JP2009111277A - METHOD OF MANUFACTURING SmCo-BASED MAGNETIC PARTICULATE AND METHOD OF MANUFACTURING MAGNETIC RECORDING MEDIUM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which a magnetic recording medium achieving higher-density recording can be manufactured. <P>SOLUTION: The method of manufacturing SmCo-based particulates includes steps of: heating a reaction solution containing Sm salt, Co salt and an organic polymer and/or a ligand compound, and a reaction solvent in which they are dissolved to produce a solid mixture containing SmCo-based particulates and the organic polymer and/or ligand compound in the reaction solution; and removing some of the organic polymer and/or ligand compound from the solid mixture by dissolving them in the solvent to obtain SmCo-based particulates having the remaining organic polymer and/or ligand compound stuck. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing SmCo-based fine particles and a method for producing a magnetic recording medium.

In a magnetic recording medium such as a computer tape for storing data for a long period of time, there is a strong demand for further increasing the recording density. In order to achieve high-density recording, it is expected that it is effective to make magnetic particles excellent in magnetic properties fine and to form a magnetic layer using the particles. For example, as a method for producing fine magnetic particles, a method for producing SmCo-based fine particles refined to the nanometer scale has been proposed (Patent Document 1).
JP 2006-245313 A

  However, in a magnetic recording medium using magnetic particles obtained by a conventional method, it is difficult to maintain magnetic conversion characteristics and the like at a sufficient level in high-density recording. For example, although the method described in Patent Document 1 can obtain fine SmCo-based fine particles, a magnetic recording medium obtained using the fine particles actually has a satisfactory level in terms of magnetic conversion characteristics and the like. It was difficult to achieve and was not fully adaptable to high density recording.

  Therefore, an object of the present invention is to provide a method that enables the manufacture of a magnetic recording medium that achieves further high density recording.

  In one aspect, the present invention relates to a method for producing SmCo-based fine particles. In the method for producing SmCo-based fine particles according to the present invention, a reaction solution containing an Sm salt, a Co salt, and an organic polymer and / or a ligand compound and a reaction solvent in which these are dissolved is heated, A step of generating a solid mixture containing SmCo-based fine particles and an organic polymer and / or a ligand compound, and removing a part of the organic polymer and / or the ligand compound from the solid mixture by dissolution in a solvent, And a step of obtaining SmCo-based fine particles to which the remaining organic polymer and / or ligand compound is attached.

  In another aspect, the present invention relates to a method for manufacturing a magnetic recording medium. The method for producing a magnetic recording medium according to the present invention comprises heating a reaction solution containing an Sm salt, a Co salt, an organic polymer and / or a ligand compound, and a reaction solvent in which these are dissolved, and in the reaction solution. A step of generating a solid mixture containing SmCo-based fine particles and an organic polymer and / or a ligand compound, and removing a part of the organic polymer and / or the ligand compound from the solid mixture by dissolution in a solvent, A step of obtaining SmCo-based fine particles to which the remaining organic polymer and / or ligand compound are adhered, and a step of preparing a magnetic coating material containing SmCo-based fine particles to which the organic polymer and / or ligand compound are adhered; And a step of forming a magnetic layer containing SmCo-based fine particles using a magnetic paint.

  In the production method according to the present invention, sufficiently refined SmCo-based fine particles are obtained by generating SmCo-based fine particles from Sm salt and Co salt in a reaction solution containing an organic polymer and / or a ligand compound. It is produced in the form of a solid mixture mixed with an organic polymer or the like. Then, by removing a part of the organic polymer or the like from the solid mixture, it is possible to manufacture a magnetic recording medium that achieves further high density recording.

  In the above step of removing a part of the organic polymer and / or the ligand compound, from the solid mixture, a part of the organic polymer and / or the ligand compound is converted into an SmCo system relative to the total mass of the organic polymer and the ligand compound. It is preferable to remove until the mass ratio of the fine particles becomes 1-10. As a result, the effect of increasing the recording density according to the present invention is particularly remarkable.

  A part of the organic polymer and / or the ligand compound may be removed from the solid mixture in a dispersion obtained by replacing the reaction solvent in the reaction solution with a solvent. In this case, a part of the solvent in which the organic polymer and / or the ligand compound is dissolved is removed, and then a magnetic paint is prepared using a dispersion liquid to which another solvent is added, thereby covering the film in a good state. A magnetic coating material in which fine particles are dispersed can be easily obtained.

  According to the present invention, a magnetic recording medium having good magnetic characteristics and electromagnetic conversion characteristics and capable of high density recording can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a cross-sectional view showing an embodiment of a magnetic tape that is a magnetic recording medium. A magnetic tape 1 shown in FIG. 1 is laminated on one surface of a tape-like support 10 and a nonmagnetic layer 20 and a magnetic layer 30 that are sequentially laminated from the support 10 side, and on the other surface of the support 10. A backcoat layer 40.

  The magnetic layer 40 contains SmCo-based fine particles. The magnetic layer 40 is formed by heating a reaction solution containing an Sm salt, a Co salt, and an organic polymer and / or a ligand compound and a reaction solvent in which the SmCo-based fine particles and the organic polymer are contained in the reaction solution. And / or forming a solid mixture containing the ligand compound, and removing a part of the organic polymer and / or the ligand compound from the solid mixture by dissolution in a solvent, and the remaining organic polymer and / or A step of obtaining SmCo-based fine particles to which a ligand compound is adhered, a step of preparing a magnetic paint containing SmCo-based fine particles to which an organic polymer and / or a ligand compound are adhered, and SmCo using a magnetic paint. Forming a magnetic layer containing system fine particles.

  SmCo-based fine particles are generated from the Sm salt and Co salt in the reaction solution by heating. Preferably, the Sm salt is samarium acetylacetonate hydrate and the Co salt is cobalt acetylacetonate hydrate.

The ratio of the Sm salt to the Co salt in the reaction solution is preferably adjusted to be about Sm: Co = 1: 3 to 1:10. As a result, SmCo ₅ having excellent magnetic properties or SmCo-based fine particles having a composition similar to this is generated. Moreover, it is preferable that the total weight of Sm salt and Co salt contained in the reaction solution is 0.1 to 10 parts by weight with respect to 100 parts by weight of the whole reaction solution.

  As the organic polymer, a hydrophilic polymer or a hydrophobic polymer can be used, and a hydrophilic polymer is preferable. For example, selected from the group consisting of poly (N-vinyl-2-pyrrolidone) (PVP), polyvinyl alcohol, polypropylene glycol, polyacrylamide, polyvinylamine, polyethyleneimine, and polyacrylic acid, polymaleic acid, polyglutamic acid and their salts At least one hydrophilic polymer can be used as the organic polymer. Alternatively, at least one hydrophobic polymer selected from the group consisting of polyurethane, polyvinyl chloride, polyamide, and polyester can be used as the organic polymer. The number average molecular weight of the organic polymer is preferably 500 to 10,000.

  A ligand compound may be used instead of or together with the organic polymer. A ligand compound is a compound that has a group having a lone electron pair and forms a complex by coordination with a metal (preferably Sm and Co). As the ligand compound, at least one organic compound selected from the group consisting of amines, carboxylic acids, phosphines, phosphine oxides, amides, and thiols can be used. These organic compounds may have an alkyl group and / or an allyl group. Specific examples of the ligand compound include oleic acid and oleylamine.

  It is preferable that the organic polymer and the ligand compound have a polar group that reacts with heat, electron beams, ultraviolet rays, or the like. Thereby, at the time of hardening of a magnetic layer, a binder, an organic polymer, and / or a ligand compound can be combined by reaction. In this case, the binder and the organic polymer and / or the ligand compound may be directly bonded, or may be bonded via another binder. Examples of the polar group include polar groups having active hydrogen such as hydroxyl group and amino group, and known reactive polar groups such as (meth) acryloyl group and epoxy group. You may use together the organic polymer etc. which have the said polar group, and well-known hardening | curing agents, such as diisocyanate.

  The total mass of the organic polymer and the ligand compound contained in the reaction solution is preferably 50 to 2000 parts by weight with respect to 100 parts by weight of the total mass of Sm and Co. When the amount of the organic polymer and the ligand compound is outside the numerical range, it is difficult to generate sufficiently finely-divided SmCo-based fine particles in a good dispersion state.

The reaction solvent preferably contains a reducing hydrophilic solvent such as an alcohol solvent. Moreover, in order to raise reaction temperature sufficiently and to advance reaction efficiently, it is desired that the reaction solvent has a certain high boiling point. Specifically, the reaction solvent contained in the reaction solution during the reaction for generating SmCo-based fine particles preferably has a boiling point of 150 ° C. or higher. Examples of the alcohol solvent include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, 1,3-propanediol, 1,2-hexanediol, and 2-methyl-2,4-pentanediol. It is preferable to include at least one selected glycol. Further, a reducing agent such as NaBH ₄ may be added to the reaction solution to promote the reduction.

  The reaction solution is prepared, for example, by preparing a Sm salt solution, a Co salt solution, and an organic polymer solution and / or a ligand compound solution, and mixing them. The Sm salt solution and the Co salt solution are prepared by, for example, dissolving an Sm salt and a Co salt in an ether solvent, respectively. Examples of the ether solvent include 1,4-dioxane, phenyl ether, and octyl ether. When the organic polymer is a hydrophilic polymer, an organic polymer solution is prepared using a hydrophilic solvent, and when the organic polymer is a hydrophobic polymer, a hydrophobic solvent is used. After mixing, the reaction solution is thoroughly stirred.

  When preparing a reaction solution using the above three or four solutions, the reaction solvent is a mixed solvent including a hydrophilic solvent and an ether solvent. However, in this case, it is preferable that the ether solvent is removed from the reaction solvent together with the water contained in the hydrophilic solvent in advance before the SmCo-based fine particles are generated.

  SmCo-based fine particles are produced from the Sm salt and Co salt by heating the reaction solution to 150 to 320 ° C, more preferably 250 to 300 ° C. SmCo-based fine particles are precipitated in a solid mixture state with an organic polymer and / or a ligand compound. The generated SmCo-based fine particles are fine particles composed of an alloy of Sm and Co, and have a particle diameter of 2 to 7 nm, for example. By generating SmCo-based fine particles in a reaction solution containing an organic polymer and / or a ligand compound, it is possible to generate sufficiently fine SmCo-based fine particles in a well dispersed state. .

  When producing SmCo-based fine particles, it is desirable to produce SmCo-based fine particles at a low concentration of, for example, about 0.1 to 10% by mass in order to produce SmCo-based fine particles in a good dispersion state. However, when such a low-concentration dispersion liquid is used as it is for the formation of a magnetic paint as it is, since the magnetic paint has a low viscosity, the variation in film thickness in the width and the longitudinal direction increases, and the application of the magnetic paint Is actually very difficult.

  After forming the solid mixture, a part of the organic polymer and / or ligand compound is removed from the solid mixture by dissolution in a solvent, and the remaining organic polymer and / or ligand compound is attached. System fine particles are obtained. Since the organic polymer and the ligand compound in the portion adhering to the SmCo-based fine particles are difficult to dissolve in the solvent, the organic polymer and / or the ligand compound in the portion existing between the SmCo-based fine particles in the solid mixture Can be selectively removed.

  More specifically, the removal (washing) of the organic polymer and / or the ligand compound is performed by, for example, removing the reaction solvent in the reaction solution into another solvent having high solubility of the organic polymer and / or the ligand compound. The dispersion can be carried out by dissolving the organic polymer and / or the ligand compound in a solvent in the dispersion obtained. After cleaning, the surface of the SmCo-based fine particles is often completely or partially covered with the remaining organic polymer and / or ligand compound.

  Solvent replacement can be performed by a method in which a part of the reaction solvent is removed from the reaction solution by filtration or removal of the supernatant, and the solvent is added thereto. It is preferable to remove the supernatant liquid while the temperature of the reaction solution is high to remove as much reaction solvent as possible. The solid mixture can be washed by dissolving the organic polymer and / or ligand compound in a solvent by stirring the obtained dispersion and / or applying ultrasonic vibration. In order to perform cleaning efficiently, it is preferable to use agitation and ultrasonic vibration in combination. At the time of washing, the dispersion is heated to a temperature not higher than the boiling point of the solvent while being refluxed as necessary. The heating temperature is preferably about room temperature to 80 ° C. In order to prevent oxidation of the SmCo-based fine particles, cleaning is preferably performed in an inert gas atmosphere.

  The time required for washing is preferably 0.25 to 24 hours, more preferably 0.5 to 12 hours. When the organic polymer or the like is removed by stirring the dispersion prepared without removing the reaction solvent from the reaction solution and drying the solid mixture, stirring for 0.25 to 3 hours is often sufficient.

  After washing by stirring the dispersion and / or applying ultrasonic vibration, some of the solvent (including the reaction solvent) in the dispersion is removed, and then another washing is performed in the dispersion obtained by adding another solvent. May be performed. The washing can be repeated until the desired amount of organic polymer and / or ligand compound is removed. Solvent replacement and washing are preferably repeated 3-5 times. Examples of the method for removing a part of the solvent include a method of removing the supernatant or removing it with an ultrafilter.

  When the organic polymer is a hydrophilic polymer, acetone, hydrophilic ketones and alcohol are preferably used for washing. As the alcohol, linear alcohols having 3 or less carbon atoms such as methyl alcohol and ethyl alcohol, and tert-butyl alcohol are used. Hydrophilic ketones include ethyl methyl ketone. On the other hand, when the organic polymer is a hydrophobic polymer, ketones such as xylene, hexane, and cyclohexanone, low-polar esters, and amides are preferably used as the solvent. In order to prevent oxidation of the SmCo-based fine particles, it is preferable to use a solvent that has been previously dehydrated and / or deoxygenated.

  The solvent used for the washing has a lower boiling point (preferably 200 ° C. or less, more preferably, lower than the reaction solvent (the solvent having the highest boiling point in the case of a mixed solvent) included in the reaction solution during the reaction for generating SmCo-based fine particles Preferably, it is a low boiling point solvent having a temperature of less than 150 ° C. Accordingly, when the magnetic layer is formed from the magnetic paint, the coating film of the magnetic paint can be easily dried, which is advantageous in terms of improving production efficiency and stabilizing the quality.

  It is preferable to remove by washing until the mass ratio of the SmCo-based fine particles to the total mass of the organic polymer and the ligand compound becomes 1 to 10. When the mass ratio exceeds 10, the dispersibility tends to decrease. On the other hand, when the mass ratio is less than 1, the SmCo particle density in the magnetic layer when used as a magnetic recording medium is lowered, and it tends to be difficult to obtain good recording / reproducing characteristics.

  Using SmCo-based fine particles with organic polymer and / or ligand compound attached, SmCo-based fine particles, organic polymer and / or ligand compound attached to SmCo-based fine particles, and binder and these are dissolved Alternatively, a magnetic coating material containing a dispersed solvent (preferably the low boiling point solvent) is prepared. In addition to the above components, the magnetic coating material may contain other components such as a dispersant, a lubricant, an abrasive, a curing agent, and an antistatic agent.

  The binder is not particularly limited as long as it is used in the magnetic layer of the magnetic recording medium, but has good compatibility with the organic polymer and / or the ligand compound from the viewpoint of improving dispersibility. Polymers are preferred. For example, when the organic polymer is a hydrophilic polymer, it is suitably used as a hydrophilic binder. In the case of a hydrophobic polymer, a hydrophobic binder is preferably used. It is particularly preferable to use the same type of polymer as the organic polymer as a binder.

  Specific examples of the hydrophobic binder include thermosetting resins or radiation curable resins such as polyvinyl chloride polymers or copolymers, polyurethane resins, polyacrylic resins, and polyester resins. Specific examples of the hydrophilic binder include poly (N-vinyl-2-pyrrolidone), polyacrylic acid, polymaleic acid, polyglutamic acid or salts thereof, vinyl alcohol, polyethylene glycol, polypropylene glycol, polyacrylamide, and polyvinylamine. And polyethyleneimine or derivatives or copolymers thereof, cellulose, water-soluble acrylic resin, water-soluble polyvinyl acetal, water-soluble polyvinyl butyral, and water-soluble urethane resin. In order to increase the coating strength of the magnetic layer, it is preferable to select the molecular weight, Curie temperature (Tg), and structure of the binder. The number average molecular weight of the binder is preferably 5,000 to 100,000, more preferably 10,000 to 50,000.

  For example, the magnetic paint removes a part of the solvent in which the organic polymer and / or the ligand compound are dissolved from the dispersion after washing, and the organic polymer and / or the ligand compound is not dissolved therein. It is prepared by a method comprising a step of adding a solvent and / or a binder to obtain a slurry (dispersion), a step of kneading the slurry, and a step of adding an additional solvent to the kneaded slurry to obtain a magnetic paint. . The step of obtaining the slurry and the step of kneading may be performed simultaneously. In this case, for example, kneading is performed while gradually adding a solvent and / or a binder to a dispersion containing SmCo-based fine particles to which an organic polymer and / or a ligand compound is attached. It is preferable to add a step of adding an additional solvent to the kneaded slurry to dilute the slurry, and dispersing the solid content in the slurry with a disperser in the diluted slurry. After the step of obtaining the slurry, the magnetic coating material may be prepared by dispersing the solid content in the slurry with a disperser in the obtained slurry without performing the kneading step. The solid content concentration of the slurry when kneading the slurry is preferably 75 to 95% by mass. By kneading the slurry having a solid content concentration in such a range, the SmCo-based fine particles and the binder are uniformly mixed, and a good dispersion state is obtained. The solid content concentration of the diluted slurry is preferably 10 to 30% by mass. By dispersing in a slurry having such a solid content concentration, a magnetic coating material in which SmCo-based fine particles are sufficiently dispersed can be easily obtained. The binder and other components added as necessary are appropriately added to the slurry before or after kneading at any stage.

  In calculating the solid content concentration, the mass of the “solid content” includes SmCo-based fine particles, organic polymers, ligand compounds, and other solid components.

  A step of forming a coating film made of a magnetic paint on the nonmagnetic layer 20, a step of subjecting the coating film to magnetic field orientation, a step of removing the solvent from the coating film, a step of smoothing the coating film, The magnetic layer 30 can be formed by a method including a step of curing the coating film. The smoothing of the coating film is preferably performed by a calendar process.

  The magnetic tape 1 includes a step of forming the magnetic layer 30 by the method as in the above embodiment, a step of forming the nonmagnetic layer 20 on one surface of the support 10, and a back surface on the other surface of the support 10. It can be manufactured by a manufacturing method further comprising a step of forming the coat layer 40.

  As the support 10, for example, a resin film such as a polyester resin such as polyethylene terephthalate and polyethylene naphthalate, a polyamide, a polyimide, and a polyamideimide film can be used.

  The nonmagnetic layer 40 is formed using a nonmagnetic coating material including nonmagnetic particles, a binder, and other components such as a dispersant, an abrasive, and a lubricant as necessary. As the nonmagnetic particles, carbon black, α iron oxide, titanium oxide, calcium carbonate, α alumina, or a mixture thereof can be used.

  In order to achieve higher recording density, when the perpendicular recording method is adopted, it is preferable to provide a soft magnetic layer containing a soft magnetic material on the support side of the magnetic layer. By providing the soft magnetic layer, perpendicular magnetic recording can be performed on the magnetic layer, and the recording density of the magnetic tape 1 can be improved as compared with the case of conventional longitudinal magnetic recording. As the soft magnetic material, an Fe alloy, a Co (cobalt) alloy, or the like can be used. The soft magnetic layer is preferably provided adjacent to the magnetic layer.

  The backcoat layer 10 is formed using a backcoat layer coating material containing carbon black or other nonmagnetic inorganic powder and a binder.

  The nonmagnetic layer 40 and the backcoat layer 10 can be formed by a method usually employed in the production of magnetic tape.

  The order of forming each layer is arbitrary except that the magnetic layer 30 is formed after the nonmagnetic layer 20 is formed. After the magnetic layer 30 is formed, the obtained laminate is cut into a desired tape shape to obtain the magnetic tape 1. Usually, the magnetic tape 1 is assembled in a predetermined cartridge.

  The present invention is not limited to the embodiment described above, and can be modified as appropriate without departing from the spirit of the invention. For example, the magnetic recording medium of the present invention may be a magnetic card or a magnetic disk.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Example Preparation of SmCo-Based Fine Particles 223.8 parts by weight of samarium acetylacetonate hydrate ([CH ₃ COCH═C (O—) CH ₃ ] ₃ Sm · xH ₂ O) was added to 20000 parts by weight of 1,4 dioxane. Dissolved to prepare an Sm salt solution. Further, 534.4 parts by weight of cobalt acetylacetonate ([CH ₃ COCH═C (O—) CH ₃ ] ₃ Co) was dissolved in 20000 parts by weight of 1,4 dioxane to prepare a Co salt solution. Furthermore, 1000 parts by weight of poly (N-vinyl-2-pyrrolidone) (PVP) was dissolved in 90000 parts by weight of tetraethylene glycol to prepare a PVP solution.

  The reaction solution obtained by adding the Sm salt solution and the Co salt solution to the PVP solution was stirred for about 12 hours. Thereafter, in order to remove moisture contained in the Sm salt raw material and the alcohol solvent, the reaction solution was heated for about 1 hour while being kept at 110 ° C. under a nitrogen stream. At this time, 1,4 dioxane used for dissolving Sm salt and Co salt was also removed together with moisture, and Sm salt and Co salt were transferred into alcohol solvent (tetraethylene glycol, boiling point 325 ° C.). Subsequently, the reaction solution was heated and refluxed at 280 ° C. for about 3 hours under a nitrogen stream to produce a solid mixture containing SmCo-based magnetic fine particles in the reaction solution. The reaction solution was separated with a capillary and solvent-substituted with absolute ethanol, and then dropped on a TEM observation grid and dried. When the residue after drying was observed by TEM, the produced SmCo-based fine particles had a particle size in the range of 2 to 7 nm.

  The reaction solution containing the solid mixture was solvent-substituted with acetone in a nitrogen gas atmosphere. The dispersion was adjusted so that the concentration of the SmCo fine particles in the dispersion after solvent substitution was about 1% by mass. The obtained dispersion was put in a reflux apparatus equipped with a stirrer and a cooling tube, and nitrogen gas was bubbled, heated to 50 ° C. and refluxed for 3 hours with stirring. After refluxing, the dispersion was allowed to stand to precipitate SmCo-based fine particles, and the supernatant was removed by 2/3 or more of the total amount. Next, the same amount of acetone as the removed supernatant is added, and the mixture is stirred for 3 hours while heating at 50 ° C. in the same manner as described above, and then the dispersion is left to settle to precipitate SmCo-based fine particles. More than 2/3 of the total amount was removed. This operation was repeated 5 times to remove excess PVP from the solid mixture. After removal of PVP, the weight ratio of the total weight of Sm and Co to PVP was about 7. After the last washing, acetone was removed so that the ratio of SmCo-based fine particles: 100 parts by weight, PVP: 14 parts by weight, and acetone: 29 parts by weight was obtained to obtain a dispersion having a solid content concentration of 80% by mass.

Preparation of magnetic coating material Dispersion containing SmCo-based fine particles to which PVP is adhered, obtained as described above: 143 parts by weight, additional polyvinyl alcohol (number average molecular weight 10,000) as a binder: 11 parts by weight, α and 6 parts by weight, phthalate:: -Al ₂ O ₃ and 2 parts by weight in addition to butyl alcohol, to obtain a solid concentration of 80% by weight of the slurry. In the slurry, SmCo-based fine particles / (total amount of polyvinyl alcohol and PVP) = 4/1 (mass ratio). The slurry was kneaded with a pressure kneader for 2 hours. After butyl alcohol was added to the kneaded slurry to dilute to a solid content concentration of 30% by mass, dispersion treatment was performed using a horizontal pin mill filled with zirconia beads. Thereafter, butyl alcohol, stearic acid: 1 part by mass, and butyl stearate: 1 part by mass were added to obtain a slurry having a solid content concentration of 10% by mass. 0.82 parts by mass of a water-soluble polyisocyanate compound was added to 100 parts by weight of this slurry to obtain a magnetic paint.

Preparation of coating material for non-magnetic layer Acicular α-Fe ₂ O ₃ (Toda Kogyo: DB-65): 85 parts by mass, carbon black (Mitsubishi Chemical: # 850B): 15 parts by mass, electron beam curable vinyl chloride resin (Acrylic modified vinyl chloride-epoxy-containing monomer copolymer: degree of polymerization 260): 15 parts by mass, electron beam curable polyester polyurethane resin (acrylic modified polyester polyurethane resin: number average molecular weight = 26000): 10 parts by mass, α-Al ₂ O ₃ : 5 parts by mass, o-phthalic acid: 2 parts by mass, methyl ethyl ketone (MEK): 10 parts by weight, toluene: 10 parts by weight, and cyclohexane: 10 parts by weight are put into a pressure kneader and kneaded for 2 hours. went. After kneading, a mixed solvent (MEK / toluene / cyclohexane = 2/2/6 (weight ratio)) was added to the obtained slurry to obtain a slurry having a solid content concentration of 30% by mass. The obtained slurry was subjected to a dispersion treatment for 8 hours in a horizontal pin mill filled with zirconia beads. Thereafter, the same mixed solvent as described above, stearic acid: 1 part by mass, and butyl stearate: 1 part by mass were added to obtain a coating material for a non-magnetic layer that is a slurry having a solid content concentration of 10% by mass.

Preparation of paint for backcoat layer Nitrocellulose (Asahi Kasei Kogyo: BTH1 / 2): 50 parts by weight, Polyester polyurethane resin (Toyobo: UR-8300): 40 parts by weight, Carbon black (Cabot: BP800): 85 parts by weight, BaSO ₄ : 15 parts by weight, copper oleate: 5 parts by mass, and copper phthalocyanine: 5 parts by mass were charged into a ball mill and dispersed for 24 hours. Thereafter, a mixed solvent (MEK / toluene / cyclohexane = 1/1/1 (mass ratio)) was added to obtain a slurry having a solid content concentration of 10 mass%. 1.1 parts by weight of an isocyanate compound (Nippon Polyurethane: Coronate-L) was added to 100 parts by weight of the resulting slurry to obtain a backcoat layer coating material.

Preparation of magnetic tape On the surface of a polyethylene terephthalate film with a thickness of 6.1 μm, the above coating for nonmagnetic layer was applied to a dry thickness of 2.0 μm, the coating film was dried, calendered, and finally an electron beam It was cured by irradiation to form a nonmagnetic layer. Next, the magnetic coating material was applied onto the nonmagnetic layer so as to have a dry thickness of 0.20 μm, the coating film was subjected to magnetic field orientation treatment, dried, and calendered to form a magnetic layer. Subsequently, the said backcoat layer coating material was applied on the back surface of the polyethylene terephthalate film so as to have a dry thickness of 0.6 μm, and the coating film was dried and calendered to form a backcoat layer. Thus, the magnetic tape raw material in which each layer was formed on both surfaces was obtained. This original magnetic tape was placed in an oven at 60 ° C. for 24 hours to thermally cure the magnetic layer. Then, it cut | judged to 1/2 inch (12.65 mm) width, and obtained the magnetic tape.

(Comparative example)
Preparation of SmCo-based fine particles A solid mixture was produced in the reaction solution in the same manner as in the above example, and the solvent was replaced with absolute ethanol without washing with acetone. Subsequently, absolute ethanol was removed by filtration using an ultrafilter to obtain a dispersion (slurry) having a solid content concentration of 80% by mass.

Preparation of magnetic paint Dispersion liquid (slurry) containing PVP and SmCo fine particles obtained above: 953 parts by weight (SmCo fine particles: 100 parts by weight, PVP: 660 parts by weight, and absolute ethanol: 193 parts by weight, SmCo System fine particles / PVP weight ratio = 0.15 / 1, solid content concentration 80 mass%) was kneaded with a pressure kneader for 2 hours. Butyl alcohol was added to the kneaded slurry to adjust the solid concentration to 30% by mass. The obtained slurry was subjected to a dispersion treatment using a horizontal pin mill filled with zirconia beads. Thereafter, butyl alcohol, stearic acid: 1 part by mass and butyl stearate: 1 part by mass were added to obtain a slurry having a solid content concentration of 10% by mass. 0.82 parts by mass of a water-soluble polyisocyanate compound was added to 100 parts by mass of this slurry to obtain a magnetic coating material.

Production of magnetic tape A magnetic tape was produced in the same manner as in the Examples except that the magnetic paint obtained above was used.

Evaluation of electromagnetic conversion characteristics The magnetic tapes obtained in the above examples and comparative examples were recorded at a recording wavelength of 0.2 μm with a MIG head using a drum tester and reproduced with a GMR head. Conversion characteristics were measured.

  Good magnetic conversion characteristics such as C / N were obtained from the magnetic tape of the example. On the other hand, no signal could be measured from the magnetic tape of the comparative example. This is presumably because the magnetic properties of the magnetic layer were too low due to the low density of magnetic particles in the magnetic layer of the magnetic tape.

It is sectional drawing which shows the magnetic tape as one Embodiment of a magnetic recording medium.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Support body, 20 ... Nonmagnetic layer, 30 ... Magnetic layer, 40 ... Backcoat layer, 100 ... Magnetic recording medium (magnetic tape).

Claims (5)

A reaction solution containing an Sm salt, a Co salt, and an organic polymer and / or a ligand compound and a reaction solvent in which they are dissolved is heated, and the SmCo-based fine particles and the organic polymer and / or the Producing a solid mixture comprising a ligand compound;
The SmCo system in which a part of the organic polymer and / or the ligand compound is removed from the solid mixture by dissolution in a solvent, and the remaining organic polymer and / or the ligand compound is attached. Obtaining fine particles;
A method for producing SmCo-based fine particles.   A part of the organic polymer and / or the ligand compound is removed from the solid mixture until the mass ratio of the SmCo-based fine particles to the total mass of the organic polymer and the ligand compound is 1 to 10. The manufacturing method according to claim 1. A reaction solution containing an Sm salt, a Co salt, and an organic polymer and / or a ligand compound and a reaction solvent in which they are dissolved is heated, and the SmCo-based fine particles and the organic polymer and / or the Producing a solid mixture comprising a ligand compound;
The SmCo system in which a part of the organic polymer and / or the ligand compound is removed from the solid mixture by dissolution in a solvent, and the remaining organic polymer and / or the ligand compound is attached. Obtaining fine particles;
Preparing a magnetic paint containing the SmCo-based fine particles to which the organic polymer and / or the ligand compound is attached;
Forming a magnetic layer containing the SmCo-based fine particles using the magnetic paint;
A method of manufacturing a magnetic recording medium.   A part of the organic polymer and / or the ligand compound is removed from the solid mixture until the mass ratio of the SmCo-based fine particles to the total mass of the organic polymer and the ligand compound is 1 to 10. The manufacturing method according to claim 3. Removing a part of the organic polymer and / or the ligand compound from the solid mixture in the dispersion obtained by solvent substitution of the reaction solvent in the reaction solution with the solvent;
The magnetic coating material is prepared by using the dispersion liquid in which another solvent is added after removing a part of the solvent in which the organic polymer and / or the ligand compound is dissolved. 4. The production method according to 4.

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