JP2003077118A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably provide a magnetic recording medium having excellent electromagnetic transducing characteristics and excellent in repetitive durability. SOLUTION: The magnetic recording medium wherein at least one magnetic layer formed by dispersing ferromagnetic powder in a bonding agent and having <=4 nm surface roughness is provided on a non-magnetic substrate has a polishing agent having an average particle size 1/3-2 times as large as the thickness of the magnetic layer and 20-200 pieces/225 μm<2> polishing agent on the surface of the magnetic layer and contains 3-10 mass% SiO2 particles except the polishing agent having 1-50 nm average particle size.

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION A ferromagnetic fine powder and a binder are separated.
Magnetic recording with scattered magnetic layers on a nonmagnetic support
Particularly excellent electromagnetic conversion characteristics and running durability in media
The present invention relates to a magnetic recording medium having [0002] Conventionally, video tapes and audio tapes have been used.
In magnetic recording media such as magnetic disks, magnetic iron oxide,
Co-modified ferromagnetic iron oxide, CrO₂, Ferromagnetic alloy powder, etc.
A magnetic layer dispersed in a binder is coated on a nonmagnetic support.
Is widely used. As needed for tape media
Then, a back coat layer is laminated on the surface opposite to the magnetic layer. This
For recording and playback of music on magnetic recording media obtained in this way
Higher original sound playback capability for audio tapes
For videotapes, the ability to reproduce the original picture
Is excellent, computer backup tape
/ The disc has good durability and no data loss
Is required. In recent years, recording wavelength has become shorter with higher density
The output decreases when the magnetic layer is thick.
Problems with self-demagnetization loss during recording and thickness loss during playback
It has become. For this reason, the magnetic layer is made thin.
However, if the magnetic layer is made thinner than about 2 μm, the magnetic layer
The effect of non-magnetic support is likely to appear on the surface, and electromagnetic conversion
There is a tendency to deteriorate characteristics and dropouts. One means for solving this problem is disclosed in
63-191315, JP-A 63-187418
As described in the Gazette, the simultaneous multi-layer coating method is used.
Provide a non-magnetic layer underneath and thin a highly concentrated magnetic coating solution.
There is a method to apply. By these inventions
The yield can be improved and good electromagnetic characteristics can be obtained.
It became so. However, higher density magnetic recording media
It is desired. Conventionally, tape damage during VTR running is reduced.
In order to eliminate this, solid lubricants such as carbon
Add liquid lubricants such as stealth, alumina oxide
Which abrasive should be added to ensure the hardness of the magnetic tape
Has been commonly used. However, solid moisture such as carbon
Increasing the amount of lubricant added reduces the surface properties in the magnetic layer.
As a result, the reproduction output is reduced. In addition, a large amount of abrasive is magnetically added.
Contact state near the gap causing wear of the head
Is a phenomenon that changes slightly and changes the playback envelope.
Cause the life of the VTR to be shortened. or,
Liquid lubricant depends on the surface of the magnetic layer and the state of presence in the layer
Therefore, there is a problem of being greatly affected by the environment and time
The Thus, magnetic tape itself is magnetic.
Wear and damage due to running contact members such as air heads and VTRs
Wear the magnetic head as much as possible
It is desirable not to. To achieve these, now
Various studies have been made until now. 1) JP-A-6-5254
No. 1 publication: average protrusion height of abrasive present on the surface of the magnetic layer
Head wear and head fouling by reducing the thickness to 15 nm or less
It is described to improve this. 2) JP-A-6-309
Publication No. 650: Lubricant content and protrusion height on the magnetic layer surface
And improve the runnability by prescribing the existence density
It is disclosed. 3) Japanese Patent Laid-Open No. 6-12651
No. 6,126,652: surface roughness of magnetic layer and
The height of protrusions on the surface of the magnetic layer and its density
Balun for both electromagnetic conversion characteristics, running performance and durability
It is disclosed that it is possible to make a good one. In recent years, high density
Recording per unit area with recording and higher recording rates
As a means to increase capacity, the recording frequency is shortened on the VTR side.
Wavelengths and magnetic recording heads have become narrower tracks.
The relative speed of the head / tape due to the high speed rotation of Linda
The tape is improved by improving the surface properties.
To reduce the specs loss with the
It has been improved. Therefore, in the above prior art, electromagnetic
It becomes impossible to obtain a balance between conversion characteristics and running durability.
It was. [0006] SUMMARY OF THE INVENTION The present invention particularly relates to the shortest description.
Recording wavelength is 0.7μm or less and track pitch is 25μm or less
In a magnetic recording medium that records and reproduces at a high density, which is below,
Magnets with excellent electromagnetic conversion characteristics and excellent durability
It is to provide an air recording medium stably. [0007] Means for Solving the Problems The present invention provides the following (1),
Achieved by (2) and (3). (1) Non-magnetic support
At least the ferromagnetic powder dispersed on the carrier in the binder
The surface roughness of the magnetic layer provided with one kind of magnetic layer is 4nm or less
1 to 2 times the thickness of the magnetic layer
The number of surface abrasives is 20-2.
00 / 225μm²And the average particle size is 1 to
SiO other than the abrasive that is 50 nm₂3 to 1 particles
0% by mass (based on magnetic material)
Magnetic recording medium. (2) Including inorganic powder and binder
It has a lower coating layer between the support and the magnetic layer.
The magnetic recording medium as described in (1) above. (3) Magnetism
The thickness of the conductive layer is 0.05 μm or more and 0.6 μm or less,
The layer thickness is 0.5 μm or more and 2.0 μm or less, and the magnetic layer
The coercive force is 158 KA / m or more and 237 KA / m or less.
The magnetic recording medium as described in (2) above, wherein [0008] BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.
To do. The coercive force Hc of the magnetic material used for the magnetic layer is 79 KA /
m to 316 KA / m, preferably 158 KA / m
The above is 237 KA / m or less. Using the magnetic material
A magnetic liquid is prepared by mixing and dispersing with a mixture, and 0.05% on the support.
By applying a thin magnetic layer of not less than 1 μm and not more than 1 μm,
Providing a durable magnetic recording medium that maintains output
The Details of the magnetic layer will be described. Magnetic recording of the present invention
The magnetic layer of the medium is formed by dispersing ferromagnetic powder in a binder.
Is. The ferromagnetic powder used is ferromagnetic iron oxide,
Cobalt-containing ferromagnetic iron oxide, barium ferrite powder or
Is a ferromagnetic metal powder or the like. F as a ferromagnetic metal powder
e, Ni, Fe-Co, Fe-Ni, Co-Ni, Co
-Ni-Fe or other simple substance or alloy is mentioned.
Within 20 mass% or less, aluminum, silicon, sulfur
Yellow, scandium, titanium, vanadium, chromium, man
Gun, copper, zinc, yttrium, molybdenum, lodge
Palladium, gold, tin, antimony, boron, barium
Tantalum, tungsten, rhenium, silver, lead, lithium
Lanthanum, cerium, praseodymium, neodymium, te
Lulu, bismuth, etc. can be included. The magnetic powder is, for example, disclosed in JP-A-8-2.
As described in Japanese Patent No. 55334, Co is Fe
10 to 40 at%, Al is 2 to 20 at%,
Sintering that Y is contained in 1 to 15 at%
It is preferable from the viewpoint that it is less and excellent in dispersibility. Ma
The ferromagnetic metal powder contains a small amount of water, hydroxide or oxide.
It may be included. Further, the magnetic recording medium of the present invention
The ferromagnetic powder used in the magnetic layer of Fe is mainly composed of Fe.
The major axis length is 0.05 to 0.19 μm and the crystal
That the child size is 100 to 230 mm, the magnetic powder
From the viewpoint of reducing noise while maintaining high filling
Good. Furthermore, it is used for the magnetic layer of the magnetic recording medium of the present invention.
The ferromagnetic powder has a coercive force of 79 to 316 KA / m.
And σs is 100 to 180 A · m²/ Kg
This reduces recording demagnetization loss and is due to thermal fluctuations.
This is preferable from the viewpoint of preventing the amount of magnetization from being reduced. In addition, strong
SSA of magnetic powder is 35-60m²/ G, pH is 7
That the above is the appropriate dispersion viscosity and binder
It is preferable from the viewpoint of affinity. Hexagonal ferrite
In the case of a ferromagnetic ferromagnetic powder, the plate diameter is 40 nm or less, preferably
35 nm or less is preferable. Hc is similar to acicular alloy powder
A range is preferred. σs is 45 to 75 A · m²/ Kg (e
mu / g), preferably 50 to 70 A · m²/ Kg (e
mu / g), plate ratio (plate diameter / thickness) of 2 to 15, preferably
Or 3-8. Average particle volume is 2000-1200
0nm^ThreePreferably 3000 to 10000 nm^ThreeIn
The The methods for producing these ferromagnetic powders are already known, and
The ferromagnetic powder used in the light is manufactured according to a known method.
Can be built. The shape of the ferromagnetic powder is not particularly limited, but
Usually acicular, granular, dice, rice granular (also called spindle shape)
U) and plate-like ones are used. Especially needle or
It is preferable to use spindle-shaped ferromagnetic powder. The present invention
In the case of a binder, a curing agent and a ferromagnetic powder,
Methyl ethyl keto used in the preparation of magnetic paints
Such as ethylene, dioxane, cyclohexanone, ethyl acetate, etc.
It is kneaded and dispersed together with the agent to form a magnetic layer forming coating. For kneading
The dispersion can be carried out according to the usual methods. The crystal used in the magnetic layer of the magnetic recording medium of the present invention.
Examples of the mixture include conventionally known thermoplastic resins and thermosetting resins.
Fats, reactive resins and the like can be used. Preferred buy
The binder is made of vinyl chloride resin, vinyl chloride-vinyl acetate resin.
Fatty, nitrocellulose and other fiber-based resins, phenoxy trees
Fat and polyurethane resin. Among them, vinyl chloride
Resin, vinyl chloride-vinyl acetate resin, polyurethane resin
Is used to make the hardness of the backcoat layer
It is better because it can be close and the back shot can be reduced.
Good. In addition, a ring structure and an ether group
Dispersibility is improved by including polyurethane resin containing
It is preferable from the viewpoint of producing. Particularly preferred binders are diols and organic binders.
Polyureta obtained by reaction with diisocyanate
Resin having a cyclic structure as the diol.
Short chain diols and long chain diones with ether linkages
17 to 17 on the basis of polyurethane resin
From what contains 40 mass% and 10-50 mass%
And the ether bond in the long-chain diol
Containing 1.0 to 5.0 mol / g of the resin
Is. Tg is -20 to 150 ° C, preferably 2
It is 0-120 degreeC, More preferably, it is 50-100 degreeC. The cyclic part of the long-chain diol is aliphatic or aromatic
In any case, the coating film Tg is preferably 50 to 150 ° C.
70 to 100 ° C, calendar processing temperature ± 30 ° C =
The coating film Tg is optimized so as to become the coating film Tg, and the calendar
Binder composition to ensure both formability and coating strength
Is preferably prepared. The binder is usually a polyisocyanate hard.
It is cured by the agent. Polyurethane resin 100
The amount of the curing agent used relative to parts by mass is 0 to 150 parts by mass, preferably
Preferably 0-100 parts by weight, more preferably 0-50 quality.
It is a quantity part. The hydroxyl group content in the polyurethane resin is:
The number is preferably 3 to 20 per molecule, more preferably
The number is preferably 4 to 5 per molecule. Per molecule
Reactivity with polyisocyanate curing agent when it is less than 3
Therefore, the strength and durability of the coating film are likely to decrease.
On the other hand, if it exceeds 20, the solubility and dispersibility in the solvent will be low.
Easy to lower. Adjust the hydroxyl group content in the polyurethane resin.
In order to adjust the
You can. Specifically, trimethylol ethane, tri
Methylolpropane, trimellitic anhydride, glycerin
, Pentaerythritol, hexanetriol, special public
Polyester polyol described in JP-A-6-64726
Dibasic acid from the raw material and the compound as a glycol component
Branched polyester having a tri- or higher functional hydroxyl group
And polyether esters. Is preferred
It is a trifunctional one.
And easily gelled. Polyurethane resin has -SO in the molecule.
_ThreeM, -OSO_ThreeM, -COOM, -PO_ThreeMM ',-
OPO_ThreeMM ', -NRR', -N⁺RR'R "COO
-(Where M and M 'are each independently a hydrogen atom,
Potassium metal, alkaline earth metal or ammonium salt
R, R ′ and R ″ are each independently an aryl group having 1 to 12 carbon atoms.
At least one polar group selected from
And particularly preferably —SO
_ThreeM, -OSO_ThreeM. The amount of these polar groups is preferred
Or 1 × 10^-Five~ 2x10^-Foureq / g, especially
Preferably 5 × 10^-Five~ 1x10^-Foureq / g. 1
× 10^-FiveIf it is less than eq / g, the adsorption to the powder is insufficient.
Therefore, the dispersibility decreases, and 2 × 10^-FourMore than eq / g
If so, the solubility in the solvent decreases, so the dispersibility decreases.
The Number average molecular weight (Mn) of polyurethane resin
Is preferably 5000 to 100,000, more preferably
Or 10,000 to 50,000, particularly preferred
Is 20,000-40,000. Less than 5000
Is low in strength and durability of the coating film. 100,000
If it is more, the solubility and dispersibility in the solvent are low. Polyureta
The cyclic structure of the resin affects the rigidity and the ether group is flexible
Contributes to sex. The above-mentioned polyurethane resin has high solubility.
Large inertia radius (molecular spread) and powder dispersibility
Is good. Also, the hardness of the polyurethane resin itself (high
Tg, high Young's modulus) and toughness (elongation)
I have. The organic solvent used in the present invention may have any ratio.
With acetone, methyl ethyl ketone, methyl isobutyl ketone
, Diisobutyl ketone, cyclohexanone, isophor
Ketones such as Ron, tetrahydrofuran, 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,
Use N-dimethylformamide, hexane, etc.
Yes. These organic solvents are not necessarily 100% pure.
In addition to the main components, isomers, unreacted substances, side reactions, decomposition
It does not matter if impurities, oxides, moisture, etc. are included.
Yes. These impurities are preferably 30% or less, more preferably
Preferably it is 10% or less. The organic solvent used in the present invention is
It is preferable that the magnetic layer and the nonmagnetic layer are the same type.
Yes. The amount added may be changed. Surface on nonmagnetic layer
High tension solvents (cyclohexanone, dioxane, etc.)
To improve coating stability, specifically upper layer solvent composition
The arithmetic mean value of is not lower than the arithmetic mean value of the lower layer solvent composition
It is important. In order to improve dispersibility
Higher polarity is preferable, and the dielectric constant is 1 in the solvent composition.
It is preferable that 50% or more of 5 or more solvents are contained. Ma
The solubility parameter is preferably 8-11.
Yes. In addition to the above components, the coating material for forming the magnetic layer contains α
―Al₂O_Three, Cr₂O_ThreeAbrasives such as carbon black
Antistatic agents, fatty acids, fatty acid esters, silicone resins
Commonly used additives such as lubricants and dispersants
Alternatively, a filler may be included. The center particle size of the abrasive is 1/3 of the upper layer thickness.
It is preferably 2 times, more preferably 1/2 to 1.5 times. 1
/ 3 or less, durability deteriorates, and if it is twice or more, head wear
Will increase. The number of surface abrasives is 20-200 / 2.
25 μm²Is preferable, 30 to 100/225 μm²
Is more preferred. If it is less than 20, head burn-in occurs.
To be born. If it is 200 or more, head wear increases. Main departure
SiO added in the bright₂Particles are 1-50 nm central particles
It is preferably spherical in diameter. More preferably 1-3
0 nm. If the particle diameter is 1 to 50 nm,
) Even if 3 to 10% by mass is added, surface properties are deteriorated.
There is almost no deterioration of electromagnetic conversion characteristics because there is no magnetic layer surface
Diffusion evenly to relax the contact between the head and the magnetic layer
Improves. Also spherical and Al₂O_ThreeMore Morse
Since the hardness is small, head wear does not increase. concrete
An example is AEROSIL. AEROSIL
  50, 200, 200CF, 380, R972, R9
74 or the like. The magnetic layer of the magnetic recording medium of the present invention has a high electric power.
In order to obtain magnetic conversion characteristics, a flat surface roughness Ra of 4 nm or less
A smooth magnetic layer. Magnetic layer Tg is 30 ° C or higher and 150 ° C
The viewpoint that the following is to improve running durability
To preferred. In addition, the thickness of the magnetic layer is digital recording performance
From the viewpoint of the sharpness of magnetization reversal to increase
~ 1μm, preferably 0.05 ~ 0.6μm, more preferred
It is 0.1 to 0.4 μm. Magnetic layer is 0.01 or more
When it is down, it is essentially no longer a magnetic layer. 1μ magnetic layer
If m or more, so-called self-demagnetization loss increases at the same time
Furthermore, the surface properties become rough. Single or multiple magnetic layers
Can be achieved. In the case of a plurality of magnetic layers, for example,
A technique such as that disclosed in Japanese Patent Laid-Open No. 6-139555 can be applied. More
In addition, the magnetic recording medium of the present invention has a squareness ratio of 0.80 or more.
And that the SFD is 0.5 or less.
This is preferable from the viewpoint of erasing characteristics. Next, the detailed contents of the lower nonmagnetic layer will be explained.
Light up. Nonmagnetic inorganic powders include metal oxides, metal carbonates,
Metal sulfate, metal nitride, metal carbide, metal sulfide, etc.
It can be selected from inorganic compounds and non-magnetic metals. Nothing
Examples of the organic compound include titanium oxide (TiO 2).₂, Ti
O), α-alumina, β-al with 90-100% alpha
Mina, γ-alumina, α-iron oxide, chromium oxide, suboxide
Lead, tin oxide, tungsten oxide, vanadium oxide, charcoal
Silicon nitride, cerium oxide, corundum, silicon nitride, titanium
Carbide, silicon dioxide, magnesium oxide, dioxide
Luconium, boron nitride, calcium carbonate, calcium sulfate
, Barium sulfate, molybdenum disulfide, goethite,
Use aluminum hydroxide alone or in combination.
You can. Particularly preferred are titanium dioxide and suboxide.
Lead, iron oxide, and barium sulfate are more preferable.
Titanium oxide or iron oxide. Nonmagnetic metals include C
u, Ti, Zn, Al and the like. These non-magnetic powders
The average particle size of the powder is preferably 0.005 to 2 μm
If necessary, combine non-magnetic powders with different average particle sizes
Or even a single non-magnetic powder with a wide particle size distribution.
It is possible to have the same effect. Especially preferred
Is a non-magnetic powder having an average particle size of 0.01 μm to 0.2 μm
It is. It is particularly preferred that the non-magnetic powder has a pH of 6-9.
That's right. Specific surface area of non-magnetic powder is 1-100m²/ G, good
Preferably 5-50m²/ G, more preferably 7 to 40 m
²/ G. The crystallite size of non-magnetic powder is 0.01μ
It is preferable that it is m-2micrometer. Oil absorption using DBP
5-100ml / 100g, preferably 10-80m
1/100 g, more preferably 20-60 ml / 100
g. The specific gravity is 1 to 12, preferably 3 to 6.
The shape can be any of needle, spindle, sphere, polyhedron and plate
There may be. The ignition loss should be 20% by mass or less.
preferable. Mohs hardness of the inorganic powder used in the present invention
The degree is preferably 4 or more. Rough surface of these powders
The nes factor is preferably 0.8 to 1.5, more preferably
What is new is 0.9 to 1.2. Stearic acid (SA)
Adsorption amount is 1-20μmol / m², More preferably 2 to
15 μmol / m²It is. At 25 ℃ of the lower non-magnetic powder
Heat of wetting into water is 20000 nJ (200 erg / c
m²) ~ 60000 nJ (600 erg / cm²)
It is preferable that it exists in a range. Also within this wet heat range
Can be used. At 100-400 ° C
The appropriate amount of water molecules on the surface is 1-10 / 100 ／.
The The pH of the isoelectric point in water is preferably between 3 and 6.
Good. On the surface of these powders, Al₂O_Three, S
iO₂TiO₂, ZrO₂, SnO₂, Sb₂O_ThreeZnO
It is preferable to surface-treat with. Especially preferred for dispersibility
Is Al₂O_Three, SiO₂TiO₂, ZrO₂In Although,
More preferred is Al.₂O_Three, SiO₂, ZrO₂It is.
These may be used in combination or used alone.
You can also. Also, surface treatment co-precipitated according to the purpose
Layer may be used, or after first treating with alumina
A structure in which the surface layer is treated with silica and vice versa
You can also. The surface treatment layer can be changed to a porous layer according to the purpose.
It's okay, but generally it's better to be homogeneous and dense.
Yes. Specific examples of the non-magnetic powder used in the present invention
Examples include UA5600, UA5605, manufactured by Showa Denko,
AKP-20, AKP-30, AKP-5 manufactured by Sumitomo Chemical
0, HIT-55, HIT-100, ZA-G1, Japan
Chemical Industries, G5, G7, S-1, Toda Industries, T
F-100, TF-120, TF-140, R516,
Ishihara Sangyo TTO-51B, TTO-55A, TTO-
55B, TTO-55C, TTO-55S, TTO-5
5D, FT-1000, FT-2000, FTL-10
0, FTL-200, M-1, S-1, SN-100,
R-820, R-830, R-930, R-550, C
R-50, CR-80, R-680, TY-50, Chita
ECT-52, STT-4D, STT-30
D, STT-30, STT-65C, made by Mitsubishi Materials
T-1, Nippon Shokubai NS-O, NS-3Y, NS-8Y,
Take-100 MT-100S, MT-100T, MT-15
0W, MT-500B, MT-600B, MT-100
F, Sakai Chemical's FINEX-25, BF-1, BF-1
0, BF-20, BF-1L, BF-10P, Dowa Mining
DEFIC-Y, DEFIC-R, Titanium Industry Y-
LOP and the thing which baked it are mention | raise | lifted. In addition, carbon black is mixed in the lower layer.
It is possible to lower the surface electrical resistance Rs, which is a known effect.
Yes. For this purpose, rubber furnaces and rubber thermals
, Black for color, acetylene black, etc.
Can be. Specific surface area is 100-500m²/ G,
Preferably 150-400m²/ G, DBP oil absorption is 2
0-400ml / 100g, preferably 30-200m
1/100 g. The average particle size of carbon black is
Usually 5 mμ to 80 mμ, preferably 10 to 50 mμ
Preferably it is 10-40 mμ. Carbon black
pH 2-10, moisture content 0.1-10%, tap density
Is preferably 0.1 to 1 g / ml. Used in the present invention
A specific example of carbon black is Cabot
Made by BLACKPEARLS 2000, 1300, 10
00, 900, 800, 880, 700, VULCAN
    XC-72, manufactured by Mitsubishi Chemical Industries, # 3050B, 3
150B, 3250B, # 3750B, # 3950B,
# 950, # 650B, # 970B, # 850B, MA
-600, made by Konronbia Carbon, CONDUCT
EX SC, RAVEN 8800, 8000, 700
0, 5750, 5250, 3500, 2100, 200
0, 1800, 1500, 1255, 1250, Akzo
-Ketjen Black EC manufactured by the company. Surface treatment of carbon black with a dispersant
Or part of the surface even if it is grafted with resin
You may use what made it graphite. Ma
Before adding carbon black to the paint,
It may be dispersed with a binder. These carbon bras
The pack does not exceed 50% by mass relative to the inorganic powder.
Can be used within a range not exceeding 40% of the total mass of the non-magnetic layer
The These carbon blacks can be used alone or in combination.
Can be used. Carbo that can be used in the present invention
For example, “Carbon Black Handbook Car Bomb”
You can refer to “The Rack Association”. Nonmagnetic layer
Binder, lubricant, dispersant, additive, solvent, dispersion method
Otherwise, the magnetic layer can be applied. In particular, the binder
The amount, type, additive, amount of added dispersant, type
A known technique relating to the adhesive layer can be applied. The thickness structure of the magnetic recording medium of the present invention is non-magnetic.
Flexible support is 1 to 50 μm, preferably 3 to 10 μm,
The total thickness of the magnetic layer and the nonmagnetic layer is a nonmagnetic flexible support.
It is used in the range of 1/100 to 2 times the thickness. Also,
To improve adhesion between nonmagnetic flexible support and nonmagnetic layer
An undercoat layer may be provided. The thickness of this primer layer
0.01-2 μm, preferably 0.02-0.5 μm
is there. Also, back the nonmagnetic support on the side opposite to the magnetic layer side.
A coat layer may be provided. This thickness is 0.1-2
μm, preferably 0.3 to 1.0 μm. these
Known undercoat layers and backcoat layers can be used. The non-magnetic flexible support used in the present invention is
Polyethylene terephthalate, polyethylene naphthalate
Polyesters, polyolefins, etc.
Rear acetate, polycarbonate, polyamide, poly
Imide, polyamideimide, polysulfone, aramid,
Known films such as aromatic polyamides can be used. Good
The aromatic polyamide resin is, for example, a general formula -NHCO-Ar₁-CONH-Ar₂− (Where Ar₁, Ar₂Is at least one aromatic ring
A divalent organic group containing 6 to 25 carbon atoms
Preferably within range) or -CO-Ar_Three-NH- (Where Ar_ThreeContains at least one aromatic ring
It is a divalent organic group and preferably has a carbon number in the range of 6-25.
Containing 50 mol% or more of the structural unit represented by
Can be. For example, paraphenylene terephthal
Luamide, paraphenylene isophthalamide, metafe
Nylene terephthalamide, metaphenyl isophthalami
The thing which consists of dodo etc. is mentioned. In addition to the phenyl nucleus
Has substituents such as nitro, alkyl, and alkoxy groups
Something to do is also included. In this aromatic polyamide
More mainly laphenylene terephthalamide
Preferably, mechanical strength and elastic modulus are large, moisture absorption is low,
In addition, it has excellent heat resistance and good mechanical and thermal dimensional stability.
Therefore, it is suitable as a material for a good high density recording medium.
Constructing an aromatic polyamide having the structure as described above
Examples of monomers include acid chlorides such as terephthalic acid chloride.
And paraphenylenediamine, metaphenylenediamine, etc.
The diamine can be mentioned. The aromatic polyamide is, for example, a patent No.
This is described in Japanese Patent No. 2628898. Also aromatic
Polyamide is also available as a commercial product.
Kasei Kogyo Co., Ltd.) and Mikutron (Toray Industries, Inc.)
I can make it. These supports are pre-corona
Discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment
You may do the reason. To achieve the object of the present invention
Includes a non-magnetic flexible support with a centerline average surface roughness
(Toff value 0.25 mm) is preferably 0.05 μm or less.
0.04 μm or less, more preferably 0.02 μm
It is necessary to use: Also these non-magnetic
The support is not just a low centerline average surface roughness.
In addition, it is preferable that there are no coarse protrusions of 1 μm or more. Also
The roughness of the surface can be added to the support as needed.
Freely controlled by the size and amount of the label
It is. Examples of these fillers include Ca,
In addition to oxides and carbonates such as Si and Ti, acrylics, etc.
Organic fine powder. Non-magnetic used in the present invention
The F-5 value in the tape longitudinal direction of the support is preferably 5-5.
0 kg / mm²The F-5 value in the tape width direction is preferably
3-30kg / mm²F-5 in the tape longitudinal direction
Generally, the value is 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 longitudinal 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 5-100kg in both directions
/ Mm²The elastic modulus is 100-2000kg / mm²Preferred
That's right. The magnetic recording medium of the present invention has a layer other than the magnetic layer.
The thing which has is included. For example, on the opposite side of the magnetic layer
Back coat layer, nonmagnetic layer containing nonmagnetic powder, soft magnetic
Soft magnetic layer containing conductive powder, second magnetic layer, cushion layer,
May have overcoat layer, adhesive layer, protective layer
Yes. These layers can perform their functions effectively.
It can be provided at an appropriate position so as to be able to. The thickness of the layer is 0.01 to 1 for the magnetic layer, for example.
μm, preferably 0.05 to 0.6 μm, more preferably
Is 0.1 to 0.4 μm, and the nonmagnetic layer is 0.1 to 3 μm.
m, preferably 0.5-3 μm, more preferably 0.6
It can be set to ˜2 μm. Nonmagnetic layer thickness is magnetic
Thicker than the layer is preferred. Also has two magnetic layers
A magnetic recording medium is also preferred. In this case, for example, the upper layer
0.2-2 μm, preferably 0.2-1.5 μm,
The lower layer can be 0.8-2 μm. The back cover formed on the magnetic recording medium of the present invention.
The thickness of the gate layer is set in the range of 0.05 to 1 μm.
Is preferred. Among them, within the range of 0.2-0.8μm
It is preferable to set to. In the back coat layer of the magnetic recording medium of the present invention,
It is preferable to use a granular oxide. With granular oxide
Of titanium oxide, α-iron oxide or a mixture thereof.
It is preferable to use either one. Titanium oxide and α-oxidation
As the iron, those usually used can be used. Ma
The shape of the particles is not particularly limited. If spherical, grains
Those having a diameter of 0.01 to 0.1 μm are also needle-shaped
In this case, it is appropriate that the needle ratio is 2 to 20,
Those having an axial length of 0.05 to 0.3 μm are preferred. grain
At least part of the surface of the oxide is modified with another compound
Or another compound, for example Al₂O_Three, SiO₂,
ZrO₂It may be covered with. The back coat layer has a car for preventing electric resistance.
Bon black is preferably used. Back coat layer
The carbon black used for
Widely used ones can be used. example
For example, furnace black for rubber, thermal black for rubber
, Carbon black for color, acetylene black, etc.
Can be used. Unevenness of backcoat layer is magnetic layer
In order not to appear in the
Is preferably 0.3 μm or less. Particularly preferred grains
The diameter is 0.01 to 0.1 μm. In addition, backcoat
The amount of carbon black used in the
Degree (transmission value of Macbeth TR-927) is 2.0 or less
It is preferable to be in the range. In order to improve running durability, the average particle size
Use two different types of carbon black
It is advantageous. In this case, the average particle size is from 0.01
A first carbon black in the range of 0.04 μm;
The average particle size is in the range of 0.05 to 0.3 μm
A combination with the second carbon black is preferred. First
The content of the carbon black of 2 is the same as that of the granular oxide and the first
When the total amount of carbon black is 100 parts by mass,
0.1 to 10 parts by weight is suitable, 0.3 to 3 parts by weight
Part is preferred. The mass ratio of particulate oxide to carbon black is
60/40 to 90/10, more preferably 70/30 to
80/20. Thus, the granular oxide is converted to carbon.
By containing a larger amount than black,
Form a backcoat layer with good dispersibility and a smooth surface.
You can. Backcoat layer shape having such a composition
The composition paint is a bag mainly composed of conventional carbon black.
High thixotropy compared to paint for forming quat
Yes. For this reason, the extrusion method and the graffiti are highly concentrated.
Via-type coating or the like can be performed. like this
By applying a high concentration paint, the film thickness is thin
Nevertheless, the adhesive strength with the support is large and the mechanical strength is high.
A backcoat layer having a high degree can be formed. The amount of binder used is that of particulate oxide and car.
10-4 with the total mass of Bon Black as 100 parts by mass
It is selected from the range of 0 part by mass, more preferably 20 to 32
Make parts by mass. Back coat formed in this way
The film strength of the layer is high and the surface electrical resistance is low. In the binder for the backcoat layer of the present invention
Are known thermoplastic resins, thermosetting resins, reactive trees
Fats and the like can be used. The magnetic recording medium of the present invention is, for example, after drying.
So that the layer thickness is within the predetermined range described above.
Apply paint to the surface of the aromatic polyamide film
It can be manufactured by vapor deposition. Multiple magnetism
Apply multiple layers of paint or non-magnetic paint sequentially or simultaneously
May be. As an applicator for applying magnetic paint
Air doctor coat, blade coat, rod coat
Coating, 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 For example, General Technology Center Co., Ltd.
-"Latest coating technology" (May 3, 1983)
1 day). In order to achieve the object of the present invention,
Known manufacturing techniques can be used as part of the process
Of course, in the kneading process, continuous kneading and processing
It is also possible to use the one with strong kneading force such as pressure kneader
Yes. Ferromagnetic when using continuous or pressure kneader
All or part of the powder and binder (but all bonds)
30% or more of the agent is preferred) and 100 ferromagnetic powders
Kneaded in the range of 15 to 500 parts by weight with respect to the parts by weight
The The details of these kneading treatments are disclosed in JP-A-1-10.
Described in Japanese Patent No. 6338 and Japanese Patent Application Laid-Open No. 64-79274
Has been. When adjusting the lower non-magnetic layer liquid
It is desirable to use a dispersion medium with high specific gravity.
Near beads are preferred. The magnetic recording medium having a multilayer structure of the present invention is applied.
The following configurations can be proposed as examples of devices and methods
The 1. Gravure coating commonly used in the application of magnetic paint
Cloth, roll coating, blade coating, extrusion coating
First, apply the lower layer with a cloth device, etc., and the lower layer is wet.
Japanese Patent Publication No. 1-46186 and Japanese Patent Application Laid-Open No. 60-
No. 238179 and JP-A-2-265672
DISCLOSURE OF SUPPORTED PRESSURE EXTRUSION EXTRACTION COATING DEVICE
Apply the upper layer by placing. 2. JP-A-63-88080, JP-A-2-17
No. 971 and JP-A-2-265672.
One with two slits for coating liquid passing through
The upper and lower layers are applied almost simultaneously by the application head. 3. It is disclosed in JP-A-2-174965
For extrusion coating equipment with backup roll
More upper and lower layers are applied almost simultaneously. Incidentally, a magnetic recording medium by agglomeration of magnetic particles.
In order to prevent deterioration of the electromagnetic conversion characteristics of
No. 95174 and JP-A-1-236968.
Coating liquid inside the coating head by the method as shown
It is desirable to impart shear to the surface. Furthermore, the viscosity of the coating solution
The degree is disclosed in Japanese Patent Laid-Open No. 3-8471.
It is necessary to satisfy the numerical range. Magnetic recording of the present invention
In order to obtain a medium, it is necessary to perform strong orientation. 0.
1T (1000G) or more solenoid and 0.2T (20
00G) or more cobalt magnets with the same polarity facing each other
Is preferred, and the orientation after drying is the highest.
It is preferable to provide a suitable drying process before orientation.
Yes. Also, it is not necessary to apply the present invention as a disk medium
An alignment method that randomizes the alignment is necessary.
The Also, change the orientation direction of the upper and lower magnetic layers
The orientation direction is always the longitudinal direction and the in-plane direction.
There is no need, and it can be oriented in the vertical and width directions. The back coat layer is an abrasive or an antistatic agent.
A bag in which any particulate component and binder are dispersed in an organic solvent
Apply the coating for forming the coat layer on the opposite side of the magnetic layer
Can be prepared. Said preferred state
Like, the use of granular oxides than carbon black
If the amount is increased, sufficient dispersibility can be secured.
Therefore, it is possible to back without roll kneading, which was conventionally required.
A paint for forming a coat layer can be prepared. Also,
-If the bon black content is low, cyclohexanone
Of residual cyclohexane after drying
Can be reduced. The applied magnetic layer is a strong layer contained in the magnetic layer.
The magnetic powder is dried after magnetic field orientation treatment. Magnetic field orientation
Can be appropriately performed by methods well known to those skilled in the art.
The The magnetic layer is super calendered after drying.
The surface is smoothed using a tool or the like. Surface smoothing treatment
Caused by the removal of solvent during drying
The voids disappear and the filling rate of the ferromagnetic powder in the magnetic layer is improved.
The Therefore, a magnetic recording tape with high electromagnetic conversion characteristics is obtained.
Can be. As the calendering roll, epoxy is used.
Heat resistance of polyimide, polyamide, polyamideimide, etc.
Use plastic rolls. Also treated with metal roll
You can also The magnetic recording medium of the present invention has good smoothness.
It is preferable to have a surface. To improve smoothness
For example, select a specific binder as described above.
It is effective to apply the above calendering treatment to the formed magnetic layer.
is there. The calendar process sets the temperature of the calendar roll to 6
0-100 ° C, preferably 70-100 ° C, especially preferred
Or 80 to 100 ° C., and the pressure is 100 to 500 kg /
cm, preferably 200-450 kg / cm, particularly preferred
Or 300 to 400 kg / cm. Obtained
The magnetic recording tape is of the desired size using a cutter etc.
It can be used after cutting. After calendar processing
Magnetic recording tape is heat-treated to reduce heat shrinkage.
It is common to do. The magnetic layer surface of the magnetic recording medium of the present invention and
The friction coefficient for SUS420J on the opposite side of
Is less than 0.5, more preferably less than 0.3, surface resistivity is preferred
Or 10^Four-10¹²Ohm / sq, 0.5% of magnetic layer
The elastic modulus in elongation is preferably 10 in both the longitudinal direction and the width direction.
0-2000kg / mm²(980-19600MP
a) The breaking strength is preferably 1 to 30 kg / cm²(9
8000 to 2940000 Pa), elasticity of magnetic recording medium
The rate is preferably 100-1500 in both the longitudinal direction and the width direction.
kg / mm²(980 to 14700 MPa) Residual growth
Is preferably any temperature below 0.5% and below 100 ° C
The heat shrinkage rate in degrees is preferably 1% or less, more preferably
Is 0.5% or less, most preferably 0.1% or less
The Glass transition temperature of magnetic layer (dynamic measured at 110 Hz
(Maximum point of loss elastic modulus in dynamic viscoelasticity measurement) is 50 ° C. or more and 12
0 ° C. or lower is preferable, and that of the lower nonmagnetic layer is from 0 ° C. to 10 ° C.
0 ° C. is preferred. Loss modulus is 1 × 10⁸~ 8x10⁹
dyne / cm²(1 × 10⁷ ~ 8x10⁸N / m²)
The loss tangent is preferably 0.2 or less.
It is preferable. If the loss tangent is too large, adhesion failure will occur.
Cheap. The residual solvent contained in the magnetic layer is preferably
100 mg / m²Or less, more preferably 10 mg / m²
The residual solvent contained in the second layer is contained in the first layer.
It is preferable that the amount is less than the residual solvent. Has a magnetic layer
The porosity is preferably 30 volumes for both the non-magnetic lower layer and the magnetic layer.
% Or less, more preferably 20% by volume or less. Void
The lower the rate, the better for achieving high output.
Depending on the purpose, it may be better to secure a certain value. Example
For example, magnetic recording for data recording where repetitive usage is important
The medium has a higher porosity and better running durability
There are many. The magnetic characteristic of the magnetic recording medium of the present invention is a magnetic field of 10K.
When measured at Oe (796KA / m)
The squareness ratio of the direction is 0.70 or more, preferably 0.80
More preferably, it is 0.85 or more. Tape running
The squareness ratio in the two directions perpendicular to the direction is the squareness ratio in the traveling direction.
It is preferably 80% or less. SFD of magnetic layer (S
Witching Field Distribu
(tion) is preferably 0.5 or less. AFM
(Atomic Force Micro Scope
RMS (root mean square) surface roughness R obtained by evaluation according to e)
_RMSIs preferably in the range of 2 nm to 15 nm. The magnetic recording medium of the present invention comprises a lower nonmagnetic layer and an upper layer.
It has a magnetic layer, but it can be a nonmagnetic layer or a magnetic layer depending on the purpose.
It is easily estimated that these physical properties can be changed.
It is to be. For example, increase the elastic modulus of the magnetic layer
Improves durability and at the same time increases the elastic modulus of the nonmagnetic layer
Lower the magnetic recording medium to hit the head
Etc. What is in each of two or more magnetic layers
Whether to bring about physical properties is a known technology related to magnetic layer stacking
Can be helpful. For example, Hc of the upper magnetic layer
Higher than lower layer Hc is Japanese Patent Publication No. 37-2218
Many publications such as Japanese Laid-Open Patent Publication No. 58-56228, etc.
There is a clear, but to make the magnetic layer thin like the present invention
Thus, recording is possible even with a magnetic layer having a higher Hc. [0054] The present invention will be described in more detail with reference to the following examples.
As will be described, the present invention is not limited to these examples
is not. <How to make magnetic tape> Magnetic layer Example 1   Ferromagnetic metal fine powder (composition Fe / Co = 100/30) 100 parts           Hc 2350 Oe (187 KA / m)           Specific surface area by BET method 49m²/ G           Crystallite size 160Å           Surface coating compound Al₂O_Three, SiO₂, Y₂O_Three           Particle size (major axis diameter) 0.09μm           Needle ratio 7           σs: 145 A · m²/ Kg (145 emu / g)   10 parts of vinyl chloride copolymer (MR-110 manufactured by Nippon Zeon)   Polyurethane resin (Toyobo UR8200) 6 parts   α-Al₂O_Three(Average particle size 0.15 μm) 5 parts   AEROSIL 200 (average particle size 12 nm) 5 parts   Carbon black (average particle size 0.08 μm) 0.5 parts   Butyl stearate 1 part   Stearic acid 5 parts   90 parts of methyl ethyl ketone   30 parts of cyclohexanone   60 parts of toluene [0055] Lower coating layer (non-magnetic)   Nonmagnetic powder α-Fe₂O_Three      80 parts of hematite           Long axis length 0.15μm           Specific surface area by BET method 52m²/ G           pH 8           Tap density 0.8           DBP oil absorption 27-38g / 100g           Surface coating compound Al₂O_Three, SiO₂   20 parts of carbon black           Average primary particle size 16nm           DBP oil absorption 80ml / 100g           pH 8.0           Specific surface area by BET method 250m²/ G           Volatiles 1.5%   12 parts of vinyl chloride copolymer (MR-110 manufactured by Nippon Zeon)   Polyester polyurethane resin (Toyobo UR5500A) 5 parts   α-Al₂O_Three(Average particle size 0.3 μm 1 part   Butyl stearate 1 part   1 part of stearic acid   100 parts of methyl ethyl ketone   50 parts of cyclohexanone   50 parts of toluene For the above-mentioned paint, each component is opened
-After kneading with a die, it was dispersed using a sand mill.
An abrasive slurry was mixed with the obtained magnetic liquid. Obtained
Polyisocyanate (Nippon Polyurethane Co., Ltd.)
Add 5 parts of Coronate L) to the coating solution of the lower coating layer,
Add 1 part of the magnetic upper layer and add methyl ethyl ketone to each.
Ton and cyclohexanone mixed solvent 40 parts is added, 1 μm
Filter with a filter having an average pore size of
The coating liquid for forming the cloth layer and the magnetic layer was adjusted. Obtained
The thickness of the lower layer coating layer coating solution after drying is 1.3 μm.
Furthermore, immediately after that, the thickness of the magnetic layer on it is
Apply a magnetic layer with a thickness of 6.5 μm so that the thickness is 0.25 μm.
The center line surface roughness of the cloth surface is 0.001 μm polyethylene
Both layers are coated simultaneously on the reeflet support.
Is still wet, 0.5T (5000G)
Cobalt magnet with magnetic force and 0.4T (4000G) magnetism
Metal roll after orientation and drying by a powerful solenoid
And a seven-stage calendar composed of epoxy resin rolls
Processing at a speed of 200 m / min at a temperature of 100 ° C.,
Thereafter, a back layer having a thickness of 0.5 μm was applied. 6.3
DVCPRO tape 12 slit to 5mm width
A 3 fraction was made. Example 1 Add 9.5 parts by mass of abrasive (alumina),
₂5 parts by mass of particles (12 nm) were added. Examples 2 and 5 SiO to be added₂The particle size was changed. Examples 3 and 4 SiO to be added₂Change the amount of added particles (30nm)
It was. Comparative Example 1 SiO₂Was not added. Comparative Example 2 SiO₂Increasing amounts of particles were added. Fine particle SiO₂Add
In Examples 1 to 5, durability (100 p
Dirty) was good. Comparative Example 1 that was not added was resistant to
Permanence deteriorated. Increased amount of Comparative Example 2 and coarse particles were added.
In Comparative Example 3, the surface property was rough and the BER was deteriorated. Table results
1 and Table 2. [0058] [Table 1] [0059] [Table 2]Comparative Example 4 increased the amount of abrasive and increased the surface abrasive.
I did it. Comparative Example 5 reduces the amount of abrasive and reduces the surface abrasive.
It was. The number of surface abrasives is 200/225 μm²is more than
And head wear increases, and if the surface abrasive is too little, Si
O₂Even when the particles were added, head contamination increased. table
The number of surface abrasives is 20-200 / 225 μm²To do
Is necessary. In Comparative Example 6, the abrasive particles are
It was larger than twice. Head wear increased. Comparative Example 7
Wears fine particle alumina abrasive and head wear exceeds 0.5μm
Increase the amount to a level that is not possible, and check if it is compatible with head contamination.
SiO₂No particles added
For this reason, the head was so dirty that durability could not be ensured. Result
The results are shown in Table 3. [0061] [Table 3] <Reproduction output> Commercial digital VTR (DV
CPRO) AJ-D750 (made by Matsushita Electric Industrial Co., Ltd.)
The BER was measured at 25 ° C. and 60% RH. <Full-length running> Business-use digital VTR (DVCPRO)
AJ-D750 (manufactured by Matsushita Electric Industrial Co., Ltd.), 23 ° C. 5
Play in 0% RH environment; repeat rewind 100 times, all
The head dirt was evaluated after a long run. Each head shoulder
-The stain on the part was judged by the 5-point method. F with many numbers
This indicates that the lid is not dirty. <Head wear> Digital VTR for business use (DVCPRO)
AJ-D750 (manufactured by Matsushita Electric Industrial Co., Ltd.), 23 ° C
Recording in a 50% RH environment; rewinding; playing 8 volumes continuously
The amount of wear was measured. <Number of surface abrasives> The surface of the tape was 2000 using SEM.
Five sheets were observed at 0 times, and the number of abrasives on the surface was counted. <Still> A digital VTR (DVCPRO) for business use
Using J-D750 (manufactured by Matsushita Electric Industrial Co., Ltd.), 23 ° C. 10
Measures time to decrease -6dB output in% RH environment
did. [0063] In order to obtain excellent electromagnetic conversion characteristics, a magnetic layer is provided.
The surface is smoothed and the surface of the magnetic layer and the head and cylinder
The contact frequency increases, the magnetic layer is scraped from the surface, and the drop
Uto and clogging increase. Abrasives to improve this
Increasing the amount increases head wear. Head wear reduction
For this purpose, the method of atomizing the abrasive is taken, but the tape
Repeatedly to reduce carbon and magnetic layer protrusions.
As a result, the contact between the abrasive and the head is not avoided,
Wear increases. Also, as the abrasive becomes smaller, the still durability
Deteriorates. Abrasives must be kept at an appropriate size
The The surface properties are smooth, and the size and surface of the abrasive
Obtaining excellent repeated durability while maintaining the number
is required. According to the present invention, strong polishing like alumina
Spherical and fine SiO without power₂Fill the magnetic layer with particles
By maintaining the surface characteristics smooth, electromagnetic conversion characteristics
Do not damage the head and increase head wear.
And found that excellent running durability was obtained.

Continued front page    (72) Inventor Kinokata Shinnosuke             2-1-12 Ogimachi, Odawara-shi, Kanagawa Prefecture             Shishi Photo Film Co., Ltd. F-term (reference) 5D006 BA07 BA10 BA19 DA04 FA02                       FA05

Claims (1)

What is claimed is: 1. A magnetic recording medium having a surface roughness of a magnetic layer of 4 nm or less, comprising at least one magnetic layer formed by dispersing ferromagnetic powder in a binder on a nonmagnetic support. The number of surface abrasives is 20 to 200/225 μm ² and the average particle size is 1 to 50 nm. A magnetic recording medium comprising 3 to 10% by mass of SiO ₂ particles other than an abrasive.