JP2011150744A - Support for magnetic recording medium and tape for data storage using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a support for a magnetic recording medium which not only has excellent stability in size but also has excellent traveling durability and excellent electromagnetic conversion characteristics and is suitable as the base film of a tape in particular for data storage of a large storage capacity. <P>SOLUTION: The support includes: a laminated film wherein a polyester layer F2 (F2 layer) is laminated on the single surface of a polyester layer F1 (F1 layer); and layers (an M1 layer and an M2 layer) which are laminated on both sides thereof, each have a thickness of 5-200 nm, and are made of metal or a metallic inorganic compound. The F1 layer contains inert particles which have a polyester intrinsic viscosity of 0.55 dl/g or more, a terminal carboxyl group concentration of 30 eq/10<SP>6</SP>g or more, and the average particle size of 50-1,000 nm. The content of the inert particles is 0.001 wt.% or more larger in the F1 layer than in the F2 layer. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a support for a magnetic recording medium used as a base film such as a data storage tape.

  Supports for magnetic recording media using a biaxially oriented polyester film are used for digital video tapes, computer backup tapes (hereinafter referred to as data tapes), and the like. In recent years, in magnetic tapes, especially data tapes that perform high-density magnetic recording, the data track has become very narrow, so slight thermal and mechanical dimensional changes during tape running and storage, and data recording Due to the difference in temperature and humidity environment at the time of reading and reading, there has been a problem that causes data reproduction failure. Therefore, magnetic recording media that support high-density recording are required to have high dimensional stability against changes in the temperature and humidity environment, tape drive tension, and the like. In particular, linear recording data tapes have high dimensions in the tape width direction. Stability was required.

  Conventionally, as a material for magnetic tape, polyethylene-2,6-naphthalenedicarboxylate (hereinafter sometimes referred to as PEN) is used in addition to polyethylene terephthalate (hereinafter sometimes referred to as PET). However, the requirements for dimensional stability required for the base film of magnetic tapes for high-density recording have become increasingly severe, and that alone has been insufficient. Therefore, as a base film that can meet the above-described requirements for dimensional stability, a magnetic recording medium support in which an M layer made of a metal or a metal-based inorganic compound is provided on a polyester film has been proposed (Patent Documents 1 and 2). ).

However, although the dimensional stability is improved by providing the reinforcing film in this way, a part of the reinforcing film laminated on the polyester side having a large particle content is lifted at the time of forming the reinforcing film or subsequent storage, There was a problem that it was scraped off during running, and the running durability and electromagnetic conversion characteristics were impaired.
In addition, since such a problem becomes more significant as the magnetic layer becomes thinner, it is an important problem particularly in a data storage base film having a storage capacity of 1 TB or more.

JP 2005-346865 A JP 2006-216194 A

  An object of the present invention is to provide a support for a magnetic recording medium which is not only excellent in dimensional stability but also excellent in running durability and electromagnetic conversion characteristics, and particularly suitable as a base film for data storage having a storage capacity of 1 TB or more. There is to do.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have found that oligomers have precipitated on the surface of the polyester layer (F1 layer) on the surface side with a rough surface, and that inert particles contained therein have aggregated. Thus, it was considered that large coarse protrusions were formed on the surface of the film (M1 layer) made of a metal or a metal-based inorganic compound formed on the F1 layer side, which might have an influence. Thus, as a result of diligent research on the polyester of the F1 layer, it has been found that when a polyester satisfying a specific intrinsic viscosity and terminal carboxyl group content is obtained, a magnetic recording medium having extremely excellent running durability and electromagnetic conversion characteristics can be obtained. The present invention has been reached.

Thus, according to the present invention, a laminated polyester film in which the polyester layer F1 (F1 layer) is laminated on one side of the polyester layer F2 (F2 layer), and a metal or metal-based metal having a thickness of 5 to 200 nm laminated on both sides thereof. A support comprising an inorganic compound layer (M2 layer and M1 layer),
The F1 layer contains inert particles having an intrinsic viscosity of polyester of 0.55 dl / g or more, a terminal carboxyl group concentration of 30 eq / 10 ⁶ g or more, and an average particle size of 50 to 1000 nm. There is provided a support for a magnetic recording medium that is 0.001% or more by weight greater than the F2 layer.

According to the present invention, as a preferred embodiment of the present invention, the surface roughness (Ra2) of the exposed surface of the M2 layer laminated on the F2 layer side is 1 to 5 nm, and the M1 layer laminated on the F1 layer side The surface roughness (Ra1) of the exposed surface is greater than Ra2 and in the range of 3 to 10 nm, and the F1 and F2 layer polyesters are polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate. , M1 layer and M2 layer through F1 layer and F2 layer, respectively, and a coating layer (C layer) containing at least one binder resin selected from the group consisting of polyester resin, acrylic resin and acrylic modified polyester resin The coating layer (C layer) contains fine particles having a particle size of 5 to 50 nm, and the frequency of particles on the coating layer surface is 1,000,000. The magnetic recording medium support comprising at least one of that 1 is billion pieces / mm ² are also provided.

  Furthermore, according to the present invention, a data storage tape comprising the magnetic recording medium support of the present invention described above and a magnetic layer formed on the surface of the M2 layer side, and a magnetic layer are formed by coating. A data storage tape whose recording method is a linear recording method is also provided.

  When the support for magnetic recording medium of the present invention is used for a base film of a data storage tape having a high recording capacity such as 1 TB or more, it not only has excellent dimensional stability but also has running durability. And a data storage tape excellent in electromagnetic conversion characteristics.

Hereinafter, the present invention will be described in detail.
The support for a magnetic recording medium of the present invention includes a laminated polyester film in which a polyester layer F1 (F1 layer) is laminated on one side of a polyester layer F2 (F2 layer), and a metal having a thickness of 5 to 200 nm laminated on both sides. Or layers of metal-based inorganic compounds (M2 layer and M1 layer).

  The polyester forming the F1 layer and the F2 layer is not particularly limited as long as it is a polyester that can be formed into a film, but is preferably an aromatic polyester, and the F1 layer and the F2 layer polyester are different types of polymers. However, the same type is preferable from the viewpoint of suppressing curling and peeling.

Examples of the aromatic polyester include polyethylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, poly-1,4-cyclohexylenedimethylene terephthalate, polyethylene-2,6-naphthalate (polyethylene-2,6-naphthalenedicarboxylate). Among them, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable. Further, from the viewpoint of further improving the dimensional stability against environmental changes, the 6,6 ′-(ethylenedioxy) di-2-naphthoic acid component described in International Publication No. 2008/096612 pamphlet, 6,6 ′-( A copolymer obtained by copolymerizing a trimethylenedioxy) di-2-naphthoic acid component and a 6,6 ′-(butylenedioxy) di-2-naphthoic acid component is also preferred.

  These polyesters may be homopolyesters or copolyesters, and those known per se can be used as the copolymerization component in the case of copolyesters. The amount of copolymerization is not particularly limited as long as the effects of the present invention are not impaired, but it is preferably 20 mol% or less, more preferably 10 mol% or less, based on the number of moles of repeating units.

What is important in the present invention is that, among the two film layers (F1 layer and F2 layer) forming the laminated polyester film, the film layer having a large content of inert particles, that is, the polyester constituting the F1 layer, has an intrinsic viscosity. Is a polyester having a terminal carboxyl group concentration of 30 eq / 10 ⁶ g or more.

  When the intrinsic viscosity of the polyester of the F1 layer is less than the lower limit, bleeding out of oligomers and dropping of protrusions become severe, and troubles such as transfer to the opposite surface and loss of smoothness are likely to occur. The intrinsic viscosity of the polyester of the preferred F1 layer is 0.57 dl / g or more, particularly 0.60 dl / g or more. In order to bring the polyester of the F1 layer into such an intrinsic viscosity range, a method of increasing the intrinsic viscosity of the raw material polymer, mild melt extrusion conditions (adopting extrusion conditions that suppress polymer degradation as much as possible), etc. It is valid. The upper limit of the intrinsic viscosity in the F1 layer is not particularly limited, but is preferably 1.0 dl / g or less, more preferably 0.8 dl / g or less, from the viewpoint of film forming properties.

In the F1 layer in the present invention, the terminal carboxyl group concentration of the polymer is 30 eq / 10 ⁶ g or more as described above. The upper limit of the preferable terminal carboxyl group concentration is 60 eq / 10 ⁶ g or less. A more preferable terminal carboxyl group concentration is 34 to 60 eq / 10 ⁶ g, particularly 36 to 55 eq / 10 ⁶ g. If the terminal carboxyl group concentration is less than the lower limit, the affinity with the inert particles contained is inferior, surface defects occur due to aggregation of the inert particles, etc., and this is not possible during film production or in the process of forming the M layer. The active particles may fall off. As a result, the flatness of the surface on the side where the magnetic layer is formed is impaired. If the terminal carboxyl group concentration is excessively increased, the affinity for the inert particles is further improved, but the flatness of the surface may be impaired when the M layer is formed on the surface of the F1 layer. As described above, it is preferably ⁶⁰ eq / 10 ⁶ g or less. Examples of the range of the terminal carboxyl group concentration include a method in which the polymer is melt-held after completion of polycondensation, and polycondensation is performed under conditions where the terminal carboxyl group concentration is higher than usual.

  The F1 layer in the present invention needs to contain more than 0.001% by weight of inert particles having an average particle diameter of 50 to 1,000 nm than the F2 layer, based on the weight of each film layer. When the content of the inert particles in the F1 layer is less than the content of the F2 layer, problems such as blocking occur in the production process of the laminated polyester film and the formation process of the M layer. The average particle diameter of the inert particles is 50 to 1,000 nm, preferably 100 to 800 nm, more preferably 150 to 700 nm, and particularly preferably 200 to 600 nm. And the content of the inert particles is 0.05 to 1% by weight, preferably 0.06 to 0.8% by weight, more preferably 0.07 to 0.6% by weight, particularly with respect to the F1 layer. Preferably it is 0.08 to 0.4 weight%.

  As the inert particles to be contained in the F1 layer, known inert particles can be suitably used. For example, crosslinked silicone resin particles, crosslinked polystyrene resin particles, crosslinked acrylic resin particles, crosslinked polyester resin particles, melamine-formaldehyde resin particles. , Polyamideimide resin particles, aluminum oxide (alumina), titanium dioxide, silicon dioxide (silica), zirconium oxide, synthetic calcium carbonate, barium sulfate, diamond, kaolin or clay. Among these, inactive particles in which a large amount of hydroxyl groups are present on the surface of the particles, which can further improve the affinity by reaction with the terminal carboxyl group of the F1 layer, are preferable. Crosslinked silicone resin, crosslinked polystyrene resin, crosslinked acrylic resin, crosslinked polyester Inert particles selected from resins, aluminum oxide, titanium dioxide, silicon dioxide (silica), kaolin, and clay are preferable, and since the particle size distribution is relatively sharp and easy to form uniform protrusions, a true spherical crosslinked silicone resin is preferable. Particles such as particles, crosslinked polystyrene resin particles, and silicon dioxide are preferred. These inert particles are not limited to one type, and two or more types may be used in combination. For example, when two or more kinds of particles having different average particle diameters are used as the inert particles, the second and third particles (fine particles) having a small average particle diameter include, for example, colloidal silica, α, γ, δ, θ, and the like. Fine particles such as alumina having the following crystal form may be used.

  The F2 layer in the present invention is a layer disposed on the surface on the side on which the magnetic layer is formed. Since the F2 layer does not contain as much inert particles as the F1 layer, it is not necessary to increase the intrinsic viscosity of the polymer so much, but it is still 0.45 dl / g or more, further 0.47 dl / g or more, particularly 0.50 dl / g. It is preferable that it is more than g. When the intrinsic viscosity of the polymer in the F2 layer is less than the lower limit, bleedout of an oligomer or the like, breakage in a film winding process, and the like are likely to occur.

  As a method of setting the intrinsic viscosity of the polymer in the F2 layer to 0.45 dl / g or more, the intrinsic viscosity of the raw material polymer is set slightly higher than 0.45 dl / g, or the melt extrusion conditions are mild (polymer degradation). Can be suitably used.

  The F2 layer in the present invention may contain substantially no particles or may contain inert particles. When the F2 layer does not substantially contain inert particles, excellent electromagnetic conversion characteristics can be obtained when a magnetic recording medium is used, but inert particles in a range that does not adversely affect the bleed out of oligomers and electromagnetic conversion characteristics. When contained, the running durability can be improved. Specifically, it is preferable that 0.001 wt% or more and less than 0.05 wt% of inert particles having a volume shape factor of 0.1 to π / 6 and an average particle size of 30 to 400 nm are contained in the F2 layer. . As specific inert particles, the same inert particles as described in the above-described F1 layer are preferably exemplified.

The support for a magnetic recording medium of the present invention comprises an M1 layer (a layer formed on the surface of the F1 layer) and an M2 layer (a layer of the F2 layer) made of a metal or a metal-based inorganic compound on the surface of each of the F1 layer and the F2 layer. A layer formed on the surface). By having the M1 layer and the M2 layer, it becomes easy to achieve both a preferable range of temperature / humidity environment change and dimensional change due to load, as compared with a magnetic recording medium support made of only a laminated polyester film. Here, the metals represent so-called simple metals, metalloids, alloys, and intermetallic compounds. Specifically, for example, simple metals such as Mg, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Pd, Ag, Sn, Pt, Au, Pb, and semi-metals include C, Si, Ge, Sb, Te, etc. It may be an intercalation compound. As the metal-based inorganic compound, for example, oxides, nitrides, carbides, borides, sulfides, and the like of the above metals can be used. Specifically, for example, oxides such as CuO, ZnO, Al ₂ O ₃ , SiO ₂ , Fe ₂ O ₃ , Fe ₃ O ₄ , Ag ₂ O, TiO ₂ , MgO, SnO ₂ , ZrO ₂ and InO ₃ And nitrides such as Si ₄ N ₃ , TiN, ZrN, GaN, TaN, and AlN, and carbides such as TiC, WC, SiC, NbC, ZrC, and Fe ₃ C. Moreover, said metal type inorganic compound may be used individually, respectively, and of course, multiple types may be mixed and used. Among these, it is preferable that the metal material which comprises M1 layer and M2 layer contains aluminum and silicon from a viewpoint of economical efficiency.

  As a method for forming the M1 layer and the M2 layer, a physical vapor deposition method or a chemical vapor deposition method can be used. Physical vapor deposition methods include vacuum vapor deposition and sputtering, and vacuum vapor deposition is common. In particular, in order to make the crystal grain size of the metal layer small and precise, it is necessary to increase the kinetic energy of the deposited material. Therefore, electron beam evaporation or sputtering is preferable.

  The thickness of each of the M1 layer and the M2 layer is preferably 5 to 200 nm, more preferably 10 to 150 nm, and most preferably 20 to 100 nm. Within this range, the metal crystal grain sizes of the M1 layer and the M2 layer can be made fine, and it is preferable because conditions such as an improvement in the reinforcing effect and no adverse effect on the surface smoothness are easily satisfied. When the thickness is less than the lower limit, the crystal formation of the metal of the M1 layer and the M2 layer is incomplete, so that the effect of increasing the strength is reduced, and the effect of improving the dimensional stability of the present invention may be reduced. On the other hand, when the thickness of the M1 layer and the M2 layer exceeds the upper limit, cracks and grain boundaries are likely to be formed, the surface of the magnetic recording medium becomes rough and electromagnetic conversion characteristics deteriorate, and the M layer repeats the manufacturing process and running. In this case, peeling or dropping is likely to occur, and productivity may be reduced.

  In the support for a magnetic recording medium of the present invention, the thickness of the M1 layer and the M2 layer is desirably equal as much as possible from the viewpoint of suppressing cupping and curling when the magnetic recording tape is used. The thickness may be slightly different so as to counteract the effects of curling. From such a viewpoint, the ratio of the thicknesses of the M1 layer and the M2 layer is preferably in the range of 0.8 to 1.25.

  The magnetic recording medium support of the present invention preferably has a Young's modulus in the longitudinal direction in the range of 5 to 20 GPa. Further, the Young's modulus in the longitudinal direction of the support is preferably 5.5 to 18 GPa, particularly 6.0 to 15 GPa. If the Young's modulus in the longitudinal direction is less than the lower limit, a dimensional change in the width direction is likely to occur due to a variation in tension generated when used as a magnetic recording tape. On the other hand, if the Young's modulus in the longitudinal direction exceeds the upper limit, it is difficult to maintain the Young's modulus in the width direction within the range, and it is difficult to maintain a stable contact state with the head.

  The support for a magnetic recording medium of the present invention preferably has a Young's modulus in the width direction of 8 to 20 GPa, more preferably 9 to 18 GPa, and particularly preferably 10 to 16 GPa. If the Young's modulus in the width direction of the support is less than the lower limit, the contact state with the magnetic head becomes unstable, and the electromagnetic conversion characteristics tend to deteriorate. On the other hand, when the Young's modulus in the width direction of the support exceeds the upper limit, the Young's modulus in the longitudinal direction of the support tends to be poor.

  The ratio of the Young's modulus (YMD) in the longitudinal direction of the support to the Young's modulus (YTD) in the width direction, YMD / YTD being 0.5 to 1.0 is stable contact with the above-mentioned head and fluctuation in tension. It is preferable from the viewpoint that both can prevent deformation in the longitudinal direction. A more preferable range of YMD / YTD is 0.55 to 0.9, particularly preferably 0.6 to 0.8.

  The support for a magnetic recording medium of the present invention preferably has a temperature expansion coefficient in the width direction of less than 0 ppm / ° C. to −5 ppm / ° C. or more. A more preferable temperature expansion coefficient in the width direction of the support for a magnetic recording medium has an upper limit of −1 ppm / ° C. or lower, a lower limit of −4 ppm / ° C. or higher, and further −3 ppm / ° C. or higher. Generally, the temperature expansion coefficient of a magnetic head used in a magnetic recording apparatus is around 7 ppm / ° C. When the temperature expansion coefficient in the width direction of the support is 0 ppm / ° C. or more, the temperature expansion in the width direction of the magnetic tape is too large than the temperature expansion of the magnetic head, so that magnetic data is recorded / reproduced. When the environment changes from a low temperature to a high temperature, the tape expands relative to the magnetic head in the width direction of the tape and easily causes a reproduction failure. When the temperature expansion coefficient in the width direction of the support is smaller than −5 ppm / ° C., the temperature expansion of the film is too small than the temperature expansion of the magnetic head. In other words, the magnetic head contracts relatively to the magnetic head, which tends to cause a reproduction failure.

  Such a temperature expansion coefficient in the width direction can be adjusted by the material and thickness of the M1 layer and the M2 layer, and the temperature expansion coefficient in the width direction and the Young's modulus of the laminated polyester film provided with the M1 layer and the M2 layer. Specifically, the temperature expansion coefficient in the width direction of the laminated polyester film can be decreased by increasing the orientation of molecular chains in that direction, that is, by increasing the draw ratio. The M layer has a very large Young's modulus compared to the laminated polyester film, and has a large temperature expansion coefficient depending on the material. Therefore, the temperature expansion coefficient of the F layer used is on the negative side. In some cases, use an M layer with a large temperature expansion coefficient, or increase the thickness of the M layer, while if the temperature expansion coefficient of the F layer to be used is not so negative, use an M layer with a small temperature expansion coefficient. It is also possible to optimize by combination such as using or reducing the thickness of the M layer.

  In the support for a magnetic recording medium of the present invention, the surface roughness Ra2 of the surface of the M2 layer, that is, the surface on which the magnetic layer is formed is preferably in the range of 1 to 5 nm, more preferably 2 to 4.5 nm. When Ra2 is larger than the upper limit, it is difficult to obtain sufficient electromagnetic conversion characteristics as a high-density magnetic recording medium. On the other hand, if Ra2 is less than the lower limit, troubles of conveyance failure may occur during the conveyance process or tape traveling, protrusions on the traveling surface may be transferred, and dust may be easily damaged during traveling. Such surface roughness of the M2 layer can be controlled by the surface roughness of the F2 layer and the thickness of the M2 layer. In order to control Ra2 to a preferred range, the surface roughness of the F2 layer is preferably in the range of 1 to 7 nm, and more preferably in the range of 2 to 5 nm, and can be adjusted by the average particle size and content of the aforementioned inert particles. . The thickness of the metal layer is as described above, and the thicker the thickness, the easier the surface becomes.

  In the support for magnetic recording medium of the present invention, the surface roughness Ra1 of the surface of the M1 layer, that is, the surface on which the magnetic layer is not formed is larger than Ra2 described above, preferably 1 nm or more, 3 to 10 nm, and further 4 It is preferably in the range of ˜8 nm, particularly 5 to 7 nm. If Ra1 is larger than the upper limit, transfer may occur to the magnetic surface side during storage, and the surface roughness on the magnetic surface side may become rough. On the other hand, when Ra1 is less than the lower limit, the running property of the tape is lowered, and a running failure may occur in the drive. Such surface roughness of the M1 layer can be controlled by the surface roughness of the F1 layer and the thickness of the M1 layer. In order to control Ra1 within a preferable range, the surface roughness of the F1 layer is preferably in the range of 3 to 12 nm, more preferably 5 to 10 nm. The thickness of the metal layer is as described above, and the thicker the thickness, the easier the surface becomes.

  The total thickness of the magnetic recording medium support of the present invention is preferably 2.0 to 6 μm. More preferably, it is 2.5-5.5 micrometers, More preferably, it is 3-5 micrometers, Most preferably, it is 3.5-4.5 micrometers. If the thickness is less than the lower limit, the tape loses its elasticity and the electromagnetic conversion characteristics deteriorate. On the other hand, if the thickness exceeds the upper limit, the tape length per one tape is shortened, so that it is difficult to reduce the size and increase the capacity of the magnetic tape.

  By the way, the support for a magnetic recording medium of the present invention has at least one kind selected from the group consisting of the aforementioned M1 layer and M2 layer, respectively, F1 layer and F2 layer, polyester resin, acrylic resin, and acrylic modified polyester resin. It is preferable to laminate | stack through the coating-film layer containing binder resin. Particularly preferred are acrylic modified polyester resins. Compared to alkyd resin, phenol resin, epoxy resin, amino resin, polyurethane resin, vinyl acetate resin, vinyl chloride-vinyl acetate copolymer, etc., by selecting any of polyester resin, acrylic resin and acrylic-polyester resin, Adhesiveness to the laminated polyester film, protrusion retention, slipperiness, and the like can be further enhanced. These polyester resins, acrylic resins and acrylic-polyester resins are preferably water-soluble or water-dispersible (may contain some organic solvent) from the viewpoint of forming a coating layer. Due to the presence of such a coating layer, problems due to precipitation of oligomers appearing on the surface of the laminated polyester film, and dropping of particles in the laminated polyester film can be suppressed.

  The water-soluble or water-dispersible polyester resin will be further described. The acid component constituting the polyester resin is terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, adipic acid, sebacic acid, Dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, 2-potassium sulfoterephthalic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt, etc. Can be exemplified. Further, the hydroxy compound component constituting the polyester resin is ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanediene. Methanol, p-xylylene glycol, ethylene oxide adduct of bisphenol A, diethylene glycol, triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethylsulfonate, di Examples thereof include polyvalent hydroxy compounds such as potassium methylolpropanoate. The polyester resin can be produced from these polyvalent carboxylic acids and polyvalent hydroxy compounds by a conventional method. In particular, from the viewpoint of producing a water-based paint, a water-dispersible or water-soluble polyester resin containing a 5-sodium sulfoisophthalic acid component or a carboxylate group is preferable. Such a polyester resin may be a self-crosslinking type having a functional group in the molecule, or may be crosslinked using a curing agent such as a melamine resin or an epoxy resin.

  The water-soluble or water-dispersible acrylic resin will be described. The acrylic component used for the production of the acrylic resin is an acrylic ester (as the alcohol residue, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2- Ethylhexyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.); methacrylate ester (alcohol residue is the same as above); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl Hydroxy-containing monomers such as acrylate and 2-hydroxypropyl methacrylate; acrylamide, methacrylamide, N-methyl methacrylamide, N-methyl acrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N Amide group-containing monomers such as dimethylolacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-phenylacrylamide, etc .; N, N′-diethylaminoethyl acrylate, N, N′-diethylaminoethyl methacrylate, etc. Examples thereof include amino group-containing monomers. These monomers include sulfonic acid groups such as styrene sulfonic acid, vinyl sulfonic acid and salts thereof (for example, sodium salt, potassium salt, ammonium salt, etc.) or a salt thereof; crotonic acid, itaconic acid, acrylic acid, Monomer containing a carboxyl group such as maleic acid, fumaric acid, and salts thereof (for example, sodium salt, potassium salt, ammonium salt, etc.) or a salt thereof; monomer containing anhydride such as maleic anhydride, itaconic anhydride, etc. Other vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trisalkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, acrylonitrile, methacrylonitrile, al Ruitakon acid monoester, vinylidene chloride, vinyl acetate, may be used vinyl chloride, a monomer such as allyl glycidyl ether combination. In this case, it is preferable that components of (meth) acrylic monomers such as acrylic acid derivatives and methacrylic acid derivatives are contained in an amount of 50 mol% or more, and those containing a methyl methacrylate component are particularly preferable. Such a water-soluble or water-dispersible acrylic resin can be self-crosslinked with a functional group in the molecule, or can be crosslinked using a crosslinking agent such as a melamine resin or an epoxy compound.

  In the present invention, the water-soluble or water-dispersible acrylic-polyester resin includes an acrylic-modified polyester resin and a polyester-modified acrylic resin. Specifically, an acrylic resin component and a polyester resin component are bonded to each other in the form of a graft type or a block type. Acrylic-polyester resin, for example, adds a radical initiator to both ends of the polyester resin to polymerize the acrylic monomer, or adds a radical initiator to the side chain of the polyester resin to polymerize the acrylic monomer. For example, or by adding a hydroxyl group to the side chain of the acrylic resin and reacting with a polyester having an isocyanate group or a carboxyl group at the terminal to form a comb polymer.

  Examples of the component constituting the acrylic-polyester resin include those exemplified for the water-soluble or water-dispersible acrylic resin or the water-soluble or water-dispersible polyester resin.

  Incidentally, the coating layer interposed between the M2 layer and the F2 layer and between the M1 layer and the F1 layer preferably contains fine particles in addition to the binder resin. In the present invention, the fine particles constituting the coating layer are polystyrene, polystyrene-divinylbenzene, polymethyl methacrylate, methyl methacrylate copolymer, methyl methacrylate copolymer cross-linked product, polytetrafluoroethylene, polyvinylidene fluoride, polyacrylonitrile. Preferred examples include particles made of organic substances such as benzoguanamine and silicone, or inorganic substances such as silica, alumina, titanium dioxide, kaolin, calcium carbonate, talc and graphite. Moreover, you may use the core-shell type particle | grains of the multilayered structure by which the inside and outside of a fine particle are comprised with the material from which each property differs. The average particle size of the fine particles is preferably in the range of 3 nm to 50 nm, and more preferably 5 nm to 30 nm, from the viewpoints of runnability and flatness.

The frequency of protrusions due to fine particles on the surface of the coating layer formed on the surface of the F2 layer in the present invention (hereinafter sometimes referred to as the F2 layer-side coating layer surface) is 1,000,000 pieces / mm ² or more 1 billion / mm ² or less, further 1 million / mm ² or more 30 million / mm ² or less, it is preferable in view of runnability in particular 3 million / mm ² or more 20 million / mm ² or less.

  The support for a magnetic recording medium of the present invention is preferably used as a support for a magnetic recording tape in which a magnetic layer requiring high dimensional stability records a coating type digital signal by a linear recording method. Among these, it is suitable for high-density magnetic recording tapes for data storage such as LTO and DLT.

  Next, the method for producing a support for a magnetic recording medium of the present invention will be described first from the method for producing a laminated polyester film. First, a polyester synthesis method in the present invention includes, for example, a first reaction in which an aromatic dicarboxylic acid or an ester-forming derivative thereof and an alkylene glycol are esterified or transesterified to synthesize a polyester precursor; It consists of a second reaction in which the product is polycondensed, and a method known per se can be adopted.

  As for the method of containing inert particles, coarse particles and the like are reduced by a filter or the like, and added in the polymerization step to create a master polyester having a large particle content, and the master polyester contains particles. It is preferable to dilute with a non-polyester in order to reduce coarse protrusions due to aggregation of inert particles.

  The laminated polyester film in the present invention is a biaxially oriented film because it is used as a base film for high-density magnetic recording media such as data storage. The biaxially oriented film can be produced by extruding the polyester described above in a molten state and stretching in the biaxial direction, and a film forming method or the like can be employed.

  For example, the polyester composition for the F1 layer containing inert particles and the polyester composition for the F2 layer containing inert particles as necessary, have a melting point (Tm) to (Tm + 70) ° C. of the polyester. At the temperature of the extruder, each is melt-extruded from the extruder, and in the extrusion die or before the die (generally the former is called the multi-manifold method, the latter is called the feed block method), and is laminated to form a laminated structure with a suitable thickness ratio, After coextrusion from the die into a film, it is rapidly cooled and solidified with a cooling roll of 20 to 70 ° C. to obtain an unstretched laminated film. Thereafter, the unstretched laminated film is 2.5 to 8.0 times in a uniaxial direction (longitudinal direction or transverse direction) at a temperature of (polyester glass transition temperature (Tg) -10) to (Tg + 70) ° C. according to a conventional method. The film is stretched at a magnification of 3.0 to 7.5, and preferably in a direction perpendicular to the stretching direction (when the first-stage stretching is the longitudinal direction, the second-stage stretching is the transverse direction). (Tg) to (Tg + 70) at a temperature of 2.5 to 8.0 times, preferably 3.0 to 7.5 times. Furthermore, you may extend | stretch again in the vertical direction and / or a horizontal direction as needed. That is, it is good to perform 2 steps, 3 steps, 4 steps, or multi-stage stretching. The total stretched area ratio is usually 9 times or more, preferably 10 to 35 times, and more preferably 12 to 30 times.

  In addition, although the above-mentioned coating film layer may apply | coat and form after forming a laminated polyester film, from the point of adhesiveness or uniformity, it is preferable until the final extending | stretching of a laminated polyester film is complete | finished. Is preferably applied by applying a coating solution to an unstretched film or a uniaxially stretched film, and then drying and stretching.

  Further, the biaxially oriented film is imparted with excellent dimensional stability by heat-set crystallization at a temperature of (Tg + 70) to (Tm-10) ° C., for example, 180 to 250 ° C. in the case of a polyethylene terephthalate film. The At that time, the heat setting time is preferably 1 to 60 seconds.

  Next, a method of providing M layers (M1 layer and M2 layer) on the laminated polyester film prepared by the above-described method will be described. Here, an example of a manufacturing method using a vacuum deposition method is given.

A polyester film is set on a film running device installed in a vacuum deposition apparatus, and vacuum deposition is performed. It is preferable to deposit in a high vacuum of 1.00 × 10 ^{−5 to} 1.00 × 10 ⁻¹ Pa. It is made to travel through a cooling metal drum of 0 to 50 ° C., the deposited material is heated and evaporated, and is formed and wound on both surfaces of the film. The film running speed is preferably 10 to 200 m / min, and more preferably 50 to 150 m / min. When the traveling speed is out of the above range, it may be difficult to set the thickness of the M layer within a preferable range, or productivity may be inferior. The method of forming the M layer on both sides is preferably provided with two heating vapor deposition devices and a cooling drum in the same vacuum layer, and vapor deposition is performed on one side by one pass. Later, two passes may be performed in which an M layer is provided on the other surface again. Of course, in the case of two passes, even in the case of one pass, the order of providing the M layer is preferably the magnetic layer side and the back coat layer side because cupping can be suppressed.

  Furthermore, after producing a magnetic recording medium support by the above method, it is preferable to perform an aging treatment in order to suppress creep deformation and improve dimensional stability. The treatment temperature is preferably from 100 to 120 ° C., and the treatment time is preferably from 10 to 40 hours, more preferably from 15 to 20 hours. Among the preferable conditions for the aging treatment, it is preferable that the treatment time is long when the treatment temperature is low, and the treatment time is short when the treatment temperature is relatively high. The processing conditions related to both temperature and time can be expressed by using the peak area of enthalpy relaxation of the laminated polyester film obtained by differential scanning calorimetry (DSC) as an index, and the peak area ΔH is 0.5 J / g. ~ 1 J / g is preferred.

  The aging treatment can be performed after preparing the laminated polyester film and before providing the M layer, but in this case, the thermal contraction rate in the longitudinal direction of the laminated polyester film becomes low, and adhesion with the can in the vapor deposition process. Decreases, the surface becomes rough, and oligomers are deposited on the film surface, which easily causes a vapor deposition process trouble. For this reason, it is preferable to perform the aging treatment after providing the M layer.

  The magnetic recording tape using the magnetic recording medium support of the present invention is preferably one in which a magnetic layer, a nonmagnetic layer, a support, and a backcoat layer are laminated in this order. It is preferable that the nonmagnetic layer has a thickness of 0.9 to 1.1 μm, and the magnetic layer has a thickness of 0.05 to 0.25 μm because it is more easily flattened. Further, the back coat layer preferably has a thickness in the range of 0.3 to 0.7 [mu] m because the traveling property of the magnetic recording tape is easily expressed. In particular, from the viewpoint of the effect of the present invention, the ratio of the thickness of the coating layer (magnetic layer, nonmagnetic layer, backcoat layer, etc.) in the magnetic recording tape is in the range of 15 to 35%, and further 22 to 30%. Preferably there is. If the thickness of the coat layer is less than the lower limit, the thickness of the non-magnetic layer and the like is reduced, and the flattening improvement effect of the magnetic layer tends to be poor. On the other hand, if the upper limit is exceeded, the improvement effect of dimensional stability is easily lost.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In addition, the characteristic of the polyester in this invention, the polyester film, and the tape for data storage was measured and evaluated by the following method.

(1) Intrinsic viscosity The intrinsic viscosity of the obtained polyester is measured at o-chlorophenol at 35 ° C, and when it is difficult to dissolve uniformly with o-chlorophenol, P-chlorophenol / 1,1, It was determined by measuring at 35 ° C. using a mixed solvent of 2,2-tetrachloroethane (40/60 weight ratio).

(2) Terminal carboxyl group concentration (eq / 10 ⁶ g)
A. Measured according to Conix method. (Makromol. Chem. 26, 226 (1958))

(3) Center plane average roughness (Ra)
Measured using a non-contact type three-dimensional surface roughness meter (manufactured by ZYGO: New View 5022) at a measurement magnification of 25 times and a measurement area of 283 μm × 213 μm (= 0.0603 mm ² ), and incorporated in the roughness meter The center plane average roughness (Ra) was determined by the surface analysis software MetroPro.

(4) Average particle diameter of inert particles (4-1) Particle diameter of additive particles in film Measured using “CP-50 Centrifuggle Particle Size Analyzer” manufactured by Shimadzu Corporation did. A particle diameter “equivalent sphere diameter” corresponding to 50 mass percent is read from an integrated curve of particles of each particle diameter calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is calculated as the average particle diameter (nm). ("Particle size measurement technology", published by Nikkan Kogyo Shimbun, 1975, pages 242-247).

(4-2) Particle size of fine particles added to the coating film The particle size of the fine particles added to the coating film was measured using a light scattering method. That is, the average particle diameter of the particles at the 50% point of the total particle size determined by the trade name “NICOMP MODEL 270 SUBMICRON SIZER” manufactured by Nicomp Instruments Inc. The diameter (nm).

(5) Glass transition point and melting point The glass transition point and melting point were measured by enclosing 10 mg of a sample in an aluminum pan for measurement and using DSC (TA Instruments, trade name: Q100) at a heating rate of 20 ° C./min. It was measured.

(6) Young's modulus The obtained laminated polyester film and support were cut out with a sample width of 10 mm and a length of 15 cm, and a universal tensile tester (Toyo Baldwin) under the conditions of 100 mm between chucks, a tensile speed of 10 mm / min, and a chart speed of 500 mm / min. Product, product name: Tensilon). The Young's modulus is calculated from the tangent of the rising portion of the obtained load-elongation curve.

(7) Humidity expansion coefficient (αh)
A sample with a width of 5 mm was cut out from the obtained film and set in a TMA4000SA manufactured by Bruker AXS so that the length between chucks was 15 mm. Under a nitrogen atmosphere at 30 ° C., the humidity was 20% RH and the humidity was 80% RH. The length of the sample was measured, and the humidity expansion coefficient (αh) was calculated by the following formula. In addition, the measurement direction is the longitudinal direction of the cut out sample, the measurement was performed 5 times, and the average value was αh.
αh = (L ⁸⁰ −L ²⁰ ) / (L ²⁰ × ΔH)
Here, L ²⁰ in the above formula is a sample length (mm) when 20% RH, L ⁸⁰ is a sample length (mm) when 80% RH, ΔH: 60 (= 80-20)% RH is there.

(8) Temperature expansion coefficient (αt)
A sample with a width of 4 mm was cut out from the obtained film, set to TMA / SS6000 made by Seiko Instruments so that the length between chucks was 20 mm, and pretreated at 80 ° C. for 30 minutes in a nitrogen atmosphere (0% RH). Thereafter, the temperature was lowered to room temperature. Thereafter, the temperature was raised from 30 ° C. to 80 ° C. at 2 ° C./min, the sample length at each temperature was measured, and the temperature expansion coefficient (αt) was calculated from the following equation. In addition, the measurement direction is the longitudinal direction of the sample cut out, the measurement was performed 5 times, and the average value was used.
αt = {(L ⁶⁰ −L ⁴⁰ )} / (L ⁴⁰ × ΔT)} + 0.5 × 10 ⁻⁶
Here, L ⁴⁰ in the above formula is the sample length (mm) at 40 ° C., L ⁶⁰ is the sample length (mm) at 60 ° C., ΔT is 20 (= 60-40) ° C., 0.5 × 10 ⁻⁶ / ° C. is the temperature expansion coefficient (αt) of quartz glass.

(9) Track deviation
On the surface M2 side of the support, a magnetic coating material and a nonmagnetic lower layer coating material having the following composition were applied by an overlay coater (the upper layer was a magnetic coating material, the coating thickness was 0.1 μm, and the thickness of the nonmagnetic lower layer was appropriately changed. ), Magnetically oriented, and dried. Next, a back coat layer having the following composition was formed on the opposite surface, and then calendered at a temperature of 85 ° C. and a linear pressure of 200 kg / cm with a small test calender device (steel / nylon roll, 5 steps), then at 60 ° C. Cure for 48 hours. The original tape was slit to a 1/2 inch width, and a length of 850 m was wound as a magnetic tape on a reel.

(Composition of magnetic paint)
・ Ferromagnetic metal powder: 100 parts by weight
-Modified vinyl chloride copolymer: 10 parts by weight
・ Modified polyurethane: 10 parts by weight
・ Polyisocyanate: 5 parts by weight
・ Stearic acid: 1.5 parts by weight
・ Oleic acid: 1 part by weight
・ Carbon black: 1 part by weight
・ Alumina: 10 parts by weight
・ Methyl ethyl ketone: 75 parts by weight
・ Cyclohexanone: 75 parts by weight
・ Toluene: 75 parts by weight
(Backcoat composition)
Carbon black (average particle size 20 nm): 95 parts by weight
Carbon black (average particle size 280 nm): 10 parts by weight
・ Α alumina: 0.1 parts by weight
・ Modified polyurethane: 20 parts by weight
-Modified vinyl chloride copolymer: 30 parts by weight
・ Cyclohexanone: 200 parts by weight
・ Methyl ethyl ketone: 300 parts by weight
-Toluene: 100 parts by weight

Set the prepared magnetic tape in the tape running tester, hold it for 5 hours with the tester under the conditions 1 and 2 below, and run it under the same condition. The change in the tape width between the two conditions was defined as “track deviation” as measured by a measuring instrument. The tape width under condition 1 temperature, humidity and tension is L1 (μm), and the tape width under condition 2 temperature, humidity and tension is L2 (μm). .
Condition 1: 10 ° C., 10% RH, tension 1N,
Condition 2: 29 ° C., 80% RH, tension 0.7 N,
Track deviation = | L2-L1 | / L1 × 10 ⁶ (ppm)
The smaller the value of the track deviation, the better the error caused by the environmental change when it is used as a high density recording magnetic tape.

(10) Dropout (DO) and running durability
The magnetic tape created in (9) above is wound around an LTO cartridge and loaded into an IBM LTO4 drive (recording head is inductive head, playback head is equipped with MR head) to record 14 GB of data signal and play it back did. A signal having an amplitude (PP value) of 50% or less with respect to the average signal amplitude was detected as a missing pulse, and four or more consecutive missing pulses were detected as dropouts. In addition, dropout evaluated 1 volume of 850m length, and converted into the number per 1m. The smaller the dropout, the better the characteristics.

Further, after the magnetic tape was repeatedly run 50 times, the above measurement was performed again, and the dropout increase rate after repeated running was determined. Based on the obtained dropout and the rate of increase after running, the following criteria were used for evaluation.
(Drop out)
◎: Number of dropouts is less than 1 / m ○: Number of dropouts is 1 / m or more and less than 3 / m △: Number of dropouts is 3 / m or more and less than 5 / m ×: Number of dropouts 5 / m or more and less than 10 / m XX: The number of dropouts is 10 / m or more (running durability)
A: Dropout increase rate is less than 5%
○: Dropout increase rate is 5% or more and less than 10% △: Dropout increase rate is 10% or more and less than 25% ×: Dropout increase rate is 25% or more and less than 50% XX: Dropout increase rate is 50% or more

(11) Number of fine particles in the coating layer
The surface of the coating layer is observed with a scanning electron microscope at a magnification of 50,000 times for 10 fields or more, and the number of protrusions based on fine particles contained in the coating layer is measured per 1 mm ^2. The frequency of fine protrusions in the film layer was determined.

[Example 1]
0.04% by weight of crosslinked polystyrene particles (crosslinked PSt) having an average particle size of 0.3 μm and 0.06% by weight of crosslinked polystyrene particles (crosslinked PSt) having an average particle size of 0.1 μm, A polyethylene terephthalate resin (PET) composition (resin 1) having an intrinsic viscosity of 0.69 dl / g and a terminal carboxyl group concentration of 33 eq / t, a crosslinked polystyrene particle having an average particle diameter of 0.1 μm Polyethylene terephthalate resin (PET) composition (resin 2) containing 0.03% by weight of crosslinked PSt and having an intrinsic viscosity of 0.58 dl / g is prepared, and these are prepared in respective film layers (F1 layer and F2 layer). ) Is melted at 300 ° C., joined at a rectangular joining block, and then melted from the die at a temperature of 20 ° C. during rotation. Extruded into a sheet on retirement drum was unstretched laminated film. At this time, the resin 1 was used for the F1 layer, the resin 2 was used for the F2 layer, and the F1 layer side was the side in contact with the cooling drum. Next, this unstretched laminated film was heated to 100 ° C. using a preheating roll and an infrared heater, and stretched at a magnification of 3.6 times in the machine direction between low-speed and high-speed rolls to obtain a longitudinally stretched film. Subsequently, a coating liquid having the following composition was applied to both surfaces of the longitudinally stretched film so that the film thickness after drying was 10 nm. Thereafter, the longitudinally stretched film coated with the coating solution is supplied to a stenter, stretched at a magnification of 5.5 times in the transverse direction while raising the temperature from 120 ° C to 170 ° C, and further heat set at 210 ° C for 5 seconds. The film was relaxed by 2% in the width direction at 170 ° C. and then cooled to obtain a biaxially stretched laminated film having a thickness of 4.4 μm.

Composition of coating liquid (solid dispersion with an aqueous dispersion of 1% by weight, the following weight% is based on the weight of the solid)
Binder (acrylic modified polyester (trade name: SH-551A, manufactured by Takamatsu Yushi Co., Ltd.)): 83% by weight
Fine particles (crosslinked polystyrene particles (average particle size 30 nm, manufactured by JSR Corporation, trade name: SX8721)): 7% by weight
-Surfactant (manufactured by Sanyo Chemical Co., Ltd., trade name: NAROACTY N-70): 10% by weight

M1 layer and M2 layer were provided on both sides of the biaxially stretched laminated film prepared by the above method by the following method. First, the obtained biaxially stretched laminated film is set in a film traveling device installed in a vacuum deposition apparatus, and after making a high vacuum of 1.00 × 10 ⁻³ Pa, through a cooling metal drum at 20 ° C. And let it run. An aluminum target is heated and evaporated with an electron beam, and the oxygen gas introduced into the vapor deposition apparatus is oxidized so that the element ratio of aluminum to oxygen in the M layer is 1: 1.2. By vapor deposition, an M layer made of an alumina film was formed. An M layer was also formed on the opposite surface by vapor-depositing in the same manner while the roll once wound after vapor deposition on one side was run so that the vapor deposition surface was reversed. The order of vapor deposition was performed in the order of M2 layer and M1 layer, and the thickness of each M layer was set to 70 nm by adjusting the electron beam intensity and the traveling speed.
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

[Example 2]
Resin 1 was changed to a PET composition having an intrinsic viscosity of 0.73 dl / g and a terminal carboxyl group concentration of 28 eq / t, and the thicknesses of the M1 layer and the M2 layer were changed to the thicknesses shown in Table 1, respectively. The same operation as in Example 1 was repeated.
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

[Example 3]
The resin 1 was changed to a PET composition having an intrinsic viscosity of 0.65 dl / g and a terminal carboxyl group concentration of 38 eq / t, and the thicknesses of the M1 layer and the M2 layer were changed to the thicknesses shown in Table 1, respectively. The same operation as in Example 1 was repeated.
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

[Example 4]
Reduce the proportion of fine particles in the coating liquid to the number of protrusions shown in Table 1, change the thickness of the coating layer as shown in Table 1, and further use the target used to form the M1 layer and M2 layer. The same operation as in Example 1 was repeated except that aluminum was changed to silicon dioxide.
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

[Example 5]
Resin 1 was changed to polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.65 dl / g and a terminal carboxyl group concentration of 38 eq / t, and resin 2 was changed to polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.58 dl / g. Changed the temperature of the cooling drum to 60 ° C, the longitudinal stretching temperature to 125 ° C, the longitudinal stretching ratio to 4.5 times, the initial transverse stretching temperature to 140 ° C, the final transverse stretching temperature to 180 ° C, and the transverse stretching ratio. Was changed to 6 times, and the same operation as in Example 1 was repeated except that the target used for forming the M1 layer and the M2 layer was changed from aluminum to silicon dioxide.
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

[Comparative Example 1]
The same operation as in Example 1 was repeated except that the intrinsic viscosity of the resin 1 was changed to 0.58 dl / g.
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

[Comparative Example 2]
The same operation as in Example 1 was repeated except that the melt retention time in the polymerization step was shortened and that the resin 1 was changed to a PET composition having an intrinsic viscosity of 0.72 dl / g and a terminal carboxyl concentration of 20 eq / t. .
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

[Comparative Example 3]
The same operation as in Comparative Example 1 was repeated except that the coating layer was not provided.
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

[Comparative Example 4]
The same operation as in Example 1 was repeated except that the thickness of the M1 layer was changed to 40 nm and the M2 layer was not provided.
Table 1 shows the characteristics of the obtained magnetic recording medium support and the magnetic tape using the same.

In Table 1, MD means the film forming direction, TD means the width direction, AlO _1.2 means incompletely oxidized alumina having an elemental cost of aluminum and oxygen of 1: 1.2, and SiO ₂ means silicon dioxide.

Claims (7)

A laminated polyester film in which a polyester layer F2 (F2 layer) is laminated on one side of a polyester layer F1 (F1 layer), and a metal or metal inorganic compound layer (M1 layer) having a thickness of 5 to 200 nm laminated on both sides And M2 layer),
The F1 layer contains inert particles having an intrinsic viscosity of polyester of 0.55 dl / g or more, a terminal carboxyl group concentration of 30 eq / 10 ⁶ g or more, and an average particle size of 50 to 1000 nm. A support for a magnetic recording medium, characterized by being 0.001% by weight or more than the F2 layer.   The surface roughness (Ra2) of the exposed surface of the M2 layer laminated on the F2 layer side is 1 to 5 nm, and the surface roughness (Ra1) of the exposed surface of the M1 layer laminated on the F1 layer side is larger than Ra2. The support for a magnetic recording medium according to claim 1, which is in the range of 3 to 10 nm.   The support for a magnetic recording medium according to claim 1, wherein the polyester of the F1 layer and the F2 layer is polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate.   The M1 layer and the M2 layer are laminated on the F1 layer and the F2 layer, respectively, through a coating layer containing at least one binder resin selected from the group consisting of a polyester resin, an acrylic resin, and an acrylic modified polyester resin. The support for a magnetic recording medium according to claim 1. The support for a magnetic recording medium according to claim 4, wherein the coating layer contains fine particles having a particle size of 5 to 50 nm, and the frequency of particles on the surface of the coating layer is 1 million to 100 million particles / mm ² .   A data storage tape comprising the magnetic recording medium support according to any one of claims 1 to 5 and a magnetic layer formed on the surface of the M2 layer side.   7. The data storage tape according to claim 6, wherein the magnetic layer is formed by coating, and the recording method is a linear recording method.