JP3365800B2 - Magnetic recording medium and magnetic recording / reproducing method - Google Patents

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

In particular, the D developed as a digital VTR
Not only is the relative speed of the magnetic tape / magnetic head as high as 20 m or more as in the 3 system, but the head core width is 1
When the width is larger than 00 μm, the gap between the magnetic head and the magnetic tape becomes large, and the head contact deteriorates as the output itself becomes smaller. In addition, the magnetic tape usually has carbon black or Mohs hardness of 8 to secure running property, charging property and head cleaning property.
Although non-magnetic particles called an abrasive as described above are used, head wear tends to increase due to an increase in the relative speed of the magnetic tape / head due to high-speed conveyance of the magnetic tape and 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 recording 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. Further, it is generally known that the filling degree is improved by performing metal-metal calendering in the calendering process of the magnetic tape in order to obtain a high-output magnetic recording medium (Japanese Patent Publication No. Sho 60-35243). ) Since the surface porosity of the magnetic layer is decreased, the hardness is increased and the cushioning property is deteriorated. As a result, the head contact is rather deteriorated and it is not enough to obtain a high output.

Summarizing the flow of the above prior art,
It can be summarized as follows. Digitization → Increased amount of recorded information / High density recording (higher output) → Improvement of volume density of magnetic recording medium (hereinafter also referred to as medium) / Higher filling of magnetic material → Thinning of tape / Head / medium Of the relative speed of the magnetic disk → deterioration of the head contact of the medium / increase of wear of the magnetic head → increase of the head core width / deterioration of the cushioning property of the magnetic layer →
The head contact of the medium is further deteriorated / reduced in output. That is, with the above-mentioned technique, the contact of the magnetic tape with the head is accompanied by the thinning of the tape, the high density of the ferromagnetic powder and the widening of the head sliding surface. It was not possible to sufficiently improve the output reduction due to the nonuniformity.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium capable of improving the head contact of a VTR, especially a digital VTR, and maintaining a high output.

[0012]

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, the magnetic recording medium comprising: The thickness is less than 12 μm, the Young's modulus in the width direction of the non-magnetic support is 1000 Kg / mm ² or more, and the non-magnetic support is obtained from the total pore volume by N ₂ gas adsorption of the magnetic layer.
An order is surface porosity 15% to 35%, the residual magnetic flux density Br of the magnetic layer is at 2800 gauss or more, the
The non-magnetic support is a polyester support and is magnetic
A magnetic recording medium characterized in that a back layer is provided on a support opposite to the layer , and the magnetic recording medium comprises a magnetic head having a magnetic head having a core width of 100 μm or more. The magnetic recording / reproducing method is characterized in that recording / reproducing is performed by the cylinder head under the condition that the relative speed between the magnetic head and the magnetic recording medium is 20 m / sec or more.

That is, the inventors of the present invention have Young's modulus of the non-magnetic support in the width direction of 1000 kg / mm ² or more, and surface porosity of the magnetic layer of 15% or more and 35% or less, more preferably 20 to 30%. By this, the mechanical characteristics of the entire magnetic recording medium are improved, thereby improving the head contact with the magnetic tape and ensuring a high filling of the ferromagnetic powder to keep the residual magnetic flux density high, so that high output can be maintained. The inventors have found the above facts and completed the present invention.

In the present invention, when the surface porosity is less than 15%, the cushioning property of the magnetic layer is lowered, the contact between the magnetic layer and the magnetic head is lowered, and the surface porosity is 35.
If it exceeds%, the packing ratio of the ferromagnetic powder is lowered and the output is lowered, which is not preferable. Further, in the present invention, the Young's modulus in the width direction (TD direction) of the non-magnetic support needs to be 1000 kg / mm ² or more, and the Young's modulus is 1 or less.
If it is less than 000 Kg / mm ² , the head contact cannot be sufficiently improved even if the surface porosity is 15% or more. Further, even if the Young's modulus is 1000 kg / mm ² or more, if the surface porosity is 35% or more, the filling degree of the ferromagnetic powder is insufficient and a sufficient output cannot be obtained.

That is, according to the present invention, the stiffness of the magnetic recording medium is defined by the Young's modulus in the width direction of the non-magnetic support and the cushioning property of the magnetic layer is defined by the surface porosity. It is considered that the magnetic recording medium is prevented from being drawn into the gap between the conventional head core and the cylinder, and at the same time, the magnetic layer surface comes into contact with the head surface so as to follow the head surface. It is possible to secure the filling rate of the ferromagnetic powder and obtain a high output.

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, Width of 80 μm or more, preferably 100 μm or more, especially 12
A VTR using a wide head of 0 μm or more, especially 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, the thickness of the nonmagnetic support, the thickness of the entire magnetic recording medium including a thickness of the magnetic layer及beauty bar click layer refers. In order to obtain a high output, the residual magnetic flux density Br is 2800 Gauss or more, preferably 2800 to 3
It is in the range of 500 Gauss, particularly preferably 2850 to 3300 Gauss, and the surface roughness of the magnetic layer is 1.5 to 4.5 nm in terms of center line average surface roughness Ra (cutoff value 0.25).
mm), preferably 2 to 4 nm, particularly preferably 2.
The range is 5 to 3.5 nm, the ferromagnetic metal powder is selected as the ferromagnetic powder to be used, and the specific surface area is 47 m.
² / g or more, preferably 53 to 70 m ² / g, and particularly preferably 50 to 60 m ² / g.

Further, a back layer having a center line average surface roughness Ra of 2 to 15 nm (cutoff value 0.25 mm) is provided on the back surface of the non-magnetic support having a magnetic layer coated for stable running. It is preferable to provide. The magnetic recording medium comprises a nonmagnetic support, consisting of a back layer provided on the opposite side of the supporting magnetic layer provided on body and magnetic layer. The magnetic layer is a ferromagnetic powder and, if necessary, powdery components such as carbon black, an abrasive, and a powdery lubricant, and a coating film in which these powdery components are dispersed in a binder. The binder is composed of a resin component and a curing agent that is blended if necessary.

In order to set the surface porosity of the magnetic layer of the present invention within the stated range, it can be adjusted by the blending amount of the resin and the additive used as the binder of the magnetic layer, but it is a non-magnetic support. It can be set most efficiently by controlling the calendering method and conditions after coating and forming the magnetic layer thereon. In particular, an apparatus used for calendering is preferably an apparatus in which a plurality of metal rolls are arranged in parallel, and, for example, a super calender roll is used.

The metal-metal calender roll may be composed of at least one pair of metal rolls, and is preferably composed of metal rolls having three or more stages.
A plurality of roll devices having various characteristics may be combined. Examples of the material of the metal roll include carbon steel and chrome molybdenum steel, and especially surface shore hardness 5
It is 0 ° to 95 °, preferably 60 ° to 90 °. The center line average surface roughness Ra of the roll surface is 1 to 10 nm at a cutoff value of 0.25 mm, preferably 1 to 5 n.
m.

Particularly, a preferred embodiment in the case of being constituted by three-stage rolls includes a constitution in which the upper and lower rolls are flat rolls and the intermediate rolls are crown rolls.
The calendering conditions are a temperature of 40 to 120 ° C., particularly preferably 60 to 90 ° C., and a linear pressure of 40 to 200 Kg / c.
m, especially 50 to 150 kg / cm, and the processing speed is 40 to 300 m / min. The number of passages between the rolls is a total of 2 or more, preferably 4 to 8 times.

By carrying out the above-mentioned calendar processing,
A magnetic recording medium having high electromagnetic conversion characteristics is provided because the surface porosity is ensured within the range of the present invention and the number of voids generated by removal of the solvent during drying is reduced and the filling rate of the ferromagnetic powder in the magnetic layer is improved. it can. If you use an elastic roll of ordinary cotton, nylon, or epoxy resin, you can keep the surface porosity large and the head hits well, but if the pressure increases above a certain level, the contact area between the roll and the object to be processed is flat. Since the roll area hitting the surface of the magnetic layer is increased due to the deformation, the effective pressure is lowered, the filling degree of the ferromagnetic powder particles is lowered, and high output cannot be obtained, which is not preferable.

On the other hand, in the case of the metal roll and the calendar of the metal roll, there is almost no deformation of the roll such that the roll area that contacts the surface of the magnetic layer becomes large. Therefore, by appropriately selecting the temperature and pressure conditions, the magnetic layer The filling degree of the ferromagnetic powder can be increased while keeping the surface porosity large. In a normal metal roll-metal roll calender device, when the pressure applied to the roll is changed, the bending of the roll also changes, so that it is not possible to apply a uniform pressure in the width direction of the roll. By using a roll with a variable crown shape (crown roll), it is possible to apply a uniform force in the width direction at all times, so apply an appropriate pressure that satisfies both the surface porosity and the filling rate of the ferromagnetic powder. It is particularly preferable because it can be easily performed. In addition, in a three-stage roll having a configuration in which the above-mentioned crown roll is replaced by a roll whose crown shape is not variable, the filling rate of the ferromagnetic powder can be increased,
It is difficult to properly adjust the surface porosity.

The surface porosity of the magnetic layer can be calculated by measuring the total pore volume by N ₂ gas adsorption under the temperature of liquid nitrogen using an autosorb. That is, saturated absorption of nitrogen
The nitrogen partial pressure is gradually increased from the adsorption curve and saturated adsorption state
It can be calculated from the desorption curve when decreasing
It Specifically, the surface porosity is AUTOSO manufactured by QUANTACHROME.
Using RB-1 SORPTION SYSTEM Model. AS-1
You can As the non-magnetic support used in the present invention,
The thickness is preferably about 5 to 10 μm, particularly about 6 to 9 μm, and the Young's modulus in the width direction is 1000 kg / mm ² or more, and particularly 1200 kg / mm ² or more. The Young's modulus in the longitudinal direction is in the range of 400 to 1200 Kg / mm ² , preferably 450 to 1000 Kg / mm ² .

As the material, polyester type such as polyethylene terephthalate and polyethylene naphthalate , particularly preferably polyethylene naphthalate (PEN) is used. 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. Regarding these supports, for example, West German Patent 3338854.
A specification, JP-A-59-116926, U.S. Pat. No. 4,388,368; Yukio Mitsuishi, "Fiber and Industry".
31, p50-55, 1975, etc. The center line average surface roughness of these supports is 0.001.
.About.0.5 .mu.m (cutoff value 0.25 mm) is preferable.

The polyethylene naphthalate used in the present invention includes a polyethylene-2,6-naphthalenedicarboxylate homopolymer, a copolymer containing 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 type 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 hardness of metallic iron among them, 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 alloy 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) Yes Kisanshio method (mainly an oxalate) reducing with a reducing gas such as hydrogen. (B) A method of reducing iron oxide with a reducing gas such as hydrogen to obtain Fe or Fe—Co particles. (C) A method of thermally decomposing a metal carbonyl compound. (D) Sodium borohydride in an aqueous solution of ferromagnetic metal,
A method of reducing by adding a reducing agent such as hypophosphite or hydrazine. (E) A method in which a ferromagnetic metal powder is electrolytically deposited using a mercury cathode and then separated from mercury. (F) A method of obtaining a fine powder by evaporating a metal in a low pressure inert gas.

As the ferromagnetic powder used in the present invention, plate-shaped 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. The specific gravity of barium ferrite is 4-6 g / cc, a specific surface area is 1m ² / g~70m ² / g. Also, if desired,
FeO _x (X = 1.33 to 1.50), Co-containing FeO
_X etc. can also be used.

As the resin component of the binder used in the magnetic layer and back layer of the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, electron beam curable resins, ultraviolet curable resins, A visible light curable resin or a mixture thereof is used. The thermoplastic resin has a softening temperature of 150 ° C. or lower, a number average molecular weight of 10,000 to 300,000, and a degree of polymerization of about 50 to 2000, more preferably 20.
0 to 600, for example, vinyl chloride vinyl acetate copolymer, vinyl chloride polymer, vinyl chloride vinyl acetate vinyl alcohol copolymer, vinyl vinylidene chloride copolymer, vinyl acrylonitrile chloride 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 Conductors (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.), a metal oxide catalyst, or a catalyst such as iron acetylacetonate. It is desirable that these compounds having a hydroxyl group or an amino group are polyfunctional. These polyisocyanates are 2 to 100 parts by weight of the total amount of the binder resin and the polyisocyanate in both the magnetic layer and the back layer.
It is preferable to use 70 parts by weight, and more preferably 5 to 50 parts by weight. Examples of these are disclosed in JP-A-60-
No. 131622 and JP-A No. 61-74138.

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, the acidic group (M such as sulfuric acid (OSO ₃ M) and ester groups, H, alkali metal, alkaline earth <br/> metals), amino acids, amino Sulfonic acids, sulfuric acid or phosphoric acid esters of aminoalcohols, amphoteric groups such as alkylbetaine type, amino groups, imino groups, imide groups, amide groups, etc. Further, hydroxyl groups, alkoxyl groups, thiol groups, alkylthio groups, halogen groups (F , Cl, Br, I), silyl group, siloxane group, epoxy group, isocyanato group,
It is preferable that the cyano group, the nitrile group, the oxo group, the acrylic group, and the phosphine group are usually contained in one or more and 6 or less, and each functional group is contained in an amount of 1 × 10 ⁻⁶ equivalent to 1 × 10 ⁻² equivalent per 1 g of the resin.

As the carbon black used in the magnetic layer and the back layer of the present invention, furnace for rubber, thermal for rubber, black for color, acetylene black and the like can be used. These carbon blacks are used for the purpose of preventing electrification of the tape, shading, adjustment of friction coefficient, improvement of durability and the like. Some examples of carbon black abbreviations in the United States are SAF, ISAF, IISAF, T, and HA.
F, SPF, FF, FEF, HMF, GPF, APF, SRF, MPF,
ECF, SCF, CF, FT, MT, HCC, HCF, MCF, LFF,
There are RCFs and the like, and those classified into ASTM standard D-1765-82a in the United States can be used. The average particle size of these carbon blacks used in the present invention is 5 to 1000.
nm (electron microscope), specific surface area by nitrogen adsorption method 1 to 800 m
² / g, pH is 4 to 11 (JIS standard K-6221-1982 method), dibutyl phthalate (DBP) oil absorption is 10 to 800 mL (milliliter) / 100 g (JIS standard K-6221-1982 method). The size of carbon black used in the present invention is 5 to 100 nm for the purpose of lowering the surface electric resistance of the coating film, and 50 to 1000 when controlling the strength of the coating film.
nm carbon black can be used. In addition, for the purpose of controlling the surface roughness of the coating film, finer carbon black is used for smoothing to reduce spacing loss.
Coarse particles of carbon black (100 nm or more) are used for the purpose of roughening the surface (less than 100 nm) to reduce the friction coefficient. 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.

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 for improving 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 of Mohs hardness of 6 or more, preferably Mohs hardness of 8 or more. Used in combination. As these abrasives, those having an average particle size of 0.005 to 5 μm are used, 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-based lubricant, silicone oil (dialkyl polysiloxane, dialkoxy polysiloxane, phenyl polysiloxane, fluoroalkyl polysiloxane (KF96, KF69 manufactured by Shin-Etsu Chemical Co., Ltd.)
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, nitrogen- and sulfur-containing heterocyclic compounds such as triazaindolizine, tetraazaindene, benzotriazole, benzodiazole, EDTA, etc., C10 ~ 40 monobasic fatty acids and any one or more of monohydric alcohols or dihydric alcohols having 2 to 40 carbon atoms, dihydric alcohols, trihydric alcohols, tetrahydric alcohols, hexahydric alcohols Fatty acid ester consisting A fatty acid ester comprising a monobasic fatty acid having 10 or more carbon atoms and a monovalent to hexavalent alcohol having a carbon number of 11 to 70 in total with the carbon number of the fatty acid, and a fatty acid having 8 to 40 carbon atoms Alternatively, fatty acid amides, fatty acid alkylamides, and fatty alcohols can 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.
Ethyl pentyl, 2-hexyldecyl stearate, isotridecyl stearate, stearic acid amide, stearic acid alkylamide, butoxyethyl stearate,
Anhydrosorbitan monostearate, anhydrosorbitan distearate, anhydrosorbitan tristearate, anhydrosorbitan tetrastearate, oleyl oleate, oleyl alcohol, lauryl alcohol, montan wax, carnauba wax, etc. alone or in combination Can be used.

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.

Examples of the dispersant and dispersion aid used in the present invention include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid and stearolic acid. , Fatty acids having 2 to 40 carbon atoms such as behenic acid, maleic acid and phthalic acid (R ₁ COOH, R ₁ is 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.), metal soap (copper oleate) composed of NH ₄ ⁺ , Cu, Pb, etc., fatty acid amide; lecithin (soybean oil lecithin), etc. Is 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 includes 2- (4
-Thiazolyl) -benzimidazole, N- (fluorodichloromethylthio) -phthalimide, 10,10'-
Oxybisphenoxysarcin, 2,4,5,6-tetrachloroisophthalonitrile, P-tolyldiiodomethylsulfone, triiodoallyl alcohol, dihydroacetoic acid, mercury phenyloleate, bis (tributyltin) oxide, salicyl There are aniride etc.

Examples of such materials include "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; nonionic surfactants such as alkylene oxide-based, glycerin-based, glycidol-based, polyhydric alcohols, polyhydric alcohol esters, and 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 group, phosphonic acid ester, phosphoric acid ester group; 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 preparing 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.W. 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. 25, 37 (1977), and other references cited in the book. 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 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 about 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 preferably subjected to the above-mentioned calendering treatment so that the center line average roughness of the magnetic layer or the back layer is preferably set to the predetermined value. In the calendered stage above,
When a curing agent is used as a component for forming the binder, 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. 50% by weight of the curing agent (particularly preferably 8
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 normal conditions using a normal 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 excess 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 a wiping material include various types of Vilene made by Japan Vilene and Toray Toray made by Toray, Kuraray WRP series made by Exaine and Kuraray, and nylon nonwoven fabrics, polyester nonwoven fabrics, rayon nonwoven fabrics, acrylonitrile nonwoven fabrics, 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, calendar 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.

[0059]

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.

[0061] 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 vinyl chloride co Polymer resin 11 parts (manufactured by Nippon Zeon Co., Ltd .: MR110) Polyurethane resin (manufactured by Toyobo Co., Ltd .: UR8200) 4.5 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: UR5500) 1 part Methyl ethyl ketone 10 parts Dispersion 2 Abrasive 13 parts (Sumitomo Chemical Co., Ltd .: HIT55 [α-Al ₂ O ₃ ) Chloride Vinyl copolymer resin 1 part (manufactured by Nippon Zeon Co., Ltd .: MR110) Cyclohexanone 60 parts Cylethylketone 40 parts [III] Polyisocyanate 8 parts (Nippon Polyurethane Co .: Coronate 3040) Stearic acid dibutylamide 0.5 parts Stearic acid 0.5 parts Butoxyethyl stearate 0.5 parts Methylethylketone 50 parts Toluene 30 parts The non-magnetic support coated with the magnetic coating is subjected to magnetic field orientation treatment and drying in a state where the magnetic coating is not dried, and then the same [II] is added to the following back layer coating composition [I] immediately before coating, The magnetic coating was applied to the back surface of the support so that the dry thickness was 0.6 μm.

Back layer coating composition (1) 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 (Nippon Zeon: MR110) 50 parts Polyurethane resin 40 parts (Toyobo Co., Ltd .: UR8300) Cyclohexanone 200 parts Methyl ethyl ketone 300 parts [II] Polyisocyanate 20 parts (Nippon Polyurethane Co., Ltd .: Coronate 3040) Methyl ethyl ketone 3500 parts Toluene 200 parts Silicone compound 0.1 parts (Shin-Etsu Chemical) (Manufactured by: KF69) Further, after drying, Following calendering the using supercalender device having the following constitutions, the temperature 80 ° C., a linear pressure 1
It was carried out 3 times at a speed of 200 Kg / cm and a speed of 200 m / min to prepare a laminate comprising a non-magnetic support, a magnetic layer and a back layer.

Configuration of Super Calender Device Three-stage Roll Calender Roll Material Shore Hardness Upper Metal Roll 80-85 ° Middle Metal Roll (Variable Crown Shape) 80-85 ° Upper Metal Roll 80-85 ° This laminate is 24 at 60 ° C. After heat treatment for a period of time to cure the polyisocyanate compound contained in the laminate, it is slit into a 1/2 inch width and polished with a polishing tape (K10000 manufactured by Fuji Photo Film Co., Ltd.) to burnish the surface of the magnetic layer. After processing, wiping material (Kuraray Co., Ltd.)
Made by: WRP736) and then wiped to 1
I made a 2-inch videotape.

The surface porosity of the magnetic layer of the obtained laminate was measured by QU
ANSO CHROME AUTOSORB-1 SORPTION SYSTEM Model. AS
After degassing at -1 to 10 ^-6 Torr or less, the total pore volume was measured. As a result, the surface porosity was 23%. Example 2 In Example 1, the Young's modulus in the TD direction of the polyethylene naphthalate of the nonmagnetic support having a thickness of 7 μm was 1500K.
A magnetic coating composition was prepared in the same manner as in Example 1 except that the amount was changed to g / mm ² .

The obtained laminate was treated in the same manner as in Example 1 to prepare a 1/2 inch video tape. The surface layer of the magnetic layer of the obtained laminate had a porosity of 22%. Example 3 A magnetic coating composition was prepared in the same manner as in Example 1 except that the Young's modulus in the TD direction of the polyethylene naphthalate of the non-magnetic support having a thickness of 7 μm was changed to 1800 Kg / mm ² . It was created.

The obtained laminate was treated in the same manner as in Example 1 to prepare a 1/2 inch video tape. The surface layer of the magnetic layer of the obtained laminate had a porosity of 23%. [Example 4] A 1 / 2-inch video tape was prepared under the same conditions as in Example 1 except that the calendering condition was changed to a linear pressure of 150 kg / cm. The surface porosity of the magnetic layer of the obtained laminate was 18%.

Example 5 A 1/2 inch video tape was prepared under the same conditions as in Example 1 except that the temperature of the calendar treatment was changed to 50 ° C. The surface porosity of the magnetic layer of the obtained laminate was 18%. Comparative Example 1 A magnetic coating composition was prepared in the same manner as in Example 1 except that the Young's modulus in the TD direction of the polyethylene naphthalate of the non-magnetic support having a thickness of 7 μm was changed to 900 Kg / mm ² . It was created.

The obtained laminate was replaced with an epoxy resin roll (hardness 100 (Rockwell M scale)) in the middle stage, and calendering conditions were linear pressure of 300 Kg / cm,
A 1/2 inch video tape was prepared by carrying out the same calendar treatment as in Example 1 except that the treatment was performed 3 times at a treatment speed of 200 m / min. The surface layer of the magnetic layer of the obtained laminate has a porosity of 25%.
Met.

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

The surface porosity of the obtained laminate was 25%. [Comparative Example 3] A laminate was prepared in the same manner as in Comparative Example 1 except that the Young's modulus in the width direction of the nonmagnetic support was changed to 1800 kg / mm ² of polyethylene naphthalate. The laminated body was subjected to the same treatment as in Comparative Example 1 to prepare a 1/2 inch video tape.

The surface porosity of the obtained laminate was 26%. [Comparative Example 4] A laminate was prepared in the same manner as in Comparative Example 1, and the obtained laminate was treated in the same manner as in Example 1 to prepare a 1 / 2-inch video tape. The surface porosity of the obtained laminate was 23%.

[Comparative Example 5] A laminate was prepared in the same manner as in Comparative Example 1, and the obtained laminate was treated in the same manner as in Example 1 to prepare a 1 / 2-inch video tape. In addition, the treatment of the obtained laminated body was performed by using a metal roll (Shore hardness of 80 to
The roll shape is 85 ° and the roll shape itself is the same as that of the first embodiment, but the roll shape cannot be changed because the hydraulic pressure inside the roll cannot be controlled. ), A calender treatment was performed at a linear pressure of 300 Kg / cm and a temperature of 80 ° C.

The surface porosity of the magnetic layer of the obtained laminate was 1
It was 0%. [Comparative Example 6] The Young's modulus in the width direction of the non-magnetic support was 150.
A 1 / ^2- inch video tape was prepared in the same manner as in Comparative Example 5 except that polyethylene naphthalate of 0 kg / mm ² was used.

The surface porosity of the obtained laminate was 10%. [Comparative Example 7] The Young's modulus in the width direction of the non-magnetic support was 180.
A 1 / ^2- inch video tape was prepared in the same manner as in Comparative Example 5 except that polyethylene naphthalate of 0 kg / mm ² was used.

The surface porosity of the obtained laminate was 9%. [Comparative Example 8] A laminated body was prepared in the same manner as in Example 2, and the obtained laminated body was calendered at a temperature of 25 ° C, a linear pressure of 100 Kg / cm, and a speed of 300 m / min with the same calender structure as in Comparative Example 2. Was performed only once to make a 1/2 inch video tape. The surface porosity of the obtained laminate was 40%.

[Evaluation Method] The residual magnetic flux density (hereinafter abbreviated as Br) was measured with a Br VSM (vibrating sample magnetometer) in a magnetic field of 10 kOe . Output The video signal output (corresponding to per head) of the prototype tape was measured using the measuring equipment shown below. Measuring equipment Matsushita Electric D3 VTR AJ-D350P Core width 130 μm type Relative speed between magnetic head and tape: 21.4 m / sec Sony Tektronix color signal generator TS-170D Advantest spectroanalyzer TR4171 Video signal measurement method A color bar signal was input to the D3VTR from a color signal generator, recorded and reproduced on a tape, and the reproduced output waveform was observed with a spectrum analyzer. The output was measured on all four channels and averaged. The spectrum analyzer settings are as follows: frequency 27.5
We read at MHz and compare.

RBW 100 kHz Sweep time 100
Millisecond start frequency 0 MHz VBW 10 kHz 128 times average stop frequency 50 MHz The output of Example 1 is set to 0 dB, and the output is shown in Table 1.

[0078]

[Table 1]

In the magnetic recording medium of the present invention, as is clear from the examples in Table 1, the non-magnetic support has a Young's modulus in the width direction of 1000 kg / mm ² or more and the surface layer of the magnetic layer has a porosity of 15% to 15%. Total thickness of 12 μm with 35% magnetic recording medium
It is possible to improve the head contact of a thin tape of less than 1 and maintain a high output, and a remarkable effect is recognized as compared with the conventional method. In Comparative Examples 1 to 3, Br was small, probably because the calender treatment was performed under normal conditions. Comparative Example 5
In No. 7, since the crown shape of the metal roll in the middle stage is not variable, the surface porosity is low and the output is not improved. In Comparative Example 4, the output is not improved because the Young's modulus in the width direction of the non-magnetic support is low.

[0080]

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 a surface porosity of the magnetic layer of 15% or more and 35% or less, The width of the VTR, especially the digital VTR, in the direction perpendicular to the scanning direction of the head sliding surface is 8
It is possible to improve the head contact of a thin magnetic tape having a total thickness of less than 12 μm with respect to a wide head of 0 μm or more, and provide a magnetic recording medium that maintains a high output. 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, the surface roughness of the magnetic layer is 1.5 nm or more and 4.5 nm or less, and the residual magnetic flux density is 2800 gauss or more. Due to this, a higher output can be obtained .

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Minoru Kanazawa               2-12-1, Ogimachi, Odawara City, Kanagawa Prefecture               Fuji Photo Film Co., Ltd. (72) Inventor Makoto Yoshimura               2-12-1, Ogimachi, Odawara City, Kanagawa Prefecture               Fuji Photo Film Co., Ltd.                (56) References JP-A-63-39133 (JP, A)                 JP-A-53-66203 (JP, A)                 JP 63-63124 (JP, A)                 JP-A-2-260124 (JP, A)                 JP 62-89221 (JP, A)                 JP-A-4-238114 (JP, A)                 JP-A-48-27706 (JP, A)                 JP-A-3-295003 (JP, A)                 JP 63-144419 (JP, A)

Claims (3)

(57) [Claims] 1. 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 total thickness of the magnetic recording medium is less than 12 μm. Young's modulus in the width direction of the body is 1000 kg
/ Mm ² or more, due to N ₂ gas adsorption of the magnetic layer
The surface porosity calculated from the total pore volume is 15 to 35%, the residual magnetic flux density Br of the magnetic layer is 2800 gauss or more, and the non-magnetic support is a polyester support.
And the back layer is on the support opposite to the magnetic layer.
A magnetic recording medium characterized by being provided . 2. The center line average surface roughness Ra of the magnetic layer.
The magnetic recording medium according to claim 1, wherein (cutoff value 0.25 mm) is 1.5 to 4.5 nm. 3. The magnetic recording medium according to claim 1 or 2, wherein the rotating cylinder head has a magnetic head having a core width of 100 μm or more, and the relative speed between the magnetic head and the magnetic recording medium is 20 m / sec or more. A magnetic recording / reproducing method characterized by performing recording / reproducing under certain conditions.