JP2002197640A - Filler material for magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which is excellent in both of durability and surface smoothness. SOLUTION: The filler material for the magnetic recording medium is composite nonmagnetic particle powder which is formed by immobilizing one or >=2 kinds of oxide particulate powder of 0.001 to 0.07 μm in average particle size selected from aluminum oxide, zirconium oxide, cerium oxide, titanium oxide, silicon oxide and molybdenum oxide to the particle surface of hematite particle powder by a silicon compound formed from tetraalkoxysilane and the content of the oxide particulate powder is 0.1 to 20 wt.% of the weight of the management particle powder. This magnetic recording medium is constituted by forming a magnetic recording layer containing a binder resin, magnetic particle powder and the filler material described above on a nonmagnetic substrate.

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 having excellent durability and surface smoothness.

[0002]

2. Description of the Related Art In recent years, as the size and weight of video and audio magnetic recording / reproducing devices have been reduced and recording has been performed for a long time, the performance of magnetic recording media such as magnetic tapes and magnetic disks has been improved. Demands for high durability and good electromagnetic conversion characteristics are increasing.

In a magnetic recording medium such as a magnetic tape or a magnetic disk, recording and reproduction are performed while being in contact with a magnetic head, so that the magnetic recording layer is liable to be worn, thereby contaminating the magnetic head and deteriorating the recording and reproduction characteristics. To cause
Conventionally, a highly durable magnetic recording medium with little wear has been demanded.

Conventionally, alumina (Al) has been used to improve the wear durability of the magnetic recording layer of a magnetic recording medium.
Attempts have been made to add various filler materials such as ₂ O ₃ ), hematite (α-Fe ₂ O ₃ ) and dichromic trioxide (Cr ₂ O ₃ ) to the magnetic recording layer.

For example, alumina (Al)_TwoO_Three)
In the case of α-Al with an amorphous phase_TwoO_ThreeUsing
Magnetic recording media (JP-A-5-36059) and specific
Α-Al having crystallinity of_TwoO_Three-Based magnetic recording media
(Japanese Patent Application Laid-Open No. Hei 7-244836). Hematy
G (α-Fe_TwoO_Three), The granular α-Fe
_TwoO_ThreeMagnetic recording media using
Publication), liquid hydrocarbons and α-Fe_TwoO_ThreeUsing magnetism
Recording media (JP-A-54-70806).
In addition, 2 chromium trioxide (Cr_TwoO_Three),
Needle-like Cr_TwoO_ThreeMagnetic recording media using
No. 2221).

However, these filler materials include:
Each has its own problems. It is known that alumina has poor dispersibility in a binder resin, and that the surface smoothness of a coating film is greatly reduced as the amount of alumina is increased. Hematite has a relatively good dispersibility in the binder resin, but it needs to be added in large amounts to obtain sufficient durability. Will decrease. Dichromium trioxide is not preferable in terms of environmental health.

In general, when the amount of these filler materials is increased, the durability is improved, but the dispersibility of the magnetic particles in the vehicle is reduced, and the surface smoothness of the coating film is greatly reduced. It is known.

Therefore, even if the amount necessary for improving the durability is added, a filler material which suppresses a decrease in the dispersibility of the magnetic particle powder in the vehicle and, as a result, a decrease in the surface smoothness of the coating film is suppressed. There is a strong demand for the magnetic recording media used.

[0009]

A magnetic recording medium excellent in both durability and surface smoothness is currently most demanded. However, a magnetic recording medium which sufficiently satisfies these characteristics has not yet been obtained. Not.

That is, in the above-mentioned conventional magnetic recording medium using a filler material for a magnetic recording medium such as alumina, hematite, and trichromium oxide, the filler material added in order to obtain durability is added. When the amount is increased, the surface smoothness of the coating film is greatly reduced, and a magnetic recording medium having excellent durability and surface smoothness cannot be obtained.

Japanese Patent Application Laid-Open No. 7-192248 describes a method in which Al or Si oxide or hydroxide fine particles deposited on the particle surface are fixed to the particle surface by compaction pulverization. As shown in Comparative Example 6 below, since a considerable amount of fine particles are detached from the particle surface, when used as a filler material for a magnetic recording medium, the dispersibility is hardly sufficient, and the durability of the obtained magnetic recording medium is poor. The sex is hardly enough.

Accordingly, it is a technical object of the present invention to provide a magnetic recording medium having both excellent durability and surface smoothness.

[0013]

The above technical object can be achieved by the present invention as described below.

That is, according to the present invention, an oxide having an average particle diameter of 0.001 to 0.07 μm selected from aluminum oxide, zirconium oxide, cerium oxide, titanium oxide, silicon oxide and molybdenum oxide is formed on the surface of the hematite particle powder. One or two or more of the compound fine particle powders are composite nonmagnetic particle powders having an average particle diameter of 0.08 to 1.0 μm, which are fixed by a silicon compound generated from tetraalkoxysilane, wherein the oxide fine particle powder is The filler material for a magnetic recording medium is 0.1 to 20% by weight based on the non-magnetic particle powder (Invention 1).

The particle surface of the hematite particle powder of the present invention 1 is previously coated with an intermediate coating comprising at least one selected from hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of silicon. A filler material for a magnetic recording medium, which is characterized by having the following characteristics (Invention 2).

Further, the present invention relates to a magnetic recording medium in which a magnetic recording layer containing a binder resin, magnetic particle powder and a filler material is formed on a non-magnetic substrate, wherein the filler material of the present invention 1 or the present invention is used. 2 and a filler material for magnetic recording medium 100
A magnetic recording medium characterized by being contained in an amount of 1 to 30 parts by weight with respect to part by weight (Invention 3).

Further, the present invention provides a non-magnetic support, a non-magnetic underlayer containing non-magnetic particle powder formed on the non-magnetic support and a binder resin, and a bonding formed on the non-magnetic under layer. A magnetic recording medium comprising a magnetic recording layer containing a dispersing agent resin, magnetic particle powder and a filler material, wherein the filler material for a magnetic recording medium of the present invention 1 or 2 is used as the filler material, and the filler material is a magnetic particle powder 100. A magnetic recording medium characterized by being contained in an amount of 1 to 30 parts by weight with respect to part by weight (Invention 4).

The structure of the present invention will be described in detail as follows.

First, the filler material for a magnetic recording medium according to the present invention will be described.

The filler material according to the present invention has an average particle diameter of 0.001 to 0.0 selected from aluminum oxide, zirconium oxide, cerium oxide, titanium oxide, silicon oxide and molybdenum oxide on the surface of the hematite particle powder.
One or more of the 7 μm oxide fine particle powders are composite nonmagnetic particle powders having an average particle diameter of 0.08 to 1.0 μm, which are immobilized by a silicon compound generated from tetraalkoxysilane.

The hematite particles in the present invention are 5 to 5 parts of hematite particles or manganese-containing hematite particles.
The core particles are black hematite particles such as manganese-containing hematite particles containing 40% by weight of manganese. Usually, since the hematite particle powder is red, the core particles are preferably black hematite particles such as manganese-containing hematite particles in consideration of the light transmittance of the obtained magnetic recording medium.

Hematite particles have various shapes, such as spherical, granular, octahedral, hexahedral, polyhedral, etc., needle-like, spindle-like, rice-granular, etc., and plate-like particles. is there. Considering the dispersibility in the vehicle, the particles are preferably granular.

When the particle shape of the hematite particles is granular, the average particle diameter is 0.075 to 0.95.
μm, preferably 0.085 to 0.65 μm, more preferably 0.095 to 0.45 μm.

When the particle shape of the hematite particles is acicular, the average particle diameter (average major axis diameter) is 0.075 to 0.95.
μm, preferably 0.085 to 0.65 μm, more preferably 0.095 to 0.45 μm, and has an axial ratio (ratio of average major axis diameter to average minor axis diameter) (hereinafter referred to as “axial ratio”). )
Is 2 to 20, preferably 2.5 to 15, more preferably 3 to 10.

When the particle shape of the hematite particles is a plate-like particle powder, the average particle diameter (average plate surface diameter) is 0.075 to 0.1.
It is 95 μm, preferably 0.085 to 0.65 μm, and more preferably 0.095 to 0.45 μm, and has a plate ratio (ratio of an average plate surface diameter to an average thickness) (hereinafter referred to as “plate ratio”). ) Is 2 to 50, preferably 2.5 to 48, more preferably 3 to 46.

The average particle size of the hematite particles is 0.9.
When it exceeds 5 μm, the obtained filler material becomes coarse particles, and the surface smoothness of the obtained magnetic recording medium decreases. When the particle size is less than 0.075 μm, aggregation tends to occur due to an increase in intermolecular force due to finer particles, so that the oxide particles are uniformly attached to the surface of the hematite particle powder and are uniformly fixed with tetraalkoxysilane. It becomes difficult to perform the chemical treatment.

When the particle shape of the hematite particles is acicular,
If the axis ratio is more than 20, entanglement between particles increases, and it becomes difficult to perform a uniform attachment treatment with fine oxide particles on the surface of the hematite particle powder and a uniform fixing treatment with tetraalkoxysilane.

When the shape of the hematite particles is plate-like,
When the plate-like ratio exceeds 50, stacking between particles increases, and it becomes difficult to perform a uniform attachment treatment with fine oxide particles on the surface of the hematite particle powder and a uniform fixing treatment with tetraalkoxysilane.

The geometric standard deviation of the particle diameter of the hematite particles is preferably 1.8 or less, more preferably 1.7 or less, and even more preferably 1.6 or less. If the geometric standard deviation value exceeds 1.8, uniform dispersion is hindered by the existing coarse particles, so that the oxide particles are uniformly attached to the surface of the hematite particles by the oxide fine particles and the tetraalkoxysilane is used. It becomes difficult to perform a uniform immobilization treatment. The lower limit of the geometric standard deviation value is 1.01, and a value less than 1.01 is difficult to obtain industrially.

The BET specific surface area of the hematite particles is preferably 1.0 to ²⁰⁰ m ² / g, more preferably 1.5 to 150 m ² / g, and still more preferably 2.0 to ²⁰⁰ m ² / g.
100 m ² / g. BET specific surface area value is 1.0 m ²
If the ratio is less than / g, hematite particles are coarse or particles are sintered between particles, and the resulting filler material is also coarse particles. The surface smoothness of the recording medium decreases. BE
When the T specific surface area exceeds 200 m ² / g, aggregation tends to occur due to an increase in intermolecular force due to finer particles. It becomes difficult to perform a uniform immobilization treatment with tetraalkoxysilane.

The volume resistivity of the hematite particles is:
Usually, it is about 1 × 10 ⁷ to 1 × 10 ⁹ Ω · cm.

The particle shape and particle size of the filler material according to the present invention greatly depend on the particle shape and particle size of hematite particles as core particles, and have a particle morphology similar to hematite particles.

That is, the filler material according to the present invention has an average particle diameter of 0.08 to 1.0 μm, preferably 0.09 to 0.7 μm, more preferably 0.1 to 0.5 μm.
μm.

In the case where granular hematite particles are used as the core particles, the average particle size is 0.08 to 1.0 μm, preferably 0.09 to 0.7 μm, more preferably 0.1 to 0.5 μm.
μm.

When the acicular hematite particles are used as the core particles, the average particle diameter (average major axis diameter) is 0.08 to 1.0 μm.
m, preferably 0.09 to 0.7 μm, more preferably 0.1 to 0.5 μm, and the axial ratio is 2 to 20, preferably 2.5 to 15, more preferably 3 to 10.

When plate-like hematite particles are used as core particles, the average particle diameter (average plate surface diameter) is 0.08 to 1.0 μm.
m, preferably 0.09 to 0.7 μm, more preferably 0.1 to 0.5 μm, and the plate ratio is 2 to 50, preferably 2.5 to 48, more preferably 3 to 46. .

When the average particle size is less than 0.08 μm, dispersion in a vehicle at the time of producing a magnetic paint becomes difficult due to an increase in intermolecular force due to finer particles,
The durability and surface smoothness of the obtained magnetic recording medium decrease. When the average particle diameter exceeds 1.0 μm, the particle size is too large. Therefore, when a magnetic recording layer is formed by using this, the surface smoothness of the coating film tends to be impaired.

When the particle shape of the filler material is acicular, if the axial ratio exceeds 20, entanglement between the particles increases, making it difficult to uniformly disperse the particles in a vehicle at the time of producing a magnetic coating material, thereby improving durability and durability. It becomes difficult to obtain a magnetic recording medium having excellent surface smoothness.

When the particle shape of the filler material is plate-like, if the plate-like ratio exceeds 50, the stacking between the particles increases, and it becomes difficult to uniformly disperse the particles in the vehicle at the time of producing the magnetic paint, and the durability is improved. In addition, it becomes difficult to obtain a magnetic recording medium having excellent surface smoothness.

The geometric standard deviation of the particle diameter of the filler material is as follows:
It is preferably 1.8 or less. If it exceeds 1.8, the coarse particles present are not preferred because they have an adverse effect on the surface smoothness of the coating film. In consideration of the surface smoothness of the coating film, it is preferably 1.7 or less, more preferably 1.6 or less. In consideration of industrial productivity, the lower limit of the geometric standard deviation of the particle diameter of the filler material is 1.01,
Those less than 1.01 are difficult to obtain industrially.

The BET specific surface area of the filler material is 1.0 to
200 m ² / g is preferred, more preferably 1.5 to 1
50 m ² / g, still more preferably 2.0 to 100 m ²
/ G. When the BET specific surface area value is less than 1.0 m ² / g, the composite non-magnetic particle powder is coarse or the particles are sintered between the particles, and the magnetic particles obtained by using this are In the recording medium, the surface smoothness of the coating film is easily impaired. When the BET specific surface area exceeds 200 m ² / g, aggregation tends to occur due to an increase in intermolecular force due to finer particles, so that dispersibility in a vehicle at the time of manufacturing a magnetic coating material is reduced.

The volume resistivity of the filler material is 1.0 ×
It is preferably at most 10 ¹⁰ Ω · cm, more preferably from 1.0 × 10 ⁵ Ω · cm to 9.0 × 10 ⁹ Ω · c.
m, still more preferably 1.0 × 10 ⁵ Ω · cm to 8.
It is 0 × 10 ⁹ Ω · cm. Volume specific resistance value is 1.0 ×
If it exceeds 10 ¹⁰ Ω · cm, the surface electrical resistance of the magnetic recording medium obtained is undesirably high.

The desorption rate of the oxide fine particles of the filler material is 15
% Or less, more preferably 12% or less.
When the desorption rate of the oxide fine particles exceeds 15%, uniform dispersion in the vehicle may be hindered by the desorbed oxide fine particles during the production of the magnetic paint, and the resulting powder is obtained. Magnetic recording media do not have sufficient durability.

The oxide fine particle powder in the filler material is as follows:
Aluminum oxide, zirconium oxide, cerium oxide,
One or more oxide fine particles selected from titanium oxide, silicon oxide and molybdenum oxide. In consideration of the durability of the obtained magnetic recording medium, it is preferable to use one or more kinds of oxide fine particles selected from aluminum oxide, zirconium oxide and cerium oxide.

The average particle diameter of the oxide fine particles is 0.00
1 to 0.07 μm, more preferably 0.002 to 0.0
5 μm.

The average particle diameter of the oxide fine particles is 0.00
If it is less than 1 μm, the oxide fine particle powder becomes too fine, and handling becomes difficult. If it exceeds 0.07 μm, the particle size of the oxide fine particle powder becomes too large with respect to the particle size of the hematite particles.
The adhesion strength of the hematite particle powder to the particle surface becomes insufficient.

The attached amount of the oxide fine particles is 0.1 to 20% by weight based on the hematite particles.

When the amount is less than 0.1% by weight, it is difficult to obtain a filler material having a sufficient polishing effect because the amount of the oxide fine particles attached is small. When the content is more than 20% by weight, the obtained filler material has a sufficient polishing effect, but since the amount of the attached oxide fine particles is large, the oxide fine particles are easily detached from the surface of the hematite particles. It is difficult to obtain a magnetic recording medium having excellent durability. Preferably it is 0.15 to 15% by weight, more preferably 0.2 to 10% by weight.

The silicon compound in the filler material according to the present invention is produced from the tetraalkoxysilane represented by the formula 1 through a heating step.

[0050]

Embedded image embedded image Si (OR) ₄ R: C ₁ -C ₅ alkyl group

Examples of the tetraalkoxysilane include tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane and tetrapentyloxysilane. Considering the effect of fixing the oxide fine particles by tetraalkoxysilane, tetraethoxysilane and tetramethoxysilane are preferable.

The coating amount of the silicon compound generated from the tetraalkoxysilane is preferably 0.01 to 5.0% by weight in terms of Si with respect to the filler material. It is more preferably 0.02 to 4.0% by weight, and even more preferably 0.03 to 3.0% by weight.

When the amount of the silicon compound formed from the tetraalkoxysilane is less than 0.01% by weight, an insufficient amount of the oxide fine particles adhering to the surface of the hematite particles is insufficient. In addition, since the oxide fine particles are easily detached from the particle surface of the hematite particles, it is difficult to obtain a magnetic recording medium having excellent durability.

With a coverage of 0.01-5.0% by weight,
Since the oxide fine particle powder adhering to the particle surface of the hematite particle powder can be sufficiently fixed, 5.0 is obtained.
There is no point in coating more than necessary by weight.

The filler material according to the present invention may be, if necessary,
The particle surface of the hematite particle powder is coated in advance with one or more intermediate coatings selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. The desorption of oxide fine particles from the particle surface of the hematite particle powder can be further reduced as compared with the case where the particles are not coated with the intermediate coating.

The coating amount of the intermediate coating was calculated by converting the amount of the hematite particles coated with the intermediate coating into Al,
O ₂ terms or terms of Al quantity and 0.01 to 20 wt% in total of SiO ₂ equivalent amount is preferred.

If the amount is less than 0.01% by weight, the effect of improving the desorption rate of the oxide fine particles cannot be obtained. 0.01 ~
When the coating amount is 20% by weight, the effect of improving the desorption rate of the oxide fine particles can be sufficiently obtained, so that it is meaningless to cover more than 20% by weight more than necessary.

The filler material according to the present invention coated with the intermediate coating has substantially the same particle size, geometric standard deviation, and BET ratio as those of the filler material according to the present invention not coated with the intermediate coating. It has a surface area value and a volume resistivity value. The desorption rate of the oxide fine particles is improved by coating with the intermediate coating, and the desorption rate of the oxide fine particles is 12%.
% Or less, more preferably 10% or less.

Next, the magnetic recording medium according to the present invention will be described.

As the non-magnetic base material of the magnetic recording medium according to the present invention, synthetic materials of polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamide imide, polyimide, etc. which are currently widely used for magnetic recording media are used. A resin film, aluminum, a metal foil or plate such as stainless steel or a variety of papers can be used, and the thickness thereof varies depending on the material, but is usually preferably 1.0 to 300.
μm, more preferably 2.0 to 200 μm.

In the case of a magnetic disk, polyethylene terephthalate is usually used as the nonmagnetic substrate, and its thickness is usually 50 to 300 μm, preferably 60 to 200 μm.
m. In the case of a magnetic tape, in the case of polyethylene terephthalate, the thickness is usually 3 to 100 μm, preferably 4 to 20 μm, and in the case of polyethylene naphthalate, the thickness is usually 3 to 50 μm, preferably 4 to 2 μm.
0 μm, in the case of polyamide, the thickness is usually 2 to 10
μm, preferably 3 to 7 μm.

The magnetic particles contained in the magnetic recording layer of the magnetic recording medium according to the present invention include maghemite particles (γ-Fe ₂ O ₃ ) and magnetite particles ( FeO ₂ ).
_x -Fe ₂ O ₃ , 0 <x ≦ 1) Co-coated magnetic iron oxide particles obtained by coating Co or Co and Fe on magnetic iron oxide particles, such as Co-coated magnetic iron oxide particles F on powder
e, Co-coated magnetic iron oxide particles containing different elements such as Co, Al, Ni, P, Zn, Si, B, and rare earth metals, metal magnetic particles containing iron as a main component, other than iron Iron alloy magnetic particle powder containing Co, Al, Ni, P, Zn, Si, B and rare earth metal, Ba, Sr or B
Plate-like magnetoplumbite-type ferrite particles containing a-Sr and Co, N
i, Zn, Mn, Mg, Ti, Sn, Zr, Nb, C
Any of plate-like magnetoplumbite ferrite particles and the like containing one or more coercive force reducing agents selected from divalent and tetravalent metals such as u and Mo can be used.

In consideration of the recent high-density recording of the magnetic recording medium, as the magnetic particles, metal magnetic particles containing iron as a main component and Co, Al, Ni, other than iron,
Iron alloy magnetic particles containing P, Zn, Si, B, rare earth metals, etc. are preferred.

The shape of the magnetic particles is not limited to acicular,
It may be any of a cubic shape, a plate shape, and the like. Here, the term "needle-shaped" means not only a needle-like shape in a literal sense but also a spindle-shaped or rice-grained shape.

The magnetic particle powder has an average major axis diameter (average plate diameter in the case of plate-like particles) of 0.01 to 0.50 μm, preferably 0.03 to 0.30 μm, and an average minor axis diameter. (Average thickness in the case of plate-like particles) 0.0007 to 0.17μ
m, preferably 0.003 to 0.10 μm, and the geometric standard deviation value is 2.5 or less, preferably 1.01 to 2.3.
It is.

When the shape of the magnetic particles is acicular,
The axial ratio is 3 or more, preferably 5 or more, and in consideration of dispersibility in a vehicle at the time of production of the magnetic coating material, the upper limit is 15 and preferably 10.

When the particle shape of the magnetic particles is plate-like, the plate-like ratio is 2 or more, preferably 3 or more, and the upper limit value is 50 in consideration of dispersibility in a vehicle at the time of manufacturing a magnetic paint. And preferably 45.

The BET specific surface area value of the magnetic particle powder is 15
m ² / g or more, preferably 20 m ² / g or more. In consideration of the dispersibility in the vehicle during the production of the magnetic paint, the upper limit is preferably 100 m ² / g, more preferably 80 m ² / g.

The magnetic properties of the magnetic particles are as follows.
9.8 to 318.3 kA / m (500 to 4,000 O
e), preferably 43.8 to 318.3 kA / m (55
0 to 4,000 Oe) and the saturation magnetization is 50 to 1
^{70Am 2 / kg (50~170emu / g} ), preferably 60~170Am ² / kg (60~170emu /
g).

The magnetic characteristics of the magnetic particle powder are as follows. In the case of the Co-coated acicular magnetic iron oxide particle powder, the coercive force value is 39.8 to 1
35.3 kA / m (500 to 1,700 Oe), preferably 43.8 to 135.3 kA / m (550 to 1,70 Oe)
0 Oe), and the saturation magnetization value is 50 to 90 Am ² / k
g (50-90 emu / g), preferably 60-90 A
m ² / kg (60-90 emu / g).

In the case of acicular metal magnetic particles or acicular iron alloy magnetic particles containing iron as a main component, the coercive force value is 63.7.
２278.5 kA / m (800 to 3,500 Oe), preferably 71.6 to 278.5 kA / m (900 to 3,
500 Oe) and the saturation magnetization is 90 to 170 Am
² / kg (90-170 emu / g), preferably 10
^{0~170Am 2 / kg (100~170emu / g} )
It is.

In the case of plate-like magnetoplumbite type ferrite particles, the coercive force value is 39.8 to 318.3 kA /
m (500-4,000 Oe), preferably 51.7-
318.3 kA / m (650 to 4,000 Oe) and a saturation magnetization of 40 to 70 Am ² / kg (40 to 70 Oe).
emu / g), preferably 45-70 Am ² / kg (4
5 to 70 emu / g).

As the binder resin contained in the magnetic recording layer of the magnetic recording medium according to the present invention, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate -Maleic anhydride copolymer, vinylidene chloride, polyurethane resin, styrene-butadiene copolymer, butadiene-acrylonitrile copolymer, polyvinyl butyral, cellulose derivative such as nitrocellulose, polyester resin, synthetic rubber resin such as polybutadiene, epoxy resin , Polyamide resin,
Polyisocyanate, electron beam-curable acrylic urethane resin and the like and a mixture thereof can be used.

Further, each binder resin has --OH, --COO
_{H, -SO 3 M, -OPO 2} M 2, polar groups such as -NH ₂ (where, M is H, Na, a K.) May be contained. Considering dispersibility of the magnetic particles and in a vehicle of the filler material in the manufacture of magnetic coating, -COOH, binder resin containing -SO ₃ M are preferable as a polar group.

The coating thickness of the magnetic recording layer in the present invention is:
It is in the range of 0.01 to 5.0 μm. If the thickness is less than 0.01 μm, it is not preferable because uniform application is difficult and uneven coating is likely to occur. If it exceeds 5.0 μm, it becomes difficult to obtain desired electromagnetic conversion characteristics due to the influence of a demagnetizing field. Preferably it is in the range of 0.05 to 1.0 μm.

The mixing ratio of the magnetic particle powder and the binder resin in the magnetic recording layer is such that the binder resin is 5 to 50 parts by weight, preferably 6 to 30 parts by weight based on 100 parts by weight of the magnetic particle powder.

When the amount of the binder resin exceeds 50 parts by weight, the amount of the magnetic particle powder in the magnetic recording layer is too small, so that the packing ratio of the magnetic particle powder is reduced and the magnetic properties are reduced. 5
If the amount is less than 10 parts by weight, the amount of the binder resin is too small relative to the amount of the magnetic particle powder, so that the magnetic particle powder is not sufficiently dispersed in the magnetic paint. It is difficult to obtain a smooth coating film. Further, since the magnetic particle powder is not sufficiently bound by the binder resin, the obtained coating film tends to be brittle.

The mixing ratio of the magnetic particles and the filler in the magnetic recording layer is such that the filler is 1 to 30 parts by weight, preferably 3 to 25 parts by weight based on 100 parts by weight of the magnetic particles.

When the amount of the filler material is less than 1 part by weight, the amount of the filler material contained in the magnetic recording layer is too small.
The durability of the magnetic recording medium becomes insufficient. Filler material is 3
If the amount exceeds 0 parts by weight, sufficient durability can be imparted to the magnetic recording medium, but nonmagnetic components increase in the magnetic recording layer, which is disadvantageous for increasing the density of the magnetic recording medium. Becomes

The magnetic recording layer may contain a commonly used lubricant, abrasive, antistatic agent and the like, if necessary.

The magnetic recording medium according to the third aspect of the present invention has a coercive force value of 3 when the filler material according to the present invention whose particle surface is not coated with an intermediate coating is used as the filler material.
9.8 to 318.3 kA / m (500 to 4,000 O
e), preferably 43.8 to 318.3 kA / m (55
0 to 4,000 Oe), the squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, and the glossiness of the coating film is 165 to 300.
%, Preferably 170 to 300%, the surface roughness Ra of the coating film
Is 10.0 nm or less, preferably 2.0 to 9.5 nm,
More preferably, 2.0 to 9.0 nm, and Young's modulus is 126.
To 160, preferably 128 to 160, and the surface electric resistance value of the coating film is 1.0 × 10 ¹⁰ Ω / cm ² or less, preferably 7.5 × 10 ⁹ Ω / cm ² or less, more preferably 5.0 × 10 ⁹ Ω / cm ² or less.
It has a running resistance of 10 ⁹ Ω / cm ² or less, a running durability of 23 minutes or more, preferably 24 minutes or more, and a magnetic head cleaning property of B or A, preferably A.

In the magnetic recording medium according to the third aspect of the present invention, when the filler material according to the present invention whose particle surface is coated with an intermediate coating is used as the filler material, the coercive force value is 39.
8 to 318.3 kA / m (500 to 4,000 Oe),
Preferably 43.8 to 318.3 kA / m (550 to
4,000 Oe) and a squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) of 0.85 to 0.95, preferably 0.8
6 to 0.95, the glossiness of the coating film is 170 to 300%, preferably 175 to 300%, and the surface roughness Ra of the coating film is 9.5.
nm or less, preferably 2.0 to 9.0 nm, more preferably 2.0 to 8.5 nm, and a Young's modulus of 128 to 160,
It is preferably 130 to 160, and the surface electric resistance value of the coating film is 1.0 × 10 ¹⁰ Ω / cm ² or less, preferably 7.5 × 1.
0 ⁹ Ω / cm ² or less, more preferably 5.0 × 10 ⁹ Ω / cm ²
cm ² or less, running durability of 24 minutes or more, preferably 25 minutes or more.
Min or more, and the cleaning property of the magnetic head is B or A, preferably A.

In consideration of high-density recording and the like, acicular metal magnetic particles or acicular iron alloy magnetic particles containing iron as a main component are used as the magnetic particles, and the surface of the particles is an intermediate coating as a filler material. When the uncoated filler material according to the present invention is used, the coercive force value is 63.7 to 278.5.
kA / m (800-3,500 Oe), preferably 7
1.6 to 278.5 kA / m (900 to 3,500 O
e), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm)
Is 0.85 to 0.95, preferably 0.86 to 0.9
5. The glossiness of the coating film is 190 to 300%, preferably 19
5 to 300%, the coating film surface roughness Ra is 9.0 nm or less, preferably 2.0 to 8.5 nm, more preferably 2.0 to 8.5 nm.
8.0 nm, Young's modulus is 126 to 160, preferably 1.
28 to 160, the surface electric resistance of the coating film is 1.0 × 10 ¹⁰
Ω / cm ² or less, preferably 7.5 × 10 ⁹ Ω / cm ² or less, more preferably 5.0 × 10 ⁹ Ω / cm ² or less, and running durability of 25 minutes or more, preferably 26 minutes or more. The cleaning property of the head is B or A, preferably A.

As the magnetic particles, needle-like metal magnetic particles containing iron as a main component or needle-like iron alloy magnetic particles are used, and the filler according to the present invention whose particle surface is coated with an intermediate coating as a filler material When the material is used, the coercive force value is 63.7 to 278.5 kA / m (800 to 3,5 kA / m).
00Oe), preferably 71.6 to 278.5 kA / m
(900 to 3,500 Oe), squareness ratio (residual magnetic flux density B
r / saturation magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, and the glossiness of the coating film is 195 to 30.
0%, preferably 200-300%, coating film surface roughness Ra
Is 8.5 nm or less, preferably 2.0 to 8.0 nm, more preferably 2.0 to 7.5 nm, and the Young's modulus is 128 to
160, preferably 130 to 160, and the surface electric resistance value of the coating film is 1.0 × 10 ¹⁰ Ω / cm ² or less, preferably 7.
5 × 10 ⁹ Ω / cm ² or less, more preferably 5.0 × 10 ⁹ Ω / cm ² or less
⁹ Ω / cm ² or less, running durability of 26 minutes or more, preferably 27 minutes or more, and head cleaning property of B or A, preferably A.

In the magnetic recording medium according to the fourth aspect of the present invention, a non-magnetic underlayer containing non-magnetic particles and a binder resin is formed between the non-magnetic support and the magnetic recording layer.

As the non-magnetic particle powder for the non-magnetic underlayer,
Usually, a nonmagnetic inorganic powder used for a nonmagnetic underlayer for a magnetic recording medium can be used. Specifically, hematite, hydrous iron oxide, titanium oxide, zinc oxide, tin oxide, tungsten oxide, silicon dioxide, α-alumina,
β-alumina, γ-alumina, chromium oxide, cerium oxide, silicon carbide, titanium carbide, silicon nitride, boron nitride, calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, titanium Barium acid or the like can be used alone or in combination, particularly, hematite,
Hydrous iron oxide, titanium oxide and the like are preferred.

In order to improve the dispersibility in the vehicle during the production of the non-magnetic paint, if necessary, the surface of the non-magnetic particle powder may be treated with aluminum hydroxide, aluminum oxide, silicon hydroxide, The surface may be treated with an oxide of silicon or the like, and if necessary, to improve various characteristics such as light transmittance, surface electric resistance, mechanical strength, surface smoothness, and durability of the obtained magnetic recording medium. , A inside the particle
l, Ti, Zr, Mn, Sn, Sb and the like may be contained.

The non-magnetic particle powder includes particles of various shapes, such as spherical, granular, octahedral, hexahedral, polyhedral, etc., acicular, spindle-shaped, rice granular, etc. There are plate-like particle powders and the like. Considering the surface smoothness of the obtained magnetic recording medium, the particle shape of the nonmagnetic particle powder is preferably acicular.

When the non-magnetic particle powder has a granular particle shape, the average particle diameter is 0.01 to 0.3 μm, preferably 0.015 to 0.25 μm, more preferably 0.02 to 0.2 μm. 2 μm, and when the particle shape is acicular,
The average major axis diameter is 0.01 to 0.3 μm, preferably 0.0
15 to 0.25 μm, more preferably 0.02 to 0.2
μm, and when the particle shape is plate-like, the average plate surface diameter is 0.1 μm.
01 to 0.3 μm, preferably 0.015 to 0.25 μm
m, more preferably 0.02 to 0.2 μm.

When the particle shape is acicular, the axial ratio is 2 to 2.
20, preferably 2.5 to 15, more preferably 3 to 1
0, when the particle shape is plate-like, the plate-like ratio is 2 to 50,
Preferably it is 2.5-48, More preferably, it is 3-46.

The nonmagnetic underlayer has a coating thickness of 0.2 to 1
A range of 0.0 μm is preferred. If it is less than 0.2 μm, it becomes difficult to improve the surface roughness of the non-magnetic support. In consideration of the thinning of the magnetic recording medium and the surface smoothness of the coating film, the thickness is more preferably in the range of 0.5 to 5.0 μm.

As the binder resin in the non-magnetic underlayer, the binder resin used in forming the magnetic recording layer can be used.

The mixing ratio of the non-magnetic particle powder and the binder resin in the non-magnetic underlayer is 5 to 2000 parts by weight, preferably 100 to 1000 parts by weight, based on 100 parts by weight of the binder resin. is there.

When the amount of the non-magnetic particles is less than 5 parts by weight, the amount of the non-magnetic particles in the non-magnetic paint is too small.
When a coating film is formed, a layer in which a nonmagnetic particle powder is continuously dispersed cannot be obtained, and the smoothness of the coating film surface becomes insufficient. 200
When the amount exceeds 0 parts by weight, the nonmagnetic particle powder is not sufficiently dispersed in the nonmagnetic paint because the amount of the nonmagnetic particle powder is too large relative to the amount of the binder resin, and as a result, a coating film is formed. In this case, it is difficult to obtain a coating film having a sufficiently smooth surface. Further, since the nonmagnetic particle powder is not sufficiently bound by the binder resin, the obtained coating film tends to be brittle.

It is to be noted that a known lubricant, an abrasive, an antistatic agent and the like used for a magnetic recording medium are required for the non-magnetic underlayer to be 0.1 to 50 parts by weight based on 100 parts by weight of the binder resin.
It may be contained in an amount of about parts by weight.

The nonmagnetic underlayer according to the fourth aspect of the present invention has a glossiness of the coating film of 176 to 300%, preferably 180 to 300%.
%, More preferably 184 to 300%, and the coating film surface roughness Ra is 0.5 to 8.5 nm, preferably 0.5 to 8.5 nm.
8.0 nm, and the strength of the coating film is such that the Young's modulus (relative value) is 124 to 160, preferably 126 to 160, and the surface electric resistance value is 1.0 × 10 ¹⁵ Ω / cm ² or less, preferably 1 .0 is × ^{10 14} Ω / cm ² or less.

In the magnetic recording medium according to the fourth aspect of the present invention, when the filler material according to the present invention whose particle surface is not coated with an intermediate coating is used as the filler material, the coercive force value is 39.8 to 318. 3 kA / m (500 to 4,000
Oe), preferably 43.8 to 318.3 kA / m (5
50 to 4,000 Oe), squareness ratio (residual magnetic flux density Br /
Saturation magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, and the glossiness of the coating film is 170 to 300.
%, Preferably 175 to 300%, the coating film surface roughness Ra is 9.5 nm or less, preferably 2.0 to 9.0 nm, more preferably 2.0 to 8.5 nm, and the Young's modulus is 128 to 1.
60, preferably 130 to 160, and the surface electric resistance value is 1.0 × 10 ¹⁰ Ω / cm ² or less, preferably 7.5 ×.
10 ⁹ Ω / cm ² or less, more preferably 5.0 × 10 ⁹
Ω / cm ² or less, running durability of 23 minutes or more, preferably 24 minutes or more, and the magnetic head cleaning property is B or A,
Preferably it is A.

The magnetic recording medium according to the fourth aspect of the present invention has a coercive force of 39.8 to less when the filler according to the present invention coated with an intermediate coating is used as the filler.
318.3 kA / m (500 to 4,000 Oe), preferably 43.8 to 318.3 kA / m (550 to 4.0 Oe)
00Oe), and the squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.96.
0.95, the glossiness of the coating film is 175 to 300%, preferably 180 to 300%, and the coating film surface roughness Ra is 9.0 nm or less, preferably 2.0 to 8.5 nm, more preferably 2.0 ~ 8.0 nm, Young's modulus is 130 ~ 160, preferably 132 ~ 160, surface electric resistance is 1.0 × 10
¹⁰ Ω / cm ² or less, preferably 7.5 × 10 ⁹ Ω / c
m ² or less, more preferably 5.0 × 10 ⁹ Ω / cm ² or less, running durability of 24 minutes or more, preferably 25 minutes or more,
The cleaning property of the magnetic head is B or A, preferably A
It is.

In consideration of high-density recording, etc., as the magnetic particles, needle-like metal magnetic particles or iron-alloy magnetic particles containing iron as a main component are used. When the uncoated filler material according to the present invention is used, the coercive force value is 63.7 to 278.5.
kA / m (800-3,500 Oe), preferably 7
1.6 to 278.5 kA / m (900 to 3,500 O
e), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm)
Is 0.85 to 0.95, preferably 0.86 to 0.9
5. The glossiness of the coating film is 195 to 300%, preferably 20
0 to 300%, the coating film surface roughness Ra is 9.0 nm or less, preferably 2.0 to 8.5 nm, more preferably 2.0 to 8.5 nm.
8.0 nm, Young's modulus is 128 to 160, preferably 1
30 to 160, the surface electric resistance value of the coating film is 1.0 × 10 ¹⁰
Ω / cm ² or less, preferably 7.5 × 10 ⁹ Ω / cm ² or less, more preferably 5.0 × 10 ⁹ Ω / cm ² or less, and running durability of 25 minutes or more, preferably 26 minutes or more. The cleaning property of the head is B or A, preferably A.

As the magnetic particles, needle-like metal magnetic particles containing iron as a main component or needle-like iron alloy magnetic particles are used, and the filler according to the present invention whose particle surface is coated with an intermediate coating as a filler material When the material is used, the coercive force value is 63.7 to 278.5 kA / m (800 to 3,5 kA / m).
00Oe), preferably 71.6 to 278.5 kA / m
(900 to 3,500 Oe), squareness ratio (residual magnetic flux density B
r / saturation magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, and the glossiness of the coating film is 200 to 30.
0%, preferably 205-300%, coating film surface roughness Ra
Is 8.5 nm or less, preferably 2.0 to 8.0 nm, more preferably 2.0 to 7.5 nm, and the Young's modulus is 130 to
160, preferably 132 to 160, and the surface electric resistance of the coating film is 1.0 × 10 ¹⁰ Ω / cm ² or less, preferably 7.
5 × 10 ⁹ Ω / cm ² or less, more preferably 5.0 × 10
⁹ Ω / cm ² or less; running durability of 26 minutes or more, preferably 27 minutes or more;
Preferably it is A.

Next, a method for producing a filler material according to the present invention will be described.

[0102] The filler material according to the present invention is obtained by adhering fine oxide particles to the surface of hematite particles, then adding tetraalkoxysilane to the hematite particles to which the fine oxide particles are adhered, and subjecting to heat treatment. Can be obtained by:

The adhesion of the oxide fine particle powder to the surface of the hematite particle powder is carried out by using one or two or more kinds selected from aluminum oxide, zirconium oxide, cerium oxide, titanium oxide, silicon oxide and molybdenum oxide. The oxide fine particle powder may be mechanically mixed and stirred, or the hematite particle powder and the colloid solution containing the oxide fine particle powder may be mechanically mixed and stirred. Considering the uniform treatment of the oxide fine particle powder on the surface of the hematite particle powder, it is preferable to use a colloid solution containing the oxide fine particle powder. In the case where a colloid solution is used, it is preferable to dry the mixture after mixing and stirring with the hematite particle powder.

As the oxide fine particle powder, any of a synthesized one and a commercially available one can be used. Examples of the colloid solution containing the oxide fine particle powder include a colloid solution containing each oxide fine particle powder such as aluminum oxide, zirconium oxide, cerium dioxide, titanium dioxide, silicon dioxide, and molybdenum oxide.

As the colloid solution containing the aluminum oxide fine particle powder, an alumina sol solution or the like (manufactured by Nissan Chemical Industries, Ltd.) can be used.

Examples of the colloid solution containing zirconium oxide fine particle powder include NZS-20A, NZS-30A,
ZS-30B or the like (all trade names, manufactured by Nissan Chemical Industries, Ltd.) can be used.

As a colloid solution containing cerium oxide fine particles, a ceria sol solution (manufactured by Nissan Chemical Industries, Ltd.) can be used.

As the colloid solution containing the titanium oxide fine particle powder, STS-01, STS-02, etc. (both trade names, manufactured by Ishihara Sangyo Co., Ltd.) can be used.

Examples of the colloid solution containing silicon oxide fine particles include Snowtex-XS and Snowtex-
S, Snowtex UP, Snowtex-20, Snowtex-30, Snowtex-40, Snowtex-C, Snowtex-N, Snowtex-O,
Snowtex-SS, Snowtex-20L, Snowtex-OL, etc. (all are trade names, manufactured by Nissan Chemical Industries, Ltd.) can be used.

Addition amount of oxide fine particles or oxide fine particles
The amount of the colloid solution containing the powder
For powder, oxide fine powder or colloidal solution
The oxide fine particle powder contained is Al₂O₃Conversion, ZrO₂
Conversion, CeO₂Conversion, TiO ₂Conversion, SiO₂Conversion or
MoO₃With respect to 100 parts by weight of the hematite particle powder,
A range of 0.1 to 20 parts by weight is preferred. 0.1 parts by weight
When full, oxide fine particles are
Insufficient amount of powder powder and sufficient polishing effect
Filler material cannot be obtained. If it exceeds 20 parts by weight
, The obtained filler material has a sufficient polishing effect
However, due to the large amount of oxide fine particles attached,
Powder easily detaches from the surface of hematite particles
Magnetic recording media with excellent durability and surface smoothness.
It is hard to be.

In order to uniformly adhere the oxide fine particle powder to the particle surface of the hematite particle powder, it is preferable to disintegrate the hematite particle powder in advance using a pulverizer.

The apparatus for mixing and stirring the hematite particle powder and the oxide fine particle powder and the mixing and stirring of the tetraalkoxysilane and the hematite particle powder having the oxide fine particle powder adhered to the particle surface include a powder layer. Preferably, a device capable of applying a shearing force is used. In particular, a device capable of simultaneously performing shearing, spatula and compression, for example, a wheel-type kneader, a ball-type kneader, a blade-type kneader, or a roll-type kneader is used. be able to. In practicing the present invention, a wheel-type kneader can be used more effectively.

Specific examples of the wheel type kneader include edge runners (synonyms for “mix miller”, “Simpson mill”, and “sand mill”), multi-mul, stots mill, wet pan mill, conner mill, and ring miller. And the like, preferably an edge runner, a multiple, a Stotts mill, a wet pan mill, and a ring muller, and more preferably an edge runner. Examples of the ball-type kneader include a vibration mill and the like. Specific examples of the blade type kneader include a Henschel mixer, a planetary mixer, and a Nauta mixer. Specific examples of the roll-type kneader include an extruder.

The conditions during mixing and stirring are such that the linear load is 19.6 to 1960 N / N so that the oxide fine particle powder adheres to the surface of the hematite particle powder as uniformly as possible.
cm (2-200 kg / cm), preferably 98-14
70 N / cm (10 to 150 kg / cm), more preferably 147 to 980 N / cm (15 to 100 kg / c)
m), the treatment time is 5 to 120 minutes, preferably 10 to 90 minutes.
The processing conditions may be appropriately adjusted within the range of minutes. The stirring speed is 2 to 2000 rpm, preferably 5 to 1000 rpm
pm, more preferably in the range of 10 to 800 rpm.

After the oxide fine particle powder is adhered to the particle surface of the hematite particle powder, tetraalkoxysilane is added, mixed, stirred and heated, whereby the oxide fine particles adhering to the particle surface of the hematite particle powder are heated. The powder is immobilized with a silicon compound generated from tetraalkoxysilane.

The conditions during the mixing and stirring are such that the linear load is 19.6 to 1960 N / cm (2) so that the tetraalkoxysilane is coated as uniformly as possible on the surface of the hematite particles to which the oxide fine particles are attached. ~ 200
Kg / cm), preferably 98-1470 N / cm (1
0 to 150 kg / cm), more preferably 147 to 98
0N / cm (15-100Kg / cm), processing time is 5
The processing conditions may be appropriately adjusted within a range of from 120 to 120 minutes, preferably from 10 to 90 minutes. The stirring speed is 2 to 2000
The processing conditions may be appropriately adjusted within the range of rpm, preferably 5 to 1000 rpm, more preferably 10 to 800 rpm.

The addition amount of the tetraalkoxysilane is preferably 0.05 to 70 parts by weight based on 100 parts by weight of the hematite particle powder. If the amount is less than 0.05 parts by weight, it is difficult to sufficiently adhere the oxide fine particle powder to such an extent that the polishing effect and durability can be improved. With the addition amount of 0.05 to 70 parts by weight, the oxide fine particle powder can be sufficiently adhered, so that it is meaningless to add more than 70 parts by weight more than necessary.

The heating temperature is usually preferably from 40 to 200 ° C., more preferably from 60 to 150 ° C. The processing time is preferably from 10 minutes to 36 hours, more preferably from 30 minutes to 24 hours. The tetraalkoxysilane becomes a silicon compound by this heating step.

If necessary, the hematite particle powder is selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide before mixing and stirring with the alkoxysilane solution. May be coated with one or more compounds.

The coating of aluminum with hydroxide or the like is as follows:
To an aqueous suspension obtained by dispersing the hematite particle powder, an aluminum compound, a silicon compound or both compounds are added and mixed and stirred, or, if necessary, by adjusting the pH value after mixing and stirring, On the particle surface of the hematite particle powder, one or two or more compounds selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide,
Next, the mixture is filtered, washed with water, dried and pulverized. If necessary, a deaeration / consolidation treatment may be performed.

As the aluminum compound, aluminum salts such as aluminum acetate, aluminum sulfate, aluminum chloride and aluminum nitrate, and alkali aluminates such as sodium aluminate can be used.

The addition amount of the aluminum compound is 0.01 to 50% by weight in terms of Al with respect to the hematite particle powder. When the content is less than 0.01% by weight, it is difficult to coat a sufficient amount of the intermediate coating on the particle surface to further reduce the detachment of the oxide fine particles from the particle surface of the hematite particle powder, A magnetic recording medium having better durability and surface smoothness cannot be obtained. If it exceeds 50% by weight, it is meaningless to add more than necessary because the coating effect is saturated.

As the silicon compound, No. 3 water glass, sodium orthosilicate, sodium metasilicate and the like can be used.

The addition amount of the silicon compound is 0.01 to 50% by weight in terms of SiO _{2 with} respect to the hematite particle powder. When the content is less than 0.01% by weight, it is difficult to coat a sufficient amount of the intermediate coating on the particle surface to further reduce the detachment of the oxide fine particles from the particle surface of the hematite particle powder, A magnetic recording medium having better durability and surface smoothness cannot be obtained. If it exceeds 50% by weight, it is meaningless to add more than necessary because the coating effect is saturated.

When an aluminum compound and a silicon compound are used in combination, A
It is preferable that the total amount of the amount in terms of 1 and the amount in terms of SiO ₂ is 0.01 to 50% by weight.

Next, a method for manufacturing a magnetic recording medium according to the third and fourth embodiments of the present invention will be described.

The magnetic recording medium according to the present invention is formed by applying a magnetic paint containing magnetic particle powder, a filler material, a binder resin and a solvent on a non-magnetic support by a conventional method to form a coating film. Orientation (Invention 3), a non-magnetic paint containing non-magnetic particle powder, a binder resin and a solvent is applied on a non-magnetic support and dried to form a non-magnetic under layer. A magnetic paint containing a magnetic particle powder, a filler material, a binder resin, and a solvent is applied to form a coating film, and then magnetically oriented (the present invention 4), followed by calendering and curing. be able to.

In kneading and dispersing the magnetic coating material, for example, a kneading machine such as a twin-screw kneader, a twin-screw extruder, a pressure kneader, a two-roll mill, or a three-roll mill can be used. Grinders, attritors, dispersers, homogenizers, ultrasonic dispersers and the like can be used.

When applying the magnetic paint, a gravure coater, reverse roll coater, slit coater,
A die coater or the like can be used. The applied sheet can be oriented in a magnetic field by the orientation of a counter magnet, the orientation of a solenoid magnet, or the like.

As the solvent, there can be used methyl ethyl ketone, toluene, cyclohexanone, methyl isobutyl ketone, tetrahydrofuran, a mixture thereof and the like which are currently widely used for magnetic recording media.

The amount of the solvent used is 65 to 1000 parts by weight in total with respect to 100 parts by weight of the magnetic particle powder. 6
If the amount is less than 5 parts by weight, the viscosity becomes too high when a magnetic coating material is used, and application becomes difficult. If the amount exceeds 1000 parts by weight, the amount of the solvent volatilized when forming a coating film is too large, which is industrially disadvantageous.

[0132]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention is as follows.

The average particle diameter of each particle powder is shown by the average value of the measured constant particle diameters of about 350 particles shown in photographs obtained by enlarging the electron micrograph four times in the vertical and horizontal directions, respectively. Was.

The axial ratio is indicated by the ratio between the average major axis diameter and the average minor axis diameter, and the plate ratio is indicated by the ratio between the average plate surface diameter and the average thickness.

The geometric standard deviation of the particle diameter was shown by the value obtained by the following method. That is, the value obtained by measuring the particle diameter shown in the above enlarged photograph, the actual particle diameter and the number of particles calculated from the measured value, according to a statistical method, the particle on the horizontal axis on the lognormal probability paper The diameter was plotted on the vertical axis as a percentage of the cumulative number of particles belonging to each of the predetermined particle diameter sections (under the integrated screen). Then, the values of the particle diameters corresponding to the cumulative number of particles of 50% and 84.13% were read from this graph, and the geometric standard deviation value =
The value was calculated according to (particle diameter at 84.13% under integrated screen) / (particle diameter at 50% under integrated screen) (geometric mean diameter). The closer the geometric standard deviation value is to 1, the better the particle size distribution.

The specific surface area was indicated by a value measured by the BET method.

The amount of Mn, the amount of Al, and the amount of Si existing inside and on the surface of the hematite particles, the amount of Al in the oxide fine particles present on the surface of the particles of the hematite particles, the Zr
The amount of Ce, the amount of Ti, the amount of Ti, the amount of Si and the amount of Mo, and the amount of Si contained in the silicon compound generated from tetraalkoxysilane are each described in “Fluorescent X-ray Analyzer 3063M
Type ”(manufactured by Rigaku Denki Kogyo Co., Ltd.)
The measurement was performed in accordance with “General X-ray Fluorescence Analysis” of “No.
The Co content of the Co-coated magnetite particle powder and the Co-coated maghemite particle powder was measured in the same manner as in the above-described measuring device and measuring method.

The amount of Si contained in the oxide of silicon, the hydroxide of silicon and the silicon compound formed from the tetraalkoxysilane, and the amount of each Si contained in the fine silicon oxide particles are as follows. The amount of Si was measured at each stage after the treatment step, and the value was obtained by subtracting the amount of Si measured at the stage before the treatment step from the measured value. In addition, coating on the particle surface of acicular hematite particle powder,
The amounts of Al contained in the existing aluminum hydroxide, aluminum oxide, and aluminum oxide fine particle powder were also shown by values obtained by the same method as the above-mentioned Si amount.

The desorption rate (%) of the oxide fine particles adhering to the hematite particle powder was shown by a value obtained by the following method. The closer the desorption rate of the oxide fine particles is to 0%, the smaller the desorption amount of the oxide fine particles from the particle surface of the hematite particle powder.

3 g of filler material and 40 ml of ethanol
After placing in a 0 ml sedimentation tube and performing ultrasonic dispersion for 20 minutes, the mixture was allowed to stand still for 120 minutes to separate the filler material and the separated oxide fine particles depending on the difference in sedimentation speed. Next, 40 ml of ethanol was again added to the filler material, and 2
After performing ultrasonic dispersion for 0 minutes, the mixture was allowed to stand for 120 minutes to separate the filler material and the detached oxide fine particles. The filler material was dried at 80 ° C. for 1 hour, and using the “X-ray fluorescence spectrometer 3063M” (manufactured by Rigaku Corporation),
The amount of Al, the amount of Zr, the amount of Ce, the amount of Ti, the amount of Si, and the amount of Mo are measured in accordance with JIS K0119 “General rules for X-ray fluorescence analysis”, and the value obtained according to the following formula is determined as the desorption rate (%) of the oxide fine particles. And

Desorption rate (%) of oxide fine particles = {(Wa
−We) / Wa} × 100 Wa: Adhesion amount of oxide particles of filler material We: Adhesion amount of oxide particles of filler material after desorption test

The specific volume resistivity of each of the hematite particle powder and the filler material was measured by measuring 0.5 g of the particle powder, and using a KBr tablet molding machine (manufactured by Shimadzu Corporation) at 1.372 × 10 ^7. Pa (140Kg / cm ² )
The sample was subjected to pressure molding at a pressure of 5 ° C. to produce a cylindrical sample to be measured.

Next, after the sample to be measured was exposed to an environment of a temperature of 25 ° C. and a relative humidity of 60% for 12 hours or more, the sample to be measured was set between stainless steel electrodes, and a Wheatstone bridge (TYPE2768 Yokogawa Hokushin Electric Co., Ltd.) And a resistance R (Ω) was measured by applying a voltage of 15V.

Next, the area A (cm ² ) and thickness t ₀ (cm) of the upper surface of the sample to be measured (cylindrical) were measured, and the measured values were inserted into the following equations to obtain the volume resistivity (Ω).・ Cm)
I asked.

Volume specific resistance (Ω · cm) = R × (A / t ₀ )

The viscosity of the paint at 25 ° C. was measured using an E-type viscometer (cone-plate viscometer) EMD-R.
The value of the apparent viscosity at a shear rate of 1.92 sec ^-1 at 25 ° C. was measured using (manufactured by Tokyo Keiki Co., Ltd.).

The magnetic properties of the magnetic particle powder and the magnetic recording medium were measured using a “vibrating sample magnetometer VSM-3S-15” (manufactured by Toei Kogyo Co., Ltd.) and the maximum external magnetic field was 795.8 kA.
/ M (10 kOe).

The thickness of each of the non-magnetic support, the non-magnetic underlayer, and the magnetic recording layer constituting the magnetic recording medium was measured as follows.

Digital electronic micrometer K351C
First, the film thickness (A) of the nonmagnetic support is measured using (manufactured by Anritsu Electric Co., Ltd.). Next, the thickness (B) of the nonmagnetic support and the nonmagnetic underlayer formed on the nonmagnetic support
(Sum of the thickness of the nonmagnetic support and the thickness of the nonmagnetic underlayer)
Is measured in the same manner.

Further, the thickness (C) of the magnetic recording medium obtained by forming the magnetic recording layer on the nonmagnetic underlayer (the thickness of the nonmagnetic support, the thickness of the nonmagnetic underlayer, and the thickness of the magnetic recording layer) Is calculated in the same manner. The thickness of the nonmagnetic underlayer is shown by (B)-(A), and the thickness of the magnetic recording layer is shown by (C)-(B).

The thickness of each layer of the magnetic recording medium having no non-magnetic underlayer is determined by measuring the thickness (A) of the non-magnetic support and the thickness (C) of the magnetic recording medium. Was determined as (C)-(A).

The glossiness of the coating film surface of the magnetic recording layer was determined by measuring the 45 ° glossiness of the coating film using “Gloss Meter UGV-5D” (manufactured by Suga Test Instruments Co., Ltd.).

The surface roughness Ra is “surfcom-57
5A "(manufactured by Tokyo Seimitsu Co., Ltd.) and the center line average roughness of the coating film after calendering was measured.

The running durability of the magnetic recording medium is as follows:
a Durability Tester MDT-3
000 "(Steinberg Associates
(Manufactured by the company), and the actual operation time at a load of 1.96 N (200 gw) and a relative speed of 16 m / s between the head and the tape was evaluated. The longer the actual operating time, the better the running durability.

The cleaning property of the magnetic head of the magnetic recording medium is described in “Media Durability Test”.
er MDT-3000 ”(Steinberg As
load of 1.96 N (2
00gw), at a relative speed of 16 m / s between the head and the tape, the head dirt after the running test was visually evaluated,
The evaluation was performed in the following four stages. The smaller the head dirt, the higher the cleaning performance of the magnetic head.

A: No head dirt. B: Slight head dirt. C: Head dirt. D: Severe dirt on the head.

The surface electric resistance value of the coating film was determined by exposing the coating film to be measured in an environment of a temperature of 25 ° C. and a relative humidity of 60% for 12 hours or more, and then slitting the metal electrode having a width of 6.5 mm to a width of 6 mm. The coated film was placed, a weight of 170 g was attached to each end of the film, and the coated film was adhered to the electrodes, and the measured value was obtained by applying a DC voltage of 500 V between the electrodes.

<Production of Filler Material> Manganese-containing hematite particle powder (particle shape: granular, average particle size 0.30 μm)
m, geometric standard deviation value 1.46, BET specific surface area value 3.6
20 kg of m ² / g, Mn content of 13.3% by weight, and volume resistivity of 2.0 × 10 ⁷ Ω · cm) were entangled with 150 l of pure water using a stirrer in order to loosen agglomeration. The mixture was passed through a “TK pipeline homomixer” (product name, manufactured by Tokushu Kika Kogyo Co., Ltd.) three times to obtain a slurry containing manganese-containing hematite particles.

Subsequently, the slurry containing the manganese-containing hematite particle powder was dispersed in a horizontal sand grinder “Mighty Mill MHG-1.5L” (product name, manufactured by Inoue Seisakusho Co., Ltd.) at a shaft rotation speed of 2000 rpm for 5 minutes.
The slurry was passed twice to obtain a dispersion slurry containing manganese-containing hematite particles.

325 mesh (having a mesh size of 44 μm) of the dispersion slurry containing the obtained manganese-containing hematite particles was obtained.
The sieve residue in m) was 0%. This dispersion slurry was separated by filtration and washed with water to obtain a cake of manganese-containing hematite particle powder. After drying the cake of the manganese-containing hematite particles at 120 ° C., 11.0 kg of dry powder was obtained.
Into an edge runner “MPUV-2” (product name, manufactured by Matsumoto Cast Iron Works, Ltd.), and 294 N / cm (3
(0 Kg / cm) for 30 minutes with stirring to loosen the aggregation of the particle powder.

Next, a ceria sol containing CeO ₂ fine particles having an average particle diameter of 0.01 μm (CeO ₂ content 20
Weight%, manufactured by Nissan Chemical Industry Co., Ltd.)
After mixing and stirring with a linear load of 20 cm (40 Kg / cm) for 20 minutes, drying was performed, and cerium oxide fine particles were attached to the surface of the manganese-containing hematite particles. In addition,
The stirring speed at this time was 22 rpm. As a result of the fluorescent X-ray analysis, the adhesion amount of the cerium oxide fine particles in the obtained manganese-containing hematite particles was 1.90% by weight in terms of CeO _{2 with} respect to the manganese-containing hematite particles in which the cerium oxide fine particles existed. there were.

As a result of electron microscopic observation, the presence of the added cerium oxide fine particle powder was hardly recognized, so that almost all of the added cerium oxide fine particle powder adhered to the surface of the manganese-containing hematite particle powder. Was admitted.

Next, tetraethoxysilane KBE 04
110 g (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) was added over 10 minutes while operating the edge runner, and the mixture was further mixed and stirred at a linear load of 392 N / cm (40 Kg / cm) for 20 minutes. The manganese-containing hematite particles having the cerium oxide particles attached thereto were coated with tetraethoxysilane. The stirring speed at this time was 22 rpm.

The obtained manganese-containing hematite particle powder was subjected to a heat treatment at 120 ° C. for 12 hours using a dryer, so that the cerium oxide fine particles were formed on the surface of the manganese-containing hematite particle powder by a silicon compound generated from tetraethoxysilane. The powder was immobilized, and at the same time, ethanol produced by hydrolysis of tetraethoxysilane and the like, residual moisture and the like were volatilized. The obtained composite non-magnetic particle powder was observed by an electron microscope, and after the immobilization treatment with the silicon compound generated from tetraethoxysilane, almost no cerium oxide fine particle powder was present. It was confirmed that almost all the particles were fixed on the surface of the manganese-containing hematite particles.

The average particle diameter of the obtained composite nonmagnetic particle powder was 0.30 μm, the geometric standard deviation of the particle diameter was 1.46,
The BET specific surface area value is 4.8 m ² / g, the volume resistivity value is 8.7 × 10 ⁸ Ω · cm, and the desorption rate of the oxide fine particles is 7.
5%. As a result of X-ray fluorescence analysis, the coating amount of the silicon compound generated from tetraethoxysilane was 0.129% by weight in terms of Si.

<Manufacture of Magnetic Recording Medium> Acicular metal magnetic particles containing iron as a main component (average major axis diameter 0.115 μm, average minor axis diameter 0.0182 μm, axial ratio 6.3, coercive force value 15)
2.0 kA / m (1,910 Oe), saturation magnetization 131
Am ² / kg (131 emu / g)) 100 parts by weight, 10.0 parts by weight of a vinyl chloride-vinyl acetate copolymer resin having a sodium sulfonate group, cyclohexanone 23.3
Parts by weight, 10.0 parts by weight of methyl ethyl ketone, 7.0 parts by weight of the composite non-magnetic particle powder obtained above, and 1.0 part by weight of carbon black fine particle powder (trade name: # 3250B, manufactured by Mitsubishi Kasei Corporation) After kneading for 20 minutes, 79.6 parts by weight of toluene, 110.2 parts by weight of methyl ethyl ketone and 1 part of cyclohexanone were added to the kneaded material.
7.8 parts by weight were added for dilution, and then mixed and dispersed by a sand grinder for 3 hours to obtain a mixed dispersion.

To the above mixed dispersion, 33.3 parts by weight of a 1/1 solution of methyl ethyl ketone / cyclohexanone containing 10.0 parts by weight of a solid content of a polyurethane resin having a sodium sulfonate group was added, and the mixture was further subjected to a sand grinder for 30 minutes. After mixing and dispersing the mixture using a filter, the mixture was filtered through a filter having an opening of 1 μm, and the filtered substance obtained was mixed with 1.0 ml of myristic acid.
5 parts of methyl ethyl ketone / toluene / cyclohexanone containing 0 parts by weight and 3.0 parts by weight of butyl stearate.
5/3/2 of methyl ethyl ketone / toluene / cyclohexanone containing 12.1 parts by weight of a 3/2 solution and 5.0 parts by weight of a trifunctional low molecular weight polyisocyanate (trade name: E-31, manufactured by Takeda Pharmaceutical Co., Ltd.) 15.2 parts by weight of the solution was mixed with stirring to produce a magnetic paint.

The composition of the obtained magnetic paint was as follows. Magnetic particle powder 100.0 parts by weight, vinyl chloride-vinyl acetate copolymer resin 10.0 parts by weight, polyurethane resin 10.0 parts by weight, composite nonmagnetic particle powder (filler material) 7.0 parts by weight, carbon black fine particle powder 1.0 parts by weight, 1.0 parts by weight of myristic acid, 3.0 parts by weight of butyl stearate, 5.0 parts by weight of trifunctional low molecular weight polyisocyanate, 56.6 parts by weight of cyclohexanone, 141.5 parts by weight of methyl ethyl ketone, 85.4 parts by weight of toluene.

The viscosity of the obtained magnetic paint was 8,210.
cP.

After the magnetic coating material was filtered through a filter having a mesh size of 1 μm, it was applied on a polyethylene terephthalate film having a thickness of 12 μm using a slit coater, and then dried to form a magnetic recording layer. After performing the calendar process and smoothing the surface,
It was cut to a width of 1.27 cm (１ ／ inch). The obtained magnetic tape was allowed to stand in a curing oven at 60 ° C. for 24 hours, and was sufficiently cured to obtain a magnetic tape. The thickness of the obtained coating film was 3.5 μm.

The magnetic properties of the magnetic tape were as follows: the coercive force value was 159.4 kA / m (2,003 Oe), the squareness ratio (Br
/ Bm) was 0.88. The gloss was 236%, the surface roughness Ra was 6.4 nm, the Young's modulus was 135, the surface electrical resistance was 8.7 × 10 ⁸ Ω / cm ² , and the durability was that the running durability time was 28.7 minutes or more. The head cleaning property was A.

[0172]

In the present invention, the most important point is that one or more oxide fine particles selected from aluminum oxide, zirconium oxide, cerium oxide, titanium oxide, silicon oxide and molybdenum oxide are formed on the surface of the hematite particle powder. By using the composite non-magnetic particle powder obtained by fixing the hematite particles and the oxide fine particles with a silicon compound generated from tetraalkoxysilane as a filler material contained in a magnetic recording layer, durability and This is a fact that a magnetic recording medium having excellent surface smoothness can be obtained.

Regarding the reason why a magnetic recording medium having excellent durability can be obtained by using the composite non-magnetic particle powder according to the present invention as a filler material, the present inventor has proposed that the surface of hematite particle powder has high Moh's hardness. By adhering the oxide fine particles and fixing the oxide fine particles with a silicon compound generated from tetraalkoxysilane, detachment of the oxide fine particles from the particle surface of the hematite particle powder could be prevented as much as possible. I think it depends.

Regarding the reason why a magnetic recording medium having excellent surface smoothness can be obtained by using the composite non-magnetic particle powder according to the present invention as a filler material, the present inventor deliberately departed from the particle surface of the composite non-magnetic particle powder. Dispersion in the system is not hindered by the oxide fine particles due to the small amount of oxide fine particles, and the oxide fine particles adhere to the particle surface of the hematite particle powder, causing irregularities on the particle surface, It is considered that mutual contact was suppressed and dispersibility in the vehicle was improved.

Regarding the immobilization mechanism by the silicon compound generated from tetraalkoxysilane, tetraalkoxysilane is easily hydrolyzed by the presence of water,
It is known that silicon dioxide is produced by dehydration by further performing a heat treatment.In the present invention, the hydroxyl groups present on the particle surface of the hematite particles and the oxide fine particles adhering to the particle surface of the hematite particle are known. Hydrolysis of tetraalkoxysilane occurs via a hydroxyl group present on the particle surface of the particles, and by heating and dehydration, the particle surface of hematite particles and oxide fine particles are formed by a silicon compound generated from tetraalkoxysilane. The present inventor believes that it is strongly bonded.

[0176]

Next, examples and comparative examples will be described.

Core Particles 1 to 5 Various hematite particle powders obtained by a known production method were prepared.

Table 1 shows the properties of the hematite particles.

[0179]

[Table 1]

Core Particle 6 A slurry containing a manganese-containing hematite particle powder was obtained in the same manner as in the embodiment of the invention using 20 kg of the manganese-containing hematite particle powder in which the aggregation of the core particles 1 was disentangled and 150 l of water. . The pH value of the redispersed slurry containing the obtained manganese-containing hematite particles was adjusted to 10.5 using an aqueous sodium hydroxide solution, and then water was added to the slurry to adjust the slurry concentration to 98 g / l.
150 liters of this slurry was heated to 60 ° C., and 2722 ml of a 1.0 mol / l sodium aluminate solution (corresponding to 0.5% by weight in terms of Al based on manganese-containing hematite particles) was added to the slurry, After holding for 30 minutes, the pH was adjusted to 7.5 using acetic acid. After maintaining in this state for 30 minutes, filtration, washing with water, drying and pulverization were performed to obtain a manganese-containing hematite particle powder whose particle surface was coated with aluminum hydroxide.

Table 2 shows the main production conditions and Table 3 shows the properties of the obtained manganese-containing hematite particles.

The type A of the coating in the surface treatment step represents an aluminum hydroxide, and S represents a silicon oxide.

Core Particles 7 to 10 Surface-treated hematite particles were obtained in the same manner as in the case of the core particles 6, except that the types of the core particles and the types and amounts of the additives in the surface treatment step were variously changed.

Table 2 shows the main treatment conditions, and Table 3 shows the properties of the obtained surface-treated hematite particles.

[0185]

[Table 2]

[0186]

[Table 3]

Oxide fine particles 1 to 5: Oxide fine particles having the properties shown in Table 4 were prepared as oxide fine particles.

[0188]

[Table 4]

Examples 1 to 10 and Comparative Examples 1 to 5: Types of core particles, types and amounts of oxide particles in the step of adhering oxide particles, line load and time of edge runner treatment, coating with tetraalkoxysilane Composite non-magnetic particle powder was obtained in the same manner as in the embodiment of the invention except that the type and amount of tetraalkoxysilane and the line load and time of the edge runner treatment in the process were variously changed.

The production conditions at this time are shown in Table 5, and various properties of the obtained composite non-magnetic particle powder are shown in Table 6.

Comparative Example 6 (Example of additional test in JP-A-7-192248): 6.0 kg of manganese-containing hematite particles of core particles 1 was mixed with water and stirred, and then 0.1 mol
1000 ml of a 1 / l aqueous sodium hydroxide solution was added to obtain a mixed suspension having a pH of 11.5.

After stirring and mixing the above-mentioned mixed suspension, the mixture was added to a suspension of 0.1%.
5 mol / l sodium aluminate aqueous solution 2200m
1 (corresponding to 0.5% by weight in terms of Al with respect to the manganese-containing hematite particle powder), followed by stirring and mixing.

Next, the suspension was stirred for 0.1%.
The pH was adjusted to 7.1 by adding a mol / l HCl aqueous solution. The required time at that time was 7 minutes. Immediately, the resultant was separated by filtration, washed with water and dried by a conventional method to obtain acicular hematite particles.

5 kg of the obtained needle-like hematite particle powder was put into an edge runner “MPUV-2” (manufactured by Matsumoto Casting Iron Works Co., Ltd.) and a linear load of 588 N / cm (60 kg) was used.
/ Cm) for 60 minutes.

Table 6 shows the properties of the obtained manganese-containing hematite particles.

[0196]

[Table 5]

[0197]

[Table 6]

<Manufacture of Magnetic Recording Medium> Examples 11 to 20, Comparative Examples 7 to 17 Except that the type of the magnetic particles, the type of the filler material and the amount of addition were variously changed, the same as in the embodiment of the present invention was carried out. Thus, a magnetic recording medium was obtained.

Table 7 shows the properties of the magnetic particles 1 to 4 used.
Shown in

[0200]

[Table 7]

Table 8 shows the manufacturing conditions of the magnetic recording medium, and Tables 9 and 10 show its characteristics.

[0202]

[Table 8]

[0203]

[Table 9]

[0204]

[Table 10]

<Production of Nonmagnetic Underlayer> Nonmagnetic particles having the properties shown in Table 11 were prepared as nonmagnetic particles 1 to 6.

[0206]

[Table 11]

Underlayer 1 Hematite particle powder 12 g of non-magnetic particles 1 shown in Table 11
And a binder resin solution (vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 30% by weight and cyclohexanone 70% by weight) and cyclohexanone to obtain a mixture (solid content 72%). The mixture was further kneaded with a plast mill for 30 minutes to obtain a kneaded product.

This kneaded material was mixed with 1.5 mmφ glass beads 9
5 g, additional binder resin solution (30% by weight of polyurethane resin having sodium sulfonate group, 70% by weight of solvent (methyl ethyl ketone: toluene = 1: 1)), cyclohexanone, methyl ethyl ketone and toluene were added to a 140 ml glass bottle, and a paint shaker was added. At 6
Mixing and dispersion were performed for a time to obtain a coating composition. Thereafter, a lubricant was added, and the mixture was further mixed and dispersed with a paint shaker for 15 minutes.

The composition of the obtained non-magnetic paint was as follows.

Nonmagnetic Particle Powder 100 parts by weight Vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 10 parts by weight Polyurethane resin having sodium sulfonate group 10 parts by weight Lubricant (myristic acid: butyl butyl stearate = 1: 1) 2 parts by weight Cyclohexanone 56.9 parts by weight Methyl ethyl ketone 142.3 parts by weight Toluene 85.4 parts by weight

Next, the above-mentioned non-magnetic paint was applied on a polyethylene terephthalate film having a thickness of 12 μm by using a slit coater, and then dried to form a non-magnetic underlayer.

Table 12 shows the main manufacturing conditions and various characteristics of the obtained nonmagnetic underlayer.

Underlayers 2 to 6 A nonmagnetic underlayer was obtained in the same manner as underlayer 1 except that the type of nonmagnetic particle powder was changed in various ways.

Table 12 shows the main manufacturing conditions and various characteristics of the obtained nonmagnetic underlayer.

[0215]

[Table 12]

<Production of Magnetic Recording Medium Having Non-Magnetic Underlayer> Example 21 Using the composite non-magnetic particles of Example 1, a magnetic paint was obtained in the same manner as in the embodiment.

After applying a magnetic paint to a thickness of 15 μm on the underlayer 1 using an applicator, orienting and drying in a magnetic field, and then performing a calendering process,
A curing reaction was performed at 0 ° C. for 24 hours, and slit to a width of 1.27 cm (0.5 inch) to obtain a magnetic tape.

The manufacturing conditions at this time are shown in Table 13, and various characteristics of the obtained magnetic recording medium are shown in Table 14.

Examples 22 to 30 and Comparative Examples 18 to 28 Magnetic recording media were obtained in the same manner as in Example 7, except that the type of the nonmagnetic underlayer and the type of the composite nonmagnetic particles were variously changed.

The manufacturing conditions at this time are shown in Table 13 and the characteristics of the obtained magnetic recording medium are shown in Tables 14 and 15.

[0221]

[Table 13]

[0222]

[Table 14]

[0223]

[Table 15]

[0224]

The filler material according to the present invention can improve the durability and surface smoothness of a magnetic recording medium obtained by using the filler material, and is therefore suitable as a filler material for a magnetic recording medium.

Further, the magnetic recording medium according to the present invention has excellent durability and surface smoothness, and is therefore most suitable for high-density recording.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroko Morii 1-4, Meiji Shinkai, Otake City, Hiroshima Prefecture F-term in the Otake Creation Center of Toda Kogyo Co., Ltd. 5D006 BA10 FA02

Claims (4)

[Claims] 1. An oxide fine particle powder having an average particle diameter of 0.001 to 0.07 μm selected from aluminum oxide, zirconium oxide, cerium oxide, titanium oxide, silicon oxide and molybdenum oxide is formed on the surface of the hematite particle powder. One or more kinds are composite non-magnetic particles having an average particle diameter of 0.08 to 1.0 μm, which are fixed by a silicon compound generated from tetraalkoxysilane,
A filler material for a magnetic recording medium, wherein the content of the oxide fine particles is 0.1 to 20% by weight based on the weight of the nonmagnetic particles. 2. The intermediate coating according to claim 1, wherein the particle surface of the hematite particle powder is at least one selected from the group consisting of aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. A filler material for a magnetic recording medium, characterized by being coated with a filler. 3. A magnetic recording medium in which a magnetic recording layer containing a binder resin, magnetic particle powder and a filler material is formed on a non-magnetic substrate, as the filler material.
3. A magnetic recording medium comprising the filler material for a magnetic recording medium according to claim 2, wherein the filler material is contained in a proportion of 1 to 30 parts by weight with respect to 100 parts by weight of the magnetic particle powder. 4. A non-magnetic support, a non-magnetic underlayer containing a non-magnetic particle powder formed on the non-magnetic support and a binder resin, a binder resin formed on the non-magnetic under layer, 3. A magnetic recording medium comprising a magnetic recording layer containing a particle powder and a filler material, wherein the filler material for a magnetic recording medium according to claim 1 or 2 is used as the filler material, and the filler material is 100 parts by weight of magnetic particle powder. 1 to 30 parts by weight of the magnetic recording medium.