JPS6157034A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To assure adhesive strength and to suppress the tackiness to a base film by using a thermoplastic polyurethane/urea resin having a low glass transition point and high softening point as a resin material for a primer coating layer. CONSTITUTION:The primer coating layer of the magnetic recording medium constituted by forming a material via the primer coating layer on a nonmagnetic base contains the thermoplastic polyurethane/urea resin obtd. by bringing long chain diol having about 500-5,000mol.wt., short chain diol having about 50- 500mol.wt., org. diamine and org. diisocyanate into reaction. The long chain diol to be used for producing the thermoplastic polyurethane/urea resin has about 500-5,000mol.wt. and is roughly divided to, for example, polyester diol, polyether diol and polyether ester glycol. The short chain diol to be used for producing the thermoplastic polyurethane/urea resin has about 50-500mol.wt. and includes, for example, ethylene glycol and propylene glycol.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks. This invention relates to improvement of the undercoat layer formed between the two layers.

[Conventional technology]

Generally, magnetic recording media are made of magnetic paint, which is made by dispersing and kneading magnetic powder, a resin binder called a binder, a dispersant, a lubricant, etc. in an organic solvent on a non-magnetic support (base film) such as a polyester film. It is manufactured by coating and drying to form a magnetic layer that becomes a recording layer.

By the way, in this type of magnetic recording medium, it is known that it is effective to provide an undercoat layer between the magnetic layer and the base film in order to improve the adhesion between them. In particular, in magnetic recording media that are highly filled with magnetic powder as the recording density increases, the undercoat layer is essential because the adhesion of the magnetic layer to the base film is poor. ing. Conventionally, a resin material such as a vinyl chloride-vinyl acetate copolymer, a polyester resin, a polyurethane resin, or a cellulose derivative is coated on the base film to form an undercoat layer. Attempts have been made to form a magnetic layer by applying a magnetic paint to the base film and to ensure adhesion between the magnetic layer and the base film.

However, when the resin materials conventionally used for the undercoat layer are flavored to improve adhesion, for example, when the base film on which the undercoat layer is formed is wound up, the above-mentioned It has the disadvantage that it sticks to the back side of the overlapping base film due to the adhesion of the undercoat layer. In addition, in order to solve this problem, it may be possible to use a resin material with a slightly higher Young's modulus at the expense of some adhesion, but in this case as well, this kind of resin material may not be compatible with the solvent contained in the magnetic paint. Since it is soluble, there is a problem in that the undercoat layer is partially dissolved during application of the magnetic paint, resulting in deterioration of the surface properties of the resulting magnetic layer.

[Problem that the invention seeks to solve]

Therefore, the present invention addresses the conflicting demands of providing adhesion required to improve the adhesion between the magnetic layer and the base film and suppressing adhesion to the back surface of the base film when wound up. Z%/L/l9
7 (7) Yo f, Km'a#Ry. . An object of the present invention is to provide a magnetic recording medium in which an undercoat layer is formed that can suppress solubility in solvents, and the magnetic layer has high adhesive strength and excellent surface properties.

[Means for solving problems]

That is, the magnetic recording medium according to the present invention is a magnetic recording medium in which a magnetic layer is formed on a non-magnetic support via an undercoat layer, wherein the undercoat layer has a molecular weight of about 500 to about 5000.
A thermoplastic polyurethane urea resin obtained by reacting a long chain diol with a molecular weight of about 50 to about 500, a short chain diol with a molecular weight of about 50 to about 500, an organic diamine and an organic diisocyanate. The objective is to ensure adhesion to the layer, suppress the tackiness of the undercoat layer itself, and at the same time improve the surface properties of the magnetic layer.

The thermoplastic polyurethane-urea resin used in the present invention is characterized by having urethane bonds and urea bonds (urea bonds) in its molecules. -3= It plays an important role in improving the glass transition temperature and can raise the softening point and lower the glass transition point.

The above-mentioned softening point and glass transition point can be set appropriately by adjusting the concentration of urethane groups and urea groups contained in the above-mentioned thermoplastic polyurethane-urea resin ζ. The softening point of the urea resin is preferably within the range of 80°C to 120°C, and the glass transition point is preferably within the range of -30°C to 20°C.

In addition, in the above-mentioned thermoplastic polyurethane-urea resin, the solubility in a solvent is similarly controlled by adjusting the concentration of urethane groups and urea groups contained in the molecule, or the ratio of urea group concentration/urethane group concentration. However, in order to prevent this resin from being soaked in the organic solvent contained in the magnetic paint when used in the undercoat layer, it is necessary to use an organic solvent that is insoluble in methyl ethyl ketone, which is commonly used, or Or melt W4
The amount is preferably 1 g or less per 100 g of carbonyl ethyl ketone.

Further, the number average molecular weight of the thermoplastic polyurethane-urea resin is preferably in the range of 10,000 to 10,000.0, more preferably 10,000 to 60,000.

When the number average molecular weight is less than 10,009, the coating film forming ability of the resin becomes opaque, and when the number average molecular weight is less than 6,000.
If it exceeds 0, there is a risk that problems will occur in paint manufacturing processes such as mixing and coating.

Next, a method for producing the thermoplastic polyurethane urea resin used for the undercoat layer in the magnetic recording medium of the present invention will be described.

Thermoplastic polyurethane-urea resins contain long chain diols,
It is obtained by polyaddition reaction of short chain diols, organic diamines and organic diisocyanates.

In this polyaddition reaction, a tetrametallic material of a long-chain diol and a short-chain diol is reacted with an organic diisocyanate in advance to prepare a prepolymer with an isocyanate group terminal, and then an organic diamine is added to extend the chain and introduce a urea group. This is done by a prepolymer method.

The long-chain diol used in the production of the thermoplastic polyurethane-urea resin has a molecular weight of about 500 to about 5,000, and is broadly classified into, for example, polyester diol, polyether diol, polyether-forming sterglycol, and the like. Specific examples of polyester diols include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, or their lower alcohol nysterates, ethylene glycol, 1. Obtained by reacting with 3-propylene glycol, ], 4-butylene gelicol, 1,6-hexane glycol, diethylene glycol, neopentyl glycol, or an ethylene oxide adduct of bisphenol A, or a mixture thereof. Polyester diols or ε to caprolactone, etc.: Examples include lactone-based polyester diols obtained by ring-opening polymerization of lactones.

Examples of the polyether diol include polyethylene glycol, polypropylene ether glycol, polyalkylene ether glycols such as polytetramethylene ether glycol, and copolymerized polyether glycols such as Corella.

Examples of polyether ester glycols include polyester glycols obtained by reacting the above polyalkylene ether glycol with an aliphatic or aromatic dicarboxylic acid as a polyol component.

The short chain diol used in the production of the thermoplastic polyurethane-urea resin has a molecular weight of about 50 to about 500, and examples thereof include ethylene glycol, propylene glycol, 4-butylene glycol, and 1,6-hexane. These include glycols, aliphatic glycols such as neopentyl glycol, aromatic diols such as ethylene oxide adducts or propylene oxide adducts of bisphenol A, and ethylene oxide adducts of hydroquinone, and polyurethane-urea resins. These can be used alone or in combination in various ratios depending on the desired properties.

′ Furthermore, examples of the organic diamine include aliphatic diamines such as tetramethylene diamine and hexamethylene diamine;
m-phenylenediamine, p-phenylenediamine, l
;'4-) lylene diamine, 2.6-) lylene diamine, m-xylylene diamine, p-xylylene diamine,
diphenylmethanediamine, 3,3'-dimethoxy-4
,4'-biphenylenediamine, a,,4-dimethyl-
4,,4'-biphenylenediamine, 4. Diaminodiphenyl ether, 1,5-naphthalenediamine, 2
Aromatic diamines such as ゜4-naphthalenediamine, 1.
Examples include alicyclic diamines such as 3-diaminomethylcyclohexane, 4-diaminomethylcyclohexane, 4,4-diaminodicyclohexylmethane, and isophoronediamine.

Examples of the organic diisocyanate include aliphatic diisocyanates such as tetramethylene diisocyanate and hexamethylene diisocyanate, 1-lm-phenylene diisocyanate, p-phenylene diisocyanate, 2,4-
Tolylene diisocyanate-1, 2.6-) lylene diisocyanate, diphenylmethane diisocyanate-1-13
, 3-dimethoxy-4,4'-biphenylene diisocyanate, cyaners 1-14. ,4. Aromatic diisocyanates such as '-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate 1-12.4-naphthalene diisocyanate-1, ■,3-diisocyanatomethylcyclohexane, 1,4- Examples include alicyclic diisocyana-1. such as diisocyanate methylcyclohexane, 4,4'-diisocyanate dicyclohexylmethane, and isophorone diisocyanate.

In producing the thermoplastic polyurethane-1 flare resin used in the present invention, the long-chain diols having a molecular weight of about 500 to about 5000 are selected from among the above-mentioned examples, particularly polyester diols, especially polybutylene adipate and polyhexamethylene adipate. , it is preferable to use polycaprolactone diol. As the short chain diol having a molecular weight of about 50 to about 500, it is particularly preferable to use a branched short chain diol among the above-mentioned examples, especially neopentyl glycol. Further, as the organic diamine, it is particularly preferable to use isophorone diamine among the above-mentioned examples. In addition, among the above-mentioned examples, especially 4 is the organic diisocyanate.
, 4-diphenylmethane diisocyanate, and isophorone diisocyanate are preferably used.

In addition, the polyaddition reaction method employed in the production of the thermoplastic polyprethane-urea resin used in the present invention includes melt polymerization in a molten state, single or mixed solvents such as ethyl acetate, methyl ethyl ketone, acetone, toluene, etc. Solution polymerization is carried out by dissolving the above-mentioned raw materials in an inert solvent, but solution polymerization is preferable for the production of resins that are often used by dissolving them in solvents, and melt polymerization is particularly preferred when preparing prepolymers. , Deaf performing a chain extension reaction! It is more preferable to perform solution polymerization by adding the above-mentioned inert solvent beforehand.

During the reaction, an organometallic compound such as an organotin compound such as stannous octylate or dibutyltinsilane clay, or a tertiary amine such as N-methylmolorin or triethylamine may be added as a catalyst. Furthermore, in order to increase the stability of the product, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, etc. may be added.

Furthermore, a hydrophilic polar group may be introduced into the thermoplastic polyurethane-urea resin. This hydrophilic polar group includes -80nM, -080aM, -COOM
, -PI3(OM)2C In the formula, M represents a hydrogen atom or an alkali metal, and M represents a hydrogen atom, an alkali metal or a hydrocarbon group. ).

Methods for introducing these hydrophilic polar groups into thermoplastic polyurethane-flare resin include (1) a method in which a hydrophilic polar group-containing compound is mixed as a raw material for thermoplastic polyurethane-1 flare resin; 2) A method of modifying the thermoplastic polyurethane-urea resin entirely with a hydrophilic polar group-containing compound having a bifunctional or trifunctional or more functional H group may be mentioned.

Examples of the hydrophilic polar group-containing chemical compound used in the method (1) above include hydrophilic polar group-containing diols, hydrophilic polar group-containing organic diisocyanates, and hydrophilic polar group-containing organic diamines. These compounds are polymerized with other raw materials to form part of the polymer molecular chain of the thermoplastic polyurethane-urea resin, and as a result, hydrophilic polar groups are introduced into the thermoplastic polyurethane-urea resin.

The hydrophilic polar group-containing diol may be, for example, a diol of the general formula (wherein, Rt is an alkylene group having 2 to 6 carbon atoms or a substituted product thereof, R2 is an alkylene group having 1 to 6 carbon atoms or a substituted product thereof, R8 and R4 represents an alkyl group having 1 to 6 carbon atoms).

Alternatively, it may be a diol having a -808M group (where M represents a hydrogen atom or an alkali metal).

This diol having a -803M group includes a carboxylic acid component not having a -sogM group, a glycol component, and a -803M group.
It is obtained by reacting a dicarboxylic acid component having an aM group.

As the carboxylic acid component not having the -8OaM group,
Terephthalic acid, isophthalic acid, orthophthalic acid, ■, 5
- Aromatic dicarboxylic acids such as naphthalic acid, p-oxybenzoic acid, aromatic oxycarboxylic acids such as I)-(hydroxyethoxy)benzoic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, etc. Examples include aliphatic dicarboxylic acids, and trio and tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid.

The glycol components mentioned above include ethylene glycol, propylene glycol, 1,3-furopanediol,
4-butanediol, 1,5-pencunediol, ■,
6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2.2.
4-1-rifthyl-1,3-pencunediol, 1.4
-Cyclohexane dimetatool, ethylene oxide and propylene oxide adducts of bisphenol A, water, ethylene oxide and propylene oxide adducts of hydrogenated bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

Further, tri- and tetraols such as trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol may be used in combination.

The dicarboxylic acid component having the -8OaM group is as follows:
5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid,
Examples include 2-potassium sulfoterephthalic acid.

In addition, the above hydrophilic polar group-containing organic diisocyanate is
It can be obtained by reacting a trifunctional or more functional polyisocyanate compound with a compound having a hydrophilic polar group.

As the above-mentioned polyisocyanate compounds, trifunctional products such as Desmodur L (manufactured by Bayer AG) and Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) are known.
Generally, a polyfunctional polyisocyanate compound is obtained by addition-reacting a polyol and polyisocyanate-1-.

Examples of the polyol include propylene glycol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, and the like.

Examples of polyisocyanates include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, naphthylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, and lysine diisocyanate. Can be mentioned.

A method for introducing the hydrophilic polar group into a trifunctional or higher functional polyisocyanate compound will be schematically shown.

■ Method of introducing -8OaM group By reacting a compound having 18OaM group in one molecule and an active hydrogen capable of reacting with -NCO group with a trifunctional or higher functional polyisocyanate compound,
Contains two or more -NGO groups in one molecule and -8OaM
A compound having a group is obtained.

Compounds having 18 OaM groups in one molecule and active hydrogen that can react with -NGO groups include the following: These compounds include trifunctional or higher functional polyisocyanate compounds and, for example, the following compounds: The addition reaction is carried out as shown in the reaction formula.

(In the reaction formula, l(, -NCO represents a trifunctional or higher functional polyisocyanate compound.) ■ Method for introducing -C00M groups When one molecule has some 〇〇M groups and -NCO groups are By reacting a compound having active hydrogen that can react with a trifunctional or more functional polyisocyanate compound,
A compound having two or more -NGO groups in the molecule and partially having 〇〇M groups is obtained.

Examples of the compound having a -COOM group in one molecule and an active hydrogen capable of reacting with the -NCO group include the following.

These compounds undergo an addition reaction with a trifunctional or higher functional polyisocyanate compound, for example, as shown in the following reaction formula.

(In the reaction formula, R, -N CO represents a trifunctional or higher functional polyisocyanate compound.) ■ Method for introducing -0808M group The reaction product of a trifunctional or higher functional polyisocyanate compound and H2SO4 is By neutralizing with etc., it is possible to determine whether - has two or more -NCO groups in the molecule and -
A compound having an os'oi group can be obtained, for example, as shown in the following reaction formula.

R-NCO+H2So 4”-NHCO-080s
HR-NHCO-0808H+NaOH -It, -NHCO"08OaNa-44-I20 (In the above reaction formula, R-NCO represents a trifunctional or more functional polyisocyanate compound.) ■ Method of introducing two -P(OM) groups j(0′ 3-competent or higher polyisocyanate-1 compound and f(aPO
By neutralizing the reaction product with 8 with NaOH, KOHfl, etc., it can be obtained, for example, as shown in the following reaction formula.

H, -NGO+1-1aPOa -R, NI(CO-
P(01-1)2R, -NI(Co-P(OH)2
+2 N a OH → NHCO-P (ONa )2
+2H20 (In the above reaction formula, II and -NCO represent a trifunctional or higher functional polyisocyanate-1 compound.

) Woodcutter Furthermore, the above-mentioned hydrophilic polar group-containing Togo diamine includes:
An equimolar reaction product of an aliphatic or alicyclic diamine and an acid anhydride as shown by the general formula % (wherein R5 and 'R8 represent a hydrocarbon group having 2 to 12 carbon atoms) and its Examples include alkali metal salts. Examples of the aliphatic or alicyclic diamines used include tetramethylene diamine, hexamethylene diamine, 1,3-diaminomethylcyclohexane, 4-diaminomethylcyclohexane, 4,4-diaminodicyclohexylmethane, and isophorone diamine. However, it is particularly preferable to use isophorone diamine. In addition, examples of the acid anhydrides include succinic anhydride, maleic anhydride, phthalic anhydride, hexahydrophthalic anhydride, 81-tetrahydrophthalic anhydride, 4-methyl-1゜2'',
Examples include '3', 6-tetrahydrophthalic anhydride.

On the other hand, as a specific example of the method (2) above, for example, (
A) C1CH2CHzS, 08M, 'CACH2'C
Hゐ'aM.

ClCH2C00M, Cj? CfhP(QM')+(
However, M is a hydrogen atom or an alkali metal; A thermoplastic polyurea resin having the following properties is dissolved in a solvent such as dimethylformamide or dimethyl sulfoxide in which both components are soluble,
Amines such as pyridine, picoline, and triedylamine: A hydrophilic polar group is introduced through a dehydrochloric acid reaction between the 0)′-〇■] group and chlorine in the presence of a dehydrochloric acid agent such as an epoxy compound such as ethylene oxide or propylene oxide. There is a way to do it. The reaction formula is as follows.゛(A-1,) TOOH1C/? CI (2CH280aM-RwOCI4
2 CI (2S C) 3M HCII (A-2)
(
“R'-OH+CeCeCH2CH20SOa 1%-
OCH2! 'CH20So a M+HCA? (A-
3) R-OH+CACH2COOM -R,'-OCH2COOM+HC7 (A-4) 1EOH+CA CI-I 2 P (OM') 2
(However, R represents a thermoplastic polyurethane-urea resin.) Although some by-products are produced, it can also be synthesized by the following method. That is, (B) HOCH2CH2SO8M, HOCHzC
H2,O8OaM.

HOCH2COOM, I-IOCHzP(OM)z
and a diisocyanate compound, for example, 4,4-diphenylmethane diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, in equimolar amounts, and one NCO group of the diisocyanate and the OH group in the above molecule are reacted. A reaction product is obtained by the reaction. Next, by reacting some of the H groups of the thermoplastic polyurethane-urea resin with the remaining NCO group, a thermoplastic polyurethane-urea resin into which a hydrophilic polar group has been introduced can be obtained.

CB-1) OCN-1j-NCO+i(OCH2CH2SoaM→
0CN-R-Nl (COOCI-I2 C1-12S
o aM1 deceased 0I-I-1-UCN-R-NJ (COO
CI-T 2 CH2So a M, R, -0CON
I-1-1 (2 NINl-lC00CI-IzCHzS
Oa+3-2) OCN-R-NCO+HOCH2CH20SQaM-O
CN-R'NHCOOCH2CH2080B MR'-
OH+0CN-1deNf(COOCf(20H20SO
aM=1 0(,'0NI-J-DirectNl-N1-lC0
0Cf (20H20SOazu-3) OCN-R-NCO+HOCHzCOOM-0CN-]
MuN1(COOCH2C00M5-oH+ocN-1<
7Nl-ICQOCH2COOM, R-OCONI-
I-1←NHCOOCH2C00M.

(B-4) OCN-1'(7NCQ-1-HOcH2P(OM)
2=23- →OCN-R=NHCOOCH2P(OM)2 (wherein, R represents thermoplastic polyurethane-urea resin,
R represents a divalent hydrocarbon group. ) By introducing the hydrophilic polar group, the affinity of the thermoplastic polyurethane-urea resin for the magnetic powder can be increased, so that when this resin is used in the undercoat layer, the magnetic powder can be densely packed. Demonstrates high adhesion to magnetic layers.

An undercoat layer is formed by coating the thermoplastic polyurethane-urea resin described above on a non-magnetic support.

The undercoat layer may be made of carbon for imparting conductivity (for example, furnace carbon, channel carbon, acetylene carbon, thermal carbon, lamp carbon, etc.), if necessary. However, furnace carbon or thermal carbon is preferable), lubricant, etc. may be added.

The non-magnetic support on which the undercoat layer is applied may include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate-1, polyolefins such as polyethylene and polypropylene, cellulose triacetate butyrate, and cellulose acetate propylene. Cell openings such as pionate, -sugar derivatives, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, polyimide, polyamide, polyamideimide, polyhydrazides, copper, tin, zinc, or non-magnetic alloys containing these, etc. non-magnetic metals, glass, pottery, ceramics such as porcelain, paper or polyethylene, polypropylene, ethylene.
Examples include papers coated with α-polyolefins having 2 to 10 carbon atoms, such as butene copolymers, etc. , disk, card, drum, etc.

Then, a magnetic layer is formed by applying a magnetic paint prepared by dispersing ferromagnetic powder in a binder and dissolving it in an organic solvent onto the undercoat layer.

Any conventional ferromagnetic powder can be used as the ferromagnetic powder used in the magnetic layer. Therefore, ferromagnetic powders that can be used include ferromagnetic iron oxide particles, ferromagnetic chromium dioxide, ferromagnetic alloy powders, and the like.

As the above-mentioned ferromagnetic iron oxide particles, when expressed by the general formula Feox, the value of X is in the range of 1.33≦1.50, that is, maghemite (γ-Fe 2011,
= 150), magnetite (Feas4.
33) and their solid solutions (FeOx, 1.33
(X(1,50).These γ-Fe20a and Fe
a04 is below normal! Obtained by manufacturing method. That is, ferrous hydroxide is produced by adding an alkali to a ferrous salt solution, and oxidized by blowing air at a predetermined temperature and pH to obtain acicular hydrated iron oxide. It is heated and dehydrated at 250 to 400°C, and then heated and reduced at 300 to 450°C in a reducing atmosphere to obtain acicular magnetite particles. Furthermore, if necessary, add 20% of the magnetite.
Acicular makhemite (γ-F
'ezOa). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. Cobalt-containing magnetic iron oxide is roughly divided into two types: doped type and coated type.
There are different types. The method for producing Co-doped iron oxide particles is as follows: (1) A method in which ferric hydroxide containing cobalt hydroxide is hydrothermally treated in an alkaline atmosphere, and the resulting powder is reduced and oxidized. (2) Goethite is synthesized. In this method, a cobalt salt solution is added in advance, the pH is adjusted, and then goethite containing cobalt is synthesized, and this is reduced and oxidized (using goethite that does not contain 31Co as a nucleus,
A reaction similar to that in (2) was carried out on 1, and CO
(4) The surface of acicular goethite or maghemite is treated in an alkaline aqueous solution containing CO salt to adsorb CO compounds, and then reduced, oxidized or There is a method of heat treatment at a relatively high temperature. In addition, CO-coated iron oxide magnetic particles are produced by mixing acicular magnetic iron oxide and cobalt salt in an alkaline aqueous solution, heating the mixture, adsorbing cobalt compounds such as cobalt hydroxide onto the iron oxide particles, and washing the mixture with water. - Obtained by drying, taking out, and then heat-treating in air or a non-reducing atmosphere such as N2 gas. Compared to Co-doped particles, CO-coated particles have superior transfer characteristics and demagnetization characteristics when formed into a tape.

The above-mentioned ferromagnetic chromium dioxide includes CrO2, or Ru and Sn for the purpose of improving the coercive force thereof.

A material containing at least one of Te, Sb, Fe, Ti, V, Mn, etc. can be used. CrO2 is basically 500% chromium trioxide (Crys) in the presence of water.
It is obtained by thermal decomposition at 400-525°C under atmospheric pressure. In addition, as for the synthesis method under atmospheric pressure, =28- CrOa is synthesized in the presence of nitrogen oxide (No) in addition to oxygen at 250
There is also a method of decomposing at ~375°C. Ferromagnetic alloy powder and shite are Fe, Co, Ni, Fe-C
o, Fe-Ni or Fe-Co-Ni, etc. can be used, and AI, Si, etc. can be used for the purpose of improving various properties.
, Ti, Cr.

Metal components such as Mn, Cu, and Zn may also be added. The methods for producing these ferromagnetic alloy powders include: (1) thermal decomposition of organic acid salts (mainly oxalates) of ferromagnetic metals and alloys, and reduction with reducing gas (2) acicular iron oxyhydroxide or these A method of reducing CO-containing or acicular magnetic iron oxide in a reducing gas (3) A method of evaporating ferromagnetic metals and alloys in an inert gas (4) A method of decomposing metal carbonyl compounds (5) ) A method of separating and removing mercury after electrodepositing ferromagnetic metal powder by wood-tone electrolysis. (6) Adding a ferromagnetic metal salt to the solution, such as sodium hypophosphite or sodium borohydride. There are methods such as wet reduction.

The binder used in the magnetic layer may be one that has been conventionally used as a binder for magnetic recording media, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, Vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer,
Vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-vinylidene chloride copolymer, methacrylic ester- styrene copolymer,
Thermoplastic polyurethane resin, phenolic resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-buta-11 diene-megacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene- Examples thereof include book diene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, alkyd resin, urea-formaldehyde resin, and mixtures thereof.

In addition to the binder and ferromagnetic powder, the magnetic layer also contains additives such as a dispersant, a lubricant, an abrasive, an antistatic agent,
Rust inhibitors and the like may also be added.

The above dispersants (pigment wetting agents) include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid,
Fatty acids with 12 to 18 carbon atoms (R7C0OH) such as lyrinic acid and stearolic acid.

R7 is an alkyl or alkenyl group having 11 to 17 carbon atoms), an alkali metal of the above-mentioned fatty acid (Li.

(Na, etc.) or alkaline earth metals (Mg, Ca, etc.).

Metal soaps consisting of Ba), fluorine-containing compounds of the above fatty acid esters, amides of the above fatty acids, polyalkylene oxide alkyl phosphate esters, trialkyl polyolefin oxy quaternary ammonium salts (alkyl has 1 to 5 carbon atoms, The olefins used include ethylene, propylene, etc. In addition, higher alcohols having a carbon number of 2 or more and sulfuric esters may also be used. These dispersants are added in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.

The above lubricants include dialkylpolysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkylmonoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms) ,
Alkoxy has 1 to 4 carbon atoms), silicone oil such as phenyl polysiloxane, fluoroalkyl polysiloxane (alkyl has 1 to 5 carbon atoms), conductive fine powder such as graphite, molybdenum disulfide, tungsten disulfide, etc. Inorganic fine powders, polyethylene, polypropylene, ethylene vinyl chloride copolymers, plastic fine powders such as polytetrafluoroethylene, α-olefin polymers, unsaturated aliphatic hydrocarbons that are liquid at room temperature (n-olefin double bonds Compound bonded to terminal carbon, approximately 2 carbons
0), monobasic fatty acids with 12 to 20 carbon atoms and 3 carbon atoms
Fatty acid esters consisting of ~12-valent alcohols, fluorocarbons, etc. can be used. These lubricants are added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of the binder.

As the abrasive, commonly used materials such as fused alumina, silicon carbide, chromium oxide (Cr2Ch), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite) are used. Ru. These abrasive agents have a Mohs hardness of 5 or more and an average particle size of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are used in an amount of 0.5 to 20 parts by weight per 100 parts by weight of the binder.
It is added in a range of parts by weight.

Examples of the antistatic agent include conductive fine powder such as carbon black and carbon black graft polymer, natural surfactants such as saponin, nonionic surfactants such as alkylene oxide, glycerin, and glycidol, higher alkyl amines, Cationic surfactants such as quaternary ammonium salts, pyridine and other heterocycles, phosphonic surfactants, anionic surfactants containing acidic groups such as carboxylic acids, sulfonic acids, phosphoric acids, sulfuric ester groups, and phosphoric ester groups. Ampholytic active agents such as sulfuric acid or phosphoric acid esters of amino alcohols, amino acids, amino sulfonic acids, and amino alcohols are used. The above conductive fine powder is added in an amount of 0.2 to 20 parts by weight, and the surfactant is added in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the binder. These surfactants may be added alone or in combination. Although these are used as antistatic agents, they can sometimes be used for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

The above rust preventives include phosphoric acid, sulfamide, quanidine, pyridine, amine, urea, zinc,!
Dicyclohexylamine nitrite, cyclohexylamine chromate, diisopropylamine nitrite, hexyl ammonium carbonate, hexate ethylene diamine carbonate, 70 pylene diamine stearate, etc. can be used. Rust prevention using volatile rust inhibitors (inorganic or organic acid salts of amines, amides, or imides) such as carbonate, quanidine carbonate, I-liechnolamine nitrite, and morpholine stearate. Improves effectiveness. These rust inhibitors are 0.01 parts by weight per 100 parts by weight of ferromagnetic fine powder.
It is used in a range of 20 parts by weight.

In addition, the constituent materials of the magnetic layer are dissolved in an organic solvent to prepare a magnetic paint, which is coated on a non-magnetic support.The solvent for the magnetic paint is a ketone type such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone. , methinope acetate, ethyl acetate, butyl acetate, ethyl lactate,
Ester types such as glycol monoethyl ether acetate, glycol ether types such as glycol dimethyl ether, glycol monoethyl ether, and dioxane, aromatic hydrocarbons such as benzene, toluene, and xylene, and fats such as hexane and heptane. Examples include chlorinated hydrocarbons such as group hydrocarbons, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorobenzene.

[For production]

As mentioned above, by forming the undercoat layer using thermoplastic polyurethane-urea resin, the undercoat layer has a certain high softening point and does not stick to the non-magnetic support when wound up. It is formed.

At the same time, adhesion to the magnetic layer is ensured, and in particular, by using a thermoplastic polyurethane-urea resin into which a hydrophilic polar group is introduced, the adhesion becomes even better.

Furthermore, the thermoplastic polyurethane-urea resin has poor solubility in organic solvents contained in magnetic paints such as methyl ethyl ketone, so when this magnetic paint is applied, the undercoat layer does not dissolve and the surface No loss of sex.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
It goes without saying that the present invention is not limited to this embodiment.

Example 1.

Molecule i10 was placed in a reaction vessel equipped with a stirring propeller, thermometer and condenser, and equipped with heating and cooling equipment.
'00 polybutylene adipate (long chain diol), neopentyl glycol (short chain diol), 4','4
- Prepare diphenylmethane diisocyanate (organic diisocyanate) and methyl ethyl ketone, 75-8
After reacting at 0° C. for 4 hours, methyl ethyl ketone was further added and the mixture was cooled to around room temperature. Next, a diamine solution in which isophorone diamine (organic diamine) was dissolved in methyl ethyl ketone and cyclohegisanone was added.

As the diamine solution is added, the solution viscosity increases rapidly, so when the predetermined viscosity is reached, a glycol corresponding to the remaining -NCO group concentration is added to modify the terminal end into an OH group, resulting in organic diamine/(long chain diol + short chain diol). = 1.6”
A polyurethane-urea resin having a molar ratio of short chain diol/long chain diol of 3 (core ratio) and a number average molecular weight of 20,000 was synthesized.

The obtained polyurethane-urea resin was made into a 0.2% solution of isopropyl alcohol, and this was applied onto a polyethylene terephthalate film at a speed of 150 m/min to form an undercoat layer, and the film was wound up.

Next, CO coated type 7-Fezoll 100 parts by weight Resin binder (trade name Nissan 5703) 30 parts by weight Lecithin 2 parts by weight CrzOa 3
A magnetic paint consisting of 200 parts by weight of methyl ethyl ketone and 200 parts by weight of toluene was prepared and coated on the undercoat layer to form a magnetic layer to prepare a sample tape.

Example 2 By the same operation as in Example 1 above, organic diamine/(long chain diol + short chain diol) = 1.0 (mole ratio), short chain diol/long chain diol - 2,5 (mole ratio) ), a polyurethane-1crea resin with a number average molecular weight of 20,000 was synthesized, and this was made into a 0.2% solution of isopropyl alcohol and placed on a polyethylene terephthalate film (150 ml).
The coating was applied at a speed of 1.5 min to form an undercoat layer and then wound up.

Next, a magnetic paint similar to that in Example 1 was applied onto the undercoat layer to form a magnetic layer to prepare a sample tape.

Comparative Example 1 A sample tape was prepared in the same manner as in Example 1, except that a polyurethane resin without 1-flare bond was used in place of the poly-1-clekune-urea resin of Example 1 above.

Comparative Example 2 A sample tape was prepared in the same manner as in Example 2 except that a polyester resin was used instead of the polyurethane-urea resin in Example 1. ,1
Comparative Example 3 Instead of the polyurethane-urea resin of Example 1,
For 100 parts by weight of phenoxy resin, poly=39-isocyanate-1 curing agent (manufactured by Nippon Polyurethane Industries, Ltd.,
Using 20 parts by weight of product name Coronate L),
A sample tape was produced in the same manner as in Example 1 except for the above.

The viscosity, adhesive strength, and S/N ratio of the video signal were examined for each sample tape obtained in each of the above Examples and Comparative Examples. The results are shown in the table below.

The above adhesive strength represents the peel strength in the 80° direction between the magnetic layer and the base film when the adhesive tape is pasted on the magnetic surface of the sample tape and the adhesive tape is peeled off from the base film together with the magnetic layer. It is something that

Table From this table, in each example according to the present invention, viscosity,
It can be seen that both the adhesive strength is good and the solubility in methyl ethyl ketone is poor, so the surface properties are good and the S/N ratio of the video signal is also good.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
Since a thermoplastic polyurethane-urea resin having a low glass transition point and a high softening point is used as the resin material for the undercoat layer, adhesive strength is ensured and tackiness to the base film is suppressed.

In addition, the thermoplastic polyurethane flare resin has poor solubility in methyl ethyl ketone, so when a magnetic paint is applied, the surface will not be roughened by the solvent contained in the paint, and the polyurethane flare resin will be smooth.
Urea resin blends well with the above magnetic paint, so
The surface properties of the magnetic layer are also very excellent.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer is formed on a non-magnetic support via an undercoat layer, the undercoat layer has a molecular weight of about 500.
~5000 long chain diol, molecular weight about 50 to about 500
A magnetic recording medium comprising a thermoplastic polyurethane-urea resin obtained by reacting a short chain diol, an organic diamine and an organic diisocyanate.