JPH0798858A - Production of coating material for magnetic recording medium and production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a coating material excellent in dispersibility of an abrasive material. CONSTITUTION:A dispersion of magnetic powder in an org. solvent contg. a binder and a dispersion of an abrasive material in an org. solvent contg. a binder are separately prepd. and mixed to obtain the objective coating material. A nonmagnetic substrate is coated with the coating material and dried to obtain the objective magnetic recording medium. The coating material contg. the abrasive material in a satisfactorily dispersed state is obtd. in a short time and the magnetic recording medium hardly dropping the abrasive material and having low head wearing property is obtd. using 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 producing a coating material for a magnetic recording medium such as a magnetic tape, a magnetic sheet and a magnetic disk, and a method for producing a magnetic recording medium using the coating material for a magnetic recording medium obtained by the method. is there.

[0002]

2. Description of the Related Art In recent magnetic recording media such as video tapes, the recording density is becoming higher year by year, and accordingly, magnetic powder having a smaller particle diameter is being used.
When the magnetic powder is made into fine particles, the surface of the magnetic layer is generally smoothed and the spacing loss with the head is reduced,
This is advantageous in obtaining high electromagnetic conversion characteristics.

However, as the magnetic powder becomes finer, the magnetic powder is more likely to fall onto the head, the cylinder, the guide roll, etc. while traveling on the deck. Therefore, it is necessary to suppress the head adhesion as much as possible by increasing the amount of the abrasive.

Abrasives used in magnetic recording media are usually α-alumina and chromium oxide. The amount of hydroxyl groups present on the surface of these particles is extremely small as compared with magnetic powders such as iron oxide and metallic iron. Therefore, the adsorption amount of the resin as the binder is naturally small. From these facts, if the amount of the abrasive contained in the magnetic layer is increased, the number of abrasive particles detached during running increases, causing scratches on the head and tape, and causing dropout, which is a problem. . Further, the surface of the abrasive particles is not sufficiently covered with the resin as the binder, which leads to deterioration of head wear.

Conventionally, the abrasive has been kneaded and dispersed in the same resin solution as the magnetic powder. It has been disclosed that a hydrophilic functional group such as a sulfo group or a carboxyl group is introduced into a binder such as vinyl chloride-vinyl acetate resin and polyurethane resin in order to improve the dispersibility of magnetic powder. However, even if these resins are used, it is insufficient to improve the dispersibility in an abrasive having a wettability lower than that of the magnetic powder. Further, the wettability and dispersibility should be improved by improving the compounding and dispersion methods to solve the above problems.

[0006]

The problem to be solved by the present invention is to improve the dispersion prescription of the abrasive by
To provide a coating material for a magnetic recording medium having sufficient dispersibility even if the amount of the abrasive added is increased, and to prevent a magnetic recording medium from causing a large amount of abrasive particles to fall off during running and not worsening head wear. To provide.

[0007]

As a result of intensive studies to solve the above problems, the present inventors have found that when a coating material for a magnetic recording medium is manufactured, a magnetic powder and a magnetic powder are added to a binder organic solvent solution. Rather than the method of producing a coating solution in which an abrasive having poorer wettability than powder is added as it is, an abrasive dispersion is prepared by thoroughly wetting the surface of the abrasive with a binder in advance. It has been found that the dispersibility of the abrasive in the binder becomes extremely good when a coating material manufacturing method of mixing with a separately prepared magnetic powder dispersion is adopted.

Further, the magnetic recording medium obtained by coating the coating material for magnetic recording medium thus obtained on a non-magnetic support and drying it is an excellent magnetic recording medium having a small head abrasion resistance. The present invention has been completed and the present invention has been completed.

That is, according to the present invention, the magnetic powder (A), the binder (B), the abrasive (C), and the organic solvent (D) are mixed as essential components to contain a binder. A method for producing a coating material for a magnetic recording medium in which a powder and an abrasive are dispersed in an organic solvent, comprising: an organic solvent dispersion liquid (X) of magnetic powder (A) containing a binder (B); ) Is mixed with an organic solvent dispersion (Y) of an abrasive (C), and a method for producing a coating material for a magnetic recording medium, and a magnetic powder (A) containing a binder (B). Organic solvent dispersion (X)
And an organic solvent dispersion (Y) of an abrasive (C) containing a binder (B) are mixed to disperse the magnetic powder and the abrasive containing the binder in an organic solvent. Provided is a method for producing a magnetic recording medium, which comprises a first step of preparing a recording medium coating material and a second step of applying the magnetic recording medium coating material to a non-magnetic support and drying the coating material.

In the present invention, the organic solvent dispersion liquid (X) of the magnetic powder (A) containing the binder (B) comprises at least the magnetic powder (A), the binder (B) and the organic solvent. The magnetic powder (A) is present in a state of being dispersed in the binder (B) and the organic solvent, while the binder (B) is present in a state of being dispersed or dissolved in the organic solvent. is there.

The organic solvent dispersion liquid (Y) of the abrasive (C) containing the binder (B) comprises at least the abrasive (C), the binder (B) and the organic solvent, The abrasive (C) is present in a state of being dispersed in the binder (B) and the organic solvent, while the binder (B) is present in a state of being dispersed or dissolved in the organic solvent.

The present invention is most characterized in that the dispersion (X) and the dispersion (Y) are mixed to produce a coating material for a magnetic recording medium. This is the first step of the present invention. .

The dispersion (X) can be prepared by mixing the magnetic powder (A), the binder (B) and the organic solvent as essential components. Specifically, for example, the binder (B) may be dissolved in an organic solvent to prepare a binder solution, and the magnetic powder (A) may be dispersed therein.

Any known and commonly used magnetic powder (A) can be used in the present invention. As the ferromagnetic needle-like powder, for example, γ manufactured by Toda Kogyo Co., Ltd., Titanium Kogyo Co., Ltd., Ishihara Sangyo Co., Ltd., Sakai Chemical Co., Ltd.
-Fe ₂ O _3, CO was allowed deposited γ-Fe ₂ O _3, or,
Examples thereof include CrO ₂ manufactured by DuPont and BASF, or metal iron magnetic powder manufactured by Kanto Denka Co., Ltd. and Dowa Kogyo Co., Ltd.

When preparing the dispersion liquid (X), the content of the magnetic powder (A) in the finally obtained magnetic layer of the magnetic recording medium is in the range of 70 to 90% by weight based on the magnetic layer. It is preferable that it is set to be, and more preferably 75 to 85% by weight.

That is, the magnetic layer is usually 10 to 30 parts by weight, preferably 15 to 2 parts by weight with respect to 100 parts by weight of the magnetic powder (A).
The binder (B) is contained within the range of 5 parts by weight. Therefore, the content of the total binder (B) in the magnetic layer is generally adjusted by the mixing ratio of the dispersion liquid (X) and the dispersion liquid (Y) described later.

Examples of the binder (B) include vinyl chloride-vinyl acetate resin, polyester resin, nitrocellulose resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, phenoxy resin, epoxy resin. , A butadiene / acrylonitrile-based copolymer, a polyurethane-based resin, and a urethane-epoxy-based resin.

Further, synthetic resins containing a hydrophilic group or a group which can be made hydrophilic by a base, for example, hydroxyl group-containing polyurethane resin, carboxy group-containing polyurethane resin, sulfo group-containing polyurethane resin, sulfobetaine group-containing polyurethane resin, carboxy group-containing chloride. Examples thereof include vinyl-vinyl acetate copolymer resins, sulfo group-containing vinyl chloride-vinyl acetate copolymer resins, and sulfobetaine group-containing vinyl chloride-vinyl acetate copolymer resins. As the carboxy group,
Carboxyl group itself, metal base of carboxyl group,
Included are carboxyl group ammonia bases and carboxyl group amine bases. On the other hand, the sulfo group includes a sulfonic acid group itself, a sulfonic acid metal base, and the like.

The sulfobetaine group has both a quaternary ammonium structure as a cation and a sulfo group structure as an anion in one group, and they form an intramolecular salt. Is.

Comparing a synthetic resin containing a hydrophilic group or a group capable of becoming hydrophilic by a base with a synthetic resin not containing such a group, the magnetic powder can be favorably dispersed in a short time. Preference is given to using synthetic resins as binders.

Examples of the organic solvent used for dissolving or dispersing the binder (B) include methyl ethyl ketone, toluene, butyl acetate, and cyclohexanone. These may be used alone or in combination of two or more. You can

The non-volatile concentration of the dispersion liquid (X) is not particularly limited, but it is generally prepared so that the viscosity of the dispersion liquid (X) can be applied to the non-magnetic support by itself.

The dispersion (Y) can be prepared by mixing the abrasive (C), the binder (B) and the organic solvent as essential components. Specifically, for example, the binder (B) may be dissolved in an organic solvent to prepare a binder solution, and the abrasive (C) may be dispersed therein.

The abrasive (C) used in the present invention is, for example, α-alumina, chromium oxide, red iron oxide, silicon carbide,
The main component may be one kind or a combination of several kinds selected from silicon nitride and titanium oxide.

Among the abrasives (C), for example, "UB-10" (average particle size 0.5 μm) manufactured by Uemura Kogyo Co., Ltd., and "AKP-15" (average particle size 0.7 μm) manufactured by Sumitomo Chemical Co., Ltd. , "A
KP-20 ”(average particle size 0.55 μm), each“ α-alumina of Pecine A6Z ”(average particle size 0.6 μm) manufactured by Pecine, and“ Chromex S-1 ”manufactured by Nippon Kagaku Kogyo Co., Ltd.
(Average particle size 0.7 μm), “Chromex U-1” (average particle size 0.3 μm), “ND-801” manufactured by Nippon Denko KK
Chromium oxides having an average particle size of 0.5 μm and “ND-802” (average particle size of 0.6 μm) are particularly preferable.

In preparing the dispersion liquid (Y), the polishing agent (C) in the magnetic layer of the finally obtained magnetic recording medium is used.
However, the content is preferably in the range of 1 to 15% by weight with respect to the magnetic layer, and more preferably 3 to 10% by weight.

As the binder (B) and the organic solvent, any of those described above which can be used when preparing the dispersion liquid (X) can be similarly used.

Comparing the binder (B) with a synthetic resin containing a hydrophilic group or a group which can be made hydrophilic by a base and a synthetic resin containing no such group, the abrasive can be dispersed well in a short time. It is preferable to use the former synthetic resin as a binder because it can be used.

The concentration of non-volatile components in the dispersion liquid (Y) is also not particularly limited, but it is generally adjusted so that the dispersion liquid (Y) itself has such a viscosity that it can be applied to a non-magnetic support. .

Binder (B) used to prepare dispersion (X)
And the binder (B) used for preparing the dispersion liquid (Y) may be the same or different. In the present invention, it suffices that the surface of the abrasive (C) having poor dispersibility be sufficiently wetted with the binder (B), and the binder (B) and the dispersion (Y) in the dispersion (X) are not necessarily required. It is not necessary to match the binder (B) in). However, when different binders (B) used for preparing the dispersion liquid (X) and the binder (B) used for preparing the dispersion liquid (Y) are combined,
It is preferable to select and combine those having good compatibility.

For example, as the binder (B) of the latter dispersion liquid (Y), not only the dispersibility of an abrasive as a paint, the short preparation time of the paint, and the low head abrasion as a magnetic recording medium,
In order to obtain a magnetic recording medium having good steel characteristics and tape damage, a synthetic resin containing a sulfo group or a sulfobetaine group, especially dispersibility of an abrasive (C), steel characteristics of a magnetic recording medium, and a tape From the viewpoint of better damage, it is more preferable to use a synthetic resin containing a sulfobetaine group. On the other hand, as the binder (B) of the former dispersion liquid (X) combined with this, it is preferable to use a synthetic resin also containing a sulfo group or a sulfobetaine group.

Examples of the synthetic resin having a sulfo group or a sulfobetaine group include, for example, a vinyl chloride-vinyl acetate copolymer resin having a sulfo group or a sulfobetaine group and a number average molecular weight of 10,000 to 15,000 and a number having a sulfo group or a sulfobetaine group. Average molecular weight 10,000 to 15,000
It is preferable to use the polyurethane resin and the like.

When the number average molecular weight (Mn) of the vinyl chloride-vinyl acetate copolymer resin and the polyurethane resin used for the binder (B) is in the above range, the number of resin molecules adsorbed on the abrasive (C) is The steric hindrance is reduced, and another resin molecule is easily adsorbed on the abrasive (C). Therefore, the amount of the resin adsorbed to the polishing agent (C) increases, and the dispersibility of the polishing agent (C) in the dispersion liquid (Y) becomes good.

Moreover, the magnetic coating film of the magnetic recording medium obtained by using the coating material for the magnetic recording medium having good dispersibility does not lower its rigidity (Young's modulus), and the head touch of the magnetic recording medium is not affected. This is preferable because the electromagnetic conversion characteristics such as the output are less likely to deteriorate as a result of being able to sufficiently maintain and reducing the spacing loss.

When the vinyl chloride-vinyl acetate resin having the sulfo group or the sulfobetaine group and the polyurethane resin having the sulfo group or the sulfobetaine group are used in combination, the mixing ratio thereof is not particularly limited, but 8: 2.
To 3: 7 (weight ratio) is preferable, and 7: 3 to 4: 6.
The range of (weight ratio) is more preferable.

Further, the binder (B) of the dispersion liquid (X) and the dispersion liquid (Y) may be combined with a crosslinking agent, if desired. Examples of the cross-linking agent include aminoplast resins, phenoplast resins, polyisocyanates, carbodiimide compounds, aziridine compounds and the like.

The dispersion liquid (X), the dispersion liquid (Y), or the magnetic recording medium coating material may further contain a lubricant, an antistatic agent, a dispersant, an anticorrosive agent, etc., at any stage, if necessary. Can be included.

The dispersion liquid (X) of the predetermined non-volatile content and the dispersion liquid (Y) of the predetermined non-volatile content, which were separately prepared as described above, were mixed in predetermined weights to obtain the magnetic powder (A). And a polishing agent (C) in a predetermined nonvolatile content concentration to obtain a coating material for a magnetic recording medium. This is the first step in the present invention.

Next, a method for manufacturing the magnetic recording medium of the present invention will be described. Applying the coating material for a magnetic recording medium obtained in the above-mentioned first step to a non-magnetic support and drying it.
This is the second step of the present invention.

The coating material for a magnetic recording medium obtained in the first step is coated on a non-magnetic support so that the dry thickness of the magnetic layer is usually 0.5 to 10.0 μm, and dried to give a magnetic recording. It can be a medium. The magnetic layer is generally applied and laid directly on the non-magnetic support, but if necessary, an anchor such as an adhesive layer or an undercoat layer may be provided between the non-magnetic support and the magnetic layer. The magnetic layer may be provided on the anchor layer after the layer is provided in advance. A non-magnetic support provided with the anchor layer may be used.

As a material for forming the non-magnetic support, any material used as a material for a non-magnetic support of a general magnetic recording medium can be used. Examples of the material include polyethylene terephthalate, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamide imide, and also metal foils such as aluminum foil and stainless steel foil.

The thickness of the non-magnetic support is usually 3 to 50 μm.
m, preferably 5 to 30 μm. In applying the magnetic coating material to the non-magnetic support, for example, a gravure coater, a reverse coater, a die coater or the like can be used.

Further, the non-magnetic support may have a back layer provided on the side where the magnetic layer is not provided.

The magnetic recording medium thus obtained can be used as it is, but it is subjected to magnetic field orientation treatment, drying,
It can be manufactured by a usual method in which the surface is smoothed and cured, and then cut.

The surface roughness of the magnetic layer of the magnetic recording medium can be adjusted, for example, by controlling the conditions of a super calendar, and the RF output of the obtained magnetic recording medium is lowered. It can be difficult to do.

Further, the squareness ratio and the residual magnetic flux density (Br)
Can be adjusted by controlling the applied magnetic field using a solenoid type orienter during the magnetic field orientation process,
The RF output of the obtained magnetic recording medium can be made difficult to decrease.

[0047]

The surface of the abrasive such as α-alumina or chromium oxide (Cr ₂ O ₃ ) has a certain amount of hydroxyl groups, although the number is very small compared to the magnetic powder. Most of these hydroxyl groups are not charged, and very few are positively or negatively charged due to ion substitution or the like.

Therefore, when the magnetic powder and the abrasive are kneaded and dispersed in the same medium, the amount of hydroxyl groups on the surface is overwhelmingly large, even if a synthetic resin having excellent dispersibility is used as a binder. The binder is preferentially adsorbed to the magnetic powder and contributes little to the improvement of the wettability and dispersibility of the abrasive. Therefore, the magnetic powder and the abrasive are individually kneaded and
By dispersing and then mixing, it was possible to further improve the dispersibility of the abrasive in the binder.

As the functional group contributing to the dispersibility of the abrasive,
Although various functional groups can be mentioned, since the hydroxyl groups to which a negatively charged functional group such as a sulfo group and a carboxy group can be bound are limited, abrasive particles of a binder made of a synthetic resin having these functional groups. The amount of adsorption to is relatively low. On the other hand, the sulfobetaine group has two polar groups having both positive and negative charges in its structure. When this approaches the two neutral hydroxyl groups on the surface of the abrasive particles, the protons of one hydroxyl group easily move to the other hydroxyl group. As a result, 2
The two hydroxyl groups are as follows.

[0050]

Embedded image 2-OH → -O ^- + ^- OH ₂

These are bonded at two points like a chelating agent with the bipolar group of the sulfobetaine group. For the reason that this bond is considered to be extremely stable, when a synthetic resin having a sulfobetaine group is selected as a binder, its adsorption power to the abrasive and its adsorption amount are the same as those of the conventional synthetic resin having a functional group. It is higher than when a binder consisting of is used, and the dispersibility of the polishing agent is dramatically improved.

Next, examples and comparative examples of the present invention will be shown.
In the examples and comparative examples described below, “parts” means “parts by weight”.

[0053]

【Example】

 Example 1

[0054]

[Table 1]

After pretreatment of the above composition components by a certain method,
The mixture was kneaded and dispersed for 36 hours using a ball mill to prepare a magnetic powder dispersion liquid (magnetic powder coating material). Next, the composition and preparation method of the abrasive dispersion (abrasive paint) are shown.

[0056]

[Table 2]

After pretreatment of the above composition components by a certain method,
The mixture was kneaded and dispersed for 50 hours using a ball mill to prepare an abrasive dispersion (abrasive coating material). If the magnetic powder paint prepared by adjusting this abrasive paint is used, the polishing agent is added to 100 parts of the magnetic powder.
So that the mixture was added in an amount of 1 part and stirred for 60 minutes to prepare a coating material for a magnetic recording medium. This paint for a magnetic recording medium had extremely excellent dispersibility of the abrasive, and the surface of the abrasive particles was sufficiently wet with the binder as with the magnetic powder.

Further, "Coronate L" (polyisocyanate compound manufactured by Nippon Polyurethane Co., Ltd.) was added to this coating so as to be 3 parts with respect to 100 parts of magnetic powder, and after stirring the coating for 30 minutes, an average pore diameter of 1 μm was obtained. It filtered using the filter which has. A thickness of 10.0 μm was applied to this magnetic recording medium coating so that the thickness of the magnetic layer after drying was 3.0 μm.
m of polyethylene terephthalate support was coated using a gravure coater.

The non-magnetic support coated with this paint was subjected to a magnetic field orientation treatment, further dried and then subjected to a super calendar treatment under certain conditions. After the curing treatment, a back layer containing carbon black as a main component was applied to the back surface of the magnetic layer by a gravure coater so that the thickness after drying was 0.6 μm. After curing process, slit 8mm width to 8
Millivideo tape was manufactured.

COMPARATIVE EXAMPLE 1 The magnetic powder coating composition of Example 1 was prepared according to the conventional formulation instead of the formulation of the present invention in which the magnetic powder and the abrasive were individually coated and then mixed together.
−1 ”8 parts was added, and the vinyl chloride-vinyl acetate resin“ MR-110 ”was changed to the vinyl chloride-vinyl acetate resin having a sulfobetaine group used in the abrasive coating material to prepare a magnetic powder and an abrasive. Was added to the same binder organic solvent solution and kneaded and dispersed. An 8 mm video tape was manufactured in the same manner as in Example 1 except for the above.

Example 2 The polishing agent "Chromex S-1" used in Example 1 was changed to α-alumina "UB-10" manufactured by Uemura Kogyo Co., Ltd.
An 8 mm video tape was manufactured in the same manner as in Example 1 except for the above.

Example 3 The polishing agent "Chromex S-1" used in Example 1 was changed to α-alumina "AKP-30" manufactured by Sumitomo Chemical Co., Ltd. An 8 mm video tape was manufactured in the same manner as in Example 1 except for the above.

The magnetic tapes obtained in Examples and Comparative Examples were evaluated by the following methods. The result is first
Shown in the table. The evaluation method will be described below.

1. S / N-Y, S / N-C, RF output It measured using Sony 8mm VTR and EV-A300. The reproduction output at 5 MHz was measured, and the value of our standard 8 mm tape was set to 0 dB, and the value was displayed as a relative value.

2. Steel characteristics 25 mm using Sony 8mm VTR, EV-A300
The tape was statically reproduced in an environment of ° C and 60% RH. R
The elapsed time until the F output decreased by 2 dB from the initial output was measured.

3. Tape damage 25mm using Sony 8mm VTR, EV-A300, 25
1 tape of 90 minutes length under the environment of ° C and 60% RH
After running for 00 passes, the surface of the magnetic layer of the tape was observed with a microscope. The degree of scratches was evaluated in three grades of ◯ to ×.

◯: Almost no scratches Δ: Intermediate of × ×: Many scratches

4. Head wear Using Sony 8mm VTR, EV-A300, 45
1 tape of 90 minutes length under the environment of ℃, 85% RH
I ran for 00 passes. Photomicrographs of the head were taken before and after running, and the worn length at the tip of the head was determined.

[0069]

[Table 3] * Method A: Kneading and dispersion processing of abrasives alone.

Method B: Kneading and dispersing an abrasive in the same solution as magnetic powder.

As can be seen from the preparation example of the coating material for a magnetic recording medium, in the method for producing a coating material for a magnetic recording medium of the present invention, a coating material for a magnetic recording medium which is particularly excellent in dispersibility of an abrasive as compared with the conventional method can be obtained in a short time. You can see that it is obtained in. Also, the first
As can be seen from the table, the magnetic recording medium produced by using the coating material obtained by the production method of the present invention has a surface of abrasive particles satisfactorily covered with a synthetic resin as a binder, and the magnetic recording medium is polished. There is little dropout of the agent. As a result, it is found that not only the head wear is small, but also the electromagnetic conversion characteristics are excellent, and the steel and tape damage characteristics are also good.

[0072]

INDUSTRIAL APPLICABILITY In the method for producing a coating material for a magnetic recording medium of the present invention, an organic solvent dispersion of an abrasive containing a binder is prepared, and the surface of the abrasive is sufficiently prepared with a synthetic resin as the binder in advance. Since it is wet and then mixed with the magnetic powder dispersion liquid, the conventional formulation of preparing the coating material in a batch has an inferior wettability to that of the magnetic powder and an abrasive that cannot obtain sufficient dispersibility in a short time. A particularly remarkable effect that a coating material for a magnetic recording medium containing both magnetic powder and an abrasive, which is dispersed in a good state in a short time, can be obtained.

Since the magnetic recording medium manufacturing method of the present invention uses the magnetic recording medium coating material obtained by the above manufacturing method,
Since the surface of the abrasive particles is satisfactorily covered with the resin and the abrasive agent does not drop off, there is a particularly remarkable effect that a magnetic recording medium with low head wear can be provided.

Claims (5)

[Claims] 1. Magnetic powder (A), a binder (B), an abrasive (C), and an organic solvent (D) are mixed as essential components, and the binder is contained in the magnetic powder and the abrasive. A method for producing a coating material for a magnetic recording medium, wherein the agent is dispersed in an organic solvent,
Mixing the organic solvent dispersion (X) of the magnetic powder (A) containing the binder (B) and the organic solvent dispersion (Y) of the abrasive (C) containing the binder (B). A method for producing a coating material for a magnetic recording medium, which is characterized. 2. The production method according to claim 1, wherein the binder (B) in the dispersion liquid (Y) is a binder made of a synthetic resin having a sulfo group or a sulfobetaine group. 3. The production method according to claim 1, wherein the binder (B) in the dispersion liquid (Y) is a binder made of a synthetic resin having a sulfobetaine group. 4. The binder (B) in each of the dispersion liquid (X) and the dispersion liquid (Y) is a binder composed of a synthetic resin having a sulfo group or a sulfobetaine group. Production method. 5. An organic solvent dispersion (X) of magnetic powder (A) containing a binder (B), and an organic solvent dispersion (Y) of abrasive (C) containing a binder (B). The first step of preparing a magnetic recording medium coating material obtained by dispersing magnetic powder and an abrasive containing a binder in an organic solvent, and applying the magnetic recording medium coating material to a non-magnetic support. A method of manufacturing a magnetic recording medium comprising the second step of drying and drying.