JPH08102046A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To obtain a magnetic recording medium having satisfactory electromagnetic transducing characteristics, especially a magnetic recording medium having satisfactory shelf stability and hardly causing the wear of a head as a magnetic recording medium obtd. by forming at least one magnetic layer contg. ferromagnetic powder dispersed in a binder on a nonmagnetic flexible substrate. CONSTITUTION: A magnetic layer contg. ferromagnetic powder and an abrasive material having 0.03-0.3μm average particle diameter is formed. The ferromagnetic powder is acicular ferromagnetic alloy powder contg. at least one kind of rare earth metal selected from among Y and lanthanides and having 120-160emu/g saturation magnetization σs, 0.04-0.2μm average major axis size and 100-300Å crystallite size.

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 particularly to a high density recording medium excellent in storage stability.

[0002]

2. Description of the Related Art Conventionally, as magnetic recording media such as video tapes, audio tapes, magnetic disks, etc., ferromagnetic iron oxide, Co modified ferromagnetic iron oxide, CrO ₂ , ferromagnetic alloy powder, etc. are dispersed in a binder. A magnetic layer provided on a non-magnetic support is widely used. JP-A-63-18
As disclosed in Japanese Patent No. 7418, the recording wavelength tends to be shortened in recent years as the recording density is increased, and as a magnetic recording medium corresponding to this, a magnetic material having a large σs and Hc and a small particle size. Is being used, and further, the self-demagnetization loss during recording is reduced,
The magnetic layer also tends to be thin to improve resolution. However, a fine magnetic particle with a high σs has a problem that the demagnetization due to oxidation when stored at high temperature is large because the thickness of the oxide film is thin. 205601 proposes that a rare earth element is added to improve the weather resistance of the magnetic recording medium.

[0003]

It has been found that the use of such a magnetic material improves the weather resistance of the magnetic recording medium, but the effect is more remarkable as the thickness of the magnetic layer is smaller. Has been done. This is because when the thickness of the magnetic layer is thin, low-frequency signals such as control signals are recorded over the entire thickness of the magnetic layer. This is probably because the decrease was large. However, it has been found that the use of a magnetic material to which a rare earth metal is added improves the weather resistance of the magnetic recording medium, but also increases the polishing power of the magnetic material and causes the head to be easily worn. .

[0004]

It is an object of the present invention to provide a magnetic recording medium having at least one magnetic layer having a ferromagnetic powder dispersed in a binder on a non-magnetic flexible support, which has good electromagnetic conversion characteristics. It is an object of the present invention to provide a magnetic recording medium, in particular, a magnetic recording medium having good storage stability and little head wear.

[0005]

It is an object of the present invention that the ferromagnetic powder contains at least one rare earth metal element selected from Y or lanthanide series metal elements, has a σs of 120 to 160 emu / g, and an average major axis. Length is 0.04 to 0.2 μm and crystallite size is 100 to 30
The magnetic layer is a needle-like ferromagnetic alloy powder of 0 angstrom, and the magnetic layer is achieved by a magnetic recording medium containing an abrasive having an average particle diameter of 0.03 to 0.3 μm. As the ferromagnetic powder used in the present invention, a ferromagnetic alloy fine powder containing Fe, Ni or Co as a main component and containing 75% or more is preferable, and at least one rare earth element selected from Y or lanthanide series metal elements. Contains metallic elements. The ferromagnetic powder used in the present invention has a σs of 120.
To 160 emu / g, preferably 125 to 160 emu / g. σs is 120 emu / g
If it is smaller than the above range, the electromagnetic conversion characteristics, particularly the reproduction output is lowered, which is not preferable. On the other hand, when σs exceeds 160 emu / g, the dispersibility of the magnetic coating liquid decreases, and it becomes difficult to form the magnetic layer.

The average major axis length of the ferromagnetic powder used in the present invention is 0.04 to 0.2 μm, preferably 0.04 to 0.18 μm, and more preferably
0.04 to 0.15 μm. The average major axis length is 0.
If it is smaller than 04 μm, a sufficient coercive force cannot be expressed, while if it is longer than 0.2 μm, a sufficient reproduction output cannot be obtained when the recording wavelength is short, which is not preferable. The crystallite size of the ferromagnetic powder used in the present invention is 100 to 300 angstroms, preferably 100 to 200 angstroms. If the crystallite size of the ferromagnetic powder is smaller than 100 angstroms, sufficient .sigma.s cannot be expressed. On the other hand, if it is larger than 300 angstroms, the reproduction output decreases, which is not preferable. In the present invention, as the lanthanide series metal element contained in the ferromagnetic alloy fine powder,
Nd, Sm, Dy, Gd, Tb and La are preferably used. In the present invention, the content of Y or the rare earth element contained in the ferromagnetic powder is preferably 0.05 to 14.0 at%, and more preferably 0.05 to 5 at based on the metal as the main component. %.

In the present invention, the ferromagnetic powder includes Al, Si, S, Sc, Ti, V, Cr and C in addition to the predetermined atoms.
u, Mo, Rh, Pd, Ag, Sn, Sb, Te, B
a, Ta, W, Re, Au, Hg, Pb, Bi, La,
Atoms such as Ce, Pr, P, Co, Mn, Zn, Ni, Sr, and B may be contained. In particular, it is preferable that the ferromagnetic powder contains 2 to 15 at% of Al with respect to Fe. These ferromagnetic fine powders include a dispersant, a lubricant, a surfactant, an antistatic agent, etc. described later,
Processing may be performed in advance before dispersion. In the present invention, the ferromagnetic alloy fine powder may contain a small amount of hydroxide or oxide. As the ferromagnetic alloy fine powder, those obtained by a known manufacturing method can be used. For example, the ferromagnetic alloy fine powder obtained by the method described in JP-A-2-205601 can be used. .
For the ferromagnetic alloy powder obtained by these methods, a known gradual oxidation treatment method, that is, a method of immersing in an organic solvent and then drying, an oxygen-containing gas is fed after being immersed in an organic solvent, It is also possible to use either a method of forming an oxide film and then drying it, or a method of applying an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent. However, it is preferable to use one that is gradually oxidized in a gas phase without using an organic solvent because of excellent weather resistance.

In the present invention, the specific surface area of the ferromagnetic powder of the magnetic layer by the BET method is preferably 40 to 80 m ² / g, more preferably 50 to 70 m ² / g.
Is. Below 40 m ² / g, noise becomes high,
If it exceeds 0 m ² / g, it is difficult to obtain surface properties, which is not preferable. In the present invention, the water content of the ferromagnetic powder is 0.01
It is preferably set to 2%. It is preferable to optimize the water content of the ferromagnetic powder according to the type of binder used. The tap density is preferably 0.3 to 1.5 g / cc or more, more preferably 0.5 to 0.2 g / cc or more. In the present invention, the pH of the ferromagnetic powder is preferably optimized according to the combination with the binder used. The range is preferably 4 to 12, and more preferably
6 to 10. In the present invention, the ferromagnetic powder is
It may contain soluble inorganic ions such as Na, Ca, Fe, Ni, and Sr, and it is generally preferable that the total amount of these inorganic ions is 500 ppm or less. However,
When the thickness of the magnetic layer is 1 μm or less using the non-magnetic layer, it is preferably 200 ppm or less, and more preferably 150 ppm or less. If it exceeds 200 ppm, it reacts with the higher fatty acid described later supplied from the non-magnetic layer to form and precipitate a fatty acid metal salt, which results in space loss, which is not preferable.

The ferromagnetic powder used in the present invention preferably has few voids, and the content of voids is preferably 2 or less.
It is 0% by volume or less, more preferably 5% by volume or less. Further, as the shape of the ferromagnetic powder, a needle-like one satisfying the above-mentioned characteristics regarding the particle size is used,
The acicular ratio is preferably 12 or less. These ferromagnetic powders preferably have a small Hc distribution. Examples of the method for that purpose include a method for improving the particle size distribution of goethite and a method for preventing the sintering of γ-hematite. The SFD of the magnetic recording medium using these ferromagnetic powders is preferably 0.1 to 0.6.
The polishing agent contained in the magnetic layer of the present invention has an α-conversion rate of 9
0% or more of α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, boron nitride, etc. Mainly known with Mohs hardness of 6 or more The above materials can be used alone or in combination, and a composite of these abrasives, that is, an abrasive whose surface is treated with another abrasive can also be used. These abrasives may contain compounds or elements other than the main component, but the main component is 90%.
If it is above, the effect is not changed. The average particle size of these abrasives should be 0.03 to 0.3 μm, preferably 0.05 to 0.25 μm or less. If the average particle size of the abrasive is less than 0.03 μm, the polishing ability is small, sufficient strength of the magnetic coating film cannot be ensured, and clogging is likely to occur. If it is larger than 3 μm, the polishing ability becomes too large,
It is not preferable because the head is easily worn. As long as the average particle diameter of these abrasives is 0.03 to 0.3 μm, a single abrasive having a wide particle size distribution can be used even if abrasives having different particle sizes are combined as needed. Good. The tap density of the abrasive used in the present invention is 0.3 to 2
g / cc, water content 0.1 to 5%, pH 2 to 1
1, the specific surface area is preferably 1 to 30 m ² / g. The shape of the abrasive used in the present invention may be needle-like, spherical, or dice-like, but some of which have corners,
Highly abrasive, which is preferable. Specific examples of the polishing agent used in the present invention include AKP-50 manufactured by Sumitomo Chemical Co., Ltd.,
HIT-50, S7, S-1, manufactured by Nippon Kagaku Kogyo Co., Ltd.
Toda Kogyo Co., Ltd. 100ED, 140ED etc. are mentioned.

In the present invention, the abrasive may be dispersed in the binder in advance and then added to the magnetic coating material.
Further, the amount of abrasive present on the magnetic layer surface and the end face of the magnetic layer of the magnetic recording medium is preferably 5 to 130 particles / 100 μm ² , and more preferably 5 to 90 particles / 100 μm ² . In the present invention, preferably, the magnetic recording medium further comprises a nonmagnetic layer in which a nonmagnetic powder is dispersed in a binder, and the magnetic layer is provided on the nonmagnetic layer. When only the magnetic layer is provided on the non-magnetic flexible support, an antistatic agent or an abrasive is added to the magnetic layer in order to improve the antistatic property and abrasivity of the magnetic recording medium. Although it is necessary to contain it and the filling rate of the ferromagnetic powder may decrease, a non-magnetic layer in which a non-magnetic powder is dispersed in a binder is provided on a non-magnetic flexible support, and the non-magnetic layer is formed on the non-magnetic flexible support. When a magnetic layer is provided, the non-magnetic layer may contain an antistatic agent or an abrasive to improve the antistatic property and polishing property of the magnetic recording medium. It is possible to prevent the filling rate of the ferromagnetic powder from decreasing,
preferable. Preferably, the non-magnetic powder contained in the non-magnetic layer is at least one non-magnetic powder selected from titanium oxide, barium sulfate, silica, α-alumina, zinc oxide, α iron oxide, cerium oxide, tin oxide and zirconia. Is.

The particle size of these non-magnetic powders is 0.0
It is preferably 1 to 2 μm, but non-magnetic powders having different particle sizes may be combined if necessary. For example, in order to impart conductivity, carbon black may be mixed in an amount of 30 parts by weight or less with respect to 100 parts by weight of the main non-magnetic powder, and Cr ₂ O ₃ having a large particle size, diamond, silicon nitride. , SiC or the like as an abrasive may be mixed with the main non-magnetic powder in an amount of 20 parts by weight or less. The tap density of the main non-magnetic powder is preferably 0.05 to 2 g
/ Cc, more preferably 0.2 to 1.5 g / cc, the water content is preferably 0.1 to 5%, more preferably 0.2 to 3%, the pH is preferably 2 to 11, and the specific surface area is preferably Is 1 to 100 m ² / g, more preferably 5 to 50 m ² / g, most preferably 7 to 40 m ² / g. The crystallite size of the main non-magnetic powder is preferably 0.01 μm to 2 μm. The oil absorption using the main non-magnetic powder DBP is preferably 5 to 100 ml / 100 g, more preferably 10 to 80 ml / 100 g, and most preferably 20 to 60 ml /.
100. The specific gravity of the main non-magnetic powder is preferably 1 to 12, more preferably 2 to 8. The main non-magnetic powder may have any of a needle shape, a spherical shape, and a dice shape. The main non-magnetic powder does not necessarily have to be 100% pure, and its surface may be treated with another inorganic compound depending on the purpose. In that case, if the purity of the main non-magnetic powder is 70% or more, the effect of the present invention is not reduced. For example, when titanium oxide is used, it is common to treat the surface with alumina. The ignition loss is preferably 20% or less.

Specific examples of the non-magnetic powder used in the present invention include UA5600 manufactured by Showa Denko KK,
UA5605, Sumitomo Chemical Co., Ltd. AKP-20,
AKP-30, AKP-50, HIT-50, HiT-
100, ZA-G1, Toda Kogyo TF-10
0, TF-120: TF-140, TT0-51B, TT0-55A, TT0-55B, T manufactured by Ishihara Sangyo Co., Ltd.
T0-55C, TT0-55S, TT0-55D, FT
-1000, FT-2000, FTL-100, FTL
-200, M-1, S-1, SN-100, Titanium Industry Co., Ltd. ECT-52, STT-4D, STT-30.
D, STT-30, STT-65C, Mitsubishi Metal Co., Ltd. T-1, Nippon Shokubai Chemical Co., Ltd. NS-0, NS
-3Y, NS-8Y and the like. The nonmagnetic powder contained in the nonmagnetic layer is preferably subjected to a surface treatment with an organic substance in order to prevent the fatty acid to be added from adsorbing to the nonmagnetic powder and to improve the wetting with the binder. Examples of the organic substance used for the surface treatment include organic acids having a pKa of 3 or less, epoxy group-containing compounds having a molecular weight of 3000 or less, silane coupling agents, titanate coupling agents, and the like. Specific examples of compounds and treatment methods are disclosed in JP-A-5-
It is disclosed in Japanese Patent No. 182178.

Further, in the present invention, when carbon black is used together with the main non-magnetic powder, the carbon black is used as a furnace for rubber, thermal for rubber, black for color, black for acetylene and acetylene black. Etc. can be used. Mosquitoes - to the specific surface area of the carbon black 100 to 500m ² / g, and preferably contains 150 to 400m ² /
DBP oil absorption of carbon black is 20-40
0 ml / 100 g, preferably 30 to 200 ml / 1
It is 00 g. The particle size of carbon black is 5 to 80 mμ, preferably 10 to 50 mμ, and more preferably 10 to 40 mμ. Preferably, the carbon black has a pH of 2 to 10, a water content of 0.1 to 10%, and a tap density of 0.1 to 1 g / CC.
In the present invention, specific examples of carbon black used together with the main non-magnetic powder include BLACKPEARLS2000, 1300, 1 manufactured by Cabot Corporation.
000, 900, 800, 880, 700, VULCA
N XC-72, Mitsubishi Kasei Kogyo Co., Ltd. # 3250
B, # 950B, # 650B, # 970B, # 850
B, CONDUCTE manufactured by Conlon Bia Carbon Co., Ltd.
X SC, RAVEN8800, 8000, 7000,
5750, 5250, 3500, 2100, 2000,
1800, 1500, 1255, 1250, Ketjen Black EC manufactured by Akzo Co., Ltd., and the like. Carbon black which has been surface-treated with a dispersant or grafted with a resin or carbon black whose surface has been partially graphitized can also be used. Further, the carbon black may be dispersed with a binder in advance before being added to the magnetic paint. These carbon blacks can be used alone or in combination with other types of carbon black. When using carbon black, the amount based on the main non-magnetic powder is preferably 0.1 to 30% by weight. Carbon black has the functions of preventing static charge of the non-magnetic layer, imparting light-shielding properties, and improving film strength, but these functions differ depending on the carbon black used. Therefore, in the present invention, the card
When using carbon black, the type, amount, and combination of carbon black are changed, and particle size, oil absorption, electrical conductivity,
It is preferable to change the pH and the like within the range described above according to the purpose.

The carbon black usable in the non-magnetic layer of the present invention can be referred to, for example, "Carbon Black Handbook" edited by Carbon Black Association.
In the present invention, the abrasive may be contained not only in the magnetic layer but also in the non-magnetic layer. In the present invention, the magnetic layer preferably contains carbon black having an average particle size of 50 to 300 mμ. If the average particle size of carbon black is less than 50 mμ, the friction coefficient tends to increase, while if the average particle size is more than 300 mμ, the surface properties are likely to deteriorate, electromagnetic conversion characteristics deteriorate, and spacing loss easily occurs. It is not preferable. Furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used as carbon black contained in the magnetic layer. The average primary particle size of carbon black is 50 to 300 mμ, preferably 70 to 280 mμ. Preferably, the carbon black has a specific surface area of 5 to 500 m ² / g, a DBP oil absorption of 10 to 400 ml / 100 g, and a pH of 2 to 1.
0, the water content is 0.1 to 10%, and the tap density is 0.1 to 1 g / cc. Carbon black which has been surface-treated with a dispersant or grafted with a resin or carbon black whose surface has been partially graphitized can also be used.

These carbon blacks may be previously dispersed with a binder before being added to the magnetic paint. These carbon blacks can be used alone or in combination with other carbon blacks. When carbon black is used, it is preferably 0.1 to 30% of the amount based on the ferromagnetic powder.
In the present invention, the carbon black contained in the magnetic layer is used for reducing the friction coefficient of the magnetic layer, but carbon black having a function of imparting a light-shielding property and improving film strength can also be used in combination. In addition, carbon black having a smaller particle size than the above-mentioned particle size, depending on the purpose,
It is also possible to use together. For the carbon black that can be used in the magnetic layer of the present invention, for example, "Carbon Black Handbook" edited by Carbon Black Association can be referred to. As the binder used in the magnetic layer and the non-magnetic layer of the present invention, conventionally known thermoplastic resins, thermosetting resins,
Examples include reactive resins and mixtures thereof. The thermoplastic resin usable in the present invention has a glass transition temperature of -1.
00 to 150 ° C, number average molecular weight of 1000 to 2
00000, preferably 10,000 to 10,000
0, a thermoplastic resin having a degree of polymerization of about 50 to about 1000 may be used.

Examples of such thermoplastic resins include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene and butadiene. Polymers or copolymers containing ethylene, vinyl butyral, vinyl acetal, vinyl ether, etc. as constituent units, polyurethane resins, and various rubber resins. Examples of the thermosetting resin or reactive resin include phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic reaction resin, formaldehyde resin, silicone resin, epoxy resin. Examples thereof include a polyamide resin, a mixture of polyester resin and isocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, and a mixture of polyurethane and polyisocyanate. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. It is also possible to use a known electron beam curable resin for the non-magnetic layer or the magnetic layer. These examples and the manufacturing method thereof are described in detail in JP-A-62-256219.

These resins can be used alone or in combination, but preferred are vinyl chloride resin, vinyl chloride vinyl acetate resin, vinyl chloride vinyl acetate vinyl alcohol resin, vinyl chloride vinyl acetate maleic anhydride. Examples thereof include a combination of at least one resin selected from the group consisting of copolymers and a polyurethane resin, or a combination of these with a polyisocyanate.
As the structure of the polyurethane resin, known materials such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. For all of these binders, COOM, S
O ₃ M, OSO ₃ M, P = O, (OM) ₂ , OP = O
(OM) ₂ , (where M is a hydrogen atom or an alkali metal base), OH, NR ₂ , N ⁺ R ₃ (R is a hydrocarbon group) epoxy group, SH, CN, etc. It is preferable to introduce at least one or more polar groups selected from the following by copolymerization or addition reaction. The amount of such a polar group is from 10 ^-1 to 10 ^-8 mol / g, preferably from 10 ^-2 to 10 ^-6 mol / g.

Specific examples of these binders used in the present invention include VAG manufactured by Union Carbite Co., Ltd.
H, VYHH, VMCH, VAGF, VAGD, VRO
H, VYES, VYNC, VMCC, XYHL, XYS
G, PKHH, PKHJ, PKHC, PKFE, MPR-TA, MPR-TA5, MP manufactured by Nisshin Chemical Industry Co., Ltd.
R-TAL, MPR-TSN, MPR-TMF, MPR
-TS, MPR-TM, 100 manufactured by Denki Kagaku Kogyo Co., Ltd.
0W, DX80, DX81, DX82, DX83, Nippon Zeon Co., Ltd. MR110, MR100, 400X1
10A, Nippon Polyurethane Co., Ltd. Nipporan N23
01, N2302, N2304, Pandex T-5105, T-R308 manufactured by Dainippon Ink and Chemicals, Inc.
0, T-5201, Barnock D-400, D-210
-80, Crisbon 6109, 7209, Byron UR8200, UR8300, RV53 manufactured by Toyobo Co., Ltd.
0, RV280, UR8600, UR-5500, Dainichiseika Kogyo Co., Ltd. Daiferamine 4020, 502
0, 5100, 5300, 9020, 9022, 702
0, Mitsubishi Kasei Kogyo Co., Ltd. MX5004, Sanyo Kasei Kogyo Co., Ltd. Sampren SP-150, Asahi Kasei Kogyo Co., Ltd. Saran F310, F210 and the like.

The binder used in the magnetic layer and the non-magnetic layer of the present invention is preferably 5 with respect to the total amount of the ferromagnetic powder contained in the magnetic layer or the non-magnetic powder contained in the non-magnetic layer.
It is used in the range of 50 to 50% by weight, more preferably 10 to 30% by weight. When a vinyl chloride resin is used, the amount is 5 to 30% by weight, when a polyurethane resin is used, it is 2 to 20% by weight, and when a polyisocyanate is used, it is 2 to 20% by weight. It is preferable to use in combination. In the present invention, when a polyurethane resin is used as the binder, the glass transition temperature is −50 to 100 ° C., the elongation at break is 100 to 2000%, and the stress at break is 0.05.
To 10 Kg / cm ² , yield point is 0.05 to 10
A polyurethane resin of Kg / cm ² is preferred. In the present invention, when the non-magnetic layer is provided, the amount of the binder, the amount of vinyl chloride resin, polyurethane resin, polyisocyanate, or other resin in the binder, the amount of the other resin, each forming the magnetic layer Resin molecular weight, polar group weight, or
The physical properties of the resin described above can be changed between the non-magnetic layer and the magnetic layer, if necessary.

The polyisocyanate used in the present invention includes tolylene diisocyanate and 4-4'-.
Diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenyl Examples thereof include isocyanates such as methanetriisocyanate, products of these isocyanates with polyalcohols, and polyisocyanates produced by condensation of isocyanates. Specific examples of these isocyanates include Coronate L, Coronet HL, and Coronet manufactured by Nippon Polyurethane Co., Ltd.
2030, Coronet 2031, Millionate MR Millionate MTL, Takeda Pharmaceutical Co., Ltd. Takenate D-102, Takenate D-110N, Takenate D-
200, Takenet D-202, Sumitomo Bayer Co., Ltd. Desmodure L, Desmodule IL, Desmodule N Desmodule HL, etc., and these may be used alone or with different curing reactivity. By utilizing them, two or more combinations can be used for both the magnetic layer and the non-magnetic layer. In the present invention, in order to improve running durability of the magnetic recording medium, the magnetic layer or the non-magnetic layer is
It preferably contains higher fatty acids. The higher fatty acid used in the magnetic layer or the non-magnetic layer is mainly a monobasic fatty acid having 10 to 26 carbon atoms, which may be saturated or unsaturated, and may be linear or branched. The carbon to which the carboxyl group is bonded may be primary, secondary, or tertiary. Specific examples of these higher fatty acids include lauric acid, palmitic acid, myristic acid, stearic acid,
Examples thereof include behenic acid, oleic acid, linolenic acid, and elaidic acid. In the non-magnetic layer, the amount of the higher fatty acid added is 0.1 to 20% by weight, preferably 0.1 to 20% by weight, based on the non-magnetic powder (when two or more non-magnetic powders are used, all of them). It is 0.1% to 10% by weight, and more preferably 0.1% to 5% by weight. In the magnetic layer, it is 0.1% to 20% by weight, preferably 0.1% to 10% by weight, and more preferably 0.1% to 5% by weight, based on the ferromagnetic powder.

Further, in the present invention, additives such as a dispersant, a lubricant, an antistatic agent, a surfactant and a plasticizer may be used depending on the purpose. As the additive, one having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect and the like is used. For example, molybdenum disulfide, tungsten disulfide graphite, boron nitride, graphite fluoride,
Silicone oil, polar group-containing silicones, fatty acid-modified silicones, fluorine-containing silicones, fluorine-containing alcohols, fluorine-containing esters, polyolefins, polyglycols, alkyl phosphates and their alkali metal salts, alkyls. Sulfuric acid ester and its alkali metal salt, polyphenyl ether, fluorine-containing alkyl sulfuric acid ester and its alkali metal salt, carbon number 12 to 2
2, monovalent, divalent, trivalent, tetravalent, pentavalent, hexavalent alcohol,
(It may contain an unsaturated bond or may be branched.), And an alkoxyalcohol having 12 to 22 carbon atoms.
Or one of monovalent, divalent, trivalent, tetravalent, pentavalent or hexavalent alcohol having 2 to 12 carbon atoms (which may contain an unsaturated bond or may be branched. ) And a mono-fatty acid ester or a di-fatty acid ester or a tri-fatty acid ester, a monoalkyl ether of an alkylene oxide polymer
Ter fatty acid ester, C8-22 fatty acid amide, C8-22 aliphatic amine, C10
To 24 fatty acid esters of fatty acids and alcohols (which may contain unsaturated bonds or may be branched) and the like can be used. Specific examples thereof include stearic acid amide, myristic acid amide, butyl stearate, oleyl oleate, octyl stearate,
Amyl stearate, isooctyl stearate, octyl myristate, butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, oleyl alcohol, lauryl alcohol. Le is given. Further, nonionic surfactants such as alkylene oxide type, glycerin type, glycidyl type, alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphonium. Or a cationic surfactant such as sulfonium, anionic surfactant containing an acidic group such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester group, phosphoric acid ester group, amino acid, aminosulfonic acid, amino alcohol Examples thereof include sulfuric acid or phosphoric acid esters, and amphoteric surfactants such as alkylbedine type. For these surfactants,
It is described in detail in "Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.). These dispersants, lubricants, antistatic agents, surfactants, additives such as plasticizers do not necessarily have to be 100% pure, and isomers, unreacted substances, side reactions other than the main component Impurities such as substances, decomposed products, and oxides may be included. The content of these impurity components is preferably 30% by weight or less, more preferably 10% by weight or less.

Additives such as these dispersants, lubricants, antistatic agents, surfactants and plasticizers used in the present invention are
The type and amount of the non-magnetic layer and the magnetic layer can be selectively used according to need. For example, a non-magnetic layer and a magnetic layer use fatty acids having different melting points to control bleeding to the surface, or esters having different boiling points and polarities to control bleeding to the surface, Improve the stability of application by adjusting the amount of activator,
It is conceivable to increase the amount of lubricant added in the intermediate layer to improve the lubricating effect. For other purposes, additives such as a dispersant, a lubricant, an antistatic agent, a surfactant, and a plasticizer are selectively used in the non-magnetic layer and the magnetic layer in the kind and the amount thereof in other modes. It goes without saying that you can do it. All or a part of the additives used in the present invention may be added in any step of the magnetic coating manufacturing process. For example, before the kneading step, it may be mixed with the ferromagnetic powder, added in the kneading step of kneading the ferromagnetic powder and the binder with a solvent, added in the dispersion step, or added after the dispersion. Alternatively, it may be added just before coating. Specific examples of these lubricants used in the present invention include NAA-102, NAA-415 and NAA-31 manufactured by NOF CORPORATION.
2, NAA-160, NAA-180, NAA-17
4, NAA-175, NAA-222, NAA-34,
NAA-35, NAA-171, NAA-122, NA
A-142, NAA-160, NAA-173K, castor hardened fatty acid, NAA-42, NAA-44, cation SA, cation MA, cation AB, cation BB, nymine L-201, nymine L-202, Naimi
S-202, Nonion E-208, Nonion P-20
8, nonion S-207, nonion K-204, nonion NS-202, nonion NS-210, nonion HS
-206, nonion L-2, nonion S-2, nonion S-4, nonion O-2, nonion LP-20R, nonion PP-40R, nonion SP-60R, nonion O
P-80R, Nonion OP-85R, Nonion LT-2
21, nonion ST-221, nonion OT-221,
Monogly MB, Nonion DS-60, Anon BF, Anon LG, Butyl stearate, Butyl laurate, Erucic acid, Oleic acid manufactured by Kanto Chemical Co., Inc., FAL-205 manufactured by Takemoto Yushi Co., Ltd., FAL-123, New Japan Chemical Co., Ltd. Company's Engerb LO, Enjorub IPM, Sansosizer-E4030, Shin-Etsu Chemical Co., Ltd. TA-
3, KF-96, KF-96L, KF96H, KF41
0, KF420, KF965, KF54, KF50, K
F56, KF907, KF851, X-22-819,
X-22-822, KF905, KF700, KF39
3, KF-857, KF-860, KF-865, X-
22-980, KF-101, KF-102, KF-1
03, X-22-3710, X-22-3715, KF
-910, KF-3935, Lion Armor Co., Ltd. Amide P, Armide C, Armoslip CP,
Lion Oil & Fat Co., Ltd. Duomin TDO, Nisshin Oil Co., Ltd. BA-41G, Sanyo Chemical Co., Ltd. Profan 2012E, Newport PE61, Ionette M
S-400, Ionette MO-200, Ionette DL
-200, Ionet DS-300, Ionet DS-
1000 Ionette DO-200 etc. are mentioned.

Examples of the organic solvent used in the present invention include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone and tetrahydrofuran, methanol,
Ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, alcohols such as methylcyclohexanol, methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate,
Esters such as glycol acetate, glycol dimethyl ether, glycol monoethyl ether, glycol ethers such as dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, cresol, and chlorobenzene, methylene chloride, ethylene chloride, Chlorinated hydrocarbons such as carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene, N, N-dimethylformamide, hexane and the like can be used in any ratio. These organic solvents are not necessarily 10
It does not have to be 0% pure, and may contain impurity components such as isomers, unreacted products, by-products, decomposition products, oxides, and water in addition to the main component. The content of these impurity components is preferably 30% by weight or less, more preferably 10% by weight or less. The organic solvent used in the present invention is
If necessary, the type and amount of the magnetic layer and the non-magnetic layer may be changed. For example, a solvent with high volatility is used for the magnetic layer to improve surface properties, and a solvent with high surface tension such as cyclohexanone and dioxane is used for the non-magnetic layer to improve coating stability and dissolve in the magnetic layer. Examples thereof include increasing the filling degree by using a solvent having a high property parameter, but the present invention is not limited to these examples.

In the magnetic recording medium according to the present invention, the thickness of the non-magnetic flexible support is preferably 1 to 100.
μm, more preferably 6 to 20 μm. The thickness of the non-magnetic layer is preferably 0.5 μm to 1
It is 0 μm, more preferably 1 to 5 μm. The thickness of the magnetic layer is 0.1 μm or more and 4.0 μm or less, preferably 0.1 μm or more and 1.0 μm or less, and when the nonmagnetic layer is provided, it is 0.1 μm or more and 0.8 μm or less. More preferable. The total thickness of the magnetic layer and the nonmagnetic layer is preferably 1/100 to 2 times the thickness of the nonmagnetic flexible support. Further, an undercoat layer is preferably provided between the non-magnetic flexible support and the non-magnetic layer in order to improve the adhesion between the non-magnetic flexible support and the non-magnetic layer. 0.01 to 2 μm, preferably 0.05
To 0.5 μm. Further, a back coat layer may be provided on the side of the non-magnetic flexible support opposite to the side of the magnetic layer.
The thickness of the backcoat layer is 0.1 to 2 μm, preferably 0.3 to 1.0 μm. These subbing layers,
As the back coat layer, known ones can be used. Examples of the non-magnetic flexible support used in the present invention include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins, cellulose triacetate, polycarbonate, polyamide, polyimide, polyamideimide. Well-known films of polysulfone, aramid, aromatic polyamide and the like can be mentioned. These supports may be previously subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, and the like. To achieve the object of the present invention, the non-magnetic flexible support has a center line average surface roughness of 0.001.
To 0.03 μm, more preferably 0.001 to 0.02 μm, and most preferably 0.001 to 0.01 μm. Also,
It is preferable that these non-magnetic supports not only have a small center line average surface roughness but also do not have coarse protrusions of 1 μm or more. Here, the surface roughness depends on the size and amount of the filler added to the support, if necessary.
You can control freely. Examples of these fillers include oxides and carbonates of Ca, Si, Ti and the like, as well as organic fine powders of acrylic and the like. The F-5 value in the tape running direction of the non-magnetic flexible support used in the present invention is preferably 5 to 50 Kg / mm ² ,
F-5 value in the tape width direction is preferably 3 to 30K
It is g / mm ² , and the F-5 value in the tape longitudinal direction is generally higher than the F-5 value in the tape width direction, but especially when it is necessary to increase the strength in the width direction. Is not the case.

Further, the non-magnetic flexible support used in the present invention is 100 ° C. in the tape running direction and the width direction,
The heat shrinkage ratio at 30 minutes is preferably 3% or less, more preferably 1.5% or less, and the heat shrinkage ratio at 30 minutes at 80 ° C. is preferably 1% or less, more preferably 0.5% or less. Is. The breaking strength of the non-magnetic flexible support is preferably 5 to 100 Kg / mm ² in both directions, and the elastic modulus is preferably 100 to 2000 Kg / mm ² . The step of producing the magnetic coating material constituting the magnetic layer of the magnetic recording medium according to the present invention comprises at least a kneading step, a dispersing step, and a mixing step which is carried out before and after these steps, if necessary. Each step may be performed in two or more stages. Ferromagnetic powder, binder, carbon black, abrasive, antistatic agent used in the present invention,
All raw materials such as lubricants and solvents can be added at the beginning or in the middle of any step. In addition, individual raw materials can be added in two or more steps.
For example, polyurethane may be added separately in a kneading step, a dispersing step, and a mixing step for adjusting viscosity after dispersion. In the present invention, conventional known manufacturing techniques for manufacturing a magnetic recording medium can be used. The kneading device includes an open kneader, a continuous kneader, and a pressure kneader.
In the kneading, the ferromagnetic powder or the non-magnetic powder and all or part of the binder (however, 30% or more of the total binder is preferable) are mixed with the ferromagnetic powder or the non-magnetic powder. The mixture is kneaded with a solvent in the range of 15 to 500 parts by weight with respect to 100 parts by weight of the non-magnetic powder. For details of these kneading processes, see JP-A-1-11-1.
No. 06338 and JP-A No. 64-79274.

In the present invention, the method for providing the magnetic layer on the non-magnetic flexible support includes gravure coating, roll coating, blade coating, extrusion coating and the like which are generally used for coating magnetic coating materials. Can be mentioned.
In the present invention, in the case of providing a non-magnetic layer and a magnetic layer on a non-magnetic flexible support, gravure coating, roll coating, blade coating, extrusion coating equipment and the like generally used in coating of magnetic paint After coating a non-magnetic layer using the above, and drying it, Japanese Patent Publication No. 46186/1989
JP-A-60-238179, JP-A-2-265672
Using the support pressure type extrusion coating device disclosed in Japanese Patent Publication, a method of coating a magnetic layer, gravure coating, roll coating, blade coating, using an extrusion coating device, etc., a non-magnetic layer is coated. While the non-magnetic layer is in a wet state, the support pressure type extrusion coating device disclosed in JP-B-1-46186, JP-A-60-238179 and JP-A-2-265672 is used. Method for coating magnetic layer, JP-A-63-
88080, JP-A-2-17971, JP-A-2-2
Japanese Patent Laid-Open No. 2-174965, a method of coating a non-magnetic layer and a magnetic layer almost simultaneously by using a coating device including a single coating head having two slits for coating liquid as disclosed in JP-A-2-174965. It is possible to use a method of applying the non-magnetic layer and the magnetic layer almost at the same time using the extrusion coating device with a backup roller disclosed in the publication. Among these methods, a method of coating the magnetic layer on the non-magnetic layer while the non-magnetic layer is in a wet state is preferable, and the non-magnetic layer and the magnetic layer are almost simultaneously formed.
The method of providing on a non-magnetic flexible support is more preferable.

The same applies to the case where two or more magnetic layers are provided in the present invention. In order to obtain the magnetic recording medium according to the present invention, as is well known, the magnetic layer undergoes a strong orientation. In order to perform the orientation, it is preferable to use a solenoid of 1000 G or more and a cobalt magnet of 2000 G or more in combination. Furthermore, the magnetic layer is appropriately dried in advance before orientation so that the orientation after drying becomes the highest. It is preferable to leave it. When the magnetic recording medium of the present invention is used as a disk medium, it is necessary to use a method of randomizing the orientation. In the present invention, heat-resistant plastic rolls such as epoxy, polyimide, polyamide, and polyimide amide can be used as the calendering roll for orientation. In addition, calendar processing can be performed between metal rolls. The calendering temperature is preferably 70 to 150 ° C, more preferably 80 to 150 ° C. The linear pressure is preferably 200 to 500 Kg / cm, more preferably 300 to 40.
It is 0 Kg / cm. The friction coefficient of the magnetic layer surface of the magnetic recording medium according to the present invention and the opposite surface thereof to SUS420J is preferably 0.5 or less, more preferably 0.3 or less, and the surface resistivity is preferably 10 ⁻⁵ to 10 ^{−. 12} ohm / sq, the elastic modulus at 0.5% elongation of the magnetic layer is preferably 100 to 2000 Kg / mm ² in the running direction and the width direction, and the breaking strength is preferably 1 to 30 Kg / cm ² . The elastic modulus of the magnetic recording medium is preferably 100 to 1500K in both the running direction and the long direction.
g / mm ² , residual spread is preferably 0.5% or less, 1
The heat shrinkage ratio at any temperature of 00 ° C. or lower is preferably 1% or lower, more preferably 0.5% or lower, and most preferably 0.1% or lower.

In the present invention, the elastic modulus of the magnetic layer is preferably 100 to 2 in both the longitudinal direction and the width direction.
000 Kg / mm ² , the elastic modulus of the non-magnetic layer is preferably 100 to 200 in both the longitudinal direction and the width direction.
It is 0 Kg / mm ² , and the elastic modulus of the magnetic layer and the non-magnetic layer may be different depending on the purpose. In the present invention, the amount of residual solvent contained in the magnetic layer and non-magnetic layer is preferably 100 mg / m ² or less, more preferably 10 mg / m ² or less.
It is mg / m ² or less. In the present invention, the porosity of the magnetic layer and the magnetic layer is preferably 30% by volume or less, more preferably 10% by volume or less. Regarding the magnetic characteristics of the magnetic recording medium according to the present invention, the squareness ratio in the tape running direction when measured with a magnetic field of 5 KOe is preferably 0.7.
It is 0 or more, more preferably 0.80 or more, and most preferably 0.90 or more. The squareness ratio in the two directions perpendicular to the tape running direction is 80% of the squareness ratio in the running direction.
% Or less is preferable. The SFD of the magnetic layer is preferably 0.6 or less. In the present invention, when the magnetic recording medium includes two or more layers, that is, one nonmagnetic layer and one magnetic layer, one nonmagnetic layer and two or more magnetic layers, and two or more nonmagnetic layers. It goes without saying that when one magnetic layer, two or more non-magnetic layers and two or more magnetic layers are included, the physical characteristics of each layer can be changed. For example, by increasing the elastic modulus of the non-magnetic layer to improve running durability, and at the same time lowering the elastic modulus of the magnetic layer than that of the non-magnetic layer, the contact of the magnetic recording medium with the head can be improved. is there.

[0029]

EXAMPLES In order to make the effects of the present invention clearer, examples will be given below. In the examples below, parts mean parts by weight. Example 1 Each component of a paint having the following composition was kneaded with a continuous kneader and then dispersed using a sand mill. To the obtained dispersion liquid, 1 part of polyisocyanate was added, 40 parts of butyl acetate was further added, and the mixture was filtered using a filter having an average pore diameter of 1 μm to prepare a coating liquid for the nonmagnetic layer. Non-magnetic powder TiO ₂ crystalline rutile 90 parts Average primary particle diameter 0.035 μm Specific surface area by BET method 40 m ² / g pH 7.0 TiO ₂ content 90% or more DBP oil absorption 27-38 ml / 100 g Surface treatment agent Al ₂ 0 ₃ Carbon black 10 parts Average primary particle diameter 16 mμ DBP oil absorption 80 ml / 100 g pH 8.0 Specific surface area by BET method 250 m ² / g Volatile content 1.5% Vinyl chloride resin (MR-110 manufactured by Zeon Corporation) 12 part -SO ₃ Na group, an epoxy group-containing polyester polyurethane resin 5 parts neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 -SO 3 Na content containing 1 × 10 ^-4 eq / g polyisocyanate 3 parts Nippon Polyurethane Coronate L Butyl stearate 1 part Stearic acid 2 parts Methyl ethyl ketone 150 parts Cyclohexanone 50 parts Furthermore, each component of the coating composition having the following composition was kneaded with a continuous kneader and then dispersed using a sand mill. To the obtained dispersion liquid, 3 parts of polyisocyanate was added, 40 parts of butyl acetate was further added to each, and the mixture was filtered using a filter having an average pore diameter of 1 μm to prepare a coating liquid for the magnetic layer.

Ferromagnetic alloy powder composition Fe / Co = 90/10 100 parts Y content 2.0 at% / Fe Al content 10.0 at% / Fe Hc 1800 Oe BET specific surface area 58 m ² / g crystallite size 175 Angstrom Particle size (average major axis length) 0.1 μm Needle ratio 7 σs 130 emu / g Water-soluble Na 10 ppm Water-soluble Ca 10 ppm Water-soluble Fe 0 ppm Vinyl chloride resin (MR-110 manufactured by Zeon Corporation) 12 parts -SO ₃ Na content 1 × 10 ⁻⁴ eq / g Degree of polymerization 300 Polyester polyurethane resin 3 parts Neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1-SO ₃ Na content 1 × 10 ⁻⁴ eq / g Polyisocyanate 3 parts Nippon Polyurethane Coronate L α-alumina (particle size 0 22 μm) 2 parts Carbon black (particle size 80 mμ) 0.5 part Butyl stearate 1 part Stearic acid 2 parts Methyl ethyl ketone 150 parts Cyclohexanone 50 parts Coating liquid for non-magnetic layer and coating liquid thus obtained Using a 2-slit die coater,
A magnetic layer is formed on a non-magnetic layer on a polyethylene terephthalate support having a center line surface roughness of 0.01 μm and a thickness of the non-magnetic layer after drying of 2 μm. Apply at the same time so that the thickness afterwards becomes 0.2 μm,
While both layers were still in a wet state, they were oriented by a cobalt magnet having a magnetic force of 3000 G and a solenoid having a magnetic force of 1500 G, dried, and then dried in a 7-stage calender consisting of metal rolls at a temperature of 90 ° C. Then, calendering was performed, and slitting was performed to a width of 8 mm to manufacture an 8 mm video tape.

Example 2 Except for using α-alumina having a particle size of 0.28 μm and carbon black having a particle size of 55 μm to prepare a coating solution for the magnetic layer, the same procedure as in Example 1 was carried out. ,
8mm video tape was manufactured. Example 3 Average major axis length is 0.15 μm and σs is 128 emu / g
And the crystallite size is 190 Å, and Y
Instead of Nd, a ferromagnetic alloy powder containing 3.5 at% of Fe with respect to Fe and carbon black having a particle size of 80 m were used to prepare a coating solution for the magnetic layer. An 8 mm video tape was manufactured in exactly the same manner as in Example 1 except that the dry thickness was 0.5 μm. Example 4 Average major axis length is 0.13 μm and σs is 127 emu / g
And the crystallite size is 180 Å, and Y
Instead of Sm, a ferromagnetic alloy powder containing 3.5 at% of Fe with respect to Fe and carbon black having a particle size of 95 mμ were used to prepare a coating solution for the magnetic layer. An 8 mm video tape was manufactured in exactly the same manner as in Example 1 except that the dry thickness of was adjusted to 0.4 μm. Example 5 Average major axis length is 0.15 μm and σs is 132 emu / g
Then, using a ferromagnetic alloy powder having a crystallite size of 185 Å and containing Tb in an amount of 2.5 at% / Fe in place of Y and carbon black having a particle size of 80 mμ, While preparing the coating solution for layers,
Example 1 using the following non-magnetic powder instead of TiO _2.
An 8 mm video tape was manufactured in exactly the same manner as in. Non-magnetic powder Barium sulfate Average primary particle size 0.050 μm Specific surface area by BET method 45 m ² / g pH 8.5 Barium sulfate content 90% or more

Example 6 A ferromagnetic alloy powder having an average major axis length of 0.11 μm, a crystallite size of 180 Å, and La in an amount of 2.5 at% / Fe instead of Y. A carbon black having a particle size of 80 μm was used to prepare a coating liquid for the magnetic layer, and 8 mm was used in exactly the same manner as in Example 1 in which the following nonmagnetic powder was used instead of TiO _2.
A video tape was manufactured. Non-Magnetic Powder α-Alumina Average Primary Particle Diameter 0.050 μm Specific Surface Area by BET Method 35 m ² / g pH 9.0 α-Alumina Content 90% or More Surface Treatment Agent Phenylphosphonic Acid Example 7 The average major axis length was 0. 11 μm, a crystallite size of 180 Å, a ferromagnetic alloy powder containing 2.5 at% of La in place of Y instead of Y, and carbon black having a particle size of 80 mμ. A coating liquid for the magnetic layer was prepared, and 8 mm was prepared in the same manner as in Example 1 using the following non-magnetic powder instead of TiO _2.
A video tape was manufactured. Non-magnetic powder α-iron oxide average primary particle diameter 0.018 μm BET specific surface area 55 m ² / g pH 6.7 α-iron oxide content 85% or more

Comparative Example 1 Ferromagnetic alloy powder having σs of 118 emu / g, α-alumina having a particle size of 0.4 μm and particle size of 16 mμ.
An 8 mm video tape was manufactured in the same manner as in Example 1 except that the carbon black of No. 1 was used. Comparative Example 2 An 8 mm video tape was manufactured in exactly the same manner as Comparative Example 1 except that Y was not added to the coating liquid for the magnetic layer. The thus obtained 8 mm video tapes of Examples 1 to 7 and Comparative Examples 1 and 2 were evaluated by the following method. Demagnetization (change of maximum magnetic flux before and after storage): Measured at Hm 5 kOe using a vibration data type flux meter (manufactured by Toei Industry Co., Ltd.). Centerline average surface roughness: Measured at a cutoff of 0.25 mm using a three-dimensional surface roughness meter (manufactured by Kosaka Laboratory). Centerline average surface roughness: AFM Long axis diameter of magnetic substance: Average particle diameter of long axis was determined by a transmission electron microscope. Crystallite size: determined by X-ray diffraction from the spread of the full width at half maximum of the diffraction lines of the (4, 4, 0) plane and the (2, 2, 0) plane. Running Durability Measurement Method: Samples at 23 ° C. and 70% RH atmosphere, Fuji Photo Film Co., Ltd. 8 mm VCR “FUJ”
Using 10 units of "IX8", P6-120 was run for 100p. The decrease in output during that time was measured, and the dirt on each part in the deck after running was evaluated.

Electromagnetic conversion characteristics: 7 MHz output: An 8 mm video deck "FUJIX8" manufactured by Fuji Photo Film Co., Ltd. was used to record a 7 MHz signal, and the 7 MHz signal reproduction output when this signal was reproduced was measured with an oscilloscope. As a reference,
Fuji Photo Film Co., Ltd. 8 mm tape SAG P6
-120 was used. Chroma output: An 8 mm VCR "FUJIX8" manufactured by Fuji Photo Film Co., Ltd. was used to record a 0.75 MHz signal superimposed on a 7 MHz carrier signal.
The reproduction output when the MHz signal was reproduced was measured with a spectrum analyzer. Envelope flatness: 8 mm from Fuji Photo Film Co., Ltd.
A 7 MHz signal was recorded using a video deck "FUJIX8", and when this signal was reproduced, the 7 MHz signal reproduction output was observed with an oscilloscope and expressed as the difference between the maximum output and the minimum output in one field.

RF output: The video signal of the image signal 501RE was recorded at the reference recording current, and the average value of the envelope value of the reproduced RF output was measured with an oscilloscope and calculated by the following equation. RF output (dB) = 20log10V / V0 Here, V: average value V0: reference value IRF: Institute of Radio Engineers pinhole: after applying a magnetic layer and before applying a back layer,
The pinhole was measured by visually observing the magnetic layer with transmitted white light. It was determined that one or less per 100 m ² was preferable. Stiffness: Using a loop stiffener tester manufactured by Toyo Seiki, a sample with a width of 8 mm and a length of 50 mm is used as a ring, and the force required to give a displacement of 5 mm at a displacement speed of 3.5 mm / sec in the inner diameter direction is expressed in mg Represent Metal component in magnetic material: 6 g of a ferromagnetic alloy powder sample
It was dissolved in HCl of N and the metal in the solution was analyzed by an atomic absorption method to determine at% with respect to Fe. By the above evaluation method,
The results of evaluating the 8 mm video tapes of Examples 1 to 7 and Comparative Examples 1 and 2 are shown in Tables 1 and 2.

Table 1 ───────────────────────────────── Example 1 Example 2 Example 3 Example 4 ───────────────────────────────── Playback output (dB) ───────────── ───────────────────── 7MHz output 7.1 7.4 6.5 6.5 6.2 ─────────────── ────────────────── Chroma output 1.2 1.3 2.4 1.8 ─────────────────── ─────────────── Output after saving (dB) (* 1) ──────────────────────── ───────── 7MHz output 6.2 6.5 5.9 5.6 ─────────────────────────── ─────── Chroma output 0.7 0.8 1.9 1.4 ────────────────────────────── ──── Demagnetization after storage −1.5 −1.4 −0.9 −0.8 (%) (* 1) ────────────────── ─────────────── Head wear 0.8 1.5 1.2 0.4 (μm) (* 2) ────────────── ──────────────────── * 1 Measure the output and maximum magnetic flux after storage for 1 week in an environment of temperature 60 ° C and humidity 90%. * 2 This is the head bite change (initial byte 20 μm) before and after 20 passes of P6-120 length using a “FUJIX8” 8 mm beam in an environment of temperature 5 ° C. and humidity 80%.

Table 2 ─────────────────────────────────── Example 5 Example 6 Example 7 Example 7 Comparison Example 1 Comparative Example 2 ─────────────────────────────────── Reproduction output (dB) ───── ────────────────────────────── 7MHz output 6.3 6.8 7.3 3.6 7.0 7.0 ─── ──────────────────────────────── Chroma output 2.8 2.3 1.9 0.3 2.6 ─ ────────────────────────────────── Output after saving (dB) (* 1) ───── ────────────────────────────── 7MHz output 5.8 6.2 6.9 3.2 2.1 ─────────────────────────────────── Chroma output 2.5 1.6 1.6 1.6 −0.2 -0.5 ─────────────────────────────────── Demagnetization after storage −0.4 -1 3 -1.6 -1.4 -20.1 (%) (* 1) ────────────────────────────── ────── Head wear 0.7 1.1 0.5 7.6 0.3 (μm) (* 2) ──────────────────── ──────────────── * 1 Same as Table 1. * 2 Same as Table 1. As is clear from Table 1 and Table 2, comparing Examples 1 to 7 according to the present invention with Comparative Examples 1 and 2, in the present invention, even after storage under high temperature and high humidity environment, It was found that the decrease of the output was small and the demagnetization was also small, and the wear of the head was significantly reduced. It was also found that the weather resistance of Examples 1 to 7 according to the present invention was significantly improved as compared with Comparative Example 2 containing no rare earth element.

Example 8 Except that the non-magnetic layer was not provided, the coating solution for the magnetic layer was applied by a two-slit die coater so that the dry thickness of the magnetic layer was 2 μm. 8
mm video tape was manufactured. Example 9 A ferromagnetic alloy powder having an average major axis length of 0.18 μm, σs of 123 emu / g, and a crystallite size of 220 angstrom without providing a non-magnetic layer was used, and Nd was substituted for Fe instead of Y. , Particle size 65m
μ of carbon black was added to prepare a coating solution for the magnetic layer, and the dry thickness of the magnetic layer was adjusted to 2.5 μm.
An 8 mm video tape was manufactured in exactly the same manner as in Example 1 except that the coating liquid for the magnetic layer was applied using a slit die coater. Comparative Example 3 Average major axis length is 0.25 μm, σs is 123 emu / g,
An 8 mm video tape was manufactured in exactly the same manner as in Example 9 except that a ferromagnetic alloy powder having a crystallite size of 320 Å and carbon black having a particle size of 80 mμ were used. The thus obtained 8 mm video tapes of Examples 8 and 9 and Comparative Example 3 were evaluated in the same manner as in Examples 1 to 7 and Comparative Examples 1 and 2. The evaluation results are shown in Table 3. As is clear from Table 3, in Examples 8 and 9 in which only a single magnetic layer was provided, reproduction was performed as compared with Comparative Example 3 before and after storage in a high temperature and high humidity environment. Output is high enough,
It was also found that the amount of head wear was reduced.

Table 3 ───────────────────────────── Example 8 Example 9 Comparative Example 3 ──────── ────────────────────── Playback output (dB) ─────────────────────── ────── 7 MHz output 5.6 4.7 1.3 ───────────────────────────── Chroma output 3. 2 1.2 0.4 ───────────────────────────── Output after saving (dB) (* 1) ─── ────────────────────────── 7MHz output 5.3 4.4 1.1 ────────────── ──────────────── Chroma output 2.9 0.7 0.1 ─────────────────── ───────── Demagnetization after storage −0.5 −0.6 −0.2 (%) (* 1) ───────────────── ──────────── Head wear 0.9 0.7 3.2 (μm) (* 2) ──────────────────── ────────── * 1 and * 2 are exactly the same as in Table 1.

Example 10 The components of a coating composition having the following composition were kneaded with a continuous kneader and then dispersed using a sand mill. To the obtained dispersion liquid, 3 parts of polyisocyanate was added, 40 parts of butyl acetate was further added to each, and the mixture was filtered using a filter having an average pore size of 1 μm to prepare a coating liquid for the first magnetic layer. did. Ferromagnetic alloy powder Composition Fe ₃ O ₄ (containing Co) 100 parts Hc 8500e Specific surface area by BET method 40 m ² / g Crystallite size 280 Å Particle size (average major axis length) 0.25 μm Needle ratio 8 σs 72 emu / g Water-soluble Na 10 ppm Water-soluble Ca 10 ppm Water-soluble Fe 0 ppm pH 8.0 The other components are exactly the same as the coating liquid for the magnetic layer of Example 1. Further, a coating liquid for the second magnetic layer was prepared in exactly the same manner as the coating liquid for the magnetic layer of Example 1. The thus-obtained coating liquid for the first magnetic layer and the coating liquid for the second magnetic layer were applied to a polyethylene having a thickness of 7 μm and a center line surface roughness of 0.01 μm using a 2-slit die coater. The second magnetic layer is formed on the first magnetic layer on the terephthalate support, and the thickness of the first magnetic layer after drying is 2.0 μm. 0.4 μm thickness
At the same time so that while coating both layers are still wet, a cobalt magnet having a magnetic force of 3000 G and 1
After being oriented by a solenoid having a magnetic force of 500 G, and dried, it was calendered at a temperature of 90 ° C with a 7-stage calender consisting of metal rolls only, slitting to a width of 8 mm, and a 8 mm video tape. Was manufactured.

Comparative Example 4 A coating solution for the first magnetic layer was prepared in exactly the same manner as in Example 10. Further, a ferromagnetic alloy powder having σs of 128 emu / g and a crystallite size of 180 Å was used, Y was not contained, and α-alumina having a particle size of 0.4 μm and carbon black having a particle size of 16 mμ were used. A coating liquid for the second magnetic layer was prepared in exactly the same manner as in Example 10 except for the above. The coating solution for the first magnetic layer and the coating solution for the second magnetic layer thus obtained were coated on a polyethylene terephthalate support in exactly the same manner as in Example 10 to prepare an 8 mm video tape. Was manufactured. The thus obtained 8 mm video tapes of Example 10 and Comparative Example 4 were obtained.
The samples were evaluated in the same manner as in Examples 1 to 7 and Comparative Examples 1 and 2. The evaluation results are shown in Table 4. As is clear from Table 4, also in Example 10 in which two magnetic layers were formed and Comparative Example 4, Example 10 according to the present invention did not contain a rare earth element and the abrasive had a particle size of 0. Compared with Comparative Example 4 having a particle size of carbon black larger than 3 μm and a particle size of carbon black smaller than 50 μm, the reproduction output after storage in a high temperature and high humidity environment is sufficiently high, and the wear amount of the head is also reduced. There was found. Example 11 An 8 mm video tape was manufactured in exactly the same manner as in Example 1 except that a ferromagnetic alloy powder having σs of 155 emu / g and a crystallite size of 190 Å was used.

Comparative Example 5 An 8 mm video tape was manufactured in the same manner as in Example 1 except that a ferromagnetic alloy powder having σs of 163 emu / g and a crystallite size of 195 Å was used. The 8 mm video tapes of Example 11 and Comparative Example 5 thus obtained were used in Examples 1 to 7 and Comparative Examples 1 and 2.
It evaluated by the method similar to. The evaluation results are shown in Table 4. In Comparative Example 5, the dispersion of the coating liquid for the magnetic layer was poor and the magnetic layer could not be formed.
As is clear from Table 5, in Example 11 according to the example of the present invention, the reproduction output was sufficiently high and the head wear amount was reduced regardless of before and after storage in a high temperature and high humidity environment. It turned out to be.

Table 4 ────────────────────────────────── Example 10 Comparative Example 4 Example 11 Comparative Example 5 ────────────────────────────────── Playback output (dB) ─────────── ──────────────────────── 7MHz output 4.9 4.2 7.8 −−−− ─────────── ─────────────────────── Chroma output 2.7 2.4 3.7 −−−− ───────────── ────────────────────── Output after saving −−−− (dB) (* 1) ────────────── ───────────────────── 7MHz output 4.3 0.3 7.0 −−−− ────────────── ──────────────────── Chroma output 2.5 1.2 2.9 −−−− ──────────────── ─────────────────── Demagnetization after storage −0.1 −0.6 −2.0 −−−− (%) (* 1) ─── ─────────────────────────────── Head wear 0.6 5.7 0.8 −−−− (μm) (* 2) ────────────────────────────────── * 1 and * 2 are exactly the same as Table 1. Is.

Example 12 The average major axis length is 0.05 μm, and σs is 125 emu / g.
Then, using a ferromagnetic alloy powder having a crystallite size of 110 angstroms, in exactly the same manner as in Example 1, 8 mm
A video tape was manufactured. The obtained 8 mm video tape was evaluated in the same manner as in Examples 1 to 7 and Comparative Examples 1 and 2. The evaluation results are shown in Table 5. As shown in Table 5, in Example 12 according to the example of the present invention, the reproduction output was sufficiently high and the wear amount of the head was decreased regardless of before and after storage in a high temperature and high humidity environment. It turned out to be. On the other hand, magnetic powders having an average major axis length of 0.04 μm or less and alloy powders having a crystallite size of 100 angstroms or less were prepared, but sufficient coercive force could not be expressed, and ferromagnetic alloy powders I couldn't get it. Example 13 An 8 mm video tape was manufactured in exactly the same manner as in Example 1 except that α-alumina having a particle size of 0.06 μm was used. Comparative Example 6 An 8 mm video tape was manufactured in exactly the same manner as in Example 1 except that α-alumina having a particle size of 0.02 μm was used. 8 mm obtained according to Example 13 and Comparative Example 6
The video tape was evaluated in the same manner as in Examples 1 to 7 and Comparative Examples 1 and 2. The evaluation results are shown in Table 5. As shown in Table 5, in Comparative Example 6 using the abrasive having a particle size smaller than 0.03 μm, the head was clogged during the evaluation test, and the evaluation test could not be performed. In Example 13 according to the present invention, it was found that the reproduction output was sufficiently high and the wear amount of the head was reduced regardless of before and after storage in a high temperature and high humidity environment.

Example 14 An 8 mm video tape was manufactured in the same manner as in Example 1 except that carbon black having a particle size of 2.60 mμ was used. Comparative Example 7 An 8 mm video tape was manufactured in exactly the same manner as in Example 1 except that carbon black having a particle size of 350 mμ was used. 8 mm obtained according to Example 14 and Comparative Example 7
The video tape was evaluated in the same manner as in Examples 1 to 7 and Comparative Examples 1 and 2. The evaluation results are shown in Table 5. As shown in Table 5, in Example 14 according to the present invention, as compared with Comparative Example 7 using carbon black having a particle size larger than 300 mμ,
It was found that the reproduction output was sufficiently high and the amount of head wear was also reduced before and after storage in a high temperature and high humidity environment.

Table 5 ─────────────────────────────────── Example 12 Example 13 Comparative Example 6 Implementation Example 14 Comparative Example 7 ─────────────────────────────────── Reproduction output (dB) ───── ────────────────────────────── 7MHz output 7.6 6.9 Not evaluable 5.2 1.2 ──── ─────────────────────────────── Chroma output 1.1 1.3 Not evaluable 1.1 0.5 0.5 ─── ──────────────────────────────── Output after saving (dB) (* 1) ─────── ──────────────────────────── 7MHz output 6.4 6.3 Not evaluable 4.70 9 ─────────────────────────────────── Chroma output 0.9 0.8 Not evaluable 0.7 0.4 ─────────────────────────────────── Demagnetization after storage -1.8 -1. 1 Unable to evaluate −1.0 −1.0 (%) (* 1) ───────────────────────────────── ─── Head wear 0.3 0.1 Not evaluable 0.1 0.1 (μm) (* 2) ──────────────────────── ──────────── * 1 and * 2 are exactly the same as in Table 1.

In summary, according to the present invention, 7 MHz
It has been found that it is possible to obtain a magnetic recording medium in which the reproduction output at 0.7 MHz and the reproduction output after storage are remarkably high, demagnetization is small, and head wear is small.

[0048]

According to the present invention, in a magnetic recording medium in which at least one magnetic layer having ferromagnetic powder dispersed in a binder is provided on a non-magnetic flexible support, the ferromagnetic powder is
Y or at least one rare earth metal element selected from lanthanide series metal elements, σs of 120 to 160 emu / g, and an average major axis length of 0.04 to 0.
It is a needle-like ferromagnetic alloy powder having a crystallite size of 100 to 300 angstroms and a magnetic layer containing an abrasive having an average particle size of 0.03 to 0.3 μm. A good magnetic recording medium,
In particular, it becomes possible to provide a magnetic recording medium having good storage stability and less head wear.

Claims (7)

[Claims] 1. A magnetic recording medium comprising at least one magnetic layer having a ferromagnetic powder dispersed in a binder on a non-magnetic flexible support, wherein the ferromagnetic powder is a Y or lanthanide series metal. Containing at least one rare earth metal element selected from the elements and having a s of 120 to 160 emu
/ G, the average major axis length is 0.04 to 0.2 μm, and the crystallite size is 100 to 300 angstroms, and the magnetic layer has an average particle size of 0. A magnetic recording medium containing an abrasive of 0.3 to 0.3 μm. 2. The magnetic recording medium according to claim 1, wherein the magnetic layer is provided on a nonmagnetic layer in which a nonmagnetic powder is dispersed in a binder. 3. The lanthanide series metal element is Nd,
The magnetic recording medium according to claim 1 or 2, which contains Sm, Dy, Gd, Tb and La. 4. The magnetic layer has a thickness of 0.1 to 4 μm.
4. The method according to claim 1, wherein
A magnetic recording medium according to item. 5. The non-magnetic powder contained in the non-magnetic layer,
5. At least one non-magnetic powder selected from titanium oxide, barium sulfate, silica, α-alumina, zinc oxide, α iron oxide, cerium oxide, tin oxide and zirconia, according to any one of claims 2 to 4. 2. A magnetic recording medium according to item 1. 6. The magnetic layer has an average particle size of 50 to 3
The magnetic recording medium according to claim 1 or 5, which contains 00 mμ of carbon black. 7. The magnetic layer is applied and provided on the non-magnetic layer while the non-magnetic layer is in a wet state, and the magnetic layer is provided. The magnetic recording medium according to 1.