JPH0817048A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium capable of high density recording and having superior output characteristics. CONSTITUTION:This magnetic recording medium consists essentially of a magnetic substrate 1, a nonmagnetic layer 2 formed on the substrate 1 and a magnetic layer 3 formed on the nonmagnetic layer 2. The magnetic substrate 1 contains soft magnetic powder or iron oxide powder having low residual magnetization.

Description

Detailed Description of the Invention

[0001]

The present invention enables high density recording,
In particular, it relates to a magnetic recording medium having excellent output characteristics.

[0002]

2. Description of the Related Art Conventionally, magnetic recording media have been widely used in the form of tapes, disks, drums or sheets. Such a magnetic recording medium is usually manufactured by coating a nonmagnetic support such as a polyester film with a magnetic coating material containing magnetic powder and a binder as main components. In recent years, in particular, there has been a demand for miniaturization of magnetic recording media and high density recording, and in order to meet such demands, for example, an attempt to improve coercive force or saturation magnetization or a magnetic layer Proposals have been made to reduce the thickness. In addition to the above requirements, there is a strong demand for a magnetic recording medium having excellent output characteristics in order to meet the demand for a high-quality magnetic recording medium. Therefore, an object of the present invention is to provide a magnetic recording medium capable of high density recording and particularly excellent in output characteristics.

[0003]

As a result of intensive studies, the present inventors have used a magnetic support in place of the conventionally used non-magnetic support, and the magnetic support is a soft magnetic powder or a low magnetic powder. It has been found that a magnetic recording medium containing a remanently magnetized iron oxide powder can achieve the above object.

The present invention has been made based on the above findings, and comprises a magnetic support, at least a nonmagnetic layer provided on the magnetic support, and a magnetic layer provided on the nonmagnetic layer. A magnetic recording medium, wherein the magnetic support contains a soft magnetic powder or a low remanent magnetization iron oxide powder.

The magnetic recording medium of the present invention will be described in detail below. As shown in FIG. 1, the magnetic recording medium according to the present invention includes a magnetic support 1, a non-magnetic layer 2 provided on the magnetic support 1, and a magnetic layer 3 provided on the non-magnetic layer 2. And a back coat layer 4 is provided on the back surface of the magnetic support 1 as required.

The magnetic support 1 comprises at least a magnetic portion A (see FIGS. 2a to 2e) consisting of a matrix component made of a thermoplastic resin and a filler component made of magnetic powder.

Examples of the thermoplastic resin include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycyclohexylene dimethylene terephthalate and polyethylene bisphenoxycarboxylate, polyolefins such as polyethylene and polypropylene, and cellulose acetate butyrate. Cellulose derivatives such as cellulose acetate propionate, vinyl-based resins such as polyvinyl chloride and polyvinylidene chloride, or polyamides, polyimides, polycarbonates, polysulfones, polyether / etherketones, polyurethanes and the like are used. These resin components may be used alone or in combination.

In the magnetic support according to the present invention, as the magnetic powder, a soft magnetic powder or an iron oxide powder having a low remanent magnetization used in a magnetic toner or the like (hereinafter referred to as "low remanent magnetization iron oxide powder") is used. ) Etc. are preferably used. Here, the soft magnetic powder is a magnetic powder known to have a high magnetic permeability and a low coercive force, which is made of a metal, a metal oxide, an alloy, an amorphous alloy, or the like. In the present invention, any soft magnetic powder can be used, but those used for so-called weak electric devices such as magnetic heads and electronic circuits are particularly preferable. ) Magnetic Properties and Applications "(Sohkabo, 1984) 36
Soft magnetic materials described on pages 8 to 376 can be used. Specific examples of the soft magnetic powder preferably used in the present invention include iron-silicon alloys, iron-aluminum alloys, iron-nickel alloys, iron-cobalt alloys, iron-cobalt-nickel alloys, nickel-cobalt alloys, sendust, manganese. -Zinc based ferrite, nickel-zinc based ferrite, magnesium-zinc based ferrite, magnesium-manganese based ferrite and the like can be mentioned.

In the present invention, only the magnetic layer is involved in recording / reproduction, and the magnetic support has a magnetic field orientation advantageous in terms of magnetic recording when forming the non-magnetic layer or the magnetic layer. It has the effect of improving. As a result of various studies, it was found that the soft magnetic powder and the low remanent magnetization iron oxide powder contained in the magnetic support give more effective magnetic field orientation as follows. That is, the low remanent magnetization iron oxide powder has a remanent magnetization of 30 emu / g or less,
Preferably 15 emu / g or less, more preferably 10 e
γ of mu / g or less and coercive force of 150 Oe or less, preferably 1200 e or less, and more preferably 1000 e or less.
--Fe ₂ O ₃ , iron oxide powder such as magnetite, etc. can be used. Further, the soft magnetic powder, the low remanent magnetization iron oxide powder and the like can be obtained in a desired size by pulverization and classification.

In the present invention, in addition to the soft magnetic powder or the low remanent magnetization iron oxide powder, a ferromagnetic powder such as a metal magnetic powder or an oxide-based magnetic powder may be used together. The preferable composition in this case is 2 to 5000 parts by weight of the ferromagnetic powder with respect to 100 parts by weight of the soft magnetic powder or the low remanent magnetization iron oxide powder. Specific examples of the above oxide-based magnetic powder include the following. γ-iron oxide magnetic powder such as iron oxide and magnetite; ferromagnetic powder obtained by adding metals such as Cr, Mn, Co and Ni to the iron oxide magnetic powder; chromium dioxide;
a, K, Fe, Mn and other metals, P and other non-metal elements or ferromagnetic oxides added thereto; fine tabular barium ferrite; some of Fe atoms in the barium ferrite are Ti, Co, Ferromagnetic powder substituted with atoms such as Zn and V. Further, as a specific example of the metal magnetic powder, Fe is
-Co, Fe-Ni, Fe-Al, Fe-Ni-Al,
Co-Ni, Fe-Co-Ni, Fe-Ni-Al-Z
n, Fe-Al-Si, etc. are mentioned.

In the present invention, the magnetic powder is surface-treated in order to improve the dispersibility of the magnetic powder such as the soft magnetic powder, the low remanent magnetization iron oxide powder and the ferromagnetic powder. May be given. The surface treatment is "Charac
terization of Powder Surfaces "; can be carried out by a method similar to the method described in Academic Press, and examples thereof include a method of coating the surface of the magnetic powder with an inorganic oxide. At this time, the inorganic oxides that can be used include Al ₂ O ₃ , SiO ₂ , and TiO ₂ .
₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , ZnO and the like can be mentioned, and when used, they can be used alone or in combination of two or more. The surface treatment can be performed by an organic treatment such as a silane coupling treatment, a titanium coupling treatment and an alumina coupling treatment other than the above method.

The magnetic support 1 may be composed of a single layer having only the magnetic portion A as shown in FIG. 2a, or as shown in FIGS. 2b to 2e, the magnetic portion A and the non-magnetic portion B may be multi-layered. It may be a structure. That is, the magnetic support 1 can have the following configurations a to e. a. As shown in FIG. 2 a, a structure consisting of a single layer of magnetic portion A only. b. As shown in FIG. 2B, the nonmagnetic portion B is provided on the surface of the magnetic portion A (the surface located on the magnetic layer 3 side in the magnetic recording medium). c. As shown in FIG. 2c, the magnetic part A is provided on the surface of the non-magnetic part B. d. As shown in FIG. 2D, a non-magnetic portion B is provided on each of the front surface and the back surface of the magnetic portion A. e. As shown in FIG. 2e, the nonmagnetic portion B is provided with magnetic portions A on the front surface and the back surface, respectively.

Here, the preferable thickness of the entire magnetic support having the structure shown in FIGS. 2A to 2E is 1 to 300 μm. Further, the ratio of the thickness of the magnetic portion A to the thickness of the non-magnetic portion B in the magnetic support having the configuration shown in FIGS.
1:99 to 99: 1, preferably 2:98 to 98: 2,
More preferably, the ratio is 5:95 to 95: 5.

The material for forming the non-magnetic portion B is not particularly limited as long as it is a non-magnetic material. However, the thermoplastic resin used as the matrix component of the magnetic portion A can be preferably used, and the thermoplastic resin can be used. Although the non-magnetic portion B can be formed only by itself, in order to control the surface property and running property of the outer surface of the non-magnetic portion B to be a predetermined value, the material for forming the non-magnetic portion B is It is preferable to use materials to which various fillers are added. Examples of the filler used in this case include the non-magnetic powder described below used for forming the non-magnetic layer, and the particle size thereof is preferably 0.8 μm or less, more preferably 0.0
2 to 0.2 μm, and its content (blending amount)
Is preferably 5% by weight or less in the non-magnetic portion, and more preferably 0.01 to 2% by weight.

The composition of the thermoplastic resin and the magnetic powder in the magnetic portion A can be changed as appropriate.
In the magnetic support having the structure shown in Tables 1 to e, 0.1 to 1000 parts by weight of the magnetic powder, preferably 0.2 to 100 parts by weight, and more preferably 0.3 to 100 parts by weight of the thermoplastic resin. 80 parts by weight is desirable.

As another structure of the magnetic support, a non-magnetic film body may be coated with a magnetic paint as shown in FIG. 2f. In this case, the non-magnetic portion is the non-magnetic film body B'and the magnetic portion is the magnetic film body A'formed by the magnetic paint containing the magnetic powder. Figure 2f
In the magnetic support having the structure shown in FIG.
10 to 1500 parts by weight of magnetic powder, preferably 200 to 1200 parts by weight, more preferably 50 parts by weight relative to 0 parts by weight.
It is desirable that the amount be 0 to 1000 parts by weight.

Next, a preferred method for producing the above magnetic support will be described separately for the magnetic support having the structure shown in FIG. 2a and the magnetic support having the structure shown in FIGS. A preferred method for producing a magnetic support having the structure shown in FIG. 2a;
After the thermoplastic resin and the magnetic powder are sufficiently dried, they are mixed in the above composition range and melt-mixed using an extruder to obtain a mixture of particles (raw material mixture for magnetic part). A method of molding using a molding machine capable of melt extrusion. The magnetic powder may be mixed at the same time as the reaction monomer is added during the polymerization of the thermoplastic resin, or may be added and mixed during the polymerization of the thermoplastic resin.

A preferred method for producing the magnetic support having the structure shown in FIGS. 2b to e; the raw material mixture for the magnetic portion and the raw material for the non-magnetic portion mainly composed of the thermoplastic resin are melt-extruded using a molding machine. A method of coextrusion to form a desired composition. In addition, as the above-mentioned "co-extrusion molding method", in addition to the method of simultaneously extrusion-molding the raw material mixture for the magnetic portion and the raw material for the non-magnetic portion to form a two-layer or multi-layer magnetic support, Either one of the raw material mixture for the magnetic portion and the raw material for the non-magnetic portion is extruded first to obtain a film-like material, and then the raw material mixture for the magnetic portion and / or the non-magnetic material is further formed on the film-like material. There is a method of forming a two-layer or multi-layer magnetic support by extrusion-molding a raw material for parts.

The magnetic support having the structure shown in FIG. 2f can be manufactured by the following method. In the process of extrusion molding using only the non-magnetic part raw material, the magnetic coating material is applied at any stage of the molding process to form the magnetic film body (magnetic part) A ′, A method for producing a magnetic support. However, in this case,
The above-mentioned magnetic film body A ′ in the configuration shown in FIG.
Is preferably one that does not swell or dissolve in the solvent used when forming the nonmagnetic layer and the magnetic layer provided on the film A ′.

When manufacturing the above magnetic support,
When forming the magnetic portion A or the magnetic film A ′, a magnetic field orientation treatment and a calender treatment can be performed, if necessary.

The magnetic support used in the present invention is obtained by manufacturing the magnetic support having the structure shown in FIG. 2f by the above-mentioned method and the like, and further, magnetic properties in the magnetic support having the structure shown in FIG. 2f. It may be manufactured by extruding the above-mentioned raw material for the non-magnetic portion or the like onto the film body A ′ or the like to form the non-magnetic portion B or the like.

The non-magnetic layer provided on the magnetic support is a layer formed by coating a non-magnetic paint on the magnetic support. The non-magnetic coating material used when forming the non-magnetic layer is preferably a coating material composed of non-magnetic powder, a binder and a solvent, or a coating material composed of the binder and the solvent. The non-magnetic powder is not particularly limited as long as it is non-magnetic, but carbon black, graphite, titanium oxide, barium sulfate, zinc sulfide, magnesium carbonate, calcium carbonate, zinc oxide, calcium oxide, magnesium oxide, tungsten disulfide. , Molybdenum disulfide, boron nitride, tin dioxide, silicon dioxide, non-magnetic chromium oxide, alumina, silicon carbide, cerium oxide, corundum, artificial diamond, non-magnetic iron oxide,
Pomegranate, garnet, silica, silicon nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, diatomaceous earth, dolomite, resinous powder and the like, among them, carbon black, titanium oxide, barium sulfate,
Calcium carbonate, alumina, non-magnetic iron oxide and the like are preferably used. The non-magnetic powder may be subjected to the surface treatment described above in order to improve the dispersibility of the non-magnetic powder.

When the non-magnetic layer contains non-magnetic powder, the particle size of the non-magnetic powder is preferably 0.001.
˜3 μm, more preferably 0.005 to 1 μm, and most preferably 0.005 to 0.5 μm. The non-magnetic powder is preferably contained in the non-magnetic layer formed by applying the non-magnetic coating material in an amount of 5 to 99% by weight, more preferably 30 to 95% by weight, and most preferably 50 to 95% by weight. It is desirable to incorporate it in the above non-magnetic paint so that it is contained by weight.

The binder may be a thermoplastic resin, a thermosetting resin, a reactive resin, or the like, which may be used alone or as a mixture.
As the binder, specifically, vinyl chloride resin, polyester, polyurethane, nitrocellulose,
Epoxy resin and the like can be mentioned.
Resins and the like described in JP-A No. 162128, page 2, upper right column, line 19 to page 2, lower right column, line 19 and the like can be mentioned. Further, the binder may contain a polar group for improving dispersibility and the like. The amount of the binder used is preferably about 5 to 100 parts by weight, and particularly preferably 5 to 70 parts by weight, based on 100 parts by weight of the non-magnetic powder.

Examples of the above-mentioned solvent include ketone-based solvents, ester-based solvents, ether-based solvents, aromatic hydrocarbon-based solvents, chlorinated hydrocarbon-based solvents, and the like. The solvents described in JP-A-57-162128, page 3, lower right column, line 17 to page 4, lower left column, line 10 and the like can be used.

In addition, the non-magnetic coating material contains additives usually used in magnetic recording media, such as a dispersant, a lubricant, an abrasive, an antistatic agent, an anticorrosive agent, an antifungal agent, and a curing agent. , Can be added if necessary. As the above additives,
Specifically, it is described in JP-A-57-162128, page 2, upper left column, line 6 to page 2, upper right column, line 10 and page 3, upper left column, line 6 to third page upper right column, line 18 and the like. Various additives may be mentioned.

To prepare the above non-magnetic paint, for example,
The non-magnetic powder and the binder are charged together with a part of the solvent into a Nauter mixer or the like to be premixed to obtain a mixture, and the obtained mixture is kneaded by a continuous pressure kneader or the like, and then it is mixed with the solvent. Examples include a method of diluting a part of the mixture, carrying out a dispersion treatment using a sand mill or the like, mixing an additive such as a lubricant, filtering, and further mixing the remaining solvent and a curing agent.

The magnetic layer provided on the non-magnetic layer is a layer formed by applying a magnetic paint on the non-magnetic layer. The magnetic paint used for forming the magnetic layer is preferably a paint containing magnetic powder, a binder, and a solvent as main components. Examples of the magnetic powder include ferromagnetic iron oxide, ferromagnetic chromium dioxide, and ferromagnetic metal powder.

The above ferromagnetic iron oxide is FeOx (1.33).
A metal such as Cr, Mn, Co, or Ni added to ≦ x ≦ 1.5) can be used. Further, the ferromagnetic chromium dioxide is CrO ₂ or Na, K, F in the CrO _2.
Metals such as e and Mn, oxides of the metals, and nonmetal elements such as P may be used. Examples of the ferromagnetic metal powder include ferromagnetic metal powders having a metal content of 70% by weight or more, and 80% by weight or more of at least one type of ferromagnetic metal (eg, Fe, Co, Ni). . Specific examples of the ferromagnetic metal powder include, for example,
Fe-Co, Fe-Ni, Fe-Al, Fe-Ni-A
1, Co-Ni, Fe-Co-Ni, Fe-Ni-Al
-Zn, Fe-Al-Si, etc. are mentioned.

The magnetic powder may contain, if necessary,
A rare earth element or a transition metal element can be contained. In addition, as the magnetic powder, fine tabular barium ferrite and some of its Fe atoms are Ti, Co, Z.
Magnetic powders substituted with atoms such as n and V can also be used. The magnetic powder may be subjected to the above-mentioned surface treatment in order to improve the dispersibility of the magnetic powder.

As the binder and the solvent used in the magnetic paint, the same binders and solvents as those used in the non-magnetic paint can be used. Also,
The amount of the binder used is preferably about 5 to 100 parts by weight with respect to 100 parts by weight of the magnetic powder, and 5 to 7 parts by weight.
It is particularly preferable to use 0 part by weight. Further, the above-mentioned additives used in the above-mentioned non-magnetic paint can be added to the above-mentioned magnetic paint.

To prepare the above magnetic paint, for example, the above magnetic powder and the above binder together with a part of the solvent are put into a Nauta mixer or the like and premixed to obtain a mixture, and the obtained mixture is continuously added. After kneading with a pressure kneader or the like, then diluting with a part of the solvent and dispersing treatment using a sand mill or the like, mixing additives such as a lubricant and filtering, and further curing agents such as polyisocyanate and the rest. And the like.

In the magnetic recording medium according to the present invention, the thickness of the magnetic layer is preferably 0.05-1.
The thickness is 5 μm, more preferably 0.1 to 1.2 μm. The thickness of the nonmagnetic layer is preferably 0.5 μm or more, more preferably 0.5 to 3.5 μm. When the thickness of the magnetic layer is less than 0.05 μm, uniform coating becomes difficult, the output decreases, and dropout increases,
This is because if the thickness exceeds 1.5 μm, the output decreases due to the thickness loss. Further, if the thickness of the non-magnetic layer is less than 0.5 μm, the stiffness of the tape will be reduced, resulting in poor head contact and reduced output.

Further, the coercive force of the magnetic layer is preferably 1300 to 2500, more preferably 1300 to 24.
It is 00 Oe. If the coercive force is less than 1300 Oe, the output characteristics in the high frequency band will be insufficient and 2500
This is because if Oe is exceeded, the head magnetic field will be insufficient and the output characteristics will deteriorate in both cases.

The magnetic recording medium according to the present invention is mainly 8 mm.
It is suitable as a magnetic tape such as a video tape or a DAT tape, but can also be used as another recording medium such as a floppy disk.

Next, an outline of the method for producing the magnetic recording medium of the present invention will be described. First, wet-on the non-magnetic coating material and the magnetic coating material on the magnetic support so that the dry thicknesses of the non-magnetic layer and the magnetic layer are the above-mentioned thicknesses.
Simultaneous multi-layer coating is performed by a wet method to form coating films for the non-magnetic layer and the magnetic layer. Next, the coating film is subjected to a magnetic field orientation treatment, followed by a drying treatment and winding. After that, calendering is performed if necessary, and then a back coat layer is further formed if necessary. Then, if necessary, for example, in the case of obtaining a magnetic tape, 40 to 70
Aging treatment is performed at a temperature of 6 to 72 hours for slitting to a desired width.

The above-mentioned simultaneous multilayer coating method is disclosed in JP-A-5-73.
No. 42, line 31 to column 43, line 31, etc. of Japanese Patent No. 883, the above-mentioned magnetic coating material for forming the above-mentioned magnetic layer is applied before the above-mentioned non-magnetic coating material for forming the above-mentioned non-magnetic layer is dried. In this method, since the boundary surface between the non-magnetic layer and the magnetic layer is smooth and the surface property of the magnetic layer is good, dropout is small, high density recording is possible, and the coating film (magnetic layer Also, a magnetic recording medium having excellent durability of the (and non-magnetic layer) can be obtained.

The magnetic field orientation treatment is performed before the magnetic paint is dried. For example, when the magnetic recording medium of the present invention is a magnetic tape, the magnetic paint is applied in a direction parallel to the coated surface of the magnetic paint. About 500 Oe or more, preferably about 1000
It can be performed by a method of applying a magnetic field of 10,000 to 10,000 Oe, a method of passing a magnetic paint through a solenoid or the like of 1,000 to 10,000 Oe in a wet state.

The drying treatment is carried out, for example, at 30 to 120 ° C.
The heating can be performed by supplying the gas heated to the above temperature. At this time, the drying degree of the coating film can be controlled by controlling the temperature of the gas and the supply amount thereof.

The above calendering treatment can be carried out by a super calendering method in which two rolls such as a metal roll and a cotton roll, a synthetic resin roll, a metal roll and a metal roll are passed. Also,
The conditions for the calendar treatment are 60 to 140 ° C. and 100
It can be up to 500 kg / cm.

The backcoat layer, which is provided if necessary, is provided on the back surface of the magnetic support (the surface on which the nonmagnetic layer and the magnetic layer are not provided), and is usually a backcoat. It is obtained by applying the back coat paint used for forming the layer on the magnetic support. The back coat paint is obtained by appropriately selecting and mixing the non-magnetic powder, the binder, the dispersant, the lubricant, the curing agent, the solvent and the like described in detail in the non-magnetic paint. The back coat paint can be prepared by a generally known back coat paint manufacturing method. In the production of the magnetic recording medium of the present invention, a finishing step such as polishing or cleaning of the magnetic layer surface may be carried out, if necessary. The non-magnetic coating material and the magnetic coating material can be applied by a generally known sequential multi-layer coating method.

[0042]

EXAMPLES Next, the magnetic recording medium according to the present invention will be described more specifically by the following examples. The present invention is not limited to this embodiment.

<Example 1> [Production of magnetic support] (Production of magnetic support) Polyethylene terephthalate particles having an intrinsic viscosity of 0.60 and Ni-Zn ferrite magnetic powder (average particle diameter 0.02 [mu] m) were used. The magnetic powder is 1
It was adjusted to be 5 wt% and melt-mixed using an extruder to obtain a mixture of particles. Then, the mixture and a polyethylene terephthalate granular material containing no magnetic material were coextruded to obtain a double-layer film. The obtained film was stretched 3.3 times in the longitudinal direction and 3.3 times in the width direction, and then heat-treated to give a total thickness of the magnetic support of 7.5 μ.
m (thickness of the magnetic portion A is 2 μm) having the structure shown in FIG. 2b was obtained.

(Production of Magnetic Support) The magnetic support was prepared in the same manner as the above magnetic support except that Mn—Zn ferrite (average particle diameter 0.015 μm) was used instead of the above Ni—Zn ferrite. , Magnetic support total thickness 7.5
A magnetic support having a structure shown in FIG. 2c having a thickness of 3 μm (thickness of the magnetic portion A) was obtained.

(Production of Magnetic Support) Instead of the above Ni—Zn ferrite as the magnetic powder, magnetite powder (average particle diameter 0.09 μm, spherical shape, coercive force 700 e, saturation magnetization 84 emu / g, residual magnetization 7 emu / 2c of the magnetic support with a total thickness of 7.5 μm (thickness of the magnetic part A is 3 μm) in the same manner as the above magnetic support except that g) was used.
A magnetic support having the structure shown in was obtained.

[Production of Nonmagnetic Support] A film having a thickness of 7.5 μm was obtained in the same manner as the above magnetic support except that only polyethylene terephthalate was used, which was used as the nonmagnetic support.

[Preparation of Magnetic Coating Material, Non-Magnetic Coating Material and Back Coating Layer Coating Material] Each of the following coating composition components except polyisocyanate, fatty acid and fatty acid ester was added to a Nauta mixer together with a part of the solvent. The mixture was charged and premixed to obtain a mixture, and the obtained mixture was kneaded by a continuous pressure kneader. Then, after diluting with a part of the solvent and dispersing with a sand mill, the fatty acid and the fatty acid ester are mixed, filtered, and the remaining solvent (and polyisocyanate) is further mixed to obtain a magnetic coating, A magnetic paint and a back coat layer paint were obtained.

(Composition of Magnetic Coating A) Needle-like metal magnetic powder mainly composed of iron (Fe: Al: Ba: Si: Ni: Co = 85: 2: 1: 1: 3: 8, coercive force 1860 Oe, saturation Magnetization 137 emu / g, average long axis length 0.1 μm, specific surface area 61 m ² / g, X-ray particle size 138 Å, axial ratio 8, moisture 0.9% 100 parts by weight Alumina (average particle size 0.3 μm, ratio Surface area 11 m ² / g) 9 parts by weight carbon black (average primary particle size 20 nm) 1 part by weight Sulfonic acid group- and epoxy group-containing vinyl chloride resin (sulfonic acid group content 1.5 × 10 ⁻⁴ eq / g, epoxy Group content 6 × 10 ⁻⁴ eq / g, average degree of polymerization 250) 9 parts by weight Sulfonic acid group-containing polyurethane (GPC number average molecular weight 25000, GPC weight average molecular weight 49000, sulfonic acid content 1.9 × 10) ^-4 eq / g) 7 parts by weight Stearic acid 1.5 parts by weight 2-Ethylhexyl oleate 2 parts by weight Polyisocyanate [Nippon Polyurethane Industry Co., Ltd. trade name "Coronate L"] 4 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 50 parts by weight Part cyclohexanone 100 parts by weight

(Composition of Magnetic Paint B) Needle-like metal magnetic powder mainly composed of iron (Fe: Al: Y: Si: Ni: Co = 65: 5: 3: 1: 1: 25 coercive force 2090 Oe, saturation magnetization 141 emu / g, average long axis length 0.11 μm, specific surface area 59 m ² / g, X-ray particle size 165 Å, axial ratio 8, water content 0.9% 100 parts by weight Alumina (average particle size 0.3 μm, specific surface area) 11 m ² / g) 9 parts by weight carbon black (average primary particle size 20 nm) 1 part by weight Sulfonic acid group- and epoxy group-containing vinyl chloride resin (sulfonic acid group content 1.5 × 10 ⁻⁴ eq / g, epoxy group Content 6 × 10 ⁻⁴ eq / g, average degree of polymerization 250) 9 parts by weight Sulfonic acid group-containing polyurethane (GPC number average molecular weight 25,000, GPC weight average molecular weight 49000, sulfonic acid content 1.9 × 10) ^-4 eq / g) 7 parts by weight Stearic acid 1.5 parts by weight 2-Ethylhexyl oleate 2 parts by weight Polyisocyanate [Nippon Polyurethane Industry Co., Ltd. trade name "Coronate L"] 4 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 50 parts by weight Part cyclohexanone 100 parts by weight

(Composition of Magnetic Paint C) Barium ferrite (coercive force 1580 Oe, saturation magnetization 52 emu / g, average particle diameter 0.05 μm, plate ratio 5) 100 parts by weight Alumina (average particle diameter 0.3 μm, specific surface area 11 m ² / g) 5 parts by weight carbon black (average primary particle size 20 nm) 3 parts by weight Sulfonic acid group- and epoxy group-containing vinyl chloride resin (sulfonic acid group content 1.5 × 10 ⁻⁴ eq / g, epoxy group-containing) Amount 6 × 10 ⁻⁴ eq / g, average degree of polymerization 250) 8 parts by weight Sulfonic acid group-containing polyurethane (GPC number average molecular weight 25000, GPC weight average molecular weight 49000, Sulfonic acid content 1.9 × 10 ⁻⁴ eq / g ) 5 parts by weight Stearic acid 1.5 parts by weight 2-ethylhexyl oleate 2 parts by weight Polyisocyanate [Nippon Polyurethane Industry Co., Ltd. Ronate L ”] 3 parts by weight Methyl ethyl ketone 80 parts by weight Toluene 40 parts by weight Cyclohexanone 80 parts by weight

(Composition of Magnetic Paint D) Needle-like metal magnetic powder mainly composed of iron (Fe: Al: Ca: Si: Ni = 92: 3: 1.5: 0.5: 3, coercive force 1260 Oe, saturation Magnetization 143 emu / g, average major axis length 0.14 μm, specific surface area 49 m ² / g, X-ray grain size 175 Å, axial ratio 11, moisture 0.7% 100 parts by weight Alumina (average grain size 0.3 μm, ratio Surface area 11 m ² / g) 7 parts by weight Carbon black (average primary particle size 20 nm) 3 parts by weight Sulfonic acid group- and epoxy group-containing vinyl chloride resin (sulfonic acid group content 1.5 × 10 ⁻⁴ eq / g, epoxy group content 6 × 10 ^-4 eq / g, average polymerization degree 250) 9 parts by weight of the sulfonic acid group-containing polyurethane (GPC number average molecular weight 25000, GPC weight average molecular weight 49000, acid content 1.9 × 1 ^-4 eq / g) 7 parts by weight 1.5 parts by weight of stearic acid, 2-ethylhexyl oleate 2 parts by weight Polyisocyanate [Nippon Polyurethane Industry Co., trade name "Coronate L"] 4 parts by weight Methyl ethyl ketone 100 parts Toluene 50 weight Part cyclohexanone 100 parts by weight

(Composition of magnetic paint E) Barium ferrite (coercive force 2930 Oe, saturation magnetization 50 emu / g, average particle diameter 0.06 m, plate ratio 5) 100 parts by weight Alumina (average particle diameter 0.3 μm, specific surface area 11 m ² / g) 5 parts by weight carbon black (average primary particle size 20 nm) 3 parts by weight Sulfonic acid group- and epoxy group-containing vinyl chloride resin (sulfonic acid group content 1.5 × 10 ⁻⁴ eq / g, epoxy group-containing) Amount 6 × 10 ⁻⁴ eq / g, average degree of polymerization 250) 8 parts by weight Sulfonic acid group-containing polyurethane (GPC number average molecular weight 25000, GPC weight average molecular weight 49000, Sulfonic acid content 1.9 × 10 ⁻⁴ eq / g ) 5 parts by weight Stearic acid 1.5 parts by weight 2-ethylhexyl oleate 2 parts by weight Polyisocyanate [Nippon Polyurethane Industry Co., Ltd. Sulfonates L "] 3 parts by weight Methyl ethyl ketone 80 parts Toluene 40 parts by weight Cyclohexanone 80 parts by weight

(Composition of Non-Magnetic Paint) Needle-like α-Fe ₂ O ₃ (average major axis length 0.07 μm, axial ratio 6, surface treated with Al ₂ O ₃ ) 100 parts by weight carbon black (average primary particle size) 0.023 μm, specific surface area 125 m ² / g, D BP oil absorption 56 g / 100 g, pH 2.5 8 parts by weight Alumina (average particle size 0.2 μm, specific surface area 14 m ² / g) 3 parts by weight Sulfonic acid group and epoxy Group-containing vinyl chloride resin (sulfonic acid group content 1.5 × 10 ⁻⁴ eq / g, epoxy group content 6 × 10 ⁻⁴ eq / g, average degree of polymerization 250) 8 parts by weight Sulfonic acid group-containing polyurethane ( GPC number average molecular weight 25000, GPC weight average molecular weight 49000, sulfonic acid group content 1.9 × 10 ⁻⁴ eq / g) 6 parts by weight Polyisocyanate [Nippon Polyurethane Industry Co., Ltd., trade name “Coronate H” X ”] 3 parts by weight Oleyl oleate 1 part by weight Myristic acid 1 part by weight Methyl ethyl ketone 80 parts by weight Toluene 40 parts by weight Cyclohexanone 120 parts by weight

(Blending Composition for Backcoat Layer) Carbon black (average primary particle size 0.028 μm, specific surface area 65 m ² / g, DBP oil absorption 53 g / 100 g, pH 2.5) 32 parts by weight carbon black (average primary particle size Particle size 0.062 μm, specific surface area 35 m ² / g, DBP oil absorption 62 g / 100 g, pH 8.0 8 parts by weight Nippon Polyurethane Co., Ltd. trade name “Nipporan 2301” 20 parts by weight Nitrocellulose (Hercules Powder Co. Manufactured by Viscosity display 1/2 second) 20 parts by weight Polyisocyanate [Takeda Pharmaceutical Co., Ltd. product name "D-250N"] 4 parts by weight Copper phthalocyanine 5 parts by weight Stearic acid 1 part by weight Methyl ethyl ketone 120 parts by weight Toluene 120 parts by weight Cyclohexanone 120 parts by weight

[Manufacture of Magnetic Recording Medium] The non-magnetic paint and the magnetic paint B were simultaneously coated on one surface of the magnetic support by a wet-on-wet method so that the dry thickness was the value shown in Table 1. Multi-layer coating was performed to form coating films for the non-magnetic layer and the magnetic layer. Then, while the coating film was in a wet state, the coating film was passed through a solenoid of 5000 Oe for magnetic field orientation treatment, dried at 80 ° C., and then wound. Then, calendering is performed under the conditions of 85 ° C. and 350 kg / cm to form a non-magnetic layer and a magnetic layer, and then the back coat layer coating material is dried to a thickness of 0.5 μm on the back surface of the magnetic support. Thus, it was dried at 90 ° C. and wound up. Then, it was aged at 50 ° C. for 16 hours and slit to a width of 3.81 mm to obtain a magnetic tape having a width of 3.81 mm for testing. Then, the magnetic characteristics of the magnetic support and the magnetic layer, and the output characteristics (7.5 MHz) of the magnetic tape were measured according to the following measuring methods. The results are shown in [Table 1].

[Measurement Method] ◎ Magnetic Properties For the magnetic support, the magnetic support was punched into a predetermined size and shape, and the magnetic layer coated on the non-magnetic layer was coated with the above-mentioned magnetic material using an adhesive tape. Only the magnetic layer was peeled from the support, punched out into a predetermined size in the same manner as the above magnetic support, and each was measured with an applied magnetic field of 10 kOe using a vibrating magnetometer.

◎ Output The obtained 3.81 mm magnetic tape for test was used for DAT for test.
It was loaded in a cassette to obtain a DAT tape cassette for testing. This DAT tape cassette for testing is commercially available as Medi
Product name "Tape Evaluat" manufactured by a Logic
or Model 4500 ”, a 7.5 MHz signal was recorded on the magnetic tape, and the output (reproduction output) when the signal was reproduced was measured. The recording wavelength at 7.5 MHz was 0.42 μm.

<Example 2> The same procedure as in Example 1 was carried out except that the above magnetic support was used as the magnetic support and the thicknesses of the non-magnetic layer and the magnetic layer were set to the values shown in Table 1, respectively. The magnetic support, magnetic layer, and magnetic tape were evaluated according to the method of Example 1. The results are shown in [Table 1].

Example 3 The magnetic support was used as the magnetic support, the magnetic paint was used as the magnetic paint, and the thicknesses of the non-magnetic layer and the magnetic layer were set to the values shown in Table 1, respectively. About the magnetic support, the magnetic layer and the magnetic tape obtained in the same manner as in Example 1,
Evaluation was carried out according to the method of. The results are shown in [Table 1].

Example 4 The same procedure as in Example 1 was carried out except that the above magnetic coating material C was used as the magnetic coating material and the thicknesses of the non-magnetic layer and the magnetic layer were set to the values shown in Table 1, respectively. About magnetic support, magnetic layer and magnetic tape,
Each was evaluated according to the method of Example 1. The results are shown in [Table 1].

Comparative Example 1 The same procedure as in Example 1 was carried out except that the above non-magnetic support was used in place of the magnetic support and the thicknesses of the non-magnetic layer and the magnetic layer were set to the values shown in Table 1. The magnetic support, the magnetic layer and the magnetic tape obtained as described above were evaluated according to the method of Example 1, respectively. The results are shown in [Table 1].

Comparative Example 2 A magnetic support, a magnetic layer and a magnetic tape obtained in the same manner as in Example 4 except that the above non-magnetic support was used in place of the magnetic support were the same as those in Example 1. It evaluated according to the method. The results are shown in [Table 1].

Comparative Example 3 A magnetic support, a magnetic layer and a magnetic tape obtained in the same manner as in Example 4 except that the above non-magnetic support was used in place of the magnetic support were the same as those in Example 1. It evaluated according to the method. The results are shown in [Table 1].

Comparative Example 4 A magnetic support was used as the magnetic support, the magnetic paint was used as the magnetic paint, and the thicknesses of the nonmagnetic layer and the magnetic layer were set to the values shown in Table 1, respectively. About the magnetic support, the magnetic layer and the magnetic tape obtained in the same manner as in Example 1,
Evaluation was carried out according to the method of. The results are shown in [Table 1].

Comparative Example 5 A magnetic support was used as the magnetic support, the magnetic paint was used as the magnetic paint, and the thicknesses of the non-magnetic layer and the magnetic layer were set to the values shown in Table 1, respectively. About the magnetic support, the magnetic layer and the magnetic tape obtained in the same manner as in Example 1,
Evaluation was carried out according to the method of. The results are shown in [Table 1].

Comparative Example 6 A magnetic support, a magnetic layer and a magnetic tape obtained in the same manner as in Example 2 except that the thicknesses of the non-magnetic layer and the magnetic layer were set to the values shown in Table 1, respectively. Evaluation was carried out according to the method of Example 1. The results are shown in [Table 1].

Comparative Example 7 The same procedure as in Example 1 was carried out except that the above magnetic support was used as the magnetic support and the thicknesses of the nonmagnetic layer and the magnetic layer were set to the values shown in Table 1, respectively. The magnetic support, the magnetic layer, and the magnetic tape were evaluated according to the method of Example 1, respectively. The results are shown in [Table 1].

[0068]

[Table 1]

As shown in Table 1, the above magnetic support containing soft magnetic powder or low remanent magnetization iron oxide was used, the thickness of the magnetic layer was 0.05 to 1.5 μm, and the magnetic layer was The magnetic tapes obtained by the above-mentioned respective examples having a coercive force of 1300 to 2500 Oe show output characteristics, while
Using a non-magnetic support that has been used conventionally,
The thickness of the magnetic layer was outside the above range (comparative example 7 could not be uniformly coated and the thickness could not be measured), and the coercive force of the magnetic layer was outside the above range (comparative example 5 had too high coercive force for recording It was confirmed that the output characteristics of those in the above example are inferior to those of each of the above-mentioned examples.

As described above, according to the magnetic recording medium of the present embodiment, excellent output characteristics can be obtained in the high frequency band.

[0071]

According to the magnetic recording medium of the present invention, high density recording is possible and excellent output characteristics can be obtained in a high frequency band.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a magnetic recording medium according to the present invention.

2A and 2B are schematic diagrams showing a structure of a magnetic support of the magnetic recording medium, FIG. 2A is a schematic view showing a structure in which only a magnetic portion is a single layer, and FIG. Schematic showing a structure in which a non-magnetic portion is provided on the surface of the portion to form two layers, (c)
Is a schematic diagram showing a configuration in which a magnetic portion is provided on the surface of a non-magnetic portion to form two layers, and (d) is a schematic diagram showing a configuration in which a non-magnetic portion is provided on each of the front surface and the back surface of the magnetic portion and forming three layers,
(E) is a schematic view showing a structure in which a magnetic portion is provided on each of the front surface and the back surface of the non-magnetic portion to form three layers, and (f) shows a configuration in which the magnetic portion is formed on the surface of the non-magnetic portion and formed into two layers. It is a schematic diagram.

Claims (3)

[Claims] 1. A magnetic recording medium comprising a magnetic support, at least a non-magnetic layer provided on the magnetic support, and a magnetic layer provided on the non-magnetic layer. Containing a soft magnetic powder or a low remanent magnetization iron oxide powder. 2. The thickness of the magnetic layer is 0.05 to 1.5 μm.
The magnetic recording medium according to claim 1, wherein the thickness of the non-magnetic layer is 0.5 μm or more. 3. The magnetic layer has a coercive force of 1300 to 25.
The magnetic recording medium according to claim 1 or 2, which is 00 Oe.