JP2003317232A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic recording medium which is formed by using a binder of a non-vinyl chloride system, is smooth, is low in an error rate and has excellent electromagnetic conversion characteristics and excellent preservable stability. <P>SOLUTION: The magnetic recording medium which has a nonmagnetic layer containing nonmagnetic powder and a binder and a magnetic layer containing ferromagnetic powder and a binder in this order on one surface of a nonmagnetic support, in which the binder contained in the nonmagnetic layer contains a (meth)acrylate copolymer and a polyurethane resin. The (meth) acrylate copolymer has a radical polymerizable monomer unit containing nitrogen and a hydrophilic polar group and the magnetic layer has microprojections of ≥15 nm in height on the surface thereof at ≥20 to <500 pieces per 900 μm<SP>2</SP>. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] The present invention is suitable for high density recording.
For more details on magnetic recording media,
There is no problem caused by discharge, and magnetic recording with excellent reliability
Related to recording media. [0002] [0002] Magnetic recording media record various information,
In addition, it is necessary to reproduce the recorded information.
It is required to have storage stability and durability. Magnetic
Recording media are usually magnetic powder, binder, organic solvent,
Magnetic layer paint containing other necessary ingredients
It is manufactured by applying it on a support such as
Built. At this time, the binder used is a magnetic material.
Excellent powder dispersibility and excellent electrical properties for magnetic recording media
It is desirable to have excellent durability at the same time
The In recent years, with the improvement in performance of magnetic recording media,
High density recording using a recording wavelength of 0.3 μm or less
Is required. Magnetic recording medium for such high density recording
Is a magnetic powder having a high coercive force Hc and a small particle size.
It is necessary to use it. However, such magnetic powder is
Since the particle size is small, it is very easy to aggregate. For this reason,
Vinyl chloride resin with excellent dispersibility and durability
Are widely used as binders for magnetic layers
Yes. [0004] However, the vinyl chloride is not suitable.
Nyl resin has poor thermal stability and energy such as light and heat.
-Decomposed by hydrogen chloride gas (HCl) in a small amount
Has the disadvantage of releasing. For this reason, the released salt
Durability of the magnetic layer due to alteration of the magnetic layer by hydrogen fluoride gas
There was a problem that the performance decreased. Hydrogen chloride gas
Oxidizes or modifies magnetic powder particles in the magnetic layer
Therefore, there is a problem of reducing the output of the magnetic recording medium.
It was. In addition, hydrogen chloride gas corrodes the recording / reproducing head.
There was also a problem of doing. Recently, in order to solve the above problems, vinyl chloride is used.
Research into binders that replace acrylic resins with nyl resins
(Japanese Patent Laid-Open No. 4-176016, Japanese Patent Laid-Open No.
(Hei 6-111279). But these are not
This solves the problem of vinyl chloride resin in the magnetic layer.
The binder used in the nonmagnetic layer
It was not related. For this reason, a nonmagnetic layer
As for the combination, the same binder as before is used.
The title vinyl chloride resin was also widely used. By the way, a nonmagnetic layer and a thin layer magnetic layer are formed on the support.
For magnetic recording media with layers stacked in this order, the thickness of the nonmagnetic layer
The thickness is several tens to several hundreds times the thickness of the magnetic layer. For this reason,
In general, the amount of binder contained in the nonmagnetic layer is
Much more than the amount of binder used. The inventors
From this fact, the bond containing vinyl chloride resin
To improve various disadvantages of magnetic recording media using a magnetic agent in the magnetic layer
To achieve this, the salt contained in the nonmagnetic layer rather than the magnetic layer
It is necessary to replace vinyl fluoride resin with acrylic resin
In consideration of the above, the binder contained in the nonmagnetic layer
investigated. [0007] The present inventors have made acrylic resin urethane.
For magnetic recording media containing a binder combined with resin in the nonmagnetic layer
Various investigations were made. As a result, conventional magnetic recording media
Acrylic tree that has been said to be used for the body
Just by using oil together with urethane resin,
Magnetic layer contact (per head) gets worse or repeats
The surface of the magnetic layer is shaved by sliding of the magnetic head
Problems such as pop-outs and head contamination.
I understood. Furthermore, in the nonmagnetic layer, the acrylic
When using urethane resin in combination with urethane resin, the surface of the magnetic layer is rough.
Spacing loss occurs, which adversely affects electromagnetic characteristics
I also found that it gives a sound. The present invention relates to a binder used in a nonmagnetic layer and
When using acrylic resin together with urethane resin
It was made to solve the problem. Snow
That is, the present invention uses acrylic resin in combination with urethane resin.
Even if the binder is used for the nonmagnetic layer,
Good hit, dropout by sliding magnetic head
And excellent running durability and storage stability without head dirt
Recording medium with low error rate
To provide a magnetic recording medium having excellent electromagnetic conversion characteristics
aimed to. In particular, the present invention is magnetically recorded on the magnetic layer.
That reproduces the recorded signal with a magnetoresistive head (MR head)
In a recording / playback system, with high output maintained
An object is to provide a reproducible magnetic recording medium. [0009] [Means for Solving the Problems] The present inventors have intensively studied.
As a result of overlapping, a polymerizable monomer unit containing nitrogen and a predetermined polarity
An acrylate copolymer having a group to a urethane resin
We found that the above problems could be solved by using together.
did. And the inventors further use this binder
With a predetermined number of microprotrusions on the nonmagnetic layer formed
Layered magnetic recording media have excellent electromagnetic characteristics
As a result, the present invention has been completed. That is, the magnetic recording medium of the present invention is non-magnetic.
Nonmagnetic layer containing nonmagnetic powder and binder on conductive support
And a magnetic layer containing ferromagnetic powder and a binder in this order.
A magnetic recording medium that is included in the nonmagnetic layer.
The mixture is (meth) acrylate copolymer and polyurethane
And a (meth) acrylate copolymer
Is a radically polymerizable monomer unit containing nitrogen (hereinafter,
"Nitrogen-containing radical polymerizable monomer") and hydrophilic electrode
And the magnetic layer has a height of 15 on the surface.
900 μm for fine protrusions of nm or more²More than 20 per 5
Has less than 00. The (meth) acrylate copolymer is
A predetermined hydrophilic polar group is added to the nitrogen-containing radical polymerizable monomer.
Have. Therefore, in the present invention, a fine nonmagnetic powder is used.
A magnetic recording medium having a well-dispersed nonmagnetic layer.
It is done. Furthermore, the binder contained in the nonmagnetic layer of the present invention
Uses (meth) acrylic copolymer in urethane resin
As a result, the (meth) acrylic copolymer
Excellent thermal stability and durability against incoming heat, light, chemicals, etc.
Excellent properties derived from polyurethane resin
It also has intramolecular cohesion. Therefore, the magnetism of the present invention
Recording media can be stored even if energy such as light or heat is applied.
Will not generate hydrogen chloride gas (corrosive gas).
Yes. Also, since no hydrogen chloride gas is generated, the magnetic recording medium
Is not modified to deteriorate the mechanical properties. That
As a result, magnetism is caused by hydrogen chloride gas released from the nonmagnetic layer.
The output is reduced due to the magnetic powder particles in the layer being affected.
Nor. In addition, it does not corrode the recording / reproducing head.
It has many advantages. In addition, the magnetic recording medium of the present invention has the above-mentioned access.
A binder that uses a related copolymer in urethane resin.
It has in a nonmagnetic layer. For this reason, it is laminated on the nonmagnetic layer
The surface smoothness of the magnetic layer uses conventional acrylic resin.
This can be improved compared to the case. The magnetic recording medium of the present invention also has a magnetic layer surface.
The number of protrusions with a height of 15 nm or more present on the surface is 900 μm
²Since the range is 20 or more and less than 500 per magnet,
Excellent surface smoothness is obtained on the surface of
It is a magnetic recording medium with low electromagnetic properties and low electromagnetic conversion characteristics.
You can. The magnetic recording medium of the present invention also has durability and
Considering the viscosity of the coating material, the acrylate copolymer
The number average molecular weight of the polymer is 10,000 to 200,000.
It is preferable that Also used in the magnetic recording medium of the present invention.
Hydrophilic polarity contained in (meth) acrylate copolymers
As a group, -SO_ThreeM, -OSO_ThreeM, -COOM,-
PO (OM)₂(However, M is hydrogen, alkali metal or hydrocarbon.
Selected from the group consisting of primary groups) and tertiary amino groups
At least one of them. Further, the non-magnetic recording medium of the present invention
The non-magnetic powder contained in the magnetic layer has a particle size of 0.5 μm
The following can be used. In addition, the magnetism of the present invention
As the ferromagnetic powder contained in the magnetic layer of the recording medium, the average length
Axis length of 0.01-0.10 μm and crystallite size of 8-18
nm (80 to 180 mm) ferromagnetic metal powder or average plate diameter
Use ferromagnetic hexagonal ferrite powder of 5 to 40 nm.
You can. Further, the thickness of the magnetic layer of the magnetic recording medium of the present invention
Is preferably in the range of 0.01 to 0.5 μm.
Yes. Also, the magnetic recording medium of the present invention has a magnetic layer.
The magnetically recorded signal is transferred to a magnetoresistive magnetic head (MR head).
For use in a magnetic recording / reproducing system
It can also be a magnetic disk or a magnetic tape. [0018] BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a magnetic recording medium of the present invention will be described.
Further details will be described. [(Meth) acrylate copolymer] Magnetic recording of the present invention
In the medium, the binder contained in the nonmagnetic layer is (meth) acrylate.
A salt copolymer. Used in the present invention
T) Acrylate copolymer is (meth) acrylate
-Based monomer units with nitrogen-containing radical polymerizability
A resin containing a monomer unit and a hydrophilic polar group. Normal,
(Meth) acrylate copolymer used in the present invention
Is at least a nitrogen-containing radical polymerizable monomer unit
And a hydrophilic polar group, and (meth) acrylic
Can contain rate-based monomer units.
It is not limited. In this specification,
“(Meth) acrylate” means acrylate and
A general term for crilate. <Nitrogen-containing radical polymerizable monomer unit>
Nitrogen-containing radical polymerizable monomer unit used in the invention
Examples of nitrogen-containing radical polymerizable monomers that can be formed include
(Meth) acrylamide, diacetone (meth) a
Kurylamide, N-methylol (meth) acrylami
N-methoxymethyl (meth) acrylamide, N-
Ethoxymethyl (meth) acrylamide, N-butoxy
Methyl (meth) acrylamide, dimethylaminopropy
(Meth) acrylamide, dimethylaminomethyl (me
Acrylate), dimethylaminoethyl (meth) acrylate
Relate, diethylaminomethyl (meth) acrelane
, Diethylaminoethyl (meth) acrylate, dimethyl
Tylaminopropyl (meth) acrylate, (meth) a
Chryroyl morpholine, morpholinoethyl (meth) ac
Relate, N-vinyloxazolidone, N-vinyl-2
-Pyrrolidone, N-vinylcarbazole, 2-vinyl-
4,6-diamino-5-triazine, 2-vinylpyridy
4-vinylpyridine, maleimide, N-phenylmer
Examples include reimide and acrylonitrile. Containing nitrogen
One or more radically polymerizable monomer units
Formed in combination with the above nitrogen-containing radical polymerizable monomer
May be. All of the nitrogen-containing radical polymerizable monomer units
The content of the polymer with respect to the mass is 35 to 60% by mass.
It is preferably 40 to 55% by mass.
Is preferred. When it is contained in an amount of 35% by mass or more, non-magnetic powder
Non-magnetic layer with improved dispersibility and good surface
This is preferable because a magnetic layer having a good surface can be obtained. On the other hand, 5
If it is 5% by mass or less, the hygroscopicity is increased and the running durability is increased.
There is no decline. <Hydrophilic polar group> Used in the present invention (medium
T) Hydrophilic polar groups contained in acrylate copolymers
Is not particularly limited as long as it is a polar group having a hydrophilic group
Has the function of improving the dispersibility of the non-magnetic powder
It is preferable that Such as hydrophilic polar groups
Is, for example, -SO_ThreeM, -PO (OM)₂, -COOM (M
Represents a hydrogen atom, an alkali metal or ammonium),
Amino groups or quaternary ammonium bases are preferred,
-SO_ThreeEspecially preferred because M can greatly contribute to dispersibility
That's right. The content of the hydrophilic polar group is 1 × 10^-6~ 50x1
0^-Fiveeq / g is preferred, 5 × 10^-6~ 20
× 10^-FiveIt is preferable that it is eq / g. 1 × 10^-6e
If q / g or more, the effect of the hydrophilic polar group can be obtained.
And 50 × 10^-FiveIf eq / g or less, the viscosity of the paint
It is not too high and the workability is not significantly reduced.
It is easy. In addition, the (meth) a used in the present invention
The acrylate copolymer has two or more types of hydrophilic polar groups.
For example, -SO_ThreeM and -COOM
You may have both. Hydrophilic to (meth) acrylate copolymer
As a method for introducing a polar group, for example, a hydrophilic polar group
(Meth) acrylate monomer unit not containing
A compound having a hydrophilic polar group in an acrylate copolymer
A method of introducing a product by an addition reaction.
The Specifically -SO_ThreeM for (meth) acrylate
As a method of introducing the polymer, a copolymer having a glycidyl group is used.
Reaction of polymerizable acrylate monomer simultaneously with copolymerization
Or after obtaining a copolymer, -SO_ThreeM
To react with a compound capable of reacting with glycidyl group containing
The law can be mentioned. The above copolymerizable copolymer having a glycidyl group
Examples of acrylate monomers include glycidyl (medium
A) Acrylate, allyl glycidyl ether, etc.
These can be used alone or in combination of two or more
May be. -SO_ThreeG and glycidyl group
Suitable compounds include, for example, sulfite and sodium sulfite.
Thorium, sodium bisulfite, potassium sulfite, sulfite
Sulfites such as ammonium acid, sulfuric acid and sodium hydrogensulfate
Such as lithium, potassium hydrogen sulfate, ammonium hydrogen sulfate, etc.
Hydrogen sulfates, taurine, taurine sodium, tauri
Potassium, taurine ammonium, sulfamic acid,
Sodium sulfamate, potassium sulfamate,
Ammonium sulfamate, sulfanilic acid, sulfa
Sodium anilate, potassium sulfanilate, sulf
Aminosulfonic acids such as ammonium anilate
I can make it. In addition, (meth) acrylate copolymers
Other methods for introducing hydrophilic polar groups include hydrophilic polar groups
Acrylic monomer having a copolymerizable monomer
The method of copolymerizing with a body can be mentioned. For example,
-SO_ThreeHydrophilicity when M is introduced as a polar group
As an acrylate monomer having a polar group, 2-a
Kurylamido-2-methylpropanesulfonic acid, vinyl
Sulfonic acid, (meth) acrylic sulfonic acid, p-styre
Unsaturated hydrocarbon sulfonic acids such as sulfonic acid and the like
Salts of (meth) acrylic acid sulfoethyl ester,
(Meth) acrylic acid sulfopropyl ester, etc.
A) Sulfoalkyl esters of acrylic acid and these
And the like. Also, -COOM
Acrylate with -COOM when introduced
Examples of the monomer include (meth) acrylic acid, male
Mention may be made of inic acids and their salts. Furthermore, a (meth) acrylate copolymer
As another method for introducing a hydrophilic polar group into a hydrophilic polar group
Copolymerize monomer mixture using group-containing radical polymerization initiator
Method of combining, chain transfer with hydrophilic polar group at one end
A method of copolymerizing a monomer mixture in the presence of an agent
be able to. Start of radical polymerization with hydrophilic polar group
Examples of the agent include ammonium persulfate and potassium persulfate.
And sodium persulfate. These la
The amount of dical polymerization initiator used is relative to the total amount of monomer mixture.
1 to 10% by mass, preferably 1 to 5%.
% By mass. In addition, it has a hydrophilic polar group at one end
As chain transfer agents, chain transfer is possible in the polymerization reaction.
And having a hydrophilic polar group at one end
Although not particularly limited, a hazard having a hydrophilic polar group at one end.
Rogenated compounds, mercapto compounds and diphenylpicryl
And hydrazine. Specific examples of the halogenated compound include
2-chloroethanesulfonic acid, 2-chloroethanesulfone
Sodium nitrate, 4-chlorophenyl sulfoxide, 4
-Chlorobenzenesulfonamide, p-chlorobenzene
Sulfonic acid, p-chlorobenzenesulfonic acid sodium
Sodium 2-bromoethanesulfonate, 4- (butyl
Lomomethyl) sodium benzenesulfonate, etc.
Is done. Among these, 2-chloroethanesulfonic acid sodium
Um, sodium p-chlorobenzenesulfonate
That's right. The mercapto compound is preferably
Is 2-mercaptoethanesulfonic acid (salt), where
“(Salt)” means that the compound includes a salt form.
means. ), 3-mercapto-1,2 propanedioe
, Mercaptoacetic acid (salt), 2-mercapto-5-ben
Zoimidazolesulfonic acid (salt), 3-mercapto-2
-Butanol, 2-mercaptobutanol, 3-merca
Put-2-propanol, N (2-mercaptopropi
E) Glycine, ammonium thioglycolate or β-
Mercaptoethylamine hydrochloride is used. these
The chain transfer agent having a hydrophilic polar group at one end is one kind or
Two or more types can be used in combination. Especially preferred
Chain transfer agent having a hydrophilic polar group at one end
Is a highly polar 2-mercaptoethanesulfonic acid (salt)
It is. The amount of these chain transfer agents used is the total amount of monomers.
The content may be 0.1 to 10% by mass, preferably
Is 0.2-5 mass%. Hydrophilic to (meth) acrylate copolymer
A copolymerizable acrylate unit for introducing polar groups
Examples of the monomer include an acrylate group containing a hydroxyl group.
Name the monomer (hereinafter referred to as “hydroxyl group-containing monomer”)
You can. Such copolymerizable hydroxyl group-containing monomers
For example, hydroxymethyl (meth) acrylate
, Hydroxyethyl (meth) acrylate, hydro
Xylpropyl (meth) acrylate, polyethylene glycol
Coal mono (meth) acrylate, polypropylene grease
Cole mono (meth) acrylate, polyethylene glycol
Polypropylene glycol mono (meth) acrylate
Glycerol mono (meth) acrylate, 3-chloro
Such as ro-2-hydroxypropyl (meth) acrylate
Hydroxyalkyl (meth) acrylates, hydroxy
Cyethyl vinyl ether, hydroxypropyl vinyl ester
Vinyl ethers such as ether and hydroxybutyl vinyl ether
Ethers, hydroxyethyl mono (meth) allylate
, Hydroxypropyl mono (meth) allyl ether,
Hydroxybutyl mono (meth) allyl ether, diethyl
Lenglycol mono (meth) allyl ether, dipropi
Lenglycol mono (meth) allyl ether, glycerin
Mono (meth) allyl ether, 3-chloro-2-hydride
(Meth) aldehydes such as loxypropyl (meth) allyl ether
List ril ethers, (meth) allyl alcohol, etc.
be able to. Also, vinyl acetate is copolymerized in a solvent
Vinyl by saponification with caustic
Alcohol-based hydroxyl groups can also be introduced. water
The amount of the monomer having an acid group is 1 to 30 mass in the total monomers.
% Is preferable. <(Meth) acrylate monomer unit>
The (meth) acrylate copolymer used in the invention is
Nitrogen-containing radical polymerizable monomer unit and hydrophilic polar group
In addition, (meth) acrylate monomer units
Preferably. (Meth) acrylate monomer units
As a (meth) acrylate monomer that can form
For example, methyl (meth) acrylate, benzyl (meth
) Acrylate, phenoxyethyl (meth) acrylate
Phenoxypolyethylene glycol (meth) acrylate
Relate, nonylphenol ethylene oxide adduct
A (meth) acrylate etc. can be mentioned. Formation of (meth) acrylate monomer units
(Meth) acrylate monomers that can be
(Meth) acrylate, allyl glycidyl ether,
Methyl vinyl ether, ethyl vinyl ether, isobut
Til vinyl ether, n-butyl vinyl ether, 2-
Ethylhexyl vinyl ether, n-octyl vinyl ether
Ether, lauryl vinyl ether, cetyl vinyl ether
And alkyl vinyl ethers such as stearyl vinyl ether
Ethers, methoxyethyl (meth) acrylate, buto
Alkoxyal such as xylethyl (meth) acrylate
Kill (meth) acrylates, glycidyl (meth) actyl
Relate, vinyl acetate, vinyl propionate, (anhydrous)
With maleic acid, acrylonitrile, vinylidene chloride, etc.
There may be. Among them, alkyl (meth) acrylate,
Allyl glycidyl ether is particularly preferred. The above alkyl (meth) acrylate is
Specifically, methyl (meth) acrylate, ethyl
(Meth) acrylate, propyl (meth) acrylate
, Butyl (meth) acrylate, isobutyl (meth)
Acrylate, pentyl (meth) acrylate, hex
Le (meth) acrylate, Octyl (meth) acrelane
, 2-ethylhexyl (meth) acrylate, lauri
Le (meth) acrylate, stearyl (meth) acrylate
And cyclohexyl (meth) acrylate
Can. (Meth) acrylate monomer units
Is one or two of the above (meth) acrylate monomers
You may form combining more than a kind. (Meth) acrylate used in the present invention
The number average molecular weight of the copolymer is 1,000 to 200,0.
00 is preferred, 10,000 to 200,0
00 is more preferable, and 10,000 to 10
More preferably, it is 0.00. 1,000 or more
If it is above, the physical strength of the resulting magnetic recording medium will decrease
It does not affect the durability.
If the number average molecular weight is 20,000 or less, the predetermined
The paint viscosity is high at the concentration, and workability may be significantly reduced.
And easy to handle. The above polymerizable monomers and chain transfer agent
In order to polymerize a polymerization reaction system containing, known polymerization methods, examples
For example, suspension polymerization, emulsion polymerization, solution polymerization, etc. can be used.
it can. Of these polymerization methods, the obtained (meth) a
The chlorate copolymer is contained in a solid state with high storage stability.
Suspension polymerization and milk have good dry workability because they can be stored easily.
It is preferable to use chemical polymerization, particularly emulsion polymerization is used.
It is preferable. Examples of suspension stabilizers in suspension polymerization include
For example, polyvinyl alcohol, polyvinyl acetate partial ken
Polyvinyl alcohol polymers such as fluoride; methylcellulose
Glucose, hydroxypropylcellulose, carboxymethyl
Cellulose derivatives such as rucellulose;
Don, polyacrylamide, maleic acid-styrene copolymer
A polymer, a maleic acid-methyl vinyl ether copolymer, etc.
Synthetic polymers; natural polymers such as starch and gelatin
Can be mentioned. As an emulsifier in emulsion polymerization,
For example, alkyl or alkyl allyl sulfate, alkyl
Or alkyl allyl sulfonate, alkyl allyl sulphone
Anionic emulsifiers such as succinate; alkyltrimethy
Ruammonium chloride, alkylbenzylammoni
Cationic emulsifiers such as umchloride; polyoxyethylene
Len alkyl phenyl ether, polyoxyethylene
Rukyruether, polyoxyethylene carboxylic acid esthetic
Nonionic emulsifiers such as The polymerization conditions are as follows: copolymerizable monomers used
Depending on the type of polymerization initiator, chain transfer agent, etc.
Generally, in an autoclave, the temperature is about 50-80 ° C,
Gauge pressure is about 1-4 MPa, time is about 5-30 hours
Preferably. Polymerization is a gas inert to the reaction
Is preferable in terms of ease of reaction control.
That's right. Examples of such gases include nitrogen and argon.
Nitrogen is preferably used from the economical point of view.
It is done. In the polymerization, the above-described polymerization reaction system is added to the above-mentioned polymerization reaction system.
In addition to the components, other components may be added. Such ingredients
For example, emulsifier, electrolyte, polymer protective colloid
Etc. [Polyurethane resin] Magnetic recording medium of the present invention
The body is made of polyurea with the above (meth) acrylate copolymer.
A binder used in combination with a tan resin is used for the nonmagnetic layer. The present invention
The type of polyurethane resin used in nonmagnetic layers
Although not limited, poly having hydrophilic polar groups
A urethane resin is preferred. Polyurethane resin having hydrophilic polar group
For example, polyester polyol having a hydrophilic polar group
Or polycarbonate polyol, polyether
A polyol having a hydrophilic polar group such as a polyol;
Polyester polyol or polyester having no hydrophilic polar group
Such as polycarbonate polyol and polyether polyol.
Which polyol has no hydrophilic polar group and diisocyanate
It can be produced from the nate. Hydrophilic
The polyol having a polar group is the main chain or side of the polyol.
The chain has the hydrophilic polar group. Hydrophilic polarity
The group-containing polyol is, for example, a divalent alcohol shown below.
A part of the dibasic acid with a hydrophilic polar group-containing diol or parent
Can be produced by changing to dibasic acid containing aqueous polar group
The As the diol having a hydrophilic polar group,
For example, sulfo (iso or terephthal) phthalic acid (Na or K
EO (ethylene oxide) adduct of PO
(Propylene oxide) adduct, aminoethanesulfone
EO adducts and PO adducts of sulfamic acids such as acids
It can be illustrated. Hydrophilic polar group-containing dibasic acid
For example, 5-sodium sulfoisophthalic acid, 5-
Potassium sulfoisophthalic acid, 5-sulfoisophthalic acid
Acid, 2-sodium sulfoterephthalic acid, 2-potassium
Examples include sulfoterephthalic acid and 2-sulfoterephthalic acid.
Can. The polyester polyol is, for example,
Also obtained by polycondensation of dihydric alcohol and dibasic acid
Ring-opening polymerization of lactones such as caprolactone
The one obtained by Representative divalent al
As for coal, ethylene glycol, propylene glycol
Coal, butanediol, 1,6-hexanediol,
Examples of glycols such as cyclohexanedimethanol
Can. As a typical dibasic acid,
Dipic acid, pimelic acid, azelaic acid, sebacic acid, fu
Examples include taric acid and terephthalic acid. Polycarbonate polyols are many
Dihydric alcohol and phosgene, chloroformate, dial
Reduction with kill carbonate or diallyl carbonate
Or a molecular weight of 300 ~ synthesized by transesterification
Polycarbonate with 20,000 and hydroxyl value of 200-300
Polyol or polycarbonate polyol and 2
Molecular weight 400-3 obtained by condensation with a polyvalent carboxylic acid
Polycarbonate polyethylene having a hydroxyl value of 5,000 and a hydroxyl value of 5 to 300
Reester polyol. Further, as a polyether polyol
Bisphenol A, hydrogenated bisphenol A, bis
Polyethylene oxide such as phenol S and bisphenol P
Sid and / or polypropylene oxide adduct, polyp
Lopylene glycol, polyethylene glycol, polyethylene
Molecular weight of tramethylene glycol, etc. 500-5,000
The polyether polyol can be used. In particular
As the polyether polyol, bisphenol A,
Hydrogenated bisphenol A and their ethyleneoxy
25-4 ether groups with propylene oxide adduct
Containing 5% by weight, preferably 30-40% by weight
Is preferred. If it contains 25% by mass or more of ether groups,
It can be dissolved in a solvent, and good dispersibility can be obtained. Also
If it is 45% by mass or less, the coating strength may not be lowered.
Therefore, durability can be maintained. In addition, the above polyol
Other polyols up to 90% by weight of the above polyols
You may mix | blend and use together. Polyurethane reacted with the above polyol
Polyisocyanate used to form resin
There are no particular restrictions, and use the ones that are normally used
Can. For example, hexamethylene diisocyanate
, Tolidine diisocyanate, isophorone diisocyanate
Anate, 1,3-xylylene diisocyanate, 1,
4-xylylene diisocyanate, cyclohexane dii
Socyanate, toluidine diisocyanate, 2,4-
Tolylene diisocyanate, 2,6-tolylene diisocyanate
Anate, 4,4'-diphenylmethane diisocyanate
, P-phenylene diisocyanate, m-phenylene
Diisocyanate, 1,5-naphthalene diisocyanate
And 3,3-dimethylphenylene diisocyanate
Can be used. As the chain extender, it is known per se.
Substance, polyhydric alcohol, aliphatic polyamine, alicyclic poly
Amines, aromatic polyamines and the like can be used. Molecule
A polyhydric alcohol in an amount of 50 to 500 is preferred. Molecular weight
If it is 50 or more, the coating film does not become brittle and has good durability.
Sex is obtained. If the molecular weight is 500 or less,
Tg does not fall too soft
The desired durability can be maintained. Polyhydric alcohol is bisphenol A, water
Bisphenol A, Bisphenol S, Bisphenol
P and their ethylene oxide, propyleneoxy
Adduct, cyclohexanedimethanol, cyclohexa
Diol, hydroquinone, bis (2-hydroxy ether
Til) tetrabromobisphenol A, bis (2-hydride)
Roxyethyl) tetrabromobisphenol S, bis
(2-Hydroxyethyl) tetramethylbisphenol
S, bis (2-hydroxyethyl) diphenylbisphe
Nord S, bis (2-hydroxyethyl) diphenylbi
Phenol, bis (2-hydroxyethyl) thiodiphe
Nord, bis (2-hydroxyethyl) bisphenol
F, biphenol, bisphenol fluorene, bisph
Rings such as enol full orange hydroxyethyl ether
A short-chain diol having a shape structure is preferred. Yo
More preferably, bisphenol A, hydrogenated bisphenol
A, bisphenol S, bisphenol P and these
Ethylene oxide, propylene oxide adduct, cyclo
Hexane dimethanol, cyclohexanediol, etc.
Aromatic and alicyclic diols. Polyurethane tree in the nonmagnetic layer of the present invention
The average molecular weight of the fat is 5,000-100,000
Preferably 10,000 to 50,000
Are more preferable. Average molecular weight is 5,000 or more
For example, the resulting nonmagnetic layer coating film becomes brittle
There is no decrease in the physical strength, which affects the durability of magnetic recording media.
I don't give it. On the other hand, molecular weight is 100,000 or less
Can be sufficiently dissolved in the solvent, and good dispersibility can be obtained.
It is. In addition, the viscosity of the paint at a given concentration increases and
It is easy to handle without any significant loss of workability.
The Polyurethane tree in the nonmagnetic layer of the present invention
When the fat contains OH groups as hydrophilic polar groups,
From the viewpoint of curability and durability
Preferably it has 2 to 40 OH groups per molecule.
And more preferably 3-20 per molecule.
Having OH groups. In the present invention, the polyurethane resin in the nonmagnetic layer
The content of fat is 10 of the (meth) acrylate copolymer.
It is preferable to be 5 to 900 parts by weight with respect to 0 parts by weight.
More preferably 150 to 300 parts by mass.
Yes. The binder used in the nonmagnetic layer of the present invention is:
It can also contain polyisocyanate as a cross-linking agent.
Yes. Polyisocyanate that can be used as a crosslinking agent
For example, tolylene diisocyanate, 4,4'-
Diphenylmethane diisocyanate, hexamethylene di
Isocyanate, xylylene diisocyanate, naphthi
Len-1,5-diisocyanate, o-toluidine dii
Socyanate, isophorone diisocyanate, trifer
Isocyanates such as nylmethane triisocyanate,
Also, these isocyanates and polyalcohols
Produced by condensation of products and even isocyanates
Polyisocyanate and the like can be used. Commercially available quotients of the above isocyanates
As the product name, for example, Coronate manufactured by Nippon Polyurethane Co., Ltd.
To L, Coronate HL, Coronate 2030, Coronate
2031, Millionate MR, Millionate MTL,
Takenate D-102, Takenate D-1
10N, Takenate D-200, Takenate D-20
2. Death Module L, Death Module manufactured by Sumitomo Bayer
Le IL, Death Module N, Death Module HL, etc.
These can be used alone or by utilizing the difference in curing reactivity.
One or more can be used in combination. The binder used in the nonmagnetic layer of the present invention is:
The above (meth) acrylate copolymer and polyurethane
In addition to resins, other resins can be used in combination.
The The content of other resins used in combination is usually the tree for the present invention.
With mass equal to or less than the total mass of fat and polyurethane resin
Yes, a resin having a hydrophilic polar group is preferred. Can be used together
Other resins are not particularly limited and have traditionally been used as binders.
Known thermoplastic resins, thermosetting resins,
Responsive resins and mixtures thereof can be used. The thermoplastic resin has a glass transition temperature of
-100 to 150 ° C. and number average molecular weight is 1,000.
~ 200,000, preferably 10,000-100,
000 can be mentioned. Specifically, chloride
Vinyl, vinylidene chloride, acrylonitrile, styrene
, Butadiene, ethylene, vinyl butyral, vinyl
Heavy weight containing acetal, vinyl ether, etc.
Examples include coalesced copolymers, various rubber resins
The Further, as a thermosetting resin or a reactive resin
For example, phenol resin, phenoxy resin, epoxy
Resin, urea resin, melamine resin, alkyd resin, active resin
Ryl reaction resin, formaldehyde resin, silicone resin
Fat, epoxy-polyamide resin, polyester resin and
And a mixture of socyanate prepolymers.
Yes. In the nonmagnetic layer of the magnetic recording medium of the present invention,
Includes the binder and non-magnetic powder. Hereafter, this
The nonmagnetic powder will be described in detail. <Nonmagnetic powder> When used in the nonmagnetic layer of the present invention.
The nonmagnetic powder that can be produced may be an inorganic substance or an organic substance. Ma
Carbon black or the like can also be used. As an inorganic substance
For example, metal, metal oxide, metal carbonate, metal sulfuric acid
Salt, metal nitride, metal carbide, metal sulfide, etc.
The Specifically, titanium oxide such as titanium dioxide, oxidation
Cerium, tin oxide, tungsten oxide, ZnO, Zr
O₂, SiO₂, Cr₂O_Three, Α-90-100% α-
Alumina, β-alumina, γ-alumina, α-iron oxide,
Goethite, corundum, silicon nitride, titanium carbide
, Magnesium oxide, boron nitride, disulfide molybdenum
, Copper oxide, MgCO_Three, CaCO_Three, BaCO_Three, Sr
CO_Three, BaSO_Four, Silicon carbide, titanium carbide, etc. alone or
Used in combinations of two or more. Preferred is α-
Iron oxide and titanium oxide. The shape of the non-magnetic powder is acicular, spherical, polyhedral
Either a plate shape or a plate shape is acceptable. Average grains of these nonmagnetic powders
The diameter is preferably 0.005 to 2 μm, but if necessary
Combine non-magnetic powders with different average particle sizes,
Even with magnetic powder, the particle size distribution was widened to achieve the same effect.
You can also Particularly preferred is 0.01 to
0.2 μm. 0.005 μm or more is good
If dispersibility is obtained and if it is 2 μm or less, the surface roughness is
It will never grow. The specific surface area of the nonmagnetic powder is 1 to
100m²/ G, preferably 5 to 70 m²/ G
More preferably, it is 10-65m²/ G. 1m²
/ G or more, the surface roughness is not too large,
100m²/ G or less in the desired amount of binder.
Can be dispersed and good dispersibility can be obtained. PH of non-magnetic powder
Is preferably pH 2-11, but the pH is 6-
Between 9 is particularly preferred. If the pH is 2 or higher,
The coefficient of friction should not be too high even under high humidity.
Yes. If the pH is 11 or less, sufficient fatty acid release
The amount is obtained and the coefficient of friction is not too great. The surface of these nonmagnetic powders is surface treated.
Al₂O_Three, SiO₂TiO₂, ZrO₂,
SnO₂, Sb₂O_Three, ZnO is preferred
Yes. Particularly preferred for dispersibility is Al.₂O_Three, SiO₂, T
iO₂, ZrO₂More preferred is Al
₂O_Three, SiO₂, ZrO₂It is. Use these in combination.
It can be used alone or can be used alone. Also eyes
Depending on the purpose, a co-precipitated surface treatment layer may be used.
After the presence of alumina, silica is present on the surface layer.
It is also possible to adopt the method of making it reverse or vice versa. Ma
The surface treatment layer may be a porous layer depending on the purpose.
However, it is generally preferred to be homogeneous and dense. Nonmagnetic powder used in the nonmagnetic 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-250BX, DPN-245, DP
N-270BX, DPB-550BX, DPN-550
RX, manufactured by Ishihara Sangyo TTO-51B, TTO-
55A, TTO-55B, TTO-55C, TTO-5
5S, TTO-55D, SN-100, MJ-7, α-
Iron oxide E270, E271, E300, S manufactured by Titanium Industry
TT-4D, STT-30D, STT-30, STT-
65C, Teica MT-100S, MT-100T, M
T-150W, MT-500B, MT-600B, MT
-100F, MT-500HD, Sakai Chemical FINEX-
25, BF-1, BF-10, BF-20, ST-M,
Dowa Mining DEFIC-Y, DEFIC-R, Nippon Air
Rosil AS2BM, TiO2P25, Ube Industries 10
0A, 500A, Y-LOP made by Titanium Industry and baked it
What was made. Particularly preferred non-magnetic powders are two.
Titanium oxide and α-iron oxide. The nonmagnetic layer includes carbon together with nonmagnetic powder.
Mixing black and lowering surface electrical resistance (Rs)
And the light transmittance can be reduced. Light transmittance
Adjustment of rubber furnace, rubber thermal, color
Black, acetylene black, etc. can be used
The Carbon block used in the nonmagnetic layer of the present invention
The specific surface area of the rack is usually 100-500m²/ G, good
Preferably 150-400m²/ G, DBP oil absorption is
Usually 20 to 400 ml / 100 g, preferably 30 to 2
00 ml / 100 g. Average carbon black grain
The child diameter is 5 to 80 nm, preferably 10 to 50 nm.
The The pH of carbon black is 2-10, and the water content is
0.1 to 10%, tap density is 0.1 to 1 g / ml
preferable. Carbon black tool used in the present invention
As a physical example, Cabot's BLACKPEAR
LS 2000, 1300, 1000, 900, 80
0, 880, 700, VULCAN XC-72, Mitsubishi
# 3050B, 3150B, 3250B, manufactured by Kasei Kogyo Co., Ltd.
# 3750B, # 3950B, # 950, # 650B,
# 970B, # 850B, MA-600, Colombia
-CONDUCTEX SC, RAVEN 8 manufactured by Bonn
800, 8000, 7000, 5750, 5250, 3
500, 2100, 2000, 1800, 1500, 1
255, 1250, Ketjen Black E made by Akzo
C and the like. Carbon black with a dispersant
Even if it is surface-treated or grafted with resin,
You can use a graphitized part of the surface.
Absent. Also, before adding carbon black to the paint,
It may be dispersed with a binder in advance. These cars
Bon black is 50% by mass based on the inorganic powder.
Range not exceeding, range not exceeding 40% of total mass of nonmagnetic layer
Can be used in These carbon blacks can be used alone or
Can be used in combination. Used in the nonmagnetic layer of the present invention.
Examples of carbon black that can be used are “carbon black”
You can refer to the Handbook for Carbon Black Association
The In addition, an organic powder is used for the nonmagnetic layer according to the purpose.
It can also be added. For example, acrylic-steel
Len resin powder, benzoguanamine resin powder, melamine
Resin powders and phthalocyanine pigments.
Reolefin resin powder, polyester resin powder,
Reamide resin powder, polyimide resin powder, polyfluoride resin powder
Ethylene fluoride resin can also be used. Nonmagnetic layer lubricant, dispersant, additive, solvent
For the agent, dispersion method, etc., the magnetic layer described later can be applied.
Yes. In particular, the amount of binder resin, type, additives, dispersant addition
As for the amount and type, well-known techniques related to the magnetic layer can be applied.
Yes. Accelerator used in the nonmagnetic layer of the present invention
The content of the copolymer is based on 100 parts by mass of the nonmagnetic powder.
And contained within the range of 2.8 to 10 parts by mass. In particular,
Content within the range of 2.8 to 5.6 parts by mass.
As a result, phenomena such as the glossiness of the surface of the nonmagnetic layer increase
As can be seen, the dispersion state of the nonmagnetic powder is good. Content is
If it is 2.8 parts by mass or more, the nonmagnetic powder is not bound.
There is no occurrence of powder falling. On the other hand, 10 parts by mass or less
If so, the dispersion state of the non-magnetic powder can be maintained well.
Therefore, the electromagnetic conversion characteristics are not affected. Next, the magnetic layer, non-magnetic support of the present invention,
Explains in more detail the manufacturing method, layer structure and physical properties
To do. [Magnetic layer] In the magnetic recording medium of the present invention, the surface of the magnetic layer is highly coated.
Microprotrusions with a thickness of 15 nm or more are 900 μm²20 per
It exists in the range of 500 or less. Magnetic layer surface of the present invention
The number of protrusions with a height of 15 nm or more on the surface is
It becomes an index of matching with the sex layer. Small protrusions with the above dimensions
If the number of wheels is 20 or more, stable running durability can be obtained.
It is done. Also, if the number of microprojections is less than 500
For example, the increase in noise of the magnetic recording medium itself can be suppressed.
High SN ratio or CN ratio when played back by MR head
Can be obtained. The number of protrusions of the above dimensions is preferable
30-350 Piece / 900μm²And even better
Or 50-200 pieces / 900 μm²It is. The microprotrusions on the surface of the magnetic layer of the present invention are a support.
It can be divided into microprotrusions caused by coating and microprotrusions related to the coating layer.
So that the fine protrusions on the surface of the magnetic layer satisfy the above range.
In addition, microprotrusions caused by the support and microscopic layers related to the coating layer
Control the protrusions. Usually, the support surface has the desired electromagnetic
Conversion characteristics and durability or support handling suitability
Therefore, minute protrusions are formed. Small surface on the surface
In order to form surface protrusions, the support is free of inorganic fine particles
Organic filler is contained. Necessary electromagnetic conversion
Fillers to obtain properties, durability, and handleability
Different particle size or particle size distribution or different particles
By mixing surface fillers and forming surface protrusions
Yes. The particle size of the fine particles added to the support is relatively large
Large particles with large particle size distribution
Is contained or the dispersion of the filler is insufficient and aggregates exist.
Even if it exists or can be dispersed, liquid feeding and film formation to the film forming machine
If it aggregates inside, so-called coarse protrusions form.
Made. Finer fillers are more difficult to disperse and agglomerate
It is easy to happen. Therefore, the support that causes the protrusion of the magnetic layer
The protrusions on the surface indicate the type of filler added to the support, particles
Size, particle size distribution, dispersion conditions, coarse particles and agglomerated particles
Control by filter condition to remove children
You can The effect of the protrusions on the surface of the support is the thickness of the coating layer.
The thickness is reduced by increasing the thickness of the
Protrusions on the surface of the layer can be reduced. Protrusion of coating layer
Are ferromagnetic powder, abrasive, carbon contained in the magnetic layer
Black, nonmagnetic powder contained in nonmagnetic layer, abrasive,
Particle size of inorganic powder such as carbon black,
Types of binders and lubricants to be dispersed, magnetic layer solution, non-magnetic
Kneading conditions, dispersion conditions, coating
Cloth layer thickness, coating and drying conditions, calendar conditions, magnetic layer surface
Can be controlled by surface treatment conditions
The The particle size of the inorganic powder is reduced.
Makes it difficult to disperse in the binder and makes it easier to form protrusions.
The The dispersion state changes depending on the combination with the binder.
The starting number changes. Regarding kneading conditions,
When kneading with a small amount of agent, it is difficult to disperse the kneaded product
Therefore, the number of protrusions tends to increase. Conversely, increase the amount of solvent
When it is weakened, the number of protrusions tends to decrease. Distribution condition and
Therefore, the dispersion time is the dispersion media used for sand mill dispersion.
Can be changed according to the hardness, specific gravity, etc.
The When the dispersion time is short, the number of protrusions increases. On the other hand, excessive
Even if the dispersion time is long, wear of the disperser and dispersion media
Condensation caused by particles causes particle aggregation and increases the number of protrusions
The The calendar conditions are generally strong (calendar pressure
Force, temperature, roll hardness, increase speed)
Protrusions can be reduced. As a method for surface treatment of the magnetic layer, a magnetic film is used.
The so-called burnish treatment is a known process
There is a rational method. Press the abrasive tape against the surface of the magnetic layer
The polishing method controls the count and pressing pressure of the polishing tape.
By rolling, the surface protrusion of the present invention is defined in the claims.
Can be controlled. Magnetic tape
Is disclosed in Japanese Patent Laid-Open No. 63-259830.
Polishing method using lapping tape (lapping tape)
Preblade method), sapphire blade method, diamond
There are wheel methods, etc.
The surface protrusions are defined in the claims by setting the processing conditions.
Can be controlled. Surface protrusion on support
Even if there are many protrusions on the coating layer, apply this surface treatment.
Thus, the protrusions on the magnetic layer surface can be reduced. that's all
To control the protrusion on the surface of the magnetic layer like
Surface defined by the magnetic recording medium of the present invention.
In order to obtain the state, use these methods in combination
Can be. The surface of the magnetic layer in the magnetic recording medium of the present invention
The microprotrusions can be obtained as follows. Magnetism
Atomic force microscope (AFM) (DIGITAL)
Using NANOSCOPE III from INSTRUMENT)
In the mode of 30 μm × 30 μm. Protrusion
The reference surface is the surface where the volume of the recess is equal, and the reference
Of microprojections when sliced on a surface 15 nm higher than the surface
By counting the number, 900μm²Hit
The number of microprojections can be determined. <Ferromagnetic powder> Used in the magnetic layer of the present invention.
There are no particular restrictions on the ferromagnetic powder, but there are no restrictions on ferromagnetic metal powder or
Is preferably hexagonal ferrite powder. (Ferromagnetic metal powder) Ferromagnetic material used in the magnetic layer of the present invention
Metal powders containing Fe as the main component (including alloys)
)) Is not particularly limited, but α-Fe is the main component.
Ferromagnetic alloy powders are preferred. These ferromagnetic metal powders
At the end, in addition to predetermined atoms, Al, Si, S, Sc, Ca,
Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag,
Sn, Sb, Te, Ba, Ta, W, Re, Au, H
g, Pb, Bi, La, Ce, Pr, Nd, P, Co,
It may contain atoms such as Mn, Zn, Ni, Sr, B, etc.
I don't know. Al, Si, Ca, Y, Ba, La, Nd, C
o, Ni, B is included in addition to α-Fe
Are preferred, especially Co, Al, Y
Is preferred. More specifically, Co is 1 for Fe.
0 to 40 atomic%, Al is 2 to 20 atomic%, Y is 1 to 15
It is preferably contained in atomic percent. These ferromagnetic metal powders are dispersed as described later.
Pre-dispersion with agents, lubricants, surfactants, antistatic agents, etc.
It can be processed. Small amount of ferromagnetic metal powder
May contain water, hydroxide or oxide
Yes. The moisture content of the ferromagnetic metal powder is 0.01-2%
Is preferred. Depending on the type of binder, the inclusion of ferromagnetic metal powder
It is preferable to optimize the water ratio. The crystallite size of the ferromagnetic metal powder is 8 to 1
It is preferably 8 nm (80 to 180 mm).
More preferably, it is ˜18 nm (100 to 180 mm).
Preferably, it is 12-16 nm (120-160 mm)
And are most preferred. The average major axis length of the ferromagnetic metal powder is favorable.
It is preferably 0.01 to 0.10 μm, more preferably
Is 0.03 to 0.09 μm, more preferably
0.03 to 0.07 μm. Average long axis length is 0.01
Stable magnetization without being affected by thermal fluctuations at μm or more
And the average major axis length is 0.10 μm or less
Noise can be kept low. Used in the magnetic layer of the present invention.
Specific surface area of ferromagnetic metal powder used by BET method (S
_BET) Is 30-50m²/ G is preferred and 3
8-48m ²More preferably, it is / g. to this
Therefore, both good surface properties and low noise can be achieved. Ferromagnetic gold
The pH of the genus powder is optimized by combination with the binder used
It is preferable to do. The range is usually pH 4-12
However, it is preferably pH 7-10. Ferromagnetic metal powder
The powder is Al, Si, P or their oxides as required
The surface treatment may be applied. The amount is strong
0.1 to 10% with respect to porous metal powder, and surface treatment is applied.
Then, adsorption of lubricants such as fatty acids is 100 mg / m²Less than
This is preferable. The ferromagnetic metal powder contains soluble Na, Ca,
May contain inorganic ions such as Fe, Ni, Sr
However, if it is 200 ppm or less, the characteristics are particularly affected.
There are few things. Further, the ferromagnetic metal powder used in the present invention
At the end, it is preferable that there are few holes, and the value is 20% by volume.
Hereinafter, it is more preferably 5% by volume or less. Also shape
As for the shape, the characteristics for the particle size shown above are satisfied.
If you add, it can be needle-shaped, granular, rice-grained or plate-shaped
No problem, but use needle-shaped ferromagnetic metal powder
Is preferred. In the case of acicular ferromagnetic metal powder, the average acicular ratio
(Arithmetic average of needle ratio (major axis length / minor axis length)) is 4 to 12
Is more preferable, and 5 to 12 is more preferable. The coercive force Hc of the ferromagnetic metal powder is preferably
160-240 kA / m (2000-3000 O
e), more preferably 170 to 230 kA / m.
(2100-2900 Oe). Also saturation flux density
The degree is preferably 150 to 300 T · m,
Preferably, it is 160 to 290 T · m. Saturation magnetization σs
Is preferably 140 to 170 A · m²/ Kg
More preferably, 145 to 160 A · m²/ Kg. (Hexagonal ferrite powder) Track density
For the purpose of raising, re-use with a magnetoresistive head (MR head)
To reduce the noise of the magnetic recording medium itself
There is a need. For that purpose, it is used in the magnetic layer of the present invention.
The average plate diameter of hexagonal ferrite powder should be 40 nm
There is. However, if the average plate diameter is less than 5 nm, thermal fluctuation
Therefore, stable magnetization cannot be expected. So, used in the present invention
The average plate diameter of the hexagonal ferrite powder is 10 to 35 nm.
Preferably, it is 15-30 nm.
Is preferred. Average plate ratio {Calculation of plate ratio (plate diameter / plate thickness)
Average} is preferably 1 to 15, and is 1 to 7
More preferably. Average plate ratio is in the range of 1-15
If so, a state in which the high filling property and orientation in the magnetic layer are maintained.
Reduce noise generation due to stacking between particles.
Can be suppressed. Hexagonal crystals in the above particle size range
Specific surface area of ferrite by BET method (S_BET) Is 1
0-200m²/ G. Specific surface area is roughly the particle plate diameter
And an arithmetic calculation value from the plate thickness. Particle plate diameter / thickness
In general, the narrower the distribution, the better. The particle plate diameter and plate thickness are
500 particles are measured from the particle TEM photograph. Distribution is normal
In many cases, it is not a distribution, but the average size is calculated
In terms of standard deviation, σ / average size = 0.1 to 2.0
is there. To sharpen the particle size distribution,
Make the reaction system as uniform as possible and disperse the generated particles.
A cloth improvement treatment is also performed. For example, acid solubility
Also known is a method of selectively dissolving ultrafine particles in liquid.
Yes. Coercive force H of magnetic material of hexagonal ferrite powder
c is 40 to 400 kA / m (500 to 5000 O
It is the range of e). The higher the coercive force Hc, the higher the density recording.
However, it is limited by the capacity of the recording head. Main departure
The coercive force Hc of hexagonal ferrite powder in Ming is preferred
Or 160-240 kA / m (2000-3000O
e), but more preferably 175-220 kA
/ M (2200 to 2800 Oe). Head tired
When the sum magnetization exceeds 1.4T, 160 kA / m (2
000 Oe) or more. Coercive force Hc
Is the particle size (plate diameter / plate thickness), the type and quality of the contained elements
Controlled by amount, element substitution site, particle generation reaction conditions, etc.
it can. The saturation magnetization σs is 40 to 80 A · m.²/ Kg
It is preferable. Higher saturation magnetization σs is preferable
However, it tends to be smaller as the particles become smaller. Saturation magnetization
In order to improve σs,
Composite with pinel ferrite, types and elements of elements
It is well known to select an additional amount. W type hexagonal crystal
It is also possible to use ferrite. When dispersing the magnetic material of hexagonal ferrite
Treat the surface of magnetic particles with a material suitable for the dispersion medium and polymer.
You can also As a surface treatment agent, for example, mineralization
Compounds and organic compounds can be used. The main compound is S
compounds such as i, Al and P, various silane coupling agents,
Various titanium coupling agents are representative examples. Surface treatment agent
Is used in an amount of 0.1 to 10% by mass relative to the mass of the magnetic material.
It is. The pH of hexagonal ferrite magnetic material is also important for dispersion
Usually, the pH is about 4-12. Dispersion medium, poly
There is an optimum value depending on the color, but the chemical stability of the medium, storage
The pH value of about 6-11 is selected as the pH value.
The Moisture contained in the hexagonal ferrite magnetic material is also affected by the dispersion.
Sounds. There is an optimum value depending on the dispersion medium and polymer.
0.01 to 2.0% is selected. As a method for producing the hexagonal ferrite powder,
Barium oxide, iron oxide, metal oxides and glass to replace iron
Boron oxide, etc. as the desired material
After mixing to become an amorphous body, it is melted and rapidly cooled.
And then reheated, washed and ground to barium
Glass crystallization method to obtain ferrite crystal powder, barium
Ferrite composition metal salt solution neutralized with alkali, by-product
After removing the material, it is heated in a liquid phase at 100 ° C or higher, and then washed.
Purify, dry and grind to obtain barium ferrite crystal powder
Hydrothermal reaction method, barium ferrite composition metal salt solution
Neutralized with rucali to remove by-products, then dried, 11
Barium ferrite crystals treated at less than 00 ° C and crushed
There is a coprecipitation method for obtaining a powder, etc.
Muferrite powder is particularly preferred. <Binder> The binder used in the magnetic layer of the present invention.
A conventionally known binder can be used as the mixture. This
As such a binder, for example, it is used in the nonmagnetic layer.
(Meth) acrylate copolymer, polyurethane resin
In addition to the above, it is exemplified as a resin that can be used in combination with the nonmagnetic layer.
Known thermoplastic resins, thermosetting resins, reactive resins and
A mixture of these can be used. <Additive> The magnetic layer of the present invention has a dispersion effect,
To provide lubrication effect, antistatic effect, plastic effect, etc.
These additives may be added. These additives include two
Molybdenum sulfide, tungsten disulfide, graphite,
Boron nitride, graphite fluoride, silicone oil, polar group
Silicone, fatty acid-modified silicone, fluorine-containing silicone
Ricone, fluorine-containing alcohol, fluorine-containing beauty treatment salon
, Polyolefin, polyglycol, polyphenyl ether
Ether, phenylphosphonic acid, benzylphosphonic acid,
Ethenylphosphonic acid, α-methylbenzylphosphonic acid,
1-methyl-1-phenethylphosphonic acid, diphenylmethan
Tylphosphonic acid, biphenylphosphonic acid, benzylphenol
Nylphosphonic acid, α-cumylphosphonic acid, toluylphos
Phosphonic acid, xylylphosphonic acid, ethylphenylphosphone
Acid, cumenylphosphonic acid, propylphenylphosphone
Acid, butylphenylphosphonic acid, heptylphenylphosphine
Phosphonic acid, octylphenylphosphonic acid, nonylphenyl
Organic phosphonic acid containing benzene ring such as phosphonic acid and its
Alkali metal salt, octylphosphonic acid, 2-ethylhexyl
Silphosphonic acid, isooctylphosphonic acid, (iso) no
Nylphosphonic acid, (iso) decylphosphonic acid, (iso)
Undecylphosphonic acid, (iso) dodecylphosphonic acid,
(Iso) hexadecylphosphonic acid, (iso) octadeci
Such as luphosphonic acid and (iso) eicosylphosphonic acid
Killphosphonic acid and alkali metal salts thereof, phosphoric acid phosphate
Benzyl phosphate, phenethyl phosphate, α-methyl phosphate
, 1-methyl-1-phenethyl phosphate, diphete phosphate
Nylmethyl, biphenyl phosphate, benzylphenyl phosphate,
Α-cumyl phosphate, toluyl phosphate, xylyl phosphate, phosphoric acid
Tilphenyl, cumenyl phosphate, propylphenyl phosphate,
Butylphenyl phosphate, heptylphenyl phosphate, octyl phosphate
Aromatic phosphates such as tilphenyl and nonylphenyl phosphate
Tellurium and its alkali metal salts, octyl phosphate, 2-phosphate
Ethylhexyl, isooctyl phosphate, phosphoric acid (iso) noni
, Phosphoric acid (iso) decyl, phosphoric acid (iso) undecyl, phosphorus
Acid (iso) dodecyl, phosphoric acid (iso) hexadecyl, phosphoric acid
Phosphorus such as (iso) octadecyl, phosphate (iso) eicosyl
Acid alkyl esters and alkali metal salts thereof, alkyl
Sulfonic acid esters and alkali metal salts thereof, containing fluorine
Alkyl sulfates and alkali metal salts thereof, laur
Phosphoric acid, myristic acid, palmitic acid, stearic acid,
Behenic acid, butyl stearate, oleic acid, linole
1 carbon atom such as acid, linolenic acid, elaidic acid, erucic acid
1 to 24 unsaturated bonds may be included or branched
Basic fatty acids and their metal salts or stearic acid
Chill, octyl stearate, amyl stearate,
Isooctyl tearate, octyl myristate, laur
Butyl butyl, butoxyethyl stearate, anhydride
Losorbitan monostearate, anhydrosorbitan
Distearate, anhydrosorbitan tristearay
Even if it contains an unsaturated bond of 10 to 24 carbon atoms such as
Monobasic fatty acids that may contain and C 2-22 insaturation
1- to 6-valent alcohol, which may contain a sum bond or be branched
, Even if it contains an unsaturated bond with 12 to 22 carbon atoms
Alkoxy alcohol or alkylene oxa
Any one of the monoalkyl ethers of idopolymers
Mono-fatty acid ester, di-fatty acid ester or polyvalent
Fatty acid ester, C2-C22 fatty acid amide, carbon
The aliphatic amine of several 8-22 can be used. Also on
In addition to hydrocarbon groups, nitro groups and F, Cl, Br, C
F_Three, CCl_Three, CBr_ThreeCarbonization of halogen-containing hydrocarbons such as
Alkyl groups, aryl groups, and groups substituted with groups other than hydrogen groups
It may have a aralkyl group. Further, alkylene oxide type, glycerin
, Glycidol, alkylphenol ethylene
Nonionic surfactants such as oxide adducts, cyclic amines,
Ester amide, quaternary ammonium salts, hydantoy
Derivatives, heterocycles, phosphonium or sulfoniums
Cationic surfactants such as carboxylic acid, sulfonic acid,
An anionic surfactant containing an acidic group such as a sulfate group,
Of amino acids, aminosulfonic acids, aminoalcohols
Both sulfuric acid and phosphate esters, alkylbetaine type, etc.
Can also be used. For these surfactants
"Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.)
Are described in detail. These lubricants and antistatic agents
Etc. are not necessarily pure and are isomers and unreacted in addition to the main component
Impurities such as products, by-products, decomposition products, oxides, etc.
I do not care. These impurities are preferably less than 30% by mass.
More preferably, it is 10 mass% or less. Specific examples of these are manufactured by NOF Corporation:
NAA-102, castor oil hydrogenated fatty acid, NAA-42,
Cation SA, Naimine L-201, Nonion E-2
08, Anon BF, Anon LG, Takemoto Yushi Co., Ltd .: FAL
-205, FAL-123, manufactured by Shin Nippon Rika Co., Ltd.
Lub OL, Shin-Etsu Chemical: TA-3, Lion Armor
Company: Armide P, Lion: Duomin TD
O, Nisshin Oil Industries: BA-41G, Sanyo Kasei: Pro
Juan 2012E, New Pole PE61, Ionette
MS-400 etc. are mentioned. These dispersions used in the magnetic layer of the present invention
Agents, lubricants, and surfactants in magnetic and nonmagnetic layers
Different types and quantities can be used as needed. example
Of course, it is not limited to the examples shown here.
However, the dispersant has the property of adsorbing or binding with polar groups.
In the magnetic layer, the surface of the ferromagnetic powder is mainly nonmagnetic.
In the layer, the polar group absorbs mainly on the surface of the non-magnetic powder.
Dispersing agents that are attached or bonded and once adsorbed are metals or metal compounds.
It is assumed that it is difficult to desorb from the surface of objects. Therefore,
The ferromagnetic powder surface or non-magnetic powder surface of the present invention is
Since it becomes a state covered with a ru group, an aromatic group, etc.
Parent to binder resin component of ferromagnetic powder or non-magnetic powder
Improved compatibility and dispersion of ferromagnetic powder or non-magnetic powder
Stability is also improved. Also, the lubricant is in a free state
Fats with different melting points in non-magnetic and magnetic layers
Uses acid to control bleed out to the surface.
Control bleeding to the surface using different esters
The stability of coating is improved by adjusting the amount of surfactant.
Lubricating effect by increasing the amount of lubricant added to the non-magnetic layer
It is conceivable to improve. Also used in the present invention
All or part of the additive is magnetic layer or non-magnetic
May be added at any step during the production of the coating liquid for the adhesive layer
Yes. For example, when mixing with ferromagnetic powder before the kneading step,
Adding in the kneading process with ferromagnetic powder, binder and solvent
When adding in the dispersion step, when adding after the dispersion,
In some cases, it is added just before coating. [Non-magnetic support] Since it is used in the present invention,
Non-magnetic supports that can be used include biaxially stretched polyethylene.
Such as terephthalate, polyethylene naphthalate, etc.
Polyesters, polyolefins, cellulose tria
Setate, polycarbonate, polyamide, polyimi
Polyamide, polysulfone, polyarami
, Aromatic polyamide, polybenzoxazole, etc.
A known film can be used. Preferably polyethylene
Terephthalate, polyethylene naphthalate, aromatic poly
Riamide. If necessary, the magnetic surface and support surface
To change the surface roughness, Japanese Patent Laid-Open No. 3-224127
Laminated type supports as shown can also be used
The These non-magnetic supports are preliminarily provided with a core.
Rona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, removal
You may perform dust processing etc. The non-magnetic support of the present invention
It is also possible to apply aluminum or glass substrate as
The In order to achieve the object of the present invention, a non-magnetic support is used.
In the Mirau method of TOPO-3D made by WYKO as a body
The measured center plane average surface roughness is SRa of 8.0 nm or less.
Lower, preferably 4.0 nm or less, more preferably 2.
It is necessary to use one of 0 nm or less. These non-magnetic
The support has a small center plane average surface roughness.
It is preferable that there is no coarse protrusion of 0.5μm or more.
Yes. Surface roughness and shape can be added to the support as necessary.
Freely controlled by the size and amount of filler used
It is what is done. As an example of these fillers
In addition to oxides and carbonates such as Ca, Si and Ti,
Examples include organic fine powders such as ril. Maximum height of support
SR_maxIs less than 1μm, 10 point average roughness SRz is 0.5μ
m or less, center plane height is SRp 0.5μm or less, center
The face valley depth SRv is 0.5 μm or less, and the center plane area ratio SSr
Is preferably 10 to 90%. Desired electromagnetic conversion
Distribution of surface protrusions on these supports to obtain properties and durability
Can be controlled arbitrarily with a filler.
0.1mm for each of the size of 0.01-1μm
²Control within the range of 0 to 2000 per unit
Can do. Nonmagnetic support F-5 used in the present invention
The value is preferably 49 to 490 MPa (5 to 50 kg / m
m²The heat shrinkage rate of the support at 100 ° C. for 30 minutes is favorable.
Preferably 3% or less, more preferably 1.5% or less, 8
The heat shrinkage rate at 0 ° C. for 30 minutes is preferably 0.5% or less.
More preferably, it is 0.1% or less. Breaking strength is 49 ~
980 MPa (5 to 100 kg / mm²), The elastic modulus is
0.98 to 19.6 GPa (100 to 2000 kg / m
m²) Is preferred. The coefficient of thermal expansion is 10^-Four-10^-8/
° C, preferably 10^-Five-10^-6/ ° C. Humidity
The expansion coefficient is 10^-Four/ RH% or less, preferably 10
^-Five/ RH% or less. These thermal characteristics, dimensional characteristics, machine
Mechanical strength characteristics differ within 10% in each direction in the surface of the support
It is preferable that they are almost equal. [Backcoat layer, undercoat layer] Used in the present invention
The back of the nonmagnetic support on which the magnetic layer is not provided
A quacoat layer may be provided. Back coat layer
On the surface of the support where the magnetic layer is not provided,
Disperse particulate components such as antistatic agent and binder in organic solvent
In the layer provided by applying the back coat layer forming paint
is there. Various inorganic pigments and carbon black as particulate components
Nitrose can be used as a binder.
Resin such as roulose, phenoxy resin, polyurethane
They can be used alone or in combination. The present invention
Of magnetic coating material and backcoat layer forming coating material
An adhesive layer may be provided on the surface. In the magnetic recording medium of the present invention,
An undercoat layer may be provided. By providing an undercoat layer
To improve the adhesion between the support and the magnetic or non-magnetic layer
be able to. For the undercoat layer, a solvent-soluble
A reester resin is used. Undercoat layer as thickness
The thing of 0.5 micrometer or less is used. [Manufacturing Method] The magnetic recording medium of the present invention is an example.
For example, non-magnetic layer coating liquid, magnetic
By applying the coating liquid to the predetermined film thickness.
To manufacture. Here, a plurality of magnetic layer coating solutions are added sequentially or in the same way.
Sometimes a multilayer coating may be applied, non-magnetic layer coating solution and magnetic layer coating
The liquid may be applied successively or simultaneously. Magnetic layer
As a coating machine for applying a coating solution or a non-magnetic layer coating solution,
Air doctor coat, blade coat, rod coat
, Extrusion coating, air knife coating, squeeze coat
, Impregnation coat, reverse roll coat, transfer
-Roll coat, gravure coat, kiss coat, cast
To coat, spray coat, spin coat etc. are available
The When applied to the magnetic recording medium of the present invention, coating
The following can be proposed as an example of an apparatus and a method for applying cloth. (1) Gravity generally applied in application of magnetic layer coating solution
A, roll, blade, extrusion coating equipment
First, apply the non-magnetic layer, and the non-magnetic layer is undried.
JP-B-1-46186, JP-A-60
-238179, JP-A-2-265672
Pressurized extrusion as disclosed in
The magnetic layer is applied by an application device. (2) JP-A-63-88080, JP-A-2-17
No. 971 and JP-A-2-265672.
One of the two coating liquid passage slits
Magnetic layer and non-magnetic layer are applied almost simultaneously with the application head.
To do. (3) It is disclosed in Japanese Patent Laid-Open No. 2-174965.
Extrusion coating with a backup roll like
Apply a magnetic layer and a non-magnetic layer almost simultaneously using a cloth device.
The Two layers having different magnetic characteristics from the above magnetic layer
It does not matter if it is separated as described above, and relates to a known multilayer magnetic layer
Configuration can be applied. Stable coating of this ultra-thin magnetic layer
Nonmagnetic support containing inorganic powder on a nonmagnetic support
With a magnetic layer on top of it.
It is desirable to apply with an et. The magnetic layer coating solution is coated with a magnetic tape.
The ferromagnetic powder contained in the coating layer of the magnetic layer coating solution.
Magnetic field orientation in the longitudinal direction using cobalt magnets and solenoids
Apply processing. In the case of a disc, no orientation device is used and
A sufficiently isotropic orientation may be obtained even with orientation.
Is a solenoid that alternately arranges cobalt magnets diagonally
Use a known random orientation device such as applying an alternating magnetic field at
Preferably it is. Isotropic orientation is a ferromagnetic metal micro
In the case of powder, in-plane two-dimensional random is generally preferred.
However, it is also possible to make a three-dimensional random with a vertical component.
it can. In the case of hexagonal ferrite powder, generally in-plane
And it tends to be three-dimensional random in the vertical direction, but in-plane 2
Dimensional randomness is also possible. Also, opposite poles
Using a known method such as a magnet, the vertical orientation
It is also possible to impart isotropic magnetic properties in the direction. In particular
When performing high density recording, vertical alignment is preferred. Also,
Circumferential orientation may be performed using a pin coat. Control the drying air temperature, air volume and coating speed.
It is preferable to control the drying position of the coating film.
The coating speed is 20 to 1000 m / min, and the temperature of the drying air
Is preferably 60 ° C. or higher. Before entering the magnet zone
Appropriate preliminary drying can also be performed. After being dried, the coating layer is subjected to a surface smoothing treatment.
Apply. For surface smoothing treatment, for example, super calendar
Rolls are used. To perform surface smoothing
As a result, vacancies caused by solvent removal during drying disappear.
However, since the packing rate of the ferromagnetic powder in the magnetic layer is improved,
A magnetic recording medium having high magnetic conversion characteristics can be obtained. Mosquito
Render treatment rolls include epoxy, polyimide,
Heat-resistant plastics such as lyamide and polyamide-imide
Can be used. Also treat with metal roll
You can also. The magnetic recording medium of the present invention has an average roughness.
Is in the range of 1 to 3 nm at a cutoff value of 0.25 mm.
The surface must have an extremely smooth surface
preferable. As the method, for example, as described above
The magnetic layer formed by selecting the ferromagnetic powder and binder of
This is done by applying a render process. Calendar processing conditions
As a matter, the temperature of the calendar roll is 60 to 100 ° C.
In the range of 70 to 100 ° C., particularly preferred
Or in the range of 80 to 100 ° C., and the pressure is 100 to 50
In the range of 0 kg / cm (98-490 kN / m),
Preferably 200-450 kg / cm (196-441
kN / m), particularly preferably 300 to 40.
In the range of 0 kg / cm (294-392 kN / m)
The The obtained magnetic recording medium can be placed using a cutting machine.
Can be cut into the desired size and used. [Layer structure] Magnetic layer of magnetic recording medium of the present invention
Is the saturation magnetization of the head used and the head gap.
Optimized according to the length and band of the recording signal, 0.01 to 0.
When the thickness is 5 μm and the magnetic layer contains ferromagnetic metal powder,
The thickness of the conductive layer is preferably 0.01 to 0.1 μm.
If the magnetic layer contains hexagonal ferrite powder, the magnetic layer
The thickness of is preferably 0.01 to 0.2 μm.
Even if the magnetic layer is separated into two or more layers having different magnetic properties
Needless to say, a configuration related to a known multilayer magnetic layer can be applied.
The When multiple magnetic layers are provided, the thickness of the magnetic layer depends on the individual magnetic layer.
The thickness of the adhesive layer. Further, in the magnetic recording medium of the present invention,
The thickness of the nonmagnetic support is preferably 3 to 80 μm.
That's right. [Physical characteristics] Saturation magnetic flux density of the magnetic layer of the present invention
Degree is 100-300T ・ m (1000-3000G)
is there. The coercive force (Hr) of the magnetic layer is 143 to 318.
kA / m (1800-4000 Oe), but preferred
Or 159 to 279 kA / m (2000 to 3500
Oe). Narrower coercive force distribution is preferable. SF
D and SFDr are 0.75 or less, more preferably 0.
6 or less. Head of magnetic recording medium used in the present invention
The coefficient of friction with respect to the
In the range of 5%, it is 0.5 or less, preferably 0.
3 or less. The surface resistivity is preferably magnetic
Surface 10^Four-10¹²Ω / sq, charge potential is -500 V to +5
Within 00V is preferable. Elasticity at 0.5% elongation of magnetic layer
The rate is preferably 0.98 to 19.6 GP in each in-plane direction.
a (100 to 2000 kg / mm²), Breaking strength is good
Preferably, 98-686 MPa (10-70 kg / m
m²) The elastic modulus of magnetic recording media is preferred in each direction in the plane
Or 0.98 to 14.7 GPa (100 to 1500 kg)
/ Mm²), Residual spread is preferably 0.5% or less, 1
The thermal shrinkage at any temperature below 00 ° C is preferably
1% or less, more preferably 0.5% or less, most preferred
Or less than 0.1%. The glass transition temperature of the magnetic layer (measured at 110 Hz).
The maximum point of loss elastic modulus of the measured dynamic viscoelasticity is 50 ~
120 ° C is preferred, and 0-100 ° C is preferred for the lower layer
That's right. Loss modulus is 1 × 10⁷~ 8x10⁸Pa (1 x 1
0⁸~ 8x10⁹dyne / cm²)
The loss tangent is preferably 0.2 or less.
Yes. If the loss tangent is too large, adhesion failure is likely to occur.
These thermal and mechanical properties are 10% in each direction in the plane of the media
Are preferably approximately equal. The residual solvent contained in the magnetic layer is preferably
100 mg / m²Or less, more preferably 10 mg / m²
It is as follows. The porosity of the coating layer is non-magnetic underlayer, magnetic
Both layers are preferably 30% by volume or less, more preferably 2%.
0% by volume or less. To achieve high output porosity
Smaller values are preferable, but depending on the purpose, a certain value should be secured.
Sometimes it is better. For example, repetitive usage is important
The higher the porosity of the disk media, the better the running durability
Often preferred. In the magnetic layer TOPO-3D mirau method
The measured center plane surface roughness Ra is 4.0 nm or less.
Preferably 3.0 nm or less, more preferably
Is 2.0 nm or less. Maximum height SR of magnetic layer
_maxIs 0.5 μm or less, and the ten-point average roughness SRz is 0.3.
μm or less, center plane mountain height SRp is 0.3 μm or less, center
The face valley depth SRv is 0.3 μm or less and the center plane area ratio SSr.
Is preferably 20 to 80%, and the average wavelength Sλa is preferably 5 to 300 μm.
Good. The surface protrusion of the magnetic layer is 0.01-1 μm
Can be arbitrarily set in the range of 0-2000
It is possible to optimize electromagnetic conversion characteristics and coefficient of friction.
Is preferable. These depend on the filler of the support.
Control of surface properties and particle size of powder added to magnetic layer
And volume, calender roll surface shape, etc.
Can be trawled. The curl should be within ± 3mm
It is preferable. The nonmagnetic layer in the magnetic recording medium of the present invention
Depending on the purpose, the non-magnetic layer and the magnetic layer
It is easily estimated that the physical properties of can be changed
That is. For example, increase the elastic modulus of the magnetic layer to improve the running durability
The elasticity of the non-magnetic layer and the magnetic layer
Decrease the magnetic recording medium to hit the head
It is. [0105] The present invention will be described in detail with reference to the following examples.
However, the present invention is not limited to these examples.
Yes. Unless otherwise specified, “part” in the examples is indicated.
“Mass” is shown. [Synthesis Example 1]Synthesis of (meth) acrylate copolymer A Equipped with a stirrer, condenser, thermometer and nitrogen gas inlet
In the obtained polymerization vessel, 360 parts of deionized water
Charge 5 parts of potassium sulfate and 1.6 parts of sodium carbonate, nitrogen
After the replacement, the temperature was raised to 57 ° C. Meanwhile, deionized water in advance
390 parts, methyl methacrylate 300 parts, N-methylo
200 parts acrylamide, 2-hydroxymethyl methyl
35 parts of tacrylate, 2-acrylamido-2-methyl
10 parts propanesulfonic acid, 1 sodium lauryl sulfate
The above polymerization vessel was prepared by mixing and emulsifying 0 parts with a homomixer.
The solution is dripped uniformly in 8 hours, and further reacted at 57 ° C for 2 hours.
To complete the polymerization, 500 parts of methanol, sodium sulfate
50 parts of thorium was added to precipitate the polymer. Precipitate
The polymer twice with 5000 parts of methanol and then degassed.
Wash 4 times with 5000 parts of on-water, filter and dry (mesh
A) An acrylate copolymer A was obtained. Sodium sulfonate
The lithium group content is 5.6 × 10^-Fiveeq / g, including hydroxyl group
The weight is 12.4 × 10^-Fiveeq / g. (Meta) a
Components and content (% by weight) of acrylate copolymer A
Table 1 shows. [0107] [Table 1] [0108] [Example 1]   Preparation of magnetic layer coating solution     100 parts of ferromagnetic needle metal powder       Composition: Fe / Co / Al / Y = 68/20/7/5 (atomic ratio),       Surface treatment layer: Al₂O_Three, Y₂O_Three,       Hc: 200 kA / m (2500 Oe),       Crystallite size: 14 nm (140 cm),       Average long axis length: 0.08 μm,       Average needle ratio: 6,       BET specific surface area: 46 m²/ G,       σs: 150 A · m²/ Kg     18 parts of polyurethane resin         (UR8200: Toyobo's sulfonic acid group-containing polyurethane resin)     Phenylphosphonic acid 3 parts     α-Al₂O_Three(Average particle size: 0.15 μm) 10 parts     Carbon black (average particle size: 20 nm) 1 part     110 parts of cyclohexanone     100 parts of methyl ethyl ketone     100 parts of toluene     Butyl stearate 2 parts     1 part of stearic acid [0109]Preparation of nonmagnetic layer coating solution     Nonmagnetic inorganic powder: α-iron oxide 85 parts         Surface treatment layer: Al₂O_Three, SiO₂,         Average long axis length: 0.15 μm,         Tap density: 0.8,         Average needle ratio: 7,         BET specific surface area: 52 m²/ G,         pH 8,         DBP oil absorption: 33ml / 100g     Carbon black 15 parts       DBP oil absorption: 120 ml / 100 g,       pH: 8,       BET specific surface area: 250 m²/ G,       Volatile content: 1.5%     (Meth) acrylate copolymer A 10 parts     9 parts of polyurethane resin       (UR8200: Toyobo's sulfonic acid group-containing polyurethane resin)     Phenylphosphonic acid 3 parts     α-Al₂O_Three(Average particle size 0.2 μm) 1 part     140 parts of cyclohexanone     170 parts of methyl ethyl ketone     Butyl stearate 2 parts     1 part of stearic acid Composition of the above magnetic layer coating solution and non-magnetic layer coating solution
For each item, each ingredient is 6 in an open kneader
After kneading for 0 minutes, the mixture was dispersed for 120 minutes by a sand mill.
Trifunctional low molecular weight polyisocyanate was added to the resulting dispersion.
6 compounds (Japan Polyurethane Coronate 3041)
After adding and stirring and mixing for another 20 minutes, the average of 1 μm
Filtration using a filter having a pore size, magnetic layer coating solution
A nonmagnetic layer coating solution was prepared. The center surface average surface roughness is 5 nm with a thickness of 6 μm.
On the polyethylene terephthalate support of
Apply the layer coating solution so that the thickness after drying is 1.8 μm.
Furthermore, immediately after that, the thickness after drying the magnetic layer coating solution is
Simultaneous multi-layer coating was carried out so that it might become 0.08 micrometer. Both layers are not yet
Conduct magnetic field orientation with a 300Tm magnet in the dry state.
Furthermore, after drying, it is a seven-stage curl made up of only metal rolls.
At a speed of 100 m / min, linear pressure of 300 kg / cm
(294kN / m), surface smoothing at 90 ° C
After that, heat curing treatment is performed at 70 ° C. for 24 hours, and 3.8
A magnetic tape was prepared by slitting to a width of mm. [Examples 2 and 3] In Example 1, nonmagnetic
(Meth) acrylate copolymer A and poly
Change the amount of urethane resin added as shown in Table 2
The magnetic tapes of Examples 2 and 3 were prepared in the same manner as in Example 1.
It was. Example 4 In Example 3, the nonmagnetic support
The holder has a thickness of 5.2 μm and a center surface average surface roughness of 1 nm.
Example 1 with the exception of polyethylene naphthalate
A magnetic tape of Example 4 was prepared in the same manner. [Comparative Examples 1 to 3] In Example 1, nonmagnetic
(Meth) acrylate copolymer A and poly
Change the amount of urethane resin added as shown in Table 2
The magnetic tapes of Comparative Examples 1 to 3 were prepared in the same manner as in Example 1.
It was. Comparative Example 4 In Example 4, the nonmagnetic layer
Coating solution (meth) acrylate copolymer A and polyurea
The amount of tan resin added was changed as shown in Table 2, and Example 4
A magnetic tape of Comparative Example 4 was prepared in the same manner as described above. the above
The results of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 3. [Example 5] Ferromagnetic powder is shown below.
To make flexible disks of Examples 5-7.
Made.Preparation of magnetic layer coating solution     100 parts of ferromagnetic plate-shaped hexagonal ferrite powder       Composition (molar ratio): Ba / Fe / Co / Zn = 1 / 9.1 / 0.2 / 0.8 ,       Hc: 195 kA / m (2450 Oe),       Average plate diameter: 26 nm,       Average plate ratio: 4,       BET specific surface area: 50 m²/ G,       σs: 60 A · m²/ Kg     18 parts of polyurethane resin       (UR8200: Toyobo's sulfonic acid group-containing polyurethane resin)     Phenylphosphonic acid 3 parts     α-Al₂O_Three(Average particle diameter: 0.15 μm) 2 parts     Carbon black (average particle size: 20 nm) 2 parts     110 parts of cyclohexanone     100 parts of methyl ethyl ketone     100 parts of toluene     Butyl stearate 2 parts     1 part of stearic acid Example 1 using each component of the magnetic layer coating solution
A magnetic layer coating solution was prepared in the same manner as described above. The thickness is 62 μm and the center surface average surface roughness is 5 n.
Example 1 on m polyethylene terephthalate support
The thickness after drying the same non-magnetic layer coating solution to 1.5 μm
And then immediately after that, the magnetic layer coating solution
Simultaneous multi-layer coating so that the thickness after drying becomes 0.12 μm
Made cloth. While both layers are still wet, frequency 5
0Hz, magnetic field strength 25mT, frequency 50Hz, 12T
・ M pass through two AC magnetic field generators
The random alignment treatment was performed. 7-stage calendar after drying
Temperature 90 ° C., linear pressure 300 kg / cm (294 kN /
m), punched to 3.7 inches, surface polishing
After polishing, the 3.7 mm liner that has been installed inside
In a Zip-disk cartridge
3.7-inch floppy (registered trademark)
I got a disc. [Examples 6 and 7 and Comparative Example 6] In Example 5,
(Meth) acrylate-based co-polymer of non-magnetic layer coating solution
As shown in Table 3, the amount of coalescence A and polyurethane was changed.
Furthermore, in the same manner as in Example 5, Examples 6 and 7 and Comparative Example
6 floppy disks were created. Obtain the sample below
Evaluation was performed by the measurement method described above. The results are shown in Table 3. [Measurement method] 1.Measuring the number of microprojections Atomic force microscope (AFM) (manufactured by DIGITAL INSTRUMENT)
30μm in contact mode using NANOSCOPE III
A range of × 30 μm was measured. Protrusion and indentation volume etc.
The reference surface is the surface to be reduced, and the surface is 15 nm higher than the reference surface.
The number of protrusions when sliced was counted. 2.Error rate (initial, after saving) Signal at 23 ° C and 50% RH for tape media
Recorded on tape with 8-10 conversion PR1 equalization method and DDS
Measured using live, for disk media (2, 7)
It was recorded on a disk and measured by the RLL modulation method. 6 more
Store for 1 week at 0 ° C and 90% RH, and error
Measured. [0121] [Table 2][0122] [Table 3] From Table 2, in the case of a magnetic tape, the nonmagnetic layer has a
(Meth) acrylate copolymer is polyurethane resin
Used in combination with fat and the number of protrusions on the surface of the magnetic layer is 20 or more 5
For less than 00 magnetic recording media, vinyl chloride resin
The same as above for magnetic recording media using polyurethane resin together
Etc., or more smoothness of the surface of the magnetic layer, before and after storage
It can be seen that the error rate is obtained. Also, (Me
A) Acrylate copolymer and polyurethane resin
When no deviation is included (Comparative Examples 1 and 3) or (Meta)
More than 10 parts by weight of acrylate copolymer
Then, the number of protrusions on the surface of the magnetic layer is 20 or less (Comparative Example 3).
Or 500 or more (Comparative Examples 1 and 2).
The rar rate has increased. From this, the (magnetic
The content of the acrylate copolymer is based on the total mass
When the amount is 10 parts by mass or less, particularly the smoothness of the magnetic layer surface and
The storage stability of magnetic recording media
The From Table 3, the magnetic tape is also a magnetic tape.
As in the case of (meth) acrylate in the nonmagnetic layer
The surface of the magnetic layer by using a polyurethane copolymer in combination with polyurethane resin
The number of protrusions of the magnetic recording medium is 20 or more and less than 500
If used, a vinyl chloride resin can be used together with a polyurethane resin.
Magnetic layer surface equivalent to or better than a magnetic recording medium
The smoothness and the error rate before and after storage can be obtained.
Karu. Also, (meth) acrylate system in non-magnetic layer
The content of the copolymer is 10 parts by mass or less with respect to the total mass.
In particular, the smoothness of the surface of the magnetic layer and the preservation of the magnetic recording medium.
It can be seen that the stability is excellent (Examples 5 to 7, ratio
Comparative Example 6). [0125] As described above, the magnetic recording of the present invention.
The medium is a predetermined acrylate copolymer polyurethane.
Non-magnetic layer contains a binder combined with resin in the non-magnetic layer
A nonmagnetic layer in which the powder is well dispersed is obtained. Also non-magnetic
The number of microprotrusions on the surface of the magnetic layer laminated on the magnetic layer
By controlling in the range, a smooth magnetic layer surface can be obtained.
The error rate can be reduced, resulting in excellent electromagnetic conversion characteristics.
And has excellent storage stability and durability
A magnetic recording medium can be provided. The magnetic recording medium of the present invention
Uses a non-vinyl chloride binder.
Highly reliable magnetic recording without the problem of hydrogen chloride gas
It can be a medium.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuhiko Meguro             2-1-12 Ogimachi, Odawara-shi, Kanagawa Prefecture             Shishi Photo Film Co., Ltd. Odawara Factory F-term (reference) 5D006 BA04 BA06 BA19 CA01 CA05

Claims (1)

What is claimed is: 1. A magnetic recording medium comprising, on a nonmagnetic support, a nonmagnetic layer containing nonmagnetic powder and a binder, and a magnetic layer containing ferromagnetic powder and a binder in this order. The binder contained in the nonmagnetic layer includes a (meth) acrylate copolymer and a polyurethane resin, and the (meth)
The acrylate copolymer has a radically polymerizable monomer unit containing nitrogen and a hydrophilic polar group, and the magnetic layer has microprojections having a height of 15 nm or more on the surface thereof.
A magnetic recording medium having 20 or more and less than 500 per μm ² .