JP2010030116A - Biaxially oriented laminated film and magnetic recording medium using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented laminated film suitable for a base film for a high density magnetic recording medium, which develops a very low humidity expansion coefficient, and also to provide a magnetic recording medium using the same. <P>SOLUTION: The biaxially oriented laminated film is obtained by laminating at least 2 layers in total number of layers of a film layer E including aromatic polyester (e), and a film layer F including polyolefin (f) with melting point of 200-280°C. The aromatic polyester (e) is a polyester containing (i) 6, 6'-(alkylenedioxy) di-2-naphthoic acid having a dicarboxylic acid component of 5 to<50 mol%, and >50 to 95 mol% other aromatic dicarboxylic acid, and (ii) C2-10 alkylene glycol having a diol component of 90-100 mol%. The total thickness of the film layer F is 15-85% with reference to thickness of the whole laminated film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biaxially oriented laminated film having excellent dimensional stability, and more specifically, to a biaxially oriented laminated film suitable for a magnetic recording medium having excellent dimensional stability against humidity change, particularly for a digital data storage tape, and The present invention relates to a magnetic recording medium using this as a base film.

  Polyester films are used in a wide range of fields such as magnetic recording media because they have excellent heat and mechanical properties. In a magnetic recording medium, particularly a magnetic recording medium for data storage, the capacity and density of a tape are considerably increased, and accordingly, the characteristic requirements for a base film are severe. In magnetic recording media for data storage that employs a linear track system, such as QIC, DLT, and higher capacity Super DLT, LTO, the track pitch is very narrow in order to realize high capacity tape. For this reason, when a dimensional change in the tape width direction occurs, there is a problem that a track shift occurs and an error occurs. These dimensional changes may be due to changes in temperature and humidity, due to tension applied during traveling, or due to changes in diameter occurring during storage in a state of being wound with high tension. When these dimensional changes are large, track deviation occurs, and an error occurs during electromagnetic conversion. For convenience of explanation, the film forming direction of the film is sometimes referred to as MD direction, longitudinal direction, or longitudinal direction, and the in-plane direction orthogonal to the film forming direction is sometimes referred to as TD direction, lateral direction, or width direction.

In order to solve such a dimensional change, Japanese Patent Laid-Open No. 5-212787 discloses a longitudinal Young's modulus (EM) and a lateral Young's modulus (ET) of 550 kg / mm ² or more and 700 kg / mm ^{2, respectively.} The ratio of both Young's moduli (ET / EM) is 1.1 to 2.0, and the shrinkage in the vertical direction when held at 70 ° C. in a relative humidity of 65% for 1 hour under no load. Is 0.02% or less, the longitudinal temperature expansion coefficient (αt) is 10 × 10 ⁻⁶ / ° C. or less, and the longitudinal humidity expansion coefficient (αh) is 15 × 10 ⁻⁶ /% RH or less. A biaxially oriented polyethylene-2,6-naphthalenedicarboxylate film is disclosed. In addition, International Publication No. 99/29488 pamphlet includes a lateral temperature expansion coefficient αt (× 10 ⁻⁶ / ° C.), a lateral humidity expansion coefficient αh (× 10 ⁻⁶ /% RH), and a load in the vertical direction. A biaxially oriented polyester film having a specific range of shrinkage rate P (ppm / g) in the transverse direction with respect to the load is disclosed. Furthermore, in the pamphlet of International Publication No. 00/76749, a dimensional change in the width direction when left standing with a load in the vertical direction, a temperature expansion coefficient αt (× 10 ⁻⁶ / ° C.) in the width direction, A biaxially oriented polyester film having a specific range of a humidity expansion coefficient αh (× 10 ⁻⁶ /% RH) and a shrinkage rate P (ppm / g) in the width direction with respect to the load when a load is applied in the longitudinal direction. It is disclosed.

  However, the methods proposed in these publications are achieved by setting stretching conditions and subsequent heat setting treatment conditions within a specific range, for example, in the width direction when a load is applied in the longitudinal direction. Shrinkage with time can be improved by increasing the longitudinal Young's modulus of the base film. On the other hand, the larger the Young's modulus in the longitudinal direction, the greater the Young's modulus in the lateral direction, in terms of polymer properties and film-forming properties. The upper limit of Young's modulus has been reduced, and as a result, the dimensional change due to temperature and humidity changes has increased, and no fundamental solution has been reached.

  By the way, Patent Document 4 proposes that the humidity expansion coefficient can be reduced by laminating polyolefin such as syndiotactic polystyrene. However, even the films described in these publications have a large humidity expansion coefficient for use as a high-capacity magnetic recording medium for data storage, and further improvements have been sought.

  Patent Documents 5 to 8 propose polyesters comprising an ester unit of an acid component mainly composed of 6,6 '-(ethylenedioxy) di-2-naphthoic acid and a diol component. This document discloses a crystalline polyester having a melting point of 294 ° C. These polyesters disclosed in Patent Documents 5 to 8 have a very high melting point and very high crystallinity, and when they are formed into a film or the like, the fluidity in the molten state is poor, and the extrusion becomes non-uniform. In addition, there is a problem that even if an attempt is made to stretch after extrusion, crystallization progresses and breaks when stretched at a high magnification.

JP-A-5-212787 International Publication No. 99/29488 pamphlet International Publication No. 00/76749 JP 2005-327411 A JP-A-60-135428 JP-A-60-212420 JP 61-145724 A JP-A-6-145323

  The present inventors first provide a film having low αt (temperature expansion coefficient) and αh (humidity expansion coefficient) in order to improve dimensional stability, particularly dimensional stability against environmental changes when temperature and humidity change. As a result of diligent investigation, a polyester having terephthalic acid, naphthalenedicarboxylic acid or the like as a dicarboxylic acid component is added to a predetermined amount of 6,6 ′-(alkylenedioxy) di-2-naphthoic acid (hereinafter referred to as ANA). It has been found that a polyester obtained by copolymerizing is a film having excellent film-forming properties, a film having excellent appearance and mechanical strength can be obtained from the copolymerized polyester, and exhibits a low αh value which is a characteristic of ANA. I filed earlier.

  However, although it is a film having such excellent dimensional stability, a further reduction in the coefficient of humidity expansion is required for a high-capacity magnetic recording medium for data storage. It is.

  Accordingly, an object of the present invention is to improve such a problem and maintain a superior mechanical property while reducing the coefficient of humidity expansion, and a biaxially oriented laminated film suitable as a base film for a high-density magnetic recording medium, and the same It is to provide a magnetic recording medium used.

  As a result of intensive studies in view of the above-described conventional technology, the inventor of the present invention maintains a mechanical characteristic by making a conventional polyester film a multilayer laminated film in which two or more specific aromatic polyesters and polyolefins are laminated. On the other hand, the present inventors have found that a biaxially oriented laminated film having improved dimensional stability against changes in humidity can be obtained, leading to the present invention.

Thus, according to the present invention, an object of the present invention is a laminated film in which a film layer E made of an aromatic polyester (e) and a film layer F made of a polyolefin (f) are laminated in at least two layers. There,
The aromatic polyester (e) is a polyester comprising an aromatic dicarboxylic acid component and a diol component, and (i) the following formula (A) in which the dicarboxylic acid component is 5 mol% or more and less than 50 mol% and 50 mol%: It is a polyester containing a repeating unit represented by the following formula (B) in excess of 95 mol% and (ii) a repeating unit represented by the following formula (C) in which the diol component is 90 to 100 mol%. And
The polyolefin (f) has a melting point in the range of 200 to 280 ° C., and the total thickness of the film layer F is achieved by the biaxially oriented laminated film in the range of 15 to 85% based on the thickness of the entire laminated film. The

（式（Ａ）中、Ｒ^Ａは炭素数２〜１０のアルキレン基、式（Ｂ）中、Ｒ^Ｂはフェニレン基またはナフタレンジイル基、式（Ｃ）中、Ｒ^Ｃは炭素数２〜１０のアルキレン基である。）

(In the formula (A), ^{R A} is an alkylene group having 2 to 10 carbon atoms, in the formula (B), ^{R B} is a phenylene group or a naphthalene-diyl group, in the formula (C), ^{R C} is 2 to 10 carbon atoms An alkylene group.)

Further, according to the present invention, as a preferred embodiment of the biaxially oriented laminated film of the present invention, the polyolefin (f) is a styrene polymer having a syndiotactic structure, the film forming direction and the width direction Young The rate is 4 GPa or more and the total of both is at most 22 GPa, and the humidity expansion coefficient in the width direction of the film is in the range of 0.1 × 10 ^{−6 to} 7 × 10 ⁻⁶ /% RH, Used in the range of −10 × 10 ⁻⁶ to 15 × 10 ⁻⁶ / ° C., a film thickness of 2 to 10 μm, and a support for a magnetic recording medium. Biaxially oriented laminated films comprising at least one of the above are also provided, and the biaxially oriented laminated films of the present invention and a magnetic layer provided on one side thereof are also provided. The magnetic recording medium comprising also provided.

  According to the present invention, the film layer E made of aromatic polyester (e) and the film layer F made of polyolefin (f) are laminated films in which two or more layers are laminated. To provide a biaxially oriented laminated film suitable for a base film of a magnetic recording medium and a magnetic recording medium comprising the same, which can reduce the dimensional change with respect to humidity change while maintaining dimensional stability based on Young's modulus and the like. And its industrial value is extremely high.

The present invention will be described in detail below.
The biaxially oriented laminated film of the present invention may be referred to as a film layer E made of an aromatic polyester (hereinafter sometimes referred to as polyester (e)) and a polyolefin (hereinafter referred to as polyolefin (f)). .) Is a laminated film in which two or more layers in total are laminated. It is to be noted that a film layer made of such a different resin can be obtained by reducing the thickness per layer by setting the sum of the number of layers of the film layer E and the film layer F (hereinafter, the total number of layers) to 4 layers or more. However, process deterioration due to delamination or the like can be further suppressed. The total number of layers is preferably 8 layers or more, further 16 layers or more, particularly 32 layers or more, and the upper limit is not particularly limited, but is preferably about 300 layers or more about 200 layers because the interface in the molten state is easily stabilized. The laminated structure of the film layer E and the film layer F is not particularly limited. However, film layers made of other resins may be laminated as long as they are usually laminated alternately and do not impair the object of the present invention.

  By the way, when the biaxially oriented laminated film of the present invention is based on the thickness of the whole laminated film, the proportion of the total thickness of the film layer F made of polyolefin (f) needs to be in the range of 15 to 85%. It is. When the ratio of the total thickness of the film layer F is less than the lower limit, the effect of improving the dimensional stability against the intended humidity change is poor. On the other hand, when the upper limit is exceeded, the resulting biaxially oriented laminated film has poor mechanical properties. Become. The ratio of the total thickness of the preferable film layer F is 20 to 80%, and further 22 to 78%.

[Film layer E]
In the present invention, the film layer E is made of polyester (e), and is mixed or copolymerized with other resins within a range not impairing the object of the present invention, for example, 10% by weight or less, preferably 5% by weight or less. It may be.
The polyester (e) in the present invention is a polyester composed of an aromatic dicarboxylic acid component and a diol component, and (i) the above formula (A) in which the dicarboxylic acid component is 5 mol% or more and less than 50 mol% and 50 mol%. It is a polyester containing a repeating unit represented by the above formula (B) in excess of 95 mol% and (ii) a repeating unit represented by the following formula (C) in which the diol component is 90 to 100 mol%. .

[Dicarboxylic acid component]
The upper limit of the content of the repeating unit represented by the formula (A) is preferably 45 mol%, more preferably 40 mol%, still more preferably 35 mol%, particularly preferably 30 mol%. The lower limit is preferably 5 mol%, more preferably 7 mol% or more, still more preferably 10 mol%, and particularly preferably 15 mol%. Accordingly, the content of the repeating unit represented by the formula (A) is preferably 5 to 45 mol%, more preferably 7 to 40 mol%, still more preferably 10 to 35 mol%, and particularly preferably 15 to 30 mol%. %.

The repeating unit represented by the formula (A) is preferably 6,6 ′-(ethylenedioxy) di-2-naphthoic acid, 6,6 ′-(trimethylenedioxy) di-2-naphthoic acid and 6 , 6 ′-(butyleneoxy) di-2-naphthoic acid-derived units are preferred. Among these, those having an even number of carbon atoms of R ^A in formula (A) are preferred, and units derived from 6,6 ′-(ethylenedioxy) di-2-naphthoic acid are particularly preferred.

  The polyester (e) in the present invention is characterized by containing a unit represented by the formula (A) in which the dicarboxylic acid component is 5 mol% or more and less than 50 mol%. If the ratio of the unit represented by the formula (A) is less than the lower limit, the effect of reducing the humidity expansion coefficient is difficult to be exhibited. Moreover, there is also an advantage that the film forming property can be improved by making the amount less than the upper limit.

Next, in the formula (B), R ^B is a phenylene group or a naphthalenediyl group. Of these, it R ^B is a naphthalene-diyl group is preferred because heat dimensional stability of the film is excellent.
Examples of the repeating unit represented by the formula (B) include units derived from terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, or combinations thereof. Of these, 2,6-naphthalenedicarboxylic acid is preferred for the same reason as above.

[Diol component]
The diol component contains 90 to 100 mol% of a repeating unit represented by the formula (C). The content of the repeating unit represented by the formula (C) is preferably 95 to 100 mol%, more preferably 98 to 100 mol%.

In the formula (C), R ^C is an alkylene group having 2 to 10 carbon atoms. Examples of the alkylene group of ^RC include an ethylene group, a propylene group, an isopropylene group, a trimethylene group, a tetramethylene group, a hexamethylene group, and an octamethylene group. Among these, units derived from ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane dimethanol, and the like are preferred as the diol component represented by the formula (C). Among these, units derived from ethylene glycol are preferable. The content of units derived from ethylene glycol in the diol component is preferably 90 mol% or more, more preferably 95 to 100 mol%, and most preferably 98 to 100 mol%.

[Polyester (e)]
The polyester (e) in the present invention contains an ester unit (-(A)-(C)-) composed of a repeating unit represented by the formula (A) and a repeating unit represented by the formula (C). The amount is preferably 5 mol% or more and less than 50 mol%, more preferably 5 to 45 mol%, still more preferably 10 to 40 mol% of all repeating units.

  Other ester units include polyalkylene terephthalate units such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, polytrimethylene-2,6-naphthalene dicarboxylate, polybutylene- Preference is given to polyalkylene-2,6-naphthalenedicarboxylate units such as 2,6-naphthalenedicarboxylate. Among these, ethylene terephthalate units and ethylene-2,6-naphthalenedicarboxylate units are preferable from the viewpoint of mechanical properties and the like, and ethylene-2,6-naphthalenedicarboxylate units are particularly preferable.

  Polyester (e) in the present invention has an intrinsic viscosity of 0.4 to 3 measured at 35 ° C. using a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (weight ratio 40/60). , Preferably 0.4 to 1.5 dl / g, more preferably 0.5 to 1.2 dl / g.

The melting point of the polyester (e) in the present invention is preferably in the range of 200 to 260 ° C, more preferably in the range of 205 to 255 ° C, particularly in the range of 210 to 250 ° C. The melting point is measured by DSC.
When the melting point exceeds the upper limit, when melt extrusion is performed, the fluidity is inferior and the discharge is likely to be non-uniform. On the other hand, if it is less than the lower limit, the film forming property is excellent, but the mechanical properties of the polyester are easily impaired.

  In general, a copolymer has a lower melting point than a homopolymer and tends to decrease mechanical strength. However, the polyester (e) of the present invention is a copolymer containing the unit of the formula (A) and the unit of the formula (B), and has a lower melting point than the homopolymer having the unit of the formula (A). However, it has an excellent characteristic that the mechanical strength is the same.

  The glass transition temperature (hereinafter sometimes referred to as Tg) of the polyester (e) in the present invention measured by DSC is preferably 80 to 125 ° C, more preferably 95 to 123 ° C, and still more preferably 110 to 120 ° C. It is in the range. When Tg is within this range, a film having excellent heat resistance and dimensional stability can be obtained. The melting point and glass transition temperature can be adjusted by controlling the type and amount of copolymerization component, dialkylene glycol as a byproduct.

[Film layer F]
In the present invention, the film layer F is made of polyolefin (f), and is mixed or copolymerized with other resins in a range that does not impair the object of the present invention, for example, 10% by weight or less, preferably 5% by weight or less. It may be. The melting point of the polyolefin (f) in the present invention needs to be 200 ° C. to 280 ° C., preferably 230 to 280 ° C., more preferably 240 to 275 ° C. The heat resistance of the biaxially oriented laminated film obtained when the melting point is less than the lower limit may be insufficient. Moreover, when melting | fusing point exceeds an upper limit, lamination | stacking with aromatic polyester may become difficult.

[Polyolefin (f)]
As the polyolefin (f) in the present invention, poly-3-methylbutene-1, poly-4-methylpentene-1, polyvinyl-t-butane, 1,4-trans-poly-2,3-dimethylbutadiene, polyvinylcyclohexane , Polystyrene, polymethylstyrene, polydimethylstyrene, polybutylstyrene and the like. Among these, a styrene polymer having a syndiotactic structure (hereinafter sometimes referred to as SPS) is preferable from the viewpoint of heat resistance and mechanical properties.

SPS in the present invention is a polystyrene having a syndiotactic structure as a stereochemical structure, and the tacticity measured by a nuclear magnetic resonance method ( ¹³ C-NMR method) is 75% in terms of dyad (two constituent units). The above is preferably 85% or more, and 30% or more, preferably 50% or more in pentad (5 structural units).

  Examples of such SPS include polystyrene, poly (alkyl styrene), poly (methyl styrene), poly (ethyl styrene), poly (propyl styrene), poly (butyl styrene), and poly (phenyl styrene). , Polystyrene, poly (p-methylstyrene), poly (m-methylstyrene), and poly (p-tertiarybutylstyrene) are preferably exemplified.

SPS in this invention may be individual, or may use 2 or more types together.
The SPS in the present invention preferably has a number average molecular weight of 10,000 or more, and more preferably 50,000 or more. When the number average molecular weight is less than the lower limit, heat resistance and mechanical properties are insufficient. On the other hand, the upper limit of the number average molecular weight is preferably 500,000 or less. When this upper limit is exceeded, film-forming property may become poor.
The polyolefin (f) in the present invention is not necessarily a single compound, and may be a mixture of two or more kinds of polyolefins.

[Surface roughness and inert particles]
The biaxially oriented laminated film of the present invention preferably has a surface roughness Ra (central surface average roughness) of at least one exposed surface of 1 to 10 nm, more preferably 2 to 10 nm, and particularly preferably 2 to 8 nm.
When any surface roughness Ra is larger than the upper limit, the surface of the magnetic layer when used in a magnetic recording medium becomes rough, and the electromagnetic conversion characteristics are likely to be deteriorated. On the other hand, if any surface roughness Ra is less than the lower limit, the surface becomes too flat, the slipperiness becomes poor, wrinkles and the like are generated, and the workability is liable to be lowered. Further, the surface roughness Ra (center plane average roughness) of the other exposed surface may be the same as the Ra, and is larger than the Ra, 5 to 20 nm, further 6 to 15 nm, particularly 8 to 12 nm. It may be. Thus, it is preferable to make the surface different in surface form because adjustment of electromagnetic conversion characteristics and running performance can be more easily performed.

  The surface roughness Ra is defined by inert particles in the film, for example, inorganic particles containing elements of Periodic Tables IIA, IIB, IVA, and IVB (for example, kaolin, alumina, titanium oxide, calcium carbonate, dioxide dioxide). Silicon), cross-linked silicone resin, cross-linked polystyrene, cross-linked acrylic resin particles such as cross-linked acrylic resin particles, or the like, or surface treatment that forms fine irregularities, for example, by coating with an easy-coating agent Can be adjusted. Further, both the film layer E and the film layer F may contain inert particles, or only one of them may contain inert particles. Furthermore, when coating with a slippery coating agent (hereinafter sometimes referred to as an application layer), it may be applied not only on one side but also on both sides. As the coating layer, those known per se, for example, those exemplified in Patent Document 3 (International Publication No. 00/76749 pamphlet) can be suitably employed.

〔Young's modulus〕
The biaxially oriented laminated film of the present invention may be referred to as a film forming direction (hereinafter, sometimes referred to as a longitudinal direction, a longitudinal direction, or an MD direction) and a width direction (hereinafter, referred to as a lateral direction or a TD direction). The Young's modulus is preferably 4 GPa or more. If either of them is less than the lower limit, even if the dimensional change due to humidity change is small, deformation due to the tension associated with the magnetic recording medium becomes large, or the dimensional change due to temperature change becomes large. There is. The sum of the Young's moduli in the film forming direction and the width direction is preferably at most 22 GPa. When the sum of the Young's modulus in the film forming direction and the Young's modulus in the width direction exceeds the upper limit, the draw ratio becomes excessively high during film formation, the film breaks frequently, and the product yield is remarkably deteriorated. A preferable upper limit of the sum of Young's moduli in the film forming direction and the width direction is 20 GPa or less, and further 18 GPa or less.

  By the way, when it is used for a linear track type magnetic tape, the Young's modulus in the film forming direction is preferably 4.5 GPa or more, 5 GPa or more, particularly 6 GPa or more from the viewpoint of reducing the elongation in the film forming direction. Further, from the viewpoint of enhancing dimensional stability against environmental changes in the width direction, the Young's modulus in the width direction is preferably 7 GPa or more, 8 GPa or more, and particularly preferably 9 GPa or more.

[Humidity expansion coefficient]
In the biaxially oriented laminated film of the present invention, the humidity expansion coefficient αh in the width direction of the film is preferably in the range of 0.1 × 10 ^{−6 to} 7 × 10 ⁻⁶ /% RH. Preferred αh is in the range of 0.5 × 10 ^{−6 to} 6 × 10 ⁻⁶ /% RH, particularly 1 × 10 ^{−6 to} 5 × 10 ⁻⁶ /% RH. In order to make αh smaller than the lower limit, the polyolefin (f) is excessively present, and the film forming property is deteriorated. On the other hand, when the upper limit is exceeded, the film is stretched due to a change in humidity, resulting in a track shift, etc. May provoke. Such αh is achieved by improving the Young's modulus in the measurement direction by stretching and mixing polyolefin.

[Temperature expansion coefficient]
The biaxially oriented laminated film of the present invention preferably has a temperature expansion coefficient αt in the width direction of the film in the range of −10 × 10 ⁻⁶ to + 15 × 10 ⁻⁶ / ° C. Preferred αt is in the range of −8 × 10 ⁻⁶ to + 10 × 10 ⁻⁶ / ° C., particularly −5 × 10 ⁻⁶ to + 8 × 10 ⁻⁶ / ° C. When αt is within the above range, the positional deviation in the film width direction with respect to the magnetic head when used as a magnetic recording tape with respect to a temperature change can be reduced, and track deviation and the like can be suppressed. Such αt is achieved by improving the Young's modulus in the measurement direction by stretching, and setting the abundance of polyolefin to the above upper limit or less.

[Film thickness]
The biaxially oriented laminated film of the present invention preferably has a total film thickness of 2 to 10 μm, more preferably 3 to 7 μm, particularly 4 to 6 μm. When this thickness exceeds the upper limit, the tape thickness becomes too thick, for example, the tape length to be put in the cassette is shortened, and a sufficient magnetic recording capacity may not be obtained. On the other hand, if the film thickness is less than the lower limit, the film thickness is thin, so that film breakage may occur frequently during film formation, or the film winding property may be poor.

  Further, the thickness per layer of the film layer E is preferably in the range of 0.02 to 1.5 μm, more preferably 0.04 to 1.0 μm, and the thickness per layer of the film layer F is 0.00. It is preferably in the range of 02 to 1.5 μm, more preferably 0.04 to 1.0 μm. If the thickness per layer of the film layer E is less than the lower limit, an extremely large number of layers must be laminated, and the process tends to be complicated. On the other hand, if the thickness per layer of the film layer E exceeds the upper limit, , Peeling between layers is likely to occur. Moreover, if the thickness per layer of the film layer F is less than the lower limit, an extremely large number of layers must be laminated, and the process is easily complicated. On the other hand, the thickness per layer of the film layer F is the upper limit. Exceeding of this will also easily cause delamination between layers. These thicknesses can be measured by cutting the laminated film with a microtome or the like in the thickness direction into ultrathin pieces and observing them with a transmission electron microscope.

[Method for producing polyester (e)]
The polyester (e) in the present invention can be produced by the following method. For example, a dicarboxylic acid component containing 6,6 ′-(alkylenedioxy) di-2-naphthoic acid and naphthalenedicarboxylic acid, terephthalic acid or an ester-forming derivative thereof, and a diol component such as ethylene glycol are reacted. A polyester precursor is produced. The obtained polyester precursor can be produced by polymerization in the presence of a polymerization catalyst. Thereafter, solid phase polymerization or the like may be performed as necessary.

[Film forming method]
The biaxially oriented laminated film of the present invention is preferably produced by the following method.
The biaxially oriented laminated film of the present invention has at least a film layer E made of polyester (e) and a film layer F made of polyolefin (f) at least in total for the purpose of imparting excellent dimensional stability against changes in humidity. A multi-layer laminated film with two layers, which gives the resulting biaxially oriented laminated film excellent dimensional stability against changes in humidity due to polyolefin (f) and excellent mechanical properties and film-forming properties due to polyester (e). can do.

  The biaxially oriented laminated film of the present invention is a simultaneous multilayer using the above-mentioned polyester (e) and polyolefin (f) as raw materials and using a feed block as proposed in paragraph 0028 of JP-A-2000-326467, for example. It can be produced by an extrusion method. That is, the aromatic polyester (e) constituting the film layer E and the polyolefin (f) constituting the film layer F are supplied to an extruder heated to about 300 ° C. after drying, using a feed block For example, melts of polyester (e) and polyolefin (f) are alternately laminated, and are spread on a die and extruded. And the sheet-like material extruded from die | dye can be manufactured using well-known film forming methods, such as a tenter method and an inflation method. Specifically, the polyester (e) is extruded at a temperature of the melting point (Tm: ° C.) to (Tm + 70) ° C., rapidly cooled and solidified to form an unstretched film, and the unstretched film is further uniaxially (longitudinal or lateral). (Tg-10) to (Tg + 70) ° C. (where Tg is the glass transition temperature of polyester (e)) and then stretched to a predetermined magnification, and then perpendicular to the stretching direction (the first stage is the longitudinal direction) Can be manufactured by using a method of stretching at a predetermined magnification at a temperature of Tg to (Tg + 70) ° C. and further heat-treating. At that time, the stretching ratio, stretching temperature, heat treatment conditions, etc. are selected and determined from the characteristics of the film. The area stretch ratio is preferably 15 to 50 times, more preferably 20 to 40 times. The heat setting temperature may be determined from the range of 190 to 250 ° C., and the treatment time may be determined from the range of 1 to 60 seconds.

In addition to the sequential biaxial stretching method, a simultaneous biaxial stretching method can also be used. Further, in the sequential biaxial stretching method, the number of stretching in the longitudinal direction and the transverse direction is not limited to one, and the longitudinal-lateral stretching can be performed by several stretching processes, and the number of stretching is not limited thereto. . For example, when it is desired to further improve the mechanical properties, the biaxially stretched film before the heat setting treatment is heat-treated at a temperature of (Tg + 20) to (Tg + 70) ° C., and further 10 to 40 ° C. higher than the heat treatment temperature. The film is stretched in the machine direction or the transverse direction, and then further stretched in the transverse direction or the longitudinal direction at a temperature 20 to 50 ° C. higher than the stretching temperature. In this case, the overall draw ratio is preferably 3.0 to 10 times.
Moreover, when providing a coating layer, it is preferable to apply | coat a desired coating liquid on the single side | surface or both surfaces of an above described laminated unstretched film or laminated uniaxially stretched film.

[Magnetic recording medium]
According to the present invention, a magnetic recording medium having the biaxially oriented laminated film of the present invention as a base film and having a magnetic layer on one side thereof is also provided. The surface on which the magnetic layer is formed is preferably the flatter surface of the biaxially oriented laminated film.
The magnetic recording medium is not particularly limited as long as the biaxially oriented laminated film of the present invention is used as a base film. For example, QIC, DLT, and linear track data such as S-DLT and LTO which are high capacity types are used. Examples include storage tape. Since the dimensional change of the base film due to changes in temperature and humidity is extremely small, a magnetic recording medium suitable for high density and high capacity that does not easily cause track deviation even when the track pitch is narrowed in order to ensure high tape capacity and Become.

  According to the present invention, the biaxially oriented laminated film of the present invention is used as a base film, and a nonmagnetic layer and a magnetic layer are formed in this order on one surface, and a backcoat layer is formed on the other surface. A magnetic recording medium is preferred. The composition of the nonmagnetic layer is not particularly limited, but a non-magnetic layer containing a fine inorganic powder such as silica, alumina, titanium dioxide or the like in a thermosetting resin or a high energy ray curable resin is used. The thickness of the nonmagnetic layer is preferably from 0.5 to 3.0 μm, more preferably from 1.0 to 2.0 μm, particularly preferably from 1.0 to 1.5 μm because the effects of the present invention are easily achieved.

  The kind of the magnetic layer on the nonmagnetic layer is preferably a so-called coating type in which magnetic powder is coated together with a binder from the viewpoint of the runnability of the magnetic recording medium. The type of magnetic powder constituting the magnetic layer is not particularly limited, and iron oxide, chromium oxide, cobalt-coated iron oxide, and metals such as iron, cobalt, iron-cobalt, iron-cobalt-nickel, cobalt-nickel, etc. These alloys are preferably used, but metals or alloys thereof are particularly desirable rather than oxides. Further, the binder constituting the magnetic layer is not particularly limited, but a thermosetting resin system and a high energy ray curable binder are preferable, and other additives may include a dispersant, a lubricant, an antistatic agent, and the like. . For example, vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane, polyisocyanate, or a mixture thereof is preferably used. The thickness of the magnetic layer is preferably in the range of 0.1 to 1.0 μm, and more preferably in the range of 0.1 to 0.5 μm because the effects of the present invention are easily achieved.

  The composition of the backcoat layer is not particularly limited, but is preferably composed of carbon black and a thermosetting resin system or a high energy ray curable binder, and as other additives, a dispersant, a lubricant, an antistatic agent. Etc. may be contained. For example, vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane, polyisocyanate, or a mixture thereof is preferably used. The thickness of the back coat layer is preferably in the range of 0.1 to 1.0 μm, and more preferably in the range of 0.3 to 0.8 μm because the effects of the present invention are easily achieved.

  In the case where the magnetic recording tape of the present invention is the above-described coating type, the ratio of the thickness obtained by subtracting the thickness of the base film from the thickness of the magnetic recording tape is 0.2 to 0.8 with respect to the thickness of the base film. It is preferable to be in the range of double, preferably 0.3 to 0.7 times, particularly 0.3 to 0.6 times. If the thickness ratio is less than the lower limit, the magnetic layer, nonmagnetic layer, and backcoat layer become thin and coating becomes difficult, and the surface properties of the base film greatly affect the surface properties of the magnetic layer and backcoat layer. However, it may cause an error or an excessive effect of suppressing the temperature expansion by the base film may appear, resulting in a track shift. When the upper limit is exceeded, the tape thickness becomes too thick, for example, the tape length to be put in the cassette becomes short and it becomes difficult to obtain a sufficient magnetic recording capacity, and the effect of suppressing the temperature expansion by the base film is sufficiently expressed. It may be difficult.

  In addition, the biaxially oriented laminated film of the present invention has a ferromagnetic metal thin film layer made of iron, cobalt, nickel, chromium or an alloy or oxide containing these as a main component by vacuum deposition or the like on its surface. A magnetic recording medium having a smaller humidity expansion coefficient than the above-described coating type can also be obtained. The metal thin film layer preferably has a thickness of 100 to 300 nm. Further, a protective layer such as diamond-like carbon (DLC) and a fluorine-containing carboxylic acid-based lubricating layer may be sequentially provided on the surface of the ferromagnetic metal thin film layer as required, for purposes, and as required. Further, if necessary, a back coat layer may be provided by a known method on the other surface of the biaxially oriented laminated film of the present invention. By doing so, it can be used as a ferromagnetic metal thin film type magnetic recording medium that is excellent in electromagnetic conversion characteristics such as output in a short wavelength region, S / N, C / N, etc., and has low dropout and error rate.

  Hereinafter, the present invention will be further described based on examples. Various physical property values and characteristics in the present invention are measured and defined as follows.

[1] Young's modulus The film was cut into a sample width of 10 mm and a length of 15 cm, and the chuck was set to 100 mm with a tensile speed of 10 mm / min and a chart speed of 500 mm / min, using a universal tensile testing device (trade name: Tensilon, manufactured by Toyo Baldwin). The Young's modulus is calculated from the tangent of the rising portion of the resulting load-elongation curve. The measurement direction was the longitudinal direction of the sample, the Young's modulus was measured 10 times, and the average value was used.

[2] Average Particle Size of Inactive Particles Measured using a CP-50 Centrifuggle Particle Size Analyzer (Centrifical Particle Size Analyzer) manufactured by Shimadzu Corporation. A particle size corresponding to 50 mass percent is read from the cumulative curve of the particle size and the abundance of each particle calculated based on the centrifugal sedimentation curve obtained, and this value is used as the average particle size. .

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

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

[5] Glass transition point and melting point 10 mg of a polyester copolymer or polyolefin is enclosed in an aluminum pan for measurement, and 20 ° C./min from 25 ° C. to 300 ° C. using DSC (TA Instruments, Q100). Measurements were taken at a rate of temperature rise, and the respective melting points and glass transition points were determined.

[6] Track deviation The composition shown below was put into a ball mill, kneaded and dispersed for 16 hours, and then 5 parts by weight of an isocyanate compound (Desmodur L manufactured by Bayer) was added and sheared and dispersed at high speed for 1 hour to obtain a magnetic paint. did.
Magnetic paint composition:
Needle-like Fe particles 100 parts by weight Vinyl chloride-vinyl acetate copolymer 15 parts by weight (Sekisui Chemical's ESREC 7 A)
Thermoplastic polyurethane resin 5 parts by weight Chromium oxide 5 parts by weight Carbon black 5 parts by weight Lecithin 2 parts by weight Fatty acid ester 1 part by weight Toluene 50 parts by weight Methyl ethyl ketone 50 parts by weight Cyclohexanone 50 parts by weight The obtained biaxially oriented laminate The film is applied to one surface of the film so that the coating thickness after drying is 0.5 μm, and then subjected to orientation treatment in a 2,500 gauss DC magnetic field, heated and dried at 100 ° C., and then subjected to super calender treatment (linear pressure). 2,000 N / cm, temperature 80 ° C.) and wound up. The wound roll was left in an oven at 55 ° C. for 3 days.

Further, a back coat layer paint having the following composition was applied to the other surface of the biaxially oriented laminated film so that the thickness after drying was 1 μm, dried, and further 12.65 mm (= 1/2 inch). The magnetic tape was obtained by cutting.
Backcoat layer paint composition:
Carbon black 100 parts by weight Thermoplastic polyurethane resin 60 parts by weight Isocyanate compound 18 parts by weight (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.)
Silicone oil 0.5 parts by weight Methyl ethyl ketone 250 parts by weight Toluene 50 parts by weight

The magnetic tape thus obtained is placed in a thermo-hygrostat and each environment (environment A: 10 ° C. 10% RH, environment B: 29 ° C. 80% RH) with a tension of 1 N applied in the longitudinal direction. ) For 5 hours, and then the width was measured with a laser dimension measuring machine. Then, the track deviation rate was calculated by the following formula.
Track deviation rate (ppm) = ((LB−LA) / LA) * 10 ⁶ −7 × (29−10)
In the above formula, LB is the width measured in environment B, LA is the width measured in environment A, 7 is the temperature expansion coefficient (ppm / ° C.) of the magnetic head, and (29-10) is the temperature change (° C.). is there. Incidentally, the humidity expansion coefficient of the magnetic head was set to 0 ppm /% RH.
The track deviation rate is better as the absolute value is smaller, and was evaluated according to the following criteria.
A: Deviation width of less than 250 ppm (track deviation is extremely good)
○: Deviation width 250 ppm or more and less than 450 ppm (good track deviation)
×: Deviation width 450 ppm or more (track deviation failure)

[7] Thickness of each layer The laminated film is fixed to an embedding capsule and then embedded with an epoxy resin. Using a microtome (ULTRACUT-S), the film is cut in a direction parallel to the film forming direction and the thickness direction to form a thin film slice of 50 nm thickness. And it image | photographed and observed using the transmission electron microscope, and measured the thickness of each layer from the photograph.

[8] Intrinsic viscosity The intrinsic viscosity of polyester is obtained by dissolving a polymer using a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (40/60 weight ratio) and measuring at 35 ° C. It was.

[9] Number average molecular weight Measured by GPC (gel permeation chromatography).

[10] Polyester (e) copolymerization amount (glycol component) 10 mg sample was dissolved at 80 ° C. in 0.5 ml of a mixed solution of p-chlorophenol: 1,1,2,2-tetrachloroethane = 3: 1 (volume ratio). Then, after adding isopropylamine and mixing well, 600 MHz ¹ H-NMR was measured at 80 ° C. using JEOL A600 manufactured by JEOL, and the amount of each glycol component was measured.
(Acid component) 60 mg of a sample was dissolved in 0.5 ml of a mixed solution of p-chlorophenol: 1,1,2,2-tetrachloroethane = 3: 1 (volume ratio) at 140 ° C., and JEOL A600 manufactured by JEOL Ltd. was used. Then, ¹³ C-NMR of 150 MHz was measured at 140 ° C., and the amount of each acid component was measured.

[Example 1]
Dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol were subjected to esterification and transesterification in the presence of titanium tetrabutoxide, and then further The polycondensation reaction is performed, and 80 mol% of the acid component is 2,6-naphthalenedicarboxylic acid component, 20 mol% of the acid component is 6,6 '-(ethylenedioxy) di-2-naphthoic acid component, glycol component As a polyester (e), a copolymerized polyester (hereinafter sometimes referred to as CoPEs1) in which 98 mol% of the polymer was an ethylene glycol component and 2 mol% of the glycol component was a diethylene glycol component was obtained. The melting point of this CoPEs1 was 240 ° C., the glass transition temperature was 117 ° C., and the intrinsic viscosity was 0.65 dl / g.

  To this polyester (e), 0.02 wt% of silicone particles having an average particle size of 0.5 μm and 0.3 wt% of silica particles having an average particle size of 0.1 μm were added to prepare a resin for the film layer E. In addition, syndiotactic polystyrene (grade: 130ZC, melting point 272, manufactured by Idemitsu Petrochemical Co., Ltd.) added with 0.02 wt% of silicone particles having an average particle diameter of 0.5 μm and 0.3 wt% of silica particles having an average particle diameter of 0.1 μm was added. ° C) was prepared as a resin for the film layer F. The polymer of the film layer E is dried at 160 ° C. for 3 hours, the polymer of the film layer F is dried at 100 ° C. for 3 hours, and then supplied to an extruder to be melted. After branching into 24 layers, the layers are joined at 300 ° C. using a multilayer feed block device in which the E layer and the F layer are alternately laminated, guided to the die while maintaining the laminated state, and cast onto the casting drum. Thus, a total of 49 laminated unstretched sheets in which E layers and F layers were alternately laminated were prepared. At this time, it adjusted so that it might become the thickness shown in Table 1 after extending | stretching by the extrusion amount of the polymer of E layer and F layer, and it laminated | stacked so that both surface layers might become E layer. The laminated unstretched sheet extruded from the die was rapidly cooled and solidified on a casting drum maintained at a surface finish of 0.3 S and a surface temperature of 60 ° C. to obtain an unstretched film.

This laminated unstretched film is preheated at 120 ° C., and further heated with an infrared heater from above 14 mm between low-speed and high-speed rolls, and heated so that the surface temperature of the film becomes 135 ° C. The film was stretched 4.7 times, rapidly cooled, then fed to a stenter, and stretched 8.5 times in the transverse direction at 140 ° C. Further, after heat setting at 200 ° C. for 30 seconds, 1.0% relaxation treatment was performed in the lateral direction at 150 ° C. to obtain a biaxially oriented laminated film having a thickness of 5.0 μm.
The characteristics of the obtained biaxially oriented laminated film and magnetic tape are shown in Table 1.

[Example 2]
In Example 1, the same operation was repeated except that the extrusion amount was adjusted to the thickness shown in Table 1, the longitudinal draw ratio was changed to 4.5 times, and the horizontal draw ratio was changed to 8 times. An axially oriented laminated film and a magnetic tape were obtained. Table 1 shows the characteristics and evaluation results of the obtained biaxially oriented laminated film and magnetic tape.

[Example 3]
In Example 1, the same operation was repeated except that the extrusion amount was adjusted to the thickness shown in Table 1, and the longitudinal draw ratio was changed to 4.3 times and the transverse draw ratio was changed to 7.8 times. A biaxially oriented laminated film and a magnetic tape were obtained. Table 1 shows the characteristics and evaluation results of the obtained biaxially oriented laminated film and magnetic tape.

[Example 4]
In Example 1, the number of layers was changed as shown in Table 1, the extrusion amount was adjusted and the thickness was changed as shown in Table 1, the longitudinal draw ratio was 4.5 times, and the transverse draw ratio was The biaxially oriented laminated film and the magnetic tape were obtained by repeating the same operation except that the temperature of the relaxation treatment was changed to 160 ° C. by 8 times. Table 1 shows the characteristics and evaluation results of the obtained biaxially oriented laminated film and magnetic tape.

[Example 5]
In Example 1, the number of layers was changed as shown in Table 1, the extrusion amount was adjusted and the thickness was changed as shown in Table 1, the longitudinal draw ratio was 4.5 times, and the transverse draw ratio was The same operation was repeated except that was changed to 8 times to obtain a biaxially oriented laminated film and a magnetic tape. Table 1 shows the characteristics and evaluation results of the obtained biaxially oriented laminated film and magnetic tape.

[Example 6]
In Example 2, the same operation was repeated except that the longitudinal draw ratio was changed to 5.2 times and the transverse draw ratio was changed to 6.4 times to obtain a biaxially oriented laminated film and a magnetic tape. Table 1 shows the characteristics and evaluation results of the obtained biaxially oriented laminated film and magnetic tape.

[Example 7]
In Example 2, instead of CoPEs1, 88 mol% of the acid component is 2,6-naphthalenedicarboxylic acid component, and 12 mol% of the acid component is 6,6 '-(ethylenedioxy) di-2-naphthoic acid component Using a copolyester in which 98 mol% of the glycol component is an ethylene glycol component and 2 mol% of the glycol component is a diethylene glycol component (hereinafter sometimes referred to as CoPEs2), the draw ratio in the machine direction is 4.1 times. A biaxially oriented laminated film and a magnetic tape were obtained by repeating the same operation except that the transverse draw ratio was changed to 7.5. The melting point of this CoPEs2 was 250 ° C., the glass transition temperature was 118 ° C., and the intrinsic viscosity was 0.65 dl / g. Table 1 shows the characteristics and evaluation results of the obtained biaxially oriented laminated film and magnetic tape.

[Example 8]
In Example 2, instead of CoPEs1, 73 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 27 mol% of the acid component was 6,6 '-(ethylenedioxy) di-2-naphthoic acid component Using a copolyester in which 98 mol% of the glycol component is an ethylene glycol component and 2 mol% of the glycol component is a diethylene glycol component (hereinafter sometimes referred to as CoPEs3), the draw ratio in the machine direction is 4.8 times. The same operation was repeated except that the transverse draw ratio was changed to 8.5 times to obtain a biaxially oriented laminated film and a magnetic tape. The melting point of CoPEs3 was 237 ° C., the glass transition temperature was 116 ° C., and the intrinsic viscosity was 0.65 dl / g. Table 1 shows the characteristics and evaluation results of the obtained biaxially oriented laminated film and magnetic tape.

[Comparative Example 1]
CoPEs1 with 0.02 wt% of silicone particles having an average particle size of 0.5 μm and 0.3 wt% of silica particles having an average particle size of 0.1 μm is dried at 160 ° C. for 3 hours, and then supplied to an extruder for melting. Then, it is led to a die and cast on a casting drum to create a single-layer unstretched sheet. The stretching in the machine direction is changed to a stretching temperature of 140 ° C. and a stretching ratio of 5.0 times, and the stretching in the transverse direction is stretched. The same operation was repeated except that the temperature was changed to 145 ° C. and the draw ratio was changed to 6.5 times to obtain a biaxially oriented film having a thickness of 5 μm and a magnetic tape. Table 1 shows the characteristics and evaluation results of the obtained biaxially oriented film and magnetic tape.

[Comparative Example 2]
In Example 1, when the extrusion amount was adjusted so as to have the thickness shown in Table 1, the laminated state of the film layer E and the film layer F was disturbed, and a uniform laminated film was not obtained. It was.

  CoPEs1, CoPEs2, and CoPEs3 in Table 1 are copolymerized polyesters in which the ratio of 6,6 ′-(ethylenedioxy) di-2-naphthoic acid component is 20 mol%, 12 mol%, and 27 mol%, respectively. , SPS is syndiotactic polystyrene, and the temperature expansion coefficient and the humidity expansion coefficient each represent a value in the width direction of the film.

  The biaxially oriented laminated film of the present invention has excellent dimensional stability against changes in humidity while maintaining mechanical properties, and can be suitably used for a base film of a magnetic recording medium.

Claims (8)

A laminated film in which a film layer E made of an aromatic polyester (e) and a film layer F made of a polyolefin (f) are laminated in at least two layers,
The aromatic polyester (e) is a polyester comprising an aromatic dicarboxylic acid component and a diol component, and (i) the following formula (A) in which the dicarboxylic acid component is 5 mol% or more and less than 50 mol% and 50 mol%: It is a polyester containing a repeating unit represented by the following formula (B) in excess of 95 mol% and (ii) a repeating unit represented by the following formula (C) in which the diol component is 90 to 100 mol%. The polyolefin (f) has a melting point in the range of 200 to 280 ° C., and the total thickness of the film layer F is in the range of 15 to 85% based on the total thickness of the laminated film. Biaxially oriented laminated film.

(In the formula (A), ^{R A} is an alkylene group having 2 to 10 carbon atoms, in the formula (B), ^{R B} is a phenylene group or a naphthalene-diyl group, in the formula (C), ^{R C} is 2 to 10 carbon atoms An alkylene group.)   The biaxially oriented laminated film according to claim 1, wherein the polyolefin (f) is a styrene polymer having a syndiotactic structure.   2. The biaxially oriented laminated film according to claim 1, wherein the Young's modulus in the film forming direction and the width direction of the film is both 4 GPa or more, and the total of both is 22 GPa at most. 2. The biaxially oriented laminated film according to claim 1, wherein the film has a humidity expansion coefficient in the width direction of 0.1 × 10 ^{−6 to} 7 × 10 ⁻⁶ /% RH. 2. The biaxially oriented laminated film according to claim 1, wherein the film has a temperature expansion coefficient in the width direction of −10 × 10 ⁻⁶ to 15 × 10 ⁻⁶ / ° C. 3.   The biaxially oriented laminated film according to claim 1, wherein the film thickness is in the range of 2 to 10 μm.   The biaxially oriented laminated film according to any one of claims 1 to 6, which is used as a base film for a magnetic recording medium.   A magnetic recording medium comprising the biaxially oriented laminated film according to claim 1 and a magnetic layer provided on one side thereof.