JPH0380423A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve dispersibility of ferromagnetic powder, traveling stability, production stability and electromagnetic conversion characteristics by incorporating specific polyurethane resin into a binder of a magnetic layer and incorporating specific amt. of fatty acid ester and magnetic powder of specified particle size into the magnetic layer. CONSTITUTION:Polyurethane resin produced by the reaction of isocyanate and polyester having a diol component derived from a diol expressed by the formula is incorporated into the binder of the magnetic layer. In the formula, R is hydrocarbon group of 1 - 6 carbon number, R' is hydrogen or hydrocarbon group of 1 - 6 carbon number, the total carbon number of R and R' is 3 - 10, and at least one of R and R' is a branched alkyl with >=3 carbon number. The obtd. magnetic layer contains 0.05 - 2pts.wt. fatty acid ester to 100pts.wt. magnetic powder. The magnetic powder has >=650 Oe coercive force and <=0.3mum average particle size.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium used for example in video tapes, audio tapes, etc., and more particularly, the present invention relates to a magnetic recording medium used for example in video tapes, audio tapes, etc. The present invention relates to a magnetic recording medium that has excellent stability, running durability, and electromagnetic conversion characteristics.

[Prior art, problem B to be solved by the invention] In recent years, for example, in the audio field, DAT (digital audio recorder) has appeared, and in the VTR field, the width is smaller than the conventional 1/2 inch width standard. narrow 8m
Due to circumstances such as the appearance of the m-width standard and its widespread use,
With regard to magnetic recording media, the demand for high-density recording is increasing, and magnetic recording media with higher performance, that is, magnetic recording media with excellent electromagnetic conversion characteristics and running durability, are desired.

In response to this demand, finely divided ferromagnetic powder has come to be used for the purpose of improving the electromagnetic conversion characteristics of magnetic recording media. Poor dispersion inside.

As a result, in a magnetic recording medium using finely divided ferromagnetic powder, the electromagnetic conversion characteristics may not be sufficiently improved. ■Some of the particles detached during running may attach to the magnetic head momentarily,
At this instant, so-called instantaneous head clogging, where the reproduction output decreases, is likely to occur.■ The smoothness of the surface of the magnetic recording medium is impaired, making the head clogging, knees, and edges more likely to occur, reducing running durability. Various problems arise, such as:

Therefore, the current situation is that a magnetic recording medium with good dispersibility of ferromagnetic powder, which does not cause a decrease in production stability, and which has excellent running durability and electromagnetic conversion characteristics, is awaited.

In particular, aliphatic dicarboxylic acids such as adipic acid and sebacic acid are used as carboxylic acids derived from the carboxylic acid component in the polyester polyol component constituting the polyurethane resin used as the binder for the magnetic layer, and glycol As the diol derived from the component, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-bentanediol, 1°6-hexanediol, neopentyl glycol, etc. are used. It's here. Furthermore, in order to improve the rigidity of the polyurethane resin, aromatic dicarboxylic acids and the like are being used as compounds derived from the carboxylic acid component. Recently, it has also been known to introduce a functional group into a polyurethane resin by using an aromatic dicarboxylic acid having a functional group such as a sulfonic acid metal salt in its molecule.

However, in order to improve the rigidity of polyurethane resin,
When aromatic dicarboxylic acids are used, the solubility of the polyurethane resin decreases, or this causes a decrease in the dispersibility of the magnetic powder.

In addition, in order to solve this problem of solubility and dispersibility, when introducing functional groups into the polyurethane resin, even if the amount of functional groups is increased or the molecular weight is increased, the aromatic dicarboxylic acid and the normal With glycol components, aggregation increases and good results cannot be obtained.

This invention has been made based on the above circumstances.

An object of the present invention is to provide a magnetic recording medium that has good dispersibility of ferromagnetic powder, excellent production stability, excellent running durability, and high electromagnetic conversion characteristics suitable for high-density recording. It's about doing.

[Means for Solving the Problems] That is, the present invention for solving the problems described above provides a magnetic recording medium comprising at least one magnetic layer on a non-magnetic support. The binder contains a polyurethane resin obtained from an isocyanate and a polyester having a diol component derived from a diol represented by the following formula (wherein, R is a hydrocarbon group having 1 to 6 carbon atoms, and Ro
is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and R
and Ro have a total number of carbon atoms of 3 to 10, and R and R
At least one of o is a branched alkyl having 3 or more carbon atoms. ) The magnetic layer contains 0.05 to 2 parts by weight of fatty acid ester based on 100 parts by weight of magnetic powder, and further the magnetic powder has a coercivity (He) of 6500e or more and 0.
．． The present invention is a magnetic recording medium characterized by having an average particle diameter of 3#Lm or less.

The nonmagnetic support and magnetic layer constituting the magnetic recording medium of the present invention will be explained below.

-Non-magnetic support- Examples of materials forming the non-magnetic support include polyethylene terephthalate and polyethylene-2,6.
- Polyesters such as naphthalates, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, and plastics such as polycarbonates. Metals such as Cu, An, and Zn, glass, and so-called new ceramics (e.g. boron nitride,
Various ceramics such as silicon carbide (silicone carbide, etc.) can also be used.

There is no particular restriction on the form of the non-magnetic support, and it may be tape-like, sheet-like, card-like, disc-like, drum-like, etc., and various materials may be used depending on the form and as necessary. can be selected and used.

When the support is in the form of a tape or sheet, the thickness is usually 3 to 1100p, preferably 3 to 50I.
It is Lm. In addition, in the case of disk-shaped or card-shaped,
Usually, it is 30 to 1100 JL. Furthermore, in the case of a drum shape, it can be made into a cylindrical shape, etc., depending on the recorder used.

The surface (back surface) of the non-magnetic support on which the magnetic layer is not provided is used to improve the running properties of the magnetic recording medium.

A back coat layer may be provided for the purpose of preventing static electricity, preventing transfer, and the like.

Furthermore, an intermediate layer (for example, an adhesive layer) may be provided on the surface of the nonmagnetic support on which the magnetic layer is provided, for the purpose of improving the adhesion between the magnetic layer and the nonmagnetic support.

one magnetic layer one A magnetic layer is provided on the non-magnetic support.

The magnetic layer in the present invention is formed from a specific magnetic powder, a specific binder, and a specific dispersant.

(Ferromagnetic Powder) In the magnetic recording medium of the present invention, the magnetic powder has a coercivity (Hc) of 6500 s or more, preferably 670 to 720 s.
0s, and the average particle diameter of the magnetic powder is 0.0s.
3 JLm or less, preferably in the range of 0.25 to 0.30 gm.

The magnetic powder has a coercivity of 6500 s or more and an average particle diameter of 0.3 Bm or less, thereby improving the dispersibility of the magnetic powder in the magnetic layer and maintaining the solubility of the binder, It is possible to improve production stability by suppressing the increase in viscosity when made into a magnetic coating material, and improve the adhesion between the magnetic powder and the binder described below in the magnetic layer, making it suitable for use as a magnetic recording medium. It is possible to improve running durability.

In other words, if the coercivity of the magnetic powder is less than 6500 s, the solubility of the polyurethane resin of the present invention will decrease, leading to agglomeration of the magnetic powder, and if the average particle diameter of the magnetic powder exceeds 0.31 Lm. , the surface of the magnetic layer becomes rough, noise components increase, and electrical characteristics deteriorate.

Further, this co-magnetic powder has a BET value of 35 m2/g or more, preferably 37 to 45 m2/g as a specific surface area.

If the BET value is less than 35 m2/g, the dispersibility may be lowered, leading to the inconvenience of agglomeration of the magnetic powder.

The magnetic powder having the above characteristics is, for example, y-Fe203. Fl! 304, iron oxide magnetic powder such as Co-adsorbed iron oxide, CO solid solution iron oxide, etc.5. F8, Ni
, Go, Fe-Ni-Co alloy, Fe-Mn-Zn
alloy, Fe-Xl-Zn alloy, Fe-Go-Ni-Or
alloy, Fe-Go-Ni-P alloy, Go-Ni alloy, etc., metal magnetic powder whose main components are Fe, Xi, Go, etc.
It can be appropriately selected from other magnetic powders such as CrO2, FeJ, Bad-6Fe 203, etc.

Preferred magnetic powders are γ-Fe2O3, CO-containing iron oxide, and Cr2O3.

The shape of the magnetic powder is not particularly limited as long as the average particle diameter and coercivity are within the specified ranges, and for example, acicular, columnar, or ellipsoidal shapes can be used. .

(Binder) The binder used in the present invention includes the following from the viewpoint of improving the rigidity of the binder and improving the dispersibility of the specific magnetic particles.
It is important to use specific polyurethane resins, which are discussed in detail below.

Further, it is preferable to use, as the binder, a vinyl chloride resin modified by introducing a functional group or a functional group that forms an intramolecular salt together with the specific polyurethane resin.

■Specific polyurethane resin This polyurethane resin is obtained by condensing a specific polyester with an isocyanate.

In the present invention, it is important to use a polyester having a diol component derived from a specific diol represented by the linear formula (I) as the specific polyester.

(However, R is a hydrocarbon group having 1 to 6 carbon atoms, and Ro
is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and R
and Ro have a total number of carbon atoms of 3 to IO, and R and R
At least one of o is a branched alkyl having 3 or more carbon atoms. ) In the above formula CI), as R, for example, a methyl group, an ethyl group, a propyl group, a butyl group, 1
- Alkyl groups such as methylpropyl group, pentyl group, 2-methylbutyl group, 3-methylbutyl group, hexyl group, 2-methylpentyl group, and 3-methylpentyl group, cycloalkyl groups such as cyclopentyl group and cycloalkyl group, and a phenyl group.

In the formula (I), Ro can be, for example, a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, an eimedylpropyl group, a pentyl group, a 2-methylbutyl group, 3
Examples include alkyl groups such as -methylbutyl group, hexyl group, 2-methylpentyl group and 3-methylpentyl group, cycloalkyl groups such as cyclopentyl group and cyclohexyl group, and phenyl group.

Preferred diols represented by the formula CI) include:
For example, etc. Among these, diol (1) and diol (2) are particularly preferred. These diols can be used alone or in combination of two or more.

In the present invention, to the extent that does not impede the purpose of the present invention,
Along with the diol represented by the formula (I), for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-bentanediol, 1,6-hexanediol, neopentyl glycol, Diethylene glycol, dipropylene glycol, 2゜2.4-)umethyl-1,3-obentanediol, 1.4-cyclohexane dimetatool,
Diols such as ethylene oxide adducts of bisphenol A, ethylene oxide adducts of hydrogenated bisphenol A, propylene oxide adducts of bisphenol A, propylene oxide adducts of hydrogenated bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; Tri- and/or tetraols such as methylolethane, trimethylolpropane, glycerin, and pentaerythritol can also be used in combination in appropriate proportions. Among them, 1,4-butanediol is preferred.

These various polyols can be used alone or in combination of two or more.

Carboxylic acids that provide the carboxylic acid component constituting the polyester include aromatic dicarboxylic acids such as terephthalic acid, inphthalic acid, orthophthalic acid, and 5-naphthalic acid; p-oxybenzoic acid, p-(hydroxyethoxy) Aromatic oxycarboxylic acids such as benzoic acid; aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid; tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid, etc. can be mentioned. Among these, preferred are terephthalic acid, isophthalic acid, adipic acid, and sebacic acid. These various carboxylic acids can be used alone or in combination of two or more.

Furthermore, in addition to the carboxylic acids mentioned above, dicarboxylic acids containing negative functional groups can also be used.

Examples of the dicarboxylic acid containing the negative functional group include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid, and 2-potassium sulfoterephthalic acid.

Examples of the isocyanate condensed with the polyester derived from the diol and carboxylic acid include 4. 2.4-) lylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate,
Hexamethylene diisocyanate, tetramethylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 4,4'-diisocyanate-diphenyl ether, 1,3-naphthalene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate , 1,3-diisocyanatemethylcyclohexane, 1,4-diisocyanatemethylcyclohexane.

4.4'-diisocyanate dicyclohexane, 4.4
'-diisocyanate dicyclohexylmethane, inphorone diisocyanate, and the like.

Furthermore, in addition to the above-mentioned isocyanates, Coronet) L (product name: manufactured by Nippon Polyurethane Industries), Desmodur L
Trifunctional isocyanates such as (trade name; manufactured by Bayer AG),
Alternatively, a urethane prepolymer containing isocyanate groups at both ends, which has been conventionally used as a curing agent, or a polyisocyanate that can be used as a curing agent can be used.

Among these, 4,4-diphenylmethane diisocyanate is preferred. The various isocyanates mentioned above can be used alone or in combination of two or more.

The amount of isocyanate used is usually 5% of the total amount of binder.
~80 parts by weight.

The molecular weight of the polyurethane resin obtained using the specific diol represented by formula (I) is not particularly limited, but is usually 2,000 to 70,000°, preferably 2o, ooo to 40,000. It is. This molecular weight is 70
．． If it exceeds 000, the viscosity of the magnetic coating material becomes unacceptably large, and the object of the present invention may not be achieved. On the other hand, if the molecular weight is less than 2,000, unreacted portions will occur during the step of applying the magnetic paint onto the non-magnetic support and curing it using a curing agent, resulting in low molecular weight components remaining. This may deteriorate the physical properties of the paint film.

Further, in this invention, the glass transition point of the polyurethane resin used as the binder is -10 to 30°C, preferably 0 to 20°C, and the glass transition point is within the above temperature range. It has the advantage that it has good calenderability in the calendering process and is also excellent in durability.

Note that this polyurethane resin can be manufactured according to a conventionally known method, so a detailed explanation thereof will be omitted.

(2) Vinyl chloride resin In the present invention, it is preferable to use a specific vinyl chloride resin into which a functional group or a functional group that forms an inner salt is introduced as a binder together with the above-mentioned specific polyurethane resin.

As the specific vinyl chloride resin, there can be mentioned a vinyl chloride resin obtained by copolymerizing a modified vinyl chloride resin and a copolymerizable heptamer.

Regardless of which vinyl chloride resin is used, what is important is that it has a functional group or a functional group that forms an intramolecular salt in the molecule.

The functional group is, for example, -503M.

-0303M, -COOM and (In mourning, M is either a hydrogen atom, lithium or sodium, and Ml and Ml are hydrogen, lithium, sodium or an alkyl group, respectively. Also, what are Ml and Ml? , which may be different from each other or may be the same).

Examples of the vinyl chloride resin to be modified to introduce the functional group include vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl propionate-vinyl alcohol copolymer, and vinyl chloride-vinyl acetate. -Vinyl maleate-vinyl alcohol copolymer, vinyl chloride-vinyl propionate-vinyl maleate-vinyl alcohol copolymer, vinyl chloride-vinyl propionate-
Vinyl maleate-acrylic glycidel ether-(2
-acrylamide-2-methylpropane potassium)-(
Examples include vinyl chloride copolymers such as allyl-2-hydroxypropyl ether) copolymer.

The vinyl chloride-based copolymer can be obtained by copolymerizing vinyl chloride hetamine, a copolymerizable hetamine containing a sulfonic acid salt, and other copolymerizable hetamines as necessary. I can do it. Since this copolymer is based on vinyl synthesis, it is easy to synthesize, and various copolymer components can be selected, so that the properties of the copolymer can be optimally adjusted.

The modification of the vinyl chloride resin is carried out by combining the vinyl chloride resin with, for example, C1-CHCl-CH2CH2SO3:H
2CH2O503M, CI-G) I 2COOM, ON
+ (However, M, Ml, and R2 each have the same meaning as above.) Distantly related compounds can be obtained by condensation with a compound containing a negative functional group and chlorine in the molecule by a dehydrochloric acid reaction. can. This is a method that utilizes polymer reactions.

The metal of the sulfonic acid or phosphate is an alkali metal (especially sodium, potassium, lithium), and potassium is particularly preferred in terms of solubility, reactivity, yield, etc.

Further, for the vinyl chloride resin having the negative functional group using a copolymerization reaction, examples of the copolymerizable monomer to be copolymerized with the vinyl chloride monomer include CH2monomer C)IsO3M' OH2Iris CHCH2S03%1GH2- C(CH3)CH2SO3MlCCH2=CH
CH2OC0CH(CH2GOOR1)SO3'CH?
=CHCH=CHCH2OCH2CH(OH)OH25
O3 Snow C (C:R3)COOCzHaSO3M+(Hl
-GHCOOC4Hss0311GH2=GICON)
(C(OR3)2cH2s03M+[However, M in the formula
l is the same as above, ], etc.

Also, as a copolymerizable monomer having a phosphate in the molecule.

OH2-CHCHZOCH2CH(OH)GH? -0-
PO: +M4Y lCH2 GHCONHC (CH3)
GHz-0-PO3H'Y? CH2-CH2H20(C
)12CH20)sP03M'X2 [However, in the sulfonate and phosphate, R4 represents an alkali metal, R1 represents an alkyl group having 1 to 20 carbon atoms, Yl is a hydrogen atom, and R4t-Jio and C) 12<H
CH20CH2GH(OH)OH2-(7) represents either Y2 is a hydrogen atom, R4, and GHz=CHC
ONHC ((:R3) represents either OH2- and 0R4, x2 is CH2-0H
-C)12-0-(CH2CH2O) #-represents either 1OH and 0R4, and m and n are 1 to
It is an integer of 100. ] Other types of copolymerizable polymers to be copolymerized with vinyl chloride as necessary include various vinyl esters, vinylidene chloride, acrylonitrile, methacrylonitrile, styrene, acrylic acid, methacrylic acid, and various other copolymerizable polymers. Examples include acrylic esters, methacrylic esters, ethylene, propylene, isobutyne, butadiene, imbrene, vinyl ethers, aryl ethers, aryl esters, acrylamide, methacrylamide, maleic acid, and maleic esters.

Vinyl chloride and a copolymerizable hexamer having a functional group are 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 a molecular weight controlling lacquer, a polymerization initiator, and a 7-mer can be applied, if necessary.

The blending amount of the vinyl chloride resin having a functional group is 30 to 80% by weight, preferably 40 to 80% by weight based on the total amount of the binder.
It is 60% by weight.

By setting the blending amount of the vinyl chloride resin having a functional group within the above range, it is possible to improve the dispersion state of the magnetic powder in the magnetic layer and improve the dispersion speed.

■Amount of binder The amount of the binder in the magnetic layer is usually 1 to 200 parts by weight, preferably 1 to 2 parts by weight, per 100 parts by weight of the magnetic powder.
~50 parts by weight.

If the amount of binder is too large, the amount of magnetic powder blended may become low and the recording density of the magnetic recording medium may decrease.
If the amount is too small, the strength of the magnetic layer may decrease and the running durability of the magnetic recording medium may deteriorate.

(1) Fatty acid ester In the present invention, it is important that the magnetic layer contains fatty acid ester in an amount of 0.05 to 2 parts by weight per 100 parts by weight of the magnetic powder.

If the content of fatty acid ester is less than 0.05 parts by weight, there will be disadvantages such as deterioration of running properties and loss of durability, while if it is contained in excess of 2 parts by weight, it will cause damage to the video deck. The first and second leads become dirty, which causes a problem in that the electrical characteristics deteriorate.

When the fatty acid ester is contained in the magnetic layer in the above content range, the friction coefficient of the magnetic layer is lowered to improve the lubricity, and the running properties and durability of the magnetic recording medium of the present invention are further improved. be done.

The fatty acid ester has a melting point of 80°C or less,
And it is desirable that the molecular weight (Mn) is 200-400.

The fatty acid ester is, for example, vinyl myristate,
Propyl myristate, butyl myristate, heptyl myristate, myristyl myristate, vinyl palmitate, propyl palmitate, isopropyl palmitate, butyl palmitate, vinyl stearate, propyl stearate, butyl stearate, amyl stearate, propyl oleate ate, allyl oleate, butyl oleate, 2-ethylhexyl palmitate, 2-
It can be appropriately selected and used from ethylhexyl myristate, 2-ethylhexyl stearate, and the like.

Among these, preferred are butyl stearate, butyl palmitate, 2-ethylhexyl palmitate,
2-ethylhexyl myristate and 2-ethylhexyl stearate.

(2) Other components In the present invention, other components forming the magnetic layer may include a dispersant, a lubricant, an abrasive, an antistatic agent, and the like.

Examples of the dispersant include lecithin, phosphoric acid ester, amine compound, alkyl sulfate, fatty acid amide, higher alcohol, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid ester, known surfactants, salts thereof, negative organic groups (e.g. -COOH,-
Examples include polymers containing salts of PO3H).

No matter which dispersant is used, the particle size is 0.2
Particulate dispersants of ~0.5 JLm, preferably 0.2-0.4 gm are desirable.

When the particle size of the dispersant is within the above range, coexistence with the specific polyurethane resin and fatty acid ester in the present invention increases the durability of the coating film, and has the effect of not impairing the electrical properties. be able to.

The various dispersants mentioned above may be used alone or in combination of two or more.

The amount of the dispersant added is as follows: For parts by weight, usually, 1 to 20 parts by weight Ru.

Examples of the lubricant include solid lubricants such as carbon black, graphite, carbon black graft polymer, molybdenum disulfide, and tungsten disulfide, silicone oil, modified silicone compounds, and fatty acids having 12 to 22 carbon atoms. .

Among these, carbon black, modified silicon compounds and fatty acids are preferred.

In particular, the fatty acid preferably has a melting point of 80° C. or less and a number average molecular weight of 200 to 400.

These may be used alone or in combination of two or more.

The amount of the lubricant used is usually 0.05 to 10 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the ferromagnetic powder.

Examples of the polishing agent include aluminum oxide, titanium oxide (TiO2), and silicon oxide (SiO1S).
i02), inorganic powders of silicon nitride, chromium oxide and boron carbide, and organic powders such as benzoguanamine resin powder, melamine resin powder and phthalocyanine compound powder.

The average particle diameter of the abrasive is usually 0.1 to 1. Ogm
preferably from 0.2 to 0.5 lm.

Further, the amount of the abrasive is usually in the range of 0.5 to 20 parts by weight based on 100 parts by weight of the ferromagnetic powder.

Examples of the antistatic agent include carbon black,
Conductive powders such as graphite, tin oxide-antimony oxide compounds, tin oxide-titanium oxide-antimony oxide compounds, and carbon black graft polymers; natural surfactants such as saponin; alkylene oxide-based, glycerin-based, glycidol-based, etc. Nonionic surfactants; higher alkylamines, quaternary pyridines, other heterocycles,
Cationic surfactants such as phosphonium and sulfocholams: Anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfate ester groups, phosphoric ester groups, diamino acids, aminosulfones, and sulfuric acid of amino alcohols. and amphoteric surfactants such as phosphoric acid esters.

These may be used alone or in combination of two or more.

The amount of the antistatic agent blended is usually 0.5 to 20 parts by weight based on 100 parts by weight of the ferromagnetic powder.

Note that the lubricant, antistatic agent, etc. do not have a single function; for example, a - compound may function as both a lubricant and an antistatic agent.

Therefore, the above classification in this invention.

The main effects are shown, and the effects of the classified compounds are not limited to the effects shown in the classification.

Next, a method for manufacturing the magnetic recording medium of the present invention will be explained.

(Manufacturing method) The magnetic recording medium of the present invention is produced by preparing a magnetic paint by cross-dispersing magnetic layer forming components such as the ferromagnetic powder and binder in a solvent, and then applying the obtained magnetic paint to the non-magnetic support. It can be manufactured by coating and drying.

The solvent used for crosstalk and dispersion of the magnetic layer forming components is as follows:
For example, acetone, methyl ethyl ketone (MEK),
Ketones such as methyl inbutyl ketone 011BK) and cyclohexanone Alcohols such as dimethanol, ethanol, propatool and butanol; Ester types such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, propyl acetate and ethylene glycol heptanoacetate ; Ethers such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran, dioxane; Aromatic hydrocarbons such as benzene, toluene, xylene, etc.; methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene, etc. halogenated hydrocarbons and the like can be used.

In kneading the magnetic paint components, the ferromagnetic powder and other magnetic paint components are charged simultaneously or individually into a mixer. For example, first, the magnetic powder is added to a solution containing a dispersant, and after kneading for a predetermined period of time, the remaining components are added and mixing is continued to obtain a magnetic paint.

Various types of kneading machines can be used for cross-mixing and dispersion. Examples of the kneading machine include a two-roll mill, a three-roll mill, a ball mill, a pebble mill, a side grinder, a Sqegvari attritor, a high-speed impeller disperser, a high-speed stone mill, a high-speed impact mill,
Dispani goo, high speed mixer, homogenizer,
Examples include ultrasonic dispersion machines.

The coating solution of the magnetic layer forming component thus prepared is coated onto a non-magnetic support by a known method.

Coating methods that can be used in this invention include, for example, gravure roll coating, knife coating, wire bar coating, doctor blade coating, reverse roll coating, dip coach ink, air knife coach ink, calendar coating, squeegee coating, Examples include kiss coating and fantin coating.

The thickness of the magnetic layer coated in this way is usually 1 to 10 pm in terms of dry thickness.

A single magnetic layer is usually formed on the support.

Two or more layers may be formed to increase density.

In addition, back coating may be applied to the back surface of the support in order to protect the support, prevent static electricity, and improve running properties.

After the magnetic layer-forming component has been applied in this way, a magnetic field alignment treatment is carried out if necessary in an undried state, and a surface smoothing treatment is usually carried out using a roller such as a super calender roll.

Next, a magnetic recording medium can be obtained by cutting into a desired shape.

The magnetic recording medium of the present invention can be used, for example, by cutting it into a long shape, as a magnetic tape such as a video tape or audio tape, or by cutting it into a disk shape.
It can be used as a floppy disk, etc. Furthermore, like ordinary magnetic recording media, it can also be used in card-like, cylindrical, or other forms.

[Example] Next, Examples and Comparative Examples of the present invention will be shown to further specifically explain the present invention. In addition, in the examples and comparative examples described below, "parts" shall represent "parts by weight."

-Preparation of polyester- In a reaction vessel equipped with a thermometer, a stirrer, and a partial reflux condenser, 679 parts of dimethyl terephthalate, 434 parts of ethylene glycol, and 2,2.4-trimethyl-1,3-
Add 1022 parts of betanediol, 0.66 parts of zinc acetate, and 0.08 parts of sodium acetate,
The transesterification reaction was carried out over 3 hours while heating to .degree.

Next, 1212 parts of sebacic acid was processed, 210 to 250 parts
After reacting for 2 hours while heating to ℃, the reaction system was depressurized to 20 mmHg over 40 minutes, and further
Polycondensation reaction was carried out for 60 minutes while heating to 240° C. under reduced pressure of ~20 m+*Hg.

A polyester was obtained from the polycondensation reaction product solution according to a conventional method.

The obtained polyester (I) had a hydroxyl value of 40. The composition of this polyester (1) is determined by NMR
The analysis revealed the following.

Terephthalic acid: 40 mol%, Sebacic acid: 60 mol%, Ethylene glycol: 44 mol%, Trimethylbentanediol: 56 mol% .

Polyesters (II) to (IV) were prepared by the same manufacturing method as this polyester (I).

Obtained polyesters (I), (II) to (EV)
cr+m is shown in Table 1.

- Preparation of urethane resin - In a reverse bottom vessel equipped with a thermometer, stirrer and reflux condenser, 1100 parts toluene, 1100 parts methyl ethyl ketone
1,000 parts of polyester (z), 170 parts of diphenylmethane diisocyanate, and 1.2 parts of dibutyltin dilaurate were added, and the reaction was carried out over 10 hours while heating to 70 to 90°C. The obtained polyurethane resin Using the same method as A, polyurethane resins BD were obtained using the polyesters (II) to (IV) (see Table 1).

(Example 1) A magnetic layer composition having the composition shown below was prepared using a ball mill.
A dispersion liquid was prepared by mixing and dispersing for 8 hours. Thereafter, a polyisocyanate compound [
A magnetic paint was prepared by adding 15 parts of Nippon Polyurethane (trade name) L (trade name: "Coronet") and mixing them.

CO-containing iron oxide ferromagnetic powder... 100 parts (H
c and particle size, see Table 2) α-k120s・・・・・・・・・5 parts (particle size is 2
(See table) Sulfonic acid metal base-containing polyvinyl chloride resin [manufactured by Nippon Zeon ■; MRIIO] 8 parts Polyurethane resin**e**e**** 7 parts (See Table 2 for types) Carbon black...・・・・・・・・・! 1 part myristic acid 1 part stearic acid
・・・・・・・・・ 1 part Butyl stearate...
...0.1 part cyclohexanone...
・・・10G part methyl ethyl ketone・・・・・・
100 parts toluene・・・・・・◆・・・ 1
00 116 First, the obtained magnetic paint was coated with a dry thickness of 31 mm.
It was applied onto a polyethylene terephthalate film having a thickness of 10 pm so that the film thickness was Lm.

A back coat layer was then applied to the back side of this film to a dry thickness of 3 parts.

Thereafter, the solvent was removed under heating, the surface was smoothed using a super calender, and the tape was cut to a width of 172 inches to produce a 1-2 inch video tape.

The characteristics of each 2-inch video tape were measured.

The results are shown in Table 2.

In addition, each characteristic was measured as follows.

Electromagnetic conversion characteristics: RF output: The output during reproduction of a 100% white signal was determined by comparing the tape of Example 1 as a reference tape.

Using Lumi-3/N and a noise meter (manufactured by Sibank), the difference in S/N of the sample at 100% white signal was determined using the tape of Example 1 as a reference and comparing it with the tape of Example 1. Ta.

Chroma S/N; HR-7100 (manufactured by Victor Japan)
The noise voltage was determined by recording at a maximum recording current of 4.5 MHz using the following.

Young's modulus was determined from the ratio of load and elongation during a tensile test of a niblastic film.

Friction coefficient; MSC tape running test machine [Yokohama system■
Measurements were made using a rubber mold under the conditions of a tape speed of 3.3 m/sec and a tape tension of 20 g.

Durability: 1 videotape made using HR-S7000 [manufactured by Victor Japan] at 40”0180%RH
It was evaluated as the number of running passes when running under the following conditions.

Dropout: Measured using a VTR dropout counter (manufactured by Shibaku).

(Examples 2 to 5 and Comparative Examples 1 to 5) In Example 1, the coercivity (He) and average particle size of the ferromagnetic powder in the magnetic paint prepared in Example 1, and the polyurethane resin shown in Table 1 A videotape was prepared in the same manner as in Example 1, except that the type of magnetic material, the average particle size of alumina in the magnetic layer, and the amount of fatty acid ester added were changed, and the properties of the obtained videotape were measured. .

The results obtained are shown in Table 2.

(Example 6) Using the magnetic paint of Example 5 as the upper layer and the magnetic paint B as the lower layer, a wet-on-wet multilayer coating method was used to coat the paint to a thickness of 1.
on a 4.5 pm polyethylene terephthalate support.
A videotape was prepared by coating the film so that the dry film thickness was 0.5 pm for the upper layer and 2.5 gm for the lower layer, and the properties of the obtained videotape were measured.

The results obtained are shown in Table 3.

In addition, magnetic paint B consists of a magnetic composition having the following structure:
After dispersion, 5 parts of polyisocyanate was added.

Magnetic paint B (lower W! Ri Gor-Fe203 (He: 680. BET: 38)
100 parts negative functional group polyvinyl chloride resin
13 parts Negative functional group polyester polyurethane resin 7 parts carbon black 10 parts myristic acid 2 parts stearic acid 1 part butyl stearate 1 part cyclohexanone
180 parts methyl ethyl ketone
120 parts toluene
120 parts (Example 7) A videotape was produced in the same manner as in Example 6, except that magnetic paint C was used as the upper layer and the magnetic paint of Example 5 was used as the lower layer. The cord characteristics were measured.

The results obtained are shown in Table 3.

In addition, the magnetic paint C is a magnetic composition having the following structure:
After dispersion, 5 parts of polyisocyanate was added.

Magnetic paint C (upper layer) Gor-Fe20Fr3 (Hc: 850. BET: 5
0) 100 parts polyvinyl chloride resin with negative functional group 13 parts polyester polyurethane resin with negative functional group 7 parts A203 (average particle size 0.3) 6 parts carbon black 3 parts myristic acid 2 parts stearic acid 1 part butyl stearate 1 part cyclohexanone
180 parts methyl ethyl ketone
120 parts toluene
120 parts (Comparative Example 6) "Magnetic paint of Example 5" used for the upper layer in Example 6 was "
A videotape was produced in the same manner as in Example 6, except that the magnetic paint of Comparative Example 5 was used, and the magnetic properties of the obtained videotape were measured.

The results obtained are shown in Table 3.

(Comparative Example 7) The “magnetic paint of Example 5” used for the lower layer in Example 7 was
Except for changing to “magnetic paint in Comparative Example 5”! A videotape was prepared using the same operating method as in Example 7, and the X-ray characteristics of the obtained videotape were measured. The results obtained are shown in Table 3.

(Evaluation) As is clear from Table 1, the magnetic recording medium of the present invention was found to be excellent in electromagnetic conversion characteristics, durability, and dropout, and not inferior in Young's modulus and coefficient of friction. Ta.

Furthermore, in the case of Examples 6 and 7 in which a multilayer was provided, it was observed that the electromagnetic conversion characteristics were improved.

[Effects of the Invention] According to the present invention, (1) A magnetic recording medium with excellent electromagnetic conversion characteristics, running durability, and dropout can be provided.

Claims (1)

[Claims] (1) In a magnetic recording medium comprising at least one magnetic layer provided on a non-magnetic support, the binder in the at least one magnetic layer is a polyester having a diol component derived from a diol represented by the following formula. Contains polyurethane resin obtained from isocyanate, and ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, R is a hydrocarbon group having 1 to 6 carbon atoms, and R'
is a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and R
and R′ have a total number of carbon atoms of 3 to 10, and R and R
At least one of ' is a branched alkyl group having 3 or more carbon atoms. ) The magnetic layer contains 0.05 to 2 parts by weight of fatty acid ester based on 100 parts by weight of magnetic powder, and further the magnetic powder has a coercivity (Hc) of 650 Oe or more and 0.
．． A magnetic recording medium characterized by having an average particle diameter of 3 μm or less.