JP5074108B2 - Biaxially oriented laminated polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented laminated polyester film which has a high level of dimensional stability for a change in the environment such as temperature and humidity, flatness and winding property. <P>SOLUTION: The biaxially oriented laminated polyester film comprises: a film layer A; and a film B which is laminated on one surface of the film layer A, and has a surface roughness (RaB) on the film B side larger than the surface roughness (RaA) on the film A side by 1.0 nm or more, wherein at least one side of film layer is made of an aromatic polyester consisting of aromatic dicarboxylic acid component and glycol component and the portion of 5 mol% or more and less than 80 mol% of the aromatic dicarboxylic acid component is made of a specified 6, 6'-(alkylene dioxy)di-2-naphthoic acid component. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a biaxially oriented laminated polyester film using an aromatic polyester copolymerized with 6,6 '-(alkylenedioxy) di-2-naphthoic acid.

  Aromatic polyesters typified by polyethylene terephthalate and polyethylene-2,6-naphthalate have excellent mechanical properties, dimensional stability and heat resistance, and thus are widely used for films and the like. In particular, polyethylene-2,6-naphthalate has mechanical properties, dimensional stability, and heat resistance superior to those of polyethylene terephthalate, so that it is used in demanding applications such as a base film for high-density magnetic recording media. It is used. However, the demand for dimensional stability in high-density magnetic recording media and the like in recent years is increasing, and further improvement of characteristics is required.

  On the other hand, Patent Documents 1 to 4 are obtained from diethyl-6,6 ′-(alkylenedioxy) di-2-naphthoate, which is an ester compound of 6,6 ′-(alkylenedioxy) di-2-naphthoic acid. Polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthoate has been proposed. According to this publication, polyethylene-6,6 '-(ethylenedioxy) di-2-naphthoate which is crystalline and has a melting point of 294 ° C. is specifically presented.

  However, since polyethylene-6,6 ′-(alkylenedioxy) di-2-naphthoate presented in these patent documents has a very high melting point and very high crystallinity, it is intended to form a film or the like. As a result, there are problems such as poor fluidity in the molten state and non-uniform extrusion, and even if trying to stretch after extrusion, crystallization progresses and breaks when stretched at a high magnification.

In Patent Document 3, a film using polyethylene-6,6 ′-(ethylenedioxy) di-2-naphthoate has a maximum temperature expansion coefficient of 10 to 35 (ppm / ° C.) and a maximum humidity expansion coefficient. 0 to 8 (ppm /% RH), the difference between the maximum and minimum temperature expansion coefficient is 0 to 6.0 (ppm / ° C.), and the difference between the maximum and minimum humidity expansion coefficient is 0 to 4.0 (ppm /% RH) teaches that a magnetic recording flexible disk with small tracking deviation can be obtained. And, specifically in the embodiment, in the film forming direction of the Young's modulus 485kg ^/ mm 2 (4.8Gpa) and the Young's modulus in the transverse direction is 1100kg ^/ mm 2 (10.9GPa), the maximum temperature expansion coefficient 19 (ppm / ° C.), minimum temperature expansion 16.5 (ppm / ° C.), maximum humidity expansion 6 (ppm /% RH), and minimum humidity expansion 4.5 (ppm / % RH) film is disclosed.

  However, the demand for improvement in recording density in recent magnetic recording media and the like is severe, and accordingly, the dimensional stability required for the base film is presented in polyethylene-2,6-naphthalate and Patent Document 3 as well as polyethylene terephthalate. It has become a situation that can not be achieved even with such a film.

JP-A-60-135428 JP-A-60-212420 JP 61-145724 A JP-A-6-145323

  An object of the present invention is to provide a biaxially oriented laminated polyester film having high dimensional stability against environmental changes such as temperature and humidity, flatness and winding property.

  In a biaxially oriented polyester film, both the humidity expansion coefficient and the temperature expansion coefficient are very closely related to the Young's modulus, and generally lower as the Young's modulus is higher. However, the Young's modulus is not increased as much as possible, and there is a limit in terms of film forming properties and securing the Young's modulus in the orthogonal direction. For this reason, when the same Young's modulus is used, it has been earnestly studied whether a film having an expansion coefficient with respect to a lower temperature and humidity can be obtained. As a result, a film made of the aforementioned polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthoate. Was considered as a suitable film because it exhibited a low coefficient of humidity expansion even when Young's modulus was low.

  However, according to the above-mentioned Patent Documents 1 to 4, although a film made of polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthoate can have a very high Young's modulus, it is perpendicular to the film. There was a problem that the Young's modulus was extremely low. Moreover, although the humidity expansion coefficient was very small, there was also a problem that the temperature expansion coefficient was very high. Incidentally, when the film disclosed in Example 1 of Patent Document 3 was viewed, the temperature expansion coefficient showed a very high value of 16.5 to 19 ppm / ° C. at the maximum.

  However, when the present inventors used 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component as a copolymerization component, surprisingly, polyalkylene-6,6 ′-(alkylenedioxy) ) A film having excellent characteristics of both di-2-naphthoate and the copolymerized aromatic polyester can be obtained, and the copolymerized aromatic polyester is used in at least one layer of the laminated film. The present inventors have found that a biaxially oriented laminated polyester film having excellent dimensional stability, flatness and winding property can be obtained, and have reached the present invention.

Thus, according to the present invention, the film layer B is laminated on one surface of the film layer A, and the surface roughness (RaB) on the film layer B side is 1.0 nm or more than the surface roughness (RaA) on the film layer A side. A large biaxially oriented laminated polyester film,
At least one of the film layers is composed of an aromatic polyester of an aromatic dicarboxylic acid component and a glycol component, and 5 mol% or more and less than 50 mol% of the aromatic dicarboxylic acid component is represented by the following formula (I):

（上記構造式（Ｉ）中のＲは、炭素数１〜１０のアルキレン基を示す。）
で表される６，６’−（アルキレンジオキシ）ジ−２−ナフトエ酸成分である二軸配向積層ポリエステルフィルムが提供される。

(R in the structural formula (I) represents an alkylene group having 1 to 10 carbon atoms.)
A biaxially oriented laminated polyester film that is a 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the formula:

As a preferred embodiment of the present invention, the film layer A has a surface roughness (RaA) in the range of 1.0 to 7.0 nm, and the film layer B has a surface roughness (RaB) of 5.0 to 15.0 nm. The film layer B has a thickness in the range of 50 to 90% with respect to the total thickness of the laminated film, and is composed of an aromatic polyester of an aromatic dicarboxylic acid component and a glycol component. 5 mol% or more and less than 50 mol% of the group dicarboxylic acid component is the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the formula (I), film layers A and B Are both composed of an aromatic polyester of an aromatic dicarboxylic acid component and a glycol component, and 5 mol% or more and less than 50 mol% of the aromatic dicarboxylic acid component is 6,6 ′-(alkyl) represented by the formula (I). range Also provided is a biaxially oriented laminated polyester film further comprising at least one of xyl) di-2-naphthoic acid component or a biaxially oriented laminated polyester film used as a base film of a magnetic recording medium Is done.

  ADVANTAGE OF THE INVENTION According to this invention, the dimensional change with respect to a temperature / humidity change is small, and also the biaxially oriented laminated polyester film excellent in flatness and winding property is provided.

  Therefore, according to the present invention, a film suitable for a base film of a high density magnetic recording medium is provided which is required to have a high degree of surface flatness, and excellent dimensional stability can be obtained by using the film of the present invention. A high-density magnetic recording medium having high performance can also be provided.

<Polyester>
In the present invention, the polyester forming the biaxially oriented laminated polyester film is composed of an aromatic dicarboxylic acid component and a glycol component, and at least one film layer contains 5 mol of the acid component of the aromatic polyester. The 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the above formula (I) is copolymerized in the range of from% to less than 80 mol%. When the copolymerization ratio of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is less than 5 mol%, the effect of reducing the humidity expansion coefficient is hardly exhibited. The upper limit is required to be less than 80 mol% from the viewpoint of moldability and the like. Surprisingly, the effect of reducing the coefficient of humidity expansion by the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is expressed very efficiently in a small amount, and almost saturated at less than 50 mol%. It is close to the state and is preferably less than 50 mol%. From such a viewpoint, the upper limit of the copolymerization amount of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is preferably 45 mol% or less, more preferably 40 mol% or less, and even more preferably 35 mol% or less. 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 an aromatic polyester copolymerized with such a specific amount of 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component for at least one film layer, both the temperature expansion coefficient and the humidity expansion coefficient are obtained. Both can produce a low film.

  Specific examples of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the structural formula (I) described above are those in which R is an alkylene group having 1 to 10 carbon atoms. 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 and the like can be mentioned. Among these, from the viewpoint of the effect of the present invention, those having an even number of carbon atoms of R in the above general formula (I) are preferable, and in particular, 6,6 ′-(ethylene A dioxy) di-2-naphthoic acid component is preferred. Specific aromatic dicarboxylic acid components other than the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the above structural formula (I) include a terephthalic acid component, an isophthalic acid component, 2,6-naphthalenedicarboxylic acid component, 2,7-naphthalenedicarboxylic acid component, and the like, and terephthalic acid component and 2,6-naphthalenedicarboxylic acid component are preferable from the viewpoint of mechanical properties of the obtained film. A 6-naphthalenedicarboxylic acid component is preferred. Examples of the glycol component include an ethylene glycol component, a trimethylene glycol component, a tetramethylene glycol component, a cyclohexanedimethanol component, and the like, and an ethylene glycol component is preferable from the viewpoint of the mechanical properties of the obtained film. It is preferable that 90 mol% or more, and 95-100 mol% is an ethylene glycol component.

  By the way, in the biaxially oriented laminated polyester film of the present invention, at least one film layer is copolymerized with a specific amount of 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the aforementioned formula (I). The other film layer may be made of any other aromatic polyester. The other film layer other than the aromatic polyester in which a specific amount of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the aforementioned formula (I) is specifically copolymerized is formed. As the aromatic polyester, polyalkylene terephthalate having a repeating unit of alkylene terephthalate such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polytrimethylene-2,6-naphthalate, polybutylene- Polyalkylene-2,6-naphthalate having alkylene-2,6-naphthalate as a repeating unit, such as 2,6-naphthalate, is preferably used. Among these, polyethylene terephthalate, polyethylene-2,6 are preferable in view of mechanical properties. − Phthalates are preferred, and polyethylene-2,6-naphthalate are preferred. Of course, from the viewpoint of dimensional stability against environmental changes, all film layers are copolymerized with a specific amount of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the aforementioned formula (I). It is preferably made of an aromatic polyester.

  The aromatic polyester in which a specific amount of the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by the aforementioned formula (I) in the present invention is copolymerized and the polyester forming the other layer are: Other copolymer components known per se may be copolymerized as long as the effects of the present invention are not impaired.

  Next, since the aromatic polyester copolymerized with the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component in the present invention tends to have a high melt viscosity, the melting point measured by DSC is It is preferable from the point of film forming property that it exists in the range of 200-260 degreeC, the range of 210-255 degreeC, especially the range of 220-253 degreeC. When the melting point exceeds the above upper limit, the melt viscosity is large, and the fluidity is inferior when molding is performed by melt extrusion, so that the discharge and the like are likely to be non-uniform, and the film forming property tends to be lowered. On the other hand, when it is less than the above lower limit, although the film forming property is excellent, the mechanical properties of the aromatic polyester copolymerized with the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component are easily impaired. Become. Usually, if other acid components are copolymerized and the melting point is lowered, the mechanical properties and the like are also lowered at the same time. The same mechanical characteristics as those of the polymer having the main repeating unit of the ester of 6,6 ′-(alkylenedioxy) di-2-naphthoic acid described in 2 can be exhibited.

  In addition, the aromatic polyester copolymerized with the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component in the present invention may be referred to as a glass transition temperature (hereinafter referred to as Tg) measured by DSC. ) Is preferably in the range of 90 to 120 ° C., more preferably in the range of 95 to 119 ° C., and particularly preferably in the range of 100 to 117 ° C. from the viewpoint of heat resistance and dimensional stability. Such a melting point and glass transition temperature can be adjusted by controlling the type and amount of copolymerization component, dialalkylene glycol as a byproduct.

  The aromatic polyester copolymerized with 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component may be used in at least one of the film layers A and B, but is more environmentally friendly. From the viewpoint of improving dimensional stability against changes, it is preferably used for a thicker film layer, and most preferably used for both film layers.

<Biaxially oriented laminated polyester film>
As described above, the biaxially oriented laminated polyester film of the present invention is obtained by laminating the film layer B on one side of the film layer A, and the surface roughness (RaB) on the film layer B side is the surface roughness on the film layer A side. The thickness (RaA) is 1.0 nm or more, preferably 2.0 nm or more, more preferably 3.0 nm or more. By making the difference in surface roughness between RaA and RaB equal to or more than the lower limit, excellent flatness and winding properties can be provided at a high level as compared with a single layer film. The upper limit of the difference between RaA and RaB is not particularly limited, but is 8.0 nm or less, preferably 5.0 nm or less, in view of preventing the surface of the film layer A from being damaged by the film layer B. Preferably it is 4.0 nm or less.

  In the biaxially oriented laminated polyester film of the present invention, the thickness of the film layer B is 50 to 90%, preferably 55 to 85%, more preferably 60 to 80, based on the thickness of the biaxially oriented laminated polyester film. % Is preferable. Since the film layer B has a surface roughness larger than that of the film layer A, the film layer B contains larger particles or more particles than the film layer A. It becomes easy to suppress by making thickness of more than a minimum into. Moreover, when it is going to collect | recover and use the part which does not become a product produced when forming a laminated | multilayer film, by making the thickness of the film layer B more than a minimum, a large amount of polymer (collection | collection | recovery in the film layer B Chip) can be used, and the film cost can be reduced. In addition, when a recovery chip is used for the film layer A, it becomes impossible to contain particles having a large particle size only in the film layer B, and it becomes difficult to adjust the surface roughness, or the flatness of the film layer A may be impaired. To do. On the other hand, when the thickness ratio of the film layer B exceeds the upper limit, the thickness of the film layer A becomes very thin, the influence of the particles of the film B layer affects the film A layer, the surface becomes rough, and the electromagnetic conversion Characteristics tend to deteriorate. From the viewpoint of dimensional stability, the aromatic polyester copolymerized with the aforementioned 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is used in a thicker film layer. Preferably, from such a viewpoint, the aromatic polyester copolymerized with the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component is preferably used for the film layer B.

  By the way, in the biaxially oriented laminated polyester film of the present invention, the surface roughness (RaA) of the film layer A is 1.0 to 7.0 nm, in order to make the obtained laminated film have excellent flatness. It is preferable to be in the range of 5 to 5.0 nm, particularly 2.0 to 4.0 nm. Moreover, in order to make the obtained laminated film have excellent winding properties, the surface roughness (RaB) of the film layer B is 5.0 to 15.0 nm, more preferably 6.0 to 10.0 nm, particularly 6.0. It is preferable to be in the range of ˜8.0 nm.

  In general, in order to increase the surface roughness of the film, the film layer on the side to be roughened may contain inert particles to form protrusions. As the inert particles to be contained, (1) heat resistant polymer particles (for example, crosslinked silicone resin, crosslinked polystyrene, crosslinked acrylic resin, melamine-formaldehyde resin, aromatic polyamide resin, polyimide resin, polyamideimide resin, crosslinked polyester, etc.) Particles), (2) metal oxides (eg, aluminum oxide, titanium dioxide, silicon dioxide (silica), magnesium oxide, zinc oxide, zirconium oxide, etc.), metal carbonates (eg, magnesium carbonate, calcium carbonate, etc.) Particles made of inorganic compounds such as metal sulfates (eg calcium sulfate, barium sulfate etc.), carbon (eg carbon black, graphite, diamond etc.) and clay minerals (eg kaolin, clay, bentonite etc.) And more (3) and the like inside precipitated particles formed by precipitation, such as externally added particles are added in the form of composite particles such as particles, such as different materials shell type using for example the core and the shell or (4) a catalyst. Among these, at least one kind of particles selected from the group consisting of a crosslinked silicone resin, a crosslinked acrylic resin, a crosslinked polyester, a crosslinked polystyrene, aluminum oxide, titanium dioxide, silicon dioxide, kaolin and clay is particularly preferable. At least one kind of particles selected from the group consisting of silicone resin, cross-linked acrylic resin, cross-linked polyester, cross-linked polystyrene, and silicon dioxide (excluding porous silica etc.) reduces the variation in particle size. It is preferable because it is easy. Of course, these may be used in combination of two or more.

  The average particle diameter of the inert particles contained in the film layer B is preferably in the range of 0.05 to 1.0 [mu] m, more preferably 0.1 to 0.8 [mu] m, and particularly 0.1 when used as a magnetic recording medium. It is preferable to be in the range of ˜0.5 μm, more preferably 0.1 to 0.3 μm. The content of the inert particles contained in the film layer B is in the range of 0.1 to 1.0% by weight, and further 0.15 to 0.5% by weight, based on the weight of the film layer. In particular, when used as a magnetic recording medium, it is preferably 0.2 to 0.4% by weight, more preferably 0.2 to 0.3% by weight. In addition, the film layer A does not contain inert particles, or when contained, the average particle size of the inert particles is in the range of 0.01 to 0.3 μm, more preferably 0.05 to 0.25 μm. In particular, when used as a magnetic recording medium, it is preferably in the range of 0.1 to 0.2 nm, more preferably 0.1 to 0.15 μm. Further, when the film layer A contains inert particles, the content of the inert particles is 0.005 to 0.3% by weight, further 0.01 to 0.2% by weight based on the weight of the film layer. %, Preferably 0.05 to 0.15% by weight, more preferably 0.1 to 0.1% by weight when used as a magnetic recording medium.

The preferred embodiment of the biaxially oriented laminated polyester film of the present invention will be further described in detail.
When the biaxially oriented laminated polyester film of the present invention is used as a base film such as a magnetic tape, at least one direction in the film surface direction has a high Young's modulus of 6.0 GPa or more so that the base film does not stretch. It is preferable to have. Moreover, the humidity expansion coefficient can be further reduced by increasing the Young's modulus in this way. The upper limit of the Young's modulus is not limited, but is usually 11 GPa. The preferred Young's modulus is in the range of 4 to 11 GPa, further 5 to 10 GPa, particularly 5.5 to 9 GPa in the longitudinal direction of the film, and 5 to 11 GPa, further 6 to 11 GPa, more preferably 7 to 10 GPa in the width direction of the film. It is in the range of 8-10 GPa.

  The biaxially oriented laminated polyester film of the present invention preferably has a temperature expansion coefficient (αt) of at least 10 ppm / ° C. in at least one direction, preferably the width direction of the film, from the viewpoint of exhibiting excellent dimensional stability. When the temperature expansion coefficient in at least one direction of the film is 10 ppm / ° C. or less, excellent dimensional stability against environmental changes can be exhibited. From the results of Patent Document 3, it is expected that when polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthalate is copolymerized, the temperature expansion coefficient is expected to increase, but the specific copolymerization. Surprisingly, the coefficient of thermal expansion can be reduced by copolymerizing in a range of amounts and stretching it. The lower limit of the temperature expansion coefficient is not limited, but is usually −15 ppm / ° C. A preferable temperature expansion coefficient (αt) is in the range of −10 to 10 ppm / ° C., further −7 to 7 ppm / ° C., particularly −5 to 5 ppm / ° C. It is preferable because it can exhibit excellent dimensional stability against dimensional changes due to.

  The biaxially oriented laminated polyester film of the present invention has a humidity expansion coefficient of 3 to 7 ppm /% RH, more preferably 3 to 6 ppm /% RH in a direction satisfying the relationship of the temperature expansion coefficient in at least one direction, preferably the width direction of the film. It is preferable from the viewpoint of dimensional stability particularly when a magnetic recording tape is used. In particular, when used as a base film for a magnetic recording tape, it is preferable that the direction in which the humidity expansion coefficient is small is the width direction of the biaxially oriented laminated polyester film because track deviation and the like can be extremely suppressed. In the present invention, the width direction of the film is a direction orthogonal to the film forming direction of the film (also referred to as a longitudinal direction or a longitudinal direction), and is sometimes referred to as a lateral direction.

  Further, for the direction in which the temperature expansion coefficient is 10 ppm / ° C. or less, at least one direction, preferably as described above, the width direction should be satisfied, but the direction orthogonal thereto is also dimensional stability point, It is preferable that the same temperature expansion coefficient, humidity expansion coefficient, and Young's modulus are satisfied.

  By the way, among magnetic recording media, in the case of a magnetic recording tape or the like in which the magnetic layer is formed only on one side, it is easy to express excellent winding properties while making the magnetic layer side flat, so that the surface of the film layer A It is preferable to form a magnetic layer and make the surface of the film layer B the traveling surface side.

<Method for producing aromatic polyester resin>
Next, a method for producing an aromatic polyester copolymerized with a 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component in the present invention will be described in detail. In addition, what was manufactured by the publicly known method can be used suitably for the aromatic polyester which has not copolymerized the 6,6'- (alkylenedioxy) di-2-naphthoic acid component.

  First, 6,6 ′-(alkylenedioxy) di-2-naphthoic acid or an ester-forming derivative thereof, for example, 2,6-naphthalenedicarboxylic acid or terephthalic acid or an ester-forming derivative thereof, for example, ethylene glycol. Reacting to produce a polyester precursor. And it can manufacture by superposing | polymerizing the polyester precursor obtained in this way in presence of a polymerization catalyst, You may give a solid phase polymerization etc. as needed. The intrinsic viscosity measured at 35 ° C. using a mixed solvent of aromatic polyester P-chlorophenol / 1,1,2,2-tetrachloroethane (weight ratio 40/60) thus obtained is 0.4. From the viewpoint of the effect of the present invention, it is preferably in the range of -1.5 dl / g, more preferably in the range of 0.5-1.3 dl / g. In addition, in the process of manufacturing the above-mentioned polyester precursor, the ethylene glycol component is used in an amount of 1.1 to 6 times, further 2 to 5 times, particularly 3 to 5 times the number of moles of all acid components. From the point of view, it is preferable.

  The reaction temperature for producing the polyester precursor is preferably at or above the boiling point of ethylene glycol, particularly preferably in the range of 190 ° C to 250 ° C. When the temperature is lower than 190 ° C., the reaction does not proceed sufficiently. When the temperature is higher than 250 ° C., diethylene glycol as a side reaction product is likely to be generated. In addition, the reaction can be performed under normal pressure, but the reaction may be performed under pressure in order to further increase productivity. More specifically, the reaction pressure is 10 to 200 kPa in absolute pressure, the reaction temperature is usually 150 to 250 ° C., preferably 180 to 230 ° C., and the reaction time is 10 to 10 hours, preferably 30 or more. It is preferably performed for 7 hours or less. A reaction product as a polyester precursor is obtained by this esterification reaction.

  In the reaction step for producing the polyester precursor, a known esterification or transesterification reaction catalyst may be used. For example, an alkali metal compound, an alkaline earth metal compound, a titanium compound, and the like can be given.

  Next, the polycondensation reaction will be described. First, the polycondensation temperature is in the range from a temperature higher than the melting point of the polymer to be obtained and 230 to 280 ° C. or lower, more preferably 5 ° C. higher than the melting point to 30 ° C. higher than the melting point. The polycondensation reaction is usually preferably performed under a reduced pressure of 30 Pa or less. If it is higher than 30 Pa, the time required for the polycondensation reaction becomes long and it becomes difficult to obtain a copolymerized aromatic polyester resin having a high degree of polymerization.

  Examples of the polycondensation catalyst include metal compounds containing at least one metal element. The polycondensation catalyst can also be used in the esterification reaction. Examples of the metal element include titanium, germanium, antimony, aluminum, nickel, zinc, tin, cobalt, rhodium, iridium, zirconium, hafnium, lithium, calcium, and magnesium. More preferable metals are titanium, germanium, antimony, aluminum, tin, etc. Among them, a titanium compound is particularly preferable because it exhibits high activity in both the esterification reaction and the polycondensation reaction.

  These catalysts may be used alone or in combination. The amount of the catalyst is preferably 0.001 to 0.5 mol%, more preferably 0.005 to 0.2 mol%, based on the number of moles of the repeating unit of the copolymerized aromatic polyester.

  Specific examples of the titanium compound as the polycondensation catalyst include tetra-n-propyl titanate, tetraisopropyl titanate, tetra-n-butyl titanate, tetraisobutyl titanate, tetra-tert-butyl titanate, tetracyclohexyl titanate, tetraphenyl titanate, and the like. Eltitanate, tetrabenzyl titanate, lithium oxalate titanate, potassium oxalate titanate, ammonium oxalate titanate, titanium oxide, titanium orthoester or condensed orthoester, titanium orthoester or condensed orthoester and hydroxycarboxylic acid A reaction product comprising an orthoester or condensed orthoester of titanium, a hydroxycarboxylic acid and a phosphorus compound, an orthoester of titanium or a condensed orthoester and at least 2 Polyhydric alcohols having a hydroxyl group, 2-hydroxy carboxylic acid, or a reaction product comprising a base and the like.

  In the polyester of the present invention, other thermoplastic polymers, stabilizers such as UV absorbers, antioxidants, plasticizers, lubricants, flame retardants, mold release agents, pigments, cores, as long as the effects of the present invention are not impaired. Agents, fillers, glass fibers, carbon fibers, layered silicates and the like may be blended as necessary. Examples of other types of thermoplastic polymers include aliphatic polyester resins, polyamide resins, polycarbonates, ABS resins, polymethyl methacrylate, polyamide elastomers, polyester elastomers, polyetherimides, polyimides, and the like.

<Film production method>
The biaxially oriented laminated polyester film of the present invention is one in which the molecular orientation in each direction is enhanced by stretching in the film forming direction and the width direction. It is preferable because the Young's modulus can be easily improved while maintaining.

  First, polyester (at least one film layer is an aromatic polyester copolymerized with the above-described 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component) is used as a raw material, dried, and then melted. Preferably, the polyester forming each layer is laminated in a die at a melting point (Tm: ° C.) to (Tm + 70) ° C. and then extruded into a film, or each is extruded from a die into a sheet in a molten state. It laminates | stacks later and it solidifies rapidly and makes a laminated unstretched film, and also this laminated unstretched film is biaxially stretched.

In order to satisfy the Young's modulus in both directions defined by the present invention, and also αt and αh, it is preferable to perform cooling with a cooling drum very quickly in order to facilitate subsequent stretching. From such a viewpoint, it is preferable that the temperature of the cooling drum is not as high as 80 ° C. as described in Patent Document 3, but as low as 20 to 60 ° C. By performing at such a low temperature, crystallization in the state of an unstretched film is suppressed, and subsequent stretching can be performed more smoothly.
Biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching.

  Here, a manufacturing method in which longitudinal stretching, lateral stretching, and heat treatment are performed in this order by sequential biaxial stretching will be described as an example. First, the first longitudinal stretching is performed by stretching the glass transition temperature (Tg: ° C.) to (Tg + 40) ° C. of the polyester forming each film layer 3 to 8 times, and then in the transverse direction from the previous longitudinal stretching. Is stretched 3 to 8 times at a high temperature at a temperature of (Tg + 10) to (Tg + 50) ° C. and further heat-set at a temperature below the melting point of the polymer and at a temperature of (Tg + 50) to (Tg + 150) ° C. for 1 to 20 seconds. It is preferable to process. In particular, from the viewpoint of enhancing the dimensional stability while making the protrusions uniform, the temperature of the heat setting treatment is preferably 180 to 220 ° C, more preferably 190 to 210 ° C for 1 to 15 seconds.

  Although the foregoing description has been described for sequential biaxial stretching, the biaxially oriented laminated polyester film of the present invention can be produced by simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are simultaneously performed, for example, the stretching ratio and stretching temperature described above. You can refer to these.

  The thickness of the biaxially oriented laminated polyester film of the present invention may be appropriately determined according to the use. When used for a base film of a magnetic recording tape, the thickness is preferably 2 to 10 μm, more preferably 3 to 7 μm, particularly 4 to 6 μm. .

  In addition, about the method of containing particle | grains, a publicly known method can be employ | adopted, for example, in the manufacturing process of polyester, you may add to a reaction system and may add to polyester by melt-kneading. From the viewpoint of dispersibility of the particles, it is preferably added to a polyester reaction system to produce a polyester composition having a high particle concentration as a master polymer, and this is mixed with a polyester composition containing no particles or having a low particle concentration. The method of combining is preferable.

  According to the present invention, the above-mentioned biaxially oriented laminated polyester 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 the surface on the film layer A side, and the back on the surface on the film layer B side. A magnetic recording tape can be obtained by forming a coat layer.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the present invention, the characteristics were measured and evaluated by the following methods.
(1) Intrinsic viscosity The intrinsic viscosity of the obtained polyester was measured at 35 ° C. by dissolving the polymer using a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (40/60 weight ratio). And asked.

(2) Glass transition point and melting point Glass transition point and melting point were measured by DSC (TA Instruments Co., Ltd., trade name: Thermal lyst 2100) at a heating rate of 20 ° C / min.

(3) Copolymerization amount As for the 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. After adding isopropylamine and mixing well, it was measured at 80 ° C. with 600 M ¹ H-NMR (JEOL A600, manufactured by Hitachi Electronics), and the amount of each glycol component was measured.
As for the aromatic dicarboxylic acid component, 50 mg of a sample was dissolved at 140 ° C. in 0.5 ml of a mixed solution of p-chlorophenol: 1, 1, 2, 2-tetrachloroethane = 3: 1, and 400 M ¹³ C-NMR ( Hitachi Electron JEOL A600) was measured at 140 ° C., and the amount of each acid component was measured.

(4) Young's modulus The obtained film was cut out with a sample width of 10 mm and a length of 15 cm, and a universal tensile testing device (product name: Toyo Baldwin, trade name: 100 mm between chucks, tensile speed 10 mm / min, chart speed 500 mm / min). Pull with Tensilon). The Young's modulus is calculated from the tangent of the rising portion of the obtained load-elongation curve.

(5) Temperature expansion coefficient (αt)
The obtained film was cut into a length of 15 mm and a width of 5 mm so that the film forming direction or the width direction of the film would be the measurement direction, set in TMA3000 manufactured by Vacuum Riko, and at 60 ° C. in a nitrogen atmosphere (0% RH). Pre-treat for 30 minutes and then allow to cool to room temperature. Thereafter, the temperature is raised from 25 ° C. to 70 ° C. at 2 ° C./min, the sample length at each temperature is measured, and the temperature expansion coefficient (αt) is 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
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 Is the temperature expansion coefficient (ppm / ° C.) of quartz glass.

(6) Humidity expansion coefficient (αh)
The obtained film was cut into a length of 15 mm and a width of 5 mm so that the film forming direction or the width direction of the film was the measuring direction, set in TMA3000 manufactured by Vacuum Riko, and a humidity of 30% RH in a nitrogen atmosphere at 30 ° C. The length of each sample at a humidity of 70% RH is measured, and the humidity expansion coefficient is calculated by the following equation. 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 ₇₀ −L ₃₀ ) / (L ₃₀ × ΔH)
Here, L ₃₀ in the above formula is a sample length (mm) when 30% RH, L ₇₀ is a sample length (mm) when 70% RH, ΔH: 40 (= 70-30)% RH is there.

Ｚｊｋは測定方法（２８３μｍ）、それと直行する方法（２１３μｍ）をそれぞれＭ分割、Ｎ分割したときの各方向のｊ番目、ｋ番目の位置における２次元粗さチャート上の高さである。 (7) Center plane average roughness (Ra)
Surface measured with a non-contact three-dimensional surface structure analysis microscope (NewView 5022) manufactured by Zygo under the conditions of a measurement magnification of 25 times and a measurement area of 283 μm × 213 μm (= 0.0603 mm ² ). The center plane average roughness Ra was determined from the following equation using analysis software.

Zjk is the height on the two-dimensional roughness chart at the j-th and k-th positions in each direction when the measurement method (283 μm) and the direct method (213 μm) are divided into M and N, respectively.

(8) Winding property At a slit speed of 60 m / min, the film roll rolled up when the film was wound up to 8000 m with a slit width of 1000 mm was observed, and the winding property was evaluated according to the following criteria.
◎: Wrinkles are not seen ○: Wrinkles are seen slightly, but there is no problem in practical use ×: Many wrinkles occur

(9) Electromagnetic conversion characteristics For measuring the electromagnetic conversion characteristics, a 1/2 inch linear system with a fixed head was used. Recording was performed using an electromagnetic induction head (track width 25 μm, gap 0.1 μm), and reproduction was performed using an MR head (8 μm). The relative speed of the head / tape is 10 m / sec, a signal with a recording wavelength of 0.2 μm is recorded, the reproduced signal is analyzed with a spectrum analyzer, the output C of the carrier signal (wavelength 0.2 μm), and the integration over the entire spectrum. The relative value with the noise N ratio as C / N ratio and Example 1 as 0 dB was determined and evaluated according to the following criteria.
◎: +1 dB or more ○: −1 dB or more, less than +1 dB ×: less than −1 dB

In addition, the magnetic recording tape used for electromagnetic conversion characteristic measurement was prepared by the following method.
First, a back coat layer paint having the following composition was applied with a die coater on one surface of the film obtained in each of the examples and comparative examples (the surface of the film layer B in the case of a laminated film) and dried. On the other surface (the surface of the film layer A in the case of a laminated film), a nonmagnetic coating material and a magnetic coating material having the following composition are simultaneously applied with a die coater while changing the film thickness, 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. The tape was slit to 12.65 mm and incorporated into a cassette to obtain a magnetic recording tape. The dried back coat layer, nonmagnetic layer, and magnetic layer had thicknesses of 0.5 μm, 1.2 μm, and 0.1 μm, respectively.

<Composition of non-magnetic paint>
-Titanium dioxide fine particles: 100 parts by weight-ESRECC A (vinyl chloride / vinyl acetate copolymer made by Sekisui Chemical): 10 parts by weight-Nipponporan 2304 (polyurethane elastomer made by Nippon Polyurethane): 10 parts by weight-Coronate L (poly from Nippon Polyurethane) Isocyanate): 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 Eslek A (vinyl chloride / vinyl acetate copolymer by Sekisui Chemical: 10 parts by weight) Nipponan 2304 (Nippon Polyurethane Polyurethane elastomer): 10 parts by weight, Coronate L (polyisocyanate made by Nippon Polyurethane): 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 back coat layer paint:>
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

(10) Thickness of Laminated Film and Film Layer 10 Laminated Films are Laminated While Excluding Air Between Layers, 10 Sheets Laminated Using Mitutoyo Dial Gauge MDC-25S in accordance with JIS Standard C2151 Measure the thickness at, and calculate the film thickness per sheet. This measurement was repeated 10 times, and the average value was defined as the thickness of the entire laminated film per sheet.
On the other hand, the thicknesses of the film layer A and the film layer B are obtained by fixing a small piece of film with an epoxy resin and cutting it with an ultrathin slice having a thickness of about 60 nm with a microtome (in parallel with the film forming direction and the thickness direction). ). This ultrathin slice sample is observed with a transmission electron microscope (H-800, manufactured by Hitachi, Ltd.). In the case of the same kind of polymer in which the boundary cannot be observed, 100 positions of the thickness where the abundance of the inert particles changes are obtained from each surface side, and the average value thereof is The thickness of the layer and the B layer was determined.

(11) Productivity of the film The film was evaluated based on the following criteria from the recoverable ratio of the recovered chips put in the film B layer.
◎: 60% or more ○: 40% or more, less than 60% ×: less than 40%

[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 was carried out to give an intrinsic viscosity of 0.66 dl / g, 73 mol% of the acid component being 2,6-naphthalenedicarboxylic acid component, and 27 mol% of the acid component being 6,6 ′-(alkylenedioxy). An aromatic polyester (A-1) for film layer A was obtained in which 98 mol% of the di-2-naphthoic acid component and glycol component were the ethylene glycol component, and 2 mol% of the glycol component was the diethylene glycol component. The aromatic polyester contained 0.1% by weight of silica particles having an average particle size of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-1) had a melting point of 240 ° C. and a glass transition temperature of 117 ° C. Similarly, the aromatic polyester for the film layer B was used except that 0.15% by weight of silica particles having an average particle diameter of 0.3 μm and 0.1% by weight of silica particles having an average particle diameter of 0.1 μm were contained. (B-1) was obtained. The aromatic polyester (B-1) had a melting point of 240 ° C. and a glass transition temperature of 117 ° C.
The aromatic polyesters (A-1) and (B-1) thus obtained are supplied to different extruders and laminated in a die so that the thickness ratio is 1: 2 at 290 ° C. The unstretched laminated film was extruded into a sheet shape on a cooling drum having a temperature of 50 ° C. while rotating in a molten state. Then, between two sets of rollers having different rotational speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 135 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 5.6. Then, this uniaxially stretched film is led to a stenter, stretched in the transverse direction (width direction) at 140 ° C. at a stretching ratio of 7.7 times, and then heat-set at 190 ° C. for 10 seconds, and biaxially oriented with a thickness of 5 μm. A laminated polyester film was obtained.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 2]
In Example 1, the inert particles contained were changed to silica particles having an average particle size of 0.15 μm, and the content was changed to 0.2% by weight, which was the same as that of the aromatic polyester (A-1). The operation was repeated to produce an aromatic polyester (A-2). In Example 1, the inert particles contained were changed to silicone particles having an average particle size of 0.5 μm and silica particles having an average particle size of 0.15 μm, and their contents were each 0.02% by weight. The aromatic polyester (B-2) was produced by repeating the same operation as the aromatic polyester (B-1) except that the content was changed to 0.2 wt%.
The aromatic polyester (A-2) thus obtained is used for the film layer A, and the aromatic polyester (B-2) is used for the film layer B, which are supplied to different extruders 290 respectively. The same as in Example 1 except that the film was laminated in a die so that the thickness ratio was 1: 1 at 0 ° C., and was extruded in a sheet shape onto a cooling drum at a temperature of 50 ° C. during rotation in a molten state to form an unstretched laminated film. The operation was repeated to obtain a biaxially oriented laminated polyester film.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 3]
What changed the inert particle of aromatic polyester (A-1) to 0.3 weight% of silica particle with an average particle diameter of 0.05 micrometer as aromatic polyester (A-3) for film layers A, and A film obtained by changing the inert particles of the aromatic polyester (B-1) to 0.2% by weight of silica particles having an average particle diameter of 0.2 μm and 0.3% by weight of silica particles having an average particle diameter of 0.05 μm An aromatic polyester (A-3) and an aromatic polyester (B-3) were obtained in the same manner as in Example 1, except that the aromatic polyester (B-3) for layer B was obtained.
The aromatic polyesters (A-3) and (B-3) thus obtained are supplied to different extruders and laminated in a die so that the thickness ratio is 1: 4 at 290 ° C. A biaxially oriented laminated polyester film was obtained by repeating the same operation as in Example 1 except that a non-stretched laminated film was extruded in the form of a sheet on a cooling drum having a temperature of 50 ° C. while rotating in a molten state.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 4]
What changed the inert particle of the aromatic polyester (A-1) to 0.2% by weight of alumina particles having an average particle size (primary particle size) of 0.06 μm was used as the aromatic polyester (A- 4) As an inert particle of aromatic polyester (B-1), 0.15% by weight of crosslinked polystyrene particles having an average particle size of 0.3 μm and alumina particles having an average particle size (primary particle size) of 0.06 μm The aromatic polyester (A-4) and the aromatic polyester (B) were obtained in the same manner as in Example 1 except that the aromatic polyester (B-4) for the film layer B was obtained by changing the content to 0.2% by weight. -4) was obtained. The aromatic polyesters (A-4) and (B-4) thus obtained are supplied to different extruders and laminated in a die so that the thickness ratio is 1: 2 at 290 ° C. A biaxially oriented laminated polyester film was obtained by repeating the same operation as in Example 1 except that a non-stretched laminated film was extruded in the form of a sheet on a cooling drum having a temperature of 50 ° C. while rotating in a molten state.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 5]
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 was carried out, the intrinsic viscosity was 0.72 dl / g, 94 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 6 mol% of the acid component was 6,6 ′-(ethylenedioxy). An aromatic polyester (A-5) for film layer A was obtained in which 99 mol% of the di-2-naphthoic acid component and glycol component were an ethylene glycol component and 1 mol% was a diethylene glycol component. The aromatic polyester (A-5) contained 0.1% by weight of silica particles having an average particle size of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-5) had a melting point of 255 ° C. and a glass transition temperature of 119 ° C. Moreover, the aromatic polyester (A-5) except that the inert particles were changed to 0.15% by weight of silica particles having an average particle size of 0.3 μm and 0.1% by weight of silica particles having an average particle size of 0.1 μm. ), An aromatic polyester (B-5) for film layer B was obtained. The aromatic polyester (B-5) had a melting point of 255 ° C. and a glass transition temperature of 119 ° C.
The aromatic polyester thus obtained was made into an unstretched laminated film in the same manner as in Example 1, and between the two sets of rollers having different rotation speeds along the film forming direction, the film surface was observed from above with an IR heater. It heated so that temperature might be set to 140 degreeC, and the extending | stretching of the vertical direction (film-forming direction) was performed by the draw ratio 5.3 time, and the uniaxially stretched film was obtained. Then, this uniaxially stretched film is guided to a stenter, stretched at a stretching ratio of 4.0 times in the transverse direction (width direction) at 140 ° C., and then heat-set at 200 ° C. for 10 seconds, and biaxially oriented with a thickness of 5 μm. A laminated polyester film was obtained.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 6]
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 was carried out, the intrinsic viscosity was 0.77 dl / g, 80 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 20 mol% of the acid component was 6,6 ′-(ethylenedioxy). An aromatic polyester (A-6) for film layer A was obtained, in which 99 mol% of the di-2-naphthoic acid component and glycol component were an ethylene glycol component and 1 mol% was a diethylene glycol component. The aromatic polyester (A-6) contained 0.1% by weight of silica particles having an average particle size of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-6) had a melting point of 252 ° C. and a glass transition temperature of 116 ° C. Further, the inert particles were changed to aromatic polyesters (A−) except that the silica particles having an average particle size of 0.3 μm were changed to 0.15% by weight and the silica particles having an average particle size of 0.1 μm were changed to 0.1% by weight. In the same manner as in 6), an aromatic polyester (B-6) for film layer B was obtained. The aromatic polyester (B-6) had a melting point of 252 ° C. and a glass transition temperature of 116 ° C.
The aromatic polyester thus obtained was made into a laminated unstretched film in the same manner as in Example 1, and between the two sets of rollers having different rotation speeds along the film forming direction, the film surface with an IR heater from above. The film was heated to a temperature of 135 ° C. and stretched in the machine direction (film forming direction) at a stretch ratio of 5.5 times to obtain a uniaxially stretched film. Then, this uniaxially stretched film is guided to a stenter, stretched at a stretching ratio of 4.3 times in the transverse direction (width direction) at 140 ° C., and then heat-set at 210 ° C. for 10 seconds to adjust the thickness of the unstretched film. Thus, a biaxially oriented laminated polyester film having a thickness of 5 μm was obtained.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 7]
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 was performed, and the intrinsic viscosity was 0.77 dl / g, 65 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 35 mol% of the acid component was 6,6 ′-(ethylenedioxy). An aromatic polyester (A-7) for film layer A was obtained in which 98 mol% of the di-2-naphthoic acid component and glycol component were an ethylene glycol component and 2 mol% was a diethylene glycol component. The aromatic polyester (A-7) contained 0.1% by weight of silica particles having an average particle size of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-7) had a melting point of 247 ° C. and a glass transition temperature of 116 ° C. Further, the inert particles were changed to aromatic polyesters (A−) except that the silica particles having an average particle size of 0.3 μm were changed to 0.15% by weight and the silica particles having an average particle size of 0.1 μm were changed to 0.1% by weight. In the same manner as in 7), an aromatic polyester (B-7) for film layer B was obtained. The aromatic polyester (B-7) had a melting point of 247 ° C. and a glass transition temperature of 116 ° C.
The aromatic polyester thus obtained was supplied to an extruder and extruded from a die at 290 ° C. onto a cooling drum having a rotating temperature of 50 ° C. in a molten state to form an unstretched film. Then, between the two sets of rollers having different rotation speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 140 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 5.5. And this uniaxially stretched film is led to a stenter, stretched at a stretching ratio of 6.0 times in the transverse direction (width direction) at 140 ° C., and then heat-set at 210 ° C. for 10 seconds to adjust the thickness of the unstretched film. Thus, a biaxially oriented laminated polyester film having a thickness of 5 μm was obtained.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 8]
Esterification and transesterification of dimethyl terephthalate, 6,6 '-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol in the presence of titanium tetrabutoxide, followed by polycondensation reaction And the intrinsic viscosity is 0.73 dl / g, 65 mol% of the acid component is terephthalic acid component, 35 mol% of the acid component is 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, glycol component An aromatic polyester (A-8) for film layer A in which 98.5 mol% of the polymer was an ethylene glycol component and 1.5 mol% of a diethylene glycol component was obtained. The aromatic polyester (A-8) contained 0.1% by weight of silica particles having an average particle diameter of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-8) had a melting point of 233 ° C. and a glass transition temperature of 91 ° C. Further, the inert particles were changed to aromatic polyesters (A−) except that the silica particles having an average particle size of 0.3 μm were changed to 0.15% by weight and the silica particles having an average particle size of 0.1 μm were changed to 0.1% by weight. In the same manner as in 8), an aromatic polyester (B-8) for film layer B was obtained in the same manner. The aromatic polyester (B-8) had a melting point of 233 ° C. and a glass transition temperature of 91 ° C.
The aromatic polyester thus obtained was made into a laminated unstretched film in the same manner as in Example 1, and the film was formed with an IR heater from above between two pairs of rollers having different rotational speeds along the film forming direction. It heated so that surface temperature might be set to 110 degreeC, extending | stretching of the vertical direction (film-forming direction) was performed by the draw ratio 5.0 times, and the uniaxially stretched film was obtained. And this uniaxially stretched film is led to a stenter, stretched at 120 ° C in the transverse direction (width direction) at a stretch ratio of 6.0 times, and then heat-set at 210 ° C for 3 seconds to adjust the thickness of the unstretched film Thus, a biaxially oriented laminated polyester film having a thickness of 5 μm was obtained.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 9]
Esterification and transesterification of dimethyl terephthalate, 6,6 '-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol in the presence of titanium tetrabutoxide, followed by polycondensation reaction And the intrinsic viscosity is 0.68 dl / g, 80 mol% of the acid component is terephthalic acid component, 20 mol% of the acid component is 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, glycol component An aromatic polyester (A-9) for film layer A in which 98 mol% of the polymer was an ethylene glycol component and 2 mol% of a diethylene glycol component was obtained. The aromatic polyester (A-9) contained 0.1% by weight of silica particles having an average particle diameter of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-9) had a melting point of 230 ° C. and a glass transition temperature of 85 ° C. Moreover, the aromatic polyester (A-9) except that the inert particles were changed to 0.15% by weight of silica particles having an average particle size of 0.3 μm and 0.1% by weight of silica particles having an average particle size of 0.1 μm. ), An aromatic polyester (B-9) for film layer B was obtained. The aromatic polyester (B-9) had a melting point of 230 ° C. and a glass transition temperature of 85 ° C.
The aromatic polyester thus obtained was used as a laminated unstretched film in the same manner as in Example 1. Then, between two sets of rollers having different rotational speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 105 ° C., and stretching in the longitudinal direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 5.0. Then, this uniaxially stretched film is led to a stenter, stretched at 115 ° C in the transverse direction (width direction) at a stretch ratio of 5.2 times, and then heat-set at 210 ° C for 3 seconds to adjust the thickness of the unstretched film Thus, a biaxially oriented laminated polyester film having a thickness of 5 m was obtained.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 10]
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 was carried out, the intrinsic viscosity was 0.70 dl / g, 70 mol% of the acid component was 2,6-naphthalenedicarboxylic acid component, and 30 mol% of the acid component was 6,6 ′-(alkylenedioxy). An aromatic polyester (A-10) for film layer A was obtained in which 98 mol% of the di-2-naphthoic acid component and glycol component were an ethylene glycol component and 2 mol% was a diethylene glycol component. The aromatic polyester (A-10) contained 0.1% by weight of silica particles having an average particle size of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-10) had a melting point of 268 ° C. and a glass transition temperature of 101 ° C. Moreover, the aromatic polyester (A-10) except that the inert particles were changed to 0.15% by weight of silica particles having an average particle diameter of 0.3 μm and 0.1% by weight of silica particles having an average particle diameter of 0.1 μm. ), An aromatic polyester (B-10) for film layer B was obtained. The aromatic polyester (B-10) had a melting point of 268 ° C. and a glass transition temperature of 101 ° C.
The aromatic polyester thus obtained was supplied to an extruder and extruded from a die at 300 ° C. in a molten state onto a cooling drum having a rotating temperature of 50 ° C. to form an unstretched film. Then, between two sets of rollers having different rotational speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 135 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 3.0. And this uniaxially stretched film is led to a stenter, stretched at a stretching ratio of 3.8 times in the transverse direction (width direction) at 140 ° C., and then heat-set at 200 ° C. for 10 seconds to adjust the thickness of the unstretched film. Thus, a biaxially oriented laminated polyester film having a thickness of 5 μm was obtained.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Example 11]
A biaxially oriented laminated polyester film was obtained in the same manner as in Example 1 except that the thickness ratio (A: B) of the film layer A and the film layer B was changed to 2: 1.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Comparative 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 was carried out to give an intrinsic viscosity of 0.66 dl / g, 73 mol% of the acid component being 2,6-naphthalenedicarboxylic acid component, and 27 mol% of the acid component being 6,6 ′-(alkylenedioxy). An aromatic polyester (A-11) for a film monolayer was obtained in which 98 mol% of the di-2-naphthoic acid component and glycol component were the ethylene glycol component, and 2 mol% of the glycol component was the diethylene glycol component. The aromatic polyester (A-11) contained 0.15% by weight of silica particles having an average particle size of 0.3 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-11) had a melting point of 240 ° C. and a glass transition temperature of 117 ° C.
The aromatic polyester thus obtained was subjected to the same operation as in Example 1 except that it was extruded in the form of a sheet onto a cooling drum having a temperature of 50 ° C. while rotating in a molten state to form an unstretched (single layer) film. Repeatedly, a biaxially oriented polyester film was obtained.
The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 2]
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 was carried out to give an intrinsic viscosity of 0.66 dl / g, 73 mol% of the acid component being 2,6-naphthalenedicarboxylic acid component, and 27 mol% of the acid component being 6,6 ′-(alkylenedioxy). An aromatic polyester (A-12) for a film monolayer was obtained in which 98 mol% of the di-2-naphthoic acid component and glycol component were an ethylene glycol component and 2 mol% was a diethylene glycol component. The aromatic polyester (A-12) contained 0.1% by weight of silica particles having an average particle size of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. The aromatic polyester (A-12) had a melting point of 240 ° C. and a glass transition temperature of 117 ° C.
The aromatic polyester thus obtained was subjected to the same operation as in Example 1 except that it was extruded in the form of a sheet onto a cooling drum having a temperature of 50 ° C. while rotating in a molten state to form an unstretched (single layer) film. Repeatedly, a biaxially oriented polyester film was obtained.
The characteristics of the obtained biaxially oriented polyester film are shown in Table 1.

[Comparative Example 3]
Dimethyl 2,6-naphthalenedicarboxylate and ethylene glycol are subjected to an esterification reaction and a transesterification reaction in the presence of titanium tetrabutoxide, followed by a polycondensation reaction to obtain an intrinsic viscosity of 0.62 dl / g. Polyethylene-2,6-naphthalate (A-13) for film layer A in which 1.5 mol% of the glycol component was a diethylene glycol component was obtained. Polyethylene-2,6-naphthalate (A-13) contains 0.1% by weight of silica particles having an average particle diameter of 0.1 μm based on the weight of the resin composition obtained before the polycondensation reaction. It was. Similarly, the film layer B was changed except that the inert particles were changed to 0.15% by weight of silica particles having an average particle size of 0.3 μm and 0.1% by weight of silica particles having an average particle size of 0.1 μm. Polyethylene-2,6-naphthalate (B-11) was obtained. These polyethylene-2,6-naphthalates (A-13) and (B-11) had a melting point of 270 ° C. and a glass transition temperature of 120 ° C.
And it was set as the unstretched laminated film like Example 1. Then, between the two sets of rollers having different rotation speeds along the film forming direction, the film surface temperature is heated from above by an IR heater so that the film surface temperature becomes 140 ° C., and stretching in the machine direction (film forming direction) is performed. A uniaxially stretched film was obtained at a magnification of 3.0. And this uniaxially stretched film is led to a stenter, stretched at a stretching ratio of 4.3 times in the transverse direction (width direction) at 140 ° C., and then heat-set at 200 ° C. for 10 seconds, and biaxially oriented with a thickness of 5 μm. A laminated polyester film was obtained.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Comparative Example 4]
In Comparative Example 3, the stretching temperature in the film forming direction is 140 ° C., the stretching ratio in the film forming direction is 4.0 times, the stretching temperature in the width direction is 140 ° C., and the stretching ratio in the width direction is 4.0 times. A biaxially oriented laminated polyester film having a thickness of 5 μm was obtained by repeating the same operation except that the heat setting treatment temperature was 200 ° C. and the thickness of the unstretched film was changed.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Comparative Example 5]
In Comparative Example 3, the stretching temperature in the film forming direction was 140 ° C., the stretching ratio in the film forming direction was 4.5 times, the stretching temperature in the width direction was 140 ° C., and the stretching ratio in the width direction was 3.4 times. A biaxially oriented laminated polyester film having a thickness of 5 μm was obtained by repeating the same operation except that the heat setting treatment temperature was 200 ° C. and the thickness of the unstretched film was changed.
The characteristics of the obtained biaxially oriented laminated polyester film are shown in Table 1.

[Reference Example 1]
As a reference example, Table 1 shows the results of Young's modulus, temperature expansion coefficient, and humidity expansion coefficient described in Example 1 of Patent Document 3.

  In Table 1, A-1 to 13 and B-1 to 11 are the types of aromatic polyester described in each example, and the ANA ratio is 6,6 ′-(alkylenedioxy) di in the total acid component. -2-Mole% of naphthoic acid component, MD indicates the film forming direction, and TD indicates the width direction of the film. In addition, the Young's modulus of the reference example 1 shows what was converted into GPa.

  The biaxially oriented polyester film of the present invention is excellent as cannot be achieved with conventional polyethylene terephthalate, polyethylene-2,6-naphthalate or polyalkylene-6,6 ′-(alkylenedioxy) di-2-naphthoate. Since it has excellent flatness and winding property while having dimensional stability, it can be suitably used particularly as a base film of a high-density magnetic recording medium.

Claims (5)

A film layer B is laminated on one side of the film layer A, and the surface roughness (RaB) on the film layer B side is 1.0 nm or more larger than the surface roughness (RaA) on the film layer A side. Because
At least one of the film layers is composed of an aromatic polyester of an aromatic dicarboxylic acid component and a glycol component, and 5 mol% or more and less than 50 mol% of the aromatic dicarboxylic acid component is represented by the following formula (I):

(R in the structural formula (I) represents an alkylene group having 1 to 10 carbon atoms.)
A biaxially oriented laminated polyester film, which is a 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component represented by:   The surface roughness (RaA) of the film layer A is in the range of 1.0 to 7.0 nm, and the surface roughness (RaB) of the film layer B is in the range of 5.0 to 15.0 nm. Axial oriented laminated polyester film. The film layer B has a thickness in the range of 50 to 90% with respect to the thickness of the entire laminated film, and is composed of an aromatic polyester of an aromatic dicarboxylic acid component and a glycol component. The biaxially oriented laminate according to claim 1 or 2, wherein 5 mol% or more and less than 50 mol% is a 6,6 '-(alkylenedioxy) di-2-naphthoic acid component represented by the formula (I). Polyester film. The film layers A and B are both made of an aromatic polyester of an aromatic dicarboxylic acid component and a glycol component, and 5 mol% or more and less than 50 mol% of the aromatic dicarboxylic acid component is represented by the formula (I) 6 The biaxially oriented laminated polyester film according to any one of claims 1 to 3, wherein the biaxially oriented laminated polyester film is a, 6 '-(alkylenedioxy) di-2-naphthoic acid component.   The biaxially oriented laminated polyester film according to any one of claims 1 to 4, wherein the biaxially oriented laminated polyester film is used as a base film of a magnetic recording medium.