JPH09312018A - Production of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process capable of producing a magnetic recording medium additionally improved in output. SOLUTION: In this process for producing the magnetic recording medium, the magnetic recording medium is produced by executing calender operation by specifying the Shore hardness (D scale) at 23 deg.C of an elastic roll constituting a calender device to >=94, specifying a calender operation temp. to >=90 to <=130 deg.C and specifying the loss tangent Δ of the viscoelastic characteristic of the elastic roll at the calender operation temp. T deg.C to Δ<0.0030385×T-0.24769.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 capable of obtaining a magnetic recording medium with improved output.

[0002]

2. Description of the Related Art Many attempts have been made to achieve the high output of a magnetic recording medium from the viewpoint of its manufacturing process. For example, various conditions (for example, temperature, linear pressure, roll material, and the like) of the calendar operation step in the manufacturing process of the magnetic recording medium greatly affect the surface properties of the magnetic layer, that is, the output of the magnetic recording medium. Optimization of the above conditions is being studied. Attempts to improve the output of a magnetic recording medium by focusing on other conditions in the calendar operation process have also been known.

For example, Japanese Patent Laid-Open No. 1-94532 discloses a method for producing a magnetic recording medium, which comprises applying a magnetic coating liquid on a non-magnetic support to form a magnetic layer, and then performing calendering treatment. It is described that a polyurethane resin having a glass transition point of 30 ° C. or higher is used as a binder of the magnetic coating liquid, and the calender treatment is performed when the residual solvent amount of the magnetic layer becomes 0.1 to 3% by weight. .

Further, in Japanese Patent Application Laid-Open No. 4-149821, the time required from the time when the magnetic powder is charged into the kneading machine to the time when the calender operation step after the application of the magnetic coating material is completed is described in the method for manufacturing a magnetic recording medium. It is described that the time is from 2 to 48 hours.

Further, JP-A-58-194142 discloses a method for producing a magnetic recording medium, which comprises applying a magnetic coating liquid on a non-magnetic support to form a magnetic layer, and then performing calendering treatment. , The humidity of the above-mentioned calendar processing atmosphere is 60% R
It is described that it is H or more.

Further, Japanese Patent Application Laid-Open No. 51-92606 describes that a polyamide resin having a Shore hardness of 70 or more is used as an elastic roll in a method for polishing a magnetic recording medium. Further, the publication also refers to the water content in the elastic roll. However, in this publication, the water content is only mentioned in relation to the frictional electrification voltage of the roll, and the water content affects the mechanical deformation of the elastic roll in relation to the Shore hardness. No impact is mentioned.

[0007]

According to the prior art, high output of a magnetic recording medium can be achieved to some extent. However, in order to meet the recent demand for higher density of a magnetic recording medium, the output of the magnetic recording medium must be further increased. There is a need for improved magnetic recording media.

An object of the present invention is to provide a method capable of manufacturing a magnetic recording medium with further improved output.

[0009]

The present invention according to claim 1, wherein a magnetic coating is applied on the support to form a magnetic layer, and then the support is formed by a nip between a metal roll and an elastic roll in a calender operation step. In the method for producing a magnetic recording medium in which the surface of the magnetic layer is smoothed, the Shore hardness (D scale) of the elastic roll at 23 ° C. is 94 or more, and the calender operating temperature is
The loss tangent Δ of the viscoelastic property of the elastic roll at 90 ° C. or higher and 130 ° C. or lower and the calender operating temperature T ° C. is Δ <0.0030385 × T-0.24769 for calendering.

The present invention according to claim 2 is the same as in the present invention according to claim 1, further comprising:
It is set to 4000 ppm.

The elastic roll used in the calendering step is one that smoothes the surface of the magnetic layer of the support by a nip with the metal roll, and therefore needs to be in a good elastic state. On the other hand, in the elastic roll, the elastic state is deteriorated due to deterioration of the material of the roll. This elastic state is the loss tangent of the viscoelastic property of the elastic roll (loss elastic modulus /
It can be known by measuring the storage elastic modulus). In the present invention, it was found that the ability of the elastic roll as an elastic body can be predicted by measuring the loss tangent, and it was confirmed that it can contribute to the production of a good quality magnetic recording medium. That is, the loss tangent of the elastic roll in the calender operation step is measured by a viscoelastic spectrum meter or the like, and if this measurement result is within the calculated range of the loss tangent, a good calendering effect is obtained using this elastic roll. Admitted that you can get.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for producing a magnetic recording medium, that is, a magnetic recording medium, that is, a magnetic layer formed by applying a magnetic coating material on a support and then subjecting the magnetic layer to a calender operation step. In the above, there is a feature in the calendar operation step.

That is, (a) the Shore hardness (D scale) of the elastic roll at 23 ° C. is 94 or more, (b) the calender operating temperature is 90 ° C. or more and 130 ° C. or less, and (c) the calender operating temperature T The loss tangent Δ of the viscoelastic property of the elastic roll at
<0.0030385 x T-0.24769 for calendar operation.

Hereinafter, these characteristic parts will be described. (a) Filler content of elastic roll, etc. Examples of the calendering device used in the calendering operation process include, for example, JP-B-61-2485 and JP-A-56-117335.
Conventionally known calenders, such as those described in Japanese Patent Application Publication No. Sho 57-4970 and the like, can be used. In the calendar operation step, generally, a metal roll is disposed on the magnetic layer side of the magnetic recording medium, and an elastic roll is disposed on the support side facing the metal roll.

The elastic roll is generally formed by coating the surface of the core of a metal roll with an elastic member. In this case, the thickness of the elastic member is preferably 1 to 20 mm, more preferably 5 to 15 mm. If the thickness is less than 1 mm, the effect of the core of the metal roll is exhibited. If the thickness is more than 20 mm, the elastic member is likely to be damaged. Examples of such an elastic roll include a cotton roll, a plastic roll, and a rubber roll. Of these, it is particularly preferable to use a plastic roll,
Among them, those using a polyester resin, a polyimide resin, or a polyether resin as the elastic member are preferable from the viewpoint of the elastic modulus.

The roll diameter of the elastic roll is not particularly limited, but is preferably 15 to 35 cm,
More preferably, it is 20 to 30 cm. By setting the roll diameter within the above range, a uniform elastic roll can be obtained.

(B) Calender operating temperature, etc. The calender operating temperature (mainly the temperature of the metal roll) is
The temperature is appropriately set according to the type and thickness of the support and the type of magnetic coating material, but in the present invention, it is preferably 90 to 130 ° C, more preferably 100 to 120 ° C.

The linear pressure of the calendering operation is appropriately set according to the type and thickness of the support and the type of magnetic coating material, but in general, it is preferably 100 to 400 kg / cm, and 200 to 350 kg / cm. More preferably, it is cm.

(C) Viscoelastic properties of elastic roll The elastic roll used in the calendering operation step has a high ability as an elastic body (not deteriorated) to obtain a high calendering effect (good calendering effect). Needed to be). In order to obtain a high calendering effect, the loss tangent Δ of the viscoelastic property of the elastic roll at the calender operating temperature T ° C. should be Δ <0.0030385 × T-0.2476.
9 is good. The loss tangent of the elastic roll can be measured with a viscoelasticity spectrometer. The loss tangent of the elastic roll at the calender operating temperature is measured with a viscoelasticity spectrometer, and if this measurement result is within the range of the above-mentioned calculated loss tangent, a good calendering effect can be obtained using this elastic roll. it can.

Although the surface roughness of the magnetic layer is lowered by the calendering step, the surface roughness of the magnetic layer before being subjected to the calendering step is preferably about 40 nm or less. The surface roughness is more preferably 4 to 15 nm, and even more preferably 4 to 12 nm. Incidentally, the surface roughness is a cutoff value of 0 defined in JIS B-0601.
It is a value measured with a center line average roughness of 25 mm.

As the support used in the method of the present invention, a known magnetic or non-magnetic support can be used without particular limitation. For example, a known resin such as polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polycarbonate, polyamide, polyimide, polyamide imide, polysulfone, aramid, and aromatic polyamide; a metal such as aluminum and copper; can do. Before forming the magnetic layer on the support, the surface thereof may be subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, or the like in advance. The preferred thickness of the support is generally between 1 and 300 μm.

The magnetic coating material applied to the above-mentioned support generally contains magnetic powder, a binder and a solvent, and if necessary, a dispersant, a lubricant such as fatty acid or its ester, and a polishing agent such as alumina. Agent, an antistatic agent such as carbon black, and an additive such as a curing agent such as polyisocyanate.

The magnetic powder is of a ferromagnetic iron oxide type, such as FeOx (1.33≤x≤1.5), Cr, Mn,
A material to which a metal such as Co or Ni is added; a ferromagnetic chromium dioxide-based material such as CrO ₂ or CrO ₂ Na, K, F
Metals such as e and Mn, oxides of these metals, or P
And a ferromagnetic metal powder type, for example, a metal content of 70% by weight or more, and a metal content of 80% by weight or more of at least one ferromagnetic metal (for example, Fe, Co, Ni, etc.).

As the binder, a cellulose resin, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinylidene chloride copolymer, a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, an epoxy resin and Polyurethane or the like can be used, but is not limited thereto. A commercially available product can also be used as the binder. Examples of such commercially available products include MR110 (epoxy group-containing vinyl chloride copolymer) manufactured by Zeon Corporation, VAGH manufactured by Nagase & Co., Ltd., and UR8200 (polyurethane) manufactured by Toyobo. .

The solvent can be used without particular limitation as long as it is suitable for dissolving the binder. Examples of such a solvent include ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ester solvents such as ethyl acetate, ether solvents such as tetrahydrofuran and dioxane, and benzene, toluene and xylene. Aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents, and the like.

The magnetic coating material obtained by mixing and dispersing the above components can be coated on the support by a known coating method such as gravure coating, spray coating or roll coating.
The dry thickness of the magnetic layer thus formed is generally
It is preferably from 0.1 to 5 μm, more preferably from 0.2 to 3 μm.

The method of the present invention is a so-called in-line calendering method in which the steps from the coating of the magnetic coating material on the support to the calendering step are carried out continuously, or after the magnetic layer has been formed, the support is once wound on a roll and then separated. It can be applied to any of the so-called off-line calendar systems that are attached to the calendar process.

In the method of the present invention, in addition to the steps described above, various steps generally used in the method of manufacturing a magnetic recording medium can be used without particular limitation. For example, after applying the magnetic paint to form a coating film, the magnetic powder in the coating film may be subjected to a magnetic field orientation treatment before the coating film is dried. Further, a finishing step such as a polishing or cleaning step of the magnetic layer surface may be performed.
The application of the magnetic paint can also be performed by a known sequential coating method. When a magnetic tape is manufactured as a magnetic recording medium, after the calendering step, aging treatment is performed at a predetermined temperature and time, and slitting to a desired width may be performed.

[0029]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the present invention is not limited to such Examples. In the following description, “part” means part by weight unless otherwise specified.

(Example 1) (Table 1) A magnetic tape was manufactured by the following procedure. First, the following composition was kneaded, dispersed, and diluted to prepare a magnetic paint. The obtained magnetic paint was applied on the surface of a PET support so that the dry thickness was 2.3 μm. While the coating film was passed through a 8000 Oe solenoid in a wet state, the magnetic powder was subjected to a magnetic field orientation treatment, and subsequently the coating film was dried with hot air at 80 ° C., and then the support was wound up. Then, using a calender device consisting of a metal roll and an elastic roll made of polyester resin (roll diameter 25 cm), a linear pressure of 250 k
g / cm, calendar operation temperature (metal roll temperature) 130 ℃
Was calendered under the conditions (operation speed (supporting speed of support) 150 m / min). In this case, a metal roll was arranged on the magnetic layer side of the magnetic tape, and the elastic roll was arranged on the support side facing the metal roll. After aging, slitting was performed to a predetermined width to obtain a magnetic tape.

-Acicular metal magnetic powder mainly composed of iron (coercive force 1500 Oe, saturation magnetization 130 emu / g, average major axis length 0.18 μm) 100 parts-alumina (average particle size 0.1 μm) 12 parts-carbon black ( Average primary particle size 20 nm) 1 part MR110 [Vinyl chloride copolymer manufactured by Zeon Corporation] 12 parts UR8200 (Toyobo polyurethane) 8 parts 2-Ethylhexyl stearate (lubricant) 1 part Palmitic acid (lubricant) 2 parts ・ Coronate L [hardening agent manufactured by Nippon Polyurethane Industry Co., Ltd.] 3 parts ・ Methyl ethyl ketone (solvent) 120 parts ・ Toluene (solvent) 80 parts ・ Cyclohexanone (solvent) 40 parts

At this time, as the elastic rolls of the calender device, those whose elastic states were changed as shown in A to F of Table 1 were used, and the above-mentioned calendering treatment was performed using each elastic roll. The elastic state of the elastic roll was changed by a combination of composition conditions. The loss tangent, which represents the elastic state of each elastic roll, was measured with a viscoelastic spectrometer and the measurement results are shown in Table 1. The viscoelasticity spectrometer used for the measurement is RDA700 manufactured by Rheometrics.
The loss tangent of each elastic roll was measured at a calender operating temperature (130 ° C).

Further, care was taken so that the amount of residual solvent which affects the calendering property was constant.

[0034]

[Table 1]

The surface roughness (Ra) and the output (dB) of the magnetic tape manufactured in this manner were measured, and the calendering effect of each elastic roll was investigated to obtain Table 1.

According to Table 1, the elastic rolls A, B and C are
The loss tangent at the calender operating temperature was small and the calendering effect was good. The elastic rolls D and E had a large loss tangent at the calender operating temperature and had a poor calendering effect. The elastic roll F was an elastic roll that was severely deteriorated after long-term use, and had a large loss tangent at the calender operating temperature, a poor roll surface condition, and an extremely poor calendering effect.

(Example 2) (Table 2) Using the elastic rolls G to L used in Example 1, calender operating conditions were linear pressure of 250 kg / cm, calender operating temperature of 90 ° C and operating speed of 150 m / min. A magnetic tape was manufactured and evaluated under the same manufacturing conditions as in Example 1 except that the treatment was performed.
Table 2 was obtained.

[0038]

[Table 2]

According to Table 2, the elastic rolls G and H had a small loss tangent at the calender operating temperature and had a good calendering effect. The elastic rolls I to K had a large loss tangent at the calender operating temperature and had a poor calendering effect. The elastic roll L is an elastic roll that is severely deteriorated due to long-term use, has a large loss tangent at the calender operating temperature, has a poor roll surface state, and has an extremely poor calendering effect.

Example 3 (Table 3) Using the elastic rolls M to R used in Example 1, the calender operating conditions were linear pressure of 250 kg / cm, calender operating temperature of 120 ° C.
A magnetic tape was manufactured and evaluated under the same manufacturing conditions as in Example 1 except that calendering was performed at an operation speed of 150 m / min.
Table 3 was obtained.

[0041]

[Table 3]

According to Table 3, the elastic rolls M and N had a small loss tangent at the calender operating temperature and had a good calendering effect. The elastic rolls O to Q had a large loss tangent at the calender operating temperature and had a poor calendering effect. The elastic roll R was an elastic roll that was severely deteriorated after long-term use, had a large loss tangent at the calender operating temperature, had a poor roll surface condition, and had an extremely poor calendering effect.

(Example 4) (Table 4) Using the elastic rolls S to U used in Example 1 and elastic rolls S to U differing only in Shore hardness, calender operating conditions were linear pressure of 250 kg / cm and calender operating temperature. 120 ℃, operating speed 150m
A magnetic tape was produced and evaluated under the same production conditions as in Example 1 except that the calender treatment was performed at a rate of 1 / min.

[0044]

[Table 4]

According to Table 4, the elastic rolls S and T had a small loss tangent at the calender operating temperature and had a good calendering effect. The elastic roll U is an elastic roll that is severely deteriorated due to long-term use and has a large loss tangent at the calender operating temperature, a poor roll surface condition, and an extremely poor calendering effect. Further, while the elastic rolls of Examples 1 to 3 had a Shore hardness (D scale) of 94 at 23 ° C., the elastic rolls of Example 4 had a Shore hardness (D scale) of 23 ° C. It was 95.5. From this, it was confirmed that even if the Shore hardness (D scale) of the elastic roll at 23 ° C. was changed, an effective magnetic recording medium could be produced if the loss tangent was within the range of the present invention.

Further, according to Table 4, the elastic rolls V, W
, The calender effect was not good even though the loss tangent at the calender operating temperature was small. It was confirmed that this was due to the effectiveness of the calender due to insufficient hardness of the elastic roll.

(Example 5) (Table 5) The same as Example 1 except that the elastic roll V used in Example 1 was used and the residual solvent amount of the coating film and the calender operating temperature were changed to 120 ° and 90 °. The magnetic tape was manufactured under the conditions, evaluated, and shown in Table 5.
I got

[0048]

[Table 5]

As a result, the loss tangent Δ is Δ <0.0030385.
Even in the range of × T-0.24769, if the amount of residual solvent is too low (300 ppm), the effect of the calender is poor, and if it is too high (4800 ppm), the amount of residual solvent after calender is large and the coating surface becomes weak. It was From the results of this experiment and Examples 1 to 4, it was confirmed that the loss tangent Δ was in the range of Δ <0.0030385 × T−0.24769, and the appropriate amount of solvent was 800 to 4000 ppm.

(Conclusion) A high calendering effect was obtained by using two combinations of calendering operation temperature T and loss tangent Δ of elastic rolls A, B, G and H, which were able to obtain a high calendering effect in Examples 1 and 2. The relationship between the calender operating temperature T ° C. and the loss tangent Δ of the viscoelastic property of the elastic roll which can be obtained was Δ <0.0030385 × T−0.24769, as shown in FIG. When the calender operating temperature T of the elastic rolls M and N of Example 3 and the elastic rolls S and T of Example 4 are inserted into the right side of the above formula for calculation, the measured value of the loss tangent Δ of the elastic roll A is calculated. It was confirmed that it was within the range of values.

[0051]

As described above, according to the present invention, it has been found that a high calendering effect can be obtained, and a magnetic recording medium with further improved output can be manufactured.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between calender operating temperature and loss tangent.

Claims (2)

[Claims] 1. A method for producing a magnetic recording medium, comprising forming a magnetic layer by coating a magnetic coating on a support and then smoothing the surface of the magnetic layer of the support by a nip between a metal roll and an elastic roll in a calender operation step. , The shore hardness (D scale) of the elastic roll at 23 ° C is 94 or more, the calender operating temperature is 90 ° C or more and 130 ° C or less, and the loss tangent of the viscoelastic property of the elastic roll at the calender operating temperature T ° C. A method of manufacturing a magnetic recording medium, which comprises performing a calendar operation with Δ of Δ <0.0030385 × T-0.24769. 2. The amount of residual solvent at the time of calendar is 800 to 4000.
The method of manufacturing a magnetic recording medium according to claim 1, wherein the content is ppm.