JP2010012651A - Biaxially oriented laminated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented film which combines high dimensional stability to temperature changes and high dimensional stability during processing at high temperatures after formation as products. <P>SOLUTION: The biaxially oriented film consists of a laminate of a layer A made of (a) an aromatic polyester and a layer B made of (b) polycycloolefin with a glass transition temperature of 110-180°C. The ratio of the thickness of the layer B is 2-60% of the total thickness of the laminated film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biaxially oriented laminated film that is excellent in dimensional stability against changes in humidity and that has suppressed elongation during processing at high temperatures.

  Polyester films have excellent thermal and mechanical properties, and are therefore used in various applications such as magnetic recording media, capacitors, flexible substrates, optical members, food packaging, and decoration.

  By the way, in the magnetic recording medium, in particular, the magnetic recording medium for data storage, as the capacity and density of the tape are increased, the characteristic requirements for the base film are becoming strict. In a magnetic recording medium 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 a 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 include those caused by temperature and humidity changes and those caused by shrinkage with time in the width direction when the vehicle is repeatedly run under high tension and high temperature and humidity. If this dimensional change is large, track deviation will occur and an error during electromagnetic conversion will occur. For convenience of explanation, the traveling direction when the film is continuously formed is referred to as a film forming direction, a continuous film forming direction, a vertical direction, a longitudinal direction or an MD direction, and an in-plane direction orthogonal to the film forming direction is defined as: It may be called a horizontal direction or a width direction.

In order to solve such a dimensional change, Patent Document 1 (Japanese Patent Laid-Open No. 2006-2142) discloses blending or laminating with a polyolefin such as syndiotactic polystyrene.
However, in the methods proposed in these publications, there is a problem that if a product such as a film is made and then processed at a high temperature, the film is stretched.
Japanese Patent Laid-Open No. 2006-2142

  An object of the present invention is to provide a biaxially oriented laminated film that has both high dimensional stability against changes in humidity and dimensional stability during processing at a high temperature after making the product.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have used the aromatic polyester (a) and a polycycloolefin having a glass transition temperature of 110 to 180 ° C. to laminate and use it with respect to humidity change. The inventors have found that the dimensional stability during processing at high temperatures can be maintained at a high level while greatly reducing the change, and the present invention has been completed.

  That is, the present invention is a laminated film in which an A layer made of an aromatic polyester (a) and a B layer made of a polycycloolefin (b) having a glass transition temperature in the range of 110 to 180 ° C. are laminated. The ratio of the thickness of the layer B is in the range of 2 to 60% based on the thickness of the entire laminated film, and provides a biaxially oriented laminated film. Further, as a preferred embodiment thereof, the main repeating unit of the biaxially oriented laminated film and aromatic polyester (a) in which the polycycloolefin (b) is a norbornene-based polycycloolefin is ethylene-2,6-naphthalenedicarboxylic acid. In the above biaxially oriented laminated film and aromatic polyester (a), the acid component is composed of the following structural formulas (I) and (II), and the proportion of the following structural formula (I) is the number of moles of all acid components. As a standard, at least one of the biaxially oriented laminated film used for the base film of the magnetic recording medium or the biaxially oriented laminated film having a glycol component in the following structural formula (III) having a range of 5 to 80 mol% Also provided are those comprising:

（上記構造式（Ｉ）中のＲ_１は炭素数１〜１０のアルキレン基を、上記構造式（ＩＩ）中のＲ_２はフェニレン基またはナフタレンジイル基、上記構造式（ＩＩＩ）中のＲ_３は炭素数２〜４のアルキレン基を示す。）

(R ₁ in the structural formula (I) is an alkylene group having 1 to 10 carbon atoms, R ₂ in the structural formula (II) is a phenylene group or a naphthalenediyl group, and R ₃ in the structural formula (III). Represents an alkylene group having 2 to 4 carbon atoms.)

  The biaxially oriented laminated film of the present invention can make the dimensional change with respect to the humidity change extremely small, and the elongation at the time of processing at high temperature is also small. Therefore, for example, the biaxially oriented film of the present invention can be suitably used as a base film of a magnetic recording medium. For example, if a magnetic recording medium is used, it is less likely to cause a track shift and is excellent in high density and high capacity. A magnetic recording medium or the like can be obtained stably.

  Furthermore, the biaxially oriented laminated film of the present invention can be suitably used as a base film of a film capacitor because it can reduce the dimensional change with respect to the humidity change, and it can be used for electric / electronic devices and automobile parts that require miniaturization and heat resistance. Suitable as a film capacitor.

[Aromatic polyester (a)]
The aromatic polyester (a) in the present invention is a polymer obtained by polycondensation of a diol component and an aromatic dicarboxylic acid component. Examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, and 6,6 ′-(ethylenedioxy) di-2-naphthoic acid. 6,6 ′-(alkylenedioxy) di-2-naphthoic acid is exemplified, and examples of the diol component include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol. Is mentioned.

  Among these, ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate is the main repeating unit from the viewpoint of dimensional stability during processing at high temperature, and ethylene-2,6-naphthalene is particularly preferable. Those having carboxylate as the main repeating unit are preferred. Moreover, what blended 10-30 weight% of polyimides to the polyester which has ethylene terephthalate as a main repeating unit is preferable.

  From the viewpoint of further improving the dimensional stability against environmental changes, the aromatic polyester (a) has an acid component consisting of the structural formulas (I) and (II), and the proportion of the following structural formula (I) is the total acid. It is preferable that it is in the range of 5 to 80 mol% based on the number of moles of the component, and that the glycol component is the following structural formula (III).

Specific examples of the acid component represented by the structural formula (I) are those in which R ₁ is an alkylene group having 1 to 10 carbon atoms, and preferably 6,6 ′-(ethylenedioxy) di -2-naphthoic acid component, 6,6 ′-(trimethylenedioxy) di-2-naphthoic acid component and 6,6 ′-(butyleneoxy) di-2-naphthoic acid component, etc. Among these, from the viewpoint of the effects of the present invention, those having an even number of carbon atoms of R ₁ in the above structural formula (I) are preferable, and in particular, 6,6 ′-(ethylenedioxy) di having 2 carbon atoms of R _1. A 2-naphthoic acid component is preferred.

  Examples of the acid component represented by the structural formula (II) include a terephthalic acid component, an isophthalic acid component, a 2,6-naphthalenedicarboxylic acid component, and a 2,7-naphthalenedicarboxylic acid component. Among these, a terephthalic acid component and a 2,6-naphthalenedicarboxylic acid component are preferable from the viewpoint of mechanical properties and the like, and a 2,6-naphthalenedicarboxylic acid component is particularly preferable.

  Specific examples of the glycol component represented by the structural formula (III) include an ethylene glycol component, a trimethylene glycol component, a tetramethylene glycol component, and the like. The mol% or more is preferably an ethylene glycol component, and more preferably 95 to 100 mol% is an ethylene glycol component.

  By the way, among the acid components of the aromatic polyester (a), the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the structural formula (I) is in the range of 5 to 80 mol%. Polymerization is preferred. If the ratio of the 6,6 '-(alkylenedioxy) di-2-naphthoic acid component is less than the lower limit, the effect of reducing the humidity expansion coefficient due to copolymerization is difficult to be exhibited. On the other hand, the upper limit is preferably 80 mol% or less, and more preferably less than 50 mol% from the viewpoint of moldability. Surprisingly, the effect of reducing the coefficient of humidity expansion by the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is very efficiently expressed in a small amount, and added at 50 mol% or more. It can also be said that the effect from the viewpoint of the coefficient of humidity expansion is saturated. From such a viewpoint, the upper limit of the copolymerization amount of the preferred 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is 45 mol% or less, further 40 mol% or less, and further 35 mol% or less. In particular, it is 30 mol% or less, and the other lower limit is 5 mol% or more, further 7 mol% or more, still more 10 mol% or more, particularly 15 mol% or more.

  By using the aromatic polyester (a) obtained by copolymerizing such a specific amount of 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, a biaxial shaft having a smaller temperature expansion coefficient and lower humidity expansion coefficient. It can be set as an oriented laminated film.

  When the aromatic polyester (a) in the present invention does not contain a 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, it is 6,6 -′- (alkyl) in o-chlorophenol at 35 ° C. When a rangeoxy) di-2-naphthoic acid component is contained, it is measured at 35 ° C. in a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (40/60 weight ratio). The intrinsic viscosity is preferably 0.40 dl / g or more, and more preferably 0.40 to 1.0 dl / g. If the intrinsic viscosity is less than 0.4 dl / g, cutting may occur frequently during film formation, or the strength of the product after forming may be insufficient. On the other hand, when the intrinsic viscosity exceeds 1.0 dl / g, productivity during polymerization is lowered.

[Polycycloolefin (b)]
The polycycloolefin (b) in the present invention is necessary for reducing the humidity expansion coefficient of the obtained biaxially oriented laminated film, and its glass transition temperature needs to be in the range of 110 to 180 ° C. Examples of the polycycloolefin (b) include norbornene-based polycycloolefins. Specific examples of norbornene-based polycycloolefins include trade names “ZEONEX” and “ZEONOR” manufactured by Zeon Corporation, and “ARTON” manufactured by JSR Corporation. When the glass transition temperature is within the above range, it is easy to maintain the film forming property while suppressing elongation during high-temperature processing.

  Since the polycycloolefin (b) in the present invention has a high glass transition temperature, it has a melting point from the point that it is easy to maintain a high film forming property when it is laminated with the aromatic polyester (a). It is preferable that it is an amorphous thing which does not have.

[Biaxially oriented laminated film]
The biaxially oriented laminated film of the present invention comprises a film layer A made of an aromatic polyester (a) and a film layer B made of the aforementioned polycycloolefin (b) laminated on at least one surface thereof.

  In the biaxially oriented laminated film of the present invention, the film layer A is composed of the above-described aromatic polyester (a), and is preferably 10% by weight or less, more preferably 5% by weight or less, as long as the object of the present invention is not impaired. Within this range, other resins may be mixed. Moreover, in the biaxially oriented laminated film of the present invention, the film layer B is composed of the above-mentioned polycycloolefin (b), and is preferably 10% by weight or less, more preferably 5% by weight within the range not impairing the object of the present invention. % Or less may be mixed with other resins.

  The ratio of the film layer B in the biaxially oriented laminated film is 2 to 60%, preferably 3 to 55%, more preferably 3 to 50%, still more preferably 5 to 45%, based on the thickness of the whole laminated film. Especially preferably, it is the range of 5-30 weight%. When the ratio of the thickness of the film layer B is below the lower limit, the effect of improving the dimensional stability with respect to the intended humidity change becomes poor. On the other hand, if the ratio of the thickness of the film layer B exceeds the upper limit, the resulting biaxially oriented film may have poor mechanical properties or may be difficult to stretch.

  The biaxially oriented laminated film has, as a preferred layer constitution, i) a two-layer constitution in which the film layer A is laminated on one side of the film layer B, ii) a three-layer constitution in which the film layer A is laminated on both sides of the film layer B, iii) A multilayer structure in which at least 4 layers of the film layer B and the film layer A are laminated is exemplified. In the case of the three-layer structure of ii), the curl resistance is further improved. Moreover, in the case of the multilayer structure of iii), even if it is the lamination | stacking of the film layer which consists of a different kind of resin, it can form into a film, without producing the deterioration of the process by interlayer peeling. In the case of the multilayer structure of iii), the preferred total number of layers is 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 500 layers from the viewpoint of preventing complication of the process. Is 250 layers. Here, the film layer A and the film layer B are preferably laminated alternately, and film layers made of other resins may be laminated as long as the object of the present invention is not impaired. In the case of the multilayer structure of iii), the thickness per layer of the film layer A is preferably in the range of 0.02 to 1.5 μm, more preferably 0.04 to 1.0 μm, and one layer of the film layer B The per-thickness is preferably 0.02 to 1.5 μm, more preferably 0.04 to 1.0 μm. When the thickness per one layer of the film layer A or the film layer B is less than the lower limit, it is necessary to laminate an extremely large number of layers, and the process is likely to be complicated. On the other hand, when the thickness per layer of the film layer A or the film layer B exceeds the upper limit, peeling between layers may occur. 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.

  Specific examples of the biaxially oriented laminated film in the present invention include the above-mentioned laminated film, and a layer structure suitable for the properties further required depending on the application can be used.

  Moreover, the biaxially oriented laminated film of the present invention may contain inert particles known per se used according to the purpose of the film. Examples of the inert particles include inorganic particles (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide) containing the elements of Periodic Tables IIA, IIB, IVA, and IVB, and crosslinked silicone resins. Further, fine particles made of a polymer having high heat resistance such as crosslinked polystyrene and crosslinked acrylic resin particles can be contained.

[Temperature expansion coefficient: αt]
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 + 5 × 10 ⁻⁶ / ° C. When αt is smaller than the lower limit, the film shrinks. On the other hand, when αt exceeds the upper limit, the film expands due to a temperature change, and when used in a magnetic recording medium, a track shift or the like may be caused.

  Such αt is achieved by improving the Young's modulus in the measurement direction by stretching, and setting the amount of polycycloolefin to be not more than the above-mentioned upper limit. When the width direction is unstretched, since the Young's modulus in the width direction is low, the temperature expansion coefficient in the above range cannot be obtained even if polyolefin is mixed.

[Humidity expansion coefficient: αh]
The biaxially oriented laminated film of the present invention preferably has a humidity expansion coefficient αh in the width direction of the film in the range of 0.1 × 10 ^{−6 to} 7 × 10 ⁻⁶ /% RH. Further preferable αh is in the range of 0.5 × 10 ^{−6 to} 6 × 10 ⁻⁶ /% RH, and particularly preferably in the range of 0.5 × 10 ^{−6 to} 5 × 10 ⁻⁶ /% RH.

  In order to make αh smaller than the lower limit, the polycycloolefin (b) is excessively present, resulting in a decrease in film forming property and a decrease in mechanical properties. On the other hand, when the upper limit is exceeded, the film stretches due to a change in humidity, which may cause a track shift when used in a magnetic recording medium. Such αh is achieved by using the polycycloolefin (b) while improving the Young's modulus in the measurement direction by stretching. When the width direction is unstretched, the Young's modulus in the width direction is low, so that the humidity expansion coefficient in the above range cannot be obtained even if polycycloolefin (b) is present.

[Young's modulus: Y]
The biaxially oriented laminated film of the present invention preferably has a Young's modulus in the film forming direction and width direction of 4 GPa or more. If the Young's modulus is smaller than the lower limit of either one, even if the dimensional change due to the humidity change is small, the magnetic recording medium may not be able to withstand the load, or may be easily deformed due to the temperature and humidity change. 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. The upper limit of the sum of Young's moduli in the preferred 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.

[Surface layer]
The biaxially oriented laminated film of the present invention may be a laminate in which other layers are further laminated on at least one surface for the purpose of imparting other functions within a range not impairing the effects of the present invention.
For example, when used in a magnetic recording medium, in order to make the magnetic layer side a flatter surface, a polyester film layer containing substantially no inert particles is applied to the magnetic layer side surface of the biaxially oriented film of the present invention. You may laminate. Also, in order to make the running surface (nonmagnetic layer) side more excellent in running properties, the inert film to be contained is made relatively large or the amount of the polyester film layer is increased in the biaxial orientation of the present invention. You may laminate | stack on the nonmagnetic layer side surface of a film. Such a laminated film is preferable from the viewpoint that it is easy to achieve both electromagnetic conversion characteristics and film winding properties when used as a magnetic recording medium.

[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 includes a method by coextrusion method using the above-mentioned aromatic polyester (a) and polycycloolefin (b) as raw materials. Preferably, the raw materials constituting each layer are laminated in a die by a co-extrusion method in a molten state and then extruded into a sheet shape, or two or more types of molten polyester are extruded from a die and then laminated and rapidly solidified by cooling. A laminated unstretched film. Moreover, when manufacturing a laminated film of four or more layers, for example, it can be manufactured by a simultaneous multilayer extrusion method using a feed block as proposed in paragraph 0028 of JP-A No. 2000-326467.

  That is, after drying the aromatic polyester (a) constituting the film layer A and the polycycloolefin (b) constituting the film layer B, the melting point (Tm: ° C.) to (Tm + 70) of the aromatic polyester (a). ) Extrusion at a temperature of ° C. Supply to an extruder heated to about 300 ° C., and using a feed block, for example, each melt is laminated alternately, spread on a die and extruded to form a laminated unstretched film.

  Thus, the laminated unstretched film extruded into a sheet in a molten state is stretched using a known film forming method such as a tenter method or an inflation method. Specifically, the unstretched film is uniaxially (longitudinal or transverse) (Tg (glass transition temperature of aromatic polyester (a): ° C.)-10) to (Tg + 70) ° C. at a predetermined magnification. Stretching, then stretching in a direction perpendicular to the stretching direction (when the first stage is the longitudinal direction, the second stage is the transverse direction) at a temperature of Tg to (Tg + 70) ° C. and further heat-treating. Can be used. At that time, a draw ratio, a draw temperature, a heat treatment condition, and the like are selected and determined from the characteristics of the film. 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, in the case of magnetic recording applications, when it is desired to further improve mechanical properties, the biaxially stretched film before the heat setting treatment is heat-treated at a temperature of (Tg + 20) to (Tg + 70) ° C. The film is stretched in the machine direction or the transverse direction at a temperature higher by -40 ° C., and further stretched in the transverse direction or the longitudinal direction at a temperature higher by 20-50 ° C. than the stretching temperature. It is preferable that the overall draw ratio in the transverse direction is 3.0 to 6.0 times.
Moreover, when providing a coating layer, it is preferable to apply | coat a desired coating liquid to the one or both surfaces of an above-mentioned unstretched film or a uniaxially stretched film.

[Magnetic recording medium]
According to the present invention, there is provided a magnetic recording medium having the above biaxially oriented laminated film of the present invention as a base film and having a magnetic layer on one surface thereof.
The magnetic recording medium is not particularly limited as long as the biaxially oriented film of the present invention is used as a base film. For example, QIC, DLT, and linear track data storage such as S-DLT and LTO which are high capacity types. For example, tape. Since the dimensional change of the base film due to changes in temperature and humidity is extremely small, it becomes a magnetic recording medium suitable for high density and high capacity that hardly causes track deviation even if the track pitch is narrowed in order to ensure a high capacity of the tape. .

  Hereinafter, the present invention will be described based on examples. Each characteristic value and evaluation method were measured and evaluated by the following methods.

(1) Melting point, glass transition point 10 mg of aromatic polyester (a) or polycycloolefin (b) is enclosed in an aluminum pan for measurement, and 25 ° C. to 300 ° C. using DSC (TA Instruments, Q100). Measured at a temperature increase rate of 20 ° C./min up to ° C., the melting point (Tma) of the aromatic polyester (a), and the respective glass transition points (the glass transition point of the aromatic polyester (a): Tga, polycycloolefin) The glass transition point (Tgb) of (b) was determined.

(2) Average particle diameter of inert particles Measured using a CP-50 type centrifugul particle size analyzer manufactured by Shimadzu Corp. (centrifugal particle size analyzer). 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) 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.

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

(5) Young's modulus The film is cut into a sample width of 10 mm and a length of 15 cm, the chuck is 100 mm, the tensile speed is 10 mm / min, and the chart speed is 500 mm / min. The Young's modulus is calculated from the tangent of the rising part of the elongation curve.
The measurement direction was the longitudinal direction of the sample, and an average value measured 10 times was used.

(6) Thickness of each layer A laminated film is cut into a triangle, fixed in an embedded capsule, and then embedded in 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 using the transmission electron microscope, it observed at the acceleration voltage of 1000 kv, image | photographed by the magnification of 10,000 times-100,000 times, and measured the thickness of each layer from the photograph.

(7) Intrinsic viscosity The intrinsic viscosity of the aromatic polyester (a) was measured at o-chlorophenol at 35 ° C. When it is difficult to dissolve uniformly with o-chlorophenol, such as when the structural unit represented by the structural formula (I) is included, P-chlorophenol / 1,1,2,2-tetrachloroethane ( (40/60 weight ratio) using a mixed solvent.

(8) TMA
Using a TMA / SS6000 manufactured by Seiko Instruments Inc., a sample cut into a width of 4 mm so that the film forming direction is the longitudinal direction is set so that the length between chucks is 20 mm, and a load of 20 MPa is applied. The temperature was raised at a temperature rate of 5 ° C./min, and the elongation percentage (%) of the film in the film forming direction at 115 ° C. was determined.
It can be said that the lower the elongation rate, the less the elongation at the time of processing at high temperature.

(9) Elongation during processing (coating spots)
On one surface of a 500 m long film slit to a width of 500 mm, a nonmagnetic paint and a magnetic paint having the following composition were simultaneously applied by a die coater, and the thicknesses of the nonmagnetic layer and the magnetic layer after drying were 1.2 μm and 0 respectively. The film is applied by changing the film thickness so as to be 1 μm, magnetically oriented and dried. Further, after calendering with a small test calender (steel roll / nylon roll, 5 stages) at a temperature of 70 ° C. and a linear pressure of 200 kg / cm, curing is performed at 70 ° C. for 48 hours. And about the obtained film with a magnetic layer, the application | coating spot was evaluated by the following references | standards by visual determination. In addition, the visual judgment is performed by installing a fluorescent lamp on the back side of the film and counting light leakage due to the loss of the magnetic layer, and this film with a magnetic layer is provided with a back coat layer as necessary. , Slit to a width of 12.65 mm, and incorporated into a cassette to make a magnetic recording tape.
◎: Application failure is less than 5 pieces / 250 m ² ○: Application failure is 5 pieces / 250 m ² or more and less than 10 pieces / 250 m ²
Δ: coating omission 10 pieces / 250 m ² or more and less than 20 pieces / 250 m ²
×: Application missing 20 pieces / 250 m ² or more

Composition of non-magnetic paint
・ Titanium dioxide fine particles: 100 parts by weight
・ Sleek A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer: 10 parts by weight
・ Nipporan 2304 (polyurethane elastomer made by Nippon Polyurethane): 10 parts by weight
Coronate L (Japanese polyurethane polyisocyanate): 5 parts by weight
・ Lecithin: 1 part by weight
・ Methyl ethyl ketone: 75 parts by weight
・ Methyl isobutyl ketone: 75 parts by weight
-Toluene: 75 parts by weight
・ Carbon black: 2 parts by weight
・ Lauric acid: 1.5 parts by weight

Composition of magnetic paint
Iron (length: 0.3 μm, needle ratio: 10/1, 1800 oersted)
: 100 parts by weight
・ Sleek A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer: 10 parts by weight
・ Nipporan 2304 (polyurethane elastomer made by Nippon Polyurethane): 10 parts by weight
Coronate L (Japanese polyurethane polyisocyanate): 5 parts by weight
・ Lecithin: 1 part by weight
・ Methyl ethyl ketone: 75 parts by weight
・ Methyl isobutyl ketone: 75 parts by weight
-Toluene: 75 parts by weight
・ Carbon black: 2 parts by weight
・ Lauric acid: 1.5 parts by weight

(10) Copolymerization amount (glycol component) 10 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 80 ° C., and isopropylamine Then, 1H-NMR of 600 MHz 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, 13C-NMR of 150 MHz was measured at 140 ° C., and the amount of each acid component was measured.

[Reference Example 1]
After transesterification of dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol in the presence of manganese acetate by a conventional method, triethylphosphonoacetate was added. Subsequently, antimony trioxide is added and polycondensed by a conventional method to obtain a polyethylene-2,6-naphthalenedicarboxylate resin (intrinsic viscosity (orthochlorophenol, 35 ° C.) 0.62, hereinafter abbreviated as PEN1). It was. As a result of measuring the concentration of each element in the resin by the atomic absorption method, Mn = 50 ppm, Sb = 300 ppm, and P = 50 ppm. In PEN1, in the polymerization stage, 0.02% by weight of silicone particles having an average particle size of 0.5 μm and 0.3% of silica particles having an average particle size of 0.1 μm in advance are based on the weight of the resin composition. Weight percent was added.

[Reference Example 2]
Dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol are subjected to esterification and transesterification in the presence of titanium tetrabutoxide, and then further The polycondensation reaction was performed, and the intrinsic viscosity was 0.62 dl / g, 80 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 20 mol% of the acid component was 6,6 ′-(alkylenedioxy). Copolymerized polyethylene-2,6-naphthalenedicarboxylate (hereinafter referred to as copolymerized PEN20) in which 99 mol% of the di-2-naphthoic acid component and glycol component are ethylene glycol components and 1 mol% is diethylene glycol components. Obtained. The copolymerized PEN 20 contained silica particles having an average particle size of 0.5 μm before the polycondensation reaction so as to be 0.2% by weight based on the weight of the resin composition to be obtained.

[Reference Example 3]
In Reference Example 2, 88 mol% of the acid component is changed to 2,6-naphthalenedicarboxylic acid component, and 12 mol% of the acid component is changed to 6,6 '-(alkylenedioxy) di-2-naphthoic acid component. Except that, the same operation was repeated to obtain a copolymerized polyethylene-2,6-naphthalenedicarboxylate (hereinafter referred to as copolymerized PEN12). The copolymerized PEN 12 contained silica particles having an average particle size of 0.5 μm before the polycondensation reaction so as to be 0.2% by weight based on the weight of the resin composition to be obtained.

[Reference Example 4]
In Reference Example 2, 73 mol% of the acid component was changed to 2,6-naphthalenedicarboxylic acid component, and 27 mol% of the acid component was changed to 6,6 '-(alkylenedioxy) di-2-naphthoic acid component. Except for the above, the same operation was repeated to obtain a copolymerized polyethylene-2,6-naphthalenedicarboxylate (hereinafter referred to as copolymerized PEN27). The copolymerized PEN27 contained silica particles having an average particle size of 0.5 μm so as to be 0.2% by weight based on the weight of the resulting resin composition before the polycondensation reaction.

[Comparative Example 1]
The obtained PEN1 was dried at 180 ° C. for 6 hours, then supplied to an extruder heated to 300 ° C., extruded using a T-type extrusion die, on a casting drum maintained at a surface finish of 0.3 S and a surface temperature of 60 ° C. The film was rapidly cooled and solidified to obtain an unstretched film. This unstretched film is preheated at 75 ° C., and further heated by an infrared heater with a surface temperature of 830 ° C. from above 14 mm between low-speed and high-speed rolls and stretched 5.1 times in the film forming direction, After quenching, it was supplied to a stenter and stretched 4.8 times in the transverse direction at 125 ° C. Subsequently, after heat-fixing at 240 ° C. for 10 seconds, 1.0% relaxation treatment was performed in the lateral direction at 120 ° C. to obtain a biaxially oriented film having a thickness of 4.5 μm. The Young's modulus of the obtained film was 8 GPa in the vertical direction and 6.5 GPa in the horizontal direction.
Table 1 shows the characteristics of the obtained biaxially oriented film and magnetic tape.

[Example 1]
PEN1 obtained in Reference Example 1 is used as a raw material for film layer A layer, a trade name “ZEONEX480R” manufactured by ZEON CORPORATION is used as a raw material for film layer B, and film layer B is laminated on one side of film layer A. A biaxially oriented laminated film is obtained by repeating the same operation as in Comparative Example 1 except that a laminated unstretched film is formed by coextrusion so that the thickness ratio (film layer B / (film layer A + film layer B) is 30%. It was.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Examples 2 and 3]
In Example 1, the same operation as Example 1 was repeated except having changed the thickness ratio of the film layers A and B as shown in Table 1.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Example 4]
In Example 1, film layer B having the same thickness is laminated on both surfaces of film layer A, and the thickness ratio (total film layer B / (film layer A + total film layer B)) is changed to 30%. These operations were repeated to obtain a biaxially oriented laminated film.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Example 5]
In Example 1, it becomes 201 layers (the film layer A is arrange | positioned on both surfaces, and the thickness of each film layer A and each film layer B is the same in each layer) alternately with the film layer A and the film layer B. The same operation was repeated except that the thickness ratio (total film layer B / (total film layer A + total film layer B)) was changed to 30% to obtain a biaxially oriented laminated film.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Example 6]
In Example 1, instead of PEN1, the same operation was repeated except that the copolymerized PEN20 obtained in Reference Example 2 was used to obtain a biaxially oriented laminated film.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Example 7]
In Example 4, instead of PEN1, the same operation was repeated except that the copolymerized PEN20 obtained in Reference Example 2 was used to obtain a biaxially oriented laminated film.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Example 8]
In Example 4, instead of PEN1, the same operation was repeated except that the copolymerized PEN12 obtained in Reference Example 3 was used to obtain a biaxially oriented laminated film.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Example 9]
In Example 4, instead of PEN1, the same operation was repeated except that the copolymerized PEN27 obtained in Reference Example 4 was used to obtain a biaxially oriented laminated film.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Example 10]
In Example 5, instead of PEN1, the same operation was repeated except that the copolymerized PEN20 obtained in Reference Example 2 was used to obtain a biaxially oriented laminated film.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Comparative Example 2]
In Example 5, the same operation was repeated except that the thickness ratio (total film layer B / (total film layer A + total film layer B)) was changed to 75% to obtain a biaxially oriented laminated film.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

[Comparative Example 3]
In Example 5, the same operation was repeated except that the trade name “ZEONEX480R” manufactured by Nippon Zeon Co., Ltd. was changed to syndiotactic polystyrene (trade name: Zalek 130ZC) manufactured by Idemitsu Kosan Co., Ltd. did.
The characteristics of the obtained biaxially oriented laminated film are shown in Table 1.

  In the column of film layer B in Table 1, resin type A is a polycycloolefin (trade name “Zeonex 480R”) manufactured by Nippon Zeon Co., Ltd., and resin type B is a syndiotactic polystyrene (trade name) manufactured by Idemitsu Kosan Co., Ltd. “Zarek 130ZC”). Further, ENA in Table 1 represents the 6,6 ′-(ethylenedioxy) di-2-naphthoic acid component represented by the above formula (I), and the ratio thereof is the moles relative to all the acid components in the aromatic polyester. %. Furthermore, in the column of the biaxially oriented film, MD is the film forming direction of the film, TD is the width direction of the film, and the ratio of the B layer is the film layer B in the case of a laminated film such as two layers, three layers or multiple layers. Is divided by the total thickness of the biaxially oriented laminated film.

  Since the biaxially oriented laminated film of the present invention has excellent dimensional stability and processability at high temperatures, it can be used as a base film for magnetic recording media and capacitors, particularly for linear recording magnetic recording tapes. It can be suitably used as a base film.

Claims (5)

  A laminated film in which an A layer made of an aromatic polyester (a) and a B layer made of a polycycloolefin (b) having a glass transition temperature in the range of 110 to 180 ° C. are laminated. A biaxially oriented laminated film characterized in that the ratio is in the range of 2 to 60% based on the thickness of the whole laminated film.   The biaxially oriented laminated film according to claim 1, wherein the polycycloolefin (b) is a norbornene-based polycycloolefin.   The biaxially oriented laminated film according to claim 1, wherein the main repeating unit of the aromatic polyester (a) is ethylene terephthalate or ethylene-2,6-naphthalenedicarboxylate. In the aromatic polyester (a), the acid component is composed of the following structural formulas (I) and (II), and the proportion of the following structural formula (I) is 5 to 80 mol% based on the number of moles of all acid components. The biaxially oriented laminated film according to claim 1, wherein the biaxially oriented laminated film has a range and a glycol component having the following structural formula (III).

(R ₁ in the structural formula (I) is an alkylene group having 1 to 10 carbon atoms, R ₂ in the structural formula (II) is a phenylene group or a naphthalenediyl group, and R ₃ in the structural formula (III). Represents an alkylene group having 2 to 4 carbon atoms.)   The biaxially oriented laminated film according to any one of claims 1 to 4, which is used as a base film for a magnetic recording medium.