JPH097162A - Magnetic recording medium - Google Patents

Abstract

PURPOSE: To attain satisfactory dispersion of magnetic powder and to improve various characteristics such as corrosion resistance by incorporating at least one of a specified 1,8-naphthalenedicarboxylic acid anhydride or its deriv. and a specified 1,8-naphthalenedicarboxylic acid or its deriv. into a magnetic layer. CONSTITUTION: At least one of a 1,8-naphthalenedicarboxylic acid anhydride or its deriv. represented by formula I and a 1,8-naphthalenedicarboxylic acid or its deriv. represented by formula II is incorporated into a magnetic layer consisting essentially of magnetic powder and a binder. Then, the dispersion of the magnetic powder is made satisfactory and the objective magnetic recording medium having high corrosion resistance, suppresseding the falling of the magnetic powder and having enhanced bonding strength of the magnetic layer to the nonmagnetic substrate is obtd. In the formulae I, II, each of R<1> and R<2> is H or a substituent, R<1> and R<2> may be mutually different substituents and may form a ring by bonding to each other and X is H or an alkali metal atom.

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 such as a magnetic tape or a magnetic disk, and more particularly to a coating type magnetic recording medium having a magnetic layer formed by coating.

[0002]

2. Description of the Related Art For example, a coating type magnetic recording medium has been conventionally used in a backup data cartridge of a computer, a video tape for a video tape recorder and the like.

In such a magnetic recording medium, a magnetic paint prepared by dispersing and kneading a ferromagnetic powder, a binder (binder resin), a dispersant, a lubricant and the like in an organic solvent is used as a non-magnetic support such as a polyester film. A magnetic layer is formed by applying and drying on top.

In recent years, in order to achieve high image quality in the field of magnetic recording, particularly in video tape recorders, higher density recording has been required. In response to this demand, iron or a magnetic metal material mainly composed of iron has been used in place of the iron oxide system which has been conventionally used as a magnetic powder for magnetic recording media and the like.

Ferromagnetic metal fine particles (ferromagnetic metal magnetic powder) composed of these iron or iron alloys are iron oxide, iron oxyhydroxide, Co, Ni, Mn, Cu, Zn, T.
It is produced by reducing iron oxide or iron oxyhydroxide containing a metal other than Fe such as i and V with hydrogen gas. These ferromagnetic metal fine particles have a large amount of magnetization, a high magnetic flux density, and a large output, and have magnetic recording characteristics superior to those of conventional iron oxide-based ferromagnetic fine particles.

However, the above-mentioned ferromagnetic metal fine particles have high surface activity and are easily oxidized in the atmosphere, so that they have the following problems. That is, during storage of the ferromagnetic metal fine particles, or during the process of forming a coating by mixing with a resin or an organic solvent,
Alternatively, after being coated on a non-magnetic support such as a polyester film to form a sheet, it is oxidized (corroded) mainly by the action of gas such as oxygen and moisture during storage under conditions such as a predetermined atmosphere, temperature and humidity. ) Progresses, and deterioration of magnetic characteristics such as saturation magnetization with time occurs, and there is a problem in storage stability.

Further, in order to obtain a magnetic recording medium having excellent magnetic characteristics, it is necessary to use a finely divided ferromagnetic powder, but such a magnetic powder is so finely dispersed in a magnetic paint that it is finely divided. Since the dispersibility tends to deteriorate, it is necessary to stably increase the dispersibility of the magnetic powder.

Conventionally, to improve the dispersibility of magnetic powder
And H₂NC₂H_FourSi (OC₂H  Coupling agents and benzoic acid derivatives as surface treatment agents
Methods of using and treating the surface of ferromagnetic powders are known
You.

However, in the magnetic recording medium using these conventional treating agents, the dispersibility of the ferromagnetic powder is somewhat good, but the powder of the magnetic layer falls off, the adhesion strength to the non-magnetic support and the corrosion resistance. There were problems such as lack of sex.

[0010]

DISCLOSURE OF THE INVENTION An object of the present invention is to have sufficient dispersibility of magnetic powder, excellent corrosion resistance, suppression of powder falling, and adhesion of a magnetic layer to a non-magnetic support. An object is to provide an improved magnetic recording medium.

[0011]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object of the present invention, the present inventor has found that 1,8-naphthalenedicarboxylic acid having a polar group on the surface of a ferromagnetic powder or a derivative thereof. Alternatively, when 1,8-naphthalenedicarboxylic anhydride or a derivative thereof is allowed to act, polar groups of these naphthalene compounds are adsorbed on the surface of the ferromagnetic powder, and a film is formed to form a ferromagnetic powder. The surface is modified, which improves the oxidation resistance (rust resistance) and dispersibility of the ferromagnetic powder, and also improves the adsorptivity with the binder resin (this is a substituent (functional group)). The present invention has been achieved by finding that it is possible to prevent the powder from falling off and improve the adhesive strength to the non-magnetic support.

That is, the present invention provides a 1,8-naphthalenedicarboxylic acid anhydride represented by the following general formula [I] or a derivative thereof in a magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a binder. And at least one of 1,8-naphthalenedicarboxylic acid represented by the following general formula [II] or its derivative is contained in the magnetic layer.

Embedded image (However, in the above general formulas [I] and [II], R ¹ and R ² are hydrogen atoms or substituents which are the same or different from each other and may jointly form a ring, and X is a hydrogen atom or Alkali metal atoms such as Na and K.)

According to the magnetic recording medium of the present invention, 1,8-naphthalenedicarboxylic acid or a derivative thereof having a polar group consisting of two carboxyl groups or a salt thereof or an anhydride thereof and 1,8-naphthalenedicarboxylic acid. When at least one of the anhydride or its derivative is contained in the magnetic layer, the polar groups of these naphthalene compounds are adsorbed on the surface of the magnetic powder, and a film is formed to improve the surface of the ferromagnetic powder. To quality. In this case, if the surface of the magnetic powder is previously treated with the above naphthalene compound and the treated magnetic powder is contained in the magnetic layer, the surface modifying action of the magnetic powder is further improved.

Thus, since the above-mentioned naphthalene-based compound, which is originally excellent in rust prevention, is adsorbed on the surface of the magnetic powder, the rust resistance (corrosion resistance or oxidation resistance) of the magnetic powder is improved. At the same time, the dispersibility of the magnetic powder in the binder and the adsorptivity to the binder are improved by the hydrocarbon group portion and the functional group portion (R ¹ , R ² ) of the naphthalene compound. In particular, by selecting functional groups as the substituents R ¹ and R ² , compatibility, adsorption, and reactivity with the binder or its curing agent are improved, and powder falling from the magnetic layer is prevented and non-magnetic support is provided. It is possible to improve the adhesive strength to the body.

Here, as the substituents R ¹ and R ² introduced into the naphthalene compound of the general formula [I] or [II], a hydrogen atom, a halogen atom such as F, Cl and Br, and _{OH, -NH 2, -NO 2,} -SO 4 K, -NH
_{(CH 2) n CH 3,} -O (CH 2) n CH 3, -N
_{(CH 3) (CH 2)} n CH 3, -NHCH (OH) CH
_{2 CH 2 CH 3, -NH (} CH 2) n CH (OH) (CH
₂ ) _m CH ₃ , an alkyl group (especially having 1 to 10 carbon atoms), an amide group, a hydrocarbon oxy group (especially having 1 to 10 carbon atoms) or -C
It is a functional group such as OOX (X is a hydrogen atom or an alkali metal atom such as Na or K), and when it is —COOX, it is jointly converted to —CO—O—CO— to form a ring. Good (however, n and m are integers (especially 1 to 18)).

Specific examples of the above-mentioned naphthalene compounds include naphthalene dicarboxylic acids or their anhydrides or their derivatives used in the examples described below, and in order to more effectively modify the surface of the magnetic powder. Each of the following compounds (1) to (28) in which a functional group is introduced into R ¹ or R ²
Can be mentioned.

[0017]

Embedded image

[0018]

Embedded image

In the magnetic recording medium according to the present invention, the addition amount of the above naphthalene compound of the general formula [I] or [II] (the total amount when both are added) is 1
It is preferably in the range of 0.1 to 7 parts by weight with respect to 00 parts by weight. If the addition amount is less than 0.1 parts by weight, the effect due to the addition is not sufficient, and if it exceeds 7 parts by weight, the amount adsorbed on the magnetic powder becomes excessive, which may be wasted.

The above-mentioned naphthalene compounds of the general formula [I] or [II] can be used in combination of not only one kind having the same general formula but also a plurality of kinds having different general formulas. You can also

Then, together with the above naphthalene compound,
For example, linear or branched alkyl acid compounds that have been used as additives (especially linear alkyl acids)
Can also be used in combination. As such an alkyl acid, a polyvalent carboxylic acid such as oxalic acid, phthalic acid, citric acid, and benzenetetracarboxylic acid is preferable, and a part of the polyvalent carboxylic acid may be adsorbed to the magnetic powder simultaneously with or separately from the naphthalene compound. As a result, the surface coverage of the magnetic powder surface can be increased.

The amount of such an additive such as an alkyl acid that can be used in combination is 0-10 with respect to 100 parts by weight of the magnetic powder.
It is preferably part by weight, and more preferably 3 to 8 parts by weight. If the addition amount exceeds 10 parts by weight, the amount may be excessive as compared with the amount adsorbed on the magnetic powder, which may be wasted.

In the magnetic recording medium of the present invention, when the magnetic powder is surface-treated with the above-mentioned naphthalene compound, the treatment method is, for example, a strong shearing force such as a kneader or a co-kneader before mixing the magnetic paint. The ferromagnetic powder and the naphthalene-based compound are mixed and dispersed by using a mixer having the same method to perform the primary dispersion and the surface treatment of the magnetic powder at the same time, or the one-shot method is used to add the naphthalene-based compound to the ferromagnetic powder and other magnetic paints A method is known in which a naphthalene compound is adsorbed on the surface of the ferromagnetic powder at the same time as kneading with the materials to prepare a magnetic coating material.

In addition, ferromagnetic powder is added to a solution prepared by dissolving or dispersing a naphthalene compound in a solvent such as methyl ethyl ketone, toluene or cyclohexanone, and after reacting for a certain period of time, it is post-treated or is used as it is as a magnetic coating material. It can also be used in the above method (in this case, the naphthalene compound may or may not be added anew). Examples of the above post-treatment include a method of washing with a solvent after filtration and drying to obtain a treated magnetic powder.

The magnetic powder (ferromagnetic powder) used in the magnetic recording medium according to the present invention is not limited as long as it is a normally used ferromagnetic powder, and it is needless to say that conventionally known ones can be used. It can also be used for ferromagnetic powders with a smaller particle size. In particular, the use of metal magnetic powder is more effective.

Examples of usable magnetic metal powders are Fe, Co, Ni, Fe-Co alloys, Fe-Ni alloys, Fe-Co-Ni alloys, Co-Ni alloys, Fe-C.
O-B alloy, Fe-Co-Cr-B alloy, Mn-Bi alloy, Mn-Al alloy, Fe-Co-V alloy, etc. are mentioned. Further, for the purpose of improving various characteristics of these magnetic powders, metal components such as Al, Si, Ti, Cr, Mn, Cu and Zn may be added.

Oxide magnetic powder can also be used, and for example, γ-Fe ₂ O ₃ and Co-containing γ-
Fe ₂ O ₃ , Fe ₃ O ₄ , Co-containing Fe ₃ O ₄ , Co-deposited γ-Fe ₂ O ₃ , Co-deposited Fe ₃ O ₄ , CrO _{2 and the} like can be mentioned.

The magnetic powder used in the magnetic recording medium according to the present invention preferably has a basicity of pH 7 or higher in order to enhance the adsorptivity with the above naphthalene compounds.

The magnetic layer of the magnetic recording medium according to the present invention comprises the above ferromagnetic powder dispersed in a binder resin.
As the binder resin used, any commonly used binder can be used.

For example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinyl acetate-acrylic acid copolymer, Vinyl chloride-vinyl acetate-maleic acid-acrylic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, ethylene-vinyl acetate copolymer, fibrin-based resin such as nitrocellulose, acrylic A resin, a polyvinyl acetal resin, a polyvinyl butyral resin, an epoxy resin, a phenoxy resin, a polyurethane resin, a polyester resin, a polyester polyurethane resin, a polycarbonate polyurethane resin or the like can be used alone or in combination. Further, other thermoplastic resin, thermosetting resin, reactive resin, electron beam irradiation curable resin, etc. may be used together.

Examples of the above-mentioned fibrin resin include cellulose derivatives such as cellulose ether, cellulose inorganic acid ester, and cellulose organic acid ester. Phenoxy resin has high mechanical strength and excellent dimensional stability.
It has advantages such as good heat resistance, water resistance, chemical resistance, and good adhesion.

Specific examples of usable binders include vinyl chloride copolymers such as "VAGH", "VYHH" and "VMCH" manufactured by Union Carbide Co., Ltd., "ESREC" manufactured by Sekisui Chemical Co., Ltd. "ESREC A-5",
"ESREC C", "ESREC M", "Denka Vinyl 1000G", "Denka Vinyl 10" manufactured by Denki Kagaku Co., Ltd.
00W ”and the like. Examples of the phenoxy resin include YP-50 and EK-35 manufactured by Tohto Kasei Co., and PKHH manufactured by Union Carbide. Examples of polyurethane resins include Acretan manufactured by Fujikura Kasei Co., PS-706 and PS-815 manufactured by Mitsui Nisso Urethane Co., and MAU- manufactured by Dainichi Seika.
2010, N-3022, DN-39 made by Nippon Polyurethane Industry Co., Ltd.
85, MG-0130, Estan 5701 manufactured by Goodrich, PANDEX 78-8 manufactured by Dainippon Ink and others.

Binders that can be used are --COOM and --SO.
₃ M, —OSO ₃ M, —PO ₃ M and —OPO ₃ M (provided that M is an alkali metal such as Na and K or a methyl group, an alkyl group such as an ethyl group). It is preferable to have at least one polar group and two or more OH groups in the molecule. In this case, the polar group promotes dispersibility of the magnetic powder because the polar group has good affinity with the surface of the magnetic powder or the naphthalene compound, and the OH group reacts with the curing agent to form a magnetic layer. Improves coating strength (durability) and contributes to prevention of powder falling.

The amount of the above polar groups is 0.03 / g of binder.
~ 0.3 mmol is preferred. When it is less than 0.03 mmol per 1 g of binder, the effect on dispersibility becomes small, and when it is more than 0.3 mmol per 1 g of binder, not only the hygroscopicity becomes high and the weather resistance deteriorates, but also the dispersibility deteriorates. It may happen. The polar group may be contained in one kind or in two or more kinds.

In order to cure the above binder and further improve the durability of the magnetic layer, it is preferable to add a curing agent. Such curing agents include aromatic isocyanates such as tolylene diisocyanate (TDI), 4,
4'-diphenylmethane diisocyanate (MDI),
Condensation types of diisocyanates such as xylene diisocyanate (XDI), metaxylene diisocyanate (MXDI), hexamethylene diisocyanate, anisole type diisocyanate and adducts with active hydrogen compounds are possible, and particularly tolylene diisocyanate (TD
The I) system is preferred. The addition amount of the curing agent is preferably 5 to 30% by weight based on the total amount of the binder.

As specific examples, various Sumidure manufactured by Sumitomo Bayern Co., Ltd., various death modules, various takenates manufactured by Takeda Pharmaceutical Co., Ltd., various coronates manufactured by Nippon Polyurethane Industry Co., Ltd. and the like can be mentioned.

In the magnetic recording medium according to the present invention, in addition to the above naphthalene compound, ferromagnetic powder and binder resin, a dispersant such as lecithin and a lubricant such as stearic acid ester may be added if necessary. An antistatic agent such as carbon black, an abrasive such as alumina, and a rust preventive may be added. As the dispersant, the lubricant, the antistatic agent, the rust preventive, and the like, any conventionally known material can be used and is not limited at all.

Examples of the non-magnetic support usable in the magnetic recording medium according to the present invention include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, aramid, and the like. It may be in the form of a film, a sheet, a tape, a disc or the like. An intermediate layer or an undercoat layer may be provided on the surface of the non-magnetic support in order to improve the adhesiveness of the magnetic layer.

FIG. 1 shows an example (for example, a video tape) of a magnetic recording medium according to the present invention. That is, on the non-magnetic support 1, there is a magnetic layer 2 containing a ferromagnetic powder whose surface is treated with the above naphthalene compound and a binder. Further, on the other surface, a back coat layer 3 mainly composed of non-magnetic powder and a binder may be provided as indicated by a chain line.

[0040]

According to the magnetic recording medium of the present invention, since the above-mentioned naphthalene-based compound which is originally excellent in rust preventive property is adsorbed on the surface of the magnetic powder, the rust preventive property of the magnetic powder is improved. (Corrosion resistance or oxidation resistance) is improved, and a hydrocarbon group portion or a functional group portion (R
¹ , R ² ) improves the dispersibility of the magnetic powder in the binder and the adsorptivity to the binder. In particular, the substituents R ¹ , R ²
By selecting a functional group as, the compatibility with the binder or its curing agent, the adsorptivity, the reactivity can be improved, the prevention of powder falling from the magnetic layer, the improvement of the adhesive strength to the non-magnetic support can be realized. .

[0041]

EXAMPLES The present invention will be described below with reference to specific examples, but it goes without saying that the present invention is not limited to the following examples.

Examples 1 to 19 Magnetic paints having the compositions shown below were prepared.

<Magnetic coating composition> Magnetic powder: Fe-Co-Ni-based metal magnetic powder (pH = 9) 100 parts by weight Naphthalene dicarboxylic acid anhydride or its derivative Amount shown in Table 1 below (magnetic powder surface treatment agent ) Binder resin: Vinyl chloride copolymer 15 parts by weight (average degree of polymerization P = 310, OSO ₃ K group: 0.07 mmol, OH group: 0.3 mmol / g) Polyurethane resin 5 parts by weight (weight average molecular weight = 30,000, SO ₃ Na group: 0.16 mmol / g) Antistatic agent: 2 parts by weight of carbon black Polishing agent: 2 parts by weight of α-alumina (Al ₂ O ₃ ) Lubricant: 1 part by weight of stearic acid 1 part by weight of butyl stearate Agent: Methyl ethyl ketone 100 parts by weight Toluene 60 parts by weight Cyclohexanone 40 parts by weight

A steel ball was placed in a 100 ml container, and the above-mentioned solvent, binder resin, various additives, and various naphthalenedicarboxylic acid anhydrides or their derivatives shown in Table 1 below were added and mixed well by a roll mill. A solution was prepared. In this case, naphthalenedicarboxylic acid anhydride or its derivative was added in the respective amounts shown in Table 1 below and mixed sufficiently to prepare the above solution, then 100 parts by weight of the ferromagnetic powder was added thereto, and the mixture was added with a paint shaker for 24 hours. A magnetic paint was prepared by stirring. After stirring this for 24 hours, add 10 parts by weight of a curing agent (trade name: Coronate L), mix with a paint shaker for another 30 minutes, coat it on a polyethylene terephthalate film, dry it, wind it after calendering, and completely cure it. After the treatment, slitting was performed to produce a magnetic tape.

Example 20 In Example 1, the magnetic metal powder was mixed with naphthalene dicarboxylic acid anhydride by a kneader, the surface of the magnetic powder was pre-treated, and the treated magnetic powder was mixed with the magnetic coating material. A magnetic tape was produced in the same manner.

Example 21 A magnetic tape was produced in the same manner as in Example 1 except that the pH of the metal magnetic powder was set to less than 7.0 (specifically, 4).

Example 22 In Example 1, as a binder resin, a hydrophilic polar group (O
A magnetic tape was prepared in the same manner except that those without SO ₃ K and SO ₃ Na) were used.

Examples 23 to 31 Each magnetic tape was produced in the same manner as in Example 1 except that the amount of naphthalene dicarboxylic acid anhydride added was changed variously.

Examples 32 to 50 Magnetic tapes were produced in the same manner as in Example 1 except that the naphthalene dicarboxylic acid anhydride or its derivative was replaced with that shown in Table 2 below in the respective addition amounts.

Example 51 In Example 32, the magnetic metal powder was mixed with naphthalenedicarboxylic acid by a kneader, the surface of the magnetic powder was pre-treated, and the treated magnetic powder was mixed with the magnetic coating material, and the other components were the same. To produce a magnetic tape.

Example 52 A magnetic tape was produced in the same manner as in Example 32 except that the pH of the metal magnetic powder was set to less than 7.0 (specifically, 4).

Example 53 In Example 32, a hydrophilic polar group (O
A magnetic tape was prepared in the same manner except that those without SO ₃ K and SO ₃ Na) were used.

Examples 54 to 62 Each magnetic tape was produced in the same manner as in Example 32 except that the addition amount of naphthalenedicarboxylic acid was changed variously.

Comparative Examples 1 to 6 A magnetic coating material was prepared in the same manner as in Example 1 except that the naphthalene dicarboxylic acid anhydride or its derivative was replaced with each compound shown in Table 3 below, and this was coated on a polyethylene terephthalate film. A magnetic tape was produced through the step of applying to a magnetic tape.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

[Table 3]

[0058]

[Table 4] * Example 20 uses treated magnetic powder. Example 21 uses magnetic powder of pH = 4. Example 22 uses a binder resin having no hydrophilic polar group.

[0059]

[Table 5]

[0060]

[Table 6]

[0061]

[Table 7]

[0062]

[Table 8]

[0063]

[Table 9] * Example 51 uses treated magnetic powder. Example 52 uses magnetic powder having pH = 4. Example 53 uses a binder resin having no hydrophilic polar group.

[0064]

[Table 10]

[0065]

For each of the magnetic tapes obtained in the above Examples and Comparative Examples, the surface glossiness, squareness ratio, powder drop,
The adhesive strength to the polyethylene terephthalate film was examined as follows, and the results are shown in Table 4 below.
The results are shown in Table 5 and Table 6.

Surface glossiness: Measured by a gloss meter with an entrance reflection angle of 45 °. Squareness ratio: Vibration sample magnetometer (VS manufactured by Toei Industry Co., Ltd.
M). Powder drop: After 90 minutes of running on a video tape recorder, the amount of powder drop on the rotary head was evaluated on a scale of 5 from 1 to 5 (in this case, the larger the number, the greater the amount of powder drop). Adhesive strength ( Adhesive strength): The amount of adhesion of the magnetic layer to the polyethylene terephthalate film was measured using an adhesive strength tester by the peel method.

[0068]

[0069]

[0070]

[0071]

[0072]

As is apparent from the data shown in Tables 4 to 6, the magnetic properties of the magnetic powder containing the naphthalene dicarboxylic acid or its derivative (including the anhydride) added to the surface of the present invention or surface-treated with it. Paint (Examples 1 to 6)
In 2), compared with Comparative Examples 1 to 6, the glossiness showing the dispersibility of the magnetic powder is improved, and the squareness ratio is also generally improved, the amount of powder falling is suppressed, and the polyethylene terephthalate The adhesive force of the magnetic coating is significantly improved.

Further, from the comparison between Example 1 and Examples 20, 21, and 22, or the comparison between Example 32 and Examples 51, 52, and 53, the surface treatment of the magnetic powder was performed in advance. As
It can be seen that it is advantageous to use one having pH ≧ 7.0 and to use one having a hydrophilic polar group as the binder resin. Further, from Examples 23 to 31 and 54 to 62, the addition amount of naphthalenedicarboxylic acid or its anhydride or a derivative thereof is 0.1 with respect to 100 parts by weight of the magnetic powder.
It is desirable to set the amount to ˜7 parts by weight (further, 1 to 5 parts by weight) from the viewpoint of relatively good performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a configuration example of a magnetic recording medium to which the present invention has been applied.

[Explanation of symbols]

 1 ... Non-magnetic support 2 ... Magnetic layer 3 ... Back coat layer

Claims (6)

[Claims] 1. A magnetic recording medium having a magnetic layer mainly composed of magnetic powder and a binder, wherein 1,8-naphthalenedicarboxylic anhydride or a derivative thereof represented by the following general formula [I] and the following general formula: A magnetic recording medium comprising at least one of 1,8-naphthalenedicarboxylic acid represented by the formula [II] or a derivative thereof in the magnetic layer. Embedded image (However, in the above general formulas [I] and [II], R ¹ and R ² are hydrogen atoms or substituents which are the same or different from each other and may jointly form a ring, and X is a hydrogen atom or It is an alkali metal atom.) 2. In the general formulas [I] and [II], R ¹ and R ² are a hydrogen atom, a halogen atom, —OH,
_{-NH 2, -NO 2, -SO 4} K, -NH (CH 2) n
_{CH 3, -O (CH 2)} n CH 3, -N (CH 3) (CH
_{2) n CH 3, -NHCH (} OH) CH 2 CH 2 C
_{H 3, -NH (CH 2)} n CH (OH) (CH 2) m CH
₃ , alkyl group, amide group, hydrocarbon oxy group or -C
OOX (X is a hydrogen atom or an alkali metal atom.)
And when -COOX is jointly -CO-O-
The magnetic recording medium according to claim 1, which may be CO-converted to form a ring (provided that n and m are integers). 3. A 1,8-naphthalenedicarboxylic acid anhydride represented by the general formula [I] or a derivative thereof, and a general formula [I
The magnetic recording medium according to claim 1, wherein the magnetic layer contains magnetic powder surface-treated with at least one of 1,8-naphthalenedicarboxylic acid represented by I] or a derivative thereof. 4. The magnetic recording medium according to claim 3, wherein the magnetic powder is basic having a pH of 7 or more. 5. The binder is --COOM, --SO ₃ M,-
At least one polar group selected from the group consisting of OSO ₃ M, —PO ₃ M and —OPO ₃ M (where M is an alkali metal atom or an alkyl group) and two or more OH.
The magnetic recording medium according to claim 1, which has a group in the molecule. 6. A 1,8-naphthalenedicarboxylic anhydride or a derivative thereof represented by the general formula [I] and a general formula [I
The addition amount of at least one of 1,8-naphthalenedicarboxylic acid or a derivative thereof represented by [I] (the total amount when both are added) is based on 100 parts by weight of the magnetic powder.
The magnetic recording medium according to claim 1, which is 0.1 to 7 parts by weight.