JP2018100339A - Polyester composition and biaxially stretched polyester film of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester composition which has a high refractive index, is excellent in workability and can be preferably used for optical application, and a biaxially stretched polyester film of the same.SOLUTION: There are provided a polyester composition which contains 95 mol% of a 2,6-naphthalenedicarboxylic acid component with respect to the total dicarboxylic acid component constituting polyester, contains 5-20 mol% of p-xylene glycol and 80-95 mol% of ethylene glycol with respect to the total diol component, has crystal melting peak of 10 J/g or more in a temperature range of 210-260°C in 1st.Run as heat characteristics by differential scan calorimetry, has a crystal melting heat quantity of less than 10 J/g in 2nd. Run, and has a glass transition temperature of 90°C or higher; and a biaxially stretched polyester film of the same.SELECTED DRAWING: None

Description

  The present invention relates to a polyester composition having excellent processability and a high refractive index equivalent to polyethylene naphthalate and a biaxially stretched polyester film comprising the same.

  Polyethylene naphthalate (hereinafter PEN), which is an aromatic polyester, has excellent mechanical properties, heat resistance, and high refractive index, and is used for optical film applications and the like.

  However, films made of PEN are generally brittle, and in some applications, mechanical properties are improved by adding a softening agent and introducing a copolymer component.

  In general, copolymerized polyethylene naphthalate has reduced crystallinity and orientation in proportion to the amount of copolymerization, and can improve brittleness. Problems may occur. Furthermore, when it is set as a laminated film, interlayer adhesiveness is also important.

  Patent Document 1 discloses a technique of making amorphous by rapidly cooling a crystalline PEN resin having a high refractive index. However, the crystallinity of the PEN resin remains as it is, and crystallization progresses when biaxially stretched, resulting in workability, that is, crackability when formed as a biaxially stretched film, delamination when formed as a laminated film, etc. There was a problem.

JP 2010-1998A

  The object of the present invention is to eliminate these conventional drawbacks, and to provide a polyester composition excellent in processability and having a high refractive index equivalent to PEN and its biaxially stretched film.

  In order to solve the above-mentioned problems, the present inventors have studied, containing 95 mol% or more of 2,6-naphthalenedicarboxylic acid component with respect to all dicarboxylic acid components constituting the polyester, and with respect to all diol components. It has been found that this is achieved by a polyester composition containing xylene glycol (hereinafter referred to as PXG) in a range of 5 mol% to 20 mol% and ethylene glycol (hereinafter referred to as EG) in a range of 80 mol% to 95 mol%.

  ADVANTAGE OF THE INVENTION According to this invention, the polyester composition which is excellent in a high refractive index and workability, and can be used conveniently for an optical use, and its biaxially stretched film can be provided.

  The polyester composition in the present invention contains 95 mol% or more of 2,6-naphthalenedicarboxylic acid component with respect to all dicarboxylic acid components constituting the polyester, and 5 mol% or more and 20 mol% of PXG with respect to all diol components. Hereinafter, EG is contained in the range of 80 mol% or more and 95 mol% or less.

As the dicarboxylic acid component constituting the polyester composition in the present invention, it is necessary to contain 2,6-naphthalenedicarboxylic acid component in an amount of 95 mol% or more based on the total dicarboxylic acid component from the viewpoint of refractive index, and further 100 mol. % Is preferable.
Moreover, you may copolymerize a conventionally well-known dicarboxylic acid component in the range which does not prevent the effect of this invention, and it is required as copolymerization amount to be less than 5 mol% with respect to all the dicarboxylic acid components. Specific examples of the dicarboxylic acid component include a terephthalic acid component, an isophthalic acid component, a phthalic acid component, and a cyclohexanedicarboxylic acid component, and two or more kinds may be used in combination.

  The diol component constituting the polyester composition in the present invention contains PXG in the range of 5 mol% to 20 mol% and EG in the range of 80 mol% to 95 mol% with respect to all diol components. There is a need to. From the viewpoint of crystal control and embrittlement suppression, PXG is preferably 5 mol% or more and 15 mol% or less, and more preferably 10 mol% or more and 15 mol% or less.

  In addition, a conventionally known diol component may be copolymerized as long as the effect of the present invention is not hindered, and examples thereof include propylene glycol, butylene glycol, neopentyl glycol, spiro glycol and the like, and two or more of them can be used in combination. May be.

  The polyester composition in the present invention is preferably amorphous. In the present invention, the term “amorphous” means 2nd. In a differential scanning calorimetry using a differential scanning calorimeter (manufactured by T.A. Instruments Japan: DSC-Q2000). It means that the heat of crystal fusion in Run is less than 10 J / g. Specifically, using 5 mg of sample, the temperature was raised from 25 ° C. to 300 ° C. at 16 ° C./min as the first temperature rise, held at 300 ° C. for 5 minutes, and then the sample was heated to 50 ° C. Allow to cool above. Next, as a second temperature increase, the temperature is increased to 300 ° C. at 16 ° C./min and held at 300 ° C. for 5 minutes. The first temperature increase is 1st. Run, the second temperature increase is 2nd. Run, 2nd. A polyester composition having a heat of crystal melting in Run of less than 10 J / g is made amorphous. In order to obtain an amorphous composition in the present invention, the 2,6-naphthalenedicarboxylic acid component is preferably contained in an amount of 95 mol% or more with respect to the total dicarboxylic acid component, and with respect to the total diol component. It is preferable that PXG is contained in the range of 5 mol% or more and 20 mol% or less, and the remaining diol component is EG.

  The polyester composition in the present invention can be obtained by performing a conventionally known transesterification reaction or esterification reaction and then performing a polycondensation reaction. For example, in a transesterification reaction, a metal compound such as a magnesium compound, a potassium compound, a manganese compound, a lithium compound, a calcium compound, or a sodium compound can be used as a catalyst, and a manganese compound is used from the viewpoint of heat resistance of the polyester composition. Furthermore, it is preferable to use manganese acetate from the viewpoint of transesterification reactivity and optical characteristics.

  In the present invention, phosphorus compounds can be used as coloring inhibitors and heat stabilizers. For example, specific phosphorus compounds include phosphoric acid, trimethyl phosphate, triethyl phosphate, phosphoric acid compounds such as triphenyl phosphate, phosphonic acid compounds such as methylphosphonic acid and ethylphosphonic acid, sodium dihydrogen phosphate, Examples thereof include alkali metal phosphate compounds such as lithium phosphate, phosphorus antioxidants, etc. Among them, it is particularly preferable to use phosphoric acid or sodium dihydrogen phosphate.

  The metal element and phosphorus element contained in the polyester composition of the present invention preferably have a molar ratio (M / P) between the metal element M and the phosphorus element P of 0.50 or more and 1.50 or less from the viewpoint of heat resistance. Furthermore, it is preferable to set it as 0.70 or more and 1.20 or less from a heat resistant point.

  A conventionally known catalyst compound can be used for the polymerization reaction in the present invention. For example, as a polymerization catalyst, antimony compounds such as antimony trioxide, antimony pentoxide, antimony acetate, and antimony glycoloxide, germanium compounds such as germanium dioxide, germanium tetrachloride, and germanium tetraethoxide, the substituent is an alkoxy group, a phenoxy group, A titanium compound that is at least one of an acylate group, an amino group, and a hydroxyl group can be used. Of these, antimony trioxide, germanium dioxide, and tetrabutoxy titanium are preferable from the viewpoint of polymerization reactivity.

  In addition, a conventionally known compound may be used in combination for the purpose of imparting functions such as antioxidation, antistatic, and ultraviolet absorption, as long as the effects of the present invention are not hindered.

The polyester composition in the present invention is preferably a biaxially stretched film from the viewpoints of oriented crystallinity, refractive index, and mechanical strength.
From the viewpoint of workability, the biaxially stretched film of the present invention preferably uses a composition that does not crystallize by heating, that is, is amorphous in the present invention, but is oriented and crystallized by stretching stress. Specifically, as a thermal characteristic by differential scanning calorimetry from the point of workability, 1st. Run has a heat of crystal melting of 10 J / g or more in a temperature range of 210 ° C. to 260 ° C. and 2 nd. The heat of crystal fusion at Run needs to be less than 10 J / g.
Such a biaxially stretched film is preferably a laminated polyester film from the viewpoint of self-recoverability that can be formed with good processability even when a recovery composition such as a film end face is used for the intermediate layer. It can also be. Furthermore, when setting it as a laminated polyester film, it is preferable to make the layer which consists of a polyester composition of this invention into an outermost layer from the point of oriented crystallinity.

  In such a laminated polyester film, as a polyester composition laminated on the polyester composition of the present invention, ethylene terephthalate units and / or ethylene naphthalate units are 30 mol% or more and 70 mol% or less of the polyester constituents from the viewpoint of processability. The glass transition temperature is preferably 90 ° C. or higher. Moreover, you may copolymerize a conventionally well-known dicarboxylic acid component in the range which does not prevent the effect of this invention. Specific examples of the dicarboxylic acid component include an isophthalic acid component, a phthalic acid component, and a cyclohexanedicarboxylic acid component, and two or more kinds may be used in combination. However, in order to make the polyester composition to be laminated have a glass transition point of 90 ° C. or higher, it is preferable to use a polyester composition composed of only ethylene terephthalate units and ethylene naphthalate units.

  The biaxially stretched polyester film of the present invention can be produced by a conventionally known method. For example, there are stretching methods such as sequential biaxial stretching and simultaneous biaxial stretching, and further, a laminating method by coextrusion using a plurality of extruders and the like.

  Next, although the manufacturing example of the polyester composition of this invention and its biaxially stretched polyester film is demonstrated in detail, it is not limited to this.

  First, dimethyl 2,6-naphthalenedicarboxylate, paraxylene glycol, ethylene glycol, antimony trioxide, and manganese acetate tetrahydrate are charged and melted at 180 ° C. in a reaction vessel in which a transesterification reaction is performed. At this time, the amount of para-xylene glycol charged must be 5 mol% or more and 20 mol% or less of the total diol component, and the amount of ethylene glycol charged is 80 mol% or more and 90 mol% relative to the total diol component. The total glycol component amount is 1.7 to 2.3 mol times the total dicarboxylic acid, and the reactivity is improved. The addition amount of antimony trioxide is preferably 50 ppm or more and 300 ppm or less as an antimony element from the viewpoint of polymerization reactivity. Furthermore, the addition amount of manganese acetate tetrahydrate is preferably 50 ppm or more and 250 ppm or less as a manganese element in terms of transesterification reactivity.

  After completion of the addition of manganese acetate tetrahydrate, methanol is distilled while gradually raising the temperature of the reaction contents to 235 ° C. while stirring. After a predetermined amount of methanol flows out, phosphoric acid and sodium dihydrogen phosphate dihydrate are added as a phosphorus compound, and excess ethylene glycol is distilled off to complete the transesterification reaction. In this case, the phosphorus compound is preferably added so that the phosphorus element content of the polyester composition is 40 ppm or more and 200 ppm or less from the viewpoint of preventing coloring and improving heat resistance.

  After completion of the transesterification reaction, the pressure is gradually reduced to 260 Torr at 235 ° C. over 15 minutes, and after distilling off excess ethylene glycol, the reaction mixture is transferred to a reaction vessel in which a polymerization reaction is performed.

  After shifting to a reaction tank in which a polymerization reaction is performed, the internal pressure of the apparatus is reduced from normal pressure to 1.0 Torr or less while the internal temperature is increased to 290 ° C. As the polymerization reaction proceeds, the melt viscosity of the reaction product rises, and when the target melt viscosity is reached, the reaction is terminated. The polyester composition is discharged from the polymerization reaction tank into a strand, cooled with water, and chipped with a cutter.

  The obtained polyester composition is dried under reduced pressure at 100 ° C. for 8 hours or more in a vacuum dryer, and after sufficiently removing moisture, it is melt-extruded into a sheet form from a T-die at 280 ° C. The molten sheet is brought into close contact with a roll cooled to a surface temperature of 10 ° C. or higher and 40 ° C. or lower and solidified by cooling to obtain an unstretched sheet. As a method for bringing the molten sheet into close contact with the roll, there are methods such as an air knife and an electrostatic application method. For example, a method of applying a static electricity using a wire electrode is preferable.

  Next, the unstretched sheet is heated to a temperature of −30 ° C. or higher and + 50 ° C. or lower with respect to the glass transition temperature of the polyester composition of the present invention, and the stretching ratio is 3.0 times or more in the longitudinal direction between rolls having different rotation speeds. Stretch with. Next, the film is stretched at a stretching ratio of 3.0 times or more in the width direction at a temperature of + 5 ° C. or more and + 50 ° C. or less with respect to the glass transition temperature of the polyester composition of the present invention by a tenter type transverse stretching machine, and directly in the tenter. A biaxially stretched polyester film can be obtained by heat-treating at 100 ° C. or higher and 220 ° C. or lower for 1 second or longer and 60 seconds or shorter while relaxing about 4% in the width direction.

  Similarly, when manufacturing a laminated polyester film, it can be set as a laminated polyester film by co-extrusion using two or more extruders. By applying a vent type twin screw extruder to the extruder at this time, it is possible to omit the polyester drying step. Furthermore, when it is set as the laminated polyester film of 101 layers or more, a static mixer and a feed block are applied, and it joins so that the layer A consisting of the polyester composition of this invention and the layer B consisting of the other polyester composition may be laminated | stacked alternately. It is preferable that both surface layer portions become layer A.

  The polyester composition thus obtained has a high refractive index equivalent to PEN, and the biaxially stretched polyester film and the laminated polyester film are excellent in processability, and thus are suitable for optical film applications.

The present invention will be described more specifically with reference to the following examples.
In addition, the measuring method of a physical property and the evaluation method of an effect were performed in accordance with the following method.

(1) Intrinsic viscosity Intrinsic viscosity was measured at 25 ° C using orthochlorophenol as a solvent.

(2) Color tone of polyester The polyester chip was measured as a Hunter value (L, b value) using a color difference meter (SM color computer model SM-T45 manufactured by Suga Test Instruments Co., Ltd.).

(3) Thermal properties of polyester (glass transition temperature, crystal melting temperature, crystal melting heat)
Using a differential scanning calorimeter (manufactured by TA Instruments Japan: DSC-Q2000), 5 mg of the sample is heated from room temperature to 300 ° C. at 16 ° C./min, and held at 300 ° C. for 5 minutes. The process is 1st. Run, the sample was allowed to cool to 50 ° C. on a metal plate, heated again to 300 ° C. at 16 ° C./min, and held for 5 minutes. A differential scanning calorimetry chart was obtained as Run. Using the differential scanning calorimetry chart, glass transition temperature (Tg), crystal melting temperature (Tm), and crystal melting heat (ΔHm) were measured using analysis software (manufactured by TI Instruments Japan: Universal Analysis 2000). .

(4) Refractive index of polyester composition An unstretched sheet having a thickness of 100 µm is obtained by melt-extruding the polyester composition. Subsequently, the refractive index was measured with an “Abbe refractometer NAR-4T” manufactured by Atago Co., Ltd. under a temperature condition of 23 ° C. using sodium D line as a light source. In the present invention, the refractive index is 1.600 or higher.

(5) Evaluation of workability of polyester film Using a test piece punching machine manufactured by Kobunshi Keiki Co., Ltd., the film is punched into a No. 5 type dumbbell shape described in JIS K-6251. The number of sheets M, in which end face cracks or peeling occurs in the case of a laminated film when punching one film at a time, is counted, and the workability is evaluated.
0 ≦ M ≦ 2: Workability A
3 ≦ M ≦ 5: Workability B
6 ≦ M ≦ 8: Workability C
9 ≦ M: Workability D
A is the best and D is the worst, and in the present invention, up to workability B is acceptable.

(6) Quantification of phosphorus element and metal element in polyester composition Using a fluorescent X-ray apparatus (model number MESA-500W) manufactured by HORIBA, Ltd., the intensity of the fluorescent X-ray of the polymer was measured. This value was converted to metal content using a calibration curve prepared in advance with a sample with known content.

Example 1
96.3 parts by weight of dimethyl 2,6-naphthalenedicarboxylate (hereinafter NDCM), 8.2 parts by weight of paraxylene glycol (hereinafter PXG), 41.6 parts by weight of ethylene glycol (hereinafter EG), 0.01% of antimony trioxide Parts and 0.055 parts by weight of manganese acetate tetrahydrate were weighed and charged in a reaction vessel for transesterification, and the contents were dissolved at 180 ° C. While stirring the dissolved contents, the temperature was gradually raised to 235 ° C. to distill methanol. After a predetermined amount of methanol flows out, 0.022 part by weight of phosphoric acid, which is a phosphorus compound, and 0.026 part by weight of sodium dihydrogen phosphate, which is an alkali metal phosphate compound, are added, and excess ethylene glycol is added. Was distilled to complete the transesterification reaction. In 15 minutes after completion of the transesterification reaction, the pressure was gradually reduced to 260 Torr, and after surplus EG was distilled off, the reaction vessel was transferred to a polymerization reactor.

  In a reaction vessel in which the polymerization was carried out, the temperature was gradually raised to 290 ° C. while stirring at 240 ° C., and the polymerization was carried out while distilling ethylene glycol. The final pressure was 0.1 Torr. When the target melt viscosity was reached, the polymerization reaction tank was returned to normal pressure with nitrogen gas, and the polyester composition was discharged into a water tank in the form of a strand. The polyester gut cooled in the water tank was cut with a cutter to obtain a polyester chip.

  The obtained polyester composition has an intrinsic viscosity of 0.60 and a refractive index of 1.617, a metal element amount M of 2.245 mol / t, a phosphorus element amount P of 2.86 mol / t, and M / P is It was 0.78. Further, when the thermal characteristics were measured using a differential scanning calorimeter (hereinafter DSC), the glass transition temperature (hereinafter Tg) was 117.3 ° C., but 1st. Run and 2nd. Neither Run nor the crystal melting temperature (hereinafter referred to as Tm) or the heat of crystal melting (hereinafter referred to as ΔHm) was detected, confirming that it was an amorphous composition.

  Subsequently, the obtained polyester composition was dried in a vacuum dryer at 100 ° C. for 8 hours, sufficiently removed water, melted at 280 ° C., melted and extruded from a T-die, and a surface temperature of 25 ° C. Then, the sheet was discharged in a sheet form on a roll that had been cooled. At that time, an unstretched film was obtained by applying static electricity using a wire-like electrode and contacting the cooling roll to solidify by cooling. Next, using a roll-type stretching machine, the preheating temperature is 115 ° C., the stretching temperature is 120 ° C., the unstretched sheet is stretched 3.0 times in the longitudinal direction, and immediately cooled with a roll cooled to a surface temperature of 25 ° C. . Next, the preheating temperature was set to 100 ° C. and the stretching temperature to 150 ° C. with a tenter type horizontal stretching machine, and the film was stretched 3.0 times in the width direction. The film was heat-fixed for 2 seconds to obtain a biaxially stretched polyester film having a film thickness of 50 μm.

  When the thermal characteristics of the obtained biaxially stretched polyester film were measured using DSC, 1st. In Run, Tm was confirmed between 210 ° C. and 260 ° C., and ΔHm was 10 J / g or more, but 2nd. In Run, Tg of 117.3 ° C. and Tm were not detected, so that orientation crystallization by stretching was confirmed. Moreover, when the workability was evaluated using a test piece punching machine, it was confirmed that there was no crack on the end face and the workability was excellent.

Examples 2-4, Comparative Examples 1-3
A polyester composition and a biaxially stretched film were obtained in the same manner as in Example 1 except that the copolymerization ratio of EG and PXG was changed.

  About Example 2, as a result of obtaining the polyester composition made into PXG10 mol% and EG90 mol%, it was confirmed that it becomes amorphous. In addition, as a result of forming the obtained polyester composition and obtaining a biaxially stretched polyester film, orientation crystallization is caused by stretching stress, but it is a film that is thermally amorphous and excellent in workability. It was confirmed that there was.

  About Example 3, as a result of obtaining the polyester composition made into PXG20 mol% and EG80 mol%, it was confirmed that it is amorphous. In addition, as a result of forming the obtained polyester composition and obtaining a biaxially stretched polyester film, orientation crystallization is caused by stretching stress, but it is a film that is thermally amorphous and excellent in workability. It was confirmed that there was.

  About Example 4, as a result of obtaining the polyester composition made into PXG5 mol% and EG95 mol%, it was confirmed that it is amorphous. In addition, as a result of forming the obtained polyester composition and obtaining a biaxially stretched polyester film, orientation crystallization is caused by stretching stress, but it is a film that is thermally amorphous and excellent in workability. It was confirmed that there was.

  As for Comparative Example 1, as a result of obtaining a polyester composition having PXG of 25 mol% and EG of 75 mol%, it was confirmed to be amorphous. Moreover, when the obtained polyester composition was formed into a film, it was not able to be made into a biaxially stretched film because it adhered to the roll during longitudinal stretching.

  Comparative Example 2 was crystalline as a result of obtaining a polyethylene naphthalate composition. Moreover, as a result of film-forming the obtained polyester composition and obtaining the biaxially stretched polyester film, 2nd. Tm and ΔHm were confirmed in Run, which was crystalline, and seven cracks were confirmed in the punching test.

About the comparative example 3, as a result of obtaining the polyester composition which made PXG100 mol%, it was crystalline. Moreover, as a result of film-forming the obtained polyester composition and obtaining the biaxially stretched polyester film, 2nd. Tm and ΔHm were confirmed in Run, which was crystalline, and ten cracks were confirmed in the punching test.
(Synthesis of other polyester compositions to be laminated)
Reference example 1
Weigh 65.6 parts by weight of dimethyl terephthalate (hereinafter referred to as DMT), 35.4 parts by weight of NDCM, 60.0 parts by weight of EG, and 0.01 parts by weight of antimony trioxide. And dissolved.

  While adding 0.055 parts by weight of manganese acetate while stirring the dissolved contents, the temperature was gradually raised to 235 ° C. to distill methanol. After a predetermined amount of methanol has flowed out, 0.022 parts by weight of phosphoric acid, which is a phosphorus compound, and 0.026 parts by weight of sodium dihydrogen phosphate, which is an alkali metal phosphate, are added to distill excess ethylene glycol. The transesterification reaction was terminated.

  In 15 minutes after completion of the transesterification reaction, the pressure was gradually reduced to 260 Torr, the initial polymerization was carried out, and then the reaction vessel for polymerization was transferred.

  In a reaction vessel in which the polymerization was carried out, the temperature was gradually raised to 290 ° C. while stirring at 240 ° C., and the polymerization was carried out while distilling ethylene glycol. The final pressure was 0.1 Torr.

  When the target melt viscosity was reached, the polymerization reaction tank was returned to normal pressure with nitrogen gas, and the polymer on the gut was discharged into the water tank. The polyester gut cooled in the water tank was cut with a cutter to obtain a polyester chip.

  The obtained polyester composition had an intrinsic viscosity of 0.60, and when thermal characteristics were measured using DSC, Tg was 112.4 ° C., but Tm and ΔHm were not detected.

Reference example 2
A polyester composition was obtained in the same manner as in Reference Example 1 except that DMT was 30 mol% and NDCM was 70 mol%. The obtained polyester composition had an intrinsic viscosity of 0.60 and Tg of 95.3 ° C., and Tm and ΔHm were not detected.

Reference example 3
A polyethylene terephthalate composition was obtained in the same manner as in Reference Example 1 except that DMT was 100 mol%. The obtained polyethylene terephthalate composition had an intrinsic viscosity of 0.60, Tg of 80.7 ° C., and Tm of 252.7 ° C.

Example 5
The polyester composition of Example 1 and the reference example 1 polyester composition were each melted at 280 ° C. by two twin-screw extruders with vents, and then in a 401-layer feed block through a gear pump and a filter. The layer A composed of the polyester composition of Example 1 and the layer B composed of the polyester composition of Reference Example 1 are joined together alternately. In addition, both surface layer parts are made to become the polyester composition of Example 1 which has the orientation crystallinity by extending | stretching. The laminate composed of 401 layers thus obtained is melt-extruded from a T-die and discharged in a sheet form onto a roll cooled to a surface temperature of 25 ° C. At that time, an unstretched film is obtained by applying static electricity and bringing it into close contact with a cooling roll and solidifying by cooling. Next, the film is stretched 3.0 times in the longitudinal direction at a stretching temperature of 120 ° C. Next, it is stretched at a stretching temperature of 150 ° C. at a stretching ratio of 3.0 times in the width direction, and heat-fixed for 5 seconds at 200 ° C. while relaxing 4% in the width direction in the tenter, and a laminated polyester having a film thickness of 50 μm. A film was obtained.

  When the thermal characteristics of the obtained laminated polyester film were measured using DSC, 1st. Run: Tm 234.3 ° C., ΔHm 29 J / g, 2nd. In Run, Tm was not detected, and orientational crystallization was caused by stretching stress, but it was confirmed that the run was a non-crystalline laminated polyester film. Moreover, when the workability was evaluated using a test piece punching machine, it was confirmed that the end face was not cracked or peeled off and was excellent in workability.

Example 6
As a result of obtaining a laminated polyester film in the same manner as in Example 9 except that the polyester composition obtained in Reference Example 2 was used for layer B, orientation crystallization was caused by stretching stress. It was confirmed that the laminated polyester film was amorphous and excellent in processability.

Comparative Example 4
A laminated polyester film was obtained in the same manner as in Example 9 except that the polyester composition obtained in Reference Example 3 was used for Layer B. As a result, 2nd. Since Tm and ΔHm were confirmed in Run, it was crystalline. In the punching test, eight cracks were confirmed.

Claims (6)

  The 2,6-naphthalenedicarboxylic acid component is contained in an amount of 95 mol% or more based on the total dicarboxylic acid component constituting the polyester, the paraxylene glycol is contained in an amount of 5 mol% or more and 20 mol% or less, and ethylene glycol is 80% based on the total diol component. A polyester composition contained in a range of from mol% to 95 mol%. The polyester composition according to claim 1, which is amorphous.   95 mol% or more of 2,6-naphthalenedicarboxylic acid component is contained with respect to all dicarboxylic acid components constituting the polyester, paraxylene glycol is contained with 5 mol% or more and 20 mol% or less with respect to all diol components, and ethylene glycol is 80 It is a polyester film contained in a range of from mol% to 95 mol%, and its thermal characteristics by differential scanning calorimetry are 1st. Run has a crystal melting peak of 10 J / g or more in the temperature range of 210 ° C. or more and 260 ° C. or less, and 2nd. A biaxially stretched polyester film in which the heat of crystal melting of Run is less than 10 J / g.   A laminated polyester film obtained by laminating one or more polyester film layers according to claim 3.   The laminated polyester film which consists of a polyester film layer whose ethylene terephthalate unit and / or an ethylene naphthalate unit are 30% or more and 70% or less of a polyester structural component, and the polyester film layer of Claim 3.   The laminated polyester film according to claim 5, wherein the glass transition temperature of the polyester film layer in which the ethylene terephthalate unit and / or the ethylene naphthalate unit is 30% to 70% of the polyester constituent is 90 ° C or higher.