JP3084308B2 - 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 by uniformly applying a magnetic paint to a web as a nonmagnetic support.

[0002]

2. Description of the Related Art In a method in which an extrusion-type coating head is relatively pressed against a supporting web in a state in which the rear face of a running web is not supported, as shown in FIG.
Before and after the coating head 7, backup rolls 5, 5 '
Is provided. The backup roll has a mechanism capable of adjusting the position independently on both sides, and by adjusting the position, the support 6 can be uniformly pressed against the slit outlet (lip) from which the application liquid is discharged.
Uniform pressing is to add uniform ejection resistance to the application liquid ejected from the slit, and is a key to uniforming the thickness in the width direction.

[0003]

If the discharge resistance changes depending on the position, the coating liquid is discharged from a position where the resistance is small, and the thickness in the width direction becomes uneven. In other words, if the support is not pressed uniformly to the lip, the yield will decrease due to the variation in thickness. In recent years, the application speed has been increased to improve productivity, or the film thickness has been reduced for high-density recording.However, an extrusion-type coating head is used without supporting the back surface. In the conventional coating method, when increasing the speed or reducing the thickness, it is necessary to increase the tension applied to the support in order to maintain optimum coating conditions. At this time, the support deforms elastically in response to the applied tension, expands in the direction in which the tension is applied, and simultaneously tries to shrink in the width direction. Changes to When this state becomes remarkable, uniform pressing of the support against the lip cannot be performed, and the ejection resistance changes locally, making uniform coating impossible. Even if the position of the backup roll provided before and after the extrusion-type coating head is adjusted, this phenomenon cannot be avoided, and this is an important problem in increasing the speed or reducing the thickness of the layer.

[0004]

As a result of various studies to solve the above-mentioned problems, stable application is achieved by setting the application portion tension within a set tension range in accordance with the physical properties of the support. Turned out to be possible. Support width direction 1
The lower limit of the coating portion tension T [kg / cm] per cm is 0.06 [kg / cm] regardless of the physical property of the support, and the upper limit is the Young's modulus E (MD direction) of the support [kg / mm]. ² ] was multiplied by the thickness t [cm] of the support (only less than 15 × 10 ⁻⁴ cm) and a constant of 0.7, it was found that the above problem could be improved. It has been found that by applying the coating under these conditions, the influence of the waving phenomenon of the support can be almost neglected, and a higher speed or a thinner layer can be achieved. That is, the tension setting formula 0.06 <T <
An excellent effect can be obtained by employing a tension T satisfying 0.7 · E (MD) · t.

[0005]

[Explanation of the embodiment]

(Example 1) Video paint (apparent viscosity 170c at a solid content of 45% and a shear rate of 3000 [l / s])
p) The Young's modulus (MD) is 550 kg / mm ² and the thickness is 14 × 10 ^-4 [c] such that the film thickness after drying is 3.5 μm.
m], a coating speed of 600 on a support having a width of 520 mm.
m / min. At this time, the application portion tension was set to 0.06.
It was set as kg / cm.

(Embodiment 2) The tension of the application part was 0.53 kg /
cm and applied.

(Comparative Example 1) The tension of the application part was 0.05 kg /
cm and applied.

(Comparative Example 2) The tension of the application portion was 0.55 kg /
cm and applied.

Example 3 Using the same paint, Young's modulus (MD) 1500 kg / mm
² , thickness 10 × 10 ⁻⁴ [cm], support width 520 mm
After drying, the coating thickness was 1 μm and the coating speed was 3
The coating was performed in the same manner as in Example 1 at a speed of 00 m / min. At this time, the application portion tension was set at 0.10 kg / cm.

(Embodiment 4) The tension of the coating section is set to 1.00.
It was set as kg / cm and coating was performed.

(Comparative Example 3) The tension of the coating portion was 1.10
It was set as kg / cm and coating was performed.

(Comparative Example 4) The coating was performed by changing the support of Example 1 to a tension of 1.00 kg / cm at the coating portion.

The results are shown in Table 1.

[0014]

[Table 1]

[0015] When the application portion tension is set to exceed the value defined by the application portion tension setting formula, when the lower limit value is divided, the transfer of the paint does not occur uniformly, and the application surface becomes thin and the upper limit value is set. When the coating was applied over the base, the deformation of the base became remarkable, resulting in stripe-shaped coating unevenness, or the coating itself could not be performed. On the other hand, if a tension within the range defined by the formula for setting the application section tension is used,
Uniform application of the magnetic paint can be achieved.

[0016]

As described above, according to the present invention, uniform application of the magnetic paint can be achieved by using a tension within the range defined by the equation for setting the tension of the application section.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a coating method used in the present invention.

[Explanation of symbols]

 5, 5 'backup roll 6 support (web) 7 nozzle for applying magnetic paint

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-117666 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/848

Claims (1)

(57) [Claims] 1. A method in which an extrusion-type coating head is relatively pressed against a web while not supporting a back surface of a running web, and a coating liquid is extruded from at least one slit of the coating head to apply the coating liquid to a support. 3. The method for producing a magnetic recording medium according to claim 1, wherein the tension applied to the coating portion for a width of 1 cm of the support is within the following range. 0.06 <T <0.7 · E (MD) · t T: Coating part tension per 1 cm of support width [kg / cm] t: Thickness of support [cm] less than 15 × 10 ⁻⁴ cm E (MD): Young's modulus of the support in the MD direction [kg / mm ² ]