JPS6093619A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve blocking resistance and durability of a magnetic recording medium by using a specific thermoplastic polyurethane-urea resin as a binder for a back coat layer. CONSTITUTION:A back coat layer 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 as a binder. Said binder has an urethane bond and an urea bond in the molecule thereof. The total concn. of the urethane group and urea group of said resin is preferably 1.8-3.0mmol/g. The number average mol.wt. of the resin is preferably in a 10,000-100,000 range. The softening point temp. of the resin is further preferably >=80 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium such as a magnetic tape, and more particularly to a so-called barafco-1 layer provided on the surface opposite to the magnetic layer in order to prevent winding irregularities, prevent charging, etc. This is related to the improvement of.

Generally, magnetic recording media are produced by coating a non-magnetic support such as a polyester film with a magnetic paint made by dispersing and kneading ferromagnetic powder, a binder, a dispersant, a lubricant, etc. A magnetic layer is formed by directly depositing a magnetic layer by means such as vacuum evaporation.Furthermore, in the past, the non-magnetic support was used to prevent irregular winding of a magnetic recording medium, to prevent static electricity, and to improve runnability. It is known to provide a so-called back coat layer in which a conductive pigment such as carbon is mixed in a binder on the side where the magnetic layer is not provided.

As the binder constituting the back coat layer, a polyurethane resin having excellent abrasion resistance and scratch resistance is often used.

However, conventionally used polyurethane resins have a low 5-softening point and poor heat resistance, so when storing tape-shaped magnetic recording media by winding them onto tape reels, etc., they cannot be stored under high temperatures or During long-term storage, the back coat layer adheres to the magnetic layer, causing the back coat layer and the magnetic layer to peel off from the nonmagnetic support, significantly impairing the performance of the magnetic recording medium. this is,
This is thought to be due to the property that the Young's modulus of the above-mentioned polyurethane resin rapidly decreases near the softening point, and suddenly reaches the flow range at a temperature above the softening point.

Therefore, in order to improve the heat resistance of the above-mentioned polyurethane resin and improve the blocking resistance of the above-mentioned back coat layer, when synthesizing the above-mentioned polyurethane resin, the proportion of low molecular weight diol, which is a raw material component, is increased and the urethane base is The use of polyurethane resins with increased concentrations in the back coat layer has been considered. In general, increasing the urethane group concentration can improve the thermal properties of polyurethane resins. For example, as the urethane group concentration in the molecule increases, a polyurethane resin with a higher softening point temperature and a lower glass transition temperature can be obtained. .

However, as mentioned above, when the urethane group concentration of the polyurethane resin increases, the polyurethane resin becomes ketone-based, alcohol-based, ester-based, aromatic hydrocarbon-based, aliphatic hydrocarbon-based, etc., which are used to manufacture magnetic recording media. It has the disadvantage that it is insoluble in general-purpose organic solvents and only slightly soluble in highly toxic solvents such as dimethylformamide and tetrahydrofuran. Solvents such as dimethylformamide and tetrahydrofuran may attack the parts of the material that they come in contact with, such as the coated surface of the non-magnetic support, causing wrinkles and unevenness, or in some cases, dissolving them. Since this occurs, there is a limit to the improvement by increasing the urethane group concentration of the polyurethane resin. Generally, the urethane group concentration of the polyurethane resin used as the binder for the back coat layer is 1. gm
The limit is about mo6/g, so the softening point temperature is 80
It is difficult to keep the temperature above ℃.

As a result of intensive studies to eliminate the drawbacks of the above-mentioned conventional products, the inventors of the present invention have discovered that the anti-blocking properties of the magnetic recording medium can be improved by using a thermoplastic polyurethane-urea resin as a binder for the back coat layer of the magnetic recording medium. The present invention has been completed by discovering that the above thermoplastic polyurethane-urea resin can improve the properties and durability, and that it can be easily dissolved in general-purpose solvents. is a magnetic recording medium provided with a back coat layer on the other side, the back coat layer having a molecular weight of about 5.
00 to about 5000 long chain diols, molecular weight about 50 to about 5
It is characterized by containing as a binder a thermoplastic polyurethane-urea resin obtained by reacting a short chain diol of No. 00, an organic diamine and an organic diisocyanate.

The thermoplastic polyurethane-urea resin used in the present invention is characterized by having urethane bonds and urea bonds (urea bonds) in its molecules. It plays an important role in improving properties, and can raise the softening point, which is a measure of heat resistance, and lower the glass transition temperature, ensuring stable physical properties of the Hasokuko-1 layer over a wide temperature range. maintained, and is extremely effective in improving blocking resistance.

The thermoplastic polyurethane-urea resin used in the present invention contains both urethane groups and urea groups, and the introduction of urea groups has a remarkable effect of improving the thermal properties of the resin as well as urethane groups, and is even more important. This is because the introduction of this urea group makes it possible to obtain a resin that is soluble in combinations of the aforementioned ketone-based, alcohol-based, ester-based, aromatic hydrocarbon-based, and aliphatic hydrocarbon-based solvents. In addition, the polar groups in the thermoplastic polyurethane-urea resin molecules (which can be made larger than the thermoplastic polyurethane resin in the urethane bonding part) strengthen the interaction between molecules and improve the physical properties of the resulting back coat layer. , which also has an effect on durability.

That is, by using the thermoplastic polyurethane-urea resin as a binder for the back coat layer of a magnetic recording medium, a magnetic recording medium with excellent blocking resistance and durability can be provided.

The total concentration of urethane groups and urea groups in the thermoplastic polyurethane-urea resin is 1.8 mmol/g.
~3. Preferably, it is Q mmol /9.

If the concentration is less than 1.3 mmol/fj, the softening point temperature of the resin will decrease and the blocking resistance will not be improved.
Moreover, if the concentration exceeds 3.0 mmol/y, it becomes insoluble in general-purpose solvents and becomes soluble only in dimethylformamide and the like. Further, the ratio of urea group concentration/urethane group concentration is preferably 0.3 to 1.6. If the ratio of urea group concentration/urethane group concentration is less than 0.3, it will become insoluble in general-purpose solvents, and if the ratio of urea group/urethane group concentration exceeds 1.6, the glass transition temperature of the resin will become high. Put it away.

Further, the number average molecular weight of the thermoplastic polyurethane-urea resin is 10,000 to 100,000, more preferably 10
The range is preferably from 000 to 60,000. If the number average molecular weight is less than 10,000, the coating film-forming ability of the resin will be insufficient, and if the number average molecular weight exceeds 60,000, there is a risk that problems will occur in paint manufacturing processes such as mixing and coating. .

Furthermore, it is desirable that the softening point temperature of the thermoplastic polyurethane-urea resin is 80°C or higher, preferably 100°C or higher. If the softening point temperature is lower than this, the properties approach those of conventional polyurethane resins, making it impossible to improve blocking resistance and physical properties.

Further, it is desirable that the glass transition temperature of the thermoplastic polyurethane-urea resin is 0°C or less, more preferably -10°C or less. If the glass transition point is higher than this, the transition region of physical properties approaches room temperature, which is not preferable.

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 roughly classified into, for example, polyester diol, polyether diol, polyether ester glycol, 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, and ethylene glycol. , 1.3-propylene glycol, Examples include polyester diols and lactone-based polyester diols obtained by ring-opening polymerization of lactones such as ε-caprolactone. Examples of the polyether diol include polyalkylene ether glycols such as polyethylene glycol, holif-1 cobylene ether glycol, and holitetramethylene ether glycol, or copolymerized polyether glycols thereof.

Further, examples of the polyether ester glycol include polyester glycols obtained by reacting di-holyalnylene 1-lene ether glycol with an aliphatic or aromatic dicarboxylic acid as a polyol component.

If the molecular weight of this long-chain diol is too small, the urethane group concentration of the resulting thermoplastic polyurethane-urea resin will become too large, resulting in poor flexibility of the resin and poor solubility in solvents, resulting in the formation of a hack coat layer. It is less preferred for use as a binder. Furthermore, if the molecular weight of the long-chain diol is too large, the content of the long-chain diol in the resin will be too high, and the urethane group concentration will be relatively very low, resulting in poor wear resistance and heat resistance of the resin. descend.

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 includes, for example, ethylene glycol, propylene glycol, 4-bunalene glycol, 1.6- These include aliphatic glycols such as hexane glycol and neopentyl glycol, aromatic diols such as ethylene oxide or propylene oxide adducts of hisphenol A, and ethylene oxide adducts of hydroquinone, and thermoplastic polyurethane-urea resins. Depending on the desired properties, these can be used alone or in combination in various quantitative ratios.

In addition, the organic diamines used in the production of the thermoplastic polyurethane-urea resin include aliphatic diamines such as tetramethylenediamine and hexamethylenecyamine;
+n-phenylene diamine, p-phenylene diamine,
2.4-1-lylenediamine, 2.6-hlylenediamine, m-xylylenediamine, p-xylylenediamine, diphenylmethanediamine, 3,3-dimethoxy-4
, 4-biphenylenediamine, 3,3-dimethyl-4゜4'-biphenylenediamine, 4,4-diaminodiphenyl ether, ■, 5-naphthalenediamine, 2.4-
Examples include aromatic diamines such as naphthalenecyamine, and alicyclic diamines such as (1), 3-diaminomethylcyclohexane, 1°4-diaminomethylcyclohexane, 4,4-diaminodicyclohegycylmethane, and inphorondiamine.

Furthermore, the organic diisocyanates used in the production of the thermoplastic polyurethane-urea resin include aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisonanate, I., ll'l-phenylene diisocyanate, p. -phenylene diisocyanate, 2.4-1-lylene diisocyanate 1-. 2.6
-1-lylene diisocyanate, diphenylmethane diisocyanate, j,j-dithi-4,4-binoenylene diisocyanate, 3,3'-dimethyl-4,4'
- Aromatic diisocyanates such as biphenylene diisocyanate, 4,4'-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, 2,4-naphthalene diisocyanate, 1,3-diisocyanate methylcyclohexane ,■.

4-diisocyanatomethylcyclohexane, 4゜4-
Diisocyanates include alicyclic diisocyanates such as dicyclohexylmethane and isophorone diisocyanate.

Furthermore, if a polyisocyanate curing agent is used in combination with the above-mentioned thermoplastic polyurethane-urea resin, a magnetic recording medium with even better wear resistance can be obtained. In addition, as the polyisocyanate curing agent, for example, polyisocyanate curing agents that can be conventionally used as a curing agent, such as brand name Coronate L (manufactured by Nippon Polyurethane Kogyo Co., Ltd.) and product name Desmodur L (manufactured by Bayer AG). You can use either one. Further, the amount of the polyisocyanate curing agent may be any amount that is normally used.

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

The thermoplastic polyurethane-urea resin used in the present invention is
It is obtained by polyaddition reaction of a long chain diol with a molecular weight of about 500 to about 5000, a short chain diol with a molecular weight of about 50 to about 500, an organic diamine and an organic diisocyanate.

In the polyaddition reaction, a mixture of a long-chain diol and a short-chain diol is reacted with an organic diisocyanate in advance to prepare an isocyanate, -1, curtain-terminated prepolymer, and then an organic diamine is added to extend the chain and form a urea group. There is a prepolymer method that involves the introduction of

Further, in the above reaction, the molar ratio of the short chain diol to the long chain diol is preferably 3 or less. If this molar ratio is too large, the urethane group concentration will become too high, and the produced polyurethane-urea resin will not be soluble in the above-mentioned general-purpose solvents used in preparing backcoat paints, making it less suitable. Ethylene glycol, 1,4-butylene glycol, ■, 6- as short chain diols
When using a straight chain diol such as hexane glycol,
The above-mentioned molar ratio is desirably 1 or less, preferably 0.5 or less, and the solubility of the resin is good when branched short-chain diols such as neopentyl glycol or ethylene oxide or propylene oxide adducts of bisphenol A are used. The above-mentioned molar ratio can be increased compared to diols.

However, even in this case, if the above-mentioned molar ratio is too large, exceeding 3, the solubility will deteriorate, which is not preferable.

In producing the thermoplastic polyurethane-urea resin used in the present invention, long-chain diols having a molecular weight of about 500 to about 5,000 are selected from among the above-mentioned examples, particularly polyester diols, especially polybutylene adipate and polyhexamethylene adipate. 1. It is preferable to use polycaprolactone diol. Further, as the short chain diol having a molecular weight of about 50 to about 500, among the above-mentioned examples, it is particularly preferable to use a branched short chain diol, especially neopentyl glycol. Further, as the organic diamine, it is particularly preferable to use isoporone diamine among the above-mentioned examples. In addition, among the above-mentioned examples, especially 4 is the organic diisocyanate.
．． ．． It is preferable to use 4-diphenylmethanediisonana-1., inphorone diisocyanate.

In addition, the polyaddition reaction method employed in the production of the thermoplastic polyurethane-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, and 1-luene. There is solution polymerization, which is carried out by dissolving the above-mentioned raw materials in an inert solvent such as In particular, when preparing a prepolymer, it is more preferable to carry out melt polymerization, and before performing the chain extension reaction, add the above-mentioned inert solvent and carry out solution polymerization.

During the reaction, an organometallic compound such as an organotin compound such as stannous octylate or dibutyltin dilaurate, or a tertiary amine such as N-methylmolorin or triethylamine may be added as a catalyst. Also, to increase the stability of the product, antioxidants, ultraviolet absorbers,
A hydrolysis inhibitor or the like may be added.

Further, the thermoplastic polyurethane-urea resin described above can be used in combination with other thermoplastic resins, thermosetting resins, or reactive resins. In this case, the blending ratio of the thermoplastic polyurethane-urea resin to the total binder of the back coat layer is preferably 5 weight percent or more. The blending ratio of thermoplastic polyurethane-urea resin to the total binder is 5
If it is less than the weight factor, hardly any improvement in the blocking resistance of the magnetic recording medium can be expected. The above-mentioned thermoplastic resin has a softening temperature of 150°C or less and an average molecular weight of 1000.
0 to 200,000 and the degree of polymerization is about 200 to 2,000, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer. Polymer, thermoplastic polyurethane elastomer, polyvinyl fluoride, vinylidene chloride-acryloni 1~
Examples include synthetic rubber-based thermoplastic resins such as lyl copolymer, butadiene-acryloni-1-lyl copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives, polyester resin, and polybutadiene. Examples of thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, melamine resins, alkyd resins, silicone resins, acrylic reactive resins, epoxy-polyamide resins, nitrocellulose-melamine resins, and polymer resins. Mixtures of molecular weight polyester resins and inocyanate prepolymers, mixtures of methacrylate copolymers and isocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, urea formaldehyde resins, low molecular weight glycols/high molecular weight diols/ a mixture of triphenylmectun triisocyaners 1 to 1;
Examples include polyamine resins and mixtures thereof.

Among the above resins, especially vinyl chloride-vinyl acetate copolymers, polyurethane resins, polyester resins, cellulose derivatives, etc. have -502M1 group, -0803M1 group, -C0
Contains hydrophilic polar groups such as 1 0M group and 2 -P(0M2) groups (Ml represents hydrogen or an alkali metal, and M2 represents hydrogen, an alkali metal, or a hydrocarbon group) in the molecule. By using the thermoplastic polyurethane-urea resin in combination with the above resin, a magnetic recording medium with improved dispersibility of conductive powder, etc. in the bank coat layer can be obtained.

Disperse the powder component in the binder described above and dissolve it in an organic solvent to prepare Yatsukko-1 paint, and apply this Hatsukko-1 paint to the side of the non-magnetic support opposite to the side on which the magnetic layer is provided. As a result, eight layers are formed.

The above-mentioned powder component includes carbon for imparting conductivity (for example, furnace carbon, channel carbon, acetylene carbon, thermal carbon, lamp carbon, etc., but furnace carbon and thermal carbon are preferable). Pigment (γ-Fe00H added to control surface roughness and improve durability)
, γ-pe2'3゜Crz(h, TiOz,
ZnO, Sin, Si 02 ・2H20, Mz03
・2SiOz・21(20,3Mgo・4 SiO2
・H2O, MgCO3・Mg (01-() 2・31
-120. Mhos, 5bz03, etc.).

In addition, as the non-magnetic support on which the above-mentioned Barafco-1 layer is applied, polyethylene terephthalate, polyethylene-terephthalate, polyethylene-
Polyesters such as 2,6-naphthalate, polyolefins such as polyethylene and polypropylene, cellulose derivatives such as cellulose triacetate butyrate and cellulose acetate propionate, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polycarbonate, polyimide, Polyamide, polyamideimide, polyhydrazides, non-magnetic metals such as copper, tin, zinc or non-magnetic alloys containing these, ceramics such as glass, earthenware and porcelain, paper or polyethylene, polypropylene, ethylene-butene copolymer Paper materials such as paper coated with or laminated with α-polyolefins having 2 to 10 carbon atoms, etc., can be mentioned.

The forms of this non-magnetic support are film, tape, sheet,
Discs, cards, drums, etc. are all good I/papers.

Furthermore, if necessary, a lubricant or the like may be added to the above-mentioned Paraco-1 layer. 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), phenylpolysiloxane, fluoroalkylpolysiloxane (alkyl has 1 to 5 carbon atoms), and other silicone oils,
Conductive fine powder such as graphite, molybdenum disulfide,
Inorganic fine powder such as tungsten disulfide, polyethylene, polypropylene, polyethylene-hinyl chloride copolymer,
Fine plastic powder such as polytetrafluoroethylene, α-olefin polymers, unsaturated aliphatic hydrocarbons that are liquid at room temperature (compounds in which an n-olefin double bond is bonded to the terminal carbon, number of carbon atoms is approximately 20), number of carbon atoms Fatty acid esters formed from 12 to 20 monobasic fatty acids and monohydric alcohols having 3 to 12 carbon atoms, fluorocarbons, and the like 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.

On the other hand, the magnetic layer is formed by coating one surface of the non-magnetic support with a magnetic paint prepared by dispersing ferromagnetic powder in a binder and dissolving it in an organic solvent.

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.

Armono, Sochimakuhemaih (r FezO3,X
=1.50), magnetite t・(Fe+04.X=
1.33) and their solid solutions (FeOx, 1.
33 <X< 1.50). These γ-Fe2O
3 and Fe30a are usually obtained by the following manufacturing method. First, add an alkali to a ferrous salt solution to generate ferrous hydroxide, oxidize it by blowing air at a predetermined temperature PH, and obtain acicular hydrated iron oxide, which is used as a starting material. as in the air 2
It is heated and dehydrated at 50 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, the magnetite may be added to 200 to 3
Acicular makhemite (γ-Fe2O3
). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing magnetic iron oxide: doped type and deposited type. The methods for producing Co-doped iron oxide particles include: (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. When doing this, add a solution of 1゛ salt for cobalt in advance, synthesize goethite containing cobalt while adjusting the pH, and reduce and oxidize it. (3) Goethite that does not contain Co is used as a core, A method of performing a reaction similar to (2) on this nucleus to grow Co-containing goethite, and then reducing and oxidizing it. (4) Aqueous alkaline solution containing CO salt on the surface of acicular goethite or maghemite. There is a method in which the Co compound is adsorbed by treatment in a vacuum, followed by reduction/oxidation or heat treatment at a relatively high temperature. In addition, CO-adhered iron oxide magnetic particles are produced by mixing acicular magnetic iron oxide and cobalt salt in an alkaline aqueous solution and heating the mixture to adsorb cobalt compounds such as co/coal hydroxide to the iron oxide particles. Wash it with water, dry it, take it out, and then
It can be obtained by heat treatment in a non-reducing atmosphere such as air or 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 may be Cr 02 or Ru or Sn for the purpose of improving coercive force.

A material to which at least one of Te, Sb, Fe, Ti, V, Mn, etc. is added can be used. CrO2 basically consists of chromium trioxide (CrO:+) in the presence of water at least 5
It is obtained by thermal decomposition at 400 to 525°C at 00 atm. In addition, as a synthesis method under atmospheric pressure, there is also a method in which Cr(h) is decomposed at 250 to 375°C in the presence of nitrogen oxide (NO) in addition to oxygen.As the ferromagnetic alloy powder, Fe
, Co, Ni, Fe-Co, Fe-N
i or Fe-Co-Ni, etc., and AI, Si, Ti, Cr for the purpose of improving various properties.

Metal components such as Mn, Cu, and Zn may 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 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 mercury electrolysis. (6) Adding a ferromagnetic metal salt to the solution, such as thorium 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, etc. -Vinyl alcohol copolymer, vinyl chloride-vinyl acetate-7leic acid copolymer, vinyl chloride-vinyritine chloride copolymer, vinyl chloride-
Acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinyritine chloride copolymer, meccrylic ester-vinylidene chloride copolymer, meccrylic ester-snarene copolymer, thermoplastic polyurethane resin, phenoxy resin, Polyvinyl fluoride, vinylidene chloride-acryloni 1-lyl copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, Examples include phenol resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, and mixtures thereof. Furthermore, a thermoplastic polyurethane-urea resin may be used in the same way as the binder used in the Barafco-1 layer, or a hydrophilic polar group may be introduced into the resin to make it compatible with the ferromagnetic powder. The magnetic layer may be cured in a short time by electron beam irradiation by improving the dispersibility or by introducing an acrylic double bond.

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,
1'2-18 carbon atoms such as lyllunic acid and stearolic acid (
7) Fatty acids (RtCOOH).

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

(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 oxo quaternary ammonium salts (alkyl has 1 to 5 carbon atoms) , olefins are ethylene, propylene, etc.). In addition to these, higher alcohols having 12 or more carbon atoms and sulfuric esters can 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.

As the moisture-fitting agent, dialkylpolysiloxane (
Alkyl has 1 to 5 carbon atoms), dialkylpolysiloxane (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 phenylpolysiloxane and fluoroalkylpolysiloxane (alkyl has 1 to 5 carbon atoms), conductive fine powder such as graphite, inorganic fine powder such as molybdenum disulfide and tungsten disulfide, polyethylene, polypropylene,
Polyethylene vinyl chloride copolymers, fine plastic powders such as polytetrafluoroethylene, α-olefin polymers, unsaturated aliphatic hydrocarbons that are liquid at room temperature (compounds in which an n-olefin double bond is bonded to the terminal carbon, carbon 20), fatty acid esters consisting of a monobasic fatty acid having 12 to 20 carbon atoms and a monohydric alcohol having 3 to 12 carbon atoms, 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 (CrzO3), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main ingredients: corundum and magnetite) are used. Ru. These abrasives 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.

Fine powder, natural surfactants such as zabonin, nonionic surfactants such as alkylene oxazine F, chrycerin, and glycidol, higher alkylamines, quaternary ammonium salts, pyridine and other IS, phosphoniums, etc. cationic surfactants, anionic surfactants containing acidic groups such as h-rubonic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, phosphoric acid ester groups, amino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols. Amphoteric activators such as the following 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 are sometimes applied for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

As the above-mentioned rust preventive agent, phosphoric acid, sulfamide, quanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, etc. can be used, but in particular, dicyclohexylamine kitrite, cyclohexylamine chromate, diisopropylamine nitrite, gel Tanolamine phosphate-1-
, cyclohexylammonium carbonate 1-, hex→
Volatile rust inhibitors (inorganic or organic acid salts of amines, amides or imides ) will improve the rust prevention effect. These rust inhibitors are used in an amount of 0.01 to 20 parts by weight per 100 parts by weight of the ferromagnetic fine powder.

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. , methyl acetate, ethyl acetate, butyl acetate, ethyl lactate,
Ester systems such as acetic acid glycol monoethyl ether, glycol ether systems such as glycol dimethyl ether, glycol monoethyl ether, and dioxane, aromatic hydrocarbons such as benzene, 1-toluene, and xylene, and aliphatic carbonization such as hexane and heptane. hydrogen, methylene chloride,
Examples include chlorinated hydrocarbons such as ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, and dichlorohenzene.

Furthermore, the present invention is not limited to a so-called coated hunting recording medium in which a magnetic layer is formed by applying a magnetic paint as described above, but also a recording medium in which a deposited substance such as a magnetic metal or alloy is deposited on a non-magnetic support. The present invention may also be applied to a ferromagnetic metal thin film type magnetic recording medium on which a magnetic layer is formed, a so-called vapor-deposited tape.

As the vapor deposition material, any material that can form a ferromagnetic thin film can be used, such as iron-Fe.

Cobal) Co, metals such as nickel N1, or Co
-Ni alloy, Fe-Co alloy, Fe-NI alloy, Co
-Ni-Fe-B alloys and the like may be mentioned.

Further, - the means for depositing the ferromagnetic thin film include vacuum evaporation, ion blating, sputtering, and the like.

The above vacuum evaporation method uses 10-' to 10-3 Torr.
O) A metal magnetic material is evaporated by resistance heating, high frequency heating, electron beam heating, etc. under vacuum, and the evaporated metal (metal magnetic material) is deposited on a non-magnetic support.
It is roughly divided into oblique deposition and vertical deposition.

In the above-mentioned oblique deposition, a ferromagnetic material is obliquely deposited on a non-magnetic support in order to obtain a high coercive force, and in order to obtain a higher coercive force, the above-mentioned oblique vapor deposition is performed in an oxygen atmosphere. Also includes things. In the above vertical deposition, bismuth Bi, thallium Tl, antimony Sb, and gallium Ga are deposited on a nonmagnetic support in order to improve deposition efficiency and obtain high coercive force.
, If /L/After forming a base metal layer such as manium Qe, a metal magnetic material is vertically deposited on the base layer.

The above ion footing method uses lo-4 to l0-3T.
DC glow discharge, R, F glow discharge is caused in an atmosphere mainly composed of o r r inert gas, usually argon gas, and metal is evaporated during the discharge.

The above sputtering method generates claw discharge in an atmosphere containing argon as a main component at IO-3 to 10-'' Torr,
The generated argon ions are used to knock out atoms on the Kugett surface, and there are two methods of generating glow discharge, such as the direct current two-pole, three-pole sputtering method, the high-frequency sputtering method, and the magnetron sputtering method that uses a magnetron discharge.

The present invention will be explained below with reference to Examples. It goes without saying that the present invention is not limited to these Examples.

Example of Resin Synthesis In a reaction vessel equipped with a heating and cooling device equipped with a stirring propeller, a thermometer, and a condenser, a compound having a molecular weight of 1
000 polybutylene adipate 100100O, 0 mol), neopentyl glycol 26 g (0.25 mol)
, 500g of 4,4-diphenylmethane diisocyanate
(2.0 mol) and methyl ethyl ketone 7009 were charged and reacted at 75 to 80°C for 4 hours, and then 900 g of methyl ethyl ketone was added and cooled to around room temperature. Next, 1224 g (0.72 mol) of isophorone diamine was added to 13'45 L of methyl ethyl ketone, 2 cyclohexanone
A diamine solution dissolved in 00 (N9) was added.

As the diamine solution was added, the viscosity of the solution increased rapidly, and when a predetermined viscosity was reached, a glycol corresponding to the concentration of the remaining --NCO groups was added to modify the terminal end into a 10H group. The obtained polyurethane-urea resin solution was a transparent viscous liquid with a solid content of 25 cm and a viscosity of 10,000 CP/25°C, and did not thicken or become thixotropic even after long-term storage, and had good liquid properties. Ta.

According to the above synthesis method, the numbers of moles of polybutylene adipate-1, neopentyl glycol, 4,4-diphenylmethane diisocyaner 1-, and inphorondiamine were arbitrarily changed to produce samples A to G as shown in Table 1. was synthesized. The properties of the resulting resin are shown in Table 1.

In addition, sample A in Table 1 is polybutylene adipate ioo
ogci, o mol), 1,4-butanediol IL9 (
0.2 mol) and 4,4-diphenylmethane diisocyanate 300. ! i' (1.2 mol), and the concentration of urethane groups that do not contain urea groups is 1.
It is a polyester polyurethane resin of about 3 mmol/i.

In addition, in Table 1, the glass transition point temperature was measured by the TBA method using Torsion Blade Analysis (manufactured by Rigaku Denki Co., Ltd.), and the softening point temperature was measured by cutting the sample with a JIS No. 2 tambell and applying a load equivalent to 5 g/100 μm. In this state, the temperature was raised at a rate of 5° C. per minute to a temperature at which the amount of deformation rapidly increased.

Example 1 CO-adhered r-Fe203 100 parts by weight Vinyl chloride-vinyl acetate copolymer 15 (U, C, C company IJ V
A OH) Polyurethane resin lO# (N-2304 manufactured by Nippon Polyurethane Co., Ltd.) Dispersant (lecithin) l ・Lubricant (Silicone oil) ■ ・Abrasive (Cr203) 2″ Methyl ethyl ketone 10υ Methyl isobutyl ketone 50# Toluene 50 # The above composition was mixed in a ball mill for 48 hours, filtered through a 3 μ filter, 2.5 parts by weight of a hardening agent (manufactured by Bayer AG, Desmodor) was added, and mixed for an additional 30 minutes to prepare a magnetic paint. This was placed on a 16 μm thick polyethylene terephthalate film with a thickness of 6 μnL after drying.
A magnetic layer was formed by coating the material to give the following properties, and after performing a magnetic field orientation treatment, it was dried and wound up. After calendering this, 100 parts by weight of carbon vinyl chloride-vinyl acetate copolymer 15 (U, C,
C, manufactured by VAGH) Thermoplastic polyurethane-urea resin 35 ・(Sample F
) Dispersing agent (lecithin) 0.5 ・Methyl ethyl ketone 180 〃 Methyl isobutyl ketone 90 ・Toluene 180 ・ A composition consisting of the following was mixed in a ball mill for 48 hours and filtered through a 1μ filter, followed by hardening agent (Desmodur L, manufactured by Bayer AG) A back coat paint prepared by adding 5 parts by weight and mixing for an additional 30 minutes is applied to the back side of the above polyethylene terephthalate film on which the magnetic layer is provided, to a coating thickness of 2 to 5 parts by weight.
A back coat layer was formed by coating to a thickness of about 3 μm. After heat-treating this, it was cut into a % inch width to create a sample tape.

Example 2 Carbon I (10 parts by weight Vinyl chloride-vinyl acetate copolymer 7.5 parts by weight (U,
V A GH manufactured by C.C.) Thermoplastic polyurethane-urea resin 17.5 ・(Sample F) Dispersant (lecithin) 0.5 to methyl ethyl ketone 180 ・Methyl isobutyl ketone 90 Toluene 180 〃 The above composition and curing agent A back coat paint was prepared using 25 parts by weight of Desmodur L (manufactured by Bayer AG), and a magnetic layer and a back coat layer were formed in the same manner as in Example 1 to prepare a sample tape.

Example 3 Carbon 100 parts by weight Vinyl chloride-vinyl acetate copolymer 17.5 (U,
C, C", manufactured by VAGI-1) Thermoplastic polyurethane resin 7.5 = (
Sample F) Dispersing agent (lecithin) 0.5" Methyl ethyl ketone 180 parts by weight Methyl isobutyl ketone 90 Toluene 11!0 = Pasokuco using the above composition and 2.5 parts by weight of a curing agent (Desmodur L, manufactured by Bayer AG) -1. A sample tape was prepared by preparing a paint and forming a magnetic layer and a bank coat layer in the same manner as in Example 1 above.

Example 4 A thermoplastic polyurethane-urea resin (sample B) was used in place of the thermoplastic polyurethane-urea resin (sample F) in the back coat paint of Example 1, and the same method as in Example 1 was used to prepare → no-pull tape. It was created.

Example 5 A sample tape was created in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (Sample C) instead of the thermoplastic polyurethane-urea resin (Sample F) in the back coat paint of Example 1. did.

Example 6 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (Sample D) instead of the thermoplastic polyurethane-urea resin (Sample F) in the back coat paint of Example 1. Created.

Example 7 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (sample E) instead of the thermoplastic polyurethane-urea resin (sample F) in the Paracco-1 paint of Example 1. It was created.

Example 8 A sample tape was prepared in the same manner as in Example 1, using a thermoplastic polyurethane-urea resin (Sample G) instead of the thermoplastic polyurethane-urea resin (Sample F) in the Paracco-1 paint of Example 1. It was created.

Comparative Example 1 A sample tape was created in the same manner as in Example 1, using polyester polyurethane resin (Sample A) in place of the thermoplastic polyurethane-urea resin (Sample F) in Parakko-1 paint of Example 1. .

The adhesive releasability and scratch resistance of the above sample tapes were measured. The measurement results are shown in Table 2.

The adhesive removability was determined by wrapping the sample tape around an IJ-ring and leaving it for 24 hours at a temperature of 40°C and a humidity of 80°C, and then visually evaluating the degree of peeling of the sample tape.
Scoring was done using a 0-point system, and the better the score, the lower the score. In addition, the above scratch resistance was determined by visually observing the scratches on the back coat layer after shuttle running a sample tape of 1O length 100 times. Evaluations were made using △ if scratches were present, and × if scratches were severe and powder falling onto the pinch roller or guide member was noticeable.

Table 2 As mentioned above, by using a thermoplastic polyurethane-urea resin as a binder for the back coat layer of a magnetic recording medium, it is possible to use a general-purpose solvent and the back coat paint is easy to handle. Furthermore, it is possible to obtain a magnetic recording medium with excellent blocking resistance and durability without the back coat layer adhering to the magnetic layer.

(Import of Procedural Amendments) December 7, 1980 Commissioner of the Japan Patent Office Kazuo Wakasugi 1, Indication of the case 1981 Patent Application No. 199574 2, Name of the invention Magnetic recording medium 3, Person making the amendment Case and Relationship of Patent Applicant Address: 6-7-35, Kitashina-yo, Tokyo Parts-Yo-ku, (
218) Sony Corporation (Name) Representative Norio Ohga 4, Agent 105 Voluntary 6, "Detailed Description of the Invention" column 7 of the specification subject to amendment, Contents of the amendment

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic layer is provided on one side of a non-magnetic support and a Barafco-1 layer is provided on the other side, the Barafco-1 layer comprises a long chain diol having a molecular weight of about 500 to about 5000; 1. A magnetic recording medium comprising, as a binder, a thermoplastic polyurethane-urea resin obtained by reacting a short-chain diol with a molecular weight of about 50 to about 500, an organic diamine, and an organic diisocyanate.