JP2010086591A - Method for manufacturing magnetic disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a magnetic disk, by which reliability of the magnetic disk is evaluated so as to pass an endurance test of loading and unloading. <P>SOLUTION: A magnetic head is brought into contact with a surface of the magnetic disk by gradually reducing air pressure of surroundings of measurement while rotating the magnetic disk, subsequently the air pressure of the surroundings of measurement is gradually increased and pressure when the magnetic head floats from the magnetic disk surface is measured, and then, under air pressure equal to or lower than the measured pressure, the air pressure of the surroundings of measurement is rapidly increased so as to detach the magnetic head from the magnetic disk surface and an amount of a lubricant attached to a slider surface of the magnetic head at this moment is determined. Thereby the result of determination and that of the endurance test of loading and unloading are correlated, and a highly reliable magnetic disk passing the endurance test of loading and unloading is obtained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a magnetic disk used as an information recording medium of a hard disk drive (HDD) mounted on a computer or the like.

  Various information recording techniques have been developed with the recent increase in information processing capacity. In particular, the surface recording density of HDDs using magnetic recording technology continues to increase at an annual rate of about 100%. Recently, an information recording capacity exceeding 250 GB has been demanded for a 2.5-inch diameter magnetic disk used for an HDD or the like. As the information recording density increases, both the circumferential linear recording density (BPI: Bit Per Inch) and the radial track recording density (TPI: Track Per Inch) are steadily increasing. Further, a technique for improving a signal-to-noise ratio (SNR) by narrowing a gap (magnetic spacing) between a magnetic layer of a magnetic disk and a recording / reproducing element of a magnetic head has been studied.

  In the HDD start / stop system, the magnetic head is retracted to the outer circumference of the disk when the magnetic disk is not used (stopped) from the CSS system (contact start / stop system) where the magnetic head is placed on the disk surface. The LUL method (load / unload method) is almost shifted. As a result, it becomes unnecessary to provide the magnetic disk with unevenness for preventing adsorption at the time of contact, so that the disk surface can be further smoothed and the flying height of the magnetic head can be narrowed.

As the flying height of the magnetic head is reduced, the possibility that the magnetic head comes into contact with the disk surface due to external impact or flight disturbance is increasing. For this reason, the magnetic disk is provided with a medium protective layer that protects the surface of the magnetic recording layer from being damaged when the magnetic head collides. A lubricant is applied to alleviate. As an example of the use of the lubricant, for example, Patent Document _1, the perfluoroalkyl polyether having the structure _{HOCH 2 -CF 2 O- (C 2} F 4 O) p- (CF 2 O) q-CH 2 OH A magnetic disk coated with a lubricant is disclosed.

  It is possible to reduce damage when the magnetic head is in contact by applying a lubricant, but if it is placed in an intermittent contact state between the lubricating layer and the disk surface due to a decrease in the flying height, it will be removed from the disk surface. Lubricant transfer to the head slider surface is likely to occur. When this amount of transfer increases, a bridging layer of the lubricating layer is formed between the head slider and the disk, and an attracting force called meniscus force is generated, which hinders stable flying of the head slider.

  In order to improve the SNR, it is indispensable to reduce the flying height of the magnetic head. Therefore, it is necessary to develop a lubricant that hardly causes transfer and to establish an evaluation method thereof. As an example of an evaluation method, for example, Patent Document 2 discloses that a flying head that floats a predetermined amount from a magnetic disk and detects a collision with a lubricant with a piezoelectric element or an AE (Acoustic Emission) sensor is used to reduce the rotational speed of the magnetic disk. The speed at which the flying head starts to slide with the liquid lubricant on the magnetic disk (TDV: Touch Down velocity) and the rotational speed of the magnetic disk are increased, and the flying head re-floats from the magnetic disk and slides and collides. A technique for obtaining the separation characteristics of the flying head from the magnetic disk surface from the difference from the speed at which the head ends (TOV: Take Off velocity) is disclosed. The same evaluation can also be performed by a TDP / TOP (Touch Down Pressure / Take off pressure) test in which the flying height of the magnetic head is controlled depending on pressure (see, for example, Patent Document 3).

The magnetic disk judged to have a large meniscus force of the lubricant and poor release characteristics by conventional TDP / TOP measurement etc. had a low pass rate in the load / unload durability test, and could be correlated. . As a result, stable quality was guaranteed for the magnetic disk. In the load / unload durability test, a magnetic disk is mounted on a hard disk drive, and the load / unload operation is repeated continuously many times, for example, 600,000 times or more. Although it is the evaluation test closest to the operation mode of the drive, it is a mounting test using a magnetic disk and a flying head, and requires a lot of time and money to obtain the result.
Japanese Patent Laid-Open No. 62-066417 JP 2007-095176 A JP 2007-115383 A

  In recent years, HDDs have been used for car navigation systems, portable music players, and the like. Since the environment such as vibration and pressure changes greatly compared to when using a conventional PC, the chance of the magnetic head colliding further increases. Higher reliability and durability than ever before will be required for magnetic disks, and tests in harsh environments such as 60 ° C and humidity 80% have been introduced and evaluated in load / unload durability tests. Yes.

  There have been an increasing number of cases where magnetic disks judged to be good in the TDP / TOP test have failed in the 60 ° C. and 80% humidity load / unload (hard L / UL) endurance test. Furthermore, since the flying height of the magnetic head is reduced to 10 nm or less, it becomes difficult to correlate the separation characteristic test with the load / unload durability test.

  The present invention has been made in view of the above points, and it is possible to obtain a highly reliable magnetic disk that can pass a load / unload durability test of an HDD whose flying height of a magnetic head is 10 nm or less. An object of the present invention is to provide a method for manufacturing a magnetic disk.

  The method of manufacturing a magnetic disk according to the present invention is a manufacturing method including an evaluation step of evaluating the lubricating layer of a magnetic disk having a lubricating layer as an uppermost layer, wherein the evaluation step rotates the magnetic disk and the magnetic layer is rotated. A magnetic head floating step of floating the magnetic head above the disk, and after rotating the magnetic disk, gradually reducing the atmospheric pressure of the measurement environment to bring the magnetic head into contact with the surface of the magnetic disk; A TOP measurement step of measuring the pressure when the magnetic head floats from the surface of the magnetic disk by gradually increasing the atmospheric pressure of the measurement environment, and the lubricant on the slider surface of the magnetic head after the TOP measurement A first head determination step for determining pass / fail of the flying characteristics of the magnetic disk based on the adhesion amount; and a TOP measurement pressure in a state where the magnetic disk is rotated. The magnetic disk is based on a rapid release step of rapidly increasing the atmospheric pressure of the measurement environment at a lower atmospheric pressure to separate the magnetic head from the surface of the magnetic disk, and the amount of lubricant adhering to the slider surface of the magnetic head. And a second head determining step for determining whether or not the flying characteristics are acceptable.

  According to this method, TOP, which is a unique value of a magnetic disk that is a magnetic disk, is measured, and determination is performed by rapidly increasing the atmospheric pressure between predetermined pressures including the measured TOP. The amount of lubricant transferred from the meniscus (liquid bridge) formed between the magnetic head and the disk surface when flying from the magnetic head to the slider of the magnetic head can be increased. Since it was found that the magnetic disk in which the lubricant adhered to the slider of the magnetic head that rapidly flew was not sufficiently reliable, lubrication in the slider of the magnetic head that rapidly flew from the disk surface By determining the adhesion of the agent, it is possible to obtain a highly reliable magnetic disk that can pass a more severe load / unload durability test.

In the method for manufacturing a magnetic disk according to the present invention, the rate of increase in atmospheric pressure in the TOP measurement step is A (Torr / sec ² ), and the rate of increase in atmospheric pressure in the rapid release step is B (Torr / sec ² ). The absolute value is preferably B ≧ 10A.

  In the magnetic disk manufacturing method of the present invention, the magnetic disk is preferably a magnetic disk used in a load / unload type hard disk drive device.

  In the magnetic disk manufacturing method of the present invention, it is preferable that the magnetic disk has a diameter of 2.5 inches or less.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in this embodiment are merely examples for facilitating the understanding of the present invention, and do not limit the present invention unless otherwise specified.

  The inventor makes a pass / fail determination (first determination) of the flying characteristics based on the presence or absence of lubricant adhesion (transfer) to the slider of the magnetic head after the TDP / TOP measurement, and performs the TOP measurement while rotating the magnetic disk. The atmospheric pressure of the measurement environment is rapidly increased at an atmospheric pressure equal to or lower than the pressure, and the pass / fail determination (second determination) of the flying characteristics is performed based on the presence or absence of lubricant adhesion (transfer) to the slider. In other words, when measuring TOP, each difference is determined in the rate of increase in pressure. In this case, TOP measurement in a state where the pressure increase rate is relatively large is evaluated under severe conditions. By performing the determination under the two conditions as described above, it is possible to perform an evaluation under a harsher environment and to determine a highly reliable magnetic disk.

  FIG. 5 is a diagram showing a process of attaching the lubricant to the slider of the magnetic head during TOP measurement. In the same figure, when the slider 200 of the magnetic head floats from the surface of the magnetic disk 100, the lubricant constituting the lubricating layer 140 formed on the medium protective layer 130 has the property of a liquid. A meniscus 300 is formed between 200 and the disk surface. By separating the magnetic head more rapidly than normal TOP, the transfer lubricant 300a transferred from the meniscus 300 to the slider 200 of the magnetic head can be increased. By adopting the evaluation under the condition of separating the magnetic head more rapidly than the normal TOP, it becomes possible to perform the evaluation corresponding to the severe 60 ° C. and 80% humidity load / unload durability test. For this reason, it is possible to correlate with the load / unload durability test, which is difficult to correlate with the load / unload durability test in normal TOP. The pressure in the measurement environment can be controlled to a specific pressure by using a vacuum pump and a cock that opens the system. In this case, an accurate control method using a program is desirable.

A method for manufacturing a magnetic disk according to an embodiment of the present invention will be described below.
(Media production)
FIG. 1 is a diagram for explaining the configuration of a magnetic disk 100 according to the present embodiment. The magnetic disk 100 shown in FIG. 1 includes a disk substrate 110, a magnetic recording layer 120, a medium protective layer 130, and a lubricating layer 140.

  As the disk substrate (magnetic disk substrate) 110, for example, a glass substrate, an aluminum substrate, a silicon substrate, a plastic substrate, or the like can be used. Preferably, a glass disk obtained by forming an amorphous aluminosilicate glass into a disk shape by direct pressing is used. The type, size, thickness, etc. of the glass disk are not particularly limited.

  The magnetic recording layer 120 has a laminated structure including layers that do not directly perform magnetic recording, such as a soft magnetic layer and an underlayer. For example, the magnetic recording layer 120 is an adhesion layer that mainly bonds the disk substrate and the magnetic layer. In the perpendicular magnetic recording method, a magnetic path is temporarily formed at the time of recording in order to pass a magnetic flux in a direction perpendicular to the recording layer. The soft magnetic layer, the underlayer for orienting the easy axis of magnetization of the magnetic recording layer in the perpendicular direction of the disk, and the magnetic layer for storing and reproducing information are formed in this order.

  The medium protective layer 130 is formed by depositing carbon by a CVD method while maintaining a vacuum. The medium protective layer 130 protects the magnetic recording layer 120 from the impact of the magnetic head. In general, carbon deposited by the CVD method has improved film hardness as compared with that deposited by the sputtering method, so that the magnetic recording layer 120 can be more effectively protected against an impact from the magnetic head.

  The lubricating layer 140 is formed by forming a film of PFPE (perfluoropolyether) by a dip coating method. PFPE has a long chain molecular structure and binds with high affinity to N atoms on the surface of the medium protective layer 130. Due to the action of the lubricating layer 140, even if the magnetic head comes into contact with the surface of the magnetic disk 100, damage or loss of the medium protective layer 130 can be prevented. After the PFPE film is formed, the bonding between the PFPE molecules and the medium protective layer 130 can be enhanced by performing a high temperature treatment or a UV treatment.

(Inspection process)
FIG. 2 is a flowchart for explaining the flow of the manufacturing method of the magnetic disk 100 according to the present embodiment.
First, the magnetic disk 100 is rotated, and the magnetic head is floated above the magnetic disk 100 by the rotation (step S10). Next, the magnetic head is brought into contact with the surface of the magnetic disk 100 by gradually reducing the atmospheric pressure in the measuring apparatus while the magnetic disk 100 is rotated at a constant speed, and the pressure (TDP) at the time of contact is made. Is measured (step S11). After confirming the contact, the atmospheric pressure is increased stepwise, and the pressure (TOP) when the magnetic head floats is measured (step S12). At this time, the absolute value of the decrease / increase rate of the atmospheric pressure is assumed to be equal.

  Here, the slider surface of the magnetic head is observed (step S13). In this case, the transfer amount of the lubricant can be evaluated by visual inspection using an optical microscope. Furthermore, quantitative investigation and determination can be performed by measuring the spectral intensity of the elements constituting the lubricant by X-ray photoelectron spectroscopy. The presence or absence of lubricant adhering to the slider surface of the magnetic head is determined by the above inspection (first determination) (step S14). If it is determined that there is no lubricant adhering to the slider surface of the magnetic head, it is determined that the magnetic disk 100 is durable (step S15). If it is determined that there is an adhering lubricant, the durability of the magnetic disk 100 is determined. It is determined that there is no (step S16).

Further, while the magnetic disk 100 is rotated, the magnetic head is pulled away from the surface of the magnetic disk 100 by rapidly increasing the atmospheric pressure from below the TOP measured in the TOP measurement process (detaching process, step S17). Here, when the rate of increasing the atmospheric pressure in the TOP measurement step is A (Torr / sec ² ), and the rate of increasing the atmospheric pressure in the separation step is B (Torr / sec ² ), the absolute value is B ≧ 10A. .

  After the separation step, the slider surface of the magnetic head is observed (step S18). In this case, the transfer amount of the lubricant can be evaluated by visual inspection using an optical microscope. Further, quantitative investigation and determination can be performed by measuring the spectral intensity of the elements constituting the lubricant by X-ray photoelectron spectroscopy. The presence or absence of lubricant adhering to the slider surface of the magnetic head is determined by the above inspection (second determination) (step S19). If it is determined that there is no lubricant adhering to the slider surface of the magnetic head, it is determined that the durability of the magnetic disk 100 is sufficient (step S20). It is determined that the durability is not sufficient (step S21).

  TOP is a value that varies depending on the individual difference between the magnetic disk 100 and the magnetic head (the surface state of the magnetic disk such as the disk surface roughness and the slider surface roughness of the magnetic head). Therefore, the TOP varies depending on the magnetic disk or the magnetic head. When determining the quality of the lubricating layer of the magnetic disk based on such TOP, it was possible to cope with the evaluation with the head flying height at the conventional level, but when the head flying height reached the 10 nm level, In severe tests such as the 80% humidity load / unload durability test, there is no correlation. In the present invention, in addition to this, individual differences between the magnetic disk 100 and the magnetic head can be absorbed by increasing the air pressure at a specific air pressure interval including TOP in the separation step, and which magnetic disk and which magnetic Even if the head is used, the separation step can be performed with the same size. As a result, it can be correlated with a severe test such as a 60 ° C. and 80% humidity load / unload durability test, and it becomes possible to judge the quality of a magnetic disk with higher reliability.

Next, examples for clarifying the effects of the present invention will be described.
In this example, a magnetic recording layer was formed in a DC magnetron sputtering method in an Ar atmosphere using a vacuum deposition apparatus on a disk substrate 110 having an outer diameter of 65 mm, an inner diameter of 20 mm, and a disk thickness of 0.635 mm. Films were sequentially formed from 120 to the lubricating layer 140. At this time, the medium protective layer 130 was formed using C ₂ H ₄ and CN by the CVD method, and the lubricating layer 140 was formed using PFPE by the dip coating method.

  In this example, three types of 2.5-inch magnetic disks 100 having different lubricating layer 140 configurations were produced. That is, the lubricating layer 140 has a film thickness of 1.4 nm and the lubricant baking temperature is 110 ° C. (magnetic disk # 1), and the lubricant layer 140 has a film thickness of 1.4 nm and the lubricant bake A magnetic disk (magnetic disk # 2) having a temperature of 90 ° C. and a magnetic disk (magnetic disk # 3) having a lubricant layer 140 thickness of 1.8 nm and a lubricant baking temperature of 110 ° C. were produced. .

(TOP measurement process)
FIG. 3 is a diagram for explaining the result of measuring the TOP of the magnetic disk 100 in this embodiment, and shows the result of measuring the magnetic disk # 1 as an example. For TOP measurement in this example, a magnetic disk test system HDF tester 2007 manufactured by Kubota Comps Co., Ltd. was used. In FIG. 3, the vertical axis indicates the AE voltage at which the vibration applied to the magnetic head is detected, the horizontal axis indicates the measured ambient pressure, and when the vertical axis indicates the detection limit value of 2 V, the magnetic head is moved to the magnetic disk. It shows that it contacted the surface of 100.

  First, a magnetic head is loaded on the magnetic disk 100 and the rotation speed (peripheral speed) of the magnetic disk 100 is fixed at 10.0 (m / sec), and then the atmospheric pressure is changed from 760 (Torr) to 240 (Torr). ) Until 5 (Torr / sec).

  As shown in FIG. 3, in the magnetic disk # 1, the detected voltage is 2 V when the atmospheric pressure is 260 (Torr). Therefore, the magnetic head is in contact with the surface of the magnetic disk # 1 at the atmospheric pressure 260 (Torr). Is shown. That is, the TDP of magnetic disk # 1 is 260 (Torr). Thereafter, when the atmospheric pressure was increased from 240 (Torr) to 760 (Torr) in increments of 5 (Torr / sec), the detected voltage became 0 V at the atmospheric pressure 390 (Torr), and the magnetic head floated from the surface of the magnetic disk # 1. That is, the TOP of the magnetic disk # 1 is 390 (Torr). Similarly, the TOP of the magnetic disk # 2 and the magnetic disk # 3 were measured and found to be 410 (Torr) and 500 (Torr), respectively.

  Next, the slider surface of the magnetic head after TOP measurement was measured using X-ray electron spectroscopy (hereinafter referred to as ESCA) (first determination). According to Japanese Patent Laid-Open No. 2000-208532, the adhesion of the lubricant was observed when the lubricant film thickness adhering to the slider rear end surface near the R / W element of the magnetic head was 5% or less of the head flying height. It was determined as NG. Since a magnetic head with a flying height of 12 nm was used, 0.6 nm was used as the judgment line. As a result, magnetic disk # 3 was NG, and no lubricant was observed on the slider surfaces of magnetic disk # 1 and magnetic disk # 2.

(Withdrawal process)
Next, with respect to the magnetic disk # 1 and the magnetic disk # 2, the magnetic head is loaded again on the magnetic disk 100, and the air pressure is decreased in increments of 5 (Torr / sec) so that the magnetic head is placed on the surface of the magnetic disk 100. After the contact, the atmospheric pressure of the magnetic disk 100 was increased by 100 (Torr / sec) with a range of TOP ± 50 (Torr) as a predetermined atmospheric pressure including the obtained TOP.

  FIG. 4 is a diagram for explaining the result of the separation step in the present embodiment, and shows the result of measuring the magnetic disk # 1 as an example. Since the TOP of the magnetic disk # 1 is 390 (Torr), the pressure from 340 (Torr) to 440 (Torr) is increased at 100 (Torr / sec). Thus, the magnetic head was rapidly pulled away from the surface of the magnetic disk 100 by rapidly increasing the atmospheric pressure of the measurement environment when the magnetic disk 100 was rotated. Similarly, in the magnetic disk # 2, the atmospheric pressure was increased from 360 (Torr) to 460 (Torr), and the magnetic head in contact with the surface of the magnetic disk 100 was rapidly pulled away.

After the magnetic head was quickly pulled apart and the atmospheric pressure was increased to normal pressure, the slider surface of the magnetic head was measured by ESCA in the same manner as described above (second determination). As a result, the slider surface of the magnetic disk # 2 was NG, and no lubricant was observed on the slider surface of the magnetic disk # 1. These results are shown in Table 1 below.

  In addition, three types of magnetic disks 100 (magnetic disks # 1 to # 3) are mounted on a load / unload type HDD, and a magnetic head with a flying height of 10 nm is used for load / unload in an environment of 60 ° C. and 80% humidity. A road durability test was conducted. Under normal usage conditions of HDD, the number of loading / unloading is about 400,000 in about 10 years. If it can withstand the same number of times in the load / unload durability test of the present embodiment, it indicates that it has higher durability. The reliability standard was set at 400,000 times or more. As a result of the load / unload durability test, the number of loads / unloads for magnetic disk # 1 exceeded 400,000 times, while that for magnetic disk # 2 was less than 300,000 times. Magnetic disk # 3 could not exceed 200,000 times.

  From this result, it was found that the magnetic disk 100 in which the lubricant was confirmed to adhere to the magnetic head slider that had rapidly floated did not have sufficient reliability. As can be seen from Table 1, in the TOP measurement process of the magnetic disk 100, a load / unload durability test is performed by determining adhesion (second determination) of the lubricant on the magnetic head slider that has rapidly floated from the medium surface. And the reliability of the magnetic disk 100 can be evaluated at a high level.

  The present invention is not limited to the above embodiments, and can be implemented with appropriate modifications. The material, number, size, processing procedure, and the like in the above-described embodiment are merely examples, and various modifications can be made within the range where the effects of the present invention are exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

  The present invention is applicable to a magnetic disk mounted on a perpendicular magnetic recording type HDD or the like.

It is a figure explaining the structure of the magnetic disc which concerns on embodiment of this invention. 5 is a flowchart for explaining a flow of a magnetic disk manufacturing method according to an embodiment of the present invention. It is a figure for demonstrating the result of having measured the TOP of the magnetic disc in the Example of this invention. It is a figure for demonstrating the result of the isolation | separation process in the Example of this invention. It is a figure which shows the lubricant adhesion process to the slider of a magnetic head at the time of TOP measurement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Magnetic disk 110 Disk substrate 120 Magnetic recording layer 130 Medium protective layer 140 Lubricating layer 200 Magnetic head slider 300 Meniscus 300a Transfer lubricant

Claims (4)

  A manufacturing method including an evaluation step of evaluating the lubrication layer of a magnetic disk having a lubrication layer as an uppermost layer, wherein the evaluation step rotates a magnetic disk and causes a magnetic head to float above the magnetic disk. With the head floating step and the magnetic disk rotated, the atmospheric pressure in the measurement environment is gradually decreased to bring the magnetic head into contact with the surface of the magnetic disk, and then the atmospheric pressure in the measurement environment is gradually increased. Then, based on the TOP measurement step of measuring the pressure when the magnetic head floats from the surface of the magnetic disk, and the amount of lubricant adhering to the slider surface of the magnetic head after the TOP measurement, the magnetic disk floats A first head determination step for determining pass / fail of the characteristics, and an atmosphere of the measurement environment at an atmospheric pressure equal to or lower than the TOP measurement pressure with the magnetic disk rotated. And determining whether or not the flying characteristics of the magnetic disk pass or fail based on a rapid separation step of separating the magnetic head from the surface of the magnetic disk by rapidly increasing the amount of lubricant and the amount of lubricant adhering to the slider surface of the magnetic head. A method of manufacturing a magnetic disk, comprising: a two-head determination step. When the rate of increase in atmospheric pressure in the TOP measurement step is A (Torr / sec ² ) and the rate of increase in atmospheric pressure in the rapid separation step is B (Torr / sec ² ), the absolute value is B ≧ 10A. 2. The method of manufacturing a magnetic disk according to claim 1, wherein:   3. The method of manufacturing a magnetic disk according to claim 1, wherein the magnetic disk is a magnetic disk used in a load / unload type hard disk drive device.   4. The method of manufacturing a magnetic disk according to claim 1, wherein the magnetic disk has a diameter of 2.5 inches or less.

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