JPS62256217A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve corrosion resistance without spoiling reproduction output by successively laminating a magnetic recording layer essentially consisting of Co, and magnetic recording layer essentially consisting of Co and Cr on a nonmagnetic substrate. CONSTITUTION:A smooth layer 12, an underlying layer 13, the magnetic recording layer 14 and a protective lubricating layer 17 are successively formed on the nonmagnetic substrate 11 consisting of an Al alloy, etc. The layer 14 consists of the 1st magnetic recording layer essentially consisting of Co and the 2nd magnetic recording layer 16 essentially consisting of Co-Cr on the layer 15. The layer 15 may be formed by using Co and Ni as the essential components or adding one kind among Fe, P. W, Pt, and Cr to Co and Ni or incorporating one kind among Pt, Y, La, Ce, Pr, Sm, Nd, and Pm as the essential component to Co. The film thickness of the layer 15 is preferably 400-800Angstrom and the film thickness of the layer 16 is preferably 300-500Angstrom . Oxygen is preferably incorporated into the layer 15.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to magnetic recording media.

(Prior Art) Most of the magnetic recording media currently in practical use have discontinuous media. The magnetic recording layer of this discontinuous medium is F
Magnetic particles such as e, Fe-Go, Fe2 o3 ° CrO2, etc. are mixed and dispersed in a binder made of organic resin, and the mixture is coated on a substrate, dried, and fired. However, as the density of recording media has increased in recent years, the magnetic recording layer has become thinner, meaning continuous thin film media in which the magnetic material is continuous within the medium, in other words, the magnetic recording layer has become thinner and has a larger coercive force. Film forming methods are shifting from mold to plating or sputtering methods.

Under such circumstances, the requirements for magnetic recording media are that the magnetic recording layer be thin and that sufficient reproduction output can be obtained. Such media generally have a magnetic recording layer made of a cobalt alloy. This type of magnetic recording medium usually has a non-magnetic base (1
), on which a smooth layer (2) is formed, an underlayer (3) mainly made of Cr is formed, a magnetic recording layer (4) is formed on top of this, and a protective and lubricating layer (5) is formed on the outermost surface. ).

(Problems to be Solved by the Invention) When a CO-Ni alloy is used as a magnetic recording layer, the thickness of the magnetic recording layer is 500 mm to 1 mm in order to obtain sufficient reproduction output.
oo people is enough. However, Co-Ni alloy alone has poor corrosion resistance, and in order to compensate for this, several hundred people have added non-magnetic layers with excellent corrosion resistance such as ACI and Cr on the magnetic recording layer. (U.S. Patent Specification Box 3.5)
20.664). However, when considering the reproduction output, it is generally said that the flying height of the magnetic head from the disk (LA magnetic recording medium) must be around 2000.For this reason, the thickness of the non-magnetic layer is approximately several hundred. This increased distance from the magnetic head to the magnetic recording layer resulted in a reduction in reproduction output due to spacing loss.

On the other hand, when a Go-Cr alloy is used as the magnetic recording layer, although it has excellent corrosion resistance, the problem inherent to the material is that the amount of saturation magnetization is small. It must be between 2,000 and 2,000 people.

Considering the future trend toward higher densities, Co-Ni alloys are a major hindrance in terms of corrosion resistance, and CO-Cr alloys are limited in their ability to be made into thin films. development was desired.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic recording medium having a magnetic recording layer that is excellent in corrosion resistance and does not impair reproduction output.

[Structure of the invention]

(Means and effects for solving the problems) The present invention provides a magnetic recording medium in which a magnetic recording layer is formed by a thin film deposition method, in which the magnetic recording layer is a first magnetic recording layer containing CO as a main component. , and a second magnetic recording layer mainly composed of CO and Cr formed on the first magnetic recording layer. As a thin film deposition method, a vacuum evaporation method, a spackle method, an ion blating method, a plating method, etc. are used.

The first magnetic recording layer suppresses an increase in film thickness and still provides good reproduction output. The second magnetic recording layer is
In addition to improving the corrosion resistance of the magnetic recording layer, its magnetic properties improve spacing loss due to increased film thickness.

The first magnetic recording layer is a layer mainly composed of Co--Ni containing 10 to 30 at% Ni and having a thickness of not more than 2000 nm.

Alternatively, the first magnetic recording layer may include CO, Pt, Y, L.
The main component is at least one element X selected from a, Ce, Pr, Sm, Nd, and pm. These Co
Elements other than
This is a layer whose main component is CO-X, which does not exceed 0.00 people.

Alternatively, the first magnetic recording layer is made by adding at least one element X selected from Fe, P, W, Pt, and Cr to CO and Ni. Nt 10 to 3
Thickness 2 containing 0 at% and 30 at% or less of additive element X
This is a layer whose main component is co-Ni-X and does not exceed 1,000 people. Additive element . When Fe is used as the additive element X, the saturation magnetization and squareness ratio are excellent compared to when only Co--Ni is used. When the additive element X is Pt, W, or P, the coercive force and squareness ratio are excellent. When the additive element X is Cr,
It increases coercive force and improves corrosion resistance.

The second magnetic recording layer is a layer mainly composed of Co--Cr containing 10 to 30 at% Cr and having a thickness of 100 to 1000 yen. The thinner the second magnetic recording layer is, the better, as long as it has corrosion resistance.

When the first magnetic recording layer mainly contains Co and N1 and the second magnetic recording layer mainly contains CO and Cr, the thickness of the first magnetic recording layer is 400 to 800 mm, and the second magnetic recording layer is 400 to 800 mm thick. By setting the thickness of the magnetic recording layer to 300 to 500 layers, an extremely stable high-density recording medium can be obtained.

The inventors have developed a first magnetic recording layer mainly composed of CO and Ni containing 10 to 30 at% Ni, and a second magnetic recording layer mainly composed of GO and Cr containing 10 to 30 at% Cr. In the magnetic recording medium having the following, various thicknesses of the first and second magnetic recording layers, which exhibit good reproduction output and excellent corrosion resistance, were examined.

First, in order to examine the corrosion resistance, an accelerated test was conducted by varying the thickness of the second magnetic recording layer made of Co--Cr from 100 to 1000 layers. The test was conducted at a temperature of 85℃ and a humidity of 8
The medium was left in a 5% constant temperature bath, and corrosion was compared based on the increase in defects. The results are shown in Figure 2. A significant increase in corrosion occurred when the Co--Cr thickness was less than 300 mm.

At this time, the thickness of the first magnetic recording layer made of Co--Ni was varied from 100 to 10,008, but the corrosion state did not depend on this thickness but only on the second magnetic recording layer. In addition, in actual media, whether a carbon lubricant layer of 100 to 300 layers is formed on the outermost surface or not depends on the presence or absence of this layer.

Next, the thickness of each layer was examined from the signal output and S/N value. The signal output with respect to the thickness of the first magnetic recording layer (Co--Ni) is as shown by the curve (18) in FIG. If the signal output and film thickness are selected within a range where the S/N ratio does not decrease, the range from 500 to 1000 will be good. If the second magnetic recording layer (Co-Cr) is laminated here, the second magnetic recording layer itself contributes to the signal, so the optimal range is the curve (20
When HCO-Cr is 300 people), the thinner one is better. However, when the number of people in the second magnetic recording layer exceeds 500, the thickness of the entire magnetic recording layer increases, and the recording density characteristics rapidly deteriorate.

From the above study results, it was found that an extremely stable high-density recording medium can be created by using 400 to 800 people for the first magnetic recording layer and 300 to 500 people for the second magnetic recording layer. .

Furthermore, by adding oxygen in the range of 5 to 15% to the first magnetic recording layer, magnetic properties and coercive force (Hc) can be improved, and it is possible to create a high-density recording medium. was discovered.

Note that a low coercive force material layer, such as a permalloy layer, is formed as an underlayer for a C0-Cr magnetic recording layer.
It is described in Publication No. 51804.

However, this uses CO--Cr as the perpendicular magnetization medium, and the underlying low coercive force material layer functions to concentrate the magnetic flux from the auxiliary magnetic pole of the perpendicular recording magnetic head onto the main magnetic pole. Therefore, the underlying low coercive force material layer does not function as a magnetic recording layer, and is clearly different from the present invention.

(Example 1) FIG. 1 is a partial sectional view of the magnetic recording medium of the present invention.

In Fig. 1, a 3.5-inch aluminum alloy disk is used as the non-magnetic substrate (11), and the surface is coated with Ni.
- Non-magnetic smooth layer (12) with PM gold and mirror polishing
was formed. A magnetic recording layer, a protective layer, a lubricating layer, etc. were formed on this using a bipolar high-frequency sputtering device. The film forming method and film forming conditions are as follows. In order to make the film thickness and magnetic properties uniform, the substrate mounting table was rotatable and rotated at 6 rpm. The initial vacuum level for film formation is 8.0.
At X10-7 TOrr, the introduced Ar gas pressure was set to 4. Ox
to'Torr, sputtering power 300W,
The test was carried out at room temperature. First, 3,000 Cr layers were formed as an underlayer (13) to improve the crystallinity of the magnetic recording layer. On top of that, as a first magnetic recording layer (15), about 700 layers of C0-Ni are applied, and then a second magnetic recording layer (IL!) is applied.
Approximately 700 pieces of Co--Cr were also formed as (16) to form a two-layer magnetic recording layer (14). Also,
A protective/lubricating layer (17) made of a carbon film of 300 to 500 layers was provided on the outermost layer.

When the magnetic properties of the magnetic recording medium thus prepared were measured, an in-plane coercivity cuff of 00 oersted was obtained, and excellent results were also obtained regarding the amount of saturation magnetization and other magnetic properties.

Further, as a result of electromagnetic conversion characteristics, head wear tests, and environmental tests, the following characteristics were obtained. Regarding electromagnetic conversion characteristics, high-density recording of 20 kbpi to 40 kbpi was possible. In the wear test with the magnetic head, we conducted a contact start/stop test of 20,000 times, which is the standard practice, and confirmed that there were no scratches on the disk surface.

In addition, regarding environmental resistance, the temperature is 80°C, the relative humidity is 80°C,
After being left at 0% for 700 hours, no change in appearance was observed and there was no increase in the number of defects, confirming sufficient corrosion resistance.

(Example 2) Similarly to Example 1, an aluminum alloy nonmagnetic substrate (11
), and the surface was anodized to alumina (A1
A non-magnetic smooth layer (12) made of a non-metallic layer (203) is formed, and a non-magnetic metal underlayer (13) is then formed as in the previous example.
), first and second magnetic recording layers (15), (16), and protection/lubrication@(17) were formed.

In this example as well, the same effects as in Example 1 were obtained.

(Example 3) A 3.5-inch aluminum alloy disk was used as the nonmagnetic substrate (11), and a nonmagnetic smooth layer (12) whose surface was N*-p plated and mirror polished was formed. 3,000 layers of Cr were formed as the underlayer (13), and about 700 layers of Co-3m containing 5 m of 16 at% were formed thereon as the first magnetic recording layer (15), and then the second magnetic recording layer (15) was formed.
As 16), about 500 pieces of Co--Cr were similarly formed to form a two-layer magnetic recording layer (14).

Further, a protective/lubricating layer (17) made of a carbon film with a thickness of 300Δ to 500Δ was provided on the outermost surface.

When the magnetic properties of this magnetic recording medium were measured, an in-plane coercive force of 800 Oe was obtained, and excellent results were also obtained regarding the amount of saturation magnetization and other magnetic properties. Furthermore, as a result of electromagnetic conversion characteristics, wear tests with magnetic heads, and environmental tests, the following characteristics were obtained. Regarding electromagnetic conversion characteristics, see 2.
High density recording of 0 kbp i to 40 kbp i was possible. In the wear test with the magnetic head, we conducted 20,000 contact start/stop tests and confirmed that there was no scratch on the disk surface.

In addition, regarding environmental resistance, the temperature is 80°C and the relative humidity is 80°C.
% for 700 hours, no change in appearance was observed, no increase in defective areas, and sufficient corrosion resistance was confirmed.

(Example 4) = 12 - first magnetic recording M (15), (:, e 20a
Approximately 6()0 Co-Ce containing t% was formed. Other conditions were the same as in Example 3. The magnetic properties of the medium thus formed have a coercive cuff of 50 oersted, and the electromagnetic conversion properties include a low frequency output of 1.0 mV, a linear recording density (
D50) 28kbpi was obtained. In addition, the corrosion resistance was also shown in Example 3.
obtained similar results.

(Example 5) A 3.5-inch aluminum alloy disk was used as the nonmagnetic substrate (11), and a nonmagnetic smooth layer (12) whose surface was plated with N1-P and mirror-polished was formed. Next, an underlayer (13) for improving the crystallinity of the magnetic recording layer.
As a result, 3,000 Cr members were formed.

On top of that, as the first magnetic recording @ (15), Ni1
7 at%, Fe, 8 at% and other Co
-N 1-Fe by about 700 people, then the second magnetic recording layer (
As 16), Co-Cr is also formed to a thickness of about 500A,
A magnetic recording layer (14) consisting of two layers was constructed. In addition, a protective/lubricating layer (17) made of 300 to 500 carbon films was provided on the outermost surface.

When the magnetic properties of the magnetic recording medium thus prepared were measured, an in-plane coercive cuff of 00 eels was obtained, and the saturation magnetization was increased by about 15% compared to the Co--Ni system. Furthermore, as a result of electromagnetic conversion characteristics, wear tests with magnetic heads, and environmental tests, the following characteristics were obtained. Regarding electromagnetic conversion characteristics, high-density recording of 20 kbp i to 40 kbp i was possible. Furthermore, an increase in output j was observed with an increase in saturation magnetization. In the wear test with the magnetic head, we conducted 20,000 contact start/stop tests and confirmed that there was no scratch on the disk surface.

In addition, regarding environmental resistance, the temperature is 80'C, the relative humidity is 80'C,
After being left at 0% for 700 hours, no change in appearance was observed and there was no increase in the number of defects, confirming sufficient corrosion resistance.

(Example 6) As the first magnetic recording layer (15), Ni15a1%, P
About 700% of Co--Ni--Pl- was formed with a composition of t5% and the rest being Co. Other conditions were the same as in Example 5. The magnetic properties of the medium thus formed have a coercive cuff of 50 oersted, and the electromagnetic conversion properties have a low frequency output of 1
．． At 0 mV, the linear recording density (D50
) 26 kbpi exceeded the 22 kbpi of the CoN i system.

(Example 7) As the first magnetic recording layer (15), Ni 25at%
About 700 people formed Co--Ni--Cr with a composition of 7% Cr and the rest Co. Other conditions were the same as in Example 5. The characteristics of the medium created in this way are as follows:
Oersted, low l or output 0.95mV, D5 (, 24
kbpi, which exceeded the Qo-Ni-based media.

(Example 8) In Fig. 1, a 3.5-inch aluminum alloy disk is used with a non-magnetic substrate (11) bound, and the surface is coated with N1
-Nonmagnetic smooth layer (12) with P plating and mirror polishing
was formed. First, 2000 Cr layers were formed as an underlayer (13) to improve the crystallinity of the magnetic recording layer. On top of that, Co-
A magnetic recording layer (14) consisting of two layers was formed by forming 500 mm of Nr and then 400 mm of Co--Cr as a second magnetic recording layer (16). In addition, a protective/lubricating layer (17) made of 200 carbon films was provided on the outermost layer.

When the magnetic properties of the magnetic recording medium thus prepared were measured, an in-plane coercive force of 800 oersted was obtained, and excellent results were also obtained regarding the amount of saturation magnetization and other magnetic properties. Furthermore, as a result of electromagnetic conversion characteristics, wear tests with magnetic heads, and environmental tests, the following characteristics were obtained. Regarding electromagnetic conversion characteristics, high-density recording of 30 kbp i was possible. In the wear test with the magnetic head, we conducted 20,000 contact start/stop tests and confirmed that there was no scratch on the disk surface.

In addition, regarding environmental resistance, the temperature is 85°C, the relative humidity is 8
Although it was allowed to stand at 5% for 1000 hours, no changes in appearance were observed, and there was no increase in the number of defects, confirming sufficient corrosion resistance.

(Example 9) Using an aluminum alloy nonmagnetic substrate (11), the surface thereof was anodized to form a nonmagnetic smooth layer (12) of a nonmetallic layer of alumina (A1203), and the rest was the same as in Example 8. A nonmagnetic metal underlayer (13), first and second magnetic recording layers (15) and (16), and a protective/lubricant layer (17) were formed on the substrate. However, the first magnetic recording layer (15) has introduced Ar.
C containing 10% oxygen by mixing 30% oxygen into the gas
An o-Nr-o film was deposited.

In this example, an in-plane coercive force of 850 oersted was obtained, and the electromagnetic conversion characteristics were increased to 32 kbf),
Regarding durability and corrosion resistance, the same effects as in the previous example were obtained.

(Example 10) As shown in FIG.
A 5 inch glass with a smooth surface was used.

A magnetic recording layer, a protective layer, a lubricating layer, etc. were formed on this using a magnetron type high frequency sputtering device.

The film forming method and film forming conditions are as follows. 3. In order to make the film thickness and magnetic properties uniform, the substrate mounting table was rotatable and rotated at an iorpm. The film was formed at an initial vacuum level of 5.0X 10' TOrr and an Ar gas pressure of 3.
, OX 1O-2 TOrr, sputtering power 100OW, and room temperature. First, CR was used as an underlayer (23) to improve the crystallinity of the magnetic recording layer.
3,500 people were formed. On top of that, a first magnetic recording layer (
As 24), about 450 people formed Co-Ni-Fe with a composition of Ni 17 at%, Fe 8 at%, and Co as the second magnetic recording layer (25), and then about 300 people formed Co-Cr as the second magnetic recording layer (25). A magnetic recording layer (26) consisting of two layers was constructed. In addition, a protective/lubricating layer (27) made of 200 carbon films was installed on the outermost layer.

When the magnetic properties of the magnetic recording medium thus prepared were measured, an in-plane coercive force of 900 oersted was obtained, and the saturation magnetization was increased by about 15% compared to the co-Ni system. Furthermore, as a result of electromagnetic conversion characteristics, wear tests with magnetic heads, and environmental tests, the following characteristics were obtained. Regarding electromagnetic conversion characteristics, high-density recording of 34 kbp i was possible. Also,
An increase in output was observed with an increase in saturation magnetization. In the wear test with the magnetic head, we conducted 20,000 contact start/stop tests and confirmed that there was no scratch on the disk surface.

In addition, regarding environmental resistance, the temperature is 85°C, the relative humidity is 8
Although it was left at 5% for 1000 hours, no change in appearance was observed and there was no increase in the number of defects, confirming excellent corrosion resistance.

(Example 11) In Fig. 5, a 3.5-inch glass with a smooth surface was used as the nonmagnetic substrate (31).A magnetic recording layer, protective layer, lubricant layer, etc. were formed on this using a magnetron-type high-frequency sputtering device. The film-forming method and film-forming strip A1 were as follows.In order to make the film thickness and magnetic properties uniform, the substrate mounting table was capable of rotation and revolution, and the table was rotated at 6 ppm.Film-forming is the initial vacuum level 5.OX 1O-7To
With rr, increase the introduction △r gas pressure to 4. OX 1O-2 Tor
The sputtering was carried out at room temperature and a sputtering power of 1000 W. First, 700 layers of CO-sm containing 16 at% Sm were formed as the first magnetic recording layer (32), then 300 layers of C0-Cr were formed on the second magnetic recording layer (33). A magnetic recording layer (34) was constructed. In addition, a protective/lubricating layer (35) made of 300 carbon films was installed on the outermost layer.

When the magnetic properties of the magnetic recording medium thus prepared were measured, an in-plane coercive force of 900 Oe was obtained, and excellent results were also obtained regarding the amount of saturation magnetization and other magnetic properties.

Furthermore, as a result of electromagnetic conversion characteristics, wear tests with magnetic heads, and environmental tests, the following characteristics were obtained. Regarding electromagnetic conversion characteristics, high-density recording of 34 kbpi was possible.

In the wear test with the magnetic head, we conducted 20,000 contact start/stop tests and confirmed that there was no scratch on the disk surface.

In addition, regarding environmental resistance, the temperature is 85°C and the relative humidity is 85°C.
% for 1000 hours, no change in appearance was observed, no increase in defective areas, and sufficient corrosion resistance was confirmed.

(Example 12) As shown in FIG. 6, 5.
A 25-inch aluminum alloy disk was used, and a nonmagnetic smooth layer (42) with N'i-P plating and mirror polishing was formed on the surface. A magnetic recording layer, a protective layer, a lubricating layer, etc. were formed on this using a magnetron type high frequency sputtering device. The film forming method and film forming conditions are as follows. In order to make the film thickness and magnetic properties uniform, the substrate mounting table was rotatable and rotated at an iorpm. Film formation is performed at an initial vacuum level of 5. Ox 10'Torr, introduction △r gas pressure 4. Oxio"rorr, sputtering power of 1000 W, and room temperature. About 700 people used Co-3m containing Sm1Bat% as the first magnetic recording layer (42), and then the second magnetic recording layer (42). 4
As for 3), about 500 pieces of co-Cr were also formed to form a two-layer magnetic recording layer (45). In addition, the outermost layer is a protective and lubricating layer made of 300 carbon films (46).
has been established.

When the magnetic properties of the magnetic recording medium thus prepared were measured, an in-plane coercive force of 950 oersted was obtained, and excellent results were also obtained regarding the amount of saturation magnetization and other magnetic properties.

Furthermore, as a result of electromagnetic conversion characteristics, wear tests with magnetic heads, and environmental tests, the following characteristics were obtained. Regarding electromagnetic conversion characteristics, high-density recording of 36 kbp i was possible. In the wear test with the magnetic head, we conducted 20,000 contact start/stop tests and confirmed that there was no scratch on the disk surface.

In addition, regarding environmental resistance, the temperature is 85°C and the relative humidity is 85°C.
% for 100 hours, no change in appearance was observed, no increase in defective areas, and sufficient corrosion resistance was confirmed.

〔Effect of the invention〕

As described above, according to the present invention, by providing two magnetic recording layers with different functions, it is possible to provide a magnetic recording medium that has excellent corrosion resistance and can be made thinner for higher density.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a magnetic recording medium according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the film thickness of the second magnetic recording layer and the increase in the number of defects in a corrosion test, and FIG. FIG. 4, FIG. 5, and FIG. 6 are partial cross-sectional views of a magnetic recording medium according to another embodiment of the present invention, respectively. FIG. 7 is a partial cross-sectional view of a conventional magnetic recording medium. (11)...Nonmagnetic base (12)...Nonmagnetic smooth layer (13)...Nonmagnetic metal underlayer (14)...Magnetic recording layer (15)...First magnetic recording Layer (16)...Second magnetic recording layer (17)...Protection/smooth layer Agent Patent attorney Nori Chika Yudo Norio Ogo Figure 4 Figure 5

Claims (8)

[Claims] (1) A first magnetic recording layer mainly composed of cobalt formed on a nonmagnetic substrate, and a second magnetic recording layer mainly composed of cobalt and chromium formed on this first magnetic recording layer. A magnetic recording medium having a layer. (2) The magnetic recording medium according to claim 1, wherein the first magnetic recording layer contains cobalt and nickel as main components. (3) A patent claim characterized in that the first magnetic recording layer mainly contains cobalt and nickel, and at least one element selected from iron, phosphorus, tungsten, platinum, and chromium. The magnetic recording medium according to item 2. (4) The first magnetic recording layer includes platinum, yttrium,
At least one selected from lanthanum, cerium, praseodymium, samarium, neodymium, and promethium
The magnetic recording medium according to claim 1, characterized in that the magnetic recording medium contains a seed element as a main component. (5) The thickness of the first magnetic recording layer is 400 Å to 80 Å.
0 Å, and the film thickness of the second magnetic recording layer is 300 Å to 50 Å.
Claim 2 characterized in that it is in the range of 0 Å.
Magnetic recording medium described in Section 1. (6) The magnetic recording medium according to claim 2, wherein the first magnetic recording layer contains oxygen. (7) The magnetic recording medium according to claim 6, wherein the oxygen content is in the range of 5 at% to 15 at%. (8) The magnetic recording medium according to claim 1, further comprising a protective/lubricant layer formed on the second magnetic recording layer.