JPH0845051A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having a high squareness ratio and high toughness and excellent in contact with a head and output characteristics by forming a metallic thin film layer on a magnetic substrate when a nonmagnetic layer and a magnetic layer are successively formed on the substrate to obtain a magnetic recording medium. CONSTITUTION:A metallic thin film layer 4 is formed on a magnetic substrate 1 and a nonmagnetic layer 2 and a magnetic layer 3 are successively formed on the layer 4. A back coating layer 5 is formed on the rear side of the substrate 1 if necessary. The layer 4 is formed by laminating a metal such as Al or Cu or a metalloid such as Si or Ge on the substrate 1 by vapor deposition, plating or other method. The objective magnetic recording medium capable of high density recording is obtd.

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 a 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 particularly excellent output characteristics in order to meet the demand for a high-quality magnetic recording medium. Therefore, it is an object of the present invention to provide a magnetic recording medium having a high squareness ratio, a strong magnetic recording medium, excellent head contact, and particularly excellent output characteristics and capable of high density recording.

[0003]

DISCLOSURE OF THE INVENTION As a result of various studies, the inventors of the present invention used a magnetic support instead of the conventionally used non-magnetic support and provided a magnetic thin film layer on the support. It has been found that a recording medium can achieve the above object.

The present invention has been made based on the above findings, and comprises a magnetic support, at least a non-magnetic layer provided on the magnetic support, and a magnetic layer provided on the non-magnetic layer. A magnetic recording medium comprising: a magnetic thin film layer provided on the magnetic support.

The magnetic recording medium of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the magnetic recording medium 10 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. It has and. In the magnetic recording medium 10, the magnetic support 1 is provided with a metal thin film layer 4, and the metal thin film layer 4 is the same as the magnetic support 1 in the magnetic support 1 and the nonmagnetic layer. It is provided between the two. Further, in the magnetic recording medium 10 shown in FIG. 1, a back coat layer 5 is provided on the back surface of the magnetic support 1 if necessary.

Next, each member (magnetic layer 3, magnetic support 1, non-magnetic layer 2 and metal thin film layer 4) constituting the magnetic recording medium 10 will be described. The magnetic support 1 has at least a magnetic portion A (see FIG. 2) including a matrix component made of a thermoplastic resin and a filler component made of magnetic powder.
(See a to e).

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.

As the magnetic powder, ferromagnetic powder such as metal magnetic powder or oxide-based magnetic powder can be used. Specific examples of the above oxide-based magnetic powder include the following. Iron oxide magnetic powder such as γ-iron oxide and magnetite; Cr, Mn,
Ferromagnetic powder containing a metal such as Co or Ni added thereto; chromium dioxide; a metal such as Na, K, Fe or Mn added to the chromium dioxide;
Ferromagnetic powder to which a non-metal element such as P or an oxide thereof is added; micro tabular barium ferrite; part of Fe atoms of the barium ferrite is Ti, Co, Zn, V
Ferromagnetic powder substituted with atoms such as. In addition, specific examples of the magnetic metal powder include Fe-Co, Fe-Ni, and Fe-A.
1, Fe-Ni-Al, Co-Ni, Fe-Co-N
i, Fe-Ni-Al-Zn, Fe-Al-Si, etc. are mentioned.

Further, in the present invention, as the magnetic powder, soft magnetic powder or iron oxide powder having a low remanent magnetization (hereinafter referred to as "low remanent magnetization iron oxide powder") used in magnetic toner is used. May be. The soft magnetic powder is a magnetic powder made of a metal, a metal oxide, an alloy, an amorphous alloy or the like and known as a powder having a high magnetic permeability and a low coercive force. 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 "(Shokabo, 1984), pages 368-376, soft magnetic materials can be used. Specific examples of the soft magnetic powder preferably used in the present invention include:
Iron-silicon alloy, iron-aluminum alloy, iron-nickel alloy, iron-cobalt alloy, iron-cobalt-nickel alloy,
Examples thereof include nickel-cobalt alloy, sendust, manganese-zinc ferrite, nickel-zinc ferrite, magnesium-zinc ferrite, magnesium-manganese ferrite, and the like. The low remanent magnetization iron oxide powder has a remanent magnetization of about 10 emu / g,
Examples thereof include magnetite powder having a coercive force of 150 Oe or less.

In the present invention, in order to improve the dispersibility of the magnetic powder such as the ferromagnetic powder, the soft magnetic powder and the low remanent magnetization iron oxide powder, the magnetic powder is surface-treated. 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 may 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, and more preferably 10 μm or less (1 to 10 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, but the thermoplastic resin used as the matrix component of the magnetic portion A can be preferably 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 the formation material. 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 appropriately changed according to the desired coercive force, saturation magnetization, etc., but in the magnetic support having the structure shown in FIGS. Is 0.1 to 1000 parts by weight of magnetic powder, preferably 0.1 to 100 parts by weight of the thermoplastic resin.
2 to 100 parts by weight, more preferably 0.3 to 80 parts by weight is desirable.

As another structure of the magnetic support, a non-magnetic film 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 constitution of the film body A ′ shown in FIG.
10 to 1500 parts by weight of magnetic powder with respect to 00 parts by weight,
Preferably 200 to 1200 parts by weight, more preferably 5
It is desirable that the amount is from 0.00 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. 2b-e is a preferred method for producing a magnetic support; the raw material mixture for the magnetic portion and the raw material for the non-magnetic portion mainly composed of the thermoplastic resin are coextruded using a molding machine capable of melt extrusion. A method of molding into a desired configuration. 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 500 parts by weight, and particularly preferably 5 to 200 parts by weight, based on 100 parts by weight of the non-magnetic powder.

Examples of the solvent include ketone solvents, ester solvents, ether solvents, aromatic hydrocarbon solvents, chlorinated hydrocarbon 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, a rust preventive, a fungicide, 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.

Further, 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-mentioned magnetic coating material, for example, the above-mentioned magnetic powder and the above-mentioned binder are charged together with a part of the solvent into a Nauter 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 dry thickness of the magnetic layer is preferably 0.
05-1.5 μm, more preferably 0.05-1.2 μm
m, most preferably 0.1 to 1 μm, and the dry thickness of the nonmagnetic layer is preferably 0.5 to 4 μm, more preferably 0.5 to 3.5 μm, and most preferably 0.5 to 3 μm.
μm.

The metal thin film layer 4 provided on the magnetic support 1 is provided by laminating a metal or a semimetal on the magnetic support 1 by a known means such as a vapor deposition method, a sputtering method or a plating method. It is a layer. Examples of the metal forming the metal thin film layer 4 include aluminum, nickel, chromium, copper, iron, silver, gold, platinum, palladium,
Examples thereof include zinc, tin, and lead. Among them, aluminum and copper are particularly preferably used because of their cost and stability after oxidation, and when the metal thin film layer is formed by vapor deposition, the vapor deposition rate is fast. Further, as the semimetal forming the metal thin film layer, silicon, germanium, arsenic,
Examples thereof include scandium and antimony. Among them, silicon is particularly preferably used in terms of cost and vapor deposition rate. The above metal and semimetal can be used alone or as a mixture appropriately mixed, and carbon,
It can also be used by alloying with nitrogen or the like.

The thickness of the metal thin film layer 4 is preferably 0.005 to 5 μm, more preferably 0.01 to 5 μm.
It is 1.0 μm. The film thickness of the metal thin film layer 4 is 0.0
If it is less than 05 μm, the effect of increasing the tape strain is insufficient, and if it exceeds 5 μm, the strain of the tape becomes too strong, and tape deformation such as cupping or curling occurs, and the head contact deteriorates. Preferably.

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

Next, the outline of the method for producing the magnetic recording medium of the present invention will be described. First, a vapor deposition method on the magnetic support,
A metal thin film layer is provided by a sputtering method, a plating method, or the like. At this time, a vapor deposition method and a sputtering method are preferable.
Further, the metal thin film layer is preferably subjected to an oxidation treatment or the like in order to improve its stability (anticorrosion property), adhesion, and hardness. Examples of the oxidation treatment include, for example, in the case of forming the metal thin film layer by vapor deposition in Japanese Patent Publication No.
A method of introducing a reactive gas such as oxygen gas, nitrogen gas, carbon dioxide gas, etc. into a metal thin film forming portion in a chamber for vapor deposition, which is described in column 2, line 27 to column 4, line 20 of Japanese Patent Publication No. 56563. Specifically, it can be carried out by the following method.

To form the metal thin film, a vacuum chamber provided with an evaporation source, an electron gun for heating the evaporation source, a reactive gas introducing nozzle adjacent to the evaporation source, a tape carrier, etc. is used. . 10 ^-4 to 10 ^-7 Tor in the above vacuum chamber
Under vacuum of r, 0.5 to 100 m of original magnetic support
It is conveyed at a traveling speed of / min and 0.0
While introducing oxygen gas in an amount of 3 to 1000 cc / min, the metal material is heated and evaporated to be laminated on the magnetic support to continuously form an oxidized metal thin film on the magnetic support. At this time, in the portion where the evaporated metal is laminated on the magnetic support, the magnetic support is usually wound around a cooling can in order to prevent deformation of the magnetic support due to heating. .

Then, on the above-mentioned metal thin film layer, first, the above-mentioned non-magnetic coating material and above-mentioned magnetic coating material are wet-coated on the above-mentioned magnetic support so that the dry thicknesses of the non-magnetic layer and the magnetic layer become the above-mentioned thickness, respectively. Simultaneous multilayer coating is performed by an on-wet method to form a coating film 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, when a magnetic tape is to be obtained, it is aged at 40 to 70 ° C. for 6 to 72 hours and slit 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, finishing steps such as polishing and 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.

In the magnetic recording medium of the present invention, the metal thin film layer 4 is formed on the back surface side of the magnetic support 1, that is, the magnetic support 1 and the back coat layer 5 as shown in FIG. It can be provided between and. It can also be provided on both the front surface and the back surface of the magnetic support 1.

[0044]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

<Example 1> [Production of magnetic support] (Production of magnetic supports b and c) ... 2 layers (upper layer is non-magnetic portion) Granules of polyethylene terephthalate having an intrinsic viscosity of 0.60 and needles And a magnetic powder of γ-Fe ₂ O ₃
The mixture 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 5 μm.
A magnetic support having a two-layer structure consisting of a magnetic portion A and a nonmagnetic portion B (having a thickness of the magnetic portion A of 1 μm) was obtained. Hereinafter, the case where the nonmagnetic portion B is used as the front surface and the magnetic portion A is used as the back surface (when used as the structure shown in FIG. 2b) in the obtained magnetic support is referred to as the magnetic support b, and the magnetic portion A is used. Is used as the front surface and the non-magnetic portion B is used as the back surface (the structure shown in FIG. 2c) is referred to as a magnetic support c.

(Production of magnetic support d): 3 layers (sandwich magnetic layer) Granules of polyethylene terephthalate having an intrinsic viscosity of 0.60 and acicular γ-Fe ₂ O ₃ magnetic powder 1 powder
The mixture was adjusted to be 5 wt% and melt-mixed using an extruder to obtain a mixture of particles. Then, the mixture was supplied with a polyethylene terephthalate granular material having no magnetic material and co-extruded to obtain a triple film having nonmagnetic portions on both sides of the magnetic portion. The obtained film is stretched and calendered, and then stretched in the longitudinal direction.
The film is stretched 3 times and 3.3 times in the width direction and then heat treated to give a total thickness of the magnetic support of 5 μm (the thickness of the magnetic portion A is 1 μm.
m, and the thickness of each of the non-magnetic portions B provided on the front surface and the back surface of the magnetic portion A was 2 μm) to obtain a magnetic support d.

[Production of Nonmagnetic Support] Extrusion molding was performed using only the above polyethylene terephthalate to obtain a film having a thickness of 5 μm, which was used as a nonmagnetic support.

[Preparation of Magnetic Paint, Non-Magnetic Paint, and Backcoat Paint] Into each of the following paint formulations, components other than polyisocyanate, fatty acid, and fatty acid ester were put into a Nauta mixer together with a part of the solvent. The mixture was 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, Magnetic paint and back coat paint were obtained.

(Composition of Magnetic Paint) Needle-like metal magnetic powder mainly composed of iron (coercive force 1860 Oe, saturation magnetization 137 emu / g, average major axis length 0.1 μm) 100 parts by weight Alumina (average particle size 0.3 μm) 9 parts by weight Carbon black (average primary particle size 20 nm) 1 part by weight Sulfonic acid group-containing vinyl chloride resin (sulfonic acid group content 1.5 × 10 ⁻⁴ eq / g) 9 parts by weight Sulfonic acid group-containing polyurethane (GPC Number average molecular weight 25,000, sulfonic acid group 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 [manufactured by Nippon Polyurethane Industry Co., Ltd., product Name "Coronate L"] 4 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 50 parts by weight Cyclohexanone 100 parts by weight

(Composition of non-magnetic coating material) Needle-like α-iron oxide (average major axis length 0.07 μm) 90 parts by weight Carbon black (average primary particle size 0.023 μm) 7 parts by weight Alumina (average particle size 0.2 μm) ) 3 parts by weight Sulfonic acid group-containing vinyl chloride resin (sulfonic acid group content 1.5 × 10 ^-4 eq / g) 5 parts by weight Sulfonic acid group-containing polyurethane (GPC number average molecular weight 25,000, sulfonic acid group content 1 9 × 10 ⁻⁴ eq / g) 8 parts by weight Oleyl oleate 2 parts by weight Myristic acid 1 part by weight Methyl ethyl ketone 60 parts by weight Toluene 30 parts by weight Cyclohexanone 90 parts by weight

(Blending of back coat paint) Carbon black (average primary particle size 0.028 μm) 32 parts by weight Carbon black (average primary particle size 0.062 μm) 8 parts by weight “Nipporan 2301” [trade name, Nippon Polyurethane Industry ( Polyurethane manufactured by Co., Ltd.] 20 parts by weight nitrocellulose (viscosity display made by Hercules Powder Co. of 1/2 second) 20 parts by weight polyisocyanate (trade name “D-250N” manufactured by Takeda Pharmaceutical Co., Ltd.) 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

[Production of Magnetic Recording Medium] The magnetic support c
2 × on the surface of (the magnetic portion A of the magnetic support c)
10 ^-FiveDeposition of aluminum under vacuum of Torr
A metal thin film layer having a thickness shown in [Table 1] was formed. Also on
When performing vapor deposition, the metal thin film forming part in the vapor deposition chamber
Oxygen gas is introduced into the chamber and vapor deposition is performed in the coexistence of oxygen gas.
Then, the metal thin film layer subjected to the oxidation treatment was prepared. Above magnetism
The width of the support c is 150 mm, and the running of the magnetic support c
The speed is 2 m / min and the amount of oxygen gas introduced is 70 c
It was c / min. Then, the non-magnetic paint and the
Magnetic paint and dry thickness of 0.2 μm and 1.
Wet-on-wet method to achieve 0 μm
More simultaneous multi-layer coating to coat non-magnetic and magnetic layers
Formed. Then, when the coating film is wet, 5000O
The magnetic field orientation processing is performed by passing through the solenoid of e.
After being dried at 0 ° C., it was wound up. Then 85
Calendered under the conditions of ℃ and 350kg / cm,
After forming the non-magnetic layer and the magnetic layer, the back surface of the magnetic support is formed.
Backcoat paint on the surface becomes dry thickness of 0.6μm
And then dry at 90 ° C, then wind
It was Then, aging treatment for 16 hours at 50 ° C
Then, slit it to a width of 8 mm to obtain the 8 mm wide structure shown in FIG.
I got a magnetic tape.

With respect to the obtained magnetic tape, the squareness ratio, the output, the output fluctuation and the stiffness were measured according to the following measuring methods. The results are shown in [Table 1]. still,
The output, the output fluctuation, and the stiffness are obtained as follows.

[Measurement Method] ◎ Square Ratio Measured with a vibrating magnetometer. The applied magnetic field at this time is 10
It was kOe. Output (7 MHz) The obtained 8 mm wide magnetic tape was loaded into an 8 mm VTR cassette to obtain a test 8 mm VTR tape cassette. Obtained test 8mm VTR tape cassette and commercial Hi8V
Using a device modified from TR, 7M was added to the above magnetic tape.
A Hz signal was recorded and the output (reproduction output) when the signal was reproduced was measured. The recording wavelength of 7MHz is 0.54μ
It was m. Output fluctuation In measuring the recording / reproducing characteristics, the value of output fluctuation between tracks defined by the following equation was measured. Output fluctuation (%) = B / A × 100 A: maximum value of output between 1 tracks [V] B: minimum value of output between tracks [V] That is, the larger the value obtained by the above equation is the output It can be said that the envelope characteristics are good with little fluctuation. ∘ Stiffness A loop-shaped test piece having a magnetic layer having a circumference of 30 mm as an outer side was prepared by sticking both ends of an approximately 60 mm section of a tape having a width of 8 mm with adhesive tape. This test piece is a stiffness tester Model PB-02 manufactured by Kyowa Tech Co., Ltd.
Then, the indenter was moved at 10 mm / min and the load when 5 mm was pushed in was measured, and this was taken as the stiffness.

Example 2 Copper was vapor-deposited on the back surface of the magnetic support c (on the nonmagnetic portion B of the magnetic support c) to form a metal thin film layer having a thickness shown in [Table 1]. A magnetic tape having the structure shown in FIG. 3 was obtained in the same manner as in Example 1 except for the above. The obtained magnetic tape was evaluated in the same manner as in Example 1. The results are shown in [Table 1].

Example 3 A metal thin film layer having a thickness shown in Table 1 was formed by vapor-depositing silicon on the front surface and the back surface of the magnetic support d (on both non-magnetic portions B of the magnetic support d). In the same manner as in Example 1 except that the magnetic thin film layer of the present invention is provided between the surface of the magnetic support d and the non-magnetic layer 2 and on the back surface of the magnetic support. Magnetic tape). The obtained magnetic tape was evaluated in the same manner as in Example 1. The results are shown in [Table 1].

Example 4 Aluminum was vapor-deposited on the surface of the magnetic support b (on the non-magnetic portion B of the magnetic support b) to form a metal thin film layer having a thickness shown in [Table 1]. ,
Further, except that the thickness of the back coat layer is 0.5 μm,
A magnetic tape having the structure shown in FIG. 1 was obtained in the same manner as in Example 1. The obtained magnetic tape was evaluated in the same manner as in Example 1. The results are shown in [Table 1].

Example 5 Copper was vapor-deposited on the surface of the magnetic support c (on the magnetic part A of the magnetic support c) to form a metal thin film layer having a thickness shown in [Table 1]. A magnetic tape having the structure shown in FIG. 1 was obtained in the same manner as in Example 1 except that the film thickness of the back coat layer was 0.4 μm. The obtained magnetic tape was evaluated in the same manner as in Example 1. The results are shown in [Table 1].

Comparative Example 1 A magnetic tape was obtained in the same manner as in Example 1 except that a non-magnetic support was used instead of the magnetic support c, and no metal thin film layer was provided. About the obtained magnetic tape,
Evaluation was carried out in the same manner as in Example 1. The results are shown in [Table 1].

Comparative Example 2 A nonmagnetic support was used in place of the magnetic support c, and aluminum was vapor-deposited on the surface of the nonmagnetic support to form a metal thin film layer having a thickness shown in [Table 1].
Further, except that the thickness of the back coat layer is 0.5 μm,
A magnetic tape was obtained in the same manner as in Example 1. The obtained magnetic tape was evaluated in the same manner as in Example 1.
The results are shown in [Table 1].

[0061]

[Table 1]

[0062]

The magnetic recording medium of the present invention has a high squareness ratio, a strong stiffness of the magnetic recording medium, excellent head contact, and particularly high output characteristics and high density recording.

[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.

FIG. 3 is a schematic cross-sectional view showing another structure of the magnetic recording medium according to the present invention.

[Explanation of symbols]

 10 magnetic recording medium 1 magnetic support 2 non-magnetic layer 3 magnetic layer 4 metal thin film layer 5 back coat layer

Claims (7)

[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. A magnetic recording medium characterized in that a metal thin film layer is provided on a support. 2. The magnetic recording medium according to claim 1, wherein the metal thin film layer is formed of a metal and / or a semimetal. 3. The magnetic recording medium according to claim 1, wherein the metal thin film layer is provided between the magnetic support and the nonmagnetic layer. 4. A magnetic recording medium according to claim 1, wherein the metal thin film layer is provided on the lower surface of the magnetic support. 5. The magnetic recording medium according to claim 3, wherein the metal thin film layer is oxidized. 6. The metal thin film layer has a thickness of 0.005 to 0.005.
The magnetic recording medium according to claim 5, which has a thickness of 5.0 μm. 7. The magnetic recording medium according to claim 5, wherein the magnetic support has a thickness of 10 μm or less, and the metal thin film layer has a thickness of 0.01 to 1.0 μm.