pressure at this time is 2 Pa.

[0135] Next, a non-magnetic recording layer containing 88(Co30Cr)-12(TiO2){Cr content 30 atomic%, the remaining portion of Co 88 mol%, TiO2 12 mol%} is formed on the first magnetic recording layer with a layer thickness of 0.3 nm by sputtering.

[0136] Then, by sputtering, a second magnetic recording layer containing an alloy of 92(Co11Cr18Pt)-5(SiO2)-3(TiO2) {Cr content 11 atom%, Pt content 18 atom%, the remaining portion being 92 mol% Co, 5 mol% SiO2, and 3 mol% TiO2} is formed on the non-magnetic recording layer with a layer thickness of 6 nm. The sputtering pressure at this time is 2 Pa.

[0137] Then, a non-magnetic recording layer of Ru was formed on the second magnetic recording layer by sputtering with a layer thickness of 0.3 nm.

[0138] Next, a third magnetic recording layer was formed on the non-magnetic recording layer by sputtering, using a target containing Co-20Cr-14Pt-3B {Cr content 20 atomic%, Pt content 14 atomic%, B content 3 atomic%, and the remainder Co}, with a sputtering pressure of 0.6 Pa and a layer thickness of 7 nm.

[0139] Toluene, vaporized as a feed gas, was used on the surface of the third magnetic recording layer to form a carbon hydride film via ion beam deposition. During the carbon hydride film formation, the feed gas flow rate supplied to the deposition chamber was initially set to 2.9 SCCM, and the reaction pressure to 0.2 Pa. Furthermore, the cathode power serving as the excitation source for the feed gas was 225 W (AC 22.5 V, 10 A). The voltage between the cathode electrode and the anode covering it was set to 75 V, the current to 1650 mA, the ion acceleration voltage to 200 V, and the current to 180 mA. The deposition time was 1.5 seconds, resulting in a carbon hydride film with a thickness of 3.5 nm. After the carbon hydride film was formed, the feed gas supply was stopped, and the deposition chamber was vented for 2 seconds.

[0140] Next, nitrogen gas was supplied to the film-forming chamber at a flow rate of 2 SCCM and a reaction pressure of 5 Pa. Furthermore, the cathode power was set to 128 W (AC 16 V, 8 A), 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 then irradiated onto the surface of the carbon hydride film, exposing it to nitrogen plasma. This process dehydrogenated and nitrided the surface of the carbon hydride film, forming a carbon nitride film as a protective layer.

[0141] Next, D5OH(XS) (trade name: MORESCO Co., Ltd.), which is the first lubricant, was dissolved in Vertrel XF (trade name: Mitsui-DuPont Fluorochemicals Co., Ltd.) to obtain a solution for forming the first lubricating layer. The concentration of the compound contained in the solution for forming the first lubricating layer was 0.3% by mass.

[0142] [Chemistry 1]

[0143]

[0144] (m in structure (i) is a positive integer.)

[0145] Next, the solution for forming the first lubricating layer is applied to the protective layer using an immersion method. Specifically, the protective layer is immersed in the solution for forming the first lubricating layer in an immersion tank placed in the immersion coating apparatus until a laminate of each layer is formed. Then, the laminate is lifted from the immersion tank at a controlled speed. This operation is performed to make the thickness of the first lubricating layer reach a certain value. In this way, the solution for forming the first lubricating layer is applied to the surface of the protective layer. Then, the surface coated with the solution for forming the first lubricating layer is dried, thereby forming the first lubricating layer on the surface of the laminate.

[0146] Next, the second lubricant of the following structural formula (ii) was dissolved in HFE7200 (trade name, manufactured by 3M) to obtain a solution for forming a second lubricating layer. The concentration of the compound contained in the solution for forming the second lubricating layer is 0.3% by mass. In addition, HFE7200 can dissolve the second lubricant of the following structural formula, but the first lubricant D5OH(XS) cannot be dissolved.

[0147] [Chemistry 2]

[0148]

[0149] (In structure (ii), m is a positive integer.)

[0150] Next, using an impregnation method, the second lubricant is applied to the surface of the laminate on which the first lubricating layer is formed, so that the thickness of the second lubricating layer becomes... Then, the surface coated with the solution for forming the second lubricating layer is dried to form the second lubricating layer on the surface of the laminate in which the first lubricating layer is formed.

[0151] Next, the surface of the laminate with the first and second lubricating layers is polished using an abrasive belt. The abrasive belt used is manufactured by Sumitomo 3M Corporation, model DQ3, and uses Al2O3 with a particle size of 0.3 μm as the abrasive material. The polishing conditions are a lamination rotation speed of 1000 rpm and a processing time of 3 seconds.

[0152] Next, LED light is irradiated onto the surface of the laminate with the first and second lubricating layers formed by the LED light source. The irradiation device uses... Figure 5 LED light illumination device, LED light source uses Figure 6 The LED light source has a center wavelength of 395nm (excluding light with a center wavelength greater than 500nm). The illumination area (light-emitting area) has a diameter of 100mm (effective area), and the light intensity within the effective area is 11W / cm². 2 The uniformity of light intensity within the effective area is within ±7% to fabricate a magnetic recording medium. LED light is irradiated onto the surface of the laminate with the first and second lubricating layers, thereby removing the second lubricating layer from the surface of the first lubricating layer and forming a lubricating layer from the first lubricating layer.

[0153] Thus, a magnetic recording medium is manufactured in which a sealing layer, a soft magnetic substrate layer, 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 third magnetic recording layer, a carbon nitride film (protective layer), and a lubricating layer are sequentially stacked on both sides of a glass substrate.

[0154] [Evaluation of the lubrication layer]

[0155] The laminate after LED irradiation and heat treatment was analyzed using ESCA, confirming that the residual layer thickness was [missing information]. The first lubricating layer was removed, and the second lubricating layer was removed.

[0156] (Lubricant layer coverage)

[0157] The coverage ratio of the lubricating layer on the fabricated magnetic recording medium was determined. The coverage ratio was calculated by immersing the magnetic recording medium, after the lubricating layer was formed, in a fluorocarbon solvent for 5 minutes, and then measuring the absorbance at approximately 1270 cm⁻¹ at the same location on the same medium before and after immersion using ESCA. This absorbance was then expressed as a percentage of the lubricating layer ((absorbance after immersion / absorbance before immersion) × 100). Vertrel XF (trade name, manufactured by Mitsui-DuPont Fluorochemicals) was used as the fluorocarbon solvent. The coverage ratio of the lubricating layer on the fabricated magnetic recording medium was 81%.

[0158] (TA (Thermosensitive) Sliding Evaluation)

[0159] The thermal slip (TA) evaluation of the fabricated magnetic recording media was performed. The TA slip evaluation used an MR head (manufactured by TDK) as the inspection head. The TA slip evaluation detects the phenomenon where the regenerated signal waveform changes due to frictional heat generated when the MR head collides with protrusions on the surface of the magnetic recording medium; this is known as thermal TA. The smoothness of the magnetic recording medium's surface is evaluated by the number of these signal occurrences (TA count). A lower TA count indicates a smoother surface. The average TA count for each side of 100 fabricated magnetic recording media was 6.

[0160] The manufacturing 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.

[0161] <Examples 2-8, Comparative Examples 1-8>

[0162] The manufacturing conditions for the first and second lubricants, as well as the processing conditions for the second lubricant, were changed to the values ​​in Tables 1 and 2. Otherwise, the magnetic recording medium was manufactured in the same manner as in Example 1, and the lubrication layer was evaluated. The manufacturing 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 lubrication layer are shown in Table 2.

[0163] In addition, in Comparative Examples 1-8, the magnetic recording medium was fabricated in the same manner as in Examples 1-8, but the removal of the second lubricating layer was performed using UV irradiation with an ultraviolet lamp (manufactured by USHIO Electric Co., Ltd.) and heat treatment. UV irradiation was performed in a nitrogen atmosphere for 10 seconds, and heat treatment was performed in a nitrogen atmosphere at 120°C for 1200 seconds.

[0164] In any of Examples 2-8 and Comparative Examples 1-8, the D4OH and D4OH(s) (both trade names, manufactured by MORESCO Co., Ltd.) used as the first and second lubricants respectively have the following structural formula (iii) and structural formula (iv) as follows. Adjustments were made to make the average molecular weight of D4OH 2000 and the average molecular weight of D4OH(s) 1600. In the solvent for the second lubricant, HFE7200 (trade name, manufactured by 3M Corporation) was used, as in Example 1. HFE7200 can dissolve the second lubricant, but the first lubricant cannot.

[0165] The structural formulas of D4OH and D4OH(s) are as follows:

[0166] CH2(OH)CH(OH)CH2OCH2CF2CF2(OCF2CF2CF2) m OCF2CF2CH2OCH2CH(OH)CH2OH···(iii)

[0167] (In structure (iii), m is a positive integer.)

[0168] Structural formula (iv):

[0169] [Chemistry 3]

[0170]

[0171] [Table 1]

[0172]

[0173] [Table 2]

[0174]

[0175] As can be seen from Tables 1 and 2, compared with Comparative Examples 1 to 8 corresponding to Examples 1 to 8, the coverage of the lubricating layer in Examples 1 to 8 is increased and the TA count is decreased. Therefore, by using the method for manufacturing a magnetic recording medium according to this embodiment, the second lubricant is removed by irradiating it with LED light, forming a lubricating layer formed by the first lubricant. This efficiently removes foreign matter from the surface of the magnetic recording medium while obtaining a magnetic recording medium with a high coverage of the lubricating layer.

[0176] Explanation of symbols

[0177] 1 Magnetic recording medium

[0178] 11-layer stack (the stacked body)

[0179] 12 lubrication layers

[0180] 20, 20A, and 20B are belts containing abrasive materials (abrasive belts).

[0181] 21 Supporting bodies

[0182] 22 Abrasive Layers

[0183] 30 LED light

[0184] 50 Polishing equipment

[0185] 60 LED light irradiation device

[0186] 61 substrate

[0187] 62 First LED Light Source

[0188] 63 Second LED Light Source

[0189] 64 Supporting Components

[0190] 65 institutions

[0191] 70 LED light source

[0192] 72 LED components

[0193] 111 substrate

[0194] 112 Magnetic Recording Layer

[0195] 113 Protective Layer

[0196] 121 First Lubricant

[0197] 122 Second Lubricant

[0198] 221 abrasive grains

[0199] 222 Adhesive

[0200] 521 A pair of grinding belt pushing mechanisms

[0201] 522 A pair of grinding belt moving systems

[0202] 521A First Grinding Belt Pushing Mechanism

[0203] 521B Second Grinding Belt Pushing Mechanism

[0204] 522A First Grinding Belt Moving System

[0205] 522B Second Grinding Belt Moving System

[0206] S grinding surface

Claims

1. A method for manufacturing a magnetic recording medium, which is a method for manufacturing a magnetic recording medium in which a lubricating layer is formed on a laminate in which a magnetic recording layer and a protective layer are sequentially stacked on a substrate, comprising: a step of applying a first lubricant and a second lubricant on the laminate, a step of polishing a surface of the laminate on which the first lubricant and the second lubricant are applied by an abrasive, and a step of removing the second lubricant on the laminate. The polishing step includes a step of pressing a belt including the abrasive against the surface of the laminate and rubbing it. The step of removing the second lubricant includes a step of irradiating light emitted by an LED light source on the laminate on which the first lubricant and the second lubricant are applied.

2. The method for manufacturing a magnetic recording medium according to claim 1, wherein the light emitted by the LED light source has a central wavelength of less than 500 nm and does not include a wavelength region having a central wavelength of 170 to 190 nm.

3. The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the step of irradiating the light emitted by the LED light source is performed at a pressure near atmospheric pressure.

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

5. The method for manufacturing a magnetic recording medium according to claim 4, wherein the second lubricant has an average molecular weight of 300 to 1000, has two or less polar groups, or does not include a polar group.

6. The method for manufacturing a magnetic recording medium according to claim 4, wherein the first lubricant has an average molecular weight of 900 to 3000 and has four to eight polar groups.

7. The method for manufacturing a magnetic recording medium according to claim 1 or 2, wherein the first lubricant is a compound represented by the following formula (1): ​ ​ ​ ​ ​ ​ ​ ​ ​ The film thickness of the first lubricant applied on the laminate is The film thickness of the second lubricant is

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