JPH06150290A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the contacting condition of a magnetic head so as to increase the output of the head by forming a magnetic layer on a tape-like nonmagnetic substrate, specifying the width-direction Young's modulus of the substrate and glass-transition temperature of the magnetic layer and the total thickness of the recording medium, and selecting the relative speed between the recording medium and head. CONSTITUTION:This recording medium is constituted by forming a magnetic layer composed mainly of the powder of a ferromagnetic metal, such as an Fe-Co-Ni alloy, etc., and a thermoplastic resin, such as a vinyl chloride-vinyl acetate copolymer, etc., on a substrate of polyethylene naphthalate. At the time of forming the recording medium, the width-direction Young's modulus of the substrate, glass-transition temperature of the magnetic layer, and total thickness of the recording medium are respectively set at >=1,000kg/mm<2>, 80-100 deg.C, and <12mum, respectively. The recording medium thus formed is brought into contact with the magnetic head of a digital VTR having a core width of >=1,000mum and slid on the magnetic head at a relative speed of >=20m/sec. Therefore, the contacting condition of the magnetic head can be remarkably improved and the output of the magnetic head can be increased.

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 comprising a magnetic layer and a non-magnetic support, and more specifically, it improves head contact in a VTR, particularly a digital VTR, and maintains high output. The present invention relates to a magnetic recording medium with less output fluctuation and less dropout.

[0002]

2. Description of the Related Art Generally, as a magnetic recording medium for audio, video, computer (disk, memory tape), etc., a magnetic layer in which ferromagnetic powder is dispersed in a binder is formed on a non-magnetic support. The magnetic recording medium provided is used. In recent years, in the field of these magnetic recording media, the practical application of digital recording with less deterioration of recording during dubbing has been progressing from conventional analog recording.

Generally, digital recording requires more signals to be recorded than analog recording, and the VTR and magnetic tape used have high image quality and high sound quality, and at the same time are compact and space-saving. Therefore, higher density recording is required. In order to achieve high-density recording, a transition of magnetization in the medium is required along the recording track at a distance as short as possible, so that the wavelength of the signal is shortened. For this reason, it is necessary to reduce the writing speed to the magnetic tape and the drawing speed at the same time as making the ferromagnetic powder into fine particles, making it highly filled, ultra-smoothing the medium surface, etc., and improving the cylinder rotation speed and magnetic tape transport speed, etc. Is being done.

Further, the diameter of the cylinder head is reduced in order to reduce the size of the VTR and the space of the magnetic recording medium, and the track of the magnetic tape is narrowed to improve the area density of recording, and the volume is reduced to improve the volume density. Is required. Especially in the case of thin tape of about 11 μm, 5400-60
It is very difficult for a small-diameter head that rotates at a high speed of about 00 rpm to stably run at a high speed of 20 m / sec or more at a magnetic tape / head relative speed. The tendency tends to increase as

Further, nonmagnetic particles called carbon black or abrasive having a Mohs hardness of 8 or more are usually used for the magnetic tape in order to secure the running property, charging property and head cleaning property. Head wear tends to increase due to an increase in the relative speed of the magnetic tape / head due to the high speed conveyance of the head and the high speed rotation of the head. In order to ensure such head wear within the optimum range, the abrasiveness of the magnetic tape is adjusted within the suitable range, and the width of the sliding surface with respect to the magnetic tape in the direction perpendicular to the head running direction (core width of the magnetic head). Has been dealt with by using a head in which the contact area of the magnetic head core with the tape is increased by expanding the magnetic field.

However, when the area of the magnetic head is increased, there is a problem that the Rf output tends to decrease and the output fluctuation tends to increase. The above-mentioned decrease in Rf output and output fluctuation occur because the magnetic tape is pulled into the head chip mounting window of the cylinder head, and the contact between the magnetic tape and the head becomes uneven. The uneven contact between the magnetic tape and the head means
This means that a gap is created between the magnetic tape and the head, and if a gap is created, loss will occur at the time of recording and at the time of reproduction, which will cause a drop in output and a fluctuation in output.

These problems are particularly noticeable in a commercial VTR video tape such as a D3 system or a D2 system capable of digitizing a recording / reproducing signal. By the way, the loss Ls during reproduction is expressed by the following equation. Ls = 54.6 (d [μm] / λ [μm]) (dB) (1) where d [μm] is the gap between the magnetic tape and the head,
λ [μm] is a wavelength. The gap between the magnetic tape and the head is determined by the pressure of the air flow between the magnetic tape and the head and the stiffness of the magnetic tape. The above problems occur because the stiffness of the magnetic tape is small mainly in the width direction.

The stiffness M of the magnetic tape can be expressed by the following equation. ^{M = Ebd 3/12 ...... (} 2) In addition, E is Young's modulus, b is a magnetic tape of width, d is the thickness of the magnetic tape. As can be seen from the expression (2), it is effective to increase the Young's modulus in the width direction of the base and to increase the total thickness of the magnetic tape in order to increase the stiffness in the width direction of the magnetic tape. Specific examples of the Young's modulus in the width direction of the base include, for example, JP-A-50-46.
303, JP-A-54-34206, JP-A-62-2
34233, JP-A-63-197643 and JP-A-6.
3-212549, JP-A-2-20924, JP-A-4-49515, U.S. Pat. No. 4,804,73.
Polyethylene terephthalate (reinforced PET) or polyethylene-2,6-naphthalate (PEN), which has a Young's modulus in the width direction higher than usual, as disclosed in No. 6 and No. 4,833,019. , Techniques using aromatic polyamides (aramids) and composite polyesters have been proposed. Further, since the stiffness is proportional to the cube of the thickness of the magnetic tape, the thickness of the magnetic tape becomes thinner. Therefore, the improvement of the Young's modulus in the width direction of the base, which is conventionally done by increasing the draw ratio, causes the magnetic tape to reach the optimum region. Can't maintain its stiffness.
Generally, in order to obtain a magnetic tape running with a head having a width of a sliding surface of about 80 μm perpendicular to the scanning direction with respect to a track width of 20 μm, polyethylene terephthalate (P
ET) film requires a thickness of 9 μm or more. Such a phenomenon becomes remarkable particularly when the width of the sliding surface of the head in the direction perpendicular to the scanning direction becomes wider, and when the width of the sliding surface in the direction perpendicular to the scanning direction becomes about 130 μm, the width direction Young Even with the increased PEN and aramid bases, a thickness of 9 μm or more is required.

Similarly, a technique has been proposed in which a non-magnetic metal layer such as aluminum is provided on a PET base by a method such as vapor deposition for the purpose of increasing stiffness (JP-A-54-74).
No. 706) has not been put to practical use because it increases the cost.

[0010]

Even with the technique described above, the output reduction due to the non-uniformity of the magnetic tape hitting the head with the thinning of the tape and the widening of the head sliding surface can be sufficiently achieved. It could not be improved. An object of the present invention is to provide a magnetic recording medium capable of improving the head contact of a VTR, especially a digital VTR, and maintaining a high output.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording medium having a magnetic layer mainly composed of a ferromagnetic powder and a binder on a tape-shaped non-magnetic support, and the width of the non-magnetic support. Direction Young's modulus is 1000 Kg / mm ² or more, and the glass transition temperature (Tg) of the magnetic layer is 80 to
The magnetic recording medium is 100 ° C. and the total thickness of the magnetic recording medium is less than 12 μm, and a magnetic layer mainly composed of a ferromagnetic powder and a binder is provided on a tape-shaped non-magnetic support. In the magnetic recording medium, the non-magnetic support has a Young's modulus in the width direction of 1000 kg / mm ² or more, and the magnetic layer has a glass transition temperature (Tg) of 80 to 80.
A magnetic recording medium characterized by being used at a temperature of 100 ° C. and a total thickness of less than 12 μm at a relative speed of 20 m / sec or more with a magnetic head having a core width of 100 μm or more. .

That is, the present inventors have a Young's modulus of the non-magnetic support in the width direction of 1000 kg / mm ² or more and a glass transition temperature of the magnetic layer of 80 to 100 ° C., preferably 8
By setting the temperature to 5 to 95 ° C., the mechanical characteristics of the entire magnetic recording medium are improved, the head contact with the magnetic tape is improved, and high output can be maintained, and the present invention has been completed.

The Young's modulus in the width direction of the non-magnetic support is 100.
When it is less than 0 kg / mm ² , the glass transition temperature of the magnetic layer is 10
If the temperature is higher than 0 ° C, the head contact can be improved, the high output can be maintained and the output fluctuation can be reduced, but when the VCR is run at the VTR by the edge crack in the slitting process, the magnetic layer falls off and causes the dropout. Become. Further, when the Young's modulus in the width direction of the non-magnetic support is 80 ° C. or less, no improvement effect is observed.

The present invention is effective for a magnetic tape used in a VTR in which the shortest recording wavelength of a magnetic recording medium is 1 μm or less, particularly 0.8 μm or less, and further, when the recording track width is 25 μm or less, particularly 20 μm or less. A VTR using a wide head having a width of 80 μm or more, particularly 120 μm or more, particularly a digital VTR, can achieve both long-time recording and downsizing / space saving. The core width mentioned here is the width of the sliding surface of the magnetic head in the direction perpendicular to the head traveling direction.

The total thickness of the magnetic recording medium of the present invention is 12 μm.
It can be set to less than 11 μm, particularly, and it is advantageous because the head contact can be secured and the recording can be performed for a long time. Further, the total thickness of the magnetic recording medium refers to the total thickness of the magnetic recording medium including the thickness of the non-magnetic support, the thickness of the magnetic layer and the back layer provided as necessary. In order to obtain a high output, the surface roughness of the magnetic layer should be the center line average surface roughness Ra.
1.5 to 4.5 nm (cutoff value 0.25 mm),
Preferably 2-4 μm, particularly preferably 2.5-3.
The range is 5 μm, a ferromagnetic metal powder is selected as the ferromagnetic powder to be used, and its specific surface area is 47 m ² / g or more, preferably 53 to 70 m ² / g, and particularly preferably,
It is in the range of 50 to 60 m ² / g.

Further, the center line average roughness Ra is provided on the back surface of the non-magnetic support which is coated with a magnetic layer for stable traveling.
Is preferably 2 to 10 nm (cutoff value 0.25 mm). The magnetic recording medium comprises a non-magnetic support, a magnetic layer provided on the support, and a back layer provided on the opposite side of the magnetic layer, if necessary. The magnetic layer is composed of a ferromagnetic powder and, if necessary, powdery components such as carbon black, an abrasive, and a powdery lubricant, and a binder in which the powdery components are dispersed. The binder is composed of a resin component and a curing agent that is blended if necessary.

The glass transition temperature of the magnetic layer of the present invention is the glass transition temperature of the resin itself used as the binder of the magnetic layer,
Blending amount of the resin, blending amount of the curing agent of the magnetic layer which is added as necessary, the degree of crosslinking (reaction) of the curing agent, and blending of a lubricant having a plasticizing effect on the binder of the magnetic layer. It can be obtained by adjusting the amount. The glass transition temperature of the magnetic layer was 30 to 120 at 110 Hz frequency using a dynamic viscoelasticity automatic measuring device (manufactured by Orientic Co., Ltd.).
It can be determined from the temperature at which the peak of the loss elastic modulus is obtained by measuring at a temperature rising rate of 2 ° C./min in the temperature range of ° C.

In the present invention, the glass transition temperature of the magnetic layer is 8
The temperature is controlled to 0 to 100 ° C, preferably 85 to 95 ° C.
The non-magnetic support used in the present invention has a thickness of 5 to 1
About 0 μm, especially about 6 to 9 μm is preferable, and the Young's modulus in the width direction is 1000 Kg / mm ² or more, especially 1200 K
It is preferably g / mm ² or more. The Young's modulus in the longitudinal direction is 400 to 1200 Kg / mm ² , preferably 450.
The range is up to 1000.

Examples of the material include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride, polycarbonate, polyimide and polyamide. , Plastics such as polysulfone can be used, but polyethylene terephthalate, polyethylene naphthalate, polyamide and polyimide are preferable, and polyethylene naphthalate (PEN) is particularly preferable. These supports may be subjected to corona discharge treatment, plasma treatment, undercoating treatment, heat treatment, dust removal treatment, metal vapor deposition treatment, and alkali treatment prior to coating. With respect to these supports, for example, the specification of West German Patent 3338854A and JP-A-59-1169.
26, U.S. Pat. No. 4,388,368; Yukio Mitsuishi, "Fiber and Industry", Vol. 31, p50-55, 1975.
It is listed in the year. The center line average surface roughness of these supports is 0.001 to 0.5 μm (cut-off value of 0.
25 mm) is preferred.

The polyethylene naphthalate used in the present invention is a copolymer containing polyethylene-2,6-naphthalenedicarboxylate homopolymer, including ethylene-2,6-naphthalenedicarboxylate repeating units in an amount of 70% by weight or more, It includes a polyester composition which does not substantially lose the properties of PEN, such as a mixture of these and another type of polymer (however, the PEN component accounts for 70% by weight or more). This PEN is a film-forming polymer.

The PEN film used in the present invention can be produced by biaxially orienting an unstretched film. Biaxial orientation is, for example, PE in sequential biaxial orientation.
A temperature higher than the glass transition temperature of N, preferably 3 to 1
The first stage is stretched at a temperature higher by 0 ° C., and then the second stage is stretched at the same temperature range as the first stage stretching temperature or 10 ° C. higher. The stretching ratio is at least 2 in the uniaxial direction, more preferably 2.5 or more, and the area ratio is preferably 6 times or more, more preferably 8 times or more. The heat treatment (heat setting) is preferably carried out under tension at a temperature of 170 ° C. or higher, more preferably 190 ° C. or higher. The upper limit of the heat treatment temperature depends on the treatment time, but it goes without saying that the film has a stable shape. The heat treatment time is preferably several seconds to several tens of seconds, more preferably 3 to 30 seconds. Then, 1.05 in the vertical direction under the conditions of (temperature lower than glass transition temperature by 10 ° C.) to (temperature lower than melting temperature by 40 ° C.).
˜2.5 times, 1.05 to 2.5 times in the transverse direction, and re-heat treatment is performed in the range of (temperature lower than glass transition temperature by 50 ° C.) to (temperature lower than melting temperature by 10 ° C.). Is preferred.

The ferromagnetic powder used in the present invention is, in particular, iron,
The effect is remarkable when a ferromagnetic metal powder containing cobalt or nickel is used, and α-Fe, Co, Ni,
Fe-Co alloy, Fe-Co-Ni alloy, Fe-Co-
Ni-P alloy, Fe-Co-Ni-B alloy, Fe-Ni
A ferromagnetic metal fine powder such as a —Zn alloy, a Ni—Co alloy, or a Co—Ni—Fe alloy is preferable.

The shape of these ferromagnetic metal powders is not particularly limited, and needle-shaped, granular, dice-shaped, rice granular and plate-shaped particles are usually used. In the case of needles, the particle size is 0.05 to 0.5 μm, preferably 0.05 to 0.5 μm.
The major axis length is 0.3 μm, particularly preferably 0.10 to 0.25 μm, and the major axis length / minor axis length is 2/1 to 25/1, preferably 3/1 to 15/1, and particularly preferably 4 / 1-12 /
1, and in the case of a plate, the plate diameter is 0.02 to 0.20.
μm, preferably 0.03 to 0.10 μm, particularly preferably 0.04 to 0.07 μm, and the plate diameter / plate thickness is 1/1.
˜30 / 1, preferably 2/1 to 10/1, particularly preferably 2.5 to 7/1.

The specific surface area (specific surface area S _BET ) of these ferromagnetic metal powders is 47 to 80 m ² / g, more preferably 53 to 70 m ² / g, and the coercive force (Hc) is 125.
0 to 2500 Oe, saturation magnetization (σ _S ) is 100 to 18
It is 0 emu / g, preferably 110 to 150 emu / g. Water content is 0.1 to 2.0% by weight, pH is 3-1
1 (5 g ferromagnetic powder / 100 g water) is preferred. The surface of these ferromagnetic metal powders is impregnated with a rust preventive agent, a surface treatment agent, a dispersant, a lubricant, an antistatic agent, etc., which will be described later, in a solvent for each purpose and is adsorbed. May be.

As the ferromagnetic metal powder, the metal content is 60% by weight or more, and 70% by weight or more of the metal content is at least one kind of ferromagnetic metal powder or alloy (eg Fe, Fe-Co, Fe-Co-Ni, Co, N
i, Fe-Ni, Co-Ni, Co-Ni-Fe), and other components (eg, Al, Si, S, 40% by weight or less, more preferably 20% by weight or less) of the metal content. S
c, Ti, V, Cr, Mn, Cu, Zn, Y, Mo, R
h, Pd, Ag, Sn, Sb, Te, Ba, Ta, W,
Re, Au, Hg, Pb, Bi, La, Ce, Pr, N
d, B, P) may be included in the alloy, iron nitride, iron carbide, and the like. In particular, in order to supplement the strength of metallic iron among these, it is desirable to provide Al, Si, or Cr individually or in a mixture on the surface layer. Further, the ferromagnetic metal powder contains a small amount of a hydroxide or oxide, an alkali metal element (Na,
K, etc.), an alkaline earth metal element (Mg, Ca, Sr), or the like. The method for producing these ferromagnetic metal powders is already known, and the ferromagnetic metal powder, which is a typical example of the ferromagnetic metal powder used in the present invention, can also be produced according to these known methods.

In particular, in the present invention, the following method can be mentioned as an example of the method for producing the ferromagnetic alloy powder used as the ferromagnetic powder. (A) Method of reducing complex organic acid salt (mainly oxalate) with reducing gas such as hydrogen: (b) Reduction of iron oxide with reducing gas such as hydrogen to obtain Fe or Fe-Co particles Method: (c) Method for thermally decomposing metal carbonyl compound: (d) Sodium borohydride in aqueous solution of ferromagnetic metal,
Method of reducing by adding reducing agent such as hypophosphite or hydrazine: (e) Method of electrolytically depositing ferromagnetic metal powder using mercury cathode and then separating from mercury: (f) Metal at low pressure Method of Obtaining Fine Powder by Evaporating in Inert Gas: Further, as the ferromagnetic powder used in the present invention, tabular hexagonal barium ferrite can also be used. Barium ferrite has a particle size of about 0.001 to 1 micron and a thickness of 1/2 to 1/20 of the diameter. Barium ferrite has a specific gravity of 4 to 6 g / cc and a specific surface area of 1 m ² / g to 7
It is 0 m ² / g.

If desired, FeO _x (X = 1.3
3 to 1.50), Co-containing FeO _x, etc. can also be used. Examples of the resin component of the binder used in the magnetic layer and the back layer of the present invention include conventionally known thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, ultraviolet curable resins, and visible light curable resins. Mold resins and mixtures of these are used.

The thermoplastic resin has a softening temperature of 150 ° C.
Hereinafter, those having a number average molecular weight of 10,000 to 300,000 and a degree of polymerization of about 50 to 2,000, more preferably 2
It is about 0 to 600, and for example, vinyl chloride vinyl acetate copolymer, vinyl chloride polymer, vinyl chloride vinyl acetate vinyl alcohol copolymer, vinyl vinylidene chloride copolymer, vinyl acrylonitrile copolymer, acrylic ester acrylonitrile. Copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon -Silicon-based resin, nitrocellulose-polyamide resin, polyvinyl chloride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose Derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, ethyl cellulose, methyl cellulose, propyl cellulose, methyl ethyl cellulose, carboxymethyl cellulose, acetyl cellulose, etc.), styrene butadiene copolymer, polyester resin, polycarbonate Resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber type thermoplastic resins, and mixtures thereof are used.

The thermosetting resin or the reactive resin has a molecular weight of 200,000 or less in the state of a coating solution.
By heating and humidifying after drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Further, among these resins, those which do not soften or melt before the resin is thermally decomposed are preferable. Specifically, for example, phenol resin, phenoxy resin, epoxy resin, polyurethane resin, polyester resin, polyurethane polycarbonate resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin (electron beam curing resin), epoxy-polyamide Resin, nitrocellulose melamine resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of methacrylate copolymer and diisocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, low molecular weight glycol / high molecular weight Examples include diol / triphenylmethane triisocyanate mixtures, polyamine resins, polyimine resins, and mixtures thereof.

These thermoplastic resins, thermosetting resins, and reactive resins have carboxylic acid (COOH), sulfinic acid, sulfenic acid, sulfonic acid (SO ₃ M), phosphoric acid (PO) as functional groups in addition to the main functional groups. (OM) (OM)), phosphonic acid, sulfuric acid (OSO ₃ M) and acidic groups such as ester groups (M is H, alkali metal, alkaline earth metal, hydrocarbon group), amino acids, amino sulfone Acids, sulfuric acid or phosphoric acid esters of amino alcohols, amphoteric groups such as alkyl betaine type, amino groups, imino groups,
Imido group, amide group, etc., hydroxyl group, alkoxyl group,
Thiol group, alkylthio group, halogen group (F, Cl,
Br, I), a silyl group, a siloxane group, an epoxy group, an isocyanato group, a cyano group, a nitrile group, an oxo group, an acryl group, and a phosphine group are usually contained in one type or more and 6 types or less,
Each functional group is 1 × 10 ⁻⁶ equivalent to 1 × 1 per 1 g of resin.
It is preferable to contain 0 ^-2 equivalent.

As the curing agent, a polyisocyanate compound is usually used. Examples of the polyisocyanate compound used in the magnetic layer and / or the back layer of the present invention include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, Isocyanates such as isophorone diisocyanate, triphenylmethane triisocyanate, and isophorone diisocyanate, products of the isocyanates and polyalcohols, and polyisocyanates of 2 to 10 mer produced by condensation of the isocyanates, or triisocyanates It is possible to use, for example, a product of polyurethane and polyurethane having a terminal functional group of isocyanate. The average molecular weight of these polyisocyanates is 100 to 20.
000 is preferable. Commercially available trade names of these polyisocyanate compounds are Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR, Millionate MTL (Nippon Polyurethane Co., Ltd., Takenate D-102, Takenate D-110N, Takenate D). -200, Takenate D-202, Takenate 300S, Takenate 500
(Manufactured by Takeda Pharmaceutical Co., Ltd.), Sumidule T-80, Sumidule 44S, Sumidule PF, Sumidule L, Sumidule N, Death Module L, Death Module I
L, Death module N, Death module HL, Death module T65, Death module 15, Death module R, Death module RF, Death module SL, Death module Z4273 (Sumitomo Bayer), etc. It can be used in combination of two or more utilizing the difference of. For the purpose of accelerating the curing reaction, hydroxyl groups (butanediol, hexanediol, molecular weight of 1000-100
No. 00 polyurethane, water, etc.), a compound having an amino group (monomethylamine, dimethylamine, trimethylamine, etc.), or a metal oxide catalyst can be used in combination. It is desirable that these compounds having a hydroxyl group or an amino group are polyfunctional. These polyisocyanates have a total amount of binder resin and polyisocyanate of 10 in both the magnetic layer and the back layer.
It is preferable to use 2 to 70 parts by weight per 0 parts by weight, and more preferably 5 to 50 parts by weight. Examples thereof are JP-A-60-131622 and JP-A-61-74.
No. 138 and the like.

These binders may be used alone or in combination, and other additives may be added. The mixing ratio of the ferromagnetic powder and the binder in the magnetic layer is 10 by weight.
The binder is used in the range of 5 to 300 parts by weight based on 0 parts by weight. The mixing ratio of the powder of the back layer and the binder is 8 to 400 parts by weight of the binder based on 100 parts by weight of the powder. As additives, carbon black,
Abrasives, lubricants, dispersants / dispersion aids, antifungal agents, antistatic agents, antioxidants, solvents and the like are added.

Furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used as carbon black used in the magnetic layer and the back layer of the present invention. These carbon blacks are used for the purpose of preventing electrification of the tape, light-shielding agent, friction coefficient adjusting agent, and improving durability. Specific examples of these carbon black abbreviations in the United States are SAF, ISAF, IISAF, T,
HAF, SPF, FF, FEF, HMF, GPF, APF, SRF, MPF
, ECF, SCF, CF, FT, MT, HCC, HCF, MCF, LFF
, RCF, etc., and those classified in ASTM standard D-1765-82a of the United States can be used. The average particle size of these carbon blacks used in the present invention is from 5 to
1000nm (electron microscope), nitrogen adsorption method specific surface area 1-80
0 m ² / g, pH 4-11 (JIS K-6221-1982 method),
Dibutyl phthalate (DBP) Lubrication amount is 10 to 800 mL
(ML) / 100g (JIS standard K-6221-1982 method). The size of carbon black used in the present invention is
Carbon black of 5 to 100 nm is used for the purpose of lowering the surface electric resistance of the coating film, and 50 when controlling the strength of the coating film.
Carbon black of ~ 1000 nm can be used.
In addition, for the purpose of controlling the surface roughness of the coating film, finer carbon black (less than 100 nm) is used for smoothing to reduce spacing loss. (100 nm or more) is used.
As described above, the kind and the addition amount of carbon black are properly used according to the purpose required for the magnetic recording medium.

Further, these carbon blacks may be surface-treated with a dispersant described later, or may be grafted with a resin before use. Further, it is also possible to use one in which a part of the surface is graphitized by treating the temperature of the furnace at the time of producing carbon black at 2000 ° C. or higher. Hollow carbon black can also be used as the special carbon black.

These carbon blacks are preferably used in an amount of 0.1 to 30 parts by weight with respect to 100 parts by weight of the ferromagnetic powder in the case of the magnetic layer, and resin 1 in the case of the back layer.
It is desirable to use 20 to 400 parts by weight with respect to 00 parts by weight. The carbon black that can be used in the present invention can be referred to, for example, "Carbon Black Handbook", edited by Carbon Black Association (published in 1972). Examples of these carbon blacks are U.S. Pat. Nos. 4,539,257, 4,614,685, and JP-A-61-924.
24, JP-A-61-99927 and the like.

The abrasive used for the magnetic layer and the back layer of the present invention is used to improve the durability of the magnetic recording medium and the head cleaning effect of the VTR, and is generally a material having a polishing action or a polishing action. , Α-alumina,
γ-alumina, α, γ-alumina, fused alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α-iron oxide, garnet, emery (main components: corundum and magnetite), garnet, silica stone, nitriding Silicon, boron nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, quartz, tripoly, diatomaceous earth, dolomite, etc., mainly consisting of Mohs hardness of 6 or more, preferably Mohs hardness of 8 or more. These abrasives used in combination have an average particle size of 0.005 to 5 μm, and particularly preferably 0.01 to 2 μm. In the case of the magnetic layer, these abrasives are added in the range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the ferromagnetic powder. In the case of the back layer, it is 0.0 with respect to 100 parts by weight of the resin described later.
It is desirable to use 1 to 5 parts by weight. Specific examples of these include AKP1 and AKP15 manufactured by Sumitomo Chemical Co., Ltd.
AKP20, AKP30, AKP50, AKP80, H
It50, Hit100, etc. are mentioned. These are described in Japanese Examined Patent Publication No. 52-28642.

As the powdery lubricant used in the magnetic layer and the back layer of the present invention, graphite, molybdenum disulfide, boron nitride, graphite fluoride, calcium carbonate, barium sulfate, silicon oxide, titanium oxide, zinc oxide, Inorganic fine powder such as tin oxide and tungsten disulfide, acrylic styrene resin fine powder, benzoguanamine resin fine powder, melamine resin fine powder, polyolefin resin fine powder, polyester resin fine powder, polyamide resin fine powder, polyimide There are fine resin powders such as fine resin powders and fine polyfluorinated ethylene resin powders.

As the organic compound type lubricant, silicone oil (dialkyl polysiloxane, dialkoxy polysiloxane, phenyl polysiloxane, fluoroalkyl polysiloxane (KF96, KF69 manufactured by Shin-Etsu Chemical Co., Ltd.) is used.
Etc.), fatty acid modified silicone oil, fluoroalcohol,
Polyolefin (polyethylene wax, polypropylene, etc.), polyglycol (ethylene glycol, polyethylene oxide wax, etc.), tetrafluoroethylene oxide wax, polytetrafluoroglycol, perfluoroalkyl ether, perfluoro fatty acid, perfluoro fatty acid ester, perfluoroalkyl sulfate ester , Perfluoroalkyl sulfonate,
Compounds in which fluorine or silicon is introduced, such as perfluoroalkylbenzene sulfonic acid ester and perfluoroalkyl phosphoric acid ester, alkyl sulfuric acid ester, alkyl sulfonic acid ester, alkyl phosphonic acid triester, alkyl phosphonic acid monoester, alkyl phosphonic acid diester, alkyl phosphoric acid Organic acids and organic acid ester compounds such as esters and succinates, triazaindolizine, tetraazaindene, benzotriazole, EDT
Heterocyclic compounds containing nitrogen and sulfur such as A, monobasic fatty acids having 10 to 40 carbon atoms and monohydric alcohols or dihydric alcohols having 2 to 40 carbon atoms, trihydric alcohols, tetrahydric alcohols, A fatty acid ester consisting of any one or two or more of a dihydric alcohol and a hexahydric alcohol, a monobasic fatty acid having 10 or more carbon atoms, and a carbon number of 11 to 70 in total with the carbon number of the fatty acid. Fatty acid esters consisting of individual monohydric to hexahydric alcohols, having 8 to 4 carbon atoms
Fatty acids of 0 or fatty acid amides, fatty acid alkyl amides, and fatty alcohols can also be used.

Specific examples of these compounds include butyl caprylate, octyl caprylate, ethyl laurate, butyl laurate, octyl laurate, ethyl myristate, butyl myristate, octyl myristate, 2-ethylhexyl myristate, Ethyl palmitate, butyl palmitate, octyl palmitate, 2-ethylhexyl palmitate, ethyl stearate, butyl stearate, isobutyl stearate, octyl stearate, 2-ethylhexyl stearate, amyl stearate, isoamyl stearate, 2 stearate.
Hexyldecyl, isotridecyl stearate, stearic acid amide, stearic acid alkylamide, butoxyethyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, anhydrosorbitan tetrastearate, oleyl. Olate, oleyl alcohol, lauryl alcohol, montan wax, carnauba wax, etc. are available and can be used alone or in combination.

As the lubricant used in the present invention, so-called lubricating oil additives can be used alone or in combination, and antioxidants (alkylphenol, benzotriazine, tetraazaindene, sulfamide) known as rust preventives are used. , Metal chelators such as guanidine, nucleic acid, pyridine, amine, hydroquinone, and EDTA), rust suppressants (naphthenic acid, alkenylsuccinic acid, phosphoric acid, dilauryl phosphate, etc.), oiliness agents (rapeseed oil, lauryl alcohol, etc.) , Extreme pressure agents (dibenzyl sulfide, tricresyl phosphate, tributyl phosphite, etc.), detergent dispersants, viscosity index improvers, pour point depressants, foam depressants and the like. These lubricants have an amount of 0.
It is added in the range of 01 to 30 parts by weight.

As the dispersant and dispersion aid used in the present invention, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, stearol, Behenic acid, maleic acid, phthalic acid, and other fatty acids having 2 to 40 carbon atoms (R ₁ COOH, R ₁ is an alkyl group having ₁ to 39 carbon atoms, phenyl group, aralkyl group), alkali metal of the above fatty acids ( Li, Na, K, etc.) or alkaline earth metal (Mg, Ca, Ba, etc.), NH ₄ ⁺ , metal soap consisting of Cu, Pb, etc. (copper oleate), fatty acid amide; lecithin (soybean oil lecithin), etc. used. In addition to these, higher alcohols having 4 to 40 carbon atoms (butanol, octyl alcohol, myristyl alcohol, stearyl alcohol) and their sulfuric acid esters, sulfonic acids, phenylsulfonic acids, alkylsulfonic acids, sulfonic acid esters, phosphoric acid monoesters, phosphoric acid diesters , Phosphoric acid triester, alkylphosphonic acid, phenylphosphonic acid, amine compounds and the like can also be used. Further, polyethylene glycol, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid metal salt, sulfosuccinic acid ester and the like can also be used. These dispersants are usually used in one or more kinds, and one kind of the dispersant is 0.005 with respect to 100 parts by weight of the binder.
Is added in the range of ˜20 parts by weight. The dispersant may be used by pre-coating it on the surface of the ferromagnetic powder or non-magnetic powder, or by adding it during dispersion. Such materials are disclosed, for example, in JP-B-39-28369, JP-B-44-17945, JP-B-48-15001, US Pat. No. 3,387,993, and JP-A-347002.
No. 1 specification and the like.

The antifungal agent used in the present invention is 2- (4
-Thiazolyl) -benzimidazole, N- (fluorodichloromethylthio) -phthalimide, 10,10'-
Oxybisphenoxysarcin, 2,4,5,6-tetrachloroisophthalonitrile, P-tolyljodomethylsulfone, triiodoallyl alcohol, dihydroacetate, mercury phenyloleate, bis (tributyltin) oxide, salicylani There are rides.

Examples of such materials are, for example, "Microbial disaster and prevention technology", 1972 engineering book, "Chemistry and industry" 32,
904 (1979) and the like. As the antistatic agent other than carbon black used in the present invention, conductive powder such as graphite, modified graphite, carbon black graft polymer, tin oxide-antimony oxide, tin oxide, titanium oxide-tin oxide-antimony oxide; saponin, etc. Natural surfactants; alkylene oxide-based, glycerin-based, glycidol-based, polyhydric alcohols, polyhydric alcohol esters, nonionic surfactants such as alkylphenol EO adducts; higher alkylamines, cyclic amines, hydantoin derivatives, amidoamines, ester amides , Quaternary ammonium salts, pyridine and other heterocycles, phosphonium or sulfonium, and other cationic surfactants; carboxylic acids, sulfonic acids, phosphonic acids,
Anionic surfactants containing acidic groups such as phosphoric acid, sulfuric acid ester groups, phosphonic acid esters, phosphoric acid ester groups; amino acids; aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, amphoteric surfactants such as alkyl betaine type Is used. These surfactants may be added alone or as a mixture. The amount of these surfactants used in the magnetic recording medium is 0.01 to 10 parts by weight per 100 parts by weight of the ferromagnetic powder. The amount used in the back layer is 0.01 to 3 per 100 parts by weight of the binder.
0 parts by weight. These are used as antistatic agents, but sometimes for other purposes, such as dispersion,
It may be applied as an improvement of magnetic properties, an improvement of lubricity, a coating aid, a wetting agent, a curing accelerator, or a dispersion accelerator.

The magnetic layer can be formed according to a usual method. For example, the ferromagnetic powder and the resin component and magnetic layer forming components such as an abrasive and a curing agent which are optionally blended are kneaded and dispersed with a solvent to prepare a magnetic coating, and the magnetic coating is applied to a non-magnetic support. It is possible to use the method of applying to. As the organic solvent used in the dispersion, kneading, and coating of the present invention, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran in any ratio; methanol, ethanol, propanol, butanol, isobutyl alcohol ,Isopropyl alcohol,
Alcohol such as methylcyclohexanol; ester such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate monoethyl ether; diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycol monoethyl ether, dioxane Ether-based compounds such as benzene, toluene, xylene, cresol, chlorobenzene, styrene and other tar-based compounds (aromatic hydrocarbons); methylene chloride, ethylene chloride, carbon tetrachloride,
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin and dichlorobenzene, N, N-dimethylformaldehyde, hexane and the like can be used. These solvents are usually used in two or more kinds at an arbitrary ratio. In addition, a trace amount of impurities (polymer of the solvent itself, water,
Raw material components, etc.) may be included. These solvents are used in an amount of 100 to 20,000 parts by weight based on 100 parts by weight of the total solid content of the magnetic layer forming coating material, the back layer forming coating material and the undercoat liquid. The solid content of the magnetic layer-forming coating material is preferably 10 to 4
It is 0% by weight. The solid content of the back layer coating material is preferably 5 to 20% by weight. An aqueous solvent (water, alcohol, acetone, etc.) can be used instead of the organic solvent.

The method of dispersion and kneading is not particularly limited, and the order of addition of each component (resin, powder, lubricant, solvent, etc.),
The addition position during dispersion / kneading, the dispersion temperature (0 to 80 ° C.) and the like can be set appropriately. For preparation of the magnetic layer-forming coating material and the back layer-forming coating material, a conventional kneading machine such as a two-roll mill, a three-roll mill, a ball mill, a pebble mill, a tron mill, a sand grinder, and a zegbari (Sz
egvari), attritor, high speed impeller, disperser, high speed stone mill, high speed impact mill, disperser,
Kneader, high speed mixer, ribbon blender, cokneader, intensive mixer, tumbler, blender,
A disperser, a homogenizer, a single screw extruder, a twin screw extruder, an ultrasonic disperser, etc. can be used. Usually, a plurality of these dispersing / kneading machines are provided for the dispersing / kneading, and the treatment is continuously performed. For details of the technique regarding kneading and dispersion, see T. C. PATTON (TC Patton) "Paint Flow and Pigment
Dispersion "(Paint Flow and Pigment Dispersion), published in 1964 by John Wiley & Sons (John Willie & Sons) and Shinichi Tanaka," Industrial Materials, "Vol. There is. As an auxiliary material for the dispersion and kneading, in order to efficiently carry out the dispersion and kneading, a steel ball having a diameter equivalent to a sphere of 10 cmφ to 0.05 mmφ,
Steel beads, ceramic beads, glass beads, organic polymer beads can be used. Also, these materials are not limited to spherical shapes. Also, US Pat. No. 2,581,414
No. 2855156 and the like. Also in the present invention, the magnetic coating material and the back layer coating material can be prepared by kneading and dispersing in accordance with the method described in the above-mentioned book or the references cited in the book.

As a method for applying the above-mentioned magnetic coating material and back layer coating material on a support, the viscosity of the coating liquid is 1 to 2
Prepared to 0000 centistokes (25 ° C), air doctor coat, blade coat, air knife coat,
Squeeze coat, impregnation coat, reverse roll coat,
Transfer roll coat, gravure coat, kiss coat, cast coat, spray coat, rod coat, forward rotation roll coat, curtain coat, bar coat, extrusion coat, spin coat, etc. can be used, and other methods are also possible. For a detailed explanation, see "Coating Industry" published by Asakura Shoten, pp. 253-277 (Showa 4
6.3.20. Issued).

The coating order of these coating liquids can be arbitrarily selected, and corona discharge treatment or the like may be carried out before the coating of the desired liquid in order to improve the adhesion to the undercoat layer or the support. When it is desired to form the magnetic layer or the back layer in multiple layers, simultaneous multilayer coating, sequential multilayer coating and the like may be performed. These are disclosed, for example, in JP-A-57-123532 and JP-B-62-37451.

By such a method, about 1 to 1 is formed on the support.
If necessary, the magnetic coating material applied to a thickness of about 200 μm may be dried in a multi-stage manner at 20 ° C. to 130 ° C. immediately after the ferromagnetic powder in the layer is dried at about 500 to 5000 G in a desired direction (vertical, longitudinal, width, random, oblique, etc.). ), That is, after the magnetic field orientation treatment, the formed magnetic layer is treated with
Dry to a thickness of 30 μm. The transport speed of the support at this time is usually 10 m / min to 900 m / min, the drying temperature is controlled at 20 ° C. to 130 ° C. in a plurality of drying zones, and the residual solvent amount of the coating film is 0.1 to 40 mg. / M ² .

After being dried in this way, the coating layer is optionally subjected to calendering so that the center line average roughness of the magnetic layer or the back layer is preferably set to the above-mentioned predetermined value. For calendar processing, for example, a super calendar roll or the like is used. By performing the calendering process, voids generated by removal of the solvent during drying are reduced and the filling rate of the ferromagnetic powder in the magnetic layer is improved, so that a magnetic recording medium having high electromagnetic conversion characteristics can be obtained.

In the calendering step, when a curing agent is used as a binder-forming component, 90% by weight or more of the curing agent contained in the magnetic layer is usually contained in the magnetic layer in an unreacted state. Therefore, at least 50% by weight (particularly preferably 8%) of the curing agent is subjected to a curing treatment.
It is desirable to carry out the subsequent treatment after the reaction of 0% by weight or more). The curing treatment includes a heat curing treatment and an electron beam curing treatment, and any method can be used in the present invention. The unreacted curing agent contained in the magnetic layer calendered by this curing reaction reacts with a resin component such as a vinyl chloride copolymer and a polyurethane resin to form a three-dimensional network crosslinked structure. To do. The heat treatment process itself is already known, and the heat treatment can be performed according to these methods also in the present invention. For example, the heat treatment is usually performed by setting the heating time to 40 ° C. or higher (preferably within the range of 50 to 80 ° C.) and the heating time to usually 20 hours or longer (preferably 24 hours to 7 days). Further, the process itself of the curing treatment by electron beam irradiation is already known, and the curing treatment can be carried out according to these methods also in the present invention.

In the present invention, the magnetic recording medium thus prepared is cut into a desired shape under ordinary conditions by using an ordinary cutting machine such as a slitter, and then wound on a plastic or metal reel. In the present invention, the surface of the magnetic layer thus formed, or the surface of the magnetic layer and the surface of the back layer are magnetic recording media (magnetic layer, back layer, edge end surface, base surface) immediately before or before winding. May be burnished with a polishing tape. These are disclosed, for example, in JP-A-63-259830.
It is disclosed in Japanese Patent Publication No.

In the wiping treatment of the magnetic recording medium, the surface layer of the magnetic recording medium is made of a non-woven fabric or the like for the purpose of removing dirt and surplus lubricant on the surface of the magnetic recording medium, the magnetic layer surface, the back layer surface, the edge end surface and the back side base. This is done by wiping the surface. Examples of such wiping materials include various types of Vilene made by Japan Vilene and Toraysee made by Toray, Kuraray WRP series made by Exaine and Kuraray, and non-woven fabric made of nylon, non-woven fabric made of polyester, non-woven fabric made of rayon, non-woven fabric made of acrylonitrile, A blended non-woven fabric or the like can also be used. In addition, tissue paper, Kimwipe, etc. can also be used. These are described in, for example, JP-A-1-201824. By this wiping treatment, the deposits and organic substances on the magnetic layer and / or the back layer are completely removed, and the frequency of dropout or clogging is reduced.

These production methods include powder pretreatment / surface treatment, kneading / dispersion, coating / orientation / drying, calender treatment, curing treatment (heat treatment, radiation (EB) treatment), cutting, burnishing, and wiping. It is desirable to carry out the treatment and winding steps continuously. See also
The method shown in Japanese Patent No. 3181 is considered to be a basic and important technique in this field. However, the order of processing is not limited to the above order.

Ferromagnetic powder or non-magnetic powder used in the present invention, binder, additive (lubricant, dispersant, antistatic agent, surface treatment agent, carbon black, abrasive, light-shielding agent,
An antioxidant, an antifungal agent, etc., a solvent and a support (which may have an undercoat layer, a back layer, a back undercoat) or a method for producing a magnetic recording medium are described in JP-B-56-26890. You can also refer to what you have.

[0055]

EXAMPLES The present invention will be described more specifically below with reference to examples. It is easily understood by those skilled in the art that the components, ratios, operation sequences, etc. shown here can be changed without departing from the spirit of the present invention. Therefore, the present invention should not be limited to the examples below. The parts in the examples and comparative examples are parts by weight.

[Example 1] [I] of the following magnetic coating composition
Was put in a kneader and sufficiently kneaded, then [II] was additionally charged and sufficiently kneaded, and [III] was added and mixed and dispersed before coating to prepare a magnetic coating material. After adjusting the viscosity of the obtained magnetic coating material, it was applied onto polyethylene naphthalate (Young's modulus in TD direction: 1100 Kg / mm ² ) of a non-magnetic support having a thickness of 7 μm so as to have a dry film thickness of 3 μm.

Magnetic coating composition [I] Ferromagnetic metal powder 100 parts (Fe metal powder, Al 5% by weight, specific surface area (S _BET ) 55 m ² / g) Phosphoric acid ester (phenyl sulfonic acid) 2 parts Oleic acid 0. 1 part Vinyl chloride copolymer resin 7 parts (Nippon Zeon Co., Ltd .: MR110) Polyurethane resin (Toyobo Co., Ltd .: UR8200) 4 parts 2 ethylhexyl palmitate 0.6 parts Cyclohexanone 60 parts Methyl ethyl ketone 80 parts [II] Dispersion 1 carbon black 1 part (manufactured by Cabot: Conductex SC) polyurethane resin (manufactured by Toyobo: UR8200) 1 part methyl ethyl ketone 10 parts dispersion 2 abrasive 13 parts (Sumitomo Chemical Co., Ltd .: HIT55 [α-Al ₂ O _3] vinyl copolymer resin, 1 part chloride (Nippon Zeon: MR 110) cyclohexanol Non 60 parts Methyl ethyl ketone 40 parts [III] Polyisocyanate 8 parts (Nippon Polyurethane Co .: Coronate 3040) Stearic acid dibutylamide 0.5 parts Palmitic acid 0.5 parts Butoxyethyl stearate 0.5 parts Methyl ethyl ketone 50 parts Toluene 30 parts The non-magnetic support coated with this magnetic coating is subjected to a magnetic field orientation treatment and drying in a state where the magnetic coating is undried, and subsequently the same [II] is added to the following back layer coating composition [I] immediately before coating. The magnetic coating material was applied to the back surface of the support so that the dry thickness was 0.6 μm.

Back Layer Coating Composition [I] Carbon Black 97 parts (Cabot Co .: BP800) Carbon Black 3 parts (Cancarb Co .: MTCI) α-Al ₂ O ₃ 0.1 part (Sumitomo Chemical Co., Ltd.) : HIT55) Barium sulfate 0.1 part (Sakai Chemical Co., Ltd .: BF1) 2-Ethylhexyl stearate 0.5 part Copper oleate 0.1 part Vinyl chloride copolymer resin 50 parts (Nippon Zeon Co., Ltd .: MR110) Polyurethane resin 40 parts (Toyobo Co., Ltd .: UR8300) Cyclohexanone 200 parts Methyl ethyl ketone 300 parts [II] Polyisocyanate (Nippon Polyurethane Co., Ltd .: Coronate 3040) 20 parts Methyl ethyl ketone 3500 parts Toluene 200 parts Silicone compound 0.1 part ( Shin-Etsu Chemical Co., Ltd .: KF69) Furthermore, after drying Continuing temperature to a calender treatment 90
℃, linear pressure 350Kg / cm, speed 200m / min 5
This was repeated to prepare a laminate composed of a non-magnetic support, a magnetic layer and a back layer.

This laminate was heated at 60 ° C. for 24 hours to cure the polyisocyanate compound contained in the laminate, and then slit into a 1/2 inch width to obtain a polishing tape (Fuji Photo Film Co., Ltd.). Manufactured by K10000), the surface of the magnetic layer was burnished, and then wiped using a wiping material (WRP736 manufactured by Kuraray Co., Ltd.) to prepare a 1/2 inch video tape.

The glass layer of the magnetic layer thus obtained had a glass transition temperature of 95 ° C., a surface roughness of 4 nm, and a back layer of 6 nm. [Example 2] The polyurethane resin used in the magnetic coating compositions [I] and [II] in Example 1 was replaced with UR55.
A magnetic coating composition was prepared in the same manner as in Example 1 except that the composition was changed to 00 (manufactured by Toyobo Co., Ltd.).

After adjusting the viscosity of the obtained magnetic paint, it was applied onto a polyethylene naphthalate (Young's modulus in the TD direction of 1500 Kg / mm ² ) of a non-magnetic support having a thickness of 7 μm so as to have a dry film thickness of 3 μm. . The obtained laminate was treated in the same manner as in Example 1 to prepare a 1/2 inch video tape. The glass transition temperature of the magnetic layer of the obtained laminate is 9
The surface roughness was 0 nm, the surface roughness was 4.2 nm, and the surface roughness of the back layer was 6.5 nm.

Example 3 The polyurethane resin used in the magnetic coating compositions [I] and [II] in Example 1 was replaced with U.
A magnetic coating composition was prepared in the same manner as in Example 1 except that R8600 (manufactured by Toyobo Co., Ltd.) was used. After adjusting the viscosity of the obtained magnetic coating material, polyethylene naphthalate (Young's modulus in the TD direction of 1800
Kg / mm ² ) and applied to give a dry film thickness of 3 μm.

The obtained laminate was treated in the same manner as in Example 1 to prepare a 1/2 inch video tape. The magnetic layer of the obtained laminate had a glass transition temperature of 85 ° C. and a surface roughness of 4.
It was 5 nm, and the surface roughness of the back layer was 7.0 nm. [Comparative Example 1] [I] of the following magnetic coating composition was put in a kneader and sufficiently kneaded, then [II] was additionally added and sufficiently kneaded, and [III] was added and mixed and dispersed before coating to obtain a magnetic coating composition. Created.

After adjusting the viscosity of the obtained magnetic coating material, it was coated on a polyethylene naphthalate (Young's modulus in the TD direction 900 Kg / mm ² ) of a non-magnetic support having a thickness of 7 μm so as to have a dry film thickness of 3 μm. . Magnetic coating composition [I] Ferromagnetic metal powder 100 parts (Fe metal powder, Al 5% by weight, specific surface area (S _BET ) 55 m ² / g) Phosphate ester (phenylsulfonic acid) 2 parts Oleic acid 0.1 part Chloride Vinyl copolymer resin 9.5 parts (manufactured by Nippon Zeon Co., Ltd .: MR110) Polyurethane resin (manufactured by Toyobo Co., Ltd .: UR8600) 5 parts 2 ethylhexyl palmitate 0.6 parts cyclohexanone 60 parts methyl ethyl ketone 80 parts [II] Dispersion 1 Carbon black 1 part (Cabot Corporation: Conductex SC) Polyurethane resin (Toyobo Co., Ltd .: UR8600) 1 part Methyl ethyl ketone 10 parts Dispersion 2 Abrasive material 13 parts (Sumitomo Chemical Co., Ltd .: HIT55 [α-Al ₂ O ₃ ]) Vinyl chloride copolymer resin 1 part (manufactured by Nippon Zeon Co., Ltd .: MR110) Cyclohexanone 0 parts Methyl ethyl ketone 40 parts [III] Polyisocyanate 4.5 parts (Nippon Polyurethane Co .: Coronate 3040) Stearic acid dibutylamide 0.5 parts Palmitic acid 0.5 parts Butoxyethyl stearate 0.5 parts Methyl ethyl ketone 50 parts Toluene 30 The obtained laminate was treated in the same manner as in Example 1 to give 1/2.
I made an inch videotape. The magnetic layer of the obtained laminate had a glass transition temperature of 70 ° C., a surface roughness of 3.9 nm and a back layer of 7.5 nm.

[Comparative Example 2] A laminate was prepared in the same manner as in Example 1 except that the TD direction Young's modulus of the non-magnetic support was changed to 1500 kg / mm ² of polyethylene naphthalate. The obtained laminated body was treated in the same manner as in Example 1 to prepare a 1/2 inch video tape.

The magnetic layer of the obtained laminate had a glass transition temperature of 70 ° C., a surface roughness of 4.0 nm and a back layer of 8.0 nm. [Comparative Example 3] [I] of the following magnetic coating composition was put in a kneader and sufficiently kneaded, then [II] was additionally added and sufficiently kneaded, and [III] was added and mixed and dispersed before coating to obtain a magnetic coating. Created.

After adjusting the viscosity of the obtained magnetic paint, it was applied onto a polyethylene naphthalate (Young's modulus in the TD direction 900 Kg / mm ² ) of a non-magnetic support having a thickness of 7 μm so as to have a dry film thickness of 3 μm. . Magnetic coating composition [I] Ferromagnetic metal powder 100 parts (Fe metal powder, Al 5% by weight, specific surface area (S _BET ) 55 m ² / g) Phosphate ester (phenylsulfonic acid) 2 parts Oleic acid 0.1 part Chloride Vinyl copolymer resin 7.5 parts (Nippon Zeon Co., Ltd .: MR110) Polyurethane resin (Toyobo Co., Ltd .: UR8200) 1.5 parts Diethylhexyl palmitate 0.6 parts Cyclohexanone 60 parts Methyl ethyl ketone 80 parts [II] dispersion Item 1 Carbon black 1 part (Cabot Corporation: Conductex SC) Polyurethane resin (Toyobo Co., Ltd .: UR8200) 1 part Methyl ethyl ketone 10 parts Dispersion 2 Abrasive material 13 parts (Sumitomo Chemical Co., Ltd .: HIT55 [α-Al ₂ O ₃ ] Vinyl chloride copolymer resin 1 part (manufactured by Nippon Zeon Co., Ltd .: MR110) Cyclohexanone 60 parts Methyl ethyl ketone 40 parts [III] Polyisocyanate 8.5 parts (Nippon Polyurethane Co .: Coronate 3040) Stearic acid dibutylamide 0.5 parts Palmitic acid 0.5 parts Butoxyethyl stearate 0.5 parts Methyl ethyl ketone 50 parts Toluene 30 The obtained laminate was treated in the same manner as in Example 1 to give 1/2.
I made an inch videotape. The glass layer of the magnetic layer thus obtained had a glass transition temperature of 102 ° C., a surface roughness of 4.4 nm, and a back layer of 6.5 nm.

[Comparative Example 4] In Comparative Example 3, the non-magnetic support was used.
Young's modulus of holding body in TD direction is 1500 kg / mm ²Po
Same as Example 1 except that the ethylene naphthalate was changed.
A laminate was prepared in this manner, and the obtained laminate was referred to as Example 1.
A 1/2 inch video tape was prepared by performing the same process.

The magnetic layer of the obtained laminate had a glass transition temperature of 102 ° C., a surface roughness of 4.3 nm and a back layer of 5.5 nm. [Comparative Example 5] A laminated body was prepared in the same manner as in Example 1 except that the ferromagnetic metal powder in Comparative Example 3 was changed to have a specific surface area (S _BET ) of 45 m ² / g. The body was treated in the same manner as in Example 1 to prepare a 1/2 inch video tape.

The magnetic layer of the obtained laminate had a glass transition temperature of 102 ° C., a surface roughness of 5.0 nm, and a back layer of 6 nm. [Evaluation method] Output difference The obtained tape was D3VTR AJ-D350P (core width: 130) manufactured by Matsushita Electric Industrial at 25 ° C and 70% RH.
μm, relative speed between magnetic head and tape: 21.4 m /
Second) Sony Tektronix color signal generator TS
-170D is used to record / reproduce the color bar signal, and the reproduction output waveform is measured for all four channels with the Advantest spectrum analyzer TR4171 to obtain the average output, and the output with the standard tape is also measured. I asked for the difference.

Dropout (DO) The obtained tape was subjected to D3VTR AJ-D350P (core width: 130) manufactured by Matsushita Electric Industrial at 25 ° C. and 50% RH.
μm) Sony Tektronix color signal generator T
The S-170OD is used to record / reproduce the color bar signal, and the Shiba Soku DO counter VH02AZ is used to measure the output of -8 dB or more and the length of 0.2 μsec or more for 10 minutes every 10 seconds. , And the average value was obtained.

The results obtained are shown in Table 1.

[0073]

[Table 1]

As is clear from the examples in Table 1, the magnetic recording medium of the present invention has a Young's modulus in the width direction of the non-magnetic support of 1000 Kg / mm ² or more and a glass transition temperature (Tg) of the magnetic layer. The magnetic recording medium having a temperature of 80 ° C. or higher and 100 ° C. or lower can improve the head contact of a thin tape having a total thickness of less than 12 μm, can maintain a high output, and is less likely to cause dropout. Then
A remarkable effect is recognized.

[0075]

As described above, the present invention provides a magnetic recording medium in which a magnetic layer containing a ferromagnetic powder, a binder, an additive and, preferably, an abrasive having a Mohs hardness of 8 or more is formed on a non-magnetic support. A magnetic recording medium characterized in that the non-magnetic support of the magnetic recording medium has a Young's modulus in the width direction of 1000 Kg / mm ² or more and the glass transition temperature of the magnetic layer is 80 ° C. or more and 100 ° C. or less. Improves the head contact of thin magnetic tape with a total thickness of less than 12 μm for a wide head with a width of 80 μm or more in the direction perpendicular to the scanning direction of the head sliding surface in a VTR, especially a digital VTR, and maintains high output, and dropout It is possible to provide a magnetic recording medium that is less likely to occur. Further, the ferromagnetic powder of the magnetic layer is a fine metal powder having a specific surface area of 47 m ² / g or more, and the surface roughness of the magnetic layer is 1 nm or more and 5 nm or less, so that higher output can be obtained. In addition, by providing a back layer having a surface roughness of 2 nm to 10 nm on the back surface of the non-magnetic support provided with a magnetic layer, extremely excellent running durability can be obtained.

[Procedure amendment]

[Submission date] December 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

Further, the diameter of the cylinder head is reduced in order to reduce the size of the VTR and the space of the magnetic recording medium, and the track of the magnetic tape is narrowed to improve the area density of recording, and the volume is reduced to improve the volume density. Is required. Particularly, in the case of a thin tape of about 11 μm, 5400 to 90
It is very difficult for a small-diameter head that rotates at a high speed of about 00 rpm to stably run at a high speed of 20 m / sec or more at a magnetic tape / head relative speed. The tendency tends to increase as

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

The total thickness of the magnetic recording medium of the present invention is 12 μm.
It can be set to less than 11 μm, particularly, and it is advantageous because the head contact can be secured and the recording can be performed for a long time. Further, the total thickness of the magnetic recording medium refers to the total thickness of the magnetic recording medium including the thickness of the non-magnetic support, the thickness of the magnetic layer and the back layer provided as necessary. In order to obtain a high output, the surface roughness of the magnetic layer should be the center line average surface roughness Ra.
1.5 to 4.5 nm (cutoff value 0.25 mm),
Preferably 2-4 μm, particularly preferably 2.5-3.
The range is 5 μm, a ferromagnetic metal powder is selected as the ferromagnetic powder to be used, and its specific surface area is 47 m ² / g or more, preferably 53 to 70 m ² / g, and particularly preferably,
5 in the range of 5 ~6 5 m ² / g.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

[0020] Also, polyethylene naphthalate in the invention, including e styrene-2,6-naphthalene dicarboxylate homopolymer, ethylene-2,6-naphthalene dicarboxylate repeating copolymers containing units 70 wt% or more , A mixture of these and other polymers (however,
The PEN component accounts for 70% by weight or more), and the polyester composition essentially does not lose the properties of PEN. This PEN is a film-forming polymer.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0057

[Correction method] Change

[Correction content]

[0057] Magnetic coating composition (I) the ferromagnetic metal powder 100 parts (Fe metal powder, Al 5 wt%, the specific surface area (S _BET) 55m ² / g) phosphate (phenylphosphonic acid) 2 parts of oleic acid 0 1 part Vinyl chloride copolymer resin 7 parts (Nippon Zeon Co., Ltd .: MR110) Polyurethane resin (Toyobo Co., Ltd .: UR8200) 4 parts 2 ethylhexyl palmitate 0.6 parts Cyclohexanone 60 parts Methyl ethyl ketone 80 parts [II] dispersion Item 1 Carbon black 1 part (Cabot Corporation: Conductex SC) Polyurethane resin (Toyobo Co., Ltd .: UR8200) 1 part Methyl ethyl ketone 10 parts Dispersion 2 Abrasive material 13 parts (Sumitomo Chemical Co., Ltd .: HIT55 [α-Al ₂ O _3] vinyl chloride copolymer resin, 1 part (Nippon Zeon: MR 110) Shikurohe Sanon 60 parts Methylethylketone 40 parts [III] Polyisocyanate 8 parts (Nippon Polyurethane Co .: Coronate 3040) Stearic acid dibutylamide 0.5 parts Palmitic acid 0.5 parts Butoxyethyl stearate 0.5 parts Methylethylketone 50 parts Toluene 30 parts The non-magnetic support coated with this magnetic coating is subjected to a magnetic field orientation treatment and drying in a state where the magnetic coating is undried, and subsequently the same [II] is added to the following back layer coating composition [I] immediately before coating. The magnetic coating material was applied to the back surface of the support so that the dry thickness was 0.6 μm.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0058

[Correction method] Change

[Correction content]

Back Layer Coating Composition [I] Carbon Black 97 parts (Cabot Co .: BP800) Carbon Black 3 parts (Cancarb Co .: MTCI) α-Al ₂ O ₃ 0.1 part (Sumitomo Chemical Co., Ltd.) : HIT55) Barium sulfate 0.1 part (Sakai Chemical Co., Ltd .: BF1) 2-Ethylhexyl stearate 0.5 part Copper oleate 0.1 part Vinyl chloride copolymer resin 50 parts (Nippon Zeon Co., Ltd .: MR 110) 40 parts polyurethane resin (manufactured by Toyobo Co., Ltd.: UR8300) 200 parts Methyl ethyl ketone 300 parts cyclohexanone (II) polyisocyanate (Nippon polyurethane Co., Ltd.: Coronate 3040) 0.1 parts 20 parts Methyl ethyl ketone 3500 parts toluene 200 parts silicone compound In addition, after drying, continue calendering at a temperature of 9 0
℃, linear pressure 350Kg / cm, speed 200m / min 5
This was repeated to prepare a laminate composed of a non-magnetic support, a magnetic layer and a back layer.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0064

[Correction method] Change

[Correction content]

After adjusting the viscosity of the obtained magnetic coating material, it was coated on a polyethylene naphthalate (Young's modulus in the TD direction 900 Kg / mm ² ) of a non-magnetic support having a thickness of 7 μm so as to have a dry film thickness of 3 μm. . Magnetic coating composition (I) the ferromagnetic metal powder 100 parts (Fe metal powder, Al 5 wt%, the specific surface area (S _BET) 55m ² / g) phosphate (phenylphosphonic acid) 2 parts 0.1 parts of oleic acid Vinyl chloride copolymer resin 9.5 parts (Nippon Zeon Co., Ltd .: MR110) Polyurethane resin (Toyobo Co., Ltd .: UR8600) 5 parts 2 ethylhexyl palmitate 0.6 parts Cyclohexanone 60 parts Methyl ethyl ketone 80 parts [II] Dispersion 1 carbon black 1 part (made by Cabot: Conductex SC) polyurethane resin (made by Toyobo: UR8600) 1 part methyl ethyl ketone 10 parts dispersion 2 abrasive 13 parts (Sumitomo Chemical Co., Ltd .: HIT55 [α-Al ₂ O ₃ ]) Vinyl chloride copolymer resin 1 part (Nippon Zeon Co., Ltd .: MR110) Cyclohexanone 60 parts Methyl ethyl ketone 40 parts [III] Polyisocyanate 4.5 parts (Nippon Polyurethane Company: Coronate 3040) Stearic acid dibutylamide 0.5 parts Palmitic acid 0.5 parts Butoxyethyl stearate 0.5 parts Methyl ethyl ketone 50 parts Toluene 30 The obtained laminate was treated in the same manner as in Example 1 to give 1/2.
I made an inch videotape. The magnetic layer of the obtained laminate had a glass transition temperature of 70 ° C., a surface roughness of 3.9 nm and a back layer of 7.5 nm.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction content]

After adjusting the viscosity of the obtained magnetic paint, it was applied onto a polyethylene naphthalate (Young's modulus in the TD direction 900 Kg / mm ² ) of a non-magnetic support having a thickness of 7 μm so as to have a dry film thickness of 3 μm. . Magnetic coating composition (I) the ferromagnetic metal powder 100 parts (Fe metal powder, Al 5 wt%, the specific surface area (S _BET) 55m ² / g) phosphate (phenylphosphonic acid) 2 parts 0.1 parts of oleic acid Vinyl chloride copolymer resin 7.5 parts (manufactured by Nippon Zeon Co., Ltd .: MR110) Polyurethane resin (Toyobo Co., Ltd .: UR8200) 1.5 parts Diethylhexyl palmitate 0.6 parts Cyclohexanone 60 parts Methyl ethyl ketone 80 parts [II] Dispersion 1 Carbon black 1 part (Cabot Corporation: Conductex SC) Polyurethane resin (Toyobo Co., Ltd .: UR8200) 1 part Methyl ethyl ketone 10 parts Dispersion 2 Abrasive material 13 parts (Sumitomo Chemical Co., Ltd .: HIT55 [α-Al ₂ O ₃ ] Vinyl chloride copolymer resin 1 part (manufactured by Nippon Zeon Co., Ltd .: MR110) Cyclohexano 60 parts Methyl ethyl ketone 40 parts [III] Polyisocyanate 8.5 parts (Nippon Polyurethane Co .: Coronate 3040) Stearic acid dibutylamide 0.5 parts Palmitic acid 0.5 parts Butoxyethyl stearate 0.5 parts Methyl ethyl ketone 50 parts Toluene 30 parts The obtained laminate was treated in the same manner as in Example 1 to give 1/2.
I made an inch videotape. The glass layer of the magnetic layer thus obtained had a glass transition temperature of 102 ° C., a surface roughness of 4.4 nm, and a back layer of 6.5 nm.

Claims (5)

[Claims] 1. A magnetic recording medium having a magnetic layer containing a ferromagnetic powder and a binder as a main component on a tape-shaped non-magnetic support, and the non-magnetic support has a Young's modulus in the width direction of 100.
A is 0 kg / mm ² or more, the glass transition temperature of the magnetic layer (Tg) is that 80 to 100 ° C., a magnetic recording medium, wherein the total thickness of the magnetic recording medium is less than 12 [mu] m. 2. A magnetic recording medium having a magnetic layer mainly composed of a ferromagnetic powder and a binder on a tape-shaped non-magnetic support, wherein the non-magnetic support has a Young's modulus in the width direction of 100.
0 kg / mm ² or more, the glass transition temperature (Tg) of the magnetic layer is 80 to 100 ° C., and the total thickness is 12
A magnetic recording medium, characterized in that the magnetic recording medium having a core width of 100 μm or more is used at a relative speed of 20 m / sec or more. 3. The center line average roughness Ra of the magnetic layer is 1.
The magnetic recording medium according to claim 1, which has a thickness of 5 to 4.5 nm (cutoff value of 0.25 mm). 4. The specific surface area of the ferromagnetic powder is 47 m ² /
The magnetic recording medium according to claim 1 or 2, which is a ferromagnetic metal powder of g or more. 5. The center line average roughness Ra is 2 to 10 nm on the surface of the non-magnetic support opposite to the surface having the magnetic layer.
3. The magnetic recording medium according to claim 1, further comprising a back layer having a cutoff value of 0.25 mm.