JPH07121870A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To eliminate unequal application of a coating liquid and to improve the smoothness of the resulted film by using gravure roll formed with microcells in positions where the ridge parts between the independent cells forming cell patterns intersect with each other. CONSTITUTION:The many independent cells 10 are inscribed as recessed parts on the surface of the gravure roll 1 of a transfer device 4 and the microcells 12 are formed as the recessed parts in the positions 11a where the ridge parts 11 between the respective cells 10 intersect with each other. The cells 12 are formed to the diameter smaller than the diameter of the cells 10 and to the shallow depth of the grooves. The two different cells are inscribed on the surfaces of the roll 1 in such a manner, by which the opening rate is increased and the transfer rate is improved. In addition, embossing and transfer defect are suppressed and the coating film having the good surface characteristic is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called coating type magnetic recording medium manufacturing method, and more particularly to a magnetic recording medium manufacturing method in which a magnetic coating material is applied by a gravure coating method.

[0002]

2. Description of the Related Art Generally, as an audio tape or a video tape, a magnetic coating material prepared by dispersing and kneading a magnetic powder, a binder, a dispersant, a lubricant, etc. in an organic solvent is coated on a non-magnetic support such as a polyester film. A so-called coating type magnetic recording medium in which a magnetic layer is formed by doing so is used.

In the production of this coating type magnetic recording medium, a method of using a coating apparatus using a roll such as a gravure roll or a reverse roll is the mainstream for coating the magnetic coating on the non-magnetic support. In particular, the direct gravure method that can apply a wide range of structural viscosities is often used.

The direct gravure system is applied onto the support by using a coating device comprising a gravure roll having a cell pattern engraved on the surface thereof and a backup roll for pressing a continuously running support against the gravure roll. This is a method of transferring liquid. That is, in this direct gravure method, the support is pressure-bonded to the backup roll by the backup roll made of an elastic material,
By rotating these rolls, the paint in the coating liquid pan is picked up in the cells arranged on the surface of the gravure roll, and the coating liquid filled in the cells is transferred onto the support to form the coating liquid. Is applied.

Conventionally, as a cell pattern engraved on the surface of the gravure roll, a diagonal pattern as shown in FIG. 6 is generally used. However, when the coating is performed using the gravure roll having the oblique cell pattern, the coating liquid is continuously transferred to the support in one direction, and thus the end portion of the support is Then, a large amount of the coating liquid flows. As a result, both ends in the width direction of the tape obtained after the coating film is dried are swollen, resulting in defective shapes and poor transfer balance, causing problems such as uneven coating.

On the other hand, a method using a gravure roll having a cell pattern formed of independent cells such as a lattice type, a trapezoidal type shown in FIGS. 7 and 8 or a hexagonal type shown in FIG. 9 is used. Are known. This method is often used in, for example, gravure printing and a step of applying a magnetic coating material on a magnetic recording medium.

[0007]

However, when the gravure roll on which the cell pattern composed of the independent cells is formed is used, the coating liquid is not continuously transferred on the support but is transferred in a dot shape. . For this reason, when applying a solid coating such as on a magnetic recording medium, the resulting coating film becomes extremely uneven, and after the transfer of the magnetic coating material, the undried coating film is smoothed by a smoothing device. However, it becomes difficult to secure good surface properties.

Particularly, when the coating thickness is increased to about 2.0 to 5.0 μm, the depth of the cell groove is increased in order to increase the volume of each cell formed on the surface of the gravure roll. For this reason, a large step is generated in the unevenness of the obtained coating film, and the unevenness of the coating film surface remains even if smoothing is performed by the smoothing device.

If the surface of the coating film thus has irregularities, an embossing phenomenon occurs and the contact waveform deteriorates.
It causes deterioration of image quality. Therefore, the present invention has been proposed in view of such circumstances, and provides a method for manufacturing a magnetic recording medium capable of eliminating coating unevenness of a coating liquid and obtaining a coating film having good surface properties. The purpose is to do.

[0010]

The present invention has been proposed to achieve the above object. That is, the present invention is a method for producing a magnetic recording medium in which a coating liquid is applied by a gravure roll on a continuously running support, and a cell pattern composed of independent cells is formed on the surface as the gravure roll, and each independent cell is formed. It is characterized in that a gravure roll is used in which minute cells are formed at positions where ridges between them intersect with each other.

In the method of manufacturing a magnetic recording medium of the present invention, basically, a single or a plurality of magnetic layers are laminated on a support. The magnetic layer is formed by applying a magnetic coating material obtained by dispersing and kneading a magnetic powder, a binder, a dispersant, a lubricant and the like in an organic solvent onto the support.

In the present invention, when the magnetic coating material is applied on the support, a gravure roll having a cell pattern formed of independent cells on the surface is used. The cell pattern of the gravure roll is not particularly limited,
Specific examples include a lattice type, a trapezoid type, and a hexagonal type.

Further, minute cells are engraved on the surface of the gravure roll at positions where ridges (cell tops) between the independent cells intersect with each other. As described above, by engraving (synchronized cell engraving) two different cells (independent cells and minute cells) on the surface of the gravure roll, the aperture ratio is increased, the transfer rate is improved, and the emboss phenomenon and It is possible to obtain a coating film in which transfer defects are suppressed and which has good surface properties.

As a method of forming these independent cells and minute cells, first, a cell pattern consisting of the above-mentioned independent cells is engraved by laser engraving capable of formatting a predetermined array, then deburring and polishing are carried out once, and then the above-mentioned minute cells are formed. The method of forming is preferred.

At this time, the surface roughness of the gravure roll is preferably 0.08 μm or less. When the surface roughness is within the above range, a good transfer rate can be ensured, the surface of the obtained coating film can be made smooth, and a coating film having excellent surface properties can be obtained.

Further, in the present invention, a back coat is formed on the surface (rear surface) of the support on which the magnetic layer is not provided for the purpose of improving the running property of the magnetic recording medium, preventing charging, and preventing transfer. A layer may be formed, a top coat layer may be formed on the magnetic layer, or an intermediate layer as a so-called undercoat layer may be formed between the magnetic layer and the support. .

These back coat layer and top coat layer,
The above gravure roll may be used when forming the intermediate layer and the like by coating. The gravure roll can be used not only in the production of the magnetic recording medium according to the present invention but also in the coating process of the coating material having a wide range of structural viscosity.

In the present invention, as the magnetic powder or the binder which is a constituent material of the magnetic layer, any conventionally known one can be used and is not particularly limited.
Examples of such conventionally known magnetic powder include Fe,
Metal materials such as Co and Ni, Fe-Co, Fe-Ni,
Fe-Al, Fe-Ni-Al, Fe-Al-P, Fe
-Ni-Si-Al, Fe-Ni-Si-Al-Mn,
Fe-Mn-Zn, Fe-Ni-Zn, Co-Ni, C
o-P, Fe-Co-Ni, Fe-Co-Ni-Cr,
Fe-Co-Ni-P, Fe-Co-B, Fe-Co-
Examples thereof include alloy materials such as Cr-B, Mn-Bi, Mn-Al, and Fe-Co-V, and iron nitride and iron carbide.

Even if a light metal element such as Al, Si, P or B is added in an appropriate amount for the purpose of preventing sintering during reduction or maintaining the shape, the effect of the present invention is not hindered.

Further, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , γ-
Betride compound of Fe ₂ O ₃ and Fe ₃ O ₄ , Co
Γ-Fe ₂ O ₃ , Co-containing Fe ₃ O ₄ , a beltride compound of γ-Fe ₂ O ₃ containing Co and Fe ₃ O ₄ , one or more metallic elements in CrO ₂ , for example Te. , Oxides containing Sb, Fe, Bi, etc. can be used.

These magnetic powders may be used alone or in combination of two or more.

As the above-mentioned binder, either a thermoplastic resin or a thermosetting resin can be used.

As the thermoplastic resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic acid ester-acrylonitrile copolymer, acrylic acid ester-vinylidene chloride copolymer , Methacrylic acid ester-vinylidene chloride copolymer, methacrylic acid ester-vinyl chloride copolymer, methacrylic acid ester-ethylene copolymer, polyvinyl fluoride, vinylidene chloride-allylonitrile copolymer, acrylonitrile-butadiene copolymer, Polyamide resin, polyvinyl butyral, cellulose derivative (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose), styrene-butadiene copolymer Polyester resin, amino resin,
There are thermoplastic resins such as synthetic rubber.

As the thermosetting resin, phenol resin,
There are epoxy resin, polyurethane resin, urea resin, melamine resin, alkyd resin, silicone resin, polyamine resin, urea formaldehyde resin and the like.

In the present invention, if necessary, a lubricant,
It is also possible to use non-magnetic reinforcing particles, conductive particles, surfactants, etc. as the constituent material of the magnetic layer. Examples of the lubricant include graphite, molybdenum disulfide, silicone oil, fatty acids having 10 to 22 carbon atoms, and fatty acid esters consisting of this and alcohols having 2 to 26 carbon atoms, terpene compounds, and oligomers thereof. is there.

Examples of the non-magnetic reinforcing particles include aluminum oxide, chromium oxide, silicon carbide, diamond, garnet, emery, boron nitride and the like. These particles are contained in an amount of 20 parts by weight based on 100 parts by weight of the magnetic powder.
Preferably, it is 10 parts by weight or less, and the average particle size is
It is 1.0 μm or less, preferably 0.5 μm or less.

Examples of the conductive particles include carbon black, graphite and other metal particles. Examples of the surfactant include nonionic, anionic, cationic and amphoteric surfactants.

Examples of the support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene,
Examples thereof include celluloses such as cellulose triacetate and cellulose diacetate, polymer materials typified by vinyl resins, polyimides and polycarbonates, and supports formed of metal, glass, ceramics and the like.

In order to form the above-mentioned magnetic layer on the above-mentioned support, the above-mentioned magnetic layer-constituting material is applied and dried as a paint. The solvent used for forming this paint is acetone,
Methyl ethyl ketone, methyl isobutyl ketone, ketone solvents such as cyclohexanone, alcohol solvents such as methanol, ethanol and propanol, methyl acetate,
Ethyl acetate, butyl acetate, propyl acetate, ethyl lactate,
Ester solvents such as ethylene glycol acetate, diethylene glycol dimethyl ether, ether solvents such as 2-ethoxyethanol, tetrahydrofuran and dioxane, aromatic hydrocarbon solvents such as benzene, toluene and xylene, methylene chloride, ethylene chloride, carbon tetrachloride, A halogenated hydrocarbon solvent such as chloroform or chlorobenzene can be used.

A roll mill, a ball mill, a sand mill, an agitator, a kneader, an extruder, a homogenizer, an ultrasonic disperser or the like is used for the dispersion / kneading for preparing the above-mentioned coating material.

[0031]

When a coating solution is applied to a continuously running support to form a coating film, a cell pattern consisting of independent cells is formed on the surface, and the ridges between the independent cells intersect with each other. By using the gravure roll having fine cells formed therein, it is possible to obtain a coating film having good surface properties without coating unevenness.

By forming two different cells (independent cells and minute cells) on the surface of the gravure roll as described above, the aperture ratio of the gravure roll is increased and the transfer rate is improved, and at the same time, it is obtained. This is because the irregularities on the surface of the coating film to be formed become smaller.

[0033]

EXAMPLES Hereinafter, specific examples of the present invention will be described, but it goes without saying that the present invention is not limited to these examples.

The present example is an example in which a magnetic coating is applied onto a polyethylene terephthalate film as a support using a gravure roll having two different cells on the surface to form a magnetic layer. First, in the present embodiment, the configuration of the coating device used for coating and forming the magnetic coating material will be described.

That is, in this coating apparatus, as shown in FIG. 1, a gravure roll 1 having a predetermined cell pattern engraved on the surface thereof and a support 2 which continuously runs with the gravure roll 1 are provided.
And a smoothing device 5 for smoothing the surface of the coating material transferred onto the support 2 by the transfer device 4.

In the transfer device 4, the gravure roll 1 is a cylindrical roll made of Fe or the like having a relatively low hardness and having a width corresponding to the coating width, and is rotatable counterclockwise in the drawing. It is said that. On the surface of the gravure roll 1, as shown in FIG. 2, a large number of hexagonal independent cells 10 are engraved as recesses, and ridges (cell tops) 11 between the individual cells 10 intersect each other. The minute cell 12 is formed as a recess at the position 11a.

The minute cell 12 is shown in FIG. 3 (A- in FIG. 2).
As shown in (A ′ cross-sectional view), the above-mentioned existing independent cell 1
The diameter is smaller than 0, and the groove is formed to have a shallow depth because the coating liquid does not escape. As described above, by engraving (synchronized cell engraving) two different cells (independent cells 10 and minute cells 12) on the surface of the gravure roll 1, the aperture ratio is increased and the transfer rate is improved. An embossing phenomenon and transfer failure are suppressed, and a coating film having good surface properties can be obtained.

Although the hexagonal shape was used as the shape of the independent cell 10 in this embodiment, the same effect can be obtained even if it is a lattice type as shown in FIGS. 4 and 5, for example. It is possible.

On the left side of the gravure roll 1 in the drawing,
A finisher roll 8 is provided. The finisher roll 8 is provided to uniformly fill the coating liquid 7 ejected from the nozzle 6 provided above the finisher roll 8 in the width direction of the gravure roll 1. That is, the coating liquid 7 ejected from the nozzle 6 is supplied to the gap between the finisher roll 8 and the gravure roll 1, and the independent cells 10 engraved on the surface of the gravure roll 1 by the finisher roll 8 and It is filled in the minute cells 12 and further transferred onto the support 2 on the surface where the gravure roll 1 contacts the surface of the support 2.

A doctor blade 9 is provided near the gravure roll 1 on the delivery side of the support 2. This doctor blade 9 is the independent cell 10 described above.
Also, it is arranged to scrape off the excess amount of the coating liquid 7 filled in the microcells 12 and limit it to a fixed amount.

Above the gravure roll 1 in the figure, the backup roll 3 is disposed so as to face it with the support 2 interposed therebetween. The backup roll 3 is a cylindrical roll having a width substantially equal to that of the gravure roll 1 and is configured to be rotatable clockwise in the drawing.

In this backup roll 3, the support 2 is pressure-bonded to the surface of the gravure roll 1, and the coating liquid 7 filled in the individual cells 10 and the microcells 12 provided on the surface of the gravure roll 1. Is satisfactorily transferred onto the support 2 and is made of an elastic roll such as rubber. Therefore, the support 2 is brought into close contact with the individual cells 10 and the minute cells 12 on the surface of the gravure roll 1 by the elastic force of the backup roll 3, and the backup roll 3 is rotated in synchronization with the gravure roll 1. The support 2 is sent out in the direction of the arrow X in the figure, and the coating liquid 7 filled in the independent cells 10 and the microcells 12 is continuously and uniformly transferred onto the support 2 for coating.

On the other hand, the support 2 having passed between the gravure roll 1 and the backup roll 3 is supported by the guide rolls 13a, 13b, 13c from the back surface side of the coating film forming surface, and the guide rolls 13a, 13b are also supported. , 13c apply an appropriate tension to ensure smooth running.

In the middle of the passage of the support 2 between the guide rolls 13a and 13b, the smoothing device 5 made of steel or the like is arranged on the side of the support 2 on which the coating film is formed. The smoothing device 5 is arranged to flatten the surface of the coating film obtained by the transfer device 4 as described above. That is, the coating film formed by the transfer device 4 is
Since the coating liquid 7 is transferred and formed on the support 2 in the cell pattern of the gravure roll 1,
Unevenness corresponding to the cell pattern remains on the surface. Therefore, by bringing the coating film formed by the transfer device 4 into contact with the smoothing device 5, the irregularities on the surface of the coating film are leveled and good surface properties are obtained.

Therefore, in this coating apparatus, the surface of the gravure roll 1 is brought into contact with the surface of the support 2 which is fed from the unwinding side and travels in the direction of the arrow X in the drawing. The coating liquid 7 filled in the cells 10 and 12 provided on the surface of the gravure roll 1 is transferred to form a coating film. At this time, since two different cells (independent cells 10 and minute cells 12) are engraved on the surface of the gravure roll 1, a good transfer rate can be ensured and coating with relatively small unevenness can be ensured. A film is obtained. Therefore, if the surface of this coating film is smoothed by the smoothing device 5, a coating film having very good surface properties can be obtained.

Therefore, the magnetic coating material was applied onto the polyethylene terephthalate film by using the application device having the above-mentioned structure. The above magnetic paint is C as magnetic powder.
o Adhering γ-Fe ₂ O ₃ or a metal magnetic powder is used, a vinyl chloride copolymer and a polyurethane resin are used together as a binder, and these magnetic materials are dispersed and mixed in methyl ethyl ketone, toluene, and cyclohexanone. It was prepared by adding additives such as lecithin.

The coating speed was 250 m / min.

With respect to the obtained coated tape, the embossing and transferability of the magnetic layer were investigated and a comprehensive evaluation was carried out.
The results are shown in Table 1 below. In the evaluation, the case where the emboss remains (poor smoothness) was evaluated as x, the practical limit was evaluated as Δ, and the case where good smoothness was obtained was evaluated as o.

[0049]

[Table 1]

Further, using the above coating apparatus, an undercoat containing carbon black or an emulsion as a main component is undercoated on the above polyethylene terephthalate film, and the embossing and transferability of the obtained undercoat layer are examined by the same method as described above. It was The results are also shown in Table 1 above.

For comparison, in the coating apparatus, the gravure roll was used in which the minute cells were not formed on the surface of the gravure roll and only the cell pattern formed of the hexagonal independent cells was engraved. When magnetic coating or undercoating was performed in the same manner as in Examples, embossing and transferability were examined by the same method, and the results are also shown in Table 1 above.

As shown in Table 1, in this embodiment,
No embossing was observed, good transferability could be secured, and the quality was remarkably improved. From this, by applying or undercoating the magnetic paint using a gravure roll having two different cells (independent cells and microcells) formed (synchronized engraving) on the surface, various kinds of viscosity in a wide range of viscosity can be obtained. It has been found that a coating film having excellent surface properties can be formed even when a paint is used.

[0053]

As is apparent from the above description, in the present invention, coating is performed using a gravure roll having a cell pattern of independent cells and a synchro cell engraved on the surface. It is possible to obtain a high transfer rate (which can be improved by about 10% as compared with the conventional one), and at the same time, it is possible to form a coating film having excellent smoothness by reducing the irregularities on the obtained coating film surface.

Further, according to the present invention, it becomes possible to transfer a coating material in a wide viscosity range, and particularly in the reverse coating method, even when a coating material having a viscosity in the range of up to about 7000 cps is used, coating unevenness is caused. It is possible to obtain a coating film having no smoothness and excellent smoothness. As a result, the top coat,
It is possible to provide a very effective coating method which can be applied to a coating process of an undercoat, an intermediate layer and the like, and further a coating process in the field of printing and the like.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a coating device used in manufacturing a magnetic recording medium to which the present invention is applied.

FIG. 2 is an enlarged front view of an essential part showing the configuration of two types of cells engraved on the surface of a gravure roll of the coating apparatus.

FIG. 3 is an enlarged sectional view of an essential part showing the configuration of two types of cells engraved on the surface of the gravure roll.

FIG. 4 is an enlarged front view of a main part showing another configuration example of two types of cells engraved on the surface of the gravure roll.

FIG. 5 is an enlarged sectional view of an essential part showing another example of the configuration of the two types of cells.

FIG. 6 is a plan view showing an example of a cell pattern of a gravure roll in a conventional coating apparatus.

FIG. 7 is a plan view showing another example of a cell pattern of a gravure roll in a conventional coating apparatus.

FIG. 8 is a plan view showing still another example of the cell pattern of the gravure roll in the conventional coating apparatus.

FIG. 9 is a plan view showing still another example of the cell pattern of the gravure roll in the conventional coating apparatus.

[Explanation of symbols]

 1 ... Gravure roll 2 ... Support 3 ... Backup roll 4 ... Transfer device 5 ... Smoothing device 6 ... Nozzle 7 ... Coating liquid 8 ... Finisher roll 9 ...・ Doctor blade 10 ・ ・ ・ Independent cell 12 ・ ・ ・ Micro cell

Claims (1)

[Claims] 1. A method of manufacturing a magnetic recording medium, wherein a coating solution is applied on a continuously running support by a gravure roll, wherein a cell pattern consisting of independent cells is formed on the surface as the gravure roll, and a space between the independent cells is formed. A method of manufacturing a magnetic recording medium, characterized in that a gravure roll is used in which minute cells are formed at positions where ridges of the ridge cross each other.