JPH07210852A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having high electromagnetic conversion characteristics for recording signals in a wide range from short wavelength to long wavelength, especially having a low error rate for digital recording and excellent overwriting characteristics. CONSTITUTION:This magnetic recording medium consists of a nonmagnetic layer essentially comprising a nonmagnetic powder and a binder resin and a magnetic layer essentially comprising a ferromagnetic powder and a binder resin formed on the nonmagnetic layer. The magnetic layer is made thin as <=1.5mum. As for the ferromagnetic powder, a hexagonal ferrite magnetic material is used. The magnetic layer is formed in such a manner that easily-magnetized axis is in a range from 20 to 70 in the plane which is perpendicular to the magnetic layer and in the longitudinal direction and that the squareness ratio in the longitudinal direction in the magnetic layer plane is 0.3-0.95 time of the squareness ratio in the direction of the easily-magnetized axis (without correction for diamagnetizing field. Further, the squareness ratio (without correction for diamagnetizing field) in the perpendicular direction to the magnetic layer is 0.2-0.9 time of the squareness ratio (without correction for diamagnetizing field) in the direction of the easily-magnetized axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic medium for high density recording, and more particularly to a magnetic recording medium having a thin magnetic layer containing hexagonal ferrite as a ferromagnetic powder on a non-magnetic layer. Related to the improvement of.

[0002]

2. Description of the Related Art Conventionally, for magnetic recording media such as video tapes, audio tapes, magnetic disks, etc., ferromagnetic iron oxide, Co modified ferromagnetic iron oxide, CrO ₂ , ferromagnetic alloy powder, etc. are used as binders. A magnetic layer in which the magnetic layer dispersed in the above is coated on a non-magnetic support is widely used. However, since these magnetic materials are usually needle-shaped and magnetized in the longitudinal direction, the effects of self-demagnetization and recording demagnetization become large in the short-wavelength recording required today, and sufficient output can be obtained. There was a problem of not having.

JP-A-58-6526 and JP-A-62.
No. 236140 proposes a magnetic recording medium using a hexagonal ferrite magnetic material. However, in these inventions, sufficient output was not obtained in the short wavelength region. Further, it is possible to further reduce self-demagnetization / recording demagnetization by orienting the hexagonal ferrite magnetic material in the in-plane vertical direction.
It is disclosed in Japanese Patent No. 249124. However, since the hexagonal ferrite has a small saturation magnetization, there is also a problem that the long-wavelength output is low particularly when vertically oriented. further,
When an isolated waveform is recorded / reproduced, the reproduction peak value appears to deviate from the origin, and there is also a problem that the waveform processing must be performed through the correction circuit.

As another method for improving the reproduction output over a wide range from the short wavelength region to the long wavelength region, Japanese Patent Laid-Open No. 48-48
-88910 and Japanese Patent Application Laid-Open No. 3-35420 disclose so-called oblique orientation in which the easy magnetization axis direction is inclined from the in-plane longitudinal direction. However, the magnetic materials used in these inventions are not specified or are acicular particles, and self demagnetization / recording demagnetization cannot be sufficiently reduced, and the output in the short wavelength region is insufficient. Further, when acicular particles are used, the magnetic substance on the extreme surface falls in the in-plane longitudinal direction due to the calendar treatment after coating, and the merit of oblique orientation cannot be fully utilized, which is why high density recording is required. There was a limit in terms.

Therefore, in Japanese Patent Laid-Open No. 4-360020, a barium ferrite magnetic material is used for the upper magnetic layer and a needle-shaped magnetic material is used for the lower magnetic layer, and an obliquely oriented magnetic layer in which the easy axis of magnetization is tilted from the in-plane longitudinal direction is used. Recording media have been proposed. As a result, the output from the long-wavelength region to the short-wavelength region is improved, and the distortion of the isolated waveform, which is considered to be caused by the perpendicular component of the magnetization, is improved. However, considering the digital records that will be important in the future, the following points were insufficient.

That is, the thickness of the magnetic layer is as thick as 2 μm or more, the half width of the isolated inverted waveform becomes wide, the interference between the waveforms becomes large as the density becomes high, and the block error rate becomes large. The overwriting property is poor due to the large thickness of the magnetic powder, and because the lower layer is the magnetic layer, it is difficult to disperse the magnetic powder compared to the non-magnetic powder. Could not be sufficiently smooth, and so on.

In order to solve the above-mentioned problems (1) and (2), the magnetic layer has been thinned, but if the magnetic layer is thinned to about 2 μm or less, the surface of the magnetic layer is likely to be affected by the non-magnetic support, and the electromagnetic field is reduced. Conversion characteristics deteriorated. For this reason, it is known that a nonmagnetic thick undercoat layer is provided on the surface of a nonmagnetic support and then the magnetic layer is provided as an upper layer.
No. 6 and Japanese Patent Application Laid-Open No. 63-191315, there is a drawback that coating defects are likely to occur when the magnetic layer is thinly coated. As a method of solving this, Japanese Patent Laid-Open No.
As disclosed in JP-A-3-191315 and JP-A-63-187418, there is a method of providing a non-magnetic layer as a lower layer by using a simultaneous multilayer coating method. According to this method, the surface of the magnetic layer can be made smooth even if the thickness of the upper magnetic layer is made thin, but as a recording medium with a high density as required today such as a digital recording system. ,
The characteristics were still insufficient. JP-A-5-29
Japanese Patent No. 0356 discloses, as a medium capable of obtaining a high output from a short wavelength region to a long wavelength region, a magnetic layer composed of a hexagonal ferrite ferromagnetic powder having a magnetization easy axis in an oblique direction and a non-magnetic lower layer. Recording media have been proposed. But,
The method disclosed therein as a means for making the easy axis of magnetization oblique is a method of using a pair of orienting magnets or a magnet for vertical orientation.
The ratio of the longitudinal orientation component or the vertical orientation component was increased, and the distribution in the easy axis direction of magnetization was insufficient for obtaining a high output. Therefore, it was not sufficient in terms of short wavelength output and overwriting characteristics which are important in high density digital recording.

[0008]

SUMMARY OF THE INVENTION The present invention has a high electromagnetic conversion characteristic in a recording signal over a wide range from a short wavelength to a long wavelength, and in particular, a magnetic recording having a low error rate in digital recording and an excellent overwrite characteristic. It is intended to provide a medium.

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have scrutinized the problems of the above-mentioned prior art, and have earnestly studied the physical properties of the magnetic layer and the magnetic substance contained in the layer structure having good electromagnetic conversion properties. As a result of the examination, a non-magnetic layer in which an inorganic non-magnetic powder was mainly dispersed in a binder was provided as a non-magnetic layer on a non-magnetic support, and the ferromagnetic powder in the thin magnetic layer on the non-magnetic layer was replaced by a hexagonal ferrite magnetic material. As a result, as a result of studying by paying attention to its magnetic orientation degree and grain arrangement, it was found that the object of the present invention can be achieved by using a magnetic layer having the following layer constitution and characteristics.

That is, in a magnetic recording medium in which a non-magnetic layer mainly composed of non-magnetic powder and a binder resin and a magnetic layer mainly composed of a ferromagnetic powder and a binder resin are provided on a non-magnetic support. The magnetic layer has a thickness of 1.5 μm or less, the ferromagnetic powder contains a hexagonal ferrite magnetic substance, and the easy axis of magnetization of the magnetic layer stands in the longitudinal direction from the magnetic layer surface. Within the range of 20 ° to 70 ° in the vertical plane, the squareness ratio in the longitudinal direction in the magnetic layer plane is 0.3 to 0.95 of the squareness ratio in the easy magnetization axis direction (without demagnetizing field correction). And the squareness ratio in the direction perpendicular to the magnetic layer surface (without demagnetizing field correction) is in the direction of the easy axis of magnetization (without demagnetizing field correction).
It is possible to achieve the above-mentioned object of the present invention by using a magnetic recording medium characterized by being 0.2 to 0.9.

In the present invention, a hexagonal ferrite is used for the ferromagnetic powder, and the thin magnetic layer of 1.5 μm or less is formed not only in the plane of the magnetic layer but also in the longitudinal direction of the magnetic layer. It is important for future high-density recording to define the direction of easy magnetization in the perpendicular plane and the squareness ratio in that direction in comparison with the squareness ratio of the magnetic layer surface and the perpendicular term of the magnetic layer. It is characterized by the fact that

The reason why the magnetic recording medium of the present invention exhibits excellent electromagnetic conversion characteristics is considered as follows. When a signal is recorded on a magnetic recording medium by a ring head, the lower portion of the magnetic layer is easily recorded in the longitudinal direction and the upper portion of the magnetic layer is easily recorded in the vertical direction due to the influence of the head magnetic field distribution. Therefore, in the magnetization inside the magnetic layer, both the longitudinal magnetization component and the perpendicular magnetization component contribute to the reproduction output. However, the ring head has a greater effect on the reproduction output of the longitudinal magnetization component, and therefore, it is disclosed in JP-A-3-28021.
As described in Japanese Unexamined Patent Publication No. 5 (1994), it is expected that the reproduction output will be improved if the residual magnetic flux density in the longitudinal direction is higher than the residual magnetic flux density in the vertical direction. However, when the recording signal has a short wavelength, the output is significantly reduced. There are three possible causes for this.

That is, the signal written on the reading side is canceled by the reversal magnetic field on the trading side, the influence of the perpendicular component of the magnetization becomes large, and the recorded magnetization becomes unstable due to the influence of the demagnetizing field ( So-called self-demagnetization).

With respect to, the easy axis of magnetization is 20 ° to 70 °.
If tilted within the range, the magnetic field direction on the trading side becomes the hard axis direction of the medium, and the signal written on the reading side becomes difficult to erase.

Regarding the above items 1 and 2, it is effective to increase the perpendicular component of the magnetization. However, if the easy axis of magnetization is made larger than 70 °, naturally the longitudinal component is decreased and the output in the long wavelength region is decreased. Also, if the vertical component is too large, the symmetry of the isolated inverted waveform becomes poor and the peak shift is large.
In digital recording, the block error rate increases unless a correction circuit is introduced.

In consideration of the above, the easy axis of magnetization of the magnetic recording medium is inclined at 20 to 70 °, preferably 30 to 50 ° from the in-plane longitudinal direction, and the ratio to the squareness ratio in the longitudinal direction is 0. .3 to 0.95, preferably 0.6 to 0.9, and the ratio to the squareness ratio in the vertical direction is set to 0.2 to 0.9, preferably 0.4 to 0.7. As a result, the optimum magnetization perpendicular component, longitudinal component, and diagonal component can be obtained. The squareness ratio in each direction is a value without demagnetizing field correction.

In the present invention, the longitudinal direction is substantially the running direction of the magnetic head, which is the longitudinal direction of the tape in the case of a magnetic tape and the circumferential direction of the magnetic recording disk. In a magnetic recording medium for a VTR having a rotary head,
Strictly speaking, the running direction of the magnetic head forms an angle with the longitudinal direction of the magnetic tape, but in the present invention, it was considered that it substantially coincides with the longitudinal direction of the magnetic tape.

However, the above-mentioned Japanese Laid-Open Patent Publication No. 4-36002.
When the thickness of the magnetic layer (overall upper and lower layers) is 2 μm or more as in JP-A-0, the self-demagnetization was large, and the effect of oblique orientation could not be sufficiently obtained. In addition, the half-value width of the isolated inverted waveform was widened, intersymbol interference was large, and the error rate during high-density recording was increased. Furthermore, the overwrite characteristic was also insufficient. Therefore, by setting the magnetic layer to have a thickness of 1.5 μm or less, an unexpected and significant improvement in the short wavelength output was observed. In addition, the error rate, which narrows the full width at half maximum of the isolated waveform, is reduced, and the overwrite characteristic is improved.

When a single layer is used, the calender moldability deteriorates, the surface roughness of the magnetic surface increases, the spacing loss increases, and the reproduction output decreases. Therefore, in the present invention, the thickness of the upper magnetic layer is 1.5 μm or less, preferably 0.8 to 0.1 μm. Interference increases and the error rate increases. In addition, the overwrite characteristic is also deteriorated, which is not preferable. If the thickness of the upper magnetic layer becomes too thin, the thickness becomes nonuniform, so the lower limit of the thickness is about 0.1 μm.

The following constitution can be used as an example of an apparatus and method for coating a magnetic recording medium having a multilayer constitution as in the present invention. 1. A lower layer is first coated by a gravure coating, a roll coating, a blade coating, an extrusion coating device or the like which is generally used for coating a magnetic layer coating liquid, and when the lower layer is in a wet state, Japanese Patent Publication No. 1-486186. The upper layer is coated by a support pressure type extrusion coating apparatus disclosed in JP-A-60-238179 and JP-A-2-265672. 2. JP-A-63-88080, JP-A-2-179
No. 71, JP-A-2-265672, the upper and lower layers are applied almost simultaneously by a single coating head having two slits for passing the coating liquid. 3. The upper and lower layers are coated almost at the same time by an extrusion coating device with a backup roll disclosed in JP-A-2-174965.

In order to prevent the deterioration of the electromagnetic conversion characteristics and the like of the magnetic recording medium due to the agglomeration of magnetic particles, JP-A-62-62
It is desirable to apply shear to the coating liquid inside the coating head by the method disclosed in Japanese Patent Publication No. 95174 or Japanese Patent Laid-Open No. 1-236968. Further, the viscosity of the coating liquid needs to satisfy the numerical range disclosed in Japanese Patent Application No. 1-312659.

Among the above-mentioned coating methods, according to the present invention,
In particular, a so-called wet-on-wet method in which the upper layer coating liquid is applied onto the lower layer coating liquid 2 or 3 while the lower layer coating liquid is still wet is preferable. Wet on
By providing the non-magnetic layer and the magnetic layer on the non-magnetic support by the wet method, there is an advantage that peeling of the non-magnetic correlation from the magnetic layer is less likely to occur and coating defects are less likely to occur.

In order to set the direction of the easy axis of magnetization and the range of the squareness ratio of the magnetic recording medium of the present invention to the above-mentioned ones, the method of magnetic orientation of hexagonal ferrite is particularly important.
It can be achieved by the following alignment method.

That is, it is a method of sequentially performing the following steps. After coating, before entering the drying zone, 3000G or more,
Longitudinal orientation is preferably made with a homopolar anti-cobalt magnet of 5000 G or more, then a vertical magnet of 1000 G or more, preferably 2000 G or more is installed in the drying zone A, and the solvent content of the coating solution before entering the drying zone A is 50 wt% or more with respect to the coating liquid,
Desirably 70 wt% or more, the solvent content after passing through the drying zone A is 20 to 50 wt%, preferably 30 to 40 wt%, and then the drying zone A (perpendicular magnetizing magnet is installed, A solenoid magnet of 1000 G or more, preferably 2000 G or more, in a drying zone B (a zone in which a solenoid magnet is installed and a drying air is fed to dry while raising the temperature) adjacent to a zone where the drying air is fed to raise the temperature to dry) Is installed and the solvent content after passing through the drying zone B is set to 10 wt% or less, preferably 5 wt% or less.

The solvent content in each zone can be controlled by the solvent composition of the coating liquid, the thickness constitution, the temperature of the drying zone, the air flow rate, and the magnetic field strength of the magnet. Further, it is desirable to install a repulsive magnet in order to eliminate the bending of the magnetic field near the outlet of the solenoid because the magnetization component in the width direction is reduced.

The above method is different from the conventional method in which the direction of the easy axis of the hexagonal ferrite and the direction of the squareness of the magnetic layer are controlled mainly in the plane of the magnetic layer and in the vertical direction, and at most in the oblique direction. Cannot be found by any means, and was first found by quantitatively defining its direction in order to make a magnetic recording medium suitable for future high-density recording as in the present invention.

Examples of the hexagonal ferrite magnetic substance contained in the ferromagnetic powder of the magnetic layer of the magnetic recording medium of the present invention include barium ferrite, strontium ferrite, lead ferrite, calcium ferrite substitutes, and Co substitutes.
Hexagonal Co powder can be used. Specific examples include magnetoplumbite-type barium ferrite and strontium ferrite, and magnetoplumbite-type barium ferrite and strontium ferrite containing a part of a spinel phase.Al, in addition to other predetermined atoms,
Si, S, Sc, Ti, V, Cr, Cu, Y, Mo, R
h, Pd, Ag, Sn, Sb, Te, Ba, Ta, W,
Re, Au, Hg, Pb, Bi, La, Ce, Pr, N
d, P, Co, Mn, Zn, Ni, Sr, B, Ge, N
It may contain atoms such as b. Generally Co-T
i, Co-Ti-Zr, Co-Ti-Zn, Ni-Ti
It is possible to use those to which elements such as —Zn and Ir—Zn are added, but particularly preferable are Co substitution products of barium ferrite and strontium ferrite.
When the SFD of the uppermost layer in the longitudinal direction is 0.3 or less, the distribution of coercive force becomes small, which is preferable. In order to control the coercive force, the particle diameter and the particle thickness are made uniform, the thickness of the spinel phase of hexagonal ferrite is made constant, the amount of substitution elements of the spinel phase is made constant, the substitution site of the spinel phase There is a method such as keeping the place of. The hexagonal ferrite used in the present invention is usually hexagonal plate-like particles, and the particle diameter means the plate width of the hexagonal plate-like particles and is measured by using an electron microscope. In the present invention, the particle diameter (plate diameter) is 0.01 to
0.2 [mu] m, particularly preferably 0.03 to 0.1 [mu] m. Further, the average thickness (plate thickness) of the fine particles is 0.001 to 0.2 μ, but particularly 0.00
3 to 0.05 μm is desirable. Further, the plate ratio (particle size / plate thickness) is 1 to 15, and preferably 3 to 7. The specific surface area (SBET) of these hexagonal ferrite fine powders by the BET method is 25 to 100 m ² / g, 40 to 70 m
² / g is desirable. When it is 25 m ² / g or less, noise becomes high, and when it is 100 m ² / g or more, it is difficult to obtain the surface property of the magnetic layer, which is not desirable. The coercive force of magnetic material is 1000 Oe or more, 40
00 Oe or less is desirable, and more preferably 1200 Oe or more and 3000 Oe or less. If it is 1000 Oe or less, the short wavelength output is lowered, and if it is 4000 Oe or more, recording by the head is difficult and it is not desirable. σs is 50 emu / g or more, preferably 6
It is 0 emu / g or more. The tap density is preferably 0.5 g / cc or more, more preferably 0.8 g / cc or more.

The thickness of the non-magnetic layer in the magnetic recording medium of the present invention is not particularly limited, but the thickness of the non-magnetic layer is usually 0.2 to
It is 5 μm, preferably 1 to 3 μm. The non-magnetic powder used in the non-magnetic layer is, for example, metal oxide, metal carbonate,
It can be selected from inorganic compounds such as metal sulfates, metal nitrides, metal carbides, metal sulfides, and the like. As the inorganic compound, for example, α-alumina having a conversion of 90% or more, β-
Alumina, γ-Alumina, Silicon Carbide, Chromium Oxide, Cerium Oxide, α-Iron Oxide, Corundum, Silicon Nitride, Titanium Carbide, Titanium Oxide, Silicon Dioxide, Sodium Oxide, Magnesium Oxide, Oxide Tank Dust, Silicon Dioxide, Boron Nitride,
Zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide and the like are used alone or in combination.

Of these, titanium dioxide, zinc oxide, iron oxide, barium sulfate, α-iron oxide and the like are preferable.
Titanium dioxide and α-iron oxide are more preferable from the viewpoint that they can be easily dispersed and a smooth surface can be formed, and there is little risk of drop-out due to undispersed substances.

The particle size of the non-magnetic powder is 0.005 to 2
μm is preferable, but non-magnetic powders having different particle sizes may be combined, or a single non-magnetic powder may be used to widen the particle size distribution to obtain the same effect. Especially desirable is 0.01 to 0.2 μm. The tap density is 0.05 to 2 g / cc, preferably 0.2 to 1.
5g / cc. Water content is 0.1-5%, preferably 0.2-3%
Is. The pH is 2-11, but a pH of 6-9 is particularly desirable. Specific surface area is 1 to 100 m ² / g, preferably 5
50 m ² / g, and more preferably a 7~40m ² / g. The crystallite size is preferably 0.01 μm to 2 μm.
DBP oil absorption is 5-100ml / 100g, desirably 10
It is 80 ml / 100 g, more preferably 20 to 60 ml / 100 g. The specific gravity is 1 to 12, preferably 3 to 6. The shape may be needle-like, spherical, polyhedral or plate-like. The loss on ignition is preferably 20% or less. The inorganic powder used in the present invention preferably has a Mohs hardness of 4 or more. The roughness factor of these powder surfaces is 0.8-
1.5 is preferable, and 0.9 to 1.2 is more preferable. The SA adsorption amount is 1 to 20 μmol / m ² , and more preferably ² to 15 μmol / m ² . 25 ° C of non-magnetic powder
Heat of wetting in water at 200 erg / cm ^{2 to} 600 er
It is desirable that g / cm ² be in the range. In addition, a solvent having a heat of wetting in this range can be used. 10
The amount of water molecules on the surface at 0 to 400 ° C is 1 to 10 pieces / 10
0A is suitable. The pH of the isoelectric point in water is preferably between 3 and 6. The surface of these powders is Al
₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb
Surface treatment with ₂ O ₃ or ZnO is desirable. Al ₂ O ₃ , SiO ₂ , TiO ₂ , and ZrO are particularly desirable for dispersibility.
₂ , more preferably Al ₂ O ₃ , SiO ₂ , Z
rO ₂ . These may be used in combination, or may be used alone. Depending on the purpose, a co-precipitated surface treatment layer may be used, or a structure in which the surface layer is first treated with alumina and then the surface layer is treated with silica, or the reverse structure may be employed. The surface treatment layer may be a porous layer depending on the purpose, but it is generally desirable that the surface treatment layer be homogeneous and dense.

Specific examples of the non-magnetic powder used in the present invention include UA5600, UA5605 manufactured by Showa Denko,
Nanotight, Sumitomo Chemical AKP-20, AKP-30,
AKP-50, HIT-55, HIT-100, ZA-
G1, manufactured by Nippon Kagaku Kogyo Co., Ltd., G5, G7, S-1, manufactured by Toda Kogyo Co., Ltd., TF-100, TF-120, TF-140,
R516, DPN250, Ishihara Sangyo TTO-51B,
TTO-55A, TTO-55B, TTO-55C, T
TO-55S, TTO-55D, FT-1000, FT
-2000, FTL-100, FTL-200, M-
1, S-1, SN-100, R-820, R-830,
R-930, R-550, CR-50, CR-80, R
-680, TY-50, Titanium Industry ECT-52, S
TT-4D, STT-30D, STT-30, STT-
65C, T-1, manufactured by Mitsubishi Materials, Nippon Shokubai NS-O,
NS-3Y, NS-8Y, TAYCA MT-100S, M
T-100T, MT-150W, MT-500B, MT
-600B, MT-100F. FINEX-2 made by Sakai Chemical
5, BF-1, BF-10, BF-20, BF-1L,
BF-10P, Dowa Mining DEFIC-Y, DEFIC
-R. It is a Y-LOP made by Titanium Industry and a product obtained by firing it.

The manufacturing method of titanium dioxide which is particularly desirable as the non-magnetic powder will be described in detail. The methods for producing these titanium oxides are mainly the sulfuric acid method and the chlorine method. In the sulfuric acid method, the source ore of illuminite is digested with sulfuric acid and Ti, Fe, etc. are extracted as sulfates. Iron sulfate is removed by crystallization, and the remaining titanyl sulfate solution is purified by filtration and then subjected to thermal hydrolysis to precipitate hydrous titanium oxide. After this is filtered and washed, impurities and impurities are washed and removed, and a particle size regulator and the like are added.
If it is fired at 1000 ° C., it becomes crude titanium oxide. The rutile type and the anatase type are classified according to the kind of the nucleating agent added at the time of hydrolysis. This crude titanium oxide is prepared by crushing, sizing, surface treatment and the like. In the chlorine method, natural or synthetic rutile is used as the raw ore. The ore is chlorinated in a high-temperature reduced state, Ti becomes TiCl ₄ and Fe becomes FeCl ₂ , and iron oxide that becomes solid by cooling is liquid TiCl ₄
And separated. The obtained crude TiCl ₄ is purified by rectification, added with a nucleating agent, and then instantaneously reacted with oxygen at a temperature of 1000 ° C. or higher to obtain crude titanium oxide. The finishing method for imparting pigmentary properties to the crude titanium oxide produced in this oxidative decomposition step is the same as the sulfuric acid method. For the surface treatment, after coarsely pulverizing the titanium oxide material, water and a dispersant are added, wet pulverization and centrifugation are performed to perform coarse particle classification. afterwards,
The fine particle slurry is transferred to a surface treatment tank where the surface coating of metal hydroxide is performed. First, a certain amount of Al, S
An aqueous salt solution of i, Ti, Zr, Sb, Sn, Zn or the like is added, and an acid or an alkali for neutralizing the aqueous solution is added, and the surface of the titanium oxide particles is coated with the produced hydrous oxide. By-produced water-soluble salts are removed by decantation, filtration and washing, and finally the slurry pH is adjusted and filtered, followed by washing with pure water. The washed cake is dried with a spray dryer or band dryer. Finally, the dried product is crushed with a jet mill to obtain a product. In addition to water-based titanium oxide powder, AlCl ₃ , SiCl ₄
It is also possible to carry out the surface treatment of Al and Si by injecting steam after passing through the steam of. For other pigment manufacturing methods, see "Characterization of Po.
wder Surfaces "Academic Pr
You can refer to ess.

Further, the surface electrical resistance (Rs), which is a known effect, can be lowered by mixing carbon black in the non-magnetic layer. For this purpose, rubber furnace, rubber thermal, color black, acetylene black,
Etc. can be used. Specific surface area is 100-500m
² / g, preferably 150 to 400 m ² / g, DBP oil absorption is 20 to 400 ml / 100 g, preferably 30 to 2
It is 00 ml / 100 g. Particle size is 5 to 80 mμ, preferably 10 to 50 mμ, more preferably 10 to 40 m
is μ. pH is 2 to 10, water content is 0.1 to 10%,
The tap density is preferably 0.1 to 1 g / CC. Specific examples of the carbon black used in the present invention include BLACKPEARLS 2000, 13 manufactured by Cabot Corporation.
00, 1000, 900, 800, 880, 700, V
ULCAN XC-72, Mitsubishi Kasei Co., Ltd., # 305
0B, 3150B, 3250B, # 3750B, # 39
50B, # 950, # 650B, # 970B, # 850
B, MA-600, manufactured by Conlon Via Carbon, CON
DUCTEX SC, RAVEN 8800,800
0,7000,5750,5250,3500,210
0,2000,1800,1500,1255,125
0, such as Ketjen Black EC manufactured by Akzo. Carbon black may be surface-treated with a dispersant or the like, may be grafted with a resin, or may be partially graphitized. Also,
Carbon black may be dispersed with a binder in advance before being added to the paint. These carbon blacks can be used within a range not exceeding 50% by weight based on the above inorganic powder and not exceeding 40% by total weight of the non-magnetic layer. These carbon blacks can be used alone or in combination. The carbon black that can be used in the present invention can be referred to, for example, "Carbon Black Handbook" edited by Carbon Black Association.

Organic powder can be used as the non-magnetic powder of the non-magnetic layer. As the organic powder, for example,
Acrylic styrene-based resin powder, benzoguanamine resin powder, melamine-based resin powder, phthalocyanine-based pigment can be mentioned, but polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, polyimide-based resin powder, polyfluorinated ethylene resin is used. It The production method is disclosed in JP-A-62-18564 and JP-A-60-2558.
Those described in Japanese Patent No. 27 can be used.

An undercoat layer has been provided in the conventional magnetic recording medium, but this is provided in order to improve the adhesive force between the support and the magnetic layer, and has a thickness of 0. When the thickness is 0.5 μm or less, the function and the constitution are different from those of the nonmagnetic layer in the invention. Also in the present invention, it is desirable to provide an undercoat layer in order to improve the adhesiveness between the non-magnetic layer and the non-magnetic support.

The non-magnetic layer in the present invention is mainly composed of non-magnetic powder, and the non-magnetic layer of the present invention may contain a small amount of magnetic material within the range in which the effects of the present invention are exhibited. Belongs to the category of. The small amount of magnetic material is 20% by weight or less based on the non-magnetic powder. If it exceeds 20% by weight, the effect of the present invention is lost.

The binder resins in the magnetic layer and the non-magnetic layer in the magnetic recording medium of the present invention are essentially the same. As the binder resin, conventionally known thermoplastic resins, thermosetting resins, reactive resins and mixtures thereof are used.
The thermoplastic resin has a glass transition temperature of -100 to 1
50 ° C., number average molecular weight of 1,000 to 200,000, preferably 10,000 to 100,000, degree of polymerization of about 50 to 1
It is about 000. Such examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid,
Acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyra
Polymers, copolymers containing polyurethane, vinyl acetate, vinyl ether, etc. as constituent units, polyurethane resins,
There are various rubber resins. Further, as the thermosetting resin or the reactive resin, a phenol resin, an epoxy resin, a polyurethane curable resin, a urea resin, a melamine resin, an alkyd resin, an acrylic reaction resin, a formaldehyde resin, a silicone resin, an epoxy-polyamide. Resin, a mixture of polyester resin and isocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, a mixture of polyurethane and polyisocyanate, and the like. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. It is also possible to use a known electron beam curable resin for each layer. For these examples and the manufacturing method thereof, see JP-A-62-
It is described in detail in Japanese Patent No. 256219. The above resins can be used alone or in combination, and are preferably selected from vinyl chloride resin, vinyl chloride vinyl acetate resin, vinyl chloride vinyl acetate vinyl alcohol resin, vinyl chloride vinyl acetate maleic anhydride copolymer, and the like. Examples thereof include a combination of at least one kind and a polyurethane resin, or a combination of these with polyisocyanate.

As the structure of the polyurethane resin, known ones such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate carbonate polyurethane, polyester polycarbonate carbonate polyurethane, and polycaprolactone polyurethane can be used. For all of the binders listed here, COO may be added as necessary to obtain better dispersibility and durability.
_{M, SO 3 M, OSO 3} M, P = O (OM) 2, O-P
═O (OM) ₂ , (wherein M is a hydrogen atom or an alkali metal base), OH, NR ₂ , N ⁺ R ₃ (R is a hydrocarbon group) epoxy group, SH, CN, and the like. It is desirable to use the above-mentioned polar group introduced by copolymerization or addition reaction. The amount of such polar group is 10 ^-1 to 10 ^-8 mol / g, preferably 1
It is 0 ^-2 to 10 ^-6 mol / g.

Specific examples of these binder resins used in the present invention are VAGH and VYH manufactured by Union Carbite Corporation.
H, VMCH, VAGF, VAGD, VROH, VYE
S, VYNC, VMCC, XYHL, XYSG, PKH
H, PKHJ, PKHC, PKFE, Nisshin Chemical Industry Co., Ltd., MPR-TA, MPR-TA5, MPR-TAL,
MPR-TSN, MPR-TMF, MPR-TS, MP
R-TM, MPR-TAO, 1000W manufactured by Denki Kagaku,
DX80, DX81, DX82, DX83, 100F
D, ZEON Corporation MR-105, MR110, MR1
00, 400X-110A, Nippon Polyurethane Co., Ltd. Nipporan N2301, N2302, N2304, Dainippon Ink and Chemicals Pandex T-5105, T-R3080,
T-5201, Barnock D-400, D-210-8
0, Crisbon 6109, 7209, Toyobo Co., Ltd. Byron UR8200, UR8300, UR-8600, UR
-5500, UR-4300, RV530, RV28
0, manufactured by Dainichiseika, Daiferamine 4020, 502
0,5100,5300,9020,9022,702
0, Mitsubishi Kasei Co., MX5004, Sanyo Kasei Co., Ltd. Sampren SP-150, TIM-3003, TIM-300
5, Asahi Kasei Corp. Saran F310, F210, etc.

The binder resin used in the non-magnetic layer or the magnetic layer is 5 to 50 relative to the non-magnetic powder or the ferromagnetic powder.
It is used in the range of wt%, preferably 10 to 30 wt%. It is preferable to use a combination of 5 to 30% by weight when using a vinyl chloride resin, 2 to 20% by weight when using a polyurethane resin, and 2 to 20% by weight of polyisocyanate. In the present invention, when polyurethane is used, the glass transition temperature is -5.
0-100 ° C., elongation at break 100-2000%, stress at break 0.05-10 kg / cm ² , yield point 0.05-
10 kg / cm ² is desirable.

In the magnetic recording medium of the present invention, the amount of binder resin in the magnetic layer and the non-magnetic layer, the amount of vinyl chloride resin, polyurethane resin, polyisocyanate, or other resin in the binder resin. It is, of course, possible to change the molecular weight of each resin forming the magnetic layer, the amount of polar groups, or the physical properties of the resin described above between the non-magnetic layer and the magnetic layer as necessary, and known techniques are applied. it can.
For example, when changing the amount of binder resin in each layer, it is effective to increase the amount of binder resin in the magnetic layer in order to reduce scratches on the surface of the magnetic layer, and to improve the head touch to the magnetic head. Is achieved by increasing the amount of binder resin in the non-magnetic layer to give flexibility.

The polyisocyanate used in the present invention includes tolylene diisocyanate, 4-4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate and naphthylene.
Isocyanates such as 1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate and triphenylmethane triisocyanate, and also
Products of these isocyanates and polyalcohols, polyisocyanates produced by condensation of isocyanates, and the like can be used. Commercially available trade names of these isocyanates are Coronate L, Coronet HL, manufactured by Nippon Polyurethane Co., Ltd.
Coronate 2030, Coronet 2031, Millionaire
To MR Millionate MTL, Takeda Pharmaceutical Co., Ltd., Takenet D-102, Takenet D-110N, Takenet D-
200, Takenet D-202, Sumitomo Bayer Co., Ltd., Desmodule L, Desmodule IL, Desmodule N Desmodule HL, etc., and these are used alone or by utilizing the difference in curing reactivity. Each layer can be used in one or more combinations.

In the magnetic layer and non-magnetic layer of the magnetic recording medium of the present invention, other materials having various functions such as a lubricant, an abrasive, an antistatic agent, a fungicide, and a dispersant are also included. Can be included. As the binder resin, the lubricant, the dispersant, the additive, the solvent, the dispersion method and the like for the magnetic layer and the non-magnetic layer, those conventionally known can be applied. In particular, with respect to the amount and type of binder resin, the amount and type of additive and dispersant added, known techniques for the magnetic layer can be applied.

Examples of the polishing agent used in the present invention include α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, artificial diamond, silicon nitride having an α-conversion rate of 90% or more, Silicon Carbide Titanium Car
Known materials such as bite, titanium oxide, silicon dioxide, boron nitride, etc., mainly having a moth of 6 or more are used alone or in combination. Further, a composite of these abrasives (abrasive surface-treated with another abrasive) may be used. These abrasives may contain compounds or elements other than the main component, but if the main component is 90% or more, the effect remains the same. The particle size of these abrasives is 0.0
1 to 2 μm is desirable, but if necessary, abrasives having different particle sizes may be combined, or a single abrasive may be used to broaden the particle size distribution to obtain the same effect. Tap density is 0.3-2 g / cc, water content is 0.1-5%,
The pH is preferably 2 to 11, and the specific surface area is preferably ¹ to 30 m ² / g. The shape of the abrasive used in the present invention is needle-like, spherical,
Although it may be in a dice shape, one having a corner in a part thereof is preferable because of high abrasivity. Specific examples of the polishing agent used in the present invention include AKP-, manufactured by Sumitomo Chemical Co., Ltd.
20, AKP-30, AKP-50, HIT-50, HI
T-100, Nippon Kagaku Kogyo KK, G5, G7, S-1, Toda Kogyo TF-100, TF-140 and the like can be mentioned. The abrasives used in the present invention can be of different types and combinations in the magnetic layer and the non-magnetic layer, and can be used properly according to the purpose. These abrasives may be dispersed in a binder in advance and then added to the magnetic paint. The number of abrasives present on the surface of the magnetic layer and the end face of the magnetic layer of the magnetic recording medium of the present invention is preferably 5 pieces / 100 μm ² or more.

In the magnetic layer and the non-magnetic layer, as described above,
A material having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect, etc. can be contained. For example, molybdenum disulfide, tungsten disulfide graphite, boron nitride, graphite fluoride, silicone oil, polar group-containing silicone, fatty acid-modified silicone, fluorine-containing silicone.
Amine, fluorine-containing alcohol, fluorine-containing ester, polyolefin, polyglycol, alkyl phosphate and its alkali metal salt, alkyl sulfate and its alkali metal salt, polyphenyl ether, fluorine-containing alkyl sulfate and its alkali metal salt,
Monobasic fatty acids having 10 to 24 carbon atoms (which may include unsaturated bonds or may be branched), and metal salts thereof (Li, Na, K, Cu, etc.) or 12 to 12 carbon atoms 22 monovalent, divalent, trivalent, tetravalent, pentavalent, hexavalent alcohol, (which may contain an unsaturated bond or may be branched), an alkoxy alcohol having 12 to 22 carbon atoms A monobasic fatty acid having 10 to 24 carbon atoms (may contain an unsaturated bond or may be branched) and monovalent, divalent, trivalent, tetravalent, pentavalent having 2 to 12 carbon atoms. , A mono-fatty acid ester, a di-fatty acid ester or a tri-fatty acid ester, which is composed of any one of hexavalent alcohols (which may be unsaturated or branched), and a monoalkyl ether of an alkylene oxide polymer. Tellur fatty acid ester, carbon 8-22 fatty acid amides, 8 carbon atoms
~ 22 aliphatic amines and the like can be used. Specific examples thereof include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, butyl stearate, oleic acid, linoleic acid, linolenic acid, elaidic acid, octyl stearate, amyl stearate, isooctyl stearate. , Octyl myristate, butoxyethyl stearate, anhydrosorbitan monostearate
Anhydrosorbitan distearate, anhydrosorbitan tristearate, oleyl alcohol,
Lauryl alcohol is an example. Further, nonionic surfactants such as alkylene oxide-based, glycerin-based, glycidyl-based, and alkylphenol-ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphonium. Or a cationic surfactant such as sulfonium, anionic surfactant containing an acidic group such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester group, phosphoric acid ester group, amino acid, aminosulfonic acid, amino alcohol Also usable are amphoteric surfactants such as sulfuric acid or phosphoric acid esters, and alkylbedine type. These surfactants are described in detail in "Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.). These lubricants,
Antistatic agents, etc. are not necessarily 100% pure, and in addition to the main components, isomers, unreacted products, by-products, decomposed products, oxides
It does not matter if impurities such as the above are included. The content of these impurities is preferably 30% by weight or less, more preferably 10% by weight or less.

The types and amounts of these lubricants and surfactants used in the present invention can be properly selected in the non-magnetic layer and the magnetic layer. For example, fatty acids having different melting points in the non-magnetic layer and the magnetic layer are used to control the exudation to the surface, the esters having different boiling points and polarities are used to control the exudation to the surface, and the amount of surfactant is adjusted. Therefore, it is considered that the stability of coating is improved, the amount of the lubricant added is increased in the intermediate layer, and the lubricating effect is improved. Needless to say, the examples are not limited to those shown here.

All or a part of the additives used in the present invention may be added at any step in the production of the magnetic and non-magnetic coating materials. For example, when the additives are mixed with the magnetic material before the kneading step, the magnetic material may be added. There are cases where it is added in a kneading step using a binder and a solvent, when it is added in a dispersion step, when it is added after dispersion, and when it is added immediately before coating. In some cases, the purpose may be achieved by applying a part or all of the additives simultaneously or sequentially after applying the magnetic layer according to the purpose. Depending on the purpose, a lubricant may be applied to the surface of the magnetic layer after calendering the surface of the magnetic layer or after completion of slitting.

Examples of commercial products of these lubricants used in the present invention are NAA-102 and NAA-4 manufactured by NOF CORPORATION.
15, NAA-312, NAA-160, NAA-18
0, NAA-174, NAA-175, NAA-22
2, NAA-34, NAA-35, NAA-171, N
AA-122, NAA-142, NAA-160, NA
A-173K, castor hardened fatty acid, NAA-42, NA
A-44, cation SA, cation MA, cation A
B, cation BB, nymine L-201, nymine L-202, nymine S-202, nonion E-20
8, nonion P-208, nonion S-207, nonion K-204, nonion NS-202, nonion NS-
210, nonion HS-206, nonion L-2, nonion S-2, nonion S-4, nonion O-2, nonion LP-20R, nonion PP-40R, nonion SP
-60R, Nonion OP-80R, Nonion OP-85
R, Nonion LT-221, Nonion ST-221, Nonion OT-221, Monoguri MB, Nonion DS-6
0, anon BF, anon LG, butyl stearate, butyl laurate, erucic acid, Kanto Chemical Co., oleic acid, Takemoto Yushi Co., FAL-205, FAL-123,
Made by Shin Nippon Rika Co., Ngerb LO, Njorbu IP
M, Sansosizer-E4030, Shin-Etsu Chemical Co., TA
-3, KF-96, KF-96L, KF96H, KF4
10, KF420, KF965, KF54, KF50,
KF56, KF907, KF851, X-22-81
9, X-22-822, KF905, KF700, KF
393, KF-857, KF-860, KF-865
X-22-980, KF-101, KF-102, KF
-103, X-22-3710, X-22-3715,
KF-910, KF-3935, Lion Armor Co., Amid P, Amid C, Amoslip C
P, Lion Oil and Fat Co., Deuomin TDO, Nisshin Oil Co., BA-41G, Sanyo Kasei Co., Profan 2012
E, Newpole PE61, Ionette MS-400,
Ionet MO-200 Ionet DL-200, Ionet DS-300, Ionet DS-1000 Ionet DO-200 and the like.

The organic solvent used in the present invention may be any ratio of ketones such as acetone, methylethylketone, methylisobutylketone, diisobutylketone, cyclohexanone, isophorone, tetrahydrofuran, methano-, etc.
Alcohols such as alcohol, ethanol, propanol, butanol, isobutyl alcohol, isopropyl alcohol, methylcyclohexanol, etc., methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycoacetate -Esters such as glycol, dimethyl ether, glycol monoethyl ether, glycol ethers such as dioxane, aromatic hydrocarbons such as benzene, toluene, xylene, cresol, chlorobenzene, methylene chloride, ethylene chloride, etc. Chlorinated hydrocarbons such as carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, N,
Those such as N-dimethylformamide and hexane can be used. These organic solvents are not necessarily 100% pure, and may contain impurities such as isomers, unreacted substances, by-products, decomposition products, oxides, and water in addition to the main components. The content of these impurities is preferably 30% by weight or less, more preferably 10% by weight or less. The organic solvent used in the present invention increases the surface roughness of the magnetic layer when the drying rate is greatly different between the magnetic layer and the non-magnetic layer. Therefore, it is desirable to use the same organic solvent for both layers if possible. The addition amount may be changed. A solvent having a high surface tension (cyclohexanone, dioxane, etc.) can be used for the non-magnetic layer to improve the stability of coating. Specifically, it is important that the arithmetic average value of the solvent composition of the upper layer does not fall below the arithmetic average value of the solvent composition of the lower layer. In order to improve the dispersibility, it is desirable that the polarity is strong to some extent, and the dielectric constant of the solvent composition is 1
It is desirable that the solvent contains 5 or more solvents by 50% by weight or more. Further, the dissolution parameter is preferably 8-11.

The thickness of the magnetic recording medium of the present invention is such that the non-magnetic flexible support has a thickness of 1 to 100 μm, preferably 4 to 20 μm.
m. The total thickness of the magnetic layer and the nonmagnetic layer is usually in the range of 1/100 to 2 times the thickness of the nonmagnetic flexible support. Further, as described above, an undercoat layer may be provided between the non-magnetic support and the non-magnetic layer or the magnetic layer to improve the adhesion. At that time, the thickness of the undercoat layer is 0.01 to
It is 2 μm, preferably 0.02 to 0.5 μm.

A backcoat layer may be provided on the side of the non-magnetic support opposite to the side of the magnetic layer. This thickness is 0.1-2
μm, preferably 0.3 to 1.0 μm. Known layers can be used as the undercoat layer and the backcoat layer. The non-magnetic support used in the present invention includes polyesters such as polyethylene terephthalate, polyethylene naphthalate, polyolefins, cellulose triacetate, polycarbonate, polyamide, polyimide, polyamideimide, polysulfone, and the like. Known films such as aramid, aromatic polyamide, and polobenzoxazole can be used, but when a thin support of 10 μm or less is used, a high-strength support such as polyethylene naphthalate or polyamide is used. Is desirable.

If necessary, a laminated type support as shown in JP-A-3-224127 may be used to change the surface roughness of the magnetic surface and the base surface. These supports may be previously subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment and the like. To achieve the object of the present invention, the center line average surface roughness of the non-magnetic flexible support has a cutoff value of 0.
08μm 0.03μm or less, preferably 0.01μ
m or less, and more preferably 0.005 μm or less. These non-magnetic supports have not only a small center line average surface roughness (Ra) but also 1 μm.
It is desirable that the above-mentioned coarse protrusions are not present.

The surface roughness profile can be freely controlled by the size and amount of the filler added to the support, if necessary.
It is what is done. Examples of these fillers include oxides and carbonates of Ca, Si, Ti and the like, as well as organic fine powders of acrylic type and the like. The maximum height SRmax of the support is 1 μm or less, and the ten-point average roughness SRz is 0.5.
μm or less, center plane peak height SRp is 0.5 μm or less, center plane valley depth SRv is 0.5 μm or less, center plane area ratio SS
r is 10% or more and 90% or less, and the average wavelength Sλa is 5 μm
As described above, the thickness is preferably 300 μm or less. The surface protrusions of these non-magnetic supports can be controlled by a filler in the range of 0 to 2000 per 0.1 mm ² in a size of 0.01 to 1 μm.

The F-5 value in the medium running direction of the non-magnetic support used in the present invention is preferably 5 to 50 Kg / mm ² ,
F-5 value in the tape width direction is preferably 3 to 30 Kg / m
m ^2, and Te - flop long side direction F-5 value Te - when it's higher than F-5 value of flop the width direction is generally, there is a particular need to increase the strength in the width direction Not so. Also, 100 ° C. in the tape running direction and the width direction of the support 3
The heat shrinkage rate at 0 minutes is preferably 3% or less, more preferably 1.5% or less, and the heat shrinkage rate at 80 ° C. for 30 minutes is preferably 1% or less, more preferably 0.5% or less.
The breaking strength in both directions 5 to 100 kg / mm ^2, modulus of 100 to 2,000 kg / mm ^2, is desirable.

The steps of producing the coating liquid for the magnetic layer and the coating liquid for the non-magnetic layer of the magnetic recording medium of the present invention are at least a kneading step, a dispersing step, and a mixing step provided before and after these steps, if necessary. Consists of. 2 for each individual process
It does not matter if it is divided into more than two stages. All raw materials such as magnetic materials, non-magnetic powders, binders, carbon blacks, abrasives, antistatic agents, lubricants and solvents used in the present invention may be added at the beginning or in the middle of any step. . In addition, individual raw materials may be divided and added in two or more steps. For example, polyurethane may be divided and added in the kneading step, the dispersing step, and the mixing step for adjusting the viscosity after dispersion. In order to achieve the object of the present invention, it goes without saying that conventionally known manufacturing techniques can be used as a part of the steps, but in the kneading step, a strong kneading force such as a continuous kneader or a pressure kneader is used. It is preferable to use those having When a continuous kneader or a pressure kneader is used, all or part of the magnetic substance or non-magnetic powder and the binder (however, 30% or more of the total binder) and 100 parts by weight of the magnetic substance are used. Kneading is performed in the range of 15 to 500 parts by weight. For details of these kneading treatments, Japanese Patent Application No. 62-264722 and Japanese Patent Application No. 62-236872.
It is described in Japanese Patent Publication No. Further, when adjusting the non-magnetic layer liquid, it is desirable to use a dispersion medium having a high specific gravity, and zirconia beads are suitable.

A heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimide amide is used as the calendering roll. Further, it is also possible to treat with metal rolls. The processing temperature is preferably 7
The temperature is 0 ° C or higher, and more preferably 80 ° C or higher. The linear pressure is preferably 200 Kg / cm, more preferably 30
It is 0 Kg / cm or more.

The magnetic layer surface of the magnetic recording medium of the present invention and its
The friction coefficient of SUS420J on the opposite side is -1
In the range of 0 ℃ to 40 ℃ and humidity of 0% to 95%
0.5 or less, preferably 0.3 or less, desired surface resistivity
More preferably, both the magnetic surface and the back surface are 10 ^Four-10¹²Ohm / s
q, the charge potential is preferably within -500V to + 500V
Yes. Elastic modulus at 0.5% elongation of magnetic layer is running direction and width direction
It is desirable to be 100-2000Kg / mm², Rupture
The strength is preferably 1 to 30 kg / cm², Magnetic recording media
The elastic modulus of is preferably 100 to 100 in both the running direction and the long direction.
1500 Kg / mm², The residual spread is preferably 0.5%
Below, heat shrinkage at any temperature below 100 ° C is desired
1% or less, more preferably 0.5% or less, most
It is preferably 0.1% or less. Glass transition temperature of magnetic layer
Degree (Loss modulus of dynamic viscoelasticity measured at 110 Hz
(Maximum point of) is preferably 50 ° C or higher and 120 ° C or lower.
It is desirable that the temperature of the non-magnetic layer be 0 ° C to 100 ° C. Loss elasticity
Rate is 1 × 10⁸~ 8 × 10⁹dyne / cm²In the range of
It is desirable that the loss tangent be 0.2 or less.
desirable. If the loss tangent is too large, adhesive failure will occur easily.
The residual solvent contained in the magnetic layer is preferably 100 mg /
m²Below, more desirably 10 mg / m²Is
The residual solvent contained in the second magnetic layer is contained in the first magnetic layer
Less than residual solvent is desirable. The sky that the magnetic layer has
The porosity is preferably 30% by volume or less for both the non-magnetic lower layer and the magnetic layer.
Lower, more preferably 20% by volume or less. Porosity is
It is desirable to be small to achieve high output, but for the purpose
Therefore, it may be better to secure a certain value. example
For example, magnetic recording media for data recording, where repeated use is important
It is preferable that running durability is higher for the body with a higher porosity
Many.

The center line surface roughness Ra of the magnetic layer is 0.008.
μm or less, preferably 0.004 μm or less,
RMS surface roughness RRMS obtained by evaluation by FM is 2 nm
It is preferably in the range of -15 nm. The maximum height SRmax of the magnetic layer is 0.5 μm or less, the ten-point average roughness SRz is 0.3 μm or less, the center plane peak height SRp is 0.3 μm or less, and the center plane valley depth SRv is 0.3 μm or less. The area ratio SSr is preferably 20% or more and 80% or less, and the average wavelength Sλa is preferably 5 μm or more and 300 μm or less. The number of surface protrusions on the magnetic layer is 0.01 to 1 μm, and the number is 0 to 2000. These are the fillers of the support
The surface can be easily controlled by controlling the surface property or the surface shape of the roll for calendar treatment.

Although the magnetic recording medium of the present invention has a non-magnetic layer and a magnetic layer, it is easily presumed that the physical properties of the non-magnetic layer and the magnetic layer can be changed according to the purpose. For example, the elastic modulus of the magnetic layer is increased to improve running durability, and at the same time, the elastic modulus of the nonmagnetic layer is made lower than that of the magnetic layer to improve the contact of the magnetic recording medium with the head.

The novel effects of the present invention will be described more specifically below with reference to the following examples.

[0061]

【Example】

<Coating Liquid A for Magnetic Layer> Hexagonal barium ferrite: 100 parts by weight (Hc: 1500 Oe, specific surface area by BET method: 40 m ² / g, average particle diameter (plate diameter): 0.05 μm, average plate thickness: 0. 01 μm, σs: 60 emu / g, surface treatment agent Al ₂ O ₃ : 5% by weight, SiO ₂ 2% by weight) Vinyl chloride copolymer: 8 parts by weight (-SO ₃ Na content: 1 × 10 ⁻⁴ eq) / g, polymerization degree: 300) polyester polyurethane resin ... 8 parts by weight (neopentyl glycol / caprolactone polyol /MDI:0.9/2 6/1, -SO ₃ Na ^{group:. 1 × 10 -4 eq /} g containing ) Α-alumina (particle size: 0.3 μm) 7 parts by weight carbon black (particle size: 0.015 μm) 1 part by weight butyl stearate 1 part by weight stearic acid 3 parts by weight MIBK 1 part by weight Cyclohexanone 91 parts by weight Toluene 91 parts by weight

<Magnetic Layer Coating Liquid B> The magnetic layer coating liquid A was the same as the magnetic layer coating liquid A except that the Hc of the hexagonal barium ferrite of the magnetic material was changed to 900 Oe.

<Coating liquid C for magnetic layer> 100 parts by weight of Co-γ-Fe ₂ O ₃ (Hc: 800 Oe, specific surface area by BET method: 45 m ² / g) Vinyl chloride copolymer: 10 parts by weight ( -SO ₃ Na content: 1 x 10 ^-4 eq / g, degree of polymerization: 300) Polyester polyurethane resin: 5 parts by weight (neopentyl glycol / caprolactone polyol / MDI: 0.9 / 2.6 / 1, -SO ₃ Na group: 1 × 10 ⁻⁴ eq / g included) α-alumina (particle size: 0.3 μm) 5 parts by weight Carbon black (particle size: 0.015 μm) 1 part by weight butyl stearate 1 Parts by weight Stearic acid 3 parts by weight MIBK 91 parts by weight Cyclohexanone 91 parts by weight Toluene 91 parts by weight

<Magnetic Layer Coating Liquid D> Magnetic Layer Coating Liquid C
The same as the coating liquid C for the magnetic layer, except that the ferromagnetic metal powder (H _c : 1500 Oe, specific surface area: 55 m ² / g) was used in place of the ferromagnetic powder Co-γ-Fe ₂ O ₃ in FIG.

<Non-magnetic layer coating liquid 1> Non-magnetic powder TiO ₂ ... 80 parts by weight (crystal type: rutile type, average primary particle size: 0.035 μm, ratio table area by BET method: 40 m ² / g, pH : 7, TiO ₂ content: 90% or more, DBP oil absorption: 27 to 38 g / 100 g, surface treatment agent Al ₂ O ₃ : 8% by weight) carbon black 20 parts by weight (average primary particle diameter: 16 mμ, DBP Oil absorption: 80 ml / 100 g, pH: 8.0, specific surface area according to BET method: 250 m ² / g, volatile matter: 1.5% by weight) Vinyl chloride copolymer: 12 parts by weight (-SO ₃ Na content : 1 × 10 ⁻⁴ eq / g, degree of polymerization: 300) Polyester polyurethane resin: 5 parts by weight (neopentyl glycol / caprolactone polyol / MDI: 0.9 / 2.6 / 1, —SO ₃ Na group: 1 ×) 10 ^-4 eq / g) Butyl stearate: 1 part by weight Stearic acid: 1 part by weight Methyl ethyl ketone: 100 parts by weight Cyclohexanone: 50 parts by weight Toluene: 50 parts by weight

<Non-magnetic layer coating liquid 2> The same as Non-magnetic layer coating liquid 2 except that the following α-iron oxide was used as the non-magnetic powder. (Average primary particle diameter: 0.1 μm, acicular ratio:
8. Specific surface area by BET method: 55 m ² / g, pH:
6)

<Magnetic Layer Coating Liquid 3> Ferromagnetic metal fine powder (Fe / Zn / Ni: 92/4/4) ... 100 parts by weight (Hc: 1500 Oe, specific surface area by BET method: 61 m ² / g, crystal) Child size: 195 Å, surface treatment agent Al ₂ O ₃ : 5% by weight, SiO ₂ : 2% by weight, particle size (major axis diameter): 0.12 μm, acicular ratio: 10, σs: 130 emu / g ) vinyl copolymer ... 9 parts by weight chloride (-SO ₃ Na ^{content: 1 × 10 -4 eq / g} , polymerization degree: 300) polyester polyurethane resin ... 7 parts by weight (neopentyl glycol / caprolactone polyol / MDI: 0.9 / 2.6 / 6/1, —SO ₃ Na group: 1 × 10 ⁻⁴ eq / g) α-alumina (particle size: 0.3 μm) ... 7 parts by weight carbon black (particle size: 0 .10 μm) 1 part by weight Butyl stearate ... 1 part by weight Stearic acid ... 3 parts by weight MIBK ... 96 parts by weight Cyclohexanone ... 48 parts by weight Toluene ... 96 parts by weight

<Magnetic Layer Coating Liquid 4> The magnetic layer coating liquid 3 was the same as the magnetic layer coating liquid 3 except that Co-adhered iron oxide having the following characteristics was used as the ferromagnetic powder. (Hc: 850 Oe (Elsted), BET specific surface area: 45 m ² / g, crystallite size: 250 Å, particle size (major axis diameter): 0.25 μm, acicular ratio: 7, σs: 80 emu /
g) Each component of each of the above coating solutions was kneaded with a continuous kneader and then dispersed using a sand mill.
To the resulting dispersion, 1 part by weight of polyisocyanate was added to the coating liquid for the non-magnetic layer, and 3 parts by weight to the coating liquid for the magnetic layer.
Further, 40 parts by weight of a mixed solvent of methyl ethyl ketone and cyclohexanone was added thereto, and the mixture was filtered using a filter having an average pore size of 1 μm to prepare each coating solution.

<Preparation of Magnetic Recording Medium> With the constitution shown in Table 1, the non-magnetic layer coating liquids 1 and 2 and the magnetic layer coating liquids 3 or 4 were dried to a thickness of 2.0 μm. Immediately thereafter, the thickness of the coating liquid A or B for magnetic layer after drying was changed to form a polyethylene naphthalate support having a thickness of 7 μm and a center line surface roughness of 0.002 μm. Coating was performed by the wet-on-wet method at a coating speed of 200 m / min. 5000G before entering the dry zone
Longitudinal orientation with a homopolar anti-cobalt magnet with magnetic force of
It was passed through a drying zone A in which a 2000 G vertical magnet was installed, and subsequently a drying zone B in which a 2000 G solenoid magnet was installed. After that, it was processed at a temperature of 90 ° C. with a 7-stage calender consisting of only metal rolls, and slit into a width of 8 mm and 3/4 inch,
An 8 mm video tape and a video tape for D2 system were manufactured. Samples of magnetic recording media having different orientations and orientations as shown in Table 2 were prepared by changing the drying temperature and the air flow rate in the A and B zones.

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[Table 1]

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[Table 2]

<Evaluation Method> (Squareness Ratio) Using a vibration sample type magnetometer (manufactured by Toei Industry Co., Ltd.), H
_The squareness ratio was measured every 10 degrees from the longitudinal direction in the in-plane direction of the magnetic layer of each sample at _m 5 kOe in the direction perpendicular to the in-plane direction of the magnetic layer. No demagnetizing field correction was performed. The direction with the largest squareness ratio was taken as the easy axis of magnetization.

(2 MHz, 7 MHz output) A 2 MHz signal and a 7 MHz signal were recorded using a FUJIX8 8 mm video deck manufactured by Fuji Photo Film Co., Ltd., and 2 MHz and 7 MHz signal reproduction outputs when the signals were reproduced were measured by an oscilloscope. It was measured. The reference is 8 mm tape SAGP6-120 manufactured by Fuji Photo Film Co., Ltd.

(Block Error Rate) Sony VTR (commonly called D2) DVR-28 RS-232C terminal on the rear panel to personal computer
It was read by NEC 98 NOTE NV. The measurement conditions were such that the values for every 4 channels were measured every 2 seconds in the SLOW mode by operating the VTR front panel, and the values were averaged for each channel. The averaged error rate every 2 seconds was obtained continuously for 90 points, and the averaged value per 2 seconds is shown in Examples and Comparative Examples.

(Overwrite erasure rate) After the sample was sufficiently demagnetized by a degausser, a 10 MHz single wave was recorded / reproduced at an optimum recording current value, and a 10 MHz single wave value was read by a spectrum analyzer. Value.
Next, overwrite the single wave of 32MHz with the optimum recording current on the same place on the tape, read the single wave component of 10MHz of that part with a spectrum analyzer, and subtract the value after overwriting from the value before overwriting. Then, the value was defined as the overwrite erase rate.

The evaluation results are shown in Table 3.

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[Table 3]

Since sample No. 27 and sample No. 28 use needle-shaped ferromagnetic powder, the direction of easy axis of magnetization on the surface of the magnetic layer that contributes to short wavelength recording is pressure-treated by a calender roll. Due to this, the improvement in the output of short wavelength was not observed, probably because it was oriented in the longitudinal direction or because there was little effect of oblique orientation. In Samples Nos. 29 to 31, the ratio of the squareness ratio in the longitudinal direction of the medium to the squareness ratio in the easy axis direction of the medium was outside the range of the present invention, and an appropriate orientation distribution was not obtained. For this reason, in Samples No. 29 and No. 30, the characteristics oriented in the longitudinal direction were strong, and the low-frequency output was decreased, the error rate was increased due to the distortion of the isolated inverted waveform, and the deterioration of overwrite erasing was observed.

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INDUSTRIAL APPLICABILITY In a magnetic recording medium having a non-magnetic layer on a non-magnetic support and a thin magnetic layer on the non-magnetic support, hexagonal ferrite is used as the ferromagnetic powder, and the direction of the easy axis of magnetization is set to the magnetic layer surface. Within a wide recording wavelength range, by setting the ratio of each squareness ratio within the range of 20 ° to 70 ° in the vertical plane and in the plane of the magnetic layer, the direction of the easy axis of magnetization and the direction perpendicular to the magnetic layer to a specific range. It is possible to obtain a magnetic recording medium which has a high output and is suitable for high density recording, which is most suitable for a digital recording system.

Claims (3)

[Claims] 1. A magnetic recording medium in which a non-magnetic layer mainly composed of non-magnetic powder and a binder resin is provided on a non-magnetic support, and a magnetic layer mainly composed of ferromagnetic powder and a binder resin is provided thereon. The thickness of the magnetic layer is 1.5 μm or less, the ferromagnetic powder is a hexagonal ferrite magnetic substance, and the easy axis of magnetization of the magnetic layer is a vertical plane standing in the longitudinal direction from the magnetic layer surface. Within the range of 20 ° to 70 °, and the squareness ratio in the longitudinal direction within the magnetic layer surface is in the range of 0.3 to 0.95 of the squareness ratio in the easy axis direction (without demagnetizing field correction). And squareness ratio in the direction perpendicular to the magnetic layer surface (without demagnetization correction)
Is 0.2 of the squareness ratio in the direction of easy magnetization axis (without demagnetization correction)
The magnetic recording medium is characterized by being 0.9. 2. The non-magnetic powder contained in the non-magnetic layer is at least one selected from titanium dioxide, barium sulfate, zinc oxide and α-iron oxide.
A magnetic recording medium according to item. 3. The magnetic recording medium according to claim 1, wherein the non-magnetic layer and the magnetic layer are provided by a wet-on-wet coating method.