JP3023719B2 - Magnetic recording media - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a magnetic tape, a magnetic sheet and a magnetic disk.

[0002]

BACKGROUND OF THE INVENTION In order to achieve high image quality of 8 mm in recent years such as Hi-Fi 8 mm video (Hi8), fine metal powder having a small axial ratio has been used (Japanese Patent Application Laid-Open Nos. 2-58727 and 2-58727).
No. 239424), an attempt has been made to improve the electromagnetic conversion characteristics by using such a metal powder as an upper layer and forming a magnetic layer into multiple layers (Japanese Patent Laid-Open No. 2-417542).

[0003] However, when a fine metal powder having a small axial ratio is used, the Young's modulus of the magnetic layer is reduced, and the temperature is reduced to 40 ° C and 80% RH.
In the full length running test of 40 ° C,
In the full-length running at 20% RH, there were problems such as a decrease in output and clogging of the head, which is probably caused by a decrease in the polishing force of the tape. The problem is that the magnetic layer is multi-layered and the lower layer uses Co-containing iron oxide, which is relatively easy to adsorb fatty acids.
(Japanese Unexamined Patent Publication No. Hei 2-417542), the degree of improvement can be improved to a considerable extent, but it has not yet been at a sufficient level. In particular, to obtain sufficient electromagnetic conversion characteristics with the Hi8 system, it is preferable that the average major axis length of the magnetic powder used in the lower layer be 0.25 μm or less and the crystallite size be 450 mm or less, but such a direction is the In the direction of lowering the rate, the conventional technology cannot improve the running durability from high humidity to low humidity.

Also, the electromagnetic conversion characteristics, for example, the level of dropout, are not at a level that can be used for the Hi8 system.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide sufficient electromagnetic conversion characteristics in the entire range from the short wave side to the long wave side, and particularly to improve the orientation of the metal magnetic powder in the outermost layer to improve the RF output and the L / S / N ratio. Another object of the present invention is to provide a magnetic recording medium which has improved running durability under conditions of high humidity to low humidity, and has excellent clogging, dropout and corrosion resistance.

In order to solve the above problems and achieve the object of the present invention, the coercive force of the magnetic material used, the relationship between the wavelength range of recording and reproduction and the axial ratio, the degree of dispersion of magnetic powder, the degree of filling and the dispersion stability. The characteristics, running characteristics, lubricity, and surface characteristics, such as dynamic friction resistance, were selected as factors to solve the problem and examined.

[0007]

The object of the present invention can be achieved by any of the following structures of the present invention. That is, A. In a magnetic recording medium provided with a magnetic layer on a non-magnetic support, the following ferromagnetic alloy powder particles having an axial ratio of less than 10 are: (1) Fe-Al-Ca-based alloy having an Al / Fe weight ratio of 0.005 to 0.2, Ca /
Fe weight ratio is 0.001-0.1 , (2) Fe-Al-Ca-Ni alloy, (3) Fe-Al-Zn alloy, (4) Fe-Ni-Al-Si-Me (Me is Mn, Zn And / or a Co) -based alloy. The magnetic layer is a multilayer magnetic layer, a lower layer containing Co-containing iron oxide is provided, and the upper layer has an axial ratio of less than 10, Fe-Al-Ca-based, Fe-Al-
Ca-Ni-based, Fe-Al-Zn-based, Fe-Ni-Al-Si -Me (Me is Mn, Zn and / or Co) was contained at least one of the configuration, some are C. 20 ° C, 60% RH, 40
° C., 80% RH and 40 ° C., kinematic at 20% RH friction coefficient .mu.k _A,
μk _B and μk _C , μk _A > μk _B , μk _A > μk _C , μk _A ≤ 0.30
The configuration to be used.

[0008] Incidentally, the structure described in B has a structure below the multilayer magnetic layer.
By containing Co-containing iron oxide, more durable electromagnetic characteristics can be obtained than before, and the effect of using Co-containing iron oxide in the lower layer is that the conventional ferromagnetic metal or alloy, ferrite is used in the upper layer. It is also exhibited when using.

In the structures C and D, in addition to the ferromagnetic alloys described in Structure A, conventionally used ferromagnetic metals or alloys, ferrites such as Fe-Al alloys can also be used.

In the present invention, the axial ratio means the average major axis length / average minor axis length of the magnetic powder particles. The above-mentioned “average major axis length” and “average minor axis length” mean the average value when measuring the major axis and minor axis of the magnetic powder particles for 500 particles with a transmission electron microscope.

The average major axis length and average minor axis length can be obtained by controlling the production conditions (eg, reduction time) during the production of the metal magnetic powder.

Although it is not clear why each of the constituent items of the present invention is effective, Fe-Al-
Ca system, Fe-Al-Ca-Ni- system, Fe-Al-Zn system, Fe-Ni-Al-Si-
By using Me (Me is Mn, Zn and / or Co), the dispersibility of the magnetic powder is greatly improved, the filling degree is extremely dense, and the Young's modulus of the recording medium (hereinafter referred to as magnetic tape) It is considered that the driving durability and the dropout level are improved. By selecting the axial ratio, high fidelity (high fidelity) to the recording wavelength range can be provided.

Further, by replacing a part of the fatty acid conventionally used as a dispersant with an organic dye compound having polar groups -COOM and -SO ₃ M, the filling degree can be increased while maintaining the dispersibility of the magnetic powder. Good running durability can be maintained by increasing the Young's modulus and increasing the lubricant consumed by the lubrication operation by providing a Co-containing iron oxide with good adsorption and retention of lubricant in the lower layer of the multilayer. Dripping.

Further, the dynamic friction coefficient μk is a factor that directly affects the running property of the magnetic tape.
Μk _A , μk _B and μk _C under three conditions of% RH, 40 ° C., 80% RH and 40 ° C., 20% RH could be determined as the most appropriate indexes for controlling the running. In addition, only when the following relations exist between μk _A , μk _B and μk _C , it was found that the above-mentioned troubles in running durability and dropout can be solved.

Μk _B < μk _A , μk _C < μk _A μk _A ≦ 0.30 μk _A , μk _B , more preferably the relation of μk _C , μk _A - μk _B > 0.02 μk _A - μk _C > 0.02 μk _A ≦ 0.25. To make μk satisfy the above relationship (1) The magnetic layer is composed of two or more layers, and a Co-containing magnetic powder surface-treated with Si and / or Al is used as a lower layer. (2) Carbon black having a BET value of 80 m ² / g or less and an oil absorption of 100 ml / 100 g or more is used for the uppermost layer.

(3) The lower layer contains a polyurethane having a Tg of 0 ° C. or higher, and the ratio (weight) of the polyurethane in the entire binder is set to 20% or less.

(4) The number of magnetic layers is two or more, and the thickness of the uppermost layer is 1.0 μm or less, more preferably 0.1 to 0.5 μm. (5) Co-containing iron oxide is used as the magnetic powder contained in the lower layer.

(6) Adjustment of the amount of additives such as lubricant and carbon black contained in the magnetic layer. (7) A binder containing a sulfo group and / or a phospho group is used as a binder.

These means may be used in appropriate combination.

In the present invention, the dynamic friction coefficient μk is
Using a tape running tester TBT-300D (Yokohama System Research Institute), apply 18 tapes to chrome-plated stainless steel 4φ pins.
It is measured at 0 ° winding, tape speed of 1.43 cm / sec and entrance tension of 20 g, and indicates μk calculated by the following equation.

Μk = (1 / π) ln (X / 20) where X represents the outlet tension (g).

The ferromagnetic alloy used for the magnetic recording medium includes Fe-Al, Fe-Al-Ca, Fe-Al-Ni, Fe-Al-Zn,
e-Al-Co, Fe-Ni, Fe-Ni-Al, Fe-Ni-Co, Fe-Ni-
Si-Al-Mn system, Fe-Ni-Si-Al-Zn system, Fe-Al-Si system, Fe-Al-Co
System, Fe-Ni-Zn system, Fe-Ni-Mi-Mn system, Fe-Ni-Si system, Fe-Mn-Z
Ferromagnetic powders such as n-based, Fe-Co-Ni-P-based, and metallic magnetic powders containing Fe as a main component are exemplified. Among them, Fe-Al-Ca-based and Fe-Al-Ca-N, which have excellent electrical properties, good corrosion resistance and good dispersibility
i-based, Fe-Al-Zn-based, Fe-Ni-Al-Si-Zn-based, Fe-Ni-Al-Si-Mn
Or Fe-Ni-Al-Si-Co-based Fe-based metal powder is selected.

Further, the preferred structure of the ferromagnetic metal powder is such that the weight ratio Al / Fe of Fe to Al contained in the ferromagnetic metal powder is 0.005 to 0.2 and the ESCA of the ferromagnetic metal powder is The content ratio of Fe atoms and Al atoms existing in the surface area of less than 100 mm at the analysis depth by Fe is Al: Fe = Al = 3
It has a structure of 0:70 to 70:30. Alternatively, the ferromagnetic metal powder contains Fe atoms, Ni atoms, Al atoms, and Si atoms, and at least one of Zn atoms and Mn atoms is contained in the ferromagnetic metal powder, and the content of Fe atoms is 90%. Atomic% or more, Ni atom content is 1 atomic% or more and less than 10 atomic%, Al atom content is 0.1 atomic% or more and less than 5 atomic%, Si
The atomic content is 0.1 atomic% or more and less than 5 atomic%, and the content of Zn atom and / or the content of Mn atom (however, when both Zn atom and Mn atom are contained) is 0.1 atom %
And less than 5 atomic%, and Fe atoms and N existing in the surface area of 100 mm or less at the analysis depth of the ferromagnetic metal powder by ESCA.
The content ratio of i atom, Al atom, Si atom, Zn atom and / or Mn atom is Fe: Ni: Al: Si: (Zn and / or Mn) in atomic ratio.
= 100: (4 or less): (10-60): (10-70): Ferromagnetic metal powder having a structure of (20-80).

[0024] In the present invention, examples of the ferromagnetic powder used in addition to the ferromagnetic alloy powder as the ferromagnetic powder in the magnetic recording _{medium, γ-Fe 2 0 3,} Co -containing γ-Fe ₂ O ₃ , Co-coated γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , Co-coated Fe ₃ O ₄ , Co-containing magnetic FeOx (3/2>X> 4/3), CrO ₂ etc. Oxide magnetic material. In particular, hexagonal ferrite such as barium ferrite is useful.

In the present invention, in the case of a multilayer magnetic layer, Co-containing iron oxide is used as a lower layer to improve the durability of electromagnetic characteristics.

[0026] The present invention - Use COOM and / or an organic dye compound having a -SO ₃ M, without the effect of improving the running durability without depending on temperature and humidity conditions, compounds of these organic dyes
The object preferably has one of the following conditions.

A) salt form b) azo compound c) compound represented by the following general formula [M] d) red dye e) molecular weight of 3000 or less

[0028]

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N ₁ , n ₂ = 0 to 5 m ₁ , m ₂ = 0 to 2 X: Cl, NO ₂ , CH ₃ , C ₂ H ₅ , OCH ₃ , OC ₂ H ₅ Y: Cl Z: Carboxyl group Alternatively, the salt may be in the form of a sulfonic acid group or a salt, and each salt of NH ₄ , an alkali metal, an alkaline earth metal, and an organic amine is preferable.

Examples of the organic dye compound having a carboxyl group and / or a sulfonic acid group represented by the general formula [M] include, but are not limited to, the following. Various substitutions are possible.

[0031]

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[0032]

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[0033]

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[0034]

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[0035]

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When the amount of the organic dye compound is less than 0.1 parts by weight of the magnetic powder, the effect is not obtained. When the amount exceeds 5 parts by weight, the strength of the magnetic layer is reduced. The addition amount is more preferably 0.3 to 4 parts by weight, and more preferably 0.5 to 4 parts by weight.

Preferred binders in the present invention are polyurethane, polyester and vinyl chloride resins. More preferably, these resins are -SO ₃ M ', -OSO ₃ M'-COOM'
And at least one selected from the group consisting of -PO (OM ″) ₂
Contains repeating units having various polar groups (provided that M ″
Represents a hydrogen atom or an alkali metal atom such as Na, K or Li, and M ′ represents a hydrogen atom, an alkali metal atom such as Na, K or Li or an alkyl group. ).

The above-mentioned polar group has an effect of improving the dispersion of the magnetic powder, and its content is 0.1 to 8.0 mol% (more preferably, 0.5 to 6.0 mol%). When the content is less than 0.1 mol%, the dispersibility is reduced, and when the content is more than 8.0 mol%, the magnetic paint tends to gel. Further, the weight average molecular weight is preferably 15,000 to 50,000.

The content of the binder in the magnetic layer is determined by the ferromagnetic powder.
Usually, 10 to 40 parts by weight (preferably 1 to 100 parts by weight)
5 to 30 parts by weight). In this case, the weight ratio of the polyurethane and / or polyester to the vinyl chloride resin is usually 90:10 to 10:90 (preferably 70:30 to 30: 7).
0). In addition, as the binder, the following resin can be used at 20 Wt% or less of all binders in addition to the above resin.

As an example, the weight average molecular weight is 10,000.
~ 200,000, for example, urethane resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, polyamide resin,
Polyvinyl butyral, cellulose derivatives (cellulose acetate butylate, cellulose diacetate, cellulose triacetate, cellulose propionate,
Nitrocellulose), styrene-butadiene copolymer, polyester resin, various synthetic rubbers, phenolic resin, epoxy resin, urea resin, melamine resin, phenoxy resin, silicone resin, acrylic reactive resin, high molecular weight polyester resin and isocyanate Examples thereof include a mixture of a prepolymer, a mixture of a polyester polyol and a polyisocyanate, a urea formaldehyde resin, a mixture of a low molecular weight glycol / high molecular weight diol / isocyanate, and a mixture thereof.

In order to improve the durability and durability of the magnetic layer of the present invention, it is preferable to include a polyisocyanate. Examples of such a polyisocyanate-based curing agent include bifunctional isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and hexane diisocyanate; Any of functional isocyanates or urethane prepolymers containing isocyanate groups at both ends, such as those conventionally used as a curing agent, and any polyisocyanate usable as a curing agent can be used. The amount of the polyisocyanate-based curing agent is 5 to 80 parts by weight of the total binder amount. The weight average molecular weight of the polyisocyanate is preferably in the range of 100 to 3,000.

In forming the magnetic layer, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and a filler may be contained as necessary.

As dispersants, caprylic acid, capric acid,
Fatty acids having 12 to 18 carbon atoms such as lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid, and salts of these alkali metals or salts of alkaline earth metals or amides thereof; polyalkylene oxide alkyl phosphates Esters; lecithin; trialkylpolyolefinoxy quaternary ammonium salts; azo compounds having a carboxyl group and a sulfonic acid group, and the like are used. These dispersants are preferably added in the range of 0.5 to 5 Wt% based on the ferromagnetic powder.

The lubricant may contain a fatty acid and / or a fatty acid ester. In this case, the addition amount of the fatty acid is preferably 0.2 to 10 Wt% based on the ferromagnetic powder,
0.5 to 5 Wt% is even better. When the amount of fatty acid is less than this range, the running property tends to decrease, and when the amount of fatty acid increases, the fatty acid exudes and the output tends to decrease. The amount of the fatty acid ester added is preferably 0.2 to 10 Wt% based on the ferromagnetic powder,
0.5 to 5 Wt% is even better. If the fatty acid ester is less than this range, the still life is liable to decrease, and if the fatty acid ester is increased, the fatty acid ester exudes and the output is liable to decrease. In order to further improve the above effects, the fatty acid and the fatty acid ester are preferably in a weight ratio of 10:90 to 90:10.

In addition to the above fatty acids and fatty acid esters, other lubricants such as silicone oil, graphite, carbon fluoride, molybdenum disulfide, tungsten disulfide, fatty acid amide, α-olefin oxide and the like are added to the magnetic layer. May be.

Examples of the abrasive include α-alumina, chromium oxide, titanium oxide, α-iron oxide, silicon oxide,
Silicon nitride, silicon carbide, zirconium oxide, zinc oxide, cerium oxide, magnesium oxide, boron nitride, and the like are used.

The average particle size of the abrasive is preferably 0.6 μm or less. The Mohs hardness is preferably 5 or more. The average particle size of the abrasive is preferably 0.05 to 0.6 μm, and 0.1 to 0.3 μm.
μm is more preferred. Examples of the antistatic agent include conductive powders such as carbon black, graphite, tin oxide-antimony oxide compounds, tin oxide-titanium oxide-antimony oxide compounds, and carbon black graft polymers; natural surfactants such as saponin; Nonionic surfactants such as alkylene oxides, glycerins and glycidols; higher alkylamines, quaternary pyridines,
Other heterocyclics, cationic surfactants such as phosphonium and sulfoniums: anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfate group, and phosphate group: amino acids, aminosulfonic acids, Examples include amphoteric surfactants such as sulfuric acid and phosphoric acid esters of amino alcohol.

These may be used singly or may be used alone.
A combination of more than one species may be used. The above antistatic agent is added in the range of 0.01 to 40% by weight based on the binder.

In general, the surface electric resistance of the magnetic layer is set to 10 ⁹ Ω-cm or less, and the light transmittance of the tape portion having the magnetic layer is set to 0.05 or less.
% Or less, carbon black particles are usually added to the magnetic layer.

The carbon black to be used is carbon black imparting conductivity (hereinafter referred to as CB ₁ ).
The beginning, carbon black imparts light-shielding the magnetic layer (hereinafter, referred to as CB ₂₎ that is added preferably.

In this case, the above carbon black C
When B ₁ and CB ₂ are used, the specific surface area (BET value) of both carbon blacks is set to 200 to 500 m ² / g for the former (furthermore, 20
0 to 300 m ² / g), and the latter is preferably 40 to 200 m ² / g. That is, if the specific surface area of CB ₁ is less than 200 m ² / g, the particle size is too large and the conductivity becomes insufficient even by adding carbon black, and if it exceeds 500 m ² / g, the particle size is too small and instead carbon black Tends to deteriorate.
The carbon black CB1 is preferably _one in which particles are connected like a tuft of grapes, so to speak, and is preferably porous and has a large specific surface area, that is, a so-called high structure level.

The specific surface area is measured by a nitrogen adsorption method (BET method) by the Brunauer-Emmett-Teller method, and the oil absorption is measured by a Cabot type oil absorption meter using DBP (dibutyl phthalate) as a vehicle. You. Examples of the solvent to be mixed with the paint for forming the magnetic layer include ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) and cyclohexanone; alcohols such as methanol, ethanol, propanol and butanol; Ester systems such as methyl, ethyl acetate, butyl acetate, ethyl lactate, propyl acetate and ethylene glycol monoacetate: ether systems such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran and dioxane: aromatic hydrocarbons such as benzene, toluene and xylene : Halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene can be used.

The magnetic paint used in the present invention is produced by kneading and dispersing a ferromagnetic powder, a binder, a dispersant, a lubricant, an abrasive, an antistatic agent and the like in a solvent. Examples of the kneading and dispersing machine used for kneading and dispersing the magnetic paint include a two-roll mill, a three-roll mill, a pressure kneader, a continuous kneader, an open kneader, a pole mill, a pebble mill,
Examples include a side grinder, a Sqegvari attritor, a high-speed impeller disperser, a high-speed stone mill, a high-speed impact mill, a disperser, a high-speed mixer, a homogenizer, and an ultrasonic disperser. In particular, dispersers capable of providing a power consumption load of 0.05 to 0.5 KW (per kg of magnetic powder) are a pressure kneader, an open kneader, a continuous kneader, a two-roll mill, and a three-roll mill.

Examples of the nonmagnetic support used in the present invention include: polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate. And plastics such as polycarbonate.

Further, metals such as Cu, Al and Zn, glass, and various ceramics such as so-called new ceramics (for example, boron nitride, silicon carbide, etc.) can also be used.

The magnetic tape of the present invention is, for example, shown in FIG.
As shown in FIG. 1, a first magnetic layer 2 and a second magnetic layer 4 are formed on a non-magnetic support 1 made of polyethylene terephthalate or the like.
Are laminated in this order. Further, the back coat layer 3 is provided on the surface of the support opposite to the lamination surface, but this is not necessarily required. An overcoat layer may be provided on the second magnetic layer. In the example of FIG. 3B, the upper layer is further divided into layers 5 and 6.

In the magnetic tape of FIG. 1, the thickness of the first magnetic layer 2 is preferably 0.5 to 4.0 μm, and the thickness of the second magnetic layer 4 or the second and third magnetic layers 5 , 6 is preferably 1.0 μm or less (eg, 0.3 μm).
According to the present invention, the outermost magnetic layers 4 and 6 and the other magnetic layers 2 and 5 (and / or 2) are defined as the former 4, 6 as the outermost layer and the latter 2, 5, or 5 and 2 as the lower layer. I do.

Of the magnetic layers 2, 4, 5, and 6, the layers 4, 6
(Further, 5) contains the above-mentioned metal magnetic powder according to the present invention (preferably less than 0.20 μm in average major axis length, average major axis length / average minor axis length <10).

In the medium of the present invention, at least one of the lower magnetic layers contains cobalt and FeOx
(However, the structure containing the magnetic powder which consists of iron oxide represented by 1.33 <x <= 1.5) is obtained.

Next, FIG. 2 shows an example of an apparatus for manufacturing the above medium.

In this manufacturing apparatus, in manufacturing the medium shown in FIG. 1A, first, the film-like support 1 fed from the supply roll 32 is extruded by the extrusion coaters 10 and 11 to form the magnetic layers 2 and 4 described above. After applying each paint, for example, 2000
It is oriented by the Gauss's pre-orientation magnet 33, and further, for example, 2
000 Gauss is introduced into a drier 34 in which a rear-stage magnet 35 is disposed, where it is dried by blowing hot air from nozzles disposed above and below.

Next, the dried support 1 with each coating layer is a super calender device comprising a combination of calender rolls 38.
After being guided to 37, where it is calendered, it is taken up by a take-up roll 39. Each paint may be supplied to the extrusion coaters 10 and 11 through an inline mixer (not shown). Note that, in the figure, the arrow D indicates the transport direction of the non-magnetic base film.

Each of the extrusion coaters 10 and 11 has a liquid pool portion.
13 and 14 are provided, and paint from each coater is overlaid in a wet-on-wet manner. In order to manufacture the medium of FIG. 1B, one more extrusion coater may be added in FIG.

In particular, the medium of the present invention is suitable when each magnetic layer is formed by wet-on-wet coating. Of course, after drying the lower layer, apply the upper layer wet-on-dry
It may be a method.

Examples of the coating method for forming the magnetic layer on the nonmagnetic support include, for example, gravure roll coating, myrbar coating, doctor blade coating, reverse roll coating, dip coating, air knife coating, and calendar coating. , Skies coating, kiss coating, extrusion coating and phantin coating.

The magnetic layer applied on the non-magnetic support is dried while performing a magnetic field orientation treatment. Next, a surface smoothing process is performed by calendaring. Thereafter, as required, burnishing or blade treatment is performed to perform slitting.

The present invention is applicable to magnetic tapes, magnetic disks, and the like.

[0068]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments.

The following components, ratios, and operation sequences can be variously changed without impairing the effects of the present invention.

(A) Examples 1 to 8 and 10 and Comparative Examples (1) to
(7): Study on the composition of the multilayer magnetic layer containing the Fe-Al-Ca-based ferromagnetic metal powder: Example 1 <Magnetic paint A for upper layer> 100 parts of Fe-Al-Ca-based ferromagnetic metal powder (Fe: Al: Ca = 100: 5: 1) (Hc: 16000e, σs: 122emμ / g, average major axis length 0.17μm, axial ratio 8) Sulfo group-containing vinyl chloride vinyl chloride resin 10 parts Sulfo group-containing polyurethane 5 parts Alumina ( 6 parts Carbon black (average particle diameter 50 mμ) 1 part Myristinic acid 2 parts Butyl stearate 1 part Methyl ethyl ketone 100 parts Cyclohexanone 100 parts Toluene 100 parts <Lower layer magnetic coating B> Magnetic powder in upper layer coating A Co
-Same as above, except that iron oxide (Hc: 800 Oe, average major axis length 0.16 μm, average minor axis length 330 °) was used. Each coating material having the above composition was prepared by kneading and dispersing. Next, a polyisocyanate compound (coronate) was added as a curing agent to the obtained upper layer magnetic paint and lower layer magnetic paint.
L: manufactured by Nippon Polyurethane Co., Ltd.), and then applied to a 10 μm-thick polyethylene terephthalate film by a wet-on-wet method. This is subjected to a magnetic field orientation treatment while the coating film is not dried, and subsequently subjected to drying and then to a calendar surface smoothing treatment to a thickness of 2.5
A magnetic layer consisting of a lower layer of μm and an upper layer of 0.5 μm was formed. Calendar conditions are temperature 80 ° C, pressure 300kg / cm ² , C / S
(Coating speed) 30 / min. Further, a coating for a back coat layer having the following composition was applied to the surface of the polyethylene terephthalate film opposite to the magnetic layer to form a back coat layer having a dried film thickness of 0.86 μm.

<Coating for Back Coat Layer> Carbon black (Raven 1035) 40 parts Barium sulfate (average particle diameter 300 mμ) 10 parts Nitrocellulose 25 parts Polyurethane (N-2301 manufactured by Nippon Polyurethane Co., Ltd.) 25 parts Polyisocyanate compound (Japan Polyurethane Corp. L) 10 parts Cyclohexanone 400 parts Methyl methyl ketone 250 parts Toluene 250 parts 8 mm video tape was prepared by slitting the thus obtained raw material.

Table 1 below shows the configurations and performance evaluation results of other similarly manufactured 8 mm video tapes.

Example 2 Fe—Al—Ca based ferromagnetic metal powder (Fe: Al:
Ca = 100: 5: 4) (Hc: 1600 Oe, σs: 12 Oemu / g, average major axis length 0.17 μm, axial ratio 7), except that Example 1 was used.

Example 3 Fe—Al—Ca ferromagnetic metal powder (Fe: Al: C
a = 100: 5: 0.5) (Hc: 1600 Oe, σs: 120 emu / g, average major axis length 0.17 μm, axial ratio 9).

Example 4 Fe—Al—Ca based ferromagnetic powder (Fe: Al: Ca =
100: 5: 0.1) (Hc: 1600 Oe, σs: 120 emu / g, average major axis length 0.17 μm, axial ratio 8).

Example 5 Fe—Al—Ca ferromagnetic powder (Fe: Al: Ca =
100: 5: 10), except that 100: 5: 10) was used.

Example 6 Fe—Al—Ca ferromagnetic powder (Fe: Al: Ca =
Same as Example 1 except that 100: 10: 2) was used.

Example 7 Fe—Al—Ca ferromagnetic powder (Fe: Al: Ca = 1) was used as the magnetic powder for the upper layer.
00: 0.5: 2) except that Example 1 was used.

Example 8 Fe—Al—Ca ferromagnetic powder (Fe: Al: Ca = 1) was used as the magnetic powder for the upper layer.
Same as Example 1 except that 00: 20: 2) was used.

Example 10 In the magnetic paint B for the lower layer in Example 1, the magnetic powder was changed to Co.
Same as above except that the contained iron oxide (Hc: 700 Oe, average major axis length 0.24 μm, average minor axis length 415 mm) was used.

Comparative Example (1) Fe—Al—Ca ferromagnetic powder (Fe: Al: Ca =
100: 5: 0.05).

Comparative Example (2) Same as Example 1 except that Fe: Al: Ca = 100: 5: 15 was used as the magnetic powder for the upper layer. Comparative Example (3) Same as Example 1 except that Fe: Al: Ca = 100: 0.2: 2 was used as the magnetic powder for the upper layer.

Comparative Example (4) Same as Example 1 except that Fe: Al: Ca = 100: 25: 2 was used as the magnetic powder for the upper layer. Comparative Example (5) Magnetic powder for upper layer Fe-Al-Ca-based ferromagnetic powder (Fe: Al: Ca = 100:
Same as Example 1 except that 5: 2 and the axial ratio 10) were used.

Comparative Example (6) Magnetic Powder for Upper Layer Fe—Al—Ca ferromagnetic powder (Fe: Al: Ca = 100:
Same as Example 1 except that 5: 2 and the axial ratio 11) were used.

Comparative Example (7) Magnetic powder for upper layer Fe-Al based ferromagnetic powder (Fe: Al = 100: 5, axial ratio)
Same as Example 1 except that 9) was used.

(B) Example 9 and Comparative Example (8): Examination of Single-Layer Magnetic Layer Containing Fe-Al-Ca System: Example 9 Using the upper layer formulation in Example 1, a film thickness of 3.0 μm was obtained. It was applied in a single layer to make an 8 mm sample. Comparative Example (8) A single layer was applied to a thickness of 3.0 μm using the upper layer formulation in the ratio-(7) to prepare an 8 mm sample.

[0087]

[Table 1]

(C) Reference Examples 11 to 15, Example 16 and Comparative Examples (9) to (11): Examination of Organic Dye Compound Having Polar Group: Reference Example 11 Ratio-Amount of myristic acid in (7) And 1 part of the organic dye compound of Exemplified Compound (19) was added.
the same as.

[0089] except for using, instead of the exemplary compound in Reference Example 12 participants -11 (5) (19) similar to ginseng -11.

[0090] Similarly, except for changing the 2 parts of the organic dye compound in Reference Example 13 participants -11.

[0091] Reference Example 14 and 1 part the amount of myristic acid in ginseng -11 undefined undefined 5 parts 〃 Reference Example 15 participants -11 undefined undefined 0.1 parts 〃 Example 16 real -1, organic dye compounds of the exemplary compound (19) Except for adding one part, the same as Real-1.

[0092] except for changing 0.05 parts quantity of the exemplary compound (19) in Comparative Example (9) participate -11 similar to ginseng -11.

[0093] except for changing the 6 parts amount of the exemplary compound (19) in Comparative Example (10) participation -11 similar to ginseng -11.

Using the upper layer formulation of Comparative Example (11), reference was made to a single layer having a thickness of 3.0 μm to prepare an 8 mm sample. Table 2 shows the results.

[0095]

[Table 2]

(D) Examples 17 to 21 and Comparative Examples (12) to (15): Examination of Dynamic Friction Coefficient: Example 17 The carbon black used for the uppermost layer in the ratio-(7) has the following characteristics. Co to be used for the lower layer
Ratio-(7) except that the contained iron oxide was changed to the one shown below
the same as.

Carbon black; average particle size 45 mμ, BET
Value 40m ² / g, Oil absorption 170ml / 100g ・ Magnetic powder used for lower layer: Magnetic iron oxide Hc 800 containing Si and Al treated Co: Oe, average major axis length 0.16μm, average minor axis length 330mm,
Si / Fe = 0.008, Al / Fe = 0.001 Example 18 The same as the ratio-(7), except that the polyurethane used for the lower layer in the ratio-(7) was changed to the one shown below.

Sulfo group-containing polyurethane Tg: 20 ° C. 3
Part Example 19 Same as Example 17 except that the film thickness of the upper layer was changed to 1.0 μm and the film thickness of the lower layer was changed to 2.0 μm.

Example 20 Same as Example 17 except that the carbon black in the upper layer formulation in Example 17 was changed to the one shown below.

Carbon black Average particle size 20mμ, BET
Value: 150 m ² / g, oil absorption: 110 ml / 100 g Example 21 Same as Example 17 except that the magnetic powder in the upper layer in Example 17 was changed to the one shown below.

Fe—Al—Ca ferromagnetic powder: Fe: Al: Ca = 100:
5: 2, Hc; 1600 Oe, σs; 120 emμ / g, average major axis length 0.16 μ
m, axial ratio 8 Comparative Example (12) Same as ratio- (7) except that carbon black used in the uppermost layer was changed to one having the following characteristics in ratio- (7).

Carbon black; average particle size 20 mμ, BET
200 m ² / g, oil absorption 110 ml / 100 g Comparative Example (13) Same as ratio -7 except that the polyurethane used for the lower layer was changed to the following in ratio-(7).

Sulfo group-containing polyurethane Tg: -23 ° C.
5 parts Comparative Example (14) Same as Example 17 except that the film thickness of the upper layer was changed to 1.5 μm and the film thickness of the lower layer was changed to 1.5 μm.

Comparative Example (15) A single layer was applied to a thickness of 3.0 μm using the upper layer formulation in Example-17 to prepare an 8 mm sample.

Table 3 shows the results.

[0106]

[Table 3]

(E) Examples 22 to 24 (Examination of magnetic powder: Part 2) Except that the Fe-Al-Ca system used for the uppermost layer in Example 1 was changed to the magnetic powder shown in Table 4, the result was actually -1. the same.

(F) Examples 25-27 The magnetic upper layer coating composition of Examples -22-24 was applied in a single layer of 3.0 μm.
8mm samples were made. The results are shown in Table 4.

[0109]

[Table 4]

(G) Examples 28 to 30 (Examination of magnetic powder: Part 3) Except that the Fe-Al-Ca system used in the uppermost layer in Example 1 was changed to the magnetic powder shown in Table 5, the result was actually -1. the same.

(H) Examples 31-33 The magnetic upper layer formulation paints of Examples -28-30 were applied in a single layer of 3.0 μm and applied in 8 m
m samples were made.

Table 5 shows the results.

[0113]

[Table 5]

: Measurement of characteristics: (a) Axial ratio The average major axis length and average minor axis length of 500 particles were measured by an electron microscope photograph, and were obtained as average major axis length / average minor axis length.

(B) RF output and chroma output (8 mm tape) Measurement was performed using an 8 mm video movie V900 (manufactured by Sony Corporation) using a noise meter 925C manufactured by Shibasoku. (Measurement unit:
dB) (c) Lumi S / N A 100% white signal is input at the reference level on the sample tape, and the reproduced video signal is input to a 921 D / 1 (Noise meter manufactured by Shibasoku Co., Ltd.). Lumi S from the value
/ N was read. (Measurement unit: dB) (d) Chroma S / N (8 mm tape) The difference between the S / N of the sample tape and the chroma signal in the chroma signal was obtained by comparison with a reference tape using a noise meter manufactured by Shibasoku. (Measurement unit: dB) (e) Dropout (D / O) For an 8mm tape, the number of dropouts that caused an output drop of -12dB or more by 5µS or more was measured using an 8mm video movie V900 (manufactured by Sony Corporation). . (f) Running durability (40 ° C, 80% RH) V-900 for 8mm wide tape as a measuring deck
(Sony), 50 passes (100 hours) of the tape running at 40 ° C, 80% temperature and humidity, and measured the ease of sticking to the head, the level of powder drop after running, and the head friction. .

The powder fall was evaluated on the following three levels based on the contamination of the deck pins and the head during cleaning.

A: There is almost no powder dropping B: Powder dusting is slightly observed C: Powder dusting is very large Regarding the sticking of the head, the sticking that did not occur in 50 passes was A, and the sticking after 30 passes was performed. Things B, 30
Those that were pasted before the pass were determined to be C.

Regarding the head wear, the wear amount of the head surface after the above-mentioned running was measured.

(G) Running Durability (40 ° C., 20% RH) S-550 (manufactured by Sony Corporation) was used as a measuring deck.
The tape was run for 2 full lengths (4 hours) at 20 ° C. and 20% temperature and humidity, and the number of head clogs in which the output decreased by 1 dB or more and the output decrease (dB) after the 2 passes were measured.

(H) Corrosion resistance After leaving the tape in an environment of NO ₂ (5 ppm) for 30 days, the image quality was evaluated and the state of clogging was evaluated.

A: no clogging B: slight clogging C: considerable clogging

[0122]

According to the present invention, a magnetic recording medium having excellent electromagnetic conversion characteristics, good running durability under conditions of high humidity to low humidity, and excellent clog, dropout and corrosion resistance. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a layer configuration of a magnetic recording medium according to an embodiment of the present invention.

FIG. 2 is a block diagram of an example of an apparatus for manufacturing a magnetic recording medium according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Non-magnetic support 2 Lower magnetic layer 3 Back coat layer 4, 6 Upper magnetic layer 5 Intermediate layer

Continuation of the front page (56) References JP-A-60-98525 (JP, A) JP-A-62-134824 (JP, A) JP-A-4-53023 (JP, A) JP-A-3-49026 (JP) JP-A-3-173925 (JP, A) JP-A-2-107701 (JP, A) JP-A-3-38005 (JP, A) JP-A-3-38306 (JP, A) 4-183803 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/716 G11B 5/706 G11B 5/70 H01F 1/06 G11B 5/708

Claims (3)

(57) [Claims] 1. A magnetic recording medium having at least one magnetic layer on a nonmagnetic layer support, wherein the magnetic layer has an axial ratio
Fe-Al-Ca system of less than 10 (however, in the above alloy composition, Al
/ Fe weight ratio; 0.005 to 0.2, Ca / Fe weight ratio; 0.001 to 0.1) or Fe-Al-Ca-Ni system, Fe-Al-Zn system, Fe-Ni-Al-Si-Me system (where Me is A magnetic recording medium comprising at least one ferromagnetic alloy powder particle of Mn, Zn and / or Co). 2. The magnetic recording medium according to claim 1, wherein the at least one magnetic layer is a multilayer, and the lower layer contains Co-containing iron oxide. 3. A magnetic recording medium in which a multilayer magnetic layer is provided on a non-magnetic support, wherein a meta layer on the uppermost layer of the multilayer magnetic layer is provided.
Lubrication coefficient against lupine at 20 ° C and 60% RH with μk
Value .mu.k _A, 40 ° C., and the value at _{80% RH μk B, 40 ℃} , 20%
When the value of RH and _{μk C, μk A> μk B} , μk A> μk C, μk A ≦ 0.30 not tighten the magnetic recording medium.