JP2011070723A - Magnetic transfer method and method for manufacturing magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high quality magnetic transfer by suppressing an inversion phenomenon to a direction reverse to an initial magnetization direction of a magnetic recording medium corresponding to an uneven area of a master carrier accompanying a deviation when adhering to the master carrier in a residual magnetization state of a multi-domain structure, and by improving a degree of separation of a transfer pattern. <P>SOLUTION: A magnetic transfer method includes: an initial magnetization process; an attachmnet process; a magnetic transfer process; and a peeling process. In the attachmnet process, a master carrier 20 and a magnetic recording medium 10 are closely attached to each other, while a magnetic field during attachmnet is applied to the master carrier 20 in the same direction as the initial magnetization direction of the magnetic recording medium 10 in the initial magnetization process. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic transfer method for magnetically transferring information to a magnetic recording medium, particularly a perpendicular magnetic recording medium, and a method for manufacturing a magnetic recording medium using the magnetic transfer method.

  In general, with the increase in the amount of information, a magnetic recording medium is desired that has a large capacity for recording a large amount of information, is inexpensive, and can read out a necessary portion preferably in a short time and can perform so-called high-speed access. It is rare. As an example of these, high-density magnetic recording media (magnetic disk media) used in hard disk devices and flexible disk devices are known, and in order to realize a large capacity, a magnetic head is scanned accurately with a narrow track width. So-called tracking servo technology plays a major role. In order to perform this tracking servo, a servo signal for tracking, an address information signal, a reproduction clock signal, and the like are recorded in a so-called preformat on the disk at certain intervals.

  As a method for performing this preformat accurately and efficiently, there is a magnetic transfer method in which information such as a servo signal carried by a master carrier is magnetically transferred to a magnetic recording medium (see, for example, Patent Documents 1 and 2).

  For this magnetic transfer, for example, a master carrier having a concavo-convex pattern with a magnetic layer on the surface of at least a convex portion corresponding to information to be transferred to a magnetic recording medium (slave medium) such as a magnetic disk medium is prepared. By applying a recording magnetic field (transfer magnetic field) in a state where the master carrier and the magnetic recording medium are in close contact with each other, a magnetic pattern corresponding to information (for example, a servo signal) carried by the concavo-convex pattern of the master carrier is magnetically recorded. Since it is transferred to a medium, it can be recorded statically without changing the relative position between the master carrier and the magnetic recording medium, accurate preformat recording is possible, and the time required for recording is also long. It has the advantage of being very short.

JP 2008-65910 A JP 2009-146557 A

  In the magnetic transfer methods disclosed in Patent Documents 1 and 2, the initial magnetization direction is obtained in a state where a master carrier having a concavo-convex pattern is closely attached to a magnetic recording medium in which the magnetic layer is uniformly perpendicularly magnetized in the initial magnetization direction. When a magnetic field for recording in the opposite direction is applied, the magnetic flux density is large in the area where the convex area of the master carrier and the magnetic recording medium are in contact, and this magnetic field for recording causes the master carrier in the magnetic layer of the magnetic recording medium to The direction of magnetization of the magnetic layer in contact with the convex region is aligned with the direction of the recording magnetic field, and is reversed in the direction opposite to the direction of initial magnetization, so that magnetic information is transferred to the magnetic layer of the magnetic recording medium. For this reason, magnetic materials having high saturation magnetization have been actively used as magnetic layer materials for master carriers.

  By the way, the magnetic layer of the master carrier is about tens of nanometers and is very thin. Therefore, when a recording magnetic field is applied, a strong demagnetizing field is generated in the magnetic layer. When the demagnetizing field becomes strong, even when a magnetic material having high saturation magnetization characteristics is used, the effective magnetic field applied to the magnetic layer decreases, and the concavo-convex magnetic layer becomes unsaturated. For this reason, even if an attempt is made to increase the applied magnetic field for the purpose of ensuring the recording magnetic field strength and to bring the magnetic layer closer to saturation by increasing the effective magnetic field applied to the magnetic layer, Since the magnetization increase rate is proportional to the applied magnetic field intensity, the magnetization increase rate is substantially equivalent to a state in which a strong magnetic field is applied to the low saturation magnetization material. As a result, the magnetic field strength on the convex portion of the master carrier is increased and the magnetization of the magnetic recording medium is almost saturated, but the magnetic field strength in the region corresponding to the concave portion is also increased, and the magnetic field strength difference between the concave and convex portions is increased. Get smaller. When servo information or the like is transferred to a magnetic recording medium in a state where the magnetic field strength difference between the concaves and convexes is small, magnetization reversal occurs in the concave-corresponding region that should not be magnetized, and the quality of the recording signal deteriorates, which becomes a problem. .

  In order to suppress the occurrence of the above problem, at least in a state where a recording magnetic field is applied, the magnetic layer itself of the master carrier is saturated with a desired magnetic field strength, and the magnetization value needs to be large. . In particular, if the magnetic value of the magnetic layer itself of the master carrier can be sufficiently increased by the recording magnetic field having the minimum strength required to magnetize the magnetic recording medium, the difference in the transfer magnetic field strength between the irregularities is increased. Can be said to be preferable.

  From the above viewpoint, when a material having magnetic anisotropy in a direction perpendicular to the surface of the magnetic layer is used as the material of the magnetic layer of the master carrier, the strength of the magnetic field for recording to be applied is minimized. It is considered that the magnetization value of the magnetic layer can be easily increased. That is, it is preferable to use a magnetic material whose apparent magnetization curve has characteristics as shown in FIG.

  However, even if a material having perpendicular magnetic anisotropy is simply selected as the material constituting the magnetic layer of the master carrier, the magnetic layer has a multi-domain structure when no external magnetic field is applied. found. In this multi-domain structure, as shown in FIG. 7B, the remanent magnetization state of the magnetic layer 48 of the master carrier 20 is a state in which upward magnetization and downward magnetization are mixed, and the magnetization direction partially Is different. (For details of the structure of the magnetic recording medium 10 and the master carrier 20 shown in FIGS. 7A to 7C, refer to the description of FIGS. 2A to 2C described later.)

  7A shows an adhesion process between the magnetic recording medium 10 initially magnetized by the initial magnetic field Hi applied in one direction perpendicular to the surface in the initial magnetization process as shown in FIG. 7A and the master carrier 20 having the multi-domain structure. In FIG. 7B, as indicated by a chain line, a part of the magnetic layer 16 of the magnetic recording medium 10 in contact with or close to the magnetic layer 48 of the convex portion 44 of the master carrier 20 has an initial magnetization direction corresponding to the multi-domain structure. Unnecessary transfer occurs in which the magnetization is reversed in the reverse direction. After that, a pressing force for contact acts, and deformation (flattening) of the master carrier 20 and the magnetic recording medium 10 causes a slight lateral displacement of nanometer order to the contact position of the convex portion 44 according to the contact. When this occurs, the portion reversed by the above unnecessary transfer moves to a position facing the recess 46. In this concave portion corresponding region, the intensity of the recording magnetic field Hd acting in the magnetic transfer step as shown in FIG. 7C is smaller than that of the convex region, so that the reversal magnetization s in that portion is also after this transfer step. As a result, the separation degree of the transfer pattern is deteriorated, the transfer quality is lowered, and the initialization signal is missing in the transfer signal.

  The present invention has been made in view of such circumstances, and magnetic recording corresponding to the concave region in the concave-convex pattern of the master carrier is performed so that unnecessary transfer does not occur when the master carrier and the magnetic recording medium are in close contact with each other. Magnetic transfer method that suppresses disturbance of initial magnetization caused by displacement of contact position at the time of contact of a medium, has a good degree of separation of transfer recorded magnetic patterns, and enables high-quality magnetic transfer, and the transfer method An object of the present invention is to provide a method for manufacturing a magnetic recording medium using the above-mentioned.

The magnetic transfer method of the present invention includes an initial magnetization step in which a magnetic layer of a magnetic recording medium is initially magnetized by applying an initial magnetic field in an initial magnetization direction that is one direction perpendicular to the surface of the magnetic layer;
An adhesion step of closely adhering a magnetic transfer master carrier having a pattern-shaped convex portion having a perpendicular magnetic anisotropy magnetic layer on the surface of the magnetic recording medium after the initial magnetization step;
A magnetic transfer step in which a magnetic field for recording is applied in a direction opposite to the initial magnetization direction in a state where the magnetic recording medium and the master carrier are in close contact with each other, and magnetic information is transferred to the magnetic recording medium;
In a magnetic transfer method including a peeling step of peeling the master carrier in close contact with the magnetic recording medium from the magnetic recording medium,
The adhesion step is characterized in that the master carrier and the magnetic recording medium are adhered to each other while applying a magnetic field during adhesion in the same direction as the initial magnetization direction to the master carrier.

  In that case, it is preferable that the magnetic field strength of the magnetic field at the time of adhesion applied in the adhesion process is not less than 0.1 times the saturation magnetic field Hs of the magnetic layer of the master carrier.

  In the peeling step, it is preferable that the master carrier and the magnetic recording medium are peeled while applying a peeling magnetic field in the direction opposite to the initial magnetization direction to the master carrier.

  At that time, it is preferable that the magnetic field strength of the peeling magnetic field is less than 1.2 times the reversal magnetic field Hn of the magnetic layer of the magnetic recording medium. Furthermore, the magnetic field strength of the peeling magnetic field is preferably 0.1 times or more the saturation magnetic field Hs of the magnetic layer of the master carrier.

  Further, after the peeling step, the magnetic field strength is equal to or less than twice the reversal magnetic field Hn of the magnetic layer of the magnetic recording medium in the same direction as the initial magnetization direction with respect to the magnetic recording medium peeled from the master carrier. It is preferable to further include an additional magnetization step of applying a magnetic field. In particular, in addition to peeling the master carrier and the magnetic recording medium while applying a magnetic field during peeling in the direction opposite to the initial magnetization direction to the master carrier in the peeling step, the magnetic recording medium after peeling It is preferable to apply the additional magnetic field.

  At this time, it is preferable that the magnetic field strength of the additional magnetic field is equal to or less than the reversal magnetic field Hn of the magnetic layer of the magnetic recording medium. Furthermore, it is preferable that the magnetic field strength of the additional magnetic field is 0.1 times or more the coercive force Hc of the magnetic layer of the magnetic recording medium.

  The “reversal magnetic field Hn” is the magnitude of the magnetic field H at the start of reversal in the Kerr loop (see FIG. 5) of the magnetic layer of the magnetic recording medium.

  The “initial magnetization direction” means within ± 10 ° with respect to the vertical direction of the surface of the magnetic recording medium, and within ± 7 ° with respect to the vertical direction of the surface of the magnetic recording medium. Including. Further, “the direction opposite to the initial magnetization direction” includes not only the true reverse direction of the initial magnetization but also the direction inclined by ± 7 ° with respect to the true reverse direction of the initial magnetization.

  The “adhesion” does not necessarily include a state in which the two are completely in close contact, but also includes a state in which they are arranged close to each other at a uniform interval, and further affects the magnetization process of the present invention between the two. It also includes a state of sandwiching a substance that does not give any odor.

  Specific examples of the magnetic recording medium include disk-shaped magnetic recording media such as a hard disk and a flexible disk. In the magnetic transfer master carrier of the present invention, the magnetic layer on the surface of the convex portion is preferably soft magnetic or semi-hard magnetic. As magnetic information to be transferred and recorded, for example, a servo signal is suitable.

  The magnetic recording medium manufacturing method of the present invention is characterized in that magnetic information is transferred by the magnetic transfer method of the present invention to manufacture a magnetic recording medium.

  According to the magnetic transfer method of the present invention, an initial magnetization step of applying an initial magnetic field in an initial magnetization direction, which is a direction perpendicular to the surface of the magnetic layer, to an initial magnetization step of the magnetic layer of the magnetic recording medium; An adhesion step of closely adhering a magnetic transfer master carrier provided with a pattern-like convex portion having a magnetic layer having perpendicular magnetic anisotropy on the surface to the magnetic recording medium after the magnetization step; and the magnetic recording medium and the magnetic recording medium A magnetic transfer step for transferring a magnetic information to the magnetic recording medium by applying a recording magnetic field in a direction opposite to the initial magnetization direction in a state where the master carrier is in close contact with the master carrier, and the master carrier in close contact with the magnetic recording medium In the magnetic transfer method including a peeling step of peeling the magnetic recording medium from the magnetic recording medium, wherein the adhesion step applies the magnetic field at the time of adhesion to the master carrier in the same direction as the initial magnetization direction. By adhering the magnetic recording medium and the magnetic recording medium, a magnetic field at the time of adhesion acts on the master carrier at the time of adhesion so that the magnetization state of the master carrier is aligned in the same direction as the initial magnetization direction. The magnetic layer of the magnetic recording medium does not have a structure, and an unnecessary inversion associated with the initial contact or proximity of the close contact does not occur in the magnetic recording medium, and the recess corresponding region caused by the shift of the contact position of the protruded portion due to the subsequent contact There is no disturbance of the initial magnetization in the (non-transfer area), the degree of separation of the transferred magnetization pattern is good, and high-quality magnetic transfer can be performed.

  In particular, when the magnetic field strength of the magnetic field at the time of adhesion applied in the adhesion process is 0.1 times or more of the saturation magnetic field Hs of the magnetic layer of the master carrier, the magnetic layer of the master carrier at the time of adhesion has a multi-domain structure. Can be reliably prevented, and the loss of the initialization side signal in the recess-corresponding region can be effectively prevented, unnecessary transfer in the non-transfer region can be reduced, and the uneven pattern shape formed on the master carrier can be accurately Corresponding to the above, the magnetic pattern can be magnetically transferred to the magnetic recording medium. As a result, the signal characteristics are improved and a good tracking servo function can be exhibited in the case of a servo signal.

  In addition, when the peeling step peels off the master carrier and the magnetic recording medium while applying a magnetic field at the time of peeling in a direction opposite to the initial magnetization direction to the master carrier, The magnetization state in the layer remains in one direction and can be prevented from partially reversing. As a result, even when the magnetic recording medium is peeled off, the magnetization is transferred to the transfer region where the initial magnetization is reversed. Can be prevented, and the quality of the transfer signal formed on the magnetic recording medium can be improved.

  In particular, when the magnetic field strength of the peeling magnetic field is less than 1.2 times the reversal magnetic field Hn of the magnetic layer of the magnetic recording medium, the non-transfer area is generated by the peeling magnetic field applied in the direction opposite to the initial magnetization direction. The initial magnetization can be prevented from being reversed unnecessarily, the degree of separation of the transferred magnetization pattern is good, and high-quality magnetic transfer can be performed.

  Furthermore, when the magnetic field strength of the magnetic field at the time of peeling is 0.1 times or more of the saturation magnetic field Hs of the magnetic layer of the master carrier, the magnetic layer of the master carrier at the time of peeling is the same as in the case of the magnetic field at the time of adhesion. The unevenness formed on the master carrier can be reliably prevented from becoming a multi-domain structure, effectively preventing the transfer side signal from being lost in the convex area, reducing unnecessary inversion in the transfer area. The magnetized pattern can be magnetically transferred to the magnetic recording medium corresponding to the pattern shape accurately.

  Further, after the peeling step, the magnetic field strength is equal to or less than twice the reversal magnetic field Hn of the magnetic layer of the magnetic recording medium in the same direction as the initial magnetization direction with respect to the magnetic recording medium peeled from the master carrier. When an additional magnetization step for applying a magnetic field is further provided, a portion having a low coercive force or a reversal magnetic field in the non-transfer area of the magnetic recording medium corresponding to the concave area in the concavo-convex pattern of the master carrier is unintentionally moved to the transfer side during transfer. It is possible to reduce the magnetization reversal region including the reversed part, and as a result, the magnetic reversal region reversed to the transfer side, which is the cause of the decrease in the separation degree of the magnetization pattern, can be separated. The degree is good and high-quality magnetic transfer can be performed.

  In particular, in addition to peeling the master carrier and the magnetic recording medium while applying a magnetic field during peeling in the direction opposite to the initial magnetization direction to the master carrier in the peeling step, the magnetic recording medium after peeling When the additional magnetic field is applied, the disturbance of the initial magnetization in both steps can be further prevented, and a synergistic effect can be obtained.

  At that time, if the magnetic field strength of the additional magnetic field is 2 times or less, particularly 1 time or less of the reversal magnetic field Hn of the magnetic layer of the magnetic recording medium, the magnetization of the transfer region reversed by the application of the recording magnetic field at the time of transfer. Can be prevented from returning to the initial magnetization direction, and the transfer of the desired magnetic information can be maintained.

  Further, if the magnetic field strength of the additional magnetic field is 0.1 times or more of the coercive force Hc of the magnetic layer of the magnetic recording medium, the magnetization reversal region in the non-transfer region can be effectively reduced, and the master carrier The magnetized pattern can be magnetically transferred to the magnetic recording medium corresponding to the formed uneven pattern shape accurately.

  On the other hand, according to the method of manufacturing a magnetic recording medium of the present invention, a good tracking servo function can be obtained by transferring and forming magnetic information such as a servo signal having excellent signal characteristics by the magnetic transfer method as described above. Thus, the pre-format process is performed in a short time by the magnetic transfer method, and the cost of the magnetic recording medium can be reduced.

  Further, according to the present invention as described above, in the magnetic layer of the magnetic recording medium after magnetic transfer, in any magnetization state of the transfer region corresponding to the convex portion of the master carrier and the non-transfer region corresponding to the concave portion. , Because stable magnetic transfer with little disturbance can be performed, the characteristics required for the magnetic layer of the master carrier and its pattern shape are relaxed, tolerance for quality and other errors is increased, and there is some non-uniformity However, since good transfer quality can be ensured, the production of the master carrier is easy and the manufacturing cost can be reduced. The same effect can be obtained with respect to the quality of the magnetic recording medium.

It is explanatory drawing which shows each process (A)-(E) of the magnetic transfer method which concerns on embodiment of this invention in order. It is explanatory drawing which shows the application of the magnetic field in an initial stage magnetization process, and the magnetization state of the magnetic layer of a magnetic recording medium. It is explanatory drawing which shows the application of the magnetic field in a contact | adherence process, and the magnetization state of the magnetic layer of a magnetic recording medium, and the magnetic layer of a master carrier. It is explanatory drawing which shows the application of the magnetic field in a magnetic transfer process, and the magnetization state of the magnetic layer of a magnetic recording medium, and the magnetic layer of a master carrier. It is a schematic block diagram of the magnetic application apparatus used for a close_contact | adherence process, a magnetic transfer process, etc. It is a schematic diagram of a magnetization curve showing the magnetic properties of the magnetic layer in the master carrier It is a schematic diagram of the Kerr loop showing the magnetic characteristics of the magnetic layer in the magnetic recording medium. FIG. 6 is a reproduction waveform diagram of a transfer signal showing an example of a loss of a signal transferred to a magnetic recording medium in an evaluation criterion of an experimental example. It is explanatory drawing which shows the application of the magnetic field in the conventional initial magnetization process, and the magnetization state of the magnetic layer of a magnetic recording medium. It is explanatory drawing which shows the application of the magnetic field in the conventional adhesion process, and the magnetization state of the magnetic layer of the magnetic recording medium and the magnetic layer of the master carrier. It is explanatory drawing which shows the application of the magnetic field in the conventional magnetic transfer process, and the magnetization state of the magnetic layer of a magnetic recording medium, and the magnetic layer of a master carrier.

  First, an outline of a magnetic transfer technique for perpendicular magnetic recording will be described with reference to FIGS. 1A to 1E are explanatory views showing steps of a magnetic transfer method for perpendicular magnetic recording. 1A to 1E, reference numeral 10 denotes a magnetic recording medium as a magnetic disk for transfer (a magnetic recording medium for a perpendicular magnetic recording medium, also referred to as a perpendicular magnetic recording medium), and reference numeral 20 denotes It represents a master carrier as a magnetic transfer master carrier.

  As shown in FIG. 1A, an initial magnetic field Hi is applied in the initial magnetization direction (downward in the figure), which is one direction perpendicular to the disk plane of the magnetic recording medium 10, so that the magnetic recording medium 10 is initialized. Magnetize (initial magnetization process).

  After performing the initial magnetization, as shown in FIG. 1B, when the magnetic carrier 10 is in close contact with the master carrier 20 in the same direction (downward in the figure) as the initial magnetization direction in the magnetic recording medium 10 to be in close contact with the master carrier 20. While applying the magnetic field Hm, the master carrier 20 having the uneven pattern and the magnetic recording medium 10 after the initial magnetization are brought into close contact (contact step).

  Further, after the magnetic recording medium 10 and the master carrier 20 are brought into close contact with each other, as shown in FIG. 1C, a magnetic field for recording Hd is applied in the direction opposite to the initial magnetization direction (upward in the figure), thereby A magnetic pattern corresponding to the concavo-convex pattern of the master carrier 20 is transferred and recorded on the recording medium 10 (magnetic transfer step).

  After the magnetic transfer step, as shown in FIG. 1D, a master carrier that is in close contact with the master carrier 20 while applying a magnetic field Hh during peeling in a direction opposite to the initial magnetization direction (upward in the figure). 20 and the magnetic recording medium 10 are peeled off (peeling step).

  Subsequently, as shown in FIG. 1E, the additional magnetic field Ha is applied to the peeled magnetic recording medium 10 in the same direction as the initial magnetization direction (downward in the drawing) to perform additional magnetization (additional magnetization step). .

  The present invention is characterized in that the magnetic recording medium 10 is brought into close contact with the master carrier 20 while applying the magnetic field Hm during close contact in the close contact step (B), and the initial magnetic field Hi in the initial magnetization step (A) is characterized in that And the application of the recording magnetic field Hd in the magnetic transfer process (C) are indispensable requirements, but the application of the magnetic field Hh at the time of peeling in the peeling process (D) and the additional magnetic field Ha in the additional magnetization process (E). Is applied in order to implement a more preferable magnetic transfer method of the present invention.

  That is, in the present invention, as a first aspect, the initial magnetic field Hi is applied to the magnetic recording medium 10 in the initial magnetization step (A), and the magnetic field Hm during adhesion is applied to the master carrier 20 in the adhesion step (B). The magnetic recording medium 10 is brought into close contact, and a magnetic field for recording Hd is applied in the magnetic transfer step (C) to magnetically transfer information, and then peeled off.

  As a second aspect, the initial magnetic field Hi is applied to the magnetic recording medium 10 in the initial magnetization process (A), and the magnetic field Hm in close contact is applied to the master carrier 20 in the close contact process (B). In the magnetic transfer step (C), a magnetic field for recording Hd is applied to magnetically transfer information, and then the magnetic recording medium 10 is peeled off while applying the peeling magnetic field Hh to the master carrier 20 in the peeling step (D). It is.

  As a third aspect, the initial magnetic field Hi is applied to the magnetic recording medium 10 in the initial magnetization process (A), and the magnetic field Hm in close contact is applied to the master carrier 20 in the close contact process (B). After the magnetic field for recording Hd is applied in the magnetic transfer step (C) and the information is magnetically transferred, the master carrier 20 and the magnetic recording medium 10 are peeled off in the peeling step (D) without applying the magnetic field Hh during peeling. The additional magnetic field Ha is applied to the magnetic recording medium 10 after peeling in the additional magnetization step (E).

  As a fourth aspect, the initial magnetic field Hi is applied to the magnetic recording medium 10 in the initial magnetization process (A), and the magnetic field Hm in close contact is applied to the master carrier 20 in the close contact process (B). And magnetically transferring information by applying a recording magnetic field Hd in the magnetic transfer step (C), and then peeling off the magnetic recording medium 10 while applying the peeling magnetic field Hh to the master carrier 20 in the peeling step (D). An additional magnetic field Ha is applied to the magnetic recording medium 10 after peeling in the additional magnetization step (E).

  Next, the magnetic transfer method will be described in more detail. FIGS. 2A to 2C show the magnetic field application and the magnetic layer 16 of the magnetic recording medium 10 and the magnetic properties of the master carrier 20 in the initial magnetization step (A), the adhesion step (B), and the magnetic transfer step (C) in the magnetic transfer method. 4 is an explanatory diagram showing a magnetization state of a layer 48. FIG. 2A to 2C schematically show a layer structure, and show a thickness and an uneven shape different from actual dimensions.

  The master carrier 20 includes a base material 42 and a magnetic layer 48. The base material 42 and the magnetic layer 48 constitute a convex portion 44 and a concave portion 46 (space). That is, the convex portion 44 has the magnetic layer 48 on the surface layer of the convex portion formed by the base material 42. Further, when a protective layer, a lubricant layer, a base layer, and the like, which will be described later, are provided on the convex portion 44, the protective layer, the lubricant layer, the base layer, and the like are also included in the convex portion 44. In the present embodiment, the magnetic layer 48 is formed in addition to the convex portion 44 for reasons such as easy manufacture, but the magnetic layer 48 may be formed only on the convex portion 44.

  The magnetic layer 48 formed on the convex portion 44 becomes a bit portion corresponding to the transfer signal. This bit portion is a portion that reverses the initial magnetization, and corresponds to a transfer portion. The concave portion 46 corresponds to a non-transfer portion where magnetization is not reversed.

<Initial magnetization process>
As described above, the initial magnetization step (A) is a step in which the magnetic layer 16 of the magnetic recording medium 10 is initially magnetized in the initial magnetization direction that is one direction perpendicular to the surface thereof. The perpendicular direction means within ± 10 ° with respect to the vertical direction of the surface of the magnetic recording medium 10, and within ± 7 ° with respect to the vertical direction of the surface of the magnetic recording medium 10. preferable.

  As shown in FIG. 2A, by this initial magnetization step, the magnetic layer 16 of the magnetic recording medium 10 is applied to the surface of the magnetic recording medium 10 by an initial magnetic field Hi applied in one vertical direction (downward in the figure). The magnetic layer 16 having an easy axis in the perpendicular direction is initially magnetized in the same direction as the initial magnetic field Hi.

  The initial magnetization of the magnetic recording medium 10 is generated by an apparatus (for example, a magnetic field applying apparatus shown in FIG. 3) that can apply a perpendicular magnetic field in an initial magnetization direction that is one direction perpendicular to the surface of the magnetic recording medium 10. This is done by generating Hi. Specifically, the initial magnetic field Hi is generated by generating a magnetic field having a strength equal to or greater than the coercive force Hc of the magnetic recording medium 10. In this initial magnetization step, when the magnetization range (magnetic field application range) is narrow, the entire surface may be initially magnetized by rotating the magnetic recording medium 10 relative to the magnetic field application means.

  In addition, the applied magnetic field for initial magnetization of the magnetic recording medium 10 includes a DC magnetic field in which a constant magnetic field is continuously applied in one direction, and an AC in which the magnitude of the magnetic field varies periodically while maintaining the magnetic field in one direction. There is a magnetic field, and the initial magnetic field Hi may be a DC magnetic field or an AC magnetic field.

<Adhesion process>
As described above, the adhesion step (B) is a step of bringing the magnetic transfer master carrier 20 into close contact with the magnetic recording medium 10 after the initial magnetization step. Then, when the master carrier 20 and the magnetic recording medium 10 after the initial magnetization process are overlapped and brought into close contact with each other, the close contact magnetic field Hm is applied in the same direction as the initial magnetization direction.

  As for the application direction of the magnetic field Hm at the time of adhesion, “the same direction as the initial magnetization direction” means within ± 10 ° with respect to the vertical direction of the surface of the magnetic recording medium. It is included within ± 7 ° with respect to the vertical direction.

  In this adhesion step, the surface of the master carrier 20 on which the protruding pattern (uneven pattern) is formed and the surface of the magnetic recording medium 10 on which the magnetic layer 16 is formed are adhered to each other with a predetermined pressing force.

  As shown in FIG. 2B, by this adhesion step, the magnetic layer 16 of the magnetic recording medium 10 and the master carrier 20 are applied to the master carrier 20 while applying a magnetic field Hm during adhesion in the same direction as the initial magnetization direction (downward in the figure). The magnetic layer 48 of the master carrier 20 to which the magnetic field Hm at the time of adhesion is applied is magnetized in the same direction as the magnetic field Hm at the time of adhesion, that is, in the same direction as the initial magnetic field. Yes.

  Therefore, the magnetic layer 48 of the master carrier 20 and the magnetic layer 16 of the magnetic recording medium 10 are magnetized in the same direction, so that a slight deviation of nanometer order is caused at the contact or proximity position in the adhesion process of both. Even if it occurs, the initial magnetization in the magnetic layer 16 of the magnetic recording medium 10 is not disturbed.

  In other words, in FIG. 7B showing the conventional adhesion process in which the magnetic field Hm is not applied, the magnetic layer 48 of the master carrier 20 to which no magnetic field is applied has an upward magnetization compared to FIG. 2B showing the adhesion process of the present invention. The magnetic layer 16 of the magnetic recording medium 10 in contact with or close to the magnetic layer 48 of the convex portion 44 of the master carrier 20 corresponds to the multi-domain structure. In part, the magnetization is reversed (transferred) in the direction opposite to the initial magnetization direction.

  Then, as shown by the chain line, when a minute displacement of nanometer order occurs at the contact position of the convex portion 44 according to the close contact, the reversed portion moves to a position facing the concave portion 46, and the reversed magnetization s of the portion is changed. The phenomenon of remaining after the transfer step (FIG. 2C) and causing the deterioration of the transfer quality is prevented by bringing the master carrier 20 and the magnetic recording medium 10 into close contact while applying the magnetic field Hm at the close contact. Can do. More specifically, the deterioration of the signal waveform corresponding to the concave portion 46 of the master carrier 20 in the signal waveform on the initialization side when the magnetic transfer is completed, that is, the transfer signal waveform formed on the magnetic recording medium 10 is reduced. Can do.

  Before the magnetic recording medium 10 is brought into intimate contact with the master carrier 20, a cleaning process (burnishing or the like) for removing minute protrusions or adhering dust on the surface is performed by a glide head, a polishing body, or the like as necessary.

  In addition, as shown in FIG. 1B, the adhesion process includes a case where the master carrier 20 is adhered to only one side of the magnetic recording medium 10 and a case where the magnetic carrier is formed on both sides. May stick. The latter case has an advantage that both sides can be transferred simultaneously.

<Magnetic transfer process>
As described above, in the magnetic transfer step (C), the magnetic recording medium H and the master carrier 20 are brought into close contact with each other, and the magnetic field for recording Hd in the direction opposite to the initial magnetization direction is applied, and the magnetic recording medium 10 is magnetized. This is a step of transferring and recording information. The direction opposite to the initial magnetization direction includes not only the true reverse direction of the initial magnetization direction but also the direction inclined by ± 7 ° with respect to the true reverse direction of the initial magnetization.

  As shown in FIG. 2C, when the magnetic field for recording Hd is applied to the magnetic recording medium 10 and the master carrier 20 that are brought into close contact with each other by this magnetic transfer step, the magnetic flux is generated between the convex portion 44 of the master carrier 20 and the magnetic recording. In the area where the medium 10 is in contact, the magnetic flux density is increased and increased, and the magnetization direction of the magnetic layer 48 of the master carrier 20 is reversed from the initial magnetization by the recording magnetic field Hd and aligned in the direction of the recording magnetic field Hd. The magnetic information is transferred to the magnetic layer of the magnetic recording medium 10. On the other hand, in the concave portion 46 of the master carrier 20, the magnetic flux generated by the application of the recording magnetic field Hd is smaller than that of the convex portion 44, the magnetization direction of the magnetic layer 16 of the magnetic recording medium 10 does not change, and the initial magnetization state is changed. I keep it. As a result, information on the magnetic pattern such as a servo signal is recorded on the magnetic layer 16 of the magnetic recording medium 10 as recording magnetization that is in the direction opposite to the initial magnetization direction.

  FIG. 3 shows an example of a magnetic transfer apparatus used for magnetic transfer. The magnetic transfer device has a magnetic field applying means 60 composed of an electromagnet in which a coil 63 is wound around a core 62, and the current of the master carrier 20 that is brought into close contact with the gap 63 by flowing current from the power source to the coil 63. A magnetic field is generated perpendicularly to the magnetic layer 48 and the magnetic layer 16 of the magnetic recording medium 10. The direction of the generated magnetic field can be changed depending on the direction of the current flowing through the coil 63. Therefore, with this magnetic transfer apparatus, initial magnetization of the magnetic recording medium 10, magnetic transfer, application of a magnetic field at the time of adhesion, application of a magnetic field at the time of peeling, and additional magnetization can be performed. It is also possible to do this.

  When magnetic transfer is performed after applying the magnetic field Hm at the time of close contact in the close contact process by the magnetic transfer device, a current in a direction opposite to the direction of the current passed through the coil 63 in the close contact process is applied to the coil 63 of the magnetic field applying means 60. Shed. Thereby, the recording magnetic field Hd can be generated in the direction opposite to the initial magnetization direction.

  Magnetic transfer is performed by applying a magnetic field for recording Hd (vertical magnetic field for transfer) one time at a time by the magnetic field applying means 60 to the whole of the magnetic recording medium 10 and the master carrier 20 in close contact with each other. It is possible to simultaneously transfer the information consisting of the recorded projection-like pattern onto the magnetic layer 16 of the magnetic recording medium 10.

  When the application range of the recording magnetic field Hd is partial, the recording magnetic field Hd is applied while rotating the magnetic recording medium 10 and the master carrier 20 in close contact with a rotating means (not shown). The magnetic transfer apparatus may be configured to magnetically transfer the information consisting of the protrusion-shaped patterns recorded on the surface 20 to the magnetic layer 16 of the magnetic recording medium 10 over the entire surface. In addition to this configuration, a mechanism for rotating the magnetic field applying unit and rotating the magnetic recording medium 10 and the master carrier 20 relative to each other may be used.

  In the present embodiment, the recording magnetic field Hd is 60 to 130%, preferably 70 to 120%, of the coercive force Hc of the magnetic material constituting the magnetic layer 16 of the magnetic recording medium 10 used in the present embodiment. Magnetic transfer is performed by applying a magnetic field of. The applied magnetic field for recording Hd becomes a magnetic field larger than the coercive force Hc when the magnetic field acting on the convex portion 44 is enhanced by the concavo-convex pattern of the master carrier 20, and the magnetization reversal is opposite to the initial magnetization direction. Get up.

  As the recording magnetic field Hd, either a DC magnetic field that applies a constant magnetic field continuously in one direction or an AC magnetic field in which the magnitude of the magnetic field varies periodically while maintaining the magnetic field in one direction can be used. .

  Further, even when the concave / convex pattern of the master carrier 20 is a negative pattern having a concave / convex shape opposite to the positive pattern of FIG. 2C, the same is achieved by setting the direction of the initial magnetic field Hi and the direction of the recording magnetic field Hd to the opposite directions. This information can be magnetically transferred and recorded. Note that the initial magnetic field Hi and the recording magnetic field Hd need to adopt values determined in consideration of the coercivity of the magnetic recording medium 10, the relative permeability of the master carrier 20 and the magnetic recording medium 10, and the like.

<Peeling process>
As described above, the peeling step (D) is a step of peeling the magnetic recording medium 10 that is in close contact with the master carrier 20 after the magnetic transfer.

  In the peeling step after this magnetic transfer step, the master carrier 20 and the magnetic recording medium 10 are peeled off while applying a peeling magnetic field Hh in the direction opposite to the initial magnetization direction. Since the magnetization of the magnetic layer 48 of the master carrier 20 is directed in one direction by the application of the peeling magnetic field Hh, the signal waveform on the transfer side when the magnetic transfer is completed (of the transfer signal waveform formed on the magnetic recording medium 10). The influence on the signal waveform corresponding to the convex portion of the master carrier can be eliminated. The reason for applying the separation magnetic field Hh is also based on the fact that the magnetic layer 48 of the master carrier 20 has a multi-domain structure.

  That is, when the magnetic transfer process of FIG. 2C is not applied to the magnetic layer 48 of the master carrier 20 before the magnetic recording medium 10 is peeled off, the magnetization state is as shown in FIG. 7B. Thus, there is a possibility that a part of the magnetic layer 16 of the magnetic recording medium 10 corresponding to the convex portion 44 is reversed in the initial magnetization direction. In order to prevent this, the magnetic field disturbance in the transfer region corresponding to the convex portion 44 can be prevented by peeling while applying the peeling magnetic field Hh in the direction opposite to the initial magnetization direction (the same direction as the recording magnetic field Hd). .

  At that time, when a strong peeling magnetic field Hh, that is, a magnetic field in a direction opposite to the initial magnetization direction, is applied to the magnetic recording medium 10 peeled from the master carrier 20, a part of the non-inverted region corresponding to the recess 46 is formed. Since there is a possibility of reversal in the transfer direction, the strength is defined as described later. Note that the direction opposite to the initial magnetization direction in the application of the magnetic field Hh during separation includes not only the true reverse direction of the initial magnetization direction but also the direction inclined by ± 15 ° with respect to the true reverse direction of the initial magnetization.

  The application of a magnetic field in the peeling process is effective for controlling the residual magnetization of the magnetic layer 48 of the master carrier 20, and this effect eliminates the influence on the transfer-side signal waveform in the transfer signal waveform formed on the magnetic recording medium 10. be able to. The remanent magnetization control of the master carrier magnetic layer by applying a magnetic field in the peeling process is remarkably effective when the magnetic layer of the master carrier is a perpendicular magnetization film, but is not particularly limited thereto, and the magnetic layer of the master carrier is not limited to this. This is also effective in the case of a non-oriented film and an in-plane magnetic anisotropic film.

  The strength of the peeling magnetic field Hh is preferably less than 1.2 times the reversal magnetic field Hn in the magnetic layer 16 of the magnetic recording medium 10. If the strength of the peeling magnetic field Hh is 1.2 times or more the reversal magnetic field Hn of the magnetic recording medium 10, the amplitude of the transfer signal formed on the magnetic recording medium may be greatly reduced.

  The strength of the reversal magnetic field Hn of the magnetic recording medium can be measured by a known Kerr effect measuring device. That is, when the Kerr rotation angle is measured while pulling the magnetic field, a Kerr loop as shown in FIG. 5 can be obtained, and the reversal magnetic field Hn, which is the magnitude of the magnetic field H at the start of reversal in the Kerr loop shown in FIG. it can.

  Further, the strength of the peeling magnetic field Hh is preferably 0.10 times or more the strength of the saturation magnetic field Hs of the magnetic layer 48 in the master carrier 20. If the strength of the peeling magnetic field Hh is less than 0.1 times the saturation magnetic field Hs of the magnetic layer in the master carrier, signal loss may not be sufficiently reduced. In addition, the intensity | strength of the saturation magnetic field Hs of the magnetic layer in a master support | carrier is calculated | required like FIG. 4 from the magnetization curve obtained using a well-known vibration sample type magnetometer as mentioned above.

<Additional magnetization process>
As described above, the additional magnetization step (E) is a step of applying an additional magnetic field Ha to the magnetic recording medium 10 after magnetic transfer in the same direction as the initial magnetization direction, and applying a perpendicular magnetic field to the surface of the magnetic recording medium 10. This is performed by generating the additional magnetic field Ha by an apparatus that can perform the process (for example, the magnetic transfer apparatus of FIG. 3).

  In the additional magnetization step after the peeling, the magnetic layer 16 of the magnetic recording medium 10 corresponding to the concave portion 46 of the master carrier 20 in the magnetic transfer step is ideally in an initial magnetization state without being reversed in the transfer direction. In fact, there is a portion where the coercive force Hc or the reversal magnetic field Hn is partially low due to variations in magnetic characteristics in the magnetic layer, and the weak magnetic field generated in the recess 46 by the application of the recording magnetic field Hd. Thus, an additional magnetic field Ha is applied in the same direction as the initial magnetization direction so that the magnetization reversed in the direction opposite to the initial magnetization direction is returned to the initial magnetization direction again. By applying the additional magnetic field Ha, deterioration of the signal waveform corresponding to the concave portion 46 of the master carrier 20 among the signal waveform on the initialization side when the magnetic transfer is completed, that is, the transfer signal waveform formed on the magnetic recording medium 10 is reduced. be able to.

  At this time, when the magnetic field strength of the additional magnetic field Ha increases, a part of the region in which the region corresponding to the convex portion 44 is transferred and reversed in the direction opposite to the initial magnetization direction by application of the recording magnetic field Hd is reversed in the initial magnetization direction. Therefore, the strength of the transfer area is defined as described later.

  The magnetic field strength of the additional magnetic field Ha is not more than twice the reversal magnetic field Hn in the magnetic layer 16 of the magnetic recording medium 10. Thereby, in the non-transfer area corresponding to the concave portion 46 of the master carrier 20, the disturbance of the initial magnetization in which the magnetic layer 16 is reversed in the transfer direction can be reduced, and the transfer area corresponding to the convex portion 44 is obtained. Since the magnetic layer 48 of the magnetic recording medium 10 can be maintained in a state of being magnetized in the transfer direction, the degree of separation of the transferred magnetization pattern is further improved, and high-quality magnetic transfer is performed. be able to.

  Further, when the magnetic field applied in the additional magnetization step is set to be less than or equal to 1 times the reversal magnetic field Hn, the magnetic layer of the magnetic recording medium is magnetized in the transfer direction in the transfer region by using a weaker magnetic field. Therefore, the degree of separation of the transferred magnetization pattern is further improved, and high-quality magnetic transfer can be performed.

  Further, by making the intensity of the additional magnetic field Ha 0.1 times or more of the coercive force Hc in the magnetic layer 16 of the magnetic recording medium 10, the magnetization direction of the magnetization switching region in the transfer region is maintained and non-transferring is performed. Since the reversal part of the region can be sufficiently returned to the initial magnetization direction, the degree of separation of the transferred magnetization pattern is good, and high-quality magnetic transfer can be performed.

  Note that this additional magnetization step may be performed only on the magnetic recording medium 10 or may be performed on other magnetic recording media 10 as long as the above effects can be obtained. Specifically, an additional magnetization process may be performed on another material or medium that has been applied to, added to, superimposed on, or bonded to the magnetic recording medium.

  Further, this additional magnetization step may be performed by rotating the magnetic recording medium 10 relative to the magnetic field applying means. Further, as the additional magnetic field Ha, either a direct-current magnetic field in which a constant magnetic field is continuously applied in one direction or an alternating-current magnetic field in which the magnitude of the magnetic field periodically varies while maintaining the magnetic field in one direction can be used.

<Description of master carrier>
The base material 42 of the master carrier 20 is manufactured using a known material such as a synthetic resin such as glass or polycarbonate, a metal such as nickel or aluminum, silicon, or carbon.

  The material of the magnetic layer 48 of the master carrier 20 is not particularly limited and can be appropriately selected from known materials according to the purpose. For example, CoPt, CoPtCr, CoCr, and the like are preferable. These may be used individually by 1 type and may use 2 or more types together. There is no restriction | limiting in particular as thickness of the magnetic layer 48, According to the objective, it can select suitably, Usually, it is about 5 nm-30 nm. Moreover, there is no restriction | limiting in particular as a formation method of the magnetic layer 48, It can carry out according to a well-known method, For example, it can carry out by sputtering method, electrodeposition (electrodeposition method), etc.

  A crystal orientation layer for magnetic layer orientation and a soft magnetic underlayer may be appropriately formed between the base material 42 and the magnetic layer 48. In particular, the soft magnetic underlayer may be composed of a single layer or a plurality of layers.

The magnetic layer 48 preferably has perpendicular magnetic anisotropy. The magnetic layer 48 has “perpendicular magnetic anisotropy” means that the perpendicular magnetic anisotropy energy measured using a known magnetic torque meter is 5 × 10 ⁵ erg / cm ³ or more. It has magnetic anisotropy. "

  Further, FIG. 4 shows a magnetization curve suitable as a magnetic material constituting the magnetic layer 48 of the master carrier 20. As a characteristic of the magnetic material, the saturation magnetization Ms in the magnetization curve is preferably 500 emu / cc or more. When the saturation magnetization Ms is less than 500 emu / cc, it has perpendicular magnetic anisotropy, and the magnetic field layer magnetization is in a saturated state. Transfer characteristics may not be ensured.

  As a characteristic of the magnetic material of the magnetic layer 48, the nucleation magnetic field Hnm is preferably a positive value (Hnm> 0). If the nucleation magnetic field Hnm is Hnm ≦ 0, a large magnetic field is generated from the magnetic layer even after the magnetic field for recording Hd is removed after the magnetic transfer is completed, and over recording occurs and a desired signal cannot be recorded. There is. The nucleation magnetic field Hnm of the magnetic layer is preferably less than or equal to the applied magnetic field strength of the recording magnetic field Hd, and the saturation magnetization Ms of the magnetic layer can be used effectively.

  The saturation magnetization Ms, nucleation magnetic field Hnm, and saturation magnetic field Hs of the magnetic layer are obtained using a known vibrating sample magnetometer. The saturation magnetization Ms is obtained by obtaining a saturation magnetization value (emu) from the magnetization curve of FIG. 4 obtained using a vibrating sample magnetometer and dividing the saturation magnetization value by the volume (cc) of the magnetic layer. It is done. Similarly, the nucleation magnetic field Hnm and the saturation magnetic field Hs are obtained from the change characteristics of the magnetization curve in FIG.

  If the coercive force Hc of the magnetic layer 48 of the master carrier 20 is too large, the magnetic layer will not be magnetized by the applied magnetic field of the recording magnetic field Hd in the magnetic transfer process. In addition, when a large recording magnetic field Hd is applied during magnetic transfer, the magnetic flux acting on the recessed area also increases and disturbs the initial magnetization. Therefore, the coercive force Hc of the magnetic layer 48 is equal to that of the perpendicular magnetic recording medium 10. The magnetic layer 16 preferably has a coercive force or less, specifically 6 kOe (477.6 kA / m) or less, and more preferably 4 kOe (318.4 kA / m) or less.

  A protective layer is formed on the surface of the master carrier 20 in order to improve mechanical, frictional properties, and weather resistance. As a material for the protective layer, a hard carbon film is preferable, and inorganic carbon, diamond-like carbon, or the like formed by sputtering can be used. A layer made of a lubricant (lubricant layer) may be further formed on the hard protective layer. As this type of lubricant, a fluorine-based resin such as perfluoropolyether (PFPE) is generally used.

<Method for producing master carrier>
An original plate (Si substrate), which is a silicon wafer with a smooth surface, is prepared, and an electron beam resist solution is applied onto the original plate by a spin coating method or the like to form a resist layer, and a baking process (prebake) is performed. .

  Next, an original plate is set on the stage of an electron beam exposure apparatus (not shown) equipped with a high-precision rotary stage or an XY stage, and an electron beam modulated in accordance with a servo signal is irradiated while rotating the original plate. A predetermined pattern on almost the entire surface of the resist layer, for example, a pattern corresponding to a servo signal extending linearly in the radial direction from the center of rotation to each track is drawn and exposed on portions corresponding to each frame on the circumference (electron beam drawing) To do.

  The resist layer is developed, and the exposed (drawn) portion is removed to form a coating layer having a desired thickness with the remaining resist layer. This coating layer becomes a mask for the next process (etching process). The resist applied on the substrate can be either a positive type or a negative type, but the exposure (drawing) pattern is reversed between the positive type and the negative type. After this development process, a baking process (post-bake) is performed in order to increase the adhesion between the resist layer and the original plate.

  Next, the original plate is removed (etched) by a predetermined depth from the surface through the opening of the resist layer. In this etching, anisotropic etching is desirable to minimize undercut (side etching). As such anisotropic etching, reactive ion etching (RIE) can be preferably employed.

  Next, the resist layer is removed. As a method for removing the resist layer, ashing can be adopted as a dry method, and a removing method using a stripping solution can be adopted as a wet method. Through the ashing process described above, a master disk on which a reverse type of a desired concavo-convex pattern is formed is produced.

  Thereafter, a conductive layer is formed on the surface of the master with a uniform thickness. As a method for forming this conductive layer, various metal film forming methods including PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), sputtering, and ion plating can be applied.

  Thus, if one layer of the conductive film is formed, an effect that the electrodeposition of the metal in the next step (electroforming step) can be performed uniformly is obtained. The conductive layer is preferably a film containing Ni as a main component. Such a film containing Ni as a main component is suitable for a conductive film because it is easy to form and is hard. Although there is no restriction | limiting in particular as a film thickness of this electroconductive layer, about several dozen nm is generally employable.

  Next, a metal plate made of metal (here, Ni) having a desired thickness is laminated on the surface of the master by electroforming (reverse plate forming step). This step is performed by immersing the master in the electrolyte of the electroforming apparatus, using the master as the anode, and energizing between the cathode and the concentration of the electrolyte at this time, pH, how to apply the current, etc. It is required that the laminated metal plate (base material 42) be carried out under optimum conditions without distortion.

  Then, the master disc on which the metal plates are laminated as described above is taken out from the electrolytic solution of the electroforming apparatus and immersed in pure water in a peeling tank (not shown). In the peeling tank, the metal plate is peeled from the master, and the base material 42 having an uneven pattern inverted from the master is obtained.

  Next, the magnetic layer 48 is formed on the uneven surface of the substrate 42. The material of the magnetic layer is made of, for example, CoPt. The thickness of the magnetic layer 48 is preferably in the range of 10 nm to 320 nm, more preferably in the range of 20 nm to 300 nm, and still more preferably 30 nm to 100 nm. The magnetic layer 48 is formed by sputtering using a target of the above material.

  Thereafter, the inner diameter and outer diameter of the base material 42 are punched into a predetermined size. Through the above process, the master carrier 20 having the concavo-convex pattern provided with the magnetic layer 48 is produced.

  On the surface of the master carrier 20, a servo pattern composed of a concavo-convex pattern is formed. Although not shown in the figure, a protective film (protective layer) such as diamond-like carbon may be provided on the magnetic layer 48 on the surface of the master carrier 20 by sputtering, and a lubricant layer is further provided on the protective film. It may be provided.

  The purpose of forming the protective layer is to prevent the magnetic layer 48 from being easily damaged when the master carrier 20 and the magnetic recording medium 10 are brought into close contact with each other, and cannot be used as the master carrier 20. In addition, the lubricant layer has an effect of preventing the occurrence of scratches due to friction occurring when contacting the magnetic recording medium 10 and improving the durability.

  Specifically, a structure in which a carbon film having a thickness of 2 to 30 nm is formed as a protective layer and a lubricant layer is further formed thereon is preferable. Further, in order to reinforce the adhesion between the magnetic layer 48 and the protective layer, an adhesion reinforcing layer such as Si may be formed on the magnetic layer 48 and then the protective layer may be formed.

<Description of magnetic recording medium>
Next, a magnetic recording medium (perpendicular magnetic recording medium) will be described. A magnetic recording medium 10 shown in FIGS. 1 and 2 is a disk-shaped magnetic recording medium such as a hard disk or a flexible disk having a magnetic recording layer 16 formed on both sides or one side, and in particular, easy magnetization of the magnetic recording layer. The perpendicular magnetic recording medium is formed in a direction perpendicular to the recording surface. Here, an example in which the magnetic layer 16 is formed on one surface of the substrate is shown, but an embodiment in which the magnetic layer is formed on both the front and back surfaces of the substrate is also possible.

  The magnetic recording medium 10 has a structure in which a soft magnetic layer (soft magnetic underlayer; SUL), a nonmagnetic layer (intermediate layer), and a magnetic layer (perpendicular magnetic recording layer) are sequentially stacked on a nonmagnetic substrate such as glass. The magnetic layer is further covered with a protective layer and a lubricating layer.

  The disk-shaped substrate is made of a nonmagnetic material such as glass or aluminum. After a soft magnetic layer is formed on the substrate, a nonmagnetic layer and a magnetic layer are formed.

  The soft magnetic layer is useful for stabilizing the perpendicular magnetization state of the magnetic layer and improving the sensitivity during recording and reproduction. The material used for the soft magnetic layer is preferably a soft magnetic material such as CoZrNb, FeTaC, FeZrN, FeSi alloy, FeAl alloy, FeNi alloy such as permalloy, and FeCo alloy such as permendur. This soft magnetic layer has a magnetic anisotropy in a radial direction (radially) from the center of the disk to the outside.

  The thickness of the soft magnetic layer is preferably 20 nm to 2000 nm, and more preferably 40 nm to 400 nm.

  The nonmagnetic layer is provided for reasons such as increasing the perpendicular magnetic anisotropy of the magnetic layer to be formed later. The material used for the nonmagnetic layer is preferably Ti (titanium), Cr (chromium), CrTi, CoCr, CrTa, CrMo, NiAl, Ru (ruthenium), Pd (palladium), Ta, Pt or the like. The nonmagnetic layer is formed by depositing the above material by a sputtering method. The thickness of the nonmagnetic layer is preferably 10 nm to 150 nm, and more preferably 20 nm to 80 nm.

The magnetic layer 16 is formed of a perpendicular magnetization film (with the easy axis of magnetization in the magnetic film oriented mainly perpendicular to the substrate), and information is recorded on the magnetic layer. Materials used for the magnetic layer are Co (cobalt), Co alloy (CoPtCr, CoCr, CoPtCrTa, CoPtCrNbTa, CoCrB, CoNi, etc.), Co alloy-SiO ₂ , Co alloy-TiO ₂ , Fe, Fe alloy (FeCo, FePt) , FeCoNi, etc.) are preferred. These materials have a large magnetic flux density and have perpendicular magnetic anisotropy by adjusting film forming conditions and composition. The magnetic layer is formed by depositing the above material by a sputtering method. The thickness of the magnetic layer is preferably 10 nm to 500 nm, and more preferably 15 nm to 200 nm.

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

[Examples 1 to 8]
A master carrier and a magnetic recording medium are prepared as follows, and the magnetic transfer method is performed in the above-described first mode (that is, the peeling magnetic field Hh and the additional magnetic field Ha are not applied). As shown in [Table 1] below, a magnetic recording medium was placed while applying a magnetic field Hm at the time of contact with a changed magnetic field strength, and then a perpendicular magnetic field for recording was applied in a state of being in close contact by applying pressure. The experimental result which calculated | required the omission degree of the waveform of the transfer signal of the magnetic recording medium after transfer is shown. The comparison is made in comparison with Comparative Example 1 in which the magnetic field Hm at the time of adhesion is not applied and Comparative Example 2 in which the magnetic field Hm at the time of adhesion in the reverse direction is applied.

<Preparation of master carrier>
An electron beam resist was applied to a thickness of 100 nm on an 8-inch Si (silicon) wafer (substrate) by spin coating. After coating, the resist on the substrate was exposed using a rotary electron beam exposure apparatus, and the exposed resist was developed to produce a resist Si substrate having a concavo-convex pattern.

  Thereafter, using the resist as a mask, the substrate was subjected to reactive ion etching to dig up the concave portions of the concave / convex pattern. After the etching treatment, the resist remaining on the substrate was washed with a soluble solvent and removed. After removal, the substrate was dried and used as a master for preparing a master carrier.

  The production of the master carrier intermediate (substrate) by the plating method will be described. A 20 nm thick Ni (nickel) conductive film was formed on the master by sputtering. The master after forming the conductive film was immersed in a sulfamic acid Ni bath, and a 200 μm thick Ni film was formed by electrolytic plating. Thereafter, the Ni film was peeled off from the master and washed to obtain a Ni master carrier intermediate (substrate).

  A method for forming the magnetic layer will be described. On the master carrier intermediate, a base layer made of a Ta film is formed by sputtering to a thickness of 10 nm, and then a Co 80 at% Pt 20 at% magnetic layer is formed on the base layer to a thickness of 30 nm. A master carrier was obtained.

  The underlayer (Ta film) is formed under the following conditions: target material: Ta, target-base distance: 200 mm, argon pressure: 0.5 Pa, DC power: 350 W. The film formation conditions for the magnetic layer are: target material: Co 80 at% Pt 20 at%, target-base distance: 200 mm, argon pressure: 0.1 Pa, DC power: 1000 W. The saturation magnetic field Hs of the magnetic layer 48 (perpendicular magnetization film) of the master carrier 20 produced in this manner was 5 kOe (398 kA / m).

  In the master carrier produced in this example, space portions (concave portions) and line portions (convex portions) are alternately formed, and a pattern for transfer having an unevenness period of 160 nm is formed.

<Preparation of perpendicular magnetic recording medium>
In this example, a soft magnetic layer, a first nonmagnetic alignment layer, and a second nonmagnetic layer are formed on a 2.5 inch (outer diameter 63.5 mm) glass substrate as a substrate of the magnetic recording medium 10 by using a sputtering method. A magnetic orientation layer, a magnetic recording layer, and a protective layer were formed in this order. Further, a lubricant layer was formed on the protective layer by a dipping method.

  CoZrNb was used as the material of the soft magnetic layer. The thickness of the soft magnetic layer was 100 nm. A glass substrate was placed facing the CoZrNb target, Ar gas was introduced at a pressure of 0.6 Pa, and a film was formed at DC 1500 W.

  Ti: 5 nm was formed as the first nonmagnetic alignment layer, and Ru: 6 nm was formed as the second nonmagnetic alignment layer. The first nonmagnetic alignment layer was disposed opposite to the Ti target, Ar gas was introduced at a pressure of 0.5 Pa, discharged at DC 1000 W, and a Ti seed layer was formed to a thickness of 5 nm. . After the formation of the first nonmagnetic alignment layer, it is arranged to face the Ru target, Ar gas is introduced at a pressure of 0.8 Pa, discharged at DC 900 W, and the second nonmagnetic alignment is performed to a thickness of 6 nm. Layers were deposited.

CoCrPtO: 18 nm was formed as the magnetic recording layer. Arranged facing the CoCrPtO target, Ar gas containing 0.06% O ₂ was introduced at a pressure of 14 Pa, and discharged at DC 290 W to produce a magnetic recording layer.

  After the magnetic recording layer was formed, it was placed facing the carbon target, Ar gas was introduced at a pressure of 0.5 Pa, and discharge was performed at 1000 W DC to form a C protective layer (4 nm). This magnetic recording medium had a coercive force Hc of 5.0 kOe (398 kA / m) and a reversal magnetic field Hn of 1.25 kOe (99.5 kA / m).

  Further, a perpendicular magnetic recording medium was prepared by applying a PFPE lubricant with a thickness of 2 nm to the magnetic recording medium by a dip method.

<Magnetic transfer process>
Initial magnetization was performed on the magnetic recording medium. The strength of the initial magnetic field Hi applied during the initial magnetization (initial magnetic field strength) was 10 kOe (796 kA / m).

  The master carrier was placed opposite to the initialized magnetic recording medium, and both were brought into close contact with the master carrier at a pressure of 1.5 MPa while applying a magnetic field Hm during close contact in the initial magnetization direction. The magnetic field at the time of adhesion applied in this adhesion process is changed stepwise from 100 Oe (7.96 kA / m) to 10000 Oe (7960 kA / m) as shown in [Table 1] described later in [Examples 1 to 8]. In addition, as [Comparative Example 1], the magnetic field at the time of adhesion in the adhesion process is not applied, and as [Comparative Example 2], the magnetic field in the direction opposite to the initial magnetization direction (application direction of the recording magnetic field at the time of magnetic transfer) is applied in the adhesion process. The case where a magnetic field having an intensity of 250 Oe (19.9 kA / m) is applied is compared.

  In the following [Table 1] to [Table 3], the unit of the magnetic field intensity is displayed as non-SI unit Oe (Oersted). Conversion to the Si unit can be performed by 1Oe = 79.6 A / m, but the description is omitted.

  Next, with the master carrier and the magnetic recording medium in close contact with each other, a magnetic field for recording Hd was applied in the direction opposite to the initial magnetization direction to perform magnetic transfer. The magnetic field strength of the recording magnetic field used for magnetic transfer was 4.7 kOe (374 kA / m).

<Transcription evaluation>
The reproduced waveform of the signal transferred by the concavo-convex pattern of the master carrier with respect to the perpendicular magnetic recording medium after the magnetic transfer was detected. For the detection, an evaluation apparatus (LS-90, manufactured by Kyodo Denshi Co., Ltd.) equipped with a GMR head having a lead width of 80 nm was used.

<Evaluation results>
“Evaluation criteria” for lack of initialization side signal will be described. It was evaluated how many initialization side signals were missing in a signal having a length corresponding to 100 periods of the concavo-convex pattern. FIG. 6 shows a part of a reproduction waveform example. As an evaluation standard, the number of missing signals on the initialization side where the signal is missing at an intensity of 75% or less of the distance between 0V (0%) of the signal amplitude and the signal peak (100%) on the initialization side is counted. The results are shown in the following [Table 1].

  In “Table 1”, “determination of signal loss” is defined as x when the number of missing pieces exceeds 20, ○ when the number of missing pieces is 20 or less, ◎ when the number of missing pieces is 10 or less, and no missing piece. The case of individual was marked as ◎ (not shown in Table 1). For example, in the case of a preformat servo signal transferred and recorded by the magnetic transfer method of the present invention, each read bit signal is not directly used, but is used as an output difference signal for servo tracking. Since the omission is allowed, the evaluation is as described above.

  From the results of the above [Table 1], when the magnetic field Hm at the time of adhesion is applied in the initial magnetization direction at the time of adhesion as in [Examples 1 to 8] of the present invention, initialization is performed compared to [Comparative Example 1] where no magnetic field is applied. It can be seen that the number of missing signals on the side decreases. It can also be seen that the number of missing signals decreases as the magnetic field strength in the initial magnetization direction at the time of adhesion increases, that is, from [Example 1] to [Example 8]. In addition, since [Examples 3 to 8] obtained particularly good results, the magnetic field strength of the magnetic field Hm at the time of adhesion applied at the time of adhesion is equal to the saturation magnetic field Hs of the magnetic layer (perpendicular magnetization film) of the master carrier. In this example, 0.1 Hs or more (500 Oe or more) is preferable with respect to 5 kOe).

  On the other hand, if a magnetic field is applied to the transfer side (in the direction opposite to the initial magnetization direction) during close contact as in [Comparative Example 2], the number of signal missing on the initialization side increases. This is because the domain of the magnetic layer of the perpendicular master carrier is oriented in the direction opposite to the initial magnetization direction, so that the initial magnetization side corresponding to the concave portion of the magnetic recording medium caused by the misalignment of the master carrier and the magnetic recording medium during adhesion This is presumably because the magnetization reversal of the portion becomes more remarkable.

[Examples 9 to 15]
The master carrier and the magnetic recording medium are the same as those in the above [Examples 1 to 8], and the magnetic transfer method applies the above-described second mode (that is, the magnetic field Hh at the time of peeling is applied in the peeling process but the additional magnetic field Ha Is not applied).

  Specifically, initial magnetization was performed on the magnetic recording medium, and the magnetic field strength of the initial magnetic field Hi at that time was 10 kOe as in [Example 1]. In the adhesion step, a pressing force of 1.5 MPa is applied, and the magnetic field Hm in the initial magnetization direction having a magnetic field strength of 2000 Oe is applied to the master carrier while being applied to the master carrier, as in [Example 6]. It was. In the subsequent magnetic transfer process, magnetic transfer was performed by applying a recording magnetic field Hd having a magnetic field strength of 4.7 kOe in the direction opposite to the initial magnetization direction, as in [Example 1]. In the subsequent peeling process, the magnetic field strength of the peeling magnetic field Hh applied to the master carrier is changed stepwise from 100 Oe to 2000 Oe in [Examples 9 to 15] as shown in [Table 2] below. While being applied in the direction opposite to the magnetization direction, the magnetic recording medium was peeled off. The experimental result which calculated | required the loss | missing degree of the waveform of the transcription | transfer signal of the magnetic recording medium after transcription | transfer and the transcription | transfer signal amplitude was shown. In addition, it shows in comparison with Comparative Example 3 in which the magnetic field Hm at the time of adhesion and the magnetic field Hh at the time of peeling are not applied.

<Transcription evaluation>
For the perpendicular magnetic recording medium after magnetic transfer, the reproduced waveform of the signal transferred by the concave / convex pattern of the master carrier was detected using the same evaluation apparatus as in [Example 1].

<Evaluation results>
The evaluation criteria in [Examples 9 to 15] evaluate initialization side and transfer side signal loss and evaluate transfer signal amplitude.

  “Evaluation of missing initialization-side and transfer-side signals” evaluated how many initialization-side signals and transfer-side signals were missing in a signal having a length corresponding to 100 periods of the concavo-convex pattern. In the reproduction waveform example shown in FIG. 6, as in the same manner as described above, the intensity of 75% or less of the signal amplitude from 0 V (0%) to the distance between the initialization side and transfer side signal peak (100%) In FIG. 6, the number of missing signals on the initialization side and transfer side where the signal is missing is counted (in the case of FIG. 6, the initialization side is three of a, b, and c, and the transfer side is one of d). Table 2]. In the “determination of signal loss”, the case where the number of missing pieces exceeds 20 is indicated as “x”, the case where the number of missing pieces is 20 or less, “◯”, the case where the number of missing pieces is 10 or less, “◎”, and the case where the number of missing pieces is 0. ◎◎ (Not in Table 2).

  In “Evaluation of transfer signal amplitude”, the transfer signal amplitude was set to p-p (peak to peak) of the signal, the signal amplitude of [Comparative Example 3] was set to 1, and the ratio was shown. In addition, as “determination of signal amplitude”, the case where the signal amplitude exceeded 0.8 was evaluated as “◎”, and the case where it was 0.8 or less was evaluated as “◯”. A comprehensive judgment is made in combination with the judgment of the signal loss.

  From the results of [Table 2] above, not only the magnetic field Hm at the time of adhesion is applied in the initial magnetization direction at the time of adhesion as in the present invention [Examples 9 to 15], but also the magnetic field at the time of separation in the direction opposite to the initial magnetization direction at the time of separation. When Hh is applied, the number of missing signals on the initialization side can be reduced and the number of missing signals on the transfer side can be reduced as compared with [Comparative Example 3] in which both magnetic fields are not applied, and the signal quality can be further improved. I understand. The number of missing signals on the transfer side decreases as the magnetic field strength in the direction opposite to the initial magnetization direction at the time of peeling increases, that is, from [Example 9] to [Example 15]. When the intensity is 0.1 Hs or more (500 Oe or more) with respect to the saturation magnetic field Hs (5 kOe in this example) of the magnetic layer of the master carrier, the number of missing signals on the transfer side is 10 or less. On the other hand, when the magnetic field strength increases as in [Examples 14 and 15], the transfer signal amplitude tends to decrease.

  The magnetic field strength of the peeling magnetic field Hh applied at the time of peeling does not decrease the transfer signal amplitude more than necessary, so that the magnetic field strength of the magnetic layer of the magnetic recording medium is 1 with respect to the reversal magnetic field Hn (1.25 kOe in this example). Less than 2 times (less than 1.5 kOe), that is, [Examples 9 to 13] is a preferable range. Furthermore, when a range in which the magnetic field strength of the separation magnetic field Hh is 0.1 Hs or more with respect to the saturation magnetic field Hs of the magnetic layer of the master carrier is taken into account, as shown in the comprehensive judgment, [Examples 11 to 13] Is the most preferred range.

[Examples 16 to 22]
The master carrier and the magnetic recording medium are the same as those in the above [Examples 1 to 15], and the magnetic transfer method applies the above-described fourth mode (that is, the peeling magnetic field Hh is applied in the peeling step, and the additional step). In this example, the additional magnetic field Ha is applied).

  Specifically, initial magnetization was performed on the magnetic recording medium, and the magnetic field strength of the initial magnetic field Hi at that time was 10 kOe as in [Example 1]. In the adhesion step, a pressing force of 1.5 MPa is applied, and the magnetic field Hm in the initial magnetization direction having a magnetic field strength of 2000 Oe is applied to the master carrier while being applied to the master carrier, as in [Example 6]. It was. In the subsequent magnetic transfer process, magnetic transfer was performed by applying a recording magnetic field Hd having a magnetic field strength of 4.7 kOe in the direction opposite to the initial magnetization direction, as in [Example 1]. In the subsequent peeling step, the magnetic carrier was peeled from the master carrier while applying a peeling magnetic field Hh having a magnetic field strength of 500 Oe in the direction opposite to the initial magnetization direction to the master carrier in the same manner as in Example 11. In the subsequent additional magnetization step, the magnetic field strength of the additional magnetic field Ha applied to the magnetic recording medium after peeling is stepwise from 200 Oe to 2500 Oe in [Examples 16 to 22] as shown in [Table 3] below. A change was made and additional magnetization was performed by applying in the initial magnetization direction. The experimental result which calculated | required the loss | missing degree of the waveform of the transcription | transfer signal of the magnetic recording medium after transcription | transfer and the transcription | transfer signal amplitude was shown.

<Transcription evaluation>
For the perpendicular magnetic recording medium after magnetic transfer, the reproduced waveform of the signal transferred by the concave / convex pattern of the master carrier was detected using the same evaluation apparatus as in [Example 1].

<Evaluation results>
The evaluation criteria in [Examples 16 to 22] are exactly the same as those in the above [Examples 9 to 15]. Similarly, the initialization side and transfer side signal missing are evaluated, and the transfer signal amplitude is evaluated. ing. A detailed description of these evaluations is omitted.

  Table 3 below shows the number of missing signals on the initialization side and the transfer side and the determination thereof, the amplitude of the transfer signal and the determination result. Determination of signal loss and signal amplitude is the same as the determination in [Table 2].

  From the results of [Table 3] above, not only the magnetic field Hm at the time of adhesion is applied in the initial magnetization direction at the time of adhesion as in the [Examples 16 to 22] of the present invention, but also the magnetic field at the time of peeling in the direction opposite to the initial magnetization direction at the time of peeling. By applying Hh and applying the additional magnetic field Ha in the initial magnetization direction only to the peeled magnetic recording medium, the number of missing signals on the initialization side can be further reduced. When the magnetic field strength of the additional magnetic field Ha increases, the number of missing signals on the initialization side becomes almost zero, but the number of missing signals on the transfer side tends to increase. As for the amplitude of the transfer signal, good characteristics are maintained by setting the magnetic field strength of the separation magnetic field Hh within a preferable range of [Table 2].

  The intensity of the additional magnetic field Ha is less than twice (2) with respect to the reversal magnetic field Hn (1.25 kOe in this example) of the magnetic layer of the magnetic recording medium so that the number of missing signals on the transfer side is 20 or less. 0.5 kOe or less) is preferable. In particular, in terms of not increasing the number of missing signals on the transfer side, the reversal magnetic field Hn (1.25 kOe in this example) is more preferably one time or less. Further, the strength of the additional magnetic field Ha is more than 0.1 times the coercive force Hc (in this example, 5 kOe), that is, [Examples 18 to 20] so that the signal loss on the initialization side becomes zero. This is a preferable range.

DESCRIPTION OF SYMBOLS 10 Magnetic recording medium 16 Magnetic layer 20 Master carrier 42 Base material 44 Convex part 46 Concave part 48 Magnetic layer 60 Magnetic field application means 62 Core 63 Coil 64 Gap Hi Initial magnetic field Hd Magnetic field for recording Hm Magnetic field at the time of contact Hh Magnetic field at the time of peeling Ha Additional magnetic field Hn Reversed magnetic field Hs Saturated magnetic field Ms Saturated magnetization Hc Coercive force

Claims (9)

An initial magnetization step in which the magnetic layer of the magnetic recording medium is initially magnetized by applying an initial magnetic field in an initial magnetization direction that is one direction perpendicular to the surface of the magnetic layer;
An adhesion step of closely adhering a magnetic transfer master carrier having a pattern-shaped convex portion having a perpendicular magnetic anisotropy magnetic layer on the surface of the magnetic recording medium after the initial magnetization step;
A magnetic transfer step in which a magnetic field for recording is applied in a direction opposite to the initial magnetization direction in a state where the magnetic recording medium and the master carrier are in close contact with each other, and magnetic information is transferred to the magnetic recording medium;
In a magnetic transfer method including a peeling step of peeling the master carrier in close contact with the magnetic recording medium from the magnetic recording medium,
In the adhesion step, the master carrier and the magnetic recording medium are adhered to each other while applying a magnetic field during adhesion in the same direction as the initial magnetization direction to the master carrier.   2. The magnetic transfer method according to claim 1, wherein the magnetic field strength of the magnetic field at the time of adhesion applied in the adhesion step is at least 0.1 times the saturation magnetic field Hs of the magnetic layer of the master carrier.   3. The magnetism according to claim 1, wherein in the peeling step, the master carrier and the magnetic recording medium are peeled off while applying a peeling magnetic field to the master carrier in a direction opposite to the initial magnetization direction. Transcription method.   4. The magnetic transfer method according to claim 3, wherein the magnetic field strength of the peeling magnetic field is less than 1.2 times the reversal magnetic field Hn of the magnetic layer of the magnetic recording medium.   5. The magnetic transfer method according to claim 3, wherein the magnetic field strength of the peeling magnetic field is 0.10 times or more the saturation magnetic field Hs of the magnetic layer of the master carrier.   After the peeling step, an additional magnetic field having a magnetic field strength equal to or less than twice the reversal magnetic field Hn of the magnetic layer of the magnetic recording medium in the same direction as the initial magnetization direction with respect to the magnetic recording medium peeled from the master carrier. The magnetic transfer method according to claim 1, further comprising an additional magnetization step to be applied.   The magnetic transfer method according to claim 6, wherein the magnetic field strength of the additional magnetic field is equal to or less than a reversal magnetic field Hn of the magnetic layer of the magnetic recording medium.   The magnetic transfer method according to claim 6 or 7, wherein the magnetic field strength of the additional magnetic field is 0.1 times or more the coercive force Hc of the magnetic layer of the magnetic recording medium.   9. A method of manufacturing a magnetic recording medium, wherein magnetic information is transferred by the magnetic transfer method according to claim 1 to manufacture a magnetic recording medium.