JP2007237350A - Cleaning medium for magnetic recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning medium for a magnetic recording apparatus, which achieves high cleaning capability to a magnetic head of a high-density magnetic recording and reproducing apparatus, especially to MR head, reduces abrasion of the head, removes contaminants with moderate cleaning capability, and restores the reproduction output. <P>SOLUTION: In this cleaning medium for the magnetic recording apparatus, a cleaning layer containing inorganic powder made of at least ferromagnetic powder and a binder, is provided on a non-magnetic support. The cleaning medium for the magnetic recording apparatus is characterized in that the surface occupying percentage of a polisher in the cleaning layer surface ranges from 2.0 to 5.0%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic recording device cleaning medium such as a magnetic head used in audio, video, and computer magnetic recording / reproducing devices, or a cleaning tape used for cleaning a running system.

  In general, recording / reproduction 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 scraping powder of the magnetic tape or dust around the apparatus 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 that cleans dirt adhering to the surface of the magnetic head and restores the reproduction output is used.

  On the other hand, the density of magnetic recording is increasing year by year, and unless the state of contact between the tip of the magnetic head and the magnetic tape is not improved, sufficient recording and reproduction cannot be performed. In order to keep the so-called head contact good, the cleaning tape not only removes dirt from the magnetic head, but also needs to adjust the shape of the head 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 is also used, and the gap length in this magnetic head is 0.4 μm or less, and slight head contamination is also caused. This will interfere with the recording / reproduction performance.

  In addition, magnetic heads have come to be used with higher density. The height of a generally used shield type MR head element is several microns or less, and the amount of head wear must be reduced as much as possible as compared with conventional metal heads such as ferrite heads and sendusts.

  In recent years, magnetic recording apparatuses that can use both vapor-deposited tape (ME tape) and metal powder tape (MP tape) have appeared, such as Hi-8 and DVC. In the vapor deposition tape, a metal thin film having high rigidity comes into contact with the magnetic head. Therefore, unless the tip of the magnetic head is sharp, it is difficult to obtain a good contact state, that is, recording / reproducing characteristics. Furthermore, since the vapor deposition tape does not contain an abrasive, there is little wear of the magnetic head at the contact, and the compatibility with the magnetic head is low. On the other hand, since the magnetic powder contains magnetic powder in the binder in the metal tape, it will come into soft contact with the magnetic head, and the head contact with the tape will not change so much depending on the shape of the head tip. In addition, since it has an abrasion force, it is well adapted to the magnetic head.

  Therefore, even if the metal tape is run against the magnetic head after running the vapor-deposited tape, there is not much change per head, but conversely, the vapor-deposited tape is run after running the metal tape. If this is done, the head contact may become unstable.

  As a prior art of a polishing tape used for polishing a magnetic head, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 62-92205) discloses an intermediate layer containing nonmagnetic powder on a nonmagnetic support, and nonmagnetic An abrasive tape in which abrasive layers containing an abrasive are sequentially laminated is disclosed. This polishing tape employs a two-layer structure to roughen the surface properties of the intermediate layer, while reducing the abrasive particle diameter of the upper polishing layer to prevent head scratches while maintaining polishing power. However, this polishing tape is for final polishing of the magnetic head, and since the surface roughness is 0.03 to 0.3 μm, it is difficult to perform appropriate polishing as cleaning with a lot of head wear. Therefore, it is not suitable for use as a cleaning tape. A magnetic tape polishing tape similar to that described above is also disclosed in Japanese Patent Application Laid-Open No. 62-94270. 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.

The MR head has a problem that the amount of head wear must be reduced as much as possible as compared with a metal head such as a ferrite head or sendust. However, an effective means for solving this problem has been desired.
JP 62-92205 A JP-A-62-94270

  The present invention is for a magnetic recording apparatus that has a high cleaning power for a magnetic head such as a high-density magnetic recording / reproducing apparatus, particularly an MR head, has little head wear, and can remove dirt with an appropriate cleaning power to restore a reproduced output. It is an object of the present invention to provide a cleaning medium.

The present invention is as follows.
1) In a magnetic recording device cleaning medium in which a cleaning layer containing at least an inorganic powder of a ferromagnetic powder and a binder is provided on a nonmagnetic support, the surface occupancy ratio of the polishing agent on the surface of the cleaning layer is 2.0. A cleaning medium for a magnetic recording device, characterized by being -5.0%.
2) The magnetic recording apparatus cleaning medium according to 1) above, wherein a nonmagnetic back layer is provided on the opposite surface of the nonmagnetic support on which the cleaning layer is provided.

  The present invention specifies the surface occupancy ratio of the abrasive on the surface of the cleaning layer in a cleaning medium for a magnetic recording apparatus in which a cleaning layer containing at least an inorganic powder of a ferromagnetic powder and a binder is provided on a nonmagnetic support. Therefore, cleaning for magnetic recording devices that has high cleaning power for magnetic heads such as high-density magnetic recording / reproducing devices, especially MR heads, less head wear, can remove dirt with an appropriate cleaning force, and can restore reproduced output. A medium can be provided.

  The basic structure of the cleaning medium of the present invention is such that a cleaning layer containing at least an inorganic powder of a ferromagnetic powder and a binder is provided on a nonmagnetic support. A preferred embodiment is a cleaning medium in which a nonmagnetic back layer is provided on the opposite surface of the nonmagnetic support provided with the cleaning layer. Another preferred embodiment is a cleaning medium in which a lower coating layer mainly comprising a nonmagnetic inorganic powder and a binder is provided between a nonmagnetic support and a cleaning layer.

  The abrasive on the surface of the cleaning layer referred to in the present invention is a particle in which part or all of the abrasive particles are exposed from the surface of the magnetic layer, and specifying the surface occupancy ratio of the abrasive is the exposed portion. It means to limit the size and number of. The surface occupancy ratio of the abrasive on the surface of the cleaning layer refers to a projected area per unit area when an exposed portion of particles exposed from the surface of the cleaning layer is projected perpendicularly onto the surface of the cleaning layer. This surface occupancy can be obtained by observing the surface of the cleaning layer using a scanning electron microscope (SEM) and analyzing the obtained SEM image by computer analysis. Details of the measurement method are described in, for example, Japanese Patent Application Laid-Open No. 9-305959, and the contents can be used in the present invention. The surface occupation ratio on the surface of the cleaning layer is 2.0 to 5.0%, preferably 2.0 to 4.0%, and particularly preferably 2.5 to 4.0%.

  If the surface occupancy exceeds 5.0%, head wear is large during cleaning, and the risk of scratching the head increases. On the other hand, if it is less than 2.0%, the cleaning power is reduced and the dirt cannot be removed.

As a method for controlling the surface occupancy rate of the abrasive, the average particle size and particle size distribution of the primary particles of the abrasive to be used should be selected, and aggregation of the abrasive particles in the coating for forming the cleaning layer should be prevented as much as possible. is important. As an example of a method for preventing the agglomeration of the abrasive, it is preferable to disperse the abrasive alone in advance using an appropriate amount of a binder and an organic solvent and form a slurry before forming a coating material for forming a cleaning layer.
The average particle diameter of the primary particles of the abrasive is preferably 0.05 to 0.5 μm, more preferably 0.1 to 0.3 μm.
The content of the abrasive is preferably 1 to 30 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the ferromagnetic powder.

  In the present invention, the cleaning layer preferably contains a fatty acid amide, a fatty acid and a fatty acid ester as a lubricant. For example, the following are illustrated as fatty acid amides, fatty acids and fatty acid esters. Examples of the fatty acid amide include fatty acid amides having 8 to 22 carbon atoms. Examples of the fatty acid include monobasic fatty acids having 10 to 24 carbon atoms and metal salts thereof (Li, Na, K, Cu, etc.). Examples of the fatty acid ester include esters of the above monobasic fatty acid having 10 to 24 carbon atoms and alcohol having 4 to 22 carbon atoms.

  The fatty acid and / or alcohol used in the fatty acid, its amide and its ester may be saturated or unsaturated, linear or branched, or have an alicyclic ring. The fatty acid and / or alcohol may have an alkoxy group, or may have an alkylene oxide polymer or a monoalkyl etherized product thereof. The fatty acid ester may be a monovalent ester or a polyvalent ester, preferably a monovalent to trivalent ester, and in the latter case, a hydroxyl group may remain. The fatty acid amide may be a monovalent amide or a polyvalent amide. In the latter case, a carboxyl group may remain. Among these fatty acid amides, fatty acids and fatty acid esters, optimum ones are selected in relation to the protrusion distribution on the cleaning layer surface. Two or more of fatty acid amides, fatty acids and fatty acid esters can be used in combination.

  Specific examples of these fatty acids and fatty acid esters include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, butyl stearate, octyl stearate, amyl stearate, Examples include isooctyl stearate, octyl myristate, butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate and the like. In addition, fatty acid amides include those derived from the above fatty acids.

  The total amount of fatty acid amide, fatty acid and fatty acid ester used in the cleaning layer is preferably from 0.1 to 10 parts by weight, more preferably from 0.5 to 5 parts by weight, based on 100 parts by weight of the ferromagnetic powder. Each use amount of fatty acid amide, fatty acid or fatty acid ester is appropriately distributed from the above range, and an optimum range is selected. In general, in terms of quantity, it is preferable that fat fatty acid amide ≦ fatty acid ≦ fatty acid ester.

  The inorganic powder mixed in the cleaning layer includes a ferromagnetic powder. Examples of the ferromagnetic powder include γ-FeOx (x = 1.33 to 1.5), Co-modified γ-FeOx (x = 1.33 to 1). .5), known ferromagnetic powders such as ferromagnetic alloy powder, barium ferrite, strontium ferrite, etc. containing α-Fe or Ni or Co as the main component (75% or more) can be used, but α-Fe is the main component. Ferromagnetic alloy powder is preferred. In addition to predetermined atoms, these ferromagnetic powders include Al, Si, S, Sc, Ca, Ti, V, Cr, Cu, Y, Mo, Rh, Pd, Ag, Sn, Sb, Te, Ba, Ta. , W, Re, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, P, Co, Mn, Zn, Ni, Sr, B, and Mg may be included. 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 other than α-Fe. In particular, Si, Al, and Y are important as surface treatments and sintering inhibitors. Co is preferably 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 previously treated with a dispersant, lubricant, surfactant, antistatic agent, etc., which will be described later. Specifically, Japanese Patent Publication No. 44-14090, Japanese Patent Publication No. 45-18372, Japanese Patent Publication No. 47-22062, Japanese Patent Publication No. 47-22513, Japanese Patent Publication No. Sho 46-28466, Japanese Patent Publication No. Sho 46-38755, Japanese Patent Publication No. 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, US Patent 3026215 No. 3031341, No. 3100194, No. 322005, No. 3389014, and the like.

  Among the ferromagnetic powders, the ferromagnetic alloy fine powder may contain a small amount of hydroxide or oxide. What was obtained by the well-known manufacturing method of the ferromagnetic alloy fine powder can be used, and the following method can be mentioned. Method of reducing complex organic acid salt (mainly oxalate) with reducing gas such as hydrogen, method of reducing iron oxide with reducing gas such as hydrogen to obtain Fe or Fe-Co particles, metal carbonyl compound A method of thermal decomposition, a method of reducing by adding a reducing agent such as sodium borohydride, hypophosphite, or hydrazine to an aqueous solution of a ferromagnetic metal, and evaporating the metal in a low-pressure inert gas to form a fine powder. How to get. The ferromagnetic alloy powder obtained in this manner is a known slow oxidation treatment, that is, a method of drying after immersing in an organic solvent, and after immersing in an organic solvent, an oxygen-containing gas is fed to form an oxide film on the surface and then dried. 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.

When the ferromagnetic powder of the cleaning layer of the present invention is expressed by a specific surface area by the BET method, it is 45 to 80 m ² / g, preferably 50 to 70 m ² / g. A surface property of 40 m ² / g or less or 80 m ² / g or more is not preferred because it is difficult to obtain surface properties. The crystallite size of the ferromagnetic powder of the cleaning layer of the present invention is 300 to 100 mm, preferably 250 to 100 mm, and more preferably 200 to 140 mm.

The saturation magnetization σs of the ferromagnetic powder is preferably 100 to 180 A · m ² / kg, more preferably 110 to 170 A · m ² / kg, and still more preferably 125 to 160 A · m ² / kg. The coercive force Hc of the ferromagnetic powder is preferably 500 to 3000 Oe (≈40 to 240 kA / m). The squareness ratio is preferably 0.6 to 0.98, and the amount of magnetization of the cleaning layer is preferably 30 to 300 mT · μm. On the other hand, the acicular ratio of the ferromagnetic powder is preferably 4 to 18, more preferably 5 to 12. The moisture content of the ferromagnetic powder is preferably 0.01-2%. It is preferable to optimize the moisture 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 4-12, but preferably 6-10. The ferromagnetic powder may be surface-treated with Al, Si, P, or an oxide thereof as required. The amount thereof is 0.1 to 10% with respect to the ferromagnetic powder, and the surface treatment is preferable because the adsorption of a lubricant such as a fatty acid is 100 mg / m ² or less. The ferromagnetic powder may contain inorganic ions such as soluble Na, Ca, Fe, Ni, and Sr. Although it is preferable that these are essentially not present, if they are 200 ppm or less, they do not particularly affect the characteristics. The ferromagnetic powder preferably has fewer pores, and the value is 20% by volume or less, more preferably 5% by volume or less.

  As the binder used for the cleaning layer and the lower coating layer, 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 1,000. Is.

  Examples of such include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, There are polymers or copolymers containing vinyl ether as a constituent unit, polyurethane resins, and various rubber resins. Thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, acrylic reactive resins, formaldehyde resins, silicone resins, epoxy-polyamide resins, polyester resins. And a mixture of an isocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, a mixture of a polyurethane and a polyisocyanate, and the like. These resins are described in detail in “Plastic Handbook” published by Asakura Shoten. Moreover, it is also possible to use a known electron beam curable resin for the lower coating layer or the upper cleaning layer.

  These examples and their production methods are described in detail in JP-A No. 62-256219. The above resins can be used alone or in combination, but preferably 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. A combination of a seed and a polyurethane resin, or a combination of these with a polyisocyanate can be mentioned. As the structure of the polyurethane resin, known structures such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, polycaprolactone polyurethane and polyolefin polyurethane can be used. Among them, it is composed of a polyurethane resin which is a reaction product containing at least a polyol and an organic diisocyanate as main raw materials, and as the polyol component, in the polyurethane resin, a short-chain diol component having a cyclic structure, a long-chain polyether polyol component, and further a molecular weight Those containing 500 to 5,000 polar group-containing long-chain polyol components are preferred.

For all binding agents indicated herein, if necessary in order to obtain more excellent dispersibility and _{durability, -COOM, -SO 3 M, -OSO} 3 M, -P = O (OM) 2, - O—P═O (OM) ₂ (wherein M is a hydrogen atom or an alkali metal base), —OH, —NR ² , —N ⁺ R ³ (R is a hydrocarbon group), epoxy group, —SH, —CN It is preferable to use one in which at least one polar group selected from sulfobetaine, phosphobetaine, carboxybetaine and the like is 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, VYHH, VMCH, VAGF, VAGD, VROH, VYES, VYNC, VMCC, XYHL, XYSG, PKHH, PKHJ, PKHC, PKFE manufactured by Dow Chemical Co. MPR-TA, MPR-TA5, MPR-TAL, MPR-TSN, MPR-TMF, MPR-TS, MPR-TM, MPR-TAO, manufactured by Nissin Chemical Industry Co., Ltd., 1000W, DX80, DX81 manufactured by Denki Kagaku , DX82, DX83, 100FD, MR-104, MR-105, MR110, MR100, 400X-110A manufactured by Nippon Zeon Co., Ltd., Nipponran N2301, N2302, N2304 manufactured by Nippon Polyurethane Co., Ltd. 5105, T-R3080, T-5201 Barnock D-400, D-210-80, Crisbon 6109, 7209, Byron UR8200, UR8300, UR8600 manufactured by Toyobo, Daiferamin 4020, 5020, 5100, 5300, 9020, 9022, 7020 manufactured by Dainichi Seika Co., Ltd., Mitsubishi Chemical MX5004 manufactured by Sanyo Chemical Co., Ltd., Sanprene SP-150, TIM-3003, TIM-3005 manufactured by Sanyo Kasei Co., Ltd., Saran F310, F210 manufactured by Asahi Kasei Co., Ltd., and the like. Among these, MR-104, MR110, MPR-TAO, MPR-TA, UR-8200, UR8300, and TIM-3005 are preferable.

  The total of the resin component and the curing agent used in the cleaning layer of the present invention (that is, the binder) is in the range of 5 to 24% by mass, preferably in the range of 8 to 22% by mass, with respect to the inorganic powder including the ferromagnetic powder. Used. The amount of the binder used in the lower coating layer is usually preferably in the range of 15 to 40 parts by mass, more preferably 20 to 30 parts by mass with respect to 100 parts by mass of the nonmagnetic inorganic powder. It is preferable to use a combination of 5 to 30% by mass when using a vinyl chloride resin, 2 to 20% by mass when using a polyurethane resin, and 2 to 20% by mass of polyisocyanate. In particular, it is desirable that the cleaning layer contains no 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., the elongation at break is 100 to 2000%, the stress at break is 0.05 to 10 kg / mm ² (≈0.49 to 98 MPa), and the yield point is 0.05 to 10 Kg / mm ² (≈0.49 to 98 MPa) is preferable.

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

  Examples of the polyisocyanate include isocyanates such as tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5 diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, and triphenylmethane triisocyanate. In addition, products of these isocyanates and polyalcohols, polyisocyanates formed by condensation of isocyanates, and the like can be used. Commercially available product names of these isocyanates include Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR, Millionate MTL, Takenate Pharmaceutical's Takenate D-102, Takenate D- 110N, Takenate D-200, Takenate D-202, Sumika Bayer's Death Module L, Death Module IL, Death Module N, Death Module HL, Dainippon Ink's Burnock D502, etc. By utilizing the difference in reactivity, the lower coating layer and the upper cleaning layer can be used in combination of two or more.

In the cleaning layer of the present invention, carbon black may be mixed as an inorganic powder. As the carbon black, furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used. Specific surface area is 5 to 500 m ² / g, DBP oil absorption is 10 to 400 ml / 100 g, particle diameter is 5 m to 300 mμ, pH is 2 to 10, moisture content is 0.1 to 10%, tap density is 0.1 to 1 g / cc is preferred. Specific examples of carbon black used in the present invention include Cabot Corporation, BLACKPEARLS 2000, 1300, 1000, 900, 800, 700, VULCAN XC-72, Asahi Carbon Corporation, # 80, # 60, # 55, # 50, # 35, manufactured by Mitsubishi Chemical Corporation, # 2400B, # 2300, # 5, # 900, # 950, # 970, # 1000, # 30, # 40, # 10B, manufactured by Conlongbia Carbon Co., CONDUCTEX SC, RAVEN 150, 50, 40, 15 and the like. Carbon black may be surface-treated with a dispersant or the like, or may be used after being grafted with a resin, or may be obtained by graphitizing a part of the surface. Further, carbon black may be dispersed in advance with a binder before being added to the cleaning layer coating. 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 amount of the ferromagnetic powder. Carbon black functions to prevent the cleaning layer from being charged, reduce the coefficient of friction, impart light-shielding properties, and improve film strength. 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 characteristics described above such as particle size, oil absorption, conductivity, pH, etc. Of course, it is possible to use properly according to the purpose.

  As an abrasive used in the cleaning layer, α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, artificial diamond, silicon nitride, silicon carbide having an α conversion ratio of 90% or more Known materials having a Mohs hardness of 6 or more, such as titanium carbide, titanium oxide, silicon dioxide, and boron nitride, are used alone or in combination. Further, a composite of these abrasives (a product obtained by surface-treating an abrasive with another abrasive) may be used. These abrasives may contain compounds or elements other than the main component, but the effect is not affected if the main component is 90% or more. Specific examples of the abrasive include AKP-20, AKP-30, AKP-50, HIT-50, HIT-60, HiT-60A, HIT-70A, HIT-80, and HIT-80G manufactured by Sumitomo Chemical Co., Ltd. HIT-100, G5, G7, S-1 manufactured by Nippon Chemical Industry Co., Ltd., TF-100, TF-140 manufactured by Toda Industry Co., Ltd., and the like.

These abrasives preferably have a tap density of 0.3 to ² g / cc, a moisture content of 0.1 to 5%, a pH of 2 to 11, and a specific surface area of 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 those having a corner in a part of the shape are preferable because of high cleaning properties. Of course, the abrasive used in the present invention can be used in accordance with the purpose by changing the type, amount and combination of the lower coating layer and the upper cleaning layer.

  As the additive used for 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 disulfide graphite, boron nitride, fluorinated graphite, silicone oil, silicone with polar group, fatty acid-modified silicone, fluorine-containing silicone, fluorine-containing alcohol, fluorine-containing ester, polyolefin, polyglycol, alkyl phosphate ester and Alkali metal salt, alkyl sulfate ester and alkali metal salt thereof, polyphenyl ether, fluorine-containing alkyl sulfate ester and alkali metal salt thereof, monovalent, divalent, trivalent, tetravalent, pentavalent carbon number 12-22 Hexavalent alcohol (which may contain an unsaturated bond or may be branched), alkoxy alcohol having 12 to 22 carbon atoms (which may contain an unsaturated bond or may be branched), carbon number 8 ˜22 aliphatic amines can be used.

  In addition, nonionic surfactants such as alkylene oxide, glycerin, glycidol, and alkylphenol ethylene oxide adducts, cations such as cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphonium or sulfoniums Surfactants, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester group, phosphoric acid ester group, amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, alkylbedines Amphoteric surfactants such as molds can also be used. These surfactants are described in detail in “Surfactant Handbook” (published by Sangyo Tosho Co., Ltd.). These lubricants, antistatic agents, and the like are not necessarily 100% pure, and may contain impurities such as isomers, unreacted materials, side reaction products, decomposed products, and oxides in addition to the main components. These impurities are preferably 30% or less, more preferably 10% or less.

  These lubricants and surfactants used in the present invention can be used properly in the lower coating layer and the cleaning layer as needed depending on the type and amount. For example, use fatty acids with different melting points in the lower coating layer and cleaning layer to control bleed out to the surface, or use esters with different boiling points and polarities to control bleed out to the surface, or adjust the amount of surfactant Thus, it is conceivable to improve the stability of coating or increase the amount of lubricant added in the lower coating layer to improve the lubrication effect. Of course, the present invention is not limited to the examples shown here. It is also preferable to add the fatty acid amide, fatty acid and fatty acid ester added to the cleaning layer to the lower coating layer.

  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 the kneading step, adding at a kneading step with an inorganic powder, a binder and a solvent, adding at a dispersing step, adding after dispersing, adding just before coating, etc. . Further, 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 can be applied to the surface of the cleaning layer after calendering or after completion of the slit.

  Examples of these lubricants used in the present invention include NAA-102, NAA-415, NAA-312, NAA-160, NAA-180, NAA-174, NAA-175, NAA- manufactured by NOF Corporation. 222, NAA-34, NAA-35, NAA-171, NAA-122, NAA-142, NAA-160, NAA-173K, castor hardened fatty acid, NAA-42, NAA-44, cation SA, cation MA, cation AB , Cation BB, Nymeen L-201, Nymeen L-202, Nymeen S-202, Nonion E-208, 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, Noni Non-2, Nonion LP-20R, Nonion PP-40R, Nonion SP-60R, Nonion OP-80R, Nonion OP-85R, Nonion LT-221, Nonion ST-221, Nonion OT-221, Monogly MB, Nonion DS -60, 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. NJolbu IPM, Sunsocizer E4030, TA-3, KF-96, KF-96L, KF96H, KF410, KF420, KF965, KF54, KF56, KF56, KF907, KF851, X-22-819, X-manufactured by Shin-Etsu Chemical 22-822, KF905, KF700, KF39 , KF-857, KF-860, KF-865, X-22-980, KF-101, KF-102, KF-103, X-22-3710, X-22-3715, KF-910, KF-3935 Lion Armor's Armide P, Armide C, Armor slip CP, Lion Oil & Fats Duomin TDO, Nissin Oilio BA-41G, Sanyo Kasei Profan 2012E, New Pole PE61, Ionette MS- 400, Ionette MO-200, Ionet DL-200, Ionet DS-300, Ionet DS-1000, Ionet DO-200, and the like.

  The nonmagnetic inorganic powder used for 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.

  Examples of the inorganic compound include α-alumina, β-alumina, γ-alumina, θ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, goethite, corundum, silicon nitride having an α conversion rate of 90% or more. , Titanium carbide, titanium oxide, silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, etc. are used alone or in combination . Particularly preferred are titanium dioxide, zinc oxide, iron oxide, and barium sulfate because of availability, cost, small particle size distribution, and many means for imparting functions, and more preferred are titanium dioxide and α. It is iron oxide.

The particle size of these non-magnetic inorganic powders is preferably 0.005 to 2 μm, but if necessary, non-magnetic inorganic powders having different particle sizes may be combined, or a single non-magnetic inorganic powder may have the same particle size distribution. It can also have an effect. The particle size of the nonmagnetic inorganic powder is particularly preferably 0.01 to 0.2 μm. The tap density is 0.05 to 2 g / ml, preferably 0.2 to 1.5 g / ml. The moisture content of the nonmagnetic inorganic powder is 0.1 to 5% by mass, preferably 0.2 to 3% by mass, and more preferably 0.3 to 1.5% by mass. The pH of the non-magnetic inorganic powder is 2 to 11, and the pH is particularly preferably between 5 and 10. The specific surface area of the nonmagnetic inorganic powder is 1 to 100 m ² / g, preferably 5 to 70 m ² / g, and more preferably 10 to 65 m ² / g. The crystallite size of the nonmagnetic inorganic powder is preferably 0.004 to 1 μm, and more preferably 0.04 to 0.1 μm. The oil absorption using DBP is 5 to 100 ml / 100 g, preferably 10 to 80 ml / 100 g, and more preferably 20 to 60 ml / 100 g. The specific gravity is 1 to 12, preferably 3 to 6. The shape may be any of a needle shape, a spherical shape, a polyhedral shape, and a plate shape, but 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 acicular nonmagnetic inorganic powder, 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.

The ignition loss is preferably 20% by mass or less, and it is considered most preferable that it does not exist. The Mohs hardness of the inorganic powder used in the present invention is preferably 4 or more and 10 or less. The roughness factor of the powder surface is preferably 0.8 to 1.5, and more preferably 0.9 to 1.2. The SA (stearic acid) adsorption amount of the 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 nonmagnetic inorganic powder into water at 25 ° C. is preferably in the range of 200 to 600 mJ / m ² . Moreover, the solvent which exists in the range of this heat of wetting can be used. The amount of water molecules on the surface at 100 to 400 ° C. is suitably 1 to 10 / 100A. The pH of the isoelectric point in water is preferably between 3 and 6.

The surface of these nonmagnetic inorganic powders is preferably a surface treated with Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , ZnO, Y ₂ O ₃ . Particularly preferred for dispersibility are Al ₂ O ₃ , SiO ₂ , TiO ₂ and ZrO ₂ , but more preferred are Al ₂ O ₃ , SiO ₂ and ZrO ₂ . These may be used in combination or may be used alone. Further, a surface-treated layer co-precipitated according to the purpose may be used, or a method of first treating with alumina and then treating the surface layer with silica, or vice versa. The surface treatment layer may be a porous layer depending on the purpose, but it is generally preferable that the surface treatment layer is 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, ZA-G1 manufactured by Sumitomo Chemical Co., Ltd., α-hematite manufactured by Toda Kogyo Co., DPN-250, DPN-250BX, DPN-245, DPN-270BX, DPN-550BX, Ishihara Sangyo Titanium oxide TTO-51B, TTO-55A, TTO-55B, TTO-55C, TTO-55S, TTO-55D, SN-100, α-hematite E270, E271, E300, STT-4D, STT-30D, STT-30, STT-65C, manufactured by Titanium Industry Co., Ltd., MT-100S, MT-100T, MT-150W, MT-500B, MT-600B, manufactured by Teica MT-100F, MT-500HD, Sakai Chemical's FINEX-25, BF-1, BF-10, BF-20, ST-M, Dowa Mining Co., Ltd. DEFIC-Y, DEFIC-R, Nippon Aerosil Co., Ltd. AS2BM, TiO2P25, Ube Industries Co., Ltd. 100A, 500A, Titanium Industry Y-LOP, and those obtained by firing it It is done.

Among the above, particularly preferable nonmagnetic inorganic powders are α-iron oxide and titanium dioxide. As α-iron oxide (hematite), those obtained under the following conditions can be used. First, the α-Fe ₂ O ₃ particle powder obtains acicular goethite particles as precursor particles by the following method. As a first method, a suspension containing ferrous hydroxide colloid obtained by adding an equal amount or more of an alkali hydroxide aqueous solution to a ferrous aqueous solution is supplied with an oxygen-containing gas at a temperature of pH 11 or more and 80 ° C. or less. A method of generating acicular goethite particles by conducting an oxidation reaction by aeration. As a second method, a goethite having a spindle shape is obtained by performing an oxidation reaction by aerating an oxygen-containing gas to a suspension containing FeCO ₃ obtained by reacting a ferrous salt aqueous solution and an alkali carbonate aqueous solution. A method of generating particles. As a third method, an oxygen-containing gas is passed through a ferrous salt aqueous solution containing a ferrous hydroxide colloid obtained by adding less than an equal amount of an alkali hydroxide aqueous solution or an alkali carbonate aqueous solution to a ferrous salt aqueous solution. Then, acicular goethite core particles are generated by performing an oxidation reaction, and then the ferrous salt aqueous solution containing the acicular goethite core particles has an amount equal to or more than Fe ^{2+ in} the ferrous salt aqueous solution. A method of growing the acicular goethite core particles by adding an aqueous alkali hydroxide solution and then venting an oxygen-containing gas. As a fourth method, an oxygen-containing gas is passed through a ferrous salt aqueous solution containing a ferrous hydroxide colloid obtained by adding less than an equivalent amount of an alkali hydroxide or alkali carbonate aqueous solution to the ferrous aqueous solution. For example, acicular goethite core particles are generated by performing an oxidation reaction, and then the acicular goethite core 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 that are usually added to improve the characteristics of the particle powder are added during the formation reaction of the goethite particles.

Then, the acicular goethite particles, which are precursor particles, are dehydrated in a temperature range of 200 to 500 ° C. or, if necessary, are annealed by a heat treatment in a temperature range of 350 to 800 ° C. to form acicular α- Fe ₂ O ₃ particles are obtained. It should be noted that there is no problem even if the acicular goethite particles to be dehydrated or annealed adhere to the surface with a sintering inhibitor such as P, Si, B, Zr, or Sb. Also, annealing by heat treatment in the temperature range of 350 to 800 ° C. is because the pores generated on the particle surface of the acicular α-Fe ₂ O ₃ particles obtained by dehydration are annealed, and the electrode of the particles This is because it is preferable that the surface is melted to close the pores to obtain a smooth surface form.

In the α-Fe ₂ O ₃ particle powder used in the present invention, acicular α-Fe ₂ O ₃ particles obtained by the dehydration or annealing are dispersed in an aqueous solution to form a suspension, and an Al compound is added. After adjusting the pH and coating the surface of the α-Fe ₂ O ₃ particles with the additive compound, it is obtained by filtration, washing with water, drying, pulverization, and if necessary, deaeration and consolidation. As the Al compound used, aluminum salts such as aluminum acetate, aluminum sulfate, aluminum chloride, and 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. When the amount is less than 0.01% by mass, dispersion in the binder resin is insufficient, and when it 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 in the present invention, one or more compounds selected from P, Ti, Mn, Ni, Zn, Zr, Sn, and Sb, as well as an Si compound, are included. It can also be coated. The 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. If it is less than 0.01% by mass, there is almost no effect of improving dispersibility by addition, and if it exceeds 50% by mass, the floating compounds other than the particle surface interact with each other.

Moreover, it is as follows regarding the manufacturing method of the titanium dioxide used for a lower layer coating layer. There are mainly a sulfuric acid method and a chlorine method for producing these titanium oxides. In the sulfuric acid method, the source ore of illuminite is digested with sulfuric acid, and Ti, Fe, etc. are extracted as sulfates. Iron sulfate is crystallized and removed, and the remaining titanyl sulfate solution is filtered and purified, followed by thermal hydrolysis to precipitate hydrous titanium oxide. After filtering and washing this, impurities are removed by washing, and after adding a particle size adjusting agent or the like, if it is baked at 80 to 1000 ° C., it becomes crude titanium oxide. The rutile type and the anatase type are classified according to the kind of nucleating agent added at the time of hydrolysis. This crude titanium oxide is prepared by pulverizing, sizing, surface treatment and the like. In the chlorine method, natural or synthetic rutile is used as the raw ore. The ore is chlorinated in a high temperature reduced state, Ti becomes TiCl ₄ and Fe becomes FeCl ₂ , and the iron oxide that has become solid upon cooling is separated from liquid TiCl ₄ . The obtained crude TiCl ₄ is purified by rectification and then added with a nucleating agent, and reacted instantaneously with oxygen at a temperature of 1000 ° C. or higher to obtain crude titanium oxide. The finishing method for imparting pigment-like properties to the crude titanium oxide produced in this oxidative decomposition step is the same as the sulfuric acid method.

In the surface treatment, after the above titanium oxide material is dry-pulverized, water and a dispersing agent are added, and coarse particle classification is performed by wet pulverization and centrifugal separation. Thereafter, the fine slurry is transferred to a surface treatment tank, where the surface of the metal hydroxide is coated. First, a predetermined amount of an aqueous salt solution such as Al, Si, Ti, Zr, Sb, Sn, and Zn is added, and an acid or alkali is added to neutralize this, and the surface of the titanium oxide particles is coated with the resulting hydrous oxide. To do. Water-soluble salts produced as a by-product are removed by decantation, filtration, and washing. Finally, the slurry pH is adjusted, filtered, and washed with pure water. The washed cake is dried with a spray dryer or a band dryer. Finally, the dried product is pulverized by a jet mill to become a product. Further, it is possible to perform surface treatment of Al and Si by passing the vapor of AlCl ₃ and SiCl _{4 to} the titanium oxide powder as well as the water system and then flowing water vapor. For other pigment production methods, see G.C. D. Parfitt and K.M. S. W. Sing “Characterization of Powder Surfaces” Academic Press, 1976 can be referred to.

Carbon black may be used in combination with the non-magnetic inorganic powder as described above. By mixing this carbon black with the lower coating layer, the surface electrical resistance Rs, which is a known effect, is reduced to obtain an antistatic effect. The light transmittance can be reduced, and a desired micro Vickers hardness can be obtained. Micro Vickers hardness is typically the lower coating ^{layer, 25~60kg / mm 2 (≒ 245~588MPa} ), preferably in order to adjust the head ^{contact, 30~50kg / mm 2 (≒ 294~490MPa} ), manufactured by NEC Using a thin film hardness tester HMA-400, a diamond triangular pyramid needle with a ridge angle of 80 degrees and a tip radius of 0.1 μm is used for the tip of the indenter.

Examples of usable carbon black include furnace for rubber, thermal for rubber, black for color, acetylene black and the like. The specific surface area of the carbon black is 100 to 500 m ² / g, preferably 150~400m ² / g, DBP oil absorption 20 to 400 ml / 100 g, preferably 30 to 200 ml / 100 g. The primary particle diameter of carbon black is 10 to 80 nm, preferably 10 to 50 nm, and more preferably 10 to 40 nm. 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 BLACKPEARLS 2000, 1300, 1000, 900, 800, 880, 700, VULCAN XC-72 manufactured by Cabot Corporation, # 3050B, 3150B, 3250B manufactured by Mitsubishi Chemical Corporation. # 3750B, # 3950B, # 950, # 650B, # 970B, # 850B, MA-600, MA-230, # 4000, # 4010, CONDUCTEX SC, RAVEN 8800, 8000, 7000, 5750, 5250, manufactured by Conlonvia Carbon , 3500, 2100, 2000, 1800, 1500, 1255, 1250, and Ketjen Black EC manufactured by Ketjen Black International. Carbon black may be surface-treated with a dispersant or the like, or may be grafted with a resin or may be obtained by graphitizing a part of the surface. Moreover, before adding carbon black to a coating material, you may disperse | distribute with a binder beforehand.

  These carbon blacks can be used in the range of 5 to 49% by mass with respect to 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.

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

  In addition, the binder resin, lubricant, dispersant, additive, solvent, dispersion method, etc. of the lower coating layer can be applied to those of the magnetic layer. In particular, with respect to the addition amount and type of binder resin, additive, and dispersant, known techniques relating to the magnetic layer can be applied.

  The organic solvent used in the lower coating layer and the cleaning layer of the present invention is an arbitrary ratio of ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, tetrahydrofuran, methanol, ethanol, propanol, butanol, isobutyl alcohol. , Alcohols such as 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, benzene , Aromatic hydrocarbons such as toluene, xylene, cresol, chlorobenzene, methylene chloride, ethylene chloride, carbon tetrachloride , Chloroform, ethylene chlorohydrin, chlorobenzene, or dichlorobenzene, N, N- dimethylformamide, those hexane and the like can be used. These organic solvents are not necessarily 100% pure, and may contain impurities such as isomers, unreacted materials, side reaction products, decomposition products, oxides, and moisture in addition to the main components. These impurities are preferably 30% or less, more preferably 10% or less.

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

  The thickness structure of the cleaning tape of the present invention is effective when the nonmagnetic support is as thin as 2.0 to 10 μm. The total thickness of the cleaning layer and the lower coating layer is used in the range of 1/100 to 2 times the thickness of the nonmagnetic support. In the cleaning medium of the present invention, preferably, the cleaning layer has a thickness of 0.05 to 1.0 μm, the lower coating layer has a thickness of 0.2 to 5.0 μm, and the support has a thickness of 2.0 to 10 μm. The total thickness of the medium (cleaning tape) is 4.0 to 15 μm. Moreover, you may provide the contact bonding layer for an adhesive improvement between a nonmagnetic support body and a lower layer coating layer. The thickness of this adhesive layer is 0.01-2 μm, preferably 0.02-0.5 μm. Further, a back layer may be provided on the surface opposite to the cleaning layer side of the nonmagnetic support. This thickness is 0.1 to 2 μm, preferably 0.3 to 1.0 μm. Known adhesive layers and back 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) or more, and biaxially stretched polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, polyamideimide, aromatic Known films such as aromatic polyamides and polybenzoxydazoles can be used. In particular, a high-strength nonmagnetic support using aramid resin or polyethylene naphthalate is preferable. These nonmagnetic supports may be subjected in advance to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment and the like.

  In order to achieve the object of the present invention, it is preferable to use a nonmagnetic 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. These non-magnetic supports preferably have not only a small center line average surface roughness but also no coarse protrusions of 1 μm or more. The adjustment of the roughness shape of the support surface can also be used to control the distribution of protrusions in the present invention. For this purpose, the size and amount of filler added to the nonmagnetic support may be appropriately selected. Examples of these fillers include oxides and carbonates such as Al, Ca, Si, and Ti, which may be crystalline or amorphous, and organic fine powders such as acrylic and melamine. Further, in order to achieve compatibility with running durability, the roughness of the surface on which the back layer is applied is preferably rougher than the roughness of the surface on which the cleaning layer is applied. The center line surface roughness of the back layer application surface is preferably 1 nm or more, more preferably 4 nm or more. When changing the roughness between the cleaning layer application surface and the back layer application surface, a dual-structured support may be used, or may be changed by providing a coating layer.

The F-5 value in the tape running direction (MD direction) of the nonmagnetic support used in the present invention is preferably 10 to 50 kg / mm ² (≈98 to 490 MPa), and the F-5 value in the tape width direction (TD direction). Is preferably 10 to 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. This is not the case when it is necessary to increase the strength. The heat shrinkage rate 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 rate at 80 ° C. for 30 minutes. Is preferably 1% or less, more preferably 0.5% or less. The breaking strength is preferably 5 to 100 kg / mm ² (≈49 to 980 MPa) in both directions, and the Young's modulus is preferably 100 to 3,000 kg / mm ² (≈0.98 to 29.4 GPa). Further, the light transmittance at 900 nm is preferably 30% or less, and more preferably 3% or less.

  The step of producing the coating material for the lower layer 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. Each process may be divided into two or more stages. All raw materials such as 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. In addition, individual raw materials may be added in two or more steps. For example, polyurethane may be divided and added in a kneading step, a dispersing step, and a mixing step for adjusting the viscosity after dispersion.

  In order to achieve the object of the present invention, it is a matter of course that a conventional known manufacturing technique can be used as a part of the process, but in the kneading process, those having a strong kneading force such as a continuous kneader and a pressure kneader are used. It is preferable to use it. Details of these kneading treatments are described in JP-A-1-166338 and JP-A-64-79274. Moreover, when adjusting the nonmagnetic layer solution of the lower coating layer, it is desirable to use a dispersion medium having a high specific gravity, and zirconia beads are preferred.

  In the case of a cleaning medium having a multi-layer structure, the following structure can be proposed as an example of a coating apparatus and method.

1. Firstly, the lower coating layer is applied by a gravure coating, roll coating, blade coating, extrusion coating device, etc., which are generally used in the application of magnetic paint, and while the lower coating layer is still wet, The upper cleaning layer is applied by a support pressure type extrusion coating apparatus disclosed in Japanese Patent No. 46186, Japanese Patent Laid-Open No. 60-238179, and Japanese Patent Laid-Open No. 2-265672.

2. The lower coating layer and the cleaning layer are formed by one coating head having two coating liquid passage slits as disclosed in JP-A-63-88080, JP-A-2-17971, and JP-A-2-265672. Apply almost simultaneously.

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

  In order to prevent agglomeration of magnetic particles, it is desirable to apply a shearing force to the coating solution in the coating head by a method as disclosed in JP-A-62-295174 and JP-A-1-236968. Further, the viscosity of the coating solution needs to 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 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, and further before orientation so that the orientation after drying is the highest. It is preferable to provide an appropriate drying step in advance.

  In addition, prior to simultaneous application of the nonmagnetic lower layer coating layer and the cleaning layer, a known method for improving adhesion by providing an adhesive layer mainly composed of a polymer, corona discharge, UV irradiation, or EB irradiation. Are preferably combined.

  Further, it is preferable to perform a calendar process in order to adjust the protrusion distribution on the surface of the cleaning layer. As the calendering roll, a heat-resistant plastic roll such as epoxy, polyimide, polyamide, polyimide amide or the like can be used. Moreover, it can also process with metal rolls. The treatment temperature is preferably 50 to 100 ° C., more preferably 80 to 100 ° C., and the linear pressure is preferably 100 to 500 kg / m (≈980 to 4900 N / m), and 200 to 400 kg / m (≈1960 to 3920 N / m). Is more preferable, and the speed is preferably 50 to 400 m / min, more preferably 100 to 300 m / min.

The friction coefficient with respect to SUS420J of the cleaning layer surface and the opposite surface of the cleaning medium of the present invention is preferably 0.1 to 0.5, more preferably 0.2 to 0.3. The surface resistivity is preferably 10 ⁴ to 10 ¹² ohm / sq, and the elastic modulus at 0.5% elongation of the cleaning layer is preferably 100 to 2,000 Kg / mm ^{2 in} both the running direction and the width direction (≈0.98 to 19.6 GPa), and the breaking strength is preferably 1 to 30 kg / mm ² (≈9.8 to 294 MPa).

The cleaning medium as a whole has a Young's modulus in the longitudinal (MD) direction of 300 to 1200 kg / mm ² (≈2.94 to 11.76 GPa) and a Young's modulus in the width (TD) direction of 200 to 1200 kg / mm ^2. (≈1.96 to 11.76 GPa) and the 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 thermal shrinkage at any temperature of 100 ° C. or less is preferably 1% or less, more preferably 0.5% or less, most preferably 0.1%. In the following, 0% is ideal. The glass transition temperature of the cleaning layer (maximum point of loss elastic modulus in dynamic viscoelasticity measurement measured at 110 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. The loss elastic modulus is preferably in the range of 1 × 10 ⁷ to 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 or less, more preferably 10 mg / m ² or less, and the residual solvent contained in the upper cleaning layer is preferably smaller than the residual solvent contained in the lower coating layer. The porosity is preferably 50% by volume or less, more preferably 40% by volume or less for both the lower coating layer and the cleaning layer.

The magnetic characteristics of the cleaning layer of the cleaning medium of the present invention are as follows. When measured with a vibrating sample magnetometer (VSM) at a magnetic field of 10 kOe {Oe = (1 / 4π) kA / m}, the coercive force Hc in the tape running direction is 500. -3000 Oe (≈40-240 kA / m). 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 preferably 1800 to 3000 Oe (≈144 to 240 kA / m). Hc and Hr in the vertical direction are preferably 1000 to 5000 Oe (≈80 to 400 kA / m). 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 depending on the purpose. The RMS surface roughness R _RMS obtained by evaluation by AFM is preferably in the range of 2 to 15 nm.

  The cleaning medium of the present invention can have a lower coating layer and a cleaning layer, but it is easily estimated that these physical properties can be changed between the lower coating layer and the cleaning layer depending on 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 tensed in the direction perpendicular to the longitudinal direction of the tape has better head contact. There are many cases.

  Examples of the present invention will be shown below, and the present invention will be described in more detail. “Parts” in the examples represents “parts by mass”.

Example 1
"Cleaning layer coating solution"
Ferromagnetic metal fine powder 100 parts Composition Fe / Co = 100/30
Hc 2500 Oe (200 kA / m)
Specific surface area by BET method 49m ² / g
Surface treatment layer Al ₂ O ₃ , SiO ₂ , Y ₂ O ₃
Average particle size (major axis diameter) 0.04μm
Average needle ratio 7
σs: 125 emu / g (125 A · m ² / kg)
Vinyl chloride copolymer MR110 (manufactured by Nippon Zeon Co., Ltd.) 2 parts Polyurethane resin 15 parts Add 50 parts of cyclohexanone and knead for 60 minutes, then α-Al ₂ O ₃ (maximum particle size 0.20 μm) dispersion A 10 parts Carbon black (average particle size 0.03 μm) 0.3 part Methyl ethyl ketone / toluene = 1/1 220 parts

And dispersed in a sand mill for 180 minutes. to this

Lubricant Butyl stearate 2 parts Stearic acid 1 part Stearic acid amide 1 part Solvent Methyl ethyl ketone 60 parts Polyisocyanate (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) 13.5 parts

The mixture was stirred for 20 minutes and filtered using a filter having an average pore size of 0.5 μm to prepare a coating solution.

  Next, the cleaning layer-forming coating solution obtained as described above is coated on a nonmagnetic support so that the thickness after drying is 0.2 μm, and the coating solution is magnetically oriented in an undried state. After drying, a back layer is applied to the other side of the cleaning layer in a thickness of 0.3 μm, dried, and then treated with a seven-stage calendar composed of a metal roll and an epoxy resin roll. The cleaning medium of the present invention was obtained by slitting the ridges. As the nonmagnetic support, polyethylene naphthalate having a thickness of 6 μm was used.

Preparation of α-Al ₂ O ₃ Dispersion A Each component of the following abrasive dispersion was placed in an alumina ceramic ball mill and mixed and dispersed for 20 hours to prepare Dispersion A.
α-Al ₂ O ₃ (maximum particle size 0.20 μm) 100 parts Polyurethane resin 10 parts Methyl ethyl ketone 60 parts

(Back layer forming coating solution)
Kneaded material 1
Carbon black (Cabot BP-800) 100 parts Nitrocellulose RS1 / 2 100 parts polyurethane Nippon polyurethane N2301 30 parts Dispersant Copper oleate 5 parts
Copper phthalocyanine 5 parts
Precipitated barium sulfate 5 parts Methyl ethyl ketone 500 parts Toluene 500 parts

  After pre-kneading the above with a roll mill,

Kneaded product 2
100 parts of carbon black
Average particle size 270nm
DBP oil absorption 36ml / 100g
pH 10.0
Specific surface area by BET method 8.5m ² / g
Nitrocellulose 100 parts polyurethane Nippon polyurethane N2301 30 parts Methyl ethyl ketone 300 parts Toluene 300 parts

  Pre-kneaded kneaded material 1 and kneaded material 2 were dispersed with a sand grinder, and after completion, the following was added to obtain a coating solution for a back layer.

Polyester resin Toyobo Byron 300 5 parts Polyisocyanate Nippon Polyurethane Coronate L 5 parts

Examples 2-3
In Example 1, Example 1 was repeated except that the amount of α-Al ₂ O ₃ dispersion A used was changed to the following.
Example 2 α-Al ₂ O ₃ dispersion A 5 parts Example 3 α-Al ₂ O ₃ dispersion A 20 parts

Example 4
The cleaning layer forming coating solution, the back layer forming coating solution, and the nonmagnetic support were the same as those used in Example 1. The following coating solution for lower layer coating layer formation was created.
"Liquid for forming lower layer coating layer"
Nonmagnetic inorganic powder α-Fe ₂ O ₃ (hematite) 85 parts Average particle size 0.13 μm
Specific surface area by BET method 55m ² / g
Surface treatment layer Al ₂ O ₃ , SiO ₂
pH 6.0-8.5

  For 10 minutes with an opener,

Polyurethane resin 13.5 parts Cyclohexanone 50 parts

And knead for 60 minutes, then

Add 200 parts of methyl ethyl ketone / cyclohexanone = 6/4 and disperse for 120 minutes,

Butyl stearate 4 parts Stearic acid amide 1 part Stearic acid 3 parts Methyl ethyl ketone 60 parts Polyisocyanate (Nihon Polyurethane Coronate L) 5 parts

The mixture was stirred for 20 minutes and filtered using a filter having an average pore size of 0.5 μm to prepare a coating solution.

Next, the thickness of the coating solution for forming the lower layer coating layer obtained as described above is further dried so that the thickness after drying is 1.4 μm. Was simultaneously coated on the support so that the thickness was 0.12 μm.
After the coating liquid is dried in an undried state, a back layer having a thickness of 0.3 μm is applied to the other surface of the cleaning layer, dried, and then formed of a metal roll and an epoxy resin roll. After being processed with the above calender, it was cut into ½ cm width to obtain the cleaning medium of the present invention.

Comparative Example 1
In Example 1, Example 1 was repeated except that the addition amount of the α-Al ₂ O ₃ dispersion A was changed to 5 parts.

Comparative Examples 2-4
Each dispersion having a different degree of dispersion of α-Al ₂ O ₃ dispersion A was prepared. That is, in Example 1, dispersions B to C were prepared by changing the mixing / dispersing treatment as follows.
Dispersion time 10 hours Dispersion B
Dispersion time 50 hours Dispersion C
In Comparative Example 2, Example 1 was repeated using the above dispersion B.
In Comparative Example 3, Example 1 was repeated using the above dispersion C.

The following measurements were performed on the various cleaning media obtained. The measurement method is shown.
Head wear:
Using an IBM LTO (Ultramium) drive (using an MR head), the cleaning tape was run for 1 hour at 23 ° C. × 70% RH, and the head height of the MR head before and after that was measured for 10 minutes. The head wear per hit was calculated.

Head cleaning power:
The output is measured in advance using an LTO (Ultra) drive manufactured by IBM using an LTO Ultrium1 data cartridge (model LTO FB UL-1 100GE) manufactured by Fuji Photo Film Co., Ltd. After that, run the standard tape created for the purpose of causing clogging with the IBM LTO (Ultramium) drive, observe the head condition with the strobe, and run when the head is heavily soiled. Stop and make sure there is no output. Then, after running each cleaning tape of the sample for 1 minute, the output was measured using the LTO Ultrium 1 data cartridge (model LTO FB UL-1 100GE) manufactured by Fuji Photo Film Co., Ltd. in advance. The difference dB between the last measured output and the first measured output was used as the head cleaning power evaluation.

Head deposits:
When the head wear was measured, the deposits on the head were observed with a microscope.

Surface occupancy ratio of abrasive on the cleaning layer surface:
The surface of the cleaning layer was measured at a magnification of 10,000 times using a scanning electron microscope (SEM). The SEM image obtained as electronic data was binarized using the photo retouching software of a personal computer, and the area distribution of the abrasive was represented as a histogram and obtained.
The results are shown in Table 1 below.

  As can be seen from the above, when the surface occupancy ratio of the abrasive on the surface of the cleaning layer is in the range of 2.0 to 5.0%, the head deposit, head wear, and head cleaning power are all excellent. I understand that

Claims (2)

  In a cleaning medium for a magnetic recording apparatus in which a cleaning layer containing at least an inorganic powder of a ferromagnetic powder and a binder is provided on a nonmagnetic support, the surface occupancy ratio of the abrasive on the surface of the cleaning layer is 2.0 to 5 A cleaning medium for a magnetic recording device, characterized by being 0.0%.   The magnetic recording device cleaning medium according to claim 1, wherein a nonmagnetic back layer is provided on an opposite surface of the nonmagnetic support to which the cleaning layer is provided.