JPH09180162A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a magnetic recording medium excellent in preservability over a long period of time, weather resistance and stability and capable of maintaining high density recording and high electromagnetic transducing characteristics by incorporating polyurethane resin using a specified aminoquinone deriv. as a polyol component as the resin binder of a magnetic layer. SOLUTION: A magnetic layer consisting essentially of ferromagnetic metal powder and a resin binder is formed on a nonmagnetic substrate to obtain the objective magnetic recording medium. Polyurethane resin synthesized from one or more kinds of polyols including an aminoquinone deriv. represented by the formula and a polyisocyanate is contained as the resin binder. In the formula, R is 1-6C alkylene or -(C2 H4 O)n -C2 H4 -[(n) is 1 or 2] and R' is 1-4C alkyl.

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, and in particular, it is excellent in electromagnetic conversion characteristics, long-term storage stability and weather resistance stability, in which the ferromagnetic metal powder added to the magnetic layer is prevented from being oxidized. The present invention relates to a coating type magnetic recording medium.

[0002]

2. Description of the Related Art Generally, a magnetic recording medium such as a magnetic tape or a magnetic disk has hitherto been a magnetic coating composition prepared by dispersing magnetic powder in a binder resin dissolved in a solvent.
The one coated on the surface of a non-magnetic support to form a magnetic layer is
Widely used.

In recent years, ferromagnetic metal powders have come to be used as magnetic powders in place of oxide magnetic powders such as iron oxide and chromium dioxide in order to provide high density recording and high output magnetic recording media. ing. Such a ferromagnetic metal powder is dispersed in a binder resin (binder) together with other appropriate additives as necessary, and is directly dispersed on a plastic film or other non-magnetic support, or at least a ferromagnetic metal powder. And a binder resin, another magnetic lower layer, or a non-magnetic lower layer containing at least a non-magnetic powder and a binder resin is used as a coating type magnetic recording medium. In the case of a medium, it is called a metal tape (MP tape) or the like and is considered as a high grade product.

[0004]

However, a coating type magnetic recording medium having a magnetic layer formed by dispersing and coating a ferromagnetic metal powder in a binder resin is a high density recording and high output magnetic recording medium. However, when the ferromagnetic metal powder in the magnetic layer is gradually oxidized by oxygen and the like in the air and is placed in a particularly bad environment, the tendency is large and the electromagnetic conversion characteristics change with time. However, there is a problem in that long-term storage stability and weather resistance stability are reduced.

In order to improve this, the surface of ferromagnetic metal powder (including ferromagnetic alloy powder, the same applies hereinafter) is oxidized to form an oxide coating layer of the ferromagnetic metal, or SiO ₂ or Al ₂
Ferromagnetic metal powder having a thin ceramic coating layer such as O ₃ formed on the surface is also used. However, even if such a coating layer is provided, the progress of oxidation cannot be sufficiently suppressed, and electromagnetic waves are not generated. There is a problem that the conversion characteristics are deteriorated with time, and long-term storage stability and weather stability are deteriorated. Further, for example, Japanese Patent Laid-Open No. 5-20676 proposes to use a ferromagnetic metal powder obtained by surface-treating a ferromagnetic metal powder with an aqueous solution of phosphoric acid or a phosphate. However, since the ferromagnetic metal powder is surface-treated with an aqueous solution of phosphoric acid or a phosphate, it cannot be used as a magnetic powder unless water is completely removed, and a step of drying a large amount of such fine powder is required. It is very difficult to handle industrially,
This is not a practical method because it increases the number of troublesome steps. Further, in the treatment step, the ferromagnetic metal powder may be corroded by phosphoric acid, phosphate, and water molecules to deteriorate the magnetic characteristics.

The present invention solves these problems, does not require a complicated process in manufacturing a magnetic recording medium, is excellent in long-term storage stability and weather stability, and can retain high density recording and high electromagnetic conversion characteristics. It is intended to provide a magnetic recording medium.

[0007]

In order to solve the above-mentioned problems, the magnetic recording medium of the present invention has a magnetic layer comprising at least a ferromagnetic metal powder and a binder resin formed on a non-magnetic support. In the coating type magnetic recording medium obtained by the above, as the binder resin, the above chemical formula (Chemical formula 1) [wherein R is a carbon number 1
6 alkylene group or _{- (C 2 H 4 O)} n -C 2 H 4 -
(Here, n represents a number of 1 or 2), and R ′ represents an alkyl group having 1 to 4 carbon atoms. ] It is characterized by containing a polyurethane resin synthesized from a polyol and a polyisocyanate in which the amino-quinone derivative represented by the above is a part or all of the polyol component.

The magnetic recording medium of the present invention contains, as a binder resin, a polyurethane resin synthesized from a polyol and a polyisocyanate in which the amino-quinone derivative represented by the chemical formula (Formula 1) is a part or all of the polyol component. Therefore, since the amino-quinone derivative structure in the binder resin exerts antioxidative properties, it is possible to prevent the ferromagnetic metal powder from being oxidized by the simple method of applying the coating type magnetic layer, which is almost the same as the conventional one, and to achieve high density recording. It is thought that it can provide high electromagnetic conversion characteristics.

In the magnetic recording medium of the present invention, an amino-quinone derivative of a polyurethane resin synthesized from a polyol in which the amino-quinone derivative represented by the chemical formula (Formula 1) is part or all of the polyol component and polyisocyanate is used. The component accounts for 1 to 60% by weight of the polyurethane resin, and the ratio of the polyurethane resin to the total binder resin is 5 to 70% by weight.
It is more preferable to provide a magnetic recording medium that can prevent oxidation of the ferromagnetic metal powder, retain high-density recording and high electromagnetic conversion characteristics, and have excellent long-term storage stability and weather stability. Even when it is out of the above range, the antioxidant function is exhibited according to the addition amount of the polyurethane resin, but when it is within the above range, long-term storage stability, weather resistance stability and dispersion stability are excellent, high density recording, high It is preferable because the electromagnetic conversion characteristics can be sufficiently exhibited.

In the magnetic recording medium of the present invention, the amino-quinone derivative represented by the chemical formula (Formula 1) is synthesized as a binder resin from a polyol in which a part or all of the polyol component is used and a polyisocyanate. A binder resin other than the polyurethane resin is contained, and the binder resin other than the polyurethane resin contains -S in the binder resin molecule.
Use of a vinyl chloride resin or polyurethane resin having a polar group selected from O ₃ M, —COOH, —PO ₃ M, and —OH (wherein M represents a hydrogen atom, an alkali metal or ammonium). Accordingly, the resin binder having these polar groups is preferable because it can firmly bond with the ferromagnetic metal powder and improve the durability of the magnetic layer.

In the magnetic recording medium of the present invention, the ferromagnetic metal powder is a powder composed of a simple ferromagnetic metal,
The ferromagnetic alloy powder is preferably a powder selected from a coated ferromagnetic metal simple substance powder whose surface is covered with an oxide coating layer or a ceramic coating layer or a ferromagnetic alloy powder. The ferromagnetic metal simple substance powder and the ferromagnetic alloy powder can provide a magnetic recording medium having particularly excellent electromagnetic conversion characteristics. Further, when a coated ferromagnetic metal simple substance powder or a ferromagnetic alloy powder whose surface is covered with an oxide coating layer or a ceramic coating layer is used, the electromagnetic conversion characteristics tend to be slightly low, but the conventional iron oxide Electromagnetic conversion characteristics are superior to those of metal oxide magnetic powders such as, and it is possible to provide a magnetic recording medium suitable for high-density recording, and it is more difficult to oxidize, so long-term storage stability and weather stability are better. It is possible to provide a magnetic recording medium.

In the magnetic recording medium of the present invention, the ferromagnetic metal powder has a saturation magnetization of 130 to 240 emu.
/ G, specific surface area 35-65 m ² / g (BET method)
Then, a ferromagnetic metal powder having an elongated shape with an axial ratio of 5 to 15 is preferable because a magnetic recording medium having more excellent electromagnetic conversion characteristics can be provided. Particularly, in the past, due to the problem of oxidative deterioration, the residual magnetic flux density (B
r) is reduced, or the saturation magnetization of the ferromagnetic metal powder that can be used to form an oxide layer or a ceramic layer on the surface is 1
Although the limit was about 60 emu / g, in the present invention, even when a ferromagnetic metal powder having a higher saturation magnetization is used, the saturation magnetization can be maintained, so that higher density recording,
A magnetic recording medium having excellent high output characteristics can be provided, which is preferable.

In the magnetic recording medium of the present invention, the surface roughness Ra of the magnetic layer is 1 to 10 nm and the squareness ratio is 0.80 or more, which means that the C / N or S / N is good. It is preferable because a magnetic recording medium suitable for high density recording can be provided.

In the magnetic recording medium of the present invention, a magnetic lower layer containing at least a ferromagnetic metal powder and a binder resin, or at least a nonmagnetic powder, is provided between the nonmagnetic support and the magnetic layer. A magnetic recording medium in which a non-magnetic lower layer containing a binder resin is further formed is more preferable. With such a multi-layered structure, the film thickness of the uppermost magnetic layer can be reduced, which facilitates recording at a shorter wavelength and enables higher density recording, which is preferable. Further, when a large amount of various additives are added to the uppermost magnetic layer, the magnetic layer surface may be roughened, or the strength and durability of the coating film may be deteriorated. It is also possible to add a transferable additive in advance and gradually transfer it to the upper layer to exert its function, which is preferable. When the lower layer is a magnetic layer, a structure suitable for long-wavelength recording such as linear audio is preferable because stable electromagnetic conversion characteristics can be secured in a wide frequency band.

[0015]

As the non-magnetic support used in the present invention, various non-magnetic supports used in magnetic recording media can be used, and the materials thereof are polyethylene terephthalate, polyethylene-2, Polyesters such as 6-naphthalate; aromatic polyamides such as aramid resin; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate;
Vinyl-based resins such as polyvinyl chloride and polyvinylidene chloride; polycarbonate, polyimide, polyamide-imide and the like. In particular, polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; aromatic polyamides such as aramid resin are preferable.

The form of these non-magnetic supports is a film,
It may be a tape, a sheet, a disk, a card, a drum, or the like, and various materials are selected as necessary according to the form. The thickness of these non-magnetic supports is about 1 to 50 μm, preferably 1 to 30 μm in the case of a film, tape or sheet. In the case of a disc or a card, it is about 0.03 to 1 mm, which may be selected according to the purpose of use. In particular, those that have been biaxially stretched are preferably used. If it is drum-shaped, it will be cylindrical, and its type will be determined according to the recorder used.

As the non-magnetic support, besides plastic, non-magnetic metals such as aluminum, copper, tin, zinc, or non-magnetic alloys containing these, depending on the application; ceramics such as glass, pottery, and porcelain; Papers, such as papers coated with or laminated with α-polyolefins having 2 to 10 carbon atoms such as paper, polyethylene or polypropylene, or ethylene-butene copolymer, can also be used.

As the ferromagnetic metal powder used for the magnetic layer, a powder of a ferromagnetic metal simple substance, a ferromagnetic alloy powder,
Examples thereof include powders selected from coated ferromagnetic metal simple substance powders or ferromagnetic alloy powders whose surface is covered with an oxide coating layer or a ceramic coating layer.

Examples of the ferromagnetic metal powder such as a powder of a ferromagnetic metal simple substance and a ferromagnetic alloy powder include, for example, Fe and C.
o, Ni, Fe-Co, Fe-Ni, Co-Ni-F
e, Co-Ni-P, Co-Ni-Fe-B, Fe-N
i-Zn, Ni-Co, Fe-N, Fe-Co-Cr,
Mn-Bi and various other known ferromagnetic metal powders are used. In particular, a ferromagnetic metal powder containing iron as a main component is preferable, and Fe, Fe-Co, Fe-Co-Cr, Fe-N and the like are more preferable.

The coated ferromagnetic metal powder or ferromagnetic alloy powder whose surface is covered with an oxide coating layer or a ceramic coating layer is a powder of the above-mentioned ferromagnetic metal alone, a powder such as a ferromagnetic alloy powder, or the like. The surface is oxidized to form a powder on which an oxide coating layer of the metal or alloy is formed, oxides of SiO ₂ , Al ₂ O _3, etc., Y ₂ O _{3 and} other rare earth metals, and other ceramics. Examples thereof include powders made of the above-mentioned ferromagnetic metal simple substance, powders such as ferromagnetic alloy powders provided as a coating layer on the surface thereof. The thickness of the coating layer is not particularly limited, but normally, 20 to 30% of the total powder particle volume is preferably used. When a coated ferromagnetic metal simple substance powder or a ferromagnetic alloy powder whose surface is covered with an oxide coating layer or a ceramic coating layer is used, the electromagnetic conversion characteristics have no coating layer. Although it tends to be slightly lower than that of the conventional metal oxide magnetic powder such as iron oxide magnetic powder, the electromagnetic conversion characteristics are superior, and it is possible to provide a magnetic recording medium with high density recording and high output characteristics. While you can
Since it is more difficult to oxidize, it is possible to provide a magnetic recording medium that is more excellent in long-term storage stability and weather stability.

As described above, when any of the ferromagnetic metal powders is used, the saturation magnetization is 130 to 240 emu / g.
Then, using a ferromagnetic metal powder having a specific surface area of 35 to 65 m ² / g (BET method) and an axial ratio of 5 to 15 and having an elongated shape (acicular shape), electromagnetic conversion characteristics are further excellent, It is preferable because it is possible to provide a magnetic recording medium excellent in high-density recording and high output characteristics.

When a multi-layer magnetic layer is formed by further providing a magnetic layer between the magnetic layer and the non-magnetic support, the magnetic powder used in the lower magnetic layer is limited to the above ferromagnetic metal powder. However, magnetic powders of oxides such as ferromagnetic iron oxide and ferromagnetic chromium dioxide may be used instead. Although not particularly limited, in the case of forming such a multilayer magnetic layer, the coercive force Hc of the lower layer is usually the coercive force Hc of the surface layer.
It is common to use a smaller one.

The content of the magnetic powder in the magnetic layer is not particularly limited, but is 70 to 80 of the total weight of the magnetic coating film.
About wt% is particularly preferable. As the binder resin used in the present invention, a polyurethane synthesized from a polyol and a polyisocyanate in which the amino-quinone derivative represented by the above chemical formula (Formula 1) is used as a part or all of the polyol component is used. The polyurethane resin may contain the amino-quinone conductor component represented by the chemical formula (Formula 1), but it is preferable that the polyurethane resin contains 1 to 60% by weight. Further, the total amount of the binder resin may be the specific polyurethane resin, but the proportion of the specific polyurethane resin used is 5 to 7 of the total weight of the binder resin.
0 wt% is particularly preferable because it is excellent in dispersion stability and can sufficiently exhibit high-density recording and high electromagnetic conversion characteristics.
In this case, it is preferable to use another binder resin together.

The above polyurethane resin is prepared by using the amino-quinone derivative represented by the above chemical formula (Formula 1) as a part or all of the polyol component to synthesize a usual polyurethane obtained by reacting a polyol with a polyisocyanate. It can be easily obtained by the method. As the polyisocyanate to be reacted, a polyisocyanate compound used in the production of a commonly used polyurethane-based binder resin may be used. For example, tolylene diisocyanate (TDI), diphenylmethane-4,4'-diisocyanate ( MDI) is a typical example.

When a binder resin other than the above-mentioned specific polyurethane is used in combination, the binder resin used in combination is, for example, a vinyl chloride-based copolymer (copolymerizable monomers such as vinyl acetate and propionic acid). Fatty acid vinyl esters such as vinyl, methyl acrylate, ethyl acrylate, propyl acrylate, lauryl acrylate, stearyl acrylate, methyl (meth) acrylates such as methyl methacrylate, ethyl methacrylate, vinylidene chloride, etc. have solvent solubility. It is preferable because it has the effect of increasing O.
Vinyl alcohol, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) as an H group-containing copolymerization monomer
Acrylate, hydroxylauryl (meth) acrylate, hydroxystearyl (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, hydroxyethyl allyl ether, hydroxypropyl allyl ether, hydroxybutyl allyl ether are polyisocyanate compounds and It is preferable because it is combined with an epoxy compound to improve the mechanical strength. In addition, maleic acid, (meth) acrylic acid, acrylonitrile, ethylene, styrene and the like can be copolymerized as required. Acrylic resins represented by polymethyl methacrylate (copolymer monomers include those similar to those used in the above vinyl chloride copolymer); nitrocellulose, cellulose acetate propionate, cellulose acetate Cellulose resins such as butyrate; polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy resin, polyester polyurethane resin, polyether polyurethane resin, polyether ester polyurethane resin, polycarbonate polyurethane resin, polyester resin, polyether resin, various types Rubber-based resins and the like can be mentioned. Among these, vinyl chloride resins and polyurethane resins are preferable as the binder resin for the magnetic layer.

In order to improve dispersibility and durability, polar groups --SO ₃ M and --CO are added to the binder resin molecule described above.
OM, -PO ₃ M, -OH, etc. (in which M is a hydrogen atom here, an alkali metal or an ammonium.) Are more preferable ones are introduced, in particular the polar group introduced vinyl chloride resin in the molecule , Polyurethane resin, etc. are preferably used.

When a back coat layer is provided, examples of the preferable binder resin for the back coat layer include nitrocellulose and phenoxy resin in addition to the above preferable binder resin for the magnetic layer.

The magnetic layer may be provided on one side or both sides of the non-magnetic support depending on the application. Generally, in the case of a magnetic recording tape, the magnetic layer is provided on one side of the non-magnetic support. In this case, a back coat layer may be provided on the surface opposite to the side provided with the magnetic layer. Also,
Although not particularly limited, in the case of a floppy disk or the like, the magnetic layer is often provided on both sides of the non-magnetic support.

The thickness of the magnetic layer differs depending on the type of magnetic recording medium and also on the surface roughness of the base film, and is not particularly limited.
Usually, it is about 1 to 4 μm. In the case of a multi-layer, the upper layer has a thickness of about 0.1 to 1 μm, and the lower layer has a thickness of about 0.9 to 3 μm for both a magnetic layer and a non-magnetic layer. Also,
When the back coat layer is provided, the thickness of the back coat layer also differs depending on the type of magnetic recording medium and the surface roughness of the base film, and is not particularly limited, but is usually 0.3. ~ 1.5μ
m, preferably about 0.4 to 0.9 μm.

When a magnetic layer or a non-magnetic layer is formed,
It is preferable to add a non-magnetic powder such as carbon black or an abrasive, or a lubricant. As the non-magnetic powder, it is also preferable to use carbon black and an abrasive together in order to impart conductivity in order to prevent electrification and to impart light-shielding property in the case of a magnetic recording tape. As the non-magnetic powder, in addition to carbon black, titanium oxide, calcium carbonate, alumina, red iron oxide, barium sulfate, CoO.Al ₂ O ₃ solid solution, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond as abrasives,
Materials having a Mohs hardness of 6 or more, such as silicon nitride, titanium carbide, silicon dioxide, and boron nitride, are preferably used.

The use ratio of these additives is not particularly limited because it varies depending on the type of the target magnetic recording medium, but usually, in the magnetic layer, the magnetic powder 1
Non-magnetic powder (carbon black
5 to 5 parts by weight, more preferably 5 to 20 and more preferably 7 to 15
Parts by weight), and 0.5 to 10 parts by weight of lubricant (particularly 2 to 4 parts by weight is more preferable in the case of a magnetic tape, 5 to 9 parts by weight is more preferable in the case of a floppy disk). To be When nonmagnetic powder is added to the back coat layer, carbon black alone may be used,
When carbon black and an abrasive are used in combination, the abrasive is preferably used in an amount of 5% by weight or less based on the total weight of the non-magnetic powder. Carbon black imparts electrical conductivity and thus prevents triboelectric charging and also functions as a light shielding material.

The proportion of the non-magnetic powder, binder resin and lubricant used in forming the back coat layer varies depending on the type of the intended magnetic recording medium, and is not particularly limited, but is usually non-magnetic. A range of 80 to 120 parts by weight of binder resin and 1 to 5 parts by weight of lubricant is preferably used with respect to 100 parts by weight of powder.

As the lubricant, a fatty acid having 12 to 22 carbon atoms, an ester of the fatty acid and an alcohol having 1 to 4 carbon atoms, the fatty acid and HO (OC ₂ H ₄ ) _n C ₄ H ₉ (n is 1 to 1)
The number of 4 is shown. ) Or an ester thereof, or a mixture of two or more thereof. In particular, it is preferable to use the fatty acid and the ester in combination in the magnetic layer.

The magnetic coating liquid or the coating liquid for the back coat layer is prepared by kneading the above components and the organic solvent. Of course, it is optional to add a dispersant, an antistatic agent, and other additives, if necessary, as long as the object of the present invention is not impaired.

The organic solvent may be appropriately selected according to the kind of the binder resin, and it is a ketone system such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; methyl acetate, ethyl acetate, butyl acetate,
Ester systems such as ethyl lactate and glycol monoethyl ether; glycol ether systems such as ether, glycol dimethyl ether, glycol monoethyl ether and dioxane; tar systems (aromatic hydrocarbons) such as benzene, toluene and xylene; methylene chloride, ethylene Chlorinated hydrocarbons such as chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin and dichlorobenzene can be selected and mixed for use.

As a method for coating the above-mentioned magnetic coating liquid or coating liquid for the back coat layer on the support, in addition to using a coating head having a slit-shaped opening, air doctor coat, blade coat, air knife coat, squeeze coat A coat, an impregnation coat, a reverse roll coat, a transfer roll coat, a gravure coat, a kiss coat, a spin coat and the like can be used.

The coating solution after coating and drying these coating solutions on a non-magnetic support is performed by a metal roll and a cotton roll, or a synthetic resin (for example, nylon,
It is preferably carried out by a supercalendering method in which a roll (such as polyurethane) or two rolls such as a metal roll and a metal roll is passed. The conditions of the super calender are a roll pressure of about 25 to 500 kg / cm ² , a temperature of about 35 to 150 ° C., and a pressure of 5 to 200 m / mi.
It is preferable that the processing speed is n.

The magnetic recording medium of the present invention obtained as described above is useful as a magnetic recording tape, a floppy disk, a magnetic card, a digital data storage, a digital video cassette tape, etc., depending on its mode.

[0039]

EXAMPLES In order to facilitate understanding of the present invention, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

(Examples 1-28 and Comparative Examples 1-5) Magnetic coating compositions were prepared according to the following formulations. Basic formulation Ferromagnetic metal powder (shown in Table 1) 100 parts by weight Binder resin Total 18 parts by weight "MR110" (-SO ₃ K group-containing vinyl chloride resin, manufactured by Nippon Zeon Co., Ltd.) The polyurethane containing the amino-quinone derivative is listed in Table 1 (the types of the amino-quinone derivative are listed in Table 1). Carbon black “SEAST S” (manufactured by Tokai Carbon Co., Ltd.) 1 part by weight α-alumina (particle size, 0 .2 μm) 8 parts by weight Polyisocyanate (“M-201”, manufactured by Nippon Polyurethane Industry Co., Ltd.) 5 parts by weight Stearic acid 1 part by weight Butoxyethoxyethoxyethyl stearate 1 part by weight Methyl ethyl ketone 120 parts by weight Toluene 120 parts by weight Cyclohexanone 40 Parts by Weight In Table 1, the material of the ferromagnetic metal powder means Comparative Example 2 and Example 16 For beauty 18 shows the material of the ferromagnetic metal powder itself used, other embodiments than these, show the material of the core in Comparative example. That is, in Examples other than Comparative Example 2 and Examples 16 and 18, and in Comparative Examples, a ceramic comprising the oxide coating layer and Al ₂ O ₃ and Y ₂ O _{3 on} the surface of the core of the material shown in Table 1. It shows a ferromagnetic powder in which a coating layer is formed.
The total thickness of the coating layer is about 20% of the total volume of the ferromagnetic powder.
Was used. A magnetic recording medium was manufactured by the following manufacturing method using the magnetic coating composition prepared by the above composition. Manufacturing method (basic) Ferromagnetic metal powder, polyvinyl chloride resin, polyurethane resin, carbon black, α-alumina and solvent are mixed and kneaded in a planetary mixer under a nitrogen atmosphere, and the solvent is added and dispersed in a sand mill for 5 to 20 hours. To do. Pore size 0.
After filtering with a 3 μm filter, polyisocyanate, a lubricant and a solvent are added to obtain a magnetic coating composition. This was dried on a polyethylene naphthalate base film (surface roughness Ra: 6 nm) having a thickness of 10 μm, and the coating thickness was 2.8.
After coating with a thickness of μm, it was oriented in a longitudinal direction by a 4000 G solenoid magnetic field and dried. Then, it was treated at 70 ° C. at a total pressure of 250 kg / cm ² at 70 ° C. by a super calender device in which nylon elastic rolls and chrome-plated metal rolls were alternately stacked, and heat-treated at 60 ° C. for 24 hours. 100 parts by weight of carbon black and a binder resin (50 parts by weight of nitrocellulose, manufactured by Toyobo Co., Ltd. "UR-820" are provided on the opposite side of the magnetic layer coating.
0 "50 parts by weight) as a main back coat layer 0.8
Formed in μm and slit to 1/2 inch width for commercial use V
It was installed in the tape cassette of TR (video tape recorder) system D5.

Magnetic recording media were manufactured by changing the ferromagnetic metal powder and the binder resin. The characteristics of these samples were measured by the following evaluation methods. The evaluation results are shown in Tables 1 and 2.

[0042]

[Table 1]

[0043]

[Table 2]

Evaluation Method Surface Roughness: Using a non-contact laser interference type three-dimensional surface roughness meter manufactured by WYKO, USA, Ra of the magnetic layer surface was measured at a magnification of 200 times.

Friction coefficient: The magnetic layer side of the tape is applied to a stainless pin having a diameter of 3 mm, wound around 180 degrees, and reciprocated with a load of 20 g. The tension and load at this time were calculated based on Euler's theorem and used as the friction coefficient (μk).

Magnetic properties: Toyo Kogyo Co., Ltd. VSM device ("VSMP-1S") was used and the maximum applied magnetic field was 10 kO.
e. The ferromagnetic metal powder was measured by filling a sample holder in an inert gas such as nitrogen gas. The magnetic recording medium was cut into 5 mm squares and stacked so that the total thickness of the magnetic layer was 3 μm or more, and the magnetic field was applied in the longitudinal direction of the tape for measurement.

Output: VT for broadcasting station manufactured by Matsushita Electric Industrial Co., Ltd.
Using the R deck ("AJD580-525"), 33.
The reproduction output of 5 MHz signal recording was measured with a spectrum analyzer. Measured values are commercially available D5 cassette tape M
It is shown as a comparative value for 60.

C / N: V for broadcasting station manufactured by Matsushita Electric Industrial Co., Ltd.
3 using TR deck ("AJD580-525")
31.5MH for reproduction output of 3.5MHz signal recording
The noise generated in z was measured with a spectrum analyzer, and the ratio of the reproduced signal output to this noise was measured.
The measured values are shown as comparative values for the commercially available D5 cassette tape M60.

Weather resistance storage property: The sample was left for 10 days in an environment of a temperature of 60 ° C. and a relative humidity of 90%, the residual magnetic flux density of the magnetic characteristics was measured, and the rate of change with respect to the initial residual magnetic flux density was defined as ΔBr.

Although the above-mentioned embodiment shows the magnetic recording medium in which the magnetic layer is directly formed on the non-magnetic support, a magnetic or non-magnetic undercoat layer is provided between the non-magnetic support and the magnetic layer. As described above, those having the same can be preferably used.

[0051]

INDUSTRIAL APPLICABILITY The magnetic recording medium of the present invention can provide a magnetic recording medium which does not require complicated steps in manufacturing the magnetic recording medium, has excellent long-term storage stability and weather resistance stability, and can maintain high electromagnetic conversion characteristics. .

In the magnetic recording medium of the present invention, an amino-quinone derivative component of a polyurethane resin synthesized from a polyol and a polyisocyanate in which the amino-quinone derivative represented by the chemical formula (Formula 1) is part or all of the polyol component. Is 1 to 60% by weight of the polyurethane resin, and the ratio of the polyurethane resin to the total binder resin is 5 to 70% by weight. Since it is possible to prevent oxidation and has excellent dispersion stability, it is possible to provide a magnetic recording medium that retains high electromagnetic conversion characteristics and has excellent long-term storage stability and weather stability.

In the magnetic recording medium of the present invention, as the binder resin, the amino-quinone derivative represented by the chemical formula (Formula 1) is synthesized from a polyol in which a part or all of the polyol component and a polyisocyanate are synthesized. A binder resin other than the polyurethane resin is contained, and the binder resin other than the polyurethane resin contains -S in the binder resin molecule.
This is a vinyl chloride resin or a polyurethane resin into which a polar group selected from O ₃ M, —COOH, —PO ₃ M, and —OH (wherein M represents a hydrogen atom, an alkali metal or ammonium) is introduced. According to the preferred embodiment of the invention, a magnetic recording medium having improved durability of the magnetic layer can be obtained by using the binder resin having these polar groups in combination, which is preferable.

In the magnetic recording medium of the present invention, the ferromagnetic metal powder is a powder composed of a simple ferromagnetic metal,
Ferromagnetic alloy powder, a powder selected from a coated ferromagnetic metal simple substance powder whose surface is covered with an oxide coating layer or a ceramic coating layer, or a ferromagnetic alloy powder is used to obtain a particularly ferromagnetic The elemental metal powder and the ferromagnetic alloy powder have excellent electromagnetic conversion characteristics, and can provide a magnetic recording medium suitable for high density recording. Further, when a coated ferromagnetic metal simple substance powder or a ferromagnetic alloy powder whose surface is covered with an oxide coating layer or a ceramic coating layer is used, the electromagnetic conversion characteristics tend to be slightly low, but the conventional iron oxide Electromagnetic conversion characteristics are superior to those of metal oxide magnetic powders such as, and it is possible to provide a magnetic recording medium suitable for high-density recording, and it is more difficult to oxidize, so long-term storage stability and weather stability are better. It is preferable because a magnetic recording medium can be provided.

In the magnetic recording medium of the present invention, the ferromagnetic metal powder has a saturation magnetization of 130 to 240 emu.
/ G, specific surface area 35-65 m ² / g (BET method)
By providing a preferred embodiment of the present invention, which is a ferromagnetic metal powder having an elongated shape with an axial ratio of 5 to 15, a magnetic recording medium having more excellent electromagnetic conversion characteristics and suitable for high density recording is provided. It is possible to do so, which is preferable. In particular, conventionally, the residual magnetic flux density (Br) of the magnetic recording medium is lowered due to the problem of oxidative deterioration, or the saturation magnetization of the ferromagnetic metal powder that can be used to form an oxide layer or a ceramic layer on the surface is Although the limit was about 160 emu / g, in the present invention, even when a ferromagnetic metal powder having a higher saturation magnetization is used, Br in a magnetic recording medium can be maintained in a higher state, so that a higher value can be obtained. A magnetic recording medium suitable for density recording can be provided, which is preferable.

In the magnetic recording medium of the present invention, the surface roughness Ra of the magnetic layer is 1 to 10 nm, and the squareness ratio is 0.80 or more. It is preferable because it can provide a magnetic recording medium having a good / N and suitable for high density recording.

In the magnetic recording medium of the present invention, a magnetic lower layer containing at least a ferromagnetic metal powder and a binder resin, or at least a non-magnetic powder is provided between the non-magnetic support and the magnetic layer. By adopting a preferred embodiment of the present invention in which a non-magnetic lower layer containing a binder resin is further formed, the thickness of the uppermost magnetic layer can be reduced, which facilitates recording at shorter wavelengths, A magnetic recording medium suitable for high-density recording can be provided, which is preferable.

Claims (7)

[Claims] 1. A coating type magnetic recording medium comprising a non-magnetic support and a magnetic layer comprising at least a ferromagnetic metal powder and a binder resin formed thereon, wherein the binder resin is represented by the following chemical formula: Chemical 1] [However, R is an alkylene group having 1 to 6 carbon atoms or-(C
₂ H ₄ O) _n —C ₂ H ₄ — (where n represents the number of 1 or 2) and R ′ represents an alkyl group having 1 to 4 carbon atoms. ] The magnetic recording medium characterized by containing the polyurethane resin synthesize | combined from the polyol which made the amino-quinone derivative shown by these all or a part of the polyol component, and polyisocyanate. 2. A polyurethane resin synthesized from a polyol and a polyisocyanate in which the amino-quinone derivative represented by the chemical formula (Formula 1) is a part or all of the polyol component, and the amino-quinone derivative component accounts for the proportion of the polyurethane resin. The magnetic recording medium according to claim 1, wherein the ratio of the polyurethane resin in the total binder resin is 5 to 70% by weight in 1 to 60% by weight. 3. The chemical formula (Formula 1) as a binder resin
Including a binder other than a polyurethane resin synthesized from a polyol and a polyisocyanate in which the amino-quinone derivative represented by a part or all of the polyol component,
Binder resins other than the polyurethane is in the binder resin _{molecules, -SO 3 M, -COOH, -PO} 3 M, -OH
(Here, M represents a hydrogen atom, an alkali metal or ammonium.) A vinyl chloride resin or a polyurethane resin into which a polar group selected from the group is introduced.
Or the magnetic recording medium according to any one of 2). 4. The ferromagnetic metal powder is a powder of a ferromagnetic metal simple substance, a ferromagnetic alloy powder, or a coated ferromagnetic metal simple substance powder or a ferromagnetic alloy powder whose surface is covered with an oxide coating layer or a ceramic coating layer. The selected powder is claim 1.
4. The magnetic recording medium according to any one of 3 to 3. 5. The saturation magnetization of the ferromagnetic metal powder is 130 to 2
40 emu / g, specific surface area 35-65 m ² / g (B
The magnetic recording medium according to claim 1, which is a ferromagnetic metal powder having an elongated shape with an axial ratio of 5 to 15 according to the ET method). 6. The surface roughness Ra of the magnetic layer is 1 to 10 nm.
6. The magnetic recording medium according to claim 1, wherein the squareness ratio is 0.80 or more. 7. A magnetic lower layer containing at least a ferromagnetic metal powder and a binder resin, or a nonmagnetic lower layer containing at least a nonmagnetic powder and a binder resin, between the nonmagnetic support and the magnetic layer. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is formed.