JPH09305939A - Cleaning medium for magnetic recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain higher cleaning property and prevent damage of a magnetic head with the cleaning property of good surface property by giving isotropy and adequate flexibility even if the shape of magnetic head is changed. SOLUTION: A lower coating layer mainly including non-magnetic organic powder and a binder is provided on a non-magnetic base and a cleaning layer including at least inorganic powder of ferro-magnetic powder and a binder is provided thereon. Moreover, a binder to be used for the lower coating layer is composed of polyurethane resin as a reaction byproduct mainly composed of at least diol and organic diisocyanate and this polyurethane resin includes short chain diol having the cyclic structure and long chain diol including ether group.

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.
Since the head is worn out a lot because it is soft, it is important that the head wear amount due to the cleaning tape is also small.

In recent years, like Hi-8 and DVC,
Magnetic recording devices that can use both vapor deposition tapes (ME tapes) and metal tapes (MP tapes) have been introduced. Since the metal thin film having high rigidity contacts the magnetic head in the vapor deposition tape, it is difficult to obtain a good contact state, that is, recording / reproducing characteristics unless the tip of the magnetic head is sharp. Further, since the vapor deposition tape does not contain an abrasive, the magnetic head wears less when it comes into contact with it, and the compatibility with the magnetic head is low. On the other hand, since the magnetic layer of the metal tape contains the magnetic powder in the binder, the metal tape comes into soft contact with the magnetic head, and the head contact with the tape does not change so much depending on the shape of the head tip. Further, since it has a wear force, it is well compatible with the magnetic head.

Therefore, even if the metal tape is run on the magnetic head after the vapor deposition tape is run, the change in head contact is not so great, but conversely, the metal tape is run after the metal tape is run. When running the tape,
The head contact may become poor.

As a prior art of a polishing tape used for polishing a magnetic head, for example, in JP-A-62-92205, an intermediate layer containing a non-magnetic powder and a non-magnetic polishing agent are provided on a non-magnetic support. A polishing tape in which polishing layers containing the same are laminated in order is disclosed. 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, it is difficult to perform proper polishing for cleaning because of a large amount of head wear, and it is not suitable for use as a cleaning tape. An abrasive tape for a magnetic head similar to the above is disclosed in JP-A-62-94.
270 and JP-A-62-92205. These also have a two-layered polishing layer, but it is difficult to perform good cleaning without damaging the magnetic head by proper polishing, and they are not suitable as a cleaning medium.

As a cleaning tape for a magnetic head, Japanese Patent Laid-Open No. 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 lower layer cleaning. A technique is disclosed in which the layer has a Young's modulus larger than that of the layer to achieve both good cleaning properties and low head wear.
However, in the cleaning tape of this prior example, both the two cleaning layers contain ferromagnetic powder, and the anisotropy of Young's modulus remarkably occurs in the tape as a whole, after using the metal tape and the vapor deposition tape. It is difficult to exhibit good cleaning performance for each shape when the shape of the magnetic head is different, and in particular, the tip shape after cleaning does not become sharp, and it is possible to bring good head contact with the vapor deposition tape. However, there is a problem that the compatibility between the metal tape and the vapor deposition tape is not sufficiently recovered.

[0009]

However, even if the magnetic head has a difference in shape as described above, the cleaning of the magnetic head can be performed by using a cleaning medium having a moderately supple and good surface property. It has been found that if the shape of the magnetic head can be adjusted, the head contact of the vapor deposition tape can be improved, and the compatibility between the metal tape and the vapor deposition tape can be sufficiently restored.

Therefore, according to the present invention, cleaning of a magnetic head of a high-density magnetic recording / reproducing apparatus or the like is performed.
It can be used for metal heads with less head wear due to sliding contact along its shape, and good cleaning can be performed regardless of the shape of the magnetic head, and the shape of the magnetic head after cleaning is not damaged. An object of the present invention is to provide a cleaning medium for a magnetic recording device which can be arranged and has good compatibility.

[0011]

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 binder used in the lower coating layer is a polyurethane resin which is a reaction product of at least diol and organic diisocyanate as main raw materials. The polyurethane resin is characterized by containing a short chain diol having a cyclic structure and a long chain diol containing an ether group.

In the polyurethane resin, it is preferable that the short-chain diol having a cyclic structure has a molecular weight of less than 500 and the long-chain diol containing an ether group has a molecular weight of 500 to 5,000. Further, the polyurethane resin contains 17 to 40% by weight of a short chain diol having a cyclic structure,
In addition, ether groups are added to the entire polyurethane resin.
It is desirable that the polyurethane resin contains 10 to 50% by weight of a long-chain diol containing 0 to 5.0 mmol / g.

On the other hand, 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.

[0014]

According to the present invention as described above, a lower coating layer mainly containing a non-magnetic inorganic powder and a binder is provided on a non-magnetic support, and an inorganic powder made of at least a ferromagnetic powder is provided thereon. A cleaning layer containing a binder is provided, and since a binder made of a specific polyurethane resin is used in the lower coating layer, the polyurethane resin has good dispersibility of non-magnetic powder. The surface property is improved and the magnetic head is not damaged. Further, by using the above-mentioned binder, the strength of the coating film is increased, and a good cleaning effect can be exhibited even when the magnetic head is heated to a high temperature due to friction.

When the polyurethane resin is used for the lower coating layer, it is used as the cleaning layer alone or as a single layer, whereas the liquid viscosity of the coating liquid for the lower coating layer is stable. It has excellent coating suitability for simultaneous or sequential coating with the cleaning layer, and a smooth surface of the cleaning layer can be obtained, whereby high cleaning properties can be obtained without damaging the magnetic head.

In the known polyurethane, when the cyclic structure or the concentration of urethane bond is increased, the solvent solubility is lowered, the dispersibility of the non-magnetic inorganic powder is lowered, the smoothness of the lower coating layer is lowered, and the polyurethane of the upper cleaning layer is lowered. Although the smoothness is also reduced, the polyurethane of the present invention has the advantage of being excellent in solvent solubility and dispersibility. It is considered that this is because the above-mentioned polyurethane contains a very small amount of hydrophilic ether groups, and therefore the dispersibility is improved because it is easily adsorbed to the non-magnetic powder of polyurethane without lowering the solvent solubility. To be In addition, since appropriate toughness can be imparted, the entire coating film does not become brittle, and there is an advantage that the repeated running property does not deteriorate.

Further, when the cleaning layer of the present invention as described above is slid on the surface of the magnetic head in contact with the surface of the magnetic head for cleaning, the strength is isotropic and the overall flexibility is moderate. As a result, a good cleaning effect can be obtained even if the shape of the magnetic head is different. That is, the non-magnetic powder in the lower coating layer is not oriented with respect to the cleaning layer containing the ferromagnetic powder, so that the strength is isotropic, the Young's modulus in the width direction is high, and the difference from the Young's modulus in the longitudinal direction is small. Become. With such a configuration, the surface property of the cleaning medium and the contact state with the magnetic head are improved, and although the magnetic head is less worn, it has a high cleaning property for removing dirt on the magnetic head in a short time.

In particular, by providing the lower coating layer containing the non-magnetic inorganic powder, when this is a magnetic layer containing the ferromagnetic powder, the ordinary needle-shaped ferromagnetic powder is oriented in the longitudinal direction and the Young's layer in the longitudinal direction. The modulus is large and the Young's modulus is small in the width direction, whereas the non-magnetic powder is not oriented and therefore isotropic in strength. As a result, the Young's modulus in the width direction is also large, The ratio of Young's modulus to the width direction can be obtained.

[0019]

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.

The binder used in the lower coating layer comprises a polyurethane resin which is a reaction product of at least a diol and an organic diisocyanate as main raw materials, and the polyurethane resin has a short chain diol having a cyclic structure and a long chain containing an ether group. It contains a chain diol.

Preferably, the cleaning layer has a thickness of 0.05 to 1.0 μm, and the lower coating layer has a thickness of 0.1.
2 to 5.0 μm, the thickness of the support is 2.0 to 10 μm, and the total thickness of the cleaning medium (cleaning tape) is 4.0 to 15 μm. The center line average surface roughness Ra of the cleaning layer is preferably 1.0 to 8.0 nm, and the center line average surface roughness Ra of the support surface is preferably 0.5 to 7.0 nm.

Next, the detailed contents of the lower coating layer will be described. First, the short-chain diol having a cyclic structure, which is a raw material of the polyurethane resin contained in the binder used in the lower coating layer of the present invention, is bisphenol A, hydrogenated bisphenol A represented by the following formula 1, bisphenol S, bisphenol. P and ethylene oxide and propylene oxide adducts thereof; cyclohexanedimethanol, cyclohexanediol, hydroquinone, bis (2-hydroxyethyl) tetrabromobisphenol A, bis (2
-Hydroxyethyl) tetrabromobisphenol S,
Bis (2-hydroxyethyl) tetramethylbisphenol S, bis (2-hydroxyethyl) diphenylbisphenol S, bis (2-hydroxyethyl) diphenylbiphenol, bis (2-hydroxyethyl) thiodiphenol, bis (2-hydroxyethyl) ) Bisphenol F, biphenol, bisphenol fluorene, bisphenol fluor orange hydroxyethyl ether,
More preferred are hydrogenated bisphenol A, bisphenol S, bisphenol P and their ethylene oxide and propylene oxide adducts; diols having aromatic and alicyclic groups such as cyclohexanedimethanol and cyclohexanediol. More preferably, hydrogenated bisphenol A represented by formula 1 and its ethylene oxide,
Propylene oxide adducts may be mentioned.

[0023]

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The content of the short chain diol in the polyurethane resin is preferably 17 to 40% by weight, more preferably 20 to 35% by weight. If it is less than 17% by weight, the resulting coating film becomes too soft and sufficient strength cannot be obtained, resulting in poor durability. On the other hand, if it is more than 40% by weight, the solubility in the solvent is lowered and the dispersibility of the non-magnetic powder is apt to be lowered, so that the surface property of the cleaning layer coated on the upper layer is apt to be lowered and the strength of the coating layer is reduced. .

The short-chain diol having a cyclic structure is
The molecular weight is preferably from 50 to 500, and more preferably from 100 to 300. When it is less than 50, the cleaning layer becomes brittle and durability is deteriorated. On the other hand, when it is more than 500, the glass transition temperature Tg of the coating layer is lowered and the coating layer is softened and the durability is lowered.

The content of the ether group in the polyurethane resin is preferably 1.0 to 5.0 mmol / g, more preferably 2.0 to 4.0 mmol / g. If it is less than 1 mmol / g, the adsorptivity to the fine powder is lowered and the dispersibility is lowered. On the other hand, when it is more than 5.0 mmol / g, the solubility in the solvent is lowered and the dispersibility is lowered.

The content of OH groups in the polyurethane resin is
The number is preferably 3 to 20 per molecule, more preferably 4 to 5 per molecule. If the number is less than 3 per molecule, the reactivity with the isocyanate curing agent is reduced, so that the strength of the coating film is reduced and the durability tends to be reduced. On the other hand, when the number is more than 20, the solubility in a solvent is reduced, and the dispersibility tends to be reduced.

The content of the long-chain diol containing an ether group, which is the main raw material of the polyurethane resin, is 10 to 50.
% By weight, more preferably 30 to
40% by weight. When the content is less than 10% by weight, the solubility in a solvent is reduced, so that the dispersibility is reduced. On the other hand, if it is more than 50% by weight, the strength of the coating film is reduced, so that the durability is reduced.

The long-chain diols are specifically bisphenol A, hydrogenated bisphenol A, bisphenol S, bisphenol P and their ethylene oxide, propylene oxide adducts, polypropylene glycol, polyethylene glycol, polytetramethylene glycol. More preferred are bisphenol A, hydrogenated bisphenol A, and ethylene oxide and propylene oxide adducts thereof, and a compound represented by the following formula 2 is particularly preferred.

[0030]

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The values of n and m are 3 to 24, preferably 3 to 20, and more preferably 4-1.
5 If n and m are smaller than 3, the urethane bond concentration increases, the solubility in a solvent is reduced, the coating film is apt to be brittle, and the dispersibility and durability are further reduced. When it is larger than 24, the coating film becomes soft and durability is deteriorated.

In the long chain diol, R is preferably the following, and more preferably R:

[0033]

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In the long-chain diol of the formula 2, X
Is preferably hydrogen or a methyl group, more preferably a methyl group. Weight average molecular weight (Mw) of this long-chain diol
Is from 500 to 5,000, and if it is more than 5,000, the coating film strength is lowered and the film becomes soft, so that the durability is lowered.

The number average molecular weight (Mn) of the polyurethane resin is preferably 5,000 to 100,000, more preferably 10,000 to 50,000, and particularly preferably 20,000 to 40,000. Fifty
When it is less than 00, the strength of the lower coating layer is lowered and the durability is lowered. On the other hand, if it is larger than 100,000, the solubility in a solvent is reduced and the dispersibility is reduced.

The glass transition temperature Tg of the polyurethane resin of the present invention is 50 to 200 ° C., preferably 80 to 200 ° C.
150 ° C, more preferably 100 to 130 ° C
It is. When the temperature is lower than 50 ° C, the strength of the lower coating layer at high temperature is lowered, so that durability and storability are lowered. Also, 20
If the temperature is higher than 0 ° C, the calender moldability is deteriorated and the surface property is deteriorated.

As the compound used for adjusting the content of the OH group in the polyurethane resin, a compound having an OH group having a functionality of 3 or more can be used. Specific examples thereof include trimethylolethane, trimethylolpropane, trimellitic anhydride, glycerin, pentaerythritol, and hexanetriol. Further, the dibasic acid used as a polyester polyol raw material and the above compound can be obtained as a glycol component. Examples include branched polyesters and polyether esters having trifunctional or higher OH groups. Preferably, it is a trifunctional one, and if it has four or more functionalities, it tends to gel in the reaction process.

The binder made of the polyurethane resin of the present invention includes -SO ₃ M, -OSO ₃ M, -COO in the molecule.
_{M, -PO 3 M '2,} -OPO 3 M' 2, -NR 2, -
N ⁺ R ₂ R'COO ^- (wherein, M is hydrogen, alkali metal, alkaline earth metal, ammonium salts, M 'is hydrogen, an alkali metal, alkaline earth metal, ammonium salt, R, R 'is an alkyl group, X is preferably contains at least one polar group selected from a halogen), and particularly preferably, -SO ₃ M, -OSO
₃ M. The amount of these polar groups is preferably 1 × 1
0 ^{-5 to} 2 × 10 ^-4 eq / g, particularly preferably 5 ×
It is 10 ^-5 to 1 × 10 ^-4 eq / g. 1 × 10 ^-5 eq /
If it is less than g, the adsorption to the non-magnetic powder mixed in the lower coating layer will be insufficient and the dispersibility will be reduced to 2 × 10 ^-4 e
If it is more than q / g, the solubility in the solvent is lowered and the dispersibility is lowered.

As the binder for the lower coating layer, a vinyl chloride synthetic resin may be used in combination with the polyurethane resin. The polymerization degree of the vinyl chloride resin that can be used in combination is 200
-600 are preferable and 250-450 are especially preferable.
The vinyl chloride resin may be a copolymer of a vinyl monomer, for example, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylonitrile and the like. In addition, cellulose derivatives such as nitrocellulose resin, acrylic resin,
Polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy resin and the like may be used in combination, and these may be used alone or in combination.

When another synthetic resin is used in combination, the polyurethane resin contained in the lower coating layer is contained in the binder in an amount of 10 to 10.
It is preferably contained in an amount of 100% by weight, and more preferably in an amount of 20 to 100% by weight. Particularly preferred is an amount of 50 to 100% by weight. If it is less than 10% by weight, the solubility in a solvent is reduced, and the dispersibility is reduced. The vinyl chloride resin is preferably contained in the binder in an amount of 10 to 80% by weight, more preferably 20 to 70%.
The amount is% by weight. Particularly preferred is an amount of 30 to 60% by weight.

Further, other diols can be used in combination with the short chain diol having a cyclic structure of the present invention. Specifically, ethylene glycol, 1,3-propylene diol, 1,2-propylene glycol, 1,4-butane diol, 1,5-pentane diol, 1,6-hexane diol, 2,2-dimethyl propane diol. , 1,
Aliphatic diols such as 8-octanediol, 1,9-nonanediol, diethylene glycol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol; alicyclic diols; and bisphenol A and bisphenol A Aromatic diols such as ethylene oxide or propylene oxide adducts, and diols such as ethylene oxide or propylene oxide adducts of N-diethanolamine can be given.

Of these, preferred are bisphenol A or hydrogenated bisphenol A ethylene oxide adducts and propylene oxide adducts, and more preferred are bisphenol A propylene oxide adducts. By using these, a coating film having high strength and high Tg due to the annular structure and high durability can be obtained.
Furthermore, the introduction of the branched CH ₃ makes it possible to obtain high dispersibility because it has excellent solubility in a solvent.

Further, an organic diisocyanate can be contained in the binder of the lower coating layer. Examples of the organic diisocyanate compound include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene-1,4-diisocyanate and xylene-1,3-.
Diisocyanate, 4-4'-diphenylmethane diisocyanate, 4,4-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 4,4'-diphenyl Propane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate,
Aromatic diisocyanates such as 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, aliphatic diisocyanates such as lysine diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and the like. Can be mentioned.

The polyisocyanate compound contained in the lower coating layer is contained in the binder in an amount of preferably 10 to 50% by weight, more preferably 20 to 40%.
% By weight. Further, when the curing treatment is performed by electron beam irradiation, a compound having a reactive double bond such as urethane acrylate can be used.

The total weight of the resin component and the curing agent (that is, the binder) is preferably in the range of 15 to 40 parts by weight, more preferably 20 to 40 parts by weight, based on 100 parts by weight of the non-magnetic powder. 30 parts by weight.

The non-magnetic inorganic powder used in the lower coating layer of the present invention can be selected from inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides and metal sulfides. .

As the inorganic compound, for example, an α conversion 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 is
Titanium dioxide, zinc oxide, iron oxide, and barium sulfate are preferred because of their easy availability, cost, small particle size distribution, and many means for imparting functions. Titanium dioxide and α-iron oxide are more preferred.

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 may be acicular, spherical, polyhedral, or plate-like, but in the case of granular non-magnetic inorganic powder, the average particle size is 0.
50% by weight or less of 08 μm or less based on the whole inorganic powder
It is desirable to include the above, and in the case of acicular non-magnetic inorganic powder, the average major axis length is 0.05 to 0.3 μm and the acicular ratio is 3
It is preferable to contain 50 to 20% by weight of the whole inorganic powder.

The loss on ignition is preferably 20% by weight or less, and it is considered most preferable not to have it. 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.

Al ₂ O is formed on the surface of these non-magnetic powders.
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 be homogeneous and dense.

Specific examples of the non-magnetic powder used in the lower coating layer of the present invention include Nanotite manufactured by Showa Denko KK, HIT-100 manufactured by Sumitomo Chemical Co., ZA-G1, α-hematite manufactured by Toda Kogyo Co., 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 preferable non-magnetic powder is 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.

Then, the acicular goethite particles as the precursor particles are dehydrated in a temperature range of 200 to 500 ° C., or
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.

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 it is less than 01% by weight, the dispersion in the binder resin is insufficient, and when it exceeds 50% by weight, Al compounds floating on the particle surface interact with each other, which is not preferable.

In the non-magnetic inorganic powder of the lower coating layer in the present invention, one or two compounds selected from P, Ti, Mn, Ni, Zn, Zr, Sn and Sb, including Al compounds and Si compounds. It is also possible to coat with 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 prepared by pulverizing, sizing and surface treatment. 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 as described above may contain carbon black, and by mixing this carbon black in the lower coating layer, the surface electric resistance Rs, which is a known effect, is lowered to obtain an antistatic effect. That is, the light transmittance can be reduced and a desired micro-Vickers hardness can be obtained. Micro Vickers hardness of the lower coating layer is usually, 25 to 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 The measurement is performed using a diamond triangular pyramid needle having a tip radius of 0.1 μm at the tip of the indenter.

Carbon blacks that can be used include furnaces for rubber, thermals for rubber, blacks for colors,
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 80 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 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 contained in the range of 5 to 49% by weight with respect to the above inorganic powder, and the total weight of the nonmagnetic layer is 4%.
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.

In addition, an organic powder may 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, those of the magnetic layer can be applied to the lubricant, dispersant, additive, solvent, dispersion method and the like of the lower coating layer. In particular, with respect to the amounts and types of additives and dispersants, known techniques relating to the magnetic layer can be applied.

Next, a detailed description will be given of the upper cleaning layer. 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. Especially in the case of a metal magnetic material, Al,
Si, Ca, Y, Ba, La, Nd, Co, Ni and B are important as elements contained in addition to α-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-mentioned ferromagnetic powder, 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 gradual oxidation treatment, that is, a method of immersing it in an organic solvent and then drying it. Any of the method of forming the oxide film on the surface by adjusting the partial pressure of oxygen gas and the inert gas without using an organic solvent can be used.

The ferromagnetic powder of the cleaning layer of the present invention is 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 or more than 80 m ² / g, it is difficult to obtain surface properties, which is not preferable. The ferromagnetic powder of the cleaning layer of the present invention has a crystallite size of 300 to 100 A, preferably 25.
0 to 100 A, more preferably 200 to 140 A.

The saturation magnetization σs of the ferromagnetic powder is 100-18.
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 binder.

The pH of the ferromagnetic powder is preferably optimized depending on the combination with the binder used. The range is 4
However, it is preferably 6-10. 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. Soluble Na, Ca, Fe, N in ferromagnetic powder
It may contain inorganic ions such as i and Sr. It is preferable that these are essentially absent, but if they are 200 ppm or less, they do not particularly affect the characteristics. Further, the ferromagnetic powder preferably has few voids, and the value thereof is 20% by volume or less, more preferably 5% by volume or less.

As the binder used in the cleaning layer of the present invention, conventionally known thermoplastic resins, thermosetting resins,
Reactive resins and mixtures thereof are used. The thermoplastic resin has a glass transition temperature of −100 to 150 ° C., a number average molecular weight of 1,000 to 200,000, preferably 10,000 to 100,000, and a polymerization degree of about 50 to 1.
It is about 000.

Examples of such a material 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 method for producing them are described in detail in JP-A-62-256219. The above resins can be used alone or in combination, but at least one selected from vinyl chloride resin, vinyl chloride vinyl acetate resin, vinyl chloride vinyl acetate vinyl alcohol resin, vinyl chloride vinyl acetate maleic anhydride copolymer is preferred. Combination of seed and polyurethane resin,
Alternatively, a combination of these with polyisocyanate can be used. The structure of polyurethane resin is polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane,
Known materials such as 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, -O
_{SO 3 M, -P = O (} OM) 2, -O-P = 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 and 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 breaking elongation 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, the amount of vinyl chloride resin, polyurethane resin, polyisocyanate, or other resin in the binder, the molecular weight of each resin forming the cleaning layer, the amount of polar groups, or the resins described above. It is of course possible to change the physical properties and the like of the lower coating layer and the cleaning layer as necessary, and known techniques can be applied.

The polyisocyanate used in the cleaning layer is tolylene diisocyanate, 4-4 '.
-Isocyanates such as diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1.5 diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, etc., and formation of these isocyanates and polyalcohols It is also possible to use a polyisocyanate produced by condensation of isocyanates.
Commercially available trade names of these isocyanates are Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR, Millionate MTL, Takenate D-102, Takenate D-102 and Takenate D- manufactured by Nippon Polyurethane Co., Ltd. 110N, Takenate D-200, Takenate D-202, Sumitomo Bayer Desmodur L, Desmodur IL, Desmodur N, Desmodul HL, Dainippon Ink & Co. Barnock D502, etc., and these are used alone or as a curing reaction. The lower coating layer and the upper cleaning layer can be used in combination of two or more by utilizing the difference in sex.

Carbon black may be mixed as an inorganic powder in the cleaning layer of the present invention as in the case of the lower coating layer. For this carbon black, a furnace for rubber, thermal for rubber, black for color, acetylene black or the like may be used. You can 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 5% by weight or less based on the amount 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 have different types, amounts, and combinations in the cleaning layer and the lower coating layer, and are based on the above-mentioned characteristics such as particle size, oil absorption, electric 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. As the abrasive, 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 may be 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, and AKP-5 manufactured by Sumitomo Chemical Co., Ltd.
0, HIT-50, HIT-60, HiT-60A, H
IT-70A, HIT-80, HIT-80G, HIT
-100, G5, G7, S-1 manufactured by Nippon Kagaku Kogyo Co., Ltd., TF-100, TF-140 manufactured by Toda Kogyo Co., Ltd., and the like.

The particle size of these abrasives is from 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 abrasives used in the present invention can be of different types, amounts and combinations of the lower coating layer and the upper cleaning layer, 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 number of abrasives present on the surface of the cleaning layer and the end surface of the cleaning layer of the cleaning medium of the present invention is preferably 5 pieces / 100 μm ² or more.

As the additive 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 of these 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. Examples thereof include 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 types and amounts of these lubricants and surfactants used in the present invention can be properly selected for the lower coating layer and the cleaning layer. 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 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, 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 acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, tetrahydrofuran and other ketones, methanol, ethanol, propanol, butanol. Alcohols such as isobutyl alcohol, isopropyl alcohol, and methylcyclohexanol; methyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate, and other esters; glycol dimethyl ether, glycol monoethyl ether, glycol ethers such as 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 organic solvent used in the present invention is preferably the same type in the cleaning layer and the lower coating layer, but the addition amount 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 constitution 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 high-strength nonmagnetic support using aramid resin or polyethylene naphthalate is preferable. 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.

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 7 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 of the cleaning layer-coated surface and the back layer-coated surface is changed, a dual-structured support may be used or a coating layer may be provided.

The F-5 value in the tape running direction (MD 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, if 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 goes without saying that conventionally known manufacturing techniques can be used as a part of the steps, but a strong kneading force such as a continuous kneader or a pressure kneader is used in the kneading step. It is preferable to use the 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 constitution can be proposed as an example of an apparatus and method for applying a cleaning medium having a multilayer constitution 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 the agglomeration of magnetic particles, a shearing force is applied to the coating liquid inside the coating head by the method disclosed in JP-A-62-95174 and 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, the ferromagnetic powder in the cleaning layer may be oriented.
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 multi-layer coating of the non-magnetic lower coating layer and the cleaning layer, an adhesive layer containing a polymer as a main component is provided, and the adhesiveness is enhanced by corona discharge, UV irradiation, and EB irradiation. It is preferable to combine known methods.

Further, if necessary, calendar processing can be carried out in order 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, it is also possible to perform processing by using 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 surface opposite thereto 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
~ 2/1.

Further, the residual elongation of the cleaning medium is preferably 0.5% or less, and the thermal shrinkage at any temperature of 100 ° C. or less is preferably 1% or less, more preferably 0.5% or less, most preferably 0%. 0.1% or less, 0
% Is ideal. Glass transition temperature of cleaning layer (1
The maximum point of the loss elastic modulus in the dynamic viscoelasticity measurement measured at 10 Hz) is preferably 50 ° C or higher and 120 ° C or lower, and that of the lower coating layer is preferably 0 ° C to 100 ° C. Loss elastic modulus is 1 ×
It is preferably in the range of 10 ⁸ to 8 × 10 ⁹ dyne / 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,
It is preferable that the residual solvent contained in the upper cleaning layer is less than the residual solvent contained in the lower coating layer. Porosity is preferably 50% by volume for both the lower coating layer and the cleaning layer
Hereafter, it is more preferably 40% by volume or less.

The magnetic characteristics of the cleaning layer of the cleaning medium of the present invention have a coercive force Hc in the tape running direction of 500 to 3000 Oe when measured by VSM at a magnetic field of 10 kOe.
It is. The squareness ratio is 0.6 to 0.98, preferably 0.80 or more, and more preferably 0.85 or more. The squareness ratio in the 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 remanence coercive force Hr in the longitudinal direction is also 1800 to 3000
Oe is preferred. Hc and Hr in the vertical direction are 1000 to 5
It is preferably 000 Oe. Further, the center line surface roughness Ra of the cleaning layer is preferably 1.0 to 7.0 nm, but the value should be appropriately set according to the purpose.
RMS surface roughness R _RMS calculated by AFM is 2 to
It is preferably in the range of 15 nm.

The cleaning medium of the present invention has a lower coating layer and a cleaning layer, but 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.

[0107]

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".

<Polyurethane Synthesis Example> First, a synthesis example of the polyurethane resin contained in the lower coating layer will be described. A container equipped with a reflux condenser and a stirrer and preliminarily replaced with nitrogen was placed in Table 1.
The diol shown in 1 was dissolved in cyclohexanone at 60 ° C. under a nitrogen stream. Then, as a catalyst, di-n-dibutyltin dilaurate was used in an amount of 6 with respect to the total amount of raw materials.
0 ppm was added and the solution was further dissolved for 15 minutes. Further, MDI and TMP shown in Table 1 were added, and the mixture was heated and reacted at 90 ° C. for 4 hours to obtain polyurethane resins 1 to 13.

Table 1 shows the OH content and molecular weight of the obtained polyurethane. The OH content of the polyurethane resin is
The number of OH groups per molecule is shown from the OH number determined by the test method of JIS K0070 and the number average molecular weight in terms of polystyrene determined using GPC. In Table 1,% means% by weight, and OH content means the number per molecule. Further, the diols in Table 1 are shown below.

HBpA: Hydrogenated bisphenol A (Rikabinol HB manufactured by Shin Nippon Rika) Compound A: Polypropylene oxide adduct of bisphenol A (molecular weight 600) Compound B: Polypropylene oxide adduct of bisphenol A (molecular weight 1000) PCL600: Polycaprolactone polyol (Molecular weight
600) PCL1000: polycaprolactone polyol (molecular weight 1000) NPG: neopentyl glycol PPG600: polypropylene glycol (molecular weight 60
0) DEIS: sulfoisophthalic acid ethylene oxide adduct TMP: trimethylolpropane.

[0111]

[Table 1]

<Example 1> This example is an example of a cleaning tape for an 8 mm video device in which a cleaning layer and a lower coating layer are formed by a coating liquid having the following composition.

[Preparation of Coating Liquid for Cleaning Layer] Ferromagnetic alloy powder (Fe / Zn / Ni = 92/4/4) 100 parts Hc 2000Oe Crystallite size 15 nm BET specific surface area 59 m ² / g Major axis diameter 0.12 μm A needle ratio of 7 σs 140 emu / g was crushed with an open kneader for 10 minutes, and then vinyl chloride copolymer 7.5 parts vinyl chloride / vinyl acetate / glycidyl methacrylate = 86/9/5 hydroxyethyl copolymer Compound added with sodium sulfonate-SO ₃ Na group content 6 × 10 ⁻⁵ eq / g Epoxy group content 1 × 10 ⁻³ eq / g Mw 30,000 Polyurethane resin (UR8300 manufactured by Toyobo Co., Ltd.) 10 parts Cyclohexanone 60 parts were kneaded for 60 minutes by adding, then abrasive Al ₂ O ₃ (particle size 0.3 [mu] m) 2 parts Ca It was dispersed in a sand mill for 120 minutes by addition of carbon black (particle size 40 nm) 2 parts Methyl ethyl ketone / toluene = 1/1 200 parts. To this, polyisocyanate (Coronate 3041 manufactured by Nippon Polyurethane) 5 parts Butyl stearate 2 parts Stearic acid 1 part Methyl ethyl ketone 50 parts were added, and the mixture was further stirred and mixed for 20 minutes and then filtered using a filter having an average pore size of 1 μm. A cleaning layer coating solution was prepared.

[Preparation of coating liquid for lower coating layer] Non-magnetic inorganic powder α-Fe ₂ O ₃ (hematite) 85 parts Average particle size 0.15 μm S _BET 52m ² / g Surface treatment agent Al ₂ O ₃ , SiO ₂ A pH of 6.5 to 8.0 was crushed with an open kneader for 10 minutes, and then a vinyl chloride copolymer 11 parts was added to a copolymer of vinyl chloride / vinyl acetate / glycidyl methacrylate = 86/9/5 and hydroxyethyl sulfonate. compounds were added to sodium salt -SO ₃ Na group content 6 × 10 ^-5 eq / g epoxide group content ^{1 × 10 -3 eq / g Mw} 30,000 polyurethane resin (number 1 in Table 1) 110 parts of cyclohexanone 60 And 200 parts of methyl ethyl ketone / cyclohexanone = 6/4 were added and dispersed by a sand mill for 120 minutes. To this was added 2 parts of butyl stearate, 1 part of stearic acid and 50 parts of methyl ethyl ketone, and the mixture was further stirred and mixed for 20 minutes, and then filtered using a filter having an average pore size of 1 μm to prepare a coating liquid for lower coating layer. Further, on a polyethylene naphthalate support having a thickness of 10 μm as a non-magnetic support, a sulfonic acid-containing polyester resin was applied as an adhesive layer using a coil bar so that the thickness after drying was 0.1 μm.

Next, the coating liquid for lower layer coating layer obtained as described above was dried to a thickness of 2.0 μm, and immediately after that, the coating liquid for cleaning layer was dried. Was 0.1 μm at the same time, and a reverse roll was used for simultaneous multilayer coating. After that, the non-magnetic support coated with the cleaning layer coating liquid is magnetically oriented with a 3000 gauss magnet in a state where the coating liquid is undried, and after drying, it is composed of a metal roll and an epoxy resin roll. 200m / m / min at a temperature of 40 ° C with a 7-stage calendar
Then, a back layer having a thickness of 0.5 μm was applied. This was slit into a width of 8 mm to produce an 8 mm video cleaning tape.

<Examples 2 to 5> In this example, the same cleaning layer coating solution as in Example 1 was used, and the lower coating layer coating solution was a polyurethane resin. Samples were prepared in the same manner as in Example 1 except for the above.

Example 6 In this example, the cleaning layer was thickened to 1.0 μm, and a sample was prepared in the same manner as in Example 1 except for the above.

Example 7 In this example, the non-magnetic support of the lower coating layer was replaced by α-Fe ₂ O ₃ hematite, and titanium oxide TiO ₂ 85 parts average particle size 0.035 μm crystalline rutile TiO 2 was used. ₂ Content 90% or more Surface treatment layer Alumina S _BET 40m ² / g True specific gravity 4.1 pH 7 was used, and other than that, a sample was prepared in the same manner as in Example 1.

Example 8 In this example, the polyurethane resin of the cleaning layer (UR8300 manufactured by Toyobo Co., Ltd.) was used as the polyurethane resin of No. 1 in Table 1, and other than that, a sample was prepared in the same manner as in Example 1. It was made.

<Comparative Examples 1 to 5 and 7> In this Comparative Example, the polyurethane resin was changed to the polyurethane resin shown in Table 3 (6 to 11 in Table 1).
A sample was prepared in the same manner as described above.

<Comparative Example 6> In this comparative example, the thickness of the cleaning layer was further increased to 1.5 μm, and a sample was prepared in the same manner as in Example 1 except for the above.

<Embodiment 9> This embodiment is an example of a cleaning disk for a floppy disk drive in which both the cleaning layer and the lower coating layer are formed by completely different formulations.

[Cleaning Layer Coating Liquid Composition] Ferromagnetic metal fine powder Co-substituted barium ferrite 100 parts Average plate diameter 0.06 μm Plate ratio 6 Specific surface area 35 m ² / g Vinyl chloride copolymer 9 parts —SO ₃ Na Group content 8 × 10 ⁻⁵ eq / g Polymerization degree 300 Fine particle abrasive (Cr ₂ O ₃ , average particle size 0.2 μm) 7 parts Toluene 30 parts Methyl ethyl ketone 30 parts After kneading the above composition with a kneader for about 1 hour further, a polyester polyurethane resin 5 parts neopentyl glycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 -SO 3 Na group content 1 × 10 ^-4 eq / g average molecular weight of 35,000 toluene 200 parts Methyl ethyl ketone 200 parts Is added and dispersed by a kneader for about 2 hours. Then, 5 parts of carbon black, Ketjenblack EC manufactured by Lion Akzo Co., Ltd. average particle size 20 to 30 mμ α-alumina 2 parts, AKP-12 manufactured by Sumitomo Chemical Co., Ltd. average particle size (longest diameter a) 0.5 μm were added to a sand grinder. Then, the dispersion treatment was performed for 2000 rpm for about 2 hours. Further, 6 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) and 6 parts of tridecyl stearate were added, and the mixture was dispersed again by a sand grinder to obtain a paint for a cleaning layer.

[Coating liquid composition for lower coating layer] Non-magnetic inorganic powder TiO ₂ 80 parts Average primary particle diameter 0.035 μm Crystalline rutile TiO ₂ content 90% or more Surface treatment agent Al ₂ O ₃ BET specific surface area 40 m ² / g DBP oil absorption amount 27 to 38 g / 100 g pH 7 carbon black 20 parts Average primary particle size 16 mμ DBP oil absorption amount 80 ml / 100 g pH 8.0 Specific surface area by BET method 250 m ² / g Volatile content 1.5% Vinyl chloride- Vinyl acetate-vinyl alcohol copolymer 12 parts —SO ₃ Na group content 5 × 10 ⁻⁴ eq / g Composition ratio 86: 13: 1 Degree of polymerization 300 Polyurethane resin (No. 1 in Table 1) 5 parts α-Al ₂ O ₃ continuous (average particle diameter 0.2 [mu] m) 5 parts butyl stearate 1 part 1 part of stearic acid Methyl ethyl ketone 200 parts the above composition After kneading at over da and dispersed using a sand mill. To the obtained dispersion liquid, 1 part of polyisocyanate was added, 40 parts of butyl acetate was further added, and the mixture was filtered using a filter having an average pore size of 1 μm to obtain a coating liquid for lower coating layer.

The cleaning layer coating material and the lower layer coating layer coating material obtained as described above were coated on a polyethylene terephthalate layer having a thickness of 75 μm, first while the lower layer coating layer coating material was placed in the wet state. The coating material for the cleaning layer was applied, and the back surface was treated in the same manner. The dry coating thickness of the lower coating layer is 2 μm, and the thickness of the cleaning layer is 0.3.
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 average particle size of the non-magnetic particles contained in the cleaning layer of the obtained cleaning disk was 0.22 μm.

Tables 2 and 2 show the results of determining the thickness of each cleaning layer, the lower coating layer, the powder type and the composition of polyurethane, and the surface roughness Ra in the samples of the cleaning media of the respective Examples and Comparative Examples as described above. 3 shows.
Further, the head wear amount, the head cleaning force, the envelope flatness (ME compatibility), and the head scratches as a result of performing the cleaning test with each sample are also shown.

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

(Method of Measuring Thickness of Cleaning Layer and Lower Coating Layer) A thickness of about 0.1 μm was cut with a diamond cutter over the longitudinal direction of the cleaning medium and observed with a transmission electron microscope at a magnification of 30,000, and a photograph thereof was taken. 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 surface 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 Diameter 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 the X-ray diffraction, in the γ iron oxide ferromagnetic powder, (4, 4, 0) plane 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
No. 00 was used to run the cleaning tape at 23 ° C. × 70% RH for 10 minutes, the head height before and after that was measured, and the head wear per minute was calculated.

(Head Cleaning Power) The output was measured in advance by EV-S900 using Hi-8 Super DC P6-120 manufactured by Fuji Photo Film Co., Ltd. afterwards,
Run a standard tape created for the purpose of causing clogging with the EV-S900, observe the head condition with a strobe, and stop running when the head is heavily soiled and there is no output. To confirm. 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. Further, the scratches on the head after running the cleaning tape were observed.

(Compatibility with vapor-deposited tape and metal tape) Using the Hi-8 deck EV-S900, a metal tape (sample tape manufactured by Fuji Photo Film Co., Ltd.) which is liable to cause uneven wear was previously used at 5 ° C. × 80% RH. Let it run for at least 2 hours in the environment. After that, Sony Hi-8ME
Record and reproduce a 7.4 MHz RF signal on E6-120 and confirm that the flatness is 80% or less. Then, run each cleaning tape of the sample for 1 minute,
Again, the Sony Hi-8ME E6-120 has 7.4.
The MHz signal is recorded and reproduced to measure the envelope flatness.

(Envelope flatness) This is a percentage of the reproduction envelope divided by excluding the portion with the largest output and the portion with the smallest output.

[0139]

[Table 2]

[0140]

[Table 3]

According to the above table, in Comparative Example 1, the content of the short-chain diol is small, and therefore the coating film becomes too soft and a sufficient head cleaning force cannot be obtained. In Comparative Example 2, since the content of the short-chain diol was large, the solubility in the solvent was lowered and the dispersibility of the nonmagnetic powder was lowered, so that the surface property of the cleaning layer was lowered and the head wear amount was reduced. Increased,
The head is scratched. In Comparative Example 3, since the content of long-chain diol is small, the solubility in the solvent is lowered, and similarly to Comparative Example 2, the head wear amount is increased and the head scratches are generated. Since Comparative Example 4 does not contain an ether group, the adsorptivity to the fine powder is lowered, and thus the surface property is lowered and the head scratches are generated. In Comparative Example 5, the content of ether groups is large, the solubility in the solvent is lowered, and similarly to Comparative Example 2, the head wear amount increases and the head scratches occur. In Comparative Example 6, since the thickness of the cleaning layer is large, the tip shape of the magnetic head after cleaning is not sharp, and the ME compatibility is low. In Comparative Example 7, since the long-chain diol content is large, the coating film strength is reduced, and sufficient cleaning power is not obtained.

On the other hand, in Examples 1 to 9 of the present invention, the head was not excessively worn, had good cleaning power and ME compatibility, and did not cause head scratches. As a result, favorable results have been obtained.

Claims (4)

[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 a binder is provided thereon. In the cleaning medium for a magnetic recording device, the binder used in the lower coating layer comprises at least a diol and a polyurethane resin which is a reaction product of an organic diisocyanate as a main raw material, and the polyurethane resin is a short chain diol having a cyclic structure. A cleaning medium for a magnetic recording device, comprising a long-chain diol containing an ether group. 2. In the polyurethane resin, the short chain diol having the cyclic structure has a molecular weight of less than 500, and the long chain diol containing an ether group has a molecular weight of 500 to 5.
The cleaning medium for a magnetic recording device according to claim 1, wherein the cleaning medium is 000. 3. The polyurethane resin contains 17 to 40% by weight of a short chain diol having a cyclic structure, and has an ether group of 1.0 to 5.0 with respect to the entire polyurethane resin.
The cleaning medium for a magnetic recording device according to claim 1, wherein a long-chain diol containing mmol / g is contained in the polyurethane resin in an amount of 10 to 50% by weight. 4. The lower coating layer and the cleaning layer are formed by a wet-on-wet coating method in which the cleaning layer is coated on the lower coating layer while the lower coating layer is in a wet state. 1. The cleaning medium for a magnetic recording device according to 1.