JPS6280825A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve practicable characteristics such as running property and durability of a recording medium and clogging of a head, etc., without spoiling an electromagnetic conversion characteristic by forming a thin ferromagnetic metallic film on a substrate on which peak-shaped projections, wrinkle-like projections and granular projections of prescribed sizes are formed. CONSTITUTION:Calcium carbonate having 1,000-1,500Angstrom is internally attached to the surface of a high-polymer film 1 constituting the magnetic recording medium to provide the gentle peak-shaped projections 2 having 100-200Angstrom average height, 2-8 deg. angle of inclination and 3X10<4>-4X10<4> pieces/mm<2> concn. The wrinkle-like projections 3 having 100-1,500Angstrom average height and the sharp granular projections 4 having 200-300Angstrom average height, 25-50 deg. angle of inclination and 15X10<6>-25X10<6> pieces/mm<2> concn. are further formed on the film 1. The thin ferromagnetic metallic film consisting of a Co-Ni alloy is formed thereon as the magnetic layer. The practicable characteristics such as running property and durability of the recording medium and clogging of the head, etc., are thus improved without spoiling the electromagnetic conversion characteristic.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a so-called ferromagnetic metal film formed by forming a ferromagnetic metal thin film as a magnetic layer on a substrate by a vacuum G1 film forming technique such as vapor deposition or sputtering. The present invention relates to a thin-film magnetic recording medium.

[Summary of the invention]

In the present invention, a ferromagnetic metal thin film is formed on a substrate having mountain-like protrusions, wrinkle-like protrusions, and granular protrusions on the surface, and the synergistic effect of these protrusions improves durability, runnability, dropout, and head. The objective is to provide a magnetic recording medium that has excellent practical characteristics such as clogging.

[Conventional technology]

Conventionally, as a magnetic recording medium, r -FezO containing r-Fe20i+Co on a substrate made of a non-magnetic material has been used.
2°Fe504. Fll containing Co! 304. r
Hertolide compounds of FezOz and FezOa,
Bertolide compounds containing Co, oxide magnetic powders such as Crow, or Fe, Co.

A magnetic layer is formed by dispersing powdered magnetic material such as alloy magnetic powder containing Ni etc. as the main component in an organic binder such as vinyl chloride-vinyl acetate copolymer, polyester resin, polyurethane resin, etc., coating it, and drying it. So-called coating-type magnetic recording media have been widely used.

In recent years, as the demand for high-density magnetic recording has increased, ferromagnetic metal thin films have been deposited directly onto substrates using vacuum thin film formation techniques such as vacuum evaporation, sputtering, and ion blating, as well as plating methods. The ferromagnetic metal thin film type magnetic recording medium created is attracting attention. This type of magnetic recording medium not only has high coercive force Hc and residual magnetic flux density Br, but also has extremely small thickness loss during recording demagnetization and reproduction because the thickness of the magnetic layer can be made extremely thin.
It has many advantages, such as the fact that it is not necessary to mix an organic binder, which is a non-magnetic material, into the magnetic layer, and the packing density of the magnetic material can be dramatically increased.

However, this ferromagnetic metal thin film type magnetic recording medium has many problems in running performance, durability, etc., which are practically important characteristics, and improvement thereof has become a major issue.

Therefore, various attempts have been made to improve these practical characteristics, for example, Japanese Patent Application Laid-Open Nos. 53-116115, 30231-1983, and 59-9.
As described in Japanese Patent No. 2428 and the like, it has been proposed to improve the above-mentioned runnability, durability, etc. by improving the surface properties of the plastic film that is the base.

[Problem that the invention seeks to solve]

By the way, according to experiments conducted by the present inventors, even when protrusions such as those described in the above publications are provided on the base, it is difficult to say that the effect is fully satisfactory; for example, the coefficient of friction is The reduction in torque is not sufficient, and the torque of the rotating drum increases accordingly, making running performance unstable.
Or, because the surface is close to a mirror surface, scratches are likely to occur during each process.
It was found that problems such as increased dropout and increased head clogging remained.

As a solution to these problems, methods such as increasing the height of the protrusions or increasing the density of the protrusions may be considered, but in this case, there is a risk that the magnetic properties and electromagnetic conversion properties will be impaired.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and is intended to improve practical characteristics such as runnability, durability, and head clogging in ferromagnetic metal thin film magnetic recording media by improving electromagnetic conversion characteristics. The aim is to improve without detracting.

Means for Solving the τ Problem] In order to achieve the above objects, the magnetic recording medium of the present invention has a surface height of 500 to 1000.

Density: I
It is characterized in that a ferromagnetic metal thin film is formed on a substrate on which granular protrusions of 500 Å and a density of 1×10 4 to 50×IO 6 pieces/ma” are formed.

That is, in the magnetic recording medium of the present invention, as shown in FIG.
A substrate (10) in which human undulations are provided as wrinkle-like protrusions (3) and organic or inorganic ultrafine particles are further attached to form granular protrusions (4) is used.

The above-mentioned mountain-like protrusions have a particle size of 500 when forming a polymer film.
It is formed by internally adding ~3000 inorganic fine particles (2), and the height from the polymer film surface is 500-
1000 people, density is lXl0'~10XIO' pieces/11
2. If the height of the mountain-like protrusions is too low, a sufficient effect cannot be expected, especially against head clogging. On the other hand, if the height of the mountain-like protrusion is too high, problems such as spacing loss will occur.

Further, it is preferable that the density is also within the above-mentioned range. In the present invention, the density of the mountain-like projections is approximately 1/10 of the density of the granular projections described below.
0, and is characterized by its height of 500 to 1000 people. The inorganic fine particles (2) used to form these mountain-like projections include calcium carbonate (CaCO
3), phosphoric acid, alumina, etc. are suitable.

The wrinkle-like protrusions (3) are undulations formed by applying and drying a dilute 3-8 solution of resin using a specific mixed medium, and the height thereof is 50 to 300. .

If the height of the wrinkled protrusions (3) is too low, it will be difficult to improve the slipperiness, and if the height exceeds 300 people, the output will decrease. Examples of resins include saturated polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyamides, polystyrene, polycarbonates, polyacrylates, polysulfones, polyethersulfones, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyphenylene oxide, and various resins such as phenoxy resins. A single substance, a mixture or a copolymer of , and those having a soluble solvent are suitable. Then, the resin obtained by dissolving these resins in the good solvent is 7 to 11,000 ppp.
By applying and drying on the surface of the polymer film (1) a solution in which a solvent that is a poor solvent for the resin and has a boiling point higher than the good solvent is added 10 to 100 times the amount of the resin to the solution. Thin layers with very fine wrinkle-like irregularities can be obtained.

The granular protrusions (4) are formed by attaching organic ultrafine particles such as acrylic resin or inorganic ultrafine particles such as silica or metal powder in a spherical or hemispherical shape after or during the formation of the wrinkle-like protrusions (3). It is formed from this. For example, as a method for forming granular protrusions made of organic ultrafine particles,
A method in which a solvent (non-solvent) that does not easily dissolve the resin is added to a thermoplastic resin solution with a concentration of 1% or less, and then applied and dried on the film surface (in this case, the formation of a core made of thermoplastic resin is achieved by adding a non-solvent). This may be carried out by precipitating in a suspended state at a certain point in time, or may be carried out in a suspended state only when it is dried after being applied onto a film surface.
This can be determined by the selection and composition of the thermoplastic resin, the solvent for dissolving it, the non-solvent to be added, etc.), or the film after adding another resin that can further fix the area around the core of the thermoplastic resin to the above compounded solution. There are methods such as applying it on the surface and drying it. The height of these granular projections is 50 to 500, and the density is 1×10 6 to 50×10 6 pieces/2 fins. If the height of the granular protrusions (4) is too low, it will be difficult to improve the slipperiness, and if the height exceeds 500 people, disturbances in the envelope will likely occur.The density is preferably set within the above-mentioned range. If the amount is too low, the effect will be insufficient, causing problems such as squeaking at high temperatures, and if it is too high, problems such as the generation of noise will occur.

Further, examples of the material of the polymer film (1) which is the main component of the substrate (10) used in the present invention include polyester, polyamide, polyimide, and the like.

A ferromagnetic metal thin film is formed as a magnetic layer by directly depositing a ferromagnetic metal material on the base (10) configured in this manner.

The ferromagnetic metal material constituting this ferromagnetic metal thin film includes metals such as Fe, Co, and Ni, or Fe-Co.
.

Fa-Ni, Co-Ni + Fe-Co-NL
Fe-Cu, Co-Cu, Co-Au, C
o-Pt.

Mn-B1, Mn-A It, Fe-Cr,
Co-Cr, Ni-Cr, Fe-Co-Cr, C
Examples include ferromagnetic alloys such as o-Ni-Cr and Fe-Co-Ni-Cr.

It may be a single N film or a multilayer film.

In addition, the means for depositing the ferromagnetic metal thin film is usually
Typical vacuum thin film forming techniques such as vacuum evaporation, ion blating, and sputtering are employed.

Here, in the vacuum evaporation method, 10-'~l O-BTorr
The ferromagnetic metal material is evaporated in a vacuum by resistance heating, high frequency heating, electron beam heating, etc., and the evaporated metal is deposited on the substrate. The ion blasting method is also a type of vacuum stem attachment method, and 10-'~l O-To
DC glow discharge and RF glow discharge are caused in an inert gas atmosphere of RR, and the above-mentioned ferromagnetic metal material is emitted en masse during the discharge. The sputtering method uses 10-' to 1
(A glow discharge is generated in an atmosphere mainly composed of argon (V'Torr), and the generated argon ions are used to knock out atoms on the target surface. , high-frequency sputtering method, magnetron sputtering method using a magnetron, etc.

In addition, when forming a ferromagnetic metal thin film by the method described above, in order to improve the adhesion between the substrate and the ferromagnetic metal thin film, or between each thin film in the case of a multilayer film, and to control the coercive force, etc. A geological layer or intermediate layer may also be provided. These base layers or intermediate layers include ^14, Si, Cr, Mn,
Examples include Zn, Bi, Ti, Cu, In, Ni1Co, Fe, and their oxides and nitrides.

Furthermore, a protective film may be formed on the above-mentioned ferromagnetic metal thin film in order to improve the corrosion resistance and runnability of the ferromagnetic metal thin film. This protective film may be an inorganic protective film made of metals or their oxides or nitrides as mentioned above for the underlayer or intermediate layer, fatty acids, or metal soaps that are alkali metal salts or alkaline earth metal salts of fatty acids. .

Examples include organic protective films such as higher alcohols, fatty acid esters, fluorine-containing compounds, and silicone oil.

[Effect]

In the present invention, a mountain-like protrusion formed on a base.

The wrinkle-like protrusions and granular protrusions work synergistically to improve the surface properties of the ferromagnetic metal thin film, ensuring practical properties such as runnability and durability without deteriorating the electromagnetic conversion properties due to spacing loss. .

〔Example〕

Calcium carbonate (CaCOx) is added internally to a height of 500~
1000 people 5 An average of 100
rugae with a height of ~150 people and an average height of 20
0 to 300 people, density 15X106 to 25X106 pieces/■
A magnetic recording medium was prepared by forming granular protrusions having a diameter of 12 and further forming a ferromagnetic metal thin film made of a Co--Ni alloy as a magnetic layer.

This was taken as an example.

On the other hand, wrinkle-like protrusions and granular protrusions were formed on a polyimide film with a smooth surface as in the previous example, and Co-N
A ferromagnetic metal thin film made of i-alloy is formed as a magnetic layer,
This was taken as a comparative example.

Regarding these Examples and Comparative Examples, Y-C/N and CC/N were first investigated as electromagnetic conversion characteristics.

The results are shown in the table below.

(Left below) From this table, it was found that there was no decrease in electromagnetic conversion characteristics even in the example in which the mountain-shaped projections were provided. When measured, it was found that there was a tendency as shown in Figure 2.

Furthermore, when we measured the change in torque (load current 2#) with running time, we found that there was a tendency as shown in FIG. 3. In other words, it can be said that the embodiments to which the present invention is applied have excellent running stability, with little increase in the coefficient of friction due to an increase in the number of shuttle runs or increase in torque due to an increase in running time.

Furthermore, in order to investigate the durability, still durability was measured, and results were obtained of approximately 35 minutes for the examples and 2 to 3 minutes for the comparative examples. As a result, it was found that the durability was also significantly improved by applying the present invention. In fact, when examining the relationship between the number of shuttle runs and the reproduction output, as shown in FIG. 4, a drastic decrease in the reproduction output was observed in the comparative example.

In addition, when the shuttle ran for 200 hours and examined the clogging rate during that time, it was found that in the comparative example, 6/20 (volume),
In the example, it was O/20 (S), and it was found that head clogging was extremely small.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since a ferromagnetic metal thin film is formed on a substrate with mountain-like protrusions, wrinkle-like protrusions, and granular protrusions, the synergistic effect of these protrusions makes the magnetic recording medium have extremely good surface properties, improving runnability and durability. It is possible to provide a magnetic recording medium with excellent properties.

Further, in the present invention, since the height of each protrusion is suppressed within a predetermined range, there is no deterioration of electromagnetic conversion characteristics due to spacing loss, etc., which is advantageous for high-density recording.

Furthermore, the magnetic recording medium according to the present invention has less head clogging, dropouts, etc., and recording and recording with less noise.
Reproduction is possible.

As described above, the magnetic recording medium of the present invention has significantly improved practical characteristics, and can be said to have great utility value.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged sectional view of a main part schematically showing the structure of a substrate used in the magnetic recording medium of the present invention. Figure 2 is a schematic characteristic diagram showing the relationship between the number of shuttle runs and friction coefficient, Figure 3 is a schematic characteristic diagram showing the relationship between running time and torque (load current), and Figure 4 is a diagram showing the relationship between the number of shuttle runs and friction coefficient. FIG. 3 is a schematic characteristic diagram showing the relationship between reproduction outputs. 2... Inorganic fine particles (forming mountain-like protrusions) 3... Wrinkle-like protrusions 4... Granular protrusions

Claims (1)

[Claims] Height 500-1000 Å on the surface, density 1 x 10^4-1
0x10^4 pieces/mm^2 mountain-like protrusions, height 50-30
0 Å wrinkle-like protrusions, and height 50-500 Å, density 1×
A magnetic recording medium characterized in that a ferromagnetic metal thin film is formed on a substrate on which granular protrusions of 10^6 to 50 x 10^6/mm^2 are formed.