JPH02199616A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain both of high-quality electromagnetic conversion characteristics and traveling durability by using a combination of specific polyurethane and vinyl chloride copolymer resin having negative functional groups such as a sulfo group as a binder or the magnetic layer. CONSTITUTION:The vinyl chloride copolymer resin containing a substd. group selected from a sulfo group, phospho group, carboxyl group, alkali metal salt of sulfo group, alkali metal salt of phospho group and alkali metal salt of carboxyl group, and the polyurethane resin having a structural unit expressed by formula I as a part of its main chain are incorporated as a binder into the magnetic recording medium. In formula I, R represents alkyl group, (m) and (n) are 1 or 2. By this method, physical properties of polyurethane are improved, which improves the traveling duarbility of the medium as well as the dispersibility of the magnetic powder. Thus, both of the electric characteristics and traveling durability of the medium are raised to a higher level.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to magnetic recording media such as magnetic tapes, magnetic sheets, and magnetic disks.

BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint made of magnetic powder, binder resin, etc. onto a support and drying it.

In recent years, magnetic recording media, especially video magnetic recording media that require short wavelength recording, have become more fine-grained than ever before.
There is a growing tendency to use magnetic powder with high magnetic force. However, as magnetic powder becomes finer and has higher magnetic force,
The cohesive force of individual particles becomes stronger, and as a result, the dispersibility and surface smoothness required for obtaining high reproduction output and good S/N ratio for short wavelength recording are no longer fully satisfied. In addition, since such recording media come into intense sliding contact with the magnetic head during recording and reproduction, repeated use causes the magnetic coating to wear out, and the magnetic powder contained in the coating tends to fall off, resulting in undesirable effects such as clogging of the magnetic head. give rise to

It is well known to use urethane resin as a binder resin for the magnetic layer of such magnetic recording media. Conventionally known urethane resins are made of a high molecular weight polyol, a diisocyanate, a chain extender (used as necessary), and
It is synthesized from a crosslinking agent.

Such urethane resin is combined with vinyl chloride resin and phenoxy resin and used as a binder for the magnetic layer.

However, in the conventional combination, the dispersibility of the highly finely divided magnetic powder is insufficient, and there is a limit to the improvement in running durability in terms of physical properties. Therefore, it is difficult to solve the above-mentioned problems associated with the use of finely divided magnetic powder and to achieve both high-level electrical characteristics and running durability.

C1 Object of the invention The object of the invention is to provide a magnetic recording medium that has excellent dispersibility of magnetic powder, good physical properties of the binder of the magnetic layer, and is capable of achieving both high-level electromagnetic conversion characteristics and running durability. It is to provide a medium.

23 Structure of the Invention and Its Effects The present invention provides a magnetic recording medium having a magnetic layer containing magnetic powder and a binder. A vinyl chloride copolymer resin containing one or more substituents selected from the group consisting of metal salts and alkali metal salts of carboxyl groups, and a structural unit represented by the following general formula [I]. The present invention relates to a magnetic recording medium characterized in that polyurethane contained in a part of the main chain is contained as the binder.

General formula (I) [R represents an alkyl group.

m and n each represent 1 or 2. According to the magnetic recording medium of the present invention, the specific polyurethane described above and the vinyl chloride copolymer resin containing a negative functional group such as the sulfo group described above are used in combination as a binder for the magnetic layer. There are some notable features.

That is, since the above structure contains both the bisphenol A component and the alkylene oxide adduct component,
By effectively demonstrating the characteristics of each of these ingredients,
Moreover, the defects of each of these components can be mutually compensated for. This improved the physical properties of the polyurethane and improved the running durability of the medium. Moreover, the dispersibility of the magnetic powder was improved by blending it with the vinyl chloride resin having a negative functional group such as the sulfo group. Furthermore, the present inventor has discovered that the above-mentioned specific polyurethane is also excellent in the dispersibility of magnetic powder, and in combination with the effect of the above-mentioned vinyl chloride resin, the dispersibility of magnetic powder is further improved. Since the falling off of magnetic powder was improved, the running durability of the medium was further improved.

Next, a polyurethane containing the structural unit represented by the above general formula as part of the main chain will be described.

Similar to the usual polyurethane synthesis method, high molecular weight polyols (molecular weight 500 to 3000) such as polycarbonate polyol, poly, ester polyol, polylactone polyol, polyether polyol, etc. and polyfunctional aromatic,
Synthesized by reacting aliphatic isocyanates. As a result, polyester polyurethane, polyether polyurethane, and polycarbonate polyurethane carbonated with phosgene or diphenyl carbonate are synthesized.

These polyurethanes are primarily produced by the reaction of polyisocyanates with polyols and optionally other copolymers, and may also be in the form of urethane resins or urethane prepolymers containing free isocyanate groups and/or hydroxyl groups; It may also be in the form of a urethane elastomer, which does not contain any reactive end groups. As the isocyanate component, various diisocyanate compounds such as hexamethylene diisocyanate (HMDI), diphenylmethane diisocyanate) C can be used.
MDI), hydrogenated MD I (H,zMD I), toluene diisocyanate (TDI), l,5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), lysine diisocyanate methyl ester (LDI), inphorone diisocyanate (IPD)
I) etc. can be used.

Polyester polyol can be synthesized by polycondensing a dicarboxylic acid component and a polyhydric alcohol component.

Polycarbonate polyols are generally synthesized by transesterification of polyhydric alcohols with dialkyl carbonates or diallyl carbonates, or can be obtained by condensation of polyhydric alcohols with phosgene.

To introduce the structural unit represented by the above structural formula into the main chain, use the following polyhydric alcohol when producing polyester polyols, polycarbonate polyols, etc., or use polyester polyols, polycarbonate polyols, etc. and polyisocyanate. When reacting,
Use the following polyhydric alcohols.

General formula [■] In addition to the above, polyols and polyhydric alcohol components that can be used during production include glycols such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol, or trimethylolpropane, hexanetriol, glycerin, and trimethylolpropane. , trimethylolethane, pentaerythritol, polytetramethylene glycol, neopentyl glycol, or any two or more selected from these glycols and polyhydric alcohols.

Polyhydric carboxylic acid components such as dicarboxylic acids that can be used in polyol production include terephthalic acid, isophthalic acid,
Examples include sebacic acid, adipic acid, trimerized lyluic acid, and maleic acid.

When reacting a polyester polyol or the like with a polyisocyanate, in addition to the diol of the above general formula, if necessary, 1,4-butanediol, l.

It is also possible to use low-molecular polyfunctional alcohols such as 6-hexanediol and 1,3-butanediol to adjust the molecular weight, resin physical properties, and the like.

Furthermore, it is also possible to use the following aromatic diols in combination.

[R represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R' represents a hydrogen atom, an alkyl group having 1 to 7 carbon atoms, or an aryl group. ] [n represents an integer of 1 to 10. ] (The following is a margin) (n indicates 1 or 2) [n indicates 1 or 2] [n indicates 1 or 2] [n indicates 1 or 2 0. ] The amount of the structural unit represented by general formula [I] introduced into the polyurethane of the present invention is 1 to 30 mo1. %, more preferably 5 to 15 mof%.

If the amount of this structural unit introduced is smaller than the above, it will be difficult to see a sufficient effect on the dispersibility of the magnetic powder. If the amount of this structural unit introduced is larger than the above, the degree of improvement in electrical properties by calendering will be reduced.

Further, the number average molecular weight of the polyurethane resin according to the present invention is 5
000-100000, more preferably 1oooo-5
Preferably, it is in the range of 0000. If the number average molecular weight is less than 5,000, the coating film-forming ability of the resin is likely to be insufficient, and if the number average molecular weight exceeds 100,000, problems may occur in paint manufacturing processes such as mixing, transport, and coating. There is.

In the structural unit represented by general formula (I), it is more preferable that R is a methyl group.

The bisphenol A alkylene oxide adduct represented by general formula (II) can be synthesized by reacting bisphenol A and alkylene oxide.

Next, the vinyl chloride copolymer resin used in the present invention will be described.

This vinyl chloride copolymer resin is a copolymerizable heptamer monochloride containing a sulfo group, a phospho group, a carboxyl group, an alkali metal salt of a sulfo group, an alkali metal salt of a phospho group, or an alkali metal salt of a carboxyl group. monomer,
and, if necessary, by copolymerizing other copolymerizable monomers. This copolymerization method is already known, and is disclosed in JP-A-60-235814 and JP-A-60-2383.
No. 06, No. 60-238309, No. 60-23837
It is stated in No. 1 etc.

Moreover, various copolymerization components can be selected, and the properties of the copolymer can be optimally adjusted.

As the alkali metal, sodium, potassium, and lithium are preferred, and potassium is particularly preferred in terms of solubility, reactivity, and yield.

Examples of the copolymerizable monomer containing a sulfo group or an alkali metal salt of a sulfo group include the following.

CH, = C) iso, M CHz = CHC) (z S Oz MCHt = C
(CHx )CHt SOa MCHt =CHCH2
0COCH(CH2C00R)503M CHt =CHCHg 0CHt CH(OH)CHI
503 M CM,=C(CHs)coocz H,So,MCH
t = CHC00C, Hs So, MCH a = CHC
ON HC(CHs) t CHt S Os M
Examples of the seven-mers containing a phospho group or an alkali metal salt of a phospho group include the following.

CHz = CHC) (t 0CHt CH(OH) C
HzO-PO, MY' CHI =CHC0NHC(CHI)t CHzO-
PO, MY" Po, MX' CH,=CHCHg O(CH, CH, O)mPOx
In the above, M is an alkali metal or a hydrogen atom, R is an alkyl group having 1 to 20 carbon atoms, Yl is M or CHz = CHCHg 0CHz CH(OH)CHt
Y is M or CHt=CHC0NHC(CHs)2CH.

XI is or OM, X" is CHx "'CHCHz O(CHt CHz O)m
- or OM. Also, n is 1 to 100, m is 1 to 10
It is an integer of 0.

Examples of carboxyl groups and monomers containing alkali metal salts of carboxyl groups include acrylic acid, methacrylic acid, maleic acid, and alkali metal salts thereof.

The above copolymerizable resin includes an epoxy group-containing monomer and/or
Alternatively, a hydroxyl group-containing monomer may be included. In this case, the running properties of the magnetic recording medium are further stabilized. This hydroxyl group may be supplied as a monomer from the beginning, or may be generated by partial hydrolysis of a copolymer using another copolymerizable monomer (for example, fatty acid vinyl such as vinyl acetate).

Examples of monomers having an epoxy group include glycidyl ethers of unsaturated alcohols such as allyl glycidyl ether and methallyl glycidyl ether, glycidyl acrylate, glycidyl methacrylate, glycidyl-P-vinyl benzoate, methylglycidyl itaconate, and glycidyl ethyl maleate. , glycidyl vinyl sulfonate, glycidyl esters of unsaturated acids such as glycidyl (meth)allylsulfonate, butadiene monooxide, vinylcyclohexene monooxide, 2
Examples include epoxide olefins such as -methyl-5,6-nipoxyhexene.

Ru. This monomer is generally used in such a range that the amount of epoxy groups in the copolymer is 0.5% by weight or more. If this proportion is less than 0.5% by weight, it becomes difficult to select conditions for introducing strong acid roots.

In other words, as the monomer containing the above hydroxyl group, as X in the monomer having -X-OH group, C
nHt n, 0CnHz n, C00CnHx and C0
Examples include organic residues represented by NHCnHx n (n is an integer of 1 to 4). Examples of monomers having this -X-OH group include (meth)acrylic acid-2-
Hydroxyethyl ester, (meth)acrylic acid-2-
C2-C4 alkanol esters of α,β-unsaturated acids such as hydroxypropyl esters, mono-2-hydroxypropyl maleates, di-2-hydroxypropyl maleates, mono- itaconic acids
Alkanol esters of unsaturated dicarboxylic acids such as 2-hydroxybutyl ester, 3-buten-1-ol, 5
-Olefinic alcohols such as hexen-1-ol,
Examples include alkanol vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether, and acrylamides such as N-methylol acrylamide and N-methylol methacrylamide.

Further, the amount of hydroxyl groups based on the 1X-OH group bonded to the resin is preferably 0.1 to 2.0% by weight.

If it is less than 0.1% by weight, the crosslinking effect of the coating film by the isocyanate compound will not be exhibited, and if it is more than 2.0% by weight,
The pot life of the paint is too short to use up, and the amount of hydroxyl groups is far smaller than that of the vinyl chloride-vinyl alcohol-vinyl acetate copolymer known for magnetic paints. Nevertheless, the crosslinking reaction with the isocyanate compound is achieved satisfactorily. The reason for this is not clear, but it is thought to be due to the fact that the hydroxyl groups that participate in the reaction are farther away from the main chain of the copolymer, increasing the degree of freedom, and that the distribution of the hydroxyl groups in the polymer is more uniform. .

Other copolymerizable monomers that can be copolymerized as necessary include known polymerizable monomers, such as various vinyl esters such as evaporated vinyl acetate and vinyl propionate, vinylidene chloride, acrylonitrile, methacrylate trile, Examples include styrene, various acrylic esters, methacrylic esters, ethylene, propylene, isobutyne, butadiene, isoprene, vinyl ethers, aryl ethers, aryl esters, acrylamide, methacrylamide, maleic esters, and the like.

The vinyl chloride copolymer preferably includes a copolymer containing vinyl chloride-vinyl acetate (hereinafter referred to as "vinyl chloride-vinyl acetate copolymer").

Examples of vinyl chloride-vinyl acetate copolymers include vinyl chloride-vinyl acetate-vinyl alcohol, vinyl chloride-vinyl acetate-vinyl alcohol, and vinyl chloride-vinyl acetate-vinyl alcohol.
Examples include copolymers of vinyl acetate-maleic anhydride, vinyl chloride-vinyl acetate-vinyl alcohol-maleic anhydride, vinyl chloride-vinyl acetate-vinyl alcohol-maleic anhydride-maleic acid, and vinyl chloride-vinyl acetate. Among the copolymers, partially hydrolyzed copolymers are also preferred.

The degree of polymerization of the vinyl chloride copolymer is preferably 100.
-600, and if the degree of polymerization is less than 100, the magnetic layer etc. tend to become sticky, and if it exceeds 600, the dispersibility becomes poor. The vinyl chloride copolymer described above may be partially hydrolyzed.

In addition, as a method for measuring the degree of polymerization, the vinyl chloride copolymer of the present invention is heated and dissolved in cyclohexanone, and the specific viscosity of the solution is measured at 30°C according to JIS K6721. is converted to JIS specific viscosity using nitrobenzene to determine the degree of polymerization.

The vinyl chloride copolymer used in the present invention is polymerized by a polymerization method such as emulsion polymerization, solution polymerization, suspension polymerization, or bulk polymerization. In either method, known techniques such as divisional addition or continuous addition of molecular weight regulators, polymerization initiators, and monomers can be applied as necessary.

The amount of the monomer containing the acidic group or its salt in the vinyl chloride copolymer used in the present invention is 0.0
It is preferably 1 to 30 mol%. If the amount of the monomer is too large, the solubility in solvents will be poor and gelation will likely occur. Moreover, if the number of seven molecules is too small, desired characteristics cannot be obtained.

The proportion of the vinyl chloride copolymer is preferably 0.2 to 12 parts by weight per 100 parts by weight of the magnetic powder in the magnetic layer.

Note that vinyl chloride copolymer resins (for example, U,
VAGH) manufactured by C1C Co., Ltd. consisted of the following copolymerized components.

→CH2CH+T OH: indicates a copolymerization unit.

However, it is thought that the CH and Co-0- groups here do not easily contribute to the crosslinking reaction with the curing agent and the like. So C
In place of H and Co, it is preferable to contain an epoxy group such as the following. Examples include copolymers having the following units.

CH (X: monomer unit portion containing a sulfo group, phospho group, carboxyl group, or an alkali metal salt thereof) Ratio of the above lipolyurethane and the vinyl chloride copolymer having the above negative functional group in the magnetic layer The weight ratio is preferably (18) to (8:2), and more preferably (3 near) to (7:3).

The content of the polyurethane according to the present invention is preferably 100-1 parts by weight per 100 parts by weight of the magnetic powder, and 5 parts by weight.
It is more preferable to use 0 to 2 parts by weight.

Examples of "rMi powder" include 1-F ez O,, F ez
O.

These intermediate oxides, cobalt-containing iron oxide magnetic powder obtained by doping or depositing cobalt atoms on these iron oxide magnetic powders, ferromagnetic chromium dioxide powder, iron nitride, iron carbide, alloy metal magnetic powder, barium ferrite, or the like titanium,
Examples include those modified with metals such as cobalt.

In the cobalt-containing iron oxide magnetic powder, the content of cobalt is preferably 1.0 to 5.0% by weight based on the total magnetic powder.

The magnetic powder preferably has a coercive force (Hc) of 600 to 1200 oersteds. The specific surface area of the magnetic powder is preferably within the range of 10 to 70 rrr/g in BET value, more preferably 35 rrrf/g or more, and more preferably 40 i/g or more.

The above specific surface area is expressed as a BET value, which refers to the surface area per unit weight, and is a physical quantity that is completely different from the average particle diameter.For example, even if the average particle diameter is the same, there are Some have a small surface area. To measure the specific surface area, for example, first heat the powder at around 250°C for 30°C.
The powder was degassed during heat treatment for ~60 minutes to remove what was adsorbed to the powder, and then introduced into a measuring device, the initial pressure of nitrogen was set to 0.5 kg/rrf, and the powder was degassed with nitrogen. Perform adsorption measurements at liquid nitrogen temperature (-195 °C) (
Generally B.

A method for measuring specific surface area called the E, T method. For details, see J, Ame, Chem, Soc, 60309 (1
938)).

This specific surface area (BET value) measuring device uses a digestion battery.
It is also possible to use the "Powder/Granule Measuring Device (Cantersorb)" co-manufactured by Digestion Ionics ■.A general explanation of the specific surface area and its measurement method can be found in ,M.DALLAVALLE,
Co-authored by CLYDEORR Jr., translated by Benta and others; published by Sangyo Toshosha), and also in ``Chemistry Handbook''.
(Applied Edition, pp. 1170-1171, edited by the Chemical Society of Japan, published by Maruzen on April 30, 1966).
/gr), which is the same as the specific surface area in this specification. ).

Next, the overall structure of the magnetic recording medium of the present invention will be further described.

In addition to the resins mentioned above, known binders for the magnetic layer can be used.

The binder that can be used in combination has an average molecular weight of about 10,000.
~200,000, such as urethane resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer,
Butadiene-acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymer, polyester resin, various Synthetic rubber, phenolic resin, epoxy resin, urea resin, melamine resin, phenoxy resin, silicone resin, acrylic reaction resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of polyester polyol and polyisocyanate, urea formaldehyde resin, Examples include mixtures of low molecular weight glycols/high molecular weight diols/isocyanates, and mixtures thereof.

Incorporating carbon black in the magnetic layer is further advantageous in terms of improving runnability and electromagnetic conversion characteristics, and also slightly improves dispersibility and reduces the amount of residual solvent in the magnetic layer.

If a light shielding carbon black is used as such carbon black, the degree of light shielding can be further increased. As the light-shielding carbon black, for example, Raben 2000 manufactured by Columbia Carbon Co., Ltd. (specific surface area: 190
po/g, particle size 1Bmμ), 2100.1170.10
00. Mitsubishi Kasei #100, #75, #40, #
35, #30, etc. can be used.

Further, as the conductive carbon black, for example, Conductex (Columbia Carbon Co., Ltd.) is used.
x) 975 (BET value (hereinafter abbreviated as BET)
250 bo/g, DBP oil absorption (hereinafter abbreviated as DBP) 170
ml/100gr, particle size 24mμ), D Dactex 900 (BET125rd/g, particle size 27mμ)
, Conductex 40-220 (particle size 20mam
), Conductex SC (BET220 rrf/g
r, DBP115 ml-/100gr, particle size 20m
μ), Cabot Vulcan (Cabot Vul
can)
gr, D B P 118 m ft / loog
r, particle size 20 mμ), Raven 1040.4201 Black Bars 2000 (particle size 15 mμ), and #44 manufactured by Mitsubishi Kasei ■.

Other carbon blacks that can be used in the present invention include Conductex (manufactured by Columbia Carbon) (
Conductex) -3C, (BET2201/
g, DB pH 5 ml/100 g, particle size 20 mμ), Cabot Vufcan 9 (B
E T140 rd/g, DB P114 ml/1
00 g, particle size 19 mμ), #80 manufactured by Asahi Carbon Co., Ltd.
(BET117 bo/g.

DBP113 ml/100 g, particle size 23 mμ), manufactured by Denki Kagaku Co., Ltd. (7) H3100 (BET32M/g, DB
P180ynj! /100g, particle size 53mμ), #22B manufactured by Mitsubishi Kasei (B ET55rrr/gSDB
P131ml! /100 g, particle size 40 mμ),
#2OB (BET56rrf/g, D, B P1
15 ml/100 g, particle size 40 m u), #3
500 (BET47rd/g, DBP2
H4ml/100g, particle size 40mμ), as well as CF-9, #4000, MA manufactured by Mitsubishi Chemical Corporation.
-600, Cabot Black Burls (Bl
ack Pearfs) L, Monarch
k) 800, Black Burls 700, Black Burls 1000, Black Burls 880,
Black Pearls 9001 Black Pearls 130
0° Black Pearls 2000, Sterling (St.
Raven 410, Raven 3200, Raven 430, Raven 450, Raven 825, Raven 1255, Raven 1035, Seaben 1000. Examples include Raven 5ooo and Ketchen Black FC.

Furthermore, in the present invention, durability can be improved by further adding a polyisocyanate curing agent to the magnetic paint containing a binder.

Examples of such polyisocyanate curing agents include bifunctional isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and hexane diisocyanate;
trifunctional isocyanates (manufactured by DesModular, manufactured by Bayer AG), or urethane prepolymers containing isocyanate groups at both ends, which are conventionally used as curing agents, and can also be used as curing agents. Any polyisocyanate can be used. The polyisocyanate curing agent is used in an amount of 5 to 80 parts by weight based on the total amount of binder.

The magnetic recording medium of the present invention has, for example, as shown in FIG.
It has a magnetic layer 2 on a non-magnetic support 1 such as polyethylene terephthalate, and if necessary, a BCC 50 is provided on the opposite side of the magnetic layer 2. Also,
As shown in FIG. 2, an overcoat layer (QC layer) 4 may be provided on the magnetic layer 2 of the magnetic recording medium shown in FIG.

Further, the magnetic recording media shown in FIGS. 1 and 2 may be provided with an undercoat layer (not shown) between the magnetic layer 2 and the support 1, or may be provided with no undercoat layer. It's okay. The support may also be subjected to corona discharge treatment.

The magnetic layer 2 can contain a fatty acid and/or a fatty acid ester as a lubricant.

Thereby, while exhibiting the respective features of both, it is possible to offset the defects that occur when used alone, improve the lubrication effect, and improve still image durability, running stability, S/N ratio, etc. In this case, the amount of fatty acid added is preferably 0.2 to 10 parts by weight per 100 parts by weight of the magnetic powder.
0 parts by weight is even better.If the fatty acid content is outside this range, the dispersibility of the magnetic powder will be reduced and the runnability of the medium will tend to decrease, and if it is too large, the fatty acid will tend to seep out and the output will drop. In addition, the amount of fatty acid ester added is preferably 0.1 to 10 parts by weight per 100 parts by weight of magnetic powder.
0.2 to 8.5 parts by weight is even better. If the amount of ester is less than this range, the effect of improving the still durability will be poor, and if it is too much, the ester will easily seep out and reduce the output.

In addition, in order to better achieve the above effects, the weight ratio of fatty acids and fatty acid esters should be set as fatty acid/fatty acid ester =
10/90 to 90/10 is preferred. Note that fatty acids also have a dispersing effect, and it is thought that by using fatty acids, the amount of other low molecular weight dispersants used can be reduced, and the Young's modulus of the magnetic recording medium can be improved by that amount.

Fatty acids may be monobasic or dibasic,
Fatty acids having 6 to 30 carbon atoms, more preferably 12 to 22 carbon atoms, are preferred. Examples of fatty acids are as follows.

(1) Caproic acid (2) Caprylic acid (3) Capric acid (4) Lauric acid (5) Myristic acid (6) Valmitic acid (7) Stearic acid (8) Isostearic acid (9) Rilunic acid (lO) Linoleic acid (11) Oleic acid (12) Elaidic acid (13) Behenic acid (14) Malonic acid (15) Succinic acid (16) Maleic acid (17) Glutaric acid (18) Adipic acid (19) Pimelic acid (20) Azelaic acid (21) Sebacic acid (22) 1,12-dodecanedicarboxylic acid (23)
Octane dicarboxylic acid Examples of the above fatty acid esters are as follows.

(1) Oleyl oleate (2) Oleyl stearate (3) Incetyl stearate (4) Dioleyl maleate (5) Butyl stearate (6) Butyl palmitate (7) Butyl myristate (8) Octyl myristate Octyl Palmitate Amyl stearate Amyl palmitate Isobutyl oleate Stearyl stearate Lauryl oleate Octyl oleate Isobutyl oleate Ethyl oleate Isotridecyl oleate 2-Ethylhexyl stearate 2-Ethylhexyl myristate Ethyl stearate 2-Ethylhexyl palmitate Isopropyl palmi tate isopropyl myristate butyl laurate cetyl-2-ethylhexalate dioleyl adipate diethyl adipate (29) diisobutyl adipate (30) diisodecyl adipate In addition to the fatty acids and fatty acid esters mentioned above, other lubricants (such as silicone oil) , carboxylic acid modification, ester modification), graphite, carbon fluoride, molybdenum disulfide, tungsten disulfide, fatty acid amide, α-olefin oxide, etc.) may be added to the magnetic layer.

Non-magnetic abrasive particles can also be added to the magnetic layer. For example, α-alumina, chromium oxide, titanium oxide, α-iron oxide, silicon oxide, silicon nitride, silicon carbide, zirconium oxide, zinc oxide, cerium oxide, magnesium oxide, boron nitride, etc. are used. The average particle diameter of this abrasive is preferably 0.6 μm or less, and the Mohs hardness is preferably 5 or more.

In addition, the magnetic layer further contains an antistatic agent such as graphite.
A dispersing agent such as powdered lecithin or phosphate ester can be added. Furthermore, carbon black can also be used in combination.

In addition, the non-magnetic particles contained in the back coat layer are
It is more preferable to set the average particle diameter within the range of 10 mμ to 1000 mμ, because within the above range, the nonmagnetic particles will not become too fine and the addition effect will be good.

Non-magnetic particles include silicon oxide, titanium oxide, aluminum oxide, chromium oxide, silicon carbide, calcium carbide,
Examples include zinc oxide, α-Fe, O, talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, molybdenum dioxide, calcium carbide, barium sulfate, and the like. In addition, organic powders such as benzoguanamine resins, melamine resins, phthalocyanine pigments, etc. can also be used, and organic powders and the above-mentioned inorganic powders can also be used in combination.

Furthermore, it is more preferable to use carbon black together with the above-mentioned non-magnetic particles. This further stabilizes the running properties of the medium, and in combination with the effect of the non-magnetic particles described above, it is possible to further improve the durability of the medium.

The thickness of the magnetic layer is preferably thin in order to achieve a high S/N ratio, and thicker in terms of running performance and still durability. Therefore, 6.0 to 1.0 μm is preferable,
More preferably, the thickness is 5.0 to 2.0 μm.

Examples of the material forming the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; plastics such as polycarbonate, etc. can be mentioned. Further C
Metals such as u, AX, and Zn, glass, and various ceramics such as so-called new ceramics (for example, boron nitride, silicon carbide, etc.) can also be used.

The form of the non-magnetic support is not particularly limited, and may include tape,
It may be a sheet, card, disk, drum, etc., and various materials can be selected and used depending on the form and as necessary.

When the non-magnetic support is in the form of a tape or sheet, the thickness is usually in the range of 3 to 100 μm, preferably in the range of 5 to 50 μm. Furthermore, in the case of a disk or card shape, the thickness can usually be within the range of 30 to 100 μm. Furthermore, in the case of a drum shape, it can be made into a cylindrical shape, etc., depending on the recorder used.

E, Example The present invention will be explained in detail below.

The ingredients, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention. In addition, in the following examples, all "parts" are parts by weight.

Preparation of Videotape First, a magnetic layer was formed on a 14 μm thick polyethylene terephthalate base film as a support in the following manner.

That is, using the specified magnetic powder shown in Table 1 below, Table 1
A magnetic paint is prepared by dispersing each resin and various additives shown in the following, and this magnetic paint is filtered through a 1 μm filter, 6 parts of trifunctional isocyanate is added, and a 4.0 μm layer is coated on a support.
It was coated thickly and supercalendered to produce magnetic layers having various compositions shown in Table 1.

Thereafter, a paint for the BC layer having the following composition was applied to the opposite surface of the magnetic layer to a dry thickness of 0.4 μm.

Carbon black (Condactex-9F5 manufactured by Columbian Carboff) 40 parts Barium sulfate (average particle size 0.1 μm) 10 parts Nitrocellulose 25 parts N-
2301 (made by Nippon Polyurethane) 25 parts Coronate L (
) 10 parts cyclohexanone
400 parts methyl ethyl ketone
250 parts toluene
250 parts A wide magnetic film having a magnetic layer and a BC layer of a predetermined thickness was obtained in this way, and this was wound up.

This film was cut to a width of A inch to produce each videotape shown in Table 1. However, the numerical values shown in Table 1 represent parts by weight.

Each component shown in Table-1 is as follows.

■ Polyurethane This polyurethane has the following composition.

1.4-Butanediol tlQ (CL)40H 42°! l1wo 1% Adipic acid 1 (00C (CI, ), C00tl Bisphenol A propylene oxide adduct 36, 1sio 1% 11.6 end O1% Methyl isobutyl ketone 86 parts by weight Methyl acetate 280 Vinyl chloride
150 Vinyl acetate
50〃CH,=CHCH,0COCH(S03
K) CH□COOC8H1? 6 Diisopropyl peroxydicarbonate (polymerization initiator) 2 The above formulation was raised to 53°C without stirring, and methyl isobutyl ketone (No. 9) was added to the polymerization initiator in the formulation. 15
After a period of time, the reactor was cooled to 30°C, and the remaining vinyl chloride was recovered, and further recovered under reduced pressure. In this way, a copolymer with a solid content of 32% and a viscosity of 70 cps (25°C) was synthesized as follows.

The following composition was charged into a reaction vessel, replaced with N2, and reacted.

MR-110 (manufactured by Zeon Corporation) Evaluation of videotape performance> Each videotape shown in Table 1 was evaluated for the characteristics shown in Table 2 below.

The measurement method for each evaluation data is as follows.

Electromagnetic conversion characteristics Rumi S/N, Rf output crab Measured using HR-37000 (manufactured by Victor).

<100 pass tape> [Registered trademark] Pack the sample tape into a V)Is cassette, 20'C160
% RH using a deck of NV-6200 (manufactured by Matsushita Electric) and repeatedly run 100 buses (100 bus tape). Regarding this, Rf output fluctuation and dropout were measured.

Dropout: Using a dropout counter VD-5M manufactured by Victor Japan Co., Ltd., the output that is longer than 15 μsec and is 20 dB or more lower than the output of the RF envelope is regarded as one dropout, and the total length is measured, and the average value per minute is calculated. I asked for it.

<Tape Damage> The tape was run over its entire length under conditions of 40° C., 80% temperature, and humidity for 100 hours, and tape damage was observed.

○: No edge bending or wakame state of the tape.

ΔD Some edges are bent and seaweed condition occurs.

×: Edges were bent over the entire length, and a seaweed condition occurred.

As shown in Table 2, the sample constructed based on the present invention is superior to the sample of the comparative example.

[Brief explanation of the drawing]

FIGS. 1 and 2 are partially enlarged sectional views showing examples of magnetic recording media. In addition, in the symbols shown in the drawings, 1...Nonmagnetic support 2...Magnetic layer 3...Back coat layer (BC layer) )4・
...... Overcoat layer (QC layer). Figure 1

Claims (1)

[Claims] 1. In a magnetic recording medium having a magnetic layer containing magnetic powder and a binder, a sulfo group, a phospho group, a carboxyl group, an alkali metal salt of a sulfo group, an alkali metal salt of a phospho group, and a carboxyl group. A vinyl chloride copolymer resin containing one or more substituents selected from the group consisting of alkali metal salts of A magnetic recording medium, characterized in that the binder contains polyurethane as the binder. General formula [I] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [R represents an alkyl group. m and n each represent 1 or 2. ]