JP3149103B2 - Manufacturing method of magnetic recording medium - Google Patents

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 increase the 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 Application Laid-Open No. 1-94532 discloses a method for manufacturing a magnetic recording medium, which comprises applying a magnetic coating solution on a non-magnetic support, providing a magnetic layer, and then performing a calendering process. 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 solution, and the calendering is performed when the residual solvent amount of the magnetic layer becomes 0.1 to 3% by weight. .

Japanese Patent Application Laid-Open No. 4-49821 discloses a method for manufacturing a magnetic recording medium, which describes a time required from the time when magnetic powder is charged into a kneading machine to the time when a calendar operation step after application of a magnetic paint is completed. It is described that it is 2 to 48 hours.

Japanese Patent Application Laid-Open No. 58-194142 discloses a method for manufacturing a magnetic recording medium, which comprises applying a magnetic coating solution on a non-magnetic support to form a magnetic layer, and then performing a calender treatment. The humidity of the calendering atmosphere is 60% R
H or more is described.

JP-A-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. Furthermore, the publication also mentions the water content in the elastic roll. However, in the publication, the water content is only mentioned in relation to the frictional voltage of the roll, and the water content affects the mechanical deformation of the elastic roll in relation to the Shore hardness. No effect is stated.

[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]

According to the first aspect of the present invention, after a magnetic layer is formed by applying a magnetic paint on a support, 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 for smoothing the surface of a magnetic layer, the elastic roll has a Shore hardness (D scale) at 23 ° C. of 94 or more, and a calender operation temperature.
The calender operation is performed at a temperature of 90 ° C. or more and 130 ° C. or less and a loss tangent Δ of the viscoelastic property of the elastic roll at a calendar operation temperature T ° C. of Δ <0.0030385 × T−0.24769.

According to a second aspect of the present invention, in the first aspect of the present invention, the amount of the residual solvent at the time of calendering is further reduced to 800 to 800.
It is set to 4000 ppm.

The elastic roll used in the calendering step is required to be in a good elastic state because the surface of the magnetic layer of the support is smoothed by nip with the metal roll. On the other hand, in the case of the elastic roll, the elastic state is reduced due to deterioration of the roll material or the like. This elastic state is determined by the loss tangent (loss elastic modulus /
It can be known by measuring the storage modulus. In the present invention, it has been found that the ability of the elastic roll as an elastic body can be predicted by measuring the loss tangent, and it has been confirmed that the elastic roll 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 the measurement result falls within the range of the calculated value of the loss tangent described above, a good calender effect is obtained using the elastic roll. Admitted that it can be obtained.

[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 properties of the elastic roll at
<0.0030385 × T−0.24769 to operate the calendar.

Hereinafter, these characteristic portions will be described. (a) Filler content of elastic roll, etc. Examples of the calendering device used in the calendering operation process include, for example, Japanese Patent Publication No. 61-2485 and Japanese Patent Application Laid-Open No. Sho 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.

[0015] The elastic roll is generally formed by coating the surface of a 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 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, the type of the magnetic paint, and the like. In the present invention, the temperature is preferably 90 to 130 ° C, and 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, the type of the magnetic paint, and the like, but is generally preferably 100 to 400 kg / cm, and preferably 200 to 350 kg / cm. More preferably, it is cm.

(C) Viscoelastic properties of the elastic roll The elastic roll used in the calendering operation step has a high calender effect, which means that it has a high capacity as an elastic body (it does not deteriorate). Required). In order to obtain a high calender effect, the loss tangent Δ of the viscoelastic property of the elastic roll at the calender operating temperature T ° C. is defined as Δ <0.0030385 × T−0.2476.
9 is good. The loss tangent of the elastic roll can be measured by a viscoelastic spectrum meter. The loss tangent of the elastic roll at the calender operating temperature is measured by a viscoelastic spectrometer, and if the measurement result is within the range of the calculated value of the loss tangent described above, a good calender effect can be obtained using the elastic roll. it can.

Although the surface roughness of the magnetic layer is reduced by the calendering step, the surface roughness of the magnetic layer before the calendering step is preferably about 40 nm or less. The surface roughness is more preferably from 4 to 15 nm, even more preferably from 4 to 12 nm. Incidentally, the surface roughness is a cutoff value of 0 defined in JIS B-0601.
It is a value measured at 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 any particular limitation. For example, a known resin such as polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polycarbonate, polyamide, polyimide, polyamide imide, polysulfone, aramid, or aromatic polyamide; a metal such as aluminum or copper; a support made of paper or the like is used. can do. Before forming the magnetic layer on the support, a corona discharge treatment, a plasma treatment, an easy adhesion treatment, a heat treatment, a dust removal treatment, and the like can be performed on the surface thereof in advance. The preferred thickness of the support is generally between 1 and 300 μm.

The magnetic paint applied on the support generally contains a magnetic powder, a binder and a solvent, and if necessary, a dispersant, a lubricant such as a fatty acid or an ester thereof, and a polishing agent such as an alumina. And additives such as an antistatic agent such as carbon black and a curing agent such as polyisocyanate.

As the magnetic powder, a ferromagnetic iron oxide-based powder such as FeOx (1.33 ≦ x ≦ 1.5), Cr, Mn,
Co, Ni or other metal added; ferromagnetic chromium dioxide type, such as CrO ₂ or CrO ₂ with Na, K, F
metals such as e and Mn or 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.).

Examples of the binder include 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, 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 any 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 paint obtained by mixing and dispersing the above components can be applied onto the support by a known coating method, for example, a 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.

In the method of the present invention, a so-called in-line calender method in which the steps from application of a magnetic coating material on a support to a calendering step are continuously performed, or the support is once wound around a roll after forming a magnetic layer, and then separately The present invention can be applied to any of the so-called off-line calendar systems that are provided in the calendar step.

In the method of the present invention, in addition to the above-described steps, various steps generally used in a method for manufacturing a magnetic recording medium can be used without any 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, an aging treatment may be performed at a predetermined temperature and time after the calendering step, and slitting may be performed to a desired width.

[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, “parts” means “parts by weight” unless otherwise specified.

Example 1 (Table 1) A magnetic tape was manufactured by the following operation. 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 operating temperature (metal roll temperature) 130 ° C
(The operation speed (running speed of the 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.

-Needle-like 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 (polyurethane manufactured by Toyobo) 8 parts ・ 2-ethylhexyl stearate (lubricant) 1 part Palmitic acid (lubricant) 2 parts ・ Coronate L [curing 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, those having changed elastic states as shown in A to F in Table 1 were used, and the above-described calendering process was performed using each elastic roll. The change in the elastic state of the elastic roll depends on the combination of the composition conditions. The loss tangent representing the elastic state of each elastic roll was measured by a viscoelastic spectrum meter, and the measurement results are shown in Table 1. The viscoelastic spectrometer used for the measurement is RDA700 manufactured by Rheometrics.
In addition, the measurement result of the loss tangent of each elastic roll was a measured value at a calendar operation temperature (130 ° C.).

Also, care was taken to keep the amount of the residual solvent affecting the calendering property constant.

[0034]

[Table 1]

The surface roughness (Ra) and the output (dB) of the magnetic tape thus manufactured were measured, and the calender effect of each elastic roll was investigated.

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

Example 2 (Table 2) Using the elastic rolls G to L used in Example 1, a calender was operated under the conditions of a linear pressure of 250 kg / cm, a calender operating temperature of 90 ° C., and an 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 showed a small loss tangent at the calender operating temperature and a good calender effect. The elastic rolls I to K had a large loss tangent at the calender operating temperature, and the calender effect was poor. The elastic roll L is an elastic roll that is severely deteriorated by long-term use, has a large loss tangent at a calender operating temperature, has a poor roll surface condition, and has an extremely poor calender effect.

(Example 3) (Table 3) Using the elastic rolls M to R used in Example 1, the calender operating conditions were as follows: linear pressure 250 kg / cm, calender operating temperature 120 ° C,
A magnetic tape was manufactured and evaluated under the same manufacturing conditions as in Example 1 except that a calendar process 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 exhibited a small loss tangent at the calender operating temperature and a good calender effect. The elastic rolls O to Q had a large loss tangent at the calender operating temperature, and the calender effect was poor. The elastic roll R is an elastic roll that is greatly deteriorated by long-term use, has a large loss tangent at a calender operating temperature, has a poor roll surface condition, and has an extremely poor calender effect.

(Example 4) (Table 4) Using the elastic rolls S to U differing only in the shore hardness from the elastic roll used in Example 1, the calender operating conditions were set to a linear pressure of 250 kg / cm and a calender operating temperature. 120 ° C, operation speed 150m
A magnetic tape was manufactured and evaluated under the same manufacturing conditions as in Example 1 except that the calendering treatment was performed at / min.

[0044]

[Table 4]

According to Table 4, the elastic rolls S and T exhibited a small loss tangent at the calender operating temperature and a good calender effect. The elastic roll U is an elastic roll that is severely deteriorated by long-term use, has a large loss tangent at a calendar operating temperature, has a poor roll surface condition, and has a very poor calendar effect. The shore hardness (D scale) at 23 ° C. of the elastic rolls of Examples 1 to 3 was 94, whereas the shore hardness (D scale) at 23 ° C. of the elastic roll of Example 4 was 95.5. As a result, it was confirmed that an effective magnetic recording medium could be manufactured as long as the loss tangent was within the range of the present invention, even if the Shore hardness (D scale) at 23 ° C. of the elastic roll was changed.

According to Table 4, the elastic rolls V, W
Had a poor calendering effect despite the small loss tangent at the calender operating temperature. It was recognized that this was caused by the effect of the calender due to insufficient hardness of the elastic roll.

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

[0048]

[Table 5]

As a result, the loss tangent Δ becomes Δ <0.0030385
Even in the range of T-0.24769, if the amount of the residual solvent is too low (300 ppm), the effectiveness of the calender is poor. If the amount is too high (4800 ppm), the residual solvent after the calender is large and the coating surface is weakened. 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 the solvent was 800 to 4000 ppm.

(Conclusion) A high calender effect was obtained by using two combinations of the calender operating temperature T and the loss tangent Δ of the elastic rolls A, B, G, and H, which were able to obtain a high calender effect in Examples 1 and 2. The relationship between the calender operating temperature T ° C. that can be obtained and the loss tangent Δ of the viscoelastic properties of the elastic roll was determined, as shown in FIG. 1, as Δ <0.0030385 × T−0.24769. When the calender operation temperature T of the elastic rolls M and N of the third embodiment and the elastic rolls S and T of the fourth embodiment is inserted into the right side of the above equation and calculated, the measured value of the loss tangent Δ of the elastic roll A is calculated. It was found to be in 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 the drawings]

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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 5/84 B29C 71/02 B29L 7:00

Claims (2)

(57) [Claims] 1. A method of manufacturing a magnetic recording medium, comprising: applying a magnetic paint on a support to form a magnetic layer; and smoothing the magnetic layer surface of the support by a nip between a metal roll and an elastic roll in a calender operation step. The shore hardness (D scale) at 23 ° C of the elastic roll is 94 or more, the calendar 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 calendar operating temperature T ° C A method for producing a magnetic recording medium, wherein a calendar operation is performed by setting Δ to Δ <0.0030385 × T−0.24769. 2. The amount of the remaining solvent at the time of calendering is 800 to 4000.
2. The method for producing a magnetic recording medium according to claim 1, wherein the content is ppm.