JP2008282537A - Method and apparatus for manufacturing magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for manufacturing a magnetic recording medium that eliminate the phenomenon, where a lubricant adhered to an end face of the magnetic recording medium (magnetic disk) results in spreading inside its media plane. <P>SOLUTION: The lubricant adhered to the end face that is to be spread in the media plane of the magnetic recording medium is wiped off. Specifically, while the magnetic disk (11), after a liquid lubricant layer is applied, is rotated; a solvent with a function of dissolving the liquid lubricant is sprayed (15) to a wiping tape (13) in a manner of spraying, the wiping tape is fed for each process; feeding of the wiping tape is stopped during the process, the wiping tape which is wet, by including the solvent is pressed against the magnetic disk by a pad (14); and then the liquid lubricant layer applied on the end face of the magnetic disk is wiped off using the wiping tape. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for manufacturing a magnetic recording medium used in an information storage device of an information processing device such as a computer and a storage device (particularly a hard disk device) mounted on a consumer device.

  In recent years, with the increase in the amount of information handled by information processing devices such as computers and the miniaturization of devices, the storage capacity of information storage devices has been increased, and magnetic recording media (hereinafter simply referred to as magnetic disks) used in information storage devices have been increased. The recording capacity is constantly increasing. Further, the rotational speed of the magnetic disk has been increased for the purpose of improving the data transfer speed along with the increase in the storage capacity, and recently, there is a model of 15,000 rpm.

  The problem of increasing the rotation is the natural vibration of the substrate due to rotation. The vibration caused by the rotation prevents stable flying of the magnetic head, and the reliability is significantly reduced. As one of these measures, recently, a glass substrate having high rigidity is used for high-rotation models. However, the current glass substrate is expensive and leads to an increase in the cost of the HDD device (hard disk device), so it is necessary to realize high rotation with a relatively inexpensive aluminum substrate.

  Therefore, in order to increase the rigidity of recent aluminum substrates, the plate thickness is increased from 0.8 mm to 1.0 mm, and further to 1.27 mm, so that the natural vibration is suppressed within an allowable range. Yes. Recently, even thick plates of 1.6 mm have been considered.

  These magnetic disks are usually formed by sequentially forming a magnetic layer and a protective layer on a nonmagnetic metal underlayer laminated on an aluminum substrate by a method such as sputtering or CVD (chemical vapor deposition). Lubricant is applied. In this lubricant application method, a liquid lubricant stock solution is diluted with a solvent (for example, a fluorocarbon-based organic solvent) to an appropriate concentration in accordance with a desired film thickness because of mass productivity and ease of equipment. After immersing the medium for a certain period of time, this medium is pulled up at a constant speed (dipping method) to evaporate the solvent and at the same time adsorb the lubricant component remaining on the medium onto the protective layer, thereby protecting it. A method of forming a thinned lubricating layer on the layer is often used. Other methods include spin coating and spraying.

JP 2003-6849 A Japanese Examined Patent Publication No. 7-58545

  However, in the process of pulling up the magnetic disk at the time of applying the lubricant, a large amount of lubricant is accumulated especially on the end face in the up-and-down direction, and the phenomenon that the lubricant diffuses to the outer peripheral portion in the plane with time. It turned out to happen. An arrow A shown in FIG. 6 is the magnetic disk pulling direction, and a dark colored portion in the surface of the magnetic disk indicates a lubricant diffusion portion.

  This type of lubricant diffusion phenomenon is especially the case where the thicker the magnetic disk is, the greater the amount of lubrication that adheres to the end face in proportion to the area. The amount also increases. The magnetic head floats on the outer periphery of the disk where the lubricant is diffused, so that the lubricant is easily transferred to the head slider. As a result, the head flying becomes unstable, and the electromagnetic conversion characteristics and the head It adversely affects seek durability. Although the current head flying height is about 10 nm, it is planned that the head flying height will be further lowered in the perpendicular magnetic recording system expected to be put to practical use in the future, and these problems of lubricant diffusion may be further exposed. Scheduled.

  In the past, the amount of lubricant adhering to the end face was not subject to control, the plate thickness of the medium was as thin as 0.8 mm or less, and the head flying height was about 15-20 nm, which is higher than current levels. Due to the relatively high cost, this type of lubricant diffusion problem did not surface.

  Currently, the diffusion of lubricant is dealt with by optimizing the concentration of the lubricant, selecting the dilution solvent to be used, and optimizing the pulling speed, but it is possible to completely prevent the diffusion of the lubricant. The current situation is not possible.

  On the other hand, Patent Document 1 and Patent Document 2 disclose proposals for making the distribution of the lubricant uniform by pressing a wiper or buff against the surface to which the lubricant is applied. In both cases, the portion subjected to wiping and buffing is limited to the in-plane of the magnetic recording medium (that is, the head floating area and recording area), and the friction characteristics such as CSS (contact start / stop) characteristics are improved. It is merely intended to prevent the head from being adsorbed, and does not serve as a solution to the problem that the lubricant adhering to the end surface of the medium as described above diffuses into the medium surface over time.

  The present invention has been made in view of the above-described problems, and its object is to wipe the lubricant adhering to the end surface of the magnetic recording medium that is expected to diffuse into the surface with a wiper dipped in a solvent. Thus, an object of the present invention is to provide a method and apparatus for manufacturing a magnetic recording medium that solves the problem that the lubricant adhering to the end face of the magnetic recording medium diffuses in the plane.

  In order to achieve the above object, the present invention of claim 1 is a method of manufacturing a magnetic recording medium formed by forming a protective layer on a magnetic layer and applying a liquid lubricant layer on the protective layer. Then, after the liquid lubricating layer is applied, a wiping tape containing a solvent having a function of dissolving the liquid lubrication while rotating the magnetic recording medium is pressed against the end face of the magnetic recording medium at a constant pressing surface pressure. The liquid lubricant layer applied to the end surface of the magnetic recording medium is wiped with the wiping tape by being pressed.

  Here, the solvent may be sprayed onto the wiping tape on the feeding side of the wiping tape.

  Further, the end face refers to a side face portion including a chamfer portion of a disc-shaped magnetic recording medium having a thickness, and at least does not include a magnetic head flying region.

  In order to achieve the above object, a fourth aspect of the present invention is an apparatus for manufacturing a magnetic recording medium formed by forming a protective layer on a magnetic layer and applying a liquid lubricant layer on the protective layer. Then, after the liquid lubricating layer is applied, a wiping tape containing a solvent having a function of dissolving the liquid lubrication while rotating the magnetic recording medium is pressed against the end face of the magnetic recording medium at a constant pressing surface pressure. It has means for pressing and wiping the liquid lubricating layer applied to the end face of the magnetic recording medium with the wiping tape.

  Here, the solvent may be sprayed onto the wiping tape on the feeding side of the wiping tape.

  In the present invention, as described above, the reason why the treated portion is limited to the end face is that wet wipe removes the lubricant, and thus all of them are common to deteriorate the lubricity of the processed surface. Assuming that this is the head flying area, even if the current head flying height is about 10 nm, intermittent contact between the medium and the head is assumed depending on the poor environment such as gas generation or dust in the hard disk drive device. This is because, since it may cause a crash, the lubricating component needs to be left as it is to prevent this.

  With the above configuration, according to the present invention, in the magnetic disk having the liquid lubricant layer, the lubricant adhering to the end surface of the magnetic disk is wiped with a wiping tape containing a solvent having a function of dissolving the lubricant. As a result, the lubricant can be properly and sufficiently wiped off, whereby the diffusion of the lubricant into the surface of the magnetic disk can be prevented and the reliability can be improved. In addition, by spraying the solvent with a spray method, the solvent can be easily and uniformly contained in the wiping tape by the required amount, so that the wiping tape containing excess solvent or non-uniform solvent was contained. An advantage of preventing inconvenience due to the use of the wiping tape can be obtained.

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

(Manufacturing method and equipment configuration)
FIG. 1 shows a schematic configuration of a manufacturing apparatus that performs wet wiping processing and ultraviolet irradiation processing on an end surface of a magnetic recording medium in an embodiment of the present invention. In FIG. 1, 11 is a magnetic recording medium after the lubricant is applied, and R is the rotation direction of the workpiece. 12 is an end wet wipe unit, 13 is a wiping tape, 14 is a pad, 15 is a solvent spray, and 16 is a solvent tank for supplying the solvent to 15. Reference numeral 17 denotes an end face UV (ultraviolet) irradiation unit, 18 denotes a UV lamp, 19 denotes a shielding plate, and 20 denotes a slit (elongated hole). Here, for convenience of explanation, the wet wiping unit 12 and the ultraviolet irradiation unit 17 are drawn together on the same screen, but it goes without saying that they may be separate and independent devices.

  When processing using the end face wet wipe unit 12, the solvent is sprayed on the feeding side of the wiping tape 13 while rotating the magnetic recording medium 11 coated with the liquid lubricant layer in a certain R direction. Is sprayed 15 and the tape 13 is fed for each processing, and the feeding of the tape 13 is stopped during the processing. Then, a wet wiping tape 13 containing a solvent in the solvent spray 15 is pressed with a constant pressing surface pressure by pressing the pad 14, and a liquid lubricating layer applied to the end surface of the magnetic recording medium 11 is formed. Wipe with wiping tape 13. An arrow shown near the wiping tape 13 indicates a direction in which the wiping tape 13 is wound and travels.

  On the other hand, when processing using the end face UV irradiation unit 17, the magnetic recording medium 11 after the liquid lubricant layer is applied is opened from the UV lamp 18 to the shielding plate 19 while rotating in the R direction of a certain direction. The end face of the magnetic recording medium 11 is irradiated with ultraviolet rays through the slit 20, and the lubricant component of the liquid lubricant layer applied to the end face of the magnetic recording medium is solidified. The size of the slit 20 is, for example, 2 mm wide × 5 mm long.

(Medium structure)
FIG. 2 shows an example of a sectional structure of a magnetic recording medium (magnetic disk) to be processed by the apparatus of FIG. In this magnetic recording medium, a nonmagnetic metal underlayer 22 is formed on an aluminum substrate (plate thickness 1.27 mm) 21, and a magnetic layer 23 and a protective layer 24 are sequentially formed thereon by a sputtering method, a CVD method, or the like. After film formation, the liquid lubricating layer 25 is applied by the dipping method described in the prior art, for example. 21 can also be applied to other non-magnetic substrates such as plastic substrates.

(Processing area)
FIG. 3 shows the maximum area of the end face contemplated by the present invention. 31 is a side surface of the medium, 32 is a chamfer portion, 33 is a head floating region, and 34 is a maximum region of an end surface intended by the present invention. The end face in the present invention refers to the entire side surface portion including the chamfer portion 32 of the disc-shaped magnetic recording medium 11 having a thickness as indicated by reference numeral 34, and does not include at least the magnetic head flying region 33.

(Example of experiment)
Using a magnetic disk as shown in FIG.
(A) What was not processed after lubricant application,
(B) A device obtained by wiping the end surface with a dry wiper using a device obtained by removing the solvent spray 10 from the end surface wet wipe unit 12 of the apparatus shown in FIG.
(C) Using the end face wet wipe unit 12 of the apparatus shown in FIG. 1, the end face was wiped with a wet wiper soaked in a solvent by spraying,
(D) Using the end face UV irradiation unit 17 of the apparatus shown in FIG. 1, a total of four types were produced by irradiating the end face of the magnetic disk with ultraviolet rays, and left at room temperature and humidity for 1 week. The state was observed with OSA (Optical Surface Analyzer) as described later.

  The wiper (also referred to as wiper tape or wiping tape) used in the processing processes (B) and (C) is TORAYSEE (registered trademark) 53203TR (product name) manufactured by Toray Industries, Inc. The solvent used is Vertrel (registered trademark) XF (product name) manufactured by DuPont. The solvent used is not particularly limited as long as it has a function of dissolving the lubricant, but is preferably the same as that used when the lubricant is applied to the magnetic disk. Furthermore, it is desirable that the wiper to be used is resistant to the solvent used in the processing (C).

As the end wiper device, the one manufactured by the applicant for in-house use as shown in FIG. 1 was used. The solvent is sprayed 15 on the feed side of the wiping tape 13 by spraying, and the tape 13 is fed every time processing is performed, and the tape 13 is stopped during processing. The wet tape 13 is pressed by a pad 14 having a hardness of 60 °. Here, if the pad 14 having an extremely low hardness is used, the outer periphery of the disk 11 may bite into the pad 14, and the head floating area 33 (see FIG. 3) in the outermost peripheral surface may be processed. Not desirable. The disk rotation speed during processing is 200 rpm, the pressing pressure is 0.5 kg / cm ² , and the processing time is 10 seconds.

The UV lamp 18 used in the processing of (D) is a combined light with wavelengths of 185 nm and 254 nm, the shortest distance from the substrate end surface of the magnetic disk 11 is set to 10 mm, and the intensity is 10 mW / cm ^{2 to} 15 mW / The treatment was performed for 10 seconds in the amount of cm ² (W is Watt). At this time, the disk 11 is rotated, and in order to selectively irradiate only the end face, the UV lamp 18 is covered with a shielding plate 19, and a slit 20 having a width of 2 mm × 5 mm is opened in a part of the shielding plate 10, By making this opening portion approach the end surface of the disk 11 most, ultraviolet rays (UV) were irradiated only to the end surface of the magnetic disk.

(results of the experiment)
As described above, a total of four types (A) to (D) described above were prepared and allowed to stand at room temperature and humidity for 1 week, and then the state of each magnetic disk surface was observed with OSA. The OSA used was OSA5100 (product name) from Candela (Candela Corporation). OSA is a laser beam of P-polarized wave (longitudinal wave) or S-polarized wave (transverse wave) that is irradiated obliquely with respect to the medium surface and detects the phase difference of the reflected light to detect the phase difference of the reflected light (for example, a magnetic layer or This is a device for quantifying the state of carbon layer) substances (carbon, lubricant, and other contaminants). This time, in order to observe the state of the lubricant in detail, the change in the phase difference between the P-polarized wave and the S-polarized wave, called the Q-polarized wave, which is more sensitive than the single P / S wave Phase difference).

  FIG. 4 is a schematic diagram of an OSA image showing the state of the surface of the magnetic disk obtained by the OSA, and the diagrams (A) to (D) in FIG. 4 correspond to the processes (A) to (D), respectively. It corresponds. The original document in FIG. 4 is a color photograph. However, if it is converted into a halftone black and white display as it is with a copying machine or the like, it becomes difficult to understand. As shown, the contrast is emphasized.

  As can be seen from FIG. 4, it can be confirmed that the wet wiper treatment of FIG. 4C and the end face ultraviolet irradiation treatment of FIG. It was. The dry wipe treatment (B) had no effect.

  The OSA determination method confirms the effect when there is no dark (dark) part of the image when the contrast range of the lubricant film thickness is adjusted to about 5 mm in image processing. This dark (dark) portion of the color indicates an increased portion of the lubricant film thickness (diffused portion from the end face).

  FIG. 5 shows the result of measuring the film thickness of the lubricant with FTIR (Fourier Transform Infrared Spectrometer) in this dark (dark) portion as shown in FIGS. 4 (A) and 4 (B). The horizontal axis in FIG. 5 indicates the angular position from the reference position on the magnetic disk surface, and the vertical axis indicates the film thickness of the lubricant. In FIG. 5, the portion where the film thickness is thicker than the peripheral portion (for example, the portion near the angle of 15 degrees and the portion near the angle of 180 degrees of the sample 1) is a portion that is displayed darker (darker) on the image by OSA. It is confirmed by the FTIR film thickness measurement that the lubricant film thickness is about 5 mm thicker than the other portions in the OSA film thickness measurement at the dark (dark) image on OSA. However, since FTIR takes time to measure, it is usually determined by an OSA image.

(Other embodiments)
The preferred embodiments and experimental examples of the present invention have been described above. However, the present invention is not limited to this, and within the scope of the claims, changes in numerical values, similar methods and materials can be used. Modifications such as substitution with a thing and combination with a well-known technique are included in the embodiments of the present invention. For example, a combination of an end face wet wipe process and an end face UV irradiation process according to the present invention is also included in the embodiment of the present invention.

It is a conceptual diagram which shows schematic structure of the manufacturing apparatus which performs a wet wipe process to the end surface of a magnetic recording medium in one Embodiment of this invention. It is sectional drawing which shows typically the example of a cross-section of the magnetic recording medium (magnetic disc) processed by one Embodiment of this invention. It is a schematic diagram which shows typically the maximum area | region of the end surface which this invention intends. It is the schematic diagram of the OSA image which shows the mode of the surface of the magnetic disk obtained by OSA (optical surface analyzer), (A) is what was not processed after lubricant application like the past, (B) As a comparative example, the end surface was wiped with a dry wiper, (C) the end surface was wiped with a wet wiper soaked with a solvent by spraying according to the present invention, and (D) the magnetic according to the present invention. It is a figure which each shows what irradiated the ultraviolet-ray to the disc end surface. It is a characteristic view showing a FTIR (Fourier Transform Infrared Spectrometer) film thickness measurement result showing that the lubricant diffusion portion in the surface of the magnetic disk is about 5 mm thicker than other portions. It is a top view which shows the lubricant diffusion part in the magnetic disk surface by a conventional technique.

Explanation of symbols

11 Magnetic recording medium after lubricant application
12 Wet end wipe unit
13 Wiping tape
14 Pad 15 Solvent spray 16 Solvent tank
17 End UV (ultraviolet) irradiation unit
18 UV lamp
19 Shield version
20 Slit (Elongated hole)
DESCRIPTION OF SYMBOLS 21 Aluminum substrate 22 Nonmagnetic metal base layer 23 Magnetic layer 24 Protective layer 25 Liquid lubrication layer 31 Side surface of medium 32 Chamfer part 33 Head floating area 34 Maximum area of end face intended by the present invention

Claims (6)

A method of manufacturing a magnetic recording medium formed by forming a protective layer on a magnetic layer and applying a liquid lubricant layer on the protective layer,
After the liquid lubricant layer is applied, a wiping tape containing a solvent having a function of dissolving the liquid lubricant is pressed against the end surface of the magnetic recording medium with a constant pressing surface pressure while rotating the magnetic recording medium. A method for producing a magnetic recording medium, comprising: wiping the liquid lubricant layer applied to the end face of the magnetic recording medium with the wiping tape.   The method of manufacturing a magnetic recording medium according to claim 1, wherein the solvent is sprayed onto the wiping tape on a feeding side of the wiping tape.   3. The magnetic recording medium according to claim 1, wherein the end surface refers to a side surface portion including a chamfer portion of a disk-shaped magnetic recording medium having a thickness, and does not include at least a magnetic head floating region. Manufacturing method. A magnetic recording medium manufacturing apparatus formed by forming a protective layer on a magnetic layer and applying a liquid lubricant layer on the protective layer,
After the liquid lubricant layer is applied, a wiping tape containing a solvent having a function of dissolving the liquid lubricant is pressed against the end surface of the magnetic recording medium with a constant pressing surface pressure while rotating the magnetic recording medium. And a means for wiping the liquid lubricant layer applied to the end face of the magnetic recording medium with the wiping tape.   5. The apparatus for manufacturing a magnetic recording medium according to claim 4, further comprising means for spraying the solvent onto the wiping tape on a feeding side of the wiping tape.   6. The magnetic recording medium according to claim 4, wherein the end surface refers to a side surface portion including a chamfer portion of a disk-shaped magnetic recording medium having a thickness, and does not include at least a magnetic head floating region. Manufacturing equipment.

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