JPS6085433A - Magnetic recording material - Google Patents

Abstract

PURPOSE:To provide a practical durability and attain a uniform reproduced output by oxidizing a metallic thin film, which has a resistance to oxidation lower than that of a magnetic layer and consists essentially of Co, to form a protective layer. CONSTITUTION:The metallic thin film which has a resistance to oxidation lower than that of the magnetic layer and consists essentially of Co is oxidized to form the protective layer of a magnetic recording medium. This metallic thin film where an oxide is formed of the protective layer must have a resistance to oxidation lower than that of the magnetic layer and must contain Co and must have uniform composition and thickness and must be continuous. For the purpose of obtaining the protective layer having a sufficient durability, it is necessary that the thickness of the metallic thin film is >=0.005mum, and it is desirable that the metallic thin film contains >=50% Co. The metallic thin film is oxidized by the method where it is left in constant-temperature and constant- humidity environments, the thermal oxidation method, the anodic oxidation method, the method using an oxidizer or acid treatment, the method where it is sintered in air, or the like, or cominations of these methods.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to magnetic recording bodies such as magnetic disks, magnetic drums, and magnetic tapes used in magnetic recording devices.

In recent years, magnetic disks and the like using a magnetic metal thin film as a recording medium (magnetic layer) have begun to be used as high-density magnetic recording bodies. The advantage of using a magnetic metal thin film for a recording medium is that it has a high saturation magnetic flux density, so the medium can be made thin, and it also has a high coercive force, making it suitable for high-density recording. Another advantage of magnetic metal thin films is that they can be easily fabricated by methods such as electroless plating, electroplating, sputtering, and vapor deposition.

By the way, the demand for higher recording densities in magnetic recording devices is increasing year by year. Reducing the separation length has become essential. Magnetic recording media such as magnetic tapes and 70 disks are used in contact with or close to a magnetic head in order to maximize recording density. In addition, in the case of magnetic disks in which the magnetic head is used by floating a minute distance from the magnetic recording material, as the performance of the magnetic recording device increases, the load on the magnetic head is reduced in order to reduce the flying distance. Contact start/stop (contact start/stop.

C55) type head flotation system is adopted. For this reason, damage to the magnetic recording medium due to the magnetic head often occurs. An effective method for preventing this is to provide a protective layer on the surface of the magnetic metal thin film, and efforts have been made to improve durability. As a protective layer, it has wear resistance and
- It must have magnetism, smoothness and strong adhesion, and be made as thin as possible. Various studies have been made for these purposes, but all have been insufficient.

Conventionally, there has been a method proposed in which a high hardness metal such as Rh or Cr is coated on the surface of the medium by electroplating. This has the disadvantage of substantially increasing the thickness of the protective layer.

Alternatively, metals such as Cr and W, 8 s 01 ,
-AA% There is a method of coating the surface of the medium with an oxide such as Os by means such as vapor deposition or sputtering, but the adhesion is insufficient and there are problems with productivity because the coating is produced in a vacuum system.

The surface of a Co or Co-Ni magnetic metal thin film is oxidized to form a protective layer with excellent wear resistance and adhesion.

A method of forming an oxide film of 0.0 was proposed.

For example, Special Publication No. 42-20025, USP 3,3
No. 53,166 proposed a method of oxidizing Co present on the surface of a metal thin film in an oxidizing atmosphere with controlled temperature and humidity to form a protective oxide film. In order to obtain a stronger oxide film, a method of anodizing, a method of acid treatment, and a method of firing in air (Japanese Patent Publication No. 49-294
No. 45, [J8P No. 3,719,525), etc. were proposed. However, with the above method, it is difficult to obtain a uniform CO oxide film over a wide treated area, and the uniformity of the reproduction output is impaired due to variations in the thickness of the protective oxide film and variations in the thickness of the residual magnetic layer. However, there was a problem in that bit errors sometimes occurred frequently. Therefore, as a method to improve this, [J8P 4,124,73
As shown in No. 6, a method has been proposed in which an intermediate layer that serves as a barrier to oxidation treatment is formed between a magnetic layer of a storage medium and a metal layer for obtaining a protective oxide film. By providing such an intermediate layer, the purpose was to prevent the reaction caused by the oxidation treatment from reaching the magnetic layer and to obtain a protective oxide film with a uniform thickness. In order to prevent corrosion and obtain a sufficient barrier effect, it was necessary to make the intermediate layer extremely thick. As described above, forming a thick intermediate layer between the recording medium and the protective oxide film, which acts as a barrier to oxidation treatment, substantially increases the thickness of the protective film, resulting in a significant deterioration of recording and reproducing characteristics.

Furthermore, as the number of laminated layers of the recording medium, intermediate layer, protective layer, and thin film increases, the process becomes more complicated and productivity is impaired. In addition, when a Ni alloy is used in the intermediate layer and oxidation treatment involves high temperature firing,
There is a risk that the intermediate layer may become magnetized, leading to a significant decrease in reproduction output.

The purpose of the present invention is to improve the above-mentioned drawbacks of the prior art, and
The object of the present invention is to provide a magnetic recording medium for high-density recording that has practical durability.

(5) Another object of the present invention is to provide a high quality and inexpensive magnetic recording medium by maintaining the uniformity of the reproduction output of a magnetic recording medium having a protective oxide film and simplifying the manufacturing process. It's about doing.

Yet another object of the present invention is to provide a magnetic recording medium having a protective oxide film that is uniform and has excellent wear resistance with good reproducibility.

According to the present invention, in a magnetic recording body in which a magnetic layer and a protective layer are provided in this order on a substrate, the protective layer is made of carbon having weaker oxidation resistance than the magnetic layer.

Provided is a magnetic recording body characterized in that it is a layer formed by oxidizing a metal thin film containing as a main component.

The base of the magnetic recording medium of the present invention may have various conventionally known shapes such as a disk shape, a drum shape, and a tape shape. The base material may be metal such as aluminum alloy or brass, resin such as Mylar or polyimide, or N on top of them.
1-P Me, Ki Membrane, Cu.

A material coated with a deposited film of Cr, etc., a sputtered film, etc. as the base of the storage medium is used.

(6) The magnetic layer of the magnetic recording body of the present invention is Fe.

A magnetic metal thin film containing at least one of Co and N as a constituent element is used. Cu as another secondary component.

Although metals such as Zn and non-metals such as P, B, and O may be contained, generally three
It is necessary to have a coercive force of 000e or more. The thickness of the magnetic layer must be 0.01 μm or more to ensure uniformity, and the thickness of the magnetic layer must be 10.0 OOBPI in one in-plane recording blade type.
In order to obtain a recording density higher than (the number of bits per inch), it is necessary to reduce the thickness to about 1.0 μm or less.

However, when using the perpendicular recording method, 1.0 μm
A magnetic layer having a thickness greater than that can also be used.

The magnetic layer according to the present invention is preferably formed by electroless plating in terms of productivity and uniformity of film thickness, but electroplating, vapor deposition, sputtering, etc. may also be used.

The metal thin film for forming the oxide of the protective layer of the present invention is required to be a metal thin film that has weaker oxidation resistance than the magnetic layer of the recording medium, contains % Co (7), and has a uniform composition. It is required to be a continuous thin metal film having a film thickness of . In order to obtain a sufficiently durable protective layer, the thickness of this metal thin film must be 0.005 μm or more, and it is desirable that this metal thin film contains 509b or more CO. This metal thin film has a force mainly composed of Co, ξ, and Mn, B, and V.

It may contain at least one selected from Fe and Zn, and may further contain at least one selected from Ni and P. Mn content is from 0.01 to 3
A range of 0 inches is used, but a range of 0.1% to 8 inches is preferred. The B content ranges from o, oois to 2°, preferably from 0.1% to 6%.

(2) The content ranges from 0.01% to 30qIb, preferably from 0.05% to 25qIb.

The Fe content ranges from O,i% to 40%.

A range of 1 inch to 30 inches is preferred. Zn content is 0.1
A range of 1 to 20% is used, with a range of 0.3% to 5% being preferred. The Ni content ranges from 0.1% to 40%, preferably from 1% to 25%. The P content ranges from 0.01% to 8% (8), but is preferably 3% or less. Mn in CO.

One of the purposes of containing B, V, Fe, and Zn is to reduce the oxidation resistance of the metal thin film. The inclusion of Ni and P increases oxidation resistance, but simultaneous eutectoid deposition of Ni is sometimes used to increase the amount of eutectoid elements other than CO in electroless 00 alloy plating. In electroless plating using P as a reducing agent, P is eutectoid. As long as the oxidation resistance of the metal thin film is lower than that of the magnetic layer, any secondary elements other than these may be contained.
The greater the difference in oxidation resistance between the metal thin film and the magnetic layer, the easier it is to obtain a magnetic recording medium of good quality. It is preferable to form the metal thin film by electroless plating, which can easily produce a continuous thin film having a uniform composition and thickness, but electroplating, vapor deposition, sputtering, etc. may also be used.

To obtain a Co-Mn alloy film by electroplating method 1, for example, Electrodeposit by Brenner.
on of Alloys volume…(ACAD
RMICPRE88 Published in 1963) 13, 140-15
A plating bath containing ammonium thiocyanate, ammonium sulfate, sodium citrate, etc. in addition to balt sulfate and manganese sulfate as shown in 0 can be used. C by electroplating method
An example of obtaining an o-Mn-P alloy film is cobalt chloride as shown in ``New Alloy Plating Method'' (published by Japan-Soviet Press) p. 142.

There is a method using a plating bath containing manganese chloride and ammonium hypophosphite. By electroless plating method, Co −
To obtain a Mn-F or Co-Ni-Mn-P alloy film, for example, the Journal of Electr.
oche-mical 5ociety, Vol.
130.44, 1983, p. 790-794, hypophosphorous acid is used as a reducing agent, cobalt sulfate or manganese sulfate is used as a metal salt, or nickel sulfate is added as a complexing agent, and an organic acid or the like is added as a complexing agent. A plating bath can be used.

To obtain Co-B or 8 alloy film with other metal elements added thereto by electroless plating, sodium borohydride, dimethylamine borane or a derivative thereof is used as a reducing agent, and cobalt sulfate or chloride is used as a metal salt. A plating bath can be used in which a cobalt salt such as cobalt, (10) a metal salt other than CO of the desired alloy is added, and additives such as an organic acid, a pH buffer, a pH adjuster, etc. are added as a complexing agent. . In the case of a 2-alloy film, it can be obtained from a plating bath containing the same components except that hypophosphite is used as a reducing agent.

In the case of electroplating, the bath components are generally smaller than those in electroless plating, and the types and compositions of the resulting alloys are wide-ranging. In the case of sputtering or vapor deposition, a wider range of alloys can be obtained by changing the target composition or the type of evaporation source element.

The protective layer can be formed by leaving the metal thin film in a constant temperature and humidity environment, by thermal oxidation, by anodic oxidation, by treatment with an oxidizing agent or acid, and by firing it in air, or any of these methods. Formed by oxidation in combination. A method of leaving it in a constant temperature/humidity environment is to form an oxidation (11) film by leaving it in air, oxygen atmosphere, or steam at a temperature of 35°C or higher and a relative temperature of 50°C or higher for 30 minutes or more. be. As the anodic oxidation method, a sulfuric acid bath, a chromic acid bath, an oxalic acid bath, etc. are used. Examples of methods using oxidizing agents or acids include strong acids such as nitric acid, sulfuric acid, hydrochloric acid, and hydrofluoric acid, formic acid, sialic acid, phosphoric acid, lactic acid,
Propionic acid, malic acid, citric acid, acetic acid, tartaric acid, aspartic acid, succinic acid, benzoic acid, butyric acid, malonic acid,
Boric acid, pyrophosphoric acid, tartronic acid, etc.September 2, 1960
Published on the 5th, published by the Chemical Society of Japan, Basic Edition of the Chemical Handbook, p. 1054~
1058 table shows i1. There is a method of forming an oxide film by immersing the substrate in a solution of 15 ITJ or a combination of two or more of weak acids and their salts, or an oxidizing agent such as potassium permanganate or hydrogen peroxide for 10 seconds or more.

For strong acids, concentrations of 0.001 to 15% are used, with a range of o, ooi to 5 yen being preferred. 0 for weak acids.
A concentration range of 0.01% to 50%, preferably 0.1% to 20% can be used. For the oxidizing agent, a concentration range of 0.1 to 40%, preferably 0.2 to 15% can be used.

Suitable conditions are selected for these concentrations and immersion time depending on the strength of the acid and oxidizing agent, the oxidation resistance of the thin metal film to be oxidized, and the thickness of the film (12). Conventionally, a temperature range of 200°C to 290°C has been used for the subsequent firing in air, but magnetic recording bodies obtained in this temperature range have a large coefficient of friction and wear due to CSS. There were problems such as easy generation of powder, and easy magnetization of the Ni alloy layer used for the base and intermediate layer of the magnetic recording body due to firing at 200° C. or higher. In the present invention, by using a metal thin film with weak oxidation resistance as described above,
It became possible to form a protective layer with sufficient durability even by firing at temperatures below 00°C. In addition, when firing at temperatures below 200°C, the surface of the protective oxide layer has not yet reached its final oxidation state, so it is highly active and allows the lubricant layer on top to adhere firmly.In this temperature range, the coefficient of friction is It's also small.

These are also one of the advantages of the present invention.

A thin layer of solid lubricant or liquid lubricant may be coated on the protective layer to further reduce the frictional force and prevent the head from coming into close contact with the magnetic recording medium.

The reason why the present invention makes it possible to significantly reduce head-medium (13) body spacing compared to the conventional technology and realize a high-quality, high-performance magnetic recording medium with few bit errors will be explained using diagrams. . An example of a method for oxidizing the metal thin film forming the protective layer is a method using acid treatment. As an acid treatment method.

The process of immersing in a 0.16 to 0.25% nitric acid solution (process A) shown in the conventionally known U8P 3,719,525, and the process of immersing it in a 0.16 to 0.25% nitric acid solution (process A), which more clearly realizes the effects of the present invention, A step (step B) of immersing in one to several acids of a weak acid such as formic acid, sialic acid, or phosphoric acid is used. The film to be treated is
A test piece with a conventionally known configuration, that is, an aluminum plate plated with N1-P alloy with a thickness of 50 μm and polished, was used as the substrate, and a Co-Ni film with a thickness of 0.08 μm was placed on top of this.
-P Magnetic layer made of plated film, N film thickness 0.05 μm
i-P Intermediate layer made of plating film, film thickness 0.05 μm
A thin metal film made of a Co-N1-P plating film was formed (test piece A), and a test piece with a thickness of 0.05 tim as a metal thin film, excluding the intermediate layer.
Mn-P, Co-Mn, Co-B, Co
A test piece (test piece B) having a structure according to the present invention using a metal layer having significantly lower oxidation resistance (14) than magnetic layers such as -Pe-P and Co is used. Test piece A was subjected to process A1 Test pieces A and B were subjected to process B, and the change in saturation magnetization of each test piece was measured using a vibrating sample magnetometer (VSM).

The trends of the results are compared and shown in the figure. The area of each test piece was kept constant, and the saturation magnetization amount is a relative value with the value of only the magnetic layer being 1.

Curve 1 is a change in saturation magnetization over time when test piece A is subjected to process A. Curve 2.3 shows the change in saturation magnetization over time when process B was applied to test pieces A and B, respectively.

Regarding curve 1 obtained by subjecting a conventional test piece to process A, oxidation of the metal thin film progresses during the first approximately 3 minutes and magnetism is lost. For the next 5 minutes, the magnetization decreases slowly and the barrier effect of the alloy intermediate layer is being reduced, but it is not sufficient and the erosion of the magnetic layer has progressed considerably. After 8 minutes of immersion, the intermediate layer does not lose its effect and the oxidation of the magnetic layer proceeds rapidly. On the other hand, when process B is applied to test piece A, the progress of oxidation of the metal thin film is (15
) is slight. Therefore, in the test piece B having the structure of the present invention, process B was applied.
It was found that when oxidation of the magnetic layer was performed, the oxidation of the magnetic layer hardly progressed after the oxidation of the metal thin film was completed in the first approximately 7 minutes as shown in curve 3. That is, it is shown that by adopting the configuration of the present invention, a barrier effect against oxidation of the metal thin film can be obtained without using an intermediate layer. This significantly reduces the head-medium spacing compared to the prior art, making it possible to record high-quality, high-performance magnetic recording media with fewer bit errors. Note that when test piece B is immersed in a strong acid solution, a relationship similar to curve 3 can be obtained by using a very low concentration, for example, for nitric acid, a concentration below step ho)'/o.

Next, the features of the magnetic recording medium according to the present invention will be explained using examples. The following example is an example showing the effects of the present invention, and it goes without saying that the object can be achieved even if the components, film thickness, processing method, etc. shown here are changed as appropriate.

(16) Example 1゜ Aluminum alloy disk (diameter 21111, thickness 1.9 tnw) whose surface was finished flat and smooth by machining ζ
By this known plating method, a non-magnetic Ni −
After forming the P alloy, the surface was machined to a mirror finish to obtain a magnetic disk substrate. Although there are many commercially available Ni-P plating solutions, Kanisen Seamer solution was used here. Furthermore, a coercive force of 6000e is applied on this substrate.
, a residual magnetic flux density of 7,300 gauss (7) After forming a magnetic layer consisting of a Co-N1-P film, which has magnetic properties and a film thickness of 0.08 pm, the film thickness is reduced to 0.005 μm or more.
By varying the range of 0.08 μm, the amount of Co was 4%.
- A metal thin film consisting of a Mn plating film was formed.

The plating method was the 1-air plating method as described above.

Next, this was immersed in a sulfuric acid solution (concentration 1 to 3q6) for several minutes to more than ten minutes, and then heated in air at around 190'C for 6 hours. The immersion time was increased according to the thickness of the Co--Mn plating film.

On the surface of the magnetic disk obtained in this way, C0-Mn
Uniform oxide (17) formed by the oxidation of the plating film.As shown in the C8S test results in Table 1, for samples with a Co-Mn plating film thickness of 0.02 μm or more, Sufficient durability for practical use was obtained.

Table 1 C8B test results (using Mn-Zn ferrite head) A recording/reproducing test was conducted on the magnetic disk obtained in this example under the following conditions.

Measurement condition Disc rotation speed: 3000 rpm Head used: track width 18.5 μm.

Cap length 0.8μtn.

Number of coil turns: 16 + 16° Head flying height: 20.2 μm Recording frequency (2F): 6.08 MHz Error slice level: 260 inches (18) - The number of errors per plane is 100 or less as shown in Table 2. It was confirmed that the thickness of the magnetic layer of the disks with each Co--Mn film thickness was sufficiently uniform for practical use.

Table 2 Recording/reproduction test results Comparative example 1゜The substrate and magnetic layer were prepared in the same manner as in Example 1, and after forming an intermediate layer made of a Ni-P plating film on the magnetic layer, the film thickness was 0.031 tmO) Co-Ni-P Me,
A magnetic disk was fabricated by forming a metal thin film consisting of a + film and oxidizing this metal thin film to use it as a protective layer. In this case, both the metal thin film and the magnetic layer are Co-Ni-P plated films, and since they have the same oxidation resistance, the aforementioned Go- This required an acid solution with a higher concentration than the treatment solution used in the treatment of the Mn film.

(19) Therefore, in order to obtain a magnetic disk in which the number of errors per surface is 100 or less under the same measurement conditions as in the recording/reproduction test described above, an intermediate layer with a thickness of o, io μm or more is required, and the thickness of the protective layer is Co-Mn plating film thickness 0 with almost the same thickness
．． The reproduction output was reduced by about 27 inches compared to the magnetic disk of Example 1 with a diameter of 0.3 μm. Also, as a metal thin film, Co-N
When i-P membrane is used and the firing temperature after immersion in sulfuric acid is set to 190°C, the durability is extremely poor and the number of C8S cycles is 100 to 200.
The wound was caused by the injury. When fired at 275° C., the C8S durability increased to about 4000 times, but the recording and reproducing characteristics were significantly deteriorated due to the magnetization of the N1-P plating layer.

Example 2 A magnetic disk was produced in the same manner as in Example 1, but in this example, a Co - with a film thickness of 0.05 μm and a Mn content of 4% was used.
The treatment liquids shown in Table 3 were used in the process of oxidizing a metal thin film made of a Mn film. In the present invention, since there is a significant difference in oxidation resistance between the metal thin film and the magnetic layer, it was possible to easily find treatment conditions (20) in which the entire metal thin film was reacted and the magnetic layer was not eroded. Concentration depending on the strength of the acid,
Suitable conditions such as dipping time are selected, and Table 3 shows the conditions used in this example as an example.

Table 3 Types of treatment liquid and immersion conditions The magnetic disk thus obtained was subjected to C8S test and recording/reproduction test in the same manner as in Example 1, and the results showed that it had sufficient durability for practical use (CSS 20,000 times or more). It was confirmed that it had error characteristics (100 or less errors per negative side). Furthermore, the playback output increased by about 32% compared to the disk of Comparative Example 1, which had the same error characteristics.

(21) Example 3 A magnetic disk was produced in the same manner as in Example 1, but in this example, a film with a thickness of 0.0 with varying amounts of metal was formed on the magnetic layer.
3 μm (7) After forming a metal thin film consisting of a Co-Mn electroplated film and treating it with 2 to 4 t of phosphoric acid solution, 1
Firing was performed at 80° C. for 8 hours. C.

- Seed membranes of 0.196 to 7 inches were used.

The magnetic disk thus obtained was subjected to a C8S test in the same manner as in Example 1. C: Scratches occur on the disc surface.
Table 4 shows the number of 8S.

Table 4 Seed content and C88 durability (22) Comparative example 2゜Produced in the same manner as Example 2, but with the intermediate layer film thickness Q, 1
9 μm, film thickness 0.04 ttm Co - Ni -
In a magnetic disk in which a protective layer was formed by immersing a metal thin film made of a P film in nitric acid and baking it at 230° C., scratches occurred after 0,883,500 cycles in a similar C8S test.

In this example, it was shown that the durability was significantly improved by including a small amount of dove in the protective layer.

Example 4 A magnetic disk was prepared in the same manner as in Example 1, but in this example, Co-B with a film thickness of 0.04 μm and a B content of 3.
A thin metal film consisting of a film was formed. The Co-B film was prepared at an acidic pH of 5 to 6 using an electroless bath containing cobalt sulfate as a metal salt, dimethylamine borane as a reducing agent, and sodium malonate and sodium citrate as complexing agents. .

After each treatment under the conditions shown in Table 5 below.

It was baked at 170°C for 25 hours.

(23) Table 5 Type of treatment liquid and immersion conditions A uniform oxide protective layer was formed on the surface of the magnetic disk thus obtained. As a result of the C8S test, it was confirmed that it withstood 20,000 cycles of C88 and had sufficient durability.

As a result of the same recording and reproducing test as in Example 1, the number of errors tends to decrease as the concentration of the processing liquid decreases, and by appropriately selecting the concentration of each processing liquid, the number of errors per page can be reduced to 10.
Less than 0 (24) discs were obtained. Also, the playback output is 3.3 times higher than that of the disk in Comparative Example 1, which has the same error characteristics.
It increased by about 4.

Example 5 A magnetic disk was prepared in the same manner as in Example 1, but in this example, a thin metal film consisting of a Co-B film with a thickness of 0.05 μm was formed on the magnetic layer, and the magnetic disk was prepared under the conditions shown in Table 6. After processing,
Firing was performed at 180°C for 15 hours.

The Co-B film used had a B content of 0.01% to 4.0%. The B content was decreased by increasing the pi of the plating bath. The same plating bath as in Example 4 was used, but on the alkaline side, aspartic acid was used as a complexing agent to increase the stability of the bath. there was.

The magnetic disk thus obtained was subjected to a C8S test in the same manner as in Example 1. C: Scratches occur on the disc surface.
The number of 8S is also shown in Table 6.

(25) Table 6 B content Processing conditions, gcss number comparison example 3゜Produced in the same manner as Example 5, but N1-P of the intermediate layer,
The plating film thickness is 0.10μm, and on top of this, a film thickness of 0.05μm is applied.
A thin metal film consisting of a Co-Ni-P plating film with a thickness of μm was formed, and this was immersed in 0.25% nitric acid for several minutes.
In a similar C8S test, scratches occurred on a magnetic disk baked at 0° C. for 15 hours to form a protective layer after approximately 150 C8S cycles. Since the intermediate layer thickness was set to 0.10 μm in order to obtain practically necessary error characteristics, the reproduction output was reduced by about 26 (26) inches compared to the magnetic disk obtained in this example. When the firing temperature is 275℃, C8S
Although the durability increased to about 5,000 times, the recording and reproducing characteristics were significantly deteriorated due to magnetization of the Ni--P plating film of the base and intermediate layer.

In Example 5, it was shown that the durability was significantly improved by containing a small amount of B in the protective layer.

Example 6 A magnetic disk was produced in the same manner as in Example 5, but in this example, the thickness of the metal thin film consisting of a Co-B plating film with a B content of 0.4 μm was changed from 0.005 μm to 0.1 μm. It was varied within the range of. The metal thin film was oxidized by immersing it in 1-10% propionic acid for several minutes and then baking it at 195°C for 15 hours.

As the results of the C8S test are shown in Table 7, the Co--B plating film thickness of 0.02 μm or more exhibited durability over 20,000 cycles of C3S. When the propionic acid treatment conditions were changed as appropriate depending on the Co-B plating film thickness, disks with the number of errors per surface of 100 or less were obtained for each film thickness.

(27) Table 7 Co-B plating film thickness and CSS number Example 7゜A magnetic disk was produced in the same manner as in Example 1, but in this example, a film thickness of 0.00000. 04pm,
C with Mn content of 1.5% and P content of 2.5%.

A metal thin film made of -Mn-P electroless plating film was treated under the conditions shown in Table 8, and then baked at 190°C for 7 hours to form a protective layer.

Table 8 Types of treatment liquid and immersion conditions (28) Co-Mn-P electroless plated film
ofmelectrochemical 5ocjet
As shown in p. 790-794 of Vol. y, Vol. 130, A4 e1983, sodium hypophosphite is used as a reducing agent, cobalt sulfate as a metal salt, manganese as a complexing agent, sodium malonate and It was prepared from a plating bath using sodium malate and ammonium sulfate as a pH buffer.

As a result of performing a recording/reproduction test on the magnetic disk obtained in this example in the same manner as in Example 1, it was found that the number of errors tends to decrease as the processing liquid concentration decreases, and by appropriately selecting the processing conditions, the number of errors per side can be reduced. A disk with less than 100 errors was obtained. Furthermore, practically sufficient durability was obtained in the C8S test. The playback output is 34% compared to the disc of Comparative Example 1, which has the same error characteristics.
The degree has increased.

Example 8゜A magnetic disk was prepared in the same manner as in Example 1 θξ In this actual example, a thin film of each of the metals shown in Table 9 below with a film thickness of 0.04 μm was formed on the magnetic layer. After being immersed in ~7% (29) acetic acid solution for several minutes, it was calcined at 190°C for 8 hours.

Table 9: Various metal thin films Co-Mn-P film, Co-Ni-Mn-P film, Journal of Electrochemical
al 5ociety, Vol.

130, Fu 4, 1983, p. 790-794. The Co-Fe-P film was prepared from an ammonia-alkaline citric acid bath using hypophosphorous acid as a reducing agent as shown in Platlnge 1967, p. 705. Co-Zn-P film is IE
EE Tran, onMag, 1966, 9.
Ammonia-alkaline citric acid 111 [Yo (30)] was prepared using hypophosphorous acid as a reducing agent as shown in No. 681. The Co film was prepared using a caustic alkaline plating bath using hydrazine as a reducing agent. Co-■ membrane is RF
It was manufactured by sputtering method.

The thus obtained magnetic disk was tested in the same manner as in Example 1, and as a result, it had durability of 520,000 CBs or more and error characteristics sufficient for practical use. The playback output increased by about 34 inches compared to the disk of Comparative Example 1, which had the same error characteristics.

Example 9 A magnetic disk was produced in the same manner as in Example 1, but in this example, the film thickness was 0.03 μm and the Mn content was 1.5%.

A thin metal film consisting of a Co-Mn-B electroless plating film with a B content of 0.6 T was formed, and a few T of phosphoric acid, oxalic acid,
100℃ after immersion in weak acids such as acetic acid and propionic acid for more than 10 minutes.
It was fired for 30 hours at a temperature ranging from 190°C to 190°C.

The thus obtained magnetic disk was tested in the same manner as in Example 1, and as a result, it had durability of more than 20,000 C3S cycles and error characteristics sufficient for practical use. Furthermore, even when the firing step was omitted in this example, durability of approximately 500 C88 cycles could be obtained.

The reproduction output increased by about 36 yen compared to the disc of Comparative Example 1, which had the same error characteristics.

Example 10 A magnetic disk was produced in the same manner as in Example 1, but in this example, a co-coated disk with a capacity of 3.5 inches and a film thickness of 0.02 μm was used.
The Mn film was a metal thin film, and the oxidation step was performed by firing in air at 195° C. for 50 hours. The thus obtained magnetic disk was tested in the same manner as in Example 1, and as a result, it had practically sufficient durability and error characteristics. The playback output is
Compared to Disc 1, which had the same error characteristics in Comparative Example 1, the error was increased by about 38 factors.

As is clear from the above examples, in a magnetic recording body in which a substrate, a magnetic layer, and a protective layer are provided in this order, the metal thin film used to form the oxide that becomes the protective layer has a higher oxidation resistance than the magnetic layer. By using a metal film with a weak strength, a magnetic recording medium with practical durability and uniform reproduction output can be obtained. In particular, compared to conventional magnetic recording bodies in which an intermediate layer is formed between the magnetic layer and the holding layer, the reproduction output can be increased by reducing the head-medium separation length, and the manufacturing process can be simplified. has extremely high practical and industrial value.

[Brief explanation of the drawing]

The drawing shows the change in the amount of saturation magnetization with respect to the immersion time in the oxidation treatment solution. (33)

Claims (3)

[Claims] (1) In a magnetic recording body in which a magnetic layer and a protective layer are provided in this order on a substrate, the protective layer oxidizes a metal thin film mainly composed of Co, which has weaker oxidation resistance than the magnetic layer. A magnetic recording body characterized by being a formed layer. (2) The protective layer force ξ has Co as the main component, and Mn
. A magnetic recording medium. (3) The protective layer mainly contains cobalt and Mn. Contains at least one selected from B, V, Fe, and Zn