JPH0562179A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To manufacture, by using an extrusion-type coating head, a recording medium wherein a change in its coating thickness is small. CONSTITUTION:In a state that the back of a running nonmagnetic web 6 is not supported, an extrusion-type coating head 7 is pressed to the web. A magnetic paint is extruded from at least one slit in the coating head; the web is coated with the paint. Two backup rolls 5, 5' are installed at the front and the rear of the coating head; the contact angle of said backup rolls with reference to the web is variable; the shape itself of the backup roll main bodies is variable and can be adjusted. It is possible to obtain a magnetic recording medium in which a change in its thickness is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnetic recording medium, and more particularly to a method for producing a magnetic recording medium by applying a magnetic coating film to a web serving as a support.

[0002]

2. Description of the Related Art In a method of applying an extrusion type coating head by pressing it relative to the web without supporting the back surface of a running web, backup rolls are provided before and after the coating head. The backup roll has a mechanism in which the position can be adjusted independently on both sides, and by adjusting the position, the web can be pressed uniformly against the slit outlet (lip) from which the coating liquid is discharged. The uniform pressing is to add a uniform discharge resistance to the coating liquid discharged from the slit, which is a key for making the thickness in the width direction uniform. If the discharge resistance changes depending on the position, the coating liquid is discharged from a position having a small resistance, and the thickness in the width direction becomes nonuniform. That is, if the pressing of the web against the lip is uneven, the yield will decrease due to the variation in thickness.

[0003]

[Problems to be Solved by the Invention] The web has a habit of being stretched or deformed. Regarding one-sided elongation, if the elongation state changes at a constant rate in the web width direction, it is possible to deal with it by adjusting the positions of the two front and back backup rolls. It may be located in the central portion or in a plurality of locations in the width direction, and the habits of the webs are different. Therefore, there is a drawback in that such a defect of the web cannot be adjusted only by adjusting the position of the backup roll finished in a fixed shape.

[0004]

As a result of various studies to solve the above problems, if a mechanism for adjusting not only the position of the backup roll but also the shape of the backup roll itself is added, I found that I could solve the problem.

That is, according to the present invention, the extrusion type coating head is relatively pressed against the web while the back surface of the traveling non-magnetic web is not supported, and the magnetic coating material is extruded from at least one slit of the coating head so as to push the web. A method of applying a magnetic recording medium, wherein the two backup rolls provided in front of and behind the coating head have variable contact angles with respect to the web, and the shape of the backup roll itself is also variable. The above problems are solved by providing a method.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A backup roll of the present invention is shown in FIG.
FIG. 2 also shows the entire structure in FIG. As shown in FIG. 1 partially broken, the backup rolls 5 and 5'of the present invention.
Has a hollow outer cylinder 1, and a roll-shaped control unit 2 using a piezo element 3 is incorporated therein. The amount of expansion of the piezo element is determined by the voltage applied from the outside, and the degree of pushing up the outer cylinder is changed by adjusting the voltage. As a result, the shape of the outer cylinder changes.

Since the outer cylinder 1 is in contact with the base film 6, it is driven from the outside at the same peripheral speed as the line speed so that the base film is not scraped. The tip of the piezo unit 2 has a structure as shown in FIG. As shown in (1), the bearing balls 4 are incorporated so that the outer cylinder 1 is less likely to be worn. Regarding the above-mentioned web defect (deformation), it is most effective to correct it by the shape change of the backup roll at the point of the last contact with the roll surface, and when incorporating it inside, the position is adjusted and incorporated. Further, since the roll shape is controlled, usually, a plurality of units are incorporated in the width direction, and each unit operates based on the data from the film thickness meter.

As another method for controlling the shape of the backup roll, hydraulic pressure may be used instead of the piezo element, and thermal expansion provided with a cooling mechanism for putting a heater inside to cool the outside is used. You can use what you did. However, considering the response of the device, it can be said that the method using the above-described piezo element or hydraulic pressure has a fast response. However, this is not limited to these methods, and any other mechanism satisfying the conditions can be sufficiently dealt with.

(Example 1) Using a coating apparatus having the structure shown in FIGS. 1 to 3 and a magnetic paint for a video tape, at a coating speed of 300 m / min, the film thickness after drying is 3 μm. The supply flow rate was adjusted so that 10 rolls were continuously coated on a 520 mm width base. In the device of the present invention, the piezo unit is divided into 10 points in the width direction with respect to the base width of 520 mm, and the outer diameter of the backup roll is 15 points.
A sample was prepared by using an iron pipe having a thickness of 0 mm and a wall thickness of 5 mm.

(Comparative Example 1) 10 rolls were continuously coated under the same conditions as in Example 1 except that the coating was performed in a state where the shape of the backup roll was not controlled (control was cut off).

(Example 2) Using audio paint A,
The thickness of the coating film after drying is 2.
After applying 2 rolls so as to have a thickness of 5 μm and thermally curing the lower layer original fabric, one of the two rolls is extruded with the audio B coating material and the upper layer thickness is dried by using the coating head and the backup roll of the present invention. It was applied so as to have a thickness of 0.2 μm to prepare an audio tape having a two-layer structure. Also,
The base width and upper layer coating speed used were the same as in Example 1.

(Comparative Example 2) Under the same conditions as in Example 2, except that the shape of the backup roll was not controlled (control was cut) in the remaining one lower roll of roll which was not used in Example 2, 2 I made a layered audio tape. At this time, the stretched and deformed state of the lower layer raw fabric was the same as in the case of Example 2. The results for the base film are compared between Example 1 and Comparative Example 1 and are shown in Table 1.

[0013]

[Table 1]

Regarding the thickness unevenness in the width direction, an X-ray film thickness meter with a spot diameter of 2 mm was used for each sample, and
The values measured every mm are shown as minimum and maximum for each of the 10 rolls. Regarding the streak defect, the number of samples in which a locally thick portion (a streak in transmission) was observed when each sample was observed in transmission was displayed.

As is clear from the results shown in Table 1, in the sample coated with the conventional backup roll, the habit of the base film itself could not be adjusted and local thickness unevenness was caused, resulting in a large variation in thickness. The result was poor uniformity. Table 2 shows the measurement results of the variation in sensitivity with respect to the coated original fabric.

[0016]

[Table 2]

As can be seen from Table 2, in the sample coated with the conventional backup roll, the elongation or deformation of the lower layer original fabric could not be adjusted, and the upper layer thickness of that portion was locally increased, and the tape When measured as a characteristic of No. 2, the thickness balance of the upper and lower layers was broken, and the sensitivity in the low and high regions fluctuated significantly in the width direction of the material, and the results are shown in Table 2. Further, in the case of Comparative Example 2, 11 reels of defective products were out of the standard of sensitivity.

[0018]

As is clear from the above results, according to the present invention, the habit of the base film itself can be adjusted, a magnetic recording medium having a uniform coating thickness can be obtained, and the sensitivity of the tape can be reduced. Can be made uniform in the width direction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the inside of a main body of an example of a backup roll of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a piezo unit of the present invention.

FIG. 3 is an overall configuration diagram of an extrusion type coating head used in the present invention.

[Explanation of symbols]

 1: Outer cylinder of backup roll 2: Piezo unit 3: Piezo element main body 4: Bearing balls 5, 5 ': Backup roll 6: Web 7: Extrusion type coating head

Claims (1)

[Claims] 1. An extruding type coating head is relatively pressed against the web while the back surface of the running non-magnetic web is not supported, and magnetic coating is extruded from at least one slit of the coating head to apply the magnetic coating to the web. A method of manufacturing a magnetic recording medium, characterized in that two backup rolls are provided in front of and behind the coating head, and the contact angle of the backup roll with respect to the web can be changed, and the shape of the backup roll body itself is also variable. Method.