JP2002298330A - Filler material for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filler material for a magnetic recording medium excellent in strength and surface smoothness and low in light transmittance. SOLUTION: The filler material for the magnetic recording medium is composite non-magnetic particle powder consisting of hematite particle powder wherein the surface of the particle is coated with an organosilane compound or polysiloxane formed from alkoxysilane and an organic pigment is adhered to the coating material and having 0.08-1.0 μm average major axis diameter and 1-200 pts.wt. organic pigment is adhered to 100 pts.wt. hematite particle powder. In the magnetic recording medium, a magnetic recording layer containing a bonding agent resin, magnetic particle powder and the filler material for the magnetic recording medium is formed on a non-magnetic substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION An object of the present invention is to provide a filler material for a magnetic recording medium of a magnetic recording medium which is excellent in strength and surface smoothness and has low light transmittance.

[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.
₂ O ₃ ), hematite (α-Fe ₂ O ₃ ) and trioxide 2
Attempts have been made to add various filler materials such as chromium (Cr ₂ O ₃ ) to the magnetic recording layer.

For example, in the case of using alumina (Al ₂ O ₃ ), a magnetic recording medium using α-Al ₂ O _{3 in} which an amorphous phase exists (Japanese Patent Laid-Open No. 5-36059) or a specific crystallinity is used. And a magnetic recording medium using α-Al ₂ O ₃ (JP-A-7-244836). In the case of using hematite (α-Fe ₂ O ₃ ), granular α
-Magnetic recording medium using Fe ₂ O ₃ (JP-A-61-19)
No. 4628) and a magnetic recording medium using a liquid hydrocarbon and α-Fe ₂ O ₃ (JP-A-54-70806).
Etc. In addition, a magnetic recording medium using needle-like Cr ₂ O ₃ (for example, Japanese Patent Application Laid-Open No. Sho 62-112221) is one using chromium trioxide (Cr ₂ O ₃ ).

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.

Conventionally, in order to reduce the amount of carbon black added to the magnetic recording layer and to reduce the light transmittance of the magnetic recording layer, carbon black adheres to the particle surface of the filler material contained in the magnetic recording layer. It is known to use a filler material (see JP-A-2001-14).
364, JP-A-2001-14365, JP-A-2001-14366)

[0010]

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 a magnetic recording medium using a filler material for a magnetic recording medium such as alumina, hematite, and dichromium trioxide, which has been conventionally used, a filler material added in order to obtain durability. 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. Because a considerable amount of fine particles are detached from the particle surface, when used as a filler material for a magnetic recording medium, it is difficult to say that the dispersibility is sufficient and the durability of the obtained magnetic recording medium is also not sufficient. is there.

JP-A-2001-14364, JP-A-2001-14365, and JP-A-2001-143 mentioned above.
No. 66, the filler material has carbon black adhered to the particle surface, so that the light transmittance and the dispersibility are improved, but the resin adsorption strength is not sufficient. Therefore, when used as a filler material for a magnetic recording medium, the strength of the obtained magnetic recording medium is hardly sufficient.

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

[0015]

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

That is, according to the present invention, an average major axis diameter of from 0.08 to 0.08, which is composed of hematite particle powder in which an organosilane compound or polysiloxane formed from alkoxysilane is coated on the particle surface, and the coating is coated with an organic pigment. 1.0
μm composite non-magnetic particle powder, wherein the amount of the organic pigment attached is 1 to 2 parts by weight per 100 parts by weight of the iron oxide particle powder.
It is a filler material for a magnetic recording medium characterized by being 00 parts by weight (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 aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. A filler material for a magnetic recording medium, which is characterized by having the following characteristics (Invention 2).

Further, according to the present invention, the particle surface is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and the coating is coated with carbon black, and further formed on the carbon black from alkoxysilane. An organosilane compound or polysiloxane is coated, and the coating has an organic pigment attached thereto.
μm composite non-magnetic particle powder, wherein the amount of the organic pigment attached is 1 to 100 parts by weight of the hematite particle powder.
It is a filler material for a magnetic recording medium, characterized in that the content is from 200 to 200 parts by weight (Invention 3).

Further, in the present invention, the particle surface of the hematite particle powder of the present invention 3 is made of at least one kind previously selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. A magnetic recording medium filler material characterized by being coated with an intermediate coating (the present invention 4).

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 support, wherein the filler material according to the first to the present invention is used. A magnetic recording medium comprising the filler material for a magnetic recording medium according to any one of the fourth aspect of the present invention, and containing the filler material in an amount of 1 to 30 parts by weight based on 100 parts by weight of the magnetic particle powder. (Invention 5).

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 binding formed on the non-magnetic under layer. In a magnetic recording medium comprising a magnetic recording layer containing a resin, a magnetic particle powder and a filler material, the filler material for a magnetic recording medium according to any one of the present inventions 1 to 4 is used as the filler material, and the filler material is used. A magnetic recording medium characterized in that it is contained in an amount of 1 to 30 parts by weight based on 100 parts by weight of magnetic particle powder (Invention 6).

The configuration 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.

In the filler material according to the present invention, the surface of hematite particles as core particles is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and the coating is coated with an organic pigment. It consists of non-magnetic particle powder.

In the present invention, black hematite particles such as hematite particles or manganese-containing hematite particles containing 5 to 40% by weight of manganese with respect to manganese-containing hematite particles are used as the core particles. 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.

In consideration of the blackness of the obtained filler material, the surface of the hematite particles is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and carbon black adheres to the coating. Hematite particles are preferred.

The coating amount of the organosilane compound or polysiloxane in the hematite particle powder in which carbon black is adhered to the surface of the hematite particle via an organosilane compound or polysiloxane formed from alkoxysilane is as follows. Alternatively, the polysiloxane-coated hematite particles powder
It is preferably 0.02 to 5.0% by weight in terms of i, and the amount of carbon black attached is preferably 1 to 30 parts by weight based on 100 parts by weight of the hematite particle powder.

The adhering carbon black may be either a carbon black layer or a partially adhering carbon black, and the organic pigment is adhered even if the alkoxysilane is partially exposed. be able to.

Hematite particles have various shapes, and include spherical, granular, octahedral, hexahedral, polyhedral, and other granular particles, and needles, spindles, and rice grains. Considering the dispersibility in the vehicle, the particles are preferred.

The particle size of the hematite particles is 0.075 to 0.95 when the particle shape is granular.
μm, preferably 0.085 to 0.65 μm, more preferably 0.095 to 0.45 μm.

When the hematite particles are 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.

The average particle size of the hematite particles is 0.9.
If it exceeds 5 μm, the obtained filler material becomes coarse particles, and the surface smoothness of the magnetic recording medium obtained using the filler material is reduced. 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 surface of the hematite particle powder is uniformly coated with alkoxysilane or polysiloxane and uniformly coated with an organic pigment. Adhesion treatment becomes difficult.

When the particle shape of the hematite particles is acicular,
If the axis ratio exceeds 20, entanglement between the particles increases, and it becomes difficult to uniformly coat the surface of the hematite particle powder with alkoxysilane or polysiloxane and to uniformly coat the particles with an organic pigment.

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. When the geometric standard deviation value exceeds 1.8, uniform dispersion is hindered by the existing coarse particles, so that the surface of the hematite particle powder is uniformly coated with alkoxysilane or polysiloxane and the organic pigment is used. Uniform adhesion treatment becomes difficult. The lower limit of the geometric standard deviation value is 1.01, and a value less than 1.01 is difficult to obtain industrially.

[0035] BET specific surface area value of hematite particles is preferably 1.0~200m ² / g, more preferably 1.5~150m ² / g, even more preferably 2.0 to
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 value exceeds 200 m ² / g, aggregation tends to occur due to an increase in intermolecular force due to finer particles, so that the surface of the hematite particles is uniformly coated with alkoxysilane or polysiloxane. In addition, it becomes difficult to perform a uniform adhesion treatment using an organic pigment.

The blackness of the hematite particle powder is, in the case of black hematite powder, usually such that the lower limit of the L ^* value exceeds 22.0 and the upper limit is 28.0, preferably 26.0. In this case, the lower limit of the L ^* value is usually 22.
0, and the upper limit is 38.0, preferably 36.0. When the L ^* value exceeds the above upper limit, the lightness increases, and it becomes difficult to obtain a filler material having a sufficient blackness.

The hemp to which the carbon black is attached
The blackness of tight particle powder is usually L ^*The lower limit of the value is 1
5.0 and the upper limit is L^*21.0 by value, preferred
Or 20.5.

The resin adsorption strength of the hematite particle powder is usually 60% or less.

The organosilane compound produced from alkoxysilane (hereinafter referred to as "organosilane compound") in the present invention is an organosilane compound produced from alkoxysilane represented by the following chemical formula 1.

[0040]

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As the alkoxysilane, specifically,
Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, etc. Can be

In consideration of the adhesion effect and desorption rate of the organic pigment, an organosilane compound formed from methyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, isobutyltrimethoxysilane, and phenyltriethoxysilane is preferable. Organosilane compounds formed from ethoxysilane, methyltrimethoxysilane and phenyltriethoxysilane are more preferred.

As the polysiloxane in the present invention, a polysiloxane represented by Chemical formula 2, a modified polysiloxane represented by Chemical formula 3, a terminal modified polysiloxane represented by Chemical formula 4, or a mixture thereof can be used.

[0044]

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[0045]

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[0046]

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In consideration of the adhesion effect and the desorption rate of the organic pigment, a polysiloxane having a methyl hydrogen siloxane unit, a polyether-modified polysiloxane, and a terminal carboxylic acid-modified polysiloxane having a terminal modified with a carboxylic acid are preferred.

The coating amount of the organosilane compound or polysiloxane is preferably 0.02 to 5.0% by weight in terms of Si with respect to the organosilane compound-coated hematite particle powder or the polysiloxane-coated hematite particle powder. , More preferably 0.03 to 4.0% by weight, and even more preferably 0.05 to 3.0% by weight.

When the content is less than 0.02% by weight, it is difficult to attach 1 part by weight or more of the organic pigment to 100 parts by weight of the hematite particle powder. When the content exceeds 5.0% by weight, the organic pigment can be attached in an amount of 1 to 200 parts by weight with respect to 100 parts by weight of the hematite particle powder.

The organic pigments in the present invention include organic blue pigments such as metal-free phthalocyanine blue, phthalocyanine blue (copper phthalocyanine), fast sky blue (sulfonated copper phthalocyanine), alkali blue, organic green pigments such as phthalocyanine green, and quinacridone red. , Organic red pigments such as permanent red and condensed azo red, and organic yellow pigments such as Hansa Yellow, Benzidine Yellow and Permanent Yellow. In view of the blackness of the resulting filler material, organic blue pigments and / or organic green pigments are used. And more preferably phthalocyanine blue.

The amount of the organic pigment to be attached is 1 to 200 parts by weight, preferably 1 to 150 parts by weight, more preferably 1 to 100 parts by weight based on 100 parts by weight of the hematite particle powder.

If the amount is less than 1 part by weight, it is difficult to obtain a filler material having a sufficient resin adsorption strength because the amount of the organic pigment attached is insufficient. When the amount exceeds 200 parts by weight, the obtained filler material has a sufficient resin adsorption strength, but since the amount of the attached organic pigment is large, the organic pigment is easily detached. At times, dispersibility in the vehicle decreases.

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.

When granular hematite particles are used as the core particles, the average particle diameter 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.

If the average particle size is less than 0.08 μm, the dispersion in the vehicle during the production of the magnetic paint becomes difficult due to the increase in the intermolecular force due to the 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, the entanglement between the particles increases, and it becomes difficult to uniformly disperse the magnetic paint in a vehicle at the time of producing the magnetic coating material. 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 1.0.
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 filler material is coarse or particles are sintered between particles, and the magnetic recording medium obtained by using the particles is In addition, the surface smoothness of the coating film is easily impaired.
When the BET specific surface area value exceeds 200 m ² / g,
Agglomeration is likely to occur due to an increase in intermolecular force due to finer particles, so that dispersibility in a vehicle during the production of a magnetic coating material is reduced.

The blackness of the filler material according to the present invention is L ^*
The lower limit of the value is 16.5, and the upper limit is 28.0, preferably 27.0. Regarding the degree of blackness of the filler material obtained using black hematite particles as the core particles, the lower limit of the L ^* value is 16.5, and the upper limit is 26.0, preferably 25.0. When the L ^* value exceeds 28.0, the lightness increases and it is difficult to say that the blackness is excellent.

Among the filler materials according to the present invention, the blackness of the filler material obtained by using hematite particles to which carbon black is attached as core particles has a lower limit of L ^* value of 1
4.5, and the upper limit is 21.0, preferably 20.5.

The resin adsorption strength of the filler material according to the present invention is 70% or more, preferably 72% or more, more preferably 74% or more.

The desorption rate of the organic pigment as the filler material is preferably 20% or less, more preferably 15% or less. When the desorption rate of the organic pigment exceeds 15%, uniform dispersion in the vehicle may be hindered by the desorbed organic pigment during the production of the magnetic paint, and the obtained magnetic recording medium Does not have sufficient durability.

The filler according to the present invention may be
The particle surface of the hematite particle powder may be previously coated with an intermediate coating composed of at least one selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. The detachment of the organic pigment from the particle surface of the hematite particle powder can be further reduced as compared with the case where the organic pigment is not coated with the coating.

The amount of coating by 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 reducing the desorption rate of the organic pigment cannot be obtained. 0.01-20
Since the effect of reducing the desorption rate of the organic pigment can be sufficiently obtained by the coating amount of weight%, it is meaningless to coat more than 20 weight% more than necessary.

The filler material according to the present invention 2 coated with the intermediate coating has a particle size substantially equal to that of the filler material according to the present invention 1 not coated with the intermediate coating.
It has a geometric standard deviation value, a BET specific surface area value, a blackness L ^* value, a resin adsorption strength, and an organic pigment desorption rate.

Further, if necessary, the filler material according to the present invention may be subjected to carbon black adhesion treatment after the particle surface of the filler material is coated with an intermediate coating.

The filler material according to the fourth aspect of the present invention has substantially the same particle size, geometric standard deviation value, BET specific surface area value, resin adsorption strength, and desorption rate of organic pigment as the filler material according to the second aspect of the present invention. ing. Further, the degree of blackness is almost the same as that of the filler material according to the third aspect of the present invention.

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

As the non-magnetic support of the magnetic recording medium according to the present invention, a synthetic material of polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamide imide, polyimide, etc., which is currently widely used for magnetic recording media, is 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 support, and its thickness is usually 50 to 300 μm, preferably 60 to 200 μm.
μm. 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 magnetic recording media, the magnetic particles include 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 producing 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 particle powder 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 properties of the magnetic particles are such that the coercive force value of the Co-coated acicular magnetic iron oxide particles is 39.8-1.
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 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 (650-4,000 Oe) and a saturation magnetization value of 40-70 Am ² / kg (40-70 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 copolymers, 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
A polar group such as H, —SO ₃ M, —OPO ₂ M ₂ , and —NH ₂ (where M is H, Na, or K) may be included. 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.

In the present invention, the coating thickness of the magnetic recording layer 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 filling 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, per 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.

In the magnetic recording medium according to the fifth aspect of the present invention, when the filler according to the first aspect is used as the filler,
The coercive force value is 39.8 to 318.3 kA / m (500 to
4,000 Oe), preferably 43.8 to 318.3 k
A / m (550-4,000 Oe), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.85-0.95,
Preferably 0.86 to 0.95, the glossiness of the coating film is 165
-300%, preferably 170-300%, and the surface roughness Ra of the coating film is 10.0 nm or less, preferably 2.0-9.
5 nm, more preferably 2.0 to 9.0 nm, the Young's modulus is 126 to 160, preferably 128 to 160, and the linear absorption coefficient is 1.20 to 5.00 μm ⁻¹ , preferably 1.2.
5 to 5.00 μm ⁻¹ , running durability of 22 minutes or more, preferably 24 minutes or more, and scratch characteristics of A or B, preferably B.

When the filler material according to the present invention 2 is used as the filler material, the coercive force value is 39.8 to 318.3.
kA / m (500-4,000 Oe), preferably 4
3.8 to 318.3 kA / m (550 to 4,000 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 170 to 300%, preferably 17
5 to 300%, 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
-8.5 nm, Young's modulus is 128-160, preferably 130-160, and linear absorption coefficient is 1.25-5.00 µm.
⁻¹ , preferably 1.20 to 5.00 μm ⁻¹ , running durability of 23 minutes or more, preferably 25 minutes or more, and a scratch characteristic of A or B, 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 magnetic particles, and the present invention is used as a filler material.
When the filler material according to the above is used, the coercive force value is 63.
7 to 278.5 kA / m (800 to 3,500 Oe),
Preferably 71.6 to 278.5 kA / m (900 to
3,500 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 gloss of the coating film is 190 to 300%, preferably 195 to 300%, and the coating film surface roughness Ra is 9.0 n.
m, preferably 2.0 to 8.5 nm, more preferably 2.0 to 8.0 nm, a Young's modulus of 126 to 160, preferably 128 to 160, and a linear absorption coefficient of 1.25 to 5.
00μm ^{- 1,} preferably 1.25~5.00μ
m ^-1 , running durability of 24 minutes or more, preferably 26 minutes or more, and scratch characteristics of A or B, preferably A.

When the acicular metal magnetic particles or the acicular iron alloy magnetic particles containing iron as a main component are used as the magnetic particles and the filler according to the present invention 2 is used as the filler, the coercive force is reduced. Value is 63.7-278.5 kA / m
(800-3,500 Oe), preferably 71.6-2.
78.5 kA / m (900 to 3,500 Oe), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.85 to
0.95, preferably 0.86 to 0.95, the glossiness of the coating film is 195 to 300%, preferably 200 to 300%,
Coating surface roughness Ra is 8.5 nm or less, preferably 2.0 nm or less.
To 8.0 nm, more preferably 2.0 to 7.5 nm, and a Young's modulus of 128 to 160, preferably 130 to 160,
The linear absorption coefficient is 1.25 to 5.00 μm ⁻¹ , preferably 1.25 to 5.00 μm ⁻¹ , the running durability is 25 minutes or more, preferably 27 minutes or more, and the scratch property is A or B, preferably A.

The magnetic recording medium according to the sixth aspect of the invention has a non-magnetic underlayer containing non-magnetic particle powder and a binder resin between a non-magnetic support and a 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 is coated 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., needle-like, spindle-like, 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.
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.

The binder resin used for forming the magnetic recording layer can be used as the binder resin in the nonmagnetic underlayer.

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 has a glossiness of the coating film of 176 to 176.
300%, preferably 180-300%, more preferably 184-300%, and the coating film surface roughness Ra is 0.1%.
5 to 8.5 nm, preferably 0.5 to 8.0 nm, and the strength of the coating film is such that Young's modulus (relative value) is 124 to 16
0, preferably 126 to 160, and a surface electric resistance of 1.
0 × 10 ¹⁵ Ω / cm ² or less, preferably 1.0 × 10
¹⁴ Ω / cm ² or less.

In the magnetic recording medium according to the present invention 6, when the filler material according to the present invention whose particle surface is not covered with the 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 130 to 1%.
60, preferably 132 to 160, and a linear absorption coefficient of 1.2.
0 to 5.00 μm ⁻¹ , preferably 1.25 to 5.00
μm ⁻¹ , running durability of 23 minutes or more, preferably 25 minutes or more, and scratch characteristics of A or B, preferably A.

When the filler material according to the present invention coated with the intermediate coating is used as the filler material, the coercive force value is 39.8 to 318.3 kA / m (50%).
0 to 4,000 Oe), preferably 43.8 to 318.
3 kA / m (550-4,000 Oe), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) of 0.85-0.9
5, preferably 0.86 to 0.95, and the glossiness of the coating film is 1
75-300%, preferably 180-300%, and the coating film surface roughness Ra is 9.0 nm or less, preferably 2.0-8.
5 nm, more preferably 2.0 to 8.0 nm, the Young's modulus is 130 to 160, preferably 134 to 160, and the linear absorption coefficient is 1.20 to 5.00 μm ⁻¹ , preferably 1.2.
5 to 5.00 μm ⁻¹ , running durability of 24 minutes or more, preferably 26 minutes or more, and scratch characteristics of A or B, preferably A.

In consideration of high-density recording and the like,
And needle-like metal magnetic particles containing iron as the main component or needle-like
Using iron alloy magnetic particle powder, particle surface as filler material
Is not coated with an intermediate coating according to the present invention
When a material 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%, coating film surface roughness Ra is 8.5 nm or less, good
Preferably 2.0 to 8.0 nm, more preferably 2.0 to 8.0 nm
7.5 nm, Young's modulus is 130 to 160, preferably 1
32-160, linear absorption coefficient 1.20-5.00 μm
^-1, Preferably 1.25 to 5.00 μm ^-1, Running resistance
Scratch characteristics with durability of 25 minutes or more, preferably 27 minutes or more
Is A or B, preferably A.

As the magnetic particles, needle-like metal magnetic particles or iron-alloy magnetic particles containing iron as a main component 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 / 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 200 to 30.
0%, preferably 205-300%, coating film surface roughness Ra
Is 8.0 nm or less, preferably 2.0 to 7.5 nm, more preferably 2.0 to 7.0 nm, and the Young's modulus is 132 to
160, preferably 134-160, with a linear absorption coefficient of 1.
20-5.00 [mu] m < ^-1 >, preferably 1.25-5.0
0 μm ⁻¹ , running durability of 26 minutes or more, preferably 28
For at least a minute, the abrasion properties are A or B, preferably A.

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

The hematite particle powder to which carbon black as the core particle powder according to the present invention is attached is prepared by mixing the hematite particle powder with alkoxysilane or polysiloxane, and coating the surface of the hematite particle powder with alkoxysilane or polysiloxane. Then, it can be obtained by mixing hematite particle powder coated with alkoxysilane or polysiloxane and carbon black fine particle powder.

The filler material according to the present invention is obtained by mixing the hematite particle powder and the alkoxysilane or polysiloxane to coat the particle surface of the hematite particle powder with the alkoxysilane or polysiloxane. Can be obtained by mixing the hematite particle powder coated with the organic pigment and the organic pigment.

The hematite particle powder is coated with the alkoxysilane or polysiloxane by mechanically mixing and stirring the hematite particle powder and the alkoxysilane solution or the polysiloxane, or spraying the hematite particle powder with the alkoxysilane solution or the polysiloxane. What is necessary is just to mix and stir mechanically while doing. Almost all of the added alkoxysilane or polysiloxane is coated on the particle surface of the hematite particle powder.

Incidentally, the coated alkoxysilane may be partially coated as an organosilane compound generated from the alkoxysilane, which is generated through a coating step. Even in this case, there is no effect on the subsequent attachment of the organic pigment.

In order to uniformly coat the surface of the hematite particle powder with the alkoxysilane or polysiloxane, it is preferable to previously disaggregate the hematite particle powder using a pulverizer.

To mix and stir the hematite particle powder and the alkoxysilane or polysiloxane, and to mix and stir the organic pigment and the hematite particle powder coated with an organosilane compound or polysiloxane formed from alkoxysilane on the particle surface. As the device, a device capable of applying a shearing force to the powder layer is preferable.
A device capable of simultaneously performing shearing, spatula and compression, for example, a wheel-type kneader, a ball-type kneader, a blade-type kneader, and a roll-type kneader can be used. In practicing the present invention, a wheel-type kneader can be used more effectively.

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 at the time of mixing and stirring are such that a linear load is set to 1 so that the alkoxysilane or polysiloxane is coated as uniformly as possible on the particle surface of the hematite particle powder.
9.6 to 1960 N / cm (2 to 200 kg / cm),
Preferably 98 to 1470 N / cm (10 to 150 Kg
/ Cm), more preferably 147 to 980 N / cm (1
5 to 100 Kg / cm), treatment time is 5 minutes to 24 hours,
Preferably, the processing conditions may be appropriately adjusted within a range of 10 minutes to 20 hours. In addition, the stirring speed is 2-2000 rpm,
Preferably 5-1000 rpm, more preferably 10-
The processing conditions may be appropriately adjusted within the range of 800 rpm.

The addition amount of the alkoxysilane or polysiloxane is 0.1 to 100 parts by weight of the hematite particle powder.
15 to 45 parts by weight are preferred. With an addition amount of 0.15 to 45 parts by weight, 1 to 200 parts by weight of the organic pigment can be attached to 100 parts by weight of the hematite particle powder.

Next, the organic pigment is added to the hematite particle powder coated with the alkoxysilane or polysiloxane, and the organic pigment is attached to the alkoxysilane coating or the polysiloxane coating by mixing and stirring. If necessary, drying or heat treatment may be further performed.

The organic pigment is preferably added little by little over time, especially over about 5 minutes to 20 hours.

The conditions for mixing and stirring are such that the linear load is 19.6 to 1960 N /
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 processing time is 5 minutes to 24 hours, preferably 10 minutes to
The processing conditions may be appropriately adjusted within a range of 20 hours. The stirring speed is 2 to 2000 rpm, preferably 5 to 1
The processing conditions may be appropriately adjusted within the range of 000 rpm, more preferably in the range of 10 to 800 rpm.

The amount of the organic pigment to be added is 1 to 200 parts by weight, preferably 1 to 150 parts by weight, more preferably 1 to 100 parts by weight, based on 100 parts by weight of the hematite particle powder. When the addition amount of the organic pigment exceeds 200 parts by weight, the obtained filler material has a sufficient resin adsorption strength, but since the amount of the attached organic pigment is large, the organic pigment is easily detached. As a result, the dispersibility in the vehicle decreases during the production of the magnetic paint.

The heating temperature in the drying or heating step is usually preferably from 40 to 200 ° C., more preferably from 60 to 1 ° C.
The temperature is 50 ° C., and the treatment time is preferably 10 minutes to 12 hours, more preferably 30 minutes to 3 hours.

The alkoxysilane used for coating the obtained filler material is subjected to these steps, and finally coated as an organosilane compound generated from the alkoxysilane.

If necessary, the hematite particle powder is selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide before mixing and stirring with alkoxysilane or polysiloxane. It may be coated with at least one kind of intermediate coating.

The coating with the intermediate coating is carried out by adding an aluminum compound, a silicon compound or both compounds to an aqueous suspension obtained by dispersing the hematite particle powder and mixing and stirring, or if necessary, mixing. PH after stirring
By adjusting the value, the particle surface of the iron oxide particle powder is coated with an intermediate coating made of at least one selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. And then
Filter, wash, dry and pulverize. 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.

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

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

The magnetic recording medium according to the fifth aspect of the present invention provides a magnetic recording medium containing a 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. After magnetic field orientation and then calendering,
It can be obtained by curing.

In the magnetic recording medium according to the sixth aspect of the present invention, a non-magnetic paint containing non-magnetic particle powder, a binder resin and a solvent is applied on a non-magnetic support and dried by a conventional method. After forming a coating film by applying a magnetic paint containing a magnetic particle powder, a filler material, a binder resin and a solvent on the non-magnetic underlayer, forming a coating film, orienting in a magnetic field, performing a calendering process, and then curing. Can be obtained.

For kneading and dispersing the magnetic paint and the non-magnetic paint, for example, a kneader may be a twin-screw kneader, a twin-screw extruder, a pressure kneader, a two-roll mill, a three-roll mill, or the like. , Ball mill,
Sand grinders, attritors, dispersers, homogenizers, ultrasonic dispersers and the like can be used.

In applying the magnetic paint and the non-magnetic paint, a gravure coater, a reverse roll coater, a 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.

[0140]

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 values of about 350 particles shown in a photograph obtained by enlarging the electron micrograph four times in the vertical and horizontal directions, respectively, and measuring about 350 particles. Was.

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

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

The amounts of Mn, Al, and Si present inside the particles and on the surface of the hematite particles and the amount of Si contained in the organosilane compound or polysiloxane formed from the alkoxysilane are each represented by “Fluorescent X”.
Ray analyzer 3063M "(manufactured by Rigaku Corporation)
And measured according to JIS K0119 “General rules for X-ray fluorescence analysis”. Further, the Co amount of the Co-coated magnetite particle powder and the Co-coated maghemite particle powder is
The measurement was performed in the same manner as in the above measuring device and measuring method.

The amount of each Si contained in the organosilane compound or polysiloxane formed from the oxide of silicon, the hydroxide of silicon, and the alkoxysilane present on the surface of the hematite particle powder is 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.

The amount of carbon black in the hematite particles to which the organic pigment and carbon black adhered to the filler material were adhered was measured using a Horiba Metal Carbon / Sulfur Analyzer EMI
A-2200 type "(manufactured by Horiba, Ltd.) and the amount of carbon was measured.

The blackness of the hematite particle powder, filler material and non-magnetic particle powder was 0.5 g for the sample and 1.5 for castor oil.
and kneaded with a Hoover-type muller into a paste,
Add 4.5g of clear lacquer to this paste, knead,
150μm (6mi)
1) A coated piece (coating thickness: about 30 μm) was prepared by using the applicator of l), and the coated piece was measured using a multi-source spectrophotometer MSC-IS-2D (manufactured by Suga Test Instruments Co., Ltd.). The measurement was carried out and represented by a color index L ^* according to JIS Z 8729.

Here, the L ^* value represents lightness, and the smaller the L ^* value, the better the blackness.

The desorption rate (%) of the organic pigment adhering to the filler was shown by the value obtained by the following method. The closer the desorption rate of the organic pigment is to 0%, the smaller the desorption amount of the organic pigment from the particle surface of the filler material is.

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 for 120 minutes, and the filler material and the separated organic pigment were separated by the sedimentation speed. Next, 40 ml of ethanol was again added to the filler material, and ultrasonic dispersion was further performed for 20 minutes, and then the mixture was allowed to stand for 120 minutes to separate the filler material and the separated organic pigment. This filler material was dried at 80 ° C. for 1 hour, the amount of the organic pigment was measured, and the value determined according to the following equation 1 was defined as the desorption rate (%) of the organic pigment.

[0152]

## EQU1 ## Desorption rate (%) of organic pigment = ｛(Wa-We) /
Wa｝ × 100 Wa: Amount of organic pigment attached to filler material We: Amount of organic pigment attached to filler material after desorption test

The resin adsorption strength indicates the degree to which the resin is adsorbed on the particle powder. The closer the resin adsorption strength obtained by the following method is to 100%, the more strongly the resin is adsorbed on the particle surface. Is shown.

First, the resin adsorption amount Ya is determined.

A mixed solvent in which 20 g of the particles to be measured and 2 g of a polyurethane resin having a sodium sulfonate group were dissolved (27.0 g of methyl ethyl ketone, 16.1 g of toluene).
2g, cyclohexanone 10.8g) 56g and 3mm
Put into a 100 ml poly bottle together with 120 g of φ steel beads, and mix and disperse with a paint shaker for 60 minutes.

Next, 50 g of this coating composition was taken out and taken out.
The mixture is placed in a 0 ml settling tube and centrifuged at 10,000 rpm for 15 minutes to separate a solid portion and a solvent portion.
Then, the concentration of the resin solid content contained in the solvent portion is quantified by a gravimetric method, and the amount of the resin present in the solid portion is obtained by subtracting the concentration from the charged resin amount. ).

Next, only the previously separated solid portion was
The whole amount was taken out into a 2 ml tall beaker, and mixed solvent (25.0 g of methyl ethyl ketone, 15.0 ml of toluene)
g, cyclohexanone 10.0 g) and 50 g.
After ultrasonic dispersion for a minute, the suspension is put into a 50 ml sedimentation tube and centrifuged at 10,000 rpm for 15 minutes to separate a solid portion and a solvent portion. Then, by measuring the resin solid content concentration in the solvent portion, the amount of resin extracted into the solvent phase among the resin adsorbed on the particle surface is quantified.

Further, the operation from the removal of the whole solid portion into a 100 ml tall beaker to the determination of the amount of resin dissolved in the solvent phase was repeated twice, and the total amount of resin extraction in the solvent phase was repeated three times. Ye (mg / g) was determined, and the value determined according to the following equation 2 was defined as the resin adsorption strength (%).

[0159]

## EQU2 ## Resin adsorption strength (%) = [(Ya-Ye) / Y
a) × 100

The viscosity of the paint at 25 ° C. was measured using an E-type viscometer (cone-plate viscometer) EMD-R.
It was shown by the value of the apparent viscosity when the shear rate at 25 ° C. was 1.92 sec ⁻¹ 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 nonmagnetic support, the nonmagnetic underlayer, and the magnetic recording layer constituting the magnetic recording medium was measured as described below.

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 nonmagnetic underlayer is determined by measuring the thickness (A) of the nonmagnetic 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 degree of light transmission is described in “Self-Recording Photoelectric Spectrophotometer U
V-2100 "(manufactured by Shimadzu Corporation) was used as the linear absorption coefficient calculated by inserting the value of the light transmittance of the magnetic recording medium into Equation 3 below. The larger the linear absorption coefficient is, the harder it is to transmit light.

In measuring the light transmittance, the same non-magnetic support as the non-magnetic support used for the magnetic recording medium was used as a blank.

[0170]

## EQU3 ## Linear absorption coefficient (μm ⁻¹ ) = [ln (1 / t)] / FT t: light transmittance at λ = 900 nm (−) FT: film thickness of magnetic recording layer (μm)

The running durability of the magnetic recording medium is as follows:
a Durability Tester MDT-3
000 "(Steinberg Associates
(Manufactured by K.K.) 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. The longer the actual operating time, the better the running durability.

The scratch characteristics were evaluated by observing the surface of the tape after running with a microscope and visually checking for the presence or absence of scratches.
A rating was given on a scale.

A: No abrasion B: Some abrasion C: Abrasion D: Severe abrasion

<Production of Filler Material> Mn-containing acicular hematite particle powder (average major axis diameter 0.162 μm, average minor axis diameter 0.0225 μm, axial ratio 7.2, geometric standard deviation 1.3)
8, BET specific surface area value 48.6 m ² / g, Mn content 1
3.7% by weight, blackness L ^* value 19.3, resin adsorption strength 5
(7.1%) 20 kg of water is crushed with 150 liters of pure water using a stirrer to dissolve the coagulation, and further passed through "TK pipeline homomixer" (product name, manufactured by Tokushu Kika Kogyo Co., Ltd.) three times. Thus, a slurry containing Mn-containing acicular hematite particle powder was obtained.

Subsequently, the slurry containing the Mn-containing acicular hematite particle powder was subjected to 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 Mn-containing acicular hematite particle powder.

The obtained dispersion slurry was 325 mesh
The sieve residue at (opening 44 μm) was 0%. The dispersion slurry was separated by filtration and washed with water to obtain a cake of Mn-containing acicular hematite particle powder. After drying the cake of the Mn-containing acicular hematite particle powder at 120 ° C., 11.0 kg of the dried powder was used as an edge runner “MPUV-2 type”.
(Product name, manufactured by Matsumoto Cast Iron Works)
Mixing and stirring were performed at 92 N / cm (40 Kg / cm) for 20 minutes to loosen the aggregation of particles.

Next, methyltriethoxysilane (trade name: TSL8123: manufactured by GE Toshiba Silicone Co., Ltd.)
A methyltriethoxysilane solution obtained by mixing and diluting 220 g with 200 ml of ethanol was added to the Mn-containing acicular hematite particle powder obtained by dissolving the agglomeration of particles while operating an edge runner.
(0 Kg / cm) and the mixture was stirred for 20 minutes.
The stirring yield at this time was 22 rpm.

Next, an organic pigment A (type: phthalocyanine blue, particle shape: granular, particle size 0.06 μm, BET
Specific surface area value 680 m ² / g, blackness L ^* value 5.2) 11
After adding the organic pigment to the methyltriethoxysilane coating, 00 g was added over 10 minutes while operating the edge runner, and further mixed and stirred for 20 minutes at a linear load of 588 N / cm (60 Kg / cm). Then, heat treatment was performed at 105 ° C. for 60 minutes using a dryer to obtain composite non-magnetic particle powder. The stirring speed at this time was 22 rpm.

The obtained filler material has an average major axis diameter of 0.3.
163 μm, the average minor axis diameter was 0.0228 μm, and the axial ratio was 7.1. The geometric standard deviation value is 1.38 and B
ET specific surface area value is 51.5 m ² / g, blackness L ^* value is 1
9.0, the resin adsorption strength is 78.6%, the desorption rate of the organic pigment is 6.5%, and the coating amount of the organosilane compound generated from methyltriethoxysilane is 0.3 in terms of Si.
0% by weight, and the amount of the attached organic pigment is 6.0 in C conversion.
1% by weight (corresponding to 10 parts by weight with respect to 100 parts by weight of Mn-containing acicular hematite particle powder). As a result of electron microscopic observation, almost no organic pigment was observed, and it was confirmed that almost all of the organic pigment was attached to the methyltriethoxysilane coating layer.

<Production of Magnetic Recording Medium> Needle-like 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 treated with 1.
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 9,600.
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 159.0 kA / m (1,998 Oe), the squareness ratio (Br
/ Bm) was 0.89. The gloss is 235%, the surface roughness Ra is 6.2 nm, the Young's modulus is 137, the linear absorption coefficient is 1.42 μm ⁻¹ , and the running durability is 29.2 hours.
Min, and the abrasion property was A.

[0186]

In the present invention, the most important point is that the particle surface of the hematite particle powder is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and a filler material having an organic pigment adhered to the coating. Is the fact that the resin adsorption strength is high and the dispersibility is excellent.

The reason for the high resin adsorption strength of the filler material according to the present invention is that the present inventor attaches an organic pigment to the particle surface of the hematite particle powder via an organosilane compound or polysiloxane. Because there is an organic pigment having a benzene ring on the particle surface of
This is considered to be due to the improved compatibility with the resin, particularly the polyurethane resin usually used for the magnetic recording layer.

Regarding the reason why the filler material according to the present invention is excellent in dispersibility, the present inventor has concluded that the organic pigment adheres to the particle surface, so that irregularities are generated on the particle surface, and the contact between the particles is reduced. It is considered that this is because the dispersion in the system is not hindered by the organic pigment because the organic pigment is suppressed and the detachment of the attached organic pigment is small.

The magnetic recording medium having the magnetic recording layer using the filler according to the present invention has excellent durability and sufficient surface smoothness. It is considered that the reason for the excellent durability is that the compatibility with the resin used for the magnetic recording medium is improved due to the improvement in the resin adsorption strength of the filler material as described above. In addition, the reason why the surface smoothness is excellent is that the organosilane compound or the polysiloxane to which the organic pigment is adhered is strongly bonded to the particle surface of the hematite particle powder, and thus is detached from the particle surface of the filler material. The present invention is based on the fact that the dispersion of the filler material in the vehicle is not hindered and that the surface smoothness of the magnetic recording layer is improved due to the improved dispersibility of the filler material itself. Are thinking.

Further, since the filler material according to the present invention is superior in blackness to conventional hematite particles, it is possible to reduce the light transmittance of the obtained magnetic recording medium. Further, when manganese-containing hematite particle powder or hematite particle powder to which carbon black is attached is used, particles having more excellent blackness can be obtained, so that the light transmittance of the magnetic recording medium can be further reduced.

[0191]

Next, examples and comparative examples will be described.

Core Particles 1 to 7 Various hematite particle powders obtained by a known production method were prepared.

Table 1 shows the properties of the hematite particle powder.

[0194]

[Table 1]

Core Particle 8 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 agglomeration 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.

In the surface treatment step, A of the type of the coating represents aluminum hydroxide, and S represents silicon oxide.

Core Particles 9 to 12 Surface-treated hematite particles were obtained in the same manner as for the core particles 8, 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.

[0200]

[Table 2]

[0201]

[Table 3]

Organic pigments A to E: Organic pigments A to C having the properties shown in Table 4 were prepared.

[0203]

[Table 4]

Examples 1 to 12 and Comparative Examples 1 to 4: Types of core particles, types and amounts of alkoxysilane or polysiloxane in the step of coating with alkoxysilane or polysiloxane, line load and time for edge runner treatment, organic Composite non-magnetic particles were obtained in the same manner as in the embodiment of the invention except that the kind and amount of the organic pigment, the line load and the time of the edge runner treatment in the pigment attaching step were variously changed.

The production conditions at this time are shown in Table 5, and various properties of the obtained filler material are shown in Table 6.

[0206]

[Table 5]

[0207]

[Table 6]

<Manufacture of Magnetic Recording Medium> Examples 13 to 24, Comparative Examples 5 to 15 The same procedures as in the embodiment of the present invention were carried out except that the type of the magnetic particles, the type of the filler material and the amount added were changed variously. Thus, a magnetic recording medium was obtained.

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

[0210]

[Table 7]

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

[0212]

[Table 8]

[0213]

[Table 9]

[0214]

[Table 10]

<Production of Non-Magnetic Underlayer> Non-magnetic particles 1 to 6 Non-magnetic particles having characteristics shown in Table 11 were prepared as non-magnetic particles.

[0216]

[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 then added to a paint shaker. 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.

Non-magnetic 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) 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 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 Nonmagnetic underlayers were 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 the characteristics of the obtained nonmagnetic underlayer.

[0225]

[Table 12]

<Production of Magnetic Recording Medium Having Nonmagnetic Underlayer> Example 25 Using the composite nonmagnetic 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 slitting was performed to a width of 1.27 cm (0.5 inch) to obtain a magnetic tape.

Table 13 shows the manufacturing conditions at this time, and Table 14 shows various characteristics of the obtained magnetic recording medium.

Examples 26 to 36, Comparative Examples 16 to 26 Magnetic recording media were obtained in the same manner as in Example 25, except that the type of nonmagnetic underlayer and the type of composite nonmagnetic particles were variously changed.

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

[0231]

[Table 13]

[0232]

[Table 14]

[0233]

[Table 15]

[0234]

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 (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C09D 7/12 C09D 7/12 201/00 201/00 G11B 5/712 G11B 5/712 (72) Inventor Hiroko Morii 1-4, Meiji-Shinkai, Otake City, Hiroshima Prefecture F-term in the Otake Creation Center of Toda Kogyo Co., Ltd. CD071 CD081 CE071 CJ281 DB001 DD001 DG001 DG011 DG221 DH001 FA281 HA026 HA216 HA436 HA446 JC38 KA12 KA15 KA20 MA03 MA14 NA22 NA25 PB11 PC08 5D006 BA09 FA00

Claims (6)

[Claims] An organosilane compound or polysiloxane formed from an alkoxysilane is coated on the surface of a particle, and a hematite particle powder having an organic pigment attached to the coating has an average major axis diameter of 0.08 to 1.0 μm. A filler material for a magnetic recording medium, which is a composite non-magnetic particle powder, wherein the amount of the organic pigment attached is 1 to 200 parts by weight based on 100 parts by weight of the hematite particle powder. 2. The intermediate coating according to claim 1, wherein the 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. The particle surface is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and the coating is coated with carbon black. Further, the organosilane compound formed from alkoxysilane on the carbon black or A composite nonmagnetic particle powder having an average major axis diameter of 0.08 to 1.0 μm comprising hematite particle powder coated with polysiloxane and having an organic pigment attached to the coating, wherein the amount of the organic pigment attached is A filler material for a magnetic recording medium, which is used in an amount of 1 to 200 parts by weight based on 100 parts by weight of hematite particle powder. 4. An intermediate coating, wherein the particle surface of the hematite particle powder according to claim 3 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. 5. 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 nonmagnetic support, wherein the filler material is used as the filler material. The filler material for a magnetic recording medium according to claim 1, wherein said filler material is a magnetic particle powder 1
A magnetic recording medium comprising 1 to 30 parts by weight with respect to 00 parts by weight. 6. A non-magnetic support, a non-magnetic underlayer containing non-magnetic particles and a binder resin formed on the non-magnetic support, a binder resin formed on the non-magnetic under layer, and a magnetic material. In a magnetic recording medium comprising a magnetic recording layer containing particle powder and a filler material, the filler material for a magnetic recording medium according to any one of claims 1 to 4 is used as the filler material, and the filler material is made of a magnetic material. Particle powder 1
A magnetic recording medium characterized by being contained in an amount of 1 to 30 parts by weight with respect to 00 parts by weight.