JPH06150297A - Magnetic recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium which is improved in dispersibility of magnetic powder in its magnetic layer and suitable for high density magnetic recording and its manufacturing method. CONSTITUTION:In this recording medium constituted of a nonmagnetic substrate and magnetic layer which is formed on the substrate and contains magnetic powder and a resin binder, the magnetic powder is surface-processed with at least one or more kinds of organic silicon compounds at a rate of 5X10<-7> to 5X10<-6> mol weight per 1-m<2> surface area measured by the BET adsorption method and dispersed in the resin binder at a ratio of 100 pts.wt. magnetic powder per <=10 pts.wt. resin binder. A specific usable silicone compound can be hexamethylcyclotrisiloxane, hexamethyldisilazane, pentadecafluorodecyl trimethoxysilane, octadecyl triethoxysilane, etc. Magnetic powder, especially, hexagonal ferrite powder having a particle size of <=0.15mum, is suitable for the magnetic powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium suitable for high density recording and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, with the spread of electronic devices such as personal word processors, personal computers and home videos, magnetic recording media such as floppy disks or video tapes have been widely used as recording media for recording a large amount of information. Has become. Above all,
Since the coating type magnetic recording medium has excellent mass productivity, it occupies most of the market.

In the production of this coating type magnetic recording medium, conventionally, γ-Fe ₂ O ₃ , CrO ₂ , Co-γ-Fe ₂ O _{3 is formed} on a substrate such as a polyester film.
Magnetic powder such as iron powder and iron powder is applied together with a resin binder. This resin binder is added in order to secure the dispersibility of the magnetic powder and the running property of the medium, and the addition amount is usually 1 per 100 parts by weight of the magnetic powder.
Greater than 0 parts by weight is required.

By the way, in recent years, along with the increase in the amount of information to be handled, there has been an increasing demand for high-density recording on magnetic recording media. Such requirements can be met by improving the orientation of the magnetic powder or the linear recording density. Then, in order to fully exert such high density recording characteristics, in the coating type magnetic recording medium, the magnetic powder is dispersed to a state close to primary particles, thereby improving the orientation ratio and improving the surface of the magnetic layer. It is necessary to make the roughness as small as possible.

In order to further improve the recording / reproducing output of the medium, the volume ratio of the magnetic powder particles in the resin binder should be maximized, that is, the filling rate of the magnetic powder particles in the resin binder should be increased as much as possible. Is required.

However, it is usually very difficult to highly disperse ultrafine particle powder in a dispersion medium. Therefore, there is a great difficulty in dispersing the ultrafine magnetic powder to which the magnetic cohesive force is further applied in the resin binder. When the dispersed state of the magnetic powder in the resin binder is not good, not only the smoothness of the formed magnetic layer is impaired and the filling rate of the magnetic powder is lowered, but also it is formed in the magnetic field orientation step after applying the magnetic paint. Moreover, the orientation ratio of the magnetic powder in the magnetic layer is reduced. As a result, in the produced magnetic recording medium, the output during recording / reproduction is reduced, and further, noise is increased, which causes inconvenience.

In order to improve the durability of the formed coating film, it is effective to increase the contents of the resin binder and the curing agent used in the magnetic paint. However, such an increase in the amount of the non-magnetic material means a reduction in the filling rate of the magnetic powder in the magnetic layer, resulting in a reduction in the reproduction output of the manufactured magnetic recording medium, which is not preferable. Therefore, there is a limit to the amount of the nonmagnetic material as a means for improving the durability of the coating film, and it has been impossible to obtain a coating film having sufficient durability only by increasing the amount of the nonmagnetic material.

That is, at present, it cannot be said that the dispersion technique of the ultrafine magnetic powder used to meet the demand for high density recording has been sufficiently established. Therefore, it is difficult to say that the smoothness and running durability of the coating film, and further the filling rate of the magnetic powder in the magnetic layer are sufficiently improved. In addition, there is a new inconvenience in terms of recording / reproducing characteristics due to the poor dispersibility of the magnetic powder.

[0009]

Therefore, until now, ultrafine magnetic powder has been filled in the magnetic layer at a high filling rate, and the durability has been improved without increasing the amount of the non-magnetic material. In order to obtain a coating film for the magnetic layer, research has been advanced from various fields in search of magnetic powder having improved dispersibility in a resin binder.

As one of attempts to improve the dispersibility of the magnetic powder, it has been proposed to coat the magnetic powder particles with various dispersants or coupling agents. For example, JP-A-4-147426 discloses coating magnetic powder with a fluorine-modified silane coupling agent.

However, this is mainly for the purpose of preventing deterioration of a magnetic recording medium using a metal magnetic powder for long-term storage, and a medium in which various magnetic powders are highly dispersed and a high packing rate is obtained. No mention is made of the means of manufacture. Nor is there any mention of means for ensuring sufficient durability of the medium.

Therefore, the present invention has been made to address such a problem, and not only enhances the dispersibility of the magnetic powder but also sets the filling rate of the magnetic powder in the magnetic layer to an extent not conventionally attempted. It is an object of the present invention to provide a magnetic recording medium which achieves high-density recording by further increasing the temperature and has sufficient durability and a manufacturing method thereof.

[0013]

First, the magnetic recording medium of the present invention will be described.

The magnetic recording medium of the present invention is a magnetic recording medium in which a magnetic layer containing magnetic powder and a resin binder is formed on a non-magnetic support, and the magnetic powder has a surface area obtained by the BET method. 5 × 10 ⁻⁷ to 5 × for 1 m ²
The surface treatment is carried out with an amount of 10 ⁻⁶ mol of at least one of the organic silicon compounds represented by the following general formulas 13, 14, 15 or 16, and the amount is 10 based on 100 parts by weight of the magnetic powder. It is characterized in that it is dispersed in the resin binder in an amount of not more than part by weight.

[0015]

[Chemical 13] (However, n represents a number of 3 to 10, and R ₁ is -H or -C.
Represents either H ₃ or a phenyl group)

[Chemical 14] (However, R is a C ₁ -C ₁₈ alkyl group, or C ₁ -C ₁₈
Any of C ₁₂ perfluoro groups, R ₂ is —OH, —O
_{CH 3, -OC 2 H 5,} -H, represents either -CH ₃ or phenyl group)

[Chemical 15] (However, n represents a number of 2 to 10, R ₀ represents -OH,-
H, or a C ₁ -C ₁₈ alkyl group, X is-
H, represents any of -CH _3, -C ₂ H ₅₎

[Chemical 16] (However, R ₂ is —OH, —OCH ₃ , —OC ₂ H ₅ ,
-H, in representing) the present invention either a -CH ₃ or phenyl group, a compound capable of depositing a surface treatment on the magnetic powder surface is represented by the above general formula, specifically, tetramethyl Organosilicon compounds such as cyclotetrasiloxane, octadecyltriethoxysilane, hexamethylcyclotrisiloxane, trimethylethoxysilane, trimethylmethoxysilane, hexamethyldisilazane, heptadecafluorodecylmethyldimethoxysilane, or heptadecafluorodecyltriethoxysilane Is exemplified.

The amount of these compounds represented by the above general formula deposited on the magnetic powder is in the range of 5 × 10 ^{-7 to} 5 × 10 ^-6 mol per 1 m ² of surface area of the magnetic powder obtained by the BET method. Is desirable. If it is less than 5 × 10 ^-7 mol, sufficient dispersion effect cannot be obtained, and 5 × 10 ^-6 m
This is because when the amount is more than ol, the dispersibility is significantly impaired.

In the magnetic recording medium of the present invention, magnetic powders which can be surface-treated with the above-mentioned surface treatment agent and used include, for example, γ-Fe ₂ O ₃ , CrO ₂ and Co-γ-F.
Needle-like magnetic powder such as e ₂ O ₃ , magnetic metal powder, or Ba
Hexagonal ferrite magnetic powder such as ferrite is exemplified.

Among these, hexagonal ferrite is
Since the easy axis of magnetization exists in the direction perpendicular to the plate surface of the plate crystal, high density recording utilizing the perpendicular magnetization component can be achieved, and thus it is particularly preferable as the magnetic powder according to the present invention.

As the hexagonal ferrite to which the surface treatment according to the present invention can be applied, for example, M-type or W-type hexagonal Ba ferrite, Sr ferrite, Pb ferrite, and substitution in which some of Fe atoms are substituted. Examples thereof include type ferrite, or solid solutions or ion-substituted products of these. The substituted type ferrite, for example the general formula AO · n below _{(Fe 12-p M p O} 18-α) ( however, A is at least one metal element selected from the group consisting of Ba, Sr, Pb and Ca And M is 2
~ Represents at least one metal element selected from hexavalent metal elements, P is a substitution amount per one chemical formula, 0 ~ 2
, N is a number of 0.7 to 4, and α is a number of 0 to 1. ) Is exemplified by ferrite.

The average particle size of the magnetic powder to which the surface treatment according to the present invention can be applied is preferably 0.15 μm or less when expressed by its longest axial dimension,
Among them, those of 0.01 to 0.1 μm are particularly preferable. If the average particle size is less than 0.01 μm, the saturation magnetization (σs) and the coercive force (Hc) become small, and a sufficient reproduction output cannot be obtained, which is not preferable. On the other hand, if the average particle size exceeds 0.15 μm, noise during reproduction tends to be significantly increased during high density recording, which is also not preferable.

As the resin binder in the magnetic recording medium of the present invention, various resins such as polyurethane resin, polyester resin, vinyl chloride resin, fibrin resin such as nitrocellulose, or a mixture or copolymer thereof are used. It can be used. The adsorptivity of these resin binders on the surface of the magnetic powder has a great influence on the dispersibility of the magnetic powder, and is very important in order to enhance the surface property of the coating film. Therefore, for these resin binders,
For example, sulfone group, sulfobetaine group, phosphate group,
It is preferable to introduce a boric acid group, a carboxyl group, or a polar group such as a metal base or an amino group thereof. If desired, an isocyanate type curing agent or an amine type curing agent may be used in combination with these resin binders as a curing agent for reacting with active hydrogen in the binder to cure the coating film after coating.

In the present invention, these resin binders have an average molecular weight (Mw) of 2,000 to 20,000.
Those in the range of are desirable. The amount of the resin binder used is preferably 10 parts by weight or less, more preferably 3 to 7 parts by weight, based on 100 parts by weight of the magnetic powder.

In the present invention, by introducing a polar group into the resin binder and limiting the average molecular weight to a small range as described above, the adsorptivity of the resin binder to the surface treatment layer of the magnetic powder can be enhanced. Further, for the same reason, the resin binder amount is also very important in ensuring the dispersibility of the magnetic powder, and by limiting the resin binder amount to the above range, a good dispersed state of the magnetic powder can be obtained, It becomes possible to secure sufficient durability of the medium. When the present invention was made, it was found that when the magnetic powder surface-treated according to the present invention was dispersed in a large amount of resin binder, the durability of the obtained medium was rather deteriorated. Has been issued.

In the magnetic recording medium of the present invention, additives usable for forming the magnetic layer include a dispersant, a lubricant,
Any material commonly used in magnetic recording media, such as an abrasive or an antistatic agent, can be used in the same manner. If necessary, these additives may be appropriately contained. it can. For example, as the lubricant, a fatty acid having 10 or more carbon atoms or a fatty acid ester-based lubricant can be used. As the abrasive, inorganic fine powder such as alumina or chromium oxide can be used, but it is necessary to select it so as to improve the durability without deteriorating the electromagnetic conversion characteristics of the medium. It is preferable to use one having a Mohs hardness of 6 or more and an average particle diameter of 0.1 to 1 μm.

Next, a method for manufacturing the magnetic recording medium of the present invention will be described.

In the method for producing a magnetic recording medium of the present invention, magnetic powder is dispersed in a resin binder to form a coating, and the obtained magnetic coating is applied on a non-magnetic support to form a magnetic layer. In the method for producing a magnetic recording medium, the surface area of the magnetic powder particles obtained by the BET method is 1 m ²
To the surface obtained by depositing 5 × 10 ^{−7 to} 5 × 10 ⁻⁶ mol of at least one of the compounds represented by the above general formulas 13, 14, 15, or 16 It is characterized in that the treated magnetic powder is dispersed in 10 parts by weight or less of a resin binder with respect to 100 parts by weight of the surface-treated magnetic powder to form a coating material.

When the magnetic powder is coated with the compound as described above, the surface treating agent made of the compound may be brought into contact with the magnetic powder in the gas phase. Alternatively,
You may make it disperse | distribute or melt | dissolve the said compound in an organic solvent, water, etc., and mix it with a magnetic powder or knead | mix it in a liquid phase.

A step of dispersing the surface-treated magnetic powder in a resin binder in the above range to form a coating material, and a step of applying the obtained magnetic coating material onto a non-magnetic support to form a magnetic layer. Can be performed in the same manner as in the case of manufacturing a normal coating type magnetic recording medium.

Another method of producing the magnetic recording medium of the present invention is to disperse magnetic powder in a resin binder to form a coating, and apply the obtained magnetic coating to a non-magnetic support to form a magnetic layer. In the method for producing a magnetic recording medium, the magnetic powder and the magnetic powder obtained by the BET method have a surface area of 1 m ² of 5 × 10 ^{−7 to} 5 × 10 ⁻⁶ mo.
An amount of at least one of the compounds represented by the above general formulas 13, 14, 15, or 16 is dispersed in 10 parts by weight or less of a resin binder based on 100 parts by weight of the magnetic powder. It is characterized by being made into paint.

[0030]

In the surface treatment of the magnetic powder relating to the magnetic recording medium of the present invention, a certain organic silicon compound is brought into contact with the ultrafine magnetic powder and deposited on the surface of the magnetic powder.
It is presumed that such an organic silicon compound is deposited on the surface of the magnetic powder particles by the following mechanism.

That is, since the surface of the particles of the ultrafine magnetic powder is very active, a certain type of organosilicon compound having a relatively small molecular weight and a high reactivity with oxygen atoms or hydroxyl groups present on the surface. Reacts easily at room temperature or with slight heating. This reaction involves ring-opening and fission of the organosilicon compound, and decomposition of the alkoxy group and the like, and the resulting active moiety binds to the particle surface of the magnetic powder. Exist in a state of being bound to the metal on the surface of the particle-M
An organosilicon compound reacts with the —OH group (M represents a metal atom) to form a siloxane bond (M-
It is considered that Si-O-bonds) are newly formed.

The above-mentioned reaction rapidly and quantitatively proceeds at room temperature. Therefore, by appropriately setting the amounts of the organosilicon compound and the magnetic powder to be contacted with each other, the organosilicon compound can be almost a single molecule based on the cross-sectional area of the chain of the siloxane bond and the surface area of the magnetic powder particle obtained from the specific surface area. It is believed that a thin layer close to the layer is formed and bonded to the entire surface of the magnetic powder.

In the practice of the present invention, the means of subjecting the magnetic powder to the surface treatment using these organic silicon compounds alone hardly contributes to the improvement of the dispersibility of the magnetic powder. Have been found. The effect of improving the dispersibility of the magnetic powder and the effect of improving the lubricity of the medium that lead to the effect of the present invention are expressed by the presence of these organic silicon compounds together with the resin binder, the dispersant, or the lubricant in the magnetic coating composition. It has been similarly found that the amount of the organic silicon compound and the amount of the resin binder are important for exhibiting the above effects.

That is, by coating the particle surface of the magnetic powder with a thin layer of these organic silicon compounds, the amount of the resin binder is 1 with respect to 100 parts by weight of the magnetic powder.
Even if the amount is reduced to 0 parts by weight or less, the medium has sufficient durability. Since the amount of the resin binder can be reduced, the filling rate of the magnetic powder can be greatly improved. Moreover, by coating the surface of the magnetic powder particles with a thin layer of the surface treatment agent, the mutual aggregation of the magnetic powder particles can be suppressed to a small level, and as a result, the medium can be reproduced with high reproduction suitable for high recording density recording. Output can be obtained.

[0035]

EXAMPLES The magnetic recording medium of the present invention and the method for producing the same will be described in detail below with reference to examples.

Example 1 In preparing Example 1 of the magnetic recording medium of the present invention, hexamethylcyclotrisiloxane was selected as the organic silicon compound as the surface treatment agent, and this was vapor-phased on the surface of the magnetic powder particles. First, surface-treated magnetic powder was prepared by the method of coating with.

In the surface treatment, Co was used as the magnetic powder.
-Ti-substituted M-type Ba ferrite magnetic powder (average particle size of 0.
045 μm, coercive force 1,000 Oe, saturation magnetization 60
emu / g, specific surface area 35 m ² / g) was used. 100 parts by weight of this magnetic powder and 2 parts by weight of hexamethylcyclotrisiloxane were placed in a hermetically sealable metal container, which was then hermetically sealed and allowed to stand in a constant temperature bath at a temperature of 60 ° C. for 10 hours. The amount of hexamethylcyclotrisiloxane deposited on the obtained surface-treated magnetic powder was 2 × 10 ⁻⁶ mol per 1 m ^{2 of the} surface area obtained by the BET method.

Next, in preparing the magnetic coating material containing the surface-treated magnetic powder, the magnetic coating material having the following composition was mixed and dispersed for 2 hours with a sand grinder.

[0039] A polyisocyanate-based curing agent (trade name: Coronate L, manufactured by Nippon Polyurethane Co., Ltd.) was added to the obtained magnetic coating material at a ratio of 5 parts by weight to 100 parts by weight of the resin binder in the coating material, followed by applying a reverse coater. It was applied onto a polyester film having a thickness of 8.0 μm. Then, after drying and calendering according to a conventional method, the obtained raw fabric was cut into a predetermined width to prepare a magnetic tape for an 8 mm VTR which is Example 1 of the magnetic recording medium of the present invention.

Example 2 In producing Example 2 of the magnetic recording medium of the present invention, hexamethylcyclotrisiloxane was selected as an organic silicon compound which is a surface treating agent, and this was selected in the gas phase on the surface of the magnetic powder particles. First, surface-treated magnetic powder was prepared by the coating method.

As the magnetic powder, magnetic metal powder mainly composed of iron (average particle diameter 0.12 μm, coercive force 1,500 Oe,
A surface-treated magnetic powder was produced in the same manner as in Example 1 except that the saturation magnetization was 125 emu / g). The amount of hexamethylcyclotrisiloxane deposited on the obtained surface-treated magnetic powder was 1 m ^{2 of the} surface area obtained by the BET method.
Was 3 × 10 ⁻⁶ mol.

Example 2 of the magnetic recording medium of the present invention was prepared in the same manner as in Example 1 except that the surface-treated magnetic powder thus obtained was used.

Example 3 Example 1 was repeated except that hexamethyldisilazane was selected as an organic silicon compound as a surface treatment agent, and the surface-treated magnetic powder was prepared by using 1 part by weight of the hexamethyldisilazane per 100 parts by weight of the magnetic powder. Example 3 of the magnetic recording medium was prepared in the same manner as in.

Example 4 By selecting pentadecafluorodecyltrimethoxysilane as an organic silicon compound as a surface treating agent and coating the surface of the magnetic powder particles with a liquid phase, the surface treated magnetic powder was first prepared. It was made.

In the surface treatment, 100 parts by weight of the magnetic powder and 3 parts by weight of the surface treatment agent were dispersed in methyl ethyl ketone, and the obtained slurry was dried and then allowed to stand at 100 ° C. for 5 hours. The amount of pentadecafluorodecyltrimethoxysilane deposited on the obtained surface-treated magnetic powder was
1 × per surface area of 1 m ² obtained by the BET method
It was 10 ^-6 mol.

Example 4 of the magnetic recording medium of the present invention was prepared in the same manner as in Example 1 except that the surface-treated magnetic powder thus obtained was used.

Example 5 In producing Example 5 of the magnetic recording medium of the present invention, the magnetic powder was not previously surface-treated with a surface-treating agent,
A magnetic recording medium Example 5 was prepared in the same manner as in Example 1 except that the magnetic coating material was prepared by the method of simultaneously mixing the untreated magnetic powder and the surface treatment agent into the magnetic coating composition. As this untreated magnetic powder, the same kind as the treated magnetic powder in [Magnetic coating composition] of Example 1 was used, and as the surface treatment agent, 4 parts by weight of octadecyltriethoxysilane was used.

Example 6 6 parts by weight of the resin binder (sulfone group-containing polyurethane resin, molecular weight 4,500) in the [magnetic coating composition] of Example 1 was replaced with 3 parts by weight of the same type resin binder having a molecular weight of 5,000. A magnetic recording medium Example 6 was prepared in the same manner as Example 1 except for the above.

Comparative Example 1 Same as Example 1 except that 6 parts by weight of the resin binder (polyurethane resin containing a sulfonic group, molecular weight 4,500) in the [magnetic coating composition] of Example 1 was increased to 12 parts by weight. Then, a magnetic recording medium comparative example 6 was manufactured.

Comparative Example 2 A magnetic recording medium comparison was carried out in the same manner as in Example 1 except that the surface-treated magnetic powder in the [magnetic coating composition] of Example 1 was replaced with the same type of untreated magnetic powder to prepare a magnetic coating. Example 2 was made.

Here, in order to investigate the effect of the present invention, the characteristics of the magnetic recording media of Examples and Comparative Examples obtained as described above were evaluated.

The coercive force (Hc) and the saturation magnetization (σs) of the magnetic powder used in this example were determined by a vibrating sample type magnetism measuring device (VSM) to give a maximum applied magnetic field of 10 kO.
It is a value measured up to e.

In evaluating the characteristics of the magnetic recording medium, the reproduction output was M with a gap length of 0.30 μm and a track width of 20 μm.
The evaluation was performed using a Toshiba 8 mm video deck equipped with an IG head. Durability is evaluated at low temperature and low humidity (5 ° C, 10
%) Environment and high temperature and high humidity (40 ° C., 80%) environment, the reproduction output in the still mode was expressed as the time when the reproduction output decreased to 70% of the initial output.

[0054]

[Table 1] As is clear from Table 1, according to the present invention, the reproduction output of the magnetic recording medium is improved and the durability is improved as compared with the comparative example.

[0055]

As described above, according to the present invention, it is possible to deposit a thin layer of an organic silicon compound on the surface of a magnetic powder and to disperse it in a small amount in a resin binder to a high degree. The dispersibility of the magnetic powder in the magnetic layer is remarkably improved, and the filling rate of the magnetic powder can be increased to a level that has not been attempted conventionally. As a result, the recording / reproducing characteristics and durability of the magnetic recording medium are improved. Therefore, the present invention provides an excellent magnetic recording medium suitable for high density recording. Further, according to the present invention, there is provided a method for manufacturing the above magnetic recording medium without requiring complicated steps.

[0056]

Claims (7)

[Claims] 1. A magnetic recording medium comprising a magnetic layer containing a magnetic powder and a resin binder formed on a non-magnetic support, wherein the magnetic powder has a surface area of 1 m obtained by a BET method.
² with respect to ^{5 × 10 -7 ~5 × 10 -6} mol of the general formalized 1 below, Formula 2, at least one organic silicon compound represented by Chemical Formula 3 or Formula 4 is surface treated, A magnetic recording medium, wherein the magnetic powder is dispersed in 10 parts by weight or less of the resin binder with respect to 100 parts by weight of the magnetic powder. [Chemical 1] (However, n represents a number of 3 to 10, and R ₁ is -H or -C.
Represents either H ₃ or a phenyl group) (However, R is a C ₁ -C ₁₈ alkyl group, or C ₁ -C ₁₈
Any of C ₁₂ perfluoro groups, R ₂ is —OH, —O
CH ₃ , —OC ₂ H ₅ , —H, —CH ₃ or a phenyl group) (However, n represents a number of 2 to 10, R ₀ represents -OH,-
H, or a C ₁ -C ₁₈ alkyl group, X is-
H, -CH _3, represents one of -C ₂ H ₅₎ ## STR4 ## (However, R ₂ is —OH, —OCH ₃ , —OC ₂ H ₅ ,
-H, represents either -CH ₃ or phenyl group) 2. The magnetic powder is hexagonal Ba ferrite magnetic powder, wherein the magnetic powder is hexagonal Ba ferrite magnetic powder.
The magnetic recording medium described. 3. The resin binder has an average molecular weight of 2,0.
2. The magnetic recording medium according to claim 1, wherein the magnetic binder is a resin binder of 00 to 20,000. 4. The resin binder is a sulfone group, a sulfobetaine group, a phosphoric acid group, a boric acid group, a carboxyl group,
Alternatively, the magnetic recording medium according to claim 1, containing at least one polar group selected from these metal bases and amino groups. 5. The average particle diameter of the magnetic powder is 0.15 μm.
The magnetic recording medium according to claim 1, which is the following magnetic powder. 6. A method for producing a magnetic recording medium, wherein magnetic powder is dispersed in a resin binder to form a coating, and the obtained magnetic coating is applied onto a non-magnetic support to form a magnetic layer. The amount of 5 × 10 ^{−7 to} 5 × 10 ⁻⁶ mol of the surface area of 1 m ² obtained by the BET method on the surface of the magnetic powder particles is represented by the following general formula 5, chemical formula 6, chemical formula 7 or chemical formula 8. The surface-treated magnetic powder obtained by depositing at least one of the compounds described above is added to 10 parts by weight of the surface-treated magnetic powder.
A method for producing a magnetic recording medium, which comprises dispersing in a resin binder in an amount of not more than part by weight to form a coating material. [Chemical 5] (However, n represents a number of 3 to 10, and R ₁ is -H or -C.
Represents either H ₃ or a phenyl group) (However, R is a C ₁ -C ₁₈ alkyl group, or C ₁ -C ₁₈
Any of C ₁₂ perfluoro groups, R ₂ is —OH, —O
CH ₃ , —OC ₂ H ₅ , —H, —CH ₃ or a phenyl group) (However, n represents a number of 2 to 10, R ₀ represents -OH,-
H, or a C ₁ -C ₁₈ alkyl group, X is-
H, represents any of -CH _3, -C ₂ H ₅₎ embedded image (However, R ₂ is —OH, —OCH ₃ , —OC ₂ H ₅ ,
-H, represents either -CH ₃ or phenyl group) 7. A method for producing a magnetic recording medium, wherein magnetic powder is dispersed in a resin binder to form a coating, and the obtained magnetic coating is applied onto a non-magnetic support to form a magnetic layer. magnetic powder, and the obtained by the BET method magnetic powder surface area 1 m ² with respect to ^{5 × 10 -7 ~5 × 10 -6} mol of the following general formalized 9, of 10, with formula 11 or of 12 At least one of the compounds represented is used for the magnetic powder 100.
A method for producing a magnetic recording medium, characterized by dispersing in a resin binder of 10 parts by weight or less with respect to parts by weight to form a coating material. [Chemical 9] (However, n represents a number of 3 to 10, and R ₁ is -H or -C.
Represents either H ₃ or a phenyl group) (However, R is a C ₁ -C ₁₈ alkyl group, or C ₁ -C ₁₈
Any of C ₁₂ perfluoro groups, R ₂ is —OH, —O
CH ₃ , -OC ₂ H ₅ , -H, -CH ₃ or a phenyl group is represented). (However, n represents a number of 2 to 10, R ₀ represents -OH,-
H, or a C ₁ -C ₁₈ alkyl group, X is-
Represents any one of H, —CH ₃ , and —C ₂ H ₅ ) (However, R ₂ is —OH, —OCH ₃ , —OC ₂ H ₅ ,
-H, represents either -CH ₃ or phenyl group)