JP2011184617A - Biaxially oriented polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film which can be made smaller in size in various processes especially when used as a base film for flexible devices, and is suitable as a base film which is excellent in processing suitability due to little curling. <P>SOLUTION: The biaxially oriented polyester film has a sea-island structure which consists of at least polyethylene terephthalate (resin A) and polyetherimide (resin B), wherein an average dispersion diameter of the island portion is 30-500 nm, and the thermal expansion coefficient (50-150°C) of at least one of the longitudinal direction or width direction of a film is 0-25 ppm/°C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a biaxially oriented polyester film excellent in thermal dimensional stability. The biaxially oriented polyester film of the present invention can be suitably used for a substrate film for flexible devices. Among them, the biaxially oriented polyester film of the present invention is used in various processes, particularly when used as a base film for organic EL displays, electronic paper, organic EL lighting, organic solar cells, and dye-sensitized solar cells. A base film having a small dimensional change, a small curl, and excellent processability can be obtained.

  In recent years, various electronic devices have applications that require weight reduction, thin film formation, flexibility in shape, and the like. In order to make an electro device flexible, a plastic film is used in place of glass that has been used as a base material in the past, but thermal dimensional stability and surface properties are major issues.

  Biaxially oriented polyethylene terephthalate film utilizes its excellent thermal properties, dimensional stability, mechanical properties, electrical properties, heat resistance, and surface properties to provide magnetic recording materials, packaging materials, electrical insulating materials, various photographic materials, graphics It is widely used as a base material for many applications such as art materials and optical display materials. However, it is thought that further improvement in physical properties is necessary for the base film for flexible devices, and in the past, methods such as blending other thermoplastic resins with polyester have been studied in order to improve the properties of the polyester film. Yes.

  Conventionally, regarding a biaxially oriented polyester film obtained by mixing polyester and a thermoplastic resin other than polyester, a film excellent in running performance and scratch resistance has been proposed (see Patent Document 1). However, this proposal is a technique for improving the scratch resistance of the film surface, which is different from the technical idea of the present invention. Actually, the technique described in the document cannot improve the thermal dimensional stability. In addition, when mixing a thermoplastic resin other than polyester with polyester, the mixing method and the specific film forming method that are important for improving the thermal dimensional stability of the film as shown in the present invention are the same. It is not disclosed in the literature.

  In addition, in films consisting of polyester and polyimide and polyimide and nano-compatible polymer, a film with improved heat resistance and thermal dimensional stability has been proposed using aromatic polyether ketone as a polymer compatible with polyimide and nano-compatibility. (See Patent Document 2). However, in this proposal, the amount of the polymer mixed with polyimide or polyimide that is nano-compatible with the polyester is large, and it may not be sufficient for effective molecular chain orientation by stretching or the like. Furthermore, this proposal has a problem that foreign matters due to unmelted materials are likely to be generated in the film, and the surface is likely to be rough.

  Furthermore, a film having improved strength and thermal dimensional stability has been proposed for a polyester film made of polyester, polyetherimide and aromatic polyamide (see Patent Document 3). However, when mixing a thermoplastic resin other than polyester in polyester, the mixing method and the specific film forming method which are important for improving the thermal dimensional stability of the film as shown in the present invention are the same patents. It is not disclosed in the literature.

JP 2001-323146 A JP 2004-123863 A JP 2000-336184 A

  Accordingly, an object of the present invention is to solve the above-mentioned problems and obtain a biaxially oriented polyester film excellent in thermal dimensional stability, and in particular, when used as a base film for flexible devices, dimensions in various steps. It is an object of the present invention to provide a biaxially oriented polyester film that can be reduced in change, small in curl and excellent in workability.

  The present invention is intended to achieve the above object and has the following characteristics.

  The biaxially oriented polyester film of the present invention is a biaxially oriented film having a sea-island structure comprising at least a polyethylene terephthalate resin (resin A) and a resin B, and has an average dispersion diameter of the island portion of 30 to 500 nm. Is a biaxially oriented polyester film having a thermal expansion coefficient (50 to 150 ° C.) in at least one direction in the longitudinal direction or the width direction of 0 to 25 ppm / ° C.

  According to a preferred embodiment of the biaxially oriented polyester film of the present invention, the thermal shrinkage rate at a temperature of 150 ° C. in at least one direction of the longitudinal direction or the width direction is 0 to 3%.

  According to a preferred embodiment of the biaxially oriented polyester film of the present invention, the glass transition temperature (Tg) of the resin B is 100 to 400 ° C., and the content of the resin B in the film is 0.1 to 10%. % By mass.

  According to a preferred embodiment of the biaxially oriented polyester film of the present invention, the island component is a resin B.

  According to a preferred embodiment of the biaxially oriented polyester film of the present invention, the resin B is represented by the following formula (1).

Or a polyetherimide having a structure represented by the formula (1) and a sulfonyl group component.

  According to a preferred embodiment of the biaxially oriented polyester film of the present invention, the biaxially oriented film comprising at least polyethylene terephthalate (resin A), resin B, and resin C, wherein the resin C is represented by the following formula (2):

A polyetherimide having a structure represented by

  According to a preferred embodiment of the biaxially oriented polyester film of the present invention, the intrinsic viscosity (IV) of the biaxially oriented polyester film is 0.68 to 1.4.

  According to a preferred embodiment of the biaxially oriented polyester film of the present invention, the micromelting peak (T-meta) immediately below the melting point of the biaxially oriented polyester film is 200 to 250 ° C.

  The said biaxially-oriented polyester film of this invention is used suitably for the film for flexible device base materials.

In the present invention, at least the resin A and the resin B are melt-kneaded to prepare a master batch satisfying the following conditions, the master batch and a polyethylene terephthalate resin (resin A) are mixed, melt-extruded, and unstretched A method for producing a biaxially oriented polyester film comprising producing a film, biaxially stretching the unstretched film in the longitudinal direction and the width direction, and subsequently performing a heat treatment.
Resin A; 30-80% by mass
Resin B: 20 to 70% by mass.

In the present invention, at least the resin A, the resin B, and the resin C are melt-kneaded to prepare a master batch that satisfies the following conditions, the master batch and a polyethylene terephthalate resin (resin A) are mixed, and melt-extruded. The method for producing a biaxially oriented polyester film according to claim 1, wherein an unstretched film is prepared, the unstretched film is biaxially stretched in the longitudinal direction and the width direction, and subsequently heat-treated.
Resin A; 30-80% by mass
Resin B + C; 20 to 70% by mass
Resin B / Resin C (weight ratio): 10/90 to 50/50.

  According to a preferred embodiment of the method for producing a biaxially oriented polyester film of the present invention, the masterbatch and the resin A are mixed, melt-extruded to produce an unstretched film, and the unstretched film is stretched in the longitudinal direction. In carrying out biaxial stretching that extends in the width direction, the stretching temperature in the longitudinal direction is set higher than the stretching temperature in the transverse direction and biaxial stretching is performed, followed by heat treatment at 205 to 255 ° C., and then at a temperature of 0 to 50 ° C. After cooling to 160 ° C. to 200 ° C. for 1 to 30 seconds.

  According to the present invention, a biaxially oriented polyester film having excellent thermal dimensional stability can be obtained. In particular, when used as a base film for a flexible device, a dimensional change in various steps can be reduced, and a biaxially oriented polyester film having a small curl and excellent workability can be obtained.

FIG. 1 is a cross-sectional view illustrating the sea-island structure of the biaxially oriented polyester film of the present invention.

  The biaxially oriented polyester film of the present invention is a crystalline polyester polyethylene terephthalate (resin A) (hereinafter referred to as “polyester terephthalate”) (hereinafter referred to as “polyester”). , Sometimes referred to as PET).

  The biaxially oriented polyester film of the present invention has a sea-island structure. The sea-island structure is a structure having a dispersed phase (island component) dispersed in a continuous phase (sea component) (for example, P.324-325 of Polymer Alloy Fundamentals and Applications 2nd Edition (1993) edited by Polymer Society of Japan). (See description of.) FIG. 1 is a cross-sectional view illustrating the sea-island structure of the biaxially oriented polyester film of the present invention, specifically, a cross-sectional view in a direction parallel to the longitudinal direction of the film and perpendicular to the film surface. A structure in which a plurality of dispersed phases (island components) 2 are dispersed in a phase (sea component) 1 is shown.

  The cross-sectional view of FIG. 1 is for understanding the sea-island structure in the present invention, and is described in “(a) Parallel to the longitudinal direction” described in the measurement method and evaluation of the average dispersion diameter of island components (dispersed phase) described later. FIG. 6 is a cross-sectional view in a “direction perpendicular to the film surface”. In the measurement method and evaluation of the average dispersion diameter described later, the cross sections in the three directions indicated by (a), (b), and (c) are observed. A simple cross section is observed. This is because the dispersed phase of the island component has a substantially spherical shape.

  The sea-island structure of the present invention refers to a structure in which the dispersion diameter of the island part is 30 nm or more. When the biaxially oriented polyester film of the present invention has a sea-island structure, the island structure becomes a constraining point when stretched, and high orientation can be imparted in the longitudinal direction and the width direction, so that thermal dimensional stability can be improved. Become. Furthermore, orientation relaxation in the heat treatment during film formation and the subsequent annealing treatment can be suppressed, both thermal expansion and thermal contraction can be suppressed, and thermal dimensional stability is easily improved. Therefore, when used as a base film for flexible devices, dimensional changes in various processes can be reduced, and a base film having a small curl and excellent processability can be obtained.

  In order to further enhance the effects as described above, it is important to cause the island portion to function as a constraining point during the stretching of the polyester film and to exhibit the effect of increasing the molecular chain orientation of the sea portion. For this reason, it is important that the average dispersion diameter of the island portion is 30 to 500 nm.

  When the average dispersion diameter of the island portion is only a structure having a dispersion diameter of less than 30 nm, it does not function as a restraint point, and the molecular chain orientation in the film longitudinal direction and / or the width direction may not be improved during film stretching. For this reason, the thermal dimensional stability of the biaxially oriented polyester film is lowered, and orientation relaxation is likely to occur during heat treatment or annealing treatment, so that process suitability and the like are likely to deteriorate.

  For example, in a sea-island structure in which an island part is formed of a resin different from the sea part, the glass transition temperature (hereinafter referred to as Tg) of the resin that forms the island part may be accompanied by a decrease in the average dispersion diameter of the island part. ) Tends to be lower than Tg when the resin is present alone. If the average dispersion diameter of the island portion is less than 30 nm, the Tg of the island portion becomes sufficiently low, and the island portion does not function as a restraint point for the sea portion.

  On the other hand, if the average dispersion diameter of the island portion of the biaxially oriented polyester film of the present invention is larger than 500 nm, film breakage due to the island portion frequently occurs during film formation, and productivity is lowered. In addition, when the film is stretched, the film surface becomes rough or voids are generated, so that the process suitability is lowered and the effects of the present invention are hardly obtained.

  The average dispersion diameter of the island portion of the biaxially oriented polyester film of the present invention is more preferably 50 to 350 nm, still more preferably 70 to 200 nm.

  In the biaxially oriented polyester film of the present invention, the island portion is preferably made of resin B, and resin B is preferably made of an amorphous resin. When the island portion is an amorphous resin, the processability with the polyester is improved and the surface of the film is easily smoothed. Here, the amorphous resin refers to a resin having a characteristic that, when a sample is measured using differential scanning calorimetry (DSC) or the like, only the glass transition temperature is detected and the melting point and the melting peak are not detected.

  The glass transition temperature of the resin B used in the present invention is preferably 100 to 400 ° C. The glass transition temperature of the resin B is more preferably 100 to 300 ° C. When the glass transition temperature is 100 to 400 ° C., the island portion in the film easily functions as a constraining point during stretching or heat treatment, and the molecular chain orientation of the sea portion in the stretching process is easily enhanced. When the molecular chain orientation is increased, it becomes easier to obtain the effect of the present invention by improving the thermal dimensional stability. Furthermore, there is an effect of reducing defects in the biaxially oriented polyester film of the present invention. For example, when the biaxially oriented polyester film of the present invention is produced by the melt film forming method, when the resin B is extruded simultaneously with the polyester, the glass transition temperature of the resin B is close to the processing temperature of the polyester. The resin B is less likely to be unmelted or poorly dispersed, and defects in the film are reduced.

  In the biaxially oriented polyester film of the present invention, the resin B constituting the island portion is preferably polyetherimide (hereinafter sometimes referred to as PEI), polyimide (hereinafter sometimes referred to as PI), poly. Ether sulfone (hereinafter sometimes referred to as PES), polysulfone (hereinafter sometimes referred to as PSU), polyamideimide (hereinafter sometimes referred to as PAI), polyarylate (hereinafter sometimes referred to as PAR). It preferably contains at least one selected from the group consisting of polycarbonate (hereinafter sometimes referred to as PC) and polyphenylene ether (hereinafter sometimes referred to as PPE).

  Resin B constituting the island portion contains at least one selected from the group consisting of PEI, PI, PES, PSU, PAI, PAR, PC, and PPE, so that the biaxially oriented polyester film of the present invention is excellent. Thermal dimensional stability can be imparted.

  In the biaxially oriented polyester film of the present invention, it is preferable to use a resin having a Tg of 210 ° C. or more as the resin B constituting the island portion. The Tg of the resin B is more preferably 220 ° C. or higher, and further preferably 230 ° C. or higher. By containing an imide group as a constituent component of the resin B, the miscibility with the polyester is improved, and film breakage is reduced or voids are easily reduced.

  The biaxially oriented polyester film of the present invention preferably contains at least two types of polyetherimide. When the biaxially oriented polyester film of the present invention contains at least two kinds of polyetherimides, the biaxially oriented polyester film of the present invention is simultaneously provided with excellent thermal dimensional stability, high orientation, and excellent surface properties. This is because it becomes easier. Specific types of polyetherimide will be described later.

  Here, PEI is a resin containing an ether bond in a polyimide constituent component composed of an imide group, and the following general formula (3)

(Wherein R ₁ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, R ₂ is a divalent aromatic residue having 6 to 30 carbon atoms, From the group consisting of alkylene groups having 2 to 20 carbon atoms, cycloalkylene groups having 2 to 20 carbon atoms, and polydiorganosiloxane groups chain-terminated with alkylene groups having 2 to 8 carbon atoms It is a selected divalent organic group.).

Examples of R ₁ and R ₂ include the following formula groups

(In the formula, n is an integer of 2 or more, preferably an integer of 20 to 50).

  From the viewpoint of affinity with the polyester constituting the biaxially oriented polyester film of the present invention, cost, melt moldability, etc., 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane as PEI The following formulas (1) and (2), which are condensates of dianhydride and m-phenylenediamine or p-phenylenediamine

The polymer (PEI) having a repeating unit represented by the formula (4), and a sulfonyl group component from the viewpoint of heat resistance:

A polymer having a repeating unit represented by (PEI) is preferably used.

  This PEI is available from SABIC Innovative Plastics under the trade name “Ultem” (registered trademark), “Ultem 1000”, “Ultem 1010-1000”, “Ultem 1040A-1000”, “Ultem 5000”, “Ultem 6000”, It is known under the registered trademark names of “Ultem CRS 5011-1000” and “Ultem XH 6050-1000” series and “Extem XH 1015” and “Extem UH 1016”.

  In the present invention, the various PEIs described above are preferably included in at least two types. By including two types of PEI, the melt processability of PEI is improved and it becomes easy to mix in PET. Furthermore, since the entanglement of the molecular chain with the polymer that forms the sea portion increases, the force from the restraint point can be more effectively transmitted to the sea portion during the stretching process, and the molecular chain orientation of the sea portion can be changed. Can be increased.

  Specifically, as the two preferred combinations, “Ultem CRS 5011-1000” and “Ultem XH6050-1000” are preferable as the resin B, and “Ultem 1010-1000” is preferable as the resin C.

  In the biaxially oriented polyester film of the present invention, it is important that the total mass of island portions having a diameter of 30 to 500 nm is 0.1 to 10% by mass of the total mass of the film. When the total mass of the island portion is 0.1 to 10% by mass of the total film mass, the mechanical properties, thermal dimensional properties, electrical properties, surface properties, heat resistance and processing of the biaxially oriented polyester film of the present invention Can increase the sex. Furthermore, the frequency of film breakage due to stretching during film formation is reduced, and the biaxially oriented polyester of the present invention can be produced at lower cost and with higher productivity. When the total film mass is less than 0.1% by mass, the function as a restraint point of the island portion does not appear, and high orientation cannot be achieved, and it is difficult to obtain the effects of the present invention. When the total film mass is larger than 10% by mass, the average dispersion diameter of the island portion tends to be large, and film tearing due to the island portion frequently occurs during film formation, resulting in a decrease in productivity. In addition, when the film is stretched, the film surface becomes rough or voids are generated, so that the process suitability is lowered and the effects of the present invention are hardly obtained. The total mass of the island part is more preferably 0.3 to 5% by mass, and further preferably 0.5 to 3% by mass. The ratio of the polymer can be examined by using NMR method (nuclear magnetic resonance method) or microscopic FT-IR method (Fourier transform microinfrared spectroscopy).

  The biaxially oriented polyester film of the present invention needs to have a thermal expansion coefficient of 0 to 25 ppm / ° C. from 50 ° C. to 150 ° C. in at least one direction of the film in the longitudinal direction or the width direction.

  In order to make the above-mentioned thermal expansion coefficient less than 0 ppm / ° C., it is necessary to extremely increase the draw ratio of the film. As a result, stretching tears occur frequently during film formation, and productivity is lowered. Moreover, since the obtained biaxially oriented film has a very low elongation at break, it is easy to break, handling properties are lowered, and workability is lowered. On the other hand, when the thermal expansion coefficient is greater than 25 ppm / ° C., the film dimensions are greatly changed due to heat in various processes, yield is deteriorated, and problems such as curling and peeling from the device layer occur. The thermal expansion coefficient is more preferably 0 to 22 ppm / ° C, and further preferably 0 to 20 ppm / ° C. Moreover, it is preferable that a thermal expansion coefficient is 0-25 ppm / degreeC in a film longitudinal direction and the width direction. The thermal expansion coefficient can be controlled by stretching conditions, but has an island structure with an average dispersion diameter of 30 to 500 nm, and can be controlled to 0 to 25 ppm / ° C. by using the stretching conditions of the present invention.

  The biaxially oriented polyester film of the present invention preferably has a thermal shrinkage rate of 0 to 1% at a temperature of 150 ° C. in at least one direction of the longitudinal direction or the width direction of the film. If the thermal shrinkage rate is less than 0%, it indicates that the film expands rather than shrinks, the film dimensions change greatly due to heat in various processes, the yield deteriorates, and the film is peeled off from the curl or device layer. Problems are likely to occur. On the other hand, if the heat shrinkage rate is greater than 1%, the film dimensions are greatly changed due to heat in various processes, yield is deteriorated, and problems such as curling and peeling from the device layer are likely to occur. The thermal shrinkage rate is more preferably 0 to 0.7%, still more preferably 0 to 0.5%. Moreover, it is preferable that a thermal contraction rate is 0 to 1% in a film longitudinal direction and the width direction. Although the thermal expansion coefficient can be controlled by annealing conditions, it has an island structure with an average dispersion diameter of 30 to 500 nm, and by using the stretching conditions of the present invention, orientation relaxation due to annealing can be suppressed. % Can be controlled.

  The biaxially oriented polyester film of the present invention preferably has an intrinsic viscosity of 0.68 to 1.40 dl / g. If the intrinsic viscosity is less than 0.68 dl / g, the molecular chain is short and highly oriented, and it is difficult to obtain the effect of improving the thermal expansion coefficient. On the other hand, if the intrinsic viscosity is greater than 1.40 dl / g, the viscosity is high in the melted state and a load is applied to the extruder during film formation, making it difficult to discharge stably, and unevenness in thickness and stretching are likely to occur. It is difficult to align and the thermal shrinkage rate tends to deteriorate. The intrinsic viscosity of the film is particularly affected by the intrinsic viscosity of the raw material. The intrinsic viscosity of the film becomes higher as the intrinsic viscosity of the raw material and the intrinsic viscosity of the master pellet are higher. The intrinsic viscosity of the film is more preferably 0.70 to 1.00 dl / g, and further preferably 0.73 to 0.90 dl / g.

  The biaxially oriented polyester film of the present invention preferably has a minute melting peak (T-meta) just below the melting point of 200 to 250 ° C. If T-meta is less than 200 ° C., the structural fixation by heat treatment is insufficient and the thermal shrinkage tends to deteriorate. On the other hand, if T-meta is higher than 250 ° C., orientational relaxation will occur extremely and the thermal expansion coefficient tends to deteriorate. T-meta is more preferably 205 to 240 ° C, and further preferably 210 to 230 ° C. T-meta can be controlled by the heat setting temperature. T-meta varies depending on the film forming machine and the film forming speed, but becomes higher as the heat setting temperature is higher.

  The biaxially oriented polyester film of the present invention preferably has a haze value of 0 to 50%. When the haze value is larger than 50%, the transparency is low, and the problem that the efficiency of the organic EL or the thin film PV is lowered tends to occur. The haze value is more preferably 0 to 30%, and still more preferably 0 to 20%. The haze value can be controlled by the average dispersion diameter of the film structure and the type of thermoplastic resin to be blended.

  The biaxially oriented polyester film of the present invention as described above is produced, for example, as follows.

  In order to produce a biaxially oriented polyester film, for example, polyester pellets are melted and discharged from a die using an extruder, and then cooled and solidified to form a sheet. At this time, filtering the polymer with a fiber-sintered stainless metal filter is a preferred embodiment for removing unmelted material in the polymer. In addition, in order to impart slipperiness, abrasion resistance and scratch resistance to the surface of the polyester film, inorganic particles and organic particles such as clay, mica, titanium oxide, calcium carbonate, carion, talc, wet silica, During dry polymerization, colloidal silica, inorganic particles such as calcium phosphate, barium sulfate, alumina and zirconia, organic particles containing acrylic acid, styrene resin, thermosetting resin, silicone and imide compound, and polyester polymerization reaction It is also a preferred embodiment to add particles (so-called internal particles) that are precipitated by the catalyst to be added.

  Furthermore, various additives such as compatibilizers, plasticizers, weathering agents, antioxidants, thermal stabilizers, lubricants, antistatic agents, whitening agents, coloring, as long as the effects of the present invention are not impaired. Agents, conductive agents, crystal nucleating agents, ultraviolet absorbers, flame retardants, flame retardant aids, pigments and dyes may be added. Subsequently, the sheet-like material molded as described above is biaxially stretched. The film is stretched biaxially in the longitudinal direction and the width direction and heat-treated.

  As the stretching method, a sequential biaxial stretching method such as stretching in the width direction after stretching in the longitudinal direction, a simultaneous biaxial stretching method in which the longitudinal direction and the width direction are simultaneously stretched using a simultaneous biaxial tenter, etc. Further, a method of combining a sequential biaxial stretching method and a simultaneous biaxial stretching method is included.

  In order to control the thermal expansion coefficient and the thermal shrinkage rate within the scope of the present invention, it is desirable that the heat treatment after the stretching process is effectively performed without causing relaxation of molecular chain orientation due to excessive heat treatment.

  And the biaxially stretched polyester film manufactured in this way is wound up by a roll. Further, in order to enhance the thermal dimensional stability, the wound biaxially stretched polyester film is preferably conveyed and annealed under tension under a certain temperature condition.

  In this invention, you may perform arbitrary processes, such as shaping | molding, surface treatment, lamination, coating, printing, embossing, and an etching, as needed to a polyester film and its polyester film roll.

  Next, regarding the method for producing a biaxially oriented polyester film of the present invention, PEI (I) having a glass transition temperature of 215 ° C. between polyethylene terephthalate (PET) of resin A and resin C, and island portions as film constituent components As a representative example, an example in which PEI (II) in which the glass transition temperature of the resin B is 245 ° C. is used as a component for forming the resin B will be described.

  Of course, the present invention is not limited to a support using PET as a constituent component, and may be one using another polymer. For example, when a polyester film is formed using polyethylene-2,6-naphthalenedicarboxylate (polyethylene-2,6-naphthalate) having a high glass transition temperature or a high melting point, it is extruded at a temperature higher than the following temperature. What is necessary is just to extend | stretch.

  First, PET is prepared. PET is manufactured by one of the following processes. (1) Using terephthalic acid and ethylene glycol as raw materials, a low molecular weight polyethylene terephthalate or oligomer is obtained by direct esterification reaction, and then a polymer is obtained by polycondensation reaction using antimony trioxide or titanium compound as a catalyst. And (2) a process in which dimethyl terephthalate and ethylene glycol are used as raw materials, a low molecular weight product is obtained by a transesterification reaction, and a polymer is obtained by a subsequent polycondensation reaction using antimony trioxide or a titanium compound as a catalyst.

  Here, the reaction proceeds even without a catalyst, but the transesterification usually proceeds using a compound such as manganese, calcium, magnesium, zinc, lithium and titanium as a catalyst. After substantial completion, a phosphorus compound may be added for the purpose of inactivating the catalyst used in the reaction.

  In the case where the polyester which is a constituent component of the biaxially oriented polyester film of the present invention contains inert particles, the inert particles are dispersed in a predetermined proportion in the form of slurry in ethylene glycol, and this ethylene glycol is added during polymerization. The method is preferred. When adding inert particles, for example, water sol or alcohol sol particles obtained at the time of synthesis of the inert particles are added without drying once, the dispersibility of the particles is good. It is also effective to mix an aqueous slurry of inert particles directly with PET pellets and knead them into PET using a vented biaxial kneading extruder. As a method for adjusting the content of the inert particles, a master pellet of a high concentration of inert particles is prepared by the above method, and this is diluted with PET that does not substantially contain inert particles during film formation. A method for adjusting the content of the active particles is effective.

  As a method of mixing PET and PEI, before melt extrusion, (1) a mixture of PET, PEI (I) and PEI (II) needs to be premelted and kneaded (pelletized) to form a master chip. In that case, a method of pre-kneading and forming a master chip using a high shear mixer with a shear stress such as a twin screw extruder is preferably used. When mixing with a twin screw extruder, from the viewpoint of reducing poor dispersion, a screw equipped with a triple twin screw type or a double twin screw type is preferably used. PET, PEI (I) and PEI (II) need to be fed simultaneously to the twin screw extruder. By simultaneously feeding, the kneading time can be lengthened, and the average dispersion diameter of PEI (II) can be controlled within the range of the present invention.

  Conventionally, since processing temperatures differ between PET and PEI, it is considered that PEI (II) in particular needs to be considerably heated compared to PET, and simultaneous feeding to a heated extruder causes deterioration of PET. There was a problem that was easy to happen. However, as a result of intensive studies by the present inventors, melt extrusion of PET, PEI (I) and PEI (II) can be achieved by controlling a certain blending ratio even when the extrusion temperature is lowered to a temperature at which PET does not easily deteriorate. Found that is possible.

  In the present invention, in the kneading for producing the master chip, the melting temperature is preferably in the range of 300 to 350 ° C, more preferably in the range of 305 to 340 ° C, and further preferably in the range of 310 to 330 ° C. As the PET used in the kneading, high-viscosity PET having IV of preferably 0.8 or more, more preferably 1.0 or more is used.

  Moreover, it is preferable that the mixing mass ratio of PET in PET / PEI (I) / PEI (II) is 30 to 80%, more preferably 35 to 70%, and further preferably 40 to 60%. is there. The mixing mass ratio of PEI (I) is preferably 1 to 60%, more preferably 10 to 50%, and still more preferably 20 to 40%. The mixing mass ratio of PEI (II) is preferably 1 to 40%, more preferably 5 to 30%, and still more preferably 10 to 25%. Regarding the mixing mass ratio, PEI (I) / PEI (II) is preferably 90/10 to 50/50.

  Moreover, when pelletizing with a twin-screw extruder, it is preferable that a screw rotation speed shall be 100-500 rotation / min., A screw rotation speed is more preferably 150-450 rotation / min, More preferably, it is 200-400 rotation. Per minute. Even when the screw rotation speed is set within a preferable range, high shear stress is easily applied, and defective dispersion is easily reduced. Further, the ratio of (screw shaft length / screw shaft diameter) of the twin screw extruder is preferably in the range of 20-60, more preferably in the range of 30-50.

  Next, after drying the obtained pellets and the raw material PET chip under reduced pressure for 3 hours or more at a temperature of 180 ° C., the mixture is heated to a temperature of 270 to 320 ° C. under a nitrogen stream or under reduced pressure so that the intrinsic viscosity does not decrease. Then, the film is supplied to the extruder so as to have a film composition, extruded from a slit-shaped die, and cooled on a casting roll to obtain an unstretched film. At this time, it is preferable to use various types of filters, for example, filters made of materials such as sintered metal, porous ceramic, sand and wire mesh, in order to remove foreign substances and denatured polymers. Moreover, you may provide a gear pump as needed in order to improve fixed_quantity | feed_rate supply property. When laminating films, a plurality of different polymers are melt laminated using two or more extruders and manifolds or merging blocks. The raw material PET chip is preferably 0.8 to 1.5 dl / g so that the film IV is in a preferable range.

  As a film composition, PEI (I) is preferably 1 to 40% by mass. PEI (I) is more preferably 3 to 30% by mass, and further preferably 5 to 20% by mass. Moreover, it is preferable that PEI (II) is 0.1-10 mass%, More preferably, it is 0.3-5 mass%, More preferably, it is 0.5-3 mass%.

  Next, the unstretched film thus obtained is stretched in the machine direction using the difference in peripheral speed of the roll (MD stretching) using a longitudinal stretching machine in which several rolls are arranged, and subsequently A biaxial stretching method in which transverse stretching is performed using a stenter (TD stretching) will be described.

  First, the unstretched film is MD stretched. Since the biaxially oriented polyester film of the present invention has an intrinsic viscosity IV higher than that of ordinary polyester, it is necessary to increase the draw ratio in order to achieve high orientation. Therefore, in MD stretching, first, stretching is performed at a high temperature, stretching is performed while loosening the molecular chain, and then stretching is performed at a reduced temperature to perform lateral stretching, thereby achieving high-magnification stretching and high orientation. This stretching method is not a molecular chain entanglement as a restraint point, but is a stretching method that is possible with the polyester film of the present invention in which the island part of the sea-island structure functions. Film tears may occur frequently.

  The initial high temperature stretching (MD stretching) is preferably in the range of (Tg) to (Tg + 40) ° C., more preferably in the range of (Tg + 5) to (Tg + 30) ° C., and even more preferably in the range of (Tg + 10) to (Tg + 20). Heated with a certain heating roll group, preferably stretched 3.0 to 6.0 times, more preferably 3.5 to 5.5 times, and still more preferably 4.0 to 4.5 times in the longitudinal direction. Then, it is preferable to cool with a cooling roll group having a temperature of 20 to 50 ° C.

  Next, low-temperature stretching (TD stretching) is performed using a stenter. The low temperature stretching temperature is preferably in the range of (MD stretching temperature-5) to (MD stretching temperature-20) ° C, and more preferably in the range of (MD stretching temperature-5) to (MD stretching temperature-15) ° C. is there. The draw ratio is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.5 times, and still more preferably 4.0 to 4.5 times.

  Subsequently, the stretched film is heat-set under tension or while relaxing in the width direction. The heat setting temperature is preferably 220 to 250 ° C, more preferably 223 to 245 ° C, and still more preferably heat treatment at a temperature of 225 to 240 ° C. The heat treatment time is preferably in the range of 0.5 to 10 seconds. The heat treatment time is preferably in the range of 0.5 to 10 seconds.

  The relaxation rate is preferably 0 to 4%. The relaxation rate is more preferably 1 to 3%. Then, after cooling to a temperature of 25 ° C., the film edge is removed and wound on the core. Thereafter, annealing treatment is performed to further enhance the effect of thermal dimensional stability. The annealing treatment temperature is preferably 160 to 200 ° C, more preferably 165 to 195 ° C, and further preferably 170 to 190 ° C. The annealing time is preferably 1 to 30 seconds, more preferably 3 to 20 seconds, and further preferably 5 to 15 seconds. The film can be annealed while being conveyed at a speed of 10 to 300 m / min and a tension of 1 to 300 N / m to obtain the biaxially stretched polyester film of the present invention.

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

(1) Average Dispersion Diameter of Island Part (Dispersed Phase) Here, the average dispersion diameter of the island part is an average equivalent circle diameter obtained on a plurality of observation surfaces, and can be obtained by the following measurement method.

  First, the cut surface of the film was observed using a transmission electron microscope under the condition of an acceleration voltage of 100 kV, and a photograph taken at 20,000 times was taken as an image into an image analyzer, and an arbitrary 100 dispersed phases were obtained. (Island portion) is selected, and image processing is performed as necessary, thereby obtaining a dispersion diameter and calculating the number average. Specifically, it is as follows.

  Cut the film in (a) a direction parallel to the longitudinal direction and perpendicular to the film surface, (b) a direction parallel to the width direction and perpendicular to the film surface, and (c) a direction parallel to the film surface. Prepared by thin section method. In order to clarify the contrast of the dispersed phase, it may be stained with osmic acid or ruthenic acid. The cut surface is observed under a condition of an acceleration voltage of 100 kV using a transmission electron microscope (Hitachi H-7100FA type), and a photograph is taken at 20,000 times. The obtained photograph was taken into an image analyzer as an image, 100 arbitrary dispersed phases were selected, and image processing was performed as necessary, whereby the size of the dispersed phase was determined as follows. The maximum length (la) and the maximum length (lb) in the film thickness direction of each dispersed phase appearing on the cut surface of (a), and the film thickness direction of each dispersed phase appearing on the cut surface of (a) Maximum length (lc), maximum length (ld) in the width direction, maximum length (le) in the film longitudinal direction and maximum length in the width direction (lf) of each dispersed phase appearing on the cut surface of (c) ) Next, the shape index I of the dispersed phase I = (number average value of lb + number average value of le) / 2, shape index J = (number average value of ld + number average value of lf) / 2, shape index K = (of la Number average value + number average value of lc) / 2, the average dispersion diameter of the dispersed phase was (I + J + K) / 3.

  Transmission electron micrographs of each sample were taken into a computer with a scanner. Thereafter, image analysis was performed using dedicated software (Image Pro Plus Ver. 4.0 manufactured by Planetron). By manipulating the tone curve, the brightness and contrast are adjusted, and then 100 points of the equivalent circle diameter of the high-contrast component of the image obtained using a Gaussian filter are randomly observed, and the average dispersion diameter is determined according to the above calculation method. Was calculated. Here, when using a negative photograph of a transmission electron microscope photograph, Leafscan 45 Plug-In manufactured by Nippon Cytex Co., Ltd. is used as the scanner, and when using a positive transmission electron microscope, the scanner is used as the scanner. GT-7600S manufactured by Seiko Epson is used, and any of them can obtain an equivalent value.

[Image processing procedures and parameters]:
・ One flattening ・ Contrast +30
・ Gauss once ・ Contrast +30, Brightness -10
-Gauss 1 time-Planarization filter: Background (black), Object width (20 pix)
Gaussian filter: size (7), strength (10).

(2) Coefficient of thermal expansion In accordance with JIS K7197 (1991), under the following conditions, the number of samples was measured for each of the longitudinal direction and the width direction of the film, and average values were taken to obtain the longitudinal direction and the width direction. The thermal expansion coefficient of
Measurement device: “TMA / SS6000” manufactured by Seiko Instruments Inc.
・ Sample size: width 4mm, length 20mm
・ Temperature condition: Increased from 30 ° C. to 175 ° C. at 5 ° C./min and hold for 10 minutes ・ Further decrease in temperature from 175 ° C. to 40 ° C. at 5 ° C./min and hold for 20 minutes ・ Load condition: constant 29.4 mN here The thermal expansion coefficient measurement range temperature is 150 ° C. to 50 ° C. when the temperature is lowered. The thermal expansion coefficient was calculated from the following formula.
Thermal expansion coefficient [ppm / ° C.] = 10 ⁶ × {(dimension at 150 ° C.) − (Dimension at 50 ° C.)} / (150 ° C.-50 ° C.).

(3) Thermal shrinkage at a temperature of 150 ° C. The thermal shrinkage was measured using the following apparatus and conditions.
・ Length measuring device: Universal projector ・ Material size: Test length 150m x Width 10mm
・ Heat treatment equipment: Gear oven ・ Heat treatment conditions: 150 ° C., 30 minutes ・ Load: 3 g
・ Calculation method Draw marked lines at 100 mm intervals on the sample before heat treatment, measure the distance between marked lines after heat treatment, calculate the heat shrinkage from the change in distance between marked lines before and after heating, and measure the dimensional stability. It was. Measurement was carried out for each film in the longitudinal direction and the width direction, and the average value was evaluated.

(4) Three-dimensional surface roughness Ra
The surface morphology of the support is measured under the following conditions using a stylus type surface roughness meter in accordance with JIS-B0601 (1994).
・ Measuring device: Kosaka Laboratory three-dimensional fine shape measuring instrument (model ET-350K)
・ Analysis equipment: Three-dimensional surface roughness analysis system (model TDA-22)
-Stylus diameter: 2 μm
・ Load of stylus: 0.04mN
・ Vertical magnification: 50,000 times ・ Cutoff: 0.25 mm
・ Feed pitch: 5μm
・ Measurement length: 0.5mm
・ Measurement area: 0.2mm2
Measurement speed: 0.1 mm / second.

(5) Intrinsic viscosity From the solution viscosity measured in orthochlorophenol at a temperature of 25 ° C, the intrinsic viscosity is calculated based on the following equation.
ηsp / C = [η] + K [η] ² × C
Here, ηsp = (solution viscosity / solvent viscosity) −1, C is the dissolved polymer weight per 100 ml of solvent (g / 100 ml, usually 1.2), and K is a Huggins constant (assuming 0.343) It is. The solution viscosity and solvent viscosity are measured using an Ostwald viscometer.

(6) Melting point (Tm), minute melting peak (Tmeta) just below the melting point
In accordance with JIS K7121-1987, a differential scanning calorimeter, DSC (RDC220) manufactured by Seiko Instruments Inc., and a disk station (SSC / 5200) manufactured by Seiko Instruments Inc. are used as a data analysis device, and 5 mg of a sample is placed on an aluminum saucer at 25 ° C. to 300 ° C. The temperature was raised to 20 ° C. at a rate of temperature rise of 20 ° C./min. At that time, the peak temperature of the endothermic peak of melting observed was defined as the melting point (Tm), and the minute endothermic peak immediately below Tm was defined as Tmeta.

(7) Glass transition temperature (Tg)
Specific heat is measured with the following equipment and conditions, and determined according to JIS K7121 (1987).
・ Device: Temperature modulation DSC manufactured by TA Instrument
-Measurement conditions-Heating temperature: 270-570K (RCS cooling method)
・ Temperature calibration: Melting point of high purity indium and tin ・ Temperature modulation amplitude: ± 1K
・ Temperature modulation period: 60 seconds ・ Temperature increase step: 5K
・ Sample weight: 5mg
Sample container: Aluminum open container (22 mg)
Reference container: Aluminum open container (18mg)
The glass transition temperature is calculated by the following formula.
Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2.

(8) Haze value of film A 10 cm × 10 cm sample was cut out from the film and measured using a fully automatic direct reading haze computer HGM-2DP (manufactured by Suga Test Instruments Co., Ltd.) based on JISK7105 (1985). This was measured repeatedly at 10 points, and the average value was taken as the haze value of the film.

(9) Measurement of resin content in film After weighing the film, it is dissolved in a mixed solvent of hexafluoroisopropanol (HFIP) / chloroform (mass ratio 50/50). When there is an insoluble component, the insoluble component is separated by centrifugation, then the mass is measured, and the structure and mass fraction of the component are measured by elemental analysis, FT-IR, and NMR methods. If the supernatant component is analyzed in the same manner, the mass fraction and structure of the polyester component and other components can be specified. Specifically, after the solvent is distilled off from the supernatant component and dissolved in a mixed solvent of HFIP / deuterated chloroform (mass ratio 50/50), the NMR spectrum of ¹ H nucleus is measured.

  In the obtained spectrum, the peak area intensity of absorption peculiar to each component (for example, aromatic proton of terephthalic acid for PET, aromatic proton of bisphenol A for PEI) is determined, and the ratio and number of protons are obtained. The blend molar ratio is calculated. Further, the mass ratio is calculated from the formula amount corresponding to the unit unit of the polymer. In this way, the mass fraction and structure of each component can be specified.

(10) Thermal dimensional stability The biaxially stretched polyester film of the present invention is cut into a width of 50 mm and a length of 100 mm, and an organic flexible device is assumed to form the following organic EL layer. Thermal dimensional stability was evaluated from the dimensional change of the film.

・ (Hole transport layer)
Polyethylene dioxythiophene / polystyrene sulfonate (PEDOT / PSS, Bayron P AI 4083, manufactured by Bayer) diluted with 65% pure water and 5% methanol as a coating solution for forming a hole transport layer (PETOT / PSS) However, excluding 10 mm at both ends) was applied using an extrusion coater so that the thickness after drying was 30 nm. After the application, a hole transport layer was formed by drying and heating at 150 ° C. for 1 hour.

・ (Light emitting layer)
A toluene solution containing 1% by mass and 0.1% by mass of PVK and a dopant, respectively, was formed on the hole transport layer by an extrusion coating method. It vacuum-dried at the temperature of 120 degreeC for 1 hour, and was set as the light emitting layer with a film thickness of about 50 nm.

・ (Electron transport layer)
A 1-butanol solution containing 0.5% by mass of an electron transporting material was similarly formed on the light emitting layer by an extrusion coating method. Vacuum drying was performed at a temperature of 60 ° C. for 1 hour to obtain an electron transport layer having a film thickness of about 15 nm. A universal projector was used as the measuring device. Thermal dimensional stability was evaluated according to the following criteria. ◎, ○, and △ are acceptable.
A: The deformation was less than 100 μm in both the longitudinal and width directions, and the organic EL layer was formed without any problem.
A: The organic EL layer was formed when the amount of deformation in at least one of the longitudinal and width directions was 100 μm or more and less than 500 μm.
Δ: Deformation of at least one of the longitudinal and width directions was 500 μm or more, or wrinkles were generated and coating unevenness of the organic EL layer occurred.
X: The organic EL layer could not be formed due to wrinkling, curling or width shrinkage of the film.

(11) Curl property A 10 cm x 10 cm sample was cut out from the film and placed in an oven at a temperature of 150 ° C for 30 minutes. Then, after leaving for 30 minutes under the conditions of a temperature of 23 ° C. and 65% RH, the curled state at the four corners was observed, the average value of the amount of warping (mm) at the four corners was obtained, and evaluated according to the following criteria. ◎, ○, and △ are acceptable.
A: The amount of warpage is less than 2.5 mm.
○: The amount of warpage is 2.5 mm or more and less than 5 mm.
(Triangle | delta): The curvature amount is 5 mm or more and less than 10 mm.
X: The amount of warpage is 10 mm or more.

(12) Process suitability (transparent conductive film formation)
Before the plasma discharge, the inside of the chamber is evacuated to 5 × 10 −4 Pa, and then argon and oxygen are introduced into the chamber to a pressure of 0.3 Pa (oxygen partial pressure is 3.7 mPa), and 36 masses of tin oxide as a target. A transparent conductive layer made of ITO having a thickness of 260 nm by direct current magnetron sputtering by applying power at a power density of 2 W / cm 2 using indium oxide containing 1% (by Sumitomo Metal Mining Co., Ltd., density: 6.9 g / cm 3) Formed. Evaluation was made according to the following criteria. ◎, ○, and △ are acceptable.
A: A transparent conductive layer was formed without any problem with a surface resistivity of less than 30 Ω / □. A: A transparent conductive layer with a slight defect was formed with a surface resistivity of 30 Ω / □ or more and less than 100 Ω /. A transparent conductive layer with many defects at a rate of 100Ω / □ or more was formed. ×: The transparent conductive layer could not be formed due to curling, width shrinkage, surface protrusions, etc. of the film.

  Embodiments of the present invention will be described based on examples.

(Reference Example 1)
194 parts by mass of dimethyl terephthalate and 124 parts by mass of ethylene glycol were charged into a transesterification reactor, and the contents were heated to a temperature of 140 ° C. and dissolved. Thereafter, while stirring the contents, 0.3 parts by mass of magnesium acetate tetrahydrate and 0.05 parts by mass of antimony trioxide were added, and a transesterification reaction was performed while distilling methanol at a temperature of 140 to 230 ° C. went. Subsequently, 1 mass part (0.05 mass part as trimethyl phosphate) of 5 mass% ethylene glycol solution of trimethyl phosphate was added. Addition of an ethylene glycol solution of trimethyl phosphate decreases the temperature of the reaction contents. Therefore, stirring was continued until the temperature of the reaction contents returned to 230 ° C. while distilling excess ethylene glycol. Thus, after the temperature of the reaction contents in the transesterification reactor reached a temperature of 230 ° C., the reaction contents were transferred to the polymerization apparatus. After the transition, the reaction system was gradually heated from a temperature of 230 ° C. to a temperature of 290 ° C., and the pressure was reduced to 0.1 kPa. The time to reach the final temperature and final pressure was both 60 minutes. After reaching the final temperature and the final pressure, the reaction was carried out for 2 hours (3 hours after the start of polymerization), and the agitation torque of the polymerization apparatus was a predetermined value (specific values differ depending on the specifications of the polymerization apparatus. The value indicated by the polyethylene terephthalate having an intrinsic viscosity of 0.60 was defined as a predetermined value). Therefore, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged into cold water in a strand form, and immediately cut to obtain PET pellet X _0.60 of polyethylene terephthalate having an intrinsic viscosity of 0.60. It was.

(Reference Example 2)
Using a rotary vacuum polymerization apparatus, the PET pellet X _0.60 obtained in the above Reference Example 1 was heat-treated at a temperature of 230 ° C. under a reduced pressure of 0.1 kPa for a long time to carry out solid phase polymerization. PET pellet X _1.0 having an intrinsic viscosity of 1.0 at a treatment time of 100 hours was obtained.

(Reference Example 3)
Using a rotary vacuum polymerization apparatus, the PET pellet X _0.60 obtained in the above Reference Example 1 was heat-treated at a temperature of 230 ° C. under a reduced pressure of 0.1 kPa for a long time to carry out solid phase polymerization. The longer the heat treatment time, the higher the intrinsic viscosity. PET pellet X _0.80 having an intrinsic viscosity of 0.80 after a treatment time of 15 hours was obtained.

(Reference Example 4)
Using a rotary vacuum polymerization apparatus, the PET pellet X _0.60 obtained in the above Reference Example 1 was heat-treated at a temperature of 230 ° C. under a reduced pressure of 0.1 kPa for a long time to carry out solid phase polymerization. The longer the heat treatment time, the higher the intrinsic viscosity. PET pellet X _0.70 having an intrinsic viscosity of 0.70 after a treatment time of 6 hours was obtained.

(Reference Example 5)
Using a rotary vacuum polymerization apparatus, the PET pellet X _0.60 obtained in the above Reference Example 1 was heat-treated at a temperature of 230 ° C. under a reduced pressure of 0.1 kPa for a long time to carry out solid phase polymerization. The longer the heat treatment time, the higher the intrinsic viscosity. PET pellet X _0.69 having an intrinsic viscosity of 0.69 after a treatment time of 5 hours was obtained.

(Reference Example 6)
Using a rotary vacuum polymerization apparatus, the PET pellet X _0.60 obtained in the above Reference Example 1 was heat-treated at a temperature of 230 ° C. under a reduced pressure of 0.1 kPa for a long time to carry out solid phase polymerization. The longer the heat treatment time, the higher the intrinsic viscosity. PET pellet X _1.45 having an intrinsic viscosity of 1.45 after a treatment time of 300 hours was obtained.

(Reference Example 7)
Using a rotary vacuum polymerization apparatus, the PET pellet X _0.60 obtained in the above Reference Example 1 was heat-treated at a temperature of 230 ° C. under a reduced pressure of 0.1 kPa for a long time to carry out solid phase polymerization. The longer the heat treatment time, the higher the intrinsic viscosity. PET pellet X _1.47 having an intrinsic viscosity of 1.47 after a treatment time of 320 hours was obtained.

(Reference Example 8)
Separately, 50 parts by mass of PET pellet X _1.0 obtained in Reference Example 2, 35 parts by mass of pellets of PEI “Ultem 1010-1000” manufactured by SABIC Innovative Plastics, and 15 parts by mass of pellets of “Ultem XH6050-1000” were separately 180 ° C. Was dried for 6 hours under a reduced pressure of 3 mmHg. Vent type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading parts with a screw diameter of 30 mm and screw length / screw diameter = 45.5 manufactured by Nippon Steel, Ltd. The temperature gradient was set to a temperature of 270 ° C. to 320 ° C. over the part. Pellets dried under reduced pressure are supplied to this extruder, melt extruded at a screw rotation speed of 300 revolutions / minute, and a residence time of 3 minutes, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut into PET / PEI (Ul 1010) / PEI (XH6050) blend pellet Y was prepared.

(Reference Example 9)
50 parts by mass of PET pellet X _1.0 obtained in Reference Example 2 and 50 parts by mass of PEI “Ultem 1010-1000” pellets manufactured by SABIC Innovative Plastics were separately added at a temperature of 180 ° C. under a reduced pressure of 3 mmHg. Dry for hours. Vent type twin-screw kneading extruder of the same direction rotation type provided with three kneading paddle kneading parts with a screw diameter of 30 mm and screw length / screw diameter = 45.5 manufactured by Nippon Steel, Ltd. The temperature gradient was set to 270 ° C. to 320 ° C. over the part. Pellets dried under reduced pressure are supplied to this extruder, melt extruded at a screw rotation speed of 300 revolutions / minute, and a residence time of 3 minutes, discharged into a strand, cooled with water at a temperature of 25 ° C., and immediately cut into PET / PEI (Ul 1010) blend pellets Z were made.

Example 1
In the extruder E heated to a temperature of 290 ° C., 78 parts by mass of PET pellet X _0.80 having an intrinsic viscosity of 0.80 obtained in Reference Example 3 and blend chip Y6.7 obtained in Reference Example 8 were used. Mass parts and 15.3 parts by mass of the blended chip Z obtained in Reference Example 9 were supplied after drying under reduced pressure at a temperature of 180 ° C. for 3 hours and introduced into a T-die die under a nitrogen atmosphere. Next, from the inside of the T die die, it was extruded into a sheet shape to obtain a molten single layer sheet, which was closely cooled and solidified by an electrostatic application method on a drum maintained at a surface temperature of 25 ° C. to obtain an unstretched single layer film.

  Subsequently, after preheating the obtained unstretched monolayer film with a heated roll group, 4.3 times MD stretching is performed at a temperature of 105 ° C., and the uniaxially stretched film is cooled by a roll group at a temperature of 25 ° C. Obtained. While holding both ends of the obtained uniaxially stretched film with clips, it is led to a preheating zone at a temperature of 85 ° C. in the tenter, and then continuously in the heating zone at a temperature of 95 ° C. in the width direction (TD direction) perpendicular to the longitudinal direction. The film was stretched 4.3 times. Subsequently, a heat treatment was performed for 5 seconds at a temperature of 230 ° C. in a heat treatment zone in the tenter, and a relaxation treatment was further performed in the 2% width direction at a temperature of 230 ° C. Subsequently, after uniformly cooling to 25 ° C., the film edge was removed, and the film was wound on a core to obtain a biaxially stretched film having a thickness of 100 μm.

  And it annealed, conveying for 10 second with the tension | tensile_strength of 20 N / m and the film speed of 30 m / min at the annealing temperature of 180 degreeC, and obtained the biaxially stretched polyester film.

When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.
(Example 2)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the master composition was changed as shown in Table 1. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Example 3)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the master composition was changed as shown in Table 1. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had characteristics excellent in thermal dimensional stability and curl property although it was slightly inferior in process suitability.

Example 4
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film forming conditions were changed as shown in Table 2. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Example 5)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film forming conditions were changed as shown in Table 2. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, although it was slightly inferior in thermal dimensional stability and curl properties, it had excellent process suitability.

(Example 6)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film forming conditions were changed as shown in Table 2. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, although it was slightly inferior in curling property, it had excellent thermal dimensional stability and process suitability.

(Example 7)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the annealing conditions were changed as shown in Table 2. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had characteristics excellent in curling properties and process suitability although it was slightly inferior in thermal dimensional stability.

(Example 8)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film forming conditions were changed as shown in Table 2. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

Example 9
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film forming conditions were changed as shown in Table 2. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Example 10)
As shown in Table 2, a biaxially oriented polyester film was prepared in the same manner as in Example 1 except that PET pellet X _0.80 as a film raw material was changed to PET pellet X _0.70 obtained in Reference Example 4. Obtained. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Example 11)
As shown in Table 2, a biaxially oriented polyester film was prepared in the same manner as in Example 1 except that PET pellet X _0.80 as a film raw material was changed to PET pellet X _0.69 obtained in Reference Example 5. Obtained. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Example 12)
As shown in Table 2, the biaxially oriented polyester film was prepared in the same manner as in Example 1 except that PET pellet X _0.80 as a film raw material was changed to PET pellet X _1.45 obtained in Reference Example 6. Obtained. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Example 13)
As shown in Table 2, a biaxially oriented polyester film was prepared in the same manner as in Example 1 except that PET pellet X _0.80 as a film raw material was changed to PET pellet X _1.47 obtained in Reference Example 7. Obtained. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Example 14)
A biaxially oriented polyester film was prepared in the same manner as in Example 1 except that “UltemXH6050-1000” manufactured by SABIC Innovative Plastics was changed to PES “RADEL A Grade A-300A” manufactured by Solvay Advanced Polymers. Obtained. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Practical example 15)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that “UltemXH6050-1000” manufactured by SABIC Innovative Plastics was changed to “UltemCRS5011-1000”. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had excellent thermal dimensional stability, curling properties and process suitability.

(Comparative Example 1)
In the extruder E heated to a temperature of 290 ° C., 80 parts by mass of the PET pellet X _0.80 having an intrinsic viscosity of 0.80 obtained in Reference Example 3 and 20 parts by mass of the blend chip Z obtained in Reference Example 9 Was supplied after being dried under reduced pressure at a temperature of 180 ° C. for 3 hours and introduced into a T-die die under a nitrogen atmosphere. Next, from the inside of the T die die, it was extruded into a sheet shape to obtain a molten single layer sheet, which was closely cooled and solidified by an electrostatic application method on a drum maintained at a surface temperature of 25 ° C. to obtain an unstretched single layer film.

  Subsequently, after preheating the obtained unstretched single layer film with a heated roll group, 4.0 times MD stretching is performed at a temperature of 95 ° C., and the uniaxially stretched film is cooled by a roll group at a temperature of 25 ° C. Obtained. While holding both ends of the obtained uniaxially stretched film with clips, it is guided to a preheating zone at a temperature of 95 ° C. in the tenter, and then continuously in the heating zone at a temperature of 105 ° C. in the width direction perpendicular to the longitudinal direction (TD direction). A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film was stretched 4.0 times. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had characteristics inferior in thermal dimensional stability, curling properties and process suitability.

(Comparative Example 2)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the master composition was changed as shown in Table 1. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had characteristics inferior in thermal dimensional stability, curling properties and process suitability.

(Comparative Example 3)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the master composition was changed as shown in Table 1. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had characteristics inferior in thermal dimensional stability, curling properties and process suitability.

(Comparative Example 4)
A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film forming conditions were changed as shown in Table 1. When the obtained biaxially oriented polyester film was evaluated, as shown in Table 4, it had characteristics inferior in thermal dimensional stability, curling properties and process suitability.

  Tables 1 to 3 summarize the master preparation conditions, master composition, film composition, film forming conditions, film structure, and film properties of Examples 1 to 13 and Comparative Examples 1 to 4.

  The biaxially oriented polyester film of the present invention can be applied to a substrate film for a flexible device having excellent thermal dimensional stability, curling properties, and process suitability. Therefore, there is a possibility of being used to obtain organic EL displays, electronic paper, organic EL lighting, organic solar cells, dye-sensitized solar cells, and the like.

1: Continuous phase (sea component)
2: Dispersed phase (island component)

Claims (12)

  A biaxially oriented film having a sea-island structure comprising at least a polyethylene terephthalate resin (resin A) and a resin B, wherein the average dispersion diameter of the island portion is 30 to 500 nm, and the longitudinal direction of the film at a temperature of 50 to 150 ° C. Or the biaxially-oriented polyester film characterized by the coefficient of thermal expansion of at least one direction of a width direction being 0-25 ppm / degrees C.   2. The biaxially oriented polyester film according to claim 1, wherein the thermal shrinkage rate at a temperature of 150 ° C. in at least one direction of the longitudinal direction or the width direction is 0 to 3%.   The glass transition temperature (Tg) of the resin B is 100 to 400 ° C, and the content of the resin B in the film is 0.1 to 10% by mass. Polyester film.   The biaxially oriented polyester film according to any one of claims 1 to 3, wherein an island component constituting the island portion is made of resin B. Resin B is represented by the following formula (1)

The biaxially oriented polyester according to any one of claims 1 to 4, which is a polyetherimide having a structure represented by formula (1) or a polyetherimide having a structure represented by the formula (1) and a sulfonyl group component. the film. A biaxially oriented film having a sea-island structure comprising at least polyethylene terephthalate (resin A), resin B and resin C, wherein the resin C is represented by the following formula (2)

The biaxially oriented polyester film according to claim 1, which is a polyetherimide having a structure represented by:   The biaxially oriented polyester film according to any one of claims 1 to 6, wherein the intrinsic viscosity (IV) of the film is 0.68 to 1.4.   The biaxially oriented polyester film according to any one of claims 1 to 7, wherein a minute melting peak (T-meta) just below the melting point is 200 to 250 ° C.   The film for flexible device base materials which uses the biaxially-oriented polyester film in any one of Claims 1-8. At least resin A and resin B are melt-kneaded to prepare a master batch satisfying the following conditions, the master batch and polyethylene terephthalate resin (resin A) are mixed, melt-extruded to prepare an unstretched film, The method for producing a biaxially oriented polyester film according to claim 1, wherein the stretched film is biaxially stretched in the longitudinal direction and the width direction and subsequently subjected to heat treatment.
Resin A; 30-80% by mass
Resin B; 20 to 70% by mass At least resin A, resin B, and resin C are melt-kneaded to prepare a master batch that satisfies the following conditions, and the master batch and polyethylene terephthalate resin (resin A) are mixed and melt-extruded to prepare an unstretched film. The method for producing a biaxially oriented polyester film according to claim 6, wherein the unstretched film is biaxially stretched in the longitudinal direction and the width direction, followed by heat treatment.
Resin A; 30-80% by mass
Resin B + C; 20 to 70% by mass
Resin B / Resin C (weight ratio): 10/90 to 50/50   When the masterbatch and the resin A are mixed, melt-extruded to produce an unstretched film, and the unstretched film is stretched in the longitudinal direction and biaxially stretched in the width direction, the stretching temperature in the longitudinal direction is set to the width. Biaxial stretching is performed at a temperature higher than the stretching temperature in the direction, followed by heat treatment at 205-255 ° C., followed by cooling to a temperature of 0-50 ° C., followed by annealing at a temperature of 160-200 ° C. for 1-30 seconds. The method for producing a biaxially oriented polyester film according to claim 10 or 11.

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