JP4004883B2 - Magnetization pattern forming method - Google Patents

Description

【０２９７】
突起がチャンファ部と当たらない位置に存在する実施例１〜４のマスクは、耐久性試験を３００ｋ回行なった時点でも、突起に問題は発生していなかった。
【０２９８】
一方、突起がチャンファ部と当たる位置に存在する比較例１のマスクは、耐久性試験を１００ｋ回行なった時点で、チャンファが当たる外径側の突起に直線状のキズが入ってしまっていた。キズからは、Ｃｒ粉が発生していた。
【０２９９】
以上の結果から、突起が磁気記録媒体のチャンファ部と当たらない位置に存在するマスクは、チャンファ部と当たる位置に存在するマスクと比べて、マスクの使用に伴う突起の磨耗・損傷・脱落等が少ないことが判る。
【０３００】
また、突起がマスクパターン領域の外径側及び内径側に加えて、マスクパターン領域内部にも存在する実施例３，４のマスクについて、磁気記録媒体と接触させた場合の磁気記録領域との間隔を干渉縞で観察した。
【０３０１】
実施例３のマスクでは、きれいな同心円状の干渉縞が観察されたことから、マスクと磁気記録領域との間隔の均一性が良い（同一円周上では間隔が同じで、内周から外周にかけて徐々に広がっている）ものと判断された。また、実施例４のマスクでは、ほとんど干渉縞が観察されなかったことから、マスクと磁気記録領域との間隔が全面で均一であるものと判断された。
【０３０２】
［II］突起の素材についての比較
続いて、以下の実施例５，６及び比較例２により、マスク表面に形成する突起の素材の違いによる効果の比較を行なった。
【０３０３】
・実施例５，６
突起形成時のＣｒの成膜条件をそれぞれ下の表−２に示す条件とした他は、上述の実施例１と同様の条件でマスクの製造及び突起の形成を行なった。
【０３０４】
・比較例２
実施例１と同様の条件でマスクを製造した後、以下の手順で突起の形成を行なった。
【０３０５】
マスクパターンが形成されている側に、ポリイミド樹脂（ＰＩＸ−１４００）をスピンコート法で３μｍの厚さとなる様に成膜した。形成されたポリイミド樹脂層の上に、更にフォトレジスト（ＭＣＰＲ−２２００Ｘ）をスピンコート法で２００ｎｍの厚さとなる様に塗布した。形成されたフォトレジスト層に、実施例１で用いたものと同様の突起形成用マスクを介して水銀キセノンランプ光をブロ−ドパンド露光した後、現像及びエッチングを行ない、更に３５０℃、４５分のぺーキングを行なって、ポリイミド樹脂からなるスペーサ用の突起を形成した。
【０３０６】
・評価
実施例５，６及び比較例２のマスクについて、実施例１と同様の方法により、突起の酸素含有率及びヌープ硬度の測定を行なった。また、耐久性試験として、実施例１と同様の方法により、実際の磁化パターンの形成時と同様に磁気記録媒体との吸着及び脱着を繰り返し、所定の時点における突起の形状を観察して、耐久性の評価を行なった。
評価の結果を下の表−２に示す。
【０３０７】
【表２】

【０３０８】
突起がクロムで形成された実施例５のマスクは、耐久性試験を２００ｋ回行なった時点で、一部が崩れた突起が発生していた。崩れた部分からは、Ｃｒ粉が発生していた。また、同じく突起がクロムで形成された実施例６のマスクは、耐久性試験を１０ｋ回行なった時点で、突起の一部が剥がれてしまっていた。先の実施例１〜４に比べてそれほど優れた結果が得られなかったのは、突起の酸素含有率に起因するものと考えられる。
【０３０９】
一方、突起がクロムではなくポリイミドで形成された比較例２のマスクは、耐久性試験を１ｋ回行なった時点で、突起の一部が剥がれてしまった。
【０３１０】
以上の結果から、突起がクロムで形成されたマスクは、突起が他の素材（ポリイミド）で形成されたマスクと比べて、マスクの使用に伴う突起の磨耗・損傷・脱落等が少ないことが判る。
【０３１１】
【発明の効果】
本発明によれば、磁気記録媒体とマスクとの間隔を均一に保つための突起が、磁気記録媒体の面取り部に接触しない様に構成され、また、これらの突起がクロムにより形成されているので、マスクの使用に伴う突起の磨耗・損傷・脱落等が少なく、また、突起により磁気記録媒体を傷つけることがなく、長期間に渉り安定に使用することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態に係るマスクを用いた磁化パターンの形成方法を説明するための模式的な断面図である。
【図２】従来技術の磁化パターンの形成方法を説明するための模式図である。
【図３】（ａ）〜（ｄ）は何れも本発明に係るマスクにおける不連続な突起の形成パターンを示す模式図である。
【符号の説明】
１ 磁気記録媒体（磁気ディスク）
２ マスク
３ 透明基材（石英）
４ クロム層
５ 酸化クロム層
６ 外部磁界
１０ 面取り部（チャンファ部）
１１ 入射光（レーザビーム）
１２ 反射光
１３ 再反射光
２１ 突起[0001]
BACKGROUND OF THE INVENTION
  The present invention is used to define the shape of a magnetization pattern to be formed when a magnetization pattern is formed on a magnetic recording medium such as a magnetic disk used in a magnetic recording apparatus.MagneticThe present invention relates to a method for forming a pattern.
[0002]
[Prior art]
Magnetic recording devices represented by magnetic disk devices (hard disk drives) are widely used as external storage devices for information processing devices such as computers, and in recent years also used as recording devices for moving image recording devices and set-top boxes. It is being done.
[0003]
A magnetic disk device usually has 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 used for recording and / or reproduction. The head includes 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.
[0004]
The recording / reproducing head is usually a flying type head and moves on the magnetic recording medium with a constant flying height. In addition to the floating type head, use of a contact head (contact type head) has been proposed in order to further reduce the distance from the medium.
[0005]
A magnetic recording medium mounted on a magnetic disk device is generally formed by forming a NiP layer on the surface of a substrate made of an aluminum alloy and the like, performing a necessary smoothing process, texturing process, etc., and then forming a metal underlayer thereon. The magnetic layer (information recording layer), the protective layer, the lubricating layer, and the like are sequentially formed. Alternatively, it is manufactured by sequentially forming a metal underlayer, a magnetic layer (information recording layer), a protective layer, a lubricating layer, and the like on the 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-plane magnetic recording media are usually subjected to longitudinal recording.
[0006]
Increasing the density of magnetic recording media is increasing year by year, and there are various techniques for realizing this. For example, the magnetic head flying height can be reduced, a GMR head can be used as the magnetic head, the magnetic material used for the recording layer of the magnetic disk can be improved, and information recording tracks of the magnetic disk can be used. Attempts have been made to reduce the interval between the two. For example, 100Gbit / inch²In order to realize the above, the track density is required to be 100 ktpi or more.
[0007]
Each track has a control magnetization pattern for controlling the magnetic head. For example, a signal used for position control of a magnetic head or a signal used for synchronization control. When the information recording track interval is narrowed to increase the number of tracks, the signal used for position control of the data recording / reproducing head (hereinafter also referred to as “servo signal”) is also adjusted in the radial direction of the disc. On the other hand, it is necessary to provide dense control, that is, to provide more precise control.
[0008]
Also, I want to increase the data recording capacity by reducing the area other than the data recording area, that is, the area used for the servo signal (servo area) and the gap between the servo area and the data recording area. There is also a great demand. For this purpose, it is necessary to increase the output of the servo signal or increase the accuracy of the synchronization signal.
[0009]
A conventionally widely used method for forming a servo signal is to make a hole in the vicinity of a head actuator of a drive (magnetic recording device), insert a pin with an encoder in that portion, and engage the actuator with the pin. Is driven to an accurate position to record a servo signal. However, since the center of gravity of the positioning mechanism and the actuator are at different positions, high-precision track position control cannot be performed, and it is difficult to accurately record servo signals.
[0010]
On the other hand, there has also been proposed a technique for forming a concave / convex servo signal by irradiating a magnetic disk with a laser beam to locally deform the disk surface to form physical irregularities. However, the flying head becomes unstable due to the unevenness, which adversely affects recording and reproduction, and it is necessary to use a laser beam having a large power to form the unevenness, which is costly, and it takes time to form the unevenness one by one. There was a problem.
[0011]
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 layer having a high coercive force, the master disk is brought into close contact with a magnetic recording medium, and a magnetizing pattern is transferred by applying an auxiliary magnetic field from the outside (USP 5,991). , 104).
[0012]
Another example is a method in which a medium is magnetized in one direction in advance, and a soft magnetic layer having a high magnetic permeability and a low coercive force is patterned on the master disk so that the master disk is in close contact with the medium and an external magnetic field is applied. It is. The soft magnetic layer acts as a shield, and the magnetization pattern is transferred to an unshielded region (Japanese Patent Laid-Open No. 50-60212 (USP 3,869,711)), Japanese Patent Laid-Open No. 10-40544 (EP 915456). ), Digest of InterMag 2000, GP-06).
[0013]
These techniques use a master disk and form a magnetization pattern on a medium by a strong magnetic field.
In general, since the strength of a magnetic field depends on a distance, when recording a magnetization pattern with a magnetic field, the pattern boundary tends to be unclear due to a 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 with each other. And, as the pattern becomes finer, it is necessary to make it closely adhere to each other without any gap, and usually both are pressure-bonded by vacuum suction or the like.
[0014]
Also, the higher the coercive force of the medium, the larger the magnetic field used for transfer and the greater the leakage magnetic field, so it is necessary to make it more intimately contact.
Therefore, each of the above techniques is easy to apply to a magnetic disk having a low coercive force and a flexible floppy (registered trademark) disk that can be easily pressed, but has a coercive force of 3000 Oe for high-density recording using a hard substrate. It is very difficult to apply to such a magnetic disk.
[0015]
That is, there is a risk that the hard disk magnetic disk may have minute dust or the like sandwiched between the hard disks and cause a defect in the medium or damage an expensive master disk. In particular, in the case of a glass substrate, there is a problem that adhesion is insufficient due to dust sandwiching and magnetic transfer cannot be performed, or cracks are generated in the magnetic recording medium.
[0016]
In the technique described in the above-mentioned Japanese Patent Application Laid-Open No. 50-60212 (US Pat. No. 3,869,711), when a pattern having an oblique angle with respect to the track direction of the disk is formed, recording is performed. However, there is a problem that only patterns with low signal strength can be created. For magnetic recording media with a high coercive force having a coercive force of 2000 to 2500 Oe or more, the pattern ferromagnetic material (shield material) of the master disk is a saturated magnetic flux such as permalloy or sendust in order to ensure the magnetic field strength of the transfer. A soft magnetic material with a high density must be used.
[0017]
However, in the oblique pattern, the magnetization reversal magnetic field is 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, and it is difficult to apply a sufficient magnetic field to a desired part during magnetic transfer, and a sufficient magnetization reversal pattern cannot be formed, making it difficult to obtain a high signal intensity. 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.
[0018]
On the other hand, the technique described in each specification of Japanese Patent Application Nos. 2000-134608 and 2000-134611 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, irradiated with an energy ray or the like through a patterned mask and locally heated, and an external magnetic field is applied while lowering the coercivity of the heating area, Recording with an external magnetic field is performed to form a magnetization pattern.
[0019]
According to the present technology, since the external magnetic field is applied by lowering the coercive force by heating, the external magnetic field need not be higher than the coercive force of the medium, and recording can be performed with a weak magnetic field. The area to be recorded is limited to the heating area, and recording is not performed even if a magnetic field is applied to the area other than the heating area, so that a clear magnetization pattern can be recorded without bringing a mask or the like into close contact with the medium. For this reason, the defect of the medium is not increased without damaging the medium or the mask by the pressure bonding.
[0020]
In addition, according to the present technology, an oblique magnetization pattern can be satisfactorily formed. This is because it is not necessary to shield the external magnetic field by the soft magnetic material of the master disk as in the prior art.
[0021]
As described above, the magnetic pattern forming technology described in the specification of Japanese Patent Application No. 2000-134611 can form various fine magnetic patterns efficiently and accurately, and also eliminates defects in the medium without damaging the medium or the mask. It is an excellent technology that does not increase.
[0022]
However, even in this technique, when a fine pattern having a line width of about 1 μm or less is formed using a mask, a non-concentric distorted interference fringe appears and the modulation may deteriorate.
[0023]
This will be described with reference to FIG. In FIG. 2, the mask 2 is formed with a non-transmissive portion made of a chromium layer 4 and a chromium oxide layer 5 on a transparent substrate 3 made of quartz, and the energy rays (incident light 11) that have passed through the mask 2 are magnetic. The recording medium (magnetic disk) 1 is irradiated.
[0024]
As shown in FIG. 2A, most of the incident light 11 once transmitted through the transmission part of the mask 2 goes straight, but a part of the light near the boundary with the non-transmission part goes around to the non-transmission part due to diffraction. . The scattered light hits the magnetic recording medium 1 and is mostly absorbed by the surface of the magnetic recording medium, but part of it is reflected. The reflected light 12 hits the mask surface non-transmitting portion again, and a part of it is re-reflected. As a result, the re-reflected light 13 interferes with the incident light 11 to increase or weaken the light. If the non-transmission part is made of a highly reflective metal such as chrome, the light that has entered the non-transmission part is reflected by the non-transmission part. Prone.
[0025]
In such a case, if the distance between the magnetic recording medium 1 and the mask 2 is kept uniform over the entire surface, interference fringes cannot be made, so that the light intensity (shading) becomes uniform over the entire surface. Further, even if the entire surface is not uniform, when a plurality of concentric circles centering on the central portion of the magnetic recording medium 1 are assumed, the distance between the magnetic recording medium and the mask is kept uniform at least on each concentric circle. Then, the interference fringes are formed concentrically.
[0026]
However, when the distance between the magnetic recording medium 1 and the mask 2 is not uniform on each concentric circle, non-concentric distorted interference fringes are observed.
[0027]
Incidentally, recording tracks are usually formed concentrically on a magnetic disk (disk-shaped magnetic recording medium), and a magnetization pattern is recorded on each track. Here, the magnetic disk is often recorded and reproduced at a constant angular velocity. In such a case, the linear velocity increases as going to the outer periphery, and in order to record the same signal on the inner periphery and the outer periphery, the physical length of the signal becomes longer toward the outer periphery. That is, the pattern line width, which is the circumferential width of the magnetization pattern to be recorded, is usually equal on each track, but tends to increase from the inner periphery to the outer periphery.
[0028]
For example, a hard disk having a diameter of 3.5 inches has a pattern line width of 1 μm on the inner periphery (radius 20 mm) and about 2 to 3 μm on the outer periphery (radius 45 mm), and the pattern line width varies greatly depending on the radial position of the disk. To do.
[0029]
According to the study by the present inventors, the optimum conditions for forming the magnetization pattern differ depending on the size of the pattern line width. One of the causes is the influence of diffraction of energy rays. In general, energy rays diffract when passing through slit-like gaps, but the diffraction angle tends to increase as the gap becomes narrower.
[0030]
For this reason, when the pattern line width is narrowed, the energy rays that have passed through the transmission part of the mask are greatly diffracted and the irradiation range is widened. Therefore, the irradiation amount of energy rays per unit area becomes small, the heating part is not heated sufficiently, the coercive force is not sufficiently lowered, and it is difficult to sufficiently magnetize, and the formed magnetization pattern There is a risk that the modulation of the output signal will deteriorate. That is, the optimum distance between the mask and the medium differs according to the pattern line width.
[0031]
Therefore, when forming patterns with different line widths on the inner and outer circumferences, a technique is proposed in which the distance between the mask and the magnetic disk is uniform on each concentric circle and larger on the outer circumference than the inner circumference of the magnetic disk. Has been. In such a case, the interference fringes are formed concentrically.
[0032]
That is, in this magnetization pattern formation technique, it is preferable that no interference fringes are observed or the interference fringes are observed concentrically.
[0033]
However, observing non-concentric distorted interference fringes is not preferable because the distance between the magnetic recording medium and the mask is not uniform on the concentric circles. If the distance between the magnetic recording medium and the mask is non-uniform on the concentric circles, a portion where the pattern is well formed and a portion where the pattern is not formed are formed on the same track, and the modulation of the output signal of the formed magnetization pattern is performed. There was a problem of getting worse.
[0034]
As a result of studies by the present inventors, it has been found that the cause of the uneven distance between the magnetic recording medium and the mask is the uneven thickness of the spacer. Since the spacer thickness is uneven, the distance between the magnetic recording medium and the mask varies on a concentric circle. If the distance changes on the concentric circles, the optical path length of the incident light changes, and accordingly, non-concentric distorted interference fringes are easily formed.
[0035]
Further, it was found that the deterioration of the modulation is less likely to occur as the distance between the magnetic recording medium and the mask, that is, the interval is narrower. As shown in FIG. 2 (b), the smaller the interval, the smaller the ratio of the incident light 11 that goes into the non-transmission part. Therefore, it can be inferred that the irradiation area does not differ as the interval decreases.
[0036]
In other words, it is important to keep the gap between the magnetic recording medium and the mask narrow and at least uniform on the concentric circle and to equalize the influence of diffraction on the concentric circle so as not to generate non-concentric distorted interference fringes. For this purpose, it has been found that it is preferable to use a thin spacer having a uniform thickness and no unevenness to keep the distance between them. However, in general, when the spacer has a thickness of about 10 μm or less, it is difficult to handle because it is too thin and has no rigidity, and the spacer is bent and wrinkled, resulting in uneven thickness, and unevenness is likely to occur.
[0037]
In view of the above, in the specification of Japanese Patent Application No. 2002-066942, the present inventors have formed a protrusion having a thickness of, for example, 0.3 μm or more and 10 μm or less on the mask surface, and this protrusion is used as a spacer in contact with the magnetic recording medium. Proposed a technique of irradiating energy rays. According to this technique, the distance between the magnetic recording medium and the mask can be kept narrow and uniform at least on a concentric circle, and as a result, a good magnetic recording medium in which the modulation of the output signal of the magnetization pattern is small can be obtained. It becomes.
[0038]
[Problems to be solved by the invention]
However, in each of the above-described conventional techniques, there is a case in which the spacer is scraped, broken, or peeled off due to some reason as the mask is used. In such a case, the spacer becomes lower, or conversely, scraps or split pieces adhere to the spacer and become higher, resulting in uneven distance between the mask and the magnetic recording medium. When the line is irradiated, the intensity of the energy line changes due to interference, and the magnetization pattern cannot be transferred with high accuracy. Therefore, the mask has to be replaced in a short period, and there is a problem that the life of the mask is shortened.
[0039]
In order to solve these problems, a method of forming the spacer with a harder material may be considered. However, simply using a hard material may damage the surface of the spacer when it is brought into contact with the magnetic recording medium. Therefore, there has been a demand for a technique that can prevent the spacer from being worn, damaged, dropped off and the like due to the use of the mask without damaging the magnetic recording medium by the spacer, and can extend the life of the mask.
[0040]
  The present invention has been made in view of the above problems. That is, an object of the present invention is to define the shape of a magnetization pattern when forming a magnetization pattern on a magnetic recording medium by combining local heating and application of an external magnetic field.TheProtrusions are provided to keep the gap between the magnetic recording medium and the mask uniform, prevent wear, damage, dropout, etc. of these protrusions during use, and without damaging the magnetic recording medium by these protrusions, Magnetization pattern shape defining mass that can be used stably over a long period of timeTheTo provide a magnetic pattern forming method usedIs.
[0041]
[Means for Solving the Problems]
As a result of diligent searches to solve the above problems, the present inventors have found that the positions where the protrusions come into contact with the magnetic recording medium and the material of the protrusions cause wear, damage, or dropout of these protrusions. I found out. Then, the present invention has been completed by finding that the above-mentioned problems can be efficiently solved by appropriately defining the position where the protrusion is provided on the mask and the material of the protrusion.
[0042]
  That is, the present inventionThe method for forming a magnetization pattern of a magnetic recording medium is as follows:Having a magnetic layer on the substrate,Provided as an inclined part in the area along the outermost peripheral edge outside the storage areaIrradiation of energy rays to a magnetic recording medium having a chamfered portion when the magnetic layer of the magnetic recording medium is irradiated with energy rays and heated, and an external magnetic field is applied to form a magnetization pattern on the magnetic layer. On the routeA mask that produces local shading in the irradiation intensity of energy raysBy interposing, the shape of the magnetization patternA method of forming a magnetization pattern of a magnetic recording medium to be formed, wherein the mask isOn at least part of the maskThe provided protrusion is the aforementionedIrradiate energy rays in contact with at least a part of the magnetic recording medium other than the chamfered portion and without contacting the chamfered portion.It was made to do.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a magnetic layer by performing a step (heating step) of irradiating the magnetic layer of the magnetic recording medium with energy rays and a step of applying an external magnetic field (magnetic field applying step) to the magnetic layer. In a method of forming a magnetized pattern, a mask for defining the shape of the magnetized pattern by interposing it in the energy beam irradiation path, and irradiating the magnetic layer with the energy beam according to the shape of the magnetized pattern to be formed The target is a mask having a mask pattern region that causes local shading in intensity.
[0046]
Note that the present invention has a mask pattern region composed of a transmission part and a non-transmission part of an energy beam as long as the mask has a mask pattern region that causes the intensity of irradiation of the energy beam to vary depending on the magnetization pattern to be formed. The present invention can be applied to any type of mask such as a mask, a mask having a mask pattern region for diffusing energy rays, and a hologram mask. In the following description, an embodiment of the present invention will be described by taking a mask having a mask pattern region composed of a transmission part and a non-transmission part of energy rays as a representative example. The mask according to the present invention is preferably used in the above-described magnetization pattern forming method, but in various other fields, particularly in the field of laser processing that requires high power and requires a fine pattern. Can also be used.
[0047]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram showing an example of a magnetization pattern forming method using a mask according to an embodiment of the present invention. A magnetic disk (magnetic recording medium) 1 is uniformly magnetized in advance in one circumferential direction by an external magnetic field. After that, the mask 3 is placed on the magnetic disk 1 and fixed with a fastening screw (not shown). The mask 2 has a transparent base 3 made of quartz formed with a non-transmissive portion made of a chromium layer 4 and a chromium oxide layer 5, and a plurality of protrusions 21 as spacers provided on the peripheral edge of the pattern region. . The protrusions 21 come into contact with the magnetic disk 1, thereby keeping the distance from the mask 2 uniform. The laser beam 11 is irradiated here. At the same time, an external magnetic field 6 is applied. This external magnetic field is in the opposite direction to the external magnetic field when it is first magnetized uniformly.
[0048]
According to the above method, since the local heating and the application of the external magnetic field are combined in forming the magnetization pattern, it is not necessary to use a strong external magnetic field as in the prior art. And even if a magnetic field is applied to a region other than the heating region, it is not magnetized, so that the magnetic domain formation can be limited to the heating region. For this reason, the domain boundary becomes clear, and a pattern with a small magnetization transition width and a very steep magnetization transition at the domain boundary and a high output signal quality can be formed. If the conditions are selected, it is possible to make the magnetization transition width 1 μm or less.
[0049]
And an energy ray is irradiated through the mask which has a pattern area | region which consists of the transmission part and non-transmission part of an energy ray, and is heated locally. Since energy rays are used for local heating, the size and power of the heated portion can be easily controlled, and the magnetization pattern can be formed with high accuracy. In addition, once a mask is created, a pattern of any shape can be formed on a medium, so that a complicated pattern or a special pattern that is difficult to make by a conventional method can be easily formed. A magnetization pattern oblique to the track can also be formed satisfactorily.
[0050]
For example, in the phase servo system of a magnetic disk, a magnetization pattern extending linearly obliquely with respect to the radius and track from the inner periphery to the outer periphery is used. Such a pattern that is continuous in the radial direction or a pattern that is oblique to the radius is difficult to produce by the conventional servo pattern forming method in which the servo signal is recorded track by track while the disk is rotated. However, according to the present invention, such a magnetization pattern can be formed easily and in a short time by one irradiation without requiring complicated calculation and complicated apparatus configuration.
[0051]
The mask only needs to have a size including at least the repeating unit of the magnetization pattern, and can be used by moving it. Therefore, the mask can be easily and inexpensively produced. In order to increase the accuracy of the pattern, it is preferable to use a single mask that covers the entire surface of the magnetic disk.
[0052]
In addition, if the beam diameter of the energy beam is made large, or an elliptical shape that is elongated horizontally, etc., if the magnetic pattern for multiple tracks or multiple sectors is irradiated in a lump, the writing efficiency will increase further, and the capacity will increase in the future. The problem that the servo writing time increases is also improved, which is very preferable.
[0053]
In the present invention, a protrusion is provided on at least a part of a mask having a mask pattern region that generates energy beam shading according to the magnetization pattern to be formed, and the protrusion is in contact with the magnetic recording medium. Irradiate the line. By providing protrusions that act as spacers on the mask itself, it is difficult to handle because it is too thin and not rigid when spacers are used, and the thickness is uneven due to bending and wrinkling. It is possible to solve the problem of being easily formed, and to keep the distance between the mask and the medium narrow and uniform at least on a concentric circle. As a result, the influence of diffraction is suppressed, and the magnetization pattern is formed according to the mask pattern. Therefore, a good magnetic recording medium with high magnetization pattern accuracy and small modulation of the output signal of the magnetization pattern can be obtained. In particular, the servo pattern has a great effect in forming the servo pattern because the modulation size greatly affects the positioning accuracy.
[0054]
Furthermore, the mask 2 according to the present embodiment is configured such that these projections can irradiate energy rays in a state where they contact at least a part other than the chamfered portion of the magnetic recording medium and do not contact the chamfered portion. Is one of the characteristics.
[0055]
As shown in FIG. 1, a general magnetic disk 1 is provided with a chamfered portion (chamfer portion) 10 in a region along the outermost peripheral end portion outside the storage region. The chamfered portion is formed as an inclined portion on the end surface of the magnetic disk 1, and there are corners at the portion where the inclination starts.
[0056]
According to the study by the present inventors, one of the causes of spacer wear, damage, dropout, etc. in the prior art is that the magnetization pattern is formed in a state where the spacer hits the inclination or corner of the chamfered portion 10. I found out that there was something. At the time of forming the magnetized pattern, adsorption and desorption are repeated by reducing the pressure and pressure of the space between the mask and the magnetic disk in order to bring the mask and the magnetic disk into close contact with each other. If this pressure reduction is repeated while the spacer is in contact with the chamfered portion's slope or corner, the spacer will be strongly pressed against the chamfered portion's slope or corner repeatedly, which will cause the spacer to wear, damage, or fall off. It is. Normally, defect management is performed on the recording area of the magnetic disk, but peripheral parts such as the chamfered part are not defect-managed, and there are many cases where foreign matter or the like exists. Therefore, the spacer may bite foreign matter adhering to the chamfered portion or the like, which may cause damage to the spacer.
[0057]
Therefore, the mask 2 according to the present invention is provided with protrusions at least at a part thereof, and these protrusions are in contact with at least a part other than the chamfered part of the magnetic disk 1 and are not in contact with the chamfered part. It is the feature that it is comprised so that can be irradiated. By configuring in this way, it is possible to prevent the protrusions from being strongly pressed against the inclination and corners of the chamfered part and to bite in foreign matter adhering to the chamfered part, etc., and the protrusions are worn, damaged, or dropped off. Etc. can be prevented.
[0058]
Another feature of the mask according to the present invention is that these protrusions are made of chromium. In the prior art, there is no particular knowledge about the material of the spacer, and a flexible and readily available material such as polyimide is generally used from the viewpoint of preventing damage to the magnetic recording medium and cost advantages. However, according to the study by the present inventors, it is considered that the use of such a material causes the wear, damage, dropout, etc. of the spacer. Therefore, by forming the protrusions with chromium, the durability of the protrusions can be improved as compared with the case where a material such as polyimide is used, and it is possible to prevent the protrusions from being worn, damaged, or dropped off. Further, since it is excellent in flexibility, the magnetic recording medium is not damaged.
[0059]
Modulation (Mod) at this time is the average output of the same pattern area is TAA (total average amplitude), and the maximum value and the minimum value in the area are AMP respectively._maxAMP_min, Mod = (AMP_max-AMP_min) / TAA × 100. However, TAA, AMP_maxAMP_minBoth are peak-to-peak values. The smaller the modulation value, the better, but considering servo tracking accuracy, it is preferably 20% or less, more preferably 10% or less.
[0060]
In addition, the distance between the mask and the magnetic disk need only be uniform on a concentric circle with the same pattern line width, and does not need to be uniform over the entire surface. Thus, the distance between the mask and the magnetic disk in the radial direction may be adjusted as appropriate. Thereby, patterns with different line widths can be easily formed on the inner and outer circumferences. That is, the density of the energy beam can be easily adjusted without finely adjusting the power of the energy beam and the pattern line width of the mask depending on the line width of the pattern, and a desired magnetization pattern can be obtained.
[0061]
Next, the mask according to the present invention will be described in detail.
The height of the protrusion is preferably as low as possible in order to narrow the distance between the mask and the pattern formation region of the magnetic recording medium and prevent the diffusion of incident energy due to diffraction, and the height is preferably 10 μm or less. More preferably, it is 7 micrometers or less, More preferably, it is 5 micrometers or less.
[0062]
When the line width of the pattern to be formed (minimum pattern width) becomes narrower than 1 μm, it is particularly affected by light diffraction. Therefore, it is desirable to make the height of the protrusion lower as the line width is narrower. .
[0063]
However, if it is too low, it may come into contact with the undulations of the magnetic recording medium, so the height is preferably 0.01 μm or more. More preferably, it is 0.1 μm or more.
[0064]
In the present application, the minimum width of the pattern means the narrowest length in the pattern. A rectangular pattern has a short side, a circle has a diameter, and an ellipse has a short diameter.
[0065]
In order to keep the distance between the mask and the pattern formation region of the magnetic recording medium uniform at least on the concentric circle, it is preferable that the height of the protrusion be uniform on the concentric circle. Therefore, the variation of the height of the protrusions on the concentric circle is preferably within ± 20% of the average height. There is no particular lower limit, but in practice there is a variation of ± 3% or more of the average height. The uniformity of the interval can be easily evaluated by observing the number, position, and shape of interference fringes.
[0066]
In order to keep the distance between the mask and the medium almost uniform on at least a concentric circle, the protrusions are continuously provided in a ring-shaped band region along the concentric circle on the mask surface, or at least three or more locations that exist evenly on the concentric circle. It is necessary to provide locally in the arc-shaped belt region.
[0067]
In any of the above cases, the protrusions may be provided in a line along the circumferential direction of the mask, or a plurality of protrusions may be provided in the radial direction.
When multiple rows of protrusions are arranged concentrically or concentrically in the radial direction of the mask, any one position in the radial direction of the mask (for example, the outermost peripheral vicinity region, the innermost peripheral vicinity region of the mask pattern region, and their It may be provided collectively in any one of the intermediate regions, etc., and any two of a plurality of positions (for example, the region near the outermost periphery of the mask pattern region, the region near the innermost periphery, and the intermediate region) The above may be distributed.
[0068]
Further, when the protrusions are provided in a plurality of rows, the heights of the protrusions in the plurality of rows may be the same or different. When the height of the protrusion is changed for each row, the distance between the mask and the magnetic recording medium tends to be narrower toward the inner periphery and wider toward the outer periphery, and accordingly, the height of the protrusion is also lower toward the inner periphery row. You may adjust so that it may become so high that a row | line | column.
[0069]
The shape of the protrusion in the circumferential direction of the mask is not particularly limited, but as a typical example, as shown in FIGS. 3A to 3C, a shape in which discrete protrusions are provided along the circumferential direction. (Spot shape) and a shape (belt shape) in which continuous protrusions are provided along the circumferential direction as shown in FIG.
[0070]
3A to 3D show the case where the projections are provided in a plurality of rows along the radial direction of the mask. In particular, when the spot-like projections are provided in a plurality of rows, FIG. As shown in FIG. 3, the positions of the spot-like projections in each row may be aligned in a lattice pattern, and as shown in FIG. 3B, the spot-like projections in each row on the circumference. The positions may be shifted and arranged in a zigzag pattern. When comparing the lattice shape of FIG. 3A and the staggered shape of FIG. 3B, if the individual projections are present at the same density, the lattice shape has the advantage that it is easier to apply a vacuum chuck and remove it. is there. Further, in the above-described ring-shaped belt region or arc-shaped belt region, as shown in FIGS. 3A and 3B, the spot-like projections may be arranged uniformly in the circumferential direction at equal intervals. As shown in c), it is possible to effectively perform the vacuum chuck by removing the protrusions in some places.
[0071]
On the other hand, when forming the belt-shaped protrusion, the ring-shaped band region or the arc-shaped band region may be continuously formed in the entire region as shown in FIG. May be. When it is continuously formed in the entire annular band region, it becomes a ring-shaped (annular) protrusion, and when it is formed continuously all over the arc-shaped band region, it becomes an arc-shaped (arc-shaped) protrusion. These belt-shaped protrusions have an advantage that the contact area is large and can be stably contacted, but there is a possibility that variations in height distribution may occur and contact unevenness is likely to occur. Therefore, discontinuous provision is preferable to continuous provision.
[0072]
Usually, since both the mask and the magnetic recording medium have some undulations, when the mask and the magnetic recording medium are brought into contact with each other, the two come into contact with each other in the most stable manner, that is, at least both of them. It is preferable that they can move with respect to each other so that the intervals on the concentric circles are as constant as possible.
[0073]
When the mask and the magnetic recording medium are brought into contact with each other by continuous protrusions on the mask, the frictional resistance is high due to the large contact area, and the relative positions of the two are difficult to move, and the movement to maintain the flatness of the mask and the magnetic recording medium May be disturbed. Therefore, it is preferable that the protrusions are provided discontinuously as in the lattice shape of FIGS. 3A and 3D and the staggered shape of FIG. That is, a plurality of protrusions are provided discretely. When the mask and the magnetic recording medium come into contact with the discontinuously formed protrusions, the frictional resistance between the two becomes low, and the distance between the medium and the mask can be more easily maintained without hindering movement in the surface direction.
[0074]
In addition, since the projections are discontinuous, there is an air passage, so that the mask and the magnetic recording medium are not attracted. Therefore, there is an advantage that even if both move in the surface direction according to the undulation, scratches due to friction hardly occur. Further, if the protrusions are provided continuously, a part of the protrusions may be easily peeled off due to stress.
[0075]
Next, a description will be given of a protrusion shape when a plurality of protrusions are provided discretely.
The protrusion shape is preferably substantially circular when viewed from the direction perpendicular to the substrate surface, that is, when the mask is viewed from directly above. This is because such a shape tends to make the projection height uniform. When heating is involved in the formation of protrusions, the change in shape accompanying heat shrinkage (so-called sinks) may increase the variation in the height of the protrusions, but in substantially circular protrusions, sink marks also occur uniformly from the surroundings. Protrusion height tends to be uniform.
[0076]
The shape of the protrusion may be such that the middle is recessed and the peripheral edge is raised (so-called crater shape), but a shape having a peak at the middle and a mountain shape is preferable. This is because the height variation due to the sink marks is uniform and the height can be easily adjusted.
[0077]
Further, the protrusion shape is preferably such that the cross section in the direction perpendicular to the mask surface is substantially rectangular. That is, the side surfaces of the protrusions are substantially vertical, and the top and bottom shapes of the protrusions are substantially equal. With such a shape, the area of the top portion that actually contacts the magnetic recording medium can be increased with respect to the bottom area of the protrusion, and the support position can be prevented from misalignment between the mask and the magnetic recording medium. This is because a margin can be provided.
[0078]
The size of the protrusion in the surface direction is preferably larger than a certain level in order to withstand the load applied to the mask and the magnetic recording medium. When the protrusion shape is substantially circular, the diameter is preferably 0.5 μm or more. More preferably, it is 1 μm or more. Further, in order to minimize the change in the interval due to elastic deformation, the diameter is preferably 5 μm or more, more preferably 10 μm or more. There is no particular upper limit on the maximum diameter, but in order to reduce the contact resistance between the mask and the magnetic recording medium, the diameter is preferably 1 mm or less, more preferably 500 μm or less. When the shape of the protrusion is not substantially circular, the length of the long side is preferably in the above numerical range. In particular, a substantially circular shape having a diameter of about 100 μm is particularly preferable.
[0079]
In the case where a plurality of protrusions are provided discretely, the distance between the protrusions is appropriately designed according to the size of the protrusions, but the distance between the mask and the medium may be kept at least substantially concentrically. . However, it is necessary to provide at least three in the plane. If the individual protrusions are considerably large, about three may be provided in the plane, but it is usually preferable to provide more. When the size of the protrusion is small, for example, if the diameter is as small as about 1 μm, the bottoms of adjacent protrusions may be in contact with each other in order to prevent deformation due to a load.
[0080]
In the present invention, as described above, the protrusion is at least a part of the mask surface, and is provided at a position that does not contact the chamfered portion of the magnetic recording medium when the mask is brought into contact with the magnetic recording medium.
[0081]
Here, the protrusion may be inside the magnetic recording area of the magnetic recording medium, outside the magnetic recording area, or may be present in both. In particular, when a protrusion is provided inside the magnetic recording area, the hardness of the protrusion is controlled by selecting a material, which will be described later (softening to some extent), so that the magnetic recording medium is not damaged during the adsorption. It becomes possible to do so. Thereby, even when the mask pattern region exists up to the vicinity of the edge of the magnetic recording medium, and it is dimensionally strict to provide the projection on the peripheral portion of the mask pattern region, the projection can be provided. . Therefore, the pattern area of the magnetic recording medium can be expanded, and a larger capacity magnetic recording medium can be obtained.
[0082]
Specifically, it is preferably provided in the peripheral area of the mask pattern area (the area near the outermost periphery and the area near the innermost periphery of the mask pattern area), and particularly at least in the vicinity of the outermost periphery of the mask pattern area in the radial direction of the mask. It is preferable to provide protrusions in two areas, the area and the innermost peripheral vicinity area. It is more preferable to further provide a protrusion in a region near the middle of these two regions. This is because if the distance between the mask and the magnetic storage medium is reduced to, for example, about 3 μm or less, the mask and the magnetic storage medium may unintentionally contact with each other in the pattern region, resulting in a scratched defect due to friction or the like. Because. In particular, when the pressure between the magnetic recording medium and the mask is reduced and attracted and fixed, the magnetic recording medium bends and is thus more likely to come into contact. Therefore, it is considered that if a gentle lower protrusion is provided near the middle of the pattern area of the mask, the magnetic storage medium is not in direct contact with the mask but in contact with the gentle protrusion, so that it is difficult to cause a defect.
[0083]
Next, characteristics required for the protrusion will be described. The protrusions are required to have characteristics such as a certain degree of lubricity, hardness, heat resistance, and solvent resistance. As described above, it is desirable that the friction between the mask and the magnetic recording medium is not so large and that the mask is relatively movable. Therefore, it is preferable that the protrusions have a certain degree of slipperiness.
[0084]
In addition, it is preferable that the mask and the magnetic recording medium do not adsorb and the mask can be easily removed so that the slipperiness is high. In the industrialization stage, since the mask is set on the magnetic recording medium by an automatic machine such as a robot, it is preferable that the mask can be easily removed when the mask and the magnetic recording medium are separated in a direction perpendicular to the surface. .
[0085]
Also, since the mask is used to transfer the magnetization pattern to a large number of magnetic recording media, if the protrusions are made of a material that is easily plastically deformed, some of the protrusions are gradually deformed, and the mask and the magnetic field at a specific position. There is a possibility that the interval between the recording media is narrowed and the occurrence of non-concentric distorted interference fringes is induced.
[0086]
Therefore, the material of the protrusion is required to be a material having sufficient hardness. For example, it is preferable that the amount of plastic deformation of the projection height of the mask after the mask has been repeatedly attached to and detached from the magnetic recording medium about 10 times is 50% or less of the original height. More preferably, it is 10% or less. For industrial use, it is preferably 10% or less.
[0087]
Furthermore, although the projections are not directly irradiated with energy rays, they may be placed on the back surface of the non-transmissive portion of the mask, so that heat in the non-transmissive portions of the mask heated by the energy rays is indirectly transmitted to the projections. Sometimes. Therefore, it is desirable that the protrusions are difficult to be deformed or decomposed by heat, and a material having a decomposition temperature of 100 ° C. or higher is preferably used. Further, the higher the energy beam power, the higher the heat resistance of the protrusions, for example, 100 mJ / cm.²When the above power is applied, the decomposition temperature is preferably 200 ° C. or higher.
[0088]
Therefore, in the present invention, as described above, chromium is used as the material of the protrusion. Chromium has high hardness and excellent durability, and also has an appropriate flexibility so that it does not damage the magnetic recording medium that comes into contact with it. In addition, it is excellent in adhesion to quartz glass generally used as a substrate, and processing operations such as sputtering described later when manufacturing the protrusions are easy.
[0089]
Furthermore, in order to give the protrusions an appropriate hardness and flexibility, it is preferable to contain a certain concentration of oxygen in addition to chromium. When forming projections with chromium by sputtering or the like, by performing sputtering in an oxygen atmosphere in addition to argon as a sputtering gas, oxygen present as a gas is caught together in chromium, and projections are formed. The crystal structure changes from the case of chromium alone and becomes amorphous. As a result, the hardness of the protrusions is reduced, but the flexibility is increased. Therefore, the brittleness of the protrusions is suppressed, and it becomes possible to prevent wear and damage.
[0090]
In order to evaluate the oxygen content of the protrusions, a technique such as Auger electron spectroscopy (AES) may be used. As a specific procedure, first, a sample is introduced into the ultra-high vacuum environment of the apparatus, and the surface contamination layer and the natural oxide film are removed by argon ion sputtering. At this time, it is desirable to set the acceleration energy of argon ions to a low energy of 2 keV or less in order to reduce the composition shift due to selective sputtering. In addition, it is desirable to monitor the state in which the surface contamination layer and the naturally produced film are removed and the inside is exposed by depth profile measurement. An AES spectrum is measured for the inside of the exposed protrusion by argon ion sputtering. Obtained Cr-LM_2,3M_4,5Opi KL_2,3L_2,3Multiplying the peak intensity by a suitable sensitivity correction coefficient, the oxygen / chromium atomic ratio is calculated, and based on this, the concentration of oxygen taken into the protrusions is evaluated.
[0091]
In the present invention, it is preferable that the oxygen / chromium atomic ratio of the protrusion measured by the above-described method or the like is 0.1 or more. More preferably, it is 0.2 or more, and more preferably 0.3 or more. However, if the oxygen content is too high, the balance between hardness and flexibility is lost, and on the contrary, there is a risk that the wear may become severe, so it is preferable to set it to 1.0 or less. More preferably, it is 0.9 or less, More preferably, it is 0.8 or less.
[0092]
Further, the hardness of the protrusion can be evaluated by measuring the Knoop hardness, for example. As a method for measuring Knoop hardness, for example, a method described later in the embodiment may be used. In the present invention, the Knoop hardness of the protrusion measured by this method is about 100 kgf / mm.²(About 980 N / mm²) It is preferable to make the above. More preferably about 200 kgf / mm²(About 1960 N / mm²) Or more, more preferably about 300 kgf / mm²(About 2940 N / mm²) That's it. Also, usually about 400kgf / mm²(About 3920 N / mm²)
[0093]
In the present embodiment, the mask having both the features of the present invention, ie, the projection formation position (position not contacting the chamfered portion of the magnetic recording medium) and the projection material (chromium) has been described. Of course, it is possible to apply only one of the features to the mask.
[0094]
When a material other than chromium is used as the material of the protrusion, it is preferable that the protrusion is made of a material that is soluble in a predetermined solvent, particularly if the protrusion is created by a technique such as photolithography at the time of forming the protrusion. However, after forming the protrusion, it may be subjected to organic solvent cleaning for the purpose of removing dust, particles and the like attached to the mask. For example, solvent resistance may be imparted to the protrusions by heat treatment or the like after creation.
[0095]
Next, the configuration of the mask according to the present invention will be described.
As described above, if the mask used in the present invention has a mask pattern that causes the density of energy rays according to the magnetization pattern to be formed, a mask pattern composed of a transmission part and a non-transmission part of the energy ray is used. Any type of mask such as a mask having a mask pattern having a mask pattern for diffusing energy rays, a hologram mask, or the like can be used.
[0096]
A mask pattern consisting of a transmission part and a non-transmission part of energy rays is formed by sputtering a metal such as chromium on a transparent substrate that is transparent to energy rays such as quartz glass, optical glass, and soda lime glass. Then, a photoresist can be applied thereon by spin coating or the like, and a desired transmissive portion and non-transmissive portion can be formed by etching or the like. In this case, the portion having the chromium layer on the transparent substrate is the energy ray non-transmitting portion, and the portion having only the master is the transmitting portion. Preferably, a chromium oxide layer is formed on the chromium layer. The chromium oxide layer can be formed only by oxidizing chromium, and has a low optical reflectance, so that it has an effect of reducing the influence of multiple reflections. Moreover, since adhesiveness with a chromium layer is excellent, it is preferable. It is also preferable to apply an antireflective coating made of a dielectric layer to the mask. This is because energy rays can be used more effectively.
[0097]
As described above, a mask pattern region is formed on the mask, and then a protrusion is formed on at least a part of the surface of the mask that should face the magnetic recording medium. Hereinafter, a method of forming the protrusions on the mask will be described. For example, the following method can be adopted.
[0098]
[Method 1]
A radiation curable or thermosetting resin layer such as polyimide is formed on the mask, and protrusions are formed on the resin layer by photolithography. In this method, since the thickness of the resin layer becomes substantially equal to the height of the protrusion, there is an advantage that the height of the protrusion can be accurately and uniformly controlled by controlling the thickness of the resin layer. Further, there is an advantage that the resin layer can be applied and removed with an etching solution in a short time.
[0099]
When the polyimide resin is a photosensitive polyimide resin, photolithography and etching may be performed as it is after the resin layer is formed. However, when the polyimide resin is a non-photosensitive polyimide resin, after forming a photoresist layer on the resin layer, Lithography, development, etching, etc. are performed.
[0100]
The resin layer is generally formed by coating, such as a dipping method or a spin coating method. Subsequently, a latent image is formed by irradiating the mask with a resin layer with laser light or the like through a projection forming mask having a pattern corresponding to the projection to be formed. Next, unnecessary portions are removed by etching with an organic solvent to form protrusions.
[0101]
Thereafter, in order to increase the hardness of the protrusion and improve the solvent resistance of the protrusion, it is preferable to promote crosslinking by performing a heat treatment or an ultraviolet irradiation treatment. As the heat treatment, there are methods such as using an oven and using an infrared lamp. At this time, depending on the material of the resin, there is a case where the sink mark at the time of curing is large, and the central portion of the protrusion is selectively reduced to form a crater. When using such a resin having a large sink at the time of curing, the shape of the protrusion is preferably substantially circular in order to make the protrusion height uniform.
[0102]
In this method, a thick resin layer may be applied to form a high protrusion. However, since a very thin resin layer is usually difficult to form, a relatively high protrusion having a protrusion height of 0.3 μm or more and 10 μm or less is used. Suitable for formation.
[0103]
[Method 2]
Moreover, you may form a processus | protrusion with an inorganic substance. This is preferable in that a protrusion having high hardness can be easily formed. Examples of inorganic substances include metals (including alloys), dielectrics such as oxides and nitrides, and carbon. There are several forming methods as follows.
[0104]
(Method 2-1)
An inorganic layer is formed on the mask, and protrusions are formed on the inorganic layer by photolithography. In this method, since the thickness of the inorganic layer becomes substantially equal to the height of the protrusion, there is an advantage that the height of the protrusion can be accurately and uniformly controlled by controlling the thickness of the inorganic layer.
[0105]
The material of the inorganic layer is not particularly limited as long as it has sufficient hardness and weather resistance, but a material that is not magnetized is preferable because it is less affected by the applied external magnetic field.
[0106]
Use of chromium or chromium oxide is preferable because protrusions can be formed in the same process as the formation of the non-transmissive portion of the mask. As a method for forming the inorganic layer, sputtering, vapor deposition, CVD, plating and the like are generally used. Subsequently, after forming a photoresist layer on the inorganic layer, photolithography is performed. A latent image is formed by irradiating the photoresist layer with laser light through a projection forming mask having a pattern corresponding to the projection to be formed. Next, development is performed, and unnecessary portions of the inorganic layer are removed by etching with an etchant or the like, thereby forming protrusions.
[0107]
According to the present method, the height of the projection formed can be arbitrarily changed by controlling the thickness of the inorganic layer and the etching amount, and thus can be applied to various projection heights. For example, it is 0.001 μm or more and 10 μm or less. If the film is formed thick, high protrusions can be formed. However, since the inorganic layer can be easily formed thinner than the resin, it is easy to form low protrusions of 0.001 μm to 3 μm that are difficult to form by a method using a resin.
[0108]
(Method 2-2)
A protrusion is formed by depositing an inorganic layer at a position where the protrusion of the mask is to be formed. That is, a shielding plate having a hole corresponding to the projection shape to be formed is placed on the mask, and an inorganic layer is formed by sputtering, vapor deposition, or the like. This method has the same advantages as (Method 2-1), and furthermore, the projections can be formed very easily and the wet process is not performed at all. Therefore, there is a possibility that foreign matter remains on the mask. It is preferable because it has a low possibility of contaminating the magnetic recording medium during transfer of the magnetization pattern. That is, photolithography of the inorganic layer is not required, the subsequent resin removal and washing steps are not required, and application of the resin is not required, and only the inorganic layer is formed.
[0109]
Further, in this method, the thickness of the inorganic layer becomes substantially equal to the height of the protrusion, and therefore there is an advantage that the height of the protrusion can be accurately and uniformly controlled by controlling the thickness of the inorganic layer.
[0110]
The material of the inorganic layer, the film formation method, and the like are the same as in (Method 2-1). However, in this method, a shielding plate is disposed between the sputtering target or the vapor deposition source and the mask when forming the inorganic layer. The shape of the protrusion can be controlled by the shape of the hole of the shielding plate, and may be a strip shape or discontinuous.
[0111]
The shielding plate is subjected to mechanical processing such as punching according to the shape of the protrusion to be produced. The material of the shielding plate is not particularly limited as long as it can be easily processed and has a certain durability. For example, a metal foil such as stainless steel (SUS), brass, or copper, or a resin film such as polyimide is used. The thickness is not particularly limited, but is preferably 10 μm or more in terms of workability and durability. On the other hand, if it is too thick, it is difficult to form an inorganic film through the hole, and it is also difficult to process it, so 1 mm or less is preferable.
[0112]
This method is suitable for forming a projection having a relatively large bottom area because the shielding plate is mechanically processed according to the projection shape. The protrusion having a large bottom area is, for example, a diameter of 0.2 mm or more for a circular shape and a side of 0.2 mm or more for a square shape. Large protrusions are physically stronger, so it is preferable in terms of strength to support a small number of large protrusions than a large number of small protrusions.
[0113]
Further, in this method, in the hole portion of the shielding plate, a portion that is shaded by the thickness of the shielding plate is difficult to form, so that it is easy to form a gentle protrusion with an inclined side surface. However, if the shape of the hole in the shielding plate is changed in the thickness direction so as to be wider toward the upper side, it is considered that a protrusion having a shape in which the side surface having a substantially rectangular cross-sectional shape is substantially rectangular can be formed.
[0114]
That is, in this method, a gentle protrusion having a large bottom area is easily formed. By the way, in the case of a hard disk, since the distance between the pattern area and the outer peripheral edge of the disk is very narrow, for example, 0.3 mm or less, when forming a gentle protrusion having a peak at the periphery of the pattern area, the base of the protrusion is the pattern area. It often spreads to. In such a case, it is preferable to form a protrusion so that the skirt extends in the non-transmissive portion in the pattern region.
[0115]
Further, it is preferable that the protrusions have at least a length in the radial direction of the disk so that the disk can be supported even if the disk and the mask are slightly misaligned. Depending on the shape of the pattern in the pattern area, the length of the protrusion in the circumferential direction of the disk may not be increased. In this case, it may be oval or elliptical.
[0116]
According to the present method, the height of the protrusion formed can be arbitrarily changed by controlling the thickness of the inorganic layer, and thus can be applied to various protrusion heights. For example, it is 0.001 μm or more and 10 μm or less. Further, since the inorganic layer can be easily formed thinner than the resin, it is easy to form a low protrusion of 0.001 μm or more and 3 μm or less which is difficult to form by a method using a resin.
[0117]
It is also easy to change the height of the protrusion depending on the location by changing the shape and position of the hole of the shielding plate during the sputtering. In addition, it is preferable that a high protrusion can be easily formed only by forming a thick film without an etching process.
[0118]
(Method 2-3)
A protrusion made of an inorganic material is formed on the mask by a so-called lift-off method. That is, when the photoresist layer on the mask is uneven by photolithography, an inorganic layer is formed on the photoresist layer, and then the photoresist layer is removed, the inorganic layer remains as a protrusion only in the portion where there is no photoresist.
[0119]
explain in detail. Photoresist is applied to the mask to a predetermined thickness, and development is performed by irradiating a laser beam in accordance with the position and shape of the protrusion to be formed, and a portion of the photoresist is removed to form irregularities. After a metal layer is formed on the protrusion according to the height of the protrusion to be formed, it is immersed in, for example, a photoresist removing solution. Then, the photoresist layer is removed and the metal layer formed thereon is removed, so that only the metal layer formed in a place where there is no photoresist remains as a protrusion.
[0120]
In this method, since the thickness of the metal layer becomes substantially equal to the height of the protrusion, there is an advantage that the height of the protrusion can be accurately and uniformly controlled by controlling the thickness of the metal layer.
[0121]
The material of the inorganic layer, the film formation method, and the like are the same as in (Method 2-1). For example, a strong alkaline solution is used as the photoresist removing solution.
[0122]
In this method, the shape of the protrusion can be controlled by the shape of the unevenness formed on the photoresist layer, and may be a belt shape or a discontinuity. Since photolithography is performed, it is suitable for forming a protrusion having a small bottom area as compared with (Method 2-2). The protrusion having a small bottom area is, for example, a diameter of less than 0.2 mm for a circle and a side of less than 0.2 mm for a rectangle.
[0123]
It is preferable that the small protrusion has a high degree of freedom in the place where it can be formed and can be formed in a narrow region. The distance between the pattern area and the outer peripheral edge of the disk can also be provided at the periphery of the hard disk, which is very narrow, for example, 0.3 mm or less.
[0124]
In addition, since the protrusions are formed by photolithography, alignment with the pattern is easy to take accurately as compared with (Method 2-2). In some cases, the pattern and the protrusion can be formed simultaneously, and the process can be greatly shortened. Furthermore, according to the lift-off method, it is easy to form a protrusion having a substantially rectangular cross-sectional shape in the direction perpendicular to the mask surface, that is, a protrusion having a side surface that is sharp. Therefore, a protrusion having a larger top area can be easily formed even with the same bottom area, and the disk can be supported even when the disk and the mask are slightly misaligned. Furthermore, it is preferable that the protrusion has a large length in the disk radial direction. As a result, it is possible to provide a margin for misalignment between the mask and the disk.
[0125]
According to the present method, the height of the protrusion formed can be arbitrarily changed by controlling the thickness of the inorganic layer, and thus can be applied to various protrusion heights. For example, it is 0.001 μm or more and 10 μm or less. Further, since the inorganic layer can be easily formed thinner than the resin, it is easy to form a low protrusion of 0.001 μm or more and 3 μm or less which is difficult to form by a method using a resin.
[0126]
By repeating the lift-off method several times, the height of the protrusion can be changed depending on the location. Further, it is preferable that an etching process of the inorganic layer is not required and a high protrusion can be easily formed only by forming a thick film.
[0127]
[Method 3]
A liquid resin is dropped on the mask where the protrusions are to be formed to form the protrusions. This method has an advantage that the projection can be formed very easily because it is not necessary to apply the entire surface of the resin, and photolithography is not required and the subsequent resin removal and washing steps are unnecessary.
[0128]
After dropping the radiation curable or thermosetting resin, it is preferable to cure the resin by heating with an oven or an infrared lamp or laser light irradiation in order to increase the hardness of the protrusion and improve the solvent resistance of the protrusion.
[0129]
At this time, depending on the material of the resin, there is a case where the sink mark at the time of curing is large, and the central portion of the protrusion is selectively reduced to form a crater. When using such a resin having a large sink at the time of curing, the shape of the protrusion is preferably substantially circular in order to make the protrusion height uniform.
[0130]
In this method, the height and size of the protrusions can be controlled by adjusting the amount and viscosity of the resin. In order to form a high protrusion, the resin amount may be increased and the viscosity may be increased. For example, it is suitable for forming a relatively high protrusion having a protrusion height of 0.3 μm or more and 10 μm or less.
[0131]
[Method 4]
Projections are formed by forming a radiation curable or thermosetting resin layer in which inorganic / organic fine particles are dispersed on a mask. This method has the advantage that projections can be formed very easily because photolithography is not required and the subsequent resin removal and cleaning steps are not required.
[0132]
The resin layer is generally formed by coating, such as a dipping method or a spin coating method. After application, it is preferable to cure the resin by heating with an oven or an infrared lamp or laser light irradiation in order to increase the hardness of the protrusion and improve the solvent resistance of the protrusion.
[0133]
The particles are not limited as long as they have sufficient hardness, but are preferable because they have little influence on an external magnetic field to which fine particles such as glass, silicon, and resin are applied. The size of the particles may be selected according to the size of the projections to be formed, but is usually about 0.3 μm or more and 10 μm or less. In order to make the projection height uniform, it is preferable that the particles to be added have a spherical shape.
[0134]
In this method, the height and size of the protrusions can be controlled by adjusting the size, shape and addition amount of the particles, the amount of resin and the viscosity. This method is suitable for forming a relatively high protrusion having a protrusion height of 0.3 μm to 10 μm, for example.
[0135]
[Method 5]
The substrate constituting the mask is irradiated with energy rays having a high energy density, and the substrate is deformed to form protrusions. Alternatively, after forming a processed layer on the base material, irradiation with energy rays having a high energy density is performed to deform the processed layer to form protrusions. As the substrate, quartz glass, soda lime glass or the like is usually used. The working layer material may be any material that can be deformed by irradiation with energy rays and has sufficient hardness. For example, when chromium or chromium oxide, which is a material for forming a non-transmissive portion, is used, the formation of the non-transmissive portion Protrusions can be formed in the same process, which is preferable. In this case, chromium, chromium oxide, or the like may be formed on the periphery of the pattern region.
[0136]
This method has an advantage that protrusions can be formed very easily because there is no need for resin application or photolithography, and no subsequent resin removal or washing step. Further, since the material of the protrusion is, for example, quartz glass of the mask base material, there is an advantage that it is easy to form a protrusion with high hardness. Furthermore, by selecting the laser irradiation conditions, a low protrusion having a height of 1 μm or less can be easily formed. A height of several to several tens of nm is also possible. Therefore, for example, it is suitable for forming a relatively low protrusion having a protrusion height of 0.001 μm to 3 μm.
[0137]
In this method, a laser beam is irradiated to the base material or processed layer of the mask. As lasers suitable for use, carbon dioxide laser (wavelength 10.6 μm), excimer laser (157, 193, 248, 308, 351 nm), fundamental wave of YAG Q-switched laser (1064 nm), double wave (532 nm), Third harmonic (355 nm), fourth harmonic (266 nm), Ar laser (488 nm, 514 nm), laser diode (780, 980, 820 nm), or the like can be given.
[0138]
When the projections are directly formed on the mask substrate such as glass or quartz, it is preferable to use a light source having a long wavelength, such as a carbon dioxide laser (wavelength 10.6 μm).
[0139]
When the projection is formed by irradiating a laser to the pattern area non-transmission part of the mask or the peripheral part of the pattern area and heating the processing layer to form a projection, the energy beam used is a laser beam having a wavelength that is absorbed by the processing layer. For example, the fundamental wave (1064 nm), the harmonic (532 nm), the third harmonic (366 nm), the fourth harmonic (266 nm), the Ar gas laser (514, 488 nm), the excimer laser (157, 193) of the YAG laser may be used. , 248, 308, 351 nm), laser diodes (780, 980, 820 nm), and the like.
[0140]
The laser to be irradiated is pulsed. However, even when a pulsed laser is originally used, a continuous wave laser may be pulsed by AOM, EOM, mechanical shutter, or the like. Irradiation with a pulsed laser makes it easy to form a substantially circular protrusion.
[0141]
The pulse width of the irradiated laser may be short when the energy density generated by the light source is high, but a pulse width of 1 nsec or more is preferable in order to generate sufficient heat in the processed layer. Further, although a projection can be created by sufficiently increasing the pulse width even with a light source having a low energy density, the pulse width is preferably about 1 second or less, more preferably 100 msec or less, in order not to unnecessarily increase the processing time.
[0142]
As a method of forming the protrusion, a laser beam is irradiated to a predetermined place while rotating the mask on a rotating body such as a spindle, and a laser beam is irradiated to a predetermined place while moving the mask on an XY stage or the like. There is a case.
[0143]
The protrusions formed as described above may be covered with another layer. For example, a carbonaceous layer such as hydrogenated carbon or amorphous carbon, or a fluorine resin layer such as Teflon (registered trademark). The carbon layer can be formed by sputtering, CVD, or the like, and since the hardness is high, the protrusion can be prevented from being scraped and lubricity can be imparted. Fluorine resin can also provide lubricity.
[0144]
When the protrusion is made of a metal such as chromium, it is preferable to cover the protrusion with another layer in order to prevent contamination of the medium due to corrosion.
[0145]
Next, the magnetization pattern forming method of the present invention will be described.
In the present invention, various combinations of local heating and external magnetic field application are conceivable, but preferably, after applying the first external magnetic field and magnetizing the magnetic thin film uniformly in a desired direction in advance, the magnetic thin film is locally applied. Simultaneously with the heating, a second external magnetic field is applied to magnetize the heating part in the direction opposite to the desired direction to form a magnetization pattern. As a result, magnetic domains opposite to each other are clearly formed, so that a magnetization pattern having a high signal intensity and good C / N and S / N can be obtained.
[0146]
First, a strong first external magnetic field is applied to the magnetic recording medium to uniformly magnetize the entire magnetic layer in a desired magnetization direction. As a means for applying the first 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.
[0147]
The desired magnetization direction is the same as or opposite to the data writing / reproducing head traveling direction (the relative movement direction of the medium and the head) in the case of a medium whose easy axis is in the in-plane direction. When the easy magnetization axis is perpendicular to the in-plane direction, it is either the vertical direction (upward or downward). Therefore, the first external magnetic field is applied so as to be magnetized as such. The application direction of the first external magnetic field is preferably any of a circumferential direction, a radial direction, and a direction perpendicular to the plate surface.
[0148]
Further, to uniformly magnetize the entire magnetic layer in a desired direction means to magnetize all of the magnetic layer in almost the same direction, but not strictly all, at least the region where the magnetization pattern is to be formed is in the same direction. It only needs to be magnetized.
[0149]
The strength of the first external magnetic field varies depending on the characteristics of the magnetic layer of the magnetic recording medium, and is preferably magnetized by a magnetic field that is at least twice the coercive force of the magnetic layer at room temperature. If it is weaker than this, magnetization may be insufficient. However, normally, it is about 5 times or less the coercive force of the magnetic layer at room temperature because of the ability of the magnetizing device used for magnetic field application. Here, the room temperature is 25 ° C., for example. The coercivity of the magnetic recording medium is substantially the same as the coercivity of the magnetic layer (recording layer).
[0150]
The magnetic layer generally has a static coercive force (sometimes simply referred to as a coercive force) and a dynamic coercive force, but it is sufficient that the local heating can be performed at least to a temperature at which the dynamic coercive force of the magnetic layer is reduced to some extent. . Of course, you may heat to the temperature where static coercive force falls. Preferably it heats to 100 degreeC or more. Magnetic layers that are affected by an external magnetic field at a heating temperature of less than 100 ° C. tend to have low magnetic domain stability at room temperature. However, it is desirable that the heating temperature be low in a range where a desired reduction in coercive force can be obtained. For example, up to the vicinity of the magnetization disappearance temperature or the Curie temperature of the magnetic layer. If the heating temperature is too high, heat diffusion to areas other than the region to be heated tends to occur, and the pattern may be blurred. In addition, the magnetic layer may be deformed. In addition, a lubricating layer made of a lubricant is usually formed on the surface of the magnetic recording medium, and the lower the heating temperature is preferable in order to prevent adverse effects such as deterioration of the lubricant due to heating. Heating may cause degradation such as decomposition or vaporization and decrease due to heating, and the vaporized lubricant may adhere to a mask or the like particularly in the case of proximity exposure. Therefore, it is desirable that the heating temperature be as low as possible in order to industrially apply the magnetization pattern forming method of the present invention to a magnetic recording medium having a lubricating layer.
[0151]
For this reason, it is preferable that the heating temperature is not higher than the Curie temperature of the magnetic layer. For example, the temperature is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, and still more preferably 200 ° C. or lower.
[0152]
Next, the direction of the second external magnetic field applied simultaneously with heating is generally opposite to the first external magnetic field. When the medium has a disk shape, the application direction of the second external magnetic field is preferably any of a circumferential direction, a radial direction, and a direction perpendicular to the plate surface.
[0153]
When using a pulsed energy beam for heating, the second external magnetic field may be applied continuously or pulsed. When the second external magnetic field is a pulsed magnetic field, it may be only a pulsed magnetic field component or a combination of a pulsed magnetic field component and a static magnetic field component. At this time, the sum of the pulsed magnetic field component and the static magnetic field component is taken as the strength of the second external magnetic field.
[0154]
The stronger the maximum intensity of the second external magnetic field, the easier the magnetization pattern is formed. Although the optimum strength varies depending on the characteristics of the magnetic layer of the magnetic recording medium, when the second external magnetic field is a static magnetic field, it is preferably 1/8 or more of the coercivity at room temperature (static coercivity). If it is weaker than this, the heating part 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. However, the coercive force at room temperature of the magnetic layer is preferably 2/3 or less, and more preferably 1/2 times or less. If it is larger than this, the magnetic domains around the heating part may be affected.
[0155]
When the second external magnetic field is a pulsed magnetic field, it is preferably 2/3 or more of the coercivity (static coercivity) at room temperature. If it is too weak, the heating area may not be magnetized well. More preferably, it is 3/4 or more of the static coercivity at room temperature. A magnetic field stronger than the static coercivity at room temperature may be applied. However, the magnetic field is smaller than the dynamic coercive force at room temperature of the magnetic layer. This is because if the second external magnetic field is larger than this, the magnetization of the non-heated region is affected.
[0156]
In the present invention, the magnetic field strength value H (Oe) can be replaced by the magnetic flux density value B (Gauss). In general, there is a relationship of B = μH (where μ represents a magnetic permeability), but since the normal magnetization pattern is formed in the air, the magnetic permeability is 1, and the relationship of B = H is established. is there.
[0157]
As a means for applying the second external magnetic field to the magnetic layer, a magnetic head may be used, or a plurality of electromagnets or permanent magnets may be used so as to generate a magnetic field in a desired magnetization direction. Different means may be used in combination. In order to efficiently magnetize a high coercive force medium suitable for high density recording, permanent magnets such as ferrite magnets, neodymium rare earth magnets, and samarium cobalt rare earth magnets are suitable.
[0158]
When the second external magnetic field is a pulsed magnetic field, only the pulsed magnetic field applying unit may be used, or a combination of the pulsed magnetic field applying unit and the static magnetic field applying unit may be used. For example, in the former, only a pulsed magnetic field is generated by an electromagnet or the like. For example, in the latter case, a static magnetic field of a certain magnitude is given by a permanent magnet or an electromagnet, and a magnetic field higher than that is applied in pulses by the electromagnet. It is preferable to use an air-core coil with a small inductance because the pulse width can be narrowed and the magnetic field application time can be shortened. Further, other yoke type electromagnets may be used instead of the permanent magnets.
[0159]
Combining a static magnetic field and a pulsed magnetic field can reduce the magnetic field applied in a pulsed manner. In general, an electromagnet becomes difficult to shorten the pulse width as the magnetic field increases, and therefore, the pulse width is easily shortened accordingly.
[0160]
Alternatively, the pulsed magnetic field can be applied by a method in which a magnet that constantly generates a magnetic field is brought close to the magnetic recording medium for a short time. For example, the medium may be rotated at a predetermined speed or higher while applying a magnetic field to a part of the magnetic recording medium with a permanent magnet.
[0161]
When the second external magnetic field is a combination of a static magnetic field and a pulsed magnetic field, the magnetic field strength of the static magnetic field is made smaller than the static coercive force of the magnetic layer at room temperature. Preferably, the static coercive force is 2/3 or less, more preferably 1/2 times or less. If it is too large, it affects the formed magnetization pattern and not only lowers the output, but also deteriorates the modulation. There is no particular lower limit, but if it is too weak, the meaning of using a static magnetic field is reduced.
[0162]
Next, the pulse width when the second external magnetic field is a pulsed magnetic field will be described. In the present invention, the pulse width of the pulsed magnetic field component of the second external magnetic field is simply referred to as the pulse width of the second external magnetic field. Here, the pulse width of the magnetic field refers to the half width.
[0163]
The pulse width of the second external magnetic field is usually 100 msec or less. Preferably it is 10 msec or less. The shorter the pulse width of the second external magnetic field, the larger the upper limit value of the magnetic field that can be applied. This is because the value of the dynamic coercive force changes depending on the application time of the magnetic field, and the dynamic coercive force of the magnetic layer at room temperature increases as the pulse width of the second external magnetic field is shortened. More preferably, it is 1 msec or less.
[0164]
However, it is preferably 10 nsec or more. If it is too short, the dynamic coercive force increases accordingly, and the second external magnetic field necessary for magnetizing the heating region increases. Although depending on the magnitude of the magnetic field, it takes time for the magnetic field to rise and fall due to the characteristics of the electromagnet, so there is a limit to shortening the pulse width. More preferably, it is 100 nsec or more. Here, the pulse width of the magnetic field indicates a half width.
[0165]
When a pulsed energy beam is used for local heating, the pulse width of the second external magnetic field is set to be equal to or greater than the pulse width of the pulsed energy beam. If it is less than this, the magnetic field will change during local heating, so that the magnetization pattern will not be formed well.
[0166]
Further, it is preferable that the pulsed energy beam and the pulsed second external magnetic field are synchronized and applied simultaneously. Normally, it is considered that the pulse width of the magnetic field is longer than the pulse width of the energy beam. In this case, a pulse of the second external magnetic field is applied, and control is performed so that the pulse of the energy beam is applied at the maximum magnetic field. Is preferred.
[0167]
A magnetic recording medium or an AFC medium with an increased dynamic coercive force is particularly effective when a pulsed magnetic field is applied as the second external magnetic field. For example, a magnetic recording medium including two magnetic layers having a stabilizing magnetic layer for keeping thermal stability together with a magnetic layer for recording can be mentioned. Since the stabilizing magnetic layer functions to suppress instantaneous magnetization reversal of the recording magnetic layer, the dynamic coercive force is high, and it is difficult to form a magnetization pattern by the conventional method. A good magnetization pattern can be formed by applying an external magnetic field in the vicinity of the static coercive force or higher to such a medium in a pulsed manner.
[0168]
The second external magnetic field can also form a plurality of magnetization patterns at once by applying the external magnetic field over the heated wide region.
[0169]
When local heating can be performed on the entire surface of the magnetic recording medium at once, it is desirable to apply a second external magnetic field to the entire surface of the medium simultaneously with the heating to form a magnetization pattern. As a result, the magnetization pattern can be formed in a shorter time and the cost can be greatly reduced. Also, in order to apply a magnetic field only to a part of the medium, the magnet arrangement is often devised or specific measures are taken so that the magnetic field does not reach other areas, but it is necessary to apply it to the entire surface. Absent. In addition, since a rotating mechanism or a moving mechanism is not necessary, the apparatus configuration is simplified and a magnetic recording medium can be obtained at a low cost.
[0170]
For example, if the medium is a small-diameter disk-shaped magnetic recording medium having a diameter of 2.5 inches or less, energy beam irradiation and magnetic field application to the entire disk surface can be performed with simple arrangement and means. More preferably, the diameter is 1 inch or less.
[0171]
In addition, when a magnetic field is applied to the disk-shaped magnetic recording medium in the circumferential direction, a circumferential magnetic field can be easily generated by flowing a large pulse current in the vertical direction to the center of the medium. This is particularly preferable when applied to a small-diameter disk-shaped magnetic recording medium having a diameter of 1 inch or less.
[0172]
Next, a method for locally heating the magnetic layer in the present invention will be described.
The heating means only needs to have a function of partially heating the surface of the magnetic layer, but considering the prevention of thermal diffusion to unnecessary parts and controllability, the power control and the size of the heated part can be easily controlled. Use energy rays such as laser.
[0173]
By using the mask in combination, it is possible to irradiate energy rays through the mask and form a plurality of magnetization patterns at a time, so that the magnetization pattern forming process is short and simple.
[0174]
It is preferable to control the heating part and the heating temperature by making the energy rays pulse rather than continuous irradiation. The use of a pulse laser light source is particularly suitable. The pulsed laser light source oscillates the laser intermittently in a pulsed manner, as compared to intermittently pulsing a continuous laser with an optical component such as an acousto-optic device (AO) or an electro-optic device (EO). It is very preferable that a laser with a high power peak value can be irradiated in a very short time and heat accumulation hardly occurs.
[0175]
When a continuous laser is pulsed by optical components, it has substantially the same power over the pulse width within the pulse. On the other hand, a pulse laser light source, for example, accumulates energy by resonance in the light source and emits a laser as a pulse at a time, so that the power of the peak is very large within the pulse and then decreases. In the present invention, in order to form a highly accurate magnetic pattern with high contrast, it is preferable to rapidly heat and then rapidly cool in a very short time, so that a pulsed laser light source is suitable.
[0176]
The medium surface on which the magnetized pattern is formed preferably 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 increase the recording density. Therefore, it is preferable that the temperature is about room temperature or lower when the pulsed energy beam is not irradiated. Room temperature is about 25 ° C.
[0177]
When using the pulsed energy beam, the external magnetic field may be applied continuously or pulsed.
[0178]
The wavelength of the energy beam is preferably 1100 nm or less. If the wavelength is shorter than this, since the diffraction effect is small and the resolution is increased, it is easy to form a fine magnetization pattern. More preferably, the wavelength is 600 nm or less. In addition to high resolution, since the diffraction is small, the space between the mask and the magnetic recording medium due to the gap is wide and easy to handle, and the magnetic pattern forming apparatus can be easily constructed. The wavelength is preferably 150 nm or more. If it is less than 150 nm, the absorption of the synthetic quartz used for the mask increases, and heating tends to be insufficient. If the wavelength is 350 nm or more, optical glass can be used as a mask.
[0179]
Specifically, excimer laser (157, 193, 248, 308, 351 nm), YAG Q-switched laser (1064 nm), second harmonic (532 nm), third harmonic (355 nm), or fourth harmonic (266 nm), Ar laser (488 nm, 514 nm), ruby laser (694 nm), and the like.
[0180]
The power of the energy beam may be selected according to the magnitude of the external magnetic field, but the power per pulse of the pulse energy beam is 1000 mJ / cm.²The following is preferable. If a power larger than this is applied, the surface of the magnetic recording medium may be damaged and deformed by pulsed energy rays. If the roughness Ra of the medium is increased to 3 nm or more and the waviness Wa is increased to 5 nm or more due to the deformation, there is a possibility that the traveling of the flying / contact type head may be hindered.
[0181]
More preferably 500 mJ / cm²Or less, more preferably 200 mJ / cm.²It is as follows. In this region, it is easy to form a magnetization pattern with high resolution even when a substrate with relatively large thermal diffusion is used. The power is 10mJ / cm²The above is preferable. If it is smaller than this, the temperature of the magnetic layer will not rise easily and magnetic transfer will hardly occur. The required power tends to increase as the pattern width becomes narrower. Also, the shorter the wavelength of the energy beam, the lower the upper limit value of the power that can be applied.
[0182]
If there is a concern about damage to the magnetic layer, protective layer, or lubricating layer due to energy rays, means for reducing the power of the pulsed energy rays and increasing the strength of the magnetic field applied simultaneously with the pulsed energy rays. It can also be taken. For example, the irradiation energy is lowered by applying a magnetic field as large as 25 to 75% of the coercive force of the magnetic recording medium at room temperature.
[0183]
In addition, when irradiating the pulsed energy beam through the protective layer and the lubricating layer, it may be necessary to re-apply after irradiation in consideration of damage (decomposition, polymerization) and the like received by the lubricant.
[0184]
The pulse width of the pulsed energy beam is desirably 1 μsec or less. If the pulse width is wider than this, the heat generated by the energy applied to the magnetic recording medium is dispersed and the resolution is likely to be lowered. When the power per pulse is the same, the thermal diffusion is smaller and the resolution of the magnetization pattern tends to be higher when the pulse width is shortened and the strong energy is irradiated at once. More preferably, it is 100 nsec or less. In this region, it is easy to form a magnetization pattern with high resolution even when using a substrate having a relatively large thermal diffusion of metal such as Al.
[0185]
When forming a pattern with a minimum width of 2 μm or less, the pulse width is preferably 25 nsec or less. That is, if the resolution is important, the shorter the pulse width, the better. The pulse width is preferably 1 nsec or more. This is because it is preferable to keep heating until the magnetization reversal of the magnetic layer is completed.
[0186]
As a kind of pulsed laser, there is a laser that can generate picosecond and femtosecond level ultrashort pulses at a high frequency, such as a mode-locked laser. In the period in which the ultrashort pulse is irradiated at a high frequency, a very short time between each ultrashort pulse is not irradiated with the laser, but is a very short time, so the heating part is hardly cooled. That is, the region once heated to the Curie temperature or higher is kept above the Curie temperature.
[0187]
Therefore, in such a case, a continuous irradiation period (a continuous irradiation period including a time during which the laser between ultrashort pulses is not irradiated) is set to one pulse. Also, the integral value of the irradiation energy amount during the continuous irradiation period is expressed as the power per pulse (mJ / cm²).
[0188]
In addition, energy beams such as lasers generally have an intensity distribution (energy density distribution) within a beam spot, and a difference in temperature rise due to energy density occurs even when the energy beam is irradiated and locally heated. For this reason, a difference in transfer strength locally occurs due to uneven heating. Therefore, it is preferable to make the intensity distribution uniform in advance on the energy rays. The distribution of the heating state in the irradiated region can be kept small, and the distribution of the magnetic strength of the magnetization pattern can be kept small. Therefore, when reading the signal intensity using the magnetic head, it is possible to form a magnetization pattern with high signal intensity uniformity.
[0189]
Examples of the intensity distribution homogenization process include the following processes. For example, homogenizers and condenser lenses are used for homogenization, or only a portion where the intensity distribution of the energy rays is small is transmitted through a light shielding plate or slit, and enlarged as necessary.
[0190]
Preferably, when the energy rays are optically divided and then homogenized by superimposing them, the energy rays can be used without waste and the use efficiency is good. In the present invention, for heating the magnetic layer, it is preferable to irradiate high-intensity energy rays in a short time. For this purpose, it is preferable to use energy without waste.
[0191]
An example of a process for equalizing the intensity distribution of energy rays will be described. For example, an energy beam having an elliptical beam shape has a short-axis direction distribution and a long-axis direction distribution. At this time, by dividing the length in the minor axis direction of the beam into, for example, three parts with a prism array (multi-cylindrical lens) or the like and superimposing them, the difference in intensity can be dispersed, and the intensity distribution in the minor axis direction can be made uniform to some extent.
[0192]
In addition, the intensity distribution in the major axis direction can be made uniform to some extent by superimposing the beam in the major axis direction after dividing it into, for example, seven parts with a prism array (multi-cylindrical lens) or the like. If both are performed together, a beam having a uniform intensity and a small intensity distribution can be obtained as a whole. However, only one axial direction may be performed as necessary. When the intensity distribution is large, the uniformity can be increased by increasing the number of divisions. These are sometimes called homogenizers.
[0193]
When two or more prism arrays in the same axial direction are passed, the same effect as that obtained by increasing the number of divisions can be obtained. Alternatively, the biaxial direction may be divided at a time using a fly-eye lens in which a large number of lenses are formed in the biaxial direction.
[0194]
Alternatively, the intensity distribution can be easily made uniform by passing energy rays through an aspherical lens such as a cylindrical lens. In particular, when the energy beam is a small-diameter beam, it is often possible to make the beam uniform enough even with this method, which is preferable because the optical system can be simplified. The small diameter means a diameter of about 0.05 to 1 mm.
[0195]
If the above process alone is not sufficient for homogenization, a light shielding plate may be used in combination to cut or narrow the peripheral part of the beam for further homogenization.
[0196]
In the mask of the present invention, the intensity distribution of energy rays is changed in accordance with the magnetization pattern to be formed, and the density (intensity distribution) of energy rays is formed on the magnetic disk surface. As a result, a plurality of or large area magnetization patterns can be formed at a time, so that the magnetization pattern forming process is short and simple. The mask is preferable because it can be easily and inexpensively produced.
[0197]
The mask does not have to cover the entire surface of the magnetic disk. If there is a size including the repeating unit of the magnetization pattern, it can be used by moving it.
The material of the mask is not limited, but if the mask is made of a nonmagnetic material in the present invention, a magnetized pattern can be formed with uniform clarity in any pattern shape, and a uniform and strong reproduction signal can be obtained.
[0198]
When a mask containing a ferromagnetic material is used, the magnetic field distribution may be disturbed by magnetization. Due to the nature of ferromagnetism, in the case of a pattern shape inclined in the radial direction of the magnetic disk or an arc-shaped pattern extending in the radial direction, the magnetic domains do not sufficiently oppose each other at the magnetization transition portion, so that it is difficult to obtain a good signal.
[0199]
The mask is disposed between the energy beam light source and the magnetic layer (magnetic recording medium). If importance is placed on the accuracy of the magnetization pattern, the closer the distance between the mask and the medium, the better. This is because the longer the distance is, the more easily the magnetization pattern is blurred due to the wraparound of the irradiated energy rays. In order to improve this and obtain a clearer pattern, a thin transmissive part that acts as a diffraction grating is formed outside the transmissive part of the mask, or a means that acts as a half-wave plate is provided. The sneak light can be canceled out by interference.
[0200]
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.
A magnetic disk may have a magnetic layer formed on both main surfaces of the disk. In this case, the magnetization pattern formation of the present invention may be performed sequentially one side at a time, or a mask, an energy irradiation system and an external magnetic field may be applied. By applying means for applying to both sides of the magnetic disk, the magnetic pattern can be formed simultaneously on both sides.
[0201]
If two or more magnetic layers are formed on one surface and you want to form different patterns for each layer, each layer can be heated individually by focusing the energy rays to be irradiated on each layer to form individual patterns. .
[0202]
When forming a magnetized pattern, a light-shielding plate that can partially shield the energy rays is provided in the region where it is not desired to irradiate the energy rays between the light source and the mask or between the mask and the medium. A structure that prevents re-irradiation of energy rays is preferable.
[0203]
The light shielding plate may be any material that does not transmit the wavelength of the energy beam to be used, and may reflect or absorb the energy beam. However, when energy rays are absorbed, it is easy to heat and affect the magnetization pattern, so that a material having good thermal conductivity and high reflectance is preferable. For example, a metal plate such as Cr, Al, or Fe.
[0204]
According to the present invention, it is possible to form a magnetized pattern with good positional accuracy and excellent signal characteristics such as modulation. Therefore, a servo pattern for controlling the position of a recording / reproducing magnetic head or a reference pattern for servo pattern recording can be used. It is preferable to use it for formation.
[0205]
The servo pattern (or a reference pattern used for recording the servo pattern) is a pattern used for controlling the position of the recording / reproducing magnetic head on the data track. For this reason, a data pattern having higher positional accuracy than the servo pattern cannot be theoretically recorded. Therefore, the servo pattern needs to be formed with higher accuracy as the recording density of the medium becomes higher.
[0206]
In the present invention, since a servo pattern or a reference pattern with high positional accuracy can be obtained, the present invention is particularly effective when applied to a magnetic recording medium for high density recording in which the track density is 40 kTPI or more.
[0207]
Further, since a magnetization pattern oblique to the track can be formed well, it is particularly suitable for an inclination pattern such as a phase servo signal.
[0208]
Furthermore, since the present invention does not use a magnetic head, the servo pattern can be recorded beyond the movable range of the head, and the servo pattern can be detected even when the head is out of the data recording area, and the head is restored. There is also an advantage that it is easy.
By using the above-described magnetization pattern forming method, a magnetic recording medium in which a precise magnetization pattern is formed and the number of defects can be easily obtained in a short time. As a result, a magnetic recording apparatus capable of high-density recording can be provided.
[0209]
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, it is necessary that the substrate does not vibrate even when rotated at a high speed during high-speed recording / reproduction, and a hard substrate is usually used. In order to obtain sufficient rigidity that does not vibrate, the substrate thickness is generally preferably 0.3 mm or more. However, if it is thick, it is disadvantageous for making the magnetic recording device thin, so that it is preferably 3 mm or less. For example, an Al alloy substrate such as Al-Mg alloy containing Al as a main component, an Mg alloy substrate such as Mg-Zn alloy containing Mg as a main component, ordinary soda glass, aluminosilicate glass, non-crystalline glass For example, a substrate made of any of silicon, titanium, ceramics, and various resins, or a combination of them can be used. Among them, it is preferable to use an Al alloy substrate or a glass substrate such as crystallized glass in terms of strength and a resin substrate in terms of cost.
[0210]
The present invention is highly effective when applied to a medium having a hard substrate. In the conventional magnetic transfer method, a medium having a hard substrate has insufficient adhesion to the master disk, and scratches and defects are generated, or the boundary of the transferred magnetic domain is unclear and the PW50 tends to spread. Then, since the mask and the medium are not pressure-bonded, there is no such problem. In particular, it is effective for a medium having a substrate that is easily cracked, such as a glass substrate.
[0211]
In the manufacturing process of the magnetic recording medium, the substrate is usually first cleaned and dried. In the present invention, it is desirable to perform cleaning and drying before formation from the viewpoint of ensuring the adhesion of each layer. .
In manufacturing the magnetic recording medium of the present invention, a metal layer such as NiP or NiAl may be formed on the substrate surface.
[0212]
In the case of forming the metal layer, a method used for forming a thin film such as an electroless plating method, a sputtering method, a vacuum evaporation method, or a CVD method can be used as the method. In the case of a substrate made of a conductive material, electrolytic plating can be used. The film thickness of the metal layer is preferably 50 nm or more. However, considering the productivity of the magnetic recording medium, it is preferably 20 μm or less. More preferably, it is 10 μm or less.
[0213]
Further, the region where the metal layer is formed is preferably the entire surface of the substrate, but only a part, for example, a region where texturing is performed can be performed.
Further, concentric texturing may be applied to the surface of the substrate or the surface on which the metal layer is formed on the substrate. In the present invention, the concentric texturing means, for example, mechanical texturing using free abrasive grains and a texture tape, texturing using a laser beam, or the like, or by using these in combination, 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.
[0214]
In general, mechanical texturing is performed in order to provide in-plane anisotropy of the magnetic layer. If it is desired to form an in-plane isotropic magnetic layer, it is not necessary to apply it.
In general, texturing using a laser beam or the like is performed in order to improve CSS (contact start and stop) characteristics. There is no need to apply the method in which the magnetic disk device is a system (load / unload system) in which the head is retracted outside the disk when not driven.
[0215]
Alumina abrasive grains are widely used as abrasive grains used for mechanical texturing, but diamond abrasive grains are extremely important from the viewpoint of an in-plane orientation medium in which the axis of easy magnetization is oriented along the texturing grooves. Demonstrate good performance. Of these, those whose surface is graphitized are most preferred.
[0216]
Since the head flying height is as small as possible is effective for realizing high-density magnetic recording, and one of the features of these substrates is excellent surface smoothness, the substrate surface roughness Ra is preferably 2 nm or less, More preferably, it is 1 nm or less. In particular, 0.5 nm or less is preferable. The substrate surface roughness Ra is a value calculated according to JIS B0601 after measurement at a measurement length of 400 μm using a stylus type surface roughness meter. At this time, the tip of the measuring needle has a radius of about 0.2 μm.
[0217]
Next, an underlayer or the like may be formed on the substrate between the magnetic layer. For the purpose of making the crystal fine and controlling the orientation of the crystal plane, the base layer is preferably composed mainly of Cr.
As the material of the underlayer containing Cr as a main component, in addition to pure Cr, V, Ti, Mo, Zr, Hf, Ta, W, Ge, Nb, Si are added to Cr for the purpose of crystal matching with the recording layer. In addition, alloys containing one or more elements selected from Cu, B, Cr oxide, and the like are also included.
[0218]
Among them, pure Cr or an alloy obtained by adding one or more elements selected from Ti, Mo, W, V, Ta, Si, Nb, Zr and Hf to Cr is preferable. The optimum content of these second and third elements varies depending on the respective element, but generally 1 atomic% to 50 atomic% is preferable, more preferably 5 atomic% to 30 atomic%, still more preferably 5 atomic%. % To 20 atomic%.
[0219]
The film thickness of the underlayer is not particularly limited so long as it can exhibit this anisotropy, but is preferably 0.1 to 50 nm, more preferably 0.3 to 30 nm, and still more preferably 0.5 to 10 nm. Substrate heating may or may not be performed during the formation of the base layer containing Cr as a main component.
[0220]
A soft magnetic layer may be provided on the underlayer between the recording layer and the recording layer. In particular, a keeper medium with little magnetization transition noise or a perpendicular recording medium in which the magnetic domain is perpendicular to the in-plane of the medium has a great effect and is preferably used.
[0221]
The soft magnetic layer only needs to have a relatively high magnetic permeability and low loss, but NiFe or an alloy to which Mo or the like is added as a third element is preferably used. The optimum magnetic permeability varies greatly depending on the characteristics of the head and recording layer used for data recording, but in general, the maximum magnetic permeability is preferably about 10 to 1,000,000 (H / m).
[0222]
Or you may provide an intermediate | middle layer as needed on the base layer which has Cr as a main component. For example, providing a CoCr-based intermediate layer is preferable because the crystal orientation of the magnetic layer can be easily controlled.
Next, a recording layer (magnetic layer) is formed. Between the recording layer and the soft magnetic layer, a layer made of the same material as the underlayer or another nonmagnetic material may be inserted. When the recording layer is formed, the substrate may or may not be heated. As the recording layer, a Co alloy magnetic layer, a rare earth-based magnetic layer typified by TbFeCo, a transition metal-noble metal-based laminated film typified by a laminated film of Co and Pd, and the like are preferably used.
[0223]
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 can be used. In addition to these Co alloys, elements such as Ni, Cr, Pt, Ta, W, B and SiO₂A compound to which a compound such as Examples thereof include CoCrPtTa, CoCrPtB, CoNiPt, and CoNiCrPtB. The thickness of the Co alloy magnetic layer is arbitrary, but is preferably 5 nm or more, more preferably 10 nm or more. Moreover, Preferably it is 50 nm or less, More preferably, it is 30 nm or less. Further, the present recording layer may be laminated with two or more layers via an appropriate nonmagnetic intermediate layer. At that time, the composition of the laminated magnetic material may be the same or different.
[0224]
As the rare earth magnetic layer, a general magnetic material can be used, and examples thereof include TbFeCo, GdFeCo, DyFeCo, and TbFe. Tb, Dy, Ho, etc. may be added to these rare earth alloys. Ti, Al, and Pt may be added for the purpose of preventing oxidative degradation. The film thickness of the rare earth magnetic layer is arbitrary, but is usually about 5 to 100 nm. Further, the present recording layer may be laminated with two or more layers via an appropriate nonmagnetic intermediate layer. At that time, the composition of the laminated magnetic material may be the same or different. In particular, the rare earth-based magnetic layer is an amorphous structure film and has magnetization in a direction perpendicular to the media plane, so that it is suitable for high recording density recording, and the method of the present invention can form a magnetization pattern with high density and high accuracy. It can be applied more effectively.
[0225]
Similarly, as the transition metal and noble metal-based laminated film capable of performing perpendicular magnetic recording, a general magnetic material can be used. For example, Co / Pd, Co / Pt, Fe / Pt, Fe / Au, Fe / Ag and the like. The transition metal and noble metal of these laminated film materials may not be particularly pure and may be an alloy mainly composed of them. The thickness of the laminated film is arbitrary, but is usually about 5 to 1000 nm. Moreover, the lamination | stacking of 3 or more types of materials may be sufficient as needed.
[0226]
Recently, an AFC (Anti-Ferromagnetic coupled) medium has been proposed in order to increase the thermal stability of magnetic domains. Two or more magnetic layers (main magnetic layer and undercoat magnetic layer) are stacked via several angstroms of Ru layer, etc., and magnetically coupled above and below the Ru layer to increase the thermal stability of the main magnetic layer. It is an enhanced medium. This medium has an apparent coercive force, and a large magnetic field is required to reverse the magnetization.
[0227]
In the present invention, the recording layer is preferably thin. This is because if the recording layer is thick, heat transfer in the film thickness direction when the recording layer is heated is poor, and it may not be magnetized well. For this reason, the recording layer thickness is preferably 200 nm or less. However, the thickness of the recording layer is preferably 5 nm or more in order to maintain the magnetization.
In the present invention, the magnetic layer as the recording layer retains magnetization at room temperature and is demagnetized during heating or magnetized by applying an external magnetic field simultaneously with heating.
[0228]
The coercivity of the magnetic layer at room temperature must be such that it retains magnetization at room temperature and is uniformly magnetized by an appropriate external magnetic field. By setting the coercive force of the magnetic layer at room temperature to 2000 Oe or more, a medium suitable for high-density recording can be obtained that can maintain a small magnetic domain. More preferably, it is 3000 Oe or more.
[0229]
In the conventional magnetic transfer method, transfer to a medium having a very high coercive force was difficult. However, in the present invention, the magnetic layer is heated to sufficiently reduce the coercive force to form a magnetized pattern. Application to a medium is preferred.
[0230]
However, it is preferably 20 kOe or less. If it exceeds 20 kOe, a large external magnetic field is required for collective magnetization, and normal magnetic recording may become difficult. More preferably, it is 15 kOe or less, More preferably, it is 10 kOe or less.
[0231]
The coercivity, local heating temperature, and second external magnetic field strength of the magnetic layer will be described. For example, a medium having a coercivity of 3500 to 4000 Oe at room temperature usually has a coercivity of 10 to 15 Oe / ° C. as the temperature rises. It decreases linearly, for example, about 2000 Oe at 150 ° C. If it is about 3000 Oe, it can be easily generated by an external magnetic field applying means, so that a sufficient magnetization pattern can be formed even by heating at about 150 ° C.
[0232]
Now, the dynamic coercive force of the magnetic layer is large in order to stably hold information recorded at a high density. The dynamic coercive force is usually a coercive force measured when the magnetic field strength is changed in a short time of 1 sec or less, that is, a coercive force with respect to a magnetic field having a pulse width of 1 sec or less. However, the value varies depending on the application time of the magnetic field and heat.
[0233]
Preferably, the dynamic coercive force in 1 sec is twice or more the static coercive force. However, if it is too large, a large magnetic field strength is required for magnetization by the second external magnetic field, so 20 kOe or less is preferable.
[0234]
An example of a procedure for measuring the dynamic coercivity of the magnetic recording medium (coercivity of the magnetic layer as the recording layer) will be described below.
[0235]
1. The coercive force of the medium at the application time t = 10 sec is obtained.
1.1 Apply a magnetic field to the maximum magnetic field strength (20 kOe) to saturate the medium.
1.2 Apply a magnetic field H1 of a predetermined strength in the negative direction (opposite the saturation direction).
1.3 Hold for 10 sec under the magnetic field.
1.4 Return the magnetic field to zero.
When the magnetization value at 1.5 1.4 is read, the residual magnetization value M1 is obtained.
1.6 The same measurement (1.1 to 1.5) is repeated while slightly changing the applied magnetic field strength. Residual magnetization values M1, M2, M3, and M4 are obtained at a total of four magnetic field strengths H1, H2, H3, and H4.
1.7 The applied magnetic field strength H at which the residual magnetization M becomes 0 is obtained from these four points. This is the coercive force of the medium at the application time t = 10 sec.
[0236]
2. The same measurement is performed for the application time t of 60 sec, 100 sec, and 600 sec, and the coercive force at each application time is obtained.
3. By extrapolating from the coercivity values obtained at 10 sec, 60 sec, 100 sec, and 600 sec, the coercivity at a shorter application time can be obtained.
For example, the dynamic coercivity at an application time of 1 nsec is also required.
[0237]
The magnetic layer needs to be magnetized with a weak external magnetic field at an appropriate heating temperature while maintaining magnetization at room temperature. Further, when the difference between the room temperature and the magnetization disappearance temperature is larger, the magnetic domain of the magnetization pattern is more easily formed. For this reason, the magnetization disappearance temperature is preferably higher, preferably 100 ° C. or higher, and more preferably 150 ° C. or higher. For example, there is a magnetization disappearance temperature near the Curie temperature (slightly below the Curie temperature) or near the compensation temperature.
[0238]
The Curie temperature is preferably 100 ° C. or higher. If it is less than 100 degreeC, there exists a tendency for the stability of the magnetic domain at room temperature to be low. More preferably, it is 150 degreeC or more. Moreover, it is preferably 700 ° C. or lower. This is because if the magnetic layer is heated too high, it may be deformed. In the present invention, the Curie temperature of an AFC (Anti-Ferromagnetic coupled) medium refers to the apparent Curie temperature of the entire medium, not the Curie temperature of the main magnetic layer.
[0239]
If the magnetic recording medium is an in-plane magnetic recording medium, saturation recording is difficult with the conventional magnetic transfer method for a magnetic recording medium with high coercive force for high density, and it is difficult to generate a magnetic pattern with high magnetic field strength. Thus, the half-value width also widens. Even with an in-plane recording medium suitable for such a high recording density, a good magnetization pattern can be formed according to this method. In particular, when the saturation magnetization of the magnetic layer is 50 emu / cc or more, the effect of applying the present invention is large because the influence of the demagnetizing field is large.
[0240]
The effect is higher at 100 emu / cc or more. However, if it is too large, it is difficult to form a magnetization pattern, so 500 emu / cc or less is preferable.
When the magnetic recording medium is a perpendicular magnetic recording medium and the magnetization pattern is relatively large and the unit volume of one magnetic domain is large, the saturation magnetization becomes large, and magnetization reversal is likely to occur due to magnetic demagnetization. It worsens the half width. However, in the present invention, it is possible to perform good recording on these media in combination with an underlayer using soft magnetism.
[0241]
These recording layers may be provided in two or more layers in order to increase the recording capacity. At this time, another layer is preferably interposed therebetween.
In the present invention, it is preferable to form a protective layer on the magnetic layer. That is, the outermost surface of the medium is covered with a hard protective layer. The protective layer functions to prevent damage to the magnetic layer due to the head and collision with the mask such as dust and dirt. When a magnetic pattern forming method using a mask is applied as in the present invention, it also serves to protect the medium from contact with the mask.
[0242]
In the present invention, the protective layer also has an effect of preventing oxidation of the heated magnetic layer. The magnetic layer is generally easily oxidized and is further easily oxidized when heated. In the present invention, since the magnetic layer is locally heated with energy rays or the like, it is desirable to previously form a protective layer for preventing oxidation on the magnetic layer.
[0243]
When there are a plurality of magnetic layers, a protective layer may be provided on the magnetic layer close to the outermost surface. The protective layer may be provided directly on the magnetic layer, or a layer having another function may be interposed between the protective layers as necessary.
[0244]
A part of the energy rays is also absorbed by the protective layer and functions to locally heat the magnetic layer by heat conduction. For this reason, if the protective layer is too thick, the magnetization pattern may be blurred due to heat conduction in the lateral direction. Further, the thinner one is preferable in order to reduce the distance between the magnetic layer and the head during recording and reproduction. Therefore, 50 nm or less is preferable, More preferably, it is 30 nm or less, More preferably, it is 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.
[0245]
The protective layer only needs to be hard and resistant to oxidation. Generally, carbon, hydrogenated carbon, nitrogenated carbon, amorphous carbon, SiC and other carbonaceous layers and SiO₂, Zr₂O_ThreeSiN, TiN, etc. are used. The protective layer may be a magnetic material.
[0246]
In particular, in order to make the distance between the head and the magnetic layer as close as possible, it is preferable to provide a very hard protective layer thinly. Accordingly, a carbonaceous protective film is preferable in terms of impact resistance and lubricity, and diamond-like carbon is particularly preferable. Not only does it play a role in preventing damage to the magnetic layer by energy rays, but it is also extremely resistant to damage to the magnetic layer by the head. The magnetization pattern forming method of the present invention can also be applied to an opaque protective layer such as a carbonaceous protective layer.
[0247]
The protective layer may be composed of two or more layers. Providing a layer mainly composed of Cr as a protective layer immediately above the magnetic layer is preferable because it is effective in preventing oxygen permeation into the magnetic layer.
[0248]
Furthermore, it is preferable to form a lubricating layer on the protective layer. It has a function to prevent damage by the mask of the medium and the magnetic head. Examples of the lubricant used for the lubricating layer include a fluorine-based lubricant, a hydrocarbon-based lubricant, and a mixture thereof, and can be applied by a conventional method such as a dip method or a spin coat method. Moreover, you may form into a film by a vapor deposition method. In order not to interfere with the formation of the magnetization pattern, the lubricating layer is preferably thin and is preferably 10 nm or less. More preferably, it is 4 nm or less. In order to obtain sufficient lubrication performance, 0.5 nm or more is preferable. More preferably, it is 1 nm or more.
[0249]
When energy rays are irradiated from above the lubricating layer, recoating or the like may be performed in consideration of damage (decomposition or polymerization) of the lubricant.
Moreover, you may add another layer to the above layer structure as needed.
In order not to impair the running stability of the flying / contact type head, the surface roughness Ra of the medium after forming the magnetization pattern is preferably kept at 3 nm or less. Note that the media surface roughness Ra is the roughness of the media surface that does not include the lubricating layer, using a stylus type surface roughness meter (model name: Tencor P-12 disk profiler (manufactured by KLA Tencor)). It is a value calculated in accordance with JIS B0601 after measurement at a measurement length of 400 μm. More preferably, it is 1.5 nm or less.
[0250]
Desirably, the surface waviness Wa of the medium after forming the magnetic pattern is kept at 5 nm or less. Wa is the undulation of the surface of the medium that does not contain a lubricating layer. After measuring with a stylus type surface roughness meter (model name: Tencor P-12 disk profiler (manufactured by KLA Tencor)) at a measurement length of 2 mm, Ra It is a value calculated according to the calculation. More preferably, it is 3 nm or less.
[0251]
By the way, the formation of the magnetization pattern on the magnetic recording medium configured as described above is performed on the recording layer (magnetic layer). It is preferable to carry out by any of the methods described after forming a protective layer, a lubricating layer, etc. on the recording layer. However, if there is no possibility of oxidation of the recording layer, it may be carried out immediately after the recording layer is formed.
[0252]
Various film forming methods for forming each layer of the magnetic recording medium may be employed. For example, physical vapor deposition methods such as direct current (magnetron) sputtering, high frequency (magnetron) sputtering, ECR sputtering, and vacuum vapor deposition may be used. Can be mentioned.
[0253]
As conditions for film formation, the ultimate vacuum, the substrate heating method and substrate temperature, the sputtering gas pressure, the bias voltage, and the like are appropriately determined according to the characteristics of the medium to be obtained. For example, in sputtering film formation, the ultimate vacuum is usually 5 × 10^-6Below Torr, substrate temperature is room temperature to 400 ° C., sputtering gas pressure is 1 × 10^-3~ 20x10^-3The Torr and bias voltage is preferably 0 to -500V.
[0254]
When the substrate is heated, it may be heated before the underlayer is formed. Alternatively, when using a transparent substrate having a low heat absorption rate, in order to increase the heat absorption rate, the substrate is heated after forming a seed layer containing Cr as a main component or an underlayer having a B2 crystal structure. Thereafter, a recording layer or the like may be formed.
[0255]
When the recording layer is a rare earth magnetic layer, from the standpoint of corrosion and oxidation prevention, the innermost and outermost portions of the disk are first masked to the recording layer, followed by the formation of the protective layer. A method in which the mask is removed and the recording layer is completely covered with a protective layer, or in the case where there are two protective layers, the recording layer and the first protective layer are masked, and the second protective layer is formed. It is preferable to remove the mask when forming the film, and to completely cover the recording layer with the second protective layer, in order to prevent corrosion and oxidation of the rare earth magnetic layer.
[0256]
Next, the magnetic recording apparatus of the present invention will be described.
The magnetic recording apparatus of the present invention includes a magnetic recording medium having a magnetization pattern formed by the above-described method, a drive unit that drives the magnetic recording medium in the recording direction, a magnetic head that includes a recording unit and a reproducing unit, and a magnetic head that is Means for moving relative to the recording medium, and recording / reproduction signal processing means for inputting a recording signal to the magnetic head and outputting a reproduction signal from the magnetic head. As the magnetic head, a floating / contact magnetic head is usually used in order to perform high-density recording.
[0257]
By using a magnetic recording medium on which a magnetic pattern such as a fine and highly accurate servo pattern excellent in signal characteristics is formed by the method of the present invention, the magnetic recording apparatus can perform high-density recording. Further, since the medium is not scratched and has few defects, recording with few errors can be performed.
[0258]
In addition, after the magnetic recording medium is incorporated in the apparatus, the magnetization pattern is reproduced by a magnetic head to obtain a signal, and the servo burst signal is recorded by the magnetic head using the signal as a reference. A precise servo signal can be easily obtained.
[0259]
In addition, after the servo burst signal is recorded by the magnetic head, if the signal recorded as the magnetization pattern according to the present invention remains in the area that is not used as the user data area, the magnetic head is displaced due to some disturbance. Since it is easy to return to a desired position, a magnetic recording apparatus in which signals by both writing methods exist has high reliability.
[0260]
A magnetic disk device, which is a typical magnetic recording device, will be described as an example.
A magnetic disk device usually has 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 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. Moving with flying height. The recording information is converted into a recording signal through a signal processing means and recorded by a magnetic head. The reproduction signal read by the magnetic head is inversely converted through the signal processing means to obtain reproduction information.
[0261]
On the disc, information signals are recorded in units of sectors along concentric tracks. Servo patterns are usually recorded between sectors. The magnetic head reads the servo signal from the pattern, thereby accurately tracking the center of the track and reading the information signal of the sector. Similar tracking is performed during recording.
[0262]
As described above, a servo pattern that generates a servo signal is required to have a particularly high accuracy because of its nature of being used for tracking when recording information. In addition, since the servo patterns that are widely used at present consist of two sets of patterns shifted from each other by 1/2 pitch per track, it is necessary to form each pattern at every 1/2 pitch of the information signal, and double the accuracy. Is required.
[0263]
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 between the center of gravity of the external pin and the actuator, and the accuracy of the servo pattern increases with the increase in track density. However, it is becoming difficult to improve the recording density and reduce the cost of the magnetic recording apparatus.
[0264]
According to the present invention, a highly accurate magnetization pattern can be formed efficiently by using the reduced imaging technique, so that the servo pattern is significantly lower in cost and in a shorter time than the conventional servo pattern formation method. For example, the track density of the medium can be increased to 40 kTPI or more. Therefore, a magnetic recording apparatus using this medium can perform recording at high density.
[0265]
In addition, when the phase servo system is used, a continuously changing servo signal can be obtained, so that the track density can be further increased, tracking at a width of 0.1 μm or less is possible, and higher density recording is possible.
[0266]
As described above, in the phase servo system, for example, a magnetization pattern extending linearly obliquely with respect to the radius from the inner periphery to the outer periphery is used. Such a pattern that is continuous in the radial direction or an oblique pattern is difficult to produce by the conventional servo pattern forming method in which the servo signal is recorded track by track while rotating the disk, and complicated calculation and configuration are required.
[0267]
However, according to the present invention, once a mask corresponding to the shape is formed, the pattern can be easily formed only by irradiating energy rays through the mask. Can be created at a low cost in time. As a result, a phase servo type magnetic recording apparatus capable of high density recording can be provided.
[0268]
The conventional mainstream servo pattern forming method is performed using a dedicated servo writer in a clean room after the medium is incorporated into a magnetic recording device (drive).
[0269]
Each drive is mounted on a servo writer, and a servo writer pin is inserted through a hole on either the front or back of the drive, and the magnetic head is mechanically moved to record one pattern along the track. For this reason, it takes a very long time of about 15 to 20 minutes per drive. Since a dedicated servo writer is used and a hole is made in the drive, it is necessary to perform these operations in a clean room, which is cumbersome in the process and increases costs.
[0270]
In the present invention, a servo pattern or a reference pattern for servo pattern recording can be recorded in a lump 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 in a very simple and short time. it can. In the magnetic recording apparatus incorporating the medium on which the servo pattern is formed in this way, the servo pattern writing step is not necessary.
[0271]
Alternatively, a magnetic recording apparatus incorporating a medium on which a servo pattern recording reference pattern is formed can write a desired servo pattern in the apparatus based on the reference pattern, and the above servo writer is unnecessary, There is no need to work in a clean room.
Further, it is not necessary to make a hole on the back side of the magnetic recording apparatus, which is preferable in terms of durability and safety.
[0272]
Furthermore, in the present invention, since the mask and the medium do not need to be in close contact with each other, damage due to contact between the magnetic recording medium and other components, or damage to the medium due to pinching of fine dust or dirt is prevented. Can be prevented.
As described above, according to the present invention, a magnetic recording apparatus capable of high-density recording can be obtained at a low cost by a simple process.
[0273]
As the magnetic head, various types 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 an MR head, a sufficient signal intensity can be obtained even at a high recording density, and a magnetic recording apparatus with a higher recording density can be realized.
[0274]
Further, when the magnetic head is floated at a low 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 highly reliable magnetic recording is obtained. An apparatus can be provided.
[0275]
Further, the recording density can be further improved by combining the signal processing circuit based on the maximum likelihood decoding method. For example, when recording / reproducing at a recording density of 13 GTPI or more, linear recording density of 250 kFCI or more, and recording density of 3 Gbits per square inch or more. Sufficient S / N can be obtained.
[0276]
Furthermore, the reproducing part of the magnetic head has a plurality of conductive magnetic layers that cause a large change in resistance due to relative changes in the magnetization directions of each other by an external magnetic field, and a conductive non-conductive layer disposed between the conductive magnetic layers. By using a GMR head composed of a magnetic layer or a GMR head using the spin valve effect, the signal intensity can be further increased, and reliability with a linear recording density of 10 Gbits per square inch or more and 350 kFCI or more. High magnetic recording apparatus can be realized.
[0277]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these Examples.
[0278]
[I] Comparison of protrusion positions on mask
First, in the following Examples 1 to 4 and Comparative Example 1, the effects due to the difference in the formation positions of the protrusions on the mask surface were compared.
[0279]
Example 1
[Manufacture of masks]
A disc-shaped quartz glass having a diameter of 120 mm and a thickness of 2.3 mm was used as a substrate, and Si was deposited on this one surface (the surface that would be in contact with the magnetic recording medium when forming the magnetic pattern) to a thickness of 100 nm ( Gas used: Ar, gas pressure: 0.6 Pa, power: 500 W, time: 53 seconds). On the formed Si layer, a photoresist (MCPR-2200X) was further applied by spin coating so as to have a thickness of 200 nm. The formed photoresist layer was exposed by irradiating with a Kr laser (wavelength 413 nm) through a mask of the same type as the mask pattern to be formed, and then developed to form a photoresist pattern from which the mask pattern was based. . Reactive ion etching (RIE) is performed using this photoresist pattern as a mask (gas used: SF₆, Flow rate: 130 seconds, power: 50 W, time: 62 seconds), the mask pattern was formed by removing the Si layer. The remaining photoresist was removed by immersing in Nagase resist strip solution N303C, and then washed and dried. Furthermore, SiO₂Was formed to a thickness of 30 mm (gas used: Ar / O₂= 7/3, gas pressure: 0.6 Pa, power: 500 W, time: 73 seconds), a mask was manufactured.
[0280]
[Formation of protrusions (spacers)]
About the mask manufactured in the above procedure, a photoresist (MCPR-2200X) was applied to the side where the mask pattern was formed so as to have a thickness of 200 nm by spin coating. The formed photoresist layer was broad-exposure with mercury xenon lamp light through a projection forming mask described later, and then developed to form a photoresist pattern as a source of the projection to be formed. Using this photoresist pattern as a mask, a Cr film was formed under the conditions shown in Table 1 below, and then immersed in acetone to remove unnecessary photoresist and Cr, followed by washing and drying, whereby a spacer made of Cr. A protrusion was formed.
[0281]
As the protrusion forming mask, a mask in which protrusions were formed in alignment on the outer diameter side and the inner diameter side of the mask pattern region of the mask was used. This projection forming mask has a square of 127 mm on a side and a plate-shaped quartz glass of 2.3 mm in thickness as a base material, and a chromium / chromium oxide film having a thickness of 110 nm is laminated on the surface thereof. A protrusion pattern is formed by removing the chromium / chromium oxide multilayer film corresponding to the shape by etching. The planar shape of the pattern of each protrusion was a circle having a diameter of 100 μm. The pattern of the protrusions on the outer diameter side is arranged in an area corresponding to the radius of the mask of 47.0 mm to 47.1 mm so as to form a row in the radial direction at intervals of about 100 μm in the circumferential direction of the mask. . The pattern of the protrusions on the inner diameter side was arranged in an area corresponding to a mask radius of 13.0 mm to 15.3 mm so as to form 12 rows in the radial direction at intervals of about 100 μm in the circumferential direction of the mask.
[0282]
The heights of the protrusions on the outer diameter side and inner diameter side of the mask pattern region formed using this protrusion forming mask were as shown in Table 1 below.
[0283]
Example 2
The mask was manufactured and the protrusions were formed under the same conditions as in Example 1 except that the Cr film formation conditions at the time of protrusion formation and the heights of the protrusions on the outer diameter side and the inner diameter side were set as shown in Table 1 below. Formation was performed.
[0284]
Examples 3 and 4
Production of the mask and projections under the same conditions as in Example 1 except that the projection forming mask described below was used and the Cr film formation conditions at the time of projection formation were changed to the conditions shown in Table 1 below. Was formed.
[0285]
As the protrusion forming mask, a mask in which protrusions are aligned and formed inside the mask pattern area in addition to the outer diameter side and the inner diameter side of the mask pattern area of the mask was used. The material and thickness of the base material and the chromium / chromium oxide multilayer film are the same as those used in Example 1. Further, the planar shape of the pattern of the individual protrusions and the arrangement of the patterns of the protrusions on the outer diameter side and the inner diameter side were the same as those used in Example 1. The pattern of protrusions in the mask pattern area is arranged in an area corresponding to a mask radius of 33.0 mm to 33.3 mm so as to be arranged in two rows in the radial direction at intervals of about 100 μm in the circumferential direction of the mask. did. The heights of the outer diameter side and inner diameter side protrusions were as shown in Table 1 below.
[0286]
The heights of the protrusions on the outer diameter side of the mask pattern region, the mask pattern region inside (intermediate portion), and the inner diameter side of the mask pattern region formed using this protrusion forming mask are shown in Table 1 below. It was street.
[0287]
Comparative example 1
The mask was manufactured and the protrusions were formed under the same conditions as in Example 1, except that the Cr film formation conditions and the protrusion heights were set as shown in Table 1 below.
[0288]
As the protrusion forming mask, a mask in which protrusions were formed in alignment on the outer diameter side and the inner diameter side of the mask pattern region of the mask was used. The material and thickness of the base material and the chromium / chromium oxide multilayer film are the same as those used in Example 1. The planar shape of the pattern of each protrusion and the arrangement of the protrusion pattern on the inner diameter side were the same as those used in Example 1. The pattern of protrusions on the outer diameter side was arranged in an area corresponding to a radius of 47.0 mm to 47.7 mm of the mask so as to be arranged in four rows in the radial direction at intervals of about 100 μm in the circumferential direction of the mask. .
[0289]
・ Evaluation
For the masks of Examples 1 to 4 and Comparative Example 1, the oxygen content of the protrusions and Knoop hardness were measured. Further, as the durability test, the adsorption and desorption with respect to the magnetic recording medium were repeated in the same manner as when the actual magnetization pattern was formed, and the durability was evaluated by observing the shape of the protrusion at a predetermined time point.
[0290]
[Measurement method of oxygen content and Knoop hardness]
The oxygen content of the protrusions was measured using Auger electron spectroscopy (AES). First, a sample was introduced into the ultra-high vacuum environment of the apparatus, and the surface contamination layer and the natural oxide film were removed by Ar ion sputtering. Subsequently, an AES spectrum is measured for the inside of the exposed Cr protrusion by Ar ion sputtering. Obtained Cr-LM_2,3M_4,5Opi KL_2,3L_2,3The oxygen intensity was incorporated into the Cr spacer to evaluate the oxygen / chromium atomic ratio by multiplying the appropriate peak intensity by an appropriate sensitivity correction coefficient.
[0291]
Further, the Knoop hardness of the protrusion was measured using a light weight micro hardness tester “MVK-1S” manufactured by Akashi Seisakusho. A diamond indenter was pressed against the sample placed on the sample stage with a weight of 5 gf to make a depression. The area of the resulting depression was measured, and the value obtained by dividing the pressing load by the depression area was recorded as Knoop hardness.
The measured oxygen content and Knoop hardness of the protrusions are shown in Table 1 below.
[0292]
[Durability test]
The durability test was performed using a durability tester manufactured by Mitsubishi Chemical. The mask and the magnetic recording medium were made to face each other, and adsorption and desorption were repeated using negative pressure and pressure air from a vacuum pump. The repetition of the adsorption / desorption was carried out with one cycle consisting of adsorption: 0.5 second, adsorption retention: 0.1 second, desorption: 0.1 second, and switching: 0.1 second for a total of 0.8 seconds. The degree of vacuum during adsorption was -70 kPa.
[0293]
A magnetic recording medium having an outer diameter of 95.0 mm (= radius of 47.5 mm) and a thickness of 1.28 mm was used. A chamfer (chamfer) portion exists in a strip shape along the outermost periphery, the width is 0.25 mm from the outermost periphery, and the angle of the chamfer is 45 degrees. In other words, a chamfer portion exists in a region outside the radius 47.5−0.25 = 47.25 mm. Accordingly, only the protrusions present on the outer diameter side of the mask of Comparative Example 1 come into contact with the chamfered portion of this magnetic recording medium.
[0294]
The mask was taken out after the specified number of adsorptions / desorptions, and the protrusions were observed with an optical microscope. Based on the cumulative number K of repeated adsorption / desorption cycles, the designated gyrus was defined as 1st time: 1K, 2nd time: 10K, 3rd time: 100K, 4th time: 200K, 5th time: 300K.
[0295]
[Durability evaluation]
Durability was evaluated based on whether or not protrusions or scratches were observed by observation with an optical microscope. When the protrusions are peeled off, the gap between the mask and the magnetic recording medium when adsorbed becomes non-uniform, and the adsorption is not performed uniformly (when the vacuum is adsorbed, air escapes between the mask and the magnetic recording medium) Does not become uniform and takes time to adsorb uniformly). Also, if there is a scratch on the protrusion, a part of the protrusion is missing from the scratch, and the fragment of the missing protrusion enters the gap between the mask and the magnetic recording medium, damaging the magnetic recording medium, This is because there is a possibility that the intervals of the above may become non-uniform.
The results of evaluation are shown in Table 1 below.
[0296]
[Table 1]

[0297]
In the masks of Examples 1 to 4 where the protrusions were not in contact with the chamfer part, no problem occurred in the protrusions even when the durability test was performed 300 k times.
[0298]
On the other hand, the mask of Comparative Example 1 in which the protrusions were in contact with the chamfer portion had linear scratches on the outer diameter side protrusions against which the chamfer hit when the durability test was performed 100 k times. Cr powder was generated from the scratch.
[0299]
Based on the above results, the mask with protrusions that do not contact the chamfer part of the magnetic recording medium is less prone to wear, damage, or drop off due to the use of the mask than the mask that is in contact with the chamfer part. I understand that there are few.
[0300]
In addition to the outer diameter side and the inner diameter side of the mask pattern area, the masks of Examples 3 and 4 in which the protrusions exist in the mask pattern area are spaced from the magnetic recording area when they are brought into contact with the magnetic recording medium. Was observed with interference fringes.
[0301]
In the mask of Example 3, since clean concentric interference fringes were observed, the uniformity of the distance between the mask and the magnetic recording area was good (the distance was the same on the same circumference, gradually from the inner circumference to the outer circumference). It has been judged that it has spread). Further, since the interference fringes were hardly observed in the mask of Example 4, it was determined that the distance between the mask and the magnetic recording region was uniform over the entire surface.
[0302]
[II] Comparison of projection material
Then, the effect by the difference in the raw material of the protrusion formed in the mask surface was compared by the following Examples 5 and 6 and Comparative Example 2.
[0303]
Examples 5 and 6
The mask was manufactured and the protrusions were formed under the same conditions as in Example 1 except that the Cr film formation conditions for forming the protrusions were the conditions shown in Table 2 below.
[0304]
Comparative example 2
After the mask was manufactured under the same conditions as in Example 1, protrusions were formed according to the following procedure.
[0305]
On the side where the mask pattern is formed, a polyimide resin (PIX-1400) was formed to a thickness of 3 μm by spin coating. A photoresist (MCPR-2200X) was further applied on the formed polyimide resin layer by spin coating so as to have a thickness of 200 nm. The formed photoresist layer was exposed to mercury xenon lamp light through a projection forming mask similar to that used in Example 1, and then developed and etched, and further at 350 ° C. for 45 minutes. Paking was performed to form spacer protrusions made of polyimide resin.
[0306]
・ Evaluation
For the masks of Examples 5 and 6 and Comparative Example 2, the oxygen content of the protrusions and Knoop hardness were measured by the same method as in Example 1. Further, as a durability test, the same method as in Example 1 was repeated, and the adsorption and desorption with the magnetic recording medium were repeated in the same manner as when the actual magnetization pattern was formed, and the shape of the protrusions at a predetermined point in time was observed. Sexuality evaluation was performed.
The results of evaluation are shown in Table 2 below.
[0307]
[Table 2]

[0308]
In the mask of Example 5 in which the protrusion was formed of chrome, a protrusion that partially collapsed occurred when the durability test was performed 200 k times. Cr powder was generated from the collapsed portion. Similarly, in the mask of Example 6 in which the protrusion was formed of chromium, a part of the protrusion was peeled off when the durability test was performed 10 k times. The reason why the results that were not so excellent as compared with the previous Examples 1 to 4 is considered to be due to the oxygen content of the protrusions.
[0309]
On the other hand, in the mask of Comparative Example 2 in which the protrusion was formed of polyimide instead of chrome, a part of the protrusion was peeled off when the durability test was performed 1 k times.
[0310]
From the above results, it can be seen that the masks with protrusions made of chrome have less wear, damage, dropout, etc. due to the use of the mask than masks with protrusions made of other materials (polyimide). .
[0311]
【The invention's effect】
According to the present invention, the projections for keeping the gap between the magnetic recording medium and the mask uniform are configured not to contact the chamfered portion of the magnetic recording medium, and these projections are formed of chromium. In addition, the wear, damage, dropout, etc. of the protrusions associated with the use of the mask are small, and the magnetic recording medium is not damaged by the protrusions and can be used stably over a long period.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view for explaining a method of forming a magnetization pattern using a mask according to an embodiment of the present invention.
FIG. 2 is a schematic diagram for explaining a conventional magnetization pattern forming method.
FIGS. 3A to 3D are schematic views showing discontinuous protrusion formation patterns in the mask according to the present invention.
[Explanation of symbols]
1 Magnetic recording medium (magnetic disk)
2 mask
3 Transparent substrate (quartz)
4 Chrome layer
5 Chromium oxide layer
6 External magnetic field
10 Chamfered part (Chamfer part)
11 Incident light (laser beam)
12 Reflected light
13 Re-reflected light
21 Protrusion

Claims (6)

In contrast to a magnetic recording medium having a magnetic layer on a substrate and having a chamfered portion formed as an inclined portion in an area along the outermost peripheral edge outside the storage area , the magnetic layer of the magnetic recording medium When a magnetic pattern is formed on the magnetic layer by irradiating with energy rays and heating and forming a magnetization pattern on the magnetic layer, a mask for causing local shading in the irradiation intensity of the energy rays is interposed in the irradiation route of the energy rays. By the magnetic pattern formation method of the magnetic recording medium for forming the shape of the magnetization pattern,
The mask has a projection provided on at least a part of the mask in contact with at least a part other than the chamfered part of the magnetic recording medium, and
It is characterized by irradiating energy rays without touching the chamfered part,
A method for forming a magnetization pattern of a magnetic recording medium. The method for forming a magnetic pattern according to claim 1 , wherein the protrusion is made of chromium. The method for forming a magnetic pattern according to claim 2, wherein the oxygen content of the protrusions is 0.1 or more and 1.0 or less in terms of atomic ratio to chromium. The Knoop hardness of the projections 100 kgf / mm ² or more, and characterized in that 400 kgf / mm ² or less, a magnetic pattern forming method according to any one of claims 1 to 3. The magnetic pattern forming method according to claim 1 , wherein the protrusion is provided in a peripheral region of the mask pattern region. The method of forming a magnetic pattern according to claim 1 , wherein the protrusion is provided inside the mask pattern region.

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