JPH0827937B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

The present invention relates to a method for manufacturing a magnetic recording medium, and more particularly to a method for manufacturing a magnetic recording medium having a surface smoothing step for the recording medium.

(Prior Art) Magnetic recording media are vinyl chloride, polycarbonate, AB
A non-magnetic support made of S resin, polyethylene terephthalate, cellulose triacetate, paper, synthetic paper, cloth, metal, etc. (hereinafter also simply referred to as a support) was coated with a magnetic layer made of magnetic powder and dried. After that, the surface of the magnetic layer is smoothed, smoothed, the packing density is improved, the thickness is made uniform, and so on. This will be explained with reference to FIG. 4. First, the support 13 pulled out from the supply roll 5 is coated with the magnetic coating liquid 15 by the magnetic liquid coating device 6 to form a magnetic layer, and then oriented as required. Then, it is introduced into the dryer 11 and dried. Next, the dried support 13 with the magnetic layer is guided to a calendering device 10 composed of a combination of a plurality of calendering rolls 3 and a drawing roll 4, and after being calendered, it is wound up on a winding roll 9.

The calender device 10 pressurizes the support 13 coated with the magnetic layer by a plurality of calender rolls 3 with a pressing force of about 200 to 300 kg / cm, and also provides induction heat generation or warm water heating provided inside the calender rolls 3. About 60 to 10 depending on the heating means
By heating at a temperature of 0 ° C., the magnetic layer is softened to smooth the surface of the magnetic layer.

(Problems to be Solved by the Invention) Since the conventional calender roll 3 is heated by the heating means provided inside the calender roll as described above, the temperature inside the calender roll in the axial direction of the calender roll 3 is generally. The distribution is not uniform, and the temperature at the center of the calender roll becomes higher than the temperature at the end of the calender roll. For this reason, as shown in FIG. 2, when the calender roll having the pressure surface straightened at room temperature is heated by the above heating means and calendered, the thermal expansion of the calender roll center portion is performed as shown in FIG. Since the amount of change in outer diameter due to is larger than that at the end of the calender roll, the calender roll 3 is deformed into a crown shape. Therefore, when the support 13 is pressed by such a deformed calender roll, the pressing force (pressure distribution) in the calender roll width direction becomes non-uniform, and the smoothness in the width direction of the magnetic layer surface of the calendered support is There was a problem of variation.

Therefore, in consideration of the amount of deformation of the calendar roll in advance, when the roll is heated, the pressing surface becomes straight,
That is, a method of forming calender rolls so that the pressure distribution becomes uniform is used, but in such a method, all calender rolls must be replaced in response to changes in the temperature conditions of calendering. Moreover, it was very difficult to accurately estimate the deformation amount of these calender rolls.

Further, since both sides of the support 13 passing between the calender rolls are alternately in contact with the calender roll surface and exposed to the atmosphere, the surface temperature of the support and the magnetic layer changes each time. For this reason, the support is repeatedly stretched and compressed, and wrinkles occur in the support.
Further, in some cases, when the wrinkles are nipped as they are by a calender roll, the calender roll surface is scratched,
There was a problem of reducing productivity.

Therefore, an object of the present invention is to solve the above problems, and to provide an apparatus for producing a magnetic recording medium in which the smoothness in the width direction of the surface of the magnetic layer on the support to be calendered is uniform and the surface property is good. To do.

(Means for Solving the Problems) The above object of the present invention is to apply a magnetic coating liquid onto a non-magnetic support to form a magnetic layer, and then to form a plurality of calendar rolls arranged in parallel. In a method for producing a magnetic recording medium, in which a magnetic layer coated on the non-magnetic support is calendered by a calendering device having a calendering device, the calendering device having a plurality of calendering rolls is surrounded by a heating chamber and heated. This is achieved by a method for manufacturing a magnetic recording medium, characterized in that the plurality of calender rolls are heated by heating the atmosphere in the chamber.

(Embodiment) Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, the support pulled out from the supply roll 5
The magnetic solution 13 is applied with the magnetic application solution 15 by the magnetic solution application device 6 to form a magnetic layer, and then introduced into the dryer 2 to be dried. Then, the dried support 13 with the magnetic layer is guided to a calendering device 1 comprising a combination of a plurality of metal calender rolls 3 and a drawing roll 4, where it is calendered and then wound on a winding roll 9. To be

The calendering device 1 is housed in the heating chamber 16, and the calendering roll 3 and the drawing roll 4 each having a cylindrical shape are surrounded by a heat insulating member 8. And the heat retaining member 8
A panel heater 7 is disposed inside of the heat insulating member 8 and the inside of the heat insulating member 8 is appropriately heated to a predetermined temperature. Therefore,
By heating the calender roll 3 from its surroundings, the temperature distribution in the axial direction of the calender roll 3 becomes uniform. Therefore, the calender roll 3 is prevented from being deformed into a crown shape because the amount of change in the outer diameter due to the thermal expansion of the central part of the calender roll 3 is larger than that of the end part of the calender roll.

Therefore, when carrying out the calendering treatment by pressing the support 13, the pressing force in the calender roll width direction becomes uniform, and the smoothness in the width direction of the magnetic layer surface of the calendered support can be made uniform. .

Further, by heating the inside of the heat insulating member 8 to a predetermined temperature as appropriate, the atmosphere inside the heat insulating member and the temperature of the calender roll surface become substantially the same, so that the front and back surfaces of the support 13 passing between the calender rolls are Even if the surfaces of the calender rolls are alternately contacted and exposed to the atmosphere, the surface temperatures of the support and the magnetic layer do not change each time. Therefore, the support is prevented from being repeatedly stretched and compressed due to the change in the surface temperature of the support to cause wrinkles.

Although a heat panel is used as the heating means inside the heat insulating member in the above embodiment, the present invention is not limited to this, and for example, a heating means using hot air such as a dryer may be used. Further, as the calender roll, it is desirable to use a metal roll in order to speed up the processing speed, but the calender roll is not limited to this, and for example, an elastic roll can be combined.

Further, based on the constitution of the present invention, for example, JP-A-57-1437
No. 37, No. 61-261819 and No. 62-18628, calendering is performed at a solvent content of the magnetic layer is high as disclosed in the specification, followed by main drying, in the heating chamber It is also possible to install an enclosed calendering device between the predryer and the main dryer.

As described above, the present invention is preferably used in a so-called in-line calendering method in which coating to calendering are continuously performed, but can also be applied to an off-line calendering method in which after coating, it is wound into a roll and calendered. it can.

Ferromagnetic fine powder is used for the magnetic layer of the magnetic recording medium of the present invention.

As the ferromagnetic fine powder, γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂
O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , γ-FeOx, Co-containing γ-Fe
Ox (X = 1.33~1.50), CrO 2, Co-Ni-P alloy, Co-Ni
-Fe-B alloy, Fe-Ni-Zn alloy, Ni-Co alloy, Co-Ni-
Known ferromagnetic fine powders such as Fe alloys can be used, and the particle size of these ferromagnetic fine powders is about 0.005 to 1 micron in length, and the ratio of shaft length / shaft width is about 1/1 to 50/1. is there. The specific surface area of the end of these ferromagnetic fine powders is 1m ² / g~70m ² / g approximately.

Further, plate-like hexagonal barium ferrite can also be used as the ferromagnetic fine powder. The particle size of barium ferrite is about 0.001 to 1 micron and the thickness is 1/2 to 1/20 of the diameter.
Is. The specific gravity of barium ferrite is 4-6 g / cc, a specific surface area is 1m ² / g~70m ² / g.

In the present invention, a binder is used for the magnetic layer together with the ferromagnetic fine powder. Examples of the binder used include conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof.

The thermoplastic resin has a softening temperature of 150 ° C. or lower, an average molecular weight of 10,000 to 300,000, and a degree of polymerization of about 50 to 2,000, such as 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, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester Styrene copolymer, urethane elastomer, nylon-silicone resin, nitrocellulose-polyamide resin, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene diacrylonitrile copolymer, polyamide resin, polyvinyl butyral, Lulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, chlorovinyl ether acrylate copolymer, amino resin, various synthetic rubbers A system thermoplastic resin and a mixture thereof are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of the coating liquid, and the resin is condensed and added when the magnetic layer-forming composition is applied, dried and then heated. And so on, resulting in infinite molecular weight. Further, among these resins, it is desirable that the resin does not soften or melt before the resin is thermally decomposed. Specifically, for example, phenol resin, epoxy resin, curable polyurethane resin, urea resin, melamine resin, alkyd resin, silicone resin, reactive acrylic resin, epoxy polyamide resin, nitrocellulose melamine resin, high molecular weight polyester resin and isocyanate. Prepolymer mixture, methacrylate copolymer and diisocyanate prepolymer mixture, polyester polyol and polyisocyanate mixture, urea formaldehyde resin, low molecular weight glycol / high molecular weight diol / triphenylmethane triisocyanate mixture, polyamide resin and There is a mixture of these.

In this case, if necessary, additives used in conventional magnetic recording media such as antistatic agents such as carbon black, dispersants, lubricants, and abrasives can be added.

As the material of the support provided with these magnetic layers, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, Examples include plastic films such as polycarbonate, polyamide resin, and polysulfone, metal materials such as aluminum and copper, and ceramics such as glass. These supports may be previously subjected to pretreatments such as corona discharge treatment, plasma treatment, undercoating treatment, heat treatment, metal vapor deposition treatment and alkali treatment. The support is
It may have any desired shape.

The coating liquid for forming the magnetic layer, which has been subjected to the dispersion treatment, includes, for example, an air doctor coat, a blade coat, an air knife coat, a squeeze coat, an impregnation coat, a reverse roll coat, a transfer roll coat, a gravure coat, a kiss coat, a cast coat, a spray coat and the like. It is coated on the support by various coating methods.

Hereinafter, a magnetic tape was produced by the method for producing a magnetic recording medium according to the present invention.

First, a magnetic layer of the following magnetic coating solution composition was applied at 25 cc / m ² on a polyethylene terephthalate support having a thickness of 15 μm,
A drying process was performed at a drying temperature of 80 ° C. for 10 seconds.

Magnetic coating liquid composition Magnetic substance (Co-containing γ-Fe ₂ O ₃ , Hc = 8000e, specific surface area 55m ² / g) 300 parts Nitrocellulose (RS1 / 2) 30 parts Polyol 30 parts Polyisocyanate 25 parts Carbon black (particle size 20 μm) 15 parts Abrasive (Cr ₂ O ₃ : particle size 0.5 μm) 3 parts Myristic acid 1.5 parts Silicon oil 1.0 parts Methyl ethyl ketone / 750 parts Cyclohexanone (weight ratio: 6/4) (However, in the above magnetic coating liquid composition All "parts" mean "parts by weight".) Next, calendering was performed by setting the nip linear pressure of the calender roll to 200 kg / cm and pressing the magnetic tape stock at a speed of 300 m / min. . The atmospheric temperature inside the calender was maintained at 80 ° C.

Then, after winding the above-mentioned magnetic tape raw material, a slitting process was carried out to form a magnetic tape having a predetermined width, and then the gloss of the surface of the magnetic tape was measured at 10 points in the tape width direction.

For comparison, a magnetic tape was manufactured under the same conditions as above using a conventional magnetic recording medium manufacturing apparatus, and the gloss of the surface of the magnetic tape was measured as a sample at 10 points in the tape width direction. However, the calender roll was an induction heating roll, and the calender roll temperature was set to 80 ° C.

 Table 1 shows the results of the above measurements.

As is clear from this result, the magnetic tape of the comparative example, which was subjected to the calendering treatment using the heating roll, had a higher gloss at the central portion of the tape than at the both end portions of the tape. This indicates that since the heating roll is deformed in a crown shape, the pressing force at the central portion in the width direction of the heating roll is higher than that at both ends, and the smoothness in the calendered magnetic tape width direction is not uniform. There is. On the other hand, the magnetic tapes of Examples produced by the magnetic recording medium manufacturing apparatus according to the present invention have substantially uniform gloss in the tape width direction and uniform smoothness in the calendered magnetic tape width direction. You can see that

(Effect of the Invention) In the method for producing a magnetic recording medium of the present invention, the calender roll group of the calendering device for performing the surface smoothing treatment of the magnetic layer coated on the support is surrounded by the heating chamber, and Since the internal atmosphere of the heat insulating material is heated by the heating means provided inside the heat insulating material in the heating chamber, the calender roll can be uniformly heated. Therefore, the pressing surface (surface) of the calender roll is uniformly heated over the entire surface, thermal deformation due to nonuniform heating is prevented, and nonuniform pressure of the calender roll on the magnetic layer can be prevented. Therefore, the smoothness in the width direction of the surface of the magnetic layer on the support to be calendered becomes uniform. Further, even if the front and back surfaces of the support passing between the calender rolls are alternately contacted with the calender roll surface and exposed to the atmospheric surface, the surface temperature of the support and the magnetic layer does not change each time. As described above, it is possible to prevent the support from being repeatedly stretched and compressed to generate wrinkles.

Therefore, according to the present invention, it is possible to provide a method for producing a magnetic recording medium that can obtain a magnetic recording medium having a uniform surface of the magnetic layer on the support and a good surface property without wrinkles.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a method for manufacturing a magnetic recording medium according to an embodiment of the present invention, FIGS. 2 and 3 are graphs showing the amount of change in outer diameter in the calender roll width direction, and FIG. It is a schematic diagram of a manufacturing method of a recording medium. (Symbols in the figure) 1,10 …… Calendar device, 2,11 …… Dryer, 3 …… Calendar roll, 4 …… Drawer roll, 5 …… Supply roll, 6 ……
Magnetic liquid coating device, 7 ... Panel heater, 8 ... Heat retaining member, 9
...... Winding roll, 13 …… Support, 15 …… Magnetic coating liquid, 16 ・ ・ ・
… Heating room.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tokuaki Miyake 2-12-1, Ogimachi, Odawara-shi, Kanagawa Fuji Photo Film Co., Ltd. (56) Reference JP-A-59-30246 (JP, A)

Claims (1)

[Claims] 1. A magnetic coating liquid is coated on a non-magnetic support,
In a method for producing a magnetic recording medium, which comprises forming a magnetic layer and then calendering the magnetic layer coated on the non-magnetic support by a calendering device having a plurality of calender rolls arranged in parallel, A method for producing a magnetic recording medium, characterized in that a calendering device having a plurality of calender rolls is surrounded by a heating chamber and the calender rolls are heated by heating an atmosphere in the heating chamber.