JPH06215360A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium good in electrical characteristic at a short wave length range by incorporating with prescribed amount of Fe atom, Al atom and the atom of rare-earth element as the element constituting a ferromagnetic metallic powder. CONSTITUTION:The magnetic recording medium has the magnetic layer containing a ferromagnetic metallic powder on a non-magnetic supporting body. The element constituting the ferromagnetic powder contains Fe atom, Al atom and rate-earth atom, and the weight ratio in whole ferromagnetic metallic powder is 2-10wt.pts. Al atom and 1-8wt.pts. atom of rate-earth element per 100wt.pts. Fe atom. And the average abundance ratio of the element forming the surface of the ferromagnetic metallic powder is 70-200 Al atoms and 0.5-30 atoms of rare-earth element per 100 Fe atoms. As the rare-earth element, one or more kinds among Sm, Nd, Y, Pr is used. In this way, the magnetic recording medium is appropriate especially for the recording medium for a digital and excellent in electrical characteristic and traveling property at a short wavelength range.

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, and more specifically, it is suitable as a digital recording medium particularly required for high density recording, including an analog recording medium excellent in electromagnetic conversion characteristics and running durability. Magnetic recording media.

[0002]

2. Description of the Related Art Conventionally, a layer containing magnetic powder is provided as an upper layer and a layer containing nonmagnetic powder is provided as a lower layer for the purpose of improving electromagnetic conversion characteristics in a magnetic recording medium. A magnetic recording medium having a multilayer structure (for example, JP-A-63-187418, JP-A-63-
No. 191315, etc.) has been proposed.

However, these magnetic recording media are not intended to be applied to digital recording media, but the film thickness of the upper layer of the multi-layer structure is relatively large, resulting in large film thickness loss and self-demagnetization loss. However, there is a problem that it is difficult to sufficiently obtain the excellent electromagnetic conversion characteristics and running durability required for a digital recording medium.

Further, in a magnetic recording medium such as a video tape, since the depth of a recorded signal varies depending on the signal, a magnetic recording having a multi-layer structure composed of magnetic layers containing magnetic powder suitable for each signal. Medium has been preferred. However, in order to manufacture such a multi-layered magnetic recording medium, multi-layer coating such as wet-on-wet method is usually adopted. However, depending on the material constitution of each layer, the viscosity of the coating material, etc. The surface gets rough,
There is a problem that the electromagnetic conversion characteristics deteriorate when the tape is reproduced.

An object of the present invention is to solve the above problems,
In particular, when forming a plurality of layers on a non-magnetic support, by preventing surface roughness of the magnetic layer, it has good electromagnetic conversion characteristics and running durability, and also has a multi-layer structure suitable for digital recording media. It is to provide a magnetic recording medium.

[0006]

As a result of intensive studies by the present inventors in order to solve the above-mentioned problems, as a magnetic layer, a layer containing a ferromagnetic metal powder having a specific composition is further obtained. The present invention has been found out that by providing this magnetic layer as the uppermost layer on a non-magnetic support, excellent electromagnetic conversion characteristics and running durability required for a digital recording medium can be obtained.

That is, the invention according to claim 1 for solving the above-mentioned problems is a magnetic recording medium having at least one magnetic layer containing a ferromagnetic powder on a non-magnetic support, wherein the ferromagnetic metal powder is used. Fe atoms, Al atoms and rare earth element atoms are contained as the elements to be formed, and the weight ratio of the elements in the whole ferromagnetic metal powder is Fe atom 1
Al atoms are 2 to 10 parts by weight, rare earth element atoms are 1 to 8 parts by weight, and the average abundance ratio of the elements forming the surface of the ferromagnetic metal powder is 10 atomic parts Fe atoms.
The number of Al atoms is 70 to 200, and the number of rare earth elements is 0.5 to 30 with respect to 0. The invention according to claim 2, wherein the ferromagnetic metal powder is The ferromagnetic metal powder further contains Na atoms and Ca atoms as elements forming the ferromagnetic metal powder, and the weight ratio of the elements in the entire ferromagnetic metal powder is less than 0.1 parts by weight of Na atoms to 100 parts by weight of Fe atoms and Ca atoms. 0.1 to 2 parts by weight, 2 to 10 parts by weight of Al atoms, 1 to 8 parts by weight of atoms of rare earth elements, and the average abundance ratio of the elements forming the surface of the ferromagnetic metal powder is 100 Fe atoms. With respect to Na atom number 2
30, Ca atom number 5 to 30, Al atom number 70 to 200,
The magnetic recording medium according to claim 1, wherein the number of atoms of the rare earth element is 0.5 to 30, and the invention according to claim 3 is characterized in that the ferromagnetic metal powder is the ferromagnetic metal powder. Further, as elements to be formed, Co atom, Ni atom and Si
An atomic weight ratio of the elements in the whole ferromagnetic metal powder is 2 to 2 Co atoms with respect to 100 parts by weight of Fe atoms.
0 parts by weight, Ni atoms 2 to 20 parts by weight, Si atoms 0.3 to
5 parts by weight, less than 0.1 parts by weight of Na atom, 0.1 atom of Ca
˜2 parts by weight, Al atoms 2 to 10 parts by weight, rare earth element atoms 1 to 8 parts by weight, and the average abundance ratio of the elements forming the surface of the ferromagnetic metal powder is 100 Fe atoms. Co atom number less than 0.1, Ni atom number less than 0.1, S
The number of i atoms is 20 to 130, the number of Na atoms is 2 to 30, the number of Ca atoms is 5 to 30, the number of Al atoms is 70 to 200, and the number of rare earth element atoms is 0.5 to 30. The magnetic recording medium according to claim 4, wherein the magnetic recording medium has a magnetic layer containing at least a ferromagnetic metal powder on a non-magnetic support, A magnetic recording medium characterized in that the average abundance ratio of elements forming the surface of the magnetic metal powder is 70 to 300 Al atoms with respect to 100 Fe atoms and 0.5 to 60 rare earth element atoms. The present invention according to claim 5 is characterized in that the atom of the rare earth element is one or more selected from the group consisting of Sm, Nd, Y and Pr. It is a magnetic recording medium described in The invention according to claim 6 is the magnetic recording medium according to any one of claims 1 to 5, wherein at least one layer is provided as a lower layer between the non-magnetic support and the magnetic layer. The invention according to claim 7 is characterized in that the dry film thickness of the magnetic layer is 0.02 to 0.6 μm, and the dry film thickness of the lower layer is 0.2 to 2.0 μm. 9. The magnetic recording medium according to claim 8, wherein the lower layer is a layer containing a needle-shaped non-magnetic powder in the invention according to claim 8. is there.

The magnetic recording medium of the present invention will be described in detail below.

--Structure of Magnetic Recording Medium-- The magnetic recording medium of the present invention comprises a non-magnetic support (A),
A magnetic layer (B) containing a ferromagnetic metal powder is laminated, and if necessary, a lower layer (at least one layer between the non-magnetic support and the magnetic layer (B) ( C) and, if necessary, an appropriate layer on the magnetic layer (B).

(A) Non-Magnetic Support The materials for forming the non-magnetic support include, for example, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose triacetate, and cellulose die. Cellulose derivatives such as acetate, polyamide,
Examples include plastics such as aramid resin and polycarbonate.

The form of the non-magnetic support is not particularly limited, and is mainly tape-like, film-like, sheet-like, card-like,
There are disc shape and drum shape.

The thickness of the non-magnetic support is not particularly limited, but in the case of a film or sheet, it is usually 2 to
The thickness is 100 μm, preferably 3 to 50 μm. In the case of a disc or a card, it is about 30 μm to 10 mm, and in the case of a drum, it is appropriately selected according to the recorder or the like.

The non-magnetic support may have a single-layer structure or a multi-layer structure. The non-magnetic support may be subjected to surface treatment such as corona discharge treatment.

A back coat layer is provided on the surface (back surface) of the non-magnetic support on which the magnetic layer is not provided, for the purpose of improving the running property of the magnetic recording medium, preventing electrification, and preventing transfer. It is preferable that an undercoat layer be provided between the magnetic layer and the non-magnetic support.

(B) Magnetic Layer The magnetic layer contains magnetic powder. Furthermore, if necessary, a binder and other components can be contained.

The thickness of the magnetic layer is usually 0.02.
To 0.6 μm, particularly preferably 0.02 to 0.4
μm. When the thickness is less than 0.02 μm,
When recording is not sufficient, an output may not be obtained at the time of reproduction. On the other hand, when it is larger than 0.6 μm, a sufficient reproduction output may not be obtained due to film thickness loss.

(B-1) Magnetic Powder In the present invention, the magnetic layer contains a specific ferromagnetic metal powder described later as an essential magnetic powder.

The ferromagnetic metal powder contains Fe, Al, and a rare earth element atom as its constituent elements, and a preferable rare earth element atom is selected from the group consisting of Sm, Nd, Y, and Pr. It is an atom of more than one species.

In the ferromagnetic metal powder according to the present invention, the weight ratio of the elements in the entire ferromagnetic metal powder is 2 to 10 parts by weight of Al atoms with respect to 100 parts by weight of Fe atoms. Is 1 to 8 parts by weight, and the average abundance ratio of elements forming the surface of the ferromagnetic metal powder is 100 to Fe atoms and 70 to 2 Al atoms.
The number of atoms of the rare earth element is preferably 0.5 to 30.

More preferably, the ferromagnetic metal powder further contains Na and Ca as constituent elements, and the weight ratio of the elements in the entire ferromagnetic metal powder is 100 Fe atoms.
With respect to parts by weight, Na atoms are less than 0.1 parts by weight,
Ca atom is 0.1 to 2 parts by weight, and Al atom is 2-1.
0 parts by weight, the rare earth element is 1 to 8 parts by weight, and the average abundance of elements forming the surface of the ferromagnetic metal powder is 100 Fe atoms and 2 Na atoms.
30, the number of Ca atoms is 5 to 30, the number of Al atoms is 70 to 200, and the number of rare earth elements is 0.5 to
Thirty.

More preferably, the ferromagnetic metal powder further contains Co, Ni and Si as its constituent elements, and the weight ratio of the elements in the entire ferromagnetic metal powder is 100 parts by weight of Fe atoms to Co. Atoms are 2 to 20 parts by weight, Ni atoms are 2 to 20 parts by weight, and Si atoms are 0.
3 to 5 parts by weight, Na atoms are less than 0.1 parts by weight, Ca atoms are 0.1 to 2 parts by weight, and Al atoms are 2 parts by weight.
-10 parts by weight, the number of atoms of the rare earth element is 1 to 8 parts by weight, and the average abundance ratio of the elements forming the surface of the ferromagnetic metal powder is 100 atomic Fe and Co atomic numbers. It is less than 0.1, the number of Ni atoms is less than 0.1, the number of Si atoms is 20 to 130, and the number of Na atoms is 2.
To 30, the number of Ca atoms is 5 to 30, the number of Al atoms is 70 to 200, and the number of rare earth element atoms is 0.5 to
Thirty.

The ferromagnetic metal powder limited as described above has a high coercive force (Hc) of 1700 Oe or more, 120
It is preferable because it has a high saturation magnetization (σ _s ) of emu / g or more and high dispersibility.

The content of this ferromagnetic metal powder in the ferromagnetic layer is usually 60 to 95% by weight, preferably 70 to 90% by weight, and particularly preferably, based on the total solid content in the layer. It is 75 to 85% by weight.

In the present invention, the magnetic layer may contain conventionally known magnetic powder.

As the conventionally known magnetism, for example, Fe
A compound represented by O _x (1.33 <x <1.5),
Ferromagnetic iron oxide powders such as Co—FeO _x (1.33 <x <1.5), metal-based metal powders containing Fe, Ni, Co, etc. as main components, among these, Fe-based metal powders, and further Ferromagnetic metal powder such as Fe-Al-based ferromagnetic metal powder,
Examples include hexagonal plate-like powder.

The ferromagnetic powder used in the present invention has a major axis diameter of less than 0.30 μm, preferably 0.04 to 0.20 μm, and more preferably 0.0.
It is preferably 5 to 0.17 μm. When the major axis diameter of the ferromagnetic powder is within the above range, the surface property of the magnetic recording medium can be improved and the electromagnetic conversion characteristics can be improved.

In the present invention, the major axis diameter (a) of the ferromagnetic powder contained in the magnetic layer and the major axis diameter (b) of the nonmagnetic powder contained in the lower nonmagnetic layer are defined. The ratio (axial ratio; b / a) is preferably 3 or less, particularly preferably 2.5 or less, and further preferably 2 or less. This is because when the axial ratio is within the above range, excellent properties such as good surface properties of the magnetic recording medium can be exhibited.

The above magnetic powder may be used alone or in combination of two or more kinds.

(B-2) Binder The binder contained in the magnetic layer is typically a vinyl chloride resin such as polyurethane, polyester or vinyl chloride copolymer, and these resins are- _{SO 3 M, -OSO 3 M,} -COOM, -PO (OM
¹ ) ₂ and a repeating unit having at least one polar group selected from sulfobetaine groups.

In the above polar group, M represents a hydrogen atom or an alkali metal such as Na, K and Li, and M ¹ represents a hydrogen atom, an alkali atom such as Na, K and Li or an alkyl group.

The polar group has the function of improving the dispersibility of the magnetic powder, and the content in each resin is 0.1 to 8.0 mol%, preferably 0.2 to 6.0 mol%. is there. When the content is less than 0.1 mol%, the dispersibility of the magnetic powder is deteriorated, and when the content is more than 8.0 mol%, the magnetic coating tends to gel. The weight average molecular weight of each resin is preferably in the range of 15,000 to 50,000.

The content of the binder is the ferromagnetic metal powder 1
It is usually 8 to 25 parts by weight, preferably 10 to 20 parts by weight, relative to 00 parts by weight.

The binder is not limited to one kind alone, and two or more kinds may be used in combination. In this case, the ratio of polyurethane and / or polyester to vinyl chloride resin is usually 90:10 by weight. It is 10:90, and preferably in the range of 70:30 to 30:70.

The polar group-containing vinyl chloride copolymer used as a binder in the present invention includes, for example, a copolymer having a hydroxyl group, such as a vinyl chloride-vinyl alcohol copolymer, and a compound having the polar group and a chlorine atom. Can be synthesized by the addition reaction of.

Regarding the technique for introducing a polar group into a vinyl chloride-based copolymer, JP-A-57-44227 and JP-A-5-44227 have been used.
8-108052, 59-8127, 60-1
No. 01161, No. 60-235814, No. 60-23
No. 8306, No. 60-238371, No. 62-121
No. 923, No. 62-146432, No. 62-1464.
No. 33 and the like are described, and these can be used in the present invention.

Next, the synthesis of polyester and polyurethane used in the present invention will be described.

Polyesters are generally obtained by reacting a polyol with a polybasic acid.

By using this known method, a polyester (polyol) having a polar group can be synthesized from a polyol and a polybasic acid partially having a polar group.

Incidentally, other polar group-introduced polyesters can also be synthesized by a known method.

Next, polyurethane will be described.

It is obtained from the reaction of polyols with polyisocyanates.

As the polyol, a polyester polyol obtained by reacting a polyol with a polybasic acid is generally used.

Therefore, when a polyester polyol having a polar group is used as a raw material, a polyurethane having a polar group can be synthesized.

Examples of polyisocyanates include diphenylmethane-4-4'-diisocyanate (MDI),
Hexamethylene diisocyanate (HMDI), tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), lysine isocyanate methyl ester (LDI) and the like can be mentioned.

As another method for synthesizing a polyurethane having a polar group, an addition reaction of a polyurethane having a hydroxyl group with the following compound having a polar group and a chlorine atom is also effective.

Cl-CH ₂ CH ₂ SO ₃ M, Cl-CH ₂ CH ₂ OSO ₂ M, Cl-
CH ₂ COOM, Cl-CH ₂ -P (= O) (OM ¹ ) _{2 As} a technique for introducing a polar group into polyurethane, JP-B-58-41565 and JP-A-57-9242 are known.
No. 2, No. 57-92423, No. 59-8127, No. 59-5423, No. 59-5424, No. 62-12.
It is described in the publications such as 1923, and these can be used in the present invention.

In the present invention, the following resins can be used together as a binder in an amount of 50% by weight or less based on the total weight of the binder.

The resin has a weight average molecular weight of 1
Vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose Derivatives (nitrocellulose etc.), styrene-butadiene copolymers, phenol resins, epoxy resins, urea resins, melamine resins, phenoxy resins, silicone resins, acrylic resins, urea formamide resins, various synthetic rubber resins, etc. .

(B-3) Other Components In the present invention, in order to improve the quality of the magnetic layer,
Additives such as an abrasive, a lubricant, a durability improver, a dispersant, an antistatic agent and a conductive fine powder can be contained as other components.

As the polishing agent, a substance known per se can be used.

The average particle size of the abrasive is usually 0.05 to 0.6 μm, preferably 0.05 to 0.6 μm.
0.5 μm, particularly preferably 0.05 to 0.3 μm
m.

The content of the abrasive in the ferromagnetic layer is usually 3 to 20 parts by weight, preferably 5 to 15 parts.
Parts by weight, particularly preferably 5 to 10 parts by weight.

Fatty acids and / or fatty acid esters can be used as the lubricant. in this case,
The amount of fatty acid added is preferably 0.2 to 10% by weight, more preferably 0.5 to 5% by weight, based on the magnetic powder. If the addition amount is less than 0.2% by weight, the running property tends to be lowered, and if the addition amount is more than 10% by weight, the fatty acid is likely to seep out to the surface of the magnetic layer or the output is likely to be lowered.

The amount of fatty acid ester added is preferably 0.2 to 10% by weight, more preferably 0.5 to 5% by weight, based on the magnetic powder. If the addition amount is less than 0.2% by weight, the still durability is apt to deteriorate, and 10
When the content exceeds the weight%, the fatty acid ester is likely to seep out to the surface of the magnetic layer and the output is likely to decrease.

When it is desired to use a fatty acid and a fatty acid ester together to enhance the lubricating effect, the weight ratio of the fatty acid and the fatty acid ester is preferably 10:90 to 90:10.

The fatty acid may be a monobasic acid or a dibasic acid and preferably has 6 to 30 carbon atoms.
The range of -22 is more preferable.

As the lubricant other than the above-mentioned fatty acids and fatty acid esters, substances known per se can be used, and for example, silicone oil, fluorinated carbon, fatty acid amide, α-olefin oxide and the like can be used.

Examples of the curing agent include polyisocyanates. Examples of the polyisocyanates include aromatic polyisocyanates such as adducts of tolylene diisocyanate (TDI) and active hydrogen compounds, and hexamethylene diisocyanate. There are aliphatic polyisocyanates such as adducts of (HMDI) with active hydrogen compounds. The weight average molecular weight of the polyisocyanate is preferably in the range of 100 to 3,000.

Examples of the dispersant include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and other fatty acids having 12 to 18 carbon atoms; salts of these alkali metals or alkaline earth metals. Or amides thereof; polyalkylene oxide alkyl phosphates; lecithin; trialkyl polyolefin oxyquaternary ammonium salts; azo compounds having a carboxyl group and / or a sulfonic acid group. These dispersants are usually
It is used in the range of 0.5 to 5% by weight with respect to the magnetic powder.

Examples of the antistatic agent include cationic surfactants such as quaternary amines; anionic surfactants containing an acid group such as sulfonic acid, sulfuric acid, phosphoric acid, phosphoric acid ester and carboxylic acid; aminosulfonic acid and the like. Examples of the amphoteric surfactant include natural surfactants such as saponin. The above-mentioned antistatic agent is usually added to the binder in an amount of 0.01
-40% by weight is added.

Further, in the present invention, conductive fine powder can be preferably used as the antistatic agent. As the antistatic agent, carbon black, graphite,
Tin oxide film or antimony solid solution tin oxide film with pigment such as tin oxide, silver powder, silver oxide, silver nitrate, organic compound of silver, metal particles such as copper powder, metal oxide such as zinc oxide, barium sulfate and titanium oxide And the like, which are coated with a conductive substance such as.

The average particle size of the conductive fine powder is
5 to 700 nm, more preferably 5 to 200 n
m.

The content of the conductive fine powder is 1 to 20 parts by weight, preferably 2 to 7 parts by weight, based on 100 parts by weight of the magnetic powder.

(C) Lower Layer The lower layer is composed of at least one layer and is formed, if necessary, with a single layer or a plurality of layers between the non-magnetic support and the magnetic layer.

The lower layer may be formed of one kind of layer or a combination of two or more kinds of layers and is not particularly limited. Examples of the lower layer include a magnetic layer containing magnetic powder (C-1) and a non-magnetic layer containing non-magnetic powder (C-).
2), a layer (C-3) containing a high magnetic permeability material, or a layer composed of a combination of these layers.
In the present invention, the nonmagnetic layer (C-2) is preferable,
Particularly preferred is a nonmagnetic layer containing needle-shaped nonmagnetic powder.

The dry film thickness of the lower layer is usually 0.1 to
The thickness is 2.5 μm, preferably 0.2 to 2.0 μm, and particularly preferably 0.5 to 2.0 μm. When the dry film thickness is larger than 2.5 μm, the surface roughness of the upper layer surface after the multi-layering increases, that is, so-called multi-layer surface roughness occurs,
In some cases, favorable electromagnetic conversion characteristics may not be obtained, while
If it is less than 0.5 μm, it becomes difficult to obtain high smoothness during calendaring, the electromagnetic conversion characteristics are deteriorated, and the meaning of providing the lower layer may be diminished.

(C-1) Magnetic Layer The lower magnetic layer contains magnetic powder. Further, it contains a binder and other components as necessary.

(C-1-1) Magnetic Powder The magnetic powder contained in the lower magnetic layer is not particularly limited, and the compounds exemplified in (B-1) can be preferably used. These magnetic powders may be used alone or in combination of two or more.

Of these magnetic powders, C is preferable.
is an _{o-FeO X (1.33 <X} <1.5). The lower magnetic layer is Co—FeO _x (1.33 <X <1.
When 5) is included, the recording wavelength is large, especially 1 μm.
The reproduction output above becomes good.

The content of the magnetic powder is usually 70 to 90% by weight, preferably 75 to 85% by weight, based on the whole solid content in the layer.

(C-1-2) Binder As the binder contained in the lower magnetic layer,
The compounds exemplified in (B-2) can be used, and the amount thereof is usually 5 to 25 parts by weight, preferably 10 to 20 parts by weight based on 100 parts by weight of the ferromagnetic metal powder.
Parts by weight.

(C-1-3) Other Components As other components contained in the lower magnetic layer,
The compounds exemplified in (B-3) can be used. The amount is not particularly limited and can be appropriately selected as long as the object of the present invention is not impaired.

(C-2) Nonmagnetic Layer The nonmagnetic layer contains nonmagnetic powder. Further, it contains a binder and other components as necessary.

(C-2-1) Nonmagnetic Powder In the present invention, various known nonmagnetic powders can be appropriately selected and used.

Examples of the non-magnetic powder include carbon black, graphite, TiO ₂ , barium sulfate and Zn.
S, MgCO ₃ , CaCO ₃ , ZnO, CaO, tungsten disulfide, molybdenum disulfide, boron nitride, Mg
O, SnO ₂ , SiO ₂ , Cr ₂ O ₃ , α-Al ₂ O
₃ , α-Fe ₂ O ₃ , α-FeOOH, SiC, cerium oxide, corundum, artificial diamond, α-iron oxide,
Examples thereof include garnet, garnet, silica, silicon nitride, boron nitride, silicon carbide, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, tribolite, diatomaceous earth and dolomite.

Of these, preferred are carbon black, CaCO ₃ , TiO ₂ , barium sulfate and α-Al.
₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, Cr ₂ O ₃
And other inorganic powders. More preferred are carbon black, TiO ₂ , and α-Fe ₂ O ₃ .

In the present invention, a non-magnetic powder having a needle-like powder shape can be preferably used. By using the acicular non-magnetic powder, the smoothness of the surface of the non-magnetic layer can be improved, and the smoothness of the surface of the uppermost layer composed of the magnetic layer laminated thereon can also be improved. As the acicular powder used at this time, α-Fe ₂
O ₃ and TiO ₂ are preferred.

The major axis diameter of the nonmagnetic powder is usually 0.50 μm or less, preferably 0.40 μm or less, and particularly preferably 0.30 μm or less.

The minor axis diameter of the non-magnetic powder is usually 0.10 μm or less, preferably 0.08 μm or less, and particularly preferably 0.06 μm or less.

The axial ratio of the non-magnetic powder is usually 2 to
It is 20, preferably 5 to 15, and particularly preferably 5 to 10. The axial ratio referred to here is the ratio of the major axis diameter to the minor axis diameter (major axis diameter / minor axis diameter).

The specific surface area of the non-magnetic powder is usually 10 to 250 m ² / g, preferably 20 to 150.
m ² / g, particularly preferably 30 to 100 m ² / g
Is.

When the non-magnetic powder having the major axis diameter, the minor axis diameter, the axial ratio and the specific surface area within the above ranges is used, the surface property of the non-magnetic layer can be improved and the surface property of the magnetic layer is also improved. It is preferable in that it can be brought into a different state.

Further, in the present invention, it is preferable that the non-magnetic powder is surface-treated with a Si compound and / or an Al compound. By using the non-magnetic powder that has been subjected to such surface treatment, the surface condition of the magnetic layer can be improved. As the content of Si and / or Al, Si is 0.1 to 1 with respect to the non-magnetic powder.
It is preferable that 0 wt% and Al are 0.1 to 10 wt%.

The content of the nonmagnetic powder in the nonmagnetic layer is usually 50 to 99% by weight, and preferably 60 to 9% by weight, based on the total of all components constituting the nonmagnetic layer.
It is 5% by weight, particularly preferably 70 to 95% by weight. When the content of the non-magnetic powder is within the above range, the surface condition of the magnetic layer and the non-magnetic layer can be improved.

(C-2-2) Binder As the binder contained in the lower non-magnetic layer,
The compounds exemplified in (B-2) can be used, and the amount thereof is 100 parts by weight of the non-magnetic powder,
Usually 5 to 150 parts by weight, preferably 10 to 120
Parts by weight.

(C-2-3) Other Components As the other components contained in the lower non-magnetic layer, the compounds exemplified in (B-3) can be used. The amount is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected.

(C-3) Layer Containing High Magnetic Permeability Material The layer containing the high magnetic permeability material contains a high magnetic permeability material. Further, it contains a binder and other components as necessary.

(C-3-1) High Magnetic Permeability Material As a high magnetic permeability material, its coercive force Hc is 0 <Hc ≦.
1.0 × 10 ⁴ (A / m), preferably 0 <Hc ≦ 5.
It is 0 × 10 ³ (A / m). When the coercive force is within the above range, the effect of stabilizing the magnetized region of the uppermost layer is exhibited as the high magnetic permeability material. When the coercive force exceeds the above range, desired properties may not be obtained due to the manifestation of properties as a magnetic material, which is not preferable.

In the present invention, it is preferable to appropriately select a material having a coercive force range as the high magnetic permeability material. Examples of such a high magnetic permeability material include a metal soft magnetic material and an oxide soft magnetic material.

As the metal soft magnetic material, Fe--S is used.
i alloy, Fe-Al alloy (Alperm, Alfeno
l, Alfer), permalloy (Ni-Fe binary alloy, and multi-component alloy in which Mo, Cu, Cr, etc. are added thereto), sendust (Fe-Si-Al {9.6 wt% Si, 5. 4% Al, the composition of which the balance is Fe}), Fe—Co alloy, and the like. Among them, sendust is preferable as a preferable metal soft magnetic material. The metal soft magnetic material as the high magnetic permeability material is not limited to those exemplified above, and other metal soft magnetic materials can be used. The high magnetic permeability material can be used alone, or
Also, two or more thereof can be used in combination.

As the soft oxide magnetic material, spinel ferrites such as MnFe ₂ O ₄ , Fe ₃ O ₄ and C are used.
oFe ₂ O ₄ , NiFe ₂ O ₄ , MgFe ₂ O ₄ , Li
_0.5 Fe _2.5 O ₄ , Mn-Zn ferrite, Ni-
Zn-based ferrite, Ni-Cu-based ferrite, Cu-Z
n type ferrite, Mg-Zn type ferrite, Li-ZN
An example is a system ferrite. Among these, Mn-Zn based ferrite and Ni-Zn based ferrite are preferable. These soft oxide magnetic materials can be used alone or in combination of two or more.

This high-permeability material is made into a fine powder by using a ball mill or other crushing device, and its particle size is 1 mμ.
It is preferably 1,000 mμ, and particularly preferably 1 mμ to 500 mμ. In order to obtain such a fine powder, the metal soft magnetic material can be obtained by spraying a molten alloy in a vacuum atmosphere. Further, the soft oxide magnetic material can be made into a fine powder by a glass crystallization method, a coprecipitation firing method, a hydrothermal synthesis method, a flux method, an alkoxide method, a plasma jet method or the like.

In the layer containing the high magnetic permeability material, the content of the high magnetic permeability material is 10 to 100% by weight, preferably 50 to 100% by weight, and more preferably 60 to 1% by weight.
It is 00% by weight. When the content of the high magnetic permeability material is within the above range, the effect of stabilizing the magnetization of the uppermost layer can be sufficiently obtained. If the content of the high magnetic permeability material is less than 50% by weight, the effect of the high magnetic permeability layer may not be obtained, which is not preferable.

The layer containing the high magnetic permeability material may contain non-magnetic particles.

(C-3-2) Binder As the binder contained in the layer containing the high magnetic permeability material in the lower layer, the compounds exemplified in (B-2) can be mentioned, and the amount thereof is It is usually 5 to 30 parts by weight, preferably 10 to 25 parts by weight, based on 100 parts by weight of the high magnetic permeability material.

(C-3-3) Other Components As the other components contained in the layer containing the high magnetic permeability material in the lower layer, the compounds exemplified in (B-3) can be mentioned. The amount is not particularly limited as long as it does not impair the object of the present invention, and can be appropriately selected.

--Manufacture of Magnetic Recording Medium-- In the case of a multilayer structure, the magnetic recording medium of the present invention is coated by a so-called wet-on-wet method in which the magnetic layer is coated when the lower layer is in a wet state. It is preferable to install it. As the wet-on-wet system, a known method used for manufacturing a multilayer structure type magnetic recording medium can be appropriately adopted.

For example, generally, a magnetic powder, a binder, a dispersant, a lubricant, an abrasive, an antistatic agent, and the like are kneaded with a solvent to prepare a high-concentration magnetic coating, and then the high-concentration magnetic coating is diluted. After preparing the magnetic paint, the magnetic paint is applied to the surface of the non-magnetic support.

Examples of the solvent include ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone; alcohols such as methanol, ethanol and propanol; methyl acetate, ethyl acetate, butyl acetate and the like. Esters; cyclic ethers such as tetrahydrofuran; halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform and dichlorobenzene can be used. These various solvents may be used alone or in combination of two or more.

In kneading and dispersing the magnetic layer forming components,
Various kneading dispersers can be used.

Examples of this kneading / dispersing machine include a two-roll mill, a three-roll mill, a ball mill, a pebble mill,
Kobol Mill, Tron Mill, Sand Mill, Sand Grinder, Sqegvari Attritor, High Speed Impeller Disperser,
High speed stone mill, high speed impact mill, disper, high speed mixer, homogenizer, ultrasonic disperser, open kneader, continuous kneader, pressure kneader and the like can be mentioned. Of the above kneading dispersers, 0.05-0.5 kW
The kneading dispersers capable of providing a power consumption load (per 1 kg of magnetic powder) are a pressure kneader, an open kneader, a continuous kneader, a two-roll mill, and a three-roll mill.

To apply the magnetic layer and the lower layer on the non-magnetic support, specifically, as shown in FIG. 1, first, the non-magnetic support 1 fed from the supply roll 32 is applied to the extrusion method. After the magnetic coating material and the lower layer coating material are multi-layered by a wet-on-wet method using the extrusion coaters 10 and 11, the orientation magnet or the vertical orientation magnet 33.
And is introduced into the dryer 34, where hot air is blown from the nozzles arranged above and below to dry it. Next, the dried non-magnetic support 1 with each coating layer is guided to a super calender device 37 composed of a combination of calender rolls 38, where it is calendered and then wound on a winding roll 39. The magnetic film thus obtained can be cut into a tape having a desired width to produce a magnetic recording tape for 8 mm video, for example.

In the above method, each paint was extruded through an in-line mixer (not shown), the coater 10,
11 may be supplied. It should be noted that in the figure, the arrow indicates the transport direction of the nonmagnetic support. Extrusion coaters 10 and 11 are provided with liquid pools 13 and 14, respectively, and the coating materials from the coaters are stacked in a wet-on-wet system. That is, immediately after applying the lower layer coating material (when it is in an undried state)
Apply multiple layers of magnetic paint.

As the extrusion coater, in addition to the two extrusion coaters 5a and 5b shown in FIG. 2, extrusion coaters 5c and 5d of the type shown in FIGS. 3 and 4 can be used. Of these, the extrusion coater 5d shown in FIG. 4 is preferable in the present invention. The lower coating material 2 and the magnetic coating material 4 are co-extruded by the extrusion coater 5d to apply multiple layers.

The magnetic field in the oriented magnet or the magnet for vertical orientation is about 20 to 10,000 Gauss, the drying temperature by the dryer is about 30 to 120 ° C., and the drying time is about 0.1 to 10 minutes. Is.

In the wet-on-wet system, a combination of a reverse roll and an extrusion coater, a combination of a gravure roll and an extrusion coater, etc. can also be used. Further, an air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, cast coater, spray coater and the like can be combined.

In the multi-layer coating in the wet-on-wet system, since the magnetic layer is coated while the lower layer located below the magnetic layer is in a wet state, the surface of the lower layer (that is, the boundary with the magnetic layer). The surface is smooth and the surface properties of the magnetic layer are good, and the adhesiveness between the upper and lower layers is also improved. As a result, especially for high density recording, high output and low noise are required, for example, the performance required as a magnetic tape is satisfied, and high durability performance is required. The peeling is eliminated, the film strength is improved, and the durability is sufficient. Further, the wet-on-wet multi-layer coating method can also reduce dropout and improve reliability.

-Surface Smoothing-In the present invention, it is also possible to carry out a surface smoothing process by calendering.

Thereafter, if necessary, burnishing or blade processing is performed for slitting.

In the surface smoothing treatment, temperature, linear pressure, C / s (coating speed) and the like can be mentioned as calendering conditions.

In the present invention, the above temperature is usually set to 5
0 to 140 ° C., the linear pressure is 50 to 400 kg / cm,
It is preferable to keep the C / S at 20 to 1,000 m / min. If these values are not satisfied, it may be difficult or impossible to keep the surface properties of the magnetic recording medium in good condition.

The thickness of the magnetic layer obtained as a result of the above processing is set to 0.02 to 0.6 μm. The layer has a thickness of 0.
If it exceeds 6 μm, the electrical characteristics are deteriorated, so that a magnetic recording medium suitable as a digital recording medium, which is the object of the present invention, cannot be obtained.

[0113]

Embodiments of the present invention will be described below.

The following components, ratios, and operation sequences can be variously modified without departing from the scope of the present invention. In the following examples, all "parts" are "parts by weight".

The respective components of the uppermost layer magnetic coating material and the lower layer coating material having the following compositions were kneaded and dispersed using a kneader and a sand mill to prepare an uppermost layer magnetic coating material and a lower layer coating material.

{Magnetic paint} Ferromagnetic metal powder: 100 parts (average major axis diameter: 0.15 μm, σ _s : 1.25 emu / g, axial ratio: 8, pH: 9.5, crystal size: 145 Å, Hc: 1700 Oe, BET: 53 m ² / g) Potassium sulfonate group-containing vinyl chloride resin: 10 parts (Japan ZEON Corporation MR-110) Sodium sulfonate group-containing polyurethane resin ・ ・ ・ ・ ・ 10 parts (Toyobo Co., Ltd. UR-8700) α-alumina ( 0.15 μm) ··· 8 parts Stearic acid ····· 1 part Butyl stearate ···· 1 part Cyclohexanone ..... 100 parts methyl ethyl ketone ..... 100 Toluene .............. 100 parts.

{Coating A for lower layer} α-Fe ₂ O ₃ --- 100 parts (major axis diameter: 0.10 μm, minor axis diameter: 0.02 μm, axial ratio: 9, BET: 55 m ^{2 /} g, pH: 7.5, crystal size: 220 Å, surface treatment with Si, Al compound, Si content 0.1% by weight, Al content 0.3% by weight) Potassium sulfonate group-containing chloride Vinyl-based resin ・ ・ ・ ・ ・ 12 parts (Nippon Zeon Co., Ltd. MR-110) Sodium sulfonate group-containing polyurethane resin ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ ・ ・ ・ ・ 8 parts (UR-8700, manufactured by Toyobo Co., Ltd.) α-alumina (average particle size: 0.2 μm) ・ ・ ・ ・ ・ ・ 5 parts Carbon black (average particle size: 15 nm, DBP oil absorption amount: 8.5ml / 100g, pH: 8.0 BET value: 255m ² / g, volatilization Min; 1.1%, tinting strength: 130%) 10 parts stearic acid 1 part butyl stearate・ ・ ・ ・ ・ ・ ・ ・ 1 part Cyclohexanone ・ ・ ・ ・ ・ ・ ・ ・ 100 parts Methyl ethyl ketone ・ ・ ・ ・ ・ ・ 100 parts Toluene ・ ・ ・ ・ ・ ・ ・ ・100 parts To each of the obtained magnetic paint and lower layer paint A, 5 parts of a polyisocyanate compound (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added.

{Lower layer paint B} The lower layer paint B is Co-γ-Fe instead of α-Fe ₂ O ₃ in the lower layer paint A.
₂ O ₃ (Hc: 650 Oe, major axis diameter: 0.22 μm,
BET value: 45 m ^{2 /} g, pH: 5.0, axial ratio 1.2,
σ _s : 75 emu / g, crystallite size: 200 Å) except that it was obtained in the same manner as the lower layer coating material A.

{Coating for lower layer C} Spherical α-Fe ₂ O ₃ (average particle diameter: 37 nm, BET value: 42 m ² / g, pH: 5 in place of needle-shaped α-Fe ₂ O ₃ in lower layer coating A) ．
5, SiAl compound (Si: 0.1% by weight, Al: 0.
(3% by weight), except that the surface treatment) was used.

[0120] acicular TiO ₂ in place of the acicular α-Fe ₂ O ₃ in {undercoating paint D} paint A for lower layer (major axis diameter: 0.
12 μm, axial ratio: 6, BET value: 40 m ² / g, pH:
7.0, SiAl compound (Si: 0.1% by weight, Al:
0.4% by weight) except that the surface treatment) was used.

{Lower-layer coating material E} Spherical TiO ₂ (average particle diameter: instead of the acicular α-Fe ₂ O ₃ in the lower-layer coating material A)
32 nm, BET value: 40 m ^{2 /} g, pH: 7.5, crystal diameter: rutile, SiAl compound (Si: 0.1% by weight,
Al: 0.3 wt%) except that the surface treatment) was used.

(Examples 1 to 16 and Comparative Examples 1 to 7 and Examples 1-1 to 1-11 and Comparative Examples 1-1 to 1-
5) Using the above-mentioned magnetic coating material containing a ferromagnetic metal powder and the above-mentioned lower layer coating material containing a non-magnetic powder shown in Table 1, a wet-on-wet system was applied to obtain a thickness of 10
After coating on a polyethylene terephthalate film having a thickness of .mu.m, a magnetic field orientation treatment is performed while the coating film is undried, followed by drying and then surface smoothing treatment with a calendar. A magnetic layer consisting of a lower layer and an uppermost layer having a specified thickness was formed.

Further, a coating material having the following composition is applied to the surface (rear surface) of the polyethylene terephthalate film on the side opposite to the magnetic layer, the coating film is dried and calendered according to the above-mentioned calendering conditions. To form a back coat layer having a thickness of 0.8 μm,
A wide original anti-magnetic tape was obtained.

Carbon black (Raven 1035) ··· 40 parts Barium sulfate (average particle size 300 nm) · 10 parts Nitrocellulose ······ 25 parts Polyurethane resin ···· 25 parts (N-2301 manufactured by Nippon Polyurethane Co., Ltd.) Polyisocyanate compound ... 10 parts (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) Cyclohexanone 400 parts Methyl ethyl ketone ... 250 parts Toluene ... 250 parts The original antimagnetic tape thus obtained is slit to 8 m.
An m-wide magnetic recording medium for video was prepared. The following evaluations were performed on this magnetic recording medium. The results are shown in Tables 2 and 3.

<Evaluation><Overallcomposition> F in the overall composition of the ferromagnetic metal powder
e, Co, Ni, Nd, Si, Al, Y, Pr, Sm,
Regarding the abundance ratio of each element of La, the wavelength dispersion type fluorescent X
Fluorescence X of each element in the sample using a line analyzer (WDX)
After measuring the line strength, it was calculated according to the fundamental parameter method (hereinafter referred to as FP method).

The FP method will be described below.

For the measurement of fluorescent X-ray, WDX system 3080 manufactured by Rigaku Denki Co., Ltd. was used under the following conditions.

X-ray tube: Rhodium tube Output: 50 KV, 50 mA Spectroscopic crystal: LiF (Fe, Co, Ni, Nd, Y, P
r, Sm, La), PET (for Al),
RX-4 (for Si) Absorber: 1/1 (Fe only 1/10) Slit: COARSE Filter: OUT PHA: 15-30 (for Al, Si), 10
~ 30 (Fe, Co, Ni, Nd, Y, Pr, Sm, L
(For a) Counting time: peak = 40 seconds, background = 40
Second (measurement at two points before and after the peak) The measurement of fluorescent X-rays is not limited to the above-mentioned device, and various devices can be used.

The following eight kinds of metal compounds were used as standard samples.

Standard sample 1 is Analytical R
effort Materials intern
alloy SRM1219 (C is 0.1
5 wt%, Mn 0.42 wt%, P 0.03 wt%, Si 0.55 wt%, Cu 0.16 wt%, N
i is 2.16% by weight, Cr is 15.64% by weight, Mo is 0.16% by weight, and V is 0.06% by weight. ).

The standard sample 2 is Analytical R
effort Materials intern
alloy SRM1250 (Ni 3
7.78 wt%, Cr 0.08 wt%, Mo 0.0
1% by weight, 16.10% by weight of Co, and 0.99% by weight of Al are contained. ).

The standard sample 3 is magnetic iron oxide powder (Mn 0.14% by weight, P 0.15% by weight, S 0.19% by weight, Si 0.36% by weight, Co 3.19% by weight). weight%,
It contains 1.26% by weight of Zn, 0.07% by weight of Ca, and 0.02% by weight of Na. ).

The standard sample 4 is a ferromagnetic metal powder (containing 2.73% by weight of Nd).

The standard sample 5 is a ferromagnetic metal powder (Sr.
Contains 97% by weight. ).

The standard sample 6 is a ferromagnetic metal powder (Ba containing 1.
It contains 40% by weight and 0.40% by weight of Ca. ).

The standard sample 7 is a ferromagnetic metal powder (La is 2.
Contains 69% by weight. ).

The standard sample 8 is a ferromagnetic metal powder (Y is 1.9).
Contains 8% by weight. ).

The weight percentages of the elements in the standard samples 1 and 2 are the values on the data sheet provided by the manufacturer, and the weight percentages of the elements in the standard samples 3 to 8 are the analysis values by the ICP emission spectrometer. This value was input as the elemental composition value of the standard sample in the calculation of the FP method below.

For the calculation of the FP method, the fundamental parameter software Version2.1 manufactured by Technos is used.
Was calculated under the following conditions.

Sample model: Bulk sample Balance component sample: Fe Input component: Measured X-ray intensity (KCPS) Analysis unit: wt% The calculated abundance ratio of each element (wt%) is Fe atom 1
It is a quantitative value by converting it as the weight% of other elements with respect to 00 weight%.

<Surface composition> Fe, Co, Ni, Nd, Si, Al in the composition on the surface of the ferromagnetic metal powder,
Regarding the abundance ratio of each element of Y, Pr, Sm, and La,
The value was calculated | required using the XPS surface analyzer.

The method will be described below.

First, the XPS surface analyzer is set under the following conditions.

X-ray anode: Mg Resolution: 1.5 to 1.7 eV (resolution is defined by the half-value width of the 3d5 / 2 peak of clean Ag.) A so-called adhesive tape is used to fix the sample. do not do. The model of the XPS surface analysis device is not particularly limited, and various devices can be used, but in the present application, ESCALAB-200R manufactured by VG was used.

Narrow scan was carried out in the following measuring range to measure the spectrum of each element. At this time, the data acquisition interval was set to 0.2 eV, and integration was performed until a count of at least the minimum count shown in Table 3 was obtained.

The energy position of the obtained spectrum is corrected so that the C peak position is 284.6 eV.

Next, COMMON DATA PROCESSING S manufactured by VAMAS-SCA-JAPAN.
YSTEM Ver. To perform data processing on 2.3 (hereinafter referred to as VAMAS software), use the software provided by each device manufacturer for the above spectrum,
Transfer to a computer that can use VAMAS software.

Then, after the transferred spectrum is converted into the VAMAS format by using the VAMAS software, the following data processing is performed.

Before starting the quantitative treatment, Co
Calibrate the unt Scale, 5
Performs point smoothing processing.

The quantitative processing is as follows.

The peak area intensity is determined in the quantitative range shown in Table 4 with the peak position of each element as the center. Next, Table 4
Using the sensitivity coefficient shown in, the atomic% of each element was determined.
The atomic number% was converted into the atomic number with respect to 100 Fe atomic numbers and used as a quantitative value.

The average abundance ratio of the elements forming the surface of the ferromagnetic metal powder present in the oriented and dried magnetic coating film according to claims 8 to 11 used in the present invention is determined by using an XPS surface analyzer. Measure that value.

Next, the XPS surface analyzer for explaining the method is set under the following conditions.

X-ray anode; Mg resolution; 1.5 to 1.7 eV (resolution is normal Ag3d
It is defined by the half-width of 5/2 peak. The XPS surface analyzer is not particularly limited, and any model can be used.
G company ESCALAB-200R was used.

Narrow scan was performed in the following measurement range,
The spectrum of each element was measured. At this time, the data capturing interval is set to 0.2 eV, and it is necessary to integrate until the target peak has a count equal to or more than the minimum count shown in Table 5.

The energy position of the obtained spectrum is corrected so that the peak position of Cl _s becomes 284.6 eV.

Next, COMMON DATA PROCESSING S manufactured by VANAS-SCA-JAPAN.
YSTEM Ver. In order to perform processing on 2.3 (hereinafter referred to as VANAS software), the software provided by each device maker is used to perform the above-mentioned spectrum analysis on the VANAS software.
Transfer to a computer that can use the software. Then, the transferred spectrum is converted into the VANAS format by using the VANAS software, and then the data processing is performed.

Before starting the quantitative processing, Co
The unt Scale is calibrated, and the smoothing process of 5 points is performed. The peak area intensity (cps * eV) is determined in the quantitative range shown in Table 6 with the peak position of each element as the center. Using the sensitivity coefficients shown below, determine the atomic% of each element. The number of atoms is 10
It is converted into the number of atoms with respect to 0 and used as a quantitative value.

Other than the above elements, the measurement was performed under the conditions shown in Table 7.

-Sample Preparation Method- Before the above measurement, the medium (magnetic tape) is pretreated.

The binder resin is removed from the magnetic tape by the plasma low temperature ashing method to expose the magnetic particles. The treatment method is selected such that the binder resin is incinerated but the magnetic particles are not damaged. For example, after the treatment was performed under the following apparatus and treatment conditions, the average abundance ratio of elements forming the surface of the oriented ferromagnetic metal powder was measured.

Device: Reiwa Shoji PL-850X Treatment condition: FORWARD POWER 100W REFLECTED POWER 5W Vacuum degree 10Pa Introduced gas type Air Discharge time 1 min. <Electrical characteristics (dB) RF output, CN ratio>; Sony Corporation With 8mm video camera CCDV-900,
The RF power (dB) at 7 MHz and 9 MHz was measured. The CN ratio is the output difference (dB) between 7MHz and 6MHz.
Was measured.

<Running durability>; temperature 40 ° C., humidity 80%
Further, the durability against running 100 times at a temperature of 0 ° C. and a humidity of 20% was evaluated as follows.

A: No hindrance B: Scratch on back surface C: Running, but frequent occurrence of D / O = 50 or more D: Running, but electrical characteristics degraded by 2 dB or more E: Driving stopped.

<Tape demagnetization rate (%)>: The tape demagnetization rate (%) was measured when the tape was left for one week in an environment of a temperature of 60 ° C. and a humidity of 90%. Based on the value of the saturation magnetic flux density B of the tape before and after standing, the tape demagnetization rate (%) was calculated by the following formula.

{(B ₁ before leaving)-(B ₂ after leaving)}
/ (B ₁ before standing) × 100 (%) <Surface roughness at the time of layering>; The surface after layering was observed with an optical microscope, and the degree was evaluated as follows.

A: The surface roughness was equivalent to that when only the uppermost layer paint was formed. B: The surface was smoother than when only the uppermost layer paint was formed. C: Only the uppermost layer paint was formed. Roughened more than when.

[0168]

[Table 1]

[0169]

[Table 2]

[0170]

[Table 3]

[0171]

[Table 4]

[0172]

[Table 5]

[0173]

[Table 6]

[0174]

[Table 7]

[0175]

According to the present invention, it is possible to provide a magnetic recording medium which is particularly suitable as a recording medium for digital use and which is excellent in electrical characteristics and running property in a short wavelength region.

[Brief description of drawings]

FIG. 1 is a diagram for explaining multi-layer coating of a magnetic layer by a wet-on-wet coating method.

FIG. 2 is a diagram showing an example of an extrusion coater for applying a magnetic paint.

FIG. 3 is a diagram showing an example of an extrusion coater for applying a magnetic paint.

FIG. 4 is a diagram showing an example of an extrusion coater for applying a magnetic paint.

[Explanation of sign]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic support 2 Lower layer coating 4 Magnetic coating 5a Extrusion coater 5b Extrusion coater 5c Extrusion coater 5d Extrusion coater 10 Extrusion coater 11 Extrusion coater 13 Liquid pool part 14 Liquid pool part 32 Supply roll 33 Orientation magnet or vertical orientation magnet 34 Dryer 37 Super Calender 38 Calender Roll 39 Winding Roll

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01F 10/14

Claims (8)

[Claims] 1. A magnetic recording medium having at least one magnetic layer containing a ferromagnetic powder on a non-magnetic support,
Fe atom, A as an element forming the ferromagnetic metal powder
1 atom and a rare earth element atom, and the weight ratio of the elements in the whole ferromagnetic metal powder is 2 to 10 parts by weight of Al atom and 1 to 8 parts by weight of atom of rare earth element with respect to 100 parts by weight of Fe atom. And the average abundance ratio of the elements forming the surface of the ferromagnetic metal powder is 70 to 200 Al atoms with respect to 100 Fe atoms, and the atomic number of rare earth elements is 0.
The magnetic recording medium is 5 to 30. 2. The ferromagnetic metal powder further contains Na atoms and Ca atoms as elements forming the ferromagnetic metal powder, and the weight ratio of the elements in the entire ferromagnetic metal powder is F.
e less than 0.1 parts by weight of Na atoms, 0.1 to 2 parts by weight of Ca atoms, 2 to 10 parts by weight of Al atoms, 1 to 8 parts by weight of atoms of rare earth elements, and more than 100 parts by weight of e atoms. The average abundance ratio of the elements forming the surface of the magnetic metal powder is F
The number of Na atoms is 2 to 30, the number of Ca atoms is 5 to 30, the number of Al atoms is 70 to 200, and the number of rare earth element atoms is 0.5 to 30 with respect to 100 e atoms. Magnetic recording medium. 3. The ferromagnetic metal powder further comprises Co atoms, Ni atoms and S as elements forming the ferromagnetic metal powder.
i atom is contained, and the weight ratio of elements in the entire ferromagnetic metal powder is 2 to 100 atomic parts of Fe atoms and 2 to Co atoms.
20 parts by weight, 2 to 20 parts by weight of Ni atom, 0.3 atom of Si
.About.5 parts by weight, less than 0.1 parts by weight of Na atoms, 0.
1 to 2 parts by weight, Al atoms 2 to 10 parts by weight, rare earth element atoms 1 to 8 parts by weight, and the average abundance ratio of the elements forming the surface of the ferromagnetic metal powder is 100 Fe atoms. Less than 0.1 Co atoms, less than 0.1 Ni atoms,
The number of Si atoms is 20 to 130, the number of Na atoms is 2 to 30, the number of Ca atoms is 5 to 30, the number of Al atoms is 70 to 200, and the number of atoms of rare earth elements is 0.5 to 30. Magnetic recording medium. 4. In a magnetic recording medium having a magnetic layer containing at least a ferromagnetic metal powder on a non-magnetic support, the average of the elements forming the surface of the ferromagnetic metal powder subjected to orientation treatment on the magnetic layer. The abundance ratio is 10 Fe atoms.
0, the number of Al atoms is 70 to 300, and the number of rare earth element atoms is 0.5 to 60. 5. The atom of the rare earth element is Sm, Nd, Y.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is one or more selected from the group consisting of and Pr. 6. The magnetic recording medium according to claim 1, wherein at least one layer is provided as a lower layer between the non-magnetic support and the magnetic layer. 7. The dry thickness of the magnetic layer is 0.02 to 0.
The magnetic recording medium according to claim 6, wherein the dry film thickness of the lower layer is 6 μm and the dry film thickness is 0.2 to 2.0 μm. 8. The magnetic recording medium according to claim 6, wherein the lower layer is a layer containing acicular non-magnetic powder.