JPH0750010A - Bonding agent for magnetic recording medium, and magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the material having the excellent surface roughness characteristic and electromagnetic conversion characteristic by using short-chain diol and short-chain diamine as main raw materials, and reducing the content of polyol having a long chain. CONSTITUTION:This is a bonding agent for magnetic recording medium comprising polyurethane resin, polyurethane urea resin and/or polyurea resin, which are reaction products, whose main raw materials are diol and/or diamine and organic diisocyanate. The diol comprises short-chain diole and long-chain diol of 0-5mol.% with respect to the entire polyurethane and/or polyurethane urea. The diamine contains the resin comprising short-chain diamine and long-chain diamine of 0-5mol.% with respect to the entire polyurethane urea resin and/or the urea resin. In this way, the short-chain diol and the short-chain diamine are used as the main raw materials, and the content of polyol having the long chain length is less. The dispersing property as the magnetic recording medium bonding agent is high. Therefore, the characteristics after the repeated running and the characteristics after the preservation for a long period are improved.

Description

Detailed Description of the Invention

[0001]

FIELD OF INDUSTRIAL APPLICATION A magnetic recording medium having a magnetic layer in which a ferromagnetic fine powder and a binder are dispersed is provided on a non-magnetic support, which is particularly excellent in electromagnetic conversion characteristics and durability. Regarding

[0002]

2. Description of the Related Art Magnetic recording media are widely used as recording tapes, video tapes, floppy disks and the like. In a magnetic recording medium, a magnetic layer in which ferromagnetic powder is dispersed in a binder (binder) is laminated on a non-magnetic support.

The magnetic recording medium is required to have a high level in various characteristics such as electromagnetic conversion characteristics, running durability and running performance. That is, in audio tapes for recording and reproducing music, a higher level of original sound reproduction capability is required. Further, the video tape is required to have excellent electromagnetic conversion characteristics such as excellent original image reproduction capability. In addition to having such excellent electromagnetic conversion characteristics, the magnetic recording medium is required to have good running durability as described above. Then, in order to obtain good running durability, an abrasive and a lubricant are usually added to the magnetic layer.

However, in order to obtain excellent running durability with the abrasive, it is necessary to increase the addition amount to some extent, which reduces the filling degree of the ferromagnetic powder.
Further, when an abrasive having a large particle size is used in order to obtain excellent running durability, the abrasive tends to excessively project on the surface of the magnetic layer. Therefore, the improvement of running durability by the abrasive often causes the above-mentioned deterioration of the electromagnetic conversion characteristics, which is a problem. When the running durability is improved by the lubricant, it is necessary to increase the addition amount of the lubricant, so that the binder is likely to be plasticized and the durability of the magnetic layer tends to decrease.

In order to improve the durability and electromagnetic conversion characteristics, the binder, which is one of the main components of the magnetic layer, naturally also plays an important role. Conventionally used vinyl chloride-based resins, cellulose-based resins, urethane-based resins, acrylic-based resins and the like have a problem that the wear resistance of the magnetic layer is poor and the running system members of the magnetic tape are contaminated.

As a method for improving such problems, a method of increasing the hardness of the magnetic layer by using a hard binder has been used. For example, a polyurethane binder obtained from a hydroxy end group-containing polycarbonate and a diisocyanate is described in JP-A-59-198530, and a polyurethane binder having -SO3M using polyester polyol as a polyol is disclosed in JP-B-58. -41565, and a polyurethane binder using a carboxyl group-containing polycaprolactone as a raw material is described in JP-A-62-201918. Further, a polyurethane binder prepared from a carboxyl group-containing polyether as a raw material is disclosed in JP-A-61-19071.
JP-A No. 62-28920 discloses a urethane urea containing a sulfonic acid tertiary amine salt, and JP-A No. 60-76017 discloses a diamine and an isocyanate. The urethane urea described in JP-A-64-78420 describes a urethane urea in which a diamine and an isocyanate further contain a carboxyl group.

As described above, the polyurethane resin or polyurethane urea resin used as the binder for the magnetic recording medium generally has a long chain having a hydrophilic segment such as polyester, polyether or polycarbonate and a weight average molecular weight of 500 or more. It is known that a diol, a diamine, a low molecular weight diol, and a diamine are composed of a chain extender having a weight average molecular weight of less than 500 and an organic diisocyanate. Further, according to the examples of the above-mentioned publications, it is described that the long chain diol in the resin is contained in an amount of 10 mol% or more. However, since the polyurethane resin or polyurethane resin has the above-mentioned hydrophilic segment, it hinders the affinity with the organic solvent, and the hydrophilic polar group easily aggregates,
There is a drawback in that the molecular chains in the organic solvent tend to spread less, which acts to impede the dispersibility of the ferromagnetic fine powder.

Further, long-chain diols having these hydrophilic segments have a problem that in the case of polyester, the ester bond group is easily hydrolyzed and the storability is deteriorated. Polyether is a polytetramethylene ether. It has a low Tg, such as glycol, polypropylene glycol, and polyethylene glycol, and is soft and has low strength. Further, polycarbonate is expensive and has a problem in storage stability.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a binder for a magnetic recording medium and a magnetic recording medium which have extremely high dispersibility, excellent long-term storability, and excellent durability under a wide range of temperature and humidity conditions. The purpose is.

[0010]

The above object of the present invention is to provide a magnetic recording medium comprising a polyurethane resin, a polyurethane urea resin and / or a polyurea resin which are reaction products containing diol and / or diamine and an organic diisocyanate as main raw materials. In the binder for use, the diol comprises a short-chain diol and a long-chain diol of 0 to 5 mol% based on the entire polyurethane resin and / or polyurethane urea resin, and the diamine is a short-chain diamine and a polyurethane urea resin and / or This can be achieved by a binder for a magnetic recording medium containing a resin composed of 0 to 5 mol% of a long-chain diamine based on the entire polyurea resin. Preferably, the short chain diol and the short chain diamine each have a weight average molecular weight of 50 to less than 500, and the long chain diol and the long chain diamine each have a weight average molecular weight of 500 to 5,000. It can be achieved by a binder for a recording medium. Further, the polyurethane resin and the polyurethane urea resin have --SO _{3 in the} molecule.
_{M, -OSO 3 M, -COOM,} -PO 3 M '2, -OP
^{_{O 3 M '2, -NR 2}} , -N + R 3 X -, -N + R 2 R'
SO ₃ ⁻ , —N ⁺ R ₂ R ^′ COO ⁻ (where M is a hydrogen atom, an alkali metal ion, or an ammonium ion, and M ^′ is a hydrogen atom, an alkali metal ion, an ammonium ion, or a C 1-12 carbon atom. An alkyl group, R, R
^′ Is an alkyl group having 1 to 12 carbon atoms, and X represents a halogen atom), and it can be achieved by a binder for a magnetic recording medium, which contains at least one polar group selected from Another object of the present invention is to provide a magnetic recording medium in which a magnetic layer containing a ferromagnetic powder and a binder is provided on at least one surface of a non-magnetic support, wherein the binder is diol and / or
Or a polyurethane resin, a polyurethane urea resin, and / or a polyurea resin, which are reaction products obtained by using diamine and an organic diisocyanate as main raw materials, and the diol is 0 to the whole short-chain diol and polyurethane resin and / or polyurethane urea resin. It is characterized by comprising 5 mol% of a long chain diol, and the diamine contains a resin comprising a short chain diamine and 0 to 5 mol% of a long chain diamine with respect to the entire polyurethane urea resin and / or polyurea resin. This can be achieved by a magnetic recording medium. Further, the above object of the present invention is a magnetic recording medium in which a lower magnetic layer or a lower nonmagnetic layer is provided on at least one surface of a nonmagnetic support, and an upper magnetic layer is provided on the lower magnetic layer, at least the magnetic layer or the nonmagnetic layer. One layer is composed of a polyurethane resin, a polyurethane urea resin and / or a polyurea resin, which is a reaction product in which a binder for binding a ferromagnetic powder or a non-magnetic powder is a diol and / or a diamine and an organic diisocyanate as a main raw material, The diol is composed of a short chain diol and 0 to 5 mol% of a long chain diol based on the entire polyurethane resin and / or polyurethane urea resin, and the diamine is 0 based on the short chain diamine and the entire polyurethane urea resin and / or polyurea resin.
This can be achieved by a magnetic recording medium characterized by containing a resin consisting of ˜5 mol% of long-chain diamine.

That is, the binder for a magnetic recording medium of the present invention is a polyurethane resin, a polyurethane urea resin and / or
Alternatively, a short-chain diol consisting of a polyurea resin, where the diol or diamine is a conventional chain extender,
It is characterized in that it is composed of a short-chain diamine as a main component, and a long-chain diol having a weight average molecular weight of 500 or more, which is usually used for these resins, is used as a whole for polyurethane resin, polyurethane urea resin and / or polyurea resin. On the other hand, since it contains only 5 mol% or less and there are few ester bonds, the storage stability is improved and the physical properties of the polyurethane are easily adjusted. The short chain diol and short chain diamine of the present invention preferably have a weight average molecular weight of 50 to less than 500, particularly preferably 62 to 300. The content of the long chain diol or the long chain diamine in the polyurethane resin, the polyurethane urea resin and / or the polyurea resin is preferably 1 to 3 mol% with respect to the entire polyurethane resin, the polyurethane urea resin and / or the polyurea resin. This is preferably 0 mol% from the viewpoint of improving the dispersibility.
However, it is preferable that the long-chain diol or the long-chain diamine be contained in the synthesis. The weight average molecular weight of the long chain diol or long chain diamine is 500 or more to 50 or more.
00, preferably 1,000 to 5,000, and 15
00-3,500 is more preferable, 2,000-3
000 diols and diamines are particularly preferred. When the weight average molecular weight is more than 5000, it becomes difficult to adjust the strength. The polyurethane resin, polyurethane urea resin and / or polyurea resin of the present invention has a weight average molecular weight of 50.
It is obtained by reacting a chain extender such as a short chain diol or a short chain amine of less than 0 with a polyisocyanate as a main raw material,
The amount of urethane bond (-NHCOO-) is about 1 to 3 mmol / g in a normal polyurethane, while it is about 5 to 5.
Since it contains 20 millimoles / g, preferably 5 to 10 millimoles / g, and particularly preferably 5 to 7 millimoles / g, the solution viscosity in a concentrated state is high, especially the viscosity of the kneaded product in the kneading process is high, and the high shearing force is high. Is obtained. Generally, there is a means of high shearing other than resin, such as reducing the amount of organic solvent in the kneading process, but this is thought to be a tendency for the ferromagnetic powder to reaggregate,
There is a drawback that the dispersibility decreases. The polyurethane resin, polyurethane urea resin, and polyurea resin of the present invention can be highly sheared and have improved dispersibility without using the above-mentioned means. Further, most of them are composed of only hard segments, so that they have high Tg, high coating strength, less likely to cause storage tackiness, and have excellent repeated running stability as a video tape.

Examples of the short-chain diol or the short-chain diamine having a weight average molecular weight of less than 500 used in the binder for magnetic recording media of the present invention include the following. Specifically, ethylene glycol, 1,3-propylene diol, 1,2-propylene glycol, 1,4-butane diol, 1,5-pentane diol, 1,6-hexane diol, 2,2-dimethyl propane diol. , 1,8
-Octanediol, 1,9-nonanediol, diethylene glycol, cyclohexane-1,4-diol,
Aliphatic diols such as cyclohexane-1,4-dimethanol, alicyclic diols, etc., aromatic diols such as bisphenol A, ethylene oxide or propylene oxide adducts of bisphenol A, ethylene oxide or propylene oxide addition of N-diethanolamine Examples thereof include diols and hydrides thereof. Alicyclic diols and aromatic diols are preferred, and cyclohexane 1,4 diol, bisphenol A, propylene oxide adduct of bisphenol A, and hydrides thereof are more preferred.

The short-chain diamines include aliphatic diamines such as tetramethylenediamine and hexamethylenediamine, m-phenylenediamine, p-phenylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, Aromatic diamines such as 4,4′-diphenylenediamine and 1,5-naphthalenediamine, 1,3-diaminomethylcyclohexanone, 1,4-diaminomethylcyclohexanone, 4,4′-diaminomethylcyclohexylmethane and isophoronediamine Examples thereof include alicyclic diamine. Aromatic diamines and alicyclic diamines are preferable, and p-phenylenediamine is more preferable,
There are 1,4-diaminocyclohexane and 4,4-diphenylenediamine.

Molecular weight 500 which can be used in the present invention
Examples of the long-chain polyol having a molecular weight of up to 5000 include the following polyether polyols, polyester polyols, polycarbonate polyols, and polyolefin polyols. As the polyether polyol, ethylene glycol, diethylene glycol, polypropylene glycol, 1,4 or 1,3-butanediol, neopentyl glycol, 1,6-hexanediol,
Glycols such as 1,8-octanediol, 1,10-decanediol, cyclohexanediol, cyclohexanedimethanol, bis (hydroxymethyl) cyclohexane, m- and p-xylylene glycol, bis (hydroxyethyl) benzene, 1,4 -Low molecular weight diols such as bis (2-hydroxyethoxy) benzene and 4,4-bis (2-hydroxyethoxy) diphenylpropane, and alkylene oxides, ethylene oxide, propylene oxide, 1, and mixtures of two or more thereof.
Examples thereof include those obtained by ring-opening polymerization or ring-opening copolymerization of a 2,1,3 or 1,4-butylene oxide adduct and a cyclic ether such as alkylene oxide or tetrahydrofuran. Examples thereof include polypropylene glycol and polyethylene-polypropylene glycol. , Polytetramethylene glycol, polytetramethylene-ethylene glycol, polytetramethylene-propylene glycol,
Mention may be made of polyhexamethylene glycol and mixtures of two or more thereof. Examples of the polyester polyol include a condensed polyester polyol obtained by reacting the above-mentioned low-molecular diol with a dicarboxylic acid, and a polylactone diol obtained by ring-opening polymerization of a lactone.

Examples of the dicarboxylic acid include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, glutaric acid, azelaic acid, maleic acid and fumaric acid, and a mixture of two or more thereof. -Caprolactone. Specific examples of these are:
Polyethylene terephthalate, polybutylene terephthalate, polyhexamethylene phthalate, polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polyneopentyl adipate, polyethylene propylene adipate, polyethylene butylene adipate, polyethylene hexamethylene adipate, polydiethylene adipate, polyethylene azelate, Polyethylene separate, polybutylene azelate, polybutylene separate, polycaprolactone diol, and mixtures of two or more thereof.

Examples of the polycarbonate polyol include compounds obtained by reacting a low molecular diol with a carbonate. The low molecular diol has 4 to 4 carbon atoms.
17, aliphatic diols such as 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol and 1,8-octanediol, 1,3- Cyclohexanediol, 1,4-dimethylolcyclohexane, 1,4
Examples thereof include cyclohexanediol, alicyclic diol such as 1,3-dimethylolhexane, and polyoxyalkylene glycol. As carbonate, ethylene carbonate, trimethyl carbonate,
Examples thereof include tetramethyl carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, and 1,2-ethylene carbonate. Polyolefins Polyolefin polyols include polybutadiene polyols. Preferred as these long-chain polyols are aromatic dicarboxylic acid type polyester polyols, polycaprolactone polyols, and polycarbonate polyols.

In addition, organic diisocyanates include 2,4
-Tolylene diisocyanate, 2,6-Tolylene diisocyanate, xylene-1,4-diisocyanate, xylene-1,3-diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4-diphenyl ether diisocyanate, 2-nitrodiphenyl-4 ．
4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1 , 5-
Diisocyanate, 3,3'-dimethoxydiphenyl-
Aromatic diisocyanates such as 4,4′-diisocyanate, aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, etc. Can be mentioned. Aromatic diisocyanates are preferable, and more preferably 4,4 diphenylmethane diisocyanate, 2,2 tolylene diisocyanate, p-
Phenylene diisocyanate and isophorone diisocyanate.

Since the short-chain diol and the short-chain diamine are used in the binder of the present invention, the chain between the polyurethane bonds is shortened, and aromatic or aliphatic groups are present in the vicinity of the urethane bond, which causes steric hindrance. It seems that good dispersibility can be obtained because the urethane bonds are prevented from associating with each other. Further, a binder for magnetic recording media having strength equivalent to that of polyurethane containing a long-chain polyol and having significantly improved storability and dispersibility can be obtained.

The content of polyurethane resin, polyurethaneurea resin and / or polyurea resin in the binder is 10
Is preferably 90 to 90% by weight, more preferably 20 to 80% by weight, particularly preferably 25 to 60% by weight. When both are mixed, the total amount is preferably within this range. If it is less than 10% by weight, the dispersibility tends to decrease, probably because the solubility in the organic solvent decreases, and also 90% by weight.
When the amount is larger, the magnetic coating film becomes softer, so that the head tends to become dirty due to repeated running and the durability tends to decrease.

The weight average molecular weight of the polyurethane resin, polyurethane urea resin and / or polyurea resin is 10,000 to 200,000, and 10,000 to 200,000.
100,000 is preferable and 20,000-800,0
00 is more preferable, and 30,000 to 70,000 is particularly preferable. These weight average molecular weights are 10,000
If it is smaller, the coating film strength tends to decrease, and the running durability tends to decrease. The weight average molecular weight of these is 200,000.
When it is more than the above, the solubility in the solvent tends to decrease, and the dispersibility tends to decrease.

The binder composed of the polyurethane resin, polyurethane urea resin and / or polyurea resin of the present invention includes -SO ₃ M, -OSO ₃ M, -COOM and -PO ₃ M.
^{_{'2, -OPO 3 M' 2}} , -NR 2, -N + R 3 X -, -N
^{_{+ R 2 R 'SO 3 -}} , -N + R 2 R' COO - ( however, M is a hydrogen atom, an alkali metal ion, an ammonium ion, M 'is a hydrogen atom, an alkali metal ion, an ammonium ion, carbon atoms 1 to 12 alkyl groups, R and R ^′ are alkyl groups having 1 to 12 carbon atoms, and X represents a halogen atom), and preferably contains at least one polar group. The amount of the polar group is 1 × 10 ⁻⁶ to 1 × 10 ⁻³ eq / g, preferably 1 × 10 ^{−5 to} 5 × 10 ⁻⁴ eq / g, and particularly preferably 2 × 10 ⁻⁵ to. It is 2 × 10 ⁻⁴ eq / g. 1 x 10
If it is less than ^-6 eq / g, it becomes difficult to adsorb to the ferromagnetic powder and the dispersibility decreases, and if it exceeds 1 × 10 ^-3 eq / g, the solution viscosity increases due to the association between polar groups and the dispersibility. Tends to decrease.

The number of hydroxyl groups in the polyurethane resin, polyurethane urea resin and / or polyurea resin is 1
2 to 20 per molecule, preferably 3.5 to 10
The number is 4 and particularly preferably 4 to 6. When it is less than 2, the reactivity with the isocyanate curing agent is low and the coating strength is lowered, and when it is more than 10, the viscosity of the coating liquid tends to be high and the dispersibility tends to be lowered. The glass transition temperature (Tg) of the polyurethane resin, polyurethane urea resin and / or polyurea resin is 40 to 150 ° C, preferably 45 to 120 ° C, particularly preferably 50 to 90 ° C. When the temperature is 40 ° C or lower, the coating film strength is low and the running durability is also low. 12
When the temperature is 0 ° C. or higher, the solubility in the solvent is lowered and the dispersibility tends to be lowered.

When the binder of the present invention is used in the magnetic layer, a vinyl chloride synthetic resin may be used in combination with the polyurethane resin, polyurethane urea resin and / or polyurea resin of the present invention. The polymerization degree of the vinyl chloride resin that can be used in combination is preferably 200 to 600, and 250 to 4
50 is particularly preferred. The vinyl chloride resin may be a copolymer of vinyl monomers such as vinyl acetate, vinyl alcohol, vinylidene chloride and acrylonitrile. In addition to the polyurethane resin, polyurethane urea resin and / or polyurea resin and vinyl chloride resin of the present invention, various synthetic resins can be used for forming each magnetic layer. For example, ethylene-vinyl acetate copolymer,
It is a cellulose derivative such as a nitrocellulose resin, an acrylic resin, a polyvinyl acetal resin, a polyvinyl butyral resin, an epoxy resin, or a phenoxy resin. These can be used alone or in combination.
When another synthetic resin is used in combination, urethane contained in the magnetic layer is preferably contained in the binder in an amount of 10 to 90% by weight, more preferably 20 to 80% by weight.
Is the amount of. An amount of 25 to 60% by weight is particularly preferable. The vinyl chloride resin is preferably contained in the binder in an amount of 10 to 80% by weight, more preferably 20 to 70% by weight. Particularly preferably 30 to 6
The amount is 0% by weight.

Further, a curing agent such as a polyisocyanate compound can be used together with the binder of the present invention.
Examples of the polyisocyanate compound include reaction products of 3 mol of tolylene diisocyanate and 1 mol of trimethylol propane (eg, Desmodur L-75 (manufactured by Bayer)), diisocyanate 3 such as xylylene diisocyanate or hexamethylene diisocyanate. Mole reaction product of 1 mole of trimethylolpropane, buret addition compound of 3 moles of hexamethylene diisocyanate, isocyanurate compound of 5 moles of tolylene diisocyanate, isocyanurate addition of 3 moles of tolylene diisocyanate and 2 moles of hexamethylene diisocyanate Mention may be made of the compounds, polymers of isophorone diisocyanate and diphenylmethane diisocyanate. The polyisocyanate compound contained in the magnetic layer is preferably contained in the binder in an amount of 10 to 50% by weight, more preferably 20 to 40% by weight.

Further, when the curing treatment is carried out by electron beam irradiation, a compound having a reactive double bond such as urethane acrylate can be used. The total weight of the resin component and the curing agent (that is, the binder) is preferably in the range of usually 15 to 40 parts by weight, more preferably 20 to 30 parts by weight, based on 100 parts by weight of the ferromagnetic powder.
Parts by weight. The ferromagnetic powder used in the magnetic recording medium of the present invention is a ferromagnetic iron oxide, a cobalt-containing ferromagnetic iron oxide or a ferromagnetic alloy powder having an S _BET specific surface area of 40 to 80 m ² /
g, preferably 50 to 70 m ² / g. The crystallite size is 12 to 25 nm, preferably 13 to 22 nm, and particularly preferably 14 to 20 nm. The major axis length is 0.05 to 0.25 μm, preferably 0.07 to
0.2 μm, particularly preferably 0.08 to 0.15
μm. Fe, Ni, Fe-C as the ferromagnetic powder
o, Fe-Ni, Co-Ni, Co-Ni-Fe and the like, and within the range of 20% by weight or less of the metal component, aluminum, silicon, sulfur, scandium, titanium, vanadium, chromium, manganese, copper, Alloys containing zinc, yttrium, molybdenum, rhodium, palladium, gold, tin, antimony, boron, barium, tantalum, tungsten, rhenium, gold, mercury, lead, phosphorus, lanthanum, cerium, praseodymium, neodymium, tellurium, bismuth. be able to. Also, a small amount of ferromagnetic metal powder in water,
It may be one containing a hydroxide or an oxide.
The method for producing these ferromagnetic powders is already known, and the ferromagnetic powder used in the present invention can also be produced according to known methods. The shape of the ferromagnetic powder is not particularly limited, but needle-shaped particles, granular particles, dice-shaped particles, rice particles, and plate-shaped particles are usually used. In particular, it is preferable to use needle-shaped ferromagnetic powder.

The above resin component, curing agent and ferromagnetic powder are kneaded and dispersed together with a solvent such as methyl ethyl ketone, dioxane, cyclohexanone, ethyl acetate and the like which are usually used in the preparation of magnetic paint to obtain a magnetic paint. Kneading and dispersion can be performed according to a usual method. In addition to the above components, the magnetic paint contains α-Al ₂ O ₃ , Cr ₂
Abrasives such as O ₃ , antistatic agents such as carbon black, lubricants such as fatty acids, fatty acid esters, silicone oils,
It may contain a commonly used additive or filler such as a dispersant. Next, the lower non-magnetic layer or the lower magnetic layer in the case where the present invention has a multilayer structure will be described. The inorganic powder used in the lower layer of the present invention is a magnetic powder,
Any non-magnetic powder is acceptable. For example, in the case of non-magnetic powder, it can be selected from inorganic compounds such as metal oxides, metal carbonates, metal sulfates, metal nitrides, metal carbides and metal sulfides. As the inorganic compound, for example, the alpha conversion rate of 90 to 10
0% of α-alumina, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium oxide,
Silicon dioxide, tin oxide, magnesium oxide, tungsten oxide, zirconium oxide, boron nitride, zinc oxide, calcium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide and the like are used alone or in combination. Particularly preferred are titanium dioxide, zinc oxide, iron oxide and barium sulfate, and more preferred is titanium dioxide.
The average particle size of these non-magnetic powders is preferably 0.005 to 2 μm, but if necessary, non-magnetic powders having different average particle sizes may be combined, or a single non-magnetic powder may be used to broaden the particle size distribution and achieve the same effect. You can also have. Particularly preferably, the average particle size of the nonmagnetic powder is 0.01 μm to 0.2.
μm. The pH of the non-magnetic powder is particularly preferably between 6 and 9. The specific surface area of the non-magnetic powder is 1 to 100 m ² / g, preferably 5 to 50 m ² / g, more preferably 7 to 40 m ²
/ G. The crystallite size of non-magnetic powder is 0.01 μm ~
2 μm is preferable. Oil absorption using DBP is 5-100
ml / 100g, preferably 10 to 80 ml / 100g, more preferably 20 to 60 ml / 100g. The specific gravity is 1 to 12, preferably 3 to 6. The shape may be needle-like, spherical, polyhedral or plate-like.

Al ₂ O ₃ and SiO are formed on the surface of these non-magnetic powders.
Surface treatment with ₂ , TiO ₂ , ZrO ₂ , SnO ₂ , Sb ₂ O ₃ , and ZnO is preferable. Al ₂ O ₃ , SiO ₂ , and T are particularly preferable for dispersibility.
iO ₂ , ZrO ₂ , and more preferably Al ₂ O ₃ , SiO ₂ ,
It is ZrO ₂ . You may use these in combination,
It can also be used alone. Depending on the purpose, a co-precipitated surface-treated layer may be used, or a method of first treating with alumina and then treating the surface layer with silica or vice versa can be adopted. The surface treatment layer may be a porous layer depending on the purpose, but it is generally preferable that it is homogeneous and dense.

By mixing carbon black in the lower layer, Rs, which is a known effect, can be lowered, and a desired micro Vickers hardness can be obtained. For this purpose, furnace black for rubber, thermal black for rubber, carbon black for color, acetylene black and the like can be used. The specific surface area of carbon black is 100 to 500 m ² / g, preferably 150 to 400 m ^2.
/ G, DBP oil absorption is 20 to 400 ml / 100 g, preferably 30 to 200 ml / 100 g. Carbon black has an average particle size of 5 to 80 mμ, preferably 10 to 50 mμ,
More preferably, it is 10 to 40 mμ. Carbon black preferably has a pH of 2 to 10, a water content of 0.1 to 10%, and a tap density of 0.1 to 1 g / ml. Specific examples of the carbon black used in the present invention include BLACKPEARLS 2000, 130 manufactured by Cabot Corporation.
0, 1000, 900, 800, 880, 700, VU
LCAN XC-72, Mitsubishi Kasei Co., Ltd., # 3050
B, 3150B, 3250B, # 3750B, # 395
0B, # 950, # 650B, # 970B, # 850
B, MA-600, Columbia Carbon Co., COND
UCTEX SC, RAVEN 8800,8000,7000,5750,
5250, 3500, 2100, 2000, 1800, 1500, 1255, 1250, Ketjen Black EC manufactured by Akzo, and the like can be mentioned.

A magnetic powder can also be used in the lower layer of the present invention. Examples of the magnetic powder include γ-Fe ₂ O ₃ , Co-modified γ-Fe ₂ O ₃ , alloys containing α-Fe as a main component, and CrO.
₂ etc. are used. In particular, Co-modified γ-Fe ₂ O ₃ is preferable. The ferromagnetic powder used in the lower layer of the present invention preferably has the same composition and performance as the ferromagnetic powder used in the upper magnetic layer. However, it is well known that the performance is changed between the upper and lower layers depending on the purpose. For example, in order to improve long-wavelength recording characteristics, it is desirable to set Hc of the lower magnetic layer lower than that of the upper magnetic layer, and Br of the lower magnetic layer higher than that of the upper magnetic layer. It is valid. In addition to the above, it is possible to impart the advantages by adopting a known multilayer structure.

As the binder, lubricant, dispersant, additive, solvent, dispersion method and the like of the lower magnetic layer or the lower non-magnetic layer, those of the magnetic layer can be applied. In particular, with regard to the amount and kind of binder, the amount and kind of additive and dispersant added, known techniques for the magnetic layer can be applied. A magnetic coating material prepared from the above materials is applied onto a non-magnetic support to form a magnetic layer. As the non-magnetic support that can be used in the present invention, known materials such as biaxially stretched polyethylene naphthalate, polyethylene terephthalate, polyamide, polyimide, polyamide imide, aromatic polyamide, and polybenzoxidazole can be used. Preferred are polyethylene naphthalate and aromatic polyamide. These non-magnetic supports are pre-corona discharge, plasma treated,
Easy adhesion treatment, heat treatment, etc. may be performed. The non-magnetic support that can be used in the present invention has a center line average surface roughness of 0.1 to 20 n at a cutoff value of 0.25 mm.
It is preferable that the surface has an excellent smoothness of m, preferably 1 to 10 nm. Further, these non-magnetic supports have not only a small center line average surface roughness but also 1
It is preferable that there are no large protrusions of μ or more.

In the method for producing a magnetic recording medium of the present invention, for example, the coating solution for the magnetic layer is preferably applied to the surface of the non-magnetic support under running, and the layer thickness after drying the magnetic layer is within the range of 0.5 to 10 μm. , And more preferably 1.5 to 7.0 μm. Here, a plurality of magnetic paints may be sequentially or simultaneously applied in multiple layers. As a coating machine for coating the magnetic coating material, air doctor coat, blade coat, rod coat, extrusion coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, gravure coat, kiss coat,
Cast coat, spray coat, spin coat, etc. can be used. For these, for example, "Latest Coating Technology" (May 31, 1983) issued by Sogo Gijutsu Center Co., Ltd. can be referred to.

When the present invention is applied to a magnetic recording medium having two or more layers, the following can be proposed as an example of the coating device and method. (1) Gravure generally applied in the application of magnetic paint,
The lower layer is first coated with a coating device such as a roll, a blade, and an extrusion, and when the lower layer is in an undried state, JP-B-1-46186 and JP-A-60-238179.
The upper layer is coated by a support pressure type extrusion coating apparatus as disclosed in Japanese Patent Laid-Open No. 2-265672. (2) JP-A-63-88080 and JP-A-2-179
No. 71, JP-A-2-265672, the upper and lower layers are applied almost simultaneously by a single coating head having two slits for passing the coating liquid. (3) The upper and lower layers are coated almost at the same time by an extrusion coating apparatus with a backup roll as disclosed in JP-A-2-174965.

A back layer (backing layer) may be provided on the surface of the non-magnetic support used in the present invention which is not coated with the magnetic coating material. Usually, the back layer is provided by applying a back layer forming coating in which a granular component such as an abrasive and an antistatic agent and a binder are dispersed in an organic solvent on the surface of the non-magnetic support which is not coated with the magnetic coating. It is a layer. An adhesive layer may be provided on the surface of the non-magnetic support on which the magnetic paint and the back layer forming paint are applied.

The applied coating layer of the magnetic coating material is dried after subjecting the ferromagnetic powder contained in the coating layer of the magnetic coating material to the magnetic field orientation treatment. After being dried in this way, the coating layer is subjected to a surface smoothing treatment. For the surface smoothing treatment, for example, a super calendar roll or the like is used. By performing the surface smoothing treatment, the voids generated by the removal of the solvent during drying disappear and the filling rate of the ferromagnetic powder in the magnetic layer improves, so that a magnetic recording medium with high electromagnetic conversion characteristics can be obtained. it can. As the calendering roll, a heat-resistant plastic roll made of epoxy, polyimide, polyamide, polyamideimide or the like is used. It can also be treated with a metal roll.

The magnetic recording medium of the present invention has a surface center line average roughness of 0.1 to 0.1 at a cutoff value of 0.25 mm.
It is preferable that the surface has extremely excellent smoothness of 4 nm, preferably 1 to 3 nm. As the method, for example, the magnetic layer formed by selecting the specific ferromagnetic powder and the binder as described above is subjected to the calendering treatment. As calendering conditions, the temperature of the calender roll is in the range of 60 to 100 ° C, preferably 70 to 100 ° C, particularly preferably 80 to 10 ° C.
The temperature is in the range of 0 ° C and the pressure is 100 to 500 kg / cm ^2.
Range, preferably 200 to 450 kg / cm ²
Range, particularly preferably 300-400 kg / c
It is preferably carried out by operating at a condition in the range of m ² . The laminate thus cured is then formed into the desired shape. The cutting can be performed under normal conditions using a normal cutting machine such as a slitter.

[0036]

The binder for magnetic recording media of the present invention uses a short-chain diol or a short-chain diamine as the diol or diamine, which is the main raw material of the polyurethane resin or polyurethane urea resin, and thus the obtained urethane resin or urethane urea is used. Since the resin has high dispersibility, the magnetic layer obtained from the composition containing the magnetic powder using the binder of the present invention has extremely high dispersibility of the ferromagnetic powder, excellent long-term storage stability, and a wide range of properties. Excellent durability under temperature and humidity conditions. Hereinafter, the present invention will be described in more detail by showing Examples of the present invention.

[0037]

【Example】

Synthetic Example 1 (Polyurethane urea resin synthetic example) A long-chain diol, a short-chain diol at a molar ratio shown in Table 1 in a container equipped with a reflux condenser and a stirrer and previously replaced with nitrogen,
Sulfoisophthalic acid dimethyl ester (DEIS manufactured by Taoka Chemical Co., Ltd., 3.0 (molar ratio)) was dissolved in diamine in cyclohexanone at 60 ° C. under a nitrogen stream. Then, 60 ppm was added to the total amount of raw materials using di-n-dibutyltin dilaurate as a catalyst, and the mixture was further dissolved for 15 minutes. Further, 37.5 (molar ratio) of 4,4′-diphenylmethane diisocyanate was added and the mixture was heated and reacted at 90 ° C. for 6 hours to give a polyurethane or polyurethane urea resin A to N.
Got The weight average molecular weight of each is shown in Table 1.

[0038]

[Table 1]

Example 1 Ferromagnetic alloy powder (composition: 94% Fe, 4% Zn, Ni2)
%, Hc1500Oe crystallite size 20 nm, major axis length 0.16 μm, major axis length / minor axis length 8, saturation magnetization (σ
s) 100 parts of 140 emu / g) was pulverized with an open kneader for 10 minutes, and then a compound (SO containing hydroxyethyl sulfonate sodium salt added to a copolymer of vinyl chloride / vinyl acetate / glycidyl methacrylate = 86: 9: 5) ₃ Na = 6 × 10 ⁻⁵ eq / g, weight average molecular weight 30,000) 10 parts, methyl ethyl ketone 60 parts were added and kneaded for 60 minutes, and then polyurethane resin (A) 10 parts (solid content) Abrasive (alumina Average particle size 0.3 μm) 2 parts Carbon black (average particle size 400 nm) 2 parts Methyl ethyl ketone / toluene = 1/1 200 parts were added and dispersed in a sand mill for 120 minutes. Polyisocyanate 5 parts (Nippon Polyurethane Coronate 3041) Butyl stearate 2 parts Stearic acid 1 part Methyl ethyl ketone 50 parts were added, and the mixture was further stirred and mixed for 20 minutes, filtered with a filter having an average pore size of 1 μm, and magnetic A paint was prepared. The thickness of the obtained magnetic coating after drying is 2.5 μm
To a surface of a polyethylene naphthalate support having a thickness of 10 μm using a reverse roll. The magnetic coating is applied to the non-magnetic support with a magnet of 3000 gauss for magnetic field orientation in the undried state, and after drying, metal roll-metal roll-metal roll-metal roll-metal roll-metal Calender treatment with a combination of rolls and metal rolls (speed 85 m / min, linear pressure 3
(00 kg / cm, temperature 90 ° C.), and then slit into a width of 8 mm. Example 2 A magnetic recording medium was produced in the same manner as in Example (1) except that the polyurethane urea resin (B) was used as the polyurethane resin (A). Example 3 A magnetic recording medium was produced in the same manner as in Example (1) except that the polyurethane urea resin (C) was used instead of the polyurethane resin (A). Example 4 A magnetic recording medium was produced in the same manner as in Example (1) except that the polyurethane resin (A) was changed to the polyurethane resin (D). Example 5 A magnetic recording medium was manufactured in the same manner as in Example (1) except that the polyurethane resin (A) was changed to the polyurethane resin (E). Example 6 A magnetic recording medium was produced in the same manner as in Example (1) except that the polyurethane resin (A) was changed to the polyurethane resin (F). Example 7 A magnetic recording medium was produced in the same manner as in Example (1) except that the polyurethane resin (A) was changed to the polyurethane resin (G). Example 8 A magnetic recording medium was produced in the same manner as in Example (1) except that the polyurethane resin (A) was changed to the polyurethane resin (H).

Example 9 Magnetic layer for upper layer ... Magnetic paint of Example 1 Magnetic layer for lower layer Co-γ-FeOx 100 parts (X = 1.45, major axis length 0.25 μm, major axis length / minor axis length 10 Crystallite size 25 nm, Hc850Oe, Br1400 gauss) Vinyl chloride copolymer (containing 0.25% by weight of sulfonic acid) 11 parts Polyurethane resin (A) 4 parts Polyisocyanate 6 parts (Coronate 3041 made by Nippon Polyurethane) Stearic acid 1 part Butyl Stearate 1 part Carbon black (average particle size 20 nm) 5 parts Methyl ethyl ketone 200 parts The coating solution was prepared using an open kneader and a sand grinder, and the upper layer film thickness was 0.2 μm and the lower layer film thickness was 2.8.
Simultaneous multi-layer coating was performed on a polyethylene terephthalate support having a thickness of 10 μm so as to have a thickness of μm. Then, magnetic field orientation was performed with a 3000 gauss magnet in a state where the magnetic coating was not dried, and after drying, calendering was performed by a combination of metal roll-metal roll-metal roll-metal roll-metal roll-metal roll-metal roll. 80m speed
/ Min, linear pressure 300 kg / cm, temperature 90 ° C.,
It was slit into a width of 8 mm.

Example 10 The procedure of Example 4 was repeated except that the lower layer magnetic coating material had the following composition. Preparation of magnetic layer for lower layer Titanium oxide 85 parts (average particle size 0.035 μm, crystalline rutile, TiO ₂ content 90% or more, surface treatment layer; alumina, S _BET 35 to 42 m ² / g, true specific gravity 4.1 , PH 6.5-8.0) Carbon black (average particle size 20 nm) 5 parts Vinyl chloride copolymer (containing 0.25 wt% sulfonic acid) 11 parts Polyurethane resin (containing 0.25 wt% sulfonic acid) 4 parts Methyl ethyl ketone: cyclohexanone = 7: 3 200 parts Comparative Example 1 The same as Example 1 except that the polyurethane resin (A) was changed to the polyurethane resin (I). Comparative Example 2 The procedure of Example 1 was repeated except that the polyurethane resin (A) was changed to the polyurethane resin (J). Comparative Example 3 The procedure of Example (1) was repeated except that the polyurethane urea resin (K) was used as the polyurethane resin (A). Comparative Example 4 The same as Example 1 except that the polyurethane resin (A) was changed to the polyurethane resin (L). Comparative Example 5 The same as Example 1 except that the polyurethane resin (A) was changed to the polyurethane resin (M). Comparative Example 6 The procedure of Example 1 was repeated except that the polyurethane resin (A) was changed to the polyurethane resin (N).

Comparative Example 7 The same as Example 9 except that the polyurethane resin (A) was changed to the polyurethane resin (I). Comparative Example 8 The procedure of Example 10 was repeated except that the polyurethane resin (A) was changed to the polyurethane resin (I).

Next, the characteristics of the video tape of Example and the video tape of Comparative Example were measured by the following measuring methods,
The measurement results are shown in Table 2. Measurement method Electromagnetic conversion characteristics: Hi8-VTR (Son
The signal was recorded and reproduced by using y-TR: 705). The S / N ratio at this time was measured with a noise meter, and the value of the tape of Comparative Example 1 was set to 0 dB and expressed as a relative value. Surface roughness Ra: cut-off of 0. by optical interference method using a digital optical profilometer (manufactured by WYKO).
It was determined as the center line average roughness Ra under the condition of 25 mm. Elongation of magnetic layer after storage: 23 ° C 50 using a stretching machine
While stretching at a rate of 5% / min in a% RH environment,
The elongation until cracks were formed in the magnetic layer was determined by a differential interference microscope. In addition, the sample when the initial elongation was set to 100% was evaluated by the elongation after storage for 1 month in a reel state at 60 ° C. and 90% RH environment. Relative value of binder weight average molecular weight after storage: weight average molecular weight of polyurethane resin and polyurethaneurea resin was determined, and weight average after storage at 60 ° C. 90% RH when initial weight average molecular weight was 100% in the same manner as above. The molecular weight was evaluated. The weight average molecular weight was determined from the standard polystyrene conversion value in a tetrahydrofuran solvent using GPC (Tosoh HLC8020). Repeatability: Using the same VTR used to measure the electromagnetic conversion characteristics under each environment of 23 ° C. and 70% RH, 9
0 minute tape was run 100 times repeatedly to observe the dirt on the video head, and video output was recorded continuously. When the first running output was 0 dB, the output decreased after the 100th running. Was measured. Video head dirt ○: No dirt was observed △: What was observed when the dirt part was wiped off ×: What was visually observed dirt

[0044]

[Table 2]

[0045]

The binder for magnetic recording media containing polyurethane, polyurethaneurea and / or polyurea of the present invention uses short chain diols and short chain diamines as main raw materials, and has a long chain polyol content. Because there are few
It has high dispersibility as a binder for magnetic recording media, and when used in the magnetic layer of magnetic recording media, or in the upper magnetic layer or lower magnetic layer, the surface roughness characteristics and electromagnetic conversion characteristics are improved, and further repeated running The subsequent characteristics and the characteristics after long-term storage were also improved.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tsutomu Okita 2-12-1, Ogimachi, Odawara-shi, Kanagawa Fuji Photo Film Co., Ltd.

Claims (7)

[Claims] 1. A binder for a magnetic recording medium comprising a polyurethane resin, a polyurethane urea resin and / or a polyurea resin, which are reaction products containing diol and / or diamine and an organic diisocyanate as main raw materials, wherein the diol has a short chain. The diol is composed of 0 to 5 mol% of a long-chain diol with respect to the entire polyurethane resin and / or the polyurethaneurea resin, and the diamine is 0 to 5 mol% with respect to the whole of the short-chain diamine and the polyurethaneurea resin and / or the polyurea resin. A binder for a magnetic recording medium, which comprises a resin consisting of the long-chain diamine. 2. The short chain diol and the short chain diamine are diols and diamines having a weight average molecular weight of 50 to 500, and the long chain diol and the long chain diamine are diols and diamines having a weight average molecular weight of 500 to 5,000. The binder for magnetic recording media according to claim 1, wherein the binder is a magnetic recording medium. 3. The polyurethane resin and the polyurethane urea resin have --SO ₃ M and --OSO _{3 in the} molecule.
^{_{M, -COOM, -PO 3 M '}} 2, -OPO 3 M' 2, -N
^{_{R 2, -N + R 3 X}} -, -N + R 2 R 'SO 3 -, -N
⁺ R ₂ R ^{'COO -} (wherein, M is a hydrogen atom, an alkali metal ion, an ammonium ion, ^M' is a hydrogen atom, an alkali metal ion, an ammonium ion, an alkyl group having 1 to 12 carbon atoms, R , R ^'carbon atoms 1 to 1
2. The binder for a magnetic recording medium according to claim 1, which is an alkyl group of 2 and contains at least one polar group selected from X is a halogen atom). 4. A magnetic recording medium in which a magnetic layer containing a ferromagnetic powder and a binder is provided on at least one surface of a non-magnetic support, wherein the binder is a reaction using diol and / or diamine and an organic diisocyanate as main raw materials. The product is a polyurethane resin, a polyurethane urea resin and / or a polyurea resin, and the diol is a short chain diol and 0 to 5 mol% of a long chain diol with respect to the entire polyurethane resin and / or polyurethane urea resin. A magnetic recording medium characterized in that the diamine contains a resin comprising a short-chain diamine and a long-chain diamine in an amount of 0 to 5 mol% based on the entire polyurethane urea resin and / or polyurea resin. 5. The short chain diol and the short chain diamine are diols and diamines having a weight average molecular weight of 50 to less than 500, and the long chain diol and the long chain diamine have a weight average molecular weight of 500 to 5,000. The magnetic recording medium according to claim 4, which is a diamine. 6. In a magnetic recording medium in which a lower magnetic layer or a lower nonmagnetic layer is provided on at least one surface of a nonmagnetic support, and an upper magnetic layer is provided thereon, at least one of the magnetic layer and the nonmagnetic layer is A polyurethane resin, a polyurethane urea resin, and / or a binder for binding a ferromagnetic powder or a non-magnetic powder, which is a reaction product of a diol and / or a diamine and an organic diisocyanate as main raw materials.
Or a polyurea resin, the diol is composed of a short chain diol and a polyurethane resin and / or a long chain diol of 0 to 5 mol% based on the whole polyurethane urea resin, and the diamine is a short chain diamine and a polyurethane urea resin and / or Alternatively, a magnetic recording medium containing a resin composed of 0 to 5 mol% of a long-chain diamine with respect to the entire polyurea resin. 7. The short chain diol and the short chain diamine each have a weight average molecular weight of 50 to less than 500, and the long chain diol and the long chain diamine each have a weight average molecular weight of 500 to 5,000. The magnetic recording medium according to claim 6.