JPH05114134A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the magnetic recording medium which enables formation of a magnetic layer and back coat layer having a uniform film thickness and excellent surface characteristics and exhibits characteristics of bright images and uniform sensitivity. CONSTITUTION:A revolving rod 5 which is formed with many grooves 5a having 30 to 70 deg. angle with an axial direction on its outer peripheral surface and has 20 to 50mm diameter is used as a smoothing device for smoothing a coating film applied by a gravure coating method.

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 material is applied by a 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.

To apply these magnetic paints on a non-magnetic support, there have been, for example, a gravure coating method, a reverse roll coating method, a die coating method (extrusion method), etc., among them, high speed and operation. The gravure method is widely used because it is easy to manage and inexpensive.

The gravure coating method uses a coating device consisting of a gravure roll having a cell pattern engraved on the surface thereof and a backup roll for press-bonding the nonmagnetic support to the gravure roll. This is a method of transferring the paint. That is, in order to apply a magnetic paint onto a non-magnetic support using this apparatus, the non-magnetic support is pressed onto a gravure roll with a backup roll made of an elastic material, and the roll surface is rotated by rotating these rolls. By picking up the paint in the coating liquid pan into each recess (cell) between the adjacent cell walls of the cell pattern engraved in the cell pattern and transferring the paint filled in the cell onto the non-magnetic support Is applied.

By the way, when the magnetic coating material is transferred by using a gravure roll, the magnetic coating material is transferred as it is on the non-magnetic support in a cell pattern engraved on the surface of the roll. Since the magnetic layer has an uneven shape, the unevenness needs to be smoothed before drying. Therefore, in the gravure coating method, usually, a smoothing device is used to smooth the undried magnetic coating film after transferring the magnetic coating material. Such a smoothing device is usually made of steel, for example, a mirror rod type as shown in FIG. 5, a key blade type type as shown in FIG. 6, and a cow nose blade type type as shown in FIG. 7 are known. ing. In these smoothing devices, the magnetic coating film is smoothed by slidingly contacting the outer peripheral surface of the smoothing device.

However, the surface of each of the above-mentioned smoothing devices has a high wettability with respect to the magnetic paint and has an extremely high affinity for the coating liquid. For this reason, when the contact area with the magnetic coating film becomes slightly larger than the appropriate area during smoothing, the magnetic coating material adheres to the smoothing device more than necessary, resulting in uneven coating. For this reason, in the above-mentioned smoothing device, it is extremely important to adjust the position of the magnetic coating film, which requires skill and it is difficult to make the thickness of the magnetic coating film stable. Further, even a slight change in tension of the non-magnetic support materially affects the film thickness of the magnetic coating film, which causes problems such as uneven coating and uneven film thickness.

In order to reduce the wetting property, a wire bar type smoothing device in which a wire is wound around a rod has been proposed as shown in FIG. However, when attempting to smooth the magnetic coating film by actually using this wire bar type smoothing device, streaks and coating unevenness occur on the magnetic coating film, and a magnetic layer having good surface properties cannot be formed.

Therefore, as shown in FIGS. 9 to 11, for example, a film having a thickness of 35 μm to 100 μm is formed on the contact portion of the magnetic coating film of the smoothing device of, for example, a mirror rod type 51, a key blade type 52, and a beef nose blade type 53. A method is also considered in which a base film 54 made of polyethylene terephthalate (PET) or the like is attached and the wetting property is improved by the base film 54.

However, when the base film 54 is used, it is extremely difficult to attach the base film 54 to the smoothing device, and for example, the contact length of the PET film with the magnetic coating film is set to an appropriate length. Adhering requires a skill, and the smoothness is affected by the cut shape of the base film 54, and it is difficult to obtain stable smoothness. Further, in the smoothing device using the base film 54, the magnetic coating film may have a streak shape depending on the composition of the magnetic paint, and the base film 54 may vibrate to cause coating unevenness.

[0010]

As described above, when the conventional smoothing device is used, the magnetic layer is formed in a streak state or with uneven coating, so that the manufactured magnetic recording medium is used as a video tape, for example. Then, various problems such as deterioration of image quality and uneven sensitivity in the case of using an audio tape occur.

Therefore, the present invention has been proposed in view of such a conventional situation, and a magnetic recording medium in which a magnetic coating film is smoothed with a uniform film thickness and stable recording / reproducing characteristics are obtained is manufactured. An object of the present invention is to provide a method for manufacturing a magnetic recording medium that can be used.

[0012]

In order to achieve the above object, a method of manufacturing a magnetic recording medium according to the present invention comprises a step of applying a coating material onto a non-magnetic support which continuously runs in a longitudinal direction,
A method for producing a magnetic recording medium, which comprises a step of smoothing a undried coating film formed by applying a coating material by bringing the undried coating film into contact with a rotating rod installed in the width direction of a non-magnetic support. In, on the surface of the rotating rod,
It is characterized in that a large number of grooves forming an angle of 30 to 70 ° with respect to the axial direction are formed.

The diameter of the rotating rod is 20 to 50.
It is characterized by being mm.

[0014]

When the outer peripheral surface of the rotating rod is brought into contact with the coating film applied on the running non-magnetic support to smooth the coating film, as the smoothing device, the shaft of the smoothing device is provided on the outer peripheral surface. When a film having a large number of grooves forming an angle of 30 to 70 ° with respect to the direction is used, a coating film having a uniform film thickness without coating unevenness is formed.

This is because when the groove is formed on the outer peripheral surface of the rotary rod, the wettability of the surface of the rotary rod with respect to the paint is improved and the adhesion is reduced. As a result, uneven coating caused by a slight change in the contact area of the rotating rod with the coating film is prevented, and a coating film having a high smoothness and a uniform film thickness is formed as described above. Further, when the diameter of the rotating rod is 20 to 50 mm, the smoothing effect is further improved and a coating film having a better surface condition is formed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings.

First, in the present invention, a non-magnetic coating material such as a magnetic coating material or a back coating material is applied onto the non-magnetic support.

For example, in the former case, 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 commonly used as magnetic paint materials in coating-type magnetic recording media. Examples include oxide magnetic powders such as γ-Fe ₂ O ₃ and Fe, C
Examples include metal magnetic powders such as o, polyvinyl chloride copolymers, 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.

On the other hand, in the latter case, a back coat paint consisting of carbon black, a binder, a solvent and the like is applied to the surface opposite to the magnetic paint to form a back coat layer. Here, as the binder and the solvent, any of those used in the above magnetic paint can be used.

To apply the above-mentioned paint, for example, the application device shown in FIG. 1 is used. The coating device includes a transfer device 3 including a gravure roll 1 having a cell pattern engraved on its surface and a backup roll 2 for pressing the non-magnetic support member onto the gravure roll 1, and a non-magnetic support member in the transfer device 3. 4 has a smoothing device 5 for smoothing the transferred paint.

The gravure roll 1 picks up the paint 7 stored in the coating liquid pan 6, fills it in the cells 8 provided on the surface thereof, and transfers it onto the non-magnetic support 4. .. The gravure roll 1 is a cylindrical roll made of Fe or the like having a relatively low hardness, and a large number of cells 8 are formed on the outer peripheral surface as, for example, quadrangular pyramid-shaped recesses.

The backup roll 2 is formed by pressing a long non-magnetic support 4 such as a polyester film onto the surface of the gravure roll 1 so that the coating material filled in the cells 8 provided in the gravure roll 1 is filled with the non-magnetic support. Magnetic support 4
For good transfer onto the top, it is made of an elastic roll of rubber or the like. Therefore, the elastic force of this roll causes the non-magnetic support 4 to come into close contact with the cells 8 on the surface of the gravure roll 1, and the paint filled in the cells 8 can be satisfactorily transferred to the non-magnetic support 4. The backup roll 2 is provided so as to face the gravure roll 1 and sends the non-magnetic support 4 in the direction of arrow X in the figure in synchronization with the gravure roll 1.

In the transfer device 3, the coating material picked up from the coating liquid pan 6 and filled in the cells 8 is scraped off at a position close to the gravure roll 1 on the supply side of the nonmagnetic support 4. A first doctor blade 12 is provided to maintain a constant amount.

Further, in the coating apparatus, the rotary rod 5 made of steel or the like for smoothing the coating film transferred by the transfer apparatus 3 having the above-mentioned structure is provided on the downstream side of the transfer apparatus 3. Is provided so that its axial direction is orthogonal to the traveling direction of the non-magnetic support 4.

That is, since the coating film 14 transferred by the transfer device 3 is transferred as it is with the cell pattern of the gravure roll 1, it has irregularities. As it is, it should be a magnetic layer or a back coat layer. I can't. Therefore, in the coating apparatus, the coating film 14 is brought into contact with the outer peripheral surface of the rotating rod 5 so as to even out the irregularities of the coating film 14 and smooth the surface.

In order to adjust the wettability of the surface of the rotating rod 5 with respect to the paint, the inclination angle θ with respect to the axial direction (direction of arrow a in the figure) is 30 on the outer peripheral surface as shown in FIGS. 2 and 3. A large number of grooves 5a having an angle of 70 degrees are engraved in a helical shape. That is, in the case where the surface of the rotating rod 5 is a smooth surface, the wettability with respect to the paint is too high, and the contact area of the rotating rod 5 with respect to the coating film 14 slightly fluctuates. Thinning or uneven coating occurs. On the other hand, when a large number of grooves 5a forming a predetermined inclination angle θ with respect to the axial direction are formed on the surface of the rotating rod 5, the wettability of the surface with respect to the coating film 14 is reduced, and the coating film having a uniform film thickness without unevenness. Will be formed.

Here, in order to obtain a good smoothing action,
The inclination angle θ of the groove 5a with respect to the axial direction is important.
That is, when the inclination angle of the groove 5a is less than 30 °, the surface of the rotating rod is close to the tooth profile, and therefore the non-magnetic support 4 is formed.
Vibrates as the vehicle travels, and if the groove inclination angle exceeds 70 °, the coating film 14 becomes wavy, and in any case, a coating film having a uniform film thickness cannot be obtained. In order to obtain a better smoothing effect, it is preferable that the groove inclination angle θ be 45 °.

The finer the grooves 5a, the better the wetting property and the formation of a uniform coating film. Therefore, it is preferable that the number of lines is large, but the number of grooves that can be formed per unit length. Considering that there is a limit, the number of lines is 20
0 to 250 lines / inch is suitable. In addition, the groove 5a
The shape of is not particularly limited, and may be formed as a recess having a substantially trapezoidal cross section as shown in FIG. 4, for example.

The diameter of the rotating rod 5 is 20 to 50 m.
m. In the rotating rod 5, the smaller the diameter is, the better the smoothing effect is exhibited, and the diameter is required to be 50 mm or less to obtain the practical smoothing effect. There is a problem in terms of.

The material of the rotating rod 5 is as follows.
Any rigid material such as steel may be used. In this embodiment, the rotary rod 5 is made of steel,
The surface was chrome-plated to maintain wear resistance.

The rotating rod 5 is rotated in the direction opposite to the traveling direction of the traveling non-magnetic support (the arrow Y direction in the figure) (so-called reverse rotation), and the number of rotations is used. If it is adjusted according to the wettability with the magnetic paint, a better smoothing effect will be exhibited. Therefore, in the present embodiment, in order to further improve smoothing, a rotating device for rotating the rotating rod 5 in the Y direction is provided together with the rotating rod 5.

Further, in the above coating apparatus, a second doctor blade 10 for scraping off the magnetic paint adhering to the smoothing device and a position near the side of the transfer apparatus 3 to which the non-magnetic support is sent out, An auxiliary smoothing device 11 to which a base film such as a PET film is attached may be provided further downstream of the smoothing device 5 such that its axial direction is the width direction of the nonmagnetic support. The auxiliary smoothing device 11
The shape may be any of a rod shape, a key blade shape, a beef nose blade shape and the like. As a result, a coating film having an even better surface condition is formed, and particularly when the coating film thickness is 20 μm or more, the auxiliary smoothing device exerts a remarkable effect, and a coating having extremely high smoothness is obtained. A film is formed.

In this embodiment, the coating apparatus having the above-mentioned structure is used, and first, the non-magnetic support is set to 250 m / meter.
While traveling at a traveling speed of min, a magnetic coating film was formed and then dried to form a magnetic layer having a film thickness of 4 to 5 μm. Then, the back coat paint is applied to the surface of the non-magnetic support opposite to the magnetic layer side by the coating device and dried,
A magnetic tape was prepared by forming a back coat layer having a film thickness of 0.7 to 1 μm.

Then, in order to confirm the effect of using the above-mentioned smoothing device, the coating states of the formed magnetic layer and back coat layer were evaluated. The results are shown in Table 1.

In the above magnetic paint, γ as magnetic powder was used.
-Fe ₂ O ₃ , polyvinyl chloride copolymer as a binder,
Polyurethane resin, methyl ethyl ketone as solvent,
Toluene and cyclohexanone were used, and a lubricant containing a fatty acid as a lubricant, a metal oxide as an abrasive, and lecithin as a dispersant was used. As the back coat paint, one made of carbon black, a binder and an additive was used.

For comparison, a magnetic tape was prepared in the same manner as above using a conventional smoothing device instead of the rotary rod having the above groove, and the coating states of the magnetic layer and the back coat layer were evaluated. The results are also shown in Table 1.

[0037]

[Table 1]

In the table, sample tape 1 to sample tape 3 are magnetic tapes produced by using the rotary rod having the above groove as a smoothing device. Among them, the sample tape 1 is the second doctor blade, A magnetic tape manufactured without using an auxiliary smoothing device, a sample tape 2 is a magnetic tape manufactured using a second doctor blade together with the above smoothing device, and a sample tape 3 is a second doctor blade and an auxiliary with the above smoothing device. This is a magnetic tape produced by using a smoothing device together. Comparative tape 1
Comparative tape 7 is a magnetic tape manufactured using a conventional smoothing device, of which comparative tape 1 is a magnetic tape manufactured using a beef-nose blade-shaped bar as a smoothing device, and comparative tape 2 is Comparative tape 3 is a magnetic tape manufactured by using a cattle-nose blade-shaped bar to which a PET film is attached as a base film, and Comparative Tape 3 is a magnetic tape manufactured by using a bar-shaped bar.
Is a magnetic tape manufactured by using a bar having a hook blade shape and a PET film attached thereto, Comparative tape 5 is a magnetic tape manufactured by using a wire rod type bar, and Comparative tape 6 is a mirror surface rod. Is a magnetic tape manufactured by using a bar of a type, and Comparative Tape 7 is a magnetic tape manufactured by using a bar of a mirror surface rod type to which a PET film is attached.

The coating state was evaluated by observing the streak state and coating unevenness of the formed magnetic layer and back coat layer, and those having no streak or coating unevenness and having a particularly good surface condition were marked with ⊚, relatively Good surface condition is expressed as O, surface condition of practical use is expressed as Δ, and surface condition that is not practical is expressed as X.

As can be seen from Table 1, in Comparative Tape 1 to Comparative Tape 7, both the magnetic layer and the back coat layer were formed in a streak state or had coating unevenness, and formed with a good surface state. It has not been. On the contrary,
In the sample tapes 1 to 3, the magnetic layer and the back coat layer are formed in good surface condition without any streaks or coating unevenness.

Therefore, from these results, when the rotating rod having the groove is used as the smoothing device, even when a thick layer (thickness of 2 μm or more) such as a magnetic layer is formed, the back coat layer can be formed. It was found that even when a thin film layer (thickness less than 2 μm) is formed, a good surface condition can be obtained in any case.

When the sample tape 1, the sample tape 2 and the sample tape 3 are compared, the surface states of the magnetic layer and the back coat layer are better in the sample tape 2 and the sample tape 3 than in the sample tape 1, especially the sample tape. In No. 3, the magnetic layer is formed with an extremely smooth surface.

Therefore, from this, it is shown that the magnetic layer and the back coat layer are formed with even higher smoothness by using the second doctor blade and the auxiliary smoothing device together with the smoothing device of the present invention. If an auxiliary smoothing device is used, especially when forming a thick magnetic layer,
It was found that the magnetic layer was formed with a very good surface condition.

[0044]

As is apparent from the above description, in the production method of the present invention, the outer peripheral surface of the rotating rod is brought into contact with the coating film applied on the traveling non-magnetic support, thereby When smoothing the coating film, the smoothing device is used as the smoothing device on the outer peripheral surface in an amount of 30 to 7 in the axial direction of the rotating rod.
Since the one having a large number of grooves forming an angle of 0 ° is used, it is possible to form a magnetic layer and a back coat layer having high smoothness and a uniform film thickness. Furthermore, since the diameter of the rotating rod is 20 to 50 mm, a more excellent smoothing effect can be obtained, and the magnetic layer and the back coat layer having an extremely smooth surface can be formed.

Therefore, according to the present invention, since a magnetic recording medium having uniform characteristics can be manufactured, a clear image can be obtained when it is used for a video tape, and uneven sensitivity occurs when it is used as an audio tape. It is possible to obtain a magnetic recording medium that exhibits uniform characteristics.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a coating device for coating a magnetic coating material on a non-magnetic support.

FIG. 2 is a schematic perspective view showing an example of a smoothing device to which the present invention is applied.

FIG. 3 is a schematic view showing a pattern of grooves formed on the outer peripheral surface of the smoothing device.

FIG. 4 is a schematic cross-sectional view showing an example of the shape of a groove formed on the outer peripheral surface of the smoothing device.

FIG. 5 is a schematic perspective view showing an example of a conventional smoothing device.

FIG. 6 is a schematic perspective view showing another example of a conventional smoothing device.

FIG. 7 is a schematic perspective view showing still another example of a conventional smoothing device.

FIG. 8 is a schematic perspective view showing still another example of a conventional smoothing device.

FIG. 9 is a schematic cross-sectional view showing an example in which a base film is attached to a conventional smoothing device.

FIG. 10 is a schematic cross-sectional view showing another example in which a base film is attached to a conventional smoothing device.

FIG. 11 is a schematic cross-sectional view showing still another example in which a base film is attached to a conventional smoothing device.

[Explanation of symbols]

 1 ... Gravure roll 2 ... Backup roll 5 ... Smoothing device

Claims (2)

[Claims] 1. A step of applying a coating material on a non-magnetic support that continuously runs in the longitudinal direction, and a undried coating film formed by applying the coating material is placed in the width direction of the non-magnetic support material. In the method for producing a magnetic recording medium, which comprises a step of smoothing the coating film by bringing the coating into contact with a rotating rod, the surface of the rotating rod has an axial direction of 30 to 70 °.
A method of manufacturing a magnetic recording medium, characterized in that a plurality of grooves having an angle of are formed. 2. The rotating rod has a diameter of 20 to 50 mm.
The method of manufacturing a magnetic recording medium according to claim 1, wherein