JPS62217423A - Magnetic recording medium having magnetic layer containing hexagonal ferrite and iron carbide - Google Patents

Abstract

PURPOSE:To improve the conductivity, light shielding property and reproduction output of a recording medium by incorporating hexagonal ferrite and iron carbide at a specific mixing ratio into the magnetic layer thereof. CONSTITUTION:This magnetic recording medium is constituted of a nonmagnetic substrate and magnetic layer contg. a ferromagnetic material and binder. The hexagonal ferrite and iron carbide are incorporated at a ratio of 95:5-55:45 by weight into the magnetic layer. The reproduction output is increased by using the above-mentioned ferrite and iron carbide in combination by taking the advantage thereof and the medium having the magnetic layer of the good conductivity and light shielding property is obtd. without the need for the aid of carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application) The present invention relates to magnetic recording media, and more particularly to the conductivity, light-shielding properties, and reproduction output of magnetic recording media.

(Prior art) With the demand for higher recording density for magnetic recording, from coated magnetic layers in which magnetic powder is dispersed in a binder,
The monocentric body was transferred to a thin metal @magnetic layer by vapor deposition, sputtering, etc., and the horizontal recording method was removed, and the demagnetization rate was reduced to 0.
The perpendicular recording method has attracted attention and has reached the stage of practical application for reasons such as its ability to approach

In the perpendicular recording system, in addition to improving the characteristics of the perpendicular head, progress has been made in the development of magnetic layer forming methods such as vacuum evaporation, plating, or coating methods, as well as magnetic materials, from the initial sputtering method for forming the 00-Cr ffl layer. .

Hexagonal ferrite, whose magnetization axis is perpendicular to the crystal plane, has been used as the material for the coating method. The hexagonal/kinuta ferrite is represented by Co-Ti-substituted Ba 7 elite.

In addition, in order to increase the reproduction output of these hexagonal ferrites, C
Combined use with o-γ-Fe, O, (%Kasho 57-21262
No. 3), and furthermore, the use of Ba ferrite in combination with iron-based metal powder has been proposed because of the insufficient low frequency output when using only Ba ferrite.

On the other hand, hexagonal ferrite is the conventionally used C
Compared to o-γ-Fe and n3, it is considerably inferior in conductivity and light shielding properties. Perhaps Co-γ-Fe20s has a small amount of Fe(n)
In contrast, hexagonal ferrite contains F
This is probably due to the fact that there is almost no e (n) or there is little diffused reflection.

Furthermore, the above-mentioned Co-γ-Fθ203 magnetic powder with a mixed composition of iron-based metal powder also lacks both conductivity and light-shielding properties. Since a dense oxide film is formed, this leads to clumping which is contrary to the improvement of the conductivity of the magnetic layer.

On the other hand, Japanese Patent Application Laid-open No. 60-124023 describes magnetic flux drop (
There is a proposal for a magnetic layer mainly made of iron carbide with high EmJ.

However, since iron carbide is made by carbonizing acicular iron oxide or iron oxyhydroxide, the material cost is high, and the shape tends to be irregular, which may cause problems with other properties. It is not preferable to use iron carbide as the main component. Moreover, the S/N expected from high Bm is not very good.

Therefore, in order to improve the W conductivity and light-shielding properties of the medium,
Although a large amount of carbon black is added to the magnetic In, the surface resistance is kept to less than 10 Ω/d by the magnetic layer using hexagonal ferrite, and the layer thickness is 4 μm and the wavelength is 900.
In order to suppress the original transmittance of nm to 0.1% or less, it is necessary to add 7 wt% or more of carbon black to the magnetic flux powder, which results in a drastic decrease in output compared to the case without carbon black. come.

(Object of the Invention) An object of the present invention is to provide a magnetic recording medium with good electrical conductivity and light-shielding properties, and a high output of image recording.

(Groove formation of the invention) An object of the present invention is to provide a magnetic recording medium in which a magnetic layer containing a ferromagnetic material and a binder is provided on a non-magnetic support. This is achieved by a magnetic recording medium that contains iron and has a mixed ratio of 95=5 to 55:45 by weight.

Next, the present invention will be explained in detail.

The hexagonal ferrite according to the present invention is expressed by the following general formula.
In the present invention, it is applied to the 1a layer of the horizontal and vertical recording systems.

General formula M'O[Fe+2-, u, 0. ,] In the formula, M1 is a divalent metal such as Ba, Sr, Pb, etc., and M is
.

Co-Ti, Co-V, Zn-Ge,
Represents at least one metal such as Zn-Nb and Zn-V, or a combination thereof. Moreover, X is 3≧X≧0. -One Shaku-- Typical examples of iron carbide include FeaC2, cementite Fθ, C, etc., including eutectic, solid solutions, and mixtures thereof with ar+, Fe2O% pure iron, etc.

The iron carbide has a saturation magnetization σ8 larger than that of 00-γ-re2n3, and has excellent conductivity and light-shielding properties.

In the present invention, by taking advantage of the characteristics of hexagonal ferrite and iron carbide, if [if] is used in combination, the reproduction output is large and it is possible to achieve conductive and light-shielding properties without requiring the help of a carbon blank. This realizes a medium with a good magnetic layer.

In addition, in the present invention, the weight mixing ratio of hexagonal ferrite/iron carbide is set to 9515 to 55/45, but 9515 provides sufficient light-shielding properties, and 90/10 suppresses the surface resistance to a sufficiently low level. I can do it.

Iron carbide is more efficient than carbon black in both conductivity and light-shielding properties, and when the amount of carbon black that provides the same light-shielding properties and conductivity as above is added,
The powder packing density is high (1), the trouble caused by the carbon blank is eliminated, and high reproduction output can be achieved in both high and low frequency ranges. However, the amount of iron carbide added is the hexagonal ferrite/
If the weight ratio of iron carbide exceeds 55/45, the reproduction output in high frequency frying will be insufficient.

If a carbon blank is used in the present invention, carbon black that imparts electrical conductivity may be added.

As the binder used in the magnetic layer or back coat layer of the present invention, wear-resistant polyurethane can be used. Or, it is mechanically strong enough to withstand bending, and has good four-wear resistance and weather resistance.

In addition to polyurethane, if iron fiber-based 1m resin and vinyl chloride-based convoluted polymer are also contained, the fractional nature of the magnetic powder in the Id magnetic layer is improved and its mechanical strength is increased. However, 1.
Juice type! If only #HiY and the vinyl chloride copolymer were used, the layer would become too hard, but this can be prevented by including the polyurethane described in section 2.

Usable fiber cord resins include cellulose ether, sululose inorganic acid ester, cellulose organic acid ester, and the like. The bipedal vinyl chloride copolymer may be partially hydrolyzed. Preferable examples of the vinyl chloride copolymer include copolymers containing vinyl chloride and vinyl acetate.

Phenoxy resins can also be used.

Phenoxy resin has advantages such as high mechanical strength, excellent dimensional stability, good heat resistance, water resistance, chemical resistance, and good adhesiveness.

These advantages are complementary to the above-mentioned polyurethane, and also help to significantly improve the stability over time in the physical properties of the tape.

Furthermore, the above-mentioned binder ponds, resins generally used in magnetic recording media, or various resins modified with hydrophilic groups, thermoplastic resins with characteristic behavior, thermosetting durable layers, reactive type resins, Mixtures with electron beam curable resins may also be used.

In order to improve the durability of the magnetic layer of the magnetic tape of the present invention, the magnetic paint can contain various curing agents, such as incyanate.

Aromatic incyanates that can be used include, for example, tolylene diincyanate (TDI) and adducts of these incyanates and active hydrogen compounds, and those with an average molecular weight in the range of 100 to 3,000 are preferable. .

Examples of aliphatic incyanates include hexamethylene diisosilane (HMD eno) and adducts of these incyanates and active hydrogen compounds. Among the adducts, those having a molecular weight in the range of 100 to 3,000 are preferable. Among the aliphatic incyanates, non-alicyclic incyanates and adducts of these compounds and active hydrogen compounds are preferable. .

The magnetic paint used to form the bipedal magnetic layer may contain additives such as dispersants, lubricants, abrasives, matting agents, and antistatic agents in addition to the carbon blank, if necessary. Good too.

Dispersion=j includes lecithin, phosphoric acid ester, amine compound, alkyl sulfate, fatty acid ester, higher alcohol, polyethylene oxide, sulfosuccinic acid,
These include sulfosuccinic acid esters, known surfactants, etc., and their salts, and also contain negative organic groups (e.g. ~C!OOH
, -PO,H) can also be used. These dispersants may be used alone or in combination of two or more. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder. These dispersants may be used to pre-treat the magnetic powder in advance.

In addition, the lubricant τ4 includes silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, lauric acid, myristic acid, monobasic fatty acid with 12 to 16 carbon atoms, and the number of carbon atoms of the fatty acid. Fatty acid esters (so-called waxes) consisting of monohydric alcohols having a total of 21 to 23 carbon atoms can also be used. These lubricants are added in an amount of 0.2 to 2 parts by weight per 100 parts by weight of the binder.

As the abrasive, commonly used materials include fused alumina, silicon carbide, chromium oxide, corundum, artificial frundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite).

These abrasives have an average particle diameter of 0.05 to 5 .mu.m, particularly preferably 0.1' to 2 .mu.m. These abrasives have a ratio of 1 part to 100 parts of binder.
It is added in a range of -20 parts by weight.

As the mantle agent, organic powder or inorganic powder can be used individually or in combination.

The organic powder used in the present invention is preferably an acrylic styrene resin, a pendylamine-based grease-resistant powder, a melamine-based pigment, a 1III pigment-based powder, or a phthalocyanine-based pigment, but includes a polyolefin-based pigment, an FD+lFj powder, and a poly-10-ester. Type 1 resin powder, polyimide resin powder, polyimide bulking powder, polyfluorinated ethylene resin powder, etc. can also be used, and inorganic powders include silicon oxide, titanium oxide, and Y oxide.
Luminium, calcium carbonate, barium sulfate, zinc oxide, tin oxide, aluminum oxide, chromium oxide, silicon carbide,
Calcium carbide, α-Fe208, talc, kaolin,
Examples include calcium sulfate, boron nitride, zinc fluoride, and molybdenum dioxide.

As the antistatic Jl that may be used, conductive powders such as carbon black, graphite, tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds; -A - -
; Class 411, -I→'' The solvents added to the bipedal paint or the diluting solvent when applying this paint are acetone,
Ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; Alcohols such as methanol, ethanol, propatool, and butanol; Esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and ethylene glycol senolycetate; Glycol dimethyl ether, Ethers such as glycol monoethyl ether, dioxane, and tetrahydrofuran; benzene,
Aromatic H hydrocarbons such as toluene and xylene; halogenated hydrocarbon rings such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform and dichlorobenzene can be used.

In addition, as a support, polyethylene terephthalate,
Polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polyphosphoramide and polycarbonate are commonly used, but Ou, Ad, Zn, etc. metal,
Glass, BN, Si carbide, porcelain, ceramics such as earthenware, etc. can also be used.

The thickness of these supports is about 3 to 100 μm in the case of a film or sheet, preferably 5 to 50 μm,
In the case of a disk or card shape (approximately 130 μb to 10 μb), in the case of a drum shape, a cylindrical shape is used, and the type is determined depending on the recorder used.

An intermediate layer for improving adhesion may be provided between the support and the magnetic layer.

Coating methods for forming the magnetic layer on the support include air doctor foot, blade coat, air knife coat, squeeze coat, impregnation foot, reverse roll foot, transfer roll coat, clavier coat, kiss coat, and casting. Coat, spray coat, etc. can be used, but are not limited to these.

(Example) The present invention will be specifically explained using examples.

Example 1 A magnetic paint was made from Pli using the following formulation.

[Magnetic paint formulation Magnetic powder 100 parts by weight Ayamin 5 parts by weight Hinyl chloride-vinyl acetate copolymer 9 parts by weight Polyurethane
9 parts by weight lecithin 3 parts by weight myristic acid 1.5 parts by weight butyl stearate) 1ffi amount 1ff (-
1+ - 3.5 parts by weight of TDI-based insilinate was added to this paint, and 4.4 parts by weight was added to the paint on polyethylene terephthalate (PET).
Coat it to a dry film thickness of μm, dry it and make it smooth.
I! It was slit to Wzl 2.65 in. At this time, no magnetic field orientation is performed.

The magnetic powder used at this time was as follows.

・0o-Ti [Convertible Ba ferrite (coercive force (HCJ9
00('is, σs58emu/g% diameter 0.06μ
In, thickness 0.02μm) ・Iron carbide (Hc920('+8, as100emu/g
, B K T value of 42 m/g] The main components of this iron carbide were identified to be Fe and C2 by X-ray diffraction.

Magnetic tapes of practical samples 1 to 4 and comparative samples 5 to 9 were prepared in which the two types of magnetic powder were mixed in the proportions shown in Table 1. The metal powder and 00-γ-F used for comparison samples
θ2o3 has the following characteristics.

Metal powder; Holoooooe, (7s130emu/
g, %BET1 straight 4577+”/g.

Oo-γ-Fe20. ; Hc 8400e, σs
76emu/gXBET value 38m1T.

Table-1 Sample 7 has carbon black (B]'CT in addition to the above formulation.
8 parts by weight of oil with a value of 220 kg/g and an oil absorption of 110 CC/100 g were added.

The results are shown in Table 2.

The reproduction output was measured by inputting and reproducing a signal with a wavelength of 0.75 μm or 3.8 μm. In addition, the light transmittance is at a wavelength of 900 m.
Measured in m.

The magnetic properties were measured with a VSM (manufactured by Toei Kogyo).

The reproduction output is shown as a relative value with Sample 7 set to 0 as the standard.

Table 2 As is clear from Table 2, the addition of iron carbide improves the surface resistance and light transmittance of metal powder and CO-γ-Fθ20.
It is clearly better than adding carbon black, and it is also much better than adding carbon black in terms of reproduction output. Addition of iron carbide is also effective in increasing the reproduction output in the low range.

On the other hand, when iron carbide is mixed in a ratio exceeding the mixing ratio of the present invention, the reproduction output in the high range (short wavelength) decreases significantly; The resistance, etc. is defective.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer containing a ferromagnetic material and a binder is provided on a non-magnetic support, the magnetic layer contains hexagonal ferrite and iron carbide in a weight ratio of 95:5. ~5
5:45.