JP2006294088A - Method for manufacturing magnetic recording medium, and center core for magnetic recording medium roll product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a magnetic recording medium capable of making the winding posture of a magnetic tape into a good shape and reducing edge breaking or the deterioration of a magnetic tape traveling property. <P>SOLUTION: In the method for manufacturing the magnetic recording medium where a wide magnetic tape original fabric 44 wound into a roll shape is cut to be wound on a tape hub 76, the bending habit of a fixed direction is formed in the state of the magnetic tape original fabric 44 by winding and heat-treating the magnetic tape original fabric 44 on a winding core 10 having an outer peripheral surface tilted in a fixed direction. Thus, the winding posture of the magnetic tape is easily improved, and edge breaking or the deterioration ofthe magnetic tape traveling property is reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a magnetic recording medium that cuts the original magnetic recording medium and winds it on a take-up hub, and a winding core that winds the original magnetic recording medium.

  Tape-like magnetic recording media used for audio, video, broadcasting, computers, etc., magnetic paint containing magnetic fine particles and resin binder is applied to a wide original film made of polyester and dried. In addition, it is manufactured by being cut into a predetermined width through various processes such as calendaring and heat treatment.

  The cut magnetic recording medium (magnetic tape) is wound around a resin tape hub. A tape winding body in which a magnetic tape is wound around such a tape hub is generally called pancake in the industry. Since the pancake is subjected to various treatments, the pancake is rewound several times and is shipped in a cassette as a final shipment form.

  However, if the winding shape of the magnetic tape wound in the cassette is not good, the edge of the magnetic tape is broken during transportation, or the running performance of the magnetic tape is deteriorated when the magnetic tape is used in a magnetic reproducing device or the like. A problem occurs.

  Normally, the magnetic tape roll 6 wound around the core 5 as shown in FIG. 6 is wound into a medium-high roll shape in which the thickness at the center of the roll is thicker than the thickness at both ends of the roll. As shown in (a) and (b), the cut magnetic tape 1 has curved wrinkles along the longitudinal direction. The curved ridge is expressed by a curved width D with respect to a predetermined linear length L when the magnetic tape is placed on a flat surface, and the state of being wound into a cassette as a final shipping form has a convex shape upward. Is indicated as +, and a concave shape is indicated as-.

  The magnetic tape 1 cut from the medium-high roll-shaped magnetic tape original is bent in the + direction, in the − direction, and in the center in the width direction of the magnetic tape original roll depending on the width direction portion of the magnetic tape original to be collected. There is a non-bent sampled from the vicinity. At this time, it is assumed that the winding shape is improved in the state of being wound in the cassette as the final shipping form, the bending is in the + direction, and the bending in the − direction is bad.

  For example, as shown in FIG. 8, when the pancake 3 is manufactured by winding the magnetic tape 1 having a curved ridge around the tape hub 2, the magnetic tape 1 having a curvature in the + direction is wound in the cassette 4. As shown in FIG. 8 (a), the magnetic tape 1 having a good shape wound along the lower flange is curved as shown in FIG. 8 (b).

Thus, if a magnetic tape having a curvature in the + direction is taken up, the winding shape is improved. However, curved wrinkles occur with almost constant probability due to the medium-high shape of the magnetic tape roll and the thickness unevenness of the magnetic tape base. A rewinding process is required. On the other hand, as a technique for manufacturing only a preferable one having a curve in the + direction, there is a method for manufacturing a magnetic tape that is bent in a certain direction by winding the magnetic tape after being cut into a tape hub with an inclination. It has been proposed (see, for example, Patent Document 1).
JP-A-9-138945

  However, when manufactured by the manufacturing method described in Patent Document 1, the number of magnetic tapes after cutting is very large, so it is inefficient to make the curve uniform, and the cost is also low. It takes a lot.

  The present invention has been made for such a problem, and it is possible to easily improve the winding shape of the magnetic tape by forming the curvature of the magnetic tape uniformly in the + direction. It is an object of the present invention to provide a method for manufacturing a magnetic recording medium that reduces edge breakage or deterioration of running performance of a magnetic tape.

  In order to achieve the above object, the present invention provides a method of manufacturing a magnetic recording medium in which a wide magnetic recording medium original wound in a roll is cut into a long shape and wound on a tape hub. The magnetic recording medium is wound and wound on a core whose outer peripheral surface is inclined in a certain direction.

  Further, the inclination of the core is obtained by calculating a difference between the diameter on the large diameter side and the diameter on the small diameter side at an interval of 12.65 mm in the axial direction of the core, and the difference is calculated as the diameter on the small diameter side. A value obtained by dividing the value obtained by dividing by 1000 is not less than 0.05 and not more than 0.35.

  According to the present invention, the heat treatment step is performed after winding the magnetic recording medium original fabric (magnetic tape original fabric) before cutting onto a core whose outer peripheral surface is inclined in a certain direction. As a result, a uniform curve is formed in the original magnetic tape. The magnetic tape wound around the tape hub after the cutting process (slit process) is uniformly curved in the + direction, as shown in FIG. Is already formed, the magnetic tape can be efficiently wound.

  In addition, it is preferable that the width | variety of the magnetic tape original fabric wound by the said core in this invention is 300 mm or more.

  As described above, according to the method for manufacturing a magnetic recording medium of the present invention, it is possible to easily improve the appearance of the magnetic tape, and to reduce edge breakage, deterioration of the running property of the magnetic tape, and the like. I can do it.

  A method for manufacturing a magnetic recording medium according to the present invention will be described below with reference to the accompanying drawings.

  First, the manufacturing process of the magnetic recording medium will be described. The manufacturing process of a magnetic recording medium is usually performed in the order of a coating / drying process, a calendar process, a heat treatment process, and a cutting (slit) process. Through these steps, the raw material of the magnetic recording medium is processed into a long magnetic recording medium (pancake) wound around a tape hub.

  FIG. 1 is a block diagram showing the coating and drying process. As shown in FIG. 1, the coating process mainly includes a delivery reel device 32, a magnetic liquid coating device 34, a first drying device 36, a back layer liquid coating device 38, a second drying device 40, and a take-up reel device 42. Is done.

  The magnetic tape original 44 delivered from the delivery reel device 32 is coated with the magnetic coating liquid by the magnetic liquid coating device 34 and then conveyed through the first drying device 36 to dry the magnetic layer. The back layer liquid is applied to the back surface (opposite side of the coated surface) of the magnetic tape original 44 from which the magnetic layer has been dried by the back layer liquid coating device 38. The original magnetic tape 44 coated with the back layer liquid is conveyed through a second drying device 40 having a drying zone and a heat treatment zone, and is subjected to drying and heat treatment.

  The original magnetic tape 44 that has passed through the second drying device 40 is introduced into the defect detection device 46. After a defect failure is detected by the defect detection device 46, the original magnetic tape 44 is taken up by the winding core 10 provided in the take-up reel device 42. Thereby, the magnetic tape original fabric 44 which apply | coated the magnetic coating liquid and the back layer coating liquid to the support body is manufactured.

  In FIG. 1, the drying zone and the heat treatment zone are provided in the second drying device 40, but the drying zone and the heat treatment zone may be separated as separate devices. Further, reference numeral 48 in FIG. 1 denotes a grooved suction drum, which controls the suction force and rotational speed of the suction drum surface and adjusts the slipping state of the support on the suction drum surface, so The tension can be adjusted, or the magnetic tape original 44 can be stably conveyed. In addition to the draw method using the grooved suction drum 48, the tension adjustment may be performed by a dancer method using a dancer roller.

  FIG. 2 is a block diagram showing the calendar process. As shown in FIG. 2, the calendar process mainly includes a delivery reel device 56, calendar rollers 58, 59, 60, a defect detection device 64, and a take-up reel device 62.

  The roll-shaped magnetic tape raw material 44 taken up by the take-up reel device 42 in FIG. 1 is transferred to the delivery reel device 56 in FIG. The transferred magnetic tape original 44 is fed out from the delivery reel device 56 and is nipped and conveyed between the calendar rollers 58 to 60. Thereby, the magnetic tape original fabric 44 is calendered to smooth the magnetic layer surface and the back layer surface.

  The calendered magnetic tape original 44 is introduced into the defect detection device 64, and the defect detection device 64 measures the position of the defect failure and the width dimension of the magnetic tape original 44. The measured magnetic tape original 44 is taken up by the winding core 10 provided in the take-up reel device 62.

  FIG. 3 is a block diagram showing a heat treatment process. The heat treatment step includes at least one of heat treatment for making the heat shrinkage rate of the roll-shaped magnetic tape original fabric 44 uniform or heat treatment for making the surface roughness of the magnetic layer surface of the magnetic tape original fabric 44 uniform. I do.

  As shown in FIG. 3, the magnetic tape original fabric 44 is carried into a temperature-controlled room 66 in a roll state, and a shaft 68 attached to the core 10 is stretched around a pair of columns 69 and 69. The temperature-controlled room 66 is maintained at a constant temperature, and the magnetic tape original fabric 44 wound around the core 10 is left for a predetermined time to perform heat treatment.

  FIG. 4 is a configuration diagram showing a slit process. As shown in FIG. 4, the slit process mainly includes a rewind reel 70, a feed roller 72, a slitter 74, and a tape hub 76.

  The rewind reel 70 is loaded with a heat-treated roll-shaped magnetic tape 44. The original magnetic tape 44 is continuously drawn from the rewind reel 70 by driving the feed roller 72.

  The feed roller 72 is a roller for running the magnetic tape original 44 and, for example, a suction drum is used. The suction drum is a drum that rotates while adsorbing the magnetic tape original fabric 44 on the surface, and a groove is formed on the surface of the drum to increase the holding force of the magnetic tape original fabric 44. As the feed roller 72, other known feed means such as a pair of nip rollers that sandwich and convey the magnetic tape original fabric 44 may be used.

  The original magnetic tape 44 fed from the rewind reel 70 by the feed roller 72 is sent to the slitter 74 while being guided by a plurality of guide rollers 78, 78. The slitter 74 includes a disk-shaped rotating upper blade 80 and a cylindrical rotating lower blade 82, and a plurality of the rotating upper blades 80 are arranged at regular intervals in the width direction of the magnetic tape original fabric 44.

  When the magnetic tape original fabric 44 is introduced between the rotating upper blade 80 and the rotating lower blade 82, the magnetic tape raw material 44 is rotated around the rotating lower blade 82, which is a receiving blade, while being rotated a plurality of times. A shearing force is applied by the upper blade 80, and it is cut into a large number (for example, 100 to 500).

  Thereby, the magnetic tapes 84 and 84 having a specified width dimension (for example, 12.65 mm, 25.4 mm, 3.81 mm, etc.) are manufactured. The magnetic tapes 84 and 84 are wound around the guide rollers 86 and 86 and then wound around the tape hubs 76 and 76.

  Through the above process, the original magnetic tape 44 becomes a pancake wound around the tape hub 76.

  Next, the core according to the present invention will be described. FIG. 5 is a perspective view showing the shape of the core and the state in which the original magnetic tape 44 is wound up.

  The winding core 10 is a rod-like magnetic tape winding core whose outer peripheral surface is inclined in a certain direction. As shown in FIG. 5A, when the diameter of the small diameter is d and the diameter on the large diameter side is D at a distance of 12.65 mm in the longitudinal direction of the core 10, the difference in diameter is expressed as D−. Let d = Δd. A value obtained by multiplying the value obtained by dividing Δd by the diameter d of the small diameter by 1000 is (Δd / d) × 1000 = A. The inclination of the core 10 is formed so that the value of A satisfies 0.05 ≦ A ≦ 0.35.

  The core 10 may have any other shape as long as the inclination is maintained. In addition, the slope is formed by attaching another member that is already formed with a slope, forming a member made of metal, resin, or the like by machining such as cutting, or the one without a normal slope is wound around the original magnetic tape. What formed by any method, such as what forms inclination by doing, can be used conveniently.

  The original magnetic tape 44 wound around the winding core 10 has a roll shape inclined in a certain direction as shown in FIG. By performing the heat treatment step shown in FIG. 3 in this state, curved wrinkles in the same direction are formed on the entire surface of the original magnetic tape 44. Thus, since the slit magnetic tape 44 is curved in the same direction, it is possible to manufacture only the curved magnetic tape 44 in the + direction, and the sorting step and the rewinding step are not necessary.

  The inclination of the winding core 10 is formed so that the value of A satisfies 0.05 ≦ A ≦ 0.35, preferably 0.05 ≦ A ≦ 0.3, and more preferably 0. Those satisfying .ltoreq.A.ltoreq.0.25 can be preferably used. When the value of A is less than 0.05, there is no effect of forming a curve, which is not preferable. On the other hand, if the value of A exceeds 0.35, the degree of bending is too large, and this is not preferable because it causes tape edge scraping during running of the magnetic tape, deterioration of durability, and generation of radiation during winding.

  The winding of the magnetic tape 44 around the core 10 whose outer peripheral surface is inclined in a certain direction may be performed in any step as long as it is before the heat treatment step, and in other cases, the magnetic tape 44 is inclined. It may be wound around a normal winding core that does not exist.

  As described above, according to the method of manufacturing a magnetic recording medium according to the present invention, a curved ridge in a certain direction is formed in the state of the original magnetic tape. Thereby, it becomes possible to easily improve the winding state of the magnetic tape, and it is possible to reduce edge breakage, deterioration of the running property of the magnetic tape, and the like.

  In the present embodiment, the magnetic recording medium used for the magnetic tape substrate 44 is manufactured with the following configuration.

  A magnetic tape (magnetic recording medium) basically means one having a magnetic layer on one side of a base film and a backcoat layer on the other side. For example, a non-magnetic tape is further provided between the base film and the magnetic layer. A magnetic recording medium having a magnetic layer may be used. Further, both surfaces may be magnetic layers.

  As the base film, those conventionally used as base film materials for magnetic recording media can be used, and non-magnetic ones are particularly preferable. Examples of these are polyesters (eg, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), mixtures of polyethylene terephthalate and polyethylene naphthalate, polymers containing an ethylene terephthalate component and an ethylene naphthalate component), polyolefins (Eg, polypropylene), cellulose derivatives (eg, cellulose diacetate, cellulose triacetate), polycarbonate, polyamide (especially aromatic polyamide, aramid), polyimide (especially wholly aromatic polyimide), and other synthetic resin films. . Among these, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), aromatic polyamide and aramid are preferable.

  The thickness of the base film is not particularly limited, but is preferably in the range of 2 to 8 μm (more preferably 3 to 8 μm, particularly preferably 3 to 7 μm).

  The magnetic layer is basically made of a ferromagnetic powder and a binder. The magnetic layer usually further contains a lubricant, carbon black as a conductive powder, and an abrasive.

  Examples of the ferromagnetic powder include γ-Fe2O3, Fe3O4, FeOx (x = 1.33 to 1.5), CrO2, Co-containing γ-Fe2O3, Co-containing FeOx (x = 1.33 to 1.5), Mention may be made of ferromagnetic metal powders and plate-shaped hexagonal ferrite powders. In the present invention, it is preferable to use a ferromagnetic metal powder or a plate-shaped hexagonal ferrite powder as the ferromagnetic powder. Particularly preferred is a ferromagnetic metal powder.

  The ferromagnetic metal powder preferably has a specific surface area of 30 to 70 m <2> / g, and a crystallite size determined by X-ray diffraction is 50 to 300A. If the specific surface area is too small, it will not be possible to sufficiently cope with high density recording, and if it is too large, it will not be possible to disperse sufficiently, so that it will not be possible to form a smooth magnetic layer, and thus it will not be able to cope with high density recording. The ferromagnetic metal powder is required to contain at least Fe, and specifically, a simple metal or an alloy mainly composed of Fe, Fe—Co, Fe—Ni, Fe—Zn—Ni, or Fe—Ni—Co. It is. As for the magnetic properties of these ferromagnetic metal powders, the saturation magnetization (σs) is 110 emu / g or more, preferably 120 emu / g or more and 170 emu / g or less in order to achieve a high recording density. The coercive force (Hc) is in the range of 800 to 3000 oersted (Oe) (preferably 1500 to 2500 Oe). And the long axis length (namely, average particle diameter) of the powder calculated | required with a transmission electron microscope is 0.5 micrometer or less, Preferably, it is 0.01-0.3 micrometer, and an axial ratio (long axis length / short axis length, The needle ratio) is 5 or more and 20 or less, preferably 5-15. In order to further improve the characteristics, non-metals such as B, C, Al, Si and P, or salts and oxides thereof may be added during the composition. Usually, an oxide layer is formed on the particle surface of the metal powder in order to stabilize it chemically.

  The plate-shaped hexagonal ferrite powder has a specific surface area of 25 to 65 m @ 2 / g, a plate ratio (plate diameter / plate thickness) of 2 to 15, and a plate diameter of 0.02 to 1.0 .mu.m. . The plate-shaped hexagonal ferrite powder has the same reason as the ferromagnetic metal powder, and high density recording becomes difficult even if the particle size is too large or too small. The plate-shaped hexagonal ferrite is a ferromagnetic material having a flat plate shape and an easy axis of magnetization in a direction perpendicular to the flat plate surface, specifically, barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and the like. The cobalt substitution product of these can be mentioned. Of these, cobalt substitutes of barium ferrite and cobalt substitutes of strontium ferrite are particularly preferable. To the plate-shaped hexagonal ferrite used in the present invention, elements such as In, Zn, Ge, Nb, and V may be added as necessary to improve the characteristics. Further, regarding the magnetic properties of these plate-shaped hexagonal ferrite powders, in order to achieve a high recording density, the particle size as described above is necessary and at the same time, the saturation magnetization (σs) is preferably at least 50 emu / g or more. Is 53 emu / g or more. The coercive force is in the range of 700 to 2000 Oersted (Oe), and preferably in the range of 900 to 1600 Oe.

  The water content of the ferromagnetic powder is preferably 0.01 to 2% by weight. It is preferable to optimize the water content depending on the type of the binder. The pH of the ferromagnetic powder is preferably optimized depending on the combination with the binder used, and the pH is usually in the range of 4 to 12, preferably in the range of 5 to 10. The ferromagnetic powder may be subjected to surface treatment with Al, Si, P, or an oxide thereof as required. The amount used in the surface treatment is usually 0.1 to 10% by weight with respect to the ferromagnetic powder. By performing the surface treatment, adsorption of a lubricant such as a fatty acid can be suppressed to 100 mg / m @ 2 or less. The ferromagnetic powder may contain soluble inorganic ions such as Na, Ca, Fe, Ni, and Sr. However, if the content is 5000 ppm or less, the properties are not affected.

  The lubricant is added to ooze out on the surface of the magnetic layer, thereby relaxing the friction between the magnetic layer surface and the magnetic head, the guide pole of the drive and the cylinder, and smoothly maintaining the sliding contact state. Examples of the lubricant include fatty acids or fatty acid esters. Examples of fatty acids include acetic acid, propionic acid, octanoic acid, 2-ethylhexanoic acid, lauric acid, myristic acid, stearic acid, palmitic acid, behenic acid, arachic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, And aliphatic carboxylic acids such as palmitoleic acid or mixtures thereof.

  Examples of fatty acid esters include butyl stearate, sec-butyl stearate, isopropyl stearate, butyl oleate, amyl stearate, 3-methylbutyl stearate, 2-ethylhexyl stearate, 2-hexyldecyl stearate, Acylation of butyl palmitate, 2-ethylhexyl myristate, butyl stearate and butyl palmitate, oleyl oleate, butoxyethyl stearate, 2-butoxy-1-propyl stearate, dipropylene glycol monobutyl ether with stearic acid , Diethylene glycol dipalmitate, hexamethylenediol acylated with myristic acid to give a diol, and various ester compounds such as glycerin oleate Can. These can be used alone or in combination. The normal content of the lubricant is in the range of 0.2 to 20 parts by weight (preferably 0.5 to 10 parts by weight) with respect to 100 parts by weight of the ferromagnetic powder of the magnetic layer.

  Carbon black is added for various purposes such as reducing the surface electrical resistance (Rs) of the magnetic layer, reducing the dynamic friction coefficient (μK value), improving the running durability, and ensuring the smooth surface properties of the magnetic layer. The Carbon black preferably has an average particle size in the range of 3 to 350 nm (more preferably 10 to 300 nm). The specific surface area is preferably 5 to 500 m <2> / g (more preferably 50 to 300 m <2> / g). The DBP oil absorption is preferably in the range of 10 to 1000 mL / 100 g (more preferably 50 to 300 mL / 100 g). The pH is preferably 2 to 10, the water content is preferably 0.1 to 10%, and the tap density is preferably 0.1 to 1 g / cc.

  Carbon black obtained by various manufacturing methods can be used. Examples of carbon black that can be used include furnace black, thermal black, acetylene black, channel black, and lamp black. Specific examples of carbon black products include BLACKPEARLS 2000, 1300, 1000, 900, 800, 700, VULCANXC-72 (above, manufactured by Cabot Corporation), # 35, # 50, # 55, # 60 and # 80. (Made by Asahi Carbon Co., Ltd.), # 3950B, # 3750B, # 3250B, # 2400B, # 2300B, # 1000, # 900, # 40, # 30, and # 10B (Mitsubishi Chemical Corporation )), CONDUCTEXSC, RAVEN150, 50, 40, 15 (above, Columbia Carbon Co., Ltd.), Ketjen Black EC, Ketjen Black ECDJ-500 and Ketjen Black ECDJ-600 (above, Lion Azo Co., Ltd.) ). The usual addition amount of carbon black is 0.1 to 30 parts by weight, preferably 0.2 to 15 parts by weight with respect to 100 parts by weight of the ferromagnetic powder.

  Examples of the abrasive include fused alumina, silicon carbide, chromium oxide (Cr2O3), corundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite). These abrasives preferably have a Mohs hardness of 5 or more (preferably 6 or more) and an average particle size of 0.05 to 1 μm (more preferably 0.2 to 0.8 μm). . The addition amount of the abrasive is usually in the range of 3 to 25 parts by weight (preferably 3 to 20 parts by weight) with respect to 100 parts by weight of the ferromagnetic powder.

  Examples of the binder for the magnetic layer include thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof. Examples of thermoplastic resins include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl A polymer or a copolymer containing acetal and vinyl ether as structural units can be given. Examples of the copolymer include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate ester-acrylonitrile copolymer, acrylate ester-vinylidene chloride copolymer. Polymer, Acrylate ester-Styrene copolymer, Methacrylate ester-Acrylonitrile copolymer, Methacrylate ester-Vinylidene chloride copolymer, Methacrylate ester-Styrene copolymer, Vinylidene chloride-Acrylonitrile copolymer , Butadiene-acrylonitrile copolymer, styrene-butadiene copolymer, and chlorovinyl ether-acrylic ester copolymer.

  In addition to the above, polyamide resins, fiber-based resins (cellulose acetate butyrate, cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resins, polyurethane resins, and various rubber resins are also used. be able to.

  Examples of thermosetting resins or reactive resins include phenolic resins, epoxy resins, polyurethane curable resins, urea resins, melamine resins, alkyd resins, acrylic reactive resins, formaldehyde resins, silicone resins, epoxy-polyamide resins, Mention may be made of a mixture of polyester resin and polyisocyanate prepolymer, a mixture of polyester polyol and polyisocyanate, and a mixture of polyurethane and polyisocyanate.

  Examples of the polyisocyanate include tolylene diisocyanate, 4-4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, and triphenylmethane triisocyanate. Mention may be made of isocyanates, products of these isocyanates with polyalcohols, and polyisocyanates produced by condensation of isocyanates.

  As the polyurethane resin, known resins having structures such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used.

  In the present invention, the binder of the magnetic layer is vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, and A combination of at least one resin selected from nitrocellulose and a polyurethane resin, or a combination of these with a polyisocyanate is preferable.

  As a binder, in order to obtain better dispersibility and durability of the resulting layer, -COOM, -SO3M, -OSO3M, -P = O (OM) 2, -OP = O may be used as necessary. (OM) 2 (M represents a hydrogen atom or an alkali metal base), —OH, —NR 2, —N + R 3 (R represents a hydrocarbon group), an epoxy group, —SH, —CN, etc. It is preferable to introduce at least one selected polar group by copolymerization or addition reaction. Such polar groups are preferably introduced into the binder in an amount of 10 @ -1 to 10 @ -8 mol / g (more preferably 10 @ -2 to 10 @ -6 mol / g).

  The binder for the magnetic layer is usually used in the range of 5 to 50 parts by weight (preferably 10 to 30 parts by weight) with respect to 100 parts by weight of the ferromagnetic powder. When a combination of vinyl chloride resin, polyurethane resin, and polyisocyanate is used as a binder in the magnetic layer, the vinyl chloride resin is 5 to 70% by weight and the polyurethane resin is 2 to 50% by weight in the total binder. % And polyisocyanates are preferably used in amounts ranging from 2 to 50% by weight.

  A dispersing agent can be added to the coating solution for forming the magnetic layer of the magnetic recording medium in order to favorably disperse the magnetic powder in the binder. Further, if necessary, conductive particles (antistatic agent) other than plasticizer, carbon black, antifungal agent and the like can be added. Examples of the dispersant include 12 to 18 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, stearic acid, and the like. A fatty acid (RCOOH, R is an alkyl group having 11 to 17 carbon atoms, or an alkenyl group), a metal soap composed of an alkali metal or an alkaline earth metal of the fatty acid, a compound containing fluorine of the fatty acid ester, Fatty acid amide, polyalkylene oxide alkyl phosphate ester, lecithin, trialkyl polyolefinoxy quaternary ammonium salt (alkyl is 1 to 5 carbon atoms, olefin is ethylene, propylene, etc.), sulfate, copper phthalocyanine, etc. Can be used. These may be used alone or in combination. The dispersant is usually added in the range of 0.5 to 20 parts by weight with respect to 100 parts by weight of the binder of the magnetic layer.

  Next, the back coat layer will be described. The backcoat layer is preferably formed from carbon black and a binder. Moreover, it is preferable that an inorganic powder or a lubricant is further added.

  It is preferable to use a combination of two types of carbon black having different average particle sizes. In this case, it is preferable to use a combination of fine particle carbon black having an average particle size of 10 to 20 nm and coarse particle carbon black having an average particle size of 230 to 300 nm. In general, by adding fine carbon black as described above, the surface electrical resistance of the backcoat layer can be set low, and the light transmittance can also be set low. Some magnetic recording devices utilize the light transmittance of the tape and are used for the operation signal. In such a case, the addition of particulate carbon black is particularly effective. In addition, particulate carbon black is generally excellent in retention of liquid lubricants, and contributes to reduction of the friction coefficient when used in combination with lubricants. On the other hand, the coarse particulate carbon black having a particle size of 230 to 300 nm has a function as a solid lubricant, and forms fine protrusions on the surface of the back layer, reducing the contact area, and reducing the friction coefficient. Contributes to reduction.

  Specific products of the particulate carbon black include the following. RAVEN2000B (18 nm), RAVEN1500B (17 nm) (above, manufactured by Columbia Carbon Co., Ltd.), BP800 (17 nm) (manufactured by Cabot), PRINTEX90 (14 nm), PRINTEX95 (15 nm), PRINTEX85 (16 nm), PRINTEX75 (17 nm) (and above) Degussa), # 3950 (16 nm) (Mitsubishi Chemical Corporation). Examples of specific products of coarse particulate carbon black include thermal black (270 nm) (manufactured by Kerncarb) and Ravenmtp (275 nm) (manufactured by Columbia Carbon).

  When two types of backcoat layers having different average particle sizes are used, the content ratio (weight ratio) of fine particle carbon black of 10 to 20 nm and coarse particle carbon black of 230 to 300 nm is the former: latter = It is preferably in the range of 98: 2 to 75:25, more preferably in the range of 95: 5 to 85:15. The content of carbon black (the total amount thereof) in the back coat layer is usually in the range of 30 to 110 parts by weight, preferably in the range of 50 to 90 parts by weight with respect to 100 parts by weight of the binder.

  It is preferable to use two types of inorganic powders having different hardnesses. Specifically, it is preferable to use a soft inorganic powder having a Mohs hardness of 3 to 4.5 and a hard inorganic powder having a Mohs hardness of 5 to 9. By adding a soft inorganic powder having a Mohs hardness of 3 to 4.5, the friction coefficient can be stabilized by repeated running. Moreover, when the hardness is within this range, the sliding guide pole is not scraped. The average particle size of the soft inorganic powder is preferably in the range of 30 to 50 nm. Examples of the soft inorganic powder having a Mohs hardness of 3 to 4.5 include calcium sulfate, calcium carbonate, calcium silicate, barium sulfate, magnesium carbonate, zinc carbonate, and zinc oxide. These can be used alone or in combination of two or more. Among these, calcium carbonate is particularly preferable. The content of the soft inorganic powder in the backcoat layer is preferably in the range of 10 to 140 parts by weight, more preferably in the range of 35 to 100 parts by weight with respect to 100 parts by weight of the carbon black.

  By adding a hard inorganic powder having a Mohs hardness of 5 to 9, the strength of the backcoat layer is enhanced and the running durability is improved. When this is used together with carbon black, there is little deterioration even with repeated sliding, and a strong backcoat layer is obtained. In addition, the addition of the inorganic powder provides an appropriate polishing force and reduces the adhesion of shavings to the tape guide pole and the like. The hard inorganic powder preferably has an average particle size in the range of 80 to 250 nm (more preferably, 100 to 210 nm).

  Examples of the hard inorganic powder having a Mohs hardness of 5 to 9 include α-iron oxide, α-alumina, and chromium oxide (Cr 2 O 3). These powders may be used alone or in combination. Among these, α-iron oxide or α-alumina is preferable. The content of the hard inorganic powder is usually in the range of 3 to 30 parts by weight, preferably in the range of 3 to 20 parts by weight with respect to 100 parts by weight of the carbon black.

  The back coat layer can contain a lubricant. The lubricant can be appropriately selected from the lubricants described in the magnetic layer. In the backcoat layer, the lubricant is usually added in the range of 1 to 5 parts by weight with respect to 100 parts by weight of the binder. Moreover, the dispersing agent described in the magnetic layer can also be added to the backcoat layer. The amount of the dispersant added can be the same as the amount added to the magnetic layer.

  As the binder for the backcoat layer, the binder described in the magnetic layer can be used. Binders that can be used include nitrocellulose resins, polyurethane resins, polyester resins, and polyisocyanates as curing agents. The binder of the backcoat layer is usually 5 to 250 parts by weight (preferably 10 to 200 parts by weight) with respect to 100 parts by weight of carbon black.

  As described above, the magnetic recording medium of the present invention may have a configuration in which a nonmagnetic layer is provided between a base film and a magnetic layer. That is, a magnetic recording medium having a nonmagnetic layer and a magnetic layer in this order on one surface of the base film and a backcoat layer on the other surface may be used.

  The nonmagnetic layer is a substantially nonmagnetic layer containing a nonmagnetic powder and a binder. This non-magnetic layer needs to be substantially non-magnetic so as not to affect the electromagnetic conversion characteristics of the magnetic layer on the non-magnetic layer, but is small enough not to affect the electromagnetic conversion characteristics of the magnetic layer. Even if the magnetic powder is contained, there is no particular problem. In addition, the nonmagnetic layer usually contains a lubricant in addition to these components.

  Examples of the nonmagnetic powder used in the nonmagnetic layer include nonmagnetic inorganic powder and carbon black. The non-magnetic inorganic powder is preferably relatively hard, and preferably has a Mohs hardness of 5 or more (more preferably 6 or more). Examples of nonmagnetic inorganic powders include α-alumina, β-alumina, γ-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, silicon nitride, titanium carbide, titanium dioxide, silicon dioxide, Mention may be made of boron nitride, zinc oxide, calcium carbonate, calcium sulfate and barium sulfate. These can be used alone or in combination. Of these, titanium dioxide, α-alumina, α-iron oxide, or chromium oxide is preferable. The average particle diameter of the nonmagnetic inorganic powder is preferably in the range of 0.01 to 1.0 μm (preferably 0.01 to 0.5 μm, particularly 0.02 to 0.1 μm).

  Carbon black is added for the purpose of imparting electrical conductivity to the magnetic layer to prevent electrification and ensuring the smooth surface properties of the magnetic layer formed on the nonmagnetic layer. As the carbon black used in the nonmagnetic layer, the carbon black described in the magnetic layer can be used. However, the carbon black used in the nonmagnetic layer preferably has an average particle size of 35 nm or less (more preferably 10 to 35 nm). The normal addition amount of carbon black is 3 to 20 parts by weight, preferably 4 to 18 parts by weight, and more preferably 5 to 15 parts by weight with respect to 100 parts by weight of the total nonmagnetic inorganic powder in the nonmagnetic layer. Part.

  As the lubricant, the fatty acid or fatty acid ester described in the magnetic layer can be used. The addition amount of the lubricant is usually in the range of 0.2 to 20 parts by weight with respect to 100 parts by weight of the total nonmagnetic powder of the nonmagnetic layer.

  As the binder for the nonmagnetic layer, the binders described for the magnetic layer described above can be used. The binder is usually used in the range of 5 to 50 parts by weight (preferably 10 to 30 parts by weight) with respect to 100 parts by weight of the nonmagnetic powder of the nonmagnetic layer. In the case of using a combination of vinyl chloride resin, polyurethane resin, and polyisocyanate as binders in the nonmagnetic layer, 5 to 70% by weight of vinyl chloride resin and 2 to 50 polyurethane resin in all binders. It is preferred to use such that the polyisocyanate is included in an amount ranging from 2% to 50% by weight. In the nonmagnetic layer, an optional component that can be added to the magnetic layer may be added.

  In the case of a magnetic recording medium having a non-magnetic layer, the method for forming the magnetic layer and the non-magnetic layer is not particularly limited, but the magnetic layer was formed after applying the non-magnetic layer coating solution on the base film. It is preferably formed using a so-called wet-on-wet coating method in which a coating solution for a magnetic layer is coated on the coating layer (nonmagnetic layer) while it is in a wet state.

  Examples of the application method by the wet-on-wet method include the following methods.

  (1) Using a gravure coating, roll coating, blade coating, or extrusion coating apparatus, a nonmagnetic layer is first formed on the base film. While the nonmagnetic layer is in a wet state, the base film pressurizing type A method of forming a magnetic layer with a roux coating device (see Japanese Patent Laid-Open Nos. 60-238179, 1-46186, and 2-265672).

  (2) A method of forming a magnetic layer and a nonmagnetic layer on a base film almost simultaneously using a coating apparatus comprising a single coating head provided with two slits for coating solution (Japanese Patent Laid-Open No. 63-88080, (See JP-A-2-17921 and JP-A-2-265672).

  (3) A method in which a magnetic layer and a nonmagnetic layer are formed almost simultaneously on a base film using an extrusion coating apparatus with a backup roller (see JP-A-2-174965). The nonmagnetic layer and the magnetic layer are preferably formed using a simultaneous multilayer coating method.

  The surface of the backcoat layer of the magnetic recording medium tends to be transferred to the surface of the magnetic layer while the tape is wound. For this reason, it is preferable that the surface of the back coat layer also has relatively high smoothness. The surface of the backcoat layer of the magnetic recording medium is adjusted so that the surface roughness Ra (centerline average roughness with a cutoff of 0.08 mm) is in the range of 0.003 to 0.060 μm. preferable. The surface roughness can be adjusted by the material of the calendar roller to be used, its surface property, pressure, speed, etc., in the surface treatment process using the calendar after the formation of the coating film.

  The magnetic layer of the magnetic recording medium having a single-layer structure having a magnetic layer on one side of the base film and a backcoat layer on the other side, manufactured according to the manufacturing method of the present invention, has a thickness of 1.0 to It is preferably in the range of 3.0 μm (more preferably, 1.5 to 2.5 μm).

  The total thickness of the magnetic recording medium having this configuration is preferably in the range of 4.0 to 12.0 μm, more preferably 4.0 to 10.0 μm.

  The thickness of the back coat layer is preferably in the range of 0.1 to 1.0 μm (more preferably 0.2 to 0.8 μm).

  The magnetic layer of a magnetic recording medium having a nonmagnetic layer preferably has a thickness in the range of 0.01 to 1.0 μm (more preferably 0.05 to 0.5 μm).

  The thickness of the nonmagnetic layer is preferably in the range of 0.01 to 3.0 μm (more preferably 0.5 to 2.5 μm).

  The ratio of the thickness of the magnetic layer to the thickness of the nonmagnetic layer is preferably in the range of 1: 2 to 1:15 (more preferably 1: 5 to 1:12).

  The total thickness of the magnetic recording medium having the nonmagnetic layer and the thickness of the backcoat layer are preferably in the same range as the magnetic recording medium having the single layer structure.

  With the above configuration, the magnetic recording medium used for the magnetic tape original 44 is manufactured.

  Next, examples of the present invention will be described. As an example, a computer backup magnetic tape is taken as an example.

  Nine types of cores are prepared in which the inclination A of the core is 0 to 0.05 in increments of 0.4. The magnetic tape is wound up to a diameter of 400 mm around each core. Heat treatment is performed at 70 degrees after winding.

  After the heat treatment, a 1/2 inch (about 12.65 mm) magnetic tape cassette is manufactured through a predetermined process. At that time, the curve of the tape to be wound is measured in a state of zero tension, and is measured as a curve value around 1 m. The winding shape and radiation were confirmed visually, and those with turbulence and radiation were marked with x. The following table shows the relationship between the amount of inclination of the core, the curvature value, and the winding shape.

表１に示すように、巻芯の傾斜の大きさＡを０．０５以上０．３５以下で磁気テープの巻き姿を良好にする効果が確認された。更に、巻芯の傾斜の大きさＡが好ましくは０．０５≦Ａ≦０．３であり、更に好ましくは０．１≦Ａ≦０．２５であるものが好適に使用できることが確認された。

As shown in Table 1, the effect of improving the winding shape of the magnetic tape was confirmed when the inclination A of the core was 0.05 or more and 0.35 or less. Furthermore, it has been confirmed that the core inclination angle A is preferably 0.05 ≦ A ≦ 0.3, more preferably 0.1 ≦ A ≦ 0.25.

The block diagram which shows an application | coating drying process. The block diagram which shows a calendar process. The block diagram which shows the heat processing process. The block diagram which shows a cutting (slit) process. The perspective view which showed the shape of the core and the state which wound up the magnetic tape original fabric The perspective view which showed the state which wound up the conventional magnetic tape original fabric. The figure which showed the curved state of the magnetic tape. The figure which showed the winding form of the magnetic tape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic tape, 2 ... Tape hub, 3 ... Pancake, 5, 10 ... Core, 32 ... Delivery reel apparatus, 34 ... Magnetic liquid application apparatus, 36 ... 1st drying apparatus, 38 ... Back layer liquid application apparatus, 40 2nd drying device, 42 ... take-up reel device, 44 ... magnetic tape substrate, 46 ... defect detection device, 48 ... grooved suction drum, 56 ... delivery reel device, 58-60 ... calendar roller, 62 ... take-up Reel device, 64 ... Defect detection device, 66 ... Constant temperature chamber, 68 ... Shaft, 69 ... Post, 70 ... Rewinding reel, 72 ... Feed roller, 74 ... Slitter, 76 ... Tape hub, 78 ... Guide roller, 80 ... On rotation Blade, 82 ... Rotating lower blade, 86 ... Guide roller, 88 ... Ear part, 90 ... Light projecting part, 92 ... Light receiving part

Claims (5)

In a method of manufacturing a magnetic recording medium in which a wide magnetic recording medium original wound in a roll shape is cut into a long shape and wound on a tape hub,
A method of manufacturing a magnetic recording medium, wherein the magnetic recording medium original sheet before cutting is wound on a winding core whose outer peripheral surface is inclined in a certain direction.   The inclination of the core is obtained by calculating the difference between the diameter on the large diameter side and the diameter on the small diameter side at an interval of 12.65 mm in the axial direction of the core, and dividing the difference by the diameter on the small diameter side. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein a value obtained by multiplying the value obtained by 1000 is 0.05 or more and 0.35 or less.   2. The magnetic recording medium that is wound and heat-treated on the winding core and cut into a long shape is curved so that an upper edge becomes longer than a lower edge during driving. A method for manufacturing a magnetic recording medium according to claim 2.   4. The method of manufacturing a magnetic recording medium according to claim 1, wherein a width of the original magnetic recording medium wound around the winding core is 300 mm or more. 5. A raw material of a wide magnetic recording medium that is cut to produce a long magnetic recording medium, and a winding core for winding the magnetic recording medium original material into a roll,
The outer periphery of the winding core is inclined in a certain direction, and the inclination determines the difference between the diameter on the large diameter side and the diameter on the small diameter side at an interval of 12.65 mm in the axial direction of the winding core, A magnetic recording medium original fabric core, wherein a value obtained by dividing the difference by the diameter on the small diameter side multiplied by 1000 is from 0.05 to 0.35.

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