JPH02247819A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent signal/noise ratio by specifying the storage elastic modulus, loss elastic modulus and loss tangent of the medium. CONSTITUTION:The magnetic layer has a magnetic layer containing ferromagnetic powder, binder, carbon black, abrasive material and lubricant is formed on one surface of a nonmagnetic supporting body, the other side of which is provided with a back coating layer containing carbon black and binder. The powder/binder ratio by weight in the magnetic layer is 100/18 to 100/40 and the powder/binder ratio in the back coating layer is 100/45 to 100/100. It is specified that the storage elastic modulus G' in the longitudinal direction of the medium at 23 deg.C is >=5.0X10<10>dyn/cm<2>, loss elastic modulus G'' >=2.0X10<9>dyn/ cm<2> and the loss tangent tandelta>=0.03.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in a magnetic recording medium comprising a nonmagnetic support, a magnetic layer, and a back layer.

(Prior art) - As a magnetic recording medium for audio, video, computer use (DIS, memory tape), etc., a magnetic layer in which ferromagnetic fine powder is dispersed in a binder is used as a non-magnetic support. A magnetic recording medium is used.

In recent years, these magnetic recording media are required to have high density recording.
It is necessary to achieve high signal/noise and low noise by making fine particles of ferromagnetic powder, alloy powder, high packing, ultra-smooth surface of magnetic recording media, etc., and high density recording in the same time. In order to do this, it is necessary to shorten the writing speed and continuous writing speed to the magnetic recording medium, and high-speed conveyance of the magnetic recording medium is required.

Running properties, charging characteristics, and head cleaning characteristics are essential for this high-speed conveyance suitability, and for this purpose carbon blanks and fillers called abrasives with a Mohs hardness of 8 or higher are used. -193533, JP 59-186125, JP 59-191133, JP 58-18983.1, JP 59-630
It is disclosed in No. 29, etc. In addition, the problem of noise generation related to the running of magnetic recording media has been variously discussed, for example, in "Broadcasting Technology, August 1980 Issue 743JtJ" and "Transactions of the Institute of Electronics and Communication Engineers, Vol. 84, No. 1, p. 62." It is explained. These are called sliding noises in the industry.
It is thought that the surface roughness of the tape, the stiffness of the tape, the amount of head polishing, etc. have an effect. However, even with these techniques, the problem of noise generation associated with the running of a magnetic recording medium has not been satisfactorily solved.

For example, in JP-A No. 58-91528, one side of a flexible base film made of a polymer molded material has an elastic modulus of 1200 kg/mrJ at 1% elongation, which is higher than the elastic modulus of the base film, in both the longitudinal direction and the middle direction. The above magnetic layer is formed, and the elastic modulus at 1% elongation is 1200 kg/m in the longitudinal direction and 11 directions, which is higher than the elastic modulus of the base film on the opposite side.
They have proposed a magnetic recording medium with a total thickness of 17 μm or less in which a back coat layer as described above is formed, and it is said that buckling or bending will not occur even if the total thickness is 17 μm or less.

However, this simply considers the magnetic recording medium in terms of its storage modulus, but the inventors of this case have conducted extensive research and found that increasing the storage modulus means making it harder, and it is durable without buckling or breaking. It was found that although the performance improved, it also became easier to pick up noise from driving and vibration, and it was found that it was necessary to eliminate this drawback.

The inventors of the present invention have observed and studied the problems of noise generation associated with the running of magnetic recording media, and have devised the present invention by obtaining a remarkable effect in reducing noise.

(Objective of the Invention) The present invention provides a magnetic recording medium that is excellent in noise reduction by specifying the storage modulus, ignition elastic modulus, and tangent loss of a magnetic recording medium in order to prevent the generation of noise related to the running of the magnetic recording medium. The purpose is to

An object of the present invention is to define the storage modulus, loss modulus, and tangent loss of a magnetic recording medium, and to provide a magnetic recording medium with excellent signal/noise.

An object of the present invention is to specify the storage modulus, loss modulus, and tangent loss of a magnetic recording medium, and to provide a magnetic recording medium with excellent RF output characteristics.

(Structure of the Invention) The present invention provides a magnetic layer containing ferromagnetic powder, a binder, a carbon blank, an abrasive, and a lubricant on one side of a nonmagnetic support, and a magnetic layer containing carbon black and a binder on the other side of the nonmagnetic support. In a magnetic recording medium provided with a back layer containing,
The weight ratio of powder/binder in the magnetic layer is 100/1.
8 to 40, the weight ratio of powder/binder in the bank layer is 100/45 to 100, and the storage modulus G' at 23° C. in the longitudinal direction of the magnetic recording medium is 5, O
x 10” dyn/- or more, loss modulus G# is 2,
OX 10' dyn/cff1 or more, loss tangent t
The magnetic recording medium is characterized in that an δ is 0.030 or more.

Preferred embodiments of the present invention are as follows.

1) Storage elastic modulus G' at 0°C in the longitudinal direction of the magnetic recording medium is 6. OX 10I0dyn/cd or more, loss modulus G' is 2. OX I O' dyn/cd
As described above, the magnetic recording medium is characterized in that the loss tangent tan δ is 0.030 or more.

2) Storage modulus G' at 50° C. in the longitudinal direction of the magnetic recording medium is 5. OX I O" dyn/- or more, loss elastic modulus G" is 1. 5 x 10' dyn/cd
As described above, the magnetic recording medium is characterized in that the loss tangent tan δ is 0.030 or more.

3) A magnetic recording medium as claimed in the claims, characterized in that the outer layer (D) has a glossiness of 150 to 180.

In the present invention, a dynamic test is adopted as a mechanical test for polymeric materials, and the results are based on the complex modulus of elasticity (col
lpIex modulus) G,
G-G'+lG'G' is its real part and is the storage modulus (storage modulus).
dulus), and G″ is its imaginary part, 1=F
It is T. G# is the loss modulus
s) and is a damping term or energy dissipation term. The angle δ representing the time delay between applied stress and strain is called the dissipation factor and is defined by the following ratio:

tan δ - G'/G' tan δ is the loss tangent, which is a damping term and is a measure of the ratio of the energy dissipated as heat to the maximum energy stored during one cycle of vibration. The definition of 0 or more is based on "Mechanical Properties of Polymers and Composite Materials", pages 7 to 11 (Kagaku Doujin).

In the present invention, the powder in the magnetic layer refers to ferromagnetic powder, carbon black, abrasive powder, etc., and the powder in the back layer refers to powder such as carbon black.

The storage modulus G', tJI loss modulus G#, and loss tangent tan δ of the present invention can be measured using a vibrating Young's modulus measuring device, such as a Rheopybron manufactured by Orientic Co., Ltd., etc. In this case as well, the measurement conditions were 23°C, 5°C.
The value of Young's modulus at 0% RH is a value measured at a vibration frequency of 11 Hz or less. These Young's moduli are values in the longitudinal direction of the magnetic recording medium or in the coating process direction, and the values in the width direction or in the direction perpendicular to the coating process are 100% to 60% of the Young's modulus in the longitudinal direction.

Storage modulus G', loss modulus G'', loss tangent t of the present invention
A magnetic recording medium satisfying an δ has a magnetic layer containing a ferromagnetic fine powder, a binder, carbon black, an abrasive, and a lubricant, and the powder/binder ratio is 100/18 to 40. In particular, the binder consists of vinyl chloride resin and/or vinyl chloride vinyl acetate resin, polyurethane resin, and polyisocyanate, and the 100% ratio thereof is 20 to 5.
The Young's modulus at 23°C of the vinyl chloride resin and/or vinyl chloride vinyl acetate resin used in the present invention is 150 to 350 kg/m cd.
The Young's modulus at 23° C. of the polyurethane resin used in the present invention is 1 to 70 kg/mrd.

By adding polyisocyanate to these materials in which magnetic powder is dispersed, the Young's modulus of the magnetic layer coating film at 23°C is 600 to 1.
Set it to 100kg/m+yr.

The bank layer of the present invention has a Young's modulus of 200 to 400 at 23°C.
kg/m rrr, and contains binder, carphone black, and other fillers, giving a powder/binder ratio of 100/45 to 100. In particular, the binder is composed of phenoxy resin and/or phenol resin, polyurethane resin and/or epoxy resin, and polyisocyanate, and the 100% ratio thereof is 20 to 50:
The Young's modulus at 23°C of the phenoxy resin used in the present invention is 150 to 350 kg.
The Young's modulus at 23°C of the polyurethane resin used in the present invention is 1 to 7 kg/mr+ (, which is 0). Polyisocyanate is added to these materials in which carbon black is dispersed, and the back layer coating film is heated at 23°C. Young's modulus of 2
00 to 400 kg/mrrr.

The nonmagnetic support of the present invention is preferably polyethylene terephthalate, and has a Young's modulus of 400 to 800 k at 23°C.
Any material that satisfies g/m cd may be used.

The glossiness of the present invention is 45 at an incident angle according to JI5 28741.
Black glass with a refractive index of 1.567 and a specular gloss of 4
It can be determined by defining the value at a reflection angle of 5 degrees as 100%.

In the magnetic recording medium of the present invention, the storage elastic modulus G' at 23°C in the longitudinal direction of the magnetic recording medium is 5. 0X
I Q” dyn/cIII or more, preferably 5°5
XIO'・dyn/cj or more, loss elastic modulus G# is 2°0
×109dyn/cm2 or more, preferably 2.5×10
By controlling the loss tangent tan δ to 0.030 or more, preferably 0.040 or more, vibrations related to running can be effectively prevented, and the vibration damping effect is particularly excellent. Vibration is significantly reduced, eliminating uneven touch between the video head and tape and variations caused by vibration.
It is believed that a magnetic recording medium with excellent signal/noise and RF specific output can be obtained by reducing the generation of A noise. In addition, the storage elastic modulus G' at 0° C. in the longitudinal direction of the magnetic recording medium is 6. By controlling the loss modulus G' to OX 10" dyn/- or more, the loss modulus G' to 2.0XIO' dyn/- or more, and the loss tangent tan δ to 0.030 or more, it is possible to effectively prevent vibrations related to running at low temperatures, and reduce the vibration effect. This is especially effective because it significantly reduces the vibration of the tape that affects the video head, reduces uneven touch between the video head and tape, and reduces the occurrence of modulation noise caused by vibration.
It is believed that a magnetic recording medium with excellent F specific output can be obtained.

In addition, the storage elastic modulus G' at 50° C. in the longitudinal direction of the magnetic recording medium is 5. OX 10" dyn/c or more, 1 place fire elastic modulus G# 1.5X10' dyn/-
Above, preferably 2. 0 x 10'dyn/c
- By controlling the m loss tangent tan δ to 0.030 or more, preferably 0°050 or more, vibrations related to running at high temperatures can be effectively prevented, and the vibration damping effect is particularly excellent. It is believed that it is possible to obtain a magnetic recording medium with excellent signal/noise and RF specific output by significantly reducing the vibration of the video head and the tape, thereby reducing the unevenness of touch between the video head and the tape, and the occurrence of illumination noise caused by vibration.

In addition, the gloss of the magnetic layer is set to 15'0-180. By setting the gloss of the bank layer to 2.5 to 7°O, the generation of noise due to head contact is reduced, and the signal/H sound and RF ratio output are excellent.

The ferromagnetic fine powder used in the present invention is T-Fe powder.
3. Co-containing (deposition, metamorphosis, top) r-F et
off % Fe30a, Co-containing (deposited, metamorphosed, doped) Fe304, FeOx, Co-containing (deposited, metamorphosed, doped) FaOx (X=1°33~1,
50), CrOt, Rn5Te, Sb, Srb
Crow, Fe, Co, Ni, Fe-Co containing at least one of Fe, Ti, V, Mns Crt Ox
alloy, Fe-Ni alloy, Fa-C.

Ni alloy, Co-N1-P alloy, Co-N1Fe-B alloy, Fa-Ni-Zn alloy, NiCo alloy, Co-N1
-Fe alloy, Fe-N alloy, Fa-Co-Cr alloy, M
Known fine ferromagnetic powders such as n-B1 alloy can be used.

The particle size of these ferromagnetic fine powders is approximately 0.005 to 1 micron in length, and the axial length/axial width ratio is 1/1 to 50/1.
That's about it. Further, the specific surface area of these ferromagnetic fine powders is about In(/g to 7 onr/g.
I! The moisture content of the magnetic fine powder is O12-2. 0wt%
It is. The moisture content of the coating liquid when these ferromagnetic fine powders are used is 0.00 to 2.00 W[%]. On the surface of these ferromagnetic fine powders, dispersants, lubricants,
These ferromagnetic fine powders may contain Sr, Pb, Mn5Ni, and C within 1 wt% by impregnating and adsorbing an antistatic agent in a solvent prior to dispersion for each purpose.
It is preferable to contain heavy metals such as d, Cr%At, SI, Ti, Cu, and Zn. Alumina or the like may be applied and melted onto these ferromagnetic fine powders.

Further, as the ferromagnetic fine powder used in the present invention, plate-shaped hexagonal barium ferrite can also be used. The particle size of barium ferrite is about 0.001 to 1 micron in diameter and the thickness is 1/2 to 1/20 of the diameter. The specific gravity of barium ferrite is 4/6g/cc and the specific surface area is 1rd
lg to 70rd/g. The surface of these ferromagnetic fine powders may be impregnated with a dispersant, a lubricant, an antistatic agent, etc., which will be described later, in a solvent for each purpose and adsorbed thereto prior to dispersion.

An example of a ferromagnetic alloy powder is one in which the metal content in the ferromagnetic alloy powder is 75% by weight or more, and the metal content is 80]ii
If more than 1% is at least! 4M ferromagnetic metal or alloy (e.g. F6% Co, Ni, Fe-Go, Fs-
Ni, Co-Ni, Go-NiFe), and other components (e.g., At, S) within a range of 20% by weight or less of the metal content.
i,S,,Sc,'ri,■,CrSMn,017%
Zn, Y, Mo, Rh, Pd, Ag, 5nSSb
,,TeXBa,Ta,W.

Re, Au, Hg, Pb, Bi, La, Cs.

Examples include alloys that may contain P', Nd, B, P), iron nitride, and the like.Furthermore, the above-mentioned ferromagnetic metals may contain small amounts of water, hydroxides, or oxides. Methods for producing these ferromagnetic metal powders are already known, and ferromagnetic alloy powder, which is a typical example of the ferromagnetic fine powder used in the present invention, can also be produced according to these known methods.

That is, examples of the method for producing ferromagnetic alloy powder include the following method.

(a) A method of reducing complex organic acid salts (mainly oxalates) with a reducing gas such as hydrogen: (b) Obtaining Fe or Fa-Co particles by reducing iron oxide with a reducing gas such as hydrogen Method: (C) Method for thermally decomposing metal carbonyl compounds: (d)
A method of reducing an aqueous solution of ferromagnetic metal by adding a reducing agent such as sodium borohydride, hypophosphite, or hydrazine: (e) After electrolytically depositing ferromagnetic metal powder using a mercury cathode, mercury and Separation method: (f) Method of obtaining fine powder by evaporating the metal in a low-pressure inert gas: When using ferromagnetic alloy powder, there is no particular restriction on its shape, but it is usually acicular, granular, or Dice-shaped, rice-grain-shaped, and plate-shaped ones are used.

The specific surface area (S bet) of this ferromagnetic alloy powder is 40
n(/g or more, preferably 45 rd
/g or more is particularly preferred.

As the binder used in the magnetic layer and back layer of the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of toooo to 300,000, and a degree of polymerization of about 50 to 2.
For example, vinyl chloride vinyl acetate copolymer, vinyl chloride copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer. Polymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, nylon silicone resin, nitrocellulose-polyamide resin, Polyfukkavinyl, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, ethylcellulose, methylcellulose) , propylcellulose, methylethylcellulose, carboxymethylcellulose, acetylcellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether acrylate copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof. etc. are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, phenoxy resin, epoxy resin, polyurethane curable resin, urea resin,
Melamine resins, alkyd resins, silicone resins, acrylic reactive resins, epoxy-polyamide resins, nitrocellulose melamine resins, mixtures of high molecular weight polyester resins and isocyanate prepolymers, mixtures of methacrylate copolymers and diisocyanate prepolymers, polyester polyols and polyisocyanate, urea formaldehyde resin, mixture of low molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanate, polyamine resin, polyimine resin, and mixtures thereof.

Additives include dispersants, lubricants, abrasives, antistatic agents, antioxidants, solvents, and the like.

These thermoplastic resins, thermosetting resins, and reactive resins are
In addition to the main functional groups, acidic groups such as carboxylic acid, sulfinic acid, sulfenic acid, sulfonic acid, phosphoric acid, sulfuric acid, phosphonic acid, phosphine, boric acid, sulfuric acid ester group, phosphoric ester group, and alkyl ester groups of these The acidic group may be in the form of Na salt, etc.), amino l! a
Neck: Amphoteric groups such as aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, alkyl betaine types,
It usually contains one to six types of amino groups, imino groups, imide groups, amide groups, epoxy groups, etc., as well as hydroxyl groups, alkosyl groups, thiol groups, halogen groups, silyl groups, and siloxane groups, and each functional group is a resin. lXl0-'eq per 1g
-IXIO-"eq is preferably included.

Examples of the polyincyanate used in the present invention include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, 0-toluidine diisocyanate, isophorone diisocyanate, and triphenylmethane diisocyanate. Isocyanates, isocyanates such as isophorone diisocyanate, products of the incyanates and polyalcohols, and 2 produced by condensation of isocyanates.
~15-mer polyisocyanate, etc. can be used. The average molecular weight of these polyisocyanates is 1
00 to 20,000 is preferable. Commercially available trade names of these polyisocyanates include Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR, Millionate M
TL (manufactured by Nippon Polyurethane), Takenate D-1
02, Takenate D-11ON, Takenate D-200
, Takenate D-202, Takenate 303S, Takenate) 50.0 (manufactured by Narita Pharmaceutical ■), Sumidur T-80
, Sumidur 44S1 Sumidur PF, Sumidur Upper 1 Sumidur N1 Desmodule New Death Module IL, Desmodur N, Death Module HL, Death Module T65, Death Module 15, Death Module R1 Death Module RF, Death Module R1 Death Module Z4273 (Resident Bayer These can be used alone or in combination of two or more by taking advantage of the difference in curing reactivity. In addition, for the purpose of promoting the curing reaction, hydroxyl groups (butanediol, hexanediol, molecular weight of 1000 to i
oooo polyurethane, water, etc.), a compound having an amino group (monomethylamine, dimethylamine, trimethylamine, etc.), or a metal oxide catalyst can also be used in combination.

It is desirable that these compounds containing hydroxyl groups and amino groups be polyfunctional. These polyisocyanates are preferably used in an amount of 5 to 40 wt% of the total amount of the binder.

Dispersants used in the present invention include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, lylunic acid, stearolic acid, etc. 10-2
6 fatty acids (R r C O OH % R +
is an alkyl group having 9 to 25 carbon atoms), alkali metals (Li, Na, NH4, etc.) or alkaline earth metals (Mg, Ca, 83, etc.) of the fatty acids mentioned above, Cu,
Metal soap consisting of Pb etc., fatty acid amide of L fatty acid;
Lecithin etc. are used. In addition, higher alcohols having 4 or more carbon atoms (phthanol, octyl alcohol, myristyl alcohol, stearyl alcohol) and their sulfuric acid esters, phosphoric acid esters, amine compounds, etc. can also be used. Further, polyalkylene oxides and their sulfuric acid esters, phosphoric acid esters, amine compounds, etc., sulfosuccinic acid, sulfosuccinic acid esters, etc. can also be used.
It is also possible to introduce Si and F substituents into these compounds in order to change their compatibility with the binder and their properties. These dispersants are usually used in one or more types, and one type of dispersant is used in an amount of o. oos~
It is added in an amount of 20 M parts.

These dispersants may be used by depositing them on the surface of the ferromagnetic fine powder or nonmagnetic fine powder in advance, or by adding them during dispersion.

In addition, preferred compounds as dispersants include surfactants such as carboxylic acids and phosphoric esters, and fluorosurfactants such as Florard FC95, FCI29, FC430, and FCI29.
C431 can be used.

The lubricants and antioxidants used in the magnetic layer and back layer of the present invention include molybdenum disulfide, boron chloride, graphite, calcium carbonate, barium sulfate, cane oxide, titanium oxide, zinc oxide, and tin oxide. , inorganic fine powder such as 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 resin Fine powder, fine resin powder such as polyfluoroethylene resin fine powder, silicone oil, fatty acid-modified silicone oil, graphite, fluorine alcohol, polyolefin (polyethylene wax, etc.), polyglycol (polyethylene oxide wax, etc.), tetrafluoroethylene oxide wax, Polytetrafluoroglycol, perfluoro fatty acid, perfluoro fatty acid ester, perfluoroalkyl sulfate, perfluoroalkyl phosphate, alkyl phosphate, polyphenyl ether, carbon number 10~
20 monobasic fatty acids and a monohydric alcohol, dihydric alcohol, or trihydric alcohol having 3 to 12 carbon atoms,
Fatty acid esters consisting of one or more of tetrahydric alcohol and hexahydric alcohol, carbon number 1
Organic compound lubricants such as fatty acid esters made of zero or more monobasic fatty acids and monovalent to hexavalent alcohols having a total of 11 to 28 carbon atoms can be used. Furthermore, fatty acids, aliphatic amides, and aliphatic alcohols having 8 to 22 carbon atoms can also be used. Specific examples of these organic compound lubricants include butyl caprylate, octyl caprylate, ethyl laurate, butyl laurate, octyl laurate, ethyl myristate, butyl myristate, ethyl myristate, ethyl valmitate, and valmitin. butyl acid, octyl balmitate, ethyl stearate, butyl stearate, octyl stearate, amyl stearate, anhydrosorbitan monostearate, anhydrosorbitan distearate,
Anhydrosorbitan tristearate, anhydrosorbitan tetrastearate, anhydrosorbitan ethylene oxide monostearate, oleyl oleate,
Oleyl alcohol, lauryl alcohol, etc. are available and can be used alone or in combination. In addition, as the lubricant used in the present invention, so-called lubricating oil additives can be used alone or in combination, such as antioxidants (alkyl phenols, etc.), rejuvenating agents (naphthenic acid, alkenyl succinic acid, dilauryl phosphate, etc.). ), oily agents (rapeseed oil, lauryl alcohol, etc.), extreme pressure agents (dibenzyl sulfide, tricresyl phosphate, tributyl phosphite, etc.), detergents and dispersants, viscosity index improvers, pour point depressants, foam stoppers There are drugs etc. These lubricants are added in an amount of 0.05 to 20 parts by weight per 100 parts by weight of the binder.

Further, as the antioxidant, heterocyclic compounds and heterocompounds such as benzotriazine, benzothiazole, benzodiazine, and EDTA can be used.

The antistatic agents used in the present invention include graphite, carbon black, carbon black graft polymer, tin oxide-antimony oxide, tin oxide, titanium oxide-tin oxide-
Conductive powders such as antimony oxide; Natural surfactants such as No. Bonin; Nonionic surfactants such as alkylene oxides, glycerin, glycidol, polyhydric alcohols, polyhydric alcohol esters, and alkylphenol Eo adducts; higher alkyl Cationic surfactants such as amines, cyclic amines, hydantoin derivatives, amidoamines, ester amides, quaternary ammonium salts, pyridine and other heterocycles, phosphoniums or sulfoniums;
Anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric ester groups, and phosphoric ester groups; Amino acids; Ampholytic surfactants such as amino sulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and alkyl betaine types. agents etc. are used.

These surfactants may be added alone or in combination, and these surfactants may be added to the surface of the magnetic recording medium in an amount of 1/d to 550/n (may be overcoated).
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 fine powder. Although these are used as antistatic agents, they are sometimes used for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

As the carbon blank used in the present invention, furnace for rubber, thermal for rubber, black for color, acetylene black, etc. can be used. Specific examples of carbon black abbreviations in the United States include SAF, l5A
F, I l5AF, T.

HAT, SPA, FF,, FEF,) IMF, GPF.

APF, SRF, MPF, ECF, SCF, CF.

FT, MT, HCC, , HCF, , MCF, LFF, R
CF, etc., and the US ASTM standard No. I)-1765-
Items classified as 82a can be used.0
The average particle size of these carbon blacks used in the present invention is 5 to 1000 millimicrons (electron microscope);
Nitrogen adsorption method specific surface area is 1 to 1500rd/g, pH is 2
~13 (JIS standard-62211982 method), dibutyl phthalate (DBP) oil absorption, 5~2000sd/1
The water content of these carbon blacks used in the present invention is 0.00 to 2 Qwt%. The size of the carbon black used in the present invention is 5 to 100 mm in order to lower the surface electrical resistance of the coating film, and 50 to 10 microns in order to control the strength of the coating film.
00 mm carbon black is used. In addition, for the purpose of controlling the surface roughness of the coating film, finer particles of carbon black (100 millimicrons or less) are used for smoothing to reduce spacing loss, and coarser particles of carbon are used for the purpose of roughening the surface and lowering the coefficient of friction. A blank (50 millimeters or more) is used. In this way, the type and amount of carbon blank to be added can be selected depending on the purpose required for the magnetic recording medium.

However, these carbon blacks may be surface-treated with a dispersant as described below, or may be grafted with a resin before use. Furthermore, a carbon blank whose surface is partially graphitized by processing the furnace at a temperature of 2000° C. or higher when manufacturing the carbon blank can also be used. Moreover, hollow carbon black can also be used as a special carbon black.

In the case of a magnetic layer, these carbon blanks are preferably used in an amount of 0.1 to 20 parts by weight per 100 parts by weight of ferromagnetic fine powder.The physical properties of carbon black and carbon black that can be used in the present invention are, for example, 1 force- "Bon Black Handbook", Carbon Blank Association Line, (published in 1971)
can be used as a reference.

The abrasive for the magnetic layer and back layer used in the present invention is a commonly used material with an abrasive or abrasive effect.
α-alumina, T-alumina, α-γ-alumina, fused alumina, silicon carbide, chromium oxide, cerium oxide, corundum, artificial diamond, α-iron oxide, garnet,
Emery (main ingredients: corundum and magnetic iron FL), garnet, silica, silicon nitride, boron nitride, molybdenum carbide,
Boron carbide, tungsten carbide, titanium carbide, quartz, tripoli, diatomaceous earth, dolomite, etc., which mainly have a Mohs hardness of 6 or more, preferably 8 or more, are used in combinations of 1 to 4. These abrasives have an average particle size of 0.005 to 5 microns, particularly preferably 0.01 to 2 microns.
It is micron. These abrasives are added in an amount of 0.01 to 200 parts by weight based on 100 parts by weight of the binder.

Organic solvents used in the dispersion, kneading, and coating of the present invention include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, isophorone, and tetrahydrofuran; methanol, ethanol, propatool, butanol, and isobutyl; Alcohols such as alcohol, isopropyl alcohol, methylcyclohexanol; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, ethyl lactate, glycol acetate monoethyl ether; diethyl ether, tetrahydrofuran, glycol dimethyl ether, glycols monoethyl ether,
Ethers such as dioxane; tars (aromatic hydrocarbons) such as benzene, toluene, xylene, cresol, chlorohenzene, and styrene; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorohenzene, etc. Chlorinated hydrocarbons, N,N-dimethylformaldehyde, hexane and the like can be used.

There is no particular restriction on the mixing method, and the order of addition of each component can be set as appropriate. For the preparation of magnetic paints and back layer paints, conventional kneading machines are used, such as two-roll mills, three-roll mills, ball mills, pebble mills, thoron mills, sand grinders, Szeg
varl), attritor high speed impeller, disperser,
High-speed stone mill, high-speed impact mill, disper, kneader-1 high-speed mixer, ribbon blender, co-kneader,
Intensive mixers, tumblers, blenders, dispersers, homogenizers, axle screw extruders, two-wheel screw extruders, ultrasonic dispersers, and the like can be used. For details on the technology related to crosstalk dispersion, please refer to T. C. PATTON, P.
a1nt Floi< and PigmentDis
persion (Paint Flow and Pigment Disversion) 1964 JohnWi
ley & 5ons (published by John Wiley & Sons) and Shin Tanaka's ``125 to 37 Industrial Materials'' (1
977) and other documents cited in the book,
For continuous processing, these cross-dispersing machines are used in appropriate combinations to feed and coat the liquid. In addition, it is also described in specifications such as U.S. Pat. and back layer paints can be prepared.

To form the magnetic recording layer, the above compositions are arbitrarily combined and dissolved in an organic solvent, and a coating solution is coated on the support and dried. When used as a tape, the thickness of the support 2.
The thickness is about 5 to 100 microns, preferably about 3 to 70 microns. In the case of a disk or card, the thickness is about 0.03 to 105 m, and in the case of a drum, it can also be used in a cylindrical shape. Materials include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene and polyethylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, polyamide, In addition to plastics such as 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, undercoating treatment, heat treatment, dust removal treatment, metal vapor deposition treatment, and alkali treatment.

Methods for coating the magnetic recording layer and back layer on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, Spray coating, barcodes, etc. can be used, and other methods are also possible, and detailed explanations of these methods can be found in "Coating, pp. 171253-277" published by Asakura Shoten (Showa 463.20).
．． Publication).

By such a method, the magnetic layer coated on the support is immediately subjected to a treatment to orient the magnetic powder in the layer in a desired direction while drying, if necessary, and then the formed magnetic layer is dried. The transport speed of the support at this time is usually 10 m.
/min~1000m/min, drying temperature is 20℃
Controlled at ~130°C. Further, the magnetic recording medium of the present invention is manufactured by subjecting it to surface smoothing processing and cutting it into a desired shape, if necessary. These manufacturing methods include filler surface treatment, kneading/dispersion, coating, heat treatment, calendaring, and
It is preferable to perform the steps of B treatment, surface polishing treatment, and cutting in succession. 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°C, and the humidity is expressed as the amount of moisture in the air.
It is 5■/d to 20■/d. These are disclosed, for example, in Japanese Patent Publication No. 40-23625, Japanese Patent Publication No. 39-28368, and US-Japanese Patent No. 3473960. Furthermore, the method disclosed in Japanese Patent Publication No. 4113181 is considered to be a basic and important technique in this field.

(Operations and effects of the present invention) Previous attempts to increase the storage modulus have been known, but the loss modulus and t-ignition tangent show small values, which improves durability. However, the present invention increases durability by increasing the loss modulus and loss tangent at a constant powder/binder ratio. In addition, it did not pick up vibration noise or sliding noise caused by running, and showed extremely good output and S/N. This is because it absorbs the movement.

These loss modulus and tangent loss are said to have viscous properties, and this is because they function to absorb energy. Incidentally, although the elastic modulus is temperature dependent, the present invention reduces the generation of noise related to running even in the temperature range of 0 to 50°C, and provides excellent RF output and S/N.

(Examples) 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 present invention should not be limited to the following examples; however, "parts" in the examples indicate "parts by weight."

(Example 1) After putting (1) of the magnetic layer composition below into a Ni-Goo and thoroughly kneading it, (IT) was added and kneaded thoroughly, and immediately before coating (
A magnetic paint was prepared by adding I[l] and mixing and dispersing it.

300 parts of Co-containing r-Fe*Os powder (nitrogen adsorption specific surface area: 35%/g, powder He: 6900e) 39 parts of vinyl chloride resin (COtH1)
400X110, manufactured by Nippon Zeon) Polyurethane resin 5 parts (Chrisbon 7209, manufactured by Dainippon Ink Co., Ltd.) Carbon black 15 parts (Palcan
C72, manufactured by Caboft Co., Ltd., average particle size 30 mμ) Abrasive: α-A1tos 18 parts (manufactured by Sumitomo Chemical Co., Ltd., HI750) Lubricant: 3 parts oleic acid 150 parts cyclohexanone (■) Polyurethane resin 10 parts (Chrisbon 7209, Dainippon Inkin 1) Butyl acetate 850 parts t@rt Butyl stearate 4 parts (Ill) Polyisocyanate 21 parts (Coronet) 3040. (Manufactured by Nippon Polyurethane Co., Ltd.) Stearic acid 3 parts Methyl ethyl ketone IOO parts After adjusting the viscosity of this magnetic paint, it was coated on a 19 μm non-magnetic support polyethylene terephthalate to a dry film thickness of 5.5 μm, and after that it was coated with a dry film thickness of 3000 μm.
It was dried while being magnetically oriented using a Gaussian magnet, and then subjected to a super calender at 85° C. to form a magnetic layer. Powder/binder was 100/22.5. Subsequently, on the back side of the non-magnetic support provided with the magnetic layer, the following backing composition (1) was added with a ball mill for cross-dispersion (If), mixed and stirred, and the prepared backing liquid was prepared to a dry film thickness of 2. OI
Im was coated to provide a back layer. Powder/binder was 100152.

Bal! ” 1 Suke Trasaku (1) Carbon Black 75 parts (MT
-CI: Nitrogen adsorption specific surface area: 10 rrr/g, average particle size 250 mμ, manufactured by Sebalco) Carbon black (Condextex SC: Nitrogen adsorption specific surface area: 200rd/g, average particle size 20 mμ, manufactured by Columbian) Polyurethane 25 parts of polycarbonate resin (FJ2, manufactured by Dainichiseika Chemical Co., Ltd.) Phenoxy resin (PKHH, Union car bioleate copper methyl ethyl ketone cyclohexanone (■)) Polyisocyanate (Coronate 2061, manufactured by Urethane Co., Ltd.) Lubricant (silicone, Lubricant KF69, Shin-Etsu Chemical) (manufactured by Nippon Polymer Co., Ltd.) 37 parts 10 parts (manufactured by Nippon Polymer Co., Ltd.) 0.1 part 700 parts 300 parts 5 parts 0.1 part 0.5 parts (oleic acid) Methyl ethyl ketone 100 parts After this, it was slit into 1-inch width and video・Manufactured tape.

(Example 2) In Example 1, 60 parts of vinyl chloride resin in the magnetic layer,
32 parts of polyurethane resin, 24 parts of polyisocyanate
(powder/binder: 100/34.8), and 64 parts of polyurethane polycarbonate resin in the bank layer.
A sample was prepared in the same manner as in Example 1 except that 17 parts of phenoxy resin was replaced with 9 parts of polyisocyanate (powder/binder: 100/90).

(Example 3) In Example 1, the magnetic layer was left as is, but the polyurethane polycarbonate resin in the bank layer was replaced with Nisten 5788.
(manufactured by Gutdrich) 30 parts, phenoxy resin 10 parts (
Powder/binder: 100/40), others: Example 1
A sample was created in the same way.

(Comparative Example 1) Vinyl chloride vinyl acetate resin 3 of the magnetic layer in Example 1
A sample was prepared in the same manner as in Example 1, except that 39 parts of nitrocellulose was used instead of 9 parts.

(Comparative Example 2) A tape was prepared by changing the magnetic layer's 39 parts of vinyl chloride resin and 5 parts of polyurethane resin (Crisbon® 209) to 44 parts of vinyl chloride resin in Example 1.
I created a sample in the same way.

(Comparative Example 3) A sample was prepared in the same manner as in Example 1 except that in Example 1, 10 parts of the phenoxy resin in the back layer was changed to 20 parts of vinyl chloride resin <400×110) to prepare a tape.

(Evaluation method) A video signal of 1M image signal 501RE was recorded at a standard recording current, and this was reproduced and passed through a 50KH high-pass filter, and the noise of the reproduced output signal was measured using a noise measuring device. The reference tape was similarly measured, and the difference between the obtained reference value and the measured value for the sample was expressed in dB.

For reproduction, the video signal of the station skin image signal 501RE is recorded at the standard recording current, and the average value of the envelope of this reproduction RF output is measured,
The reproduced RF output sensitivity with respect to the reference value is shown.

Procedural amendment

Claims (1)

[Claims] A magnetic recording comprising: a magnetic layer containing ferromagnetic powder, a binder, carbon black, an abrasive, and a lubricant provided on one side of a nonmagnetic support; and a back layer containing carbon black and a binder provided on the other side of the nonmagnetic support. In the medium, the weight ratio of powder/binder in the magnetic layer is 100/18 to 40.
and the weight ratio of powder/binder in the back layer is 10
0/45 to 100, and the storage modulus G' at 23° C. in the longitudinal direction of the magnetic recording medium is 5.0×10^1^
0dyn/cm^2 or more, loss modulus G″ is 2.0×1
0^9dyn/cm^2 or more, loss tangent tanδ is 0.
030 or more.