JP2002183918A - Cleaning medium for magnetic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning medium for a magnetic recording device having high cleaning power for a magnetic head without a scratch on the magnetic head and little wear of the head. SOLUTION: The cleaning medium for a magnetic recording device has a lower coating layer mainly containing nonmagnetic inorganic powder and a binder applied on a nonmagnetic supporting body and has a cleaning layer containing at least inorganic powder of ferromagnetic powder and a binder formed thereon. The binder used for the lower coating layer consists of a polyurethane resin as the reaction product from polyols and organic diisocyanates as the main source material. As for the polyol component, the polyurethane resin contains a short-chain diol component having a cyclic structure by 15 to 40 m.%, a long-chain polyether polyol component by 10 to 50 m.% and a polar group-containing long-chain polyol component having 500 to 5,000 molecular mass.

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 In general, recording / reproducing of a magnetic recording apparatus for video, audio, and computer is performed by sliding a magnetic head and a magnetic medium such as a magnetic tape while contacting each other. At this time, if shavings of the magnetic tape or dust around the device adhere to the surface of the magnetic head, the reproduction output decreases, and further, no output is obtained. In order to recover such a reduced reproduction output, a cleaning medium such as a cleaning tape for cleaning the dirt adhering to the surface of the magnetic head and restoring the reproduction output is used.

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 a magnetic head and a 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 shape of the head to some extent. Particularly, in recent years, a magnetic head of a magnetic recording / reproducing apparatus for performing high-density recording such that the shortest recording wavelength is 1 μm or less has been used. The recording / reproducing performance is hindered.

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

In recent years, like Hi-8 and DVC,
A magnetic recording device that can use both a vapor deposition tape (ME tape) and a metal powder tape (MP tape) has appeared. Since a metal thin film having high rigidity comes into contact with the magnetic head of 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. Furthermore, since the vapor deposition tape does not contain an abrasive, the magnetic head is less worn by the contact and has low conformability with the magnetic head. On the other hand, a metal tape has a magnetic layer in which a magnetic powder is contained in a binder. In addition, since it has an abrasion force, it is well adapted to a magnetic head.

Therefore, when the metal tape is moved relative to the magnetic head after the vapor deposition tape is run, the change per head is not so large. When running the tape,
There is a case where the head contact becomes poor.

As a prior art of a polishing tape used for polishing a magnetic head, for example, Japanese Patent Application Laid-Open No. 62-92205 discloses a non-magnetic support comprising an intermediate layer containing a non-magnetic powder and a non-magnetic abrasive. There has been disclosed a polishing tape in which polishing layers are sequentially laminated. This polishing tape adopts a two-layer structure,
While the surface properties of the intermediate layer are roughened, the abrasive particles in the upper polishing layer are made finer to prevent head scratches while maintaining the polishing power. For polishing, surface roughness of 0.0
Since the thickness is 3 to 0.3 μm, it is difficult to perform appropriate polishing for cleaning because of a large amount of head wear, which is not suitable for use as a cleaning tape. A polishing tape for a magnetic head similar to the above is disclosed in Japanese Patent Laid-Open No. 62-94.
No. 270 and JP-A-62-92205. These also have a two-layer polishing layer, but it is difficult to perform good cleaning without damaging the magnetic head by appropriate polishing, and is not suitable as a cleaning medium.

Japanese Patent Laid-Open Publication No. Hei 6-139531 discloses a cleaning tape for a magnetic head which has 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 determined by lowering the lower cleaning layer. A technique has been disclosed in which the layer is made larger than the Young's modulus of the layer to achieve both good cleaning properties and low head wear.
However, in the cleaning tape of this prior example, the two cleaning layers both contain ferromagnetic powder, and the anisotropy of the Young's modulus as a whole tape occurs remarkably. When the shape of the magnetic head is different, it is difficult to exhibit good cleaning properties for each shape, especially 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 restoration of compatibility between the metal tape and the vapor deposition tape is insufficient.

As described above, even if there is a difference in the shape of the magnetic head, it is possible to remove stains on the magnetic head and to adjust the shape of the magnetic head by using a cleaning medium having a moderately supple and good surface property. If possible, it is possible to improve the head contact of the evaporation tape,
It has been found that compatibility between the metal tape and the vapor deposition tape can be sufficiently restored.

Therefore, the applicant of the present invention has conducted a study on cleaning a magnetic head of a high-density magnetic recording / reproducing apparatus or the like. Provided is a cleaning medium for a magnetic recording apparatus which can perform good cleaning irrespective of the shape, can adjust the shape without damaging the tip of the magnetic head after cleaning, and has good compatibility. This cleaning medium for a magnetic recording device is provided with a lower coating layer mainly containing a non-magnetic inorganic powder and a binder on a non-magnetic support, and a cleaning medium containing at least an inorganic powder of a ferromagnetic powder and a binder thereon. And a binder used for the lower coating layer comprises a polyurethane resin which is a reaction product containing 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 an ether group. However, there is a problem that the strength of the coating film is not sufficient due to insufficient dispersibility of the nonmagnetic inorganic powder, and the cleaning effect is not sufficiently satisfied. Was.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cleaning medium for a magnetic recording apparatus which has a high cleaning power for a magnetic head, has no scratch on the magnetic head, and has little head wear. Things.

[0012]

According to the present invention, an undercoating layer mainly containing a nonmagnetic inorganic powder and a binder is provided on a nonmagnetic support, and at least an inorganic powder of a ferromagnetic powder and a binder are provided thereon. In the cleaning medium for a magnetic recording device provided with a cleaning layer containing: a binder resin used for the lower coating layer is a polyurethane resin which is a reaction product mainly composed of a polyol and an organic diisocyanate. The polyol component is a short chain diol component having a cyclic structure in the polyurethane resin in an amount of 15 to 40% by mass, a long chain polyether polyol component in an amount of 10 to 50% by mass, and a polar group-containing length having a molecular weight of 500 to 5000. A cleaning medium for a magnetic recording device, comprising a chain polyol component. The present invention preferably has the following aspects. (1) The polar group-containing long-chain polyol component contains a polar group such that the polar group becomes 1 × 10 ⁻⁵ eq / g to 2 × 10 ⁻⁴ eq / g with respect to the polyurethane resin. Item 6. A cleaning medium for a magnetic recording device according to item 1. (2) The polar group-containing long-chain polyol component is -SO ₃ M, -OSO
₃ M, -COOM, -PO ₃ M ₂ , -OPO ₃ M ₂ , -NR ₂ , -N ⁺ R ₂ R´COO- (where M is a hydrogen atom, an alkali metal, ammonium, R,
R 'represents an alkyl group having 1 to 12 carbon atoms), wherein the cleaning medium has at least one kind of polar group selected from the group consisting of: (3) The polyurethane resin has 3 to 2 OH groups per molecule.
A cleaning medium for a magnetic recording device, comprising zero. (4) The magnetic layer, wherein the lower coating layer and the cleaning layer are formed by a wet-on-wet coating method in which a cleaning layer is coated thereon while the lower coating layer is in a wet state. Cleaning media for recording devices.

According to the present invention as described above, a lower coating layer mainly containing a nonmagnetic inorganic powder and a binder is provided on a nonmagnetic support, and at least an inorganic powder of a ferromagnetic powder and a binder are provided thereon. And a cleaning layer including
In the lower coating layer, the short-chain diol component having a cyclic structure as the polyol component is 15 to 40% by mass, the long-chain polyether polyol component is 10 to 50% by mass, and the molecular weight is 500 to 500%.
The use of a binder made of a polyurethane resin containing a polar group-containing long-chain polyol component of 5,000, particularly a molecular weight of 50
By using the polar group-containing long-chain polyol component of 0 to 5000, the dispersibility of the nonmagnetic powder in this polyurethane resin is further improved, so that the surface property of the cleaning layer applied on the upper layer is further improved, and And the head wear can be reduced. Further, the use of the above-mentioned binder further increases the strength of the coating film, and can exert excellent cleaning power even when the temperature of the magnetic head becomes high due to friction during cleaning.

In the known polyurethane, when the cyclic structure and the urethane bond concentration increase, the solvent solubility decreases, the dispersibility of the nonmagnetic inorganic powder decreases, the smoothness of the lower coating layer decreases, and the upper cleaning layer has Although the smoothness is also reduced, the polyurethane of the present invention has the advantages of being excellent in solvent solubility and dispersibility. This is because the polyurethane contains a very small amount of hydrophilic ether groups and also contains a polar group-containing long-chain polyol component. It is considered that the dispersibility was improved due to the ease of removal. In addition, since an appropriate toughness can be provided, the whole coating film does not become brittle, so that there is an advantage that the repetitive running property does not decrease.

Further, when cleaning is performed by bringing the cleaning layer into contact with the surface of the magnetic head and performing cleaning with the cleaning medium of the present invention as described above, the strength is isotropic and the overall flexibility is moderate. Thereby, a good cleaning effect can be obtained even if the shape of the magnetic head is different. That is, the nonmagnetic inorganic powder of the lower coating layer is not oriented with respect to the cleaning layer containing the ferromagnetic powder, and therefore, is strongly isotropic. With such a configuration,
The surface properties of the cleaning layer of the cleaning medium and the state of contact with the magnetic head are improved, and the wear of the magnetic head is small, but the cleaning property for removing dirt on the magnetic head in a short time is excellent.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic structure of the cleaning medium of the present invention is that a non-magnetic support is composed of a lower coating layer mainly composed of a non-magnetic inorganic powder and a binder, and at least a ferromagnetic powder on the lower coating layer. A cleaning layer containing an inorganic powder and a binder is provided.

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 to 1.0 μm.
The thickness is 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 details of the lower coating layer will be described. The binder used for the lower coating layer is composed of a polyurethane resin which is a reaction product containing at least a polyol and an organic diisocyanate as main raw materials. 15 to 40% by mass, 10 to 50% by mass of a long-chain polyether polyol component, and a molecular weight of 500
5,000 to 5000 polar group-containing long-chain polyol components. This polyurethane resin will be described. Hereinafter, this polyurethane resin is also referred to as “polyurethane resin for the present invention”.

First, bisphenol A, hydrogenated bisphenol A, bisphenol S, hydrogenated bisphenol S, bisphenol P, hydrogenated bisphenol P, hydrogenated bisphenol P, and cyclohexane are used as the short-chain diol component having a cyclic structure, which is a raw material of the polyurethane resin for use in the present invention. Dimethanol,
Aromatics such as cyclohexanediol and hydroquinone,
Diols having an alicyclic group and those which can be selected from ethylene oxide or propylene oxide adduct thereof, and those having a molecular weight of less than 500 are preferable. Among these, preferred are bisphenol A,
Examples include hydrogenated bisphenol A and their ethylene oxide adducts and propylene oxide adducts. More preferred is hydrogenated bisphenol A. The content of the short-chain diol component having a cyclic structure in the polyurethane resin for use in the present invention is 15 to 40% by mass, and preferably 20 to 35% by mass. More preferably 22 to
30% by mass. If it is less than 15% by mass, the resulting coating film will be too soft, failing to obtain sufficient strength, resulting in reduced still durability. On the other hand, if it exceeds 40% by mass, the solubility in a solvent is reduced, the dispersibility of the ferromagnetic powder is reduced, and a magnetic recording medium having excellent electromagnetic conversion characteristics cannot be obtained.

The long-chain polyether polyol component as a raw material of the polyurethane resin for use in the present invention includes polyalkylene glycols such as polypropylene glycol, polyethylene glycol and polytetramethylene glycol.
Polyether polyols obtained by adding polyethylene oxide and / or polypropylene oxide to cyclic diols such as bisphenol A, hydrogenated bisphenol A, bisphenol S and bisphenol P are used. Preferred are propylene oxide adduct of bisphenol A, ethylene oxide adduct of bisphenol A, ethylene oxide adduct of hydrogenated bisphenol A, and propylene oxide adduct of hydrogenated bisphenol A. The molecular weight is between 500 and 5000, preferably between 600 and 3000. If it is 5000 or more, T
g decreases, the strength also decreases, and the durability decreases.

The ether content of the polyurethane resin for use in the present invention is preferably 1 to 5 mmol / g. Particularly preferably, it is 2 to 4 mmol / g. When the content of the ether group is less than 1 mmol / g, the adsorptivity to the non-magnetic inorganic powder decreases, and the dispersibility decreases. 5
If it is at least mmol / g, the solubility in the solvent will decrease, and the dispersibility will decrease. In the present invention, since the polyurethane resin for use in the present invention has a cyclic structure, the coating film strength is high, the durability is excellent, the solubility in a solvent is high, and the dispersibility is excellent.

The polar group of the polar group-containing long-chain polyol component which is a raw material of the polyurethane of the present invention includes -SO
_{3 M, -OSO 3 M, -COOM} , -PO 3 M 2, -OPO
_{3 M 2, -NR 2, -N} + R 2 R'COO - ( wherein M represents a hydrogen atom, an alkali metal, ammonium, R, R 'represents an alkyl group having 1 to 12 carbon atoms) those selected from Is used. As the polyol skeleton structure, polyester polyol, polyether polyol, polyether ester polyol, polycarbonate polyol and the like are used. Specifically, 5-sodium sulfoisophthalic acid, 5-potassium isophthalic acid, sodium sulfoterephthalic acid, potassium terephthalic acid, 2-sodium sulfo-1,4-butanediol, 2-potassium sulfo-
Dicarboxylic acid or glycol having a polar group such as 1,4-butanediol, sodium bis (2-hydroxyethyl) phosphinate, dimethylolpropionic acid, sodium dimethylolpropionate, sodium sulfosuccinic acid, together with other glycols and dicarboxylic acids A polar group-containing polyester polyol obtained by dehydration condensation, a polar group-containing polyester polyol obtained by ring-opening polymerization of a lactone such as ε-caprolactone using the above polar group-containing diol as an initiator, and a polar group-containing diol such as ethylene oxide and propylene oxide And a polar group-containing polyether diol to which an alkylene oxide is added.

Other glycols used in the polyester polyol include ethylene glycol, 1,3
-Propanediol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-
There are aliphatic glycols such as octanediol, 1,9-nonanediol, diethylene glycol and dipropylene glycol, and alicyclic glycols such as cyclohexanediol and cyclohexanedimethanol. As other dicarboxylic acids, aliphatic or aromatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid, phthalic acid, isophthalic acid, terephthalic acid and naphthalenedicarboxylic acid are used.

Preferred are, for example, polyester polyols obtained by dehydrating and condensing 5-sodium sulfoisophthalic acid / isophthalic acid / neopentyl glycol.
Polyester polyol obtained by ring-opening polymerization of ε-caprolactone using ethylene oxide adduct of 5-potassium sulfoisophthalic acid as an initiator, 2-sodium sulfo-1,
Examples thereof include polyether polyol obtained by adding propylene oxide to 4-butanediol. Molecular weight 50
It is 0 to 5000, preferably 600 to 2500.
When a polar group is introduced into polyurethane using this polyol, the distribution of the polar group in the polyurethane molecule is reduced, and dispersibility and dispersion stability are improved. If the molecular weight is too large, the amount of polar groups that can be introduced into the polyurethane decreases, and the dispersibility decreases. The amount of the polar group in the polyurethane is preferably such that the amount of the polar group is 1 × 10 ⁻⁵ eq / g to 2 × 10 ⁻⁴ eq / g. When the number increases, the viscosity of the solution tends to increase due to association between polar groups, and the dispersibility tends to decrease.

The glass transition temperature Tg of the polyurethane resin for use in the present invention is preferably 45 to 120 ° C., and more preferably 50 to 90 ° C. If the temperature is higher than this, the strength of the coating film is low, and the running durability is reduced. The weight average molecular weight of the polyurethane resin for use in the present invention is 10,000 to 200,000,
0000-100,000 is preferred, and 20,000
~ 800,000 is more preferable, and 30,000-7
000 is particularly preferred. If the weight average molecular weight is less than 10,000, the coating film strength tends to decrease, and the running durability tends to decrease. These have a weight average molecular weight of 2
If it is more than 000, the solubility in a solvent tends to decrease, and the dispersibility tends to decrease.

Further, as the short-chain diol used in the polyurethane resin for use in the present invention, a diol other than the above can be used in combination. Specifically, ethylene glycol, 1,3
-Propylene diol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethylpropanediol, 1,8-octanediol, 1,9 Aliphatic diols such as nonanediol, diethylene glycol, cyclohexane-1,4-diol and cyclohexane-1,4-dimethanol, and alicyclic diols.

Examples of the organic diisocyanate compound contained as a raw material of the polyurethane resin for use in the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene-1,4-diisocyanate, 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'-diphenylpropane diisocyanate, m -Phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-
Aromatic diisocyanates such as 1,5-diisocyanate and 3,3'-dimethoxydiphenyl-4,4'-diisocyanate; aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate and lysine diisocyanate; isophorone diisocyanate; hydrogenated tolylene diisocyanate Alicyclic diisocyanates such as isocyanate and hydrogenated diphenylmethane diisocyanate can be exemplified. The diisocyanate compound contained in the polyurethane is preferably contained in the binder in the range of 10 to 50% by mass, and more preferably in the range of 20 to 40% by mass.

A synthetic resin of vinyl chloride may be used in combination with the polyurethane resin of the present invention. The polymerization degree of the vinyl chloride resin that can be used in combination is preferably from 100 to 600,
200 to 450 are particularly preferred. The vinyl chloride resin may be a copolymer of a vinyl monomer, for example, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylonitrile and the like. Further, a cellulose derivative such as a nitrocellulose resin, an acrylic resin, a polyvinyl acetal resin, a polyvinyl butyral resin, an epoxy resin, a phenoxy resin, or 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 for use in the present invention preferably contains 10 to 100% by mass in the binder, and more preferably 20 to 100% by mass. Particularly preferably, the amount is 50 to 100% by mass. 1
If it is 0% by mass or less, the solubility in the solvent is reduced, and the dispersibility is reduced.

The vinyl chloride resin contains 10% in the binder.
It is preferably contained in an amount of from 80 to 80% by mass, and more preferably from 20 to 70% by mass. Particularly preferably, the amount is 30 to 60% by mass. For the lower coating layer, a curing agent can be used together with a binder. Examples of the curing agent include a polyisocyanate curing agent and an epoxy curing agent, and a polyisocyanate curing agent is preferable. Examples of the polyisocyanate curing agent, the organic diisocyanate compound, the diisocyanate and trimethylolpropane,
Reaction products with polyhydric alcohols such as glycerin, for example, the reaction product of 3 mol of tolylene diisocyanate with 1 mol of trimethylolpropane, the reaction product of xylylene diisocyanate or the reaction product of 3 mol of hexamethylene diisocyanate with 1 mol of trimethylolpropane, etc. There is. Further, as an isocyanurate type polyisocyanate obtained by polymerizing a diisocyanate compound, such as tolylene diisocyanate and hexamethylene diisocyanate;
There are 5,7-mers. Further, there is polymeric MDI which is a multimer of MDI. In the case of performing a curing treatment by electron beam irradiation, a compound having a reactive double bond such as urethane acrylate can be used.

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

The total mass of the resin component and the curing agent (that is, the binder) is based on 100 parts by mass of the nonmagnetic inorganic powder.
Usually, it is preferably in the range of 15 to 40 parts by mass,
More preferably, it is 20 to 30 parts by mass.

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

The particle size of these non-magnetic inorganic powders is 0.3.
The thickness is preferably from 005 to 2 μm, but if necessary, non-magnetic inorganic powders having different particle sizes may be combined, or even a single non-magnetic inorganic powder may have a similar particle size distribution to achieve the same effect. Particularly preferably, the particle size of the nonmagnetic inorganic powder is 0.01 to 0.2 μm. Tap density is 0.05 to 2 g / ml, preferably 0.2 to 1.5
g / ml. The water content of the nonmagnetic inorganic powder is 0.1 to 5
%, Preferably 0.2 to 3% by mass, more preferably 0.3 to 1.5% by mass. The pH of the nonmagnetic inorganic powder is from 2 to 11, and the pH is particularly preferably from 5 to 10. The specific surface area of the nonmagnetic inorganic powder is 1 to 100 m ² / g,
Preferably 5 to 70 m ² / g, more preferably 10 to 6
5 m ² / g. The crystallite size of the nonmagnetic inorganic powder is preferably 0.004 to 1 μm, and 0.04 to 0.1 μm.
Is more preferred. Oil absorption using DBP is 5-100m
1/100 g, preferably 10-80 ml / 100 g,
More preferably, it is 20 to 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. In the case of a granular nonmagnetic inorganic powder, an average particle size of 0.08 μm or less is contained in an amount of 50% by mass or more based on the whole inorganic powder. In addition, in the case of the acicular nonmagnetic inorganic powder, a powder having an average major axis length of 0.05 to 0.3 μm and an acicular ratio of 3 to 20 is contained in an amount of 50% by mass or more based on the whole inorganic powder. Is preferred.

It is preferable that the ignition loss is 20% by mass or less, and it is considered that it is most preferable that the ignition loss is not present. 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 layer non-magnetic inorganic powder in water at 25 ° C. is 20
It is preferably in the range of 0~600mJ / m ^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
Pcs / 100A is appropriate. PH of isoelectric point in water is 3
It is preferably between 6 and 6.

The surface of these non-magnetic inorganic powders is made of Al_Two
O_Three, SiO_Two, TiO_Two, ZrO _Two, SnO_Two, Sb
_TwoO_Three, ZnO, Y_TwoO_ThreeSurface-treated
preferable. Al is particularly preferable for dispersibility._TwoO_Three, Si
O_Two, TiO_Two, ZrO_TwoIs more preferable.
Al_TwoO_Three, SiO_Two, ZrO_TwoIt is. These are
Can be used together or used alone
You. Also, using the surface treatment layer co-precipitated according to the purpose
After treating with alumina, the surface layer is
Mosquito treatment or vice versa.
Wear. Also, the surface treatment layer can be made porous depending on the purpose.
Although it does not matter, it is generally preferred that the material be homogeneous and dense.

Specific examples of the non-magnetic inorganic powder used in the lower coating layer of the present invention include Nanotite manufactured by Showa Denko KK, HIT-100 and ZA-G1 manufactured by Sumitomo Chemical Co., α-hematite manufactured by Toda Kogyo KK, and DPN. -250, DPN-250
BX, DPN-245, DPN-270BX, DPN-
550BX, Ishihara Sangyo Titanium Oxide TTO-51B,
TTO-55A, TTO-55B, TTO-55C, T
TO-55S, TTO-55D, SN-100, α hematite E270, E271, E300, STT-4D, STT-30D, STT-30, STT manufactured by Titanium Industry Co., Ltd.
-65C, Teica MT-100S, MT-100T,
MT-150W, MT-500B, MT-600B, M
T-100F, MT-500HD, FINE made by Sakai Chemical Co.
X-25, BF-1, BF-10, BF-20, ST-
M, DEFIC-Y and DEFIC-R manufactured by Dowa Mining Co., Ltd., AS2BM and TiO2P25 manufactured by Nippon Aerosil Co., Ltd. 100A and 500A manufactured by Ube Industries, Y-LOP manufactured by Titanium Industry, and fired products thereof.

Among the above, particularly preferred non-magnetic inorganic powders are α-iron oxide and titanium dioxide. As α-iron oxide (hematite), those obtained under the following conditions can be used. First, ac-like goethite particles as precursor particles are obtained from the α-Fe ₂ O ₃ particle powder 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. To generate needle-like goethite core particles by performing an oxidation reaction, and then, to an aqueous ferrous salt solution containing the needle-like goethite core particles, an equivalent amount or more with respect to Fe ²⁺ in the aqueous ferrous salt solution. A method of growing the needle-like goethite nucleus particles by adding an alkali hydroxide aqueous solution of the above, and then passing an oxygen-containing gas through. 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. In addition,
There is no problem even if different elements such as Ni, Zn, P, and Si, which are usually added to improve the properties of the particle powder during the reaction of forming goethite particles, are added.

Then, the acicular goethite particles, which are precursor particles, are dehydrated in a temperature range of 200 to 500 ° C.
If necessary, needle-like α-Fe ₂ O ₃ particles are obtained by annealing at a temperature 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 surface of the acicular α-Fe ₂ O ₃ particles obtained by dehydration, so that the particles are extremely polarized. 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
Particle powder is obtained by dispersing needle-like α-Fe ₂ O ₃ particles obtained by dehydration or annealing into an aqueous solution to form a suspension,
An α-Fe ₂ O ₃ was added by adding an Al compound and adjusting the pH.
After coating the additive compound on the particle surface of the particles, filtration,
It can be obtained by washing with water, drying, pulverizing and, if necessary, further performing deaeration / 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 addition amount of the Al compound is 0.01 to 50% by mass in terms of Al with respect to the α-Fe ₂ O ₃ particle powder. 0.
When the amount is less than 01% by mass, the dispersion in the binder resin is insufficient, and when the amount exceeds 50% by mass, 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 according to the present invention, one or two of compounds selected from P, Ti, Mn, Ni, Zn, Zr, Sn and Sb, including an Al compound and a Si compound. It can also be coated using more than one species. The addition amount of these compounds used together with the Al compound is in the range of 0.01 to 50% by mass with respect to the α-Fe ₂ O ₃ particle powder. When the amount is less than 0.01% by mass, there is almost no effect of improving the dispersibility by the addition, and when the amount exceeds 50% by mass, compounds floating on 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. Rutile type and anatase type are classified according to the type of 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 a 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.

The surface treatment is performed by dry grinding the above titanium oxide material.
After that, add water and dispersant, wet mill and centrifuge
Classification is performed. After that, the fine slurry is transferred to the surface treatment tank.
Where the metal hydroxide is surface coated. Ma
First, a predetermined amount of Al, Si, Ti, Zr, Sb, Sn, Z
An aqueous solution of a salt such as n is added to neutralize the acid, or
Add alkali and form hydrated oxide to form titanium oxide particles
Cover the child surface. Water-soluble salts produced as by-products are decantersi
Solution, filtration and washing, and finally the slurry pH
Is adjusted and filtered, and washed with pure water. Washed case
Ki is dried by spray dryer or band dryer
Is done. Finally, this dried product is crushed by a jet mill,
Become a product. Also, not only water-based but also titanium oxide powder
AlCl _Three, SiCl_FourSteam then flows through the steam
And Al and Si surface treatment can be performed. So
G.D.Parfitt and K.S.W.
Sing "Characterization of Powder Surfaces" Academic
Press, 1976.

Carbon black may be used in combination with the non-magnetic inorganic powder as described above. By mixing this carbon black into the lower coating layer, the surface electric resistance Rs, which is a known effect, is reduced, and the antistatic effect is reduced. , The light transmittance can be reduced, and a desired micro-Vickers hardness can be obtained. The micro Vickers hardness of the lower coating layer is usually 25 to 60 kg / mm ² (# 245
To 588 MPa), preferably 30 to 50 kg / mm ² (〜294 to 490 MPa) for adjusting the head contact.
a) The measurement is performed by using a diamond triangular pyramid needle having a ridge angle of 80 ° and a tip radius of 0.1 μm as a tip of an indenter using an NEC thin film hardness meter HMA-400.

Examples of usable carbon black include furnace for rubber, thermal for rubber, black for color,
Acetylene black and the like. The specific surface area of these carbon blacks is 100 to 500 m ² / g, preferably 150 to 400 m ² / g, and the DBP oil absorption is 20 to ⁴ m ² / g.
00ml / 100g, preferably 30-200ml / 100g.
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 the carbon black used in the present invention include BLACKPEA manufactured by Cabot Corporation.
RLS2000, 1300, 1000, 900, 80
0,880,700, VULCAN XC-72, # 3050B, 3150B, 3250 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.
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 can be used in a range of 5 to 49% by mass based on the nonmagnetic inorganic powder and in a range not exceeding 40% of the total mass of the nonmagnetic layer. These carbon blacks can be used alone or in combination. The carbon black that can be used in the present invention can be referred to, for example, “Carbon Black Handbook” edited by Carbon Black Association.

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

In addition, the lubricant, dispersant, additive, solvent, dispersing method and the like of the lower coating layer can be the same as those of the magnetic layer. In particular, with respect to the amounts and types of additives and dispersants, known techniques for the magnetic layer can be applied.

Next, the upper cleaning layer will be described in detail. First, as the inorganic powder to be mixed into the cleaning layer, a ferromagnetic powder is included.
γ-FeOx (x = 1.33 to 1.5), Co-modified γ-
FeOx (x = 1.33 to 1.5), α-Fe or N
Known ferromagnetic powders such as ferromagnetic alloy powder containing i or Co as a main component (75% or more), barium ferrite, and strontium ferrite can be used, but a ferromagnetic alloy powder containing α-Fe as a main component is preferable. These ferromagnetic powders include not only predetermined atoms but also Al, Si, S, Sc, C
a, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, A
g, Sn, Sb, Te, Ba, Ta, W, Re, Au,
Hg, Pb, Bi, La, Ce, Pr, Nd, P, C
It may contain atoms such as o, Mn, Zn, Ni, Sr, B, and Mg. In particular, in the case of a metal magnetic material, Al,
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 mass with respect to Fe. Si, Al, and Y are contained between 0 and 10% by mass. 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, and JP-B-47 -18509, JP-B-47-18573, JP-B-39-10307,
JP-B-48-39639, U.S. Pat.
No. 3031341, No. 3100194, No. 32
No. 42005, No. 3389014 and the like.

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

The ferromagnetic powder of the cleaning layer of the present invention was B
The specific surface area by the ET method is 45 to 80 m ² / g, and preferably 50 to 70 m ² / g. 40m ² /
g or less, or 80 m ² / g or more, it is not preferable because it is difficult to obtain surface properties. The ferromagnetic powder of the cleaning layer of the present invention has a crystallite size of 300 to 100 °, preferably 25 to 100 °.
It is 0 to 100 °, more preferably 200 to 140 °.

The saturation magnetization s of the ferromagnetic powder is 100 to 18
0 A · m ² / kg is preferable, and 110 is more preferable.
To 170 A · m ² / kg, more preferably 125 to 16
0 A · m ² / kg. The coercive force Hc of the ferromagnetic powder is 5
It is preferably from 00 to 3000 Oe (≒ 40 to 240 kA / m). The squareness ratio is preferably 0.6 to 0.98, and the magnetization amount of the cleaning layer is preferably 30 to 300 mT · μm. On the other hand, the needle ratio of the ferromagnetic powder is preferably from 4 to 18, and more preferably from 5 to 12. The water content of the ferromagnetic powder is 0.0
It is preferable to set it to 1 to 2%. It is preferable to optimize the water content of the ferromagnetic powder depending on the type of the binder.

It is preferable that the pH of the ferromagnetic powder is optimized by a combination with the binder used. The range is 4
-12, 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
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. The ferromagnetic powder preferably has a small number of vacancies, and its value is preferably 20% by volume or less, more preferably 5% by volume or less.

As the binder used in the cleaning layer, conventionally known thermoplastic resins, thermosetting resins, reactive resins and mixtures thereof are used. Further, it is preferable to use the polyurethane resin for the present invention together. As the thermoplastic resin, the glass transition temperature is -100 to 150 ° C, the number average molecular weight is 1,000 to 200,000, preferably 10,000 to 100,000, and the degree of polymerization is about 50 to 1,
It is about 000.

Such examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid,
Acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene,
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, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic-based reactive resin, formaldehyde resin, silicone resin,
Examples include epoxy-polyamide resins, mixtures of polyester resins and isocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, and mixtures of polyurethanes and polyisocyanates. 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 preferred are at least one selected from vinyl chloride resin, vinyl chloride vinyl acetate resin, vinyl chloride vinyl acetate vinyl alcohol resin and vinyl chloride vinyl acetate maleic anhydride copolymer. Combination of seed and polyurethane resin,
Or those obtained by combining these with a polyisocyanate. The structure of the 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 obtained by introducing at least one or more polar groups selected from phosphobetaine, carboxybetaine and the like by copolymerization or addition reaction. The amount of such a polar group is 10 ^-1 to 10 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6 mol / g.

Specific examples of these binders used in the present invention include VAGH, V manufactured by Union Carbide.
YHH, VMCH, VAGF, VAGD, VROH, V
YES, VYNC, VMCC, XYHL, XYSG, P
KHH, PKHJ, PKHC, PKFE, Nissin Chemical Industries' MPR-TA, MPR-TA5, MPR-TA
L, MPR-TSN, MPR-TMF, MPR-TS,
MPR-TM, MPR-TAO, 100 manufactured by Denki Kagaku
0W, DX80, DX81, DX82, DX83, 10
0FD, MR-104, MR-10 manufactured by Zeon Corporation
5, MR110, MR100, 400X-110A, Nipporan N2301, N230 manufactured by Nippon Polyurethane Co.
2, N2304, Pandex T- manufactured by Dainippon Ink and Chemicals, Inc.
5105, T-R3080, T-5201, Burnock D-400, D-210-80, Crisbon 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, Samprene SP-150 manufactured by Sanyo Kasei, TIM-300
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 and TIM-3005 are preferred.

The binder used in the cleaning layer of the present invention is 5 to 24% by mass based on the inorganic powder including the ferromagnetic powder.
, Preferably in the range of 8 to 22% by mass. 5 to 30% by mass when using a vinyl chloride resin,
When a polyurethane resin is used, it is preferable to use a combination of these in a range of 2 to 20% by mass and for a polyisocyanate in a range of 2 to 20% by mass. 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 / m
m ² (≒ 0.49~98MPa), the yield point 0.05
10 kg / mm ² (ｍｍ0.49 to 98 MPa) is preferred.

The cleaning medium of the present invention comprises two or more layers. Therefore, the amount of the binder, the amount of the vinyl chloride resin, the polyurethane resin, the polyisocyanate or the other resin in the binder, the molecular weight of each resin forming the cleaning layer, the amount of the polar group, or the resin 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 needed, and known techniques can be applied.

As the polyisocyanate used in the cleaning layer, tolylene diisocyanate, 4,4 ′
-Diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1.5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, triphenylmethane triisocyanate and other isocyanates, and the production of these isocyanates and polyalcohols Products, and polyisocyanates formed by condensation of isocyanates can be used.
Commercially available trade names of these isocyanates include Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR, Millionate MTL, Takenate D-102 and Takenate D-, manufactured by Takeda Pharmaceutical Co., Ltd. 110N, Takenate D-200, Takenate D-202, Desmodule L, Desmodule IL, Desmodule N, Desmodule HL manufactured by Sumitomo Bayer, and Burnock D502 manufactured by Dainippon Ink and the like. These are used alone or cured. The lower coating layer and the upper cleaning layer can be used in combination of two or more by utilizing the difference in the properties.

In the cleaning layer of the present invention, carbon black may be mixed as an inorganic powder in the same manner as in the lower coating layer. The carbon black may be a furnace black for rubber, a thermal black for rubber, black for color, acetylene black or the like. Can be. The specific surface area is 5 to 500 m ² / g,
The DBP oil absorption is 10 to 400 ml / 100 g, the particle size is 5 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 Industries,
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 partially graphitizing the surface. Further, 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 mass or less based on the ferromagnetic powder. Carbon black has functions such as antistaticity of the cleaning layer, reduction of friction coefficient, provision of light-shielding properties, and improvement of film strength, and these differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention are different in type, amount and combination in the cleaning layer and the lower coating layer, and are based on the above-mentioned properties such as particle size, oil absorption, conductivity and pH. Of course, it is possible to use them properly according to the purpose.

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

The particle size of these abrasives is 0.01 to 2
Although μm is preferred, abrasives having different particle sizes may be combined as needed, or a single abrasive may have a similar particle size distribution to achieve the same effect. The tap density is preferably 0.3 to ² g / cc, the water content is preferably 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. The compounding amount of the abrasive as the inorganic powder of the cleaning layer is determined by the ferromagnetic powder 10
It is 1 to 45% by mass relative to 0% by mass. The abrasive used in the present invention can be of a different type, amount and combination for the lower coating layer and the upper cleaning layer described above, and can be used properly according to the purpose. These abrasives may be added to the magnetic paint after dispersion treatment with a binder in advance. The abrasive present on the surface of the cleaning layer and the end surface of the cleaning layer of the cleaning medium of the present invention is preferably 5/100 μm ² or more.

As the additives used in the lower coating layer or the cleaning layer of the present invention, those having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect and the like are used.
Molybdenum disulfide, tungsten graphite disulfide,
Boron nitride, fluorinated graphite, silicone oil, silicone with polar groups, 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 of numbers 12 to 22, monobasic fatty acids of carbon numbers 10 to 24 (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 mono-fatty acid ester or di-fatty acid ester or tri-fatty acid ester consisting of: a fatty acid ester of a monoalkyl ether of an alkylene oxide polymer; a fatty acid amide having 8 to 22 carbon atoms;
An aliphatic amine having 8 to 22 carbon atoms can be used.

Specific examples thereof include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, butyl stearate, oleic acid, linoleic acid, linolenic acid, elaidic acid, octyl stearate, amyl stearate, and stearic acid. Isooctyl, octyl myristate, butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, oleyl alcohol, 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, sulfate ester group, phosphate ester group, amino acids, aminosulfonic acids, sulfuric acid or phosphate esters of amino alcohols, 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.

These lubricants and surfactants used in the present invention can be used in the lower coating layer and the cleaning layer in different types and amounts as needed. For example, controlling the bleeding to the surface using fatty acids with different melting points in the lower coating layer and cleaning layer, controlling bleeding to the surface using esters with different boiling points and polarities, or adjusting the amount of surfactant By doing so, it is conceivable to improve the stability of coating or to increase the amount of lubricant to be 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 the inorganic powder before the kneading step, when adding in the kneading step with the inorganic powder and the binder and the solvent, when adding in the dispersing step, when adding after dispersing, there are cases where it is added just before coating . 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. Further, depending on the purpose, a lubricant may be applied to the surface of the cleaning layer after calendering or after slitting.

Examples of commercial products of these lubricants used in the present invention include NAA-102 and NAA-4 manufactured by NOF Corporation.
15, NAA-312, NAA-160, NAA-18
0, NAA-174, NAA-175, NAA-22
2, NAA-34, NAA-35, NAA-171, N
AA-122, NAA-142, NAA-160, NA
A-173K, castor hardened fatty acid, NAA-42, NA
A-44, Cation SA, Cation MA, Cation A
B, cation BB, Nimeen L-201, Nimeen L-202, Nimeen S-202, Nonion E-20
8, Nonion P-208, Nonion S-207, Nonion K-204, Nonion NS-202, Nonion NS-
210, Nonion HS-206, Nonion L-2, Nonion S-2, Nonion S-4, Nonion O-2, Nonion LP-20R, Nonion PP-40R, Nonion SP
-60R, Nonion OP-80R, Nonion OP-85
R, Nonion LT-221, Nonion ST-221, Nonion OT-221, Monogly MB, Nonion DS-6
0, anone BF, anone LG, butyl stearate, butyl laurate, erucic acid, oleic acid manufactured by Kanto Chemical Co., FAL-205, FAL-123 manufactured by Takemoto Yushi Co., Ltd.
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, Newpole PE61, Ionet MS-400, Ionet MO-200, Ionet DL-200, Ionet DS-300, Ionet DS-1000, and Ionnet DO-200.

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

The type of the organic solvent used in the present invention is preferably the same for the cleaning layer and the lower coating layer, but the amount of addition may be changed. It is preferable to improve the stability of coating by using a solvent having a high surface tension (such as cyclohexanone or dioxane) for the lower coating layer. It is important that the value is not below the average. In order to improve the dispersibility, it is preferable that the polarity is somewhat strong, and it is preferable that the solvent composition has a solvent having a dielectric constant of 15 to 20 in an amount of 50% by mass or more. Further, the dissolution parameter is preferably from 8 to 11.

The thickness configuration 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 this adhesive layer is 0.01 to 2 μm, preferably 0.02 to 0.5 μm. Further, a backcoat layer may be provided on the side of the nonmagnetic 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 (≒ 735 MPa).
The above, biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide,
Known films such as polyimide, polyamide imide, aromatic polyamide, and polybenzoxydazole can be used. In particular, a high-strength nonmagnetic support using an aramid resin or polyethylene naphthalate is preferred. These nonmagnetic supports may be subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment and the like in advance.

In order to achieve the object of the present invention, it is necessary to use a non-magnetic support having a center line average surface roughness Ra of 0.5 to 7 nm on the surface on which the cleaning layer is applied. Further, 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 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, which may be crystalline or amorphous, and acryl-based or melamine-based organic fine powders. 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, more preferably 4 nm or more. When the roughness between the cleaning layer application surface and the back layer application surface is changed, a dual-structured support may be used, or the roughness may be changed by providing a coating layer.

The F-5 value of the non-magnetic support used in the present invention in the tape running direction (MD direction) is preferably 10 to 5
0 kg / mm ² (≒ 98-490 MPa), F-5 value in the tape width direction (TD direction) is preferably 10-30 kg.
/ Mm ² (≒ 98 to 294 MPa), and the F-5 value in the longitudinal direction of the tape is generally higher than the F-5 value in the tape width direction, but it is particularly necessary to increase the strength in the width direction. Sometimes it is not. The heat shrinkage of the non-magnetic 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% or less, and the heat shrinkage at 80 ° C. for 30 minutes. Is preferably 1% or less, more preferably 0.5% or less. The breaking strength was 5 to 100 kg / mm ^{2 in} both directions (# 49 to 980 M
Pa), Young's modulus is 100 to 3,000 Kg / mm
² (≒ 0.98 to 29.4 GPa) is preferred. Also,
The light transmittance at 900 nm is preferably 30% or less, more preferably 3% or less.

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

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

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

1. First, a lower coating layer is applied by a gravure coating, a roll coating, a blade coating, an extrusion coating device, etc., which are generally used in 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, a lower coating layer and a cleaning layer are applied almost simultaneously by one coating head having two built-in coating liquid passage slits.

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

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

In order to obtain the cleaning medium of the present invention, an orientation treatment of the ferromagnetic powder of the cleaning layer may be performed.
This orientation is preferably performed by using a solenoid having a magnetic force of 100 mT or more and a cobalt magnet having a magnetic force of 200 mT or more in the same polarity facing each other. It is preferable to provide an appropriate drying step in advance.

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

Further, if necessary, a calendar process can be performed to adjust the surface roughness. A heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimide amide can be used as the calendering roll. Further, the treatment can be performed between metal rolls. The processing temperature is preferably 50-100.
° C and a linear pressure of preferably 100 to 500 kg / m (≒ 9
80-4900 N / m) and the speed is 50-400 m / min.

The coefficient of friction of the cleaning layer surface of the cleaning medium of the present invention and the opposite surface thereof to SUS420J is preferably 0.1 to 0.5, and more preferably 0.2 to 0.3. The surface resistivity is preferably 10
The elastic modulus at ⁴ to 10 ¹² ohm / sq and the 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 (≒ 0.98-19.6 GP
a), the breaking strength is preferably 1~30Kg / mm ² (≒
9.8-294 MPa).

The cleaning medium as a whole is
Young's modulus in the machine direction (MD) is 300 to 1200 kg / mm
² (≒ 2.94 to 11.76 GPa) and the Young's modulus in the width (TD) direction is 200 to 1200 kg / mm ² (≒ 1.96 to
11.76 GPa), and the ratio of Young's modulus in the longitudinal direction / Young's modulus in the width direction is 1/2 to 2/1.

Further, the residual elongation of the cleaning medium is preferably 0.5% or less, and the heat shrinkage at any temperature of 100 ° C. or less is preferably 1% or less, more preferably 0.5% or less, and most preferably 0% or less. 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 from 50 ° C to 120 ° C, and that of the lower coating layer is preferably from 0 ° C to 100 ° C. Loss modulus is 1 ×
10 ⁷ -8 × 10 ⁸ Pa 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
Hereinafter, it is more preferably 10 mg / m ² or less, and it is preferable that the residual solvent contained in the upper cleaning layer is smaller than the residual solvent contained in the lower coating layer. The porosity of both the lower coating layer and the cleaning layer is preferably 50% by volume or less, more preferably 40% by volume or less.

The magnetic properties of the cleaning layer of the cleaning medium of the present invention are as follows: a magnetic field of 10 kOe ｛Oe = (１ ／ π) k
When measured by VSM in A / m｝, the coercive force Hc in the tape running direction is 500 to 3000 Oe (≒ 40 to 240 kA /
m). The squareness ratio is 0.6 to 0.98, preferably 0.80 or more, and more preferably 0.85 or more. It is preferable that the squareness ratio in the two directions perpendicular to the tape running direction be 80% or less of the squareness ratio in the running direction. The SFD of the cleaning layer is preferably 0.6 or less, more preferably 0.5 or less, and ideally 0. The longitudinal remanence coercive force Hr is also 1800-3
000 Oe (≒ 144-240 kA / m) is preferable. Hc and Hr in the vertical direction are 1000 to 5000 Oe ($ 80
４００400 kA / m). Further, the center line surface roughness Ra of the cleaning layer is 1.0 to 7.0 n.
Although m is preferable, its value should be set appropriately according to the purpose. RMS surface roughness R determined by AFM evaluation
Preferably, the _RMS is in the range from 2 to 15 nm.

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

[0093]

EXAMPLES Examples of the present invention will be shown below to explain the present invention in further detail. “Parts” in the examples indicates “parts by mass”. Synthesis Example 1 (Synthesis Example of Polyurethane Resin) A reflux condenser and a stirrer were provided, and the diols shown in Table 1 were dissolved in cyclohexane at 60 ° C. in cyclohexane under a nitrogen atmosphere. Next, as a catalyst, di-n-dibutyltin dilaurate was used in an amount of 6 to the total amount of raw materials.
0 ppm was added and the mixture was further dissolved for 15 minutes. Next, the MDI shown in Table 1 was added, and the mixture was heated and reacted at 90 ° C. for 2 hours.
A CO polyurethane prepolymer was synthesized. The NCO content of the obtained prepolymer was quantified, trimethylolpropane having the same mole as the NCO content was added, and the mixture was further heated and reacted for 4 hours, and polyurethane resins A to J having terminal branched OH,
L and M were obtained. Further, a polyurethane resin K to which trimethylolpropane was not added was similarly produced. The OH content was adjusted by adjusting the MDI content shown in Table 1.
Table 1 shows the OH content and molecular weight of the obtained polyurethane. The content of the polar group is indicated by 10 ⁻⁵ eq / g. The OH content of the polyurethane resin was represented by the number of OH groups per molecule from the OH value determined by the test method of JIS K00070 and the number average molecular weight in terms of polystyrene determined by GPC.

Polyurethane Synthesis Example 2 A polyol obtained by subjecting bisphenol A to an ethylene oxide addition reaction in the same manner as described in Example 1 of JP-A-1-267829, and 4.4-
Diphenyl metadidiisocyanate is converted to polyisocyanate
Polyurethane resin P was synthesized by using it as a component, and is shown in Table 1.

[0095]

[Table 1]

The meanings of the abbreviations in Table 1 are as follows. Short-chain diol: Short-chain diol component having a cyclic structure HBpA: Hydrogenated bisphenol A Long-chain diol: Long-chain polyether polyol component Compound A: Bisphenol A PO (propyleoxide)
Adduct (molecular weight 600) n = 3-4 Compound B: Bisphenol A PO (Propylene oxide)
Adduct (molecular weight 1000) n = 12-13 Compound C: Bisphenol A PO (Propylene oxide)
Adduct (molecular weight 500) n = 3-4 Polar group-containing diol: Polar group-containing long-chain polyol component A: SIS / IP / NPG polyester Molecular weight 1200 A: DEIS ε-caprolactone adduct molecular weight 21
00 C: DEIS propylene oxide adduct molecular weight 7
00 d: SIS / BD / APA polyester molecular weight 5
000 e: SIS / BD / APA polyester molecular weight 6
000 SIS: 5-sodium sulfoisophthalic acid DEIS: 5-sodium sulfoisophthalic acid ethylene oxide adduct NPG: neopentyl glycol IP: isophthalic acid BD: 1,4-butanediol APA: adipic acid MDI: 4,4-diphenylmethane diisocyanate Nate TMP: Trimethylolpropane

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 solution having the following composition. “Cleaning layer coating liquid” Ferromagnetic metal fine powder Composition Fe / Co = 100/30 100 parts Hc: 2350 Oe (≒ 188 kA / m), Specific surface area by BET method (S _BET ): 49 m ² / g Crystallite size : 160Å Surface treatment layer: Al ₂ O ₃ , SiO ₂ , Y ₂ O ₃ Average major axis length: 0.09 μm Needle ratio: 7 σs: 145 Am · m ² / kg Vinyl chloride / vinyl acetate / glycidyl methacrylate Compound (SO ₃ Na = 6 × 10 ⁻⁵ eq / g, epoxy = 10 ⁻³ eq / g, Mw) obtained by adding hydroxyethylsulfone-tonate salt to a copolymer (86/9/5 (weight ratio)) 7.5 parts Polyurethane resin A 6 parts Kneaded with 50 parts of cyclohexanone for 60 minutes as described above, and then 15 parts of α-Al ₂ O ₃ (average particle size: 0.15 μm) dispersion liquid 15 parts Carbon black (average particle size) 0.5 part: methyl ethyl ketone / tolue = It was dispersed in a sand mill for 120 minutes by adding 1/1 220 parts. 8 parts of polyisocyanate (Coronate 3041 made by Nippon Polyurethane), 1 part of butyl stearate, 1 part of stearic acid, 8 parts of methyl ethyl ketone, 60 parts of stirring, stirring for 20 minutes, filtration using a filter having an average pore diameter of 1 μm, and cleaning. A layer coating solution was prepared.

“Coating liquid for lower coating layer” Non-magnetic inorganic powder α-Fe ₂ O ₃ (hematite) 85 parts Average particle size: 0.13 μm S _BET : 55 m ² / g Surface treatment layer: Al ₂ O ₃ , SiO ₂ The pH: 6.0-8.5 was pulverized with an opener for 10 minutes, and then hydrolyzed to a vinyl chloride / vinyl acetate / glycidyl methacrylate copolymer (86/9/5 (weight ratio)). Ethyl sulfone-tonate salt added compound (SO ₃ Na = 6 × 10 ⁻⁵ eq / g, epoxy = 10 ⁻³ eq / g, Mw = 30000) 7.5 parts Polyurethane resin A 6 parts Cyclohexanone 50 above And kneading for 60 minutes, then add 200 parts of methyl ethyl ketone / cyclohexane = 6/4 and mix for 60 minutes, then polyisocyanate (Coronate 3041 manufactured by Nippon Polyurethane) 8 parts Butyl stearate 1 part Stearic acid 8 Part methyl ethyl ketone 60 Was added and stirred for 20 minutes, filter having an average pore size of 1 [mu] m - filtration was used to prepare a coating solution.

Next, the coating solution for the lower coating layer obtained as described above was dried to a thickness of 2.0 μm, and immediately thereafter, the coating solution for the cleaning layer was dried. Was applied simultaneously using a reverse roll so that the thickness was 0.1 μm. Thereafter, the non-magnetic support coated with the cleaning layer coating solution is dried for 30 minutes while the coating solution is not dried.
A magnetic field orientation was performed with a 0 mT magnet, dried, treated with a seven-stage calender composed of a metal roll and an epoxy resin roll, and then cut into 8 mm width.

Examples 2 to 9 Examples 2 to 9 were prepared in the same manner as in Example 1 except that the polyurethane resin A for the cleaning layer and the lower coating layer was changed to the polyurethane resin shown in Table 2.

Example 10 In Example 1, the cleaning layer was the same as that of Example 1 except that
A sample was prepared in the same manner as in Example 1, except that a coating solution for the coating layer for the lower layer was used, and a coating solution for the lower layer coating layer in which the nonmagnetic inorganic powder was changed to titanium oxide was used. Titanium oxide Average particle size: 0.035 μm Crystal form: rutile TiO ₂ content: 90% or more Surface treatment layer: Alumina S _BET : 40 m ² / g True specific gravity: 4.1 pH: 7.0

Comparative Examples 1 to 6 Samples were prepared in the same manner as in Example 1 except that the polyurethane resin A of the cleaning layer and the lower coating layer was changed to the polyurethane resin shown in Table 2. Table 2 shows the properties of the obtained tape.
Shown in Table 2 shows the characteristics of the cleaning media of the examples and the comparative examples obtained as described above. Here, the measuring method of each measured value is shown. Center line average surface roughness Ra: Ra of an area of about 250 μm × 250 μm was measured using TOPO3D manufactured by WYKO. The measurement wavelength is about 650 nm, with spherical and cylindrical corrections. This method is a non-contact surface roughness meter that measures by light interference. Head wear: 23 ° C using Hi-8 deck EV-S900
The cleaning tape was run at × 70% RH for 10 minutes, the head height before and after the cleaning tape was measured, and the head wear per minute was calculated. Head cleaning power: H made by Fuji Photo Film Co., Ltd. in advance
The output is measured by the EV-S900 using the i-8 super DCP6-120. After that, run the standard tape created for the purpose of causing clogging with the EV-S900, observe the head status with a strobe, stop running when the head becomes dirty, and output. Make sure there is none. Then, after running each cleaning tape of the sample for 1 minute, the output of Hi-8DC P6-120 manufactured by Fuji Photo Film Co., Ltd. recorded in advance was measured, and the output measured last and first were measured. The difference dB from the output was evaluated as the head cleaning force. In addition, cleaning table
The head was scratched after running.

[0103]

[Table 2]

According to the above table, in Comparative Example 1, since the content of the short-chain diol was small and the content of the long-chain diol was large, the coating film became too soft and sufficient head cleaning power was not obtained. In Comparative Example 2, the content of the short-chain diol was large, and the content of the long-chain diol was small, so that the solubility in the solvent was reduced and the dispersibility of the nonmagnetic inorganic powder was reduced. As a result, the wear of the head is increased, and the head is damaged. Other comparative examples using polyurethane resins other than the present invention are also inferior in head wear and cleaning power as compared with the examples.

In the first to eleventh embodiments of the present invention, it is possible to obtain a preferable result as a cleaning medium for a magnetic head without abrasion of the head being excessive, having a good cleaning power and ME compatibility, and having no head scratch. Have been obtained.

[0106]

According to the present invention, a lower coating layer mainly containing a non-magnetic inorganic powder and a binder is provided on a non-magnetic support, and a cleaner containing at least an inorganic powder of a ferromagnetic powder and a binder is provided thereon. For magnetic recording device provided with a coating layer
In the polishing medium, the polyol component of the polyurethane resin, which is a reaction product containing a polyol and an organic diisocyanate as the main raw materials, is specified as the binder used in the lower coating layer, whereby the polyurethane resin is derived from a polyol. Since a polar group is contained, a cleaning medium for a magnetic recording apparatus which has a high cleaning power for a magnetic head, is free from scratches on the magnetic head, and has little head wear can be provided.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoru Hayakawa 2-1-1, Ogimachi, Odawara-shi, Kanagawa F-Term in Fuji Photo Film Co., Ltd. (Reference) 4J034 BA08 CA04 CB03 CC01 CC12 CC23 CC26 CC45 CC61 CC67 DA01 DB04 DF01 DF02 DF32 DF33 DF34 DG03 DG04 DG05 DG22 DG23 DG27 DG28 DH02 HC03 HC12 HC13 HC17 HC22 HC61 HC64 HC67 HC70 HC71 HC73 MA02 MA03 QA07 RA14

Claims (1)

[Claims] An undercoating layer mainly containing a non-magnetic inorganic powder and a binder is provided on a non-magnetic support, and a lower layer containing at least an inorganic powder of a ferromagnetic powder and a binder is provided thereon.
In a cleaning medium for a magnetic recording apparatus provided with a cleaning layer, the binder used for the lower coating layer comprises a polyurethane resin which is a reaction product mainly composed of a polyol and an organic diisocyanate. In the polyurethane resin, the short-chain diol component having a cyclic structure is 15 to 40% by mass, the long-chain polyether polyol component is 10 to 50% by mass, and the molecular weight is 500 to 50%.
CLEANING MEDIUM FOR MAGNETIC RECORDING APPARATUS, INCLUDING A POLAR GROUP-CONTAINING LONG CHAIN POLYOL COMPONENT.