JPH09265611A - Cleaning medium for magnetic recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the occurrence of damage to a magnetic head in the manner of preventing the sticking of chips to a cleaning medium due to the electrostatic charge at the time of cleaning by providing a lower coating layer consisting of a non-magnetic inorganic powder containing a carbon black having the specified particle diameter, under the cleaning layer. SOLUTION: The lower coating layer consisting of the non-magnetic inorganic powder, 5-49weight% of which are carbon black having the average primary particle diameter of 10-90nm, and a hinder is provided on a non-magnetic material, and the cleaning layer contacting a ferromagnetic powder is formed thereon by a wet-on-wet coating system. When the cleaning is carried out by making the cleaning layer to slide in contact with the surface of the magnetic head, the conductivity of the cleaning medium is improved without adversely affecting the cleaning ability, such as deterioration since the carbon black is combined in the lower coating layer, and the sticking of the chips to the cleaning medium is eliminated by preventing the electrostatic charging, thus the occurrence of scratch on the magnetic head is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning medium for a magnetic recording apparatus such as a magnetic head used for a magnetic recording / reproducing apparatus for audio, video and computer or a cleaning tape used for cleaning a traveling system. is there.

[0002]

2. Description of the Related Art Generally, recording / reproduction of a magnetic recording apparatus for video, audio, and computer is performed by bringing a magnetic head and a magnetic medium such as a magnetic tape into contact with each other and sliding. At this time, if shavings of the magnetic tape or dust around the device adheres to the surface of the magnetic head, the reproduction output becomes low, and further no output can be obtained. In order to recover the reproduction output thus reduced, a cleaning medium such as a cleaning tape for cleaning the dirt attached to the surface of the magnetic head and restoring the reproduction output is used.

[0003] On the other hand, the density of magnetic recording has been increasing year by year, and unless the state of contact between the tip of the magnetic head and the magnetic tape is improved, sufficient recording and reproduction cannot often be performed. In order to keep the so-called head contact satisfactorily, it has become necessary for the cleaning tape not only to clean the magnetic head but also to adjust the head shape to some extent. In particular, in recent years, a magnetic head of a magnetic recording / reproducing apparatus that performs high-density recording such that the shortest recording wavelength is 1 μm or less has been used. The recording / reproducing performance will be hindered.

In the past, ferrites having a high surface hardness have been mainly used for magnetic head materials, but metal heads such as sendust have been used in order to increase the density. Metal heads are compared to ferrite heads.
Because of the softness, the wear of the head increases, so it is important that the amount of wear of the head by the cleaning tape is small.

[0005] As a prior art of a polishing tape used for polishing a magnetic head, for example, Japanese Patent Application Laid-Open No. 62-92205 discloses an intermediate layer containing a non-magnetic powder and a non-magnetic abrasive on a non-magnetic support. There has been disclosed a polishing tape in which polishing layers are sequentially laminated. This polishing tape adopts a two-layer configuration,
While the surface properties of the intermediate layer are made rougher, the particle size of the abrasive particles in the upper polishing layer is made finer to prevent head scratches while maintaining the polishing power. For polishing, the surface roughness is 0.0
Since it is 3 to 0.3 μm, there is much head wear,
It is easily scratched and is not suitable for use as a cleaning tape. The same magnetic head polishing tapes as described above are disclosed in JP-A-62-94270 and JP-A-62-94270.
It is also disclosed in -92205. These also have a two-layered polishing layer, but they are not suitable in terms of obtaining a strong cleaning force without damaging the magnetic head.

As a cleaning tape for a magnetic head, Japanese Patent Application Laid-Open No. Hei 6-139531 discloses a two-layer structure in which two cleaning layers are provided on a flexible support, and the Young's modulus of the upper cleaning layer is reduced by lower cleaning. A technique has been disclosed in which the layer is made larger than the Young's modulus of the layer to achieve both good cleaning properties and low head wear.
However, the cleaning tape of this prior example has a configuration in which both of the two cleaning layers contain ferromagnetic powder, and there is room for improvement with respect to a demand for ensuring strong cleaning properties of the tape as a whole and not damaging the magnetic head. Have.

[0007]

However, when the magnetic head is cleaned using the cleaning medium, shavings are generated, and if the shavings adhere to the cleaning medium, the magnetic head may be damaged. And
It has been found that the adhesion of the scraped powder is caused by the cleaning medium being easily charged.

Therefore, according to the present invention, the cleaning of the magnetic head of the high-density magnetic recording / reproducing apparatus is performed.
It has less head wear and can be used for metal heads, and it has a high cleaning ability to remove dirt with a high cleaning force and restore the reproduction output, and it is possible to prevent the charging of the cleaning medium without impairing the cleaning ability. An object of the present invention is to provide a cleaning medium for a magnetic recording device that does not damage the magnetic head after cleaning.

[0009]

A cleaning medium for a magnetic recording apparatus according to the present invention, which has solved the above-mentioned problems, has a lower coating layer mainly containing a non-magnetic inorganic powder and a binder, which is provided on a non-magnetic support. A cleaning layer containing at least an inorganic powder of ferromagnetic powder and a binder is provided thereon, and the nonmagnetic inorganic powder used in the lower coating layer has a content of 5 to 49.
% By weight is carbon black having an average primary particle diameter of 10 to 90 nm.

The inorganic powder of the cleaning layer is
It is preferable to contain 5% by weight or less of carbon black with respect to the ferromagnetic powder.

It is preferable that the cleaning layer is formed by a wet-on-wet coating method in which the lower coating layer is coated and then formed in a wet state.

[0012]

According to the present invention as described above, the lower layer coating layer containing the non-magnetic inorganic powder and the cleaning layer containing the ferromagnetic powder are provided on the non-magnetic support. Since 5 to 49% by weight of the non-magnetic inorganic powder of the coating layer is carbon black having an average primary particle diameter of 10 to 90 nm, when the cleaning layer is brought into contact with the surface of the magnetic head to perform cleaning. The magnetic head can be strongly cleaned with a smooth surface of the cleaning layer, and the carbon black is mixed in the lower coating layer to improve the conductivity of the cleaning medium without adversely affecting the cleaning property, which makes charging difficult. As a result, the shavings generated by the cleaning do not adhere to the cleaning medium, and Standing can be prevented occurrence of a magnetic head wounds due, also, the cleaning medium magnetic head during cleaning not to damage the magnetic head without things like rise to electrostatic breakdown can be obtained.

If the cleaning layer contains a small amount of carbon black, a smooth cleaning layer can be obtained without impairing the dispersibility of the ferromagnetic powder, and good cleaning power can be exhibited.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below. The basic structure of the cleaning medium of the present invention is as follows: a non-magnetic, flexible support, a lower coating layer mainly composed of a non-magnetic inorganic powder and a binder, and an inorganic powder of at least a ferromagnetic powder thereon. And a cleaning layer containing a binder.

Of the non-magnetic inorganic powder used in the lower coating layer, 5 to 49% by weight has an average primary particle diameter of 10 to 90 n.
m carbon black. Further, it is preferable that the cleaning layer contains carbon black in an amount of 5% by weight or less based on the ferromagnetic powder.

The thickness of the cleaning layer is preferably as thin as 0.05 to 1.0 μm, and the center line average surface roughness Ra of the cleaning layer surface is 1.0 to 1.0 μm.
It is preferably formed to have a smooth thickness of 7.0 nm.

The cleaning layer is formed by applying the lower coating layer on a support and then applying a cleaning layer on the lower coating layer while the lower coating layer is still wet. It is applied by a method (simultaneous or sequential wet application method). The total thickness of the cleaning medium (cleaning tape) is preferably 4 to 15 μm, the thickness of the support is 2 to 10 μm, and the thickness of the lower coating layer is 0.2 to 5.0 μm.

As the magnetic properties of the cleaning layer, the squareness ratio (residual magnetic flux density Br / maximum magnetic flux density Bm) in the magnetization curve measured with an external magnetic field of 10 kOe is 0.6.
0.98, and the coercive force Hc is 500 to 3000 Oe.
It is. The center line average surface roughness R of the support surface
a is preferably from 0.5 to 7.0 nm.

Next, the details of the lower coating layer will be described. First, the inorganic powder used in the lower coating layer of the present invention is a non-magnetic powder, and is selected from inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides, and metal sulfides. be able to.

As the inorganic compound, for example, a gelatinization ratio of 90
% Or more α-alumina, β-alumina, γ-alumina,
θ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, goethite, corundum, silicon nitride,
Titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, etc. are used alone or in combination. Particularly preferred are titanium dioxide, zinc oxide, iron oxide, and barium sulfate, because they are easily available, cost, small in particle size distribution, and many means for imparting functions, and more preferred are titanium dioxide and α. It is iron oxide.

The particle size of these non-magnetic powders is 0.00
The thickness is preferably from 5 to 2 μm, but if necessary, non-magnetic powders having different particle sizes may be combined, or even a single non-magnetic powder may have the same effect by broadening the particle size distribution. Particularly preferably, the particle size of the non-magnetic powder is 0.01 to 0.2 μm. Tap density is 0.05 ~
It is 2 g / ml, preferably 0.2 to 1.5 g / ml. The water content of the non-magnetic powder is 0.1 to 5% by weight, preferably 0.2 to 3% by weight, more preferably 0.3 to 1.5% by weight. The pH of the nonmagnetic powder is 2 to 11, but p
H is particularly preferably between 5 and 10. The specific surface area of the nonmagnetic powder 1 to 100 m ² / g, preferably 5 to 70 m ² /
g, more preferably 10 to 65 m ² / g. The crystallite size of the non-magnetic powder is preferably 0.004 to 1 μm,
0.04 to 0.1 μm is more preferable. Oil absorption using DBP is 5 to 100 ml / 100 g, preferably 10 to 100 ml / 100 g.
80 ml / 100 g, more preferably 20-60 ml /
100 g. The specific gravity is 1 to 12, preferably 3 to 6.

The shape of the above-mentioned non-magnetic inorganic powder may be acicular or granular (including polyhedral shapes from spherical to cubic), but in the case of granular non-magnetic inorganic powder, the average particle diameter is 0.08 μm. 5 for the whole inorganic powder
It is desirable that the content is 0% by weight or more, and in the case of a needle-shaped nonmagnetic inorganic powder, a powder having an average major axis length of 0.05 to 0.3 μm and a needle ratio of 3 to 20 is used for the entire inorganic powder. It is preferable to contain 50% by weight or more.

It is preferable that the ignition loss is 20% by weight or less, and it is considered that it is most preferable that there is no ignition loss. Mohs hardness of the inorganic powder used in the present invention is 4 or more,
Those having 10 or less are preferred. The roughness factor of the surface of these powders is preferably 0.8 to 1.5, and more preferably 0.9 to 1.2. SA (stearic acid) adsorption amount of inorganic powder is 1 to 20 μmol / m
² , more preferably ^{2 to} 15 μmol / m ² . The heat of wetting of the lower coating non-magnetic powder in water at 25 ° C. is 200 to
It is preferably in the range of 600 erg / cm ² . Further, a solvent having a range of the heat of wetting can be used. The amount of water molecules on the surface at 100 to 400 ° C is 1 to 10
Pieces / 100A is suitable. PH of isoelectric point in water is 3
It is preferably between 6 and 6.

On the surface of these nonmagnetic powders, Al ₂ O
₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂
It is preferable to perform a surface treatment with O ₃ , ZnO, and Y ₂ O ₃ . Especially preferred for dispersibility are Al ₂ O ₃ , SiO ₂ ,
TiO ₂ and ZrO ₂ are more preferable, and Al ₂ is more preferable.
O ₃ , SiO ₂ and ZrO ₂ . These may be used in combination or may be used alone. Further, a co-precipitated surface treatment layer may be used according to the purpose, or a method of first treating with alumina and then treating the surface layer with silica, or vice versa, may be employed.
Although the surface treatment layer may be a porous layer depending on the purpose, it is generally preferable that the surface treatment layer is homogeneous and dense.

Specific examples of the non-magnetic powder used in the lower coating layer of the present invention include Nanotight manufactured by Showa Denko KK, HIT-100 and ZA-G1 manufactured by Sumitomo Chemical Co., Ltd., α-hematite manufactured by Toda Kogyo, and DPN- 250, DPN-250BX,
DPN-245, DPN-270BX, DPN-550
BX, Titanium oxide TTO-51B, TTO manufactured by Ishihara Sangyo
-55A, TTO-55B, TTO-55C, TTO-
55S, TTO-55D, SN-100, α hematite E270, E271, E300, STT manufactured by Titanium Industry
-4D, STT-30D, STT-30, STT-65
C, MT-100S, MT-100T, MT-
150W, MT-500B, MT-600B, MT-1
00F, MT-500HD, Sakai Chemical Company FINEX-2
5, BF-1, BF-10, BF-20, ST-M, Dowa Mining Co., Ltd. DEFIC-Y, DEFIC-R, Nippon Aerosil Co., Ltd. AS2BM, TiO2P25, Ube Industries 100A, 500A, Titanium Industry Y. -LOP and the thing which baked it.

Among the above, particularly preferred nonmagnetic powders include α
-Iron oxide and titanium dioxide. As α-iron oxide (hematite), those obtained under the following conditions can be used. First, from the α-Fe ₂ O ₃ particle powder, acicular goethite particles as precursor particles are obtained by the following method. As a first method, a suspension containing a ferrous hydroxide colloid obtained by adding an equal amount or more of an aqueous alkali hydroxide solution to a ferrous aqueous solution is mixed with an oxygen-containing gas at a temperature of 80 ° C. or less at a pH of 11 or more. A method in which needle-like goethite particles are generated by performing an oxidation reaction by aeration. As a second method, spindle-like goethite is formed by passing an oxygen-containing gas through a suspension containing FeCO ₃ obtained by reacting an aqueous ferrous salt solution and an aqueous alkali carbonate solution to perform an oxidation reaction. How to generate particles. As a third method, an oxygen-containing gas is passed through an aqueous ferrous salt solution containing a ferrous hydroxide colloid obtained by adding less than an equal amount of an aqueous alkali hydroxide solution or an aqueous alkali carbonate solution to an aqueous ferrous salt solution. By performing an oxidation reaction to generate needle-like goethite core particles, and then into an aqueous ferrous salt solution containing the needle-like goethite core particles,
A method of growing the acicular goethite nucleus particles by adding an equal amount or more of an alkali hydroxide aqueous solution to Fe ²⁺ in the ferrous salt aqueous solution and then ventilating an oxygen-containing gas. As a fourth method, an oxygen-containing gas is passed through an aqueous ferrous salt solution containing a ferrous hydroxide colloid obtained by adding an aqueous solution of an alkali hydroxide or an alkali carbonate less than the same amount as the aqueous ferrous solution. An oxidation reaction is performed to generate acicular goethite nucleus particles, and then the acicular goethite nucleus particles are grown in an acidic to neutral region. It should be noted that there is no problem even if different elements such as Ni, Zn, P, and Si, which are usually added for improving the properties of the particle powder during the reaction of forming goethite particles, are added.

The needle-like goethite particles, which are precursor particles, are dehydrated in a temperature range of 200 to 500 ° C.
If necessary, needle-like α-Fe ₂ O ₃ particles are obtained by annealing in a temperature range of 350 to 800 ° C. by a heat treatment. Note that there is no problem even if the needle-like goethite particles to be dehydrated or annealed have a sintering inhibitor such as P, Si, B, Zr, or Sb attached to the surface. Annealing by heat treatment at a temperature in the range of 350 to 800 ° C. is performed by annealing pores formed on the particle surface of the acicular α-Fe ₂ O ₃ particles obtained by dehydration, so that the particles become extremely polar. This is because it is preferable that the surface is melted to cover the pores to form a smooth surface form.

The α-Fe ₂ O ₃ used in the present invention
The particle powder is a suspension obtained by dispersing the acicular α-Fe ₂ O ₃ particles obtained by dehydration or annealing in an aqueous solution,
The Al compound is added to adjust the pH, and the α-Fe ₂ O ₃ is added.
After coating the particle surface of the particles with the additive compound, filtration,
It can be obtained by washing with water, drying, pulverizing and, if necessary, further performing degassing / consolidation treatment. Aluminum compounds used are aluminum acetate, aluminum sulfate, aluminum chloride,
Aluminum salts such as aluminum nitrate and alkali aluminates such as sodium aluminate can be used.
In this case, the amount of the Al compound added is 0.01 to 50% by weight in terms of Al based on the α-Fe ₂ O ₃ particle powder. 0.
When the amount is less than 01% by weight, the dispersion in the binder resin is insufficient, and when the amount exceeds 50% by weight, Al compounds floating on the particle surface interact with each other, which is not preferable.

In the nonmagnetic inorganic powder of the lower coating layer in the present invention, one or two of compounds selected from P, Ti, Mn, Ni, Zn, Zr, Sn, and Sb, including an Al compound and a Si compound. It can also be coated using more than one species. The addition amount of these compounds used together with the Al compound is in the range of 0.01 to 50% by weight based on the α-Fe ₂ O ₃ particle powder. When the amount is less than 0.01% by weight, there is almost no effect of improving the dispersibility by the addition. When the amount exceeds 50% by weight, compounds floating on the surfaces other than the particle surface interact with each other, which is not preferable.

The production method of titanium dioxide used for the lower coating layer is as follows. The methods for producing these titanium oxides are mainly a sulfuric acid method and a chlorine method. In the sulfuric acid method, a source ore of illuminite is digested with sulfuric acid, and Ti, Fe, and the like are extracted as sulfates. Iron sulfate is removed by crystallization separation, and the remaining titanyl sulfate solution is filtered and purified, and then thermally hydrolyzed to precipitate hydrous titanium oxide. After filtering and washing this,
After removing impurities by washing and adding a particle size regulator and the like, the mixture is calcined at 80 to 1000 ° C. to obtain 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. The crude titanium oxide is manufactured by pulverization, sizing, surface treatment and the like. In the chlorine method, natural rutile or synthetic rutile is used as the raw ore. The ore is chlorinated in high-temperature reduction state, Ti is TiCl ₄ and Fe is F
The iron oxide which became eCl ₂ and became solid by cooling is separated from liquid TiCl ₄ . The obtained crude TiCl ₄ is purified by rectification, then a nucleating agent is added, and the mixture is instantaneously reacted with oxygen at a temperature of 1000 ° C. or more 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, coarse particles are classified by dry pulverizing the titanium oxide material, adding water and a dispersant, wet pulverizing and centrifuging. After that, the fine slurry is transferred to a surface treatment tank, where the surface coating of the metal hydroxide is performed. First, a predetermined amount of Al, Si, Ti, Zr, Sb, Sn, Z
An aqueous salt solution such as n is added, and an acid or alkali for neutralizing the aqueous solution is added, and the surface of the titanium oxide particles is coated with the generated hydrated oxide. By-product water-soluble salts are removed by decantation, filtration and washing, and finally the slurry pH
Is adjusted and filtered, and washed with pure water. The washed cake is dried with a spray drier or a band drier. Finally, this dried product is crushed by a jet mill,
Become a product. Further, it is also possible to apply Al and Si surface treatment by passing steam of AlCl ₃ and SiCl ₄ into titanium oxide powder and then flowing steam into the titanium oxide powder. For other pigment production methods, see GDParfitt and KS
W.Sing ”Characterization of Powder Surfaces” Acade
You can refer to mic Press, 1976.

The non-magnetic inorganic powder of the lower coating layer as described above contains 5 to 49% by weight of carbon black having an average primary particle diameter of 10 to 90 nm, and the binder for dispersing these inorganic powders is as follows. It will be described later.

By mixing the carbon black in the lower coating layer, the surface electric resistance Rs can be lowered to obtain an antistatic effect, the light transmittance can be reduced, and a desired micro Vickers hardness can be obtained. it can. The micro Vickers hardness of the lower coating layer is usually 25
60 kg / mm ^2, preferably in order to adjust the head contact, a 30 to 50 kg / mm ^2, using a NEC-made film hardness meter HMA-400, an edge angle of 80 degrees, the tip radius 0.1
The measurement is performed by using a diamond triangular pyramid needle of μm at the tip of the indenter.

Examples of usable carbon black include furnace for rubber, thermal for rubber, black for color,
Acetylene black and the like. The specific surface area of the carbon black is 100 to 500 m ² / g, preferably 150~400m ² / g, DBP oil absorption amount from 20 to 4
00 ml / 100 g, preferably 30-200 ml / 100 g.
The primary particle size of carbon black is 10 to 90 nm, preferably 10 to 50 nm, more preferably 10 to 40 nm.
It is. The carbon black preferably has a pH of 2 to 10, a water content of 0.1 to 10%, and a tap density of 0.1 to 1 g / ml.

Specific examples of the carbon black used in the present invention include BLACKPEA manufactured by Cabot Corporation.
RLS2000, 1300, 1000, 900, 80
0,880,700, VULCAN XC-72, # 3050B, 3150B, 3250 manufactured by Mitsubishi Kasei.
B, # 3750B, # 3950B, # 950, # 650
B, # 970B, # 850B, MA-600, MA-2
30, # 4000, # 4010, CONDUCTEX SC, RAVEN880 manufactured by Konlon Via Carbon
0,8000,7000,5750,5250,350
0, 2100, 2000, 1800, 1500, 125
5,1250, Akzo Ketjen Black EC
And so on. Carbon black may be used after being surface-treated with a dispersant or the like or grafted with a resin, or may be one obtained by partially graphitizing the surface. Further, the carbon black may be dispersed in a binder before adding it to the paint.

These carbon blacks are used in an amount of from 5 to 49% by weight based on the weight of the inorganic powder, and 4% of the total weight of the nonmagnetic layer.
It can be used within a range not exceeding 0%. 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.

Further, an organic powder can be added to the lower coating layer according to the purpose. For example, acrylic styrene-based resin powder, benzoguanamine resin powder, melamine-based resin powder, phthalocyanine-based pigment, but also polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, polyimide-based resin powder, polyfluorinated ethylene resin also Can be used. As the production method, those described in JP-A-62-18564 and JP-A-60-255827 can be used.

In addition, the binder, lubricant, dispersant, additive, solvent, dispersing method and the like of the magnetic layer can be applied to the lower coating layer. In particular, with respect to the amount and type of binder, the amount and type of additive and dispersant added, known techniques for the magnetic layer can be applied.

Next, the upper cleaning layer will be described in detail. First, as the inorganic powder to be mixed into the cleaning layer, a ferromagnetic powder is included.
γ-FeOx (x = 1.33 to 1.5), Co-modified γ-
FeOx (x = 1.33 to 1.5), α-Fe or N
Known ferromagnetic powders such as ferromagnetic alloy powder containing i or Co as the main component (75% or more), barium ferrite, and strontium ferrite can be used, but ferromagnetic alloy powder containing α-Fe as the main component is preferable. These ferromagnetic powders include not only predetermined atoms but also Al, Si, S, Sc, C
a, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, A
g, Sn, Sb, Te, Ba, Ta, W, Re, Au,
Hg, Pb, Bi, La, Ce, Pr, Nd, P, C
It may contain atoms such as o, Mn, Zn, Ni, Sr, B, and Mg. In particular, in the case of a metal magnetic material, Al, S
i, Ca, Y, Ba, La, Nd, Co, Ni, and B are α
-It is important as an element contained in addition to Fe. In particular, Si, Al, and Y are important as surface treatments and sintering inhibitors. Preferably, Co is contained in an amount of 2 to 40% by weight based on Fe. Si, Al and Y are contained between 0 and 10% by weight. These ferromagnetic powders may be preliminarily treated with a dispersant, a lubricant, a surfactant, an antistatic agent, and the like before dispersion before dispersion. Specifically,
-14090, JP-B-45-18372, JP-B-4
7-22062, JP-B-47-22513, JP-B-46-28466, JP-B-46-38755, JP-B-47-4286, JP-B-47-12422, JP-B-47-17284, JP-B-47 -18509, JP-B-47-18573, JP-B-39-10307,
JP-B-48-39639, U.S. Pat.
No. 3031341, No. 3100194, No. 32
No. 42005, No. 3389014 and the like.

Among the above ferromagnetic powders, the ferromagnetic alloy fine powder may contain a small amount of hydroxide or oxide. A ferromagnetic alloy fine powder obtained by a known production method can be used, and the following method can be used. A method of reducing a complex organic acid salt (mainly oxalate) with a reducing gas such as hydrogen, a method of reducing iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe—Co particles, Thermal decomposition method, reduction method by adding reducing agent such as sodium borohydride, hypophosphite or hydrazine to aqueous solution of ferromagnetic metal, reduction of fine powder by evaporating metal in low pressure inert gas And how to get it. The ferromagnetic alloy powder thus obtained is subjected to a known slow oxidation treatment, that is, a method of immersing in an organic solvent and then drying, and immersing in an organic solvent and then feeding an oxygen-containing gas to form an oxide film on the surface and drying. Any of the methods of forming an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent can be used.

The ferromagnetic powder of the cleaning layer of the present invention was B
The specific surface area by the ET method is 45 to 80 m ² / g, and preferably 50 to 70 m ² / g. 40m ² /
If it is less than g, noise increases, and if it is more than 80 m ² / g, it is difficult to obtain surface properties, which is not preferable. The crystallite size of the ferromagnetic powder of the cleaning layer of the present invention is 300 A or less, preferably 250 to 100 A, more preferably 200 to 1
40A.

The saturation magnetization σs of the ferromagnetic powder is 100 to 18
0 emu / g is preferable, and 110-170 is more preferable.
emu / g, more preferably 125 to 160 emu / g.
The coercive force Hc of the ferromagnetic powder is preferably from 500 to 3000 Oe. The squareness ratio is preferably 0.6 to 0.98, and the amount of magnetization of the cleaning layer is preferably 0.03 to 0.3 Gauss · cm. On the other hand, the needle ratio of the ferromagnetic powder is preferably 4 to 18,
More preferably, it is 5-12. The water content of the ferromagnetic powder is preferably 0.01 to 2%. It is preferable to optimize the water content of the ferromagnetic powder depending on the type of the binder.

It is preferable that the pH of the ferromagnetic powder is optimized by the combination with the binder used. The range is 4-1
2, but preferably 6 to 10. The ferromagnetic powder may be subjected to a surface treatment with Al, Si, P or an oxide thereof, if necessary. The amount thereof is 0.1 to 10% with respect to the ferromagnetic powder, and it is preferable that the surface treatment is performed so that the adsorption of a lubricant such as a fatty acid becomes 100 mg / m ² or less. Ferromagnetic powder contains soluble Na, Ca, Fe, Ni,
It may contain an inorganic ion such as Sr. It is preferable that these are essentially absent, but if they are 200 ppm or less, they do not particularly affect the characteristics. The ferromagnetic powder preferably has a small number of vacancies, and the value is preferably 20% by volume or less, more preferably 5% by volume or less.

As the binder used in the cleaning layer and the lower coating layer of the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins and mixtures thereof are used. Glass transition temperature is-
100-150 ° C, number average molecular weight 1,000-20
0000, preferably 10,000 to 100,00
0, the degree of polymerization is about 50 to 1,000.

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,
There are polymers or copolymers containing butadiene, ethylene, vinyl butyral, vinyl acetal, vinyl ether and the like as constituent units, polyurethane resins, and various rubber resins. In addition, as a thermosetting resin or a reactive resin, a phenol resin, an epoxy resin, a polyurethane curing resin, a urea resin, a melamine resin, an alkyd resin, an acrylic reaction resin, a formaldehyde resin, a silicone resin,
Examples include epoxy-polyamide resin, a mixture of polyester resin and isocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, and a mixture of polyurethane and polyisocyanate. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. In addition, a known electron beam-curable resin can be used for the lower coating layer or the upper cleaning layer.

These examples and the production method thereof are described in detail in JP-A-62-256219. The above resins can be used alone or in combination, but preferred are at least one selected from vinyl chloride resin, vinyl chloride vinyl acetate resin, vinyl chloride vinyl acetate vinyl alcohol resin and vinyl chloride vinyl acetate maleic anhydride copolymer. Examples include a combination of a species and a polyurethane resin, or a combination of these with a polyisocyanate. Known polyurethane resin structures such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, polycaprolactone polyurethane, and polyolefin polyurethane can be used. For all binding agents indicated herein, if necessary in order to obtain more excellent dispersibility and durability, -COOM, -SO ₃ M, -OSO
₃ M, -P = O (OM) ₂ , -OP = O (OM)
₂ (or M per a hydrogen atom or an alkali metal ^{salt), - OH, -NR 2,} -N + R 3 (R is a hydrocarbon group), epoxy group, -SH, -CN, sulfobetaine,
It is preferable to use one in which at least one or more polar groups selected from phosphobetaine, carboxybetaine and the like are introduced by copolymerization or addition reaction. The amount of such a polar group is 10 ^-1 to 10 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6 mol / g.

Specific examples of these binders used in the present invention include VAGH, V manufactured by Union Carbide.
YHH, VMCH, VAGF, VAGD, VROH, V
YES, VYNC, VMCC, XYHL, XYSG, P
KHH, PKHJ, PKHC, PKFE, Nissin Chemical Industries' MPR-TA, MPR-TA5, MPR-TA
L, MPR-TSN, MPR-TMF, MPR-TS,
MPR-TM, MPR-TAO, 100 manufactured by Denki Kagaku
0W, DX80, DX81, DX82, DX83, 10
0FD, MR-104, MR-10 manufactured by Zeon Corporation
5, MR110, MR100, 400X-110A, Nipporan N2301, N230 manufactured by Nippon Polyurethane Co.
2, N2304, Pandex T- manufactured by Dainippon Ink and Chemicals, Inc.
5105, T-R3080, T-5201, Burnock D-400, D-210-80, Chris Bonn 6109,
7209, Byron UR8200, UR8 manufactured by Toyobo
300, UR8600, Daiferamine 4020, 5020, 5100, 5300, 9020, manufactured by Dainichi Seika Co., Ltd.
9022, 7020, MX5004 manufactured by Mitsubishi Chemical Corporation, Sampren SP-150, TIM-300 manufactured by Sanyo Kasei Co., Ltd.
3, TIM-3005, Saran F310 manufactured by Asahi Kasei Corporation
F210 and the like. Among them, MR-104, M
R110, MPR-TAO, MPR-TA, UR-82
00, UR8300, TIM-3005 are preferred.

The binder used in the cleaning layer of the present invention is 5 to 24% by weight based on the inorganic powder including the ferromagnetic powder.
, Preferably in the range of 8 to 22% by weight. 5 to 30% by weight when using a vinyl chloride resin,
When a polyurethane resin is used, it is preferable to use them in combination in the range of 2 to 20% by weight and for the polyisocyanate in a range of 2 to 20% by weight. In particular, it is desirable that the cleaning layer does not contain polyisocyanate and the lower coating layer contains polyisocyanate.

In the present invention, when polyurethane is used, the glass transition temperature is -50 to 100 ° C., and the elongation at break is 1
00 to 2000%, breaking stress 0.05 to 10 kg / c
m ² and the yield point are preferably 0.05 to 10 kg / cm ² .

The cleaning medium of the present invention comprises two or more layers. Therefore, the amount of binder, vinyl chloride resin in the binder, polyurethane resin, polyisocyanate,
Alternatively, it is of course possible to change the amount of other resin, the molecular weight of each resin forming the cleaning layer, the amount of the polar group, or the physical properties of the resin described above between the lower coating layer and the cleaning layer as necessary. Yes, known techniques can be applied.

The polyisocyanate used in the present invention includes tolylene diisocyanate, 4-4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1 ·
Isocyanates such as 5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate and triphenylmethane triisocyanate, products of these isocyanates and polyalcohols, and polyisocyanates produced by condensation of isocyanates are used. can do. Commercially available trade names of these isocyanates include Coronate L, Coronate HL, Coronate 2030, Coronate 2031, and Millionate M manufactured by Nippon Polyurethane Co., Ltd.
R, Millionate MTL, Takeda D manufactured by Takeda Pharmaceutical Co.
-102, Takenate D-110N, Takenate D-2
00, Takenate D-202, Desmodur L, Desmodur IL, Desmodur N, Desmodur HL manufactured by Sumitomo Bayer Co., Ltd., and Vernock D502 manufactured by Dainippon Ink and the like. The lower coating layer and the upper cleaning layer can be used in combination of two or more.

In the cleaning layer of the present invention, carbon black may be mixed as an inorganic powder in the same manner as in the lower coating layer. The carbon black may be a furnace black for rubber, a thermal black for rubber, black for color, acetylene black or the like. Can be. The specific surface area is 5 to 500 m ² / g,
The DBP oil absorption is 10 to 400 ml / 100 g, the particle size is 5 mμ to 300 mμ, the pH is 2 to 10, and the water content is 0.1.
The tap density is preferably 0.1 to 1 g / cc.
Specific examples of the carbon black used in the present invention include BLACKPEARLS 200 manufactured by Cabot Corporation.
0, 1300, 1000, 900, 800, 700, V
ULCAN XC-72, manufactured by Asahi Carbon Co., # 80, #
60, # 55, # 50, # 35, manufactured by Mitsubishi Kasei Kogyo Co., Ltd., #
2400B, # 2300, # 5, # 900, # 950,
# 970, # 1000, # 30, # 40, # 10B, CONDUCTEX SC, manufactured by Konlon Via Carbon
RAVEN 150, 50, 40, 15 and the like. Surface treatment of carbon black with a dispersant,
It may be used by grafting with a resin or by using a part of the surface graphitized. Before adding the carbon black to the coating material for the cleaning layer, the carbon black may be dispersed in a binder in advance. These carbon blacks can be used alone or in combination.

When carbon black is used, it is preferably used in an amount of not more than 5% by weight of the ferromagnetic powder. Carbon black has the functions of preventing the cleaning layer from being charged, reducing the friction coefficient, imparting light-shielding properties, improving the film strength, etc. These differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention are changed in kind, amount, and combination in the cleaning layer and the lower coating layer, and are based on the above-mentioned properties such as particle size, oil absorption, conductivity, and pH. Of course, it is possible to use them properly according to the purpose.

The cleaning layer may contain an abrasive as an inorganic powder, such as α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide having an α conversion of 90% or more. Known materials having a Mohs hardness of 6 or more such as α-iron oxide, corundum, artificial diamond, silicon nitride, silicon carbide titanium carbide, titanium oxide, silicon dioxide, and boron nitride are used alone or in combination. Further, a composite of these abrasives (abrasive whose surface is treated with another abrasive) may be used.
These abrasives may contain compounds or elements other than the main component, but the effect remains unchanged if the main component is 90% or more. Specific examples of the abrasive include AKP-20, AKP-30, AKP-50, H, manufactured by Sumitomo Chemical Co., Ltd.
IT-50, HIT-60, HiT-60A, HIT-
70A, HIT-80, HIT-80G, HIT-10
G5, G7, S-1 manufactured by Nippon Kagaku Kogyo Co., Ltd., and TF-100, TF-140 manufactured by Toda Kogyo Co., Ltd.

The particle size of these abrasives is 0.01 to 2
Although μm is preferable, abrasives having different particle sizes may be combined as needed, or a single abrasive may have the same effect by widening the particle size distribution. The tap density is preferably 0.3 to ² g / cc, the water content is 0.1 to 5%, the PH is 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 may be any of a needle shape, a spherical shape, and a dice shape, but a shape having a corner in a part thereof is preferable because of high cleaning property. The amount of the abrasive as the inorganic powder in the cleaning layer is determined by the ferromagnetic powder 10
It is 1 to 45% by weight with respect to 0% by weight. The abrasive used in the present invention can be of different types, amounts and combinations for the lower coating layer and the upper cleaning layer described above, and can be used properly according to the purpose. These abrasives may be added to the magnetic paint after being subjected to dispersion treatment with a binder in advance. The abrasive present on the surface of the cleaning layer and the end surface of the cleaning layer of the cleaning medium of the present invention contains 5 abrasives.
Pcs / 100 μm ² or more is preferable.

As the additives used in the lower coating layer or the cleaning layer of the present invention, those having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect and the like are used.
Molybdenum disulfide, tungsten graphite disulfide,
Boron nitride, fluorinated graphite, silicone oil, silicone having a polar group, fatty acid-modified silicone, fluorine-containing silicone, fluorine-containing alcohol, fluorine-containing ester, polyolefin, polyglycol, alkyl phosphate and its alkali metal salt, alkyl sulfate and Its alkali metal salts, polyphenyl ethers,
Fluorine-containing alkyl sulfates and alkali metal salts thereof, monobasic fatty acids having 10 to 24 carbon atoms (which may contain unsaturated bonds or may be branched), and metal salts thereof (Li, Na, K, Cu, etc.) or a monovalent, divalent, trivalent, tetravalent, pentavalent, hexavalent alcohol having 12 to 22 carbon atoms (which may contain an unsaturated bond or may be branched), carbon Alkoxy alcohols having 12 to 22 carbon atoms, monobasic fatty acids having 10 to 24 carbon atoms (may contain unsaturated bonds or may be branched)
And any one of monohydric, divalent, trivalent, tetravalent, pentavalent, and hexahydric alcohols having 2 to 12 carbon atoms (including an unsaturated bond,
A monofatty acid ester or a difatty acid ester or a trifatty acid ester comprising: a fatty acid ester of a monoalkyl ether of an alkylene oxide polymer; a fatty acid amide having 8 to 22 carbon atoms;
An aliphatic amine having 8 to 22 carbon atoms 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, and stearic acid. Isooctyl, octyl myristate, butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, oleyl alcohol and lauryl alcohol.
Also, nonionic surfactants such as alkylene oxides, glycerin, glycidol, and alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, cations such as phosphonium or sulfoniums -Based surfactants, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, and phosphoric acid ester groups, amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of aminoalcohols, alkylbedines An amphoteric surfactant such as a mold can also be used. 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,
In addition to the main components, impurities such as isomers, unreacted products, by-products, decomposed products, and oxides may be contained. These impurities are preferably 30% or less, more preferably 10% or less.

The type and amount of these lubricants and surfactants used in the present invention can be properly used in the lower coating layer and the cleaning layer as needed. For example, controlling the bleeding to the surface using fatty acids with different melting points in the lower coating layer and cleaning layer, controlling bleeding to the surface using esters with different boiling points and polarities, or adjusting the amount of surfactant By doing so, it is conceivable to improve the stability of coating, or to increase the amount of lubricant added in the lower coating layer to improve the lubricating effect. Of course, the present invention is not limited to the examples shown here.

Further, all or a part of the additives used in the present invention may be added at any step of the paint production. For example, when mixing with an inorganic powder before a kneading step, when adding in a kneading step with an inorganic powder, a binder and a solvent, when adding in a dispersing step, when adding after dispersing, there is a case where it is added just before coating, and the like. . In some cases, the purpose may be achieved by applying a part or all of the additive simultaneously or sequentially after applying the cleaning layer according to the purpose. Depending on the purpose, a lubricant may be applied to the surface of the cleaning layer after calendering or after slitting.

Examples of commercial products of these lubricants used in the present invention include 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, Nimeen L-201, Nimeen L-202, Nimeen 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, Monogly MB, Nonion DS-6
0, Anone BF, Anone LG, butyl stearate, butyl laurate, erucic acid, oleic acid manufactured by Kanto Chemical Co., FAL-205, FAL-123 manufactured by Takemoto Yushi,
Engelbu LO and Enjorbu IP manufactured by Nippon Rika Co., Ltd.
M, Sansocizer-E4030, TA- manufactured by Shin-Etsu Chemical Co., Ltd.
3, KF-96, KF-96L, KF96H, KF41
0, KF420, KF965, KF54, KF50, K
F56, KF907, KF851, X-22-819,
X-22-822, KF905, KF700, KF39
3, KF-857, KF-860, KF-865, X-
22-980, KF-101, KF-102, KF-1
03, X-22-3710, X-22-3715, KF
-910, KF-3935, Armid P, Armid C, Armoslip CP manufactured by Lion Armor, Duomin TDO manufactured by Lion Yushi, BA manufactured by Nisshin Oil
-41G, Sanyo Kasei's Profan 2012E, New Pole PE61, Ionet MS-400, Ionet MO-200, Ionet DL-200, Ionet DS-300, Ionet DS-1000, and Ionet DO-200.

The organic solvent used in the lower coating layer and the cleaning layer of the present invention may be any ratio of ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone and tetrahydrofuran, methanol, ethanol, propanol and butanol. , Alcohols such as isobutyl alcohol, isopropyl alcohol, and methylcyclohexanol; esters such as methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, and glycol acetate; glycol ethers such as glycol dimethyl ether, glycol monoethyl ether, and dioxane System, aromatic hydrocarbons such as benzene, toluene, xylene, cresol, chlorobenzene, methylene chloride, ethylene chloride , Carbon tetrachloride, chloroform,
Chlorinated hydrocarbons such as ethylene chlorohydrin and dichlorobenzene, N, N-dimethylformamide, hexane and the like can be used. These organic solvents are not necessarily 10
It is not 0% pure, and may contain impurities such as isomers, unreacted materials, by-products, decomposed products, oxides, and moisture in addition to the main components. These impurities are preferably 30% or less,
More preferably, it is 10% or less.

The type of the organic solvent used in the present invention is preferably the same for the cleaning layer and the lower coating layer, but the amount of addition may be changed. It is preferable to use a solvent having high surface tension (cyclohexanone, dioxane, etc.) for the lower coating layer to improve the stability of the coating. Specifically, the arithmetic mean of the solvent composition of the cleaning layer is the arithmetic of the solvent composition of the lower coating layer. It is essential that it does not fall below the average value. In order to improve the dispersibility, it is preferable that the polarity is strong to some extent, and it is preferable that the solvent composition contains a solvent having a dielectric constant of 15 to 20 by 50% by weight or more. Further, the dissolution parameter is preferably from 8 to 11.

The thickness structure of the cleaning tape of the present invention is effective when the nonmagnetic support is as thin as 2.0 to 10 μm. The total thickness of the cleaning layer and the lower coating layer is 1/100 to 2 times the thickness of the nonmagnetic support. Further, an adhesive layer for improving adhesion may be provided between the nonmagnetic support and the lower coating layer. The thickness of the adhesive layer is 0.01 to 2 μm, preferably 0.02 to 0.5 μm. Further, a back coat layer may be provided on the side of the non-magnetic support opposite to the side of the cleaning layer. This thickness is 0.1 to 2 μm, preferably 0.3 to 1.0 μm. Known adhesive layers and back coat layers can be used.

The non-magnetic support used in the present invention has a micro Vickers hardness of 75 kg / mm ² or more,
Known films such as biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyamide imide, aromatic polyamide, and polybenzoxdazole can be used. In particular, a nonmagnetic support using an aramid resin, polyethylene naphthalate, or polyethylene terephthalate is preferred. These nonmagnetic supports may be subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, or the like in advance.

In order to achieve the object of the present invention, it is necessary to use a non-magnetic support having a center line average surface roughness Ra of 0.5 to 8 nm on the surface on which the cleaning layer is applied. It is preferable that these non-magnetic supports not only have a small center line average surface roughness but also have no coarse protrusions of 1 μm or more. The surface roughness shape can be freely controlled by the size and amount of the filler added to the non-magnetic support as needed. Examples of these fillers include oxides and carbonates of Al, Ca, Si, Ti and the like, whether crystalline or amorphous, and organic fine powders such as acrylic or melamine. Further, in order to achieve compatibility with running durability, it is preferable that the surface on which the back layer is applied is rougher than the surface on which the cleaning layer is applied. The center line surface roughness of the back layer coating surface is preferably 1 n
m or more, more preferably 4 nm or more. When the roughness between the cleaning layer application surface and the back layer application surface is changed, a dual-structured support may be used, or the roughness may be changed by providing a coating layer.

The F-5 value in the tape running direction (HD direction) of the non-magnetic support used in the present invention is preferably 10-5.
0 kg / mm ² , the F-5 value in the tape width direction (TD direction) is preferably 10 to 30 kg / mm ² , and the F-5 value in the longitudinal direction of the tape is higher than the F-5 value in the tape width direction. However, this is not always the case when it is necessary to increase the strength in the width direction. The heat shrinkage of the nonmagnetic support in the tape running direction and the width direction at 100 ° C. for 30 minutes is preferably 3% or less, more preferably 1.5%.
The heat shrinkage ratio at 80 ° C. × 30 minutes is preferably 1% or less, more preferably 0.5% or less. The breaking strength is 5-100 kg / mm ^{2 in} both directions, and the Young's modulus is 100
3,000 kg / mm ² is preferred. Also, 900nm
Is preferably 30% or less, more preferably 3% or less.

The step of producing the coating material for the lower coating layer and the cleaning layer of the cleaning medium of the present invention comprises at least a kneading step, a dispersing step, and a mixing step provided before and after these steps as necessary. Each step may be divided into two or more steps. All the raw materials such as the ferromagnetic powder, binder, carbon black, abrasive, antistatic agent, lubricant, and solvent used in the present invention may be added at the beginning or during any step. Also,
The individual raw materials may be divided and added in two or more steps. For example, kneading step of polyurethane, dispersing step,
It may be divided and added in the mixing step for adjusting the viscosity after dispersion.

In order to achieve the object of the present invention, it is a matter of course that a conventional known manufacturing technique can be used as a part of the process. However, in the kneading step, a strong kneading force such as a continuous kneader or a pressure kneader is used. It is preferable to use one that has When a continuous kneader or a pressure kneader is used, all or a part of the ferromagnetic powder and the binder (however, preferably 30% or more of the total binder) and the ferromagnetic powder 100 are used.
The kneading treatment is performed in a range of 15 to 500 parts per part. The details of these kneading processes are described in JP-A-1-166338.
And JP-A-64-79274. When preparing the non-magnetic layer liquid of the lower coating layer, it is desirable to use a dispersion medium having a high specific gravity, and zirconia beads are suitable.

The following configuration can be proposed as an example of an apparatus and a method for applying a cleaning medium having a multilayer configuration as in the present invention.

1. First, a lower coating layer is applied by a gravure coating, a roll coating, a blade coating, an extrusion coating device, etc., which are generally used for applying a magnetic paint.
While the lower coating layer is still wet,
186, JP-A-60-238179, JP-A 2-2
An upper cleaning layer is applied by a support pressure type extrusion coating apparatus disclosed in Japanese Patent No. 65672.

2. JP-A-63-88080, JP-A-Hei-2
No. 17971 and JP-A-2-265672, the lower coating layer and the cleaning layer are applied almost simultaneously by one coating head having two built-in coating liquid passage slits.

3. The lower coating layer and the cleaning layer are applied almost simultaneously by an extrusion coating apparatus with a backup roll disclosed in JP-A-2-174965.

In order to prevent agglomeration of the magnetic particles, a shearing force is applied to the coating liquid inside the coating head by a method disclosed in JP-A-62-95174 or JP-A-1-236968. Is desirable. Further, the viscosity of the coating liquid must satisfy the numerical range disclosed in JP-A-3-8471.

In order to obtain the cleaning medium of the present invention, an orientation treatment of the ferromagnetic powder of the cleaning layer may be performed.
This orientation is preferably performed using a solenoid having a magnetic force of 1,000 G or more and a cobalt magnet having a magnetic force of 2,000 G or more in the same polarity facing each other. Further, the orientation after drying is maximized. It is preferable to provide an appropriate drying step before the alignment.

Before the simultaneous application of the non-magnetic lower coating layer and the cleaning layer, a bonding layer containing a polymer as a main component is provided, or the adhesion is improved by corona discharge, UV irradiation, or EB irradiation. It is preferable to combine known methods.

Further, if necessary, a calendar process can be performed to adjust the surface roughness. A heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimide amide can be used as the calendering roll. Further, the treatment can be performed between metal rolls. The processing temperature is preferably 15 to 50 ° C,
The linear pressure is preferably 5 to 100 kg / m, and the speed is 50 to
400 m / min.

The coefficient of friction of the cleaning layer surface of the cleaning medium of the present invention and the opposite surface thereof to SUS420J is preferably 0.1 to 0.5, more preferably 0.2 to 0.3. The surface resistivity is preferably 10
The elastic modulus at ⁴ to 10 ¹² ohms / sq and 0.5% elongation of the cleaning layer is preferably 100 in both the running direction and the width direction.
２，2,000 kg / mm ² , breaking strength is preferably 1
30 kg / cm ² .

The cleaning medium as a whole is
Young's modulus in the longitudinal (MD) direction is 300 to 1200 kg / mm
^2. The Young's modulus in the width (TD) direction is 200 to 1200 kg /
mm ² , and the Young's modulus in the longitudinal direction / Young's modulus in the width direction is 1/2
It is preferable to provide them so as to be 2/1. Further, the residual elongation of the cleaning medium is preferably 0.5% or less,
The thermal shrinkage at any temperature below 100 ° C. is preferably 1% or less, more preferably 0.5% or less, most preferably 0.1% or less, and 0% is ideal. The glass transition temperature of the cleaning layer (the maximum point of the loss elastic modulus in the dynamic viscoelasticity measurement measured at 110 Hz) is 50 ° C. or more and 120 ° C.
The following is preferable, and that of the lower coating layer is preferably 0 ° C to 100 ° C. The loss modulus is 1 × 10 ⁸ to 8 × 10 ⁹ dyne /
It is preferably in the range of cm ² , and the loss tangent is preferably 0.2 or less. If the loss tangent is too large, adhesion failure is likely to occur. The residual solvent contained in the cleaning layer is preferably 100 mg / m ² or less, more preferably 10 mg / m ² or less, and the residual solvent contained in the upper cleaning layer is preferably smaller than the residual solvent contained in the lower coating layer. . The porosity of the lower coating layer and the cleaning layer is preferably 50% by volume or less, more preferably 40% by volume or less.
% By volume or less.

The magnetic properties of the cleaning layer of the cleaning medium according to the present invention, as measured by a VSM with a magnetic field of 10 kOe as described above, are such that the coercive force Hc in the tape running direction is 500-500.
3000 Oe. The squareness ratio is 0.6 to 0.98,
It is preferably 0.80 or more, and more preferably 0.1.
It is 85 or more. The squareness ratio in two directions perpendicular to the tape running direction is preferably 80% or less of the squareness ratio in the running direction. The SFD of the cleaning layer is preferably 0.6 or less, more preferably 0.5 or less, and ideally 0. The longitudinal remanence coercive force Hr is also 1800
~ 3000 Oe is preferred. It is preferable that Hc and Hr in the vertical direction be 1000 to 5000 Oe. further,
The center line surface roughness Ra of the cleaning layer is 1.0 to 7.0.
Although nm is preferable, its value should be set appropriately according to the purpose. RMS surface roughness R _RMS calculated in evaluation by AFM is preferably in the range of 2 to 15 nm.

Although the cleaning medium of the present invention has a lower coating layer and a cleaning layer, it is easily presumed that the physical properties of the lower coating layer and the cleaning layer can be changed according to the purpose. For example, the elastic modulus of the cleaning layer is increased to improve running durability, and at the same time, the elastic modulus of the lower coating layer is made lower than that of the cleaning layer to improve the contact of the cleaning medium with the head. It is also effective in the present invention to improve the head contact by changing the method of tensifying the support, and the support tensified in the direction perpendicular to the longitudinal direction of the tape has better head contact. Often.

[0081]

Next, the present invention will be described in detail with reference to examples and comparative examples of the present invention. In the examples, "parts" indicates "parts by weight".

<Example 1> Each of the coating liquid for the lower coating layer and the coating liquid for the cleaning layer having the following composition was kneaded with a continuous kneader, and then dispersed using a sand mill.

[Coating liquid composition for lower coating layer] Non-magnetic inorganic powder α-Fe ₂ O ₃ (DPN-250BX manufactured by Toda Kogyo Co., Ltd.) 80 parts Average particle diameter 0.1 μm Specific surface area by BET method 60 m ² / g pH 5. 6 carbon black 20 parts average primary particle diameter 16 nm DBP oil absorption 80 ml / 100 g pH 8.0 specific surface area by BET method 250 m ² / g volatile matter 1.5% vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 parts -N (CH ₃ ) ₃ ⁺ Cl ⁻ Polar group 5 × 10 ⁻⁶ eq / g content Composition ratio 86: 13: 1 Polymerization degree 240 Polyester polyurethane resin 8 parts Basic skeleton 1,4-BD / phthalic acid / HMDI Molecular weight 10200 Hydroxyl group content ^{0.23 × 10 -3 eq / g -SO} 3 Na group content 1 × 10 ^-4 eq / g butyl stearate 1 part 1 part methyl ethyl stearate Ketone 200 parts [Cleaning layer coating solution composition] ferromagnetic metal powder (Fe-Co-Y-Al ) 100 parts Fe / Co / Y / Al 51/30/6/2 Hc 2200Oe BET method specific by surface area 60 m ² / G Crystallite size 170A Particle size (major axis diameter) 0.09 μm Needle ratio 4 σs 137 emu / g Vinyl chloride copolymer 12 parts —SO ₃ Na group content 1 × 10 ⁻⁴ eq / g Polymerization degree 300 polyester polyurethane resin 3 parts neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 -SO 3 Na group content 1 × 10 ^-4 eq / g α- alumina (particle size 0.17 .mu.m) 4. 5 parts Carbon black (particle size 100 nm) 1 part Butyl stearate 1 part Stearic acid 2 parts Methyl ethyl ketone 200 parts Obtained Polyisocyanate was added to the dispersion thus obtained, 5 parts of the coating solution for the lower coating layer, 6 parts of the cleaning layer, and 40 parts of butyl acetate were added to each, and the mixture was filtered using a filter having an average pore size of 1 μm. Then, the coating liquids for forming the lower coating layer and the cleaning layer were respectively prepared.

The obtained coating liquid for the lower coating layer was dried so that the thickness after drying was 1.2 μm, and immediately after that, the coating liquid for the cleaning layer was adjusted to have a thickness after drying. Simultaneous multi-layer coating was performed on a polyethylene terephthalate support having a thickness of 7 μm and a center line surface roughness of the cleaning layer coating surface of 0.01 μm so that the thickness becomes 0.3 μm, and 3000 G while both layers were still wet Oriented by a cobalt magnet with a magnetic force of 1,500 G and a solenoid with a magnetic force of 1,500 G, and dried, then a 7-stage calender consisting of a metal roll and an epoxy resin roll was used, and the temperature was 40 ° C.
/ Min, and then a back layer having a thickness of 0.5 μm was applied. Slit this to a width of 8 mm,
A video cleaning tape was produced.

Example 2 In this example, 5 parts of carbon black and α-Fe ₂ were used as the non-magnetic inorganic powder of the lower coating layer.
A sample was prepared in the same manner as in Example 1 except that the amount of carbon black was reduced to 95 parts of O ₃ .

Example 3 In this example, 40 parts of carbon black was used as the non-magnetic inorganic powder of the lower coating layer and α-Fe.
_A sample was prepared in the same manner as in Example 1 except that the amount of carbon black was increased by setting ₂ O ₃ to 60 parts.

Comparative Example 1 In this comparative example, α-F containing no carbon black in the non-magnetic inorganic powder of the lower coating layer was used.
A sample was prepared in the same manner as in Example 1 except that 100 parts of e ₂ O ₃ was used.

Comparative Example 2 In this comparative example, 50 parts of carbon black was used as the non-magnetic inorganic powder of the lower coating layer and α-Fe.
_A sample was prepared in the same manner as in Example 1 except that the amount of carbon black was increased with 50 parts of ₂ O ₃ .

<Example 4> In this example, the thickness of the cleaning layer was thinned to 0.13 μm, and the other sample was manufactured in the same manner as in Example 1.

<Embodiment 5> In this embodiment, the thickness of the lower coating layer is as thin as 0.8 μm.
A sample was prepared in the same manner as described above.

Example 6 In this example, a sample was prepared in the same manner as in Example 1 except that the lower coating layer had a large thickness of 3 μm.

Example 7 In this example, a sample was prepared in the same manner as in Example 1 except that the carbon black in the lower coating layer had a large average primary particle diameter of 40 nm.

Example 8 In this example, a sample was prepared in the same manner as in Example 1 except that the average primary particle diameter of carbon black in the lower coating layer was further increased to 84 nm.

Comparative Example 3 In this comparative example, a sample was prepared in the same manner as in Example 1 except that the average primary particle diameter of carbon black in the lower coating layer was further increased to 94 nm.

<Example 9> In this example, the compounding amount of the abrasive (α-alumina) in the cleaning layer was reduced from 4.5% by weight to 2.5% by weight. A sample was prepared in the same manner.

Example 10 In this example, a sample was prepared in the same manner as in Example 1 except that TiO ₂ was used as the nonmagnetic inorganic powder of the lower coating layer instead of α-iron oxide.

<Embodiment 11> In this embodiment, as the ferromagnetic powder for the cleaning layer, Ba ferrite is contained in place of Fe / Co / Y / Al. Other than that, a sample is prepared in the same manner as in Embodiment 1. .

<Example 12> In this example, the amount of carbon black compounded in the cleaning layer was increased to 5% by weight, and the amount of abrasive was set to 7.5% by weight. A sample was prepared in the same manner.

<Embodiment 13> This embodiment is an example of a cleaning disk for a floppy disk drive. The coating liquid for the cleaning layer contains Ba ferrite as a ferromagnetic powder, and the composition of the coating liquid for the lower coating layer is the same as in Example 1 above.

The coating material for the cleaning layer and the coating material for the lower coating layer were applied on polyethylene terephthalate having a thickness of 75 μm, firstly, the coating material for the lower coating layer, and then while still wet, the coating material for the cleaning layer. , The back side was processed similarly. The dry coating film thickness of the lower coating layer is 2.5μ
m, and the thickness of the cleaning layer was 0.5 μm. Thereafter, a calendaring treatment was performed to obtain a cleaning medium. Thereafter, the cleaning medium was punched out to 3.5 inches, placed in a 3.5-inch cartridge having a liner installed inside, and a predetermined mechanical component was added to obtain a cleaning disk.

The results of determining the thickness of each cleaning layer, the lower coating layer, the powder type, the average particle size of carbon black, the blending amount, etc. in the samples of the cleaning medium as in the above Examples and Comparative Examples are shown. The results are shown in Tables 1 to 3. Further, the measured values of the head wear amount, the head cleaning force, the head scratches and the surface roughness and the surface electric resistance as a result of the cleaning test with each sample are also shown. Table 1 shows an example of changing the amount of carbon black in the lower coating layer, Table 2 shows an example of changing the thickness of the cleaning layer or the lower coating layer and an example of changing the particle size of carbon black in the lower coating layer, and Table 3 shows Other examples of composition changes are shown. The surface electric resistance in the table indicates, for example, 9 * E8 means 9 × 10 ⁸ .

Here, the measuring method of each measured value is shown.

(Method for measuring thickness of cleaning layer and lower coating layer) A thickness of about 0.1 μm was cut out with a diamond cutter over the length of the cleaning medium, and observed with a transmission electron microscope at a magnification of 30,000. I took a picture. The print size of the photo is A4 size.

After that, the interface was visually judged by observing the shape difference between the ferromagnetic powder and the non-magnetic powder of the cleaning layer and the lower coating layer, and the edge of the cleaning layer was also black. Then, Zeiss image processing device IB
In AS2, the interval between the bordered lines was measured. The length of the sample photograph was over a range of 21 cm, and measurement was performed by taking measurement points. The simple average value of the measured values at that time was defined as the thickness of the cleaning layer and the lower coating layer.

(Specific surface area by BET method) Canter soap (manufactured by US Canter Chrome Co., Ltd.) was used. 250 ° C, 3
After dehydration in nitrogen atmosphere for 0 minutes, BET single point method (partial pressure 0.3
0).

(Magnetic characteristics) Coercive force Hc, residual magnetic flux density B
r, squareness ratio, magnetization amount, etc. were measured using a vibrating sample magnetometer (manufactured by Toei Kogyo Co., Ltd.) with an external magnetic field of Hm10 kOe.
Determined based on the magnetization curve. The maximum magnetic flux density Bm was determined by the above-described cleaning layer thickness measuring method.

(Center line average surface roughness) TO manufactured by WYKO
Using PO3D, the medium surface is about 250 by MIRAU method.
Ra in an area of μm × 250 μm was measured. The measurement wavelength is about 650 nm, and spherical and cylindrical corrections are added. This method is a non-contact surface roughness meter that measures by light interference.

(Particle diameters of ferromagnetic powder and non-magnetic powder) A method and image analysis apparatus Carl Zeiss Co., Ltd. in which a transmission electron microscope photograph is taken and the minor axis diameter and the major axis diameter of the ferromagnetic powder are directly read. The average particle diameter was determined by appropriately using a method of tracing and reading a transmission type micrograph with IBASS1 manufactured.

(Ferromagnetic powder crystallite size) By X-ray diffraction, in the γ iron oxide ferromagnetic powder, (4, 4, 0) planes and (2, 2)
It was determined from the spread of the half-value width of the diffraction line on the (2,0) plane. In the case of a metal ferromagnetic powder, it is similarly obtained from the spread of the half value width of the diffraction lines on the (1,1,0) plane and the (2,2,0) plane.

(Head wear) Hi-8 deck EV-S9
Using 00, the cleaning tape was run at 5 ° C. × 80% RH for 10 minutes, and the head height before and after the cleaning tape was measured to determine the head wear amount.

(Head Cleaning Power) The output was measured in advance with EV-S900 using Hi-8 Super DC P6-120 manufactured by Fuji Photo Film Co., Ltd. afterwards,
Run a standard tape made for the purpose of causing clogging with the EV-S900, observe the head status with a strobe, stop running when there is much dirt on the head, and have no output Check. Then, after running each cleaning tape of the sample for 1 minute, previously recorded Hi-8 Super DC manufactured by Fuji Photo Film Co., Ltd.
The output of P6-120 was measured, and the difference dB between the output measured first and the output measured last was used as the evaluation of the head cleaning force.

The cleaning power of the cleaning disk is 3.5 inches F operating on MS-DOS.
D-apparatus, standard MS-DOS of Fuji Photo Film Co., Ltd.
A head dirt is generated on a formatted head dirt-generating disk to make data reading impossible. Next, a cleaning disk is inserted and operated for 60 seconds. Thereafter, it was determined whether reading from the data disk was possible.

(Surface Electric Resistance) The cleaning tape was slit into a tape having a width of 8 mm, and the cleaning disk was measured by cutting a sheet sample into a width of 8 mm. Its surface electrical resistance is measured by the International Electrotechnical Commission standard (IE
C STANDARD) Publication 735-3.2.

Tables 1 to 3 show Examples 1 to 1 of the present invention.
In No. 3, the head is not excessively worn and the head is not scratched, the cleaning power is good, the surface electric resistance is small, and the antistatic effect is obtained, which is suitable as a cleaning medium for the magnetic head. Has been.

[0115]

[Table 1]

[0116]

[Table 2]

[0117]

[Table 3]

Claims (2)

[Claims] 1. A lower coating layer mainly containing a non-magnetic inorganic powder and a binder is provided on a non-magnetic support, and a cleaning layer containing at least an inorganic powder of ferromagnetic powder and the binder is provided thereon. Of the non-magnetic inorganic powder used for the lower coating layer, 5 to 4
A cleaning medium for a magnetic recording device, characterized in that 9% by weight is carbon black having an average primary particle diameter of 10 to 90 nm. 2. The cleaning medium for a magnetic recording device according to claim 1, wherein the inorganic powder of the cleaning layer contains 5% by weight or less of carbon black with respect to the ferromagnetic powder.