JP5257098B2 - Magnetic recording medium, tape cartridge, and tape drive system - Google Patents

Description

  The present invention relates to a magnetic recording medium having a magnetic layer, a method for manufacturing the magnetic recording medium, a tape cartridge, and a tape drive system.

  Conventionally, magnetic recording media having a magnetic layer containing magnetic powder or the like provided on the surface are widely known as video tapes, audio tapes, and the like. In order to record more information on these magnetic recording media, higher recording density and shorter wavelength recording are in progress.

  In addition, in order to correspond to a recording medium on which information is recorded at high density, an AMR (Anisotropic Magneto Resistive) head, a GMR (Giant Magneto Resistive) head, or a TMR (Tunneling Magneto Resistive) head is used. A head (MR (magneto resistive) head) is used. These magnetoresistive heads may be subject to electrostatic breakdown (ESD (electrostatic discharge) breakdown) due to electrostatic discharge with the surface of the magnetic layer. In recent years, along with the high density recording and short wavelength recording on the magnetic recording medium described above, the magnetoresistive effect element used in the magnetoresistive effect type magnetic head has been miniaturized. Destruction is a bigger problem.

  In order to prevent electrostatic breakdown of the magnetoresistive head, it is conceivable to reduce the surface electrical resistance value on the magnetic layer side of the magnetic recording medium and suppress charging on the surface of the magnetic layer. In Cited Document 1, the surface electrical resistance value on the magnetic layer side is reduced by coating the surface of the ferromagnetic powder contained in the magnetic layer with carbon black fine particles. Further, in Cited Document 2, the surface non-recording layer formed as the lower layer of the magnetic layer is internally added with carbon black adherent particles in which carbon black fine particles are adhered to the surface of the silica particles, so that the surface electricity on the magnetic layer side is added. The resistance value is reduced.

JP 2002-260214 A (paragraphs [0006], [0010]) Japanese Patent Laying-Open No. 2005-4858 (paragraph [0016], FIG. 2)

  However, the coating of the surface of the ferromagnetic powder with carbon black fine particles and the internal addition of carbon black deposited particles to the lower non-recording layer are not sufficient as an ESD countermeasure depending on the use environment. For example, in a low-humidity environment where static electricity is likely to occur, the magnetoresistive magnetic head may be electrostatically broken.

  In view of the circumstances as described above, an object of the present invention is to provide a magnetic recording medium, a method for manufacturing the magnetic recording medium, a tape cartridge, and a tape drive system that can suppress electrostatic breakdown of the magnetoresistive head. There is to do.

In order to achieve the above object, a magnetic recording medium according to an embodiment of the present invention includes a support, a nonmagnetic layer, and a magnetic layer.
The support has a first main surface.
The nonmagnetic layer is laminated on the first main surface and contains inorganic particles and first carbon black.
The magnetic layer is laminated on the nonmagnetic layer and contains ferromagnetic powder and second carbon black.

  According to the magnetic recording medium, since the first and second carbon blacks having conductivity are contained in the magnetic layer and the nonmagnetic layer, respectively, the electric charge charged on the surface of the magnetic recording medium on the magnetic layer side is magnetic. It can move in layers and nonmagnetic layers. Therefore, it is possible to prevent electric charges from accumulating on the surface of the magnetic recording medium on the magnetic layer side. Thereby, the discharge of static electricity from the magnetic recording medium to the magnetoresistive effect type magnetic head can be suppressed, and electrostatic breakdown of the magnetoresistive effect type magnetic head can be suppressed. Here, the first and second carbon blacks may be the same carbon black or different carbon blacks.

The second carbon black may have a specific surface area of 30 m ² / g or more and 130 m ² / g or less. The content of the second carbon black may be 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the ferromagnetic powder. The specific surface area mentioned here is the surface area per unit mass of the powder.

  As a result, it is possible to obtain a magnetic recording medium that realizes good C / N (Carrier to Noise ratio) characteristics, that is, good electromagnetic conversion characteristics, while suppressing electrostatic breakdown of the magnetoresistive head.

  The content of the first carbon black may be 20 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of the inorganic particles.

  The magnetic recording medium may further include a backcoat layer containing a third carbon black on the second main surface opposite to the first main surface.

  Thereby, electric charges charged on the surface of the magnetic recording medium on the magnetic layer side can move in the magnetic layer, the nonmagnetic layer, and the backcoat layer.

A method for manufacturing a magnetic recording medium according to an aspect of the present invention includes applying a first paint containing inorganic particles and first carbon black to a main surface of a support.
A second paint containing ferromagnetic powder and second carbon black is applied on the first paint.

  The first paint becomes a nonmagnetic layer containing the first carbon black, and the second paint becomes a magnetic layer containing the second carbon black.

  In the step of applying the second paint, the second paint may be applied after the first paint is dried.

For example, when the second paint is applied before the first paint is dried, the first carbon black enters the second paint or the second carbon black enters the first paint. There are cases. Then, even if the first and second paints contain the first and second carbon blacks in fixed amounts, the first and second contained in the nonmagnetic layer and the magnetic layer of the manufactured magnetic recording medium. Variation occurs in the content of the carbon black of No. 2.
Therefore, in the above manufacturing method, by adopting the above construction method, a magnetic material having a nonmagnetic layer and a magnetic layer respectively containing a predetermined amount of first and second carbon black contained in the first and second paints. A recording medium is manufactured. Thereby, a magnetic recording medium capable of suppressing electrostatic breakdown of the magnetoresistive effect type magnetic head can be manufactured with high yield.

A tape cartridge according to an aspect of the present invention includes a magnetic recording medium, a reel, and a cartridge body.
The magnetic recording medium includes a support having a main surface, a nonmagnetic layer laminated on the main surface and containing inorganic particles and first carbon black, and a ferromagnetic powder laminated on the nonmagnetic layer. And a magnetic layer containing the second carbon black.
The reel is wound with the magnetic recording medium.
The cartridge main body rotatably accommodates the reel.
Thereby, the discharge of static electricity from the magnetic recording medium to the magnetoresistive effect type magnetic head can be suppressed, and the electrostatic breakdown of the magnetoresistive effect type magnetic head can be suppressed.

A tape drive system according to an aspect of the present invention includes a magnetic recording medium and a drive.
The magnetic recording medium includes a support having a main surface, a nonmagnetic layer laminated on the main surface and containing inorganic particles and first carbon black, and a ferromagnetic powder laminated on the nonmagnetic layer. And a magnetic layer containing the second carbon black.
The drive has a magnetoresistive effect magnetic head for reproducing a signal recorded on the magnetic recording medium.
Thereby, the discharge of static electricity from the magnetic recording medium to the magnetoresistive effect type magnetic head can be suppressed, and the electrostatic breakdown of the magnetoresistive effect type magnetic head can be suppressed.

  As described above, according to the present invention, the electrostatic breakdown of the magnetoresistive effect type magnetic head can be suppressed.

1 is a schematic diagram showing a tape drive system according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a magnetic recording medium according to an embodiment of the present invention. It is a figure for demonstrating the manufacturing method of the magnetic-recording medium based on one Embodiment of this invention in which a wet on dry system is used. It is a table | surface which shows the specific surface area of various carbon black contained in the coating material for magnetic layers of each sample demonstrated in the Example of this invention. It is a table | surface which shows the kind and content of carbon black contained in the magnetic coating material of each sample demonstrated in the Example of this invention. It is a table | surface which shows the combination of the coating material for magnetic layers and the coating material for nonmagnetic layers of each sample demonstrated in the Example of this invention. It is a table | surface which shows the result of the various measurement and evaluation which were performed about each sample demonstrated in the Example of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, materials and methods are exemplified, but this does not mean that the materials and methods are limited.

[Tape drive system]
FIG. 1 is a schematic diagram showing a tape drive system according to an embodiment of the present invention. The tape drive system 100 includes a tape cartridge 1 and a drive 2.

  The tape cartridge 1 includes a magnetic recording medium 3, a tape reel 4 around which the magnetic recording medium 3 is wound, and a cartridge main body 5 that rotatably accommodates the tape reel 4. The magnetic recording medium 3 will be described in detail later as a magnetic recording medium according to an embodiment of the present invention.

  The drive 2 has a cartridge mounting portion 6 to which the tape cartridge 1 is mounted and a magnetic head 7. The drive 2 also has a magnetic recording medium guide mechanism having a guide body 8 such as a plurality of guide pins and guide rollers for guiding the magnetic recording medium 3 drawn from the tape cartridge 1 to the magnetic head 7. . The magnetic head 7 has a recording head unit and a reproducing head unit (not shown). The recording head unit records a signal on a magnetic recording medium. The reproducing head unit has a magnetoresistive effect element (MR element) and reproduces a signal recorded on the magnetic recording medium. As the MR element, for example, an AMR element, a GMR element, a TMR element, or the like is used.

  In the tape drive system 100 of the present embodiment, a tape winding unit 9 that is paired with the tape reel 4 is disposed outside the tape cartridge 1, and the magnetic reel 7 is interposed between the tape reel 4 and the tape winding unit 9. Thus, the magnetic recording medium 3 reciprocates. As a result, signal recording / reproduction by the magnetic head 7 is performed.

[Magnetic recording medium]
FIG. 2 is a schematic cross-sectional view showing a magnetic recording medium according to an embodiment of the present invention. The magnetic recording medium 10 includes a base film 11, a nonmagnetic layer 12 laminated on one main surface of the base film 11, and a magnetic layer 13 laminated on the nonmagnetic layer 12. The base film 11 also has a back coat layer 14 laminated on the main surface opposite to the main surface on which the nonmagnetic layer 12 and the magnetic layer 13 are laminated.

[Base film]
As the base film 11, a plastic film is typically used. Examples of the plastic film include polyesters, polyolefins, cellulose derivatives, vinyl resins, and the like. Examples of polyesters include polyethylene terephthalate and polyethylene naphthalate. Examples of polyolefins include polyethylene and polypropylene. Examples of cellulose derivatives include cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate. Examples of the vinyl resin include polyvinyl chloride and polyvinylidene chloride. In addition, polycarbonate, polyimide, polyamide, polyamideimide, or the like may be used as the plastic film.
In addition to the plastic film, a metal or alloy such as aluminum, copper, or titanium, paper, ceramics, single crystal silicon, or the like may be used as the base film 11. Moreover, in this embodiment, although the base film 11 which has a film-like form is used, what has forms, such as a tape, a sheet | seat, a disk, a card | curd, a drum, etc., is not restricted to this, For example, may be used. .

[Nonmagnetic layer]
The nonmagnetic layer 12 contains carbon black 15, inorganic particles 16, a binder (not shown) and various optional additives.

  Examples of the inorganic particles 16 contained in the nonmagnetic layer 12 include silica, titanium oxide, alumina, α-iron oxide, and calcium carbonate. Examples of the shape of the inorganic particles 16 include a needle shape, a spherical shape, and a plate shape.

  Examples of the carbon black 15 contained in the nonmagnetic layer 12 include furnace black, thermal black, acetylene black, channel black, and lamp black. These carbons may be used alone or in combination. Carbon may be surface-treated with a dispersant or the like, graphitized with a resin, or part of the surface graphitized.

  The content of the carbon black 15 in the nonmagnetic layer 12 is 20 to 100 parts by weight when the inorganic particles 16 are 100 parts by weight. As a result, good surface smoothness of the magnetic recording medium 10 is realized, and the surface electrical resistance value on the magnetic layer 13 side is reduced. Electric breakdown is suppressed.

As the binder contained in the nonmagnetic layer 12, various binder resins can be used. For example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-acetic acid. Vinyl-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid-vinylidene chloride copolymer Polymer, methacrylate ester-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl Butler , Cellulose derivatives, styrene - butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea - formaldehyde resin, or mixtures thereof.
Among these, a polyurethane resin, a polyester resin, or an acrylonitrile-butadiene copolymer is supposed to impart flexibility, and a cellulose derivative, a phenol resin, or an epoxy resin is assumed to impart rigidity. Yes. When these mixtures are used as a binder, durability may be improved by including, for example, an isocyanate compound as a crosslinking agent.

  Examples of various optional additives contained in the nonmagnetic layer 12 include a dispersant, a lubricant, an abrasive, an antistatic agent, and a rust preventive agent. These are contained in the nonmagnetic layer 12 as necessary.

  As the solvent used for forming the nonmagnetic layer 12, any solvent may be used as long as it is a paint adjusting solvent. For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Solvents, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ester, glycol ether solvents such as glycol monoethyl ether and dioxane, aromatic hydrocarbons such as benzene, toluene and xylene Examples of the solvent include organic chlorine compound solvents such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene.

  Although the thickness of the nonmagnetic layer 12 is not limited, for example, if the thickness of the nonmagnetic layer 12 is 3 μm or less, the surface electrical resistance value on the magnetic layer 13 side of the magnetic recording medium 10 is reduced and the magnetic recording medium 10 Thinning is achieved. Further, when a force is applied from the outside, a change due to the stress of the magnetic recording medium 10 is suppressed.

[Magnetic layer]
The magnetic layer 13 contains carbon black 17, ferromagnetic powder 18, and a binder (not shown).

  Examples of the ferromagnetic powder 18 contained in the magnetic layer 13 include, but are not limited to, a powder of ferromagnetic iron oxide, ferromagnetic chromium dioxide, ferromagnetic alloy, or iron nitride.

  As the binder contained in the magnetic layer 13, any of those exemplified as the binder resin contained in the nonmagnetic layer 12 may be used.

  As the carbon black 17 contained in the magnetic layer 13, any of those exemplified as the carbon black 15 contained in the nonmagnetic layer 12 may be used. Further, carbon black similar to the carbon black 15 may be contained in the magnetic layer 13 as the carbon black 17. Alternatively, carbon black different from the carbon black 15 may be contained in the magnetic layer 13 as the carbon black 17.

  Since the magnetic layer 13 and the nonmagnetic layer 12 contain conductive carbon blacks 17 and 15, respectively, the charges charged on the surface of the magnetic recording medium 10 on the magnetic layer 13 side are charged with the magnetic layer 13 and the nonmagnetic layer 12. You can move in. Accordingly, it is possible to prevent electric charges from accumulating on the surface of the magnetic recording medium 10 on the magnetic layer 13 side. Thereby, electrostatic discharge from the magnetic recording medium 10 to the MR head is suppressed, and electrostatic breakdown of the MR head can be suppressed.

The specific surface area of the carbon black 17 in the magnetic layer 13 is 30 m ² / g or more and 130 m ² / g or less. For example, carbon black 17 having a particle size of 20 nm and a specific surface area of 110 m ² / g can be used. The content of carbon black 17 in the magnetic layer 13 is 5 parts by weight or more and 10 parts by weight or less when the ferromagnetic powder 18 is 100 parts by weight.

When the specific surface area of the carbon black 17 contained in the magnetic layer 13 is smaller than the above range or the content is less than the above range, charges are accumulated on the surface on the magnetic layer 13 side, and the electrostatic capacity of the MR head is increased. Destruction may not be suppressed. On the other hand, when the magnetic layer 13 contains carbon black having a specific surface area larger than the above range or the carbon black content is more than the above range, the conductivity of the magnetic recording medium may become too high. As a result, charges charged on a tape reel included in the tape cartridge, a guide included in the tape drive system, or the like may be discharged to the MR head through the magnetic recording medium.
In addition, when the carbon black having a specific surface area larger than the above range is contained, the magnetic orientation of the ferromagnetic powder 18 of the magnetic layer 13 becomes insufficient, and a favorable squareness ratio cannot be obtained. It is also conceivable that the magnetic characteristics of 13 are deteriorated. A decrease in the magnetic characteristics of the magnetic layer 13 leads to a decrease in C / N characteristics, that is, a decrease in electromagnetic conversion characteristics.

  However, by setting the specific surface area and the content of the carbon black 17 in the magnetic layer 13 within the above ranges, the C / N characteristic, that is, the good electromagnetic conversion, while suppressing the electrostatic breakdown of the MR head. A magnetic recording medium in which the characteristics are realized can be obtained.

  As the solvent used for forming the magnetic layer 13, any of those exemplified as the paint adjusting solvent used for the nonmagnetic layer 12 may be used.

  The thickness of the magnetic layer 13 is not limited, but is typically 0.2 μm or less. By reducing the thickness of the magnetic layer 13, the short wave output and the C / N characteristics in the magnetic recording medium 10 can be improved.

[Back coat layer]
The back coat layer 14 contains carbon black 19, a binder (not shown), inorganic particles, and various optional additives. Any of these may be used as long as they are exemplified in the above description.

  Since the back coat layer 14 contains the carbon black 19, the charge charged on the surface of the magnetic recording medium 10 on the magnetic layer 13 side moves in the magnetic layer 13, the nonmagnetic layer 12, and the back coat layer 14. can do.

  Further, when the magnetic recording medium 10 is wound around a tape reel, the magnetic recording medium 10 is stacked in multiple layers around the tape reel. At this time, the back coat layer 14 is overlaid on the surface of the magnetic layer 13. Therefore, by forming the back coat layer 14 with good surface smoothness, it is possible to maintain the surface smoothness of the magnetic layer 13 during winding on the tape reel. Further, when the magnetic recording medium 10 is running, there may be a problem of resistance or friction due to contact between the guide roller of the drive and the magnetic recording medium 10, for example. However, the formation of the backcoat layer 14 can reduce the resistance and maintain the running property of the magnetic recording medium 10 satisfactorily. Further, deterioration of the magnetic recording medium 10 due to friction can be prevented.

  Further, the nonmagnetic layer 12 and the magnetic layer 13 may be laminated on the main surface of the magnetic recording medium 10 on the side where the backcoat layer 14 is laminated, instead of the backcoat layer 14. In this case, since signals are recorded on both main surfaces of the magnetic recording medium 10, a large capacity signal can be recorded.

[Method of manufacturing magnetic recording medium]
A method for manufacturing a magnetic recording medium according to an embodiment of the present invention will be described. First, a predetermined base film is prepared. Next, paints for the nonmagnetic layer and the magnetic layer are prepared. These coating materials are prepared by kneading and dispersing the materials contained in the above-described nonmagnetic layer and magnetic layer together with a predetermined solvent. Examples of the kneading method include a method using a continuous biaxial kneader (extruder), a kneader, a pressure kneader and the like.

  Next, the coating for the nonmagnetic layer is applied to the main surface of the base film, and the coating for the magnetic layer is applied thereon. Examples of the method for applying the coating material for the nonmagnetic layer and the magnetic layer include coating methods such as gravure coating, extrusion coating, air doctor coating, and reverse roll coating.

  In the method for manufacturing a magnetic recording medium according to the present embodiment, the so-called wet-on-dry method is applied in which the coating for the magnetic layer is applied after the coating for the nonmagnetic layer applied to the main surface of the base film is dried. Is used.

  FIG. 3 is a diagram for explaining a method of manufacturing a magnetic recording medium according to this embodiment in which the wet-on-dry method is used. In FIG. 3, the same reference numerals are used for materials similar to those described in FIG.

When the magnetic recording medium 20 is manufactured by the wet-on-wet method, the carbon black 15 of the nonmagnetic layer 12 enters the magnetic layer 13 or the carbon black 17 of the magnetic layer 13 enters the nonmagnetic layer 12. There are cases. Then, even if the coating materials for the nonmagnetic layer 12 and the magnetic layer 13 contain the fixed amounts of carbon blacks 15 and 17, respectively, they are contained in the nonmagnetic layer 12 and the magnetic layer 13 of the manufactured magnetic recording medium 20. The content of the carbon blacks 15 and 17 varies.
However, since a wet-on-dry method is used in the present embodiment, a certain amount of carbon blacks 15 and 17 contained in the coating material for the nonmagnetic layer 12 and the magnetic layer 13 are included. A magnetic recording medium 20 having the magnetic layer 13 is manufactured. As a result, the magnetic recording medium 20 capable of suppressing electrostatic breakdown of a highly sensitive magnetic head such as an MR head can be manufactured with a high yield.

  In addition, the wet-on-wet method is used as the coating method of the magnetic layer 13 within a range where carbon black is not mixed between the nonmagnetic layer 12 and the magnetic layer 13 or within a range where desired tape characteristics are obtained. May be used.

  The back coat layer is formed by applying the coating material for the back coat layer adjusted by the kneading method to the base film by the same application method.

  Samples 1-14 were made to illustrate the examples of the present invention. Production of Samples 1 to 14 is as follows.

  First, a base paint constituting the magnetic layer was prepared according to the following composition. By containing a predetermined amount of carbon black having a specific surface area shown in FIG. 4 in this base paint, magnetic paints 2 to 7 described later were produced. FIG. 5 shows the type and content of carbon black contained in each magnetic coating material. Here, the magnetic paint 1 was a paint that did not contain carbon black in the base paint.

[Composition of base coating for magnetic layer]
Fine ferromagnetic powder: 100 parts by weight (iron-cobalt alloy metal magnetic powder (average major axis length: 0.10 μm))
First binder: 9 parts by weight (vinyl chloride copolymer (average polymerization degree 300))
Second binder: 9 parts by weight (polyester polyurethane resin (weight average molecular weight 41200, Tg 40 ° C.))
Inorganic powder (abrasive): 8 parts by weight (α-alumina (particle size 200 nm, specific surface area 11.1 m ² / g))
Lubricant: Stearic acid: 1 part by weight
Butyl stearate: 2 parts by weight Solvent: Methyl ethyl ketone: 20 parts by weight Toluene: 20 parts by weight Cyclohexanone: 10 parts by weight

  The above fine ferromagnetic powder, binder, inorganic powder, lubricant and selected carbon black are kneaded with a kneader, further diluted with methyl ethyl ketone, toluene, and cyclohexanone, then dispersed in the sun middle, and the coating for the magnetic layer. did. Thereafter, 4 parts by weight of polyisocyanate (Japanese polyurethane curing agent “Coronate L”) was added and stirred to prepare a magnetic layer coating material.

Next, a coating material for the nonmagnetic layer was prepared.
[Composition of paint for nonmagnetic layer]
First inorganic particles: α-iron oxide (acicular, average long axis length 0.1 μm): 95 parts by weight Second inorganic particles: spherical α-Al ₂ O ₃ (particle size 100 nm, specific surface area 48 m ² / g) )): 5 parts by weight First binder: vinyl chloride copolymer (average polymerization degree 300): 9 parts by weight Second binder: polyester polyurethane resin (quantity average molecular weight 41200, Tg 40 ° C.)): 9 Part by weight Lubricant: Butyl stearate: 2 parts by weight Solvent: Methyl ethyl ketone: 70 parts by weight Toluene: 70 parts by weight Cyclohexanone: 40 parts by weight Carbon black (particle size 100 nm, specific surface area 110 m ² / g): 20, or 100 parts by weight

  The inorganic particles, binder, lubricant, and carbon black were kneaded with a kneader, further diluted with methyl ethyl ketone, toluene, and cyclohexanone, and then dispersed in the sun middle to obtain a coating for a nonmagnetic layer. Thereafter, 3 parts by weight of polyisocyanate (Japanese polyurethane curing agent “Coronate L”) was added and stirred to prepare a coating for the nonmagnetic layer. Here, as shown in the composition table, two types of coating materials for the nonmagnetic layer were prepared: those containing 20 parts by weight of carbon black and those containing 100 parts by weight.

  FIG. 6 is a table showing combinations of the magnetic layer coating materials 1 to 7 and two types of nonmagnetic layer coating materials. Samples 1 to 14 were manufactured as follows using the magnetic layer coating material and the nonmagnetic layer coating material in the combination shown in FIG.

  As a base film, a polyethylene terephthalate film having a thickness of 5.0 μm is prepared, and a nonmagnetic layer coating is first applied to a thickness of 1.0 μm, followed by a magnetic layer coating having a thickness of 0. It was applied so as to be 1 μm. Then, the magnetic field orientation process was performed, and it dried and wound up. Further, a calendar treatment was performed, and after curing, the back coat layer coating was applied to the film surface opposite to the nonmagnetic layer and the magnetic layer to form a back coat layer having a thickness of 0.6 μm. The backcoat layer coating material was prepared by adding 10 parts by weight of polyisocyanate (Japanese polyurethane curing agent “Coronate L”) to the backcoat layer coating material having the following composition and stirring.

[Composition of paint for back coat layer]
Inorganic powder (carbon black, particle size 40 nm): 100 parts by weight First binder: Polyester polyurethane resin (quantity average molecular weight 71200): 13 parts by weight Second binder: phenoxy resin (average polymerization degree 100): 43 Part by weight Third binder: Nitrocellulose resin (average polymerization degree 90): 10 parts by weight Solvent: Methyl ethyl ketone: 500 parts by weight Toluene: 500 parts by weight

  The wide tape thus obtained for each combination shown in FIG. 6 was slit into a 1/2 inch width. Further, the slit tape was incorporated into a 1/2 inch one reel cartridge (LTO (Linear Tape Open) format) of 820 m. These slit tapes and cartridges incorporating the tapes were designated as samples 1 to 14, respectively.

  About the manufactured samples 1-14, the electrical resistance value of the surface of each magnetic layer side was measured. In addition, running characteristics and electromagnetic conversion characteristics were evaluated. FIG. 7 is a table showing the results of measurement and evaluation. Each measuring method and evaluation method are shown below.

[Electric resistance value]
The magnetic layer side of the magnetic recording medium was brought into contact with a pair of parallel electrodes having an interelectrode distance of 25.4 mm, and a load of 80 gf was applied to both ends of the magnetic recording medium. In this state, a voltage of DC 100 V was applied between the electrodes, and the resistance was measured with a super insulation resistance meter. A value obtained by dividing the obtained resistance value by the area of the magnetic recording medium between the electrodes was defined as an electric resistance value.

[Running characteristics]
An LTO drive (manufactured by HP (Hewlett-Packard)) is used, and the entire length of the MR head element is run for 2500 passes in an environment of a temperature of 20 ° C. and a relative humidity of 10% RH (Relative Humidity). Microscope) (scanning electron microscope). Evaluation was made on the surface of the MR head element in which the dissolution mark of the metal film element called ESD mark was not confirmed as good (◯), and on the surface of the MR head element as defective (×).

[Electromagnetic conversion characteristics]
For each sample 1-14, a recording magnetic head (MIG (metal in gap), gap 0.15 μm) was used to record a signal having a wavelength of 0.3 μm, and then the MR head (gap 0.2 μm) was recorded on the reproducing head. ) Was used to reproduce the signal. Note that the C / N characteristics when the noise level was set at ± 2 MHz from the output of each single frequency and the reproduced signal were evaluated. The C / N value shown in FIG. 7 is a relative value when the C / N value of the magnetic recording medium produced by the magnetic layer coating material 1 and the nonmagnetic layer coating material containing 15 parts by weight of carbon black is 0.0 dB. Value.

For Samples 1 and 2, as shown in FIG. 7, the occurrence of ESD traces on the MR head element surface was confirmed. Since carbon black is not contained in the magnetic layer coating material 1, it is considered that a charged charge is accumulated on the surface of the magnetic layer and discharge to the MR head due to the charge is generated.
On the other hand, with respect to Samples 3 to 14, ESD traces were not generated on the surface of the MR head element, and good running characteristics were obtained. In Samples 3 to 14, since the magnetic layer and the nonmagnetic layer each contain conductive carbon black, the electric charge charged on the magnetic layer side surface of the magnetic recording medium passes through the magnetic layer and the nonmagnetic layer. Can move. Therefore, it is possible to prevent electric charges from accumulating on the surface of the magnetic recording medium on the magnetic layer side. As a result, electrostatic discharge from the magnetic recording medium to the MR head can be suppressed, and electrostatic breakdown of the MR head can be suppressed.

  Looking at the electrical resistance values of Samples 3, 5, 7, 9, 11, and 13, it is larger than the electrical resistance value of Sample 2 in which the occurrence of ESD traces was confirmed. However, as described above, in Samples 3, 5, 7, 11, and 13, since the magnetic layer and the nonmagnetic layer contain carbon black, the charge amount of the magnetic recording medium can be suppressed, and the MR head can be electrostatically destroyed. Can be suppressed.

  On the other hand, when Samples 3 to 10 and Samples 11 to 14 were compared, it was confirmed that Samples 3 to 10 had better C / N characteristics than Samples 11 to 14. As explained above, this can be considered to be a result brought about by the specific surface area and content of carbon black contained in the magnetic layer.

Samples 3 to 10 have magnetic layers formed of magnetic layer coatings 2 to 5. The specific surface area of the carbon black contained in the magnetic layer coatings 2 to 5 is in the range of 30 m ² / g to 130 m ² / g. The content is 5 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the ferromagnetic powder contained in the magnetic layer coating material. On the other hand, in Samples 11 to 14, the magnetic layer is formed of the magnetic layer coating material 6 or 7. The content of carbon black contained in the magnetic layer coating 6 and 7 is similar to the magnetic layer coating 2-5, a specific surface area greater than 130m ² / g, a 180 m ² / g.

From this, the specific surface area of the carbon black contained in the magnetic layer is 30 m ² / g or more and 130 m ² / g or less, and the content is 5 parts by weight or more with respect to 100 parts by weight of the ferromagnetic powder of the magnetic layer, It can be seen that the content may be 10 parts by weight or less. In other words, by setting the specific surface area and content of carbon black contained in the magnetic layer within the above range, the C / N characteristic, that is, the good electromagnetic conversion characteristic, while suppressing the electrostatic breakdown of the MR head. Can be obtained.

  As mentioned above, although embodiment and the Example of this invention were described, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, the above-described tape cartridge according to an embodiment of the present invention may have a ground circuit for grounding the magnetic recording medium. For example, a tape cartridge insertion slot in a drive is often made of metal. The tape cartridge is provided with a ground circuit for electrically connecting the metal insertion slot and the magnetic recording medium. Thereby, it is possible to further prevent charged charges from accumulating on the surface of the magnetic recording medium on the magnetic layer side, and to suppress electrostatic breakdown of the MR head.

  In the above embodiment, a tape cartridge is configured by winding a magnetic recording medium on a single tape reel. However, the present invention is not limited to this, and the present invention can be applied to a tape cartridge having two tape reels. Good.

DESCRIPTION OF SYMBOLS 1 ... Tape cartridge 2 ... Drive 3 ... Magnetic recording medium 4 ... Tape reel 5 ... Cartridge main body 6 ... Cartridge mounting part 7 ... Magnetic head 8 ... Guide body 9 ... Tape winding part 10, 20 ... Magnetic recording medium 11 ... Base film DESCRIPTION OF SYMBOLS 12 ... Nonmagnetic layer 13 ... Magnetic layer 14 ... Backcoat layer 15, 17, 19 ... Carbon black 16 ... Inorganic particle 18 ... Ferromagnetic powder 100 ... Tape drive system

Claims (3)

A first main surface, a support to which the first to have a second major surface opposite the main surface, the thickness was formed to be 5.0 .mu.m,
First carbon black laminated on the first main surface and having inorganic particles and a specific surface area of 110 m ² / g and a content of 20 parts by weight or 100 parts by weight with respect to 100 parts by weight of the inorganic particles. DOO containing a non-magnetic layer thickness is formed so as to be 1.0 micron m,
It has a laminated surface laminated on the nonmagnetic layer and a surface opposite to the laminated surface, and has a ferromagnetic powder, a specific surface area of 30 m ² / g or 130 m ² / g, and a content of containing a second carbon black is 5 parts by weight or 10 parts by weight based on 100 parts by weight of the magnetic powder, the magnetic layer thickness is formed so as to be 0.1 [mu] m,
The laminated on the second main surface, contains a third of the carbon black, comprising a back coat layer thickness is formed so as to be a 0.6 micron m,
The surface electrical resistance value on the surface side of the magnetic layer is 6.9 × 10 ⁶ Ω / cm ² or more and 8.8 when the content of the first carbon black in the nonmagnetic layer is 20 parts by weight. × 10 ⁶ Ω / cm ² or less, and when the content of the first carbon black is 100 parts by weight, 9.6 × 10 ⁴ Ω / cm ² or more and 2.7 × 10 ⁵ Ω / cm ² The following is a magnetic recording medium. A first main surface, a support to which the first to have a second major surface opposite the main surface, the thickness was formed to be 5.0 .mu.m,
First carbon black laminated on the first main surface and having inorganic particles and a specific surface area of 110 m ² / g and a content of 20 parts by weight or 100 parts by weight with respect to 100 parts by weight of the inorganic particles. DOO containing a non-magnetic layer thickness is formed so as to be 1.0 micron m,
It has a laminated surface laminated on the nonmagnetic layer and a surface opposite to the laminated surface, and has a ferromagnetic powder, a specific surface area of 30 m ² / g or 130 m ² / g, and a content of containing a second carbon black is 5 parts by weight or 10 parts by weight based on 100 parts by weight of the magnetic powder, the magnetic layer thickness is formed so as to be 0.1 [mu] m,
Laminated on the second on the main surface, containing the third carbon black, and a back coat layer thickness is formed so as to be a 0.6 micron m,
The surface electrical resistance value on the surface side of the magnetic layer is 6.9 × 10 ⁶ Ω / cm ² or more and 8.8 when the content of the first carbon black in the nonmagnetic layer is 20 parts by weight. × 10 ⁶ Ω / cm ² or less, and when the content of the first carbon black is 100 parts by weight, 9.6 × 10 ⁴ Ω / cm ² or more and 2.7 × 10 ⁵ Ω / cm ² below the magnetic recording medium is,
A reel on which the magnetic recording medium is wound;
A cartridge body that rotatably accommodates the reel;
A tape cartridge comprising: a ground circuit for grounding the magnetic recording medium. (A)
A first main surface, a support to which the first to have a second major surface opposite the main surface, the thickness was formed to be 5.0 .mu.m,
First carbon black laminated on the first main surface and having inorganic particles and a specific surface area of 110 m ² / g and a content of 20 parts by weight or 100 parts by weight with respect to 100 parts by weight of the inorganic particles. DOO containing a non-magnetic layer thickness is formed so as to be 1.0 micron m,
It has a laminated surface laminated on the nonmagnetic layer and a surface opposite to the laminated surface, and has a ferromagnetic powder, a specific surface area of 30 m ² / g or 130 m ² / g, and a content of containing a second carbon black is 5 parts by weight or 10 parts by weight based on 100 parts by weight of the magnetic powder, the magnetic layer thickness is formed so as to be 0.1 [mu] m,
Laminated on the second on the main surface, containing the third carbon black, and a back coat layer thickness is formed so as to be a 0.6 micron m,
The surface electrical resistance value on the surface side of the magnetic layer is 6.9 × 10 ⁶ Ω / cm ² or more and 8.8 when the content of the first carbon black in the nonmagnetic layer is 20 parts by weight. × 10 ⁶ Ω / cm ² or less, and when the content of the first carbon black is 100 parts by weight, 9.6 × 10 ⁴ Ω / cm ² or more and 2.7 × 10 ⁵ Ω / cm ² below the magnetic recording medium is,
A reel on which the magnetic recording medium is wound;
A cartridge body that rotatably accommodates the reel;
A tape cartridge having a ground circuit for grounding the magnetic recording medium;
(B) a drive having a magnetic head including a reproducing head unit composed of a magnetoresistive effect element for reproducing a signal recorded on the magnetic recording medium;
(C) A tape drive system comprising: a ground portion electrically connected to the ground circuit of the tape cartridge.

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