JP5073041B2 - Stamper - Google Patents

Description

  The present invention relates to a stamper for transferring a pattern, and more particularly, to a stamper used when transferring an uneven pattern of a stamper to a recording medium.

  In recent years, as the recording density of information recording media has improved, the marks recorded on the media have become finer. In order to facilitate the formation of fine recording marks, there is a need for a fine processing technique for forming a concavo-convex pattern of about 100 nm or less on a recording medium. As such microfabrication technology, fine pattern formation by lithography such as electron beam (EB) lithography and focused ion beam (FIB) lithography, and fine pattern formation by nanoimprint lithography (NIL) A method of combining transfer to a medium substrate has been studied.

  On the other hand, as a medium technology aiming at high recording density, for example, a magnetic recording system using a discrete track recording (DTR) medium having a data area and a servo area is known. The uneven track pattern on the recording layer of the DTR medium is formed by etching. In order to perform pattern transfer on a resist layer used as an etching mask, a stamper having a concavo-convex pattern corresponding to the track shape is pressed into contact (for example, see Patent Document 1).

  Further, an optical disk represented by a CD (compact disc), a DVD (digital versatile disc) or the like is also required to have a large capacity, and development of an optical disk having a multilayer structure is progressing. In order to manufacture an optical disk having a multilayer structure, for example, a resin transparent substrate manufactured by injection molding from a Ni stamper and a resin transparent stamper similarly manufactured by injection molding are bonded together via a 2P resin, and ultraviolet rays (UV ) To cure the 2P resin, peel off the transparent stamper, transfer the pattern, and form a multilayered medium film having a thickness of several tens of μm on the transferred pattern. (For example, refer to Patent Document 2).

With the increase in recording density of information recording media, hard disk drives (HDD) are required to have higher accuracy access performance. For this reason, it has become increasingly important to reduce the repetitive run-out ( RRO) of the track pattern of the recording medium. Such repeatable run-out has been evaluated by the HDD after the recording medium is completed, for example, it is calculated using a position error signal sampled when the head follows the track of the recording medium. (For example, refer to Patent Document 3).

  However, since the RRO of the DTR medium largely depends on the characteristics of the stamper used in the process of the DTR medium, it has been required to reduce the RRO of the stamper.

JP 2004-110896 A JP 2003-281791 A JP 2007-12258 A

  An object of the present invention is to provide a recording medium having a sufficiently low RRO in the concave / convex pattern of the stamper for transferring the discrete track pattern of the recording layer of the recording medium.

The stamper of the present invention is a stamper having a concentric or spiral concavo-convex pattern formed by injection molding and forming a track pattern on the recording layer surface of the recording medium,
The concavo-convex pattern has a main area corresponding to a data area including a data recording part and an address part, and a dummy area other than the main area, and the concavo-convex pattern of the dummy area has its repeatable runout rotated. When the frequency is set as the reference primary, it is 1 nm or less between the 15th and 40th orders.

  According to the present invention, the RRO of the stamper can be reduced.

Sectional drawing which shows an example of the manufacturing method of a DTR medium Block diagram showing a schematic configuration of a stamper evaluation apparatus for reproducing a stamper Sectional view showing an example of pattern transfer method Sectional drawing which shows another example of the pattern transfer method The figure which shows the magnetic recording / reproducing apparatus which records / reproduces a magnetic recording medium The figure which shows the eccentric order and displacement amount of the dummy groove | channel by Example 1. The figure which shows the eccentric order and displacement amount of the drive by Example 1 The figure which shows the eccentric order and displacement amount of the dummy groove | channel by Example 2. The figure which shows the eccentric order and displacement amount of the drive by Example 2. The figure which shows the eccentric order and displacement amount of the dummy groove | channel by Example 3. The figure which shows the eccentric order and displacement amount of the drive by Example 3 The figure which shows the eccentric order and displacement amount of the dummy groove | channel by a comparative example Diagram showing eccentricity and displacement of a drive according to a comparative example

  The stamper of the present invention has a concentric or spiral concavo-convex pattern for forming a track pattern on the recording layer surface of the recording medium on one main surface. The concave / convex pattern has a main area corresponding to a data area including a data recording part and an address part, and a dummy area other than the main area. In the stamper of the present invention, the repeatable run-out of the uneven pattern in the dummy region is from the 15th to the 40th when the rotation frequency is set as the reference primary.

When the stamper of the present invention is used, the RRO of the recording medium can be reduced, and a highly reliable recording medium can be obtained. FIG. 1 schematically illustrates an example of a method for manufacturing a DTR medium according to the present invention. To do.

  First, as shown in FIG. 1A, a magnetic layer 12 is formed on a substrate 11, and a resist 21 is applied thereon. Subsequently, as shown in FIG. 1B, a stamper 31 having a concavo-convex pattern is prepared, the pattern surface of the stamper 31 is opposed to the resist 21, and the pattern of the stamper 31 is transferred to the resist 21 by imprinting. Thereafter, as shown in FIG. 1C, the resist residue remaining in the recesses of the resist 21 is removed by reactive ion etching using oxygen gas. Further, as shown in FIG. 1D, the magnetic layer 12 is etched and processed by ion milling using the patterned resist 21 as a mask. As shown in FIG. 1E, the remaining resist 21 is removed by oxygen ashing. If necessary, the recess is filled with a non-magnetic material (not shown), and a protective film 13 is formed on the entire surface as shown in FIG.

  Here, the imprint method is roughly classified into the following three types.

1) Thermal imprint method This imprint method is excellent in mass productivity because a Ni stamper can be used for the mold. However, since imprinting is performed by heating and cooling both the substrate to be imprinted and the mold, it takes time to raise and lower the temperature, and it has been considered that throughput cannot be increased and that it is not suitable for mass production. This is because the mold and the mold support have a large heat capacity, and heating and cooling take time. Therefore, it is conceivable to provide the apparatus with a mechanism for forcibly cooling the mold support, but this is a large-scale mechanism. In addition, in order to transfer a nanometer-sized pattern to a large area, a mold that is designed to be imprinted uniformly over the entire surface is required, but forced cooling to such a specially designed mold is required. It is difficult to incorporate the mechanism.

2) High-pressure imprint method This imprint method is also excellent in mass productivity because a Ni stamper can be used for the mold. In addition, since it is not necessary to incorporate a special mechanism in the apparatus, a dedicated mold (mold support) capable of satisfactorily transferring a nanometer size pattern over a large area can be used. However, high pressure is required to transfer the pattern well, and the Ni stamper itself may be deformed. Further, since the resist is elastically deformed, it takes about one minute until it is completely deformed by imprinting.

3) Photoimprint method This imprint method is a method of imprinting on a photocurable resin using a mold (quartz, diamond, etc.) that transmits light, and is excellent in shape transferability and throughput. However, it is difficult to produce a mold that transmits light.

  NIL has been studied on various methods such as a combination of the above three methods. However, in particular, 1) the thermal imprint method and 2) the high pressure imprint method have a problem that the throughput is poor.

  Next, the RRO evaluation method for the stamper will be described.

  Here, a resin stamper for a 1.8 inch magnetic recording medium molded to a thickness of 0.6 mm is taken as an example.

  This resin stamper has a data area in the range of r = 15.0-23.0 mm and a dummy groove in the range of r = 25.0-26.0 mm. The dummy grooves were concentric, with a track pitch of 0.4 μm (L / G = 200 nm / 200 nm) and a depth of 50 nm.

  In the above example, the dummy area does not exist on the magnetic recording medium. However, the dummy area may be formed on the magnetic recording medium by being present between the inner circumference or the data area. In this case, the RRO can be directly examined from the dummy area of the magnetic recording medium.

  An apparatus for examining the RRO of the stamper will be described below.

  FIG. 2 is a block diagram showing a schematic configuration of an RRO evaluation apparatus for examining the RRO by reproducing the dummy groove of the stamper.

  As shown in the figure, the stamper is a stamper made of resin, for example. A semiconductor laser light source 120 is used as the light source. The wavelength of the emitted light is, for example, in the violet wavelength band in the range of 400 nm to 410 nm. The emitted light 110 from the semiconductor laser light source 120 is converted into parallel light by the collimator lens 121, passes through the polarization beam splitter 122 and the λ / 4 plate 123, and enters the objective lens 124. Thereafter, the light passes through the substrate of the stamper S and is condensed on the surface of the substrate where the groove is formed. At this time, the numerical aperture of the laser (hereinafter referred to as NA) varies depending on the target medium. For example, in the case of a resin stamper, the NA is about 0.5 to 0.7 when the evaluation method is such that the inside of the resin stamper having a thickness of 0.6 mm is transmitted. On the other hand, in the case of a stamper using a material that does not transmit light, such as a Ni stamper, or when regenerating the surface of a resin stamper, the NA is adjusted to 0.85 or more, or the resin material is equivalent to a thickness of 0.6 mm An aberration correction plate can be inserted between the laser and the stamper. The reflected light 111 from the information recording layer of the stamper is again transmitted through the substrate of the stamper D, transmitted through the objective lens 124 and the λ / 4 plate 123, reflected by the polarization beam splitter 122, and then transmitted through the condenser lens 125. Is incident on the photodetector 126.

  The light receiving unit of the photodetector 127 is normally divided into a plurality of parts, and outputs a current corresponding to the light intensity from each light receiving unit. The output current is converted into a voltage by an unillustrated I / V amplifier (current / voltage conversion) and then input to the arithmetic circuit 140. The input voltage signal is arithmetically processed by the arithmetic circuit 140 into a tilt error signal, an HF signal, a focus error signal, a track error signal, and the like. The tilt error signal is for tilt control, the HF signal is for reproducing information recorded on the optical disc D, the focus error signal is for focus control, and the track error The signal is used for tracking control.

  The objective lens 124 can be driven by the actuator 128 in the vertical direction, the disc radial direction, and the tilt direction (radial direction and / or tangential direction), and is controlled by the servo driver 150 so as to follow the information track on the stamper D. Is done.

  In this evaluation apparatus, an example of the wavelength of the semiconductor laser is in the range of 400 to 410 nm. However, the wavelength is not limited to this and may be shorter. In the case of this evaluation apparatus, the track pitch of the dummy groove of the stamper can be made narrower than 0.4 μm, for example. If the semiconductor laser has a long wavelength, the track pitch of the dummy groove of the stamper needs to be wider than 0.4 μm. The track pitch can be determined by the laser spot diameter. When the tracking using the push-pull method of the evaluation apparatus is performed, the track pitch of the stamper dummy groove can be 0.5 to 1.2 times the laser spot diameter. The laser spot diameter can be expressed by λ / NA. For example, when the laser wavelength is 405 nm and NA is 0.65, the dummy groove track pitch can be set to 0.31 μm to 0.75 μm. For example, when a fixed laser having a wavelength of 355 nm and NA of 0.85 is used, the laser spot diameter can be 0.42 μm and the minimum track pitch can be 0.2 μm. If the track pitch is too wide, the dummy area becomes wider and the laser spot diameter of the evaluation apparatus tends to increase, and the data area tends to be evaluated roughly. On the other hand, a laser whose wavelength is narrower than 355 nm is difficult to handle and is not practical. Accordingly, the lower limit of the track pitch of the dummy groove can be set to 0.2 μm.

  The stamper of the present invention can be regenerated using such an RRO evaluation apparatus. In this example, DDU-1000 manufactured by Pulstec was used. The laser wavelength at this time was 405 nm and NA was 0.65.

  Next, the RRO evaluation method for the stamper will be described.

A stamper is set in the evaluation apparatus, and the stamper is rotated at a linear velocity of 1.2 m / sec. The linear velocity tends to decrease as the frequency increases from the point where the device has the tracking characteristic (servo gain characteristic). For this reason, it is possible to examine the higher-order component of RRO more accurately by amplifying the amount of displacement in the order when it is slower than the minimum rotation speed of the spindle motor. In this evaluation apparatus, one rotation of the disk is converted into a frequency, which is used as the rotation frequency, and the eccentric order is represented by this rotation frequency.

  Laser is irradiated, and the tilt and offset are adjusted to the maximum difference signal (push-pull signal) to perform tracking. Frequency analysis of the push-pull signal after tracking was performed using an FFT analyzer (CF-5210 manufactured by Ono Sokki Co., Ltd.).

  Next, the peak-to-peak value of the same push-pull signal was examined with tracking turned off and only the focus adjusted. This peak-to-peak voltage value corresponds to a 1/2 track pitch displacement amount. The displacement amount was calculated by dividing the voltage value at each frequency measured with the FFT analyzer by the peak-to-peak voltage value. Note that the measurement conditions of the FFT analyzer are that one track is measured 100 times, the averaged data is measured once, and the maximum value obtained by measuring the track 5 times in the dummy area is the displacement. This calculation result was used as the RRO of the stamper in the present invention. Of these, the 15th to 40th order displacements were noted with the rotational frequency of the stamper as the primary reference. If it is less than 15th order, an error due to the position where the stamper is placed tends to occur, and a stable displacement amount can be obtained to some extent even if it does not measure to a place exceeding 40th order.

  Here, in the above example, the dummy groove uses a stamper in which the ratio of land to groove is 1: 1, but the invention is not limited to this. Due to the characteristics of the device for examining the RRO characteristics, the value PP / SUM obtained by normalizing the amplitude (pp) of the push-pull signal PP with the voltage value (pG) of the sum signal SUM is at least PP / SUM <0.1. Then, since tracking becomes impossible, it is possible to select a land-to-groove ratio that enables tracking so as not to occur.

  Hereinafter, the present invention will be described more specifically with reference to examples.

  In the following example, a case where a DTR type magnetic recording medium is manufactured by using several resin stampers and transferring a concavo-convex pattern to an ultraviolet curable resin layer applied to a medium substrate will be described.

  The DTR type magnetic recording medium has a plurality of servo areas and a plurality of data areas divided by these servo areas, and each servo area is formed with a preamble portion, an address portion, and a burst portion. A discrete track is formed. Each figure is a schematic diagram for promoting explanation and understanding of the invention, and shapes, dimensions, ratios, etc. are different from actual ones, but these should be appropriately changed in design in consideration of the following explanation and known technology. Can do.

  First, a method for manufacturing a recording medium common to each example and comparative example will be described.

  The transparent stamper is produced by the following method.

  First, a resist was applied to the master, and a servo area and a data area were drawn by electron beam lithography to produce a resist master. A positive resist was used, and the resist thickness was 50 nm. The concavo-convex pattern corresponding to the discrete track in the data area had a track pitch (TP) of 100 nm (L / G = 70 nm / 30 nm) and a depth of 50 nm. A concentric groove was also formed 5 mm outside the data portion. The track pitch of this groove was 400 nm (L / G = 200 nm / 200 nm) and the depth was 50 nm.

  The resist master was electroformed to produce an Ni stamper for injection molding. As the Ni stamper, any of a so-called father stamper manufactured from the original master, a mother stamper copied from the father stamper by electroforming, and a sun stamper further copied from the mother stamper by electroforming may be used. .

  Transparent stampers A to D were prepared using a cycloolefin polymer (COP) by injection molding using a Ni stamper.

  Polycarbonate (PC) may be used as the material for the transparent stamper. However, considering releasability with 2P resin, COP, cycloolefin copolymer (COC), polymethyl methacrylate (PMMA), etc. may be used. preferable. Moreover, in each material, you may mix the organic compound which has a fluorine substituent or silicon as a mold release agent.

  As shown in FIG. 3A, magnetic layers 52 were formed on both surfaces of a donut glass substrate 51 that is a medium substrate.

  As the magnetic layer, a so-called perpendicular double-layer medium having a perpendicular magnetic recording layer on a soft magnetic (backing) layer can be formed.

  For the soft magnetic (backing) layer, a material containing Fe, Ni, and Co can be used. Examples of such materials include FeCo alloys such as FeCo and FeCoV, FeNi alloys such as FeNi, FeNiMo, FeNiCr, and FeNiSi, FeAl alloys, FeSi alloys such as FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, and FeAlO. Examples thereof include FeTa, FeTaC, and FeTaN, and FeZr alloys such as FeZrN.

  The perpendicular magnetic recording layer can contain Co as a main component and Pt. Furthermore, an oxide-containing material can also be used. As this oxide, for example, silicon oxide, titanium oxide or the like can be used.

  In the perpendicular magnetic recording layer, magnetic particles (crystal grains having magnetism) can be dispersed in the layer. The magnetic particles may have a columnar structure that vertically penetrates the perpendicular magnetic recording layer. By forming such a structure, the orientation and crystallinity of the magnetic particles in the perpendicular magnetic recording layer are improved, and as a result, a signal / noise ratio (S / N ratio) suitable for high-density recording can be obtained. It becomes possible. In order to obtain such a structure, the amount of oxide to be contained is important. The oxide content can be 3 mol% or more and 12 mol% or less with respect to the total amount of Co, Cr, and Pt. Furthermore, it is possible to make it 5 mol% or more and 10 mol% or less. When the above range is used as the content of oxide in the perpendicular magnetic recording layer, when the layer is formed, the oxide is precipitated around the magnetic particles, and the magnetic particles can be isolated and miniaturized. .

  The thickness of the perpendicular magnetic recording layer can be 5 to 60 nm. Furthermore, the thickness of the perpendicular magnetic recording layer can be 10 to 40 nm. When the thickness of the perpendicular magnetic recording layer is in the range of 5 to 60 nm, it can operate as a magnetic recording / reproducing apparatus suitable for higher recording density. If the thickness of the perpendicular magnetic recording layer is less than 5 nm, the reproduction output tends to be too low and the noise component tends to be higher. If the thickness of the perpendicular magnetic recording layer exceeds 60 nm, the reproduction output is too high. There is a tendency to distort the waveform.

  On the magnetic layer 52 on one side of the glass substrate 51, an ultraviolet curable resin having a viscosity of 5 cps (hereinafter referred to as 2P resin) is spin-coated so as not to reach the center hole, and is shaken for 30 seconds at 10000 revolutions to obtain a thickness. A 2P resin layer 61 having a T1 of 60 nm was formed.

  As shown in FIG. 3B, a resin-made first transparent stamper 71 on which an uneven pattern was formed was prepared.

In the vacuum chamber 81, one surface of the glass substrate 51 and the pattern surface of the first transparent stamper 71 were bonded together via the 2P resin layer 61 in a vacuum atmosphere of 10 ³ Pa or less.

  As shown in FIG. 3C, the vacuum was released, and the 2P resin layer 61 was cured by irradiating UV through the first transparent stamper 71 under atmospheric pressure. The time required for curing depends on the curing characteristics of the polymerization initiator contained in the 2P resin used and the ability of the UV light source, but can usually be cured in several tens of seconds.

  As shown in FIG. 3D, the first transparent stamper 71 was peeled from the glass substrate 51 to form a 2P resin layer 61 to which the concavo-convex pattern was transferred. The thickness T2 of the 2P resin layer 61 remaining in the recess was 30 nm.

  Next, as shown in FIG. 4A, a 2P resin having a viscosity of 5 cps is spin-coated on the magnetic layer 52 previously formed on the other surface of the glass substrate 51 so as not to reach the center hole. The 2P resin layer 62 having a thickness T1 of 60 nm was formed by shaking off for 30 seconds by rotation.

As shown in FIG. 4B, a resin-made second transparent stamper 72 having a concavo-convex pattern is prepared, and another glass substrate 51 is formed in a vacuum chamber 81 in a vacuum atmosphere of 10 ³ Pa or less. The surface and the pattern surface of the second transparent stamper 72 were bonded together via the 2P resin layer 62.

  As shown in FIG. 4C, the vacuum was released and the 2P resin layer 62 was cured by irradiating UV through the second transparent stamper 72 under atmospheric pressure.

  As shown in FIG. 4D, the second transparent stamper 72 was peeled from the glass substrate 51 to form a 2P resin layer 62 to which the concavo-convex pattern was transferred. The thickness T2 of the 2P resin layer 62 remaining in the recess was 30 nm.

  Although the 2P resin is applied to the glass substrate in the above figure, the 2P resin may be applied to the pattern surface of the transparent stamper, or the 2P resin may be applied to both the glass substrate and the transparent stamper.

  Next, residual removal of 2P resin was performed by oxygen gas RIE (reactive ion etching). Subsequently, magnetic material processing was performed by etching using an Ar ion beam (Ar ion milling) using an etching mask from which residues generated in the imprint process were removed. Further, after milling, the 2P resin was peeled off, and unevenness was filled with a nonmagnetic material. Etch back is performed until the carbon protective film on the magnetic film is exposed. After the etch back, a C protective film was formed to produce a magnetic recording medium.

  FIG. 5 is a diagram showing a magnetic recording / reproducing apparatus that performs RRO evaluation and recording / reproducing of a magnetic recording medium.

  In this magnetic recording apparatus, a magnetic recording medium 62, a spindle motor 63 that rotates the magnetic recording medium 62, a head slider 64 that includes a recording / reproducing head, and a head suspension assembly that supports the head slider 64 are provided inside a casing 61. (Suspension 65 and actuator arm 66), a voice coil motor 67, and a circuit board.

  The magnetic recording medium 62 is attached to a spindle motor 63 and rotated, and various digital data are recorded by a perpendicular magnetic recording method. The magnetic head incorporated in the head slider 64 is a so-called composite type head, and includes a single magnetic pole structure write head and a read head using a GMR film, a TMR film, or the like. A suspension 65 is held at one end of the actuator arm 66, and the head slider 64 is supported by the suspension 65 so as to face the recording surface of the magnetic recording medium 62. The actuator arm 66 is attached to the pivot 68. A voice coil motor 67 is provided at the other end of the actuator arm 64 as an actuator. The head suspension assembly is driven by the voice coil motor 67 to position the magnetic head at an arbitrary radial position of the magnetic recording medium 61. The circuit board includes a head IC, and generates a drive signal for the voice coil motor, a control signal for controlling reading and writing by the magnetic head, and the like. Using this magnetic disk device, the RRO of the processed magnetic recording medium was measured by examining the displacement of the position error track servo signal. Similarly, using this magnetic disk device, recording was performed on a processed magnetic recording medium, and the bit error rate of the reproduced signal was measured.

Example 1
The RRO of the dummy groove of the transparent stamper A produced by injection molding was evaluated.

  The result is shown in FIG.

  FIG. 6 is a graph showing the relationship between the eccentricity order and the displacement amount.

  As shown in the drawing, the maximum displacement amount was 0.65 between the 15th and 40th orders.

  Next, a perpendicular magnetic recording layer was formed as follows.

A glass substrate (amorphous substrate MEL3 manufactured by MYG, diameter 2.5 inches) is housed in a film forming chamber of a DC magnetron sputtering apparatus (C-3010 manufactured by Anelva), and the ultimate vacuum is 1 × 10 ⁻⁵ Pa. The inside of the deposition chamber was evacuated until

  On this substrate, as a soft magnetic layer, Co 90 at% -Zr 5 at% -Nb 5 at% of 100 nm and a Ru film of 20 nm were formed to form a soft magnetic backing layer.

Next, (Co86 at% —Ir14 at%)-8 mol% SiO ₂ was formed to 5 nm as the underlayer, and Co 28 at% —Cr 6 at% Pt 16 at% —8 mol% SiO ₂ was formed to 15 nm as the perpendicular magnetic recording layer.

  Further, 2P resin was applied to the perpendicular magnetic recording layer as described above, and using this transparent stamper A, a pattern was transferred as described above to produce a magnetic recording medium, and RRO evaluation was performed with a hard disk drive. The result is shown in FIG.

  FIG. 7 is a graph showing the relationship between the eccentricity order and the drive fluctuation amount.

  As shown, the result was good.

When the recording characteristics were evaluated with a hard disk drive (HDD), a good result was obtained with a bit error rate (bER) of 5e- ⁷ . The bit error rate in this embodiment is defined as good when it is 1 × 10 ⁻⁶ or less when the track center is measured.

(Example 2)
When the RRO of the dummy groove of the transparent stamper B produced by injection molding in the same manner as in Example 1 was evaluated, the maximum displacement amount was 0.54 between the 15th and 40th orders. The results are shown in FIG. Similarly, when a magnetic recording medium was prepared using the transparent stamper B and RRO evaluation was performed with a hard disk drive, it was better than Example 1. The results are shown in FIG.

Also in the recording characteristic evaluation, the bit error rate was as good as 2.0 × 10 ⁻⁷ .

(Example 3)
When the RRO of the dummy groove of the transparent stamper C produced by injection molding in the same manner as in Example 1 was evaluated, the maximum displacement amount between 15th and 40th orders was very good at 0.30. The results are shown in FIG. Similarly, when a magnetic recording medium was prepared using the transparent stamper C and RRO evaluation was performed with a hard disk drive, it was better than Example 1. The results are shown in FIG. Also, in the recording characteristic evaluation, the bit error rate was as good as 8.5 × 10 ⁻⁸ .

(Comparative example)
When the RRO of the dummy groove of the transparent stamper D produced by injection molding in the same manner as in Example 1 was evaluated, the maximum displacement amount between the 15th and 40th orders was 1.5, which was very bad. The results are shown in FIG. Similarly, when a magnetic recording medium was prepared using the transparent stamper D and RRO evaluation was performed with a hard disk drive, it was very bad as shown in FIG.

In the evaluation of recording characteristics, the bit error rate was as bad as 5.5 × 10 ^−5, and the recording / reproduction signal was not reliable.

  The above experimental results are summarized in Table 1 below.

  When a magnetic recording medium using a stamper having a 15 to 40th order stamper RRO of 0.5 to 1.0 was used, good RRO characteristics could be obtained in drive evaluation.

If the RRO of the stamper is lower than 0.5, the evaluation result in the drive tends to be even better. On the other hand, when the RRO of the stamper was larger than 1.0, the evaluation result in the drive was bad.

  From the above experimental results, there is a correlation between the 15th to 40th order RRO evaluation results of the stamper and the drive evaluation result when the magnetic recording medium is used, and the RRO of the stamper is evaluated without completing the magnetic recording medium. Therefore, a quicker inspection becomes possible. In particular, in the case of a resin stamper, the value of the stamper RRO varies greatly depending on the injection molding condition. Therefore, it is possible to create a good magnetic recording medium by selecting the injection molding condition that makes this RRO value good. Become.

  In the above, the method of manufacturing the discrete track type magnetic recording medium including the data area and the servo area using the present invention has been described. However, the present invention is not limited to this, and the method of the present invention is an optical disk represented by CD, DVD, etc. It can apply also to manufacture.

  Although the embodiments of the present invention have been described above, the present invention can be variously modified within the scope of the gist of the invention described in the claims.

  In addition, the present invention can be variously modified without departing from the scope of the invention in the implementation stage. Furthermore, various inventions can be configured by appropriately combining a plurality of components disclosed in the embodiment.

    Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 12 ... Magnetic layer, 13 ... Protective film, 21 ... Resist, 31 ... Stamper, 51 ... Glass substrate, 52 ... Magnetic layer, 61, 62 ... 2P resin layer, 71, 72 ... 1st and 2nd Transparent stamper

Claims (5)

It has a concentric or spiral concavo-convex pattern for forming a track pattern on the surface of a recording layer of a recording medium, which is created by injection molding . A stamper made of resin that is 1 nm or less between the 15th and 40th orders,
The stamper, wherein the uneven pattern includes a main area corresponding to a data area including a data recording portion and an address portion of the recording medium, and a dummy area other than the main area.   2. The stamper according to claim 1, wherein the stamper is selected from the group consisting of nickel, resin, and glass.   2. The stamper according to claim 1, wherein the uneven pattern of the dummy region has a track pitch of 0.2 μm or more and 0.75 μm or less.   The stamper according to claim 1, wherein the repeatable run-out is 0.5 nm or less between the 15th and 40th orders.   The stamper according to any one of claims 1 to 4, wherein the stamper transfers a transfer pattern to the resist layer surface by an imprint method.

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