JP2000268360A - Production of magnetic tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a magnetic tape having high reliability by removing bumps generated at the edge of a groove made in a back coat layer thereby ensuring good traveling characteristics while suppressing generation of a dropout. SOLUTION: A magnetic tape 10 has a magnetic layer containing a ferromagnetic powder and a binder on one side of a support and a back coat layer on the other side thereof wherein a groove is made on the surface of the back coat layer by irradiating with a laser beam and then bumps generated at the edge of the groove are removed. Preferably, the bumps are removed using an abrasive means, e.g. an abrasive tape or blade, independently or in combination. More preferably, the magnetic tape is subjected to wiping process following to the removing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a magnetic tape having a magnetic layer on one side of a support and a back coat layer on the other side.

[0002]

2. Description of the Related Art Magnetic tapes are widely used as audio tapes, video tapes, or tapes for recording computer data. The magnetic tape generally has a structure in which a magnetic layer is provided on one side of a support made of a flexible material such as a synthetic resin, and a back coat layer is provided on the other side. Further, as a magnetic tape advantageous for higher density recording, a magnetic tape having a structure in which a nonmagnetic layer is further provided between the support and the magnetic layer has been proposed. The back coat layer is provided mainly for the purpose of improving running characteristics such as running durability, and functions advantageously for recent high-speed use of magnetic tapes.

[0003] Generally, a magnetic tape is coated, dried, calendered, cut, surface-processed by a blade, and inspected while a raw film sent from a feeder wound in a roll is transported by rollers. It is manufactured through a process and a winding process to a winding machine (including winding to a cassette or the like). In general, a capstan roller is used to move the film (or tape) between the steps or between the steps, and the film is conveyed by hanging the film on the roller and rotating the roller.

[0004]

In recent years, in order to improve productivity, in each manufacturing process (especially, a surface treatment process using a blade and a winding process to a winding machine), there is a tendency to increase a tape conveying speed. is there. When the tape transport speed is increased, the tape entrains air in the above-mentioned blade processing step, and the tape floats on the capstan roller,
In some cases, the tape slips and normal conveyance becomes difficult. When such a transport failure occurs, the tape is apt to be damaged by the edge of the tape, such as a capstan roller, a guide roller, or an improper contact of the tape edge with the blade in the blade processing step, and the edge portion is broken, rubbed, or peeled off. Problem arises.

In order to solve the problem of damage to the tape edge caused by the high-speed transport of the tape as described above, the applicant of the present application has formed a groove by irradiating a laser beam to the surface of the back coat layer of the magnetic tape. By applying a groove to the tape to prevent air from being entrapped by the tape on the roller to prevent the occurrence of slipping, a patent has been filed for an invention relating to a magnetic tape processing method that enables stable high-speed transport of the tape. (Japanese Patent Application No. 10-348450)

The present inventors have further studied the performance of the magnetic tape having grooves formed by laser light on the surface of the back coat layer, such as quality and running characteristics. According to the study, when a groove is formed on the surface of the back coat layer using laser light, a bulge occurs at the edge portion around the groove, and this bulge adversely affects the running characteristics and recording reproducibility characteristics of the magnetic tape. It turned out to be easier. That is, when the recording / reproducing system is mounted with such a raised magnetic tape and repeated running, the raised portion is scraped off by the running system, and as a result, shavings (components of the back coat layer) are powdered. It was found that the particles spread in the system, and the powdery substances adhered to the surface of the magnetic layer, causing a drop in running performance and clogging of the magnetic head, thereby causing dropout. In particular, since recording at shorter wavelengths and narrower tracks have been promoted due to the recent increase in recording density, even fine powders which have not been a problem in the past can cause dropout.

An object of the present invention is to remove bumps generated at the edges of the grooves formed in the backcoat layer, thereby ensuring good running characteristics and reducing the occurrence of dropouts, thereby achieving high reliability. An object of the present invention is to provide a method for manufacturing a magnetic tape. Another object of the present invention is to provide a method of manufacturing a magnetic tape having a back coat layer suitable for high-speed conveyance in a magnetic tape manufacturing process.

[0008]

According to the research of the present inventors,
A magnetic tape that can perform recording and reproduction with high reliability by eliminating the bulge at the edge of the groove formed by irradiating the back coat layer with laser light, thereby avoiding troubles such as clogging of the head due to the powdery material. It has been found that can be produced. Specifically, by performing a removal treatment using a polishing tape, a blade, or the like, it was possible to efficiently remove the swelling and to form a back coat layer having a surface suitable for high-speed conveyance.

The present invention relates to a surface of a back coat layer of a magnetic tape having a magnetic layer containing a ferromagnetic powder and a binder on one side of a support and a back coat layer on the other side of the support. And forming a groove by irradiating the groove with a laser beam, and then removing a bulge generated at an edge portion of the groove.

The method for producing a magnetic tape of the present invention preferably has the following aspects. (1) A method for producing a magnetic tape in which the swelling is removed using at least one means selected from a polishing tape, a fixed blade, a diamond wheel, and a rotating blade. (2) A method for producing a magnetic tape, in which the step of removing swelling is performed using a polishing tape in combination with the step of using a fixed blade, a diamond wheel, or a rotating blade. (3) A method for producing a magnetic tape, in which the swelling is removed using a polishing tape, and further using at least one of a fixed blade, a diamond wheel, and a rotating blade. (4) A method of manufacturing a magnetic tape in which a wiping process is further performed after the bulging removal process.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method of manufacturing a magnetic tape according to the present invention, a groove is formed by irradiating a laser beam to a surface of a back coat layer of a magnetic tape, and then a bulge generated at an edge portion of the groove is removed. It is characterized by the following. Note that the magnetic tape basically means a magnetic tape having a configuration having a magnetic layer on one side of a support and a back coat layer on the other side of the support, for example,
A magnetic tape having a configuration in which a nonmagnetic layer is further provided between the support and the magnetic layer may be used.

A method of removing a bulge generated at an edge portion of a groove, which is a feature of the present invention, will be described with reference to the accompanying drawings. FIG. 1 is a plan view schematically showing grooves formed on the surface of the back coat layer of the magnetic tape along the longitudinal direction. FIG. 2 is a partial cross-sectional view schematically showing a bulge generated at an edge portion of the groove of the back coat layer in the AA cross section of FIG. 1 and 2, a magnetic tape 10 is an example of a magnetic tape having a configuration in which a nonmagnetic layer 2 and a magnetic layer 3 are provided on one side of a support 1 and a back coat layer 4 is provided on the other side. Have been.

The grooves 5a and 5b on the surface of the back coat layer 4
Are formed by laser light irradiation. The method of forming the groove is described in Japanese Patent Application No. 10-348450 as described above, and the groove can be formed by using this method in the present invention. Briefly describing the method of forming the groove, the laser light emitted from the light source while moving the magnetic tape in the longitudinal direction by the transport means using an optical system including a light source for emitting a laser beam and the transport means of the tape. Is applied to a predetermined processing position on the back side of the magnetic tape by an optical system, whereby a groove can be formed along the longitudinal direction of the magnetic tape. As a laser beam, an argon laser beam is preferably used. Groove 5
Due to the formation of a and 5b, as shown in FIG. 2, bulges 6a and 6b occur at the edge portions of these grooves.

Preferred examples of the method for removing the bulge at the edge of the groove according to the present invention include a method using a polishing tape, a method using a means such as a blade, or a method using a combination of these methods. Can be mentioned. When a method using a polishing tape is used, the polishing tape to be used is not particularly limited, but it is preferable to use a polishing tape containing diamond particles (Mohs hardness of 10) as a polishing material in consideration of production efficiency, finished state, and the like. . In this case, the average particle diameter of the diamond is 0.1 to 5 μm (more preferably, 0.5 to 3 μm).
μm). Further, the content of diamond particles in all abrasives is preferably in the range of 0.1 to 5% by weight (more preferably, 0.5 to 3% by weight).

The removal of the bulge at the edge of the groove using a magnetic tape can be performed, for example, by the following method. The polishing tape is applied with a predetermined contact angle (30 to 120 degrees) and a tension (50 to
200 g (１ ／ inch width)). Then, the magnetic tape is rotated at a predetermined speed (60 to 1).
200 cm / min or 1-20 m / min), tension (5
While running at 0 to 200 g (1/2 inch width), the polishing tape is run at a predetermined speed (0.5 to 3 cm / min) in the direction opposite to the running direction of the magnetic tape, so that the edge of the groove is The swelling of the portion can be removed.

At least one means (hereinafter, grinding means) selected from a fixed blade, a diamond wheel, and a rotating blade removes a bulge at an edge portion of the groove.
Can be done with As a fixed blade, for example,
Sapphire blades are preferred. Also when removing the bulge at the edge of the groove using these grinding means,
It is preferable to set the speed and tension during running of the magnetic tape within the range when using the above-mentioned polishing tape. When a rotating blade or diamond wheel is used, the magnetic tape is brought into contact with these means at a predetermined contact angle while rotating these grinding means at a constant rotational speed in the direction opposite to the running direction of the magnetic tape. By doing so, swelling can be removed. The rotation speed of the grinding means and the number of times of contact with the magnetic tape are determined as appropriate.

In the present invention, the bulge at the edge of the groove on the surface of the back coat layer is removed by a method using a polishing tape and a method using at least one grinding means selected from a fixed blade, a diamond wheel, and a rotating blade. Is preferably performed in combination with the above. The combination method is not particularly limited, but it is preferable that after the ridge is removed using a polishing tape, the ridge is further removed using at least one of the above-mentioned grinding units. After removal of the bulge at the edge of the groove, paper, leather, non-woven fabric (nylon,
It is preferable to perform a wiping process using a wiping material such as polyester, rayon, acrylonitrile, or a nonwoven fabric made of a blend. By this treatment, shavings (powder composed of the components of the back coat layer) generated by the polishing tape or the grinding means can be almost completely removed from the surface of the back coat layer.

FIG. 3 is a diagram schematically showing a preferred example of a method for removing a bulge generated at an edge portion of a groove according to the present invention. As shown in FIG. 3, the magnetic tape 10 fed from the feed roll 16 is conveyed at a predetermined speed by the feed roll 17, and the magnetic tape 10 is pressed by the polishing tape 11 pressed by the pad 14 so as to contact at a predetermined angle. Then, a removal process is performed by the fixed blade 12 to remove the bulge at the edge of the groove on the surface of the back coat layer. The magnetic tape 10 from which the bulge has been removed is further subjected to a wiping process by the wiping member 13 pressed by the pad 15,
It is wound up by the winding roll 20, and a series of removal and wiping processes is completed. The polishing tape 14 in the swelling removal process and the wiping material 17 in the wiping process are wound around rotating rolls 18 and 19, respectively, and can run at a predetermined speed.

The method of manufacturing a magnetic tape according to the present invention is characterized in that, as described above, the bulge generated at the edge of the groove formed on the surface of the back coat layer of the magnetic tape is removed. Therefore, the magnetic tape itself can be manufactured using a conventional manufacturing method. less than,
A method for manufacturing a magnetic tape will be described. As the support, those conventionally used as a support material for a magnetic tape can be used, and a non-magnetic support is particularly preferable. Examples of these include polyesters (eg, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), a mixture of polyethylene terephthalate and polyethylene naphthalate, a polymer containing an ethylene terephthalate component and an ethylene naphthalate component),
Synthetic resin films such as polyolefins (eg, polypropylene), cellulose derivatives (eg, cellulose diacetate, cellulose triacetate), polycarbonate, polyamides (among which are aromatic polyamides and aramids), and polyimides (among which are wholly aromatic polyimides). Can be. Among these, polyethylene terephthalate (PET), polyethylene naphthalate (PE)
N), aromatic polyamides and aramids are preferred. The thickness of the support is not particularly limited, but is 2.0 to 8.0 μm.
(More preferably, 3.0 to 7.0 μm, particularly preferably 4.0 to 6.5 μm).

The magnetic layer is basically formed of a ferromagnetic powder and a binder. Further, the magnetic layer usually further contains a lubricant, carbon black as a conductive powder, and an abrasive. As the ferromagnetic powder, for example, γ
_{-Fe 2 O 3, Fe 3 O} 4, FeOx (x = 1.33~
1.5), CrO ₂ , Co-containing γ-Fe ₂ O ₃ , Co-containing FeOx (x = 1.33 to 1.5), ferromagnetic metal powder, and plate-like hexagonal ferrite powder. In the present invention, it is preferable to use a ferromagnetic metal powder or a plate-like hexagonal ferrite powder as the ferromagnetic powder. Particularly preferred is a ferromagnetic metal powder.

The ferromagnetic metal powder preferably has a particle specific surface area of 30 to 70 m ² / g, and a crystallite size determined by X-ray diffraction of 50 to 300 A. 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 sufficiently disperse the magnetic layer. It is necessary that the ferromagnetic metal powder contains at least Fe.
e, Fe-Co, Fe-Ni, Fe-Zn-Ni or F
It is a simple metal or an alloy mainly composed of e-Ni-Co. Regarding the magnetic properties of these ferromagnetic metal powders, in order to achieve a high recording density, the saturation magnetization (σs) is 110 emu / g or more, preferably 120 emu / g or more.
It is not less than mu / g and not more than 170 emu / g. The coercive force (Hc) is 800 to 3000 Oersted (Oe).
(Preferably, 1500 to 2500 Oe). The major axis length of the powder (that is, the average particle diameter) determined by a transmission electron microscope is 0.5 μm or less, preferably 0.01 to 0.3 μm, and the axial ratio (major axis length / minor axis length, Needle ratio) is 5 or more and 20 or less, preferably 5 to
Fifteen. In order to further improve the properties, B,
Non-metals such as C, Al, Si, and P, or salts and oxides thereof may be added. Usually, an oxide layer is formed on the particle surface of the metal powder for chemical stabilization.

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

The ferromagnetic powder has a water content of 0.01 to 2
It is preferable to set the weight%. It is preferable to optimize the water content depending on the type of the binder. P of ferromagnetic powder
H is preferably optimized by the combination with the binder used, and its pH is usually in the range of 4 to 12, preferably 5 to 10. The ferromagnetic powder may be subjected to a surface treatment with Al, Si, P, or an oxide thereof, if necessary. The amount used for the surface treatment is usually 0.1 to 10% by weight based on 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. Ferromagnetic powder contains soluble Na, Ca, Fe, Ni, and S
In some cases, inorganic ions such as r are included, but if the content is 5000 ppm or less, there is no effect on the characteristics.

The lubricant is added in order to alleviate the friction between the surface of the magnetic layer and the magnetic head, the guide pole of the drive and the cylinder by oozing out to the surface of the magnetic layer, and to maintain the sliding state smoothly. . Examples of the lubricant include a fatty acid and a fatty acid ester. As fatty acids, for example, acetic acid, propionic acid,
Aliphatic carboxylic acids such as octanoic acid, 2-ethylhexanoic acid, lauric acid, myristic acid, stearic acid, palmitic acid, behenic acid, arachinic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, and palmitoleic acid or these And mixtures thereof.

Examples of the fatty acid ester include butyl stearate, sec-butyl stearate, isopropyl stearate, butyl oleate, amyl stearate, 3-methylbutyl stearate, 2-ethylhexyl stearate, and 2-hexyldecyl. Stearate, butyl palmitate, 2-ethylhexyl myristate, a mixture of butyl stearate and butyl palmitate, oleyl oleate, butoxyethyl stearate, 2-butoxy-1-propyl stearate, dipropylene glycol monobutyl ether and stearic acid Acylation of diethylene glycol dipalmitate, hexamethylenediol with myristic acid to form diols, and various esterifications of glycerin oleate Compounds can be mentioned. These can be used alone or in combination. The usual content of the lubricant is in the range of 0.2 to 20 parts by weight (preferably 0.5 to 10 parts by weight) based on 100 parts by weight of the ferromagnetic powder of the magnetic layer.

[0026] Carbon black, reduce the surface electric resistance of the magnetic layer (Rs), reduction of the dynamic friction coefficient (mu _K value), improvement of running durability, and various such to ensure a smooth surface of the magnetic layer It is added for the purpose. Carbon black has an average particle diameter of 3 to 350 nm (more preferably, 10 to 3 nm).
00 nm). The specific surface area is 5 to 500 m ² / g (more preferably 50 m ² / g).
３００300 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 2 to 10, and the water content is 0.1 to
Preferably, the tap density is 10% to 1 g / cc.

As the carbon black, those obtained by various production 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 and 13
00, 1000, 900, 800, 700, VULCA
N XC-72 (from Cabot Corporation), # 35, #
50, # 55, # 60 and # 80 (all manufactured by Asahi Carbon Co., Ltd.), # 3950B, # 3750B, # 3250
B, # 2400B, # 2300B, # 1000, # 90
0, # 40, # 30, and # 10B (all manufactured by Mitsubishi Chemical Corporation), CONDUCTEX SC, RAVEN1
50, 50, 40, 15 (all manufactured by Columbia Carbon), Ketjen Black EC, Ketjen Black E
CDJ-500 and Ketchen Black ECDJ-6
00 (all manufactured by Lion Aguso Co., Ltd.). The usual addition amount of carbon black is 0.1 to 30 parts by weight with respect to 100 parts by weight of the ferromagnetic powder.
Preferably, it is in the range of 0.2 to 15 parts by weight.

As the abrasive, for example, fused alumina,
Silicon carbide, chromium oxide (Cr ₂ 0 _3), corundum, artificial corundum, diamond, artificial diamond, garnet, emery: can be exemplified (the main component corundum and magnetite). These abrasives have a Mohs hardness of 5 or more (preferably 6 or more) and an average particle size of 0.0
Those having a size of 5 to 1 μm (more preferably, 0.2 to 0.8 μm) are preferable. The amount of the abrasive is usually in the range of 3 to 25 parts by weight (preferably 3 to 20 parts by weight) based on 100 parts by weight of the ferromagnetic powder.

Examples of the binder for the magnetic layer include a thermoplastic resin, a thermosetting resin, a reactive resin, and a mixture thereof. Examples of thermoplastic resins include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid,
Acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, and a polymer containing as a structural unit, or a copolymer containing vinyl ether can be given. . As the copolymer, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer,
Vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride copolymer, acrylate-styrene copolymer, methacrylate-acrylonitrile copolymer, methacrylate -Vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, styrene-butadiene copolymer, chlorovinyl ether-acrylic acid ester copolymer be able to.

In addition to the above, polyamide resins, cellulose resins (cellulose acetate butyrate, cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resins, polyurethane resins, various rubber resins Etc. can also be used.

The thermosetting resin or the reactive resin includes, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic reaction resin, formaldehyde resin, silicone resin, epoxy resin. Examples thereof include a polyamide resin, a mixture of a polyester resin and a polyisocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, and a mixture of a polyurethane and a polyisocyanate.

Examples of the polyisocyanate include tolylene diisocyanate, 4-4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Examples include isocyanates such as 5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, and triphenylmethane triisocyanate, products of these isocyanates and polyalcohols, and polyisocyanates formed by condensation of isocyanates. .

As the polyurethane resin, known resins having a structure 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 for the magnetic layer is a vinyl chloride resin, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a vinyl chloride-vinyl acetate-maleic anhydride copolymer. It is preferable to constitute a combination of at least one resin selected from coalesced and nitrocellulose and a polyurethane resin, or a combination of these with a polyisocyanate.

As the binder, -COO may be used if necessary in order to obtain better dispersibility and durability of the obtained layer.
_{M, -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 represents a hydrocarbon group), epoxy group, -S
It is preferable to use at least one polar group selected from H, -CN, etc. by introducing it through a copolymerization or addition reaction. Such a polar group is 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 5 to 50 parts by weight (preferably 10 to 3 parts by weight) per 100 parts by weight of the ferromagnetic powder.
0 parts by weight). When a vinyl chloride resin, a polyurethane resin, and a polyisocyanate are used in combination 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 all the binders. % And the polyisocyanate is preferably present in an amount ranging from 2 to 50% by weight.

A dispersant can be added to the coating liquid for forming the magnetic layer of the magnetic tape in order to disperse the magnetic powder in the binder. If necessary, a plasticizer, conductive particles (antistatic agent) other than carbon black, an 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, and stearolic acid. Fatty acids (RCOOH, R is an alkyl group having 11 to 17 carbon atoms,
Or an alkenyl group), a metal soap of an alkali metal or an alkaline earth metal of the fatty acid, a fluorine-containing compound of the fatty acid ester, an amide of the fatty acid,
Polyalkylene oxide alkyl phosphate, lecithin, trialkyl polyolefin oxy quaternary ammonium salt (alkyl has 1 to 5 carbon atoms, olefin is ethylene, propylene, etc.), sulfate, copper phthalocyanine, etc. it can. These may be used alone or in combination. The dispersant is usually added in the range of 0.5 to 20 parts by weight based on 100 parts by weight of the binder of the magnetic layer.

Next, the back coat layer will be described.
The back coat layer is a layer mainly containing carbon black. In the back coat layer, it is preferable to use two types of carbon black having different average particle sizes. In this case, the average particle size is 10
It is preferable to use 30 nm fine particle carbon black and coarse particle carbon black having an average particle size of 150 to 300 nm. In general, the surface electric resistance of the back coat layer can be set low by the addition of fine carbon black as described above. In addition, fine carbon black is generally excellent in holding power of a liquid lubricant, and contributes to reduction of a friction coefficient when used in combination with a lubricant. On the other hand, the coarse-grained carbon black having a particle size of 150 to 300 nm has a function as a solid lubricant, and also forms fine projections on the surface of the back layer to reduce the contact area and reduce the friction coefficient. Contribute to reduction.

In the case of using two types having different average particle sizes in the back coat layer, 10 to 30 nm
The content ratio (weight ratio) of the fine particle carbon black to the coarse particle carbon black of 150 to 300 nm is preferably in the range of former: latter = 10: 90 to 90:10, more preferably 30:70. ７０70: 30. Also, the content of carbon black (the total amount when two types are used) in the back coat layer is preferably 50 parts by weight with respect to 100 parts by weight of the binder.
To 500 parts by weight, more preferably 100 parts by weight.
It is in the range of 300 parts by weight. As the binder used for the back coat layer, those described for the magnetic layer can be used. It is preferable to use a nitrocellulose resin and a polyester polyurethane resin in combination. In this case, it is preferable to use the binder so that nitrocellulose is contained in a proportion of 70% by weight or more.

It is preferable to add an inorganic powder having a Mohs hardness of 5 to 9 to the back coat layer for the purpose of imparting repeated running durability to the tape and strengthening the back coat layer. When inorganic powder is used with carbon black,
Deterioration is less with repeated sliding, resulting in a strong backcoat layer. When an inorganic powder having a Mohs hardness of 5 to 9 is used, an appropriate polishing force is generated, and the adhesion of shavings and the like to the tape guide pole and the like is reduced. The inorganic powder having a Mohs hardness of 5 to 9 has an average particle size in the range of 0.01 to 1 μm (more preferably 0.05 to 0.5 μm, particularly preferably 0.08 to 0.3 μm). Is preferred.

Examples of the 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. Of these, α-iron oxide or α-alumina is preferred. The content of the inorganic powder having a Mohs hardness of 5 to 9 is 0.01 to 100 parts by weight of carbon black.
5 parts by weight, preferably 0.02 to 2 parts by weight.

The back coat layer may contain a lubricant. The lubricant can be appropriately selected from the lubricants described for the magnetic layer. In the back coat layer, the lubricant is generally used in an amount of 1 to 5 with respect to 100 parts by weight of the binder.
It is added in the range of parts by weight. Further, the dispersant described for the magnetic layer can be added to the back coat layer. In particular, it is preferable to use copper oleate, copper phthalocyanine, and barium sulfate in combination as a dispersant for the back coat layer. The dispersant is preferably added in the range of 0.5 to 25 parts by weight based on 100 parts by weight of the binder.

The magnetic tape of the present invention may have a structure in which a non-magnetic layer is further provided between the support and the magnetic layer. That is, the magnetic tape may have a non-magnetic layer and a magnetic layer on one side of the support in this order, and have a back coat layer on the other side of the support. The non-magnetic layer is a substantially non-magnetic layer containing a non-magnetic powder and a binder. The non-magnetic layer needs to be substantially non-magnetic so as not to affect the electromagnetic conversion characteristics of the magnetic layer on it, but a small amount of the non-magnetic layer is sufficient to not affect the electromagnetic conversion characteristics of the magnetic layer. It does not matter particularly if the magnetic powder of the present invention is contained. Usually, the non-magnetic layer contains a lubricant in addition to these components.

Examples of the non-magnetic powder used in the non-magnetic layer include non-magnetic inorganic powder and carbon black. The nonmagnetic inorganic powder is preferably relatively hard, and preferably has a Mohs hardness of 5 or more (more preferably 6 or more). Examples of non-magnetic inorganic powder 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, boron nitride, zinc oxide, calcium carbonate, Calcium sulfate and barium sulfate can be mentioned.
These can be used alone or in combination.
Among these, titanium dioxide, α-alumina, α-
Iron oxide or chromium oxide is preferred. The average particle size of the nonmagnetic inorganic powder is 0.01 to 1.0 μm (preferably,
0.01 to 0.5 μm, especially 0.02 to 0.1 μm)
Is preferably within the range.

Carbon black is added for the purpose of imparting conductivity to the magnetic layer to prevent electrification and ensuring the smooth surface properties of the magnetic layer formed on the non-magnetic layer. As the carbon black used in the nonmagnetic layer, the carbon black described in the above magnetic layer can be used. However, carbon black used in the non-magnetic layer has an average particle diameter of 35 nm or less (more preferably, 10 to 35 n
m) is preferred. The usual addition amount of carbon black is 3 to 20 parts by weight, preferably 4 to 18 parts by weight, based on 100 parts by weight of the total nonmagnetic inorganic powder in the nonmagnetic layer.
Parts by weight, more preferably 5 to 15 parts by weight.

As the lubricant, the fatty acids or fatty acid esters described for the magnetic layer can be used. The amount of the lubricant to be added depends on the total amount of non-magnetic powder 10 in the non-magnetic layer.
It is usually in the range of 0.2 to 20 parts by weight with respect to 0 parts by weight.

As the binder for the non-magnetic layer, the binder described for the magnetic layer can be used. The binder is used in an amount of usually 5 to 50 parts by weight (preferably 10 to 30 parts by weight) based on 100 parts by weight of the nonmagnetic powder of the nonmagnetic layer. When a non-magnetic layer is used in combination with a vinyl chloride resin, a polyurethane resin, and a polyisocyanate as a binder, the total binder contains 5 to 70% by weight of the vinyl chloride resin and 2 to 5% by weight of the polyurethane resin.
0% by weight, and 2-50% by weight of polyisocyanate
It is preferable to use it in such an amount as to be contained in the range.
In the non-magnetic layer, optional components that can be added to the magnetic layer may be added.

In the magnetic tape of the present invention, in the step of manufacturing the magnetic tape, a step of removing a bulge generated at an edge portion of a groove formed on the surface of the back coat layer, preferably, further performing a wiping step after the removing step Except for providing, it can be manufactured according to a conventional manufacturing process. Therefore, a magnetic tape can be manufactured by a series of processing steps from a step of preparing a coating solution for forming each layer to a step of applying each of these coating solutions on a support to a drying step.

When a magnetic tape having a non-magnetic layer is produced, the magnetic layer is coated with a coating solution for forming a non-magnetic layer on a support, and then the formed coating layer (non-magnetic layer) is in a wet state. It is preferable to use a so-called wet-on-wet coating method in which a coating solution for forming a magnetic layer is coated thereon.

The wet-on-wet coating method includes, for example, the following method. (1) A non-magnetic layer is first formed on a support using a gravure coating, a roll coating, a blade coating, or an extrusion coating device. Method for forming a magnetic layer by a lug coating device (Japanese Patent Application Laid-Open No. 60-23817)
9, JP-B 1-46-186, JP-A-2-26567
No. 2). (2) A method in which a magnetic layer and a non-magnetic layer are formed almost simultaneously on a support using a coating apparatus comprising a single coating head having two coating liquid slits (Japanese Patent Laid-Open No. 63-880)
No. 80, JP-A-2-17921 and JP-A-2-265672
No. each publication). (3) A method of forming a magnetic layer and a non-magnetic layer almost simultaneously on a support using an extrusion coating apparatus with a backup roller (see Japanese Patent Application Laid-Open No. 2-174965). Is preferably formed using a simultaneous multilayer coating method.

The magnetic layer of a single-layer magnetic tape having a magnetic layer on one side of the support and a back coat layer on the other side manufactured according to the manufacturing method of the present invention has a thickness of 1. 0 to 3.0 μm (more preferably, 1.5 to
2.5 μm). The overall thickness of the magnetic tape having this configuration is 4.0 to 12.0 μm,
More preferably, it is preferably in the range of 4.0 to 10.0 μm). Further, the thickness of the back coat layer is 0.1 mm.
1 to 1.0 μm (more preferably, 0.2 to 0.8 μm
m).

The thickness of the magnetic layer of the magnetic tape having the non-magnetic layer is preferably in the range of 0.1 to 1.0 μm (more preferably 0.1 to 0.8 μm). Further, the thickness of the nonmagnetic layer is preferably in the range of 1.0 to 3.0 μm (more preferably, 1.5 to 2.5 μm). The ratio of the thickness of the magnetic layer to the thickness of the non-magnetic layer is
1: 2 to 1:15 (more preferably 1: 3 to 1: 1
It is preferably in the range of 2). It is preferable that the entire thickness of the magnetic tape having the non-magnetic layer and the thickness of the back coat layer are in the same range as the magnetic tape having the single-layer structure.

[0053]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples. In addition, "part" shown below represents "part by weight".

[Example 1] [Preparation of coating solution for forming nonmagnetic layer and coating solution for forming magnetic layer] (Component for forming magnetic layer) 100 parts of ferromagnetic metal powder [Composition / Fe: Co = 90: 10 ( Atomic ratio) Coercive force (Hc): 1850 (Oe) Specific surface area by BET method: 58 m ² / g Crystallite size: 175 ° Saturation magnetization (σs): 130 emu / g Particle size (average major axis diameter): 0.09 μm acicular ratio: 7.0 pH: 8.6 water soluble Na: 70 ppm soluble Ca: 10 ppm water soluble Fe: 10 ppm] polar group (-SO ₃ K groups) containing vinyl chloride copolymer 12 parts (-SO ₃ K group content: 5 × 10 ⁻⁶ mol / g, degree of polymerization 350 Epoxy group content: 3.5% by weight in monomer units, MR-110, manufactured by Nippon Zeon Co., Ltd. Polar group (—SO ₃ Na group) ) Containing polyester polyurethane Resin 3 parts [neopentyl glycol / caprolactone polyol / diphenylmethane-4,4'-diisocyanate (MDI) = 0.9 / 2.6 / 1 (weight ratio) -SO ₃ Na group content: 1 × 10 ^-4 mol / G] polyisocyanate 3 parts [Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.] α-alumina (particle size: 0.2 μm) 5 parts carbon black (particle size: 0.10 μm) 0.5 part butyl stearate 1 Part Stearic acid 2 parts Methyl ethyl ketone 150 parts Cyclohexanone 50 parts

(Non-magnetic layer forming component) Non-magnetic powder Titanium dioxide TiO ₂ (rutile type) 90 parts [TiO ₂ content: 90% or more Average primary particle diameter: 0.035 μm Specific surface area by BET method: 40 m ² / g pH: 7.0 DBP oil absorption: 27~38mL / 100g Mohs hardness: 6.0 surface coating compound (A1 ₂ 0 _3): 1.5 wt%] carbon black [manufactured by Mitsubishi carbon Co.] 10 parts ( Average primary particle size: 16 nm DBP oil absorption: 80 mL / 100 g pH: 8.0 Specific surface area by BET method: 250 m ² / g Volatile content: 1.5% Chlorine containing polar group (—SO ₃ K group, epoxy group) vinyl copolymer 12 parts [MR-110, Nippon Zeon Co., Ltd.] polar group (-SO ₃ Na group) containing polyester polyurethane resin 5 parts [neopentyl glycol / caprolactone Emissions polyol / diphenylmethane-4,4'-diisocyanate (MDI) = 0.9 / 2.6 / 1 ( weight ratio) -SO ₃ Na group 1 × 10 ^-4 mol / g containing] Polyisocyanate 3 parts [Coronate L , Manufactured by Nippon Polyurethane Industry Co., Ltd.] Butyl stearate 1 part Stearic acid 2 parts Methyl ethyl ketone 150 parts Cyclohexanone 50 parts

Each of the components forming the magnetic layer or the non-magnetic layer was kneaded with a continuous kneader, and then dispersed using a sand mill. To each of the obtained dispersions, 3 parts of the above polyisocyanate was added together, and 40 parts of butyl acetate was further added to each of the dispersions, and the mixture was filtered through a filter having an average pore diameter of 1 μm to obtain a coating liquid for forming a magnetic layer. A coating solution for forming a non-magnetic layer was prepared.

[Preparation of Backcoat Layer-Forming Coating Solution] (Backcoat Layer-Forming Component) Carbon Black 100 parts (Average Primary Particle Diameter: 17 nm DBP Oil Absorption: 75 mL / 100 g pH: 8.0 Specific Surface Area by BET Method : 220 m ² / g Volatile content: 1.5% Bulk density: 0.25 g / cm ³ ) Nitrocellulose resin 100 parts Polyester polyurethane resin 30 parts [Nipporan, manufactured by Nippon Polyureta Industry Co., Ltd.] Dispersant: Copper oleate 10 Part Copper phthalocyanine 10 parts Barium sulfate (precipitation) 5 parts Methyl ethyl ketone 500 parts Toluene 500 parts Carbon black 100 parts (average primary particle diameter: 270 nm DBP oil absorption: 36 mL / 100 g pH: 8.5 Specific surface area by BET method: 200 m ² / G α-alumina (particle size: 0.2 μm) Part

After kneading the above components with a continuous kneader,
It was dispersed using a sand mill. 1 μm of the resulting dispersion
The mixture was filtered using a filter having an average pore diameter of m to prepare a coating solution for forming a back coat layer.

[Preparation of Magnetic Tape] The obtained coating solution for forming a non-magnetic layer and the coating solution for forming a magnetic layer are coated on the non-magnetic layer so that the dried non-magnetic layer has a thickness of 2.1 μm. Simultaneous multi-layer coating was performed on a polyethylene terephthalate (PET) support (thickness: 6 μm) such that the thickness of the dried magnetic layer was 0.2 μm. Next, while both layers were still in a wet state, orientation treatment was performed using a cobalt magnet having a magnetic force (magnetic flux density) of 3000 Gauss and a solenoid having a magnetic force (magnetic flux density) of 1500 Gauss. Thereafter, drying was performed to provide a nonmagnetic layer and a magnetic layer.

Next, on the other side of the support, the coating liquid for forming the back coat layer is dried to a thickness of 0.5.
μm, then dried and provided with a back coat layer, a non-magnetic layer and a magnetic layer on one surface of the support,
And the magnetic recording laminated body roll which each provided the back coat layer on the other surface was obtained.

Thereafter, the obtained magnetic recording laminate roll was subjected to calendering by a 7-stage calendering machine (temperature: 90 ° C., linear pressure: 300 kg / cm ² ) composed of only metal rolls, and was イ ン チ inch thick. A magnetic tape was obtained by slitting to width.

[Formation of Groove on Surface of Back Coat Layer of Magnetic Tape] The surface of the back coat layer of the magnetic tape was irradiated with a laser beam under the following conditions to form a groove along its longitudinal direction (FIG. 1). reference). Laser light: Argon laser light (wavelength: 515 nm, output: 40 mW) Beam diameter: 10 μm Number of concave grooves: 100 / (１ ／ inch width) Groove shape: 0.37 μm depth, 5 μm width Back coat layer It has been confirmed that, due to the formation of the above-mentioned groove, a bulge as shown in FIG.

[Removal of bulge at the edge of groove] Polish the surface of the back coat layer with a polishing tape [Abrasive: diamond (average particle diameter: 1.0 μm, 2.0% by weight based on all abrasives, Mohs hardness: 10] ) / Cr ₂ O ₃ / Vengara, trade name: MA20000, manufactured by Fuji Photo Film Co., Ltd.], and then a nonwoven fabric as a wiping material (trade name: WRP736, Kuraray Co., Ltd.) Made)
The magnetic tape according to the present invention was manufactured by removing the bulge at the edge portion of the groove by performing a wiping process using the same.

(Polishing Treatment with Polishing Tape) The back surface of the polishing tape was pressed with a pad, and the polishing tape was set at a contact angle of 80 ° and a tension of 80 g (イ ン チ inch width) to form a back coat of the polishing tape and the magnetic tape. The layers were brought into contact. Then, the magnetic tape is run at a speed in the range of 1 to 20 m / sec, while the polishing tape is run at 1.5 cm / min in a direction opposite to the running direction of the magnetic tape by a rotating roll, so that the backing is performed. The surface of the coat layer was polished.

Example 2 The same procedure as in Example 1 was carried out except that the surface of the back coat layer was polished with a polishing tape and then the surface of the back coat layer was further ground with a sapphire blade as described below. (Refer to FIG. 3).

(Grinding by Sapphire Blade) A set of four sapphire blades (width: 5 mm, length: 35 mm, tip angle: 60 degrees, manufactured by Kyocera Corp.)
The contact angle with the back coat layer of the magnetic tape was set to 80.
The surface of the back coat layer was ground by a single contact at a tape tension of 80 g (1/2 inch width).

Example 3 A magnetic recording medium according to the present invention was prepared in the same manner as in Example 1 except that the surface of the back coat layer was polished with a polishing tape and the surface of the back coat layer was further ground with a diamond wheel. A tape was made.

(Grinding by Diamond Wheel)
A diamond wheel (diameter: 70 mm, particle size: 3) in which diamond is sintered to a thickness of 2 mm around an iron core material.
No. 000, manufactured by Oriental Diamond Co., Ltd.)
pm in the direction opposite to the running direction of the back coat layer,
The surface of the backcoat layer was ground by contacting the tape once with a contact angle of 180 degrees and a tension of 80 g (1/2 inch width).

Example 4 A magnetic recording medium according to the present invention was prepared in the same manner as in Example 1 except that the surface of the back coat layer was polished with a polishing tape and then the surface of the back coat layer was further ground with a rotating blade. A tape was made.

(Grinding by Rotating Blade) Cylindrical metal (length: 35 mm, diameter: 20 mm, inner diameter of cavity:
12mm), length 35mm, cross-section 5
A rotating blade body provided with one sapphire blade having the shape of an equilateral triangular prism (mm:
65 degrees) at 1000 rpm in a direction opposite to the running direction of the back coat layer, and the tape is rotated at a contact angle of 120 degrees and a tension of 8
By contacting at 0 g (１ ／ inch width), the surface of the back coat layer was ground.

Example 5 A magnetic tape according to the present invention was manufactured in the same manner as in Example 3, except that the grinding process was performed with a diamond wheel, and then the grinding process was performed with a sapphire blade performed in Example 2. Produced.

Comparative Example 1 The procedure of Example 1 was repeated, except that the polishing treatment was not performed using a polishing tape.
A magnetic tape for comparison was produced.

[Evaluation of Performance as Magnetic Tape] Using the obtained magnetic tapes, the following performance evaluation was performed. (1) Evaluation by Dropout After Repeated Running The magnetic tapes of the examples and the comparative examples were assembled in a DLT cartridge, and were run 1000 times in an actual magnetic recording / reproducing system. Evaluation was made by measuring the number of occurrences of dropouts after running. The evaluation was performed according to the following criteria. A: Less than 10 dropouts per 100 m on all tracks B: 10 or more dropouts per 100 m on one track

(2) Evaluation by Powder Drop on the Magnetic Head or Running System after Repeated Running The magnetic tapes of the examples and comparative examples were incorporated in a DLT cartridge, and the actual magnetic recording / reproducing system was run 1000 times repeatedly. . The state of powder falling on the magnetic head or the traveling system after traveling (the state of adhesion of shavings) was visually observed and evaluated by a microscope. A: Almost no powder drop is observed. B: Powder drop is considerably observed. The above evaluation results are shown in Table 1.

[0075]

[Table 1]

From the results shown in Table 1, it was found that a groove was formed on the surface of the back coat layer by a laser beam, and then a bulge at an edge portion generated by the formation of the groove was removed to produce a film according to the present invention. In the case of a magnetic tape (Examples 1 to 5), it can be seen that even when the tape is repeatedly run in the system, the occurrence of dropout is small and powder drop hardly occurs. On the other hand, in Comparative Example 1,
Since the swelling has not been removed, the swelling is scraped off after repeated running, the debris spreads in the system, and powder drops easily occur, so the number of occurrences of dropouts is also increasing. Understand.

[0077]

According to the manufacturing method according to the present invention, the bulge generated at the edge of the groove formed in the back coat layer is removed, so that good running performance is exhibited, the occurrence of dropout is small, and the reliability is improved. High magnetic tape can be obtained. In addition, since the magnetic tape manufactured in this manner has a back coat layer suitable for a manufacturing line by high-speed conveyance, there is no manufacturing trouble and the magnetic tape can be manufactured with high productivity.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing grooves formed on a surface of a back coat layer of a magnetic tape along a longitudinal direction thereof.

FIG. 2 is a partial cross-sectional view schematically showing a bulge generated at an edge portion of a groove of a back coat layer in the cross section AA in FIG. 1;

FIG. 3 is a diagram schematically showing a preferred example of a method of removing a bulge generated at an edge portion of a groove according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 support 2 non-magnetic layer 3 magnetic layer 4 back coat layer 5a 5b groove 6a 6b swelling 10 magnetic tape 11 polishing tape 12 fixing blade 13 wiping material 14 pad (for polishing tape) 15 pad (for wiping material) 16 delivery roll 17 Feed roll 18 Rotating roll (for polishing tape) 19 Rotating roll (for wiping material) 20 Winding roll

Claims (3)

[Claims] The present invention relates to a magnetic tape having a magnetic layer containing a ferromagnetic powder and a binder on one side of a support and a back coat layer on the other side of the support. A method of manufacturing a magnetic tape, comprising: forming a groove by irradiating light; and removing a bulge generated at an edge portion of the groove. 2. The method according to claim 1, wherein the swelling is removed by using at least one means selected from a polishing tape, a fixed blade, a diamond wheel, and a rotating blade.
3. The method for producing a magnetic tape according to claim 1. 3. The method for producing a magnetic tape according to claim 1, wherein a wiping process is further performed after the swelling is removed.