JPH05298675A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To enhance smoothness and durability by forming a magnetic recording layer contg. ferromagnetic powder dispersed in a binder on a nonmagnetic substrate, regulating the thickness of the recording layer to <=0.7mum and previously treating the solid powder existing in the recording layer with a coupling agent. CONSTITUTION:A magnetic recording layer contg. ferromagnetic powder dispersed in a binder is formed on a nonmagnetic substrate. The thickness of the recording layer is regulated to <=0.7mum. The solid powder existing in the recording layer is previously treated with a coupling agent having an amino group, an epoxy group, a hydroxyl group, a phosphoric acid group or an isocyanato group as a functional group which reacts with an org. matrix. When the coupling agent has an alkoxy group, the number (X) of the carbon atoms of the alkoxy group is allowed to satisfy Y<X<3Y (where Y is given by dividing the ionic radium of the core atom by the distance between carbon atoms). By this structure, satisfactory dispersibility and coatability are ensured and a magnetic recording medium excellent in smoothness and durability is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, particularly a high density magnetic recording medium such as a video tape, a floppy disk, a tape for computer.

[0002]

2. Description of the Related Art Conventionally known magnetic recording materials are well kneaded with an organic binder and a ferromagnetic fine powder, a pigment dispersant, an antistatic surfactant, an antiaging agent, a lubricant, etc., together with an organic solvent. However, it is a magnetic paint, which is applied to a plastic base or an appropriate support and dried. The high-density tapes produced in this way, especially video tapes, floppy disks, and computer tapes, often suffer from deterioration of durability due to peeling of the magnetic surface and dropout, causing serious failure. It was Further, recently, in order to achieve a large capacity and a small size of recording, the density of a magnetic recording medium is being urged, and it is indispensable to reduce the thickness of a magnetic layer by high-density packing, but the surface treatment agent that has been conventionally used. As an amino group-containing silane coupling agent,
Triazine thiol and the like have been used, but the durability was deteriorated and the dropout was increased as the film was made thinner, which was not satisfactory.

In general, a magnetic tape is a long tape having a wide width and a large number of slits are formed at one time by using a rotary blade or the like. However, the magnetic material and the binder and the magnetic layer and the support are bonded to each other. If it is insufficient, it is considered that a crack phenomenon, which is a potential destruction, will occur, and these will gradually increase during running, and will gradually drop off from the ear portion of the magnetic tape, resulting in dropout.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium which is excellent in dispersibility, coatability, smoothness and durability.

[0005]

The above object of the present invention is to provide a magnetic recording medium having a magnetic recording layer formed by dispersing ferromagnetic powder in a binder on a non-magnetic support. 0.
This is achieved by a magnetic recording medium characterized in that a solid powder present in a magnetic recording layer having a thickness of 7 μm or less is treated with a coupling agent.

The coupling agent preferably has an amino group, an epoxy group, a hydroxyl group, a phosphoric acid group or an isocyanate group as a functional group which reacts with the organic matrix,
When the coupling agent contains an alkoxy group, the number of carbon atoms of the alkoxy group is preferably within the following range.

Y <X <3Y where X: carbon number of alkoxy (natural number) Y: (ionic radius of nuclear atom) / (carbon-carbon distance) The present inventors have found that the coupling agent of the present invention is magnetic. By treating the body, it is possible to reduce the thickness of the above-mentioned magnetic recording layer, significantly reducing the defects of conventional high-density magnetic tapes and magnetic disks, and wear resistance and durability of the magnetic layer head and recorder guide. Has been found to significantly improve. As a result, the strength of the thin film is improved, durability performance is improved, dropouts are reduced, the kneading process of high shear by a pressure kneader, etc. can be omitted, and the dispersion time can be shortened and stagnation stability can be improved. It was

Furthermore, it has been found that the magnetic tape treated with the magnetic layer thereby has very little powder falling from the edge of the tape when slit by a constant slitting method.

Further, when the method of the present invention is adopted, the adhesion between the magnetic substance and the binder becomes extremely strong, so that the powder drop-out resulting from the crack of the potential destruction of the magnetic layer can be drastically reduced. It's up to you.

Specific examples of the coupling agent of the present invention are shown below, but the present invention is not limited thereto.

[0011]

[Chemical 1]

[0012]

[Chemical 2]

[0013]

[Chemical 3]

[0014]

[Chemical 4]

[0015]

[Chemical 5]

[0016]

[Chemical 6]

[0017]

[Chemical 7]

It is considered that such a coupling agent of the present invention serves as a bridge between an organic substance and an inorganic substance by a strong chemical bond. The amount of the coupling agent used can be in the range of 0.2% to 5% (weight) with respect to the magnetic substance and the inorganic particles, and is preferably 1% to 3% (weight). The treatment method includes (1) a method in which the coupling agent is diluted with water to form a 0.5 to 1% aqueous solution, which is thoroughly mixed with a magnetic material in a blender and then dried (2) A cup in a suitable organic solvent Method of dissolving ring agent and treating with magnetic material (3) Method of dissolving saturation of water in a suitable organic solvent and dissolving coupling agent therein (4) Directly in magnetic coating solution The method of adding a coupling agent was tried, but it was found that the method of (1) or (2) was the best.

The same can be said for the additive particles in the above method, and it is understood that the effect is most remarkable when treated with the silane coupling agent in the particle state.

Examples of the non-magnetic support 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 plastics such as polyamide and polycarbonate. Can be mentioned.

Further, metals such as Cu, Al and Zn, glass, boron nitride, Si and ceramics such as carbide can be used.

The thickness of these non-magnetic supports is a film,
In the case of a sheet, it is about 3-100 μm, preferably 5-50
μm, about 30 μm to 10 mm in the case of a disc or a card, and cylindrical in the case of a drum, and its shape is determined according to the recorder used. An intermediate layer or an undercoat layer may be provided on the surface of the non-magnetic support to improve the adhesiveness.

In the magnetic recording layer of the magnetic recording medium of the present invention, ferromagnetic barium ferrite (hereinafter abbreviated as Ba-ferrite) is used as the magnetic particles. A preferable Ba-ferrite magnetic powder that can be used in the present invention is that at least a part of Fe in the Ba-ferrite powder is C.
Average particle size substituted by o and Zn (diagonal length of plate surface of hexagonal ferrite) [300-900] Å, plate ratio (diagonal length of plate surface of hexagonal ferrite is calculated as plate thickness The value obtained by dividing by) is 2.0 to 10.0, and the coercive force is 350 to 2000 Oe.

The Ba-ferrite powder has a coercive force controlled to an appropriate value by partially replacing Fe with Co.
Further, by partially substituting with Zn, it is possible to realize a high saturation magnetization which cannot be obtained only by Co substitution, and to obtain a magnetic recording medium having a high reproduction output and excellent electromagnetic conversion characteristics. Further, by substituting a part of Fe with Hb,
It is possible to obtain a magnetic recording medium having a higher reproduction output and excellent electromagnetic conversion characteristics. Further, in the Ba-ferrite of the present invention, a part of Fe may be substituted with a transition metal such as Ti, In, Mn, Cu, Ge and Sn.

In the present invention, the reason why the average particle size of Ba-ferrite, the plate ratio, and the coercive force are preferably in the above preferred ranges is as follows. That is, if the average particle size is less than 300Å, the reproduction output when used as a magnetic recording medium becomes insufficient, and conversely, if it exceeds 900Å, the surface smoothness when used as a magnetic recording medium deteriorates significantly, and the noise level increases. It may become too high, and if the plate ratio is less than 2.0,
When used as a magnetic recording medium, the perpendicular orientation ratio suitable for high-density recording cannot be obtained. Conversely, when the plate ratio exceeds 6.0, the surface smoothness when used as a magnetic recording medium deteriorates significantly, and the noise level becomes high. If the coercive force is less than 350 Oe, it becomes difficult to retain the recording signal, and if it exceeds 2000 Oe, the head limit may be saturated and recording may be difficult. ..

As a method for producing the magnetic powder used in the present invention, for example, oxides and carbonates of each element necessary for forming the desired Ba-ferrite are formed into a glass such as boric acid. It is melted together with the substance, and the obtained melt is rapidly cooled to form glass, and then this glass is heat-treated at a predetermined temperature to precipitate the desired Ba-ferrite crystal powder, and finally the glass component is removed by heat treatment. In addition to the glass crystallization method, the coprecipitation-firing method, the hydrothermal synthesis method, the flux method, the alkoxide method, the plasma jet method and the like can be applied.

In the present invention, any magnetic material known as magnetic particles may be contained in the magnetic layer.

For example, γ-Fe ₂ O ₃ and Co-containing γ-Fe ₂ O ₃
Or Co-coated γ-Fe ₂ O ₃ such as _{Co-γ-Fe 2 O 3} , Fe 3 O 4, Co
Co-γ-Fe ₃ O ₄ , C such as containing Fe ₃ O ₄ or Co deposited Fe ₃ O ₄
Oxide magnetic materials such as rO ₂ and others, such as Fe, Ni, Fe-Ni
Alloy, Fe-Co alloy, Fe-Ni-P alloy, Fe-Ni-Co alloy, Fe-Mn-
Zn alloy, Fe-Ni-Zn alloy, Fe-Co-Ni-Cr alloy, Fe-Co-Ni-P
Examples thereof include metal magnetic powders containing Fe, Ni, and Co as main components, such as alloys, Co-P alloys, and Co-Cr alloys. In addition, these metal magnetic materials may contain an element such as Si, Cu, Zn, Al, P, Mn, or Cr, or a compound thereof as an additive.

As the binder forming the magnetic recording layer of the present invention, a polyurethane resin having abrasion resistance can be used. It has a strong adhesive force to other substances, is mechanically tough against repeated application of force or bending, and has good wear resistance and weather resistance. In addition to the polyurethane resin, a fibrous resin and a vinyl chloride copolymer may be used in combination. However, the layer becomes too hard only with the fibrous resin and the vinyl chloride copolymer, which can be prevented by the presence of the above-mentioned polyurethane resin. Examples of usable fibrin resin include cellulose ether, cellulose inorganic acid ester, and cellulose organic acid ester.

The vinyl chloride resin is preferably a vinyl chloride-vinyl acetate-containing copolymer or a vinyl chloride-vinyl acetate-vinyl alcohol-containing copolymer, a vinyl chloride-vinyl propionate-vinyl alcohol copolymer, Examples thereof include vinyl chloride-vinyl acetate-vinyl maleate-vinyl alcohol copolymers and vinyl chloride-vinyl propionate-vinyl maleate-vinyl alcohol copolymers. The above-mentioned polyurethane and vinyl chloride-based copolymer may be partially hydrolyzed.

As the vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, polyurethane resin and the like, it is particularly preferable to use a resin modified by introducing a functional group, particularly a negative functional group.

Examples of the functional group in the resins include, for example, --SO ₃ M, --OSO ₂ M, --COOM, and --P (═O) (O
M ₁ ) (OM ₂ ), where M is a hydrogen atom, lithium metal or sodium metal, and M ₁ and M ₂
Are each hydrogen atom, lithium metal, potassium metal, sodium metal and alkyl group. Further, M ₁ and M ₂ may be different from each other or may be the same. ) And the like.

These functional groups include resins such as vinyl chloride resins, polyester resins, polyurethane resins and the like, for example, Cl-CH ₂ CH ₂ SO ₃ M, Cl-CH ₂ CH ₂ OSO ₂ M, Cl-CH _{2 COOM, Cl-CH 2 -P (} = O) (OM 1) (OM 2) ( however, M, M ₁ and M ₂ have the same meanings as defined above.) negative functional groups in the molecule, such as And a compound containing chlorine can be obtained by condensation by a dehydrochlorination reaction. Among the resins thus obtained, those obtained by introducing a negative functional group into a vinyl chloride resin or a polyurethane resin are preferable.

In the present invention, from the binder resins described above, conventionally used non-modified vinyl chloride resin, polyurethane resin or polyester resin, and a resin modified with a functional group are mixed. Alternatively, a fibrin resin, a phenoxy resin or the like may be used in combination. Phenoxy resin has high mechanical strength, excellent dimensional stability, good heat resistance, water resistance, and chemical resistance.
It has advantages such as good adhesiveness. These advantages are complementary to the above-mentioned polyurethane resin in length and shortness, and can significantly improve the temporal stability of the physical properties of the magnetic recording medium of the present invention. Furthermore, a thermoplastic resin, a thermosetting resin, a reactive resin, an electron beam irradiation curable resin, or the like having a specific usage system may be used in combination.

The amount (B) of the binder with respect to the ferromagnetic powder in the magnetic recording layer of the present invention is 5 to 30% by weight. In addition,
In order to improve the durability of the magnetic recording layer of the magnetic recording medium of the present invention, the magnetic coating may contain various curing agents and the magnetic recording layer may be formed by the method described below.

Examples of such a curing agent include isocyanates such as aromatic isocyanates and aliphatic isocyanates. Examples of aromatic isocyanates include tolylene diisocyanate (TDI) and adducts with these isocyanate active hydrogen compounds, and those having an average molecular weight in the range of 100 to 3,000 are preferable. Examples of the aliphatic isocyanate include hexamethylene diisocyanate (HMDI) and adducts of these isocyanates with active hydrogen compounds.
Among these aliphatic isocyanates and adducts of these isocyanates and active hydrogen compounds, those having a molecular weight of 100 to 3,000 are preferable. Among the aliphatic isocyanates, non-alicyclic isocyanates and adducts of these compounds and active hydrogen compounds are preferable. The magnetic recording layer may contain a dispersant contained in the magnetic paint used to form the magnetic layer, and if necessary, a lubricant, an abrasive, an antistatic agent, etc. You may include the additive of.

Examples of the dispersant used in the present invention include phosphoric acid esters, amine compounds, alkyl sulfates, fatty acid amides, higher alcohols, polyethylene oxides, sulfosuccinic acid, sulfosuccinic acid esters, known surfactants and the like. The salt of the polymer dispersant having a negative organic group (for example, —COOH) can also be used. Examples of the dispersant include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, fatty acids having 12 to 18 carbon atoms such as oleic acid, and salts of these alkali metals or alkaline earth metals. Are amides; polyalkylene oxide alkyl phosphates; lecithin; trialkyl polyolefinoxy quaternary ammonium acids; azo compounds having a carboxyl group and a sulfonic acid group. These dispersants are added within the range of 0.5 to 5% by weight with respect to the ferromagnetic powder. These dispersants may be used alone or in combination of two or more.

The carbon black used in the magnetic recording layer of the present invention includes, for example, Conductex 975 (specific surface area 250 m ² /
g, particle size 24mμ), Conductex 900 (specific surface area 1
25m ² / g, particle size 27mμ), Conductex 40-220
(Particle size 20mμ), Conductex SC (particle size 20m
μ), Cabot Vulcan XC-
72 (specific surface area 254 m ² / g, particle size 30 mμ), Vulcan P
(Particle size 20 mμ), Raven 1040, 420, Black Pearls L2000 (particle size 16 mμ), conductive carbon black such as Mitsubishi Kasei Co. # 44. This carbon black having an oil absorption of 90 m ² (DBP) / 100 g or more is desirable in that it easily takes a structure structure and exhibits higher conductivity. Carbon blacks other than those mentioned above include, for example, MONARCH 1400 (average particle size; 13.0n;
m, pH; 2.5), MONARCH 1300 (average particle size; 13.0 nm,
pH: 2.5), MONARCH 1000 (average particle size: 16.0nm, p
H; 2.5), MOGUL L (BLACH PEARLS L, average particle size; 2
4.0nm, pH; 3.0), REGAL 400R (REGAL 400, average particle size; 25.0nm, pH; 3.0), etc.
ROYAL SPECTRA manufactured by Carbon Co., Ltd. (average particle size: 10.0 nm, p
H; 4.0), NEO SPEDTRA MARK1. (Average particle size: 11.0 nm,
pH: 4.0), NEO SPECTRA MARK 2. (Average particle size: 13.0n)
m, pH; 3.0), NEO SPECTRA AG (average particle size; 13.0n
m, pH; 3.0), SUPERBA (average particle size; 15.0 nm, p
H; 3.2), NEO SPECTRA MARK 4. (Average particle size: 16.0 nm,
pH: 4.5, RAVEN 5000 (average particle size: 12.0 nm, p
H; 2.8), RAVEN 7000 (average particle size; 15.0 nm, pH; 2.
1), RAVEN 5750 (Average particle size; 15.0 nm, pH; 2.1), R
AVEN 5250 (Average particle size: 20.0 nm, pH: 2.2), RAVEN 3
500 (Average particle size: 16.0 nm, pH: 2.5), RAVEN 1255
(Average particle size; 23.0nm, pH; 2.5), RAVEN 1040 (Average particle size; 28.0nm, pH; 2.8), RAVEN 1035 (Average particle size; 27.0nm, pH; 3.5), RAVEN 14 powder (Average particle size 59.0 nm, pH; 3.0) and the like.

The carbon blacks shown below can also be used in the present invention.

[0040] BLACK PEARLS 280 manufactured by Cabot Corporation of the United States
(Average particle size: 41 nm), BLACK PEARLS 170 (Average particle size: 50
nm), BLACK PEARLS160 (average particle size: 50 nm), BLACK
PEARLS 130 (average particle size; 75 nm), BLACK PEARLS 120 (average particle size; 75 nm), etc. made by Colombian Carbon
RAVEN 500 (Average particle size: 52.9 nm), RAVEN 450 (Average particle size: 75.4 nm), RAVEN 430 (Average particle size: 82.1 nm), RAVE
N 420 (Average particle size; 85.7 nm), RAVEN 410 (Average particle size;
100.6 nm), RAVEN T230 (average particle size; 56.2 nm), RAVEN H
20 Powder (Average particle size; 59.9 nm), RAVEN 22 Powder
(Average particle size; 82.6nm), RAVEN 16 powder (Average particle size;
67.8nm), RAVEN 14 powder (average particle size: 54.6n
m ,,), RAVEN MT-P (average particle size; 280.0 nm), # 22B (average particle size; 40.0 nm) manufactured by Mitsubishi Kasei Co., Ltd., CF
-9 (Average particle size: 40.0 nm), # 3500 (Average particle size: 40.0 nm)
Etc. Denka HS-100 (average particle size: 53.0 nm), etc., Asahi Carbon Co., Ltd. HS-500 (average particle size: 76.0 nm), etc.

In the magnetic layer, as a lubricant, silicone oil, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, monobasic fatty acid having 12 to 16 carbon atoms (eg myristic acid, stearin). Acid), and fatty acid ester (for example, butyl stearate oleyl oleate) composed of a monohydric alcohol having 3 to 26 carbon atoms can be used. These lubricants are 0.2 for 100 parts by weight of binder.
Added in the range of up to 20 parts by weight.

Non-magnetic abrasive particles may also be added.
As the abrasive, commonly used materials such as fused alumina, silicon carbide, chromium oxide, corundum, artificial corundum, artificial diamond, garnet, and emery (main components: corundum and magnetite) are used. As these abrasives, those having an average particle diameter of 0.05 to 5 μm are used.
It is particularly preferably 0.1 to 2 μm. These abrasives are added in the range of 1 to 20 parts by weight with respect to 100 parts by weight of the binder. Therefore, the magnetic layer has improved packing density and dispersibility of the ferromagnetic magnetic powder such as Ba-ferrite. The important point in the present invention is that the dry film thickness of the magnetic layer is 0.1 to 4.0 μm.
m, preferably 0.1 to 2.0 μm. If the film thickness of the magnetic layer exceeds 4.0 μm, the surface resistivity of the magnetic layer becomes high and the dropout of the magnetic recording medium increases. On the other hand, when the film thickness of the magnetic layer is thinner than 0.1 μm, the surface of the magnetic layer is roughened and the Lumi S of the magnetic recording medium is
/ N and chroma S / N are reduced.

The magnetic powders to which the present invention is applied include not only those explained in the examples described later, but also those of general ferromagnetic powder such as iron-cobalt-nickel. Further, as the other solid additive particles, inorganic particles such as carbon black, graphite, molybdenum disulfide, tungsten disulfide, clay, silica, carbonate, alumina powder, polishing material, and metal oxide are particularly effective and fluororesin. Fine powder Even if organic particles such as polyolefin resin fine powder and polyamide resin fine powder are contained, there is no special effect. In particular, the effect of these solid additive particles is added as an antistatic agent, a lubricant, a surface matting agent, and a tape durability improver, and is often used in general tape manufacturing methods.

[0044]

The present invention will be described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

Examples 1, 2, 3 and Comparative Examples 1, 4 are Co-γ
Iron oxide magnetic powder Examples 4 and 5 and comparative examples 2 and 5 are barium ferrite magnetic powders Examples 6 and 7 and comparative examples 3 and 6 are metallic iron magnetic powders Cobalt iron oxide magnetic powders Hc 730 Oe and BET 25m ² / g Barium ferrite magnetic powder Hc 750 Oe, BET 35 m ² / g Metal iron magnetic powder Hc 1600 Oe, BET 45 m ² / g In the examples, "part" means "part by weight".

Example 1 As the method for treating solid powder, solid powder well treated by the method according to (1) or (2) above was applied as a paint with the following composition, and this was applied to evaluate as a magnetic disk sample.

Magnetic powder 100 parts Alumina powder (HIT50) (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Carbon black (Vulcan XC-72 manufactured by Cabot Corporation, USA) 10 parts Coupling agent (exemplified compound 55) 2 parts Polyurethane (N2304) 6 parts Vinyl chloride / vinyl acetate copolymer (VAGH) 8 parts Cyclohexanone 100 parts Methyl ethyl ketone 100 parts Toluene 100 parts Example 2 A sample was prepared in the same manner as in Example 1 except that only the magnetic powder was surface-treated.

Example 3 A sample was prepared in the same manner as in Example 1 except that the alumina powder and carbon black were surface-treated.

Comparative Example 1 A sample was prepared in the same manner as in Example 1 (with the coupling agent removed) except that no surface treatment was performed.

Comparative Example 4 Phosphate ester (Toho Kagaku Kogyo Phosphanol R) was used as a dispersant instead of the coupling agent without surface treatment.
A sample was prepared in the same manner as in Example 1 except that E610) was used.

Example 4 A sample was prepared in the same manner as in Example 1 except that barium ferrite was used as the magnetic powder.

Example 5 A sample was prepared in the same manner as in Example 2 except that barium ferrite was used as the magnetic powder.

Comparative Example 2 A sample was prepared in the same manner as in Comparative Example 1 except that barium ferrite was used as the magnetic powder.

Comparative Example 5 A sample was prepared in the same manner as Comparative Example 4 except that barium ferrite was used as the magnetic powder.

Example 6 A sample was prepared in the same manner as in Example 1 except that metallic iron was used as the magnetic powder.

Example 7 A sample was prepared in the same manner as in Example 2 except that metallic iron was used as the magnetic powder.

Comparative Example 3 A sample was prepared in the same manner as in Comparative Example 1 except that the magnetic powder was changed to metallic iron.

Comparative Example 6 A sample was prepared in the same manner as in Comparative Example 4 except that the magnetic powder was metallic iron.

The film thickness of the magnetic layer is from Example 1 to Example 7.
Application was performed at 0.5 μm.

Comparative Examples 1 to 6 show the film thickness of the magnetic layer.
Application was performed at 0.5 μm.

Example 8 A sample was prepared in the same manner as in Example 1 except that the film thickness of the magnetic layer was 0.1 μm.

Example 9 A sample was prepared in the same manner as in Example 1 except that the thickness of the magnetic layer was 0.2 μm.

Example 10 A sample was prepared in the same manner as in Example 1 except that the thickness of the magnetic layer was 0.7 μm.

Comparative Example 7 A sample was prepared in the same manner as in Example 1 except that the thickness of the magnetic layer was 0.8 μm.

Comparative Example 8 A sample was prepared in the same manner as in Example 1 except that the thickness of the magnetic layer was 1.0 μm.

Comparative Example 9 A sample was prepared in the same manner as in Example 1 except that the thickness of the magnetic layer was 2.0 μm.

Comparative Example 10 A sample was prepared in the same manner as in Comparative Example 1 except that the thickness of the magnetic layer was 0.8 μm.

Comparative Example 11 A sample was prepared in the same manner as in Comparative Example 4 except that the thickness of the magnetic layer was 0.8 μm.

Comparative Example 12 A sample was prepared in the same manner as Comparative Example 1 except that the thickness of the magnetic layer was 1.0 μm.

Comparative Example 13 A sample was prepared in the same manner as Comparative Example 4 except that the thickness of the magnetic layer was 1.0 μm.

Comparative Example 14 A sample was prepared in the same manner as in Comparative Example 1 except that the thickness of the magnetic layer was 2.0 μm.

Comparative Example 15 A sample was prepared in the same manner as Comparative Example 4 except that the thickness of the magnetic layer was 2.0 μm.

Comparative Example 16 A sample was prepared in the same manner as in Example 1 except that a silane coupling agent (alkoxy group having 1 carbon atom) was used as the coupling agent.

Example 11 A sample was prepared in the same manner as in Comparative Example 16 except that the exemplified compound 57) was used.

Example 12 A sample was prepared in the same manner as in Comparative Example 16 except that the exemplified compound 58) was used.

Comparative Example 17 A sample was prepared in the same manner as in Comparative Example 16 except that the alkoxy group had 5 carbon atoms.

Comparative Example 18 A sample was prepared in the same manner as in Example 1 except that a titanate coupling agent (having 2 carbon atoms in the alkoxy group) was used as the coupling agent.

Example 13 A sample was prepared in the same manner as in Comparative Example 18 except that the exemplified compound 59) was used.

Example 14 A sample was prepared in the same manner as in Comparative Example 18 except that the exemplified compound 60) was used.

Example 15 A sample was prepared in the same manner as in Comparative Example 18 except that the exemplified compound 61) was used.

Comparative Example 19 A sample was prepared in the same manner as in Comparative Example 18 except that the alkoxy group had 9 carbon atoms.

Comparative Example 20 A sample was prepared in the same manner as in Example 1 except that a chromium-based coupling agent (alkoxy group having 4 carbon atoms) was used as the coupling agent.

Example 16 A sample was prepared in the same manner as in Comparative Example 20 except that the exemplified compound 62) was used.

Example 17 A sample was prepared in the same manner as in Comparative Example 20 except that the exemplified compound 63) was used.

Example 18 A sample was prepared in the same manner as in Comparative Example 20 except that the exemplified compound 64) was used.

Comparative Example 21 A sample was prepared in the same manner as Comparative Example 20 except that the alkoxy group had 15 carbon atoms.

Comparative Example 22 A sample was prepared in the same manner as in Example 1 except that a zirconia-based coupling agent (alkoxy group having 5 carbon atoms) was used as the coupling agent.

Example 19 A sample was prepared in the same manner as in Comparative Example 22 except that the exemplified compound 65) was used.

Example 20 A sample was prepared in the same manner as in Comparative Example 22 except that the exemplified compound 66) was used.

Example 21 A sample was prepared in the same manner as in Comparative Example 22 except that the exemplified compound 67) was used.

Comparative Example 23 A sample was prepared in the same manner as in Comparative Example 22 except that the alkoxy group had 17 carbon atoms.

Example 22 A sample was prepared in the same manner as in Example 1 except that the exemplified compound 1) was used.

Example 23 A sample was prepared in the same manner as in Example 4 except that the exemplified compound 1) was used.

Example 24 A sample was prepared in the same manner as in Example 6 except that the exemplified compound 1) was used.

Example 25 A sample was prepared in the same manner as in Example 1 except that the exemplified compound 10 ') was used.

Example 26 A sample was prepared in the same manner as in Example 4 except that the exemplified compound 10 ') was used.

Example 27 A sample was prepared in the same manner as in Example 6 except that the exemplified compound 10 ') was used.

Example 28 A sample was prepared in the same manner as in Example 1 except that the exemplified compound 11) was used.

Example 29 A sample was prepared in the same manner as in Example 4 except that the exemplified compound 11) was used.

Example 30 A sample was prepared in the same manner as in Example 6 except that the exemplified compound 11) was used.

Example 31 A sample was prepared in the same manner as in Example 1 except that the exemplified compound 21) was used.

Example 32 A sample was prepared in the same manner as in Example 4 except that the exemplified compound 21) was used.

Example 33 A sample was prepared in the same manner as in Example 6 except that the exemplified compound 21) was used.

Example 34 A sample was prepared in the same manner as in Example 1 except that the exemplified compound 16) was used.

Example 35 A sample was prepared in the same manner as in Example 4 except that the exemplified compound 16) was used.

Example 36 A sample was prepared in the same manner as in Example 6 except that the exemplified compound 16) was used.

The structural formulas of the coupling agents used in Comparative Examples are shown below.

Comparative Example 16: CH ₂ ═C (CH ₃ ) COOC ₃ H ₆ Si (OCH ₃ ) ₃ Comparative Example 17: CH ₂ ═C (CH ₃ ) COOC ₃ H ₆ Si (OC ₅ H ₁₁ ) ₃ Comparison Example 18: (C ₂ H ₅ O) ₂ Ti (OCOC ₁₇ H ₃₅ ) ₂ Comparative Example 19: (C ₉ H ₁₉ O) ₂ Ti (OCOC ₁₇ H ₃₅ ) ₂ Comparative Example 20: (C ₄ H ₉ O) ₂ Cr (OCOC ₂₅ H ₅₁ ) ₂ Comparative Example 21: (C ₁₅ H ₃₁ O) ₂ Cr (OCOC ₂₅ H ₅₁ ) ₂ Comparative Example 22: (C ₅ H ₁₀ ) ₂ Zr (OCOC ₂₅ H ₅₁ ) ₂ Comparative Example 23: (C ₁₇ H ₃₅ O) ₂ Zr (OCOC ₂₅ H ₅₁ ) ₂ The samples prepared above were evaluated by the following evaluation methods.

(Evaluation Method) (1) Dispersibility Evaluation was carried out by measuring the gloss level with a VG-ID type gloss meter / digital gonio gloss meter manufactured by Nippon Denshoku Industries Co., Ltd.

(2) Smoothness The surface roughness Ra is shown.

Stylus type surface roughness meter [SE, manufactured by Kosaka Laboratory Ltd., SE
3FK type].

(3) Coating Property The coating film surface during and after coating was visually observed and evaluated.

⊚: Very good Δ: Poor ○: Good ×: Very bad (4) Durability The magnetic head was loaded in a recording / reproducing apparatus and a magnetic head manufactured by Toshiba Corp. 4M was used.
Drive B-PD-211, sliding at a pressure of 20 g / cm ² , and rotating at a disk rotation speed of 300 rpm, the temperature and humidity were changed with the running time until the playback output reached 70% of the initial output as the durability time. Evaluated.

The results are shown in Tables 1, 2, 3, 4, 5, 6, 7 below.
Shown in.

[0115]

[Table 1]

[0116]

[Table 2]

[0117]

[Table 3]

[0118]

[Table 4]

[0119]

[Table 5]

[0120]

[Table 6]

[0121]

[Table 7]

As can be seen from the above results, the examples of the present invention are superior to the comparative examples.

[0123]

The magnetic recording medium according to the present invention has excellent dispersibility, smoothness, and durability.

Claims (3)

[Claims] 1. A magnetic recording medium having a magnetic recording layer in which ferromagnetic fine powder is dispersed in a binder on a non-magnetic support, wherein the magnetic recording layer has a thickness of 0.7 μm or less. A magnetic recording medium characterized in that the solid powder present in the magnetic recording layer is treated with a coupling agent. 2. The magnetic recording medium according to claim 1, which is treated with a coupling agent having an amino group, an epoxy group, a hydroxyl group, a phosphoric acid group, or an isocyanate as a functional group that reacts with the organic matrix. 3. A magnetic recording medium characterized in that the alkoxy group which reacts with the surface of the magnetic powder is treated with a coupling agent whose carbon number of the alkoxy group is within the range of the value shown by the following formula. However, X: carbon number of alkoxy (natural number) Y <X <3Y, where Y: ionic radius of nuclear atom / carbon-
Distance between carbons