JPS6212921A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic tape having a good electromagnetic conversion characteristic as well as tape properties including runnability, durability, etc. by maintaining the surface pressure for pinching between parallel rolls to be brought into press contact with each other at >=700kg/cm<2> in the case of pinching a magnetic recording medium and subjecting the medium to a calender treatment. CONSTITUTION:The surface pressure for pinching between the parallel rolls to be brought into press contact in the stage of subjecting the magnetic recording medium to the calender treatment by pinching the medium in the press contact parts between plural pieces of the parallel rolls including mirror surface metallic rolls to be subjected to the press contact is maintained at >=700kg/cm<2>. The average surface roughness Ra of the parallel roll surfaces to be brought into press contact with each other under >=10<3>kg/cm<2> is preferably <=0.15mum and the average surface roughness of the mirror surface metallic rolls to be used for heating by contacting with the magnetic layer side is preferably <=0.05mum. Revolving shafts of the elastic roll 1 and heating roll 3 are provided in parallel and the heating roll is kept at 60-120 deg.C. The magnetic tape 2 is passed therebetween at 30-150m/min and is pinched. The pinching part of the elastic roll 1 is deformed to the surface conforming to the pinching part of the heating roll in the stage of the calender treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a magnetic recording medium, and particularly to a calendering method.

(Prior Art) Magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks are widely used in the audio, video, and computer fields. Among these, for example, regarding magnetic tape in the video field, when recording or playing back images, the cassette is loaded into a video deck, and the tape is guided by a guide ball or guide roller. While running, the magnetic head rubs and scans the magnetic head. In order to record images on magnetic tape or reproduce them in this way, in order to improve the sensitivity, especially the output in the high frequency range, it is necessary to prevent the sliding condition of the magnetic tape against the magnetic head from changing. The surface of the magnetic layer is finished smooth. The magnetic layer is designed to have improved runnability and durability against magnetic heads, guide rollers, etc.

Further, regarding the magnetic layer, a back coat layer is often provided on the back surface of the magnetic tape to improve running properties and durability because it has a similar effect on the above-mentioned fluctuation in the rubbing state.

On the other hand, the back side of the magnetic tape is roughened to reduce the contact area with route members such as guide poles provided on the travel route of the magnetic tape in video decks, etc., thereby reducing frictional resistance. . The degree of roughness in this case is, for example, a center line surface roughness Ra of 0.10 to 0.05 pm with a surface roughness cutoff of 0.08 mrtt.

The dynamic friction coefficient .mu. is controlled to 0.10 to 0.36 to ensure that no trouble occurs due to surface irregularities and that running performance and durability are improved. This surface roughening is controlled by adding organic or inorganic fillers to the back coat layer and other constituent layers of the magnetic tape, and the aforementioned smoothing of the magnetic tape surface is taken into account during the smoothing and orientation treatment immediately after coating, as well as during the drying process. At the same time, so-called calendering is used as an important smoothing means.

That is, after drying a magnetic tape on which a magnetic layer is formed on a support by a coating method, or after drying a back coat layer or other structural layer, the magnetic tape is subjected to a calender treatment in which the magnetic tape is pressed between the parallel rolls and heated. In this case, one of the rolls to be pressed is a mirror-finished metal roll as a heating roll, and the other is used as an elastic roll. The elastic roll is made of resin or metal, which has elasticity relative to the other roll but has high hardness.

Generally, in calendering, it is effective to bring the magnetic layer side into contact with a heating roll and apply a linear pressure of 50 to 1000 kg/cm (JP-A-49-104611, JP-A-55-1).
No. 35629 and No. 58-189839).

However, the conventionally disclosed technology focuses on the material of the elastic roll and the linear pressure conditions with a focus on the calender effect, and has not been studied from the perspective of improving the productivity of magnetic tape. Regarding the conventional manufacturing method, the calendering process is also not satisfactory.

(Objective of the Invention) An object of the present invention is to provide an efficient method for manufacturing a magnetic tape having good tape physical properties such as electromagnetic conversion characteristics, running properties, and durability.

Another object of the present invention is to provide a calendering method that achieves the above objects.

(Structure of the Invention) An object of the present invention is to manufacture a magnetic recording medium in which a magnetic recording medium is subjected to calendering by being pinched at a pressure contact portion between a plurality of parallel rolls including mirror-finished metal rolls subjected to pressure contact. This is achieved by a method for manufacturing a magnetic recording medium characterized in that the surface pressure between the parallel rolls that are in pressure contact is 700 kg/(i or more).

In addition, as an aspect of the present invention, the above-mentioned surface pressure is t03kg/(
, d or more is more preferable.

Further, it is preferable that the average surface roughness Ra of the parallel roll surfaces that are in pressure contact with each other is 0.15 μm or less. Further, the average surface roughness of the mirror-finished metal roll used for heating that contacts the magnetic layer side is preferably 0.10 μm or less, and more preferably 0.10 μm or less.
．． The thickness is preferably 0.05 μm or less.

In addition, the configuration of multiple parallel rolls including a mirror-finished metal roll (heating roll) that is subjected to pressure contact is such that the number of heating rolls is small (the axis of each parallel roll is the same on the premise that it is subjected to pressure contact once by an elastic roll). It may be in a plane and/or in a curved surface formed by parallel lines, or a heating roll and an elastic roll may be connected in pairs.

(effect)　　゛ The present invention will be explained with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an elastic roll made of hard resin such as polyamide resin, polyurethane resin, crosslinked polyester resin, phenolic resin, epoxy resin, etc.
Or metal is used.

2 is a magnetic tape coated with a magnetic layer and other constituent layers;
1 is a magnetic layer, and 22 is a support. Although the back coat layer and other constituent layers are omitted in the illustrated example, they may be provided if necessary.

3 is a metal heating roll. Incidentally, the elastic roll may be provided with a cooling or heating mechanism as required.

The rotational axes of the elastic roll 1 and the heating roll 3 are arranged in parallel, and the heating roll is heated to 60 to 120'C, and the magnetic tape 2 is passed between them at 30 = 150 m/min and compressed.

During the calendering process, the pinching portion of the elastic roll 1 is deformed to become a surface along the pinching portion of the heating roll. At this time, the knob width (width) 2b in the pinching part is expressed by the following formula (1).

In the formula, p' is the load per unit length, that is, the linear pressure (kg/C1r
L), using the above formula (1), the surface pressure σ (kg/i
) is determined by the following formula (2) r.

σ-p'/2b...(2) In the present invention, as σ increases and Ra of the roll surface decreases, the S/N of the magnetic tape or the electromagnetic conversion characteristics of high Rf output decreases. will improve.

Furthermore, the effect of surface pressure σ is 700kg/cr! Since it shows a tendency to saturate at some point, its upper limit is determined by economic considerations such as the cost of calender rolls and the running cost of calender treatment. Also, the lower limit of Ra is selected by oneself depending on technical and economical limits.

(Example) Next, a concrete explanation will be given using examples.

Example 1 The following four types of elastic rolls were used.

The Young's modulus of the heating roll (metal) is 1oooooo kg
/i.

After dispersing the magnetic paint (composition: 510 parts of magnetic iron oxide, 20 parts of carbon black, 40 parts of vinyl chloride-vinyl acetate resin), it was applied onto a 14 μm polyethylene terephthalate film using a doctor method to a dry film thickness of 6 μm and dried. Heating roll temperature 80℃ using 4 types of elastic rolls on the back
, processing speed 4Q m/min processing number 1-8, line pressure 1
Calendar treatment was performed at 9/cIrL from 50 to 350 (9/i from surface pressure 150 to 1,500).

At this time, the relationship between the high Rf output and S/N of the magnetic tape and the surface pressure of the clamping portion was investigated, and the result was as shown in FIG. 2.

Here, S/N is the S/N when a signal with a center frequency of 4 MHz can be recorded, and the output of a signal similar to Rf high output is based on Konica SR Normal (manufactured by Konica Magnetex). It is expressed as a relative value.

From this, when the surface pressure is 700klil/i, the S/N and Rf high output reach the standard value, and when it becomes 1d or more at 700kg/i, there is a tendency to saturate, and the performance improvement slows down.
/cm2 or more is useful in terms of production technology because the uniformity of quality can be easily changed.

Example 2 Various elastic rolls with different average surface roughnesses had an average surface roughness of 0.
．． A surface pressure of 70 is achieved by combining a 05 μm metal heating roll.
Calendar treatment was performed in the range of 0 kg/(-J or higher (heating roll 80°C, processing speed 40 m/m1n)
.

Types of elastic rolls, Ra, and hollowed-out magnetic tape Table-1 Note that the S/N and Rf outputs are based on the case of gold gold rolls.

Example 3 Next, calendering was performed at 80° C. and a surface pressure of 700 klilΔ using metal rolls having different center line average roughnesses Ra as shown below, and the performance (S/N, output) was compared. The results are shown in Table 2 below.

Table 2 S/N and Rf ratio output values are based on the case of Ra=0.15.

From Table-1 and Table-2, Ra is 0.15 regardless of the roll material.
If it is less than 0.15, there is no problem in performance, but if it is greater than 0.15, performance deteriorates.

[Brief explanation of drawings]

Figure 1 shows the cross sections of the elastic roll, magnetic tape, and heat control roll during calendering according to the present invention. represent FIG. 2 is a graph showing the relationship between surface pressure, S/N, and Rf specific output. Applicant Konishiroku Photo Industry Co., Ltd. Figure 1

Claims (2)

[Claims] (1) In a method of manufacturing a magnetic recording medium, the magnetic recording medium is subjected to calendering by being pressed between a plurality of parallel rolls including mirror-finished metal rolls that are pressed together at a pressure contact portion between the parallel rolls that are pressed. The surface pressure between the two is 700kg/cm
A method for manufacturing a magnetic recording medium, characterized in that the magnetic recording medium is ^2 or more. (2) The method for manufacturing a magnetic recording medium according to claim 1, wherein the center line average surface roughness Ra of the parallel roll surfaces is at least 0.15 or less.