JP2003162809A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium having a high short- wavelength output when reproduced using an MR head, a low medium noise, and little thermal asperity, in which fine hexagonal ferrite agglomerates are removed, and in which the dispersion is facilitated. <P>SOLUTION: The magnetic recording medium is provided with a nonmagnetic layer in which a nonmagnetic powder is dispersed in a binder on a supporting body, and a magnetic layer made by dispersing a ferromagnetic powder in the binder thereon. In the magnetic recording medium, the magnetic layer has the mean tabular diameter of 10-40 nm and the coercive force Hc of 135-400 kA/m, and includes a hexagonal ferrite magnetic powder through a wet classification process. <P>COPYRIGHT: (C)2003,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention
Concerning recording media, especially ferromagnetic powder and binders
Application type in which magnetic layer is formed by applying magnetic paint on support
In connection with other magnetic recording media, the magnetoresistive effect is used for reproduction.
Low noise when used in a system using an MR head
And a hexagonal blowjob on a magnetic layer that is suitable for high-density recording
Related to a magnetic recording medium for high-density recording including [0002] Conventionally, video tape and audio tape
, Computer tape, flexible disk, etc.
As magnetic recording media, ferromagnetic iron oxide, Co-modified ferromagnetism
Iron oxide, CrO₂, Ferromagnetic metal powder, hexagonal Ferai
A magnetic layer in which a binder is dispersed in a binder is coated on the support.
Is widely used. Among these, hexagonal ferrite
It is known that it has excellent high-density recording characteristics (for example,
For example, JP-A-60-157719, JP-A-62-1
No. 09226, JP-A-3-280215).
In JP-A-5-12650, the ferrite is used.
The thickness of the magnetic layer is 0.1 to 0.6 μm, and the magnetic layer is supported.
A nonmagnetic layer thicker than the magnetic layer is provided between
It is supposed to improve wavelength output, erasing characteristics and durability. Special
Kaihei 5-225547 discloses a nonmagnetic layer on a support.
And a magnetic material containing magnetic powder of 0.1 μm or less on it.
Disclosure of a magnetic recording medium provided with a conductive layer, excellent high frequency characteristics,
In addition, the signal overwriting characteristics are good and the durability is also good.
Provides a recording medium. Recently, a data recording system for a computer.
High-sensitivity read head using the magnetoresistive effect
(MR head) is used, system noise is magnetic recording
Dominated by noise from the medium. JP 7-1
No. 82646 discloses a medium using Ba ferrite.
It has been proposed to reproduce with an MR head. Medium noise
To reduce the size of ferromagnetic particles
However, it is affected by thermal fluctuations as the ferromagnetic particles become finer.
Therefore, it is estimated that the stability of the magnetization transition region is a problem.
ing. The stability of magnetization is KuV / kT (Ku is magnetic
Isotropic constant, V is particle volume, k is Boltzmann constant, T is absolute
(Vs. temperature). Hexagonal ferrite is saturated
Ku is about 1/3 to 1/2 of the ferromagnetic metal powder, so Ku
It is difficult to increase the thermal fluctuation. Hot sauce
From the viewpoint of measures against fluctuations, saturation magnetization is large even for fine particles.
It is hoped that the threshold and Ku are large. JP 5
9-151340 discloses SiO as a glass component.₂The
Even if it is the same plate diameter and specific surface area,
That it is possible to obtain Ba ferrite with a large particle size.
It has been. JP-A-60-77129 discloses S
rO, CaO, SiO ₂High by specifying the content of
Barium ferrite powder with saturation magnetization is obtained. The plate diameter is 10 to 40 nm and the thermal fluctuation is small.
Glass component to obtain fine particulate hexagonal ferrite and
A small amount of impurities in the raw material was examined. SiO₂Including
Glass (SiO2 as glass component)₂If you add
SiO in the food₂Make hexagonal ferrite)
When it does, it becomes difficult to remove the glass component with a weak acid,
The hexagonal ferrite aggregates of 0.5-10μm size are magnetic
Mixed into the powder. Using such raw materials, thin layer magnetism
In addition to causing streaks when forming a conductive layer,
This causes unevenness of the adhesive layer and causes noise. Magnetic layer surface
The presence of these aggregates in the
Furthermore, when replaying with MR head, thermal asperi
MR head with particularly high reproduction sensitivity
It becomes a problem when using. [0005] The present invention is based on the above-mentioned conventional technique.
The fine hexagonal system, which was made in view of the problems of surgery
Removes ferrite agglomerates, facilitates dispersion, and reduces MR head
The short wavelength output is high when reproduced using
Magnetic recording media with low thermal asperity
The purpose is to provide. [0006] The object of the present invention is to provide a support.
A nonmagnetic layer in which nonmagnetic powder is dispersed in a binder is placed on top.
In addition, a magnetic material in which ferromagnetic powder is dispersed in a binder.
In the magnetic recording medium provided with the layer, the magnetic layer is an average plate
Diameter 10-40nm, coercive force Hc 135-400kA
/ M, hexagonal ferrite magnet that has undergone a wet classification process
Achieved by a magnetic recording medium characterized by containing
Made. Further, the magnetic recording medium of the present invention includes the magnetic layer.
Thickness of 0.01 to 0.5 μm, residual magnetic flux density × magnetic layer
The thickness is preferably 0.5 to 100 mT · μm. The present invention relates to a hexagonal crystal having undergone a wet classification process.
Ellite magnetic powder is used for the magnetic layer. The wet classification process consists of six
In this process, wet classification is applied to tetragonal ferrite magnetic powder.
The Wet classification means that hexagonal ferrite magnetic powder is wet
Say to be classified by state. Soaked in liquid when wet
Can be obtained. Liquid is not particularly limited, but usually
Water is preferred, especially clean without impurities such as ion exchange water
Water is preferred. There are no particular restrictions on the classification means
Is the settling speed of hexagonal ferrite magnetic powder charged into the liquid
A means of classifying is preferred according to the difference in degree, especially water tank is preferred.
Good. As for Minamata, the rising water flow velocity gradually goes from high to low.
And hexagonal ferrite magnets
While the size of the powder goes over its overflow
So that smaller ones will overflow later
Those designed are preferred. That is, large size
Is settled and separated at a stage where the rising water flow velocity is higher. This
The size of the hexagonal ferrite magnetic powder here is six
If the tetragonal ferrite magnetic powder is agglomerated,
Refers to the size of the agglomerates.
Say the size of. Water tank for treating hexagonal ferrite magnetic powder
As a device, from a small diameter settling pipe to a large diameter settling pipe
A continuous water tank device with multiple settling tubes arranged in series
The The shape of the settling tube is a cross-sectional area by a plane perpendicular to the long axis.
If is constant, there is no particular limitation. Such wet classification
Manufactured from various raw materials described later by going through the process
Agglomerates mixed in hexagonal ferrite magnetic powder are effective
Is excluded. In addition, the average plate diameter referred to in the present invention is a wet component.
The hexagonal ferrite magnetic powder obtained through the
Say what is measured. Hexagonal system after wet classification
Ferrite magnetic powder has a desired size (ie, in the present invention).
Overflow or sedimentation)
In the former case, it is further concentrated by sedimentation.
Or concentrating with a centrifuge and then dried. Hexagonal ferrite magnet subjected to wet classification
The powder may be produced by a known method,
At least hexagonal ferrite magnetic powder was produced
It may be after any process as long as it is later, but no impurities are mixed.
Those in the same state are preferred. Preferably, for example, glass
Crystallization method, hydrothermal synthesis method, flux method, coprecipitation / flac
The hexagonal ferrite is formed by the process such as grinding, weak acid treatment,
What was washed with water, respectively. Hexagonal ferrite magnet used in the present invention
Powder is BaFe1 with M-type structure₂O_{1 9}, W-shaped Ba
Me₂Fe₁₆O₂₇(Me is a substituted element) or they
Hexagonal ferrite with some of its atoms replaced by other elements
These magnetic powders are manufactured by the above method etc.
It is. Collect and wash hexagonal ferrite during production
Sometimes, microcrystals coexist with substances that strongly adsorb on the particle surface.
Immediately after the precipitation, organic molecules are adsorbed on the surface.
It is also preferable to perform wet classification after that. The organic matter to be adsorbed is used in the manufacturing process of magnetic recording media.
P more than fatty acids added in (pKa is 4.2 or more)
Organic compounds containing a polar group with small Ka and salts thereof
preferable. In the vitrification crystal method, glass components can be removed.
It has been proposed to use acetic acid, but with the progress of washing
Both use strong acids with smaller pKa than acetic acid
Therefore, it can be adsorbed on the surface of the magnetic powder, which is preferable. The present invention
There are compounds with a pKa of 4 or less that can be used for
As a polar group, -PO (OH)₂, -OPO (O
H)₂, -SO_ThreeH, -SO₂H etc. As compounds having these polar groups,
Minomethylphosphonic acid, aminoethylphosphone
Acid, phenylphosphonic acid (1.8), p-ethylbenzene
Nzen phosphonic acid, aminotrimethylene phospho
Acid, ethylenediaminetetramethylene phosphone
Acid, hexamethylenediaminotetramethylene phospho
Acid, diethylenetriaminopentamethylene phospho
Acid, triethylenetetraaminohexamethylenephos
Phonic acid, tetraethylenepentaaminoheptamethylene
Phosphonic acid, pentaethylene hexaamino octame
Methylene phosphonic acid such as tylene phosphonic acid;
Tylenediphosphonic acid, ethylene-1,1'-dipho
Sulfonic acid, ethylene-1,2'-diphosphonic acid,
Propylene-1,1'-diphosphonic acid, propylene
-1,3'-diphosphonic acid, hexamethylene-1,
6-diphosphonic acid, 2,4-dihydroxypentamethene
Tylene-2,4-diphosphonic acid, 2,5-dihydro
Xylhexamethylene-2,5-diphosphonic acid, 2,
3-dihydroxybutylene-2,3-diphosphone
Acid, 1-hydroxybenzyl-1,1'-diphospho
Acid, 1-aminoethylene-1,1'-diphosphone
Alkylene diphosphonic acids such as acids; Hydroxymethyle
Diphosphonic acid, 1-hydroxyethylene-1,
1'-diphosphonic acid, 1-hydroxypropylene-
1,1'-diphosphonic acid, 1-hydroxybutylene
-1,1'-diphosphonic acid, 1-hydroxyhexa
Hydroxy such as methylene-1,1'-diphosphonic acid
Alkylene-1,1'-diphosphonic acid; phenoxy
Organic phosphonic acid such as phosphonic acid (1.95)
 Α-naphthyl phosphate, phenyl phosphate, diphenyl phosphate,
Phenylphosphinic acid, Benzenesulfonic acid (2.55), p-to
Ruene sulfonic acid, 4-hydroxyphenyl sulfone
Acid, hydroquinonesulfonic acid, benzene-2,5-dis
Sulfonic acid, 4-butylbiphenyl-3'-sulfonic acid
Any aryl sulfonic acid; sulfamyl acid (1.6
5) Phenylsulfamic acid, methanesulfonic acid,
Alkyl sulfonic acids such as rufosuccinic acid;
Sulfinic acid, sulfinic acid such as methylsulfinic acid,
Phthalic acid (pKa₁= 2.75), terephthalic acid
(PKa₁= 3.54), maleic acid (pKa₁= 1.7
5) Malonic acid (pKa ₁= 2.65)
Acids, benzoylhydroxylamine, phenoxy
Nylsulfohydroxylamine, benzohydroxamic acid
(2.3) and the like, particularly ethylenediaminetetra
Methylenephosphonic acid, diethylenetriaminopenta
Methylene phosphonic acid and phenyl phosphonic acid are preferred.
Good. In the above, the number in parentheses attached to the compound
The value is a pKa value. The organic matter was shown in acid form
Their salts, such as sodium salts, potassium salts, etc.
Alkali metal, ammonium salt (alkyl-substituted ammonium)
May be used instead of organic substances)
However, both organic substances and their salts may be used. Ma
In addition, even if the organic substance (or its salt) used is a kind
There may be more than one species, and organic and organic salts are the same species.
It may be different or different. In the method of the present invention
The acid dissociation constant (pKa) of the organic substance is 4 or less.
Is preferable, more preferably 3.8 or less, and pK
If a exceeds 4, the dispersibility improving action tends to decrease.
The Hereinafter, it is used for a magnetic layer (also referred to as an upper layer).
The hexagonal ferrite magnetic powder will be described. The present invention
As a hexagonal ferrite magnetic powder contained in the upper layer of burrs
Um ferrite, strontium ferrite, lead blow
, Calcium ferrite substitutes, Co substitutes, etc.
Is mentioned. Specifically, magnetoplumbite type bar
Lumium ferrite and strontium ferrite, and
Magneto-plumbite type bar containing some spinel phases
Examples of such materials are lithium ferrite and strontium ferrite.
Other than the specified atoms, Al, Si, S, S
c, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, A
g, Sn, Sb, Te, Ba, Ta, W, Re, Au,
Hg, Pb, Bi, La, Ce, Pr, Nd, P, C
o, Mn, Zn, Ni, Sr, B, Ge, Nb, etc.
It may include children. In general, Co-Ti, Co-
Ti-Zr, Co-Nb, Co-Ti-Zn, Co-Z
n-Nb, Ni-Ti-Zn, Nb-Zn, Ni-T
i, Zn-Ti, Zn-Ni and other elements added
Can be used. From the SFD perspective, pure mug
Netoplumbite type ferrite has more spinel layers.
It is more preferable than composite type ferrite containing. Control coercive force
To control the composition, particle size, particle thickness, hexagonal
Spinel that controls the thickness of the spinel phase of ferrite
The substitution site of the spinel phase that controls the amount of substitution element in the phase
There are methods such as controlling the location of Used in the present invention
Hexagonal ferrite magnetic powder is usually hexagonal plate-like powder
The size is measured as follows. In the present specification, hexagonal ferrite magnets
Various powder sizes (hereinafter referred to as “powder size”)
")" Is a high-resolution transmission electron micrograph and image.
It is obtained from the image analyzer. High resolution transmission electron microscope
Trace the outline of the powder in the photo with an image analyzer.
You can ask. That is, powder size is powder
The shape of the needle is spindle, spindle, or column (however, the height is
Larger than the major axis), the major axis of the powder
Hexagonal ferrite magnetism expressed by length, that is, long axis length
The shape of the powder is like a plate or column (like thickness)
(Supreme height is less than the maximum major axis of the plate or bottom)
The maximum major axis of the plate surface or bottom surface, that is, the plate diameter,
The shape of the body is spherical, polyhedral, unspecified, etc., and
If the major axis of the powder cannot be identified from the shape, use a circle.
It is represented by the equivalent diameter. The equivalent circle diameter is obtained by the circle projection method.
Say something. In addition, the average powder size of the powder is the above powder
This is the arithmetic average of the body size.
The measurement was performed as described above. once
The particle means an independent powder without aggregation. The powder
The average acicular ratio of the body is the length of the minor axis of the powder in the above measurement.
Measure the short axis length (the longest axis perpendicular to the long axis)
And specify the arithmetic mean of the (major axis length / minor axis length) value of each powder.
The Here, the minor axis length is the definition of the above powder size.
If the length of the minor axis constituting the powder is the same,
Refers to the thickness or height, i.e. the plate thickness, respectively,
Since there is no distinction between major and minor axes, (major axis length / minor axis length) is
Considered 1 for convenience. And if the shape of the powder is specific,
For example, in the case of the above definition of powder size, the average powder size
Is the average major axis length.
Izu is called the average plate diameter, and the arithmetic average of (plate diameter / plate thickness)
It is called a flat plate ratio. For the same definition, the average powder size
It is called uniform particle size. Standard deviation /
The average value is expressed as a coefficient of variation.
The In the present invention, the hexagonal ferrite magnetic powder is flattened.
The flat plate diameter is 10 to 40 nm, preferably 15 to 35 nm.
It is a range. The average thickness of the magnetic powder is usually 2 to 1
Although it is 5 nm, 4 to 10 nm is particularly preferable. Average board
The coefficient of variation in diameter and average plate thickness is preferably small, 0 to
35% is preferred. More preferably, it is 0 to 30%
The Furthermore, the average plate ratio is preferably 1.5 to 4, and
It is preferably 2 to 3.8. Average plate diameter is not 10nm
When full, it has a high specific surface area and is difficult to disperse.
It ’s not good. Also, coercive force of hexagonal ferrite magnetic powder
Hc is 135-400 kA / m, 150-350
kA / m is preferred. Large Hc is anisotropy constant (Ku)
To increase the thermal stability of magnetization.
preferable. When Hc is less than 135 kA / m, high density recording is possible.
It is difficult to achieve, and if it exceeds 400 kA / m, the recording head machine
It is difficult to exert its ability. Also, saturation magnetization σs
Is 35 to 58 A · m²/ Kg is preferred, 40-55
Am²/ Kg is more preferable. 35A ・ m²Less than / kg
Magnetic flux density of the magnetic layer is reduced and high output is obtained.
Absent. In addition, the hexagonal ferrite magnetic powder BE
Specific surface area by T method (S_BET) Is usually 30-150m²/
g, but 40-120m²/ G is preferred. 30m²
If less than 1 / g, the attractive force between particles is large and stacking
150 becomes difficult and noise becomes high, and 150
m²/ G is difficult to disperse and surface properties are difficult to obtain
It is not preferable. The moisture content is preferably 0.3 to 2.0%.
Good. The water content of the magnetic powder is optimal depending on the type of binder.
Is preferable. Wet-classified magnetic powder is needed
Al, Si, P, Zr, Mg or oxides thereof
Surface treatment may be performed with hydride or hydroxide. Like
Or Al₂O_Three・ NH₂O or SiO₂・ NH₂O
Depending on the binder used.
It is preferable to change the rate. The amount is based on the magnetic powder
Fatty acid etc. when it is 0.1-10 mass% and surface treatment
Adsorption of lubricant of 100mg / m²Less preferred
Yes. The magnetic powder contains soluble Na, Ca, Fe, Ni, S
It may contain inorganic ions such as r and Ba, but the total amount
Less is preferable, but 0-100 ppm or less
In particular, it does not affect the characteristics. Tap density is 0.5g /
ml or more is preferred and 0.8 g / ml or more is more preferred
Yes. Reproduction output due to saturation of MR head
In order to prevent deterioration of the magnetic recording medium of the present invention
Then, residual magnetic flux density (Br) × magnetic layer thickness (δ) is 0.5.
˜100 mT · μm is preferable. Over 100mT ・ μm
This is preferable because saturation of the MR head is likely to occur.
Yes. The residual magnetic flux density is preferably 70 to 200 mT, and
Preferably it is the range of 70-180 mT. Magnetic
The thickness of the layer is preferably 0.01 to 0.5 μm, more preferably
Preferably it is the range of 0.02-0.3 micrometer. Magnetic
The coercive force of the sex layer is preferably 135 to 450 kA / m,
150-400 kA / m is preferable. The present invention is hexagonal
It is in the direction to unify the size distribution of ferrite magnetic powder
So SFD, ie switching field
It has the effect of improving distribution, 0.30
1.00 is preferable, and 0.30 to 0.80 is more preferable.
Yes. SFD is the differential curve of the magnetic hysteresis curve.
The value obtained by dividing the half-value width ΔHc of (dB / dH) by Hc.
The Further, the squareness ratio (SQ) of the magnetic layer is preferably set to 0.
50-0.70, more preferably 0.55-0.65
It is a range. In the magnetic recording medium of the present invention, the magnetic layer is bonded.
The mixture resin is a conventionally known thermoplastic resin, thermosetting resin,
A reactive resin or a mixture thereof can be used. Thermoplastic tree
As fat, glass transition temperature is -100 to 150 ° C, several
Average molecular weight is 1000-200000, preferably 10
000-100,000, degree of polymerization is about 50-1000
belongs to. Such binder resins include vinyl chloride.
, Vinyl acetate, vinyl alcohol, maleic acid, acrylic
Rylic acid, acrylic acid ester, vinylidene chloride, acrylic
Ronitrile, methacrylic acid, methacrylate ester,
Tylene, butadiene, ethylene, vinyl butyral, vinyl
Nylacetal, vinyl ether, etc. as structural units
Polymers or copolymers, polyurethane resins,
There is a resin. In addition, a thermosetting resin or a reactive resin is used.
Phenol resin, epoxy resin, polyurethane cured
Mold resin, urea resin, melamine resin, alkyd resin, active resin
Lil-based reaction resin, formaldehyde resin, silicone tree
Fat, epoxy-polyamide resin, polyester resin and
Mixture of socyanate prepolymer, polyester poly
A mixture of allol and polyisocyanate, polyurethane and
And a mixture of polyisocyanates. In the above binder resin, more excellent ferromagnetic powder
In order to obtain the dispersion effect of the powder and the durability of the magnetic layer,
-COOM, -SO_ThreeM, -OSO_ThreeM, -P = O
(OM)₂, -OP = O (OM)₂(M is more than
Hydrogen atom or alkali metal base), -OH, -NR
₂, -N⁺R_Three(R is alkyl, alkenyl, acyl.
Group, allyl group), epoxy group, -SH, -CN, etc.
Copolymerize at least one selected polar group or
It is preferable to use the one introduced by the addition reaction. This
The amount of polar groups such as^-1-10^-8Mol / g,
Preferably 10^-2-10^-6Mol / g. Binder used in the magnetic recording medium of the present invention
The resin is preferably in the range of 5 to 50 mass% with respect to the ferromagnetic powder.
Preferably, it is used in the range of 10 to 30% by mass. PVC
When using a nyl resin, 5 to 100% by mass, polyurea
2-50% by mass when using tan resin, polyisocyanate
The net combines these in the range of 2-100% by mass.
Are preferably used. Also, hexagonal ferrite magnetic powder for the magnetic layer
The degree of filling of the hexagonal ferrite magnetic powder used is σs
And the maximum magnetic flux density (Bm) (Bm / 4πσ
s), and in the present invention, the value is preferably
1.1-3.2 g / cm^ThreeMore preferably, 1.
2 to 3.0 g / cm^ThreeIt is. In the present invention, a place where polyurethane is used.
The glass transition temperature is −50 to 100 ° C. and the elongation at break is 1
00 to 2000%, breaking stress is 0.49 to 98 MPa,
The yield point is preferably 0.49 to 98 MPa. As a polyisocyanate used in the present invention,
Tolylene diisocyanate, 4,4'-diphenyl
Lumethane diisocyanate, hexamethylene diisocyanate
Net, xylylene diisocyanate, naphthylene
1,5-diisocyanate, o-toluidine diisocyanate
Net, isophorone diisocyanate, triphenyl
Isocyanates such as tan triisocyanate, and
Formation of these isocyanates and polyalcohols
Products and products formed by condensation of isocyanates.
A lysocyanate or the like can be used. these
Commercially available product names for isocyanates include:
Made by this polyurethane company, Coronate L, Coronate HL,
Coronate 2030, Coronate 2031, Millionet
TOMR Millionate MTL, Takeda Pharmaceutical, Takenate
D-102, Bamboo D-110N, Bamboo D-
200, Takenet D-202, manufactured by Sumitomo Bayer,
S module L, death module IL, death module
N, death module HL, etc.
Two or more combinations using differences in cure reactivity
You can use it. In the magnetic layer of the magnetic recording medium of the present invention, the
Usually, lubricant, abrasive, dispersant, antistatic agent, dispersant, acceptable
Elements with various functions including plasticizers, antifungal agents, etc.
A material can be contained depending on the purpose. As a lubricant used in the magnetic layer of the present invention
Is a dialkylpolysiloxane (wherein alkyl has 1 to
5), dialkoxypolysiloxane (alkoxy is charcoal)
1 to 4 prime numbers), monoalkyl monoalkoxy polysilos
Xane (alkyl is 1 to 5 carbon atoms, alkoxy is carbon
1 to 4), phenylpolysiloxane, fluoroalkyl
Rupolysiloxane (alkyl has 1 to 5 carbon atoms)
Silicon oil; Conductive fine powder such as graphite; Disulfur
Inorganic powders such as molybdenum fluoride and tungsten disulfide;
Reethylene, polypropylene, polyethylene vinyl chloride
Plastics such as copolymers and polytetrafluoroethylene
Fine powder; α-olefin polymer; saturated fat solid at room temperature
Fatty acid (10 to 22 carbon atoms); unsaturated fat that is liquid at room temperature
Group hydrocarbon (the n-olefin double bond is bonded to the terminal carbon)
Combined compounds, about 20 carbon atoms); 12-20 carbon atoms
Monobasic fatty acids and monohydric alcohols with 3 to 12 carbon atoms
Fatty acid esters and fluorocarbons
Can be used. Among the above, saturated fatty acids and fatty acid esters
It is preferable to use both in combination. fat
Ethanol is the alcohol used as the raw material for acid esters
Ru, butanol, phenol, benzyl alcohol, 2
-Methylbutyl alcohol, 2-hexyldecylalco
, Propylene glycol monobutyl ether, ethyl
Lenglycol monobutyl ether, dipropylene glycol
Cole monobutyl ether, diethylene glycol mono
Monoal such as butyl ether and s-butyl alcohol
Coles, ethylene glycol, diethylene glycol
, Neopentyl glycol, glycerin, sorbitan
And polyhydric alcohols such as derivatives. Also fatty acids
As acetic acid, propionic acid, octanoic acid, 2-ethyl
Hexanoic acid, lauric acid, myristic acid, stearin
Acid, palmitic acid, behenic acid, arachidic acid, olein
Acid, linoleic acid, linolenic acid, elaidic acid, palmito
Aliphatic carboxylic acids such as oleic acid or mixtures thereof
Can be mentioned. Specific examples of fatty acid esters include butyl
Stearate, s-butyl stearate, isopropyl
Stearate, butyl oleate, amyl stearate
, 3-methylbutyl stearate, 2-ethylhexyl
Rustearate, 2-hexyldecyl stearate,
Til palmitate, 2-ethylhexyl myristate,
A mixture of butyl stearate and butyl palmitate,
Toxiethyl stearate, 2-butoxy-1-propi
Rustearate, dipropylene glycol monobutyl ether
Di-ethylene with ether acylated with stearic acid
Glycol dipalmitate, hexamethylene diol
Glycerol acylated with myristic acid
List various ester compounds such as oleate of serine
You can. Furthermore, the magnetic recording medium is used under high humidity.
Reduces the hydrolysis of fatty acid esters that often occur
Branching / straightening of raw fatty acids and alcohols
Select chain, cis / trans isomeric structure, branching position
Things are done. These lubricants are 100 parts by weight of binder.
Usually, it is added in the range of 0.2 to 20 parts by mass.
The The following compounds are further used as lubricants:
You can also That is, silicon oil, graphi
Molybdenum disulfide, boron nitride, graphite fluoride, fluorine
Alcohol, polyolefin, polyglycol, alkyl
Such as ruphosphoric acid ester and tungsten disulfide. As an abrasive used in the magnetic layer of the present invention
Is a commonly used material of α, γ alumina, molten aluminum
Mina, corundum, artificial corundum, silicon carbide, oxide
Rom (Cr₂O_Three), Diamonds, artificial diamonds,
Garnet, emery (main components: corundum and magnetite),
αFe₂O_ThreeEtc. are used. These abrasives are Mohs hard
The degree is 6 or more. Specific examples include Sumitomo Chemical Co., Ltd.
AKP-10, AKP-15, AKP-20, AKP-
30, AKP-50, AKP-1520, AKP-15
00, HIT-50, HIT60A, HIT60G, H
IT70, HIT80, HIT82, HIT-100,
Nippon Chemical Industry Co., Ltd., G5, G7, S-1, chromium oxide
K, Uemura Kogyo UB40B, Fujimi Abrasive WA8
000, WA10000, LANDS LS600F
  0 / -1 / 4, MD-200 manufactured by Tomei Dia, MD-
150, MD-100, MD-70, IRM 0-1 /
4F, IRM 0-1 / 4FF, manufactured by GE 0-1 / 1
0, 0-1 / 4, MyPolex made by DoPunt 1
/ 10QG, 1 / 8QG, TF10 manufactured by Toda Kogyo Co., Ltd.
0, TF140, TF180 and the like. Average grain
Those with a diameter of 0.05-1 μm have an effect.
It is preferably 0.05 to 0.5 μm. Abrasive
As well as two or more types of abrasives.
It is also suitable for use in the case of fine diamond.
When used in combination with an abrasive, the amount added to the magnetic material is reduced to 0.
It can be reduced to about 1%. Total of these abrasives
The amount is 1 to 20 parts by mass, preferably 100 parts by mass of the magnetic material.
Or it adds in 1-15 mass parts. 1 part by weight
If the amount is too small, sufficient durability cannot be obtained, and more than 20 parts by mass.
If it is too much, the surface property and filling degree deteriorate. These abrasives are
Addition to magnetic paint after dispersion treatment with binder
It doesn't matter. In the magnetic layer of the magnetic recording medium of the present invention,
Contains conductive particles as an antistatic agent in addition to non-magnetic powders
You can also Especially as an antistatic agent, carbon
Adding black reduces the surface electrical resistance of the entire medium.
It is preferable in terms of lowering. Carbon bomb bra which can be used in the present invention
Rubber hooks, rubber thermals, color boots
Rack, conductive carbon black, acetylene black
Etc. can be used. Specific surface area is 5-500m²/
g, DBP oil absorption is 10 to 1500 ml / 100 g, granule
The child diameter is 5 to 300 nm, the pH is 2 to 10, and the water content is 0.
1 to 10%, tap density is 0.1 to 1 g / cm^ThreePrefer
Good. Specific examples of carbon black used in the present invention
As an example, manufactured by Cabot, BLACKPEARLS
  2000, 1300, 1000, 900, 800, 7
00, VULCAN XC-72, manufactured by Asahi Carbon Corporation, #
80, # 60, # 55, # 50, # 35, Mitsubishi Chemical Corporation
# 3030B, # 3040B, # 3050B, # 3
230B, # 3350B, # 9180B, # 2700,
# 2650, # 2600, # 2400B, # 2300,
# 950B, # 900, # 1000, # 95, # 30,
# 40, # 10B, MA230, MA220, MA7
7. Columbian Carbon, CONDUCTEX
SC, RAVEN 150, 50, 40, 15, Rio
Negzo Ketjen Black EC, Ketjenbra
ECDJ-500, Ketjen Black ECDJ-
600 or the like. Carbon black is a dispersant
Surface treatment or oxidation treatment of carbon black
Even if it is grafted with resin,
You may use a rafite. Also,
Before adding carbon black to magnetic paint,
It may be dispersed with a binder. Carbon Bomber on the magnetic layer
When using a hook, the amount relative to the magnetic material is 0.1-30.
It is preferable to use even mass%. Further non-magnetic
3 to 20% by mass based on the total nonmagnetic powder
It is preferable. In general, carbon black is an antistatic agent.
As well as reducing the friction coefficient, providing light-shielding properties, suitable for film strength
There are functions such as above, these are carbon black used
Varies by Therefore, these cars used in the present invention
Bon Black changes its type, amount, and combination,
The characteristics shown above, such as noise, oil absorption, conductivity, pH, etc.
Of course, it is possible to use properly according to the purpose.
The Carbon black that can be used is, for example, “Carbon
Refer to the Rack Handbook "Carbon Black Association"
Can do. Contains the hexagonal ferrite magnetic powder of the present invention
A magnetic recording medium including a magnetic layer is formed between a support and a magnetic layer.
As long as the structure is provided with a nonmagnetic layer, there is no particular limitation, and public
An intelligent layer configuration is possible. Nonmagnetic layer (also called the lower layer)
A layer in which nonmagnetic powder is dispersed in a binder resin is preferred.
Yes. The nonmagnetic powder used for the nonmagnetic layer includes various types.
Things can be used. For example, α-a with an α conversion rate of 90% or more
Lumina, β-alumina, γ-alumina, silicon carbide, acid
Chromium oxide, cerium oxide, α-iron oxide, getite, co
Random, silicon nitride, titanium carbide, titanium oxide,
Silicon dioxide, boron nitride, zinc oxide, calcium carbonate,
Calcium sulfate, barium sulfate, etc. alone or in combination
Used in. As fine and grain-sized,
α-Iron oxide, Getite, Titanium oxide, Zinc oxide are suitable
It is. The particle size of these nonmagnetic powders is 0.01-1
μm is preferable, but if necessary, the particle size is different.
By combining magnetic powder, single non-magnetic powder
However, it is possible to have the same effect by widening the particle size distribution.
Yes. Dispersion with increased interaction with the binder resin used
In order to improve the properties, the non-magnetic powder used is surface-treated.
It may be. Present on the particle surface by surface treatment
Examples of materials include silica, alumina, silica-alumina, etc.
Inorganic materials are also formed by coupling agents.
Also good. Tap density is 0.3-2g / cm^ThreeThe water content is
0.1 to 5% by mass, pH is 2 to 11, specific surface area is 5 to 1
00m²/ G is preferred. The shape of the non-magnetic powder is a needle
, Spherical, dice or plate. Specific examples of non-magnetic powders include
Industrial nano-tight, Sumitomo Chemical HIT-100, HIT-
80, Toda Kogyo α-iron oxide DPN-250BX, DP
N-245, DPN-270BX, DPN-550R
X, DBN-450BX, DBN-650RX, DAN
-850RX, Titanium oxide TTO-51B manufactured by Ishihara Sangyo,
TTO-55A, TTO-55B, TTO-55C, T
TO-55S, TTO-55D, SN-100, titanium
Industrial titanium oxide STT-4D, STT-30D, ST
T-30, STT-65C, Teica titanium oxide MT-
100S, MT-100T, MT-150W, MT-5
00B, MT-600B, MT-100F, MT-50
0HD, Sakai Chemical's FINEX-25, BF-1, BF-
10, BF-20, ST-M, Dowa Mining Iron Oxide DEF
IC-Y, DEFIC-R, AS2B manufactured by Nippon Aerosil
M, TiO2 P25, Ube Industries 100A, 500
A and the thing which baked it are mentioned. As described above, a plurality of coating layers are formed on the support.
Can produce a high recording density magnetic recording medium.
The simultaneous coating method creates an ultra-thin magnetic layer.
Since it can be put out, it is particularly excellent. Simultaneous application method
Formula, that is, the specific method of wet-on-wet method
As a law, Gravure coating commonly used in magnetic paints
Cloth, roll coating, blade coating, extrusion coating
First apply the lower layer with a cloth device and the layer is still wet.
For example, Japanese Patent Publication No. 1-446186,
JP-A-60-238179 and JP-A-2-265
SUPPLATOR PRESSURE TYPE EXTROL disclosed in Japanese Patent No. 672
A method of applying an upper layer with a version application device; Japanese Patent Laid-Open Nos. 63-88080 and 2
No. 17971 and JP-A-2-265672
Built-in two slits for passing coating liquid as disclosed in
Lower coating liquid and upper coating liquid by the applied coating head
A method of applying almost simultaneously, It is disclosed in Japanese Patent Laid-Open No. 2-174965.
Extrusion application with backup roll
A method of applying the upper layer and the lower layer almost simultaneously by means of an apparatus;
Etc. Apply by wet-on-wet method
The flow characteristics of the magnetic layer coating solution and the non-magnetic layer coating solution are
The closest possible field is the boundary between the coated magnetic and nonmagnetic layers.
A magnetic layer with uniform surface thickness and little thickness fluctuation.
Can be obtained. The fluidity of the coating solution is determined by the powder in the coating solution.
Because it strongly depends on the combination of powder and binder resin,
Pay particular attention to the selection of non-magnetic powders for use in non-magnetic layers
There is a need. The support of this magnetic recording medium is usually 3 to 1.
00μm, preferably 3-20 when used in tape form
μm, 25 when used as a flexible disk
˜80 μm is preferable, and the nonmagnetic layer provided on the support is
Usually 0.5 to 5.0 μm, preferably 0.5 to 3 μm
It is. The thickness of the magnetic layer is preferably 0.01 to 0.5 μm
m, more preferably 0.05 to 0.3 μm. Ma
For purposes other than the magnetic layer and the nonmagnetic layer
It can also be formed accordingly. For example, support and lower layer
An undercoat layer may be provided between them to improve adhesion.
Yes. This thickness is usually 0.01-1 μm, preferably
0.05 to 0.3 μm. Also carries a magnetic layer
A back layer may be provided on the side of the support opposite to the surface.
Absent. This thickness is usually 0.1 to 1.0 μm, preferably
Is 0.3 to 1.0 μm. These subbing layers,
A known layer can be used. Disc-shaped magnetic recording media
In some cases, a structure including the magnetic layer on both sides or one side is provided.
Can be. There are no particular restrictions on the support used in the present invention.
However, a commonly used one can be used.
Examples of materials that form the support include polyethylene
Phthalate, polyethylene, polypropylene, polycar
Bonate, polyethylene naphthalate, polyamide, polyester
Riamideimide, polyimide, polysulfone, polyether
Films of various synthetic resins such as telsulfone and Al
Name metal foils such as minium foil and stainless steel foil
it can. In order to effectively achieve the object of the present invention, support is provided.
The surface roughness of the body is the centerline average surface roughness Ra (cut-off
Value of 0.25 mm) is 0.03 μm or less, preferably 0.0
It is 2 μm or less, more desirably 0.01 μm or less.
Also, these supports simply have the centerline average surface roughness.
In addition to being small, there should be no coarse protrusions of 1 μm or more
Is preferred. The roughness of the surface can be
Depending on the size and amount of filler added to the
It is to be rolled. As an example of these fillers
Of oxides and carbonates such as Ca, Al, Si, Ti
Other examples include fine organic resin powders such as acrylic. Book
The F-5 value in the web running direction of the support used in the invention is
Preferably 49 to 490 MPa, F-5 in the web width direction
The value is preferably 29.4 to 294 MPa, and the web
Long hand direction F-5 value is higher than web width F-5 value
Generally, it is necessary to increase the strength in the width direction.
This is not the case when there is a need. Also, the web running direction and width direction of the support
The heat shrinkage at 100 ° C for 30 minutes is preferably 3% or less
And more desirably 1.5% or less at 80 ° C. for 30 minutes.
Preferably has a heat shrinkage of 1% or less, more desirably
0.5% or less. Breaking strength is 49-98 in both directions
0MPa, elastic modulus is desired to be 980-19600MPa
Yes. The organic solvent used in the present invention can have any ratio.
With acetone, methyl ethyl ketone, methyl isobutyl ketone
, Diisobutyl ketone, cyclohexanone, isophor
Ketones such as Ron and tetrahydrofuran, methanol,
Ethanol, propanol, butanol, isobutyl alcohol
Alcohol, isopropyl alcohol, methylcyclohex
Alcohols such as sanol, methyl acetate, butyrate
, Isobutyl acetate, isopropyl acetate, ethyl lactate,
Esters such as glycol acetate, glycol dimethyl ester
Ether, glycol monoethyl ether, dioxane,
Glycol ethers such as benzene, toluene,
Aromatic charcoal such as silene, cresol, chlorobenzene
Hydrides, methylene chloride, ethylene chloride,
Carbon tetrachloride, chloroform, ethylene chlorohydrin,
Chlorinated hydrocarbons such as dichlorobenzene, N, N-di
Methylformamide, hexane, etc. can be used.
These organic solvents are not necessarily 100% pure,
In addition to min, isomers, unreacted materials, side reactions, decomposition products, oxidation
It does not matter if impurities such as things and moisture are included. these
The impurity content is preferably 30% or less, more preferably 1
0% or less. If necessary, the organic solvent used in the present invention
The type and amount of each layer may be changed. Volatile in the lower layer
The surface of the lower layer is improved by using a highly soluble solvent.
High tension solvents (cyclohexanone, dioxane, etc.)
To improve the stability of the coating, the solubility parameter in the magnetic layer
An example of this is to increase the filling degree using a high solvent.
Is not limited to these examples.
Of course. The magnetic recording medium of the present invention comprises the ferromagnetic powder.
Organic binder together with binder resin and other additives if necessary
Kneading and dispersing using a medium, applying a magnetic paint on the support,
Obtained by orientation and drying as required. Magnetic coating material for magnetic recording medium of the present invention, non-magnetic
The process of manufacturing paint is at least a kneading process, a dispersion process
And mix as needed before and after these steps.
It consists of a joint process. Each process has two or more stages.
It does not matter if it is left. Magnetic material used in the present invention, non-
Magnetic powder, binder, carbon black, abrasive, antistatic
All raw materials such as stoppers, lubricants and solvents
Alternatively, it may be added in the middle. In addition, individual raw materials
May be added in two or more steps. Example
For example, polyurethane kneading process, dispersion process, viscosity after dispersion
It may be divided and added in the mixing step for adjusting the degree. When mixing and dispersing magnetic paints, various types of
A kneader is used. For example, a two-roll mill, a three-roll
Lumill, Ball mill, Pebble mill, Tron mill, Sand
Grinder, Segvari, Atla
High speed impeller disperser, high speed stone mill, high
Fast impact mill, disper, kneader, high speed mixer, ho
You can use a generator, ultrasonic disperser, etc.
The In the kneading process, continuous kneader, pressure kneader, etc.
It is possible to use a magnetic recording medium that has a strong kneading force.
Is preferable for obtaining a high Br. Continuous kneading or pressurization
When using a kneader, all or all of the magnetic material and binder
Part (but 30% or more of the total binder is preferred) and
Range of 15 to 500 parts by mass per 100 parts by mass of magnetic material
And kneaded. For details of these kneading processes
JP-A-1-106338, JP-A-64-7927
No. 4 publication. In the present invention, JP-A-62-2
Using the simultaneous multi-layer coating method as shown in 221933
Can be produced more efficiently. Included in the magnetic layer of the magnetic recording medium of the present invention.
The residual solvent is preferably 100 mg / m²Below, further
Preferably 10 mg / m²Is included in the magnetic layer
Less residual solvent than the residual solvent contained in the nonmagnetic layer.
It is preferable. The porosity of the magnetic layer is favorable for both the lower layer and the upper layer.
Preferably it is 30% by volume or less, more preferably 10% by volume.
It is as follows. The porosity of the nonmagnetic layer is larger than the porosity of the magnetic layer
The threshold is preferable, but the nonmagnetic layer has a porosity of 5% by volume or more.
If it is small, it does not matter. The present invention uses a lower layer and a magnetic layer depending on the purpose.
It is easily estimated that these physical properties can be changed.
Is Rukoto. For example, by increasing the elastic modulus of the magnetic layer,
Lowers the elastic modulus of the lower layer than the magnetic layer.
To improve the contact of the magnetic recording medium with the head.
is there. By such a method, it is coated on the support.
If necessary, the magnetic layer or the like is oriented with the ferromagnetic powder in the layer
After the treatment, the formed magnetic layer is dried. Must
Surface smoothing is performed if necessary, or cut into a desired shape
Thus, the magnetic recording medium of the present invention is manufactured. The elastic modulus at 0.5% elongation of the magnetic layer is the web.
Desirably 980-19600M in both coating direction and width direction
Pa, breaking strength is desirably 9.8 to 294 MPa, magnetic
The elastic modulus of the air recording medium is desired in both the web application direction and width direction
Preferably 980-14700 MPa, residual spread is desirable
Is the heat yield at any temperature below 0.5% and below 100 ° C.
The reduction ratio is desirably 1% or less, and more desirably 0.5%.
Hereinafter, it is most desirably 0.1% or less. The magnetic recording medium of the present invention is used for video applications,
Tape for computer backup applications, etc.
Floppy disk for data recording
Or a magnetic disk,
For digital recording applications where live signal loss is fatal
This is particularly effective for media. In addition, nonmagnetic layers and magnetic properties
The thickness of the magnetic layer is 0.5 μm or less due to the multilayer structure of the layers.
Overwriting characteristics with high electromagnetic conversion characteristics
To obtain a high-density, large-capacity magnetic recording medium
it can. The novel features of the present invention are specifically illustrated in the following examples.
explain. [0059] EXAMPLES Specific examples of the present invention will be described below.
The present invention is not limited to this. Production Examples 1-9 <Formation of hexagonal ferrite magnetic powder 1> Hexagonal blowjob
As a raw material for the production of oxides, various compounds in terms of oxides
Weighed as follows. [0060] B₂O_Three               4.7 moles SiO_Three           0.47 mole BaCO_Three         10.0 mole Fe₂O_Three           11.3 mol CoCO_Three         0.56 mol ZnO 0.50 mol Nb₂O_Five          0.12 mol Mix the above composition with a powder mixer.
And then put it into a Pt-Rh crucible with a stirrer.
Melting at 1300-1350 ° C for 2 hours in a frequency induction furnace
And a certain amount between rotating stainless steel cooling twin rolls
Pour and quench to create amorphous flakes.
The crushed powder was crushed. The amorphous body is then placed in a ceramic container.
2cm thick and transported in an electric furnace maintained at 500 ° C
Immediately after being held for 6 hours in an electric furnace maintained at 750 ° C.
And kept for 5 hours. Then, room temperature metal hopper
The treated product was put into a container and cooled to obtain crystal powder. The crystal powder
The powder was pulverized with a planetary mill. <Formation of hexagonal ferrite magnetic powders 2 and 3>
As a raw material for producing cerite, various compounds are converted into oxides.
Weighed as follows. [0062] B₂O_Three               4.7 moles BaCO_Three         10.0 mole Fe₂O_Three(Si / Fe (atomic ratio) = 0.005) 10.8 mol CoCO_Three         0.54 mol ZnO 0.50 mol Nb₂O_Five          0.12 mol Amorphous under the same conditions as the formation of hexagonal ferrite magnetic powder 1
Flakes were formed and crushed. The amorphous material is then
Electric container 2cm thick and kept at 500 ° C
Electric furnace transported into the furnace and held at 750 ° C after holding for 6 hours
Immediately transported inside and held for 5 hours (crystallization of magnetic powder 2
conditions). Next, the amorphous body is made 2 cm thick in a ceramic container.
Hiroge is transported in an electric furnace maintained at 550 ° C and kept for 5 hours
Immediately after holding, transfer it to an electric furnace maintained at 750 ° C.
The time was maintained (crystallization conditions of the magnetic powder 3). Then magnetic
Magnetic powders 2 and 3 were produced in the same manner as powder 1. <Formation of hexagonal ferrite magnetic powder 4> BaCl₂・ 2H₂1.4 mol of O FeCl₂・ 6H₂O 13 mol CoCl₂・ 6H₂O 0.1 mol TiCl_Four                  0.1 mole Is dissolved in 20 L of pure water.
It added so that it might become 0.1 atomic%. NaOH 500
0g, Na₂CO_Three  1250 g was dissolved in 40 L of pure water.
The aqueous solution was mixed and stirred to obtain a coprecipitate. Dry, grind,
Add NaCl as flux and heat at 800 ° C for 5 hours
Heat, react and cool. <Recovery of magnetic substance Condition 1> Vitrification crystal method
35% by volume acetic acid aqueous solution of magnetic powders 1, 2, and 3 prepared in
Etching process (80 ° C, hold for 5 hours) using
The lath component was removed. Settling and removing the supernatant
It was collected. Disperse the recovered microcrystals in a large amount of ion-exchanged water.
Scattered, settled and washed with water repeatedly. Judgment by electrical conductivity
After that, put the barium ferrite suspension into the water tank device.
It was. A certain amount of ion exchange in a continuous water tank device with different cross-sectional areas
The magnetism in ion-exchanged water that has overflowed and overflowed ion-exchanged water
The body was placed in a tank and concentrated. 100 ° C after dehydration
Example of production
1 to 3 ferromagnetic powders were obtained. <Recovery condition of magnetic substance 2> Vitrification crystal method
Using the magnetic powder 1 prepared in step 35 with 35% by volume acetic acid aqueous solution
Etching (80 ℃, hold for 5 hours) and glass components
Was removed. Settling, removing the supernatant and collecting the microcrystals
It was. Disperse the recovered microcrystals in a large amount of ion-exchanged water,
It was allowed to settle and washed with water repeatedly. To ion exchange water
Liquid containing 1% by weight of phosphonic acid (magnetic powder and aqueous solution
The ratio is 1:20) by weight, and the recovered microcrystals are added and stirred.
The mixed suspension was put into a water tank device. Different cross-sectional areas
Pour a certain amount of ion-exchanged water into the continuous water tank,
-The magnetic substance in the ion-exchanged water that has flowed is submerged in the tank.
Concentrated by precipitation. After dehydration, dry at 100 ° C
The ferromagnetic powder of Production Example 4 was obtained
It was. <Recovery condition of magnetic substance 3> Coprecipitation flux
Add magnetic powder 4 prepared by the method to ion-exchanged water, stir and settle
After falling, it was filtered. Collect recovered microcrystals with a large amount of ion-exchanged water.
Washed with water, allowed to settle and repeated washing with water. Judgment by electrical conductivity
After that, put the barium ferrite suspension into the water tank device
did. A certain amount of ions in a continuous water tank device with different cross-sectional areas
The magnetism in the ion-exchanged water that has overflowed and overflowed the ion-exchanged water
The sex body was placed in a tank and concentrated. 100 ° C after dehydration
Example of production
5 ferromagnetic powder was obtained. <Recovery of magnetic substance 4> Recovery of magnetic substance 1, 2,
3 to collect the magnetic powder recovered without using a continuous water tank treatment device.
After dehydration, it is dried at 100 ° C and further consolidated with a Mahler
The ferromagnetic powder of the manufacture examples 6-9 was obtained by processing. The ferromagnetic powders of Production Examples 1 to 9 were obtained by the X-ray diffraction method.
Analysis showed a magnetoplumbite structure. Ferromagnetic
Observation of powder by transmission electron microscope and measurement of average powder size
did. In the field of view of a TEM photo printed 30000 times
The number of aggregates of 0.5 to 10 μm was measured (in Table 1).
(Described in “TEM observation piece / field of view”). At 250 ° C in nitrogen
Degassed for 30 minutes, and the specific surface area was measured by the BET method. Magnetism
The gas characteristics are measured with an applied magnetic field of 800 kA / m using VSM.
Set. The results are shown in Table 1. [0069] [Table 1]<Preparation of paint> Display of “part” in the examples
Indicates “parts by weight”.   Magnetic liquid formula 1 100 parts of barium ferrite (shown in magnetic powder table 2) Binder resin         14 parts of vinyl chloride copolymer           (-SO_Three1 × 10 K group^-Foureq / g, polymerization degree 300)         Polyester polyurethane resin 5 parts           (Neopentyl glycol / Caprolactone polyol / MDI             = 0.9 / 2.6 / 1, -SO_ThreeNa group: 1 × 10^-FourContains eq / g ) α-alumina (average particle size: 0.15 μm) 2 parts Carbon black (average particle size: 30 nm) 5 parts Butyl stearate 2 parts Stearic acid 3 parts 125 parts of methyl ethyl ketone 125 parts of cyclohexanone [0071]   Magnetic liquid formula 2 100 parts of barium ferrite (shown in magnetic powder table 3) Binder resin         15 parts of vinyl chloride copolymer           (-SO_Three1 × 10 K group^-Foureq / g, polymerization degree 300)         Polyester polyurethane resin 6 parts           (Neopentyl glycol / Caprolactone polyol / MDI             = 0.9 / 2.6 / 1, -SO_ThreeNa group: 1 × 10^-FourContains eq / g ) α-alumina (average particle size: 0.15 μm) 3 parts Carbon black (average particle size: 30 nm) 5 parts Butyl stearate 10 parts 5 parts butoxyethyl stearate Isohexadecyl stearate 2 parts Stearic acid 3 parts 125 parts of methyl ethyl ketone 125 parts of cyclohexanone [0072] Non-magnetic liquid formula 1 80 parts of acicular hematite                 (S_BET: 55m²/ G,                   Average long axis length: 0.10 μm, average needle ratio: 7,                   pH: 8.8, aluminum treatment: Al₂O_ThreeAs 1% by mass) 20 parts of carbon black                 (Average particle size: 17 nm,                   DBP oil absorption: 80 ml / 100 g,                   S_BET: 240m²/ G, pH: 7.5) Binder resin         14 parts of vinyl chloride copolymer           (-SO_Three1 × 10 K group^-Foureq / g, polymerization degree 300)         Polyester polyurethane resin 5 parts           (Neopentyl glycol / Caprolactone polyol / MDI             = 0.9 / 2.6 / 1, -SO_ThreeNa group: 1 × 10^-FourContains eq / g ) Phenylphosphonic acid 3 parts Butyl stearate 3 parts Stearic acid 3 parts 280 parts of 1: 1 mixed solvent of methyl ethyl ketone and cyclohexanone [0073] Non-magnetic liquid formulation 2 80 parts of acicular hematite                 (S_BET: 55m²/ G,                   Average long axis length: 0.10 μm, average needle ratio: 7,                   pH: 8.8, aluminum treatment: Al₂O_ThreeAs 1% by mass) 20 parts of carbon black                 (Average particle size: 17 nm,                   DBP oil absorption: 80 ml / 100 g,                   S_BET: 240m²/ G, pH: 7.5) Binder resin         15 parts of vinyl chloride copolymer           (-SO_Three1 × 10 K group^-Foureq / g, polymerization degree 300)         Polyester polyurethane resin 5 parts           (Neopentyl glycol / Caprolactone polyol / MDI             = 0.9 / 2.6 / 1, -SO_ThreeNa group: 1 × 10^-FourContains eq / g ) Phenylphosphonic acid 3 parts Butyl stearate 10 parts 5 parts butoxyethyl stearate Isohexadecyl stearate 2 parts Stearic acid 3 parts 280 parts of 1: 1 mixed solvent of methyl ethyl ketone and cyclohexanone The above magnetic liquid formulations 1 and 2 and non-magnetic liquid formulations
For each of 1 and 2, pigment, polyvinyl chloride and treatment
After kneading 50% by mass of each solvent with a kneader,
Add a polyurethane resin and the remaining ingredients to create a sand grin
Dispersed with Non-isocyanate was added to the resulting dispersion.
Add 15 parts to the magnetic liquid and 14 parts to the magnetic liquid.
Add 30 parts of cyclohexanone to each and average 1 μm
Filter using a filter with a pore size to form a non-magnetic layer
And a coating solution for forming a magnetic layer were prepared. <Production of tape; Examples 11 to 15, comparison
Examples 11 to 14> Thickness of coating liquid 1 for lower nonmagnetic layer obtained
Dry on a 7 μm polyethylene terephthalate support
Apply to a thickness of 1.5 μm later, and
Immediately after the coating layer for the lower non-magnetic layer is still wet
In addition, by controlling the amount of magnetic liquid formulation 1 applied,
Wet simultaneous multilayer coating is applied so that the layer thickness is the same.
While in a wet state, it passes through the aligning device and is longitudinally aligned.
It was. At this time, the oriented magnet was a rare earth magnet (surface magnetic flux 500 m
T) after passing through solenoid magnet (magnetic flux density 500m
T) To the extent that the orientation does not return in the solenoid
The magnetic layer was further dried and wound up. Then gold
Roll temperature is controlled by a seven-stage calendar composed of genus rolls
Apply a calender treatment at 90 ° C to create a web-like magnet
Air recording medium is obtained, and it is slit to 8 mm width to 8 mm
A videotape sample was created. Magnetic characteristics of sample
Properties, surface roughness, and electromagnetic conversion characteristics were measured. <Preparation of flexible disk; Example 2
1, 22 and Comparative Example 21> Prescription 2 for lower nonmagnetic layer obtained
68 μm thick polyethylene terephthalate
Coating on the support so that the thickness after drying is 1.5 μm
Immediately thereafter, the coating layer for the lower nonmagnetic layer is still wet.
In the state, the magnetic layer coating liquid according to magnetic liquid formulation 2
Use magnetic layer simultaneous wet coating, both layers still wet
The same polarity with a central magnetic field strength of 398 kA / m while in the wet state
After passing through the counter rare earth magnet and orienting in the longitudinal direction,
Magnetic field strength 24kA / m at frequency 50Hz, then frequency
Two magnetic field strength AC magnetic fields of 12 kA / m at 50 Hz
Random alignment treatment was performed by passing through the generator. This
As a result, an orientation degree ratio of 98% or more could be obtained. Already
Similarly, apply, orient, and dry on one support surface after 7 steps.
Processed with a calendar at a temperature of 90 ° C and a linear pressure of 300 kg / cm
Went. Punched to 3.7 mm, thermo-treated (70 ° C
24 hours) to accelerate the curing process of the coating layer,
Varnished with a tape to remove surface protrusions
Post-processing was performed. 3.7 mm of liner already installed inside
Cartridge (ZIP-dis manufactured by IOMEGA, USA)
And add the required mechanical parts,
A 3.7 mm floppy disk was obtained. Magnetic characteristics of sample
Properties, surface roughness, and electromagnetic conversion characteristics were measured. Electromagnetic conversion characteristics: <Evaluation of tape> MIG on 8 mm deck for data recording
Head (head gap 0.2μm, track width 17μ
m, saturation magnetic flux density 1.5T, azimuth angle 20 °)
MR head (SAL bias, MR element is Fe-N
i, track width 6μm, gap length 0.2μm, ajma
Equipped with an angle of 20 °). Using the MIG head,
The relative speed of the head and head is 10.2 m / sec, 1 / 2T
b (λ = 0.5μm) The optimum recording current from the input / output characteristics
The signal was recorded with this current and reproduced by the MR head.
C / N is from the peak of the regenerative carrier to the demagnetization noise.
The resolution bandwidth of the spectrum analyzer is 100
It was set to kHz. Ratio of each magnetic powder after normal washing
The result is shown assuming that Comparative Example 11 is 0 dB. <Evaluation of flexible disk> Output, S
/ N measurement is RAW100 manufactured by GUZIK (US).
Type 1 disc evaluation device and joint electronic system Co., Ltd.
With pin stand LS-90, 1Gbit / in²Kula
Equipped with a hard disk head with a radius of 24.6m
Reproduction at linear recording density 90KFCI at position m
Force and noise level after DC erase and measure S / N
Asked. The error rate of the disc is the above linear recording density.
Record (2, 7) RLL modulation method on the disk and measure the signal.
Set. The comparative example 21 which performed normal water washing was set to 0 dB.
Results are shown. Surface roughness: The surface roughness is measured by WYKO (US
Optical interference 3D roughness meter “TOPO-3” manufactured by Arizona)
D ”was used to measure a 250 μm square sample area. Measurement
In calculating the fixed value, tilt correction, spherical correction, cylindrical correction
Correcting for equality according to JIS-B601, center plane
The average roughness Ra was defined as the surface roughness value. Magnetic characteristics: Magnetic characteristics are vibration sample type magnetometer
(Made by Toei Industry Co., Ltd.) with an external magnetic field of 800 kA / m.
The measurement was performed parallel to the orientation direction. Magnetic layer thickness: The magnetic layer thickness is the same as the longitudinal direction of the magnetic recording medium.
Cross to a thickness of about 0.1μm with a diamond cutter
Extruded and observed at 50000 times using a transmission electron microscope
I took a picture of it. Photo print size is A
The total magnification printed with 4-A5 is 200000 times
It was. After that, ferromagnetic powder and non-magnetic layer of magnetic layer, lower non-magnetic layer
Focusing on the shape difference of the functional powder, the interface is visually judged and blackened
The surface of the magnetic layer was black as well. That
Later, at the image processing apparatus IBAS2 manufactured by Zeiss
The length of the line was measured. The length of the sample photo is 21cm
In this case, the measurement was performed 85 to 300 times. Measured value at that time
Was the magnetic layer thickness. [0081] [Table 2] [0082] [Table 3]In the table, “actual-” indicates an example, and “ratio-” indicates a ratio.
A comparative example is shown. Magnetic powder produced by the production method of the present invention is TEM.
The number of agglomerated particles during observation is reduced to 1/10 or less.
The magnetic recording medium using a magnetic body is a magnetic powder that has been washed with water.
Compared with magnetic recording media using
It was. Focusing on noise, the magnetic recording medium of the present invention is compared with each other.
Significantly lower than the example, resulting in high C / N
Realized. In addition, the error rate was significantly reduced. The hexagonal ferrite powder used in the present invention
Has a narrow size distribution due to the wet classification process.
The average plate diameter is 10 to 40 nm and the presence of aggregates
Since the amount can be reduced, it is suitable for MR heads.
A magnetic recording medium having excellent conversion characteristics can be provided.

Claims (1)

What is claimed is: 1. A nonmagnetic layer in which nonmagnetic powder is dispersed in a binder is provided on a support, and a magnetic layer in which ferromagnetic powder is dispersed in the binder is provided thereon. In the magnetic recording medium provided,
The magnetic layer has an average plate diameter of 10 to 40 nm, a coercive force Hc of 135 to 400 kA / m, and contains a hexagonal ferrite magnetic powder that has undergone a wet classification process.