DE19752953A1 - Strip-like magnetic recording medium - Google Patents

Abstract

Strip-like magnetic recording medium comprises a substrate with a magnetic layer consisting of a ferromagnetic metal powder dispersed in a binder. The magnetic layer has a product of coercive force Hc(Oe) within the machine direction of the strip and magnetic flux phi m (G.cm) of 100-160.

Description

The present invention relates to a particle-containing magnetic recording medium comprising a plastic carrier with a magnetic layer applied thereto, comprising dispersed in a binder fine ferromagnetic Powder, and especially excellent has electromagnetic properties and durability. In particular, the present invention relates to a Recording and playback of digital signals with high Density-appropriate magnetic recording medium.

Magnetic recording media are widely used as Audio tapes, videotapes, computer tapes, computer diskettes and the like. The density of a magnetic recording medium became higher annually and the recording wavelength became shorter, and recording systems from analogue to digital System were discussed.

Regarding the need for higher quality records Density was a particulate magnetic Recording medium by applying a dispersion a ferromagnetic powder in a binder on a Carrier is formed, a magnetic Recording film medium, wherein the magnetic Recording layer, a vacuum-deposited cobalt alloy covers, in electromagnetic properties because of  low packing density of a ferromagnetic powder inferior. With the improvement of performance ferromagnetic powder and the progress of Coating technology of extremely thin layers in the However, years ago, it was almost the same level the electromagnetic properties as in film media reached. Further, a particulate magnetic is Recording medium in terms of productivity and the Superior corrosion resistance.

Such particulate magnetic recording media need a high level of performance in different ways have properties such as running resistance and Runnability, as well as in the electromagnetic Properties. That is, car bands for Sound recording / playback must have a higher degree of Playability of the original sound have. videotapes must have excellent electromagnetic properties, like the ability to play the original image.

Particulate magnetic recording media do not have to only such superior electromagnetic properties but also an excellent one Running resistance as described above. In general Be an abrasive and a lubricant in a Magnetic layer incorporated facing the achievement of excellent running stability.

To use an abrasive excellent However, it should be stable Addition amount increased to some extent, leading to Reduction of the packing density of the ferromagnetic powder leads. If an abrasive with a large Particle diameter is used to get an excellent To maintain running resistance, the abrasive particles tend  furthermore, excessively on the surface of the magnetic layer excel. Accordingly, the improvement in the Running resistance by an abrasive in some cases for the deterioration of the electromagnetic properties.

To improve the running quality by incorporating a lubricant, such as a fatty acid and a Fatty acid ester, its added amount should be increased. The Binder, however, is prone to the increased amount of lubricant for curing, and the durability of the magnetic layer tends by being humiliated.

Furthermore, it is understood that the binder, the one the major component of the magnetic layer is also one important role in improving the durability and the electromagnetic properties plays.

A particle-containing magnetic recording medium whose Magnetic layer thickness by attaching a non-magnetic Layer between the magnetic layer and the carrier reduced is well known. To achieve even higher Recording density became a particle-containing magnetic Recording medium with a thinner magnetic layer, the contains even finer ferromagnetic metal powder, required. This minimization of ferromagnetic Metal powder causes a lowering of the Dispersibility, resulting in deterioration of the Surface properties of the magnetic layer and the Deterioration of electromagnetic properties, which makes it difficult to ensure durability.

A binder resin with excellent durability, in which a ferromagnetic metal powder and a non-magnetic Powders have excellent dispersibility, and the one with the elasticity (elongation) compatible hardness  (i.e., a high Tg and a high elastic modulus), is most useful as a binder for a particulate magnetic recording medium preferred.

As videotape for the digital video cassette (DVC) for Consumer video recorder (SD specification) is suitable today is a band of a magnetic Recording medium used in practice, by a Vacuum film forming technique is formed. Because one particle-containing magnetic recording medium containing a ferromagnetic metal powder used, the film medium superior in terms of durability and economy is, it is very beneficial if the particle-containing medium used for consumer purposes for DVC. There are, however a problem in that it is very difficult with the particulate medium unchanged satisfactory to obtain electromagnetic properties, in particular Overwriting properties, even if a binder with excellent properties as described above becomes.

One means for improving the overwriting properties is to reduce the coercive force (Hc) and make the thickness of the magnetic layer thin, but the mere decrease of Hc results in a decrease in the saturation magnetic flux density Φm of the magnetic layer, lowering the reproduction output level. That is, for the purpose of improving the overwriting characteristics without decreasing the reproduction output level, it is necessary to increase the packing density of the fine magnetic powder contained in the magnetic layer by reducing the magnetic layer thickness or increasing the saturation magnetic flux density Φm of the magnetic layer by using a magnetic powder having a high degree of saturation magnetization σ _s increase. However, when σ _{s of} the magnetic powder is increased, the surface properties of the magnetic layer are deteriorated by the orientation disturbance of the magnetic powder due to the magnetostatic interaction between the magnetic powders, and thereby the output level is lowered.

That is, in the particle-containing medium suitable for DVC No conditions have yet been found under which satisfactory durability, playback output levels and Overwriting properties can be maintained constant.

It is an object of the present invention particle-containing magnetic recording medium with high Durability and excellent electromagnetic Features, such as playback output levels and Override features to provide.

The present invention may include a particulate magnetic recording medium, in particular a band-like particle-containing magnetic recording medium for DVC (a band-like magnetic recording medium sometimes becomes simple as particle-containing magnetic Providing recording medium) a non-magnetic (i.e., plastic) carrier having a magnetic layer applied thereto, comprising one in one Binder dispersed ferromagnetic metal powder, comprising and in which the magnetic recording medium is the same Overwrite properties like those of the film medium, high Output level and low noise properties, has, in which the Magnetic layer a product Π of coercive force Hc (Oe) within the machine direction of the belt and the magnetic flux Φm (G.cm) is from 100 to 160 (where within the Machine direction of the belt is the longitudinal (i.e. Machine) direction of the band in band-like particle-containing magnetic recording medium means).  

The present invention has solved the above problem by setting the magnetic properties of the magnetic layer within the specified range. That is, the magnetic layer of the present invention satisfies the following equation (1):

Π = Hc × Φm = 100 to 160 (1)

where Hc is the coercive force within the machine direction in Oe (Oersted) units, and Φm is the magnetic flux per Area unit of the magnetic layer is represented by G.cm as a unit (G means Gauss).

In the present invention, Π is 100 to 160, preferably 110 to 150, and most preferably 120 to 140. If Π is less than 100, the Reproduction output level, in particular the output level long wavelength, humiliated, and when Π 160 exceeds the overwriting characteristics are degraded.

As means for obtaining the prescribed in the present invention Π can be the use of ferromagnetic metal powders with specific surface area S _BET , measured by the BET method, and σ _s within specific ranges, the regulation of the strength of the magnetic layer and the use of polyurethane resins with a as a binder resin and the like as examples, but the means are not limited thereto.

The ferromagnetic metal powders used in the present invention preferably have an S _BET of 30 m ² / g to less than 50 m ² / g, more preferably from 35 to less than 50 m ² / g, and especially preferably from 40 to less than 50 m ² / g, and a σ _s of preferably 140 to 170 emu / g, more preferably 145 to 170 emu / g, and especially preferably 150 to 170 emu / g.

Preferred polyurethane resins for use in the Present invention are polyurethane resins with a cyclic structure and an ether group, e.g. B. by the reaction of short-chain diols (ie the first diols) with a cyclic structure (eg with a cyclic Hydrocarbon group), long chain diols (i.e. second diols) containing an ether group, and Diisocyanate can be obtained.

It is believed that the cyclic structure of such Polyurethane resins contributes to the rigidity and the ether group flexibility, so that as a result Solubility improves and the radius of gyration (extent of a molecule), which improves the Dispersibility of the above powder leads to the same Time the hardness (i.e., a high glass transition temperature Tg and a high modulus of elasticity) and the elasticity (elongation) of the polyurethane resin as such by such structures compatible with each other, thereby improving the Durability is achieved.

The polyurethane resin preferably has 3 to 20 and especially preferably 4 to 5 OH groups per molecule. If the number of OH groups less than 3 per molecule, is the strength of the coated film, because the reactivity with a polyisocyanate curing agent is lowered, and as Result, the durability tends to decrease. If the number on the other hand, the solubility is higher than 20 Solvent lowers, and thereby tends the Decrease dispersibility.  

A compound with three or more functional OH groups can be used to regulate the OH group content of the Polyurethane resin can be used. Special examples close trimethylolethane, trimethylolpropane, Trimellitic anhydride, glycerin, pentaerythritol, hexanetriol etc. Examples thereof further include branched ones Polyester and polyetherester each having three or more functional OH groups consisting of a dibasic acid and one of the preceding compounds as Glycol component obtained as polyester polyol starting materials used in conventional processes which are disclosed in JP-B-6-64726 (here used term "JP-B" means a "tested Japanese Patent publication "). Preferred are those with three OH groups. When the compound has four or more OH groups has gelation during the reaction occur.

The polyurethane compound preferably contains at least one polar group in the molecule selected from -SO ₃ M, -OSO ₃ M, -COOM, -PO ₃ MM ', -OPO ₃ MM', -NRR 'and -N⁺RR'R '' COO ', wherein M and M' each represent a hydrogen atom, an alkali metal ion, an alkaline earth metal ion or an ammonium ion, and R, R 'and R''each represents an alkyl group having 1 to 12 carbon atoms. Particularly preferred among them are -SO ₃ M and -OSO ₃ M. The content of the polar group is preferably 1 × 10 ^-5 to 2 × 10 ^-4 equivalent / g, and more preferably 5 × 10 ^-5 to 1 × 10 ^-4 equivalent /G. When the content is lower than 1 × 10 ^-5 equivalent / g, the adsorption of the polyurethane resin on ferromagnetic powders is insufficient, and thereby the dispersibility is lowered; On the other hand, if the content is higher than 2 × 10 ^-4 equivalent / g, the solubility of the polyurethane resin in a solvent is lowered, and the dispersibility is lowered.

Short-chain diols (ie the first diols) with a cyclic structure mean diols with a saturated or unsaturated cyclic structure and a molecular weight less than 500, d. H. Diols with an aromatic or alicyclic structure, such as bisphenol A, by the hydrogenated bisphenol A represented by the following formula (I), Bisphenol S, bisphenol P, ethylene oxide and / or propylene oxide adducts these bisphenols, cyclohexanedimethanol, Cyclohexanediol etc.

Particularly preferred among these are those represented by formula (I) represented hydrogenated bisphenol A and ethylene oxide and / or Propylene oxide adducts thereof.

The short-chain diol (ie the first diol) with a cyclic structure is selected from those with a molecular weight of 50 to less than 500, especially preferably from 100 to 400, and most preferably from 100 to 300. If the molecular weight is lower than 50, will the magnetic layer becomes brittle and the durability is lowered. If on the other hand, the molecular weight is 500 or more (i.e. in the case when the short chain diol (i.e., the first diol) in the present invention is not used), the Glass transition temperature Tg of the magnetic layer is lowered, and the polyurethane resin becomes too soft, and as a result, the Durability deteriorates.

The short-chain diol (ie the first diol) with the above described cyclic structure may in combination with  other diols with a molecular weight of less than 500 be used. Specific examples thereof include straight chain or branched diols, e.g. For example, ethylene glycol, 1,3-propylenediol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethylpropanediol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol and ethylene oxide and / or propylene oxide adducts of N-diethanolamine.

An applied film having high strength, high Tg and high durability can be obtained due to the cyclic structure using these compounds. Further, excellent solubility in a solvent can be obtained by the introduction of branched CH ₃ to thereby obtain high dispersibility.

The content of the short-chain diol units in the polyurethane resin is preferably 17 to 40 wt .-% and particularly preferably 20 to 30% by weight. If the content is lower than 17% by weight, the applied film is too soft to get enough To maintain strength, resulting in the reduction of the durability leads. If the content is higher than 40% by weight, it becomes further the solubility in a solvent is lowered, and as The result is the dispersibility of the ferromagnetic Powder tends to be reduced, and thereby tend to electromagnetic characteristics, as well as the Strength of the obtained magnetic layer is lowered.

Long-chain diols (ie the second diols) are diols with a molecular weight of 500 or more, and preferred specific examples thereof include ethylene oxide and / or Propylene oxide adducts of bisphenol A, hydrogenated bisphenol A, Bisphenol S and bisphenol P, polypropylene glycol, Polyethylene glycol and polytetramethylene glycol. By is the compound represented by the following formula (II) particularly preferred.  

R is at least one member of the following groups:

In formula (II), n and m are each a number from 3 to 24, preferably from 3 to 20 and more preferably from 4 to 15. When n or m is less than 3, the urethane bond concentration is increased, and the solubility in one Solvent is reduced, the applied film is brittle, and further the dispersibility and the Durability lowered. If n or m is greater than 24, then the applied film is too soft, and the rest durability is decreased.

In the long chain diol represented by the formula (II) (i.e., the second diol), R is preferred by the following Formula (i) or (ii) shown.  

R is particularly preferably represented by formula (i).

In the long chain diol represented by the formula (II) (i.e., in the second diol), X preferably represents a hydrogen atom or a methyl group, particularly preferably a methyl group Group. Here are all X, enclosed by n or m in parentheses are not always the same. If z. B. n is 2, Two X groups can be hydrogen atoms or methyl groups or one of the two X groups can be a hydrogen atom and the other may be a methyl group.

Because the polyurethane resins particularly preferably used in the present invention have a cyclic structure, they can assure high film strength and excellent durability, and they can further have excellent solubility in a solvent and high dispersibility because they are the CH ₃ branches of introduced propylene have.

The weight average molecular weight (Mw) of the long chain Diol (i.e., the second diol) is 500 to 5,000 the weight-average molecular weight exceeds 5,000, the strength of the applied film is lowered, and The film becomes too soft, resulting in durability  is reduced. Therefore, the preferred weight average molecular weight between 700 and 3,000.

The content of the ether group-containing long-chain Diol units is preferably 10 to 50% by weight, especially preferably 30 to 40 wt .-%, based on the polyurethane resin. If the content is less than 10% by weight, the Solubility of the resin in a solvent lowered what leads to a reduction in dispersibility. If the On the other hand, the content is larger than 50% by weight Strength of the coated film is lowered, and as Result is the durability reduced. The content of in the long-chain diol units contained ether group preferably 1.0 to 5.0 mmol, more preferably 2.0 to 4.0 mmol, per gram of the polyurethane resin. If the salary is lower than 1 mmol / g, the adsorbability is on magnetic powders and dispersibility is low reduced. On the other hand, when the content is larger than 5.0 mmol / g is the solubility is reduced in a solvent, and as a result, the dispersibility is lowered.

The number average molecular weight (Mn) of the Polyurethane resin is preferably 18,000 to 56,000, more preferably 23,000 to 34,000, and the weight average of the molecular weight (Mw) is preferably 30,000 to 100,000, more preferably 40,000 to 60,000. If Mn and Mw are lower than these ranges, the strength of the Magnetic layer reduces and therefore the durability reduced. On the other hand, if they are larger than these areas are the solubility of the polyurethane resin in one Solvent is reduced, and that is why Dispersibility reduced.

The glass transition temperature Tg of the polyurethane resin is 0 to 200 ° C, preferably 30 to 150 ° C and more preferably  30 to 130 ° C. If Tg is lower than 0 ° C, that is Strength of the magnetic layer at high temperatures degrades, and as a result, the durability and the Storage stability lowers. If Tg is greater than 200 ° C is the calender plasticity of the resin is decreased, and as a result, the electromagnetic properties deteriorated.

If a binder is used in the magnetic layer, can Vinyl chloride-based resins (eg, a vinyl chloride polymer or copolymer containing vinyl chloride as a repeating unit contained) in combination with the above polyurethane resins be used. Vinyl chloride-based resins used in Combination can be used, preferably one Degree of polymerization from 200 to 600, more preferably from 250 to 450. Vinyl chloride-based resins with Vinyl monomers, e.g. Vinyl acetate, vinyl alcohol, Vinylidene chloride, acrylonitrile, etc., are copolymerized, can be used. Furthermore, polyurethane resins can also in combination with cellulose derivatives, such as nitrocellulose, an acrylic resin, a polyvinyl acetal resin, a Polyvinyl butyral resin, an epoxy resin, a phenoxy resin etc., to be used. These resins can be used alone or in Combination can be used.

If polyurethane resins in combination with others synthetic resins are used, the content of the Polyurethane resins in the magnetic layer preferably 10 to less than 100% by weight, more preferably 20 to less as 100 wt .-%, based on the total amount of the binder. If the content of the polyurethane resins is lower than 10% by weight, the solubility in a solvent is reduced, resulting in a reduced dispersibility results.  

In the present invention, polyisocyanate compounds, preferably organic diisocyanate, as a Component for forming a urethane bond of the above Polyurethane resins or as a curing agent for crosslinking Polyurethane resins or others, in combination with each other used resins.

Examples of organic diisocyanate compounds include aromatic diisocyanates, e.g. B. 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-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate etc., aliphatic diisocyanates, e.g. B. lysine diisocyanate, and alicyclic diisocyanates, e.g. B. isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated Diphenylmethane diisocyanate, etc., a.

The content of in the coating, z. B. the magnetic layer and the below described lower coating (in hereinafter referred to as "lower layer") contained Polyisocyanate compound is preferably 5 to 15 wt .-%, particularly preferably 10 to 40 wt .-%, based on the amount the binder (the sum of the resin components and the hardener).

The total amount of hardener comprising a polyurethane resin and an isocyanate compound is 50% by weight or more, based on the total amount of the binder resin.

If the coating by electron beam irradiation Hardened, can bond with a reactive Double bond, e.g. As urethane acrylate can be used.  

Tg of the magnetic layer according to the invention is preferably 30 to 150 ° C, more preferably 50 to 120 ° C.

The amount of binder is generally 15 to 40 parts by weight, particularly preferably 20 to 30 parts by weight, per 100 parts by weight of the ferromagnetic powder. As described later, is the amount of binder if a lower layer is applied, generally 5 to 35 parts by weight, based on the non-magnetic powder or soft magnetic Powder.

Examples of carbon black for use in the present invention include furnace black for rubbers, thermal black for rubbers, carbon black for coloring, acetylene black, etc. The carbon black for use in the present invention preferably has a specific surface area (S _BET ) of 5 to 500 m ² / g, a DBP absorption of 10 to 400 ml / 100 g, an average particle size of 5 to 300 mμ, a pH from 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 for use in the present invention include BLACKPEARLES 2000, 1300, 1000, 900, 800 and 700 and VULCAN XC-72 (manufactured by Cabot Co.), # 80, # 60, # 55, # 50 and # 35 (manufactured by Asahi Carbon Co.), # 2400B, # 2300, # 900, # 1000, # 30, # 40 and # 10B (manufactured by Mitsubishi Chemical Corp.) and CONDUCTEX SC, RAVENS 150, 50, 40 and 15 ( manufactured by Columbia Carbon Co., Ltd.). The carbon black for use in the present invention may be previously treated with a dispersant, grafted with a resin, or a part of the surface thereof may be graphitized before use. The carbon black may be dispersed in a binder prior to addition to the magnetic coating solution. The carbon black can be used alone or in combination. The carbon black is preferably used in an amount of 0.1 to 30% by weight based on the amount of the ferromagnetic powder. The carbon black can perform various functions such as the prevention of static electricity, the reduction of the friction coefficient, the imparting of light-shielding properties, and the improvement of the film strength. Such functions vary depending on the type of the type of horse to be used. Accordingly, in the present invention, of course, it is possible to select and specify the types of carbon blacks to be added to the magnetic layer and the below-described lower layer, as well as their respective amounts and combinations due to the above-mentioned various properties such as grain size, oil absorption amount, electrical conductivity, and so on PH value. With respect to the carbon black for use in the present invention, e.g. See, for example, the disclosure in "Handbook of Carbon Blacks" (edited by the Carbon Black Association of Japan).

The magnetic layer according to the invention preferably contains an abrasive. As the abrasive agent usable in the present invention, any known materials which are substantially Mohs' hardness of 6 or more may be used alone or in combination. Examples of such abrasives include, for. For example, α-alumina having an α-conversion of 90% or more, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, artificial diamond, silicon nitride, silicon carbide, titanium carbide, titanium oxide, silicon dioxide and boron nitride. Among them, preferred are α-alumina, chromium oxide, α-iron oxide and artificial diamond. Composites composed of these abrasives (those obtained by surface treatment with other abrasives) may also be used. Other compounds or elements as the main component are frequently contained in the abrasives, but the intended effect can be achieved so far as the content of the main component is 90% or more. Abrasives preferably have a particle size of 0.01 to 2 microns. If desired, multiple abrasives each having a different grain size may be combined, or a single abrasive having a broad grain size distribution may be employed to achieve the same effect as a combination. Preferred for use in the present invention are those abrasives having a tap density of 0.3 to 2 g / ml, a water content of 0.1 to 5%, a pH of 2 to 11 and a specific surface area (S _BET ) of 1 to 30 m ² / g.

The shape of the abrasive to be used in the present invention may be any acicular, spherical or cubic shape. Preferably, the abrasive has a shape with partial edges because this results in a high abrasive property. Specific examples of the abrasives for use in the present invention include AKP-20, AKP-30, AKP-50, HIT-50, HIT-60, HIT-70, HIT-80, HIT-80G, HIT-100 (manufactured by Sumitomo Chemical Co., Ltd.), G5, G7 and S-1 (manufactured by Nippon Chemical Industrial Co.), and TF-100 and TF-140 (manufactured by Toda Kogyo Corp.). It is of course possible in the present invention to independently select kinds, amounts and combinations of the abrasives to be added to the below-described lower layer and the magnetic layer according to the purpose of use. The abrasives may be previously dispersed in a binder, and the resulting dispersion may be added to the magnetic coating solution. The amount of the abrasive grains present on the surface and on the edges of the magnetic layer in the magnetic recording medium of the present invention is preferably 5 grains / 100 μm ² or more.

As other additives, in the magnetic layer of the can be used in the present invention those with a sliding effect, an antistatic effect, a dispersing effect and a plasticizer effect become. Examples of other additives include Molybdenum disulfide, tungsten disulfide, graphite, boron nitride, Graphite fluoride, silicone oil, containing polar groups Silicones, fatty acid-modified silicones, fluorine-containing Silicones, fluorine-containing alcohols, fluorine-containing esters, Polyolefins, polyglycols, alkyl phosphates and their Alkali metal salts, alkyl sulfates and their alkali metal salts, Polyphenyl ethers, fluorine-containing alkyl sulfates and their Alkali metal salts, monobasic fatty acids with 10 to 24 Carbon atoms (which contain an unsaturated bond may or may be branched) and their metal salts (eg with Li, Na, K or Cu), mono-, di-, tri-, tetra-, Penta or hexaalcohols having 12 to 22 carbon atoms (the may contain an unsaturated bond or branched may be), alkoxy alcohols having 12 to 22 carbon atoms, Monofatty acid esters, difatty acid esters or triflic acid esters, from a monobasic fatty acid with 10 to 24 Carbon atoms (which contain an unsaturated bond may or may be branched) and a member of mono, Di-, tri-, tetra-, penta- and hexa-alcohols with 2 to 12 Carbon atoms (which contain an unsaturated bond may or may be branched), Fatty acid esters of monoalkyl ethers of alkylene oxide polymers, Fatty acid amides having 8 to 22 carbon atoms and aliphatic amines having 8 to 22 carbon atoms.

Specific examples of such additives include Lauric, myristic, palmitic, stearic, Behenic acid, butyl stearate, oleic acid, linoleic acid, Linolenic acid, elaidic acid, octyl stearate, amyl stearate, Isooctyl stearate, octyl myristate, butoxyethyl stearate,  Anhydrosorbitan monostearate, anhydrosorbitol distearate, Anhydrosorbitan tristearate, oleyl alcohol and lauryl alcohol on. In addition, other additives that used include nonionic surfactants such as alkylene oxides, Glycerols, glycidols or alkylphenol-ethylene oxide adducts; cationic surfactants, such as cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocyclic Compounds, phosphonium compounds or sulfonium Links; anionic surfactants containing an acidic group, such as Carboxylic acid, sulfonic acid or phosphoric acid, or sulfate Contain groups or phosphate groups; and amphoteric Surfactants, such as amino acids, aminosulfonic acids, sulfates or Phosphates of aminoalcohols or alkylbetaines. The Details of these surfactants are in "Handbook of Surfactants" (published by Sangyo Tosho Publishing Co., Japan) described. These lubricants and antistatic agents need not always 100% pure and can contaminate, such as isomers, unreacted substances, by-products, Decomposition products and oxides, in addition to the main component contain. However, the content of such impurities is preferably 30% or less, more preferably 10% or fewer.

The types and amounts of these are described below lower layer and magnetic layer to be used lubricant and surfactants may be suitably selected appropriately. For example, Both the lower layer and the magnetic layer can be separated different fatty acids with one each different melting point, to the exudation to prevent the fatty acids from reaching the surface or they can use different esters with one each different boiling point or different polarity included to prevent the exudation of the ester to the surface prevent. Also in the lower layer and the amount of surfactant to be used in the magnetic layer so  adjusted to improve the coating stability, or the amount of surfactant in the lower layer is increased to to improve the sliding action of their surface. The Examples are by no means limited thereto.

All or part of those in the present invention using additives can be used for magnetic Coating solution in every step of production be added. For example, Can the additives with a ferromagnetic powder mixed before the kneading step be during the kneading step of a ferromagnetic Powder, a binder and a solvent added may be added during the dispersing step can be added after the dispersing step or can be added just before coating. Conveniently, there is a case where the goal reaches can be by adding all or part of the additives simultaneously with or consecutively after application of the Magnetic layer are applied. Purpose accordingly the lubricant on the surface of the magnetic layer after the Calender treatment or after completion of slitting be applied.

Examples of commercial lubricants used in the can be used in the present invention NAA-102, NAA-415, NAA-312, NAA-160, NAA-180, NAA-174, NAA-175, NAA-222, NAA-34, NAA-35, NAA-171, NAA-122, NAA-142, NAA-160, NAA-173K, castor oil-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, Nonion O-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, Monogri MB, Nonion DS-60, Anon BF, Anon LG,  Butyl stearate, butyl laurate and erucic acid (manufactured by Nippon Oils and Fats Co.); Oleic acid (manufactured by Kanto Chemical Co.); FAL-205 and FAL-123 (manufactured by Takemoto Oils and Fats Co.); Enujerubu LO, Enujerubu IPM and Sansosyzer E4030 (manufactured by New Japan Chemical Co., Ltd.); TA-3, KF-96, KF-96L, KF-96H, KF410, KF420, KF965, KF54, KF50, KF56, KF907, KF851, X-22-819, X-22-822, KF905, KF700, KF393, KF-857, KF-860, KF-865, X-22-980, KF-101, KF-102, KF-103, X-22-3710, X-22-3715, KF-910 and KF-3935 (manufactured by Shin-Etsu Chemical Co.); Armide P, Armide C and Armoslip CP (manufactured by Lion Ahmer Co., Ltd.); Duomin TDO (manufactured by Lion Corp.); BA-41G (manufactured by The Nisshin Oil Mills, Ltd.); Profan 2012E, Newpole PE61, Ionet MS-400, Ionet MO-200, Ionet DL-200, Ionet DS-300, Ionet DS-1000 and Ionet DO-200 (manufactured by Sanyo Chemical Industries Ltd.).

Those in the magnetic layer or other layers at the time the coating to be used organic solvent can be used in any proportions. examples for Suitable organic solvents include ketones, such as Acetone, methyl ethyl ketone, methyl isobutyl ketone, Diisobutyl ketone, cyclohexanone, isophorone, tetrahydrofuran; Alcohols, such as methanol, ethanol, propanol, butanol, Isobutyl alcohol, isopropyl alcohol and methylcyclohexanol; Esters, such as methyl acetate, butyl acetate, isobutyl acetate, Isopropyl acetate, ethyl acetate and glycol acetate; glycol ethers, such as glycol dimethyl ether, glycol monoethyl ether and dioxane; aromatic hydrocarbons, such as benzene, toluene, xylene, Cresol and chlorobenzene; chlorinated hydrocarbons, such as Methylene chloride, ethylene chloride, carbon tetrachloride, Chloroform, ethylene chlorohydrin and dichlorobenzene; N, N- Dimethylformamide, dimethylacetamide and hexane. The organic solvents for use in the present Invention need not necessarily be 100% pure  and may contain impurities in addition to the main component such as isomers, unreacted substances, By-products, decomposition products, oxides and water. however the content of such impurities is preferably 30% or less, more preferably 10% or less. The Types of in the magnetic layer and the lower layer too The organic solvents used are preferably same. Their contents can be varied. For example, becomes a Solvent with a high surface tension (eg. Cyclohexanone or dioxane) in the lower layer, to improve the coating stability. It is special essential that the arithmetic mean of the Surface tension of the solvent composition of Magnetic layer is higher than that of the lower layer. to Improvement of the dispersibility is the polarity preferably high to a certain extent. It is preferred that a solvent having a relative permittivity of 15 to 20 in an amount of 50% by weight or more of Solvent composition is included. The Solubility parameter is preferably 8 to 11.

The shape of the particle-containing magnetic according to the invention Recording medium is essentially arbitrary, z. B. a ribbon, a disc, a train or a ticket.

The layer structure of the particle-containing invention magnetic recording medium can be freely selectable as long as the structure is basically a carrier with a magnetic layer applied thereto. For example, includes the Structure a carrier with only a magnetic layer on it, or, as an example, a structure may be given a magnetic layer and a carrier with one in between attached lower layer comprises. Specifically, as Examples of a structure which is a single magnetic layer comprises a multilayer structure comprising a plurality of  Magnetic layers comprises, and a multi-layer structure, the a magnetic layer and a non-recording layer, be specified. Here magnetic layer means a layer which contains a ferromagnetic powder and through Magnetism can record / play, and Non-recording layer means substantially no Ferromagnetic powder containing layer, d. H. a non-magnetic layer or a soft magnetic layer, usually a non-magnetic powder or a soft magnetic powder included.

The thickness of each layer in the layer structure is z. B. as follows.

• (1) In the case of a single magnetic layer: 0.2 to 5 μm, preferably 0.5 to 3 microns.
• (2) In the case of a multi-layered structure wherein the upper layer applied to the lower layer is a magnetic layer.
  • (a) When the upper layer and the lower layer are magnetic layers:
    Upper layer: generally 0.2 to 2 μm, preferably 0.2 to 1.5 μm.
    Lower layer: 0.8 to 3 μm.
  • (b) When the upper layer is a magnetic layer and the lower layer is a non-magnetic layer:
    Upper layer: generally 0.05 to 1 μm,
    preferably 0.05 to 0.5 microns and
    more preferably 0.1 to 0.3 microns.
    Lower layer: 0.8 to 3 μm.
  • (c) When the upper layer is a magnetic layer and the lower layer is a soft magnetic layer:
    Upper layer: generally 0.05 to 1 μm,
    preferably 0.1 to 0.5 microns and
    more preferably 0.1 to 0.3 microns.
    Lower layer: 0.8 to 3 μm.

In the present invention, a band-like, particle-containing magnetic recording medium having a Layer density of 3.0 to 8.8 microns preferred.

When the particle-containing magnetic Recording medium comprises a multi-layer structure are the polyurethane resins described above preferably in least the uppermost layer, more preferably in each Layer included.

Examples of ferromagnetic metal powders which are described in the can be used in the present invention include Fe, Ni, Fe-Co, Fe-Ni, Co-Ni, Co-Ni-Fe, etc. as a single substance or alloy powder thereof. examples for Alloy powders include those that follow Contain elements in the range of 20% by weight or less, based on the total amount of the metal component: aluminum, Silicon, sulfur, scandium, titanium, vanadium, chromium, manganese, Copper, zinc, yttrium, molybdenum, rhodium, palladium, gold, Tin, antimony, boron, barium, tantalum, tungsten, rhenium, silver, Lead, phosphorus, lanthanum, cerium, praseodymium, neodymium, tellurium or Bismuth. Ferromagnetic metal powder can be a small Amount of water, hydroxide or an oxide. Procedure for  Production of ferromagnetic powders are already well known, and ferromagnetic powders for use in The present invention may also be used in accordance with well-known methods are produced.

In the present invention are preferred ferromagnetic metal powders containing 10 to 40 at% Co, 2 to 20 atom% Al and 1 to 15 atom% Y, in each case based on Fe, contain.

Ferromagnetic metal powders have a crystallite size of generally 80 to 200 Å, preferably 90 to 180 Å and more preferably 120 to 170 Å. The length of the long axis is generally 0.04 to 0.2 microns, preferably 0.05 to 0.13 μm and more preferably 0.06 to 0.1 μm. Ferromagnetic metal powders have a pH of preferably 7 or more. Ferromagnetic metal powders have one Coercive force (Hc) of generally 1,500 to 3,000 Oe, preferably from 1 905 to 2 750 Oe and even more preferably from 2,000 to 2,300 Oe.

The shape of the ferromagnetic metal powder is not specially limited, but it is usually one acicular shape, a granular shape, a cube shape, a Spindle shape or a blackboard shape. The ferromagnetic Metal powder with a needle-like shape or a Spindle shape is particularly preferably used.

Ferromagnetic metal fine powders can be a small amount of a hydroxide or an oxide. ferromagnetic fine metal powders can be made by well-known methods be prepared as a method involving the reduction a composite salt of an organic acid (mainly an oxalate) with a reducing gas, e.g. For example, hydrogen, comprises; a process involving the reduction of iron oxide with  a reduced gas, e.g. As hydrogen, to Fe or to obtain Fe-Co particles; a procedure that the Pyrolysis of a metal carbonyl compound; on Process which involves the addition of a reducing agent, e.g. B. Sodium borohydride, a hypophosphite or hydrazine, to a aqueous solution of a ferromagnetic metal to to carry out the reduction; and a procedure that the Evaporation of a metal in an inert gas of low Pressure to obtain a fine powder. The way obtained ferromagnetic alloy powder, one of various well-known gradual Oxidation treatments can be carried out in the be used in the present invention, for. A method, the immersion of powders in an organic Solvent and then drying; on Process that involves the immersion of powders in an organic Solvent and subsequent introduction of a oxygen-containing gas and drying to oxide films to form on their surfaces; and a procedure that the Formation of oxide films on the surfaces of the powder by Regulation of the partial pressure of an oxygen gas and a Inert gases without using an organic solvent includes.

Ferromagnetic powders are preferred Needle-shaped ratio of 4 to 18, particularly preferred from 5 to 12, and a water content of 0.01 to 2%. The Water content of the ferromagnetic powders is preferred optimized by selecting the types of binders.

The pH of the ferromagnetic powders is preferred by the Optimized combination with the binder to use. The pH range is 4 to 12, preferably 7 to 10. Soluble inorganic ions (eg, Na, Ca, Fe, Ni, Sr, etc.) sometimes contained in ferromagnetic powders, but the  Properties of ferromagnetic powders are not especially affected when the content is 200 ppm or less is.

Ferromagnetic powders for use in the present Invention preferably have small void volumes, and their Value is 20% by volume or less, more preferably 5 Vol .-% or less.

The above-described resin components, hardener and ferromagnetic powders are kneaded and usually in the preparation of a magnetic coating solution used solvents dispersed, for. B. with Methyl ethyl ketone, dioxane, cyclohexanone, ethyl acetate, etc., to to form a magnetic coating solution. The kneading and dispersing may be done according to conventional methods be performed.

A magnetic coating solution may contain, in addition to the above components, an abrasive, e.g. As α-Al ₂ O ₃ , Cr ₂ O ₃ , etc., an antistatic agent, for. As carbon black, a lubricant, for. For example, fatty acid, fatty acid esters, silicone oil, etc., generally used additives such as a dispersant, or a filler.

The lower non-magnetic layer or lower Magnetic layer, in the event that the present invention Using a multilayer structure will be described below. The lower layer of the present invention contains preferably inorganic powder. Inorganic powders can either a magnetic powder or a non-magnetic one Be powder.

Inorganic powders present in the lower layer of present invention are preferably non-magnetic  Powder. They can be selected from the the following inorganic compounds, such as metal oxide, Metal carbonate, metal sulfate, metal nitride, metal carbide, Metal sulfide, etc. Examples of inorganic compounds are selected from the following compounds, and they may be used alone or in combination, e.g. For example, α-alumina with an α-co-transformation of 90% or more, β-alumina, γ-alumina, θ-alumina, Silicon carbide, chromium oxide, cerium oxide, α-iron oxide, goethite, Corundum, silicon nitride, titanium carbide, titanium oxide, Silica, tin dioxide, magnesium oxide, tungsten oxide, Zirconia, boron nitride, zinc oxide, calcium carbonate, Calcium sulfate, barium sulfate and molybdenum disulfide. Of these Compounds are particularly preferred titanium dioxide, zinc oxide, Iron oxide and barium sulfate, and even more preferred Titanium dioxide and α-iron oxide.

Such non-magnetic powders preferably have a particle size of 3 μm or less. If desired, a plurality of non-magnetic powders each having a different particle size may be combined, or a single non-magnetic powder having a broad particle size distribution may be employed to achieve the same effect as such a combination. A particularly preferred particle size of the non-magnetic powders is 0.01 to 0.2 μm. The non-magnetic powders for use in the present invention have a tap density of 0.05 to 2 g / ml, preferably 0.2 to 1.5 g / ml; a water content of 0.1 to 5 wt .-%, preferably from 0.2 to 3 wt .-% and particularly preferably from 0.3 to 1.5 wt .-%; a pH of 2 to 11, more preferably between 7 and 10; a specific surface area (S _BET ) of 1 to 100 m ² / g, preferably of 5 to 70 m ² / g and particularly preferably of 10 to 65 m ² / g; a crystallite size of 0.004 to 1 μm, particularly preferably 0.04 to 0.1 μm; an oil absorption amount using dibutyl phthalate (DBP) of 5 to 100 ml / 100 g, preferably 10 to 80 ml / 100 g, and more preferably 20 to 60 ml / 100 g; and a specific gravity of 1 to 12, preferably 3 to 6. The shape of the non-magnetic powder may be a needle-shaped, spherical, polyhedral or tabular form.

The ignition loss of the non-magnetic powders is preferably 20% by weight or less, substantially zero is most preferable. The above-described inorganic powders for use in the present invention preferably have a Mohs hardness of 4 to 12. The surface roughness factor of these powders is preferably 0.8 to 1.5, more preferably 0.9 to 1.2. The SA (stearic acid) absorption amount of these inorganic powders is preferably 1 to 20 μmol / m ² , more preferably 2 to 15 μmol / m ² . The heat of wetting of the non-magnetic powders contained in the lower layer in water of 25 ° C. is preferably 200 to 600 erg / cm ² . Solvents having a heat of wetting within this range can be used in the present invention. The appropriate number of water molecules on the surface at 100 to 400 ° C is 1 to 10 molecules / 100 Å ² . The pH of the isoelectric point in water is preferably 3 to 9.

At least part of the surface of these non-magnetic powders is preferably covered with at least one of Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ or ZnO. Preferable in terms of dispersibility are Al ₂ O _3, SiO _2, TiO ₂ and ZrO _2, and particularly preferred are Al ₂ O _3, SiO ₂ and ZrO _2. They can be used singly or in combination. A surface treatment method may be carried out by co-precipitation, alternatively, the surface treatment of the particles to be covered may be performed first with alumina, and then the alumina-covered surface may be coated with silica or vice versa according to the purpose. The surface-covering layer may be a porous layer, if necessary, but a homogeneous and dense surface is generally preferred.

Specific examples of non-magnetic powders for Use in the lower layer of the invention Nanotite (manufactured by Showa Denko Co., Ltd.), HIT-110 and ZA-G1 (manufactured by Sumitomo Chemical Co., Ltd.), DPN-250, DPN-250BX, DPN-245, DPN-270BX, DPB-550BX and DPN-550RX (manufactured by Toda Kogyo Corp.), titanium oxide TTO-51B, TTO-55A, TTO-55B, TTO-55C, TTO-55S, TTO-55D, SN-100, MJ-7, α-iron oxide E-270, E271 and E300 (manufactured by Ishihara Sangyo Kaisha Ltd.), STT-4D, STT-30D, STT-30 and STT-65C (manufactured by Titan Kogyo Co., Ltd.), MT-100S, MT-100T, MT-150W, MT-500B, MT-600B, MT-100F and MT-500HD (manufactured Teika Co., Ltd.), FINEX-25, BF-1, BF-10, BF-20 and ST-M (manufactured by Sakai Chemical Industry Co., Ltd.), DEFIC-Y and DEFIC-R (manufactured by Dowa Mining Co., Ltd.), AS2BM and TiO 2 P 25 (manufactured by Nippon Aerosil Co., Ltd.), 100A and 500A (manufactured by Ube Industries Co., Ltd.) and Y-LOP and its annealed product (manufactured by Titan Kogyo Co., Ltd.).

Especially preferred non-magnetic powders are titanium dioxide and α-iron oxide. The production of α-iron oxide (hematite) is carried out as follows. α-Fe ₂ O ₃ powders are obtained from acicular goethite particles as precursor particles. Goethite particles are obtained by one of the following ordinary methods: (1) a method in which an aqueous alkali hydroxide solution is added to an aqueous ferrous salt solution in an equivalent or larger amount to thereby obtain a suspension containing Ferrous hydroxide colloid, and in which an oxygen-containing gas is then introduced into the obtained suspension at pH 11 or more and at 80 ° C or less to form acicular goethite particles by the oxidation reaction, (2) a method of wherein an aqueous ferrous salt solution is reacted with an aqueous alkali carbonate solution to thereby obtain a FeCO ₃ -containing suspension, and then an oxygen-containing gas is introduced into the obtained suspension to form spindle-shaped goethite particles by the oxidation reaction (3) a method wherein an aqueous alkali hydroxide solution or an aqueous alkali carbonate solution is added to a w to give an aqueous ferrous salt solution in an equivalent or less amount, thereby obtaining an aqueous ferrous salt solution containing an iron (II) hydroxide colloid, and then adding an oxygen-containing gas to the resulting aqueous iron (II ) salt solution to obtain acicular goethite seed particles by the oxidation reaction, wherein thereafter an aqueous alkali carbonate solution is added to the aqueous ferrous salt solution containing the needle-shaped goethite seed particles in an equivalent or higher amount based on Fe ²⁺ in the aqueous ferrous salt solution is added, and then again an oxygen-containing gas is introduced into the aqueous ferrous salt solution to grow the acicular goethite seed particles, and (4) a process wherein an aqueous alkali hydroxide solution or an aqueous alkali carbonate solution is equivalent to an aqueous ferrous salt solution or an amount thereof is added to obtain an aqueous ferrous salt solution containing an iron (II) hydroxide colloid, and then an oxygen-containing gas is introduced into the resulting aqueous ferrous salt solution to form a needle-shaped one To form goethite seed particles by the oxidation reaction, and thereafter growing the acicular goethite seed particles in an acidic or neutral environment.

Furthermore, different types of elements, such as Ni, Zn, P or Si, which generally become reaction solution during the goethite particle-forming reaction for improving the Properties of the particle powder are added be included.

Needle-shaped α-Fe ₂ O ₃ particles can be obtained by dehydrating acicular goethite particles which are the precursor particles in the range of 200 to 500 ° C, and further, if necessary, annealing the particles by heat treatment at 350 to 800 ° C ,

A sintered inhibitor such as P, Si, B, Zr or Sb can be applied to the Surface of the dehydrated or too glowing acicular goethite particles are applied.

The reason why the annealing is carried out by heat treatment at 350 to 800 ° C is that it is preferable to fill in the voids which have appeared on the surface of the acicular α-Fe ₂ O ₃ particles obtained by the dehydration Melt the outer surface of the particles to fill to obtain smooth surfaces.

The α-Fe ₂ O ₃ particle powder for use in the present invention can be obtained by dispersing acicular α-Fe ₂ O ₃ particles obtained by dehydration or annealing in an aqueous solution to prepare a suspension, adding Al compounds, and adjusting the pH, covering the surface of the acicular α-Fe ₂ O ₃ particles with the above-described additives, filtering, washing, drying, pulverizing and, if necessary, performing other treatments such as deaeration, densification and the like. Aluminum salt such as aluminum acetate, aluminum sulfate, aluminum chloride and aluminum nitride, and alkali aluminate such as sodium aluminate may be used as the aluminum compound. In this case, the addition amount of the Al compounds is 0.01 to 50% by weight as Al and based on the α-Fe ₂ O ₃ powder. When the content is less than 0.01% by weight, the dispersion in the binder resin is insufficient, and if it exceeds 50% by weight, the Al compounds suspended around the surfaces of the particles adversely interact with each other. The inorganic non-magnetic powder for use in the lower layer of the present invention may be covered with one or two or more of P, Ti, Mn, Ni, Zn, Zr, Sn and Sb as well as a Si compound and Al compounds become. The content of these compounds used together with the Al compounds is 0.01 to 50% by weight, based on the α-Fe ₂ O ₃ particle powder. When the content is less than 0.01% by weight, the improvement in dispersibility by the addition can hardly be obtained, and when it exceeds 50% by weight, the Al compounds which are suspended around the surfaces of the particles interact are disadvantageous with each other.

The production process of titanium dioxide is as follows. The production process of titanium dioxide mainly includes a sulfuric acid method and a chlorine method. A sulfuric acid process involves the leaching of crude ores from ilmenite and the extraction of Ti and Fe as sulfate. Ferrous sulfate is removed by crystallization separation, the resulting titanyl sulfate is purified by filtration, hydrous titanium oxide is precipitated by thermal hydrolysis, the precipitated product is filtered and washed, impurities are removed by washing, and then a particle size adjusting agent is added thereto at 80 to 1 Annealed 000 ° C, whereby crude titanium oxide is obtained. The rutile type and the anatase type are separated by the type of nucleating agent added in the hydrolysis. This crude titanium oxide is pulverized, sieved and surface-treated. In the chlorine process, natural rutile and synthetic rutile are used as raw ores. The ores are chlorinated in a high temperature reduction state, Ti becomes TiCl ₄ and Fe becomes FeCl ₂ , and the iron oxide solidified by cooling is separated from the liquid TiCl ₄ . The crude TiCl _{4 obtained} is purified by fractionation, then a nucleating agent is added and reacted immediately with oxygen, whereby crude titanium oxide is obtained. The finishing process for imparting the pigment property to the crude titanium oxide formed in the oxidation decomposition process is the same as in the sulfuric acid process.

After the above titanium oxide material is dry-ground, water and a dispersant are added, the grains are wet-ground, and rough grains are size-processed by means of a centrifugal separator. Subsequently, a fine grain slurry is put into a surface treatment bath, and the surface covering with a metal hydroxide is carried out here. First, a predetermined amount of an aqueous solution of salts such as Al, Si, Ti, Zr, Sb, Sn and Zn is added to the tank, acid or alkali is added to neutralize the solution, and the surfaces of the titanium oxide particles become covered with the produced hydrous oxide. The by-produced water-soluble salts are removed by decantation, filtration and washing, the pH of the slurry is finally adjusted, and the slurry is filtered and washed with pure water. The washed cake is dried using a spray drier or belt dryer. The dried product is finally ground with a jet mill, whereby the product is obtained. Besides the water system, it is also possible to perform the surface treatment by introducing AlCl ₃ and SiCl ₄ vapor into the titanium oxide powder and then passing water vapor to perform the surface treatment with Al and Si. Regarding the method of preparation of pigments thereafter, reference can be made to GD Parfitt and KSW Sing, Characterization of Powder Surfaces, Academic Press (1976).

By incorporating carbon black into the lower non-magnetic Layer can have a desired microhardness after Vickers in addition to the well-known effects of Reduction of Rs and the transmittance can be obtained.

The Vickers microhardness of the lower non-magnetic layer is generally 25 to 60 kg / mm ² , preferably 30 to 50 kg / mm ² , for head touch control. The Vickers microhardness measurement is carried out by means of a thin film hardness meter HMA-400 manufactured by NEC Co., Ltd. using a diamond-made three-sided pyramid needle having an edge angle of 80 ° and a tip radius of 0.1 μm attached to the top of the stamp. The transmittance is standardized so that the absorption of infrared light of wavelength 900 nm or so is generally 3% or less, e.g. For example, absorption for VHS should be 0.8% or less. Furnace black for rubbers, thermal black for rubbers, carbon black for coloring, acetylene black, etc. can be used therefor.

The carbon black for use in the nonmagnetic layer of the present invention has a specific surface area (S _BET ) of 100 to 500 m ² / g, preferably 150 to 400 m ² / g, a DBP absorption of 20 to 400 ml / 100 g, preferably from 30 to 200 ml / 100 g, an average particle size from 5 to 80 mμ, preferably from 10 to 50 mμ and particularly preferably from 10 to 40 mμ, a pH from 2 to 10, a water content from 0.1 to 10% and a tap density of 0.1 to 1 g / ml. Specific examples of the carbon blacks for use in the present invention include BLACKPEARLES 2000, 1300, 1000, 900, 800, 880 and 700 and VULCAN XC-72 (manufactured by Cabot Co.), # 3050B, # 3150B, # 3250B, # 3750B, # 3950B, # 950, # 650B, # 970B and # 850B, MA-600 (manufactured by Mitsubishi Chemical Corp.), CONDUCTEX SC, RAVENS 8800, 8000, 7000, 5750, 5250, 3500, 2100, 2000, 1800, 1500 , 1255 and 1250 (manufactured by Columbia Carbon Co., Ltd.) and Ketjen Black BC (manufactured by Akzo Co., Ltd.). The carbon black for use in the present invention may be previously surface-treated with a dispersant, grafted with a resin, or a part of its surface may be graphitized before use. The carbon black may be dispersed in a binder prior to addition to the magnetic coating solution. Carbon black can not exceed 50% by weight based on the above inorganic powders and does not exceed 40% by weight based on the total weight of the nonmagnetic layer within a range. Carbon black can be used singly or in combination.

With regard to the carbon blacks for use in the present invention Invention may, for. For example, refer to the disclosure in Handbook of Carbon Blacks "(edited by Carbon Black Association of Japan).

Organic powders may be appropriate in the bottom Layer can be used. Examples of such organic Powders include an acrylic acid resin powder Benzoguanamine resin powder, a melamine resin powder and a Phthalocyanine pigment. In addition, a Polyolefin resin powder, a polyester resin powder, a  Polyamide resin powder, a polyimide resin powder and a Polyethylenfluoridharzpulver also be used. their Manufacturing methods are disclosed in JP-A-62-18564 and JP-A-60- 255827 (the term "JP-A" as used herein means "Unexamined Published Japanese Patent Application").

An underlayer is in a common magnetic Recording medium for the purpose of improving the Adhesive strength between the carrier and the magnetic layer or the lower non-magnetic layer attached. In one Solvent soluble polyesters are used for this purpose used, and the thickness is generally 0.5 microns or fewer.

Binders, lubricants, dispersants, additives, Solvent, dispersing method, etc., which are described in Magnetic layer can be used in the lower layer be used. In particular, in terms of quantities and types of binders, additives and quantities and Types of the dispersants may include well-known methods of Prior art with respect to the magnetic layer on the lower layer are applied.

Thermoplastic resins with a glass transition temperature of -100 to 150 ° C, a number average molecular weight of 1 000 to 200 000, preferably from 10 000 to 100 000, one Degree of polymerization of about 50 to 1,000, can be found in the can be used in the present invention. Examples of this include polymers or copolymers containing the following Contain compounds as a structural unit, a, z. B. Vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, Acrylic acid, acrylate, vinylidene chloride, acrylonitrile, Methacrylic acid, methacrylate, styrene, butadiene, ethylene, Vinyl butyral, vinyl acetal, vinyl ethers, etc., and Polyurethane resins and various rubber resins.  

Examples of thermosetting resins and reactive resins used in the usable in the present invention Phenolic resins, epoxy resins, curable type polyurethane resins, Urea resins, melamine resins, alkyd resins, acrylic reactive resins, Formaldehyde resins, silicone resins, epoxy-polyamide resins, Mixtures of polyester resin and isocyanate prepolymer, Mixtures of polyester polyol and polyisocyanate and Mixtures of polyurethane and polyisocyanate. The details for these resins are in "Plastic Handbook", Asakura Shoten, described. It is also possible to use known resins from Electron beam curable type in the lower coating or an upper magnetic layer.

These resins can be used singly or in combination. Examples of preferred combinations include at least one member of vinyl chloride resins, vinyl chloride-vinyl acetate resins, vinyl chloride-vinyl acetate-vinyl alcohol resins and vinyl chloride-vinyl acetate-maleic anhydride copolymers with polyurethane resins, or combinations of these resins with polyisocyanate. As polyurethane resins, those having well-known structures can be used, e.g. Polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, polycaprolactone polyurethane, polyolefin polyurethane, etc. Those polyurethane resins having a cyclic structure and an ether group are particularly preferable. Preferably, at least one or more polar groups from the following groups are incorporated into the above binder by copolymerization or addition reaction for the purpose of further improving dispersibility and durability, e.g. B. -COOM, -SO ₃ M, -OSO ₃ M, -P = O (OM) ₂ , -OP = O (OM) ₂ (wherein M represents a hydrogen atom or an alkali metal salt group), -OH, -NR ² , -N⁺R ³ (R represents a hydrocarbon group), an epoxy group, -SH, -CN, sulfobetaine, phosphobetaine or carboxybetaine. The content of the polar group is about 10 ^-1 to 10 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6 mol / g.

Specific examples of binders for use in the VAGH, VYHH, VMCH, VAGF, VAGD, VROH, VYES, VYNC, VMCC, XYHL, YXSG, PKHH, PKHJ, PKHC and PKFE (manufactured by Union Carbide Co., Ltd.), MPR-TA, MPR-TA5, MPR-TAL, MPR-TSN, MPR-TMF, MPR-TS, MPR-TM and MPR-TAO (manufactured by Nisshin Chemical Industry Co., Ltd.), 1000W, DX80, DX81, DX82, DX83 and 100FD (manufactured from Electro Chemical Industry Co., Ltd.), MR-104, MR-105, MR-110, MR-100 and 400X-110A (manufactured by Nippon Zeon Co., Ltd.), Nippollan N2301, N2302 and N2304 (manufactured by Nippon Polyurethane Co., Ltd., Japan), Pandex T-5105, T-R3080, T-5201, Burnock D-400, D-210-80, Cris of 6109 and 7209 (manufactured by Dainippon Chemicals and Ink Co., Ltd.) Vylon UR8200, UR8300, RV530 and RV280 (manufactured by Toyobo Co., Ltd., Japan), Daipheramine 4020, 5020, 5100, 5300, 9020, 9022 and 7020 (manufactured by Dainichi Seika K.K.), MX5004 (manufactured by Mitsubishi Chemical Corp.), Sunprene SP-150 and TIM-3003 (manufactured by Sanyo Chemical Industries Co. Ltd.), Salan F310 and F210 (manufactured by Asahi Chemical Industry Co., Ltd.), etc. Of these, MR-104, MR-110, UR-8200, UR-8300, UR-8700 and reaction products, the diols and containing organic diisocyanate as main components, preferred, and polyurethane having a cyclic structure and with an ether group is preferred.

The above is an explanation for the case when the lower one Layer is a non-magnetic layer. Specific Examples of soft magnetic powder in the lower Layer, include granular Fe, Ni, granular magnetite, Fe-Si, Fe-Al, Fe-Ni, Fe-Co, Fe-Co-Ni, Fe-Al-Co (Sendust) alloy, Mn-Zn ferrite, Ni-Zn ferrite,  Mg-Zn ferrite, Mg-Mn ferrite and those in Akinobu Chikazumi, Physics of Ferromagnetic Substances (last volume), Magnetic Properties and Applications, pages 368-376, Shoka-bo, Japan (1984).

These non-magnetic and soft magnetic powder are preferably provided with at least one compound selected from Al ₂ O ₃₁ SiO _2, TiO _2, ZrO ₂₁ SnO _2, Sb ₂ O ₃ and ZnO coated. Preferable in terms of dispersibility are Al ₂ O _3, SiO _2, TiO ₂ and ZrO _2, and particularly preferred are Al ₂ O _3, SiO ₂ and ZrO _2. They can be used singly or in combination. A surface treatment method may be carried out by co-precipitation, alternatively, the surface treatment of the particles to be covered may be performed first with alumina, and then the alumina-covered surface may be coated with silica or vice versa according to the purpose. The surface cover layer may be a porous layer, if necessary, but a homogeneous and dense surface is generally preferred.

The lower layer according to the invention may also contain magnetic powders as organic powder. Magnetic powders that can be used include γ-Fe ₂ O ₃ , Co-modified γ-Fe ₂ O ₃ , alloys containing α-Fe as the main component, and CrO ₂ . The magnetic powders of the lower layer may be suitably selected, and the effect of the present invention does not depend on the kind of the magnetic powders. However, the properties of the upper and lower layers are varied according to the respective purposes. For example, it is preferable to set Hc of the lower magnetic layer lower than that of the upper magnetic layer to improve the recording characteristics at long wavelengths, and it is effective to make Br of the lower magnetic layer higher than that of the upper magnetic layer. Besides, various advantages can be obtained by adapting conventional multilayer structures.

A carrier according to the invention is preferably a non-magnetic plastic carrier and has a Vickers microhardness of 75 kg / mm ² or more, and well-known films can be used, e.g. Biaxially oriented polyethylene naphthalate, polyamide, polyimide, polyamideimide, aromatic polyimide and polybenzoxazole. In particular, a non-magnetic carrier using aromatic polyamide or polyethylene naphthalate available from Toray Industries Inc. as "Aramides" and from Asahi Chemical Industry Co., Ltd. as "Aramica" is preferable.

The non-magnetic support can be previously with a Corona discharge treatment, plasma treatment, Bonding treatment, heat treatment or Dust removal treatment are treated. The non-magnetic Carrier for use in the present Invention has an arithmetic surface center roughness on the side of the non-magnetic support on which the Magnetic layer is applied, from 0.1 nm to 10 nm, preferably from 0.2 nm to 6 nm and more preferably from 0.5 nm to 4 nm. Further, it is desirable that the non-magnetic Carrier for use in the present Invention not just a little arithmetic Surface center roughness has, but is also free of rough highlights of 1 micron or more on the Surface. The surface roughness of the carrier can regardless of the size and amount of the to the vehicle be regulated to be added to the filler. examples for Fill fillers that can be used for this purpose Oxides or carbonates of Al, Ca, Si or Ti as well organic fine powder of organic substances, such as  Acrylate materials and melamine materials, and they can be either kristalloaid or amorphous. The Surface roughness on the side on which the backing layer is applied, is preferably rougher than the side on the magnetic layer is applied to it with the To make running stability compatible. The arithmetic Surface center roughness of the backing layer coated side is preferably 1 nm or more, more preferably 4 nm or more. The surface roughness the coated with the magnetic layer side and with the Backsize coated side can be made using a Double support can be varied, or it can through Application of a coating can be varied.

The non-magnetic support for use in the present invention preferably has an F-5 value of 10 to 50 kg / mm ² in the tape running direction and an F-5 value of 10 to 30 kg / mm ² in the tape transverse direction. In general, the F-5 value in the machine direction of the belt is higher than that in the transverse direction thereof. However, this ratio does not apply to the case where the transverse strength of the tape should be particularly increased. The thermal shrinkage at 100 ° C for 30 minutes of the non-magnetic support for use in the present invention is preferably 3% or less, and more preferably 1.5% or less, both in the tape running direction and in the width direction, and further the thermal shrinkage at 80 ° C for 30 minutes is preferably 1% or less, more preferably 0.5% or less in both directions. The tensile strength of the support is preferably 5 to 100 kg / mm ² in both directions, and its elastic modulus is preferably 100 to 2,000 kg / mm ² in both directions. Further, the transmittance at 900 nm is preferably 30% or less, more preferably 3% or less.

A back coating (a backside layer) comprising inorganic particles and a binder, can be applied to the back surface of the carrier that with the Magnetic layer coated surface side opposite, be applied. A backcoating is one on the Side of the carrier applied layer on which no magnetic coating is applied. The backing layer will applied by applying a coating solution for a backside layer comprising granular components, e.g. B. an abrasive and an antistatic agent, and an in an organic solvent dissolved binder. When Granular components can be different inorganic Pigments and carbon black are used, and single or Mixtures of different resins, such as nitrocellulose, Phenoxy resins, vinyl chloride resins, polyurethane resins are known as Binder used.

When a particle-containing magnetic recording medium of the present invention is a belt-like medium preferably applied a backsheet layer.

In addition, an adhesive layer on the Coating surfaces of the magnetic coating solution and a backcoat-forming coating solution the non-magnetic support can be applied.

The process for producing the magnetic layer Coating compositions for use in magnetic recording medium according to the invention at least one kneading step, a dispersing step and optionally mixing steps before and / or after the kneading and Dispergierschritten be performed. Each of these Steps can consist of two or more individual stages be composed. Materials, such as a ferromagnetic Powder, a binder, carbon black, an abrasive, a  Antistatic agent, a lubricant, a solvent and the like for use in the present invention can be used in be added to each step at any time. each Material can be spread over two or more steps be added. For example, can be distributed in one polyurethane Kneading step, a dispersing step or a mixing step for adjusting the viscosity after dispersion be added. To achieve the objective of the present The invention can be partially covered by the above steps conventional techniques are performed. However, to first time a high remanent flux density (Br) of the particulate magnetic recording medium of can be obtained using this invention strong kneading machines, such as a continuous kneader or a pressure kneader. If a continuous kneader or a Compressor is used, all or part of the ferromagnetic powder and binder (preferably 30% or more the total binder) in the range of 15 parts to 500 parts per 100 parts of the ferromagnetic powder is kneaded. Details of this kneading are disclosed in JP-A-1-166338 and US-A-5 300,244. In the production of a Magnetic layer solution, a non-magnetic layer solution and of Abrasives are preferably dispersing media used a high specific gravity, and Zirconia pearls are very suitable for this purpose.

Examples of apparatus and methods for applying a multi-layer structure as in the present invention are described below.

• 1. First, the bottom coating is through Gravure coating, roll coating, Blade coating or extrusion coating, the usually when applying a magnetic Coating solution can be used, applied, and the  upper magnetic layer is applied, while the lower Coating is still wet by means of the method described in US-A-4,480,583, US-A-4 681,062 and US-A-5,302,206 Carrier pressure type extrusion coating apparatus.
• 2. The upper layer and the lower layer become applied almost simultaneously using the method described in US-A-4 854,262, US-A-5,072,688 and US-A-5,302,206 Brush, with two slots for feeding the Coating solution is equipped.
• 3. The upper layer and the lower layer will be almost simultaneously using the method disclosed in JP-A-2-174965 coated extrusion coating apparatus coated with a counter-pressure roller is equipped.

To prevent the reduction of electromagnetic Characteristics of the particulate magnetic Recording medium due to agglomeration of Magnetic powder, it is preferred with a shearing force on the Coating solution in the coating head with those described in US Pat. No. 4,828,779 and JP-A-1-236968. Regarding the viscosity of the coating solution should the range of the numerical disclosed in US-A-4,994,306 Values are enough.

The magnetic layer of the particle-containing invention magnetic recording medium must have a strong Orientation be subjected. It is preferable to one Magnetic coil of 1,000 G or more, preferably 3,000 G or more, and a cobalt magnet with the same polarity and to arrange opposite position, and it is preferable that the orientation by magnetic fields of 2 000 G or more, preferably 4,000 G or more and more preferably 6,000 G or more is performed. It is too  preferably, a suitable drying step before Orientation provided so that the orientation of the Drying is the highest. It is known that the tendency of the easy axis of magnetization in a vertical direction for The high-density records are effective, regardless of whether acicular or tabular, and a combination thereof also effective.

Before the simultaneous multi-layer application of a non-magnetic Layer and a magnetic layer are the Applying an adhesive layer comprising a polymer as Main component, and a corona discharge treatment and Irradiation with UV and EB preferred for amplification of Bonding strength combined.

The use of heat-resistant plastic rollers, such as Epoxy, polyimide, polyamide and polyimidamide, is effective for the calender treatment. Metal rollers are also for the Treatment suitable. The treatment temperature is preferably 70 to 120 ° C, particularly preferably 80 to 100 ° C. The Web pressure is preferably 200 to 500 kg / cm, especially preferably 300 to 400 kg / cm or more.

The surface of the magnetic layer and its opposite surface of the particulate magnetic recording medium of the present invention have a coefficient of friction against SUS420J of preferably 0.1 to 0.5, more preferably 0.2 to 0.3. The inherent surface resistivity Rs is preferably 10 ⁴ to 10 ¹² Ω / sq (Ω / area), the elastic modulus at 0.5% elongation of the magnetic layer is preferably 100 to 2,000 kg / mm ^{2 in} both the running direction and the transverse direction the tensile strength is preferably 1 to 30 kg / cm ² , the modulus of elasticity of the particle-containing magnetic recording medium is preferably 100 to 1,500 kg / mm ² , both in the machine direction and in the transverse direction, the permanent elongation is preferably 0.5% or less, and the thermal shrinkage at each temperature of 100 ° C or less is preferably 1% or less, more preferably 0.5% or less, and most preferably 0.1% or less, ideally 0%. The glass transition temperature of the magnetic layer (the maximum of the loss of modulus of elasticity by measuring the dynamic viscoelasticity at 110 Hz) is preferably 30 ° C to 150 ° C, and that of the lower coating is preferably 0 ° C to 100 ° C. The modulus of elasticity loss is preferably within the range of 1 × 10 ⁸ to 8 × 10 ⁹ dyn / cm ² , and the loss tangent is preferably 0.2 or less.

If the loss tangent is large, attachment loss tends to occur. The residual amount of the solvent in the magnetic layer is preferably 100 mg / m ² or less, more preferably 10 mg / m ² or less, and the residual solvent amount in the upper magnetic layer is preferably smaller than that in the lower layer. The void ratio is preferably 30% by volume, more preferably 20% by volume, in each of the non-magnetic lower coating and the magnetic layer. The void ratio is preferably smaller, but in some cases, a certain value is preferably ensured depending on the purpose. For example, a high void ratio in a particle-containing magnetic recording medium for recording data which is repeatedly used contributes to good durability in many cases.

A band-like particle-containing magnetic Recording medium, which is a particularly preferred Embodiment of the present invention, shows a squareness ratio in the machine direction of  0.85 or more and a panel distribution ("switching field distribution ", abbreviated as SFD) in the Machine direction of 0.41 or less, if at a magnetic field of 10 kOe through Vibration sample magnetometer ("vibrating sample magnetometer ", VSM) Record deep in the magnetic layer, and the overwriting properties can be improved by increasing the Orientation of the magnetic powder and performing a sharp and uniform magnetization reversal in the Depth direction of the magnetic layer can be improved.

As means for obtaining an SFD of 0.41 or less in the machine direction of the particle-containing magnetic recording medium, the following points can be enumerated.

• (1) The orientation will be right after applying the Magnetic layer with a permanent magnet of 5 000 Gauss or less performed.
• (2) Before dispersing with a sand mill, a Kneading using an open kneader or a continuous kneader.
• (3) When the dispersion is carried out with a sand mill, dispersing media having a specific gravity of 2.5 or more, preferably dispersing beads containing ZrO ₂ as a main component are used.
• (4) The dispersion of the ferromagnetic powder and the non-magnetic powder is separated, and then each of the predetermined quantities is mixed, and the dispersion is continued.  
• (5) SFD of the ferromagnetic powder is set to 0.6 or less lowered.
• (6) When the length of the long axis is 0.05 to 0.13 μm amounts are long magnetic powder with a Crystallite size of 200 Å or less is selected.

The above squareness ratio is especially preferably 0.85 to 0.95, most preferably 0.86 to 0.92.

A particularly preferred range of the SFD is 0.1 to 0.35 and most preferably 0.15 to 0.30.

Two squareness ratios in the two directions, the make a right angle with the running direction of the band, d. H. the direction parallel to the tape surface and the tape orthogonal crossing and perpendicular to the surface of the strip Direction, preferably 80% or less. The remanent Coercive force Hr in machine direction is also preferably 1 800 Oe to 3 000 Oe. Hc and Hr in the vertical Direction are preferably 1 000 Oe to 5 000 Oe.

It is preferred that the RMS surface roughness (R _RMS ) of the magnetic layer measured using AFM (Atomic Force Microscope) is 2 nm to 15 nm.

When the particle-containing magnetic particle of the present invention Recording medium for digital video cassettes for VCR is used for entertainment purposes, the saturation magnetization is preferably 0.03 to 0.13 G.cm, and the surface chlorine content is no longer as 0.3 in relation to the surface Fe content, i. H. in terms of a Cl / Fe intensity ratio caused by ESCA is obtained.  

The problem that the in the recording / playback head of Video recorders used for entertainment use Ferrite tends to corrosion, depends on the surface chlorine content together. That's why this problem got through Reduction of the ratio of the surface chlorine content to Fe amount to 0.3 or less, preferably 0.2 or less than the intensity ratio obtained by ESCA, solved. It is further preferred that the mechanical Strength of the tape using Vinyl chloride resin / urethane resin in the lower layer to maintain and the vinyl chloride content in the top Reduce magnetic layer. Because of this structure can the content of the chlorine atoms in the magnetic layer without Reduction of the mechanical strength of the band reduced become. Furthermore, the problem can to a certain extent by removing the excess binder in the Surface layer dissolved by a surface treatment even if a vinyl chloride resin is in the top one Magnetic layer is used.

The binder resin for use in the magnetic layer of The present invention can be described above Polyurethane resin alone or in combination with other resins his. It is preferred to use such resins as to avoid the resins to be used in combination, the develop a corrosive gas, such as Vinyl chloride resin to prevent the corrosion of the thin film head and to prevent the MR head.

The measured under an external magnetic field of 10 kOe Saturation magnetization is 0.03 to 0.13 g.cm, preferably 0.04 to 0.10.  

The coercive force Hc of the magnetic layer is 2,000 to 3,000 Oe, preferably 2,000 to 2,800 Oe.

The surface roughness Ra of the magnetic layer measured under Using a 3D mirror (a product of WYCO) is equal to or less than 4 nm and preferably equal to or less than 3 nm.

In the following examples and comparative examples "part" means "part by weight" and "%" means "% by weight".

[Examples 1 to 6, Comparative Examples 1 and 2]

example 1 Coating solution for upper magnetic layer

Ferromagnetic metal powder 100 parts Fe / Co, atomic ratio: 100/30 @ Al / Fe, atomic ratio: 7.7 / 100 @ Y / Fe, atomic ratio: 6.8 / 100 @ HC: 2 250 Oe @ S _BET : 45 m² / g @ Crystallite size: 170 Å @ Length of the long axis: 0.09 μm @ Pin-lock ratio: 8 @ σ _s : 156 emu / g @ Vinyl chloride polymer 10 parts MR110 (manufactured by Nippon Zeon Co., Ltd., Japan) @ Polyurethane Resin A (shown in Table 1) 6 parts α-Al ₂ O ₃ (average particle size: 0.15 μm) 5 parts Carbon black (average particle size: 80 nm) 0.5 parts butyl stearate Part 1 stearic acid 5 parts methyl ethyl ketone 90 parts cyclohexanone 30 parts toluene 60 parts

Coating solution for lower layer

Non-magnetic powder, α-Fe ₂ O ₃ 80 parts Length of the long axis: 0.15 μm @ S _BET : 52 m ² / g @ pH: 8 @ Tap density: 0.8 @ DBP oil absorption: 27 to 38 ml / 100 g @ Surface covering compound: Al ₂ O ₃ , SiO ₂ @ soot 20 parts Average primary particle size: 16 nm @ DPB oil absorption: 120 ml / 100 g @ AL = L <pH: 8.0 @ S _BET : 250 m ² / g @ AL = L <Volatile content: 1.5% @ Vinyl chloride polymer MR104 (manufactured by Nippon Zeon Co., Ltd., Japan) 12 parts Polyurethane Resin A (shown in Table 1) 5 parts α-Al ₂ O ₃ (average particle size: 0.2 μm) Part 1 butyl stearate Part 1 stearic acid Part 1 methyl ethyl ketone 100 parts cyclohexanone 50 parts toluene 50 parts

Table 1 Polyurethane resin A

Molecular weight: 36,000, Tg: 94 ° C structure

Hydrogenated Bisphenol A 0.6 mol Polypropylene oxide adduct of bisphenol A 0.3 mol Sodium salt of bis-2-hydroxyethyl) -5-sulfoisophthalate 0.05 mol Diphenylmethane diisocyanate (MDI) 1.0 mol trimethylolpropane 0.05 mol -SO ₃ Na group (6.0 × 10 ^-5 equivalents / g)

The above compositions of the coating solutions for the upper layer and the lower layer became corresponding mixed in an open blender and then with a sand mill dispersed. To each of the resulting dispersions were added 5 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd., Japan) 40 parts of a solvent mixture of methyl ethyl ketone and cyclohexanone. Each solution was replaced by a Filter with a mean pore diameter of 1.0 μm filtered to the top and the coating solution to get lower layers.

These coating solutions were simultaneously applied to a Polyethylene naphthalate carrier with a thickness of 5.2 microns and an arithmetic mean surface roughness of 0.001 μm on the side where the magnetic layer is applied should, multi-coated. The coating solution of lower layer was in a dry thickness of 1.5 microns immediately afterwards the coating solution was applied upper magnetic layer applied to the lower layer to  to give a magnetic layer with a thickness of 0.13 μm. The magnetic powders were with a cobalt M 28631 00070 552 001000280000000200012000285912852000040 0002019752953 00004 28512agnet with a magnetic force of 5 000 G and a magnetic coil with a Magnetic force of 4 000 G oriented, while both layers were still wet. After drying, the coating became a calender treatment with 7-stage calenders comprising metal rollers and epoxy resin rollers, at 100 ° C at subjected to a speed of 200 m / min. Then it became a backside layer having a thickness of 0.5 μm applied. The obtained sheet was cut to a width of Cut 6.35mm to make a DVC videotape.

Example 2

A DVC video tape was produced in the same manner as in Example 1 except that the following ferromagnetic metal powders were used.
Ferromagnetic metal powder: 100 parts

Fe / Co, atomic ratio: 100/30
Al / Fe, atomic ratio: 10/100
Si / Fe, atomic ratio: 1/100
Y / Fe, atomic ratio: 6/100
Hc: 2,150 Oe
S _BET : 49 m ² / g
Crystallite size: 160 Å
Length of the long axis: 0.09 μm
Pin-lock ratio: 7
σ _s : 150 emu / g

Example 3

A DVC video tape was produced in the same manner as in Example 1 except that the following ferromagnetic metal powders were used.
Ferromagnetic metal powder: 100 parts

Fe / Co, atomic ratio: 100/30
Al / Fe, atomic ratio: 12/100
Si / Fe, atomic ratio: 0.5 / 100
Y / Fe, atomic ratio: 7/100
Hc: 2 200 Oe
S _BET : 50 m ² / g
Crystallite size: 120 Å
Length of the long axis: 0.06 μm
Pin-lock ratio: 6
σ _s : 140 emu / g

Comparative Example 1

A DVC videotape was made in the same way as in example 1, except that the thickness of the magnetic layer on a value outside the scope of the present invention was increased.

Comparative Example 2

A DVC videotape was made in the same way as in example 1, except the thickness of the magnetic layer on one Value outside the scope of the present invention increases has been.

Example 4

A DVC video tape was produced in the same manner as in Example 1 except for using the following ferromagnetic metal powders.
Ferromagnetic metal powder: 100 parts

Fe / Co, atomic ratio: 100/30
Al / Fe, atomic ratio: 10/100
Y / Fe, atomic ratio: 6/100
Hc: 2,150 Oe
S _BET : 59 m ² / g
Crystallite size: 95 Å
Long axis length: 0.04 μm
Pin-lock ratio: 4
σ _s : 140 emu / g

Example 5

A DVC videotape was made in the same way as in example 1, except the following ferromagnetic Metal powders were used. Ferromagnetic metal powder: 100 parts

Fe / Co, atomic ratio: 100/30
Al / Fe, atomic ratio: 11/100
Y / Fe, atomic ratio: 5/100
Hc: 2,150 Oe
S _BET : 48 m ² / g
Crystallite size: 180 Å
Length of the long axis: 0.08 μm
Pin-lock ratio: 7
σ _s : 135 emu / g

Example 6

A DVC videotape was made in the same way as in example 1, except that the polyurethane resin A in the upper and lower layers with the following polyurethane resin B was exchanged.  

Polyurethane resin B Neopentylglycol / caprolactone polyol / MDI = 0.9 / 2.6 / 1 (containing 1 × 10 ^-4 equiv./g -SO ₃ Na)

The properties of the thus obtained magnetic Recording medium of Examples and Comparative Examples were measured according to the following methods. The obtained Results are shown in Table 2.

Scoring System Half-Tb-output level

A camcorder DJ-1 (a product of Matsushita Electric Industrial Co., Ltd.) was modified to Tb: BIT distance, and the signal output was at a frequency of 1/2 Tb (21 MHz). The electrical recording current corresponded to the drive control. A reference tape "MTR1221" for DVC was used as 0 dB. In general -1.0 dB or more practicable, preferably -0.5 dB or more.

1/90-Tb-output level

A camcorder DJ-1 (a product of Matsushita Electric Industrial Co., Ltd.) was modified to Tb: BIT distance, and the signal output at a frequency of 1/90 Tb (464 MHz) was measured. The electrical recording current corresponded to the drive control. The reference band "MTR1221" for DVC was used as 0 dB. In general -1.0 dB or more practicable, preferably -0.5 dB or more.  

1/75 Tb signal O / W (overwriting properties)

First, 1/75 Tb frequency signals were on the above modified DJ-1 camcorder recorded. Then these were 1/75 Tb signals, and the output level became measured. Then an overwriting was done using Data signals performed, and those after clearing remaining 1/75 Tb signals were used with a Spectrum analyzer measured. The difference between the 1/75 Tb signal outputs before and after Data signal recording was used as an O / W erasure factor used. The same measurement was made using the Reference tape "MTR1221" performed for DVC use, and the difference was used as 1/75 Tb signal O / W. In general, +1.0 dB or less is practical, preferably +0.5 dB or less.

Ra

The surface arithmetic mean roughness was below Use of a digital optical surface measuring device ("Profilometer", a product of WYKO) by the light interference method under the conditions of a limit measured from 0.25 mm.

Hc, Φm, Π

The magnetic properties were parallel to Orientation direction using a magnetometer Sample vibration type (a product of Toei Kogyo K.K.) measured under an external magnetic field of 10 kOe.  

The following facts are shown in Table 2:
Examples 1 and 2: The output level and overwriting properties are balanced. These are desirable examples.

Example 3: Because the Π value approaches the upper limit, the overwriting properties were medium quality.

Comparative Example 1: Because the Π value is the upper limit exceeded, the overwriting properties were inferior.

Comparative Example 2: Because the Π value is lower than that lower limit was, the 1/90 output level was inferior and the 1/2 Tb output level of medium quality.

Example 4: Because S _{BET of} the magnetic powder exceeded the desired range, the surface property of the recording medium was inferior, and the 1/2 Tb output level and the overwriting properties were of intermediate quality.

Example 5: Because the σ _{s of} the magnetic layer was lower than the desired range, the output level and overwriting properties were of medium quality.

Example 6: Because the binder resin is replaced by polyurethane resin B was replaced, the surface property was inferior, and the 1/2 Tb output level and overwriting characteristics were of medium quality.

Therefore, by regulating the magnetic properties Inside the prescribed area a magnetic Recording medium can be obtained, the excellent  Overwrite properties, playback output levels and Running resistance has.

Examples 7 to 11 and Comparative Examples 3 to 7 Example 7 Single magnetic layer coating solution

Fine ferromagnetic metal powder 100 parts Fe / Co, atomic ratio: 100/30 @ Al / Fe, atomic ratio: 8/100 @ Y / Fe, atomic ratio: 6/100 @ HC: 2 250 Oe @ S _BET : 45 m ² / g @ Crystallite size: 170 Å @ Particle size (long axis diameter): 0.09 μm @ Pin-lock ratio: 8 @ σ _s : 156 emu / g @ Vinyl chloride copolymer MR110 (manufactured by Nippon Zeon Co., Ltd., Japan) 10 parts Polyurethane resin UR-8200 (manufactured by Toyobo Co., Ltd., Japan) 6 parts α-Al ₂ O ₃ (average particle size: 0.15 μm) 5 parts Carbon black (average particle size: 0.8 μm) 0.5 parts butyl stearate Part 1 stearic acid 5 parts methyl ethyl ketone 90 parts cyclohexanone 30 parts toluene 60 parts

The above coating solution compositions were used in mixed with an open kneader and then with one Sand mill dispersed. To the resulting dispersion were 5 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd., Japan) 40 parts of a mixed solution of methyl ethyl ketone and Added cyclohexanone. The solution was replaced by a Filter with an average pore diameter of 1 μm filtered to obtain a coating solution.

Coating solution for the lower layer (non-magnetic Layer)

Non-magnetic powder, α-Fe ₂ O ₃ (hematite) 80 parts Length of the long axis: 0.15 μm @ S _BET : 52 m ² / g @ pH: 8 @ Tap density: 0.8 @ DBP oil absorption: 27 to 38 ml / 100 g @ Surface covering compound: Al ₂ O ₃ , SiO ₂ @ soot 20 parts Mean primary particle size: 16 mμ @ DPB oil absorption: 120 ml / 100 g @ AL = L <pH: 8.0 @ S _BET : 250 m ² / g @ AL = L <volatile content: 1.5% @ Vinyl chloride copolymer @ MR104 (manufactured by Nippon Zeon Co., Ltd., Japan) 12 parts Polyester polyurethane resin with cyclic structure and polyether group 5 parts α-Al ₂ O ₃ (average particle size: 0.2 μm) Part 1 butyl stearate Part 1 stearic acid Part 1 methyl ethyl ketone 100 parts cyclohexanone 50 parts toluene 50 parts

The above compositions for the coating solution of bottom layer were mixed in an open kneader and then dispersed with a sand mill. 5 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd., Japan) became the resulting dispersion solution of the lower one Layer added, and then were 40 parts of a Solution mixture of methyl ethyl ketone and cyclohexanone for Dispersion solution added. The solution was replaced by a Filter with a mean pore diameter of 1 μm filtered to form a coating solution for the lower To obtain coating.

These coating solutions were used simultaneously as Multiple layer on a polyethylene naphthalate carrier with a thickness of 5.2 microns and an arithmetic Surface center roughness of 0.001 μm on the side to which a magnetic layer should be applied, applied. The lower layer coating solution was treated with a dry thickness of 1.5 microns, and immediately thereafter The coating solution of the upper magnetic layer was placed on the lower layer applied to the magnetic layer with a Thickness of 1.5 microns to give. The magnetic powders were with a cobalt magnet with a magnetic strength of 5 000 G and a magnetic coil with a magnetic strength of 4 000 G oriented while both layers were still wet. After this The applied layer became a drying Calender treatment with calenders in seven stages, comprising Metal rollers and epoxy resin rollers, at 100 ° C at a Subjected to speed of 200 m / min. Then one became Back layer applied with a thickness of 0.5 microns. The  the web obtained was cut to a width of 6.35 mm, to make a DVC videotape.

Examples 8 to 11 and Comparative Examples 3 to 7

Video tapes were made in the same manner as in Example 7 except that the conditions are as in Table 3 have been changed.

Each videotape in Examples 7 to 11 and the Comparative Examples 3 to 7 were to the following Properties examined. The measuring methods are as follows.

Scoring System

1/2 Tb output level:
Evaluated in the same manner as in Example 1.
1/2 TB CNR:
The 1/2 Tb signal frequency was recorded by the prescribed electric recording current. Then, the total noise and the amplifier noise were measured at 2/1 Tb signal output level, 1 / 2.25 Tb frequency and 1 / 1.8 Tb frequency. The measurements were all performed with a resolution width of 30 kHz. The definition of band noise is as follows.
N _band = (N _tot ² - N _amp ² ) ^1/2
N _tot = (N _tot ¹ + N _tot ² ) ^{/ 2}
N _tot ¹ : total noise at 1 / 2.25 Tb frequency
N _tot ² : total noise at 1 / 1.8 Tb frequency
N _amp : amplifier _noise at 1/2 Tb frequency
The ratio of the 1/2 Tb output level to N _band is taken as the C / N ratio (CNR) and the reference band "MTR1221" is used as the 0 dB for DVC use.
Values of -2 dB or more are acceptable.
1/75 Tb O / W (overwriting properties):
Evaluated in the same manner as in Example 1.
1/4 Tb O / W:
First, signals were recorded at 1/4 Tb frequency on the above modified DJ-1 camcorder. Then, these 1/4 Tb signals were reproduced and the output level was measured. Then, overwriting was performed using data signals, and the 1/4 Tb signal remaining after erasing was measured with a spectrum analyzer. The difference between the 1/4 Tb signal output levels before and after the data signal recording was used as the O / W erasure factor. The same measurement was carried out using the reference tape "MTR1221" for DVC use, and the difference was taken as 1/4 Tb O / W.
Values of +2 dB or more are acceptable.
Hc, Φm, Π:
The evaluations were carried out in the same manner as in Example 1.

The results of the evaluations of the above properties each videotape in Examples 7 to 11 and in the  Comparative Examples 3 to 7 are in the following Table 3.  

It is clearly evident from the results in Table 3, that the samples in which Π within the range of 100 to 160, in which the ferromagnetic metal powder Fe as the major component with a long axis length of 0.05 to 0.13 microns and a crystallite size of 80 to 200 Å in which the thickness of the magnetic layer is 0.05 to 0.5 μm and SFD within the machine direction plane 0.41 or less is excellent Overwriting properties and playback output levels and have low noise.

Examples 12 to 19, Reference Examples 1 to 7 and Comparative Examples 8 and 9 Coating solution of the lower layer (non-magnetic): (Coating Composition A)

Non-magnetic powder, α-Fe ₂ O ₃ (hematite) 80 parts Length of the long axis: 0.15 μm @ S _BET : 52 m ² / g @ pH: 9 @ Tap density: 0.8 @ Surface covering compound: Al ₂ O ₃ , SiO ₂ @ soot 20 parts Mean primary particle size: 16 mμ @ DPB oil absorption: 80 ml / 100 g @ AL = L <pH: 8.0 @ S _BET : 250 m ² / g @ AL = L <volatile content: 1.5% @ Vinyl chloride copolymer @ MR104 (manufactured by Nippon Zeon Co., Ltd., Japan) 12 parts AL = L <polyurethane (see Table 5) α-Al ₂ O ₃ (average particle size: 0.2 μm) Part 1 butyl stearate Part 1 stearic acid Part 1 methyl ethyl ketone 100 parts cyclohexanone 50 parts toluene 50 parts

Coating solution of the lower layer (non-magnetic): (Coating Composition B)

Non-magnetic powder, TiO ² (titanium oxide) 80 parts Mean primary particle size: 0.02 μm @ S _BET : 70 m ² / g @ pH: 7 @ Tap density: 0.8 @ Surface covering compound: Al ₂ O ₃ , SiO ₂ @ soot 20 parts Mean primary particle size: 16 mμ @ DPB oil absorption: 80 ml / 100 g @ AL = L <pH: 8.0 @ S _BET : 250 m ² / g @ AL = L <volatile content: 1.5% @ Vinyl chloride copolymer @ MR104 (manufactured by Nippon Zeon Co., Ltd., Japan) 12 parts AL = L <polyurethane (see Table 5) α-Al ₂ O ₃ (average particle size: 0.2 μm) Part 1 butyl stearate Part 1 stearic acid Part 1 methyl ethyl ketone 100 parts cyclohexanone 50 parts toluene 50 parts

Magnetic coating solution (magnetic layer):

Fine ferromagnetic metal powder A to E as shown in Table 4 100 parts Vinyl chloride copolymer @ (MR 110 manufactured by Nippon Zeon Co., Ltd., Japan) @ AL = L <polyester polyurethane resin (see Table 5) A and B as shown in Table 5 @ α-Al ₂ O ₃ (average particle size: 0.15 μm) 5 parts Carbon black (average particle size: 0.08 μm) 0.5 parts butyl stearate Part 1 stearic acid 5 parts methyl ethyl ketone 90 parts cyclohexanone 30 parts toluene 60 parts

Table 4

Table 5

AL = L <A. Molecular weight: 36,000, Tg: 94 ° C Hydrogenated Bisphenol A 0.6 mol Polypropylene oxide adduct of bisphenol A 0.3 mol Sodium salt of bis (2-hydroxyethyl) -5-sulfoisophthalate 0.05 mol diisocyanate 1.0 mol trimethylolpropane 0.05 mol -SO ₃ Na group (6.0 × 10 ^-5 equivalents / g) @ B. Molecular weight: 40,000, Tg: 64∘C @ neopentylglycol 3.2 mol cyclohexanedimethanol 0.7 mol hydroxypivalic 0.8 mol phthalic 4.4 mol diisocyanate 1.0 mol -SO ₃ Na group (6.0 × 10 ^-5 equivalents / g)

The above compositions of the coating solutions for the lower coating and the upper magnetic layer were each mixed in an open kneader and then with a Sand mill dispersed. To each resulting dispersion were 5 parts of polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Co., Ltd., Japan), and Further, 40 parts of a mixed solution were made Methyl ethyl ketone and cyclohexanone added. Every solution was passed through a filter with a mean pore diameter filtered at 1 micron to the coating solutions for the to obtain the lower coating and the upper magnetic layer.

In Reference Examples 1 to 4, the same became Vinyl chloride resins, urethane resins and hardener to the top Magnetic layer and added to the lower coating. In Examples 12 to 18, Reference Examples 5 and 6 and  Comparative Examples 8 and 9 were a urethane resin and a hardener is added to the upper magnetic layer, and a Vinyl chloride resin, a urethane resin and a hardener were added added lower non-magnetic layer. These Coating solutions were simultaneously used as a multilayer onto a polyethylene naphthalate support having a thickness of 5.0 μm and an arithmetic mean surface roughness of 0.002 μm on the side to which the magnetic layers should be applied, applied. The Coating solution of the lower layer was treated with a dry thickness of 1.2 microns applied, and immediately thereafter The coating solutions of the upper magnetic layer were on the lower layer is applied to the magnetic layer with to give a thickness of 0.03, 0.12 or 0.3 microns. The Magnetic powders were mixed with a cobalt magnet Magnetic strength of 6 000 G and a magnetic coil with a Magnetic strength of 5 000 G oriented, while both layers were still wet. After drying, the applied Layer of calendering calendering in 7 stages, comprising metal rollers, at 90 ° C at a speed subjected to 200 m / min. Then a backside layer was made applied with a thickness of 0.5 microns. The preserved railway was cut to a width of 8 mm. The Magnetic layer surface of the web thus obtained was with a belt cleaning machine with a nonwoven fabric and a pressed against the belt surface at an acute angle Sapphire blade attached to a machine with feed and Winding element connected to the cut product was, cleaned. This was an 8mm DVC videotape manufactured.

An abrasive belt was attached to the above purifier connected so that it is the magnetic layer surface touched, and the same tape was cleaned 10 more times, to remove the binder on the belt surface. in the  Reference Example 7 was the tape of Reference Examples 3 and in Example 19, the tape of Reference Example 4 is used.

The results obtained are shown in Table 6. The Evaluation methods are as follows.

Scoring System Thickness of the magnetic layer

The sample with a thickness of about 0.1 microns was with a Diamond cutter in the machine direction of the magnetic Medium cut out with an electron microscope from Transmission type and 30 000-fold magnification observed and photographed. The print size of the photograph was A4 (i.e., 21.0 cm x 29.7 cm). The inventors paid attention to the Difference of forms of ferromagnetic powder and the non-magnetic powder of the magnetic layer and not magnetic layer and marked the interface and the Surface of the magnetic layer after visual assessment black. Thereafter, the length of the marked lines was passed through an image processing apparatus "IBAS2" (manufactured by Zeiss) measured. The measurement was over a length of 21 cm the Sample photography performed at random measurement points. The mean of the simple addition of the measured values was taken as the thickness of the magnetic layer.

Surface roughness Ra of the magnetic layer

Ra an area of about 250 nm × 250 nm was with a Three-dimensional light interference roughness meter "TOPO3D" (a product of WYKO, Arizona, USA) according to the MIRAU method measured. The wavelength of the measurement was 650 nm, and spherical compensation and cylindrical compensation were used.  

Electromagnetic properties Output level of the output wavelength 0.488 μm

The output level became at a relative speed of 10.2 m / s using Fuji's reference ME tape Photo Film Co., Ltd. and an external drum tester measured. An Fe-head was used and Bs was 1.5T. The value was recorded and with one as below defined optimal electrical recording current played.

The output level of the recording wavelength is 0.488 μm preferably in the range of -2 dB to +2 dB.

Overwriting erasure factor

Square wave signals of the recording wavelength 22 μm were using an external drum tester recorded, the output level was reproduced and measured. The square wave signals of Recording wavelength 0.488 μm was recorded thereon and reproduced, and the output level of Recording wavelength 22 .mu.m was with a Spectrum analyzer read. The ratio of the output level the wavelength 22 microns before and after the Overwrite record was used as overwrite delete factor taken. -20 dB or less is preferable as an absolute value.

head corrosion

The magnetic layer was coated with a specimen through Vapor deposition of a permalloy film on a PET basis was made, brought into contact and in one  Environment of 60 ° C and 90% relative humidity for one Week stored, and the corrosion of the vapor-deposited Permalloy film was evaluated. The evaluation was done by visual observation using a microscope with 50x magnification in three steps from G: none Eradication, M: Formation of Eradication and B: 2 or more Earrations performed.

running durability

Under conditions of 23 ° C and 70% relative humidity and using ten 8mm video devices FUJIX8 (a Product of Fuji Photo Film Co., Ltd.) became a band respectively Run through 100 times. The reduction of Output level and staining within the device after passing through were evaluated.

G: The reduction of the output level was less than 3 dB, and staining on any part of the Drive disk was observed with the eye.

M: The reduction of the output level was less than 3 dB, but there was considerable staining on each Part on the drive plate with the eye watched.

B: The reduction of the output level was 3 dB or more.

Chlorine quantity on the surface / amount of iron on the surface

Evaluation using ESCA (PHI560 type, manufactured by Φ-Co.) Under the following conditions:

measurement conditions

Mg ANODE: 300 W, flow energy: 100 eV
Cl1s, N1s, Fe2p3 / 2 peaks were scanned in detail.

Area intensity ratio of each peak was determined by Cl / Fe and N / Fe.

Measuring time: about 10 minutes.  

Table 6

Table 6 (continued)

Table 6 (continued)

Table 6 (continued)

A magnetic recording medium that records with high density and excellent Overwriting properties, running stability and Possesses corrosion resistance, can by forming a extremely thin magnetic layer, the ferromagnetic fine Contains powder, and reduction of the chlorine content on the Surface to be obtained.

Although the invention in detail and with reference to specific If examples have been described, it will be apparent to those skilled in the art be that different changes and modifications can be made without departing from its scope departing.

Claims (10)

1. Tape-like magnetic recording medium comprising a Carrier with a magnetic layer applied thereto, comprising a binder dispersed in a binder ferromagnetic metal powder, wherein the Magnetic layer a product Π of coercive force Hc (Oe) within the machine direction of the belt and the Magnetic flux Φm (G.cm) from 100 to 160. The tape-type magnetic recording medium according to claim 1, wherein the ferromagnetic metal powder has a _BET specific surface area _BET as measured by the BET method of 30 m ² / g to less than 50 m ² / g and a saturation magnetization σ _s of 140 to 170 emu / g. 3. Tape-like magnetic recording medium according to Claim 1, wherein the coercive force Hc of the ferromagnetic metal powder from 1,950 to 2,750 Oe is. 4. Tape-like magnetic recording medium according to Claim 1, wherein the ferromagnetic metal powder Fe as the main component and 10 to 40 atom% Co, 2 to 20 atom% Al and 1 to 15 atom% Y, in each case on Fe, contains. 5. Tape-like magnetic recording medium according to Claim 1, wherein the magnetic layer has a thickness of 0.05  to 0.3 μm, a coercive force Hc of 2,000 to 2 400 Oe, a saturation magnetization of 0.03 to 0.13 G.cm and a ratio of the amount of chlorine on the Surface to Fe amount on the surface of 0.3 or has less. 6. Tape-like magnetic recording medium according to Claim 1, wherein a non-magnetic layer, the contains inorganic powder, between the carrier and the Magnetic layer is attached. 7. Tape-like magnetic recording medium according to Claim 1, wherein the ferromagnetic metal powder is a Length of the long axis of 0.05 to 0.13 microns and a Crystallite size of 80 to 200 Å and the thickness the magnetic layer 0.05 to 0.5 microns and SFD in the Machine direction is 0.41 or less. 8. Tape-like magnetic recording medium according to Claim 1, wherein the binder is a polyurethane resin contains a cyclic hydrocarbon group and contains an ether linkage. 9. Tape-like magnetic recording medium according to Claim 1, wherein the magnetic layer in addition at least one abrasive selected from α-alumina, Chromium oxide, α-iron oxide and artificial Diamond, contains. 10. Tape-like magnetic recording medium according to Claim 1, wherein a backside layer comprising a binder having dispersed therein inorganic Particles deposited on the surface of the support is that of the side coated with the magnetic layer opposite.