JPH0817046A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium capable of high density recording and excellent especially in output characteristics while ensuring superior running performance of a substrate at the time of production. 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 coefft. mum of kinematic friction of the magnetic substrate 1 is within the range of 0.10-0.70.

Description

Detailed Description of the Invention

[0001]

The present invention enables high density recording,
In particular, the present invention relates to a magnetic recording medium having excellent output characteristics and excellent running properties of a support during production.

[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, in order to meet the requirements for high-quality magnetic recording media, particularly excellent output characteristics,
Further, there is a strong demand for a magnetic recording medium having excellent support runnability during production. Therefore, an object of the present invention is to provide a magnetic recording medium capable of high density recording, particularly excellent in output characteristics, and excellent in running property of a support during production.

[0003]

As a result of intensive studies, the present inventors have used a magnetic support instead of the conventionally used non-magnetic support, and the dynamic friction coefficient μ of the magnetic support is within a specific range. It has been found that the magnetic recording medium in (1) can achieve the above object.

The present invention has been made on the basis of the above findings, and is a magnetic device comprising a magnetic support, a non-magnetic layer provided on the magnetic support, and a magnetic layer provided on the non-magnetic layer. The recording medium is a dynamic friction coefficient μ of the magnetic support.
The present invention provides a magnetic recording medium characterized by satisfying 0.10 ≦ μ ≦ 0.70.

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 has at least a magnetic portion A (see FIGS. 2a, 2c and 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.

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 elements 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. 2c and e, a multilayer of magnetic portion A and non-magnetic portion B. It may be a structure. That is, the magnetic support 1 is
The following configurations a, c and e can be adopted. a. As shown in FIG. 2 a, a structure consisting of a single layer of magnetic portion A only. c. As shown in FIG. 2C, the nonmagnetic portion B is provided on the surface of the magnetic portion A (the surface of the magnetic recording medium located on the magnetic layer 3 side). 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, 2c and 2e is 1 to 300 μm. 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. 2c and e is 1:99 to 99: 1, preferably 2:98 to 9.
It is preferably 8: 2, more preferably 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 the magnetic support having the structure shown in FIGS. In the body, 0.1 to 1000 parts by weight of magnetic powder, preferably 0.2 to 100 parts by weight, and more preferably 0.3 to 80 parts by weight, relative to 100 parts by weight of the thermoplastic resin.
It is desirable to use parts by weight.

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 of manufacturing 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. 2c and e. 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. 2c and 2e; the raw material mixture for the magnetic portion and the non-magnetic portion raw material 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 "coextrusion molding method",
In addition to the method of simultaneously extruding 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, the raw material mixture for the magnetic portion and the raw material for the non-magnetic portion Either one is extruded first to obtain a film-like material, and then the above-mentioned raw material mixture for magnetic part and / or the above-mentioned raw material for non-magnetic part is extruded onto the film-like material to form a two-layer or multi-layered material. There is a method of forming a magnetic support.

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 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 to improve dispersibility. 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 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.

Thus, in the magnetic recording medium according to the present invention, the dry thickness of the magnetic layer is preferably 0.05 to.
1.5 μm, more preferably 0.05 to 1.2 μm, 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 It is 3.5 μm, most preferably 0.5 to 3 μm.

In the magnetic recording medium according to the present invention, the dynamic friction coefficient μ of the magnetic support is preferably 0.10 to 0.70, more preferably 0.10 to 0.
60. This is because if the dynamic friction coefficient μ is less than 0.10, the output decreases and it cannot be put to practical use.
This is because if it exceeds 0.70, sticking or slippage occurs, and it becomes impossible to run during coating.

Next, the 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 carried out 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 above 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.

Further, the calendering treatment can be carried out by a super calendering method in which two rolls such as a metal roll and a cotton roll or 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 as necessary, is provided on the back surface (the surface on which the nonmagnetic layer and the magnetic layer are not provided) of the magnetic support 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.

[0039]

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 a): Single layer A polyethylene terephthalate granular material having an intrinsic viscosity of 0.60 and barium ferrite magnetic powder were mixed with the magnetic powder. Body 1
The mixture was adjusted to 0 wt% and melt-mixed using an extruder to obtain a mixture of particles, which was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours. Then, the mixture was formed into a film by adjusting the discharge amount (thickness) using a biaxial stretching film forming machine equipped with a die capable of melt extrusion. The obtained film has a lengthwise direction of 3.3 times and a width direction of 3.3 times.
The film was double-stretched and then heat-treated to obtain a magnetic support a having a thickness of 7.2 μm and the structure shown in FIG. 2a.

(Production of magnetic support c): 2 layers (upper magnetic part) Granules of polyethylene terephthalate having an intrinsic viscosity of 0.60 and acicular γ-Fe ₂ O ₃ magnetic powder are added to the magnetic powder. Body 1
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 polyethylene terephthalate granules having no magnetic material and co-extruded to obtain a double-layer film having a magnetic part in the upper part and a non-magnetic part in the lower part. 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 7.2 μm (thickness of the magnetic portion A of 1.5 μm). A magnetic support c having the structure shown in FIG.

(Production of magnetic support e) ... 3 layers (nonmagnetic part sandwiched by magnetic part) Granules of polyethylene terephthalate having an intrinsic viscosity of 0.60 and acicular γ-Fe ₂ O ₃ magnetic powder. The magnetic powder is 1
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 magnetic portions on both surfaces of the non-magnetic portion. The resulting film is
The 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 7.2 μm (thickness of the nonmagnetic portion B of 6.0 μm, nonmagnetic portion B of The thickness of the magnetic parts A provided on the front and back surfaces is 0.6 μm
A magnetic support e of m) was obtained.

[Production of Nonmagnetic Support] A film having a thickness of 7.2 μm was obtained in the same manner as the above magnetic support a except that only polyethylene terephthalate was used, which was used as a nonmagnetic support.

[Preparation of Magnetic Paint, Non-Magnetic Paint and Backcoat Paint] Into each of the following paint compositions, 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.

(Blending 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 1 part by weight Polyisocyanate (Coronate of Nippon Polyurethane Industry Co., Ltd.) L) 4 parts by weight Methyl ethyl ketone 100 parts by weight Toluene 50 parts by weight Cyclohexanone 100 parts by weight

(Blending of Non-Magnetic Paint) Needle-shaped α-iron oxide (average major axis length 0.07 μm) 100 parts by weight Carbon black (average primary particle size 0.023 μm) 8 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) 8 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 Polyisocyanate [Nippon Polyurethane Industry Co., Ltd., trade name “Coronate HX”] 2 parts by weight Oleyl oleate 0.8 parts by weight Myristic acid 1.5 parts by weight Methyl ethyl ketone 70 Parts by weight toluene 30 parts by weight cyclohexanone 100 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 (Ltd. ) Polyurethane] 20 parts by weight Nitrocellulose (Viscosity display made by Hercules Powder Co. of 1/2 second) 20 parts by weight Polyisocyanate (Takeda Pharmaceutical Co., Ltd., trade 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

[Production of Magnetic Recording Medium] The above magnetic support c
The non-magnetic coating material and the magnetic coating material on the surface of, so that the dry thicknesses are 0.4 μm and 1.6 μm, respectively.
Simultaneous multi-layer coating was carried out by the wet-on-wet method 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. Next, 85 ℃, 350kg / cm
After forming a non-magnetic layer and a magnetic layer by calendering under the conditions described in 1., a back coat paint is applied on the back surface of the above magnetic support to a dry thickness of 0.6 μm, and dried at 90 ° C. And then wound up. Then, it was aged at 50 ° C. for 16 hours and slit into 8 mm width to obtain an 8 mm width magnetic tape. With respect to the magnetic support c, the running property during coating of the nonmagnetic layer on the surface thereof,
The dynamic friction coefficient of the magnetic support and the output characteristics (7.7 MHz) of the magnetic tape were evaluated according to the following methods. The results are shown in [Table 1].

[Evaluation Method] ◎ Dynamic Friction Coefficient of Magnetic Support μ The above magnetic support was slit into a tape, and a tape running tester [Kyowa Tech Co., Ltd., trade name “TBT300”] was used.
D ”], and attach it to a 5 mm stainless steel fixed pin.
Tension T ₁ = 20 gf and contact angle of wrapping angle θ (2 radians) were applied to drive at 14.4 mm / sec. The dynamic friction coefficient μ was determined by the following equation, where T ₂ is the tension required for running the tape. μ = (1 / θ) ln (T ₂ / T ₁ )

Output Characteristics The obtained 8 mm wide magnetic tape was loaded into a VTR cassette to obtain a test VTR tape cassette. V for this test
The TR tape cassette was loaded into a device obtained by modifying a commercially available Hi8VTR, a 7.7 MHz signal was recorded on the magnetic tape, and the output (reproduction output) when the signal was reproduced was measured. The recording wavelength at 7.7 MHz was 0.54 μm.

Comparative Example 1 The nonmagnetic support and the magnetic tape obtained in the same manner as in Example 1 except that the nonmagnetic support was used were evaluated in the same manner as in Example 1. The results are shown in [Table 1].

Comparative Example 2 Example 1 is the same as Example 1 except that the support is adjusted to have a predetermined friction coefficient (μ = 0.85) by adjusting the particle size and the addition amount of the non-magnetic powder. The magnetic support and the magnetic tape obtained in the same manner were evaluated in the same manner as in Example 1. The results are shown in [Table 1].

<Comparative Example 3> Except that in Example 1, the support was adjusted to have a predetermined friction coefficient (μ = 0.07) by increasing the particle size of the non-magnetic powder and adjusting the addition amount. The support and the magnetic tape obtained in the same manner as in Example 1 were evaluated in the same manner as in Example 1. The results are shown in [Table 1].

[0054]

[Table 1]

As shown in Table 1, the dynamic friction coefficient μ is 0.
It was confirmed that the support of Example 1 in the range of 10 to 0.70 had normal running properties during coating, and the output of the magnetic tape using this was 0 dB. On the contrary,
Even if the dynamic friction coefficient of the support is within the above range, the magnetic tape using the conventionally used non-magnetic support (Comparative Example 1) shows no abnormality in the running property during coating. It was confirmed that the output was reduced as a magnetic tape. In addition, even if the magnetic support has a dynamic friction coefficient exceeding the upper limit of the above range or a dynamic friction coefficient less than the lower limit of the above range (Comparative Examples 2 and 3), it is not coated. May not be stable and the coating may become inoperable,
It was confirmed that the output of the obtained magnetic tape was lowered.

[0056]

INDUSTRIAL APPLICABILITY The magnetic recording medium according to the present invention is superior in output characteristics to the conventional one and is superior in running property of the support during production.

[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.

FIG. 2 is a schematic view showing a structure of a magnetic support of the above magnetic recording medium, (a) is a schematic view showing a structure in which only a magnetic portion is formed as a single layer, and (c) is a non-structure. Schematic showing a structure in which a magnetic portion is provided on the surface of the magnetic portion to form two layers, (e)
Is a schematic diagram 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 a three-layer structure, and FIG. is there.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic support, a non-magnetic layer provided on the magnetic support, and a magnetic layer provided on the non-magnetic layer. The dynamic friction coefficient μ is 0.10 ≦ μ ≦ 0.
70. A magnetic recording medium according to the present invention.