JPH02265011A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the recording medium having an excellent traveling property and durability by providing a primer coating layer having a prescribed average surface roughness on a base body and forming a ferromagnetic metallic thin film thereon. CONSTITUTION:The primer coating layer having 10 to 50Angstrom average surface roughness Ra is formed on the base body and the ferromagnetic metallic thin film is formed is formed thereon. Namely, the deterioration of the traveling property and durability is of a problem if the average surface roughness Ra is below 10Angstrom and conversely electromagnetic conversion characteristics are insufficient if the above-mentioned roughness exceeds 50Angstrom and that is way, the values between these values are adopted. Further, the reason for regulating the surface roughness not by the max. value Rmax of the height but by the average surface roughness Ra lies in that, if abnormal projections are detected, the large value is resulted at the max. value Rmax of the height and, therefore, the average surface roughness Ra is more adequate in order to examine the surface characteristic over the entire part of the tape. The regulation of the average surface roughness Ra to 10 to 50Angstrom is attained merely by forming grainy projections, wrinkly projections, etc., on the primer coating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] In the present invention, a ferromagnetic metal thin film is deposited on a substrate by a vacuum thin film forming technique such as vapor deposition or sputtering. The present invention relates to a so-called metal thin film type magnetic recording medium.

(Summary of the Invention) The present invention provides a magnetic recording medium in which a ferromagnetic metal thin film is adhered and formed on a substrate. The aim is to improve running performance and durability while maintaining conversion characteristics.

[Conventional technology]

Ferromagnetic metals such as so-called evaporated tapes f! ! Film-type magnetic recording media not only have high coercive force and residual magnetic flux density, but also
The ferromagnetic metal thin film that is the magnetic layer has a number of advantages, such as extremely thin recording demagnetization and thickness loss, and the ability to dramatically increase the packing density of the magnetic material. It is expected to be used in the fields of high-density recording and short wavelength recording.

By the way, this ferromagnetic metal thin film type magnetic recording medium has excellent characteristics in terms of the ability of the magnetic layer itself, as mentioned above, but the surface properties of the ferromagnetic metal thin film, which is the magnetic layer, are As a result, there are many problems with running performance, durability, etc., which are important characteristics in practical use, and improvement of these problems has become a major issue.

Due to this situation, there is an urgent need to improve the surface properties of ferromagnetic metal thin films, and the idea has arisen to control the surface properties of ferromagnetic metal thin films by controlling the surface properties of non-magnetic supports. .

For example, in Japanese Patent Application Laid-open No. 60-179924, in order to solve the problem of poor running properties when used as a magnetic tape, the surface roughness of the Heath film is set to 0.03 to 0.0 at the maximum height.
There is a description that it is sufficient to specify 8 μm.

[Problem to be solved by the invention]

However, recent advances in higher density recording,
With the trend toward shorter wavelength recording, it is no longer possible to determine surface properties simply from the viewpoint of runnability. For example, if a Heath film with a surface roughness within the range described in the above-mentioned publication is used, 4. Although there are few problems in running performance, deterioration of electromagnetic conversion characteristics becomes a problem.

Therefore, the present invention has been proposed in view of the conventional situation, and has not only excellent running performance and durability, but also
The object of the present invention is to provide a magnetic recording medium that has excellent electromagnetic conversion characteristics and is compatible with high-density recording and short wavelength recording.

[Means for Solving the Problem] As a result of intensive studies to achieve the above-mentioned object, the present inventors have determined that the surface roughness of the non-magnetic support can be reduced to a much smaller area than previously thought. It was concluded that by setting the value within a predetermined range, it is possible to ensure electromagnetic conversion characteristics compatible with short wavelength recording, and the running performance and durability are also at a practical level.

The present invention was completed based on the results of such studies, and includes forming an undercoat layer with an average surface roughness Ra of 10 to 50 on a substrate, and further forming a ferromagnetic metal thin film thereon. It is characterized by:

This is because if the average surface roughness Ra is less than 10 people, the running performance and durability will deteriorate and the practical level will not be reached, and if it exceeds 50 people, the electromagnetic conversion characteristics will be insufficient. In addition, in the present invention, the surface roughness is defined as the maximum height Rm
Average surface roughness Ra (center line average surface roughness) instead of ax
The reason for this is that when an abnormal protrusion is detected, the maximum height value Rmax will be a large value, and it is determined that the average surface roughness Ra is more suitable for checking the surface quality of the entire tape. by.

In order to keep the average surface roughness Ra within the above range, it is sufficient to provide an undercoat layer to form so-called granular protrusions, wrinkle-like protrusions, etc. Furthermore, it is sufficient to form so-called granular protrusions, wrinkle-like protrusions, etc. by dispersing fine particles in a non-magnetic support. A gentle protrusion (so-called mountain-like protrusion)
may be used together.

The granular protrusions are formed, for example, by adhering organic ultrafine particles such as acrylic resin or inorganic ultrafine particles such as silica or metal powder in a spherical or semispherical shape, and can also be formed into a suitable granular shape by applying a dilute emulsion. A protrusion is formed. These granular protrusions are present on the substrate in a state in which the particle shape of these organic ultrafine particles, inorganic ultrafine particles, or emulsion remains.

The wrinkle-like protrusions are formed as a continuous film or a discontinuous film, for example, by applying an emulsion onto the substrate and further by stretching the emulsion.

These granular projections and wrinkle-like projections are formed by applying an emulsion as described above, but the emulsion used may be either an aqueous emulsion solution or a non-aqueous emulsion, and even latex etc. can be used. It is. In addition, the types of synthetic resins contained in the emulsion include thermoplastic resins such as polypolymers and copolymers such as vinyl acetate, acrylic esters, vinylidene methacrylate esters, vinyl diethylene chloride, and styrene, and thermoplastic resins such as epoxy resins. Curable resins, synthetic rubbers such as butadiene-styrene copolymers, pucdiene-acrylonitrile copolymers, etc. are not particularly limited.

In the magnetic recording medium of the present invention, the above-mentioned granular projections, wrinkle-like projections, etc. are formed by providing an undercoat layer, and a ferromagnetic metal is coated on a substrate with an average surface roughness Ra of 10 to 50. A thin film is formed as a magnetic layer.

As the ferromagnetic metal material A constituting the bow ferromagnetic metal thin film, any material used in this type of medium can be used. Specifically, metals such as Fe, Co, and Ni, and F
e -Co alloy, Fe-Ni alloy, Co-Ni alloy, F
e-Co-Ni alloy, FC-co-B alloy Co-N1-
Alloys such as Fe-B alloy, Co-P↑ alloy Co-N1-P1 alloy, Co-Cr alloy, or these with Cr,
Examples include those to which metals such as Aff are added, and furthermore, Co-0 type thin films and the like are also applicable.

Further, as the means for forming the above-mentioned ferromagnetic metal thin film, vacuum browning method, ion blasting method, sputtering method, etc. are usually typified. The so-called vapor phase mebuki technology is adopted.

Note that method 4 described in -1- When forming a ferromagnetic metal thin film from a ferromagnetic metal thin film, for example, in order to improve the adhesion between the substrate and the ferromagnetic metal thin film, or to control the coercive force of the ferromagnetic metal (W) film, some kind of underlayer or intermediate layer is added. Layers may be provided. Furthermore,
In order to improve the corrosion resistance and runnability of the ferromagnetic metal thin film, a protective layer containing a lubricant, rust preventive, etc. may be formed. In this case, any conventionally known base layer, intermediate layer, protective layer, etc. can be used.

[Effect]

By providing an undercoat layer with an average surface roughness R,a of 10-50 on the substrate 1-, the true contact area between the ferromagnetic metal thin film surface and the magnetic Hen't point is reduced, and this reduces the coefficient of friction. Permanence on the downside is also ensured.

At this time, the excellent electromagnetic conversion characteristics of the ferromagnetic metal thin film type magnetic recording medium are not impaired.

[Examples] Hereinafter, the present invention will be explained based on specific examples. It goes without saying that the present invention is not limited to these examples.

In this example, the base has a width of 150 mm and a thickness of 10 μm.
Using a polyethylene terephthalate film (PE1 film), CoeoN i as a ferromagnetic metal material
20 (The number 7 does not represent atomic percent.) An alloy material having the composition shown in -r'y is used, the traveling speed of the substrate is 20 m/min, the minimum incident angle for oblique evaporation is 45°, and oxygen A ferromagnetic metal thin film (Co-Ni) was deposited on the PET film to a thickness of 2000 mm by vacuum evaporation at a flow rate of 250 co/min.
Cut it into widths and use it as sample rubber.

Each sample tape has a back coating and a top coating.

Here, an undercoat layer was provided on the surface of the substrate to form granular protrusions, wrinkle-like protrusions, and even mountain-like protrusions, and the average surface roughness Ra thereof was controlled. For example, in Example 1 and Comparative Example 1, the average surface roughness Ra was controlled by combining mountain-like projections and wrinkle-like projections7, while in Example 2 and Comparative Example 2, the average surface roughness Ra was controlled by combining mountain-like projections and granular projections, and in Example 3, Wrinkled projections and granular projections, and in Example 4, mountain-like projections and wrinkled projections.

The average surface roughness Ra was controlled depending on the combination of granular protrusions. The surface roughness of each non-pull tape is as shown in Table 1.

Surface roughness: I, side diameter: 0.3μm using Talystep
Measurement was performed using 1 pressure and 2 cm.

Table 1: Electromagnetic conversion characteristics (Y-
C/N), still durability, shuttle durability 11, and dropout were measured. The electromagnetic conversion characteristics were determined as relative values based on the coated metal tape. The recording wavelength is 055gm. Still durability was evaluated using an 8 mm VTR (manufactured by Sony Corporation, EV, SL) as the time required for the reproduction output to drop to half (recording wavelength 0.7 μm). Shuttle durability was evaluated by the decrease in output j after running the shuttle 100 times. A case where a 16 dB decrease in output continued for 10 microseconds was regarded as one dropout, and the number of dropouts per minute was determined. The results are shown in Table 2.

Table 2 It can be seen from this table that as the average surface roughness increases, the still durability and shuttle durability tend to improve. However, when the average surface roughness exceeds 60 (Comparative Example 1, Comparative Example 2), electromagnetic conversion characteristics, which are important characteristics for performing high-density recording and short wavelength recording, are insufficient.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since an undercoat layer with an average surface roughness Ra of 10 to 50 is provided on the substrate, and a ferromagnetic metal thin film is formed on this, the surface properties of the ferromagnetic metal thin film are improved, and the runnability and durability are improved. A magnetic recording medium with excellent properties can be provided.

Further, if the average surface roughness is within the above range, electromagnetic conversion characteristics can be sufficiently ensured, and it is possible to provide a magnetic recording medium that can handle high-density recording and short wavelength recording.

Patent applicant: Sony Corporation

Claims (1)

[Claims] A magnetic recording medium characterized in that an undercoat layer having an average surface roughness Ra of 10 to 50 Å is formed on a substrate, and a ferromagnetic metal thin film is further formed thereon.