JPS604567B2 - magnetic recording medium - Google Patents

Description

Detailed Description of the Invention The present invention relates to a magnetic recording medium, which has particularly excellent stability against pressure, heating, etc., has little change in coercive force over time, and has improved transfer characteristics, erasing characteristics, and coercive force distribution. This invention relates to a magnetic recording medium using ferromagnetic iron oxide.

The production of high-density magnetic recording materials requires magnetic materials with high coercive force and excellent squareness ratio.

In order to increase the coercive force of iron oxide magnetic powder, it is effective to solidify the Co, and this method is described in Japanese Patent Publication No. 41-6
No. 538, No. 41-27719 (U.S. Pat. No. 35739)
No. 80), No. 42-6113, No. 48-10994, No. 48-1575y, No. 49-4264, JP-A No. 47-22707, No. 48-1998, No. 48-5
No. 1297, No. 48-54497, No. 48-7609
No. 7, US Pat. No. 48-87397, US Pat. No. 48-10159y, US Pat. No. 3,117,933, US Pat. No. 3,671,435, US Pat. however,
In Co-containing magnetic iron oxide made by any method, Co-containing maghemite (y-Fe203),
When magnetic recording bodies such as magnetic tapes are prepared using Co-containing magnetite (Fe304), these magnetic recording bodies have the drawback that they are unstable when subjected to pressure and heating, and the recorded information signal becomes weak.

In addition, the disadvantages of Co-containing magnetic iron oxide include uneven distribution of coercive force due to uneven Co content in magnetic iron oxide, poor stability of coercive force over time, and deterioration of erasing characteristics and transfer characteristics when used as a magnetic recording medium. It is.

Various methods are known for improving Co-containing ferromagnetic iron oxide, which is unstable under pressure and heat. For example, in order to improve thermal stability, in addition to Co ions**, other metal ions A method of adding
No. 3, Tokuseki No. 48-27298, No. 48-2729, No. 48-76097, etc.

Further, methods for improving the Co adsorption method are also known, and are described in Japanese Patent Application Laid-Open No. 481-87397, US Patent No. 377,050, and the like. However, the ferromagnetic iron oxide obtained by these methods is unstable against mechanical shock, pressure, etc., has uneven coercive force distribution, changes in coercive force over time, has poor erasing characteristics, and has poor transfer characteristics. However, since improvements in these areas are insufficient, this is an area for future improvement of Co-containing ferromagnetic iron oxide.

On the other hand, as a ferromagnetic iron oxide with improved stability over time, pressure demagnetization properties, etc., a bertolide compound (Fe○x,
1.33<x<1.50) is known, and the
-10307 and No. 48-3963y are described.

Magnetite (Fe304) and maghemite (Two Fe
203) forms a continuous solid system, and the intermediate state of the bertolide compound can be expressed as Fe○x (1.33<x<1.50). Here, x represents the oxidation state of the iron atom by x÷X core×{2×(Temuwani%>13×<Takudenmu%)}.

In the present invention, as the oxidation degree of ferrite containing Co and Cr other than iron as a solid solution, M having the same content as above is defined by the following formula.

Book number X life The time can be determined using optical X-ray method, atomic absorption method, mass spectrometry, etc.

There are divalent and trivalent iron atoms, which can be determined by oxidation-reduction calculations. Special Public Sho 3
The bertolide compounds described in No. 9-10307 and No. 48-3963y are particularly stable against pressure demagnetization and changes over time, but the coercive force of this compound is approximately 300 to 40 e.
This is insufficient for high-density magnetic recording media, which are in high demand these days. The magnetic recording medium obtained by the present invention has high coercive force, excellent squareness ratio, less demagnetization due to pressure and heating, and has good transfer characteristics and erasure rate, making it ideal for high-density magnetic recording media. It is. The first object of the present invention is to provide Co and Cr that are stable against pressure and mechanical shock.
An object of the present invention is to provide a magnetic iron oxide containing.

The second object is to provide a magnetic iron oxide containing Co and Cr that exhibits less demagnetization upon heating.

The third object is to provide a magnetic iron oxide containing Co and Cr whose coercive force hardly changes over time.

The fourth object is to provide a magnetic iron oxide containing Co and Cr that has an excellent coercive force distribution.

The fifth object is to provide a magnetic iron oxide containing Co and Cr that has an excellent SP ratio.

A sixth object is to provide a magnetic iron oxide containing Co and Cr that has excellent erasing properties.

The present invention achieves the above-mentioned objects, and includes Co and C
Bertolide compounds of magnetite and maghemite containing r are surprisingly stable against pressure and heating.
This is based on the fact that the magnetic recording material using the above-mentioned bertolide compound has excellent characteristics, such as less change in coercive force over time and excellent transfer characteristics, erasing characteristics, and coercive force distribution.

The above-mentioned bertolide compound is a ferromagnetic iron oxide bertolide compound containing Co and Cr and having a value of M of 1.33<M<1.50, which is represented by the following general formula.

M 1000 x Kai x {2 x (considered cloud fog) 13 pieces x zumasu cloud%} a
tomic%, that is, the present invention is a magnetic recording medium shown below.

[1} In a magnetic recording body in which a magnetic layer mainly composed of ferromagnetic fine powder and a binder is provided on a substrate, the above-mentioned ※※ ferromagnetic fine powder has a value of M expressed by the following general formula of 1.33<
A magnetic recording material characterized in that it is a ferromagnetic iron oxide bertolide compound containing Co and Cr with M<1.50.

M 1000 x Core x {2X〈Key Rust Moat〉13×〈JMuzuru}■
In a magnetic recording body in which a magnetic layer mainly composed of ferromagnetic fine powder and a binder is provided on a substrate, the ferromagnetic fine powder is 6
Ferromagnetic iron oxide containing Fe30 ions of 6.7a mic % or more, Co ions of latomic % or more and 0.
2tomjc% or more of Cr ions are solidly removed, and the value of M shown in the following general formula is 1.33.
A magnetic recording body characterized by being a ferromagnetic iron oxide bertolide compound containing Co and Cr with <M<1.50.

M = Ki x Sister
．． 5 to 20% is an effective range in the field of magnetic recording, but high-density magnetic recording materials with a coercive force of 500 to 150 e (e.g. video cassettes, video disks, video sheets, master tapes, magnetic cards, COM For use in magnetic disks for commercial use, magnetic sheets for COM, memory tapes, data cassettes, etc.), it is particularly preferable that the amount of Co added is in the range of 1 to 10%.

When the addition of Cr is 0.1% or more, improvements in coercive force distribution, transfer characteristics, and erasing characteristics were observed, but conversely, when the amount of Cr is large, coercive force and saturation magnetization deteriorate, so it is not practical. .3
15% is preferred.

The value of M (degree of oxidation) is 1.33<M<1.50,
1.35 to 1.48 is preferable, and 1 is particularly preferable.
．． 36 to 1.44, and magnetic iron oxide containing Co and Cr having an M value in this range is less demagnetized by pressure and heating, has less change in coercive force over time, and has excellent transfer and erasing characteristics. was confirmed to be improved. The method for producing the ferromagnetic iron oxide used in the present invention is as follows:
One method is preferred.

'1} Ferromagnetic iron oxide (Fe304, y-Fe203,
A method in which Co and Cr hydroxides are adsorbed on the surface of FeOX (1.33<x<1.50), and the degree of oxidation is adjusted to 1.33<M<1.50 by oxidation or reduction treatment.

'2} A method in which Co and Cr hydroxides are adsorbed on the surface of goethite (Q-Fe00H), dehydrated and reduced, and the oxidation degree is adjusted to 1.33 and M<1.50. '3} Using goethite as a core, a layer of goethite containing Co and 'Cr is grown on the surface to obtain goethite containing Co and Cr, which is dehydrated and reduced to an oxidation degree of 1.33<M.
How to adjust to <1.50. {4'Grow a layer of goethite on the surface of the core of goethite containing Co and Cr to obtain goethite containing Co and Cr, which is dehydrated,
A method of reducing and adjusting the oxidation degree to 1.33<M<1.50.

The Co and Cr salts that can be used in the above production method can be water-soluble salts. Water-soluble cobalt salts are compounds that supply cobalt ions in water, and include mono- to tetravalent compounds such as inorganic salts, inorganic acid salts, organic acid salts, and salts of cobalt. Specifically, cobalt chloride, cobalt sulfate,
Cobalt nitrate, cobalt bromide, cobalt fluoride, cobalt iodine, cobalt perchlorate, cobalt acetate, cobalt benzoate, cobalt hexamine chloride, cobalt hexamine nitrate, cobalt hexamine sulfate, cobalt acobetamine chloride , ethylenediamine cobalt chloride, ammonium cobalt sulfate, alum [KCo(S04)2.1 is 20], cesium hexafluorocobalt, heteropolyacid salt (Ki 20, Coo2, Mo03, 6.20), cobalt aluminate, cobalt chloride, cobalt L-aspartate, cobalt borate, cobalt carbide, cobalt carbonyl, cobalt platinum chloride, cobalt cyclohexane butyl, cobalt-2-ethylhexoate, cobalt boron fluoride, cobalt silicon fluoride, cobalt formate , cobalt gluconate, cobalt glycine, cobalt molybdate, cobalt lactate, cobalt laurate, cobalt naphthenate, cobalt nitride, cobalt oleate, cobalt boronate, cobalt boride, cobalt chromate, cobalt citrate, cobalt cyanide, Cobalt ferrocyanide, cobalt hexachlorostannate, cobalt oxalate, cobalt phosphate, cobalt phosphite, cobalt selenate, cobalt selenite, cobalt sulfamate, cobalt thiocyanate, cobalt potassium oxalate, cobalt selenide, These include cobalt silicate, cobalt fluorosilicate, cobalt stannate, cobalt titanate, and cobalt tungstate.

Among these, cobalt chlorides, sulfates, nitrates,
Particularly suitable are bromide, fluoride, iodide, perchlorate, acetate, benzoate, hexamine chloride salt, hexamine nitrate salt, hexamine sulfate salt, acobentamine chloride salt, ethylenediamine chloride salt, ammonium sulfate salt, etc. ing.

Water-soluble chromium salts include chromium chloride, chromium bromide,
Chromium iodide, chromium thiocyanate, chromium sulfate, chromium potassium sulfate, chromium ammonium sulfate, chromium nitrate, chromium acetate, chromium oxalate, chromyl chloride, chromyl fluoride, ammonium chromate, potassium chromate, sodium chromate, chromium Calcium acid, potassium dichromate, sodium dichromate, chromic anhydride, ammonium tetrathiocyanatodiamminechromate {(NH
4) Cr[(NCS)4](NH3)2・ratio 0}" Potassium orioxalate chromate K3[Cr(C204
)3]-3 days 20, r-hydroxoacoenneaammine dichromate chloride {[Cr2(OH) (0 stars)
(Nfan) 9] CI5}, hexaamminechromium chloride {
[Cr(NH3)6]CI3・日20}, potassium hexacyanochromate {K3[Cr(CN)6]}, etc. are used, but when forming a hydroxide, water-soluble Cr(m ) It is preferable to use salt.

Examples of the alkali used in the present invention include alkali hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkali hydroxides such as calcium hydroxide and barium hydroxide; ammonium hydroxide, aqueous ammonia, and mixtures thereof. It is.

These alkaline substances are dissolved in water or a mixture of water and an organic solvent miscible with water. It is desirable that the alkaline hydroxide solution be used as a solution with a concentration of 0.001N or more. In order to deposit Co and Cr metals on the Fe○x surface, Fe○x slurry (Fe○x
water-soluble Co salt, C
d and mix thoroughly, add a reducing agent, set the pH temperature, and react.

At this time, in order to make the reaction proceed uniformly, cobalt plating,
A complexing agent used in chrome plating may be used in combination.
The pH is selected to be optimal for each reducing agent, and the temperature is selected in the range of 20 to 9,000 to promote the reaction. Examples of reducing agents include boro/hydride (borohydride) compounds, hydrazine and its humble conductors, and hypophosphites. Bolo/,
Hydride compounds include borane, borazane, borohydride, sodium borohydride, potassium borohydride,
One or more types of borohydride compounds such as dimethylaminoborane and jetylaminoborane or derivatives thereof are used.

Hypophosphite is hypophosphorous acid (phosphinic acid) ion: [
PH202]-, and hypophosphites include ammonium hypophosphite, sodium hypophosphite, magnesium hypophosphite, aluminum hypophosphite, potassium hypophosphite, hypophosphite IJ calcium phosphate, manganese hypophosphite, iron hypophosphite, cobalt hypophosphite,
These include nickel hypophosphite, zinc hypophosphite, barium hypophosphite, cerium hypophosphite, lead hypophosphite, and uranyl hypophosphite.

Among these, ammonium salts, sodium salts, magnesium salts, potassium salts, calcium salts, etc. are particularly suitable.

The thus obtained magnetic iron oxide with adsorbed Co and Cr is washed with water, filtered, and dried.

The drying temperature is important and is preferably 40 to 80 qo; if it exceeds 80°C, oxidation will proceed rapidly, and preferably 50 to 60 qo.
It is best to dry at o. Moreover, it is most preferable to dry under reduced pressure at 50 to 60 degrees Celsius. The ferromagnetic iron oxide in the present invention obtained by the above method is dispersed with a binder,
It is coated onto a substrate (support) using an organic solvent and dried to form a magnetic layer to form a magnetic recording medium.

Regarding the manufacturing method of the magnetic paint used in the present invention,
No. 1186, No. 47-28043, No. 47-28045, No. 47-28046, No. 47-28048, No. 47-3
It is described in detail in publications such as No. 1445.

The magnetic paints described in these documents mainly contain ferromagnetic powder, binder, and coating solvent, and may also contain additives such as dispersants, lubricants, abrasives, and antistatic agents.
As the binder used in the present invention, well-known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

As a thermoplastic resin, the softening temperature is 150°C or less, the average molecular weight is 10,000 to 200,000, and the degree of polymerization is about 200 to 2.
For example, vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, and acrylic acid ester.

Nitrile copolymer, acrylic acid 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, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate) , nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof. Examples of these resins are listed in Taruko Sho 37-6877, 39-1.
No. 2528, No. 39-19282, No. 40-534y,
No. 40-209070, No. 41-9463, No. 41-14
No. 05y, No. 41-16985, No. 42-6428, 4
No. 2-11621, No. 43-4623, No. 43-1520
No. 6, No. 44-288y, No. 44-17947, No. 44-18232, No. 45-14020, No. 45-14500
No., 47-18573, 47-22063, 47-
No. 22064, No. 47-22068, No. 47-22069
No. 6, 47-22070, 48-27886, U.S. Patent No. 3144352; U.S. Patent No. 3419420; U.S. Patent No. 349
No. 9789: Described in No. 3713 of the same No. 7. As a thermosetting resin or a reactive resin, it is 20% in the state of a coating liquid.
It has a molecular weight of 0,000 or less, and by adding it after coating and drying, the molecular weight due to reactions such as condensation and addition becomes infinite.

Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, epoxy resin, polyurethane evening-curing resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy polyamide resin, high molecular weight polyester resin, and isocyanate resin. Mixtures of polymers, mixtures of methacrylate copolymers and diisocyanate prepolymer, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols/high molecular weight diols/
A mixture of triphenylmethane triisocyanate, a polyamine resin, a mixture thereof, etc. are used. Examples of these resins include Japanese Patent Publication Nos. 39-8103, 40-19779, 41-7192, 41-8016, and 41-142.
No. 75, No. 42-1817, No. 43-12081, 4
No. 4-28023, No. 45-14501, 45-249
No. 02, No. 46-13103, No. 47-22065, 4
7-22066, 47-22067, 47-220
No. 72, No. 47-22073, No. 47-28045, 4
No. 7-28048, No. 47-28922, U.S. Pat. No. 31
44353; Ship No. 20090; Ship No. 343751; Ship No. 3597273; Ship No. 3781210: Ship No. 378
It is described in No. 1211.

These binders may be used alone or in combination;
Other additives may be added.

The mixing ratio of the ferromagnetic powder and the binder is 10 to 400 parts by weight, preferably 30 to 20 parts by weight, per 10 parts by weight of the ferromagnetic powder. In addition to the above-mentioned binder and fine ferromagnetic powder, additives such as a dispersant, a lubricant, an abrasive, and an antistatic agent may be added to the magnetic recording layer.

Dispersants include cabrylic acid, capric acid, lauric acid,
Fatty acids with 12 to 18 carbon atoms such as myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, stearolic acid (R, COO, R, is a fatty acid with 11 to 17 carbon atoms) Alkyl groups); metal soaps made of alkali metals (Li, Na, K, etc.) or alkali metals (Mg, Ca, Ba) of the above-mentioned fatty acids; lecithin, etc. are used.

In addition, higher alcohols having 1 or more carbon atoms and sulfuric acid esters can also be used. These dispersants are added in an amount of 1 to 2 parts by weight based on the weight of the binder io. Lubricants include silicone oil, graphite, molybdenum disulfide, tungsten disulfide, fatty acid esters consisting of a hard monobasic fatty acid with 12 to 1 carbon atoms and a monohydric alcohol with 3 to 12 carbon atoms, and 17 carbon atoms. Fatty acid esters made of one or more monobasic fatty acids and a -hydric alcohol having a total carbon number of 21 to 2 carbon atoms can be used.

These lubricants are used in an amount of 0.2 to 10 parts by weight of the binder 10.
It is added in an amount of 2 parts by weight. Regarding these, the specifications of Japanese Patent Publication No. 43-2388, Japanese Patent Application No. 42-28647, Tokubuta No. 43-81543, U.S. Patent No. 34
No. 70021; No. 3492235; No. 3497411
No. 3523086, No. 3625760; 36
No. 30772; No. 3634253; No. 3642539
No. 3687725; “IBM Technical
Disclosure B mountain letjn''Vol.
9, No. 7, Pa saddle 779 (December 1966); “
ELEKTRONIK” 1961, No. 12, Pa
ge38 beats are listed. Commonly used abrasive materials include fused alumina, silicon carbide chromium oxide, corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite). These abrasives have an average particle diameter of 0.05 to 5 mm, particularly preferably 0.1 to 2 Å. These abrasives are added in an amount of 7 to 2 parts by weight per 100 parts by weight of the binder. Regarding these, please refer to Japanese Patent Application No. 48-26749, US Patent No. 3007807; US Patent No. 3041196;
No. 25: British Patent No. 1145349; West German Patent (D
T-PS) No. 853211. Natural surfactants such as saponin as antistatic agents; nonionic surfactants such as alkylene oxide, glycerin, and glycidol; higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, phosphonium or Cationic surfactants such as sulfoniums; anionic surfactants containing acidic groups such as carboxylic acids, sulfonic acids, phosphoric acids, sulfate ester groups, and phosphoric acid ester groups; sulfuric acid or phosphate esters of amino acids, aminosulfonic acids, and amino alcohols Ampholytic activators such as

Some examples of surfactant compounds that can be used as antistatic agents are disclosed in U.S. Pat.
No. 2288226, No. 2676122, No. 26
No. 76924, No. 2676975, No. 2691566
No. 2727860, No. 2730498, No. 27
No. 42379, No. 2739891, No. 3068101
No. 3158484, No. 3201253, No. 32
No. 10191, No. 3294540, No. 3415649
No. 3441413, No. 3442654, No. 34
No. 75174, No. 3545974, OLS No. 1942665, British Patent No. 1077317
No. 1198450, etc., "Synthesis of surfactants and their applications" by Ryohei Oda et al. (Saimten 196 Sanno edition);
A. W. "Surf S Active Agents" by IJ Bay (Interscience/Government Inc. 1958 edition); T. P. "Encyclopedia Op Surf S Active Age, Vol. 2" (Chemical Publications Company, 1964 potato edition); "Surfactant Handbook" 6th edition (Sangyo Tosho Co., Ltd., December 1966) by Sisley. 20th), etc.

These surfactants may be added alone or in combination.

These are used as antistatic agents, but are sometimes used for other purposes, such as dispersion, improving magnetic properties,
It may also be used to improve lubricity or as a coating agent.
To form the magnetic recording layer, the above-mentioned composition is dissolved in an organic solvent and applied as a coating solution onto a support.

The thickness of the support is about 5 to 50 rm, preferably 10 to 40 rm.
The surface of the mountain is good, and the materials used include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and polycarbonate. . The above support is used for the purpose of preventing static electricity, preventing transfer, etc.
The surface opposite to the side on which the magnetic layer is provided is a so-called back coat (
backcoat).

Regarding the back coat, for example, US Patent No. 280,440
No. 1, No. 3293066, No. 3617378, No. 3
No. 062676, No. 3734772, No. 347659
No. 6, No. 2643048, No. 2803556, No. 2
No. 887462, No. 2923642, No. 299745
No. 1, No. 3007892, No. 3041196, No. 3
No. 11542, No. 3166688, etc. Further, the support may be in any form such as a tape, sheet, card, disk, or drum, and various materials may be selected as necessary depending on the form. Methods for applying the magnetic recording layer onto the support include air doctor coating, plaid coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, and spray coating. can be used, and other methods are also possible, and specific explanations of these are described in detail in "Coating Engineering", pages 253 to 27, published by Asakura Shoten (published in 1968).

Organic solvents used during coating include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propanol, and butanol; methyl acetate, ethyl acetate, butyl acetate, and ethyl lactate. , glycol acetate,
Ester types such as monoethyl ether; glycol ether types such as ether, glycol dimethyl ether, glycol monoethyl ether, dioxane; benzene,
Tar-based (aromatic hydrocarbons) such as toluene and xylene;
methylene chloride, ethylene chloride carbon tetrachloride,
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene can be used.

By such a method, the magnetic layer coated on the support is optionally treated to orient the magnetic powder in the layer, and then the formed magnetic layer is dried.

If necessary, the magnetic recording medium of the present invention is manufactured by subjecting it to surface smoothing processing or cutting it into a desired shape. In this case, the orientation magnetic field is approximately 500 to 2000 AC or DC.
Gauss, and the drying temperature is about 50 to 100℃.
Drying time is about 3 to 10 minutes.

The magnetic recording medium of the present invention has the following effects and advantages. [i- The magnetic iron oxide containing Co and Cr according to the present invention is different from the previously used Co-containing y-Fe.
The amount of pressure demagnetization is significantly smaller than that of Fe304 with 203 and Co, and a magnetic recording medium using this material can stably record and store information signals.

(ii) The magnetic iron oxide containing Co and Cr according to the present invention has an extremely small amount of demagnetization due to heating, and when the magnetic material according to the present invention is used in, for example, a video cassette, recording is possible even when the temperature rises due to contact with a head. The information signal obtained is stable.

(iii) The magnetic iron oxide containing Co and Cr according to the present invention promotes changes in coercive force over time by adjusting the degree of oxidation, and does not cause any change in coercive force over time in a magnetic recording medium using this. You can prevent it from getting too tight.

G's "Magnetic iron oxide containing Co and Cr according to the present invention can be used in combination with conventionally used Co-containing y-Fe203, Co
-Compared to Fe304 containing Fe304, the coercive force distribution is uniform and it is suitable for manufacturing high-density magnetic recording bodies.

M The magnetic recording material using magnetic iron oxide containing Co and Cr according to the present invention has excellent transfer characteristics and erasing characteristics.

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 components, 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.

0 In the following examples, the uniformity of coercive force distribution is B
- The differential waveform of the day curve was taken and its degree was investigated from its half width (ΔHc).

Example 1 Q-Fe00HI0k9 was dehydrated in air at 400°C to form Q
-Fe203, and then reduced to Fe304 at 350 oo in a hydrogen stream.

After cooling to room temperature, the surface layer of Fe304 is gently oxidized and stabilized under low oxygen partial pressure, and then taken out and subjected to coercive force (Hc).
) 38 Hiro, saturation magnetization (os) 84. Magnetic iron oxide wind with an oxidation degree x=1.335 was obtained at $mu/night. Six parts of 200 ta each of this magnetic iron oxide were collected, leaving one part and the other five parts.
Each part was placed in a constant temperature bath kept at 60o0 for 0.5 days.
Oxidation was allowed to proceed for 1, 3, 7, and 15 days.

Their magnetic properties and oxidation degree (x) are shown in Table 1. 200 pieces of each of the 6 types of Fe○x thus obtained were taken and dispersed in water for 2 nights to form a slurry.

COS04・7day20 (Reagent 1
class) 15.3ta Cr (N03) 3・Hata 20
(Reagent grade 1) 32.7 evening *Wednesday
Add a solution with a composition of 500 ml, stir for 10 minutes, and add NaOH (1st class reagent).
15.6 ta water 50
A solution with a composition of 0M was gradually added and then stirred for 30 minutes.

Next, the Co and Cr contents of the six types of powders obtained after washing with water, filtering in an oven, and drying at 5,000 ℃ were examined using the crab light X-ray method, and it was found that all of the Co and Cr in the charged amount was adsorbed within the measurement error. Was. These six types of powder were each heat-treated at 350°C for 1 hour in a nitrogen atmosphere, cooled to room temperature, and taken out.
and 6 types of magnetic iron oxides containing Cr (1-1), (1
-2), (1-3), (1-4), (1-5), and (1-6) were obtained.

Their magnetic properties are shown in Table 1.

Table 1 The coercive force of the magnetic iron oxide containing Co and Cr thus obtained did not change at all over time and was saturated in about 40 days.

Table 1 also shows the coercive force after 45 days. Example 2 When 800 g of the magnetic iron oxide prepared in Example 1 was kept in a constant temperature bath at 60 qo for 4 hours to proceed with oxidation, the coercive force (Hc
) 39 e, saturation magnetization (os) 81. Magnetic iron oxide {B' with a step mu/unit and acid strength x=1.40 was obtained.

Divide this magnetic iron oxide into 4 parts of 200 ta each and divide them into 1st grade reagent COS04.75○ as shown in Table 2.
The same treatment as in Example 1 was carried out using 20 units of Cr(N03)3 and NaOH in the charged amounts. Four types of magnetic iron oxides (2-1) and (2-2) containing Co and Cr thus obtained
, (2-3), and (2-4) are shown in Table 4.

Table 2 Example 3 Using the magnetic iron oxide {B} obtained in Example 2, the following amounts of lagoonal cobalt salt, water-soluble chromium salt, and sodium hydroxide (all of these are first grade reagents) were added. Magnetic iron oxides (3-1), (3-2), (3-3) (3-4), (3-3) containing Co and Cr were processed using the same machine as Example 1 using
-5) and (3-6) were obtained.

Their magnetic properties are shown in Table 3. (3-1) C.

CI2/Mother's Day 20 13-
0ta Cr (N03) 31 Group 20 3
2.7 ta NaOH 1
5.6 evening (3-2) CoC12/Mother LO
13.0 TAC 12/Mother's Day 20
21.8 polyNaOH
15.6 evening (3-3) CoC1
2. Mother LO 13.0ta KC
r(S04)2・1 is 20 40. Salmon NaOH I9.2
Evening (3-4) Co (N03) 2
15.9taCr(N03)3
32.7taNaOH
15.6 evening (3-5) Co(N03)2
15.9taCrC13・
Mother's Day 20 21-8 Na
OH 15.6 evening (3-6) Co (N03) 2
15.9 Ta KCr (S04) 2.1 is 20
40.9taNaOH
I9.2 Table 3 Example 4 When the magnetic iron oxide prepared in Example 1 was kept in a constant temperature bath at 60 oo for 72 hours to proceed with oxidation, the coercive force (Hc) was 39 e, and the saturation magnetization (〇s) was 80. ．． Sheath mu/yu, oxidation degree x=1
．． 43 magnetic iron oxide was obtained.

Divide this iron oxide into 3 parts of 200 t each and add 2 parts of water to each part.
In the evening, it dispersed and became a slurry. COS04/7 days 20 1 for each of the three types of slurry
5.3 Ta Cr (N03) 3, carp 20,
32.7 Yusui 50
A solution having a composition of 0 and 0 was added and allowed to stand for 10 minutes.

This was reduced by changing the reduction conditions as shown in Table 4, and Co and Cr were precipitated on the iron oxide, washed with water, and dried. After that, heat treatment was performed for 1 hour at 350:00 in a nitrogen atmosphere, and Co and C having magnetic properties as shown in Table 4 were obtained.
Magnetic iron oxides containing r (4-1) (4-2), (4-
3) was obtained. Table 4 Example 5 As a starting material, y-Fe203 having an average particle size of 0.55 μm, a ball ratio (major axis/minor axis) of 8, and a coercive force of 3550 e was used.

This Y-Fe203200 was dispersed in water to form a slurry. COS04/7th 2014/8 evening Wednesday 200
The liquid dissolved in the cry and Cr(N03)3・Group 2031.
6. Add a solution of 200 g of water dissolved in 200 g of water to the above slurry and add 1
I worshiped the lights for 0 minutes. A solution prepared by dissolving 15.1 parts of NaOH in 500 parts of water was gradually added to the slurry, and stirring was continued for 30 minutes after the addition. After washing with water, filtering and drying, 35,000
It was refunded at The reduction conditions were Day 2: A mixed gas of N2 = 1:3 was flowed at 500 c/min for 60 minutes. (Q only for 500
When flowing for 60 minutes, y-Fe203 completely becomes Fe30.
It became 4. ) The magnetic material thus obtained has a coercive force (Hc) of 55 feet and a saturation magnetization (os) of 78. Hoko mu/
In the evening, e of ΔHc17 and oxidation degree M were 1.47.

The content of Co and Cr by crab light X-ray is 2.0% each.
, 2.9%. The coercive force of this magnetic material showed little change over time, and the coercive force after 45 days was 57 e. Example 6 A solution obtained by dissolving 1st class reagent FeS04. The reaction was carried out while blowing in the solution at a rate of 2/min, and the reaction was completed 3 minutes after the liquid turned yellow. Next, the temperature of the reaction solution was increased to 5
000, and while adjusting the pH to 6.0 with NaOH solution, FeSO4・7 days 20 3509, COS0
4th and 7th 20 14.8 evening, Cr (N03) 31 Cape 2
On the evening of 031.7, a solution containing 1 part water was added at a constant speed for 4 hours to grow crystals.

Afterwards, add Su-NaOH solution to raise the pH to 9.0.
The reaction was completed after 0 minutes of aging. When washed with water and treated in a furnace, it contained Co and Cr - Fe00 days 225
I got the evening. When analyzed using crab light X-rays, the Co content was 2. Touch mic%, Cr content is 3. The touch was mjc%. The obtained goethite was dehydrated in air at 400 qo to give Q3-Fe203, and then reduced at 350 qo in a hydrogen stream. After cooling to room temperature, the surface layer of Fe304 was gently oxidized and stabilized at low oxygen partial pressure, and then taken out. In this state Hc 57buta, os81.8emu/evening, △H
c15 e and oxidation degree M = 1.34.
4. After aging at room temperature for 40 days, the coercive force was 60 legs e and the degree of oxidation was 1.40. When this magnetic iron oxide containing Co and Cr was kept in a 6000 temperature bath for 4 hours, the coercive force was 59 e, the saturation magnetization was 80.3 emu/t, and AH
A magnetic material having an oxidation degree M of 1.41 was obtained.

Example 7 Reagent 1st grade FeS04 7th 20350 evening, Reagent 1st grade Cr
(N03)3・Rainbow L031. ? A solution prepared by dissolving 50 parts of 1st class NaOH in 1 part of water was added to a solution of 50 parts of the reagent 1st grade NaOH dissolved in 2 parts of water. The reaction was completed 30 minutes after the color turned yellow.

Next, the temperature of the above reaction solution was raised to 5000℃, and NaOH
FeS04・7 days 20 while adjusting the pH to 6.0 with a solution
At 350 pm, on the 7th and 20 15 pm, a solution prepared by dissolving COSQ in 1 water was added at a constant speed for 4 hours to grow crystals.

After that, add NaOH solution and raise the boat to 9.0.
The mixture was aged for 0 minutes and the reaction was completed. After washing with water and over-drying in an oven, Q-Fe containing Co and Cr was obtained. According to crab light X-ray analysis, the Co content was 2.0%.
The Cr content was 2.95%. When dehydration, reduction, and constant temperature bath treatment were performed under the same conditions as in Example 6, the coercive force (
Hc) 59 e, saturation magnetization (〇s) 79. &mu/evening,
△Hc15, oxidation degree M=1.40 Co and Cr
A magnetic iron oxide containing .

Example 8 Q-Fe00 day with a particle size of 0.6 mm is used as the starting material.

This Q-Fe was dispersed in 2.5 g of water to form a slurry. COS04/7th 2020 evening, Cr(N0
3) A solution prepared by dissolving 3. Insect L042.6 in 500 g of water was added to the above chiller and stirred for 10 minutes. To this, a solution prepared by dissolving 20.3 parts of 1st grade NaOH in 500 parts of water was gradually added, and after the addition was completed, the mixture was stirred for 30 minutes. Q-Fe0 which adsorbed Co and Cr by washing with water, oven heating and drying
I got 305 ta for 0 days. When the amounts of Co and Cd were examined using crab light X-rays, they were 1.98% and 2.96%, respectively. When dehydration and reduction were carried out under the same conditions as in Example 5 and kept in a constant temperature bath of 6000 for 48 hours, the e of coercive force (Hc) was 57.
, saturation magnetization (os) 79. Dan mu/evening, △Hc15 e
A magnetic iron oxide containing Co and Cr with an oxidation degree M=1.41 was obtained. Example 9 Fe○x containing Co and Cr in the same manner as in Example 1
Got slurry.

After repeating decantation 3 times, take a slurry of 60 mm as magnetic iron oxide, add 3% thickener CMC to it to increase the viscosity, orient it in a magnetic field of 80 mm, and then slowly dry at 5 mm. I let him do it and got a block. The block was placed in an electric furnace and treated at 35 psi for 1 hour in a nitrogen atmosphere, and cooled at a rate of 5° C./min.

Coercive force (Hc) 56e, saturation magnetization (os) 80.0e
A magnetic iron oxide with a magnetic flux, ΔHc13, and an oxidation degree M=1.42 was obtained. When the Co and Cr contents were examined using crab light X-rays, they were 1.95% and 3.0%, respectively. Comparative Example 1 The magnetic iron oxide of Example 1 was kept in a constant overflow tank of 6000 for 48 hours, coercive force (Hc) e of 39, saturation magnetization (〇s) 80.5 emu/night, oxidation degree x = A magnetic iron oxide of 1.41 was obtained.

This magnetic iron oxide powder was dispersed in water to form a slurry.

A cobalt sulfate aqueous solution (COS04/7th 2015.4 evening + 500 liters of water) was added to this slurry, and after lighting for 10 minutes, a sodium hydroxide aqueous solution (NaOH 4.4 liters + 500 liters of water) was added to the slurry.
00') was gradually added, and after the addition was finished, the mixture was stirred for 30 minutes.

After washing with water, filtering in an oven, and drying at 60o○,
Heat treatment was performed for 50,001 hours, and after cooling, the product was taken out into the air. The magnetic properties of the Co-containing magnetic iron oxide obtained in this way are coercive force (Hc) 5370e and saturation magnetization (〇s) 79.4e.
Mu', ΔHc181, oxidation degree x=1.42, and the coercive force after standing for 45 days changed to 58 e.

It was also found by crab light X-ray method that it contained 2.0% Co. Comparative Example 2 Magnetic iron oxide 200 g as in Comparative Example 1 was dispersed in water 2 Z to form a slurry.

After adding a cobalt sulfate aqueous solution (COS04/7th, 2030, 500 yen) to this slurry and lighting it for 10 minutes,
Sodium hydroxide aqueous solution (NaOH 8.59 10 water 500
(I) was added gradually, and after the addition was finished, the lantern was held for 30 minutes. After washing with water, heating in a furnace, and drying with L6P0, heat treated in air at 30,000C for 2 hours to produce Co-containing maghemite (y-Fe Phantom 3).
) was obtained. This Co-containing y-Fe203 has coercive force (Hc
) 60 e, saturation magnetization (os) 72.0 emu/event, △
It shows Hc187, and according to the crab light X-ray method, it is 4.0%.
It contained Co.

Example 10 Examples 1, 2, 4, 5, 6, 7, 8, and Comparative Example 1,
For each 30 parts of magnetic iron oxide obtained in step 2, 40 parts of vinyl chloride/vinyl acetate (87:13) copolymer epoxy, 3 base silicone oil (dimethylpolysiloxane), 5 parts toluene sulfone. Acid ethylamide 7 parts ethyl acetate
25 Ikarito Methyl Ethyl Ketone
A composition of 25 eaves was prepared, thoroughly kneaded in a ball mill, and 20 parts of Disk Module L-75 (trade name: polyisocyanate compound manufactured by Bayer AG) was added and uniformly mixed and dispersed to obtain a magnetic paint.

This paint was applied to a PET base (25 mm thick) with a dry thickness of 10 mm.
The magnetic tape thus obtained was applied in a depletion tester and pressed after running 300 times. The amount of demagnetization was measured.

Further, the magnetic tape was saturated, the magnetic flux density was measured at room temperature, the sample was immersed in boiling water for 20 minutes, cooled to room temperature, the magnetic flux density was measured, and heating demagnetization was measured. Transfer characteristics (SP ratio) are JI
Measured by SC-55421971.

The erasure rate was recorded at standard input level + IM old, DN-34
Wave-1 (DENON, manufactured by Nippon Columbia) was used with an erase current of 0. Measured in Hiro.

The results of such measurements are shown in Table 5.

Fe304, which has magnetic properties, has a Fe30 ion of 66.7a.
tomic%, and y-Fe203 is Fe3
Ten ions are 10 melon tomic%. Table 5 shows the results of measuring the atomic % of Fe30 ions in Examples and Comparative Examples of the present invention. The Fe30 ion was determined by the oxidation titration method among the capacitance methods (Handbook of Analytical Chemistry, revised 2nd edition, p. 101 (1971)). SatoshiConventional Co-containing magnetic iron oxide is mainly Co-containing y-Fe2
03 (M±1.5) is used because Fe304 changes quickly to y-Fe203 and the degree of oxidation can be controlled, and this material can be manufactured stably and has stable magnetic properties. There was an advantage.

However, Co-containing y-Fe203 has a pressure demagnetization of 30 to 5
0%, and heating demagnetization is also as large as 15 to 20%, resulting in a weakened recorded information signal. Also, Co-containing F
As can be seen from the results in Table 5, the amount of pressurized demagnetization due to mechanical pressure impact for e304 is 30 to 40%, and Co-containing Zy-
There is no big difference from Fe203, but heating demagnetization is possible with Co-Fe.
Much improved compared to 203. Further considering the oxidation degree and pressure demagnetization amount of magnetic iron oxide from Table 5, it is 1.35SM.
S.I. 48 has a small amount of pressure demagnetization, but especially 1.
36SMSI. The one using magnetic Z iron oxide in the range of 44 is preferable because the amount of demagnetization is small.

The Co-modified magnetic iron oxide with M=1.5 of Comparative Example 2 has poor pressure demagnetization, heat demagnetization, SP ratio, and erasure rate, and can be used as a magnetic tape, which Bell does not have. Comparative example 1 (M=
1.42), both pressure demagnetization and heating demagnetization can be used and are available in Bell, but the erasure rate and SP ratio are low and can be used, which is not available in Bell.

Sample No. 1-1 (M=1.34) is heating demagnetization, S
Both the P ratio and the erasure rate are usable and at an acceptable level, but the pressure demagnetization is large. Also sample no. 1-6 (M=1.4
Sample No. 8) had slightly larger pressure demagnetization. 5 (M=
1.47) requires a little more pressure demagnetization and heat demagnetization, but both of these can be used and are included in the bell.

In this way, the present invention can improve the erasure rate of Co-containing y-Fe○x, S
The P ratio was improved. Next, when examining the degree of oxidation and changes in coercive force over time, we found that the degree of oxidation and coercive force were 1.35 mm. The number of 48 pieces is at least a few.

△Hc, which is considered to represent the uniformity of coercive force, is Co
There is an e improvement of about 30-4 for the Co and Cr additions over the Co and Cr additions. The magnetic recording medium according to the present invention has an S
The P ratio was improved by 2-&old, and the erasure rate was improved by 15-2 by 6. This result also corresponds to the improvement in ΔHc. These differences are thought to be due to some kind of interaction among Co, Cr, and Fe, but when Co and Fe are constant and the amount of Cr is changed, there is also a sign of improvement when 0.1% Cr is added to Fe. I can see it. Co-containing magnetic iron oxide in an intermediate oxidation state has greatly improved pressure demagnetization;
This was further improved by adding .

In addition, △Hc, SP ratio, and erasure rate are also improved by adding 〇 in addition to Co, and magnetic tapes made using magnetic iron oxide containing Co and Cr are stable against depletion and have a high SP ratio. , a magnetic tape with excellent erasure rate. As can be seen from Table 4, a magnetic tape with high saturation magnetization and excellent sensitivity, frequency characteristics, and signal-to-noise ratio could be produced. Comparative Example 3 The magnetic iron oxide of Example 1 was placed in a thermostatic oven at 485 °C.
Hold time, coercive force (Hc) 391G saturation magnetization (os)
80. After that, magnetic iron oxide with an oxidation degree x=1.41 was obtained.

200 g of this magnetic iron oxide was dispersed in 2 g of water to form a slurry. Add chromium nitrate aqueous solution (Cr(N03)3.
After adding 20, 32.7 ml of bait + 500 ml of water and letting it stand for a minute, add a sodium hydroxide aqueous solution (NaOHIO.
Gradually add 500 yen of [) in evening + water, and after adding 3
I worshiped the lights for 0 minutes. After passing through a water washing oven and drying at 6,000 ℃, heat treatment was performed in a nitrogen atmosphere for 350,001 hours, and after cooling, it was taken out into the air. Evening The magnetic properties of the Cr-containing magnetic iron oxide thus obtained were Hc38 e, os79. umbrella mu/evening,
The e-oxidation degree M of ΔHc·12 was 1.41.

Here, the synergistic effect of Co-Cr is summarized in Comparative Example 3, Example 1, and Comparative Example 1 described above.

That is, in the case of the present invention containing Co and Cr (Example 1)
, samples 1-4), case of Co only (comparative example 1) Cr
(Comparative Example 3), when neither Co nor Cr is included (
Example 1, sample 1-4 raw material) 35 was standardized in view of the coercive force (Hc), coercive force distribution (ΔHc), and that the coercive force distribution generally increases as the coercive force increases. In order to make a comparison, the value of ΔHc/Hc was calculated and Table 6 was created.

The larger the coercive force, the better; on the other hand, the coercive force distribution is closely related to the erasing rate in tape characteristics, and the smaller the distribution, the better. Therefore, the smaller the relative value ΔHc/Hc, the better the characteristics. Table 6 As is clear from Table 6, Example 1 has a high coercive Hc and a very small ΔHc/Hc value, giving a good value.

Claims (1)

[Scope of Claims] 1. In a magnetic recording body in which a magnetic layer mainly composed of ferromagnetic fine powder and a binder is provided on a substrate, the ferromagnetic fine powder has a value of M expressed by the following general formula of 1.35. <M<1.4
8. A magnetic recording material characterized in that it is a ferromagnetic iron oxide bertolide compound containing Co and Cr. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ 2. In a magnetic recording material in which a magnetic layer mainly composed of ferromagnetic fine powder and a binder is provided on a substrate, Fe^3 in which the ferromagnetic fine powder is 66.7 atomic% or more ferromagnetic iron oxide containing ^+ ions is dissolved in solid solution with 1 atomic% or more of Co ions and 0.3 atomic% or more of Cr ions, and the value of M shown in the following general formula is 1.35. A magnetic recording material characterized in that it is a ferromagnetic iron oxide bertolide compound containing Co and Cr with <M<1.48. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼