WO2019103370A1

WO2019103370A1 - Polyester resin composition and biaxially oriented polyester film comprising same

Info

Publication number: WO2019103370A1
Application number: PCT/KR2018/013639
Authority: WO
Inventors: 황신영; 김태영; 백지원; 박준용; 이부연; 김도균
Original assignee: 에스케이케미칼주식회사
Priority date: 2017-11-22
Filing date: 2018-11-09
Publication date: 2019-05-31
Also published as: JP2021504512A; DE112018005965T5; KR20190059216A; CN111433262A

Abstract

The present invention relates to a polyester resin composition and a polyester film comprising the same, the polyester resin composition comprising a polyester resin comprising a polycondensate of a dicarboxylic acid component containing terephthalic acid and isophthalic acid, and a diol component containing cyclohexanedimethanol.

Description

2019/103370 1 »(: 1 ^ {2018/013639

【Specification】

Title of the Invention

A polyester resin composition and an axially stretched polyester film containing the same

TECHNICAL FIELD

Cross-reference with related application (s)

The present application claims the benefit of priority based on Korean Patent Application No. 10-2017- 0156747, filed on November 22, 2017, the entire contents of which are incorporated herein by reference.

The present invention relates to a polyester resin composition and a biaxially stretched polyester film containing the same.

TECHNICAL BACKGROUND OF THE INVENTION

In recent years, metal materials have been replaced with plastic materials in order to reduce the weight of automobiles. However, plastic materials used for these automobile parts are required to have high heat resistance and slim to reduce their volume. Among these parts of the automobile parts, the flexible flat cable (FFC) among the parts of the electric device is the connection cable used to connect between the PCB (Priced Board) or the PBA In addition, since the FFC is flexible and can be folded, it is widely used as a connection connector inside an electronic device such as a mobile phone.

Generally, FFCs are produced by using PET (polyethylene terephthalate) stretched film. However, since PET stretched film has a heat resistance of about 130 ^° C, FFC using PET stretched film is a major component of automotive powertrain and engine control parts . &Lt; / RTI > Accordingly, attempts have been made to improve the heat resistance by coating / laminating a PET stretched film. However, it is difficult to provide a PET stretched film with high heat resistance that can withstand a high temperature of 150 ° C or higher. 2019/103370 1 »(: 1 ^ {2018/013639

On the other hand, a polyimide film having high heat resistance is also applied to the above-mentioned ash: application, but the polyimide film has a disadvantage that it is difficult to be reused in the future because it is a thermosetting resin.

DISCLOSURE OF THE INVENTION

[Problem to be solved]

The present invention is to provide a polyester resin composition having high heat resistance and high moisture resistance, and an axially stretched polyester film containing the same.

MEANS FOR SOLVING THE PROBLEMS

According to one embodiment of the present invention, there is provided a polyester resin comprising a polycondensate of a dicarboxylic acid component comprising terephthalic acid and isophthalic acid and a diol component comprising a cyclic nucleic acid dimethanol, The polyester resin has a melting temperature of 250 or more and a melt temperature (¾) and a melt crystallization temperature (difference (¾-¾)

And the polyester resin has a cooling crystallization temperature of < RTI ID = 0.0 >

Or more can be provided.

According to another embodiment of the present invention, the axially stretched polyester film formed using the polyester resin composition may be provided.

A polyester resin composition according to a specific embodiment of the present invention and a biaxially stretched polyester film for a flexible flat cable including the polyester resin composition will be described in more detail below. The present inventors have found that a polyester resin comprising a polycondensation product of a dicarboxylic acid component containing terephthalic acid and isophthalic acid and a diol component containing a cyclic nucleic acid dimethanol has a melt temperature of 250

And the difference (¾-¾ (:) between the melting temperature (¾ ₁ ) and the melting crystallization temperature

, And the cooling crystallization temperature (占 폚) and the glass transition temperature (0 day)

1.0 ₀ ^ with this later to the possible production of an unstretched sheet thickness it is possible to increase the elongation when making oriented films, it was confirmed through experiments that it can improve the heat resistance and hygroscopicity, and completed the present case greater. 2019/103370 1 »(: 1 ^ {2018/013639

Specifically, the biaxially stretched polyester film of one embodiment comprises a polyester resin comprising a polycondensate of a dicarboxylic acid component comprising terephthalic acid and isophthalic acid and a diol component comprising cyclic nucleic acid dimethanol. The melting temperature of the polyester resin was 250

Or more, 250-350

Or 253 to 340. < / RTI > If the melting temperature of the polyester resin is less than 2501 :, there is a problem that the polyester resin can not be applied to parts requiring low heat resistance and requiring high heat resistance.

The polyester resin has a melt temperature (占 0 and a melt crystallization temperature (占 :)) of

Or 45 to 1201: or 50 to 1151 :. The polyester resin has a difference between the melting temperature and the melt crystallization temperature

, The polyester resin is rapidly crystallized while being cooled from a molten state (about ¾) to a molten crystallized state (¾) after the polyester resin has a thickness of at least 1.0 袖 m, and at the same time, It is difficult to form a new sheet.

Further, the polyester resin has a cooling crystallization temperature of < RTI ID = 0.0 >

90 °. The polyester resin has a difference between the cooling crystallization temperature and the glass transition temperature

, The glass transition state (glass transition temperature: 0 占 at the time of heating (heating) in order to proceed the process of drawing the non-stretched sheet), the cooled crystallization state (the region reaching the hole is shortened and crystallized rapidly, Thus, stretching may be difficult.

That is, since the polyester resin has a melting temperature of 2501: or more, it can exhibit high heat resistance, and the melting temperature and the melt crystallization temperature

And the cooling crystallization temperature and the glass transition temperature

It is possible to achieve moldability and extensibility.

The content of isophthalic acid contained in the polyester resin is 3 to 20 mol%, 5 to 20 mol%, 6 to 18 mol%, 8 to 16 mol%, 10 to 14 mol% per day of the total dicarboxylic acid component If the content of isophthalic acid exceeds 20 mol%, the heat shrinkage ratio may be high due to a high heat shrinkage at a high temperature of 150 or higher. If the content of isophthalic acid is less than 3 mol%, the thickness of the transparent non- 2019/103370 1 »(: 1 ^ {2018/013639

Since the stretching ratio is also limited, the elongation rate is reduced when the stretched film is produced, so that desired mechanical properties and heat resistance can not be obtained.

The molar ratio of the dicarboxylic acid component and the diol component contained in the polyester resin may be 1: 1 to 2, or 1: 1.2 to 1.8. If the molar ratio of the dicarboxylic acid component and the diol component is less than 1: 1, the melting temperature may be lowered and the heat resistance may be deteriorated. If the molar ratio is more than 1: 2, the moldability may be deteriorated and desired mechanical properties may not be obtained.

The dicarboxylic acid component may contain, in addition to the terephthalic acid and isophthalic acid, at least one other dicarboxylic acid selected from the group consisting of 2,6-naphthalenedicarboxylic acid, dimethylisophthalic acid, and dimethyl 2,6-naphthalenedicarboxylic acid But are not limited thereto. The content of the other dicarboxylic acid component may be 20 mol% or less, 0.1 to 20 mol%, and 5 to 15 mol% based on the total dicarboxylic acid component.

Also, the diol component may further include an aliphatic diol having 2 to 20 carbon atoms, for example, ethylene glycol, diethylene glycol, 1,4-butanediol, 1,3-propanediol, and neopentyl glycol &Quot; selected from ^" one or more other diol components. &Quot; The content of the other diol component may be 20 mol% or less, 0.1 to 20 mol%, and 5 to 15 mol% based on the total diol component.

The polyester resin may have an intrinsic viscosity (IV) of 0.4 to 1.2 ₍₁₁ , 0.5 to 1.0, or 0.7 to 0.911 / _§ ). If the intrinsic viscosity is less than 0.4 (11, the melting temperature is lowered, The number average molecular weight of the polyester resin is preferably in the range of 15,000 to 50,000 / 1, 20,000 to 45,000 / ₁₀₁ or 25,000 to 40,000. _§ ^ 1 is the number of days. the number average molecular weight above 15,000

If lower than the melting temperature can be lowered in heat resistance, when 50,000 _§ ^ 1 rather than not get the desired mechanical properties, moldability is lowered.

In addition, the polyester resin is from 50,000 to 150,00¾ /, 1, 140 to 60,000, 00¾ / US ₀₁ weight average molecular weight or 70,000 to 2019/103370 1 »(: 1 ^ {2018/013639

130,000 _§ / 1. The weight average molecular weight, and can be a 50,000細wall ₀₁ is less than the melting temperature decreases the heat resistance becomes low, 150,000 _§ ^ ₀₁ exceeds rather not get the desired mechanical properties, moldability is lowered.

The polyester resin preferably has a melt crystallization temperature of 150 to 2301 :. If the melt crystallization temperature of the polyester resin is less than 1501, the effect of heat settling (¾) may be reduced during post-processing or using an actual stretched film, which may make it difficult to impart shape stability of the final stretched film. High shrinkage may occur. If the melt crystallization temperature exceeds 230 ", it may become difficult to produce a transparent unoriented sheet upon film extrusion. According to another embodiment of the present invention, a biaxially stretched polyester film formed using the polyester resin composition can be provided. The biaxially stretched polyester film exhibits heat resistance at a high temperature of 150 to 200 ° (:), and can be applied generally to safety parts such as automobile powertrain, engine control and steering apparatus, and particularly excellent heat resistance, moisture resistance, The flexible flat cable can be used as a material for this. Typically, the flexible flat cable material can control the thickness of the film up to 1.2

The ET film has a heat resistance of about 130 ", which makes it vulnerable to heat. Therefore, there has been an attempt to use a polycyclohexanediylsilylene dimethylene terephthalate film in a component requiring heat resistance. However,

Film has a high glass transition temperature of 0¾) and a high melting temperature (¾).

However, the conventional method has a problem that the crystallization is rapidly performed immediately after extrusion using the melt crystallization temperature (¾ (:) higher than the melt crystallization temperature!)) And the thickness of the transparent unoriented sheet is considerably limited to approximately 0.1 have. If the thickness of the transparent unoriented sheet is as thin as about 0.1 占, the elongation rate in the stretching process may be lowered. On the other hand, in the conventional film, due to the low crystallization temperature (¾ (:)), when the temperature is elevated (heated) in order to proceed the process of drawing the unstretched sheet, 2019/103370 1 »(: 1 ^ {2018/013639

In the cooling crystallization state (the section where the bamboo reaches is shortened to crystallize rapidly and it is difficult to set the drawing processing conditions, there is a problem that drawing is difficult.

However, the polyester resin according to the one embodiment is the melting temperature (¾ ₁₎ and melt crystallization temperature (¾ (:) of the car (¾-¾ (:) 451: or more, wherein the polyester resin has a cooling crystallization temperature Since the difference (¾ (:) and glass transition temperature 0) between _-140 ° and 0 ° is not less than 40 °, the crystallization rate can be delayed immediately after extrusion so that the maximum thickness of the transparent non-

The crystallization speed can be retarded in the stretching process, so that the stretching of the non-stretched sheet can be easily performed, and the heat resistance of the polyester film Can be improved.

The biaxially stretched polyester film according to another embodiment may be a multilayer film or a laminate (thermally adhesive) film of two or more layers coextruded with the polyester resin composition.

Specifically, after melting the two or more of the polyester resin composition in the different extruder, after sending the molten resin into the die, and laminated in two or more layers,, blown犯1 a _«1) or casting犯greater for比) Or the like can be used to provide a multilayered film (or a laminated film) of a non-stretched film. Each layer included in the non-extensible multilayer film is transparent and may have a thickness of about 1.2 or more. At this time, the two or more polyester resin compositions may be the same composition, or may be other compositions having different components or contents. On the other hand, the unstretched multi-layer film can be biaxially stretched in the longitudinal direction and the transverse direction to obtain a biaxially stretched polyester film excellent in heat resistance and the like. The biaxially stretched polyester film may have a heat shrinkage ratio of less than 0.5%, 0.01 to 0.4%, or 0.01 to 0.3% at 1501: 30 minutes, a heat shrinkage ratio of less than 1.0% at 200 ° C for 30 minutes, 0.01 to 0.9%, or 0.01 to 0.8%. It can be confirmed that such a biaxially stretched polyester film has a remarkably low heat shrinkage at a temperature of 150 to 200 and is excellent in high heat resistance. In addition, the dyed stretched dolly ester film is excellent in moisture resistance. Specifically, when the temperature is 85 ^° C and the relative humidity is 85%, the moisture absorption rate is 1% or less, 0.01 to 0.9%, or 0.01 to 0.8 %.

On the other hand, the production method of the biaxially stretched polyester film is not limited to this. For example, after the polyester resin composition is vacuum-dried and sufficiently removed moisture, the polyester resin composition is fed to an extruder and heated at a temperature of 200 to 300 ° C Extruded, and molded into a sheet form from a T-shaped indentation. The thus obtained sheet material is cooled and fixed on a cooling drum on a mirror surface to obtain an unoriented sheet. At this time, it is preferable to use the electrostatic application method for the purpose of improving the adhesion with the cast drum. Thereafter, the obtained unstretched sheet is stretched in the longitudinal direction (longitudinal direction or mechanical direction, MD: mechanical direct ion). The longitudinal orientation is preferably a condition for lowering the crystal orientation and promoting thermal crystallization. After stretching in the longitudinal direction, stretching is performed in the transverse direction (transverse direction, TD) to obtain a biaxially stretched film after heat treatment.

In this case, the stretching ratio may be 2 to 5 times, preferably 2.5 to 5 times, more preferably 2.5 to 4.0 times in the longitudinal direction, 2.5 to 5 times in the transverse direction, preferably 3 to 4.5 times, May be 3.2 to 4.2 times.

The stretching temperature is the glass transition temperature (Tg) of the polyester resin + 5 ^° C to

Tg + 50 ^° C, or Tg + 10r to Tg + 40 ^° C. At this time, the lower the Tg, the better the stretchability, but the breakage may occur. When the stretching temperature is in the range of Tg + 10 ° C to Tg + 40 ° C, the brittleness of the produced film can be improved. In addition, the longitudinal stretching speed may be 22 to 500 m / min, 25 to 400 m / min, or 25 to 200 m / min. In this case, when the longitudinal stretching speed is 22 m / min or more, it is advantageous to maintain the intended orientation in the present invention, and since the crystallization is imparted depending on the longitudinal stretching speed and the stretching ratio, the transverse stretching speed may vary depending on the longitudinal stretching condition .

【Effects of the Invention】 2019/103370 1 »(: 1 ^ {2018/013639

According to the present invention, a polyester resin composition excellent in high heat resistance and high moisture resistance and a polyester film containing the polyester resin composition can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

1 is a graph showing the measurement results of the moisture absorption rate of the film of Example 1 00 and Comparative Example 1).

2 is a graph showing the measurement results of the hydrolysis ratio (intrinsic viscosity retention rate) of the film of Example 1 (Example 1 (1 ') and Comparative Example 1).

3 is a photograph of the surface of the film when evaluating the hydrolysis ratio (intrinsic viscosity retention) of the film of Example 1) and Comparative Example 1).

4 is a photograph of the surface of the film before and after the evaluation of oligomers in Example 1 (? 01) and Comparative Example 1).

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the contents of the present invention are not limited by the following examples. Example 1

1) Preparation of polyester resin composition

1, 4-cyclohexanedic acid dimethanol 2.01 _,, dicarboxylic acid 1.8 containing terephthalic acid and isophthalic acid in a molar ratio of 95 mol%: 5 mol%

Triethyl phosphate 0.4, titanium oxide

For the w to the esterification reaction: the catalyst of the Ti atom content 15 wt%) 0.2 _§ and antimony trioxide (the catalyst of the antimony atom content 83.5% by weight) added to 0.2 ₈ to the reactor, at atmospheric pressure 280 ° (for 3 hours . Then, the esterification reaction product under a pressure of 0.5 to 1比295 ° (: temperature in 150 minutes heating by esterification reaction product condensation ₍₁₎ ₀₁ for the (: ₀₁₁ (1 _{611 331} ^ ₀₁₁₎ to the polyester A resin was prepared and processed into a chip form.

2) Production of biaxially stretched polyester film

The polyester resin chips were melt-extruded in an extruder and molded and cooled in a sheet form. The resultant sheet was stretched 3.6 times in the longitudinal direction (1)), Width direction 1)). The stretched film was heat-set at 2381 ° C to obtain a biaxially stretched polyester film. Examples 2 and 3

A biaxially stretched polyester film was obtained in the same manner as in the production method of Example 1, except that the isophthalic acid content was used in the molar ratio shown in Table 1 below. Comparative Example 1

Terephthalic acid (1.21 _g) and ethylene glycol (1.2 _g) were added to the reaction tank,

258 ° (: in performing a conventional polymerization of polyethylene terephthalate _(則:.. Has been the polymer is produced, and processing them in the form of a chip melting and extruding them in an extruder and a sheet was molded and cooled, the longitudinal (ppya) , Stretched to 4.0 times in the width direction 01) to prepare a polyethylene terephthalate film. Comparative Examples 2 to 4

A biaxially stretched polyester film was obtained in the same manner as in the production method of Example 1, except that the isophthalic acid content was used in the molar ratio shown in Table 1 below. evaluation

1. Measurement of glass transition temperature, etc. by DSC analysis.

The polyester resins of Examples 1 to 3 and Comparative Examples 1 to 5 were analyzed by DSC (differential scanning calorimetry) to determine glass transition temperature (Tg), cold crystallization temperature (Tcc) zat ion temperature, melting temperature (Tm) and melt crystallization temperature (Tmc) were measured. Specifically, the polyester resin was heated at 30 ^° C to 320 ° C at a temperature raising rate of 10 ° C / min using a DSC, held for 5 minutes, quenched to 30 ° C 2019/103370 1 »(: 1 ^ {2018/013639

And kept for 5 minutes. Thereafter, the cold crystallization temperature (¾ (:) and the melting temperature 0 °) were measured at a heating rate of 10 ° (: / min) at 30 ° (glass transition temperature 0 °) The melt crystallization temperature (((:) was measured while keeping the temperature at 320 占 폚 for 5 minutes and then cooling to 301 占 폚 at a cooling rate of 1017 minutes. The results are shown in Table 1 below.

2. Measure the maximum thickness of transparent Hanmi-drawn sheet

The maximum thickness of the transparent non-stretched sheet was measured before melt-extruding the polyester resin of Examples 1 to 3 and Comparative Examples 1 to 5 in the extruder and stretching in the longitudinal direction (01) and the transverse direction (01)), The results are shown in Table 1 below.

3. Measurement of maximum elongation

The unstretched sheets of Examples 1 to 3 and Comparative Examples 1 to 5 were subjected to biaxial stretching in both longitudinal and transverse directions, and the maximum elongation was measured. The results are shown in Table 1 below.

4. Measurement of area heat shrinkage

For the films of Examples 1 to 3 and Comparative Examples 1 to 5, the film was cut so that one edge was parallel to the machine direction (longitudinal direction) and the other edge was perpendicular to the machine direction (transverse direction) A sample of X 100 ₁₁ square film was prepared. After holding the film for 30 minutes in a 150 oven in which air was circulated, the sample was taken out, and the change in length in the longitudinal direction and in the transverse direction was measured at room temperature, and the longitudinal and transverse heat shrinkage ratios were calculated according to the following formula 1. In the same manner, the film was held in an oven at 200 [deg.] (For 30 minutes, and the heat shrinkage ratio was calculated. The results are shown in Table 1 below.

[Formula 1]

100

Is the length before heat treatment, and is the length after heat treatment. 5. Evaluation of tensile elongation retention

Films of Example l (PCT) and Comparative Example l (PET) were maintained at a temperature of 121 DEG C., 48 hours and 60 hours under a pressure condition of 10 (> Relative Humidity and 2 atm (Pressure Cooker Test. And the tensile elongation retention was measured. The results are shown in Table 1 below.

6. Evaluation of moisture absorption rate

The films of Example l (PCT) and Comparative Example l (PET) were maintained at 85 [deg.] C and 85% relative humidity for 5000 hours, and the increased weight was measured and plotted in Fig. The moisture absorption rate after 5000 hours was calculated, and the results are shown in Table 1 below.

7. Hydrolysis evaluation

(1) Intrinsic viscosity measurement

The films of Example 1 and Comparative Example 1 were dissolved in o-chlorophenol at a concentration of 1.2 g / dl and the intrinsic viscosity was measured at 35 ° C using a Ubbelodhe viscometer.

(2) The hydrolysis rate (intrinsic viscosity retention rate)

The films of Example ₁ and Comparative Example 1 were maintained at a temperature of 85 ° C and 85% relative humidity for 5000 hours, and the degree of intrinsic viscosity was measured. The results are shown in the graph of FIG. The hydrolysis ratio (intrinsic viscosity retention ratio) after 5000 hours is shown in Table 1 below. The surface of Example KPCT after 5000 hours and Comparative Example 1 (PET) was photographed and shown in Fig.

8. Oligomer evaluation

Example 1 and Comparative Example 1 In order to examine elution of oligomers in a film, the film was heat-treated in an oven at 150 ° C for about 60 minutes, and the change was observed using a haze meter. The results are shown in the following Table 1 .

Haze Meter: NIPPON DENSH0KU Model NDH-7000 2019/103370 1 »(: 1 ^ {2018/013639

9. Evaluation of dielectric breakdown voltage

A flexible flat cable was produced using the films of Example 1 and Comparative Example 1, and the voltage at which the film was broken and short-circuited was read by applying to the adjacent conductors: 1,00 for 60 seconds. The results are shown in the following Table 1 .

[Table 11

-: Isophthalic acid to 100 mol% of the dicarboxylic acid component contained in the polyester resin (content of Kawashima

- PCT ^** : A test called a Pressure Cooker Test (PCT) or Autoclave test that evaluates whether a product can withstand a high temperature / high humidity environment. The test was conducted at 121 ° C, 100% relative humidity and atmospheric pressure of 2 atm. According to the above Table 1, it was confirmed that the films of Examples 1 to 3 had a lower heat shrinkage rate than that of the film of Comparative Example 1, excellent heat resistance, excellent moisture absorption resistance, hydrolysis resistance and electrical characteristics.

.

Claims

2019/103370 1 »(: 1 ^ {2018/013639

[Claims]

Claim 11

A polyester resin comprising a polycondensate of a dicarboxylic acid component comprising terephthalic acid and isophthalic acid and a diol component comprising a cyclic nucleic acid dimethanol,

The polyester resin has a melt temperature of 250

Or more,

The polyester resin had a melt temperature (: ¾) and a melt crystallization temperature (¾

[Claim 2]

The method according to claim 1,

The content of the isophthalic acid is 3 to 20 mol% based on the total dicarboxylic acid component.

[Claim 3]

The method according to claim 1,

Wherein the dicarboxylic acid component further comprises at least one other dicarboxylic acid component selected from the group consisting of 2,6-naphthalene dicarboxylic acid, dimethyl isophthalic acid, and dimethyl 2,6-naphthalene dicarboxylic acid,

The content of the other dicarboxylic acid component is 20 mol% or less based on the total dicarboxylic acid component.

Claim 4

The method according to claim 1,

Wherein the diol component further comprises at least one other diol component selected from the group consisting of ethylene glycol, diethylene glycol, 1,4-butanediol, 1,3-propanediol, and neopentyl glycol,

The content of the other diol component is preferably 20 mol% or more, 2019/103370 1 »(: 1 ^ {2018/013639

Or less.

[Claim 5]

The method according to claim 1,

Wherein the dicarboxylic acid component and the diol component have a molar ratio of 1: 1 to 2, respectively.

[Claim 6]

The method according to claim 1,

Wherein the polyester resin has an intrinsic viscosity (IV) of 0.4 to 1.2 ₍₁₁ ;

[7]

The method according to claim 1,

Wherein the polyester resin has a number average molecular weight of 15,000 to 50,000.

8.

The method according to claim 1,

Wherein the polyester resin has a weight average molecular weight of 50,000 to 150,000.

9]

The method according to claim 1,

Wherein the polyester resin has a melt crystallization temperature of 150 to 2301:.

Claim 10

A biaxially stretched polyester film formed using the polyester resin composition of any one of claims 1 to 9. 2019/103370 1 »(: 1 ^ {2018/013639

Claim 11

11. The method of claim 10,

Wherein the polyester resin composition is a multilayer film or a laminate film of two or more co-extruded biaxially stretched polyester films.

Claim 12

11. The method of claim 10,

The biaxially stretched polyester film is a biaxially stretched polyester film for a flexible flat cable.

Claim 13

11. The method of claim 10,

The biaxially stretched polyester film is a biaxially stretched polyester film having a heat shrinkage ratio of less than 0.5% at 150 ° C. for 30 minutes and a heat shrinkage ratio of less than 1.0% at 200 ° C. for 30 minutes.

14.

11. The method of claim 10,

The biaxially stretched polyester film has a stretch ratio of 2 to 3

Stretched 5 times, and stretched 2 to 5 times with respect to the transverse direction 1).

15.

11. The method of claim 10,

The biaxially stretched polyester film 1211: a temperature of, 100% costume daeseup also, and in high-temperature high-humidity test (0) ₀ urinary near) the pressure conditions of 2atm, the tensile elongation retention of 50% or more after 48 hours, 60 A biaxially stretched polyester film having a tensile elongation retention ratio of 30% or more after lapse of time. 2019/103370 1 »(: 1 ^ {2018/013639

Claim 16

11. The method of claim 10,

The biaxially stretched polyester film is a biaxially stretched polyester film having a moisture absorption rate of 1% or less when the temperature is 851: 5 and the relative humidity is 5%.