JP5332436B2 - Support for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a support for a high density magnetic recording medium which allows stable film-forming without a surface defect or a tear in a vapor deposition process, in particular, to provide a support which, when the substrate is used for a magnetic recording medium, reduces dimensional change due to environmental change and also improves close contact with a head by protruding a tape to a magnetic layer to exhibit excellent electromagnetic conversion characteristics. <P>SOLUTION: The support for magnetic recording medium includes a polyester film and layers (M layers) including metallic oxide formed on the both sides of the polyester film. The concentration of oxygen in the M layers is 45-70 at.%. T/T<SB>M</SB>value is 46-250, and the surface resistivity of an Mb layer is 1.0&times;10<SP>9</SP>to 1.0&times;10<SP>14</SP>&Omega; and the surface resistivity of an Ma layer is smaller than that of the Mb layer, where the thickness of the polyester film is represented by T and the sum of the thickness of the M layer (Ma layer) provided on one side (side A) and the M layer (Mb layer) provided on the other side (side B) is represented by T<SB>M</SB>. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a support used for a magnetic recording medium such as a magnetic tape, and a magnetic recording medium provided with a magnetic layer on the support.

  Biaxially stretched polyester film is used for various applications because of its excellent thermal properties, dimensional stability, mechanical properties, and ease of control of surface morphology, and is particularly useful as a support for magnetic recording media. Are known. In recent years, magnetic recording media such as magnetic tapes have been required to have higher density in order to reduce the weight, size, and capacity of substrates. In order to achieve high density recording, it is useful to shorten the recording wavelength, reduce the recording track, and reduce the thickness of the magnetic tape. However, with the narrowing of recording tracks and the thinning of magnetic tapes, there is a problem that recording tracks are liable to shift due to deformation due to heat during tape running and changes in temperature and humidity during tape storage. Therefore, there is an increasing demand for improvement in characteristics such as dimensional stability in the usage environment and storage environment of the tape.

  From this viewpoint, a support for a magnetic recording medium has been developed in which a polyester film using polyethylene terephthalate, polyethylene naphthalate, or the like is strengthened using a stretching technique. Furthermore, in addition to the stretching technique, a method of providing a reinforcing layer such as a metal on one or both sides of a polyester film for the purpose of improving dimensional stability against temperature and humidity as disclosed in the following documents (Patent Document) 1, Patent Document 2, and Patent Document 4) are disclosed.

  However, when the reinforcing layer is made of metal, it is highly conductive and has a property of reflecting light because of metal bonding, so that light is not transmitted due to the influence of the metal reinforcing film in the film thickness control when the magnetic layer is applied. There is a problem, and the film thickness control tends to be difficult. As a result, the film thickness of the magnetic layer varies and the magnetic tape tends to have a high error rate. In addition, since the electrical conductivity is high, current flows in the magnetic tape due to static electricity or leakage current, which may cause the magnetic head to short-circuit or break down. Further, the metal is weaker than the oxide and has a small effect of suppressing the expansion / contraction of the polyester film.

  On the other hand, when the reinforcing layer is an oxide or other compound, it has a property of being hard but not ductile due to ionic bonds. Therefore, a crack (crack) is produced by tension. In addition, since the oxide has a hygroscopic property, the effect of improving the dimensional stability against humidity is small, and the dimensional stability may be deteriorated by the hygroscopic expansion of the reinforcing layer itself.

  In addition, when a reinforcing layer such as a metal is provided on one or both sides of the polyester film, the difference in physical properties such as the expansion amount with respect to temperature and humidity between the reinforcing layer and the polyester film, and the heat received by the polyester film in the forming process of the reinforcing layer. Since the internal distortion of the film increases due to stress such as winding tension or the like, there is also a problem that when processed into a magnetic tape, bending (capping) occurs in the width direction, and the head contact deteriorates.

  As a method for improving cupping, for example, a method of applying a heat treatment to a magnetic tape (Patent Document 3) or a method of controlling the thickness of the reinforcing layer such as a nonmagnetic metal or metal oxide layer on both sides of a polyester film ( Patent document 4) is disclosed.

However, the method disclosed in Patent Document 3 cannot improve the dimensional stability in the usage environment and storage environment of the tape. Moreover, in the said patent document 4, since a metal film is formed previously from the surface which provides a magnetic layer, there exists a problem that a surface is easy to generate | occur | produce a damage | wound.
JP-A-7-272247 JP 2003-30818 A JP 2001-184635 A JP 2006-277920 A

  The object of the present invention is to solve the above-mentioned problems and to enable stable film formation without surface defects or tears due to heat loss in the vapor deposition process, and in particular, there is little dimensional change due to environmental changes when used as a magnetic recording medium. An object of the present invention is to provide a support for a high-density magnetic recording medium that has improved adhesion to the head and excellent electromagnetic conversion characteristics by curving the tape convexly toward the magnetic layer.

In order to achieve the above object, the present invention provides a magnetic recording medium in which a layer (M layer) containing a metal-based oxide is provided on both sides of a polyester film, and the curvature of the magnetic tape defined below is less than 1 mm. The oxygen concentration of the M layer is 45 to 70 at. The thickness of the polyester film is T, the thickness of the M layer (Ma layer) provided on one surface (surface A) and the thickness of the M layer (Mb layer) provided on the other surface (surface B) when the sum of the thicknesses was TM, the value of T / T _M is 71-250, a surface resistivity of Ma layer ^{1.0 × 10 3 ~1.0 × 10 8} Ω, the surface of the Mb layer It is characterized by a support for a magnetic recording medium having a resistivity of 1.0 × 10 ^{9 to} 1.0 × 10 ¹⁴ Ω and a surface resistivity of the Ma layer being smaller than that of the Mb layer.
Curvature when using magnetic tape:
When the magnetic tape is cut out to a length of 20 mm and placed on a flat glass plate so that the magnetic layer is on the top, the magnetic tape is convexly curved toward the magnetic layer, and the measurement is performed in the width direction of the magnetic tape. Distance between the center and the glass plate

  The support for magnetic recording medium of the present invention is capable of stable film formation without surface defects or tearing due to heat loss in the vapor deposition process, and in particular, when it is used as a magnetic recording medium, there is little dimensional change due to environmental changes, and the tape Can be curved convexly toward the magnetic layer, thereby improving the adhesion to the head and providing a support for a high-density magnetic recording medium having excellent electromagnetic conversion characteristics.

  In the support of the present invention, a layer containing a metal oxide (hereinafter referred to as M layer) is provided on both sides of a polyester film, and the oxygen concentration of this M layer is 45 to 70 at. %. Examples of the metal oxide include Cu, Zn, Al, Si, Fe, Ag, Ti, Mg, Sn, Zr, In, Cr, Mn, V, Ni, Mo, Ce, Ga, Hf, Nb, and Ta. The oxygen concentration (oxygen atom content) in the average composition when the composition analysis is performed is 10 at. The thing which is more than%. At. % Is an abbreviation of atomic%.

  The metal oxide may contain different metal components on both surfaces, and may contain a mixture of a plurality of types of metal components, but more preferably, the surface resistivity is controlled. For ease of use, it is better to contain the same kind of metal component on both surfaces. Among these, from the viewpoint of dimensional stability, productivity, and environmental properties, it is preferable that at least one of aluminum, copper, zinc, silver, and silicon elements is included, and more preferably, the aluminum element is a main component. preferable. However, it is preferable that the metal component constituting the metal-based oxide does not contain a magnetic metal because it affects reading and writing when the magnetic recording medium is used. The magnetic metal here represents Fe, Co, or Ni.

  The oxygen concentration of the M layer of the present invention is 45 to 70 at. %. It is preferable that the oxygen concentration is within the range of the present invention because a support having extremely good dimensional stability due to environmental changes can be obtained. When the oxygen concentration of the M layer is larger than the range of the present invention, an M layer having a hard but brittle and non-ductile property is formed, and due to the tension or stress applied to the support in the vapor deposition process or the magnetic recording medium manufacturing process, Cracks may occur in the M layer and the dimensional stability may be significantly reduced. In addition, if the oxygen concentration of the M layer is smaller than the range of the present invention, it becomes difficult to make the surface resistivity of each M layer within the range of the present invention, or the total light transmittance is decreased. It may be difficult to control the film thickness when applying the layer.

  The M layer of the present invention is formed on both sides from the viewpoints of dimensional stability and bending with respect to environmental changes. When formed on only one side, the dimensional stability when used as a magnetic recording medium may not be satisfied, and the curvature in the width direction may be excessively increased to deteriorate the electromagnetic conversion characteristics. .

  As a method for forming the M layer, physical vapor deposition or chemical vapor deposition can be used. There are two types of physical vapor deposition methods for polyester films: vacuum vapor deposition and sputtering. The vacuum vapor deposition method is particularly preferred because of easy control of the surface resistivity. Among them, the electron beam vapor deposition method is preferred because of the rigidity of the film quality. Is particularly preferred. Moreover, it is important for the order of vapor deposition to perform vapor deposition from the Mb layer mentioned later from a viewpoint of the damage | wound of the surface of M layer, or the countermeasure against the heat loss at the time of vapor deposition.

  The thickness (T) of the polyester film of the present invention can be appropriately determined according to the application, but usually 3 to 7 μm is preferable for the magnetic recording medium application. Especially, in the case of a high density magnetic recording medium use, 3-6 micrometers is preferable, More preferably, it is 4-6 micrometers. When the thickness is smaller than 3 μm, the tape becomes dull, so that the contact with the magnetic head is deteriorated and the electromagnetic conversion characteristics may be deteriorated. When the thickness is larger than 7 μm, the tape length per one tape is shortened, which makes it difficult to reduce the size and increase the capacity of the magnetic tape.

When the sum of the thickness of the M layer (Ma layer) provided on one surface (surface A) and the thickness of the M layer (Mb layer) provided on the other surface (surface B) is T _M , The thickness ratio (T / T _M ) of the support is preferably 46 to 250, more preferably 46 to 200. If the thickness ratio is smaller than the range of the present application, the curve becomes too large, the contact property with the magnetic head becomes poor, and the electromagnetic conversion characteristics tend to deteriorate. On the contrary, if it is larger than the range of the present invention, the dimensional stability may not be improved and the high temperature crack durability tends to be lowered.

The surface resistivity of the Mb layer of the present invention is 1.0 × 10 ^{9 to} 1.0 × 10 ¹⁴ Ω, and the surface resistivity of the Ma layer needs to be smaller than that of the Mb layer. By making the surface resistivity of the Mb layer formed first within the range of the present invention, the adhesion between the Mb layer and the cooling can is not lowered, so the cooling efficiency is not lowered, and the Ma layer to be formed next. This is preferable because surface defects (wrinkles) and film breakage due to heat loss during the vapor deposition process do not occur.

  The heat loss referred to here is the wrinkle of the base film that occurs during vapor deposition. Efficiently releases the latent heat of vapor deposition particles and radiation heat from the vapor deposition source to the cooling can side due to poor adhesion between the film and the cooling can. When the film cannot be formed, the temperature rise of the film itself cannot be partially suppressed, the part softens and causes wrinkles, and in a severe case, the film is torn.

From the viewpoint of a deterrent effect on the curvature generated in the magnetic tape manufacturing process, the surface resistivity of the Mb layer is preferably 1.0 × 10 ^{10 to} 1.0 × 10 ¹³ Ω. When the surface resistivity of the Mb layer is within the range of the present application, the adhesion between the Mb layer and the cooling can is improved, and it becomes possible to suppress the thermal history and thermal shrinkage of the base film when forming the Ma layer. .

  In general, the surface resistivity is affected by the abundance of metal elements having metal bonds on the surface of the M layer. The surface resistivity can be controlled by adjusting the oxygen gas introduction amount at the time of vapor deposition, the position of the oxygen gas supply nozzle, the evaporation amount of the metal component, and the film conveyance speed. Although the influence of the evaporation amount of the metal is particularly great, it can be basically handled by controlling the evaporation amount of the metal and the introduction amount of the oxygen gas. If the amount of metal evaporation is constant, if the amount of oxygen gas introduced is reduced, the proportion of metal atoms having metal bonds increases, and the surface resistivity decreases. Conversely, if the amount of oxygen gas introduced is increased, the proportion of metal atoms having a metal bond decreases, and the surface resistivity increases. If the amount of introduced oxygen gas is constant, the surface resistivity increases when the metal evaporation amount is decreased, and the surface resistivity decreases when the metal evaporation amount is increased. At this time, from the viewpoint of uniform thickness of the M layer, it is preferable to supply the oxygen gas in the same direction as the flow direction of the metal vapor. It is also preferable to provide oxygen gas supply nozzles on both the upstream side (unwinding side) and the downstream side (winding side) in the film transport direction to control the amount of oxygen gas introduced.

  If the amount of oxygen introduced on the unwinding side is larger than the amount of oxygen introduced on the winding side, the oxygen concentration in the vicinity of the interface between the film and the M layer becomes relatively higher than that on the surface side of the M layer, and oxidation is efficiently promoted. The desired oxygen concentration and surface resistivity can be obtained.

  Regarding the oxygen gas introduction amount, preferably, the oxygen gas introduction amount between the unwinding side and the winding side of the oxygen gas supply nozzle is a ratio of 4: 6 to 8: 2, and further a ratio of 5: 5 to 7: 3. Is effective in adjusting the oxygen concentration and surface resistivity of the M layer, and is a method of supplying oxygen gas near the cooling can by increasing the height of the oxygen gas supply nozzle when forming the Mb layer. Is also effective in controlling the surface resistivity within the scope of the present application. Even if the oxygen concentration in the M layer satisfies the desired range, the oxidation reaction is controlled by the introduction direction and angle of the oxygen gas, the height of the supply nozzle, and the gas introduction ratio of both nozzles. Metal bonding can be controlled, and the surface resistance value can be appropriately controlled.

  Control of oxygen concentration and surface resistivity both depend on the supply of oxygen. However, in this application, since the surface resistivity is considered to be affected by the metal-metal bond in the extreme surface layer, it is problematic to focus on the site different from the oxygen concentration, that is, the oxygen concentration meaning the oxidation state of the entire M layer. It has come to be solved.

The surface resistivity of the Ma layer of the present invention needs to be smaller than that of the Mb layer from the viewpoint of controlling the curvature generated in the magnetic tape manufacturing process so as to be curved in a convex shape toward the magnetic layer side, that is, the Ma layer side. Yes, preferably 1.0 × 10 ^{3 to} 1.0 × 10 ⁸ Ω, and more preferably 1.0 × 10 ^{4 to} 1.0 × 10 ⁷ Ω.

  In order to set the surface resistivity of the Ma layer and the oxygen concentration of the layer within the range of the present invention, the oxygen gas introduction amount can be appropriately adjusted on the unwinding side and the winding side. In particular, in order to make the surface resistivity of the Ma layer smaller than the surface resistivity of the Mb layer and within a specific range, the ratio of the amount of oxygen gas introduced between the unwinding side and the winding side is 5: 5 to 5: 5. A ratio of 9: 1, particularly 6: 4 to 8: 2, is effective. Furthermore, the method of reducing the height of the oxygen gas supply nozzle when forming the Ma layer and supplying oxygen gas in the vicinity of the crucible is also effective in controlling the surface resistivity within the scope of the present application.

By setting the surface resistivity of the Ma layer and the Mb layer within the range of the present invention, the temperature expansion coefficient is also specified in proportion to the abundance of the metal element having a metal bond in each M layer. As a result, since the Ma layer having a low surface resistivity has a higher proportion of metal elements than the Mb layer, the temperature expansion coefficient of the Ma layer is larger than the expansion coefficient of the Mb layer .

  In particular, since the support of the present invention has a larger thermal expansion coefficient of the Ma layer than that of the Mb layer, the Ma layer side on which the magnetic layer is applied can be controlled to be convexly curved. As a result, it is considered that a magnetic recording medium having good electromagnetic conversion characteristics can be obtained because adhesion between the magnetic tape and the magnetic head is increased.

  The Young's modulus of both M layers of the present invention is preferably such that the Young's modulus of the Ma layer is smaller than the Young's modulus of the Mb layer from the viewpoint of promoting the convex curvature of the Ma layer side. The Young's modulus of the M layer is not limited because it is determined by the type of metal material constituting the M layer and the thickness of the M layer. For example, when the metal material constituting the M layer is aluminum, the Young's modulus of the Ma layer is not limited. Is preferably 50 to 120 GPa, and the Mb layer is preferably 80 to 200 GPa. The Young's modulus of the Ma layer is obtained from the following prediction formula of the composite Young's modulus presented by Nielsen. Similarly, the Young's modulus of the Mb layer is obtained from the following prediction formula.

Here, E: Young's modulus of the support [GPa], _{E F:} Young's modulus of the polyester film _{[GPa], E M a:} Ma layer Young's modulus of [GPa], T: thickness of the polyester film [μm], T _M a: the thickness of Ma layer [[mu] m].

  The thermal expansion coefficients of both M layers of the present invention are preferably such that the thermal expansion coefficient of the Ma layer is larger than that of the Mb layer from the viewpoint of promoting the convex curvature of the Ma layer side. The thermal expansion coefficient of the M layer is not limited because it is determined by the type of metal material constituting the M layer and the thickness of the M layer. For example, when the metal material constituting the M layer is aluminum, the heat of the Ma layer The expansion coefficient is 1 to 20 ppm / ° C., and the Mb layer is preferably −10 to 0 ppm / ° C. The thermal expansion coefficient of the Ma layer is obtained from the following thermal expansion coefficient prediction formula of the composite film presented by Nielsen. Similarly, the thermal expansion coefficient of the Mb layer is obtained from the following prediction formula.

Here, α: coefficient of thermal expansion of the support [ppm / ° C.], α _F : coefficient of expansion of the polyester film [ppm / ° C.] E _F : Young's modulus [GPa] of the polyester film, φ _F : relative to the total thickness of the support the thickness of the polyester film ratio, alpha _Ma: expansion coefficient Ma layer _{[ppm / ℃], E M} a: Ma layer Young's modulus of [GPa], φ _Ma: is a thickness ratio of Ma layer to the total support.

The sum of the thicknesses of the Ma layer and the Mb layer (T _M ) of the support of the present invention is preferably 20 to 100 nm. More preferably, it is 30-100 nm, More preferably, it is 40-90 nm. T _M is thin and dimensional stability in the width direction is likely to deteriorate when a magnetic tape than the range of the present invention. Further, the T _M is thicker than the range of the present invention, the bending control force decreases that occur in the magnetic tape manufacturing process, there are cases where contact with the magnetic head is deteriorated, resulting a good electromagnetic characteristics It may disappear.

  The thickness of the Mb layer of the present invention is preferably set to 50 nm or less from the viewpoint of promoting the convex curvature of the Ma layer side and improving the contact property with the magnetic head. When the thickness of the Mb layer exceeds the range of the present application, the Ma layer side may not be curved in a convex shape, or conversely, the Mb layer side may be curved in a convex shape.

  The thickness of the Ma layer of the present invention is not particularly limited, but if it is set to 50 nm or more, the surface resistance is low, that is, the high temperature crack durability due to the synergistic effect of the ductility effect by the Ma layer having a low degree of oxidation and the reinforcement effect by the thickness of the Ma layer It is more preferable because of good properties.

  Examples of the polyester constituting the polyester film used for the support of the present invention include polymers having an acid component such as aromatic dicarboxylic acid, alicyclic dicarboxylic acid or aliphatic dicarboxylic acid or a diol component as a structural unit (polymerization unit). It is preferable that

  Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid. Acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and the like can be used. Among them, terephthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid can be preferably used. . As the alicyclic dicarboxylic acid component, for example, cyclohexane dicarboxylic acid or the like can be used. As the aliphatic dicarboxylic acid component, for example, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like can be used. These acid components may be used alone or in combination of two or more.

  Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2′-bis (4 '-Β-hydroxyethoxyphenyl) propane and the like can be used. Among them, ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, diethylene glycol and the like can be used, and particularly preferably. , Ethylene grease It can be used Lumpur like. These diol components may be used alone or in combination of two or more.

  The polyester may be copolymerized with a monofunctional compound such as lauryl alcohol or phenyl isocyanate, trimellitic acid, pyromellitic acid, glycerol, pentaerythritol, 2,4-dioxybenzoic acid, etc. Trifunctional compounds and the like may be copolymerized within a range in which the polymer is substantially linear without excessive branching or crosslinking. In addition to the acid component and diol component, the present invention includes aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid, m-hydroxybenzoic acid, and 2,6-hydroxynaphthoic acid, p-aminophenol, and p-aminobenzoic acid. As long as the effect is not impaired, the copolymerization can be further carried out.

  The polyester used for the support of the present invention is preferably polyethylene terephthalate or polyethylene naphthalate from the viewpoints of strength, heat resistance, and productivity. Further, these copolymers and modified products may be used, and polymer alloys with other thermoplastic resins may be used. In particular, a polymer alloy of a polyester resin and a polyimide resin is preferable because the heat resistance (glass transition temperature) can be controlled by the mixing ratio, and the polymer can be designed according to the use conditions.

  The polyester film used for the support of the present invention preferably has a laminated structure of two or more layers. In particular, for use in magnetic recording media, the front and back surfaces have smooth surfaces to obtain excellent electromagnetic conversion characteristics, transport during film formation and processing, and the running and durability of magnetic tape. In order to impart, a surface form having a relatively rough surface roughness is required. Also in this sense, the film preferably has a laminated structure of two or more layers.

  The polyester film used for the support of the present invention is not particularly limited in order to impart easy slipping, abrasion resistance, scratch resistance and the like to the film surface, but inorganic particles and organic particles can be used. Of course, one kind of particles or two or more kinds of particles may be used in combination. Specific types include, for example, clay, mica, titanium oxide, calcium carbonate, wet silica, dry silica, colloidal silica, calcium phosphate, barium sulfate, alumina silicate, kaolin, talc, montmorillonite, alumina, zirconia and the like. Organic particles containing particles, acrylic acid, styrene resin, silicone, imide and the like as constituent components may be added.

  The average particle diameter of the inert particles contained is 0.01 to 0.8 μm in order to obtain the desired surface roughness Ra of both M layers and to obtain excellent electromagnetic conversion characteristics as a magnetic recording medium. In particular, it is preferable to have a particle size of 0.02 to 0.3 μm. In addition, when two or more types of inert particles having different particle diameters are contained, it is preferable that the respective average particle diameters (measurement methods are described later) are all within the above range.

  The content of the inert particles is 5% by mass or less, preferably 0.05 to 3% by mass as the whole film.

  The support of the present invention is various additives within the range not inhibiting the present invention, such as compatibilizers, plasticizers, weathering agents, antioxidants, heat stabilizers, lubricants, antistatic agents, whitening agents, and coloring. Agents, conductive agents, crystal nucleating agents, ultraviolet absorbers, flame retardants, flame retardant aids, pigments, dyes, and the like may be added.

  The support of the present invention may be subjected to any processing such as heat treatment, microwave heating, molding, surface treatment, laminating, coating, printing, embossing, etching, and ultraviolet irradiation as necessary.

  The total light transmittance of the support of the present invention is preferably 20 to 78%. If it is higher than 78%, since the oxidation has progressed too much, the M layer becomes hard and brittle, and it tends to cause cracks due to tension and curvature. If the total light transmittance is less than 20%, the thickness control tends to be impossible when forming the magnetic layer. The lower limit of the total light transmittance is more preferably 25%. On the other hand, the upper limit is more preferably 70%, and still more preferably 60%.

  In the support of the present invention, the surface roughness Ra of the Ma layer is preferably 0.3 nm to 10 nm. Ra is preferably 0.5 nm to 8 nm. When Ra is smaller than 0.3 nm, the friction coefficient with a transport roll or the like becomes large in film production, processing steps, etc., which may cause a process trouble. Further, when used as a magnetic tape, the friction with the magnetic head is increased, and the magnetic tape characteristics are liable to deteriorate. When the surface roughness Ra is larger than 10 nm, when used as a magnetic tape for high-density recording, the magnetic surface side becomes rough, and the electromagnetic conversion characteristics tend to deteriorate.

  The surface roughness Ra of the Mb layer of the support of the present invention is preferably 5 to 20 nm. When Ra is smaller than 5 nm, a friction coefficient with a conveyance roll etc. becomes large in film production, a processing process, etc., and process troubles easily occur. Further, when used as a magnetic tape, the friction with the guide roll increases, and the tape running performance and running durability tend to be lowered. Moreover, when surface roughness Ra is larger than 20 nm, when storing as a film roll or a pancake, the surface protrusion tends to be transferred to the surface on the opposite side, and the electromagnetic conversion characteristics tend to deteriorate. Furthermore, in the vapor deposition process, heat loss may occur due to a significant decrease in the adhesion between the Mb layer and the cooling can during the deposition of the second Ma layer. As a result, film tearing is likely to occur. From the viewpoint of process stability and electromagnetic conversion characteristics, the surface roughness Ra of the Mb layer is preferably 5 to 15 nm.

  The support of the present invention preferably has a Young's modulus in the width direction of 7 to 12 GPa. More preferably, it is 7-12 GPa. When the pressure is less than 7 GPa, the film extends in the longitudinal direction due to the tension in the longitudinal direction in the tape drive, and contracts in the width direction due to the elongation deformation, so that the problem of recording track deviation is likely to occur. If it is greater than 12 GPa, tape breakage may occur easily. In addition, the Young's modulus in the longitudinal direction tends to be insufficient.

  The support of the present invention preferably has a Young's modulus in the longitudinal direction of 7 to 12 GPa. More preferably, it is 7.5-10GPa. If it is less than 7 GPa, the longitudinal tension in the tape drive causes the tape to extend in the longitudinal direction, and at the same time, the tape contracts in the width direction, resulting in a deterioration in dimensional stability in the width direction. Is likely to occur. If it is greater than 12 GPa, the tape is liable to break, and the Young's modulus in the width direction tends to be insufficient.

  In the present invention, the longitudinal direction of the support refers to the same direction as the longitudinal direction of the polyester film (also referred to as MD direction), and generally refers to the film forming direction of the film. Moreover, the width direction of a support body points out the same direction as the width direction of a polyester film (it is also called TD direction), and means the direction orthogonal to the said longitudinal direction.

  In the method for producing a polyester film used for the support of the present invention, polyester pellets are preferably discharged from a die by melt extrusion using an extruder, and the discharged polymer is cooled and solidified to form a sheet. At that time, it is preferable to filter the polymer with a fiber-sintered stainless steel filter because it can remove unmelted material in the polymer and obtain a film without coarse protrusions.

  As the stretching method of the polyester film used for the support of the present invention, the longitudinal direction and the width direction are determined using a sequential biaxial stretching method such as stretching in the width direction after stretching in the longitudinal direction, a simultaneous biaxial tenter or the like. A simultaneous biaxial stretching method in which stretching is performed simultaneously, and a method in which a sequential biaxial stretching method and a simultaneous biaxial stretching method are combined are included.

  Hereinafter, the method for producing the support of the present invention will be described as an example in which polyethylene terephthalate (PET) is used as polyester. Of course, the present application is not limited to PET, and when other polymers such as a polymer having a high glass transition temperature or a high melting point are used, appropriate adjustments such as extrusion and stretching at a temperature higher than the following temperatures may be made. It is possible to produce a support.

  First, a method for producing polyester will be described using polyethylene terephthalate as an example.

  The polyethylene terephthalate used in the present invention is produced by any one of the following processes. (1) Using terephthalic acid and ethylene glycol as raw materials, a low molecular weight polyethylene terephthalate or oligomer is obtained by direct esterification reaction, and then a polymer is obtained by polycondensation reaction using antimony trioxide or titanium compound as a catalyst. Process (2) A process in which dimethyl terephthalate and ethylene glycol are used as raw materials, a low molecular weight product is obtained by transesterification, and then a polymer is obtained by polycondensation reaction using antimony trioxide or a titanium compound as a catalyst. Here, the reaction proceeds even without a catalyst, but the transesterification usually proceeds using a compound such as manganese, calcium, magnesium, zinc, lithium, titanium as a catalyst, and the transesterification reaction is carried out. After the completion of the reaction, a phosphorus compound may be added for the purpose of inactivating the catalyst used in the reaction.

  Moreover, when making the polyester which comprises a film contain an inert particle, the method to which an inert particle is disperse | distributed in the form of a slurry in ethylene glycol in a predetermined ratio, and adding this ethylene glycol at the time of superposition | polymerization is preferable. When adding inert particles, for example, water sol or alcohol sol particles obtained at the time of synthesis of the inert particles are added without drying once, the dispersibility of the particles is good. It is also effective to mix an aqueous slurry of inert particles directly with PET pellets and knead them into PET using a vented biaxial kneading extruder. As a method for adjusting the content of the inert particles, a master pellet of a high concentration of inert particles is prepared by the above method, and this is diluted with PET that does not substantially contain inert particles during film formation. A method for adjusting the content of the active particles is effective.

  The obtained PET pellets were dried under reduced pressure at 180 ° C. for 3 hours or more, and then supplied to an extruder heated at 280 to 320 ° C. under a nitrogen stream or under reduced pressure so as not to lower the intrinsic viscosity. The film is extruded from a die and cooled on a casting roll to obtain an unstretched film. At this time, it is preferable to use various types of filters, for example, filters made of materials such as sintered metal, porous ceramics, sand, and wire mesh, in order to remove foreign substances and altered polymers. Moreover, you may provide a gear pump as needed in order to improve fixed_quantity | feed_rate supply property. When laminating films, a plurality of different polymers are melt laminated using two or more extruders and manifolds or merging blocks.

  Next, this unstretched film is guided to a simultaneous biaxial stretching tenter, for example, and biaxial stretching is simultaneously performed in the longitudinal and width directions. The stretching speed is preferably 100 to 20,000% / min in both the longitudinal and width directions. More preferably, it is 500-10,000% / min, More preferably, it is 2,000-7,000% / min. When the stretching speed is less than 100% / min, the film is exposed to heat for a long time. In particular, the edge portion is crystallized to cause stretching breakage, and the film-forming property is lowered. However, the Young's modulus of the produced film may be lowered. On the other hand, if it is higher than 20,000% / min, entanglement between molecules is likely to occur at the time of stretching, and the stretchability may be lowered, making it difficult to stretch at a high magnification.

  The stretching temperature varies depending on the type of polymer used, but can be determined using the glass transition temperature Tg of the unstretched film as a guide. The temperature in the first stretching step in each of the longitudinal direction and the width direction is preferably in the range of Tg to Tg + 30 ° C, more preferably Tg + 5 ° C to Tg + 20 ° C. When the stretching temperature is lower than the above range, film tearing frequently occurs and the productivity is lowered, or the redrawability is lowered, and it may be difficult to stably stretch at a high magnification. In addition, when the stretching temperature is higher than the above range, particularly the edge portion is crystallized to cause stretching breakage, the film forming property is lowered, the molecular orientation does not advance sufficiently, and the Young's modulus of the produced film is lowered. There are things to do.

  And when the manufacturing process of a polyester film includes multistage stretching, that is, a re-stretching process, the first stage stretching temperature is as described above, but the second stage stretching temperature is preferably Tg + 40 ° C. to Tg + 120 ° C., more preferably. Is Tg + 60 ° C. to Tg + 100 ° C. When the stretching temperature is out of the above range, the film may be broken frequently due to insufficient heat amount or excessive crystallization, resulting in a decrease in productivity or a sufficient decrease in orientation, resulting in a decrease in strength. is there.

  On the other hand, the stretching ratio varies depending on the type of polymer used and the stretching temperature, and also in the case of multistage stretching, but the total area stretching ratio (total longitudinal stretching ratio × total transverse stretching ratio) is in the range of 20 to 40 times. It is preferable to do so. More preferably, it is 25 to 35 times. The total draw ratio in one direction of the longitudinal direction and the width direction is preferably 2.5 to 8 times, and more preferably 3 to 7 times. If the draw ratio is smaller than the above range, uneven drawing or the like may occur and the processability of the film may be reduced. Moreover, when a draw ratio is larger than the said range, stretch breaks occur frequently and productivity may fall.

  When extending | stretching by multiple steps | paragraphs regarding each direction, 2.5 to 5 times is preferable and, as for the draw ratio in each of the longitudinal direction of the 1st step, and the width direction, More preferably, it is 3 to 4 times. Moreover, the preferable area draw ratio in the first stage is 8 to 16 times, and more preferably 9 to 14 times. These stretch ratio values are particularly suitable when the simultaneous biaxial stretching method is employed, but can also be applied to the sequential biaxial stretching method.

  Moreover, 1.05-2.5 times are preferable and, as for the draw ratio in one direction in the case of performing redrawing, More preferably, it is 1.2-1.8 times. The area stretching ratio for re-stretching is preferably 1.4 to 4 times, more preferably 1.9 to 3 times.

  Subsequently, this stretched film is heat-treated under tension or while relaxing in the width direction. As for the heat treatment conditions, the heat treatment temperature is preferably 150 ° C. to 230 ° C., and the heat treatment time is preferably in the range of 0.5 to 10 seconds. It is preferable to perform the heat treatment process in two or more stages. In particular, the first stage heat treatment temperature is preferably set to 180 to 230 ° C., more preferably 190 to 220 ° C. The temperature is set to be lower than that in the first stage, preferably 150 to 200 ° C, more preferably 150 to 180 ° C. Further, it is more preferable that only the second heat treatment step is relaxed at a relaxation rate of 1 to 5% in the width direction. According to the multi-step heat treatment process described above, molecular chain relaxation effectively proceeds while increasing dimensional stability against changes in Young's modulus and temperature / humidity, so that it is stored under a load that is an effect of the present invention. It becomes easy to improve the storage stability showing the dimensional change when doing.

  Thereafter, the film edge is removed and wound on a roll. And it is preferable to heat-process with a hot air oven etc. in the state (roll film) which wound the film around the core. The heat treatment of the roll film is performed in two or more stages. The atmospheric temperature of the heat treatment can be determined based on the glass transition temperature (Tg) of the biaxially stretched film, and is in the range of (Tg-80) to (Tg-30) ° C., more preferably (Tg-75). ) To (Tg-35) ° C., more preferably (Tg-70) to (Tg-40) ° C. The preferable treatment time is in the range of 10 to 360 hours, more preferably in the range of 24 to 240 hours, and still more preferably 72 to 168 hours. It is preferable that the total time of the heat treatment of the roll film performed in multiple stages is within the above range.

  Next, a method for providing a layer (M layer) containing a metal-based oxide on both sides of the PET film obtained as described above will be described.

  In order to form the M layer on the surface of the PET film, for example, a vacuum deposition apparatus as shown in FIG. 2 is used. In this vacuum vapor deposition apparatus 11, the polyester film 14 travels inside the vacuum chamber 12 from the unwinding roll 13 to the winding roll 18 through the guide roll 15, the cooling drum 16, and the like. At that time, the metal material 19 in the crucible 23 installed in the vapor deposition chamber 17 is heated and evaporated by the electron beam 21 irradiated from the electron gun 20, and the oxygen supply nozzle 24a (unwinding side oxygen supply) is supplied from the oxygen gas cylinder 22. Nozzle) and 24b (winding side oxygen supply nozzle) introduce oxygen gas and deposit it on the polyester film on the cooling drum 16 while oxidizing the evaporated metal. The vapor deposition part is appropriately controlled by the mask 26. Since the present invention requires M layers on both sides, after depositing a metal-based oxide on one surface (first side), the single-side vapor-deposited polyester film is removed from the take-up roll section 18 and set on the unwind roll section 13. Similarly, a metal-based oxide is deposited on the opposite surface (second surface). In this vacuum deposition apparatus 11, the oxygen supply nozzle is arranged before and after the crucible 23 as a deposition source, that is, the unwinding side oxygen supply nozzle 24a and the unwinding side oxygen supply nozzle 24b so that the surface resistivity can be easily controlled. Are arranged on the unwinding side and the winding side, respectively, and the oxygen supply nozzle has a mechanism in which the flow rate is controlled by the gas flow rate control device 25 and the height can be adjusted appropriately. Further, the oxygen supply nozzle has a blowout port so that the metal vapor and the oxygen gas flow in the same direction. At this time, when the angle of the nozzle is adjusted so that the angle θ formed by the rectilinear direction 27 of the oxygen gas injected from the outlet and the tangent 28 having the lower vertex A of the cooling can as a contact is 45 ° to 80 °, A dense and homogeneous M layer can be formed without disturbing the scattering of metal vapor by oxygen gas (see FIG. 3). The height of the oxygen gas supply nozzle is such that the closer the distance to the film is, the more the film loses heat due to the effect of rapid oxidation reaction heat. Therefore, the linear distance 29 connecting the oxygen outlet and the lower vertex of the cooling can 29 Adjusts the height of the nozzle to a position that does not become 1/5 or less of the distance 30 between the cooling can and the crucible disposed immediately below.

Here, the inside of the vacuum chamber 12 is preferably decompressed to 1.0 × 10 ^{−8 to} 1.0 × 10 ² Pa. Further, in order to form a dense M layer with few deteriorated portions, it is preferable to reduce the pressure to 1.0 × 10 ^{−6 to} 1.0 × 10 ⁻¹ Pa.

  The cooling drum 16 preferably has a surface temperature in the range of −40 to −15 ° C. More preferably, it is −30 to −20 ° C. Further, at the time of vapor deposition of the second Ma layer, the surface temperature of the cooling drum is preferably −40 to −30 ° C. from the viewpoint of curvature control.

  The electron beam 21 is preferably performed with an output of 2.0 to 8.0 kW. More preferably, it is 3.0-7.0 kW, More preferably, it exists in the range of 4.0-6.0 kW. Note that the metal material 19 may be heated and evaporated by directly heating the crucible.

  Oxygen gas is introduced into the vacuum chamber 12 at a flow rate of 0.5 to 10 L / min using the gas flow rate control device 25. It is 0.5 to 4.5 L / min when forming the Ma layer, and 4.5 to 10 L / min when forming the Mb layer. If the oxygen introduction amount on the unwinding side is larger than the oxygen introduction amount on the winding side, the oxygen concentration in the vicinity of the interface between the film and the M layer becomes relatively higher than that on the surface side of the M layer, and oxidation is efficiently performed. The desired oxygen concentration and surface resistivity can be obtained.

  As for the conveyance speed of the polyester film in the inside of the vacuum chamber 12, 20-200 m / min is preferable. More preferably, it is 30-100 m / min, More preferably, it is 40-80 m / min. When the conveyance speed is slower than 20 m / min, it is necessary to considerably reduce the evaporation amount of the metal in order to control the M layer thickness as described above. Therefore, since it is necessary to reduce the amount of oxygen gas introduced, it becomes very difficult to control the degree of oxidation. When the conveyance speed is higher than 200 m / min, the contact time with the cooling drum is shortened, so that tears and wrinkles are generated due to heat, and productivity tends to be reduced. In addition, the metal vapor and the oxygen gas are likely to be formed in an insufficient reaction state, and the degree of oxidation may be difficult to control.

  The conveying tension of the polyester film inside the vacuum chamber 12 is preferably 50 to 150 N / m. More preferably, it is 70-120 N / m, More preferably, it is 80-100 N / m. However, it is preferable that the conveyance tension is weaker than that of the first surface during the evaporation of the second surface. The transport tension on the second surface is preferably 5 to 30 N / m lower than the transport tension on the first surface, more preferably 7 to 25 N / m, and still more preferably 10 to 20 N / m. This is because the polyester film loses the force to shrink due to heat load during the vapor deposition of the first side, and when it is run with the same transport tension as the first side during the vapor deposition of the second side, tears and wrinkles due to heat occur, This is because productivity tends to be impaired. Furthermore, when the surface roughness of the polyester film varies depending on the surface, it is preferable to deposit the rough surface first. This is to improve the adhesion to the cooling drum during the second-side vapor deposition. Vapor deposition may be performed one side at a time, or both sides may be performed in one step.

  In order to stabilize the M layer and improve the denseness after the deposition, it is preferable to return the inside of the vacuum deposition apparatus to normal pressure and to rewind the wound film. In particular, it is preferable to perform humidification rewinding because the chance of contact between the water vapor and the M layer is increased. Aging is preferably performed at a temperature of 20 to 50 ° C. for 1 to 3 days, and more preferably, aging is performed in an environment with a humidity of 60% or more and no condensation.

As a method for manufacturing the magnetic recording medium, for example, the method described below can be used. First, a support for magnetic recording media slit to a width of 0.1 to 3 m is transported at a tension of 10 to 30 kg / m, and a magnetic coating and a nonmagnetic coating are applied on the magnetic layer surface side of the support with an extrusion coater ( The upper layer is made of a magnetic paint, the coating thickness is 0.1 μm, and the thickness of the non-magnetic lower layer is appropriately changed), magnetically oriented, and dried at a drying temperature of 100 ° C. Next, a back coat is applied to the non-magnetic layer surface side, calendered at a temperature of 70 to 100 ° C. and a linear pressure of 100 to 300 kg / cm with a small test calender (steel / nylon roll, 5 stages), and then wound up. The tape material is slit into a 1/2 inch width to produce a pancake, and then a specific length of the pancake is incorporated into a cassette to obtain a cassette tape type magnetic recording medium. Here, examples of the composition of the magnetic paint include the following compositions, but are not limited thereto.
(Composition of magnetic paint)
Ferromagnetic metal powder: 100 parts by mass Modified vinyl chloride copolymer: 10 parts by mass Modified polyurethane: 10 parts by mass Polyisocyanate: 5 parts by mass Stearic acid: 1.5 parts by mass Oleic acid: 1 part by mass Carbon black: 1 part by mass α-alumina: 10 parts by mass Methyl ethyl ketone: 75 parts by mass Cyclohexanone: 75 parts by mass Toluene: 75 parts by mass (composition of nonmagnetic paint)
-Modified polyurethane: 10 parts by mass-Modified vinyl chloride copolymer: 10 parts by weight-Methyl ethyl ketone: 75 parts by mass-Cyclohexanone: 75 parts by mass-Toluene: 75 parts by mass-Polyisocyanate: 5 parts by mass-Stearic acid: 1.5 Part by mass-Oleic acid: 1 part by mass (backcoat composition)
Carbon black (average particle size 20 nm): 95 parts by mass Carbon black (average particle size 280 nm): 10 parts by mass α-alumina: 0.1 parts by mass Modified polyurethane: 20 parts by mass Modified vinyl chloride copolymer: 30 parts by mass-Cyclohexanone: 200 parts by mass-Methyl ethyl ketone: 300 parts by mass-Toluene: 100 parts by mass In addition, specific applications of the magnetic recording medium include, for example, data recording applications, specifically computer data backup applications, It can be suitably used for recording digital images such as video.

(Methods for measuring physical properties and methods for evaluating effects)
The characteristic value measurement method and effect evaluation method in the present invention are as follows.

(1) Composition analysis of M layer (oxygen concentration)
The composition analysis in the depth direction is performed under the following conditions. The carbon concentration is 50 at. The depth exceeding% is defined as the interface between the M layer and the polyester film, the surface layer to the interface are divided equally into 5 parts, and the composition analysis is performed using the center point of each section as the measurement point. An average value is calculated from the composition of each measurement point obtained, and is defined as the average composition in the present invention.

Measuring apparatus: X-ray photoelectron spectrometer Quantera-SXM manufactured by PHI, USA Excitation X-ray: monochromatic AlKα1,2 line (1486.6 eV)
X-ray diameter: 100 [μm]
Photoelectron escape angle: 45 °
Raster area: 2 x 2 [mm]
Ar ion etching: 2.0 [kV] 1.5 × 10 ⁻⁷ [Torr]
Sputtering speed: 3.68 nm / min (Si ₂ O conversion value)
Data processing: 9-point smoothing
Element information is obtained from the peak binding energy value, and the composition is quantified (at.%) Using the area ratio of each peak.

(2) Thickness of film and M layer The cross-sectional observation is performed under the following conditions by changing the place and performing 10 fields of view, and the average value of the obtained thickness [nm] is calculated to be the film thickness and the thickness of the M layer [nm]. .

Measuring device: Transmission electron microscope (TEM) Hitachi H-7100FA type Measurement conditions: Acceleration voltage 100 kV
Measurement magnification: 200,000 times Sample adjustment: Ultrathin film section method Observation plane: TD-ZD cross section (TD: width direction, ZD: thickness direction)
Number of measurements: 3 points per field of view and 10 fields of view are measured.

(3) Surface resistivity Since the measurable device varies depending on the range of surface resistivity, first, the support is measured by the method of i), and the sample whose surface resistivity is too low to be measured is measured according to ii). Measure by method. The average value of five measurement results is defined as the surface resistivity in the present invention.
i) High resistivity measurement Based on JIS-C2151 (1990), it measures using the following measuring apparatus.
・ Measuring device: Digital ultra-high resistance / micro ammeter R8340 manufactured by Advantest Corporation ・ Applied voltage: 100V
・ Application time: 10 seconds ・ Measurement unit: Ω
・ Measurement environment: Temperature 23 ℃ Humidity 65% RH
-Number of measurements: Measure 5 times.
ii) Low resistivity measurement Measured using the following measuring device in accordance with JIS-K7194 (1994).
・ Measurement device: Lorester EP MCP-T360, manufactured by Mitsubishi Chemical ・ Measurement environment: temperature 23 ° C., humidity 65% RH
-Number of measurements: Measure 5 times.

(4) Total light transmittance Measured using the following measuring device in accordance with JIS-K7105 (1981). The transmittance at five points is measured in the longitudinal direction with respect to the center of the support, and the average value of the measurement results is defined as the total light transmittance in the present invention.

Measuring device: Nippon Denshoku Industries Co., Ltd. Turbidimeter NDH5000
Light source: Halogen lamp 12V, 50W
Light receiving characteristics: 395 to 745 nm
Measurement environment: Temperature 23 ° C Humidity 65% RH
Number of measurements: Measure 5 times.

(5) Surface roughness Ra
Using an atomic force microscope, 20 fields of view were measured at different locations. About the obtained image, three-dimensional surface roughness was computed by Roughness Analysis of Off-Line function, and centerline average roughness Ra was measured. The conditions are as follows.

Measuring device: NanoScope III AFM (manufactured by Digital Instruments)
Cantilever: Silicon single crystal Scanning mode: Tapping mode Scanning range: 30μm
Scanning speed: 0.5Hz
Flatten Auto: Order 3
(6) Young's modulus The Young's modulus was measured using an Instron type tensile tester according to the method defined in ASTM-D882 (1997). The measurement was performed under the following conditions.

Measuring device: Orientec Co., Ltd. film strong elongation automatic measuring device
“Tensilon AMF / RTA-100”
Sample size: width 10 mm x test length 100 mm,
Tensile speed: 200 mm / min Measurement environment: temperature 23 ° C., humidity 65% RH
(7) Young's modulus of Ma layer The Young's modulus of each M layer was calculated | required from the following formula, respectively.

Here, E: Young's modulus of the support [GPa], _{E F:} Young's modulus of the polyester film _{[GPa], E M a:} Ma layer Young's modulus of [GPa], T: thickness of the polyester film [μm], T _M a: the thickness of Ma layer [[mu] m].

The support member has M layer is formed on both sides, by 30 minutes immersion product in 1N hydrochloric acid The Young's modulus was calculated E _F of the peeled polyester film both surfaces of the M layer. Separately, in order to obtain a support from which only the Mb layer has been peeled off, a cotton swab is soaked with hydrofluoric acid, and only the Mb layer is peeled off while taking care not to apply force to the support. The Young's modulus is measured according to the description, and this is substituted into the above equation as the Young's modulus E of the support to measure the Young's modulus of the Ma layer. In the same manner, the Young's modulus of the opposite Mb layer can also be measured.

    At this time, the direction of the sample size may be either the longitudinal direction or the width direction, but it is unified so that it does not differ between the support and the polyester film, and further, when the Young's modulus of the Ma layer is different in the longitudinal direction and the width direction, The larger value is taken as the Young's modulus of the Ma layer.

(8) Temperature expansion coefficient Pre-treatment is performed under the following conditions, and the temperature is increased again from 23 ° C. to 50 ° C. at the above temperature increase rate, and the change amount ΔL [μm] of the film from 30 ° C. to 40 ° C. at that time And the temperature expansion coefficient [ppm / ° C.] of the support was calculated from the following formula.

Measuring device: TMA TM-3000 manufactured by Vacuum Riko Co., Ltd., heating controller TA-1500
Sample size: width 4mm x test length 15mm
Load: 0.5g
Sample pretreatment temperature: 23 ° C. → 50 ° C. → 23 ° C.
Temperature increase rate: 1 ° C / min Measurement temperature: 23 ° C → 50 ° C
Temperature expansion coefficient [ppm / ° C.] = 10 ⁵ × {(ΔL / (15 × 10 ³ )) / (40-30)}
(9) Temperature expansion coefficient of Ma layer The temperature expansion coefficient of each M layer was calculated | required from the following formula, respectively.

Here, α: coefficient of thermal expansion of the support [ppm / ° C.], α _F : coefficient of expansion of the polyester film [ppm / ° C.] E _F : Young's modulus [GPa] of the polyester film, φ _F : relative to the total thickness of the support the thickness of the polyester film ratio, alpha _Ma: expansion coefficient Ma layer _{[ppm / ℃], E M} a: Ma layer Young's modulus of [GPa], φ _Ma: is a thickness ratio of Ma layer to the total support.

The support having M layers on both sides was immersed in 1N hydrochloric acid for 30 minutes to peel off the M layers on both sides, and then the temperature expansion coefficient was measured as described in (8) above. It was used as a thermal expansion coefficient alpha _F polyester film. Subsequently, with a cotton swab dipped in hydrochloric acid, the support from which only the Mb layer has been peeled off, taking care not to apply force to the support, the temperature expansion coefficient α of the support is determined by the method (8) above. Asked. The temperature expansion coefficient of the Ma layer is measured by substituting it into the above equations. In the same way, the temperature expansion coefficient of the opposite Mb layer can also be measured.

    At this time, the direction of the sample size may be either the longitudinal direction or the width direction, but it is standardized so that it does not differ between the support and the polyester film. Further, when the thermal expansion coefficient of the Ma layer is different between the longitudinal direction and the width direction, The larger value is taken as the coefficient of thermal expansion coefficient of the Ma layer.

(10) Average particle diameter (dispersion diameter)
The cross section of the film is observed at a magnification of 10,000 using a transmission electron microscope (TEM). At this time, when particles having a size of 1 cm or less can be confirmed on the photograph, the TEM observation magnification is further observed at a high magnification of 50,000 to 100,000. The section thickness of TEM is about 100 nm, and the measurement is performed at 100 fields or more at different locations. The average of the equivalent circle equivalent diameters measured was defined as the average particle diameter of the inert particles.

  When two or more kinds of particles having different particle diameters are present in the film, the number distribution of the equivalent circle equivalent diameter is a distribution having two or more peaks. In this case, each peak value is defined as the average particle diameter of each particle.

(11) Particle content 1 g of polymer was put into 200 ml of 1N-KOH methanol solution and heated to reflux to dissolve the polymer. 200 ml of water was added to the solution after dissolution, and the liquid was then centrifuged to settle the particles, and the supernatant was removed. Water was further added to the particles, and washing and centrifugation were repeated twice. The particles thus obtained were dried, and the content of the particles was calculated by measuring the mass of the particles.

Equipment: Bruker DRX-500 manufactured by Bruker
Solvent: HFIP / deuterated chloroform Observation frequency: 499.8 MHz
Standard: TMS (tetramethylsilane) (0 ppm)
Measurement temperature: 30 ° C
Observation width: 10 KHz
Data point: 64K
acquisition time: 4.952 seconds
pulse delay time: 3.048 seconds Integration count: 256 (12) Glass transition temperature (Tg) and polyester melting temperature (Tm)
Specific heat was measured with the following equipment and conditions, and determined according to JIS K7121 (1987).

Apparatus: Temperature modulation DSC manufactured by TA Instrument
Measurement condition:
Heating temperature: 270-570K (RCS cooling method)
Temperature calibration: Melting point of high purity indium and tin Temperature modulation amplitude: ± 1K
Temperature modulation period: 60 seconds Temperature rising step: 5K
Sample weight: 5mg
Sample container: Aluminum open container (22 mg)
Reference container: Aluminum open container (18mg)
The glass transition temperature was calculated by the following formula.

Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2
(13) Dimension measurement in the width direction A support slit to a width of 1 m is transported at a tension of 20 kg / m, and a magnetic coating and a non-magnetic coating having the following composition are applied on the Ma layer of the support by multilayer coating using an extrusion coater ( The upper layer is made of magnetic paint, the coating thickness is 0.2 μm, the lower layer is made of non-magnetic paint and the coating thickness is 0.9 μm), magnetically oriented, and dried at a drying temperature of 100 ° C. Next, after applying a back coat having the following composition on the Mb layer on the opposite side, it was 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) and then wound up. . The original tape is slit into a 1/2 inch (1.27 cm) width to make a pancake. Next, a length of 200 m from this pancake is incorporated into a cassette to form a cassette tape.
(Composition of magnetic paint)
Ferromagnetic metal powder: 100 parts by mass [Fe: Co: Ni: Al: Y: Ca = 70: 24: 1: 2: 2: 1 (mass ratio)]
[Long axis length: 0.09 μm, axial ratio: 6, coercive force: 153 kA / m (1,922 Oe), saturation magnetization: 146 Am ² / kg (146 emu / g), BET specific surface area: 53 m ² / g, X-ray Particle size: 15 nm]
-Modified vinyl chloride copolymer (binder): 10 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
Modified polyurethane (binder): 10 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
Polyisocyanate (curing agent): 5 parts by mass (Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd.)
2-ethylhexyl oleate (lubricant): 1.5 parts by mass Palmitic acid (lubricant): 1 part by mass Carbon black (antistatic agent): 1 part by mass (average primary particle size: 0.018 μm)
Alumina (abrasive): 10 parts by mass (α alumina, average particle size: 0.18 μm)
-Methyl ethyl ketone: 75 parts by mass-Cyclohexanone: 75 parts by mass-Toluene: 75 parts by mass (composition of non-magnetic paint)
Modified polyurethane: 10 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
-Modified vinyl chloride copolymer: 10 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
-Methyl ethyl ketone: 75 parts by mass-Cyclohexanone: 75 parts by mass-Toluene: 75 parts by mass-Polyisocyanate: 5 parts by mass (Coronate L (trade name) manufactured by Nippon Polyurethane Industry Co., Ltd.)
・ 2-ethylhexyl oleate (lubricant): 1.5 parts by mass Palmitic acid (lubricant): 1 part by mass (backcoat composition)
Carbon black: 95 parts by mass (antistatic agent, average primary particle size 0.018 μm)
Carbon black: 10 parts by mass (antistatic agent, average primary particle size 0.3 μm)
Alumina: 0.1 part by mass (α alumina, average particle size: 0.18 μm)
Modified polyurethane: 20 parts by mass (number average molecular weight: 25,000, sulfonic acid group content: 1.2 × 10 ⁻⁴ equivalent / g, glass transition point: 45 ° C.)
-Modified vinyl chloride copolymer: 30 parts by mass (average polymerization degree: 280, epoxy group content: 3.1% by mass, sulfonic acid group content: 8 × 10 ⁻⁵ equivalent / g)
• Cyclohexanone: 200 parts by mass • Methyl ethyl ketone: 300 parts by mass • Toluene: 100 parts by mass Take out the tape from the cassette tape cartridge, put the sheet width measuring device prepared as shown in FIG. Measure. The sheet width measuring device shown in FIG. 1 is a device that measures the width dimension using a laser, and fixes the magnetic tape 9 to the load detector 3 while setting it on the free rolls 5 to 8, and the end portion A weight 4 serving as a load is hung on. When the laser beam 10 is oscillated on the magnetic tape 9, the laser beam 10 oscillated linearly in the width direction from the laser oscillator 1 is blocked only at the portion of the magnetic tape 9 and enters the light receiving unit 2. The width is measured as the width of the magnetic tape. The average value of the three measurement results is defined as the width in the present invention.

Measuring device: Sheet width measuring device manufactured by Ayaha Engineering Co., Ltd. Laser oscillator 1, light receiving unit 2: Laser dimension measuring device LS-5040 manufactured by Keyence Corporation
Load detector 3: Load cell CBE1-10K manufactured by NMB
Constant temperature and humidity chamber: SE-25VL-A manufactured by Kato Co., Ltd.
Load 4: Weight (longitudinal direction)
Sample size: width 1/2 inch x length 250 mm
Holding time: 5 hours Number of measurements: Measured 3 times.
(Width dimension change rate)
The width dimension (l _A , l _B ) is measured under two conditions, and the dimensional change rate is calculated by the following equation. The dimensional stability is evaluated according to the following criteria. X is rejected.

A condition: 10 ° C, 10% RH, tension 1.0N
B condition: 29 ° C, 80% RH, tension 0.6N
Width change rate [ppm] = 10 ⁶ × ((l _B -l _A ) / l _A )
Excellent: width dimensional change rate of 0 [ppm] or more and less than 500 [ppm] Good: width dimensional change rate of 500 [ppm] or more and less than 700 [ppm] Poor: width dimensional change rate of 700 [ppm] or more (14) Heat Loss Visible light was applied from the back surface (Mb layer side) of the support, and the Ma layer side was visually observed and evaluated according to the following judgment.

    Excellent: No surface defects due to heat loss during vapor deposition.

    Good: There is a surface defect having a length of 10 mm or less (no surface defect having a length exceeding 10 mm).

    Defect: There is a surface defect whose length exceeds 10 mm.

(15) Curving (cupping)
i) Curvature of the support The one end of the support cut to 150 mm in the longitudinal direction and 50 mm in the width direction is affixed to the paper with cellophane tape so that the Mb layer side is up. Judging.

    Excellent: Curves (curls) convexly toward the Ma layer.

    Good: Does not curl.

    Defect: Curved (curled) convex toward the Mb layer.

ii) Curvature of magnetic tape The magnetic tape prepared in (13) above is cut out by 20 mm in length, and is left on a flat glass plate so that the top is a magnetic layer. The gap with the glass surface was measured 10 times, and the average value was evaluated according to the following judgment.

    Excellent: Curved convex toward the magnetic layer, and the gap between the magnetic tape and the glass plate is less than 1 mm.

    Good: No gaps are observed (not convex or concave).

    Defect: It is convexly curved toward the magnetic layer, and the gap between the magnetic tape and the glass plate is 1 mm or more.

          Alternatively, the magnetic layer side is curved in a concave shape.

(16) Electromagnetic conversion characteristics (electric characteristics)
The cassette tape produced in the above (13) was evaluated by recording and reproducing (recording wavelength 0.55 μm) in an environment of 23 ° C. and 50% RH using a commercially available IBM LTO drive 3580-L11. In addition, based on the C / N value of Comparative Example 1, the determination was made according to the following, and those having a circle or higher were determined to have good adhesion to the head.

◎: 1.0 dB or more ○: 0 dB or more to less than 1.0 dB △: -1.0 dB or more to less than 0 dB ×: less than −1.0 dB (17) High temperature crack durability Tensile tester After pulling with a specific elongation amount, the surface state is observed with a differential interference microscope. The conditions are as follows. In addition, it is judged that Δ or ○ is a substantially usable film.

Tensile tester Measuring device: Automatic measuring device "UCT-100" made by Orientec Co., Ltd.
Sample size: width 10 mm x test length 100 mm,
Tensile speed: 10% / min Tensile tension: 1N and 2N (Tension tester is stopped when the specified tension is reached)
Measurement environment: Temperature 100 ° C
Differential interference microscope Measuring device: Leica DMLB HC manufactured by Leica Microsystems Co., Ltd. Observation magnification: 1,000 times ○: When no crack occurred at 2N tension △: No crack occurred at 1N tension, but 2N tension When a crack occurs at x: When a crack occurs at a tension of 1N

  Based on the following examples, embodiments of the present invention will be described. Here, polyethylene terephthalate is expressed as PET, and polyetherimide is expressed as PEI.

Example 1
0.1 part by mass of magnesium acetate tetrahydrate was added to 194 parts by mass of dimethyl terephthalate and 124 parts by mass of ethylene glycol, and a transesterification reaction was performed while distilling methanol at 140 to 230 ° C. Next, after adding 0.05 part by mass of trimethyl phosphate ethylene glycol solution and 0.05 part by mass of antimony trioxide and stirring for 5 minutes, the reaction system was heated from 230 ° C. to 290 ° C. while stirring the low polymer at 30 rpm. While gradually raising the temperature to 0 ° C., the pressure was reduced to 0.1 kPa. The time to reach the final temperature and final pressure was both 60 minutes. When the polymerization reaction is carried out for 3 hours and a predetermined stirring torque is reached, the reaction system is purged with nitrogen and returned to normal pressure to stop the polycondensation reaction. A particulate PET pellet 1 was obtained.

  Similarly, using an ethylene glycol slurry containing spherical silica (average particle size: 60 nm) as inert particles in ethylene glycol, PET pellets 2 having a particle content of 2% by mass and an intrinsic viscosity of 0.68 (A surface: Magnetic surface side), PET pellet 3 having an intrinsic viscosity of 0.68 (B surface: traveling surface side) containing 2% by mass of spherical crosslinked polystyrene (average particle size: 0.3 μm), and spherical crosslinked polystyrene (average particle) PET pellets 4 (B surface: running surface side) each having an intrinsic viscosity of 0.68 and containing 1% by mass of a diameter of 0.8 μm) were obtained.

  Further, a co-rotating vent type twin-screw kneading extruder with three kneading paddle kneading parts heated to 300 ° C. (manufactured by Nippon Steel Works, L / D (screw length L / screw diameter D)) = 45.5), 50% by mass of the PET pellets 1 obtained as described above and 50% by mass of the pellets of polyetherimide “Ultem 1010” (intrinsic viscosity 0.68) manufactured by GE Plastics are supplied. It was melt extruded at 300 rpm, discharged into a strand, cooled with water at a temperature of 25 ° C., and then immediately cut to produce a blend chip (I).

  In Extruder A heated to 280 ° C. using Extruders A and B, the blend chip (I) obtained above, PET pellet 1 and PET pellet 2 had a PEI content of 5 mass%, spherical silica The pellets (A-side) mixed so that the particle concentration is 0.2% by mass was dried under reduced pressure at 180 ° C. for 3 hours and then supplied to the extruder B that was also heated to 280 ° C. The blend chip (I), PET pellets 1, 3 and 4 obtained by the above process were prepared by using 0.15% by mass of spherical crosslinked polystyrene particles having a PEI content of 5% by mass, an average particle size of 0.3 μm, and an average particle size of 0. Pellets (B side) mixed so that .8 μm spherical crosslinked polystyrene particles were 0.01% by mass were dried at 180 ° C. for 3 hours under reduced pressure, and then supplied. Two layers were laminated in a T-die (lamination ratio A / B = 7/1), solidified by cooling while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C., and a laminated unstretched film was produced.

  This unstretched film was biaxially stretched using a simultaneous biaxial tenter having a linear motor clip. Simultaneously in the longitudinal direction and the width direction, the film was stretched 3.3 × 3.4 times at a temperature of 100 ° C. and a stretching speed of 6,000%, and cooled to 70 ° C. Subsequently, the film was re-stretched 1.3 × 1.5 times in the longitudinal direction and the width direction at a temperature of 170 ° C. at the same time. After heat treatment at a temperature of 200 ° C. for 5 seconds under a constant tension of 1 MPa in both the longitudinal direction and the width direction, under a constant length in the longitudinal direction and with a relaxation treatment of 5% in the width direction, at 150 ° C. for 1 second, Subsequently, the film was gradually cooled at 100 ° C. for 2 seconds to produce a biaxially oriented polyester film having a thickness of about 5 μm, and wound into a roll.

Next, after setting the obtained polyester film on the film traveling device installed in the vacuum deposition apparatus and reducing the pressure to 1.50 × 10 ⁻³ Pa, it passes through a −20 ° C. cooling metal drum. The polyester film was run at a conveyance speed of 60 m / min and a conveyance tension of 100 N / m. At this time, the angle θ of each of the oxygen supply nozzles arranged before and after the crucible in the arrangement as shown in FIG. 2 (the straight direction of the oxygen gas introduced from the oxygen supply nozzle outlet and the lower vertex A of the cooling can as a contact) The angle of intersection with the tangent (see FIG. 3)) is 60 °, and the linear distance between the nozzle outlet and the lower vertex A of the cooling can is 4/5 of the crucible-cooling can distance (see FIG. 3). The angle and height are adjusted to adjust the oxygen introduction rate on the unwinding side to 3 L / min and the oxygen introduction rate on the winding side to 1.6 L / min. 5 kV) was evaporated by heating, and a vapor-deposited thin film layer (thickness 30 nm) of aluminum oxide was formed on the B surface of the film and wound. Next, A side is vapor-deposited. The surface temperature of the cooling metal drum is −35 ° C., the conveyance speed is 45 m / min, the conveyance tension is 70 N / m, the oxygen introduction amount on the unwinding side is 2.8 L / min, and the oxygen introduction amount on the winding side is 1.8 L / min. The aluminum oxide vapor deposition thin film was vapor deposited and wound in the same manner except that the thickness was changed to 40 nm and the thickness was 40 nm.

  After vapor deposition, the inside of the vacuum vapor deposition apparatus is returned to normal pressure, the wound film is rewound in an atmosphere of 30 ° C. and 80% RH, and then aged in an atmosphere of 30 ° C. and 80% RH for 12 days to support a recording medium. Got the body. The characteristics of the recording medium support were as shown in Tables 1 and 2 and had excellent characteristics when used as a magnetic tape.

( Reference Example 2)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 6 μm. The obtained film was set in a vacuum deposition apparatus, and the oxygen introduction amount on the unwinding side during the deposition of the Mb layer was adjusted to 3.4 L / min, and the oxygen introduction amount on the winding side was adjusted to 2.3 L / min. The conveyance speed was changed to 30 m / min and conveyance tension 90 N / m. Further, the recording medium support shown in Table 1 was obtained in the same manner as in Example 1 except that the film transport speed during the deposition of the Ma layer was changed to 30 m / min and the transport tension of 70 N / m.

( Reference Example 3)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 4.5 μm. The obtained film is set in a vacuum vapor deposition apparatus, and the oxygen introduction amount on the unwinding side at the time of vapor deposition of the Mb layer is adjusted to 3.2 L / min, and the oxygen introduction amount on the winding side is 2 L / min. Was changed to 90 m / min. Further, the recording shown in Table 1 was performed in the same manner as in Example 1 except that the oxygen introduction amount on the unwinding side during the deposition of the Ma layer was changed to 2.8 L / min and the oxygen introduction amount on the winding side was 1.3 L / min. A medium support was obtained.

( Reference Example 4)
The stretching ratio conditions were changed in the same manner as in Example 1 to prepare a biaxially oriented polyester film having a thickness of 5 μm. The obtained film was set in a vacuum deposition apparatus, and the oxygen introduction amount on the unwinding side during the deposition of the Mb layer was adjusted to 3.5 L / min, and the oxygen introduction amount on the winding side was adjusted to 2.3 L / min. The conveyance speed was changed to 90 m / min. Further, the same procedure as in Example 1 was performed except that the unloading side oxygen introduction amount at the time of deposition of the Ma layer was 3 L / min, the winding side oxygen introduction amount was 1.3 L / min, and the film conveyance speed was changed to 60 m / min. Thus, the recording medium support shown in Table 1 was obtained.

( Reference Example 5)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 5.3 μm. The obtained film is set in a vacuum vapor deposition apparatus, and the oxygen introduction amount on the unwinding side during the deposition of the Mb layer is adjusted to 4 L / min, and the oxygen introduction amount on the winding side is 2.7 L / min. Was changed to 30 m / min. Further, in the same manner as in Example 1 except that the amount of oxygen introduced on the unwinding side during deposition of the Ma layer was 2.3 L / min, the amount of oxygen introduced on the winding side was 1 L / min, and the film conveyance speed was changed to 45 m / min. Thus, the recording medium support shown in Table 1 was obtained.

( Reference Example 6)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 4.5 μm. The obtained film was set in a vacuum deposition apparatus, and the oxygen introduction amount on the unwinding side during the deposition of the Mb layer was adjusted to 3.2 L / min, and the oxygen introduction amount on the winding side was 2.1 L / min. The conveyance speed was changed to 90 m / min. Further, Example 1 except that the amount of oxygen introduced on the unwinding side during deposition of the Ma layer was 1.1 L / min, the amount of oxygen introduced on the winding side was 0.4 L / min, and the film conveyance speed was changed to 180 m / min. Similarly, the recording medium support shown in Table 1 was obtained.

(Example 7)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 4.5 μm. The obtained film was set in a vacuum deposition apparatus, and the oxygen introduction amount on the unwinding side during the deposition of the Mb layer was adjusted to 3.2 L / min, and the oxygen introduction amount on the winding side was 2.1 L / min. The conveyance speed was changed to 180 m / min. Further, the recording medium support shown in Table 1 was obtained in the same manner as in Example 1 except that the film conveyance speed during the deposition of the Ma layer was changed to 180 m / min.

( Reference Example 8)
The stretching conditions were changed in the same manner as in Example 1 to prepare a biaxially oriented polyester film having a thickness of 5.5 μm. The obtained film was set in a vacuum vapor deposition apparatus, and Mb and Ma layers were provided under the same conditions as in Example 2 to obtain a magnetic recording medium support shown in Table 1.

( Reference Example 9)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 4.8 μm. The obtained film was set in a vacuum vapor deposition apparatus, and Mb and Ma layers were provided under the same conditions as in Example 1 except that the film conveyance speed was changed to 38 m / min. Got the body.

(Comparative Example 1)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 4.5 μm. The obtained film is set in a vacuum vapor deposition apparatus, and adjusted to an unloading side oxygen introduction amount of 4 L / min and an unwinding side oxygen introduction amount of 1.7 L / min when depositing the Mb layer. Was changed to 60 m / min. Further, in the same manner as in Example 1 except that the amount of oxygen introduced on the unwinding side during deposition of the Ma layer was 5 L / min, the amount of oxygen introduced on the winding side was 3 L / min, and the film conveyance speed was changed to 45 m / min. A support for a recording medium shown in 1 was obtained.

(Comparative Example 2)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 4.5 μm. The obtained film was set in a vacuum deposition apparatus, and the film transport speed during deposition of the Mb layer was changed to 45 m / min, and the film transport speed during deposition of the Ma layer was changed to 30 m / min. In the same manner as in Example 1, the recording medium support shown in Table 1 was obtained.

(Comparative Example 3)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 4.5 μm. The obtained film is set in a vacuum deposition apparatus, and the oxygen introduction amount on the unwinding side during the deposition of the Mb layer is adjusted to 1 L / min, and the oxygen introduction amount on the winding side is 0.2 L / min. Was changed to 45 m / min in the same manner as in Example 1 to obtain a recording medium support shown in Table 1.

(Comparative Example 4)
By changing the stretching conditions in the same manner as in Example 1, a biaxially oriented polyester film having a thickness of 5 μm was produced. The obtained film is set in a vacuum deposition apparatus, the angle between the oxygen supply nozzle outlet and the lower vertex of the cooling can is 80 ° during the deposition of the Mb layer, and the distance between the nozzle and the lower portion of the cooling can is the crucible. -The cooling can distance was set to 2/5, the oxygen introduction amount on the unwinding side was adjusted to 6.3 L / min, and the oxygen introduction amount on the winding side was 4.3 L / min, and the film conveyance speed was changed to 38 m / min. Further, in the same manner as in Example 1 except that the amount of oxygen introduced on the unwinding side during deposition of the Ma layer was 4 L / min, the amount of oxygen introduced on the winding side was 1.7 L / min, and the film conveyance speed was 38 m / min. Thus, the recording medium support shown in Table 1 was obtained.

(Comparative Example 5)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 4.5 μm. The obtained film is set in a vacuum vapor deposition apparatus, and adjusted to an unloading side oxygen introduction amount of 4 L / min and an unwinding side oxygen introduction amount of 1.7 L / min when depositing the Mb layer. Was changed to 38 m / min. Further, the recording medium support shown in Table 1 was obtained in the same manner as in Example 1 except that the Ma layer was not formed.

(Comparative Example 6)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 5.3 μm. The obtained film is set in a vacuum deposition apparatus, and the oxygen introduction amount on the unwinding side during the deposition of the Mb layer is adjusted to 3.3 L / min, and the oxygen introduction amount on the winding side is 2 L / min. Was changed to 180 m / min. Further, Example 1 except that the amount of oxygen introduced on the unwinding side during the deposition of the Ma layer was 2.8 L / min, the amount of oxygen introduced on the winding side was 1.3 L / min, and the film conveyance speed was changed to 180 m / min. Similarly, the recording medium support shown in Table 1 was obtained.

(Comparative Example 7)
The stretching conditions were changed in the same manner as in Example 1 to produce a biaxially oriented polyester film having a thickness of 5.3 μm. The obtained film is set in a vacuum deposition apparatus, the angle between the oxygen supply nozzle outlet and the lower apex of the cooling can is 40 ° during the deposition of the Ma layer, and the nozzle height is between the outlet and the cooling can. The height of one-sixth of the straight line connecting the lower apex was changed to 0.5 L / min for the oxygen introduction on the unwinding side, 0.3 L / min for the oxygen introduction on the winding side, and the film conveyance speed was changed to 60 m / min. Except for the above, the recording medium support shown in Table 1 was obtained in the same manner as in Example 1.

It is a schematic diagram of the sheet | seat width measuring apparatus used when manufacturing the support body of this invention. It is a schematic diagram of the vacuum evaporation system used when manufacturing the support body of this invention. FIG. 3 is a schematic diagram for determining an angle between a cooling can and an oxygen gas introduction pipe in FIG. 2.

Explanation of symbols

1: Laser oscillator 2: Light receiving unit 3: Load detector 4: Weight (load)
5: Free roll 6: Free roll 7: Free roll 8: Free roll 9: Magnetic tape 10: Laser beam 11: Vacuum deposition apparatus 12: Vacuum chamber 13: Unwinding roll unit 14: Polyester film 15: Guide roll 16: Cooling Drum 17: Deposition chamber 18: Winding roll unit 19: Metal material 20: Electron gun 21: Electron beam 22: Oxygen gas cylinder 23: Crucible 24a: Unwinding side oxygen gas supply nozzle 24b: Winding side oxygen gas supply nozzle 25: Gas flow control device 26: Mask 27: Straight direction of oxygen gas introduced from oxygen supply nozzle outlet 28: Tangential line 29 having contact point with lower vertex of cooling can 29: Nozzle outlet and lower apex A of cooling can Connecting straight distance 30: Crucible-cooling can distance θ: Angle between the straight direction of oxygen gas and the cooling can A Lower vertex of the cooling can

Claims (7)

A support for a magnetic recording medium in which a layer (M layer) containing a metal-based oxide is provided on both sides of a polyester film, and the curvature when the magnetic tape is defined below is less than 1 mm, the oxygen of the M layer The concentration is 45 to 70 at. The thickness of the polyester film is T, the thickness of the M layer (Ma layer) provided on one surface (surface A) and the thickness of the M layer (Mb layer) provided on the other surface (surface B) when the sum of the thicknesses was TM, the value of T / T _M is 71-250, a surface resistivity of Ma layer ^{1.0 × 10 3 ~1.0 × 10 8} Ω, the surface of the Mb layer A support for a magnetic recording medium having a resistivity of 1.0 × 10 ^{9 to} 1.0 × 10 ¹⁴ Ω and a surface resistivity of the Ma layer smaller than that of the Mb layer.
Curvature when using magnetic tape:
When the magnetic tape is cut out to a length of 20 mm and placed on a flat glass plate so that the magnetic layer is on the top, the magnetic tape is convexly curved toward the magnetic layer, and the measurement is performed in the width direction of the magnetic tape. Distance between the center and the glass plate The support for magnetic recording media according to claim 1, wherein TM is 20 to 100 nm and the thickness of the Mb layer is 50 nm or less. The support for a magnetic recording medium according to claim 1 or 2, wherein none of the M layers contains a magnetic metal. The support for magnetic recording media according to claim 1, wherein the total light transmittance is 20 to 78%. The support for a magnetic recording medium according to any one of claims 1 to 4, wherein the surface roughness Ra of the Ma layer is 0.3 to 10 nm. The support for a magnetic recording medium according to any one of claims 1 to 5, wherein the surface roughness Ra of the Mb layer is 5 to 20 nm. A magnetic recording medium comprising a support for a magnetic recording medium according to any one of claims 1 to 6 and a magnetic layer coated on the surface on which the Ma layer is provided.

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