Method for manufacturing magnetic recording medium

Abstract

Provided is 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. The method for manufacturing a magnetic recording medium in which a lubricating layer is formed on a laminate includes a step of applying a first lubricant and a second lubricant to the laminate, a step of polishing the surface of the laminate to which the first lubricant and the second lubricant have been applied with a polishing material, a step of removing the second lubricant from the laminate, and a step of forming the lubricating layer on the laminate. The average molecular weight of the first lubricant is higher than the average molecular weight of the second lubricant, the polarity of the first lubricant is higher than the polarity of the second lubricant, and the polishing step includes a step of pressing and rubbing a tape containing a 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 ultraviolet light, or a step of heating the laminate coated with the first lubricant and the second lubricant.

Description

Technical Field

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

[0002] In recent years, magnetic storage devices have been mounted on various products such as personal computers, cameras, and storage systems, and their importance has increased. A magnetic storage device is a device having a magnetic recording medium for storing electronic data by magnetic recording. For example, there is a hard disk drive (HDD).

[0003] In a general magnetic recording medium, for example, a base layer, an intermediate layer, a magnetic recording layer, and a protective layer are sequentially formed on a non-magnetic substrate, and a multilayer film stack structure having a lubricating layer coated on the surface of the protective layer is provided. In the protective layer and the lubricating layer, the magnetic recording medium is provided to prevent wear damage due to contact sliding with a magnetic head and deterioration of durability. 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] For the purpose of improving the adhesion of the lubricating layer to the protective layer, various treatments are known for the lubricating layer. For example, in Patent Document 1, a method is disclosed in which a heat treatment is performed on the coated lubricating layer, and further a light irradiation treatment using an ultraviolet lamp is performed.

[0005] In addition, in order to remove foreign matters and protrusions on the surface of the protective layer, the surface of the magnetic recording medium is belt polished by a polishing belt. At this time, it is known to perform belt polishing to prevent scratching of the surface of the protective layer, and belt polishing is performed after the formation of the lubricating layer.

[0006] In addition, Patent Document 2 discloses a method for manufacturing a magnetic recording medium in which, after the formation of the protective layer, a first lubricant having no terminal group is coated on the surface, belt polishing is performed, and then the first lubricant is removed using a solvent, and a second lubricant having a terminal group is coated.

[0007] Prior Art Documents

[0008] Patent Documents

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

[0010] Patent Document 2: Japanese Patent Laid-Open No. 2002-222519 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] When manufacturing a magnetic recording medium, after forming a lubricating layer, tape polishing is performed, so that the lubricity of the lubricating layer can reduce the occurrence of scratches and the like. However, the lubricant and film thickness used for the lubricating layer are sometimes not suitable for tape polishing.

[0013] As in the manufacturing method of the magnetic recording medium of Patent Document 2, after considering processing using a first lubricant suitable for tape polishing and then removing it, a second lubricating layer suitable for the magnetic recording medium is coated. However, in this case, there are the following problems. That is, contaminants dissolved in the solvent used for removing the lubricant and the lubricant reattach to the processing substrate, which causes foreign matters on the surface of the magnetic recording medium. In addition, it is difficult to completely remove the lubricant bonded to the protective layer using a solvent, and the remaining solvent causes foreign matters on the surface of the magnetic recording medium. In addition, it reduces the coverage rate of the surface of the magnetic recording medium by the lubricating layer and complicates the manufacturing process of the magnetic recording medium.

[0014] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing a magnetic recording medium that can efficiently remove foreign matters on the surface of the magnetic recording medium and has a high coverage rate by the lubricating layer.

[0015] Method for solving the problem

[0016] The present invention has the following configuration.

[0017] [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 laminated on a substrate, and includes the following steps:

[0018] A step of coating a first lubricant and a second lubricant on the above laminate,

[0019] A step of polishing the surface of the laminate coated with the first lubricant and the second lubricant with an abrasive, and

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

[0021] The average molecular weight of the first lubricant is higher than the average molecular weight of the second lubricant,

[0022] The polarity of the first lubricant is higher than the polarity of the second lubricant,

[0023] The above polishing step includes a step of pressing a tape containing an abrasive against the surface of the above laminate and rubbing it,

[0024] The step of removing the second lubricant includes: a step of irradiating ultraviolet rays to the laminate coated with the first lubricant and the second lubricant, or a step of heat-treating the laminate coated with the first lubricant and the second lubricant.

[0025] [2] According to the manufacturing method of the magnetic recording medium described in [1], the average molecular weight of the second lubricant is 300 to 1000, the number of polar groups is 2 or less, or it does not contain polar groups.

[0026] [3] According to the manufacturing method of the magnetic recording medium described in [1] or [2], 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.

[0027] [4] According to the manufacturing method of the magnetic recording medium described in any one of [1] to [3], the film thickness of the first lubricant coated on the laminate is The film thickness of the second lubricant is

[0028] [5] According to the manufacturing method of the magnetic recording medium described in any one of [1] to [4], the step of irradiating the ultraviolet rays is performed in an inert gas atmosphere or in a vacuum.

[0029] [6] According to the manufacturing method of the magnetic recording medium described in any one of [1] to [5], the step of the heat treatment is performed in an inert gas atmosphere.

[0030] Effects of the Invention

[0031] According to one aspect of the present invention, foreign substances on the surface of the magnetic recording medium can be efficiently removed, and the coverage rate of the lubricating layer can be improved. Brief Description of the Drawings

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

[0033] Figure 2 A diagram for explaining an example of a method of forming a lubricating layer.

[0034] Figure 3 An enlarged cross-sectional view showing an example of a belt including an abrasive used in polishing.

[0035] Figure 4 A diagram showing an example of a polishing apparatus used in the step of polishing the surface of the laminate with an abrasive.

[0036] Description of Reference Numerals

[0037] 1 Magnetic recording medium

[0038] 11 Laminate (laminated body)

[0039] 12 Lubricating layer

[0040] 21 Abrasive

[0041] 31 Ultraviolet irradiation

[0042] 32 Heat treatment

[0043] 40, 40A, 40B Abrasive belt

[0044] 41 Support

[0045] 42 Abrasive layer

[0046] 111 Substrate

[0047] 112 Magnetic recording layer

[0048] 113 Protective layer

[0049] 121 First lubricant

[0050] 122 Second lubricant

[0051] 421 Abrasive grains

[0052] 422 Binder

[0053] 50 Polishing device

[0054] 521 Pair of abrasive belt pressing mechanisms

[0055] 522 Pair of abrasive belt moving systems

[0056] 521A First abrasive belt pressing mechanism

[0057] 521B Second abrasive belt pressing mechanism

[0058] 522A First abrasive belt moving system

[0059] 522B Second abrasive belt moving system

[0060] S Polishing surface Detailed implementation manners

[0061] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, for ease of understanding of the description, the same reference numerals are assigned to the same components in each drawing, and repeated descriptions are appropriately omitted. In addition, the scale of each component in the drawings may sometimes be different from the actual one. In this specification, "~" indicating a numerical range means including the values described before and after it as the lower limit value and the upper limit value, unless otherwise specified.

[0062] 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.

[0063] [Magnetic Recording Medium]

[0064] Figure 1 FIG. 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. Figure 1 As shown, the magnetic recording medium 1 has lubricating layers 12 on both sides of a laminate (both are referred to as the laminated body).) 11.

[0065] 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 sides of the substrate 111.

[0066] 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 aluminum alloy can be used, and for example, a non-metal substrate formed of a non-metal material such as glass can be used. In addition, on the surfaces of these metal substrates and non-metal substrates, for example, a NiP alloy layer can be formed using a plating method, a sputtering method, or the like.

[0067] The magnetic recording layer 112 is a layer provided for recording and reproducing information. For example, it is provided for storing data by reversing the direction of magnetization by the magnetic energy supplied from the magnetic head of an HDD and maintaining the state of the magnetization.

[0068] The magnetic recording layer 112 uses an FePt-based alloy having an L1 0 structure, a CoPt-based alloy having an L1 0 structure, a CoCrPt-based alloy, or the like.

[0069] The magnetic recording layer 112 can be formed by a known method such as a sputtering method or an ion beam deposition method.

[0070] The protective layer 113 suppresses the corrosion of the magnetic recording layer 112, and when the magnetic head contacts the magnetic recording medium 1, it protects the surface of the magnetic recording medium 1 from damage, and is provided to improve the corrosion resistance of the magnetic recording medium 1.

[0071] The protective layer 113 can be formed of known materials, for example, using a hard carbon film, diamond-like carbon (DLC).

[0072] The film formation of the protective layer 113 can use known methods such as sputtering method, ion beam film formation method, etc.

[0073] The surface of the protective layer 113 can be hydrogenated or nitrided. By hydrogenating or nitriding the surface of the protective layer 113, the bonding force with the lubricating layer 12 formed thereon can be improved. That is, since the first lubricant coated on the protective layer 113 has polarity, a strong bond is formed with the hydrogen atoms and nitrogen atoms on the surface of the protective layer 113. In particular, the surface of the protective layer 113 is preferably nitrided.

[0074] The lubricating layer 12 is provided to suppress the wear of the surface of the magnetic head and the magnetic recording medium 1 when the magnetic head contacts the magnetic recording medium 1 and to improve the corrosion resistance of the magnetic recording medium 1.

[0075] The thickness of the lubricating layer 12 is preferably By making the thickness of the lubricating layer 12 Thereby, the wear of 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 is shortened, enabling high recording density.

[0076] [Manufacturing method of magnetic recording medium]

[0077] The manufacturing method of the magnetic recording medium according to the present embodiment includes the following steps: a step of forming a laminate 11 in which a magnetic recording layer 112 and a protective layer 113 are sequentially laminated on both surfaces of a substrate 111 (laminate forming step), a step of coating a first lubricant 121 and a second lubricant 122 on 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 with an abrasive (polishing step), and a step of removing the second lubricant 122 on the laminate 11 (removing step). The manufacturing method of the magnetic recording medium according to the present embodiment may include other steps such as a step of forming an adhesion layer, a soft magnetic base layer, a seed layer, or an orientation control layer between the substrate 111 and the magnetic recording layer 112. In addition, when a plurality of magnetic recording layers 112 are laminated, the manufacturing method of the magnetic recording medium according to the present embodiment may include a step of forming a non-magnetic recording layer between the magnetic recording layers 112.

[0078] In the manufacturing method of the magnetic recording medium according to the present embodiment, first, a laminate 11 in which a magnetic recording layer 112 and a protective layer 113 are sequentially laminated on both surfaces of a prepared substrate 111 is formed (laminate forming step).

[0079] The laminate 11 can be formed by general film-forming methods for the magnetic recording layer 112 and the protective layer 113.

[0080] First, the magnetic recording layer 112 is formed on both surfaces of the substrate 111. As a method for forming the magnetic recording layer 112, general film-forming methods such as sputtering method (sputtering method) can be used.

[0081] In the sputtering method, a target containing the material for forming the magnetic recording layer 112 can be used.

[0082] As a target containing the material for forming the magnetic recording layer 112, for example, an FePt-based alloy having an L1 0 structure, a CoPt-based alloy having an L1 0 structure, a CoCrPt-based alloy, etc. can be used.

[0083] As the sputtering method, a DC sputtering method, a DC magnetron sputtering method, an RF sputtering method, etc. can be used.

[0084] When forming the magnetic recording layer 112, if necessary, RF (Radio Frequency) bias, DC bias, pulsed DC, and pulsed DC bias, etc. can be used.

[0085] As a reactive gas, O 2 gas, H 2 O gas, N 2 gas, etc. can be used.

[0086] The sputtering gas pressure is appropriately adjusted so that the characteristics of each layer are optimized, usually in the range of about 0.1 Pa to 30 Pa.

[0087] Next, a protective layer 113 is formed on the magnetic recording layer 112. As a method for forming the protective layer 113, there is no particular limitation. For example, an RF-CVD (Radio Frequency-Chemical Vapor Deposition) method in which a raw material gas containing a hydrocarbon is decomposed by high-frequency plasma for film formation, an IBD (Ion Beam Deposition) method in which the raw material gas is ionized by electrons emitted from a filament for film formation, an FCVA (Filtered Cathodic Vacuum Arc) method in which a solid carbon target is used for film formation without using a raw material gas, etc., general film-forming methods can be used.

[0088] Next, the first lubricant 121 and the second lubricant 122 are coated on the laminate 11 (coating step). Use Figure 2 To illustrate an example of the formation method of the lubricating layer 12.

[0089] On a laminate 11 in which a magnetic recording layer 112 and a protective layer 113 are sequentially laminated on both surfaces of a substrate 111, after applying a first lubricant 121 and a second lubricant 122, the surface of the laminate 11 is polished with an abrasive 21. Then, the second lubricant 122 on the laminate 11 is removed by ultraviolet irradiation 31 or heat treatment 32. Thus, the first lubricant 121 forms a lubricating layer 12 of the magnetic recording medium 1.

[0090] That is, after applying the first lubricant 121 and the second lubricant 122 on the surface of the laminate 11, in the process of ultraviolet irradiation 31 or heat treatment 32, the second lubricant 122 is removed, so that the first lubricant 121 remains on the surface of the protective layer 113. When applying the first lubricant 121 on the protective layer 113, ideally it is preferably that the entire surface of the protective layer 113 is covered with the first lubricant 121, but a part of the surface of the protective layer 113 may not be coated and remain. At this place, there is a case where the second lubricant 122 is applied.

[0091] In addition, in the process of ultraviolet irradiation 31 or heat treatment 32, it is preferable that the second lubricant 122 is completely removed, and a part of it may remain.

[0092] In the present embodiment, the removal of the second lubricant 122 is performed by ultraviolet irradiation 31 or heat treatment 32. As described above, the removal of the lubricant used in the polishing process has been conventionally performed by washing with a solvent. However, according to the research of the present inventors, in the solvent used for washing, in addition to the removed lubricant, contaminants generated by polishing are also dissolved, and this solvent remains on the washed surface for a long time, whereby the contaminants and the lubricant reattach to the substrate to be processed, and it has been clarified that this becomes the cause of foreign matters on the surface of the magnetic recording medium. In addition, it is difficult to completely remove the lubricant combined with the protective layer by solvent washing, and it has been clarified that the remaining lubricant generally becomes the cause of the occurrence of foreign matters on the surface of the magnetic recording medium.

[0093] In the present embodiment, the removal of the second lubricant 122 on the laminate 11 is performed by ultraviolet irradiation 31 or heat treatment 32, that is, a dry process. Therefore, the second lubricant 122 or the contaminants dissolved therein are quickly vaporized and leave the surface of the laminate 11. Therefore, these are not the cause of foreign matters on the surface of the magnetic recording medium. In addition, by setting the conditions of ultraviolet irradiation 31 or heat treatment 32 to be conditions capable of vaporizing the second lubricant 122, the second lubricant 122 on the laminate 11 can be completely removed. In addition, for the simplicity of the formation process of the lubricating layer 12, a manufacturing method of a magnetic recording medium with high productivity can be provided.

[0094] 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.

[0095] Among the organic compounds used as lubricants, as functional groups, it includes hydroxyl group, amino group, amide group, carbonyl group, carboxyl group, cyano group, phenyl group, methyl group, etc. Among these, as polar functional groups (polar groups), it has hydroxyl group, amino group, amide group, carbonyl group, carboxyl group, cyano group.

[0096] The average molecular weight of the first lubricant 121 is 900 - 3000, and the number of polar groups contained in the structural formula of the first lubricant 121 is preferably 4 - 8.

[0097] The average molecular weight of the second lubricant 122 is 300 - 1000, and the number of polar groups contained in the structural formula of the second lubricant 122 is 2 or less, or preferably does not contain polar groups.

[0098] As the polar groups possessed by the first lubricant 121 and the second lubricant 122, hydroxyl group, amide group, and cyano group are preferred, and among these, hydroxyl group is particularly preferred. By having the above - preferred polar groups, the first lubricant 121 can be applied to the lubricating layer 12 of the magnetic recording medium 1, and the second lubricant 122 is suitable for polishing the surface of the laminate 11. Moreover, when performing the above - mentioned ultraviolet irradiation 31 or heat treatment 32, the effect of rapidly removing the second lubricant 122 or the contaminants dissolved therein is improved. In addition, by allowing the first lubricant 121 to remain on the laminate 11, the bonding strength between the protective layer 113 and the first lubricant 121 can be increased, thereby further reducing foreign substances on the surface and further increasing the coating rate of the magnetic recording medium 1 using the lubricating layer 12.

[0099] The coating of the first lubricant 121 and the second lubricant 122 can use well - known methods such as the dipping method, spin - coating method, and vapor method. The dipping method is a method in which after immersing the laminate 11 in a liquid in which the lubricant is dissolved, the laminate 11 is lifted at a certain speed to form a lubricant film on the surface of the laminate 11. The spin - coating method is a method in which after coating a liquid in which the lubricant is dissolved on the surface of the laminate 11, the laminate 11 is rotated at a high speed for a certain time to form a lubricant film on the laminate 11. The vapor method is a method in which the laminate 11 is placed in a vacuum container, and the lubricant vaporized by heating is introduced into the vacuum container to form a lubricant film on the laminate 11.

[0100] When the dipping method or spin coating method is used for coating the second lubricant 122, the solvent for dissolving the second lubricant needs to be selected from any one of solvents that do not dissolve the first lubricant 121, solvents that are hardly soluble, or solvents that remain a certain film thickness even when dissolved.

[0101] The first lubricant 121 forms the lubricating layer 12 of the magnetic recording medium 1. Therefore, the film thickness of the first lubricant 121 is It is preferable in terms of suppressing wear on the surface 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.

[0102] The film thickness of the second lubricant 122 is preferably If the film thickness of the second lubricant 122 is Then it can be suitable for polishing the surface of the laminate 11. In addition, removing the second lubricant 122 by ultraviolet irradiation 31 or heat treatment 32 can also be carried out in a short time, so the productivity of the magnetic recording medium 1 can be improved.

[0103] In the process of polishing the laminate 11 with the abrasive 21, a method can be used in which a belt (abrasive belt) containing the abrasive 21 is pressed against the surface of the laminate 11 and rubbed. The polishing method and polishing device will be described in detail with reference to the figures.

[0104] Figure 3 It is an enlarged cross-sectional view showing an example of the abrasive belt 40 used during polishing. Figure 3 As shown, the abrasive belt 40 grinds the laminate 11 by sliding the grinding surface S relative to the surface of the laminate 11.

[0105] The abrasive belt 40 has an abrasive layer 42 on the support 41. The abrasive layer 42 has: abrasive grains 421, and an adhesive 422 that binds the abrasive grains 421 to each other while binding the abrasive grains 421 to the support 41 and causing the abrasive grains 421 to adhere to the abrasive layer 42.

[0106] The material constituting the support 41 is not particularly limited, and various resins such as polyethylene terephthalate are used.

[0107] The abrasive grains 421 can be used as the abrasive 21 contained in the abrasive belt 40. As the abrasive grains 421, for example, particles having chromium oxide, α-aluminum oxide, silicon carbide, non-magnetic iron oxide, diamond, γ-aluminum oxide, α,γ-aluminum oxide, fused alumina, corundum, synthetic diamond, etc. can be cited. The abrasive grains 421 can be particles formed of these materials. These can be one kind or a suitable combination of two or more kinds.

[0108] As the adhesive 422, there is no particular limitation. For example, a thermosetting resin, a thermoplastic resin, a photosensitive resin, etc. can be used. The resin used as the adhesive 422 can be used alone as one kind, or two or more kinds can be used in combination.

[0109] In addition, a lubricating film 43 can be provided on the surface of the polishing surface S.

[0110] Figure 4 It is a diagram showing an example of a polishing apparatus used in the process of polishing the surface of the laminate 11 with the abrasive 21. Figure 4 As shown, the polishing apparatus 50 has: a pair of abrasive belts 40 (abrasive belts 40A, 40B) arranged oppositely to sandwich the laminate 11 from both sides, a rotation support mechanism 51, and a belt movement mechanism 52. In the polishing apparatus 50, the abrasive belts 40A, 40B can be arranged oppositely to sandwich the laminate 11 from both sides, and polishing processing can be efficiently performed on both sides of the laminate 11 simultaneously.

[0111] The rotation support mechanism 51 rotates the laminate 11 in the circumferential direction (arrow r direction) while supporting the central opening of the laminate 11.

[0112] The belt movement mechanism 52 presses the abrasive belts 40A, 40B in the direction of arrow F on the surfaces of both sides of the rotating laminate 11, and at the same time, moves the abrasive belts 40A, 40B relatively in the radial direction of the laminate 11.

[0113] In addition, the belt movement mechanism 52 has: a pair of abrasive belt pressing mechanisms 521 and a pair of abrasive belt movement systems 522 that are arranged oppositely to sandwich the laminate 11 via the abrasive belts 40A, 40B.

[0114] The pair of abrasive belt pressing mechanisms 521 has a first abrasive belt pressing mechanism 521A and a second abrasive belt pressing mechanism 521B. The pair of abrasive belt movement systems 522 has a first abrasive belt movement system 522A and a second abrasive belt movement system 522B.

[0115] That is, the belt movement mechanism 52 has: a first abrasive belt movement system 522A and a first abrasive belt pressing mechanism 521A arranged on one side while clamping the laminate 11, and a second abrasive belt movement system 522B and a second abrasive belt pressing mechanism 521B arranged on the other side.

[0116] The first abrasive belt movement system 522A has a supply roller and a winding roller (not shown), and first guide rollers 523A-1 to 523A-4 arranged below the supply roller and the winding roller, and moves the abrasive belt 40A in the direction of arrow Ra.

[0117] The second abrasive belt moving system 522B has a supply roller and a winding roller (not shown), and second guide rollers 523B-1 to 523B-4 disposed below the supply roller and the winding roller, and moves the abrasive belt 40B in the direction of arrow Rb.

[0118] In the present invention, the step of removing the second lubricant 122 from the laminate 11 uses a step of irradiating the laminate 11 with ultraviolet rays or a step of heat-treating the laminate 11.

[0119] For the step of irradiating the laminate 11 with ultraviolet rays, a known irradiation source can be used. As a known irradiation source, for example, an ultraviolet lamp or an LED lamp can be cited. The emission wavelength, emission output, and irradiation time used for these lamps are appropriately selected under the processing conditions capable of removing the second lubricant 122. Further, the processing conditions for improving the bonding force of the first lubricant 121 to the protective layer 113 are preferably considered. Specifically, for the ultraviolet lamp, it is preferably appropriately selected from three types of peak wavelengths: 100 nm to 280 nm, 280 nm to 315 nm, and 315 nm to 400 nm. In addition, for the LED lamp, since the control of the emission wavelength is easy, the design of the LED lamp is possible according to the type of lubricant used, so it is preferred.

[0120] Considering the productivity of the magnetic recording medium, the irradiation time is preferably within 1 minute. Therefore, it is preferred to adjust the emission output so as to end the processing within this time.

[0121] In addition, if the step of irradiating ultraviolet rays is performed in the atmosphere, ozone is generated, which sometimes has an adverse effect on the manufacture of the magnetic recording medium. Therefore, in order to suppress the generation of ozone, it is preferred to perform the step of irradiating ultraviolet rays in an inert gas atmosphere or in a vacuum.

[0122] For the step of heat-treating the laminate 11, a known heat source can be used. As a known heat source, for example, a halogen lamp heater, a ceramic heater, a resistance heating heater, and an LED lamp heater can be cited. The heating temperature and heating time using these heat sources are appropriately selected under the processing conditions capable of removing the second lubricant 122, and the processing conditions for improving the bonding force of the first lubricant 121 to the protective layer 113 are preferably considered.

[0123] Considering the productivity of the magnetic recording medium, the heating time is preferably within 15 minutes. Therefore, it is preferred to adjust the heating time so as to end the processing within this time. From the aspect of the ease of design of the heating device, the heating temperature is preferably 120°C or lower. In addition, since a large amount of degassing is released from the heat source and the degassing is taken into the laminate 11, it sometimes has an adverse effect on the manufacture of the magnetic recording medium. In order to suppress the influence caused by degassing, the step of heat treatment is preferably performed in an inert gas atmosphere.

[0124] Thus, the method for manufacturing a magnetic recording medium according to this embodiment includes a coating step, a polishing step, and a removing step. In the coating step, the average molecular weight of the first lubricant coated on the laminate 11 is higher than that of the second lubricant coated on the first lubricant, and the polarity of the first lubricant is higher than that of the second lubricant. The polishing step includes a step of pressing the abrasive belt 40 against the surface of the laminate 11 and rubbing it. The removing step includes an ultraviolet ray step of irradiating ultraviolet rays on the laminate 11 coated with the first lubricant 121 and the second lubricant 122 or a heat treatment step of subjecting the laminate 11 coated with the first lubricant 121 and the second lubricant 122 to a heat treatment. The removing step can remove the second lubricant 122 by ultraviolet irradiation 31 or heat treatment 32 while forming the first lubricant 121 as the lubricating layer 12, thereby improving the coverage rate of the lubricating layer 12 on the laminate 11 and reducing the generation amount of foreign matters generated on the surface of the lubricating layer 12. Thus, according to the method for manufacturing a magnetic recording medium according to this embodiment, foreign matters on the surface of the magnetic recording medium 1 can be efficiently removed, and a magnetic recording medium with a high coverage rate of the lubricating layer 12 can be manufactured.

[0125] As described above, for the magnetic recording medium 1 manufactured by using the method for manufacturing a magnetic recording medium according to this embodiment, there are few foreign matters on the surface of the magnetic recording medium 1 and the coverage rate of the lubricating layer 12 is high. Therefore, wear damage caused by contact sliding with the magnetic head can be suppressed, and the durability can be improved. The magnetic recording medium 1 can maintain excellent electromagnetic conversion characteristics and can stably have a high recording density. Therefore, it can be suitably used for a magnetic recording / reproducing device. The form of the magnetic recording / reproducing device is not particularly limited as long as it has a magnetic recording medium manufactured by using the method for manufacturing a magnetic recording medium according to this embodiment, and it can be a magnetic recording / reproducing device that records magnetic information on the magnetic recording medium by using a heat-assisted recording method or the like.

[0126] In addition, in this embodiment, the magnetic recording medium may include any one of one or more adhesion layers, soft magnetic base layers, seed layers, and orientation control layers between the substrate 111 and the magnetic recording layer 112. One or more of these layers may be laminated.

[0127] In this embodiment, the magnetic recording medium may include a plurality of magnetic recording layers laminated. At this time, a non-magnetic recording layer may be laminated and provided between the magnetic recording layers.

[0128] As described above, the embodiments are described. The above embodiments are presented as examples and do not limit the present invention by the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention and are included in the invention described in the claims and its equivalents.

[0129] Example

[0130] Hereinafter, based on the examples, this embodiment will be specifically described. This embodiment is not limited by these examples.

[0131] <Example 1>

[0132] [Manufacture of Magnetic Recording Medium]

[0133] The washed glass substrate (manufactured by HOYA Corporation, 2.5 inches in outer shape) is housed in the film formation chamber of a DC magnetron sputtering device (C-3040 manufactured by ANELVA Corporation), and the film formation chamber is evacuated until the vacuum degree reaches 1×10 -5 Pa. Then, a 10-nm thick adhesion layer is formed on the glass substrate by sputtering using a Cr target.

[0134] Next, a soft magnetic base layer is formed on the adhesion layer by sputtering. As the soft magnetic base layer, a first soft magnetic recording layer, an intermediate layer, and a second soft magnetic recording layer are sequentially formed. First, using a target of Co-20Fe-5Zr-5Ta {Fe content 20 atomic %, Zr content 5 atomic %, Ta content 5 atomic %, the remaining part Co}, a first soft magnetic recording layer with a layer thickness of 25 nm is formed at a substrate temperature of 100 °C or lower. Next, an intermediate layer formed of Ru with a layer thickness of 0.7 nm is formed. Then, a second soft magnetic recording layer formed of Co-20Fe-5Zr-5Ta with a layer thickness of 25 nm is formed.

[0135] Next, a 5-nm thick seed layer is formed on the soft magnetic base layer by sputtering using a Ni-6W {W content 6 atomic %, the remaining part Ni} target.

[0136] Then, on the seed layer, by sputtering, as the first orientation control layer, a Ru layer with a layer thickness of 10 nm and a sputtering pressure of 0.8 Pa is formed. Next, on the first orientation control layer, by sputtering, as the second orientation control layer, the sputtering pressure is 1.5 Pa, and a Ru layer with a layer thickness of 10 nm is formed.

[0137] Next, by sputtering, on the second orientation control layer, to make it contain 91(Co15Cr16Pt)-6(SiO 2 )-3(TiO2 ) {An alloy with 15 atomic % Cr, 16 atomic % Pt, and the balance being 91 mol % Co, 6 mol % SiO 2 6, and 3 mol % TiO 2 3} forms the first magnetic recording layer with a thickness of 9 nm. The sputtering pressure at this time is 2 Pa.

[0138] Next, by sputtering, on the first magnetic recording layer, an non-magnetic recording layer containing 88(Co30Cr)-12(TiO 2 ) {An alloy with 30 atomic % Cr and the balance being 88 mol % Co, and 12 mol % TiO 2 12} forms with a thickness of 0.3 nm.

[0139] Then, by sputtering, on the non-magnetic recording layer, an second magnetic recording layer containing 92(Co11Cr18Pt)-5(SiO 2 )-3(TiO 2 ) {An alloy with 11 atomic % Cr, 18 atomic % Pt, and the balance being 92 mol % Co, 5 mol % SiO 2 5, and 3 mol % TiO 2 3} forms with a thickness of 6 nm. The sputtering pressure at this time is 2 Pa.

[0140] Then, by sputtering, on the second magnetic recording layer, a non-magnetic recording layer formed of Ru forms with a thickness of 0.3 nm.

[0141] Next, by sputtering, on the non-magnetic recording layer, using a target containing Co-20Cr-14Pt-3B {20 atomic % Cr, 14 atomic % Pt, 3 atomic % B, and the balance being Co}, with a sputtering pressure of 0.6 Pa, a third magnetic recording layer forms with a thickness of 7 nm.

[0142] On the surface of the third magnetic recording layer, using vaporized toluene as a source gas, a hydrogenated carbon film is formed as a protective layer by ion beam evaporation. When forming the hydrogenated carbon film, first, the gas flow rate of the source gas supplied to the film formation chamber is 2.9 SCCM, and the reaction pressure is 0.2 Pa. Further, the cathode power as the excitation source of the source gas is 225 W (AC22.5 V, 10 A). Also, the voltage between the cathode electrode and the anode electrode covering the cathode electrode is 75 V, the current is 1650 mA, the ion acceleration voltage is 200 V, the current is 180 mA, and the film formation time is 1.5 seconds, and the hydrogenated carbon film forms with a thickness of 3.5 nm. After the formation of the hydrogenated carbon film, the supply of the source gas is stopped, and the film formation chamber is evacuated for 2 seconds.

[0143] Next, nitrogen gas was supplied to the film formation chamber at a gas flow rate of 2 SCCM and a reaction pressure of 5 Pa. Moreover, the cathode power was 128 W (AC 16 V, 8 A), the voltage between the cathode electrode and the anode electrode was 75 V, the current was 1000 mA, the ion acceleration voltage was 200 V, the current was 90 mA, and the treatment time was 1 second. Nitrogen ions formed from nitrogen gas were irradiated onto the surface of the carbon-hydrogen film, exposing it to nitrogen plasma. Thus, dehydrogenation and nitridation of the surface of the carbon-hydrogen film were performed.

[0144] Next, D5OH(XS) of the following structural formula (i) (trade name: manufactured by Matsumura Petrochemical Research Institute (MORESCO) Co., Ltd.), which is the first lubricant, was dissolved in Vertrel XF (trade name, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.) to obtain a solution for forming the first lubricating layer. The concentration of D5OH(XS) contained in the solution for forming the first lubricating layer was 0.3 mass%.

[0145] [Chemical formula 1]

[0146]

[0147] (m is a positive integer)

[0148] Next, using the dipping method, the solution for forming the first lubricating layer was coated on the protective layer. That is, the laminate having each layer formed thereon was immersed in the solution for forming the first lubricating layer placed in the dipping tank of the dipping coating apparatus, and then the laminate was lifted from the dipping tank at a constant speed. Such an operation was performed so that the layer thickness of the first lubricating layer became as such, and the solution for forming the first lubricating layer was coated on the surface of the protective layer. Then, the surface coated with the solution for forming the first lubricating layer was dried, thereby forming the first lubricating layer on the surface of the laminate.

[0149] Next, the second lubricant of the following structural formula (ii) was dissolved in HFE7200 (trade name, manufactured by 3M Company) to obtain a solution for forming the second lubricating layer. The concentration of the second lubricant contained in the solution for forming the second lubricating layer was 0.3 mass%. In addition, HFE7200 can dissolve the second lubricant of the following structural formula, but the first lubricant D5OH(XS) cannot be dissolved.

[0150] [Chemical formula 2]

[0151]

[0152] (m is a positive integer)

[0153] Next, using the dipping method, the second lubricant was coated on the surface of the laminate on which the first lubricating layer was formed. So that the layer thickness of the second lubricating layer became Then, the surface coated with the solution for forming the second lubricating layer is dried, thereby forming the second lubricating layer on the surface of the laminate on which the first lubricating layer is formed.

[0154] Next, the surface of the laminate on which the first lubricating layer and the second lubricating layer are formed is polished with an abrasive belt. The abrasive belt used is the DQ3 model manufactured by Sumitomo 3M Limited, which uses Al with a particle size of 0.3 μm as the abrasive material. 2 O 3 The polishing conditions are a rotational speed of 1000 rpm for the laminate and a processing time of 3 seconds.

[0155] Next, ultraviolet rays are irradiated onto the surface of the laminate on which the first lubricating layer and the second lubricating layer are formed. The ultraviolet irradiation uses an ultraviolet lamp manufactured by Ushio Electric Inc., and the irradiation time is 10 seconds in a nitrogen atmosphere.

[0156] Next, heat treatment is performed on the surface of the laminate on which the first lubricating layer and the second lubricating layer are formed. The heat treatment is carried out at 120 °C for 1200 seconds in a nitrogen atmosphere. By subjecting the surface of the laminate on which the first lubricating layer and the second lubricating layer are formed to heat treatment, the second lubricating layer is removed from the surface of the first lubricating layer, and a lubricating layer containing the first lubricating layer is formed. Thus, a magnetic recording medium is manufactured in which an adhesion layer, a soft magnetic base 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 non-magnetic recording layer, a third magnetic recording layer, a carbon nitride film (protective layer), and a lubricating layer are sequentially laminated on both sides of a glass substrate.

[0157] [Evaluation of the lubricating layer]

[0158] The laminate after ultraviolet irradiation and heat treatment was analyzed by ESCA, and it was confirmed that the remaining layer thickness was of the first lubricating layer, and the second lubricating layer was removed.

[0159] (Coating rate of the lubricating layer)

[0160] The coating rate of the lubricating layer of the manufactured magnetic recording medium was measured. The coating rate was measured as the percentage of the ratio ((absorbance after immersion / absorbance before immersion) × 100) by immersing the magnetic recording medium after forming the lubricating layer in a fluorocarbon solvent for 5 minutes and measuring the absorbance near 1270 cm-1 at the same position of the same medium before and after immersion using ESCA. The fluorocarbon solvent used was Vertrel XF (trade name, manufactured by Mitsui DuPont Fluorochemical Co., Ltd.). The coating rate of the lubricating layer of the manufactured magnetic recording medium was 80%.

[0161] (TA (thermal sensitivity) sliding evaluation)

[0162] TA sliding evaluation of the manufactured magnetic recording medium. The TA sliding evaluation uses an MR head as the inspection head. The TA sliding evaluation detects the frictional heat generated when the MR head collides with the protrusions on the surface of the magnetic recording medium, and the phenomenon that the signal waveform regenerated by the MR head changes, that is, thermosensitive TA. The smoothness of the surface of the magnetic recording medium is evaluated by the occurrence count of this signal (TA count). The smaller the TA count, the higher the smoothness of the surface of the magnetic recording medium. The average TA count per surface of 100 manufactured magnetic recording media is 7.

[0163] The treatment conditions of the second lubricant and the evaluation results of the lubricating layer in Example 1 are shown in Table 1.

[0164] <Examples 2 to 11, Comparative Examples 1 to 4>

[0165] The production conditions of the first lubricant and the second lubricant and the treatment conditions of the second lubricant were changed to the values in Table 1. Except for this, magnetic recording media were produced in the same manner as in Example 1 and evaluated. The production conditions and evaluation results are shown in Table 1. In addition, D4OH and D4OH(s) (both are trade names: manufactured by Matsumura Petrochemical Research Institute (MORESCO) Co., Ltd.) used as the first lubricant and the second lubricant in any of Examples 2 to 11 and Comparative Examples 1 to 4 have the following chemical formula (iii) and structural formula (iv). Adjustments were made so that the average molecular weight of D4OH was 2000 and the average molecular weight of D4OH(s) was 1600.

[0166] Structural formulas of D4OH and D4OH(s):

[0167] CH 2 (OH)CH(OH)CH 2 OCH 2 CF 2 CF 2 (OCF 2 CF 2 CF 2 ) m OCF 2 CF 2 CH 2 OCH 2 CH(OH)CH 2 OH…(iii)

[0168] (m is a positive integer)

[0169] Structural formula (iv):

[0170] [Chemical formula 3]

[0171]

[0172] In Comparative Example 5, the removal of the second lubricant was not performed by ultraviolet irradiation or heat treatment (dry treatment), but by washing with a solvent (wet treatment). The solvent used was HFE7200, and the washing was performed by spin washing.

[0173] [Table 1]

[0174]

[0175] [Table 2]

[0176]

[0177] From Table 1 and Table 2, in each of the examples, the coverage rate of the lubricating layer was 74% or more, and the TA count was 10 or more. On the other hand, in each of the comparative examples, the TA count was 15 or more. Thus, by using the manufacturing method of the magnetic recording medium according to the present embodiment, ultraviolet irradiation or heat treatment is performed to remove the second lubricant, and a lubricating layer is formed, thereby efficiently removing foreign substances on the surface of the magnetic recording medium and obtaining a magnetic recording medium with a high coverage rate of the lubricating layer.

Claims

1. A method for manufacturing a magnetic recording medium, comprising forming a lubricating layer on a laminate having a magnetic recording layer and a protective layer sequentially laminated on a substrate, the method comprising the following steps: a step of applying a first lubricant and a second lubricant to the laminate, a step of polishing the surface of the stacked body coated with the first lubricant and the second lubricant with a grinding material, and a step of removing the second lubricant on the stacked body, The average molecular weight of the first lubricant is higher than the average molecular weight of the second lubricant, The polarity of the first lubricant is higher than the polarity of the second lubricant. The polishing step includes a step of pressing a belt containing an abrasive material against the surface of the laminate and rubbing the belt against the surface of the laminate. The step of removing the second lubricant includes: A step of irradiating the laminated body coated with the first lubricant and the second lubricant with ultraviolet rays, or a step of heat-treating the laminated body coated with the first lubricant and the second lubricant.

2. The method for manufacturing a magnetic recording medium according to claim 1, The second lubricant has an average molecular weight of 300 to 1000, and has two or less polar groups or contains no polar groups.

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

4. The method for producing a magnetic recording medium according to claim 1 or 2, The thickness of the first lubricant applied on the laminate is The film thickness of the second lubricant is 5. The method for producing a magnetic recording medium according to claim 1 or 2, The step of irradiating with ultraviolet rays is performed in an inert gas atmosphere or in a vacuum.

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

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