Method for manufacturing magnetic recording media

Abstract

The objective is 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 the lubricating layer. [Solution] The present invention relates to 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 laminated on a substrate in that order, the method comprising 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 are applied with an abrasive; and removing the second lubricant from the laminate, wherein the burning step includes pressing a tape containing the abrasive onto the surface of the laminate and rubbing it, and the step of removing the second lubricant includes irradiating the laminate to which the first lubricant and the second lubricant are applied with light emitted from an LED light source.

Description

Technical Field

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

Background Art

[0002] Magnetic storage devices have been mounted in various products such as personal computers, video recorders, and data servers in recent years, 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] In order to increase 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 a light irradiation treatment using an ultraviolet lamp is further performed.

[0005] In addition, in order to remove foreign substances 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 project] [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 process the tape varnish 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, this presents the following problems. 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 any 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 the 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 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, comprising the step of removing the second lubricant, which includes irradiating the laminate coated with the first lubricant and the second lubricant with light emitted from an LED light source. [2] The method for manufacturing a magnetic recording medium according to [1], wherein the light emitted from the LED light source has a central wavelength of less than 500 nm and does not include the wavelength range of 170 to 190 nm. [3] A method for manufacturing a magnetic recording medium according to [1] or [2], wherein the step of irradiating with light emitted from the LED light source is performed under a pressure near atmospheric pressure. [4] The average molecular weight of the first lubricant is higher than that of the second lubricant. A method for manufacturing a magnetic recording medium according to any one of [1] to [3], wherein the polarity of the first lubricant is higher than the polarity of the second lubricant. [5] The method for manufacturing a magnetic recording medium according to [4], wherein the second lubricant has an average molecular weight of 300 to 1000 and contains two or fewer polar groups. [6] The method for manufacturing a magnetic recording medium according to [4], wherein the first lubricant has an average molecular weight of 900 to 3000 and contains 4 to 8 polar groups. [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 on the laminate is 5 to 10 Å, and the film thickness of the second lubricant is 5 to 20 Å.

Effect of the Invention

[0012] According to one aspect of the present invention, it is possible to provide a method for manufacturing a magnetic recording medium that can efficiently remove foreign substances on the surface of the magnetic recording medium and has a high coverage rate by the lubricating layer.

Brief Description of the Drawings

[0013] [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 an outline of the method for manufacturing a magnetic recording medium according to an embodiment of the present invention. [Figure 3] It is an enlarged cross-sectional view showing an example of a tape containing an abrasive used when burnishing. [Figure 4] 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. [Figure 5] It is a cross-sectional schematic diagram showing an example of an LED light irradiation apparatus used in the manufacture of a magnetic recording medium. [Figure 6] It is a perspective schematic diagram showing an example of a light source of an LED irradiation apparatus.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For ease of understanding the description, the same reference numerals are assigned to the same components in each drawing, and duplicate descriptions are omitted as appropriate. Also, the scales of the respective members in the drawings may be different from the actual ones. In this specification, "~" indicating a numerical range means that the numerical values described before and after it are included as the lower limit value and the upper limit value, unless otherwise specified. Also, when only the unit of the upper limit value is described in the numerical range represented by "~", it means that the lower limit value is also in the same unit.

[0015] Hereinafter, a method for manufacturing a magnetic recording medium according to an embodiment of the present invention will be described. 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> FIG. 1 is a cross-sectional view showing an example of a magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to this embodiment. As shown in FIG. 1, the magnetic recording medium 1 has lubricating layers 12 on both surfaces of a laminate (also referred to as a laminated body) 11.

[0017] The laminate 11 includes a magnetic recording layer 112 and a protective layer 113 laminated in this order from the substrate 111 side on both surfaces of the substrate 111.

[0018] The substrate 111 is formed of a non-magnetic material. For the substrate 111, for example, a metal substrate formed of a metal material such as an aluminum alloy may be used, or a non-metal substrate formed of a non-metal material such as glass may be used. Also, a NiP alloy layer may be formed on the surfaces of these metal substrates and non-metal substrates using, for example, a plating method or a sputtering method.

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

[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 top of the protective layer 113 is polar, 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] <Method for manufacturing magnetic recording media> Figure 2 shows an example of an 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 (laminated body formation step), applying a first lubricant 121 and a second lubricant 122 onto the laminate 11 (application step), burning the surface of the laminate 11 coated with the first lubricant 121 and the second lubricant 122 with an abrasive (burnishing step), and removing the second lubricant 122 from the laminate 11 (removal step). The burnishing step includes pressing a tape containing an abrasive (abrasive tape) 20 onto the surface of the laminate 11 and rubbing it (rubbing step), and the removal step includes irradiating the laminate 11 coated with the first lubricant 121 and the second lubricant 122 with light emitted from an LED light source (also called "LED light") 30 (LED light irradiation step).

[0029] 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.

[0030] 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 irradiating it with LED light 30 emitted from 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, thus forming the lubricating layer 12.

[0031] In this embodiment, LED light 30 emitted from an LED light source is used to remove the second lubricant 122. As mentioned above, conventionally, the lubricant used in the varnish process was removed by cleaning with a solvent. However, the inventors' investigation revealed that the solvent used for cleaning contained not only the lubricant to be removed but also contaminants generated during varnish, and that this solvent remained on the surface of the protective layer 113, which was the surface to be cleaned, for some time. It became clear 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 became clear 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.

[0032] In this embodiment, the removal of the second lubricant 122 on the laminate 11 is performed by a dry process involving irradiation with LED light 30 emitted from an LED light source. As a result, 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 irradiation conditions of the LED light 30 emitted from the LED light source 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.

[0033] [Laminate formation process] In the manufacturing method of the 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).

[0034] The laminate 11 can be formed using a general method for depositing the magnetic recording layer 112 and the protective layer 113.

[0035] 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.

[0036] In the sputtering method, a target containing the material for forming the magnetic recording layer 112 can be used.

[0037] 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, and a CoCrPt-based alloy having an hcp structure can be used.

[0038] Sputtering methods that can be used include DC sputtering, DC magnetron sputtering, and RF sputtering.

[0039] When forming the magnetic recording layer 112, RF (Radio Frequency) bias, DC bias, pulsed DC, and pulsed DC bias may be used as needed.

[0040] O2 gas, H2O gas, and N2 gas may be used as the reactive gas.

[0041] 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.

[0042] 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.

[0043] [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).

[0044] 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.

[0045] 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.

[0046] 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 easy to select irradiation conditions for the LED light 30 that gasifies the second lubricant 122 without gasifying the first lubricant 121 when removing the second lubricant 122 with LED light 30 emitted from an LED light source in the light irradiation step of the removal step described later.

[0047] 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.

[0048] 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 LED light irradiation conditions that gasify the second lubricant 122 without gasifying the first lubricant 121 when removing the second lubricant 122 with LED light 30 emitted from an LED light source in the light irradiation step of the removal step described later.

[0049] 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 LED light irradiation conditions that gasify the second lubricant 122 without gasifying the first lubricant 121 when removing the second lubricant 122 with LED light 30 emitted from an LED light source in the light irradiation step of the removal step described later.

[0050] 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 irradiating with light emitted from the LED light source described above, 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.

[0051] For applying the first lubricant 121 and the second lubricant 122, known methods such as the dipping method, the spin coating method, and the vapor coating method can be used. The dipping method is a method in which a film of lubricant is formed on the surface of the laminate 11 by immersing the laminate 11 in a liquid containing dissolved lubricant and then pulling up the laminate 11 at a constant speed. The spin coating method is a method in which a film of lubricant is formed on the laminate 11 by applying a liquid containing 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 in which a film of lubricant is formed 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.

[0052] When using a dip method or spin coating method to apply the second lubricant 122, the solvent used to dissolve the second lubricant must be one of the following: a solvent that does not dissolve the first lubricant 121, a solvent that does not dissolve it easily, or a solvent that dissolves it but leaves a certain film thickness.

[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 is suitable for varnishing the surface of the laminate 11. Furthermore, the second lubricant 122 can be removed in a short time by irradiation with light emitted from the LED light source, thereby increasing the productivity of the magnetic recording medium 1.

[0055] [Burning process] Next, the surface of the laminate 11 is burnished with an abrasive (burnishing process).

[0056] 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.

[0057] Figure 3 is an enlarged cross-sectional view showing an example of a polishing tape 20 used when burning. As shown in Figure 3, the polishing tape 20 polishes the laminate 11 by sliding the polishing surface S against the surface of the laminate 11.

[0058] 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.

[0059] The material constituting the support 21 is not particularly limited, and various resins such as polyethylene terephthalate can be used.

[0060] 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.

[0061] 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.

[0062] Alternatively, a lubricating film 23 may be provided on the surface of the polished surface S.

[0063] Figure 4 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 4, the burnishing apparatus 50 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 51, and a tape moving means 52. In the burnishing apparatus 50, 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.

[0064] The rotational support means 51 rotates the laminated body 11 in the circumferential direction (direction of arrow r) while supporting the central opening of the laminated body 11.

[0065] The tape moving means 52 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.

[0066] Furthermore, the tape moving means 52 includes a pair of abrasive tape pressing means 521 and a pair of abrasive tape running systems 522, which are positioned opposite each other so as to sandwich the laminate 11 from both sides via the abrasive tapes 20A and 20B.

[0067] The pair of abrasive tape pressing means 521 comprises a first abrasive tape pressing means 521A and a second abrasive tape pressing means 521B. The pair of abrasive tape running systems 522 comprises a first abrasive tape running system 522A and a second abrasive tape running system 522B.

[0068] In other words, the tape moving means 52 includes a first polishing tape pressing means 521A and a first polishing tape running system 522A arranged on one side of the laminate 11, and a second polishing tape pressing means 521B and a second polishing tape running system 522B arranged on the other side.

[0069] The first abrasive tape transport system 522A includes a supply roll and a winding roll (not shown), and first guide rolls 523A-1 to 523A-4 arranged below the supply roll and winding roll, and transports the abrasive tape 20A in the direction of arrow Ra.

[0070] The second abrasive tape transport system 522B includes a supply roll and a winding roll (not shown), and second guide rolls 523B-1 to 523B-4 arranged below the supply roll and winding roll, and transports the abrasive tape 20B in the direction of arrow Rb.

[0071] [Removal process] Next, as shown in Figure 2, the second lubricant 122 on the laminate 11 is removed (removal step).

[0072] The removal process includes an LED light irradiation process in which light emitted from an LED light source is irradiated onto the laminate 11, which has a first lubricant 121 and a second lubricant 122 applied to its surface. By irradiating the second lubricant 122 on the laminate 11 with LED light 30 emitted from 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.

[0073] In the LED light irradiation process, it is preferable that the second lubricant 122 is completely removed, but some of it may remain.

[0074] The LED light 30 emitted from the LED light source tends to be parallel light, which suppresses its spread to the surroundings. Therefore, only the second lubricant 122 on the laminate 11 can be efficiently heated and decomposed, and the second lubricant 122 can be removed under conditions that allow it to be gasified.

[0075] It is preferable that the central wavelength of the LED light 30 be less than 500 nm. LED light 30 with a central wavelength of less than 500 nm gasifies and easily decomposes organic compounds commonly used as lubricants. Therefore, by setting the central wavelength of the LED light 30 to less than 500 nm, it becomes easy to select conditions in which the second lubricant 122 is gasified without gasifying the first lubricant 121.

[0076] Preferably, the LED light 30 does not include the wavelength range of 170-190 nm in its central wavelength. Light in the wavelength range of 170-190 nm often decomposes oxygen and generates ozone. During the manufacturing of the magnetic recording medium 1, ozone may decompose environmental substances, which may become pollutants and adhere to the surface of the magnetic recording medium 1. However, since the LED light 30 does not include the wavelength range of 170-190 nm in its central wavelength, the generation of ozone can be suppressed.

[0077] Furthermore, by using an LED light source that emits LED light 30 having the central wavelength described above, the LED light irradiation process can be carried out in the atmosphere, that is, under a pressure near atmospheric pressure or in an atmospheric environment, and the LED light irradiation device can be simplified, thereby reducing the manufacturing cost of the magnetic recording medium 1 and the LED light irradiation device.

[0078] In the manufacturing method of the magnetic recording medium of this embodiment, the LED light irradiation step is preferably performed 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 can be reduced, and the risk of contamination of the magnetic recording medium 1 during processing can be reduced.

[0079] (LED light irradiation device) An example of an LED light irradiation device used in the removal process of the manufacturing method of a magnetic recording medium according to this embodiment will be described. Figure 5 is a schematic cross-sectional view showing an example of an LED light irradiation device used in the removal process of the manufacturing method of a magnetic recording medium according to this embodiment. As shown in Figure 5, the LED light irradiation device 60 includes a first LED light source 62 that processes the substrate 61 by emitting (irradiating) LED light (first LED light) to one surface (processing surface) 61a of the substrate 61, a second LED light source 63 that heat-treats the substrate 61 by emitting LED light (second LED light) to the other surface (processing surface) 61b of the substrate 61, and a mechanism 65 that supports the outer peripheral end 61c of the substrate 61 with a support member 64 and moves the substrate 61 in and out between the first LED light source 62 and the second LED light source 63. In Figure 5, the mechanism 65 for moving the substrate 61 and the support member 64 in and out has the function of raising and lowering the substrate 61 up and down as indicated by the arrows.

[0080] Figure 6 shows a schematic perspective view illustrating an example of a light source for the LED light irradiation device 60. As shown in Figure 6, the LED light source 70, which constitutes the first LED light source 62 and the second LED light source 63, is composed of numerous LED elements 72 attached to the main body 71 of the LED light source 70. These numerous LED elements 72 attached to the main body 71 of the LED light source 70 are arranged to face the two processing surfaces 61a and 61b of the substrate 61 shown in Figure 5.

[0081] Each LED element 72 is arranged so that the light it emits has a directional property with a central axis perpendicular to the main surface 71a of the main body 71 of the LED light source 70. Preferably, the directional property of the LED elements 72 is ±60° or less with respect to the central axis.

[0082] Here, the directional angle of the LED element 72 is defined as the angle relative to the central axis at which the illuminance becomes 50%, with the brightest point of the LED element 72 being the central axis and the illuminance along the central axis being 100%. Note that, as shown in Figure 5, there is an opening in the center of the substrate 61, so the LED light source 70 does not need to have the LED element 72 located near the center of the main body 71.

[0083] As described above, the LED light irradiation device 60 is equipped with a first LED light source 62 and a second LED light source 63, and by using the LED light source 70 having the configuration shown in Figure 6 for the first LED light source 62 and the second LED light source 63, both surfaces (processing surfaces 61a and 61b) of the substrate 61 can be processed at high speed. Therefore, by using the magnetic recording medium 1 on the substrate 61, the LED light irradiation device 60 can process both surfaces of the magnetic recording medium at high speed, thereby increasing the productivity of the magnetic recording medium 1.

[0084] In the LED light irradiation device 60, it is preferable that 50% or more of the LED light from the first LED light source 62 and the second LED light source 63 is directly irradiated onto the substrate 61. By adopting this configuration, the LED light irradiation device 60 can concentrate the LED light emitted from the first LED light source 62 and the second LED light source 63 onto the substrate 61, preventing the LED light from irradiating components other than the substrate 61, thereby increasing the processing speed and suppressing the generation of impurities.

[0085] 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. By adopting such a configuration, the LED light irradiation device 60 can concentrate the LED light emitted from the first LED light source 62 and the second LED light source 63 onto the substrate 61, thereby increasing the processing speed.

[0086] In the LED light irradiation device 60, it is preferable that the LED light emitted from the first LED light source 62 and the second LED light source 63 has a central wavelength of less than 500 nm and does not include the wavelength range of 170 to 190 nm. By setting the central wavelength of the LED light emitted from the first LED light source 62 and the second LED light source 63 to less than 500 nm, it becomes easy to select conditions for gasifying only the second lubricant 122. Furthermore, by ensuring that the LED light emitted from the first LED light source 62 and the second LED light source 63 does not include the wavelength range of 170 to 190 nm, the decomposition of oxygen and the generation of ozone can be suppressed.

[0087] In the LED light irradiation device 60, it is preferable to include a control device that causes the first LED light source 62 and the second LED light source 63 to emit light only when the substrate 61 is placed between the first LED light source 62 and the second LED light source 63. Note that when the substrate 61 is placed between the first LED light source 62 and the second LED light source 63, it means when the substrate 61 is in the state shown in Figure 5.

[0088] By adopting this configuration, the LED light irradiation device 60 can reduce the degradation of the other LED light source caused by heat generated when LED light from one of the first LED light sources 62 or the second LED light source 63 irradiates the other LED light source. Furthermore, by emitting light from the first LED light source 62 and the second LED light source 63 only during processing, the LED light irradiation device 60 can achieve a longer lifespan for the first LED light source 62 and the second LED light source 63, and reduce the power consumption of the LED light irradiation device 60.

[0089] As described above, the method for manufacturing a magnetic recording medium according to this embodiment includes a coating step, a burning step, and a removal step. The burning step includes a scraping step in which an abrasive tape 20 is pressed against the surface of the laminate 11 and rubbed. The removal step includes an LED light irradiation step in which LED light is irradiated onto the laminate 11 coated with the first lubricant 121 and the second lubricant 122. The removal step removes the second lubricant 122 and forms the first lubricant 121 as a lubricating layer 12 using LED light 30 emitted from an LED light source. This increases the coverage rate of the lubricating layer 12 on the laminate 11 and reduces 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.

[0090] 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.

[0091] In this embodiment, the magnetic recording medium 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 together.

[0092] In this embodiment, the magnetic recording medium may include a plurality of stacked magnetic recording layers. In this case, non-magnetic recording layers may be stacked between the magnetic recording layers.

[0093] 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]

[0094] The embodiments will be described in detail below based on examples, but the embodiments are not limited to these examples.

[0095] <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.

[0096] 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.

[0097] 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.

[0098] Subsequently, a Ru layer with a thickness of 10 nm was deposited on the seed layer as a first orientation control layer using sputtering, with a sputtering pressure of 0.8 Pa.

[0099] Next, a Ru layer with a thickness of 10 nm was formed on the first orientation control layer as a second orientation control layer by sputtering, using a sputtering pressure of 1.5 Pa.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] [ka] (In structural formula (i), m is a positive integer.)

[0109] 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.

[0110] 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).

[0111] [ka] (In structural formula (ii), m is a positive integer.)

[0112] Next, the second lubricant was applied to the surface of the laminate where the first lubricating layer had formed, using the dip 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 formed by drying the surface to which the second lubricating layer-forming solution had been applied.

[0113] 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.

[0114] Next, the surface of the laminate on which the first and second lubricating layers were formed was irradiated with LED light from an LED light source. The LED light irradiation device shown in Figure 5 was used as the irradiation device, and the LED light source shown in Figure 6 was used as the LED light source. The LED light source had a central wavelength of 395 nm (it did not contain light with a central wavelength of 500 nm or more), an irradiation area (emission area) with a diameter of 100 mm (effective area), and a light intensity of 11 W / cm² within the effective area. 2 A magnetic recording medium was fabricated with a uniformity of light intensity within the effective region of ±7%. By irradiating the surface of a laminate on which a first lubricating layer and a second lubricating layer are formed with LED light, 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.

[0115] 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.

[0116] [Evaluation of the lubrication layer] The laminated material after LED irradiation and heat treatment was analyzed using ESCA, and it was confirmed that the first lubricating layer with a thickness of 7 Å remained, while the second lubricating layer had been removed.

[0117] (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 been formed, in a fluorocarbon solvent for 5 minutes, and measuring the difference between 1270 cm² and the same location on the same medium before and after immersion. -1 The absorbance in the vicinity was measured using ESCA, and the ratio was calculated as a percentage ((absorbance after immersion / absorbance before immersion) × 100). Bartrell XF (trade name, manufactured by Mitsui DuPont Fluorochemicals) was used as the fluorocarbon solvent. The coverage rate of the lubricating layer of the fabricated magnetic recording medium was 81%.

[0118] (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 the 100 fabricated magnetic recording media was 6 per surface.

[0119] 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.

[0120] <Examples 2-8, Comparative Examples 1-8> 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 second lubricant 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.

[0121] In Comparative Examples 1 to 8, magnetic recording media were prepared in the same manner as in Examples 1 to 8, but UV irradiation using an ultraviolet lamp (manufactured by Ushio Inc.) and heat treatment were used to remove the second lubricating layer. UV irradiation using an ultraviolet lamp was performed in a nitrogen gas atmosphere for a duration of 10 seconds, and heat treatment was performed in a nitrogen gas atmosphere at 120°C for 1200 seconds.

[0122] D4OH and D4OH(s) (both trade names, manufactured by MORESCO Corporation), used as the first and second lubricants in any of Examples 2-8 and Comparative Examples 1-8, 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.

[0123] Structural formulas of D4OH and D4OH(s): CH2(OH)CH(OH)CH2OCH2CF2CF2(OCF2CF2CF2) m OCF2CF2CH2OCH2CH(OH)CH2OH ···(iii) (In structural formula (iii), m is a positive integer.)

[0124] Structural formula (iv): [ka]

[0125] [Table 1]

[0126] [Table 2]

[0127] From Tables 1 and 2, Examples 1 to 8 showed improved lubrication layer coverage and lower TA counts compared to Comparative Examples 1 to 8, which correspond to Examples 1 to 8. Therefore, it can be said that by using the manufacturing method of the magnetic recording medium according to this embodiment, removing the second lubricant by irradiating it with LED light, and forming a lubrication 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]

[0128] 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 30 LED lights 50 Burnishing Machine 60 LED light irradiation device 61 circuit boards 62 1st LED light source 63 2nd LED light source 64 Support Member 65 Mechanism 70 LED light sources 72 LED elements 111 circuit board 112 Magnetic recording layer 113 Protective layer 121 First Lubricant 122 Second lubricant 221 abrasive grains 222 Binder 521 Pair of abrasive tape pressing means 522 Pair of abrasive tape transport systems 521A First polishing tape pressing means 521B Second polishing tape pressing means 522A First polishing tape transport system 522B 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 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, comprising the step of removing the second lubricant, which includes irradiating the laminate coated with the first lubricant and the second lubricant with light emitted from an LED light source.

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

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

4. 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 or 2, wherein the polarity of the first lubricant is higher than the polarity of 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 and contains two or fewer polar groups, or does not contain any.

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 contains 4 to 8 polar groups.

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

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