JPH0522969B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a magnetic tape, and more particularly to a thin magnetic tape suitable for long-term use. (Prior art and its problems) Polyethylene terephthalate films have recently been used mainly as supports for magnetic tapes. In particular, polyethylene terephthalate film with a thickness of about 8 to 16 μm is used for home video cassette tapes, such as β-format and VHS tapes, and polyethylene terephthalate film with a thickness of about 4 to 12 μm is used for audio cassette tapes. . In particular, a balanced type polyethylene terephthalate film that has equal strength and dimensional stability in the length and width directions is used. In order to use this home videotape for a long time, it is possible to make the support film about 2/3 thinner, and for this purpose, re-stretched polyethylene terephthalate film is used to increase the longitudinal strength and Young's modulus. can be easily considered. That is, stretching vibrations in the longitudinal direction of the tape due to tension fluctuations in the longitudinal direction of the tape due to frictional force and fluctuations thereof during running of the magnetic tape appear as jitters. To solve this problem, in order to make the elongation rate per unit tension the same based on thinning the support (for example, elongation rate/150g load), make the Young's modulus in the length direction inversely proportional to the thickness. It turned out that the higher the price, the better. However, it has been found that as long as polyethylene terephthalate film is used, there is a limit to increasing the Young's modulus in the longitudinal direction. That is, depending on the method of hot stretching after solvent forming, it is almost impossible to increase the Young's modulus in the longitudinal direction to a desired level while maintaining the Young's modulus in the width direction at a constant level. It has also been proposed to make the Young's modulus in the width direction of certain aromatic polyamide films larger than that in the length direction, but this is not sufficient from the viewpoint of drastic improvement of jitter characteristics. However, it was found that it had the disadvantage of being weak against mechanical shock and easily tearing. [Means for solving the problem] As a result of studying various support films for home video and the like that can be recorded for long periods of time, the present inventors found that a specific aromatic polyamide film has a high Young's modulus and is not easily torn. The present invention was achieved by discovering that the tape is tough and has extremely favorable videotape properties without problems such as tape wrinkles or folding even in thin films due to its high Young's modulus in the longitudinal direction. It is something. That is, the present invention provides a magnetic tape in which a magnetic layer is provided on a non-magnetic flexible support, wherein the non-magnetic flexible support is an aromatic polyamide film, and the thickness of the film is 3 to 8 μm. , a magnetic tape having a tensile Young's modulus in the longitudinal direction of 1300 Kg/mm ² or more, an end tear resistance in any direction of 1 Kgf or more, and a light transmittance at 600 nm of 60% or more. I will provide a. The aromatic polyamide film as a non-magnetic flexible support in the present invention has the following general formula (),
It is produced using a polymer of general formula () or a copolymer thereof. or (In the formula, R ₁ , R ₂ and R ₃ are

【formula】

【formula】

【formula】

【formula】

[Formula] These hydrogen atoms may be substituted with a functional group such as halogen, methyl, ethyl, methoxy, nitro, or sulfone. m and n are average degrees of polymerization and are about 50 to 1000. ) Polymers other than the above-mentioned components may be copolymerized or blended with the aromatic polyamide used in the present invention in an amount of about 20 mol % or less. Particularly preferred aromatic polyamides are poly(P-phenylene terephthalamide) or poly(P-benzamide). When producing a film from these polymers, dimethylacetamide, dimethylformamide, N-methylpyrrolidone, hexamethylphosphoramide, γ-butyrolactone, tetramethylurea, dioxane, etc., or a mixed solvent thereof,
Alternatively, a solvent in which an inorganic salt such as lithium chloride, calcium chloride, lithium carbonate, or lithium nitrate is added may be used, but preferably, the polymer is produced from a dope prepared by dissolving the polymer in sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, etc. This is what I did. In the case of these mineral acid dopes, a so-called optically anisotropic dope may be formed, but after this dope is discharged from a die, it is converted into an optically isotropic dope by heating or humidification, and then wet solidified. A film with an extremely high Young's modulus can be conveniently produced by uniaxially or biaxially stretching the film in a wet state after washing and drying while limiting shrinkage. The film used in the present invention must have a thickness of 3 to 8 μm. When the thickness exceeds 8μm,
It becomes impossible to satisfy both the demand for a tape that can record for a long time and the demand for a compact and lightweight tape.
On the other hand, in the case of a film with a diameter of less than 3 μm, it is difficult to handle it and it is difficult to exhibit good videotape characteristics. Since the aromatic polyamide film has an edge tear resistance of 1 kg or more, it is stable against mechanical shock when used as a videotape. The film used in the present invention preferably has an end tear resistance of 2 kg or more. In addition, the center line average surface roughness of the aromatic polyamide film (see Ra, JIS B0601 (1976) and ASA B46-1 (1962)) is 0.03 μm or less, which reduces the noise of the magnetic recording medium. preferred for. The aromatic polyamide film of the present invention includes:
The material used has a tensile Young's modulus in the longitudinal direction of 1300 Kg/mm ² or more. This value of Young's modulus is directly related to the jitter characteristics of the videotape. The tensile Young's modulus in the longitudinal direction is preferably 1500 Kg/mm ² or more, more preferably 1700 Kg/mm ² or more. On the other hand, the Young's modulus in the width direction is preferably 800 Kg/mm ² or more,
More preferably, it is 1000 Kg/mm ² or more. Further, the aromatic polyamide film of the present invention preferably has a breaking elongation of 10% or more in both the length direction and the width direction. Furthermore, the breaking strength in the length direction is 40Kg/mm ²
The above is preferable. The polyamide film of the present invention is transparent, and more specifically, it is preferable to have a light transmittance of 60% or more at 600 nm because it is less likely to wrinkle. The support (film) of the present invention may contain dispersed inorganic substances such as silica, talc, and calcium sulfate as a smoothing agent. The magnetic layer used in the magnetic recording medium of the present invention is a coating-type magnetic layer formed by coating, orienting, and drying a magnetic paint made by kneading and dispersing ferromagnetic fine powder in a binder, an additive, a solvent, etc. and ferromagnetic metals,
A precipitated magnetic layer is formed by depositing an alloy or the like by paper deposition or plating, such as vacuum evaporation, electroless plating, sputtering, or ion plating. Magnetic paints mainly consist of ferromagnetic fine powder, binder, and coating solvent, and may also contain additives such as dispersants, lubricants, abrasives, antistatic agents, rust preventives, and anti-cold agents. As the above-mentioned ferromagnetic fine powder, ferromagnetic iron oxide, ferromagnetic chromium dioxide, ferromagnetic alloy powder, etc. can be used. The above ferromagnetic iron oxide is a ferromagnetic iron oxide whose x value is in the range of 1.33≦x≦1.50 when expressed by the general formula FeOx, that is, maghemite (γ-Fe ₂ O ₃ ,
= 1.50), magnetite (Fe ₃ O ₄ ,
<1.50). The above x value is x = 1/200 {2 x (atomic% of divalent iron) + 3 x (
atomic% of trivalent iron)}. A divalent metal may be added to these ferromagnetic iron oxides. Divalent metals include Cr, Mn,
These include Co, Ni, Cu, Zn, etc., and are added in an amount of 0 to 10 atomic% relative to the iron oxide. The above ferromagnetic chromium dioxide is composed of CrO ₂ and Na, K, Ti, V, Mn, Fe, Co, Ni, Tc,
Metals such as Ru, Sn, Ce, Pb, semiconductors such as P, Sb, Te, or oxides of these metals from zero to
20wt% added _CrO2 is used. The acicular ratio of the above ferromagnetic iron oxide and ferromagnetic chromium dioxide is about 2/1 to 20/1, preferably 5/1.
1 or more, and an average length in the range of about 0.2 to 2.0 μm is effective. The above ferromagnetic alloy powder has a metal content of 75 wt% or more, and 80 wt% or more of the metal content is at least one ferromagnetic metal (i.e., Fe, Co,
Ni, Fe, −Co, Fe−Ni, Co−Ni, or Co−
Ni-Fe), and the metal content is 20wt% or less, preferably 0.5 to 5wt% of Al, Si, S, Sc,
Ti, V, Cr, Mn, Cu, Zn, Y, Mo, Rh, Pd,
Ag, Su, Sb, Te, Ba, Ta, W, Re, Au,
It has a composition of Hg, Pb, Bi, La, Ce, Pr, Nd, B, P, etc., and may also contain a small amount of water, hydroxide, or oxide. The above-mentioned ferromagnetic alloy powder is a particle having a major axis of about 0.5 μm or less. As the binder for the magnetic layer, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used. Thermoplastic resins with a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 200 to 2,000, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, etc. Polymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer Polymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivatives (cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, various synthetic rubber-based thermoplastic resins (polybutadiene, polychloroprene, polyisoprene, styrene-butadiene copolymers, etc.), and mixtures thereof. The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the coating liquid state, but when added after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol-formalin-novolak resin, phenol-formalin-resol resin, phenol-furfural resin, xylene-formaldehyde resin, urea resin, melamine resin, drying oil-modified alkyd resin, carbonic acid resin-modified alkyd resin, maleic acid resin. Modified alkyd resins, unsaturated polyester resins, epoxy resins and curing agents (polyamines, acid anhydrides, polyamide resins, etc.),
Terminal isocyanate polyester moisture curable resin, terminal isocyanate polyether moisture curable resin, polyisocyanate prepolymer (compound having 3 or more isocyanate groups in one molecule obtained by reacting a diisocyanate and a low molecular weight triol, diisocyanate) trimers and tetramers), polyisocyanate prepolymers and resins containing active hydrogen (polyester polyols, polyether polyols, acrylic acid copolymers, maleic acid copolymers, 2-hydroxyethyl methacrylate copolymers, para-hydroxystyrene copolymers) , others), and mixtures thereof. These binders may be used alone or in combination, and other additives may be added. The mixing ratio of the ferromagnetic powder and the binder is preferably 8 to 400 parts by weight of the binder to 100 parts by weight of the ferromagnetic powder.
Used in a range of 10 to 200 parts by weight. In addition to the above-mentioned binder and fine ferromagnetic powder, the magnetic layer may contain additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, a rust preventive, and an antistatic agent. Dispersants include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid,
Resin acids with 12 to 18 carbon atoms such as linolenic acid and stearolic acid (R ₁ COOH, R is an alkyl or alkenyl group with 11 to 17 carbon atoms); Alkali metals of the above fatty acids (Li, Na, K, etc.) ) or alkaline earth metals (Mg, Ca, Ba); fluorine-containing compounds of the above-mentioned fatty acid esters; amides of the above-mentioned fatty acids; polyalkylene oxide alkyl phosphates; resitin; Tetraammonium salts (alkyl having 1 to 5 carbon atoms, olefin being ethylene, propylene, etc.) are used. In addition, 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 a lubricant, dialkyl polysiloxane (alkyl has 1 to 5 carbon atoms), dialkoxypolysiloxane (alkoxy has 1 to 4 carbon atoms), monoalkyl monoalkoxy polysiloxane (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 powders such as graphite; inorganic fine powders such as molybdenum disulfide and tungsten disulfide; polyethylene , plastic fine powder such as polypropylene, polyethylene vinyl chloride copolymer, polytetrafluoroethylene;
a-olefin polymer; unsaturated aliphatic hydrocarbon that is liquid at room temperature (a compound in which an n-olefin double bond is bonded to the terminal carbon, approximately 20 carbon atoms); carbon number 12-
Fatty acid esters consisting of 20 monobasic fatty acids and monohydric alcohols 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. Commonly used abrasive materials include fused alumina, silicon carbide, chromium oxide (Cr ₂ O ₃ ), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite). be done. These abrasives have a Mohs hardness of 5 or more and an average particle size of
A size of 0.05 to 5μ is used, particularly preferably 0.1 to 2μ. These abrasives are binders 100%
It is added in an amount of 0.5 to 20 parts by weight. Antistatic agents 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 alkylamines, and quaternary surfactants. Cationic surfactants such as ammonium salts, pyridine and other heterocycles, phosphoniums or sulfoniums; Anionic surfactants containing acidic groups such as carboxylates, sulfones, phosphoric acid, sulfuric ester groups, and phosphoric ester groups; Amino acids ,
Ampholytic activators such as aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and the like 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. Phosphoric acid, sulfamide, guanidine, pyridine, amine, urea, zinc chromate, calcium chromate, strontium chromate, etc. can be used as rust inhibitors, but in particular, dicyclohexylamine nitrite, cyclohexylamine chromate, diisopropylamine nitrite,
Volatile rust inhibitors such as diethanolamine phosphate, cyclohexylammonium carbonate, hexamethylene diamine carbonate, propylene diamine stearate, guanidine carbonate, triethanolamine nitrite, morpholine stearate (mineral or organic acid salts of amines, amides or imides) The rust prevention effect is improved by using acid salts). 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. As preventive agents, saltylanilide, bis(tributyltin) oxide, mercury phenyloleate, copper naphthenate, zinc naphthenate, mercury naphthenate,
Pentachlorophenol, trichlorophenol, p-dinitrophenol, sorbic acid, p-
Butyl oxybenzoate, dihydroacetoic acid, etc. are used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the binder. Examples of organic solvents used as coating solvents include ketone systems such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester systems such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and acetic acid glycol monoethyl ether;
Glycol ethers such as ether, glycol dimethyl ether, glycol monoethyl ether, and dioxane; Tars (aromatic hydrocarbons) such as benzene, toluene, and xylene; methylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene and other chlorinated hydrocarbons can be selected and used. The magnetic powder and the above-mentioned binder, dispersant, lubricant, abrasive, antistatic agent, rust preventive agent, antistatic agent, solvent, etc. are kneaded to form a magnetic paint. During kneading, the magnetic powder and each of the above-mentioned components are fed into a kneader either simultaneously or individually one after another. For example, there is a method in which magnetic powder is added to a solvent containing a dispersant and kneaded for a predetermined period of time to obtain a magnetic paint. Various types of kneading machines are used for kneading and dispersing magnetic paint. For example, two-roll mill, three-roll mill, ball mill, pepple mill, tron mill,
These include sand gliders, Sxegvari attritors, high-speed impeller dispersers, high-speed stone mills, high-speed impact mills, dispers, kneaders, high-speed mixers, homogenizers, and ultrasonic dispersers. Methods for coating the magnetic recording layer on the support include air doctor coating, blade coating,
Reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, spray coating, spin coating, etc. can be used, and other methods are also possible. Specific examples of these can be explained, for example, in "Coating Engineering" published by Asakura Shoten. It is described in detail on pages 237 to 277 (published on March 20, 1972). In the case of a multilayer magnetic tape, a magnetic layer is coated on a non-magnetic support by the above-mentioned coating method, dried, and this process is repeated to form two magnetic layers by a continuous coating operation. Alternatively, two magnetic layers may be provided simultaneously by a multilayer simultaneous coating method. The thickness of the magnetic layer is applied so that the dry thickness is about 10 μm or less, preferably in the range of 0.5 to 6 μm.
In the case of multiple layers, the total amount falls within the above range. Further, this dry thickness is determined by the use, shape, specifications, etc. of the magnetic tape. Furthermore, the conveyance speed of the strip support to be coated is determined by the desired coating amount (coating film thickness) and the supply amount of the magnetic coating liquid, and is 50 cm/sec.
700m/sec. is desirable. By such a method, the magnetic layer coated on the support is optionally treated to orient the magnetic powder in the layer as described above, and then the formed magnetic layer is dried. If necessary, the magnetic tape of the present invention is manufactured by subjecting it to surface smoothing processing and cutting it into a desired shape. In particular, in the present invention, it has been found that by subjecting the magnetic recording layer to surface smoothing treatment, a magnetic tape with a smooth surface and excellent wear resistance can be obtained.
This surface smoothing treatment is performed by smoothing treatment before drying or by calendering treatment after drying. The orientation treatment is performed under the following conditions. The orientation magnetic field is approximately 500 to 3000 Oe in alternating current or direct current. The orientation direction of the magnetic material is determined by its use. i.e. sound tape, small video tape,
In the case of a memory tape, etc., the orientation is parallel to the length direction of the tape, and in the case of a broadcast video tape, etc., it is oriented at an angle of 30° to 90° with respect to the length direction. Further, in the case of multilayer structure, the upper layer and the lower layer may be oriented in different directions. The drying temperature of the magnetic layer after orientation is approximately 50 to 120℃.
Preferably 70-100°C, particularly preferably 80-90°C
The air flow rate is 1 to 5 Kl/m ² , preferably 2 to 3
The ^drying time is approximately 30 seconds to 10 minutes, preferably 1 to 5 minutes. To smoothen the surface of the coating film before drying the magnetic layer, a method such as a magnetic smoother, smoothing coil, smoothing blade, smoothing blanket, etc. may be used as necessary. After the magnetic layer has dried, the surface of the coating film is calendered using a super calender that passes between two rolls, such as a metal roll and a cotton roll, or a synthetic resin (such as nylon or polyurethane) roll, or a metal roll and a metal roll. Preferably, this is done by law. The conditions for super calendaring are approximately 25 to 50 kg/cm of inter-roll pressure, and approximately 35 kg/cm of pressure between the rolls.
Preferably, it is carried out at a temperature of -150°C and a processing speed of 5-200 m/min. Temperature and pressure above these upper limits have an adverse effect on the magnetic layer and non-magnetic support. Also, if the processing speed is less than about 5 m/min, the surface smoothing effect cannot be obtained;
If it is more than that, the processing operation becomes difficult. The aromatic polyamide film of the present invention as a non-magnetic flexible support is coated with a dry thick undercoat layer of polyester resin, polyurethane elastomer, alcohol-soluble polyamide resin, etc. in order to improve the adhesion of the magnetic layer and the back layer described below. Taste approx. 0.03~
The thickness may be 2 μm, preferably in the range of 0.05 to 1.5 μm. In addition, the support of the present invention has a surface opposite to the side on which the magnetic layer is provided (back surface) for the purpose of preventing static electricity, preventing transfer, preventing wow and flutter, improving the strength of the magnetic tape, and making the back surface matte. May have a backcoat. This back layer is composed of at least one additive such as the above-mentioned lubricant, abrasive, and antistatic layer, and in some cases, a dispersing agent for uniformly dispersing these, the above-mentioned binder, and a coating solvent. A coating solution obtained by kneading and dispersing the above-mentioned materials is applied onto the back surface of the above-mentioned support and dried. Either the magnetic layer or the back layer may be provided on the support first. Preferred additives commonly used are carbon black, graphite, talc, Cr ₂ O ₃ , α-
Fe ₂ O ₃ (red iron), silicone oil, etc., and the binder is preferably a thermosetting resin or a reactive resin. Approximately 30 to 85 wt%, preferably 40 to 80 wt% in the case of inorganic compound additives based on the total solid content of the back layer
In the case of organic compound additives, they are provided at a mixing ratio of about 0.1 to 30 wt%, preferably 0.2 to 20 wt%. or,
The dry thickness can be arbitrarily selected in the range of about 0.5 to 5.0 μm depending on the total thickness, use, shape, purpose, etc. of the magnetic tape. On the other hand, in the case of the above-mentioned deposited magnetic layer, iron, cobalt, nickel and other ferromagnetic metals, or Fe
−Co, Fe−Ni, Co−Ni, Fe−Si, Fe−Rh, Fe
-V, Co-P, Co-B, Co-Si, Co-V, Co
-Y, Co-La, Co-Ce, Co-Pr, Co-Sm,
Co-Mn, Fe-Co-Ni, Co-Ni-P, Co-Ni
-B, Co-Ni-Ag, Co-Ni-Nd, Co-Ni-
Ce, Co-Ni-Zn, Co-Ni-Cu, Co-Ni-Hg,
Co-Ni-W, Co-Ni-Re, Co-Mn-P, Co
−Zn−P, Co−Pb, Co−Sm−Cu, Co−Ni−
A strong layer is formed by forming a ferromagnetic alloy such as Zn--P, Co--Ni--Mn--P into a thin film by a deposition method such as a vapor deposition method or a plating method. Vapor deposition method is a method in which a substance or its compound is deposited on a substrate as vapor or ionized vapor in a gas or vacuum space. Aimetsuki (Chemical Vapor)
This corresponds to the Deposition Act, etc. The plating method refers to a method of depositing a substance on a substrate from a liquid phase, such as electroplating or electroless plating. In the paper deposition method, these conditions vary greatly depending on the method and material, but the general singularities are as shown in Table 1 below.

〔Effect of the invention〕

By using the support according to the present invention, a thin tape with excellent jitter properties that could not be obtained with conventional tapes can be obtained, and it is also resistant to folds, wrinkles, tears, etc., and the support is free from scratches. Since a difficult magnetic tape was obtained, it is very useful as a videotape for long-term recording and/or as a lightweight videotape. [Example] The present invention will now be described in more detail with reference to Examples. Those skilled in the art will readily understand that the components, proportions, order of operations, etc. shown herein may be changed without departing from the spirit of the invention. Therefore, the invention should not be limited to the following examples. [Aromatic polyamide film] Poly(p-phenylene terephthalamide) with an intrinsic viscosity (measured in H ₂ SO ₄ at 25°C, C = 0.5 g/dl) of 5.7 is dissolved in 99.7% sulfuric acid at a polymer concentration of 12.0%. A dope with optical anisotropy was obtained at 60°C. This dope is put into a tank, and a 1.5m curved pipe from the tank to the die is maintained at approximately 70℃.
Cast from a die with a slit of 0.15 mm x 300 mm onto a mirror-polished Hastelloy belt maintained at 110°C, and placed in an atmosphere of 90°C and relative humidity of 88%.
After being kept for 20 seconds, it was coagulated with water at about 5°C to form a film continuously. The coagulated film was taken out and washed with water at room temperature, and the film still containing water was stretched under various conditions, and then dried at a fixed length in an open environment at 220°C to obtain a film. The stretching conditions and film properties are summarized in Table 2 (numbers 1 to 3 are films of the present invention, and the others are films outside the present invention. For comparison, a polyethylene terephthalate film was also used. .

[Manufacture of magnetic tape]

After kneading the compositions shown in Table 3, they were placed in a Pall mill and dispersed for 24 hours.
Adduct of 1 mol of tolylene diisocyanate and 1 mol of trimethylolpropane, 75% by weight solution in ethyl acetate, NCO content approximately 13.3% by weight Bayer
7 parts of Desmoteur L-75 (manufactured by AG) were added to the mixture, followed by high-speed shear dispersion for 1 hour and filtration through a filter with an average pore size of 2 μm to obtain a magnetic coating solution. The viscosity of this coating liquid was 35 c.p.

【table】

[Table] The above magnetic coating liquids are numbered 1 to 1 as shown in Table 2 above.
It was coated onto each film in step 6 to the dry thickness shown in Table 4 below, and then subjected to magnetic field orientation treatment in the length direction of the film using a 2500 Gauss DC magnetic field for 0.02 seconds, and heated at 100°C for 2 minutes. Dry. The resulting wide magnetic web was rolled using a metal roll (chrome-plated steel roll: back-up roll) and a nylon roll (calender roll) at an inter-roll pressure of 50 kg/cm, a temperature of 60°C, and
Supercalendering was carried out at a processing speed of 30 m/min. This wide magnetic web is slit,
Six types of magnetic tapes with a width of 8 mm were obtained. Each characteristic of the above magnetic tape was measured and the following 4.
Shown in the table.

【table】

【table】

Claims (1)

[Claims] 1 The thickness is 3 to 8 μm, the tensile Young's modulus in the longitudinal direction is 1300 Kg/mm2 ^or more, the end tear resistance in any direction is 1 Kgf or more, and the light transmittance at 600 nm is 60% or more. A magnetic tape in which a magnetic layer is provided on a nonmagnetic flexible support made of an aromatic polyamide film.