JPS6273414A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To form the titled magnetic recording medium having excellent durability without increasing the spacing loss and film thickness by regulating Young's modulus of the Co vertically magnetized film to >=9,000kg/mm<2>. CONSTITUTION:In the magnetic recording medium obtained by forming a Co- base vertically magnetized film on a nonmagnetic carrier, Young's modulus of the Co-base vertically magnetized film is regulated to >=9,000kg/mm<2>. To improve the mechanical properties of the vertically magnetized film having >=9,000kg/mm<2> Young's modulus, the pores at the grain boundary must be reduced and the crystal grains are closely packed. To reduce the pores at the grain boundary, atoms and molecules are thermally diffused into the grain boundary after the Co-base vertically magnetized film is formed, atoms and molecules are penetrated into the grain boundary by a plasma method, atoms and molecules are implanted in the grain boundary by ion implantation or a method for controlling the conditions in forming the vertically magnetized film can be exemplified.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magnetic recording medium using a perpendicular magnetization recording method, and particularly to a magnetic recording medium formed by forming a Co-based perpendicular magnetization film as a magnetic layer. It is.

[Summary of the invention]

The present invention improves the mechanical properties of the perpendicular magnetization film itself by setting the Young's modulus of the Co-based perpendicular magnetization film formed on a non-magnetic support to 9000 kg/ms" or more, thereby reducing the spacing loss and the film. The objective is to improve the durability of magnetic recording media without increasing the thickness.

[Conventional technology]

Conventionally, in magnetic recording media used as storage media for computers, audio tape recorders, video tape recorders, etc., a magnetic layer deposited on a substrate has magnetization in a direction horizontal to the substrate surface. (It is common to record information in the in-plane direction (d).

However, in the case of recording using in-plane direction magnetization, as the wavelength of the recording signal becomes shorter, that is, as the recording density increases, the demagnetizing field within the medium increases and the residual magnetic flux density attenuates.
This has the disadvantage that the reproduction output decreases.

Therefore, in order to cope with the progress of higher density recording of recording signals and shorter recording wavelengths, a perpendicular magnetization recording type magnetic recording medium in which recording is performed by magnetization in the thickness direction of a magnetic layer has been proposed. According to this perpendicular magnetization recording method, as the recording wavelength becomes shorter, the demagnetizing field becomes smaller, so the recording density can be dramatically increased.
Very advantageous for high-density recording.

As the magnetic recording medium of the perpendicular magnetization recording method, Co-
Magnetic recording media, in which a Co-based alloy material such as a Cr alloy is deposited on a non-magnetic support such as a polymer film using a vacuum thin film formation technique such as vapor deposition or sputtering, are being actively developed and researched to form a perpendicularly magnetized film. There is.

However, this type of i-air recording medium has many problems with durability and runnability, and improvement thereof has become a major issue. In order to put these magnetic recording media into practical use as magnetic tapes or magnetic disks, sufficient durability is essential.

To this end, various types of protective films are being considered, and research and development is underway to improve durability.

[Problem that the invention seeks to solve]

However, the method of providing a protective film has two major drawbacks: an increase in spacing loss and an increase in the film thickness of the medium.

For example, the protective film provided to improve durability has had an adverse effect on electromagnetic conversion characteristics, such as a drop in output and deterioration of frequency characteristics.

Alternatively, when the film thickness of the medium increases, problems such as bending called curling and loss of flexibility of the medium occur.

SUMMARY OF THE INVENTION Therefore, the present invention has been developed to solve the above-mentioned drawbacks of the prior art, and provides a magnetic recording medium that has excellent durability without increasing spacing loss or film thickness. With the goal.

[Means for solving problems]

As a result of intensive research to achieve the above objectives, the present inventors discovered that improving the mechanical properties of the perpendicularly magnetized film itself is effective in improving durability, and completed the present invention. A magnetic recording medium comprising a Co-based perpendicular magnetization film formed on a non-magnetic support, characterized in that the Co-based perpendicular magnetization film has a Young's modulus of 9000 kg/l 2 or more. It is something.

A magnetic recording medium to which the present invention is applied is a magnetic recording medium in which a Co-based alloy material is directly deposited on a non-magnetic support to form a Co-based perpendicularly magnetized film serving as a magnetic layer.

The alloy material constituting the Co-based perpendicular magnetization film is C
o-Cr, Co-V, Go-Os, C.

Co-based alloy materials such as -Ru, Co-Re, Go-Mn, etc. are mentioned, and these Co-based alloy materials include Nb, Mo,
Additional elements such as W and Rh may be added.

As a method for forming the above-mentioned perpendicular magnetization film, a vacuum thin film forming technique represented by a vacuum evaporation method, an ion blating method, a sputtering method, etc. is employed. Here, in the vacuum evaporation method, 1O
The Co-based alloy material is evaporated under a vacuum of -4 to 10 Torr by resistance heating, high frequency heating, electron beam heating, etc., and the evaporated metal is deposited on a nonmagnetic support. The ion blating method is also a type of vacuum deposition method, in which DC glow discharge and RF glow discharge are generated in an inert gas atmosphere of 10-4 to 10-' Torr, and the above-mentioned Co-based alloy material is evaporated during the discharge. It is something.

In the sputtering method, a glow discharge is caused in an atmosphere mainly composed of argon at 10-3 to 10-' Torr, and the generated argon ions are used to knock out atoms on the target surface. There are the pole and three-pole spacing methods, the high-frequency spacing method, and the magnetron packing method using a magnetron.

In the present invention, the Co-based perpendicular magnetization film has a Young's modulus of 9,000 kg/12 or more.

According to the experiments conducted by the present inventors, when the Young's modulus of the Co-based perpendicularly magnetized film is set to 9000 kg/min or more, the mechanical properties of the perpendicularly magnetized film itself are improved, and the spacing loss and film thickness are increased. For example, by changing the Young's modulus of the Co-based perpendicular magnetization film, we investigated its still durability (measured as the number of rotations until the output decreases). As shown in FIG. 1, it was found that the durability rapidly improved when the Young's modulus was 9000 kg/l! or more.

The mechanical properties of a Co-based perpendicularly magnetized film largely depend on the properties of its crystal grain boundaries, and by making the crystal grain boundaries denser, the mechanical properties are improved and the durability of the medium is improved. In other words, in order to increase the Young's modulus of the perpendicularly magnetized film to 9000 kg/ma 2 or more and to improve its mechanical properties, the crystal grain boundaries of this perpendicularly magnetized film should be in a state with few vacancies so that the crystal grains are densely packed. As a method to make this grain boundary a state with few vacancies, there is a method of thermally diffusing one molecule of an atom into the grain boundary after forming a Co-based perpendicular magnetization film, or a method of thermally diffusing one molecule of an atom into the grain boundary with a plasma method, etc. Examples include a method of injecting two molecules of atoms, a method of injecting two molecules of atoms into crystal grain boundaries using an ion implantation method, and a method of controlling conditions during the production of a perpendicularly magnetized film.

[Effect]

By setting the Young's modulus of the Co perpendicularly magnetized film to 9000 kg/m'' or more, durability is ensured by the mechanical properties of the perpendicularly magnetized film itself.Therefore, there is no spacing loss or increase in film thickness.

〔Example〕

The present invention will be explained below using specific experimental results.

In this experiment, a structure was used in which a 0.5 pm thick Go-Cr sputtered film (containing approximately 17 to 18 wt % Cr) was deposited as a Co-based perpendicularly magnetized film on a 50 μm thick polyimide base.

The Go-Cr sputtered film was deposited by RF sputtering, and the sputtering conditions were as follows.

Spacking conditions Spacking equipment RF 2-pole sputtering equipment target
Target Argon pressure: 3 to 30 mTorr Substrate temperature: Cr pellets are uniformly arranged on a Co plate (2001 mm diameter) at an area ratio of 19%
170℃ Substrate-target distance 60 iris 1RF power
150W RF power density 0.96W/! Further, the Young's modulus of the Co--Cr sputtered film was controlled by the Ar pressure during sputtering. As shown in Figure 2, by lowering the Ar pressure during sputtering, the Young's modulus of the perpendicularly magnetized film is greatly improved, and as shown in Figure 3, the crystal grain size of the growing film is also reduced. As a result, there are fewer vacancies at grain boundaries. Note that the Young's modulus here is determined by measuring the Young's modulus of a recording medium sample including the base and the Young's modulus of only the base from which the Co-Cr sputtered film is removed, and the Young's modulus of the composite material (assuming linearity). The Young's modulus of only the Co--Cr sputtered film was calculated as the apparent Young's modulus from the model.

According to the above method, the apparent Young's modulus is 2500 kg/
as", 6300 kg/■m", 11000
A Co-Cr sputtered film having a weight of 2 kg/dragon 2 was prepared, and Comparative Example 1. Comparative example 2. This is an example.

Scanning electron micrographs of the fracture surfaces of these samples (450 magnification)
00 times) are shown in Figures 4, 5, and 6, respectively.When observing these membrane structures, those with a small Young's modulus have a clear columnar structure, sparse grain boundaries, and many vacancies. for,
It was found that when the Young's modulus is large, the grain boundaries become dense and the columnar structure becomes unclear.

Furthermore, scratch strength and still durability were measured for each of the above Examples and Comparative Examples.

The above scratch strength was measured using a continuous load double scratch strength tester manufactured by Shinraikagakusha. The principle of measurement is that when the moving table with the sample fixed starts moving, the continuous weight is also weighted the same distance away from the fulcrum, and pressure proportional to the moving distance is applied to the sample. The weight is read as the scratch strength. Test measurement conditions are moving weights 100g and 200g.
The scratching speed of the sapphire needle was 10 days/sec, and the reading of the starting point of the scratch was performed 10 times on the -sample using a differential interference microscope, and the average value was taken as the reading.

Still durability was measured by cutting each sample to a diameter of 3.5 inches and measuring the number of rotations until the RMS reproduction output of a recording signal with a wavelength of 1 μm decreased.

The results are shown in the table below.

Table From this table, it can be seen that in the examples in which the Young's modulus was 9000 kg/mm or more and the grain boundaries were dense, there was a significant improvement in durability and mechanical strength compared to other comparative examples [Effects of the invention] As is clear from the explanation, in the present invention,
The Young's modulus of the Co-based perpendicular magnetization film is 9000 kg/x*
``With the above, since the number of vacancies at the grain boundaries is reduced, the mechanical properties of the perpendicularly magnetized film itself can be improved, and a highly durable magnetic recording medium can be provided. Unlike the case of forming a protective film, there is no spacing loss or increase in film thickness, and it is extremely advantageous in terms of magnetic conversion characteristics, curling, flexibility of the medium, etc.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between the Young's modulus of a perpendicularly magnetized Co film and still durability. Figure 2 is a characteristic diagram showing the relationship between the Ar pressure during sputtering and the Young's modulus of the obtained perpendicularly magnetized Co film.
The figure is a characteristic diagram showing the relationship between the Ar pressure during sputtering and the crystal grain size of a Co perpendicularly magnetized film. Figure 4 is a scanning electron micrograph (45,000x magnification) showing the crystal structure on the fracture surface of a Co perpendicularly magnetized film with a Young's modulus of 2,500 kg/n'', and Figure 5 shows a crystal structure with a Young's modulus of 6,300 kg/n''.
A scanning electron micrograph (magnification: 45,000 times) showing the crystal structure on the fracture surface of a Co perpendicularly magnetized film of kg/dragon f.
FIG. 6 is a scanning electron micrograph (magnification: 45,000 times) showing the crystal structure on the fracture surface of a Co perpendicularly magnetized film having a Young's modulus of 11,000 kg/w''.

Claims (1)

[Claims] A magnetic recording medium comprising a Co-based perpendicular magnetization film formed on a non-magnetic support, wherein the Co-based perpendicular magnetization film has a Young's modulus of 9000 kg/mm^2 or more.