JPH06339664A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To manufacture efficiently a magnetic recording medium of low dropout error by collecting scattered coating with a collection plate installed on the feeding side of a nonmagnetic support in the neighborhood of a contact part of a gravure roll and a backup roll. CONSTITUTION:A collector 9 for collecting coating mist which is generated when coating is transcribed to a nonmagnetic support 2 is installed in a wedge shaped space formed by the nonmagnetic support 2 and a gravure roll 1 in the neighborhood of a contact part of the gravure roll 1 and a backup roll 3. The collector 9 has a good surface property since it collects coating mist which is generated at the cleavage of a meniscus membrane, before mist moves to the surface of the film and the gravure roll 1.

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 in which a magnetic coating film and a non-magnetic coating film are formed by a direct gravure coating method.

[0002]

2. Description of the Related Art Generally, audio tapes and video tapes are coated with a magnetic paint prepared by dispersing and kneading a ferromagnetic powder, a binder, a dispersant, a lubricant, etc. in an organic solvent on a non-magnetic support such as a polyester film. By doing so, the magnetic layer is formed. Further, in order to prevent winding disorder of the magnetic tape and to improve the surface property, running property, durability, etc., it is formed by applying a back coat paint to the back surface side of the non-magnetic support on which the magnetic layer is not provided. It is widely practiced to provide a back coat layer.

By the way, for coating these magnetic paints on a non-magnetic support, there have been, for example, a direct gravure coating system, a reverse roll coating system, a die coating system (extrusion system), etc. ,
The direct gravure coating method is often used because of its excellent operability, easy management, and low cost.

In the direct gravure coating method, a coating device consisting of a gravure roll having a cell pattern engraved on the surface thereof and a backup roll for pressing the nonmagnetic support onto the gravure roll is used to coat the nonmagnetic support on the nonmagnetic support. This is a method of transferring liquid paint. That is, in order to apply a magnetic coating on a non-magnetic support using this apparatus, for example, the coating is supplied to the contact portion of a gravure roll and a furnisher roll provided in contact with the gravure roll,
The supplied paint is filled in the cell in a constant amount by contact between the gravure roll and the finisher roll. Then, the non-magnetic support is brought into contact with the gravure roll filled with the paint in the cell, and the non-magnetic support is pressure-bonded to the gravure roll with a backup roll made of an elastic material, and these rolls are rotated in synchronization. The paint is applied by transferring the paint filled in the cell onto a non-magnetic support.

[0005]

By the way, in the pressure-bonding portion of the clavier roll and the backup roll where the paint is transferred to the non-magnetic support in this way, the excess paint (post-beat) that is not involved in the transfer is non-magnetic. It is pushed out to the accepting side of the support. On the other hand, the paint involved in transfer forms a meniscus film (front beat) on the delivery side of the non-magnetic support. The meniscus film is split into a non-magnetic support side and a gravure roll side by running of the non-magnetic support and rotation of the gravure roll, and the meniscus film split into the non-magnetic support side is transferred onto the non-magnetic support.

However, when the meniscus film is divided into the non-magnetic support side and the gravure roll side, the paint is scattered and a paint mist is generated, which may adhere to the surface of the magnetic coating film or the cells of the gravure roll. is there. The paint mist adhering to the surface of the magnetic coating film remains as paint foreign matter on the magnetic layer of the manufactured magnetic recording medium, causing dropout during recording and reproduction, which adversely affects recording and reproduction.
In addition, the paint mist adhering to the inside of the cell of the gravure roll causes clogging of the cell and causes uneven coating of the coating film.

Therefore, in the conventional direct gravure coating method, the running speed of the non-magnetic support, the pressure bonding state of the roll, and the size of the meniscus film are controlled for the purpose of suppressing the generation of paint mist that causes such inconvenience. Is being attempted.

That is, the splitting ratio of the meniscus film, the size of splitting, and the amount of paint mist scattered depend on the pressure applied between the gravure roll and the backup roll or between the gravure roll and the finisher roll, whether the pressure is good or bad, and the nonmagnetic support It changes depending on the running speed and the size of the meniscus film.

Of these, the change in the amount of paint mist scattered by the running speed of the non-magnetic support is relatively simple, and when the running speed of the non-magnetic support is reduced, the size of the meniscus film is reduced, and the paint The amount of mist scattered is also reduced.

Therefore, in order to reduce the amount of paint mist scattered, it is considered first to reduce the running speed of the non-magnetic support. However, it is not preferable to reduce the running speed of the non-magnetic support because it lowers the productivity. Therefore, the running speed of the non-magnetic support should be set as high as possible so that the roll is pressed against the meniscus film. It can be said that it is desirable to reduce the amount of paint mist scattered by controlling the size of the paint.

However, control of the paint mist by the pressure of pressure between rolls and the state of pressure bonding is very delicate,
In addition, since it is difficult to maintain a constant value and has no sustainability, the coating speed must be reduced to about 250 m / min at the same time.

On the other hand, if it is attempted to reduce the amount of paint mist scattered by reducing the size of the meniscus film, the amount of paint mist scattered can be reduced to some extent, but if the meniscus film is further reduced, the paint Remarkable skipping that is not transferred occurs, resulting in uneven coating. In addition, the degree of division of the meniscus film is disturbed, and the scattering of the paint mist is reduced.

Therefore, the present invention has been proposed in view of such a conventional situation, and in the case of forming a magnetic coating film and a non-magnetic coating film on a non-magnetic support, a high coating speed is used. However, it is an object of the present invention to provide a method for manufacturing a magnetic recording medium, in which a paint mist does not adhere to the surface of a coating film or the surface of a gravure roll and a magnetic recording medium with a low dropout frequency can be efficiently manufactured.

[0014]

In order to achieve the above-mentioned object, a method of manufacturing a magnetic recording medium according to the present invention comprises supplying a coating material into a cell provided on the surface of a rotating gravure roll to form a gravure roll. When transferring the paint onto the non-magnetic support that continuously travels between the backup rolls that are in pressure contact with the gravure roll, a collecting plate that is provided on the delivery side of the non-magnetic support in the vicinity of the pressure contact portion between the gravure roll and the backup roll. According to the present invention, the scattered paint scattered from the pressure contact portion is collected.

Further, the collecting plate is a bent plate formed by bending a plate-shaped body. Further, the bending radius of the bent portion of the bent plate is 3 to 5 mm. Further, the collecting plate is covered with a magnetic sheet.

Further, the collecting plate is characterized by being covered with a polymer film.

[0017]

When the magnetic coating film and the non-magnetic coating film are formed on the non-magnetic support by using the direct gravure coating method, the non-magnetic support in the vicinity of the pressure contact portion between the gravure roll and the backup roll is prepared. If a collecting plate for collecting scattered paint is provided on the delivery side of the body, the paint mist scattered from the meniscus film formed at the pressure contact part by this collecting plate will not be transferred to the coating surface or gravure roll surface. Will be collected. Therefore, the adhesion of the paint mist to the coating film surface and the clogging of the gravure roll due to the paint mist are prevented, and a magnetic layer having a good surface property without uneven coating is formed. This eliminates the need for pressure-bonding between rolls to prevent the generation of paint mist itself, pressure-bonding, delicate adjustment of the meniscus film size, and slower coating speeds. The medium is efficiently manufactured by a simple control operation.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described with reference to the drawings.

In this embodiment, a non-magnetic paint such as a magnetic paint or a back coat paint is applied on the non-magnetic support.

In the former case, for example, a magnetic coating film is formed by applying a liquid magnetic coating material composed of magnetic powder, a binder, a solvent and the like onto a non-magnetic support. The magnetic powder, binder, and solvent used in the magnetic paint may be any of those generally used as the material of the magnetic paint in the coating type magnetic recording medium. As an oxide magnetic powder such as γ-Fe ₂ O ₃ or Fe, Co
Examples thereof include metal-based magnetic powders, polyvinyl chloride-based copolymers and polyurethane resins as binders, and methyl ethyl ketone, toluene, cyclohexanone, etc. as solvents. Further, a lubricant, an abrasive, a dispersant, etc. may be added to the magnetic paint.

In the latter case, a back coat paint composed of carbon black, a binder, a solvent, etc. is applied to the surface opposite to the magnetic paint to form a back coat layer. As the binder and the solvent, any of those used in magnetic paints can be used.

To apply the above-mentioned paint, for example, the application device shown in FIG. 1 is used.

In the coating apparatus, the gravure roll 1 having the cell pattern engraved on the surface and the backup roll 3 for pressing the nonmagnetic support 2 onto the gravure roll 1 and the cell 4 provided on the surface of the gravure roll 1 are used. It comprises a finisher roll 5 for supplying a fixed amount of paint therein.

The gravure roll 1 transfers the paint filled in the cells 4 onto the non-magnetic support 2. The gravure roll 1 is a cylindrical roll made of Fe or the like having a relatively low hardness.
A large number of the cells 4 are engraved as, for example, quadrangular pyramidal recesses.

The backup roll 3 is formed by pressing a long non-magnetic support 2 such as a polyester film onto the surface of the gravure roll 1 so that the coating material filled in the cells 4 provided in the gravure roll 1 is filled with the non-magnetic support. Magnetic support 2
For good transfer to the top, it is made of an elastic roll such as rubber. Therefore, the elastic force of the roll causes the non-magnetic support 2 to come into close contact with the cells 4 on the surface of the gravure roll 1, and the coating material filled in the cells 4 can be satisfactorily transferred to the non-magnetic support 2. The backup roll 1 is provided so as to face the gravure roll 1 and sends the non-magnetic support 4 in the direction of the arrow X in the figure in synchronization with the gravure roll 1.

The furnisher roll 5 is for filling a fixed amount of paint into the cells 4 provided on the surface of the gravure roll 1, and is also made of an elastic roll such as rubber. The furnisher roll 5 is provided in contact with the gravure roll 1, and the coating material 6 is supplied by a nozzle 7 to a wedge-shaped space formed by the contact between the furnisher roll 5 and the gravure roll 1. It is designed to be. The paint 6 supplied to the wedge-shaped space sequentially moves into each cell 4 provided on the surface of the rotating gravure roll 1, and the finisher roll 5
A certain amount is filled in the cell by contact with.

Further, in the above coating apparatus, a smoothing device 8 for smoothing the transferred coating film 17 is provided on the downstream side of the gravure roll 1, whereby the cell pattern of the gravure roll 1 is transferred. The unevenness of the applied paint is leveled to form a smooth magnetic coating film. The smoothing device 8 may be either a film smoother type device made of a flexible film or the like, or a bar smoother type device made of a cylindrical rigid material.

Further, in the coating apparatus, the non-magnetic support 2 and the gravure roll 1 on the feeding side of the non-magnetic support 2 near the pressure contact portion between the gravure roll 1 and the backup roll 3 are formed. In a wedge-shaped space,
A collecting device 9 for collecting paint mist generated when the paint is transferred to the non-magnetic support 2 is provided.

That is, in such a coating apparatus, as shown in FIG.
As shown in FIG. 3, at the pressure contact portion between the clavier roll 1 and the backup roll 3 where the paint is transferred to the non-magnetic support 2, the paint filled in the cell 4 is transferred to the non-magnetic support 2 on the meniscus film side. The meniscus film 10 is divided into the non-magnetic support 2 side and the gravure roll 1 side by the running of the non-magnetic support 2 and the rotation of the gravure roll 1, and the meniscus film 10 is divided into the non-magnetic support 2 side. Membrane 10
Is transferred onto the non-magnetic support 2 to form a coating film 17.

However, when the meniscus film 10 is divided into the non-magnetic support 2 side and the gravure roll 1 side, the paint is scattered and a paint mist 11 is generated. This paint mist 11 adheres to the coating film and remains as paint foreign matter,
It becomes a cause of dropout, or adheres to the inside of the cell 4 of the gravure roll 1 to cause clogging, causing uneven coating.

The collector 9 coats the paint mist 11 which is generated when the meniscus film 10 is split.
7 surface, for collecting before the transfer to the gravure roll 1 surface, which prevents the coating mist from adhering to the surface of the coating film 17 and the surface of the gravure roll 1 and has good surface properties without uneven coating. Thus, a magnetic layer and a non-magnetic layer are formed. Further, as a result, it is not necessary to press-bond the rolls 1, 3 and 5 to each other in order to prevent the generation of paint mist itself, delicately adjust the meniscus film amount, and reduce the coating speed. A low magnetic recording medium can be efficiently manufactured by a simple control operation.

For the collecting device 9, for example, a plate-like collecting plate made of stainless steel or the like having a width substantially equal to the width of the gravure roll is used. When such a collecting plate is provided so as to be as close as possible to the meniscus film 10 with the width direction parallel to the rotation axis direction of the gravure roll 1, the paint mist 11 scattered from the meniscus film 10 is coated with a coating film 17 Before being transferred to the surface, the surface of the gravure roll 1, it is attached and collected in the vicinity of one side edge of the collecting plate facing the meniscus film.

Here, the collecting plate may be a bent plate formed by bending a plate-shaped body in the width direction. When the bent part of such a bent plate is provided on the meniscus film side, the paint mist scattered from the meniscus film is more efficiently attached and collected because the bent part has a large thickness and a large surface area. . In addition, the radius of curvature of the bent portion, which is suitable for attaching the paint mist, is 3 to 5 mm.

When the coating material applied at this time is a magnetic coating material, it is advisable to coat the surface of the collecting plate with a magnetic sheet. The magnetic paint mist is attracted by the magnetic force of the magnetic sheet and effectively adheres to the collecting plate.

The collecting plate is fixed on a frame body 14 having substantially the same size as that of the collecting plate 13 as shown in FIG. 3, and a pair of supporting members arranged together with the supporting frame body 14 at predetermined positions. It functions as the collecting device 9 by being supported by the tables 15a and 15b.

That is, the support frame body 14 to which the collecting plate 13 is fixed has a collecting plate fixing portion 14a which is framed in substantially the same size as the collecting plate 13 and the meniscus film 10 of the collecting plate fixing portion 14a. The support portion 14b extends from the framework of one side of the side and is formed by bending in a hook shape at an intermediate portion. On the other hand, a pair of support bases 1 supporting such a support frame 14
5a and 15b are arranged as opposed to each other as rectangular parallelepiped rising walls, and substantially rectangular parallelepiped blocks 16a and 16b are projectingly provided on the opposed surfaces. In the substantially rectangular parallelepiped blocks 16a and 16b, slide portions 17a and 17b on which the support portion 14b of the support frame body 14 slides are formed as grooves of a size sufficient for the support portion 14b of the support frame body 14 to slide. It is formed along the direction substantially orthogonal to the first rotation axis. In addition, this slide unit 1
7a and 17b have an end portion on the gravure roll 1 side as a wall surface, and an end portion on the opposite side to the gravure roll 1 is open, and the support frame is provided from the opposite side to the open gravure roll 1. The support portion 14b of the body 14 is inserted and fixed in position by hitting the wall surface on the gravure roll 1 side.

Therefore, in the collecting device 9, the collecting plate 13 is fixed to the collecting plate fixing portion 14a of the supporting frame body 14, and the supporting portion 14b of the supporting frame body 14 to which the collecting plate 13 is fixed is fixed.
The slide parts 17a, 17 of the support bases 15a, 15b.
Insert from the open side of b and slide until it hits the wall surface of the meniscus film side. On the other hand, when the collector plate 13 is contaminated by the paint mist and needs to be replaced, this time, the support portion 14b of the support frame body 14 is slid to the side opposite to the gravure roll 1 to open it from the open side. I will take it out.

In such a coating apparatus, the paint mist 11 scattered from the meniscus film 10 is collected by the collector plate 13.
Of the paint mist 11 is not uniform in distribution, especially from the area facing both ends of the meniscus film 10, that is, from both ends of the collecting plate 13. The paint mist 11 adheres particularly in the region of 20 to 150 mm. Therefore, as shown in FIG. 4, a portion having a width of 20 to 150 mm is separated as a divided collecting plate 13a from the end of the collecting plate 13 on which the paint mist 11 is concentrated, and the separated surface of the divided collecting plate 13a is separated. It is advisable to dispose the divided collecting plate 13b so as to be attachable to and detachable from the collecting plate main body 13b, for example, by applying a sliding mechanism to the opposite surfaces of the separating surface. If only the divided collecting plate 13a is replaced when the contamination of the region facing the end of the gravure roll 1 progresses, the frequency of large-scale replacement work for replacing all the collecting plates can be reduced. Also, the cleaning work of the collecting plate is simplified.

Alternatively, as shown in FIG. 5, the collecting plate 1 is
3 may be covered with a polymer film 18 such as poly (ethylene terephthalate) (PET). When the collecting plate 13 is covered with the polymer film 18, the paint mist 11 adheres to the covered polymer film 18, so that when the paint mist 11 becomes contaminated and needs to be replaced, If the polymer film 18 coated on is removed and discarded, cleaning of the collecting plate becomes unnecessary.

Next, the magnetic coating medium is coated on the non-magnetic support 2 by actually changing the coating speed to 200 m / min, 250 m / min and 360 m / min using the above coating device. Example Medium 1 to Example Medium 3) were produced, and the number of paint foreign matters formed on the surface of the formed magnetic layer, the state of uneven coating due to skipping, and the number of dropouts during recording / reproduction were evaluated. The results are shown in Table 1.

The non-magnetic support 2 is PE.
T film is used, and Co that becomes magnetic powder as magnetic paint
An adhering γ-Fe ₂ O ₃ , a vinyl chloride copolymer polyurethane resin as a binder, and lecithin as an additive were dispersed in a mixed solvent of methyl ethyl ketone, toluene, and cyclohexanone. For comparison, magnetic recording media (Comparative Medium 1 to Comparative Medium 3) were prepared in the same manner except that a coating device without the collecting device 9 was used. The number of dropouts generated during recording and reproduction was evaluated. The results are also shown in Table 1.

[0042]

[Table 1]

In Table 1, the state of paint foreign matter formation was evaluated by the number of paint foreign matter having a diameter of 20 to 60 μm observed on the magnetic layer after coating and drying. /0.5 m ² or less, Δ indicates 10 to 30 pieces / 0.5 m ² (dropout quality limit), and x indicates 30 pieces / 0.5 m ² or more. In the case of coating unevenness caused by skipped stitches, ○ indicates no coating unevenness caused by skipped stitches, Δ indicates 1-2 coating unevenness caused by skipped stitches (within the quality limit), and × indicates skipped stitches. The case where the coating unevenness is continuously observed is shown. The number of dropouts was measured by recording / reproducing a magnetic recording medium having a magnetic layer surface-treated with a video tape recorder (Matsushita, HG-6000). It was carried out by counting the number of occurrences of out with a counter (manufactured by Sony Corporation, trade name type C-II).

As can be seen from Table 1, the example medium 1 to the example medium 3 produced by using the coating device equipped with the collecting device 9 uses the coating device not equipped with the collecting device 9. Compared with the comparative medium 1 to the comparative medium 3 produced by the above, the coating speed was set to be the same. In each case, coating foreign matter formation and uneven coating due to skipping were suppressed. The number of occurrences of is small. Particularly, in the example medium 3, the coating speed is 3
Despite being set at a high speed of 60 m / min, the state of paint foreign matter formation and coating unevenness is within the quality limit, and the number of dropout occurrences is suppressed within the practical range.

From the above, in the direct gravure coating method, the use of the collector plate prevents coating foreign matter from adhering to the coating film surface and the gravure roll surface, and provides coating with good surface properties without coating unevenness. It was found to be effective in efficiently forming a film.

[0046]

As is apparent from the above description, in the present invention, when the magnetic recording medium is manufactured by the direct gravure coating method, the non-magnetic support in the vicinity of the pressure contact portion between the gravure roll and the backup roll is used. Since the collector plate provided on the delivery side of the roller collects the scattered paint that scatters from the pressure contact part, the pressure between the rolls and the pressure and the size of the meniscus film to prevent the generation of paint mist itself. It is possible to prevent the formation of paint foreign matter on the surface of the coating film and the clogging of the gravure roll due to the foreign matter of paint, without making fine adjustments to the coating speed and reducing the coating speed. Therefore, according to the present invention, it is possible to efficiently manufacture a magnetic recording medium having a low dropout frequency with a simple control operation.

[Brief description of drawings]

FIG. 1 is a schematic view showing a configuration example of a coating device used in a manufacturing method to which the present invention is applied.

FIG. 2 is a schematic view showing a meniscus film formed at a pressure contact portion between a gravure roll and a backup roll.

FIG. 3 is a schematic perspective view showing a configuration example of a collecting device provided in the coating device.

FIG. 4 is a schematic plan view showing another example of a collecting device provided in the coating device.

FIG. 5 is a schematic side view showing still another example of the collecting device provided in the coating device.

[Explanation of symbols]

 1 ... Gravure roll 2 ... Non-magnetic support 3 ... Backup roll 4 ... Cell 5 ... Finisher roll 6 ... Paint 7 ... Nozzle 8 ... Smoothing device 9 ... collection device 10 ... meniscus film 11 ... paint mist 13 ... collection plate 14 ... frame 17 ... coating film

Claims (5)

[Claims] 1. When a paint is supplied into a cell provided on the surface of a rotating gravure roll and the paint is transferred onto a non-magnetic support that continuously runs between the gravure roll and a backup roll that is in pressure contact with the gravure roll. , Manufacturing of a magnetic recording medium characterized in that scattered paint scattered from the pressure contact portion is collected by a collector plate provided on the delivery side of the non-magnetic support in the vicinity of the pressure contact portion between the gravure roll and the backup roll. Method. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the collecting plate is a bent plate formed by bending a plate-shaped body. 3. The bending radius of the bending portion of the bending plate is 3
3. The method for producing a magnetic recording medium according to claim 2, wherein the magnetic recording medium is about 5 mm. 4. The method of manufacturing a magnetic recording medium according to claim 2, wherein the collecting plate is covered with a magnetic sheet. 5. The method for producing a magnetic recording medium according to claim 2, wherein the collecting plate is covered with a polymer film.