JPH06162479A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium having a high output over a wide frequency range, generating slight noise, fit for high density recording and excellent in corrosion resistance. CONSTITUTION:A magnetic layer contg. flat platy magnetic powder of hexagonal ferrite and acicular metallic magnetic powder is formed on a nonmagnetic substrate to obtain the objective magnetic recording medium. The coercive force of the magnetic powder of hexagonal ferrite is 800-1,900Oe, that of the metallic magnetic powder is 800-1,900Oe and the difference in coercive force between the magnetic powders is as small as + or -10%. The ratio between the magnetic powder of hexagonal ferrite and the metallic magnetic powder is (95-50):(5-50).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape, a magnetic sheet or a magnetic disk.

[0002]

BACKGROUND OF THE INVENTION Coating type magnetic recording media such as magnetic tapes are
Produced by coating a magnetic paint obtained by kneading magnetic powder such as γ-Fe ₂ O ₃ , a binder, various additives and a solvent on a base film (non-magnetic support) such as a polyester film. ing.

By the way, the conventional magnetic recording medium manufactured in this manner has a problem in terms of high density recording, and therefore, a magnetic recording medium using barium ferrite magnetic powder has been proposed. For example, a coating type magnetic recording medium has been proposed in which barium ferrite magnetic powder and acicular metal iron magnetic powder are contained in a magnetic layer (Japanese Patent Laid-Open No. 61-233421).

However, the magnetic recording medium according to this proposal has not been fully satisfactory.

[0005]

DISCLOSURE OF THE INVENTION In the course of earnestly researching the above-mentioned problems, the problems in a coating type magnetic recording medium in which barium ferrite magnetic powder and acicular metal magnetic powder are contained in a magnetic layer It has been found that this is not only due to the large amount of the magnetic metal powder, but also because there is an excessive difference in the magnetic characteristics between the barium ferrite magnetic powder and the magnetic metal powder, particularly the coercive force.

For example, the coercive force of the barium ferrite magnetic powder disclosed in Japanese Patent Laid-Open No. 61-233421 is 85.
The coercive force of the metal magnetic powder is 1200, while it is 0 Oe.
It is also known that there is a problem that the S / N is low due to the difference in the magnetic properties of both magnetic powders. Further, it was found that there is a problem in the corrosion resistance because of the large amount of metal magnetic powder.

The present invention has been achieved based on such knowledge, and an object of the present invention is to provide high output over a wide frequency range, low noise, and suitable for high density recording. Further, it is to provide a magnetic recording medium having excellent corrosion resistance. An object of the present invention is a magnetic recording medium comprising a non-magnetic support and a magnetic layer containing flat hexagonal ferrite magnetic powder and acicular metal magnetic powder, wherein the hexagonal crystal is used. The coercive force of the system ferrite magnetic powder is 800 to 1900 Oe, the coercive force of the metal magnetic powder is 800 to 1900 Oe, and the coercive force of the hexagonal ferrite magnetic powder and the metal magnetic powder is ± 10%.
Within the range of about 100% and the ratio of the hexagonal ferrite magnetic powder to the metal magnetic powder is 95
It is achieved by a magnetic recording medium characterized by being ˜50 / 5 to 50.

The present invention will be described in detail below. It is important that the acicular magnetic powder used in the magnetic recording medium of the present invention is a metal magnetic powder, not an oxide-based ferromagnetic powder such as ferromagnetic iron oxide or ferromagnetic chromium dioxide. . For example, Fe, Co-Ni, Co-Ni-P,
Fe-Ni-P, Fe-Ni-Zn, Fe-Co, Fe
-A metal magnetic powder such as Ni-Co is used.

It is also important that the magnetic powder is a metal magnetic powder having a coercive force of about 800 to 1900 Oe. That is, if the coercive force of the metal magnetic powder is less than 800 Oe, which is too small, and if the coercive force of the hexagonal ferrite magnetic powder described later is large, the magnetic properties of the two become too different, and the S / N decreases. This is because if a problem occurs and the coercive force of the hexagonal ferrite magnetic powder is made small in terms of S / N, then the reproduction output itself becomes small. On the contrary, when the coercive force of the metal magnetic powder exceeds 1900 Oe and is too large, the same is true. Therefore, the coercive force needs to be about 800 to 1900 Oe.

The saturation magnetization σs is about 100 to 160 em.
u / g metal magnetic powder is preferable, and the length of the metal magnetic powder in the major axis direction is about 0.1 to 0.3 μ.
m, and the needle-like ratio is preferably about 5 to 20.
As the flat magnetic powder, a hexagonal ferrite magnetic powder represented by BaO.6Fe ₂ O ₃ or a part of Ba or Fe represented by the above chemical formula is Ti, Cr, Co, Zn, In, M.
It is possible to use barium ferrite magnetic powder substituted with a metal such as n, Cu, Ge or Nb.

In particular, it is important to use flat magnetic powder having a coercive force of about 800 to 1900 Oe. That is, when a tabular magnetic powder having a coercive force deviating from about 800 to 1900 Oe is used, the coercive force of the hexagonal ferrite magnetic powder and the metal magnetic powder is hard to be within the range of ± 10%, and S / N
This is because the problem of the decrease in the value cannot be improved.
The hexagonal ferrite magnetic powder has a thickness of about 0.0
Those having a size of 03 to 0.1 μm and a diameter of about 0.03 to 0.5 μm are preferable.

Barium ferrite magnetic powder (hexagonal ferrite magnetic powder) is obtained by a solid phase reaction method, a coprecipitation-heating reaction method, a hydrothermal synthesis method, an oxide flux method, a molten salt method, a glass crystallization method, or the like. To be Above all, a barium ferrite component is mixed with a glass-forming substance typified by B ₂ O ₃ ,
Melts at a temperature of 1300 ° C or higher, rapidly cools this to obtain glass (amorphous body), heats this glass again to a temperature of 700 ° C or higher to crystallize, and extra glass substances and acids are heated in hot water. What was obtained by the glass crystallization method, such as dissolving by, for example, washing with water and drying.

Further, not only the hexagonal ferrite magnetic powder and the metal magnetic powder having the above characteristics are used,
The ratio of hexagonal ferrite magnetic powder / metal magnetic powder is 95.
It was also important that it was -50 / 5-50. That is, by reducing the amount of the metal magnetic powder to less than 50 wt%, the problem of corrosion resistance when using the metal magnetic powder is solved. The ratio of hexagonal ferrite magnetic powder / metal magnetic powder is preferably about 80-60 / 20-40 (weight ratio).

As the binder (binder) used in the magnetic layer (magnetic coating film) of the magnetic recording medium, a thermoplastic resin, a thermosetting resin, a reactive resin or a mixture thereof can be used in combination. For example, as the thermoplastic resin, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester -Vinylidene chloride copolymer, acrylic acid ester-styrene copolymer, methacrylic acid ester-acrylonitrile copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, urethane elastomer, polyfluorination Vinyl, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer,
Polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, various synthetic rubber thermoplastic resins (Polybutadiene, polychloroprene, polyisoprene, styrene-butadiene copolymer, etc.) and mixtures thereof. These binder resin components are used in an amount of about 10 to 100 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the magnetic powder.

In the magnetic coating film of the magnetic recording medium, in addition to the above-mentioned components, as a commonly used additive in this field, a dispersant, a lubricant, an abrasive, an antistatic agent, a rust preventive, a fungicide, etc. May be added. As the dispersant, a fatty acid having 12 to 18 carbon atoms (R ₁ COOH, R ₁ is an alkyl or alkenyl group having 11 to 17 carbon atoms), an alkali metal (Li, Na, K, etc.) of the above fatty acid, or an alkali Earth metal (Mg,
Ca, Ba, etc.) metal soap, fluorine-containing compound of the above fatty acid ester, amide of the above fatty acid,
Examples thereof include polyalkylene oxide alkyl phosphates, lecithin, and trialkylpolyolefinoxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms, olefin has ethylene, propylene, etc.). In addition to these, there are higher alcohols having 12 or more carbon atoms, sulfuric acid esters and the like.
These dispersants may be added in an amount of 10 parts by weight or less based on 100 parts by weight of the magnetic powder.

As the lubricant, the above-mentioned dispersant is also effective, but dialkyl polysiloxane (wherein the alkyl group has 1 carbon atom)
~ 5), dialkoxy polysiloxane (alkoxy group has 1 to 4 carbon atoms), monoalkyl monoalkoxy polysiloxane (alkyl group has 1 to 5 carbon atoms, alkoxy group has 1 to 4 carbon atoms), phenyl Polysiloxane, fluoroalkylpolysiloxane (alkyl group has 1 to 5 carbon atoms
Individual) silicone oil, conductive fine powder such as graphite, inorganic fine powder such as molybdenum disulfide, tungsten disulfide, plastic fine powder such as polyethylene, polypropylene, polyethylene-vinyl chloride copolymer, polytetrafluoroethylene, etc. α-Olefin polymer, unsaturated aliphatic hydrocarbon which is liquid at normal temperature, fatty acid ester composed of monobasic aliphatic having 12 to 20 carbon atoms and monohydric alcohol having 3 to 12 carbon atoms, fluorocarbons, etc. Is mentioned. These lubricants are added in the range of 0.1 to 15 parts by weight with respect to 100 parts by weight of the magnetic powder.

Examples of the abrasive include fused alumina, silicon carbide, chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main components: conradam and magnetite). As these abrasives, those having a Mohs hardness of 5 or more and an average particle diameter of 0.05 to 5 μm are used, and particularly preferably 0.1 to 2 μm. And these abrasives are 0.5-1 with respect to 100 weight part of magnetic powder.
It is added in the range of 5 parts by weight.

As the antistatic agent, conductive fine powder such as carbon black, natural surfactant such as saponin, nonionic surfactant such as alkylene oxide, glycerin and glycidol, higher alkylamines, quaternary ammonium. Salts, pyridine and other heterocycles, cation surfactants such as phosphonium or sulfonium, anionic surfactants containing carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester group, acid group such as phosphoric acid ester group, amino acids, amino sulfone Examples thereof include amphoteric activators such as acids and sulfuric acid or phosphoric acid esters of amino alcohols. Such conductive fine powder is added in the range of 0.01 to 10 parts by weight with respect to 100 parts by weight of magnetic powder. You may add the said surfactant individually or in mixture. Although these are used as antistatic agents, they are sometimes used for other purposes such as dispersion, improvement of magnetic properties, improvement of lubricity, and coating aid.

The material of the non-magnetic support used for the magnetic recording medium is polyeletin terephthalate (PET),
Polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose derivatives such as cellulose acetate propionate, polyvinyl chloride, polyvinylidene chloride, etc. Of vinyl resin, plastics such as polycarbonate, polyimide, polyamide-imide, etc., paper, baryta or polyethylene, polypropylene, ethylene-butene copolymer and the like having 2 to 1 carbon atoms
Papers such as paper coated or laminated with 0 α-polyolefins can also be used. These non-magnetic supports may be transparent or opaque depending on the purpose of use.

Solvents used for the production of magnetic paints include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate and glycol monoethyl ether acetate. Solvent, ether, glycol dimethyl ether, glycol monoethyl ether, glycol ether type solvent such as dioxane, tar type (aromatic hydrocarbon type) solvent such as benzene, toluene, xylene, methylene chloride, ethylene chloride, carbon tetrachloride A chlorinated hydrocarbon solvent such as chloroform, ethylene chlorohydrin, or dichlorobenzene can be appropriately selected and used.

Magnetic powder, binder and the like are kneaded to form a magnetic coating material. At the time of kneading, the magnetic powder and the above-mentioned components are all introduced into the kneading machine at the same time or individually. In kneading and dispersing the magnetic paint, various kneading machines such as a two-roll mill, a three-roll mill, a ball mill, a pebble mill, a tron mill, a sand glider, and an S
zegvari attritor, high speed impeller disperser,
High speed stone mill, high speed impact mill, disper, kneader, high speed mixer, homogenizer, ultrasonic disperser, etc.

Any method may be used to apply the magnetic paint onto the non-magnetic support. For example, a gravure method, a reverse method, an extrusion method and the like can be mentioned, but other methods are also possible. And
Plate-like hexagonal ferrite magnetic powder and acicular metal magnetic powder, a binder, a magnetic paint prepared by kneading and dispersing various additives in a solvent, applied on a non-magnetic support, orientation, Then, a coating type magnetic recording medium is obtained by curing. If necessary, a surface smoothing treatment may be performed or a desired shape may be cut to obtain a magnetic recording medium.

The present invention will be specifically described below with reference to examples.
In the following examples, only an example of a magnetic tape will be described. However, since it is an example of a high band 8 mm tape, it is natural that it is used for a large capacity floppy disk and is not limited by the examples. Not something.

[0024]

【Example】

[Example 1] Fe-based metal magnetic powder (Fe: 96 wt%, Ni: 2 wt%, Al-Si-O: 2 wt%, average major axis length 0.17 µm, average minor axis length 0.02 µm, coercive force 1550 Oe, σs 123 emu / g) 30 parts by weight Hexagonal plate barium ferrite magnetic powder (average thickness 0.008 μm, average diameter 0.05 μm, coercive force 1520 Oe, σs 58 emu / g) 70 parts by weight Vinyl chloride resin 8 parts by weight Parts Urethane resin 8 parts by weight Conductive carbon black 1 part by weight Spherical alumina (particle size 0.15 μm) 6 parts by weight Toluene 260 parts by weight Methyl ethyl ketone 260 parts by weight Cyclohexanone 40 parts by weight After thoroughly mixing and stirring the above composition, 9.8μ of magnetic paint obtained by adding 4 parts by weight of polyisocyanate compound
A magnetic layer is formed by applying a dry thickness of 2.8 μm on a m-thick PET film by a direct gravure method, and a conductive carbon black-containing paint is dried on the other side to a dry thickness of 0.5 μm. Was applied to form a back coat layer, and thereafter, a magnetic tape for 8 mm video was prepared through a usual process.

Example 2 5 parts by weight of the Fe-based metal magnetic powder and 95 parts of barium ferrite magnetic powder in Example 1 were used.
A magnetic tape was prepared in the same manner as the weight part. [Example 3] The Fe-based metal magnetic powder in Example 1 was added to
A magnetic tape was prepared in the same manner with 0 parts by weight and 60 parts by weight of barium ferrite magnetic powder.

Example 4 Instead of the hexagonal barium ferrite magnetic powder in Example 1, an average thickness of 0.00
8 μm, average diameter 0.05 μm, coercive force 1400 Oe,
A hexagonal plate-shaped barium ferrite magnetic powder having a σ s of 57 emu / g was similarly used to prepare a magnetic tape.

Comparative Example 1 2 parts by weight of the Fe-based metal magnetic powder and 97 parts of barium ferrite magnetic powder in Example 1 were used.
A magnetic tape was prepared in the same manner as the weight part. [Comparative Example 2] Fe-based metal magnetic powder in Example 1 was added to 6
A magnetic tape was prepared in the same manner with 0 parts by weight and 40 parts by weight of barium ferrite magnetic powder.

[Comparative Example 3] Instead of the Fe-based metal magnetic powder in Example 1, the average major axis length was 0.17 μm, the average minor axis length was 0.02 μm, the coercive force was 1350 Oe, and σs 126e.
mu / g Fe-based metal magnetic powder (Fe: 95 wt%, N
i: 4 wt%, Al-Si-O: 1 wt%) was performed in the same manner to prepare a magnetic tape.

[Comparative Example 4] Instead of the barium ferrite magnetic powder in Example 1, an average thickness of 0.008 μm,
Average diameter 0.05 μm, coercive force 1350 Oe, σs 57
A magnetic tape was prepared in the same manner using emu / g hexagonal barium ferrite magnetic powder. [Comparative Example 5] Instead of the Fe-based metal magnetic powder in Example 1, the average major axis length was 0.2 μm, and the average minor axis length was 0.05 μm.
m, coercive force 680 Oe, σ s 110 emu / g, Fe-based metal magnetic powder, and average thickness of 0.01 μm and average diameter of 0.1 μ instead of barium ferrite magnetic powder.
Hexagonal tabular barium ferrite magnetic powder having m, coercive force of 720 Oe and σs 57 emu / g was similarly used to prepare a magnetic tape.

[Characteristics] With respect to the magnetic tapes obtained in each of the above examples, the characteristics such as the saturation magnetic flux density, the still durability, the corrosion resistance, the C / N, etc. were examined using a deck obtained by modifying a commercially available high band 8 mm VTR. Table 1 shows the still durability and corrosion resistance, and FIG. 1 shows the C / N.

Table-1 Saturated magnetic flux density (G) Still durability (dB) Corrosion resistance (ΔBs,%) Example 1 2200-1.56 Example 2 1950-1.11 Example 3 2300-1. 7 7 Example 4 2200-1.65 Comparative Example 1 1850-1.20 Comparative Example 2 2500-3.612 Comparative Example 3 2250-1.67 Comparative Example 4 2200-1.56 Comparative Example 5 2050-1.76 According to these, the one according to the present invention is rich in still durability and corrosion resistance, has a high output from a long wavelength region to a short wavelength region, and has a small noise. It can be seen that the recording and reproducing characteristics are excellent.

[Brief description of drawings]

FIG. 1 is a graph showing frequency characteristics of C / N.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a non-magnetic support and a magnetic layer containing flat plate-shaped hexagonal ferrite magnetic powder and acicular metal magnetic powder, said hexagonal ferrite The coercive force of the magnetic powder is 800 to 1900 Oe, the coercive force of the metal magnetic powder is 800 to 1900 Oe, and the coercive force of the hexagonal ferrite magnetic powder and the metal magnetic powder is approximately within 10%. A magnetic recording medium characterized in that the ratio of the hexagonal ferrite magnetic powder and the metal magnetic powder is about the same and the former / the latter is 95 to 50/5 to 50.