JPS5982624A - Thin film type magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the bonding strength of a magnetic layer and the resistance of a magnetic recording medium to curling due to the effect of temp. and humidity by forming a polymer layer having a restricted modulus of tensile elasticity on one side or both sides of a substrate and a thin film of a ferromagnetic body contg. practically no org. high molecular compound on the surface of the polymer layer. CONSTITUTION:A polymer layer having >0.5-20mum thickness and 10-<350kg/ mm.<2> modulus of tensile elasticity is formed on one side or both sides of a substrate having >=350kg/mm.<2> modulus of tensile elasticity, and a thin film of a ferromagnetic body contg. practically no org. high molecular compound is formed on the surface of the polymer layer. The thickness of the polymer layer is half or less of the thickness of the substrate. The polymer layer is made of a vinyl chloride polymer, an acrylic polymer, an acrylate polymer or the like. The ferromagnetic thin film is a thin film type magnetic recording layer or a vertical magnetic recording layer, and it is formed by depositing a magnetic metal such as Fe, Co or Ni or a magnetic metallic compound such as Fe-Co, Fe-Ni or Fe- Co-Ni by plating, vacuum deposition, sputtering, ionic plating or other method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and particularly to a thin film magnetic recording medium.

Conventionally, magnetic recording media have been made by dispersing oxide-based ferromagnetic powder represented by γ-Fe, O, or metal-based ferromagnetic powder represented by Fe in an organic polymer (binder). So-called coated magnetic recording media, which are coated on the surface of non-magnetic substrates such as plastic films, aluminum, and glass, have been used. The binder in this case is necessary for coating the ferromagnetic powder as a strong coating film with wear resistance.

From the viewpoint of magnetic properties, it is an unnecessary additive that lowers the magnetic flux density. In other words, from the perspective of improving magnetic recording density, it is important to eliminate as much as possible of unnecessary components in terms of magnetic properties in the magnetic layer.
A desirable requirement is to make the film thin.

In recent years, in order to meet this requirement, so-called thin-film magnetic recording media have been developed, which are formed by plating a thin film of ferromagnetic material itself on a substrate, vacuum evaporation, sputtering, ion blating, etc.

Some of them are already in use. All of the devices that have been put into practical use, whether coating type or thin film type, have been longitudinal recording methods, but very recently, thin film magnetic recording media have been used, which is an order of magnitude faster than previous longitudinal recording methods. A perpendicular magnetic recording method that allows high recording density has been developed.

Improving recording density is not just a necessity in today's information society due to the high degree of integration.

This is necessary from the viewpoint of improving the sound quality, image quality, and reliability of information during playback, and it is also an issue that will be forever pursued for magnetic recording media. In this sense, thin-film magnetic recording media are the trend of an era.

In particular, the practical application of thin film magnetic recording media useful for perpendicular recording systems will continue to attract attention.

However, thin-film magnetic recording media have the following problems: (1) The ferromagnetic thin film is substantially made only of a flexible, inflexible magnetic metal layer, and has a different thermal expansion coefficient and humidity expansion coefficient from the substrate; (1) ferromagnetism; Due to the fact that the absolute thickness of the body thin film itself is small, it has the following practical disadvantages.

■ Formation process of ferromagnetic thin film or temperature during practical use,
Changes in humidity cause curling and deformation of magnetic recording media.

■ If this deformation is large, cracks will occur in the thin ferromagnetic film, resulting in output fluctuations and dropouts during magnetic recording and reproduction. Also, the crack was the trigger.

Scratches and detachment of the ferromagnetic thin film occur.

Essentially, no matter how high the recording density is, if there are practical drawbacks such as those mentioned above, there will be problems in terms of long-term use and reliability, and it will not be possible to use it widely and with peace of mind. have not been able to fully utilize their strengths.

The present inventor conducted extensive research in view of this problem and arrived at the present invention.

That is, the object of the present invention is to improve the adhesive strength of the magnetic layer and the curl resistance of a magnetic recording medium due to the effects of temperature and humidity.

Our objective is to provide all thin-film magnetic recording media with excellent practical characteristics such as playback output.

The present invention has the following configuration to achieve all of the above objects.

That is, on one or both sides of a substrate with a tensile modulus of 550 kg/mm' or more, a layer with a thickness exceeding 0.5 μm is applied.
The thickness is within 0μ, and the thickness is 1A or less of the substrate.

Tensile modulus is 10/mm” or more 650kg, 7m
The invention is characterized by a thin-film magnetic recording medium comprising a polymer layer with a thickness of less than m'' and a thin gold film of a ferromagnetic material that does not substantially contain an organic polymer compound on the surface of the polymer layer. .

In the present invention, the tensile modulus is 350 k6/mm"
The above substrate is not particularly limited as long as it has a tensile modulus of 350 kg/mm'' or more.

Specifically, polyesters such as niha, polyethylene terephthalate, and polyethylene 2.6 naphthalate.

Examples include polyolefins such as polypropylene, polycarbonates, acrylonitrile, acrylic, polyphenylene sulfide, aromatic polyamides, plastic films, sheets, and plates such as polyimides, metal foils or plates such as aluminum, diralmin, titanium, copper, and glass. Ru.

Among these, plastic films are suitable in terms of flexibility, flatness, mechanical properties, etc., and biaxially stretched ones are particularly preferred because they can easily achieve a tensile modulus of 350 kg/mm'. The higher the tensile modulus, the less deformation due to tension, etc. during practical use of the magnetic recording medium.

In addition to improving dimensional stability, the substrate can be made thinner, leading to an increase in recording density per volume.
This is preferable in terms of the structure of the present invention.

Although the upper limit of the tensile modulus is not particularly regulated,
Practically, it can be used up to about 2.000 kg/mm.The preferred range of tensile modulus is 400 kg/mm.
500 bags/mm or more, preferably 500 bags/mm or more.

It is preferably used in terms of dimensional stability, thinning, and shape retention.

Thickness of the substrate vi1 Type, form, characteristics, etc. of the magnetic material.

Although it cannot be determined generally, since it is determined by taking into account various requirements, a range of 2 μm to 3 mm is useful.

Especially if the substrate is a plastic film.

A range of 3μ to 200μ, preferably 6μ to 100μ is desirable.

In the present invention, the tensile modulus of the substrate is 350 k
If the thickness of the substrate is less than this range, the magnetic recording medium itself will not have the toughness, and if the dimensional change is large, the same problem will occur, which is not desirable.On the other hand, if the thickness of the substrate exceeds the above range, it is not desirable. This is undesirable because the recording density relative to the total volume of the magnetic recording medium decreases.

In the present invention, the polymer layer with a tensile modulus of 10 kg/mm2 or more and less than 550 kg/mm'' may be one that is composed entirely of polymer compounds with a tensile modulus within this range, but there are specific examples. is a vinyl chloride polymer.

Acrylic polymer, acrylic ester polymer.

Methacrylic acid ester polymer, diallyl phthalate polymer, amide polymer, acrylonitrile polymer 1
．． Polysulfone polymers, ether polymers, ketone polymers, epoxy polymers.

There are many others such as these and other copolymers.

It may be a graft, a block, or a blend, or it may be composed of two or more layers thereof. In particular, the polymer layer has a solubility parameter (5ol).
utility Parameter) is 85 or higher.

It is preferable that a portion consisting of a monomer (constituent unit) containing oxygen, nitrogen, sulfur, chlorine, etc. in the molecule is contained in an amount of 50 weight φ or more in order to increase the peeling resistance between each layer. Further, the thickness of the polymer layer needs to be more than 0.5μ and within IA of the substrate or 20μ.

If this thickness is less than 0.5μ, the object of the present invention cannot be achieved. If it exceeds - or exceeds 920μ, the magnetic recording medium itself will deteriorate in toughness and change in dimensions, which is undesirable. Various known methods such as coating, laminating, etc. can be used to coat the entire polymer layer on one or both sides of the substrate.

The thin film layer made of a ferromagnetic material that does not substantially contain an organic polymer compound according to the present invention is a so-called thin film magnetic recording layer or a perpendicular magnetic recording layer, and the latter is more preferable, and specifically, Fe, Go , magnetic metals such as Ni, F
e-Co, Fe-Ni, , Fe-Co-Ni, G
Alloys such as o-Cr, C0-Rh, C0-Cr-N1, γ-Fe 20 h, Fe 30 a HCr O
It is provided by a magnetic metal compound such as 21COF r CON I P by a full plating method, a vacuum evaporation method, a sputtering method, an ion blating method, etc., and its thickness is 0.05μ to 5.0μ, preferably 0.0μ. .08μ to 1
．． A range of 0μ is desirable.

These ferromagnetic materials not only have poor malleability as a mechanical property, but also, as a result of detailed measurements by the inventors,
The elongation at break of a thin film of 5 μ or less is significantly smaller than that of the bulk, at most 1 inch or less, and most of it is 0.5 μ or less. It was found that cracks were formed.

In addition, the temperature expansion coefficient of a ferromagnetic thin film is 5 to 13x10
/°o, which is smaller than that of most substrate plastic films, and the substrate plastic film also has a significantly larger coefficient of humidity expansion. For this reason, if a thin film layer is directly formed on the surface of a substrate without using the entire polymer layer, curling or deformation may occur due to changes in temperature and humidity during the formation process or during use, or cracks may occur in the thin film layer. The result is that on the other hand.

When a thin film layer is formed after forming a polymer layer as in the present invention, there is no deformation or cracking, and there are no dropouts or output fluctuations, probably because the polymer layer acts as a buffer against changes in the external environment. It is possible to obtain a thin-film type magnetic recording medium with good durability and low oxidation.

The magnetic recording medium according to the present invention has high-density recording characteristics as a thin-film magnetic recording medium, and at the same time has adhesive strength, impact resistance, and abrasion resistance close to those of a coated magnetic recording medium, and has durability and Tape as a reliable high-density magnetic recording medium
It can be widely used in the form of cards or disks.

Note that the tensile modulus in the present invention is;
In the case of an anisotropic material, the initial elastic modulus is the initial elastic modulus when the specimen is stretched according to 2318-72.

It is the average value of the value in the direction showing the maximum value within the plane and the value in the direction perpendicular to it within the plane.

Nine embodiments of the present invention will be described below.

Example 1 Polysulfone (USA U "Ctfff" - 1-te/l/”) to 4
μ was applied (polysulfone was applied on a glass plate under the same conditions, and the tensile modulus was measured.
0 kg/mm"). A co-Cr plate (cr:
As a target, a Co--Cr film with a thickness of 0.5 μm was prepared by high-frequency magnetron sputtering. The obtained material exhibited magnetic anisotropy in the direction perpendicular to the substrate and had a coercive force of 400 oersteds.

Even when this material was bent with a curvature of ID mm, no cracking or peeling occurred, and it exhibited sufficient flexibility. Further, in a peel test using a polyester adhesive tape (manufactured by Nitto Denko, m61B), no peeling occurred and sufficient adhesive strength was exhibited. Furthermore, this thing is a mini-floppy disk drive (manufactured by Apple Inc.,
All signals are recorded and reproduced using a device modified to Disk II)'.
Thereafter, a 24-hour continuous rotation test was performed, and all recorded symbols were reproduced.

The head touch was good, and the reproduction output was unchanged from before rotation, and no change was observed in the magnetic layer when observed under a microscope.

Example 2 Tensile modulus is 1200 kg/mm” and thickness is 9μ
On one side of the biaxially stretched aromatic polyamide film of
μ was applied. ("Cotax" LH601 was applied on a glass plate under the same conditions and peeled off.

When the tensile modulus was completely measured, it was 120kg/n.
Met). A Co-Cr plate (Cr 19% by weight) was placed on the acrylic resin side of the film substrate thus obtained.
As all targets, a co-cr film with a thickness of 0.5 μm was created by direct current magnetron sputtering. The obtained magnetic film exhibited magnetic anisotropy in the direction perpendicular to the substrate and had a coercive force of 500 oersteds.

Even if you bend this thing 10 times with a 9 curvature of 10 mm, there will be 9 cracks.
It exhibited sufficient flexibility without causing peeling.

Also, temperature range 10°0 to 40'o, humidity range 20%
Even when the storage atmosphere was changed from RH to 80% RH, there was no deformation of the substrate or cracking of the magnetic film.

Furthermore, all this stuff has a mini-floppy disk drive (
All signals were recorded and reproduced using a modified device made by Apple Inc., and then a 24-hour continuous rotation test was performed and all recorded signals were reproduced. The head touch was good, the reproduction output was unchanged from before rotation, and no change was observed in the magnetic layer when observed under a microscope.

Example 6 At was applied to the polysulfone surface of the substrate film obtained in Example 1.
f O,06p, then Co-Ni (75:
25 weight ratio) -<0.2μ, each thin film was formed by vacuum evaporation. This material has magnetic anisotropy in the horizontal direction.

It had a coercive force of 600 Qei. Various property tests were conducted on this product in accordance with Example 1, but no changes were observed in any of the properties compared to before the test.

Patent Applicant Coming/Stock Company Procedures
Correction self b8. i2. / Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office (Monday/Monday, 1980) 1. Indication of the case: Patent Application No. 178369 of 1983 2. Title of the invention: Thin-film magnetic recording medium 3. Person making the amendment: Relationship with the case: Patent applicant Voluntary action 5. No increase in the number of inventions due to amendment 6. Subject of amendment 1lIl "Detailed description of the invention" column (1)
Book, page 4, line 12, ``Atsuga'' is corrected to [thickness is j].

(2) Same, page 5, line 7 Correct [dirarumin] to "duralumin".

(3) "Polymer, acrylic polymer" from page 6, line 20 to page 7, line 1 is defined as [polymer, nylidene chloride polymer, vinyl acetate polymer, vinyl fluoride polymer, Corrected as styrene polymer, butadiene polymer, urethane polymer, polyester polymer, and acrylic polymer J.

(4) Same page 12, line 20 Correct rQeJ to ``Oersted J.

173-

Claims (1)

[Claims] On one or both sides of a substrate with a tensile modulus of 350 kg/mm" or more, with a thickness of more than 0.5 μm and within 20 μm, and with a tensile modulus of 1/2 or less of that of the substrate. 10
kg/mm'' or more and less than 350 kg/mm''. A thin film magnetic recording medium comprising a ferromagnetic thin film layer substantially free of organic polymer compounds on the surface of the polymer layer. .