JPH041915A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic conversion characteristics, traveling durability and edge damages by forming a specified magnetic layer on the one side of a nonmagnetic supporting body and forming a specified back layer on the other side of the supporting body. CONSTITUTION:A magnetic layer containing at least a ferromagnetic powder and a binder is provided on the one side of a nonmagnetic supporting body, and a back layer is provided on the other side of the supporting body. The Young's modulus of the magnetic layer in the longitudinal direction is specified to 1,500 - 2,300kg/mm<2>, while the Young's modulus of the nonmagnetic supporting body in the longitudinal direction is specified to 300 - 700kg/mm<2>. The back layer is made 0.2 - 1.0mum thick with Young's modulus in the longitudinal direction of 300 - 1,500kg/mm<2> and the Young's modulus of the magnetic recording medium in the longitudinal direction is specified to 600 - 1,300kg/mm<2>. Thus, traveling durability, electromagnetic conversion characteristics and edge damages of the medium can be improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording medium, and in particular to an electromagnetic conversion system,
This invention relates to a magnetic recording medium with improved running durability, video head contact, and edge damage.

[Conventional technology]

In recent years, especially in magnetic recording media for video, in order to lengthen recording and playback times as much as possible when incorporated into cassettes and cartridges, reducing the thickness of magnetic tape weakens the mechanical strength of the magnetic recording medium, making recording and playback difficult. , during fast forwarding, rewinding, loading, and unloading, the edges of the magnetic tape come into contact with the guide member that restricts the running of the magnetic tape or the flange for restricting the loading magnetic tape, causing buckling or breakage. There are cases,
Also, curls and wrinkles are more likely to occur.

For this reason, when manufacturing plastic films such as polyester films, reinforced films stretched in the longitudinal or width directions are used as the base film of magnetic tapes, or in addition to improving the base film, a magnetic layer with a high elastic modulus is used as the base film. In other words, attempts have been made to improve the mechanical strength of magnetic tape by forming it on a non-magnetic support, but this is not yet sufficient, and as the thickness of magnetic tape becomes thinner, buckling and breakage of the tape edge can be effectively prevented. difficult to prevent.

Therefore, in order to eliminate such drawbacks, one side of a flexible non-magnetic support made of a polymer molded material has an elastic modulus (Young's modulus) higher than that of the non-magnetic support at 1% elongation. Form a magnetic layer with an elasticity of 1200 kg/mm" or more in both the longitudinal and width directions, and on the opposite side, the elastic modulus at 1% elongation is higher than the elastic modulus of the non-magnetic support and is 1 in both the longitudinal and width directions.
Total thickness 1 with a back layer of 200kg/+nm” or more
A magnetic recording medium of 7g11 or less has been proposed (Japanese Unexamined Patent Publication No. 58-91528).However, since the Young's modulus of the magnetic layer in the longitudinal direction is approximately 850 kg/mm2, The running durability was insufficient, the toughness (hardness and elongation) for the magnetic head was insufficient, and there were problems with clogging and durability. Also, the Young's modulus of the nonmagnetic support is 7.
Since it was about 50 kg/rnm2, running stability was insufficient and edge damage occurred.

In addition, for magnetic recording tapes with a total thickness of 4.0 to 14.5 Ja, the ratio of the base thickness to the magnetic layer thickness should be set to 322 from 2:3.
and the ratio of the Young's modulus of the nonmagnetic support and the magnetic layer to 1:
A magnetic recording tape has also been proposed which is characterized by having a tensile strength of between 2:1 and a tensile strength of 0.5% elongation of do·'/16 kg or more for the total thickness d(Ilm). (Japanese Unexamined Patent Publication No. 53-66202).

However, the Young's modulus of the magnetic layer is about 1,740 kg/mm'', and the nonmagnetic support is also about 870 to 2,400 kg/mm'', so that the Young's modulus of the entire magnetic recording medium is high. As a result, the head touch is unbalanced,
Therefore, there were problems such as the output waveform being distorted.

[Purpose of the invention]

The objects of the present invention are to improve per video head, specifically the output waveform, to improve running durability, specifically head clogging, to improve electromagnetic conversion characteristics, specifically video output, and to An object of the present invention is to provide a magnetic recording medium with improved edge damage.

[Structure of the invention]

An object of the present invention is to provide a magnetic recording medium in which a magnetic layer having at least ferromagnetic powder and a binder is provided on one surface of a non-magnetic support with a non-magnetic support sandwiched therebetween, and a back layer is provided on the other surface. , Young's modulus in the longitudinal direction of the magnetic layer is 1500~
2300 kg/mm2, the Young's modulus of the nonmagnetic support in the longitudinal direction is 300 to 700 kg/mm, and the Young's modulus of the back layer in the longitudinal direction is 300 to 1500 kg/mm.
mm2, the thickness of the back layer is 0.2 to 1.0 μm, and the Young's modulus in the longitudinal direction of the magnetic recording medium is 600 to 1.0 μm.
This is achieved by a magnetic recording medium characterized by a weight of 1300 kg/mm2.

Further, an object of the present invention is that the crystallite size of the ferromagnetic powder is 250A or less, and the Br/Bm of the magnetic layer is 0.8.
This can be achieved by a magnetic recording medium with a value of 5 or more,
More preferably, this can be achieved by a magnetic recording medium characterized in that the magnetic layer has a thickness of 2 to 4-1 and the non-magnetic support has a thickness of 5 to 12-.

In particular, the back layer in the present invention has a layer structure that is not used for normal magnetic recording and reproducing, and is provided on the other surface of the support opposite to the magnetic layer provided on one surface of the non-magnetic support. There are no limitations and any layer structure is allowed. For example, the back layer is usually formed by applying a paint containing a polymer as a binder and an appropriate amount of inorganic powder, but in the present invention, the manufacturing method is not particularly limited, and a film-like material can be formed. It may be provided by adhering to the non-magnetic support, or if a layered structure is possible, only a binder may be used, and the same material as the non-magnetic support may be included.

In the present invention, the Young's modulus in the longitudinal direction refers to the Young's modulus in the longitudinal direction, which is measured using a universal tensile tester (manufactured by Toyo Baudwin).
It means the stress expressed when the length is 0 mm and it is stretched by 0°5% at a tensile speed of 50 mm/min.

Further, the respective thicknesses of the magnetic layer, nonmagnetic support, and back layer in the present invention mean their respective dry thicknesses unless otherwise specified.

The crystallite size of the ferromagnetic powder used in the present invention is calculated from the half-width of the peaks of the diffraction lines of the (110) plane and the (220) plane using an X-ray diffractometer.

The present invention defines and controls the Young's modulus in the longitudinal direction of the entire magnetic recording medium, so that
It has improved running durability, electromagnetic conversion characteristics, and edge damage. If the Young's modulus of the entire magnetic recording medium is too large, contact with the video head will be poor and the output waveform will deteriorate. This is thought to be because when the video tape is wrapped around the cylinder of the video deck, the video tape is too hard to wrap tightly around the video deck. On the other hand, if the Young's modulus in the longitudinal direction of the entire magnetic recording medium is too small, the contact with the video head will be improved, but edge damage will occur. That is, the scope of the present invention is a range in which edge damage does not occur and the contact with the video head is good.

Further, the present invention is characterized in that the Young's modulus in the longitudinal direction of the magnetic layer is extremely large. Increasing the Young's modulus in the longitudinal direction of the magnetic layer makes it harder, prevents the magnetic layer from being scraped, improves running durability, and improves head clogging. Furthermore, dropout is also improved as the repeated running durability is improved.

On the other hand, the Young's modulus in the longitudinal direction of the nonmagnetic support has the function of adjusting the Young's modulus in the longitudinal direction of the entire magnetic recording medium.
This contributes to improving the head hit and edge damage.

In addition, the Young's modulus in the longitudinal direction of the back layer contributes to the Young's modulus in the longitudinal direction of the entire magnetic recording medium, and if the thickness is too thin, scratches will occur in the back layer, dropouts will occur, and repeated running durability will deteriorate. - If the blade is too thick, the surface properties of the back layer will deteriorate, the unevenness of the back layer will be transferred to the magnetic layer, the S/N will deteriorate, and the electromagnetic conversion characteristics will deteriorate. Therefore, by setting the thickness of the back layer within the range of the present invention, it is possible to achieve both repeated running durability and tape warping.

In this way, in the present invention, by controlling the Young's modulus in the longitudinal direction of the magnetic layer, non-magnetic support, back layer, and tape as a whole, it is possible to simultaneously improve video head contact, running durability, electromagnetic conversion characteristics, and edge damage. This is what I did.

Furthermore, in the present invention, the crystallite size of the ferromagnetic powder is set to 250.
Even better results can be obtained by making the Br/Brn of the magnetic layer preferably 0.85 or more. In other words, setting the crystallite size of the ferromagnetic powder to 250A or less means making the particles extremely fine, and the ratio of Br (residual magnetic flux density) to Bm (maximum magnetic flux density), that is, the squareness ratio, is 0. A value of 85 or higher means that extremely fine ferromagnetic powder is well-dispersed and neatly oriented, which reduces noise, improves output, and improves electromagnetic conversion characteristics, as well as improves the magnetic layer. The Young's modulus increases, the durability of the magnetic layer improves, and the running durability improves.
Contributes to improving edge damage. The thickness of the magnetic layer and the non-magnetic support is important for adjusting the Young's modulus in the longitudinal direction of the entire magnetic recording medium, and is also important for controlling the thickness of the entire magnetic recording medium as a tape for long-term recording or recording. is important.

The Young's modulus (E+) in the longitudinal direction of the magnetic layer is 1500 to 2
500kg/mm2, preferably 1500-2000
It is in the range of kg/mm2. If it is less than 1500 kg/rnm2, it will cause problems in running durability, and in particular, the clogging properties will be poor, so it is not preferable. If it is more than 2500 kg/rnm2, the coating will become brittle and the slitting properties will be poor, causing the slit surface to fall off, Cracks are more likely to occur.Furthermore, the adhesion with the non-magnetic support becomes poor.

The Young's modulus (E2) of the nonmagnetic support in the longitudinal direction is 300
-700 kg/mm2, preferably 400-70
0 kg10+m".The Young's modulus is 30
If it is less than 0 kg/+mm2, the end face of the tape will be seriously damaged when the tape runs, resulting in unstable recording or
Recording and playback become impossible. The Young's modulus is 700
If it exceeds kg/+nm2, the contact with the magnetic head becomes unstable, resulting in unstable recording or a state in which recording and reproduction cannot be performed.

The Young's modulus (E3) of the back layer in the longitudinal direction is 300 to 1.
500 kg/mm2, preferably 400-1
It is in the range of 400 kg/mm2. The Young's modulus is 30
If it is less than 0 kg/mm2, adhesion to the surface of the magnetic layer may occur during long-term storage, or, for example, back layer peeling failure may occur due to sticking to a roll in a calender during the manufacturing process. If the Young's modulus is greater than 1500 kg/mm, the adhesion to the non-magnetic support will be poor, and the back layer film on the edge of the tape will peel off during running, causing dropouts and clogging of the magnetic head.

Further, the thickness of the back layer is 0.2 to 1.0 μm,
Preferably, it is in the range of 0.3 to 0.8. 0. 2
j! When I is less than 1, scratches on the back layer tend to occur during repeated running, and dropouts increase. Also, 1.
If it exceeds OJa, the surface properties will deteriorate and the tape will warp, which is not preferable.

The above Young's modulus E, SE2, and E are E1≧E3≧
It is preferable that the relationship is E2.

In the present invention, the means for adjusting the Young's modulus E2 and E3 in the longitudinal direction of the magnetic layer, nonmagnetic support, and back layer is not particularly limited, but preferably includes the following description. It will be done.

a. Adjustment of Young's modulus of magnetic layer ■ Select a binder composition that will hold the ferromagnetic powder.

For example, examples of the composition include those in which resins described below are appropriately combined.

(2) Limiting the crystallite size and shape of the ferromagnetic powder.

For example, the acicular ratio (the ratio of the length in the longitudinal direction and the length (width) in the width direction of magnetic material particles as observed by electron microscopy, measured at 50
0 to 1000) is 1:8 or more, that is, 0
．． By making it 125 or less, the Young's modulus can be improved, Br/Bm can be increased (and the electromagnetic conversion characteristics (especially video 8) can be improved.

■ The type, amount, and size of other inorganic powder additives such as abrasives and antistatic agents contained in the magnetic layer, as well as the type and amount of liquid additives such as lubricants and dispersants. For example, the average particle size of the inorganic powder is between lO~2.00
0 nm, preferably in the range of 20 to 1,000 nm. The amount of the inorganic powder added is preferably in the range of 2 to 20 parts by weight per 100 parts by weight of the ferromagnetic powder, and the amount of the binder is 15 parts by weight.
A range of 40 parts by weight is preferred. Moreover, the range of the liquid additive is preferably 1 to 10 parts by weight per 100 parts by weight of the ferromagnetic powder.

b. Young's modulus adjustment of non-magnetic support ■ Select materials.

■ Processing the material by known means.

For example, in the case of a polyester film, the Young's modulus in the length direction and, if desired, the Young's modulus in the width direction can be set at the longitudinal and transverse stretching levels of a general non-crystalline unstretched polyethylene terephthalate film. Note that the Young's modulus in the width direction does not have to be 300 to 700 kg/mm'.

C. Young's modulus adjustment of back layer ■ Select the binder composition that will serve as the membrane base.

For example, the binder composition may include an appropriate combination of resins described below, and is selected in consideration of the glass transition point (Tg>, etc.).

■ Selecting the material type, amount added, size, etc. of the inorganic powder additive, and the type and amount added of liquid additives such as lubricants and dispersants.For example, the average particle size of the inorganic powder is 5 to 11,000.
n, preferably in the range of 10 to 500 nm.

The amount of binder added is 50 to 100 parts by weight of inorganic powder.
A range of 200 parts by weight is preferred. Moreover, the range of the liquid additive is preferably 0.5 to 10 parts by weight per 100 parts by weight of the inorganic powder.

Further, the back layer preferably has protrusions on its surface. For example, the surface protrusions of the back layer are formed as an inorganic powder, preferably by mixing and combining coarse particles and fine particles. Inorganic powders include carbon black, graphite, tungsten disulfide, molybdenum disulfide, boron nitride, titanium black, Sin, C
aCO3, Al2O3, Fe2O3, TlO2, MgO
Examples include 5ZnO and CaO.

Among the above, carbon black and CaCO3 are preferred, and the coarse particles and fine particles may be of the same type or different types.

As a coarse particle powder, the average particle size is 50 to 50Qn.
m is preferable, particularly preferably 100 to 40
0nffl is preferred.

As a fine particle powder, the average particle size is 10 to 50 nm.
Preferably.

Also, as a weight ratio, coarse particle powder: fine particle powder is 0.5
:100-5:100 is preferable.

The ferromagnetic powder with a crystallite size of 250 Å or less used in the present invention is preferably a single metal or an alloy, and is preferably in the range of 250 Å or less. By setting the crystallite size to 250 Å or less, noise in electromagnetic conversion characteristics decreases, and the C/N ratio is improved.

The manufacturing method for reducing the crystallite size to 250 Å or less is disclosed in Japanese Patent Application Laid-open No. 6
0-29589 etc.

The ferromagnetic powder used in the present invention is not particularly limited as long as it does not violate the above conditions, but for example, the metal content is 75% by weight or more, and the metal content is 80% by weight.
The above is at least one ferromagnetic metal or alloy (eg, Fe, Co, Ni.

Fe-Co, Fe-N15Co-NiXCo-Nl-F
e, Co-N1-PSCo'-Ni-Fe-BSFe-
Ni-ZnSFe-Co-Cr), and other components (e.g., Al5Si,
S % S CN TI SV % Cr %Mn,
CuSZn, Y, Mo, Rh, Pd, Ag.

Sn, 5bSTe, Ba, Ta, W, Re, Au.

Hg5PbSB l5La, Ce5Pr, Nd, B.

Examples include alloys that may contain P).

In particular, examples of the method for producing the ferromagnetic powder used in the present invention include the following method.

(a) A method of thermally decomposing an organic acid salt of a ferromagnetic metal and reducing it with a reducing gas such as hydrogen.

゛(b) Reducing acicular oxyhydroxides, acicular oxyhydroxides containing other metals, or acicular iron oxides obtained by heating these oxyhydroxides with a reducing gas such as hydrogen. Method.

(C) A method of thermally decomposing a metal carbonyl compound.

(d) A method in which ferromagnetic powder is evaporated in an inert gas at low pressure.

(e) A method of obtaining a ferromagnetic powder by reduction using a reducing substance (borohydride compound, hypophosphite, hydrazine, etc.) in an aqueous solution of a metal salt capable of producing a ferromagnetic substance.

(f) A method in which ferromagnetic metal powder is electrolytically deposited using a mercury cathode and then separated from mercury.

In the present invention, ferromagnetic powder produced by any of the above methods can be used, but from the viewpoint of both magnetic properties and cost (b
) is particularly preferred.

The ferromagnetic powder that can be used in combination with the present invention is not particularly limited, and the above-mentioned ferromagnetic powders include alloys outside the scope of the present invention, metal ferromagnetic powders, metal oxide-based ferromagnetic powders, etc.
r' Fezes, Co-containing (deposited, metamorphosed, doped)
T Fe1O3, Fe5o4, Co-containing (deposited, metamorphosed, doped) Fear
50), CrO2, Rn5Te, Sb, 5rSFe,
Ti.

CrO containing at least one type of V, Mn5Cr20*
2. Platy hexagonal barium ferrite can be mentioned, and these can be used in an amount of 1 to 90 parts by weight based on 100 parts by weight of the ferromagnetic powder of the present invention.

As a method that can be used in combination, a method of mixing ferromagnetic powder and a method of providing a plurality of layers can be used. When providing multiple layers, a magnetic layer containing alloy ferromagnetic powder on the side in contact with the recording/reproducing head;
Below that, a magnetic layer of the above-mentioned metal oxide-based ferromagnetic powder is placed at 99°C.
It can be provided at a thickness ratio of /1 to 10/99.

The binder used in the magnetic layer and/or back layer of the present invention is a known thermoplastic resin, thermosetting resin, radiation-curable resin, or reactive resin that has been conventionally used as a binder for magnetic recording media. or a mixture thereof.

The thermoplastic resins include acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, and methacrylic acid ester vinylidene chloride copolymer. , methacrylate styrene copolymer, vinyl chloride copolymer (details below), polyurethane resin (details below),
Urethane elastomer, nylon-silicon resin, nitrocellulose-polyamide resin, polyvinyl fluoride,
Vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (methyl cellulose,
Ethyl cellulose miacetyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, cellulose acetate butyrate, cellulose diacetate,
Examples include cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, and various synthetic rubber-based thermoplastic resins.

When a vinyl chloride copolymer or a cellulose derivative is used in the magnetic layer of the present invention, the softening temperature is 40°C or higher and 200°C.
The following are preferable, and their number average molecular weight is 1000 to
100,000, preferably 5000 to 50000, Tg is 40°C or higher, preferably 60°C or higher, and when they are used for the back layer, their number average molecular weight is 1000 to 150,000, Preferably 1
0.000 to 100,000, and Tg is 50°C or higher, preferably 65°C or higher.

The above-mentioned thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and its molecular weight becomes extremely large when heated after coating and drying, such as phenol. resin, phenoxy resin,
Epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, silicone resins, acrylic reaction resins, epoxy-polyamide resins, nitrocellulose melamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, methacrylates, etc. Mixtures of polymers and diisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, mixtures of polyisocyanates such as low molecular weight glycols/high molecular weight diols/triphenylmethane triisocyanate, polyamine resins, polyimine resins, and these Examples include mixtures.

Further, as the radiation-curable resin, a resin having at least one carbon-carbon unsaturated bond in the molecule that can be cured by radiation irradiation can be used. Examples of radiation-curable resins include adding a compound having at least one carbon-carbon unsaturated bond in the molecule to the vinyl chloride copolymer or polyurethane resin as a copolymer component during polymerization. Examples include those manufactured by incorporating it by coalescence or reaction with a resin. The compound having at least one carbon-carbon unsaturated bond in the molecule is preferably a compound containing at least one (meth)acryloyl group in the molecule, and such a compound further contains a glycidyl group or a hydroxyl group. You can leave it there.

Furthermore, a compound that can be polymerized by radiation irradiation may be added to the binder. Such compounds include (meth)acrylic esters, (meth)acrylamides, allyl compounds, vinyl ethers, vinyl esters, vinyl heterocyclic compounds, N-vinyl compounds, styrenes, and (meth)acrylic acid. , crotonic acid, itaconic acid, olefins, etc. Among these, particularly preferred are compounds having two or more (meth)acryloyl groups in one molecule, such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, Examples include pentaerythritol tetra(meth)acrylate, a reaction product of polyisocyanate and poly(meth)acrylate, and the like.

The vinyl chloride copolymer used in the present invention is not particularly limited, but preferred specific examples include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acetic acid copolymer. Vinyl-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer-vinyl alcohol copolymer, vinyl chloride-
Examples include vinyl propionate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-acrylic acid copolymer, vinyl chloride-vinyl acetate-acrylic acid-vinyl alcohol copolymer, and oxidized versions of these copolymers. be able to.

In particular, vinyl chloride copolymers having polar groups such as carboxylic acid groups or salts thereof, sulfonic acid groups or salts thereof, phosphoric acid groups or salts thereof, amino groups, and hydroxyl groups are used to improve dispersibility in ferromagnetic powder. preferable.

Further, as the polyurethane, a polyurethane manufactured by a known polyurethane manufacturing method from a polyol such as a polyether polyol or a polyester polyol, a diisocyanate, and a chain extender if necessary can be used. .

The polyols are, for example, compounds such as polyether dione, polyester dione, polycarbonate dionove, polycaprolactone diol.

Typical examples of the polyether polyol include polyalkylene glycols such as polyethylene glycone polypropylene glycol.

The above polyester polyol can be synthesized, for example, by polycondensation of a dihydric alcohol and a dibasic acid, ring-opening polymerization of lactones, such as caprolactone, and the like. Typical dihydric alcohols include ethylene glycone polypropylene glycol, butanediol, 1
．． Examples include glycols such as 6-hexanecyonovecyclohexanedimethanol. Furthermore, typical dibasic acids include adipic acid, pimelic acid, azelaic acid, sebacic acid, phthalic acid, and terephthalic acid.

Further, the polycarbonate polyol can be prepared, for example, by the general formula (I) HO-R'-OH (1) [wherein R1 is, for example, ([:112)h(n = 3
~14), synthesized by condensation or transesterification of a polyhydric alcohol having phosgene, chloroformate, dialkyl carbonate or diaryl carbonate,
A polycarbonate polyol having a molecular weight of 300 to 20,000 and a hydroxyl value of 20 to 300, or the polycarbonate polyol and the general formula (II) HOOC-R''-COOH (II) [wherein R2 is, for example, a carbon number of 3 to 6] represents an alkylene group, a 1,4-1,3- or 1,2-phenylene group, or a 1,4-11,3- or 1゜2-cyclohexylene group. It is a polycarbonate polyester polyol having a molecular weight of 400 to 30,000 and a hydroxyl value of 5 to 300, obtained by condensation with carboxylic acid.

Other polyols, such as polyester ether polyol, may be blended with the above polyol in an amount up to 90% by weight of the above polyol.

The polyisocyanate used to form the polyurethane by reacting with the polyol is not particularly limited, and commonly used polyisocyanates can be used.

For example, hexamethylene diisocyanate, toridine diisocyanate, isophorone diisocyanate, 1,3
-xylylene diisocyanate, 1.4-xylylene diisocyanate, cyclohexane diisocyanate, toluidine diisocyanate, 2. 4-tolylene diisocyanate, 2,6-tolylene diisocyanate), 4.
4°-diphenylmethane diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, 1,5-naphthylene diisocyanate, 3.3'
-dimethylphenylene diisocyanate, dicyclohexylmethane diisocyanate, and the like.

Examples of the chain extender include the aforementioned polyhydric alcohols, aliphatic polyamines, alicyclic polyamines, and aromatic polyamines.

The above polyurethane is, for example, -C00M group, -SO,
M group, -0PO, N2 group, -0M group (however, M is hydrogen,
Indicates sodium or potassium. ) may contain polar groups such as.

Further, the binder may further contain a compound having two or more isocyanate groups (polyisocyanate). Examples of such polyisocyanate compounds include tolylene diisocyanate), 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Incyanates such as 5-diisocyanate, 0-toluidine diisocyanate, isophorone diisocyanate, and triphenylmethane triisocyanate, reaction products of these isocyanates and polyalcohols, and polyisocyanates produced by condensation of these isocyanates. can be mentioned. Examples of the above polyisocyanates include Coronate HL, Coronate H, and Coronate EH from Nippon Polyurethane Industries.

Coronate 2030, Coronate 2031, Coronate 2036, Coronate 3015, Coronate) 3041,
Coronate 2014, Millionate MR, Millionate MTL, Daltosec 1350, Daltosec 2170
, Daltosec 2280, Takenate from Takeda Pharmaceutical Company Ltd.) D-102, Takenate D-11ON, Takenate D
-200, Takenate D-202, Sumidur N75 from Sumitomo Bayer, Desmoji: L from West German Bayer
1-L1 Desmodur IL, Desmodur N1 Desmodur HL, and are sold by Dainippon Ink and Chemicals under trade names such as Parnock D-850 and Burnock D-802.

The mixing ratio of the ferromagnetic powder and the binder in the magnetic layer of the magnetic recording medium of the present invention is preferably 10 to 30 parts by weight of the binder per 100 parts by weight of the ferromagnetic powder.

A preferable binder composition for the magnetic layer of the magnetic recording medium of the present invention has a degree of polymerization of 50 to 500, and -8 sM,
JSOJ, -PO3M2, -0PO3M2 etc. (here M
20 to 70% by weight of a vinyl chloride copolymer having a polar group selected from hydrogen, alkali metal, ammonium, etc.) in the binder, and 5 to 50% by weight of polyurethane with a molecular weight of 1 to 500,000, 10~ polyisocyanate compound
Examples include resin compositions containing 60% by weight and 5 to 30% by weight.

It is desirable that the glass transition temperature of the binder composition for the magnetic layer is 30°C or higher, preferably 40°C or higher.

Similarly, the binder composition for the back layer has a polymerization degree of 30 to 1.
30-80% by weight of 50 nitrocellulose, 5-40% by weight of polyurethane, and 1% of polyisocyanate compound.
Examples include resin compositions containing 0 to 60% by weight and 1 to 10% by weight of others. The glass transition temperature of the binder composition for the back layer is preferably 40°C or higher, particularly preferably 60°C or higher.

In the case of a radiation-curable resin composition containing an unsaturated bond-containing monomer, the radiation irradiated in the radiation treatment for curing the magnetic layer and/or back layer includes electron beam, T
Although rays, β rays, ultraviolet rays, etc. can be used, electron beams are preferable. Electron beam irradiation is performed using an electron beam accelerator.

If the radiation to be irradiated is an electron beam, 50 to 500 kV,
Preferably, one with an accelerating voltage of 100 to 300 kV is used. The absorbed dose is generally 1 to 50 megarads, preferably 2 to 15 megarads. Also, the temperature is
The temperature can be appropriately selected within the range of 30 to 120°C.

In addition to the above-mentioned ferromagnetic powder and binder, the magnetic recording medium of the present invention may contain various other additives such as carbon black, fillers, abrasives, dispersants, antistatic agents, lubricants, etc. can be included in the magnetic color and/or back layer. The content of these various additives is preferably lower than the content of the binder.

The above-mentioned carbon black includes known carbon blacks such as furnace black, color black,
Any carbon black can optionally be used, such as acetylene black.

Carbon black whose surface is partially grafted may also be used. The fine-particle carbon black and coarse-particle carbon black may be used together.

The filler is not particularly limited, and examples include particles of tungsten disulfide, calcium carbonate, titanium dioxide, magnesium oxide, zinc oxide, calcium oxide, lithopone, and talc, which may be used alone or in combination. can be used.

The above-mentioned abrasives are commonly used materials with abrasive or polishing properties, such as fused alumina, α-alumina,
γ-alumina, α-T-alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α
- Iron oxide, garnet, emery (main components: corundum and magnetite), garnet, silica, silicon nitride, boron nitride, molybdenum carbide, boron carbide, tungsten carbide, titanium carbide, quartz, tripoli, diatomaceous earth, dolomite, etc. are magnetic. This is a typical example from the viewpoint of durability of the magnetic layer of the recording medium. In particular, it is preferable to use a combination of one to four types of abrasives having a Mohs hardness of 6 or higher.

Dispersants include fatty acids having 9 to 22 carbon atoms (e.g., caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, lylunic acid, stearol). acids, etc.),
Metal soaps made of the above fatty acids and alkali metals (L1SNa, etc.) or alkaline earth metals (Mg, Ca, Ba, etc.), esters of the above fatty acids, and compounds thereof in which part or all of the hydrogen atoms are replaced with fluorine atoms. Compounds, amides of the above fatty acids, aliphatic amines, higher alcohols, polyalkylene oxide alkyl phosphates, esters of esters of alkyl polates, sarcosinates, alkyl ether esters, trialkyl polyolefin oxy quaternary ammonium salts, and Known dispersants such as lecithin can be mentioned. When a dispersant is used, it is usually used in an amount of 0.05 to 20 parts by weight per 100 parts by weight of the binder used.

As antistatic agents, conductive fine powder such as carbon black graft polymer; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide, glycerin, and glycidol; higher alkylamines, quaternary Cationic surfactants such as ammonium salts, phosphoniums or sulfoniums; anionic surfactants containing acidic groups such as carboxylic acids, sulfonic acids, phosphoric acids, sulfuric ester groups, phosphoric ester groups; amino acids, aminosulfonic acids, amino acids, etc. Amphoteric surfactants such as sulfuric acid or phosphoric acid esters of alcohols are used. When the above-mentioned conductive fine powder is used as an antistatic agent, it is used in an amount of, for example, 0.2 to 20 parts by weight per 100 parts by weight of the binder, and when a surfactant is used, it is used in an amount of 0.2 to 20 parts by weight. 1-10
Used in parts by weight range.

As a lubricant, the above-mentioned fatty acids, higher alcohols, fatty acid esters consisting of a monobasic fatty acid having 12 to 20 carbon atoms and a monohydric or polyhydric alcohol having 3 to 20 carbon atoms, such as butyl stearate and sorbitan oleate, can be used. , mineral oil, animal and vegetable oil, olefin low polymer, α-olefin low polymer, silicone oil, fine graphite powder,
Known lubricants such as fine molybdenum disulfide powder and fine Teflon powder and lubricants for plastics can be mentioned. The amount of lubricant added can be arbitrarily determined according to known techniques.

There is no particular restriction on the solvent used for crosstalk, and any solvent that is normally used for preparing magnetic paints can be used.

There is no particular restriction on the kneading method, and the order of addition of each component can be set as appropriate.

For preparing magnetic paints and back layer paints, ordinary kneading machines,
For example, two-roll mill, three-roll mill, whole mill, pebble mill, thoron mill, sand grinder, Szegvari, attritor, high-speed impeller, dispersion machine, high-speed stone mill, high-speed impact minopede disper, Nigu, high-speed mixer, homogenizer. and an ultrasonic dispersion machine.

The above-mentioned additives such as dispersants, antistatic agents, and lubricants are not strictly limited to having only the above-mentioned effects; for example, if the dispersant is lubricant It may also act as an agent or antistatic agent. Therefore, it goes without saying that the effects of the compounds exemplified by the above classifications are not limited to those listed in the above classifications, and when using a substance that has multiple effects, the amount added should be It is preferable to decide in consideration of the action and effect.

In addition, detergent dispersants, viscosity index improvers, pour point depressants,
Antifoaming agents and the like can also be added.

The viscosity of the magnetic paint prepared in this way is usually 60
~200 ps.

The magnetic paint and/or the back layer paint can be applied directly onto the non-magnetic support, but it is also possible to apply the magnetic paint and/or the back layer paint directly onto the non-magnetic support. , corona discharge treatment, electron beam irradiation treatment) and then coating on a nonmagnetic support.

Examples of coatings on non-magnetic supports include air doctor coating, blade coating, rod coating, extrusion coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, Examples include methods such as spray coating, barcodes, spin codes, etc., and methods other than these can also be used. Simultaneous multilayer coating (wet on wet method) may also be used.

The coating thickness is such that the magnetic layer of the finally obtained magnetic recording medium has a thickness of 2 to 4 mm, and the back layer has a thickness of 0.2 to 1 mm. Oj-
It is preferable that the thickness be within the range of .

The nonmagnetic support used in the present invention is not particularly limited, and commonly used nonmagnetic supports can be used. Examples of materials forming the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and polyethylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and vinyl such as polyvinyl chloride and polyvinylidene chloride. In addition to plastics such as resins, polycarbonate, polyamide, and polysulfone, metals such as aluminum and copper, and ceramics such as glass can also be used. Prior to coating, these supports may be subjected to corona discharge treatment, plasma treatment, undercoat treatment, heat treatment, dust removal treatment, metal vapor deposition treatment, and alkali treatment. Regarding these supports, for example, West German patent 333885
4A, JP 59-116926, U.S. Patent No. 4388
No. 368; Yukio Mitsuishi, "Textiles and Industry" Volume 31, p50
~55. Described in 1975, etc.

The surface roughness (Ra: optical interference type surface roughness) of the support is preferably 8 nm or less, preferably 5 nm or less. Further, the surface roughness of the magnetic side of the nonmagnetic support and the surface roughness of the back side may be the same or different. However, the surface roughness of the magnetic side is preferably within the above range, and the surface roughness of the back side does not need to be within this range.

When forming the magnetic layer and the back layer using paint, the forming method is not particularly limited and any method can be used. For example, when applying and/or after coating the magnetic layer and/or back layer, and when curing both layers, apply conditions such as physical pressure, heat, radiation, etc. (in addition to simply applying energy for film curing, and/or application for surface treatment such as deformation of the back layer surface and physical treatment such as polishing), and the order in which the application is applied to the magnetic layer and/or back layer is from back layer to magnetic layer, It is possible to select from among magnetic layer→back layer or simultaneous magnetic layer and back layer, and to appropriately select the order of film curing of the magnetic layer and/or back layer, and to combine them as appropriate.

Specifically, for example, when using a magnetic paint and a back layer paint using a polyisocyanate compound and a polyurethane that crosslinks with the polyisocyanate compound as a binder, after the magnetic layer is applied and dried, the back layer is applied and dried, and then the back layer is applied and dried in a calendar. Line pressure 40
Examples include processing at a speed of 0 kg/cm, a speed of 150 m/min, and a temperature of 80°C.

The calendar device used in the present invention is not particularly limited, but for example, at least one pair (
Examples include combinations of rigid rolls and elastic rolls of two stages, preferably three stages or more, and combinations of rigid rolls. This rigid roll has, for example, a center surface roughness (R
a: Cutoff value, 0.25rnm) is the dimensional surface roughness of the tip ball of 0.5 to 2. Onm is preferred, and examples include rolls made of various steels with hard chrome plating or ceramic coating on the surface, rolls with a roll surface made of cemented carbide, and the like. In addition, the concentric surface roughness of the elastic roll is 1.0 to 5. Qnm is preferred. An example of an elastic roll is a nylon roll.

Further, the surface of the magnetic layer and/or back layer after formation of the magnetic layer and/or back layer can be physically polished or ground.

Polishing or grinding means include polishing tapes, polishing wheels, blades, rotary blades, etc. with a Mohs hardness of 6 to 10.
An example of this is a polishing device using polishing materials such as:

In addition, the magnetic layer coated on the support by such a method can be treated, for example, by immediately drying the ferromagnetic powder in the layer and orienting it in a desired direction, if necessary. Dry. The transport speed of the support at this time is usually 10 m/min to 1000 m/min, and the drying temperature is controlled at 20°C to 130°C. If necessary, the magnetic recording body of the present invention is manufactured by subjecting it to the above-mentioned surface smoothing process or cutting it into a desired shape. In these manufacturing methods, it is preferable that the steps of surface treatment of the filler, kneading/dispersion, coating, heat treatment, calendering, radiation irradiation (EB) treatment, surface polishing treatment, and cutting are performed continuously. Moreover, the process can be divided into several parts as necessary.

In these processes, temperature and humidity are controlled, and the temperature is 10°C to 130°, and the humidity is expressed as the amount of moisture in the air.
It is 5 mg/m' to 20 mg/m'.

These include, for example, Japanese Patent Publication No. 40-23625, Japanese Patent Publication No. 39-28368, and U.S. Patent No. 347396.
It is shown in the specification of No. 0, etc. Also, special public service 41-1
The method disclosed in Japanese Patent No. 3181 is considered to be a fundamental and important technique in this field.

〔Effect of the invention〕

The present invention has a Young's modulus of 60 in the longitudinal direction of the entire magnetic recording medium.
By setting it to 0 to 1300 kg/rnm2, the video head contact and edge damage are improved at the same time, and the Young's modulus in the longitudinal direction of the magnetic layer is set to 1500 to 2300 kg/rnm2.
mm2 improves running durability, improves head clogging, improves repeatability, and reduces dropouts. Furthermore, the Young's modulus in the longitudinal direction of the nonmagnetic support adjusts the Young's modulus in the longitudinal direction of the entire magnetic recording medium, contributing to improvements in head contact and edge damage. The longitudinal Young's modulus of the back layer contributes to the longitudinal Young's modulus of the entire magnetic recording medium, and its thickness contributes to both repeated running durability and electromagnetic conversion characteristics. Furthermore, preferably, the crystallite size of the ferromagnetic powder of the present invention is 250 Å or less, and the Br/Brn of the magnetic layer is 0.8.
By setting it to 5 or less, it is possible to improve electromagnetic conversion characteristics, running durability, and edge damage at the same time.

〔Example〕

The present invention will be explained in more detail below using Examples. It will be readily understood by those skilled in the art that the components, proportions, order of operations, etc. shown herein may be modified without departing from the spirit of the invention.

Therefore, the invention should not be limited to the examples below. In addition, parts in Examples and Comparative Examples indicate parts by weight.

Comparative Examples 1 to 6, Examples 1 to 14 Magnetic coating compositions having the following composition components of the magnetic layer (the crystallite size of the ferromagnetic powder and 13r/13m were
Shown in the table. ) were sufficiently mixed and dispersed, and a back layer coating composition having the following back layer composition components was coated on both sides of a non-magnetic support having the thickness and Young's modulus shown in Table 1, respectively, to the dry thickness shown in the table. Apply it evenly and let it dry.

Thereafter, it was calendered using a combination of a metal roll and a plastic roll, and slit into gmm pieces to form a magnetic tape. In addition, the calender treatment is performed so that the calender surface roughness on the magnetic layer side (that is, the calender surface roughness in contact with the magnetic layer surface) is 1.5 parts m, and the calender surface roughness on the back layer side (that is, the calender surface roughness in the back layer is 1.5 parts m). 4. Indicates the roughness of the calender surface in contact with the surface. Onm was selected. Further, the calender temperature was adjusted to 80° C. and the linear pressure was adjusted to 400 kg/cm.

Young's modulus in the longitudinal direction of the magnetic layer of Comparative Example 1 (hereinafter, Young's modulus in the longitudinal direction of the magnetic layer, non-magnetic support, and back layer is simply referred to as Young's modulus): 800 kg/mm2
was carried out with the following composition.

Magnetic coating composition Ferromagnetic alloy powder 100 parts (Fe-
N1-Co, needle ratio 1:6) MRP-TM
10 parts (vinyl chloride/vinyl acetate copolymer,
(manufactured by Tanemizu Kagaku ■) Crisbon 7209 10 parts (polyurethane, manufactured by Dainippon Ink ■) Coronet) L 5 parts (polyisocyanate, Nippon Polyurethane side part) Myristic acid (
Fatty acids) Butyl stearate 1 part 2 parts Methyl ethyl ketone 150 parts Butyl acetate 150 parts I got it by adjusting.

Magnetic coating composition A: 10 to 20 parts of MR-110 (sulfonic acid functional group-containing vinyl chloride copolymer, manufactured by Nippon Zeon) B: 1 IR-83005 to 10 parts (polyurethane, manufactured by Toyobo) C: Coronat 5 ~10 parts (polyisocyanate, manufactured by Nippon Polyurethane) Myristic acid (fatty acid) 1 part Butyl stearate (fatty acid ester) 2 parts Methyl ethyl ketone
150 parts Butyl acetate 150 parts Examples 1 to 14 and Comparative Examples 1 to 60 Back layer coating compositions were prepared by using the following composition and changing the mixing ratio of the binder D-F as shown in Table 1. percentage.

Back layer coating composition Carbon black 100 parts (average particle size 20nrn) Carbon black 2 parts (average particle size 200nm) D: Nitrocellulose 40-70 parts (degree of polymerization 100) E: Niraporan 2301 10-40 parts (
Polyurethane resin, manufactured by Nippon Polyurethane) F: Coronate L 20-70 parts Methyl ethyl ketone solvent 500 parts Toluene solvent
200 parts butyl acetate solvent
The properties of the 300 copies of magnetic tape obtained were evaluated by the following evaluation method, and the results are shown in Table 1.

Output waveform: 8mrnVTR (FUJIX-8)! ,
: Set the measurement sample, record it, and view the playback output with an oscilloscope (manufactured by Rieter Electronics, 30600). Head contact is evaluated using this oscilloscope waveform. Those with excellent head contact have a uniform waveform as a whole and a large area (this was taken as 100%). If the head contact is poor, part or the entire area of the waveform is small.

○: Output waveform is 80% or more.

Δ: Output waveform is 50% to 80%.

X: Output waveform is 50% or less.

Head clogging F): 8 mn+VTR (F[IJ
IX-8)! : After setting the measurement sample and recording the video signal, playback is repeated and the playback signal is continuously recorded on recording paper using a recorder.

At this time, the location where the reproduction signal is no longer output is determined to be head clogging.

X: There is a portion where no output is produced for more than 1 minute.

○: Stable playback at low output.

The video output magnetic tape was incorporated into a 3mm video cassette, and this was recorded and played back using a 3mm VTR (F[]JIX-8), and the relative values with respect to the reference tape were taken.

Edge damage: Incorporate a magnetic tape into a go+m video cassette and transfer it to an 8+nm VTR (FLIJIX
-8), the edges of the tape were observed and evaluated using a microscope after running 1000 passes repeatedly.

○: No edge damage at all △: Slight damage has occurred in two or less areas in one field of view when observed at X400 using a microscope.X: Damage has occurred at two or more places in one field of view when observed at DO (dropout) 28mmVT after repeated driving
R (Fujix8) was connected to a dropout counter (Shibaku VHOI BZ), and dropouts that dropped by 10 CI8 or more in 15 μsec were counted against the output of 5M7.

X: 50 or more DOs compared to the initial number of DOs.

○: 50 or less compared to the initial number of DOs.

In addition, the crystallite size was determined using an X-ray diffractometer as α-Fe(11
It was calculated from the half width of the peaks of the diffraction lines of the 0) plane and the (220) plane. Acicularity ratio was measured by electron micrograph.

Young's modulus was calculated using a universal tensile tester (manufactured by Toyo Baudouin) using a sample of 8 ml T1 width 100 mm length and the stress when elongated by 0.5% at a tensile speed of 50 mm/min.

As can be seen from the results shown in Table 1, in Comparative Example 1, where the magnetic layer Young's modulus was as low as 800 kg/mm', clogging of the magnetic head occurred due to repeated durability. on the other hand,
When the magnetic layer had a high Young's modulus of 1500 kg/mm 2 or more, there were no troubles caused by repeated running.

Looking at the Young's modulus of the non-magnetic support, it is 300 kg/m
If it is less than m2, as shown in Comparative Example 2, the tape edge will be seriously damaged during repeated running. Also, 700 kg/m
If it is larger than m', the output waveform will be inferior as in Comparative Examples 3 and 6. With a nonmagnetic support having a Young's modulus of 300 to 700 kg/mm 2 , there was no damage to the output waveform or tape edge.

Regarding the back layer, when the thickness of the back layer was as thin as 0.1 - as in Comparative Example 4, other characteristics were satisfied, but D◯ increased after repeated running. In addition, as shown in Comparative Example 5, 1. O
When it was larger than j-, the electromagnetic conversion characteristics were poor.

In addition, the Young's modulus of the entire tape is 600 to 13.
In the range of 00 kg/mm', there was no edge damage, but in Comparative Example 2, where the value was smaller than 600 kg/mm2, tape edge damage was observed.

Moreover, if it is larger than 1300 kg/mm2, the output waveform is inferior as in Comparative Examples 3 and 6.

hand Continued Supplementary Ordinary position Date of July 1991

Claims (3)

[Claims] (1) A magnetic layer having at least ferromagnetic powder and a binder on one surface of the non-magnetic support with the non-magnetic support in between,
In a magnetic recording medium having a back layer on the other surface, the Young's modulus in the longitudinal direction of the magnetic layer is 1500 to 2300k.
g/mm^2, the Young's modulus in the longitudinal direction of the nonmagnetic support is 300 to 700 kg/mm^2, and the Young's modulus in the longitudinal direction of the back layer is 300 to 1500 kg/mm^2
and the thickness of the back layer is 0.2 to 1.0 μm, and the Young's modulus in the longitudinal direction of the magnetic recording medium is 600 to 130.
A magnetic recording medium characterized in that the magnetic recording medium is 0 kg/mm^2. (2) The magnetic recording medium according to claim 1, wherein the ferromagnetic powder has a crystallite size of 250 Å or less, and the magnetic layer has a Br/Bm of 0.85 or more. (3) The magnetic recording medium according to claim 1 or 2, wherein the magnetic layer has a thickness of 2 to 4 μm, and the nonmagnetic support has a thickness of 5 to 12 μm.