JPH08273160A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium having high coercive force and high reproduction output by forming a magnetic film having a prescribed compsn. by sputtering under a prescribed pressure of inert gas when a magnetic layer is formed. CONSTITUTION: A 1st underlayer 2, a 2nd underlayer 3, a 3rd underlayer 4, a magnetic layer 5, a protective layer 6 and a lubricative layer 7 are successively formed on a glass substrate 1 to obtain a magnetic disk. When the magnetic layer 5 is formed, a magnetic film 5 having a compsn. represented by the formula Co100-a-b Nia Crb [where (a) is 20-30at.% and (b) is 8-12at.%] is formed by sputtering under 0.5-7mTorr pressure of inert gas. The objective magnetic recording medium having high coercive force and high reproduction output and generating low noise at the time of reproduction is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic recording medium used in a magnetic disk device or the like.

[0002]

2. Description of the Related Art In recent years, demands for high recording density recording on magnetic recording media such as hard disks have become increasingly severe.

Here, in general, a magnetic recording medium such as a hard disk is one in which an underlayer, a magnetic layer and a protective layer are sequentially formed on a non-magnetic substrate, and a head slider on which a magnetic head is mounted is floated on the magnetic recording medium. While recording and reproducing. Therefore, in order to realize high density recording of this magnetic recording medium, in addition to high coercive force of the magnetic layer, low flying of the head slider and CSS (contact st
It is important to realize high durability against art and stop). That is, it is necessary to reduce the distance between the magnetic head and the magnetic layer at the time of recording / reproducing to allow high-density recording / reproducing by moving the head slider at a low flying height. In addition, when this low-flying traveling is performed, during repeated operation (CSS) of switching between sliding traveling and floating traveling when the head slider starts and stops traveling,
Since the physical / mechanical load applied to the magnetic head and the magnetic recording medium increases rapidly, it is necessary to improve the durability of the magnetic head and the magnetic recording medium in CSS (high CSS durability). Further, with the increase in recording density, it is more strictly required to reduce noise during reproduction.

By the way, in many current hard disks, an aluminum alloy substrate is used as a non-magnetic substrate, the surface of which is Ni--P plated and polished, and then textured to give an appropriate surface roughness. After that, the underlayer, the magnetic layer, the protective layer and the like are sequentially formed by the sputtering method. That is, the head slider is attracted to the magnetic recording medium during CSS so that irregularities due to the surface roughness due to texture processing appear on the surface of the protective layer through the underlayer and the magnetic layer, or
The frictional force between the two is prevented from becoming larger than a predetermined value.

However, it has been found that this method has a limit in realizing the above-mentioned high coercive force, low levitation running and high CSS durability. This means that the surface irregularities are formed by texture and then the underlying layer and the magnetic layer having irregularities are formed following the irregularities, so that the incident angle of sputtered particles may vary depending on the location. Because of this, the crystal to be grown is not always formed well in the process of forming the underlayer and the magnetic layer.
It is considered to be one. In addition, the mechanical properties such as hardness of the aluminum alloy substrate are not always sufficient to satisfy the mechanical durability required for achieving low floating running and high CSS, and further, the underlayer, It has become necessary to perform physical and chemical treatments such as heat treatment at a higher temperature in order to make the magnetic layer and the protective layer have good characteristics. It has been found that physical and chemical resistance such as corrosion resistance is not sufficient.

Recently, a magnetic recording medium using a glass substrate as a non-magnetic substrate has attracted attention as a medium having a high possibility of realizing high density recording more easily. This is because it has been found that the mechanical / physical / chemical durability of glass and the fact that its surface can be formed relatively easily with high planar accuracy are more suitable for realizing high-density recording. That is, a magnetic recording medium using this glass substrate is a glass substrate whose surface has been precision-polished, and an underlayer, a magnetic layer, a protective layer and the like are immediately formed in that order, unlike the case where an aluminum substrate is used. The surface of the substrate is not subjected to texturing, but the protective layer itself is used to impart irregularities. Therefore, the underlayer and the magnetic layer are
Since it is formed on a very smooth surface, it is easy to control the crystal growth of each when forming the underlayer and the magnetic layer,
A layer with good properties can be obtained relatively easily. Regarding the roughness of the surface of the protective layer, the one using an aluminum substrate indirectly indicates the roughness of the surface of the substrate on the protective layer via the underlayer and the magnetic layer, so that the roughness can be controlled. Although not always easy, in the case of using a glass substrate, the roughness can be directly determined by the protective layer itself, so that the roughness can be controlled relatively easily.

[0007]

By the way, as described above, in order to realize high-density recording, it is important to realize high coercive force, low flying height, and high CSS durability. This alone is not enough. In other words, with higher density recording, higher reproduction output is also required, and regarding noise during reproduction, a level that has not been a problem in the past must be taken into consideration. It has become clear that we also have to improve.

According to the research conducted by the present inventors, these characteristics are exhibited when a magnetic film is formed by a sputtering method.
It has been found that it depends to a large extent on the composition of the magnetic film and the condition of the inert gas pressure during the formation of the magnetic film.

The present invention has been made under the background described above, and has a high coercive force and a high reproduction output, and
It is an object of the present invention to provide a magnetic recording medium that produces less noise during reproduction.

[0010]

In order to solve the above-mentioned problems, a method of manufacturing a magnetic recording medium according to the present invention has (Step 1) a step of forming at least an underlayer and a magnetic layer on a substrate. In the method of manufacturing a magnetic recording medium, the magnetic layer forming step is performed by sputtering Co _100-ab by sputtering under an inert gas pressure of 0.5 to 7 mTorr.
Ni _a Cr _b (however, a and b represent atomic%, and 20 ≦ a
≦ 30, 8 ≦ b ≦ 12) is formed, and a magnetic film having a composition of (30 ≦ 8 ≦ b ≦ 12) is formed. Or a first underlayer forming step of forming a first underlayer made of Ti, and Cr, Mo, Zr, B, Si, Zn,
A second underlayer forming step of forming a second underlayer composed of one or more layers containing an element selected from W, V, and Ta. (Structure 3) The structure is characterized in that the inert gas is a mixed gas containing Ar and Kr as main components.

[0011]

According to the above configuration 1, in the magnetic layer forming step, Co _100-ab Ni _a Cr is formed by sputtering under an inert gas pressure of 0.5 to 7 mTorr.
_b (however, a and b represent atomic%, and 20 ≦ a ≦ 30, 8
By forming the magnetic film having a composition of ≦ b ≦ 12, it becomes possible to obtain a magnetic recording medium having a high coercive force and a high reproduction output and having a small noise during reproduction.

The first reason is that the composition ratio of Co, Ni, and Cr makes the grain size of the magnetic grains in the magnetic film small and the zigzag domain wall generated in the transition region of the recording bit small. Therefore, it is considered that the medium noise is reduced, and at the same time, the improvement of coercive force due to the promotion of the magnetic separation degree between the magnetic grains contributes.

Secondly, the inert gas pressure is set to a low pressure of 0.5 to 7 mTorr during the film formation of the magnetic layer. By reducing the gas pressure to this extent, the probability that the sputtered particles will collide with the gas component is reduced, and the mean free path is lengthened. Therefore, the energy loss until the sputtered particles collide with the substrate is small, the magnetic separation degree of the magnetic particles is further increased by the implantation effect on the film, and the coercive force is increased by the synergistic effect with the separation side effect by the above composition. It is thought that they are making it higher.

Further, according to the structure 2, even if the thickness of the second underlayer is relatively thin due to the presence of the first underlayer, the growth of the crystal grains of the magnetic layer formed thereon can be made favorable. In addition, as the configuration 3, as the inert gas A
By using a mixed gas containing r and Kr as main components, it is possible to make the effect of the invention of the configuration 1 or 2 more remarkable.

[0015]

【Example】

(Embodiment 1) FIG. 1 is a schematic sectional view showing a structure of a magnetic recording medium manufactured by a method of manufacturing a magnetic recording medium according to a first embodiment of the present invention. Hereinafter, with reference to FIG.
The magnetic recording medium manufactured by the manufacturing method according to the first embodiment will be described, and then the manufacturing method of the magnetic recording medium of Example 1 will be described.

As shown in FIG. 1, the magnetic recording medium manufactured by the manufacturing method of this embodiment is, in short, on the glass substrate 1 in order of the first underlayer 2, the second underlayer 3, and the third underlayer. The magnetic disk has an underlayer 4, a magnetic layer 5, a protective layer 6, and a lubricating layer 7.

The glass substrate 1 is made of chemically strengthened glass having an outer diameter of 65 mmφ, a central hole diameter of 20 mmφ and a thickness of 0.9 mm.
Disk-shaped, and both main surfaces have a surface roughness of Rm
It was precision-polished to have an ax of 30 Å.

Here, the chemically strengthened glass constituting the glass substrate 1 contains SiO _{2 in a} weight percentage as a main component.
Is 62 to 75%, Al ₂ O ₃ is 5 to 15%, LiO ₂ is 4 to 10%, Na ₂ O is 4 to 12%, and ZrO ₂ is 5.5.
With each containing ~15%, Na ₂ O / ZrO
The weight ratio of ₂ is 0.5 to 2.0, the weight ratio of Al ₂ O ₃ / ZrO ₂ chemically strengthened glass is 0.4 to 2.5, N
What was chemically strengthened by ion exchange treatment in a treatment bath containing a ions and / or K ions (for details, see JP-A-5-32431) was used.

The first underlayer 2 is a thin film of Al having a thickness of about 60 Å.

The second base film 3 is a Cr film having a thickness of about 600 Å.

The third underlayer 4 is a Cr film having a thickness of about 1200 Å.

The magnetic layer 5 is a CoNiCr film having a thickness of about 500 Å. Here, the composition of the CoNiCr film is an atomic ratio of Co: Ni: Cr = 65: 25:
It has a composition of 10 (a = 25, b = 10).

The protective layer 6 comprises a Cr layer 61 having a thickness of about 50 Å formed on the magnetic layer 5 and a carbon (C) film having a thickness of about 300 Å formed on the Cr layer 61. It consists of two layers.

The lubricating layer 7 is a lubricant made of perfluoropolyether (for example, AM2001 manufactured by Montedison Co.).
Is applied to the protective film 6 by a dipping method to form a film thickness of about 20 Å.

Next, a method of manufacturing the magnetic recording medium of the above-mentioned embodiment will be described.

First, a chemically strengthened glass was prepared with an outer diameter of 65 mm.
φ, the hole diameter of the central part is 20 mmφ, and the thickness is 0.9 mm.
The glass substrate 1 is obtained by precision polishing so that the thickness becomes 0 angstrom.

Next, the glass substrate 1 is heat-treated, the first underlayer 2 is formed, the second underlayer 3 is formed, the third underlayer 4 is formed, and the magnetic layer 5 is formed on the glass substrate 1. Film forming and protective layer 6
Each step of the film formation is continuously performed using an in-line sputtering device.

As the in-line sputtering device, a well-known in-line type DC magnetron sputtering device was used. Although not shown, this in-line sputtering apparatus includes a first chamber in which a substrate heater is provided, a second chamber in which an Al target and a Cr target are sequentially installed, a Cr target and a Co target in the transport direction.
A third chamber in which a NiCr target is sequentially installed, and a fourth chamber in which a Cr target and a C (carbon) target are sequentially installed are provided.

Then, when the glass substrate 1 is introduced into the first chamber via the load lock chamber, the glass substrate 1 is successively transported in the respective chambers by a predetermined transport device at a predetermined constant speed. During that time, the following film formation and processing are performed.

That is, first, in the first chamber, the substrate is heated at 375 ° C. for 2 minutes.
In the second chamber, the first underlayer 2 has a film thickness of 60 Å and the second underlayer 3 has a film thickness of 60 Å.
A Cr film of 0 angstrom is sequentially formed. In the third chamber, a Cr film having a film thickness of 1200 angstrom as the third underlayer 4 and a CoCrTa film having a film thickness of 500 angstrom as the magnetic layer 5 are sequentially formed. Fourth
In this chamber, a Cr film 61 having a film thickness of 50 Å and a C film 62 having a film thickness of 300 Å, which form the protective layer 6, are sequentially formed. The pressure in each chamber is reduced to a pressure of 1 × 10 ⁻⁵ Torr or less,
As the sputtering gas, a mixed gas of argon (Ar; 80 to 98% by volume) and krypton (Kr; 2 to 20% by volume) is used. The sputtering gas pressure is 5 mTorr in the second chamber and 2 mTor in the third chamber.
rr, 5 mTorr in the fourth chamber.

Next, the substrate on which the protective layer 6 has been formed is taken out of the in-line sputtering apparatus, and the surface of the protective layer 6 is coated with perfluoropolyether by a spin coating method to form a lubricating layer having a thickness of 20 angstroms. 7 was formed to obtain a magnetic recording medium according to Example 1.

(Examples 2 to 4) 1.5 mTorr and 7 mT were obtained by changing only the pressure of the mixed gas of argon and krypton in the step of forming the magnetic layer 5 in Example 1 described above.
Those having an orr of 1.2 mTorr were Examples 2, 3, and 4, respectively.

(Embodiment 5) The composition is the same as that of Embodiment 1 except that the composition ratio of the magnetic layer 5 in Embodiment 1 is changed to Co: Ni: Cr = 67: 25: 8 (of the magnetic layer 5). Example 5 had a gas pressure of 2 mTorr during film formation.

(Embodiment 6) The composition ratio of the magnetic layer 5 in the embodiment 1 is set to Co: Ni: Cr = 64: 25: 11.
Example 6 was the same as Example 1 except that the magnetic pressure was 2 mTorr when the magnetic layer 5 was formed.

(Embodiment 7) The composition ratio of the magnetic layer 5 in Embodiment 1 is set to Co: Ni: Cr = 70: 20: 10.
And the gas pressure at the time of forming the magnetic layer 5 is 1.5 m
Example 7 has the same configuration as that of Example 1 except that it is changed to Torr.

(Embodiment 8) The composition ratio of the magnetic layer 5 in the above-mentioned Embodiment 1 is set to Co: Ni: Cr = 60: 30: 10.
And the gas pressure at the time of forming the magnetic layer 5 is 4 mTo
Example 8 has the same configuration as that of Example 1 except that it is changed to rr.

(Embodiment 9) Argon (Ar) alone is used as the inert gas in Embodiment 1 described above, and the composition ratio of the magnetic layer 5 is Co: Ni: Cr = 60: 30: 10. , The gas pressure when forming the magnetic layer 5 is 4 mTorr
Example 9 was the same as Example 1 except that it was changed to r.

(Comparative Examples 1 and 2) Argon alone was used as the inert gas in Example 1 described above, and the argon gas pressure in the process of forming the magnetic layer 5 was changed to 9 mTorr.
r, 15 mTorr (both exceed 7 mTorr)
Comparative Examples 1 and 2 were used.

(Comparative Example 3) The composition ratio of the magnetic layer 5 in Example 1 was set to Co: Ni: Cr = 69: 25: 6.
Comparative Example 3 had the same configuration as that of Example 1 except that (Cr was less than 8%) and the gas pressure during film formation of the magnetic layer 5 was changed to 5 mTorr.

(Comparative Example 4) The composition ratio of the magnetic layer 5 in Example 1 was set to Co: Ni: Cr = 60: 25: 15.
Comparative Example 4 had the same configuration as that of Example 1 except that (Cr exceeds 12%) and the gas pressure during film formation of the magnetic layer 5 was changed to 4 mTorr.

(Comparative Example 5) The composition ratio of the magnetic layer 5 in the above Example 1 was set to Co: Ni: Cr = 75: 15: 10.
Comparative Example 5 had the same configuration as that of Example 1 except that (Ni was less than 20%) and the gas pressure during film formation of the magnetic layer 5 was changed to 1 mTorr.

(Comparative Example 6) The composition ratio of the magnetic layer 5 in Example 1 was set to Co: Ni: Cr = 55: 35: 10.
Comparative Example 6 has the same configuration as that of Example 1 except that (Ni exceeds 30%) and the gas pressure during film formation of the magnetic layer 5 is changed to 3 mTorr.

FIG. 2 shows the above Examples 1 to 9 and Comparative Examples 1 to 1.
It is the figure which showed the result of having measured the characteristic of the magnetic recording medium of 6 as a table.

The coercive force (Hc) was measured by cutting out a sample of 8 mmφ from the manufactured magnetic recording medium, applying a magnetic field in the film surface direction, and measuring the maximum external applied magnetic field of 10 kOe with a vibrating sample magnetometer. .

The recording / reproducing characteristics (reproducing output and medium noise) were measured as follows. That is, by using the obtained magnetic disk, the flying height of the magnetic head is 0.
A thin film head of 055 μm is used, the relative speed between the thin film head and the magnetic disk is 6 m / s, and the linear recording density is 70 kfcc.
The recording / reproducing output at (linear recording density of 70,000 bits per inch) was measured. Further, the noise spectrum during signal recording and reproduction was measured by a spectrum analyzer with a carrier frequency of 8.5 MHz and a measurement band of 15 MHz. The thin film head used in this measurement has 50 coil turns, a track width of 6 μm, and a magnetic head gap length of 0.25 μm.

As is clear from the table of FIG. 2, the inert gas pressure in the step of forming the magnetic layer 5 is 0.5 to 7 mTorr.
r, and the composition of the magnetic layer 5 formed is Co
_100-ab Ni _a Cr _b (however, a and b represent atomic%,
20 ≦ a ≦ 30 and 8 ≦ b ≦ 12), all the obtained magnetic recording media have a coercive force of 1580.
It can be seen that it has excellent characteristics of Oe or more, reproduction output of 165 μV or more, and medium noise of 2.8 μVrms or less.

On the other hand, the argon gas pressure during the film forming process of the magnetic layer 5 was 9 mTorr and was 7 mT.
In Comparative Example 1 exceeding orr, the coercive force is 1500 O
e, the reproduction output is 160 μV, which is lower than that of each example, and conversely, the medium noise is 2.9 μVrms, which is larger than that of any example, and any of the characteristics is inferior to the examples.

Similarly, the argon gas pressure is set to 15 mTorr.
In Comparative Example 2 in which r is even larger and exceeds 7 mTorr,
The coercive force was 1400 Oe and the reproduction output was 155 μV, which were all lower than those of the examples, and conversely, the medium noise was 3.1 μVrms, which was larger.
It is further inferior to the examples.

Also, in Comparative Example 3 in which the Cr content in the composition of the magnetic layer 5 was 6% and less than 8%, the coercive force was 1500 Oe and the reproduction output was 160 μV. On the contrary, the medium noise is 3.0 μVrms, which is higher than that of any of the examples, and the characteristics are inferior to those of the examples.

Further, in Comparative Example 4 in which the Cr content in the composition of the magnetic layer 5 is 15% and exceeds 12%, the medium noise is 2.3 μVrms, which is at the same level as that of the example, but the coercive force. Is 1570 Oe, playback output is 15
At 5 μV, all of them are lower than those of the examples, so that the overall characteristics are inferior to the examples.

The Ni content in the composition of the magnetic layer 5 is 1
In Comparative Example 5, which is 5% and less than 20%,
The coercive force is 1300 Oe and the reproduction output is 155 μV, which are lower than those of the examples, and conversely, the medium noise is 4.
The value is 1 μVrms, which is higher than any of the examples, and any of the characteristics is inferior to the examples.

The Ni content in the composition of the magnetic layer 5 is 3
In Comparative Example 6 which is 5% and exceeds 30%, the coercive force is 1600 Oe, which is equivalent to that of the embodiment, and the medium noise is also low, that is, 2.2 μVrms, which is equivalent to that of the embodiment, but the reproduction output is 150 μV. Since it is lower than each example, the overall characteristics are inferior to the examples.

Although the present invention has been described with reference to the embodiments, the present invention includes the following modifications and applications.

In the above-mentioned embodiments, an example in which aluminosilicate-based chemically strengthened glass is used as the substrate is given.
Other glasses such as borosilicate, aluminoborosilicate, quartz glass and soda lime glass can be used. These can be easily finished by polishing the surface to a surface roughness Rmax of 100 angstroms or less. Further, the outer diameter of the substrate may be smaller and the thickness may be thinner. Furthermore, the substrate does not have to be glass, and may be an aluminum substrate, a ceramic substrate, or a polymer film.

Further, in the embodiment, the case where the first underlayer is Al is mentioned, but this is not limited to Ti, Si, Pb, Cu,
The main component may be any one or more of In and Ga.

Further, in the embodiment, the case where the second underlayer is Cr is mentioned, but it is TiW, Mo, Ti, T.
A non-magnetic material such as a, W, Zr, Cu, Al, Zn, In or Sn can be used. In addition, these underlayers are 2
It may be composed of more than one layer.

The base layer, the magnetic layer, the protective layer and the like can of course be formed by using a normal sputtering apparatus, that is, a static facing type sputtering apparatus, instead of the in-line sputtering apparatus.

Further, in the embodiment, the example in which the protective layer has a two-layer structure of the Cr layer and the C layer is given. However, as the protective layer, another material may be used instead of the Cr layer. , As examples thereof, Mo, Ti, TiW, CrMo, Ta, W,
Non-magnetic materials such as Si and Ge, or oxides of these,
Nitride, carbide, etc. may be used. In addition, this layer may be two or more layers. Further, instead of the C layer, for example, a SiO ₂ , SiN, SiC, ZrO ₂ film may be used, or a hard material such as silica particles may be dispersed in a film material such as an organic silicon compound.

Further, although perfluoropolyether was used as the material of the lubricating layer in the examples, a fluorocarbon liquid lubricant or a lubricant consisting of an alkali metal salt of sulfonic acid can also be used. The film thickness is preferably 10 to 30 Å, and the reason is 10
If it is less than angstrom, the wear resistance cannot be sufficiently improved, and if it exceeds 30 angstrom, the wear resistance is not improved and a problem of spacing loss occurs.

[0060]

As described above in detail, according to the present invention, in the magnetic layer forming step, Co _{100-ab is formed} by sputtering under an inert gas pressure of 0.5 to 7 mTorr.
Ni _a Cr _b (however, a and b represent atomic%, and 20 ≦ a
By forming a magnetic film having a composition of ≦ 30 and 8 ≦ b ≦ 12, it is possible to obtain a magnetic recording medium having a high coercive force and a high reproduction output, and a small noise during reproduction. It is the one.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a magnetic recording medium manufactured by a method of manufacturing a magnetic recording medium according to a first embodiment of the present invention.

FIG. 2 is a table showing the results of measuring the characteristics of the magnetic recording media of Examples 1-9 and Comparative Examples 1-6.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... 1st foundation layer, 3 ... 2nd foundation layer, 4
... third underlayer, 5 ... magnetic layer, 6 ... protective layer, 7 ... lubricating layer.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number for FI Technical indication H01F 41/18 H01F 41/18 (72) Inventor Isao Kawaka 2-7 Nakachuai, Shinjuku-ku, Tokyo No. 5 In Hoya Co., Ltd. (72) Inventor Hisao Kawai 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo In Hoya Co., Ltd.

Claims (3)

[Claims] 1. A method of manufacturing a magnetic recording medium, comprising the steps of forming at least an underlayer and a magnetic layer on a substrate, wherein the magnetic layer forming step is sputtering under an inert gas pressure of 0.5 to 7 mTorr. By Co
_100-ab Ni _a Cr _b (however, a and b represent atomic%,
20 ≦ a ≦ 30, 8 ≦ b ≦ 12). A method for producing a magnetic recording medium, comprising forming a magnetic film having a composition of 20 ≦ a ≦ 30 and 8 ≦ b ≦ 12. 2. The first underlayer forming step of forming a first underlayer made of Al or Ti, and the C underlayer forming step,
a second underlayer forming step of forming a second underlayer composed of one or more layers containing an element selected from r, Mo, Zr, B, Si, Zn, W, V and Ta. The method of manufacturing a magnetic recording medium according to claim 1. 3. The gas mixture according to claim 1, wherein the inert gas is a mixed gas containing Ar and Kr as main components.
A method of manufacturing a magnetic recording medium according to 1.