JP2011227965A - Method of manufacturing magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a magnetic recording medium that is greatly improved in number of times of repetitive transfer by one master information carrier.SOLUTION: The present invention relates to the method of manufacturing the magnetic recording medium that includes a process of magnetically transferring an information signal from the master information carrier M on which a transfer pattern corresponding to the information signal is formed to the magnetic recording medium W which has at least a magnetic layer formed on a nonmagnetic substrate while applying an external magnetic field from the side of the master information carrier M after putting the magnetic recording medium W and the master information carrier M one over the other, the method being characterized in using the master information carrier M which is repetitively usable for the magnetic transfer and also in including a process of cleaning the magnetic recording medium W using a cleaning fluid including an alkali cleaner before putting the master information carrier M and magnetic recording medium W one over the other.

Description

  The present invention relates to a method of manufacturing a magnetic recording medium, and more particularly to a technique for cleaning a magnetic recording medium before performing magnetic transfer.

  The recording density of a hard disk drive (hard disk drive), which is a kind of magnetic recording / reproducing apparatus, is currently increasing by 1.5 times or more per year, and it is said that this trend will continue in the future. Accordingly, development of a magnetic head and a magnetic recording medium suitable for increasing the recording density has been advanced. In the latest magnetic recording apparatus, the track density has reached 320 kTPI.

  For this reason, in a magnetic recording medium having a high track density, the tracking servo technology of the magnetic head plays an important role in order to accurately scan the magnetic head on the track. Specifically, in current hard disk drives, tracking servo signals, information signals such as address information signals and reproduction clock signals (hereinafter referred to as servo signals, etc.) are recorded at regular angular intervals during one round of the disk. Has been. Control is performed to correct the position of the magnetic head so that the magnetic head accurately scans the track while detecting the position of the magnetic head based on these signals reproduced from the magnetic head at regular intervals. ing.

  Therefore, the servo signal and the like described above serve as a reference signal for the magnetic head to accurately scan the track, and high positioning accuracy is required for writing these signals. For this reason, in a conventional hard disk drive manufacturing site, a servo signal recording device (hereinafter referred to as a servo writer) incorporating a high-precision position detection device is used to write a servo signal or the like to a magnetic recording medium. It has been broken. Further, the servo writer has a structure in which a large number of magnetic recording media are chucked on one spindle and servo signals and the like are simultaneously written on these magnetic recording media in order to increase productivity.

  However, the writing of servo signals and the like by the servo writer described above has the following problems. That is, it takes a lot of time to write signals over a large number of tracks while positioning the magnetic head with high accuracy, and in order to further increase the productivity, it is necessary to operate many servo writers simultaneously. . However, if the number of servo writers to be introduced is increased, a large amount of cost is required for maintenance. Further, if the number of magnetic recording media that can be chucked at the same time is increased by extending the spindle, blurring is likely to occur during rotation, leading to a decrease in writing accuracy on the magnetic recording medium. Therefore, the number of magnetic recording media that can be chucked on one spindle is naturally limited. These problems become more serious as the track density of the magnetic recording medium improves and the number of tracks increases.

  Therefore, writing the servo signal, etc. to the magnetic recording medium is not performed by a servo writer, but using a master information carrier on which a magnetic transfer pattern corresponding to all servo signals, etc. is written, the signal written on the master information carrier is A method has been proposed in which magnetic transfer is performed collectively on a magnetic recording medium (see, for example, Patent Document 1).

  Specifically, in this method, a signal written on the master information carrier is magnetically transferred to the magnetic recording medium while applying a magnetic field as energy for transfer from the outside while the master information carrier and the magnetic recording medium are in close contact with each other. To do. As a result, it is possible to perform a writing operation such as a servo signal on the magnetic recording medium in a short time. Such a master information carrier can be used repeatedly.

JP 10-40544 A JP 2001-6169 A JP 2000-203889 A Japanese Patent Laid-Open No. 10-106229 Japanese Patent Laid-Open No. 11-277339

  By the way, when performing the magnetic transfer described above, if there are abnormal projections or the like on the surface of the magnetic recording medium, when the magnetic recording medium and the master information carrier are overlapped, the magnetic recording medium or A problem arises in that a concave portion occurs on the surface of the master information carrier, resulting in incomplete magnetic transfer.

  Since the master information carrier used for magnetic transfer is very expensive, in order to reduce the manufacturing cost of the magnetic recording medium, the total number of times that one master information carrier can be transferred before it is damaged due to wear or the like ( It is important to increase the number of times of use.

  Therefore, the surface of the magnetic recording medium is burnished to remove protrusions and dust on the surface, and then the master information carrier is superposed on the magnetic recording medium for magnetic transfer, thereby using the master information carrier. It has been proposed to increase the number of times (for example, see Patent Document 2).

  Here, the cleaning of the substrate surface and the like performed in the manufacturing process of the magnetic recording medium is roughly classified into wet cleaning using a cleaning liquid and dry cleaning using a wiping tape or the like. Although the former wet cleaning is superior to the latter dry cleaning, the dirt removed from the magnetic recording medium contained in the cleaning liquid may reattach to the medium surface. For this reason, wet cleaning is mainly used for cleaning nonmagnetic substrates for magnetic recording media such as aluminum alloy and glass, which do not require so high cleaning performance, as described in Patent Document 3, for example.

  In addition, wet cleaning may be used for cleaning the magnetic recording medium. However, in order to prevent re-attachment of corrosion and dirt such as Fe and Co contained in the magnetic recording medium, a short time of about several seconds using pure water. Limited to spin cleaning. Further, many particles such as sputter dust adhere to the surface of the magnetic recording medium, and wiping using a woven fabric or a non-woven fabric is considered to be more effective for removing these particles. .

  However, according to the study by the present inventors, by performing the above-described burnishing treatment on the surface of the magnetic recording medium, wiping treatment using a woven cloth or the like on the surface of the magnetic recording medium and the master information carrier, wet cleaning, etc. It has been found that even when the protrusions and dust on the surface are removed, the transfer pattern becomes incomplete before the master information carrier is damaged due to wear. In this case, it is still difficult to increase the total number of times that can be repeatedly transferred by one master information carrier to a number of times that is sufficient to be applied to commercial production.

  The present invention has been proposed in view of such conventional circumstances. When magnetic transfer is performed using a master information carrier that can be repeatedly used, the total number of times that can be repeatedly transferred by one master information carrier. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium in which the quality is greatly improved.

  As a result of intensive studies to solve the above problems, the present inventors have found that the magnetic transfer pattern by the master information carrier is incomplete due to ions represented by metal corrosives adhering to the surface of the master information carrier. It was elucidated that the slightly corroded metal residue on the surface of the magnetic recording medium was transferred and accumulated little by little on the master information carrier. In addition, metal corrosives and the like slightly remaining on the surface of the magnetic recording medium are of a level that cannot be removed by normal burnishing, wiping, cleaning, etc., and these are accumulated little by little on the master information carrier, It has been clarified that it is difficult to remove these substances by entering the recesses of the information carrier and wiping the transfer surface of the master information carrier. Furthermore, it has been elucidated that the accumulated material entering the concave portion of the master information carrier gradually erodes the convex portion of the master information carrier and reduces the transfer accuracy by the master information carrier.

  Therefore, the present inventors provide a step of cleaning the magnetic recording medium using a cleaning liquid containing an alkaline cleaner before performing magnetic transfer to the magnetic recording medium using the master information carrier. It has been found that metal corrosives and the like slightly remaining on the surface can be prevented from being transferred to the master information carrier, and the number of times of use of the master information carrier can be dramatically improved, and the present invention has been completed.

That is, the present invention provides the following means.
(1) After superimposing a magnetic recording medium having at least a magnetic layer on a nonmagnetic substrate and a master information carrier on which a transfer pattern corresponding to an information signal is formed, an external magnetic field is applied from the master information carrier side. A magnetic recording medium manufacturing method including a step of magnetically transferring an information signal from the master information carrier to the magnetic recording medium while applying
A step of using a master information carrier that can be repeatedly used when performing the magnetic transfer and cleaning the magnetic recording medium with a cleaning liquid containing an alkaline cleaner before superimposing the master information carrier and the magnetic recording medium. A method of manufacturing a magnetic recording medium, comprising:
(2) The method for manufacturing a magnetic recording medium according to (1), wherein the magnetic recording medium is cleaned by immersing it in a cleaning solution in a cleaning tank.
(3) The preceding item (1), wherein the alkaline detergent contains at least one of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, ammonia, and tetramethylammonium hydroxide as an active ingredient. ) Or the method for producing a magnetic recording medium according to (2).
(4) The method for producing a magnetic recording medium according to (3), wherein the concentration of the alkaline detergent in the cleaning liquid is in the range of 0.000001 mass% to 0.1 mass%.
(5) The magnetic recording medium is cleaned using the cleaning liquid containing the alkali cleaning agent, and then the magnetic recording medium is cleaned using pure water. The method for producing a magnetic recording medium according to any one of the above.
(6) The method for manufacturing a magnetic recording medium according to any one of (2) to (5), wherein ultrasonic vibration is applied to the cleaning liquid in the cleaning tank.

  As described above, in the present invention, a master information carrier that can be used repeatedly when performing magnetic transfer is used, and a cleaning liquid containing an alkaline cleaning agent is used before superimposing the master information carrier and the magnetic recording medium. By providing the step of cleaning the magnetic recording medium, it is possible to efficiently remove metal corrosives and the like slightly remaining on the surface of the magnetic recording medium.

  Therefore, according to the present invention, when the master information carrier and the magnetic recording medium are superimposed, it is possible to prevent metal corrosives and the like from being transferred from the magnetic recording medium to the master information carrier. It is possible to dramatically increase the total number of times that the information carrier can repeatedly transfer. As a result, an effect of greatly reducing the production cost of the magnetic recording medium can be obtained.

FIG. 1 is a cross-sectional view for explaining the magnetic transfer process of the present invention. FIG. 2 is a cross-sectional view showing an example of a magnetic recording medium. FIG. 3 is a perspective view showing an example of a magnetic recording / reproducing apparatus.

  Hereinafter, a method for manufacturing a magnetic recording medium to which the present invention is applied will be described in detail with reference to the drawings. In the drawings used in the following description, in order to make the features easy to understand, the portions that become the features may be schematically shown for convenience, and the dimensional ratios of the portions are not always the same as the actual ones.

  In the method of manufacturing a magnetic recording medium to which the present invention is applied, a magnetic recording medium having at least a magnetic layer formed on a nonmagnetic substrate and a master information carrier on which a transfer pattern corresponding to an information signal is formed are superimposed. The method includes a step of magnetically transferring an information signal from the master information carrier to a magnetic recording medium while applying an external magnetic field from the master information carrier side (referred to as a magnetic transfer step). A process of cleaning the magnetic recording medium using a cleaning liquid containing an alkaline cleaning agent (referred to as a medium cleaning process) before using the master information carrier that can be repeatedly used and before superimposing the master information carrier and the magnetic recording medium. It is characterized by providing.

(Medium washing process)
Specifically, in the medium cleaning process of the present invention, a cleaning liquid L containing an alkaline cleaner is used for cleaning the magnetic recording medium. This is a slight amount of contaminants that remain on the surface of the magnetic recording medium and cannot be removed by burnishing, wiping, spin cleaning, etc., especially ionic impurities such as metal corrosion. This is because, for the purpose of removal, the use of this alkaline cleaner reduces the corrosion of the magnetic layer containing Fe, Co, etc., and can remove these contaminants with a high detergency.

  Alkaline detergent is a detergent whose liquidity is alkaline. Generally, a surfactant such as polyoxyethylene alkyl ether, an alkali component such as NaOH or KOH, a solvent such as glycol ether, and a thickening agent. Including agents. In this invention, what contains potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, ammonia, tetramethylammonium hydroxide etc. can be used as an active ingredient of an alkali cleaning agent, and by using these, A high cleaning effect can be obtained.

  Since the magnetic recording medium contains the above-described easily corroding elements such as Fe and Co, cleaning of the magnetic recording medium has been limited to cleaning with a non-aqueous cleaning liquid using a fluorine compound or the like. In the present invention, since a cleaning liquid containing an alkaline cleaning agent is used, the magnetic recording medium is hardly corroded by the cleaning liquid, and contaminants attached to the surface of the magnetic recording medium can be removed with high cleaning power. In particular, by setting the concentration of the alkaline cleaning agent in the cleaning liquid in the range of 0.000001 mass% (0.01 ppm) to 0.1 mass% (1000 ppm), the effect can be enhanced, and more preferably The range is 0.1 to 20 ppm. On the other hand, when the concentration of the alkaline detergent in the cleaning liquid is less than 0.01 ppm, the cleaning effect is reduced. Conversely, when the concentration of the alkaline cleaning agent in the cleaning liquid exceeds 1000 ppm, the alkaline cleaning agent becomes a magnetic recording medium. This causes contamination of the magnetic recording medium and the master information carrier.

  Further, the medium washing process of the present invention may be a multistage process. Specifically, after cleaning the magnetic recording medium using a cleaning liquid containing an alkaline cleaner, the magnetic recording medium is subjected to an extremely short time such as spin cleaning using pure water or pulling and drying using dry air. It is preferable to perform immersion cleaning for a period of time. In the medium cleaning step of the present invention, the cleaning power can be increased by adding an alkaline cleaning agent to the cleaning liquid. However, if these alkaline cleaning agents remain on the surface of the magnetic recording medium, this causes contamination of the magnetic recording medium and the master information carrier.

  In order to prevent this, in the present invention, after the magnetic recording medium is cleaned using a cleaning liquid containing an alkaline cleaner, spin cleaning using pure water or immersion cleaning for a very short time is performed on the magnetic recording medium. By performing the above, it is possible to increase the detergency of the magnetic recording medium without leaving alkali on the surface of the magnetic recording medium. After the cleaning, it is preferable to quickly dry the magnetic recording medium using a spin drying method, a dry air drying method, or the like.

  In the medium cleaning step of the present invention, the magnetic recording medium is preferably cleaned by immersing it in a cleaning solution in a cleaning tank. As a result, a small amount of contaminants remain on the surface of the magnetic recording medium and cannot be removed by burnishing, wiping, spin cleaning, conventional wet cleaning, etc., especially ions represented by metal corrosion. Can be efficiently removed. In the present invention, it is possible to further increase the cleaning power by applying ultrasonic vibration to the cleaning liquid in the cleaning tank.

  As described above, in the medium cleaning step of the present invention, in addition to the dust and foreign matter adhering to the surface of the magnetic recording medium W, it slightly remains on the surface of the magnetic recording medium W described above, burnishing, It is possible to efficiently remove an amount of contaminants, particularly ionic impurities represented by metal corrosives, which cannot be removed by wiping, spin cleaning, conventional wet cleaning, and the like. In addition, after the cleaning, it is possible to perform advanced medium cleaning that prevents these from reattaching to the surface of the magnetic recording medium W. As a result, it is possible to obtain a magnetic recording medium W having a clean surface that cannot be obtained by a conventional method.

(Magnetic transfer process)
In the magnetic transfer process, a writing operation such as a servo signal is performed by magnetic transfer on the magnetic recording medium whose surface is cleaned by the medium cleaning process of the present invention. Specifically, in this magnetic transfer step, first, the signal recording surface of the magnetic recording medium is initially magnetized. This initial magnetization is performed by applying an initial DC magnetic field in one direction in the track direction in the case of an in-plane magnetic recording medium, and in one direction perpendicular to the medium surface in the case of a perpendicular magnetic recording medium. This is done by applying an initial DC magnetic field.

  This initial DC magnetic field can be applied using a permanent magnet or an electromagnet. As the permanent magnet, it is preferable to use an NdFeB-based sintered magnet that is more stable and has a strong magnetic force. In addition, it is preferable to apply the initial DC magnetic field in a non-contact state with the magnetic recording medium in order to maintain the cleanliness of the surface of the magnetic recording medium.

  Next, as shown in FIG. 1, the signal recording surface of the magnetic recording medium W after application of the initial DC magnetic field, and the transfer surface of the master information carrier M on which a transfer pattern corresponding to a servo signal or the like is formed. Are brought into close contact with each other with a predetermined pressing force. In this state, an external magnetic field for transfer is applied from the opposite side of the transfer surface of the master information carrier M using the magnetic field generating means G while moving the magnetic field generating means G relatively in the track direction X. To do. This external magnetic field for transfer is a magnetic field in the opposite direction to the initial DC magnetic field. Thereby, in the magnetic recording medium W, magnetization reversal occurs at a position facing the transfer pattern of the master information carrier M, and a magnetization pattern corresponding to a servo signal or the like is written by magnetic transfer.

  The master information carrier M can be manufactured by a known method. Specifically, when manufacturing such a master information carrier M, first, an electron beam resist is applied to the surface of a silicon wafer by spin coating. Thereafter, this resist is irradiated with an electron beam modulated in accordance with a servo signal or the like using an electron beam exposure apparatus, and after exposing and developing the resist, silicon is removed by removing unexposed portions. A resist pattern corresponding to the transfer pattern is formed on the wafer.

  Next, using this resist pattern as a mask, a reactive etching process is performed on the silicon wafer, and a portion not masked with the resist is dug down. After this etching process, the resist remaining on the silicon wafer is removed by washing with a solvent. Thereafter, the silicon wafer is dried to obtain a master for producing a master information carrier.

  Next, a conductive layer made of Ni is formed on the master with a thickness of about 10 nm by sputtering. Thereafter, a Ni layer having a thickness of several microns is formed on the master by electroforming using the master on which the conductive layer is formed. Thereafter, the Ni layer is removed from the master, and the Ni layer is washed, etc., to obtain the Ni base material 100 having the convex portions 100a and the concave portions 100b formed on the surface.

  Next, the magnetic layer 101 is formed on the surface of the Ni substrate 100. As the magnetic layer 101, the same magnetic layer used in the magnetic recording medium W can be used. Of the magnetic layer 101 formed on the surface of the Ni base material 100, the portion of the magnetic layer 101 where the convex portion 100a is formed is used for magnetic transfer to the magnetic recording medium W, and the concave portion 100a is formed. The portion of the magnetic layer 101 thus formed is not used for magnetic transfer because it does not contact the magnetic recording medium W.

Further, a protective film (not shown) is formed on the surface of the Ni base 100 similarly to the magnetic recording medium W. This protective film is for enhancing the wear resistance of the master information carrier M, and a hard carbon film having a thickness of about several nm is used.
Through the above steps, a master information carrier M on which a transfer pattern corresponding to a servo signal or the like is formed can be obtained.

  The magnetic field generating means G is composed of an electromagnet or a permanent magnet. In the case of an in-plane magnetic recording medium, an external magnetic field for transfer is generated in the other direction of the track, and in the case of a perpendicular magnetic recording medium, An external magnetic field for transfer is generated in the other direction perpendicular to the medium surface. The magnetic field generating means G can be rotated in the track direction X to the center of the magnetic recording medium W while generating an external magnetic field in the same direction in the radial direction of the magnetic recording medium W.

  Here, the magnetic recording medium W built in the hard disk drive generally has a magnetic layer 201 formed on both surfaces of the non-magnetic substrate 200, and a single hard disk drive has a plurality of magnetic recording media. W is often built-in. For this reason, in a hard disk drive, a plurality of magnetic heads are integrally moved by a stack structure, but the track width of the magnetic recording medium W is becoming increasingly narrower, so that data is written on the signal recording surface of one magnetic recording medium W. It is difficult to position the magnetic head on another signal recording surface using the servo signal or the like because of the accuracy of the stack structure of the head.

  Therefore, in the magnetic transfer process of the present invention, it is preferable to write servo signals and the like on both surfaces of the magnetic recording medium W by magnetic transfer. Specifically, both surfaces of the magnetic recording medium W are sandwiched between a pair of master information carriers M. In this state, an external magnetic field for transfer is applied from the side opposite to the transfer surface of the master information carrier M using the magnetic field generating means G. Thereby, servo signals and the like can be written on both surfaces of the magnetic recording medium W.

  In addition, the coercive force Hc of the magnetic layer 201 is usually 320 kA / m (about 4000 Oe) or more. Therefore, in the magnetic transfer process of the present invention, after the magnetic layer 201 is initially DC magnetized, both sides of the magnetic recording medium are sandwiched between the master information carriers M, and a magnetic field having a magnetic transfer strength is applied via the master information carrier M. It is preferable to perform magnetic transfer.

  In the magnetic transfer process of the present invention, magnetic transfer is performed on the magnetic recording medium W whose surface has been highly cleaned by the medium cleaning process. Therefore, when the master information carrier M and the magnetic recording medium W are overlapped, It is possible to prevent the metal corrosive matter or the like slightly remaining on the surface of the magnetic recording medium W described above from being transferred and accumulated little by little on the master information carrier M. In particular, it is possible to prevent such accumulated material from entering the concave portion 100b of the transfer surface of the master information carrier M and eroding the convex portion 100a while deteriorating the magnetization pattern written on the magnetic recording medium W. .

  Therefore, according to the present invention, it is possible to dramatically increase the total number of times that can be repeatedly transferred by one master information carrier M, and as a result, it is possible to greatly reduce the production cost of the magnetic recording medium. It is.

(Magnetic recording medium)
Next, an example of a magnetic recording medium manufactured by applying the present invention is shown in FIG.
As shown in FIG. 2, the magnetic recording medium includes a soft magnetic underlayer 2 including two soft magnetic layers 2a antiferromagnetically coupled by a spacer layer 2b on a nonmagnetic substrate 1, and an orientation control layer 3. The perpendicular magnetic layer 4, the protective layer 5, and the lubricant film 6 are sequentially laminated.

  The perpendicular magnetic layer 4 includes three layers of a lower magnetic layer 4a, an intermediate magnetic layer 4b, and an upper magnetic layer 4c, and a nonmagnetic layer 7a is interposed between the magnetic layer 4a and the magnetic layer 4b. By sandwiching the nonmagnetic layer 7b between the magnetic layer 4b and the magnetic layer 4c, the magnetic layers 4a to 4c and the nonmagnetic layers 7a and 7b are alternately stacked.

  As the nonmagnetic substrate 1, for example, a metal substrate made of a metal material such as aluminum or an aluminum alloy may be used. For example, a nonmetal substrate made of a nonmetal material such as glass, ceramic, silicon, silicon carbide, or carbon. May be used. In addition, it is also possible to use a substrate in which a NiP layer or a NiP alloy layer is formed on the surface of the metal substrate or nonmetal substrate by using, for example, a plating method or a sputtering method.

  As the glass substrate, for example, amorphous glass or crystallized glass can be used, and as the amorphous glass, for example, general-purpose soda lime glass or aluminosilicate glass can be used. In addition, as the crystallized glass, for example, lithium-based crystallized glass can be used. As the ceramic substrate, for example, general-purpose aluminum oxide, a sintered body mainly composed of aluminum nitride, silicon nitride, or the like, or a fiber reinforced material thereof can be used.

  The nonmagnetic substrate 1 has an average surface roughness (Ra) of 1 nm (10 mm) or less, preferably 0.5 nm or less, from the viewpoint of suitable for high recording density recording with a magnetic head flying low. preferable. Further, it is preferable that the surface fine waviness (Wa) is 0.3 nm or less (more preferably 0.25 nm or less) from the viewpoint of being suitable for high recording density recording with the magnetic head flying low. In addition, it is possible to use a magnetic head having a chamfered portion at the end face and a surface average roughness (Ra) of at least one of the side surface portion of 10 nm or less (more preferably 9.5 nm or less). Preferred for stability. In addition, microwaviness (Wa) can be measured as surface average roughness in a measuring range of 80 μm, for example, using a surface roughness measuring device P-12 (manufactured by KLM-Tencor).

  Further, when the nonmagnetic substrate 1 is in contact with the soft magnetic underlayer 2 mainly composed of Co or Fe, there is a possibility that the corrosion progresses due to the adsorption gas on the surface, the influence of moisture, the diffusion of the substrate components, and the like. is there. In this case, it is preferable to provide an adhesion layer between the nonmagnetic substrate 1 and the soft magnetic underlayer 2, thereby suppressing these. In addition, as a material of the adhesion layer, for example, Cr, Cr alloy, Ti, Ti alloy, or the like can be selected as appropriate. The thickness of the adhesion layer is preferably 2 nm (20 mm) or more.

  As the soft magnetic layers 2a and 2c, it is preferable to use a material containing Fe: Co in a range of 40:60 to 70:30 (atomic ratio). Moreover, in order to improve the magnetic permeability and corrosion resistance, it is preferable to contain any one selected from Ta, Nb, Zr, and Cr in the range of 1 to 8 atomic%. As the spacer layer 2b, Ru, Re, Cu, or the like can be used. Among these, it is particularly preferable to use Ru.

  The orientation control layer 3 is for improving the recording / reproducing characteristics by refining the crystal grains of the perpendicular magnetic layer 4. The orientation control layer 3 is not particularly limited, but it is preferable to use a layer having an hcp structure, an fcc structure, or an amorphous structure. In particular, it is preferable to use a Ru alloy, a Ni alloy, a Co alloy, a Pt alloy, or a Cu alloy. Further, these alloys may be multilayered. For example, it is preferable to adopt a multilayer structure of Ni-based alloy and Ru-based alloy, a multilayer structure of Co-based alloy and Ru-based alloy, or a multilayer structure of Pt-based alloy and Ru-based alloy from the substrate side.

  Here, in the initial part of the perpendicular magnetic layer 4 immediately above the orientation control layer 3, disorder of crystal growth is likely to occur, which causes noise. In this case, it is preferable to provide a nonmagnetic underlayer 8 between the orientation control layer 3 and the perpendicular magnetic layer 4. The occurrence of noise can be suppressed by replacing the disturbed portion of the initial portion with the nonmagnetic underlayer 8.

As the nonmagnetic underlayer 8, it is preferable to use a material composed mainly of Co and further containing an oxide. The Cr content is preferably 25 atomic% or more and 50 atomic% or less. As the oxide, for example, oxides such as Cr, Si, Ta, Al, Ti, Mg, and Co are preferably used, and among them, TiO ₂ , Cr ₂ O ₃ , SiO _{2, and the} like are preferably used. it can. The content of the oxide is preferably 3 mol% or more and 18 mol% or less with respect to the total mol amount of the magnetic particles, for example, an alloy such as Co, Cr, and Pt calculated as one compound.

As the magnetic layers 4a, 4b, and 4c, it is preferable to use a material mainly containing Co and further containing an oxide. Examples of the oxide include Cr, Si, Ta, Al, Ti, Mg, and Co. The oxide is preferably used. Among _{them, TiO 2, Cr 2 O 3} , SiO ₂ or the like can be suitably used. The lower magnetic layer 4a is preferably made of a complex oxide to which two or more kinds of oxides are added. Among these, Cr ₂ O ₃ —SiO ₂ , Cr ₂ O ₃ —TiO ₂ , Cr ₂ O ₃ —SiO ₂ —TiO _{2 and the} like can be preferably used.

As a material suitable for the magnetic layers 4a, 4b, and 4c, for example, 90 (Co14Cr18Pt) -10 (SiO ₂ ) {Cr content of 14 atomic%, Pt content of 18 atomic%, and the balance of Co magnetic particle is one molar concentrations calculated as compound 90 mol%, 10 _mol% oxide composition consisting _{SiO 2}, 92 (Co10Cr16Pt)} -8 (SiO 2), other _{94 (Co8Cr14Pt4Nb) -6 (Cr 2} O 3), (CoCrPt _{) - (Ta 2 O 5)} , (CoCrPt) - (Cr 2 O 3) - (TiO 2), (CoCrPt) - (Cr 2 O 3) - (SiO 2), (CoCrPt) - (Cr 2 O 3 _{) - (SiO 2) - (} TiO 2), (CoCrPtMo) - (TiO), (CoCrPtW) - (TiO 2), (CoCrPtB _{- (Al 2 O 3),} (CoCrPtTaNd) - (MgO), (CoCrPtBCu) - (Y 2 O 3), (CoCrPtRu) - can be exemplified compositions such as (SiO _2).

  In the present invention, the perpendicular magnetic layer 4 can be composed of four or more magnetic layers. For example, in addition to the magnetic layers 4a and 4b, a magnetic layer having a granular structure is composed of three layers, and a magnetic layer 4c not containing an oxide is provided thereon, and a magnetic layer not containing an oxide is also provided. The layer 4c may have a two-layer structure and be provided on the magnetic layers 4a and 4b.

  In the present invention, it is preferable to provide the nonmagnetic layer 7 between three or more magnetic layers constituting the perpendicular magnetic layer 4. By providing the nonmagnetic layer 7 with an appropriate thickness, magnetization reversal of individual films can be facilitated, and dispersion of magnetization reversal of the entire magnetic particles can be reduced. As a result, the S / N ratio can be further improved.

The protective layer 5 is for preventing corrosion of the perpendicular magnetic layer 4 and preventing damage to the medium surface when the magnetic head comes into contact with the magnetic recording medium. For the protective layer 5, a conventionally known material can be used. For example, a material containing C, SiO ₂ , ZrO ₂ or the like can be used. The thickness of the protective layer 5 is preferably 1 to 10 nm from the viewpoint of high recording density because the distance between the magnetic head and the magnetic recording medium can be reduced.

  The lubricant film 6 is formed, for example, by applying a lubricant such as perfluoropolyether, fluorinated alcohol, or fluorinated carboxylic acid on the protective layer 5.

  By the way, in the conventional method of manufacturing a magnetic recording medium, a wiping process, a burnishing process, and a magnetic transfer process are performed after the above-described lubricant application process. In contrast, in the method of manufacturing a magnetic recording medium to which the present invention is applied, the medium cleaning step is performed before the magnetic transfer step. The medium washing step is preferably performed before the lubricant application step.

  That is, the medium cleaning process of the present invention is performed for the purpose of removing contaminants on the surface of the magnetic recording medium that cannot be removed by the wiping process or the burnishing process. These contaminants may be difficult to clean and remove after the lubricant application process, wiping process, and burnishing process. The reason is speculated that if the contaminant is covered with the lubricant film 6, it becomes difficult to remove it due to its water repellency. After the wiping process and the burnishing process, the contaminant is removed from the surface of the magnetic recording medium. It may be difficult to remove it.

  In the medium cleaning process, it is possible to remove a certain amount of powdery substances such as sputter dust, but the effect of scrubbing, wiping and scraping the surface of the magnetic recording medium as in the wiping process and burnishing process. Therefore, it is difficult to remove the powdery substance firmly attached to the surface of the magnetic recording medium. Therefore, the medium cleaning step is preferably used in combination with the wiping step and the burnishing step.

  The wiping step is performed using a cloth wiping tape or the like as described in Patent Document 4, for example. That is, in this wiping step, the surface of the wiping tape is pressed against the surface of the magnetic recording medium by a rubber contact roll or pad while the wiping tape is moved relative to the surface of the magnetic recording medium. It is a process of wiping lightly. By performing such processing, spatter dust and the like adhering to the surface of the magnetic recording medium is removed, so that the flying height of the magnetic head can be further reduced.

  Further, as the wiping tape used in the wiping step, a wiping tape obtained by slitting a cloth made of ultrafine fibers into a belt shape, a woven or knitted fabric of ultrafine fiber multifilament yarn, or the like is used.

  Further, the wiping method of the magnetic recording medium using such a wiping tape is specifically the surface of the wiping tape (wiping surface) on the surface of the magnetic recording medium while rotating the magnetic recording medium. This is done by pressing. As a result, sputter dust or the like adhering to the surface of the magnetic recording medium is wiped off, and the medium surface is cleaned.

  The wiping tape is stretched between the supply reel and the take-up reel, is sequentially supplied from the supply reel, and is sequentially taken up by the take-up reel. In the course of running from the supply reel side to the take-up reel side, the surface (back surface) opposite to the wiping surface of the wiping tape is pressed by a backing roll such as rubber or felt, and the wiping surface is a magnetic recording medium. Pressed against the surface.

  The burnishing step is a step of polishing the surface with a polishing tape in order to remove protrusions on the surface of the magnetic recording medium. As a result, the flying height of the magnetic head in the hard disk drive is further reduced, and a gap is formed between the magnetic recording medium and the master information carrier M in the magnetic transfer step, resulting in a blurred transfer pattern. Can be prevented from being damaged.

  Such a burnishing process is performed using a polishing tape coated with alumina abrasive grains, as described in Patent Document 5, for example. That is, this burnishing step is a step of lightly polishing the surface of the medium by pressing a polishing tape against a surface of the magnetic recording medium with a rubber contact roll. By performing such processing, abnormal protrusions and the like on the surface of the magnetic recording medium are removed.

  As a polishing tape (burnish tape) used in the burnishing process, a tape formed by forming an abrasive layer on a polyester base film is usually used. This abrasive layer slides in contact with the surface of the magnetic recording medium, so that fine dust adhering to the surface of the medium is removed and abnormal protrusions etc. existing on the surface of the medium are polished and removed. Thus, the surface of the medium is smoothed.

  As an abrasive, chromium oxide, α-alumina, silicon carbide, nonmagnetic iron oxide, diamond, γ-alumina, α, γ-alumina, fused alumina, corundum, artificial, having an average particle size of about 0.05 μm to 50 μm Diamond or the like is used.

  Such burnishing is performed by pressing the abrasive surface of the polishing tape against the surface of the magnetic recording medium while rotating the magnetic recording medium. Thereby, the protrusions on the surface of the magnetic recording medium are polished and removed, and the surface of the medium is smoothed. Here, the polishing tape is stretched between the supply reel and the take-up reel, is sequentially supplied from the supply reel, and is sequentially taken up by the take-up reel. And while traveling from the supply reel side to the take-up reel side, the surface (back surface) opposite to the abrasive surface of the abrasive tape is pressed by a backing roll such as rubber or felt, etc., and the abrasive surface of the abrasive tape Is pressed against the surface of the magnetic recording medium.

  After the magnetic transfer step, a glide inspection is performed on the obtained magnetic recording medium. The glide inspection is a step of inspecting the surface of the magnetic recording medium by actually moving the magnetic head to check if there are any projections. In other words, when recording / reproducing is performed on a magnetic recording medium using a magnetic head, if there is a protrusion on the surface of the magnetic recording medium that is higher than the flying height (the distance between the medium and the magnetic head), the magnetic head May cause damage to the magnetic head or defects in the magnetic recording medium. In the glide inspection, the presence or absence of such high protrusions is inspected.

  Usually, a certification test is performed on a magnetic recording medium that has passed the glide test. The certification inspection is similar to normal hard disk drive recording / reproduction, after a predetermined signal is recorded on the magnetic recording medium with a magnetic head, the signal is reproduced, and the resulting reproduction signal is used to record the magnetic recording medium. Impossibility is detected, and the quality of the medium, such as the electrical characteristics of the magnetic recording medium and the presence or absence of defects, is confirmed.

  The magnetic recording medium manufactured by applying the present invention is different from the conventional certification test because the servo signal and the like are already written. In other words, in the magnetic recording medium manufactured by applying the present invention, a servo signal or the like magnetically transferred to the magnetic recording medium is used to perform a test in which reading / writing is performed with the magnetic head positioned at a specific location.

(Magnetic recording / reproducing device)
Next, FIG. 3 shows an example of a magnetic recording / reproducing apparatus (hard disk drive) having a magnetic recording medium manufactured by applying the present invention.
This magnetic recording / reproducing apparatus records and reproduces information on the magnetic recording medium 50 manufactured by applying the present invention shown in FIG. 2, a medium driving unit 51 that rotationally drives the magnetic recording medium 50, and the magnetic recording medium 50. And a recording / reproducing signal processing system 54. The head driving unit 53 moves the magnetic head 52 relative to the magnetic recording medium 50. Further, the recording / reproducing signal processing system 54 can process data input from the outside and send a recording signal to the magnetic head 52, process a reproducing signal from the magnetic head 52, and send the data to the outside. ing. Further, as the magnetic head 52 provided in the magnetic recording / reproducing apparatus, a magnetic head suitable for a higher recording density having a GMR element utilizing a giant magnetoresistive effect (GMR) as a reproducing element can be used.

  According to the magnetic recording / reproducing apparatus, an excellent hard disk can be obtained by adopting a magnetic recording medium manufactured by applying the present invention to the magnetic recording medium 50 having a high recording density, high-speed writing, and excellent electromagnetic conversion characteristics. It can be a drive.

  Hereinafter, the effects of the present invention will be made clearer by examples. In addition, this invention is not limited to a following example, In the range which does not change the summary, it can change suitably and can implement.

Example 1
In Example 1, first, a cleaned glass substrate (manufactured by Konica Minolta Co., Ltd., 2.5 inches in outer diameter) is accommodated in a film forming chamber of a DC magnetron sputtering apparatus (C-3040 made by Anelva Co., Ltd.), and the ultimate vacuum is achieved. After evacuating the film formation chamber to 1 × 10 ⁻⁵ Pa, an adhesion layer having a thickness of 10 nm was formed on the glass substrate using a 60Cr-40Ti target. Further, on this adhesion layer, a target of 46Fe-46Co-5Zr-3B {Fe content 46 atomic%, Co content 46 atomic%, Zr content 5 atomic%, B content 3 atomic%} was used. A soft magnetic layer having a layer thickness of 34 nm was formed at a substrate temperature of 100 ° C. or less, and a Ru layer was formed thereon with a layer thickness of 0.76 nm, and then a 46Fe-46Co-5Zr-3B soft magnetic layer was further formed. A film thickness of 34 nm was formed and used as a soft magnetic underlayer.

  Next, on the soft magnetic underlayer 2, Ni-6W {W content 6 atomic%, remaining Ni} target and Ru target were sequentially formed with a layer thickness of 5 nm and 20 nm, respectively. It was set as the orientation control layer.

Next, 84 (Co12Cr16Pt) -16TiO ₂ (film thickness: 3 nm), Ru47.5Co (film thickness: 0.5 nm), 91 (Co11.5Cr13Pt10Ru) -4SiO as a magnetic layer having a multilayer structure on the orientation control layer 3. ₂ -3Cr ₂ O ₃ -2TiO ₂ (thickness 3 nm), was laminated Co15Cr16Pt6B (thickness 3 nm).
Next, a carbon protective layer having a thickness of 2.5 nm was formed by CVD, and the magnetic recording medium of Example 1 was obtained.

The magnetic recording medium manufactured by the above method was washed with ultrapure water. The cleaning process of Example 1 consists of a three-stage cleaning process, and the cleaning tanks used in each cleaning process are all made of SUS, have a volume of 20 liters, and 500 W of ultrasonic vibration is applied to the inside. Then, 15 liters of ultrapure water was added to each washing tank, and 0.1 ppm of KOH was added to the first washing tank. The magnetic recording medium was immersed in this three-stage washing tank in order and washed in each washing tank for 30 seconds. The magnetic recording medium after washing was quickly lifted and dried using dry air.
A lubricant film made of perfluoropolyether with a thickness of 15 angstroms was formed on the surface of the magnetic recording medium by dipping.

  A wiping process was performed on the magnetic recording medium coated with the lubricant. As the wiping tape, a peelable composite fiber having a wire diameter of 2 μm made of nylon resin and polyester resin was used. In the wiping process, the rotational speed of the magnetic recording medium was 300 rpm, the feeding speed of the wiping tape was 10 mm / second, the pressing force when pressing the wiping tape against the magnetic recording medium was 98 mN, and the processing time was 5 seconds. In the wiping treatment, perfluoropolyether was sprayed on the wiping tape to form a lubricant film of about 0.01 μm on the tape surface.

  The magnetic recording medium subjected to the wiping process was burnished. The burnish tape used was a polyethylene terephthalate film on which crystal growth type alumina particles having an average particle size of 0.5 μm were fixed with an epoxy resin. In the burnishing, the rotational speed of the magnetic recording medium was 300 rpm, the polishing tape feed speed was 10 mm / second, the pressing force when pressing the polishing tape against the magnetic disk was 98 mN, and the treatment time was 5 seconds.

  Initial magnetization was applied to the burnished magnetic recording medium. Specifically, a magnetic field of 10 kOe penetrating the magnetic recording medium was applied to both data surfaces of the magnetic recording medium using an NdFeB-based sintered magnet.

A master information carrier for magnetic transfer was brought into close contact with both data surfaces of the magnetic recording medium subjected to initial magnetization at a pressure of 98 mN, and a recording magnetic field was applied from the back surface of the master information carrier for magnetic transfer. The intensity of this recording magnetic field was 4 kOe, and the transfer time was 10 seconds. On the master information carrier for magnetic transfer, a pattern such as a servo signal of 271 k tracks / inch is formed, the track is 120 nm wide, the width between tracks is 60 nm, and the pattern step is 45 nm. As a master information carrier for magnetic transfer, a Ru film having a layer thickness of 10 nm is formed on a Ni substrate constituting a convex portion by using a DC sputtering method, and a 70Co-5Cr-15Pt-10SiO ₂ alloy having a layer thickness of 20 nm as a magnetic layer. A film, a 70Co-5Cr-15Pt alloy film having a layer thickness of 15 nm, and a CVD carbon film having a layer thickness of 20 nm were stacked in this order as a protective layer.

  The magnetic recording medium manufactured by the above method was periodically sampled and evaluated. Specifically, the reproduction characteristics of the servo signal were measured using a read / write analyzer (model number: RWA1632; manufactured by GUZIK, USA) and a spin stand (model number: S1701MP). In this apparatus, a servo signal or the like recorded on a magnetic recording medium is read, and the magnetic head can be positioned using this signal. At this time, a magnetic head using TuMR is used as an evaluation magnetic head, and the S / N ratio at the time of servo signal reading is evaluated. When the S / N ratio is 16.0 dB or less, magnetic transfer is performed. Judged to be bad. As a result, in Example 1, 32,000 times of magnetic transfer were possible.

(Comparative Example 1)
In Comparative Example 1, KOH was not added to the first-stage washing tank of Example 1. That is, ultrapure water was used for all the three-stage washing tanks. As a result, in Comparative Example 1, 5000 times of magnetic transfer were possible.

(Examples 2 and 3)
In Examples 2 and 3, 0.1 ppm of NaOH (Example 2) or 0.3 ppm (Example 3) of tetramethylammonium hydroxide was added to the first-stage washing tank of Example 1 instead of KOH. did. As a result, magnetic transfer was possible 38000 times in Example 2 and 35000 times in Example 3.

DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic board | substrate 2 ... Soft magnetic underlayer 2a ... Soft magnetic layer 2b ... Spacer layer 3 ... Orientation control layer 4 ... Perpendicular magnetic layer 4a, 4b, 4c ... Magnetic layer 5 ... Protective layer 6 ... Lubricant film 7a, 7b DESCRIPTION OF SYMBOLS ... Nonmagnetic layer 8 ... Nonmagnetic underlayer 50 ... Magnetic recording medium 51 ... Medium drive part 52 ... Magnetic head 53 ... Head drive part 54 ... Recording / reproduction signal processing system 100 ... Ni base material 100a ... Convex part 100b ... Concave part 101 ... Magnetic layer 200 ... Nonmagnetic substrate 201 ... Magnetic layer W ... Magnetic recording medium M ... Master information carrier G ... Magnetic field generating means

Claims (6)

After superimposing a magnetic recording medium having at least a magnetic layer on a non-magnetic substrate and a master information carrier on which a transfer pattern corresponding to an information signal is formed, an external magnetic field is applied from the master information carrier side. However, a method of manufacturing a magnetic recording medium including a step of magnetically transferring an information signal from the master information carrier to the magnetic recording medium,
A step of using a master information carrier that can be repeatedly used when performing the magnetic transfer and cleaning the magnetic recording medium with a cleaning liquid containing an alkaline cleaner before superimposing the master information carrier and the magnetic recording medium. A method of manufacturing a magnetic recording medium, comprising: providing a magnetic recording medium.   2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the cleaning of the magnetic recording medium is performed by immersing in a cleaning liquid in a cleaning tank.   The alkaline cleaning agent contains at least one or more of potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, ammonia, and tetramethylammonium hydroxide as an active ingredient. A method for producing the magnetic recording medium according to claim.   4. The method of manufacturing a magnetic recording medium according to claim 3, wherein the concentration of the alkaline cleaning agent in the cleaning liquid is in the range of 0.000001 mass% to 0.1 mass%.   The magnetic recording medium is cleaned with a cleaning liquid containing the alkaline cleaning agent, and then the magnetic recording medium is cleaned with pure water. A method for producing the magnetic recording medium according to 1.   6. The method of manufacturing a magnetic recording medium according to claim 2, wherein ultrasonic vibration is applied to the cleaning liquid in the cleaning tank.

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