JPS59167842A - Vertical magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium suitable for high density recording and having excellent durability by providing successively a high permeability magnetic layer made of thin film of high permeability magnetic alloy and a vertical magnetizing layer made of thin film taking ferromagnetic powder and a binder as major components. CONSTITUTION:A vertical magnetic recording head 1 consists of a main magnetic pole 1a and an auxiliary magnetic pole 1b wound with a coil 2, and a vertical magnetic recording medium 3 is formed by a vertical magnetizing layer 3a, a high permeability magnetic layer 3b, and a nonmagnetic support base 3c. The high permeability magnetic alloy is formed on the support base 3c in the form of thin film for the magnetic layer 3b by the method such as sputtering, vapor-deposition, ion plating or the like, and then application of a magnetic field in the horizontal direction to the thin film face and heat treatment or the like are performed. The magnetizing layer 3a is formed by coating a magnetic paint taking the ferromagnetic powder and the binder as the major components in the form of thin film on the magnetic layer 3b formed above, applying a magnetic field to the coated face in vertical direction so as to orient the easy magnetization axis in vertical direction and drying the layer. Thus, a recording medium suitable for high density recording and having durability is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a recording medium used in a perpendicular magnetic recording system particularly suitable for high-density recording.

The conventional perpendicular magnetic recording system enables higher-density recording than the general horizontal magnetic recording system, and the recording medium used is an ideal system with the feature of being stably magnetized without being subjected to demagnetizing fields. It is currently being put into practical use as a recording method.An example of a typical perpendicular magnetic recording method is shown in Figure 1 (in the figure, 1 indicates the main magnetic pole 1).
A perpendicular magnetic recording head consisting of an auxiliary magnetic pole 1b around which a coil 2 is wound, 3 a perpendicular magnetic layer 3, a high permeability magnetic layer 3;
perpendicular magnetic recording medium consisting of b and non-magnetic support 3c, 4
To explain magnetic force, first, perpendicular magnetic recording head 1
When a signal current for recording is passed through the coil 2, the auxiliary magnetic pole 1b is excited depending on the strength of this current, the main magnetic pole ja is magnetized by the magnetic field, and the magnetic flux 4 is further magnetized by the magnetic field of the main magnetic pole 1a. Since it penetrates the recording medium 3, the perpendicular magnetization layer 3a of the recording medium 3 is magnetically recorded in a direction perpendicular to the medium surface. At this time, the high permeability magnetic layer 3b of the recording medium 3 is the entire layer 3 including the perpendicular magnetic layer 3a.
At the same time as increasing the residual magnetization of m, 3b, rad 1
The main magnetic pole of 1. This plays a major role in increasing the recording and reproducing efficiency by bringing the auxiliary magnetic pole (b) and the auxiliary magnetic pole (b) magnetically close to each other. Note that the recording medium 3 used here is a non-magnetic support 3 such as a polyester film or a polyimide film.
A high permeability magnetic layer 3b was provided on C by forming a high permeability magnetic alloy such as -Zo-Malloy (Fe-Ni alloy) into a thin film by sputtering, vapor deposition, or ion blasting. Thereafter, a ferromagnetic material such as C6-Cr alloy or Ba-ferrite is formed into a thin film thereon by a similar method to provide a perpendicular magnetization layer 3a.

However, since the perpendicular magnetic recording layer on the surface of the recording medium for the perpendicular magnetic recording system is made of a thin ferromagnetic film, it is possible to obtain high output. .

(1) During the recording, reproducing, and erasing processes, the frictional resistance of members such as the recording head and guide poles for guiding the recording medium is large (and therefore easy to wear out).

(2) Easily corroded by environmental conditions, especially at high temperatures and high humidity.

(3) When subjected to impact force during handling, the surface layer is particularly susceptible to damage. In addition, both the perpendicular magnetization layer and the high permeability magnetic layer are formed by a method that requires vacuum equipment, such as star-stuttering, vapor deposition, or ion blating, so (4) the cost is high and the manufacturing speed is slow; There is also the problem of poor productivity.

Conventionally, to solve the problems (1) to (3), a method has been adopted, for example, to provide a protective layer such as a lubricant or metal oxide on the perpendicular magnetic layer, but such a method is not suitable for high output and Good frequency characteristics cannot be obtained, and even if it is good when used as an audio tape, video tape, etc., it becomes noticeable even if the magnetic head is operated more than 10,000 times on the same track as in floppy disks, flexible disks, etc. It is not effective for products that require durability without reducing output.

Purpose The purpose of the present invention is to solve the above-mentioned problems. It is an object of the present invention to provide a perpendicular magnetic recording medium that eliminates the drawbacks of a perpendicular magnetic recording medium, has high output and good frequency characteristics in high-density recording, and has excellent durability and productivity.

Structure The perpendicular magnetic recording medium of the present invention is a perpendicular magnetic recording medium in which a high permeability magnetic layer and a perpendicular magnetic layer are sequentially provided on at least one surface of a non-magnetic support, in which the high permeability magnetic layer is made of a high permeability magnetic alloy. The perpendicular magnetization layer is a thin film mainly composed of ferromagnetic powder and a binder.

The high magnetic permeability magnetic layer of the present invention is made by forming a high permeability magnetic alloy into a thin film on a non-magnetic support by sputtering, vapor deposition, ion blating, etc. in the same way as in the past. It is formed by applying a magnetic field, heat treatment, etc. so that it has high magnetic permeability and low coercive force (in the in-plane direction). The appropriate thickness of the layer is about 0.1 to 1 μm. Here, as the non-magnetic support, a plastic film such as polyester or polyimide; paper; a non-magnetic metal plate such as A2; a glass plate, etc. can be used; however, a plastic film is usually used. In addition, examples of high permeability magnetic alloys include permalloy (re-Ni alloy), Mo-nozo-malloy, and Cu.
-Mo-noξ-Malloy etc. are used. It is also possible to form a high permeability magnetic layer by a coating method, but in the case of a coating method, there are difficulties in terms of materials, and the unevenness of the film surface is thicker than in methods such as sputtering or vapor deposition. (To become,
In particular, when a perpendicular magnetization layer is formed on top of it using the same coating method, it becomes difficult to control the smoothness and thickness of the surface layer.
As a result, the output fluctuation f (modulation) during recording and reproduction becomes large, which is not preferable.

On the other hand, the perpendicular magnetization layer of the present invention is obtained by applying a thin film of magnetic paint containing ferromagnetic powder and a binder to the high permeability magnetic layer formed by 51C as described above. It can be formed by applying a magnetic field in the vertical direction to orient the axis of easy magnetization in the vertical direction and drying.

Note that in order to achieve orientation, heat treatment may be performed along with application of a magnetic field during coating. The thickness of the layer can be appropriately selected depending on the application, but is usually about 0.5 to 3 μm. As the coating means, conventional means such as a blade coater, reverse roll coater, gravure roll coater, air 1-4 coater, spinner coater, etc. are employed.

Here, the ferromagnetic powders include Ba ferrite, Co7 elite, Co-Fe alloy, Co-Ni alloy, Fe-Co
-Ni alloy, CrO@, etc.

The shape and size of these powders are not particularly limited, but considering the improvement of the axial ratio during recording and reproduction, the size is 0.5μ.
Hereinafter, it is preferable that the shape has a length/gravity ratio close to 1.

The binder is used to uniformly disperse the ferromagnetic powder in the coating of the perpendicularly magnetized layer and to bind the coating to the underlying high permeability magnetic layer. Such binders include thermoplastic resins, thermosetting resins, or reactive resins, electron beam curable resins or monomers, and mixtures thereof. Specifically, the thermoplastic resin has a softening temperature of 150'C or less, an average molecular weight of 10,000 to 20,000, and a polymerization degree of 1.
00 to 1000, such as vinyl chloride-vinylacetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride Copolymer, acrylic ester
Styrene copolymer, methacrylic acid ester-acrylonitrile copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene - Acrylonitrile copolymers, polyamides, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate,
tate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester,
Examples include chlorovinyl niterulac IJ/I/acid ester copolymer, amine resin, various synthetic rubbers, and mixtures thereof. Thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reactive resins, mixtures of high molecular weight polyesters and isocyanate prepolymers, and methacrylic resins. Examples include mixtures of acid acid copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyinocyanates, mixtures of low molecular weight glycols, high molecular weight diols, and triphenylmethane triisocyanate, polyamine resins, and mixtures thereof. can.

Examples of resins or monomers that can be cured by electron beams include resins containing radically polymerizable unsaturated groups in their molecules, such as acryloyl groups, methacrytetrayl groups, allyl groups, vinyl ether groups, and acrylamide groups, preferably acryloyl groups. Preferred examples include epoxy acrylate, polyester acrylate, and polyurethane acrylate. In any case, the above binder is usually used in an amount of 10 to 200 parts by weight per 100 parts by weight of the ferromagnetic powder.

In addition to the above-mentioned materials, conventional additives such as dispersants, lubricants, and antistatic agents can be added to the perpendicular magnetization layer of the present invention. Dispersants include fatty acids having 12 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, lylunic acid, and stearolic acid; Alkali metal salts such as Ll, Na, Ni or MP, Ca,
Metal soaps made of alkaline earth metal salts such as Ba; lecithin; higher alcohols having 12 or more carbon atoms and their sulfuric esters can be used. These dispersants/agents are usually added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder. As a lubricant, silicone oil, graphite,
Molybdenum disulfide, tungsten disulfide, carbon number 12 ~
Fatty acid esters consisting of 16 monobasic fatty acids and a monohydric alcohol having 3 to 12 carbon atoms, with a total carbon number of 21 including the monobasic fatty acids with 17 or more carbon atoms and the carbon number of this fatty acid. Fatty acid esters consisting of ~25 monohydric alcohols, etc. can be used. These lubricants are usually
It is added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder. As the antistatic agent, conductive powders such as carzen black, graphite, carbon black graft polymers, etc., and various surfactants such as cationic and anionic mono-ampholytic surfactants can be used.

EXAMPLE A high permeability magnetic layer having a thickness of 1 μm was provided on a polyester film by sputtering KMO-/''-Malloy under the following conditions for about 20 minutes.

Back pressure: l, 'QXIO-Torr Argon gas pressure: 5. OX 10-'' Torr high frequency electric crab 600W Support temperature = 150°C The coercive force of this high magnetic permeability magnetic layer was 0.5 oersted, and the magnetic permeability was 5000 at maximum.

Next, a magnetic paint with the following formulation is applied on this high permeability magnetic layer.
It was coated using a Mars roll coater and then dried while applying a perpendicular magnetic field of 800 Gauss to form a perpendicular magnetic layer having a thickness of 2 μm, thereby obtaining a perpendicular magnetic recording medium.

Ba-ferrite ioo parts by weight Vinyl chloride-vinyl acetate copolymer 15” Epoxy resin 71 Polyamide
5' car in black
71 Olein Knowledge
11 Methyl ethyl ketone 2
00 lThe Br/Bm ratio in the perpendicular direction of this perpendicular magnetization layer was 0.45.

Comparative Example A perpendicular magnetic recording medium was prepared in the same manner as in the example except that the high magnetic permeability layer was not provided and a perpendicular magnetic layer was provided directly on the support.

Next, for each recording medium obtained as described above, the first
When high-density recording was performed using the perpendicular magnetic recording method shown in the figure, a frequency characteristic curve as shown in FIG. 2 (A in the figure is a product of the present invention and B is a comparative product) was obtained. In addition, when we conducted a durability test on the same track, we found that even after 5 million times of processing, the playback output of each sample was 80% compared to the initial output.
%, and it was confirmed that it had the same durability as a floppy disk (horizontal magnetic recording method) using a conventional coating method.

Effects As described above, the perpendicular magnetic recording medium of the present invention provides high output and good frequency characteristics in high-density recording, and at the same time, since the perpendicular magnetic layer is formed by a coating method, it has excellent durability and high productivity. can get.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a perpendicular magnetic recording system applied to the perpendicular magnetic recording medium of the present invention, and FIG. 2 is a frequency characteristic curve diagram of the perpendicular magnetic recording media obtained in Examples and Comparative Examples.

Claims (1)

[Claims] 1. In a perpendicular magnetic recording medium in which a high permeability magnetic layer and a perpendicular magnetization layer are sequentially provided on at least one surface of a non-magnetic support, the high permeability magnetic layer is made of a thin film of a high permeability magnetic alloy,
A perpendicular magnetic recording medium characterized in that the perpendicular magnetization layer is made of a thin film mainly composed of ferromagnetic powder and a binder.