JP2006268922A - Manufacturing method of magnetic recording medium, and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a magnetic recording medium which can reduce errors by making a surface of the magnetic recording medium smooth, and a magnetic recording medium. <P>SOLUTION: When taking up a base film F which is to be treated with heat to a winding core S, the base film F is taken up by the winding core S by pressing a contact roller 22 heated to the temperature higher than room temperature against a periphery of the base film F taken up by the winding core S, Thereby back surface transference can be reduced and occurrence of errors can be reduced. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a magnetic recording medium and a magnetic recording medium, and more particularly to a method for manufacturing a magnetic recording medium such as a magnetic tape and a magnetic recording medium.

  In general, a magnetic tape is manufactured by a process of [application] → [calendar] → [heat treatment] → [slit]. Here, in the heat treatment step performed after the calendering process, the base film to be heat-treated is wound around a core to form a roll, and left in an environmental atmosphere at a predetermined temperature in a roll state for a predetermined time. Heat treatment is applied.

  However, when the base film is heat-treated in the roll state as described above, the back coat layer having a rough surface is pressed against the surface of the magnetic layer and deformed (the back surface appears), and the surface roughness (Ra) increases. There was a problem of doing.

In order to solve such a problem, in Patent Document 1, when the base film is wound around the core, the base film is wrapped on a contact roller having a lower surface friction coefficient at both axial ends than at the axial central portion. It has been proposed to wind up the base film while pressing the outer peripheral surface of the base film with the contact roller. Further, Patent Document 2 proposes that when the base film is wound around the core, the base film is wound while pressing the outer peripheral surface of the base film with a touch roller having a hole in the ridge. Further, in Patent Document 3, it is proposed that when the base film is wound around the core, hot air is blown onto the base film and the base film is wound while being heated to Tg (glass transition temperature) or higher.
JP 2002-348002 A JP 2002-12348 A JP-A-6-295435

  However, as the recording density increases, the surface of the magnetic layer is required to have high smoothness, and the conventional winding method has a drawback that sufficient smoothness that satisfies the product requirements cannot be obtained. . In particular, a product having a recording capacity of 100 GB or more has a drawback that an error is likely to occur unless sufficient smoothness is obtained on the surface of the magnetic layer.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method of manufacturing a magnetic recording medium and a magnetic recording medium capable of reducing errors by smoothing the surface of the magnetic recording medium. .

  In order to achieve the above object, a first aspect of the present invention provides a magnetic recording medium including a step of winding a belt-like flexible base film around a core to form a roll and heat-treating the roll. In the manufacturing method, when the base film to be heat-treated is wound around the core, the base film is pressed against a periphery of the base film wound around the core while pressing a contact roller heated to a temperature higher than room temperature. It is wound around the winding core.

  According to the first aspect of the present invention, when the base film to be heat-treated is wound around the core, the contact roller heated to a temperature higher than room temperature is pressed against the outer periphery of the base film wound around the core, The base film is wound around the core. In this way, by applying heat and pressure simultaneously and winding the base film around the core, the wrinkles of the base film are extended, and the back surface image is reduced.

  According to a second aspect of the present invention, in order to achieve the above object, in the method of manufacturing a magnetic recording medium according to the first aspect, the thickness of the base film is 10 μm or less.

  According to the invention described in claim 2, when a base film having a thickness of 10 μm or less is used, a particularly remarkable effect can be obtained.

  According to a third aspect of the present invention, in order to achieve the above object, the magnetic recording medium is manufactured by the method for manufacturing a magnetic recording medium according to the first or second aspect.

  According to the third aspect of the present invention, a highly smooth magnetic recording medium free from wrinkles and back surface projection is obtained by simultaneously applying heat and pressure to wind up the base film on the core and heat-treating it. Can do.

  According to the method of manufacturing a magnetic recording medium and the magnetic recording medium according to the present invention, the surface of the magnetic recording medium can be smoothed to reduce errors.

  The best mode for carrying out a method of manufacturing a magnetic recording medium and a magnetic recording medium according to the present invention will be described below with reference to the accompanying drawings.

  As described above, a magnetic tape as a magnetic recording medium is manufactured in the process of [application] → [calendar] → [heat treatment] → [slit].

  In the coating step, a strip-shaped flexible base film is fed from the raw fabric roll, and a magnetic layer is applied on one surface and a backcoat layer is formed on the other surface in the coating portion. The base film on which the magnetic layer and the back coat layer are formed is wound around a core and formed into a roll shape.

  In the calendar process, the base film is passed between a plurality of calendar rollers, whereby the base film F is sandwiched and heated and pressed at each nip between the calendar rollers, and the surface of the base film F is smoothed. FIG. 1 is a diagram showing a schematic configuration of a calendar device 10 used in a calendar process. As shown in the figure, the roll-shaped base film F is set on the rewinding reel 12 and sent out from the rewinding reel 12 to the calendar unit 14. A plurality (seven in this case) of calendar rollers 16, 16,... Are arranged on the calendar section 14 so that the base film F is arranged so as to be in contact with each other. .. Travels while being guided by guide rollers 18, 18. And in the running process, it is nipped at the nip between the calender rollers 16, 16,... And heated and pressed to smooth the surface. The base film F passed between the calendar rollers 16, 16,... Is wound around the core S set on the take-up reel 20 and formed into a roll shape.

  At this time, the base film F is wound around the core S while being pressed on the outer peripheral surface by the contact roller 22 and formed into a roll shape. The winding of the base film F will be described in detail later.

  In the heat treatment step, as shown in FIG. 2, for example, the base film F in a roll state after the calendar treatment is placed in a thermostat 30 and left for a predetermined time in an environmental atmosphere at a predetermined temperature (50 ° C. or higher) to perform the heat treatment. . Note that the heat treatment method is not limited to this, and the heat treatment may be performed by gradually raising the temperature.

  In the slitting process, the base film F in a roll state after the heat treatment is sent out to the slit portion, and is slit in the longitudinal direction with a predetermined width at the slit portion. FIG. 3 is a diagram showing a schematic configuration of the cutting device 40 used in this slit process. As shown in the figure, the roll-shaped base film F is set on a rewinding reel 42 and sent out from the rewinding reel 42 to the slit portion 44. A transport path for the base film F is formed between the rewind reel 42 and the slit portion 44 by a plurality of guide rollers 46. In order to adjust the transport speed of the base film F in the middle of the transport path. The friction roller 48 is provided. The slit portion 44 cuts a wide and strip-like base film F into a plurality of tapes T having a predetermined width by a pair of upper and lower rotary blades 50 and 52, and the tape T cut by the slit portion 44 causes the guide roller 54 to be cut. Through the winding core 56 set on the take-up reel 56.

  As described above, the magnetic tape is manufactured in the process of [application] → [calendar] → [heat treatment] → [slit], but the base film F is still wound around the core S after the calendar process. When heat treatment is performed in a roll state, the back coat layer is pressed against the surface of the magnetic layer to cause back surface reflection, resulting in an increase in surface roughness (Ra).

  Therefore, in the present embodiment, when the base film F to be heat-treated is wound around the winding core S in order to reduce such back surface exposure, as shown in FIG. 1, the contact roller heated to a temperature higher than room temperature. The base film F is wound around the core S while being pressed against the outer periphery of the base film F wound around the core S with a predetermined pressure.

  Thus, when the base film F is wound around the core S, it is wound on the core S while applying heat and pressure, and formed into a roll shape so that the base film F is heat-treated in the next heat treatment step. Occurrence of surface projection or the like is suppressed. This is presumably because the surface pressure generated during the heat treatment is reduced by winding the base film F around the core S by applying heat and pressure.

  The configuration of the contact roller 22 is not particularly limited as long as heat and pressure can be applied to the base film F wound around the core S. For example, a tube made of SUS (stainless steel). Further, a contact roller having a structure in which a rotating outer tube plated with HCr on the surface is held by a bearing and an infrared heater is built in the core side can be used. In this case, the surface of the outer tube may be a metal or a rubber such as NBR (Nitrile-Butadiene Rubber). The heating means may be another internal heater or an induction heating method in which the outer tube itself generates heat.

  Further, the temperature of the contact roller 22 is not particularly limited as long as it is higher than room temperature, but is preferably 40 ° C. or higher, more preferably 60 ° C. or higher and preferably Tg or lower of the base film. . This is because if the heating exceeds the Tg of the base film, other characteristics may be affected.

  In the present embodiment, the number of contact rollers 22 is one, but the number of contact rollers is not particularly limited, and the base film F is wound around the core using a plurality of contact rollers. You may make it wind up to S. Further, the base film F may be wound around the core S in combination with other rollers having a rubber outer periphery.

  Further, a means for raising the temperature of another superheated roller or the like is provided so as not to contact the roll of the base film F being directly wound immediately before winding, and in combination with this, the base film F is wound around the core S. The order of installation at that time is not particularly limited.

  In this embodiment, when the base film F after the calendering process is wound around the core S, the contact roller 22 is wound around the core S while applying heat and pressure. If the process is a process other than the calendar process, the base film F is wound around the core S while applying heat and pressure by the contact roller 22 when the base film F processed in that process is wound around the core S. Shall be taken. For example, when heat-treating the base film F in a roll state after the coating process, when winding the coated base film F around the core, the contact film is wound around the core while applying heat and pressure. .

  The material of the core S is not particularly limited and may be a metal such as aluminum, FRP (Fiber Reinforced Plastics) or CFRP (Carbon Fiber Reinforced Plastics). ) Etc. Similarly, the diameter of the core S is not particularly limited.

  In the present embodiment, the base film is heat-treated at 50 ° C. or higher in the heat treatment step, but the temperature and time of the heat treatment are not particularly limited. In addition, the heat treatment method may be in a constant temperature bath as in this embodiment, or may be gradually raised in temperature.

  Further, in the present embodiment, the case where the magnetic tape is manufactured in the process of [application] → [calendar] → [heat treatment] → [slit] has been described as an example. However, the method of manufacturing a magnetic tape to which the present invention is applied. However, the present invention is not limited to this. For example, the same can be applied to the case of manufacturing in the process of [Coating] → <Heat treatment> → [Calendar] → [Heat treatment] → [Slit] → <Surface treatment / heat treatment / servo light> → [Entrainment]. (The steps in <parentheses> are performed as necessary). That is, the present invention can be applied to all methods of manufacturing a magnetic recording medium including a step of heat-treating a base film wound around a core.

  Moreover, the kind of base film is not specifically limited, PEN, PET, an aramid etc. can be considered. The effect of the present invention is remarkably obtained when a base film having a thickness of 10 μm or less is used.

  Further, the field of use of the magnetic tape obtained by the production method according to the present invention is not particularly limited, but an effect can be obtained by using it for a magnetic tape used for backup of computer data, for example.

  Hereinafter, a magnetic tape used for backup of computer data will be described. In this case, the magnetic tape basically means a magnetic film having a magnetic layer on one side of the base film and a back coat layer on the other side. For example, a nonmagnetic layer is further provided between the base film and the magnetic layer. It may be a magnetic tape having a configuration. Further, both surfaces may be magnetic layers.

  As the base film, those conventionally used as a base film material for magnetic tape can be used, and a non-magnetic one is 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-Fe ₂ O ₃ , Fe ₃ O ₄ , FeOx (x = 1.33 to 1.5), CrO ₂ , Co-containing γ-Fe ₂ O ₃ , and Co-containing FeOx (x = 1.33-1.5), ferromagnetic metal powder and plate-shaped hexagonal ferrite powder. 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 has a specific surface area of preferably 30 to 70 m ² / g, and the crystallite size determined by X-ray diffraction method 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 μm. is there. The plate-shaped hexagonal ferrite powder has the same reason as the ferromagnetic metal powder, so that 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 required 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 (Cr ₂ O ₃ ), 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 the binder, as necessary to obtain the durability of the layer obtained more excellent _{dispersibility, -COOM, -SO 3 M, -OSO} 3 M, -P = O (OM) 2, -O _{-P = O (OM) 2 (} M represents a hydrogen atom or an alkali metal salt,.), - OH, -NR 2, -N + R 3 (R is a hydrocarbon group.), an epoxy group, - It is preferable to use at least one polar group selected from SH, —CN and the like 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 tape 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) (above, manufactured by Degussa), # 3950 (16 nm) (manufactured by 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 tape of the present invention may have a configuration in which a nonmagnetic layer is provided between the base film and the magnetic layer. That is, a magnetic tape 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 tape 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 is a coating formed after applying the non-magnetic layer coating liquid on the base film. It is preferably formed by using a so-called wet-on-wet coating method in which a magnetic layer coating solution is applied to a 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 back coat layer of the magnetic tape 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 back coat layer of the magnetic tape is preferably adjusted so that its surface roughness Ra (centerline average roughness with a cutoff of 0.08 mm) is in the range of 0.003 to 0.060 μm. . 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 a magnetic tape 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 3 It is preferably in the range of 0.0 μm (more preferably, 1.5 to 2.5 μm).

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

  The effect by the structure of this invention is demonstrated by the following tests.

  When the base film to be heat-treated is wound only on the core by applying pressure with the contact roller and when it is wound by applying heat and pressure with the contact roller, the occurrence of wrinkles, the occurrence of errors, and the Ra of the magnetic layer Inspected.

  The base film was calendered after coating, wound around a core having a diameter of 300 mm, and formed into a roll. After winding, heat treatment was performed at 80 ° C. for 30 hours in the roll state. After the heat treatment, the rolled base film was stored at room temperature, and a magnetic tape was manufactured through a predetermined process after the slit.

  The contact roller was brought into direct contact with the base film being wound on the winding core and pressed, and contact pressure was applied at 500N. Moreover, when heating, it wound up by setting surface temperature to 50 degreeC. In addition, the contact roller used what hold | maintained the rotating outer pipe | tube which carried HCr plating on the surface by the SUS pipe | tube with the bearing, and built the infrared heater in the core side.

  Table 1 shows the occurrence of wrinkles on the original fabric after heat treatment and the errors detected by Ra and S-DLT (Super Digital Liner Tape) drive on the magnetic layer surface measured by AFM (Atomic Force Microscope). became.

表１に示すように、コンタクトローラで加圧するだけでなく、コンタクトローラで加圧、加熱しながら、ベースフィルムを巻芯に巻き取ることにより、皺の発生とバック面写りを低減でき、エラーも低減できることが確認された。

As shown in Table 1, not only is the pressure applied by the contact roller, but the base film is wound around the winding core while being pressurized and heated by the contact roller, thereby reducing wrinkles and back surface image errors. It was confirmed that it can be reduced.

Explanatory drawing of calendar process Explanatory drawing of heat treatment process Schematic configuration diagram of the cutting device used in the slitting process

Explanation of symbols

  F ... Base film, S ... Core, 10 ... Calendar device, 22 ... Contact roller, 30 ... Constant temperature bath, 40 ... Cutting device

Claims (3)

In a method for manufacturing a magnetic recording medium, the method includes a step of winding a belt-shaped flexible base film around a core to form a roll, and performing a heat treatment in the state of the roll.
When the base film to be heat-treated is wound around the core, the base film is applied to the core while pressing a contact roller heated to a temperature higher than room temperature on the outer periphery of the base film wound around the core. A method for producing a magnetic recording medium, comprising winding up.   The method of manufacturing a magnetic recording medium according to claim 1, wherein the base film has a thickness of 10 μm or less.   A magnetic recording medium manufactured by the method for manufacturing a magnetic recording medium according to claim 1.

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