JP2010250869A - Magnetic recording medium and magnetic recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress occurrence of dust in forming a discrete pattern. <P>SOLUTION: A recording region of a magnetic recording layer has a non-smooth surface formed of a protruding and recessed track pattern and a protruding and recessed servo pattern, and its non-recording region has a non-smooth surface formed of a protruding and recessed pseudo pattern, respectively. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic recording medium having a discrete track on the surface of a magnetic recording layer, and a method for manufacturing the same.

  In recent years, in order to improve the medium recording density of a hard disk drive (HDD) that is a magnetic recording device, a discrete track recording medium (DTR medium) in which recording tracks are physically separated has been proposed.

  This is to increase the recording density in the track direction by providing grooves on the medium surface to divide the track. With this medium, the servo pattern can be engraved with irregularities at the same time as providing grooves between tracks, so if you devise patterning, you do not have to record servo signals one by one as before. Can also be improved.

  In the process of manufacturing the DTR medium, an imprint stamper is pressed against the resist applied on the surface of the magnetic recording layer, the uneven pattern is transferred to the resist, and the magnetic recording layer is processed using the resist as a mask.

  However, in the electron beam drawing process for producing the pattern master, it takes a drawing time proportional to the drawing area. Therefore, drawing is usually performed only in the recording area where the pattern is required, and therefore there is no pattern outside the recording area. Smooth surface. Since the etching speed is completely different between the uneven surface such as the servo pattern or track pattern in the recording area and the smooth surface of the non-recording area provided on the inner and outer circumferences of the recording area, uniform etching can be performed. Absent. For this reason, the peeled state of the resist becomes non-uniform, and the resist material used as a mask tends to remain in the final product, which becomes a dust source and causes problems such as medium contamination and magnetic head crashes.

  For this reason, for example, a DTR medium has been proposed in which a tapered recess is formed on the outer peripheral edge of a magnetic disk where dust is likely to be generated in the DTR medium manufacturing process (see, for example, Patent Document 1). This medium attempts to prevent the head from crashing even when the medium surface is lowered one step in advance and dust adheres.

  However, the reason why the resist remains in the final product is that, in the resist stripping process after pattern formation, there is a difference in etching rate between the region where the pattern is present and the region where the pattern is not present. Therefore, there is a demand for a measure for eliminating this lack of peeling.

  Further, if the portion where peeling is insufficient is further etched, it becomes over-peeling, and the pattern is damaged or the magnetic material is damaged. Therefore, it cannot be adjusted to a region where the etching rate is slow.

JP 2006-209913 A

  It is an object of the present invention to provide a magnetic recording medium capable of suppressing the generation of dust when forming a discrete pattern on a magnetic recording layer, and a magnetic recording / reproducing apparatus using the same.

  The magnetic recording medium of the present invention includes a disk substrate having a central hole, and a magnetic recording layer provided on at least one main surface of the disk substrate, and the recording area of the magnetic recording layer has an uneven track pattern and a servo. It has a non-smooth surface formed by a pattern, and the non-recording area has a non-smooth surface formed by a concavo-convex pseudo pattern.

  The recording medium includes a disk substrate having a central hole and a magnetic recording layer provided on at least one main surface of the disk substrate, and a recording area of the magnetic recording layer is formed by an uneven track pattern and a servo pattern. A magnetic recording medium having a smooth surface and having a non-smooth surface whose non-recording area is formed by an uneven pseudo pattern, a mechanism for supporting and rotating the perpendicular magnetic recording medium, and the perpendicular magnetic recording medium A magnetic head having an element for recording information and an element for reproducing recorded information, and a carriage assembly that movably supports the magnetic head with respect to the perpendicular magnetic recording medium. A magnetic recording / reproducing apparatus comprising:

  When the present invention is used, generation of dust when a discrete pattern is formed on a magnetic recording layer can be suppressed.

It is a front view showing an example of the magnetic recording medium of this invention. It is the schematic showing the structure of the metal mold | die for resin stamper shaping | molding used for this invention. It is sectional drawing showing the process of forming the magnetic recording medium based on this invention. It is a figure showing an example of the mode of resist peeling. It is a figure explaining the position of the recording area in the imprint process, and a non-recording area. It is a figure showing the oblique observation result of the magnetic recording medium based on this invention. It is a figure showing the resist thickness nonuniformity measurement result in an example of the magnetic recording medium after an imprint. It is a figure showing the resist thickness nonuniformity measurement result in other examples of the magnetic recording medium after an imprint. It is process drawing of the manufacturing method of Ni stamper. It is a figure showing an example of the magnetic recording / reproducing apparatus concerning this invention.

  The magnetic recording medium of the present invention is used for perpendicular magnetic recording, and includes a disk substrate having a center hole and a perpendicular magnetic recording layer provided on at least one main surface of the disk substrate and having a non-smooth surface.

  This non-smooth surface is provided in the recording area and non-recording area of the perpendicular magnetic recording layer.

  The non-smooth surface of the recording area is formed by an uneven track pattern and a servo pattern, and the non-smooth surface of the non-recording area is formed by an uneven pseudo pattern.

  Also, the magnetic recording / reproducing apparatus of the present invention includes the perpendicular magnetic recording medium, a mechanism for supporting and rotating the perpendicular magnetic recording medium, an element for recording information on the perpendicular magnetic recording medium, and a recorded A magnetic head having an element for reproducing information; and a carriage assembly that supports the magnetic head movably with respect to a perpendicular magnetic recording medium.

  According to the present invention, when a discrete pattern is processed on the surface of the magnetic recording layer, the resist layer formed as a mask has a non-smooth surface not only in the recording area but also in the non-recording area. The speed becomes more uniform and uniform etching can be performed. By uniform etching, the resist can be peeled uniformly, and generation of dust due to the resist residue can be suppressed.

  The non-smooth surface used in the present invention can be provided outside of 9.1 mm from the center of the magnetic recording layer when a 1.8-inch disk substrate is used. As a result, the etching rate in the vicinity of the outer periphery of the magnetic recording layer where resist peeling is likely to occur can be made uniform.

  When a 2.5-inch disk substrate is used, the non-smooth surface can be provided outside 13.5 mm from the center of the magnetic recording layer. As a result, the etching rate in the vicinity of the outer periphery of the magnetic recording layer where resist peeling is likely to occur can be made uniform.

  Furthermore, the non-smooth surface can be provided from the center hole side end portion to the outer peripheral side end portion on one main surface of the magnetic recording layer. For example, in addition to the recording area, a non-smooth surface can be formed from a non-recording area provided on the inner periphery side of the recording area to a non-recording area provided on the outer periphery of the recording area. This makes it possible to make the etching rate more uniform.

  Further, the depth of the unevenness of the pseudo pattern is preferably about the same as the groove depth of the recording track, and the depth of the unevenness of the pseudo pattern of the non-recording area to be finally engraved on the magnetic recording medium is the groove depth of the recording track. The thickness can be ± 2 nm. If the groove depth of the recording track is outside the range of ± 2 nm, it tends to be difficult to make the etching rate uniform.

  For example, when pattern transfer is performed using a stamper, a pseudo pattern is formed in a non-recording area in a so-called imprint process in which a resist is applied to the stamper by a coating method such as a spin coating method or a spray method and pressed against a magnetic recording medium. If there is, the resist flow is obstructed there, so that it is possible to selectively apply the resist only to the surface area of the stamper, and it is possible to prevent contamination to an extra portion.

  If the resist flows not only to the surface area of the stamper but also to an unnecessary area outside the magnetic recording medium, it wraps around and causes various problems such as medium contamination, resist thickness unevenness, and contamination of the resist coating apparatus. Cause problems.

  In addition, if a pseudo pattern is provided in the non-recording area, it is possible to prevent the resist that has been pushed and flown out when the stamper is pressed in the imprint process, not only at the time of application, from protruding to the edge of the magnetic recording medium. Therefore, it is highly effective in preventing contamination of the discrete type magnetic recording medium.

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

  FIG. 1 is a front view showing an example of the magnetic recording medium of the present invention.

  As shown in FIG. 1, the magnetic recording medium 44 includes a disk substrate having a central hole, and a magnetic recording layer provided on at least one main surface of the disk substrate, and the recording area 46 of the magnetic recording layer is uneven. The non-smooth surface formed by the track pattern and the servo pattern, and the non-recording area 45 provided inside and the non-recording area 47 provided outside thereof are each formed by a concavo-convex pseudo pattern. It has a non-smooth surface.

  As shown in FIG. 1, in the example of the magnetic recording medium of the present invention, for example, a concavo-convex pattern is formed on the entire surface of the medium from the inner diameter hole including the non-recording area to the outer diameter end, and the structure does not have a smooth surface. I can do it. At this time, the track groove and the servo pattern are naturally carved in the recording area, but an arbitrary pseudo pattern may be used in the non-recording area. However, desirably, a pseudo pattern having dimensions on the same order as the pattern carved in the recording area is still effective.

  FIG. 2 is a schematic view showing an example of the configuration of a resin stamper molding die used in the present invention.

  As shown in the figure, the resin stamper molding die 30 has a fixed side mold plate 1 having a metal stamper mounting surface 12 mirror-polished in a random direction, a metal stamper 3, and a fixed side mold plate 1. , And a moving side mold plate 2 arranged opposite to each other with a metal stamper 3 interposed therebetween. The metal stamper 3 is provided, for example, on a spiral or concentric circular screet track, a concave / convex shape for the recording area corresponding to the servo shape, and an inner periphery and an outer periphery of the concave / convex shape for the recording area. For example, a main surface 3a having a non-recording region uneven shape having a spiral or concentric pattern, and another main surface 3b mirror-polished, and the other main surface 3b is a metal stamper mounting surface 12 is placed in contact with. Reference numeral 40 schematically represents a disk-shaped resin stamper that can be injection-molded using the mold 30.

  As shown in the main surface 3a, the metal stamper 3 has a non-smooth surface not only in the recording area of the magnetic recording layer but also in the non-recording area.

  The uneven shape for the non-recording region is not limited to the spiral or concentric shape, and may be, for example, a pseudo servo pattern shape, a radial shape, a dot shape, and a lattice shape as long as it can form a non-smooth surface. Various shapes such as can be used.

  FIG. 3 is a cross-sectional view showing a process of forming a magnetic recording medium having a discrete track using a resin stamper obtained from the mold shown in FIG.

  In order to form a magnetic recording medium using a resin stamper, a resin stamper 40 is obtained by injection molding using a mold shown in FIG. First, a metal having a concave / convex pattern 3a corresponding to a discrete track and a servo pattern, for example, a Ni stamper 3 is placed on the fixed-side mold plate 1 so that the concave / convex pattern 3a faces the moving-side mold plate 2. The mold plate 1 and the moving side mold plate 2 are combined, and the molten injection molding resin is injected into the cavity from the injection hole 6 leading to the central portion of the fixed side mold plate 1. Subsequently, after pressurizing by mold clamping, cooling is performed to perform injection molding. The center portion of the molded body is punched out with a cut punch (not shown), and a disk-shaped resin stamper 40 having a center hole is obtained. On the surface 3a of the metal stamper 3, not only the tracks and servo patterns in the recording area but also the non-recording areas provided on the inner and outer peripheral sides thereof are engraved. For this reason, the resin stamper 40 formed using this as a mold is transferred with unevenness corresponding to the track and servo pattern of the recording area and unevenness of the non-recording area provided on the inner periphery and outer periphery thereof. As the injection molding resin material, for example, cycloolefin polymer, polycarbonate, acrylic, or the like can be used.

  Next, as shown in FIG. 3A, a magnetic recording medium 44 having a disk substrate 48 and a magnetic recording layer 41 formed thereon is prepared, and an ultraviolet curable resin 43 is applied to the surface of the magnetic recording layer 41. Then, the resin stamper 40 is pressed thereon and cured by irradiating with ultraviolet rays (UV imprint).

  Subsequently, as shown in FIG. 3B, the resin stamper 40 is peeled off from the ultraviolet curable resin. The resin stamper is peeled off to expose not only the track and servo pattern, but also the ultraviolet curable resin layer to which the unevenness has been transferred in the non-recording areas provided on the inner and outer peripheral sides thereof.

Thereafter, as shown in FIG. 2C, the residue of the UV curable resin 43 in the pattern recesses is removed by, for example, CF ₄ gas or O ₂ gas dry etching, and the surface of the magnetic recording medium 41 is exposed in the recesses in the recess / protrusion pattern. Bottom out.

  Further, as shown in FIG. 3D, the surface of the magnetic recording layer 41 is processed by ion milling such as Ar, using the ultraviolet curable resin 43 as a mask. As a result, irregularities are formed on the surface of the magnetic recording layer 41 in the irregularities of the tracks and servo patterns and also in the non-recording areas provided on the inner and outer circumferences. The surface of the magnetic recording medium 41 is processed by ion milling.

  Thereafter, as shown in FIG. 3E, the ultraviolet curable resin 43 is removed by dry etching to obtain a discrete track magnetic recording medium 44 '.

  If necessary, the obtained magnetic recording medium can be subjected to post-processes such as embedding a non-magnetic material in a pattern recess, applying a lubricant, and polishing a tape.

  The magnetic recording medium handled here is 1.8 inches, for example, a diameter of 48 mm ± 0.2 mm, a center hole diameter of 12.01 mm ± 0.01 mm, and a thickness of 0.508 mm ± 0.05 mm. A 5-inch medium (diameter 65 mm ± 0.2 mm, center hole diameter 20.01 mm ± 0.01 mm, thickness 0.635 mm ± 0.05 mm) can also be used.

  In the step of peeling the resist (here, UV curable resin) leading to FIGS. 3D and 3E, there is a problem that the resist material remains in the final product and becomes a source of dust generation.

  FIG. 4 is a diagram for explaining an example of resist peeling.

As shown in FIGS. 4A and 4B, since the surface area is different between the pattern area (recording area) 101 and the non-pattern area (non-recording area) 102, ashing separation (for example, CF) by a dry process is performed. ₍₄ gas or O ₂ gas), the peeling rate is greatly different. Specifically, the part without the pattern has a lower peeling rate, and even when the pattern 43 of the magnetic recording medium 44 is exposed after the peeling of the mask 43 in the area 101 with the pattern is completed, Resist residue 43 'remains as shown in FIG. Further, if dry etching is continued with respect to the exposed pattern, the characteristics of the magnetic material and the pattern shape are damaged, so that further resist peeling cannot be performed.

  Therefore, if a concavo-convex pattern is formed on the entire surface of the medium from the inner diameter hole including the non-recording area to the outer diameter end, and there is no flat part (mirror part), the resist peeling rate is uniform over the entire surface of the medium. Thus, such a problem of remaining resist can be prevented. Furthermore, if the pseudo pattern recorded in the non-recording area at this time is a pattern having a dimension of the same order (for example, several tens of nanometers) as the pattern carved in the recording area, the resist peeling rate is further increased. It is consistent and effective.

  An example of the imprint process of FIG. 3 and another effect of the present invention will be described with reference to FIG.

  FIG. 5 is a diagram for explaining the positions of the recording area and the non-recording area in the imprint process in which the stamp is formed by attaching the stamper on which the track and servo pattern are formed to a magnetic recording medium via a resist material. It is.

Here, the stamper is a resin stamper (generally cycloolefin polymer, polycarbonate, acrylic, etc.) prepared by injection molding, but a metal stamper (generally Ni) may be used directly without the injection molding process. As the resist material, an ultraviolet curable resin (acrylic or epoxy) that is cured by UV light, an SOG (spin-on glass) material that is transferred by pressurization, or the like is used. The stamper and the magnetic recording medium may have different inner and outer diameters. As shown in the figure, when the inner diameter and outer diameter of the medium are Min, Mout, the inner diameter and outer diameter of the information recording area are Pin and Pout, and the inner diameter and outer diameter of the pseudo pattern are DPin and DPout,
The following relationship should be satisfied.

DPout ≧ Mout ＞ Pout
DPin ≤ Min <Pin
That is, the pseudo pattern exists so as to cover from the inner diameter end to the outer diameter end of the medium. In this way, the mask peeling rate is made uniform at various points in the medium.

  Next, using the method shown in FIG. 3, an ultraviolet ray is formed on the recording surface of a magnetic recording medium having a glass disk substrate having a diameter of 48 mm and a center hole diameter of 12 mm and a magnetic recording layer made of Co and Pt having a thickness of 40 nm. An acrylic (or epoxy) resin was used as the resin mask material to form a magnetic recording medium having a concavo-convex shape in the recording area and the non-recording area and having a discrete track.

  For comparison, a magnetic recording medium in which the uneven shape was not formed in the non-recording area was produced.

  The obtained magnetic recording medium was observed obliquely with a MicroMax manufactured by Tanaka Machine Sales Co., Ltd.

  FIG. 6 shows the measurement results of the medium from which the resist material could be removed without remaining in the final product.

  FIG. 6 is a diagram showing the oblique observation result of the DTR medium according to the present invention.

. FIG. 6A shows the measurement result of the DRT medium according to the present invention.

  As shown in the figure, the peripheral contamination source is removed by the effect of the present invention as described above, and no resist residue is seen.

  FIG. 6B is a diagram showing a comparative example of the present invention, and the non-recording area provided in the outer peripheral portion does not have an uneven shape.

  In FIG. 6B, it can be seen that there is a white shining resist residue on the outer periphery.

  In addition, by doing so, another effect of the present invention occurs. The resist is generally applied by spin coating or spraying. The resist material has an extremely low viscosity of several mPas (generally 30 mPas or less) because it is necessary to transfer a fine pattern by coating with a thickness of several tens of nm. For this reason, the resin flows to an unnecessary area outside the recording area and the medium, and the resin flows around to cause various problems such as medium contamination and resist thickness unevenness. Therefore, if a pseudo pattern is provided also in the non-recording area as in the present invention, the unevenness of the pseudo pattern inhibits the flow of the resist, and the contamination to an extra portion can be prevented.

As an example of preventing the trouble that the resist material described above flows into an extra portion such as a resist coating apparatus, a diagram showing a result of measuring the resist thickness unevenness of the medium after imprinting is shown in FIG. For example, a magnetic recording medium as shown in FIG. 3B from which the stamper was peeled from the resist was placed on a MicroMax manufactured by Tanaka Kikai Co., Ltd., and observed by irradiating polarized light. In the obtained image, thickness unevenness is measured by shading.

  In the medium according to the present invention in which the groove is provided in the inner peripheral portion, the flow of the resist to the extra portion is obstructed by the groove in the inner peripheral portion, and as shown in FIG. You can see that it has not happened.

  On the other hand, in the comparative example having no groove on the inner peripheral portion, as shown in FIG. 7B, the resist flowing into the inner periphery comes into contact with the inner diameter hole (or a jig for fixing the inner diameter hole at the time of spinning). It can be seen that the flow has changed and spiral thickness unevenness has occurred.

  Furthermore, when a 2.5-inch disk substrate is used and unevenness is provided in the recording area and non-recording area outside 13.5 mm from the center of the magnetic recording layer, similarly, after imprinting, a stamper is formed from the resist. When the surface state was observed by irradiating the magnetic recording medium from which the film was peeled off with the deflected light, it can be seen that there is almost no unevenness of the resist thickness as shown in FIG.

  A method for manufacturing a metal (Ni) stamper to be mounted on a mold will be described with reference to FIG.

  As shown in FIG. 9A, an electron beam resist is first applied on a Si wafer.

  Next, as shown in FIG. 9B, the electron beam resist is exposed to a pseudo pattern according to the area of the magnetic recording medium in addition to the track and the servo pattern by the electron beam. However, it is not desirable that the pseudo pattern has a very fine structure because there are restrictions on the recording time and the performance of the exposure device. The depth is preferably on the same order as the tracks and servo patterns.

  Subsequently, as shown in FIG. 9C, the exposed portion or the unexposed portion is dissolved by developing the electron beam resist, and the recording area including the track and the servo pattern, and the inner circumference of these recording areas and Concavities and convexities 22 'are formed for the outer non-recording area.

  Further, as shown in FIG. 9 (d), after conducting the conductive treatment on the unevenness 22 'of the electron beam resist, Ni plating is performed, and the pattern is duplicated with Ni to produce the Ni father stamper 23. .

  Thereafter, the Ni mother stamper 24 is produced from the Ni father stamper 23 by Ni plating.

  If necessary, sun stampers and daughter stampers can be created.

  Further, as shown in FIG. 9 (f), the back surface of the Ni mother stamper 24 is polished, the center hole and the outer periphery are machined to form a donut shape, and attached to the injection mold.

  Here, the Ni stamper is attached to a mold and a resin stamper is produced by injection molding. However, patterning may be performed directly on the magnetic recording medium by imprinting using the Ni stamper.

  FIG. 10 is a block diagram showing an example of a magnetic recording / reproducing apparatus using the discrete magnetic recording medium of the present invention.

  A rigid magnetic disk 121 for recording information according to the present invention is mounted on a spindle 122 and is driven to rotate at a constant rotational speed by a spindle motor (not shown). A slider 123 mounted with, for example, a single pole type recording head for recording information by accessing the magnetic disk 121 and an MR head for reproducing information is attached to the tip of a suspension 124 made of a thin plate spring. Yes. The suspension 124 is connected to one end side of an arm 125 having a bobbin portion for holding a drive coil (not shown).

  On the other end side of the arm 125, a voice coil motor 126, which is a kind of linear motor, is provided. The voice coil motor 126 is composed of a drive coil (not shown) wound around the bobbin portion of the arm 125, and a magnetic circuit composed of a permanent magnet and a counter yoke arranged so as to sandwich the coil.

  The arm 125 is held by ball bearings (not shown) provided at two positions above and below the fixed shaft 127, and is driven to rotate and swing by a voice coil motor 126. That is, the position of the slider 123 on the magnetic disk 121 is controlled by the voice coil motor 126. In FIG. 12, reference numeral 128 denotes a lid.

  As described above, according to the present invention, when transferring the track groove and the servo pattern to the magnetic recording medium, the concave / convex pattern is formed not only on the recording area but also on the entire surface of the disk from the inner diameter hole to the outer diameter end, thereby providing a smooth surface. I decided not to do it. As a result, when the resist material used as a mask at the time of patterning is removed by dry etching, the resist peeling rate can be made uniform over the entire surface of the disk including the non-recording surface, and generation of dust can be suppressed. .

  In addition to the above effect, for example, when pattern transfer is performed using a stamper, a process of applying a resist to the stamper by a spin coat method or a spray method and pressing the resist on a magnetic recording medium is a so-called imprint process. If there is a pseudo pattern, the resist flow is obstructed there, so that it is possible to selectively apply the resist only to the recording area. As a result, contamination such as resist material remaining on the final medium, particularly the edge of the medium, can be prevented, and the dust source can be removed from the product.

  48 ... disk substrate, 41 ... magnetic recording layer, 44 ... magnetic recording medium, 43 ... resist

Claims (6)

  A non-smooth surface including a disk substrate having a central hole and a magnetic recording layer provided on at least one main surface of the disk substrate, wherein the recording area of the magnetic recording layer is formed by an uneven track pattern and a servo pattern And the non-recording area has a non-smooth surface formed by an uneven pseudo pattern.   The magnetic recording medium according to claim 1, wherein the non-smooth surface is provided outside 9.1 mm from the center of the magnetic recording layer.   The magnetic recording medium according to claim 1, wherein the non-smooth surface is provided outside 13.5 mm from the center of the magnetic recording layer.   The magnetic recording medium according to claim 1, wherein the non-smooth surface is provided from a central hole side end portion to an outer peripheral end portion on one main surface of the magnetic recording layer.   2. The magnetic recording medium according to claim 1, wherein the depth of the unevenness of the pseudo pattern is a groove depth of the recording track ± 2 nm.   6. The magnetic recording medium according to claim 1, a mechanism for supporting and rotating the magnetic recording medium, an element for recording information on the magnetic recording medium, and recorded A magnetic recording / reproducing apparatus comprising: a magnetic head having an element for reproducing information; and a carriage assembly that supports the magnetic head movably with respect to the magnetic recording medium.

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