JPH07122018A - Magnetic disk and its production - Google Patents

Abstract

PURPOSE:To provide the magnetic disk having a high density and a good traveling property of a head. CONSTITUTION:This magnetic disk is constituted by forming concentrical or spiral tracks on a nonmagnetic substrate 4 and forming non-track parts 2 consisting of nonmagnetic films between the tracks 1. The disk is provided projecting parts 3 consisting of nonmagnetic materials having a rectangular shape projecting from the track parts 1 at a ratio of 1/10<2> to 1/10<5> of the surface area in such a manner that total sum of the surface area thereof distributes uniformly in the non-track parts 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk, and more particularly to a high density magnetic disk having its magnetic film separated for each track and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a means for improving the recording density of a magnetic disk, a method of separating a magnetic film of a magnetic disk into tracks is disclosed in Japanese Patent Laid-Open No. 62-256225 (known example 1) and US Pat. It is disclosed in known example 2). According to this method, when the magnetic head is displaced, the signal noise ratio (S / N) is more advantageous than that of the magnetic film, so that the track density can be increased and the recording density can be increased. .

On the other hand, a method of forming irregularities on the surface of the magnetic disk is used as a method of preventing the magnetic head from adsorbing to the magnetic disk and improving the running property of the magnetic head with respect to the magnetic disk. For example, the applicant of the present application first
A method for forming irregularities by using etching is disclosed in Japanese Patent Laid-Open No.
It was proposed in Japanese Patent No. 173917 (publicly known example 3). According to this method, the running reliability of the magnetic head becomes extremely high. Further, as a method of satisfying these two characteristics, that is, improvement of recording density and improvement of running reliability of a magnetic head, a magnetic film is separated for each track by a non-magnetic film,
Further, a method of forming unevenness by projecting the non-magnetic film from the magnetic film is disclosed in, for example, JP-A-1-279421 (known example 4).
And Japanese Patent Laid-Open No. 4-89616 (known example 5).

[0004]

However, the above-mentioned known examples 1 and 2 do not give sufficient consideration to the running reliability of the head, and the known example 3 relates to the improvement of the recording density, especially the displacement of the head. Effective measures are not taken. The known examples 4 and 5 are said to satisfy both characteristics of the improvement of the recording density and the improvement of the running reliability of the magnetic head. However, in the protruding part which is in contact with the head, which is deeply related to the running reliability of the head. The area is not specified, and the magnetic disk configuration is insufficient for the running reliability of the head. An object of the present invention is to provide a magnetic disk having a high recording density and a very good head running reliability.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and the invention according to claim 1 is "concentric or spiral, directly on a non-magnetic substrate or via an underlayer. -Shaped track portions are formed of a magnetic thin film, and in a magnetic disk in which the non-track portions of the non-magnetic film are formed between the respective tracks, a non-magnetic protrusion portion having a rectangular cross section protruding from the track portions is formed. A magnetic disk provided such that the total surface area thereof is uniformly distributed in the non-track portion at a ratio of 1/10 ² to 1/10 ⁵ of the surface area of the non-magnetic substrate. ” ,

According to a second aspect of the present invention, "a protective film is formed so as to cover the surface of the non-track portion including the track portion and the protruding portion of the magnetic thin film. Magnetic disk. "

According to a third aspect of the present invention, "a first step of forming a protrusion of a non-magnetic material in at least a region of the non-magnetic substrate to be the non-track portion, and the track portion of the non-magnetic substrate are formed. 2. A method of manufacturing a magnetic disk according to claim 1, further comprising a second step of forming a magnetic thin film in the power region.

[0008]

According to the above-mentioned structure of the present invention, the concentric or spiral magnetic thin film track portion is provided, so that the deterioration of the signal-to-noise ratio when the head is displaced is reduced. This is because the magnetic interaction between adjacent recording signal tracks becomes smaller by separating the magnetic thin film for each track, compared to the case where the magnetic thin film is continuously and uniformly formed. This is because the demagnetization of the recording signal does not easily occur even if is smaller, and the reproduction noise due to the influence of the adjacent recording tracks is smaller. Therefore, the reduction in the signal noise ratio when the head is displaced can be reduced as compared with the case where the magnetic thin film is continuously and uniformly formed, and a magnetic disk having a high recording density with a smaller track interval is possible. Become.

Further, the running reliability of the head is deeply related to the area where the head and the magnetic disk actually come into contact with each other, and the frictional force between the head and the magnetic disk is greatly affected by this contact area. High running reliability of the head can be obtained by forming the parts so that the total surface area thereof is 1/10 ² to 1/10 ⁵ of the surface area of the non-magnetic substrate. Furthermore, since the projecting portion is provided only in the non-track portion, the track portion on which the magnetic thin film is formed has a uniform surface, which may increase the probability of occurrence of a reproduction signal error. Absent. That is, in the case where the magnetic thin film is formed on the surface on which the magnetic thin film is formed as in the case of the magnetic disk described in the above-mentioned publicly known example 3, the convex portion is formed on the magnetic thin film track portion. If so, the distance from the head becomes closer in the protruding portion, and the probability that a reproduction signal having an excessively high level is obtained and a reproduction signal error occurs, but the structure of the present invention causes such a problem. Nothing.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partially enlarged view of a magnetic disk according to the present invention, and FIG. 2 is an enlarged sectional view schematically showing an AB cross section in FIG. Further, FIGS.
It is a figure which shows typically the cross section of the magnetic disc in each manufacturing process of the magnetic disc which concerns on this invention. A magnetic disk which is an example of the present invention was manufactured as follows. The magnetic thin film track portion 1 and the projecting portion 3 formed in a part of the non-track portion 2 between the magnetic thin film tracks, which were separated concentrically, were produced as follows. First, a negative photoresist layer 5 (ONNR-20 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to a soda-lime glass substrate 4 having a mirror-polished surface (average roughness Ra of 0.001 μm or less) by 0.4 μm by a spin coating method. Formed (FIG. 3). Then, ultraviolet rays are exposed through the photomask 6 (FIG. 4). Here, a plurality of openings 6a are formed in the photomask 6, and the plurality of openings 6a are evenly distributed in the non-track portion 2 to be formed later, and the total area thereof is the same as that of the magnetic disk. The area of the recording / reproducing portion (the magnetic thin film track portion 1 and the non-track portion 2) was set to 1/10 ³ .

After the unexposed photoresist is removed by development (FIG. 5), the exposed glass substrate surface is dry-etched with CF ₄ gas (FIG. 6), and the patterned photoresist 5 is removed by a wet method. The area ratio to the magnetic disk recording / reproducing part is 1/10 ³ , and the height is 0.100 μm.
A glass substrate 4 having a protrusion 4a having a rectangular cross section was obtained (FIG. 7). Then, on the uneven surface of the glass substrate 4 having the protrusion 4a having a rectangular cross section, a thickness of 0.045 μm is formed by a sputtering method.
m of Cr film as the underlayer 7, and Co of 0.07 μm thickness
A CrTaPt alloy film is sequentially formed as the magnetic layer 8. After that, a positive photoresist layer 9 (TSMR-V3 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied on the magnetic layer 8 by spin coating to form 0.5 μm (FIG. 8). Then, the photomask 10 having the openings 10a having a concentric circle width of 2 μm and a track pitch of 4 μm is aligned so that the openings 10a overlap the protrusions 4a, and ultraviolet rays are exposed through the photomask 10 (FIG. 9). Next, after removing the photoresist exposed by development (FIG. 10), dry etching is performed with Ar gas to remove the exposed magnetic film (FIG. 11), and the concentric resist 9 is removed by a wet method to separate the photoresist. The magnetic layer 8 is formed (FIG. 12). Here, the glass substrate 4
Depending on the height of the protrusion 4a formed on the surface and the thickness of the magnetic layer 8, the protrusion 4a is 0.03 μm from the surface of the separated magnetic layer 8.
The protrusion 4a has a rectangular cross section, which is a non-magnetic material. At this time, if the height of the protrusion 4a and the thickness of the magnetic layer 8 are taken into consideration, the amount of protrusion from the surface of the magnetic layer 8 can be freely controlled.

A carbon protective film 11 having a thickness of 0.025 μm is formed on these uneven surfaces by a sputtering method, and then a lubricating layer 12 having a thickness of 0.003 μm is formed on the protective film 11.
By coating (Fomblin AM2001 manufactured by Montecatini Co., Ltd.) (FIG. 13), magnetic disks according to the embodiments of the present invention as shown in FIGS. 1 and 2 were obtained. The photomasks 6 and 10 have, for example, a Cr thin film on the surface,
After rotating the quartz glass substrate on which the positive photoresist film was sequentially formed, and irradiating the photoresist film with a laser beam which was signal-modulated so that only the patterned openings of the photomasks 6 and 10 were irradiated. Can be formed by dissolving and removing the photoresist film in the exposed portion and etching away the exposed Cr thin film.

Next, two comparative examples (Comparative Example 1 and Comparative Example 2) whose characteristics should be compared with those of the above Example will be described. (Comparative Example 1) A magnetic disk of Comparative Example 1 having a sectional structure shown in FIG. 14 was produced. The manufacturing method is as follows. Soda-lime glass substrate 1 whose surface, which is a non-magnetic substrate, is mirror-polished (average roughness Ra 0.001 μm or less)
Cr of 0.045 μm thick on the surface of No. 3 by sputtering method
The film is used as a base layer 14, and CoCrT having a thickness of 0.07 μm is used.
The aPt alloy film is used as the magnetic layer 15, and the thickness is 0.025 μm.
The carbon film of 1 is sequentially formed as the protective film 16. Next, Comparative Example 1 was produced by applying a 0.001 μm-thick lubricating layer 17 (Fomblin AM2001, manufactured by Montecatini) on the protective film 16.

(Comparative Example 2) A magnetic disk of Comparative Example 2 having a sectional structure shown in FIG. 15 was produced. As shown in FIGS. 16 (a) to 16 (g), the manufacturing method is such that the surface of the non-magnetic substrate is mirror-polished (average roughness Ra0.
Positive photoresist layer 19 (manufactured by Tokyo Ohka Kogyo Co., Ltd., TSMR-) on a soda-lime glass substrate 18
V3) is applied to form 0.5 μm by spin coating (FIG. 16a). Then, ultraviolet rays are exposed through a photomask 20 having openings (20a) having a concentric circle width of 2 μm and a track pitch of 4 μm (FIG. 16b), and the photoresist exposed by development is removed (FIG. 16c), and then the exposed glass is exposed. The substrate surface was dry-etched with CF ₄ gas to form a concentric groove 18b having a depth of 0.145 μm (FIG. 16d). On this substrate, a Cr film having a thickness of 0.045 μm was used as an underlayer 21 and CoC having a thickness of 0.07 μm was formed.
After forming the rTaPt alloy film as the magnetic layer 22 by the sputtering method (FIG. 16e), the concentric resist was removed by the wet method. At this time, the Cr underlayer and the magnetic layer on the concentric resist pattern are removed simultaneously with the resist (FIG. 16f). As a result, the Cr underlayer 21 and the magnetic layer 22 were formed inside the concentric groove 18b on the surface of the glass substrate 18, and the non-track portion 18a protruding 0.03 μm from the magnetic layer 22 was formed. On this disc,
After forming a carbon film having a thickness of 0.025 μm as a protective film 24 by a sputtering method, a lubricating layer 25 having a thickness of 0.001 μm (manufactured by Montecatini Co., Fomblin AM200)
Comparative Example 2 was prepared by applying 1).

Next, the evaluation results of the recording / reproducing characteristics and the running performance of the magnetic head for the magnetic disk of the embodiment of the present invention and the magnetic disks of Comparative Examples 1 and 2 will be described. (A) Evaluation of recording / reproducing characteristics With respect to the magnetic disks of the above Examples and Comparative Examples 1 and 2, a magnetic disk device was constructed by combining with a thin film magnetic head, and the recording / reproducing characteristics were evaluated as follows. First, the disks of Example and Comparative Example 2 were fixed so that the centers of the magnetic film tracks separated circumferentially were aligned with the center of the spindle rotation axis, the disks were rotated, and the track centers of the thin film magnetic head with a track width of 3 μm were adjusted. The head was positioned so as to align with the center of the disk magnetic film track, and a 3.5 MHz signal was recorded. Next, the head is positioned so that the center of the magnetic film track adjacent to this is aligned with the center of the track of the magnetic head, and a signal of 5 MHz is recorded. After this,
The head was moved again to the track on which the 3.5 MHz signal was recorded, and the reproduction output and S / N were measured.

Furthermore, the following measurement was performed as a measurement when the head is displaced. As described above, after reproducing and measuring the 3.5 MHz signal, the 0.5 μm head was moved to the adjacent track side where the 5 MHz signal was recorded, and the reproducing output and S / N of the 3.5 MHz signal were measured. . Further, in Comparative Example 1, the disk was fixed to a rotary spindle and rotated, and the head used in the measurement of the recording / reproducing characteristics of Example and Comparative Example 2 was used, and 3.5 MH was used.
The z signal was recorded, the head was moved to the adjacent portion so that the track pitch was 4 μm, and the 5 MHz signal was recorded. The track pitch is set to 4 μm here for the purpose of comparing the track pitches with those of Example and Comparative Example 2. 3.5MH after recording 5MHz signal
The head was moved again to the track recorded at z, and its reproduction output and S / N were measured. In addition, as a measurement in the case where the position of the head is displaced, the 0.5 μm head is moved to the adjacent track side where a signal of 5 MHz is recorded.
The reproduction output and S / N of the 5 MHz signal were measured.

Table 1 is a summary of the above measurement results. As is clear from the results of Table 1, in Examples and Comparative Example 2 having the separated magnetic film tracks, the output and the S / N were hardly deteriorated with respect to the displacement of the head, but they were continuous and uniform. In Comparative Example 1 having the magnetic film of No. 3, when the head was misaligned, both output and S / N deteriorated. When the magnetic film tracks are separated in this way,
It can be seen that by using a head having a track width larger than the width of the separated magnetic film track, the recording / reproducing characteristics are less deteriorated due to the positional deviation of the head, which is advantageous in increasing the recording density.

The separated track width, track pitch, and track width of the head affect the recording / reproducing characteristics when the head is misaligned. However, as described above, it is effective against the displacement of the head, and the magnetic recording medium having the separated magnetic film is suitable for increasing the recording density because the magnetic interaction between the magnetic film tracks is small. .

[Table 1]

(B) Evaluation of Running Performance of Magnetic Head For the magnetic disks of the above-mentioned Examples and Comparative Examples 1 and 2, the head pressure of the magnetic head on the magnetic disk was 2.9 g / m.
m ² and linear velocity 6.4 m / sec, Al ₂ O ₃ -Ti
The CSS (contact start stop) test was conducted up to 50,000 times using the C head, and the results shown in Table 2 were obtained.

[Table 2]

As is clear from the results of Table 2, Comparative Examples 1 and 2 have high static friction coefficient and dynamic friction coefficient at the beginning of the CSS test, and the adsorption phenomenon between the head and the disk occurs by CSS500 times, and the magnetic head Is not good at running. On the other hand, as in the embodiment, it has a non-magnetic protrusion 3 having a rectangular cross section that protrudes from the surface of the separated magnetic thin film.
In addition, the magnetic disk in which the total surface area of the protrusions 3 is evenly distributed at a ratio of 1/10 ³ of the surface area of the non-magnetic substrate has low static friction coefficient and dynamic friction coefficient at the initial CSS test and after 50,000 times. It can be seen that the head running reliability is extremely good.

The protrusion 3 with respect to the surface area of the non-magnetic substrate
In order to see the relationship between the ratio of the total area of the magnetic head and the running property of the magnetic head, regarding the relationship between the average coefficient of dynamic friction and the number of CSSs with respect to the magnetic disk prepared in the same manner as in the above-mentioned embodiment by changing only the ratio. evaluated. The result is
This is shown in FIGS. In the figure (a), the ratio of the total area of the protrusions 3 to the surface area of the non-magnetic substrate is 2.2 × 10 ⁻³ for the curve plotted with □, and 9 is the curve plotted with +. The curves plotted with .2 × 10 ^-3 and ⋄ marks are 3.3 × 10 ^-2 , and the curves plotted with Δ marks are 6.5 × 10 ^-2 , respectively. Similarly, in the same figure (b), the curve plotted with □ is 8.8 × 10 ⁻⁶ , and the curve plotted with + is
3.0 × 10 ⁻⁵ , the curve plotted with ◇ is 1.1 ×
The curve plotted with 10 ⁻⁴ and Δ is 2.8 × 10 ⁻⁴ ,
, Respectively.

As can be seen from FIG. 6A, the ratios are 3.3 × 10 ^-2 (⋄) and 6.5 × 10 ^-2 (Δ).
The average dynamic friction coefficient of the magnetic disk has a large initial value of 0.6 or 0.9, and increases sharply as the number of CSS increases. On the other hand, the ratio is 2.
The average dynamic friction coefficient of the magnetic disks of 2 × 10 ⁻³ (square mark) and 9.2 × 10 ⁻³ (+ mark) is relatively small at the initial value of 0.2 or 0.4, and the CSS is 30,000 times.
In the process of, the value is almost constant, which shows that the running property of the head is good. Further, referring to FIG. 4B, the average dynamic friction coefficient of the magnetic disk having the ratio of 2.8 × 10 ⁻⁴ (marked with Δ) is the initial value and 300.
0.2 to 0.1 in any of the 00 CSS processes
Although it shows a small value of about 5, the average dynamic friction coefficient starts to increase on the contrary when the ratio becomes smaller, and the ratio becomes 8.8.
The average dynamic friction coefficient of the magnetic disk of × 10 ^-6 (marked with □) is 0 when the number of times of CSS of 15,000 is exceeded.
It can be seen that the value exceeds 4 and the running property of the head begins to deteriorate. Therefore, it can be seen that the running property of the head is good when the ratio of the total area of the protrusions 3 to the surface area of the non-magnetic substrate is in the range of about 1/10 ² to 1/10 ⁵ .

[0023]

As described above, according to the present invention,
The track portion on which information is to be recorded is formed of a concentric or spiral magnetic thin film, and the non-track portion between the tracks has a projecting portion of a non-magnetic material having a rectangular cross section protruding from the track portion. In addition, since the total surface area of the protrusions is a magnetic disk uniformly distributed at a ratio of 1/10 ² to 1/10 ⁵ of the surface area of the non-magnetic substrate, the magnetic head has an unprecedented excellent running reliability. And a magnetic disk having a high recording density can be obtained without deteriorating the reproduction output and the S / N with respect to the magnetic property and the head position shift. Further, in particular, in order to reduce the flying height of the head, when a substrate having a small surface roughness is used as the non-magnetic substrate, a protrusion having a rectangular cross section is formed on the outermost surface of the magnetic recording medium. Even when the magnetic head was repeatedly run, its running performance was excellent, almost unchanged from the initial stage.

[Brief description of drawings]

FIG. 1 is a partially enlarged view schematically showing an embodiment of a magnetic disk of the present invention.

FIG. 2 is an enlarged cross-sectional view schematically showing the AB cross section in FIG.

FIG. 3 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 4 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 5 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 6 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 7 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 8 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 9 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 10 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 11 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 12 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 13 is an explanatory diagram of a manufacturing process of an embodiment of the magnetic disk of the present invention.

FIG. 14 is an enlarged cross-sectional view schematically showing a first comparative example to be compared with the embodiment of the magnetic disk of the present invention.

FIG. 15 is an enlarged sectional view schematically showing a second comparative example to be compared with the embodiment of the magnetic disk of the present invention.

FIG. 16 is an explanatory diagram of the manufacturing process of the second comparative example.

FIG. 17 is a graph plotting the relationship between the average dynamic friction coefficient and the number of times of CSS.

[Explanation of symbols]

 1 Track part 2 Non-track part 3 Projection part 4 Soda-lime glass substrate 5 Negative type photoresist layer 6 Photomask 7 Underlayer 8 Magnetic layer 9 Positive type photoresist layer 10 Photomask 11 Protective film 12 Lubricating layer 13 Soda Lime glass substrate 14 Underlayer 15 Magnetic layer 16 Protective film 17 Lubricating layer 18 Soda lime glass substrate 19 Positive photoresist layer 20 Photomask 21 Underlayer 22 Magnetic layer 24 Protective film 25 Lubricating layer

Claims (3)

[Claims] 1. A non-magnetic substrate, directly or through an underlayer,
In a magnetic disk in which concentric or spiral track portions are formed of a magnetic thin film and a non-track portion of a non-magnetic film is formed between each track, a non-magnetic material of rectangular cross section protruding from the track portions is formed. The total surface area of the protrusions is 1/10 of the surface area of the non-magnetic substrate.
A magnetic disk characterized by being provided so as to be uniformly distributed in the non-track portion at a ratio of ² to 1/10 ⁵ . 2. The magnetic disk according to claim 1, wherein a protective film is formed so as to cover the surfaces of the track portion and the non-track portion including the protruding portion of the magnetic thin film. 3. A first step of forming a projection of a non-magnetic material on at least a region of the non-magnetic substrate to be the non-track portion, and a magnetic thin film is formed on a region of the non-magnetic substrate to be the track portion. 2. The method for manufacturing a magnetic disk according to claim 1, further comprising a second step of: