US20050248866A1 - Magnetic pattern transferring method for performing magnetic pattern transfer while correcting a magneticallly different part - Google Patents

Abstract

A magnetic-pattern transferring method is a method for transferring a magnetic pattern to a magnetic recording medium. The method comprises steps as follows. In a master transferring step, a magnetic field is applied to a master placed close to the magnetic recording medium. The magnetic field excites a magnetic layer having a pattern patterned on the master according to the magnetic pattern. Thereby, the pattern of the magnetic layer is transferred to the magnetic recording medium. In a pattern-difference measuring step, a magnetic condition of the magnetic recording medium is measured so as to measure a magnetically different part between the pattern transferred to the magnetic recording medium and the magnetic pattern. In a magnetic transferring step, a pattern transfer is performed to the magnetic recording medium by using the master while applying the magnetic field so as to correct a magnetic condition of the magnetically different part.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention generally relates to a magnetic pattern transferring method and a magnetic-pattern transferring device for transferring a predetermined magnetic pattern to a magnetic recording medium, such as a magnetic disk mounted on a magnetic storage device used widely as a device, such as an external storage device for a computer, and a method for manufacturing a master used in a magnetic transfer, etc., and more particularly, to a technology suitable for transferring control-signal information, such as a servo signal, an address signal, and a reproduction clock signal, data, and an OS (Operating System) to a magnetic recording medium product beforehand.
• 2. Description of the Related Art
• In recent years, a magnetic storage device has been provided with a larger capacity and a higher recording density. Accordingly, as information has been increasing in amount, a magnetic recording medium has been desired to have a large capacity enabling a recording of a large amount of information, and to be accessible in a short time, while being available at a low cost. Realizing such a magnetic recording medium entails a use of a tracking servo technology that enables a magnetic head to scan a narrow track with high precision.
• In a large-capacity magnetic recording medium, a magnetic pattern including a tracking servo signal is preformatted at a certain interval in one round of a magnetic disk. A magnetic head reads this magnetic pattern and corrects its positioning so as to run on a track with high precision.
• Conventionally, such a magnetic recording medium including a predetermined magnetic pattern as mentioned above has been manufactured by recording medium by medium, and track by track, using a servo information recording device used exclusively for a magnetic recording medium. The servo information recording device requires a mechanism for positioning a recording head with high precision, and therefore is expensive. Additionally, as a magnetic recording medium has a larger capacity, recording a magnetic pattern thereon takes a longer time. Accordingly, in a process of manufacturing a large-capacity magnetic recording medium, a step of recording a magnetic pattern occupies a large proportion of the process, raising a manufacturing cost.
• Under the heretofore-described circumstances, a technology replacing the above-mentioned track-by-track recording has been proposed. In this technology, a disk including a magnetic layer patterned according to a magnetic pattern is prepared as a master, and the magnetic pattern is transferred to a magnetic recording medium product via the master.
• In this transferring method using the master, applying an external magnetic field to the master in contact with a magnetic recording medium to be preformatted excites the above-mentioned magnetic layer to perform a magnetic transfer. Thus, this transferring method using the master can manufacture a magnetic recording medium having a predetermined magnetic pattern in a short time, with simple manufacturing steps, and at a low cost.
• As mentioned above, the master includes the magnetic layer (a soft magnetic material) patterned at a position corresponding to a predetermined magnetic pattern concerning servo information, etc. Applying the external magnetic field to this master in contact with the magnetic recording medium excites the soft magnetic material so as to transfer the magnetic-layer pattern patterned on the master to the magnetic recording medium.
• Since the above-mentioned master has a fine pattern, the master is manufactured by using a lithographic technology generally used in manufacturing a semiconductor, etc. The master is manufactured by applying a photoresist on a substrate, exposing the substrate with using a photomask corresponding to a magnetic pattern, developing the magnetic pattern, etching the magnetic pattern, sputtering a soft magnetic material on the magnetic pattern, etc.
• On one hand, since a semiconductor chip is considerably small, the semiconductor chip is simply discarded once the semiconductor chip has a defective pattern. On the other hand, since a magnetic recording medium has a considerably large area compared to the semiconductor chip, a defective pattern formed at one part makes the whole magnetic recording medium defective; therefore, a patterning of the magnetic recording medium is required to be controlled with higher precision so as to include no defective pattern as a whole. That is, the patterning of the magnetic recording medium requires a more precise measurement control, compared to a patterning of the semiconductor chip.
• Furthermore, in order to provide a magnetic recording medium with a still higher recording density, an even finer pattern needs to be formed on the above-mentioned master with high precision. However, the above-mentioned lithographic technology has been facing a limit in forming a highly precise pattern.
• FIG. 1 illustrates a conventional magnetic-pattern transferring device100. InFIG. 1, amaster110 is placed on amagnetic recording medium120. A predeterminedmagnetic field105 is applied from amagnet101 functioning as a magnetic field generating means. Themaster110 has amagnetic layer111 patterned according to a predetermined magnetic pattern based on a preset servo signal, etc. In a state shown inFIG. 1, themagnetic layer111 is excited by being subjected to themagnetic field105 so that a magnetic-layer pattern of themagnetic layer111 is transferred to themagnetic recording medium120 as a transferredpattern121.
• However, when the above-mentioned magnetic-layer pattern is finer, it is difficult to control a width and a depth of themagnetic layer111 by using the contemporary lithographic technology. Therefore, the pattern of themagnetic layer111 formed on themaster110 “deviates” subtly from the original magnetic pattern. Specifically, the pattern of themagnetic layer111 formed on themaster110 includes a magnetically-different part from the predetermined magnetic pattern. Accordingly, themagnetic recording medium120 manufactured by a magnetic transfer using thismaster110 inevitably has the transferredpattern121 different from the original magnetic pattern.
• Additionally, in the above-mentioned transferring method using the master, when applying the external magnetic field to the master in contact with the magnetic recording medium as a slave, strong and weak magnetic fields originate from the magnetic layer. Based on this phenomenon, a predetermined transferred pattern corresponding to magnetic information can be formed on the magnetic recording medium. More specifically, whereas the magnetic field becomes weaker right under the magnetic layer arranged in the master, a strong magnetic field occurs at an edge of the magnetic layer. These strong and weak magnetic fields enable a transferred pattern corresponding to original magnetic information to be formed on the magnetic recording medium.
• However, since there exists a certain transition width in magnetizing the magnetic recording medium as described above, a displacement, i.e., a transfer error may occur between the edge of the magnetic layer of the master and a magnetized part formed on the magnetic recording medium.
• FIG. 2 illustrates how the magnetic pattern is transferred to the magnetic recording medium0.120 by using themaster110. Themagnetic layer111 is patterned on the undersurface of themaster110 at a position corresponding to magnetic information to be transferred. Bringing thismaster110 close to themagnetic recording medium120 and applying themagnetic field105 externally causes the transferredpattern121 to be formed on themagnetic recording medium120 between two parts of themagnetic layer111, ideally. That is, ideally speaking, as shown in an upper illustration ofFIG. 2, each of magnetized parts composing the transferredpattern121 is formed right between edges of adjacent parts of themagnetic layer111. Then, when an ideal transfer is performed to themagnetic recording medium120, a waveform of a signal reproduced from the magnetic recording medium accurately reflects the original magnetic information, as shown in a lower graph ofFIG. 2.
• However, as mentioned above, a transfer error occurs in an actual transfer to the magnetic recording medium.FIG. 3 illustrates a case where an “extended blur” occurs in the transferredpattern121 on themagnetic recording medium120. When the “extended blur” occurs, an extension part121BR extended from right under the edge of themagnetic layer111 is formed in the transferredpattern121 on themagnetic recording medium120, as shown in an upper illustration ofFIG. 3. Thus, when the “extended blur” occurs, a waveform of a signal reproduced from the magnetic recording medium unfavorably becomes displaced from the original magnetic information, as shown in a lower graph ofFIG. 3.
• Additionally, in another case contrary to the “extended blur” shown inFIG. 3, a “reduced blur”, i.e., an reduction part is formed between right under the edge of themagnetic layer111 and the transferredpattern121 on themagnetic recording medium120, though not shown in the figures.
• As described above, the transferred pattern being formed at a position displaced from the expected position (right under the edge of the magnetic layer111) on the magnetic recording medium results in failure to accurately transfer necessary information to a magnetic recording medium product.
SUMMARY OF THE INVENTION
• It is a general object of the present invention to provide an improved and useful magnetic pattern transferring method, a magnetic-pattern transferring device, and a technology for restraining a transfer error, in which the above-mentioned problems are eliminated.
• A more specific object of the present invention is to provide a magnetic pattern transferring method and a magnetic-pattern transferring device which can accurately transfer an original magnetic pattern to a magnetic recording medium while correcting a magnetically different part included in a master, and to provide a technology for restraining a transfer error from causing a problem on a magnetic recording medium by contriving a magnetic pattern formed on a master.
• In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a method for transferring a magnetic pattern to a magnetic recording medium capable of recording magnetic information, the method comprising:
• • a master transferring step of applying a magnetic field to a master placed close to the magnetic recording medium, the magnetic field exciting a magnetic layer having a pattern patterned on the master according to the magnetic pattern, so as to transfer the pattern of the magnetic layer to the magnetic recording medium;
  • a pattern-difference measuring step of measuring a magnetic condition of the magnetic recording medium after the master transferring step so as to measure a magnetically different part between the pattern transferred to the magnetic recording medium and the magnetic pattern; and
  • a magnetic transferring step of performing a pattern transfer to the magnetic recording medium by using the master while applying the magnetic field so as to correct a magnetic condition of the magnetically different part.
• According to the present invention, the pattern transfer is performed to the magnetic recording medium while applying the magnetic field so as to correct the magnetic condition of the magnetically different part of the transferred pattern measured in the pattern-difference measuring step. Therefore, even though the magnetic-layer pattern formed on the master includes the part magnetically different from the original magnetic pattern, the magnetically different part can be corrected so that the original magnetic pattern is transferred to the magnetic recording medium.
• Additionally, in the magnetic pattern transferring method according to the present invention, the magnetic transferring step may control the magnetic field by changing a magnitude of an electric current supplied to an electromagnet in synchronization with positional information of the magnetically different part, the electromagnet generating the magnetic field applied for performing the pattern transfer.
• Additionally, in the magnetic pattern transferring method according to the present invention, the magnetic transferring step may control the magnetic field by changing a distance between a permanent magnet and the master in synchronization with positional information of the magnetically different part, the permanent magnet generating the magnetic field applied for performing the pattern transfer.
• According to the present invention, the magnetic field correcting the magnetic condition of the magnetically different part is supplied while confirming the position of the magnetically different part formed on the magnetic recording medium. Thereby, the original magnetic pattern can be surely formed on the magnetic recording medium.
• Additionally, in the magnetic pattern transferring method according to the present invention, the magnetic transferring step may preferably perform the pattern transfer while monitoring the magnetic field applied from the electromagnet or the permanent magnet.
• According to the present invention, the magnetic transfer is performed to the magnetic recording medium while confirming the condition of the magnetic field correcting the magnetically different part. Thereby, the original magnetic pattern can be more surely formed on the magnetic recording medium.
• In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic-pattern transferring device transferring a magnetic pattern to a magnetic recording medium capable of recording magnetic information, the device comprising:
• • a master including a magnetic layer having a pattern patterned according to the magnetic pattern;
  • a magnet applying a magnetic field exciting the magnetic layer to the master placed close to the magnetic recording medium so as to transfer the pattern of the magnetic layer to the magnetic recording medium; and
  • a controller controlling the magnetic field applied from the magnet so as to correct a magnetic condition of a magnetically different part between the pattern transferred to the magnetic recording medium and the magnetic pattern.
• According to the present invention, the controller controls the magnetic field applied from the magnet so as to correct the magnetically different part of the transferred pattern upon performing the pattern transfer to the magnetic recording medium. Therefore, even though the magnetic-layer pattern formed on the master includes the part magnetically different from the original magnetic pattern, the magnetically different part can be corrected so that the magnetic-pattern transferring device can transfer the original magnetic pattern accurately to the magnetic recording medium.
• Besides, the above-mentioned magnet can be used both for applying a constant magnetic field so as to simply transfer the magnetic-layer pattern formed on the master to the magnetic recording medium, and for applying a magnetic field so controlled as to correct the magnetically different part.
• Additionally, the magnetic pattern transferring device according to the present invention may preferably further comprise a memory preliminarily storing difference data indicating the magnetically different part so that the controller controls the magnetic field applied from the magnet according to the difference data.
• According to the present invention, the controller controls the magnetic field applied from the magnet surely according to the difference data indicating the magnetically different part. Therefore, the magnetic-pattern transferring device can transfer the original magnetic pattern accurately to the magnetic recording medium.
• Additionally, the magnetic pattern transferring device according to the present invention may further comprise a magnetic reproducing head measuring a magnetic condition of the magnetic recording medium so as to detect a magnetically different part detection signal indicating the magnetically different part, wherein the difference data is created according to the magnetically different part detection signal.
• According to the present invention, the magnetic reproducing head provided for measuring the magnetic condition of the magnetic recording medium can indirectly measure a “deviation” of the magnetic-layer pattern formed on the master. By using this measurement result as the difference data stored in the memory, the magnetic-pattern transferring device can perform a series of steps for performing a pattern transfer to the magnetic recording medium while applying the magnetic field correcting the magnetically different part.
• Additionally, in the magnetic pattern transferring device according to the present invention, the magnet may be an electromagnet generating the magnetic field applied to the master, the magnetic field being controlled by changing a magnitude of an electric current supplied to the electromagnet, or may be a permanent magnet generating the magnetic field applied to the master, the magnetic field being controlled by changing a distance between the permanent magnet and the master.
• According to the present invention, when the electromagnet or the permanent magnet is used as the magnet applying the magnetic field, the intensity of the magnetic field applied to the master can be properly adjusted.
• Additionally, the magnetic pattern transferring device according to the present invention may further comprise a magnetic sensor detecting the magnetic field applied from the magnet so as to supply a magnetic-field detection signal indicating a condition of the magnetic field to the controller, wherein the controller controls the magnetic field applied from the magnet by using the magnetic-field detection signal.
• According to the present invention, the magnetic-pattern transferring device performs the magnetic transfer to the magnetic recording medium while the magnetic sensor confirms the condition of the magnetic field correcting the magnetically different part. Thereby, the magnetic-pattern transferring device can form the original magnetic pattern on the magnetic recording medium more surely.
• Additionally, the magnetic pattern transferring device according to the present invention may preferably further comprise a difference position detecting unit detecting a position of the magnetically different part on the magnetic recording medium so as to supply a position detection signal indicating the position of the magnetically different part to the controller, wherein the controller controls the magnetic field applied from the magnet positioned opposite the magnetically different part according to the position detection signal.
• According to the present invention, the magnet can supply the magnetic field correcting the magnetically different part while the controller confirms the position of the magnetically different part. Thereby, the magnetic-pattern transferring device can more surely form the original magnetic pattern on the magnetic recording medium.
• In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a method for manufacturing a master used for a-magnetic transfer, the method comprising:
• • a first-master manufacturing step of manufacturing a first master including a predetermined magnetic pattern based on magnetic information;
  • a magnetic-pattern-transferring step of transferring the magnetic pattern to a magnetic recording medium by using the first master;
  • an error confirming step of confirming an amount of a transfer error between the magnetic pattern transferred to the magnetic recording medium and the predetermined magnetic pattern; and
  • a second-master manufacturing step of manufacturing a second master as an authentic master based on a correction magnetic pattern so formed as to offset the amount of the transfer error.
• Additionally, the master manufacturing method according to the present invention may further comprise a step of forming the correction magnetic pattern by shifting an edge position of a magnetic layer to be formed on the authentic master from an edge position of a magnetic layer formed on the first master according to the amount of the transfer error so as to offset the amount of the transfer error.
• According to the present invention, the transfer error is corrected in'the authentic master. This authentic master can be used to transfer magnetic information to the magnetic recording medium with accuracy.
• In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic recording medium including magnetic signal marks formed acros s tracks adjacent to one another, the magnetic signal marks representing magnetic information, wherein the magnetic signal marks adjacent to each other share an overlapping area.
• According to the present invention, the adjacent magnetic signal marks are formed so as to overlap each other. This shortens an outer periphery of the magnetic signal marks as a whole. Accordingly, the edge positions inflicted with transfer errors also become shorter as a whole so as to restrain influences of the transfer errors.
• In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a method for manufacturing a magnetic recording medium, the method comprising the steps of:
• • preparing a modulated master including a modulated magnetic pattern so modulated from a predetermined magnetic pattern corresponding to magnetic information as to reduce a number of edges; and
  • transferring the modulated magnetic pattern to the magnetic recording medium by using the modulated master so as to form a transferred pattern on the magnetic recording medium.
• According to the present invention, the transferred pattern formed on the magnetic recording medium also has a small number of edges, reducing influences of transfer errors.
• In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic information reproducing device loaded with a magnetic recording medium including magnetic information transferred thereto by using a modulated master including a modulated magnetic pattern so modulated from a predetermined magnetic pattern corresponding to the magnetic-information as to reduce a number of edges; the device comprising:
• • a pattern demodulating device demodulating the modulated magnetic pattern so as to reproduce the magnetic information transferred to the magnetic recording medium.
• According to the present invention, the magnetic-information reproducing device can reduce influences of transfer errors by reproducing the magnetic information from the magnetic recording medium including the transferred pattern having a small number of edges.
• Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is an illustration of an example of a conventional magnetic-pattern transferring device;
• FIG. 2 illustrates a transfer of a magnetic pattern to a magnetic recording medium by using a master;
• FIG. 3 illustrates a case where an “extended blur” occurs in a transferred pattern on the magnetic recording medium;
• FIG. 4 is an illustration used for explaining a basic principle according to one aspect of the present invention;
• FIG. 5 illustrates a structure of a magnetic-pattern transferring device according to a first embodiment of the present invention;
• FIG. 6 illustrates a structure of a magnetic-pattern transferring device according to a second embodiment of the present invention;
• FIG. 7 illustrates a structure of a magnetic-pattern transferring device according to a third embodiment of the present invention;
• FIG. 8 is an illustration outlining steps for manufacturing an authentic master according to a fourth embodiment of the present invention;
• FIG. 9 illustrates the authentic master including a correction magnetic pattern;
• FIG. 10A andFIG. 10B are magnified views of a part of tracks formed on a surface of a conventional magnetic recording medium;
• FIG. 10C is a magnified view of a part of tracks formed on a surface of a magnetic recording medium according to a fifth embodiment of the present invention;
• FIG. 11 illustrates a conventional example of a magnetic transfer of 6-bit data;
• FIG. 12A illustrates a conversion table according to a sixth embodiment of the present invention;
• FIG. 12B illustrates a modulated master formed based on data converted by the conversion table;
• FIG. 13 illustrates a reproduction signal reproduced from a magnetic recording medium and data reproduced by using a gate signal;
• FIG. 14 illustrates a conversion table used for reversely looking up reproduced data; and
• FIG. 15 illustrates a series of steps from forming the modulated master, through manufacturing the magnetic recording medium, to loading and reproducing the magnetic recording medium on a magnetic information reproducing device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• A description will now be given, with reference to the drawings, of embodiments according to the present invention.FIG. 4 is an illustration used for explaining a basic principle according to one aspect of the present invention.
• InFIG. 4, amaster4 is placed on amagnetic recording medium7, and a magnetic field is applied from amagnet1 functioning as a magnetic field generating means, as described with reference toFIG. 1. However, in the present invention, in case a pattern transferred to themagnetic recording medium7 “deviates” as described hereinbefore, an intensity of the magnetic field applied to themaster4 is properly controlled so as to neutralize the deviation.
• Specifically, when a pattern (a magnetic-layer pattern) is formed on themaster4 by using the above-mentioned lithographic technology, the magnetic-layer pattern occasionally differentiates subtly from an original magnetic pattern. Thereupon, in the present invention, the magnetic-layer pattern formed on themaster4 is measured beforehand so as to confirm a part (a magnetically different part) different from the original magnetic pattern. Then, a magnetic transfer is performed to themagnetic recording medium7 while the magnetic field is applied so as to correct a magnetic condition of this magnetically different part to an original condition. Therefor, the magnetic field applied from themagnet1 to themaster4 is so arranged as to correct the above-mentioned magnetically different part. This arrangement is described in detail hereinafter.
• Here, a description will be given, with reference toFIG. 4, of an instance where the magnetic field is controlled so as to neutralize the magnetically different part according to the present invention.FIG. 4 shows two parts I and II of themaster4 and themagnetic recording medium7, the two parts I and II being distant from each other. In the left part I, the original magnetic pattern is formed on themaster4 such that soft magnetic layers6-1 are formed at anappropriate interval6. However, in the right part II, a problem in patterning themaster4 causes soft magnetic layers5-1 to be formed at aninterval5 wider than the original magnetic pattern.
• Conventionally, when thewider interval5 is formed as in the right part II of themaster4 shown inFIG. 4, a constant magnetic field is applied from themagnet1 such that a relatively wide magnetic pattern is transferred to themagnetic recording medium7. As a result of this, the magnetic pattern transferred to themagnetic recording medium7 “deviates” as a whole, as mentioned above.
• However, in the present invention, as indicated by arrows representingmagnetic fields2 and3, the intensity of the applied magnetic field is controlled according to patterning conditions of the magnetic layers formed on themaster4. Specifically, in a magnetic transfer performed in the part II of themaster4 having an inaccurate patterning dimension, the smallmagnetic field3 is applied, compared to themagnetic field2 used in a magnetic transfer performed in the part I, so that amagnetic pattern8 formed on themagnetic recording medium7 in the part II correctively becomes a magnetic pattern similar to amagnetic pattern9 formed in the part I.
• Accordingly, even though the magnetic-layer pattern formed on themaster4 includes a part magnetically different from the original magnetic pattern as designed, a transferred pattern corresponding to the original magnetic pattern can be formed on themagnetic recording medium7 while the magnetically different part is corrected.
• Besides, as also described hereinafter in the following embodiments, first performed in the present invention is a master transferring step of transferring the magnetic-layer pattern included in themaster4 to themagnetic recording medium7 by applying a constant magnetic field to themaster4. By this master transferring step, the magnetically different part included in the magnetic-layer pattern formed on themaster4 is reflected, as it is, on a transferred pattern formed on themagnetic recording medium7. In a pattern-difference measuring step coming next, a magnetic condition of themagnetic recording medium7 having the transferred pattern including the magnetically different part is measured so as to find a difference from the original magnetic pattern. Based on a measurement result of this pattern-difference measuring step, difference data is created.
• The difference data is stored in a storing means, such as a memory. Subsequently, in a magnetic transferring step, a pattern transfer is performed to themagnetic recording medium7 while the magnetic field applied from themagnet1 is controlled based on this difference data.
• That is, after the magnetically different part is measured in the master transferring step and the pattern-difference measuring step, only the magnetic transferring step is repeated for performing the pattern transfer while applying the magnetic field so as to correct the magnetically different part. Only these steps can manufacture the magnetic recording medium having the original magnetic pattern. In this course, it is preferred that the magnetic field be applied so as to correct the magnetically different part while confirming the magnetically different part by referring to positional information supplied from a sensor detecting the magnetically different part. The following embodiment sets forth an example of an arrangement for obtaining the above-mentioned positional information.
• Hereinbelow, descriptions will be given of embodiments according to the one aspect of the present invention.
First Embodiment
• In a first embodiment of the present invention, an electromagnet is used as the magnetic field generating means, and the intensity of the magnetic field applied to the master is controlled by changing an electric current supplied to this electromagnet, so as to form the original magnetic pattern on the magnetic recording medium.
• FIG. 5 illustrates a structure of a magnetic-pattern transferring device10 according to the first embodiment.
• As shown inFIG. 5, amaster12 is placed on amagnetic recording medium11. Themagnetic recording medium11 and themaster12 have forms of a disc, and are unitarily rotated in a direction indicated by a curvy arrow X in close contact with each other by a spindle13-1 of amotor13.
• In the present embodiment, a photo interrupter20 (a difference position detecting unit), for example, is provided in the vicinity of the spindle13-1 so as to detect a status of a rotation of the spindle13-1. A detection signal of thephoto interrupter20 is supplied to amain controller18 as a rotationalposition detection signal21. Themain controller18 is described in detail hereinafter. It is noted that themagnetic recording medium11 and themaster12 are fixed at predetermined positions with respect to the spindle13-1 so that a rotational position of themagnetic recording medium11 and themaster12 can be located by referring to the rotationalposition detection signal21.
• Anelectromagnet14 is provided as a magnetic field generating means opposite to the upper surface of themaster12. Thiselectromagnet14 is arranged underneath astage15 to be movable in a radial direction of themaster12. Thestage15 is connected to astage controller17. Thisstage controller17 controls a driving source (not shown in the figure) of thestage15 so as to set theelectromagnet14 at a desired position in a direction indicated by a double-headed arrow Y.
• Theelectromagnet14 is connected to acurrent controller16. Thecurrent controller16 controls a magnitude of an electric current supplied to theelectromagnet14 so as to vary the intensity of a magnetic field generated from theelectromagnet14, i.e., a magnetic field applied to themaster12.
• Further, the magnetic-pattern transferring device10 comprises themain controller18, as mentioned above. Themain controller18 detects the rotational position of themaster12 according to the above-mentioned rotationalposition detection signal21 so as to recognize a position, in a circumferential direction, of a magnetically different part included in a magnetic pattern formed on themaster12. Upon applying a constant magnetic field from theelectromagnet14, the magnetic pattern formed on themaster12 is transferred to themagnetic recording medium11 as a transferred pattern including the magnetically different part. Additionally, themain controller18 comprises amemory19. Thememory19 stores difference data obtained by comparing the transferred pattern including the magnetically different part with the original magnetic pattern.
• By using the rotationalposition detection signal21, themain controller18 supplies drive signals to thestage controller17 and thecurrent controller16 so as to control the position of theelectromagnet14 and the magnetic field generated therefrom. More specifically, themain controller18 refers to the rotationalposition detection signal21 so as to specify the position of the magnetically different part in the circumferential direction, and causes thestage controller17 to move theelectromagnet14 properly in the radial direction so as to position theelectromagnet14 opposite the magnetically different part. Themain controller18 also causes thecurrent controller16 to correct the magnetic field applied from theelectromagnet14 so as to neutralize an error of the magnetically different part. In the present embodiment, themain controller18, thestage controller17 and thecurrent controller16 function as magnetic field controlling means.
• According to the magnetic-pattern transferring device10 configured as describe above, even though the magnetic pattern formed on themaster12 includes the magnetically different part, the magnetically different part can be corrected so as to eliminate the deviation of the pattern transferred on themagnetic recording medium11 and form the original magnetic pattern thereon.
• Besides, although the present first embodiment detects and uses the status of the rotation of the spindle13-1 so as to detect the rotational position of themagnetic recording medium11 and themaster12, this configuration may be replaced by other configurations that can recognize the rotational position. For instance, a predetermined mark may be printed on an outer periphery of the master so that the mark is detected by a sensor, such as a CCD.
• In addition, the difference data stored beforehand in thememory19 may be created as follows. First, the constant magnetic field is applied from theelectromagnet14 so as to transfer a pattern reflecting the magnetically different part included in themaster12 to themagnetic recording medium11. Then, thismagnetic recording medium11 is retrieved from the magnetic-pattern transferring device10, and a magnetization of themagnetic recording medium11 is reproduced and measured by an evaluation device, such as a magnetic reproducing device. The difference data can be created from this measurement result and be stored in thememory19.
• Variation 1
• In the above-described first embodiment, the magnetic pattern formed on themaster12 is measured beforehand, and is stored in thememory19 as correction data (difference data), such that themain controller18 causes the magnetic field to be applied according to the correction data so as to correct the magnetically different part.
• Here, a description will be given, also with reference toFIG. 5, of avariation1 of the above-described first embodiment, further comprising a magnetic reproducing head reading the magnetic pattern.
• FIG. 5 includes a magnetic reproducinghead mechanism30. The magnetic reproducinghead mechanism30 has a configuration in which amagnetoresistive element31 used for a magnetic reproduction is mounted on a front end of anarm35 revolved by anactuator unit33. Driven by theactuator unit33, themagnetoresistive element31 is moved above the upper surface of themaster12 in a radial direction indicated by a white arrow Z. It may be arranged that themain controller18 perform a drive control of theactuator unit33 by supplying adrive control signal34.
• In thepresent variation1, the magnetic-pattern transferring device10 has a function of confirming a magnetically different part included in a magnetic-layer pattern formed on themaster12. The constant magnetic field is applied from theelectromagnet14 to themaster12 so as to transfer the pattern to themagnetic recording medium11. The pattern transferred to themagnetic recording medium11 is detected (reproduced) by themagnetoresistive element31.
• A magnetically differentpart detection signal32 is supplied from themagnetoresistive element31 to themain controller18 so that the magnetically different part included in the magnetic-layer pattern formed on themaster12 is indirectly measured. Thereafter, the magnetic pattern formed on themaster12 is compared with the original magnetic pattern so as to store a difference therebetween in thememory19, as in the first embodiment. Then, the magnetic pattern transfer to the magnetic recording medium is repeated while correcting the pattern, as described above.
• According to thepresent variation1, since a step of detecting the magnetically different part included in the magnetic-layer pattern formed on the master12 (the above-mentioned master transferring step and the above-mentioned pattern-difference measuring step) can also be performed, the magnetic-pattern transferring device0.10 can perform a series of the steps.
Second Embodiment
• A magnetic-pattern transferring device according to a second embodiment of the present invention has a function of monitoring the magnetic field applied from the magnetic field generating means to the master so as to transfer the magnetic pattern to the magnetic recording medium with higher precision.
• FIG. 6 illustrates a structure of a magnetic-pattern transferring device40 according to the second embodiment. Elements inFIG. 6 that are identical or equivalent to the elements of the magnetic-pattern transferring device10 shown inFIG. 5 are referenced by the same reference marks, and will not be described in detail. The magnetic-pattern transferring device40 comprises amagnetic sensor41 as a means for monitoring the magnetic field applied from the magnetic field generating means so as to detect the applied magnetic field and feed back detected information (a magnetic-field detection signal) to themain controller18. Thus, the magnetic-pattern transferring device40 according to the present second embodiment can control transferring conditions with higher precision.
• As avariation2 in the present second embodiment, the magnetic-pattern transferring device40 may comprise the magnetic reproducinghead mechanism30, as in thevariation1 in the first embodiment, so as to detect the magnetic-layer pattern formed on themaster12.
Third Embodiment
• In a third embodiment of the present invention, a permanent magnet is used as the magnetic field generating means, and the intensity of the magnetic field applied to the master is controlled by changing distance between this permanent magnet and the master, so as to form the original magnetic pattern on the magnetic recording medium.
• FIG. 7 illustrates a structure of a magnetic-pattern transferring device50 according to the third embodiment.
• Elements inFIG. 7 that are identical or equivalent to the elements of the magnetic-pattern transferring device10 shown inFIG. 5 are referenced by the same reference marks, and will not be described in detail.
• The magnetic-pattern transferring device50 according to the present third embodiment comprises a vertically movingstage52 and astage controller53 controlling a movement of the vertically movingstage52 so as to change a distance from apermanent magnet51 to the upper surface of themaster12. Thestage controller53 is controlled by themain controller18, as in the first embodiment. In the present embodiment, themain controller18, thestage controller17 and thestage controller53 function as magnetic field controlling means.
• In the present third embodiment, too, the magnetically different part included in themaster12 is measured beforehand, and is stored in thememory19 as correction data, such that themain Controller18 causes the magnetic field to be applied according to the correction data so as to correct the magnetically different part. In this course, the distance from thepermanent magnet51 to the upper surface of themaster12 is changed by moving the vertically movingstage52 so as to change the intensity of the magnetic field applied to themaster12, characteristically in the present third embodiment.
• According to the magnetic-pattern transferring device50 configured as describe above, even though the magnetic pattern formed on themaster12 includes the magnetically different part, the magnetically different part can be corrected so as to transfer the original magnetic pattern to themagnetic recording medium11.
• Additionally, the magnetic-pattern transferring device50 according to the present third embodiment may further comprise themagnetic sensor41 described in the second embodiment so as to monitor the magnetic field applied from thepermanent magnet51. Thereby, themain controller18 controls a feedback so as to transfer the original magnetic pattern to themagnetic recording medium11 with high precision.
• Further, as avariation3 in the present third embodiment, the magnetic-pattern transferring device50 may comprise the magnetic reproducinghead mechanism30, as in thevariation1 in the first embodiment, so as to detect the magnetic-layer pattern formed on themaster12.
• As described above, the magnetic-pattern transferring device controls the intensity of the magnetic field applied upon transferring the magnetic pattern formed on the master to the magnetic recording medium. Therefore, even though the magnetic-layer pattern formed on the master includes the magnetically different part, the magnetic-pattern transferring device can transfer the original magnetic pattern to the magnetic recording medium while correcting the magnetically different part.
• Whereas the heretofore described one aspect of the present invention solves the problem caused in the course of manufacturing the master (i.e., the magnetically different part included in the magnetic-layer pattern), the hereinbelow described other aspect of the present invention solves a problem concerning a transfer error occurring upon transferring the magnetic pattern formed on the master to the magnetic recording medium. The other aspect of the present invention includes three preferred embodiments (fourth to sixth embodiments). Hereinbelow, descriptions will be given of these three embodiments in order.
Fourth Embodiment
• First, the fourth embodiment includes an error confirming step of preliminarily confirming a transfer-error amount due to the above-described “extended blur” and the “reduced blur”. A correction magnetic pattern is so formed as to correct the transfer-error amount confirmed in the error confirming step. Based on this correction magnetic pattern, an authentic master is manufactured. A highly precise magnetic pattern-transfer can be realized by bringing the manufactured master close to a magnetic recording medium and applying an external magnetic field so as to transfer the magnetic pattern formed on the master to the magnetic recording medium.
• Besides, once the transfer error amount is confirmed in the error confirming step, the authentic master can be manufactured similarly. Additionally, as the error confirming step, a preliminary experiment, etc. may be performed aside from a series of the manufacturing steps so as to obtain the above-mentioned transfer-error amount. Alternatively, the above-mentioned transfer-error amount may be obtained by being estimated in a simulation, etc. The fourth embodiment incorporates the error confirming step prior to manufacturing the authentic master.
• Here, a description will be given of the fourth embodiment according to the present invention.FIG. 8 is an illustration outlining steps for manufacturing the authentic master including the error confirming step according to the fourth embodiment.
• Firstly, afirst master63 having a predetermined magnetic pattern based on magnetic information to be transferred to a magnetic recording medium is manufactured as follows. Thefirst master63 is manufactured in the same manner as conventionally. In step-A shown inFIG. 8, a step of generating and exposing a magnetic pattern is performed as a first stage of manufacturing thefirst master63. Specifically, a photosensitive material is applied on asubstrate60 provided for the first master, and an exposingdevice70 performs an exposing process to the photosensitive material according to a predetermined magnetic pattern to be transferred. The predetermined magnetic pattern is generated by a magnetic-pattern generating device71. In the exposingdevice70, while apattern controller72 positions apositioner73, thepositioner73 projects a laser or an electronic beam so as to expose the photosensitive material applied on thesubstrate60.
• Subsequently, in step-B, a step of developing and smoothing the magnetic pattern is performed as a second stage of manufacturing thefirst master63. In this step-B, apattern development78, anetching79, a magnetic-layer formation80, and asurface smoothing process81 are performed so as to finish manufacturing thefirst master63. In the above-mentioned step-A and step-B, the master is manufactured by using the lithographic technology, as conventionally.
• A characteristic part of the present fourth embodiment starts with step-C including the error confirming step for confirming a transfer-error amount. In this step-C, thefirst master63 is set in amagnetic transferring device90, while apositioner91 positions thefirst master63, so as to perform a magnetic transfer to amagnetic recording medium67. Then, a transferred pattern formed on themagnetic recording medium67 is evaluated by a transfer-precision evaluating device95. This transfer-precision evaluating device95 compares the predetermined magnetic pattern (a targeted pattern) generated by the magnetic-pattern generating device71 based on the magnetic information with the transferred pattern (a resulting pattern) actually formed on themagnetic recording medium67 so as to confirm the transfer-error amount. Information concerning this transfer-error amount is supplied to a correction-magnetic-pattern generating device97.
• This correction-magnetic-pattern generating device97 generates a correction magnetic pattern65 (shown inFIG. 9) including a magnetic-layer pattern so patterned as to offset the above-mentioned transfer-error amount.FIG. 9 illustrates anauthentic master64 including the correctionmagnetic pattern65. As shown inFIG. 9, theauthentic master64 includes the correctionmagnetic pattern65 having a magnetic layer65-1 shifted by a pattern correction amount ω at edge positions thereof so as to offset the transfer-error amount. According to the above-described arrangement, even though a transfer error occurs upon transferring the magnetic pattern formed on the master to the magnetic recording medium, a transferredpattern68 corresponding to the predetermined magnetic pattern can be formed on themagnetic recording medium67.
• Besides,FIG. 9 illustrates an example of the correction magnetic pattern correcting the “extended blur” occurring in the transferred pattern. In a case of the “extended blur” where a magnetized part68-1 composing the transferredpattern68 formed on themagnetic recording medium67 is extended at edge positions thereof, the correctionmagnetic pattern65 is so generated that the edge positions of the magnetic layer65-1 are shifted outwardly by the pattern correction amount ω so as to offset this “extended blur”. In a case of the “reduced blur”, the correctionmagnetic pattern65 is generated in a converse manner to the above-mentioned case of the “extended blur”, such that the edge positions of the magnetic layer65-1 are shifted inwardly by the pattern correction amount co so as to offset the “reduced blur”.
• As shown inFIG. 8, after the correctionmagnetic pattern65 is generated by the correction-magnetic-pattern generating device97 as described above, theauthentic master64 is manufactured as a second master through the step-A and the step-B, as in manufacturing thefirst master63. Since theauthentic master64 includes the correctionmagnetic pattern65 so formed as to offset the transfer-error amount, the transfer error occurring upon transferring the magnetic pattern to themagnetic recording medium67 can be restrained so as to realize an accurate pattern transfer to themagnetic recording medium67. Accordingly, a waveform of a signal reproduced from themagnetic recording medium67 accurately reflects the original magnetic pattern, as shown in a lower graph ofFIG. 9.
Fifth Embodiment
• The fifth embodiment focuses on that the transfer error such as the “extended blur” occurs at the edge positions of the magnetic-layer. A magnetic recording medium according to the present fifth embodiment is so structured as to restrain influences of the transfer error. Hereinbelow, a description will be given of the fifth embodiment.FIG. 10A toFIG. 10C are magnified views of a part of tracks formed on a surface of the magnetic recording medium.
• Servo information (magnetic information) used for causing a magnetic head to follow a track is required to be written as a signal crossing over a plurality of tracks, for a purpose of calculating an amount of a positional error from a particular track based on a magnitude of a reproduction signal reproduced from bits (hereinbelow referred to as magnetic signal marks) of the signal crossing over the tracks. Alternatively, the servo information is required to be written, as cycles of a signal composed of magnetic signal marks adjacent to each other in a linear form crossing the tracks obliquely, for a purpose of calculating an amount of a positional error based on a phase difference of the cyclic signal. Each of the above-mentioned magnetic signal marks corresponds to the magnetized part composing the pattern transferred from the master to the magnetic recording medium. Accordingly, the transfer error occurs at a perimeter of each of the magnetic signal marks.
• Thereupon, in the present fifth embodiment, in a case of transferring the positional servo information crossing over the tracks, the adjacent magnetic signal marks are agglomerated under predetermined conditions so as to create an overlapping area. This agglomeration shortens a peripheral length of edges of the transferred-pattern formed on the magnetic recording medium. This shortened peripheral length enables restraining influences of the transfer error.
• Hereinbelow, a more detailed description will be given, with reference toFIG. 10A toFIG. 10C, of the fifth embodiment.
• As shown inFIG. 10A, a servo information signal is transferred on a conventional magnetic recording medium as a transferred pattern including magnetic signal marks not overlapping each other but shifted by ½ of a width of each of the magnetic signal marks. Peripheral lengths of edges of the transferred pattern including the not overlapping magnetic signal marks total (10a+10b).
• Additionally, as shown inFIG. 10B, another conventional magnetic recording medium has a pattern including adjacent magnetic signal marks contacting each other. In this case, edges of the magnetic signal marks have a shorter peripheral length totaling (6a+10b) so as to preferably reduce an incidence of transfer errors.
• However, it is still preferable that a transferred pattern formed on a magnetic recording medium include as few transfer errors as possible.
• Thereupon, the magnetic recording medium according to the present fifth embodiment has a pattern including positively overlapped magnetic signal marks. Specifically, as shown inFIG. 10C, the magnetic signal marks are overlapped by ⅓ of a length of each of the magnetic signal marks in a circumferential direction as indicated by arrows shown inFIG. 10C so that edges of the magnetic signal marks have a still shorter peripheral length totaling (6a+3b/16). This still shorter peripheral length enables restraining influences of the transfer error more surely.
• A master forming the transferred pattern as illustrated inFIG. 10C can be used to form the magnetic recording medium including the pattern having the still shorter total peripheral length according to the present embodiment. The present embodiment can restrain influences of the transfer error with simple arrangements.
Sixth Embodiment
• In the sixth embodiment of the present invention, a master including a modulated pattern restraining the transfer error such as the “extended blur”is manufactured; a magnetic recording medium is manufactured by using this master; and the magnetic recording medium is reproduced while being demodulated by a magnetic information reproducing device. Hereinbelow, a description will be given of the sixth embodiment.
• FIG. 11 illustrates a conventional example of a magnetic transfer of 6-bit data (1,1,1,1,1,1). When this 6-bit data is transferred to amagnetic recording medium120 without any contrivances, transfer errors occur at six positions A to F corresponding to edge positions of magnetic layers formed in amaster110, as described above. As can be understood fromFIG. 11, as the number of edges increases, the incidence of transfer errors also increases.
• Thereupon, the present sixth embodiment uses a modulated master including a modulated magnetic pattern so modulated as to reduce the number of edges. Specifically, a conversion table as illustrated inFIG. 12A is provided in a hereinafter-described modulated-magnetic-pattern generating device. For example, this conversion table converts the above-mentioned 6-bit data (1, 1, 1, 1, 1, 1) into 10-bit data (1, 0, 0, 0, 1, 0, 1, 0, 0, 1).
• Based on this converted data (10-bit data), a modulatedmaster150 is formed as shown inFIG. 12B. This modulatedmaster150 includes a modulatedmagnetic pattern151 composed of 4 bits and 3 bits with 2 bits therebetween. Transferring with this modulatedmaster150 reduces the number of transfer errors which occur at only four positions A to D. Accordingly, the modulatedmagnetic pattern151 shown inFIG. 12B can largely restrain transfer errors occurring on amagnetic recording medium155, compared to the non-modulated magnetic-layer pattern shown inFIG. 11.
• As described above, the present sixth embodiment converts original data into a signal reducing the number of edges, and transfers a pattern including the reduced number of edges restraining the occurrence of transfer errors so as to increase a transferring precision.
• FIG. 13 illustrates a reproduction signal reproduced from themagnetic recording medium155 and the 10-bit data reproduced by using a gate signal. Besides, a reproducing process indicated inFIG. 13 is performed by the magnetic information reproducing device loaded with themagnetic recording medium155.
• The magnetic information reproducing device comprises a pattern demodulating device including a conversion table used for reversely looking up the reproduced data as shown inFIG. 14. The reproduced data is demodulated by the pattern demodulating device so as to be converted into the original data. Specifically, when transferred data having the composition of 4 bits and 3 bits with 2 bits therebetween is read by a magnetic head, and the 10-bit data (1, 0, 0, 0, 1, 0, 1, 0, 0, 1) is obtained by the gate signal, the original data, i.e., the 6-bit data (1, 1, 1, 1, 1, 1) can be obtained by performing a reverse lookup in the conversion table provided in the pattern demodulating device.
• FIG. 15 illustrates a series of steps from forming the modulated master including the modulated magnetic pattern, through manufacturing the magnetic recording medium, to loading and reproducing this magnetic recording medium on the magnetic information reproducing device. The steps according to the present sixth embodiment shown inFIG. 15 include approximate parts to the manufacturing steps-according to the above described fourth embodiment shown inFIG. 8. Elements inFIG. 15 that are identical or equivalent to the elements shown inFIG. 8 are referenced by the same reference marks, and will not be described in detail. Instead, the following description will be given mainly of characteristic points of the present sixth embodiment.
• In step-A shown inFIG. 15, a step of generating and exposing the modulatedmagnetic pattern151 is performed as a first stage of manufacturing the modulatedmaster150. The step-A shown inFIG. 15 is distinctive from the step-A shown inFIG. 8 by including a process of modulating original data OR into the modulatedmagnetic pattern151 having a small number of edges by a modulated-magnetic-pattern generating device171. Aside from this point, the step-A is performed in the same manner as in the fourth embodiment. Specifically, the photosensitive material is applied on thesubstrate60 provided for the modulated master, and the exposingdevice70 performs an exposing process for the modulatedmagnetic pattern151. Subsequently, in step-B, a step of developing and smoothing the modulated magnetic pattern is performed as a second stage of manufacturing the modulatedmaster150. This step-B is the same as in the above-described fourth embodiment.
• The modulatedmaster150 manufactured in the step-A and the step-B is set in themagnetic transferring device90 so as to perform a magnetic15 transfer to themagnetic recording medium155. Thereby, a transferred pattern corresponding to the modulatedmagnetic pattern151 of the modulatedmaster150 can be formed on themagnetic recording medium155.
• Themagnetic recording medium155 is loaded and used on a magneticinformation reproducing device200, such as a hard disk device. In the magneticinformation reproducing device200, a reproduction analog signal read by amagnetic head210 is digitalized by aread channel202. The resulting digital data corresponds to the modulated 10-bit data (1, 0, 0, 0, 1, 0, 1, 0, 0, 1). This 10-bit data is demodulated by apattern demodulating device204 so as to obtain the original data OR corresponding to the 6-bit data (1, 1, 1, 1, 1, 1).
• As described above, since the present sixth embodiment uses the modulated magnetic pattern so modulated as to reduce the number of edges, the sixth embodiment can restrain transfer errors occurring upon transferring the magnetic pattern from the master to the magnetic recording medium.
• In addition, although themagnetic recording medium155 including the transferred pattern corresponding to the modulatedmagnetic pattern151 is immediately loaded on the magneticinformation reproducing device200 in the above-described sixth embodiment, themagnetic recording medium155 may be loaded on the magneticinformation reproducing device200 after an accurate transfer to themagnetic recording medium155 is confirmed by a transfer evaluating device. In this case, the transfer evaluating device may comprise the same pattern demodulating device as described above.
• The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.
• The present application is based on. Japanese priority applications No. 2001-270998 filed on Sep. 6, 2001 and No. 2001-359311 filed on November 26, 2001, the entire contents of which are hereby incorporated by reference.

Claims (5)

1-14. (canceled)

15. A magnetic recording medium including magnetic signal marks formed across tracks adjacent to one another, the magnetic signal marks representing magnetic information, wherein said magnetic signal marks adjacent to each other share an overlapping area.

16-17. (canceled)

18. The magnetic recording medium claimed inclaim 15, wherein the magnetic signal marks are overlapped in a circumferential direction.

19. The magnetic recording medium claimed inclaim 15, wherein the magnetic signal marks are overlapped by ⅓ of a length of each of the magnetic signal marks.

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