JPH07176047A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To produce a recording medium of high output and high durability by applying a magnetic coating material on both surfaces of a supporting body at one time, or by coating the one surface with this coating material and then coating the other surface while the coating material first applied is not dried, and then performing at least orienting or non-orienting treatment on both surfaces at one time. CONSTITUTION:A sheet like supporting body 1 is supplied from a supply roll 20 and carried by a driving roll 21 for carrying. In the coating step of a magnetic coating material, both surfaces of a magnetic layer are coated with extrusion coaters 2 of an extrusion system disposed on both surfaces of the supporting body 1. The magnetic layer may be formed by coating the one surface at first and then coating the other surface while the first applied coating material is not dried. The guide roller 22 is used to apply coating pressure. A smoother 3 is used to smooth the coating surface. Then the supporting body 1 is carried to a drying step and orienting step. The first and second drying zones 12, 14 are not used to dry the coating material but used to control the viscosity of the coating material.

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 such as a magnetic disk or a magnetic sheet.

[0002]

2. Description of the Related Art Conventionally, such as a flexible disk shown in FIG. 13 (in the figure, 1 is a support, 7 is a magnetic layer),
As a means for forming a magnetic recording medium having magnetic layers on both sides, a magnetic coating is first applied to one side of a sheet-like support, magnetic field orientation and drying are performed, and then calendering is performed, and then the support is re-applied. A method of performing the same processing on the other surface and finally punching it into a disk shape (hereinafter referred to as a conventional method) has been adopted.

However, the above-mentioned means have various inconveniences. That is, at the coating stage of the magnetic coating, since the support is warped at the stage where the treatment on one side is completed, the coating on the magnetic layer coating on the other side is not successful and the film thickness becomes uneven. Had a different film thickness depending on the surface.

Regarding the magnetic field orientation, the degree of orientation varies depending on the surface, and even in the drying step, since the coating film is attached on one side, the thermal conductivity also varies, and the dry state of both sides (residual solvent). The amount, surface roughness, and void) were different.

Further, in the calendering process, the surface to which the magnetic paint has been previously applied is to be calendered twice as much as the other surface, so that compaction (compressibility) and surface property (surface There was a difference in roughness or hardness).

Therefore, since the formed magnetic recording material such as a flexible disk is also warped or bent, or the surface properties, the film thickness, etc. are different depending on the surface, there are variations in the electromagnetic conversion characteristics and durability. there were.

To further describe the problems concerning magnetic field orientation,
The magnetic powders disclosed in JP-A Nos. 50-72605, 52-117601, 53-62505, etc. are concentrically formed on the surface of the support (hereinafter sometimes referred to as a circle). In the case of the magnetic field orientation technology, it is difficult to align and detect the centers of circles in the conventional method because the magnetic field orientation is performed separately on both sides. (An example of a concentric circular flexible disk is shown in FIG. 14 (b), where 36 represents magnetic powder.)

Further, Japanese Examined Patent Publication Nos. 63-41132 and 63-4113.
In the technique of magnetic field orientation of magnetic powder in the direction perpendicular to the surface of a support, which is disclosed in each publication of No. 4, etc., when the viscosity of the coating film is low, the magnetic powder particles are likely to rotate and it is difficult to arrange them in the vertical direction. For this reason, it is necessary to adjust the viscosity of the coating film, but in the conventional method, there is a difference in the thermal conductivity depending on the surface as described above, and therefore a difference in the degree of orientation also occurs (example of a cross-sectional view of vertical orientation). Figure 14
(Shown in (c)).

In addition to the above, the technique relating to alignment is disclosed in Japanese Patent Laid-Open No.
-14307, 52-108805, 53-104206, 61-
No. 289531, No. 61-289532, JP-A No. 2-47012 and the like are disclosed, but none of them can solve the above problems because simultaneous coating on both sides is not performed.

Regarding the method of transporting the support, after providing a coating film on one surface of the support, at the stage when the coating film loses fluidity, while supporting the coating surface by gas pressure,
The technology of providing a coating film on the other side is
-57385. However, in this technique, since the second stage coating is applied to the support on the roller that blows out the gas, there is a problem in that the support is swayed by the flow of the gas and is not stable, and unevenness occurs.

[0011]

The object of the present invention is that the coating state of the magnetic layers formed on both sides, the orientation state of the magnetic powder, the degree of compression by a calender roll, the electromagnetic conversion characteristics, etc. are equal to each other, and the high output and the high output are high. It is an object of the present invention to provide a method for manufacturing a durable magnetic recording medium.

[0012]

The present invention provides a method for producing a magnetic recording medium having a magnetic layer containing magnetic powder on both sides of a support,
(1) coating the magnetic layers on both sides of the support at the same time,
Alternatively, a step of applying the other layer to the remaining surface in an undried state after applying on one side, and (2) after that, a support having the magnetic layers applied on both sides is passed through a magnetic field to apply the magnetic powder. The present invention relates to a method for manufacturing a magnetic recording medium, which comprises the step of orienting or non-orienting (an example of a non-orienting flexible disk is shown in FIG. 14A).

The above-mentioned orientation is preferably performed concentrically on the support or in a direction perpendicular to the support.

When using an electromagnet for the concentric orientation, it is preferable to use one of the following methods. (1) Insert another AC electromagnet (B) having an outer diameter smaller than this into the central portion of the coreless AC electromagnet (A), and make the currents I _A and I _B flowing through (A) and (B) Combined electromagnets adjusted to be unequal are placed on both sides of the support. (2) An alternating current electromagnet having a coil wound in an annular shape is arranged on both sides of the support. (3) A plurality of AC electromagnets are arranged in a circular shape or a semicircular shape, and are arranged on both sides of the support.

It is also preferable that after the magnetic layers are coated on both sides, calendering is performed on both sides simultaneously.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of a manufacturing process of a flexible disk according to the present invention. For example 0.5 m thick
The sheet-shaped support 1 having a width of m and a width of 30 cm is supplied from a supply roll 20 and conveyed by a conveyance drive roll 21.

In the step of applying the magnetic coating material, for example, an extrusion type extrusion coater 2 is provided on both sides of the support 1 (hereinafter sometimes referred to as S ₀ and S ₁ ).
A magnetic layer (not shown) is coated on both sides by. As shown in FIG. 2, the magnetic layer is coated with S ₁ while it is undried after coating on the S ₀ surface.
2 (a) or 2 (b) method of applying a surface and S ₀
Figure 2 for applying the surface and S ₁ side simultaneously (c) or FIG. 2
Although there is the method (d), both are within the scope of the present invention.

In FIG. 2, 22 is a guide roller for applying a coating pressure, and 3 is a smoother for smoothing the coated surface. Further, 4 is a reverse roll coater.

Examples of coaters that can be used in the present invention include:
Extrusion type extrusion coater 2 described above,
In addition to the reverse roll coater 4, there are a gravure roll coater, an air doctor coater, a blade coater, an air knife coater, a squeeze coater, an impregnating coater, a transfer roll coater, a kiss coater, a cast coater, a spray coater, and the like. These can be used in combination as in d).

When two or more magnetic layers or conductive layers are laminated on both sides, the above coaters can be installed in combination of two or more on both the S ₀ surface and the S ₁ surface. Alternatively, an extrusion coater as shown in FIGS. 3B and 3C may be used.

That is, in FIG. 3, FIG. 3A shows an example in which the single layer extrusion coaters 2 are used in parallel, and the magnetic layer 7 is used.
Is a wet-on-wet coating method in which the magnetic layer 8 is formed on it while it is not dried. Also,
3 (b) and 3 (c) are also wet-on-wet systems, but FIG. 3 (b) is an example using an extrusion coater 5 having two discharge ports 9, and FIG. 3 (c). This is an example of using an extrusion coater 6 having two liquid reservoirs 10 but one discharge port 9.

At the stage where the magnetic layers 7 (and 8) are not dried, the transport drive roll 21 is, for example, one as shown in FIG. Since this drive roll has a large number of air outlets 23 and air inlets 24 on the roll surface, and is paired so as to sandwich the support 1,
It is possible to convey the support 1 without contacting the roll.

The roll used for the guide roll 22 is also
In the area where the undried magnetic layer is conveyed, a non-contact roll similar to the above-mentioned drive roll 21 is used (the drive roll 21 or the guide roll 22 is also used in many other ways than shown). The non-contact rolls described above may be used for both the drive roll 21 and the guide roll 22 except for the area where the undried magnetic layer is conveyed, but rolls having a flexible roll surface may be used.

The support 1 which has completed the above-mentioned coating process of the magnetic coating material is next subjected to a drying and orientation process. Drying of the magnetic layer is one of the important factors when performing magnetic field orientation such as non-orientation shown in FIG. 14 (a), circumferential orientation shown in FIG. 14 (b), and vertical orientation shown in FIG. 14 (c). Is. That is, since the viscosity of the magnetic paint or the coating film changes depending on the degree of drying and the movement of the magnetic particles in the magnetic paint is limited, the orientation state can be controlled by utilizing this.

The viscosity of the magnetic paint or coating film depends on the formula of the paint,
Although it changes depending on the transport speed, coater conditions, etc., in the present embodiment, it is possible to avoid the influence of other fluctuation factors by adjusting the drying conditions.

That is, in this embodiment, as shown in FIG. 1, the drying and aligning steps are performed by the first aligning zone 11 and the first drying zone 1.
2, the second orientation zone 13, the second drying zone 14, and the in-dryer orientation zone 15 are installed in this order. Here, the first and second drying zones 12 and 14 are characterized in that the purpose is not to dry the coating film paint but to adjust the viscosity. In particular, in the case of circumferential orientation or vertical orientation, in order to eliminate the influence of mechanical orientation by the extrusion coater 2, it is preferable to perform non-orientation before this orientation. For this purpose, the first orientation zone 11 It is desirable to use the second drying zone 14 as a means for non-orientation and to perform circumferential or vertical orientation in the in-dryer orientation zone 15.

Any drying means may be used in each of the above-mentioned drying zones, such as irradiation with warm air, ultraviolet rays, visible rays, infrared rays, or the like.

Next, the orientation method will be described in detail.

FIG. 5 is a diagram showing an example of non-orientation using the permanent magnet 16. FIG. 5A is an example of non-orientation in which the N poles and the S poles are alternately directed toward the magnetic layer surface with a certain distance from the S ₀ surface and the S ₁ surface. The magnets facing each other across the support 1 have the same poles facing each other (that is, NN, SS).
Opposing type). In this case, the strength of the magnetic field is the coercive force Hc of the magnetic powder.
Need to be smaller than. If the strength of the magnetic field is larger than Hc of the magnetic powder, the movement of the magnetic powder becomes too vigorous and the surface property of the magnetic layer may deteriorate.

On the other hand, the orientation of the magnet in FIG. 5 (b) is almost the same as that in the above (a), but the distance of each permanent magnet 16 from the support 1 is the closest at the beginning of orientation and gradually increases. The difference is that they are placed away from each other. In this arrangement,
Since a strong magnetic field is applied first and the magnetic field is gradually attenuated, the magnetic field strength can be made larger than that of the magnetic powder Hc at the stage of starting the alignment, and therefore, the magnetic powder can be more effectively unoriented. It is possible to

FIG. 6 is a diagram showing an example of non-orientation using an electromagnet. In FIG. 6A, the support 1 is penetrated into two coreless DC electromagnets 17 placed in series (34
Indicates a DC power supply). The magnetic powder is oriented by the first magnet in the longitudinal direction of the support 1, and then the second magnet exerts a force to orient in the opposite direction.
In this case, by appropriately adjusting the magnetic field strength by the variable resistor 19 and the viscosity of the magnetic coating material by the drying zone, it is possible to effectively make the magnetic powder non-oriented.

FIG. 6B shows a method of penetrating the support 1 into the coreless AC electromagnet 18, and FIG. 6C shows a pair of coreless or cored AC electromagnet 18 of the support 1. It is a method of arranging on the S ₀ surface and the S ₁ surface with a certain distance (35 represents an AC power supply). When the non-orientation is performed using the alternating magnetic field as described above, the number of electromagnets can be halved as compared with the case where the direct current is used, which is preferable because the apparatus is simplified.

FIG. 7 (a) is a diagram showing an example of concentric orientation means using a permanent magnet. The permanent magnets 16 mounted on the rotating belt 26 (or chain) rotated by the rotating means 25 at equal intervals move at the same speed as the transport speed of the support 1 while rotating (spinning) by the driving means not shown. To do. The permanent magnet 16 used here is an example shown in FIGS.

In FIG. 7A, the center of rotation of the permanent magnet 16 is substantially stationary at one point of the support 1 (because the magnet and the support 1 are adjusted so that the conveying speeds are equal). Therefore, it is possible to perform the orientation as shown in FIG. 14 (b) concentrically around this point. Regarding the center point of the permanent magnet 16, it is necessary to match the centers of the S ₀ surface side and the S ₁ surface side, but regarding the rotation speed when rotating the permanent magnet 16, the S ₀ surface side and the S ₁ surface side are the same. Even if there is some deviation on the surface side, it is acceptable. Further, the spacing between the permanent magnet 16 and the support 1 is made closer at the beginning of the orientation and is gradually moved away as it progresses, so that the orientation in a strong magnetic field and the disturbance of magnetic powder generated when the magnet is moved away are avoided. It becomes possible to do both effectively.

An example of the permanent magnet 16 used for the concentric orientation will be described with reference to FIGS. 7 (b) to 7 (d). In the same figure (b), four rod-shaped permanent magnets are combined in a cross shape and the center is fixed. This combined magnet is arranged on the rotating belt 26 by means of a handle (not shown) attached to the central portion. Further, it is necessary to use this combined magnet while rotating (spinning) it by a driving means (not shown). By doing this, the magnetic powder is
It can be oriented concentrically as shown in (b).

FIG. 6C shows an example using a horseshoe-shaped magnet. Also in this case, it is possible to concentrically orientate by using while rotating (spinning) around the handle as in the case of (b).

Further, in FIG. 6D, a plurality of permanent magnets having N-poles (or S-poles) are arranged on the periphery of a polygonal (not necessarily rectangular shape as shown in the figure) table. This is an example of a combined magnet in which one permanent magnet having an S-pole (or N-pole) at the tip is arranged in the central portion. By forming the peripheral N-pole and the center S-pole so that the heights thereof are different, the magnetic powder exhibits a spiral fluid behavior in this magnetic field (the above-mentioned N-pole and S-pole have different heights). , Which is higher and which is lower). Unlike the cases of (b) and (c), the combined magnet of this example exhibits the above-mentioned spiral fluid behavior without rotating (spinning), so it is not always necessary to rotate.

8 and 9 are views showing an example of concentric orientation means using an AC electromagnet. When a small diameter coreless coil (B) is inserted in the center of the coreless coil (A) and currents flowing in (A) and (B) are I _A and I _B , respectively, FIG. _In this example, the current is adjusted so that _A ≠ I _B. In this way, by making the currents in the center and the outer periphery stronger and weaker to break the balance of the magnetic field, a spiral magnetic field can be created, so that the magnetic powder can be concentrically oriented.

In the example of (a) and the examples of (b) and (c) described later, unlike the example of FIG. 7 which uses a permanent magnet, it is not necessary to move the magnet in accordance with the movement of the support 1, Since the device can be fixedly used, the device can be downsized, which is advantageous. The reason is that since this magnet is an electromagnet, a magnetic field can be freely generated or extinguished by turning the current on and off. That is, by turning on and off the current of the electromagnet at regular intervals, the magnetic powder on the support 1 is oriented concentrically at regular intervals.

FIG. 6B shows a ring shape (that is, a donut shape).
This is an example in which an AC electromagnet is formed. Since such an annular continuous coil generates a spiral magnetic field when an electric current is applied, it is possible to perform a desired concentric orientation.

On the other hand, FIG. 9A is an example in which a plurality of AC electromagnets similar to those shown in FIG. 6C are combined in a circular shape. The magnetic field obtained in this example also has the same spiral shape as in FIG. 8B, and can be concentrically oriented. However, since it is composed of a plurality of AC electromagnets, it is possible to perform orientation by separating it into semicircles, as shown in FIG. 9B, for example. In this way, for example, by separating and orienting into semicircles (not limited to semicircles, 4 semicircles, etc.), it is possible to reduce the influence of the leakage magnetic field, and it is possible to arrange in multiple rows in parallel, which improves mass productivity. There are advantages such as superiority.

Further, FIG. 10 is a diagram showing an example of vertical orientation using the permanent magnet 16. FIG. 10 (a) is an example in which the magnets at the start of the alignment are the closest to the distances from the S ₀ surface and the S ₁ surface, and the distance is gradually increased with two magnets as one set. As for the orientation of the permanent magnet 16, as shown in the drawing, the N pole is arranged on one surface of the support 1 and the S pole is arranged on the opposite surface. By making the N pole and the S pole face each other (N-S facing each other) in this way, the magnetic component can be oriented in the vertical direction as shown in FIG. 14 (c). The reason why the distance between the permanent magnet 16 and the support 1 is changed little by little is to prevent the reversal of the magnetic particles due to the stray magnetic field, and thus the surface smoothness can be improved.

FIG. 2B shows the permanent magnet 16 from the support 1.
This is an example in which the distance is set to be the longest at the start of the alignment and gradually made closer. In this example, the magnetic shield plate 27 is used to reduce the influence of the leakage magnetic field. When this shield plate is used, it is possible to avoid disturbed magnetism in directions other than the target direction (here, the vertical direction) that the magnetic powder receives when it escapes from the magnetic field, so that vertical alignment can be efficiently performed.

FIG. 6C shows an example using a horseshoe-shaped permanent magnet 16. In this case, it is preferable to place the magnet in a direction close to a right angle with respect to the transport direction of the support 1 as shown in the figure. By doing so, for example, the magnetic powder vertically oriented with the S ₀ surface N pole and the S ₁ surface S pole becomes the S ₀ surface S pole and the S ₁ surface N pole.
Since it is not necessary to pass a magnetic field in the opposite direction of the pole, the orientation direction is not disturbed.

FIG. 11 is a diagram showing an example of vertical alignment using an electromagnet. FIG. 3A shows an example using the DC electromagnet 17, and since the magnetic field direction is constant, the magnetic powder is vertically oriented without any problem. On the other hand, FIG. 7B shows an example using the AC electromagnet 18, and when the viscosity of the magnetic paint is low,
Although the magnetic powders repel each other and become non-oriented as in the example of FIG. 6B, vertical orientation can be performed by increasing this viscosity to some extent. However, the entire magnetic layer does not have a uniform vertical alignment, and the vertical alignment portion and the other portions are repeated in accordance with the phase of the alternating current.

After the orientation of the magnetic powder and the drying of the solvent and the like as described above are completed, the support 1 is next subjected to a calendering step. This calendar has a 28
It is a process of molding and smoothing by. In this case, the figure
As shown in FIG. 12 (a), H / R (heating roll made of metal, ceramic, etc.) is arranged on one side of the support 1, and C / R (compression roll made of resin) is arranged on the other side of the support. A pair of rolls are arranged so that they are paired with R, and then H / R and C / R are arranged in reverse as shown in the figure.
It can be used as a set (these rolls use a plurality of sets as needed). Here, since the calendar is performed by H / R, the calendar processing is performed the same number of times on each side.

Further, as shown in FIG. 6B, both sides may be subjected to calendering simultaneously on both sides by using H / R (also in this case, a plurality of pairs of rolls may be used if necessary). it can). In particular, when carrying out calendering on both sides simultaneously, it is necessary that the rolls on both sides have high smoothness, thermal conductivity and hardness.

Therefore, as the material for forming the H / R, metals and ceramics are preferable, and Fe-based and N-based materials are particularly preferable.
In addition to i-based transition metals, it is preferable to use Si-based transition metals having high hardness.

As described above, in the present embodiment, since the number of times of calendering performed on the S ₀ surface and the S ₁ surface is the same, as shown in FIG. 13, the formed magnetic recording medium (here, 1 Is a support, and 7 is a magnetic layer.) The magnetic layers 7 on both sides are molded with the same degree of compression, and therefore the performances are almost the same. As a result, the obtained flexible disk is excellent in the quality of the S ₀ surface and the S ₁ surface.

The support 1 which has undergone the calendering process is shown in FIG.
Enter the dancer roller 29 shown in FIG. 2 and adjust the gap between the transport speed of the support 1 in the steps up to this point and the transport speed of the support 1 in the subsequent steps.

Finally, a punching process is started. When the orientation of the magnetic powder is non-orientation or vertical orientation (excluding the case of using an alternating current), the detector 30 is not necessary because the entire magnetic layer has these orientations.

However, in the case of concentric circular orientation and vertical orientation by alternating current, a punching machine 31 linked with the detector 30 is required in order to accurately punch a correctly oriented portion.

The detector 30 used here is preferably a non-contact type so as not to damage the surface of the magnetic layer and reduce the yield. Of these, the optical type is particularly preferable, and the transmissive type is used when the magnetic layer is a thin film or a single layer, and the reflective type is used when the magnetic layer is a thick film or a multilayer. These detections are performed using infrared rays, visible rays, ultraviolet rays, X-rays, or the like.

As an example of the above-mentioned detection, for example, in the detection of the center position of concentric circular orientation, three points each in the longitudinal direction and the width direction of the support 1, a total of nine points, are detected, and the arithmetic circuit 32 is operated. When the punching was performed after the correction was performed, the error from the center position was within several tens of microns.

The flexible disks punched by the punching machine 31 are accumulated in a container (not shown),
It is sent to the process such as performance inspection. On the other hand, the unnecessary support 1 after punching is wound up by the winding roll 33 and then disposed.

Next, an example in which the performance of the flexible disk manufactured by the manufacturing method according to the present invention and the performance of the flexible disk manufactured by the conventional method are compared will be shown.

<Magnetic paint> The following components were sufficiently kneaded and dispersed by a kneader and a ball mill, and then 5 parts of a polyisocyanate compound (Coronate L: manufactured by Nippon Polyurethane Co., Ltd.) was added and mixed immediately before coating, A magnetic paint for the magnetic layer and a carbon black paint for the conductive layer were prepared.

Magnetic paint: Barium ferrite magnetic powder 100 parts (BET value 32 m ² / g, coercive force (Hc) 600 Oe) Polyurethane resin (UR8300: Toyobo Co., Ltd.) 6 parts Vinyl chloride-vinyl acetate-vinyl alcohol Polymer 6 parts (MR110: manufactured by Nippon Zeon Co., Ltd.) α-alumina 7 parts Oleyl oleate 5 parts Cyclohexanone 200 parts Toluene 50 parts Methyl ethyl ketone 50 parts

Carbon black paint: Carbon black (manufactured by Cabot USA: 100 parts Black Pearls L (BET value 138 m ² / g, particle size 24 mμ) Polyurethane resin (UR8300) 40 parts Vinyl chloride-vinyl acetate-vinyl alcohol polymer ( MR110) 40 parts Cyclohexanone 600 parts Toluene 200 parts Methyl ethyl ketone 200 parts

Next, various kinds of the above carbon black paint and magnetic paint were sequentially coated on a 75 μm-thick polyethylene terephthalate base film by a wet-on-wet system with an extrusion type extrusion coater of FIG. 3 (a). This was subjected to non-orientation, concentric orientation or vertical orientation, and was calendered after drying.

In the above, the apparatus shown in FIG. 1 and the double-sided coating method shown in FIG. On the other hand, for the conventional method, single-sided treatment is performed as described above,
After that, each coating material was similarly sequentially applied to the opposite surface of the polyethylene terephthalate base film to effect orientation, and after drying, calender treatment was performed. The thickness of the dry film in each example was 2.0 μm for both the magnetic layer and the conductive layer. The magnetic film thus obtained was punched into a disk shape having a diameter of 86 mm and housed in a cassette to manufacture a magnetic disk.

Further, the above magnetic powder was replaced with iron oxide containing Co (BE
T24m ² / g, Hc730 Oe) or ferromagnetic metal powder (BE
A magnetic disk was manufactured in the same manner as described above, except that T4 3.0 m ² / g, Hc1640 Oe) was used. Table 1 shows the performance of each magnetic disk.

Table 1 ^{* 1} Magnetic powder Example ^{* 3} Fluctuation rate Comparative example ^{* 3} Fluctuation rate ^{* 2} S ₀ ^{* 2} S ₁ (%) ^{* 2} S ₀ ^{* 2} S ₁ (%) ──────── ───────────────────────── None A 45 44 2.25 46 42 9.09 Allocation B 56 56 0 56 53 5.50 C 50 49 2.02 51 47 8.16 Yen A 49 49 0 40 35 13.3 Circulation B 62 61 1.63 45 38 16.9 Vertical A 48 48 0 49 44 10.75 Direct B 58 57 1.74 58 54 7.14 C 57 56 1.77 57 52 9.17 * 1 Magnetic powder type. A ... Co-containing iron oxide, B ... Ferromagnetic metal powder, C ... Barium ferrite. * 2 S ₀ and S ₁ mean each magnetic layer surface of the flexible disk. That is, if one side is S ₀ (side 0),
The opposite surface is S ₁ (side 1). The numerical value shown in this column is the average value of the standardized output (unit: nV _PP / μm · turn · m 2 / s) in the innermost track of 2f, and when the magnetic powder is Co-containing iron oxide. Recording density is 17 _K
FRPI (Flux Reversals Per Inch), and in the case of ferromagnetic metal powder and barium ferrite, the recording density is 35 _K FRPI. * 3 The volatility was calculated as follows.

As is clear from the results shown in the table, the flexible discs prepared by the examples according to the present invention have a difference in normalized output between the S ₀ and S ₁ surfaces (= variation rate).
Is more than 0 to 2%, which is significantly smaller than 5.5 to 16.9% of the comparative example. In addition, the output value is high especially in the circumferential orientation. That is, the flexible disk of the present example has the same molding conditions on both sides, and therefore has a uniform and high output.

The present invention has been described above with respect to various embodiments, but these embodiments can be further modified based on the technical idea of the present invention.

For example, various simultaneous coatings in FIG.
In addition to transporting the support 1 horizontally, the coating can be performed while being inclined or transported vertically. In particular, when vertical coating is performed, the influence of gravity on the S ₀ and S ₁ surfaces becomes equal, so that there is an advantage that it is easy to balance the amount of coating liquid fed to the coater, and uneven coating is less likely to occur. .

[0068]

According to the production method of the present invention, the magnetic paint is applied to both surfaces of the support at the same time, or after applying one surface, it is applied to the remaining surface while still undried. Alignment or non-orientation, drying, calendering, etc. are performed at least on both sides simultaneously.

Therefore, the warp of the support, which has been a problem in the conventional single-sided coating and single-sided processing methods, and the uneven coating of the magnetic coating, which is caused by the warp, the non-uniformity of the film thickness, and the single-sided processing are the causes. , The degree of orientation of the S ₀ and S ₁ planes, the degree of compression, the difference in surface smoothness, etc. are all solved.

The magnetic recording medium obtained by the production method of the present invention is such that the coating state of the magnetic layers formed on both sides, the orientation state of the magnetic powder, the compression degree by the calender roll, the electromagnetic conversion characteristics, etc. are equal to each other, and Excellent in high output and high durability.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a manufacturing process of a magnetic recording medium according to the present invention.

FIG. 2 is a diagram showing an example of a coating method of the magnetic recording medium.

FIG. 3 is a diagram showing an example of a coater head of the same.

FIG. 4 is a view showing an example of a carrier roll of the support.

FIG. 5 is a diagram showing an example of non-orientation using permanent magnets.

FIG. 6 is a diagram showing an example of non-orientation using an electromagnet.

FIG. 7 is a diagram showing an example of concentric orientation with a permanent magnet.

FIG. 8 is a diagram showing an example of concentric orientation with an electromagnet.

FIG. 9 is a diagram showing another example of concentric orientation by the electromagnet.

FIG. 10 is a diagram showing an example of vertical alignment with a permanent magnet.

FIG. 11 is a diagram showing an example of vertical alignment with an electromagnet.

FIG. 12 is a diagram showing an example of a calendar roll of the same.

FIG. 13 is a diagram showing an example of a sectional view of the magnetic recording medium.

FIG. 14 is a diagram showing an example of an orientation state of the magnetic recording medium.

[Explanation of symbols]

 1 Support 2, 5, 6 Extrusion Coater 4 Reverse Roll Coater 7, 8 Magnetic Layer 11 1st Orientation Zone 12 1st Drying Zone 13 2nd Orientation Zone 14 2nd Drying Zone 15 Alignment Zone in Dryer 16 Permanent Magnet 17 DC Electromagnet 18 AC electromagnet 20 Supply roll 21 Transport drive roll 22 Guide roll 28 Calendar roll 29 Dancer roller 30 Detector 31 Punching machine 32 Arithmetic circuit 33 Winding roll 36 Magnetic powder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Minoru Yasuda No. 1 Sakura-cho, Hino City, Tokyo Konica Stock Company

Claims (7)

[Claims] 1. A method for producing a magnetic recording medium having a magnetic layer containing magnetic powder on both sides of a support, comprising: (1) coating the magnetic layer on both sides of the support simultaneously;
Alternatively, a step of applying the coating to the remaining surface in a non-dried state after coating on one side, and (2) after that, the support having the magnetic layers coated on both sides is passed through a magnetic field to apply the magnetic powder. A method of manufacturing a magnetic recording medium, comprising the step of orienting or non-orienting. 2. The manufacturing method according to claim 1, wherein the orientation is concentrically formed on the support. 3. An AC electromagnet (B) having an outer diameter smaller than that of the coreless AC electromagnet (A) is inserted in the center of the AC electromagnet (A),
The combination electromagnets adjusted so that the currents I _A and I _B applied to (A) and (B) are not equal are arranged on both surfaces of the support, and the orientation is performed concentrically. The manufacturing method described in. 4. The manufacturing method according to claim 1, wherein alternating current electromagnets each having a coil wound in an annular shape are arranged on both surfaces of the support, and the orientation is concentrically formed. 5. The manufacturing method according to claim 1, wherein a plurality of alternating current electromagnets are arranged in a circular shape or a semicircular shape and are arranged on both surfaces of the support, and the orientation is concentrically formed. . 6. The manufacturing method according to claim 1, wherein the orientation is performed in a direction perpendicular to the support. 7. The manufacturing method according to claim 1, wherein after the magnetic layer is coated on both sides, calendering is performed on both sides simultaneously.