JP2001014663A - Manufacture of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of manufacturing a magnetic recording medium suitable for a high density recording and having an excellent electromagnetic conversion characteristics, wherein a thin magnetic layer is applied directly to a non-magnetic supporting body and the magnetic layer has an excellent surface property. SOLUTION: A paint 2 for a pseudo lower layer containing a solvent having >=150 deg.C b.p. is applied onto a non-magnetic supporting body 1. A magnetic paint 3 consisting of ferromagnetic powder dispersed in a bonding agent is applied onto the paint 2 for a pseudo lower layer while the paint 2 for a pseudo lower layer is still wet. A magnetic layer consisting of the magnetic paint 3 is formed on the non-magnetic supporting body 1 by evaporation of the paint 2 for a pseudo lower layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a magnetic recording medium such as a magnetic tape and a magnetic disk, and more particularly to a method for manufacturing a magnetic recording medium having a magnetic layer coated with a magnetic paint.

[0002]

2. Description of the Related Art As a magnetic recording medium, a magnetic layer is prepared by dispersing a ferromagnetic powder, a binder, various additives, and the like together with an organic solvent, coating a prepared magnetic coating material on a non-magnetic support, and drying. A so-called coating type magnetic recording medium to be formed is known. In a coating type magnetic recording medium, metal fine particles are used as ferromagnetic powder in order to increase the average number of particles per unit volume of the magnetic layer for the purpose of high density recording.

A coating type magnetic recording medium using fine metal particles is used as a recording medium for computers such as an audio magnetic tape, a video magnetic tape, a high-density flexible disk, and a backup data cartridge. The medium has become mainstream.

In order to realize high-density recording in a coating type magnetic recording medium, the average number of particles per unit volume of a magnetic layer is increased by using metal fine particles as a ferromagnetic powder, It is important to minimize the spacing loss by super-smoothing the surface and reduce the output loss due to recording demagnetization. Therefore, studies have been made on increasing the coercive force and saturation magnetization of the ferromagnetic powder, making the coercive force distribution of the ferromagnetic powder uniform, making the magnetic layer thinner, and the like.

[0005] In a coating type magnetic recording medium, the self-demagnetization loss can be greatly reduced by thinning the magnetic layer. However, when the thickness of the magnetic layer formed by applying the magnetic paint on the non-magnetic support is, for example, 1 μm or less, the surface shape of the non-magnetic support tends to appear on the surface of the magnetic layer. Therefore, when the thickness of the magnetic layer is 1 μm or less, there is a problem that it is difficult to smooth the surface of the magnetic layer.

In the case where a magnetic paint is applied on a non-magnetic support to form a magnetic layer having a thickness of 0.5 μm or less, for example, the thickness of the magnetic layer is extremely small. The solvent used for the coating is vaporized quickly, and the surface of the applied magnetic coating is easily dried. Therefore, when the magnetic paint is applied using the application device, the extruding port of the paint and the surface of the magnetic paint come into contact with each other, and a large contact resistance is likely to occur. As a result, the magnetic layer could not obtain a smooth surface state.

As described above, when the magnetic layer is directly provided on the non-magnetic support by applying the magnetic paint on the non-magnetic support, it is difficult to make the magnetic layer thinner and smooth the surface. In order to solve this problem, when the magnetic layer is made thinner, a multilayer coating type structure in which a nonmagnetic layer made of a nonmagnetic paint is interposed between the nonmagnetic support and the magnetic layer is adopted.

As a coating method of the multi-layer coating type, a three-lip or four-lip die coater provided with two slits through which a non-magnetic paint and a magnetic paint are respectively extruded is used. A multilayer coating method of applying a paint and a magnetic paint has been proposed. In particular, a wet multi-layer coating method (wet-on-wet coating method) in which a non-magnetic paint is applied while layering a magnetic paint in a wet state is preferable.

By interposing a non-magnetic layer formed by applying a non-magnetic paint composed of a non-magnetic powder and a binder between the non-magnetic support and the magnetic layer, the surface shape of the non-magnetic support can be improved. Are less likely to appear on the surface of the magnetic layer, and the surface of the magnetic layer can be smoothed. Further, since the magnetic layer is formed on the non-magnetic layer, the thickness of the magnetic layer can be reduced.

[0010]

However, when the above-mentioned wet-on-wet coating method is used, unevenness in coating and streaks occur in the step of applying the non-magnetic paint on the non-magnetic support. Sometimes. When a magnetic paint is applied on a non-magnetic paint having a poor surface shape as described above, uneven coating and streaks may occur on the surface of the magnetic layer, and the surface of the magnetic layer may not be smoothed. . Further, in a magnetic recording medium in which a nonmagnetic layer and a magnetic layer are provided on a nonmagnetic support, the overall thickness cannot be reduced.

For this purpose, a coating for a pseudo-underlying layer composed of a solvent is applied on a non-magnetic support in place of the non-magnetic layer, and a magnetic layer is coated on the coating for the pseudo-underlying layer, and then the coating for a pseudo-underlying layer is applied. There is a method in which a magnetic layer is formed on a nonmagnetic support by vaporization. According to this method, since the magnetic layer is directly laminated on the nonmagnetic support, the thickness of the entire magnetic recording medium can be reduced. However, even with this approach,
The surface of the magnetic layer cannot be smoothed.

In view of the above, the present invention has been proposed in view of such a conventional situation. A thin magnetic layer is provided directly on a non-magnetic support, and the magnetic layer has good surface properties. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium having excellent electromagnetic conversion characteristics, which is suitable for high-density recording.

[0013]

In order to achieve the above-mentioned object, a method for producing a magnetic recording medium according to the present invention is directed to a method for producing a coating for a suspected lower layer containing a solvent having a boiling point of 150 ° C. or higher by a non-magnetic support. On the non-magnetic support, by coating the magnetic paint formed by dispersing the ferromagnetic powder in the binder while the paint for the pseudo lower layer is in a wet state, and the paint for the pseudo lower layer is vaporized, It is characterized in that a magnetic layer made of a magnetic paint is formed.

In the method for manufacturing a magnetic recording medium according to the present invention having the above-described structure, the magnetic paint is applied while the paint for the suspected lower layer is wet, so that the magnetic paint can be applied thinly. The thickness of the magnetic layer can be reduced.

Further, since the pseudo-underlayer coating contains a solvent having a boiling point of 150 ° C. or higher, it is necessary to apply the pseudo-underlayer coating on the non-magnetic support and then apply the magnetic coating on the pseudo-underlayer coating. During this time, the paint for the lower layer is less likely to evaporate. As a result, the paint for the suspected lower layer maintains a good moisture state, so that the magnetic paint can be uniformly applied on the paint for the suspected lower layer, and as a result, the surface properties of the applied magnetic paint are improved. be able to.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method for manufacturing a magnetic recording medium according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, a magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to the present invention first includes a non-magnetic support 1 and a non-magnetic support 1 coated on the non-magnetic support 1. A lower layer paint 2 and a magnetic paint 3 to which the suspect lower layer paint 2 is applied in a wet state are provided. Then, as will be described in detail later, the magnetic recording medium is the one in which the magnetic layer 4 is finally formed on the non-magnetic support 1 as shown in FIG. Become.

Further, the present invention is not limited to the method of manufacturing a magnetic recording medium having the above-described structure, and a back coat layer may be formed on a surface opposite to a surface on which a magnetic layer is provided on a non-magnetic support. May be applied to the method of manufacturing a magnetic recording medium provided with

In this magnetic recording medium, as the nonmagnetic support 1, a polyester resin such as polyethylene terephthalate and polyethylene, an aromatic polyamide resin film, and the like can be used.

The coating 2 for the lower layer consists of a solvent and has a boiling point of 1
Contains a solvent at 50 ° C or higher. The addition amount of the solvent having a boiling point of 150 ° C. or more is preferably 55 to 85% by weight based on the total solvent contained in the coating material 2 for the suspected lower layer. In other words, the solvent used for the suspected lower layer coating material 2 mainly has a boiling point of 150 ° C. or more, and a solvent having a boiling point of less than 150 ° C. may be used in combination.

Examples of the solvent having a boiling point of 150 ° C. or higher include:
Cyclohexanone (boiling point: 156.0 ° C, vapor pressure: 3.9m
mHg), methylcyclohexanone (boiling point 170.0
° C, vapor pressure 3.0mmHg), cyclohexanol (boiling point 161.0 ° C, vapor pressure 0.9mmHg), methylcyclohexanol (boiling point 174.0 ° C, vapor pressure 0.3mm)
Hg) and the like. Among them, it is preferable to use cyclohexanone.

Examples of the solvent having a boiling point of less than 150 ° C., which is used in combination with the coating material 2 for the lower layer, include methyl ethyl ketone (boiling point: 79.6 ° C., vapor pressure: 71.2 mmHg), toluene (boiling point: 110.0 ° C., (Vapor pressure 22.0mmHg)
And the like.

The magnetic layer 4 is formed by applying a magnetic paint 3 comprising at least a ferromagnetic powder and a binder.

Specifically, as the ferromagnetic powder, Fe—C
o, Fe-Ni, Fe-Co-Ni, Co-Ni, Fe
-Mn-Zn, Fe-Co-Ni-P, Fe-Co-C
Metal particles mainly composed of Fe, Co, and Ni such as r-B are exemplified. Further, γ-Fe ₂ O ₃ , Fe ₃ O ₄ , γ-Fe
Belt compound of ₂ O ₃ and Fe ₃ O ₄ , γ-Fe ₂ O ₃ containing Co, γ-Fe ₃ O ₄ containing Co, γ-Fe ₂ O ₃ containing Co and containing Co berthollide compound of γ-Fe ₃ O ₄ to, one or more metal elements CrO _2, for example Te, Sb, Fe, B oxide was contained and the like, and the like. Further, hexagonal plate-like ferrite can also be used, and Co-T is used for controlling the coercive force.
i, Co-Ti-Zn, Co-Ti-Nb, Co-Ti
Those obtained by adding -Zn-Nb, Cu-Zr, Ni-Ti, etc. to hexagonal plate-like ferrite can also be used.

One of these ferromagnetic powders can be used alone, or two or more can be used in combination. The specific surface area of the ferromagnetic powder is 20 to 90 m ^2.
/ G, more preferably 25 to 70 m ² / g. When the specific surface area is in the above range,
As the shape of the ferromagnetic powder becomes finer, high-density recording becomes possible, and a magnetic recording medium having excellent noise characteristics can be obtained.

As the binder, conventionally known binders can be used. For example, polymers such as vinylidene chloride, acrylates, methacrylates, styrene, butadiene, acrylonitrile and the like, or polyurethane resins which are copolymers, Polyester resins and the like can be mentioned.

If necessary, additives such as a dispersant, an internal additive, an abrasive, an antistatic agent, and a rust preventive may be added to the magnetic paint 3. As these additives, any conventionally known additives usually used in magnetic recording media can be used.

As the solvent used for forming the magnetic coating material 3, conventionally known solvents can be used, for example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, methyl acetate and ethyl acetate. Esters, glycol ethers such as glycol dimethyl ether and dioxane, and aromatic hydrocarbons such as toluene and xylene.

When applying the coating material 2 for the dummy lower layer and the magnetic coating material 3 on the nonmagnetic support 1, the coating material 2 for the dummy lower layer is wetted by a so-called wet-on-wet coating method (wet multilayer coating method). When in the state, the magnetic paint 3 is applied.
At this time, a die coater having a lip configuration of three lips or four lips is used as a coating device.

Specifically, for example, a die coater 5 as shown in FIG. 3 is used. The die coater 5 has a die head 8 composed of a first slit 6 and a second slit 7 so that the suspect lower layer paint 2 and the magnetic paint 3 are extruded, respectively. In the die head 8, a pseudo lower layer coating liquid reservoir 9 to which the pseudo lower layer coating 2 is supplied and a magnetic coating liquid reservoir 10 to which the magnetic coating 3 is supplied are formed. That is, in the die head 8, the suspect lower layer coating liquid reservoir 9 and the first slit 6 are connected, and the magnetic coating liquid reservoir 10 and the second slit 7 are connected. In the die coater 5, the non-magnetic support 1 is hung on the pair of guide rollers 11, and the die head 8 is disposed on the non-magnetic support 1 so as to face the non-magnetic support 1 at a predetermined interval.

In the die coater 5 configured as described above,
The non-magnetic support 1 and the magnetic coating 3 are extruded from the first slit 6 and the second slit 7 at the same time as the non-magnetic support 1 travels at a predetermined speed in the direction indicated by the arrow A in FIG.

More specifically, first, the suspect lower layer paint 2 extruded from the first slit 6 is applied to the running non-magnetic support 1.
Applied on top. Next, the magnetic coating material 3 extruded from the second slit 7 is applied on the wet lower-layer coating material 2 in a wet state. It is appropriate that the pseudo lower layer coating material 2 contains a solvent having a boiling point of 150 ° C. or higher. Thereby, the suspicious lower layer paint 2 can be kept in a wet state from the time when the suspicious lower layer paint 2 is applied on the non-magnetic support 1 to the time when the magnetic paint 3 is overlaid and applied. Can be uniformly applied on the coating material 2 for the pseudo lower layer.

The applied magnetic coating material 3 uniformly dissolves in the wet lower-layer coating material 2. That is, the paint 2 for the pseudo lower layer is gradually impregnated into the magnetic paint 3 and integrated.
Next, the suspect lower layer paint 2 is vaporized. As a result, as shown in FIG. 2, the magnetic layer 4 is directly formed on the nonmagnetic support 1.

As a result, the thickness of the magnetic layer 4 can be reduced. Further, the surface of the magnetic layer 4 formed after the pseudo lower layer coating material 2 is vaporized is smoothed and has good surface properties.

At this time, the solvent having a boiling point of 150 ° C. or more is 55 to 85
It is preferably contained in the range of weight%. If the amount of the solvent having a boiling point of 150 ° C. or more is less than 55% by weight, the coating 2 for the pseudo-underlayer is too fast to vaporize. For this reason,
The magnetic coating material 3 cannot be applied uniformly on the dummy lower layer coating material 2, and there is a possibility that the coating may be missing. On the other hand, the boiling point is 15
When the addition amount of the solvent at 0 ° C. or higher is more than 85% by weight, the vaporization of the coating material 2 for the pseudo lower layer is too slow. For this reason, there is a possibility that the magnetic coating material 3 does not uniformly dissolve in the coating material 2 for the suspicious lower layer, resulting in a missing coating.

Therefore, by adding a solvent having a boiling point of 150 ° C. or more in the range of 55 to 85% by weight, the paint 2
Between the application of the magnetic paint 3 on the non-magnetic support 1 and the application of the magnetic paint 3 on top of each other, it is possible to keep the paint 2 for the suspected lower layer in a good wet state, It becomes possible to apply the coating more evenly.

The thickness of the magnetic layer 4 is preferably not more than 0.5 μm. When the thickness of the magnetic layer 4 is set to be larger than 0.5 μm, the magnetic paint 3
May not be applied uniformly. When the thickness of the magnetic layer 4 is larger than 0.5 μm, the suspected lower layer paint 2 impregnated in the magnetic paint 3 hardly evaporates, and the suspected lower layer paint 2 remaining on the magnetic layer 4 is removed. More. Thereby, there is a possibility that the surface state of the magnetic layer 4 is deteriorated and the electromagnetic conversion characteristics are deteriorated.

Therefore, by setting the thickness of the magnetic layer 4 to 0.5 μm or less, the coating 2 for the pseudo lower layer does not remain, and the magnetic layer 4 having excellent surface properties can be obtained. As a result, electromagnetic conversion characteristics suitable for high-density recording are provided.

The thickness of the suspicious lower layer paint 2 was set to 10 μm in a wet state.
Preferably, it is in the range of m to 15 μm. When the thickness of the pseudo lower layer paint 2 is reduced to less than 10 μm in a wet state, the pseudo lower layer paint 2 is applied on the magnetic support 1 until the magnetic paint 3 is overlaid and applied. There is a possibility that the coating material 2 cannot keep the wet state uniform. on the other hand,
When the thickness of the pseudo lower layer paint 2 is set to be greater than 15 μm in a wet state, the magnetic lower paint 3 is excessively impregnated in the magnetic paint 3 and the magnetic paint 3 is separated, so that a coating defect may occur. . In addition, the thickness of the suspect lower layer paint 2 is set to 15 in a wet state.
If the thickness is larger than μm, there is a possibility that the coating material 2 for the pseudo lower layer remains on the dried magnetic layer 4. Further, if the thickness of the pseudo lower layer paint 2 is greater than 15 μm in a wet state, there is a risk that the pseudo lower layer paint 2 may overflow from both sides of the first slit 6 irrespective of the weight ratio of the solvent constituting the pseudo lower layer paint 2. is there.

Therefore, by setting the thickness of the pseudo lower layer paint 2 in the range of 10 μm to 15 μm in a wet state, the magnetic paint 3 can be thinly and uniformly applied on the pseudo lower layer paint 2.

In this method, the magnetic layer 4 directly formed on the non-magnetic support 1 is subjected to a calendering treatment as necessary to smooth the surface, or the non-magnetic support 1
A back coat layer may be provided on the surface opposite to the surface on which the magnetic layer 4 is formed. As the material of the back coat layer, any of those commonly used for magnetic recording media can be used.

Then, the magnetic recording medium is manufactured by slitting or punching into a desired shape. The magnetic recording medium manufactured by such a manufacturing method has a highly smooth surface of the magnetic layer 4, has excellent surface properties, and has high electromagnetic conversion characteristics. Become.

[0043]

EXAMPLES Hereinafter, a plurality of samples were prepared as specific examples and comparative examples of the present invention, and using these samples, the weight ratio of the solvent constituting the coating for the suspected lower layer was examined.

A magnetic tape was prepared as a sample.

Sample 1 Each component of the magnetic paint was weighed and mixed according to the following composition, kneaded by a kneader, and then dispersed by a sand mill to prepare the magnetic paint.

<Magnetic paint composition>-Ferromagnetic powder: 100 parts by weight of Fe-based metal ferromagnetic powder-Binder: 16 parts by weight of polyvinyl chloride resin (manufactured by Toyobo Co., Ltd.) 4 parts by weight of polyester polyurethane-Additive: 2 parts by weight of carbon Parts Al ₂ O ₃ 5 parts by weight Stearic acid 1 part by weight Heptyl stearate 1 part by weight Lubricant: methyl ethyl ketone 150 parts by weight Cyclohexanone 150 parts by weight

Next, the solvent constituting the coating for the lower layer was weighed according to the following composition, and was prepared at the following weight ratio.

<Coating for pseudo lower layer> 15% by weight of methyl ethyl ketone (boiling point 79.6 ° C.) 85% by weight of cyclohexanone (boiling point 156.0 ° C.)

Then, the magnetic coating material and the coating material for the pseudo lower layer prepared as described above were applied to a nonmagnetic support made of polyethylene terephthalate having a thickness of 7.0 μm by wet coating using a die coater. Thereafter, an orientation treatment was performed by a solenoid, and after drying, a calendar treatment was performed, and a curing treatment was performed. Note that the thickness of the coating for the pseudo lower layer coating was 13 μm. On the other hand, the thickness of the magnetic layer is 0.3 μm.
The adjustment of the die coater, for example, the adjustment of the gap between the nonmagnetic support and the lip of the die coater, the adjustment of the amount of paint supplied, and the like were performed so as to obtain m.

In order to improve the running property, a back coat layer was formed on the surface of the non-magnetic support opposite to the surface on which the magnetic layer was formed. As the back coat layer, a mixture of carbon black as a nonmagnetic powder, polyester polyurethane as a binder, and a mixture of methyl ethyl ketone and toluene as a solvent was used.

Then, a slit was made to a width of 8 mm to produce a magnetic tape.

Samples 2 to 8 Magnetic tapes were prepared in the same manner as in Sample 1, except that the solvents for the paints for the lower layer were mixed at the weight ratios shown in Table 1.

With respect to Samples 1 to 8 prepared as described above, the coating unevenness, surface properties, and electromagnetic conversion characteristics of the magnetic layer were evaluated. The evaluation methods are described below.

<Coating unevenness> As a judgment of evaluation, when the magnetic layer was finally formed, there was no coating unevenness and a stable magnetic layer was obtained. The case where fine adjustment or the like was required was indicated by Δ, and the case where coating unevenness occurred and the magnetic layer was not stable was indicated by ×.

<Surface Properties> The surface roughness was evaluated by measuring the center line average roughness (Ra).

<Electromagnetic Conversion Characteristics> A 7 MHz signal was recorded at an optimum recording current on a magnetic tape slit to a width of 8 mm.
The output level of this signal was measured by a spectrum analyzer. The output level reference tape is a magnetic tape for 8 mm VTR (8 mmH manufactured by Sony Corporation).
i8 tape) as a relative value when the output level is 0 dB.

Table 1 shows the results of the above characteristic evaluations and the weight ratios of the solvents constituting the coating for the suspected lower layer.

[0058]

[Table 1]

* The-mark in the table indicates that measurement is impossible because the measured values vary greatly.

As can be seen from Table 1, the paint for the suspected lower layer contains cyclohexanone as a solvent having a boiling point of 150 ° C. or higher, and the weight ratio of cyclohexanone is 55 to 55 with respect to the total solvent contained in the paint for the suspected lower layer. In samples 1 to 3 which were 85% by weight, it was found that there was no application unevenness of the magnetic paint, the surface properties of the magnetic layer were good, and there were excellent electromagnetic conversion characteristics.

On the other hand, as shown in Samples 5 and 6, a solvent having a boiling point of 7
When 100% by weight of methyl ethyl ketone having a boiling point of 9.6 ° C. is used, toluene having a boiling point of 110 ° C. and a boiling point of 7% are used.
When methyl ethyl ketone at 9.6 ° C. was mixed at 50% by weight, the coating unevenness was extremely severe, and it was difficult to form a magnetic layer. This is because the pseudo-underlayer coating consisting only of a solvent having a low boiling point is too fast to vaporize, so that when applying the pseudo-underlayer coating on the non-magnetic support, a uniform wet state cannot be maintained, and the magnetic coating cannot be used. This is because it cannot be applied uniformly.

From the above, the boiling point of the paint for the suspected lower layer was 150.
It has been found that it is suitable to contain a solvent at a temperature of at least 0 ° C.

As shown in Sample 4, when 100% by weight of cyclohexanone was used as the solvent having a boiling point of 150 ° C. or higher to be contained in the coating for the pseudo lower layer, coating unevenness of the magnetic coating was observed, It was also found that the surface properties were poor and the electromagnetic conversion characteristics were low. It has a boiling point of 150 ° C
If the coating for the pseudo-underlying layer consisting only of the above-mentioned solvent is too slow to evaporate, the magnetic coating 3 does not uniformly dissolve in the coating for the pseudo-underlayer 2 and coating unevenness is likely to occur.

Furthermore, as shown in Samples 7 and 8, when cyclohexanone was used as a solvent having a boiling point of 150 ° C. or higher and 50% by weight as a solvent to be contained in the coating for the pseudo underlayer, the coating unevenness was severe and the magnetic layer was formed. Was difficult. This is because, as in the case of sample 5, the pseudo-underlayer paint having a boiling point of 150 ° C. or more and the content of the solvent of 50% by weight is too fast to vaporize, so that the pseudo-underlayer paint is applied on the non-magnetic support. This is because a uniform wet state cannot be maintained during the coating, and the magnetic paint cannot be applied uniformly.

As described above, the content of the solvent having a boiling point of 150 ° C. or more was 55% with respect to the total solvent contained in the coating for the lower layer.
It was found that the content was more preferably set to 85% by weight.

[0066]

As described above, in the method for manufacturing a magnetic recording medium according to the present invention, the coating for the suspected lower layer has a boiling point of 15%.
Since the solvent containing 0 ° C or more is contained, the coating for the pseudo-underlayer has good moisture between the time when the coating for the pseudo-underlayer is applied on the non-magnetic support and the time when the magnetic coating is applied onto the coating for the pseudo-underlayer. State can be maintained. For this reason, according to this method, the magnetic paint can be uniformly applied on the paint for the suspected lower layer, and as a result, the surface properties of the magnetic paint can be improved.

Thus, according to the method of manufacturing a magnetic recording medium of the present invention, it is possible to manufacture a magnetic recording medium having a magnetic layer having good surface properties and excellent electromagnetic conversion characteristics suitable for high-density recording. it can.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a magnetic recording medium according to the present invention before a coating for a pseudo lower layer is vaporized.

FIG. 2 is a cross-sectional view of a main part of the magnetic recording medium according to the present invention after a pseudo lower layer paint is vaporized.

FIG. 3 is a schematic diagram illustrating an example of a coating apparatus of the coating film forming system.

[Explanation of symbols]

0 Non-magnetic support, 2 paint for suspected lower layer, 3 magnetic paint,
4 magnetic layer, 5 die coater, 6 first slit, 7
Second slit, 8 die head, 9 Suspended lower part paint liquid reservoir, 10 magnetic paint liquid reservoir, 11 guide roller

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D075 AE06 CA48 DA04 DB48 DC28 EC30 EC54 5D112 AA03 AA05 AA22 BB01 BD09 CC02

Claims (4)

[Claims] 1. A pseudo-underlayer paint containing a solvent having a boiling point of 150 ° C. or higher is applied on a non-magnetic support, and the ferromagnetic powder is used as a binder while the pseudo-underlayer paint is in a wet state. A method for producing a magnetic recording medium, comprising: forming a magnetic layer of a magnetic paint on a non-magnetic support by applying a dispersed magnetic paint in a multi-layered manner and vaporizing the pseudo lower layer paint. 2. A solvent having a boiling point of 150.degree.
The method for manufacturing a magnetic recording medium according to claim 1, wherein: 3. The method according to claim 1, wherein the thickness of the magnetic layer is 0.5 μm or less. 4. The method according to claim 1, wherein the solvent having a boiling point of 150 ° C. or higher is cyclohexanone.