JPS598046B2 - Jikiki Rokutai - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium suitable for magnetic tapes, magnetic disks, and the like.

Conventionally, magnetic iron oxide, which is a ferrimagnetic material, has been used as a magnetic material for magnetic recording media, as is well known.

On the other hand, chromium dioxide is ferromagnetic and
(1) Large saturation magnetization, (2) Small electrical resistance, (3
) Excellent magnetic properties such as less pressure demagnetization, (the directions of the tetrapacked crystal anisotropy axis and the shape anisotropy axis are close to each other, and (5) the ability to change the Curie point) It also has

In order to use chromium dioxide as a magnetic recording medium, the coercive force must be 2000e or more.

The following methods are available for producing chromium dioxide with high coercive force. (1) Tokuko Sho 32-6087, Tokuko Sho 36
- A method of thermally decomposing chromium trioxide under high temperature and high pressure in the coexistence of water, as described in Japanese Patent No. 18657.

As an improved method of this method, as described in Japanese Patent Publication No. 36-8839, Japanese Patent Publication No. 38-829, and Japanese Patent Publication No. 40-2889, ruthenium dioxide, antimony compounds,
A method of obtaining chromium dioxide with high coercive force by adding specific substances such as tellurium compounds and iron compounds (hereinafter such substances are referred to as modifiers). (2) As described in US Pat. No. 3,117,093, a method of obtaining a chromium oxide having a chromium valence of 4 or more and 6 or less by heating under high temperature and high pressure.

By using a modifier in this method as well, chromium dioxide having even higher coercive force can be obtained. (
3) As described in Japanese Patent Publication No. 42-11617, a method in which a trivalent chromium compound such as chromium oxide or chromium hydroxide is heated together with an oxidizing agent at high temperature and pressure.

By using a modifier in this method as well, chromium dioxide having even higher coercive force can be obtained. (
4) Other methods of obtaining chromium dioxide under low pressure include a method of producing it from chromyl chloride and a method of producing it from a mixture of chromium nitrate and chromium oxide.

The above-mentioned modifiers have the effect of greatly changing the magnetic properties of chromium dioxide, and are divided into modifiers that change the coercive force and modifiers that change the Curie point.

The former includes Sb, Te, Sn, Ru, P, W, and their compounds; the latter includes Fe, Ru, and their compounds to raise the Curie point, and S, P, and F to lower the Curie point. ．． , Mn. V-Ni, its compounds (for example, Japanese Patent Publications No. 36-8839, No. 38-829, No. 38-18188, No. 47-5739, No. 48-21)
874, 49-9360, JP-A-48-74500,
48-655001 48-40692, 49-1
8793, USP3, O34, 988, FrP2, lO
8,364).

In addition, the residual magnetization of chromium dioxide is reversible with respect to temperature changes, and by utilizing this property, the chromium dioxide tape is brought into contact with the master tape with a high Kyuri point near the Kyuri single point (110 to 125 acid C). A duplication method called thermal transfer, which copies the signal of the master tape, is known (
For example, Special Publications No. 35-18225, No. 43-21273,
(See 43-3234).

At this time, the support (
For example, binders (PET, TAC), plasticizers, lubricants may deteriorate, shrink, expand, etc. due to heat, reducing the mechanical strength of the chromium dioxide tape, or the copied signal may be the same as that of the master tape. This may cause negative effects such as loss of performance. Therefore, chromium dioxide tape is used for thermal transfer. When used as a slave tape, it is necessary to lower the level of chromium dioxide. Therefore, in the present invention,
We provide chromium dioxide that has high coercive force and high saturation magnetization, and has low coercive force and high saturation magnetization.The chromium dioxide has low coercive force, high coercive force, and high saturation magnetization, making it suitable as a slave tape during thermal transfer using the chromium dioxide as a magnetic material. It is an object of the present invention to provide a magnetic recording medium with excellent orientation. The inventors,
Experiments were carried out to examine changes in the magnetic properties of modified chromium dioxide, in which at least one of Sb and Sb compounds and at least one of CO and CO compounds were used together as modifiers for chromium dioxide.

In this experiment, the number of chromium dioxide kiyuri points decreased significantly (1
It was found that the temperature decreases by 0°C or more, with a maximum decrease of 22°C. The results of this experiment are shown in the graph of the attached drawing. This graph assumes that the amount of Sb in the modifier is constant at 0.13 at%, and that CO
The graph shows changes in magnetic properties when denatured by varying the amount of , especially changes in single point (curve 1), coercive force (curve 2), and saturation magnetization (curve 3). Here, the coercive force (Hc) and saturation magnetization (σs) are measured using a vibrating sample magnetometer (VSM-, manufactured by Toei Kogyo) with a measurement magnetic field of 50,000 s, and the single point of Kyuri (Tc) is measured using the same VSM-. After saturation magnetization, the external magnetic field was set to zero, and the residual magnetization was measured from the temperature change. From this graph, it can be seen that even a very small amount of CO content significantly lowers the amount of CO. The present invention is based on the above findings, and consists of using chromium dioxide modified with Sb and CO as a ferromagnetic material, and forming a magnetic layer containing the ferromagnetic fine powder and a binder as main components on a support. The gist is a magnetic recording medium provided.

In the present invention, the content of Sb and CO is preferably 0.001 to 10 at% SbI:. 0.01~10
% CO, more preferably 0.01 to 5 atomic % Sb and 0.05 to 5 atomic % CO.

The present invention will be explained in detail below.

Chromium dioxide modified with Sb and CO contains Sb component and C
The O component is added to and mixed with cucum oxide having a chromium valence of 4 or more, and the mixture is heated in an autoclave in the presence of water for 30 minutes.
Obtained by thermal decomposition at 00 to 500°C.

The above-mentioned Sb component may be either Sb alone or an Sb compound, and examples of the Sb compound include Sb, O3, Sb2O5
,Sb2S3,Sb2S,,SbCl3,SbC/5,
Any material containing Sb such as SbF, etc. may be used.

The above CO component may be either simple CO or a CO compound, and the CO compound is COSO4.7H2.
0,C0(NO3)2・6H20,C0C12・6H2
0,C00,C0304,C0(CH3CO2)2・4
Anything containing CO such as H20, C0(0H)2 etc. may be used. These Sb simple substance or Sb compound and CO simple substance or CO compound are combined when the valence of chromium is 4.
To mix into chromium oxide, which is more than a ball mill,
Vibration mill, impact mill, roll mill, mouth mill,
Mechanical pulverization and mixing may be performed using a cutter mill, mortar, etc., and wet pulverization and mixing are particularly effective.
3. When water-soluble salts are used as Sb and CO, an aqueous solution of the salts may be prepared and mixed with chromium oxide. The content of Sb and CO components can be easily controlled by adding the required amounts during raw material blending, since the Sb and CO added at the time of raw material blending remain in the modified chromium dioxide that is finally obtained.

The amount of water present during the above-mentioned thermal decomposition should be in the range of 0.01 parts to 100 parts per 1 part of the mixture, since if it is too large, the pressure inside the container will become too high.

The modified chromium dioxide of the present invention obtained by the above method is dispersed with a binder, and a base (support) is prepared using an organic solvent.
A magnetic layer is formed by coating and drying the magnetic recording material.

Regarding the manufacturing method of magnetic coating, see Japanese Patent Publication No. 45-186, 47.
-28043, 47-28045, 47-2804
It is described in detail in publications such as No. 6, No. 47-28048, and No. 47-31445.

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

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 20.
0 to 2000, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile 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 derivative (cellulose acetate butyral) (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, Mixtures of these and the like are used.

Examples of these resins are given in Japanese Patent Publication No. 37-6877, 39-
No. 12528, No. 39-19282, No. 40-5349, No. 40-20907, No. 41-9463, 41-14
No. 059, No. 41-16985, No. 42-6428, 4
No. 2-11621, No. 43-4623, No. 43-1520
No. 6, No. 44-2889, No. 44-17947, 44-
No. 18232, No. 45-14020, No. 45-14500
No., 47-18573, 47-22063, 47-
No. 22064, No. 47-22068, No. 47-22069
No. 47-22070, No. 48-27886, U.S. Pat. No. 3,144,352: U.S. Pat. No. 3,419,420: U.S. Pat.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating solution, but when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition.

Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, epoxy-polyamide resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, Mixtures of methacrylate copolymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanate, polyamine resins, and mixtures thereof, etc. be. Examples of these resins are given in Japanese Patent Publication Nos. 39-8103, 40-9779, 41
-7192, 41-8016, 41-14275, 42-18179, 43-12081, 44-2
No. 8023, No. 45-14501, No. 45-24902, No. 46-13103, No. 47-22065, No. 47-2
No. 2066, No. 47-22067, No. 47-22072, No. 47-22073, No. 47-28045, No. 47-2
No. 8048, No. 47-28922, U.S. Pat. No. 3,144
, No. 353: No. 3,320,090: No. 3,447,
No. 510: No. 3,597,273: No. 3,781,2
No. 10; described in No. 3,781,211.

These binders may be used alone or in combination.

The mixing ratio of the ferromagnetic powder and the binder is 10 to 400 parts by weight, preferably 30 to 200 parts by weight, per 100 parts by weight of the ferromagnetic powder. Additives include dispersants, lubricants, abrasives, antistatic agents, and the like.

Dispersants include chifurylic acid, chipurinic acid, lauric acid,
Fatty acids with 12 to 18 carbon atoms (RCOOH.
(R is an alkyl group having 11 to 17 carbon atoms), metal soaps, lecithin, etc. made of the alkali metals (Li, Na, K, etc.) or alkaline earth metals (Mg, Ca, Ba) of the fatty acids mentioned above are used. .

In addition, 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. Lubricants include silicone oil, graphite, molybdenum disulfide, tungsten disulfide, fatty acid esters consisting of monobasic fatty acids with 12 to 16 carbon atoms and monohydric alcohols with 3 to 12 carbon atoms, and 17 carbon atoms. Fatty acid esters made of monobasic fatty acids and monohydric alcohols having 21 to 23 carbon atoms in total can be used.

These lubricants are used in amounts of 0.2 to 100 parts by weight of binder.
It is added in an amount of 20 parts by weight. Regarding these, the specifications of Japanese Patent Publication No. 43-23889, Japanese Patent Application No. 42-28647, Japanese Patent Application No. 43-181543, U.S. Patent No. 3,
No. 470,021: No. 3,492,235: No. 3, 4
No. 97,411: No. 3,523,086: No. 3,62
No. 5,760: No. 3,630,772: No. 3,634
, No. 253: No. 3,642,539: No. 3,687,
No. 725: 21BM Technicai Disc10s
ureBu11etinIV01.9,7167,Pa
ge779 (December 1966): “ELEKTRON
IK'' 1961, .4612, Page 38O, etc.

Commonly used abrasive materials include fused alumina,
silicon carbide chromium oxide, corundum, artificial corundum,
Diamonds, synthetic diamonds, garnet, emery stones (main ingredients: corundum and magnetite), etc. are used.

These abrasives have an average particle diameter of 0.05 to 5 .mu.m, particularly preferably 0.1 to 2 .mu.m. These abrasives are used in an amount of 7 to 2 parts by weight per 100 parts by weight of the binder.
It is added in an amount of 0 parts by weight. Regarding these, Japanese Patent Application No. 48-126749 and U.S. Patent No. 3,007,80
No. 7: No. 3,041,196: No. 3,293,066
No. 3,630,910, No. 3,687,725: British Patent No. 1,145,349: West German Patent (DT
-PS) No. 853,211. Antistatic agents include natural surfactants such as saponin, nonionic surfactants such as alkylene oxide, glycerin, and glycidol, higher alkylamines, quaternary ammonium salts, pyridine and other heterocycles, phosphonium or sulfonium. cationic surfactants such as carboxylic acids, sulfonic acids, phosphoric acids, sulfuric acid ester groups, anionic surfactants containing acidic groups such as phosphoric ester groups, amino acids, aminosulfonic acids, sulfuric acid or phosphoric esters of amino alcohols, etc. Amphoteric activators and the like are used.

Some examples of surfactant compounds that can be used as antistatic agents include U.S. Pat.
, No. 472, No. 2,288,226, No. 2,676,
No. 122, No. 2,676,924, No. 2,676,9
No. 75, No. 2,691,566, No. 2,727,86
No. 0, No. 2,730,498, No. 2,742,379
No. 2,739,891, No. 3,068,101, No. 3,158,484, No. 3,201,253,
No. 3,210,191, No. 3,294,540, No. 3,415,649, No. 3,441,413, No. 3
, No. 442,654, No. 3,475,174, No. 3,
No. 545,974, West German Patent Publication (0LS) 1,9
No. 42,665, British Patent No. 1,077,317, 1
, No. 198, 450, etc., "Synthesis of Surfactants and Their Applications" by Ryohei Oda et al. (Maki Shoten 1964 edition): A.
W. Written by Bayley. "Encyclopedia of Surf S Active Agents" (Interscience Publications Inc. 1958 Edition): "Encyclopedia of Surf S Active Agents, Volume 2" by T.P.
1964 edition): Described in books such as "Surfactant Handbook" 6th edition (Sangyo Tosho Co., Ltd., December 20, 1964).

These surfactants may be added alone or in combination.

They are primarily 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 and as a coating aid.
A magnetic coating obtained by dissolving each of the above-mentioned components in an organic solvent is applied onto a support.

The thickness of the support is about 5 to 50 μm, preferably 10 to 40 μm.
The diameter is preferably about .mu.m, 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 coated with a so-called back coat (Ba
ckcOat). Regarding back coats, for example, U.S. Pat.
No. 93,066, No. 3,617,378, No. 3,06
No. 2,676, No. 3,734,772, No. 3,476
, No. 596, No. 2,643,048, No. 2,803,
No. 556, No. 2,887,462, No. 2,923,6
No. 42, No. 2,997,451, No. 3,007,89
No. 2, No. 3,041,196, No. 3,115,420
No. 3,166,688, etc.

Further, the form of the support may be tape, sheet, card, disk, drum, etc., and various materials are selected as necessary depending on the form.

Examples of organic solvents used in the above magnetic paint include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, methanol, ethanol,
Alcohols such as propanol and butanol, esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate, monoethyl ether, ethers,
Glycol ethers such as glycol dimethyl ether, glycol monoethyl ether and dioxane, tars (aromatic hydrocarbons) such as benzene, toluene and xylene, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorcedrine, dichlor Chlorinated hydrocarbons such as benzene can be used.

Methods for applying the above magnetic coating onto the support include air doctor coating, plaid coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, scratch coating, cast coating, and spray coating. etc., and other methods are also possible, and detailed explanations thereof are given in "Coating Engineering", pages 253 to 277, published by Asakura Shoten (published on March 20, 1972).

By such a method, the magnetic coating layer coated on the support is optionally treated to orient the magnetic powder in the layer, and then dried. If necessary, the magnetic recording medium of the present invention is manufactured by subjecting it to surface smoothing or cutting it into a desired shape. In this case, the orientation magnetic field is about 500 to 2000 Gauss with alternating current or direct current, and the drying temperature is about 50 Gauss.
~100°C, and drying time is approximately 3 to 10 minutes.

The magnetic recording body of the present invention obtained as described above uses modified chromium dioxide having high coercive force and high saturation magnetization as a magnetic material and having a low single point, so magnetic tape, magnetic drum, magnetic sheet, etc. It is particularly suitable as a slave tape for thermomagnetic recording.

Next, examples of the present invention will be given.

Example 1 (Manufacture of modified chromium dioxide) Weigh the raw materials A to E shown in Table 1, first thoroughly mix chromium oxide, Sb compound and CO compound, then add water and further mix in a 111 glass beaker. did.

Thereafter, A-E was placed in a 501 autoclave, and the temperature was raised to 350°C at a rate of 60°C/hour in an external electric furnace, and maintained at 350°C for 3 hours. After cooling, the sample was taken out from the container, washed with water, and dried. The magnetic properties of the sample thus obtained are shown in Table 1 along with the composition of the raw material. Coercive force and saturation magnetization were measured using a vibrating sample magnetometer (VSM-, manufactured by Toei Kogyo) at a measurement magnetic field of 50,000 e. The single point of Kyuri was also obtained using VSM-, with the external magnetic field set to zero after saturation magnetization, and from the temperature change of residual magnetization. Example 2 (Production of modified chromium dioxide) CrO, 85O9 and Sb2O3l. 69 was added and thoroughly mixed to make 9 types of samples, and placed in a 111 glass beaker.
To this, add COSO4・7H20 and water to A-1 shown in Table-2.
The following composition was added and thoroughly mixed.

9 Place the two beakers in a 5011 autoclave and heat to 35°C at a heating rate of 6°C/hour using an external electric furnace.
The temperature was raised to 0°C and maintained at this temperature for 3 hours.

After cooling, the sample was taken out from the container, washed with water, and dried. The magnetic properties of the sample thus obtained and the composition of the raw material are shown in Table 2. The magnetic properties were measured in the same manner as in Example 1. The above relationship between the amount of CO and the magnetic properties is shown in the graph of the attached drawing as described in the main text.

Example 3 (Manufacture of magnetic recording material) 1-A, 1-C, 1-D, 2-A, obtained in Examples 1 and 2
2-E, 2-1, 300 parts each of six types of modified chromium dioxide, 40 parts of vinyl chloride vinyl acetate copolymer (molecular weight 40,000, copolymerization ratio 87/13), epoxy resin (bisphenol A and epichloro
30 parts hydrin solution, hydroxyl group content 0.1
6. Molecular weight 470, epoxy content 0.36-0.44
, specific gravity (20°C) 1.181) Silicone oil (dimethylpolysiloxane) 5 parts Toluenesulfonic acid ethylamide 7 parts Ethyl acetate 25
0 parts Methyl ethyl ketone 250 parts of the composition were added, thoroughly kneaded in a ball mill, and further 20 parts of Dismodyur L-75 (trade name, polyisocyanate compound manufactured by Bayer AG) were added and uniformly mixed and dispersed to form a magnetic paint. .

This paint was applied to a PET base (25 μm thick) with a dry thickness of 10 μm.
The film was coated so as to have a diameter of μ, then oriented in a magnetic field at 10,000 e, dried, and slit. The B-H characteristics of the thus obtained magnetic tape were measured using the same SM- as in Examples 1 and 2, and a single spot was measured in the same manner as for the powder samples of Examples 1 and 2.

The results obtained are shown in Table 3. From the results in Table 3, the modified CrO used as a raw material! It can be seen that there is only a slight change between the powder and the magnetic tape obtained at one point. When compared with 1-D (modified only with Sb), which is also a comparative example, there is no difference in Br/Bm, and it can be said that it is an excellent magnetic tape. The results of Examples 1 to 3 will be discussed together.

One piece of CrO2 modified only with Sb without using CO was prepared in Example 1-D and as known from the literature.
The temperature is 16-120°C.

CrO2 modified with CO and Sb are both lower than these values, with a maximum decrease of about 23°C. CrO2(1-C) modified only with CO without using Sb also slightly lowers the Kiyuri point, but CrO2(1-C) modified with CO and Sb decreases slightly.
-A, l-B) the amount of decrease is greater.

In addition, the one modified only with CO (1-C) has a significantly lower coercive force value and is completely insufficient to be used as a magnetic recording medium. (The material modified with 5Sb shows sufficient characteristics as a magnetic recording material.

It can be seen that when CO is used in combination with Sb, even if its content is minute, it significantly lowers the score.

In particular, CrO containing 0.05 to 5.0 at% of CO,
has a well-balanced coercive force and saturation magnetization, and is extremely suitable for use in magnetic recording media. In addition, the magnetic recording material according to the present invention has characteristics equal to or better than those of a magnetic recording material using ordinary CrO2, and also has a low curvature point, so that when used as a slave tape during thermal transfer, Thermal transfer could be performed at low temperatures.

Therefore, the properties of the support, binders, plasticizers, lubricants, etc. were not impaired, and the signals from the master tape were transferred correctly.

[Brief explanation of the drawing]

The accompanying drawings show the relationship between the amount of CO and magnetic properties in the magnetic material of the present invention.

Claims (1)

[Claims] 1. A magnetic recording body comprising a magnetic layer mainly composed of ferromagnetic fine powder and a binder provided on a support, characterized in that the ferromagnetic fine powder is chromium dioxide modified with Sb and Co. record body.