JP2006233038A - Biaxially oriented polyester film and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-quality biaxially oriented polyester film having small heat shrinkage and amount of creep deformation and excellent thermal dimensional stability and planarity without deposition of oligomers in thermal processing steps in various industrial material uses and having excellent winding habit resistance. <P>SOLUTION: The biaxially oriented polyester film is a biaxially oriented film comprising a polyester comprising ethylene terephthalate units as main constituent units and a polyimide as constituent components. The film has 0-0.2% absolute value of heat shrinkage percentage at 100°C in both the longitudinal and the width directions of the film and <0.15% amount of creep deformation. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyester film having excellent thermal dimensional stability.

  More specifically, the biaxially oriented polyester film has excellent flatness, a property that suppresses oligomers that precipitate on the surface when the film is heated (oligomer resistance), and a property that is difficult to curl (winding resistance). It is about.

  Polyester films are widely used in various applications depending on their physical and thermal properties. In particular, by molecular orientation by stretching in the biaxial direction of length and width, it has excellent strength, durability, transparency, flexibility, surface properties, electrical insulation, chemical resistance, etc. It is used in various fields that are in great demand such as recording media, circuit materials, plate making / printing materials, optical materials and other industrial materials, agriculture, packaging and building materials. However, since the strain due to biaxial stretching remains in the molecular chain, the molecular chain strain is released by heating and contracts. This heat shrinkage characteristic is used to develop a shrink film for packaging and the like, but in general, this heat shrinkage is often an obstacle in the above-described applications. On the other hand, it has a property that dimensional change (creep deformation) occurs when a load is applied for a long time under heating. When a polyester film is used for various industrial materials, a material having excellent thermal dimensional stability such as heat shrinkage and creep properties has been demanded.

  In general, in order to improve the thermal dimensional stability, a method of releasing strain of the molecular chain by biaxially stretching and then heat-fixing subsequent to transverse stretching in a tenter is taken. Although the amount of heat shrinkage decreases according to the temperature of this heat setting, this heat setting alone cannot completely remove the distortion, causing a problem that heat shrinkage remains. Conventionally, in order to remove this residual strain, a method of removing this residual strain by narrowing the rail width on the tenter exit side to slightly contract in the width direction has been adopted. However, in this method, heat shrinkage in the width direction can be removed, but heat shrinkage in the longitudinal direction cannot be removed. For this reason, various studies have been made in the past regarding methods for removing thermal contraction in the longitudinal direction. For example, Patent Document 1 proposes a method of performing relaxation processing in the longitudinal direction by gradually reducing the clip interval of the tenter. However, in this method, the relaxation rate is limited due to problems with the apparatus, and heat shrinkage is not sufficiently removed. If the relaxation rate is increased, the clip gap before relaxation increases, and the film physical properties of the clip gripping part and the non-gripping part are uneven. The problem arises that becomes large. Patent Document 2 proposes a method of providing a longitudinal relaxation treatment apparatus using an oven during a film forming process. However, in consideration of the film forming speed, if the processing temperature is increased, the film surface will be wavy and the flatness will deteriorate, so the temperature will not be increased so much that heat shrinkage will be removed sufficiently. The problem of not being done arises.

  In order to obtain a film product having a low heat shrinkage rate, Patent Document 3 proposes a method of heat-treating a biaxially stretched film in a roll shape in an atmosphere of 100 to 130 ° C. for 6 hours or more. In this method, since heat treatment is performed for a long time, wrinkles due to tightening occur and the film flatness deteriorates, and oligomers in the polyester are deposited on the film surface to contaminate the film surface and deteriorate the quality. There was a problem that caused process contamination.

  On the other hand, when the polyester film is used for a magnetic recording medium, the curling process after coating the magnetic layer causes problems such as wrinkling when stored for a long time after winding under tension. When a polyester film is used as a material or a sheet material for an electronic blackboard, there is a problem that curling is caused by winding and storing in the application. This curling problem is an unavoidable problem as a polyester film mainly composed of polyethylene terephthalate.

Further, as a film made of polyethylene terephthalate and polyimide, for example, Patent Document 4 proposes. However, this film has insufficient thermal dimensional stability, and the problem of curling has not been solved.
Japanese Patent Publication No. 4-28218 Japanese Patent Publication No. 60-226160 JP-A-60-103517 JP 2000-141475 A

  An object of the present invention is to solve the above problems, and to provide a high-quality polyester film excellent in flatness and oligomer resistance and excellent in curling resistance, and a method for producing such a film.

  The film of the present invention is a film composed of polyester and polyimide, and it has been found that an excellent film can be formed by defining the thermal dimensional stability, and the present invention has been completed. That is, the biaxially oriented polyester film of the present invention contains polyester and polyimide containing ethylene terephthalate units as constituent units as constituent components, and the creep deformation amount at 100 ° C. in both the longitudinal direction and the width direction is less than 0.15%. In addition, the absolute value of the heat shrinkage rate at 100 ° C. is 0 to 0.2% in both the longitudinal direction and the width direction of the film.

  Hereinafter, preferred embodiments of the present invention will be described. The polyester referred to in the present invention includes an ethylene terephthalate unit, and is preferably a polymer containing at least 70 mol% or more, more preferably 80 mol% or more of the unit. The acid component is mainly composed of terephthalic acid, but a small amount of other dicarboxylic acid components may be copolymerized, and the glycol component is mainly composed of ethylene glycol, but other glycol components are copolymerized components. May be added as Examples of dicarboxylic acids other than terephthalic acid include aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, isophthalic acid, diphenylsulfone dicarboxylic acid, benzophenone dicarboxylic acid, 4,4′-diphenyldicarboxylic acid, and 3,3′-diphenyldicarboxylic acid. Examples thereof include aliphatic dicarboxylic acids such as acid, adipic acid, succinic acid, azelaic acid, sebacic acid and dodecanedioic acid, and alicyclic dicarboxylic acids such as hexahydroterephthalic acid and 1,3-adamantane dicarboxylic acid. Examples of glycol components other than ethylene glycol include chlorohydroquinone, methylhydroquinone, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenylsulfone, 4,4′-dihydroxydiphenyl sulfide, and 4,4′-. Aromatic diols such as dihydroxybenzophenone and p-xylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,4 -Aliphatic and alicyclic diols such as butanediol, 1,6-hexanediol and neopentylglycol can be mentioned. Furthermore, in addition to the acid component and glycol component, aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid, m-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, p-aminophenol, p-aminobenzoic acid, etc. If the amount is small enough not to impair the object of the present invention, it can be further copolymerized.

  Polyethylene terephthalate is usually produced 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. Process (2) A process in which dimethyl terephthalate and ethylene glycol are used as raw materials, a low molecular weight product is obtained by transesterification, and then a polymer is obtained by polycondensation reaction using antimony trioxide or titanium compound as a catalyst. Here, the reaction proceeds even without a catalyst, but the transesterification usually proceeds using a compound such as manganese, calcium, magnesium, zinc, lithium, titanium as a catalyst, and the transesterification is substantially carried out. After completion of the reaction, a phosphorus compound may be added for the purpose of inactivating the catalyst used in the reaction. The esterification or transesterification reaction is usually carried out under a temperature condition of 130 to 260 ° C, and the polycondensation reaction is usually carried out at a temperature of 220 to 300 ° C under a high vacuum. Examples of the phosphorus compound include phosphorous acid, phosphoric acid, phosphoric acid triester, phosphonic acid, and phosphonate, but are not particularly limited. Two or more of these phosphorus compounds may be used in combination.

  The polyimide of the present invention is not particularly limited as long as it is a polyimide that has melt moldability and is compatible with polyester. For example, tetracarboxylic acid and / or acid anhydride thereof, aliphatic primary monoamine, aromatic primary Examples thereof include a polymer obtained by dehydration polycondensation with one or two or more compounds selected from the group consisting of monoamines, aliphatic primary diamines and aromatic primary diamines. Of these, polyetherimide containing an ether bond in the polyimide constituent component is preferable from the viewpoint of melt moldability with polyester and handleability.

  The term “compatible” as used herein can be determined from the fact that the glass transition temperature (Tg) of a chip obtained by blending is single. The single glass transition temperature means that there is only one glass transition temperature between the glass transition temperature of polyester and the glass transition temperature of polyimide in differential scanning calorimetry (DSC) measurement. If two or more glass transition temperatures are observed between the glass transition temperature of the polyester and the glass transition temperature of the polyimide, the compatibility between the polyester and the polyimide is insufficient, and the film tends to break during film production. May decrease.

  In the present invention, the timing of adding the polyimide to the polyester is not particularly limited, but it may be added before polymerization of the polyester, for example, before the esterification reaction, or after polymerization and before melt extrusion. Further, before melt extrusion, polyester and polyimide may be pelletized and used.

  When using the polyetherimide preferable as a polyimide for the film of this invention, content in the film of polyetherimide is 5 to 30 weight% with respect to the composition which comprises a film, Preferably it is 7 to 25 weight%, More preferably, it is 10 to 20% by weight, from the viewpoint of easy obtaining of the film of the present invention, from the viewpoint of thermal dimensional stability, oligomer resistance, and curling resistance. Since the melt viscosity of polyester and polyetherimide is greatly different, if the content of polyetherimide is lower than the above range, it may be difficult to make them compatible with each other even if kneaded sufficiently in a melt extruder, When the content of the polyetherimide in the film layer exceeds 30% by weight, extrusion and stretching become difficult and productivity may be lowered. In addition, even when using polyimides other than polyetherimide, it is preferable that it is the same content as the above.

  Moreover, antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, crystal nucleating agents, inorganic particles, organic particles, and the like may be added to the film of the present invention as necessary. In particular, inorganic particles and organic particles are effective for imparting slidability to the surface of the film and enhancing the handleability of the film. Specific examples of inorganic particles include oxides such as silicon oxide, aluminum oxide and titanium oxide, composite oxides such as kaolin, talc and montmorillonite, carbonates such as calcium carbonate and barium carbonate, sulfates such as calcium sulfate and barium sulfate. Further, titanates such as barium titanate and potassium titanate, phosphates such as calcium phosphate, and the like can be used. It is not necessarily limited to these. Silicon oxide may be spherical or porous.

  Specific examples of organic particles include polystyrene or crosslinked polystyrene particles, styrene / acrylic and acrylic crosslinked particles, vinyl particles such as styrene / methacrylic crosslinked particles, benzoguanamine / formaldehyde, silicon, and polytetrafluoroethylene. Although particles can be used, the present invention is not limited to these, and any particles may be used as long as at least a part of the parts constituting the particles is insoluble in the resin constituting the film.

  The particle size, blending amount, shape, etc. of these additive particles can be appropriately selected according to the surface roughness required for each film application. Incidentally, the average particle size is preferably 0.01 μm or more and 3 μm or less, and the addition amount is preferably 0.001 wt% or more and 5 wt% or less. One kind of additive particles may be used, but two or more kinds of particles having different average particle diameters may be added in combination.

  In the present invention, a biaxially oriented film containing polyester and polyimide containing ethylene terephthalate units as constituent units as a constituent component, a temperature in the vicinity of the glass transition temperature (Tg) of the biaxially oriented film, that is, (Tg-40) ° C. It is preferable to perform heat treatment at (Tg + 30) ° C., preferably (Tg−30 ° C.) to (Tg + 20) ° C., more preferably (Tg−20) ° C. to (Tg + 10) ° C. for 1 hour or longer, preferably 10 hours or longer. It is preferable from the viewpoints of thermal dimensional stability and flatness that the heat treatment is performed for 24 hours at room temperature. If the treatment temperature is less than (Tg-40) ° C., the time required for the aging treatment may become long, and thermal dimensional stability and curling resistance may not be obtained. On the other hand, when the treatment temperature exceeds (Tg + 30) ° C., oligomers may precipitate on the film surface, or excessive tightening may cause wrinkles on the film and deteriorate flatness. If the treatment time is less than 1 hour, thermal dimensional stability and curling resistance may not be obtained. Although the upper limit of processing time is not specifically limited, 170 hours or less are preferable from a viewpoint of cost.

  The surface roughness of the biaxially oriented polyester film of the present invention is not particularly limited, but the ratio of centerline average roughness (Ra) to maximum roughness (Rt), Rt / Ra is 15 to 8, preferably 10 to 9. If it is, the effect of the thermal dimensional stability by the above-mentioned heat treatment appears clearly, and it is preferable from the viewpoint of flatness. Furthermore, in order to prevent deterioration in film flatness, there is no die streak thickness unevenness at the time of melt extrusion, and the film surface thickness unevenness is 10% or less, preferably 5% or less in both the longitudinal direction and the width direction. It is also preferable that the film flatness does not deteriorate even when tightening due to heat treatment occurs.

  In the biaxially oriented polyester film of the present invention, the absolute value of the heat shrinkage at 100 ° C. is 0 to 0.2%, more preferably 0 to 0.15%, and most preferably 0 to 0 in both the longitudinal direction and the width direction of the film. 0.1%. When the thermal shrinkage rate is out of the above range, the flatness of the film and the anti-winding tendency tend to decrease.

  Further, the amount of creep deformation of the biaxially oriented polyester film of the present invention at 100 ° C. is less than 0.15%, preferably less than 0.10%, more preferably 0.07 in both the longitudinal direction and the width direction of the film. %. When the amount of creep deformation is 0.15% or more, curling resistance and flatness tend to be lowered. The lower limit of creep at 100 ° C. is 0.005% from the viewpoint of the production method. Even if less than 0.005% is obtained, a large amount of oligomer precipitation and a decrease in elastic modulus may occur.

  In the biaxially oriented polyester film of the present invention, the sum of the elastic modulus in the film longitudinal direction and the width direction is 5 to 15 GPa, preferably 6 to 12 GPa. If the elastic modulus is less than 5 GPa, it may be difficult to handle because there is no waist. On the other hand, if it exceeds 15 GPa, deformation and curling may occur easily. When the ratio Ymd / Ytd of the elastic modulus Ymd (GPa) in the film longitudinal direction and the elastic modulus Ytd (GPa) in the width direction is 0.85 to 1.5, more preferably 0.9 to 1.2 It is preferable from the viewpoint of flatness of the film and curling resistance.

  Further, the relational expression 0.04Y-S between the heat shrinkage rate S (%) at 100 ° C. in the film longitudinal direction and the elastic modulus Y (GPa) in the film longitudinal direction is 0.07 or more, more preferably 0.08 or more, More preferably, 0.09 or more is preferable from the viewpoint of flatness and curling resistance.

  When the intrinsic viscosity of the film of the present invention is 0.5 to 0.8 (dl / g), preferably 0.55 to 0.75, and more preferably 0.6 to 0.7, the thermal dimensional stability From the viewpoints of surface property, flatness, oligomer resistance, and curling resistance.

  The thickness of the biaxially oriented polyester film of the present invention can be appropriately adjusted in the range of 0.5 μm to 400 μm according to the use of the film. 2.0 μm to 10 μm for magnetic tape applications, 0.5 μm to 15 μm for capacitor applications, 12 μm to 250 μm for circuit material applications, 25 μm to 200 μm for electrical insulation material applications, 25 to 200 μm for projection screens and electronic blackboard applications Is preferred.

  Next, although the specific example of the manufacturing method of the biaxially-oriented polyester film of this invention is demonstrated, it is not limited to the following description. First, an example using polyethylene terephthalate and polyetherimide as polyimide is shown. The polyetherimide is not particularly limited, and for example, “Ultem” (manufactured by General Electric) can be used.

  First, terephthalic acid and ethylene glycol are esterified, or dimethyl terephthalate and ethylene glycol are transesterified to obtain bis-β-hydroxyethyl terephthalate (BHT). Next, while this BHT is transferred to a polymerization tank, it is polymerized by heating to 280 ° C. under reduced pressure. At this time, a predetermined amount of polyetherimide may be added. If necessary, the obtained polyester pellets are subjected to solid phase polymerization under reduced pressure. In the case of solid phase polymerization, after preliminarily crystallizing at a temperature of 180 ° C. or lower in advance, solid phase polymerization is performed at 190 to 250 ° C. under reduced pressure of about 1 mmHg for 3 to 50 hours, and an intrinsic viscosity of 0.5 to 1.5 is obtained. (Dl / g) pellets are made.

  Also, the polymerized polyethylene terephthalate pellets and the polyetherimide pellets are mixed at an arbitrary ratio, supplied to a vent type twin-screw kneading extruder heated to 270 to 300 ° C., melt-extruded, and both are kneaded. . Further, if necessary, the obtained chip may be put into the twin-screw extruder again and extrusion may be repeated until they are compatible. By the kneading, polyethylene terephthalate and polyetherimide are compatible with each other, and mixed polyester pellets having a single glass transition point can be obtained.

  When particles are contained in the film, it is preferable to add a predetermined proportion of particles in the form of a slurry to ethylene glycol and disperse it, and then polymerize the ethylene glycol with terephthalic acid. When adding the particles, for example, if the water sol or alcohol sol obtained at the time of particle synthesis is added without drying, the dispersibility of the particles is good.

  As a method for adjusting the content of polyetherimide or particles, a pellet containing a high concentration of polyetherimide prepared by the above method or a PET master pellet containing a high concentration of particles is prepared, A method of adjusting each content by diluting with polyester pellets substantially free of particles when filming is effective.

  Next, these polyester, polyetherimide, and pellets containing particles, or the blended pellets were dried under reduced pressure at 110 to 190 ° C. for 3 hours or more, and then heated to a temperature of 270 to 320 ° C. It puts into an extruder, discharges in a sheet form using a T-die, this sheet-like product is brought into close contact with a cooling drum having a surface temperature of 20 to 70 ° C., and is cooled and solidified to obtain an unstretched film. The T-die has a slit interval of 0.2 mm to 5 mm, preferably 0.4 to 2 mm, and the draft ratio of the unstretched film in the present invention is preferably in the range of 1.1 to 30, more preferably It is 1.5-25, Most preferably, it is 2-20. The draft ratio here refers to the ratio of the gap between the base slit / the unstretched film. If the draft ratio is less than 1.1, the film strength may be insufficient. If the draft ratio exceeds 30, the planarity of the film may be insufficient. The draft ratio can be set by controlling the setting conditions of the extruder, the film forming speed, and the like. Moreover, it is preferable to use an electrostatic application casting method for casting. Furthermore, it is preferable to use various filters, for example, a filter made of a material such as sintered metal, porous ceramic, sand, and wire mesh, in order to remove foreign matters and denatured polymer in the molten polymer. Further, if necessary, a method of installing a static mixer and a gear pump in the polymer flow path to control the polymer extrusion rate is effective for obtaining the effects of the present invention.

  Next, this unstretched film is first stretched in the longitudinal direction. Stretching in the longitudinal direction is usually performed using a roll. The surface material of the preheating and stretching roll group is preferably a non-adhesive material such as Teflon (registered trademark) or silicon rubber. The stretching temperature in the longitudinal direction is higher than the glass transition temperature (Tg) of the polymer constituting the polyester, that is, (Tg) to (Tg + 70 ° C.), preferably (Tg + 5 ° C.) to (Tg + 60 ° C.), more preferably ( It is preferable that it is (Tg + 10 degreeC)-(Tg + 50 degreeC). Stretching in the longitudinal direction is performed in one stage or in multiple stages of two or more stages, and is stretched in a range of 2 to 8 times, preferably 2.5 to 7 times, at a stretching speed of 5,000 to 50,000% / min. It is preferable. The both ends of the uniaxially stretched film are guided to a tenter while being held by clips. After preheating in the tenter, the film is stretched in the width direction at a temperature of 80 to 160 ° C. at 2.5 to 6 times, preferably 3 to 5 times at a stretching speed of 1,000 to 30,000% / min. . Further, the biaxially stretched film may be further stretched in at least one direction. This stretched film is heat-set under tension or while relaxing in the width direction. A preferable heat setting temperature is 170 to 245 ° C, more preferably 180 to 240 ° C, and still more preferably 190 to 230 ° C. The time is preferably in the range of 0.5 to 60 seconds. The relaxation rate is preferably 1 to 10% from the viewpoint of reducing the thermal contraction rate in the width direction, more preferably 2 to 8%, and still more preferably 3 to 7%.

  Furthermore, the film is cooled and wound up to room temperature, if necessary, while being subjected to relaxation heat treatment in the longitudinal direction and the width direction, to obtain a biaxially oriented polyester film.

  Furthermore, as a method for producing the biaxially oriented polyester film of the present invention, a dimensional change due to heat, which is the fate of the biaxially oriented film, is sufficiently reduced in both the longitudinal direction and the width direction, and a film having good flatness is obtained. It is. When the film is biaxially stretched by the above-described method and heat-set, the film is preferably heat-treated at a glass transition temperature of Tg-40 ° C. to Tg + 30 ° C. for 1 hour or longer, so that the biaxially oriented polyester film of the present invention is easily obtained. . In general, in the process of heating and cooling a film, it is considered that an increase in shrinkage stress comparable to the length changed by heating is observed. When the heat shrinkage stress is large under the above-described heat treatment temperature conditions, tightening may become strong. By including the polyimide of the present invention, it is preferable from the viewpoint of flatness and curling resistance that the film has a heat shrinkage stress of 4 MPa or less, preferably 3 MPa or less.

  When the biaxially oriented polyester film of the present invention is heat-treated under the above conditions, the biaxially oriented polyester film comprising polyester and polyimide as constituent components, only the heat setting during conventional film formation due to the synergistic effect of both the polyimide content and the heat treatment. Thus, the remaining strain was removed, and a film excellent in thermal dimensional stability, flatness, oligomer resistance and curling resistance was obtained without causing a decrease in elastic modulus.

  Hereinafter, the present invention will be described based on examples and comparative examples.

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

(1) Creep deformation amount The film was sampled to a width of 2 mm, and set to TMA TM-3000 manufactured by Vacuum Riko Co., Ltd. and a heating control unit TA-1500 so that the test length was 15 mm. The temperature was increased at a rate of 100 ° C. Thereafter, a load of 10 MPa was applied to the film, and the length of the film at the load arrival point was set to L0 (μm). The length of the film when held for 30 minutes under these conditions was L30 (μm). The change over time in the amount of film expansion and contraction was measured, and the amount of creep deformation was determined from the following equation.

Creep deformation (%) = {(L30−L0) / L0} × 100
Here, creep is a phenomenon in which strain increases with time under a constant stress.

(2) Glass transition temperature Tg
Using a DSC “RDC220” made by Seiko Electronics Co., Ltd. as a differential scanning calorimeter (DSC) and a disk station “SSC / 5200” made by Seiko Electronics Co., Ltd. Then, after melting for 5 minutes at a temperature of 300 ° C., it is rapidly cooled in liquid nitrogen. The sample was heated from room temperature at a rate of temperature increase of 20 ° C./min to obtain a temperature rising DSC curve. Based on the transition from the glassy state to the rubbery state observed at this time, the straight line equidistant from the extended straight line of each baseline in the vertical axis direction and the curve of the step change part of the glass transition intersect. The temperature was the glass transition point (Tg).

(3) Polyimide content measurement in polyester film It melt | dissolves in the suitable solvent (for example, HFIP / deuterochloroform) which melt | dissolves both polyester and a polyimide, and measures the NMR spectrum of 1H nucleus. In the obtained spectrum, find the peak area intensity of absorption peculiar to polyester and polyimide (for example, absorption of aromatic protons of terephthalic acid in the case of PET, absorption of imide aromatic protons in polyimide), and the ratio and number of protons. The blend molar ratio is calculated. Further, the weight ratio is calculated from the formula amount corresponding to the unit unit of each polymer. The measurement conditions are, for example, the following conditions, but are not limited to this because they differ depending on the type of polymer.

Equipment: BRUKER DRX-500 (Bruker)
Solvent: HFIP / deuterated chloroform Observation frequency: 499.8 MHz
Standard: TMS (0ppm)
Measurement temperature: 30 ° C
Observation width: 10KHz
Data point: 64K
acquisition time: 4.952 seconds
Pulse delay time: 3.048 seconds Integration count: 256 times In addition, composition analysis may be performed by a microscopic FT-IR method (Fourier transform microscopic infrared spectroscopy) as necessary. In that case, it calculates | requires from ratio of the peak resulting from the carbonyl group of polyester, and the peak resulting from other than that substance. In order to convert the peak height ratio to the weight ratio, a calibration curve is prepared with a sample whose weight ratio is known in advance, and the polyester ratio relative to the total amount of polyester and other substances is determined. The PEI ratio is determined from this and the particle content. Moreover, you may use together an X-ray microanalyzer as needed.

(4) Thermal shrinkage rate of film The thermal shrinkage rate was measured under the following conditions in accordance with JIS C2318 (revised 9.7.20).
Sample size: width 10 mm, marked line interval 200 mm
Measurement conditions: temperature 100 ° C., treatment time 30 minutes, no-load-state heat shrinkage rate was obtained from the following equation.
Thermal contraction rate (%) = [(L0−L) / L0] × 100
L0: Mark interval before heat treatment L: Mark interval after heat treatment.

(5) Elastic modulus of film It was measured using an Instron type tensile tester according to the method defined in ASTM-D882 (revised 1997.5.10.). The measurement was performed under the following conditions.
Measuring device: Orientec Co., Ltd. film strong elongation automatic measuring device “Tensilon AMF / RTA-100”
Sample size: width 10 mm x test length 100 mm,
Tensile speed: 10 mm / min Measurement environment: temperature 23 ° C., humidity 65% RH.

(6) Surface roughness Ra, Rt
The center line average roughness Ra and the maximum roughness Rt (both in nm) were measured using a high-precision thin film level difference measuring instrument ET-10 manufactured by Kosaka Laboratory. The conditions were as follows. The measurement was performed 10 times by scanning in the film width direction, and the average value was taken.

(Measurement condition)
Stitch tip radius: 0.5 μm
Stylus load: 5mg
Measurement length: 1.0 mm
Cut-off value: 0.25mm
(7) Intrinsic Viscosity of Polyester Film The value calculated from the following equation from the solution viscosity measured at 25 ° C. in orthochlorophenol was used.

ηsp / C = [η] + K [η] ² · C
Where ηsp = (solution viscosity / solvent viscosity) −1, C is the weight of dissolved polymer per 100 ml of solvent (g / 100 ml, usually 1.2), and K is the Huggins constant (assuming 0.343) is there. The solution viscosity and solvent viscosity were measured using an Ostwald viscometer. The unit is indicated by [dl / g].

(8) Planarity A film cut to A4 size was placed on a cork board, the film was squeezed with a stick wound with a non-woven fabric, air was excluded, and the planarity was visually determined according to the following criteria.

A: No part lifted up from the cork plate is observed, and no protrusions and bumps due to the pressed marks are observed. ○: There are no more than three parts lifted up from the cork board, and there are one or less protrusions of protrusions. : There are four or more portions that have been lifted from the cork plate, or two or more protrusion-like uneven traces.

(9) Oligomer resistance A film is attached to a mold and heated in a hot air dryer at 150 ° C. for 30 minutes to forcibly precipitate a low molecular weight substance on the film surface. This surface is subjected to aluminum vapor deposition, and observed with a differential interference microscope photograph with a total magnification of 400 times. The total area s and the photograph observation area S of the precipitated low molecular weight body on the photograph are measured, and the ratio of the oligomer precipitation area to the film surface area is determined. This was observed with 50 visual fields, and the average value was taken as the oligomer precipitation index.
Oligomer index = (s / S) × 100
Evaluation was determined as follows.

◎: Oligomer index 0 to less than 0.5 ○: 〃 0.5 to less than 1.0 ×: 〃 1.0 or more
“◎” is preferable, but “○” is practically acceptable.

(10) Curling resistance A film of 20 cm in the longitudinal direction and 4 cm in the width direction was wound around a 10 mmφ SUS rod with a load of 3 MPa in the longitudinal direction of the film and left in an atmosphere of 40 ° C. and 70% RH for 48 hours. Then, after standing in a 25 ° C. and 65% RH atmosphere for 12 hours, the wound film was removed from the SUS rod, and 15 minutes later, the equivalent circular diameter (mm) of the film formed into a cylindrical shape was measured with a curl and determined as follows. did.
A: The diameter is 60 mm or more. B: The diameter is 35 mm or more and less than 60 mm. X: The diameter is less than 35 mm.

Example 1
Calcium acetate was added as a transesterification reaction catalyst to a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, and heated to increase the temperature to distill methanol to conduct transesterification. Subsequently, antimony trioxide as a polymerization catalyst and phosphoric acid as a heat stabilizer were added to the transesterification reaction product and transferred to a polycondensation reaction tank. Next, the inside of the reaction system is gradually reduced in pressure while being heated, and the inside is stirred at 290 ° C. under reduced pressure to polymerize while distilling methanol, and the intrinsic viscosity is 0.65 and the intrinsic viscosity is 0.85 by solid phase polymerization. Polyethylene terephthalate (pellet A) was prepared.

Next, polyethylene terephthalate (50% by weight) having an intrinsic viscosity of 0.85 and polyetherimide pellets ("Ultem 1010" (Registered trademark of General Electric)) (50% by weight) were bent-type biaxially heated to 280 ° C. The mixture was supplied to a kneading extruder and melt-extruded at a shear rate of 100 sec ⁻¹ to obtain pellets containing 50% by weight of polyetherimide (pellet B).

  Further, 2 wt% of calcium carbonate particles having an average particle size of 0.5 μm were added to polyethylene terephthalate during polymerization to obtain a polymerized pellet (pellet C).

  Pellets prepared by mixing 70%, 20%, and 10% by weight of pellets A, B, and C, respectively, were vacuum dried at 180 ° C. for 3 hours, and then melt-extruded with an ordinary 280 ° C. extruder. The film was wound on a casting drum having a surface temperature of 25 ° C. by using an electric application cast method, cooled and solidified, and drawn at a draft ratio (ratio of gap between base slit / unstretched film) of 10 to prepare an unstretched film.

  Next, this unstretched film was stretched 3.4 times at a temperature of 103 ° C. in a longitudinal direction by a roll-type stretching machine, and then stretched 3.6 times at a temperature of 110 ° C. in a width direction using a tenter. After heat treatment at 0 ° C. for 8 seconds, 4% relaxation treatment was performed in the width direction, and after cooling to room temperature, the film edge was removed, and a biaxially oriented polyester film having a thickness of 100 μm was wound with a tension of 4 MPa. The biaxially oriented polyester film thus obtained was heat-treated at 80 ° C. for 48 hours with a hot air drier and allowed to stand at room temperature for 24 hours to obtain the biaxially oriented polyester film of the present invention. The amount of creep deformation at 100 ° C. of the biaxially oriented polyester film before heat treatment was not as good as 0.13%, but the biaxially oriented polyester film of Example 1 heat treated at 80 ° C. for 48 hours was made of glass. The transition temperature is 90 ° C., the intrinsic viscosity is 0.62 (dl / g), the thermal shrinkage rate and the creep deformation amount are as shown in Table 1, and the thermal dimensional stability is excellent, and the oligomer resistance, flatness, and curling resistance. All the characteristics of were good.

(Example 2)
Pellets mixed with 20% by weight, 70% by weight, and 10% by weight of pellets A, B, and C, respectively, were extruded in the same manner as in Examples to produce unstretched films.

  Subsequently, this unstretched film was stretched 3.2 times in the longitudinal direction at a temperature of 115 ° C. by a roll stretching machine, and then stretched 3.3 times at a temperature of 120 ° C. in the width direction using a tenter. After heat treatment at 0 ° C. for 8 seconds, 6% relaxation treatment was performed in the width direction to obtain a biaxially oriented polyester film having a thickness of 50 μm. This biaxially oriented polyester film has a glass transition temperature of 110 ° C. and an intrinsic viscosity of 0.65 (dl / g). Table 1 shows the properties of the obtained film.

(Examples 3 and 4, Comparative Example 1)
Except for changing the mixing amount of pellets A and B and the longitudinal stretching temperature of Example 4 to 110 ° C., biaxial stretching was performed in the same manner as in Example 1, followed by heat setting, and the glass transition temperature of Example 3 A biaxially oriented polyester film having a Tg of 85 ° C., a Tg of Example 4 of 98 ° C., and a Tg of Comparative Example 1 of 78 ° C. was formed. Thereafter, heat treatment was performed under the conditions shown in Table 1 to prepare a biaxially oriented polyester film having a thickness of 100 μm. In Examples 3 and 4, films excellent in flatness, oligomer resistance and curling resistance were obtained. In Comparative Example 1, since the pellet B was not used, the film effect of the present invention was not obtained.

(Example 5)
The biaxially stretched film having a Tg of 98 ° C. wound up in Example 4 was heat-treated at 115 ° C. for 8 hours and left at room temperature for 24 hours to obtain a biaxially oriented polyester film. Although the film flatness was slightly inferior to that of Example 4, there was no problem in practical use, and the effect of the film of the present invention was obtained.

(Example 6)
Pellet A with an intrinsic viscosity of 0.85 and pellets B and C mixed at a ratio of 76%, 14%, and 10% by weight are vacuum dried at 180 ° C for 3 hours, then melt extruded to create an unstretched film Then, the film was stretched 3.2 times at a temperature of 103 ° C. in the longitudinal direction, then stretched 3.6 times at a temperature of 110 ° C. in the width direction using a tenter, heat treated at 210 ° C. for 8 seconds, and then 6 times in the width direction. % Relaxation treatment and cooling to room temperature, the film edge was removed, and a 100 μm thick biaxially oriented polyester film was wound up. The biaxially oriented film polyester thus obtained was heat-treated at 60 ° C. for 72 hours with a hot air drier and allowed to stand at room temperature for 24 hours to obtain the biaxially oriented polyester film of the present invention. The glass transition temperature of the biaxially oriented polyester film before heat treatment was 88 ° C., and the intrinsic viscosity was 0.71 (dl / g). Although the curling resistance was slightly inferior, there was no problem in practical use, and the film characteristics as shown in Table 1 were sufficient.

(Comparative Example 2)
The biaxially stretched film having a Tg of 88 ° C. wound up in Example 6 was heat treated at 40 ° C. for 72 hours to obtain a film. The heat shrinkage rate was 0.25%, and the creep deformation amount was 0.17%. As shown in Table 1, sufficient products were not obtained.

(Comparative Example 3)
The biaxially stretched film having a Tg of 90 ° C. wound up in Example 1 was heat-treated at 130 ° C. for 6 hours to obtain a film. The amount of creep deformation was 0.16%, and as shown in Table 1, a sufficient amount was not obtained.

(Comparative Example 4)
85 parts by weight of polyethylene-2,6-naphthalate (PEN) pellets having an intrinsic viscosity of 0.60, 10 parts by weight of PEN pellets having an intrinsic viscosity of 0.60 containing 2% by weight of calcium carbonate particles having an average particle diameter of 0.5 μm, and A mixed material of 5 parts by weight of a pellet of polyetherimide (GE Plastics Ultem 1010) was dried under reduced pressure at 150 ° C. for 1 hour and then at 180 ° C. for 2 hours, and then supplied to an extruder heated to 300 ° C. The film was closely cooled and solidified while applying an electrostatic charge to a cast drum having a surface temperature of 25 ° C. to produce an unstretched film. This unstretched film was stretched 4.3 times in the longitudinal direction at a temperature of 140 ° C. using a roll stretching machine, and further stretched 4.5 times in the width direction at a temperature of 145 ° C. using a tenter. After heat treatment at a temperature of 225 ° C. for 2 seconds under a long length, 5% relaxation treatment was performed in the width direction, and after cooling to room temperature, the film edge was removed, and a 100 μm thick biaxially oriented polyester film was wound with a tension of 4 MPa. I took it. The biaxially oriented film thus obtained was subjected to heat treatment at 80 ° C. for 48 hours with a hot air dryer and left at room temperature for 24 hours to obtain a biaxially oriented PEN film. As shown in Table 1, the film was inferior in flatness and curling resistance.

  The film according to the present invention is a high-quality film that has low heat yield and creep deformation, excellent flatness and oligomer resistance, and is used for various industrial materials that require curling resistance and thermal dimensional stability, such as winding. It can be widely used in storage-type projection screens, electronic blackboard films, circuit boards, magnetic recording media, process paper / release materials, plate-making printing materials, optical / display materials, etc., and its industrial value is extremely high.

Claims (4)

Polyester and polyimide containing an ethylene terephthalate unit as a structural unit are included as structural components, the creep deformation at 100 ° C. is less than 0.15% in both the longitudinal direction and the width direction, and the longitudinal direction and the width direction of the film A biaxially oriented polyester film having an absolute value of heat shrinkage at 100 ° C. of 0 to 0.2% for any of the above. The biaxially oriented polyester film according to claim 1, wherein the polyimide is polyetherimide, and the content of the polyetherimide in the film is 5 to 30% by weight. The intrinsic viscosity of the film is 0.5 to 0.8 (dl / g), and the relationship between the thermal shrinkage rate S (%) at 100 ° C. in the longitudinal direction of the film and the elastic modulus Y (GPa) in the longitudinal direction of the film is The biaxially oriented polyester film according to claim 1 or 2, satisfying the following formula.
0.04Y-S ≧ 0.07 A biaxially oriented film containing an ethylene terephthalate unit as a constituent unit and a polyester and polyimide as constituent components, with the glass transition temperature of this biaxially oriented film as Tg, (Tg-40) ° C. to (Tg + 30) ° C. for 1 hour The manufacturing method of the biaxially-oriented polyester film in any one of Claims 1-3 heat-processed above.