JP2006236466A - Master carrier for magnetic transfer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance durability of a master carrier for magnetic transfer. <P>SOLUTION: The master carrier 3 for magnetic transfer is characterized in that a ratio of the initial surface energy to the initial surface energy of a slave medium becomes 1.2 or more by providing a protective layer 34 constituted of a carbonaceous hard material to the surface of the master carrier 3 for magnetic transfer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic transfer master carrier having on its surface a transfer pattern corresponding to information to be transferred to a transfer medium.

  As a method for preformat recording or data recording of servo signals, etc. on magnetic recording media, a master carrier (patterned master carrier) in which a transfer pattern of servo signals etc. having a magnetic layer at least on the surface layer is formed in an uneven shape or an embedded structure Is applied to a magnetic recording medium having a magnetic recording layer (transfer medium (slave medium)), and a magnetic field for transfer is applied to the magnetic recording medium by applying a transfer magnetic field to the magnetic recording medium. Magnetic recording methods for recording have been proposed.

  When the magnetic recording medium is a disk-shaped medium such as a hard disk or a high-density flexible disk, an electromagnetic device or permanent magnet is attached to one or both sides of the magnetic recording medium in a state where a disk-shaped master carrier is in close contact with one or both surfaces. A magnetic field applying device using a magnet device is provided to apply a magnetic field for transfer. In addition, since magnetic transfer to a large number of slave media is performed using one master carrier, the close contact and peeling of the slave media with respect to the master carrier are repeated.

  As described above, the magnetic transfer is performed by bringing the master carrier and the slave medium into close contact with each other. However, if foreign matter is present between the two, the close contact between the two becomes insufficient and the transfer quality is lowered, or the magnetic layer of the master carrier is reduced. Problems such as destruction occur. Since the master carrier takes a very long time to manufacture, it is inevitable to improve the durability so that one master carrier can perform magnetic transfer to more slave media. Therefore, it is necessary to prevent the generation of foreign matter so that no foreign matter is interposed between them.

In the magnetic transfer method, in the process of adhesion and delamination between the master carrier and the slave medium, the magnetic layer of the master carrier is delaminated or missing, which becomes a foreign object when they are in close contact with each other and ends the life of the master carrier. There is a problem that causes it. In order to solve this problem, for example, Patent Documents 1 and 2 propose a master carrier having a protective layer formed on the surface in order to improve the durability of the magnetic transfer master carrier and reduce the frequency of foreign matter generation.
Japanese Patent Laid-Open No. 11-273070 JP 2000-195048 A

  However, even if a protective layer is formed on the surface, if a great force is applied to the peeling of the master carrier and the slave medium, the master carrier may be deformed or the slave medium may be damaged. It has become clear that magnetic layer film peeling and film destruction occur. A part of the magnetic layer film that has been peeled off or broken becomes a foreign matter interposed between the master carrier and the slave medium, causing the above-described problems such as a decrease in adhesion between the two and a breakage of the master carrier.

  The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a master carrier for magnetic transfer with reduced generation of foreign matter and improved durability.

The magnetic transfer master carrier of the present invention is a magnetic transfer master carrier having on its surface a transfer pattern corresponding to information to be transferred to a transfer medium,
The ratio of the initial surface energy to the initial surface energy of the transfer medium is 1.2 or more.

  The ratio of the initial surface energy to the initial surface energy of the transfer medium is (initial surface energy of the master carrier) / (initial surface energy of the slave medium). The initial surface energy is the surface energy before the two are first brought into close contact with each other. A lubricant is applied to the surface of the slave medium, and the surface energy of the slave medium is generally lowered due to the transfer of the lubricant after close contact with the master carrier.

  On the surface of a solid / liquid, a force that attempts to make the surface as small as possible by an intermolecular force acts. Therefore, in order to form the surface of a certain material, a force against the intermolecular force is required. The amount of work required to form this surface is surface energy.

  In the present invention, as the initial surface energy, a value obtained by converting the contact angle measurement result of water and methylene iodide is used.

  The magnetic transfer master carrier of the present invention is preferably provided with a protective layer on the surface. Moreover, it is desirable that this protective layer is formed of a carbon-based hard material. Specific examples of the carbon-based hard material include a carbon film and a diamond-like carbon film (DLC film).

  A master carrier for magnetic transfer generally includes a substrate and a magnetic layer provided on the substrate. As a method for changing the surface energy, the surface energy of the magnetic layer is changed by changing the film formation conditions of the magnetic layer. For example, a method of changing the surface energy of the protective layer may be used when a protective layer is further provided on the magnetic layer. Changing the surface energy of the magnetic layer will change the magnetostatic characteristics during magnetic transfer. Therefore, when providing a protective layer on the magnetic layer, use a method that changes the surface energy of the protective layer. Is more desirable. The surface energy can be increased by reducing the film formation pressure when forming the magnetic layer or the protective layer by sputtering, and the surface energy can be reduced by increasing the film formation pressure.

  According to the inventors' research, when the ratio of the initial surface energy of the master carrier to the transferred medium is 1.2 or more, compared to the case where the initial surface energies of both are substantially equal and have no energy difference. It became clear that the force required for peeling was halved. The magnetic transfer master carrier of the present invention has a ratio of the initial surface energy to the initial surface energy of the medium to be transferred of 1.2 or more. It is possible to reduce deformation of the master carrier and damage to the transfer medium that occur when the carrier and the transfer medium are peeled off, and to reduce peeling and breakage of the magnetic layer film. The effect of reducing the peeling off or breakage of the magnetic layer film is synonymous with the effect of suppressing the generation of foreign matter, that is, the deterioration of transfer quality due to the generation of foreign matter can be suppressed, and the durability of the magnetic transfer master carrier can be improved. In addition, by improving the durability of the master carrier, it is possible to increase the number of sheets transferred to the transfer medium using one master carrier, and an effect of cost reduction can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a partial perspective view of the surface of the magnetic transfer master carrier of this embodiment, and FIG. 2 shows a partial cross-sectional view of the master carrier of FIG.

  The master carrier 3 of the present embodiment is formed in a disk shape as shown in FIG. 3 described later, and arranged in the track direction on the surface according to information to be transferred to the magnetic recording medium as a slave medium. It has a transfer pattern consisting of irregularities. The information to be transferred includes, for example, a servo signal, but may include other various data. A partial pattern of the concavo-convex pattern 36 is, for example, as shown in FIG. In FIG. 1, an arrow X indicates a circumferential direction (track direction) in a disk-shaped master carrier, and an arrow Y indicates a radial direction.

  2 shows a II-II cross-sectional view of the master carrier 3 shown in FIG. 1, that is, a cross-sectional view along a plane perpendicular to the plane and parallel to the track direction X. FIG.

  The master carrier 3 includes a substrate 31 having a concavo-convex pattern on the surface, a ferromagnetic layer 32 formed in order on the substrate 31, and a protective layer. Here, all the layers are formed over the entire surface along the concavo-convex pattern. The ferromagnetic layer 32 may be provided only on the upper surface of the convex portion of the concave-convex pattern.

  The substrate 31 may be non-magnetic, but preferably has ferromagnetism, particularly preferably made of Ni or an alloy containing Ni as a main component. The substrate 31 having a concavo-convex pattern on the surface can be produced using a stamper method, a photolithography method, or the like. The height of the convex portion of the substrate (the depth of the concavo-convex pattern) is, for example, 20 to 800 nm, the length of the convex portion of the concavo-convex pattern is 50 nm to 5 μm, and the length in the circumferential direction is 50 nm to 5 μm. .

  As the magnetic material of the ferromagnetic layer 32, one having a high saturation magnetization (Ms) is preferable, and Co, Co alloy (CoNi, CoNiZr, CoNbTaZr, etc.), Fe, Fe alloy (FeCo, FeCoNi, FeNiMo, FeAlSi, FeAl, FeTaN). ), Ni, Ni alloy (NiFe). Particularly preferred are FeCo and FeCoNi. As the ferromagnetic layer 32, a magnetic layer having a small coercive force such as soft magnetism or semi-hard magnetism is mainly used. Formation of the ferromagnetic layer 32 on the substrate 31 can be performed using a sputtering method, a magnetic material using a vacuum film forming means such as a vacuum deposition method or an ion plating method, a plating method, or the like.

  The protective layer 34 is a hard protective layer mainly composed of carbon, and is a carbon film or a diamond-like carbon (DLC) film. The thickness of this protective layer is preferably 3 to 20 nm. The protective layer 34 can be formed by sputtering, and the surface energy of the protective layer is adjusted by adjusting the film forming pressure during sputtering, that is, the initial surface energy of the master carrier is adjusted. The surface energy can be increased by reducing the film formation pressure during sputtering, and the surface energy can be reduced by increasing the film formation pressure. The initial surface energy Es of the slave medium is measured, and the deposition pressure is adjusted so that the ratio Em / Es of the initial surface energy Em of the master carrier to the initial surface energy Es is 1.2 or more. For example, when the slave medium is a general hard disk medium having a lubricant formed on the outermost surface, the surface of the hard disk medium is inactive due to the presence of the lubricant, and the initial surface energy Es is 50 to 50. 55 mN / m. Therefore, the deposition pressure during deposition of the protective layer is such that Em is 60 to 66 mN / m or more (Em = 60 mN or more when Es = 50 mN / m, Em = 66 mN or more when Es = 55 mN / m). Adjust. For example, in the case of a master carrier comprising a substrate made of Ni and a ferromagnetic layer made of FeCo as a protective layer, an initial surface energy of 55 to 75 mN / m can be obtained by changing the pressure at the time of carbon film formation. The master carrier can be obtained.

  As the slave medium 2, a disk-shaped magnetic recording medium having a coating type magnetic recording layer or a metal thin film type magnetic recording layer, such as a hard disk medium or a high-density flexible disk, can be used.

  In the case of a magnetic recording medium having a metal thin film type magnetic recording layer, Co, Co alloy (CoPtCr, CoCr, CoPtCrTa, CoPtCrNbTa, CoCrB, CoNi, Co / Pd, etc.), Fe, Fe alloy (FeCo FePt, FeCoNi) can be used. The magnetic layer preferably has a high magnetic flux density, and has magnetic anisotropy in the in-plane direction for in-plane recording and in the vertical direction for perpendicular recording, in order to perform clear transfer. The preferred magnetic layer thickness is 10 to 500 nm, more preferably 20 to 200 nm.

  In addition, a nonmagnetic underlayer is preferably provided under the magnetic layer (on the substrate side) in order to give the magnetic layer the necessary magnetic anisotropy. As the underlayer, Cr, CrTi, CoCr, CrTa, CrMo, NiAl, Ru, Pd, etc. can be used, but the crystal structure and lattice constant coincide with the crystal structure and lattice constant of the magnetic layer provided thereon. You need to choose what you want. The thickness of the preferred nonmagnetic layer is 10 to 150 nm, more preferably 20 to 80 nm.

  Further, in the case of a perpendicular magnetic recording medium, a soft magnetic backing layer may be provided under the nonmagnetic underlayer in order to stabilize the perpendicular magnetization state of the magnetic layer and improve the sensitivity during recording and reproduction. . As this backing layer, NiFe, CoCr, FeTaC, FeAlSi, or the like can be used. The thickness of the preferable backing layer is 50 to 2000 nm, more preferably 60 to 400 nm.

  Next, an embodiment of a magnetic transfer method for transferring information to a slave medium using the magnetic transfer master carrier of the present invention will be described.

  FIG. 3 is a perspective view showing the slave medium 2 and the master carriers 3 and 4. The slave medium is, for example, a disk-shaped magnetic recording medium such as a hard disk or a flexible disk having a magnetic recording layer formed on both sides or one side. Further, in the present embodiment, the disk-shaped substrate 21 is provided with the in-plane magnetic recording layers 22 on both surfaces (see FIG. 5), and the recording surfaces 2b and 2c are formed.

  The master carrier 3 is the same as that shown in the above embodiment, and a concavo-convex pattern corresponding to the servo signal is formed in the servo area 35 as the concavo-convex pattern for the lower recording surface 2b of the slave medium 2. Further, the master carrier 4 is formed with an uneven pattern for the upper recording surface 2 c of the slave medium 2, which has the same layer structure as the master carrier 3.

  Although FIG. 3 shows a state where the magnetic recording medium 2 and the master carriers 3 and 4 are separated from each other, the actual magnetic transfer is performed by using the transfer patterns of the recording surfaces 2 b and 2 c of the magnetic recording medium 2 and the master carriers 3 and 4. This is done with the surface in close contact.

  FIG. 4 is a perspective view showing a schematic configuration of a magnetic transfer apparatus for performing magnetic transfer using the magnetic transfer master carrier of the present invention. The magnetic transfer device 1 obtains a close contact force by bringing the air inside the transfer holder 10 that holds the master carrier 3 and 4 and the slave medium 2 in close contact with each other and the internal space of the transfer holder 10 into a vacuum state to obtain a close contact force (not shown) A contact pressure applying means comprising a vacuum suction means and a magnetic field applying means 55 for applying a transfer magnetic field while rotating the transfer holder 10 are provided.

  The magnetic field applying means 55 includes electromagnet devices 50 and 50 disposed on both sides of the transfer holder 10, and a coil 53 is wound around a core 52 having a gap 51 extending in the radial direction of the transfer holder 10 of the electromagnet device 50. It will be. Both electromagnet devices 50, 50 generate magnetic fields in the same direction parallel to the track direction. The magnetic field applying means 55 may be a permanent magnet device instead of the electromagnet device. The magnetic field applying means in the case of perpendicular recording can be composed of electromagnets or permanent magnets with different polarities disposed on both sides of the transfer holder 10. That is, in the case of perpendicular recording, a transfer magnetic field is generated in a direction perpendicular to the track surface.

  Further, the magnetic field applying means 55 is configured so that the electromagnet devices 50 and 50 on both sides move toward and away from each other or the transfer holder 10 is inserted between the electromagnet devices 50 and 50 so as to allow the opening / closing operation of the transfer holder 10. The electromagnet devices 50 and 50 or the holder 10 are configured to move.

  The transfer holder 10 includes a left-side holder 11 and a right-side other holder 12 that can be moved toward and away from each other. The slave medium 2 and the master carrier 3 are accommodated in an internal space formed inside the transfer holder 10. The slave medium 2 and the master carrier 3 are overlapped and brought into close contact with each other in a state where the center positions are matched by the decompression of the internal space.

  One master carrier 3 and slave medium 2 for transferring information such as a servo signal to one side of the slave medium 2 are held by suction or the like on the pressing surface of the one side holder 11, and the slave surface is The other master carrier 4 for transferring information such as servo signals to the other surface of the medium 2 is held by suction or the like.

  Support shafts project from the center positions of the back surfaces of the one-side holder 11 and the other-side holder 12, are supported by the apparatus main body, and are linked to a rotation mechanism to be rotated during magnetic transfer.

  In addition, the internal space of the transfer holder 10 is depressurized to a predetermined degree of vacuum at the time of close contact to obtain close contact between the slave medium 2 and the master carriers 3 and 4, and the close contact surface is vented to improve the close contact. In addition to increasing the pressure, compressed air is introduced when the atmosphere is released and when it is peeled off.

  Next, a magnetic transfer method using the magnetic transfer apparatus 1 will be described. The transfer holder 10 of the magnetic transfer apparatus performs magnetic transfer to a plurality of slave media 2 by a set of master carriers 3 and 4. First, the master carriers 3 and 4 are respectively attached to the one-side holder 11 and the other-side holder 12. Keep the position aligned. Then, with the one-side holder 11 and the other-side holder 12 in an open state in which the one-side holder 11 and the other-side holder 12 are spaced apart, the slave medium 2 that has been initially magnetized in one of the in-plane direction and the vertical direction is set in the center position and then the other-side holder 12 is Move closer to the holder 11 to close it. The internal space of the transfer holder 10 containing the slave medium 2 and the master carriers 3 and 4 is depressurized by vacuum suction, and the slave medium 2 and the master carriers 3 and 4 are uniformly adhered to each other by applying an adhesion force. In order to apply the adhesion, in addition to vacuum suction, the transfer holder may be mechanically pressurized from the outside.

  Thereafter, the electromagnet device 50 is brought close to both sides of the transfer holder 10, and a transfer magnetic field is applied in a direction almost opposite to the initial magnetization by the electromagnet device 50 while rotating the transfer holder 10, according to the transfer pattern of the master carriers 3 and 4. The magnetized pattern is transferred and recorded on the magnetic recording layer of the slave medium 2.

  FIG. 5 is a diagram for explaining a basic process of magnetic transfer to the in-plane magnetic recording medium. FIG. 5A is a process of applying a magnetic field in one direction and initial DC magnetization of the slave medium. (B) is a step of bringing the master carrier and the slave medium into close contact with each other and applying a magnetic field in a direction substantially opposite to the initial DC magnetic field. FIG. (C) shows the state of the recording / reproducing surface of the slave medium after magnetic transfer. FIG. In FIG. 5, only the lower recording surface 2b side of the slave medium 2 is shown.

  As shown in FIG. 5A, an initial DC magnetic field Hin in one direction in the track direction is applied to the slave medium 2 in advance to cause the magnetization of the magnetic recording layer 22 to be initially DC magnetized. Thereafter, as shown in FIG. 5 (b), the recording surface 2b of the slave medium 2 and the transfer pattern surface of the master carrier 3 are brought into close contact with each other, and in the track direction of the slave medium 2, the initial DC magnetic field Hin is in the opposite direction. A transfer magnetic field Hdu is applied. At the place where the transfer pattern of the slave medium 2 and the master carrier 3 is in close contact, the magnetic field for transfer Hdu is sucked into the convex portion of the master carrier 3, and the magnetization of the slave medium 2 corresponding to this portion is not reversed and other portions The initial magnetization is reversed. As a result, as shown in FIG. 5C, information (servo signal in this case) corresponding to the uneven pattern of the master carrier 3 is magnetically transferred to the magnetic recording layer 22 of the lower recording surface 2b of the slave medium 2. To be recorded. Here, the magnetic transfer by the lower master carrier 3 to the lower recording surface 2b of the slave medium 2 has been described, but the upper recording surface 2c of the magnetic recording medium 2 is also brought into close contact with the upper master carrier 4 in the same manner. I do. Note that the magnetic transfer to the upper and lower recording surfaces 2b and 2c of the magnetic recording medium 2 may be performed simultaneously or sequentially one by one.

  Note that the initial DC magnetic field and the transfer magnetic field need to adopt values determined in consideration of the coercivity of the slave medium, the relative permeability of the master carrier and the slave medium, and the like.

  The basic process of magnetic transfer shown in FIG. 5 is for the case where the slave medium is an in-plane recording medium. However, when the slave medium is a perpendicular recording medium, the initial magnetization direction and the application of the transfer magnetic field are applied. The direction may be a direction perpendicular to the surface. In the case of perpendicular recording, the initial magnetization of the portion in close contact with the convex portion of the master carrier is reversed and the initial magnetization of the other portion is not reversed. As a result, the magnetization pattern corresponding to the concavo-convex pattern is transferred.

  Next, the evaluation results of the magnetic transfer master carrier of the examples and comparative examples of the present invention will be described.

<First Evaluation Method and Result>
First, master carriers of examples and comparative examples will be described. Here, not the same shape as the master carrier used for transfer, but a magnetic layer and a protective layer formed on a flat Ni substrate prepared for the adhesion test was used.

  A magnetic layer (FeCo: film thickness = 100 nm) was formed on a Ni substrate (20 × 50 mm), and a carbon film (film pressure = 10 nm) was formed thereon as a protective layer by sputtering. The surface energy of the carbon film was controlled by changing the film forming pressure. The film formation pressure in each example and comparative example is as shown in Table 1.

  As the slave medium, a general hard disk medium (coercive force Hc≈276.5 kA / m (= 3500 Oe), surface energy = 55 mN / m) having a surface coated with a lubricant was used.

Table 1 shows the relationship between the initial surface energy ratio (initial surface energy of the master carrier / initial surface energy of the slave medium) and the force (adhesion force) necessary for peeling. The surface energy value was calculated from the contact angle measurement result of purified water and methylene iodide. The adhesion force is read as the force required for slave peeling using a dedicated jig and a spring gauge after the master / slave is brought into close contact at a pressure of 5 kg / cm ^2. It is the average of the measured values measured once.

  As shown in Table 1, when the surface energy ratio is 1.2 or more, which is within the scope of the present invention, the adhesion is nearly half the value compared to the case where the surface energy ratio is about 1 (Comparative Example 2), which is very reduced. It became what was done.

<Second evaluation method and result>
The second evaluation method and results will be described.

  As the master carriers of Examples 4 to 6 and Comparative Examples 3 and 4, a 2.5-inch Ni substrate having a bit pattern of 80 to 170 μm formed on the surface as a signal pattern was used, and a film thickness of 150 μm was formed on the substrate. The FeCo magnetic layer was formed, and a carbon film having a thickness of 5 μm was formed as a protective layer by sputtering. Here, the surface energy of the carbon film was controlled by changing the film formation pressure. The film formation pressure in each example and comparative example is the same as those in Examples 1 to 3 and Comparative Examples 1 and 2 shown in Table 1, and the same results are obtained for the initial surface energy, energy ratio, and adhesion. was gotten. The conditions for the slave medium, the surface energy, and the adhesion are determined in the same manner as in the first evaluation method.

Here, in order to evaluate the durability, the increase in the number of defects on the slave surface after 10,000 adhesion and peeling between the master carrier and the slave medium was measured. Here, the average value of n = 3 is shown. The number of slave defects was measured using a defect inspection machine (RS1350: manufactured by Hitachi). The target defect was a micro defect having a size of about sub μm to 1 μm.

  As shown in Table 2, compared with the increased number of defects for Comparative Examples 3 and 4, the Examples 4 to 6 having an initial surface energy ratio of 1.2 or more and a small adhesion force have 3 increased defects. It became clear that the durability was extremely high.

  As described above, by setting the initial surface energy ratio of the master carrier to the slave medium to be 1.2 or more, the force at the time of peeling is reduced, the deformation of the master carrier that occurs at the time of peeling, the slave damage is suppressed, and the master carrier It was possible to extend the life of the resin, that is, to improve the durability.

Partial perspective view of the surface of the magnetic transfer master carrier Sectional view of the magnetic transfer master carrier of FIG. Perspective view showing master carrier and slave medium The perspective view which shows schematic structure of a magnetic transfer apparatus The figure which shows the basic process of the magnetic transfer method to an in-plane magnetic recording medium

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic transfer apparatus 2 Slave medium 2a Substrate 2b, 2c Magnetic layer (magnetic recording layer)
3,4 Master carrier
10 Transfer holder
31 Board
32 Ferromagnetic layer
34 Protective layer
35 Servo area
36 Uneven pattern
50 Electromagnet device
55 Magnetic field application means

Claims (3)

A magnetic transfer master carrier having a transfer pattern on the surface according to information to be transferred to a transfer medium,
A master carrier for magnetic transfer, wherein a ratio of initial surface energy to initial surface energy of the transfer medium is 1.2 or more.   2. The master carrier for magnetic transfer according to claim 1, wherein a protective layer is provided on the surface.   3. The master carrier for magnetic transfer according to claim 2, wherein the protective layer is made of a carbon-based hard material.

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