JP2003123226A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium suitable for high density digital recording, and in more detail, a coat type magnetic recording medium suitable for reproduction, using an MR (magnetoresistive) head. SOLUTION: In this magnetic recording medium, a lower layer non-magnetic layer including non-magnetic powder and a binding agent is provided on a non-magnetic flexible base material, and a magnetic layer including ferromagnetic powder and a binding agent is provided on the lower layer non-magnetic layer. The rate of content by volume of the ferromagnetic powder contained in the magnetic layer is >=40%, the ferromagnetic powder is ferromagnetic alloy powder, wherein grain volume is 3,000 to 25,000 nm<3> , and in the ferromagnetic alloy powder, the volume ratio of a metallic part to grain volume is 25 to 60%.

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention relates to a magnetic recording medium, in particular,
High-density magnetic recording suitable for reproduction using an MR head
It relates to the medium. [0002] Conventionally, video tapes and audio tapes have been used.
Magnetic recording media such as magnetic disks and magnetic disks
Iron, Co-modified ferromagnetic iron oxide, CrO₂, Ferromagnetic alloy powder
A magnetic layer in which a binder is dispersed in a binder is coated on a nonmagnetic support.
Are widely used. Recording wavelength with high density in recent years
The output tends to be low when the magnetic layer is thick.
Problems of self-demagnetization loss during recording and thickness loss during playback
Is getting bigger. Therefore, make the magnetic layer thin.
However, if the magnetic layer is thinned to about 2 μm or less,
The effect of non-magnetic support tends to appear on the surface of the magnetic layer,
There is a tendency to deteriorate electromagnetic characteristics and dropout. One means for solving this problem is disclosed in
No. 63-191315, JP-A 63-187418
As shown in the figure, a non-magnetic layer is applied to the lower layer using the simultaneous multilayer coating method.
A method to apply a thin magnetic coating solution with a high concentration
is there. These inventions have dramatically improved yield.
Good electromagnetic characteristics can be obtained.
However, a higher density magnetic recording medium is desired. On the other hand, magnetic heads have conventionally applied magnetic induction.
However, in recent years,
Then, MR using the change of magnetoresistance according to the amount of magnetization of the medium
High-density digital notation whose head is mainly a hard disk
Widely used in the recording field, high-density recording tapes and
It is spreading to the field of kibble discs. MR Head
A lot of research has been done on the problems of magnetic recording using
Many papers have been published. However,
Most of these studies are for metal thin film media.
However, there are examples of research on coated media with a thin magnetic layer.
Few. The inventors used a coating-type recording medium with excellent productivity.
In order to improve the suitability for MR heads
I came across a new medium. [0005] The object of the present invention is to reproduce
MR head, especially anisotropy (Anisotropy)
Electromagnetic conversion during recording and playback using a (tropic) MR head
By providing a coating type magnetic recording medium having good characteristics
In addition, more specifically, it has a short recording wavelength of λ = 0.5 μm or less.
To provide a magnetic recording medium with excellent recording / reproduction performance.
The [0006] Means for Solving the Problems The present inventors have described the above-mentioned problems.
To achieve the structure and magnetic properties of magnetic and non-magnetic layers
As a result of diligent investigation, the particle volume and particle volume
Ferromagnetic alloy powder in which the volume ratio of the metal part is within a predetermined range
A magnetic recording medium containing a certain amount of powder in the magnetic layer is an MR head.
Good electromagnetic conversion characteristics during recording and playback using
As a result, the present invention has been completed. The magnetic recording medium of the present invention has a nonmagnetic flexible support.
A lower nonmagnetic layer containing nonmagnetic powder and a binder is provided on the holder.
A magnetic layer containing ferromagnetic powder and a binder
A magnetic recording medium comprising the ferromagnetic layer
The volume content of the powder is 40% or more, and the ferromagnetic powder is
Particle volume is 3000-25000nm^ThreeA ferromagnetic alloy powder
The ferromagnetic alloy powder has a volume of the metal part relative to the particle volume.
The ratio is 25 to 60%. The present invention
In the magnetic recording medium, the magnetic layer has a Bm of 0.2T (2000G)
And φr of the magnetic layer is 2.51 × 10^-2T ・ μm （251
G · μm) or less. Magnet of the present invention
The recording medium uses at least the MR head for playback.
It is preferably used for a recording / playback system. [0008] BEST MODE FOR CARRYING OUT THE INVENTION A reproduction MR head currently in practical use.
Anisotropic Magnetroresistive
The mainstream uses the effect. This head (MR element)
The resistance changes due to the magnetic field from the medium, and the MR element senses
Regenerative voltage between electrodes sandwiching MR element by passing current
I'm taking it out. MR elements have a certain amount of magnetic flux from the medium.
The MR element is saturated at the top, and the operating range of the element is linear
Waveform distortion and pulse asymmetry occur. SAL Bai
AS method (bias method to form a soft magnetic film adjacent to the MR element)
In the case of the MR head used, the saturation magnetic flux density of the MR film and SAL film
The film thickness should be Bm, Bs, Tm, Ts, and the track width should be W.
For example, the maximum magnetic flux allowed at the tip of the MR element is BmTmW + BsTs
W. On the other hand, the residual magnetic flux density of the medium is Br, the magnetic layer thickness
If δ is δ and there is a magnetization reversal on the MR head gap
In addition, the amount of magnetic flux absorbed by the MR element is 2BrδW. this
The amount of magnetic flux absorbed by the MR element exceeds the allowable magnetic flux of the MR element.
The MR element is saturated. Therefore, MR head does not saturate
As the medium conditional expression, the following expression is derived. 2Brδ ≦ BmTm + BsTs (1) In the present invention, reproduction is performed with a rotary drum mounted MR head.
It was investigated. The specifications of the head are as follows. Shield type
SAL bias system with structure, track width is 6μm, gap length between shields
Is 0.2μm, the azimuth angle is ± 20 degrees, and the MR film is made of Fe-Ni.
Maloy, height 4μm, film thickness 0.025μm, saturation flux density 1.0
T (10000 G), SAL film is Co-Zr-Mo soft magnetic material, film thickness is 0.
03μm, saturation magnetic flux density is 0.84T (8400G). By
Thus, the condition of the magnetic recording medium for preventing the head from being saturated is Brδ
≦ 2.51 × 10^-2T ・ μm (251G ・ μm). like this
In addition, the upper limit of the residual magnetization amount φr (= Brδ) of the magnetic recording medium is
It is determined from the saturation limit according to the specifications of the MR head. Magnetic of the present invention
The recording medium is provided on the assumption that it will be used on the MR head.
The medium φr is 2.51 × 10^-2T ・ μm （251G ・
μm) or less. In the magnetic recording medium of the present invention, φr is
2.51 × 10^-2MR head even if T ・ μm (251G ・ μm) or less
High C / N while suppressing output drop during playback using
Is intended to be obtained. So, this departure
In a bright magnetic recording medium, the particle size of the ferromagnetic alloy powder
(Child volume) 3000-25000nm^ThreeAnd a ferromagnetic alloy
By defining the ratio of the metal part in the powder as 25-60%,
2.51 × 10^-2When T ・ μm (251 G ・ μm) or less
Also, a high C / N ratio can be obtained during reproduction on the MR head. Ma
In addition, lower φr (magnetic layer thinning, magnetic layer Bm low)
Lower) improves the recording density characteristics and reduces the half-value width (PW50)
Narrow. C / N improvement is smaller than conventional magnetic particles
Magnetic material particles having a product and the magnetic material in the magnetic layer
By increasing the volume ratio to 40% or more,
Increase the number of magnetic particles, that is, the density of magnetic particles to reduce noise
This can be achieved. In addition, the present invention
For magnetic recording media, the volume ratio of the metal part of the ferromagnetic alloy powder
Of 25-60%, and the ferromagnetic alloy powder in the magnetic layer
Set the volume ratio to 40% or more (as a result of binders etc.
By reducing the content of organic matter, the MR head
Playback output can be secured. Included in the magnetic layer of the magnetic recording medium of the present invention
The volume content of the ferromagnetic powder is 40% or more, and the ferromagnetic powder
If the volume content of the powder is less than 40%, anisotropic
(Anisotropic) Ensuring sufficient playback output in MR head
Can not. The upper limit of the volume content of the ferromagnetic powder is specified in particular.
Although there are additives such as binders and voids in the magnetic layer
In fact, it is about 60%. However, the strength of the magnetic layer is reduced
55% is a practical upper limit when ensuring durability such as
The Volume content of ferromagnetic powder contained in magnetic layer
Adsorbs on the surface of the binder and magnetic particles in the magnetic layer.
Compound that improves the dispersibility of magnetic particles in the binder
By reducing the amount of (dispersant) added, the above range can be obtained.
You can. Reducing the amount of binder and reducing the amount of ferromagnetic powder in the magnetic layer
As a specific method for increasing the volume ratio, for example, a magnetic layer
Polyurethane resin as a binder resin contained in
Preferably 50-100% by weight of mixture resin, more preferred
Or 70 to 100% by weight, and ferromagnetic powder of magnetic layer
Preferably 5-18% by weight of total binder resin relative to
More preferably, a method of 5 to 12% by weight is used.
Can do. Examples of the polyurethane resin include diols.
And reaction products made mainly from organic diisocyanate
Made of a certain polyurethane resin, as a diol component
Is a short-chain diol unit having a cyclic structure and an ether group.
It preferably contains a long-chain diol unit. And
This polyurethane resin is a short chain dihydrate having a cyclic structure.
Containing 17-40% by weight of all units in polyurethane resin
And ether groups on the entire polyurethane resin
Long chain diol units containing 1.0-5.0 mmol / g
It is a binder containing 10 to 50% by weight in the resin.
Is preferred. A short-chain diol having a cyclic structure is saturated
Or having an unsaturated cyclic structure and a molecular weight of less than 500
Means diol. For example, bisphenol A, below
Hydrogenated bisphenol A and bisphenol represented by the formula 1
Nord S, bisphenol P and their ethylene oxide
Xoxide, propylene oxide adduct, cyclohexanedi
Aromatic and alicyclic such as methanol and cyclohexanediol
Diols having a group are preferred. [0015] [Chemical 1] More preferably, the hydrogenated bishydride represented by the formula 1 is used.
Phenol A and its ethylene oxide, propylene
And oxide adducts. The short-chain diol having a cyclic structure is
Usually selected from those having a molecular weight of 50 or more and less than 500
The In addition, together with the short-chain diol having the cyclic structure,
Usually, other diols with molecular weight less than 500 are used in combination
Can do. Specifically, ethylene glycol, 1,3-
Propylene diol, 1,2-propylene glycol,
1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 2,2-dimethylpropane
Diol, 1,8-octanediol, 1,9-nonane
Diol, diethylene glycol, N-diethanol
Addition of ethylene to ethylene oxide or propylene oxide
And straight chain or branched diols such as products. By using these, a ring structure is formed.
A coating film with higher strength and higher Tg and higher durability was obtained.
It is. Further branch CH_ThreeTo improve solubility in solvents
Since it is excellent, high dispersibility can be obtained. In polyurethane resin
The content of short-chain diol units is preferably 17 to 40% by weight.
More preferably, it is 20 to 30% by weight. The long chain diol has a molecular weight of 500.
It means the above diol, specifically, bisphenol
A, hydrogenated bisphenol A, bisphenol S or bi
Sphenol P, ethylene oxide, propyleneoxy
Or a combination of both, polypropylene
Glycol, polyethylene glycol, polytetramethyl
Lenglycol is preferred, especially represented by Formula 2 below
Compounds are preferred. [0020] [Chemical 2] The values of n and m are preferably 3 to 24.
That's right. In the long-chain diol, R is the following:
 Is preferred, [0022] [Chemical 3] More preferred are those. Also, the length of Equation 2
In the chain diol, X is a hydrogen atom or a methyl group
And a methyl group is more preferable. N or m
All X's in parentheses need not be the same
In addition, a hydrogen atom and a methyl group may be mixed. The present invention
The polyurethane resin used in a particularly preferred embodiment of
As it has an annular structure, it has high coating strength and excellent durability.
Propylene branched CH_Three So that it can be dissolved in a solvent.
Excellent solution and excellent dispersibility. Weight average molecular weight of long chain diol (Mw)
Is usually 500 to 5000, preferably 700
It is suitable to be selected from the range of ~ 3000. A
The content of long-chain diol units containing a tellurium group is
It is preferably 10 to 50% by weight in the resin.
It is suitable that it is preferably 30 to 40% by weight.
The The ether group content of the long-chain diol unit is
It is preferable that it is 1.0-5.0 mmol / g in a urethane resin.
More preferably, it is 2.0 to 4.0 mmol / g.
Is appropriate. Number average molecular weight (Mn) of polyurethane resin
Is preferably 18000-56000, more preferably
Or 23,000 to 34000, weight average molecular weight
(Mw) is preferably 30,000 to 100,000,
More preferably, it is suitable from 40,000 to 60,000.
It is right. Glass transition temperature Tg of polyurethane resin
Is usually 0 to 200 ° C., preferably 30 to 1
50 ° C, more preferably in the range of 30-130 ° C
It is appropriate. The above polyurethane resin is vinyl chloride.
Synthetic resins such as resin may be used together, but urethane resin
The higher the ratio, the lower the surface tension of the magnetic liquid.
Therefore, the magnetic layer thickness unevenness and thickness fluctuations during coating and drying are suppressed.
You can control. The polyurethane resin is non-
It is also preferable to blend in the magnetic layer. Hands that further improve separation with a small amount of binder.
As a stage, aromatic to modify the surface of the ferromagnetic powder in the magnetic layer
Organic acid compound (dispersant) to 1 kg of ferromagnetic alloy powder
Preferably 0.1 to 0.8 mol, more preferably 0.2
It is mentioned to contain -0.5 mol. The aromatic organic acid compound is at least ferromagnetic.
It strongly adsorbs to various powders including alloy powder,
A thing with high affinity with a polyurethane resin is preferable. Obedience
As an aromatic organic acid compound, the dissociation constant is as much as possible.
Large (strong acid) is preferable, and organic having a pKa value of 3 or less
Acids or their salts are suitable. In addition to free acids, aromatic organic acid compounds include
Or salts thereof, such as esters, etc.
Just in case. In addition, adsorption to the powder described above is physical adsorption.
In addition, it is a concept including chemisorption including a covalent bond.
As an organic acid having a pKa value of 3 or less, α-naphthyllin
Acid, phenylphosphoric acid, diphenylphosphoric acid, p-ethylbenzene
Zenphosphonic acid, phenylphosphonic acid, phenylphosphine
Finic acid, methanesulfonic acid, benzenesulfonic acid, p
-Toluenesulfonic acid, naphthalene-α-sulfonic acid,
Naphthalene-β-sulfonic acid or a salt thereof
is there. As the usage of the aromatic organic acid compound,
There is no particular limitation as long as the above properties can be exhibited,
Preferably, ferromagnetic alloy powder and binder in paint preparation
Can be added simultaneously when kneading or ferromagnetic powder
Prior to kneading with the binder, the aromatic organic acid into the ferromagnetic powder
Surface treatment of the compound can be mentioned. Such a good
The aromatic organic compound is preferably contained also in the lower layer,
Usually 0.1 to 0.5 mol / kg of magnetic inorganic powder
Preferably in the range of 0.1 to 0.35 mol.
You can. Included in the magnetic layer of the magnetic recording medium of the present invention
Ferromagnetic powder has a particle volume of 3000-25000nm^ThreeThe ferromagnetic combination
Gold powder. The particle volume of ferromagnetic powder is 25000nm^ThreeBeyond
As a result, the number of magnetic particles per unit volume decreases and noise increases.
C / N decreases with increasing. The ferromagnetic powder of the present invention is
Ferromagnetic alloy powder, particle volume is 3000nm^ThreeLess than
There is a problem that magnetism cannot be maintained. Fine particles
For fetalization, it contains atoms such as Al and Y in addition to Fe-Co,
The atomic weight ratio of Y is increased to obtain fine particles at the goethite stage.
It is preferable to aim for. In the manufacturing process of ferromagnetic powder
Reduce the size of the reducing furnace used to reduce the temperature during reduction and firing.
Smaller variation in particle volume by reducing variation
Can be obtained. Also, set the reduction temperature low.
It can be reduced and fired slowly to achieve ferromagnetic powder.
The crystallite size (Dx) and SFD of the metal part of
Can be. On the other hand, if the reduction temperature is set high,
Σs of the conductive powder can be increased, but in this case
Particles are processed for a short time while suppressing temperature fluctuations.
It is important to suppress product variation. Included in the magnetic layer of the magnetic recording medium of the present invention
The ferromagnetic powder is a ferromagnetic alloy powder. With ferromagnetic alloy powder
As a result, the waveform distortion of the isolated regenerative wave is small and equalization is achieved.
There is an advantage that the waveform correction load is small. Ferromagnetic
As the alloy powder, an alloy mainly composed of Fe or Fe-Co is used.
preferable. As the shape, flat needle-like particles are preferable.
A manufacturing method is described in Japanese Utility Model Publication No. 10-340805. In addition, electric
Magnetic conversion characteristics include output, C / N ratio, and recording density characteristics.
Above all, the recording density characteristics are the symmetry of the isolated waveform and the half-value width.
(PW50) is narrow and has excellent high-density recording characteristics
It is determined whether or not. Therefore, in the present invention, the ferromagnetic alloy
By using powder, the symmetry of the isolated waveform is high and high.
Magnetic recording media with excellent density recording characteristics can be obtained.
The Included in the magnetic layer of the magnetic recording medium of the present invention
Ferromagnetic alloy powder is the ratio of the volume of the metal part to the particle volume.
The rate is 25-60%. Ferromagnetic alloy powder consists of metal parts and gold
It consists of a metal oxide and the volume of the metal part relative to the particle volume
When the ratio is less than 25%, the output is secured even if the MR head is used.
Can not do. Also, ferromagnetic alloy powder particles
When the volume ratio of the metal part to the volume exceeds 60%, storage
Deterioration of magnetic properties, especially when stored at high temperatures,
It is not preferable. The volume ratio of the metal part in the ferromagnetic alloy powder
Was calculated by the following formula. Long axis of ferromagnetic alloy powder
If the cross section perpendicular to the direction is a circle, a cylindrical model is assumed and magnetic
The volume of the body and the volume of the metal part are the minor axis length a, the major axis of the magnetic body
Length is L, crystallite size by X-ray diffraction is Dx (metal part), X
The oxide film thickness by line diffraction was calculated below as SL. Volume of magnetic material V = 4 / 3π (a / 2)^Three+ π (a / 2)²× L Volume of metal part Vm = 4 / 3π (D_X/ 2)^Three+ π (D_X/ 2)²× (L-2 × S
L) The field perpendicular to the long axis direction of the ferromagnetic alloy powder is an ellipsoidal field.
In the case of a cylindrical model, the volume of the magnetic material and the metal part
For the volume, the long width of the longer oval section is a and the short width is b
Calculated below. Volume of magnetic material V = 4 / 3π (a / 2) (b / 2)²+ π (a / 2) (b / 2) × L Volume of metal part Vm = 4 / 3π ((a-2 × SL) / 2) ((b-2 × SL) / 2)²
+ π × ((a-2 × SL) / 2) ((b-2 × SL) / 2) (L-2 × SL) Fine particle formation of ferromagnetic powder and volume ratio of metal part
The rate adjustment is, for example, a reaction that produces iron oxyhydroxide
Add water-soluble Al salt and rare earth metal salt such as Y to the system.
Co-containing iron oxyhydroxide with solid solution of Al and rare earth metal
Make, adjust the content ratio of Co / Al / rare earth metal at that time,
Then, reduction and firing are performed slowly at a low temperature, and then slow acid
O in the conversion process₂Adjust gas concentration and processing time
And can be done with. Co content of ferromagnetic powder is Fe
On the other hand, 10-30at%, preferably 15-25at%, Al content is 5
~ 15at%, preferably 8-15at%, rare earth metal content is 5
~ 15at%, preferably 8-15at%
The The long axis length L of the magnetic material is preferably 0.03 to 0.1 μm.
Or 0.03 to 0.08 μm, more preferably 0.03 to 0.06 μm.
Yes, crystallite size D by X-ray diffraction_X(Metal part size) is 0.008
~ 0015μm, preferably 0.008 ~ 0.0125μm
Is appropriate. Iron oxide film thickness SL by X-ray diffraction is 0.0005.
~ 0.003μm, preferably 0.001 ~ 0.0025μm
It is appropriate. The magnetic recording medium of the present invention obtains a high output.
From this point of view, Bm of the magnetic layer is 0.2T (2000G) or more
It is preferable. However, improve the recording density characteristics
From the point of view of narrowing PW50, Bm is 0.5T (5000
G) The following is preferable. Magnetic recording medium of the present invention
Specifically, the magnetic layer of 0.2-0.5T (2000-5000G), good
Preferably it has a Bm of 0.2-0.4T (2000-4000G).
Is appropriate. Also, as mentioned above, the magnetic layer thickness is saturated
Considering the limit, φr is 2.51 × 10^-2T ・ μm （251G ・
μm) or less, specifically 0.5 × 1
0^-2~ 2.51 × 10^-2T ・ μm (50 ～ 251G ・ μm)
It is preferable to make it thinner. By doing so,
The half width (PW50) can be narrowed without being summed. φr
Is appropriately selected from the viewpoint of securing output. Magnetism
SQ of the layer should be 0.7-0.95, preferably 0.8-0.95
Is appropriate. Is Hc of the magnetic layer a viewpoint of suppressing a demagnetizing field?
High Hc, for example, 143.3 to 238.8 kA / m
(1800-3000 Oe), preferably 159.2-222.9 kA / m (200
0-2800 Oe) is suitable. Next, the lower nonmagnetic layer of the present invention (hereinafter simply referred to as “non-magnetic layer”).
The detailed contents of “lower layer”) will be described. Book
Nonmagnetic inorganic powder used in the lower layer of the invention is, for example, gold
Metal oxide, metal carbonate, metal sulfate, metal nitride, metal
Select from inorganic compounds such as carbides, metal sulfides, etc.
You can. As an inorganic compound, for example, a gelatinization rate of 90%
Α-alumina, β-alumina, γ-alumina, θ
-Alumina, silicon carbide, chromium oxide, cerium oxide,
α-iron oxide, goethite, corundum, silicon nitride, tita
Carbide, titanium oxide, silicon dioxide, tin oxide, acid
Magnesium fluoride, tungsten oxide, zirconium oxide
, Boron nitride, zinc oxide, calcium carbonate, calcium sulfate
Cium, barium sulfate, molybdenum disulfide, etc.
Or used in combination. Particularly preferred is titanium dioxide.
Tan, zinc oxide, iron oxide, barium sulfate, more preferred
Preferred are titanium dioxide and alpha iron oxide. The particle size of these nonmagnetic inorganic powders is 3 μm.
m or less is preferred, but the particle size varies as required
Combine with non-magnetic inorganic powder or stand alone non-magnetic inorganic powder
Even at the end, the particle size distribution can be widened to have the same effect.
it can. Particularly preferred is a particle support of non-magnetic inorganic powder.
The size is 0.01 μm to 0.2 μm. Especially non-magnetic
When the machine powder is a granular metal oxide, the average particle size is
0.08 μm or less is preferred, and is a needle-shaped metal oxide
The major axis length is preferably 0.3 μm or less, and 0.2 μm
The following is more preferable. The particle size of nonmagnetic inorganic powder
The measurement of is the same as in the case of the ferromagnetic metal powder. T
Pop density is 0.05-2 g / ml, preferably 0.2-
1.5 g / ml. The water content of the nonmagnetic inorganic powder is 0.
1 to 5% by weight, preferably 0.2 to 3% by weight, more preferred
It is 0.3 to 1.5% by weight. Non-magnetic inorganic powder
The pH is 2 to 11, but the pH is particularly preferably between 7 and 10.
Good. Nonmagnetic inorganic powder has a specific surface area of 1-100m²/
g, preferably 5 to 70 m²/ G, more preferably 10
~ 65m²/ G. Crystallite size of nonmagnetic inorganic powder
Is preferably 0.004 μm to 1 μm, 0.04 μm to
0.1 μm is more preferable. Dibutyl phthalate (DB
Oil absorption using P) is 5 to 100 ml / 100 g, preferably 1
0-80ml / 100g, more preferably 20-60ml / 100g
is there. The specific gravity is 1 to 12, preferably 3 to 6. shape
May be needle-shaped, spherical, polyhedral, or plate-shaped. The ignition loss is preferably 20% by weight or less.
Preferably, it is considered most preferable that it does not exist. Book
The nonmagnetic inorganic powder used in the invention has a Mohs hardness of 4
Above, 10 or less is preferable. Of these powder surfaces
The roughness factor is preferably 0.8 to 1.5, and
A preferred roughness factor is 0.9 to 1.2.
SA (stearic acid) adsorption amount of non-magnetic inorganic powder is 1-2
0 μmol / m²More preferably, 2 to 15 μmol / m²In
The The heat of wetting of the nonmagnetic inorganic powder in water at 25 ° C. is 2.0.
× 10^-Five~ 6.0 × 10^-FiveJ / cm²(200erg / cm²~ 60
0erg / cm²) Is preferable. Also this
Solvents in the wet heat range can be used. 10
The amount of water molecules on the surface at 0-400 ° C is 1-10 / 100Å
Is appropriate. The pH of the isoelectric point in water is between 3 and 9.
It is preferable. The surface of these nonmagnetic inorganic powders is surface treated.
Al₂O_Three , SiO₂, TiO₂, ZrO₂, SnO₂, Sb₂O_Three , Zn
O 2 is preferably present. Especially preferred for dispersibility
Things are Al₂O_Three , SiO₂, TiO₂, ZrO₂But more preferred
Stuff is Al₂O_Three , SiO₂, ZrO₂It is. These are a combination
May be used alone or may be used alone. Ma
Alternatively, a co-precipitated surface treatment layer may be used depending on the purpose.
First, alumina is present in the surface layer and then silica is present.
It is also possible to adopt the method of making it reverse or vice versa.
The surface treatment layer may be a porous layer depending on the purpose.
Although not homogeneous, it is generally preferred to be homogeneous and dense. Nonmagnetic inorganic powder used in the lower layer of the present invention
As specific examples, NanoTite manufactured by Showa Denko, Sumitomo Chemical
GIT HIT-100, ZA-G1, Toda Kogyo DPN-250, DPN-250B
X, DPN-245, DPN-270BX, DPB-550BX, DPN-550RX Ishihara
Titanium oxide TTO-51B, TTO-55A, TTO-55B, TTO-55C,
TTO-55S, TTO-55D, SN-100, MJ-7 α-iron oxide E270, E27
1, E300, STT-4D, STT-30D, STT-30, STT-
65C, Teika MT-100S, MT-100T, MT-150W, MT-500B, M
T-600B, MT-100F, MT-500HD. Sakai Chemical FINEX-25, BF-
1, BF-10, BF-20, ST-M, Dowa Mining DEFIC-Y, DEFIC-
R, Nippon Aerosil AS2BM, TiO2P25, Ube Industries 100
A, 500A, Y-LOP made by Titanium Industry and its baked products
Can be mentioned. A particularly preferred nonmagnetic inorganic powder is titanium dioxide.
And α-iron oxide. α-Iron oxide (hematite) is
It is carried out under the following conditions. α-Fe₂O_ThreePowder
Is equivalent to the usual (1) ferrous iron
Contains ferrous hydroxide colloid obtained by adding aqueous potassium solution.
Oxygen at a temperature of pH 11 to 80 ° C.
A needle-like gater by venting the contained gas and performing an oxidation reaction
(2) ferrous salt aqueous solution and charcoal
FeCO obtained by reacting with acid-alkali aqueous solution_ThreeThe
Oxygen-containing gas is bubbled through the suspension
To generate goethite particles with spindle shape
(3) Alkali hydroxide aqueous solution with less than equivalent amount in ferrous aqueous solution
Hydroxic acid obtained by adding solution or alkaline carbonate solution
Oxygen-containing gas in ferrous salt aqueous solution containing ferrous iodide colloid
A needle-shaped goethite core particle by performing an oxidation reaction by aeration
And then the acicular catite containing the particles
In the ferrous salt aqueous solution, Fe in the ferrous salt aqueous solution²⁺Against
After adding an equal amount or more of an aqueous alkali hydroxide solution,
The needle-like goethite core particles are grown by aeration of gas.
And (4) less than an equivalent amount of hydroxide
Obtained by adding aqueous solution of alkali or alkali carbonate
Oxygen in ferrous salt aqueous solution containing ferrous hydroxide colloid
A needle-like gater by venting the contained gas and performing an oxidation reaction
In the acidic or neutral region
Obtained by a method of growing the acicular goethite core particles
The obtained acicular goethite particles are used as precursor particles. It should be noted that the particle powder during the goethite particle formation reaction
Ni, Z that are usually added to improve the properties of the powder
Even if different elements such as n, P, and Si are added, there is no problem.
Yes. 200 to 5 of acicular goethite particles, which are precursor particles
Dehydrate in the temperature range of 00 ° C or 3 if necessary
Annealing by heat treatment in the temperature range of 50-800 ° C
Needle-like α-Fe₂O_ThreeGet the particles. It should be noted that the needle gator to be dehydrated or annealed is used.
Iite particles contain P, Si, B, Zr, Sb, etc. on the surface
Even if the anti-sintering agent is attached,
Yes. Baked by heat treatment in the temperature range of 350-800 ° C
The dulling is acicular α-Fe obtained by dehydration.₂O_Threegrain
By annealing the pores generated on the surface of the child particles,
Smooth surface morphology by melting the extreme surface of the metal and blocking the pores
This is because it is preferable. Also obtained by dehydration or annealing.
Acicular α-Fe₂O_ThreeThe particles are dispersed in an aqueous solution to form a suspension.
For example, by adding an Al compound and adjusting the pH, the α
-Fe₂O_ThreeThe additive compound was coated on the particle surface of the particle
After filtration, washing with water, drying, grinding, if necessary further deaeration, pressure
A dense treatment or the like may be performed. Al compound used is vinegar
Aluminum acid, aluminum sulfate, aluminum chloride
Aluminum salts such as aluminum nitrate and aluminum acid
Alkaline aluminate such as soda can be used.
The In this case, the amount of Al compound added is α-Fe.₂O_ThreeParticle powder
Usually 0.01 to 50% by weight in terms of Al with respect to the powder
The In addition to the Al compound,
P, Ti, Mn, Ni, Zn, Zr, Sn, Sb
Coating with one or more compounds selected from
You can also. These chemicals used with Al compounds
The amount of compound added is α-Fe, respectively.₂O_ThreeAgainst particle powder
Usually, it is in the range of 0.01 to 50% by weight. Regarding the production method of titanium dioxide, it is as follows.
It is. The production methods of these titanium oxides are mainly sulfuric acid and chlorine.
There is a law. The sulfuric acid method digests the source ore of illuminite with sulfuric acid.
Ti, Fe, etc. are extracted as sulfates. Iron sulfate
Crystallize and remove, and filter the remaining titanyl sulfate solution
After that, thermal hydrolysis is performed to precipitate hydrous titanium oxide.
The This is filtered and washed, and then impurities are removed by washing.
After adding a regulator etc., burn at 80-1000 ° C
In this case, it becomes crude titanium oxide. Rutile and anatase types are hydrolyzed
It is divided according to the kind of nucleating agent added at the time of decomposition. This
Crushed, sized, surface-treated, etc.
To do. Chlorine method uses natural or synthetic rutile for raw ore
I can. Ore is chlorinated in high temperature reduced state, Ti is T
iCl_FourFe is FeCl₂And becomes solid by cooling
Iron oxide is liquid TiCl_FourSeparated. Obtained
Crude TiCl_FourIs purified by rectification followed by addition of nucleating agent
And react instantaneously with oxygen at a temperature of 1000 ° C. or higher,
Crude titanium oxide is obtained. Crude acid produced in this oxidative decomposition process
The finishing method for imparting pigmentary properties to titanium fluoride is sulfuric acid.
Same as the law. Surface treatment is dry grinding of the titanium oxide material.
After that, add water and dispersant, wet pulverization, and coarse particles by centrifugation
Classification is performed. Then, the fine slurry is a surface treatment tank
Here, the surface coating of the metal hydroxide is performed.
First, a predetermined amount of Al, Si, Ti, Zr, Sb, Sn,
Add an aqueous salt solution such as Zn to neutralize the acid, or
Is a hydrous oxide produced by adding alkali and titanium oxide
The particle surface is coated. By-product water-soluble salts are decanted
Removal by filtration, filtration and washing, and finally slurry p
Adjust H, filter and wash with pure water. Washed ke
Use a spray dryer or a band dryer to dry the cake.
It is dried. Finally, the dried product is crushed by a jet mill.
And become a product. In addition to aqueous systems, titanium oxide powder
AlCl on the body_Three, SiCl_FourThrough the steam of the steam
A surface treatment can also be applied. Other pigment manufacturing methods
About G.D.Parfitt and K.S.W.Sing "Characteriza
tion of Powder Surfaces "Academic Press, 1976
Can be. Known by mixing carbon black in the lower layer
Lowering Rs, which is the effect of, and reducing light transmittance
Can with desired micro Vickers hardness
Can be obtained. The micro Vickers hardness of the lower layer is usually
0.245 to 0.588 GPa (25 to 60 kg / mm²)
 , Preferably 0.294-0.49 GPa (30-50 k
g / mm²NEC thin film hardness tester HMA-40
0, diamond with a ridge angle of 80 degrees and a tip radius of 0.1 μm
Measure using a Mondo triangular pyramid needle at the tip of the indenter. Light transmission
The rate of absorption of infrared rays with a wavelength of about 900 nm is generally 3% or more.
Below, for example, VHS standardized to be 0.8% or less
Has been. For this purpose, rubber furnaces, rubber supports
-Use black, color black, acetylene black, etc.
Can be. Ratio table of carbon black used in the lower layer
The area is usually 100-500m²/ G, preferably 15
0-400m²/ G, DBP oil absorption is usually 20-40
0ml / 100g, preferably 30-200ml / 100g
Is appropriate. The particle size of carbon black is usually 5 to
It is appropriate that the thickness is 80 nm, preferably 5 to 20 nm.
Usually, the pH of carbon black is 2-10, and the water content is
0.1 to 10%, tap density is preferably 0.1 to 1 g / ml.
Good. Specific of carbon black used in the present invention
An example is BLACKPEARLS manufactured by Cabot Corporation.
2000, 1300, 1000, 900, 800, 88
0, 700, VULCANXC-72, manufactured by Mitsubishi Chemical Corporation #
3050B, 3150B, 3250B, # 3750B,
# 3950B, # 950, # 650B, # 970B, #
850B, MA-600, Columbian Carbon C
ONDUCTEX SC, RAVEN8800, 8000, 700
0, 5750, 5250, 3500, 2100, 2000, 1800, 1500, 125
5, 1250, Akzo Ketchen Black EC, etc.
I can get lost. Surface treatment of carbon black with a dispersant
Or even if it is grafted with resin,
You may use what was graphitized. Ma
Before adding carbon black to the paint,
It may be dispersed with a binder. These carbon bras
Do not exceed 50% by weight of the nonmagnetic inorganic powder.
In a range not exceeding 40% of the total weight of the nonmagnetic layer
it can. These carbon blacks can be used alone or in combination
Can be used. Carbon black that can be used in the lower layer is an example
"Carbon Black Handbook" Carbon Black Association "
Can be helpful. Also, organic powder in the lower layer
It can also be added depending on the purpose. For example,
Polystyrene resin powder, benzoguanamine resin powder,
Lamin resin powder, phthalocyanine pigment
However, polyolefin resin powder, polyester resin powder
Powder, polyamide resin powder, polyimide resin powder,
A fluorinated ethylene resin can also be used. Made of
The method is disclosed in Japanese Patent Laid-Open Nos. Sho 62-18564 and 60-255827.
You can use what is written. The undercoat layer is provided on a general magnetic recording medium.
This is done with the support and the magnetic layer or below.
It is provided to improve the adhesion with the layer.
Solvent-soluble polyester is used. Thickness is
It is generally 0.5 μm or less. As the polyisocyanate used in the present invention,
Is tolylene diisocyanate, 4,4'-diphenyl
Methane diisocyanate, hexamethylene diisocyanate
, Xylylene diisocyanate, naphthylene-1,
5-diisocyanate, o-toluidine diisocyanate
, Isophorone diisocyanate, triphenylmethane
Isocyanates such as triisocyanate and the like
Products of these isocyanates and polyalcohols
Polyisocyanate formed by condensation of isocyanates
Cyanate is preferred. Of these isocyanates
Commercially available product names are made by Nippon Polyurethanes
Coronate L, Coronate HL, Coronate 2030,
Coronate 2031, Millionate MR, Millionate
MTL, Takenate D-102, Takeda
To D-110N, Takenate D-200, Takenate D
-202, Sumitomo Bayer's Death Module L, Desmo
Jules IL, Death Module N, Death Module HL
These can be used alone or by utilizing the difference in curing reactivity
Two or more combinations are used for the lower and upper layers
be able to. These polyisocyanates are
Usually 0-50% by weight, preferably with respect to the binder resin
0 to 30% by weight used for the entire lower binder resin
Usually, 0 to 40% by weight, preferably 0 to 25% by weight is used.
It is. The magnetic recording medium of the present invention comprises two or more magnetic layers.
When composed of, the amount of binder resin occupies in the binder
Vinyl chloride resin, polyurethane resin, polyisocyanate
Sheet or other resin amount, magnetic layer is formed
The molecular weight of each resin, the polar group weight, or the resin mentioned above
Changing the physical properties etc. between the lower layer and the upper layer as necessary
Of course, it is possible to apply known techniques for multilayer magnetic layers.
Can be used. Improved thixotropy of the lower non-magnetic liquid
The amount of binder resin in the lower layer to ensure dispersibility
(Including curing agent) to 100 parts by weight of nonmagnetic inorganic powder
Preferably 14 to 25 parts by weight, more preferably 1
4 to 20 parts by weight may be mentioned. Carbon bra
Improve the thixotropy of the liquid by increasing the ratio of
In order to ensure dispersibility,
From short-chain diols and long-chain diols containing ether groups
It is preferable to contain the urethane resin which becomes. However, below
Increase the surface tension of non-magnetic liquid layer, unevenness of upper / lower interface, thickness
The binder in the lower nonmagnetic layer is
It is preferable that the main component is a bi-resin. Carbon bra used for the magnetic layer of the present invention
As the rack, those exemplified for the nonmagnetic layer can be applied. carbon
Before adding black to magnetic paint,
It may be distributed. These carbon blacks are simple
Can be used alone or in combination. Carbon tube
When using a rack, the amount of the ferromagnetic alloy powder
0.1 to 10% by weight, preferably 0.1 to 3% by weight,
It is preferable to use at 0.5 to 1.5% by weight.
That's right. Carbon black is an antistatic and friction coefficient for the magnetic layer.
There are functions such as reduction, light shielding, and film strength improvement.
Vary depending on the carbon black used. Therefore, this departure
These carbon blacks used for light are upper and lower layers
Change the type, amount, combination, particle size, oil absorption,
Based on the above-mentioned characteristics such as conductivity, pH, etc.
Of course, it is possible to use them properly. Magnet of the present invention
Carbon black that can be used in
Refer to the “Black Handbook” edited by the Carbon Black Association.
You can. As the abrasive used in the present invention, the alpha conversion rate is used.
90% or more of α-alumina, β-alumina, silicon carbide
Element, chromium oxide, cerium oxide, α-iron oxide, colanda
, Artificial diamond, silicon nitride, silicon carbide, titanium
-Bite, titanium oxide, silicon dioxide, boron nitride, etc.
Mainly known materials of Morse 6 or higher alone or in combination
Used in. In addition, a composite of these abrasives (
You may use abrasives that have been surface-treated with other abrasives)
Yes. These abrasives contain compounds or elements other than the main component
May be included, but it is effective if the main component is 90% or more.
The result is unchanged. The particle size of these abrasives is 0.0
1 to 0.2 μm is preferable, but if necessary, particle size
A combination of different abrasives or even single abrasive
The diameter distribution can be widened to have the same effect.
Tap density is 0.3-2 g / cc, moisture content is 0.1-5
%, PH is 2 to 11, specific surface area is 1 to 30 m²/ G is preferred
Good. The abrasive used in the present invention has a needle shape,
Either spherical or dice may be used, but a part of the shape
It is preferable that it has high polishing properties. Used in the present invention
Specific examples of abrasives that can be used include HIT manufactured by Sumitomo Chemical Co., Ltd.
-60A, HIT-70, HIT-80, HIT-80
G, HIT-100, DuPont Mypolex 1/10
UG, Mypolex 1 / 8UG, etc. In the present invention
The abrasive used is the type, amount and combination of the lower and upper layers
Of course, it is possible to change it according to the purpose.
is there. These abrasives are pre-dispersed with a binder.
After that, it may be added to the magnetic paint. Magnet of the present invention
The surface existing on the magnetic layer surface and the magnetic layer end face of the air recording medium
5 abrasives / 100μm²The above is preferable. As an additive used in the present invention, lubrication
Effect, antistatic effect, dispersion effect, plasticity effect, etc.
Things are used. Molybdenum disulfide and tungsten disulfide
Ten graphite, boron nitride, graphite fluoride, silicon
Oil, polar silicone, fatty acid-modified silicone
Fluorine, silicone, fluorine-containing alcohol,
Fluorine-containing ester, polyolefin, polyglycol
, Alkyl phosphate esters and alkali metal salts thereof,
Alkyl sulfates and alkali metal salts thereof, poly
Phenyl ether, fluorine-containing alkyl sulfate ester
And its alkali metal salt, monobasic having 10 to 24 carbon atoms
Fatty acids (whether they contain unsaturated bonds or are branched)
And their metal salts (Li, Na, K,
Cu, etc.) or monovalent, divalent, and trivalent carbon atoms of 12 to 22 carbon atoms
, Tetravalent, pentavalent, hexavalent alcohols (including unsaturated bonds)
May also be branched), 12 to 2 carbon atoms
2 alkoxy alcohols (including unsaturated bonds,
May be branched), one having 10 to 24 carbon atoms
Basic fatty acids (including unsaturated bonds, but also branched)
And C1-C12 monovalent, bivalent, and trivalent
Any one of valence, tetravalent, pentavalent and hexavalent alcohol
It may contain a union or it may be branched)
Mono-fatty acid ester or di-fatty acid ester
Or tri-fatty acid ester, alkylene oxide polymer
Monoalkyl ether fatty acid ester, 8 to 2 carbon atoms
2 fatty acid amides, aliphatic amines having 8 to 22 carbon atoms, etc.
Can be used. Specific examples of these include lauric acid, my
Listic acid, palmitic acid, stearic acid, behenic acid,
Butyl stearate, oleic acid, linoleic acid, linole
Acid, elaidic acid, octyl stearate, steari
Amyl acid, Isooctyl stearate, Myristic acid
Octyl, butoxyethyl stearate, anhydroso
Rubitan monostearate, anhydrosorbitans
Tearate, anhydrosorbitan tristearate,
Oleyl alcohol, lauryl alcohol
The In addition, alkylene oxide, glycerin,
Ricidol-based, alkylphenol ethylene oxide
Nonionic surfactants such as adducts, cyclic amines, esters
Amides, quaternary ammonium salts, hydantoin derivatives
Body, heterocycles, phosphonium or sulfonium, etc.
Cationic surfactant, carboxylic acid, sulfonic acid, phosphorus
Contains acidic groups such as acids, sulfate groups, and phosphate groups
Anionic surfactant, amino acids, aminosulfonic acid
Amino acid sulfuric acid or phosphate esters,
An amphoteric surfactant such as a ruquilvedine type can also be used.
For these surfactants, see “Surfactant Handbook”.
It is described in detail in (published by Sangyo Tosho Co., Ltd.). This
These lubricants, antistatic agents, etc. are not necessarily 100% pure.
In addition to the main components, isomers, unreacted substances, side reactions,
It does not matter if impurities such as demolition materials and oxides are included. This
These impurities are preferably 30% by weight or less, more preferably
Or it is 10 weight% or less. These lubricants and interfaces used in the present invention
Use the type and amount of activator in the lower layer and magnetic layer as needed.
Can be divided. For example, the melting point differs between the lower layer and the magnetic layer.
The boiling point to control the bleeding to the surface using the fatty acid
Ooze out to the surface using esters with different polarity
Control the stability of coating by adjusting the amount of surfactant
Increase the amount of lubricant added in the lower layer to improve the lubrication effect.
Of course, only the examples shown here
It is not limited to. Also, all of the additives used in the present invention.
Or part of it can be added at any stage of magnetic coating production.
For example, it can be mixed with ferromagnetic metal powder before the kneading process.
When mixing, kneading with ferromagnetic metal powder, binder and solvent
If added in the process, if added in the dispersion process, after dispersion
In some cases, it may be added immediately before coating.
In addition, after applying the magnetic coating layer according to the purpose,
Is a sequential application, applying some or all of the additive
The purpose may be achieved. Depending on the purpose
After calendering or after slitting, the magnetic layer
A lubricant can also be applied to the surface. Product examples of these lubricants used in the present invention
As NAF-102, NAA-41 manufactured by Nippon Oil & Fats Co., Ltd.
5, NAA-312, NAA-160, NAA-18
0, NAA-174, NAA-175, NAA-22
2, NAA-34, NAA-35, NAA-171, N
AA-122, NAA-142, NAA-160, NA
A-173K, castor hardened fatty acid, NAA-42, NA
A-44, Cation SA, Cation MA, Cation A
B, cation BB, Naimine L-201, Naimine
L-202, Naimine S-202, Nonion E-20
8, Nonion P-208, Nonion S-207, Nonio
K-204, Nonion NS-202, Nonion NS-
210, Nonion HS-206, Nonion L-2, Noni
ON S-2, Nonion S-4, Nonion O-2, Nonio
LP-20R, Nonion PP-40R, Nonion SP
-60R, Nonion OP-80R, Nonion OP-85
R, Nonion LT-221, Nonion ST-221,
Nonion OT-221, Monoguri MB, Nonion DS-6
0, Anon BF, Anone LG, Butyl stearate, B
Chill laurate, erucic acid, oleic acid manufactured by Kanto Chemical Co.,
Takemoto Yushi Co., Ltd. FAL-205, FAL-123, New Japan
Rigel's NJELB LO, NJELB IPM, Sun
Sizer E4030, TA-3 manufactured by Shin-Etsu Chemical Co., KF-
96, KF-96L, KF96H, KF410, KF4
20, KF965, KF54, KF50, KF56, K
F907, KF851, X-22-819, X-22-
822, KF905, KF700, KF393, KF-
857, KF-860, KF-865, X-22-98
0, KF-101, KF-102, KF-103, X-
22-3710, X-22-3715, KF-910,
KF-3935, Lion Armor's Armide P,
Armide C, Armoslip CP, manufactured by Lion Oil & Fats Co., Ltd.
Deyuomin TDO, Nisshin Oil Industries BA-41G, Sanyo
Seisha Profan 2012E, New Pole PE61,
IONET MS-400, IONET MO-200,
Onet DL-200, Ionet DS-300, Ion
Net DS-1000, Ionnet DO-200, etc.
Can be mentioned. 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, tetrahydrofuran, and methanol
Ethanol, propanol, butanol, isobuty
Alcohol, isopropyl alcohol, methylcyclo
Alcohols such as hexanol, methyl acetate, acetic acid
Butyl, isobutyl acetate, isopropyl acetate, ethyl lactate
, Esters such as glycol acetate, glycol dimethyl
Ether, glycol monoethyl ether, dioxa
Glycol ethers such as benzene, toluene
, Xylene, cresol, chlorobenzene, etc.
Aromatic hydrocarbons, methylene chloride, ethylene chlora
Id, carbon tetrachloride, chloroform, ethylene chlorohydride
Chlorinated hydrocarbons such as phosphorus and dichlorobenzene, N,
N-dimethylformamide, dimethylacetamide, f
Things such as xanthan can be used. These organic solvents must be
Is not 100% pure and is an isomer in addition to the main component, unreacted
Impurities such as products, by-products, decomposition products, oxides and moisture
It does not matter if you are rare. These impurities are less than 30% by weight
Is more preferable, and more preferably 10% by weight or less.
The organic solvent used in the present invention is the same for the magnetic layer and the lower layer.
The same is preferable. The amount added can be changed.
Absent. Solvent with high surface tension (cyclohexanone,
Uses dioxane, etc.) to improve coating stability, specifically
The arithmetic mean value of the upper solvent composition is the arithmetic average of the lower solvent composition.
It is important not to fall below the average. Improve dispersibility
In order to achieve this, it is preferable that the polarity is somewhat strong.
Among them, a solvent having a dielectric constant of 15 to 20 is 50% by weight or less.
Preferably included. The dissolution parameter is 8
It is preferably ~ 11. The thickness structure of the magnetic recording medium of the present invention is a support.
Is suitably 1 to 100 μm.
This is effective when a thin support of 8 μm is used. Magnetic layer
And the thickness of the lower layer is 1/100 to the thickness of the support.
It is suitable to use in the range of 2 times. Also with the support
It is preferable to provide an adhesive layer between the lower layers to improve adhesion.
Good. The thickness of the adhesive layer is preferably 0.01 to 2 μm.
Or 0.02 to 0.5 μm. Ma
In addition, a back coat layer is provided on the opposite side of the support from the magnetic layer side.
It doesn't matter. This thickness is 0.1 to 2 μm, preferably
Is suitably 0.3 to 1.0 μm. these
As the adhesive layer and back coat layer, known ones can be used.
The support used in the present invention has a micro Vickers hardness.
Is 75kg / mm²The above is a biaxially stretched polymer.
Liethylene naphthalate, polyamide, polyimide, poly
Riamideimide, aromatic polyamide, polybenzoxy
A known film such as dazole can be used. Especially the east
Entered as “Aramid” manufactured by Le or “Aramika” manufactured by Asahi Kasei
Aromatic polyamide or polyethylene naphtha
A support using a rate is preferred. The corona discharge is previously applied to these supports.
Treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, etc.
May be performed. In order to achieve the object of the present invention,
The center line average surface roughness of the surface on which the magnetic layer of the holder is applied is 10
nm or less 0.1 nm or more, preferably 6 nm or less 0.2
nm or more, more preferably 4 nm or less, 0.5 nm or more
Are preferably used. Also these support
The body not only has a low centerline average surface roughness,
It is preferable that there are no coarse protrusions of μm or more. Also surface
The roughness shape of the filler added to the support as needed
It can be freely controlled by size and quantity.
The Examples of these fillers include Al and C.
a, crystalline, amorphous with oxides or carbonates such as Si, Ti
Any organic fine powder such as acrylic or melamine
The end is mentioned. Also, to achieve compatibility with running durability
The roughness of the surface to which the back layer is applied is applied to the magnetic layer
It is preferable that the surface is rougher than the surface roughness. Center of back layer application surface
The line surface roughness is preferably 1 nm or more and 20 nm or less, and
Preferably it is 2 nm or more and 8 nm or less.
The When changing the roughness between the magnetic layer coating surface and the back layer coating surface
In this case, a dual structure support may be used.
It may be changed by providing a teeing layer. Method of running the tape of the support used in the present invention
The F-5 value for the direction is preferably 0.098 to 0.49 GPa
(10-50kg / mm²), F-5 value in the tape width direction
Is preferably 0.098 to 0.294 GPa (10 to 3
0 kg / mm²F-5 value in the longitudinal direction of the tape
Is generally higher than the F-5 value in the tape width direction.
However, when it is necessary to increase the strength in the width direction,
Not limited. Also, the tape running direction and width direction of the support
The thermal shrinkage at 100 ° C for 30 minutes is preferably 3% or less
Lower, more preferably 1.5% or less, at 80 ° C. for 30 minutes
The thermal shrinkage is preferably 1% or less, more preferably 0.
5% or less. Breaking strength is 0.049 ~ in both directions
0.98 GPa (5-100 kg / mm²), The elastic modulus is
0.98 to 19.6 GPa (100 to 2,000 kg /
mm²) Is preferred. Also, the light at 900 nm in the present invention
The transmittance is preferably 30% or less, more preferably 3% or less.
It is below. Producing the magnetic coating material of the magnetic recording medium of the present invention
At least a kneading step, a dispersing step, and this
From the mixing process provided as needed before and after these processes.
The Even if each process is divided into two or more stages
It doesn't matter. The binder, antistatic agent, and moisture used in the present invention
Ingredients such as lubricants and solvents are added at the beginning or middle of any process.
You can add it. In addition, two or more individual materials
It may be added in portions. For example, polyuree
Tan resin kneading step, dispersion step, viscosity adjustment after dispersion
It may be divided and added in the mixing step. Object of the present invention
To achieve the magnetic carbon black or abrasive
Disperse separately from metal powder and mix immediately before application
Prevents the magnetic material from agglomerating and
Can control the height of carbon and abrasive protrusions
The Magnetic layer liquid, non-magnetic layer liquid, or abrasive dispersion
When preparing, use a dispersion medium with high specific gravity.
Desirably, zirconia beads are preferred. In the present invention, a magnetic recording medium having a multilayer structure is provided.
An example of an apparatus and method for simultaneous multilayer coating is as follows.
Can propose. 1) Gravure coating generally used for magnetic coating
Cloth, roll coating, blade coating, extrusion coating
First, apply the lower coating layer using a cloth device, etc.
In the wet state, Japanese Patent Publication No. 1-446186 and JP
It is disclosed in Japanese Patent Laid-Open No. 60-238179 and Japanese Patent Laid-Open No. 2-265672.
With the support pressurization type extrusion coating device
An upper magnetic layer is applied. 2) JP-A 63-88080, JP-A 2-1797
As disclosed in Japanese Patent No. 1 and Japanese Patent Laid-Open No. 2-265672
One coating head with two built-in slits
The upper and lower layers are applied almost simultaneously. 3) The backup disclosed in Japanese Patent Laid-Open No. 2-174965
Upper and lower layers by extrusion coating equipment with prowl
Are applied almost simultaneously. Incidentally, a magnetic recording medium by agglomeration of magnetic particles.
In order to prevent the deterioration of electromagnetic conversion characteristics, etc.
As disclosed in JP-A-74 and JP-A-1-236968
Apply shear to the coating solution inside the coating head
It is desirable. Furthermore, regarding the viscosity of the coating solution,
Magnetic liquid viscosity at shear rate D500 [1 / S] is 300cps or less
Above, the viscosity of the magnetic liquid at 45000 [1 / S] is 7.5 to 12 cps
It is preferable. Non-magnetic liquid at shear rate 500 [1 / S]
Viscosity at 200 cps or higher, viscosity at 45000 [1 / S] is 14 cps
The following is preferable. In order to obtain the magnetic recording medium of the present invention, it is powerful.
It is preferable to perform proper orientation. Long length for magnetic tape
Oriented in the direction, but not less than 0.1T, preferably not less than 0.3T
Solenoid and cobalt magnets facing the same pole, 0.2T or more, preferred
It is preferable to use a magnetic field of 0.25 T or more in combination.
In order to prevent high orientation in the initial stage of drying, it is suitable in advance before orientation.
It is preferable to provide a drying step. Also floppy
-In the case of (registered trademark) discs, random orientation is applied.
It is. The orientation conditions are the same as for magnetic tape.
For example, frequency 50H
z magnetic field strength 0.025T (250 gauss) and frequency
Two with a magnetic field strength of 0.012T (120 Gauss) at 50Hz
Pass through the AC magnetic field generator with two magnetic field strengths,
Randomly oriented. In addition, a nonmagnetic layer and a magnetic layer are simultaneously applied.
Before applying a polymer-based adhesive layer
Corona discharge, ultraviolet (UV) irradiation, electron beam irradiation
Combining known methods to increase adhesion by
preferable. In addition, Epoxy as a calendar processing roll
Resistance of Si, polyimide, polyamide, polyimide amide, etc.
Use a heat-resistant plastic roll or metal roll.
Use. Also, metal rolls and plastic rolls
Zhi or metal roll and plastic roll vs. roll
Can be processed. The processing temperature is preferably 70 to
120 ° C, more preferably 80-100 ° C or higher
The The linear pressure is preferably 200 to 500 kg / cm.
More preferably, it is 300-400 kg / cm or more. The magnetic layer surface and the surface of the magnetic recording medium of the present invention.
The friction coefficient for SUS420J on the opposite side of
Is 0.1 to 0.5, more preferably 0.2 to 0.3
is there. The surface resistivity is preferably 10^Four-10¹²Ohm
/ Sq, the elastic modulus at 0.5% elongation of the magnetic layer is the running direction,
Preferably in the width direction, 0.98 to 19.6 GPa (10
0 to 2,000kg / mm²), Preferably the breaking strength
0.0098-0.294GPa (1-30kg / cm
²) The elastic modulus of the magnetic recording medium is favorable in both the running direction and the width direction.
Preferably, 0.98 to 14.7 GPa (100 to 1,50
0 kg / mm²), The residual elongation is preferably 0.5% or less
Below, heat shrinkage at any temperature below 100 ° C is preferred
1% or less, more preferably 0.5% or less, more
Is preferably 0.1% or less, and 0% is ideal. Magnetism
Glass transition temperature of the layer (of dynamic viscoelasticity measurements measured at 110 Hz)
The maximum point of loss modulus is preferably 30 ° C or higher and 150 ° C or lower.
The lower layer preferably has a temperature of 0 to 100 ° C. Loss bullet
Sexuality is 1 × 10⁷~ 8x10⁸Pa (1 × 10⁸~ 8x1
0⁹dyne / cm²) Is preferable, and loss tangent
Is preferably 0.2 or less. If the loss tangent is too large, adhesion failure is likely to occur.
Yes. The residual solvent contained in the magnetic layer is preferably 100 m
g / m²Or less, more preferably 10 mg / m²Is
The residual solvent contained in the upper layer is the residual solvent contained in the lower layer.
Less is preferred. The porosity of the magnetic layer is below
Preferably both the magnetic layer and the magnetic layer are 30% by volume or less.
Or 20% by volume or less. Porosity provides high output
For this purpose, a smaller value is preferable.
It may be better to secure. For example, repeated use
In magnetic recording media for data recording where emphasis is placed on high porosity
In most cases, running durability is preferable. Using an atomic force microscope (AFM) of the magnetic layer
Root mean square roughness R obtained by evaluation_RMSIs from 2 nm to 15 nm
It is preferable to be in the range. [0080] Next, the detailed contents of the present invention will be described by examples.
Explain physically. In the examples, “parts” is indicated as “parts by mass”.
Means. Nonmagnetic layer       Nonmagnetic powder α-Fe₂O_Three                                   85 parts           Average long axis length 0.1μm           Specific surface area by BET method 48m²/ G           pH 8, Fe₂O_Three90% or more content           DBP oil absorption 27-38ml / 100g           Surface coating agent Al₂O_Three       Carbon black 15 parts           Average primary particle size 16nm           DBP oil absorption 80ml / 100g           pH 8.0           Specific surface area by BET method 250m²/ g           Volatiles 1.5%       8 parts of vinyl chloride copolymer           MR-110 manufactured by Zeon Japan       The following polyurethane resin A 4 parts       Phenylphosphonic acid 3 parts       Butyl stearate 1 part       1 part of stearic acid       100 parts of methyl ethyl ketone       50 parts of cyclohexanone       50 parts of toluene Synthesis of polyurethane resin A A vessel equipped with a reflux condenser and a stirrer and previously purged with nitrogen
Hydrogenated bisphenol A and bisphenol A propylene
Oxide adduct (molecular weight 700), polypropylene
Recall (molecular weight 400) and bis (2-hydroxy ester)
Til) sulfoisophthalate sodium salt
24: 14: 10: 2 ratio of cyclohexanone and dimethyl
In a mixed solvent containing acetoamide in a weight ratio of 50:50
It melt | dissolved and melt | dissolved at 60 degreeC under nitrogen stream. As a catalyst,
Di-n-dibutyltin dilaurate
60 ppm was added to the total amount. Next, MDI (4, 4
-Diphenylmethane diisocyanate)
Equimolarly with the sum and react for 6 hours at 90 ° C.
Containing 4.0 nmol / g of a sulfur group and -SO_ThreeNa group
Is 8 × 10^-Five/ G Mw 45000 introduced Mn25
000 polyurethane resin A was obtained. Magnetic layer         100 parts of ferromagnetic alloy powder (see Table 1)         Phenylphosphonic acid 5 parts         Polyurethane resin A Table 2 reference part         α-alumina (particle size 0.18 μm) Refer to Table 2         Carbon black (particle size 0.08μm) 0.5 part         Butyl stearate 1 part         Stearic acid 3 parts         90 parts of methyl ethyl ketone         30 parts of cyclohexanone         60 parts of toluene In the above-mentioned non-magnetic layer coating, each component is continuously kneaded.
After kneading with a sand, use a sand mill to separate with glass beads.
Scattered. 1 part of polyisocyanate in the resulting dispersion
added. Magnetic top layer is alumina, carbon black and chloride
3 parts of vinyl, 5 parts of methyl ethyl ketone, cyclohexane
After kneading the ingredients except 5 parts of xanone with a continuous kneader
Disperse with glass beads using a sand mill. Before
The remaining ingredients for 6 hours with a steel ball in a ball mill
Sprinkle and filter, mix with dispersed magnetic paint,
1.5 parts of isocyanate was added. The nonmagnetic intermediate layer and magnetism
In addition, methyl ethyl ketone,
Add 40 parts of cyclohexanone mixed solvent and average 1 μm
Filter using a filter with a pore size, non-magnetic layer, magnetic
A coating solution for forming a conductive layer was prepared. Non-magnetic obtained
The coating solution for the adhesive layer is further removed so that the thickness after drying becomes 2 μm.
Immediately after that, the thickness of the magnetic layer becomes 0.05 μm on it.
Thus, the thickness of the center line is 7 μm and the surface roughness of the center line (cut-off value 0.
25mm) is 0.01μm polyethylene terephthalate
Apply simultaneous multi-layer coating on the support, both layers are still wet
Edge with a magnetic force of 0.3T (3000G) while in the state
Solenoi with a magnet and 0.15T (1500G) magnetic force
It is composed of metal rolls only after orientation and drying
Processing at a temperature of 90 ° C with a 7-stage calendar, 6.35 mm
The tape was manufactured by slitting to the width. Evaluation method (1) Hc, Br Using a vibration data type magnetometer (manufactured by Toei Kogyo), Hm796 kA
/ m (10 kOe). (2) Output, CNR The output and CNR were measured using a drum tester. relative
The speed was 10.5 m / sec. The used head has a recording head.
Recording wave with MIG head with Bs 1.2T and gap length 0.22μm
Optimal recording power for signals with a single frequency (21 MHz) of 0.5 μm long
Recorded in flow. The above-described MR head was used for reproduction. Shiboku
Using a noise spectrum measured by a spectrum analyzer manufactured by
Find the ratio of the playback output and the noise level after erasing the DC erase.
It was. Half value which is the pulse width at 50% of the peak of isolated regenerative wave
The width PW50 was obtained from an isolated reproduction wave having a recording frequency of 1.02 MHz. 【table 1】[0084] [Table 2]Explanation of Examples and Comparative Examples Comparative Example 1 (example not satisfying all claims of this case)
The standard of evaluation was used. Example 1 is a strong magnet contained in a magnetic layer.
The volume content of the conductive powder is 40% or more and is contained in the magnetic layer.
Ferromagnetic powder has a particle volume of 3000-25000nm^ThreeWithin
A ferromagnetic alloy powder, and grains of the ferromagnetic alloy powder.
When the volume ratio of the metal part to the child volume is in the range of 25-60%
An example. In Example 1, Bm of the magnetic layer is 0.2 T or more
Above, φr of magnetic layer is 2.51 × 10^-2T ・ μm or less
The In Example 2, the magnetic layer is made thinner than in Example 1, and φr
This is an example of lowering. Example 3 shows fine ferromagnetism with high σs
Using alloy powder B, φr is 0.011T ・ μm (110G ・ μ
m). Example 4 is a fine magnetic particle with a low σs.
Using synthetic metal powder C, φr is 0.02T ・ μm (200G ・
μm). In Example 5, the particle size is ferromagnetic.
Larger F than gold powder A to C, φr is 0.0125T ・
This is an example of μm (125 G · μm). Example 6 is an example
In contrast to 1, the amount of abrasive is reduced to reduce the magnetism in the magnetic layer.
This is an example of increasing the volume ratio of the body. No embodiment of the present invention
This is also a high output, MR head saturation phenomenon does not occur,
C / N was high. In addition, the full width at half maximum (PW50) is narrow and high density recording is possible.
Excellent recording characteristics. Comparative Example 2 is a fine magnetic particle with low σs
Alloy powder D, φr 0.0035T ・ μm (35G ・ μ
m). Comparative Example 3 is a fine magnetic particle with low σs
Ratio of magnetic material in magnetic layer
This is an example of lowering to 35.5%. However, φr is 0.011T ・ μm
This is an example of securing (110 G · μm). Comparative Example 1 has high output
However, a saturation phenomenon occurred on the MR head, resulting in a decrease in C / N. Ma
Compared to the examples, the full width at half maximum (PW50)
It was inferior. Comparative Example 2 has a large output drop and low C / N.
I gave it. Compared to the examples, the full width at half maximum (PW50) is wide and high.
The density recording characteristics were inferior. Comparative Example 3 is similar to Comparative Example 2.
The force drop was large and the C / N was reduced. Also, with examples
Compared to its wide half-value width (PW50), it has poor high-density recording characteristics.
It was.

Claims (1)

What is claimed is: 1. A magnetic layer comprising a nonmagnetic flexible support comprising a lower nonmagnetic layer containing nonmagnetic powder and a binder, and a ferromagnetic powder and binder thereon. A magnetic recording medium provided with
The volume content of the ferromagnetic powder contained in the magnetic layer is 40%.
The ferromagnetic powder has a particle volume of 3000-25000n.
m is ³ and which is ferromagnetic alloy powder, the magnetic recording medium the ferromagnetic alloy powder, wherein the ratio of the volume of the metal part to particle volume is 25 to 60%.