JP3597450B2 - Method of manufacturing magnetic recording medium, magnetic recording medium, and magnetic recording device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a magnetic recording medium, a magnetic recording medium, and a magnetic recording device.
[0002]
[Prior art]
A magnetic recording device represented by a magnetic disk device is widely used as an external storage device of an information processing device such as a computer, and has recently been used as a video recording device or a recording device for a set-top box.
A magnetic disk device generally includes a shaft for fixing one or more magnetic disks in a skewered manner, a motor for rotating a magnetic disk joined to the shaft via a bearing, and a magnetic disk used for recording and / or reproduction. A head, an arm to which the head is attached, and an actuator that can move the head to an arbitrary position on the magnetic recording medium via the head arm. It is moving at a flying height.
[0003]
A magnetic recording medium mounted on a magnetic disk device generally has a NiP layer formed on the surface of a substrate made of an aluminum alloy or the like, performs a required smoothing process, texturing process, and the like, and then forms a metal base layer thereon. , A magnetic layer (information recording layer), a protective layer, a lubricating layer, and the like are sequentially formed. Alternatively, it is manufactured by sequentially forming a metal base layer, a magnetic layer (information recording layer), a protective layer, a lubricating layer, and the like on a surface of a substrate made of glass or the like. Magnetic recording media include in-plane magnetic recording media and perpendicular magnetic recording media. In the longitudinal magnetic recording medium, longitudinal recording is usually performed.
[0004]
The protective layer on the magnetic layer prevents the magnetic layer from being damaged due to the collision of the flying magnetic head or sliding with the contact type head, and the lubricating layer provides lubricity between the magnetic head and the medium. With this configuration, recording / reproduction with a flying / contact magnetic head is possible. Since the distance between the magnetic layer and the head can be reduced by using the floating type / contact type head, information can be recorded at a much higher density than an optical disk, a magneto-optical disk, or the like using a head of another type.
[0005]
The speed of increasing the density of magnetic recording media is increasing year by year, and there are various techniques for achieving this. For example, improvements such as reducing the flying height of the magnetic head, adopting a GMR head as the magnetic head, increasing the magnetic material used for the recording layer of the magnetic disk to have a high coercive force, and improving the information recording track of the magnetic disk Attempts have been made to reduce the distance between the two. For example, 100Gbit / inch ² Is required to have a track density of 100 ktpi or more.
[0006]
Each track is formed with a control magnetization pattern for controlling the magnetic head. For example, it is a signal used for position control of the magnetic head or a signal used for synchronization control. If the number of tracks is increased by narrowing the interval between information recording tracks, a signal used for controlling the position of the data recording / reproducing head (hereinafter, sometimes referred to as a “servo signal”) is also adjusted in the radial direction of the disk. On the other hand, it must be densely provided, that is, provided with a larger number so that precise control can be performed.
[0007]
Also, there is a request to increase the data recording capacity by reducing the area other than the area used for data recording, that is, the area used for the servo signal and the gap between the servo area and the data recording area to increase the data recording area. large. For this purpose, it is necessary to increase the output of the servo signal and the accuracy of the synchronization signal.
Conventionally, a method widely used for manufacturing is to make a hole near a head actuator of a drive (magnetic recording device), insert a pin with an encoder into the hole, engage the actuator with the pin, and accurately mount the head. It is driven to a position to record a servo signal. However, since the center of gravity of the positioning mechanism is different from the center of gravity of the actuator, highly accurate track position control cannot be performed, and it has been difficult to accurately record servo signals.
[0008]
On the other hand, there has also been proposed a technique of forming an uneven servo signal by irradiating a magnetic disk with a laser beam to locally deform the disk surface to form physical unevenness. However, the flying head becomes unstable due to the unevenness, which adversely affects recording and reproduction. It is necessary to use a laser beam having a large power to form the unevenness, which increases the cost. It takes time to form the unevenness one by one. There was a problem.
[0009]
For this reason, a new servo signal forming method has been proposed.
One example is a method in which a servo pattern is formed on a master disk having a magnetic film with a high coercive force, the master disk is brought into close contact with a magnetic recording medium, and an auxiliary magnetic field is applied from outside to transfer the magnetization pattern (US Pat. No. 5,991,91). No. 104).
Another example is a method of preliminarily magnetizing a medium in one direction, patterning a soft magnetic film having a high magnetic permeability and a low coercive force on a master disk, bringing the master disk into close contact with the medium, and applying an external magnetic field. The soft magnetic layer functions as a shield, and a magnetization pattern is transferred to an unshielded area (Japanese Patent Laid-Open No. 50-60212).
[0010]
Alternatively, the medium is magnetized in one direction in advance, a ferromagnetic film such as a soft magnetic material is provided on the master disk and patterned, and the master disk is brought into close contact with the medium and a magnetic field is applied from the outside to magnetize the soft magnetic material. (See Japanese Patent Application Laid-Open No. 10-45544, Digest of InterMag 2000, GT-06). Regardless of whether it is a shield or a magnetic recording source, both techniques use a master disk and form a magnetization pattern on the medium by a strong magnetic field.
[0011]
In general, the strength of the magnetic field depends on the distance, and when recording a magnetized pattern with the magnetic field, the pattern boundary is likely to be unclear due to the leakage magnetic field. Therefore, in order to minimize the leakage magnetic field, it is essential to bring the master disk and the medium into close contact. Further, as the pattern becomes finer, it is necessary to make the pattern adhere completely without any gap. Usually, both are pressed by vacuum suction or the like.
[0012]
Further, as the coercive force of the medium increases, the magnetic field used for transfer increases, and the leakage magnetic field also increases.
Therefore, the above technique is easy to apply to a flexible floppy disk that is easily pressed and a magnetic disk having a low coercive force that does not need to be adhered very strongly, but the coercive force for high-density recording using a hard substrate is high. It is very difficult to apply to a magnetic disk having 3000 Oe or more.
[0013]
In other words, a magnetic disk having a hard substrate may cause a defect in a medium when fine dust or the like is sandwiched at the time of close contact, or may damage an expensive master disk. In particular, in the case of a glass substrate, there has been a problem that the adhesion is insufficient due to the interposition of dust, so that magnetic transfer cannot be performed, and a crack occurs in the magnetic recording medium.
Further, the technique described in Japanese Patent Application Laid-Open No. 50-60212 has a problem that a pattern having an oblique angle with respect to the track direction of a disk can be recorded, but only a pattern having a weak signal intensity can be formed. was there. For a high-coercivity magnetic recording medium having a coercive force of 2000 to 2500 Oe or more, a ferromagnetic material (shielding material) for a pattern of a master disk is made of a saturated magnetic flux such as permalloy or sendust in order to secure a magnetic field strength for transfer. The use of a soft magnetic material with high density is inevitable.
[0014]
However, in the oblique pattern, the magnetic field of the magnetization reversal is in a direction perpendicular to the gap formed by the ferromagnetic layer of the master disk, and the magnetization cannot be tilted in a desired direction. As a result, a part of the magnetic field escapes to the ferromagnetic layer, so that it is difficult to apply a sufficient magnetic field to a desired portion during magnetic transfer, and it is difficult to form a sufficient magnetization reversal pattern and to obtain a high signal strength. With such an oblique magnetization pattern, the reproduction output is greatly reduced more than the azimuth loss with respect to the pattern perpendicular to the track.
[0015]
In order to solve these problems and provide a method for efficiently and accurately forming a magnetization pattern, the present inventors locally heat a magnetic thin film and apply an external magnetic field to the magnetic thin film. It has been found that a combination of the steps can accurately and efficiently form a magnetization pattern serving as a servo signal of a magnetic recording medium, and has been proposed in Japanese Patent Application Nos. 2000-25854 and 2000-48721.
[0016]
This technology forms a magnetization pattern on a magnetic recording medium by combining local heating and application of an external magnetic field. For example, the medium is magnetized in one direction in advance, and the medium is locally heated by irradiating energy rays or the like through a patterned mask, and an external magnetic field is applied while lowering the coercive force of the heated area, and applied to the heated area. Recording by an external magnetic field is performed to form a magnetization pattern.
[0017]
According to the present technology, since the external magnetic field is applied by lowering the coercive force by heating, the external magnetic field does not need to be higher than the coercive force of the medium, and recording can be performed with a weak magnetic field. Then, the area to be recorded is limited to the heated area, and no recording is performed even when a magnetic field is applied to the area other than the heated area. Therefore, a clear magnetization pattern can be recorded without bringing a mask or the like into close contact with the medium. Therefore, the medium and the mask are not damaged by the pressure bonding, and the defect of the medium is not increased.
[0018]
In addition, according to the present technology, an oblique magnetization pattern can be formed well. This is because there is no need to shield the external magnetic field with the soft magnetic material of the master disk as in the related art.
[0019]
[Problems to be solved by the invention]
As described above, the magnetization pattern forming technology described in the specification of Japanese Patent Application No. 2000-134608 and Japanese Patent Application No. 2000-134611 can form various fine magnetic patterns efficiently and accurately, and also damages a medium and a mask. This is an excellent technique that does not cause an increase in the number of defects in the medium.
[0020]
As a result of further study, in this technology, the lubricant on the magnetic recording medium may evaporate and lose weight due to local heating, resulting in a decrease in the impact resistance of the medium to the magnetic head and a possibility of insufficient durability. I understood.
In addition, it was found that when the magnetization pattern was formed continuously, the evaporated lubricant gradually adhered to the mask. The attached lubricant may diffract the energy beam used for heating, impair the clarity of the formed magnetic pattern, and reduce the signal output.
[0021]
Therefore, the present invention relates to a technique for forming a magnetization pattern on a magnetic recording medium by combining local heating and application of an external magnetic field, whereby a magnetic recording medium having high impact resistance and durability can be obtained, and a signal can be obtained even if continuous production is performed. It is an object of the present invention to propose a method of manufacturing a magnetic recording medium in which the output does not decrease, and to provide a magnetic recording medium and a magnetic recording apparatus which can perform high-density recording and have high durability in a short time and at low cost.
[0022]
[Means for Solving the Problems]
In light of the above-described situation, the present inventors have conducted intensive studies, and as a result, combined the step of locally heating the magnetic thin film and the step of applying an external magnetic field to the magnetic thin film to change the magnetization pattern of the magnetic recording medium. By forming a lubricating layer on the magnetic recording medium after the formation, it has been found that a magnetic recording medium and a magnetic recording apparatus having high impact resistance to a magnetic head can be obtained, and the present invention has been accomplished.
[0023]
That is, the method for manufacturing a magnetic recording medium of the present invention is a method for manufacturing a magnetic recording medium comprising a magnetic thin film having a magnetization pattern formed on a substrate and a lubricating layer, wherein the method is disposed near the magnetic recording medium. Forming the magnetization pattern by simultaneously irradiating the magnetic recording medium with energy rays through the mask means to locally heat the magnetic thin film and applying an external magnetic field to the magnetic thin film. A first lubricating layer thinner than the lubricating layer is formed on the magnetic thin film before forming the magnetic pattern, and a second lubricating layer is applied on the first lubricating layer after forming the magnetic pattern. Form It is characterized by the following.
According to the present invention, since the local heating and the application of the external magnetic field are combined in forming the magnetization pattern, only the heating area can be magnetized with a weak magnetic field without using a strong external magnetic field as in the related art. Then, even if a magnetic field is applied to a region other than the heating region, it is not magnetized. For this reason, the formed magnetic pattern has a clear magnetic domain boundary, a small magnetic transition width, a very steep magnetic transition at the magnetic domain boundary, and high output signal quality. Therefore, a magnetic recording medium and a magnetic recording apparatus suitable for high-density recording, on which a highly accurate magnetization pattern is formed, can be obtained at low cost.
[0024]
Further, since it is not necessary to press the medium against the mask, there is no risk of damaging the medium or the mask and increasing defects of the medium.
In the present invention, since the lubricating layer is formed on the magnetic recording medium after the formation of the magnetization pattern, the lubricating layer of the magnetic disk does not become insufficient unlike the related art. Therefore, it is possible to provide a magnetic recording medium and a magnetic recording apparatus having high impact resistance and durability to the magnetic head in a short time and at low cost. Since the lubricating layer may be absent or thin before the magnetic pattern is formed, the lubricating layer does not easily adhere to the mask, and the clarity of the magnetic pattern can be maintained even when the mask is continuously manufactured using a single mask. And a sufficient signal output can be obtained.
[0025]
Preferably, a first lubricating layer is formed beforehand on the magnetic thin film before forming the magnetization pattern, and a second lubricating layer is formed after forming the pattern. The presence of the first lubricating layer enables recording / reproduction using a magnetic head before forming a magnetic pattern, and enables various inspections and evaluations.
For example, the position and frequency of a defect can be inspected by recording and reproducing a specific pattern with a magnetic head. If the inspection is performed before the formation of the magnetized pattern, the specific pattern used for the inspection is overwritten with the desired magnetized pattern. Further, since the magnetization pattern is formed only on the medium that has passed the inspection, useless steps are reduced, which is advantageous in terms of cost.
[0026]
If the first lubricating layer has a thickness of 2.0 nm or less, the amount of evaporation of the lubricant is small even when locally heated due to the small amount of liberated lubricant, so that adhesion to the mask can be suppressed, which is preferable. However, in order to withstand recording and reproduction by a magnetic head, the film thickness is preferably 0.1 nm or more.
Alternatively, if the first lubricating layer is removed before the formation of the magnetized pattern after the magnetic recording medium is inspected by the magnetic head, evaporation of the lubricant due to local heating is eliminated, so that the mask is not contaminated.
[0027]
The lubrication layer may be formed only after the formation of the magnetization pattern. For example, there is a case where the inspection with the magnetic head is not performed or a case where the inspection is performed after the formation of the magnetization pattern.
When the local heating is performed by energy beam irradiation, it is easy to control the size and the power of the portion to be heated, and it is possible to accurately form a magnetization pattern. The energy beam is preferably a pulsed energy beam having a pulse width of 10 μsec or less. If the heating time width at the same position by the energy beam is 10 μsec or more, the heat generated by the applied energy is dispersed, the heating area is widened, and the resolution tends to decrease. Further, the pulse width is preferably 1 nsec or more. This is because it is preferable to keep the heating until the magnetization reversal of the magnetic thin film is completed.
[0028]
If a masking means is used at the time of energy beam irradiation, a complicated magnetization pattern can be formed simply and in a short time by one irradiation. Also, a special pattern that is difficult to record with a magnetic head can be easily formed.
For example, in a phase servo method for a magnetic disk, a magnetization pattern that extends linearly obliquely with respect to a radius and a track from the inner circumference to the outer circumference is used. Such a continuous pattern in the radial direction or a pattern oblique to the radius is difficult to produce by a conventional servo pattern forming method of recording a servo signal one track at a time while rotating the disk. According to the present invention, such a magnetization pattern can be formed simply and in a short time by a single irradiation, without requiring a complicated calculation or a complicated device configuration.
[0029]
The mask need not cover the entire surface of the magnetic disk. Even if the size includes the repetition unit of the magnetization pattern, it can be used by moving it, and a mask can be easily and inexpensively formed.
As the mask means, it is preferable to use a mask having a transmission part that partially transmits the energy beam, a so-called photomask. Since a photomask is easy to produce and good processing accuracy can be easily obtained, a highly accurate mask can be obtained and a highly accurate magnetization pattern can be formed.
[0030]
In order to suppress the adhesion of the lubricant to the mask means, it is preferable to provide a gap between the mask means and the medium during local heating.
It is preferable to form a protective layer on the magnetic thin film, because it is possible to prevent the magnetic thin film from being damaged by collision with a head or a mask or dust and dirt sandwiched between the masks. If the protective layer is too thick, the magnetization pattern may be blurred due to heat conduction in the lateral direction. Further, it is preferable that the thickness is thinner in order to reduce the distance between the magnetic thin film and the head during recording and reproduction. Therefore, the thickness is preferably 50 nm or less, more preferably 30 nm or less, and still more preferably 20 nm or less. However, in order to obtain sufficient durability, the thickness is preferably 0.1 nm or more, more preferably 1 nm or more.
[0031]
Further, it is preferable to keep the surface roughness Ra of the medium after forming the magnetic pattern at 3 nm or less so as not to impair the running stability of the flying head. The medium surface roughness Ra is the roughness of the medium surface not including the lubricating layer, and is a value calculated according to JIS B0601 after measuring with a stylus type surface roughness meter at a measurement length of 400 μm. . More preferably, the thickness is 1.5 nm or less.
[0032]
It is preferable to provide an underlayer under the magnetic thin film for refining the crystal of the magnetic thin film and controlling the orientation of the crystal plane.
The Curie temperature of the magnetic thin film is preferably 100 ° C. or higher. Below 100 ° C., the stability of the magnetic domain at room temperature tends to be low. It is more preferably at least 150 ° C. Particularly preferably, it is 180 ° C. or higher. The temperature is preferably 700 ° C. or less. If the magnetic thin film is heated to an excessively high temperature, it may be deformed.
[0033]
According to the present invention, a precise magnetization pattern can be formed, and a pattern in which a unit pattern is repeated can be easily formed. Therefore, the present invention is suitable for forming a control magnetic pattern of a magnetic head used for recording and / or reproduction of a medium. I have. In particular, it is highly effective when used for forming a servo pattern for tracking a recording / reproducing head on a data track or a reference pattern for writing a servo pattern. This is because recording is more difficult as the pattern is relatively simple, and the higher the density and the higher the precision, the higher the cost of the magnetic recording medium.
[0034]
The magnetic recording medium of the present invention is a magnetic recording medium comprising a magnetic thin film having a magnetization pattern formed on a substrate and a lubricating layer. With body A step of irradiating the magnetic recording medium with energy rays through a mask means disposed near the magnetic recording medium to locally heat the magnetic thin film, and simultaneously applying an external magnetic field to the magnetic thin film. To form the magnetization pattern A first lubricating layer thinner than the lubricating layer is formed on the magnetic thin film before forming the magnetic pattern, and a second lubricating layer is applied on the first lubricating layer after forming the magnetic pattern. Formed It is characterized by the following.
According to the present invention, the precision of the magnetization pattern is not limited by the patterning precision and the alignment precision of the mask, so that a fine magnetization pattern is formed with high precision. Then, a pattern is formed in which the magnetization transition width is small, the magnetization transition at the boundary of the magnetic domain is very steep, and the quality of the output signal is high.
[0035]
In addition, since it can be easily manufactured in a very short time and does not adhere to the master disk unlike the conventional case, the medium has few scratches and defects.
Furthermore, since the thickness of the lubricating layer can be made sufficiently large, impact resistance and durability are high. The lubricating layer does not easily adhere to the mask even when continuous manufacturing is performed, so that the signal output of the magnetization pattern is high. Since a high-quality precise magnetic pattern can be formed and a pattern that repeats a unit pattern can be easily formed, it is suitable for forming a control magnetic pattern of a magnetic head used for recording and / or reproducing of a medium.
[0036]
In particular, it is highly effective when used for forming a servo pattern for tracking a recording / reproducing head on a data track or a reference pattern for writing a servo pattern. This is because recording is more difficult as the pattern is relatively simple, and the higher the density and the higher the precision, the higher the cost of the magnetic recording medium.
The present invention Magnetism The magnetic recording device includes a magnetic recording medium, a driving unit that drives the magnetic recording medium in a recording direction, a magnetic head including a recording unit and a reproducing unit, a unit that relatively moves the magnetic head with respect to the magnetic recording medium, A magnetic recording apparatus having a recording / reproduction signal processing unit for performing a recording signal input to a head and a reproduction signal output from a magnetic head, wherein the magnetic recording medium is Of the present invention It is a magnetic recording medium. As a magnetic head, a floating / contact magnetic head is usually used to perform high-density recording.
[0037]
Since a magnetic recording medium on which a magnetic pattern such as a fine and highly accurate servo pattern is formed is used, such a magnetic recording apparatus can perform high-density recording. Further, since the medium has no scratches and few defects, recording with few errors can be performed.
Further, since the thickness of the lubricating layer of the magnetic recording medium can be made sufficiently large, the device has high impact resistance and durability. Then, even when the medium is continuously manufactured, the lubricating layer is hardly adhered to the mask, so that the signal output of the magnetization pattern is high.
[0038]
After the magnetic recording medium is assembled in the apparatus, the magnetization pattern is reproduced by a magnetic head to obtain a signal, and the signal is used as a reference to record a servo burst signal in the magnetic recording apparatus. Thus, a precise servo signal can be easily obtained.
Also, even after recording the servo burst signal with the magnetic head, if a signal recorded as a magnetization pattern according to the present invention remains in an area not used as a user data area, the magnetic head may be displaced due to some disturbance. Is easily returned to a desired position, and therefore a magnetic recording apparatus in which signals by both writing methods are present has high reliability.
[0039]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail.
A magnetic recording medium, such as a magnetic disk, on which recording and reproduction are performed by a flying head / contact head, usually has a lubricating layer as the uppermost layer. Without a lubricating layer, it is difficult to protect against impact and friction due to contact with the magnetic head, and it is difficult to obtain a magnetic recording medium having high impact resistance and durability.
[0040]
However, when a magnetization pattern is formed by combining local heating and application of an external magnetic field, heating reduces a portion of the lubricant on the magnetic recording medium due to evaporation. In addition, the lubricant may decrease due to contact with the mask.
Reduction of the lubricating layer lowers impact resistance and durability to the magnetic head. In the present invention, after forming a magnetization pattern by combining local heating and application of an external magnetic field, a high lubricating layer is formed to obtain a sufficiently thick lubricating layer, thereby achieving high impact resistance and durability to a magnetic head. I do.
[0041]
In the present invention, two embodiments can be considered for forming the lubricating layer.
Embodiment A: The lubrication layer is not formed before the formation of the magnetization pattern, and the lubrication layer is formed only after the formation of the magnetization pattern.
Embodiment B: The first lubrication layer is already formed before the formation of the magnetization pattern, and the second lubrication layer is formed again after the formation of the magnetization pattern.
[0042]
Hereinafter, each embodiment will be described in detail.
[1] Embodiment A
For example, a magnetic disk in which a NiAl underlayer, a CrMo underlayer, a Co-based alloy magnetic thin film, a diamond-like carbon protective layer, and the like are provided on a glass substrate or an aluminum alloy substrate by a sputtering method.
[0043]
After that, a defect inspection (certification) is performed by, for example, a non-contact optical surface inspection device. Since a high-speed inspection can be performed and a magnetic head is not used, a lubricating layer is not required. Next, a magnetization pattern is formed. For example, by magnetizing a magnetic thin film uniformly in a desired magnetization direction with a strong external magnetic field before heating a magnetic disk, and then applying a reverse external magnetic field while heating a desired portion to near the Curie point, and magnetizing the magnetic thin film. A magnetization pattern is formed, and then a lubrication layer is formed.
[0044]
First, a strong external magnetic field is applied to the magnetic disk to uniformly magnetize the entire magnetic thin film in a desired magnetization direction. As a means for applying an external magnetic field, a magnetic head may be used, or a plurality of electromagnets or permanent magnets may be arranged so as to generate a magnetic field in a desired magnetization direction. Further, these different means may be used in combination.
In the case of a medium having an easy axis of magnetization in the in-plane direction, the desired magnetization direction is the same as or opposite to the traveling direction of the data writing / reproducing head (the relative movement direction of the medium and the head). When the axis of easy magnetization is perpendicular to the in-plane direction, it is one of the perpendicular directions.
[0045]
Next, the surface of the magnetic thin film of the magnetic disk is partially heated, and the temperature is raised to the magnetization extinction temperature near the Curie point of the magnetic thin film. Magnetize in the direction. Thus, a magnetization pattern is formed. The heating means only needs to have a function of partially heating the surface of the magnetic thin film, but in consideration of prevention of heat diffusion to unnecessary parts and controllability, it is easy to control the power control and the size of the part to be heated. Those using energy rays such as lasers are preferred.
[0046]
By irradiating the disk with the energy beam through the mask means and heating, a magnetization pattern can be formed more easily in a shorter time.
As a means for applying a weak external magnetic field, a magnetic head may be used, or a plurality of electromagnets or permanent magnets may be arranged so as to generate a magnetic field in a desired magnetization direction. Further, these different means may be used in combination.
[0047]
It is preferable that the formed magnetic pattern has a magnetization transition width of ± 70% of the maximum magnetization value of the magnetic thin film of 1 μm or less.
Finally, a lubricant is applied to form a lubricating layer.
According to the embodiment A, since the lubricating layer is not provided at the time of forming the magnetization pattern, the energy beam used for heating is not scattered, diffracted or hindered by the lubricating layer. Since the mask and the magnetic recording medium can be in close contact with each other and the lubricant does not adhere to the mask, diffraction of energy rays can be minimized. Therefore, it is possible to form a highly accurate magnetization pattern that is clear and has a high signal output.
[0048]
Then, a lubricating layer having a sufficient thickness can be provided after the pattern is formed, so that the magnetic head has high impact resistance and durability.
Conventionally, a manufactured magnetic disk is subjected to a burnishing process using a burnishing head, in which a protrusion having a height equal to or greater than a predetermined height is removed, then the presence or absence of the protrusion is inspected. Inspection (certification) for inspecting the frequency and frequency.
[0049]
This embodiment is preferably applied to the case where recording / reproducing, inspection, and evaluation are not performed by the magnetic head before the formation of the magnetic pattern. For example, before pattern formation, an inspection without using a magnetic head such as a non-contact optical surface inspection device can be performed. The inspection may be performed with a magnetic head after a lubricating layer is formed after pattern formation. Alternatively, it is conceivable that the inspection using the magnetic head is not performed at all.
[0050]
The formation of the lubricating layer is generally performed by applying a lubricant, and an optional coating process such as a spin coating method, a pull-up coating method, and a spray coating method is used. In order to uniformly form a lubricating layer on a large amount of medium in a short time, a pull-up coating method is suitable.
As the lubricant, perfluoropolyether having an ester bond, dialkylamidocarboxylic acid, perchloropolyether, stearic acid, sodium stearate, phosphate ester, and the like are preferable. The ester bond may be located anywhere in the molecule, but it is more preferable to have a functional group of the ester bond at the end, since the movable portion in the molecule becomes longer and lubricity is easily obtained.
[0051]
Especially in the main chain, -C _a F _2a Perfluoropolyether having an O-unit (where a is an integer of 1 to 4) and having a functional group of an ester bond at a terminal is preferable. More preferred are perfluoroethers represented by the following general formula (I).
RO- (A ¹ -OA ² -O) _x -R (I)
(However, A ¹ , A ² Is CF ₂ And / or C ₂ F ₄ And A ¹ And A ² CF that constitutes ₂ And C ₂ F ₄ Ratio (CF ₂ / C ₂ F ₄ ) Is 5/1 to 1/5, X is 10 to 500, and R is an alkyl group having 1 to 20 carbon atoms containing a hetero atom or a fluorine-substituted alkyl group. )
For example, Fomblin-Z-DOL manufactured by Ausimont is CF ₂ CF ₂ O and CF ₂ It is a polymer of O, has a linear structure, and has an ester group -COOR (where R represents an alkyl group optionally substituted by fluorine) at both ends. Further, the demnum type (SP or SY) manufactured by Daikin Industries, Ltd. is a homopolymer of hexafluoropropylene oxide, and an ester group -COOR (where R represents an alkyl group which may be substituted by fluorine) at one end. Having.
[0052]
The number average molecular weight of the lubricant is preferably in the range of 100 to 10,000. More preferably, the number average molecular weight is from 2,000 to 6,000. If the molecular weight is low, the vapor pressure is generally high, evaporates little by little after coating, and moves away from the desired film thickness with time. Conversely, when the molecular weight is high, the viscosity is generally high and the desired lubricity may not be obtained in some cases.
[0053]
Preferably, Fomblin-Z-DOL (trade name), Fomblin-Z-Tetraol (trade name) manufactured by Ausimont, and the like are used.
As a solvent for dissolving these, for example, a fluorocarbon type, alcohol type, hydrocarbon type, ketone type, ether type, fluorine type, aromatic type, etc. are used.
Further, in order to enhance the chemical bond between the lubricant and the medium, it is preferable to perform a heat treatment after the formation of the lubricating layer. The heating temperature is 50 ° C. or higher, but may be appropriately selected within a range lower than the decomposition temperature of the lubricant. It is usually 100 ° C. or less.
[0054]
The coating thickness of the lubricant is preferably 10 nm or less. Even if the thickness is too large, a certain level of lubricity cannot be obtained, and excess lubricant moves to the outer peripheral side with the rotation of the disk, and the film thickness distribution at the inner and outer peripheries tends to occur. However, if the thickness is too small, desired lubricity cannot be obtained. It is more preferably at least 1 nm, particularly preferably at least 1.5 nm.
[2] Embodiment b
For example, a NiAl underlayer, a CrMo underlayer, a Co-based alloy magnetic thin film, a diamond-like carbon protective layer, and the like are provided on a glass substrate or a substrate such as an aluminum alloy by a sputtering method. Next, a first lubrication layer is formed to manufacture a magnetic disk.
[0055]
After that, after the protrusions having a predetermined height or more are removed in a burnishing process by a burnishing head, the presence or absence of the protrusions is inspected, and a magnetic head records and reproduces a specific pattern to inspect the position and frequency of the defect. Inspection (certification) is performed.
Next, a magnetization pattern is formed in the same manner as in Embodiment A.
[0056]
According to Embodiment B, since the first lubricating layer is formed, recording / reproduction using a magnetic head can be performed before forming the magnetic pattern, and various inspections and evaluations can be performed. For example, the position and frequency of a defect can be inspected by recording and reproducing a specific pattern with a magnetic head. If the inspection is performed before the formation of the magnetized pattern, the specific pattern used for the inspection is overwritten with the desired magnetized pattern. Further, since the magnetization pattern is formed only on the medium that has passed the inspection, useless steps are reduced, which is advantageous in terms of cost.
[0057]
Incidentally, the lubricating layer usually has a fixed portion and a free portion. The lubricant on the magnetic recording medium (usually, the outermost surface is a protective layer because it is a protective layer) is bonded and fixed to the surface of the medium. That is, it is strongly bonded to the protective layer and the magnetic layer. On top of that, there is loose lubricant which is not fixed. In order for the magnetic recording medium to have sufficient durability, both the fixed portion and the free portion need to be present in appropriate amounts.
[0058]
According to the study of the present inventors, it is considered that most of the lubricating layer, which loses weight by heating, is mostly a free part, and the loss of the fixed part is small.
Therefore, ideally, it is preferable that the first lubricating layer only forms a fixed portion that does not easily volatilize even when heated. For this purpose, the first lubricating layer is preferably provided as thin as possible, and preferably has a thickness of 2.0 nm or less. Since the film thickness is small, scattering, diffraction and interference of energy rays can be reduced. Since the amount of the liberated lubricant is small and the amount of evaporation is small even when locally heated, the adhesion to the mask can be suppressed. As a result, it is possible to form a highly precise magnetization pattern that is clear and has a high signal output. More preferably, it is 1.0 nm or less.
[0059]
In order to maintain long-term durability and impact resistance to the magnetic head, it is necessary to provide a thick lubricating layer, for example, preferably 1.5 nm or more. Can withstand. Therefore, in order to withstand short-time recording / reproducing with a magnetic head, the thickness of the first lubricating layer is preferably 0.1 nm or more, more preferably 0.5 nm or more.
[0060]
Alternatively, after inspecting the magnetic recording medium with a magnetic head, the first lubricating layer may be removed prior to forming the magnetization pattern. In this case, when forming a magnetization pattern, the energy beam used for heating is obstructed by the lubricating layer, or when a mask is used, a gap is formed between the mask and the magnetic recording medium for the lubricating layer and the accuracy of the energy beam wraparound increases. Problems such as reduction can be reduced, which is preferable. Further, since the evaporation of the lubricant due to the heating is eliminated, the mask is not contaminated. For example, the first lubricant layer can be cleaned and removed with a cleaning agent in which the lubricant forming the first lubricant layer is soluble.
[0061]
After the pattern is formed, a second lubricating layer having a sufficient thickness can be provided to compensate for the lubricating layer reduced by the heating step or to re-form the removed lubricating layer. High impact resistance and durability. However, since the second lubricating layer only has to compensate for the loose part, the second lubricating layer may be thinner than a case where it is formed only once. If the lubricating layer is too thick, there is a problem that the head is attracted to the medium and does not float.
[0062]
The formation of the lubricating layer is generally performed by applying a lubricant, and an optional coating process such as a spin coating method, a pull-up coating method, and a spray coating method is used. In order to uniformly form a lubricating layer on a large amount of medium in a short time, a pull-up coating method is suitable. However, in order to form a thin film, a spin coating method in which the lubricating layer is shaken off by centrifugal force is also suitable.
[0063]
Further, it is preferable that the concentration of the lubricant at the time of forming the second lubricating layer is lower than the concentration of the lubricant at the time of forming the first lubricating layer. Preferably, the concentration is about 50% or less of the first lubricant concentration, and more preferably about 10 to 20% of the first lubricant concentration.
The lubricant for forming the second lubricant layer may be different from the lubricant for the first lubricant layer, but it is preferable to use the same lubricant in order to simplify the process. When the same lubricant is used for the first and second lubrication layers, the number of lubrication layers becomes one as a whole.
[0064]
As the lubricant and its solvent, the same ones as described in Embodiment A can be applied.
Depending on the type of the lubricant, the film thickness that becomes a fixed portion by being chemically bonded to the medium slightly varies, but is generally in the range of 0.5 to 1.0 nm. In general, those having a polar group at the terminal are thicker. For example, the Fomblin-Z-DOL (trade name) series manufactured by Ausimont has a relatively thin fixed portion because the terminal is not a polar group. Also, if the molecular weight is high, the viscosity is high and the flow characteristics are not good, so that the flow tends to be difficult and the thickness tends to be thick.
[0065]
Alternatively, in order to accurately control the lubricant film thickness, the lubricant may be washed and removed using an arbitrary solvent before the formation of the magnetization pattern, and the lubricant pattern may be applied again after the formation of the magnetization pattern.
The solvent used for cleaning may be any solvent that has high solubility of the lubricant and does not corrode the medium. For example, fluorocarbons, alcohols, hydrocarbons, ketones, ethers, fluorines, aromatics, etc. Is used.
[0066]
Further, in order to enhance the chemical bond between the lubricant and the medium, it is preferable to perform a heat treatment after the formation of the lubricating layer. The heating temperature is 50 ° C. or higher, but may be appropriately selected within a range lower than the decomposition temperature of the lubricant. It is usually 100 ° C. or less.
The total thickness of the lubricant is preferably 10 nm or less. Even if the thickness is too large, a certain level of lubricity cannot be obtained, and excess lubricant moves to the outer peripheral side with the rotation of the disk, and the film thickness distribution at the inner and outer peripheries tends to occur. However, if the thickness is too small, desired lubricity cannot be obtained. It is more preferably at least 1 nm, particularly preferably at least 1.5 nm.
[0067]
Hereinafter, preferable conditions common to the embodiments A and B will be described.
In the present invention, the following aspects can be taken as a combination of the step of locally heating the magnetic thin film and the step of applying an external magnetic field to the magnetic thin film.
Embodiment 1: A method of forming a magnetized pattern by magnetizing a magnetic thin film uniformly in a desired direction with a strong external magnetic field before heating, and then heating and demagnetizing a desired portion to a magnetization extinction temperature, for example, near the Curie point. According to this, the magnetization pattern can be formed most easily. Further, since the magnetic thin film is uniformly magnetized, normal magnetic recording can be performed after forming a magnetized pattern by this method.
[0068]
Aspect 2: Magnetization pattern by magnetizing a magnetic thin film uniformly in a desired direction with a strong external magnetic field before heating, and then heating a desired portion to a magnetization extinction temperature, for example, near the Curie point, and simultaneously applying a weak magnetic field to demagnetize it. How to form. According to this, demagnetization can be completely performed, and a magnetization pattern with a large signal intensity can be obtained.
Aspect 3: A method in which a weak external magnetic field is applied simultaneously with heating to magnetize only the heating portion in the direction of the external magnetic field, thereby forming a magnetization pattern. According to this, the magnetization pattern can be formed most easily, and the external magnetic field may be weak.
[0069]
Aspect 4: A method of forming a magnetized pattern by magnetizing a magnetic thin film uniformly in a desired direction with a strong external magnetic field before heating, and then heating a desired portion and simultaneously applying a weak magnetic field in a direction opposite to that before heating. . According to this, a magnetization pattern having the strongest signal intensity and good C / N and S / N can be obtained.
Hereinafter, each embodiment will be described.
[0070]
The direction of the external magnetic field of the first aspect differs depending on the type of the magnetic thin film of the magnetic recording medium. In the case of a medium in which the axis of easy magnetization is in the in-plane direction, the magnetic thin film is applied so as to be magnetized in the same direction or the opposite direction to the traveling direction of the data writing / reproducing head (the relative movement direction of the medium and the head). . Further, when the magnetic recording medium has a disk shape, the magnetic recording medium can be applied so as to be magnetized in the radial direction. When the axis of easy magnetization is perpendicular to the in-plane direction, the magnetic thin film is applied so as to be magnetized in any of the perpendicular directions.
[0071]
The strength of the magnetic field depends on the characteristics of the magnetic thin film of the magnetic recording medium, and it is preferable that the magnetic thin film is magnetized by a magnetic field at least twice the coercive force at room temperature. If it is lower than this, the magnetization may be insufficient. However, the coercive force of the magnetic thin film at room temperature is preferably 5 times or less in view of the capability of the magnetizing device used for applying the magnetic field.
In Embodiment 2, the direction and intensity of the external magnetic field before heating are exactly the same as in Embodiment 1.
[0072]
The direction of the magnetic field applied at the same time as the heating is in the direction perpendicular to the in-plane direction when the easy axis is in the in-plane direction, and in the medium direction when the easy axis is perpendicular to the in-plane direction. In-plane direction. Thus, the magnetic field is applied to erase the magnetization.
The strength of the magnetic field depends on the characteristics of the magnetic thin film of the magnetic recording medium, but is smaller than the coercive force of the magnetic thin film at room temperature. Preferably, the magnetic field is at least 1/8 of the coercive force of the magnetic thin film at room temperature. If it is lower than this, the heating unit may be magnetized again in the same direction as the surroundings under the influence of the magnetic field from the surrounding magnetic domains during cooling.
[0073]
However, it is preferable that the coercive force of the magnetic thin film at room temperature is not more than 1/2 times. If it is larger than this, the magnetic domains around the heating unit may be affected.
The heating may be performed at a temperature at which the coercive force of the magnetic thin film is reduced. For example, the heating is near the Curie temperature, which is the temperature at which the magnetic thin film disappears. Preferably, it is heated to 100 ° C. or higher. Magnetic thin films that are affected by an external magnetic field below 100 ° C. tend to have low domain stability at room temperature. Further, the heating temperature is preferably set to 700 ° C. or lower, particularly preferably 400 ° C. or lower. If it exceeds this, the magnetic thin film may be deformed.
[0074]
The direction of the external magnetic field at the same time as the heating in the aspect 3 differs depending on the type of the magnetic thin film of the magnetic recording medium. In the case of a medium in which the axis of easy magnetization is in the in-plane direction, the magnetic thin film is applied so as to be magnetized in the same direction or the opposite direction to the traveling direction of the data writing / reproducing head (the relative movement direction of the medium and the head). . Further, when the magnetic recording medium has a disk shape, the magnetic recording medium can be applied so as to be magnetized in the radial direction. When the axis of easy magnetization is perpendicular to the in-plane direction, the magnetic thin film is applied so as to be magnetized in any of the perpendicular directions.
[0075]
The strength of the magnetic field is the same as the strength of the external magnetic field at the same time as the heating in the second embodiment. The heating temperature is the same as in the second embodiment.
In Embodiment 4, the direction and intensity of the external magnetic field before heating are exactly the same as those in Embodiment 1.
The strength of the magnetic field applied simultaneously with the heating is the same as in the second embodiment, but the direction is applied in the opposite direction to the direction of the pre-heating magnetic field so that the magnetization is locally reversed. The heating temperature is the same as in the second embodiment.
[0076]
When an external magnetic field is applied simultaneously with heating, a plurality of magnetization patterns can be formed at once by applying the external magnetic field over a wide area of the heated area.
When the local heating is performed by energy beam irradiation, it is easy to control the size and the power of the portion to be heated, and it is possible to accurately form a magnetization pattern.
In the present invention, it is preferable to irradiate an energy ray through a mask means and locally heat. Once a mask is formed, a magnetized pattern of any shape can be formed on a medium, so that a complicated pattern or a special pattern that has been difficult to make by a conventional method can be easily formed.
[0077]
For example, in a phase servo method for a magnetic disk, a magnetization pattern that extends linearly obliquely with respect to the radius from the inner circumference to the outer circumference is used. Such a continuous pattern or an oblique pattern in the radial direction is difficult to produce by a conventional servo pattern forming method of recording a servo signal one track at a time while rotating a disk, and requires a complicated calculation and configuration.
[0078]
However, once a mask corresponding to the shape is created, the pattern can be easily formed simply by exposing the mask at a desired position on the disk.
The mask means may be any as long as it forms the density of the energy beam on the surface of the magnetic disk corresponding to the magnetization pattern to be formed. For example, a photomask having a transmission portion that transmits an energy ray according to a pattern, or a hologram mask in which a hologram that forms a specific pattern on a medium is recorded. Thereby, a plurality of or a large area of the magnetized pattern can be formed at a time, so that the magnetized pattern forming step is short and simple. According to the hologram mask, a sharp and clear pattern can be easily formed even if the distance between the mask and the medium is sufficiently long. However, a photomask is preferable because it can be easily and inexpensively formed.
[0079]
Alternatively, an imaging optical system may be used as the mask means. For example, an energy beam from a laser light source is expanded by a beam expander, and the light is incident on a mask unit. In this method, an energy ray having a density distribution of the mask means exiting the mask means is incident on the imaging lens, and the density distribution of the energy ray is imaged on the disk surface. This method is effective for forming a magnetic pattern of a small-diameter magnetic recording medium into a magnetic pattern because the pattern having the density of the energy beam is narrowed down. This method may also be referred to as a reduced imaging method, a reduced projection method, or the like.
[0080]
Although the material of the mask is not limited, if the mask is made of a non-magnetic material in the present invention, a magnetized pattern can be formed with uniform clarity in any pattern shape, and a uniform and strong reproduced signal can be obtained.
It is not preferable to use a mask containing a ferromagnetic material because the magnetic field distribution is disturbed by magnetization. Due to the ferromagnetic properties, in the case of a pattern shape obliquely inclined from the radial direction of the magnetic disk or an arc-shaped pattern extending in the radial direction, it is difficult to obtain a good quality signal because the magnetic domains do not sufficiently oppose each other at the magnetization transition portion.
[0081]
The mask is arranged between the energy beam light source and the magnetic thin film. If importance is placed on the accuracy of the magnetization pattern, it is preferable that all or part of the mask is in contact with the medium. For example, when the mask is allowed to stand on the medium, a part of the medium that is not in contact with the medium is formed due to undulation of about several μm. However, the pressure applied to the mask and the medium is 100 g / cm so as not to form indentations or damage to the medium. ² The following is assumed.
[0082]
In order to suppress the damage of the medium and the mask means and the generation of defects due to the pinching of dust or the like, it is preferable to provide a gap between the mask means and the medium at least in the magnetization pattern forming region of the medium.
When the first lubricating layer is provided before the formation of the magnetization pattern, it is also preferable to provide a gap between the mask means and the medium in order to minimize the adhesion of the lubricant to the mask means. .
[0083]
As a method for maintaining the gap between the magnetic pattern forming region of the magnetic recording medium and the mask means, any method may be used as long as both can be maintained at a fixed distance. For example, the mask and the medium may be held by a specific device to keep a certain distance. In addition, a spacer may be inserted between the two and at a location other than the magnetization pattern forming region. A spacer may be formed integrally with the mask itself.
[0084]
If a spacer is provided between the mask means and the magnetic recording medium at the outer peripheral portion and / or the inner peripheral portion of the magnetic pattern forming region of the medium, the effect of correcting the undulation on the surface of the magnetic recording medium is produced, so that the accuracy of forming the magnetic pattern is reduced. It is good because it goes up.
Hereinafter, a method of forming a magnetization pattern using a photomask will be described.
A mask in which a plurality of transmission portions are formed in accordance with a magnetization pattern to be formed is prepared, and a laser beam is irradiated on the magnetic thin film through the mask. If the beam diameter is set to be large or horizontally elongated, elliptical shape, etc., and irradiating the magnetized pattern for a plurality of tracks at once, the writing efficiency will be further increased and the servo writing time will increase as the capacity increases. Improved and very favorable.
[0085]
The mask is usually formed by sputtering metal such as Cr on a glass master, applying a photoresist, exposing and developing this according to the desired pattern, and then creating the desired transmissive and non-transmissive parts by etching etc. Then, finally, the photoresist layer is removed to manufacture the semiconductor device. In this case, a portion having a Cr layer on the glass master becomes an energy ray non-transmitting portion, and a portion of the glass master alone becomes a transmitting portion.
[0086]
When external magnetization is applied simultaneously with heating, it is preferable that an external magnetic field can be simultaneously applied to a plurality of transmission portions of the mask.
The minimum gap between the mask means and the magnetic recording medium is preferably at least 1 μm. The lubricant can be prevented from contacting and adhering to the mask means. In addition, most of dust that easily adheres to the medium and cannot be easily removed by air blow or the like is usually less than 1 μm. If the interval is less than 1 μm, the undulation of the medium surface may cause unexpected contact between the magnetized pattern forming portion and the mask means, which may damage the mask or the magnetic recording medium. More preferably, it is 5 μm or more. The spacing is set to 1 mm or less. If it is larger than this, the diffraction of the energy ray is large and the magnetization pattern is apt to be blurred.
[0087]
For example, when an excimer laser (248 nm) is used to transfer a 2 × 2 μm pattern (a pattern having 2 μm transmissive portions and 2 μm non-transmissive portions alternately) formed on a photomask to a medium, the distance between the mask and the medium is increased. Must be kept at about 25 to 45 μm or less. If the distance is longer than this, the pattern of light and dark of the laser beam is not clear due to the diffraction phenomenon. In the case of a 1 × 1 μm pattern (a pattern having 1 μm transmitting portions and 1 μm non-transmitting portions alternately), the distance is set to about 10 to 15 μm or less.
[0088]
When a photomask is used, it is preferable to keep the distance from the medium as short as possible within the above range. This is because the longer the distance, the more easily the magnetic pattern is blurred due to the wraparound of the irradiated energy beam. In order to improve this and obtain a clearer pattern, by forming a thin transmission part that functions as a diffraction grating outside the transmission part of the mask, or by providing a means that functions as a half-wave plate The wraparound light can be canceled by interference.
[0089]
On the other hand, when a hologram mask is used, the distance from the medium to the medium is adjusted so that the distance from the holographic pattern to the image forming plane is determined in advance. Note that by using a prism, the mask and the medium can be brought close to each other.
A magnetic disk may have a magnetic thin film formed on both main surfaces of the disk. In such a case, the magnetic pattern formation of the present invention may be performed one by one, sequentially, or may be performed by a mask means, an energy irradiation system, and an external magnetic field. The means for applying the magnetic field can be installed on both sides of the magnetic disk to simultaneously form a magnetization pattern on both sides.
[0090]
The energy ray used in the present invention is only required to be able to partially heat the surface of the recording layer, but is preferably a laser because it can prevent irradiation of unnecessary parts with the energy ray.
In particular, use of a pulse laser light source is preferred. A pulsed laser light source oscillates a laser intermittently in a pulsed manner. Compared to a continuous laser which is intermittently pulsed by an optical component such as an acousto-optic device (AO) or an electro-optic device (EO), it is pulsed. It is very preferable that a laser having a high power peak value can be irradiated in a very short time and heat accumulation hardly occurs.
[0091]
When a continuous laser is pulsed by an optical component, the pulse has substantially the same power over the pulse width. On the other hand, a pulsed laser light source accumulates energy by resonance in the light source, for example, and emits the laser at once as a pulse. In the present invention, in order to form a magnetization pattern having high contrast and high accuracy, it is preferable to rapidly heat the film in a very short time and then rapidly cool it. Therefore, a pulse laser light source is suitable.
[0092]
It is preferable that the medium surface on which the magnetization pattern is formed has a large temperature difference between when the pulsed energy beam is irradiated and when it is not irradiated, in order to increase the pattern contrast or the recording density. Therefore, it is preferable that the temperature be lower than room temperature when the pulsed energy beam is not irradiated. Room temperature is about 25 ° C.
The heating time width at the same position by the energy beam is desirably 10 μsec or less. If the pulse width is wider than this, the heat generated by the energy applied to the magnetic recording medium by the energy rays is dispersed, and the resolution is likely to be reduced. More preferably, it is 100 nsec or less. In this region, even when a substrate such as Al having a relatively large thermal diffusion of a metal is used, a magnetization pattern with high resolution is easily formed. Particularly preferably, it is 25 nsec or less. Further, the pulse width is preferably 1 nsec or more. This is because it is preferable to keep the heating until the magnetization reversal of the magnetic thin film is completed. More preferably, it is set to 3 nsec or more.
[0093]
As one type of pulsed laser, there is a laser such as a mode-locked laser which can generate picosecond and femtosecond level ultrashort pulses at a high frequency. During the period of irradiating the ultrashort pulse at a high frequency, the laser is not irradiated for a very short time between each ultrashort pulse, but the heating portion is hardly cooled because it is a very short time. That is, the region once heated to a temperature equal to or higher than the magnetization erasing temperature is maintained at a temperature equal to or higher than the magnetization erasing temperature.
[0094]
Therefore, in such a case, the continuous irradiation period (the continuous irradiation period including the time during which the laser is not irradiated between the ultrashort pulses) is defined as one pulse. In addition, the integral value of the irradiation energy amount during the continuous irradiation period is calculated as the power per pulse (mJ / cm). ² ).
The power per pulse of the pulsed energy beam is 1000 mJ / cm ² It is preferable to set the following. If a power larger than this is applied, the surface of the magnetic recording medium may be damaged and deformed by the pulsed energy rays. If the roughness Ra becomes 3 nm or more and the undulation Wa becomes 5 nm or more due to deformation, there is a possibility that the traveling of the flying / contact type head may be hindered.
[0095]
More preferably, 500 mJ / cm ² Or less, more preferably 100 mJ / cm ² It is as follows. In this region, a magnetization pattern with high resolution is easily formed even when a substrate having relatively large thermal diffusion is used. The power is 10mJ / cm ² It is preferable to make the above. If it is smaller than this, the temperature of the magnetic thin film does not easily rise and magnetic transfer hardly occurs.
[0096]
In the case where the power per pulse is the same, a shorter pulse width and irradiation with a stronger pulse at a time tend to reduce the thermal diffusion and increase the resolution of the magnetization pattern.
When the substrate used in the present invention is a metal or alloy such as Al, the thermal conductivity is large, so that the locally applied heat does not spread to a portion other than the desired portion and does not distort the magnetization pattern. The power is 30 to 120 mJ / cm to prevent physical damage to the substrate due to excessive energy. ² Is preferable.
[0097]
When the substrate is made of ceramics such as glass, the power is 10 to 100 mJ / cm because heat conduction is less than that of Al or the like and heat is accumulated more at the pulsed energy beam irradiation site. ² Is preferable.
When the substrate is made of a resin such as polycarbonate, the power is 10 to 80 mJ / cm because the heat is accumulated more at the pulsed energy beam irradiation site and the melting point is lower than that of glass or the like. ² Is preferable.
[0098]
If the magnetic thin film, the protective layer, and the lubricating layer are likely to be damaged by the energy beam, a measure may be taken to reduce the power of the pulsed energy beam and increase the intensity of the magnetic field applied simultaneously with the pulsed energy beam. Can also be taken. For example, in the case of an in-plane recording medium, 25 to 75% of the coercive force at room temperature is applied, and in the case of perpendicular recording, a large force of 1 to 50% is applied to lower the irradiation energy.
[0099]
The wavelength of the energy ray is preferably 1100 nm or less. If the wavelength is shorter than this, the diffraction effect is small and the resolution is increased, so that a fine magnetization pattern is easily formed. More preferably, the wavelength is 600 nm or less. In addition to high resolution, there is an advantage that the spacing between the mask and the magnetic recording medium by the gap can be widened due to small diffraction, handling is easy, and the magnetic transfer apparatus is easy to configure. Further, the wavelength is preferably 150 nm or more. If it is less than 150 nm, the absorption of synthetic quartz becomes large, making it difficult to use a mask. If the wavelength is 350 nm or more, the optical glass can be used as a mask.
[0100]
Specifically, an excimer laser (248 nm), a second harmonic (532 nm), a third harmonic (355 nm), or a fourth harmonic (266 nm) of a Q switch laser (1064 nm) of YAG, an Ar laser (488 nm, 514 nm), Ruby laser (694 nm) and the like.
When the medium has a disk shape, the direction of application of the external magnetic field is preferably one of a circumferential direction, a radial direction, and a direction perpendicular to the plate surface.
[0101]
As a means for applying an external magnetic field to the magnetic thin film, a magnetic head may be used, or a plurality of electromagnets or permanent magnets may be arranged so as to generate a magnetic field in a desired magnetization direction. May be used in combination.
When forming a magnetization pattern, a light-shielding plate capable of partially shielding energy rays is provided between a light source of the energy rays and the mask means, or in an area where irradiation between the mask means and the medium is not desired. It is preferable to provide a structure for preventing re-irradiation of energy rays.
[0102]
The light-shielding plate may be any as long as it does not transmit the wavelength of the energy beam used, and may reflect or absorb the energy beam. However, if the heat of the energy ray is absorbed, it is likely to be heated to influence the magnetization pattern. Therefore, a material having good thermal conductivity and high reflectance is preferable. For example, a metal plate such as Cr, Al, and Fe is used.
It is preferable that the substrate of the magnetic recording medium of the present invention be made of glass because the amount of heat given by the energy rays dispersed by thermal diffusion is small and energy can be used efficiently. In addition, there is also an effect that the resolution of the magnetization pattern is increased due to the small heat diffusion. When the present invention is applied to a glass substrate, it is also resistant to entrapment of dust and the like, and the magnetic recording medium is not cracked and the mask is not damaged due to the hardness of the substrate surface.
[0103]
According to this method, a more precise magnetization pattern can be formed than before, and a pattern that repeats a unit pattern can be easily formed. Therefore, the method is suitable for forming a magnetic pattern for controlling a magnetic head used for recording and / or reproduction of a medium. ing. In particular, the relatively simple pattern, the higher the density and the higher the precision, the more difficult the recording, and the main cause of the increase in the cost of the magnetic recording medium. The effect is great when used for forming a servo pattern or a reference pattern for writing a servo pattern. Since writing of these specific patterns is performed at a pitch of half the data track pitch, it was difficult to secure the writing accuracy.However, applying this method makes it easy to write patterns for high density. Can be.
[0104]
Next, the configuration of the magnetic recording medium of the present invention will be described.
As the substrate in the magnetic recording medium of the present invention, an Al alloy substrate containing Al as a main component such as an Al-Mg alloy, a Mg alloy substrate containing Mg as a main component such as an Mg-Zn alloy, or a normal soda A substrate made of glass, aluminosilicate glass, amorphous glass, silicon, titanium, ceramics, various resins, a substrate obtained by combining them, or the like can be used. Among them, it is preferable to use an Al alloy substrate, a glass substrate such as crystallized glass in terms of strength, and a resin substrate in terms of cost, since the advantage that the mask means and the magnetic recording medium do not contact each other is particularly advantageous.
[0105]
In the manufacturing process of the magnetic disk, the substrate is usually washed and dried first, and in the present invention, it is preferable to perform washing and drying before forming the substrate from the viewpoint of ensuring the adhesion of each layer.
In manufacturing the magnetic recording medium of the present invention, a metal coating layer such as NiP may be formed on the substrate surface.
[0106]
When the metal coating layer is formed, a method used for forming a thin film such as an electroless plating method, a sputtering method, a vacuum evaporation method, and a CVD method can be used. In the case of a substrate made of a conductive material, it is possible to use electrolytic plating. The thickness of the metal coating layer may be 50 nm or more. However, in consideration of the productivity of the magnetic disk medium, the thickness is preferably 50 nm or more and 500 nm or less. More preferably, it is 50 nm or more and 300 nm or less.
[0107]
Further, the region where the metal coating layer is formed is desirably the entire surface of the substrate, but it is also possible to implement only a part, for example, only the region to be textured.
Also, concentric texturing may be applied to the substrate surface or the substrate surface on which the metal coating layer is formed. In the present invention, concentric texturing is, for example, mechanical texturing using free abrasive grains and texture tape or texturing using a laser beam, or by using these together, by polishing in the circumferential direction. A state in which a large number of minute grooves are formed in the circumferential direction of the substrate is referred to.
[0108]
The most preferred type of loose abrasive grains for mechanical texturing is diamond abrasive grains, especially those whose surfaces have been graphitized. Alumina abrasive grains are widely used as abrasive grains for mechanical texturing, but diamond abrasive grains are particularly considered from the viewpoint of in-plane orientation media that orients the axis of easy magnetization along the texturing grooves. Has extremely good performance. Although the cause has not been clarified at present, extremely reproducible results have been obtained.
[0109]
It is effective for the realization of high-density magnetic recording that the flying height of the head is as small as possible, and Ra of the substrate surface is 2 nm or less, further 1 nm or less because one of the features of these substrates is excellent surface smoothness. Is preferable, and in particular, it is preferably 0.5 nm or less. However, the determination of Ra here is based on the case where measurement is performed using a stylus type surface roughness meter. At this time, the tip of the measuring needle has a radius of about 0.2 μm.
[0110]
Next, an underlayer or the like may be formed between the substrate and the magnetic thin film layer. The underlayer aims at miniaturizing the crystal and controlling the orientation of the crystal plane, and a layer mainly composed of Cr is often used.
As a material of the underlayer containing Cr as a main component, in addition to pure Cr, Cr, V, Ti, Mo, Zr, Hf, Ta, W, Ge, Nb, Si, Also includes those to which second and third elements such as Cu and B are added, and Cr oxide. Among them, those having pure Cr, Ti, Mo, W, V, Ta, Si, Nb, Zr and Hf are preferable. The optimum content of the second and third elements differs depending on the respective elements, but is generally 1 at% to 50 at%, preferably 5 to 30 at%, more preferably 5 to 20 at%. Atomic% range.
[0111]
The thickness of the underlayer may be enough to exhibit this anisotropy, and is 0.1 to 50 nm, preferably 0.3 to 30 nm, and more preferably 0.5 to 10 nm. The substrate may or may not be heated during the formation of the underlayer mainly composed of Cr.
A soft magnetic layer may be provided on the underlayer in some cases. Particularly, a keeper medium having a small magnetization transition noise or a perpendicular recording medium in which magnetic domains are perpendicular to the plane of the medium has a large effect and is often used.
[0112]
The soft magnetic layer is not particularly limited as long as it has a relatively high magnetic permeability and a small loss, and is arbitrary. Representative examples thereof include NiFe and a material obtained by adding Mo or the like as a third element thereto. . Although the optimum magnetic permeability greatly varies depending on the characteristics of the head used for data recording and the characteristics of the recording layer, it is generally preferable that the maximum magnetic permeability be about 10 to 1,000,000 (H / m).
[0113]
Next, a recording layer is formed. A layer of the same material as the underlayer or another non-magnetic material may be inserted between the recording layer and the soft magnetic layer. When forming the recording layer, the substrate may or may not be heated.
As the recording layer, a Co alloy magnetic film, a rare earth magnetic film represented by TbFeCo, a transition metal / noble metal laminated film represented by a laminated film of Co and Pd, and the like are used.
[0114]
As the Co alloy magnetic layer, a Co alloy magnetic material generally used as a magnetic material such as pure Co, CoNi, CoSm, CoCrTa, CoNiCr, and CoCrPt is usually used. Elements such as Ni, Cr, Pt, Ta, W, and B, and SiO ₂ May be added. For example, CoCrPtTa, CoCrPtB, CoNiPt, CoNiCrPtB and the like can be mentioned. The thickness of the Co alloy magnetic layer is arbitrary, but is usually 5 to 50 nm, preferably 10 to 30 nm. The recording layer may be formed by laminating two or more layers via an appropriate non-magnetic intermediate layer or directly. At that time, the composition of the magnetic materials to be laminated may be the same or different.
[0115]
As the rare earth magnetic layer, a rare earth magnetic material generally used as a magnetic material such as TbFeCo, GdFeCo, DyFeCo, and TbFe is used. These rare earth alloys may be added to Tb, Dy, Ho or the like to form a quaternary system, or Ti, Al, or Pt may be added for the purpose of preventing oxidative deterioration. The film thickness of the rare earth magnetic layer is optional, but is usually about 5 to 100 nm. The recording layer may be formed by laminating two or more layers via an appropriate non-magnetic intermediate layer or directly. At that time, the composition of the magnetic materials to be laminated may be the same or different. In particular, the rare earth magnetic layer is suitable for high recording density recording because it has an amorphous structure film and has magnetization perpendicular to the media plane, and the recording of the present invention can be applied more easily.
[0116]
Similarly, as a laminated film of a transition metal and a noble metal system suitable for perpendicular magnetic recording, a laminated film material generally used as a magnetic material such as Co / Pd, Co / Pt, Fe / Pt, Fe / Au, and Fe / Ag is usually used. Is used. The transition metal and the noble metal of these laminated films need not be particularly pure, and may be an alloy mainly containing them. The thickness of the laminated film is arbitrary, but is usually about 5 to 1000 nm. In addition, the method of lamination is arbitrary, and it is not always necessary to laminate two materials.
[0117]
In the present invention, the magnetic thin film as the recording layer retains magnetization at room temperature and is demagnetized when heated, or magnetized when an external magnetic field is applied simultaneously with heating.
The coercive force of the magnetic thin film at room temperature needs to maintain its magnetization at room temperature and be uniformly magnetized by an appropriate external magnetic field. Preferably it is 2000 Oe or more. This is because the magnetic thin film of the high-density recording medium is preferably 2000 Oe or more. It is more preferably at least 2500 Oe, particularly preferably at least 3000 Oe.
[0118]
Larger coercive force at room temperature is preferable because high density recording is possible. In the conventional magnetic transfer method, it was difficult to transfer to a medium having a very high coercive force. However, in the present invention, since the magnetic thin film is heated and the coercive force is sufficiently reduced to form a magnetization pattern, the coercive force is large. Application to the medium is preferred.
However, it is preferably 20,000 Oe or less. If it exceeds 20,000 Oe, a large external magnetic field is required for collective magnetization, and normal magnetic recording may be difficult.
[0119]
The magnetic thin film needs to be magnetized by a weak external magnetic field at an appropriate heating temperature while maintaining magnetization at room temperature. Also, when the difference between the room temperature and the magnetization extinction temperature is larger, the magnetic domains of the magnetization pattern can be easily formed clearly. For this reason, the magnetization extinction temperature is preferably higher, preferably 100 ° C. or higher, and more preferably 150 ° C. or higher. For example, there is a magnetization extinction temperature near the Curie temperature (slightly below the Curie temperature) or near the compensation temperature.
[0120]
The Curie temperature is preferably 100 ° C. or higher. Below 100 ° C., the stability of the magnetic domain at room temperature tends to be low. It is more preferably at least 150 ° C. Particularly preferably, it is 180 ° C. or higher. The temperature is preferably 700 ° C. or less. If the magnetic thin film is heated to an excessively high temperature, it may be deformed.
In the longitudinal magnetic recording medium, the track width is becoming narrower due to the recent increase in density, and the influence of magnetic bleeding due to recording by a head is becoming relatively large, and in particular, magnetic bleeding is large with positioning signals such as servo signals. And the accuracy of the head position cannot be maintained, and the error rate may increase.However, according to the recording method of the present invention, the recording is selectively performed only in the spot where the temperature is rapidly increased. Magnetic bleeding is less likely to occur and higher density recording can be performed.
[0121]
Preferably, the saturation magnetization of the magnetic thin film is 50 emu / cc or more in order to magnetically detect a signal with a magnetic head such as an MR, GMR, or TMR head. In this case, since the influence of the demagnetizing field is great, it is desirable that the pulse width be as narrow as possible so that the temperature of the portion where the magnetization has been inverted by the heating and the external magnetic field drops sharply.
More preferably, it is 100 emu / cc or more. However, if it is too large, it is difficult to form a magnetized pattern. Therefore, it is preferably 500 emu / cc or less.
[0122]
On the other hand, when the magnetic recording medium is a perpendicular magnetic recording medium, the demagnetizing effect upon heating demagnetization or heating magnetization is small, which is suitable for applying the present invention. Preferably, in order to magnetically detect a signal with a magnetic head such as an MR head, the saturation magnetization of the magnetic thin film is set to 50 emu / cc or more. More preferably, it is 100 emu / cc or more. However, if it is too large, it is difficult to form a magnetized pattern. Therefore, it is preferably 500 emu / cc or less. However, if the saturation magnetization is large, unintended magnetization reversal is likely to occur due to magnetic demagnetization, and extra pulses and noise are generated. Therefore, it is effective to provide the above-described soft magnetic layer under the magnetic thin film.
[0123]
In particular, when the magnetization pattern is relatively large and the unit volume of one magnetic domain is large, the magnetization reversal is likely to occur, so it is preferable to provide a soft magnetic layer.
In the present invention, it is preferable to form a protective layer on the magnetic thin film. That is, the outermost surface of the medium is covered with the hard protective layer. The protective layer functions to prevent damage to the magnetic thin film due to collision with a head or a mask at the time of formation of a magnetic pattern or pinching of dust and dust between the mask and the head. This is especially important when the magnetization pattern forming process is performed in the normal atmosphere. When there are a plurality of magnetic thin films, a protective layer may be provided on the magnetic thin film near the outermost surface. The protective layer may be provided directly on the magnetic thin film, or may have another layer interposed therebetween as required.
[0124]
As the protective layer, a carbonaceous layer such as carbon, hydrogenated carbon, nitrogenated carbon, amorphous carbon, ₂ , Zr ₂ O ₃ , SiN, TiN, and other hard materials can be used. It may be transparent or opaque. In terms of impact resistance and lubricity, a carbonaceous protective film is preferred, and diamond-like carbon is particularly preferred. Not only does it play a role in preventing the magnetic thin film from being damaged by the energy rays, it also becomes extremely resistant to damage to the magnetic thin film by the head.
[0125]
Part of the energy beam is also absorbed by the protective layer, and acts to locally heat the magnetic thin film by heat conduction. For this reason, if the protective layer is too thick, the magnetization pattern may be blurred due to the heat conduction in the lateral direction. Further, it is preferable that the thickness is thinner in order to reduce the distance between the magnetic thin film and the head during recording and reproduction. Therefore, the thickness is preferably 50 nm or less, more preferably 30 nm or less, and still more preferably 20 nm or less. However, in order to obtain sufficient durability, the thickness is preferably 0.1 nm or more, more preferably 1 nm or more.
[0126]
Further, the protective layer may be composed of two or more layers. It is preferable to provide a protective layer immediately above the magnetic layer with a layer containing Cr as a main component, since the effect of preventing oxygen permeation to the magnetic layer is high.
In the present invention, as described above, the lubrication layer is formed on the uppermost layer of the magnetic recording medium. Further, it is preferable to keep the surface roughness Ra of the medium after forming the magnetic pattern at 3 nm or less so as not to impair the running stability of the flying head. The medium surface roughness Ra is the roughness of the medium surface not including the lubricating layer, and is a value calculated according to JIS B0601 after measuring with a stylus type surface roughness meter at a measurement length of 400 μm. . More preferably, the thickness is 1.5 nm or less.
[0127]
More preferably, the surface waviness Wa of the medium after the formation of the magnetization pattern is kept at 5 nm or less. Wa is the waviness of the medium surface not containing the lubricating layer, and is a value calculated according to the Ra calculation after measuring with a stylus type surface roughness meter at a measurement length of 2 mm. More preferably, the thickness is 3 nm or less.
The formation of the magnetic pattern on the magnetic recording medium is performed on the recording layer, and is usually performed by a conventional method after forming the protective layer or the protective film and the lubricating layer. If there is no concern about this, it may be performed immediately after the formation of the recording layer.
[0128]
The method for forming each layer of the magnetic recording medium is arbitrary, and examples thereof include a physical vapor deposition method such as a direct current (magnetron) sputtering method, a high frequency (magnetron) sputtering method, an ECR sputtering method, and a vacuum vapor deposition method.
There are no particular restrictions on the conditions at the time of film formation, and the ultimate vacuum, substrate heating method and substrate temperature, sputtering gas pressure, bias voltage, and the like may be appropriately determined by the film forming apparatus. For example, in the case of sputtering film formation, the ultimate vacuum degree is usually 5 × 10 ^-6 Torr or less, substrate temperature from room temperature to 400 ° C., sputtering gas pressure is 1 × 10 ^-3 ~ 20 × 10 ^-3 Torr and the bias voltage are generally 0 to -500V.
[0129]
In film formation, when the substrate is heated, it may be performed before the formation of the underlayer, or when a transparent substrate having a low heat absorption is used, Cr is used as a main component in order to increase the heat absorption. The substrate may be heated after forming a seed layer or a base layer having a B2 crystal structure, and then a recording layer or the like may be formed.
When the recording layer is a rare-earth magnetic film, the innermost and outermost parts of the disk are first masked, the film is formed up to the recording layer, and then the protective layer is formed from the viewpoint of preventing corrosion and oxidation. In this case, the mask is removed and the recording layer is completely covered with the protective film. If the protective layer is composed of two layers, the film is formed while the recording layer and the first protective layer are masked. It is preferable to remove the mask when forming the film, and to completely cover the recording layer with the second protective film because corrosion and oxidation of the rare earth magnetic layer can be prevented.
[0130]
The magnetic recording medium of the present invention is a magnetic recording medium in which a magnetic thin film is provided on a substrate, wherein a magnetization pattern is formed by a step of locally heating the magnetic thin film and a step of applying an external magnetic field to the magnetic thin film. After that, a lubricating layer is formed.
According to the present invention, the precision of the magnetization pattern is not limited by the patterning precision and the alignment precision of the mask, so that a fine magnetization pattern is formed with high precision. Then, a pattern is formed in which the magnetization transition width is small, the magnetization transition at the boundary of the magnetic domain is very steep, and the quality of the output signal is high.
[0131]
In addition, since it can be easily manufactured in a very short time and does not adhere to the master disk unlike the related art, there are few scratches and defects.
Furthermore, since the thickness of the lubricating layer can be made sufficiently large, impact resistance and durability are high. The lubricating layer does not easily adhere to the mask even when continuous manufacturing is performed, so that the signal output of the magnetization pattern is high. Since a high-quality precise magnetic pattern can be formed and a pattern that repeats a unit pattern can be easily formed, it is suitable for forming a control magnetic pattern of a magnetic head used for recording and / or reproducing of a medium.
[0132]
In particular, it is highly effective when used for forming a servo pattern for tracking a recording / reproducing head on a data track or a reference pattern for writing a servo pattern. This is because recording is more difficult as the pattern is relatively simple, and the higher the density and the higher the precision, the higher the cost of the magnetic recording medium.
The magnetic recording apparatus of the present invention includes at least one magnetic recording medium described above, a driving unit that drives the magnetic recording medium in a recording direction, a magnetic head including a recording unit and a reproducing unit, and a magnetic recording head. This is a magnetic recording apparatus having means for relatively moving with respect to a medium, and recording and reproduction signal processing means for inputting a recording signal to a magnetic head and outputting a reproduction signal from the magnetic head.
[0133]
Since a magnetic recording medium on which a magnetic pattern such as a fine and highly accurate servo pattern is formed is used, such a magnetic recording apparatus can perform high-density recording. Further, since the medium has no scratches and few defects, recording with few errors can be performed.
Further, since the thickness of the lubricating layer of the magnetic recording medium can be made sufficiently large, the device has high impact resistance and durability. Then, even when the medium is continuously manufactured, the lubricating layer is hardly adhered to the mask, so that the signal output of the magnetization pattern is high.
[0134]
After the magnetic recording medium is assembled in the apparatus, the magnetization pattern is reproduced by a magnetic head to obtain a signal, and the signal is used as a reference to record a servo burst signal in the magnetic recording apparatus. Thus, a precise servo signal can be easily obtained.
Also, even after recording the servo burst signal with the magnetic head, if a signal recorded as a magnetization pattern according to the present invention remains in an area not used as a user data area, the magnetic head may be displaced due to some disturbance. Is easily returned to a desired position, and therefore a magnetic recording apparatus in which signals by both writing methods are present has high reliability.
[0135]
A magnetic disk device, which is a typical magnetic recording device, will be described as an example.
A magnetic disk device usually includes a shaft for fixing one or more magnetic disks in a skewered manner, a motor for rotating a magnetic disk joined to the shaft via a bearing, and a magnetic disk used for recording and / or reproduction. A head, an arm to which the head is attached, and an actuator that can move the head to an arbitrary position on the magnetic recording medium via the head arm. It is moving at a flying height. The recording information is converted into a recording signal via a signal processing means and recorded by a magnetic head. Further, the reproduction signal read by the magnetic head is inversely converted through the signal processing means to obtain reproduction information.
[0136]
On the disk, information signals are recorded in sector units along concentric tracks. Servo patterns are usually recorded between sectors. The magnetic head reads a servo signal from the pattern, thereby accurately performing tracking at the center of the track, and reads an information signal of the sector. Tracking is also performed during recording.
[0137]
As described above, a servo pattern for generating a servo signal is required to have a particularly high precision due to its property of being used for tracking when recording information. In addition, since the servo pattern which is frequently used at present is composed of two sets of patterns which are shifted from each other by ピ ッ チ pitch, it is necessary to form the servo pattern at every の pitch of the information signal. Is required.
[0138]
However, in the conventional servo pattern forming method, the write track width is limited to about 0.2 to 0.3 μm due to the influence of vibration caused by the difference in the center of gravity between the external pin and the actuator. However, it is becoming difficult to improve the recording density and reduce the cost of the magnetic recording apparatus.
According to the present invention, since a highly accurate magnetization pattern can be efficiently formed by using a mask exposure method, a servo pattern can be accurately formed in a much shorter time and a shorter time than a conventional servo pattern forming method. It is possible to increase the track density of the medium to, for example, 40 kTPI or more. Therefore, a magnetic recording device using this medium can perform high-density recording.
[0139]
When the phase servo system is used, a servo signal that changes continuously can be obtained, so that the track density can be further increased, and tracking with a width of 0.1 μm or less is possible, and higher density recording is possible.
As described above, in the phase servo method, for example, a magnetization pattern that extends obliquely and linearly with respect to the radius from the inner circumference to the outer circumference is used. Such a continuous pattern or an oblique pattern in the radial direction is difficult to produce by a conventional servo pattern forming method of recording a servo signal one track at a time while rotating a disk, and requires a complicated calculation and configuration.
[0140]
However, according to the present technology, once a mask according to a shape is once created, the pattern can be easily formed only by exposing the mask at a desired position on the disk. , Can be created inexpensively. As a result, it is possible to provide a phase servo type magnetic recording device capable of high-density recording.
In the conventional mainstream servo pattern forming method, a dedicated servo writer is used in a clean room after a medium is incorporated in a magnetic recording device (drive).
[0141]
Each drive is mounted on a servo writer, and the pins of the servo writer are inserted through holes in either the front or rear surface of the drive, and the magnetic head is moved mechanically to record one pattern at a time along the track. Therefore, it takes a very long time of about 15 to 20 minutes per drive. These operations need to be performed in a clean room because a dedicated servo writer is used and holes are formed in the drive, which is a complicated process and increases the cost.
[0142]
According to the present invention, a servo pattern or a reference pattern for recording a servo pattern can be collectively recorded by irradiating an energy beam through a mask in which a pattern is recorded in advance, and a servo pattern can be formed on a medium very simply and in a short time. The magnetic recording apparatus incorporating the medium on which the servo pattern is formed as described above does not require the servo pattern writing step.
[0143]
Alternatively, a magnetic recording device incorporating a medium on which a servo pattern recording reference pattern is formed can write a desired servo burst signal in the device based on the reference pattern. In addition, there is no need for work in a clean room, and a magnetic recording apparatus having a highly accurate servo pattern can be obtained at a simple process at a low cost.
[0144]
Further, it is not necessary to make a hole on the back side of the magnetic recording device, which is preferable in terms of durability and safety.
Further, by providing a gap between the mask and the medium, it is possible to prevent deformation and damage of the medium due to contact with the mask and damage to the medium due to pinching of fine dust or dust, thereby preventing generation of defects.
[0145]
As described above, according to the present invention, a magnetic recording device capable of performing high-density recording with high reliability can be obtained in a simple process at low cost.
Various magnetic heads such as a thin film head, an MR head, a GMR head, and a TMR head can be used.
By configuring the reproducing section of the magnetic head with the MR head, a sufficient signal intensity can be obtained even at a high recording density, and a magnetic recording apparatus having a high recording density can be realized.
[0146]
When the magnetic head is levitated at a height lower than the conventional height of 0.001 μm or more and less than 0.05 μm, the output is improved and a high device S / N is obtained, and a large capacity and high reliability are obtained. A magnetic recording device can be provided. Further, the recording density can be further improved by combining a signal processing circuit based on the maximum likelihood decoding method. For example, when recording / reproducing at a recording density of 13 kTPI or more, a linear recording density of 250 kFCI or more, and a recording density of 3 Gbits or more per square inch, Also obtains a sufficient S / N.
[0147]
Further, the reproducing portion of the magnetic head is composed of a plurality of conductive magnetic layers that generate a large resistance change due to a relative change in their magnetization directions due to an external magnetic field, and a conductive non-magnetic layer disposed between the conductive magnetic layers. By using a GMR head composed of a magnetic layer or a GMR head utilizing the spin valve effect, the signal strength can be further increased, and the reliability with a linear recording density of 10 Gbit or more per square inch and 350 kFCI or more. It is possible to realize a magnetic recording device with high performance.
[0148]
【Example】
Hereinafter, the magnetic recording medium of the present invention will be described in detail. However, the magnetic recording medium is not limited to the examples unless it exceeds the gist of the invention.
(Example 1)
A 2.5 inch diameter aluminosilicate glass substrate is washed and dried, and the degree of vacuum reached thereon is 1 × 10 ^-7 Torr substrate temperature: 350 ° C., bias voltage: −200 V, sputtering gas pressure: Ar × 3 × 10 ^-3 Under the condition of Torr, NiAl is 600 ₉₄ Mo ₆ 100 ° and Co as the recording layer ₇₂ Cr ₁₈ Pt ₁₀ Was deposited at 220 ° and carbon (diamond-like carbon) was deposited at 50 ° as a protective layer. The surface roughness Ra was 0.5 nm, and the undulation Wa was 0.5 nm.
[0149]
A fluorine-based lubricant layer was formed thereon by dipping and pulling up. A solution prepared by diluting Fomblin-Z-DOL4000 manufactured by Ausimont Co., Ltd. with a chlorofluorocarbon-based solvent PF5060 was filled in a tank, and the disk was immersed in the tank. After baking this at 100 ° C. for 40 minutes, the film thickness of the lubricant was measured using FT-IR and found to be 1.5 nm.
[0150]
Thus, a magnetic disk for in-plane recording having a coercive force of 3000 Oe and a saturation magnetization of 310 emu / cc at room temperature was obtained. The Curie temperature of the recording layer was 250 ° C.
Subsequently, a defect inspection (certification) using a magnetic head was performed on the entire surface of the magnetic disk.
Next, in order to form a magnetization pattern, after fixing the magnetic disk on the spindle, a gap of about 10 μm is left on the magnetic disk, and as shown in FIG. A mask having transmission portions provided radially every 45 ° was arranged, and both were rotated at 2 rpm. The mask is made of quartz glass as a base material and has a non-transmissive portion formed by a Cr layer having a thickness of 20 nm.
[0151]
Excimer pulse laser with wavelength λ = 248 nm, pulse width: 25 nsec, power: 80 mJ / cm ² , Spot: 10 mm * 30 mm (1 / e of peak energy) ² A 12-degree fan-shaped light-shielding plate is installed at the laser irradiation port of the excimer laser having a diameter of 12 °, and the pulse is repeatedly irradiated with 30 pulses at a frequency of 1 Hz. Was applied with a permanent magnet to transfer a magnetic pattern.
[0152]
The presence or absence of the formation of the magnetic pattern was confirmed by developing the magnetic pattern with a magnetic developer and observing with an optical microscope. As a result, a pattern corresponding to the transmitting portion and the non-transmitting portion of the mask was transferred onto the magnetic disk.
When the film thickness of the lubricant was examined using FT-IR, it was reduced to 1.0 nm. The same fluorine-based lubricant as the first time was applied using a spin coater while rotating the medium at 80 rpm, and then dried by rotating at 4000 rpm to re-apply the lubricant. After the application, the lubricant film thickness was measured using FT-IR and found to be 1.7 nm. When a CSS test was performed on this magnetic disk, no head crash occurred up to 200,000 times.
[0153]
Further, a magnetization pattern was generated on a magnetic disk under exactly the same conditions, the magnetization pattern was reproduced with a hard disk MR head having a read width of 0.9 μm, and the waveform was confirmed with an oscilloscope. The output of the observed waveform was equivalent to the output of the magnetization pattern written using a normal magnetic head.
(Example 2)
A magnetic disk was manufactured in the same manner as in Example 1. Subsequently, a defect inspection (certification) using a magnetic head was performed on the entire surface of the magnetic disk.
[0154]
Next, the lubricant was washed away by using an ultrasonic cleaner with the solvent used for diluting the lubricant. When the film thickness of the lubricant was measured using FT-IR, it was found that there was no lubricant.
An attempt was made to transfer a magnetization pattern to this magnetic disk in the same manner as in Example 1.
When the presence or absence of the formation of the magnetized pattern was confirmed, a pattern corresponding to the transmitting portion and the non-transmitting portion of the mask was transferred onto the magnetic disk.
[0155]
Next, the same fluorine-based lubricant as the first time was applied using a spin coater while rotating the medium at 80 rpm, and then rotated at 4000 rpm and dried to apply the lubricant again. After the application, the lubricant film thickness was measured using FT-IR and found to be 1.5 nm.
Further, a magnetization pattern was generated on a magnetic disk under exactly the same conditions, the magnetization pattern was reproduced with a hard disk MR head having a read width of 0.9 μm, and the waveform was confirmed with an oscilloscope. The output of the observed waveform was equivalent to the output of the magnetization pattern written using a normal magnetic head.
[0156]
(Comparative Example 1)
A magnetic disk was manufactured in the same manner as in Example 1. Subsequently, a defect inspection (certification) using a magnetic head was performed on the entire surface of the magnetic disk. An attempt was made to transfer a magnetization pattern to this magnetic disk in the same manner as in Example 1.
When the presence or absence of the formation of the magnetized pattern was confirmed, a pattern corresponding to the transmitting portion and the non-transmitting portion of the mask was transferred onto the magnetic disk.
[0157]
When the film thickness of the lubricating layer was examined using FT-IR, it was reduced to 1.0 nm. When a CSS test was performed on this magnetic disk, a head crash occurred at 20,000 times. It is considered that the durability was insufficient because the free portion of the lubricating layer disappeared.
Further, a magnetization pattern was generated on the magnetic disk under exactly the same conditions, and the magnetic pattern was reproduced with an MR head for a hard disk having a read width of 0.9 μm, and the waveform was confirmed with an oscilloscope. The output of the observed waveform was equivalent to the output of the magnetization pattern written using a normal magnetic head.
[0158]
(Example 3)
A magnetic disk was manufactured in the same manner as in Example 1 except that a fluorine-based lubricant was applied as a lubricating layer to a thickness of 0.7 nm by a dipping and pulling method. A solution prepared by diluting Fomblin-Z-DOL4000 manufactured by Ausimont Co., Ltd. with a chlorofluorocarbon-based solvent PF5060 was filled in a tank, and the disk was immersed. did. It was 0.7 nm when the lubricant film thickness was measured using FT-IR.
[0159]
Subsequently, a defect inspection (certification) using a magnetic head was performed on the entire surface of the magnetic disk. 10,000 such magnetic disks were manufactured.
A magnetic pattern was continuously formed on these magnetic disks in the same manner as in Example 1. The same mask was used without replacement, but no stain on the mask was observed. The following evaluation was performed on the first, 1,000th, 3,000th, 5,000th, and 10,000th discs.
[0160]
When the presence or absence of the formation of the magnetized pattern was confirmed, the patterns corresponding to the transmitting portions and the non-transmitting portions of the mask were transferred onto the magnetic disks in all the disks.
Next, the same fluorine-based lubricant as the first time was applied using a spin coater while rotating the medium at 80 rpm, and then rotated at 3000 rpm and dried to apply the lubricant again. After coating, the lubricant film thickness was measured using FT-IR and was 1.7 nm.
[0161]
The formed magnetization pattern was reproduced with an MR head for a hard disk having a read width of 0.9 μm, and the waveform was confirmed with an oscilloscope. The output of the observed waveform was usually equivalent to the output of the magnetization pattern written using the magnetic head. Further, when a CSS test was performed, no head crash occurred up to 200,000 times.
[0162]
(Example 4)
A magnetic disk was manufactured in the same manner as in Example 1 except that the lubricating layer was not provided. Subsequently, a defect inspection (certification) was performed on the entire surface of the magnetic disk by a non-contact type optical surface inspection apparatus. 10,000 such magnetic disks were manufactured.
[0163]
A magnetic pattern was continuously formed on these magnetic disks in the same manner as in Example 1. The same mask was used without replacement, but no stain on the mask was observed. The following evaluation was performed on the first, 1,000th, 3,000th, 5,000th, and 10,000th discs.
When the presence or absence of the formation of the magnetized pattern was confirmed, the patterns corresponding to the transmitting portions and the non-transmitting portions of the mask were transferred onto the magnetic disks in all the disks.
[0164]
Next, a fluorine-based lubricant was applied by a dipping and pulling method, and baked at 100 ° C. for 40 minutes. It was 1.5 nm when the lubricant film thickness was measured using FT-IR.
The formed magnetization pattern was reproduced with an MR head for a hard disk having a read width of 0.9 μm, and the waveform was confirmed with an oscilloscope. The output of the observed waveform was usually equivalent to the output of the magnetization pattern written using the magnetic head. Further, when a CSS test was performed, no head crash occurred up to 200,000 times.
[0165]
(Comparative Example 2)
A magnetic disk was manufactured in the same manner as in Example 1. The thickness of the lubricating layer was 1.5 nm. Subsequently, a defect inspection (certification) using a magnetic head was performed on the entire surface of the magnetic disk. 10,000 such magnetic disks were manufactured.
A magnetic pattern was continuously formed on these magnetic disks in the same manner as in Example 1. When the same mask was used without replacing the mask, the attached matter started to be observed after about 3000 sheets.
[0166]
After the completion of 10,000 sheets, the film thickness of the deposit on the mask was examined using FT-IR and found to be 0.20 nm. Elemental analysis of the deposit on the mask used for this transfer with a secondary ion mass spectrometer detected peaks of carbon and fluorine, and it was found that the deposit was a lubricant.
The following evaluation was performed on the first, 1,000th, 3,000th, 5,000th, and 10,000th discs.
[0167]
When the presence or absence of the formation of the magnetized pattern was confirmed, the patterns corresponding to the transmitting portions and the non-transmitting portions of the mask were transferred onto the magnetic disks in all the disks.
When the lubricant film thickness was measured using FT-IR, it was reduced to 1.0 nm. When a CSS test was performed on these magnetic disks, a head crash occurred at 20,000 times. It is considered that the durability was insufficient because the free portion of the lubricating layer disappeared.
[0168]
The formed magnetization pattern was reproduced with an MR head for a hard disk having a read width of 0.9 μm, and the waveform was confirmed with an oscilloscope. The output of the observed waveform gradually decreased as compared with the output of the magnetization pattern written using the magnetic head, and became 90% for 3000 sheets, 85% for 5000 sheets, and 80% for 10,000 sheets. As a result, the signal strength also decreased.
[0169]
【The invention's effect】
According to the present invention, it is possible to provide a method for manufacturing a magnetic recording medium on which a pattern can be efficiently and accurately formed and which has high impact resistance and high durability. As a result, a highly durable magnetic recording medium and a magnetic recording device capable of high-density recording can be provided in a short time and at low cost.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a mask means used in a first embodiment of the present invention.

Claims (5)

A method for manufacturing a magnetic recording medium comprising a magnetic thin film having a magnetization pattern formed on a substrate and a lubricating layer, wherein the magnetic recording medium is irradiated with energy rays through mask means disposed near the magnetic recording medium. And simultaneously with the step of locally heating the magnetic thin film, the step of applying an external magnetic field to the magnetic thin film, when forming the magnetization pattern ,
Forming a first lubricating layer thinner than the lubricating layer on the magnetic thin film before forming the magnetic pattern, and applying a second lubricating layer on the first lubricating layer after forming the magnetic pattern to form the lubricating layer A method for manufacturing a magnetic recording medium, comprising: 2. The method for manufacturing a magnetic recording medium according to claim 1 , wherein after forming the first lubricating layer, the magnetic recording medium is inspected by a magnetic head, a magnetization pattern is formed, and then a second lubricating layer is formed. . 3. The method for manufacturing a magnetic recording medium according to claim 1, wherein the magnetization pattern is a control magnetization pattern for a magnetic head used for recording / reproduction. A magnetic recording medium body formed by providing a magnetic thin film and a lubricant layer magnetization pattern is formed on the substrate, the irradiating an energy beam to the magnetic recording medium through a mask means disposed in the vicinity of the magnetic recording medium A step of applying an external magnetic field to the magnetic thin film at the same time as the step of locally heating the magnetic thin film, the step of applying the external magnetic field to the magnetic thin film; A magnetic recording medium, wherein a lubricating layer is formed, and a lubricating layer is formed by applying a second lubricating layer on the first lubricating layer after forming a magnetization pattern . A driving unit that drives the magnetic recording medium in the recording direction, a magnetic head that includes a recording unit and a reproducing unit, a unit that moves the magnetic head relative to the magnetic recording medium, a recording signal input to the magnetic head, and a magnetic head. A magnetic recording apparatus having a recording / reproducing signal processing means for outputting a reproducing signal according to claim 4 , wherein after the magnetic recording medium according to claim 4 is assembled in said magnetic recording apparatus, a control magnetization pattern is formed by a magnetic head. A magnetic recording apparatus wherein a signal is reproduced to obtain a signal, and a servo burst signal is recorded by the magnetic head based on the signal.

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