JPH1166537A - Magnetic recording media - Google Patents

Abstract

(57) Abstract: A coating film comprising a non-magnetic layer and a magnetic layer is formed with high-precision surface smoothness and has a reduced electric resistance, so that spacing loss and Improvement of electromagnetic conversion characteristics and dropout characteristics by reducing output loss. SOLUTION: A non-magnetic pigment of a non-magnetic paint for forming a non-magnetic layer 3 is made of a needle-like non-magnetic fine powder obtained by applying a non-magnetic conductive material and conducting a conductive treatment. The non-magnetic fine powder is subjected to a surface treatment for applying an aluminum compound to a non-magnetic conductive material to impart an affinity to a binder. The non-magnetic fine powder is subjected to an organic substance treatment for imparting lipophilicity to an organic solvent by adsorbing a polyhydric alcohol to a non-magnetic conductive material. On the non-magnetic support 2, the above-mentioned non-magnetic paint and magnetic paint are simultaneously applied in multiple layers to form a coating film having a high-precision surface smoothness composed of the non-magnetic layer 3 and the magnetic layer 4.

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 such as a magnetic tape or a floppy disk, and more particularly, to a method for forming a nonmagnetic layer by applying a nonmagnetic paint on a nonmagnetic support. The present invention relates to a magnetic recording medium having a magnetic layer formed by applying a magnetic paint thereon.

[0002]

2. Description of the Related Art In recent years, due to a strong demand for high-density recording, magnetic recording media have been widely used for audio and video applications, floppy disk drives for computer peripheral devices, backup devices, and the like. Improvements have been made in the characteristics, such as the correspondence to the density recording and the improvement in the recording / reproducing characteristics. In magnetic recording media, to achieve high-density recording, for example, the surface is smoothed with high precision to minimize spacing loss, and at the same time, the output due to recording demagnetization is reduced by thinning the magnetic layer. Investigations have been made to control the loss.

[0003] A magnetic recording medium has a magnetic layer formed on a surface of a non-magnetic support made of, for example, polyethylene terephthalate (PET) in the form of a film by applying a magnetic paint or depositing a magnetic powder. In the coating type magnetic recording medium, the so-called simultaneous multi-layer coating method in which a non-magnetic layer and a magnetic layer are simultaneously formed on the surface of a non-magnetic support carrier in the same process is adopted to cope with the above-described high density. Is planned. A magnetic recording medium manufactured by the simultaneous multi-layer coating method has a feature that a thin film magnetic layer having good surface characteristics is formed on a magnetic recording medium manufactured by a single layer coating method.

[0004] In the following description, the term "magnetic recording medium" refers to a simultaneous multilayer coating type magnetic recording medium unless otherwise specified.

[0005]

Incidentally, in such a magnetic recording medium, a post-processing step after the magnetic layer forming step,
That is, a calendering step, a back coat layer forming step, a cutting step, or the like is performed. If the formed coating film has a large electric resistance, various problems occur due to electrostatic charging. That is, the magnetic recording medium has a problem in that, for example, the magnetic recording medium is stuck to a travel guide or the like due to electrostatic charging, causing a traveling failure phenomenon, or the electromagnetic conversion characteristics such as a dropout characteristic being deteriorated due to the attachment of dust and the like. Was. For this reason, in the magnetic recording medium, in order to reduce the electric resistance of the coating film, for example, measures such as using a conductive pigment or adding carbon black to the non-magnetic paint for forming the non-magnetic layer have been taken.

[0006] Further, the surface characteristics of a magnetic recording medium greatly depend on the characteristics of the non-magnetic paint forming the non-magnetic layer and the magnetic paint forming the magnetic layer. In the magnetic recording medium, when the characteristics of the magnetic paint and the non-magnetic paint are largely different, phenomena such as coating streaks, color unevenness, and thickness unevenness are likely to occur. Such a phenomenon causes not only poor appearance of the magnetic recording medium, but also variations in the electromagnetic conversion characteristics of the magnetic recording medium and noise due to irregularities in the interface between the magnetic layer and the nonmagnetic layer.

That is, when carbon black is added to a magnetic recording medium in order to reduce electric resistance, the carbon black has a high liquid absorbing property and a poor dispersibility, so that it has a high precision surface smoothness. Is difficult to obtain. The conductive pigment is generally tin (Sn) doped with antimony (Sb).
Alternatively, titanium oxide (TiO ₂ ) particles coated with a tin compound (SnO ₂ ) are used. Titanium oxide particles subjected to such a conductive surface treatment have a problem that it is difficult to produce a magnetic recording medium having high-precision surface smoothness due to extremely large hydrophilicity and poor dispersibility in an organic solvent. There is. Furthermore, since the spherical titanium oxide particles subjected to the conductive surface treatment greatly differ from the acicular magnetic powder of the magnetic paint and the paint properties, the so-called compatibility deteriorates and good coatability cannot be obtained. There was a problem.

Accordingly, the present invention solves the above-mentioned problems of the conventional magnetic recording medium, and has excellent electromagnetic conversion characteristics because the electric resistance is small and the coating film is formed while maintaining high precision smoothness. It has been proposed for the purpose of providing a magnetic recording medium having dropout characteristics and suitable for high-density recording of information signals and the like.

[0009]

A magnetic recording medium according to the present invention that achieves the above object is characterized in that a nonmagnetic paint obtained by dispersing at least a nonmagnetic pigment and a binder in a solvent is coated on a nonmagnetic support. Then, a non-magnetic layer is formed, and a magnetic paint formed by dispersing at least a magnetic fine powder and a binder in a solvent is applied on the non-magnetic layer to form a magnetic layer. The nonmagnetic pigment is subjected to a conductive treatment by applying a nonmagnetic conductive material made of tin or a tin compound doped with antimony to the surface thereof, and the aluminum compound is applied to the nonmagnetic conductive material. Needle-like nonmagnetic fine powder, for example, titanium oxide fine powder, which has been subjected to a surface treatment for imparting affinity to a binder, is used. The non-magnetic pigment is subjected to a conductive treatment by applying a non-magnetic conductive material made of tin or a tin compound doped with antimony to the surface thereof, and a polyhydric alcohol is adsorbed on the non-magnetic conductive material. Needle-like non-magnetic fine powder, for example, titanium oxide fine powder, which has been subjected to an organic substance treatment for imparting lipophilicity is used.

According to the magnetic recording medium of the present invention configured as described above, needle-like non-magnetic fine powder such as titanium oxide is used for the non-magnetic pigment of the non-magnetic paint, so that Since the coating properties of the acicular magnetic powder and the coating properties thereof are the same, the two coatings are in a mutually compatible state, and the applicability is improved. In addition, since the magnetic recording medium is subjected to a tin-antimony conductive treatment on the surface of the non-magnetic fine powder, the electric resistance is reduced, so that a running failure phenomenon due to electrostatic charging and adhesion of dust and the like are suppressed. As a result, electromagnetic conversion characteristics such as dropout characteristics are improved.

Further, in the magnetic recording medium, an aluminum compound is applied to a non-magnetic fine powder which has been subjected to a conductive treatment to impart an affinity to a binder and the dispersed state of the non-magnetic fine powder in the non-magnetic paint Is stable, a non-magnetic layer whose surface is smoothed with high precision is formed, and a magnetic layer with high smoothness is formed on this non-magnetic layer. In addition, since the magnetic recording medium is imparted with lipophilicity by adsorbing polyhydric alcohol to the non-magnetic fine powder subjected to the conductive treatment,
The dispersibility of the non-magnetic fine powder in the non-magnetic paint is improved to form a non-magnetic layer whose surface has been smoothed with high precision, and the magnetic layer which has been smoothed with high precision is formed on this non-magnetic layer. It is formed.

Therefore, according to the present invention, by forming a magnetic layer having a highly accurate surface smoothness on the non-magnetic layer, spacing loss and output loss are reduced, and electromagnetic conversion characteristics and dropout characteristics are improved. An excellent high-precision magnetic recording medium can be obtained.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. The magnetic recording medium 1 shown in FIG. 1 is a magnetic tape used for a video tape recorder or the like, and a non-magnetic paint, which will be described in detail later, is applied as a first layer on a main surface of a non-magnetic support carrier 2. Layer 3
Is formed, and a magnetic paint, which will be described in detail later, is applied as a second layer on the nonmagnetic layer 3 to form the magnetic layer 4. The non-magnetic layer 3 and the magnetic layer 4 can be separated from the non-magnetic paint and the magnetic paint in the same process without passing through the coating process of the non-magnetic paint, the drying process of the non-magnetic paint, the coating process of the magnetic paint, and the drying process of the magnetic paint. The paint is applied. Of course, the magnetic tape 1 may be one in which a plurality of coating layers such as an undercoat layer and a plurality of magnetic layers having different compositions are formed on the main surface of the nonmagnetic support 2. A magnetic layer is formed as an upper layer.

The magnetic tape 1 is limited by the specification conditions of the main unit such as a video tape recorder, etc., but usually, the thickness of the coating film is formed to be about 1 μm to 5 μm as a whole, and the magnetic layer 4 and the non-magnetic The thickness ratio with the layer 3 is 1: 3
To 1:30. The coating film is
If the film thickness is too thin, there arises a problem that unevenness of the nonmagnetic support carrier appears on the surface, and if it is too thick, there arises a problem that the strength is impaired. Although not shown, a back coat layer may be formed on one main surface (back surface) of the non-magnetic support 2 on the magnetic tape 1 for the purpose of improving running characteristics and preventing interlayer adhesion. In addition, the magnetic tape 1 may be a so-called double-sided recording type magnetic tape in which the nonmagnetic layer 3 and the magnetic layer 4 described above are formed on one main surface of the nonmagnetic support 2.

The non-magnetic support 2 includes not only polyethylene terephthalate (PET) but also polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose triacetate, cellulose diacetate and the like. Cellulose derivatives are also used. The non-magnetic support 2 is made of synthetic resin such as vinyl resin, polyimides, and polycarbonates, metal, glass,
Ceramics or the like or a material obtained by depositing aluminum or the like on these may also be used. Further, as the non-magnetic support carrier 2, not only a film material but also a sheet material or a tape material is used.

As the magnetic coating material for forming the magnetic layer 4, a coating material in which a cross-linking agent, non-magnetic reinforcing particles, a surfactant and the like are dispersed in an organic solvent together with a ferromagnetic fine powder and a binder is used. As the magnetic powder, ferromagnetic metal fine powder or ferromagnetic iron oxide fine powder is used. Examples of the ferromagnetic metal fine powder include metal powders such as Fe, Co, and Ni, and Fe-C
o, Fe-Ni, Fe-Al, Fe-Ni-Al, Fe
-Al-P, Fe-Ni-Si-Al, Fe-Ni-S
i-Al-Mn, Fe-Mn-Zn, Fe-Ni-Z
n, Co-Ni, Co-P, Fe-Co-Ni, Fe-
Co-Ni-Cr, Fe-Co-Ni-P, Fe-Co
-B, Fe-Co-Cr-B, Mn-Bi, Mn-A
1, alloy fine powder such as Fe-Co-V, iron nitride fine powder, iron carbide fine powder, and the like. For the purpose of preventing sintering or maintaining shape during reduction, Al, Si,
An appropriate amount of light metal elements such as P and B may be added.

As the ferromagnetic iron oxide fine powder, γ-
Fe ₂ O ₃ , Fe ₃ O ₄ , γ-Fe ₂ O ₃ and Fe ₃ O ₄
, A Co-containing γ-Fe ₂ O ₃ , C
o-containing Fe ₃ O ₄ , Co-containing γ-Fe ₂ O ₃ and F
e ₃ berthollide compound with O _4, 1 or more metal elements CrO _2m (e.g. Te, Sb, Fe, Bi
And the like, or a hexagonal plate-like ferrite or the like. Further, the oxide magnetic powder contains M
Type, W type, Y type, Z type barium ferrite, strontium ferrite, calcium ferrite, lead ferrite, and Co-Ti, C
o-Ti-Zn, Co-Ti-Nb, Co-Ti-Zn
What added -Nb, Cu-Zr, Ni-Ti, etc. is also used.

The ferromagnetic fine powder may be used alone or in combination of two or more of the above. Further, these ferromagnetic fine powders have a specific surface area of 20.
m ² / g to 90 m ² / g, preferably 25 m ² / g to 70 m ² / g. Ferromagnetic fine powder
By using a specific surface area within this range,
It is possible to obtain a magnetic recording medium having excellent noise characteristics by enabling high-density recording by fine particles.

The ferromagnetic fine powder has a major axis diameter of 0.05.
μm to 2.0 μm, the ratio of the major axis diameter to the minor axis diameter being 3: 1 to 30: 1, preferably 4: 1 or more is used. In the ferromagnetic fine powder, the metal powder is 75% by weight or more, and 80% by weight or more of the metal component is constituted as a ferromagnetic metal.

As the binder, a thermoplastic resin or a thermosetting resin is used. As a thermoplastic resin, the softening point temperature is 1
50 ° or less, average molecular weight of 10,000 to 20,000,
Those having a degree of polymerization of about 150 to 2,000 are used. The thermoplastic resin is specifically, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinylidene chloride copolymer,
Vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate -Vinylidene chloride copolymer, methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, acrylonitrile -Butadiene copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrose) Loin), styrene-butadiene copolymer, polyester resin, amino resin, synthetic rubber or the like is used.

As the thermosetting resin, specifically, phenol resin, epoxy resin, polyurethane resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, urea formaldehyde resin and the like are used.

Further, as the binder, the above-mentioned synthetic resin having a polar group is used. As the polar group, [-SO
_{3 M], [- OSO 3} M], [- COOM], [- (O
=) P (OM ¹ ) (OM ² )]. In addition,
M, M ¹ and M ^{2 each} represent a hydrogen atom or lithium,
It is an alkali metal such as potassium and sodium. Also,
M ¹ and M ² may be the same or different. The polar groups include [-NR ¹ R ² ] and [-N
A side chain type having a terminal group of R ¹ R ² R ³ + X-] or a main chain type polar group of [> NR ¹ R ² + X-] can also be used. R ¹ , R ² and R ³ are each a hydrogen atom or a hydrocarbon group, and [X−] is a halogen element ion such as fluorine, chlorine, bromine and iodine, or an inorganic / organic ion. Further, as the polar group, -O
H, -SH, -CN, an epoxy group and the like can also be used.

The introduction amount of these polar groups is 10 ^-1 mol / g.
To 10 ^-8 mol / g, more preferably 10 ^-2 mol / g to 10 ^-6 mol / g. Since the binder has the above-mentioned polar group, the binder has an excellent adsorbability to the magnetic fine powder, and has an effect of suppressing aggregation of the magnetic fine powder and improving dispersibility in the coating material.

The binder is used in an amount of 1 to 200 parts by weight, preferably 1 to 50 parts by weight, based on 100 parts by weight of the magnetic fine powder. When the amount of the binder used is too large, the ratio of the magnetic fine powder in the magnetic layer becomes relatively low, resulting in a decrease in output, and when the amount used is too small, the mechanical strength of the magnetic layer decreases. As a result, the running durability of the magnetic medium is reduced. As the binder, the above-mentioned binders may be used alone or in a combination of two or more.

As the crosslinking agent, for example, polyisocyanates such as toluene diisocyanate, their adducts or alkylene diisocyanates, and their adducts are used. The amount of the polyisocyanate to be added to the binder is 5 to 80 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the binder. Further, the cross-linking agent may be used in a non-magnetic paint for forming a non-magnetic layer 3 described later.

As the lubricant, graphite, molybdenum disulfide, tungsten disulfide, silicone oil, fatty acid having 10 to 22 carbon atoms or fatty acid ester comprising alcohol having 2 to 26 carbon atoms, terpene compound , These oligomers and the like are used. The lubricant is added not only to the magnetic paint forming the magnetic layer 4 but also to the non-magnetic paint forming the non-magnetic layer 3 as necessary.

Non-magnetic reinforcing particles include aluminum oxide (α, β, γ), chromium oxide, silicon carbide, diamond, garnet, emery, boron nitride, titanium carbide, titanium carbide, titanium oxide (rutile, anatase)
Are used. The amount of the nonmagnetic reinforcing particles used is 20 parts by weight, preferably 10 parts by weight or less based on 100 parts by weight of the magnetic powder. The non-magnetic reinforcing particles have a Mohs hardness of 4 or more, preferably 5 or more, a specific gravity of 2 to 6, preferably 3 to 5, and an average particle size of 1 to 5.
Those having a size of 0 μm or less, preferably 0.5 μm or less are used.

As the surfactant, amphoteric surfactants such as nonionic, anionic and cationic surfactants are used. These surfactants are used not only in the magnetic paint for forming the magnetic layer 4 but also in the non-magnetic paint for forming the non-magnetic layer 3 according to the type and the amount of the surfactant.

Examples of the organic solvent include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, alcohol solvents such as methanol, ethanol and propanol, methyl acetate, ethyl acetate, butyl acetate, propyl acetate and the like. Ethyl lactate, glycol acetate monoethyl ether, ester solvents such as ethylene glycol acetate, ethyl ether, glycol dimethyl ether, glycol monoethyl ether,
Ether solvents such as 2-ethoxyethanol, tetrahydrofuran and dioxane; aromatic hydrocarbon solvents such as benzene, toluene and xylene; and chlorinated hydrocarbon solvents such as methylene chloride, carbon tetrachloride, chloroform and chlorobenzene. used.

The above-mentioned magnetic coating material is formed by dispersing and kneading the above-mentioned materials by, for example, a roll mill, a ball mill, a sand mill, an agitator, a kneader, an extruder, a homogenizer, an ultrasonic disperser or the like.
Of course, these devices are also used when dispersing and kneading each material of a non-magnetic paint described later to form a paint.

As the magnetic coating material for forming the nonmagnetic layer 4, a coating material in which a crosslinking agent, a lubricant, a surfactant and the like are dispersed in an organic solvent together with a nonmagnetic pigment and a binder is used. As the non-magnetic pigment, a fine powder made of rutile-type titanium oxide (TiO ₂ ) having acicularity equivalent to the above-mentioned ferromagnetic fine powder is used. The surface of the non-magnetic pigment is subjected to a conductive treatment as described later and an aluminum compound is adhered thereto. The non-magnetic pigment includes, in addition to titanium oxide, non-magnetic iron oxide having needle-like properties such as α-Fe ₂ O ₃ , goethite, anatase type titanium oxide, tin oxide, tungsten oxide, silicon oxide, oxide Fine powders such as zinc, chromium oxide, cerium oxide, titanium carbide, BN, α-alumina, β-alumina, γ-alumina, calcium sulfate, barium carbonate, strontium carbonate, and barium titanate are used alone or in combination. Can be

The rutile type titanium oxide has a major axis diameter of 0.05.
μm to 0.3 μm, the ratio of the major axis diameter to the minor axis diameter is 3: 1 or more, and the BET specific surface area is 20 m ² / g to 60 m.
² / g of fine powder is used. Rutile type titanium oxide is
By using the fine powder in this range, the dispersibility at the time of coating is maintained, and the nonmagnetic layer 3 which is smoothed with high precision is formed, thereby forming the smoothed magnetic layer 4. To do. Therefore, the magnetic recording medium 1
A coating layer smoothed with high precision is formed, so that modulation noise characteristics are excellent and the effect of spacing loss is reduced. When the BET specific surface area is larger than the above range, the dispersibility in the coating material is deteriorated, and when the BET specific surface area is smaller, the rutile type titanium oxide has sufficient surface smoothness to withstand high density recording. It becomes difficult.

Titanium oxide can be prepared by neutralizing and hydrolyzing titanium tetrachloride, neutralizing sodium titanate or hydrolyzing titanium alkoxide. It is produced by an oxidizing method or the like. In addition, as a method of producing the acicular titanium oxide of the fine particles, a neutralization hydrolysis method of titanium tetrachloride is preferable.

The rutile-type titanium oxide is subjected to a conductive treatment for providing conductivity by applying a non-magnetic conductive material to the surface thereof, and a surface treatment for applying an aluminum compound. As the non-magnetic conductive material, for example, tin (Sn) or tin oxide (SnO ₂ ) doped with antimony (Sb) is used. The conductive treatment method of applying the non-magnetic conductive material involves co-precipitating by adjusting the pH in a state in which an aqueous solution in which a tin compound is dissolved is added to a suspension of fine titanium oxide powder and uniformly dissolved. To deposit tin on the surface of the titanium oxide fine powder.
Furthermore, the titanium oxide fine powder on which the tin is adhered is coprecipitated by adjusting the pH in a state where an aqueous solution in which an antimony compound is dissolved is added to the suspension and the solution is uniformly dissolved. A trace amount of antimony is deposited.

The rutile-type titanium oxide fine powder is fired to produce Sb-doped Sn-coated rutile-type titanium oxide having a surface coated with a tin oxide layer doped with antimony. Sb-doped Sn-deposited rutile-type titanium oxide is provided with good conductivity by containing a trace amount of pentavalent antimony (Sb) in tetravalent tin oxide (SnO ₂ ). The amount of tin is 25 atm in Sn / Ti ratio.
% To 35 atm% is appropriate. Further, as the amount of antimony, an Sb / Sn ratio of 19 atm% is appropriate.

As the aluminum compound, for example, sodium aluminate, potassium aluminate, aluminum sulfate, aluminum hydrochloride and the like are used. In the surface treatment for applying the aluminum compound, the titanium oxide fine powder subjected to the conductive treatment as described above is dispersed in an aqueous solvent to form a slurry, and a predetermined amount of an aqueous solution of the aluminum compound is added to the slurry. By adding an acid or a basic neutralizing agent to the slurry while stirring, fine titanium oxide powder having an aluminum compound (alumina) adhered to its surface precipitates and precipitates. The neutralization precipitation is performed at a temperature of 20 ° C. to 60 ° C. in order for the aluminum compound to be formed as a stable and uniform adhered layer on the surface of the titanium oxide fine powder.

After the neutralization precipitation is completed, the slurry is subjected to filtration, washing, and drying treatments, and is further pulverized to produce a titanium oxide fine powder to which an aluminum compound is adhered. The appropriate amount of aluminum to be treated is 0.2% to 2.0% by weight in terms of the ratio to the powder, but the optimum coating amount varies depending on the specific surface area. If the processing amount of aluminum is too small, its effect is not sufficiently exhibited, and if it is too large, the conductivity of the titanium oxide fine powder subjected to the conductive treatment is impaired.

As the binder in which the above-mentioned fine titanium oxide powder is dispersed, the same thermoplastic resin or thermosetting resin as the binder used in the magnetic paint is used. Specific examples of the binder include, as its skeleton resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer. Polymers, acrylate-acrylonitrile copolymers, acrylate-vinylidene chloride copolymers, methacrylate-vinylidene chloride copolymers, methacrylate-styrene copolymers, thermoplastic polyurethane resins, phenoxy resins, polyolefins Vinyl chloride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, polyurethane resin There will be used. In addition, a phenol resin, an epoxy resin, a urea resin, a melamine resin, an alkyd resin, a urea-formaldehyde resin, or the like is used as the binder. As the binder, one kind or a mixture of these resins is used.

As described above, a binder having a polar group is effective since the dispersion stability is improved by the modification and adhesion of the aluminum compound to the surface of the nonmagnetic conductive material as described above. It is. The polar group is the same as the polar group of the synthetic resin used for the binder of the magnetic paint described above, and specifically, a sulfonic acid group, a sulfate group, a carboxylic acid group, and a salt thereof, and a tertiary group Amine group,
A quaternary ammonium base, a phosphate group, a phosphate group and the like are used. Among these polar groups, a metal salt of a sulfonic acid group or a sulfate group is particularly effective.

As the crosslinking agent, a trifunctional isocyanate compound, for example, a reaction product of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate, or an isocyanate which is a cycloaddition polymer of 3 mol of diisocyanate is used in combination. . The durability of the non-magnetic paint is improved by adding these crosslinking agents. Further, the cross-linking agent may be used by being added not only to the non-magnetic paint constituting the non-magnetic layer 3 but also to the above-described magnetic paint constituting the magnetic layer 4. The cross-linking agent can be added to the magnetic paint and the non-magnetic paint in an equal amount, or may be added at an arbitrary ratio.

Examples of the organic solvent include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and glycol monoethyl ether; Ether solvents such as glycol dimethyl ether, glycol monoethyl ether, dioxane, and tetrahydrofuran; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene And the like are selected and used.

The non-magnetic paint is prepared by adding a non-magnetic pigment, a binder, a cross-linking agent, etc. to the above-mentioned organic solvent, and, like the magnetic paint, a roll mill, a ball mill, a sand mill, an agitator, a kneader, an extruder, a homogenizer, It is dispersed and kneaded using a sonic disperser or the like. The non-magnetic paint and the magnetic paint are simultaneously and multi-layer coated on the non-magnetic support 2 to form the non-magnetic layer 3 and the magnetic layer 4, and a die coater is generally used as a coating machine. As the die coater, a lip structure of a two-lip method, a three-lip method, a four-lip method, or the like is used.

The magnetic tape 1 manufactured as described above
Since the non-magnetic layer 3 was formed with a non-magnetic paint using titanium oxide fine powder having acicularity as a non-magnetic pigment, the non-magnetic layer 3 was formed with a magnetic paint containing the acicular magnetic powder. Of the magnetic layer 4 to be applied is improved. The magnetic tape 1 is made of titanium oxide fine powder of S
Since the electrical resistance is reduced by performing the n / Sb conductive treatment, a traveling failure phenomenon due to static electricity charging and adhesion of dust and the like are suppressed. Furthermore, magnetic tape 1
Since the aluminum compound is adhered to the surface of the titanium oxide fine powder, the affinity with the polar group-containing binder resin in the organic solvent is improved, and the dispersion stability is improved.
The non-magnetic layer 3 having good surface smoothness is formed. Therefore, in the magnetic tape 1, the magnetic layer 4 having high-precision surface smoothness is formed on the non-magnetic layer 3, so that the electromagnetic conversion characteristics are high and spacing loss and output loss are reduced.

As described above, the magnetic tape 1 is made of Sn / S
b. A non-magnetic layer formed by applying a surface-treated non-magnetic paint for applying an aluminum compound to the surface of a non-magnetic pigment comprising titanium oxide fine powder subjected to the conductive treatment and imparting an affinity with a binder. Although No. 3 was formed, the present invention is not limited to such a configuration. The magnetic tape described below as the second embodiment is characterized in that the above-mentioned nonmagnetic pigment is subjected to an organic substance treatment for adsorbing a polyhydric alcohol to impart lipophilicity.

The non-magnetic coating material for forming the non-magnetic layer 4 of the second embodiment is the same as the magnetic tape described above except for the surface treatment method applied to the acicular titanium oxide of the non-magnetic pigment. The description is omitted for the same reason.
The surface of the titanium oxide is denatured by performing the Sn / Sb conductive treatment as described above and then performing the polyhydric alcohol deposition treatment in an organic solvent, an aqueous solution, or a gas phase. Examples of the polyhydric alcohol include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, and trimethylolpropane. Polyhydric alcohols are not particularly limited in terms of skeleton and molecular weight, but those having relatively low molecular weight and high hydrophilicity are effective because they have little desorption in an organic solvent.

The magnetic tape 1 has good surface smoothness because the polyhydric alcohol is adsorbed on the fine titanium oxide powder contained in the non-magnetic paint to improve the dispersibility in an organic solvent. The non-magnetic layer 3 is formed. Therefore, in the magnetic tape 1, the magnetic layer 4 having high precision and smoothness is formed on the non-magnetic layer 3, the electromagnetic conversion characteristics are high, and the spacing loss and the output loss are reduced.

[0047]

[Embodiments] Hereinafter, the first embodiment and the second embodiment will be described with reference to Examples 1 and 2 respectively.
This will be described specifically. Of course, it goes without saying that the present invention is not limited to these examples.
Example 1-1 A needle-like titanium oxide having a Sn / Sb conductive treatment (Sb-doped SnO ₂ conductive treatment) prepared by the above-described method as a nonmagnetic pigment of a nonmagnetic paint was applied to a magnetic tape. Fine powder is used. This Sb-doped SnO ₂ -coated titanium oxide fine powder is suspended in an aqueous solution under basic conditions to form a slurry, and a predetermined amount of an aqueous solution of sodium aluminate is added while stirring the slurry. Further, the Sb-doped SnO ₂ -coated titanium oxide fine powder is neutralized to pH 7 by gradually dropping sulfuric acid after the suspension is stirred at room temperature, so that the aluminum compound is coated on the surface. Dressed and deposited. The Sb-doped SnO ₂ titanium oxide fine powder is subjected to a pulverizing treatment through a filtration, washing, and drying process, thereby becoming an Sb-doped SnO ₂ -coated titanium oxide fine powder whose surface is coated with alumina.

As for the Sb-doped SnO ₂ -coated titanium oxide fine powder, the aluminum processing amount (% by weight) and the specific surface area (m ² / g) were obtained by appropriately changing the above-mentioned conditions during the synthesis. Another example magnetic tapes having different major axis diameters (μm) and different axis diameter ratios are prepared. The specific surface area is RAPIDS manufactured by Micrometrics.
B using URFACE AREA ANALYZER
It was measured by the ET method. Further, the major axis diameter and the minor axis diameter were each measured from a photograph taken with a transmission electron microscope x 100,000 times, and were determined by the average value of 200 points, and the axial ratio between the major axis diameter and the minor axis diameter was determined.

Example 1-1 The magnetic tape was made of Sb-doped S
The specifications of the nO ₂ -coated titanium oxide fine powder are as follows: alumina treatment amount 1.50% by weight, specific surface area 45 m ² / g, major axis diameter 0.0
7 μm, and the axial ratio between the major axis diameter and the minor axis diameter is 3.5.

Next, in Example 1-1, a magnetic tape was prepared by using the above-mentioned Sb-doped SnO ₂ -coated titanium oxide fine powder as a non-magnetic pigment, and using 100 parts by weight of titanium oxide fine powder polyvinyl chloride resin (Nippon Zeon Co., Ltd.). 8 parts by weight Polyester polyurethane resin (UR-8200 manufactured by Toyobo Co., Ltd.) 8 parts by weight Fatty acid ester 2 parts by weight Methyl ethyl ketone 90 parts by weight Cyclohexanone 90 parts by weight Non-magnetic prepared by mixing and dispersing The non-magnetic layer 3 is formed by the paint.

Example 1-1 The magnetic tape was composed of 100 parts by weight of α-iron oxide (α-Fe ₂ O ₃ ) powder, 10 parts by weight of polyvinyl chloride resin (MR-110 manufactured by Zeon Corporation), and 10 parts by weight of polyester polyurethane resin. UR-8200 manufactured by Toyobo Co., Ltd. 10 parts by weight Carbon black (Conductex-SC manufactured by Columbian) 2 parts by weight α-Al ₂ O ₃ (particles having an average particle diameter of 0.3 μm) 5 parts by weight Stearic acid 1 part by weight Methyl ethyl ketone 150 parts by weight The magnetic layer 4 is formed of a magnetic paint prepared by mixing and dispersing cyclohexanone at a composition of 150 parts by weight.

As the α-iron oxide powder, one having a magnetic property and a powder property with a saturation magnetization of 130 Am ^{2, a} coercive force of 130 kA / m, a specific surface area of 58 m ² / g, and a needle ratio of 5 is used.

Example 1-1 A magnetic tape was prepared by simultaneously applying the above-described non-magnetic paint and magnetic paint on a PET (polyethylene terephthalate) film using a 4-lip type die coater, and then performing a magnetic orientation step and a drying treatment. It is manufactured by passing through a process, a calendering process, and a curing process, further forming a back coat layer, and cutting this into an 8 mm width. Example 1-1 The magnetic tape has a non-magnetic layer 3
Is 2.0 μm, and the thickness of the magnetic layer 4 is 0.2 μm.
Thus, the film thickness ratio is set to 10.

Example 1-2 A magnetic tape was produced in the same manner as in Example 1-1 described above, except that the alumina treatment amount was 1.30% by weight, the specific surface area was 40 m ² / g, and the major axis diameter was 0.1 mm. Sb-doped SnO ₂ -coated titanium oxide fine powder having a specification of 13 μm and an axial ratio of a major axis diameter to a minor axis diameter of 5.5 is used. The magnetic tape of Example 1-3 had an alumina treatment amount of 0.83% by weight, a specific surface area of 25 m ² / g, and a major axis diameter of 0.3.
Sb with a specification of 0 μm and an axial ratio of the major axis diameter to the minor axis diameter of 7.5
Doped SnO ₂ -coated titanium oxide fine powder is used. Further, in Example 1-4, the magnetic tape had an alumina processing amount of 0.5.
50% by weight and specific surface area of 15 m ² / g, but Sb-doped SnO ₂ -coated titanium oxide fine particles having a major axis diameter of 1.00 μm, an axial ratio of a major axis diameter to a minor axis diameter of 15, and coarse particles. Powder is used. The magnetic tape of Example 1-5 had an alumina treatment amount of 1.10% by weight, a specific surface area of 34 m ² / g, and a major axis diameter of 0.04 μm. Sb-doped Sn with specifications almost spherically similar to .1
O ₂ -coated titanium oxide fine powder is used.

Embodiment 1-6 Magnetic Tape to Embodiment 1-1
(1) The magnetic tape has a major axis diameter of 0.13 μm, an axial ratio of the major axis diameter to the minor axis diameter of 5.5, and a particle specification of Sb-doped SnO ₂ coated titanium oxide fine particles equivalent to Example 1-2. Powders are used, but powders having different amounts of deposition by appropriately changing the conditions during the alumina treatment are used. Example 1-6 Sb-doped SnO ₂ -coated titanium oxide fine powder of a magnetic tape had an alumina treatment amount of 0.12% by weight and a specific surface area of 42 m ² / g. Example 1-7 Sb of Magnetic Tape
The doped SnO ₂ -coated titanium oxide fine powder has an alumina treatment amount of 0.68% by weight and a specific surface area of 40 m ² / g.
Example 1-8 Sb-doped SnO ₂ -coated titanium oxide fine powder of a magnetic tape had an alumina treatment amount of 2.70% by weight and a specific surface area of 39 m ² / g. Also, the Sb-doped SnO ₂ -coated titanium oxide fine powder of the magnetic tape of Example 1-9 is
Alumina treatment amount is 4.00% by weight, specific surface area is 38 m ²
/ G.

Example 1-10 The magnetic tape was made of Sb-doped S manufactured in the same manner as in Example 1-1.
An nO ₂ -coated titanium oxide fine powder is used, and a Sb-doped SnO ₂ -coated titanium oxide fine powder obtained by subjecting a surface modification with potassium aluminate to an alumina treatment is used. The magnetic tapes of Examples 1-11, Sb-doped SnO ₂ was modified surface by performing a process of neutralization with sodium hydroxide with addition of aluminum sulfate to the slurry of Sb-doped SnO ₂ deposited titanium oxide fine powder Fine titanium oxide powder is used.

Table 1 summarizes the specifications of the Sb-doped SnO ₂ -coated titanium oxide fine powder used in the magnetic tapes of the above embodiments.

[0058]

[Table 1]

Comparative Example 1-1 On the other hand, a magnetic tape was prepared using Sb-doped SnO ₂ -coated titanium oxide fine powder not subjected to alumina treatment, and had a specific surface area of 45 m ² / g, a major axis diameter of 0.13 μm, The axial ratio of the major axis diameter to the minor axis diameter is 5.5, and S in Example 1-2 described above except for the amount of alumina treatment.
The specifications are almost the same as those of the b-doped SnO ₂ -coated titanium oxide fine powder. Further, with respect to Comparative Example 1-2 magnetic tape,
It is made using Sb-doped SnO ₂ -coated titanium oxide fine powder which has been subjected to alumina treatment with an alumina treatment amount as small as 0.03 wt%. The magnetic tape of Comparative Example 1-2 had a specific surface area of 45 m ² / g, a major axis diameter of 0.13 μm, and an axial ratio of the major axis diameter to the minor axis diameter of 5.5. The specifications are almost the same as those of the Sb-doped SnO ₂ -coated titanium oxide fine powder of Example 1-2.

Further, Comparative Example 1-3 The magnetic tape was prepared by using Sb-doped SnO ₂ -coated titanium oxide fine powder having an alumina treatment amount of 5.00 wt% and excess alumina treatment. The magnetic tape of Comparative Example 1-3 had a specific surface area of 33 m ² / g, a major axis diameter of 0.15 μm, and an axial ratio of the major axis diameter to the minor axis diameter of 5.3. Comparative Example 1-4 The magnetic tape was made using acicular α-iron oxide (α-Fe ₂ O ₃ ) powder in which the nonmagnetic pigment had no conductivity. In this Comparative Example 1-4 magnetic tape, the specifications of the needle-like α-iron oxide powder were a specific surface area of 53 m ² / g, a major axis diameter of 0.15 μm, and an axial ratio of the major axis diameter to the minor axis diameter of 6.5. . The specifications of the non-magnetic pigments of the comparative example 1-1 magnetic tape to the comparative example 1-4 magnetic tape are the same as those of the magnetic tapes of the respective examples.
It is summarized in.

The magnetic resistance (Ω / s) of the coating film before forming the back coat layer was measured for each of the magnetic tapes of the examples and the magnetic tapes of the comparative examples manufactured as described above.
q. ), Surface roughness SRa of the magnetic layer 4 (nm), electromagnetic conversion characteristics (dB) and dropout characteristics (times / min.)
Was measured and evaluated. The electric resistance was measured using a two-electrode surface electric resistance meter (GH RESISTANS METER manufactured by YHP). The surface roughness is measured using an optical interference roughness meter (H
The center surface average roughness SRa was evaluated using ZYGO manufactured by P Corporation. The evaluation of the electromagnetic conversion characteristics was performed using a measuring machine obtained by assembling the magnetic tape of each example and the magnetic tape of each comparative example into a Hi-8 cassette and modifying a commercially available Hi-8 video deck.
The recording / reproducing output of MHz was evaluated assuming that the output of the magnetic tape of Example 1-2 was 0 db. The dropout characteristics were evaluated by the same method at a recording / reproducing output of 7 MHz at 10 db, 3 μsec. The average value of the number of signal dropouts for one minute was measured and evaluated by a dropout counter.

The electrical resistance of each sample magnetic tape and the comparative sample magnetic tape, the surface roughness of the magnetic layer 4,
Table 2 shows the results of the measurement and evaluation of the electromagnetic conversion characteristics and the dropout characteristics.

[0063]

[Table 2]

Embodiment 1-1 Magnetic Tape to Embodiment 1-3
The magnetic tape is made of a non-magnetic pigment contained in the non-magnetic coating forming the non-magnetic layer 3 by using Sb-doped SnO ₂ -coated titanium oxide obtained by subjecting acicular fine particles to alumina treatment. And the surface roughness SRa was in the range of 5.1 nm to 6.5 as is clear from Table 2.
Very good surface smoothness of nm was obtained. Therefore, the magnetic tapes of Examples 1-1 to 1-3 have good electromagnetic conversion characteristics, a small electric resistance of the nonmagnetic layer 3 and excellent dropout characteristics.

Similarly, in the magnetic tapes of Examples 1-6 to 1-11, the non-magnetic pigment of the non-magnetic paint for forming the non-magnetic layer 3 was subjected to alumina treatment for fine needle-like particles. Since the Sb-doped SnO ₂ -coated titanium oxide was used, the suitability for application with a magnetic paint was improved, and as is clear from Table 2, a very good surface roughness SRa was obtained and the surface smoothness was obtained. The result that the conversion characteristic was good and the electric resistance of the nonmagnetic layer 3 was small and the dropout characteristic was also excellent was obtained.

On the other hand, in Example 1-4, in the magnetic tape, the nonmagnetic pigment of the nonmagnetic paint forming the nonmagnetic layer 3 was made of coarse particles of Sb-doped Sn having a major axis diameter of 1,000 μm.
Since the O ₂ -coated titanium oxide was used, the surface roughness of the non-magnetic layer 3 was poor even though the alumina treatment was performed. The surface smoothness and the electromagnetic conversion characteristics were deteriorated. Further, in Example 1-5 magnetic tape, Sb-doped SnO ₂ -coated titanium oxide having a small particle diameter was used as the non-magnetic pigment of the non-magnetic paint for forming the non-magnetic layer 3.
Since the particles were almost spherical, having an axis ratio of 1.1 between the major axis and the minor axis, the suitability for application with the magnetic paint was poor, and the surface smoothness and electromagnetic conversion characteristics were deteriorated. .

On the other hand, in Comparative Example 1-1, the magnetic tape of the Sb-doped SnO ₂ -coated titanium oxide fine powder in which the non-magnetic pigment of the non-magnetic paint forming the non-magnetic layer 3 was not subjected to the alumina treatment was used. Since it is used, the dispersibility in the binder becomes poor, and it becomes difficult to form the nonmagnetic layer 3 with good surface smoothness. Therefore, Comparative Example 1-1
The magnetic tape includes a magnetic layer 4 formed on the non-magnetic layer 3.
It was also difficult to form the surface smoothness with high precision, and it was found that the electromagnetic conversion characteristics deteriorated.

In Comparative Example 1-2, although the Sb-doped SnO ₂ -coated titanium oxide fine powder was subjected to alumina treatment in the magnetic tape, the dispersion was insufficient to sufficiently improve the dispersibility in the binder. This makes it difficult to form the nonmagnetic layer 3 with good surface smoothness. Therefore,
In Comparative Example 1-2, it was difficult to form the surface smoothness of the magnetic layer 4 formed on the nonmagnetic layer 3 with high precision, and it was clarified that the electromagnetic conversion characteristics deteriorated.

Further, in the magnetic tape of Comparative Example 1-3, when the alumina powder was excessively treated with the Sb-doped SnO ₂ -coated titanium oxide fine powder, the electrical resistance increased and the dropout characteristics deteriorated. It became clear. In Comparative Example 1-4, the use of needle-like α-iron oxide powder as the non-magnetic pigment improved the dispersibility in the binder, and provided relatively accurate surface smoothness. However, it has been found that the electromagnetic resistance or the dropout characteristic is deteriorated due to poor shape after coating due to electrostatic charging and entrainment of dust due to high electric resistance.

Each of the magnetic tapes of the second embodiment also has a non-magnetic layer 3
The Sb-doped SnO ₂ -coated titanium oxide fine powder prepared by the above-described method is used as the non-magnetic pigment of the non-magnetic paint for forming the above. As described later, each of the magnetic tapes of the second embodiment was treated with an organic substance using a treating agent comprising a polyhydric alcohol such as trimethylolpropane, glycerin, or diethylene glycol, and the surface thereof was modified to form Sb-doped S.
Fine powder of titanium oxide deposited on nO ₂ is used. Example 2
1 magnetic tape to Example 2-5 magnetic tapes were prepared using trimethylolpropane with respect to Sb-doped SnO ₂ -coated titanium oxide fine powders having different particle sizes by using different synthesis conditions. What performed the process which denatures the surface by performing the gaseous phase process on the conditions of ° C is used. The throughput of trimethylolpropane is CHN
It was measured by an analyzer and the weight ratio to the Sb-doped SnO ₂ -coated titanium oxide fine powder was 2%.

Embodiment 2-1 Magnetic Tape to Embodiment 2-5
Table 3 shows the measurement results of the specific surface area (m ² / g), major axis diameter (μm), and axis diameter ratio of the Sb-doped SnO ₂ -coated titanium oxide fine powder for the magnetic tape. These measurements are performed using the same measuring equipment as in the first embodiment described above. Further, the magnetic tapes of Examples 2-1 to 2-5 were obtained from the obtained Sb-doped Sn.
A nonmagnetic paint prepared by mixing and dispersing O ₂ -coated titanium oxide fine powder with the same composition as in the first embodiment is applied.

Further, in the magnetic tapes of Examples 2-1 to 2-5, a magnetic paint prepared by mixing and dispersing with the same composition as in the first embodiment described above was used.
The lip type die coater is used to simultaneously and repeatedly apply the specific magnetic paint onto PET. Note that the magnetic tapes of Examples 2-1 to 2-5 are the magnetic and powder characteristics of the α-Fe metal magnetic powder mixed with the magnetic paint, the tape width, the nonmagnetic layer 3 and the magnetic layer 4. Is equivalent to that of the first embodiment described above.

Example 2-1 The magnetic tape was specifically
Sb-doped SnO ₂ -coated titanium oxide fine powder having a specific surface area of 45 m ² / g, a major axis diameter of 0.07 μm, and an axial ratio of the major axis to the minor axis of 3.5 is used. Example 2-2
The magnetic tape has a specific surface area of 40 m ² / g and a major axis diameter of 0.13.
Sb-doped SnO ₂ -coated titanium oxide fine powder having a specification of μm and an axial ratio of a major axis diameter to a minor axis diameter of 5.5 is used. Furthermore, the magnetic tape of Example 2-3 had a specific surface area of 25 m ² /
g, Sb-doped SnO ₂ -coated titanium oxide fine powder having a major axis diameter of 0.30 μm and an axial ratio of the major axis diameter to the minor axis diameter of 7.5 is used. Furthermore, the magnetic tape of Example 2-4 has a specific surface area of 15 m ² / g, a major axis diameter of 1.00 μm, and an Sb-doped SnO ₂ specification having a major axis diameter / minor axis diameter ratio of 15.
Fine titanium oxide powder is used. Example 2-5 The magnetic tape had a specific surface area of 34 m ² / g and a major axis diameter of 0.04 μm.
m, an Sb-doped SnO ₂ -coated titanium oxide fine powder having a specification of an axis ratio between the major axis diameter and the minor axis diameter of 1.1 is used.

In Example 2-6, magnetic tape was prepared using glycerin (special reagent grade) as a treating agent.
Sb-doped SnO ₂ -coated titanium oxide fine powder which has been subjected to a gas phase treatment at 0 ° C. to modify its surface is used. The processing amount of glycerin was measured by a CHN analyzer, and was 1.2% by weight based on the Sb-doped SnO ₂ -coated titanium oxide fine powder. Example 2
The -6 magnetic tape is obtained by simultaneously applying a non-magnetic paint formed using the Sb-doped SnO ₂ -coated titanium oxide fine powder together with the magnetic paint described above. As described in Table 3, the specifications of the Sb-doped SnO ₂ -coated titanium oxide fine powder were as follows:
₂ Specific surface area 40 m ² / g equivalent to titanium oxide fine powder to be applied,
The major axis diameter is 0.13 μm, and the axial ratio between the major axis diameter and the minor axis diameter is 5.5.
It is.

Further, the magnetic tape of Example 2-7 was prepared using diethylene glycol (special reagent grade) as a treating agent.
Sb-doped SnO ₂ -coated titanium oxide fine powder which has been subjected to a gas phase treatment at a temperature of 00 ° C. to modify its surface is used. The throughput of diethylene glycol is CH
The weight ratio to the fine powder of Sb-doped SnO ₂ -coated titanium oxide was 1.5%, as measured by an N analyzer. Example 2-7 The magnetic tape was prepared using the Sb-doped SnO
₍₂₎ A non-magnetic paint made into a paint using the applied titanium oxide fine powder is simultaneously and repeatedly applied together with the above-described magnetic paint. Sb-doped SnO ₂ deposited titanium oxide fine powder specifications, as described in Table 3, Example 2-2 Magnetic tapes Sb-doped SnO ₂ deposited titanium oxide fine powder equivalent specific surface area 40 m ² / g, The major axis diameter is 0.13 μm, and the axial ratio between the major axis diameter and the minor axis diameter is 5.5.

On the other hand, the magnetic tape of Comparative Example 2-1 was made of Sb-doped S
This S was prepared using nO ₂ -coated titanium oxide fine powder.
The specification of the b-doped SnO ₂ -applied titanium oxide fine powder is such that the specific surface area is 50 m ² / g, the major axis diameter is 0.07 μm, and the axial ratio between the major axis diameter and the minor axis diameter is 3.5. In Comparative Example 2-2 Magnetic tapes, polyhydric Sb-doped SnO ₂ not subjected to organic treatment with an alcohol using a deposition of titanium oxide fine powder is created, the Sb-doped SnO ₂ deposited titanium oxide fine powder specifications Has a specific surface area of 45 m ² / g and a major axis diameter of 0.13
μm, and the axial ratio of the major axis diameter to the minor axis diameter is 5.5. Further, the magnetic tape of Comparative Example 2-3 is made of acicular α-Fe ₂ O ₃ magnetic powder in which the non-magnetic pigment has no conductivity, and the other components are prepared in the same manner as in the above-described embodiment. Comparative Example 2-3 Magnetic tapes, α-Fe ₂ O ₃ magnetic powder specification the specific surface area 53m ² / g, long axis length 0.15 [mu] m, and axial ratio 6.5 with the major axis diameter and minor axis diameter Have been.

Table 3 summarizes the specifications of the Sb-doped SnO ₂ -coated titanium oxide fine powder and α-Fe ₂ O ₃ magnetic powder used in the magnetic tapes of the examples and the comparative example.

[0078]

[Table 3]

The magnetic resistance (Ω / s) of the coating film before the formation of the back coat layer was measured for each of the magnetic tapes of the examples and the magnetic tapes of the comparative examples manufactured as described above.
q. ), Surface roughness SRa of the magnetic layer 4 (nm), electromagnetic conversion characteristics (dB) and dropout characteristics (times / min.)
Was measured and evaluated. The measurement and evaluation of these characteristic values were performed in the same manner as in the magnetic tape of the first embodiment and the magnetic tape of the comparative example.

The electric resistance of each sample magnetic tape and the comparative sample magnetic tape, the surface roughness of the magnetic layer 4,
Table 4 shows the results of the measurement and evaluation of the electromagnetic conversion characteristics and the dropout characteristics.

[0081]

[Table 4]

Embodiment 2-1 Magnetic Tape to Embodiment 2-3
The magnetic tape is formed by using Sb-doped SnO ₂ -coated titanium oxide made of needle-like fine particles obtained by applying an organic substance treatment with a polyhydric alcohol to a non-magnetic pigment of a non-magnetic paint forming the non-magnetic layer 3. Since the dispersibility in the organic solvent is improved and the suitability for coating is excellent, the nonmagnetic layer 3 having high-precision surface smoothness is formed. Therefore, as is clear from Table 4, the magnetic tapes of Example 2-1 to Example 2-3 have extremely good surface smoothness with a surface roughness SRa of 5.1 nm to 6.5 nm. The electromagnetic conversion characteristics are good, the electric resistance of the nonmagnetic layer 3 is small, and the dropout characteristics are excellent.

Similarly, in the magnetic tapes of Examples 2-6 and 2-7, the non-magnetic pigment of the non-magnetic paint for forming the non-magnetic layer 3 was treated with an organic material using a polyhydric alcohol. Doped Sn consisting of fine particles of
By using O ₂ -coated titanium oxide, the dispersibility in an organic solvent is improved, and the non-magnetic layer 3 having a high-precision surface smoothness is formed since the coating suitability is excellent. Accordingly, the magnetic tapes of Example 2-6 and Example 2-7 had a surface roughness SRa of 6.
An extremely good surface smoothness of 3 nm or 5.9 nm is obtained, the electromagnetic conversion characteristics thereof are good, the electric resistance of the nonmagnetic layer 3 is small, and the dropout characteristics are also excellent.

On the other hand, in the magnetic tape of Example 2-4, since the nonmagnetic pigment used was Sb-doped SnO ₂ -coated titanium oxide having a major axis diameter of 1,000 μm and having a major axis of 100 μm, polyhydric alcohol was used. Despite the organic material treatment, the surface roughness SRa was increased and the surface smoothness and electromagnetic conversion characteristics were deteriorated. Further, in the magnetic tape of Example 2-5, the nonmagnetic pigment used was Sb-doped SnO ₂ -coated titanium oxide having a small particle diameter, and the ratio of the major axis to the minor axis was 1.1, which was almost 1.1. Since the particles were nearly spherical, their suitability for application with a magnetic paint was poor, and surface smoothness and electromagnetic conversion characteristics were deteriorated.

On the other hand, the magnetic tapes of Comparative Example 2-1 and Comparative Example 2-2 were made of Sb-doped Sn in which the non-magnetic pigment was not treated with an organic substance using a polyhydric alcohol.
Since the O ₂ -coated titanium oxide fine powder is used, the dispersibility in an organic solvent is deteriorated, and it is difficult to form the nonmagnetic layer 3 with good surface smoothness. Therefore, in the magnetic tape of Comparative Example 2-1 and the magnetic tape of Comparative Example 2-2, it is difficult to form the surface smoothness of the magnetic layer 4 formed on the nonmagnetic layer 3 with high accuracy. It became clear that the characteristics deteriorated. Comparative Example 2-3
The magnetic tape uses a needle-like α-Fe ₂ O ₃ magnetic powder as a non-magnetic pigment instead of the Sb-doped SnO ₂ -coated titanium oxide fine powder, so that the surface is highly dispersible in an organic solvent and has relatively high precision. Although it was possible to obtain smoothness, it was clarified that the electromagnetic resistance or the drop-out characteristic was deteriorated due to poor shape after coating due to electrostatic charging and entrapment of dust etc. due to high electric resistance.

[0086]

As is apparent from the above description, according to the magnetic recording medium of the present invention, the nonmagnetic pigment of the nonmagnetic paint forming the nonmagnetic layer is subjected to the Sn / Sb conductive treatment and the aluminum compound is treated. By using a non-magnetic fine powder such as acicular titanium oxide, which is improved in dispersibility by imparting an affinity with a binder by applying a non-magnetic paint and a magnetic paint, The coating suitability is improved, and a coating surface having high precision smoothness is formed. Therefore, the magnetic recording medium is improved in electromagnetic conversion characteristics by reducing spacing loss and output loss,
By reducing the electric resistance, a running failure phenomenon due to static electricity charging and adhesion of dust and the like are suppressed, and dropout characteristics are improved.

Further, according to the magnetic recording medium of the present invention, the non-magnetic pigment of the non-magnetic paint for forming the non-magnetic layer contains Sn.
A non-magnetic fine powder such as acicular titanium oxide is used, which has a conductive treatment of / Sb and adsorbs a polyhydric alcohol to impart lipophilicity, thereby improving dispersion stability in an organic solvent. Thus, the applicability between the non-magnetic paint and the magnetic paint is improved, and a coating film surface having high precision smoothness is formed. Therefore, the magnetic recording medium improves the electromagnetic conversion characteristics by reducing the spacing loss and the output loss, and also suppresses the traveling failure phenomenon due to static electricity charging and the adhesion of dust and the like by reducing the electric resistance. The dropout characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a magnetic tape shown as an embodiment of the present invention.

[Explanation of symbols]

1 magnetic tape, 2 non-magnetic support carrier, 3 non-magnetic layer,
4 Magnetic layer

Claims (4)

[Claims] 1. A non-magnetic coating formed by dispersing at least a non-magnetic pigment and a binder in a solvent on a non-magnetic support to form a non-magnetic layer. In a magnetic recording medium on which a magnetic layer is formed by applying a magnetic paint obtained by dispersing a powder and a binder in a solvent, the non-magnetic pigment is subjected to a conductive treatment by applying a non-magnetic conductive material to its surface. A needle-like non-magnetic fine powder which has been subjected to a surface treatment to impart an affinity with a binder by applying an aluminum compound to the non-magnetic conductive material is used. Magnetic recording medium. 2. A non-magnetic paint comprising a non-magnetic pigment and a binder dispersed in a solvent is applied on a non-magnetic support to form a non-magnetic layer, and a non-magnetic layer is formed on the non-magnetic layer. In a magnetic recording medium on which a magnetic layer is formed by applying a magnetic paint obtained by dispersing a powder and a binder in a solvent, the non-magnetic pigment is subjected to a conductive treatment by applying a non-magnetic conductive material to its surface. A magnetic recording medium characterized by using a needle-like nonmagnetic fine powder which is applied and treated with an organic substance to impart lipophilicity by adsorbing a polyhydric alcohol to the nonmagnetic conductive material. 3. The non-magnetic fine powder constituting the non-magnetic pigment has a specific surface area of 20 m ² / g to 60 m ² / g, a major axis diameter of 0.05 μm to 0.4 μm, and a major axis diameter of The magnetic recording medium according to claim 1, wherein acicular titanium oxide fine particles having a ratio to a minor axis diameter of 3: 1 or more are used. 4. The non-magnetic conductive material used for the conductive treatment,
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is tin or a tin compound doped with antimony.