JPS5891523A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium preventng magnetic transfer and generating low noise by forming a magnetic layer and a layer contg. superparamagnetic fine powder. CONSTITUTION:A layer 3 contg. fine powder of a superparamagnetic body dispersed in resin is formed on the back side of a nonmagnetic support 1, or it is superposed between the support 1 and a magnetic layer 2. Maghemite, magnetite, a Berthollide compound of maghemite with magnetite, nickel ferrite, cobalt ferrite, chromium dioxide, iron, cobalt, nickel, an Fe-Co alloy, an Fe-Ni alloy or an Ni-Mn alloy is uded as the superparamagnetic body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium that prevents magnetic transfer and has low noise.

A magnetic recording medium generally has a magnetic recording layer formed by coating a mixture of magnetic powder and a binder on a non-magnetic support such as a polyester base.

The finer the magnetic powder used in this magnetic recording medium, the more
It is well known that 87M has been improved and the recording density has also increased, and Prayer Tape is commercially available as a "low noise tape." However, although such tapes have improved noise characteristics and recording density, they suffer from magnetic characteristics and magnetic transfer characteristics (a phenomenon in which magnetic recording is transferred as noise from a magnetically recorded magnetic layer to an undistributed layer). ), it cannot be avoided that there will be a negative impact on such points. That is, as the powder becomes smaller, the magnetic transfer characteristics deteriorate, and when an attempt is made to increase the packing density in order to improve the magnetic characteristics, the magnetic transfer characteristics become even worse.

Furthermore, as magnetic recording media have become more compact and have longer recording times, the use of thin film bases has become commonplace, and as a result, magnetic transfer has become increasingly popular.

Conventionally, as a method for preventing magnetic transfer,
No. 286131, JP 51349-55304, JP 51349-55304, JP 51349-55304 No. 5
1-137403! Multilayer magnetic recording media have been proposed as described in various publications such as No. 1, No. 53-16604, and the like. In other words, the second layer is relatively stable against magnetic transfer.
This method covers the first magnetic recording layer with a magnetic recording layer of tI! It is said that high sensitivity and high output can be easily obtained using the &l magnetic recording layer, and magnetic transfer characteristics can also be suppressed well.

However, this method has the disadvantage that noise is generated due to the formation of irregularities at the interfaces of the layers since the coating is performed in multiple layers.

An object of the present invention is to provide a new magnetic recording medium in which the drawbacks of conventional methods are improved.

That is, an object of the present invention is to provide a magnetic recording medium with improved magnetic transfer characteristics without adversely affecting the magnetic characteristics.

The above object of the present invention is achieved by a magnetic recording medium characterized in that it has a magnetic recording layer and an I containing superparamagnetic fine powder (hereinafter referred to as the superparamagnetic layer of the present invention).

The superparamagnetic layer of the present invention can be provided at any position of the magnetic recording medium to achieve the object of the present invention, but it is preferably provided on the back side of the non-magnetic support, or on the back side of the non-magnetic support and magnetic recording medium. It is provided between the layers.

Generally, in a magnetic recording medium, mixing the magnetic recording layer with other layers causes noise due to the formation of irregularities at the layer interfaces, so the superparamagnetic layer of the present invention is provided on the back side of the nonmagnetic support. It is particularly preferable.

Generally, when a ferromagnetic particle becomes smaller than a certain size, the energy In-V (K!l: anisotropy energy, v:
Due to the decrease in particle volume, the thermal energy kT (
k: Boltzmann constant, T: absolute temperature),
While the magnetic moments in the particles remain uniform, they fluctuate due to thermal agitation, becoming a superparamagnetic material that exhibits the behavior of a paramagnetic material with a large magnetic moment.

The present invention utilizes the properties of this superparamagnetic material.

The present invention can achieve the above object of the present invention by a magnetic recording medium having a layer containing such a superparamagnetic substance, and the particle size of the superparamagnetic fine powder is less than SOOm,
Preferably it is 10-10OA.

The superparamagnetic material of the present invention is! ghemite, magnetite,
With magnetite! Examples include the bertholide compound of Guntaishi, nickel 7-elite, cobalt 7-elite, sulfur pm dioxide, iron, cobalt, nickel, iron-cobalt alloy, iron-nickel alloy, and nickel-manganese alloy.

The superparamagnetic material of the present invention can be manufactured by any method, but typical manufacturing methods are listed below. B) Ferromagnetic powder, such as magnetite, metal, or alloy, is ground in a ball mill over a long period of time to form superparamagnetic powder into ultrafine particles. 02. The metal carbonyl compound is thermally decomposed.

3. The organic acid salt of a ferromagnetic metal is thermally decomposed and further reduced with a reducing gas.

4] Evaporate the ferromagnetic metal in an inert gas at low pressure.

5. Add a reducing agent to a solution containing a ferromagnetic metal salt to reduce it.

6. A fine magnetite powder is obtained by adding an alkali to an acidic solution containing 1. and C in a ratio of 1:IA.

The method for producing the superparamagnetic material of the present invention is described, for example, in U.S. Pat. No. 4,252,671 and JP-A-554
-6ISla publication.

In the present invention, when forming the superparamagnetic layer of the present invention, a resin solution in which the superparamagnetic material of the present invention is dispersed is applied, so that the particle size of the superparamagnetic material is reduced to 300.
The manufacturing methods 2 and 6 above are preferred because they need to be less than 0.0 mm and uniformly dispersed in the solution.

In the superparamagnetic layer of the present invention, the superparamagnetic material is uniformly dispersed in a resin. The resin used for this superparamagnetic layer is a known film-formable resin. Any resin can be used.

In the present invention, the resin used to disperse the superparamagnetic material is preferably a resin that can coordinate with the superparamagnetic material, but even if it does not have coordination ability, a surfactant may be used. Any resin can be used by using.

The preferred resin includes styrene-4-vinylpyridine copolymer.

Polystyrene can also be used as a resin for dispersing superparamagnetic materials.

Preferred examples of the superparamagnetic material of the present invention are listed below.

Production Example-1 A solution of 30 g of styrene/4-vinylpyridine copolymer (weight average molecular weight 5oooo, styrene/4-bi=K-Hi!J Syn-9a/5) in 100 co of dichrosebenzene was heated with argon. Prepare a four-bottle flask equipped with an inlet pipe, a cooling pipe, a thermometer, and a stirrer, and gradually add 501 tt of iron pentacarbonyl to it.
Heat and stir at 14B°C for 24 hours.

After the reaction is completed, the raw material is pressurized to remove large iron powder particles to obtain a dispersion liquid in which fine iron particles of 10 to 200× are uniformly dispersed.

This is referred to as superparamagnetic paint-1.

Production Example 2 A dispersion in which fine nickel powder is uniformly dispersed is obtained in the same manner as Production Example 1 except that nickel tetracarbonyl is used instead of iron pentacarbonyl in Production Example 1.

1 This is referred to as superparamagnetic paint-2.

Production Example-3 1M aqueous solution of ferrous sulfate and ferric sulfate 1000
d into a mixing tank, and 6N NaOH aqueous solution was added dropwise while mixing. After the pH reaches 3, stir and mix for about 20 minutes to prepare a magnetite colloid solution, then add 640 ml of 10% sodium oleate solution and mix for 30 minutes. When the mixing is stopped and the liquid is allowed to stand still, a layer containing magnetic particles with a large amount of air bubbles is separated into the upper part, and a layer containing water and sodium sulfate is separated into the lower part.

Toluene 1 in which 200g of polystyrene was dissolved
When oood is added, the bubbles disappear in a short time and a dark brown oil layer is formed. Drain the water layer so that only the oil layer remains. Magnetite F having a large particle size is removed using a centrifuge to obtain a dispersion liquid in which fine magnetite powder of 10 to 200 μm is uniformly dispersed.

This is referred to as superparamagnetic paint-3.

The superparamagnetic paint is applied to the opposite side of the magnetic recording layer of the nonmagnetic support, or to the same side as the magnetic recording layer, by any known method.

The magnetically recorded sound according to the present invention is produced by coating a solution of a binder in which a ferromagnetic material is dispersed on a non-magnetic support or on the superparamagnetic layer of the present invention (dispersed magnetic recording medium 2 or a non-magnetic support). It may also be formed by depositing a ferromagnetic material on the body (vapor deposition magnetic recording medium).

The dispersed magnetic recording medium will be explained below.

Examples of the ferromagnetic material used in the magnetic recording layer according to the present invention include ferromagnetic iron oxide, ferromagnetic ferrite, ferromagnetic oxidized aluminum, ferromagnetic metal powder, and ferromagnetic alloy powder.

The ferromagnetic material contained in the magnetic recording layer is used in various proportions, but preferably 100 to 500 parts by weight of the ferromagnetic material to 100 parts by weight of the binder, particularly preferably 25 parts by weight.
0-400 parts by weight. If the amount added is less than 100 parts by weight, the residual magnetic flux density (Br) will be low, resulting in a decrease in output. If the amount added exceeds 500 parts by weight, the wear resistance of the magnetic layer will decrease and the coating properties during manufacturing will be reduced. becomes worse.

In the present invention, a solution of a binder in which a ferromagnetic material is dispersed (
It can be manufactured by coating a magnetic coating (magnetic paint) on a non-magnetic support.

In general, magnetic paints mainly consist of a ferromagnetic material, a binder, and a solvent, and also contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and the like, if necessary.

This magnetic coating material is prepared by dissolving and dispersing the composition described above in an organic solvent, and is coated onto a nonmagnetic support to form a magnetic recording layer.

Regarding the manufacturing method of the magnetic paint used in the present invention,
No. 5-15, No. 39-26794, No. 43-186, No. 47-28043, No. 4 Hu 28045, No. 4
Fu No. 28046, No. 4'F-1!8048, No. 47
-31445, 48-11162, 48-21
No. 331, No. 48-33683, Soviet Patent Specification 30
It is described in detail in various publications such as No. 8033.

As the binder used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

The thermoplastic resin has a softening temperature of 150°C or less and an average molecular weight of 10,000 to 200,000. Degree of polymerization is about 20
0 to 2000, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer,
Cyclized vinyl-tolyl copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, acrylic ester-styrene copolymer, methacrylic ester-acrylenitrile copolymer combination, methacrylic acid ester-cyclized vinylidene copolymer, methacrylic acid ester-styrene copolymer,
Urethane elastomer, polyvinyl fluoride, vinylidene chloride-ataryloethryl copolymer, Atarita nitrile-butadiene copolymer, boria resin, polyvinyl butyral, cellulose derivative (cellulose acetate petite F1 cellulose dye) Acetate, 7-striacetate, cellulose bionate, nitro-7-striacetate, styrene-butadiene copolymer, polyester resin, chlorovinyl ether-acrylate, sulfuric acid ester copolymer, amino resin, various Synthetic rubber-based thermosetting resins and mixtures thereof are used. These resins are:
Special Publication No. 37-687 Ma, No. 39-12528, No. 3
No. 9-19182, No. 40-53.

No. 40-2!0907, No. 41-9463, No. 1-14059, No. 41-16985, No. 42-
No. 6428, No. 4N-11621, No. 43-4623
No. 43-15806, No. 44-4889, No. 4
4-1'F947, 44-181!32, same arrival δ
-1410, 45-14500, 47-185
No. 73, No. 47-22063, No. 47-22064, No. 47-42068, No. 4γ-8069, No. 4 Fuggo'yo, No. 48-2'7886, U.S. Patent No. 3,144 , No. 352, No. 3,419,420
No. 3,499,789, No. 3゜713.88
It is described in the specification of No. 7.

The thermosetting resin or reactive resin has a molecular weight of 2oo, ooo or less in the state of a coating liquid, and after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Moreover, among these resins, those which do not soften or melt before the resin is thermally decomposed are preferable. Specifically, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melar resin, alkyd resin, silicone resin, acrylic reaction resin, high molecular weight polyester am, and incyanate prepoly! - mixtures of methacrylic-salt copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyinsyanates, urea formaldehyde resins, mixtures of low molecular weight glyfur/high molecular weight diols/) liphenylmethane triisocyanate, Poly. These include amino resins and mixtures thereof.

These resins are disclosed in Japanese Patent Publications Nos. 39-8103 and 40-9.
No. 779, No. 41-7192, No. 4: L-8016, No. 41-143! Fu-b, same 4. i! -18179, 43-110.511, 44-5!805!3
No. 45-141101, No. 4B-44902,
Same number 46-13108, same number 4 Fu ff1g067, same number 4 Fu 2207.2, same number 4 Fu ago 73, same number Fu J! No. 8045, No. 4 Fu No. 8048, No. 47-2
No. 8922, U.S. Patent No. 5,144°353, #! Mr. No. 320,090, No. 3,431610, No. 3.59'FJ73, No. 3. 8'l, No. 210, No. 3°181.211.

These binders may be used alone or in combination.

Typical additives added to magnetic record #IN as needed will be described below.

Dispersants used include caprylic acid, capric acid,
Fatty acids with 12 to 18 carbon atoms (ROOOH, R
is an alkyl group having 11 to 1 carbon atoms): an alkali gold II (Li, lr, etc.) or alkaline earth metal (-Mg) of the above fatty acid.

Metallic stones consisting of Oa, Ba, etc.); lecithin, etc. are used. In addition to these, higher alcohols having 12 or more carbon atoms and sulfuric esters may also be used. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder.

These dispersants are disclosed in Japanese Patent Publication Nos. 39-28369 and 44
948, U.S. Pat. No. 48-IBOOI, U.S. Pat.

The lubricants used include silicone oil, carbon black, graphite, and carbon black Graph 7 Topoli! -1 Molybdenum disulfide, tungsten disulfide, fatty acid esters (so-called These lubricants are added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder.These are described in Japanese Patent Publication Nos. 43-23889 and 43-8154.
: Publications such as No. 5, U.S. Patent No. 3,470,021, U.S. Patent No. 3,492°235, U.S. Pat.
086 to 3.52, 3,625,160,
Same No. 3,630,772, Same No. 554.253,
Specifications of the same No. 3.642,539 and the same No. 68'1725, X B M T@ohnioal Disa
losurv)ull*tin Tol, 9, 4f, Page '7ftj (ZS Month, 1966)
: ILIIC'l'lLO[]C1961ill,
As described in Pagesea et al.

'1　□8ゎ, 1□57. Yo, -3-Eoh.

Materials include fused alumina, silicon carbide oxide term, corundum, artificial corundum, diamond, artificial diamond, Zakutai stone, emery (main components: corundum and magnetite)
etc. are used. These abrasives have an average particle size of 0.05
~5μ in size is used, particularly preferably 0.5μ in size.
1-2. # These abrasives are added in an amount of 7 to 20 parts by weight per 100 parts by weight of the binder. These abrasive materials are disclosed in Japanese Patent Application Laid-Open No. 115510/1980, US Patent No. 3007.807, US Patent No. 3,041,196, US Patent No. 3,687.725, British Patent No. 1,145,
No. 349, West German Patent (DT-pit) 853,
It is described in the specification of No. 211.

The anti-traffic agents used include conductive powders such as graphite, carbon black, and carbon placket polymers; natural surfactants such as saponin; and nonionic surfactants such as alkylene oxide, glycerin, and glycidol. :Higher alkylarines, quaternary ammonium salts, pyridine, other cyclocycles, cationic surfactants such as phosphonium or sulfonium: cardanic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, phosphoric ester groups, etc. Anionic surfactants containing acidic groups such as diamino acids, aminosulfonic acids, and amphoteric surfactants such as sulfuric acid or phosphoric acid diester chains of amino alcohols are used. These surfactants that can be used as antistatic agents are disclosed in U.S. Pat. No. 2,211,623, formula 2
40,4 No. 2, No. 2,288,226, No. 2.
No. 676,122, No. 2,616,924, No. 2
, No. 616゜915, No. 2,691,566, No. 2,727,860, No. 2,730,498, No. 2.142.379, No. 2゜〒39,891 issue,
Same No. 068,101, Same No. 3,158,484,
Same No. 201,253, Same No. 3,210,191,
Same No. 294,540, No. 13,415,649, No. 441,413, No. 3,442,654, No. 3.4'l, 174, No. 3.1545 ,97
No. 4, West German Patent Publication (OI+8) No. 1,942゜666, British Patent No. LOf No. 7,317, No. 1.1
9 Kame No. 450, etc., Ryohei Oda et al.'s ``Synthesis of Surfactants and Their Applications'' (Maki Shoten 19g4If-edition); Mu V. Peiri's ``Surface Active Agents'' (Interscience Published in Koboleteid 1956 edition): T,! 1. Medical books such as "Encyclopedia op Surface Active Agents Volume 2" (Kenkarpa Pritzsch Company 1964 edition): "Surfactant Handbook" 6th edition (Sangyo Tosho Co., Ltd., August 20, 1964) These surfactants may be added alone or in mixtures.They are used as antistatic agents, but are sometimes used for other purposes, such as dispersion, improving magnetic properties, etc. It may also be used to improve lubricity or as a coating aid.

The solvents used include ketones such as a7tone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propatool, and butanol; methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol acetate. Ester types such as monoethyl ether; glycol ether types such as diethyl ether, glycol dimethyl ether, glycol monoethyl ether, and dioxane; tar types (aromatic hydrocarbons) such as benzene, toluene, and xylene; methylene chloride, ethylene chloride , tetracyclic carbon II, clereform, ethylene chlorohydrin, dichlorobenzene chlorinated hydrocarbons, and the like can be used.

Note that the magnetic recording layer of the present invention usually has a thickness of 8s to Q.

It is sufficient to apply the film so that it has the same dry film thickness as the voice.

In addition, the materials used for the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene-46-naphthalate, polyolefins such as bolyb-tetrapyrene, cellulose triacetate, and hexa-p-s diacetate. Plastics such as russe derivatives and polycarbonate, non-magnetic metals such as Ou and Zn, glass, porcelain, pottery and the like are used.

Contraf) The thickness of the non-magnetic support is approximately 5 to 10011181 degrees in the case of a film or sheet, preferably 6 to 181 degrees.
60μ, and in the case of disks and cards, O, S
~10m14ii degree and 1 If it is drum-shaped, it is circular, and its shape is determined depending on the recorder used.

The magnetic powder and the above-mentioned binder, dispersant, lubricant, abrasive, antistatic agent, solvent, etc. are kneaded to form a magnetic powder.

For kneading, the magnetic powder and each of the above-mentioned components are fed into a mixing machine either simultaneously or individually one after another. For example, there is a method of first adding magnetic powder to a solution containing a dispersant, waiting for a predetermined period of time, then adding the remaining components and continuing cross-mixing to obtain a magnetic paint.

Various types of crosstalk machines are used to disperse crosstalk. For example, two roll rolls, three roll rolls, bowl rolls, pebble rolls, sand grinders, Isngvari attritors, high speed impeller dispersers, high speed spindles, high speed impact mills, disper kneaders. 1 High-speed mixer, homogenizer, ultrasonic disperser, etc.

What is the technology related to crosstalk distribution? , O, PATTON arrival Pa1nt Flow &! l(l Pigm@nt
Dispersion (1964 John Wil
ley & 8on-).

Also, US time 11?1112, 58 No. 14, M#L85
It is also stated in each book 11111 of No. 156.

As a coating method for coating the magnetic coating material onto the support to form a magnetic recording layer, Air Doctor! -), plaid drawstring, air knife coat, style X:l-)
,! Dip coat, reverse reel coat, transfer four foot, clavier coat, kiss foot, cassi coat, spray coat, etc. can be used, and other methods are also possible, and detailed explanations of these can be found in [
It is described in detail in Coating Engineering Jass, pages 27 to 27 (Published March 1933, BO).

By such a method, the magnetic recording layer coated on the support is optionally treated to orient the magnetic powder in the layer, and then the formed magnetic recording layer is dried. Further, if necessary, the magnetic recording unit of the present invention is manufactured by subjecting it to a surface smoothing process and cutting it into a desired shape.

In this case, the orientation magnetic field is approximately 500 ~ go
oo Gauss, and the drying temperature is about BQ~Woo''C
The degree of drying and drying time are about 3 to 10 minutes.

Methods for orienting magnetic powder are also described in the patents listed below.

For example, U.S. Patent No. 949,840;
6゜359, same No. 3,001,891, same No. 3,1
No. 72.776, No. 3,416,949, $3,
Specifications of No. 473,960, No. 3681.138, Japanese Patent Publication No. 3 g-3427, No. 39-48368
No. 40-4315!4, No. 40-23615,
These include publications such as No. p141-13181, No. 4J3-13043, and No. 48-49122.

The orientation direction of the magnetic material is determined by its use. That is, in the case of sound tapes, small video tapes, and memory tapes, it is parallel to the length of the tape, and in the case of broadcast video tapes, it is 30° to 90' to the length.
It is oriented with an inclination of .

The present invention will be explained in more detail below using examples.

It will be readily understood by those skilled in the art that the ingredients, proportions, order of operations, etc. shown herein may be modified without departing from the spirit of the invention.

Therefore, the invention should not be limited to the examples below. In addition, in the following examples, all "parts" indicate "parts by weight."

Example-1 Coercive force 390 oersted, residual magnetic flux density approximately 2300 Gauss, needle-shaped particle size 0.5 s? 31 parts of e104 powder was mixed with 8 parts of vinyl chloride-vinyl acetate copolymer, 1 part of dispersant, 30 parts of methyl isobutyl ketone (MIIIK), 15 parts of methyl ethyl ketone (MNK), and 16 parts of toluene.
Disperse and mix in a ball cell for 48 hours to harden the magnetic paint.Next, the magnetic paint was mixed in 9. as shown in FIG. A magnetic recording layer is formed by coating and drying on a polyester base film having a thickness of #I so that the film thickness after drying becomes Isμ. This will be referred to as Comparison Tape-1. On the back of this comparative tape-1,
As shown in Wi, so that the dry film thickness is 1μ,
The superparamagnetic paints 1, 2, 1 and 5 (11) were applied to prepare and complete the present invention's magnetic coatings 1, 1, 3 and 3.

EXAMPLE - DESCRIPTION Superparamagnetic paints 1, 2 and 3 were applied onto the same polyester base film as in Example 1, and then the magnetic material of Example 1 was applied and dried in the same manner as in Example 1. 1-ki tape-4.5 and 6 were made.

The comparative tape-1 and the magnetic tape of the present invention-1,
The magnetic transfer effects of 2, 3, 4, Is, and 6 were measured using conventional methods, and the results are shown in Table 1.Table 1 As can be seen from the results in Table 1, the magnetic transfer effects of the present invention
It can be seen that the magnetic transfer of the tape has been significantly improved compared to the comparison tape.

Moreover, the magnetic tape of the present invention 1. Lazy and 3 are magnetic tape-
Compared to 4, 5 and 6, there was less noise (it had excellent sound quality).

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a magnetic recording medium according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of a magnetic recording medium according to a second embodiment of the present invention.01...Nonmagnetic support body
2... Magnetic recording layer 3... Superparamagnetic layer agent Yoshimi Kuwahara

Claims (1)

[Claims] A magnetic recording medium comprising a magnetic recording layer and a layer containing superparamagnetic fine powder.