JPH03697B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a magnetic recording medium, and particularly to a magnetic recording medium having orientation, durability, wear resistance, and high output. Magnetic recording media are usually manufactured by applying a magnetic paint containing magnetic powder and a binder component that binds the powder to the substrate onto a non-magnetic substrate such as a polyester film, and drying the coating. This magnetic recording medium is required to have excellent electrical properties as well as durability and wear resistance. Therefore, the binder component used has excellent dispersibility of magnetic powder, and has high sensitivity and
There is a need for something that can provide excellent electrical properties such as a high signal-to-noise ratio, as well as improve the durability of the magnetic recording medium by improving the abrasion resistance and heat resistance of the magnetic layer. As described above, the binder component plays an extremely important role in terms of the characteristics of the magnetic recording medium. Many thermoplastic resins or thermosetting resins are used as the polymer used as the binder, and in particular, mixed systems of vinyl chloride-vinyl acetate resins, cellulose derivatives, epoxy resins, polyamide resins, etc., and polyurethane resins are used. It is used. However, when a mixture of the above resins is used, there are problems with the compatibility and dispersibility of the resins, as well as with the abrasion resistance, surface properties, etc. of the manufactured magnetic recording medium. 100 as one way to improve these shortcomings.
A binder consisting of a thermoplastic urethane resin with a % modulus of 30 to 100 Kg/cm ² , a thermoplastic urethane resin with a 100% modulus of 20 Kg/cm ² or less, and a cellulose resin was proposed in Japanese Patent Publication No. 1641/1983. ing. However, this technology has not yet achieved sufficient dispersibility, durability, abrasion resistance, non-video properties, powder removal, etc. A first object of the present invention is to provide a magnetic recording medium having a novel binder composition. A second object of the present invention is to provide a magnetic recording medium with excellent wear resistance. A third object of the present invention is to provide a magnetic recording medium with excellent video characteristics. A fourth object of the present invention is to provide a magnetic recording medium with less dust falling off. The above objects of the present invention are to have a tensile strength of 200
A soft urethane resin with a tensile strength of less than Kg/cm ² and an elongation at break of 900% or more (hereinafter referred to as the soft urethane resin of the present invention), and a hard urethane resin with a tensile strength of 200 Kg/cm ² or more and an elongation at break of less than 900%. This is achieved by a magnetic recording medium (hereinafter referred to as the magnetic recording medium of the present invention) containing a type urethane resin (hereinafter referred to as the hard type urethane resin of the present invention) and a cellulose resin. The method for measuring the tensile strength and elongation at break in the present invention is based on Japanese Industrial Standards (JIS) K-6301.
is described in detail. The measurement method will be explained below. A 100μ thick urethane resin film is heated at 80℃.
10 minutes, followed by heat treatment at 120℃ for 10 minutes, then 25℃,
After being left in an atmosphere of 55%RH (relative humidity) for 3 days,
Under the same conditions, tensile strength is measured at 200 mm/min using No. 2 dumbbells according to JISK-6301. The results of the later examples show that the magnetic recording medium of the present invention has better properties such as abrasion resistance, video characteristics, and dust removal than conventional magnetic recording media that combine soft-type urethane resin, hard-type urethane resin, and cellulose resin. As can be seen from the above, it was unexpected that the material had far superior properties. The soft urethane resin and hard urethane resin used in the present invention contain organic dibasic acids such as phthalic acid, adipic acid, dimerized linoleic acid, and maleic acid, and organic dibasic acids such as ethylene glycol, propylene glycol, butylene glycol, and diethylene glycol. Glycols or trimethylolpropane, hexanetriol, glycerin,
trimethylolpropane, hexanetriol,
A polyester polyol synthesized by reaction with polyhydric alcohols such as glycerin, trimethylolethane, and pentaerythritol, or any two or more polyols selected from these glycols and polyhydric alcohols; or , ε-caprolactam, α-methyl-1-caprolactam, ε-methyl-ε-caprolactam,
Lactone-based polyester polyols synthesized from lactams such as γ-butyrolactam; or polyols such as polyether polyols synthesized from ethylene oxide, propylene oxide, butylene oxide, etc., to tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate Polyester polyurethane resins and polyether polyurethane resins urethanized with diisocyanate compounds such as , hexamethylene diisocyanate, and metaxylylene diisocyanate are used. These urethane resins according to the invention are mainly produced usually by the reaction of polyisocyanates and polyols, and also in the form of urethane resins or urethane prepolymers containing free isocyanates and/or hydroxyl groups.
Alternatively, it may be in the form of something that does not contain these reactive terminal groups, such as a urethane elastomer. Since the methods for producing urethane resins, urethane prepolymers, urethane elastomers, curing and crosslinking methods, etc. are well known in the art, detailed explanation thereof will be omitted. Nitrocellulose, ethylcellulose, acetylcellulose, cellulose acetate butyrate, cellulose propionate, and the like can be optionally used as the cellulose resin according to the present invention, but nitrocellulose (NC) is preferred in the present invention. The soft-type urethane resin and hard-type urethane resin of the present invention may be mixed in any proportion, but
The weight ratio is preferably 5:95 to 95:5, particularly preferably 80:20 to 20:80. The urethane resin and cellulose resin consisting of the soft urethane resin and the hard urethane resin according to the present invention may be mixed in any proportion, but the weight ratio
Preferably, they are mixed in a ratio of 99:1 to 50:50. Furthermore, in order to improve the durability of the magnetic recording medium of the present invention, it is preferable that the magnetic layer contains polyisocyanate or isocyanate as a hardening agent. Examples of the above-mentioned isocyanates include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate. Examples of the polyisocyanate include an adduct of diisocyanate and a trivalent polyol, a pentamer of diisocyanate, and a decarboxylation compound of 3 moles of diisocyanate and water. Examples of these include an adduct of 3 moles of tolylene diisocyanate and 1 mole of trimethylolpropane, an adduct of 3 moles of metaxylylene diisocyanate and 1 mole of trimethylolpropane, a pentamer of tolylene diisocyanate, and 3 moles of tolylene diisocyanate. A pentamer consisting of 2 moles of hexamethylene diisocyanate and a decarboxylated product obtained by reacting 3 moles of hexamethylene diisocyanate with 1 mole of water can be easily obtained industrially. Examples of the magnetic powder used in the present invention include γ-Fe ₂ O ₃ powder, Fe ₃ O ₄ powder, and Co-containing γ-Fe ₂ O _{3 powder.}
powder, Co-containing Fe ₃ O ₄ powder, CrO ₂ powder as well as Fe powder,
Various magnetic powders such as metal powders such as Co powder and metal alloy powders are widely included. In the present invention, the above ferromagnetic powder, a composition comprising the soft urethane resin of the present invention, a hard urethane resin, and a cellulose resin, or a composition further containing isocyanate or polyisocyanate are mixed and dispersed. Such a magnetic paint is obtained. The magnetic paint according to the present invention contains ferromagnetic powder, the soft urethane resin of the present invention, the hard resin, the cellulose resin, and the coating solvent as main components, and in addition, a dispersant, a lubricant, an abrasive agent, etc. as necessary. Contains additives such as antistatic agents and antistatic agents. This magnetic paint is
A magnetic recording layer is formed by dissolving and dispersing the above-mentioned composition in an organic solvent and coating it on a nonmagnetic support to obtain the magnetic recording medium of the present invention. Regarding the manufacturing method of the magnetic paint used in the present invention,
Special Publication No. 35-15, No. 39-26794, No. 43-186,
No. 47-28043, No. 47-28045, No. 47-28046,
No. 47-28048, No. 47-31445, No. 48-11162,
It is described in detail in various publications such as No. 48-21331, No. 48-33683, and Soviet Patent Specification No. 308033. Although the mixed urethane resin and cellulose resin according to the present invention are used as a binder, in the present invention, other known binders may be used in combination as long as the purpose of the present invention is achieved. Can be done. Other binders used include unsaturated prepolymers such as malenanic anhydride types, urethane acrylic types, and electron beam curable resins.
Epoxy acrylic type, polyester acrylic type, polyether acrylic type, polyurthane acrylic type, polyamide acrylic type, etc., or as a multifunctional monomer, ether acrylic type, urethane acrylic type, epoxy acrylic type, phosphate ester acrylic type, aryl type, etc. Examples include hydrocarbon type. Additives used in the magnetic recording layer according to the present invention will be explained. Dispersants used include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid,
Fatty acids with 12 to 18 carbon atoms such as linoleic acid and linolenic acid (RCOOH, R is an alkyl group or alkenyl group with 11 to 17 carbon atoms): Alkali metals (Li; Na, K, etc.) or alkali of the above fatty acids Metal soaps made of earth metals (Mg, Ca, Ba, etc.):
Lecithin etc. are used. In addition, the number of carbon atoms is 12
In addition to the above-mentioned higher alcohols and these, sulfuric esters and the like can also be used. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder. These dispersants are disclosed in Japanese Patent Publication Nos. 39-28369 and 44
−17945, Publication No. 48-15001, U.S. Patent No.
It is described in specifications such as No. 3587993 and No. 3470021. Examples of lubricants include silicone oil, carbon black, graphite, carbon black graft polymer, molybdenum disulfide, tungsten disulfide, monobasic fatty acids having 12 to 16 carbon atoms, and carbon Number of atoms is 21-23
Fatty acid esters (so-called waxes) consisting of monohydric alcohols can also 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. Regarding these, special public
Publications such as No. 23889 and No. 43-81543, U.S. Patent No. 3470021, U.S. Patent No. 3492235, U.S. Patent No. 3497411,
Same No. 3523086, Same No. 3625760, Same No. 3630772,
Specifications of No. 3634253, No. 3642539, and No. 3687725, IBM Technical Disclosure
Bulletin Vol.9, No.7, Page 779 (December 1966):
Described in ELEKTRONIK 1961 No. 12, Page 380, etc. Commonly used abrasives include fused alumina, silicon carbide, chromium oxide,
Corundum, artificial corundum, diamond, artificial diamond, garnet, emery (main ingredients:
corundum and magnetite) etc. are used. These abrasives have an average particle diameter of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are added in an amount of 7 to 20 parts by weight per 100 parts by weight of the binder. These abrasive materials are disclosed in Japanese Patent Application Laid-Open No. 115510/1983, US Patent No. 3007807, US Patent No. 3041196, US Patent No. 3687725, and British Patent No.
No. 1145349 and West German Patent (DT-PS) No. 853211. The antistatic agents used include: conductive powders such as graphite, carbon black, and carbon black graft polymers; natural surfactants such as saponin; nonionic surfactants such as alkylene oxide, glycerin, and glycidol; and high-grade Cationic surfactants such as alkylamines, quaternary ammonium salts, pyridine, other heterocycles, phosphoniums or sulfoniums: Contains acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfuric acid ester groups, phosphoric ester groups, etc. Anionic surfactants: amino acids, aminosulfonic acids,
Ampholytic activators such as sulfuric acid or phosphoric acid esters of amino alcohols are used. These surfactants that can be used as antistatic agents are US Pat. Nos. 2271623, 2240472,
No. 2288226, No. 2676122, No. 2676924, No. 2676975, No. 2691566, No. 2727860,
Same No. 2730498, Same No. 2742379, Same No. 3068101,
Same No. 3158484, Same No. 3201253, Same No. 3210191,
Same No. 2739891, Same No. 3294540, Same No. 3415649,
Same No. 3441413, Same No. 3442654, Same No. 3475174,
No. 3545974, West German Patent Publication (OLS)
1942665, British Patent No. 1077317, British Patent No. 1198450
Including the specifications such as the number, "Synthesis of surfactants and their applications" by Ryohei Oda et al. (Maki Shoten 1964 edition): A.
"Encyclopedia of Surf S Active Agents" by W. Bayley (Interscience Publications, Inc. 1958 edition): "Encyclopedia of Surf S Active Agents Volume 2" by T.P. Sisley (Chemical Publishing Company, 1964 edition): It is described in books such as "Surfactant Handbook" 6th edition (Sangyo Tosho Co., Ltd., December 20, 1960). 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. To form the magnetic recording layer, the above-mentioned composition is dissolved in an organic solvent and applied as a coating solution onto a non-magnetic support. Organic solvents used during coating include: ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone; alcohols such as methanol, ethanol, propanol, butanol; methyl acetate,
Ester systems such as ethyl acetate, butyl acetate, emulsion ethyl acetate, and glycol monoethyl acetate; glycol ether systems such as diethyl ether, glycol dimethyl ether, glycol monoethyl ether, and dioxane; tar systems such as benzene, toluene, and xylene (aromatic carbonized Hydrogen): methylene chloride, ethylene chloride, carbon tetrachloride,
Chlorinated hydrocarbons such as chloroform, ethylene chlorohydrin, and dichlorobenzene can be used. Materials for the non-magnetic support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, plastics such as polycarbonate,
Non-magnetic metals such as Cu, Al, Zn, glass, porcelain,
Ceramics such as pottery are used. The thickness of these non-magnetic supports is approximately 3 to 100 μm in the case of a film or sheet, preferably 5 μm.
~50μm, and in the case of disk or card shape,
It is about 0.5 to 10 mm, and if it is drum-shaped, it is cylindrical, and its shape is determined depending on the recorder used. The surface of the nonmagnetic support opposite to the side on which the magnetic layer is provided may be coated with a so-called backcoat for the purpose of preventing static electricity, preventing transfer, and the like. Regarding back coats, for example, U.S. Patent No.
No. 2804401, No. 3293066, No. 3617378, No. 3062676, No. 3734772, No. 3476596,
Same No. 2643048, Same No. 2803556, Same No. 2887462,
Same No. 2923642, Same No. 2997451, Same No. 3007892,
It is described in the specifications of the same No. 3041196, the same No. 3115420, the same No. 3116688, etc. Further, the form of the support may be tape, sheet, card, disk, drum, etc., and various materials are selected as necessary depending on the form. The magnetic powder and the above-mentioned binder, dispersant, lubricant, abrasive, antistatic agent, solvent, etc. are kneaded to form a magnetic paint. During kneading, the magnetic powder and the above-mentioned components are all fed into a kneader simultaneously or individually one after another. For example, there is a method in which magnetic powder is first added to a solution containing a dispersant and kneaded for a predetermined period of time, and then the remaining components are added and kneading is continued to obtain a magnetic paint. Various kneaders are used for kneading and dispersing. For example, two-roll mill, three-roll mill, ball mill, pebble mill, sand glider,
Szegvari attritor, high speed impeller disperser,
These include high-speed stone mills, high-speed impact mills, disper kneaders, high-speed mixers, homogenizers, and ultrasonic dispersers. The technology related to kneading and dispersion is written by TCPATTON.
Paint Flow and Pigment Dispersion (1964)
(published by John Willey & Sons). It is also described in the specifications of US Pat. No. 2,581,414 and US Pat. No. 2,855,156. Coating methods for coating the magnetic coating material onto the support to form a magnetic recording layer include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, and gravure coating. Coat, kiss coat, cast coat, spray coat, etc. can be used, and other methods are also possible. Specific explanations of these methods can be found in "Coating Engineering" published by Asakura Shoten, pages 253 to 277 (published March 20, 1972). ) is described in detail. By such a method, the magnetic recording layer coated on the support is optionally treated to orient the magnetic powder in the layer, and then the formed magnetic recording layer is dried. Further, if necessary, the magnetic recording body of the present invention is manufactured by subjecting it to surface smoothing processing or cutting it into a desired shape. In this case, the orienting magnetic field is approximately 500
~2000 gauss or so, and the drying temperature is approximately 50~100 gauss
The drying time is approximately 3 to 10 minutes. Methods for orienting magnetic powder are also described in the patents listed below. For example, US Patent No. 1949840, US Patent No. 2796359
No. 3001891, No. 3172776, No. 3172776, No. 3001891, No. 3172776, No.
Specifications of No. 3416949, No. 3473960, No. 3681138, Japanese Patent Publication No. 32-3427, No. 39-28368,
No. 40-23624, No. 40-23625, No. 41-13181,
Publications such as No. 48-13043 and No. 48-39722. The orientation direction of the magnetic material is determined by its use. The present invention will be explained in more detail below using Examples. The ingredients, proportions, order of operations, etc. shown here are as follows:
It will be readily understood by those skilled in the art that modifications may be made without departing from the spirit of the invention. The magnetic recording medium of the present invention can be used not only for audio, video, and computers, but also for magnetic cards,
It can also be used for magnetic sheets, magnetic disks, magnetic drums, etc. Therefore, the invention should not be limited to the following examples. Example-1 Pandex T- as a soft urethane resin
5610 (manufactured by Dainippon Ink and Chemicals Co., Ltd.) (Tensile strength
155Kg/cm ² elongation at break 1000%), as a hard urethane resin, Crisbon 4216 (manufactured by Dainippon Ink Chemical Co., Ltd.)
(MEK solid content 30% tensile strength 680Kg/cm ² , elongation at break 530%) Cellnova BTH1/
2 (manufactured by Asahi Kasei Co., Ltd., nitrocellulose) to prepare the compositions shown in Table 1 below.

[Table] After thoroughly mixing and dispersing the above composition in a ball mill, Coronate L (a polyisocyanate manufactured by Nippon Polyurethane Co., Ltd.) was mixed with 75% by weight of acetic acid containing an adduct of 1 mol of trimethylolpropane and 3 mol of tolylene diisocyanate. 100% of the above composition (ethyl solution)
A magnetic paint was prepared by adding 1.05g per gram and mixing uniformly. This magnetic paint was applied to one side of a polyethylene terephthalate film with a thickness of 15 microns to a dry film thickness of 5 microns while applying a magnetic field of 2000 Gauss. The wide sample thus obtained was supercalendered and then slit to a width of 12.65 mm to obtain a videotape sample of the present invention (A-1). Furthermore, as shown in Table 1, Pandex T-
Cellnova BTH1/2 using 5610 and Chrisbon 4216
A videotape produced in the same manner as in Example-1 without containing was used as a comparative sample (S-1). Example-2 MAU-2010 as soft urethane resin
(manufactured by Dainichiseika Co., Ltd.) (Tensile strength 30Kg/cm ² , elongation at break 1175%), PS- as a hard urethane resin
623 (manufactured by Mitsui Nisso Urethane Co., Ltd.) (Tensile strength 500~
550Kg/cm ² , elongation at break approximately 5%), and Cellnova
Example using ETH1/2 with the composition shown in Table 2-
A videotape was produced in the same manner as in Example 1 and designated as the present invention sample (A-2).

[Table] Furthermore, as shown in Table 2, N-5103 (manufactured by Nippon Polyurethane Co., Ltd.) (tensile strength 600 to 650 Kg/cm ²
(Elongation at break 740-770%), Paraprene 22S (manufactured by Nippon Polyurethane Co., Ltd.) (tensile strength 500 Kg/cm ² , elongation at break 600%) and Cellnova BTH1/2, without adding isophorodiisocyanate. A videotape produced in the same manner as in the example was used as comparative sample-2 (S-2). Comparative sample similar to comparative sample (S-2) but excluding Cellnova BTH1/2 -
3 (S-3) was created. The characteristics of the above-mentioned samples (A-1), (A-2) of the present invention and comparative samples (S-1), (S-2), (S-3) were measured as shown in Table 3, and the results were Obtained.

[Table] From the results shown in Table 3, the samples of the present invention were excellent in orientation, abrasion resistance (still properties), electromagnetic properties, and powder drop properties.

Claims (1)

[Claims] 1. A soft polyurethane resin with a tensile strength of less than 200 Kg/cm ² and an elongation at break of 900% or more, and a soft polyurethane resin with a tensile strength of 200 Kg/cm ² or more and an elongation at break of 900%.
1. A magnetic recording medium comprising a magnetic layer containing a hard polyurethane resin and a cellulose resin. 2. The magnetic recording medium according to claim 1, wherein the cellulose resin is nitrocellulose.